img051 img052 img053 img054 img055 img056 img057 img069 img070 img071 img072 img073 img074 img075 img076 img133 img134 img135 img136 img137 img138 img139 img086 img087 img088 img089 img090 img036 img037 img038 img039 img040 img041 img091 img092 img093 img094 img095 img096 img097 img098 img016 img017 img018 img019 img020 img021 img022 img042 img043 img044 img045 img046 img028 img029 img030 img031 img115 img116 img117 img118 img119 acknowledgement s(1) editorial i am very pleased to serve as the editor-in-chief for the journal of agricultural and marine sciences (jams). jams is a peer reviewed open access journal published by the college of agricultural and marine sciences (cams), sultan qaboos university (squ). this research-agricultural and marine sciences” and later it was re-named as the journal of agricultural and marine sciences (jams). it has now reached its 25 years of publication and is serving the agricultural sciences by disit to the next stage of progress. jams publishes original fundamental and applied research articles in a wide variety of disciplines of agriculture and natural resources. the journal is intended to serve a wide range of specialists and bring together quality papers dealing with agricultural economics, natural resource economics, animal and veterinary sciences, bioresources, soil sciences, water management, agriculence, human nutrition, plant production, plant protection, rural environment, and coastal zone management. views, book reviews, short notes, editorials, letters to the editor, snapshot and perspective papers in the broader areas of agricultural and marine sciences. perspective papers are short papers that present an opinion or novel interpretation of existing ideas or data. snapshots papers focus on a high quality illustration and these should not exceed one page and list only a maximum of 3 references. these papers illustrate the common saying “one picture is worth a thousand words”. i would like to take this opportunity to thank dr. michel claereboudt for his dedication to the progress of jams. i would also like to thank all earlier editors and associate editors for their contribution towards jams and to bring it to its current level. i would like to welcome the new editor, dr. mohammad farooq and all associate editors, dr. haytham ali, dr. ali al-maktoomi, dr. velazhahan rethinasamy, dr. daniel blackburn, dr. zaher al-attabi and dr. lokman zaibet. the editorial team is committed to developing the the current plan is to publish two regular issues per year. we will attempt to publish perspective articles regularly addressing issues related to the gcc, especially oman. books published, especially from cams and oman, will be considered for review and will be published in the jams. as we reached 25 years of publishing the jams, we would like to celebrate this occasion by publishing a special issue in 2020 or early 2021. the theme would be, “progress of agricultural and marine sciences in the sultanate of oman”. the target would be to publish review articles mainly focusing on major areas of agricultural and marine sciences. we would like to encourage academics, researchers and professionals working in the areas of agricultural and for possible publication in the jams. success with the support of the new editorial board members. i would like to express my appreciation to dr. rahma al-mahrooqi, (chair, squ publication committee) and dr. abdullah al-sadi (dean, cams) for their continued support toward me and my editorial team. editor-in-chief, jams journal of agricultural and marine sciences 2020, 25(1): 01 issn: online: 2410-1079 & print: 2410-1060 doi: 10.24200/jams 1 research paper journal of agricultural and marine sciences 2023, 28(2): 14–17 doi: 10.53541/jams.vol28iss1pp14-17 received 6 february 2022 accepted 22 february 2023 الربح املتوقع من تغذية املاعز بفضالت الدواجن اجملففة ابستخدام اشعة الشمس كمكمل غذائي أ.أ بيلو*1، ب.ج. ديساي2، ج.س. دهيكايل3 و م. بيلو4 profitability of feeding sun-dried poultry dropping based diets as supplement to goat a.a. bello1*, b. g. desai2, j. s. dhekale3 and m. bello4 a.a. bello1*,( ) aabello2003@yahoo.co.uk, 1department of animal health and production technology, college of agriculture, mokwa, p.m.b 109, niger state, nigeria. 2department of animal husbandry and dairy science, college of agriculture, dr. b.s.k.k.v, dapoli, pin: 415 712 dist. ratnagiri, maharashtra, india. 3department of agricultural economics, college of agriculture, dr. b.s.k.k.v, dapoli, pin: 415 712 dist. ratnagiri, maharashtra, india. 4department of home economics, college of education, minna, p.m.b 39, niger state, nigeria. introduction least cost feeding of livestock is immensely essen-tial for the best productivity. under productivity of livestock is attributed to the insufficient and exorbitant high costs of feeds (beigh et al., 2017). therefore, comparatively low cost agricultural and industrial by-products are essential for profitable livestock production enterprises. it could be achieved by reducing feed costs (sontakke et al., 2014 thus, non-conventional feeds can be used to minimize feed cost, and add to self-sufficiency in nutrients from the local feed sources (bello, 2016; bello and tsado, 2014; sontakke et al., 2014; mubi et al., 2008; aro and tewe, 2007; onimisi and omage, 2006; ndubueze et al., 2006; saleh et al., 2002; belewu and adeneye, 1996; zinn et al., 1996; ibeawuchi et al., 1993). sun-dried poultry droppings could be the non-conventional feed resources. this study was therefore designed to find profitability of the sun-dried poultry dropping when it was used in supplemented diet (i.e. finger millet straw) to konkan kanyal goats. materials and methods experimental location this study was carried out at the institutional livestock farm, goat unit of department of animal husbandry and dairy science farm, college of agriculture, dapoli, india. it is located at 280 m above mean sea level (msl) and in the subtropical region at 17045’ north latitude and 13012’ east longitude. the area is characterized by hilly terrain. the soil is lateritic and acidic. the soil is low in fertility, having poor water holding capacity. the climate is warm and humid with 3500 mm average annual rainfall. the maximum temperature at dapoli is about 33.40c in summer and 21.10c in winter while, relative humidity ranges from 55 to 96 percent. experimental feed three experimental diets were used for the study, finger millet straw, green fodder as basal diets and supplementary diets. five supplementary diets were prepared. the abstract. the profitability of feeding dried poultry droppings-based diet as a supplement in goat production enterprise was analyzed in this present study. the data generated in the study was analyzed using gross margin analysis and profitability ratio. the result of the budgetary analysis showed that the highest total cost of rs 855.9/goat was incurred, the highest total revenue of rs 1254.3/goat, highest gross margin of rs 773.24/goat and highest net farm income of rs 713.24/goat were observed for the supplemented treatment groups (t2-t5). the profitability ratio gave the best benefit-cost ratio of 4.62, a rate of return of 3.62, a gross ratio of 0.22 and an expense structure ratio of 0.12. this suggests that feeding of dried poultry droppings-based diet to goats is a profitable enterprise. this present study, therefore, recommends the supplementation of sun-dried poultry dropping based diet at 80% inclusion level for maximum profitability of goat production enterprises. keywords: economics; goats; sun-dried poultry dropping based diet امللخــص: مت يف هــذه الدراســة حتليــل الربــح املتوقــع مــن تغذيــة املاعــز بنظــام غذائــي يعتمــد علــى فضــات الدواجــن اجملففــة كمكمــل يف شــركات إنتــاج املاعــز. مت حتليــل البيــاانت الناجتــة عــن الدراســة ابســتخدام حتليــل اهلامــش اإلمجــايل ونســبة الرحبيــة. حيــث أظهــرت نتيجــة حتليــل امليزانيــة أنــه مت تكبــد أعلــى تكلفــة إمجاليــة قدرهــا 855.9 روبيــة / ماعــز، وأعلــى إمجــايل إيــرادات بلغــت 1254.3 روبيــة / عنــزة ، وأعلــى هامــش إمجــايل قــدره 773.24 روبيــة / ماعــز ، و لوحــظ أن أعلــى دخــل مزرعــة صــاٍف قــدره 713.24 روبيــة / ماعــز كان للمجموعــات الــي مت إعطائهــا املكمــات )t2-t5(. كذلــك أعطــت نســبة الرحبيــة أفضــل نســبة فائــدة إىل التكلفــة و قدرهــا 4.62 ، ومعــدل عائــد 3.62 ، ونســبة إمجاليــة قدرهــا 0.22 ونســبة هيــكل املصاريــف 0.12. و هــذا يشــر إىل أن تغذيــة املاعــز مــن فضــات الدواجــن اجملففــة هــي مشــروع مربــح. لذلــك ، توصــي هــذه الدراســة إبضافــة فضــات الدواجــن اجملففــة ابلشــمس يف غــذاء املاعــز عنــد مســتوى إدراج بنســبة 80٪ لتحقيــق أقصــى قــدر مــن الرحبيــة لشــركات إنتــاج املاعــز. الكلمات املفتاحية: اقتصادايت؛ املاعز. نظام غذائي يعتمد على فضات الدواجن اجملففة ابلشمس 15research paper bello, desai, dhekale, bello supplementary diets consisted of the following: 100% concentrate, 20% dried poultry droppings concentrate based diet, 40% dried poultry droppings concentrate based diet, 60% dried poultry droppings concentrate based diet 80% dried poultry droppings concentrate based diet. experimental animals and their management thirty konkan kanyal goats, aged 9-12 months and with an average weight of 13.66 kg, were used in this present study. the goats were randomly assigned to five treatments designated t1-t5 comprising of three replicates with two animals per replicate. the animals were kept in individually designed pens. the experimental animals were sprayed against ectoparasites, dewormed orally against endoparasites and treated with a wide-ranging antibiotic to prevent bacterial infections. thereafter, animals were randomly assigned into five experimental groups and fed for three weeks. the feeding trial was conducted for 90 days. the animals were penned in solitary confinement. experimental design the experimental design used was the randomized block design (rbd). thirty konkan kanyal goats aged 9-12 months with an average weight of 13.66 kg were used for this study. the goats were randomly assigned to five treatments designated t1-t5 comprising of three replicates with two animals per replicate. animal feeding the experimental animals were fed at 3% of their body weight (bw). one-third (1/3) were fed as green feed, two-thirds (2/3) were fed as dry feeds while out of this dry feed two-thirds (2/3) were fed as dry roughages and one-third (1/3) were fed as concentrates. the level of inclusion of dried poultry dropping in the treatments is t1 0%, t2 20%, t3 40%, t4 60% and t5 80%. chopped finger millet straw (2 cm long) was offered to the animals as basal diets. the goats were fed in individually designed pens. the experimental animals were weighed at the start of the experiment, subsequently (i.e. weekly). an adaptation period of 21 days was allowed before data was collected for 90 days. the animals were dewormed, dipped against ectoparasites and dosed with antibiotics as prophylaxis before the commencement of the experiment. clean fresh clean water was offered throughout the study. data analysis data generated in this present study were analyzed using gross margin analysis, net farm income and profitability ratio to achieve the objectives of this study. gross margin = total revenue – total variable cost (1) total cost = fixed cost + variable cost (2) net farm income = total revenue – total cost (3) benefit-cost ratio = total revenue/total cost (4) expense structure ratio = fixed cost/variable cost (5) rate of returns = net profit/total cost (6) gross ratio (gr) = total cost/total revenue (7) result and discussion cost and return analysis table 1 reveals the estimated cost and returns analysis as obtained from feeding sun-dried poultry dropping based diet as supplement for goats using average cost (i.e. fixed and variable cost) and average body weight gained by each of the treatment group. the average chevon price/kg was lowest (rs 857.5) in control treatment group (t1) and was the highest (rs.1130.5) in supplemented treatment group (t5) followed by (t4) (rs 1067.5); total revenue was the highest in t5 (rs 1254.30), keenly followed by t4 (rs 1185.95) and was the lowest in t1 (rs 958.38). the net farm income in t1 was (rs 102.48) but was the highest in t5 (rs 713.24) followed by t4 (rs 652.45) respectively. gross margin result followed a similar trend as was observed for total revenue and net farm income in which the highest values were recorded for supplemented treatment group t5 (rs 773.24), followed by t4 (rs 712.45) and least in t1 (rs 162.48). this present study revealed that feeding dried poultry droppings based diet as a supplement to goats was profitable and it is in agreement with the earlier findings (bello, 2016; jokthan et al., 2013; anigbogu and nwagbara, 2013; fawola and fajemisin, 2011.). the inclusion of poultry litter in the diet of ruminants reduces feed costs and increased farmer’s income. profitability and estimated viability table 2 reveals the profitability and estimated viability of the feeding trial with sun-dried poultry dropping based diet as supplement. the cost-benefit ratio ranged from 0.94 (i.e. t1) to 4.62 (i.e. t5). from the result of this present study supplemented treatment group (t2t5) showed cost-benefit ratios as 1.60, 1.91, 4.26 and 4.62, respectively. this implies that supplementation of sun-dried poultry dropping based diet was profitable. it is commonly considers that any business with cost-benefit ratio higher than one means is profitable, and equals to one means break-even, while less than one indicates loss (olagunju et al., 2007). the gross ratio ranged from 1.06 (i.e. t1) to 0.22 (i.e. t5). this implies in t1, for every rs 1.00 returns to goat feeding, rs.1.06 are being spent, while for t5 for every rs 1.00 returns while 22 paisa is being spent. the rate of returns ranged from -0.06% in t1 to 3.62% in t5. this shows that for every rs. 1.00 invested into goat feeding in t1 (i.e. -0.06 paisa) was lost by the farmer and in t5 for every rs 1.00 invested into goat feeding rs. 3.62 was gained by the farmer. the expense structure ratio ranged from 0.08 (i.e. t1) to 0.12 (i.e. t5). the best value was observed in supplemented treatment groups (i.e. 0.12) which implied that about 12% of the total cost of production 16 squ journal of agricultural and marine sciences, 2023, volume 28, issue 2 profitability of feeding sun-dried poultry dropping based diets as supplement to goat was made up of fixed cost component. this makes goat farming a valuable venture because an increase in production with variable cost also leads to increase in total revenue while the fixed cost remained constant. conclusion this present study showed that goats fed diets with sundried poultry droppings had better weight gain, total revenue, and net farm income, thus increasing the profitability of goat production. therefore, it is recommended that goats supplemented with sun-dried poultry dropping based diet up 80% inclusion level has the best net profit. references anigbogu nm, nwagbara nnn. (2013). performance of west african dwarf goat fed maize offal diets supplemented with dry poultry excreta. revue d’elevage et de médecine vétérinaire des pays tropicaux 66(2): 51-56. aro so, tewe oo. (2007). performance and carcass yields of barrows fed dried poultry waste as a replacement for palm kernel cake. african journal of biotechnology 6: 487-492. table 1. cost and return of feeding sun-dried poultry dropping based diet as supplement for goats: s.n. statements t1 t2 t3 t4 t5 1 initial average body weight of goats (kg) 12.45 13.85 13.93 13.38 14.00 2 average body weight gain (kg/ goats) 2.45 2.58 2.67 3.05 3.23 3 average total feed consumed (kg/ goats) 55.43 55.58 59.57 58.72 60.01 4 initial live weight cost (rs) 4357.5 4847.5 4875.5 4683 4900 5 final live weight cost (rs) 5215 5750.5 5810 5750.5 6030.5 variable cost 6 total cost of feed (rs) 667.9 326.9 350.5 345.5 353.06 7 average material cost (rs) 105 105 105 105 105 8 depreciation cost of material (10%) 10.5 10.5 10.5 10.5 10.5 9 misc. expenditure (drug, water and labour, etc.) 12.5 12.5 12.5 12.5 12.5 10 total variable cost 795.9 454.9 478.5 473.5 481.06 fixed cost 11 cost of house rent 60.00 60.00 60.00 60.00 60.00 12 total cost 855.9 514.9 538.5 533.5 541.06 sales returns 13 average chevon price (350rs/kg) 857.5 903 934.5 1067.5 1130.5 14 average total manure obtained (kg/ goats) 40.35 48.48 42.05 47.38 49.52 15 total price of manure (2.5 rs / kg) 100.88 121.2 105.13 118.45 123.8 16 total returns (rs) 958.38 1024.2 1039.63 1185.95 1254.3 17 net profit/goat (rs) 102.48 509.3 501.13 652.45 713.24 18 gross margin 162.48 569.3 561.13 712.45 773.24 rupees-dollar= rs.66.23 $ 1.00 t1: had 0% sun-dried poultry dropping based diet (sdpdbd) inclusion; t2: 20% sdpdbd; t3: 40% sdpdbd; t4: 60% sdpdb and t5 80% sdpdb table 2. profitability ratios treatment cost-benefit ratio expense structure ratio gross ratio rate of return value value value value t1 0.94 0.08 1.06 -0.06 t2 1.60 0.13 0.62 0.60 t3 1.91 0.13 0.52 0.91 t4 4.26 0.13 0.23 3.26 t5 4.62 0.12 0.22 3.62 t1: had 0% sun-dried poultry dropping based diet (sdpdbd) inclusion; t2: 20% sdpdbd; t3: 40% sdpdbd; t4: 60% sdpdb and t5 80% sdpdb 17research paper bello, desai, dhekale, bello belewu ma, adeneye ja. (1996). the effects of broiler litter as a protein sources in the performance of bunaji (white fulani) bull calves. nigeria journal of animal production 23: 66-71. bello aa. (2016). economics of feeding sun-dried poultry dropping based diets on growing rams consuming sorghum stover. iranian journal of applied animal science 6: 595-598. bello aa, tsado dn. (2014). effects of supplementing sorghum (sorghum bicolor l. moench) stover with dried poultry dropping based diet on the performance of growing yankasa ram. iosr journal of agriculture and veterinary science 7: 34-39 beigh ya, ganai am, ahmad ha. (2017). prospects of complete feed system in ruminant feeding: a review. veterinary world 10: 424-437. fawola ts, fajemisin an. (2011). performance and micro minerals utilization by west african dwarf ram fed rumen content-poultry droppings mixed diet. in: proceedings of 36th annual conference, nigerian society for animal production (nsap), university of abuja, nigeria, volume 36, p. 533-535. ibeawuchi ja, danjuma d, oguntona t. (1993). the value of dried poultry waste as protein supplement for growing borno white goats. discovery and innovation 5: 63-68. jokthan ge, muhammad sa, osuhur cu. (2013). effect of cotton seed cake replacement with broiler litter on performance of yankasa rams fed maize husk basal diets. futa journal of research science 1: 147-155. mubi aa, kibon a, mohammed id. (2008). utilization of alkali treated sorghum stover supplemented with poultry litter for growing heifers in the north east region of nigeria. asian journal of animal and veterinary advances 3: 183-186. ndubueze a.i, ukachukwu sn, ahamefule fo, ibeawuchi ja. (2006). milk yield and composition of grazing white fulani cows fed poultry waste cassava peel based diets. pakistan journal of nutrition 5: 436-440. olagunju fi, adesiyan io, ezekiel aa.(2007) .economic viability of cat fish production in oyo state, nigeria. journal of human ecology 21: 121-124. onimisi pa, omage jj. (2006). evaluation of poultry litter as feedstuff for growing rabbits. livestock research for rural development 18: article 163. saleh hm, elwan km, el-fouly ha, ibrahim ii, salam am, el-ashry ma. (2002). the use of poultry waste as a dietary supplement for ruminants. in: development and field evaluation of animal feed supplementation packages. proceedings of the final review meeting of an iaea. technical co-operation regional afra project organized by the joint fao/iaea division of nuclear techniques in food and agriculture and held in cairo, egypt. 25-29 november, 2000. sontakke u, kale v, bose b, kumar m. (2014). in: non-conventional feeds and agro-industrial by product: their scope and future demand for livestock production culled. https://en.engormix.com (accessed on 6 september 2019). zinn ra, baraja sr, montario m, shen yc. (1996). protein and energy value of dehydrated poultry excreta in diets for feedlot cattle. journal of animal science 74: 2331-2335. img047 img048 img049 img050 img058 img062 img063 img064 img065 img066 img067 img068 img077 img078 img079 img080 img081 img082 img083 img084 img085 img120 img121 img122 img123 img124 img125 research paper journal of agricultural and marine sciences vol. 22 (1): 63-66 doi: 10.24200/jams.vol22iss1pp63-66 received 10 apr 2016 accepted 7 nov 2016 feasibility of growing stevia (stevia rebaudiana) at jabal al-akhdar, sultanate of oman salim ali al-rawahi*1, amna mahmoud al-toobi1 and mohammed issa al-balushi1 *1 salim ali al-rawahi ( ) sultan qaboos university, college of agricultural and marine sciences, department of soils, water and agricultural engineering. box 34, al-khod 123. sultanate of oman. email: sarawahy@squ.edu.om introduction stevia or “sweet herb” is a plant originating from mountainous regions of brazil and paraguay. in the sixteenth century, europeans became aware of stevia leaves which are 20-30 times sweeter than sugar. its leaves can be dried and stored and can be used in raw form. stevia has a short growth season and does not affect blood sugar levels and does not have the neurological or renal side effects associated with some of the artificial sweeteners (tanaka et al., 1997). stevia is commercially grown in many countries which include paraguay, brazil, uruguay, central america, china, thailand, the united states. it is considered an important natural sweetener in both japan and korea, and has been safely used in these countries for decades. it is used to make sweet sauces, pickles, beverages, etc. japan is one of the largest single consumers of stevia in the world. with using of stevia, there have been no anomalies observed in cell, enzyme, chromosomal or other significant physiological parameters during toxicity tests. stevia has not been associated with any form of cancer or birth defects (brunsick, 2008). جدوى منونبتة ستيفيا )stevia rebaudiana( يف اجلبل األخضر، سلطنة عمان سامل علي الرواحي*1 وآمنة حممود التويب1 وحممد عيسى البلوشي1 abstract. oman is one of the top nine countries in the world with highest prevalence of diabetes. there is therefore more awareness among the people to take necessary precautions to preserve their health by reducing their sugar consumption and replacing it with low calorie sweeteners. stevia is a natural herbal sweetener that is safe and does not have the neurological or renal side effects associated with some of the artificial sweeteners. a feasibility study to grow stevia was undertaken after obtaining the seeds that were initially planted in greenhouse to study their growth habits under controlled conditions. the plants were then transferred to the field in jabal al-akhdar at an elevation of 1079 m above sea level where temperatures were appropriate for stevia growth in summer since it was within its tolerant temperature range. two types of stevia plants were transferred to ja for the three months field study; those that originated directly from seeds and those from transplant cuttings. drip irrigation system with timer was installed with two laterals each having six emitters spaced 60 cm apart and each supplying 2 liters of water per day. moderate fertilizer npk was applied. five out of six plants in each of the two plots grew very well to the end of the season. some insects were attracted by the sweetness of the leaves but proper measures were taken to prevent damage. results show that it is feasible to grow stevia in ja in summer. keywords: stevia rebaudiana; growth conditions; soil type; sultanate of oman. امللخــص: عمــان هــي واحــدة مــن أكثــر تســع دول يف العــامل مــن حيــث نســبة انتشــار مــرض الســكري. ولــذا فــإن هنالــك وعيــا متزايــدا بــن النــاس يف اختــاذ االحتياطــات الالزمــة للحفــاظ علــى صحتهــم وذلــك عــن طريــق احلــد مــن اســتهالك الســكر واســتبداله باحملليــات قليلــة الســعرات احلراريــة. ومــن املعلــوم أن ســتيفيا هــي عشــبة طبيعيــة وآمنــة ميكــن اســتخدامها كبديــل للمحليــات الصناعيــة، وليــس هلــذه النبتــة آثــار جانبيــة عصبيــة أو آثــار علــى الكلــى كمــا هــو احلــال مــع بعــض مــن احملليــات الصناعيــة . ولقــد أجريــت دراســة يف جامعــة الســلطان قابــوس حــول إمكانيــة زراعــة ســتيفيا يف ســلطنة عمــان وذلــك بعــد احلصــول علــى البــذور مــن مصادرهــا ، ومت يف البدايــة زراعتهــا يف بيــت حممــي لدراســة عــادات منوهــا حتــت ظــروف خاضعــة للرقابــة . مث مت نقــل النباتــات إىل احلقــل يف اجلبــل األخضــر علــى ارتفــاع 1079 مــر فــوق مســتوى ســطح البحــر حيــث كانــت درجــات احلــرارة مالئمــة لنمــو ســتيفيا يف الصيــف. مت نقــل نوعــن مــن نباتــات ســتيفيا إىل اجلبــل األخضــر وذلــك لدراســة هذيــن النوعــن ملــدة ثالثــة أشــهر؛ خيتلــف النوعــان مــن حيــث أن أحدهــا قــد نشــأ مباشــرة مــن البــذور وأمــا اآلخــر فقــد نتــج مــن تقليــم الســيقان. مت تركيــب نظــام الــري بالتنقيــط مــع وجــود مؤقــت يف اثنــن مــن اخلطــوط الفرعيــة حبيــث أن كال منهمــا بــه ســتة نقاطــات تبعــد 60 ســم عــن بعضهــا البعــض وتعطــي كل منهــا لريــن مــن املــاء يوميــا. مت إضافــة نســبة متوازنــة مــن أمســدة النيروجــن والفســفور والبتســيوم. ولقــد لوحــظ أن مخســة مــن أصــل ســتة مــن النباتــات يف كل مــن قطعــي األرض منــت بشــكل جيــد جــدا حــى هنايــة املوســم. وقــد جذبــت حــالوة األوراق بعــض احلشــرات ولكــن مت اختــاذ التدابــر املناســبة ملنــع الضــرر. وأظهــرت النتائــج أنــه مــن املمكــن أن تنمــو ســتيفيا يف اجلبــل األخضــر يف موســم الصيــف. الكلمات املفتاحية: ستيفيا, خالية من السعرات احلرارية, جبل األخضر, درجات احلرارة مالئمة, الري بالتنقيط 64 squ journal of agricultural and marine sciences, 2017, volume 22, issue 1 feasibility of growing stevia (stevia rebaudiana) at jabal al-akhdar, sultanate of oman uses of stevia leaves since it is a natural sweetener, stevia has great potential of being used as sweetening agent in products like biscuits, jams, chocolates, ice-creams, baked foods, soft drinks, soda, candies and also common beverages like dip tea, coffee and herbal tea that are targeted particularly at the diabetics and also the health conscious consumers. the leaves can be used in chocolates and candies and does not encourage tooth decay (megeji et al., 2005) . market outlook stevia has a future potential for expansion. because stevia has generated considerable media attention and interest in recent years, producers could benefit from the growing consumer awareness of this crop. stevia may prove to be profitable for small-scale growers who are willing to develop or cultivate a market through local farmers markets, other direct markets, or for wholesale to smaller distributors (kerczicn et al., 1998). oman is ranked ninth among countries with the highest prevalence of diabetes in the world. as a result, people are becoming more aware of their health and sugar consumption is going down and is getting replaced by low calorie sweeteners (al-yaarubi, 2011). as indicated above, stevia is gaining more acceptance in many countries. some of these countries import stevia and many of them, particularly those having appropriate ecological conditions grow it. different parts of oman offer these favorable conditions at least in some parts of the year. the jabal al-akhdar (ja) is a mountainous agricultural area in the north of oman with elevation of 1079 m above sea level where temperatures are appropriate for stevia growth in summer since it was within its tolerant temperature range. some other areas in the north are close to sea level which could also have a potential of growing this herbal healthy sweetener in spring even as an intercrop between fruit trees like date palm, while in the south, which has monsoon season, it could be grown under any shaded area. the objective of this project was to assess the feasibility of growing stevia in the field in ja in summer. methodology climatological summary of the area since the objective of this project was to determine the feasibility of growing stevia plants in the field in ja, the preceded greenhouse period of two months after germination study could be considered as an integral part of the project since it laid down the basis of producing transplants for the three months field study that was appropriately timed to start in june 2012. the project was hosted on one of the terraces in a family farm in al-manakher, jabal al-akhdar. climatological summary of the area was obtained from the directorate general of meteorology and air navigation of the ministry of transport and communications to help estimate the three month period when stevia transplants could be planted in the field in al-manakher, ja within its tolerant temperature range (ttr) of 20°c-37°c. the climatological summary of 2011 obtained was from saiq weather station of the ministry but was used to estimate al-manakher’s climate because of its closeness to saiq. since the temperature range of an area for a given period of the year approximately repeats itself every year, the projected period selected for 2012 starting from early june to at least end of august was found to favorably fit stevia’s ttr. table 1. soil texture profile in the study area. terrace sand (%) silt (%) clay (%) texture upper 52.8 27.8.8 19.4.8 loam lower 52.6 30 17.4 loam table 2. soil ph and electric conductivity (ec) of the study area. terrace upper #1 upper #2 lower #1 lower #2 ec (ds m-1) 0.91 0.61 9.61 11.41 ph 8.50 8.54 7.89 7.85 figure 1. three of the stevia plants growing on a terrace at al-manakher in ja. the fine mesh net used to protect the plants from insect attack is visible in the background. 65research article al-rawahi, al-toobi, and al-balushi 25°c with ample light. it took 4 days for the seeds to germinate. they were irrigated initially with diluted hoagland nutrient solution for about one week and later at full strength until one month. this was then followed with npk compound fertilizer blended with trace elements in irrigation water. at 2-month age, the usual time for transplanting stevia plants in the field, the seedlings were transferred to temperature-controlled greenhouse at agricultural experiment station (aes) on squ campus where they were transplanted into larger pots. these plants could not have been grown in the field at aes or ja since the temperatures were outside the range of 2037°c. the plants were intended to remain in the greenhouse throughout their 5-month growth to maturity. throughout their growth in the greenhouse, temperature control was set between 24°c and 25°c. the second batch of seeds were germinated in greenhouse at aes early april 2012 for later transplanting in the field at al-manakher, ja in early june 2012. propagation of mature plants as transplants for ja by the end of may the plants originating from the first batch of seeds reached maturity and those that survived were three. they were propagated by cuttings to produce more stevia plants for transplanting on ja terrace in al-manakher. the idea of propagating more stevia plants by cuttings was tried and it produced favorable results. it involved dipping the cuttings into rooting hormone and planting them into a vermiculite-perlite mixture with potting soil in a closed glass box (1m x 1m x 1m) at 28°c and opened every 3-4 days for spraying some water. after four weeks the cuttings had very good root formation. the new plants were taken to al-manakher for transplanting on 24th june, 2012 on one of the terraces where transplanting stevia seedlings from seed took place on 2nd june, 2012 on the same terrace. as mentioned above, the size of the terrace was 4m by 2m. shading screen unlike in its country of origin, stevia cannot withstand direct sunlight in our region due to its higher solar intensity but does very well with ample diffused light both in greenhouse as well as in the field within its required temperature range of 20-37°c. the greenhouse at aes had automatically sufficient shading but the plants growing in the field at al-manakher needed 60% shading screen. plant protection precaution was taken at the very beginning to avoid stevia leaves from being subjected to pesticide spray since they are the overall yield component of the plant and consumed in raw. pesticide accumulation in the leaves could have a direct health risk. so, a mosquito net (fig. 1) was used to cover the plants from pest attack. as a matter of fact, small grasshoppers were noticed to have attacked some of the leaves a few days after transplanting at the terrace in al-manakher. immediate land preparation land was plowed initially with a disc plow or harrowed to break down the clods. one of the two terraces measuring 4m x 2m each was reserved to grow 12 plants with spacing of 60 cm between each plant. soil type the texture of soil samples from two terraces were determined using the hydrometer method and soil ph and electrical conductivity of the saturation extract were determined. table 1 shows that the texture of the upper and lower terraces are both loamy. this is the most moderate texture in terms of aeration and water-holding capacity. it is very suitable for stevia. table 2 shows that the salinity level of lower terrace had very high salinity level which is unsuitable for most crops while that of upper terrace had low salinity level that is suitable for most crops including stevia. irrigation system a drip irrigation system with timer was installed with two laterals each having six emitters spaced 60 cm apart as recommended for stevia spacing. so there were 12 emitters growing on the terrace. the timer was set to daily irrigate the plants morning and afternoon for a 15-minute duration each providing 2 liters of water per day. germinating stevia seeds according to ever stevia canada (esc) inc., the company from which the seeds were obtained, there are two conditions for favorable germination of stevia: (1) acidic ph (5.5-6.5) condition and (2) simultaneously a lot of aeration and high moisture availability for its root system. acidic ph of water was obtained by drop wise addition of concentrated nitric acid to water while shaking until the ph of around 6.0 was reached. there was no problem of incompatibility using nitric acid since it is a nitrate source which is a plant nutrient but at a very low concentration and for very short time i.e. until germination of stevia seeds took place. combination of high aeration and high moisture availability around the stevia root system was accomplished by using jiffy-7 (compacted peat moss) after its expansion following its water absorption from the water pool in the container, then grooving it in the middle to form a 2 cm top layer to accommodate sand and laying the seed on surface of sand and slightly compressed to have intimacy with the sand particles providing both good aeration as well as moisture from the surrounding jiffy-7. this way the seeds were simultaneously facilitated with plenty of aeration through sand particles and also through which plenty moisture flow from the surrounding high water holding capacity jiffy-7. the first batches of seeds were germinated at the end of january 2012 in air-conditioned room in cams at 66 squ journal of agricultural and marine sciences, 2017, volume 22, issue 1 feasibility of growing stevia (stevia rebaudiana) at jabal al-akhdar, sultanate of oman action was taken to make sure that the edges of the net was well laid down on the ground to avoid any entrance of pest into the sweet stevia leaves. removal of weeds was done manually. results and discussion taking stem growth measurements of stevia plants since the economical part of the plant are the leaves it is very important to achieve highest vegetative growth. the development of the plant was monitored by taking observations of the height of the plant and counting the number of leaves of different lengths each week. the leaves from 3 cm to 5 cm were considered as small leaves, from 5 cm to 7.5 cm medium leaves and 7.5 cm and higher as large leaves. the number of large and medium leaves impact on photosynthesis process contributes more to the plant growth. the small leaves contribute less to rate of growth. there were four subplots and each subplot contained three plants (see figures 2 and 3). the plants from subplots i and ii originated from seeds. the results show that stevia could grow and complete its growth to maturity in jabal akhdhar. the plants were harvested on 10 september 2012. conclusion oman has a potential for growing stevia except in summer as intercrop with date palms or other fruit trees. however, for ja, as mentioned above, stevia can be grown in summer when temperatures from june to september are more favorable and similar to where stevia initially originated. commercial production of stevia should be given consideration by the private sector in oman. acknowledgements the authors very much appreciate the awareness raised by dr. michel claereboudt about the importance of stevia as a natural non-diabetic sweetener and his encouragement to grow it in oman. efforts made by the departmental senior technician mr. hamed ali al-busaidi for installation of the irrigation system at the beginning of the project and removal of the system after project completion are also highly appreciated. references al-yaarubi s. 2011. diabetes care in oman: obstacles and solutions. squ medical journal 11(3): 343–348. brusick j. 2008. a critical review of the genetic toxicity of steviol and steviol glycosides. food chemistry and toxicology 46(7): 583-591. megeji nw, kumar jk, singh v, kaul vk and ahuja, p.s. 2005. introducing stevia rebaudiana. a natural zero-calorie sweeteners, current cell science. 88(5): 801-804. savita sm, sheela k, sunanda s, ramakrishna p. 2004. stevia rebaudiana – a functional component for food industry. journal of human ecology, 15(4): 261264. kerzicn, k.l., stendell n., mc muny and hagan, d. 1998. food characteristics of recipes using stevia sweetner a proposed herbal sugar substitute. journal of the americal dietetic association, 99: a29. tanaka t., zhang h., jiang z.h. and kouno, i. 1997. relationship between hydrophobicity and structure of hydrolysable tannins, and association of tannins with crude drug constituents in aqueous solution. chemical and pharmaceutical bulletin, 45: 1891-1897. p3 p5 p1 p2 p4 p6 0 50 100 5 10 time (weeks) le ng th (c m ) figure 2. plants from subplots i and ii that originated from seeds. there was a general trend of increased growth with time. plant 6 died after week 5. p11 p12 p7 p8 p10 0 30 60 90 2.5 5.0 7.5 time (weeks) le ng th (c m ) figure 3. plants form subplots iii and iv that resulted from propagation of mature stevia plant stems. there was general trend of increased growth with time except for plant 11 that died at second week. img032 img033 img034 img035 img157 img158 img159 img160 img161 img162 img163 img164 img042 img043 img044 img045 img046 img047 img048 img049 img099 img100 img101 img102 img103 img104 img105 img106 img107 img108 img109 img110 img023 img024 img025 img026 img027 research paper journal of agricultural and marine sciences vol. 24 : 24– 29 doi: 10.24200/jams.vol24iss1pp24-29 reveived 12 dec 2018 accepted 5 mar 2019 evaluation of energy use efficiency for greenhouse cucumber production in barka, oman *nawal khamis al-mezeini, abdulrahim m. al-ismaili, said m. tabook *nawal khamis al-mezeini ( ) nawal@squ.edu.om, department of soils, water and agricultural engineering, college of agricultural and marine sciences, sultan qaboos university, box 34, al-khod, 123. introduction greenhouses provide higher production and more efficient water consumption in compari-son to open-field cropping (abdel-rahman and abdel-magid 1993; maf 2009). as a result, the number of greenhouses in oman was increased 5 times between 2003-2015 (al-ismaili et al. 2017). cucumber (cucumis sativus l.) is the most commonly grown greenhouse vegetable worldwide (mohammadi and omid 2010; omid et al. 2011) and this is also the case in oman where more than 90% of greenhouses are used for cucumber cultivation (maf 2013). this could be attributed to its fast growth, and good nutritional and economic value (al-kiyoomi 2006; al-sadi et al. 2010). although greenhouses provide high yield, they also require high energy consumption to achieve this yield (bolandnazar et al. 2014; heidari and omid 2011). energy-use efficiency (eue) is considered one of the most important factors contributing to agricultural sustainability (firoozi et al. 2014). such energy analysis helps in managing greenhouse production system by identifying the wasteful energy parameters and proposing management approaches (bolandnazar et al. 2014). eue in greenhouse production has been used by many researchers to assess greenhouse cropping systems (hamedani et al. 2011; taki et al. 2013). for instance, mohammadi and omid (2010) investigated the eue of greenhouse cucumber production. results revealed that cucumber production consumed 148.836 gj ha-1 of the total energy input and diesel fuel was found to be the main energy consuming factor. in another study, heidari and omid (2011) investigated the eue (output-input ratio) for cucumber and tomato greenhouse production. results indicated that the eue was 1.48 and 0.69 for حتليل كفاءة إستخدام الطاقة إلنتاج حمصول اخليار يف بركاء، ُعمان نوال املزيين وعبدالرحيم اإلمساعيلي* وسعيد تبوك abstract. sustainable agricultural production can be assessed through energy-use efficiency (eue). this paper aims to evaluate the eue for cucumber greenhouse production in oman. data were obtained through face to face interview with farmers. results indicated that total energy inputs (e.g. electricity, water, fertilizers and chemicals) and total energy output (cucumber yield) were 1171.637 gj ha-1 and 89.943 gj ha-1, respectively. the highest energy input in the greenhouse production was electricity, consuming 88% of total energy input. electricity had the highest impact in cucumber greenhouse production and 99% of this electricity goes to cooling the greenhouse. when all energy inputs were classified into their different forms; direct (d) and indirect (id), and renewable (r) and non-renewable (nr), the highest portion of total energy forms in greenhouse cucumber production was for d and nr energy. the eue and energy productivity (ep) were found to be 0.08 and 0.10 ton gj-1, respectively. the energy use in greenhouse cucumber production was found to be inefficient and solar energy needs to be considered to improve the sustainable cucumber greenhouse production in oman. keywords: energy-use-efficiency; cucumber; greenhouse; energy productivity; energy forms. املســتخلص: ميكــن تقييــم اإلنتــاج املســتدام للزراعــات احملميــة مــن خــال حتليــل كفــاءة إســتخدام الطاقــة، هتــدف هــذه الدراســة إىل تقييــم كفــاءة إســتخدام الطاقــة يف البيــوت احملميــة املزروعــة مبحصــول اخليــار يف ســلطنة عمــان، مت احلصــول علــى البيانــات عــن طريــق إجــراء مقابــات مــع املزارعــن )وجهــا لوجــه(، وأوضحــت النتائــج إن الكميــة اإلمجاليــة للطاقــة املســتخدمة والناجتــة مــن البيــوت احملميــة وصلــت اىل 1171.637 و 89.943 )جيجاجول/هكتار(علــى التــوايل، وتعــد الكهربــاء أكــر مدخــات البيــوت احملميــة املســتهلكة للطاقــة حيــث يقــدر إســتهاكها للطاقــة مبعــدل %88 مــن إمجــايل الطاقــة املســتخدمة، لذلــك تعــد الكهربــاء أكــر العوامــل املســتهلكة للطاقــة وقــد وجــد أن معظــم الكهربــاء يتــم إســتهاكها يف تريــد البيــوت احملميــة، وعندمــا مت تقســيم الطاقــة إىل أنواعهــا األربعــة وهــي الطاقــة املباشــرة والغــر مباشــرة واملتجــددة والغــر متجــددة، وجــد أن الطاقــة املباشــرة والغــر متجــددة هــي أكــر أنــواع الطاقــة املســتخدمة يف البيــوت احملميــة، كمــا توصلــت النتائــج إىل أن كفــاءة اســتخدام الطاقــة وانتــاج الطاقــة مــن البيــوت احملميــة وصلــت الى0.08 و 0.01 )طــن/ جيجاجول(علــى التــوايل، ويف اخلتــام فــإن كفــاءة اســتخدام الطاقــة يف البيــوت احملميــة غــر فعالــة، ومــن أجــل حتقيــق اإلســتدامة يف الزراعــة احملميــة، فإنــه ينصــح بإســتخدام الطاقــة الشمســية إلنتــاج الطاقــة الــي حيتاجهــا البيــت احملمــي. الكلمات املفتاحية: كفاءة إستخدام الطاقة، اخليار، البيت احملمي، إنتاجية الطاقة، أنواع الطاقة. 25research article al-mezeini, al-ismaili, tabook tomato and cucumber, respectively which reflected an inefficient energy use in cucumber greenhouse production. diesel fuel was also the major contributing factors for both cucumber and tomato production (mohammadi and omid 2010). in strawberry greenhouses a total energy of 805.380 gj ha-1 were consumed (banaeian et al. 2011) and diesel fuel was the major energy depleting factor with 78% of the total energy. it appears thus that diesel fuel is the major variable influencing the eue of greenhouse production. in these studies, diesel fuel was mainly used to power heaters to provide temperature suitable growing environment. in oman, where weather conditions are generaly hot, heaters are not necessary but cooling systems (generally fan-pad evaporative cooling systems) are used instead. in such conditions, eue of cooled greenhouses needs to be evaluated. therefore, this study aimed to investigate the eue of evaporative-cooled greenhouse systems in oman using major energy performance indicators for instance eue, energy productivity (ep) and net energy (ne). table 1. the energy equivalents correspond to each inputs and output use in greenhouse cucumber production. inputs and output (unit) energy equivalent (mj unit-1) reference inputs: human labour (h) 1.96 (taki et al., 2013) machinery (h) 13.06 (mohammadi and omid 2010; ozkan et al. 2007) chemical fertilizers (kg): nitrogen (n) 66.14 (mohammadi and omid 2010; shrestha 1998) phosphate (p2o5) 12.44 (mohammadi and omid 2010; shrestha 1998) potassium (k2o) 11.15 (mohammadi and omid 2010; shrestha 1998) calcium 1.12 (mohammadi and omid 2010) micro 120.00 (banaeian et al. 2011; mohammadi et al. 2008) manure (kg) 0.3 (mohammadi and omid 2010) chemicals (kg) 120.00 (mohammadi and omid 2010) water (m3) 1.02 (mohammadi and omid 2010; mousavi-avval et al. 2011) electricity (kwh) 11.93 (hatirli et al. 2005; mousavi-avval et al. 2011) seeds (kg) 1.00 (mohammadi and omid 2010) outputs: cucumber (kg) 0.8 (mohammadi and omid 2010) table 2. the statistical summary of energy inputs (gj ha-1) and output (ton ha-1) for cucumber production. inputs (unit) mean sd min max a. inputs (gj ha-1) human labour 7.110 3.653 1.372 14.112 machinery 1.221 0.496 0.560 1.959 chemical fertilizers 62.582 55.535 18.793 180.802 manure 0.008 0.004 0.000 0.015 chemicals 5.775 3.370 1.714 10.971 water 6.323 2.499 2.463 9.748 electricity 1025.352 360.885 557.157 1550.185 seeds 0.001 0.000 0.001 0.001 b. output cucumber (ton ha-1) 98.937 28.321 58.583 149.349 26 squ journal of agricultural and marine sciences, 2019, volume 24, issue 1 evaluation of energy: use efficiency for greenhouse cucumber production in barka, oman materials and methods data were collected through a survey of 8 cucumber greenhouses farmers in barka region, sultanate of oman who agreed to participate in the survey. cucumber is the most cultivated crops in greenhouses. data were obtained through face to face interviews of the farmers which encompassed questions related to all expenses related to the greenhouses for three months (seeding-to-harvesting) during the cropping season (summer 2017). the greenhouses were quonset with polyethylene covering and fan-pad evaporative cooling system (fig. 1). all greenhouses were of similar type, covering material and cooling system. the standard dimensions of greenhouses were 0.035 ha. the average row and plant spacing were 133 cm and 50 cm, respectively. cucumber plants were trained to grow vertically in the greenhouse (fig. 2). the average ambient temperature was around 29°c during the study period. the 8 inputs considered in this study were human labor, machinery, chemical fertilizers chemicals, manure, electricity, water for irrigation and seeds and the single output was yield. the selection of the inputs was based similar studies from which we omitted diesel fuel which is not used in the greenhouses surveyed (mousavi-avval et al. ,2011; mohammadi and omid 2010 ; omid et al. 2011). for energy performance analysis, all inputs and output were converted into single energy unit, with conversion values obtained from different sources (table 1). eue, ep and ne were calculated using equations 1-3, respectively (mohammadi et al. 2008; ozkan et al. 2011). eue = energy output (gj ha-1)/energy input (gj ha-1) (eq. 1) ep = cucumber output (kg ha-1)/energy input (gj ha-1) (eq. 2) ne = energy output (gj ha-1)–energy input (gj ha-1) (eq. 3) in general, the energy inputs used in agricultural production systems are classified into direct (d) and indirect (id), and renewable (r) and non-renewable (nr) energies (mohammadi et al. 2010; mohammadi et al. 2008). the direct energy inputs involve human labour, water, and electricity, the indirect energy involves seeds, fertilizers, manures, chemicals, and machinery, the renewable energy inputs includes human labour, seeds, manure and water and the non-renewable energy accounts for chemicals, fertilizers, machinery and electricity. results and discussion the descriptive summary of inputs used for cucumber production and output are presented in table 2. there table 3. amount of inputs and output in cucumber production. inputs (unit) quantity per unit area (ha) total energy equivalent (gj ha-1) percentage (%) of total energy sd* a. inputs human labour (h) 3627.454 7.110 0.607 3.653 machinery (h) 93.464 1.221 0.104 0.496 chemical fertilizers (kg): 2035.497 59.847 5.108 38.179 nitrogen 609.533 40.315 3.441 phosphate (p2o5) 610.364 7.593 0.648 potassium (k2o) 752.171 8.387 0.716 calcium 34.143 0.038 0.003 micro 29.286 3.514 0.300 manure (kg) 20535.714 6.161 0.526 3.239 chemicals (kg) 48.129 5.775 0.493 3.370 water (m3) 6199.506 6.323 0.540 2.499 electricity (kwh) 85947.357 1025.352 87.514 360.885 seeds (kg) 0.857 0.001 0.000 total energy input (gj ha-1) 1171.637 100.000 b. output cucumber (ton ha-1) 112.429 89.943 100.000 32.180 total energy output (gj ha-1) 89.943 * represents the standard deviation of energy inputs (gj ha-1) and energy output (ton ha-1) 27research article al-mezeini, al-ismaili, tabook were variations among inputs and output which implied that there was a potential efficiency improvement for cucumber greenhouse farmers. thus, eue of greenhouses was evaluated hereafter. the inputs with their equivalent energy values consumed in cucumber production for the studied greenhouses are illustrated in table 3. average yield was 112.428 ton ha-1 which is equivalent to a total energy output of 89.943 gj ha-1. results also revealed that 1171.637 gj ha-1 of total energy input were needed in the production of cucumber crop. electricity, chemicals and chemical fertilizers were calculated as 1025.352, 5.775 and 59.847 gj ha-1, respectively. among all energy inputs, electricity was the highest energy consuming factor with a total of 88% (fig. 3). this high electricity consumption was further analyzed and the analysis revealed that most of this electricity was consumed by the cooling system (fig. 3) as the temperature sometimes exceeds 50°c (al-ajmi and abdel-rahman 2001; al-sadi et al. 2011). to limit this use of non-renewable energy, it is recommended to investigate the use of alternative power sources such as solar energy to operate the cooling system (fans and pumps). the euf, ep and ne of cucumber production were 0.08, 0.10 tons gj-1 and -1081 gj ha-1 respectively (table 5). in the literature, the eue for greenhouse cucumber production was considered inefficient when it equals to 0.017 (zarini et al. 2013) or even as high as 0.64 (mohammadi and omid 2010). therefore, the eue of the surveyed greenhouses in this study was (0.08) should also be considered inefficient. this eue in cucumber greenhouse production could be increased by either increasing crop yield or by decreasing inputs consumption. the average ep (0.10 ton gj-1) for greenhouse cucumber production was lower than the reported values of 0.80 (mohammadi and omid 2010), 0.55 (heidari and omid 2011) and 0.50 (omid et al. 2011). this indicates that every kilogram of cucumber in the surveyed greenhouses in oman consumed 5-8 times more input energy than the greenhouses cited above. the high negative value of ne (-1081.690 gj ha-1) indicates that energy being lost in cucumber production. this can be attributed to the high electricity consumption consumed by the cooling systems. in iran, omid et al. (2011) and (bolandnazar et al. 2014) found that the ne for greenhouse cucumber production gave also negative values (-55.553 and -149.317 gj ha-1, respectively) due to the high fuel consumption for heating (more than 50% of the total inputs energy). since, energy consumption for temperature adjustment (heating or cooling system) is the highest among all inputs in greenhouse cucumber table 4. energy forms (d, id, r and nr) in cucumber production in oman. form of energy energy value (gj ha-1) % of total energy input d a 1038.785 88.66 idb 73.005 6.23 r c 19.595 3.32 nrd 1092.20 93.219 total energy input 1171.637 100.00 a -involves human labour, water, electricity. b -involves seeds, fertilizer, manure, chemicals, machinery. c -involves human labour, seeds, manure, water. d -involves chemicals, fertilizer, machinery, electricity. table 5. energy use efficiency in cucumber production in oman. items unit value sd e input gj ha -1 1171.64 374.58 e output gj ha -1 89.94 25.75 yield ton ha-1 112.43 32.18 eue unitless 0.08 0.03 ep ton gj-1 0.10 0.04 ne gj ha-1 -1081.69 361.78 figure 1. quonset greenhouse with polyethylene covering and (a) fan-(b) pad evaporative cooling figure 2. the greenhouse vertical cultivation 28 squ journal of agricultural and marine sciences, 2019, volume 24, issue 1 evaluation of energy: use efficiency for greenhouse cucumber production in barka, oman production; the existing heating/cooling systems need improvement in order to achieve a more efficient energy use and sustainable crop production. the percentage of total energy inputs as d, id, r and nr energy is shown in table 4. it was found that the d energy inputs (e.g. human labour, water, electricity) followed by nr energy inputs (e.g. chemicals, fertilizer, machinery, electricity) were the highest energy consumers and the r energy forms (e.g. human labour, seeds, manure, water) were the lowest energy consumers. other investigators, such as, ozkan et al. (2007), kizilaslan (2009), mohammadi and omid (2010), banaeian et al. (2011) and zarini et al. (2013) reported similar outcomes. the tetra-inoculum (tm+tc+gr+gn) reported highest average of dry weight of plants which was 710 mg/ plant compared with negative and positive control which was 86 and 479 mg/plant respectively, followed by the treatment of tri-inoculum (tc+gr+gn) which was 602 mg/plant. the combined application of gr+gn exhibited significant increase in the dry weight of plant which was 559 mg/plant. tariq and magee (1990) found that volatile components of garlic extracts inhibited germination of the microconidia, macroconidia and mycelium of the f. oxysporum f. sp. lycopersici in vitro. al-rahmah et al. (2013) has been found that ginger extracts has strong fungistatic and fungicidal activities against f. oxysporum and pythium aphanidermatum with minimal inhibitory concentration. furthermore, sahar et al. (2013) proved that foliar application of topsin-m with concentration of 0.1 % was significantly reduced the disease incidence of fusarium wilt disease on eggplant. conclusion this study investigates the eue of greenhouse cucumber production. results revealed that the total energy output for greenhouse cucumber production was 12 times lower than the total energy inputs. the eue in greenhouse cucumber production was inefficient and electricity was the major energy consuming factor. fan-pad evaporative cooling system was the major consumer of the electricity and thus the existing cooling systems need be improved to achieve better efficient energy. highest energy form in greenhouse cucumber production was the nr energy. special attention has to be given to this form of energy in order to achieve sustainable cucumber production. solar energy needs to be exploited to improve the sustainable cucumber greenhouse production in oman. references abdel-rahman ha, abdel-magid im. 1993. water conservation in oman. water international. 18(2): 95102. al-ajmi h, abdel-rahman ha. 2001. water management intricacies in the sultanate of oman. the augmentation–conservation conundrum. water international. 26(1): 68-79. al-ismaili am, al-mezeini n, jayasuriya h. 2017. controlled environment agriculture in oman: facts and mechanization potentials. agricultural mechanization in asia, africa, and latin america. 48(2): 45-51. al-kiyoomi ks. 2006. greenhouse cucumber production systems in oman: a study on the effect of cultivation practices on crop diseases and crop yields [phd]. 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journal of agriculture and crop sciences. 5(13): 1437. research article journal of agricultural and marine sciences 2021, 26(2): 51–55 doi: 10.24200/jams.vol26iss2pp51-55 reveived 24 july 2020 accepted 17 dec 2020 seroprevalence of trypanosoma evansi infections among dromedary camels (camelus dromedaries) in north ash-sharqiya governorate, sultanate of oman a. h. al-kharusi1, elshafie i. elshafie2,5*, k. e. m. ali4, r. al-sinadi1, n. baniuraba3, f. al-saifi1 and y. al-mawali1 elshafie i. elshafie2,5*( ) eielshafie@squ.edu.om, 1ministry of agriculture, fisheries wealth and water resources, sultanate of oman, 2department of animal and veterinary sciences, college of agricultural and marine sciences, sultan qaboos university, muscat pc. 123, sultanate of oman, 3nizwa university, sultanate of oman, 4veterinary pharmacy, abu yahya alabrawi trad, sultanate of oman, 5central veterinary research laboratory, al amarat, p.o. box 8076, khartoum, sudan. introduction parasite remains a major constraint for optimum animal production throughout the world. try-panosoma evansi, which belongs to the genus trypanosoma, subgenus trypanozoon is a blood parasite that infects domestic livestock and wild animals; and caused disease called surra (bargash et al., 2014). the parasite has a wide geographical distribution in many االنتشار املصلي لعدوى امِلثـَْقِبيَّة اإليفانسيَّة بني اإلبل وحيدة السنام يف حمافظة مشال الشرقية، سلطنة عمان أمل محد اخلروصية، الشفيع ابراهيم الشفيع، كمال على، راشد السنيدي، اندية بين عرابة، فاطمة السيفية، حيىي املعويل abstract. trypanosoma evansi is a well-known hemoprotozoa that infects diverse domestic and wild animals worldwide and causes a devastating disease called surra. this research aimed to investigate seroprevalence of trypanosoma evansi and its associated risk factors in dromedary camels in north ash-sharqiya governorate, sultanate of oman. a total of 4364 serum samples was collected from three willayat in north ash-sharqiya governorate of sultanate of oman; ibra (926, 21.2%), qabil (1119, 25.6%) and bidiyah (2319, 53.1%). samples were examined for the presence of antibodies against t. evansi using card agglutination test for t. evansi (catt/t. evansi). binary logistic regression was used to study the association of t. evansi seroprevalence and risk factors such as location, gender, purpose and age of camels. the overall seroprevalence of t. evansi detected by catt/t. evansi test was 38% (1659/4364, ci: 36.6-39.5%). there was a significant difference (p=0.001) between location and t. evansi seroprevalence, whereas the highest seroprevalence was found in ibra (49.9%, ci: 46.7-53.1%) followed by bidiyah (35%, ci: 33-36.9%) and qabil (34.5%, ci: 31.8-37%). camels from ibra were almost two times more likely to have circulating antibodies of t. evansi than camels from bidiyah (or=1.89, ci: 1.591-2.168). the results of this study showed a significant difference between seroprevalence and sex (p=0.023), whereas the age of camels did not show any significant difference (p>0.05). to our knowledge, this is the initial research that indicated that t. evansi antibodies were circulating among camels in oman, and further research needs to be tackled to study the molecular characterization of t. evansi and its prevalence in other animal species. furthermore, cross-sectional studies of t. evansi from different regions in oman warrant further investigation. keywords: camels, t. evansi, catt, seroprevalence, oman امللخص:املِثـَْقِبيَّــة اإليفانســيَّة هــو نــوع معــروف مــن األوليــات وحيــدة اخلليــة يصيــب احليــواانت األليفــة والربيــة املتنوعــة يف مجيــع أحنــاء العــامل ويســبب وحيــدة اإلبــل يف هبــا املرتبطــة اخلطــر وعوامــل اإليفانســيَّة للمثقبيــات املصلــي االنتشــار دراســة إىل البحــث هــذا يهــدف الزنبــور. يســمى مرًضــا الســنام مبحافظــة مشــال الشــرقية، ســلطنة عمــان. مت مجــع 4364 عينــة مــن مصــل الــدم مــن ثــاث والايت يف حمافظــة مشــال الشــرقية ســلطنة عمــان. إبــراء )926، ٪21.2(، القابــل )1119، ٪25.6(، بديــة )2319، ٪53.1( مت فحــص وجــود األجســام املضــادة ضــد املِثـَْقِبيَّــة اإليفانســيَّة ابســتخدام اختبــار تــراص البطاقــة للِمثـَْقِبيَّــة اإليفانســيَّة )catt(. مت اســتخدام االحنــدار اللوجســي الثنائــي لدراســة االرتبــاط بــن االنتشــار املصلــي للِمثـَْقِبيَّــة اإليفانســيَّة وعوامــل اخلطــر مثــل املوقــع واجلنــس والغــرض والعمــر لإلبــل. كان االنتشــار املصلــي الكلــي للِمثـَْقِبيَّــة اإليفانســيَّة املكتشــف بواســطة اختبــار تــراص البطاقــة للِمثـَْقِبيَّــة اإليفانســيَّة )catt( 38% (1659/4364, ci: 36.6-39.5%(. كان هنــاك فــرق إحصائــي )p = 0.001( بــن املوقــع واالنتشــار املصلــي )ci: 33-36.9٪ ،35٪( تليهــا بديــة )ci: 46.7-53.1٪ ،49.9٪( للِمثـَْقِبيَّــة اإليفانســيَّة، حيــث مت العثــور علــى أعلــى معــدل انتشــار مصلــي يف إبــراء والقابــل )ci: 31.8-37٪ ،34.5٪(. كانــت اإلبــل مــن إبــراء أكثــر عرضــة مبرتــن لوجــود األجســام املضــادة املنتشــرة مــن املِثـَْقِبيَّــة اإليفانســيَّة مقارنــة جبمــال بديــة )or = 1.89، ci: 1.591-2.168(. أظهــرت النتائــج يف هــذه الدراســة فرقــاً احصائيــا بــن االنتشــار املصلــي واجلنــس )p = 0.023(، بينمــا مل يظهــر عمــر اإلبــل أي فــرق إحصائــي )p> 0.05(. علــى حــد علمنــا، هــذا هــو البحــث األويل الــذي أشــار إىل أن األجســام املضــادة للِمثـَْقِبيَّــة اإليفانســيَّة توجــد بــن اإلبــل يف عمــان، وهنــاك احلاجــة إىل املزيــد مــن البحــث لدراســة خصائــص املِثـَْقِبيَّــة اإليفانســيَّة وانتشــارها يف أنــواع احليــواانت األخــرى، عــاوة علــى ذلــك، يتطلــب مزيــدا مــن البحــث والدراســات للِمثـَْقِبيَّــة اإليفانســيَّة يف مناطــق خمتلفــة مــن عمــان. الكلمات املفتاحية: اإلبل، املِثـَْقِبيَّة اإليفانسيَّة، اختبار تراص البطاقة، االنتشار املصلي، سلطنة عمان 52 squ journal of agricultural and marine sciences, 2021, volume 26, issue 2 seroprevalence of trypanosoma evansi infections among dromedary camels (camelus dromedaries) in north ash-sharqiya governorate, sultanate of oman tropical and subtropical countries due to the adaptation of mechanical transmission by different types of hematophagous flies, such as tabanus, stomoxys, lyperosia and haematobia species (desquenes et al., 2013). the disease was reported in camels from different regions of the kingdom of saudi arabia (altaqi et al., 2011; amoudi et al., 2011; el-wathiq et al., 2016), in kuwait (al-taqi, 1989) and united arab emirates (chaudhary and iqbal, 2000). camels along with horses and dogs are considered the principal hosts to the parasite and this may show symptoms, such as fever, anorexia, and edema (abdel-rady, 2008). the disease has a significant impact on animal’s health, production and efficiency and can result in death of animals if no timely treatment is offered. some biochemical changes have been documented in camels related to trypanosoma infection in dromedary camels. (sazmand et al., 2011). the disease causes infertility in the dromedary camels by changing plasma steroids concentration and semen characteristics (al-qarawi et al., 2004). the disease can be diagnosed by parasitological methods, such as microhematocrit centrifugation technique and microscopic examination of thin blood smears (babeker and hassab, 2014; bennoune et al., 2013; bogale et al., 2012; hagos, 2009) and serological methods such as elisa and card agglutination test for t. evansi (catt/t. evansi) (babeker et al., 2014; zayed et al., 2010; hagos, 2009). the introduction of molecular diagnosis enhanced the accuracy of t. evansi detection due to the dynamics of parasitaemia (baraghash et al., 2014; tehseen et al., 2015). the card agglutination test was more common to be used for screening a large numbers of animals under field conditions (uilenberg, 1998). on the other hand, the catt test can render false positive results due to the circulation of antibodies. the estimated number of camels in the sultanate of oman is 242833 heads (agriculture censuses, 2013). the highest density of the camel population in oman is located in the dhofar governorates, as most people use camels for milk and meat production. the second highest density of camels is in ash-sharqiya north governorate with a total of 21577 camels and mostly are raced camels. since the first detection of the parasite in 1984 (srivastava,1984) and the continuing reports of the disease from the ministry of agriculture, fisheries wealth and water resources, trypanosoma evansi was wandering in the country and negligible cohort study has been done to identify the frequency and risk factors of the disease in livestock. due to lack of work on seroprevalence of trypanosoma among camel population in oman, the present study was planned to determine the seroprevalence and risk factors of t. evansi in omani camels in north ash-sharqiya governorate using serological techniques. materials and methods study area and sampling collection this study was conducted in three willayat in north ash-sharqiyah (ibra, qabil and bidiyah). a total of 4364 camel blood samples were collected between july 2014 and november 2015 from ibra (283 farms), qabil (260 farms) and bidiyah (394 farms). ten millilitres of blood was collected from jugular vein of each camel in a plain tube and transported in a cool box to the lab for screening t. evansi using card agglutinin test (catt/ t. evansi). information on location, sex, age and camel purpose were collected during blood sample collection. in this study, camels were divided into three groups according to age (<5, 5-10 and >10 years old). diagnosis of serum by serological examination card agglutination test for t. evansi kit (catt/ t. evansi) was used to detected anti-trypanosome antibodies in serum of infected animal by direct agglutination method according to the manufacturer’s instructions (institute of tropical medicine, antwerp, belgium). the antigen contains fixed, freeze-dried and stained bloodstream from trypanosomes type rotat 1.2, a predominant variable antigen type of trypanosome evansi expressed during the early course of infection (bajyana-songa and hamers, 1988). about 2.5 ml of catt/t. evansi buffer was added to a vial of freeze dried catt/ t. evansi antigen and shake the vial immediately for a few seconds to obtain homogeneous suspension. then 0.5 ml of catt/t. evansi buffer was added to a positive and negative control. on the test area of the card, one drop (45 μl) of the homogenized catt/t. evansi antigen was added in each test area and 25 μl of the serum diluted at 1:4 with pbs ph 7.2 according to the manufacturer’s instructions was then added. the reaction was mixed using a stirring rod and the test card was rotated for 5 minutes for subsequent reading of the results. statistical analysis the statistical analysis was conducted using spss version 20 (ibm, spss) at a = 0.05 significance level. seroprevalence and associated risk factors were conducted at 95% confidence level. univariate analysis for individual risk factors to identify association between the seroprevalence and the potential risk factors were tested using pearson chi-square or fisher exact test. a binary logistic regression was used to examine the significance that revealed by the univariate analysis and to determine odds ratio. results and discussion out of 4364 blood samples examined using catt/t. evansi, 1659 (38%, ci: 36.6-39.5%) were found to be seropositive for t. evansi (table 1). the frequency of infection was high in ibra 49.9% (462/926, ci: 46.7-53.1%) 53research article al-kharusi, elshafie, ali, sinadi, baniuraba, al-saifi, al-mawali followed by bidiyah 35% (811/2319, ci: 33-36.9%) and qabil 34.5% (386/1119, ci: 31.8-37%). there was significant difference between disease seroprevalence and location (x2 =70.43, p=0.001) (table 2). based on logistic regression, camels that sampled from ibra region were 1.89 times more likely to have circulating antibodies against t. evansi than camels sampled from bidiyah region (or=1.89, 95%ci: 1.591-2.168). the results showed a significant difference between seroprevalence and sex (p=0.023). the female had highest infection rate 38.7% (1435/3706) than male 34% (224/658). the female seropositive camels were about 1.2 times more likely than male camels. moreover, there was no significant association between diseases seroprevalence and the purpose (p=0.053). despite the non-significance difference, camels used for production 38.6% (1488/3858) had a higher rate of being seropositive than racing camels 34.1% (168/493). on the other hand, there was no statistical significant difference between diseases seroprevalence and the age (p>0.05) (table 1). to our knowledge, this is the initial study that provides information about the seroprevalence of t. evansi infections in three regions in oman using serological test (catt/t. evansi). the results showed significant difference between diseases seroprevalence and camel sex and sample location. on the other hand, there is no significant difference between the diseases seroprevalence with camel age and purpose of camels. the overall seroprevalence of t. evansi infections was found to be 38%. our finding is relatively lower than the results reported in saudi arabia with a seroprevalence of 39.4% by card agglutination test with considerable differences between eastern and central regions (al-afaleq et al., 2015). the seroprevalence of this study was higher than other studies done in ethiopia by bogale et al. (2012), birhanu et al. (2015), hagos et al. (2009), and in somalia by mohamoud (2017), who reported a prevalence of t. evansi in camels 18.22%, 13.76%, 24.88%, 15.9% respectively. however, our results of t. evansi seroprevalence was relatively lower than that reported in sudan and egypt as estimated to be 52.2% and 43.5% respectively (babeker and hassab elrasoul, 2014; abdel-rady 2008). since catt/t. evansi cannot differentiate between current and past infections, the higher seroprevalence of t. evansi revealed by this research may be attributed either to genetic variation of camels breeds existed in same farms or weak farm management programs adopted by camel’s owner as the causative agent was reported in the country without comprehensive study to reveal its distribution. trypanosoma evansi seroprevalence was higher in ibra (49.9%) than qabil and bidiyah, this might be due to environmental factors as ibra is a mountainous area and had wetland that may enhance the propagation of the parasite vectors, whereas qabil and bidiyah are sand areas with significantly less vector density. in the present study, a significant difference was reported in camel sex, the highest seroprevalence of trypanosoma evansi was observed in female 38.7% followed by male 34%. this result in accordance with that found by babeker and hassab elrasoul (2014) and mohamoud (2017). however, our results are not in line with study done by bogale et al. (2012) which showed that a higher infection rates in males (20.25%) compared to female (17.72%) with approximately similar prevalence rates among both sexes. study conducted by bhutto et table 1. : association of location, age and sex with seroprevalence of trypanosoma evansi using card agglutination test (catt/ t. evansi). risk factors no. catt/ t. evansi chi-square p-value positive (%) negative (%) location ibra qabil bidiyah 926 1119 2319 462 (49.9) 386 (34.5) 811 (35) 464 (50.1) 733 (65.5) 1508 (65) 70.43 0.001* age (years) <5 5-10 >10 1555 2152 649 608 (39.1) 811 (37.7) 237 (36.5) 947 (60.9) 1341 (62.3) 412 (63.5) 1.49 0.47 sex male female 658 3706 224 (34) 1435 (38.7) 434 (66) 2271 (61.3) 5.19 0.023* purpose race production 493 3858 168 (34.1) 1488 (38.6) 325 (65.9) 2370 (61.4) 3.74 0.053 *significant association (p<0.05) 54 squ journal of agricultural and marine sciences, 2021, volume 26, issue 2 seroprevalence of trypanosoma evansi infections among dromedary camels (camelus dromedaries) in north ash-sharqiya governorate, sultanate of oman al. (2010) indicated that females were more susceptible to the infection with trypanosoma species as host immunity decreased during pregnancy and lactation period. despite the non-significant result of the age, we observed an increase in t. evansi seroprevalence in younger camels with age less than five years (39.1%) as compared to camels with age between five and ten years (37.7%). this study disagreed with previous studies, which found that adult camels were more susceptible to have the diseases than younger camels (mohamoud, 2017; atarhouch et al., 2003). detection of antibodies against t. evansi in the host does not necessarily indicate a current infection since antibodies can persist for 2.3–22.6 months after trypanocidal treatment (monzón et al., 2003). therefore, younger camels of age less than five years have a higher chance of encountered antibodies against t. evansi in their blood compare to the elder one. in addition, younger camels are used to transport to different places in country for racing purposes and exposing these animals to infections. camels used in production showed higher percentage of t. evansi seroprevalence than camels using for race 34.1% and 38.6%, respectively. this might be because camel’s keepers care more about racing camels and keep them in open area for grazing, provide them with sufficient complementary diet and treat them against parasites whereas, camels that used for production get less care from camel owner. this could also be due to disparity in management, veterinary care, and parasite control offered to race camels compared to production animals. conclusion to our knowledge, this research was the initial report on t. evansi infections in oman by using card agglutination test (catt/t. evansi). the results showed that the t. evansi was circulating in camels within the investigated areas and certain potential risk factors may be associated with the spreading of the disease in the country. the disease might cause great economic losses due to impairment of camel’s health, which leads to decrease in production and performance. this study was done in north ash-sharqiya governorate of sultanate of oman, so further studies are highly needed to investigate the prevalence of the diseases in different parts of oman in different livestock using different diagnostic techniques. acknowledgement we would like to thank the agriculture development fund for supporting the project and all staff of general directorate of agriculture and animal wealth of north and south al-sharqiya governorate for their collaboration in samples collection. conflict of interest the authors declare that they have no conflict of interest. references abdel-rady a. 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(2018). manual of diagnostic tests and vaccines for terrestrial animal. chapter, 3.4.16, world organization for animal health, paris, p. 1222-123. sazmand a, rasooli a, nouri m, hamidinejat h, hekmatimoghaddam s. (2011). serobiochemical alterations in subclinically affected dromedary camels with trypanosoma evansi in iran. pakistan veterinary journal 31(3): 223-226. srivastava vk, obeid hm, elbosadi sm. (1984). trypanosomiasis in camels in the sultanate of oman. tropical animal health and production 16: 1-7 (article 148). uilenberg g. (1998). a field guide for the diagnosis, treatment and prevention of african animal trypanosomosis, food and agriculture organization of the united nations. rome, italy. zayed aa, habeeb sm, allam nat, ashry hmz, mohamed ahh, ashour aa, taha ha. (2010). a critical comparative study of parasitological and serological differential diagnostic methods of trypanosoma evansi infections in some farm animals in egypt, american-eurasian. journal of agricultural and environmental sciences 8(6): 633-642. research paper journal of agricultural and marine sciences vol. 23 : 40– 47 doi: 10.24200/jams.vol23iss1pp40-47 reveived 01 feb 2018 accepted 17 sep 2018 integrated management of the fusarium vascular wilt disease of cucurbita pepo in iraq *safaa n. hussein *safaa n. hussein ( ) safaahussein1979@uomustansiriyah.edu.iq environmental engineering department, faculty of engineering, university of mustansiriyah, iraq introduction zucchini (cucurbita pepo l. var. giromontina) of the family cucurbitaceae is an important vegeta-tive crop in iraq and worldwide (hassan, 1991), the total cultivated area in iraq was 39836 ha with production of 167576 tons (css, 2012). this crop infected by many harmful plant pathogens and the fungus fusarium oxysporum, the causal agent of the fusarium wilt disease is one of them. serious economic losses were observed last decade in the zucchini production area due to this pathogen. in poland, this pathogen was observed for the first time in 2008 in the tunnel and field cultivation of infected zucchini fields (jamiołkowska et al., 2011). in south korea, the pathogen was isolated for the first time from infected zucchini plants in 2013 (choi et al., 2015). symptoms appears as stunning, wilting of the foliage system, drying older leaves, brown discoloration in the vascular system of the plant and eventually plant death especially during the period of flowering and fruit setting (lee and park, 2001). fusarium wilt disease controlled usually through crop rotation, soil fumigation or solarization, using resistance cultivars, biological control and grafting on the rootstocks of resistant host, but eventually this pathogen is not easy to control using single method of plant protection (agel and martyn, 2013). application of chemical fungicides is the fastest effective means of disease control (nicholson, 2007), some systematic fungicide such as benomyl, carbendazim and thiophanate methyl proved positive efficiency against broad range of the soilborne pathogenic fungi including fusarium spp. (rajput at al., 2006; amini and sidovich, 2010). botanicals (natural plant extracts) used more recently as eco-friendly means of plant disease control alternative to the chemicals, natural extraction of some plant species such as neem (azadirachta indica), ginger (zingiber officinale) and garlic (allium sativum) fungicidal activity against number of the plant pathogens including species belonging to the األدارة املتكاملة ملرض الذبول الوعائي الفيوزارمي يف cucurbita pepo يف العراق صفاء نعمت حسني* abstract. fusarium vascular wilt disease is one of the most harmful diseases that affect a broad range of plant species including zucchini (cucurbita pepo). the objective of the research was to investigate the presence of the phytopathogenic fungus fusarium oxysporum the causal agent of the disease in zucchini fields. forty five isolates of f. oxysporum were isolated from four locations in province of dyala during 2014-2015. isolate foq9 was the most virulent in the in vitro pathogenicity test. in vitro significant suppression efficiency were observed of the fungicides topsin m 70 wp (tm) and tecto 500 sc (tc) and two botanical extract solution extracted from garlic (gr) and ginger (gn) against the pathogen on the potato sucrose agar (psa). in greenhouse experiments all of the agents decreased the percentage of disease incidence and severity significantly, while the tetra-inoculum (tm+tc+gr+gn) was superior which exhibited 0% disease incidence and severity compared to the negative control which was 95% and 79% respectively. also the combined application of the botanical extracts (gr+gn) reduced disease incidence and severity significantly. all of the treatment increased plant growth criteria represented by dry weight of the plant compared to the control. keywords: fusarium oxysporum; garlic extract; ginger extract; pcr; tecto; topsen m. cucurbita pepo املســتخلص: يعــد مــرض الذبــول الوعائــي الفيوزارمــي احــد اهــم االمــراض الضــارة الــي تصيــب طيــف واســع مــن النباتــات ومنهــا القــرع f. املســبب للمــرض يف حقــول القــرع. مت عــزل 45 عزلــة مــن الفطــر fusarium oxysporum هــدف البحــث للتحــري عــن وجــود الفطــر املمــرض . foq9 مــن 4 مناطــق خمتلفــة يف حمافظــة ديــاىل خــال الفــرة 2014-2015. مت اختبــار امراضيــة العــزالت الفطريــة خمتربيــاً وكانــت العزلــة oxysporum األكثــر امراضيــة. واظهــرت نتائــج التشــخيص اجلزيئــي ان 29 عزلــة مــن العــزالت الفطريــة تعــود للفطــر fusarium spp. . خمتربيــاً حققــت معامــات املبيــد الفطــري الكيميائــي wp (tm 70 topsin m( واملبيــد tc 500 tecto) sc( و حماليــل املســتخلصات النباتيــة الطبيعيــة املســتخلصة مــن الثــوم )gr( والزجنبيــل )gn( زيــادة معنويــة يف معــدل تثبيــط الفطــر املمــرض علــى الوســط الزرعــي أكاروز البطاطــا )psa(. وحتــت ظــروف البيــت الزجاجــي حققــت مجيــع العوامــل املســتخدمة خفضــاً معنويــاً يف النســبة املئويــة للمــرض وشــدته، وقــد تفوقــت معاملــة اللقــاح الرباعــي )tm+tc+gr+gn( علــى باقــي املعامــات إذ بلغــت نســبة املــرض وشــدته يف معاملتهــا 0% قياســاُ اىل معاملــة املقارنــة الــي بلغــت 95% و 79% علــى التتابــع ، كمــا حققــت معاملــة تداخــل املســتخلصات النباتيــة )gr+gn( خفضــاً معنويــاً يف نســبة املــرض وشــدته. كمــا ان مجيــع املعامــات حققــت زيــادة معنويــة يف معايــر منــو النباتــات متمثلــًة بالــوزن اجلــاف للنبــات قياســاً اىل معاملــة املقارنــة. الكلمات املفتاحية: تفاعات البلمرة املتسلسلة، فيوزاريوم اوكسيسبوريوم، مبيد توبسن م، مبيد تيكتو، مستخلص الثوم، مستخلص الزجنبيل. 41research article hussein bacteria and fungi through direct inhibition activity or via enhancing plant growth and plant resistance (sanjay and tiku, 2009; al.samarrai at al., 2012). integrated management of the plant diseases demonstrated high efficiency in controlling several plant pathogens globally, throughout using multiple strategies and tactics to maintain the pathogen under the economic injury (el khoury and makkouk, 2010). this study aimed to estimate the disease control ability of the both fungicides topsin m 70 wp and tecto 500 sc and two botanical extracts solutions were garlic (a. sativum.) and ginger (zingiber officinale) each agent individually and in combination against f. oxysporum in vitro and under greenhouse conditions. materials and methods isolation and identification of the pathogen thirty six samples were collected from different symp-tomatic zucchini plants. samples were taken from four areas in the iraqi province of diyala (north east of the capital baghdad) during the growing season in 20142015. segments (0.5 cm) from the root and stem of the samples were washed under running tap water for 25 min and surface disinfected with 0.5% sodium hypochloride solution for 3 min. four segments were then placed in petri dishes (9 cm) containing sterilized psa mixed with 200 mg\l of the antibiotic (amoxicillin) and incubated at 25 °c for 7 days. each fungal growth around the segments were transferred individually on the separate psa plate and incubated for 7 days, each isolate purified using single spore method as described in hussein (2014). isolates were identified morphologically based on the cultural characteristics of colony, diameter, table 1. pathogenicity effect of fusarium spp. isolates to zucchini seeds location isolate germination (%) location isolate germination (%) control 100.0 muqdadia fom10 35.0 khalis fok1 60.0 muqdadia fom11 42.5 khalis fok2 22.5 muqdadia fom12 60.0 khalis fok3 40.0 khanaqin foq1 22.5 khalis fok4 37.5 khanaqin foq2 17.5 khalis fok5 42.5 khanaqin foq3 15.0 khalis fok6 65.0 khanaqin foq4 42.5 khalis fok7 22.5 khanaqin foq5 45.0 khalis fok8 20.0 khanaqin foq6 47.5 khalis fok9 47.5 khanaqin foq7 35.0 khalis fok10 65.0 khanaqin foq8 32.5 khalis fok11 27.5 khanaqin foq9 5.0 khalis fok12 22.5 khanaqin foq10 25.0 khalis fok13 40.0 khanaqin foq11 52.5 muqdadia fom1 57.5 khanaqin foq12 47.5 muqdadia fom2 40.0 khanaqin foq13 60.0 muqdadia fom3 40.0 khanaqin foq14 42.5 muqdadia fom4 15.0 khanaqin foq15 22.5 muqdadia fom5 32.5 khanaqin fos1 40.0 muqdadia fom6 20.0 mindly fod2 30.0 muqdadia fom7 30.0 mindly fod3 30.0 muqdadia fom8 35.0 mindly fod4 47.5 muqdadia fom9 22.5 mindly fod5 42.5 lsd (0.05) = 2.4 each number is the mean of 4 replicates. 42 squ journal of agricultural and marine sciences, 2018, volume 23, issue 1 integrated management of the fusarium vascular wilt disease of cucurbita pepo in iraq radial growth and microscopic characteristics of conidiophores, microconidia, macroconidia and chlamydospore (booth, 1971; domsch et al., 2007). identification was confirmed in the plant protection department/ college of agriculture/ university of baghdad. the percentage of appearance and frequency was calculated using the following formulae (hussain and juber, 2014): appearance (%) = spec occ / sample t x 100 in which spec occ is the samples of species occurrence) and sample t the total no.of samples ,and frequency (%) = n occ / n t x 100 where n occ is the number of segments that showed infection and n t is the total number of segments used in the experiment. pathogenicity test in-vitro experiments were conducted to estimate pathogenicity ability of the 45 initially isolates of f. oxysporum on the seed of the zucchini cultivar amjad. spore suspensions of the pathogen were prepared and amended to 108 cfu/ml using hemocytometer. ten ml of the spore suspension were added to the petri dish containing 6 layers of the sterile filter paper (9 cm) and 10 mlsterile distilled water, 10 seeds of the zucchini were added to each plate and incubated at 25°c for 14 days, four replicates amended for each treatment. the percentage of the seed germination was calculated according to the formula below: ge (%) = seed g/ seedt x 100 where seed g is the number of seeds that germinated and seedt the number of seed used in the trial (elouaer and hannachi, 2012). molecular identification assay dna extraction dna of the 45 initially isolated of f. oxysporum were extracted for the pcr detection, mycelium of each isolate collected individually with a sterile spatula from potato dextrose agar medium (pda) after 7 days of incubation table 2. molecular identification of the fusarium spp. isolates isolate result of amplification isolate result of amplification fok1 fom11 + fok2 + fom12 fok3 + foq1 + fok4 foq2 fok5 + foq3 + fok6 + foq4 + fok7 foq5 + fok8 + foq6 fok9 + foq7 + fok10 foq8 fok11 + foq9 + fok12 foq10 + fok13 + foq11 fom1 foq12 + fom2 + foq13 fom3 + foq14 + fom4 + foq15 + fom5 fos1 fom6 + fod2 + fom7 + fod3 + fom8 + fod4 fom9 + fod5 + fom10 table 3. mean inhibition effect of the fungicides and botanical extracts in vitro. (n = 4) treatment inhibition (%) control (foq9) 0.00 foq9 + tm 100.00 foq9 + tc 100.00 foq9 + gr 88.06 foq9 + gn 80.89 lsd (0.05) = 0.53 foq9 = isolate of f. oxysporum, tm= topsin m 70 wp, tc= tecto 500 sc, gr= garlic extract, gn= ginger extract. figure 1. pcr amplification of dna samples of fusarium spp. using universal primers (its-fu-f and its-fu-r): m= dna ladder, c= negative control 43research article hussein table 4. effect of the fungicides and botanical extracts in controlling fusarium wilt disease under greenhouse conditions. no. treatment germination (%) incidence (%) severity (%) dry weight (mg/plant) 1 control 100.0 0.0 0.0 479 2 foq9 30.0 95.0 79.0 86 3 tm 100.0 0.0 0.0 479 4 tc 100.0 0.0 0.0 484 5 gr 100.0 0.0 0.0 571 6 gn 100.0 0.0 0.0 589 7 fos9+tm 87.5 67.5 41.8 444 8 fos9+tc 80.0 70.0 45.0 395 9 fos9+gr 75.0 65.0 50.5 292 10 fos9+gn 77.5 67.5 56.0 301 11 fos9+tm+tc 92.5 37.5 33.0 487 12 fos9+tm+gr 92.5 50.0 45.5 498 13 fos9+tm+gn 95.0 52.5 41.3 474 14 fos9+tc+gr 100.0 50.0 45.3 502 15 fos9+tc+gn 100.0 55.0 40.8 480 16 fos9+gr+gn 100.0 47.5 30.3 559 17 fos9+tm+tc+gr 95.0 35.0 23.5 545 18 fos9+tm+tc+gn 100.0 30.0 21.8 586 19 fos9+tm+gr+gn 100.0 25.0 19.5 595 20 fos9+tc+gr+gn 97.5 32.5 23.5 602 21 fos9+tm+tc+gr+gn 100.0 0.0 0.0 710 lsd (0.05) 0.84 2.0 14.76 71 each number reflects 4 replicates. figure 2. inhibition effect of the fungicides and botanical extracts against f. oxysporum in vitro a. topsin m 70 wp, b. tecto 500 sc, c. garlic extract, d. ginger extract. columns are replicates. 44 squ journal of agricultural and marine sciences, 2018, volume 23, issue 1 integrated management of the fusarium vascular wilt disease of cucurbita pepo in iraq at 25±2°c, lyophilized and grinded, fungal dna extraction kit were used of chelex 100 kit (bio-rad laboratories, inc., usa). dnas were maintained at -20°c until used. polymerase chain reaction assay (pcr) universal primer pair its-fu-f and its-fu-r which is specific for the species of fusarium were used with the following nucleotide sequences: 5`-caactcccaaacccctgtga-3`and 5`-gcgacgattaccagtaacga-3` (abd-elsalam et al., 2003). the master mix of redtaq readymix pcr reaction mix (sigma-aldrish, usa) were used in the pcr reaction , each 20μl of the pcr reaction consist of 10μl redtaq readymix, 8.6μl pcr h2o, 0.4μl forward primer, 0.4μl reverse primer at the concentration of 5 pmol and 1.0μl template dna at the concentration of 50 ng/µl. thermocycler (applied biosystems 2720 thermal cycler, usa) as programmed at the optimized amplification parameter according to the method of hussein (2016) except the annealing step which set at 58°c for 1 min, negative control were amended as pcr mixture free of dna in each run. pcr products were size fractionated on 1.5% agarose gel (bio basic, canada) using loading quick 100 bp dna ladder (toyobo, japan) added as 6 μl per lane, gels were visualized using micro doc system with u.v. transilluminator (cleaver, uk). botanical extracts preparation natural extracts of garlic and ginger were prepared by blending 100 gm of dried garlic cloves and 100 gm of fresh ginger rhizome with 250 ml sterile distilled water for 5 min and completed to 1000 ml with sterile distilled water. the suspensions were filtered through sterile cheesecloth into sterile conical flask (mohana and raveesha, 2007). inhibition activity assay inhibition activity of the fungicides and botanical extracts were estimated using poisoning food technique on the psa medium, the fungicide topsin m 70 wp (tm), active ingredient is thiophanate methyl (produced by nippon soda co. limited, jappan) was prepared according to the manufacturer instructions at a concentration of 1.5 g/l, the fungicide tecto 500 sc (tc), active ingredient is thiabendazole (produced by syngenta, switzerland) at the concentration of 2 ml/l, one milliliter of each fungicide (tm and tc) and 1 ml of each botanical extracts (gr and gn) individually added to the petri plate, the plates were prepared by 15-20 ml of autoclaved psa, each plate inaculcated with 0.5 cm disc of the fungal isolate foq9 (7 days old), the control was the fungal isolate fos9 alone. four replicates were prepared for each treatment, the plates were incubated at 25°c until the radial growth of the pathogen reached the edge of plate in the control. the inhibition zones were calculated using the following formula: inhibition (%) =r r / r × 100 (mohana and raveesha,2007) where r = radial growth of mycelium in control, r = mycelial growth in treatment. assessment efficacy of the fungicide and botanical extracts under greenhouse conditions experiment was conducted under greenhouse conditions to evaluate the disease controlling ability of the fungicides and botanical extracts individually and in combination. plastic pots of 13 cm diameter were filled with autoclaved mixture of soil and compost (1:1). the treatment were tm, tc, gr, gn, foq9+tm, foq9+tc, foq9+gr, foq9+gn, foq9+tm+tc, foq9+tm+gr, foq9+tm+gn, foq9+tc+gr, foq9+tc+gn, foq9+gr+gn, foq9+tm+tc+gr, foq9+tm+tc+gn, foq9+tm+gr+gn, foq9+tc+gr+gn, foq9+tm+tc+gr+gn, foq9 (negative control) and positive control (without any treatment). fungal inoculum prepared by adding 5 discs (0.5 cm) of the fungus 7 days old to each 100 gm of the autoclaved pennisetum glaucum in sterile conical flask with 10 ml sterile distilled water and incubated 7 days at 25 ±2°c. the fungal inoculum were added figure 3. control fusarium wilt disease under greenhouse conditions a1.treatment of (fos9+tm+tc+gr+gn), a2. negative control, b. treatment of (fos9+gr+gn), c. negative control 45research article hussein to the pots as 10 g/pot and watered, after 3 days each pot received 10 seeds of zucchini cultivar of amjad, the fungicide tm and tc, and the botanical extracts gr and gn were soil drenched as 10 ml/pot on the same day of seeds transplanting and at the same concentration of the previous experiment. percentage of the seed germination was calculated after 15 days of seeds transplanting. percentage of the disease incidence and severity were calculated after 60 days of seeds transplanting according to the following formula: disease incidence (%) =(no.of infected plants)/ (total no.of plants assessed)×100 (masood et al.,2010) the disease severity index (dsi) was estimated using the score chart of (0-7) rates which was described by schneider (1984) and the percentage of the disease severity was calculated using the following formula: dsi (%)= (σ (f x v))/(n × x)×100 (grau and radke,1982) results and discussion isolation and identification of the pathogen the results indicated that the soilborne fungus f. oxysporum was predominant, which exhibited 78.57 % percentage of appearance with frequency of 62.50 %. the high density of this pathogen in the soil of these areas may be due to inadequate agricultural practices such as repeated crop cultivate annually without crop rotation, weak cleanup process from infected plant debris. furthermore, chlamydospores of the fungus can survive in the soil for several years even in the absence of a host (stover, 1962). saprophytic fungi such as aspergillus spp., rhizopus spp. and pen’cillium spp. appeared with percentage ranged between 15.5024.40 % and frequency of 19.40-25.00 %. pathogenicity test the forty five isolates of fusarium spp., which identified morphologically as f. oxysporum showed variation in their pathogenicity in vitro, while the percentage of seed germination ranged between 5.0 – 90.0 % (table 1), the isolate foq9 exhibited 5.0 % percentage of seed germination, followed by the isolate fom4 and foq 2 were they exhibited 15.0 %, 17.5 % germinated respectively. this variation between the isolates may be due to enzyme secreting (irzykowska et al., 2012) ability. molecular identification assay results of the dna amplification of the 45 fungal isolates showed that 29 isolates were amplified positively with the universal primer of fusarium spp. (table 2), as they generated bands at 570 bp (fig. 1). the rest of the isolates didn’t amplify with theses primers, and this is may be because of technical errors. inhibition activity assay according to table 3, all of the agents used in this experiment significantly reduced the fungal radial growth of the f. oxysporum, so far both of the fungicides topsin m 70 wp and tecto 500 sc exhibited 100.0% percentage of inhibition, while the botanical extracts of garlic and ginger exhibited 88.06%, 80.89% respectively, compared to control which filled the plates after 7 days of incubation (fig. 2). sahar et al. (2013) found that in vitro experiment topsin m inhibited the growth of f. oxysporum significantly as 76.66 %. assessment efficacy of the fungicides and botanical extracts under greenhouse conditions the results showed that all of the agents used individually and in combination increased the percentage of the seed germination up to 75-100 % compared to the negative control (pathogen alone) which was 30 % (table 4). all of the treatments reported significant disease controlling ability, while the percentage of the disease incidence and severity ranged between 0-70 %, 0-56 % respectively compared to the negative control which was 95 % and 79 % respectively, among these the treatment of tetra-inoculum (tm+tc+gr+gn) was superior which exhibited 0 % percentage of disease incidence and severity, followed by the tri-inoculum (tm+gr+gn) which was 25.0 %, 19.5 % respectively. further, the treatment of botanical extracts in combined application (gr+gn) reduced the disease incidence and severity to 47.5 % and 30.3 % respectively, which reflect a positive efficiency of the natural extracts in plant diseases control as alternative to chemicals or in combination with them to preserve the environment from harmful effect of the chemicals (fig. 3). the tetra-inoculum (tm+tc+gr+gn) reported highest average of dry weight of plants which was 710 mg/ plant compared with negative and positive control which was 86 and 479 mg/plant respectively, followed by the treatment of tri-inoculum (tc+gr+gn) which was 602 mg/plant. the combined application of gr+gn exhibited significant increase in the dry weight of plant which was 559 mg/plant. tariq and magee (1990) found that volatile components of garlic extracts inhibited germination of the microconidia, macroconidia and mycelium of the f. oxysporum f. sp. lycopersici in vitro. al.rahmah et al. (2013) has been found that ginger extracts has strong fungistatic and fungicidal activities against f. oxysporum and pythium aphanidermatum with minimal inhibitory concentration. furthermore, sahar et al. (2013) proved that foliar application of topsin-m with concentration of 0.1 % was significantly reduced the disease incidence of fusarium wilt disease on eggplant. 46 squ journal of agricultural and marine sciences, 2018, volume 23, issue 1 integrated management of the fusarium vascular wilt disease of cucurbita pepo in iraq reference abd-elsalam ka, ibrahim na, mohmed s.k., mohmed aa, joseph av. 2003. pcr identification of fusarium genus based on nuclear ribosomal-dna sequence data. african journal of biotechnology 2 (4):82-85. agel, ds, martyn rd. 2013. fusarium wilt of watermelon and other cucurbits. the plant health instructor. doi: 10.1094/phi-i-2007-0122-01. al samarrai g, singh h, syarhabil m. 2012. evaluating eco-friendly botanicals (natural plant extracts) as alternatives to synthetic fungicides. annals of agricultural and environmental medicine, 19(4): 673-676. al rahmah an, mostafa aa, abdel-megeed a, yakout sm, hussein sa. 2013. fungicidal activities of certain methanolic 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management: innovation-development process, springer dordrecht, doi.org/10.1007/978-1-4020-8992-3_12. schneider, r.w. 1984. effects of nonpathogeneic strains of fusarium oxysporum on celery root infection by 47research article hussein fusarium oxysporum f. sp. apii and a novel use of the lineweaver-burk double reciprocal plot technique. phytopathology. 74: 646-653. stover rh. 1962. fusarium wilt (panama disease) of bananas and other musa species. phytopathological, wallingford, uk: cab international. p 4. tariq vn, magee ac. 1990. effect of volatiles from garlic bulb extract on fusarium oxysporum f. sp. lycopersici. mycological research 94(5) 617-620. doi:10.1016/ s0953-7562(09)80662-x research paper journal of agricultural and marine sciences 2022, 27(1): 77–89 doi: 10.53541/jams.vol27iss1pp77-89 received 04 feb 2021 accepted 16 april 2021 optimum stocking density of ‘koi’ carp (cyprinus carpio) in combination with different plant species in an aquaponic system buthaina al-khaziri*, azhar al-busaidi, zainab al-ghatami, and wenresti gallardo buthaina al-khaziri*( ) buthainakhamis@gmail.com, department of marine science & fisheries, college of agricultural & marine sciences, sultan qaboos university, sultanate of oman introduction in response to an increase of human population and the various challenging issues of climate change, soil corruption, decrease in fish population, increase in utilization of natural resources such as water and soil, and water scarcity (merino et al., 2012) there is a need to develop and utilize production systems that are environment-friendly. one production system is aquaponics which is a closed-loop system that combines aquaculture and hydroponics without the use of the soil (hussain et al., 2016). aquaponics work on the principle of the nitrogen cycle, wherein dissolved waste created from the production system is successfully changed over to plant nutrients by advantageous nitrifying bacteria. it )cyprinus carpio( الكثافة املثلى لرتبية أمساك الكوي كارب مع نبااتت خمتلفة يف نظام اإلستزراع األحيومائي بثينه اخلزيري*، أزهار البوسعيدي، زينب الغتامي، و وينريسيت جاالردو abstract. to maximize profits from aquaponic system, a high-price ‘koi’ carp (cyprinus carpio) produced at sultan qaboos university was used. this study consisted of two experiments. the first experiment aimed to determine the optimal stocking density of ‘koi’ carp in an aquaponic system. in the second experiment, the optimal density of ‘koi’ carp based on the first experiment was used in combination with tomato, eggplant, and mint as a control from the first experiment. the aquaponic system consisted of 9 pairs of glass tanks; in each pair water was recirculating with the use of a submersible pump. in the first experiment, ‘koi’ carp fry (0.4-0.5 g each) were stocked at 50, 100 and 150 individuals per tank (0.1 m3) in combination with mint and the ornamental plant petunia. fish were stocked in tanks with and without plants. results show that ‘koi’ carp stocked at 100 per tank without plants had significantly better growth (mean final weight of 7.5 g from the initial weight of 0.4-0.5 g). fish stocked in tanks with plants, ‘koi’ carp at 50 per tank had significantly better growth (mean final fish weight of 5.2 g from the initial weight of 0.4-0.5 g). survival rate was highest at 50 per tank with or without plants. mint growth was better in tanks with 50 fish per tank. petunia had flowers in all treatments. water quality parameters were within optimal range even at high fish stocking densities. overall, stocking density of 50 fish per tank can be recommended based on survival data. in the second experiment, 30 ‘koi’ carp juveniles were stocked in all tanks without plants (i.e. 6.5 g, 5.5 g and 6.1 g respectively) for each treatment in combination with mint, tomato, and eggplant. growth and survival rates of koi (30 fish per tank) in combination with mint, eggplant and tomato were high with a weight gain of 21.3, 17.6, 17.6 g and survival rate of 90%, 95.5% and 87.8%, respectively. the results showed that ‘koi’ can be successfully grown with different plants in an aquaponic system. keywords: aquaponics, koi carp, cyprinus carpio, eggplant, mint, petunia امللخــص:مت اســتخدام أمســاك الكــوي كارب )cyprinus carpio( عــايل الســعر واملنتــج يف جامعــة الســلطان قابــوس مــن أجــل حتقيــق أقصــى قــدر مــن األرابح من نظام االستزراع النبايت والسمكي يف هذه الدراسة، واليت تتكون من جتربتني: هدفت التجربة األوىل إىل حتديد الكثافة املثلى لرتبية أمساك الكوي كارب يف نظام الزراعــة األحيومائيــة. أمــا يف التجربــة الثانيــة فقــد مت اســتخدام الكثافــة املثلــى ألمســاك الكــوي كارب بنــاًء علــى التجربــة األوىل مــع الطماطــم والباذجنــان والنعنــاع كعنصــر حتكــم مــن التجربــة األوىل. يتكــون نظــام الزراعــة األحيومائيــة مــن 9 أزواج مــن اخلــزاانت الزجاجيــة، حيــث يتــم إعــادة تدويــر املــاء يف كل زوج إبســتخدام مضخــة غاطســة، ففي التجربة األوىل، مت ختزين زريعة أمساك الكوي كارب )0.4-0.5 جرام لكل منها( عند 50 و 100 و 150 زريعة لكل خزان )0.1 مرت مكعب3( مع النعناع ونبــات الزينــة البطونيــة. مت تربيــة األمســاك يف خــزاانت مــع وبــدون نبــااتت، حيــث أوضحــت النتائــج أن أمســاك الكــوي كارب املخزنــة عنــد 100 زريعــة لــكل حــوض بــدون نبات كان هلا منو أفضل )متوسط الوزن النهائي 7.5 جرام من الوزن األويل 0.4-0.5 جرام(. وقد متتعت األمساك اليت مت تربيتها يف أحواض مع النبااتت مبعدل 50 زريعــة لــكل خــزان بنمــو أفضــل )متوســط الــوزن النهائــي لألمســاك البالــغ 5.2 جــرام مــن الــوزن األويل البالــغ 0.4-0.5 جــرام(، وكان معــدل البقــاء علــى قيــد احليــاة أعلــى يف اخلــزاانت الــيت حتتــوي علــى 50 مسكــة مــع أو بــدون نبــااتت، وكان منــو النعنــاع أفضــل يف اخلــزاانت مــع 50 مسكــة لــكل حــوض، وقــد لوحــظ أن البطونيــة كانــت مزهــرة يف مجيــع التجــارب، وكانــت معايــر جــودة امليــاه ضمــن النطــاق األمثــل حــى عنــد الكثافــة العاليــة لتخزيــن األمســاك. ميكــن التوصيــة بشــكل عــام برتبيــة األمســاك البالغــة يف كثافــة مقدارهــا 50 مسكــة لــكل حــوض بنــاًء علــى بيــاانت البقــاء علــى قيــد احليــاة. يف التجربــة الثانيــة، مت وضــع 30 مــن صغــار أمســاك الكــوي كارب يف مجيــع األحــواض اخلاليــة مــن النبــااتت )أي 6.5 جــرام ، 5.5 جــرام ، 6.1 جــرام علــى التــوايل( لــكل جتربــة مــع النعنــاع والطماطــم والباذجنــان، ولوحــظ أن معــدالت منــو وبقــاء أمســاك الكــوي كارب )30 مسكــة لــكل حــوض( مــع النعنــاع والباذجنــان والطماطــم كانــت عاليــة مــع زايدة يف الــوزن بلغــت 21.3 و 17.6 و 17.6 جــرام ومعــدل بقــاء ٪90 و 95.5٪ و 87.8٪ علــى التــوايل، وكخالصــة فقــد أظهــرت النتائــج أنــه ميكــن زراعــة الكــوي كارب بنجــاح ابســتخدام نبــااتت خمتلفــة يف نظــام تربيــة األحيــاء املائيــة. الكلمات املفتاحية: الزراعة األحيومائية، كوي كارب، ابذجنان، نعناع، البطونية. 78 squ journal of agricultural and marine sciences, 2022, volume 27, issue 1 optimum stocking density of ‘koi’ carp (cyprinus carpio) in combination with different plant species in an aquaponic system converts ammonia released from fish and residual feed to nitrate to be used by the plants for their growth. recycling aquaculture systems already produce large volumes of fish in a small footprint without aquaponics. it also allows for expanded generation utilizing a similar volume of water and nutrient input. by this technique, it is possible to reduce wastes and related natural effects, and in the meantime produce fish and plant crops as well as increase financial income (schmautz et al., 2017). due to the global drop in oil prices and the lack of job opportunities, the government of the sultanate of oman headed to strengthen its sustainable wealth, such as agriculture and fisheries sector. the sultanate of oman is considered one of the areas with scarcity of water, thus, aquaponics is an ideal solution to enhance the economy of the country and providing job opportunities along with reducing water consumption. currently, the government, represented by the ministry of agriculture and fisheries, is working to provide support for many projects in this field. ‘koi’ carp (cyprinus carpio) is an ornamental fish with high market demand because of its color patterns. it has great demand in south east asian countries, and being hardy in nature, it is highly suitable for garden pools and aquariums. limited information on ‘koi’ carp culture in aquaponics system is available (hussain et al., 2016). the main objectives of this experiment were to determine the optimal density of ‘koi’ carp (cyprinus carpio) stocked in tanks with and without plants (mint and petunia) in aquaponic system, to determine the feasibility of growing ‘koi’ carp and plants in one tank to maximize space. it also aimed to optimize the growth of ‘koi’ carp stocked with different plants (i.e. mint, eggplant, and tomato). materials and methods eighteen (18) units of glass tanks (80×40×40 cm) containing 100-liter of tap water were set up in pairs. all tanks were identical allowing replication of experimental treatments. nine of the 18 tanks were without plants the other 9 tanks were with plants. the fish tanks without plants were placed on a platform while the fish tanks with plants were placed on the floor. all tanks were connected with air stones to provide dissolved oxygen to the fish and plants. each fish tank without plants was connected to fish tank with plants with a pipe or hose to allow water to flow by gravity from the fish tank without plants to the fish tanks with plants. the fish tanks with plants had gravels on the bottom and a vertical layer of gravels in net bags on one end of the tank before the submersible pump to filter the water from solid wastes and bring the filtered water back to the fish tank without plants. each tank had a 3-cm thick styrofoam covering the entire water surface. for fish tanks without plants there was a small opening for the feed to be given. for fish tanks with plants, each styrofoam cover (i.e. polyethylene raft) had 13 -15 evenly-spaced holes for the plants as shown in figure 1. experiment 1 all 18 tanks were used to grow ‘koi’ carp (cyprinus carpio) with an average of initial weights of 0.4-0.5 g each stocked at 50, 100, 150 fish per tank (i.e. 0.1 m3). the lower 9 tanks were planted with mint and petunia in each tank. both plants were cut (i.e. 10 cm long) and wrapped around with cotton on the lower part and placed in a plastic seedling container with open bottom to allow the roots to go down into the water. the experiment was conducted for 91 days. experiment 2 the upper 9 units were used to grow ‘koi’ carps of the initial weight of 6.5 g, 5.5 g and 6.1 g for each treatment at the same stoking density of 30 juvenile per tank. the lower 9 tanks were used to grow mint, eggplant and tomato in each tank. the same growing method was used as in the first experiment. the experiment was conducted for 56 days. figure 1. the aquaponics system; upper tanks had fish only, lower tanks had fish and plants 79research paper al-khaziri, al-busaidi, al-ghatami, gallardo fish, plants and water sampling every week, ph, dissolved oxygen (do, mg/l) and temperature (oc) were measured. fish weights were measured every month. samples of 10, 20, 30 fish were weighed from treatments 1, 2, 3 from both fish tanks without plants (upper tanks) and fish tanks with plants (lower tanks) in the first experiment, and 30 fish from each tank were measured in the second experiment. the length of 10 mint plants from each tank were measured, and the number of flowers of 10 petunia were counted in the first experiment and the length of all plants were measured in the second experiment. data analysis all collected data such as weights of fish and lengths of mint branches were plotted in microsoft excel program. average and standard error of mean were calculated and the graphs were plotted. anova was calculated for weight of fish and height of mint followed by tukey’s test for significant difference at p<0.05. results experiment 1 growth of fish: in the fish tanks without plants, the final weights of fish in treatment 1 (50 fish/tank), treatment 2 (100 fish/tank) and treatment 3 (150 fish/tank) were 5.0 g, 7.5 g and 6.6 g from the initial weight of 0.42 g, 0.48 g and 0.52 g, respectively (figure 2), corresponding to weight gain of 4.5, 7.02, and 6.08 g, respectively, in 90 days. there were significant differences in growth of fish at different stocking densities (p-value = 0.04). there were significant different between treatment 1 and 2 (p-value = 0.04), however “ there were no significant different between treatment 1 and 3 (p-value = 0.19) and 2 and 3 (p-value = 0.57) ”. in tanks with plants, the final weights of fish in treatment 1 (50 fish/tank), treatment 2 (100 fish/tank), treatment 3 (150 fish/tank) were 5.2 g, 4.1 g, 3.8 g from the initial weight of 0.51 g, 0.47 g and 0.47 g respectively (figure 2). final weight at 50 per tank figure 2. growth (average weight and standard error of mean) of fish in tanks with and without plants. figure 3. survival rate of fish in fish tanks without and with plants, after 91 days. 80 squ journal of agricultural and marine sciences, 2022, volume 27, issue 1 optimum stocking density of ‘koi’ carp (cyprinus carpio) in combination with different plant species in an aquaponic system was significantly different from those at 100 and 150 per tank (p-value = 0.04). there were significant different between treatment 1 and 3 (p-value = 0.04), however “ there were no significant different between treatment 1 and 2 (p-value = 0.09) and 2 and 3 (p-value = 0.90) ”. survival rate: the average survival rate of fish in treatment 1 (50 fish/tank), treatment 2 (100 fish/tank), treatment 3 (150 fish/tank) was 51.3%, 20.7% and 22.7% respectively in fish tanks without plants and 81.3%, 52.3% and 46.2% in fish tanks with plants from the initial number of fish 50, 100 and 150 (figure 3). growth of plants: the average final lengths of mint in treatment 1 (50 fish/tank), treatment 2 (100 fish/tank), treatment 3 (150 fish/tank) was 46.3 cm, 37.5 cm and 36.3 cm, respectively from the initial length of 10 cm (figure 4). however, there was no significant difference in growth of mint at different fish stocking densities (p-value = 0.17). the initial number of petunia flowers in treatment 1 (50 fish/tank), treatment 2 (100 fish/tank), treatment 3 (150 fish/tank) was 14, 14, 18 respectively (figure 5) and the final number of petunia flowers in treatment 1 (50 fish/ tank), treatment 2 (100 fish/tank), treatment 3 (150 fish/ tank) was 19, 23, 20, respectively (figure 5). water quality dissolved oxygen: the dissolved oxygen (do) in the fish and plant tanks was fluctuating. it ranged from 3.49 to 8.16 mg/l. do was highest in treatment 1 (50 fish/tank), whereas, the lowest do concentration was in treatment 3 (150 fish/tank) (figure 6 and 7). temperature: the temperature in the fish and plant tanks was fluctuating. it ranged from 29.73 to 36.17°c (figure 8 and 9), decreasing towards the end of summer when the experiment ended. figure 4. growth (average length and standard error of mean) of mint plants. figure 5. number of flowers produced by petunia plants in the aquaponics system with different fish densities. 81research paper al-khaziri, al-busaidi, al-ghatami, gallardo ph: the ph in the fish and plant tanks was fluctuating but within optimal range. it ranged from 6.72 to 7.82. ph was highest in treatment 1 (50 fish/tank), whereas, the lowest ph concentration was in treatment 2 (100 fish/ tank) (figures 10 and 11). experiment 2 growth of fish: fish weight: the final weights of fish in treatment 1 (fish with mint), treatment 2 (fish with eggplant) and treatment 3 (fish with tomato) was 27.8 g, 23.1 g and 23.7 g from the initial weight of 6.5 g, 5.5 g and 6.1 g, respectively (figure 12), corresponding to weight gain of 21.3, 17.6 and 17.6 g, respectively. there were no significant differences in growth of fish in combination with different plants (p-value = 0.12). fish length: the final lengths of fish in treatment 1 (fish with mint), treatment 2 (fish with eggplant) and treatment 3 (fish with tomato) was 11.1 g, 10.7 g and 10.5 g from the initial weight of 5.5 g, 5.0 g and 5.7 g, respectively (figure 13). there were no significant differences in growth of fish at different plants (p-value = 0.26). survival rate: the average survival rate of fish in treatment 1 (fish with mint), treatment 2 (fish with eggplant), treatment 3 (fish with tomato) was 90%, 95.5% and 87.8% respectively from the initial number of 30 fish (figure 14). growth of plant: the average final length of mint was 39.5 cm from the initial length of 10 cm, eggplant was 47.4 cm from the initial length of 41.7 cm and tomato was 28.4 cm from the initial length of 1.6 cm (figure 15). for the tomato plants, white spots were observed in the upper surfaces of the leaves that appear to be oidium disease (kiss et al., 2001) water quality dissolved oxygen: the dissolved oxygen (do) in all treatment was fluctuating. it ranged from 3.49 to 8.16 mg/l. do was highest in treatment 1 (fish with mint), whereas, the lowest do concentration was in treatment 3 (fish with tomato) (figure 16). figure 6. dissolved oxygen (do) in fish tanks without plants. figure 7. dissolved oxygen (do) in fish tanks with plants. 82 squ journal of agricultural and marine sciences, 2022, volume 27, issue 1 optimum stocking density of ‘koi’ carp (cyprinus carpio) in combination with different plant species in an aquaponic system temperature: the temperature in the fish and plant tanks was fluctuating. it ranged from 20.70 to 31.07°c (figure 17), decreasing towards the start of winter when the experiment ended. ph: the ph in the fish and plant tanks was fluctuating but within optimal range. it ranged from 6.38 to 7.29 (figure 18). nutrients: figure 19 shows concentrations of phosphate, nitrate and sulphate in each treatment per sampling month. the nitrate concentration was highest in the last month (23-nov). it also shows higher rate of increase in the treatment with mint and a steady increase in the treatment with eggplant. the phosphate concentration was highest in 7-aug for both treatments with mints and eggplants, and highest in 5-jul in the treatment with tomatoes. phosphate concentration tend to decrease in 23-nov for the treatments of mint and eggplant where it shows some increase in the treatment with tomatoes. sulphate concentration was high in the treatment with eggplant, and shows some fluctuation for both treatments of eggplant and tomato. it also shows some steady increase in the treatment with mint. figure 20 shows the concentrations of potassium, calcium magnesium and sodium in each treatment per sampling month. there was an increase in potassium in the treatment with mint, while it was fluctuating in treatments with eggplant and tomato. the calcium concentration increased in the last month for all the treatments, where it reached almost the same concentration. there was an increase in magnesium in all treatments, where the concentration was almost the same in the last month. on 7-aug, the concentration of magnesium in the treatment with tomatoes showed some decrease, while it continued to increase in the other treatments. there was a small increase in the concentration of sodium in all treatments with small decrease in the last month in the treatment with eggplant. the figure also shows sodium concentration was highest in the treatment with eggplant. figure 8. temperature in fish tanks without plants. figure 9. temperature in fish tanks with plants. 83research paper al-khaziri, al-busaidi, al-ghatami, gallardo discussion experiment 1 fish growth at different stocking densities with or without plants: stocking density of fish is regarded as one of the most sensitive factors affecting growth rate, size variation and mortality determining productivity of a culture system (hussain et al., 2016). prithwiraj et al. (2008) reported an inverse relationship between stocking density and individual size of koi carp (cyprinus carpio) in concrete tanks, primarily due to the shared food among individuals. in our experiment we aimed to determine the optimal stocking density for the aquaponic system. as we stocked the ‘koi’ carp at different densities (50, 100, and 150 fish/tank) and different state of environment (fish tanks without plants and fish tanks with plants), the data indicate that fish had different growth rates. fish growth was higher in fish tanks without plants and this may be due to the tank volume. the plant tanks had gravels on the bottom and vertical layer of gravels in net bags on one end of the tank which reduces the living space of fish. in the three months of sampling of fish in tanks with or without plants and fish with plants, the increase in the fish weight was almost 0.5 g, whereas the increase of the weight between the third and the last samplings was higher by 1.73, 4.30 and 3.64 g, respectively in the fish tanks without plants, and 1.53, 1.08 and 1.42 g, respectively in the fish tanks with plants. according to knaus and palm (2017), the optimal temperature for cyprinus carpio is between 25 and 30°c, which is suggested to be the reason of the increase for the fish weight at the last month. effect of stocking density on growth of ‘koi’ carp: our hypothesis was that there will be a negative relationship between stocking density and fish growth, since increase in the stocking density will normally decrease the growth of fish. this study confirms our hypothesis as the results show that fish growth in the fish tanks without plants was significantly higher in treatment figure 10. ph in fish tanks without plants. figure 11. ph in fish tanks with plants. 84 squ journal of agricultural and marine sciences, 2022, volume 27, issue 1 optimum stocking density of ‘koi’ carp (cyprinus carpio) in combination with different plant species in an aquaponic system 1 (50 fish/tank) from first sampling to third sampling (i.e. 0.42±0.05 g, 1.71±0.20 g, 3.27±0.46 g). while in the last sampling the growth rate in treatment 2 (i.e. 100 fish/tank) “increased which may due to the death of fish in this experiment resulting in reduced density and thus an increase in the fish weight”. however, in the fish tanks with plants, the fish growth was significantly higher in treatment 1 (i.e. 5.24±0.45 g) followed by treatment 2 (i.e. 4.12±0.43 g). the lowest growth in fish was observed in treatment 3 (i.e. 3.85±0.33 g). according to karakatsouli et al. (2010), fish density can be affected by the light intensity inside the fish tanks, which affects fish behavior, stress, and growing performance. moreover, it has been found that some species including ‘koi’ carp culture can be highly sensitive to nitrogen toxicants, where depression of feeding can be one of the common problems if the water quality is sub-standard and the higher density can results in higher nitrogen toxicants in the tank (prithwiraj et al., 2008). the reduction of space availability for fish, can increase aggressive behavior and food competition, which can in turn cause stressful conditions, decrease survival rate (jha, et al, 2008) and reduce growth rate (nuwansi et al., 2021). survival rate of the fish during the experiment were significantly higher in treatments 1 for both fish tanks without plants and fish tanks with plants (51.3% and 81.3% respectively). during the first months of experiment, the number of dead fish increased especially in the treatment 2 and 3. according to jha et al. (2007), ‘koi’ carp can adapt to fluctuating and extreme temperature but if the temperatures increase beyond the thermal limit the mortality will increase too. the maximum critical temperature of ‘koi’ carp is 35oc where the minimum critical temperature is 15oc (zutshi et al., 2020). plant growth: the length of mint in all treatments at the end of experiment did not show any significant difference (p ≥0.05). according to knaus and palm (2017), the optimal water temperature in aquaponics system for figure 12. weight (mean and standard deviation) of fish in combination with different plants. figure 13. length (mean and standard deviation) of fish in combination with different plants. 85research paper al-khaziri, al-busaidi, al-ghatami, gallardo plant production between 22 and 24 °c. in this study, the number of petunia flower increased during the first 3 sampling and that may be due to temperature decreasing and started to decrease in the last sampling due to decrease in ph. physico-chemical water parameters: water quality factors (temperature, ph, dissolved oxygen) changed during the experiment. the temperature was fluctuating, ranging from 29.73 to 36.17oc. at the beginning it was high during summer and then it decreased due to the start of fall season. the dissolved oxygen was high in all the treatment at the beginning of experiment due to clean tanks. later on it started to decrease due to the increased production of wastes which were acted upon by decomposing bacteria that also consumed the oxygen. treatment 1 in both fish tanks without plants and fish tanks with plants had high do due to lower density of fish in this treatment. according to shete et al. (2017), in aquaponics system the optimal level of ph of the water for the process of nitrification, survival and growth of fish and plants is 7. in this study, we indicate that the ph in treatment 1 in both fish tanks without plants and fish tanks with plants were in the range of 7.17-7.43 and 7.12-7.48, respectively) which is favorable for the growth of fish and plant. experiment 2 effects of the plants on fish growth and survival: as the results show, the treatment where the fish gained more weight was the one with mint (mean initial weight 6.5 g, mean final weight 27.8 g), whereas both treatments of the eggplant and tomato were almost the same (i.e. mean initial weight 5.5, 6.1, and mean final weight 23.1, 23.7 g, respectively) and this is also true for the fish length (i.e. mean final length of 11.1, 10.7, 10.5 cm, respectively). the survival rate was best in the second treatment where eggplants were planted followed by mint and then tomato. from the results, the treatment where the ‘koi’ carp have gained more weight and length and has the best growth rate was the treatment with the mint. figure 14. survival rate of fish, after 56 days. figure 15. growth (average length and standard deviation) of plants. 86 squ journal of agricultural and marine sciences, 2022, volume 27, issue 1 optimum stocking density of ‘koi’ carp (cyprinus carpio) in combination with different plant species in an aquaponic system plants growth: mint grew faster than eggplant and tomato because mint is a low-nutrient-demand plant whereas eggplant and tomato are high-nutrient-demand plants because they are fruiting plants (somerville et al., 2014). growth of eggplant was slower but it started to produce flowers and fruits at the end of the experiment. the increase of plans growth and flower production was due to the increase of nutrients supplied by the fish, where higher stocking density of fish results in higher nutrients supplied and higher plant growth (nuwansi et al., 2021). the nutrients from fish tank wastewater provide better environments for plant growth and produce higher yields than soil grown yields (nuwansi et al., 2021). in the last month, the tomato plants started to have white spots like a powder on their stems and the upper surfaces of the leaves. according to kiss et al. (2001), these white spots are caused by powdery mildew fungi oidium spp that can be avoided by providing the best conditions for tomato plants to grow and supplying a sufficient amount of potassium. physico-chemical water parameters: fish health, welfare, and plant requirements of the plants are directly affected by water quality parameters (nuwansi et al., 2021). both the dissolved oxygen and the temperature were fluctuating during the months of experiment. the dissolved oxygen was higher in the first treatment with the mint (8.16 mg/l) and it reached lowest in the third treatment with the tomato where it reached 3.49 mg/l and this may be due to the higher demand of tomato roots for oxygen. the temperature ranged between 20.7oc and 31.07oc. the range of ph was optimal during the months of experiment where it was between 6.38 and 7.29. nutrients: for the treatments with the mint, the concentrations of nitrate, sulfate, sodium, potassium, calcium, and magnesium were increasing during the three months, whereas the phosphate concentration decreased in the third month of sampling. the nitrate, calcium, and magnesium concentrations were increasing for the treatment with eggplant while the other nutrients showed some decrease in the third month. figure 16. dissolved oxygen (do) in fish tanks with different plants. figure 17. temperature in fish tanks with different plants. 87research paper al-khaziri, al-busaidi, al-ghatami, gallardo finally, the concentrations of nitrate, sodium, and potassium increased for the treatment with tomatoes, while phosphate showed some decrease in the concentration during the three months. the other micronutrients showed some decrease in the second month and increase in the third month of sampling. the decrease in the second month could be due to the increased uptake of the plants while the increase in the third month could be due to the accumulation of nutrients from the feeds. in the case of nitrates, the increase could be due to the increased conversion of ammonia to nitrite and then to nitrate by the nitrifying bacteria (somerville et al, 2014). although some of the nutrients can be toxic to the fish like nitrate, it is the most important nutrient that figure 18. ph in fish tanks with different plants. figure 19. concentrations of phosphate, nitrate and sulphate in fish tanks with different plants. 88 squ journal of agricultural and marine sciences, 2022, volume 27, issue 1 optimum stocking density of ‘koi’ carp (cyprinus carpio) in combination with different plant species in an aquaponic system can enhance plants productivity (nuwansi et al., 2021). conclusion in the first experiment using ‘koi’ fry with initial weight of 0.4-0.5 g stocked at 50, 100 and 150 fry per tank (i.e. 0.1 m3) with or without plants, the stocking density of 50 fish per tank with plants is considered the optimal density for ‘koi’ carp growth. mint grew better in combination with fish at 50 per tank while the number of petunia flowers varied. water quality was better at lower fish stocking density. in the second experiment using ‘koi’ juveniles with average initial body weight of 6 g stocked at 30 fish per tank, mint grew best compared to eggplant and tomato. growth and survival rates of ‘koi’ in combination with mint, eggplant and tomato were high. this research indicates that ‘koi’ carp can be successfully grown in combination with mint, petunia, eggplant and tomato in an aquaponic system. acknowledgements thanks to trc-furap for funding the research and to majed al alawi, mohamed al-wahaibi, mohammed al-qarni, ahmed al-azwani and ahmed al-souti for their help in conducting the experiment particularly during sampling and in feeding the fish. references hussain t, verma ak, tiwari vk, prakash c, rathore g, shete ap, nuwansi kk. (2014). optimizing ‘koi’ carp, cyprinus carpio var. ‘koi’ (linnaeus, 1758), stocking density and nutrient recycling with spinach in an aquaponic system. journal of the world aquaculture society 45(6): 652-661. jha p, barat s, sarkar k. (2007). comparative effect of live food and manured treatments on water quality and production of ornamental carp, cyprinus carpio var. ‘koi’ l., during winter, summer, monsoon and post-monsoon growout experiments in concrete tanks. journal of applied ichthyology 23(1): 87-92. karakatsouli n, papoutsoglou es, sotiropoulos n, mourtikas d, stigen-martinsen t, papoutsoglou se. (2010). effects of light spectrum, rearing density and light intensity on growth performance of scaled and mirror common carp cyprinus carpio reared under recirculating system conditions. aquacultural engineering 42(3): 121-127. kiss l, cook r, saenz g, cunnington j, takamatsu s, pascoe i, bardin m, nicot p, sato y, rossman a. (2001). identification of two powdery mildew fungi, oidium neolycopersici sp. nov. and o. lycopersici, infigure 20. concentrations of potassium, calcium, magnesium and sodium in fish tanks with different plants. 89research paper al-khaziri, al-busaidi, al-ghatami, gallardo fecting tomato in different parts of the world. mycology research 105(6): 684–697. knaus u, palm h. (2017). effects of the fish species choice on vegetables in aquaponics under spring-summer conditions in northern germany (mecklenburg western pomerania). aquaculture 473: 62-73. merino g, barange m, blanchard jl, harle j, holmes r, allen i, rodwell ld. (2012). can marine fisheries and aquaculture meet fish demand from a growing human population in a changing climate? global environmental change 22(4): 795-806. nuwansi kkt, verma ak, chandrakant mh, prabhath gpwa, peter rm. (2021). optimization of stocking density of koi carp (cyprinus carpio var. koi) with gotukola (centella asiatica) in an aquaponic system using phytoremediated aquaculture wastewater. aquaculture 532. prithwiraj j, sudip b. (2008). the effect of stocking density on growth, survival rate, and number of marketable fish produced of koi carps, cyprinus carpio vr. koi in concrete tanks. journal of applied aquaculture 17(3): 89-102, schmautz z, graber a, jaenicke s, goesmann a, junge r, smits th. (2017). microbial diversity in different compartments of an aquaponics system. archives of microbiology 199(4): 613-620. shete a, verma a, chadha nk, prakash c, chandrakant m, nuwansi kk. (2017). evaluation of different hydroponic media for mint (mentha arvensis) with common carp (cyprinus carpio) juveniles in an aquaponic system. aquaculture international 25(3): 1291-1301. somerville c, cohen m, pantanella e, stankus a, lovatelli a. (2014). small-scale aquaponic food production: integrated fish and plant farming. fao fisheries and aquaculture technical paper no. 589. rome, fao. 262 p. zutshi, b., singh, a., & dasgupta, p. (2020). impact of transient temperature disturbance on the oxidative stress indices and glucose levels of juvenile koi carps (c yprinus carpio var koi). the journal of basic and applied zoology, 81(1), 1-8. research paper journal of agricultural and marine sciences 2020, 25(2): 58–66 doi: 10.24200/jams.vol25iss2pp58-66 received 18 mar 2020 accepted 08 june 2020 antibacterial activity and chemical composition of crude extract and oil of zygophyllum (fagonia) luntii (baker) 1894 (family zygophyllaceae) riaz shah1*, suad j.a. alabri2, ameera s.m ashehi2, nasser s.s. asiyabi2, wafa k.a. almamari2, jamal n. alsabahi3 huda al-ruqaishi3 riaz shah1*( ) riazshah@squ.edu.om,1department of plant sciences, college of agricultural and marine sciences, sultan qaboos university, al-khoud-123, muscat, sultanate of oman. 2college of science, sultan qaboos university, al-khoud-123, muscat, sultanate of oman. 3central analytical laboratory, college of agricultural and marine sciences, sultan qaboos university, al-khoud-123, muscat, sultanate of oman. introduction around 80% of the world population use tradi-tional medicine which is often based on medici-nal plants (martins, 2013; oyebode et al., 2016). around 75% of commercial drugs launched in the world النشاط املضاد للبكترياي والرتكيب الكيميائي للمستخلص اخلام وزيت زيغوفيللوم )فاجونيا( لونيت )بيكر( 1894 )عائلة زيغوفيلالسي( رايض شاه 1* ، سعاد ج. العربية 2 ، أمرية س.م. الشحية 2 ، انصر س.س. السيايب 2 ، وفاء ك.أ. املعمرية 2 ، مجال ن. الصباحي 3 ، هدى خ. الرقيشية 3 abstract. wild plants such as zygophyllum luntii, from the zygophyllaceae family, have traditionally been used for medicinal purposes in oman. the present study investigated (i) the antibacterial activity of the crude extracts (leaves, stem and roots) and the oil (leaves); and (ii) the hydrocarbon contents and fatty acid methyl ester (fame) components from z. luntii. these extracts were tested against escherichia coli, staphylococcus aureus, and pseudomonas aeruginosa using well diffusion assays utilizing muller hinton agar (mha). antibacterial activity was observed with the z. luntii leaf extract and significant differences (f=14.06, df=2, p=0.002) were found among e. coli, p. aeruginosa and s. aureus. the highest inhibition was observed against p. aeruginosa, with an inhibition zone of 15.5 ± 2.6 mm, followed by e. coli and s. aureus with inhibition zones of 11.3 ± 1.5 mm and 3.5 ± 4.7 mm, respectively. the z. luntii extracts showed effectiveness within 50-60% against e. coli and p. aeruginosa as compared to ciprofloxacin. the hydrocarbon contents and the fame components of the extracts were determined with gas chromatography-mass spectrometry (gc-ms). a total of 20, 19, and 8 compounds were detected from leaf, stem, and root extracts, respectively. heneicosane, docosane, and tricosane were found in the highest concentration in the leaves, hop-22(29)-en-3.beta.-ol and β-sitosterol were found in the stems, and docosane and tricosane were found in the roots of z. luntii. nine types of fatty acids methyl esters were detected in the oil extracted from leaves with methyl esters of palmitic acid, linolenic acid, and oleic acid constituting 90% of the oil. this is the first report on antibacterial activity and chemical composition of z. luntii. keywords: zygophyllum luntii, antibacterial activity, gas chromatographymass spectrometry (gc-ms), fatty acid methyl ester (fame) zygophylاملســماة الســقطرية ، مــن عائلــة زيغوفيلالســي zygophyllum luntii املس��تخلص يتــم اســتخدام النبــااتت الربيــة مثــل زيغوفيللــوم لونــي: laceae بشــكل تقليــدي يف عمــان لألغــراض الطبيــة. حبثــت هــذه الدراســة عــن النشــاط املضــاد للبكتــرياي للمســتخلصات اخلــام مــن األوراق والســاق .z. luntii واجلذوروالزيــت املســتخلص مــن األوراق. مت الكشــف علــى مركبــات مــن اهليدروكربــوانت واألمحــاض الدهنيــة يف مســتخلص األوراق لنبتــة seudomonas aerugi� و staphylococcus aureus و escherichia coli مت اختبــار هــذه املســتخلصات ضــد بعــض األنــواع مــن البكتــرياي مثــل nosa بطريقــة فحوصــات االنتشــار اجليــد إبســتخدام أجــار مولــر هينتــون املناســب لنمــو هــذه األنــواع مــن البكتــرياي. لوحــظ نشــاط مضــاد للجراثيــم مــن p. فقد لوحظ أعلى تثبيط ضد . s. aureus و p. aeruginosa و e. coli ووجدت فروق ذات داللة إحصائية بني z. luntii مستخلصات نبات aeruginosa مع منطقة تثبيط 15.5 ± 2.6 مم ، تليها e. coli و s. aureus مع مناطق تثبيط 11.3 ± 1.5 مم و 3.5 ± 4.7 مم على التوايل. أظهــرت مســتخلصات z. luntii فعاليــة يف حــدود 50-60 ٪ ضــد e. coli و p. aeruginosa مقارنــة مــع النمــوذج التجــاري سيربوفلوكساســني. مت تعريــف مركبــات اهليدروكربــوانت واألمحــاض الدهنيــة يف املســتخلصات إبســتخدام جهــاز الفصــل الكروماتوجــرايف الغــازي املرتبــط مبستشــعر الطيــف الكتلــي (gc-ms) . مت الكشــف عــن ماجمموعــه 20 و 19 و 8 مــن املركبــات مــن مســتخلصات األوراق والســاق واجلــذور علــى التــوايل. مت العثــور .3-en)29( 22-hop علــى اهليدركربــوانت هينيكوســان و دوكوســان وتريكوســان كأعلــى تراكيــز للمركبــات يف األوراق ، ومت العثــور علــى مركــب beta.-ol ومركب بيتا سيستريول يف السيقان ، كما مت العثور على مركبات دوكوسان وتريكوسان يف اجلذور املوجودة يف z. luntii . مت الكشف عــن تســعة أنــواع مــن األمحــاض الدهنيــة يف الزيــت املســتخرج مــن األوراق مــع نســب عليــا جملمــوع تراكيــز محــض الباملتيــك ومحــض اللينولينيــك ومحــض األوليــك شــكلت مانســبته 90٪ مــن الزيــت. يعتــرب هــذا هــو التقريــر األول علــى مســتوى الدراســات البحثيــة عــن النشــاط املضــاد للبكتــرياي والرتكيــب .z. luntii الكيميائــي لـــنبات ، (gc-ms) لكلم��ات املفتاحي��ة: زيغوفيللــوم لونــي ، النشــاط املضــاد للبكتــرياي ، جهــاز الفصــل الكروماتوجــرايف الغــازي املرتبــط ابالطيــف الكتلــي (fame) إســرت امليثيــل الدهنيــة األمحــاض 59research paper shah, alabri, ashehi, asiyabi, almamari, alsabahi, al-ruqaishi global market yearly are extracted or isolated from natural resources and about 25% of the prescribed pharmaceutical drugs are based on plant chemicals (orhan, 2012). plants are the major source of secondary metabolites, which are used to treat various diseases (hossain et al., 2013; akhtar et al., 2017; raqiya and hossain, 2017; asma et al., 2017; hossain, 2018; said et al., 2018). medicinal plants are found in many places in the world; however, they are found more in tropical regions (alsalt, 2012). family zygophylllaceae includes many medicinally important plants spices including several species of zygophyllum. zygophyllum have antitumor, antioxidant and analgesic properties, and have been used for the treatments of cancer, fever, asthma, urinary discharges, toothache, stomach problems and kidney diseases (ahsan et al., 2007; satpute et al., 2009). zygophyllum species were found to be potent antifungal and antibacterial agents (zhang et al., 2008; gupta et al., 2009) and contained many biologically active chemical constituents, such as alkaloids, saponins, terpenoids, sterols, flavonoids, coumarins and trace elements (beier, 2005). zygophyllum luntii distribution is restricted to the horn of africa region, including djibouti, oman, somalia and yemen (beier, 2005). it grows on sand as well as gravel, from sea level up to 1950 m altitude. in oman, z. luntii is found in the foot of dhofar mountains along with several other species of zygophyllum (z. bruguieri, schweinfurtii, indica, mahrana and ovalifolia) (mosti, et al., 2012). the current study explored two objectives. firstly, antibacterial activity of the z. luntii extract (leaves, stems and roots) and leaf oil against escherichia coli, staphylo� coccus aureus and pseudomonas aeruginosa were investigated. secondly, hydrocarbon contents of the plant extracts and lipids fatty acid methyl ester were determined (fame) components of the oil extracted from leaves by gas chromatographymass spectrometer (gc-ms). materials and methods collection and preparation of plant materials roots, leaves, and stems of z. luntii were gathered from the botanical garden at sultan qaboos university, oman. these parts were cleaned with tap water followed by distilled water to remove any dust and soil. the plant parts were then further divided into two portions; one was dried in the oven at 70°c for 8 h and then ground into a fine powder and other portion was kept fresh in a refrigerator at 4°c. plant extracts preparation for anti-bacterial test the dried powder of the leaves, stem and roots was dissolved in 70% methanol (1:3, w/v) and then kept in a shaker for extraction at room temperature for 24 h. then, methanol was dissipated from the sample using oven to get the crude extract which was re-suspended in dimethylsulfoxide (dmso) for application in the antibacterial test. lipid extraction from leaves around 470g of the fresh leaves with 1 l of distilled water were grinded by a blender. the solution was mixed with the solvent (chloroform: methanol in 2:1 ratio) to separate the lipids and then evaporated in a rotary evaporator. the extract was filtered through charcoal. the obtained oil (1 g) was kept in storage at 4°c until utilization for further tests. anti-bacterial assay muller hinton agar cm0337 from oxiod (part of thermo fisher scientific) was used in well diffusion assay. mha contains beef dehydrated infusion 300.0 g/l, casein hydrolysate 17.5 g/l, starch 1.5 g/l and agar 17.0 g/l. amount of 38 g of mha was suspended in 1 l of distilled water, boiled and sterilized by autoclaving at 121°c for 15 min. three strains of pathogenic bacteria e. coli atcc 25922, p. aeruginosa atcc 27853, and s. aureus atcc 25923 were utilized as test microorganisms. these clinical isolates were obtained from microbiology laboratory at sultan qaboos university hospital. these strains are for antibiotic testing and fall under the american type collection culture (atcc). furthermore, these strains were sub cultured in liquid broth for a period of 6 to 8 hours. the well diffusion assay was conducted utilizing muller hinton agar (mha). the assay of leaves, stem and roots extract activity was carried out in nine mhas plates which were replicated three times. for every plate, four discs were used one each for leaves, stem, roots and an antibiotic standard (ciprofloxacin) as positive control. discs of 6 8 mm diameter were removed from agar with a sterile glass pasture pipette and filled with 30 μl of the sample extract or standard. at the same time, three mhas plates were used for oil using a similar procedure where three discs were used for every plate; two discs for oil and one disc for antibiotic standard. zone inhibition was investigated after incubating agar plates at 37°c. sample preparation and extraction for gc-ms analysis fresh leaf, stem and root samples were weighed and grinded using a mechanical grinder. then, 50 ml of 70% methanol was added to each grinded sample and placed in an ultrasonic water bath working at 50–60 khz with power of 350 w for 30 min at room temperature. by using a rotary vacuum evaporator, the methanol was evaporated and the extracts were concentrated. the crude extracts were dissolved in hexane, filtered by microfiltration (0.45 µl syringe) and injected to gc-ms. 60 squ journal of agricultural and marine sciences, 2020, volume 25, issue 2 antibacterial activity and chemical composition of crude extract and oil of zygophyllum (fagonia) luntii (baker) 1894 (family zygophyllaceae) perkin elmer clarus 600 gc system, fitted with a rtx5ms capillary column (30 m × 0.25 mm i.d. × 0.25 μm film thickness; maximum temperature, 350°c), coupled to a perkin elmer clarus 600c ms. ultra-high purigas chromatography-mass spectrometry (gc/ ms) analysis gc-ms conditions for samples extracted from leaves, stem and roots: gc-ms analysis was performed on a figure 1. comparison of anti-bacterial activity (inhibition zone in mm) among escherichia coli atcc 25922, staphylococ� cus aureus atcc 25923 and pseudomonas aeruginosa atcc 27853 in well diffusion assays exposed to zygophyllum luntii extracts and ciprofloxacin. bars designated by the same letters are not statistically significant at α0.05 figure 2. comparison of anti-bacterial activity (inhibition zone in mm) of the zygophyllum luntii extracts and ciprofloxacin against escherichia coli atcc 25922, pseudomonas aeruginosa atcc 27853 and staphylococcus aureus atcc 25923 well diffusion assays. bars designated by the same letters are not statistically significant at α0.05 61research paper shah, alabri, ashehi, asiyabi, almamari, alsabahi, al-ruqaishi ty helium (99.9999%) was used as carrier gas at a constant flow of 1.0 ml/min. the injector, transfer line and ion source temperatures were 280°c, 270°c and 270°c, respectively. the ionizing energy was 70 ev. electron multiplier (em) voltage was obtained from auto tune. all data were obtained by collecting the full-scan mass spectra within the scan range 40-550 amu. the injected sample volume was 1 μl with a split ratio of 10:1. the oven temperature program was 60°c at a rate of 80°c per minute to 280°c hold for 25 minutes. the total run time was 53.5 minutes. gc/ms conditions for the oil extracted from leaves: fatty acid methyl ester (fame) compounds were detected by the gc-ms equipment as mentioned above. the helium gas flow rate was 0.7 ml/min. the injector, transfer line and ion source temperatures were 250°c, 250°c and 220°c, respectively. the initial oven temperature was set at 50°c (holds for 8 minutes) and increased to 250°c in a rate of 40°c per minute. all data were obtained by collecting the full-scan mass spectra within the scan range 35-500 amu. the unknown compounds were identified by comparing the spectra obtained with mass spectrum libraries (nist 2011 v.2.3 and wiley, 9th edition). statistical analysis data on antibacterial assays from leaves, stems and roots, and the three bacterial strains were analysed separately using one-way analysis of variance (anova) in past (https://past.en.lo4d.com/windows). means were separated by dunn’s multiple comparison test and differences were considered significant at p<0.05. table 1. compounds identified in the leaf, stem and root extracts of zygophyllum luntii by gc-ms name of compound retention time (min) percent (%) leaves pentadecane 13.64 0.33 tetradecane, 2,6,10-trimethyl16.43 0.68 oxalic acid, allyl octyl ester 16.81 0.32 unidentified 17.02 0.61 octadecane 17.79 0.34 nonadecane 18.73 0.90 eicosane 19.02 5.84 heneicosane 21.57 12.30 docosane 22.60 12.72 tricosane 23.26 12.93 tetracosane 24.24 9.94 pentacosane 25.36 10.42 hexacosane 26.21 7.63 heptacosane 27.13 5.84 octacosane 27.87 5.82 nonacosane 28.70 5.03 triacontane 29.62 4.10 hentriacontane 30.71 1.84 dotriacontane 31.99 2.42 tetratriacontane 36.24 0.13 stem hexadecanal 18.33 2.60 phytol 21.50 5.22 unidentified 22.22 2.70 unidentified 23.20 0.38 unidentified 24.20 0.27 unidentified 25.18 0.47 heptacosane 26.90 0.35 octacosane 27.80 0.22 supraene 28.14 0.95 unidentified 28.60 0.46 triacontane 29.50 0.29 hentriacontane 30.64 0.38 vitamin e acetate 31.40 1.24 dotriacontane 31.93 0.64 name of compound retention time (min) percent (%) tritriacontane 33.40 1.23 β-sitosterol 34.36 11.02 heptatriacontane 35.40 0.80 hop-22(29)-en-3.beta.-ol 35.90 69.95 octatriacontane 37.70 0.84 roots docosane 22.60 14.04 tricosane 23.49 14.36 tetracosane 24.43 12.54 pentacosane 25.36 4.02 pentacosane 25.54 5.33 hexacosane 26.24 6.67 octacosane 27.13 43.05 tetratriacontane 36.24 1.15 62 squ journal of agricultural and marine sciences, 2020, volume 25, issue 2 antibacterial activity and chemical composition of crude extract and oil of zygophyllum (fagonia) luntii (baker) 1894 (family zygophyllaceae) result and discussion antibacterial assays significant antibacterial activity was observed in the z. luntii leaves extract and significant differences (f=14.06, df=2, p=0.002) were found among e. coli, p. aerugino� sa and s. aureus (figure 1). the highest inhibition was observed against p. aeruginosa (15.5 ± 2.64 mm) then e. coli (11.25 ± 1.50mm) and s. aureus (3.50±4.72 mm). the inhibition zones of the stem (f=2.03, df=2, p=0.187) and root (f=0.68, df=2, p=0.530) extracts did not differ significantly among the three bacterial strains. oil from leaves did not produce any inhibition in e. coli but had significantly higher inhibition (f=229.4, df=2, p<0.001) in p. aeruginosa (9.5±0.58mm) and s. aureus (6.75±0.96mm). ciprofloxacin had significantly different inhibition zones (f=73.3, df=2, p<0.001) among the three bacterial strains. the highest inhibition zone by the commercial antibiotic was against p. aeruginosa (30.75± 0.96 mm) then e. coli of (25.0± 0.82 mm) and lowest against s. aureus (19.50±1.91 mm). the inhibition in the stem, root and leaves extracts, and oil from leave was significantly lower than ciprofloxacin against e. coli (f=29.8, df=4, p<0.001), p. aerugi� nosa (f=11.7, df=4, p<0.001) and s. aureus (f=9.9, df=4, p<0.001) (figure 2). the stem extract was more active against p. aeruginosa while root extract was more active against s. aureus. leaves extract showed more activity against e. coli. the oil showed some antibacterial activity against p. aeruginosa and s. aureus but not e. coli. overall, the z. luntii extracts were active against both gram-positive (s. aureus) and gram-negative bacteria (e. coli and p. aeruginosa), though they were more active against the latter. the ethanol extracts of intact leaf of z. arabica showed an inhibition zone of only 6.08 mm against e. coli and did not inhibit the growth of s. aureus (alam et al., 2010). the ethanol whole plant extract of f. cretica produced inhibition zones of 15 mm, 15 mm and 14 mm against e. coli, p. aeruginosa and s. aureus, respectively (sajid et al., 2011) which are similar to our results. the crude extract of z. arabica from sinai showed broad antimicrobial spectrum against gram-positive, gram-negative, spore-forming and acid-fast bacteria (el-hefnawi, 1999). it is obvious that leaves extracts from zygophyllum spp including z. luntii have antibacterial properties. the percent effectiveness of the z. luntii extracts were compared to ciprofloxacin against e. coli, p. aeru� ginosa and s. aureus by subtracting the extract inhibition zone sizes from the ciprofloxacin (figure 3). the calculated percent effectiveness against e. coli was 47.0±4.8%; against p. aeruginosa was 57.1±8.1%; and against s. aureus was 19.4±24.2%. the percent effectiveness against e. coli and p. aeruginosa was significantly higher compared to s. aureus (f=10.54, df=2, p=0.005). alam et al. (2010) produced callus of z. arabica by tissue culture and found that the callus extract was more effective against serratia marcescens, e. coli and acetobacter aceti subsp. liquefaciens (inhibition zones = 32.67, 33.92 and 34.83 mm respectively) than the crude extract of the intact leaf (iz=6.08 mm) suggesting higher antibacterial effects of callus extract against gram – ve bacteria. several pathogens are increasingly developing resistance, particularly to broad-spectrum antibiotics (kunin, 1993). resistant e. coli isolates have been reported from humans using disk diffusion method against ciprofloxacin (22% with the highest of 52% reported from iran), cefotaxime (31.2%–58%) and ceftazidime (10%–57.4%) (pormohammad et al., 2019). some of the gram-positive drug resistant bacteria include s. aureus, streptococcus table 2. compounds detected in the oil extracted from zygo� phyllum luntii leaves by gc-ms name of compound retention time (min) percent (%) leaves caprylic acid methyl ester 11.58 0.12 capric acid methyl ester 18.27 0.19 lauric acid, methyl ester 24.29 0.74 myristic acid, methyl ester 29.83 0.81 palmitic acid, methyl ester 34.93 34.55 palmitoleic acid, methyl ester 35.90 1.70 oleic acid, methyl ester 39.78 23.99 linoleic acid, methyl ester 40.57 5.81 linolenic acid, methyl ester 41.73 32.09 figure 3. percent effectiveness of the zygophyllum luntii extracts compared to ciprofloxacin against escherichia coli atcc 25922, staphylococcus aureus atcc 25923 and pseudomonas aeruginosa atcc 27853, and s. aureus well diffusion assays. bars designated by the same letters are not statistically significant at α0.05 63research paper shah, alabri, ashehi, asiyabi, almamari, alsabahi, al-ruqaishi figure 4. chromatogram of compounds in leaves (a), stem (b) and roots (c), and fatty acids methyl esters (fame) in oil (d) extracted from zygophyllum luntii leaves detected by gc/ms. 64 squ journal of agricultural and marine sciences, 2020, volume 25, issue 2 antibacterial activity and chemical composition of crude extract and oil of zygophyllum (fagonia) luntii (baker) 1894 (family zygophyllaceae) pneumoniae, and enterococcus spp., and the gram-negative drug resistant bacteria acinetobacter baumannii, klebsiella pneumoniae, e. coli, and p. aeruginosa (lister et al., 2009). our results also indicated reduced sensitivity of s. aureus and e. coli to ciprofloxacin. the z. luntii callus extract may help in managing antibacterial resistant pathogens of different strains gas chromatography-mass spectrometry (gc/ ms) analysis higher number of compounds was identified in the leaves (n=20) and stem (n=19) extract compared to roots (n=8) extracts of z. luntii while 6 compounds could not be identified (table 1). the retention time (rt) of all compounds varied between 13.64 to 37.7 minutes. the unidentified compounds were present in a relatively low amount. heneicosane, docosane and tricosane were present in higher quantities in the leaves extract. hop22(29)-en-3.beta.-ol (69.95%) was present in higher quantities in the stem extract while the root extract had octacosane in high quantities. palmitic acid, linolenic acid and oleic acid were the main components of oil extracted from leaves (table 2). heptacosane, heneicosane, tetradecane have been reported with antimicrobial activity (elshiekh and abdelmageed, 2015). beta-acids are an important component of hops (humulus lupulus l. family cannabaceae) soft resins and usually isolated as by-products during hop processing (mccallum et al., 2019). hexahydro-β acids showed strong antibacterial activity and good stability (liu et al., 2019). noticeably, hop-22(29)-en-3. beta.-ol had the highest percentage compared to other compounds. close retention time of 22-27 minutes in roots compounds showed their similar affinity to stationary phase. both retention time and peak area (%) for docosane (c22) and tricosane (c23) (22.60 minutes and 23.26 minutes, and 12.72% and 12.93%, respectively) did not show wide variation. these two compounds were present in leaves and roots but not in stems. the n-alkane fractions (hydrocarbons c22-c35) was detected in the leaves extract of z. luntii which have been detected in vegetable oils by gc/ms (troya et al., 2015). these compounds are more common in plant extracts. species of zygophyllum have been found to contain saponins (abdel-khalik et al., 2001), alkaloids (sharawy and alshammari, 2009), terpenoids (perroni et al., 2007), sterols (shoeb et al., 1994), flavonoids (ibrahim et al., 2008), proteins and amino acids (sharma et al., 2010), coumarins (alam et al., 2010) and trace elements (fatima et al., 1999). the presence of such chemical ingredients in zygophyllum spp. would contribute to the medical properties, including stimulating the immune system in humans, treating and preventing the development of chronic diseases (beier, 2005), and the vitality to resist such types of pathogenic bacteria used in this study. oil extract from leaves nine different types of fatty acids methyl esters (fame) were found in oil extracted from z. luntii leaves. palmitic acid, linolenic acid, and oleic acid were the main compounds and represented 90% of the oil (fig.4). there was no study found on z. luntii that explored the fatty acid content. however, seven fatty acids including the oleic acid, palmitic acid and linoleic acid were found in other zygophyllum species e.g. f. arabica l (alam et al., 2010) and f. cretica (soad, 1994). conclusion extracts from leaves, stem, and roots of z. luntii had significant antibacterial activity against e. coli, p. aerugino� sa and s. aureus. the extracted oils had activity against only p. aeruginosa and s. aureus. the commercial antibiotic ciprofloxacin had reduced activity against s. aureus and e. coli. the z. luntii extracts showed about 50-60% effectiveness against e. coli and p. aeruginosa compared to ciprofloxacin. hop-22(29)-en-3. beta.-ol, hexahydro-β acids, and fame compounds could 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(2015). classification of vegetable oils according to their botanical origin using n-alkane profiles established by gc–ms. food chemistry 167: 36–39. zhang w, krohn k, draeger s, schulz b. (2008). bioactive isocoumarins isolated from the endophytic fungus microdochium bolleyi. journal of natural products 71(6): 1078-1081. research paper journal of agricultural and marine sciences vol. 22 (1): 36-41 doi: 10.24200/jams.vol22iss1pp36-41 reveived 10 jun 2016 accepted 15 nov 2016 computer vision technique to classify dates based on hardness naeema h. al-shekaili1, annamalai manickavasagan2*, nawal k. al-mezeini2, m. shafiur. rahman1 and negib. guizani1 2*annamalai manickavasagan ( ) sultan qaboos university, college of agricultural and marine sciences, department of soils, water and agricultural engineering. box 34, al-khod 123. sultanate of oman. current email: mannamal@uoguelph.ca. 1 sultan qaboos university, college of agricultural and marine sciences, department of food science and nutrition. introduction date palm (phoenix dactylifera, l.) is one of the oldest and most important staple crops in the middle east and north africa. the sultanate of oman is ranked among the top ten date producing countries in the world with approximately 49% of cultivable land area (fao 2010). although date production was 276,400 mt in 2010 (fao, 2010), only about 5,000 tons was exported (zaabanot, 2011). the low level of export from oman is due to improper sorting of dates to ensure higher quality as expected by consumers (al-marshudi, 2002). according to the codex standard, the quality attributes to grade dates are colour, flavor (sugar level), moisture content and absence of defects, such as insect damage, and surface damage (kader and hussein, 2009). moisture content in dates is important because excessive loss of water causes drying, consequently they becomes hard (kader and hussein, 2009; rahman and al-farsi, 2005). hardness beyond a critical value is considered as a defect in dates as it affects the physical properties and consumer acceptability. dates can be subdivided into: soft, semi-dry (semi-hard) and dry (hard) according to their moisture content or hardness (kader and hussein, 2009; al-janobi, 1998). hard dates are chewy and tough with strong curvy and zigzag textured skin (rahman and al-farsi, 2005). dates are processed into different products and the choice of the date types for a given product depends on the final product. for example, soft dates are used to manufacture date syrاستخدام تقنية تصوير احلاسوب يف تصنيف التمور حسب الصالبة نعيمة حارب الشكيلي1 ومنيكافا سجان أنامايل2* ونوال مخيس املزيين2 وحممد شفري رمحان1 وجنيب قيزاين1 abstract. hardness is one of the important attributes in determining the quality of dried fruits. hardness assessment is normally carried out by manual inspection. this method is time consuming, laborious, expensive and subjective. the objective of this study was to develop a computer vision system with a monochrome camera to classify dates based on hardness. date samples were obtained from three different growing regions in oman and graded into soft, semi-hard, and hard classes based on hardness. a total of 1800 date samples were imaged individually using a monochrome camera (600 dates / class). histogram and texture features were extracted from the acquired monochrome images and used in the classification models. the overall classification accuracies in three class model (soft, semi-hard, and hard) were 66% and 71% for linear discriminant analysis (lda) and artificial neural network (ann), respectively. it was improved to 84% and 77% in lda and ann, respectively while using two class model (soft and hard (semi-hard and hard together)). the histogram features were more contributing in the date classification based on hardness than image texture features. computer vision technique has great potential to develop online quality monitoring systems for dates and other dried fruits. keywords: dates; hardness; histogram features; texture features; gray scale images امللخــص: تعتــر الصالبــة مــن أهــم اخلصائــص يف تقييــم جــودة الفواكــة اجلافــة. ويتــم تقييــم الصالبــة عــادة عــن طريــق التفتيــش اليــدوي، إال أن هــذه الطريقــة تتطلــب اجلهــد والوقــت الطويــل، كمــا أهنــا باهضــة وغــري موضوعيــة. هتــدف هــذه الدراســة إىل تطويــر أســلوب التصويــر باســتعمال احلاســوب متصــال بكامــريا تصويــر أحاديــة اللــون هبــدف تصنيــف التمــور اعتمــاداً علــى الصالبــة. وقــد مت احلصــول علــى عينــات التمــور مــن 3 مناطــق خمتلفــة بســلطنة عمــان وصنفــت هــذه التمــور إىل 3 فئــات: لينــة، شــبه صلبــه، وصلبــه. حيــث مت تصويــر جممــوع 1800 عينــة )600 عينــة لــكل فئــة( باســتعمال كامــريا التصويــر أحاديــة اللــون. وقــد مت اســتخراج مالمــح قــوام التمــور مــن الرســم البيــاين واســتخدمت كنمــوذج تصنيــف. وقــد حققــت إمجــال تصنيــف التمــور باســتعمال منــوذج الثــالث فئــات )اللينــة، شــبه صلبــه، وصلبــه( دقــة تقــدر بـــ66% و 79% عنــد اســتعمال طريقــة التحليــل اخلطــي التمييــزي )lda( و طريقــة التحليــل اخلطــي املتــدرج )ann( علــى التــوايل. كمــا حققــت النتائــج نســب دقــة أعلــى عنــد اســتعمال منــوذج الفئتــن )فئــة لينــة، وفئــة شــبه صلبــه، وصلبــه معــا( تقــدر بـــ 84% و 77% بطريقــة )lda( و)ann( علــى التــوايل. وقــد كانــت مســامهة مالمــح الرســم البيــاين أوضــح مــن مالمــح القــوام يف تصنيــف التمــور. ميتلــك التصويــر باســتعمال احلاســوب قــدرات عاليــة ميكــن اســتخدامها لتطويــر أنظمــة مراقبــة جــودة التمــور والفواكــة اجلافــة األخــرى عــر األنرتنــت. الكلمات املفتاحية: التمور ، الصالبة ، مالمح الرسم البياين ، مالمح القوام ، صور املقياس الرمادي 37research article al-shekaili, manickavasagan, al-mezeini, rahman, guizani up while hard dates are used to produce flour. therefore hardness is one of the important parameters used to evaluate and classify dates in industry. the presence of hard dates in other grades affects the acceptability of the whole batch and yields low values in domestic and international markets. in general, hardness assessment is carried out by the traditional method of visual inspection or mechanical methods like diagonal metal plate method or vacuum systems (huxsoll and reznik, 1969; chesson et al., 1979; al-janobi, 2000). the visual inspection method is subjective, laborious and expensive, whereas mechanical methods are sample-destructive nature and conducted only on representative samples. an objective non-destructive method for sorting of dates based on hardness would be highly beneficial for online quality assessment and monitoring of dates in handling facilities. therefore the objective of this study was to determine the ability of a computer vision system with a monochrome camera to classify dates based on hardness. the monochrome camera was selected because of its low cost, image size and faster image handling and processing capabilities. computer based image processing techniques or computer vision technologies replace the traditional method of human inspection towards achieving better, faster, and automated operations (patel et al., 2012; pour-damanab et al., 2012). it gives a meaningful description for the object by duplicating human vision using different algorithms to assess the quality (narendra and hareesh, 2010). it is used to characterize colour, texture and complex geometric properties (chandraratne et al., 2003). computer vision is used in food industry for the classification, quality evaluation, sorting, grading, and defect detection (du and sun, 2006; brosnan and sun, 2004). the application of computer vision in the date industry is scarce (lee et al., 2008a). schmilovitch et al. (1999) developed a semi-automated vision system for maturity determination of fresh dates using nir scanner. al-janobi (2000) graded saudi dates (sifri variety) based on colour and texture with an average error of 1.8% using a colour camera. a computer vision system for the grading of dates based on fruit size and skin delamination using reflected nir imaging showed 10% higher accuracy over human inspection and a reduction in labor cost by 75% (lee et al., 2008b). in another study, using a rgb colour imaging system to grade dates into 3 categories based on size, shape, flabbiness intensity and defects yielded 80% accuracy (al-ohali, 2011). materials and methods sample collection samples of dates of the fard variety, the most processed variety in oman, were obtained from three major dates growing regions: al-batinah, al-dakhliah and al-sharqiah. the dates were sorted into three classes based on hardness (hard, semi-hard and soft) by an experienced grader and confirmed by a manager in bright sun dates company, oman. from each region, a representative sample of 600 dates (200 per class), in total 1800 samples, were selected and used in this study. image acquisition system a monochrome camera (model: xcd-x700, sony, japan) was used to acquire uncompressed 8-bit images of resolution 1024×768 pixels with a charge coupled device (ccd) sensor. it was placed at a height of 1 m in order to simulate the application in handling facilities. images were taken in a dark room while illuminating the sample with two fluorescent lights (36 w, model: dulux l, osram, italy). the camera was connected to the computer through ieee 1394 cable. the camera was calibrated using white and black standard colour cards (digital kard xl, dgk colour tools, usa) before starting each batch of imaging. image analysis and classification model the region occupied by date sample in the monochrome image was segmented from the background using matlab (version 7.6.0) (fig. 1). histogram and texture features of the grayscale information for the region pertaining to date sample were extracted and analyzed statistically (at α ≤ 0.05). the details of the extracted features are given in table 1. the classification accuracy of a linear discriminant analysis (lda) and stepwise linear discriminant analysis (slda) was performed with spss software. similarly the accuracy of a back propagation neural network (bpnn) was obtained using matlab. discussion although date samples used in this study belonged to the same variety, regional differences existed in their figure 1. process involved in the segmentation of dates from the background from left to right (a) original monochrome image (b) adjusted monochrome image (c) binary image (d) binary image after the morphological operations to reduce noise (e) segmented date. 38 squ journal of agricultural and marine sciences, 2017, volume 22, issue 1 computer vision technique to classify dates based on hardness external properties such as colour, shape and size. in general, hard dates were brighter in colour compared to soft and semi-hard dates. however, there were several overlaps in gray scale values across different classes and regions and interfered in the classification. features extracted from monochrome images histogram features the histogram features of the date samples from different regions are shown in table 2. there was a difference between soft, semi-hard and hard dates in the mean gray value. the maximum and minimum mean gray values were associated with hard and soft dates, respectively. this indicated that the hard dates were brighter in colour compared to the soft and semi hard dates. there was no difference in the mean gray value of the dates from the al-dakhliah and al-batinah regions. standard deviation and variance of the soft, semi-hard and hard dates varied significantly. it was the highest for soft dates and the lowest for hard dates. there was no difference in the standard deviation and variance of the dates from al-batinah and al-sharqiah regions. the smoothness was different between the three classes of dates with maximum and minimum values for soft and hard dates, respectively. however, there was no difference in smoothness between dates from the al-sharqiah and al-dakhliah regions. there was a difference in eccentricity between three classes with hard dates having the highest values and soft dates the lowest values. the eccentricity of the dates was not different between the al-batinah and al-sharqiah regions. the growing regions produced differences in solidity of date samples. the extent of three classes of dates was significantly different. the highest and lowest value was obtained for hard and soft dates, respectively. table 1. features extracted from monochrome images. features definition* histogram features mean gray value average of the gray values of all the pixels in an image standard deviation standard deviation of all the pixels in an image variance variance of all the pixels in an image smoothness measure of the relative smoothness of the intensity in a region eccentricity ratio of distance between the foci of the ellipse and its major axis length solidity proportion of the pixels in the convex hull that are in a region extent proportion of the pixels in the bounding box that is in the region texture features (glcm**) contrast measure of contrast between a pixel and its neighbor over the whole image correlation measure of how correlated a pixel is to its neighbor over the whole image energy sum of squared elements in the glcm homogeneity similarities of pixels maximum probability maximum occurrence of the gray level entropy measure of the randomness of intensity image cluster prominence measure of the skewness of a matrix cluster shade measure of the lake of symmetry dissimilarity measure of the dissimilarity between the pixels * manickavasagan et al. (2008a,b); basavaraj and vishwanath (2009); gonzalez et al. (2010) ** gray level co-occurrence matrix table 2. mean values of histogram features extracted from monochrome images of dates (n=200). feature region al-batinah al-dakhliah al-sharqiah soft semihard hard soft semihard hard soft semihard hard mean gray value 45.69 48.34 57.16 45.88 49.03 56.38 47.50 53.84 61.91 standard deviation 39.26 37.34 33.44 36.07 35.08 33.98 39.62 36.22 32.90 smoothness 0.9993 0.9992 0.9990 0.9992 0.9991 0.9990 0.9993 0.9992 0.9989 eccentricity 0.7754 0.7820 0.7958 0.7950 0.8127 0.8089 0.7633 0.7861 0.7959 solidity 0.9867 0.9871 0.9866 0.9862 0.9861 0.9864 0.9848 0.9861 0.9861 extent 0.7996 0.8047 0.8124 0.8096 0.8134 0.8164 0.7959 0.8048 0.8160 39research article al-shekaili, manickavasagan, al-mezeini, rahman, guizani texture features the values of texture features for dates are given in table  3. the soft dates had more contrast than the semihard and hard dates. however, there was no difference in the contrast of semi-hard and hard dates. it was maximum for al-batinah and minimum for al-sharqiah regions. the correlation of dates varied significantly with respect to classes and regions. there was no difference in the energy between the three classes. however, there was a difference in the energy between the three regions. the homogeneity of date samples from three regions was different with maximum and minimum values for al-sharqiah and al-batinah regions, respectively. however, the homogeneity of hard and semi-hard dates was not different. there was no difference in the maximum probability between three classes of dates. on the other hand, the maximum probability between the three regions was significantly different. the al-sharqiah region had the highest and al-dakhliah had the lowest probability. the entropy, cluster prominence and cluster shade of the date samples from three regions were different. the al-dakhliah region had the highest entropy, cluster prominence and cluster shaded while al-sharqiah had the lowest values. however, there was no difference in the entropy, cluster prominence and cluster shaded between the three classes of dates. the soft dates were more dissimilar in comparison to semi hard and hard dates. but there was no difference in the dissimilarity of semi-hard and hard dates. table 3. mean values of texture features extracted from monochrome images (n=200). feature region al-batinah al-dakhliah al-sharqiah soft semihard hard soft semihard hard soft semihard hard contrast 0.0246 0.0241 0.0232 0.0235 0.0230 0.0240 0.0222 0.0221 0.0215 correlation 0.9956 0.9956 0.9956 0.9956 0.9957 0.9958 0.9951 0.9953 0.9953 energy 0.8839 0.8859 0.8893 0.8876 0.8876 0.8789 0.9060 0.9017 0.9038 homogeneity 0.9995 0.9995 0.9995 0.9995 0.9995 0.9995 0.9996 0.9996 0.9996 maximum probability 0.9381 0.9392 0.9411 0.9402 0.9402 0.9352 0.9505 0.9482 0.9493 entropy 0.2349 0.2317 0.2262 0.2291 0.2291 0.2424 0.1992 0.2063 0.2027 cluster prominence 1824.32 1798.46 1754.3 1779.45 1779.99 1883.85 1532.95 1592.93 1562.43 cluster shade 138.34 136.25 132.71 134.66 134.70 143.259 114.96 119.70 117.34 dissimilarity 0.00351 0.00344 0.00331 0.003367 0.0032 0.00343 0.00318 0.00316 0.00307 table 4. classification accuracy (%) of date samples in three and two class models. region lda* slda** selected features for slda three-class model al-batinah 59 58 mean gray value, variance and extent al-dakhliah 67 66 mean gray value, eccentricity, smoothness, cluster prominence and maximum probability al-sharqiah 76 75 mean gray value, variance, extent, correlation and smoothness all regions together 66 66 mean gray value, standard deviation, variance, extent, correlation, smoothness, dissimilarity and maximum probability two-class model al-batinah 83 83 mean gray value, variance and extent al-dakhliah 87 87 mean gray value, variance, solidity, extent , smoothness, cluster prominence and maximum probability al-sharqiah 86 85 mean gray value, standard deviation and extent all regions together 83 84 mean gray value, standard deviation, solidity, extent, smoothness, entropy, maximum probability * all sixteen features were used in the linear discriminant analysis (lda) ** most contributing features were used in the stepwise linear discriminant analysis (slda) 40 squ journal of agricultural and marine sciences, 2017, volume 22, issue 1 computer vision technique to classify dates based on hardness classification models linear discriminant analysis (lda) the features extracted from the monochrome images were used to determine the efficiency of this technique in sorting of dates based on hardness. in the first approach, the date samples were classified into three groups namely soft, semi-hard and hard (three class model). in some applications, dates are graded into only two categories such as soft and hard. therefore in the second approach, the date samples were classified into two groups namely soft and hard (semi hard and hard together) (two class model). analyses were also performed by considering each region separately and combined together. table 4 shows the accuracies obtained in different approaches. in three class models, it was in the range of 58% to 76%. the highest and lowest classification accuracies were obtained for the al-sharqiah and the al-batinah regions, respectively. while analyzing all regions together, there was no difference between lda and stepwise linear discriminant analysis (slda) with most contributing factors. the slda selected mostly histogram features for the classification. this indicates that histogram features are more contributing than the texture features in the classification of dates based on hardness. similarly, basavaraj and vishwanath (2009) reported that texture features including contrast, correlation, energy, entropy, homogeneity and dissimilarity were not sufficient for the classification of bulk sugary foods. on the other hand, chandraratne (2003) reported that image texture features were suitable indicators for beef tenderness because the r2 value was 0.621 while using geometrical features and 0.746 with texture features. also, li et al. (1999) and li et al. (2001) mentioned the same about the importance of texture features in classification of beef tenderness. in two class models, the classification accuracy was 83% to 87%. the highest classification in this approach was achieved for al-sharqiah region. zayas et al. (1996) obtained 63% accuracy for hard wheat and 91% accuracy for soft wheat in two class model, using monochrome images. li et al. (2001) classified the steaks using colour camera into rough and tender with an accuracy of 83%. artificial neural network (ann) the classification accuracies of ann for three class model are shown in table 5. the misclassification was observed between the soft and semi-hard and hard and semi hard dates. the overall accuracy obtained was 71%. fadel (2007) used colour camera and obtained a classification accuracy of 100%, 80%, 80%, 60% and 80% for fard, khalas, lolo, bomaan and berhi dates varieties, respectively using probabilistic neural network. while grading the dates into three grades according to size, shape, flabbiness intensity, and defects using rgb images, al-ohali (2011) obtained 55% to 80% classification accuracy. in two class model, the classification accuracy of the hard dates was higher than soft dates (table 6). the overall accuracy in the two class model was 77%. conclusion a computer vision system with monochrome camera was developed to classify dates based on hardness with varying degree of success. the classification was carried out with histogram and texture features extracted from the monochrome images of dates using lda and ann. the classification accuracies of two class models were higher than three class models in both lda and ann. in slda, histogram features contributed more for classification than texture features. the potential of computer vision technique for hardness determination in dates must be investigated with other cameras such as nir and rgb colour cameras to improve classification accuracy. acknowledgements the authors would like to acknowledge the research council (trc) in sultanate of oman for funding this work under the project “development of computer vision technology (cv) for the quality assessment of dates in oman”. references al-janobi, a. 1998. application of co-occurrence matrix method in grading date fruits. paper no. 98 – 3024. asae meeting presentation, king saud university. al-janobi, a. 2000. date inspection by color machine vision. journal of king saud university of agricultural science 12: 69 – 79. al-marshudi, a.s. 2002. oman traditional date palms: production and improvement of date palms in oman. tropicultura 20: 203 – 209. al-ohali, y. 2011. computer vision based date fruit table 5. accuracies (%) of ann to classify dates according to hardness in the 3-class model. from / to soft semi-hard hard soft 76 22 2 semi-hard 17 68 15 hard 5 25 70 table 6. accuracies (%) of ann to classify dates according to hardness in the 2-class model. from / to soft hard soft 69 31 hard 16 84 41research article al-shekaili, manickavasagan, al-mezeini, rahman, guizani grading system: design and implementation. journal of king saud university, computer and information sciences 23: 29 36. basavaraj, s.a. and vishwanath, c. b. 2009. texture based identification and classification of bulk sugary food objects. icgst-gvip j 9: 9-14. brosnan, t. and sun, d. 2004. improving quality inspection of food products by computer vision-a review. journal of food engineering 61: 3-16. chandraratne, m.r., samarasinghe, s., kulasiri, d., frampton, c., bekhit, a.e.d. and bickerstaffe, r. 2003. prediction of lamb tenderness using texture features. research report, lincoln university, issn 1174 6696. chesson, j.h., burkner, p.f. and perkins, r.m. 1979. an experimental vacuum separator for dates. transactions of asae, 22: 16 20. du, c. and sun, d. 2006. learning techniques used in computer vision for food quality evaluation: a review. journal of food engineering 72: 93 55. fadel, m. 2007. date fruits classification using probabilities neural networks. agricultural engineering international: the cigr journal (cigr commission internationale du genie rural j). manuscript id 07 003. ix: 1-10. fao. 2010. http://faostat.fao.org/site/339/default.aspx. access done on 14th january 2013. gonzalez, r.c., wood, r.e. and eddins, s.l. 2011. digital image processing using matlab. new delhi: tata mcgraw hill education private limited. huxsoll, c.c. and reznik, d. 1969. sorting and processing mechanically harvested dates. date grower’s institute report 46: 8 10. kader, a. and hussein, m. 2009. harvest and postharvest handling of dates. project on the development of sustainable dates palm production system in the gcc countries of arabian peninsula. international center for agricultural research in the dry areas. lee, d., archibald, j. , chang, y. and gerco, r. 2008a. robust color space conversion and color distribution analysis technique for date maturity evaluation. journal of food engineering 88: 364 372. lee, d., schoenberger, r., archibald, j. and mccollum, s. 2008b. development of a machine system for automatic date grading using digital reflective near-infrared imaging. journal of food engineering: 388 398. li, j., tan,j., martz, f.a. and heymann, h. 1999. image texture feature as indicators of beef tenderness. meat science 53, 17 22. li, j., j. tan and p. shatadal. 2001. classification of tough and tender beef by image texture analysis. meat science 57: 341 346. manickavasagan, a., sathya, g. and jayas,d.s. 2008a. comparison of illumination to identify wheat classes using monochrome images. computer and electronics in agriculture 63: 237-244. manickavasagan, a., sathya, g., jayas, d.s. and white, n.d.g. 2008b. wheat class identification using monochrome images. journal of cereal science 47: 518-527. narendra, v.g. and hareesh, k.s. 2010. quality inspection and grading of agricultural and food products by computer vision – a review. international journal of computer application 2: 43-65. patel, k.k., kar, a., jha, s.n. and khan, m.a. 2012. machine vision system: a tool for quality inspection of food and agricultural products. journal of food science and technology 49: 123-141. pour-damanab, a.s., jafary, a. and rafiee, s. 2012. kinetics of the crust thickness development of bread during baking. journal of food science and technology, doi: 10.1007/s13197-012-0872-z. rahman, m.s. and al-farsi, s. 2005. instrumental texture profile analysis (tpa) of date flesh as function of moisture content. journal of food engineering 66: 505 511. schmilovitch, z., hoffman, a., egozi, h., ben-zvi, r., bernstin ,z. and alchanatis,v. 1999. maturity determination of fresh dates by near infrared spectrometry. journal of the science of food and agriculture 79: 86 90. zaabanot, a. 2011. improve date syrup production in oman – case study. published in oman daily, saturday 8th october, edition no11085: 22. zayas, i.y., martin, c.r., steele, j.l. and katsevich, a. 1996. wheat classification using image analysis and crush-force parameters. transactions of the asae, 39: 2199 2204. technical notes journal of agricultural and marine sciences 2021, 26(1): 57–61 doi: 10.24200/jams.vol26iss1pp57-61 reveived 14 oct 2020 accepted 05 dec 2020 correlation between sensory and instrumental textural attributes of date palm (phoenix dactylifera l.) fruits: technical note vandita singh1,*, mohammad shafiur rahman2, nejib guizani2, hakikulla shah3 vandita singh1,*( ) vandita31@gmail.com, 1department of food science and human nutrition, college of applied and health sciences, a’sharqiyah universit y, p. o. box 42, ibra, oman,2department of food science and nutrition, college of agricultural and marine sciences, sultan qaboos universit y, muscat, oman, 3department of biological science and chemistry, college of arts and sciences, universit y of nizwa, post box 33, pc 616, nizwa, oman, introduction texture, defined as the sensory manifestation of food structure and the way this structure reacts to the forces applied and it represents the junction of all the mechanical, geometric, and superficial attributes of a product, sensed through mechanical, tactile, visual, and hearing receptors (rahman, 2009; rahman et al., 2020). assessment of textural attributes by either instrumental method (i.e. textural profile analysis, tpa) and or by sensory methods is of great interest in food technology (rahman, 2019). the correlation obtained between sensory and instrumental texture measurements could be used to assess quality control parameters, consumers liking and their overall acceptability for product development or improvement, and it is also useful to improve the instrumental method for better pairing with sensory results (aguirre et al., 2018; kurotobi et al., 2018). date fruits (dfs) are popular staple food in the middle east as well as, source of income for many families. the dfs are commercially important and sold as fresh (i.e. rutab) and dried (i.e. tamar) (chandrasekaran and bahkali, 2013). hence, there is a great amount of research in the field of df including their phytochemical contents (al-hinai et al., 2013; essa et al., 2019; hossain et al., 2014; singh et al., 2013; singh et al., 2012). the growing food industry is also utilizing the dfs to produce variety of products (e.g. biscuits, flavored dairy products, and chocolate). texture is a critical property of the fruit that can dominate quality of the product. in the past decade few studies have focused on the instrumental texture of the df (al-hinai et al. 2013). the growing date industries demands for assessing the sensory analysis of date fruits. the fruits quality is assessed based on texture, flavor, color, and nutritional properties (ismail et al., 2008).the sensory textural characteristics are recognized as critically important factors of food choice (grunert, 2015; االرتباط بني السمات املقيمة حسيا و ابألجهزة لفاكهة شجرة النخيل )التمر( (.phoenix dactylifera l): مالحظة فنية فانديتا سينغ1 ، * ، حممد شفيور الرمحن2 ، جنيب غيزاين2 ، حقيق هللا شاه3 abstract. food industries are constantly looking for optimum instrumental methods that can consistently estimate sensory textural qualities of food products. monitoring texture using instrumental methods is cheaper over time than maintaining a sensory quality panel. however, a good correlation between sensory and instrumental textural attributes is highly needed. in the present research, we aimed to report the correlation between instrumental and sensory textural attributes of date fruit varieties. specifically, instrumental texture profile analysis(tpa) and sensory textural attributes were correlated. we found significant correlations between sensory and instrumental tpa attributes of date fruit varieties and this suggests a great promise for developing quality control. keywords: date fruits, sensory analysis, instrumental texture, phoenix dactylifera, correlation املســتخلص:تبحث الصناعــات الغذائيــة ابســتمرار عــن األســاليب اآلليــة املثلــى اللــي متكنهــا مــن تقديــر جــودة صفــات الرتكيــب النســيجي احلســي للمنتجــات الغذائيــة. تعــد متابعــة النســيج ابســتخدام األجهــزة أرخــص مــع مــرور الوقــت مــن احلفــاظ علــى لوحــة ملقيمــي اجلــودة احلســية. ومــع ذلــك، مــن الضــرورة أن يوجــد ارتبــاط وعالقــة جيــدة بــن الســمات احملــددة حســيا و تلــك احملــددة ابألجهــزة. هدفنــا يف البحــث احلــايل هــو حتديــد االرتبــاط بــن الســمات املقيمــة حســيا و ابألجهــزة لنســيج أصنــاف مــن فاكهــة التمــر. و ابلتحديــد، كان هنــاك ارتبــاط بــن الســمات احملــددة حســيا و ابســتخدام اجلهــاز املخصــص لتحليــل النســيج )tpa( لفاكهــة التمــر و قــد كان هــذا االرتبــاط ذو أمهيــة إحصائيــة؛ ممــا يعــي أن هنــاك إمكانيــة لتطويــر مراقبــة اجلــودة ابســتخدام األجهــزة. الكلمات املفتاحية: مثار التمر، التحليل احلسي، النسيج اآليل، فينيكس داكتيليفريا (phoenix dactylifera)، االرتباط 58 squ journal of agricultural and marine sciences, 2021, volume 26, issue 1 correlation between sensory and instrumental textural attributes of date palm (phoenix dactylifera l.) fruits: technical note rahman, 2019). generally, sensory methods are more useful in developing new products and defining product standards in comparison with instrumental method (i.e. tpa). although sensory analysis (i.e. descriptive method) require a panel training and maintenance, however, it is not only time-consuming and expensive, but also demands proper reference standards for calibration (joyner, 2018). hence, attempt have been made to establish the relationship or predictive model between sensory attributes and instrumental parameters (li et al., 2020; taniwaki et al., 2010). there is continuous industrial search for certain instrumental techniques for forecasting the sensory textural attributes of final processed products and/or even raw materials (barbieri et al., 2018; li et al., 2020; rahman et al., 2020; taniwaki et al. 2010). instrumental methods have advantage, as they tend to offer precise results (rahman et al., 2020). generally, instrumental results can be directly linked to chemical and physical properties permitting the investigator to achieve a mechanistic understanding of experimental differences. instruments are more sensitive to small alterations between samples and capable to detect trends in quality loss before it can be detected by humans (mestres et al., 2019; rahman et al., 2020; yu et al., 2017). instruments can be used to yield large amounts of data without objection, making them excellent screens in quality control operations (yu et al., 2017). the data on the instrumental and sensory textural attributes of 9 date fruit varieties as a function of their physicochemical characteristics were published earlier (singh et al., 2013; singh et al., 2015). hence, we aimed in this paper to report the correlation between the instrumental and sensory textural attributes of date fruit varieties. materials and methods nine batches of dfs at tamar stage (figure 1) with different quality levels were obtained from the local market at muscat. all the samples were stored at -20˚c until used for the analysis (singh et al., 2013). instrumental texture profile analysis (tpa) different instrumental textural attributes (i.e. hardness; adhesiveness; springiness; cohesiveness; resilience; gumminess; chewiness; elasticity) of date fruits samples were measured earlier (singh et al., 2013). briefly, all experiments were conducted at room temperature (25 ± 2°c). one pitted date was divided into two halves and one side was placed over another. it was then pressed to prepare a flat slab. a typical force-time graph of two-cycle instrumental tpa for different date samples was analyzed (singh et al., 2013). textural sensory analysis the textural sensory attributes (i.e. hardness; adhesiveness; springiness; cohesiveness; resilience; gumminess; chewiness; elasticity) of date fruits were assessed by 20 trained-panels (squ students) using descriptive test. the panelists were trained on how to assess the defined attributes with respect to the provided references. the training proceeds with the actual samples. more details were presented in the earlier published work (singh et al. 2015). statistical analysis experimental data were analyzed using past software. multivariate analysis (mva) was performed to determine the correlations between sensory and instrumental textural characteristics of dfs (hammer et al., 2001). mva including pearson’s (i.e. linear) and spearman’s correlation matrix were run using all sensory and instrumental textural attributes. linear and spearman’s correlations were used to determine the relationships between each variable for the p values ≤ 0.05 and p≤ 0.10. results and discussion the instrumental forces for texture analysis were correlated with sensory attributes. correlation results showed that instrumental hardness were significantly correlated with sensory hardness, along with adhesivefigure 1. photos of date samples used for the textural studies 59technical notes singh, shafiur, guizani, hakikulla shah ness, springiness, cohesiveness, chewiness and elasticity (p<0.05) in both linear and spearman’s correlation, and with sensory resilience (p<0.1) linearly (table 1). in the literature, often instrumental hardness are significantly correlated with the sensory hardness (prakash et al., 2005; tao et al. 2020). similar correlation was reported for instrumental hardness with sensory hardness in cooked rice (p<0.05) (prakash et al., 2005). significant correlations were also observed in the cases of instrumental hardness and springiness with sensory hardness and springiness (p<0.001) when 21 different foods samples, for examples caramel, egg white, cream cheese, corn muffin were considered (meullenet et al. 1998). in the case of baked product, young’s modulus correlated with sensory elasticity. conversely, instrumental cohesiveness and chewiness did not show correlations with sensory cohesiveness and chewiness (p>0.05). however, correlations of these two attributes were significantly improved when the variables were transformed with logarithmic function (i.e. non-linearity) (p<0.05) (meullenet et al., 1998). we observed similar results for our instrumental cohesiveness, which did not show any linear correlation however, correlation was improved in spearman’s correlation with sensory cohesiveness (p<0.1), chewiness and resilience (p<0.05). further, our results showed that instrumental resilience was correlated with sensory resilience (p>0.10) and with other sensory attributes, such as hardness, adhesiveness, springiness, cohesiveness, chewiness and elasticity in both pearson’s and spearman’s correlations. instrumental adhesiveness and springiness did not show significant correlations (p>0.10) with the any of the sensory attributes in both pearson’s and spearman’s correlations. similar results were reported in the case of cooked rice, where instrumental adhesiveness did not show any correlation with sensory stickiness (p>0.05) (prakash et al., 2005). the poor correlation between sensory and tpa springiness was not surprising since similar results were reported recently (nishinari et al., 2019). moreover, instrumental gumminess showed linear correlation with sensory hardness and elasticity (p<0.05) and with sensory adhesiveness, springiness, cohesiveness and chewiness (p<0.10). instrumental chewiness was significantly correlated with sensory chewiness (p<0.05) and with all others sensory attributes except gumminess. in the case of cereal snack bars, sensory attributes of chewiness, firmness, and crumbliness showed very high degrees of correlations (p<0.001) with the instrumental tpa (kim et al., 2009). similarly, chinese moon cake showed instrumental hardness, chewiness, and stickiness highly correlated with the sensory data (jia et al., 2008). instrumental elasticity 1 was correlated with sensory elasticity in both linear and spearman’s correlation. it was linearly correlated with sensory cohesiveness chewiness (p<0.05), hardness, adhesiveness (p<0.1). further, correlation with sensory hardness (p<0.05), springiness (p<0.1) was improved in spearman’s. instrumental elasticity 2 did not show any linear correlation with respective sensory attributes however, in spearman correlation, it was related to sensory gumminess (p<0.05), springiness (p<0.1). out of eight sensory attributes studied, four were well predicted with their respective instrumental measurements, while others i.e. adhesiveness, cohesiveness, springiness and gumminess were not correlated with their respective instrumental attributes. table 1. coefficients of linear and spearman correlation between sensory and instrumental texture measurements for nine varieties of date fruits instrumental sensory attributes attributes linear correlation spearman’s correlation ha ad sp co re gu ch es ha ad sp co re gu ch es ha * * * * * * ns * * * * * * ns ns * * ad ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns sp ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns co1 ns ns ns ns ns ns ns ns ns ns ns * * * ns * ns re * * * * * * ns * * * * * * * * ns * * gu1 * * * * * * * ns ns * * * * * ns * ns ns ns ns * * ch1 * * * * * ns * * * * * * * ns * * e1 * * * * ns * ns ns * * * ns * * ns ns ns ns * e2 ns ns ns ns ns ns ns ns ns ns * * ns ns * ns ns * p<0.05; ** p<0.10; ns: no significant correlations note: ha: hardness; ad: adhesiveness; sp: springiness; co: cohesiveness; re: resilience; gu: gumminess; ch: chewiness; e: elasticity 60 squ journal of agricultural and marine sciences, 2021, volume 26, issue 1 correlation between sensory and instrumental textural attributes of date palm (phoenix dactylifera l.) fruits: technical note this may be due to the difference in compression plate size and test sample in tpa, which may lead to variance in major cutting or shearing of the sample (kim et al., 2009). the lack of cutting or shearing may lower the correlation values between instrumental and sensory attributes (battaglia et al., 2020; paula and conti-silva, 2014). conclusion in the current study, sensory and instrumental textural attributes were correlated. the evaluation of texture obtained by instrumental measurements of dates had a significant correlation with the sensory evaluation of textural parameters. among the eight sensory attributes studied, four were well predicted with their respective instrumental measurements. these attributes were hardness, resilience, chewiness, and elasticity. the significant correlations between the sensory attributes and the instrumental measurements showed great promise for developing quality control during the selection of dates for commercial processing. acknowledgement authors acknowledge the sultan qaboos university for phd scholarship to vandita singh. she appreciates the support of the a’sharqiyah university to complete this manuscript from her thesis. the authors declare no conflict of interest. references aguirre m, owens c, miller r, alvarado c. (2018). descriptive sensory and instrumental texture profile analysis of woody breast in marinated chicken. poultry science 97(4): 1456-1461. al-hinai kz, guizani n, singh v, rahman ms, al-subhi l. (2013). instrumental texture profile analysis of date-tamarind fruit leather with different types of hydrocolloids. food science and technology research 19(4): 531-538. barbieri s, bendini a, balestra f, palagano r, rocculi p, toschi tg. (2018). sensory and instrumental study of taralli, a typical italian bakery product. european food research and technology 244(1): 73-82. battaglia c, vilella gf, bernardo ap, gomes cl, biase ag, albertini tz, pflanzer sb. (2020). comparison of methods for measuring shear force and sarcomere length and their relationship with sensorial tenderness of longissimus muscle in beef. journal of texture studies 51(2): 252-262. chandrasekaran m, bahkali ah. (2013). valorization of date palm (phoenix dactylifera) fruit processing by-products and wastes using bioprocess technology review. saudi journal of biological sciences 20(2): 105-120. essa mm, singh v, guizani n, manivasagam t, thenmozhi aj, bhat a, ray b, chidambaram sb. (2019). phoenix dactylifera l. fruits date fruit ameliorate oxidative stress in 3-np intoxicated pc12 cells. international journal of nutrition, pharmacology, neurological diseases 9(1): 41-47. grunert kg. (2015). the common ground between sensory and consumer science. current opinion in food science 3: 19-22. hammer ø, harper da, ryan pd. (2001). past: paleontological statistics software package for education and data analysis. palaeontologia electronica 4(1): 1-9 (article 4). hossain mz, waly mi, singh v, sequeira v, rahman ms. (2014). chemical composition of date-pits and its potential for developing value-added product-a review. polish journal of food and nutrition sciences 64(4): 215-226. ismail b, haffar i, baalbaki r, henry j. (2008). physico-chemical characteristics and sensory quality of two date varieties under commercial and industrial storage conditions. lwt-food science and technology 41(5): 896-904. jia c, kim ys, huang w, huang g. (2008). sensory and instrumental assessment of chinese moon cake: influences of almond flour, maltitol syrup, fat, and gums. food research international 41(9): 930-936. joyner hs. (2018). explaining food texture through rheology. current opinion in food science 21: 7-14. kim ej, corrigan v, hedderley d, motoi l, wilson a, morgenstern m. (2009). predicting the sensory texture of cereal snack bars using instrumental measurements. journal of texture studies 40(4): 457-481. kurotobi t, hoshino t, kazami y, hayakawa f, hagura y. (2018). relationship between sensory analysis for texture and instrument measurements in model strawberry jam. journal of texture studies 49(4): 359369. li p, wu g, yang d, zhang h, qi x, jin q, wang x. (2020). applying sensory and instrumental techniques to evaluate the texture of french fries from fast food restaurant. journal of texture studies 51(3): 521-531. mestres c, briffaz a, valentin d. (2019). rice cooking and sensory quality. rice. elsevier. p.385-426. meullenet jf, lyon b, carpenter ja, lyon c. (1998). relationship between sensory and instrumental texture profile attributes. journal of sensory studies 13(1): 77-93. nishinari k, fang y, rosenthal a. (2019). human oral processing and texture profile analysis parameters: bridging the gap between the sensory evaluation and the instrumental measurements. journal of texture studies 50(5): 369-380. 61technical notes singh, shafiur, guizani, hakikulla shah paula am, conti-silva ac. (2014). texture profile and correlation between sensory and instrumental analyses on extruded snacks. journal of food engineering 121: 9-14. philipp c, buckow r, silcock p, oey i. (2017). instrumental and sensory properties of pea protein-fortified extruded rice snacks. food research international 102: 658-665. prakash m, ravi r, sathish h, shyamala j, shwetha m, rangarao g. (2005). sensory and instrumental texture measurement of thermally processed rice. journal of sensory studies 20(5): 410-420. rahman ms. (2009). food properties: an overview. food properties handbook. crc press, boca raton, fl. p. 16-23. rahman ms. (2019). traditional foods, sensory excitements and pleasure. traditional foods. springer, new yourk. p.273-292. rahman ms, afaf k-e, al-attabi z, khan ms, al bulushi im, guizani n, al-habsi n. (2020). selected sensor technology innovation in food quality and safety. science and technology innovation for a sustainable economy. springer, new york. p.59-88. singh v, guizani n, al-alawi a, claereboudt m, rahman ms. (2013). instrumental texture profile analysis (tpa) of date fruits as a function of its physico-chemical properties. industrial crops and products 50: 866-873. singh v, guizani n, al-zakwani i, al-shamsi q, al-alawi a, rahman m. 2015. sensory texture of date fruits as a function of physicochemical properties and its use in date classification. acta alimentaria 44(1): 119-125. singh v, guizani n, essa m, hakkim f, rahman m. (2012). comparative analysis of total phenolics, flavonoid content and antioxidant profile of different date varieties (phoenix dactylifera l.) from sultanate of oman. international food research journal 19(3): 1063-1070. taniwaki m, sakurai n, kato h. (2010). texture measurement of potato chips using a novel analysis technique for acoustic vibration measurements. food research international 43(3): 814-818. tao k, yu w, prakash s, gilbert rg. (2020). investigating cooked rice textural properties by instrumental measurements. food science and human wellness 9(2): 130-135. yu l, turner m, fitzgerald m, stokes j, witt t. (2017). review of the effects of different processing technologies on cooked and convenience rice quality. trends in food science & technology 59: 124-138. book review journal of agricultural and marine sciences 2020, 25(1): 48 doi: 10.24200/jams.vol25iss1pp48 reveived 07 mar 2020 accepted 11 mar 2020 a review of “traditional foods: history, preparation, processing and safety” by mohammed al-khusaibi, nasser al-habsi and mohammad shafiur rahman (editors). springer nature, switzerland ag, 2019. isbn: 978-3-030-24619-8 nejib guizani, reviewer* ( ) guizani@squ.edu.om, department of food science and nutrition, college of agricultural and marine sciences, sultan qaboos university, p. o. box 34-123, oman. book review this 302 pages book covers a plethora of traditional foods from the mena region (north africa and gcc countries), the mediterranean region as well as from india and china. the book is divided in 10 chapters. chapter 1 is a very short but concise introduction and overview of traditional foods around the world. chapters 2 to 8 deal with traditional foods form different parts of the word. chapter 2: arab traditional foods: preparation, processing and nutrition. chapter 3: gcc traditional foods: preparation and processing. chapter 4: traditional foods in maghreb: production and research progress. chapter 5: chinese traditional foods: preparation and processing. chapter 6: indian traditional foods: preparation, processing and nutrition. chapter 7: mediterranean foods and human health. the chapters also deal with a diversity of ingredients; vegetables, fruits, meat, fish and dairy products and a diversity of methods of preparation, such as cooking, drying, fermentation, and spices. each chapter, with some variations, talks about ingredients, preparation/processing methods, nutritional values, custom of eating, and safety. many traditional foods discussed in this book provide excellent nutrition from sustainable resources, with some containing nutraceutical properties that make them not only a source of cultural and traditional value, but also valuable options for addressing the growing need for food resources. what is novel about this book is that the concepts of safety, sensory properties and food laws and regulations are not omitted as the book dedicated 3 chapters to these topics. chapter 8: safety, nutrition and functionality of traditional foods; chapter 9: laws and regulations of traditional foods: past, present and future. chapter 9 is supported with examples of legislations from the european union, the middle east, africa, china, south east asia, and latin america. chapter 10 talks about the pleasure and excitement that traditional foods provide to the consumer. this chapter also discusses the role of spices on the sensory attributes of traditional foods as well as the sensory aspects of selected traditional foods. information provided in each chapter is well referenced. most of the chapters are complemented by an illustration of the different foods and their preparation through colorful and attractive pictures. the contributing authors of the book are experts in food science and technology, food safety, food laws and regulations, and nutrition; they represent various regions of the world. even though the book is appropriately named, it gives the impression that it covers traditional foods from all over the world. traditional foods from europe, the americas, sub-sahara africa and oceania are however not covered in this book. the editors with their experience may consider the edition of a second book that includes traditional foods from the missing regions. this book is the first scientific reference that addresses the importance of the traditional foods in the life of people in the covered geographical regions. it is an excellent compilation of information on traditional foods and may serve as a reference and a resource for food scientists and nutritionist in academia and the food industry. it may also be recommended as a supplementary reference book reference for graduate and undergraduate in food science and nutrition, home economics and other social sciences fields. it is also recommended for libraries or individuals having a special interest in foods. i enjoyed reading this book. research paper journal of agricultural and marine sciences vol. 24 : 44– 50 doi: 10.24200/jams.vol24iss1pp44-50 reveived 25 nov 2018 accepted 15 mar 2019 evaluation of salinity intrusion in arable lands of al-batinah coastal belt using unmanned aerial vehicle (uav) color imagery *sawsana hillal al-rahbi, yaseen ahmed al-mulla, hemanatha jayasuriya *sawsana al-rahbi ( ) s.h.rahbi1@gmail.com, department of soils, water and agricultural engineering, ollege of agricultural and marine sciences, sultan qaboos university, box 34, al-khod 123. introduction the sultanate of oman is considered as an arid country with an average annual rainfall of about 100 mm. although agriculture occupies about 5% of the total area of oman distributed around eleven governorates (regions), the agricultural sector consumes more than 93% of the total water demand. al-batinah north governorate represents the largest area of oman’s agricultural lands (table 1) covering 24% of the total agricultural area of the country and is considered to be oman’s most important agricultural area as it produces 65% of the omani agricultural production with crops such as dates, fruits, vegetables and forage crops such as alfalfa and rhodes grass (choudri et al. 2015a; choudri et al. 2013). the population in al-batinah has sharply increased since 2003: i.e. by more than 100,000 people within 7 years. subsequently, the socioeconomic activities; active ports, coastal tourism projects, industrial activities, infrastructure development, intensive agriculture and urbanization have been rapidly taken place in this coastal zone (choudri et al. 2015c). such activities are related to population growth and have led to increasing pressures on natural resources including groundwater, agriculture and land use (lawley et al. 2016). it also has resulted in some environmental challenges such as seawater intrusion, water and soil salinition and desertification (choudri et al. 2015a). the management plans to mitigate the environmental challenges are constrained by the shortage of information about the interaction between the development activities and the environment (rishi and mudaliar 2014). in general, lack of information about the global, national and local land resources may lead to management plans تقييم تسرب امللوحة يف احلزام الزراعي يف ساحل الباطنة ابستخدام الصور امللونة امللتقطة من طائرة بدون طيار سوسنة بنت هالل الرحيب* وياسني بن أمحد املال وهيماناثا جاياسوريا abstract. salinity by seawater intrusion due to excess groundwater pumping for irrigation is a major environmental challenge in the coastal areas of the sultanate of oman. increasing salinity levels moving inward the arable lands is happening in a rapid manner. thus, salinity needs to be evaluated and quantified using a fast and accurate method. the objective of this study was to estimate salinity intrusion in al-batinah coastal belt using color aerial imaging. the study was conducted in five randomly selected sites at increasing distances from the seashore of al-suwaiq area in al-batinah region of northern oman. color aerial images were acquired for each site with an unmanned aerial vehicle (uav). images were enhanced by orthorectification in envi software. a green leaf index (gli) was obtained from each site image using matlab software. image analysis results were compared with the results of analyzed soil and water samples taken for ground-truth verification. there was a strong negative correlation between the distance from the seashore and the soil ec of each site (r = -0.95). similarly, the mean value of gli increased as the salinity levels decreased, r= -0.96 and -0.92 for soil ec and water ec, respectively. we demonstrated the possibility of the use of color images taken by a uav to accurately quantify the effect of soil salination on vegetation along the costal belt. keywords: seawater intrusion; salinity dynamics; uav; image processing; gli. املســتخلص: متثــل امللوحــة حتديًــا بيئًيــا كبــرًا يف املناطــق الســاحلية يف عمــان. حيــث أن حركــة امللوحــة بإجتــاه األراضــي الداخليــة الصاحلــة للزراعــة تســر بســرعة عاليــة، لــذا فهنــاك حاجــة ماســة للكشــف عــن حركــة التملــح وتقييمهــا باســتخدام طريقــة ســريعة ودقيقــة. اهلــدف مــن هــذه الدراســة هــو تقييــم حركــة امللوحــة داخــل حــزام الباطنــة الســاحلي باســتخدام تقنيــات التصويــر اجلــوي امللــون. وقــد أجريــت الدراســة يف مخســة مواقــع خمتــارة بطريقــة عشــوائية تبعــد مبســافات خمتلفــة عــن شــاطئ واليــة الســويق. مت إلتقــاط الصــور اجلويــة امللونــة لــكل موقــع بواســطة طائــرة بــدون طيــار. ومت حتســني الصــور هندســيا كخطــوة اوىل يف عمليــة حتليــل الصــور اجلويــة. مث مت حســاب مؤشــرإخضرار األوراق )gli( املســتنبط مــن صــورة كل موقــع. بعــد ذلــك متــت مقارنــة حتاليــل الصــور مــع حتاليــل الرتبــة واملــاء يف عمليــة التحقــق وربــط املســتنبط بالواقــع. كان هنــاك ارتبــاط ســليب قــوي بــني املســافة مــن شــاطئ البحــر وملوحــة الرتبــة لــكل موقــع )معامــل إرتبــاط =0.95-(. وباملثــل، زادت قيمــة )gli( مــع اخنفــاض مســتويات امللوحــة، معامــل إرتبــاط = 0.96مللوحــة الرتبــة ومعامــل إرتبــاط = 0.92مللوحــة امليــاه. أوضحــت نتائــج هــذا العمــل البحثــي إمكانيــة اســتخدام الطائــرات بــدون طيــار مثبتــة بكامــرا ملونــة لتقديــر وحتليــل تأثــر البعــد عــن شــاطئ البحــر علــى مســتويات امللوحــة يف الرتبــة وامليــاه، وكذلــك علــى حالــة الغطــاء النبــايت يف األراضــي الصاحلــة للزراعــة مبنطقــة الباطنــة. الكلمات املفتاحية: تسرب امللوحة، ديناميكية التملح، الطائرات بدون طيار، حتليل الصور، مؤشر إخضرار األوراق 45research article al-rahbi, al-mulla, jayasuriya without environmental concerns (mulder et al. 2011). thus, there is a necessity for accurate, cost-effective and timely monitoring method to update the information on the status changes in the arable lands of coastal area (mishra 2014), in order to develop a framework for the decision makers to manage the environmental problems. bajjali (2003) has conducted a study to assess the ground water quality in oman by analyzing 20,000 wells across different regions. the study indicated that al-batinah coast is the most affected area with groundwater salinity in oman, where the water salinity ranges from 5 to 44 ds/m (choudri et al. 2015c). as reported by choudri et al. (2015b), ministry of regional municipalities and water resources collected salinity data from 18 different wells in al-batinah region during the years 1991, 1993, 2005 and 2010 (table 2). the collected data suggested that water salinity has increased gradually in all examined wells within the last two decades. furthermore, water salinity is an important factor in soil salinity (al-belushi 2003; hussain 2005). approximately 52% of al-batinah lands are affected by soil salinity (al-mulla et al. 2010). between the years 2000-2005, the percentage of the agricultural lands affected with soil salinity has increased by about 7% (al barwani and helmi 2006). in addition, soil salinity is considered as one of the main reasons of desertification in arid and semi-arid regions and so in al-batinah coast particularly (al-belushi 2003; choudri et al. 2015b). on the other hand, soil salinition is considered as one of the main reduction factors of omani dates exportation which decreased by 2,000 mt within a 5-year period (2007-2011). similarly, production of date palm in al-batinah region has steadily declined within the last few years mainly due to groundwater salinity (al-yahyai and khan 2015). although there are many studies investigated the salinity levels in al-batinah region using the traditional field visits and lab analysis, there is no documented evidences on evaluation of salinity change inward the coastal belt, and particularly using areal imaging technique. therefore, the objective of this study was to analyze salinity change inward al-batinah coastal belt using images collected from an unmanned aerial vehicle (uav) combined with color imaging techniques. table 1. area of the agricultural lands in each governorate of sultanate of oman (feddan) governorate agricultural land area (feddan)* percentage % muscat 11,555.85 3.26 dhofar 65,921.13 18.57 musandum 3,242 0.91 al buraimi 16,123.21 4.54 ad dakhiliyah 45,732.97 12.88 al batinah north 85,118.27 23.98 al batinah south 48,984.53 13.80 ash sharqiyah south 15,206.87 4.28 ash sharqiyah north 27,523.27 7.75 adh dhahirah 33,295.08 9.38 al wusta 2,307.9 0.65 total 355,011.1 100 *(m.a.f 2013) figure 1. the study area location 46 squ journal of agricultural and marine sciences, 2019, volume 24, issue 1 evaluation of salinity intrusion in arable lands of al-batinah coastal belt using unmanned aerial vehicle (uav) color imagery samples (one sample from each site) were collected from the irrigation water sources (wells) of each site and were kept in a clean plastic container and transferred to the lab for analysis. the ec of each water sample were measured using ec meter. image acquisition aerial images were taken by a digital color camera with 12.4 megapixels resolution. the camera was mounted on a quadcopter uav (model: phantom-3-pro, dji inc., china). site images were taken from (130-275) m above the ground according to each site area. the captured images were saved in jpg format, which is a common format for realistic images and readable in different image processing softwares. the images were transferred to the computer to be analyzed. image analysis orthorectification was conducted as a pre-processing technique in order to enhance the site images and to decrease image distortion. the environment for visualizing images (envi) software (version 5.0.3, exelis visual information solutions inc., us) was used for image orthorectification using ground control points (gcps) and replacement sensor model (rsm). the gcps were collected using google earth software (version: 7.1.7.2600, google inc.). several vegetation indices which depends only on color bands; green leaf index (gli), visible atmospherically resistant index (vari) and triangular greenness index (tgi). gli has been commonly used in thresholding the green vegetation in aerial images of canopy scales (chianucci et al. 2016; hunt jr et al. 2013; macfarlane and ogden 2012). thus, gli was computed (eqn. 1) to determine canopy attributes within each site materials and methods study area the study was conducted in al-suwaiq area (23° 50’ 58” n, 57° 26’ 19” e). it is located at the south part of al-batinah north governorate (fig. 1). the climate of al-suwaiq is characterized as dry with average annual humidity of 32% and high evapotranspiration rate. the average air temperature of the coastal area is 28.5 °c and 17.8 °c in the mountain area. the average rainfall rate in al-suwaiq (as a part of al-batinah region) is 50 mm/year, varying in time and places within the region (kwarteng et al. 2009) . sites selection five sites were randomly selected within 0.3 to 6 km inland distance from the seashore of oman through the agricultural land within the study area. samples collection and analysis in each of the five randomly selected sites, five locations were selected randomly to collect soil samples. a global positioning system device (garmin etrex legend cx gps, usa) was used to register each location coordinates. at each location, three soil samples were collected from three different depths; 5 cm, 20 cm and 50 cm. around 500 g of soil were taken with an auger to represent each depth. each sample was kept in a clean plastic bag and annotated separately. a total of 75 soil samples were collected representing 5 sites × 5 locations × 3 depths. the saturation method was used to obtain soil extract from soil samples. each soil extract was investigated for electrical conductivity (ec) which is expressed by deci-siemens per meter (ds m-1). in addition, water figure 2. the locations of the selected sites 47research article al-rahbi, al-mulla, jayasuriya using matlab software (version: 9.0.0.341360, mathwork inc., usa). gli= (2g-r-b)/(2g+r+b) (1) where g, r and b are the digital values (0-255) of the green, red and blue bands of each pixel . the gli value of each pixel in the site image were calculated using equation 1. the gli values were reconstructed by applying the matlab function (inpaint_nans.m). then, the gli pixel values were averaged to get the gli value of the whole image. statistical analysis pearson correlation coefficient was calculated to compare soil and water ec of each site with site distance from seashore. regression analysis were used to estimate soil and water salinity using the distance from the seashore and the value of gli. the method followed in this paper is illustrated in figure 3. table 3. the correlation coefficient of each salinity parameter salinity parameter correlation coefficient soil ec (5 cm) -0.94992 soil ec (20 cm) -0.87461 soil ec (50 cm) -0.7105 water ec -0.48239 table 2. location of salinity monitoring wells in al-batinah region with the observed salinity (ppm) in 1991, 1993, 2005 and 2010 well id location (e) location (n) 1991* 1993* 2005* 2010* n-101 578701 2621460 1504 1632 2112 3072 n-92 582083 2620091 839 833 835 849 t-52 584162 2622750 1606 2214 8262 12288 n-79 585655 2617956 800 931 1280 1798 b-49 586184 2622605 7379 8896 8979 9126 t-30 591740 2621062 9280 9421 10682 14784 n-107 575993 2623943 1187 1112 5114 10432 b-70 571376 2627585 5440 6573 6144 11520 b-73 572962 2627174 7571 7424 8800 9728 b-83 568271 2628276 8410 6298 9600 12160 t-46 585991 2621972 6720 7507 13120 16576 n-63 590404 2619803 1382 1312 5133 14656 b-31 594298 2620548 4032 4902 11494 11514 n-53 591385 2616842 1344 672 1293 1792 n-71 587411 2619729 1427 1267 1958 3590 n-111 568658 2623958 774 833 1760 1837 n-66 588832 2617526 2138 1760 1978 2323 t-85 569008 2627063 3994 3610 6278 8896 *observed salinity concentration (ppm#) #ppm = ds/m x 640 (ec = 0.1 to 5 ds/m), ppm= ds/m x 800 (ec > 5 ds/m) soil and water sample collection aerial image acquisition (uav) image enhancement (orthorectivication) color band separation (r, g, b) mean value of enhanced gli regression analysis salinity vs gli salinity analysis (ec) figure 3. soil ec (ds m-1) of each site (1-5) at different soil depths (5, 20 and 50 cm) 48 squ journal of agricultural and marine sciences, 2019, volume 24, issue 1 evaluation of salinity intrusion in arable lands of al-batinah coastal belt using unmanned aerial vehicle (uav) color imagery results soil and water analysis the level of soil ec of the collected samples at different depths of 5, 20 and 50 cm were decreased with the increase of the soil depth, as shown in figure 4. effect of seashore on salinity levels the effect of site location from seashore on salinity levels is illustrated in figure 5. as the distance between the seashore and the selected sites increased, the water ec and soil ec decreased gradually. to investigate the effect of site location on the salinity levels, the water ec soil ec at different depths (5, 20, 50 cm) were correlated with the distance from the seashore as shown in table 3. water ec had the lowest correlation with the distance from the seashore (r = -0.48). on the other hand, the ec of the soils in 5 cm depth had the highest correlation. regression analysis was done to estimate the soil ec in 5 cm depth by knowing the distance from the shore using eqn. 2 (fig. 6). y= -2.7671 x+22.643 (r2 =0.902) (2) where y is the ec (ds/m) of the top layer of soil and x is the distance from the seashore (km) to the selected site. image analysis the image of site 2 is shown as an example in figure 7. the averaged values of gli had a strong negative correlation with soil ec (r= -0.96) and water ec (r= -0.92). the gli value of site image can be used to estimate site soil ec (eqn. 3) and water ec (eqn. 4) (fig. 8). y= -2.0737 x+16.15 (r² = 0.9128) (3) where y is the soil ec (ds/m) and x is the mean value of gli of the site image. y = -2.3241x + 13.887 (r² = 0.8429) (4) 0 5 10 15 20 0 2 4 6 8 distance from the sea (km) e c (d s /m ) variable soilec waterec figure 5. soil and water ec (ds m-1) of each site (1-5) and site distance from the seashore 0 5 10 15 20 25 0 2 4 6 distance from the sea (km) e c (d s /m ) depth 5cm 20cm 50cm water figure 6. the regression analysis between the sites’ distance from the seashore and their water ec and soil ec in different depths (5,20,50 cm) 0 5 10 15 20 25 5 25 50 soil depth (cm) e c (d s /m ) location site1 site2 site3 site4 site5 figure 4. steps followed to estimate soil and water salinity using gli 49research article al-rahbi, al-mulla, jayasuriya where y is the water ec (ds/m) and x is the mean value of gli of the site image. discussion soil and water salinity decreased as the site is located farther from the seashore (fig. 5). site (3) showed relatively unexpected increase in salinity levels, which could be due to the farming practices in the site. all other sites showed clear negative correlation between the distance to the site from the seashore and the salinity levels. on the other hand, an excellent correlation was observed while investigating the ec of soils from different depths with the distance from seashore (table 3). the top soil layers showed the highest values of soil salinity, where that could be due to salt accumulation on the soil surface as reported by herrero et al. (2003). it also had the strongest correlation (r= -0.95) with distance from the seashore. the gli mean values of the images ranged from -1.2 to 6.8. the positive value of gli was assigned to the green leaves or stems while the negative value was for non-green site objects like; soils, buildings, woods and other non-living items (louhaichi et al. 2001). in this study it was found that the lowest mean value of gli was -1.2 for site 1 with the highest salinity level. in general, the results proved that the soil and water salinity had strongly affected the vegetation quantity and quality (greenness), where the mean green value (gli) declined as the salinity increased. vegetation soil salinity index (vssi) were used by tran et al. (2018) to estimate salinity intrusion from landsat 8 images with r2 = 0.6957. the salinity levels can be estimated by the mean value of gli with relatively strong values of coefficient of determination, compared to other vegetation indices. conclusion this research proved the effect of salinity intrusion on site location from the seashore. the five randomly selected sites within the agricultural land belt with different distances from the seashore showed a decline in salinity levels as the site become far from the seashore. the effect of distance on soil salinity could be represented as a regression model. mainly, this research demonstrated the possibility of using uav with affordable digital camera to estimate the vegetation cover. the results showed figure 7. orthorectification process of site number 2 0 5 10 15 20 −2.5 0.0 2.5 5.0 7.5 gli (average) e c (d s /m ) substrate soil water r2 = 0.91r2 = 0.84 figure 8. the regression analysis between gli mean value of each site image and salinity levels of the site 50 squ journal of agricultural and marine sciences, 2019, volume 24, issue 1 evaluation of salinity intrusion in arable lands of al-batinah coastal belt using unmanned aerial vehicle (uav) color imagery a strong negative correlation between salinity levels and gli as an indicator of vegetation status. salinity assessment using uav colour images is coast efficient, timeless and more accurate in relative to field and satellite assessments. nevertheless, more image processing techniques may strength the possibility of aerial images in estimation of salinity effects on vegetation cover. acknowledgement the authors thank the research council (trc) of sultanate of oman for funding this study (project no. org/ebr/13/004 coastal ecosystem management for sustainable development: a case study of al-batinah region, oman). a special thanks for dr. b. s. choudri as he was the principle investigator (pi) of the project. references al-belushi a. 2003. desertification in 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landsat 8 oli data in the mekong delta, vietnam. research paper journal of agricultural and marine sciences 2020, 25(2): 13–21 doi: 10.24200/jams.vol25iss2pp13-21 received 01 jan 2019 accepted 16 may 2020 optimal density of asian seabass (lates calcarifer) in combination with the omani abalone (haliotis mariae), brown mussel (perna perna) and seaweed (ulva fasciata) in a land-based recirculating integrated multitrophic aquaculture (imta) system balqees al-rashdi1, wenresti gallardo1,*, gilha yoon1, hussein al-masroori1 wenresti gallardo1,*( ) gallardo@squ.edu.om, 1department of marine science and fisheries, college of agricultural and marine sciences, sultan qaboos university, sultanate of oman. introduction a quaculture provides socio-economic benefits such as employment, food provision and income generation, but if not done properly, it can lead to adverse environmental impacts which usually come with the development of commercial aquaculture activities (fao, 2018). by-product wastes in culturing species fed artificial diets in monoculture system are very high (troell et al., 2003). environment-friendly aquaculture techniques and systems, for example recirculating aquaculture systems (ras), are necessary to ensure sustainable aquaculture development. one of the aquaculture systems that has high potential for environmental protection is the integrated multi-trophic aquaculture or imta (neori et al., 2004; chopin, 2006). imta can be sea-based culture system or land-based recirculating system. it involves the culture of a number of species belonging to different trophic levels, some of them are fed while others are extractive, in which the particulate تأثريالكثافة املثالية للقاروص اآلسيوي )lates calcarifer( باالشرتاك مع أذن البحر العامين )haliotis mariae( وبلح البحر البني )perna perna( واألعشاب البحرية )ulva fasciata( يف نظام متكامل لالستزراع املايئ متعدد التغذية )imta( قائم عىل نظام تدوير أريض بلقيس الراشدي1,2 وويرنيتيس جاالردو1 وجلها يون1 وحسني املرسوري1 abstract. an experiment was conducted to develop a land-based recirculating integrated multi-trophic aquaculture (imta) system using a combination of the omani abalone (haliotis mariae) and asian seabass (lates calcarifer) as fed species, brown mussel (perna perna) and seaweed (ulva fasciata) as extractive species. specifically, this study was carried out to determine the optimal seabass density (20, 40 and 60 individuals per 500-liter tank) on water quality, growth and survival of the cultured species in the system. sampling of all species was done every two weeks to check their growth. water samples were taken every two weeks for analysis of ammonia, nitrite, nitrate, phosphate, and silicate. measurements of temperature, dissolved oxygen and salinity were done daily. growth of abalone and mussels were higher in fish densities of 20/tank and 40/tank, respectively, while growth and survival of seabass were not significantly different between densities. biomass of seaweeds decreased during the experiment period. temperature, dissolved oxygen and salinity were within optimum levels. ammonia levels decreased as nitrite increased but in some cases it remained high while nitrates did not increase, indicating that nitrites were not converted to nitrates most likely due to the lack of efficient bio-filtration in the mussel tanks. keywords: abalone; seabass; mussel; ulva; imta املســتخلص: أجريــت يف هــذه الدراســة تجربــة لتطويــر نظام متكامل لالســتزراع املايئ متعــدد التغذية )imta( قائــم عىل نظام تدوير أريض باســتخدام ــاب ــر )perna perna( واألعش ــح البح ــع بل ــذى م ــواع تتغ ــيوي )lates calcarifer( كأن ــاروص اآلس ــامين )haliotis mariae( والق ــر الع أذن البح البحريــة )ulva fasciata( كأنــواع اســتخراجية، وكان الهــدف الرئيــيس لهــذه التجربــة هــو تحديــد كثافــة القــاروص املثــىل )20 أو 40 أو 60 ســمكة لــكل خــزان ذو ســعة 500 لــرت( عــىل جــودة امليــاه ومنو وبقاء األنواع املســتزرعة يف النظــام. تم أخذ عينات مــن جميع األنواع كل أســبوعني للتحقق من منوهــا، كــام تــم أخــذ عينــات املياه كل أســبوعني لتحليل األمونيــا والنيرتيت والنيرتات والفوســفات والســيليكات، أمــا درجة الحرارة واألكســجني املذاب وامللوحــة فقــد تــم قياســها يوميــاً. وقــد وجــد أن منــو أذن البحــر وبلح البحــر كان أعىل يف كثافة األســامك مــن 20/خــزان و 40/خزان عىل التــوايل، بينام مل يكــن منــو وبقــاء القــاروص مختلفــني بشــكل كبــري بني الكثافات. وقــد لوحظ أن الكتلــة الحية من األعشــاب البحرية قد إنخفظت خالل فــرتة التجربة وكانــت درجــة الحــرارة واألكســجني املــذاب وامللوحة ضمن املســتويات املثــىل، وقد لوحظ أيضــا إنخفاض مســتويات األمونيا مع زيــادة النيرتيت، لكنها ظلــت مرتفعــة يف بعــض الحــاالت بينــام مل تــزد النيرتات، األمــر الذي يشــري إىل أن النيرتيت مل يتم تحويلها إىل نيرتات عىل األرجح بســبب نقص الرتشــيح الحيــوي الفعــال يف خزانات بلــح البحر. الكلامت املفتاحية : أذن البحر، القاروص اآلسيوي، بلح البحر، أعشاب بحرية، النظام املتكامل لالستزراع املايئ متعدد التغذية 14 squ journal of agricultural and marine sciences, 2020, volume 25, issue 2 optimal density of asian seabass (lates calcarifer) in combination with the omani abalone (haliotis mariae), brown mussel (perna perna) and seaweed (ulva fasciata) in a land-based recirculating integrated multi-trophic aquaculture (imta) system and dissolved wastes (uneaten feeds, feces, excretion) of other species are utilized by another species. imta requires a careful selection of ecologically and economically important species, some of which can efficiently utilize the wastes from the production of the other species, thus, preventing pollution or eutrophication. in a conventional aquaculture system, wastes go to the environment causing over-enrichment and algal bloom which may eventually cause mass mortalities of cultured and wild species when there is algal die-off and oxygen depletion. among the extractive organisms that can be used in an imta system are bivalves and seaweeds. bivalve species such as the mussel perna perna can filter suspended particles and utilize organic matters in the water (cheshuk et al., 2003; macdonald et al., 2011) while seaweeds or macroalgae can take up nitrates which have been converted from ammonia and nitrite by the nitrifying bacteria. among the seaweeds, ulva fasciata which is an intertidal green macroalga with high nutrient absorption ability of up to 80% ammonia input (neori et al., 2000), can be used as the bio-filtration component in an imta system (chopin et al., 2001; al-hafedh et al., 2015). in this study, we used the commercially important omani abalone haliotis mariae (al-rashdi et al., 2008) and asian seabass or “barramundi” lates calcarifer as the fed species and the brown mussel perna perna and seaweed ulva fasciata as the extractive species. the omani abalone is naturally present in the coastal region of the southern part of oman where it is heavily exploited due to its commercial value. to prevent its depletion, the ministry of agriculture and fisheries wealth of the sultanate of oman is producing juveniles in the hatchery for stock enhancement purposes; however, culturing them in a land-based imta system has not been tested yet. if it can be proven that the omani figure 1. imta system of interconnected tanks with recirculating water system. water from abalone to seaweed tanks flow by gravity while water from seaweed tanks are brought back to abalone tanks by submersible pumps figure 2. average weight of abalone in combination with seabass at low (20 fish per tank), medium (40 fish per tank) and high (60 fish per tank) density. error bars are standard deviation 15research paper al-rashdi, gallardo, yoon, al-masroori for the culture abalone (haliotis mariae), seabass (lates calcarifer), mussel (perna perna), and seaweed (ulva fasciata). due to lack of tanks and space, replication was not possible. initially, 30 individuals of abalone, fish and mussel were selected randomly for weight and length measurements before distributing them to the tanks. the fishes were stocked at 20, 40 and 60 pieces per tank, hereafter designated as low, medium and high fish density. seaweeds were distributed at 2 kg per tank. the abalone and mussels were distributed at 75 pieces per tank. the experiment was conducted for 6 weeks (42 days). abalone, sea bream and mussel tanks were placed under a roof to prevent direct exposure to sunlight and high temperatures, and to minimize water evaporation. the seaweed tanks were placed outside to allow some sunlight needed for photosynthesis but they were covered with a green mesh to minimize direct sunlight and abalone can survive and grow in a land-based recirculating imta system, then there is another option for their population to be maintained. one of the critical factors in a culture system is the stocking density of the cultured species. the objective of the study was to determine the optimal density of the asian seabass lates calcarifer as one of the fed species in the land-based recirculating imta system, in relation to water quality, and the growth and survival of the cultured species. materials and methods system design and operation the imta system (figure 1) consists of interconnected 500-l tanks with recirculating water system. tanks were organized in three rows, each row containing four tanks figure 3. average shell length of abalone in combination with seabass at low (20 fish per tank), medium (40 fish per tank) and high (60 fish per tank) seabass density. error bars are standard deviation figure 4. average weight of seabass at low (20 fish per tank), medium (40 fish per tank) and high (60 fish per tank) density. error bars are standard deviation 16 squ journal of agricultural and marine sciences, 2020, volume 25, issue 2 optimal density of asian seabass (lates calcarifer) in combination with the omani abalone (haliotis mariae), brown mussel (perna perna) and seaweed (ulva fasciata) in a land-based recirculating integrated multi-trophic aquaculture (imta) system excessive heat. each seaweed tank was installed with a submersible pump that recirculates the water back to the abalone tank and the rest of the tanks at a rate of 1,200 liters per hour. the initial feeding rate for seabass was 5% body weight and the amount of feed given to each fish tank was determined by the respective fish density. on the second, third and fourth week, the feeding rate was changed to 3% of body weight and the feed amount was adjusted according to fish density. the abalone were fed with ulva from the seaweed tanks, approximately 10% of the abalone biomass. sampling sampling of all species was done every two weeks to check their growth. water samples were taken every two weeks for measurement of water quality (ammonia, nitrite, nitrate, phosphate, and silicate). measurements of temperature, dissolved oxygen and salinity were done daily at 8:30 am and 4:30 pm. statistical analysis repeated measures anova was performed to determine any significant difference between treatments, followed by tukey’s test to identify which treatments were significantly different. results and discussion growth of abalone the average initial weight of abalone was 1.4 g (figure 2). at low fish density, abalone weight was increased until at the end of experiment while at medium fish density, abalone weight increased on week 2 but decreased on week 4 and increased again on week 6. at high fish denfigure 5. average length of seabass at low (20 fish per tank), medium (40 fish per tank) and high (60 fish per tank) density. error bars are standard deviation figure 6. average weight of mussels in combination with low (20 fish per tank), medium (40 fish per tank) and high (60 fish per tank) seabass density. error bars are standard deviation 17research paper al-rashdi, gallardo, yoon, al-masroori sity, abalone weight decreased on week 2, increased on week 4 and decreased again on week 6. the average final weight was 2.2 g, 1.6 g and 1.2 g, at low, medium and high fish densities of 20, 40 and 60 individuals per tank, respectively. the p-value corresponding to the f-statistic of one-way anova was less than 0.05 which indicated significant difference between treatments. tukey’s hsd test results showed no significant difference in abalone growth between treatment 1 (low fish density) and treatment 2 (medium fish density), and between treatment 2 (medium fish density) and treatment 3 (high fish density); however, there was significant difference between treatment 1 (low fish density) and treatment 3 (high fish density) as growth of abalone in treatment 1 (low fish density) was higher. at high fish density, water quality was not as good (i.e. high ammonia and nitrite) as in low fish density, therefore, growth of abalone was better in the treatment with low fish density. as shown in the water quality data in section 3.5, ammonia, for example, was lower at low fish density. the initial average length of abalone was 1.8 cm (figure 3). at all three fish densities, abalone shell length increased although there were minor fluctuations among weeks. the average final length of abalone in relation to low, medium and high fish density was 2.2 cm, 2.1 cm, and 2.0 cm, respectively, without significant difference among them. although there was significant difference in abalone weight between treatment 1 (low fish density) and treatment 3 (high fish density), there was no significant difference in terms of shell length indicating that body weight and shell length are not proportional or correlated and that weight is a better indicator of abalone growth. figure 7. average length of mussels in combination with low (20 fish per tank), medium (40 fish per tank) and high (60 fish per tank) seabass density. error bars are standard deviation. figure 8. weight of seaweeds at low (20 fish per tank), medium (40 fish per tank) and high (60 fish per tank) seabass density during the 6-week experiment period 18 squ journal of agricultural and marine sciences, 2020, volume 25, issue 2 optimal density of asian seabass (lates calcarifer) in combination with the omani abalone (haliotis mariae), brown mussel (perna perna) and seaweed (ulva fasciata) in a land-based recirculating integrated multi-trophic aquaculture (imta) system growth and survival of seabass the initial average weight of seabass was 14.4 g (figure 4). seabass weight increased from week 0 to week 6. the average final weights at low, medium and high density were 37.2 g, 33.6 g and 27.4 g, respectively. the p-value corresponding to the f-statistic of one-way anova was higher than 0.05, suggesting that the treatments were not significantly different at different fish densities for that level of significance. the tukey hsd test was also applied and showed the same result. for commercial culture of sea bass in cages, stocking density of 15-20 fish/m3 is recommended (gaitan and toledo, 2009). in the present experiment, the fish densities (20, 40 and 60/tank) in the 500-liter tanks are equivalent to 40, 80 and 120 fish/m3 which are higher than the recommended stocking densities. in terms of biomass per cubic meter the initial densities tested are equivalent to 0.58, 1.15 and 1.73 kg/m3. ardiansyah and fotedar (2016) reported that a stocking density of lower than 18.75 kg/m3 is recommended for culturing in integrated recirculating aquaculture systems. the initial average length of seabass was 9.4 cm. its increase during the 6-week culture period is shown in figure 5. the average final length of sea bass in treatment 1 (20 fish/tank), treatment 2 (40 fish/tank) and treatment 3 (60 fish/tank) were 13.4 cm, 13.1 cm and 12.9 cm, respectively, and were not significantly different (p>0.05). the fish survival rates were 100, 100 and 98% at low, medium and high fish density, respectively. the slightly higher mortality in the high density tank may be due to the relatively higher ammonia concentration observed in this tank. however, since the difference was not significant, this suggests that the fish densities used in the experiment can be also be used in commercial culture even if it is higher than the recommended density for commercial culture of seabass in non-imta system, at least for these relatively small fish. growth of mussels the initial average weight of mussels was 2.2 g. its growth during the 6-week culture period is shown in figure 6 with a decrease in mussel weight at high seabass density while at low and medium seabass density, mussel weight increased. the average final weights of mussels in combination with low (20 fish per tank), medium (40 fish per tank) and high (60 fish per tank) fish densities were 2.6 g, 2.8 g and 1.5 g, respectively. the average final weight of mussels in combination with low and medium fish densities were significantly higher than with high seabass densities (p = 0.026), indicating that the high fish density did not result in good growth of the mussels. the number of mussels may have not been enough to filter the suspended particles coming from the tanks with high fish density. the initial average length of mussels was 2.6 cm and its increase in length during the 6-week culture period is shown in figure 7. the average final lengths of mussels in combination with low (20 fish per tank), medium (40 fish per tank) and high (60 fish per tank) fish densities were 2.9 cm, 3.1 cm and 2.5 cm, respectively. similar to the data on mussel weight, the growth in length of mussels was not high when combined with fish at high density. this suggests a need to increase the number of mussels in the next experiment. growth of seaweeds the initial average weight of seaweeds was 2,000 g. figure 8 shows a significant decrease in biomass at week 2 and onwards. the final weights of seaweeds were 292.5 g, 327.3 g and 304.7 g, respectively, in combination with low (20 fish per tank), medium (40 fish per tank) and high (60 fish per tank) seabass densities. initially some seaweeds were taken and fed to the abalone but when their growth was not good, artificial feeds were instead given to the abalone. overall there was a decrease in the final weight of seaweeds. this could be due to high temperature and the difference of environmental condition in the experiment area (al-hail) figure 9. concentration (mg/l) of ammonia, nitrite and nitrate at low, medium and high fish densities. 19research paper al-rashdi, gallardo, yoon, al-masroori compared to the origin of seaweeds which were brought from dhofar region which is usually cooler at temperatures ranging from 21 to 26 °c although the algae were acclimatized for one week prior to the experiment. the low density of fish resulted in low waste production, thus, low production of nitrates needed for the seaweeds to grow. yousef et al. (2014) suggested that increasing fish effluent flow in the seaweed culture tanks allows to duplicate the biomass yield. also, they stated that the increase in water flow is adequate to maintain a high yield and that the stocking rate of 3 kg m-3 for ulva seems to be the best one. water quality concentrations of ammonia, nitrite and nitrate in the recirculating system are shown in figure 9. at low fish density (20 per tank) the concentration of ammonia increased on week 4 and decreased on the week 6, while the nitrite increased on the week 4 and then levelled off and the nitrate increased on week 6. at medium fish density (40 per tank), ammonia increased on week 2 and decreased on weeks 4 and 6 while nitrite increased on week 4 and then levelled off and nitrate was gradually increasing. at high fish density (60 per tank), ammonia increased on week 2 and decreased on week 4 and increased on week 6 while nitrite increased on week 4 and decreased on the week 6 and nitrate was slightly increasing. these three cases indicate the conversion of ammonia to nitrite and then to nitrate but at medium and high fish densities, ammonia build up was earlier (week 2) than at low fish density (week 4). temperature and salinity temperature in the culture tanks ranged from 20 to 29°c (figure 10). at the beginning it was high during summer and then it decreased due to the start of winter season. in seabass culture, optimum temperature for growth and food conversion ranged between 26-32°c (kungvankij et al., 1984). in our set up, salinity in abalone, seabass, mussels, and seaweed tanks ranged from 35.7 to 41.7 ppt. the reason why the salinity levels fluctuated could be due to addition of fresh water to lower the high salinity levels occurring in some tanks. dissolved oxygen dissolved oxygen in seabass tanks ranged from 4.6 to 7.2 mg/l (figure 11). at the beginning, the dissolved oxygen was high in all the tanks due to clean water used at the start of the experiment. later on it started to decrease due to the increased production of waste which was acted upon by decomposing bacteria that consumed the oxygen along with the other species. this could also be due to the decrease in seaweeds biomass towards the later part of the culture period while dissolved oxygen level became constant as the waste utilization stabilized. in the next experiments, we are considering to do the following: (i) increase the number of mussels in the biofilter tank in order to increase the filtration of suspended particles, (ii) add biofilter mat to increase the substrates (in addition to the mussels as substrates) for nitrifying bacteria, (iii) add sea cucumbers in the biofilter tank, for the utilization of detritus and pseudofeces of mussels, (iv) test other extractive species such as seaweeds particularly gracilaria which have been found to be functioning as a natural filter for ammonia and nitrate (largo et al., 2016), and (v) test the effect of partial recirculation (8-12 hours only) instead of 24 h recirculation, on water quality, growth and survival of cultured organisms and on the cost and benefit. conclusion there was no significant difference in seabass growth and survival at densities of 20, 40, and 60 per 500-liter tank. however, the highest growth of abalone and musfigure 10. average temperature and salinity in all tanks during the experiment period. 20 squ journal of agricultural and marine sciences, 2020, volume 25, issue 2 optimal density of asian seabass (lates calcarifer) in combination with the omani abalone (haliotis mariae), brown mussel (perna perna) and seaweed (ulva fasciata) in a land-based recirculating integrated multi-trophic aquaculture (imta) system sels were in low and medium fish density (20 and 40 seabass per tank, respectively). seaweeds showed a decrease in biomass during the experiment. water quality parameters, such as temperature and dissolved oxygen were within optimum levels. ammonia levels decreased as nitrite increased but in some cases it remained high while nitrates did not increase, indicating that nitrites were not converted to nitrates most likely due to the lack of efficient bio-filtration in the mussel tanks. this is the first report on the growth of the omani abalone haliotis mariae together with the asian seabass lates calcarifer, brown mussel perna perna, and seaweed ulva fasciata in a land-based recirculating integrated multi-trophic aquaculture (imta) system. although results may not be highly conclusive due to lack of space and tanks for replication of treatments, the results are useful for further work to validate the findings that will lead to the development of land-based imta system especially for the omani abalone. acknowledgements this study was carried out with funding by squ internal grant (ig/agr/fish/15/04). the abalone, mussels and seaweeds were provided by the ministry of agriculture and fisheries wealth through dr. lubna al-kharusi, mr. salim al-ghassani, and mr. salem khoom. thanks to mr. ahmed al-souti for his help in transporting the abalone, mussels and seaweeds from salalah, mr. mohammed al-mahfudhi for his help in monitoring and sampling during the experiment, and mr. harib al-habsi for the analysis of ammonia, nitrite and nitrate. references al-hafedh ys, alam a, buschmann ah. 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(2000). a sustainable integrated system for culture of fish, seaweed and abalone. aquaculture 186: 279-291. troell m, hailing c, neori a, chopin t, buschmann ah, kautsky n. (2003). integrated mariculture: asking the right questions. aquaculture 226: 69-90. research article journal of agricultural and marine sciences 2021, 26(2): 64–71 doi: 10.24200/jams.vol26iss2pp64-71 received 30 oct 2020 accepted 12 april 2021 moh a m m ad z a k i r hos s a i n 2 *( ) m z hos s a i n@squ .e du .om, c ollege of e conom ic s a nd pol it ic a l s c ience, su lt a n q aboos un iversit y, mu s c at , om a n . introduction bangladesh is an agro-based developing country and striving hard for rapid development of its economy. agriculture is the mainstay of bangladesh economy and it contributes about 16.3% of the gross domestic product (gdp) (bbs, 2014). potato ranks fourth in the world (325.3 million tons). the potato production (8.0 million tons) is among all the vegetables in respect of area coverage and production; and it contributes 55% of the total vegetable production in bangladesh (bbs, 2009). it is one of the leading vegetable crops to fulfill the demand of carbohydrate in bangladesh. onion is one of the most important spice crops and currently it is cultivated in 0.128 million hectares of land and around 1.1 million metric tons are produced with average yield of 8.25 tons/ha. potato contains 62% water, 29.8% carbohydrates, 6.3% protein, 0.1% mineral, 0.4% fibers and vitamin c. among the bulb spices, garlic ranks the third in terms of planting area (37072 hectares) and production (164392 metric tons) and its cultivation covered 7% of the total area used for spices. the average yield of garlic is 4.43 metric tons per hectare (bbs, 2010). considering the price scenario, proper understanding of agricultural price mechanism and their forecasts can help the farmers in many ways such as: (i) plan and decide about the production portfolio, (ii) develop marketing strategy to improve profits, (iii) traders to know the market trends and, (iv) government to augment economic developments in the nation. the policy makers of the country needs an accurate early information about the status of different crops such as onion, garlic and potato. therefore, accurate منوذج النمو والتنبؤ أبسعار بعض املنتجات الزراعية يف بنغالديش حممد عبدهلل املأمون، حممد زاكر حسني، شيخ حممد سامي وخوندكر حممد مصطفيز رمحان abstract. the aim of this paper was to explore the appropriate deterministic time series model using the latest selection criteria considering the price pattern of onion, garlic and potato products in bangladesh (january 2000 to december 2016). it appeared from our analysis that the time series data for the prices of potato was first order homogenous stationary but onion and garlic were found to be the second order stationary. four different forecasting models namely, linear trend model, quadratic trend model, exponential growth model, and s-curve trend model were used to find the best fitted model for the prices of above mentioned products in the bangladesh. three accuracy measures such as mean absolute percentage error (mape), mean absolute deviation (mad) and mean squared deviation (msd) were used for the selection of the best fitted model based on lowest value of forecasting error. lowest values of these errors indicated a best fitted model. after choosing the best growth model by the latest model selection criteria, prices of selected agricultural commodities were forecasted using the following time-series analysis methods: simple exponential method, double exponential method using the time period from january 2017 to december 2021. the findings of this study would be useful for policy makers, researchers, businessmen as well as producers in order to forecast future prices of these commodities. keywords: agricultural commodity prices, forecasting, growth models, time series models, model selection criteria, accuracy measures. امللخــص:كان اهلــدف مــن هــذه الورقــة هــو استكشــاف منــوذج السالســل الزمنيــة احلتميــة املناســبة ابســتخدام أحــدث معايــر االختيــار مــع األخــذ يف االعتبــار منــط أســعار البصــل والثــوم ومنتجــات البطاطــس يف بنغالديــش )ينايــر 2000 إىل ديســمرب 2016(. اتضــح مــن التحليــل أن بيــاانت السالســل الزمنيــة ألســعار البطاطــس كانــت اثبتــة ومتجانســة مــن الدرجــة األوىل بينمــا اســعار البصــل والثــوم كانــت اثبتــة الدرجــة الثانيــة. مت اســتخدام أربعــة منــاذج خمتلفــة للتنبــؤ وهــي منــوذج االجتــاه اخلطــي ومنــوذج االجتــاه الرتبيعــي ومنــوذج النمــو األســي ومنــوذج االجتــاه منحــى s للعثــور علــى أفضــل منــوذج مالئــم ألســعار املنتجــات املذكــورة أعــاله يف بنغالديــش. مت اســتخدام ثالثــة مقاييــس دقــة مثــل متوســط النســبة املئويــة للخطــأ املطلــق )mape( ، واالحنــراف املطلــق )mad( واالحنــراف الرتبيعــي املتوســط )msd( الختيــار أفضــل منــوذج مناســب بنــاًء علــى أدىن قيمــة خلطــأ التنبــؤ. أقــل قيــم هلــذه األخطــاء تشــر إىل أفضــل منــوذج مالئــم. بعــد اختيــار أفضــل منــوذج منــو وفًقــا ألحــدث معايــر اختيــار النمــوذج ، مت التنبــؤ أبســعار ســلع زراعيــة خمتــارة ابســتخدام طــرق حتليــل السالســل الزمنيــة التاليــة: الطريقــة األســية البســيطة ، الطريقــة األســية املزدوجــة يف الفــرتة الزمنيــة مــن ينايــر 2017 حــى ديســمرب 2021. نتائــج هــذه الدراســة ســتكون مفيــدة لواضعــي السياســات والباحثــني ورجــال األعمــال وكذلــك املنتجــني مــن أجــل التنبــؤ ابألســعار املســتقبلية هلــذه الســلع. الكلمات املفتاحية: أسعار السلع الزراعية، التنبؤ، مناذج النمو، مناذج السالسل الزمنية، معاير اختيار النموذج، مقاييس الدقة. growth model and forecasting prices of some agricultural products in bangladesh mohammad abdullah al mamun1, mohammad zakir hossain2*, sheikh mohammad sayem3, and khondaker md. mostafizur rahman4 65research article al mamun, hossain, sayem, rahman forecasting prices of agricultural products support the policy makers and planners to make policy decision regarding supply, demand and import/export of potato in the country. a number of work have been done by researchers on the forecasting prices and production of rice, wheat, maize, sugarcane and different types of pulses. however, negligible work have been reported on the three important food products, e.g., onion, garlic and potato in bangladesh. a number of forecasting models for projecting the agricultural crops and vegetables have been used earlier. hassan et al. (2013) worked on forecasting coarse rice in bangladesh using deterministic trend models (e.g. linear, quadratic and cubic) and it revealed that cubic model was the best fitted model for projecting agricultural grain on the basis of model selection criteria namely, r2 (coefficient of determination), (adjusted coefficient of determination), rmse (root mean squared error), aic (akaike information criterion), bic (bayesian information criterion), mae (mean absolute error) and mape (mean absolute percentage error). rahman et al. (2013) determined best fitted growth model on forecasting of pulse production in bangladesh. they used growth model and it revealed that the cubic model was found to be the best model for pigeon pea, chickpea and field pea pulse production. akhter (2013) conducted a research on forecasting of rice production in bangladesh and it revealed that both the quadratic linear and cubic models were proved to be the equally better fitted models for rice production in bangladesh. a very common practice to estimate the growth rate of rice production using accuracy model namely, exponential or compound model (akhter and jaim, 2002; barua and alam, 2000; jabber and jones, 1997). karim et al. (2010) had worked on the forecasting of wheat production in bangladesh. furthermore, abid et al. (2018) had completed a research on exponential growth model for forecasting of growing area and production of potato crops in pakistan. in fact, it is necessary to estimate the growth model that best fits the time series data before performing growth analysis. from the multiple literature review on forecasting determination models, it showed that research work have been completed on forecasting of onion, garlic and potato production in daily/month/yearly production data set basis using multiple determination time series model. wholesale price of rice, spice crops including masur, gram, kheshari, field pea, black gram and mung bean had been completed using accuracy model estimation (rahman et al., 2013). but there is negligible work on forecasting prices of three important commodities namely, onion, garlic and potato in the context of bangladesh. due to the escalation of prices of vegetables and spice crops, price determination is difficult to maintain equilibrium position of demand and supply in competitive market. government is always anxious about how to determine price equilibrium in order to make the seller and buyer equally benefited; and producer can earn maximum profits for their products. in this context, early forecasting about the probable prices of vegetables and spice crops could help the policy makers to predict the probable prices of their desired product. forecasting is very important in decision making cases at all levels in different economic sectors; particularly in agriculture sector. in this sector, the policies and decisions are characterized by risks and uncertainty largely due to varied yields, and relatively low price elasticity of demand. to reveal the price pattern and to make the best forecast prices of the selected products, appropriate time series models based on the observed data are necessary. deterministic type of time series models, often called growth models, such as linear, quadratic, cubic, exponential, compound, inverse, power, and s-shaped are very quick to estimate, inexpensive and easy to understand. therefore, these models are widely used to estimate the growth rate of time series data. before performing growth analysis it is necessary to identify the growth model that best fits the time series data. in this paper, an attempt is made to identify the best models for the three selected agricultural commodity prices in bangladesh using the latest available criteria, such as mape, mad (mean absolute deviation), and msd (mean squared deviation) (gujarati, 2016). in this paper, another attempt is made to describe the growth scenario in order to forecasts of the prices of these three important commodities in bangladesh. data and methodology the present study was conducted using secondary time series data on the prices of three commodities namely, potato, onion and garlic in bangladesh (january 2000 to december 2016). the monthly data of the wholesale prices of the three commodities (tk. per quintal) from the year january 2000 to december 2016 were collected from department of agricultural marketing (dam), food planning and monitoring unit (fpmu) under the ministry of food system management division. these secondary data were used to analyze and achieve the specific objectives of this study. in this study, the growth models were used to describe the behavior of variable changing with respect to time. integrated variable exhibited a systematic variation or trend. if the trends are completely predictable, it is called as deterministic trend. the specification of a deterministic trend can be functional form of time. the mathematical form of deterministic trend can be as follows: y = α + β t (1) it is important to note that this type of model is called deterministic in which no reference is made to the source and nature of the underlying randomness in the series. forecasts obtained by this particular model can often be usefully combined with oth66 squ journal of agricultural and marine sciences, 2021, volume 26, issue 2 growth model and forecasting prices of some agricultural products in bangladesh er forecasts in order to get overall superior forecasts. analytic techniques four different forecasting models (i.e., linear trend model, quadratic trend model, exponential growth model, and s-curve model) were used to find the best fitted model for area and production of potato, onion and garlic in bangladesh (khan et al., 2014). the following forecasting models were used: liner trend model: y = α + β t + ϵ (2) quadratic trend model: y = a + b t + ct 2 + ϵ (3) exponential growth model: y = d[ex p( f t ϵ)] (4) s-curve model (pearl-reed logistic trend model): y = (5) where, y is the time series considered, t represents time taking integer values starting from 1, ϵ is the regression residual, α, β, a,b,c, d, f, g, k, l, m are the coefficients of the models. criteria used for model selection in the case of two or more competing models for conducting the diagnostic checks, the best model is selected by using the criteria such as mape, mad and msd. the definition and some related materials are briefly given in the following sections. exponential smoothing exponential smoothing methods (esm) are a family of forecasting models. they use weighted averages of past observations to forecast new values. this method was initially developed by robert g. brown and further developed by the forecasting inventory control systems. exponential smoothing is a forecasting method that the observed time series data are weighted unequally. two types of exponential smoothing models are widely used namely, simple exponential smoothing (ses) and double exponential smoothing (des). simple exponential smoothing, ses for short, is a time series forecasting method for univariate data without a trend or seasonality. it requires a single parameter, called α, also called the smoothing factor or smoothing coefficient. this parameter controls the rate at which the influence of the observations at prior time steps decay exponentially. the value of α is often set to a value between 0 and 1. large values mean that the model pays attention mainly to the most recent past observations, whereas smaller values mean more of the history is taken into account when making a prediction. a value close to 1 indicates fast learning (that means, only the most recent values influence the forecasts), whereas a value close to 0 indicates slow learning (past observations have a large influence on forecasts). formula for simple exponential smoothing is: (6) where p̂t+1 is the forecast prices at time t+1; pt is the actual price at time t; (obervered); p ̂t is the forecast of pt; and 0<α<1 is the smoothing parameter. double exponential smoothing is an extension to exponential smoothing that explicitly adds support for trends in the univariate time series. double exponential smoothing (des) computes a trend forecasting equation by applying a special weighting function and emphasizing on the most recent time periods. this method supports the trends that change in two ways: an additive and a multiplicative, depending on whether the trend is linear or exponential, respectively. the des makes use of the following formulas: (7) (8) (9) in the des method, the most decisive parameters are smoothing constants α and γ both of which belong between 0 and 1. the forecasts generated by holt’s linear method display a constant trend (increasing or decreasing) indecently into the future. mean square error (mse) has the same unit of measurement as the square of the quantity being estimated. it is defined as: (10) where, n is the sample size, k is the total number of estimable parameters and ût is the difference between the observed and estimated values. the model with minimum mse is assumed to describe the data series more adequately. root mean square error (rmse) is defined as: (11) where, n is the sample size and k is the total number 67research article al mamun, hossain, sayem, rahman of estimable parameters and ût is the difference between the observed and estimated values. the model with minimum rmse is assumed to describe the data series more adequately. mean absolute deviation (mad) is an average of absolute deviations of individual observations from the central value of a series. it is defined as: (12) where ut =xt-x ̅, which stands for the deviations of the individual observations from the mean, and absolute means that the signs of the deviations whether positive or negative are ignored. mean absolute percent error (mape), the fourth model selection criterion is defined as: (13) where n is the number of observations, yt is the observed value and ut is the difference between the observed and estimated values. results and discussion stationary test since the data series was found to be non-normal, augmented dickey fuller (adf) test was conducted to make the series stationary. the results indicated that the series was made stationary at 1st order difference and 2nd order difference with p-value of 0.01, 0.05, 0.10 levels of significance. the trend component of the data was removed in order to make it suitable for price forecasting. model selection criteria model selection is an important part of any statistical analysis. the models considered for this study were estimated for the monthly wholesale prices of potato in bangladesh during january 2000 to december 2016. all the model selection criteria were used in this study to identify the best fitted model for forecasting purpose and also for explaining the growth patterns of the commodities. interpretation of the model selection criteria is considered based on the lowest value of mape, mad, and msd. diagnostic measures for the selection of the best fitted model from table 1, it is clearly appeared that for onion, the values of mape, mad and msd are 28, 656, 1023026, respectively; for garlic, the values of mape, mad and msd are 32, 1751, and 7845835, respectively; and for potato, the values of mape, mad and msd are 31, 353, and 211023, respectively, all of which are smaller for exponential model as compared to other growth models. therefore, the exponential growth model was found to be the best fitted model for the trend analysis on the prices of these three agricultural products. it is on the basis of smaller values of accuracy and thus this model is being selected as a best model for forecasting. from figure 1 we see that the graphs of actual prices and predicted prices for three selected commodities are slightly fluctuated at time. as the actual values and predicted values showing similar seasonal cyclical pattern, therefore it clearly indicates that the exponential model is more suitable for forecasting. the figure 2 is constructed between actual prices and predicted prices of onion, potato and garlic. in comparison to the actual prices and predicted prices for onion, the prices of onion are accounted for tk. 1344/100 kg to tk. <2000/100 kg (jan-2000 to may-2005), tk. 1214/100 kg to tk. 8000/100 kg (june-2005 to jan-2014), tk. <2000/100 kg to tk. 6000/100 kg (feb-2014 to jan2016). in the comparison to the actual prices and predicted prices for garlic, the prices of garlic are accounted for tk. 5000/100 kg to tk.10000/100 kg (jan-2000 to april-2007), tk. <5000/100 kg to >10000/100 kg (may2007 to jan-2010), tk. <20000/100 kg to tk.15000/100 kg (feb-2000-dec-2016). in comparison to the actual prices and predicted prices of potato, the prices of potato are accounted for tk.1000/100 kg to tk.2000/100 kg (jan-2000 to sep-2006), tk. <2000/100 kg to tk. <3000/100 kg (oct-2006 to sep-2009), tk. 2000/100 kg to tk. 3000/100 kg (oct-2009 to dec-2015), tk.1000/100 kg to tk. 2000/100 kg (jan-2016 to dec-2016). the comparison of actual prices and predicted prices show similar value and the seasonal cyclical pattern is shown upturn and downturn with time. since actual price and predicted price are shown similar value, it is ready to better forecasting. in figure 3, we constructed a line graph for comparing the predicted prices and residuals for accuracy of forecasting for our selected three agricultural commodities. residual values mean the difference between the predicted values and observed values. in residual, if the prices of three commodities are equal to zero, this line is actually the best fitted line. in the predicted prices and residual for onion, the prices of onion is equal to zero or close to zero. the predicted prices is shown upturn and downturn pattern which accounted for tk. 1344/100 kg to tk. <4000/100 kg (jan-2000 to nov2005), tk. <2000/100 kg to tk.8000/100 kg (dec-2005 to jan-2014), respectively. similarly, the predicted prices of garlic and potato are shown upturn and downturn in a graph where residual is equal to zero or close to zero. thus it is clear that we are estimating best fitted model for forecasting using data set from january 2000 to december 2016. in figure 4, forecasted prices (jan-2017 to dec 2021) of our selected three agricultural products have been estimated based on the actual prices of commodities from 68 squ journal of agricultural and marine sciences, 2021, volume 26, issue 2 growth model and forecasting prices of some agricultural products in bangladesh table 1. : criteria for best fitted model prices of the agricultural products (onion, garlic and potato) with comparison accuracy measurements among trend models. model fitted trend equation accuracy measures onion mape mad msd linear y= 981 + 13.19 t 31 668 986716 quadratic y= 1006 + 12.46 t + 0.0035 t2 31 668 986594 exponential y = 1129.92 × (1.00588t) 28 656 1023026 s curve y = (105)/[24.4701 + 8.0844×(0.988668t)] 27 649 1080658 trend fitted trend equation accuracy measures garlic mape mad msd linear y = 2256 + 29.36 t 38 1862 7555079 quadratic y= 2495 + 22.4 t + 0.0340 t2 37 1852 7543983 exponential y= 2619.46 × (1.00539t) 32 1751 7845835 s curve y = (105)/[18.2718 + 33.2841×(0.975665t)] 33 1887 9078596 trend fitted trend equation accuracy measures mape mad msd potato linear y= 582.6 + 6.417 t 33 355 204289 quadratic y = 596.1 + 6.02 t + 0.0019 t2 33 355 204253 exponential y = 629.132 × (1.00552t) 31 353 211023 s curve y = (104)/[7.10205 + 18.4221×(0.971589t)] 32 378 238562 data source: department of agricultural marketing (dam) during 2000 to 2016 figure 1: trend analysis model for regarding the prices of agricultural products, from january 2000 to december 2016 figure 1. trend analysis model for regarding the prices of agricultural products, from january 2000 to december 2016. 69research article al mamun, hossain, sayem, rahman comparison of actual price vs predicted price using exponential smoothing model figure 2: cross-section line graph for the measure of comparison the price between actual wholesale price and predicted wholesale price (tk. /100kg) for onion, garlic and potato, january 2000 to december 2016. figure 2. cross-section line graph for the measure of comparison the price between actual wholesale price and predicted wholesale price (tk/100kg) for onion, garlic and potato, january 2000 to december 2016. residual analysis on predicted values vs residuals using exponential smoothing model figure 3: comparison between the predicted prices and residuals for three selected agricultural products from january 2000 to december 2016 figure 3. comparison between the predicted prices and residuals for three selected agricultural products from january 2000 to december 2016. 70 squ journal of agricultural and marine sciences, 2021, volume 26, issue 2 growth model and forecasting prices of some agricultural products in bangladesh january 2000 to december 2016. the forecasted prices are clearly shown upturn and downturn pattern like as the previous seasonal cyclical pattern graph. therefore, we can conclude that accurate forecasting has been completed using data accuracy measurement and estimation process through comparison between actual price and predicted price and also predicted price and residual. conclusion this study showed that exponential growth model was appropriate for forecasting future estimates of the prices of three agricultural products in bangladesh based on the lowest values of the forecasting errors. the forecast values of the three selected agricultural products clearly showed the increasing trend. therefore, forecasting prices of these three crops could enable the policy makers and government to take wiser steps for attaining price equilibrium to maintain the demand and supply in the market. furthermore, based on these forecasting price information, both the seller and buyer of these products could be equally benefitted and the producers are expected to earn maximum profits from their products. references abid sn, jamal mz, zahid s. (2018): exponential growth model for forecasting of area and production of potato crop in pakistan. pakistan journal of agricultural research 31(1): 24-28. akhter mw, jaim mh. (2002). changes in the major food grains production in bangladesh and their sources during the period from 1979/80 to 1998/99. the bangladesh journal of agricultural economics 25(1): 1-16. akhter r. (2013). forecasting of rice production in bangladesh. research journal of agriculture and forestry sciences 1(7): 15-17. barua p, alam s. (2000). growth, price instability and flexibility of major crops in bangladesh. the bangladesh journal of agricultural economics 23(1&2): 103-114. bbs. (2009). bangladesh bureau of statistics, statistical yearbook of bangladesh-2002. statistics division, ministry of planning, government of the people`s republic of bangladesh, dhaka. bbs. (2010). bangladesh bureau of statistics, statistical yearbook of bangladesh-2002. statistics division, ministry of planning, government of the people`s republic of bangladesh, dhaka. bbs. (2014). bangladesh bureau of statistics, statistical yearbook of bangladesh-2002. statistics division, ministry of planning, government of the people`s republic of bangladesh, dhaka. gujarati dn. (2016). the analysis of time series: an introduction. 6th edition, chapman and hall/crc press, boca raton, fl, us. forecast analysis using exponential smoothing model figure 4: forecasted prices of three agricultural products (potato, onion and garlic) in bangladesh, from january 2017 to december 2021 figure 4. forecasted prices of three agricultural products (potato, onion and garlic) in bangladesh, from january 2017 to december 2021. 71research article al mamun, hossain, sayem, rahman hassan mf, islam ma, imam mf, sayem sm. (2013). forecasting coarse rice prices in bangladesh, department of agricultural statistics, bangladesh agricultural university. agriculture 22(1&2): 193 – 201. jabber ma, jones rp. (1997). the growth of mv rice production and adoption in bangladesh. the bangladesh journal of agricultural economics 20(2): 1-19. karim m, awal m, akter m. (2010). forecasting of wheat production in bangladesh. bangladesh journal of agricultural research 35(1): 17-28. khan as, masood, ma. 2014. trend analysis and forecasting of maize area and production in khyber pakhtunkhwa, pakistan. european academic research 2(4): 4653-4664. rahman nmf, rahman mm, baten, ma. (2013). modeling for growth and forecasting of pulse production in bangladesh. research journal of applied sciences, engineering and technology 5(24): 5578-5587. rahman, nmf, aziz, ma, rahman mm, mohammad m. (2013). modeling on grass pea and mung bean pulse production in bangladesh using arima model. iosr journal of agriculture and veterinary science 6(1): 20-31. research paper journal of agricultural and marine sciences 2021, 26(1): 13–20 doi: 10.24200/jams.vol26iss1pp13-20 reveived 03 may 2020 accepted 16 nov 2020 effect of storage conditions on postharvest quality of tomatoes: a case study at market-level mai al-dairi, pankaj b. pathare*, adil al-mahdouri pankaj b. pathare* ( ) pankaj@squ.edu.om; pbpathare@gmail.com, department of soils, water and agricultural engineering, college of agricultural & marine sciences, sultan qaboos university, oman introduction globally, one-third of the total fresh food pro-duced is lost during food supply chain before reaching to the consumers (gautam et al., 2017; munhuewyi, 2012). despite all of the benefits derived from any fresh produce, postharvest losses make them unprofitable and useless (sarma, 2018). postharvest losses of fresh produce can be encountered during harvesting, storing, handling, packaging, transporting and marketing operations (sibomana et al., 2016). the nature of fresh produce is one of the main causes of postharvest losses along the whole value chain as they are highly perishable (parfitt et al., 2010), respire and live even after harvesting (kader and rolle, 2004). improper harvesting method and equipment, inadequate storage and packaging facilities are the factors contributing to the postharvest losses in fresh produce (chebanga et al., أتثري ظروف التخزين على جودة الطماطم بعد احلصاد: دراسة حالة على مستوى السوق مي الدايري، ابنكاج ابثري*، عادل احملذوري abstract. postharvest loss is one of the main obstacles for ensuring food security in oman as it leads towards reduced fresh produce quantity, quality and market value. the aim of this study was to determine the postharvest losses due to quality reduction in fresh produce of tomato during storage at market level in oman. this paper consisted of two separate studies. firstly, a semi-structure survey was conducted to collect the data from the market vendors. secondly, fresh tomatoes were also purchased from the market and were stored in the laboratory at 10oc and 22oc for 12 days. all data were analyzed using spss statistical software. the results of the survey showed that 35% of respondents suggested that the color and texture are the most important quality attributes attracted by the consumers. two days period was the best duration to store fresh produce in the current market. about 55% of the respondents mentioned that the nature of the produce was the most important factor causing postharvest losses along the supply chain. the results of the experiments showed a significant (p<0.05) changes of color attributes such as lightness (l*), redness or greenness (a*), total color change (∆e), weight loss and firmness during 12 days at both temperature conditions. however, no significant impact of both factors on yellowness or blueness (b*), chroma, hue and total soluble solid (tss) values was observed. this study indicated high changes in weight loss, lightness, redness, total color change and firmness in tomato stored at 22°c. the lower was the lightness (4.96) and firmness (11.18 n) and the greater was the redness (12.22) and weight loss (16.6%), caused the greater the rejection by the customers of the tomato at market level. accordingly, storage temperature played a critical role on the improvement and development of tomato and any perishable fresh produce along the supply chain. keywords: color, market, postharvest losses, quality, texture, tomato املســتخلص:تعترب خســارة مــا بعــد احلصــاد إحــدى العقبــات الرئيســية أمــام ضمــان األمــن الغذائــي يف ســلطنة عمــان ألهنــا تــؤدي إىل اخنفــاض كميــة املنتجــات الطازجــة وجودهتــا وقيمتهــا الســوقية. كان اهلــدف مــن هــذه الدراســة هــو حتديــد خســائر مــا بعــد احلصــاد بســبب اخنفــاض جــودة املنتجــات الطازجــة مــن الطماطــم أثنــاء التخزيــن علــى مســتوى الســوق يف عمــان. تتألــف هــذه الورقــة مــن دراســتن منفصلتــن. اشــتملت األوىل علــى إجــراء مســح ميــداين شــبه هيكلــي جلمــع البيــاانت مــن ابئعــي الســوق. واشــتملت الدراســة الثانيــة علــى مجــع البيــاانت املخربيــة علــى نــوع مــن الطماطــم الطازجــة احملليــة، حيــث مت ختزينهــا يف املختــرب عنــد 10 درجــة مئويــة و 22 درجــة مئويــة ملــدة 12 يوًمــا. مت حتليــل مجيــع البيــاانت ابســتخدام برانمــج احلزمــة اإلحصائيــة للعلوم اإلجتماعية )spss(. وأظهرت نتائج املســح امليداين أن 35٪ من املســتجيبن أشــاروا إىل أن اللون وامللمس مها أهم مسات اجلودة اليت جتذب املســتهلكن. وقــد كانــت فــرة التخزيــن املفضلــة للمنتجــات الطازجــة يف الســوق هــي يومــان. ذكــر حــوايل 55٪ مــن املســتجيبن أن طبيعــة املنتــج كانــت العامــل األكثــر أمهيــة يف حــدوث خســائر مــا بعــد احلصــاد علــى طــول سلســلة التوريــد. أظهــرت نتائــج التجــارب تغــريًا مؤثــراً )p>0.05( يف مســات اللــون مثــل اخلفــة )*l(، اإلمحــرار أو اإلخضــرار )*a(، تغــري اللــون الكلــي )e∆(، فقــدان الــوزن و الصابــة خــال 12 يــوم يف مجيــع درجــات حــرارة التخزيــن. ومــع ذلــك ، مل ياحــظ أي أتثــري كبــري لــكا العاملــن علــى اإلصفــرار أو اإلزرقــاق )*b(، صفــاء اللــون، تشــبع اللــون وقيــم املــواد الصلبــة الذائبــة الكليــة )tss(. أشــارت هــذه الدراســة إىل حــدوث تغــريات كبــرية يف فقــدان الــوزن واخلفــة، واالمحــرار، وتغــري اللــون الكلــي وثبــات الطماطــم املخزنــة عنــد 22 درجــة مئويــة. كلمــا قلــت اخلفــة )4.96( و الصابــة )11.18 نيوتــن( و أزداد االمحــرار )12.22( وفقــدان الــوزن )16.6٪( ،حيــث زاد رفــض الزابئــن للطماطــم علــى مســتوى الســوق. وفًقــا لذلــك ، تلعــب درجــة حــرارة التخزيــن دورًا مهًمــا يف حتســن الطماطــم وأي منتجــات طازجــة قابلــة للتلــف علــى طــول سلســلة التوريــد. الكلمات املفتاحية: اللون، السوق، خسائر ما بعد احلصاد، اجلودة، الصابة، الطماطم. 14 squ journal of agricultural and marine sciences, 2021, volume 26, issue 1 effect of storage conditions on postharvest quality of tomatoes: a case study at market-level 2018). cultural practices (semida et al., 2019), environmental factors (singh et al., 2014), poor transportation services (caixeta-filho and péra, 2018) and improper market facilities are other important causes of the postharvest losses (sharma and singh, 2011). at market level, the incidence of fresh produce quality losses and deterioration can occur due to poor management (sharma and singh, 2011) and performance of traders, processors, producers, retailers and other labors in the marketing system. absence of technical awareness and knowledge on postharvest losses (sarma, 2018), limited marketing strategies and information (rolle, 2006), and lack of efficient communication between producers and buyers are other factors leading to postharvest damage on fresh produce at market level (arah et al., 2015). moreover, losses during marketing can occur due to non-existence of adequate postharvest infrastructure, technologies (aujla et al., 2011) and sanitation, packaging, loading, unloading and storage (kader and rolle, 2004). additionally, inappropriate storage facilities can cause high quantitative losses compared to the qualitative losses in fresh produce (ayomide et al., 2019). subsequently, negative impacts on several parameters such us nutritional status, consumer acceptance and income are affected (sarma, 2018; seyoum and woldetsadik, 2004). postharvest losses in fresh produce at market level in oman are estimated between 3-19 % (opara, 2003). tomato (solanum lycopersicum) is one of the major and popular fresh produce in the world (costa and heuvelink, 2018; guan et al., 2018; sarma and ali, 2019). statistics display that the production of tomatoes in sultanate of oman ranked first among other vegetables like onions (allium cepa) (ona, 2017), cucumbers (cucumis sativus) and potatoes (solanum tuberosum) which reach up to 199,132 tons (886 ha cultivated area) in 2018 after it was 39,586 tons (2532 ha cultivated area) in 2000 (figure 1) (faostat, 2020). it is a vital source of nutrients (ayandiji et al., 2011; erba et al., 2013), minerals (sarma, 2018; sibomana et al., 2015) with various benefits to human body (arab and steck, 2000; bhowmik et al., 2012) like vitamins (a, b and c), amino acids, calcium, copper, sodium (mandal et al., 2018), antioxidants, lycopene and carotenoids that are responsible for reducing the incidence of some chronic and vascular diseases (arah et al., 2015; tadesse et al., 2015). tomato production can be a source of income (addo et al., 2015) in most of the developing countries (arah et al., 2015; sarma, 2018). the quality of tomato can be recognized predominantly by flavor, texture, color and nutritional value (kader and rolle, 2004). due to the current postharvest problems, losses in tomato could reach to 50% worldwide (addo et al., 2015). during marketing, temperature is the main factor that impacts tomato quality as it directly influences the rate of losses. proper control of temperature condition is the most suitable way to retain the quality of fresh produce during the whole supply chain (arah et al., 2015). basically, temperature can influence tomato color, firmness and flavor (tadesse et al., 2015). storage below 10°c cause poor color development of tomato (khairi et al., 2015), however, storage at 20°c and 30°c reduce tomato firmness and weight loss (tadesse et al., 2015). storing tomato at low temperature can decrease the metabolic activity of tomato. high increase in temperature can elevate transpiration rate, respiration rate and ethylene production rate. however, chilling temperature can reduce tomato quality due to the incidence of chilling injuries (atanda et al., 2011). most of the studies reported that storage temperature around 10°c is the most appropriate storage temperature condition for maintaining the quality (cantwell et al., 2009; khairi et al., 2015; ponce-valadez et al., 2016) and delaying softening of tomato (ayomide et al., 2019). relative humidity (rh) is another important factor during storage of tomato (ramaswamy, 2014), which can influence its texture and weight loss (el-ramady et al., 2015). the optimal relafigure 1. tomato annual production among other vegetables in oman. (faostat, 2020) 15research paper al dairi, pankaj, al-mahdouri tive humidity values for green and firm ripe tomato are 85-95% and 90-95%, respectively (suslow and cantwell, 2009). application of proper temperature and humidity management practices at market level plays a significant role to reduce postharvest food losses at market level. therefore, the aim of this study was to determine vendor’s knowledge on postharvest practices and their related losses at market level and to correlate them with local tomato produce quality losses during storage using laboratory experiments. materials and methods market survey the study was conducted in the central market of fruits and vegetables, muscat, sultanate of oman. this market was selected due to its large-scale of sales and availability of different fresh produces compared to other markets in muscat. a semi-structure survey was designed as a tool for data collection by conducting short interviews with the 20 vendors. the questionnaire consists of formal questions and it was pre-reviewed and tested to provide the desired wide-range of responses from the vendors. the purpose of this survey was to determine the vendor’s knowledge about postharvest quality and losses in fresh produce. laboratory experiment about 32 kg of tomatoes were purchased from the market and delivered to postharvest laboratory, college of agriculture and marine sciences at sultan qaboos university. tomatoes with no bruising signs, uniform color and shape were selected to be tested for some quality analysis for total period of 12 days at two days intervals. the tomatoes were stored at 10°c with 85±5% rh and 22°c with 45±5% rh (simulate market storage temperature). each storage condition consisted of seven groups of tomato samples for storage time (temporal) assessment. each group included five replicates. temperature/rh prop (model: tes 13604, tes electrical corp., taiwan) was used to measure temperature and relative humidity. tomato quality measurements electric weight balance (model: gx.4000, japan) was used to weigh each tomato group. the percentage of weight loss in tomato was calculated using the equation (eq. 1) applied by moneruzzaman et al. (2009): color value of each tomato sample was measured using a colorimeter (model: tes 135a, tes electrical corp., taiwan) which expresses the color values of l* (lightness), a*(redness, greenness) and b*(yellowness, blueness). the devise was calibrated using a white standard tile (l*=93.90, a*= 3.13, b*= 3.20). total color differences, (eq. 2), chroma (eq.3) and hue angle in (eq.4) (pathare et al., 2013) were respectively calculated to show color changes (bal et al., 2011) during 12 days at 10°c and 22°c. hand penetrometer (model: ft 327, effegi, italy) was used to determine each tomato firmness by using the standard method of oecd (2018) at two days interval. kleinhenz and bumgarner (2012) procedure was used to identify total soluble solid by using hand-held refractometer calibrated in o brix at 22ºc. data analysis in order to determine, the effect of storage time and temperature on tomato quality parameters, analysis of variance (anova) was performed by using spss 20.0 (international business machine crop., usa) software. results and discussions survey analyses the analysis of the semi-structure survey of the vendors showed that 75% of the participants were (from the age of 31-40) and this age is almost appropriate for people to sell fruits/vegetables products especially for those who are searching for a job. this is an active age of the community who can establish an excellent marketing network. almost, 50% of the vendors were school graduate, this helped to facilitate good and rapid understanding of the respondents to the survey. this also pays the attention for the vendors to know the most common fresh produce consumed by people and getting more knowledge about postharvest and its related losses. the majority of the respondents were non-omani (90%) because omani farms owners let their labors (from other nationalities) to sell their fruits/vegetables on the market. 16 squ journal of agricultural and marine sciences, 2021, volume 26, issue 1 effect of storage conditions on postharvest quality of tomatoes: a case study at market-level vegetables vendor’s observations on postharvest quality, losses and practices four of these 20 vendors were from closed markets (retail shops), but the other 16 were from an open markets (retail shade). the temperature of the closed markets was between 18oc to 23oc. on the other hand, the temperature of the open markets was 32.7oc in the dates of conducting this survey. for consumer preference on a specific product, color and texture were having the highest attention by the consumers for a specific fresh produce as suggested by 35% of the vendors compared with flavor and money. generally, color is the most significant quality preference of any fresh produce (tadesse et al., 2015) as well as texture (batu, 2004) and the availability of undesirable color and texture in any fresh produce can consider as a serious problem encountered during the supply chain. about 60% of the vendors are more likely to store their products for two days. however, others prefer to store them for three and five days. vendors are storing their products within time that is not exceeding these specific periods due to the lack of ventilated storage utilities (negasi et al., 2013). high temperature (tilahun, 2010) was also one of the reasons that make vendors storing their products for not more than 5 days as it was characterized to reduce the quality of fresh produce as it can reach to 45°c in oman. some of the vendors were not storing their products as they were selling the whole amount in the same day. there were several factors causing postharvest losses along the supply chain as stated by the vendors. for example, 55% of the vendors suggested that nature of the product was the most important barrier causing fresh produce losses as they are highly perishable (nath et al., 2018), sensitive (parfitt et al., 2010) and required careful storage, transportation and handling facilities (kader, 2013) before they reach to the market. this is followed by marketing problems, improper harvesting and other causes due to infections with 30%, 10% and 5% respectively. summary of vendor’s respondents on postharvest quality, losses and practices is shown in table 1. tomato quality analysis: experimental results weight loss: the results showed a significant effect (p<0.05) of storage days and temperature on tomato weight loss. in the current study, high weight loss was recorded with 16.6% in tomato stored at 22°c compared to 3.18% losses at 10°c for 12 days storage period. ambient storage condition showed the ability to increase weight loss of tomato due to high water dehydration (fagundes et al., 2015), transpiration (žnidarčič et al., 2010) and respiration rate (žnidarčič and požrl, 2006). furthermore, ayomide et al. (2019) stated that low relative humidity (45±5%) at 22°c was responsible for the reduction of water content in fresh produce leading to weight loss. similar findings were recorded by pinheiro et al. (2013) on the stored fresh tomato. these results were in agreement with different studies in which a progressive increase was also found in weight loss during storage time at 8°c, 12°c, 20°c for 20 days (park et al., 2018), at 34°c for 10 days (pila et al., 2010) and at room temperature, 12°c and 5°c for two weeks (javanmardi and kubota, 2006). these findings were also in accordance with that of abiso et al. (2015) who reported high percentage of weight loss in tomato with different maturity stages after 10 days storage at room temperature that could be mainly due to respiration and transpiration with a minimum loss in tomato stored at cold temperature. overall, low weight loss in tomato at low storage temperature can be resulted from the ability of cold stored tomato to affect vapor pressure and increase water retention. color measurements: color measurements of this study showed that l* value was significantly (p<0.05) affected by storage time and temperature (table 2). l* value decreased from 14.13±1.68 to reach 11.76±0.63 on day 0 and 12, respectively, at 10°c storage. however, the reduction was three times higher on tomato stored at ambient storage condition as it became 4.96±0.55 in the last day of storage. at 12 day of storage, study showed 64.89% reduction on lightness on tomato stored at 22°c compared to only 16.77% at 10°c. this attributed to tomato darkening resulted from the synthesis of carotenoids (yahia et al., 2007). similarly, storage days and temperature showed a statistical difference (p<0.05) with a* value as tomato color altered from bright green (-) to dark red (+) color (table 2). storage at 22°c decreased a* values of tomato from -2.19±0.83 on day 0 to 8.02±1.59 and 12.22±0.98 on day 6 and 12 respectively. in contrast, a* value was increased table 1. summary of vegetables vendor’s responses on questionnaire (%) consumer preference on a specific product days of storing the products the main barrier of postharvest losses texture 35% 2 60% infection 5% color 35% 3 20% improper harvesting 10% flavor 20% 5 20% nature of the product 55% money 10% 7 0% marketing problems 30% 17research paper al dairi, pankaj, al-mahdouri slowly to reach 1.53±0.51and 5.68±0.72 on day 6 and 12 respectively after it was 2.19±0.83 on day 0 at 10°c. the a* value increment at 22°c occurred due to ethylene biosynthesis (hatami et al., 2012), synthesis of lycopene and degradation of chlorophyll (lópez and gómez, 2004) that allowed for the intensification of red color (weingerl and unuk, 2015). this can also advocate what has been recorded by munhuewyi (2012), where tomato kept at ambient condition can provide an ideal environment for tomato ripening that is categorized with increasing redness compared to cold storage condition. messina et al. (2012) found the same behavior in tomato stored for 7 and 14 days. regarding storage at cold temperature, guillén et al. (2006) reported similar results on different variety of tomato cultivars at 10°c for 28 days. table 2 presents b* value (mean±sd) at 10°c and 22°c for 12 days storage conditions. there was no significant (p>0.05) change on b* value of fresh tomato at both storage conditions during the whole period of storage. same results of non-significance on b* value were recorded by lópez and gómez (2004) during storage. total color change ∆e during storage is consider as a result of changes in l*, a* and b* values. storage days showed a significant impact (p<0.05) on color differences ∆e value of tomato stored at 10°c and 22°c. overall color differences (∆e) was mostly higher for ambient stored tomato (20.05±4.56) compared to optimum temperature (7.74±4.07) after 12 days of storage (table 2). moreover, no changes (p>0.05) occurred in chroma and hue values during 12 days at both storage temperature conditions (table 2). however, tadesse et al. (2015) showed a significant differences in chroma and hue stored for 16 days at 4, 20 and 30°c. firmness: the data showed that firmness of stored tomato was significantly (p<0.05) affected by storage time and temperature. in the day last of storage, the highest value (49.64 n) was reported in tomato stored at 10°c while the storage at 22°c reported the lowest value (11.18 n) (table 2). moisture losses (lana et al., 2005), degradation of polysaccharide (teka, 2013) and degradation of tomato cell wall were due to enzymes activation could be the main reason for decreasing firmness during storage (hatami et al., 2012). slow increase of firmness was shown on tomato firmness stored at 10°c due to the increment of relative humidity, which had the ability to slow softening and enhance/retain the firm status of tomato during storage (ayomide et al., 2019). the findings of firmness reduction were in agreement with tigist et al. (2013) who stated storage at 22°c reduced the firmness of tomatoes. total soluble solids (tss): tomato total soluble solid (tss) ranged from (4.04 to 4.48) °brix in this study (table 2). the highest value (4.48 °brix) was recorded on day 10 in tomato stored at 10°c where the lowest value (4.04 °brix) was shown on day 6 and 10 in tomato stored at 22°c. therefore, the study revealed no statistical differences (p>0.05) of storage days and temperature on tomato total soluble solid (tss). similarly, wills and ku (2002) experienced the same finding of non-significance after storing tomato for 10 days at ambient room temperature. table 2. quality parameters data of tomato at two storage conditions during12 days of storage. quality parameter storage temperature storage days 0 2 4 6 8 10 12 l* 10°c 22°c 14.13±1.68 14.13±1.68 12.39±1.56 12.37±0.55 13.25±1.07 9.09±0.72 13.26±1.13 7.81±0.63 13.36±1.56 6.34±0.71 11.87±1.75 5.95±0.75 11.76±0.63 4.96±0.55 a* 10°c 22°c -2.19±0.83 -2.19±0.83 0.45±1.26 2.64±2.58 1.1±0.15 5.88±0.63 1.53±0.51 8.02±1.59 2.7±0.49 9.15±1.33 3.0±0.63 10.13±0.73 5.68±0.72 12.22±0.98 b* 10°c 22°c 54.36±4.42 54.36±4.42 52.40±1.23 49.22±2.56 54.02±3.36 44.80±2.68 56.95±4.95 50.96±1.01 54.52±1.83 41.72±5.25 54.74±6.68 41.99±3.10 56.90±2.20 46.35±6.28 ∆e 10°c 22°c 5.94±4.02 8.42±2.45 5.94±3.59 13.98±5.33 6.12±2.72 18.70±10.98 6.60±1.03 19.14±5.44 7.86±2.06 19.81±5.65 7.74±4.07 20.05±4.56 chroma 10°c 22°c 54.41±4.40 54.41±4.40 52.41±1.24 49.34±2.53 54.03±3.36 45.19±2.60 56.97±4.95 51.60±0.90 54.59±1.85 42.74±5.05 54.82±6.65 43.20±2.99 57.18±2.25 47.94±6.23 hue 10°c 22°c -1.53±0.01 -1.53±0.01 0.93±1.38 5.27±18.74 1.55±0.003 7.72±1.28 1.54±0.008 6.52±1.11 1.51±0.007 4.65±1.02 1.51±0.01 4.16±0.51 1.47±0.009 3.79±0.40 firmness (n) 10°c 22°c 34.73±3.92 34.73±3.92 37.08±3.73 32.18±5.30 41.79±3.83 27.27±6.77 43.16±2.75 21.78±1.45 46.89±2.06 20.01±1.08 48.46±2.55 12.16±1.57 49.64±2.35 11.18±1.08 tss (%) 10°c 22°c 4.12±0.17 4.12±0.17 4.26±0.23 4.08±0.08 4.10±0.23 4.32±0.44 4.42±0.34 4.04±0.05 4.30±0.18 4.16±0.08 4.48±0.04 4.04±0.05 4.34±0.18 4.12±0.17 18 squ journal of agricultural and marine sciences, 2021, volume 26, issue 1 effect of storage conditions on postharvest quality of tomatoes: a case study at market-level conclusion color and texture of fresh tomato were highly affected by time and storage temperature. this indicated the significance of these two parameters as they greatly affect consumer’s acceptance in markets. this agreed what had been responded in the questionnaire as most of the vendors suggested that color and texture were the top consumer’s preference for a specific food product. similarly, weight loss, l*and a*, were influenced by storage days at 10°c and 22°c. most of these quality parameters were almost retained at low temperature (10°c). no significant changes were observed for b*, chroma, hue and tss values at both storage conditions for 12 days storage. this study indicated that storage temperature was one of the vital factors, which required high monitoring along postharvest supply chain and marketing. acknowledgement the authors would like to thanks sultan qaboos university for funding this study through internal grant (ig/agr/swae/19/03). references abiso e, satheesh n, hailu a. 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(2015). chemical and fruit skin colour markers for simple quality control of tomato fruits. croatian journal of food science and technology 7(2): 76-85. wills r, ku v. (2002). use of 1-mcp to extend the time to ripen of green tomatoes and postharvest life of ripe tomatoes. postharvest biology and technology 26(1): 85-90. yahia e, soto-zamora g, brecht j, gardea a. (2007). postharvest hot air treatment effects on the antioxidant system in stored mature-green tomatoes. postharvest biology and technology 44(2): 107-115. žnidarčič d, ban d, oplanić m, karić l, požrl t. (2010). influence of postharvest temperatures on physicochemical quality of tomatoes (lycopersicon esculentum mill). journal of food agriculture & environment 8(1): 21-25. žnidarčič d, požrl t. (2006). comparative study of quality changes in tomato cv.‘malike’(lycopersicon esculentum mill.) whilst stored at different temperatures. acta agriculturae slovenica 87(2): 235-243. research paper journal of agricultural and marine sciences vol. 22 (1): 2-7 doi: 10.24200/jams.vol22iss1pp2-7 received 15 apr 2016 accepted 15 nov 2016 evaluating continuous application of treated sludge on soil and plant productivity ahmed al-busaidi*, mushtaque ahmed and baby shaharoona * ahmed al-busaidi ( ) sultan qaboos university, college of agricultural and marine sciences, department of soils, water and agricultural engineering. box 34, al-khod 123. sultanate of oman. email: ahmed 99@squ.edu.om introduction sewage sludge is a byproduct of sewage treatment processes, comprised of organic materials, macro and micronutrients, some toxic metals, microorganisms, and micro-pollutants. the nutrient elements present in the sewage sludge could help in fulfillment of the nutrientional requirement of the plants and the organic matter could act as soil conditioner. this is due to the fact that sewage sludge contains high amounts of plant nutrients for instance, nitrogen, phosphorus, calcium and magnesium but usually these are deficient in potassium (logan and harrison, 1995). usually, the applications of sewage sludge could improve soil physical properties such as porosity, bulk density, aggregate stability and water holding capacity. nonetheless, its continuous application could result in the accumulation of potentially toxic heavy metals. the accumulation and availability of heavy metals associated with sewage sludge is strongly influenced by soil ph, cation exchange capacity, organic matter, and mobility and speciation of specific metals (korboulewsky et al., 2002). generally, the application of higher amounts of sewage sludge to soil has been found to increase the bioavailability of heavy metals, however, the low doses of sewage sludge are not found to cause significant increases in heavy metal concentrations (kulling, 2001). sewage sludge amendment increases the production of a variety of plants including vegetables, cereals, grasses and trees (ramulu, 2002). the consumption of such plants might pose a serious risk to human health (hue and ranjith, 1994). in oman, haya water company is mixing treated sewage bio-solids with green waste to produce compost تقييم اإلضافة املستمرة للحماة املعاجلة لرتبة وإنتاجية النبات امحد البوسعيدي*1و مشتاق امحد1 و بييب شحروذا1 abstract. kala compost is a mixture of treated sewage bio-solids and green wastes. it can improve soil fertility and plant growth. however, long-term application of treated sewage bio-solids could result in heavy metals accumulation and some health problems. the objective of this study was to evaluate the effect of a long run application of kala compost mixed with chemical fertilizer on soil and plant productivity. soil and plant (mainly cucumber) samples were taken from 12 greenhouses that received kala compost continuously for the last five years. no symptoms of physical or chemical problems were observed in the greenhouses and measured soil samples. moreover, the soil had sufficient values of different nutrients for plant growth and all measured micronutrients (heavy metals) were within the safe limit and below the range of the international standards. an excellent growth was observed in all grown plants and no symptoms of elements deficiency were found. chemical analysis of fruit samples did not show any accumulation of heavy metals and all measured elements were within the safe limit and did not exceed the international standards. it can be concluded that kala compost was a good media for plant growth that can enrich the soil with different elements needed for higher yield. however, more monitoring is needed with treated bio-solid application but good management could be the key to avoid any adverse effect of any contaminant. keywords: kala compost; heavy metal; plant growth امللخــص: مســاد كال هــو خليــط مــن احلمــاة املعاجلــه والبقايــا النباتيــة وهــو يســاعد علــى حتســن خصوبــة الرتبــة ومنــو النبــات. ولكــن اإلضافــة املســتمرة والطويلــة قــد تــؤدي إىل تراكــم العناصــر الثقيلــة، وقــد تــؤدي إىل أضــرار صحيــة. هتــدف هــذه الدراســة إىل تقييــم تأثــر اإلضافــة املســتمرة لســماد كال خملوطــا مــع الســماد الكيمــاوي علــى الرتبــة ومنــو النبــات. عينــات مــن الرتبــة والنبــات )غالبــا اخليــار( قــد أخــذت مــن اثنــا عشــر بيتــا حمميــا أضيــف هلــا مســاد كال ملــدة مخــس ســنوات. نتائــج الدراســة تلخصــت يف أنــه مل تالحــظ أي مؤشــرات ملشــاكل فيزيائيــة أو كميائيــة علــى نباتــات البيــوت احملميــة وحــى عينــات الرتبــة. وكذلــك أثبتــت النتائــج أن الرتبــة كانــت هبــا عناصــر غذائيــة تدعــم منــو النبــات، وأن مســتوى العناصــر الثقيلــة كان يف املســتوى اآلمــن وكان متوافًقــا مــع املعايــر الدوليــة. وكذلــك أعطــى النبــات منــوا جيــدا ومل يالحــظ عليــه أي نقــص للعناصــر الغذائيــة. وبالنســبة حملصــول اخليــار مل يالحــظ عليــه أي تراكــم للعناصــر الثقيلــة وكانــت القــراءات يف املســتوى اآلمــن ومل تتخطــى املعايــر الدوليــة. لذلــك نســتنتج أن مســاد كال كان وســطا زراعيــا جيــدا لنمــو النبــات وميــد الرتبــة بالعناصــر الغذائيــة الالزمــة إلنتــاج عــايل. ومــع هــذا فأنــه يوصــى أن تتــم املراقبــة املســتمرة للرتبــة والنبــات عنــد إضافــة احلمــاة املعاجلــة، واإلدارة الســليمة قــد تكــون احلــل األمثــل لتجنــب تراكــم أي ملوثــات بالرتبــة والنبــات. الكلمات املفتاحيه: مساد كال; العناصر الثقيلة ; منو النبات 3research article al-busaidi, ahmed, and shaharoona called kala compost that can be used for agriculture, landscaping and for individual gardens. however, a high application of sewage bio-solids could result in heavy metals accumulation and many health problems. therefore, the objective of this study was to evaluate farmer practices in continuous application of treated sludge (kala compost) on soil and plant productivity. the work could help the interested stakeholders to understand the research achievements in soil fertility and quality horticultural crop production through regulated usage of kala compost. materials and methods the study was carried out in two farms with 59 greenhouses. the first farm is located in the barka area (b) in the al-batinah region where kala compost has been applied continuously for the last 5 years. kala compost made of biosolids, green waste, horse bedding and scrap wood. it has been used as a fertilizer for different crops grown in open field and greenhouses. moreover, other fertilizers such as chemical fertilizer (npk) and chicken manure have been applied too. the rate of application was 20 kg of kala compost + 20  kg of chicken manure + 3 kg of n:p:k (15:15:15) fertilizer per 41.5 m2. many vegetables and fruits have been grown in the farm such as cucumber, cabbage, eggplant, hot pepper, date palm, mango, lemon, etc. the study was focused on 12 greenhouses where the farmer has been growing cucumber (cucumis sativus). the site was visited twice (january & june 2015) and each time soil, water and plant samples were taken from all greenhouses. the second farm was in the al-hamra (h) area in the dakhiliyah region where the kala compost has been applied continuously for last 5 years. the farm is mainly greenhouses with cucumber (cucumis sativus) plants. excellent yields were obtained and commercially sold to different markets. for the study, 12 greenhouses were selected and samples for soil, water and plants were taken in both visits during january and june 2015. soils extracts were obtained using the saturation paste method while plants extracts were obtained using acid digestion method. final extracts were sent to reputed laboratory for macro and micro elements analysis. results irrigation water both farms are irrigated by groundwater using the drip irrigation system. the quality of water is good for irrigation with a low concentration of salts (table 1). if the soil is well managed, it is not expected to have problems with salt accumulation. comparing heavy metals concentrations with recommended values mentioned in table 1, it can be seen that all measured elements are below the maximum limit which means this water is suitable for agriculture. however, boron was detected which may cause some accumulation in the soil with the long term application of this water if poor management is practiced. nevertheless, the higher concentrations of toxic metals do not necessarily mean toxicity to the plants. as metals availability and uptake by plants in agricultural environments is related to i) the activity of metal ions in the solution, which depends upon ph, pe, concentration and composition, ii) the concentration and ratios of accompanying elements that influence the uptake and transport of that metal ion by roots, and iii) numerous environmental factors (pessarakli, 1999). soil samples the general soils of both locations are loamy soil which is one of the best types of soils for agricultural practices (table 2). barka soil has more silt which can absorb and keep more water whereas al-hamra soil has more sand that could enhance leaching process of extra salts and improve soil aeration. additions of organic fertilizers enhance soil fertility and improve soil structure. table 1. elemental concentrations in irrigation water. parameter ph ecw ca k na mg p fe ni unit ds/m mg/l mg/l mg/l mg/l mg/l mg/l mg/l barka 8.25 1.15 44.26 4.23 97.89 33.12 0.003 <0.002 <0.01 hamra 8.10 1.23 53.98 3.69 60.94 42.60 0.001 <0.002 <0.01 parameter b cu zn pb mo co cd cr hg unit mg/l mg/l mg/l mg/l mg/l mg/l mg/l mg/l µg/l barka 0.31 0.003 0.011 <0.003 <0.010 <0.001 <0.001 0.032 <0.03 hamra 0.25 0.002 <0.004 <0.003 <0.010 <0.001 <0.001 <0.006 <0.03 recommended * 0.75 0.05-1 2-5 0.1 0.01 0.1 * source: cpcb (2002) table 2. soil textural analysis. location sand (%) clay (%) silt (%) texture barka 36.4 8.8 54.8 silt loam hamra 51.6 5.2 43.2 sandy loam 4 squ journal of agricultural and marine sciences, 2017, volume 22, issue 1 evaluating continuous application of treated sludge on soil and plant productivity ramulu (2002) found that organic matter added to the soil as sewage sludge composts improved the soil properties, such as bulk density, porosity and water holding capacity. in general, the higher organic matter proportion in sludge decreased bulk density and increased the aggregate stability. these improvements in soil physical properties increased water-holding capacity by promoting higher water retention in sludge-amended soils (ojeda et al., 2003). using different fertilizers to improve soil fertility is good but over-application of any fertilizer could cause salt accumulation in the soil surface. from (fig. 1), it can be seen that most soils had high values of soil salinity at the beginning of the growing season, which comes normally from heavy application of different fertilizers such as chemical fertilizer (npk), organic manure (chicken) and kala compost. those salts were found in the greenhouses that were prepared for the new season or plants were in the initial stage of growth. over application of irrigation water was the main reason for decreasing soil salinity and leaching down or moving salts away from root zones which can be seen at the end of the growing season in the greenhouses that had big or harvested plants (fig. 2). moreover, those salts can be considered as nutrients that are needed by plants and will be consumed by the time. in general, organic compost such as kala is rich with nutrients which could increase the salinity value but at the same time those salts will be slowly released to the soil and support plant growth for a long time without any problem of toxicity. this finding was also supported by kulling (2001) and logan and harrison (1995) when they reported that sewage sludge is composed of organic compounds, macronutrients, wide range of micronutrients, non-essential trace metals, organic micro pollutants and microorganisms. the macronutrients in sewage sludge serve as a good source of plant nutrients and the organic constituents provide beneficial soil conditioning properties. more salts in the soil mean more nutrients are available for the plant. an adequate amount of major nutrients (npk) can be seen in the soil samples (table 3). however, presence in high amount of some salts like na could cause toxicity problem for the plants. therefore, leaching and good management are required to get the full benefits of all nutrients with maximum yield. this finding is also supported by hernandez et al. (1991) when they conducted a study to analyze the influence of sewage sludge application to a calciorthid soil on the soil availability of macronutrients (n, p, and k) and heavy metals (fe, cu, zn, mn, ni, cr, cd, and pb). total n and extractable n and p contents increased in the sludge-amended soil. micronutrients or heavy metals are the most critical elements in the soil. their values could be indicators for soil fertility or contamination. from (fig. 2), it can be seen that values for all micronutrients and heavy metals are within the acceptable ranges and even the maximum values for all measured elements were less than the international acceptable maximum values (table 4). some values were found in soils that had a high amount of salts indicating they were close to fertilizer contents, even though the concentrations of heavy metals did not exceed the international standards. high value of boron could be resulting from continuous accumulation of 0 5 10 15 20 25 barka hamra location s oi l s al in ity (e c e, d s /m ) end start figure 1. soil salinity at the beginning and at the end of the growing season. table 3. soil elemental analysis. concentrations are in mg·kg -1 (ppm). ca p k na mg n min 5.07 0.23 3.47 3.68 2.58 1500 max 133.24 2.13 248.87 121.67 44.16 11200 average (n=28) 32.03 0.87 75.90 42.32 16.65 5600 table 4. micronutrients concentrations in the studied soils. all concentrations are in ppm except hg in ppb. parameter fe ni b cu zn pb mo co cd cr hg min 0.000 0.004 0.060 0.005 0.001 <0.001 0.010 0.000 <0.0003 <0.002 <0.01 max 0.039 0.103 0.496 0.102 0.096 <0.001 0.062 0.023 <0.0003 <0.002 <0.01 average 0.012 0.024 0.238 0.037 0.029 <0.001 0.027 0.003 <0.0003 <0.002 <0.01 recommended* 1000 75-100 50-140 200-300 300 not fixed 3-6 150 * source: cpcb (2002). 5research article al-busaidi, ahmed, and shaharoona boron from irrigation water as shown in table 1. these findings were in parallel with hernandez et al. (1991) when they found that the extractability of fe, cu, mn, zn and pb increased due to sludge application as compared to the control. plant samples plants growth and yields were excellent in both farms. the mature plants looked healthy and full of fruits (fig. 3). initial salts applied to the soil as fertilizer were pushed away from the root zone creating enriched environment for growth around the plants. therefore a high yield resulted without facing any problem of nutrient deficiency. it seems that kala compost and other fertilizers were creating a good environment for plants by releasing multi-nutrients, reducing evaporation and keeping much water in the root zone. in addition, high rates of sludge application could increase the cation exchange capacity, which could help to retain essential plant nutrients within the rooting zone due to additional cation binding sites (soon, 1981). the harvested cucumber had a high amount of good nutrients such as ca, k, mg and p (table 5). those values resulted from rich soil that supported plant growth as shown in tables 3 and 4. good results were also found in nielson et al. (1998) study when the municipal biosolids were added to cultivate carrots and chard on irrigated soils. a significant increase in yield was found in plants growing bio-solid amended soil as compared to those grown in non-amended soil. in addition, a similar study with cotton (g. hirsutum) also showed advancement of flowering and fruiting by 2–3 weeks under sludge-amended soil as compared to fertilizer amended ones (tsakou et al., 2001). the faster development and greater biomass production in plants grown in sludge-amended soil may be responsible for an early reproductive cycle. moreover, the complex of organic and the inorganic compounds of sewage were broken down into simpler forms, and thus the final treated sludge became useful and beneficial to the seedling growth (metcalf and eddy, 2003). long-run consumption of some heavy metals in vegetables or fruits could cause some health problems. as it can be seen from (fig. 4) that all measured heavy metals were within the acceptable levels, even the maximum values were below the recommended values (table 6). it can be noticed that nickel values are high and exceed the international limits. however, its original values in the soil samples were low and within the international standards. an excess amount of this element in the fruits could be related to human activities and plant absorption ratio. if it is present in high values in the soil, this may cause some growth problems. extra samples were taken from cabbage plant and no problem was observed in plant growth or heavy metals concentrations even ni concentration was low (3 mg/kg) and within the recommended values. nickel is a transition metal and found in natural soils at trace concentrations. however, its concentration is increasing in certain areas by human 0.00 0.05 0.10 0.15 0.20 b cu zn mo ni fe co cr pb cd element c on ce nt ra tio n (p pm ) figure 2. average concentrations of soils micronutrients. figure 3. growing cucumber plants in both farms. 6 squ journal of agricultural and marine sciences, 2017, volume 22, issue 1 evaluating continuous application of treated sludge on soil and plant productivity activities such as mining works, emission of smelters, burning of coal and oil, sewage, phosphate fertilizers and pesticides. an excess of ni in soil causes various physiological alterations and diverse toxicity symptoms such as chlorosis and necrosis in different plant species. plants grown in high ni containing soil showed impairment of nutrient balance and resulted in disorder of cell membrane functions. other symptoms observed in ni treated plants were related with changes in water balance. in general, many factors influence the uptake of metals and include the growing environment, such as temperature, soil ph, soil aeration, eh condition (particularly of aquatic environment) and fertilization, competition between the plant species, the type of plant its size, the root system, the availability of the elements in the soil or foliar deposits, the type of leaves, soil moisture and plant energy supply to the roots and leaves. several studies have evaluated the tissue concentrations of nutrients and heavy metals in plants when grown in the sewage sludge amended soil. the accumulation pattern varied with soil type, plant species, phenology and chelating effects of other metals (mahler et al., 1980). in dowdy and larson’s (1975) study, cd, zn, ni, hg and other toxic metals were high in sweet corn when grown on sludge-amended soil, but the accumulation was less in corn kernels than in leaves and roots. generally, the accumulation of heavy metals depends on soil managements and plant selectivity. pescod (1992) concluded that the concentrations of heavy metals in seeds were within normal level when treated wastewater effluent was used. such results make it clear that heavy metal in soil are not readily bio-available for crop uptake and do not represent a threat to quality of crop consumption. conclusion it can be concluded that fertilizers and composts such as kala applied in this study were good conditioners for the soil as they supported plants with many elements needed for high yield. soil and plant chemical analysis did not show any indications of heavy metal accumulation. five years of application of kala compost did not cause any environmental or potential human health problems. therefore, we believe it is safe to apply kala compost to some agriculture crops if good management is applied. moreover, it is recommended that long-term records on application of kala compost alone is required, so clear findings can be obtained. acknowledgements the authors would like to thank staff from sultan qaboos university for their support in collecting and analyzing soil, water and plant samples. special thanks to haya water company and usaid (fabri) for their financial support. references cpcb (central pollution control board), 2002. parivesh, newsletter from cpcb. available at http://cpcb.nic. in/iimlko.pdf dowdy, r.h. and larson, w.e. 1975. the availability of sludge borne heavy metals to various vegetable crops. j. environ. qual., 4: 278-282. hernandez, t., moreno, j.i., and costa, f. 1991. influence of sewage sludge application on crop yields and heavy metal availability. soil sci. plant nutr., 37 (2): 201–210. hue, n.v. and ranjith, s.a. 1994. sewage sludges in ha0 20 40 60 fe zn b ni cu cr pb co mo cd element c o n c e n tr a ti o n ( p p m ) figure 4. average concentration of micronutrients in cucumber fruits cultivated on kala compost. table 5. soil textural analysis. all values in mg·kg -1 (ppm). element ca k na mg p min 2500 11300 1300 2050 3500 max 5850 23900 6000 2900 5650 average (n=8) 4343 18771 2829 2514 4450 table 6. micronutrients concentrations in the studied soils. all in ppm except hg in ppb. parameter fe ni b cu zn pb mo co cd cr min 38.5 3 25 3.5 22 2.5 2.5 2.5 1.25 2.5 max 87 40 25 13 52 2.5 2.5 2.5 1.25 2.5 average (n=8) 67.43 21.36 25 6.79 33.29 2.5 2.5 2.5 1.25 2.5 recommended * 450 5-10 30-40 50-60 2.5-5 1.5 5-20 * source: cpcb (2002). 7research article al-busaidi, ahmed, and shaharoona waii: chemical composition and reactions with soils and plants. water air soil pollut., 72: 265–283. korboulewsky, n., dupouyet, s. and bonin, g. 2002. environmental risks of applying sewage sludge compost to vineyards: carbon, heavy metals, nitrogen, and phosphorous accumulation. j. environ. qual., 31: 1522– 1527. kulling, d., stadelmann, f. and herter, u. 2001. sewage sludge – fertilizer or waste? ukwir conference, brussels. logan, t.j. and harrison, b.j. 1995. physical characteristics of alkaline stabilized sewage sludge (n-vitro soil) and their effects on soil properties. j. environ. qual., 24: 153–164. mahler, r.j., bingham, f.t., sposito, g. and page, a.l. 1980. cadmium enriched sewage sludge application to acid and calcareous soils, relation between treatment, cd in saturated extracts and cd treatment. j. environ. qual., 9: 359–364. metcalf and eddy, 2003. wastewater engineering: treatment, disposal, and reuse, fourth ed. mcgraw-hill publishing company ltd., new york. nielson, g.h., hogue, e.j., nielson, d.,and zebarth, b.j. 1998. evaluation of organic wastes as soil amendments for cultivation of carrot and chard on irrigated sandy soils. can. j. soil sci., 78: 217–225. ojeda, g., alcaniz, j.m. and ortiz, o. 2003. runoff and losses by erosion in soils amended with sewage sludge. land degrad. dev., 14 (6): 563–573. pescod, m.,1992. wastewater treatment and use in agriculture. bull. fao #47 (125) (rome). pessarakli, m. 1999. handbook of plant and crop stress. crc, usa. ramulu, u.s. 2002. reuse of municipal sewage and sludge in agriculture. scientific publishers, jodhpur, india. soon, y.k. 1981, solubility and sorption of cadmium in soils amended with sewage sludge. j. soil sci., 32: 85–95. tsakou, a., roulia, m. and christodoulakis, n.s. 2001. growth of cotton plants (gossypium hirsutum) as affected by water and sludge from a sewage treatment plant: i. plant phenology and development. bull. environ. contam. toxicol., 66: 735–742. research paper journal of agricultural and marine sciences vol. 22 (1): 48-57 doi: 10.24200/jams.vol22iss1pp48-57 reveived 20 apr 2016 accepted 20 dec 2016 use of renewable energy for desalination in urban agriculture in the gcc countries: possibilities and challenges salem al-jabri * and mushtaque ahmed * salem al-jabri ( ) sultan qaboos university, college of agricultural and marine sciences, dpt. of soils, water and agricultural engineering. box 34, al-khod 123. sultanate of oman. email: salemj@squ.edu.om introduction the gulf cooperation council (gcc) was es-tablished in 1981 with six member countries: bahrain (bh), kingdom of saudi arabia (ksa), kuwait (kw), sultanate of oman (om), qatar (qr), and united arab emirates (uae). historically, the geographical location of the arabian gulf provided a focal استخدام الطاقة املتجددة لتحلية املياه يف الزراعة احلضرية يف دول جملس التعاون اخلليجي: الفرص والتحدايت سامل اجلابري ومشتاق أمحد abstract. the current dependence of the gcc countries on fossil oil and gas is unwise in terms of economic and environmental sustainability. gcc countries must consider the use of renewable energy to cope with price fluctuations of oil and gas in the global market and to lower the emission of green house gases. the demand for food and water in the gcc countriesis increasing due to high growth rate of population. given the weather conditions and available amounts of natural water resources, the demand on food and water cannot be met unless alternative sources of water are considered. several studies pointed out that the desalination technology is probably the only option for producing ample amounts of water for food production in arid environments. this work explores the potential of use of desalination technology for producing irrigation water in gcc countries, with special emphasis on experience of the sultanate of oman compared with that of spain. desalination can always provide a tailored-quality irrigation water at any climatic conditions. the main challenge for considering desalination for agriculture is purely economic; where gcc countries could consider it only if intensive horticulture of high-value cash crops, such as vegetables and flowers in controlled environments, is considered. disposal of brine water is also a challenge and must be done at an additional cost. depending on the quality of desalinated water, several studies showed that solar-operated desalination technologies are in a mature stage and economically viable. therefore, solar energy can make the desalination technology an attractive option to sustain agriculture and food supply in gcc countries. keywords: desalination; renewable energy; urban agriculture; irrigation; brine disposal. امللخــص: تعتمــد دول جملــس التعــاون اخلليجــي حاليــاً علــى النفــط األحفــوري والغــاز يف توفــر الطاقــة الالزمــة للتنميــة عمومــاً ولتحليــة امليــاه خصوصــاً. إن املعــدالت احلاليــة الســتهالك الطاقــة غــر متوافــق واألعــراف األساســية لالســتدامة االقتصاديــة والبيئيــة. لذلــك جيــب علــى دول اجمللــس اختــاذ خطــوات جــادة حنــو التقليــل مــن اهلــدر العــام للطاقــة وإحــالل الطاقــة املتجــددة وذلــك مــن أجــل خفــض إنبعاثــات ملوثــات اهلــواء الــي تســهم يف زيــادة اإلحتبــاس احلــراري وتغــر املنــاخ. كمــا تســاهم الطاقــة املتجــددة يف النــأي باقتصاديــات دول اجمللــس عــن أضــرار تقلبــات أســعار النفــط العامليــة. ويف املقابــل فــإن الطلــب علــى املــاء يف هــذه الــدول يف تزايــد مســتمر وبوتــرة عاليــة. ونظــراً للظــروف اجلويــة وكميــات املــوارد املائيــة الطبيعيــة املتاحــة، فإنــه ال ميكــن تلبيــة الطلــب علــى الغــذاء واملــاء إال إذا اعتــرت مصــادر بديلــة للميــاه. ولقــد خلصــت دراســات عــدة إىل أن تكنولوجيــا حتليــة امليــاه هــي اخليــار الوحيــد إلنتــاج كميــات وافــرة مــن امليــاه إلنتــاج الغــذاء يف البيئــات اجلافــة. يستكشــف هــذا العمــل إمكانيــة اســتخدام تكنولوجيــا حتليــة ميــاه البحــر إلنتــاج ميــاه الــري يف دول جملــس التعــاون اخلليجــي، مــع الرتكيــز بشــكل خــاص علــى جتربــة ســلطنة عمــان مقارنــة مــع إســبانيا. إن حتليــة امليــاه ميكــن أن توفــر ميــاه الــري ذات جــودة مصممــة يف أي ظــرف مــن الظــروف املناخيــة وبشــكل مســتمر. إن املــردود االقتصــادي ميثــل العائــق الرئيســي إلحــالل خيــار التحليــة ألغــراض الــري والزراعــة. وتعتــر التجربــة اإلســبانية مثــااًل حيتــذى بــه يف هــذا املوضــوع، حيــث جنــح املزارعــون هنــاك يف اســتخدام تقنيــة التحليــة لزراعــة حماصيــل ذات مــردود عــاٍل يف احلقــول والبيــوت احملميــة، مثــل الفواكــه والزهــور واخلضــراوات الورقيــة الطازجــة. ويعتــر التخلــص مــن امليــاه املرجتعــة العاليــة امللوحــة التحــدي الثــاين والــذي يضــر كثــراً بالبيئــة إذا مل يتــم التخلــص منــه بطــرق علميــة تتــواءم مــع املقومــات البيئيــة. إن تكلفــة التخلــص مــن امليــاه املرجتعــة كذلــك يعتــر عبئــاً اقتصاديــاً. وقــد بينــت دراســة أجريــت حديثــاً أن املــزارع الــي اســتخدمت امليــاه احملــالة يف ســلطنة عمــان ســتكون جمديــة اقتصاديــاً إذا كانــت املنتجــات ذات قيمــة عاليــة يف األســواق أســوة بالنمــوذج األســباين. كمــا بينــت العديــد مــن الدراســات أن تقنيــات حتليــة امليــاه الــي تعمــل بالطاقــة الشمســية هــي يف مرحلــة ناضجــة وبإمكاهنــا أن توفــر الكثــر مــن التكلفــة يف جمــاالت الــري والزراعــة. لذلــك فيجــب علــى دول جملــس التعــاون اخلليجــي أن تســتثمر يف اســتخدام الطاقــة الشمســية لتحليــة امليــاه ألغــراض الزراعــة ضمــن منظومــة متكاملــة تضمــن اســتدامة الزراعــة وتوفــر الغــذاء علــى املســتوى احمللــي، كمــا توفــر الدخــل املناســب للمــزارع يف ظــل ظــروف بيئيــة مناســبة. الكلمات املفتاحية: حتلية املياه، الطاقة الشمسية، الزراعة، االستدامة 49research article al-jabri, ahmed significance to the ggc members, especially with the discovery of oil and gas reserves after world war ii. since then, the gcc members experienced a dramatic change in general lifestyle and became the pivotal centre for energy at the global market. the gcc countries own 33.1% of oil reserves, the world’s largest, and 20.8% of the global reserves of the natural gas. consequently, gcc members became a centre of development and many expatriates and cooperants started to dwell in the region for business opportunities, which caused the region to also have one of the highest population growth rate in the world (oxford economics, 2015). figure 1 presents the trend of population growth in the gcc for the period 1995-2014 (gcc statistical bulletin, 2016), which implies the population has doubled in just less than 20 years. expatiates are becoming a high proportion of the overall population of the gcc countries when compared with their local citizens. for example, expatriates represent about 33% and 85% of total population of ksa and uae, respectively (gcc statistical bulletin, 2016). most of these expatriates are of low skills and, due to their educational level and native culture, pay little attention to water scarcity, among other natural resources. energy consumption in gcc energy requirements in the gcc have increased dramatically due to a rapid increase in development of infrastructure and population growth and due to improvement of lifestyle standards and hygiene. figure 2 indicates that gcc countries are spending staggering amounts of energy to generate electricity for various reasons, but mainly for water desalination. even though energy saving may look unnecessary, the gcc countries must undertake practical steps to reduce energy consumption in order to increase efficiency and reduce emissions of greenhouse gases. energy-related challenges that face the gcc members are fluctuations of international oil prices, the emergence of new export competitors, the discovery of shale oil and gas in some countries, and subsidy programs for energy and water at the national level. moreover, some gcc countries are facing constraints in gas production capacity that force them to import it from neighboring members or iran. therefore, they must invest in new technologies to enhance their gas production rather than depending on the imports (economist intelligence unit, 2010). the proceeding implies that gcc countries should, therefore, undertake firm measures towards energy sustainability through (i) introducing energy-efficiency measures; (ii) investing in clean fuel and renewable energy supplies; (iii) improving water efficiency; and (iv) investing in new water desalination capacity. water status in the gcc countries the gcc members are classified as arid countries and characterized by low and erratic rainfall rates, limited groundwater reserves, high evapotranspiration rates (about 3000 mm per year), and low recharge rates for groundwater aquifers. moreover, the increase in global warming due to greenhouse emissions and climate change worsen the situation in the region and results in prolonged periods of droughts. the intergovernmental panel on climate change (ipcc 2007a; 2007b; 2014) predicted that the region will face some environmental stresses due to the increase in gas emissions, which may include high incidence of reduced flows, declines in rainfall, and higher temperatures. table 1 lists some important figures regarding the hydrologic cycle in the gcc countries (world bank, 2005). highlights from table 1. water resources reserves in the gcc countries. country area (km2) mean annual rainfall (mm) groundwater recharge (mm3 y-1) non-renewable reserves (mm3) bahrain 652 30-140 110 negligible kuwait 17 818 30-140 160 n/a oman 300 000 80-400 900 102 000 qatar 11 610 20-150 50 negligible saudi arabia 2 149 690 30-550 3 850 428 400 uae 83 600 80-160 190 n/a source: world bank (2005). 0 10 20 30 40 50 1995 2000 2005 2010 2015 year po pu la tio n (m ill io ns ) figure 1. total population (millions) of gcc countries between 1995 and 2014. source: gcc statistical bulletin (april, 2016). 50 squ journal of agricultural and marine sciences, 2017, volume 22, issue 1 renewable energy for desalination in urban agriculture in the gcc table 1 are the erratic rainfall rates and low annual recharge water rates. this situation made gcc countries not consider groundwater reserves as a strategic source for drinking water. gcc members are currently considering desalination as the sole source for drinking water. ironically, gcc countries are considered one of the highest per-capita users of water in the world. ahmed et al. (2016) pointed that the gcc countries consume relatively more water than the world’s average and is estimated at 816 m3/capita-year. the world’s average is estimated at 500 m3/capita-year, (pwc, 2014). with such limited resources, the per capita of water has declined over the period 1970-2012 (fig. 3). obviously, this is due to the increase of population, water-intensive lifestyle, and high abstraction rates from groundwater aquifers (which are much greater than recharge rates). 0 200 400 600 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 year m ill io ns t on s of o il eq ui va le nt country bh ksa kw om qa uae figure 2. total energy consumption (millions tons of oil equivalent), for gcc countries between 2000 and 2020. data for 2005-2007 are actual; for 2008-2010 are estimated; and for 2011-2020 are forecasted. source: economist intelligence unit (2009). 0 400 800 1200 1970 1980 1990 2000 2007 2012 year m 3 c ap ita −1 y ea r− 1 country bh ksa kw om qa uae figure 3. changes of annual renewable water per capita between 1970 and 2012 for the gcc countries. source: world bank (2005). 51research article al-jabri, ahmed despite the low contribution towards gcc’s national gdp (<5%), the agricultural sector consumes most of the water resources available annually (fig. 4). the gcc countries are aware of the upcoming competition in the energy market and that oil and gas probably will not last forever. therefore, given the current status of water in the gcc countries and the concerns regarding climate change related to the oil and gas industry, proactive and innovative approaches should be considered to reduce the dependency on oil and gas as sources of energy, and find alternative sources of water to reduce pressure on finite groundwater resources. based on the recent review of literature, we are suggesting considering desalination technology for providing irrigation water for growing value crops for sustaining agriculture and fresh food supplies in the gcc countries and reduce the demand on finite groundwater resources, while sustaining the environment. this work reviews the international experience of the world for using desalination for agriculture. it highlights the opportunities, challenges, and the environmental risks of considering desalination technologies for agriculture in the gcc countries. moreover, we are presenting an example for the use of the technology for producing irrigation water from al batinah coast in the sultanate of oman. we are exploring the use of renewable energies to operate desalination facilities in order to minimize the desalination costs and environmental risks. finally, concluding remarks on the overall use of desalination technology are presented. desalination for agriculture: opportunities and challenges over abstraction of groundwater in gcc is much higher than rates of recharge from erratic and low rainfalls. over abstraction resulted in drop of groundwater levels to critical levels that resulted in many environmental and social issues. in coastal aquifers of oman, for example, groundwater dropped to levels below the static seawater level, which caused an imbalance of water pressures between sea level and those at the coastal aquifers. this, in turn, caused seawater to contaminate the coastal aquifers of al batinah, the most extensive agricultural region in the country (zekri, 2009). farmers have no source of water except groundwater and, therefore, rich agricultural soils were spoiled by saline irrigation water (al-belushi 2003; bajjali 2003; al barwani and helmi 2006; choudri et al. 2013). the salinization of agricultural soils is a huge loss to the farmers in terms of (i) deterioration of soil quality, (ii) loss of crop yields due to salinity stresses, and (iii) growing salt-tolerant crops of low economic returns. this situation suggests considering alternative sources of water in conjunction with innovative techniques for water management for the sake of sustaining agriculture in gcc countries, especially at coastal cities. al khamisi et al. (2013) suggested using treated wastewater (tww) in conjunction with groundwater for irrigation in efforts to minimize groundwater abstraction and enhance hydrostatic pressures of coastal aquifers of al batinah (oman). however, this option cannot be economically feasible when costs of transportation and distribution networks are added to the overall value of irrigation water. moreover, al 0 25 50 75 1990 1994 2003 2007 year pe rc en ta ge w at er a va ila bl e country bh ksa kw om qa uae figure 4. agricultural use of water in gcc countries as percent of total consumption, 1990-2007. data for kuwait(kw) in 2007 is missing. source: world bank (2005). 52 squ journal of agricultural and marine sciences, 2017, volume 22, issue 1 renewable energy for desalination in urban agriculture in the gcc jabri et al. (2012) explored the option of injecting surplus tww into coastal aquifers to reduce the extent of seawater intrusion. however, artificial recharge using tww is costly and only a small fraction of injected water could be recovered (bouwer, 2002). the quality of recharging water could lead to changes in physical and chemical characteristics of the soil and aquifer. some impurities, such as microbes, heavy metals or trace elements, if present in recharging water will contaminate the aquifer, and will be very expensive to contain and clean (bouwer, 2002). elimelech and philip (2011) identified desalination of sea and brackish waters is the only practical option to provide water in ample amounts beyond the hydrologic cycle in arid environments. due to advancement in desalination technology, lattermann et al. (2010) argued that the costs of wastewater treatment and desalination are likely to be similar in 2015 and beyond, especially in the us. world’s experience on desalination for agriculture many countries are utilizing desalination technology as a source for irrigation water. spain is the leading country in the world, where 22% of its desalination capacity (14 million m3/day) goes for irrigating high value crops (zarzo et al., 2012). examples of crops grown in spain with desalinated water are fresh vegetables, fruits, tomatoes, pepper, watermelons, oranges, and table grapes. kuwait uses about 13% of its desalination capacity (1 million m3/day) for agriculture (burn et al., 2015). saudi arabia, the world’s largest single producer of desalinated water, utilizes only 0.5% of its desalination capacity for agriculture. other countries, such as italy, australia, china, chile, qatar, bahrain, and usa are using desalinated water for agriculture at varying amounts. figure 5 shows that only 2% of global desalinated water is used for agricultural purposes (adapted from burn et al., 2015). farmers in al batinah, and other coastal areas in oman, are starting to use small-size desalination units to produce good-quality irrigation water for their farms (al jabri et al., 2015). opportunities and challenges of adopting desalination for agriculture desalination for agriculture has many advantages as identified by burn et al. (2015): • tailored quality for irrigation; • assured supply; • enables agricultural products of consistent quality; • production may be increased compared with other sources of water; • desalinated water may achieve a higher resale price due to quality and supply assurance; and • desalinated water, i.e. good-quality water, allows recovery of saline soils. the choice of desalination technology is influenced by the quality of intake water, cost of energy, energy demand, and value of desalinated water. the adoption of desalination technologies to produce irrigation water has many challenges. the main challenge is economic: desalination is still an expensive option for agriculture. this is because the size of a desalination unit is relatively small, which implies water is produced at high cost. energy-efficient desalination technologies will make this option an appropriate one for providing irrigation water. moreover, desalination costs can be reduced by using more efficient irrigation systems and intensifying agriculture of high-value crops. due to the advancement of desalination and filtration technologies, the current cost of desalination is only about 1/6 of that in 1970s (fao, 2003). another challenge to desalination of agriculture is environmental: the amount and disposal means of brine discharge. the desalination process using reverse osmosis (ro) technology produces brines at about 60% of feed water volume at almost twice the salinity level of the intake water (fao, 2003). therefore, inland desalination is hindered by means of brine disposal and adds an additional cost. however, high recovery of desalinated water is available with new technologies, such as memarmy other irrigation tourism electricity industrial municipal 0 20 40 60 global desalination capacity (%) d es tin at io n figure 5. global desalination capacities by sector (burn et al., 2015). 53research article al-jabri, ahmed brane distillation, which should reduce disposal costs per unit of water produced (burn et al., 2015). ahmed et al. (2002) discussed brine disposal in oman. however, there is no work conducted in the gcc countries regarding inland disposal of brines from desalination units for agriculture. brine disposal in the ocean requires a given dilution ratio set by environmental agencies at a given country. the quality of desalinated water usually meets irrigation requirements in terms of total dissolved salts (tds) with an electrical-conductivity (ec) value of 0.2-0.3 ds/m. depending on the source of feed water, however, caution must be taken when it comes to the level of boron (b) and tds in desalinated water. the b-concentration in irrigation water should be less than 0.50 mg/l, tds of less than 450 mg/l, and chloride concentration of less than 105 mg/l (shaffer et al., 2012). boron in neutral and acidic environments passes through the ro filters and its concentration may reach 2.0 mg/l, which is very toxic to many fruits and vegetables. zarzo (2012) listed some crops that are “semi-tolerant” to b concentration of 1.0 mg/l. special filters are needed to remove extra b, which means extra cost is need to added to the desalination costs. another issue with desalination processes is the removal of divalent cations; such as calcium, magnesium, and sulfates. these cations stabilize the structure of agricultural soils and are plant nutrients. this means re-mineralization of desalinated water is needed and can be done at an extra cost to the process of desalination. extent of desalination for agriculture in gcc: oman as an example al jabri et al. (2015) explored the use of desalination in the al batinah coast with the following indicators (i) cost of desalination unit, (ii) operation and maintenance costs (o&m), (iii) purpose of desalination, (iv) amounts and quality of desalinated and reject brines, (v) means of disposal of brines, and (vi) types of crops grown. table 3 summarizes cost and energy requirements of the desalination units used in the coastal farms in al batinah. all units used are based on the ro technology. energy tariffs in oman are subsidized and are in the range of riyal omani (omr) 0.01-0.025 per kwh. most units shown are assembled locally from imported parts. imported whole units are also available in oman and neighboring uae. table 4 lists some chemical properties of intake, desalinated, and brine waters and means of brine disposal. desalinated water produced meets irrigation requirements. most visited farms did not have greenhouses and desalinated water is used to irrigate date palms and field vegetables and other crops. this implies that farmers are not considering the economics and profitability issues here. the other issue is how do farmers dispose the high saline brine water. obviously, farmers are not aware of the environmental impacts of dumping this water in soil pits and old wells. brine water immediately destroys the structure of the soil and contaminates immediate aquifers. the deterioration of soil structure causes low infiltration capacities and, therefore, brine water remains stagnant over soil surface for prolonged periods of time. some farmers stop operating desalination units and, hence stop irrigating, until stagnant water disappears from the soil’s surface or wells. farmers are considering brine disposal is the only barrier for them to use desalination units at their farms in al batinah coast (personal communication). economics of desalination for agriculture in al batinah coast in oman farmers in oman pay 10 baisas (bz) per kwh (0.01  omr/kwh), while the cost of electricity generation is 25 bz. once the distribution infrastructure is added, the total cost of electricity including is estimated at 50 bz/kwh. al-jabri et al. (2015) presented an analysis on the real cost of desalination for the farmers in al batinah. water used for desalination in oman is brackish table 2. characteristics of some desalination units used at farm level in oman. model of desalination unit small medium large production capacity (m3/day) 11.5 19.0 38.0 cost of the unit (omr) 3,000 4,500 6,000 o & m (omr) 420 480 600 energy requirements (kwh/m3) 2.7 3.0 3.5 table 3. chemical properties of intake, desalinated, and brine water and means of brine disposal. intake water desalinated water brine means of brine disposal electrical conductivity (ds m-1) 8.09 0.36 25.6 soil pits, soil surface, old wells ph 7.2 7.1 7.31 areas outside the farm 54 squ journal of agricultural and marine sciences, 2017, volume 22, issue 1 renewable energy for desalination in urban agriculture in the gcc with total dissolved salts (tds) of about 10 000 mg/l. the life span of desalination units in oman is about 10 years (personal communications). assuming an interest rate of 12% (common in oman for small loans) and 10yr life span, the total cost of desalination to the farmer varies from 215 to 310 bz/m3 (fig. 6). the difference between what the farmers pay and the real cost of energy is indirect subsidy. therefore, the farmers can make a profit at the current subsidized energy prices on the conditions of growing high-value crops. the fao (2006) report described the economic conditions at which farmers can make profit by using desalination technology in oman. they should grow high-return crops; such as peppers, eggplants, cucumbers, onions, okra, carrots, cherry tomatoes, strawberry, and capsicums. it should be noted here that the fao (2006) report has not included the cost of brine disposal in this analysis. renewable energy for desalination for agriculture the global trend in energy market is to reduce energy demand through development of more energy-efficient technologies and finding substitutes for the fossil fuel. the gcc countries are aware of the world’s increased competition in energy market and must be ready for the future. they must look for alternative sources of energy due to ever increasing demand for fresh water and energy in the gulf. in the meantime, they must work on developing technologies that utilize renewable sources of energy to sustain the environment and reduce the demand on energy and finite groundwater. technologies that are based on renewable sources of energies, such as wind, solar, geothermal; can be greatly utilized for water desalination (serpen et al., 2010; goosen et al, 2010). coupling renewable energies with desalination systems has a great environmental and industrial potentials in water-scarce countries (mahmoudi et al., 2008, 2010; goosen and shayya, 1999). the effective integration of a source of renewable energy with a desalination system will allow gcc countries to address water shortage at city levels without any impact on air pollution and global warming due to climate change. furthermore, this approach will help bypass the problems of rising fuel prices and decreasing fossil fuel supplies (goosen et al., 2011). this section discusses the opportunities and challenges of utilizing solar energy for desalination of water to grow vegetable crops in urban cities for sustaining natural environment and water resources. solar energy for water desalination renewable energies for use in desalination processes include wind, solar thermal, photovoltaic and geothermal. renewable energy that operate the desalination systems are categorized into: (i) those which include distillation processes driven by heat produced directly by the renewable energy system (res), and (ii) those which include membrane and distillation processes driven by electricity or mechanical energy produced by res. solar energy can be used to desalinate brackish water in remote areas or areas that require small amounts of water on daily basis (al-hallaj et al., 1998). solar energy can be used directly as thermal or can be converted into electrical energy to drive desalination units that are based on reverse osmosis. thermal energy can be used with solar ponds or collectors. photo-voltaic cells are used to convert solar energy into electricity. solar thermal power plant is another choice for this conversion. solar stills and solar ponds for desalination goosen et al. (2000) discussed thoroughly the use of solar stills for water distillation (fig. 1 therein). it can be used where the demand is low and enough land is available. it is used to produce small amounts of fresh water. solar stills can be extended to improve the performance and amounts of water produced (goosen et al., 2000). solar ponds combine solar energy collection with longterm storage (goosen et al., 2011). a solar pond stores energy by having a salt concentration gradient in the pond. water surface at the pond has an ambient temperature. however, the bottom of the pond, where the salt concentration is highest, is much higher temperature (about 90°c). the temperature difference is large enough, where the heat is used to generate energy for desalination (fig. 2b of goosen et al., 2011) or to drive the vapor generator of an organic rankine cycle engine (wright, 1982). solar ponds have a rather large storage capacity, which allows seasonal as well as diurnal thermal energy storage (goosen et al., 2000). solar photovoltaic (pv) systems for desalination solar panels directly convert solar energy into electrical energy via solar cells (kalogirou, 2005). solar cells are made from semiconductor materials such as silicon 0.2 0.3 0.4 0.5 0.6 10 20 30 40 50 energy cost (bz/kwh) d es al in at io n c os t ( bz m −3 ) type large medium small figure 6. cost of desalination (1 baiza: bz = 0.001 or) of brackish water (10g·l-1) in the sultanate of oman for agriculture. 55research article al-jabri, ahmed and are connected with other cells to form a pv module. any number of pv modules can be combined to form an array, which will supply the power required by the load (kalogirou, 2005). energy storage equipment (batteries) and necessary accessories, such as charge controllers and inverters, are needed to store energy and convert direct current form pv cells to alternating current. the life expectancy of the system can be up to 30 years. desalination units, based on reverse osmosis (ro) or electrodialysis (ed), that utilize solar energy are mature technologies and readily available in the market. the feasibility of pv-powered ro or ed systems, as valid options for desalination at remote sites, has also been proven (childs et al., 1999). the main problem of these technologies is the high cost and, for the time being, the availability of pv cells. goosen et al. (2011) cites several studies that compare the use of solar energy with different desalination methods, such as thermal and distillation technologies. they conclude that all solar-driven desalination can be used for small-scale water production, except probably for pv-ro technology. a patented direct drive engine (dde) converts heat to the hydraulic power required by ro is projected to be more than three times greater than that which would be obtained by ro driven by a dish stirling electricity generation system or pv power (goosen et al., 2011). burgess and lovegrove (2005) noted that the project becomes less attractive due to the advances in conventional ro. the choice of the ro desalination plant capacity depends on the daily and seasonal variations in solar radiation levels, on the buying and selling prices for electricity, and on the weight given to fossil fuel displacement (burgess and lovegrove , 2005). a conceptual layout for a solar dish based system with power generation and ro desalination is shown in (fig. 7). conclusion substantial amounts of oil and gas are used in the process of desalination in the gcc countries, which produces huge amounts of emissions that significantly contribute to global warming and climate change. sources of renewable energy for desalinating sea and brackish water in urban cities in the gcc must be utilized to meet increasing demand on water for food production and reduce gas emissions. given the weather conditions and amounts of natural water resources in gcc region, desalination is probably the only choice for providing substantial amounts of water for irrigation at any time with a tailored quality. economic and environmental issues are the constraints for adapting desalination technologies for agricultural purposes. economic constraints can be greatly reduced with solar-operated reverse-osmosis units in conjunction with intensive agriculture of high-value horticultural crops. environmental constraints are alleviated with safe disposal of brines into the sea, or through evaporation ponds. however, the latter option needs to be thoroughly explored within the context of environmental regulations of each gcc country. figure 7. combined dish-based solar thermal power generation and ro desalination (burgess and lovegrove, 2005). 56 squ journal of agricultural and marine sciences, 2017, volume 22, issue 1 renewable energy for desalination in urban agriculture in the gcc references ahmed, m., shayya, w.h., hoey, d. and al-handaly, j. 2002. brine disposal from inland desalination plants: research needs assessment. water international. 27:194-201. ahmed, m., al jabri, s. and choudri, b.s. 2016. green challenges and some technological solutions in the water sector of the gulf cooperation council countries. in: m. abdel raouf and m. luomi (ed.) the green economy in the gulf. routledge, 2 park square, milton park, oxon ox14 4rn, london, uk. al barwani, a. and helmi, t. 2006. sea water intrusion in a coastal aquifer: a 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economical evaluation of desalination processes for potable water from seawater, middle east j. sci. res. 12. wright, j.d. 1982. selection of a working fluid for an organic rankine cycle coupled to a salt-gradient solar pond by direct-contact heat exchange, j. sol. energy eng. 104: 286-293. world bank. 2005. a water sector assessment report on the countries of the cooperation council of the arab states of the gulf. report no. 32539-mna. zarzo, d., campos, e. and terrero, p. 2012 spanish experience in desalination for agriculture. desalin. water treat. 51: 53-66. zekri, s. 2009. controlling groundwater pumping online. j. environ. mang. 90:3581-3588. doi:10.1016/j. jenvman.2009.06.019. research paper journal of agricultural and marine sciences vol. 23 : 92– 98 doi: 10.24200/jams.vol23iss1pp92-98 reveived 01 mar 2018 accepted 27 sep 2018 antifouling properties of chitosan coatings on plastic substrates 1,2laila al-naamani, 3thirumahal muthukrishnan, 4joydeep dutta, 5sergey dobretsov 1,2laila al-naamani ( ) lnaamani@hotmail.com 1department of marine science and fisheries’ sultan qaboos university, 123 al-khoud, oman.2ministry of municipalities and water resources, muscat, sultanate of oman.3department of biology, sultan qaboos university, 123 al-khoud, oman.4functional materials division, materials and nano physics department, ict school, kth royal institute of technology, se-164 40, kista, stockholm, sweden. 5center of excellence in marine biotechnology, sultan qaboos university, 123 al-khoud, oman. introduction natural and biodegradable biopolymers are cur-rently receiving great interest to be used as al-ternative to petroleum polymers in terms of raw material supply and waste product reduction (leceta et al. 2013). chitosan is a biocompatible, biodegradable and bioactive biopolymer, which can be used in diverse industrial applications (chatelet et al. 2001). it exhibits numerous interesting physicochemical and biological properties with various applications in water treatment, agriculture, biomedicine, food industry, and marine antifouling management (cestari et al 2007; el-sawy et al. 2010; ramya et al. 2012; luo & wang 2013; cai et al. 2016; al-naamani et al. 2017). chitosan possesses antimicrobial properties against a number of bacteria, fungi and algae (benhabiles et al. 2012; lam & diep 2015; park et al. 2016). antimicrobial properties of chitosan are due to the positively charged nh2+ ions which interact with the negatively charged molecules in the microbial cell membranes leading to disruption of the cells (coma et al. 2003; alisashi & aïder 2012). the efficiency of the bactericidal effect of chitosan is dependent on various factors, such as microorganism strain or species, environmental conditions (ph, temperature), molecular weight and concentration of chitosan as well as its physical state (solution or film) (kong et al. 2010; leceta et al. 2013). according to the field of application, chitosan can be modified to form powder, flakes, gel beads, fibres or membranes and several other forms (wang & shen 2000; pitakpoolsil & hunsom 2014; zhang et al. 2015). chitosan films or membranes have found their ways in various industrial applications such as water desalination, as coating for food applications, wound dressing, and tissue engineering (goy 2009; sudha et al. 2015). films can be easily prepared by dissolving chitosan powder or flakes in diluted acid solutions like acetic acid, and then casting the resulting solution on a flat surface or خصائص طالء الشيتوزان املضاد للحشف على ألواح البالستيك ليلى النعماين1,2 وثريومهال موثوكريشنان3 وجويديب دوتّا4 وسرجي دوبريتسوف5 abstract. in the current study, chitosan coatings were fabricated on plastic substrata and investigated for their antifouling activities. scanning electron microscopy (sem) and water contact angle measurement (wca) of the fabricated chitosan films showed smooth and hydrophilic surface with wca below 60°c. in the first experiment, chitosan coating on plastic substrate showed 88% reduction in settlement of bryozoan bugula neritina larvae compared to the control after 3 hours incubation at dark conditions with no larval mortality. in the second experiment, the antimicrobial activity of chitosan was evaluated by coating plastic panels with the prepared chitosan solution and immersing the coated samples in seawater at controlled environmental conditions for two weeks. biofilms scraped from immersed chitosan coated panels showed no bacteria after 1 week of immersion. after the second week of immersion, less than 1500 bacteria/mm2 were observed on the chitosan-coated panels compared to more than 105 bacteria/mm2 on uncoated ones. thus, this study proved the efficiency of chitosan coatings against microand macro-fouling. keywords: chitosan; anti-larval activity; antifouling activity; bryozoan; biofilms. املســتخلص:يف الدراســة احلاليــة، مت طــالء مــادة الكيتــوزان علــى ألــواح بالســتيكية وحبــث إمكانيــة اســتخدامها كمــادة مضــادة للرتســبات احليويــة البحريــة. أظهــرت حتاليــل املســح باجملهــر اإللكــرتوين وقيــاس زاويــة االتصــال بامليــاه علــى أن أغشــية الكيتــوزان تتكــون مــن ســطح أملــس وحمــب للمــاء بزاويــة اتصــال مــع املــاء بدرجــة اأقــل مــن ٦٠. طــالء الكيتــوزان علــى األســطح البالســتيكية أظهــر معــدل اخنفــاض يف جتمــع يرقــات bugula neritina بنســبة ٨٨٪ مقارنــًة باألســطح غــري املطليــة بعــد ٣ ســاعات مــن احلضانــة يف ظــروف مظلمــة. كمــا مل يتــم مالحظــة أي وفيــات يف الريقــات خــالل التجربــة. مت تقييــم النشــاط املضــاد للميكروبــات ملــادة الكيتــوزان عــن طريــق غمــر األلــواح البالســتيكية املطليــة هبــذه املــادة يف كميــة مــن ميــاه البحــر مــع وجــود ظــروف بيئيــة متحكــم هبــا. حتليــل األغشــية احليويــة املرتســبة يف األلــواح املطليــة بالكيتــوزان واملغمــورة يف املــاء أظهــر عــدم وجــود أي بكرتيــا بعــد أســبوع واحــد مــن التجربــة. بعــد األســبوع الثــاين ، تالحــظ وجــود أقــل مــن ١٥٠٠ بكرتيا/ملــم علــى األلــواح املطليــة بالكيتــوزان مقارنــة بأكثــر مــن ١٠٥ بكرتيا/ملــم علــى األلــواح الغــري مطليــة. بالتــايل، فــإن هــذه الدراســة تثبــت كفــاءة طــالء الكيتــوزان ضــد الرتســبات احليويــة البحريــة. الكلمات املفتاحية: الرتاكم احليوي على األسطح املغمورة، 93research article naamani dipping or coating of any substrate, and finally allowing them to dry (krajewska 2005; goy 2009). biofouling is the undesirable attachment and growth of micro(bacteria and diatoms) and macro-fouling (bryozoans, barnacles, mussels, etc.) organisms on manmade installations (wahl 1989). maritime industries spent billions of us dollars to prevent and control biofouling. current ways of controlling biofouling include the use of toxic antifouling coatings that kill organisms and pollute the environment (hellio & yebra 2009). thus, non-toxic antifouling solutions are urgently needed. due to chitosan biodegradability, low toxicity to eukaryotes and environmental safety, chitosan films have been proposed as a green approach to prevent biofouling and as an alternative to toxic biocides (pelletier et al. 2009). chitosan was proven as a successful antifouling coating for membranes (zhao et al. 2003; zhou et al. 2010). a study by yang et al. (2011) found that stainless steel functionalised with chitosan and hydroxyethylmethacrylate (hema) polymer reduced protein adsorption, bacterial adhesion, and exhibited antibacterial activity against e. coli. chitosan films in laboratory experiments inhibited growth of fouling microorganisms, such as pseudomonas and bacillus (machul et al. 2015; zhou et al. 2013). a two months field study in northern canadian waters was conducted with chitosan-based coatings (pelletier et al. 2009). while the results of the study demonstrated promising antibacterial activity, the coating did not have any activity against algae. in our previous study, chitosan-zinc oxide nanocomposite coatings prevented growth of fouling diatoms and marine bacteria in laboratory and mesocosm experiments (al naamani et al. 2017). at the same time, the antifouling effect of chitosan films on larval settlement of major fouling species, like the bryozoan bugula neritina (dahms et al. 2004), has not been investigated. the aims of this study were to: 1) fabricate chitosan coatings and characterise their physical and chemical properties, and 2) determine antifouling activity of chitosan coatings against microand macro-fouling organisms in laboratory experiments. materials and methods preparation of chitosan solution two and a half grams of commercial chitosan powder of medium molecular weight with 110 cps viscosity and 95.6% deacetylation (tru-nutra nutraceuticals llc, india) were mixed with a volume of 100ml of 2% acetic acid (sigma aldrich, usa) to prepare 2.5% chitosan solution. the solution was kept under constant stirring for 24h at 25°c. the viscous solution was coated on plastic substrates and allowed to dry for 24h at 26°c. the resulting coatings were characterized using ftir spectrophotometery, scanning electron microscopy (sem) and water contact angle. the chitosan coatings were analysed directly using ftir spectroscopic equipment (perkinelmer, usa, frontiertm), in a spectral range from 4000 to 400 cm-1 at a resolution of 4 cm-1. surface morphologies of dry coatings were characterized using jeol jsm-7200 (japan) field emission scanning electron microscope (fesem) working at 20 kv. the water contact angle (wca) of coated substrates was measured using a theta lite attension tensiometer (biolin scientific, sweden) using a sessile drop technique to determine the films hydrophobicity (al-fori et al. 2014). a drop of 5µl water was placed in five different positions on each coating’s surface. the right and left contact angles of each drop were measured and a mean water contact angle (wca) was calculated from the resulting two values. activity assessments of chitosan coatings on surfaces anti-larval activity assessment to determine the anti-larval activity of chitosan, the prepared chitosan solution in acetic acid was coated on plastic panels (low density polyethylene, size 1cm2) and allowed to dry overnight. three replicates of chitosan coated plastic panels were placed into a 24-well plate (corning costar, usa). uncoated clean plastic panels were used as a control. each well was filled with 1 ml seawater containing the bryozoan bugula neritina larvae. adult broodstocks of b. neritina were collected from pilings and floating rafts at marina bandar rowdah. larvae were obtained according to the method described by bryan et al. (1997) and only newly (i.e., within 10min) released larvae were included in the bioassays. experiments were conducted under dark conditions by covering the 24-well plate with aluminium foil. in each well, the number of dead larvae, attached larvae and the total number of larvae were counted under a dissecting microscope (zeiss, germany, magnification 10x) after 1h, 2h and 3h. the percentages of larval mortality and larval settlement were calculated as follows (equations 1 and 2). larval mortality (%)=(ndl)/(tl)×100 eq.(1) larval settlement (%)=(nsl)/(tl)×100 eq.(2) where ndl is the number of dead larvae, tl is the total number of larvae and nsl is the number of settled larvae. anti-microfouling activity to determine the antifouling activity of the chitosan in a small scale microcosm experiment, three different coatings were prepared: (a) 2.5% chitosan solution, (b) commercial two component non-toxic paint (hempadur 45182, hempel, denmark) mixed with 2.5% chitosan solution at a ratio of 1:1 (v:v), (c) commercial two component non-toxic paint (hempadur 45182, hempel, denmark). plastic panels (acrylic, 7.5 cm × 2.5 cm) were cleaned and both sides of the panels then painted with 94 squ journal of agricultural and marine sciences, 2018, volume 23, issue 1 antifouling properties of chitosan coatings on plastic substrates a brush with each of the coatings. the coatings were allowed to dry for 24 hours at room temperature. uncoated clean plastic panels were used as a control. each panel was immersed vertically in a separate beaker containing seawater. beakers were incubated at 26°c for 2 weeks. each treatment and the control were replicated three times. after 1 week and 2 weeks, panels were removed. biofilms from the whole area of the panel were scraped from the surface into eppendorf tubes using a sterile scalpel. the remaining traces of the biofilm were rinsed with distilled water into the tube. ten µl of the resulting biofilm suspension from each tube were added on a microscope glass slide and mixed with 10µl of sybr green 1 stain (sigma, aldrich, usa) and incubated for 10 min. finally, slides were analysed by an epifluorescence microscope. the number of bacteria in 20 randomly selected fields of view (muthukrishnan et al. 2017) was counted and the total abundance of bacteria within 1 mm2 was calculated. results and discussion chitosan film characterization the ftir spectra of chitosan coatings (figure 1a) showed a characteristic peak at 3362 cm-1 for n–h and o–h stretching. peaks corresponding to amide i and amide ii were observed at 1662 cm-1 and 1598 cm-1, respectively. the characteristic peak at 1046 is attributed to c-o stretching. the main absorption peaks of chitosan films have been reported to be at 1650 cm−1, attributed to c=o stretching (amide i), 1558 cm-1 attributed to n-h bending (amide ii) and 1382 cm-1 attributed to c-n stretching (amide iii). the broad bands above 3000 cm-1 assigned to o-h and n-h bonds while absorption peaks at 1050 cm-1 were attributed to c-o stretching (fernandez-saiz et al. 2007; leceta et al. 2013). the sem images and wca results showed a smooth and hydrophilic surface of chitosan coatings as shown in figures 1b and 1c. anti-larval activity of chitosan coating bugula neritina is a common fouling marine bryozoan with a short pelagic larval stage which can be found in warm temperate and subtropical waters worldwide (ryland et al. 2011; linneman et al. 2014). bugula larvae have barrel-shaped bodies with their surfaces mostly covered with cilia that are referred to as a ciliated corona. those cilia assist the larvae in swimming (price et al. 2017). the effect of chitosan coatings on the mortality and settlement of the bryozoan bugula neritina larvae after 3 hours incubation in dark conditions is shown in table table 1. effect of chitosan coating on bugula neritina larval mortality and settlement after 1, 2, and 3 hours of incubation at dark conditions. control is seawater. % larval mortality % larval settlement 1h 2h 3h 1h 2h 3h control 0 0 0 100±0 100±0 100±0 chitosan 0 0 0 12±6.3 12±6.3 12±6.3 figure 1. (a) ftir spectra of chitosan coating on plastic panels using 2.5% chitosan dissolved in 2% acetic acid, (b) sem image of the chitosan coating, (c) water control angle of the chitosan coating. 95research article naamani 1. results showed no larval mortality during the whole experiment. a 10-fold significant decrease in settlement of the larvae on chitosan films in comparison with the control was observed (table 1). all larvae settled in the control and no changes in the settlement rate were observed during the incubation period. overall, there was no difference in the larval settlement between 1h, 2h and 3h on chitosan film and the control. this can be explained by the fact that b. neritina has fast settling larvae that attach to the substratum within one hour (bryan et al. 1997). to our knowledge, this is the first study stating the effect of chitosan on the mortality and settlement of b. neritina larvae. previously, rasmussen et al. (2002) investigated the settlement of cyprids of balanus amphitrite on chitosan gel crosslinked with glutaraldehyde. the authors observed a reduction in larval settlement to 35% when chitosan concentration was 2%. the settlement of b. neritina larvae on the surface of 8×10 cm plastic panels coated with low density polyethylene (ldpe), polypropylene (pp), polyvinyl chloride (pvc) and high density polyethylene (hdpe) was studied by li et al. (2016). the authors reported higher larval settlement on the surface of panels coated with ldpe, pp, and pvc, compared to hdpe and glass panels after immersion in water for 4 days. the influences of organic films, such as chitosan, pp, pvc, etc., on larval settlement is not yet clear. it was suggested that physical, chemical and biological factors of the substratum, such as roughness, chemical properties of the substratum, presence of biofilms and other species, could affect larval settlement in the field (clare et al. 1992; faimali et al. 2004; dobretsov et al. 2006; qian et al. 2007; li et al. 2016). antimicrobial experiment the experiment showed that the lowest bacterial abundances were found on chitosan coatings; no bacteria after 1 week and <1500 bacteria/mm2 after 2 weeks of immersion were observed (fig. 2). the highest densities of bacteria were found on the control substrata after 1 and 2 weeks of the experiment. the non-toxic antifouling paint was more effective than the mixture of non-toxic paint and chitosan (fig. 2). only a few algal cells were observed in the control samples. comparatively, higher numbers of algal cells were observed on samples coated with non-toxic paint. however, no algal cells were observed on both the panels coated with a mixture of non-toxic paint and chitosan solution and that of only chitosan solution. in the marine environment, the antifouling activity of chitosan was directly evaluated by pelletier et al. (2009). they demonstrated antibacterial activity of 20% chitosan coating after 14 days of immersion in the sea, while 5% chitosan coating did not have any antifouling activity. antibacterial activity of chitosan with concentration less that 2% chitosan was observed against ba0 5 10 week 1 week 2 b ac te ria l c ou nt (1 04 m m −2 ) coating control non−toxic paint chitosan + non−toxic paint chitosan figure 2. bacterial abundances on plastic panels coated with commercial non-toxic paint, commercial non-toxic paint mixed with 2.5% chitosan coating in ratio (1:1) and 2.5% chitosan coating. the control represents an uncoated panel. figure 3. bacterial cells as observed by epifluorescence microscopy at 1000x magnification in (a) biofilms scraped from the uncoated control plastic panels, and (b) biofilm scraped from panels coated with a mixture of chitosan and non-toxic paint. cells were stained with cybr green i dye. 96 squ journal of agricultural and marine sciences, 2018, volume 23, issue 1 antifouling properties of chitosan coatings on plastic substrates cillus sp., vibrio and pseudomonas sp., which are known to be involved in the biofouling process (sekiguchi et al. 1994; jumaa et al. 2002; no et al. 2002; rasmussen & østgaard 2003). it is well known that the cationic amine group in the chitosan molecule has a major role in its antimicrobial activity, as it forms electrostatic interactions with anionic group on the cell membrane of bacterial cells, which eventually lead to cell death (rabea et al. 2003; alisashi & aïder 2012). however, in our experiment chitosan charge has minor effect because of high ph of seawater (6.9-7.2) which neutralize most of the positive charges in chitosan’s amino groups. rasmussen & østgaard (2003) suggested that surface energy was the crucial factor to prevent bacterial adhesion to the hydrophilic surface provided by chitosan at conditions of high ph. the anti-algal effect of chitosan was previously reported by ravi kumar (2000). however, no anti-algal activity of chitosan was observed by other researchers (pelletier et al. 2009). conclusion in this experiment, chitosan solution was used to fabricate coatings characterised by ftir, sem and wca. this chitosan solution was applied as a coating on acrylic plastic and antifouling effect against macroand micro-fouling organisms was studied. the results of this study proved the effectiveness of chitosan coatings on the settlement inhibition of bugula neritina compared to the control. the chitosan films also significantly reduced the density of fouling bacteria compared to non-toxic paint and control (no coating) when immersed in a natural seawater environment for two weeks. those results suggest that chitosan is suitable to be used as coating component in order to prevent marine micro-and macro-fouling. acknowledgements the authors acknowledge financial support from the research council of oman (trc, rc/agr/fish/16/01). we thank priyanka sathe for her assistance in conducting 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einen et al., 1999; grisdale-helland et al., 2013). thus, high feed intake is required for efficient production in salmon farming. a fish may only respond to a feed particle when it is within a certain distance from the fish, and to assure high feed intake, feed pellets must be available to each individual fish. in commercial salmon farming, the feed is commonly spread over a large area of the surface, assuming this has a positive effect on feed intake. in norwegian salmon farming, the early stages up to smolt of approximately 100 g have traditionally been kept in land based farms, whereas salmon in the growout phase up to slaughter size is kept in net pens in the sea. in later years the trend is to keep the fish longer in the land based farms, which implies an upscaling of the tanks which may reach 1000 m3 water volume or more (gorle et al., 2019). environmental conditions, such as استهالك سمك السلمون األطليس لالعالف مع أو بدون نرش االعالف عىل السطح توريد سينوف1,4 ،تورين ترستوي1,4، توربرن اسجارد1,4 ،كرستوفر رستو2,4 مورتن اوملت الفر2,3,4 و جو ارف الفردسن2,4 abstract. in intensive salmon farming, it is common practice to spread the feed over a large surface area, assuming that spreading of the feed increases feed intake in the fish. however, the impact on the feed pellets during spreading results in feed loss due to pellet breakage. in this study, feed intake, growth and signs of aggressive behavior was compared in salmon fed without or with spreading of the feed on the surface area of the tanks. atlantic salmon (salmo salar) with initial body weight 0.6 kg were kept in 3.3 m 3 tanks supplied with sea water (salinity 32 %, mean temperature 11 °c) for one month. the salmon were fed one meal daily, either by dropping the feed from one point, or by spreading the feed over the water surface. feed intake and growth was measured. fin damage was given a score at termination of the trial as a measure of competitive behavior during feeding. the relative feed intake (i.e. percent of body weight per day) in salmon fed without spreading or with spreading of the feed was 0.63±0.05 and 0.64±0.02 %, respectively. the growth rate was identical in salmon fed without or with spreading of the feed, and no significant difference in variance in final weight was found. no difference in fin damage for salmon fed without or with spreading of the feed was revealed. the data showed that for the conditions used in this trial, spreading of feed had no influence on feed intake or growth of salmon. keywords: atlantic salmon; spreading of feed; feed intake; feeding behavior. امللخــص: املســتخلص: مــن الشــائع يف االســتزراع املكثــف للســلمون نــرش االعــالف عــىل مســاحة كبــرة مــن الســطح، عــىل افــراض أن انتشــار األعالف يزيــد مــن اســتهالك األســاك لألعــالف. ولكــن هــذا االمــر يؤثــر عــىل حبيبــات األعــالف أثنــاء انتشــارها ويعطــي فقدانــا اكــر لألعــالف بســبب تكســر الحبيبــات. لقــد اجريــت هــذه الدراســة ملقارنــة تنــاول األعــالف والنمــو وعالمــات الســلوك العــدواين يف أســاك ســلمون تــم تغذيتهــا بــدون أو مــع نــرش األعــالف عــىل ســطح الخزانــات. تــم تنفيــذ التجــارب عــىل ســمك الســلمون األطلــيس ) ســلمو ســالر( مــع وزن جســم أويل 0.6 كجــم. تــم حفــظ االســاك يف خزانــات )3.3 م3( مــزودة مبيــاه البحــر ) امللوحــة 32 ٪ ، متوســط درجــة الحــرارة 11 درجــة مئويــة( ملــدة شــهر واحــد. تــم تغذيــة الســلمون وجبــة واحــدة يوميــا، إمــا عــن طريــق إســقاط التغذيــة مــن نقطــة واحــدة كقطــارة، أو عــن طريــق نــرش األعــالف عــىل ســطح املــاء. تــم قيــاس كميــة التغذيــة والنمــو. تــم رصــد درجــة تــرر زعنفــة الســلمون كمقيــاس للســلوك التنافــيس أثنــاء التغذيــة. كانــت كميــة التغذيــة النســبية )النســبة املئويــة مــن وزن الجســم يوميــا( يف ســمك الســلمون بــدون انتشــار أو مــع انتشــار األعــالف 0.63 ± 0.05 و 0.64 ± 0.02٪ ، عــىل التــوايل. وكان معــدل النمــو متطابقــا يف تغذيــة الســلمون بــدون أو مــع انتشــار ااالعــالف، ومل يوجــد هنــاك فــرق كبــر يف التبايــن يف الــوزن النهــايئ للســلمون. باالضافــة اىل ذلــك، مل يوجــد فــرق يف أرضار الزعانــف التــي تتغــذى عــىل الســلمون بــدون أو مــع انتشــار العلــف. أظهــرت نتائــج البيانــات النهائيــة أنــه بالنســبة للظــروف املســتخدمة يف هــذه التجربــة، مل يكــن النتشــار العلــف تأثــرا عــىل تغذبــة او منــو ســمك الســلمون. الكلات املفتاحية: سمك السلمون، األطليس، انتشار األعالف، استهالك العلف، سلوك التغذية 21research paper aas, ytrestøyl, åsgård, skøien, alver, alfredsen light, temperature, oxygen levels, salinity and water current affect behavior in salmon in sea cages, and feeding induces the changes in the behavior (reviewed by oppedal et al., 2011). in tanks, the behavior is restricted by the volume of the tank. volume and design of the tanks have been shown to affect feed intake and growth in salmon (espmark et al., 2017; føre et al., 2018). in salmon farming in sea cages as well as in land based farms, the feed is usually transported from a storage unit to the cages or tanks with a pneumatic system where the feed is carried by air through a pipe system, and a spreader may be mounted on the outlet of the pipe. spreading of the pellets can be controlled by adjusting the air stream in the system (alver et al., 2016; oehme et al., 2012). air stream is a main factor for pellet breakage in the feeding system (aas et al., 2011a), and moderate spreading of feed is therefore advantageous to avoid losses due to pellet breakage. feeds with physical pellet quality that is optimal for the feeding systems may not be optimal for the fish (aas et al., 2017; aas et al., 2011b; oehme et al., 2014) and losses due to pellet breakage may be weighed against losses due to suboptimal fish growth. feed loss also occurs when uneaten feed pellets sink to the bottom of the tank. it is difficult to quantify uneaten feed, but 7% of the total feed in salmon farming has been suggested (gjøsæter et al., 2008). clearly, good feeding routines produce minimal feed spill. reduced feed utilization and growth also represent losses. as high feed intake is a prerequisite for high feed utilization in salmon (einen et al., 1995; einen et al., 1999; grisdale-helland et al., 2013), some overfeeding may be necessary to achieve maximum feed intake and feed utilization. optimal feeding routines in salmon farming implies minimal pellet breakage and minimal feed spill while maximal feed intake is assured. at fish farms, control of feeding is assisted by camera systems. models intending to optimize feeding are also derived (alver et al., 2004; alver et al., 2016; skøien et al., 2016). spreading of feed across the surface is assumed to increase feed intake in fish by making feed available to all individuals and minimize hierarchical behavior during feeding. the manner of feed dispersal influences the equality of access of feed among individuals (reviewed by attia et al., 2012). at restricted feeding, the aggression level may be high (jones et al., 2010), and localized feeding may result in larger growth variation among individuals than when feed is dispersed. growth and aggression levels related to feed dispersion is poorly documented. as spreading is correlated to pellet breakage (aas et al., 2011a), such information is crucial in order to optimize feeding routines. in the present study, the effect of spreading of feed on feed intake was tested in 3.3 m3 tanks. atlantic salmon were fed either from one single point over the tank with no spreading on the water surface, or the feed was spread over a large area of the water surface. feed intake, growth and signs of competitive behavior (fin erosion) was measured. materials and methods fish trial a tank experiment with atlantic salmon with mean initial body weight 607 g was run in for 30 days with approximately 100 fish per tank in triplicate at nofima’s research station for sustainable aquaculture at sunndalsøra, norway. the fish were kept in octahedral tanks (quadratic with the corners ‘cut’; 2×2 m surface and volume 3.3 m3) supplied with sea water (salinity 32‰) in a flow through system with mean water temperature 11.0 °c (sd 1.6, range 7.5-13.4 °c, logged every 5 min) and at continuous light. the feed was distributed with poro ex 04 automatic feeders (poro ab, kåge, sweden). for tanks with spreading of the feed on the surface, a poro ex 06 spreader was connected to the feeder, and the spreading area was assumed to cover the whole surface of the tank. for tanks without spreading of the feed on the water surface, the spreader was dismounted, so that the feed fell into the water from the opening of the feeding automat in a small area of a few cm2. prior to the trial, the tanks were standardized with regard to water flow (80 l·min-1), water velocity and spreading of feed. the water current was measured in all tanks just below the feeder, 40 cm from the tank wall and at 30 cm depth. the overall mean current was 23 cm·s-1 (table 1). in the three tanks with spreading of the feed, each spreader was manually adjusted so that a largest possible area of the tank was covered, but without losing pellets out of the tank. as pellets met the water surface, they started to sink and followed the circular water current until they settled on the tank bottom. during this movement through the table 1. measurement of water current (cm s-1) measured below the feeder, 40 cm from the tank wall and at 30 cm depth. data are given as mean and sd (n=10) no spreading spreading tank number 208 209 214 207 213 215 water current, cm s-1 22 23 23 24 23 23 sd=4 sd=3 sd=3 sd=6 sd=3 sd=2 22 squ journal of agricultural and marine sciences, 2020, volume 25, issue 1 feed intake in atlantic salmon fed with or without surface spreading of feed water volume, the feed was available for the fish. after some circular movements on the tank bottom, the pellets followed the water flow out of the outlet in the center in the bottom of the tank. the spreading of pellets in time was measured by running the feeding system for 3 s in one tank without and one tank with spreader, with no fish in the tanks. the time (s) from start of feeding to the first and the last pellet reached the bottom of the tank was recorded (n=10, table 2). the difference between first and last pellets, which expresses the time the feed was in the water column, was 12 and 15 s in a tank without and with spreading, respectively. the difference was not significant with anova (p<0.05). the salmon were fed a commercial feed with pellet size 4.5 mm (skretting supreme, skretting, stavanger, norway). the physical properties of the feed are shown in table 3. the fish was fed one meal daily, lasting from 9 to 10 am. the feed intake was estimated by collecting and weighing uneaten feed and measuring dry matter. the recovery (%) of uneaten feed was estimated by following the same routine as in the trial, but with no fish in the tanks. the recovery value was used to correct the amount of uneaten feed, and daily feed intake was calculated as feed given minus corrected uneaten feed (helland et al., 1996). all tanks were fed the same amount of feed, and the size of the ration was adjusted daily based on the last three days’ feed intake aiming at 20 % overfeeding in the tanks with highest feed intake. sampling at start and end of the trial, biomass was recorded and the fish counted. at termination of the trial, the individual weight of 30 fish from each tank was also registered. the fin damage of these 30 fish was evaluated by a scoring system where dorsal, caudal, pelvic and pectoral fins were given an integer score from 0 (no visible damage) to 4 (severe damage), and damages were classified as fin erosion, split fin, deformed fin, hemorrhage or asymmetric fins. at handling and weighing, the fish were sedated with aqui-s® (clove oil, isoeugenol 2-5 mg l-1). measurement of physical feed quality diameter and length of the pellets were measured with an electronic caliper. bulk density was measured by loosely pouring the feed from a funnel into a 1000 ml measuring cylinder. sinking velocity was measured in a 1.3 m high cylinder with tight bottom and filled with 34‰ sea water at 10 °c and start and end of 1 m distance marked on the outside. the time the pellets used for sinking 1 m was recorded for one pellet at a time. calculation feed intake, given on dry matter (dm) basis, was estimated according to helland et al. (1996). (1) recovery was estimated by following the experimental feeding routines, but with no fish in the tanks: (2) (3) the relative feed intake (rfi, % of body weight per day) and specific growth rate (sgr, %) and thermal growth coefficient (tgc) are calculated from the following equations as: (4) (5) (6) where, sum daydegrees = number of days in trial×mean temperature (˚c). statistical analysis tank data were analyzed with one-way anova (t-test). individual data were compared with a hierarchical (nested) anova using the ‘nested’ procedure in sas. the score data (individual data) were also analyzed with a nested anova after arcsine transformation of the score data divided by 4 (to obtain data in the range 0-1). anova of original data and transformed data gave corresponding results. variance among treatments was analyzed by comparing the standard deviations with oneway anova. a significance level of α=0.05 was used for all statistical analyses. statistical analyses were per23research paper aas, ytrestøyl, åsgård, skøien, alver, alfredsen formed with the sas 9.4 computer software (sas, usa). results there was no mortality in the trial and the fish appeared to be at good health. there were no significant differences in feed intake or growth. the total feed intake was 132±10 and 127±1 g (dry matter basis) per individual in salmon fed without or with spreading of the feed, respectively. the relative feed intake (% of body weight per day) in salmon fed without spreading or with spreading of the feed was 0.63±0.05% and 0.64±0.02%, respectively. the growth rate was 0.97% per day for both groups (table 4). comparing the body weight of 30 individual fish from each tank did not reveal any effect of spreading the feed on variance in body weight (table 5). no significant effect of spreading the feed was found on scoring of fin damage (table 6). the damage on the dorsal fins was mainly fin erosion and some split fins and deformed fins. the damage on the caudal fins was also mainly classified as fin erosion, but some split fins and red spots were also present. for pectoral fins, split fins were the most common damage, followed by fin erosion and red spots. for pelvic fins, there were very little damage except some split fins. in one tank (tank number 215, with spreading of feed), several fish had red spots in the skin. the reason for this is unknown. in the other tanks, the fish generally appeared normal for salmon of this size kept in tanks. discussion a tank experiment was chosen to test whether spreading of the feed affects feed intake in atlantic salmon. compared to experiments in sea cages, a tank experiment has the advantages that spreading of feed, feed intake and growth can be measured with high accuracy, and it can be run at a relatively low cost. data from small scale studies are not necessarily valid for large scale conditions (espmark et al., 2017). as for all trials, the data from the present study are only representative for the conditions used in this study. there was large difference in spreading pattern on the water surface depending on whether the feed was spread or not, which represents spreading in space. feed is also spread in time, and the feed is available for the salmon while sinking through the water. numerically, spreading of the feed on the water surface resulted in a longer time in the water (table 2), although this was not significantly different (p < 0.05) from the time the pellets were in the water when feeding from one point. there was some variation in these measurements as all pellets follow different routes through the water column. there was a difference among pellets in sinking velocity (skøien et al., 2016). the 10 replicates did not reveal any significant difference in spreading in time. the overall mean sgr was 0.97% per day, which is in accordance with (austreng et al., 1987) or just below (skretting, 2011) expected growth of salmon of this size at this temperature. according to skretting (2011), atlantic salmon of 600 and 800 g are expected to grow 1.28 and 1.14 % per day, respectively, at 11 °c. a period of one or two weeks for acclimation to new conditions is normal in salmon trials. this was also observed in the present trial, where the feed intake was moderate, but gradually increasing, during the first ten days. thereafter, the feed intake was as expected, and the overall growth in the trial was only slightly below expected values. it can therefore be assumed that the feed intake and growth was at normal levels during the last 20 days of the trial. the feed intake was very similar in both treatment groups, showing that in this trial, spreading of the feed on the water surface did not affect the mean feed intake in salmon. spreading the feed on the water surface is generally believed to reduce variance in feed intake and correspondingly, body weight, in fish (attia et al., 2012; ryer and olla, 1996). this is assumed to be due to that feeding from one point may favor the most dominant individuals whereas when spreading the feed, it is available to all individuals. the variation in individual body weight when salmon were fed without spreading versus with spreading the feed was measured by comparing the standard deviations. an anova of these standard deviations did not indicate any effect of spreading of the feed on variation in final body weight. the individual body weight at start was not measured because this require extra handling of the fish, which imply extra stress to the fish, which again may lead to reduced feed intake in the trial. the variation in body weight at start of the trial was assumed to equal in both treatment groups as fish was allocated randomly to the experimental tanks. the salmon was fed full ration in the present trial, whereas at restricted feeding, competitive behavior may result in larger differences in feed intake when the fish is fed table 2. time(s) from start of feeding till first and last pellet reached the tank bottom, and the difference, at 3 s feeding in one tank without and one tank with spreading and with no fish in the tank. data are given as mean and sd (n=10) without spreading with spreading first pellet 7 sd=1 7 sd=1 last pellet 19 sd=5 22 sd=4 difference 12 sd=4 15 sd=5 table 3. pellet length and diameter, bulk density and sinking velocity of the feed used in the trial (mean and sd) physical properties of the feed pellet diameter (mm) 4.6 sd=0.3 (n=20) pellet length (mm) 7.5 sd=1.0 (n=20) bulk density (g l-1) 650 sd=2.1 (n=3) sinking velocity (m s-1) 11.2 sd=0.9 (n=20) 24 squ journal of agricultural and marine sciences, 2020, volume 25, issue 1 feed intake in atlantic salmon fed with or without surface spreading of feed without spreading of feed than when the feed is spread (juell, 1995; ryer and olla, 1996). the trial was not designed as a growth trial. to reveal significant effects of growth in salmon, a doubling in weight during the experiment is often used as a rule of thumb. in the present trial, the growth was 32.5%. there was a slight difference in body weight in the two treatment groups, but the tgc, which is independent of body size, was also identical in salmon fed with or without spreading of feed. since the growth rate was exactly the same in both treatment groups, it can be concluded that spreading of the feed did not affect growth. scoring of fin damage was used as a measure of hierarchical, aggressive behavior. restricted feeding has been shown to increase fin damage in atlantic salmon (noble et al., 2008). with the two feeding patterns used in the present trial, no differences in score of fin damage were found. spatially concentrated feed delivery is believed to increase competition (juell, 1995; symons, 1971) but this effect may not be seen due to the overfeeding in the present study. this, together with feed intake and body weight data, indicates that there is no need for using the feed spreader under the conditions used in this trial if feed is sufficiently available. as all handling and spreading of feed increases the risk of pellet breakage (aas et al., 2011a), the feed should rather be distributed from one point, without the spreader. the spreading of feed in time in the water volume is related to the sinking velocity of the feed. furthermore, pellet size will affect spreading of the feed in the water volume, since small pellets will be scattered in the water compared to larger pellets where the feed is concentrated in larger particles. such factors can be taken into account to adjust spreading of feed, in addition to spreading on the surface. the response distance in fish, which is the maximum distance fish responds to a feed particle, depends on several factors, such as fish species, fish size, swimming speed, light conditions, water turbidity, characteristics of the feed and experimental conditions. response distances in the range 5-25 cm have been measured for large fish (60 cm and larger) of different species under variable experimental conditions (summarized by richmond et al., 2004). in a fish tank of limited volume and with feed following the movement of the swirl as in the present study, the fish has a high probability of being within this distance of some of the feed particles during a meal. in a large sea cage, even when spreading the feed over a large area, the density of feed particles is considerably smaller in most of the cage volume (alver et al., 2004; alver et al., 2016; skøien et al., 2016), and feeding behavior with high swimming activity is probably necessary for the fish to be able to feed to satiation. in a sea cage with circumference 150 m or more and variable wind and water table 4. body weight, growth and feed intake in atlantic salmon fed without or with spreading of the feed on the water surface for 30 days data are given as mean ± standard error of mean (sem; n=3) without spreading with spreading initial body weight (g) 618 ± 4 596 ± 17 final body weight (g) 818 ± 15 789 ± 19 individual weight gain (g) 201 ± 14 193 ± 6 weight gain (%) 32.5 ± 2.2 32.5 ± 1.3 sgr (% per day) 0.97 ± 0.06 0.97 ± 0.03 tgc 2.6 ± 0.2 2.6 ± 0.1 feed intake (g per individual, dry matter) 132 ± 10 127 ± 1 relative feed intake (% of body weight per day) 0.63 ± 0.05 0.64 ± 0.02 table 5. final body weight of 30 randomly selected individuals from each tank of atlantic salmon fed without or with spreading of the feed on the water surface for 30 days no spreading spreading tank number 208 209 214 207 213 215 mean weight (g) 782 771 851 779 765 806 sd 207 188 197 163 148 210 maximum (g) 1132 1358 1289 1052 1255 1436 minimum (g) 464 409 498 412 479 306 25research paper aas, ytrestøyl, åsgård, skøien, alver, alfredsen current, the effect of spreading versus no spreading of feed may be different from the data obtained in a tank experiment. since feed pellets are prone to breaking upon spreading (aas et al., 2011a) the feed should not be spread needlessly. to optimize feeding routines, it is therefore necessary to measure the effect of spreading the feed in large-scale sea cages also. conclusion no significant differences in feed intake or growth were found in salmon fed from one point or feed spread over the water surface in 3.3 m3 experimental tanks. neither was there any effect of spreading of the feed on variation in body weight, or in fin damage. in the present trial thus, spreading the feed on the water surface did not improve any of the measured parameters compared to feeding the fish from one point. acknowledgements the staff at nofima’s research station for sustainable aquaculture at sunndalsøra, and especially frode nerland, is acknowledged for running the fish trial, and roger selset for technical advice. this study was funded by the centre for research-based innovation in aquaculture technology (create) and their partners. references aas ts, oehme m, he g, sørensen m, lygren i, åsgård t. (2011a). analysis of pellet degradation of extruded high energy fish feeds with different physical qualities in a pneumatic feeding system. aquacultural engineering 44(1): 25-34. aas ts, sixten hj, hillestad m, sveier h, ytrestøyl t, hatlen b, åsgård t. (2017). measurement of gastrointestinal passage rate in atlantic salmon (salmo salar) fed dry or soaked feed. aquaculture reports 8: 49-57. aas ts, terjesen bf, sigholt t, hillestad m, holm j, refstie s, baeverfjord g, rørvik k-a, sørensen m, oehme m . (2011b). nutritional responses in rainbow trout (oncorhynchus mykiss) fed diets with different physical qualities at stable or variable environmental conditions. aquaculture nutrition 17: 657-670. alver mo, alfredsen ja, sigholt t. (2004). dynamic modelling of pellet distribution in atlantic salmon (salmo salar l.) cages. aquacultural engineering 31(1-2): 51-72. alver mo, skøien kr, føre m, aas ts, oehme m, alfredsen ja. (2016). modelling of surface and 3d pellet distribution in atlantic salmon (salmo salar l.) cages. aquacultural engineering 72-73: 20-29. attia j, millot s, di-poï c, bégout ml, noble c, sanchez-vazquez fj, terova g, saroglia m, damsgård b. (2012). demand feeding and welfare in farmed fish. fish physiology and biochemistry 38(1): 107-118. austreng e, storebakken t, åsgård t. (1987). growth rate estimates for cultured atlantic salmon and rainbow trout. aquaculture 60(2): 157-160. einen o, holmefjord i, åsgård t, talbot c. (1995). auditing nutrient discharges from fish farms: theoretical and practical considerations. aquaculture research 26: 701-713. einen o, mørkøre t, thomassen ms. (1999). feed ration prior to slaughter a potential tool for managing product quality of atlantic salmon (salmo salar). aquaculture 178(1-2): 149-169. espmark åm, kolarevic j, åsgård t, terjesen bf. (2017). tank size and fish management history matters in experimental design. aquaculture research 48(6): 2876-2894. føre m, alver mo, alfredsen ja, senneset g, espmark å, terjesen bf. (2018). modelling how the physical scale of experimental tanks affects salmon growth performance. aquaculture 495: 731-737. gjøsæter j, otterå h, slinde e, nedreaas k, ervik a. (2008). effekter af spillfôr på marine organismer. bergen, institute of marine research, norway. annual series. no. 1.11 (in norwegian). gorle jmr, terjesen bf, summerfelt st. (2019). hydrodynamics of atlantic salmon culture tank: effect of inlet nozzle angle on the velocity field. computers and electronics in agriculture 158: 79-91. grisdale-helland b, lemme a, helland sj. (2013). threonine requirement for maintenance and efficiency of utilization for threonine accretion in atlantic salmon smolts determined using increasing ration levels. aquaculture 372-375: 158-166. helland sj, grisdale-helland b, nerland s. (1996). a simple method for the measurement of daily feed intake of groups of fish in tanks. aquaculture 139(1-2): 157-163. table 6. scoring of fin damage in 30 randomly selected individuals from each tank of atlantic salmon fed without or with spreading of the feed on the water surface for 30 days. damage of each fin was given a score from 0 (no visible damage) to 4 (severe damage). data are given as mean±sem., where sem is calculated from the pooled standard deviation of data from all individuals (n=90) within each treatment without spreading with spreading dorsal fin 2.0 ± 0.1 1.8 ± 0.1 caudal fin 1.8 ± 0.1 1.7 ± 0.1 pectoral fins 1.6 ± 0.1 1.5 ± 0.1 pelvic fins 0.6 ± 0.1 0.5 ± 0.1 26 squ journal of agricultural and marine sciences, 2020, volume 25, issue 1 feed intake in atlantic salmon fed with or without surface spreading of feed jones hac, hansen la, noble c, damsgård b, broom dm, pearce gp. (2010). social network analysis of behavioural interactions influencing fin damage development in atlantic salmon (salmo salar) during feed-restriction. applied animal behaviour science 127(3): 139-151. juell je. 1995. the behaviour of atlantic salmon in relation to efficient cage-rearing. reviews in fish biology and fisheries 5(3): 320-335. noble c, kadri s, mitchell df, huntingford fa. (2008). growth, production and fin damage in cage-held 0+ atlantic salmon pre-smolts (salmo salar l.) fed either a) on-demand, or b) to a fixed satiation–restriction regime: data from a commercial farm. aquaculture 275(1): 163-168. oehme m, aas ts, olsen hj, sørensen m, hillestad m, li y, åsgård t. (2014). effects of dietary moisture content of extruded diets on physical feed quality and nutritional response in atlantic salmon (salmo salar). aquaculture nutrition 20: 451-465. oehme m, aas ts, sørensen m, lygren i, åsgård t. (2012). feed pellet distribution in a sea cage using pneumatic feeding system with rotor spreader. aquacultural engineering 51: 44-52. oppedal f, dempster t, stien lh. (2011). environmental drivers of atlantic salmon behaviour in sea cages: a review. aquaculture 311(1-4): 1-18. richmond he, hrabik tr, mensinger af. (2004). light intensity, prey detection and foraging mechanisms of age 0 year yellow perch. journal of fish biology 65(1): 195-205. ryer ch, olla bl. (1996). growth depensation and aggression in laboratory reared coho salmon: the effect of food distribution and ration size. journal of fish biology 48(4): 686-694. skretting. fiskeføde [internet]. stavanger, norway: skretting; (2011) available from: http://www.fwww. skrettingguidelines.com (in norwegian) (accessed 12 july 2019). skøien kr, aas ts, alver mo, romarheim oh, alfredsen ja. (2016). intrinsic settling rate and spatial diffusion properties of extruded fish feed pellets. aquacultural engineering 74: 30-37. symons pek. (1971). behavioural adjustment of population density to available food by juvenile atlantic salmon. journal of animal ecology 40(3): 569-587. research paper journal of agricultural and marine sciences vol. 23 : 81 – 91 doi: 10.24200/jams.vol23iss1pp81-91 reveived 31 dec 2017 accepted 03 oct 2018 extraction of natural pigments from marine algae *1tanveer alam,2lubna najam,3ahmed al harrasi * dr. tanveer alam ( ) tanveer@unizwa.edu.om 1*uon chair of oman’s medicinal plants & marine natural products, university of nizwa, sultanate of oman . 2department of chemistry, dav (pg) college, ccs university, muzaffar nagar, up, india. 3*uon chair of oman’s medicinal plants & marine natural products, university of nizwa, sultanate of oman introduction there are two types of pigments: natural and syn-thetic. synthetic pigments are mainly coal tar derivatives made from chemicals which are by products of coal distillation. many synthetic dyes are controversial and banned in many countries for use in food products because of safety concerns. use of these synthetic pigments in personal care products also adds health risks. some of these dyes contain impurities like lead acetate which are toxic to nervous system. some commonly used synthetic pigments are allergens, irritants and some others are known carcinogens. thus, there is an increasing demand for natural pigments percieved as less toxic for use in food products, pharmaceuticals and cosmetics. many plants contain dyes and pigments (other than chlorophyll) which may serve as colorants and may have other roles e.g.; in photosynthesis, insect attractants etc. natural pigments represent an apparently more sustainable sources of colorants than synthetic counterparts. other than higher plants (angiosperm and gymnosperm), microalgae are good alternatives of carotenoids and phycobiliproteins for natural colors. microalgae belong to an heterogenous group of microorganisms. microalgae are small, unicellular monocellular or multicellular, autotrophic, colorful and grow generally in water and they may be either eukaryotic or prokaryotic. production of pigments from microalgae has a number of advantages such as cheaper and easy production, easier extraction, higher yields, no lack of raw materials and no seasonal variations. the status of microalgal applications in aquaculture, food, speciality chemicals and environmental applications has been reviewed (apt and behrens, 1991; muller-feuga, 2000; pulz et al., 2001; benemann et al., 2002). in this review our focus is on extraction of microalgal pigments as natural colors, factors affecting their yield, extraction methods and their applications. major pigments of the microalgae which are used as pigments are carotenoids and phycobiliproteins. the pigments are characteristic of certain algal groups as indicated in table 1 (dring 1982). chlorophylls and carotenes are generally fat soluble molecules that can be extracted from thylakoid membranes with organic solvents such as acetone, methanol or dimethyl sulfoxide the phycobilins and peridinin, in contrast, are water soluble and can be extracted from algal tissues after the organic solvent extraction of chlorophyll in those tissues. استخالص ملّوانت طبيعية من طحالب حبرية تنوير عالم ولبىن جنم وأمحد احلراصي abstract. the pigment content in microalgae is a specific feature of each species. pigments from natural sources are gaining more importance mainly due to health and environmental issues. algae contain a wide range of pigments. three major classes of pigments are chlorophylls, carotenoids (carotenes and xanthophylls) and phycobilins (phycocyanin and phycoerythrin). phycocyanin and phycoerythrin belong to the major class of phycobilins photosynthetic pigment while fucoxanthin and peridinin belong to carotenoid group of photosynthetic pigment. macroand microalgae (including cyanobacteria) have been recognized to provide a wide diversity of metabolites including pigments for energy capture and photo-protection. keywords: chlorophyll; phycobillins; microalgae; cyanobacteria; pigments املســتخلص: للصبغيــات يف الطحالــب اجملهريــة ميــزة خاّصــة متّيــز كل نــوع منهــا. وامللّونــات الطبيعيــة تكتســب أمهّيــة كبــرة بســبب آثارهــا اإلجيابيــة علــى الصّحــة والبيئــة. حتتــوي الطحالــب علــى أنــواع كثــرة مــن الصبغيــات. ثالثــة أكــر أقســام الصبغيــات هــي: كلوروفيــالت )اليخضــور(، كاروتينويــدات )كاورتــني، زونتفيــل( َو فيكوبيلينــات )فيكوســينني ، فيكوارتريــن(. فيكوســينني َو فيكوارتريــن تنتميــان إىل القســم األكــر مــن صبغيــات فيكوبيلينــات التمثيــل الضوئــي. كمــا أّن فيكوزونتــني َو بريدينــني تنتميــان إىل جمموعــة صبغــة كاروتينويــد التمثيــل الضوئــي. الطحالــب الكــرى واجملهريــة مبــا فيهــا البكتريــا الزرقــاء )ســيانوبكتريا( تُعــرف بقدرهتــا علــى توفــر كمّيــة متنّوعــة مــن املســتقلبات مبــا فيهــا صبغيــات التقــاط الطاقــة و احلمايــة بفعــل الضــوء. الكلمات املفتاحية: كلوروفيالت )اليخضور(، فيكوبيلينات، الطحالب اجملهرية، البكتريا الزرقاء )سيانوبكتريا(، الصبغيات. 82 squ journal of agricultural and marine sciences, 2018, volume 23, issue 1 extraction of natural pigments from marine algae objectives main objective of this work is to summarize the natural pigments from marine species of microalgae. common algal pigments the following pigments are industrially important products. chlorophylls this photosynthetic green pigment is mainly derived from chlorella spp. chlorophyll as a food colorant is found to exhibit anti-mutagenic property (fig.1,2). this is accomplished by inducing production of carcinogen detoxifying enzymes, and thereby reducing the risk of cancer. β-carotene dunaliella salina a halophilic green algae is used for β -carotene production. this pigment is used mainly as food colorant that imparts a yellow-orange color. apart from its use as a colorant, d. solina is used popularly as a nutraceutical additive because it is rich in vitamin a. fucoxanthin this pigment, derived from phaeophytes, is used for coloring food products brown. this fat reducing properties are well documented. peridinin peridinin is a light-harvesting apocarotenoid, a pigment associated with chlorophyll. the most popular algal source of this pigment is the dinoflagellate, amphidinifigure 1. chemical structure of chlorophyll a. figure 2. chemical structure of chlorophyll b. figure 3. chemical structure of β-carotene. figure 4. chemical structure of antheraxanthin. figure 5. chemical structure of astaxanthin. figure 6. chemical structure of cantaxanthin. 83research article alam, najam and al-harrasi um carterae (hofmann et.al, 1996) but is found in many other species. phycoerythrin red pigment, phycoerythrin is extracted from red algae (rhodophyta). the species most commonly used for phycoerythrin production is porphyridium cruentum. it is cultured in artificial seawater with added potassium nitrate and optimum temperature of growth for porphyridium is 21°c. phycocyanin blue pigment, phycocyanins are derived from blue green algae (cyanophyta). the most popular algal source of this pigment is spirulina platensis. it requires an alkaline ph range of 7.2 to 9.0 and a salinity of 30 g/l. in the wild, spirulina grows at 27°c. extraction of algal pigment chlorophylls and carotenoids are generally fat soluble molecules and can be extracted from thylakoid membranes with organic solvents such as acetone, methanol or dimethyl sulfoxide. the phycobilins (phycoerythrin & phycocyanin) and peridinin, in contrast, are water soluble and can be extracted from algal tissues after the organic solvent extraction of chlorophyll in those tissues. chlorophylls industrial extraction of these pigments involves homogenization (disintegration) of algal biomass, followed by solvent treatment using an organic solvent mixture (chloroform-hexane-ether-methanol) (jaffrey and humphrey, 1975; strickland and parsons, 1968; unesco, 1966; mackinney, 1941; porra et. al. 1989; lichtenthaler and wellburn, 1983; kaczmar, 2004). pigments can be extracted from seaweeds by a variety of techniques. it is important to note that light, heat, extremes of ph, and oxygen cause the destruction of pigment extracts. the extracts should be kept cold and worked with in the lowest light possible throughout the procedure. the rationale behind the extraction techniques is to disrupt cell integrity as much as possible, thereby removing pigment molecules from intrinsic membrane proteins. freezing the tissue with liquid nitrogen, and grinding the still frozen tissue in with a mortar and pestle or blender, overcomes some of the problems of working with material that produces large amounts of viscous polysaccharides. “freeze-thawing” tissue also breaks down cellular membranes, but may liberate more polysaccharides. finely ground tissue can be then homogenized in organic solvent to further disrupt cellular membranes, and to liberate pigment molecules from the light harvesting pigment protein complexes. once the pigments are extracted into appropriate figure 7. chemical structure of fucoxanthinol. figure 8. chemical structure of lutein. figure 9. chemical structure of peridinin figure 10. chemical structure of phycoerythrin figure 11. chemical structure of chemical structure of fucoxanthin. 84 squ journal of agricultural and marine sciences, 2018, volume 23, issue 1 extraction of natural pigments from marine algae solvents they can be separated chromatographically by tlc or hplc for spectral analysis and identification. pigment concentrations in hydrocarbon solvents can be estimated with various emparical formulae linking absorbances at different wave lenghts to concentrations. however, these formulas are predictive and may overestimate some pigment concentrations (seely et al. 1972). uncoupling pigments from the pigment binding proteins can change the absorption patterns of the pigments, resulting in shifts in maxima from 10 to 50 nm, when compared with spectra measured for intact tissues. carotenoids carotenoids are lipophilic colored compounds that are found in higher plants (gymnosperms & angiosperms) and algae as well as in non-photosynthetic organisms like fungi and bacteria. carotenoids are found in the form of isomers, viz. all trans, 9-cis, 13-cis, 5-cis forms (wang et al., 1994) more than 600 carotenoids are known (some important ones are, β-carotene, astaxanthin, cantaxanthin, lutein etc.) and their chemical structure is based on a 40-carbon polyene which is the backbone of the molecule (fig. 1). the polyene system imparts carotenoids their distinctive molecular structure, their chemical properties and their light absorbing characteristics. the hydrocarbon carotenoids are named carotenes, whereas oxygenated derivatives are known as xanthophylls. in xanthophylls, oxygen can be present as oh groups (as in canthaxanthin), or as combination of both as in astaxanthin (huguera-ciapara et al., 2006). at present carotenoid production from microalgae refers only to astaxanthin and β-carotene from haematococcus pluvialis and dunaliella salina, respectively. in astaxanthin producing organisms like phaffia rhodozyma (yeast) or h. pluvialis (algae), carotenoid are located in cytoplasmic lipid globules (lang, 1968; johnson and an, 1991). such extra-plastidic carotenoids are also referred to as secondary carotenoids (grung et al., 1992). h. pluvialis represents the richest biological source of this pigment and is being cultivated at large scale by several companies, using different approaches. commercially grown h. pluvialis can accumulate > 30 g of astaxanthin kg-1 dry biomass (olaizola and huntley, 2003). another important source for the production of β-carotene is the green, unicellular alga dunaliella salina. β-carotene obtained from dunaliella has many advantages like increased absorption by human body, high efficiency, isomeric composition and it can be produced up to 14% of dry wt. of the biomass in a very short time (metting, 1996). the carotenoid pigment astaxanthin has important applications in the cosmetics, nutraceuticals, food and feed industries. astaxanthin is a strong colouring agent and a potent antioxidant (guireen et al., 2003). contrary to advantages using microalgae as source of natural colourants, some disadvantages have also been reported. production of microalgae at large scale is associated with disadvantages like little process control (borowitzka, 1992), high co2 consumption with low efficiency (chaumont, 1993), contamination problems and optimal requirements of high amounts of salt, water and solar radiation (ogbonna and tanaka, 2000). for these reasons, alternative strategies/improvement of operating systems such as extensive open ponds (pulz, 2001, gomez and gonzalez, 2004), natural ponds (gomez and gonzalez, 2004), paddle wheel driven raceway/ ponds (pulz, 2001), tubular photo bioreactors (garcia-gonzalez et al., 2005), large bags (pulz, 2001) were suggested and tried to increase the β-carotene production. extraction efficiency and productivity of β-carotene from dunaliella can be enhanced many folds by using a biphasic bioreactor consisting of an aqueous and a biocompatible organic phase (hejazi et al., 2002, 2003, 2004). nowadays industries use closed tubular bioreactors for the production of carotenoids (gonzalez et al., 2005). this bioreactor has been found preferable for biomass and astaxanthin production from h. pluvialis (lopez et al., 2006). extraction of carotenoid pigments extraction and purification are two steps in carotenoid production from microalgae (lee et al., 1999). table 1. pigment composition of several algal groups (during 1982) division common name botanical name major pigment chlorophyta green algae chlorella sp. chlorophyll b charophyta charophytes spirogyra chlorophyll b euglenophyta euglenoids euglena gracilis chlorophyll b phaeophyta brown algae fucus vesiculosus chlorophyll c1 + c2, fucoxanthin chrysophyta yellow-brown or golden brown algae dunaliella salina chlorophyll c1 + c2, fucoxanthin pyrrhophyta dinoflagellates amphidinium carterae chlorophyll c2, peridinin cryptophyta cryptomonads cryptomonas sp. chlorophyll c2, phycobilins rhodophyta red algae porphyridium cruentum phycoerythrin, phycocyanin cyanophyta blue-green algae spirulina plat-ensis phycoerythrin, phycocyanin figure 12. chemical structure of phycocyanin. 85research article alam, najam and al-harrasi first step biomass is separated from liquid media by centrifugation. some alternative methods like flocculation, filtration etc. can also be used (molina grima et al., 2004). second step separated biomass needs to be quickly processed to avoid spoiling. the most acceptable methods are spray-drying, drum drying, freeze drying (lyophilization) and sun drying. β-carotene is extracted from wet dunaliella paste by different processes, using vegetable oils with or without chemicals, liquid or supercritical co2 extraction, crystallization and others. the supercritical fluid extraction of carotenoids from the microalgae d. salina, c. vulgaris, spirulina pacifica, and nannochloropsis gaditana has been reported by many workers with promising results (lorenzo et al., 1991; mendes et al., 1995, 2003; careri et al., 2001; macias-sanchez et al., 2005). dynamic extraction of carotenoids with supercritical co2 from a marine strain of synechococcus sp. was investigated with regard to operation pressure and temperature effects on extraction efficiency (montero et al., 2005). a biphasic aqueous/organic system to force the extraction of β-carotene into the medium is applied to dunaliella cultures. in this system, a biocompatible organic solvent is in contact with aqueous phase where the cells develop accumulation of pigments, β-carotene is continuously extracted into the organic phase overcoming low water solubility of the product and facilitating product recovery and continuous operation (salter and kell, 1995; hejazi et al., 2002, 2003). extraction methods the extraction techniques of cell components usually make use of chemical, mechanical and/or enzymatic proceses. in this work only the chemical and mechanical procedures were used, alone or simultaneously, with the aim of maximizing the extraction process efficiency. figure 13 shows a diagram where the different elementthat were used to extract then identify and quantify pigments in the microalgae, are presented under a structured sequence. the following methods were used to analyze the algal pigments in different extracts. (table 2, 3 & 4) thin layer chromatography concentration of carotenoid the carotenoid content of seaweeds was determined by the method of kirk and allen, 1965. the extract that was used for the chlorophyll estimation was used for carotenoid estimation also. the same chlorophyll extract was measured at 480nm in uv-spectrophotometer to estimate the carotenoid containing the following formula (eq. 1). carotenoid (µg/g) eq. (1) = a480 + (0.114 × a663) – (0.638 × a645) a = absorbance at respective wavelengths (nm). applications of carotenoids nutritional value: most of the natural pigments have high nutritional value unlike their synthetic counterparts (jin et al., 2003) because synthetic pigments conacetone (a) jh(1975) s(1968) unesco(1966) mk(1941) p(1989) lt(1983) k(1983) methanol (m) ethanol (e) 24 h 24 h 24 h 20 min 24 h 20 min 24 h (8ºc) 24 h (6ºc) (sdt) (sdt) (sdt) (sdt) (sdt)(sdt) (fz) (fz) (fz) (fz) (fz)(fz) (u) (u) (u) (u) (u) (u)(u) (u) microalgae (fn) reference equation extraction time cell disruption figure 13. items tested to compare different methods of pigments evaluation. abbreviations: st : standard, u: ultrasound, f: freezing/unfreezing, fn: freezing/unfreezing with liquid n2 86 squ journal of agricultural and marine sciences, 2018, volume 23, issue 1 extraction of natural pigments from marine algae tain mainly trans-forms and natural pigments cis-form (von laar et al., 1996). antioxidant and anticancer properties: β-carotene has been shown to have antioxidant and anticancer properties (becker, 2004). pigmentation in fish: major application of astaxanthin carotenoid is as pigmentation source in aquaculture, primary salmon trout and red sea bream (guerin et al., 2003; cysewski and lorenz, 2004). eco-friendliness: the process of manufacturing of natural pigments from algae does not involve the application of hazardous chemicals. the majority of the biomass are biodegradable and can also be reused as fodder, bio-fertilizers, etc. non-toxicity and non-carcinogenicity: natural pigments derived from algae have been certified as safe for application as food colorants. dyes: chlorophyll derivatives (chlorophyllin) are used for dyeing of fabrics such as wool, acetate derivatives and cotton. pharmaceuticals: β-carotene has market applications like food coloring agent, as provitamin a (retinol) in food and animal feed, as an additive to cosmetics and multivitamin preparations and as a health food product under the antioxidant claim (johnson and schroeder, 1996; edge et al., 1997). cosmetics: algal pigments are used for adding exotic pigments to soaps, shampoo, hand wash. macroalgae are a source of good pigments for various hair coloring table 2. empirical equations used to evaluate the concentration of pigments using methanol, acetone and ethanol as extraction solvent. acetone jeffrey and humphrey (1975) μg chlorophyll/ml medium = (11.85 a664 – 1.54 a647 – 0.08 a630) υ/(lv) strickland and parsons (1968) μg chlorophyll/ml medium = (11.66 a665 – 1.31 a645 – 0.14 a630) υ/(lv) unesco (1966) μg chlorophyll/ml medium = (11.64 a663 – 2.16 a645 – 0.10 a630) υ/(lv) methanol mackinney (1941) μg chlorophyll/ml medium = 13.43 a665 υ/(lv) porra et.al. (1989) μg chlorophyll/ mlmedium = (16.29 a665 – 8.54 a652) υ/(lv) lichtenthaler (1983) μg chlorophyll/ml medium = 15.65 a666 μg total carotenoids/ml medium = [ (1000 a470 – 44.76 a666)/221] ethanol kaczmar (2004) μg chlorophyll/ml medium = (11.64 a663 – 2.16 a645 – 0.10 a630) υ/(lv) a is the absorbance at respective wave lengths (nm) , v means the volume of solvent used (ml), l is the spectrophotometric cell length (cm) and v is the sample volume (ml). table 3. rf values of different pigments s. no. pigment rf value solvent system 1 chlorophyll a 0.68 7:3(petroleum ether : acetone) 2 chlorophyll b 0.54 7:3(petroleum ether : acetone) 3 chlorophyll c 0.03 7:3(petroleum ether : acetone) 4 β-carotene 0.94 7:3(petroleum ether : acetone) 5 fucoxanthin 0.51 7:3(petroleum ether : acetone) 6 lutein 0.43 7:3(petroleum ether : acetone) 7 violaxanthin 0.22 7:3(petroleum ether : acetone) 8 neoxanthin 0.08 7:3(petroleum ether : acetone) table 4. wavelength maxima for pigments in various solvents. s. no. pigment wavelength maxima solvent 1 chlorophyll a 428.5, 660.5 diethyl ether 2 chlorophyll c1 629.1 100 % acetone 3 chlorophyll b 452.5, 642 diethyl ether 4 chlorophyll c2 630.6 90% acetone 5 chlorophyll c2 629.6 100% acetone 6 chlorophyll c2 630.9 90% acetone 7 chlorophyll c 447, 533 or 449, 635 90% acetone 8 β carotene 452, 470 ethanol 9 lutein 446, 474 ethanol 10 violaxanthin 442, 470 ethanol 11 neoxanthin 437, 466 ethanol 12 myxoxanthophyll 445, 471, 503 ethanol 13 siphonoxanthin 455 ethanol 14 peridinin 455 ethanol 87research article alam, najam and al-harrasi products due to their long lasting properties.xanthophylls, astaxanthin has many applications in cosmetics products. paint additives: beer yeast diatoms are also used in paint additives, other than algal pigments, due to the iridescent nature of their silica shells. feed industries: xanthophylls, astaxanthin has many applications in feed industries like as poultry. major application of this carotenoid is the pigmentation in egg yolk. phycobiliproteins structure of phycobiliproteins the phycobiliproteins are antennae protein pigments found in cyanobacteria, rhodophytes, cryptomonads and cyanelles (glazer, 1994). the phycobiliproteins are present as phycobilisomes anchored on the thylakoid membranes and lie adjacent to the photosynthetic reaction centre of the ps ii in cyanobacteria and red algae. these chromoproteins are classified into 3 groups based on the presence of different chromophores among them (gantt, 1980, 1994; glazer, 1985; zilinskas, 1986; rowan, 1989; sidler 1994; mac coll, 1998; ducret et al., 1998). these groups are (1) phycoerythrin (pe) λmax 480 nm-570 nm; (2) phycocyanin (pc) λmax 590-630 nm and phycoerythrocyanin (pec) λmax 630-665 nm (3) allophycocyanin (apc) λmax 620-665 nm. core of phycobiliproteins is composed of allophycocyanin from which arise six rods of varying length consisting of phycocyanins to the proximal side of the core and phycoerythrins to the distal side of the core (fig. 14). extraction and purification methods phycocyanin phycocyanin is water-soluble and can be easily extracted as a protein-pigment complex (chaiklahan et al., 2012). phycocyanin was extracted from the wet biomass of spirulina using the following methods: extraction was done using 100mm phosphate buffer (ph 7.0) at a ratio of 1:100 (w/v) with continuous stirring at 300 rpm at room temperature for 4 hrs. the sample was centrifuges at 4800 × g for 15 minutes to remove cell debris. the crude extract was first filtered through a 5 μm membrane at flow rate of 150 ml min-1.and then through 0.8/0.2 μm membrane at flow rate of 100 ml min-1. the phycocyanin was then filtered again through a membrane with a molecular cut-off of 50 kda at 69 kpa and 75 ml min-1. finally the filtrate was lyophilized to get the phycocyanin powder. mechanical cell disintegration methods are currently preferred for large-scale operations (gacesa and hubble, 1990; kula and schutte, 1987) since a complete disintegration of the biomass is desired, with high product and activity yields. allophycocyanin, a bluish green protein and cpc, a blue protein have the major absorption (λmax) in the visible region of 650-655 nm and 610-620 nm, respectively, with emission light at 660 nm and 637 nm respectively (bryant et al., 1979; sekar and chandramohan, 2007). determinations of these phycobiliproteins by spectrophotometry have been assessed by different authors (furuki et al., 2003; chaiklahan et al., 2012). the purity ratio of the phycocyanin extract is determined by the a620/a280 ratio. high purity in the extract refers to high purity ratios (chaiklahan et al., 2012). absorbance ratio ≥ 0.7 refers to food grade pigment, while reagent and analytical grade correspond to 3.9 and ≥ 4.0 respectively (borowitzka, 2013). c-phycocyanin concentration the c-phycocyanin concentration (cpc) in mg.ml-1 was calculated from the optical densities at 652 and 620 nm, using eq. 2 (bennett and bogorad, 1973): cpc =(od620 0.474od652 ) /5.34 eq.(2) extraction yield: the extraction yield was calculated using eq. 3 (silveira et al., 2007). yield =(cpc)v/db eq.(3) where yield is the extraction yield of phycocyanin in mg of c-phycocyanin /dry biomass (g), v is the solvent volume (ml) and db is the dry biomass (g). calculation of phycocyanin content (c-pc): (kursar and alberte 1983) the c-pc and apc concentration (μg/ml) were defigure 14. schematic structure of the pigments in a phycobilisome. 88 squ journal of agricultural and marine sciences, 2018, volume 23, issue 1 extraction of natural pigments from marine algae termined spectrophotometrically from equations 1 and 2. c-pc = 166(a618 ) -108(a650) eq.(4) a-pc = 200(a650 ) -52.3(a618) eq.(5) where a refers to absorption at the indicated wave lengths phycoerythrin phycoerythrin is a red coloured phycobiliprotein with absorption maxima range at 565 nm. purity is usually determined as the absorbance ratio of a565/a280 which defines the relationship between the presence of phycoerythrin and other contaminating proteins. a purity ratio a565/a280 >4 corresponds to diagnostics and pharmaceutical grade phycoerythrin (benavides and rito-palomares, 2004). phycoerythrin is an intracellular protein, the general purification process relies in three stages: 1. protein extraction by cell disruption, 2. primary recovery and 3. purification. disruption methods like sonication, mechanical maceration and lysozyme treatment have been successfully used to extract phycoerythrin from microalgae. choosing the right cell disruption method has a significant impact in the recovery of the overall process. benavides and rito-palomares (2006) used aqueous two-phase system (atps) to concentrate and purify phycoerythrin. aqueous two-phase system is an advantageous technique due to its biocompatibility and can easily be scaled. the authors found that it is possible to concentrate phycoerythrin in the peg-rich top phase using a peg 1450-phosphate system. the system constructed with a volume ratio (vr) of 1, peg 1450 of 24.9% (w/w), phosphate concentration of 12.6% (w/w) and ph value of 8 allowed the recovery of phycoerythrin with a 2.9 purity ratio. purification is achieved by chromatographic methods like ion exchange chromatography, hydroxyapatite chromatography, gel filtration and expanded bed absorption chromatography. calculation of phycoerythrin content (pe): (beer and eshel, 1985) the following equations are proposed for correct calculations of pigment concentrations (e, phycoerythrin; c, phycocyanin, mg ml-1 in red algal crude extracts: pe (mg/ml) = [(a564 a592) (a455 a592) x 0.2] x 0.12 eq.(6) c (mg/ml) = [(a618 a645) (a592 a645) x 0.15] x 0.15 eq.(7) where a refers to absorption at the indicated wave lengths. applications in food coloring: one of the most important application of phycocyanin is its use in food items. it is used as a colourant in chewing gums, popscicles, candies, soft drinks, dairy products and cosmetic also in the industry for lipsticks and eye liners. the major organisms exploited are spirulina for phycocyanin and the red alga porphyridium for phycoerythrin (roman et al., 2002). dyes: phycobiliproteins are used for dyeing of fabrics such as wool and cotton in japan, thailand and china. phycocyanin derived from s. platensis is used as a natural pigment in food items such as chewing gums, dairy products and jellies (santago-santos et al., 2004), as a dye in pharmaceutical and cosmetic industry (batista et al., 2006). pure phycobiliproteins are also widely used as fluorescent labeling agents (glazer, 1994; telford et al., 2001). due to their antioxidant and anti-inflammatory properties, both c-pc and apc are also potential therapeutic agents. (zhang et al., 2000, romay et al., 2003). phycocyanin colorants in general are non-toxic and non-carcinogenic. uses of phycocyanin in foods include the coloring of fermented milk products, ice creams, chewing gum, soft drinks, alcoholic drinks, desserts, sweet cake decoration, and milk shakes. conclusion important pigments (chlorophyll a, b and c, β-carotene, astaxanthin, xanthophylls, and phycobiliproteins) are produced by many microalgae. synthetic pigments are used in food, cosmetics, beverages , nutraceutical and pharmaceutical industries. synthetic pigments are having harmful effects, natural pigments become an attractive option from microalgal pigments. though algal pigments have the drawback of unstable at high temperature, an effective solution involves using thermophilic algal pigments. due to increased interest in bio-fuels and food supplements of algal origin, in the recent times, there is widening scope for industries to exploit the availability of other algal products, 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β-carotene. journal of photochemistry and photobiology b: biology 33: 157-162. wang, xd, krinsky ni, benotti pn, russell rm. 1994. biosynthesis of 9-cis retinoic acid from 9-cis-β-carotene in human intestinal mucosa in vitro. archives of biochemistry and biophysics 313: 150-155. zhang s, yao s, wang w, xie j, zhang j, zhao j, jiang l. 2000. studies on the kinetics of reactions between phycobiliproteins and hydroxyl radicals by a pulse radiolytic technique. chinese science bulletin 45(10): 896-899. zilinskas ba, greenwald ls 1986. phycobilisome structure and function. photosynthesis research 10: 7-35. research paper journal of agricultural and marine sciences vol. 22 (1): 18 – 26 doi: 10.24200/jams.vol22iss1pp18-26 received 15 aug. 2016 accepted 19 dec 2016 evaluation of some water saving devices in urban areas: a case study from the sultanate of oman hayder a. abdel rahman*1, halima a. al-farsi2, mushtaque ahmed1 and matheus f. a. goosen3 *1 hayder abdel rahman ( ) sultan qaboos university, college of agricultural and marine sciences, department of soils, water and agricultural engineering, box 34, al-khod 123. sultanate of oman. email: hayderar@squ.edu.om. 2 ministry of regional municipalities and water resources, muscat, sultanate of oman. 3 office of research and graduate studies, alfaisal university, riyadh, saudi arabia. introduction the mean annual rainfall throughout most of oman is less than 100 mm with marked regional variations in local rainfall amounts. the available water resources of the sultanate are estimated at 1267 mm³ (million cubic meters) and the water demand is about 1645 mm³, resulting in an annual water deficit of 378 mm³. (mrmwr, 2008). the per capita water consumption is reported as 200 liters/day. in some areas, particularly the coastal regions, water abstractions has largely exceeded the rate of groundwater recharge, which lead to continuous lowering of the water table and sea water intrusion (al-ajmi and abdel rahman, 2001). saving in domestic water is sought as part of an integrated conservation/augmentation plan. domestic water is more expensive compared to agricultural and industrial water. domestic water in the muscat governorate (capital area) comes mainly from desalination plants that cost 0.5 omr ($1.3) per cubic meter to produce and is subsidized by the government and distributed to the public at the rate of 0.44 omr ($1.14) including transport costs (mhew, 2002). the total daily volume of desalinated water produced for domestic purposes in the capital was 221,260 m3/day generated from 6 desalination plants. the maximum daily demand for water in the region was estimated at 233,000 m3/day and was recorded in october while the minimum daily demand stood at 148,000 m3/day reported in february. the average household water use worldwide varies from 190 to 285 liters per person per day and breaks down as 42% for toilet use, 32% for bathing, 14% for laundry, 8% for kitchen and 4% for cooking purposes. plumbing retrofit programs have been recognized as the quickest and simplest way to reduce demand for potable water and soften the impact such demand places on a تقييم بعض أجهزة توفري املياه يف املناطق احلضرية: دراسة حالة من سلطنة عمان حيدر عبد الرمحن*1 وحليمة الفارسي2 ومشتاق أمحد 1 وماثيوس غوسن3 abstract. water saving devices (wsds) sustain demands for potable water, soften impacts on supply systems and inflict a positive effect on wastewater treatment systems. this study evaluated the effect of some wsds in oman. a questionnaire survey and some case studies were used. the survey results revealed that the pipe line system network for water supply accounted for about 67.7%, whereas the rest mainly use tankers. around 37.2% of the participants received consumed 25000 45000 liters per household per month. case studies showed no significant difference in household water usage before and after installation of wsds due to pre-installed aerators. toilet bags and dual flush toilets were not effective promoting users to flush. however, wsds were significantly effective in restaurants, mosques, hotels and government buildings. water consumption in shopping centres and hospitals slightly decreased. retrofitting programs that involve replacement of existing plumbing equipment and residential water audit programs are recommended. keywords: urban water; water saving devices; domestic water conservation. امللخــص: تعمــل أجهــزة توفــر امليــاه علــى اســتدامة امليــاه الصاحلــة للشــرب، وختفيــف الضغــوط علــى أنظمــة اإلمــداد، وتوقــع أثــرا إجيابيــا علــى أنظمــة معاجلــة ميــاه الصــرف الصحــي. وقــد قيمــت هــذه الدراســة تأثــر بعــض أجهــزة توفــر امليــاه يف ســلطنة عمــان. ومت اســتخدام اســتبيان مســحي لذلــك وإجــراء بعــض دراســات احلالة. كشــفت نتائج املســح أن شــبكة خطوط األنابيب إلمدادات املياه قد شــكلت حوايل 67.7٪، يف حني أن بقية الســكان يســتخدمون الناقالت بشــكل رئيســي. وتراوح االســتهالك الشــهري حلوايل 37.2٪ من املشــاركني يف االســتبيان بني 25000 و 45000 لرت لكل أســرة. وأظهرت دراســات احلالــة عــدم وجــود فــرق كبــر يف اســتخدام امليــاه املنزليــة قبــل وبعــد تركيــب أجهــزة توفــر امليــاه وذلــك بســبب أجهــزة خلــط اهلــواء املثبتــة مســبقا يف صنابــر امليــاه. ومل تكــن أكيــاس املراحيــض واملراحيــض ذات التدفــق املــزدوج فعالــة حيــث أدت إىل تشــجيع املســتخدمني علــى التنظيــف أكثــر مــن مــرة. ومــع ذلــك، كانــت أجهــزة توفــر امليــاه فعالــة بشــكل كبــر يف املطاعــم واملســاجد والفنــادق واملبــاين احلكوميــة. واخنفــض اســتهالك امليــاه يف مراكــز التســوق واملستشــفيات قليــال. وتوصــى الدراســة بربامــج إلعــادة التهيئــة تنطــوي علــى اســتبدال معــدات الســباكة القائمــة وبرامــج تدقيــق امليــاه الســكنية. الكلمات املفتاحية: املياه يف املناطق احلضرية، أجهزة توفر املياه، احلفاظ على املياه املنزلية 19research article rahman, al-farsi, ahmed , goosen water supply system (al-rumikhani. 2000). lallana et al. (2001) reported that aerators (taps with air devices) and taps with thermostats could save up to 50% water whereas those equipped with infrared sensors could save up to 80%. devices that limit shower flow could inflict a 10—40% water savings. toilets are the biggest water-guzzling appliances in homes (13-16 liters per flush). water saving devices in this respect fall into five categories (garcía and cortés, 1989): low flush toilets using smaller tanks and a specially designed bowl to give the same flush power but with less water, toilets using displacement technologies such as a plastic container that can be filled with water and placed in a toilet tank to reduce the amount of water used per flush, vacuum and waterless toilets, and toilet cycle diverters that diverts water to the tank and less to the toilet bowl. water saving showerheads includes thermostatic mixers with a calibrated dial, allowing the temperature to be set from experience, and showerheads that create finer drops. different forms of water saving taps exist: faucet aerators that break the flowing water into fine droplets and taps with sensors and push back device taps with pressure reduction–flow regulators; and commercial “power-spray” washers with vigorous spray patterns. urinals can save water compared with toilets, but will waste a considerable amount of water if incorrectly installed. typically, urinals account for about 20 percent of office water use, but this figure can vary a good deal. urinals that use no water, other than for daily cleaning, are now widely available. more than 4.8 billion gallons of water are flushed down toilets each day in the united states (jensen, 1991). the most important source of saving is in toilet replacement or modification which gives more than 61% of water saving, but it costs more than the other devices. toilet dams, which hold back a reservoir of water when the toilet is flushed, can also be used instead of plastic container to save water. two anti-slip ribs at both ends insure dams remain in place when installed. the dams also have a high saving percentage of 51%. there is a great potential to reduce water consumption by installing low-flush toilets in new construction and building rehabilitation or remodelling. effective january 1, 1994, the energy policy act of 1992 (public law 102-486) required that all new toilets produced for home use must operate on 6 liters per flush or less. toilets that operate on 13 liters per flush were continued to be manufactured, but their use was to be limited to certain commercial applications effective january l, 1997. in mexico, efforts have been made to improve the water use efficiency of traditional toilets by placing containers, bricks, bags filled with water or plastic compartments in the tank to reduce its capacity (garcía and cortés, 1990). most of these methods, however, reduce the toilet’s siphoning effect. according to tests carried out by the mexican institute of water technology (garcía and cortés, 1991) a viable option for saving water in these fixtures is to lengthen the discharge siphon, which reduces water consumption. showers take second place in water demand at home in mexico city and regulations specify that the discharge from showers should not exceed 10 l/min. this can be accomplished by using new shower-head designs or flow reducers. flow reduction in basin and sink faucets is achieved by using aerators, which add air to the stream and disperse it, increasing the spread and therefore the washing efficiency. another option that has been explored, with excellent results, is the installation of valves or sensors that activate the water flow only when the hands are placed beneath them. a study carried out by the imta showed that a basin faucet equipped with a sensor discharged 1.5 l/min at a pressure of 0.2 kg/cm2 and 5.9 l/min at a pressure of 2.5 kg/cm2 (garcía and cortés, 1989). savings in washing machines are achieved by loading them with the appropriate weight of clothes, using the water levels necessary for efficient operation, or using washers that require less water. there are basically two types of washing machines: front loaders and tub machines (top loaders); the first type can use up to half the amount of water — 50% of the hot water and 33% of the detergent — required by the second type. the manufacture of efficient washing machines has reduced water consumption by up to 24% in comparison with traditional models. the volume of water used by dish washers varies between 49 and 95 liters per day. however, more efficient models have been introduced that require only 36 to 45 liters per day. in oman, in a study that was implemented in 1998 under the auspices of the ministry of regional municipalities, environment and water resources (mrmewr), wsds were installed in the ministry building in ruwi (mwr,1998). the main objectives were to assess wsds performance, percentage of water savings, water users’ responses and feedback. the experiment duration was from 1/6/1993 until 1/12/1996. on average the number of employees before installing wsds was 186 and after installing were 209. water bills before and after installation was compared and analyzed. the highest monthly consumption before installation was in july with an average rate of 313.24 liters per person and with the lowest monthly consumption in february with average consumption rate of 181.35 liters per person. whereas after installation, the highest monthly consumption was in september with average rate of 247 liters per person and with the lowest monthly consumption in february with a average consumption rate of 133.21 liters per person. the average monthly consumption before installing was 236.27 liters per person and after installation it came down to 205.59 liters per person. the net average water saving per month was 30.68 liters per person with a saving percentage of 13%. considering an average number of employees of 209, the total water consumption was 49380.4 liters/month. thus, the total monthly water savings was 6420 liters which is equivalent to total annual 20 squ journal of agricultural and marine sciences, 2017, volume 22, issue 1 evaluation of some water saving devices in urban areas water saving of 77033 liters. by multiplying the cost of one liter (0.44 beiza) by the total water savings 77033 liters; the total annual financial saving was 34 omr and 170 omr for the whole life span of the devices 5 years. the feedback from the questionnaire indicated that 17% of the water users knew that wsds were installed and 83% of the water users did not have any problems or annoyed while using retrofitted aerators tabs (mwr, 2000). materials and methods a questionnaire was designed to test public attitudes towards the water saving devices, knowledge about water shortage in the sultanate and willingness to install water saving devices, and other related information. about 125 questionnaires were distributed through students from sultan qaboos university to university students, colleagues, friends, neighbors and others so that it can be explained to them if there were any ambiguities or misunderstandings. the second part of the study was supported by the ministry of regional municipalities and water resources (mrmwr). the work was carried out by introducing the wsds at pilot sites, which were selected with direct guidance and supervision from mrmewr, of some voluntaries who accepted the installation of wsds. sites selected, were from government buildings, public houses and commercials buildings. readings were taken on a daily basis at the same time. the pilot sites reported here were two private villas, one hotel, one restaurant, one government building, one mosque, and one commercial building. water meters for the sites with defective meters were first replaced. automated data loggers for continuous loggings were then installed in the seven sites namely two villas in ghobrah, muscat city centre, al araimi mosque, the grill house restaurant, holliday inn hotel and the ministry of regional municipalities and water resources’ building. monitoring commenced for three months after installation of wsds. all owners agreed to cooperate in the study. in return for their cooperation they received a variable-load washing machine, which presumably would serve the purposes of the study. different types of wsds were installed including aerators, toilet bags or dual flush toilets, lowflow shower heads and variable-load washing machines. for all sites the mean water consumption before installation of wsds was compared against mean water consumption after installation of wsds using t-test comparison of means for data sets with unequal numbers. significance factor was taken as 95%. results and discussion i. questionnaire the questionnaire results were analyzed using the statistical program for social science (spss). the questionnaires were distributed among various categories of participants. participants (60% males) with a high level of education (university) represented 56.5%, whereas those with medium and low levels of education constituted 29 and 14.5% respectively; 79% of the participants being in the age group of 20 – 40 years. most of the participants were government employees (71.4%) with housewives representing only 6.7%. thirty five per cent of the participants earned an income of $1,000 – 15,000 per month whereas 47% and 18% drew monthly incomes less than $500 and more than $1,500 respectively. the majority of the participants (40.3%) had a family size of 3-5 persons, whereas family size of 1-2 persons per family represented the lowest percentage (6.7%). pipe line network system as a water source at home accounted for 67.7% in the study, whereas those who transported water through tankers to their homes accounted for 21%, while those who used a mixture of tankers and the pipeline accounted for 6.5% and others (e.g. own well) accounted for 4.8%. it was indicated from the water bills paid that 37.2% of the participants used 25,000 45,000 liters per month per household where as 12.4% used less than 10,000 liters and 21.5% used more than 45,000 liters per month per household. the pattern of water use at home during bath using the shower accounted for 86.1% and those who were filling the bath tub accounted for 13.9%. whereas 78.9% of the participants kept the tap running intermittently when shaving and brushing, 21.1% kept the tap running continuously. in ranking house compartments, 31.7% said that the kitchen and the bathroom used the most amount of water, where as 19.5% attributed this to the washing machine and 17.1% said that irrigating gardens and plants used the most. about 78% of the participants were not using any water saving methods at their homes and yet, 76% of the participants considered themselves as water savers. different types of water saving devices were employed by those using wsds and almost 30% of them utilized sensors in their taps whereas 18% applied either push types or a combination. the survey revealed a high awareness (88%) about the water problem of the country. about 14% of the participants felt that installing wsds at homes wouldn’t make any difference; 86% felt that the effects would be moderate to significant and 70% were willing to install the water saving devices in their houses. yet 92% of those surveyed expected to benefit from using water saving devices in term of money and help solving water shortage problems of the country, with a significant positive correlation at the 0.01 level between the willingness of 21research article rahman, al-farsi, ahmed , goosen the participant to install the water saving devices and to buy those devices. about 86% of the participants felt that there was a significant relationship between water consumption and social status of water user, which means that as income increases water consumption increases because of the lifestyle changes and water consuming facilities found such as gardens, swimming pools, and washing machines. there was a significant correlation between the monthly income of the participants and their average water bill per month, while no correlation existed between the size of the family and the average water bill per month and this was attributed to the size of the house, presence of a cultivated area (garden), age of the kids and living habits. 2. case studies 2.1 private villas table 1 shows the average weekly water consumption of the two villas reported in this study as deducted from the billing authority (oman investment and finance company). villa i had eleven occupants, seven of whom were children under 18, whereas villa 2 had seven occupants three of whom were children. seven aerators, 5 toilet bags, 4 low-flow showerheads, 2 sensor activated taps and one variable-load washing machine were installed in villa 1, whereas an extra aerator was installed in villa 2. comparison of water consumption data, to detect any increase or decrease in water consumption was performed by using the adjustment factors for water consumption which were calculated as a deviation from the average weekly value for water consumption. weekly 0.0 2.5 5.0 7.5 sep−2011 nov−2011 jan−2012 mar−2012 may−2012 jul−2012 date d ai ly c on su m pt io n (m 3 ) before/after installation after before 0 5 10 sep−2011 nov−2011 jan−2012 mar−2012 may−2012 jul−2012 sep−2012 date d ai ly c on su m pt io n (m 3 ) before/after installation after before figure 1. daily water consumption in villa 1 (top) and villa 2 (bottom) before and after installation of water saving devices (wsds). the weekly average (m-3·d-1) is presented in the background. 22 squ journal of agricultural and marine sciences, 2017, volume 22, issue 1 evaluation of some water saving devices in urban areas water consumption data were then adjusted for seasonal variations using these factors, in the absence of ample water consumption data to properly account for seasonality and the variable nature of water consumption. a comparison between weekly figures before and after installation of wsds was performed using a one-tailed t-test with a significance level of 95%. no apparent significant differences in water consumption before and after installation of wsds were detected for both villas, as can be seen from (fig. 1) and table 2. the average daily water consumption decreased from 2.40 to 2.28 m3 in villa 1, but increased from 2.66 to 3.23 m3 in villa 2. this was attributed to the fact that faucets in houses were already equipped with aerators, so no significant water savings were detected by installing new aerators. toilet bags and dual flush toilets were not effective and prompted users to flush twice. lowflow showerheads were probably effective but their effect was masked by the negative effect of other wsds. water consumption varied mostly depending on whether or not an outdoor water use existed. the average water use per inhabitant for the two villas was 180 – 260 l/day and 350 – 470 l/day respectively. the higher value was due mainly to the use of the garden water. these figures compare well with those in neighboring gulf cooperation council countries (gcc). 2.2 muscat city centre muscat city centre is the largest shopping centre in oman. water use varies according to the day of the week and the shopping season. occupancy of the centre is difficult to quantify as there are no checks on people entering the structure. for this reason, the only reliable information was obtained through historic water meter data. it is worthy to note that the number of people entering city centre is quite large. the average water consumption per person is on the order of 5-10 liters per day considering that not all customers use toilets or ablution rooms. as such, on average over 10,000 people enter the centre for diverse purposes on a daily basis. the daily water consumption on week days was slightly more after installation of wsds (216.66 m3) compared to that before (199.65 m3), while on weekends the average daily use was 220.23 m3 before and 206.32 m3 after as shown. although this slight difference might be due to seasonal effects, it is probably due to that customers on weekends use ablution rooms more frequently than during weekdays and hence the savings in weekends and their absence during weekdays. the mean weekly consumption decreased from 1,682 m3 to 1,496 m3 before and after installation of wsds respectively. to determine whether this difference is significant or not, a t-test was conducted. although mean water consumption after installation of wsds was lower by 185.77m3, the calculated t value (t-stat) of 0.95 was lower than critical value (t-critical one tail) of 1.30. this indicates no significant water savings after installation of wsds at 95% confidence level. it seems that the combination of toilet bags and self-closing taps, which were installed in city centre, were not significantly effective in reducing water consumption and people tend to flush the toilets twice and keep pressing on taps to keep the water running. 2.3 al-araimi mosque al araimi mosque is a new and relatively small mosque with 8 toilets and 28 faucets for ablution, all of which table 1. weekly water consumption (m3) and adjustment factors for the two villas. month villa i villa 2 consumption adj. factor consumption adj. factor january 11.97 0.73 16.26 0.87 february 16.75 1.02 17.75 0.95 march 24.16 1.47 13.77 0.74 april 22.17 1.35 27.07 1.45 may 21.90 1.33 24.61 1.32 june 20.32 1.23 21.00 1.13 july 17.61 1.07 20.55 1.10 august 9.80 0.60 14.45 0.77 september 11.74 0.71 17.27 0.93 october 17.03 1.03 19.19 1.03 november 12.19 0.74 15.63 0.84 december 11.97 0.73 16.26 0.87 total 197.62 223.81 average 16.47 18.65 st. deviation 4.89 4.05 23research article rahman, al-farsi, ahmed , goosen were fitted with toilet bags and self-closing taps, respectively. collected data before and after the installation of wsds is illustrated in (fig. 2) and (table 2). the average weekly water consumption decreased following installation of wsds by 41%; from 1.58 m3 to 0.93 m3. the calculated t value (t-stat) of 6.62 was larger than critical value (t-critical one tail) of 1.70. consequently, water consumption decreased significantly following installation of wsds. the comparison of these results with those of city centre, where similar wsds were installed, reveals the effect of individual wsds. in al araimi mosque, the ratio of toilet bags to self-closing taps is 8:28 whilst in muscat city centre it is 52:70. as visitors to shopping centres use toilets more than those going to the mosque, it could be safely asserted that self-closing taps are far more effective in reducing water consumption. 2.4 the grill house restaurant in the grill house restaurant occupancy was comparable during weekdays and during weekends. the restaurant itself has four toilets and five wash basins. the former was equipped with dual flush toilets while the latter was equipped with self-closing taps. again seasonality effect was visible in the data illustrated in (fig. 3) and (table 2). calculated means indicated that the mean weakly use was 89.83 m3 and 50.14 m3 before and after the installation of wsds respectively, with a 44% decrease in water consumption following installation of wsds. this decrease is significant as determined from the results of the t-test. the calculated t-value of 6.67 was larger than critical value (t-critical one tail) of 1.68. consequently, water consumption decreased significantly following intable 2. comparision of daily water consumption before and after installing water saving devices. significance (sign.) is based on a one-tail t-test with α = 0.05. location water saving measures water use (m3·d-1) before after sign. villa 1 aerators, toilet bag, low-flow showerhead, sensor activated taps, variable load washing machine 2.40 2.28 n.s. villa 2 aerators, toilet bag, low-flow showerhead, sensor activated taps, variable load washing machine 2.66 3.23 ns muscat city centre toilet bags, self-closing taps 240.2 213.7 * al araimi mosque toilet bags, self-closing taps 0.22 0.13 * grill house restaurant dual flush toilets, self-closing taps 12.83 7.16 * hotel holiday inn low-flow showerheads 101.7 90.5 * ministry (mrmewr) building aerators, sensor-activated taps, toilet bags 1.76 0.89 * 0 1 2 3 feb−2011 apr−2011 jun−2011 aug−2011 date d ai ly c on su m pt io n (m 3 ) before/after installation after before figure 2. daily water consumption in al-araimi mosque before and after installation of water saving devices (wsds). the weekly average (m3·d-1) is presented in the background. 24 squ journal of agricultural and marine sciences, 2017, volume 22, issue 1 evaluation of some water saving devices in urban areas stallation of wsds. this is a further confirmation that self-closing taps are effective in reducing water consumption and a further insight that dual flush toilets might have some effect on reduction of water consumption as well. 2.5 holiday inn hotel holiday inn hotel in al khuwair has 123 rooms in total. there are two restaurants, a small gymnasium and a swimming pool. all toilets are operating on a half -flush cycle. water consumption before and after installation of wsd is illustrated by (fig. 4) and (table 2). descriptive statistics showed that the mean weekly consumption before installation was 711.98 m3 and decreased to 633.47m3 after the installation of the wsds. the calculated t value of 1.71 was larger than critical value (t-critical one tail) of 1.67, consequently water consumption decreased significantly following installation of wsds. as indicated in table 2, water consumption decreased significantly over that consumption prior to installation of wsds. the effect of individual devices could not be isolated in that which device is more effective in saving water. however, in view of the volume of water applied, it is thought that low-flow showerheads might have had an effect. 0 5 10 15 20 dec−2011 feb−2012 apr−2012 jun−2012 aug−2012 date d ai ly c on su m pt io n (m 3 ) before/after installation after before figure 3. daily water consumption in grill house restaurant before and after installation of water saving devices (wsds). the weekly average is presented in the background. 0 50 100 150 200 sep−2011 nov−2011 jan−2012 mar−2012 may−2012 jul−2012 sep−2012 date d ai ly c on su m pt io n (m 3 ) before/after installation after before figure 4. daily water consumption at the holiday inn hotel before and after installation of water saving devices (wsds). the weekly average is presented in the background. 25research article rahman, al-farsi, ahmed , goosen 2.6 mrmewr building the ministry of regional municipalities and water resources building bathrooms were fitted with 24 aerators for 24 faucets and 24 sensor-activated taps. in addition, they were fitted with 24 toilet bags. patterns of water consumption are illustrated in (fig. 5) and (table 2). as expected, averages during weekdays (0.92m3/ day) exceed those during weekend (0.83m3/day). this is understandable considering that weekends are days of inactivity in the building. also it was noted that water consumption increased from beginning of june to mid of july due to the summer season. most of the staff normally takes their leave during july september. it is worthy to note though that installation of wsds stabilized and reduced water usage. as illustrated by the figure, water use was initially staggered but became more clustered with a clear pattern after the installation of wsds. descriptive statistics showed that the mean weekly consumption before installation was 12.317 m3 and decreased to 6.284 m3 after the installation of the wsds. the calculated t value (t-stat) of 4.32 was larger than critical value (t-critical one tail) of 1.70, consequently water consumption decreased significantly to about 50% following installation of wsds. 3. analysis and limitations of the case study results the aforementioned consistent results indicate that overall wsds are indeed significantly effective in reducing water consumption. the most powerful devices include self-closing taps, low-flow showerheads, and sensor-activated taps. ineffective devices include aerators and toilet bags. aerators are ineffective because most modern faucets nowadays are already equipped with aerators. hence, installing additional aerators would not add any value in terms of significant water savings. toilet bags are ineffective because low-flush toilets are specially designed whereby a low flush does clean the bowl. this is not the case for toilet bags installed on conventional bowls which eventually cause the toilet user to flush at least twice for effective cleaning and this may be one of the reasons for the houses inconsistent results. also the fact that the owners of the houses may claim that they are making greater effort to conserve water although measurement of specific actions such as frequency of laundry car washing and garden watering that habits are largely unchanged. in contrast, self-closing taps did reduce water consumption drastically in several public places and hence are recommended in mosques ablution rooms, restaurants, and schools. they are also recommended in large shopping centres despite the fact that their benefit was masked by the presence of other ineffective devices in the city centre shopping mall. low-flow showerheads demonstrated their benefit clearly in hotels. sensor-activated taps are probably the most effective wsds as they reduced water consumption significantly in the mrmewr building. these should be installed wherever users can afford their elevated costs like banks, shopping malls and hotels. it is strongly recommended that wsds are used for all new public and commercial buildings in oman, although the study shows that omani are the lowest water consumers amongst gcc countries. it is believed that the effectiveness of water saving may increase drastically if self closing taps are used or low flow showerheads. selection of wsd should take into account the cultural and religious values of the receiving people that was clearly reflected in the results. in discussions with household owners, a consistent pattern of answers were received 0 1 2 3 feb−2012 apr−2012 jun−2012 aug−2012 date d ai ly c on su m pt io n (m 3 ) before/after installation after before figure 5. daily water consumption in the ministry of regional municipalities and water resources (mrmewr) before and after installation of water saving devices (wsds). the weekly average is presented in the background. 26 squ journal of agricultural and marine sciences, 2017, volume 22, issue 1 evaluation of some water saving devices in urban areas regarding the low flush toilets, that they ended up pressing the push button either twice (in case of toilet bags) or both buttons in terms of the dual flush. also in the selection of the self closing taps for al-araimi mosque, care was taken in selecting the appropriate device in terms of the time required for ablution, water flow rate and ease of use, in order not to cause any frustration to the praying person. therefore a wall-mounted device with a slightly higher flow and adjustable time features was chosen. conclusion and recommendations the study concluded the pipe line system was the main source of water delivery to homes as indicated by 67.7% of the participants. most people in the study area were not using any water saving methods at their homes, yet 76% considered themselves as water savers. it was indicated that there is a high awareness of water shortage in the country; 92% of participants were expecting benefits from using water saving devices in terms of money and alleviating water shortage problems. participants were readily willing to install water saving devices in their houses. the case studies revealed that the most effective devices in saving water were sensor-activated taps followed by self-closing taps followed by low-flow showerheads. wsds were significantly effective in reducing water consumption in restaurants, mosques, hotels and government buildings. water consumption in shopping centres decreased but not statically significant. aerators were not effective, as taps come already equipped with aerators. toilet bags were not effective as the bowl itself must be originally designed to handle a low flush. a flush with a toilet bag was found ineffective in cleaning the bowl and thus users flushed twice thus increasing water use rather than decreasing it. a similar experience was encountered in dual flush cisterns. this study showed that there was no significant difference in water consumption before and after installation of wsds at homes. this was due to the fact that faucets in houses were already equipped with aerators so no savings were achieved by installing new aerators. toilet bags and dual flush toilets were not effective and prompted users to flush twice. the low-flow showerheads were probably effective but their effect was masked by the negative effect of other wsds. the amount of water consumption per inhabitant ranged from 100 l/day·inhabitant to about 350 l/day·inhabitant. the higher value was due mainly to a public use of the garden water. these figures compared well with those in neighboring gulf council countries. the limitations of this study were that more than one wsd type was installed in any single establishment. the quantification of the effect of any particular wsd device alone became difficult. an important parameter that was missed, as a result, was water use per wsd. retrofitting programs that involve replacement of existing plumbing equipment with that uses less water, and residential water audit programs that involve sending trained water auditors to participating family homes, free of charge, to encourage water conservation efforts are recommended. it is thought that achieving water savings in the range of 20-30% as originally thought is an over-ambitious target mainly because houses will not benefit significantly from wsds, as determined in this study. the target reduction should probably be revised to 10-15% reduction. acknowledgements the authors wish to express gratitude and thanks to the ministry of regional municipalities and water resources for their great support in financing this study and providing the data to complete this paper. references al-ajmi, h. a. and abdel rahman, h. a. 2001. water management intricacies in the sultanate of oman: the augmentation-conservation conundrum. water international, (journal of the iwra). il, usa. 26(1): 69 79 al-rumikhani, y. 2000. an investigation of water saving devices performance and saving studies. proceeding of wsta 5th gulf water conference, doha, vol. 1, 317-332. cortez m. and petronilo 1993. low consumption toilets and other domestic water saving devices evaluation. proceedings of conserve 93: the new water agenda, las vegas: 7-10. garcia, b. a. and cortes, m. p., 1989. final report of project ue-9003, mexican institute of water technology, cuernavaca, morelos, mexico. garcia, o. j. 1991. utilization of wastewater in the rivetex company. mexican institute of water technology, cuernavaca, morelos, mexico. jensen, r. 1991. indoor water conservation. texas water resources 17(4). lallana et al. 2001. industrial water demand management and cleaner production potential : a case study of three industries in bulawayo, zimbabwe. mhew 2002. desalination water production costs. directorate of water, ministry of housing, electricity and water, muscat, sultanate of oman. mrmwr 2008. water resources in the sultanate of oman. ministry of regional municipalities and water resources. mwr 1998. the impact of water savers on the reduction of water consumption in headquarters’ building. ministry of water resources. research paper journal of agricultural and marine sciences 2022, 27(1): 90–98 doi: 10.53541/jams.vol27iss1pp90-98 received 15 jan 2021 accepted 06 june 2021 relationship between induction of novel somaclonal variants and types of organogenesis in muskmelon (cucumis melo l.) a.k.m. mohiuddin1, zaliha christine abdullah2, m.k.u. chowdhury3, k. harikrishna4, and suhaimi napis5* suhaimi napis5*( ) suhaimi@upm.my and akmmohiu@yahoo.com, department of cell and molecular biology, faculty of biotechnology and biomolecular sciences, university putra malaysia, 43400 serdang, selangor d.e., malaysia. introduction muskmelon (cucumis melo l.) species is a val-ued agricultural crop and widely cultivated in asia, america and european countries (al mawaali et al., 2017). however, it is highly prone to a wide range of diseases, which can result reduced yield and quality (jelaska, 1986). therefore, availability of useful alternative agronomically important traits will be more useful for speedy development of desired variety as compared to conventional breeding for muskmelon improvement (pijnacker and ramulu, 1990, mohiuddin et. al., 1998). the in vitro-generated variation and induction of somaclonal variation can improve the genetic diversity and may also amplify the pre-existing genetic heterogeneity in somatic cells, thus facilitating the overall breeding and improvement of the economically im العالقة بني استقراء املتغريات اجلسدية اجلديدة و أنواع األعضاء يف الشمام (cucumis melo l.) أ.ك.م. حمي الدين1، زليحة كريستني عبد هللا2،. م.ك. تشودري3 ، ك. هاريكريشنا4، و سحيمي انبيس5* abstract. a comparative study on induction of somaclonal variation in muskmelon (cucumis melo l.) cv. birdie regenerants obtained through direct and indirect organogenesis was carried out. two types of non-meristematic explants (e.g. cotyledon and petiole) were used for this study. a significantly lower (p<0.05) frequency of variation was observed in muskmelon somaclones regenerated via direct organogenesis (ms medium with bap) compared to indirect (ms medium with bap and 2,4-d). morphological study revealed that the somaclones regenerated from proximal cotyledon, petiole and distal cotyledon explants through direct organogenesis did not show any variation in elongation medium at the concentrations of bap 0.1, 0.3 and 0.5 mg-l, respectively. in contrast, higher number of morphologically somaclonal variants was obtained from these explants at the same concentration of bap obtained through indirect organogenesis. other concentrations of bap, on the other hand, added to the elongation medium showed higher percentage of somaclones with different types of novel variations, e.g. early flowering including higher number of flowers, slow growth of shoots with variant shape of leaves having long and thick petioles, and stubby shoot apices including flattened stem. these variations could be the prime genetic materials to develop new varieties of muskmelon, e.g. high yielding variety, early, late variety, dwarf variety, and variety with desirable body configurations. the results suggest that specific concentrations of bap or combinations of bap and 2,4-d have a significant (p<0.05) influence on the induction of novel somaclonal variations in muskmelon regenerants. future cytogenetic and molecular studies reveal that the novel genetic variations at the chromosome level in somaclonal variants can exist. keywords: muskmelon, novel somaclones, direct and indirect organogenesis, variety development. امللخص:دراســة مقارنــة حــول حتريــض التبايــن اجلســدي يف الشــمام ).cucumis melo l(. مت إجــراء جتديــدات الطيــور الــي مت احلصــول عليهــا مــن خــال تكويــن األعضــاء املباشــرة وغــر املباشــرة. مت اســتخدام نوعــني مــن النبــااتت املســتأصلة غــر اإلنشــائية )مثــل الفلقــة والســويقات( هلــذه الدراســة. لوحــظ تواتــر أقــل بشــكل ملحــوظ )p <0.05( يف التغــر somaclones الشــمام املتجــدد عــن طريــق تكويــن األعضــاء املباشــر )وســط ms مــع bap( مقارنــة ابلغــر مباشــر )وســط ms مــع bap و d-2،4(. كشــفت الدراســة املورفولوجيــة أن somaclones الــي مت جتديدهــا مــن نبــااتت الفلقــات القريبــة ، والنبــااتت الســويقية ، والنبــااتت البعيــدة مــن خــال تكويــن األعضــاء املباشــر مل تظهــر أي اختــاف يف وســط االســتطالة بركيــزات bap 0.1 و 0.3 و 0.5 ملغــم / لــر علــى التــوايل. يف املقابــل ، مت احلصــول علــى عــدد أكــر مــن املتغــرات اجلســدية النســيلة شــكلًيا مــن هــذه النبــااتت املســتأصلة بنفــس تركيــز bap الــذي مت احلصــول عليــه مــن خــال تكويــن األعضــاء غــر املباشــر. مــن انحيــة أخــرى، أظهــرت تركيــزات أخــرى مــن bap املضافــة إىل وســط االســتطالة نســبة مئويــة أعلــى مــن somaclones مــع أنــواع خمتلفــة مــن االختافــات اجلديــدة، علــى ســبيل املثــال اإلزهــار املبكــر يشــمل عــدًدا أكــر مــن األزهــار ، منــو بطــيء للراعــم ذات أشــكال خمتلفــة مــن األوراق ذات أعنــاق طويلــة ومسيكــة ، ومقرمشــات قصــرة صلبــة مبــا يف ذلــك الســاق املســطحة. ميكــن أن تكــون هــذه االختافــات هــي املــواد اجلينيــة األساســية لتطويــر أنــواع جديــدة مــن الشــمام ، علــى ســبيل املثــال تنــوع عــايل الغلــة ، تنــوع مبكــر ، متأخــر ، تنــوع قــزم ، ومتنــوع مــع تكوينــات اجلســم املرغوبــة. تشــر النتائــج إىل أن تركيــزات معينــة مــن bap أو جمموعات من bap و d-2،4 هلا أتثر كبر )p <0.05( على حتريض االختافات اجلســدية اجلديدة يف جتديدات الشــمام. تكشــف الدراســات الوراثيــة اخللويــة واجلزيئيــة املســتقبلية أن االختافــات اجلينيــة اجلديــدة علــى مســتوى الكروموســوم يف املتغــرات اجلســدية ميكــن أن توجــد. الكلمات املفتاحية: الشمام، somaclones ، تكوين األعضاء املباشر وغر املباشر، تنمية األصناف. 91research paper mohiuddin, z. abdullah, chowdhury, harikrishna, napis portant plants (patnaik et al., 1999). in vitro technique can also be used to induce economically useful agronomic characteristics into crop to increase productivity without loss of available desired genetic characters (mohiuddin, 1998). the ability to produce morphologically normal plants at high frequency with little or no somaclonal variation as well as induction of high frequency of variations in somaclones is a prerequisite to the application of tissue culture techniques in crop improvement (mohiuddin et al., 2000, & 2003, ren et al., 2012). application of in vitro tissue culture techniques to crop improvement has been focused on selection for herbicide resistance, stress tolerance, amino acid over production, rice fortification having fe and zn, disease resistance, etc. from somaclonal variants (larkin and scowcroft, 1981; evenor et al., 1994; al-noor et al., 2019). it has been known over the five decades that cultured plant cell and tissue undergo various morphological and genetic changes especially in chromosome numbers and ploidy level during in vitro culture (murashige and nakano, 1966, ren et al., 2013). this change is also known as somaclonal variation displayed among in vitro tissue culture-derived plants and it has been described for several plant species (larkin and scowcroft, 1981; orton 1984; bajaj, 1990; mofidabadi et al., 2001; shasthree et al., 2009; saraswat and kumar, 2019). considerable work in muskmelon tissue culture has been conducted (moreno et al., 1985; trulson and shahin, 1986; niedz et al., 1989; oridate et al., 1992; gray et al., 1993; mohiuddin et al., 1998, and ren et al., 2013) but to our best knowledge negligible report has been evaluated yet on relationship in production of morphologically normal somaclones (true-to-type) at high frequency through direct organogenesis as well as induction of novel somaclonal variants in muskmelon plants via indirect organogenesis. this present study was aimed to investigate the extent of true-to-type somaclone production (no variation) and induction of novel somaclonal variants as observed phenotypically in muskmelon regenerants and obtained through direct and indirect organogenesis. materials and methods plant materials this study focused on the birdie cultivar of muskmelon, which is the most widely used in malaysia as a fruit crop. testas were removed manually from mature seeds of birdie (sakata seed corp., japan) and sterilized by 20% clorox (containing 5.25% sodium hypochlorite) with one drop of ‘tween 20’ for 15 min followed by 3x wash with sterile distilled water. the seeds were then aseptically germinated on filter paper soaked with ms (murashige and skoog, 1962) liquid medium in petri dishes having 3% sucrose. after eight days cotyledons were separated from germinated seedlings and cut into four pieces by a transverse cut followed by a longitudinal cut. the proximal cotyledons (attached to hypocotyls) and distal cotyledons were used for this study. the second-top-leaf petiole was used as explant, obtained from 21-day-old muskmelon seedlings germinated in ms solid medium in magenta boxes having 2% phytagel (sigma, usa). each petiole was bisected into equal pieces (4-5 mm long) and it was used in this study. somaclone induction and elongation medium both cotyledon and petiole explants were cultured aseptically on somaclone induction medium (sim) consisting of ms nutrients, ms vitamins, 3% sucrose, 2 g-l phytagel, and bap at the concentration of 1.0 and 2.0 mg-l either alone (direct organogenesis) or in combination with 2,4-d at 0.1 and 0.3 mg-l (indirect organogenesis). ten explants of each type were cultured on sim containing each concentrations of bap alone or in combinations with 0.1 and 0.3 mg-l 2,4-d. this was repeated 5 (five) times. subsequently, 15-day-old somaclones as obtained from direct and indirect organogenesis and these were then cultured onto somaclone elongation medium (sem) containing ms medium supplemented with bap at 0.07, 0.1, 0.3, 0.5 and 0.7 mg-l. root induction medium and culture conditions the elongated somaclones derived from proximal cotyledons, distal cotyledons and petioles were rooted in ms medium containing naa at the concentrations of 0.01, 0.05 and 0.03 mg-l, respectively (mohiuddin, 1998). all the media combinations were adjusted to ph 5.7 before autoclaving at 121°c for 15 minutes at 1.05 kg/cm2 pressure (15-20 psi). cultures were incubated in the growth chamber at 26±1°c under 16/8 h light (39.3 µmol m-2 s-1)/dark regime. evaluations of somaclonal variants the extents of variations were evaluated morphologically on the somaclones after elongation in sem for four weeks at each concentration of bap as mentioned earlier. for the identification of morphologically trueto-type somaclones (no variation) and variants (having variation) obtained from each explant of muskmelon at each formulation of hormone(s) were closely examined. variations in somaclones were scored of the following quantitative traits: (i) early flowering including higher number of flowers, (ii) slow growth of shoots with deformed shape of leaves having long and thick petiole, and (iii) stubby shoot apices with flattened stem. on the other hand, normal somaclones were scored of the following quantitative traits: (i) normal organ development, (ii) rapid growth, (iii) normal flower formation and fruit development, (iv) good root induction ability and (v) ability to acclimatize to the ambient environmental conditions. 92 squ journal of agricultural and marine sciences, 2022, volume 27, issue 1 relationship between induction of novel somaclonal variants and types of organogenesis in muskmelon (cucumis melo l.) statistical analysis the data were statistically analysed by analysis of variance (anova). duncan’s multiple range test (dmrt) was also carried out to show the significance of relationship among the percentage result (mean) of somaclones either morphologically normal or variant obtained through the direct or indirect organogenesis. results huge numbers of somaclone primordia were initiated from muskmelon explants cultured on somaclone induction medium (figure 1a). somaclones induced from proximal and distal cotyledons and petiole explants of muskmelon via direct organogenesis, elongated faster in elongation medium compared to the somaclones as obtained from identical explants via indirect organogenesis. moreover, proximal cotyledon-derived somaclones elongated earlier than somaclones derived from either distal cotyledon or petiole explants. the distal cotyledon derived somaclones obtained from both direct and indirect organogenesis, however, elongated slower as compared to other two explant-derived somaclones. the proportion of morphologically normal (trueto-type) and variant somaclones induced from different explants varied at identical concentration of bap in elongation medium (tables 1 and 2). similarly, the proportion of normal and variant somaclones induced through either direct or indirect organogenesis from different explants also varied to identical bap concentration (tables 1 and 2). bap at the concentration of 0.1, 0.3 and 0.5 mg-l significantly (p<0.05) induced the highest rates (100%) of morphologically normal somaclones (figure 1b) through direct organogenesis from proximal cotyledon, petiole and distal cotyledon, respectively (table 1). other concentrations of bap also induced normal somaclones but at lower rates. sem having 0.007 and 0.7 mg-l bap induced the lowest rates of normal somaclones from all explants (table 1). on the other hand, the rates figure 1. somaclone and its variation. a) somaclone primordia initiated from proximal cotyledon, b) shoots elongated in shoot elongation medium, c) morphologically normal somaclones, d) early flowering obtained in somaclones, e) slow growth of shoots with distorted leaves having long and thick petioles, f) stubby shoot apices and g) successfully acclimatized somaclones. 93research paper mohiuddin, z. abdullah, chowdhury, harikrishna, napis of morphologically normal somaclones obtained via indirect organogenesis were generally lower as compared to the direct organogenesis (table 1). no significant difference was observed among the rates of normal somaclones induced through indirect organogenesis from proximal cotyledon, distal cotyledon and petiole explants at the different concentrations of bap (table 1). from the result in this study, it was found that the direct organogenesis at specific concentrations of bap 0.1, 0.3 and 0.5 mg-l did not produce any somaclonal variants morphologically in proximal cotyledon (figure 1c), petiole and distal cotyledon of muskmelon, respectively (table 2). however, other concentrations of bap induced somaclonal variants from all three explants of muskmelon. ms medium containing 0.7 mg-l bap induced a significantly higher (p<0.05) rate of somaclonal variants from proximal cotyledon (29%) and petiole explants (20%), while ms medium having bap 0.07 mg-l induced the highest rate of somaclonal variants from distal cotyledon explants (27%) through direct organogenesis (table 2). the rates of morphologically variant somaclones, on the other hand, obtained through indirect organogenesis were higher compared to that of direct organogenesis (table 2). about 2 to 4 folds higher somaclonal variants were found in indirect organogenesis as compared to direct organogenesis (table 2). no significant effect was observed among the different rates of somaclonal variants induced from explants at different concentrations of bap through indirect organogenesis (table 2). the morphologically normal somaclones obtained from the three different explants via direct organogenesis were longer height at different concentrations of bap than those obtained through indirect organogenesis (table 3). bap at 0.1, 0.3 and 0.5 mg-l produced normal somaclones from proximal cotyledon, distal cotyledon and petiole through direct organogenesis, which attained lengths of 9.2 cm, 7.9 cm and 9.1 cm, respectively. however, at these bap concentrations, normal somaclones were 6.4, 5.1 and 4.7 cm in length from respective explants obtained through indirect organogenesis which is considerable lower (table 3). furthermore, lower height was observed in the somaclonal variants obtained from all three explants through direct and indirect organogenesis (table 4). on average, lowest height attained from table 1. variations on production of morphologically normal somaclones of muskmelon obtained through direct and indirect organogenesis bap (mg/l) production of precent (%) morphological normal somaclones direct organogenesis indirect organogenesis proximal cotyledon distal cotyledon petiole proximal cotyledon distal cotyledon petiole 0.07 93±2.7a 73±5.2b 85±4.7ab 74±1.6 a 80±8.1a 67±6.6a 0.1 100±0.0a 79±4.0b 91±2.3a 71±4.3 a 63±5.6a 64±1.7a 0.3 84±3.4b 86±2.1a 100±00a 62±3.7 a 75±3.9a 72±2.9a 0.5 82±3.0b 100±0.0a 86±2.8ab 68±0.8 a 76±4.3a 62±6.5a 0.7 71±3.4c 80±6.3b 80±5.9b 62±6.5 a 74±4.5a 57±4.9a note: percentage results are means of five replications±standard error. means with the same letters (superscript) within same columns are not significantly different (p<0.05) table 2. variations on production of novel somaclonal variants of muskmelon attained through direct and indirect organogenesis bap (mg/l) production of precent (%) of somaclonal variants direct organogenesis indirect organogenesis proximal cotyledon distal cotyledon petiole proximal cotyledon distal cotyledon petiole 0.07 7±4.7 b 27±3.3 a 15±5.4 b 26±1.0 a 20±8.4 a 33±4.2 a 0.1 0.0±0.0 c 21±2.8 a 9±3.8 b 29±2.8 a 37±3.4 a 36±1.0 a 0.3 16±2.6 a 14±3.6 a 0.0±0.0 c 38±2.2 a 25±2.4 a 28±2.0 a 0.5 18±2.3 a 0.0±0.0 b 14±2.1 b 32±0.5 a 24±3.0 a 38±3.9 a 0.7 29±2.2 a 20±6.4 a 20±6.5 a 38±3.9 a 26±2.9 a 43±2.9 a note: percentage results are means of five replications±standard error. means with the same letters (superscript) within columns are not significantly different (p<0.05). 94 squ journal of agricultural and marine sciences, 2022, volume 27, issue 1 relationship between induction of novel somaclonal variants and types of organogenesis in muskmelon (cucumis melo l.) somaclonal variants regenerated from explants through indirect organogenesis in comparison to direct (table 4). early flowering (ef) was the most common novel variants observed in muskmelon somaclones (figure 1d) with higher rates attained frequently from all explants through direct and indirect organogenesis (tables 5 and 6). maximum percent of ef (e.g. 14% and 19%) was obtained at 0.7 mg-l bap from proximal cotyledon explants through direct and indirect organogenesis, respectively. on the other hand, regenerated novel variants (e.g. slow growth, sg) of shoots with distorted leaves having long and thick petioles (fig. 1e) and stubby shoot apices (ssa) with flatted stem (figure 1f ) was found comparatively lower in number than ef via both direct and indirect organogenesis (tables 5 and 6). the rate of somaclonal variants obtained from proximal cotyledon, distal cotyledon and petiole explants ranged from 4 to 14% of ef, 2 to 9% of sg with variant shape of leaves and 2 to 6% of ssa with flattened stem via direct organogenesis (table 5). however, these novel variants ranges increased when plants were regenerated via indirect organogenesis (table 6). no variations were observed in the somaclones obtained through direct organogenesis from proximal cotyledon, petiole and distal cotyledon explants at bap 0.1, 0.3 and 0.5 mg-l, respectively (table 5). however, proximal cotyledon at bap 0.1 mg-l induced 14%, 11% and 4% of ef, sg and ssa novel variants, respectively through indirect organogenesis (table 6). similarly, petiole explants also induced above mentioned novel variants (e.g. 13%, 9% and 6%) in same order at 0.3 mg-l bap, respectively via indirect organogenesis. consequently, distal cotyledons at the concentration of 0.5 mg-l bap induced 12% of ef, and 6% of each sg and ssa novel variants via indirect organogenesis (table 6). the other concentrations of bap, on the other hand, showed mostly a higher percentage (%) of novel somaclonal variants as obtained through indirect organogenesis (table 6). although different types of novel somaclonal variants were obtained via direct organogenesis from all explants but no ssa variants was attained in the medium containing 0.07 mg-l of bap from proximal cotyledon explants via direct organogenesis (table 5), whereas same explant at same concentration of bap produced 5% ssa novel variant via indirect organogenesis (table 6). moreover, bap at 0.1 and 0.5 mg-l also did not produce same (ssa) novel variant from petiole explants of muskmelon through direct organogenesis while the same bap concentrations table 3. variations on average height of normal somaclones obtained through direct and indirect organogenesis bap (mg/l) average height of morphological normal somaclones (in cm) direct organogenesis indirect organogenesis proximal cotyledon distal cotyledon petiole proximal cotyledon distal cotyledon petiole 0.07 8.6±0.1 7.2±0.3 8.7±0.2 5.8±0.2 4.8±0.1 4.6±0.1 0.1 9.2±0.1 6.6±0.3 8.8±0.2 6.4±0.3 4.9±0.1 4.8±0.1 0.3 8.9±0.2 7.9±0.2 7.8±0.2 6.8±0.2 5.1±0.1 4.9±0.1 0.5 8.7±0.1 7.8±0.2 9.1±0.1 6.2±0.2 5.6±0.1 4.7±0.1 0.7 6.6±0.3 7.6±0.2 7.2±0.4 6.4±0.2 5.3±0.1 4.7±0.1 note: average results are means of five replications±standard error. table 4. variations on average height of novel somaclonal variants obtained through direct and indirect organogenesis bap (mg/l) average height of somaclonal variants (in cm) direct organogenesis indirect organogenesis proximal cotyledon distal cotyledon petiole proximal cotyledon distal cotyledon petiole 0.07 7.8±0.5 0.0±0.0 6.9±0.2 7.1±0.1 5.9±0.4 4.8±0.5 4.8±0.3 6.2±0.4 0.0±0.0 6.7±0.6 6.6±0.3 7.7±0.5 0.0±0.0 6.8±0.5 4.5±0.3 5.4±0.2 4.9±0.1 4.8±0.2 5.0±0.2 5.1±0.2 4.3±0.1 4.5±0.2 4.7±0.2 4.8±0.2 4.7±0.2 4.4±0.1 4.3±0.1 4.5±0.2 4.0±0.1 4.5±0.3 0.1 0.3 0.5 0.7 note: average results are means of five replications±standard error 95research paper mohiuddin, z. abdullah, chowdhury, harikrishna, napis induced ssa novel variants in 7% and 8% of shoots obtained via indirect organogenesis (tables 5 and 6). the mean height (in parentheses) of novel somaclonal variants obtained from different explants of muskmelon at all concentrations of bap through direct organogenesis was greater (table 5) than the height (in parentheses) of novel somaclonal variants obtained through indirect organogenesis (table 6). the ranges height of novel somaclones initiated through direct organogenesis from proximal cotyledon was 4.9 9.5 cm, from distal cotyledon was 3.8 8.0 cm and from petiole was 3.7 8.7 cm in height (table 5). on the other hand, the height ranges were lower when somaclonal variants regenerated through indirect organogenesis (table 6) as compared to direct organogenesis (table 5). average height of novel somaclonal variants found in plants regenerated from proximal cotyledon through direct organogenesis is relatively higher as compared to distal cotyledons and petiole. average lowest height was found in plants regenerated from distal cotyledon as compared to two other explants (table 5). a similar trend was also observed in height of novel somaclonal variants as initiated from all explants through indirect organogenesis (table 6). the somaclones as well as novel variants induced roots vigorously in ms medium containing naa at the concentrations of 0.01 and 0.03 mg-l and successfully acclimatized to the ambient humidity level in soil (figure 1g). discussion there is no doubt that genetic variation especially morphological variations of plant cells cultured in vitro conditions is a general phenomenon (skirvin, 1978; constantin, 1981; ren et al., 2013; al-noor et al., 2019) and has now been known for over 50 years. larkin and scowcroft (1981) reported that in vitro plant cell culture table 5. effect of direct organogenesis on production of novel somaclonal variants in muskmelon cv. birdie bap (mg/l) percentage of novel somaclonal variants proximal cotyledon distal cotyledon petiole ef sg ssa ef sg ssa ef sg ssa 0.07 4 (9.5±0.1) 3 (5.6±0.0) 0 13 (5.4±0.1) 9 (3.9±0.1) 5 (5.2±0.0) 8 (7.8±0.1) 4 (4.0±0.1) 3 (6.9±0.0) 0.1 0 0 0 11 (5.3±0.1) 6 (3.9±0.1) 4 (4.8±0.1) 7 (8.7±0.1) 2 (4.0±0.0) 0 0.3 9 (7.9±0.1) 5 (4.9±0.0) 2 (7.2±0.0) 7 (7.6±0.1) 5 (4.0±0.1) 2 (6.9±0.0) 0 0 0 0.5 10 (8.1±0.1) 5 (5.0±0.1) 3 (7.0±0.0) 0 0 0 9 (8.4±0.1) 5 (3.9±0.0) 0 0.7 14 (6.8±0.1) 9 (4.9±0.1) 6 (5.3±0.1) 12 (8.0±0.1) 6 (3.8±0.1) 2 (7.8±0.0) 11 (4.9±0.1) 6 (3.7±0.1) 3 (4.8±0.0) note: ef: early flowering including higher number of flowers, sg: slow growth of shoots with variant shape of leaves having long and thick petiole, ssa: stubby shoot apices and flattened stem. the numbers in the parentheses are average heights of novel variants in cm ± standard error table 6. effect of indirect organogenesis on production of novel somaclonal variants in muskmelon cv. birdie bap (mg/l) percentage of novel somaclonal variants proximal cotyledon distal cotyledon petiole ef sg ssa ef sg ssa ef sg ssa 0.07 16 (5.8±0.3) 5 (4.7±0.2) 11 (4.4±0.1) 11 (3.9±0.2) 10 (4.1±0.1) 12 (4.4±0.5) 5 (4.6±0.2) 4 (5.2±0.1) 11 (5.3±0.5) 7 (4.9±0.1) 10 (5.2±0.4) 7 (4.6±0.2) 16 (5.0±0.4) 13 (5.2±0.1) 12 (5.9±0.2) 11 (5.2±0.5) 7 (3.3±0.5) 11 (3.7±0.0) 8 (3.9±0.4) 6 (3.4±0.2) 8 (3.6±0.1) 6 (5.0±0.2) 10 (4.7±0.4) 4 (4.6±0.1) 6 (5.2±0.1) 7 (5.0±0.3) 17 (5.0±0.2) 18 (4.9±0.1) 13 (5.1±0.5) 18 (4.3±0.1) 19 (5.1±0.1) 8 (3.6±0.1) 11 (3.4±0.2) 9 (3.7±0.0) 12 (3.3±0.3) 14 (3.8±0.1) 8 (4.5±0.1) 7 (4.2±0.5) 6 (4.5±0.1) 8 (4.5±0.3) 10 (4.4±0.4) 0.1 14 (5.2±0.2) 0.3 16 (5.5±0.0) 0.5 15 (5.6±0.3) 0.7 16 (5.5±0.1) note: ef: early flowering including higher number of flowers, sg: slow growth of shoots with variant shape of leaves having long and thick petiole, ssa: stubby shoot apices and flattened stem. the numbers in the parentheses are average heights of novel variants in cm ± standard error. 96 squ journal of agricultural and marine sciences, 2022, volume 27, issue 1 relationship between induction of novel somaclonal variants and types of organogenesis in muskmelon (cucumis melo l.) itself generated genetic variability, was so called somaclonal variation, in the regenerants. during in vitro regeneration studies, a number of somaclones was found in r0, r1 and r2 generations in medicinally important cucurbit, citrullus ccolosynthis (l.) schrad (shasthree et al., 2009). our experiments conducted on muskmelon through direct and indirect organogenesis confirmed this conspicuous phenomenon. interestingly, it was observed that greater number of morphologically normal somaclones obtained via direct organogenesis produced lower rate of plants with variations compared to indirect organogenesis. this may be due to the minimal production of callus by the cytokinin-type-hormone, bap, added in the direct organogenesis protocol. high frequency multiple shoots were formed on ms nutrient medium containing cytokinins through direct organogenesis without intervening callus phase in passiflora foetida l. (anand et al., 2012). plant regeneration from explants via an intermediate callus stage (indirect organogenesis) was often associated with more variations than regenerants induced via direct organogenesis whereby little or no callus was produced (harini and sita, 1993). the addition of auxin (2,4-d) to bap in sim resulted in lower rates of induction of normal shoots suggesting that the presence of 2,4-d in the medium may inhibit the production of phenotypically normal somaclones, which resulted increase in the production of somaclonal variants. on the other hand, bap at concentrations of 0.1, 0.3 and 0.5 mg-l did not produce any somaclonal variants obtained from proximal cotyledon, petiole and distal cotyledon explants through direct organogenesis, while the reverse trend was observed in indirect organogenesis. it can be suggested that muskmelon shoots with normal traits can be obtained at certain concentration of bap through direct organogenesis. it should be noted that the production of morphologically normal shoots is an important factor to ensure success of genetic manipulation (gene transformation) experiments of cucurbits e.g. muskmelon for variety development (mohiuddin et al., 2000). there are some more reports found available on variety developed through direct organogenesis in tomato (ewa et al., 2000) and garlic (taşkın et al., 2013) even production of true-to-type in vitro-propagated aloe vera l. plants (khatun et al., 2018) and virus free plant variety (ahmed et al., 2019). various types of novel variants such as early flowering, slow growth with long and thick petioles, and stubby shoot apices were observed among the shoots of muskmelon derived from different explants. shasthree et al. (2009) also observed a number of variations in habit, leaf and tendrillar character, fruit number, sizes, colours, and seed coat colours. similar variation was observed in gametoclonal variation in populus euphratica (mofidabadi et al., 2001) as well as somaclonal variation of cucumber (mohiuddin et al., 2003). our study confirmed that the range of morphogenic changes in somaclones was significantly higher when somaclones were obtained through indirect organogenesis. this technique could be utilized for the production of somaclonal variants like early variety, late variety, early flowering and/ high yielding variety, dwarf variety needs less nutrients, variety with desirable body configurations of muskmelon, etc. there are several published reports indicating above mentioned achievements obtained from sugarcane early variety development (sreenivasan and jalaja, 1983), early flowering in both woody bamboo (yuan et. al., 2017) and in swertia chirayita, an endangered medicinal herb (sharma et. al., 2014). other achievements similar to our findings were also obtained from dwarf variety generally needs less nutrients or other purpose like ornamental plant production (leva and petruccelli, 2011), production of high yielding variety observed in fruit crops (harsimrat and manjot, 2020), and variety with desirable body configurations to produce new genotypes for breeding purposes (vitamvas et. al., 2019). finally, we could say that this study shows that the production of normal somaclones or novel variant somaclones is therefore greatly influenced by the growth regulator selected in in vitro method. conclusion greater number of novel somaclonal variants were obtained significantly from muskmelon explants through indirect organogenesis as compared to direct organogenesis. these variants could be the leading genetic materials to develop new varieties of muskmelon with especial agronomically important characteristics for future variety development program. acknowledgement akkm is expressing sincere thanks to the ministry of science, technology and the environment, malaysia for graduate assistantship (irpa grant no. 01-028-05-50304). abbreviation bap 6-benzylaminopurine 2,4-d 2,4-dichlorophenoxyacetic acid naa naphthalene acetic acid references ahmed ms, dilnawaz ag, jacqueline b, satomi h, manuel z, aslam j, muhammad zi, shahid ia. 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(2017). flowering of woody bamboo in tissue culture systems. frontiers plant science 8: 1-8 (article 1589). research paper journal of agricultural and marine sciences 2021, 26(1): 37–46 doi: 10.24200/jams.vol26iss1pp37-46 reveived 17 feb 2020 accepted 22 aug 2020 mean sea level variability along the northern coast of the oman sea and its response to monsoon and the north atlantic oscillation index from tide gauge measurement s. hassanzadeh1,*, f. hosseinibalam1 smaeyl hassanzadeh1,*( ) shz@phys.ui.ac.ir, department of physics, university of isfahan, 81746-73441, isfahan, iran,1 department of physics, university of isfahan, 81746-73441, isfahan, iran introduction the coastal environment is very vulnerable to the changes in the mean sea level, wave heights and wave direction. many forces in the atmosphere and the ocean influence the sea level. thus, the sea level integrates a great number of physical processes in the environment and therefore can be a representative parameters for monitoring the relationship between oceanic and atmospheric parameters. this study of sea-level variability is usually undertaken from hindcasts of the last decades (somot et al., 2006) and from the available tide gauges and satellite altimeters data. sea level changes can be divided into dynamic and quasi-static components (stammer et al., 2013). for various reasons, the sea level can be changed quite differently from one region to another (ding et al., 2001). according to eshghi et al. (2020), the inverted barometer effect was significant in the north-western indian ocean. siddig et al. (2019) estimated the linear trend using monthly mean residual sea level and they found the highest trend values was at mina salman about 3.4 0±0.98 mm/year and abu ali pier about 3.1±0.7 mm/year. therefore, it is necessary to study the sea level changes locally or regionally to understand the various geophysical processes associated with the sea level variability. the oman sea, also called the oman gulf, is located at the north of the arabian sea (figure 1). the gulf of oman is strongly influenced by outflow from the hormuz strait. from fall through mid-spring, متوسط التباين يف مستوى سطح البحر على طول الساحل الشمايل لبحر عمان واستجابته للرايح املومسية ومؤشر تذبذب مشال األطلسي من مقياس املد واجلزر س. امسعیل حسن زاده و ف. حسینی ابالم abstract. sea level analysis along the northern coast of the oman sea was investigated on the basis of tide gauge measurements. meteorological parameters, along with monsoon and nao (north atlantic oscillation) indices were used to study the response of sea level to local and global forcing. the relation between sea level and forces were examined. low correlation coefficient (-0.35) between sea level and atmospheric pressure at chabahar indicated that the response to atmospheric pressure was not an inverse barometric. the nature of local inverse barometric effects were examined through a series of statistical models. analysis between sea level and atmospheric pressure reveals a significant coherence, which meant that along the northern coast of oman sea, mean sea level responded to atmospheric pressure as an inverse barometer. it can be noticed that the difference between atmospheric pressure and mean sea level was due to alongshore wind stress forcing and was consistent with that expected from ekman dynamics. the four eof modes capture 87.16% for the x-component and 94.70% for the y-component of the total variance and were statistically significant. linear regression and arima model forecasts were fitted to sea level and compared to the actual data. even though both models gave similar results, the arima model performed considerably better. keywords: the oman sea, tide gauge, arima, monsoon املســتخلص: مت حتلیــل مســتوى ســطح البحــر علــى طــول الســاحل الشــمايل لبحــر عمــان علــى أســاس قیاســات املــد واجلــزر، حیــث اســتخدمت مؤشــرات األرصــاد اجلويــة إىل جانــب مؤشــرات الــرايح املومسیــة وتذبــذب مشــال األطلســي لدراســة اســتجابة مســتوى ســطح البحــر للتأثــرات احمللیــة والعاملیــة وفحــص العالقــة بینهــا وبــن مســتوى ســطح البحــر. ووجــد أن معامــل االرتبــاط املنخفــض )-0.35( بــن مســتوى ســطح البحــر والضغــط اجلــوي يف تشــاهبار يشــر إىل أن االســتجابة للضغــط اجلــوي مل تكــن أتثــرات جويــة معكوســة، حیــث مت فحــص طبیعــة التأثــرات اجلويــة العكســیة احمللیــة مــن خــالل سلســلة مــن النمــاذج اإلحصائیــة، وقــد كشــف التحلیــل بــن مســتوى ســطح البحــر والضغــط اجلــوي عــن وجــود متاســك كبــر، ممــا يعــي أن متوســط مســتوى ســطح البحــر علــى طــول الســاحل الشــمايل لبحــر عمــان قــد اســتجاب للضغــط اجلــوي بشــكل عكســي، وقــد لوحــظ أن الفــرق بــن الضغــط اجلــوي ومتوســط مســتوى ســطح البحــر حــدث بســبب أتثــر إجهــاد الــرايح علــى طــول الشــاطئ والــذي كان متســًقا مــع املتوقــع مــن دينامیكیــات إيكمــان، ووجــد أن أوضــاع eof األربعــة قــد إلتقطــت مــا مقــداره 87.16٪ للمكــون x و 94.70٪ للمكــون y مــن التبايــن اإلمجــايل والــي كانــت ذات داللــة إحصائیــة، وقــد مت ضبــط االحنــدار اخلطــي وتوقعــات منــوذج arima علــى مســتوى ســطح البحــر ومقارنتهــا ابلبیــاانت الفعلیــة، وعلــى الرغــم مــن أن كال النموذجــن أعطیــا نتائــج مماثلــة إال أن أداء منــوذج arima كان األفضــل. الكلمات املفتاحية: الكلمات املفتاحیة: حبر عمان، مقیاس املد واجلزر، arima ، الرايح املومسیة 38 squ journal of agricultural and marine sciences, 2021, volume 26, issue 1 mean sea level variability along the northern coast of the oman sea and its response to monsoon and the north atlantic oscillation index from tide gauge measurement satellite ssts suggested a plume of outflow water owing as a coastal current along the oman and emirate coast to ras al hadd at the edge of the arabian sea (johns et al., 1999). this would imply that at least through part of the year this outflow from the hormuz strait consists of deep water layer and a modified surface layer that must together balance the inflow component. the seasonal upwelling and circulation are also important along the coast of iran in the oman sea. the seasonal and inter-annual variations in the circulation of the gulf of oman is significant (figure 1). the northern side of the gulf of oman has consistent upwelling associated with the sw monsoon along the pakistani coast (figure 1). upwelling along the western, iranian coast is more variable. in 1995, for example, this coast was associated with upwelling filaments that moved to the west and even entered the outer edges of the strait of hormuz. other years suggest less extensive upwelling although there is localized upwelling at the mouth of the strait in all the years examined. in this study, data from two tide gauges and meteorological parameters in the oman sea as well as data set of the gridded ekman transport, the north atlantic oscillation (nao) index and the monsoon index of the indian ocean were used. methodology tide gauge data and mean sea level hourly time series of tides were obtained from the national cartographic center of iran (ncc) and monthly means of atmospheric parameters were gathered from the islamic republic of iran meteorological organization. atmospheric pressure, air temperature and wind data records were obtained from offshore stations at chabahar and jask (figure 1). water level is measured using a mechanical float gauge manufactured by the ott companyin germany. tidal records were monitored with 30 min sampling and 1 cm resolution. the 30 minute values were converted to hourly values using software developed by ncc. the tide gauges in the iranian tide gauge network were connected to benchmarks established by ncc. ncc did the precise leveling, i.e., they were responsible for determining the vertical distance between the bench marks and the contact point at the tide gauge. the leveling was performed several times every year. the ncc benchmarks were connected to the iranian national leveling network. the tide gauge was calibrated by making its readings equal to the observations on a tide pole installed beside the tidal station. all observations are compared with tidal predictions. if the inspection of the data revealed errors in observed heights, the data were corrected by ncc. ncc used a ‘‘modified’’ indian spring low water (islw) as chart datum. the quality of the iranian tide gauge network was approved by ioc/ gloss, technical report (hareide, 2004). the monsoon and nao indices were obtained from web. hourly tide gauge data from both chabahar and jask stations were used in this study. an example of 1997 tide gauge record at chahbahar is shown in figure 2. the daily mean sea levels were calculated by averaging the hourly data of the whole day and are shown in figure 3. the monthly sea level data available for chabahar from 1993 to 2005 and for jask from 1997 to 2005 are shown in figure 4. sea level was high in summer and was low in winter at both stations. interannual variability was also apparent as this appeared relatively coherent between stations. the annual mean of the sea level at both stations are shown in figure 5. the highest mean sea level occurred in 1999 and 2004 at chabahar and in 2003 at jask. the figure 1. circulation of the oman sea and northern arabian sea and the location of the tide gauge, chabahar and jask (johns et al., 1999) figure 2. hourly sea level variability at chabahar on the north coast of the oman sea 39research paper hassanzadeh, hosseinibalam annual cycle was common to both tide gauges in the northern coast of the oman sea. the seasonal variability had a close relation with the wind and atmospheric pressure. as the monthly data were not removed from this effect, a marked seasonally in monthly average was appeared. the behavior of the seasonal variability is presented in the figure 6.the seasonal variability in both stations showed a gradual increase in the sea level between february and june, the highest value in june and lowest in january (figure 6). then it began to decrease until december at chabahar and until february at jask. the ranges were about 14 cm in chahbar and about 20 cm in jask. the major peak in june occurred during the southwest monsoon. monthly data on sea level, atmospheric pressure, air temperature, sea surface height (ssh), local wind, monsoon and nao indices were analyzed. the monthly and yearly averages for each data set were computed and different statistical analyses were applied. in the first exploratory approach, correlations between sea level and each of the explanatory variables were produced by calculating the pearson correlation coefficient, and corresponding p-values, between the time series. the empirical orthogonal function (eof) technique was used to define the patterns of spatial and temporal behavior of the ekman transport. this technique was also referred to the principal component analysis (pca). the eof decomposition was used to extract the dominant modes of spatial and temporal variability of the signal (preisendorfer, 1988). modelling response and sea level prediction the role of different climate forcings that might affect the northern coast of the oman sea is statistically explored in this section. a linear regression and an auto-regressive integrated moving average (arima) model were fit to mean sea level and forcings as predictors for each station and then were used to forecast sea level. the ekamn transport was first decomposed in its pcs. the arima models are ar models with differencing or moving average terms. the multiple regression was used to observe sea level, sl, as the dependent variable in the regression model of the following form: eq.(1) where independent variables p, t and w are the atmospheric pressure, temperature and wind, respectively, and a, b, and c are the coefficients. pci is the ith pc of the ekman transport and di is the corresponding coefficient, and n is the number of pcs included in the model. owing to possible significant correlation between different sea level forcing inputs, the results from the univariate model are likely to be affected. the statistical way to take the correlation between input forcing into account was to perform a multivariate regression analysis of mean figure 3. daily sea level variability at chabahar (top) and jask (bottom) on the north coast of the oman sea 40 squ journal of agricultural and marine sciences, 2021, volume 26, issue 1 mean sea level variability along the northern coast of the oman sea and its response to monsoon and the north atlantic oscillation index from tide gauge measurement sea level on predictors. multivariate regression was performed to confirm the relationship between sea level and forcing inputs. thus, regression model enabled to predict sea level using pressure, temperature, wind and ekman transport forcing. autoregressive integrated moving average model of degree p, d and q, arima (p, d, q), was a combination of ar and ma with differencing. where, p is the number of autoregressive terms, d is the number of non-seasonal differences, and q is the number of lagged forecast errors in the prediction equation (box and jenkins, 1976). lags of the differenced series appearing in the forecasting equation are called “auto-regressive” terms, lags of the forecast errors are called “moving average” terms, and a time series which needs to be differenced to be made stationary is said to be an “integrated” version of a stationary series. for non-stationary data one should apply arma description to the series of differences of appropriate order, thus yielding arima model (autoregressive integrated moving average). it can be written as: eq.(2) where, ∇d is a differential operator of degree d: ∇d xt=(xt-xt-1)d. usually d = 0,1,2. a forecast generated by the above process is given by: a forecast with least mean squared error, m periods ahead, is a conditional expected value of random variable xt in time t, which can be written as: eq.(4) thus, the forecast is: eq.(5). to calculate conditional expected values in the equation above one can assume that: et[xt-j]=xt-j, where xt-j, in time t already known, one leaves without changes, where xt+j, still unknown are replaced with their forecasts et[et-j]=et-j, where e_(t-j), in time t already known, one specifies as eq.(6) the monthly data were used to compare the predictive ability of the multiple linear regression based on the predictor variables and arima model based on mean sea level time series. the results of the linear regression model fitting for monthly mean sea level at chabahar and jask can be found in figure 10. the results of the arima model for monthly mean sea level series at chabahar and jask are also shown in figure 10. the arima model was based on time series of the mean sea level using the formula given above. four arima models with different orders were used to analyze the cases with two stations for chabahar from 1993 to 2005 and for jask from 1997 to 2005. the model parameters including the arima coefficients denoted by p, d, and q are estimated according to the box-jenkins methods (box and jenkins, 1976) and for chabahar is shown in table 1. the optimal order of the arima models was chofigure 4. monthly sea level variability at chabahar (top) and jask (bottom) on the north coast of the oman sea figure 5. annual mean sea level at chabahar (top) and jask (bottom)on the north coast of oman sea 41research paper hassanzadeh, hosseinibalam sen by bayesian information criterion (bic) (sawa, 1978). minimum bic values are used to determine the best performance of the arima model because the bic places more emphasis on the parsimony of the model. hence, arima (1, 1, 1) and arima (2, 1, 1), shown in table 1, were selected to forecast the mean sea level. the predicted of arima (1, 1, 1) models are shown in fig. 10. the predictions are in agreement with the relevant observations. we compared the forecasting performance of alternative models of the mean sea level. four models are included in the comparison: the arima, models shown in table 1. forecasting performance was compared in terms of three criteria: r-squared, root mean square error (rmse) and mean absolute percentage error (mape). table 1 summarizes the main diagnostic and forecasting performance measures for the models. the model with the best overall performance is the arima (1.1.1). in summary, the arima (1,1,1) model has a number of desirable features. all its coefficients are statistically significant, most of them at the 1% level. it can be used to determine the mean sea level. finally, it has the best forecasting performance of the models considered. figure 10 shows the similarity between fits of the linear regression and arima models for chabahar and jask respectively. both models predicted seasonality of the data for the sea level. the arima models are more accurate for forecasting the mean sea level than the linear regression models. the two models predicted similar forecasts for sea level, but the greater accuracy for the arima models are attributed to their dynamic nature and their ability to incorporate new information in forecasting by containing lagged terms of the forcing functions as explanatory variables. results and discussion effect of meteorological parameters on sea level changes sea level changes are mainly due to variations in the regional and global meteorological parameters. atmospheric pressure variations and the thermal effect are the most important caused of sea level changes (gomis, et al., 2008 and juncheng, et al., 2009 and hosseinibalam, et al., 2007). the inverted barometer (ib) effect approxtable 1. testing result of selected autoregressive moving average (arima) models for chabahar structure bic (normalized) r-squared rmse mape arima (1, 1, 1) 0.566 0.887 0.684 0.178 arima (2, 1, 1) 0.642 0.889 0.647 0.166 arima (2, 1, 2) 1.199 0.942 0.490 0.109 arima (1, 1, 2) 1.499 0.959 0.415 0.099 note: bic (bayesian information criterion), rmse (root mean square error, mean absolute percentage error (mape) figure 6. seasonal change of sea level at chabahar (top) and jask (bottom) on the north coast of oman sea 42 squ journal of agricultural and marine sciences, 2021, volume 26, issue 1 mean sea level variability along the northern coast of the oman sea and its response to monsoon and the north atlantic oscillation index from tide gauge measurement imately related the oceanic response to the atmospheric pressure fluctuations. in coastal areas the onshore-offshore wind component can directly push water toward the shore or away from it. usually the more dominant effect was caused further offshore by the longshore wind component, which can raise or lower the water level because the coriolis force caused transport to the right of the wind direction. air temperature affected sea level by warmth caused by the greenhouse effect. a sea level rise could probably be caused by thermal expansion of the water column due to a decrease in water density caused by it being warmed. in a first exploratory approach, correlation coefficients between sea level and each of the above parameters as explanatory variables were found by calculating the pearson correlation coefficient, and corresponding p-values, between each time series. atmospheric pressure the correlation coefficient (r) between monthly atmospheric pressure and monthly sea-level data for chabahar was (r =-0.35) with p-value 0.00 and for jask is (r =-0.75) with p-value 0.00. the p-values for all coefficients were less than 0.05, thus the chabahar station had a weak negative correlation with the atmospheric pressure. the weak correlation coefficients meant that the oman sea mean level at chabahar station did not respond to atmospheric pressure as an inverse barometer effect, or strong deviation from isostatic response was observed. the non-barometric response to local atmospheric pressure partly represented an influence of sea level anomalies farther east due to the alongshore component of wind stress and it generally forced a large response than the onshore component. this was consistent with that expected from ekman dynamics and upwelling (figure 1). but, the ocean response to atmospheric pressure variations was close to the isostatic ones at jask (r =-0.75), the response depended on the water flux dynamics at the hormuz strait. in the open ocean and for periods longer than a few days, the sea level response to atmospheric pressure forcing was close to an isostatic response (fu and pihos, 1994; gaspar and ponte, 1997) and is well known by an inverse barometer effect: a 1-mbar increased in atmospheric pressure induced a sea level decrease of 1.01 cm. ducet et al. (1999) examined the validity of the inverse barometer approximation for the black sea mean level using 5 years of topex/poseiden data. they found very significant deviations from the inverse barometer response. they suggested that the deviation attributed to narrowness of the bosphorus strait and it had limiting role in water exchange. also the mediterranean mean sea level to atmospheric pressure departed from a standard inverse barometer effect due to the limiting role of the strait of gibraltar (candela, 1991). alothman et al. (2014) showed that at the mina sulman gauge there was no correlation between atmospheric pressure and sea level when the ib effect was subtracted from the data. gomez-enri et al. (2004) found that at mid and high latitudes in the indian ocean. they suggested that the relation between atmospheric pressure variations and sea level fluctuation (bf) values indicated a response near to the isostatic one; however, at low latitudes strong deviations from the isostatic response were observed. they observed some specific zones with values between 0.60 and 0.40 cm/mb, where the oceanic response was clearly far from isostatic (south of india, thailand gulf, south of indonesia and the east region of madagascar), contrary to that observed in the atlantic basin. chabahr figure 7. coherence between mean sea level and atmospheric pressure of the oman sea for chabahar station. frequency is (cycles/month). figure 8. coherence between mean sea level and air temperature of the oman sea for chabahar station. frequency is (cycles/month) 43research paper hassanzadeh, hosseinibalam located in low latitude in the north of the indian ocean, therefore the deviation from the isostatic response was expected. coherence analysis between atmospheric pressure and sea level in order to study the response of mean sea level at the northern coast of the oman sea to atmospheric pressure more fully, coherence between two parameters was observed. coherence between atmospheric pressure and sea level is shown in figure. 7. if the coherence value was unity, then the response of the sea level to the atmospheric pressure should be inverse barometer. it can be seen from figure 7 that the coherence was unity. this means that in the northern coast the oman sea, mean sea level responded to atmospheric pressure as an inverse barometer at low frequencies. it can be noticed that the low correlation (-0.35) between atmospheric pressure and mean sea level found in the previous section was due to the combination of other interrelated physical parameters, such as air temperature, steric effect, evaporation, wind and ekman transport, and this played an important role in mean sea level changes, interfering with the atmospheric pressure response. the behavior of the response of the oman sea mean level to atmospheric forcing at least in the northern coast was different from the one in the persian gulf because of the hormuz strait, which was pure inverse barometer (hassanzadeh et al., 2007). atmospheric temperature and wind the correlation coefficients (r) between monthly sea-level and air temperature and wind data for chabahar were 0.35 and 0.16, respectively. for jask the correlation coefficient (r) between monthly sea-level and air temperature and wind data were 0.70 and 0.39, respectively. hereafter, we present the same coherence analysis as before, but between the mean level of the oman sea and air temperature and wind at chabahar station. results of the coherence analysis are shown on figure 8 for mean sea level and air temperature. the most striking point to notice was the strong coherence, around 0.6, 0.8 and 1.0, for different periods with an almost steady gain at about 2.0., which meant that temperature had significant effect on mean sea level variations. the correlation between air temperature and atmospheric pressure showed that these parameters were highly inter-correlated. the same coherence analysis with the wind data was also performed, and this is shown in figure 9. interestingly, it lead to a much lower value at lower frequencies and noisier coherence at high frequencies, which meant that wind had no direct significant effect on mean sea level variations. the wind effect would yield water level proportional to wind stress, because of the associated ekman transport and ekman upwelling along the iranian coast around the chabahar gulf as it can be seen from figure 1. the coherence analysis of the corresponding time series revealed an oscillatory behavior between mean sea level and other variables. the annual peak was dominant and contained the major energy in the time series and it can be seen for coherency of mean sea level and atmospheric pressure. the coherency between mean sea level and air temperature and wind indicated an annual and a semiannual signal. there were some coherency peaks at high and low frequencies which were not significant. the atmospheric pressure was minimum in summer while the temperature was maximum, and vice versa. it was obvious that the annual cycle was dominant in the atmospheric pressure and air temperature. there was also a weak semiannual cycle in the coherency of wind. this can be due to the variability associated with the strong monsoonal forcing over the northern indian ocean. the annual cycle was prominent in the wind speed. other forces in this section, we consider the ekman dynamic in order to examine the wind forcing and also, the external factors, nao and monsoon that may affect the sea level in this area need be investigated. sea level anomalies were affected by the global climate change as well as by abnormal local climate changes (church et al., 2006). for example, barzandeh et al. (2018) showed that the sea level anomaly responds to wind-driven coastal upwelling, as a regional phenomenon. the ekman transport can be calculated in terms of wind stress, τ, sea water density, ρw=1025 kg m -3, a dimensionless drag coefficient, cd=1.4×10 -3, and air density, ρa=1.22 kg m -3, with the following formula: eq.(7) eq.(8) where, wind stress components are: eq.(9) and eq.(9) ƒ is the coriolis parameter defined as twice the vertical component of the earth’s angular velocity, ω, about the local vertical given by ƒ=2ωsin(θ) at latitude θ. finally, the x subscript co rresponds to the zonal component and the y subscript to the meridional one. eof analysis was used to study for spatial and temporal linked variability by analyzing mean sea level and ekman transport. this method partitioned the temporal variance of the 44 squ journal of agricultural and marine sciences, 2021, volume 26, issue 1 mean sea level variability along the northern coast of the oman sea and its response to monsoon and the north atlantic oscillation index from tide gauge measurement highly correlated data into a small number of orthogonal spatial patterns called eigenvectors and corresponding orthogonal time coefficients. these eigen functions have a series of coefficients in time that modulate them are ranked in decreasing order according to the percent of the variance. in general, each mode has an associated variance, non-dimensional spatial pattern, and dimensional time series. the set of orthogonal functions are derived from the data itself. the first eigenvector is virtually the same as an overall average pattern of ekman transport in this case. the ekman transport input data steps on n grid points. the initial eof analysis was performed on the ekman transport. the results of the analysis demonstrated that over 48.90% of the mean square of the data was contained in the first function and that 87.16% of the mean square was captured by the first four modes of east-west component. also, it demonstrated that over 48.20% of the mean square of the data was contained in the first mode and that 94.70% of the mean square the data was captured by the first fourth of the north-south component of the ekman transport. the correlation coefficients (r) of sea level with ekman transport were found for both stations. significant correlation coefficients, r=-0.70 (p-value=0.00) for chabahar, and r=-0.40 (p-value =0.00) for jask. the north atlantic oscillation (nao) was recognized as the foremost mode of variability in the north atlantic region with major impacts in europe and further afield (hurrell, 1995; cullen and demenocal, 2000) especially in the winter. sea level in black sea was significantly correlated with winter nao only in spring (tsimplis et al., 2004), but sea level in the persian gulf was not correlated with the winter nao index (hassanzadeh et al., 1995). the contributions of linear change and the nao to sea-level variability in the northern coast of the oman sea were investigated in this study. the monthly nao indices of each year was used, which are represented by the sea-level difference between azores atmospheric pressure high and icelandic low. the correlation coefficients (r) between monthly nao and monthly sea-level data for chabahar was r =-0.05 and for jask it was r =-0.07. the p-values for all coefficients were less than 0.05, thus both stations had a weak negative correlation with the nao. correlation coefficients between time series of indian summer monsoon index and sea-level was calculated. the correlations coefficients, r =0.26 p = 0.12, for chabahar and r =-0.07 p = 0.73, for jask were obtained. thus the sea-level at these tide gauges was little affected by indian ocean monsoon. the sea level change appears to response to the ekman transport which would be expected from the wind stress regimes. sea level response to nao and monsoon was negligible compared with the response to regional forcings. eof analyses was performed to find relations between the sea level and the ekman transport. in the following, the ekman transport variability is discussed in terms of the four time series of the leading pc mode. figure 10. comparison of fitted linear regression and arima models with the observation figure 9. coherence between mean sea level and wind of the oman sea for chabahar station (frequency, cycles/ month) 45research paper hassanzadeh, hosseinibalam conclusion the correlation analysis showed that the response of the oman sea mean level was deviated from inverse barometer. the coherence analysis revealed a significant coherence value between sea level and atmospheric pressure and did not validate the non-inverse barometer effect. other causes of sea level variation in this region, such as steric effects associated with non-propagating seasonal variations or the existence of baroclinic rossby and kelvin waves in the indian ocean. it seemed that importance can be explained by the inverse barometer deviation. the departure from inverse barometer was due to the combination of other interrelated physical processes, such as air temperature, steric effect, evaporation, wind and ekman transport, which played an important role in mean sea level changes and interfering with the atmospheric pressure response. sea level response to nao and monsoon was negligible compared with the response to regional forcings. the linear regression model was fitted to the mean sea level and forcing functions and arima (2,0,2) models used various lagged values to forecast mean sea level. the accuracy of the forecasted using arima is better than linear regression models. acknowledgement the authors gratefully acknowledge the support of the department of research and technology of university of isfahan for this work. moreover, we thank the department of oceanography and prof. g. weatherly, for hosting visits to florida state university, tallahassee, fl, when this work was carried out. references alothman go, bos, ms, fernandes, rms, m.e. ayhan, me. (2015). sea level rise in the north-western part of the arabian gulf. journal of geodynamics 81: 105–110. barzandeh a, eshghi n, hosseinibalam f, and hassanzadeh s. (2018). wind-driven coastal upwelling along the northern shoreline of the persian gulf. bollettino di geofisica teorica e applicata 59: 301-312. box gep, jenkins gm. (1976). time series analysis: forecasting and control. holden-day, san francisco, usa. candela j. (1991). the gibraltar strait and its role in the dynamics of the mediterranean sea. dynamics of atmospheres and oceans 15(3-5): 267-299. church ja, white nj, hunter jr. (2006). sea-level rise at tropical pacific and indian ocean islands. global planetary change 5: 155-168. cullen hm, demenocal pb. (2000). north atlantic influence on tigris-euphrates stream flow. international journal of climatology 20: 853–863. ding x, zheng d, chen y, chao j, li z. (2001). sea level change in hong king from tide gauge measurements of 1954-1999. journal of geodesy 74: 683-689. eshghi n, barzandeh a, hosseinibalam f, hassanzadeh, s. (2020). investigating dynamic and static aspects of regional sea level changes in the north-western indian ocean, bollettino di geofisica teorica e applicata 61(2): 249-270. fu ll, pihos g. (1994). determining the response of sea level to atmospheric pressure forcing using topexrposeidondata. journal of geophysical research 99: 24633–24642. gaspar p, ponte r. (1997). relation between sea level and barometric pressure determined from altimeter data and model simulations. journal of geophysical research 102: 961–971. gomez-enri j, villares p, brouno m, catalan m. (2004). evidence of different ocean responses to atmospheric pressure variations in the atlantic, indian and pacific basin as deduced from ers-2 altimeter data. annales geophysicae 22: 331-345. gomis d, ruiz s, sotillo gm, alvarez-fanjul e, terradas j. (2008). low frequency mediterranean sea level variability: the contribution of atmospheric pressure and wind. global and planetary change 83: 215-229. hassanzadeh s, kiasatpour a, hosseinibalam f. (2007). sea-level response to atmospheric forcing along the north coast of persian gulf. meteorology and atmospheric physics 95: 223-237. haredide d. (2004). iranian tide gauge network ioc/ gloss, technical report (http://www.pol.ac.uk/ psmsl/reports.gloss/general/). hosseinibalam f, hassanzadeh s, kiasatpour a. (2007). interannual variability and seasonal contribution of thermal expansion to sea level in the persian gulf. deep-sea research i 54: 1474–1485. hurrell jw. (1995). decadal trends in the north atlantic oscillation: regional temperatures and precipitation. science 269: 676–679. johns ew, jacobs ag, kindle cj, murray ps, carron m. (1999). arabian marginal seas and gulf. report of a workshop held at stennis space center, mississippi, usa. juncheng z, jianli z, ling d, peiliang l, lei l. (2009). global sea level and thermal contribution. journal of ocean university of china 8(1): 1-8. preisendorfer rw. (1988). principal component analysis in meteorology and oceanography. developments in atmospheric science, elsevier, netherlands, 425 pp. sawa t. (1978). information criteria for discriminating among alternative regression models. econometrica 46:1273–1291. 46 squ journal of agricultural and marine sciences, 2021, volume 26, issue 1 mean sea level variability along the northern coast of the oman sea and its response to monsoon and the north atlantic oscillation index from tide gauge measurement siddig na, al-subhi, a. m., alsaafani, m. a. (2019). tide and mean sea level trend in the west coast of the arabian gulf from tide gauges and multi-missions satellite altimeter. oeanologia 218: 1-11. stammer d, cazenave a, ponte rm, tamisiea, me. (2013). causes for contemporary regional sea level changes. annual review of marine science 5: 21-46. somot s, sevault f, deque m. (2006). transient climate change scenario simulation of the mediterranean sea for the 21st century using a high-resolution ocean. climate dynamics 27: 851–879. tsimplis mn, josey sa, rixen m, stanev ev. (2004). on the forcing of sea-level in the black sea. geophysical research letters 109: c08015. wunsch c. (1972). bermuda sea level in relation to tides, weather, and baroclinic fluctuations. reviews of geophysics 10: 1–49. research paper journal of agricultural and marine sciences 2022, 27(2): 50–58 doi: 10.53541/jams.vol27iss2pp50-58 received 03 april 2021 accepted 27 oct 2021 using ca-markov model to predict land use/land cover changes in bayer and al-bassit region, latakia, syria ola ali merhej1*, mahmoud kamel ali2, ali thabeet3 ola ali merhej1,*( ) olamerhej@gmail.com, 1general organization of remote sensing, 2forestry and ecology departmentagriculture facultytishreen universitysyria, 3natural resources department agriculture facultyaleppo universitysyria. introduction the changes of land use/land cover (lulc) are modifications of the earth’s surface made by hu-man activities (roy et al., 2015). these changes are huge land surface transformations (meles, 2008) and they are critical factors for ecological degradation of environment (hamad et al., 2018). lulc changes in all life sides happen because of many natural and human factors or variables (ali, 2009). moreover, human activities and natural processes influence the lulc changes and cause a large modification and even conversion of land use. this may create problems that can affect the environment (singh et al., 2015). because of its importance to understanding the earth’s interactions, lulc changes research has occupied an important place in the internationally active fields of study (lambin et al., 2003). remote sensing and geographic information systems are important tools to analyze and simulate the lulc changes (roy et al., 2015). they are extensively utilized for understanding lulc changes by determining the past and the present status (ozturk, 2015). multi-temporal satellite images were used to monitor vegetation cover changes through prepared lulc maps (palmer and fortescue, 2003). multiple satellite images of the same study area, which gained on different dates. these provide planners with the opportunity to monitor land cover changes by utilizing alternative parameters, such as vegetation indices. in addition, within an rs–gis environment, many spatial modeling techniques have been used for understanding the land use dynamics (li and yeh, 2000; he et استخدام منوذج ca-markov للتنبؤ بتغريات استعماالت األراضي/الغطاء األرضي يف منطقة الباير والبسيط، الالذقية، سورية عال علي مرهج1*، حممود كامل علي2، علي اثبت3 abstract. recently, land use change models have become important tools to support the analysis of land use dynamics. this research was aimed at the evaluating and predicting the land use/land cover change dynamics in bayer and al-bassit region of northwestern latakia, syria. in this paper, we used cellular automata and markov chain models to predict the lulc changes that are likely to occur by 2030 in bayer and al-bassit region. three landsat images acquired in the years of 1992, 2005, and 2018 were classified using maximum likelihood classification algorithm and used as the input data for ca-markov models. kappa index was used to validate the model, and the overall accuracy recorded 79.34%. based on a transition area matrix and transition rules a lulc map for the year 2030 were predicted. compared to the lulc status of the reference year 2018, a significant reduction is likely to occur in 2030 in the forest area. this reduction might be in favor of the growth of agricultural land and urban area. the result shows ca-markov model ability to predict future lulc changes in bayer and al-bassit region, and its importance for planners and land use managers. keywords: ca-markov, idrisi, land use change, remote sensing, satellite images, syria. امللخــص: مؤخــراً، أصبحــت منــاذج تغــر اســتعماالت األراضــي أداة مهمــة لدعــم حتليــل ديناميكيــات اســتعماالت األراضــي. هــدف هــذا البحــث إىل تقييــم ديناميكيــات تغــر اســتعماالت األراضــي/ الغطــاء األرضــي والتنبــؤ هبــا يف منطقــة البايــر والبســيط الواقعــة مشــال غــرب الالذقيــة، ســورية. يف هــذه الدراســة، مت اســتخدام كل مــن منــوذج األتومــاات اخللويــة وسلســلة ماركــوف للتنبــؤ بتغــرات lulc الــي مــن احملتمــل أن حتــدث يف عــام 2030 يف منطقــة البايــر والبســيط. مت تصنيــف ثــالث صــور الندســات ُملَتقطــة يف أعــوام 1992 و2005 و2018 ابســتخدام خوارزميــة االحتماليــة القصــوى، واســتخدمت اخلرائــط الناجتــة كبيــاانت إدخــال لنمــوذج ca-markov. اســتخدم مؤشــر كااب للتحقــق مــن صحــة النمــوذج، وســجلت الدقــة اإلمجاليــة 79.34 %. اســتناداً إىل مصفوفــة منطقــة االنتقــال وقواعــد االنتقــال، مت التنبــؤ خبريطــة lulc لعــام 2030.مقارنــة حبالــة lulc للســنة املرجعيــة 2018، مــن املرجــح أن حيــدث اخنفــاض كبــر يف مســاحة الغــاابت يف عــام 2030. قــد يكــون هــذا االخنفــاض لصــاحل النمــو يف األراضــي الزراعيــة واملناطــق احلضريــة. اخلالصــة. ُتظهــر النتيجــة قــدرة منــوذج ca-markov علــى التنبــؤ ابلتغــرات املســتقبلية يف lulc يف منطقــة البايــر والبســيط، وأمهيتــه للمخططــن ومديــري اســتعماالت األراضــي. الكلمات املفتاحية: منوذج camarkov، ادريسي، تغر استعماالت األراضي، االستشعار عن بعد، صور األقمار الصناعية، سورية. 51research paper merhej, ali, thabeet a mediterranean climate type with a rainy winter and a long dry summer characterizes the study area. brown mediterranean soil is the main type of soils, formed on hard calcium rocks, in the study area, which is highly washed, well-structured, rich in organic matter and iron oxides (verheye and de la rosa, 2005). the altitude above sea level is between 300 and 1400 meters, and the average rainfall ranges between 800 and 1200 mm/year. forest cover, covering more than 70% of the area, characterizes the area. bayer and al-bassit forests are the best and most important forests in terms of area and diversity in syria, consisting mainly of conifers, oaks and many other species. villages are located in the western and southern parts of area, the majority of people living there depend on agriculture in their livelihoods, so agricultural land is mostly concentrated around the villages. data collection and processing three landsat images were used in this study: 1992, 2005 and 2018, and downloaded freely from the united state geological survey (usgs, 2018). table 1 presents the characteristic of these images. the preprocessing of the images including geometric, radiometric and topographic corrections was applied to the images as in ali et al. (2018) using erdas imagine software (v.15). the maximum likelihood algorithm (mlc) which falls under supervised classification was used for the image classification process (gong and howarth, 1992; richards and xiuping, 1999). lulc classes were categorized into four classes: water, urban, agriculture and forest. classification accuracy assessment was performed for each lulc map by calculating kappa statistics for the accuracy assessment and the overall accuracy (congalton and green 2008). these use maps used for land were then exported by arcmap v. 10.3 software into ascii files in order to predict land use change in idrisi al., 2008). this is needed to provide valuable information for decision-makers to support sustainable development (fan et al., 2007). lulc models are used to improve better understand the land use changes caused by human activities (brown et al., 2012). many types of spatial and statistical models have been used to analyze and predict lulc changes, including multinomial logistic regression models (millington et al., 2007), markov model (hathout, 1988), cellular automata (ca) (clarke and gaydos, 1998), empirical-statistical models (veldkamp and fresco, 1996) and others (ren et al., 2019). ca and markov modeling have widely used in the fields of spatial and geographic, where they have given sufficiently accurate results especially in the changes of land use (al-shalabi et al., 2013; zadbagher et al., 2018; hamad et al., 2018); and urban growth simulation (siddiqu et al., 2018; nasehi et al., 2019). in syria, negligible real study was done to predict land use/land cover changes. this research attempts at evaluating and simulating the dynamics of spatio-temporal land use/land cover changes in bayer and al-bassit region of northwestern latakia, syria. the main objectives were to: (a) map and assess the lulc changes under different categories using landsat images acquired in 1992, 2005, and 2018; and (b) predict the future lulc map in 2030 using ca-markov model. materials and methods study area bayer and al-bassit region extends between longitudes (350 47’ 49.2”, 360 15’ 57.44” e) and latitudes (350 57’ 0.6”, 350 35’ 42.7” n) and encompasses an area of 7300 km2. it lies in the northwestern part of the coastal mountains in north and north-west latakia, syria (figure 1). figure 1. geographic position of the study area, bayer and al-bassit region, latakia, syria. 52 squ journal of agricultural and marine sciences, 2022, volume 27, issue 2 using ca-markov model to predict land use/land cover changes in bayer and al-bassit region, latakia, syria selva (v 17.0). in idrisi selva, the modules “markov, ca-markov, and validate” were used for projecting the 2018 land use map for bayer and al-bassit. data analysis classification accuracy assessment: to validate lulc maps resulted from image, the “accuracy assessment” tool in erdas imagine was used as in merhej et al. (2020). this tool compares a set of points distributed within each map with what they are in reality, calculates the overall accuracy and kappa statistics (for calculations see jensen 2003). google earth maps and more than 200 ground control points (gcp) distributed throughout the study area were used in the assessment process. the coordinates of these points were recorded using “garmin etrex” gps, then we arranged them with the type of land cover for each point within excel. by arcmap v. 10.3, the excel file was imported and converted to shape file, which was used in accuracy assessment process. percentage of land use change: to achieve the percentage of land use changes, firstly, a table contains the area and the percentage of change for each lulc class was developed, then the trend of change, which is percentage change, was calculated using the following equation: trend = (observed change/total change)×100 (1) to obtain an annual rate of change, the trend was divided by 100 and multiplied by the number of study years: 1992 – 2005 (13 years), 2005 – 2018 (13 years). markov model: markov model is often used in researches of change in ecosystems, whether in monitoring, analyzing or quantifying this change (subedi et al. 2013). it is also used to predict the amount of land use change and the state stability of land development in the table 1. characteristics of the landsat images used in this study. landsat sensor path/row date acquired spatial resolution landsat 5 tm 174/035 12/09/1992 30 m landsat 5 tm 174/035 16/09/2005 30 m landsat 8 oli 174/035 06/10/2018 30 m future (parsa et al. 2016; weng 2002), and it can be represented mathematically as equation 2: s(t,t+1)=pij×s(t) (2) where s(t) is the system status at time of t; s(t+ 1) is the system status at time of t+1; and pij: the transition probability matrix in a state which was calculated as equations 3 and 4: (3) (0≤pij≤1) (4) where p is the transition probability; pij is the probability of converting from current state i to another one j in next time; and pn is the state probability of any time (kumar et al., 2014). to predict how a specific variable changes over time, markov took the past states of the variable into consideration. markov model has the ability to determine the amount of conversion between land use classes and the rate of conversion among land use classes, which makes the model optimistic in land use change modeling. idrisi selva was used to present markov model. ca-markov model: to simulate the change of land cover over time, the spatial contiguity and probable spatial transitions (i.e. place in a specific area) were defined (subedi et al., 2013). the combination of markov model and cellular automata “ca-markov” were calculated from equation 5 (sang et al., 2011): s (t,t+1)=f (s(t),) (5) where s (t,t + 1) is the state of the system at time t and t+1, operating according to the principle that the state was the likely to occur at any time (n). transition probability and transition area matrices were created by applying markov and ca_markov modules in idrisi selva. while the transition probability matrix assessed, the change probability of a pixel in a land use category into another one during a period was determined. the transition area matrix contained the expected number of changed pixels during the same period (for more details see zadbagher et al., 2018). in order to predict table 2. land use land cover distribution (1992, 2005, 2018). land cover 1992 2005 2018 area (km2) % area (km2) % area (km2) % water urban agriculture forest total 11.39 41.97 326.96 342.74 723.1 1.58 5.80 45.22 47.40 100 11.55 41.11 328.67 341.81 723.1 1.60 5.69 45.45 47.27 100 12.48 61.44 407.14 242.05 723.1 1.73 8.51 56.30 33.47 100 53research paper merhej, ali, thabeet the 2018 lulc map, which was generated to evaluate the model accuracy, a transition probability matrix was created using 1992 and 2005 land use maps. the iteration number in ca-markov depended on the number of years between the base and projected lulc maps, and the default contiguity filtered of a kernel size of 55 pixels was used (subedi et al. 2013). model accuracy assessment kappa indices used to validate ca markov prediction for the spatial patterns of future change (lambin et al., 2003). kappa statistics were suggested by pontius (2002) for testing accuracy in terms of change location (kappa for location) and number of correct cells (kappa for quantity). the validation was applied by comparing the actual land use map with a predicting map (al-sharif and pradhan, 2013). lulc maps of 1992 and 2005, which were derived from landsat images classification to predict 2018 lulc (projected, 2018), then it was compared with actual 2018 lulc (actual 2018) (yang et al., 2008; al-sharif and pradhan, 2013). because of kappa statistics’ drawback (i.e. wrong or high values of accuracy) (wu et al., 2015) and confusion of the accuracy assessment (ahmed et al. 2013), cross-tabulation were used (pontius and millones, 2011). therefore, the overall kappa coefficient and kappa index of agreement (kia) were performed using cross-tabulation for respective lulc categories. when reasonable result and a good level of confidence were achieved, the 2030 lulc map was predicted. results and discussion land use/land cover status table 2 clarifies the static land use/land cover distribution in square kilometers derived from lulc maps for the years 1992, 2005 and 2018. figure 2 shows lulc maps derived from landsat image classification as used the years in this study. figure 2 also shows that forest cover followed by agricultural areas, occupied the most of the study area. the 2005 map shows the decline of forest concentrates in al-bassit region due to the large fire that occurred at the end of 2004. in the 2018 map, the decline of forests in favor of agriculture was clearly indicated by the excessive deforestation during the years of war (2011 and thereafter), it was achieved with the purpose of heating on the one hand, and switching to agricultural use on the other. that is confirmed in table 2, where vegetation covered (forests and agriculture) during the study period (1992 to 2018) the most of bayer and al-bassit region. in 1992, the vegetation covered accounts for 92.62% of the total area of bayer and al-bassit region, distributed to 326.96 km2 of agriculture and 342.74 km2 of forests. the other land use types covered 53.36 km2, of which 11.39 km2 was water and 41.97 km2 was urban (figure 2). within this thirteen years’ gap (1992 –2005), vegetation cover maintained a good stability (92.72%), because of the afforestation projects implemented during the 1990s. on the other hand, around 99.76 km2 of forest land had been lost and converted to agriculture and other human induced land uses (78.47 km2) between 2005 and 2018. thus, it was found that in 2018, forest area was reduced to 33.47% (242.05 km2) of the total area, while there was a sharp increase in agriculture land sharing almost 10.85% (407.14 km2 of the total area of bayer and al-bassit). there was also a steady increase in urban during 2005 –2018 periods. accuracy assessment of mlc the “accuracy assessment” tool was used to evaluate the classification accuracy on each lulc map. gcp were used to validate the 2018 map, while google earth images were used for the 1992 and 2005 maps. the results showed that the overall accuracy values were 89.23%, 89.38% and 88.28%, respectively. on the same hand, kappa index values were recorded 0.85, 0.86 and 0.84, respectively. the values were close and consistent, and gave excellent confidence to the lulc mapping. land use/land cover change rate and trend: the study period used in this project was divided into two partial periods. the first period was between 1992 and 2005, while the second was between 2005 and 2018. the positive change means that an object has increased its existence and the negative change, on the opposite, decreased its existence. both the positive and negative changes in the second period (20052018) showed a significant increase as compared to the first period (19922005). the total changes in the first period were about 4 km2, while in the second period were table 3. lulc change of bayer & al-bassit and its environs: 1992, 2005 and 2018. change lulc 1992-2005 2005-2018 annual rate % area (km2) trend % area (km2) trend % 1992-2005 2005-2018 water urban agriculture forest 0.16 -0.86 1.72 -0.94 4.32 -23.37 46.79 -25.52 0.93 20.43 78.46 -99.76 0.47 10.24 39.31 -49.98 0.56 -3.04 6.08 -3.32 0.06 1.33 5.11 -6.50 54 squ journal of agricultural and marine sciences, 2022, volume 27, issue 2 using ca-markov model to predict land use/land cover changes in bayer and al-bassit region, latakia, syria about 200 km2. this indicated that rapid changes had happened as loss and gain trends, due to the impacts of the war crisis on this area (merhej et al., 2019). from table 3, there seems to be a reduction (a negative change) in urban area in the first period and a sharp increase in the second one. whereas urban area decreased by 23.37% between 1992 and 2005 and increased by 10.24% between 2005 and 2018. this may be a result of the shift towards housing rather than farming, confirming the increase of agricultural area so, as it rose by 46.79% in the first period, this expansion fell to 39.31% in the second period. furthermore, water class showed an increase of 4.32% in the first period (19922005) due to the good precipitation in that period. this agrees with results reported in neighboring antakya (in turkey) which has climatic conditions similar to those of this study region. the period of 1990-2004 was characterized as a wet period except the dry season of 1990-2000 (karabulut, 2015). in the second period (20052018), there was a slight difference in the water category at the study area due to the disastrous drought as recorded between 2005 and 2010 (mohammed et al., 2019), followed by a wet period between 2010 and 2018. the entire period of this study has witnessed a sharp decline in the proportion of forests, where the distribution of forests can be worrying. the forest category fell by -25.52% in the first period and continued to decline rapidly between 2005 and 2018 by -49.98%. this decline in forest area was due to a number of causes, such as overcutting, forest fires, as well as land fragmentation and conversion to agriculture land. forest decline was evident throughout the whole study period and the annual decline rate reached 3.32% in the first period and 6.5% in the second period. according to rajab (2008) forest decreased in latakia by 32.2% between 1991 and 2004, and converted to agricultable 4. the table of transitional probability derived from applying markov model using the lulc map of 1992 and 2018. lulc 1992 92-05_transition_probabilities 2005 water urban agriculture forest water urban agriculture forest 0.8698 0.0018 0.0001 0.0008 0.0344 0.5145 0.0725 0.0068 0.0006 0.3951 0.9461 0.3888 0.0952 0.0886 0.0464 0.5386 table 5. the validation analysis: agreement/ disagreement components. agreement kappa indices agreegridcell agreequantity agreechance 0.5 0.18 0.2 disagreegridcell disagreequantity 0.0991 0.0295 kstandard kno klocation klocationstrata 0.7934 0.8392 0.8329 0.8329 figure 2. lulc maps for the bayer and al-bassit region 55research paper merhej, ali, thabeet ture lands and urban and other human uses. in addition, about 8 km2 converted to agriculture lands in al-bassit after the fire in 2004 (kassas, 2008). transition probability matrix in order to simulate the future lulc changes, markov model was applied for the period of 1992–2005 to calculate both the transition probability matrix and the transition area matrix. the raw classes represented the land cover types in 1992 map, while the 2005 land cover types were represented in the column classes (table 4). the used iteration number was 13, which was the years number between the base map (2005) and projected map in 2018 (figure 3a). as seen from table 4, agriculture during the study shows a high probability of remaining as agriculture in 2005 with a value of 0.9461, which signifies a high level of stability. as well, water class showed a probability as high as 0.8698 to stay as water in 2005. urban and forest classes, on the other hand, could likely change to other land use classes in this period with a high level of instability. while the probability of changing from urban class to agriculture was 0.3951, the urban stability value was 0.5145. this might be a false projection of this class if we made the drought events in the region (karabulut, 2015) as an exception. indeed, forest class showed a 0.5386 probability of remaining as forest and a 0.3888 probability of converting to agriculture class. this, therefore, showd an undesirable change (reduction). model validation ca-markov model was validated using validate tool in gis modeling in idrisi. this statistical method differentiated between error and agreement by elements due to the specification of quantity and location. table 5 clarifies kappa statistics for quantity and location derived from comparing the 2018 predicted lulc map to the 2018 actual lulc map. the results of kappa statistics for location show that kno was 0.8392, klocation was 0.8329, klocation strata was 0.8329 and kstandard was 0.7934. according to mondal et al. (2016), these results indicated that ca markov model had a high ability to define the location of future change on a grid cell level (the perfect klocation value is 1). table 5 also shows that there is an excellent agreement between the simulated and actual lulc maps of 2018 where the kstandard is more than 0.75 (fleiss et al., 2003). the correct agreement of grid cell, agreement of quantity and agreement due to chance represented by 50, 18 and 20%, respectively. on the opposite, the model was with the disagreement grid cell (i.e. 9.91%) and disagreement quantity (i.e. 2.95%). these results agreed with those by table 6. the expected area of the lulc categories in the projected maps for 2018 and 2030 for bayer and al-bassit region. lulc categories lulc areas in 2018 projected map (km2) lulc areas in 2030 projected map (km2) water urban agriculture land forests total 10.1655 30.2058 181.4467 501.7235 723.5415 7.80 38.2034 203.1873 474.3433 723.5415 figure 3. the projected lulc maps for the year of 2018 (a), and 2030 (b) 56 squ journal of agricultural and marine sciences, 2022, volume 27, issue 2 using ca-markov model to predict land use/land cover changes in bayer and al-bassit region, latakia, syria halmy et al. (2015) and indicated that ca markov could be used successfully in the lulc changes prediction. simulation of future changes in 2030 after evaluating the accuracy of the applied model and gaining good values of reliability, ca-markov model was used to obtain the 2030 lulc map, shown in figure 3b. figure 3 shows the expected spatial distribution of land use categories in the years of 2018 and 2030 in the study area, and table 6 clarifies the expected areas for each lulc category. the agricultural areas can expand at the expense of forests in several patches in bayer and al-bassit region, continued their existence and expansion in the years 2005 and 2018, especially in the northern parts. the expected decreased area of forests in 2030 was 27.38 km2 (3.78% of the study area) corresponding to an expected increase in the area of agricultural land in 2030 by 21.74 km2 (3%) (table 3). the urban areas are concentrated and expanded in the south western part of the study area, and we can notice that the northern border of the study area can be converted from forest category to urban in 2030 (figure 3). on the other hand, a decrease in the water category by a small percentage, amounting to 0.32% was noted (table 6), and it can be explained that it may be a reflection of the drought periods that passed in the period 2005-2018 and appeared in the transition probability matrix, and this was confirmed by what appears when comparing the maps for the years 2018 and 2030. conclusion in summary, it was found that the forest area decreased significantly during the period 1992-2018 mainly in favor of agricultural lands and urban areas. the ca markov model showed very good results of agreement between the actual and predicted lulc maps on the level of location and quantity. ca markov can be improved by adding many factors that affect the land use changes like topographic, social and economic factors. therefore, the ca markov would be a suitable model to predict future land use change in the bayer and al-bassit region. acknowledgement thanks to dr. ayman al-rubaie, who gave me the opportunity to complete this paper references ahmed b, ahmed r, zhu x. 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(2018). modeling land use/land cover change using remote sensing and geographic information systems: case study of the seyhan basin, turkey. environment monitoring and assessment 12 (190): 494-509. img050 img051 img052 img053 research paper journal of agricultural and marine sciences 2020, 25(2): 30–38 doi: 10.24200/jams.vol25iss2pp30-38 received 21 oct 2019 accepted 16 april 2020 effect of storage time on the quality of smoked hetroclarias a. a. ayeloja1,*, w. a. jimoh1, t. o. uthman2, m. o. shittu3 a. a. ayeloja1,*( ) ayeloja2@gmail.com,1department of aquaculture and fisheries, university of ilorin, pmb 1515 ilorin, kwara state, nigeria. 2bilogical science department, tai solarin university of education, ijagun ogun state, nigeria. 3department of fisheries technology, federal college of animal health and production technology moor plantation, ibadan, nigeria. introduction f ish is one of the important source of protein, and it has high commercial and medicinal values due to the presence of essential amino acids, other nitrogenous compounds, water, lipids, carbohydrates, minerals and vitamins (marwa, 2015; ayeloja et al., 2011a). zulema (2014) recommended the consumption of fish as it prevents cardiovascular and other diseases. ravichandran et al. (2011) also reported that fish is a good source of antimicrobial peptides, which defend the body against dreadful human pathogens. fish also contributes to income, employment generation and foreign exchange earning of many countries (zulema, 2014). fish contains all the essential amino acids, hence it is called “complete protein”; thereby making its consumption a necessity (pawar and sonawane, 2013). heliene (2016) also stated that fish have high levels of polyunsaturated fatty acids that are important for the promotion and maintenance of health as well as minerals, such as calcium, phosphorus, sodium, potassium and magnesium. however, fish is highly perishable and considerable losses in quality could occur before consumption if not properly handled, processed and stored. therefore, it is a concern for the fisheries industry all over the world (huss et al., 2004). fresh fish deteriorates very quickly after harvesting due to the actions of enzymes and bacteria (akande, 1996). fish quality is a complex concept involving a number of factors (jinadasa, 2014). to reduce fish spoilage, various preservation and processing methods are employed including freezing, chemical preservation, salting, smoking and frying (ayeloja et al., 2018). however, smoking is one of the تأثري وقت التخزين عىل جودة hetroclarias املدخن ايلوها و جيمو و عثامن و شيتو abstract. in this study, the effect of storage time on the quality of smoked heteroclarias was studied. samples (108) of heteroclarias (average weight 210 ± 15 g) were used. proximate, mineral composition (ca, na, fe and mg), biochemical, amino acid and sensory characteristics were evaluated. data obtained was subjected to analysis of variance (anova), while the sensory data was subjected to nonparametric test (i.e. kruskal wallis test). smoked heteroclarias was good nutritional quality in terms of compositions, such as protein, fat, carbohydrate, mineral and amino acids; however, these compositions were decreased with the increase of storage at ambient temperature. glutamic acid was the most predominant amino acid and the highest non-essential amino acid (neaa), while lysine was the most predominant essential amino acid (eaa). there was higher concentration of non-essential amino acids than essential amino acids, and eaa/neaa ratio (0.86 – 0.93) indicated that the fish was excellent in terms of protein quality. predicted protein efficiency ratio (pper) ranged between 3.44-3.61 and its biological value ranged between 79.84-75.04. chemical score and teaa (total essential amino acid) decreased with the increase of storage time and its texture reduced significantly (χ2 = 12.207, p≤0.01) with the increased storage period. smoked heteroclarias could be recommended for the consumption owing to its retained nutritional quality. keywords: storage time; quality; smoked; heteroclarias. hetroclarias املدخنــة. حيــث تــم اســتخدام عينــات حــوايل 108 مــن hetroclarias املســتخلص: متــت دراســة تأثــري زمــن التخزيــن عــىل جــودة )متوســط الــوزن 210 ± 15 جــم(. تــم تقييــم الخصائــص الكيميائيــة ، الرتكيــب املعــدين )ca, na, fe and mg( ، الكيمياء الحيويــة ، األحامض األمينية kruskal. يف حني تحليــل البيانات الحســية باســتخدام،)anova( والخصائــص الحســية. خضعــت البيانــات التــي تــم الحصــول عليها لتحليــل التبايــن wallis test كانــت hetroclarias املدخنــة ذات جــودة غذائيــة جيدة من حيث الرتكيب الكيميايئ ، مثل الربوتــني والدهون والكربوهيدرات واملعادن واألحــامض األمينيــة. ومــع ذلــك ، تقلصــت كمية هذه الرتكيبات مع زيادة التخزيــن يف درجة الحرارة املحيطة. كان حمض الجلوتاميك هو األكرث شــيوًعا مــن األحــامض األمينيــة وأعــىل األحــامض األمينيــة غــري الرضوريــة )neaa(، بينــام كان الليســني هــو األكرث شــيوًعا من بني األحــامض األمينية األساســية eaa/neaa )0.93 0.86(وجــد أن تركيــز األحــامض األمينيــة غــري الرضوريــة أعــىل مــن األحــامض األمينيــة األساســية ، وأشــارت نســبة . )eaa ( إىل أن األســامك كانــت ممتــازة مــن حيــث جــودة الربوتــني. تراوحت نســبة كفــاءة الربوتــني املتوقعة بــني 3.44-3.61 وتراوحــت قيمتهــا البيولوجية بني = χ2(79.84-75.04. انخفضــت الدرجــة الكيميائيــة وإجــاميل األحــامض األمينيــة األساســية مــع زيــادة وقــت التخزيــن وتناقص قوامه بشــكل ملحــوظ p ,12.207≥0.01(، مــع زيــادة فــرتة التخزيــن. ميكــن التوصيــة hetroclarias املدخــن لالســتهالك بســبب جودته الغذائيــة املحتفظ بها hetroclarias ، الكلامت املفتاحية : وقت التخزين ، الجودة ، املدخن 31research paper ayeloja, jimoh, uthman, shittu most popular method of fish processing in developing countries like nigeria (ayeloja, 2019). smoking provides good taste and aroma to fish and it extends fish shelf life. this is due to the effects of dehydration, antimicrobial and antioxidant activities of several components from smoke, such as formaldehyde, carboxylic acids and phenols (serkan et al., 2010). however, there is limited information on the effect of storage time on the quality of smoked heteroclarias, which is one of the most cultured fish species. heteroclarias is more cultured due to its superior growth, improved survival and general hardiness than culturing the pure breed of either clarias gariepinus or heterobranchus bidorsalis (obe, 2014). owodehinde et al. (2018) reported that heterobranchus is a hybrid product of h. bidorsalis (♂) x c. gariepinus (♀) which are fresh water fish. heteroclarais is produced from the two species due to their uniqueness and prominence among commercial fish farmers in africa and these fishes are tasty, hardy and tolerant to poor quality of growing water (ekelemu, 2010). however, consumers rarely have information about the nutritional quality of smoked heteroclarias and its quality changes during storage, thus the need for this study. this study aimed to determine the nutritional quality of smoked heteroclarias as well as to examine the effect of ambient storage on its proximate, mineral, biochemical, amino acid and sensory qualities. materials and methods sample collection total 108 samples of heteroclarias (average weight 210 + 15g) were collected at a commercial fish farm within ilorin metropolies, kwara state, north-central nigeria. these were taken to laboratory; and were gutted, washed and smoked similar to the modified method of ayeloja et al. (2015) (figure 1). the smoking was performed using niomr (nigeria institute of oceanography and marine research) smoking kiln, which was manually powered using charcoal as fuel. the smoked fish was stored at ambient temperature (27 ± 3°c) and samples were collected at every fortnight (i.e., 0, 14, 28, 42 and 56 days) for proximate, mineral, biochemical; and samples for organoleptic assessment and amino acid analysis were collected at day 0, 28 and 56, respectively. composition analysis proximate compositions of fish were determined by conventional method (aoac, 2000). petri dish was cleaned and weighed. then 1.0 g of each of the grounded fish samples was measured in each petridish and then weighed. they were each transferred into the oven at 105°c for 3 hours. after the first 3 hours, the petridish was removed from the oven, allowed to cool and weighed. the petridish was returned into the oven and was brought out after an hour and weighed again; this process was repeated until a constant weight was achieved and moisture content was determined. the crude protein was determined using kjeldahl method. the fish sample (either smoked or frozen) was ground into a fine or smooth texture. a known weight (5.0 g) of the fish sample is then weighed into a long necked kjedahl flask along with 5 g of copper sulphate anhydrous and 5 g of sodium sulphate anhydrous. then, 25 ml of concentrated sulphuric acid (h2so4) was added. the flask was gently placed and the content was heated, the heating continued until a clear solution was obtained. the digestion was performed between 3 to 5 hours. the clear hot solution obtained was allowed to cool and solution was filtered using filter paper. then, 5 ml of the filtered digested sample was poured into the protein determination equipment and 10 ml of 40% naoh was added followed by a distillation process. the steam being passed in the reactor condenses and drops into a conical flask containing boric acid (5 ml) until the mixture changes color. after changing color, 50 ml of the liquid was collected and titrated with 0.01 m of hcl until the color (green) changed to deep blue. for the estimation of fat content, the dried samples left after moisture determination were finely ground and the fat was extracted for 4 hours with a non-polar solvent (i.e. ethyl ether) using soxhlet extraction method. after extraction, the solvent was evaporated and the extracted fat was weighed. ash was determined by burning the dried sample in a furnace at 550°c for 4 h. the difference in weights before and after burning gave the total ash content. the total carbohydrate content was determined by subtracting the sum of the percentage moisture, ash, crude lipid, and crude protein from 100%. mineral composition and other biochemical test crucible was cleaned, weighed and then 5.0 g of ground fish sample was measured into each crucible. this was transferred into the oven at 60°c for 45 minutes to 1 hour. after oven drying, the sample was weighed into a conical flask and was digested using nitric acid and hydrochloric acid. after digestion, the concentration of the minerals was determined using pinnacle 900t atomic absorption spectrophotometer (aas). the total volatile base nitrogen (tvbn), trimethyl amine (tma), ph, peroxide value (pv) and free fatty acid (ffa) were determined following the method of pearson (1982). amino acid analysis the preparation of the fish samples was adapted from the procedure described by benitez (1989). the fish samples were dried to a constant weight, defatted, and hydrolyzed (bligh and dyer, 1959). these were evaporated in a rotary evaporator and loaded into the applied biosystems pth amino acid analyzer model 120a. 32 squ journal of agricultural and marine sciences, 2020, volume 25, issue 2 effect of storage time on the quality of smoked hetroclarias ed. approximate area of each peak was then obtained by multiplying the height with the width at half-height. the norleucine equivalent (ne) for each amino acid in the standard mixture was calculated using the formula: where, ne is an internal standard. a constant s was calculated in g/100g protein using the following formula: finally, the amount of each amino acid present in the sample was calculated in g/100 g protein using the formula: where nh is net height, w is width @ half height, nleu = norleucine. the period of analysis lasted for 45 minutes. to determine nitrogen in the separated sample for analyzing tryptophan, a 200 mg ground sample was weighed, wrapped in whatman filter paper (no. 1) and the procedure for nitrogen determination for amino acids as described was repeated. percentage nitrogen was calculated. predicted protein efficiency ratio (pper) the predicted protein efficiency ratio (pper) was estimated by using the equation given by alsmeyer et al. (1974): amino acid score (aas) the essential amino acid score was calculated based on the whole hen’s egg amino acid profiles (paul and southgate, 1976) essential amino acid index (eaai) the essential amino acid index (eaai) was calculated using the ratio of test protein to the reference protein for each ten essential amino acids (oser, 1959) as: where, p is test protein, and s is standard whole egg protein. hydrolysis a known weight (2.0 g) of the defatted sample was weighed into a glass ampoule and 7 ml of 6 n hcl was added. in order to avoid possible oxidation of some amino acids during hydrolysis such as methionine and cystine, nitrogen was passed into the ampoule to expel oxygen. the glass ampoule was then sealed with bunsen burner flame and placed in an oven preset at 105±5°c for 22 hours. the ampoule was allowed to cool before broken open at the tip and the content was filtered to remove the humins. the filtrate was then evaporated to dryness at 40°c under vacuum by a rotary evaporator. the residue was dissolved with 5 ml to acetate buffer (ph 2.0) and stored in plastic specimen bottles, which were kept in a freezer. it is noteworthy that hydrolysis procedure was unable to determine tryptophan since it is chemically decomposed by 6n hcl during acid hydrolysis. tryptophan to identify tryptophan, a separate sample of the defatted sample was hydrolysed using antioxidants such as dodecanethiol to replace 6 n hydrochloric acid (hcl), thereby preserving tryptophan. the tryptophan in the known sample was hydrolyzed with 4.2 m sodium hydroxide (maria et al., 2004). the known sample was dried to constant weight, defatted and hydrolyzed; and defatted sample (2.0 g) was weighed into glass ampoule. it is recommended that alkaline hydrolysis produced higher tryptophan recovery than acid hydrolysis. sodium hydroxide was used instead of barium hydroxide to avoid problems of precipitation and adsorption of tryptophan (maria et al., 2004). nitrogen was passed into the ampoule to expel oxygen and it was then sealed with bunsen burner flame. the sealed ample was placed in an oven preset at 105±5°c for 4 hours. the ampoule was allowed to cool and the content was filtered to remove the humins. the filtrate was then neutralized to ph 7.0 and evaporated to dryness at 40°c using a rotary evaporator under vacuum. the residue was dissolved in 5 ml of borate buffer (ph 9.0) and stored in plastic specimen bottles, which were kept in a freezer. loading of hydrolysate into a pth analyser sixty microliter of the hydrolysate was loaded in the analyzer. this was dispensed into the cartridge of the analyzer. the analyzer is designed to separate and analyze free acidic, neutral and basic amino acids. the period of the analysis lasted for 45 minutes. to calculate amino acid values, an integrator attached to analyzer calculated the peak area proportional to the concentration of each of the amino acid. the net height of each peak produced by the chart recorder of tsm (each representing an amino acid) was measured. the half-height of the peak on the chart was found and the width of the peak on the half-height was accurately measured and record33research paper ayeloja, jimoh, uthman, shittu biological value (bv) the biological value (bv) was calculated by the method of oser (1959): bv= 1.09 (eaai) 11.73 (8) organoleptic assessment the various smoked fish species were subjected to consumer preference evaluation using based on 5-point hedonic scale modified from tobor (1994) and eyo (2001). odor, flavor and texture were the sensory attributes examined, the following grades were allotted depending on their qualities: 8 ≤ 10 = excellent, 6 ≤ 8 = very good, 4 ≤ 6 = good, 2 ≤ 4 = bad and ≤ 2 = worst. thirty semi-trained panelists from department of aquaculture and fisheries, faculty of agriculture university of ilorin kwara state, nigeria were used for the assessment. statistical analysis spss 16.0 version was used for the statistical analysis. data collected on descriptive organoleptic assessment using hedonic scale were subjected to nonparametric test (kruskal wallis test). while other data were subjected to analysis of variance (anova) using f-test to determine the significant difference between the treatments. means of the significantly different treatments were separated using duncan multiple range test at 95% confidence value. samples for laboratory analysis were replicated thrice to aid statistical analysis. results the result for the proximate composition of smoked heteroclarias is presented on table 1. the result indicates that the moisture content of smoked heteroclarias ranged from 26.44 ± 0.01 to 27.37 g/100 g sample ± 0.06 within a storage time of 56 days. the highest moisture content (27.37 g/100 g sample ± 0.06) was recorded on the 56th day of storage, while the lowest moisture content 26.44 g/100 g sample ± 0.01 was recorded on day 0; which was immediately after smoking. the moisture content of the fish increased significantly (p≤0.05) with the increased storage time through the period of the storage (56 days).the percentage crude protein content of the fish ranged from 45.37 g/100 g sample ± 0.15 to 48.96 g/100 g sample ± 0.03 within a storage time of 56 days. there was no significant difference (p>0.05) in the crude protein content for the first 14 days of storage but later significantly increased (p≤0.05) from day 28 until storage period. the highest crude protein value of 48.96 g/100 g sample ± 0.03 was recorded on the day 0 before fish was stored at ambient, while the lowest value of 45.37 g/100 g sample ± 0.15 was recorded on the 56th day of storage. the crude lipid content of the fish ranged between 18.73 ± 0.12 to 20.42 g/100 g sample ± 0.02 within a storage period of 56 days. the highest crude lipid content (20.42 g/100 g sample ± 0.02) was recorded at day 0, which was the lowest crude lipid content (18.73 g/100 g sample ± 0.12) was recorded on the 56th day of storage. the lipid content of the fish decreased significantly (p≤0.05) with the increased storage time through the storage period (56 days). the ash content of the fish differed significantly (p≤0.05) during the first 14 days of storage. however, there was no significant difference (p>0.05) in the ash content of the fish from day 28 until the remaining period of storage. the percentage carbohydrate content of smoked heteroclarias ranged between 2.02 ± 0.01 to 6.38 g/100 g sample ± 0.27 during the storage period of 56 days. no significant difference (p>0.05) was observed for the first 2 weeks of storage but later significantly differed (p≤0.05) from 28 days untable 1. proximate composition (g/100g sample) of smoked heteroclarias with increased storage time day 0 day 14 day 28 day 42 day 56 moisture 26.44 ± 0.01a 26.78 ± 0.02b 26.91 ± 0.08c 27.17 ± 0.05d 27.37 ± 0.06e crude protein 48.96 ± 0.03d 48.96 ± 0.02d 46.86 ± 0.08c 45.91 ± 0.08b 45.37 ± 0.15a crude lipid 20.42 ± 0.02d 20.02 ± 0.01c 19.00 ± 0.20b 18.94 ± 0.12ab 18.73 ± 0.12a ash 2.16 ± 0.02a 2.24 ± 0.01b 2.16 ± 0.03a 2.16 ± 0.03a 2.15 ± 0.02a cho (carbohydrate) 2.02 ± 0.01a 2.01 ± 0.01a 5.07 ± 0.16b 5.82 ± 0.21c 6.38 ± 0.27d *mean with different superscript in the row indicates significant difference at p< 0.05 figure 1. flow chart for the production of smoked catfish, heteroclarias 34 squ journal of agricultural and marine sciences, 2020, volume 25, issue 2 effect of storage time on the quality of smoked hetroclarias til the remaining 56 days of storage. table 3 presents the effect of storage time on biochemical quality of smoked heteroclarias. the highest tma value (24.16 ± 0.02 mgn/100 g) and the lowest value (21.02 ± 0.01 mgn/100 g) was recorded with values increasing significantly (p≤0.05) from day 0 to day 42 of storage time and decreased significantly (p>0.05) from day 42 to day 56 of storage time. the highest tvbn value (32.86 ± 0.02 mgn/100 g) and the lowest (30.37 ± 0.01 mgn/100g) was recorded. it was observed that the tvbn increased significantly (p≤0.05) from day 0 to day 28 of storage time and decreased significantly (p>0.05) from day 28 to day 56. the ph had no significant differences (p>0.05) with increased in storage time. the pv had no significant differences (p>0.05) with the increase in storage time. the highest ffa (7.83 g/100 g fat ± 0.02) and the lowest value (6.92 g/100 g fat ± 0.00 ) was observed. however, ffa decreased significantly (p>0.05) from day 0 to day 28 and slightly increased significantly at day 42 but decreased significantly from day 42 to day 56 of storage time. amino acid profile the amino acid profile of heteroclarias spp. muscles at different storage time (day 0, day 28 and day 56) are presented in table 4. eighteen amino acids (10 essential, 8 non-essential) were observed in the fish with their mean values as shown in the table 4. the highest and lowest mean value at day 0 was observed in glutamic acid (14.38 g/100 g crude protein, cp) and tryptophan (0.84 g/100 g cp) respectively. the highest and lowest mean value at day 28 was observed in glutamic acid (13.36 g/100 g cp) and tryptophan (0.87 g/100 g cp), respectively. the highest and lowest mean value at day 56 was observed in glutamic acid (14.91 g/100 g cp) and cystine (0.61 g/100 g cp), respectively. an increase in amino acid content was observed across storage time (i.e. as storage time increases) in leucine (from 7.28 ± 0.10 to 7.36 ± 0.08 to 7.59 ± 0.29 g/100 g cp) and aspartic acid (from 9.91 ± 0.02 to 10.00 ± 0.03 to 9.97 ± 0.11 g/100 g cp), which increased at day 28 but decreased slightly at day 56. decrease content was observed across storage time in valine (from 5.00 ± 0.04 to 4.65 ± 0.08 to 3.74 ± 0.08 g/100 g cp), methionine (from 2.94 ± 0.08 to 2.33 ± 0.10 to 1.74 ± 0.04 g/100 g cp), glycine (from 8.18 ± 0.18 to 8.15 ± 0.17 to 5.25 ± 0.10 g/100g cp), tyrosine (from 3.19 ± 0.12 to 2.93 ± 0.25 to 2.92 ± 0.11 g/100 g cp) and serine (from 4.81 ± 0.08 to 4.62 ± 0.11 to 3.77 ± 0.10 g/100 g cp). in phenylalanine (from 4.43 ± 0.00 to 3.72 ± 0.00 g/100 g cp), tryptophan (from 0.87 ± 0.04 to 1.73 ± 0.00 g/100g cp), proline (from 6.14 ± 0.21 to 4.42 ± 0.08 g/100 g cp), arginine (from 6.88 ± 0.25 to 6.20 ± 0.1 g/100 g cp ), histidine (from 2.27 ± 0.04 to 2.09 ± 0.11 g/100 g cp), cystine (from 0.97 ± 0.00 to 0.61 ± 0.00 g/100 g cp) and alanine (from 6.43 ± 0.08 to 5.80 ± 0.06 g/100 g cp), an increase was observed at day 28, followed by a decreased at 56 days after smoking. decrease was observed at day 28 with an increase at day 56 in lysine (from 8.54 ± 0.00 to 8.51 ± 0.04 to 8.91 ± 0.49 g/100g cp), isoleucine (from 4.23 ± 0.05 to 3.11 ± 0.62 to 4.01 ± 0.07 g/100g cp), glutamic acid (from 14.38 ± 0.21 to 13.36 ± 0.06 to 14.91 ± 0.11 g/100 g cp) and threonine (from 4.36 ± 0.04 to 3.80 ± 0.20 to 5.00 ± 0.01 g/100 g cp). in one-way anova test of the samples, no significant difference (p>0.05) was observed in leucine, lysine, table 2. mineral composition of smoked heteroclarias (mg/100 g ash) with increased storage time mineral day 0 day 14 day 28 day 42 day 56 calcium (ca) 6.15 ± 0.07d 5.85 ± 0.07c 5.60 ± 0.00b 5.44 ± 0.06a 5.33 ± 0.04a sodium (na) 1.05 ± 0.07b 0.95 ± 0.07b 0.81 ± 0.01a 0.77 ± 0.02a 0.70 ± 0.01a iron (fe) 0.41 ± 0.01d 0.39 ± 0.01d 0.34 ± 0.02c 0.28 ± 0.03b 0.21 ± 0.01a magnesium (mg) 4.35± 0.21d 3.95 ± 0.07c 3.45 ± 0.07b 3.25 ± 0.07ab 3.00 ± 0.00a *mean with different superscript in the row indicates significant difference at p<0.05 table 3. effect of storage time on biochemical quality of smoked heteroclarias. tma (mgn/100 g) tvbn (mgn/100 g) ph pv (meq. peroxide/kg) ffa (g/100 g fat) day 0 21.02+0.01a 30.37+0.01a 7.43+0.06a 8.47+0.01b 7.83+0.02c day 14 22.50+0.02b 31.50+0.01c 7.57+0.06c 8.70+0.01e 7.41+0.01b day 28 24.09+0.11c 32.86+0.02d 7.43+0.06d 8.65+0.01d 7.38+0.03b day 42 24.16+0.02c 32.73+0.56d 7.63+0.06d 8.61+0.01c 7.40+0.00b day 56 21.08+1.14a 30.95+0.07b 7.63+0.06b 8..22+0.01a 6.92+0.00a means ± sd with different superscript in the same column indicating significant differences at p ≤ 0.05. note: tma= trimethylamine, tvbn= total volatile base nitrogen, pv= peroxide value, ffa= free fatty acid. 35research paper ayeloja, jimoh, uthman, shittu isoleucine, cystine, tyrosine, aspartic acid and histidine content of the sample throughout the storage period. a significant difference (p≤0.05) was noticed in phenylalanine, threonine, glutamic acid, valine and methionine content of the sample at all storage times. no significant difference was observed in arginine between the periods of 0-28 days and 0-56 days of storage (p>0.05), however a significant difference was noticed between 28 and 56 days of storage (p≤0.05). alanine, tryptophan, proline, glycine and serine showed similar trend of no significant difference (p>0.05) at day 0 and 28 days, but a statistical variation (p≤0.05) was noted at 56 days of storage. table 5 shows the protein quality parameters of heteroclarias as a function of storage time. a decrease in total amino acid was observed with the increased storage time. a higher concentration of total non-essential amino acid was recorded than total essential amino acid. the table also records the ratio of eaa to neaa, which was 0.86 at the beginning of the storage period, decreased slightly at day 28 to 0.84 and slightly increased at day 56 to 0.93. tryptophan was recorded as the limiting amino acid in the sample with chemical scores of 0.47 and 0.48 at day 0 and day 28 respectively while at day 56, valine was recorded as the limiting amino acid in the sample with chemical scores of 0.50. the highest eaai value of 0.84 was recorded at day 1 and decreased to 0.80 and increased slightly to 0.83 at day 28 and day 56, respectively. the predicted protein efficiency ratio (pper) ranged between 3.44 to 3.61 g/100 g cp. the highest and least biological values were recorded in day 0 and day 28, respectively. table 6 indicates the amino acid scores of the fish in relation to the amino acid scoring pattern of whole hen’s egg protein. the values were found to be favorable in fish sample at day 0 of smoking and decreased at the end of storage period. lysine had the highest amino acid score ranging from 1.37 to 1.38 g/100 g cp. tryptophan and valine were observed as the limiting amino acid with values ranging between 0.47 to 0.96 g/100 g cp and 0.50 to 0.67 g/100 g cp, respectively. in table 7, the taste panelist scores allotted for texture of smoked heteroclarias reduced significantly (χ2 = 12.207, p≤0.01) with increased storage period, whereas no significant (χ2= 1.628, 8.982, p>0.05) decrease in the physical quality of odor and flavor was observed during storage period. discussion the result of the proximate composition of smoked heteroclarias (table 1) was similar to that reported for other smoked fresh water fishes (ayeloja et al., 2011a; abraha et al., 2018). the result indicated that crude protein varied within 48.96 and 45.3 g/100 g sample) and it reduced with the increase of storage time. the reduction of lipid was observed, while the moisture and carbohydrate were increased with the increase of storage time. simtable 4. changes in amino acid profile (g/100 g cp) of hybrid catfish (heteroclarias spp) across storage time amino acids day 0 day 28 day 56 essential (g/100 g protein) leucine 7.28±0.10a 7.36±0.08a 7.59±0.29a lysine 8.54±0.00a 8.51±0.04a 8.91±0.49a isoleucine 4.23±0.05a 3.11±0.62a 4.01±0.07a phenylalanine 4.00±0.14b 4.43±0.00a 3.72±0.00c tryptophan 0.84±0.05b 0.87±0.04b 1.73±0.00a valine 5.00±0.04a 4.65±0.08b 3.74±0.08c methionine 2.94±0.08a 2.33±0.10b 1.74±0.04c arginine 6.67±0.06ab 6.88±0.25a 6.20±0.12b threonine 4.36±0.04b 3.80±0.20c 5.00±0.01a histidine 2.19±0.02a 2.27±0.04a 2.09±0.11a non essential (g/100g) cystine 0.85±0.00 0.97±0.00 0.61±0.00 alanine 6.41±0.16a 6.43±0.08a 5.80±0.06b glutamic acid 14.38±0.21b 13.36±0.06c 14.91±0.11a glycine 8.18±0.18a 8.15±0.17a 5.25±0.10b serine 4.81±0.08a 4.62±0.11a 3.77±0.10b aspartic acid 9.91±0.02a 10.00±0.03a 9.97±0.11a proline 5.69±0.44a 6.14±0.21a 4.42±0.08b tyrosine 3.19±0.12a 2.93±0.25a 2.92±0.00a 2.93±0.25a 2.92±0.00a means ± sd with different superscript in the same column indicating significant differences at p ≤ 0.05. table 5. changes in quality parameters of amino acid profile of heteroclarias with increased storage time. protein quality day 0 day 28 day 56 parameters taa (g/100g) 99.47 96.81 92.38 teaa (g/100g) 46.05 44.21 44.33 tneaa (g/100g) 53.42 52.60 47.65 eaa/neaa 0.86 0.84 0.93 cs (g/100g) 53.33 51.67 50.13 eaai 0.84 0.80 0.83 bv 79.84 75.04 78.36 pper (g/100g) 3.44 3.50 3.61 note: taa= total amino acids; teaa= total essential amino acid; tneaa= total non-essential amino acid; eaai = essential amino acid index; cs= chemical score; bv= biological value; pper= predicted protein efficiency ratio. 36 squ journal of agricultural and marine sciences, 2020, volume 25, issue 2 effect of storage time on the quality of smoked hetroclarias ilar results were reported by ayeloja et al., 2011b and mosarrat et al. (2016). they mentioned these changes could induce the gradual degradation of initial crude protein to more volatile products, such as total volatile bases, hydrogen sulphide and ammonia. table 2 shows that ca (6.15-5.33 mg/100 g ash) was the most abundant mineral in smoked heteroclaraias followed by mg (4.353.00 mg/100 g ash). adeyemi et al. (2013a) observed similar result in the case of trachurus trachurus. they reported that calcium was the most abundant mineral in raw and smoked trachurus trachurus. table 3 shows that the tma, tvbn, ph and pv of smoked heterobranchus increased significantly (p>0.05) with increase storage time until 42days, while the ffa decreased with the increase in storage time. khanipour and mirzakhani (2013) reported that the ph, pv and tvb-n values of hot smoked rainbow trout (oncorhynchus mykiss) increased with increasing storage time. mosarrat et al. (2016) also reported an increase of tvbn of smoked chapila (hamilton-buchanan, 1822), kaika (hamilton-buchanan, 1822) and baim (hamilton-buchanan, 1822) when stored at ambient temperature, which was attributed to the formation of volatile amine compounds by autolytic process. adeyemi et al. (2013b) also gave similar report that the tvbn of smoked trachurus trachurus increased from 28.12 ± 0.38 mg n/100 g to 31.90 ± 0.3 mgn/100 g during storage. the recommended limit of acceptability of tvbn for fish is 20-30 mg n per 100 g (daramola et al., 2007), while kirk and sawyer suggested a value of 30 – 40 mg n/100 g as the upper limits. the results in this study was observed within these values. the values recorded for pv in this study (8.22 – 8.70) is lower than those reported by adeyeye et al. (2015) for smoked fishes sold in lagos nigeria (9.05 9.35 eroxide/kgrespectively). eighteen amino acids (10 essentials, 8 non-essentials) were observed in heteroclarias (table 4). glutamic acid had the highest concentration among the amino acid and the non-essential amino acids while tryptophan was the least concentrated. while lysine was the most concentrated essential amino acid and tryptophan was the least concentrated essential amino acid in the fish. the amino acids reduced significantly (p<0.05) with the increase in storage time. shiming et al. (2013) equally observed that glutamic acid was the most predominant amino acid and the non-essential amino acid in yellowfin tuna (thunnus albacares) and big eye tuna (thunnus obesus), while the lysine was the most predominant essential amino acid. this study established that heteroclarias contained amino acid as required by human. the glycine is major component of human skin collagen, together with other amino acids such as alanine, proline, arginine, serine, isoleucine, and phenylalanine form polypeptides (zhao et al., 2010). a decrease in protein quality parameters of heteroclarias with the increase in storage time was observed in this study (table 5). a higher concentration of total non-essential amino acid was recorded than total essential amino acid. eaa to neaa ratio is an index to define the quality of the protein (elshehawy et al., 2016). the ratio of eaa to neaa in this study ranged between 0.86 and 0.93 which was higher than 0.71 as reported for gilt head sea bream (sparus aurata) and 0.65 reported for sea urchin roe (pinto, 2007). the chemical score and teaa decreased with the increase in storage time, the eaai ranged between 0.84 and 0.80. the predicted protein efficiency ratio (pper) ranged between 3.44 to 3.61 g/100 g cp was higher than 2.22 as recorded for c. table 6. amino acid scores and indispensable amino acid index (iaai) of heteroclarias essential amino acids amino acid scores (g/100g) whole egg protein (g/100 g sample) fao/who provisional amino acid scoring pattern (g/100g) day 1 day 28 day 56 leucine 0.88 0.89 0.91 8.3 7.0 lysine 1.38 1.37 1.37 6.2 5.5 isoleucine 0.76 0.56 0.72 5.6 4.0 phenylalanine 0.78 0.87 0.73 5.1 +tyr 6.0 tryptophan 0.47 0.48 0.96 1.8 1.0 valine 0.67 0.62 0.50 1.5 5.0 methionine 0.92 0.73 0.54 3.2 +cys 3.5 arginine 1.09 1.13 1.02 6.1 histidine 0.83 0.91 0.95 2.4 threonine 0.85 0.75 0.98 5.1 4.0 eaai 0.84 0.80 0.83 eaai = essential amino acid index; whole hen’s egg protein: adopted from paul and southgate (1976); fao/who provisional amino acid scoring pattern: fao/who (1973) 37research paper ayeloja, jimoh, uthman, shittu anguillaris and 1.92 recorded for o. niloticus (adeyeye et al. 2009). the biological value of heteroclarias ranged between 79.84 to 75.04. table 6 shows that the amino acid scored as compared to egg protein. the values obtained for smoked heteroclarias were found to be far lower than that of whole egg and it decreased with the increase of storage period. lysine had the highest amino acid score ranging from 1.37 to 1.38 g/100 g cp, while the values for tryptophan and valine were observed to be very low ranging between 0.47 to 0.96 g/100 g cp and 0.50 to 0.67 g/100g cp, respectively. the quality of the texture of smoked heteroclarias (table 7) reduced significantly (χ2 = 12.207, p≤0.01) with increased storage period. however, the taste panel observed no significant (χ2 = 1.628, 8.982, p>0.05) decrease in the odor and flavor of the fish during the storage period. conclusion this study established that smoked heteroclarias had good nutritional quality in terms of compositions, which decreased with the increase of storage at ambient temperature. minerals were abundant with highest ca followed by mg. glutamic acid was the most predominant amino acid and the non-essential amino acids and tryptophan was the least concentrated; while lysine was the most predominant essential amino acid and tryptophan was the least concentrated essential amino acid in the fish. this study established that heteroclarias could provide good concentration of amino acid as require for human. the ratio of eaa to neaa ranged between 0.86 and 0.93 and the predicted protein efficiency ratio (pper) obtained in this study was higher than many other fish species. the biological value of heteroclarias ranged between 79.84 and 75.04. its chemical score and teaa decreased with increase in storage time. however, its texture quality reduced significantly (χ2 = 12.207, p≤0.01) with increased storage period. references abraha b, admassu h, mahmud a, tsighe n, shui xw, fang y. (2018). effect of processing methods on nutritional and physico-chemical composition of fish: a review. moj food process technology 6(4): 376‒382. adeyeye sao, oyewole ob, obadina ao, omemu am, adeniran oe, oyedele ha, abayomi so. (2015). quality and safety assessment of traditional smoked fish from lagos state, nigeria. international journal of aquaculture 5(15): 1-9. adeyeye ei. (2009). amino acid composition of three species of nigerian fish: clarias anguillaris, oreochromis niloticus and cynoglossus senegalensis. journal of food chemistry 113:43-46. adeyemi ot, osilesi oo, onajobi f, adebawo o, oyedemi so, afolayan aj. (2013a). effect of processing on the proximate and mineral compositions of trachurus trachurus: a fish commonly consumed in nigeria. journal of emerging trends in engineering and applied sciences 4(3):378-385. adeyemi ot, osilesi oo, onajobi f, adebawo o, afolayan aj. (2013b). stability study of smoked fish, horse mackerel (trachurus traichurus) by different methods and storage at room temperature. african journal of biochemistry research 7(6): 98-106. akande gr. (1996). nutritional values of smoked clarias gariepinus from major markets in southwest, nigeria. global journal of science frontier research (d) 15(6): 33-34. aoac. (2000). official methods of analysis, 17th ed. aoac international, gaithersburg, maryland, usa. ayeloja aa. (2019). sensory quality of smoked clarias gariepinus (burchell, 1822) as affected by spices packaging methods. international journal of food properties 22(1): 704–13 ayeloja aa, george foa, jimoh wa, shittu mo, abdulsalami sa. (2018). microbial load on smoked fish commonly traded in ibadan, oyo state, nigeria journal of applied science and environmental management 22(4): 493-497. ayeloja aa, george foa, obasa so, sanni l o, ajayi aa. (2011a). effects of length of delay after slaughter (lodas) on raw catfish clarias gariepinus. journal of american science 7(6): 508-512. ayeloja aa, george foa, obasa so, sanni lo. (2011b). effect of post-slaughter time intervals on the quality of the african catfish, clarias gariepinus (burchell, 1822). american journal of food technology 6(9): 790-797. ayeloja a a, george foa, akinyemi aa and atanda oo. (2015). proximate and mineral composition of spiced smoked catfish clarias gariepinus (burchell, 1822). journal of agricultural science and environtable 7. effect of storage time on organoleptic quality (i.e. consumer preference) of smoked heteroclarias day 0 day 14 day 28 day 42 day 56 χ2 p-value odor 8.27 7.80 8.00 7.73 8.00 1.63 0.80 flavor 8.87 7.90 8.07 7.93 8.73 8.98 0.06 texture 9.33 8.00 8.00 7.93 8.33 12.21* 0.02 kruskal wallis test (χ2) is significant along the row p≤0.05. 38 squ journal of agricultural and marine sciences, 2020, volume 25, issue 2 effect of storage time on the quality of smoked hetroclarias ment 15(2): 68-74. daramola ja, fasakin ea, adeparusi eo. (2007). changes in physicochemical and sensory characteristics of smoke-dried fish species stored at ambient temperature. african journal of food, agriculture, nutrition and development 7(6): 1-16. ekelemu jk. (2010). differential growth patterns of clarias gariepinus, heterobranchus bidorsalis and hybrid heteroclarias fed commercially prepared diets. agriculture and biology journal of north america 1(4): 658-661. elshehawy sm, el-fatah gaa, mutwally hm. (2016). amino acids pattern and fatty acids composition of the most important fish species of saudi arabia. research & reviews: journal of food and dairy technology 4 (3): 27-36. heliene lr, porto ac, leal c, victor emf, gandhi r. (2016). evaluation of the chemical composition of fish species captured in the lower stretch of itapecuru river, maranhao, brazil. international journal of advances in agricultural & environmental engineering 3(1): 181-186. huss hh. (2004). assurance of sea food quality. fao of fisheries technical paper 334, food and agriculture organization. jinadasa bk. (2014). determination of quality of marine fishes based on total volatile nitrogen test (tvn). nature and science 12(5): 106-107. khanipour aa, mirzakhani n. (2013). effect of different packaging methods on shelf life of hot smoked rainbow trout (oncorhynchus mykiss) during storage at 0-2ºc. iranian journal of fisheries sciences 12(3): 620-628. kirk rs, sawyer r. (1991). nitrogen determination. pearson’s composition and analysis of foods. longman scientific publisher: london, p. 29-36. marwa mm. (2015). effects of freezing storage on the biochemical composition in muscles of saurida undosquamis (richardson, 1848) comparing with imported frozen. international journal of fisheries and aquatic studies 3(2): 295-299. mosarrat nn, gulshan al, subhash cc, farzana bf, mohajira b. (2016). shelf-life quality of smoke-dried freshwater sis fish; chapila (gudusia chapra, hamilton-buchanan; 1822) kaika (xenentodon cancila, hamilton-buchanan; 1822) and baim (mastacembelus pancalus, hamilton-buchanan; 1822) stored at laboratory condition (26-31oc). journal of agriculture and veterinary science 9(3): 23-32. obe bw. (2014). growth performance and nutrient utilization of catfish hybrid (heterobranchus bidorsalis x clarias gariepinus) fed fermented sorghum (sorghum bicolor) waste meal diets. international journal of applied science and technology 4(3): 130-136. owodeinde fg, ndimele pe, fakoya ka, adewolu ma, anetekhai ma. (2018). growth performances of clarias gariepinus, heterobranchus bidorsalis and their hybrid (heteroclarias) in earthen ponds in badagry, southwest, nigeria department of fisheries, faculty of science, lagos state university. nigerian journal of fisheries and aquaculture 5(2): 122–131. pawar sm, sonawane sr. (2013). fish muscle protein highest source of energy. international journal of biodiversity and conservation 5(7): 433–435. pinto jf. (2007). feeding interruption and quality of cultured gilthead sea bream. food chemistry journal 100: 1504-1510. ravichandran s, kumaravel k, florence pe. (2011). nutritive composition of some edible fin fishes. international journal of zoological research 7: 241–251. serkan k, sevim k, bekir t. (2010). the effect of storage temperature on the chemical and sensorial quality of hot smoked atlantic bonito (sardasarda, bloch, 1838) packed in aluminum foil. turkish journal of fisheries and aquatic science 10: 439-443. shiming p, chao c, zhaohong s, lu w. (2013). amino acid and fatty acid composition of the muscle tissue of yellowfin tuna (thunnus albacares) and bigeye tuna (thunnus obesus). journal of food and nutrition research 1(4): 42-45. zhao f, zhuang p, song c, shi zh, zhang lz. (2010). amino acid and fatty acid compositions and nutritional quality of muscle in the pomfret, pampus punctatissimus. journal of food chemistry 118(2): 224-227. zulema cp. (2014). chemical composition of fish and fishery products. in: handbook of food chemistry, springer-verlag, berlin heidelberg. p. 128. research papers journal of agricultural and marine sciences 2023, 28(2): 28–37 doi: 10.53541/jams.vol28iss2pp28-37 received 3 march 2022 accepted 16 may 2023 حتليل جنس العاملني يف جمال ممارسات إدارة إنتاج دجاج التسمني يف والية دلتا، نيجرياي ثيوفيلوس مييب غبيغيب وأكورونكو شيناغوروم بريل * gender analysis of practitioners of broiler production management practices in delta state, nigeria theophilus miebi gbigbi and pearl chinagorom e-okoronkwo* theophilus miebi gbigbi( ) gbigbitheophilusmiebi@yahoo.com, department of agricultural economics, delta state university, abraka delta state, nigeria introduction globally, it has been proven that the animal food source most especially the broiler chicken (gal-lus gallus domesticus) which connotes birds grown for the goal of meat is very essential for normal mental and physical development of man (beutler, 2007). broiler chicken are very cost-effective and also widely accepted because of the nutritional and organoleptic properties, such as amino acids, fats and oil and vitamins (ugwu, 1990). the broiler rearing provides a means through which transformation can be achieved in animal protein consumption which is seen in the expansion of smallholder broiler farmers in the country at large. the subsequent endorsement from institutions like world health organization (who) has set a tremendous pace in the development of poultry industry which is the forerunner of other agri-based industries. in nigeria, poverty has led to the dependence of over 70% of the rural population on poultry for their livelihoods and economic survival (united nations, 2007), abstract. despite women’s substantial participation and productive inputs, their role in broiler production has often being underestimated or ignored by the society. this study was conducted to provide information on the gap that existed on the management technologies observed by the male and female disparity. this study examined gender analysis of broiler production management practices, profitability and constraints. a sample size of 104 respondents was used by the multistage sampling procedure. data was analyzed using descriptive and inferential statistics. the major findings were, the mean age for the males and females were 45 years and 43 years with majority of the females acquiring higher education than the males. the stock size for the male and female practitioners was 185 birds and 327 birds with mean income of ₦122, 880.86 and ₦172, 221.72. there was insufficient access to extension services and credit by the practitioners. the predominant management practices adopted were vaccinated by male (93.2 %) and female (100.0%); feeding practices male (84.7%) and female (100.0%) whereas, biosecurity and waste recycle were least adopted. respondents’ best reasons for adopting of broiler management practices increased profits of male (96.6%) and female (95.6%). the male and female respondents realized a profit of ₦340, 154.24 and ₦433, 991.01 respectively. the most serious constraint experienced by both was price fluctuation (male = 86.4% and female =80.0%). the results showed relationship between the farming experience, extension access, insurance and bird age and adoption. we concluded that adopting the identified broiler management practices by the practitioners could improve production and income. this study revealed that females performed better than males in the adoption of broiler management technologies. the provision of credit, extension and insurance services and improvement in management practices can address the serious constraints faced by broiler production practitioners. keywords: broiler practitioners, production, adoption, gender, management practices امللخــص: علــى الرغــم مــن مشــاركة املــرأة الكبــرية ومدخالهتــا اإلنتاجيــة، فــإن دورهــا يف إنتــاج دجــاج التســمني غالًبــا مــا يتــم التقليــل مــن شــأنه أو جتاهلــه مــن قبــل اجملتمــع. أجريــت هــذه الدراســة لتوفــري معلومــات عــن الفجــوة املوجــودة يف تقنيــات اإلدارة والــي لوحظــت مــن خــالل التبايــن بــني الذكــور واإلانث. يف هــذه الدراســة مت حتليــل جنــس العاملــني يف جمــال ممارســات إدارة إنتــاج دجــاج التســمني وكذلــك الرحبيــة والقيــود. مت اســتخدام حجــم عينــة مــن 104 مســتجيبني مــن خــالل إجــراء أخــذ العينــات متعــدد املراحــل. مت حتليــل البيــاانت ابســتخدام اإلحصــاء الوصفــي واالســتنتاجي. أشــارت النتائــج الرئيســية للدراســة أن متوســط العمــر للذكــور واإلانث 45 ســنة و43 ســنة علــى التــوايل مــع حصــول غالبيــة اإلانث علــى تعليــم أعلــى مــن الذكــور. كان حجــم املخــزون للممارســني مــن الذكــور واإلانث 185 طائــرًا و327 طائــرًا مبتوســط دخــل ₦ 122 و880.86 و ₦ 172 و221.72 علــى التــوايل. مل يكــن هنــاك وصــول كاف إىل خدمــات اإلرشــاد واالئتمــان مــن قبــل املمارســني. وجــدت الدراســة أن املمارســات اإلداريــة الســائدة املتبعــة حتصــني الذكــور )٪93.2( واإلانث )٪100.0(، أمــا ابلنســبة ملمارســات التغذيــة ذكــور )٪84.7( وإانث )٪100.0( يف حــني أن األمــن احليــوي وإعــادة تدويــر النفاايت كانت أقل املمارســات إتباعا. أشــارت الدراســة اىل أن من أفضل أســباب تبين ممارســات إدارة دجاج التســمني من قبل عينة الدراســة هو زايدة أرابح الذكور )٪96.6( واإلانث )٪95.6(. حيث حقق املشاركون يف الدراسة من الذكور واإلانث رحًبا مبقدار ₦ 340 و154.24 و ₦ 433 و 991.01 على التوايل. كان أخطر املعوقات الي واجهها العاملني هو تقلب األسعار )الذكور = ٪86.4 واإلانث = ٪80.0(. أظهرت النتائج العالقة بني جتربة تربية الدجاج والوصول اىل اإلرشــاد والتأمني وعمر الطيور والتبين. خلصنا إىل أن تبين ممارســات إدارة دجاج التســمني احملددة من قبل املمارسني ميكن أن حيسن اإلنتاج والدخل. أظهرت هذه الدراسة أن أداء اإلانث كان أفضل من أداء الذكور يف تبين تقنيات إدارة دجاج التسمني. ميكن أن يــؤدي توفــري خدمــات االئتمــان واإلرشــاد والتأمــني وحتســني ممارســات اإلدارة إىل معاجلــة القيــود اخلطــرية الــي يواجههــا ممارســو إنتــاج الدجــاج الالحــم. الكلمات املفتاحية: ممارسي تربية الدواجن، اإلنتاج، التبين، اجلنس، ممارسات اإلدارة 29research papers gbigbi, e-okoronkwo hence making the broiler enterprise a very good source of income for both male and female farmers because of the huge market share it has. again, poultry plays a profound role as an instrument for curbing poverty, improving livelihoods and reducing unemployment in communities, societies and the country at large (makenete et al., 2008). with the increasing number of males and females in the broiler production enterprise, the future prospects of expanding the production for more profit is very necessary. gender is not just about women, it pertain to men and women. gender denotes to social, political economic and cultural characteristics and chances that are related with being male and female (ezedinma and okechukwu, 2013). in the broiler production process, the farmer is concerned with efficiency in the use of inputs to achieve either cost minimization, output maximization and profit maximization or a combination of the three objectives (rubina and haisnan, 2011). over the past decades, an awareness on gender issues in the world’s development and progress has increased (rahman et al., 2007). there has been an increasing recognition of women’s contributions to agricultural production particularly broiler production today. women are critical actors in the management of poultry resources and most farms activity in all parts of the world while men drift to the cities searching for paid employment. it was reported that 60-80% of agrarian activities which women engaged-in differ from one region to another for different farm-based activities (egwuma et al., 2018). the target of every entrepreneur is to attain the highest possible profit and the potential for profitability is hinged on the fact that nigeria still imports poultry products such as frozen foods to make up for the short fall in demand (gueye, 2002). it is evidently clear that with the right knowledge of investing in broiler production and the ability of the farmer to engage in proper management practices, there is room for an impressive yield in profits for the farmer. despite the profitability and worth of the poultry business, particularly the broiler chicken in the nation’s economy, broiler farms still face challenges which are inimical to the development of the firm. this challenge is due to inefficient management conducted on the farms which has resulted to drastic loss of birds (high bird mortality), diseases and parasites, poor feeding and housing preparation and also marketing problems thereby reducing the level of protein consumption by the population, reduced sustainability and even the living standard amongst farmers and their households. hence, management is important to sustain poultry production (alabi and aruna, 2006). in nigeria, among array of livestock farming engaged by women in most rural areas, broiler production stands prominent and has received government reassurances through innovation dissemination, source of inputs and technical assistance on broiler production provided by adp extension arm of ministry of agriculture of diverse states of nigeria (nwaru et al., 2010). there is therefore the need to streamline any existing disparity in relationship between men and women in their involvements in farm activities and decision making process on farms. good management, such as proper housing preparation, routine health practices and growing the standard of cleanliness which involves biosecurity practices, medication and mitigation should be conceded to attain sustainable protein consumption, reduction in poverty and improvement in the standard of living of the producers (rahman et al., 2007). despite women’s substantial participation and productive inputs, their role in livestock production has often being underestimated or, ignored by the society (ifad, 2007). most importantly the female gender constitutes the most user groups collecting the poultry produce, such as eggs and meat in order to tackle the subsistent needs of their families. therefore, the practice of sustainable poultry management is not complete without their participation. however, government policies and management strategies have remained blind and have also ignored the intimate relationship between gender and poultry management, hence women continue to agonize and their drudgery increases (gbigbi et al., 2010). gbigbi (2017) investigated the factors affecting profit efficiency of broiler producers in nigeria. a mean profit efficiency of 65% was recorded in the area of study. the factors which influenced the profit efficiency of broiler production were gender, age, experience and training while cooperative membership exerted a significant effect on their profit inefficiency level at 1%. ezeh et al. (2012) asserted that level of education is related to the efficient management of broiler farms, such as light enclosure, vaccination, medication and feeding can bring about significant improvement in productivity of broiler production. ovharhe et al. (2020) positioned that most family members are involved as work force in backyard poultry farm business and that men, women and progenies play designated roles in the poultry investments. this contributes to food security and income generation. having appraised the gaps in the poultry sector and agricultural business, it became pertinent to undertake a study on the examination of the gender analysis of practitioners of broiler production management practices in delta state, nigeria. this study focused on some relevant objectives, such as to: (i) describe the socio-economic features of male and female, (ii) identify the various broiler management practices, (iii) examine the factors influencing the men and women decision to adopt broiler management practices, (iv) determine the major constraints militating against broiler management practices, (v) identify the reasons for adopting the broiler management practices and, and (vi) determine the costs and returns of broiler production by gender. the research hypothesis: there 30 squ journal of agricultural and marine sciences, 2023, volume 28, issue 2 gender analysis of practitioners of broiler production management practices in delta state, nigeria is no significant difference in adoption level of management practices between the male and female categories. materials and methods many poultry farms involved in broiler production activities are located in clusters of communities in okpe local government, delta state. based upon this, it became appropriate to choose it for the study. delta state geographical coordinates are 5o26n, 5o57e and 5.433on 5.9 50oe (npc, 2006). a multistage sampling procedure was utilized to draw respondents for the study. firstly, purposive sampling of fifteen communities namely ohore, ometa, orerokpe, oku-uvo, adeje, okuokoko, meredje, evrieyen, otemewo, jeddo, obokodo, ughoton, adagbarassa, egborode and oha. in the second stage the respondents were randomly and proportionally selected based on the size of farmers’ involvement in each community. in all, a total of 104 broiler farmers were selected from a large population of 346 broiler farmers (table 1). data collection primary data was used in the study. it was collected using well-structured questionnaire and interview schedule, which was administered to the broiler producers. the questionnaire collected information on these variables which included management, cost and returns of the broiler business, constraints and the socioeconomic characteristics of the farmers. method of data analysis: data for the study was analyzed with descriptive and inferential statistics. objectives (i), (ii), (iii) and (v) was realized with descriptive statistics such as mean, frequency distribution and percentage with objective (iii) was achieved with multiple regression model, objective (vii) was achieved with the cost and returns analysis. model specification the implicit specification of the model was given as: y = f (x1, x2, x3 ----------xn). the explicit form of the model was given as: y = b0 + b1 x1 + b2 x2 + b3 x3 + b4 x4 + b5 x5 + b6 x6 + e where y is percentage of the index of management practices, x1 is age (years), x2 is educational level (years), x3 is family size, x4 is labour (man-days), x5 is experience (years), x6 is credit accessibility (dummy = 1 if yes, otherwise = 0), x7 is extension services access (dummy = 1 if yes, otherwise = 0), x8 is insurance use (dummy = 1 if yes, otherwise = 0), x10 is stock size (number of birds), x11 is age of birds (weeks), x12 is mortality rate (%), b0 is intercept, b1-b12 is coefficient of parameter estimates, and e is error term. results and discussion results in table 2 reveals that the predominant age for men was 25-37 years, while the women ranged from 38-49 years. they were followed by those between 38 and 49 years having 25.5% for male and the females 25-37 years respectively. the mean age of the males was 45 years and 43 years for women hence they are vibrant to engage in broiler management practices. educational attainment at tertiary level was 44.1% for male and 66.7% for female. this shows that the female attained more tertiary educational level than the male. there is needed for education to unlock the potential of farmers to make them risk averse and improves the adoptability of best practices (fao, 2008). table 1. result of random sampling of respondents community farmers’ population respondents sampled (30%) ohore 19 6 ometa 16 5 oreokpe 44 13 oku-uvo 22 7 adeje 16 5 okuokoko 25 8 meredje 44 13 evrieyen 9 3 otomewo 19 6 jeddo 25 8 gbokodo 41 9 ughoton 13 4 adagbarassa 9 3 eghorode 25 8 oha 19 6 total = 15 346 104 31research papers gbigbi, e-okoronkwo table 2. socioeconomic attributes of broiler producers variable frequency (n =59) frequency(n=45) age (years) male category female category 25 – 37 21 (35.7) 13 (28.8) 38 – 49 15 (25.5) 21 (46.5) 50 – 57 13 (22.1) 8 (17.7) 58 – 67 10 (15.3 3 (6.6) mean 45 years 43 years educational status no formal education 10 (16.9) 8 (17.8) primary education 8 (13.6) 1 (2.2) secondary education 15 (25.4) 6 (13.3) tertiary education 26 (44.1) 30 (66.7) marital status married 45 (76.3) 34 (75.6) single 12 (20.3) 4 (8.9) divorced 0 3 (6.7) widowed 0 4 (8.9) widower 2(3.4) 0 farming experience (years) 1-9 42 (71.2) 44 (97.7) 10-17 10 (17) 1 (2.2) 18-30 7 (11.9) 0 (0) mean 3 7 stock size 15 – 60 15 (25.5) 3 (6.67) 70 – 125 11 (18.7) 2 (4.44) 130 – 300 11 (18.7) 3 (6.67) 330 – 650 12 (20.4) 34 (75.6) 700 – 2000 10 (17) 3 (6,67) mean 185 birds 327 birds income (₦) <50,000 6 (10.2) 2 (4.4) 50,000 – 99,999 18 (30.5) 6 (13.3) 100,000 – 199,999 30 (50.4) 21 (46.7) 200,000 – 299,999 5(8.5) 15 (33.3) 300,000 and above 0 (0) 1 (2.2) mean 122880.86 172221.72 cooperative membership yes 16 (27.1) 40 (88.9) no 43 (72.9) 5 (11.1) extension activities yes 12 (20.3) 16 (35.6) no 47 (79.7) 33 (73.3) farm insurance practice yes 2 (3.4) 3 (6.7) no 57 (96.6) 43 (95.6) household size 1-3 15 (25.4) 11 (24.4) 4-6 41 (69.5) 27 (60.3) 7-9 3 (5.1) 7 (15.6) mean 5 4 credit access yes 23(39.0) 7(15.6) no 36(61.0) 38(84.4) 32 squ journal of agricultural and marine sciences, 2023, volume 28, issue 2 gender analysis of practitioners of broiler production management practices in delta state, nigeria the result showed that 76.3% of male respondents were married while the single and widower accounted for 23.7%. for the female respondents, 75.6% and 8.9% accounted for those who were married and single. only 15.6% of them were divorced and widowed. the high percentage of married respondents has implications for household size which in turn influences the broiler management practices. ovharhe et al. (2020) opined that most backyard poultry farmers were married with small household size which was advantageous for cheap labour in small scale poultry farming. the result revealed that 71.2% of the male respondents had experience of 1-9 years followed by 17% who had between 10-17 years of experience and 11.9% had 18-30 years of experience. on the other hand, 97.7% of female respondents had 1-9 years of experience as against the male respondents and the least years of farming experience of respondents was 2.2% having 10-17 years of experience. the mean farming experience age of male and female respondents were three and seven years respectively. this suggests that female respondents had more farming experience because they engaged more of their time on poultry farming, which gave them more ability to combine resources in an optimal manner, given the available resources (nhemachama and hassan, 2007). the finding in this study indicated that 25.5% of male respondents had stock size of 15-60 birds followed by 20.4% and 18.7% having 330-650 and 70-125 birds, similarly another 18.7% had 130-300 birds. also 17% the least, had stock size between 700-2000 birds. while, the female respondents had (28.8%) stock size of 15-60 birds followed closely by 28.8% having 130-300 birds. about 26.6% of the female respondents had 70-125 birds. while only 6.7% had 700-2000 birds. the implication of this result is that the female respondents participated actively in carrying out these management practices which in turn increased their profit margin for expansion or increase in stock size. the finding revealed that those who earned less than ₦50,000 were 4.4% for the female respondents while the male respondents were 10.2%. those who earned ₦50,000 to ₦99,999 were 13.3% of the female respondents whereas the proportion of male respondents earning the same amount was 30.5%. however, those earning ₦100,000₦199,999 were having 46.7% for the female respondents and the male respondents was (50.4%) respectively. moreover, those who earned ₦200,000 to ₦300,000 and above in the female respondents are 35.5% while the male respondents 8.5% in this category. the mean income of the female respondents was ₦172,221.72 and ₦ 122,880.86 for the male respondents. this was not surprising because the female stock more birds than male. ovharhe and gbigbi (2016) reported a similar average income level per annum of poultry producers in fadama iii project in delta state of nigeria. respondents’ male (55.9%) and female (88.9%) belong to cooperative societies in gender disaggregation. this is obvious since more female are seeking for investment capital from cooperative which is a cheaper source than formal banking bureaucracy. about 20.3 percent of male (20.3%) and 35.6% of female had contact to extension workers on monthly basis. ovharhe et al. (2020) reported about the poor extension outreach in delta state. respondents’ male (3.4%) and female (6.7%) belong to farm insurance bodies. this result corroborate gbigbi and ikechukwuka (2020) findings on accessibility to insurance in nigeria. this is very poor. it calls for awareness creation in the broiler production business. the predominant household size range between 4-6 persons for both categories. this was followed by those who had between 1-3 family members. but still about 5.1% of the male respondents had household size of 7-9 persons as against 15.6% for the females. the average household size for both the males and females was 5 persons and 4 persons respectively. moderate household size was reported in the region. the result showed that more males table 3. management practices adopted by respondents adoptable management practices male female n = 59 responses (%) n = 45 responses (%) vaccination 55 93.2 45 100.0 feeding practices 50 84.7 45 100.0 record keeping 52 88.1 42 93.3 disease management 48 81.4 41 91.1 marketing system 48 81.4 37 82.2 stocking density 36 61.0 28 62.2 litter management 51 86.4 29 64.4 housing management 42 71.2 29 64.4 light management 36 61.0 23 51.1 biosecurity 23 39.0* 17 37.8* waste recycle 25 42.4* 16 35.6* source: field survey data, 2019 *below average implies low adoption rate. multiple responses 33research papers gbigbi, e-okoronkwo (39%) had access to credits than their female counterpart (15.6%). this is congruent with gbigbi and ikechukwuka (2020) that only a negligible people obtained credit. this could have negative implications on effective management of practices. management practices utilized by respondents entries in table 3 shows the different types of broiler management practices of respondents disaggregated by gender. the predominant management practices adopted amongst others were vaccination by male (93.2 %) and female (100.0%); feeding practices male (84.7%) and female (100.0%) respectively. the practice of biosecurity and waste recycle has not gained ground in the location of study for both the male and female broiler farmers. the results disclosed that the male folks adopted more of the broiler management technologies in some areas than their female counterparts and vice versa. reasons for adopting of broiler management practices as disaggregated by gender, result in table 4 shows that respondents’ best reasons for adopting of broiler management practices were increase profits by 96.6% male table 4. reasons for adoption of management practices by respondents reasons male female n = 59 responses (%) n = 45 responses (%) increase profits 57 96.6 43 95.6 efficient financial management 49 83.1 41 91.1 early recognition, prevention and treatment of disease. 46 78.0 40 88.9 efficient diet of birds to increase production 47 79.7 39 86.7 reduce cost of production 50 84.7 37 82.2 efficient physical management 29 49.2 32 71.1 reliability in price and quality of feed 27 45.8 29 66.7 better organization of stocking 23 39.0* 22 48.9* source: field survey data, 2019. *below average implies low reason table 5. cost and returns of respondents items male (mean) ₦ female (mean) ₦ day old chicks 13587.97 21236.27 feeds 146832.20 203993.22 medication 11501.44 16387.71 veterinary services 7250.59 8886.0169 transportation 1367.80 1705.08 labour 14161.02 15359.32 water 957.63 786.44 equipment 39209.32 60719.15 bulbs 7853.39 12337.46 electricity 1623.73 1133.90 wheel barrow 933.90 1155.25 stores 1033.90 907.62 shovels 1890.68 3748.31 hoes 928.81 1337.29 cutlass 3040.68 4773.56 total cost 252173.05 354466.61 number of birds sold 587994.92 782237.29 poultry droppings sold 4349.32 6067.80 total revenue 592344.24 788305.10 profit 340154.24 433991.01 source: field survey data, 2019. 34 squ journal of agricultural and marine sciences, 2023, volume 28, issue 2 gender analysis of practitioners of broiler production management practices in delta state, nigeria and 95.6% female. while the lowest reasons were better organization of stocking by 39% male and 48.9% female. this infers that poultry producers do not have issues with stock arrangements. cost and returns analysis the result (table 5) showed that the total revenues of the male and female respondents were ₦592, 344.24 and ₦788, 305.10 respectively and the total cost of production were ₦252, 173.05 for the male respondents and ₦354, 466.61 for the female respondents. however, the female and male respondents had profits of ₦340, 154.24 and. ₦433, 991.01 separately. the implication of this result indicates that the female earned more compared to their male counterparts in the study area. this findings is different from gbigbi (2017) that male farmers income per annum were higher that female.in nigeria. constraints faced by broiler farmers for the male and female gender, the most serious constraints experienced were the problem of price fluctuation (86.4% and 80.0%), financial difficulty (71.2% and 80.0%), predators attack (78.0% and 77.8%), losses due to viral diseases (72.9% and 84.4%), and lack of facilities (66.1% and 64.4%) respectively. the less serious constraints to both were malnutrition, inadequate knowledge of vaccination, lack of veterinary services, high interest rate and inadequate marketing facilities. hence they could not affect the level of adoption of management practices by both categories of respondents. factors influencing adoption of broiler management practices the criteria for selecting the lead equation were number of significant variables, magnitude of r-square and table 6. constraints faced by the respondents (multiple responses) perceived constraints male female n = 59 responses (%) n = 45 responses (%) price fluctuation 51 86.4 36 80.0 financial difficulty 42 71.2 36 80.0 problem of predators 46 78.0 35 77.8 loss due viral disease 43 72.9 38 84.4 problem of ectoparasites 39 66.1 36 80.0 lack of facilities 39 66.1 29 64.4 problem of spoilage 38 64.4 34 75.6 lack of technique 34 57.6 29 64.4 inadequate marketing facilities 25 42.4* 15 33.3* inadequate knowledge of vaccination 20 33.9* 19 42.2* malnutrition 28 47.5* 21 46.7* lack of veterinary services 23 39.0* 16 35.6* high interest rate 28 47.5* 21 46.7* source: field survey data, 2019. *below average implies less serious constraints table 7. factors influencing adoption of broiler management practices (male) variables coef. std. err. t age -0.037113 0.0231361 -1.60 educational qualification 0.0470147 0.0209786 2.24** stocksize 0.386497 0.0191869 2.01** farming experience 0.0095106 0.0155625 0.61 house hold size 0.000897 0.024067 0.04 labour used in man-days 0.0082348 0.0226344 0.36 mortality rate -0.0146033 0.0166115 -0.88 credit access -0.034495 0.0233975 -1.47 extension access 0.423123 0.0179987 2.35** farm insurance 0.0428668 0.0238195 1.80* bird age 0.3734668 0.0188023 19.86** _cons 0.0756044 0.1194828 0.63 source: field survey data, 2019. **, * significant at 5% and 10% 35research papers gbigbi, e-okoronkwo a priori expectation. the exponential function was chosen as the lead equation for these criteria for the male respondents and double log function was chosen as the lead equation for the criteria of the female respondents and double log for both gender pooled regression (table 7). the results presented for the male respondents includes education, stock size, extension access, insurance and age of birds were significant. educational attainment was positive and significant at 5% probability level. this implies that increase in educational level can lead to a corresponding increase in the adoption of broiler management technologies. this means that farmers with higher educational attainment would prefer more adoption of management practices in order to enhance profit of the farm. and this is in accordance with the a-priori expectation. the coefficient of stock size was positive and significant. this means that a unit increase in stock size will leading to an increase in the adoption of broiler management practices. the coefficient of the access to extension services had a positive significant relationship with adoption of broiler management practices. this implies that a unit increase in access to extension services can lead to a unit increase in the adoption of broiler management practices. the coefficient of insurance was positive and significant. this suggest that a unit increase in insurance use can lead to a corresponding increase in the adoption of broiler management practices. the coefficient of the bird age was positive and statistically significant at 1% probability level. this means that increase in bird age will lead to a corresponding increase in the adoption of broiler management practices. the coefficients for farming experience was significant at 5% level and positively affected the level of adoption of broiler management practices of female respondents. the positive coefficient of farming experience of the female respondents implies that any increase in farming experience will result in increased adoption of broiler management practices by the farmers respectivetable 8. factors influencing adoption of management practices (female) variables coef. std. err. t age -0.0741208 0.0397425 -1.87* educational qualification -0.217197 0.2377444 -0.91 stocksize 0.0112116 0.076606 0.15 farming experience 0.5120179 0.1667688 3.07** household size 0.0045498 0.094551 0.05 labour used in man-days 0.0710373 0.0803996 0.88 mortality rate -0.0270327 0.0834433 -0.32 credit access 0.1717716 0.081196 2.12** extension access 0.1919735 0.1753499 1.09 farm insurance 0.2391126 0.0787231 3.04** bird age 0.6228541 0.0963497 6.46** _cons 0.671355 0.3935401 1.71 source: field survey data, 2019. **, * significant at 5% and 10% table 9. factors influencing adoption of management practices (female) variables coef. std. err. t age -0.0143 0.0343 -0.42 educational qualification -0.1179 0.1602 -0.74 stock size 0.0354 0.0965 0.37 farming experience 0.2833 0.1045 2.71** house hold size 0.0376 0.0719 0.52 labour used in man-days -0.0686 0.0806 -0.85 mortality rate 0.0319 0.0828 0.39 credit access 0.0840 0.0726 1.16 extension access 3.4949 0.1483 23.6*** farm insurance 2.6341 0.0794 33.2*** bird age 0.9167 0.0842 10.88** _cons 0.6143 0.2825 2.17 **, * significant at 5% and 10% 36 squ journal of agricultural and marine sciences, 2023, volume 28, issue 2 gender analysis of practitioners of broiler production management practices in delta state, nigeria ly. as stated by bassey and okon, (2008), experience has been found to enhance the use of improved practices. the coefficient of age was negative and significant as 10% probability level. this implies that increase in age of respondent will lead to a decrease in the adoption of broiler management practices. the coefficient of credit access was positively signed and significant at 5% level of probability. this depicts that farmers with more access to credit had increased probability of adoption of broiler management practices in the study area. the coefficient of insurance was positive and significant at 5% probability level. this suggest that increase in insurance use will lead to an increase in adoption of broiler management practices in the study area. the coefficient of bird age was positively significant at 1% probability level. this means increase in bird age will lead to the same increase in the adoption of broiler management practices by the female folks in the study area. factors influencing adoption of broiler management practices (pooled result) the pooled result for male and female respondents showed that only farming experience, extension access, insurance and bird age were significant in influencing adoption of broiler management practices. the coefficients for farming experience exerted a positively significant relationship in the level of adoption of the male and female respondents at 5% respectively. this implies that farming experience can result in increased adoption of broiler management practices. this finding support the findings of gbigbi et al.(2010) respectively who stated that highly experienced farmers are known to have accumulated enough knowledge through several years of trial and error. the coefficient of access to extension services was positive and significant at 5% probability level. this implies that a unit increase in access to extension services can lead to corresponding increase in adoption of broiler management practices. the coefficient of insurance use was positive and significant at 5% probability level. this implies that a unit increase in insurance use will lead to a corresponding increase in the adoption of broiler management practices. the coefficient of bird age was positive and highly statistically significant at 1% probability level meaning that a unit increase in bird age will lead to the same increase in the adoption of broiler management practices. conclusion based on evidence from the study, it was concluded that the adoption of broiler management practices was carried out by female respondents than the male respondents in the areas of cooperative membership, access to fund and profit from business. broiler farmers showed the best reasons for adoption of management practices and increased profitability by both male and female. on gender disaggregation, performances were closely high in the use of adoptable practices such as vaccination, feeding equipment, proper record keeping, stocking density, litter management, housing management and disease management. the least adopted were biosecurity and waste recycle which are yet to gain ground. one of the most serious constraints was financial difficulty. besides, since identified constraints were manageable, with the adoption of improved broiler management practices, poultry farmers’ living standard would be positively impacted in delta state, nigeria. based on the finding of the study, the following recommendation were made: (i) biosecurity measures should be taken in order to prevent the introduction and the spread of disease in a poultry flock. as this was seen to be least adopted amongst other management practices. (ii) extension services should be made available in order to ensure continuous training on improved housing, feeding, predators and disease control. (iii) government should ensure that farmers have adequate access to credit facilities and also insurance policies in order to expand their farm for profits. references alabi ra, aruna mb. (2006). technical efficiency of family poultry production in niger-delta, nigeria. journal of central european agriculture 6(4): 531-538. beutler a. (2007). introduction to poultry production in saskatchewan, university of saskatchewan, saskatoon, saskatchewan, s7n 5a8. http://www.agriculture.gov.sk.ca. egwuma h, muhammed ae., ojeleye oa, oladimeji yu, hassan aa. (2018). adoption of recommended broiler management practices among women farmers in igabi local government area of kaduna state. nigerian journal of agricultural extension 19(4): 31-39. ezedinma c, okechukwu ru. 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(1990).the economics of small ruminant production by small holder farmers. unpublished ph. d. thesis, university of nigeria, nsukka, nigeria. united nations economic commission for africa. (2007). africa review report on agriculture and rural development. united nations economic commission for africa, addis ababa, nigeria. research paper journal of agricultural and marine sciences vol. 22 (1): 75-86 doi: received 20 mar 2016 accepted 25 dec 2016 *1 andreas buerkert. ( ) organic plant production & agroecosystems research in the tropics & subtropics (opats), university of kassel, steinstr. 19, 37213 witzenhausen, germany. email: tropcrops@ uni-kassel.de 2 animal husbandry in the tropics and subtropics, university of kassel and gorg-august-universität göttingen, steinstr. 19, 37213 witzenhausen, germany. introduction located at the eastern tip of the arabian penin-sula, the sultanate of oman is characterized by a hyperarid, subtropical climate with an annual precipitation of 0 to 240 mm compared to a potential evapotranspiration of >2000 mm (nagieb et al. 2004). under such harsh arid conditions, where water is the most limiting factor for plant production, the millennia-old mountain oases systems in northern oman have recently received considerable attention of scientists interested in the causes of the apparent sustainability of these agroecosystems (wichern et al. 2004; buerkert et al. 2005; golombek et al. 2007; siebert et al. 2007). one determinant of the bio-physical sustainability of omani irrigated oasis agriculture is the turnover of carbon (c) and plant nutrients (n, p, and k) for which solid field data from irrigated subtropical conditions are scarce. the existing studies reported high application rates of organic fertilizer to the man-made terrace soils leading to the apparent accumulation of organic c despite very high emanation of gaseous c and n (wichern et al. 2004; buerkert et al. 2010). soil organic mater (som) not only supplies energy and nutrients for macro-microorganisms and plants, it also contributes to soil textural stability and water holding capacity (nyberg et al. 2006) thereby also governing drainage, a key component in irrigated agricultural systems (luedeling et al. 2005). the turnover of som is heavily controlled by the characteristics of organic matter (c/n ratio and the concentration of lignin and secondary metabolites such as tannins), soil properties (ph, clay content, redox potential), macro and microorganism communities, crop management practices, and by environmental factors (kladivko et al. 1987; deng and tabatabai 2000; de neve and hofman 2002; agehara and warncke 2005; burgos et al. 2006). microbial activities are known to be altered by the water معدالت الكربون واملغذايت يف ثالث واحات جبلية بعمان حممد ناصر الرواحي1 ومارتينا مالباي1 وإفا شلغت2 وأندرياس بوركرت1* abstract. carbon (c) and nitrogen (n) fluxes of two cropping systems in three mountain oases of al jabal al-akhdar mountains of northern oman were determined in 2008/09 and 2009/10. these comprised garlic at ash sharayjah (1,900 m asl) and masayrat (1,030 m asl), pomegranate in ash sharayjah and qasha’ (1,640 m asl), and date palm groves at masayrat. goat manure was applied to garlic fields at 47 and 40 t dry matter (dm) ha-1 at ash sharayjah and 42 and 37 t dm ha-1 at masayrat. pomegranates at ash sharayjah and qasha’ received cattle dairy manure at 66 and 60 t dm ha-1 yr-1. annual total gaseous c losses varied from 20.9 to 61.2 t c ha-1 to which ch4-c contributed < 2%. total annual c surpluses were 12.5 t ha-1 in garlic fields at ash sharayjah, while c deficits of -5.5 t ha-1 were obtained at masayrat. annual c surpluses in pomegranate and date palm were 16.7, 7.5, and 1.7 t ha-1 in ash sharayjah, qasha’, and masayrat. date palm groves had total annual n surpluses of 1857 kg n ha-1 while pomegranate fields at ash sharayjah and qasha’ had annual surpluses of 1414 and 1500 kg n ha-1. keywords: al jabal al akhdar; gaseous emission; leaching; nutrient use efficiency; soil organic matter. امللخــص: مت حتديــد تدفقــات الكربــون والنيرتوجــن لنظامــي حمصولــن يف ثــالث واحــات جبليــة باجلبــل األخضــر مشــال عمــان يف عامــي 2009/2008 و 2010/2009. وقــد اشــتملت علــى حمصــول الثــوم يف منطقــة الشــرجية )1900 مــرت فــوق ســطح البحــر( واملســرات )1030 مــرت فــوق ســطح البحــر( وحمصــول الرمــان يف املنطقــة الشــرجية وقشــع )1640 فــوق ســطح البحــر( وبســاتن خنيــل التمــر يف املســرات. متــت إضافــة روث املاعــز علــى حقــول الثــوم مبعــدالت 47 و40 طــن مــن املــادة اجلافــة لــكل هكتــار يف الشــرجية و42 و37 طــن لــكل هكتــار يف املســرات. وقــد تلقــى حمصــول الرمــان يف الشــرجية وقشــع روث األبقــار مبعــدالت 66 و60 طنــا لــكل هكتــار يف الســنة. وقــد تراوحــت االنبعاثــات الكليــة مــن الغــازات الكربونيــة بــن 20.9 و 61.2 طــن مــن الكربــون للهكتــار وســامهت فيهــا امليثــان بنســبة تقــل عــن 2 يف املائــة. وبلغــت الفوائــض اإلمجاليــة الســنوية للكربــون 12.5 طنــا للهكتــار يف حقــول الثــوم يف الشــرجية، يف حــن مت احلصــول علــى عجــز للكربــون بلــغ 5.5 طنــا للهكتــار يف املســرات. يف حــن بلغــت الفوائــض الســنوية يف حماصيــل الرمــان وخنيــل التمــر 16.7 و7.5 و1.7 طنــا للهكتــار يف الشــرجية وقشــع واملســرات علــى التــوايل. وبلــغ إمجــايل فائــض خنيــل التمــر مــن النيرتوجــن 1857 كيلوغرامــا للهكتــار يف الســنة يف حــن أهنــا بلغــت 1414 و1500 كغــم للهكتــار يف حقــول الرمــان بالشــرجية وقشــع. الكلمات املفتاحية: اجلبل األخضر، االنبعاثات الغازية؛ الرشح، كفاءة استخدام املغذيات، املواد العضوية. carbon and nutrient balances in three mountain oases in northern oman mohamed nasser al-rawahi1, martina melapie1, eva schlecht2 and andreas buerkert1* 76 squ journal of agricultural and marine sciences, 2017, volume 22, issue 1 carbon and nutrient balances in three mountain oases in northern oman status in the soil leading to aerobic or anaerobic conditions, so that mineralization takes different pathways (franzluebbers 1999; cannovo et al. 2004). similarly, the presence of plants stimulates soil c and nutrient mineralization through root exudation (paré et al. 2000; zaman and chang 2004). in this study, we used a soil system balance approach (mikkelsen 2005) by (i) measuring horizontal inputs and outputs of c, n, p, and k, and (ii) quantifying fluxes of gaseous c and n emissions and leaching of mineral n and p on representative terraced fields in three oases of different altitudes in al jabal al akhdar mountains of northern oman. we hypothesized that c and nutrient turnover are faster in low altitude oases because of their higher ambient temperature and more frequent irrigation-dependent wet-dry cycles. table 1. soil chemical properties (0-0.15 m) of the selected fields (n = 6) before and after cropping cycles at the oases of ash sharayjah, masayrat ar ruwajah and qasha’, northen oman (2008-2009). oases crop year cropping cycle corg% n% p(olsen) p2o5 g/100g k mg/g ec ds/m ph caco3 ash sharayjah garlic 2009 beginning end 2.76 3.10 0.25 0.34 0.016 0.022 0.14 0.40 0.20 8.17 45.4 2010 beginning end 3.68 4.13 0.31 0.37 0.025 0.027 0.20 0.24 0.17 8.37 44.3 pomegranate 2009 beginning end 3.72 4.19 0.38 0.42 0.031 0.040 0.31 0.33 0.25 8.10 44.7 masayrat garlic 2009 beginning end 5.95 6.19 0.39 0.43 0.024 0.016 0.14 0.12 0.24 7.97 38.9 2010 beginning end 5.34 6.87 0.33 0.50 0.013 0.019 0.14 0.14 0.15 8.10 37.2 date palm 2009 beginning end 6.93 5.57 0.31 0.46 0.006 0.010 0.11 0.14 0.20 7.87 40.0 qasha’ pomegranate 2009 beginning end 2.41 2.87 0.30 0.35 0.014 0.022 0.16 0.17 0.16 8.26 36.6 figure 1. relief map based on a 100 m digital elevation model of al jabal al akhdar mountain in northern oman showing the location of the three study oases of ash sharayjah, qasha’, and masayrat ar ruwajah. map previously published in die erde 145(4): 162-174. 77research article al-rawahi, melapie, schlecht and buerkert materials and methods study area the study was carried out in the mountain oases of ash sharayjah (57°39’30”e, 23°04’10”n, 1900 m asl) located on the top of the wadi muaydin watershed, adjoining the edge of the sayq plateau in the northern hajar mountains of oman (fig. 1). just below this oasis is the village of qasha’ (57°39’50”e, 23°04’00”n, 1640 m asl), while the lowest oasis of the watershed is masayrat ar ruwajah (57°40’13”e, 23°02’37”n, 1030 m asl). the terraced agricultural area of ash sharayjah amounts to 14.4 ha and farmers irrigate their terraces with water from two springs that emerge near the neighboring oasis of al’ayn which was not included in this study. qasha’ contains 2.6 ha of terraced fields and obtains its water also from one of the springs of al’ayn, from where the water flows through a steep channel down to the oasis. in ash sharayjah and qasha’ crops are dominated by temperate species such as alfalfa (medicago sativa l.), garlic, oat (avena sativa l.), onion (allium cepa l.), wheat (triticum spp.) pomegranate, peach (prunus persica l.), and rose (rosa damascena l.) for rose water production. agriculture in masayrat (3.3 ha), in turn, is dominated by the annuals alfalfa (medicago sativa l.), maize (zea mays l.), sorghum (sorghum bicolor l. moench) and barley (hordeum vulgare l.), and the typical subtropical perennials date palm and lime (citrus aurantiifolia l. swingle). the three oases were selected due to their representative character reflecting altitudinal differences in the typical oasis agriculture of this hyperarid region (al-rawahi et al. 2014a). at each oasis, six representative fields were monitored during two growing seasons (2008/09-2009/10) for annual crops, and during one year for perennial crops in order to investigate fluxes of c and nutrients in typical oasis cropping systems. to this end garlic and pomegranate were selected in ash sharayjah, pomegranate in qasha’, and garlic and date palm in masayrat. soil properties and climatic conditions in each field three subsamples of the topsoil (0-0.15 m) were collected randomly, air dried, sieved to <2 mm, and pooled before and after each cropping cycle or once per year in the case of perennials. prior to determining particle size distribution in the soil using the sieve-pipette method (gee and bauder, 1986), organic matter and calcium carbonate (caco3) were destroyed by addition of hydrogen peroxide (h2o2) and hydrochloric acid (hcl), respectively. soil ph was measured in a 1:2.5 distilled water solution, whereas soil salinity was determined as electrical conductivity (ec) in a 1:10 water solution using a digital conductivity meter (gmh 3410, ghm-greisinger, regenstauf, germany). soil total c and n were measured by a thermal conductivity detector (vario max chn analyser, elementar analysensysteme gmbh, hanau, germany). the percentage of caco3 in soil was calculated using the volumetric calcimeter method (williams, 1948). soil p was extracted with sodium bicarbonate (nahco3) according to watanabe and olsen (1965) and measured by spectrophotometry (u-2000, hitachi ltd, tokyo, japan). for soil k analyses, samples were extracted with calcium acetate lactate and measured with a flame photometer (743 autocal, instrumentation laboratory co, lexington, ma, usa). to estimate micro-climate differences of the three oases reflecting the effect of the different elevations, air temperature and relative humidity were recorded at 30 min intervals throughout the research period using hobo-pro® climate loggers (onset, bourne, ma, usa). in addition to these devices full watchdog® weather stations (spectrum technologies inc., plainfield, il, usa) were placed at ash sharayjah and masayrat. sampling and analysis during harvest, garlic plant samples were collected from three 1m2 subsamples in each of the six fields at each location, weighted to obtain total fresh matter, sundried to constant weight for dm determination, and subsequently ground to <2 mm for c and nutrient analtable 2. total amounts of goat and cattle dairy manures and concentrations of nitrogen (n), phosphorus (p), potassium (k), and carbon (c) in that have been applied by farmers at the oases of ash sharayjah, qasha’, and masayrat ar ruwajah, al jabal al akhdar (northern oman) during the experimental period (2008-2009). crop oases type year total application t(dm)ha-1 n p k c mg g-1 % garlic sharayjah goat 2008/09 2009/10 47 40 22.5 24.0 3.0 4.4 13.6 13.5 46.42 42.82 garlic masayrat goat 2008/09 2009/10 42 37 25.2 22.3 3.3 4.5 10.2 14.3 50.20 36.32 pomegranate sharayjah cattle 2009 66 25.3 3.8 31.4 37.25 pomegranate qasha’ cattle 2009 60 25.2 7.1 26.2 28.53 date palm masayrat goat 2009 78 25.2 3.3 13.2 47.20 78 squ journal of agricultural and marine sciences, 2017, volume 22, issue 1 carbon and nutrient balances in three mountain oases in northern oman ysis. for pomegranate and date palms fruit yields were quantified for each tree. to this end the total number of pomegranate fruits was counted and classified into three categories: small, medium, and big. subsequently, average weight, volume, and nutrient concentrations were determined from representative samples to compute fruit yield per tree and surface area occupied. plant and manure samples were oven-dried at 60°c, ground (<2 mm), and analysed for c, n, p, and k as described above for the soil samples. for samples of irrigation water, of which frequency and amounts were determined regularly, dissolved organic carbon (doc) and total n were measured using a dimatec 100® chn-analyzer (dimatec analysentechnik gmbh, essen, germany). horizontal c and nutrient fluxes horizontal balances were determined by calculating the differences between the total amounts of c, n, p, and k in all inputs such as manures, mineral fertilizers (if applicable), planted garlic cloves, irrigation water, and rainfall and outputs such as crop removals at harvest including understory maize (wherever present in planted perennials) and fruit yields of pomegranate and date palm. in order to account for the contribution of roots to c balances, total amount of photosynthetic c was estimated for garlic and understory maize by multiplying total harvested dm by a factor of 1.4 based on the assumption that 30% of the total assimilated c was allocated to root dm and exudation (kuzyakov and domanski 2000). apparent nutrient use efficiency (nue) horizontal nutrient fluxes were used to calculate nue for the different cropping systems: (∑ nutrient output with harvest products / ∑ nutrient inputs) (hedlund et al. 2003). for perennial trees, understory maize was included in output calculations wherever present. vertical carbon and nutrient fluxes collection and analysis of leachates cumulative leaching losses of mineral n and p were quantified with mixed-bed ion-exchange resin cartridges (bischoff 2007; lang and kaupenjohann 2004; predotova et al. 2011). to this end pvc-cartridges were filled with a 2:3 mixture of anion-cation exchange resins and pure silica sand of 120–700 µm (majan glass co., sohar, oman; siegfried et al., 2011). for each cropping system, seven cartridges were buried in each of the selected fields below the rooting zone at 0.50 m depth and removed after each crop harvest or annually for pomegranate and date palm. after removal from the soil, the resin-sand mixture was separated horizontally into five layers to be able to determine a concentration gradient within each cartridge. from each layer, a subsample of 30  g was extracted eight times with 100 ml of 0.5m nacl by shaking for one hour followed by filtration into a plastic vial. subsequently, samples were analyzed for their concentration of leached nutrients with an icpaes (spectroflame, spectro gmbh, kleve, germany). time (months) a pr -0 8 m ay -0 8 ju n08 ju ly -0 8 a ug -0 8 s ep -0 8 o ct -0 8 n ov -0 8 d ec -0 8 ja n09 f eb -0 9 m ar -0 9 a pr -0 9 m ay -0 9 ju n09 ju ly -0 9 a ug -0 9 s ep -0 9 o ct -0 9 n ov -0 9 d ec -0 9 ja n10 f eb -1 0 m ar -1 0 a pr -1 0 m ay -1 0 ju n10 te m pe ra tu re ( ºc ) 0 10 20 30 40 ash sharayjah masayrat qasha' figure 2. mean monthly air temperatures recorded at the oases of ash sharayjah, qasha’, and masayrat ar ruwajah in northern oman during the research period. modified after data published in die erde 145(4):162-174. masayrat ar ruwajah time (months) a pr -0 8 m ay -0 8 ju n08 ju ly -0 8 a ug -0 8 s ep -0 8 o ct -0 8 n ov -0 8 d ec -0 8 ja n09 fe b09 m ar -0 9 a pr -0 9 m ay -0 9 ju n09 ju ly -0 9 a ug -0 9 s ep -0 9 o ct -0 9 n ov -0 9 d ec -0 9 ja n10 fe b10 m ar -1 0 a pr -1 0 m ay -1 0 ju n10 0 20 40 60 80 100 120 140 160 180 ash sharayjah p re ci pi ta tio n (m m ) 0 20 40 60 80 100 120 140 160 180 figure 3. average monthly precipitation (mm) recorded at the oases of ash sharayjah and masayrat ar ruwajah, al jabal al akhdar (oman) from april 2008 to june 2010. 79research article al-rawahi, melapie, schlecht and buerkert calculations of annual cumulative leaching losses of n and p were made following the approach described by siegfried et al. (2011). monitoring of gaseous c and n emissions on the same fields where leaching cartridges were installed, gaseous emissions of co2-c, ch4-c, nh3-n and table 3. annual horizontal inputs, outputs and partial balances of carbon (c), nitrogen (n), phosphorus (p), and potassium (k) for garlic, pomegranate, and date palm fields (n = 6) at the oases of ash sharayjah, qasha’, and masayrat ar ruwajah in northern oman (2008-2009). partial balances values with different superscript letters were significantly different (p<0.05, lsd). crop oases source input and output (kg·ha-1·yr-1) c n p k garlic sharayjah manure 38632 2001 317.2 1170.9 cloves (sowing) 16 1 0.2 1.5 irrigation water 41 57 0.0 0.3 rainfall 162 34 n.a n.a photosynthetic c 22771 total 61620 2093 317.4 1172.7 crop yield -16265 -1069 -191.1 -1486.2 partial balance 45355a 1024c 126.3cd -313.5c garlic masayrat manure 38132 1878 306.1 955.0 cloves (sowing) 16 1 0.2 1.4 irrigation water 121 103 0.0 0.5 rainfall 113 13 n.a n.a photosynthetic c 21963 total 60345 1995 306.3 956.9 crop yield -15688 -1011 -244.2 -1427.2 partial balance 44657a 984c 62.1d -470.3c pomegranate sharayjah manure 24728 1682 249.7 2084.9 irrigation water 33 46 0.0 0.2 rainfall 138 29 n.a n.a photosynthetic c* 7536 total 32435 1757 249.7 2085.1 crop yield -2238 -39 -7.8 -70.8 understory maize -5383 -209 -46.0 -308.4 partial balance 24814b 1509b 195.9bc 1705.9a pomegranate qasha’ manure 17237 1524 430.7 1585.7 irrigation water 58 62 0.0 0.2 rainfall 138 29 n.a n.a photosynthetic c n.a total 17433 1615 430.7 1586.0 crop yield -2728 -39 -8.5 -72.8 partial balance 14705b 1576b 422.2a 1513.2a date palm ma manure 36452 1946 256.0 1019 irrigation water 154 131 0.0 0.6 rainfall 101 21 n.a n.a photosynthetic c* 5085 total 41792 2098 256.0 1019.3 crop yield -1788 -16 -3.0 -39.6 understory maize -3632 -131 -33.0 -96.8 partial balance 36372a 1951a 220.0b 882.9b * photosynthetic c was estimated only for understory maize. 80 squ journal of agricultural and marine sciences, 2017, volume 22, issue 1 carbon and nutrient balances in three mountain oases in northern oman n2o-n were measured using a photo-acoustic infrared multi-gas analyzer (innova 1312-5, airtech instruments, ballerup, denmark; predotova et al., 2010, 2011). a cuvette of 0.30 m diameter and 0.11 m height made of standard pvc tube was used to tightly cover pvc rings installed in the soil of the experimental field in order to create a closed chamber, while inside temperature and humidity were monitored with an attached thermo-hygrometer sensor (pce-313 a, paper-consult engineering group, meschede, germany). measurements were conducted immediately after the first irrigation and repeated for three days during each irrigation cycle in order to estimate emission rates at different soil moisture levels (day of irrigation event, day in the middle of the irrigation cycle, and day before the next irrigation event). for each measurement day, gaseous emissions were quantified from three replicates in all four rings installed in each cropping system (totaling 12 measurements per day). at the same time, volumetric soil water content was determined at 0.05 m depth with a tdr/ fdr soil moisture meter (theta probe sensor attached to infield7b instrument, ums, munich, germany). soil temperature was recorded with a digital thermometer (carl roth gmbh, karlsruhe, germany). emission measurements were conducted in the early afternoon hours (12:00 – 02:00 pm) representing the highest emission rates during the hottest hours in these agroecosystems (buerkert et al. 2010). for an annual extrapolation of our daily measurements of afternoon gaseous c and n losses, the average percentage changes in emissions between minimum and maximum emission rates (morning/midday) measured at the same oases in a previous study were used to estimate daily average emission values (al-rawahi et al. 2014b). total carbon and nutrient balances total balances of c, n, p, and k were calculated as the difference between horizontal balances minus vertical fluxes. since we were unable to obtain complete plant nutrient data for pomegranate and date palm (due to difficulties to account for nutrient storage in woody plant parts and roots, and losses by twigs and leaves), these calculations had only limited value. to partly fill this data gap, we assumed that approximately 39 % of the total annual emitted c was derived from root respiration and root-derived organic matter microbial respiration (atarashi-andoh et al. 2011). without consideration of c stored in leaves, stem, and growing roots, this percentage was considered as the photosynthetic c input allocated to below-ground roots and consequently deducted from the total gaseous c emitted from both species for total c balance calculations. statistical analysis data were analyzed using spss version 17.0 (spss inc., chicago, usa), while graphs were made with sigma plot 10.0 (systat software inc., san jose, ca, usa). the analysis of variance was followed by lsd post-hoc multiple mean comparisons to test for differences between the two cropping systems (annual versus perennial species). data of which residuals were not normally distributed were log-transformed before statistical analysis. table 4. annual cumulative leaching losses of mineral nitrogen (n) and phosphorus (p) (mean ± one standard error) determined by ion exchange resin cartridges from the experimental fields at the oases of ash sharayjah, qasha’, and masayrat ar ruwajah, oman (2008-2009). cumulative leaching g ha-1 year-1 crop oases mineral (n) mineral (p) garlic ash sharayjah 452 ± 26.9 25 ± 2.8 garlic masayrat 613 ± 65.2 102 ± 27.1 pomegranate ash sharayjah 232 ± 31.5 3 ± 0.5 pomegranate qasha’ 48 ± 7.7 7 ± 0.67 date palm masayrat 73 ± 13.8 4 ± 1.5 2008/2009 2009/2010 0 5 10 15 20 25 30 35 0 5 10 15 20 25 30 35 nov jan feb april 0 20 40 60 80 nov jan/feb april 0 20 40 60 80 time (months) 0 2000 6000 4000 8000 10000 12000 14000 16000 18000 ash sharayjah masayrat ar ruwajah 0 2000 4000 6000 8000 10000 12000 14000 16000 18000 0 20 40 60 80 100 120 140 160 0 20 40 60 80 100 120 140 160 c o 2 -c e m is si on (g ·h a1 · h1 ) c h 4 -c e m is si on (g ·h a1 · h1 ) n h 3 -n e m is si on (g ·h a1 · h1 ) n o 2 -n e m is si on (g ·h a1 · h1 ) figure 4. emissions of co2-c, ch4-c, nh3-n, and n2o-n, from garlic fields at the oases of ash sharayjah and masayrat ar rawajah throughout two growing seasons (2008/2009–2009/2010). vertical bars indicate ± one standard error of the mean. 81research article al-rawahi, melapie, schlecht and buerkert results soil properties and climatic conditions soils of the man-made irragric anthrosols on the terraces were similar for all three oases and classified as loamy soils with a particle size distribution of about 15% clay, 41% silt, and 44% sand. high inorganic carbon (cinorg) was determined in all soil samples reflecting a caco3 concentration of 44% at ash sharayjah and 40% at masayrat. soil ph averaged 8.2 at ash sharayjah, 8.0 at qasha’, and 8.3 at masayrat. also, soil organic c was higher at masayrat than at ash sharayjah and at qasha’ (table  1). average ambient air temperature was 21.2°c at ash sharayjah, 21.6°c at qasha’, and 25.4°c at masayrat (fig. 2). in 2009, annual precipitation totaled 205 mm at ash sharayjah and 224 at masayrat, while in 2010 more rainfall events occurred and annual precipitation totaled 639 and 379 mm at ash sharayjah and masayrat, respectively (fig. 3). garlic fields received a total precipitation of 131 mm at ash sharayjah and 43 mm at masayrat during the growing season from november 2008 to april 2009. rainfall was higher during the second season (2009/2010) with cumulative values of 299 mm at ash sharayjah and 124 mm at masayrat. horizontal c and nutrient fluxes manure was the main source of c and nutrient inputs (table 3). although we tried to select fields with similar application rates of manure, application depended on cropping system (annual versus perennial species), availability and frequency of irrigation water, distance and access to the fields, and season (winter versus summer). manure was surface applied by the farmers 2-3 times during the experimental period on the irrigated garlic fields forming a manure layer of 0.03 m height. at ash sharayjah, garlic fields received goat manure at average rates of 47 and 40 t dm ha-1 during the growing seasons of the years 2008/2009 and 2009/2010, respectively (table 2). similarly, goat manure was applied to garlic fields at masayrat with an average application rate of 42 and 37 t dm ha-1 during the 2-years growing seasons. farmers also applied goat manure to date palms at masayrat at an average rate of 78 t dm ha-1. in contrast, pomegranates at ash sharayjah and qasha’ received cattle dairy manure at 66 and 60 t dry matter ha-1. average annual inputs of c and n from manure were 62% of total c and 95% of total n in ash sharayjah garlic fields and 63% of c and 94% of n in masayrat garlic table 5. estimated annual carbon and nitrogen gaseous losses from selected experimental fields at the oases of ash sharayjah, qasha’,and masayrat, northern oman (2008-2009). data represent means ± one standard error. crop oases gas afternoon emission mean ± std. error kg·ha-1·year-1 estimated annual losses ha-1·year-1 garlic sharayjah co2-c 49442 ± 3036 ch4-c 449.1 ± 108.24 32.8 t c nh3-n 106.9 ± 16.66 n2o-n 67.3 ± 8.52 108.6 kg n garlic ma co2-c 59279 ± 3958 ch4-c 506.0 ± 107.95 50.2 t c nh3-n 108.6 ± 17.03 n2o-n 122.3 ± 12.12 156.5 kg n pomegranate sharayjah co2-c 31164 ± 2381 ch4-c 597.2 ± 112.22 20.9 t c nh3-n 75.3 ± 15.42 n2o-n 75.7 ± 16.04 93.4 kg n pomegranate qasha’ co2-c 27756 ± 2328 ch4-c 377.0 ± 73.79 18.5 t c nh3-n 73.3 ± 14.17 n2o-n 48.7 ± 8.91 76.3 kg n date palm masayrat co2-c 72420 ± 4827 ch4-c 466.5 ± 81.42 61.2 t c nh3-n 68.1 ± 9.86 n2o-n 68.5 ± 7.55 92.7 kg n 82 squ journal of agricultural and marine sciences, 2017, volume 22, issue 1 carbon and nutrient balances in three mountain oases in northern oman fields, whereas average annual inputs of photosynthetic c were 37 and 36% of total c in garlic fields at ash sharayjah and masayrat, respectively. total annual c and nutrient inputs in garlic fields were similar (p>0.05) in both oases (table 3). as a result, garlic total dm yield and annual horizontal balances for both oases were not significantly different (p>0.05). although our data showed major differences between annual and perennial cropping systems, partial c balances of garlic and date palm were not significantly different (p>0.05). nitrogen surpluses, in contrast, were significantly larger (p<0.05) in date palm than in all other crops. phosphorus and k partial balances of pomegranate at qasha’ and date palm at masayrat were similar to those of pomegranate at ash sharayjah. although annual horizontal k balances in garlic fields of both oases were negative, they were positive for pomegranate and date palm. average annual c, n, p, and k exported with understorey maize were 4.3, 4.9, 3.4 and 1.4-fold higher than in pomegranate yields at ash sharayjah and 6.9, 9.9, 1.4 and 1.0-fold higher than in harvested dates. compared to pomegranate, date palm fields received higher c and n inputs and lower p and k inputs. partial balances of c, n, and p in date palm therefore were 46, 29 and 12% higher than balances calculated from pomegranate 0 2000 4000 6000 8000 10000 12000 0 20 40 60 80 100 120 140 160 ash sharayjah-pomegranate masayrat-date palm qasha`-pomegranate 0 5 10 15 20 25 jun sept nov jan april 0 5 10 15 20 25 c o 2 -c e m is si on (g ·h a1 · h1 ) c h 4 -c e m is si on (g ·h a1 · h1 ) n h 3 -n e m is si on (g ·h a1 · h1 ) n o 2 -n e m is si on (g ·h a1 · h1 ) time (months) figure 5. emissions of co2-c, ch4-c, nh3-n, and n2o-n, from garlic fields at the oases of ash sharayjah and masayrat ar rawajah throughout two growing seasons (2008/2009–2009/2010). vertical bars indicate ± one standard error of the mean. 30 -1500 -1000 -500 0 500 1000 1500 n p k -15000 -10000 -5000 0 5000 10000 15000 c ash sharayjah masayrate am ou nt o f c (k g· ha -1 ·y ea r-1 ) am ou nt o f n , p , k (k g· ha -1 ·y ea r-1 ) figure 6. annual total balances of carbon (c), nitrogen (n), phosphorus (p), and potassium (k) in garlic fields (n = 6) at the oases of ash sharayjah and masayrat ar ruwajah in northern oman. data represent means of two growing seasons (2008/2009 – 2009/2010) with vertical bars indicating ± one standard error. 83research article al-rawahi, melapie, schlecht and buerkert at ash sharayjah, while k balance was 48% lower. apparent nutrient use efficiency nue annual apparent nue was highest in garlic with average n, p, and k use efficiencies of 51, 60, and 127% at ash sharayjah and 50, 60, and 149% at masayrat. average apparent nues of pomegranate at ash sharayjah, qasha’, and date palm at masayrat were 15, 3, and 7%, respectively. in perennial trees, pue and kue tended to be higher for pomegranate at ash sharayjah (22 and 19%) compared to date palm at masayrat (14 and 13%), while pue and kue was with 2 and 5% smallest in pomegranate at qasha’. cumulative leaching losses most mineral n was leached as no3-n, whereas nh4-n was below detection limit for all cartridges. annual cumulative leaching losses of mineral n and p were much higher in garlic fields than in perennial crops (table 4). annual mineral n leaching losses ranged between 0.45-0.61 kg n ha-1 year-1 for garlic and 0.23-0.07 kg n ha-1 year-1 for perennial trees. apparent annual mineral p leaching from perennial trees was below 0.01 kg p ha-1 year-1. gaseous emissions estimated annual gaseous c and n losses were higher in garlic than in perennial cropping systems (table 5) and regardless of the cropping system gaseous c were higher at masayrat than at ash sharayjah despite the higher application rate of manure at the latter site. total annual gaseous n losses from garlic fields were 109 ha-1 year-1 at ash sharayjah and 157 kg n ha-1 year-1 at masayrat, whereas annual gaseous c losses were 33 t ha-1 year-1 at ash sharayjah and 50 t c ha-1 year-1 at masayrat. while nh3-n constituted 63% of total gaseous n losses in garlic fields at ash sharayjah, they were 48% at masayrat. regardless of cropping system and altitude, nh3-n and n2o-n fluxes were highest during the first few days after manure application and gradually decreased thereafter (fig. 4). for perennials time dependent fluxes of c and n were surprisingly similar across the three oases (fig. 5). in january, flux rates obtained their annual minima. total estimated gaseous nh3-n and no2-n losses were highest in pomegranate at ash sharayjah (93 kg n ha-1 year-1) and at qasha’ (76 kg n ha-1 year-1) despite the much higher temperature and manure application rate in date palm at masayrat (93 kg n ha-1 year-1). co2-c emissions in date palm at masayrat were about 3-times higher than in pomegranate at ash sharayjah and qasha’, reaching a maximum flux rate of 11 kg ha-1 h-1 in september (fig. 5). consequently, annual gaseous c losses in perennials were 21, 19, and 61 t c ha-1 year-1 at ash sharayjah, qasha’, and masayrat, respectively (table 5). total carbon and nutrient balances total annual c balances of garlic fields were positive (a surplus of 12.5 t ha-1) for ash sharayjah and in deficit (-5.5 t ha-1) for masayrat (fig. 6), while annual n balances in garlic were with 915 and 826 kg ha-1 similarly positive at ash sharayjah and masayrat. annual p surpluses were with 130 kg ha-1 twice as positive in garlic at ash sharayjah than at masayrat (60 kg p ha-1). garlic annual k balances, in contrast, were negative in both oases reflecting the high amounts of k exported with the harvested produce (table 3). annual c surpluses in pomegranate and date palm were 16.7, 7.5, and 1.7 t ha-1 at ash sharayjah, qasha’, and masayrat, respectively (fig. 7). at manure application rates of 78 t ha-1 year-1, date palm had with 1860 kg n ha-1 the highest total annual n surplus, while the average annual k balance was 880 kg ha-1. pomegranate at ash sharayjah and qasha’ had annual n surpluses of 1410 and 1500 kg ha-1. total annual p surpluses in pomegranate at ash sharayjah were 196 kg ha-1 and at qasha’ 420 kg ha-1, whereas annual k surpluses amounted to 1710 and 1510 kg ha-1. discussion the surprisingly large n2o-n fluxes from garlic fields at masayrat compared to the prevailing dominance of nh4-n in fields at ash sharayjah (table 5) may be caused by the difference in wet-dry cycles at both locations. over the 180 day growing season there were 15 cycles at the high altitude oasis of ash sharayjah compared to 26 cycles at the low altitude oasis of masayrat. annual c losses from date palm at masayrat were 67% higher than from pomegranate at ash sharayjah and masayrat which probably reflected the very high annual manure input of 78 t dm ha-1 to date palm fields as well as the c 0 500 1000 1500 2000 2500 10000 15000 20000 n p k ash sharayjah qasha' masayrat a m o u n t o f c , n , p, k ( kg ·h a -1 ·y e a r1 ) figure 7. annual total balances of carbon (c), nitrogen (n), phosphorus (p), and potassium (k) in pomegranate fields (n = 6) at oases of ash sharayjah and qasha’ and date palm fields at oasis of masayrat ar ruwajah in northern oman during the period of april 2009 to april 2010. data represent means with vertical bars indicating ± one standard error. 84 squ journal of agricultural and marine sciences, 2017, volume 22, issue 1 carbon and nutrient balances in three mountain oases in northern oman much higher air temperature at the low altitude oasis of masayrat (fig. 2). in their study of gaseous n and c losses from the northern oman costal plain of al-batinah, siegfried et al. (2011) reported similarly high fluxes that were related to a very fast c and nutrient turnover. although they used lower manure application rates than in our study, total gaseous n and c losses were similar. this it is likely due to the very high temperatures in the omani lowlands. regardless of the cropping system, cumulative annual leaching losses of mineral n and p were very low compared to the findings from sandy lowland soils by siegfried et al. (2011). these low rates may be due to a combination of low seepage, differences in the particle size distribution and the higher organic c content of our soils. in any case, it should be noted that the resin technique used to measure leachates does not quantify organic n and p. ouédraogo at al. (2001) have reported that the application of large amounts of organic matter can lead to an increase of soil cation exchange capacity (cec) in subtropical soils and jarecki et al. (2008) reported that the higher cec in clay soils led to a substantial adsorption of nh4 +. also, szili-kovács et al. (2007) reported that application of organic substrates may enhance n immobilization in the microbial biomass as a result of the high nutrient exports in harvested garlic, nutrient surpluses in perennials were much higher, especially for n and k. carbon balances, instead, seemed to largely depend on c inputs from manure and photosynthetic c rather than on c exports at harvest. despite the higher application rates of goat manure to garlic fields, k inputs to pomegranate were higher given the use of cow manure in this system. our results indicate that cattle manure had a much higher k concentration than goat manure (table 1). although the manure rates in date palm were higher than in garlic, both systems had similar horizontal c balances, whereby our total annual c and nutrient exports were much lower than in the more intensively managed palm groves studied by buerkert et al. (2005). this difference may also be due to a serious infection of the date palms at musayrat with the dubas bug (ommatissus binotatus lybicus) during our experimental period leading to unusually low date yields. during their life cycle and development, these insects attract deleterious fungi that feed on honeydew on infected leaves and fruits which causes a reduction of photosynthesis and subsequent growth depression (klein and venezian 1985). annual apparent nue was much higher in annual crops than in perennials. similar to our results, data obtained from 197 countries indicated average use efficiencies of 50% for n, 40% for p, and 75% for k (sheldrick et al., 2002). the lower nue of the perennial trees compared to garlic was largely due to much lower nutrient outputs in fruit production. however, calculation of the annual apparent nue in perennial trees based on harvested yield does not take into account total nutrient uptake and storage by the trees (hedlund et al., 2003). the high k uptake by garlic crops raise questions about soil k sources. further investigations can play an important role in assessing the effect of soil k depletion on longterm crop production. the reliability of our total c balances is severely hampered by the lack of reliable data on root c contributions which has been the subject of much recent research (kuzyakov et al. 2001; kuzyakov 2002; werth and kuzyakov 2008; pumpanen et al. 2009). from their comprehensive studies under controlled conditions kuzyakov and larionova (2006), concluded that root respiration contributed approximately 40% to the total co2 efflux from soils. kelting et al. (1998) have partitioned soil respiration into: (1) 32% as a root respiration, (2) 20% as a microbial respiration in the rhizosphere, and (3) 48% as root free soil respiration (basal respiration). a recent study (atarashi-andoh et al. 2011) on the partitioning soil heterotrophic and autotrophic respiration using 14c concluded that about 31-39% of the total co2 efflux from the soil were from root-derived c. such isotopes studies would be necessary to trace the fate of the assimilated c by annual and perennial trees in agroecosystems such as of our study. conclusion the patterns of annual c and n emissions reflected the high application rate of manure as well as the variation of air temperature along the altitudinal gradient within the three oases. the removal of k in harvested garlic greatly exceeded inputs. our data indicate a very high soil biological activity in all three oases and support previous findings demonstrating the very high c and n turnover under irrigated subtropical conditions such as in our study area. to better tailor plant nutrient uptake to release from the large amounts of manure applied, further research is necessary that systematically examines the role of manure quality and incorporation on decomposition. acknowledgements we thank the farmers of al jabal al akhdar and the agricultural extension centre of the ministry of agriculture and fisheries at sayh qatanah (oman) who supported this research infrastructurally. we are also thankful to eva wiegard and claudia thieme for their analytical assisting. this work was funded by the deutsche forschungsgemeinschaft (dfg) within the graduate research training group 1397 ‘regulation of soil organic matter and nutrient turnover in organic agriculture’ at university of kassel-witzenhausen, germany. 85research article al-rawahi, melapie, schlecht and buerkert references agehara, s., and warncke, d.d. 2005. soil moisture and temperature effects on nitrogen release from organic nitrogen sources. soil science society of america journal 69(6):1844-1855. al-rawahi, m.n., brinkmann, k., schlecht, e., and buerkert, a. 2014. effects of changing water availability on land-use in irrigated mountain oases of al jabal al akhdar, northern oman. die erde 145(4):162-174. al-rawahi, m.n., melapie, m., and buerkert, a. 2014. nitrogen and carbon emissions from al jabal al akhdar oasis systems in northern oman. journal of oman studies 18:13-24. atarashi-andoh, m., koarashi, j., ishizuka, s., and hirai, k. 2011. seasonal patterns and control factors of co2 effluxes from surface litter, soil organic carbon, and root-derived carbon estimated using radiocarbon signatures. agricultural and forest meteorology 153:149-158. buerkert, a., jahn, h., golombek, s.d., al-rawahi, m.n., and gebauer, j. 2010. carbon and nitrogen emissions from stored manure and cropped fields in irrigated mountain oases of oman. journal of agriculture and rural development in the tropics and subtropics 111:65-73. buerkert, a., nagieb, m., siebert, s., khan, i., and almaskri, a. 2005. nutrient cycling and field-based partial nutrient balances in two mountain oases of oman. field crops research 94:149-164. burgos, p., madejón, e., cabrera, f. 2006. nitrogen mineralization and nitrate leaching of a sandy soil amended with different organic wastes. waste management and research 24:175-182. cannovo, p., richaume, a., and lafolie, f. 2004. fate of nitrogen and carbon in the vadose zone: in situ and laboratory measurements of seasonal variations in aerobic respiratory and denitrifying activities. soil biology & biochemistry 36:463-478. cuttle, s. 2002. nutrient budgets as a tool for researchers and farmers. uk organic research 2002, aberystwyth, united kingdom. de neve, s., hofman, g. 2002. quantifying soil water effects on nitrogen mineralization from soil organic matter and from fresh crop residues. biology and fertility of soils 35(5):379-386. deng, s.p., and tabatabai, m.a. 2000. effect of cropping systems on nitrogen mineralization in soils. biology and fertility of soils 31(3):211-218. franzluebbers, a.j. 1999. microbial activity in response to water-filled pore space of variably eroded southern piedmont soils. applied soil ecology 11(1):91-101. gee, g,w., bauder, j.w. 1986. particle size analysis. in: klute, a. 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buerkert, a. 2004. field measurements of the co2 evolution rate under different crops during an irrigation cycle in a mountain oasis of oman. applied soil ecology 25:85-91. wichern, f., müller, t., joergensen, r.g., and buerkert, a. 2004. effects of manure quality and application forms on soil c and n turnover of a subtropical oasis soil under laboratory conditions. biology and fertility of soils 39(3):165-171. williams, d.e. 1948. a rapid manometer method for the determination of carbonate in soils. soil science society of america journal 13:127-129. zaman, m., and chang, s.x. 2004. substrate type, temperature, and moisture content affect gross and net n mineralization and nitrification rates in agroforestry systems. biology and fertility of soils 39(4):269-279. research paper journal of agricultural and marine sciences 2022, 27(2): 10–18 doi: 10.53541/jams.vol27iss2pp10-18 received 25 july 2021 accepted 11 january 2022 can the irrigation of soils with amoxicillin-enriched water cause the proliferation of bacteria resistant to antibiotics among culturable heterotrophic aerobic soil bacteria? adhari al-kalbani1, daniel menezes-blackburn1,*, buthaina al-siyabi1, mohamed al-kasbi2, ahmed al-busaidi2 daniel menezes-blackburn1( ) danielblac@squ.edu.om, 1department of soil, water and agricultural engineering, college of agricultural and marine science, sultan qaboos university, muscat, sultanate of oman, 2environment authority, qurum, muscat, sultanate of oman. introduction the reuse of treated wastewater is one of the al-ternative methods for increasing water conserva-tion and sustainability, especially the use of treated wastewater for irrigation can be highlighted. the use of treated wastewater for irrigation may positively affect soil fertility and increase crop yields (asano, 1988). there are nonetheless safety issues associated with soil irrigation with treated wastewater, namely the presence of microbial pathogens, heavy metals, organic pollutants (asano, 1988; epa, 2012), and pharmaceuticals such as antibiotics (wu et al., 2014). antibiotics are bioactive compounds secreted by certain microbial species, which directly inhibit the growth of other competing bacteria (negreanu et al., 2012). amoxicillin belongs to the β-lacهل ميكن أن يؤدي ري الرتبة ابملياه الغنية ابملضاد احليوي األموكسيسيلني )amoxicillin( إىل انتشار البكترياي املقاومة لألموكسيسيلني بني بكترياي الرتبة اهلوائية غري ذاتية التغذية )البكترياي العضوية(؟ عذاري الكلباين1، دانيال مينيزيس بالكبرين1 *، بثينة السيايب1، حممد الكاسيب2 ، أمحد البوسعيدي2 abstract. this study investigated the short-term impact of irrigation with amoxicillin solutions on the presence of the amoxicillin-resistance trait among culturable soil heterotrophic aerobic bacteria. the microcosm experimental design consisted of 15 days of incubation of 10 g soil samples irrigated daily with distilled water containing increasing doses of amoxicillin (0, 0.1, 1, 10, 100, 1000 µg g-1 of soil day-1). the hypothesis was that continuous daily addition of antibiotics would increase the proportion of antibiotic-resistant bacteria in soils. after the incubation period, the total and antibiotic resistance heterotrophic aerobic bacteria communities were assessed through serial dilution of soil suspensions, followed by agar plate culture enumeration, isolation, identification and microscopy observation. the presence of antibiotic-resistant bacteria was also evaluated directly on treated wastewater used for field irrigation before this microcosm study to assess the amoxicillin-resistant bacteria bioaugmentation hypothesis. results indicated that the amoxicillin resistance was widespread among bacteria present in both treated wastewater used for irrigation and in the receiving soil. a microcosm experiment was attempted as a ‘proof of concept’ to demonstrate that irrigation with treated wastewater containing antibiotics would exert selective pressure and promote the proliferation of antibiotic resistance bacteria. unexpectedly, the results from the microcosm incubations indicated the daily addition of amoxicillin did not increase bacterial antibiotic resistance trait abundance in soils, which even significantly decreased for all tested doses. the antibiotic-resistant species identified among the isolates were pseudomonas mosselii, p. otitidis, p. mendocina, p. flavescens, stenotrophomnas maltophilia, bacillus thuringiensis, aeromonas veronii, candida parapsilosis, streptomyces violaceoruber and microbacterium barkeri. keywords: treated wastewater, amoxicillin antibiotic, antibiotic resistance bacteria. امللخص:حبثــت هــذه الدراســة يف التأثــري قصــري املــدى لــري الرتبــة ابمليــاه املعاجلــة الغنيــة ابملضــاد احليــوي أموكسيســيلني )amoxicillin( علــى وجــود مســة مقاومــة للمضــاد احليــوي أموكسيســيلني بــني البكتــرياي اهلوائيــة غــري ذاتيــة التغذيــة )amoxicillin resistance heterotrophic bacteria( يف الرتبــة القابلــة للزراعــة. مت تصميــم الدراســة التجريبيــة ابســتخدام 10 جــرام مــن الرتبــة املرويــة يوميــا ابملــاء املقطــر الــي حتتــوي علــى جرعــات متزايــدة مــن املضــاد احليــوي أموكسيســيلني )0، 0.1، 1، 10، 100، 1000 ميكروغــرام /اليــوم/ الرتبــة( ملــدة حضانــة 15 يومــا. كانــت الفرضيــة املبدئيــة هــي أن اإلضافــة اليوميــة املســتمرة للمضــادات احليويــة مــن احملتمــل أن تزيــد نســبة البكتــرياي املقاومــة للمضــادات احليويــة يف الرتبــة. بعــد انتهــاء فــرتة احلضانــة، مت تقييــم جممــل جممــوع اجملتمعــات البكتــرياي اهلوائيــة غــري ذاتيــة التغذيــة املقاومــة للمضــادات احليويــة مــن خــالل التخفيــف املتسلســل لعينــات الرتبــة، تليهــا حســاب صفيحــة قطعــة هــالم اآلجــار، والعــزل البكتــريي، والتعــرف والكشــف عــن األنــواع البكترييــة، واملالحظــة اجملهريــة. مت أيًضــا تقييــم وجــود البكتــرياي املقاومــة للمضــادات احليويــة مباشــرة علــى ميــاه الصــرف الصحــي املعاجلــة املســتخدمة للــري amoxicillin resistance heterotrophic( امليــداين قبــل هــذه الدراســة املصغــرة لتقييــم فرضيــة الــزايدة احليويــة للبكتــرياي املقاومــة لألموكسيســيلني bacteria(. أشــارت النتائــج إىل انتشــار البكتــرياي املقاومــة لألموكسيســيلني يف ميــاه الصــرف الصحــي املعاجلــة املســتخدمة يف الــري ويف الرتبــة املســتقبلة للميــاه. مت تطبيــق الدراســة املصغــرة »كدليــل علــى املفهــوم« إلثبــات أن الــري مبيــاه الصــرف الصحــي املعاجلــة احملتويــة علــى مضــادات حيويــة مــن شــأهنا أن متــارس ضغطًــا انتقائًيــا وتعــزز مــن تكاثــر ومنــو البكتــرياي املقاومــة للمضــادات احليويــة. وبشــكل غــري متوقــع، أشــارت النتائــج أيضــا إىل أن اإلضافــة اليوميــة ملضــادات األموكسيســيلني ال تزيــد مــن مقاومــة البكتــرياي للمضــادات احليويــة يف الرتبــة، والــي اخنفضــت بشــكل ملحــوظ جلميــع اجلرعــات املختــرة. العــزالت البكترييــة املقاومــة الــي مت تعريفهــا فصائلهــا pseudomonas mosselii, p. otitidis, p. mendocina, p. flavescens, stenotrophomnas maltophilia :هــي ,bacillus thuringiensis, aeromonas veronii, candida parapsilosis, streptomyces violaceoruber microbacterium barkeri. الكلمات املفتاحية: مياه الصرف الصحي املعاجلة، املضاد احليوي أموكسيسيلني )amoxicillin( ، البكترياي املقاومة للمضادات احليوية. 11research paper al-kalbani, blackburn, al-siyabi, al-kasbi, al-busaidi tam group of antibiotics, and it is one of the most widely used antibiotics in human and veterinary medicine (diz dios et al., 2006). amoxicillin is an antibiotic of the amino-penicillin group used against a broad spectrum of gram-positive and gram-negative bacteria (croydon and sutherland 1970). clavulanic acid is a natural substance produced by streptomyces clavuligerus and has slight antibacterial activity but a very high inhibition of many β-lactamases. it is usually added to amoxicillin to increase its half-life. low concentrations of clavulanic acid (0.05-2 µg ml-1) cause irreversible time-dependent inactivation of many of the β-lactamases, including penicillinases produced by staphylococcus aureus (reading and cole, 1977). there is increasing societal concern about the evolving antibiotic resistance of natural bacteria, with special concerns expected to occur when antibiotics are continuously released into soil and water environments (bisht et al., 2009). therefore, leading to the continuous search for new generations of antibiotic compounds (czekalski et al., 2012). in this short-term study, amoxicillin was used because it has been reported to have a short half-life compared to other antibiotics (diz dios et al., 2006). many antibiotics are poorly absorbed in the human digestive tract, and it is estimated that 25% to 75% of the ingested antibiotics are excreted in faeces (ash et al., 2002). in both animals and humans, up to 95% of antibiotics can be excreted in an unaltered state (elmund et al. 1971). most of the antibiotics used for animals and humans are not entirely removed in wastewater treatment plants (wwtps). as a result, treated wastewater are a natural reservoir of residual concentrations of antibiotic and antibiotic-resistant bacteria (ar). wastewater treatment plants are not designed to remove or monitor pharmaceuticals (pruden et al., 2013). due to this low removal efficiency, multiple antibiotics in municipal wastewater and treatment plants were frequently detected in previous studies, e.g. zhang and li (2011). the combination of antibiotics, nutrients, and bacteria in treated domestic sewage wastewater could potentially result in the selection of antibiotic resistance among bacterial populations present in the environment (negreanu et al., 2012). soil organic matter represents an important source of energy and nutrients for microorganisms and plants (fahrenfeld et al., 2013; menezes-blackburn et al., 2013). soil microbial biomass, activity, taxonomic and functional diversity have strong correlation with soil health and have been considered as good biological indexes (menezes-blackburn et al., 2020). the application of irrigation water containing antibiotic resistant bacteria to soil represents a possible contamination source for crops, groundwater and receiving water bodies. many environmental factors such as temperature, ph, moisture, organic matter content, and others, may enhance the survival of pathogenic microbes on agricultural lands (trevisan et al., 2002). antibiotic-resistant pathogenic bacteria may spread across the environment by several different routes, including treated and untreated sewage effluents, sludge and agricultural runoff (al-bahry et al., 2007). however, antibiotic resistances are often formed when antibiotics are misused or overused; new bacteria strains arise that are no longer sensitive to these drugs. the presence of selective pressure of antimicrobial drug usage is responsible for the natural development of bacterial antibiotic resistance (al-bahry et al. 2015). under optimal conditions, bacteria multiply very rapidly, with generation times ranging from minutes to hours. the high number and short generation times allow for a high likelihood of spontaneous mutations to occur, allowing any given population of bacteria a significantly high genetic diversity to naturally occur (al-bahry et al., 2015). treated and untreated sewage effluents may pose risks for groundwater pollution. in oman, e. coli isolated from contaminated wells were found to be resistant to multiple antibiotics, possibly due to the contamination with sewage effluents (al-bahry et al., 2014). introducing antimicrobial agents into the environment might influence the change in the physiological traits of bacteria through the selection pressure over naturally occurring bacterial communities (martinez, 2009). the bactericidal or bacteriostatic agents (ab) inhibit microbial growth either by: a) targeting membranes or cell walls; b) targeting protein synthesis through the ribosomal subunits as tetracycline, and fluoroquinolones; or c) interfering with the nucleic acid synthesis (sengupta et al., 2013). nowadays, the overuse of antibiotics is considered the main cause of the emergence of antibiotic-resistant pathogens, resulting in direct risk for human health (mcardell et al., 2003). this short-term study investigated the scenario in which irrigating soil with antibiotic containing treated wastewater could propagate antibiotic resistance in soils. the specific objectives were to: a) evaluate the response soil bacteria enumeration for increasing doses of amoxicillin and the relative proportion of amoxicillin antibiotic resistant strains among the culturable heterotrophic aerobic bacterial community; and b) evaluate the abundance and proportion of amoxicillin antibiotic resistance within the heterotrophic aerobic bacterial community present on the treated wastewater currently used for irrigation, to verify if this is a possible source of antibiotic-resistant bacterial inoculum to soils. methodology site of soil sample and treated wastewater collection the soil sample used from the microcosm incubation study was collected from sultan qaboos university agricultural experiment station from a site irrigated with treated wastewater for five months (23°35’52.7”n 58°09’50.4”e) during spring 2019. the sampling location 12 squ journal of agricultural and marine sciences, 2022, volume 27, issue 2 can the irrigation of soils with amoxicillin-enriched water cause the proliferation of bacteria resistant to antibiotics among culturable heterotrophic aerobic soil bacteria? is 49 mamsl and 9.27 km from the coastline, free from the influence of seawater intrusion. approximately one kg of soil was collected from the top 5 cm of and sieved to below 2 mm particle size. the soil background physicochemical properties were 44.24% sand, 54.84 % silt, 0.92 % clay, electrical conductivity on the saturated paste extract (ece) of 8.3 ds m-1, ph 8 and 0.33 % soil organic matter by loss on ignition. the water holding capacity was measured as the soil moisture content (g g-1) remaining after one day of free drainage of a saturated 20 g soil sample covered with a plastic film to prevent evaporation. seventy per cent of this moisture content was used during initial microcosm incubation conditions. the treated wastewater was collected from the irrigation system at the same site and moved to the laboratory for immediate microbial analyses. soil microcosm incubation with amoxicillin amoxicillin-clavulanic acid (am-cl) was chosen for being the most commonly used antibiotic, due to its common occurrence in treated wastewater effluents, and as a result of its short half-life and high soil degradation (up to 80%) (braschi et al., 2013). the human adult’s standard dosage of amoxicillin (0.5 mg/kg/day) was taken as a reference maximum dosage treatment. to simulate a constant addition of amoxicillin through daily irrigation with treated wastewater, a logarithmic increase dosage was designed as 0, 0.001, 0.01, 0.1, 1 and 10 mg kg-1 day-1. these antibiotic solutions (0.1 ml 10 g-1 soil) were added daily for 15 days in triplicate incubations. each of the 10 g incubation replicates was kept at open-air room temperature (25±1.34 °c) to avoid moisture buildup and anoxic conditions and were daily mixed after amoxicillin application. enumeration of amoxicillin-resistant heterotrophic aerobic bacteria soil bacterial colonies were examined from soil matrices by suspending 10 g of freshly collected soil samples (kept at 4 oc) in 95 ml of saline solution (0.85% nacl2). samples were shaken at 100 rpm for 10 min, and soil suspensions were then subjected to four sequential 10× dilutions. for each sample, four replicates were used to increase accuracy. luria bertani (lb) agar was used a basal general-bacteria-growth-media in three conditions, either: a) unamended (control); (b) amended with 0.5 mg ml-1, or (c) 20 mg ml-1 of (am-cl) , and were used to cultivate heterotrophic aerobic bacteria without and with antibiotic resistance respectively. the lb agar media plates were inoculated with 0.1 ml of the freshly prepared soils suspensions and incubated at room temperature for 72 hours, to ensure enough time for bacterial growth. the bacteria colonies were enumerated (abundance) and calculated as colony-forming units per gram of soil (cfu g-1). the relative proportion of antibiotic-resistant culturable bacteria was calculated by comparing the number of cfus growing on plates with antibiotics compared to the number of cfus growing on control plates without antibiotics. the same agar medium and growth conditions were used for soil suspensions and the fresh treated wastewater sample. bacteria strain isolation, identification and microscopy antibiotic-resistant bacterial colonies able to grow on the amoxicillin-supplemented lb-agar medium were isolated in pure culture by standard streak-clean procedure on fresh lb-agar medium supplemented with 20 mg ml-1 (am-cl). the bacterial colonies’ morphology was examined both through direct naked eye observation of figure 1. average culturable bacteria enumeration in luria bertani agar (cfu ml-1) medium inoculated of treated wastewater used for soil irrigation at the agricultural experiment station at sultan qaboos university. columns labelled with different letters are statistically different (tukey p≤0.05). 13research paper al-kalbani, blackburn, al-siyabi, al-kasbi, al-busaidi colony colour, shape and texture, and through brightfield microscopy with gram-staining for distinguishing between the different isolates. bacterial species identification was performed by using a maldi bio-typer (bruker co., uk) based on proteomic fingerprinting analysed by high-throughput maldi-tof mass spectrometry. statistical analysis the data obtained were subjected to analysis of variance (one way anova) and subsequently, tukey’s hsd test was used to separate the means of the selected soil properties. the significance level was defined as p≤0.05. results amoxicillin-resistant heterotrophic aerobic bacteria in treated waste water a considerable fraction of wastewater bacteria were able to grow in lb medium supplemented amoxicillin-clavulanic acid (0.5 or 20 µg ml-1) as shown in figure s1. the average bacterial cells present in the control lb medium (without amoxicillin-clavulanic acid) was 240 cfu ml-1 (figure 1). in the plates containing 0.5 and 20 µg ml-1 of amoxicillin, the abundance of bacteria colonies was 140 and 90 cfu ml-1, respectively. this corresponds to a very high proportion of the total cfu in control plates, approximately 58.3% and 37.5% for plates containing 0.5 µg ml-1 and 20 µg ml-1 of amoxicillin, respectively. considering a hypothetical irrigation with 5 l m-2 day-1, a total of 1.20×106 cfu m-2 would be the daily inoculation of these soils with highly amoxicillin-clavulanic acid-resistant bacteria. average culturable bacteria enumeration in luria bertani agar (cfu ml-1) medium inoculated of treated wastewater used for soil irrigation at the agricultural experiment station at sultan qaboos university. columns labelled with different letters are statistically different (tukey p≤0.05). in soils, the average soil bacterial cfu g-1 enumeration in lb medium supplemented with 0.5 µg ml-1 was not significantly reduced with regards to the control (figure 2). whereas in lb medium supplemented with 20 µg ml-1 amoxicillin the reduction in cfu g-1 was significantly decreased by two orders of magnitude. therefore, the lb medium supplemented with 20 µg ml-1 was used for further soil studies. curiously, in the soils irrigated with treated wastewater for five months before the experiment, the proportion of bacterial cells culturable in lb medium supplemented with 20 µg ml-1 was only one per cent of the control lb-agar medium; much lower than the 37.5% observed directly on the treated wastewater. it is worth noticing that amoxicillin-resistant bacteria were found to be present in the soil even when no antibiotic or wastewater was applied. the visual aspect lb agar plates of heterotrophic aerobic showing total bacterial cell growth with much lower abundance at 20 µg ml-1 of amoxicillin can be seen in figure s2. average culturable bacteria enumeration in luria bertani agar (cfu ml-1) medium inoculated suspensions of soils irrigated with treated wastewater at the agricultural station at sultan qaboos university. columns labelled with different letters are statistically different (tukey p≤0.05). amoxicillin-resistant heterotrophic aerobic bacteria in soil irrigated with amoxicillin solutions microcosm assays in this microcosm experiment, the abundance of antibiotic resistance bacteria was evaluated after 15 days of soil incubation with amoxicillin-clavulanic acid added daily with the irrigation water (0, 0.001, 0.01, 0.1, 1 and 10 mg amoxicillin kg-1 soil day-1). the same lb medium figure 2. average culturable bacteria enumeration in luria bertani agar (cfu ml-1) medium inoculated suspensions of soils irrigated with treated wastewater at the agricultural station at sultan qaboos university. columns labelled with different letters are statistically different (tukey p≤0.05). 14 squ journal of agricultural and marine sciences, 2022, volume 27, issue 2 can the irrigation of soils with amoxicillin-enriched water cause the proliferation of bacteria resistant to antibiotics among culturable heterotrophic aerobic soil bacteria? cultivation conditions described herein was followed for the microcosm soil samples (0.5 and 20 µg amoxicillin ml-1). amoxicillin only negatively affected the total culturable bacteria cfu g-1 soil at the 1 mg kg-1 soil day-1 dose, and at 10 mg kg-1 soil day-1, the cfu g-1 soil even significantly increased. there was an intensive and significant decrease in the total and relative abundance of antibiotic-resistant bacteria in soils treated with higher doses of amoxicillin (figure 3). this effect was contrary to our central hypothesis that the addition of am-cl would increase the relative abundance of this trait. the total bacterial cfu g-1 soil in all samples where amoxicillin-clavulanic acid was added was below 105 cfu g-1. on the other hand, the average bacterial cfu g-1 soil was 2.42x106 cfu g-1 at incubation conditions without amoxicillin addition. enumeration of bacteria colony forming units (cfu g-1 soil) in luria bertani agar medium lb medium with or without amoxicillin supplementation (0 and 20 µg amoxicillin ml-1). soil samples treated with 0, 0.1, 1, 10, 100, 1000 mg kg-1 of soil sample day-1 for 15 days. columns labelled with different letters are statistically different (tukey p≤0.05). the relative proportion (%) of antibiotic resistance bacteria was dramatically and significantly decreased nearly ten folds for soils receiving amoxicillin (figure 4). . the daily application of am-cl reduced the % of amoxicillin-tolerant heterotrophic aerobic bacterial figure 3. enumeration of bacteria colony forming units (cfu g-1 soil) in luria bertani agar medium lb medium with or without amoxicillin supplementation (0 and 20 µg amoxicillin ml-1, unshaded and unshaded bars respectively). soil samples treated with 0, 0.1, 1, 10, 100, 1000 mg kg-1 of soil sample day-1 for 15 days. columns labelled with different letters are statistically different (tukey p≤0.05). figure 4. relative abundance (%) of bacteria colony forming units (cfu g-1 soil) able to grow in luria bertani agar medium lb medium containing 20 µg amoxicillin ml-1 medium with regards to 0 µg amoxicillin ml-1 controls. soil samples were treated with 0, 0.1, 1, 10, 100, 1000 mg kg-1 of soil sample day-1 for 15 days. columns labelled with different letters are statistically different (tukey p≤0.05). 15research paper al-kalbani, blackburn, al-siyabi, al-kasbi, al-busaidi abundance in all treatments. the percentage differences in antibiotic resistant bacteria were not statistically significant among the am-cl treated soil samples. moreover, the relative bacterial abundance in lb-agar supplemented with 20 µg am-cl ml-1 was on average 0.5% for amoxicillin treated soils with respect to control lb plates. whereas it was over 4% for the control soils without amoxicillin. relative abundance (%) of bacteria colony forming units (cfu g-1 soil) in luria bertani agar medium lb medium containing 20 µg amoxicillin ml-1 medium compared to 0 µg amoxicillin ml-1 controls. columns labelled with different letters are statistically different (tukey p≤0.05). antibiotic-resistant bacteria isolation, identification and microscopy the isolated am-cl resistant microorganisms were identified at the species level using maldi bio-typer (brooker-uk) and observed by bright light microscopy. based on these tests, the majority of the am-cl resistant bacteria isolated from treated wastewater were gram-negative, and in soil, most were gram-positive. the bacterial shape, arrangement, and structure of pure isolated colonies were also recorded. among isolates, the positively identified strains were pseudomonas mosselii, pseudomonas otitidis, pseudomonas mendocina, stenotrophomnas maltophilia (pseudomonas beteli), pseudomonas flavescens, bacillus thuringiensis aeromonas veronii, candida parapsilosis, streptomyces violaceoruber, microbacterium barkeri. figure 5. petri dish lb-agar-streaked colonies image and gram-stained bright light microscopy (1000x amplification) image of the microbial strains isolated in this study. the species identification was performed using maldi-biotyper. 16 squ journal of agricultural and marine sciences, 2022, volume 27, issue 2 can the irrigation of soils with amoxicillin-enriched water cause the proliferation of bacteria resistant to antibiotics among culturable heterotrophic aerobic soil bacteria? amoxicillin-clavulanic acid-resistant strains isolated from treated wastewater (a to f ) and from soils (g to l) irrigated with the same treated wastewater. isolation, purification and continuous propagation of these strains were performed using luria bertani-agar medium supplemented with 20 µg amoxicillin ml-1. species identification was performed with maldi bio-typer (id>97%). discussion hundreds of different bacteria species can be isolated even from tertiary treated wastewater (wu et al., 2014). based on the work from karthikeyan et al. (2006), during the sewage treatment process, only partial antibiotic removal is achieved, and treated wastewater contains a trace amount of a variety of antibiotics. bacteria exposed to antibiotic compounds may be selected for their antibiotic resistance traits. nevertheless, minimal inhibitory concentrations may not be exceeded in treated wastewaters (martinez, 2009). bacterial communities exposed to inhibitory antibiotic concentrations can be enriched for antibiotic resistance, and this is related to an overall higher antibiotic concentration in natural environments (gullberg et al., 2011). contrary to our hypothesis and the current literature, in our study, less antibiotic resistance was obtained with the addition of am-cl through irrigation. hereby, we cannot suggest amoxicillin-clavulanic acid in treated wastewater would increase the abundance of antibiotic resistance bacterial traits in the soils. amoxicillin-clavulanic acid stored at room temperature is known to be labile to bacterial degradation, and more than 30% of amoxicillin-clavulanic acid degraded can be degraded after seven days (gullberg et al. 2011). the dissolved antibiotic in water is highly affected by environmental conditions, such as temperature ad ph (gullberg et al., 2011). amoxicillin clavulanic may be degraded and become a nutrient source to bacterial cells. we speculate here that this may have caused an overgrowth of low generation time bacteria sensitive to amoxicillin that benefited from the rapid degradation of this antibiotic and were stimulated by the freshly added carbon source. moreover, several studies demonstrated that other compounds other than antibiotics could cause the proliferation of antibiotic-resistant bacteria in a process known as cross-resistance. these are usually due to the presence of a high concentration of quaternary ammonium compounds (qacs) (sidhu et al. 2001), triclosan and triclocarban (used in soaps and other household compounds) (aiello et al., 2005), or even heavy metals (baker-austin et al., 2006). the average bacteria biomass is about four times higher in the treated wastewater samples than in freshwater samples, and their diversity can be ten folds higher (aiello et al., 2005; diz dios et al., 2006). chlorination, ozonation, and uv radiation post-treatment disinfection processes were successful treatments against microbial agents, and pharmaceutical ingredients can significantly reduce the risks associated with soils irrigated with treated wastewater (epa, 2012). using classical methods to quantify antibiotic-resistant bacteria can only evidence a small fraction (<1%) of the total community, and due to this fact, serial dilution and agar culturing methods are often inaccurate to represent the whole soil system (amann et al., 1995). the data presented reflect changes in the culturable antibiotic-resistant aerobic heterotrophic bacteria, and may not describe trends in the rest of the soil community. among the isolated amoxicillin-resistant strains, two were unidentifiable by maldi biotyper. four were pseudomonas strains, gram-negative, rod-shaped, and motile by a single polar flagellum. pseudomonas mosselii, pseudomonas otitidis, pseudomonas mendocina, pseudomonas mendocina, pseudomonas flavescens. some of them are known opportunistic pathogens, but mostly these are commonly found in soil, water, plants, sewage and animals. little is known about the antimicrobial mechanisms (rapsinski et al. 2016). other gram-negative antibiotic-resistant bacteria found were stenotrophomnas maltophilia (pseudomonas beteli), aeromonas veronii and streptomyces violaceoruber. two amoxicillin-resistant gram-positive bacteria were isolated: microbacterium barkeri, common in sewage samples, and bacillus thuringiensis used to control insects for agriculture and public health purposes (mizuki et al., 1999). surprisingly not all isolated microbes were bacteria. one isolate from a soil sample treated with 0.1 µg amoxicillin g-1 soil day-1 and cultivated/propagated in lb plates containing 20 µg ml-1 was identified as rhodotorula mucilaginosa. a common environmental yeast found in air, soil, lakes, and ocean water. it produces pink to red colonies that are unicellular lacking pseudohyphae and hyphae. it is the most common microorganism isolated from the hands of hospital employees and patients (strausbaugh et al., 1996). conclusion the effluent of treated wastewater used for irrigation carry antibiotic-resistant bacteria that may be an inoculum source to soil environments. a significant fraction of bacterial colonies isolated from soils (4%) resists amoxicillin and clavulanic acid antibiotics. the total antibiotic-resistant bacteria abundance was significantly decreased when the soil was incubated with increasing dose of antibiotics. this study sets an important precedent that irrigation with wastewater containing amoxicillin-clavulanic acid does not propagate this trait in soils by directed evolution. this is likely due to the quick degradation of this antibiotic in soil environments. in addition, more studies are required for clarifying what the antibiotic resistance traits present are, and if there is an effective transfer and survival of wastewater antibiotic-resistant communities in soils. 17research paper al-kalbani, blackburn, al-siyabi, al-kasbi, al-busaidi acknowledgement the authors are thankful to squ and the research council (oman) for financing this study through the projects ig/agr/swae/19/02 and rc/rg-agr/ swae/19/01. the authors acknowledge the financing from oman water and wastewater services company, diamhaya through the project r/agr/swae/18/01. references aiello ae, marshall b, levy sb, della-latta p, lin sx, larson e. (2005). antibacterial cleaning products and drug resistance. emerging infectious diseases 11(10): 1565-1570. al-bahry s, el shafie a, al busaidy s, al hinai j, al shidi i. 2007. antibiotic-resistant salmonella spp. from human and non-human sources in oman. emhj-eastern mediterranean health journal (13): 49-55. al-bahry sn, mahmoud i, paulson j, al-musharafi s. 2015. antibiotic resistant bacteria in terrestrial and aquatic environments: a review. the international arabic journal of antimicrobial agents 4(3:2): 1-11. al-bahry sn, mahmoud iy, al-musharafi sk, al-gharaibi i, al-harthy nk, al-zadjali ha. 2014. microbial and chemical pollution of water-wells relative to sewage effluents in oman. iafor journal of sustainability, energy and the environment 1(1):35-56. amann ri, ludwig w, schleifer k-h. 1995. phylogenetic identification and in situ detection of individual microbial cells without cultivation. microbiological reviews 59(1): 143-169. asano t. 1988. wastewater reclamation and reuse. journal water pollution control federation 60(6): 854-856. ash rj, mauck b, morgan m. 2002. antibiotic resistance of gram-negative bacteria in rivers, united states. emerging infectious diseases 8(7): 713-716. baker-austin c, wright ms, stepanauskas r, mcarthur j. 2006. co-selection of antibiotic and metal resistance. trends in microbiology 14(4): 176-182. bisht r, katiyar a, singh r, mittal p. 2009. antibiotic resistance-a global issue of concern. asian journal of pharmaceutical clinical research 2(2): 34-39. braschi i, blasioli s, fellet c, lorenzini r, garelli a, pori m, giacomini d. 2013. persistence and degradation of new β-lactam antibiotics in the soil and water environment. chemosphere 93(1): 152-159. croydon e, sutherland r. 1970. -amino-p-hydroxybenzylpenicillin (brl 2333), a new semisynthetic penicillin: absorption and excretion in man. antimicrobial agents chemotherapy 10: 427-430. czekalski n, berthold t, caucci s, egli a, bürgmann h. 2012. increased levels of multiresistant bacteria and resistance genes after wastewater treatment and their dissemination into lake geneva, switzerland. rontiers in microbiology 3: 1-18 (article 106). diz dios p, tomas carmona i, limeres posse j, medina henriquez j, fernandez feijoo j, alvarez fernandez m. 2006. comparative efficacies of amoxicillin, clindamycin, and moxifloxacin in prevention of bacteremia following dental extractions. antimicrobial agents chemotherapy 50(9): 2996-3002. elmund gk, morrison s, grant d, nevins m. 1971. role of excreted chlortetracycline in modifying the decomposition process in feedlot waste. bulletin of environmental contamination toxicology 6(2): 129-132. epa. 2012. 2012 guidelines for water reuse. us environmental protection agency, office of wastewater management, office. fahrenfeld nl, ma y, o’brien m, pruden a. 2013. reclaimed water as a reservoir of antibiotic resistance genes: distribution system and irrigation implications. frontiers in microbiology 4: 1-10 (article 130). gullberg, e., cao, s., berg, o. g., ilbäck, c., sandegren, l.,hughes, d., & andersson, d. i. (2011). selection of resistant bacteria at very low antibiotic concentrations. plos pathogens 7(7): 1-9 (article e1002158). karthikeyan k, meyer mt. 2006. occurrence of antibiotics in wastewater treatment facilities in wisconsin, usa. science of the total environment 361(1-3): 196-207. martinez jl. 2009. environmental pollution by antibiotics and by antibiotic resistance determinants. environmental pollution 157(11): 2893-2902. mcardell cs, molnar e, suter mj-f, giger wj. 2003. occurrence and fate of macrolide antibiotics in wastewater treatment plants and in the glatt valley watershed, switzerland. environmental sciencetechnology 37(24): 5479-5486. menezes-blackburn d, al-ismaily s, al-mayahi a, al-siyabi b, al-kalbani a, al-busaid h, al-naabi i, al-mazroui m, al-yahyai r. 2020. impact of a nature-inspired engineered soil structure on microbial diversity and community composition in the bulk soil and rhizosphere of tomato grown under saline irrigation water. journal of soil science and plant nutrition 1-14. menezes-blackburn d, jorquera ma, greiner r, gianfreda l, de la luz mora m. 2013. phytases and phytase-labile organic phosphorus in manures and soils. critical reviews in environmental science and technology 43(9): 916-954. mizuki e, ohba m, akao t, yamashita s, saitoh h, park y. 1999. unique activity associated with non-insecticidal bacillus thuringiensis parasporal inclusions: in vitro cell-killing action on human cancer cells. journal of applied microbiology 86(3): 477-486. negreanu y, pasternak z, jurkevitch e, cytryn e. 2012. impact of treated wastewater irrigation on antibiotic resistance in agricultural soils. environmental science technology 46(9): 4800-4808. pruden a, larsson dj, amézquita a, collignon p, brandt 18 squ journal of agricultural and marine sciences, 2022, volume 27, issue 2 can the irrigation of soils with amoxicillin-enriched water cause the proliferation of bacteria resistant to antibiotics among culturable heterotrophic aerobic soil bacteria? kk, graham dw, lazorchak jm, suzuki s, silley p, snape jr. 2013. management options for reducing the release of antibiotics and antibiotic resistance genes to the environment. environmental health perspectives 121(8): 878-885. rapsinski gj, makadia j, bhanot n, min z. (2016). pseudomonas mendocina native valve infective endocarditis: a case report. journal of medical case reports 10(1): 1-5. reading c, cole m. 1977. clavulanic acid: a beta-lactamase-inhibiting beta-lactam from streptomyces clavuligerus. antimicrobial agents chemotherapy 11(5): 852-857. sengupta s, chattopadhyay mk, grossart h-p. 2013. the multifaceted roles of antibiotics and antibiotic resistance in nature. frontiers in microbiology 4: 47. sidhu ms, heir e, sørum h, holck a. 2001. genetic linkage between resistance to quaternary ammonium compounds and β-lactam antibiotics in food-related staphylococcus spp. microbial drug resistance 7(4): 363-371. strausbaugh lj, sewell dl, tjoelker rc, heitzman t, webster t, ward tt, pfaller ma. 1996. comparison of three methods for recovery of yeasts from hands of health-care workers. journal of clinical microbiology 34(2): 471-473. trevisan d, vansteelant j, dorioz jm. 2002. survival and leaching of fecal bacteria after slurry spreading on mountain hay meadows: consequences for the management of water contamination risk. water research 36(1): 275-283. wu x, conkle jl, ernst f, gan j. 2014. treated wastewater irrigation: uptake of pharmaceutical and personal care products by common vegetables under field conditions. environmental science technology 48(19): 11286-11293. zhang t, li b. 2011. occurrence, transformation, and fate of antibiotics in municipal wastewater treatment plants. critical reviews in environmental science technology 41(11): 951-998. research paper journal of agricultural and marine sciences vol. 23 : 58 – 67 doi: 10.24200/jams.vol23iss1pp58-67 reveived 6 mar 2018 accepted 7 oct 2018 antimicrofouling activities of marine macroalga dictyota dichotoma from the red sea alaa aref abdullah gadhi, mohsen m. o. el-sherbiny, abdul mohsin a. al-sofyani, mohammad abdulaziz ba-akdah, *sathianeson satheesh *sathianeson satheesh ( ) ssathianeson@kau.edu.sa. department of marine biology, faculty of marine sciences, king abdulaziz university, jeddah, saudi arabia introduction in the marine environment, biofilm development on hard surfaces is the initial process, which subse-quently will lead to the attachment of marine organisms, a process commonly known as biofouling growth on substrates (satheesh et al. 2016). the attachment of bacterial communities will help the settlement of higher organisms on the surfaces (hadfield and paul 2001; huang et al. 2012). biofouling, involve all settling organisms such as microfoulers (bacteria, fungi, protozoans, microalgae) and macrofoulers such as barnacles, tube worms, mussels, and bryozoans (stoodley et al. 2002; satheesh and wesley 2008). generally, biofouling is a main concern for underwater man-made structures and a costly problem for marine technology sectors which needs frequent cleaning and antifouling measures (armstrong et al. 2000; qian et al. 2009; satheesh et al. 2016). for example, biofilm formation and subsequent biofouling may increase 14% of the fuel cost in ships and 8%–29% loss in propulsive power has also been attributed to due to mature marine biofilms (schultz et al. 2004; salta et al. 2013). due to the economic loss, various antibiofilm and antifouling strategies are currently practiced in the marine technology sector (satheesh et al. 2016; dahms and dobretsov 2017). the most common antifoulants are األنشطة املضادة للحشف ألحد أنواع الطحالب البحرية )dictyota dichotoma( من البحر األمحر عالء عارف عبداهلل قادي1 وحمسن حممد الشربيىن2 وعبد احملسن السفياين3 وحممد عبد العزيز باعكضة4 وساتيش ساتيانسون* abstract. marine organisms produce a variety of secondary metabolites mainly for achieving the defence against the competitors and predators. these compounds could be used as natural product antifoulants for the management of biofouling growth on marine structures. to understand the antifouling defence strategies of marine macroalgae, the macroalga dictyota dichotoma was collected from the obhur creek of red sea, saudi arabia and extracted using methanol. surface and total extraction methods were performed and tested against a bacterial strain isolated from the microfouling assemblages. the extracts obtained from the macroalgal samples have strong antibacterial and antibiofilm activities against the bacterial strain isolated from the marine microfouling assemblages. the percentage of growth varied significantly between the bacterial culture treated with extracts and control. the total extracts showed strong bacterial growth inhibitory activities in culture plate method. in microtitre plate assay, surface extract showed higher biofilm inhibitory activity than total extract. gc-ms analysis indicated considerable variations in the metabolic profile of the surface and total extracts with higher number of compounds in the surface extract. this study revealed the importance of surface-associated compounds in antifouling defence mechanism of the marine macroalgae. keywords: seaweeds; biofouling; antifouling; bioactive compounds; biofilms; chemical defence; red sea املســتخلص: تنتــج الكائنــات البحريــة جمموعــة متنوعــة مــن املنتجــات الثانويــة بشــكل رئيســي لتحقيــق الدفــاع ضــد املنافســن واملفرتســن. وميكــن اســتخدام هــذه املركبــات كمضــادات لتكويــن احلشــف وإدارة منــو الكائنــات احلشــفية علــى اهليــاكل البحريــة. يهــدف هــذا العمــل ايل فهــم اســرتاتيجيات الدفــاع املضــادة للحشــف مــن الطحالــب البحريــة الــي مت مجعهــا مــن البحــر األمحــر. مت مجــع أحــد الطحالــب الكبــرة وهــو dictyota dichotoma مــن خــور أحبــر يف البحــر األمحــر ، اململكــة العربيــة الســعودية واســتخالص هــذه املــواد الثانويــة باســتخدام امليثانــول. مت إجــراء هــذا االســتخالص مــن كل مــن الطبقــة الســطحية ومن الطحلب الكلي واختبارها ضد ســاللة بكترية معزولة من جمموعات حشــفيه. حتتوي املســتخلصات الي مت احلصول عليها من العينات الكليــة هلــذا الطحلــب علــى أنشــطة قويــة مضــادة للبكترياوكذلكضــد الســاللة البكتريــة املعزولــة مــن الطبقــة احليويــة املكونــة للحشــف.تفاوتت نســبة النمــو بشــكل كبــر بــن البكتريــا الــي متــت معاجلتهــا باملســتخلصات واملعاملــة املرجعيــة. أظهــرت املســتخلصات الكليــة فعاليــة مثبطــة لنمــو البكتريــا يف طريقــة الزراعــة علــى األطبــاق. بينمــا باســتخدام طريقــة االختبــار باســتخدام اطبــاق اإلليــزا، أظهــر املســتخلص الســطحي فعاليــة مثبطــة للطبقــة الســطحية أعلــى مــن املســتخلص الكلــي للطحلــب. وقــد أظهــر حتليــل كروماتوجرافيــا الغــاز املقــرتن مبطيــاف الكتلــة gc-ms تباينــات كبــرة يف شــكل وتركيــب املركبــات الثانوية الناجتة عن عملية األيضلكل من الســطح واملســتخلصات الكلي للطحلب مع عدد أكرب من املركبات الناجتة من الطبقة الســطحية. . كشــفت هــذه الدراســة عــن أمهيــة املركبــات الســطحية املســتخرجة مــن الطحالــب البحريــةيف آليــة الدفــاع املضــادة للحشــف. الكلمات املفتاحية: الكلمات الدالة:الطحالب البحرية، املضادة للحشف، مركبات نشطة، الدفاع الكيميائي، البحر االمحر 59research article gadhi, el-sherbiny, al-sofyani, ba-akdah, satheesh mainly based on heavy metals (copper, zinc) or tributyltin (tbt) and applications of these compounds creates many harmful problems to the environment (bellas 2006; thomas and brooks 2010). these chemical coatings are not only toxic to fouling organisms but also toxic to other non-target organisms (fingerman 1998; hoch 2001). tbt is considered as one of the most toxic materials discharged into the marine environment due to antifouling applications (evans et al. 1995). international maritime organization (imo) banned the use of tbt coatings because of the toxic effects to marine organisms and environment (satheesh et al. 2016). among marine organisms, macroalgae attracted much attention for the natural product research (de nys et al. 1995; sudatti et al. 2008). this was evidenced by the large number of publications available in the scientific domain (see reviews: perez et al. 2016; dahms and dobretsov 2017). marine macroalgae are particularly exposed to many epiphytes (those organisms settling on it) in the environment. to avoid the settlement of organisms on their surfaces, the macroalgae are reported to produce chemically active metabolites (plouguerné et al. 2008). these compounds are of interest due to many drug leads that are isolated from the macroalgae. some studies have analysed the effects of macroalgal secondary metabolites on the planktonic bacterial community (nylund and pavia 2005; paul et al. 2006; dubber and harder 2008; lam et al. 2008). lu et al. (2008) observed that macroalgae such as ulva clathrata have an inhibitory effect on vibrio anguillarum, a fish and mussel pathogen. table 1. compounds identified from the total extract of d. dichotoma based on the peaks observed in the gc-ms spectrum sl. no retention index compound name molecular weight (g mol-1) 1 1937 ethyl pentyl phthalate 264 2 2573 4-methoxy-3-[(2,4,6-trichlorophenoxy)methyl] benzaldehyde 344 3 659 2-butynol 70 4 2434 dihexyl phthalate 334 5 2235 phthalic acid, butyl hexyl ester 306 6 2633 1,2-benzenedicarboxylic acid, butyl decyl ester 362 7 2832 phthalic acid, butyl dodecyl ester 390 8 2171 pthalic acid butyl ioshexyl ester 306 9 3589 propanoic acid, 3,3’-thiobis-didodecyl ester 514 10 3986 propanoic acid, 3,3’-thiobis-ditetradecyl ester 570 11 2011 octadecyl trifluroacetate 366 12 1710 undecane, 3-cyclohexyl 238 13 4085 hexadecane,1,1-bis (dodecyloxy) 594 0 10 20 control surface extract total extract treatment p er ce nt ag e gr ow th figure 1. percentage of bacterial growth by d. dichotoma extracts. bacterial growth was measured using spectrophotometric method for 5 h. a negative percentage indicates inhibition of bacterial growth in compariton to the control. control growth is that observed without extract treatment. error bars indicate the standard deviation of the mean (n=3). 0 5 10 control surface extract total extract treatment c ol on y fo rm in g u ni t ( 10 5 m l− 1 ) figure 2. numbers of colony forming units (cfus) in the presence and absence of extracts (total and surface) of d. dichotoma. growth inhibitory activity was studied by traditional culture plate method. error bars indicate the standard deviation of the mean (n=3). control=without extract treatment. 60 squ journal of agricultural and marine sciences, 2018, volume 23, issue 1 antimicrofouling activities of marine macroalga dictyota dichotoma from the red sea in this study, the macroalga dictyota dichotoma collected from the jeddah coastal waters of red sea was screened for antimicrobial and antibiofilm activities against bacterial strain isolated from marine biofilms. the main objective of this study was to analyse the role of surface-associated molecules in achieving the chemical defence of macroalgae against the microfouling organisms. result obtained in this study will improve our knowledge of the chemical defence strategies of macroalgae and lead to the isolation of novel metabolites from the red sea macroalgae that can be used as natural product antifoulants. materials and methods the macroalga dictyota dichotoma (hudson) j.v. lamouroux (class: phaeophyceae) was collected from the obhur creek on the jeddah coast (near king abdulaziz university marine station, obhur) and transported to the laboratory. in the laboratory, macroalgal samples were rinsed with filtered (millipore, 0.47µm) seawater to remove the debris and other attached organisms and used for extraction. total extraction and surface extraction were followed in order to extract as much as active compounds from the algal samples. methanol was the solvent used for both types of extraction. about 10 g fresh algal samples were used for both surface and total extraction. in total extraction, the fresh macroalgal samples were extracted using methanol (5 ml) after grinding the wet samples using pestle and mortar. the macerated samples were kept in methanol for 5 h at room temperature in dark and after that centrifuged at 3000 rpm to remove the solid part. the solvent part was collected and maintained at -20ºc until further analysis. the surface molecules were extracted by dipping the algal samples in methanol (5 ml) for 10 seconds. after that, the extract table 2. compounds identified from the surface extract of d. dichotoma by gc-ms analysis (continued on next page) sl. no retention index compound name molecular weight (g mol-1) 1 1117 azetidin-2-one 3,3-dimethyl-4-(1-aminoethyl)142 2 1517 2-formyl histamine 139 3 1744 benzene ethanamine, 2,5-difluorobeta.,3,4-trihydroxy-n-methyl219 4 931 octodrine 129 5 1081 1-(5-bicyclo[2.2.1] heptyl) ethylamine 139 6 1662 benzene propanoic acid, .alpha.-(1-aminoethyl)-, [r-(r*,r*)]193 7 2135 propanamide, 3-(3,4-dimethylphenylsulfonyl)241 8 1171 benzene ethanamine, .alpha.-methyl135 9 1716 benzene methanol, 2-(2-aminopropoxy)-3-methyl195 10 907 p-xylene 106 11 907 o-xylene 106 12 2220 4-oxatricyclo[4.2.1.0(3,7)]nonane-9-carboxamide, 5-oxo-n-(phenyl-methyl)271 13 1190 benzene ethanol, .alpha.,.beta.-dimethyl150 14 824 1,3-cyclopentadiene, 5-(1-methylethylidene)106 15 1369 3-pyridine carboxaldehyde, o-acetyloxime, (e)164 16 1500 piperidine, 3-phenyl161 17 1307 cathinone 149 18 2135 propanamide, 3-(3,4-dimethylphenylsulfonyl)241 19 1913 n-methyl-n-(toluene-4-sulfonylmethyl)-acetamide 241 20 1334 phenyl propanolamine 151 21 806 methylpent-4-enylamine 99 22 1294 1-methyl decylamine 171 23 2190 cystine 240 24 1787 dl-alanyl-dl-norleucine 202 25 1891 nitro-l-arginine 219 26 1451 n(epsilon)-methyl-1-lysine 160 61research article gadhi, el-sherbiny, al-sofyani, ba-akdah, satheesh was centrifuged and maintained at -20ºc for antibiofilm assays. bacterial growth inhibition assay (spectrophotometer assay) the bacterial strain vibrio harveyi (ncbi genbank accession number: ky266820) isolated from the marine biofilm developed on nylon nets submerged in the jeddah coastal waters of the red sea (balqadi et al. 2017) was used as a target bacteria for antibiofilm assays. before starting the antibiofilm assays, the bacterial strain was inoculated into marine nutrient broth (zobell marine broth, himedia, india). the broth was kept at 28ºc in an incubator for 48 h and after the incubation, the optical density (od) of the culture was adjusted to 1 at 530 nm (sayem et al. 2011) to maintain equal bacterial cells. three millilitres of bacterial culture was taken in test tubes and 50 µl macroalgal extract (both surface and whole tissue extracts) was added and the control tubes were maintained without any extracts. methanol control was also maintained and no growth inhibition activity was observed. the optical density of the bacterial culture was measured at 670 nm (modified from pan et al. 2014) in a spectrophotometer for a period of 5 h (od was measured at one-hour intervals for 5 h duration). the experiment was carried out in replicate (n=3) and the mean ± standard deviation values were considered. the percentage of bacterial growth/inhibition was calculated using the following formula (viju et al. 2016). eq.(1) where gr is the growth rate and od is optical density at the beginning (odinitial) and at the end of the experiment table 2 (continued). compounds identified from the surface extract of d. dichotoma by gc-ms analysis sl. no retention index compound name molecular weight (g mol-1) 27 1904 5-(prop-2-enoyloxy) pentadecane 282 28 1693 imidazole, 2-amino-5-[(2-carboxy) vinyl]153 29 1673 pentafluoropropionic acid, pentadecyl ester 374 30 1613 tetradecyl trifluoroacetate 310 31 1773 pentafluoropropionic acid, hexadecyl ester 388 32 1435 heptafluorobutyric acid,n-tridecyl ester 396 33 1669 4-heptafluorobutyryloxy hexadecane 438 34 1440 dimethyl phthalate 194 35 1508 benzoic acid, 2-(1-oxopropyl)-, methyl ester 192 36 1555 phenol, 2,6-bis(1,1-dimethylethyl)206 37 2255 pentanoic acid, 5-hydroxy-, 2,4-di-t-butylphenyl esters 306 38 1484 1-(3,6,6-trimethyl-1,6,7,7a-tetrahydrocyclopenta[c]pyran-1-yl)ethanone 206 39 1555 phenol, 3,5-bis(1,1-dimethylethyl)206 40 1549 3-trifluoroacetoxytetradecane 310 41 1639 diethyl phthalate 222 42 1729 phthalic acid, allyl ethyl ester 234 43 1937 phthalic acid, ethyl pentyl ester 264 44 2235 phthalic acid, butyl hexyl ester 306 45 2434 1,2-benzenedicarboxylic acid, butyl octyl ester 334 46 2037 dibutyl phthalate 278 47 1973 1,2-benzenedicarboxylic acid, butyl 2-methylpropyl ester 278 48 1341 hexasiloxane, 1,1,3,3,5,5,7,7,9,9,11,11-dodecamethyl430 49 1580 benzoic acid, 3-methyl-2-trimethylsilyloxy-, trimethylsilyl ester 296 50 1710 octasiloxane, 1,1,3,3,5,5,7,7,9,9,11,11,13,13,15,15-hexadecamethyl578 51 1526 heptasiloxane, 1,1,3,3,5,5,7,7,9,9,11,11,13,13-tetradecamethyl504 52 1339 silane, trimethyl[5-methyl-2-(1-methylethyl)phenoxy]222 62 squ journal of agricultural and marine sciences, 2018, volume 23, issue 1 antimicrofouling activities of marine macroalga dictyota dichotoma from the red sea (odfinal). bacterial growth inhibition assay (culture plate method) the bacterial culture (od530=1) was also used to study the growth inhibition activities of macroalgal extracts by culture plate method. the bacterial culture (3 ml) was taken in a test tube and 50 µl algal extract was added. bacterial culture without macroalgal extract treatment was considered as a control. the test tubes with bacterial cultures treated with macroalgal extracts and controls (in replicates, n=3) were then incubated for 24 h at 28ºc. after 24 h, 100 µl of bacterial culture from the test tube was spread on marine agar plates and the culture plates were incubated at 28ºc in an incubator for 24-48 h. the bacterial colonies developed in each plate was counted and mean (± standard deviation) colony counts were expressed as colony forming units, cfu, ml-1. effects of macroalgal extracts on cell surface hydrophobicity of bacteria the bacterial cell surface hydrophobicity was measured according to the math (microbial adhesion to hydrocarbons) assay described by rosenberg et al. (1980). about 3 ml of bacterial culture was taken in test tubes and 50 μl of macroalgal extract was added. after 1 h the od of the culture was measured at 530 nm in a spectrophotometer. to this culture, 300 μl of hexane was added and vortexed for 1 min. the culture was then left for 10 min. to allow the separation of two phases. the aqueous phase of the culture was separated and used for od measurement as above. the percentage of hydrophobicity (hb(%) was calculated using the following formula. eq.(2) where hb(%) is the percentage hydrophobicity as measured by bacterial cell adherence to hexane and a is the optical density at 530 nm, before (a0) and after (a) washing the cell suspension with hexane. biofilm growth inhibition activity of macroalgal extracts microtiter plate assay the anti-settlement activity of macroalgal extracts against the bacteria was determined by the 96-well microtiter plate method described by coffey and anderson (2014). the bacterial culture (od adjusted to the od 1.0 at 530 nm) was used for the antibiofilm assay. the wells of the microtitre plate were filled with 100 μl of bacterial culture and 5 µl of the extracts were added. the controls were maintained without adding any extract. the plates were incubated at 28ºc for 24 h. after incubation, the plate was inverted to remove the unattached bacterial cells and rinsed with sterile water. after that, 150 µl of 0.1% crystal violet was added to each well of the microtiter plate. the plates were kept for 10 min. for staining of the cells and after 10 min. the plate was inverted to remove crystal violet stain. the wells were rinsed again with sterile water to remove the excess stain. finally, glacial acetic acid (150 µl ) was added to each well and kept for 10 min. after 10 min., the plates were read at 630 nm in a biotek plate reader (winooski, usa). isolation and identification of the pathogen the bioactive compounds present in surface and total extracts of d. dichotoma was analysed by gc-ms (shimadzu gc-ms qp 2010, japan, faculty of meteorology, environment and arid land agriculture, king abdulaziz university). the protocol described by el-din and el-ahwany (2016) for macroalgal extracts was used for the gc-ms analysis. the crude algal extracts were partially purified through silica gel column and analysed in a capillary silica column (30 m ×0.25mm×0.25µm) using helium as carrier gas (1.5 ml for 1 min). the mass spectrometer was operated in the electron impact (el) mode at 70 ev in the scan range of 40–700 m/z. the following ms conditions were used for getting the spectrum: split ratio: 1:10, injected volume: 1 μl, injector temperature: 250°c, the oven temperature: initially 70°c for 3 min and 0 1 2 3 control surface extract total extract treatment pe rc en ta ge h yd ro ph ob ic ity figure 3. effect of d. dichotoma extracts (total and surface extracts) on hydrophobicity of biofilm forming bacterial cells. control=without extract treatment. error bars indicate the standard deviation of the mean (n=3). 0.0 0.2 0.4 0.6 control surface extract total extract treatment o pt ic al d en si ty a t 6 30 n m figure 4. antibiofilm activity of d. dichotoma extracts (total and surface extracts) against vibrio harveyi. error bars indicate the standard deviation of the mean (n=3). 63research article gadhi, el-sherbiny, al-sofyani, ba-akdah, satheesh then increased to 250°c at 14°c min−1. the peaks observed in the gc-ms spectrum where compared with those available in nist 11 – mass spectral library for the identification of the compounds. statistical analysis the data obtained from biofilm bacterial growth inhibition assay was analysed by one-way analysis of variance (anova) followed by post hoc tukey’s test. student’s ‘t’ test was used to analyse the difference in biofilm inhibition activity of algal extracts and control. for all statistical tests p<0.05 was considered as significant. results bacterial growth inhibition assayspectrophotometric method. the biofilm bacterial culture treated with d. dichotoma extracts showed negative growth during the 5 h period. the biofilm bacterial culture without any treatment showed a growth of 20.82 % during 5 h period under laboratory conditions (fig 1). the total extract treated bacterial culture showed a negative growth of -3.11% during the experiment period (5 h). the bacterial culture treated with the surface extract of the d. dichotoma also revealed negative growth (-6.152 %) compared to control. one-way anova showed a significant variation in bacterial growth percentage between control and extract treated cultures (f = 127; df = 2, 8; p < 0.05). however, the bacterial growth inhibiting activity of total extract and surface extract did not differ significantly (post hoc tukey test: total extract vs surface extract, p=0.3). bacterial growth inhibition-culture plate method in traditional culture plate method, the total extract exhibited strong growth inhibitory activity than the surface extract. the bacterial culture without any treatment showed 1,140,000 cfu, ml-1 in culture plates (fig. 2). about 665,000 cfu, ml-1 colonies were observed on the culture plates containing the bacteria treated with the total extract of d. dichotoma. in surface extract treatment, the number of colonies observed was comparatively higher than the total extract treatment (988,000 cfu, ml-1). effects of macroalgal extracts on hydrophobicity of biofilm–forming bacterial cells the bacterial cell surface hydrophobicity of the biofilm-forming bacteria under normal conditions (control, without any algal extract treatment) was 0.9% (fig. 3). however, when treated with algal extracts the bacterial cell hydrophobicity was either reduced or increased. the total extract of d. dichotoma reduced the bacterial cell surface hydrophobicity by 0.7%. however, treatment with surface extract showed an increase in bacterial cell surface hydrophobicity (3.1%). quantification of biofilm prevention by macroalgal extracts: microtitre plate assay the results of microtitre plate assay revealed that the macroalgal extracts inhibited the biofilm formation (fig. 4). the inhibition of biofilm growth was evidenced by the low od values observed from the cultures treated with the extracts. the bacterial cultures treated with total extract showed an od value of 0.48 and for surface extract treatment the od was observed as 0.36. also, the od values were significantly lower than the control (student’s-t test: total extract, t = 4.3, df = 2, p = 0.02; surface extract t = -3.47, df = 2; p = 0.03). gc-ms analysis of macroalgal extracts gc-ms analysis of macroalgal extracts revealed considerable differences between total and surface extracts (fig 5). the total extract of d. dichotoma revealed 13 compounds in the gc-ms spectrum (table 1). most of the compounds are identified as phthalic acid derivatives. the compounds identified include ethyl pentyl phthalate, 4-methoxy-3-[(2,4,6-trichlorophenoxy) methyl] benzaldehyde, dihexyl phthalate, phthalic acid butyl dodecyl ester and phthalic acid butyl isohexyl ester. about 52 compounds (table 2) were identified from the surface extract of d. dichotoma which include azetidine-2-one 3,3-dimethyl-4-(1-aminoethyl), 2-formyl histamine, benzene ethanamine, 2,5-difluorobeta.,3,4-trihydroxy-n-methyl, -oxatricyclo [4.2.1.0(3,7)] nonane-9-carboxamide, 5-oxo-n-(phenylmethyl), 1,3-cyclopentadiene, 5-(1-methylethylidene) and piperidine, 3-phenyl. discussion marine macroalgae are abundant in coastal ecosystems and play key roles in ecosystem functioning (ba-akdah et al. 2016). as herbivory is high in marine ecosystems, the algae possess several defence systems against herbivores (paul et al. 2001). macroalgae also show antifouling defence by different ways such as the use of chemical and physical defences (burns et al. 2003; da gama et al. 2014) or symbiotic relationships between epibionts (e.g., bacteria) (satheesh et al. 2016). due to these chemical defence, macroalgae are one of the most important groups for natural product antifouling research (nylund et al. 2007; hellio et al. 2009; viano et al. 2009; saha and wahl 2013; othmani et al. 2016; carvalho et al. 2017; salama et al. 2017). in the present study, surface and total extracts of the macroalgae d. dichotoma was tested against three important properties growth, cell surface hydrophobicity and biofilm formation (attachment) of the marine bacterial strain isolated from marine microfouling assemblages. the growth of the bacteria was inhibited by both surface and total extracts, though a higher percentage 64 squ journal of agricultural and marine sciences, 2018, volume 23, issue 1 antimicrofouling activities of marine macroalga dictyota dichotoma from the red sea of inhibition was observed in bacterial cultures treated with surface extracts (except in the culture plate method). further, the extracts also possess antimicrobial activity that was evidenced by the negative growth percentages (indicating a decrease in bacterial counts from the beginning) observed in spectrophotometer assay. antimicrobial activity of the genus dictyota have been reported widely in the literature (águila-ramírez et al. 2012; antonysamy et al. 2015). the macroalgal extracts used in this study changed the bacterial cell hydrophobicity which is essential for attachment on surfaces. bacterial cell surface hydrophobicity may play important role in biofilm formation on surfaces (choi et al. 2013). this increase in cell surface hydrophobicity may be due to the release of outer membrane vesicles as an adaptive mechanism against the toxicity of extracts. previous studies by baumgarten et al. (2012) reported the release of membrane vesicles by the bacterium pseudomonas putida strain dot-t1e due to the toxicity of long-chain fatty alcohols, edta and heat. generally, the if the hydrophobicity of the bacterial cell surface increases, then there will be a stronger attachment on hydrophobic surfaces and vice versa (kochkodan et al. 2008; giaouris et al. 2009; krasowska et al. 2014). hence, if the hydrophobicity is low then the bacteria prefer to settle on hydrophilic surfaces. in this study, the macroalgal extracts affected the normal hydrophobicity of the bacterial cells, but the attachment process may depend on other factors including surface characters and environmental conditions. chemical defence strategies of macroalgae and other organisms in the marine ecosystems are the topics of research in recent years (da gama et al. 2014; lopanik 2014; rhode et al. 2015; sacristan-soriano et al. 2017). the difference between the bioactivities of surface and whole-tissue extracts of marine organisms have not been studied detail (nylund et al. 2007). in this study, bacterial growth (spectrophotometer method) and biofilm inhibitory activity (microtitre plate assay) of the surface extract were higher than the total extract. the good performance of surface extract in antibiofilm assay raises the further question on the source of the secondary metabolites. many studies indicated that the epibiotic microbial communities associated with marine organisms are providing the defence to the host against the colonizers and competitors (see review: satheesh et al. 2016). further, fresh algal samples were used for surface and total extraction in this study. hence, the possibility for the presence of metabolites from epibiotic microbial sources cannot be ruled out in both surface and total extracts. the concentration of metabolites in tissue extracts (total extract) may also be higher than the surface extracts (sudatti et al. 2006). this difference may be due to the chemical defence mechanism in macroalgae that usually store the compounds in tissues and transported to the surfaces (see review: da gama et al. 2014). however, results from the gc-ms analysis in this study confirmed an important aspect that the surface extract possess higher number of metabolites than the total extract. the good performance of surface extract in anti-settlement assay might be due to the presence of a large num35 40 44 65 76 93 105 121 135 149 163 177 195 207 222 249 267 281 299 315 327 341 352 371 387 405 426 440 475 491 0 25 50 75 100 100 200 300 400 500 m/z r el at iv e su rfa ce a re a 35 40 44 69 84 100 119 131 147 163 191 207 219 235 251 264 281 295 313 327 342 355 369 383 401 415 429 461 475 491 0 25 50 75 100 100 200 300 400 500 m/z r el at iv e su rfa ce a re a a b figure 5. gc-ms analysis of d. dichotoma extracts. a). gc-ms spectrum obtained for total extract, b). gc-ms spectrum of surface extract. 65research article gadhi, el-sherbiny, al-sofyani, ba-akdah, satheesh ber of compounds, which need further studies. some of the compounds identified from the surface extract such as azetidine-2-one, piperidine, propanamide and imidazole derivatives have potent pharmacological activities (olgen et al. 2008; noolvi et al. 2014; sharma et al. 2016; zhang et al. 2017). imidazole and piperidines exhibited antifouling activities in previous studies (majik et al. 2014; huang et al. 2014). among the compounds present in both surface extracts total extracts, phthalic acid derivate is reported to possess antifouling activities (ganti et al. 2006). in conclusion, the bioactive compounds present in the extract of d. dichotoma could be used as natural product antifoulants. the presence of many compounds in the surface extract confirmed the role of surface-associated molecules in antifouling chemical defence of marine macroalgae. while the source of surface-associated molecules needs further investigation, these metabolites could be used as a potential compounds for 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marine bacterial biofilm. journal of natural products 72: 1299-1304. viju n, satheesh s, punitha smj. 2016. antibiofilm and antifouling activities of extracellular polymeric substances isolated from the bacteria associated with marine gastropod turbo sp. oceanological and hydrobiological studies 45: 11-19. wang kl, wu zh, wang y, wang cy, xu y. 2017. mini-review: antifouling natural products from marine microorganisms and their synthetic analogs. marine drugs 15: 266. zhang x, lei p, sun t, jin x, yang x, ling y. 2017. design, synthesis, and fungicidal activity of novel thiosemicarbazide derivatives containing piperidine fragments. molecules 22: 2085. research paper journal of agricultural and marine sciences 2022, 27(2): 28–40 doi: 10.53541/jams.vol27iss2pp28-40 received 30 dec 2020 accepted 15 nov 2021 fish by-products consumption and discard pattern in nigeria b. egbedi*, and a. o. osibona b. egbedi*( ) brakemi.egbedi@gmail.com, department of marine sciences, university of lagos, nigeria. introduction fish is an important source of livelihood for peo-ple in both developing and developed countries. its contribution to food security is particularly important in nigeria, where malnutrition, unbalanced nutrition, protein shortage, hunger and serious health problems are widespread (akinyele, 2009). according to amao et al. (2006), fish contributes 13.4 kg/person per year of the animal protein consumed in nigeria, however, this value is below the global average fish consumption level of 20.5 kg/person per year (fao, 2018). despite its significant role, fish supply in nigeria from all its sources (i.e. artisanal fisheries, aquaculture, industrial fishing and importation) have failed to meet the country’s domestic demand (akinrotimi et al., 2011), which is on the increase due to the increasing population growth in nigeria and changing consumers’ preferences (adewunmi, 2015). amao et al., (2006) argued that the short fall in fish supply in nigeria can also be attributed to the non-maximization and sustainable utilization of aquatic resources, some of which include by-products. there is no standard definition for the term ‘by-product’ (rustad et al., 2011). it has been defined by kim and mendis (2006) as fish leftovers which are not regarded as ordinary marketable products. ananey-obiri and tahergorabi (2018) defined it as the remaining parts of fish left over after processing, which are often not considered as استهالك الـمنتجات الثانوية من األسـماك ومنط التخلص منها يف نيجرياي ب .إغبدي*، و أ. أوسيبوان abstract. significant portions of by-products are generated and discarded throughout the fish supply chain. to reduce the discard of these by-products and ensure their proper utilization, there is a need to ascertain its discard and consumption pattern among fish consumers. the main aim of this study was to investigate the by-products fish consumers in lagos state, nigeria regard as waste; discard and consume. factors which influence the discard and consumption of these by-products were also investigated. using a multistage sampling procedure, a structured questionnaire was used to obtain information from 300 respondents in three local government areas (lgas) in lagos state, nigeria and the data collected were analyzed using descriptive and inferential statistics. the results show that the scales (92%) were the most discarded by-product followed by gut (89%), gills and fins (85%). the skin was the most consumed by-product while the gut was the least consumed. the three major reasons given by the respondents for the discard of these by-products were that they considered them uneatable, useless and a waste. several interrelating factors, such as social factors, type of fish species and socio-demographic characteristics also influenced the by-products respondents in this study regard as waste; discard and consume. the results in this study indicated that the scales, gut, gills, and fins were largely discarded and underutilized by fish consumers in lagos state, nigeria. there is a need for research on sustainable ways to recover and utilize discarded by-products for the development of value-added products and for the realization of a sustainable circular economy. keywords: fish by-products; waste; fish discard; consumption; nigeria. الـــملخص:يتم التخلــص مــن الكثــر مــن املنتجــات الثانويــة يف مجيــع مراحــل سلســلة توريــد األمســاك. ولتقليــل التخلــص مــن هــذه املنتجــات وضمــان االســتخدام الســليم هلــا، هنــاك حاجــة للتأكــد مــن منــط التخلــص منهــا واســتهالكها بــن مســتهلكي األمســاك. اهلــدف الرئيســي مــن هــذه الدراســة هــو التحقــق مــن مســتهلكي املنتجــات الثانويــة لألمســاك يف واليــة الغــوس، نيجــراي بشــأن اعتبــار هــذه املنتجــات نفــاايت: ســواء التخلــص منهــا أو اســتهالكها. كمــا مت دراســة العوامــل الــي تؤثــر علــى التخلــص مــن هــذه املنتجــات واســتهالكها. ابســتخدام إجــراء أخــذ العينــات متعــدد املراحــل، مت توزيــع اســتبيان علــى الفئة املســتهدفة )300 مســتجيب( للحصول على معلومات يف ثالث مناطق حكومية حملية )lgas( يف والية الغوس، نيجراي ومت حتليل البياانت الي مت مجعها ابســتخدام اإلحصاءات الوصفية واالســتنتاجية. أظهرت النتائج أن قشــور الســمك )92٪( هي عبارة عن منتجات اثنوية يتم يف الغالب التخلــص منهــا كنفــاايت، تليهــا األمعــاء )89٪(، واخلياشــيم والزعانــف )85٪(. كان اجللــد هــو املنتــج الثانــوي األكثــر اســتهالًكا بينمــا كانــت القنــاة اهلضميــة أقــل اســتهالًكا. إن األســباب الرئيســية الثالثــة الــي قدمهــا اجمليبــون علــى االســتبيان بشــأن التخلــص مــن هــذه املنتجــات هــي اعتبارهــا غــر صاحلــة لــألكل وعدميــة الفائــدة وابلتــايل مــن النفــاايت. هنالــك العديــد مــن العوامــل املرتابطــة، مثــل العوامــل االجتماعيــة، وأنــواع األمســاك واخلصائــص االجتماعيــة والدميوغرافيــة الــي أثــرت علــى إجــاابت املشــاركون يف هــذه الدراســة. أشــارت نتائــج هــذه الدراســة إىل أن القشــور، واألمعــاء، واخلياشــيم، والزعانــف يتــم التخلــص منهــا بشــكل كبــر وغــر مســتغلة بشــكل كاٍف مــن قبــل مســتهلكي املنتجــات الســمكية يف واليــة الغــوس، نيجــراي. هنــاك حاجــة للبحــث عــن االســتخدام األفضــل هلــذه املنتجــات الثانويــة مــن أجــل حتقيــق االســتدامة. الكلمات املفتاحية: منتجات األمساك الثانوية؛ نفاايت؛ التخلص من األمساك، االستهالك؛ نيجراي. 29research paper b. egbedi, and a. o. osibona fitting for human consumption. according to rustad et al. (2011), by-products can be understood as any edible or inedible raw material remaining after the production of the main products. in this study, by-products are defined as any part of fish besides the flesh or fillet. in nigeria, the term ‘discard’ and ‘waste’ refer to two separate terms. the former refers to by-products that are thrown away by consumers or respondents for any reason, while the latter refers to by-products which cannot be used for any application (i.e., by-products considered worthless). by-products are generated during the processing of fish obtained from both capture fisheries and aquaculture (olsen et al., 2014) and they include scales, heads, viscera, fins, skin, bones, and frames (ananey-obiri and tahergorabi, 2018). there are varying estimates of the volume of by-products generated worldwide (rustad et al., 2011). pastoriza et al. (2003) claimed that by-products make up about three-quarter of the total weight of the catch, while suresh et al. (2018) reported that they can make up about 50-80% of the total catch, depending on the fish species and level of processing. although some of the by-products have been utilized in the production of low-price ingredients, such as fish meal, fish oil, fish silage, fish fertilizer, fish sauce (suresh et al., 2018); the bulk of it is discarded (falch et al., 2006) at seas, rivers or landfills. this creates disposal and pollution problems as well as the underutilization of the nutrients contained in the by-products (suresh et al., 2018). fish by-products contain protein, lipid, minerals (ghaly et al., 2013) as well as other valuable compounds (rustad et al., 2011). they can be used to produce value added products, such as amino acids, proteins, collagen, gelatin, oil, enzymes, bioactive peptides (ghaly et al., 2013), which in turn can be used to solve problems related to food security and help in generating additional revenue and employment opportunities in the fisheries industry. to effectively exploit these by-products generated from the fisheries industry (both from capture fisheries and aquaculture) in the development of value-added products, knowledge about its consumption and discard pattern among nigerian consumers must be established. research on the consumption, preferences, and market for by-products in asia (tonsberg et al., 1996); iceland (arason, 2003) and norway (jonsson and vidarsson, 2016) have been documented. the head of fish makes up the bulk of fish by-product by volume and export from the icelandic fisheries. other by-products, such as the skin is exported to countries like canada and spain, but a fraction is also used in the production of leather (arason, 2003). the chinese are acclaimed for consuming every part of fish, and the part of fish not eaten are largely used in chinese traditional medicine. in taiwan, most fish by-products are used and those not used, such as gall bladder and eyes, are sometimes exported to japan for fish oil production. milk fish and eel offal are consumed in taiwan. taiwan is also known as norway’s largest export market for salmon heads which are used in the preparation of fish soup. (tonsberg et al., 1996). many africans show a strong preference to fresh fish in its whole form, and when by-products are generated, they have been used as non-conventional supplementary feed or as ingredients for compounded feed as a source of animal protein and mineral especially in small-scale aquaculture farms in countries such as kenya (nyandat, 2007) and nigeria. according to ayinla (2007), fish by-products from processing companies were used in the production of fish meal for use as feed in aquaculture farms before the closure of the only fish meal processing plant in nigeria. there is paucity of information on the consumption and discard pattern of fish by-products among fish consumers in nigeria. the knowledge of nigerian consumers’ attitude towards fish by-products may increasingly contribute to its improvement in terms of recovery, maximization, and sustainable utilization. the main aim of this study was to investigate the by-products respondents in lagos state regard as waste; discard and consume. furthermore, this study aimed at determining the factors which influence the discard and consumption of by-products in the study area using three indices: respondents’ responses, socio-demography and consumption of fish species. lagos state was chosen for this study because it is a coastal state and one boasting of major fish markets with a high fish consumption pattern among its inhabitants. materials and methods study area lagos state is located in the south-western part of nigeria. it is bordered in the north and east by ogun state; in the west by republic of benin, in the south by the atlantic ocean and it stretches over 180 km along the guinea coast of the bight of benin on the atlantic ocean. in terms of land mass, it is the smallest state in nigeria, yet it has the highest urban population (lasg, 2018). about 22% of its total land mass comprises an extensive network of lagoons, rivers, creeks swamps and estuaries (olaoye et al., 2014). lagos which is the 6th megacity in the world is nigeria’s economic, financial, and commercial nerve center. it is dominated by the yoruba ethic group and is divided into 20 local government areas (lgas) and 37 local council development areas (lcdas) respectively (lasg, 2018). sampling procedure and data collection this study used a non-experimental survey design that consisted of the administration of questionnaires to obtain reliable data as well as to document respondent’s perceptions of fish by-products. the questionnaire comprised of questions pertaining to the aim of this survey. information on the socio-demographic characteristics of the respondents; possible factors that affect fish 30 squ journal of agricultural and marine sciences, 2022, volume 27, issue 2 fish by-products consumption and discard pattern in nigeria by-product discard and the most frequently consumed fish species were retrieved. a complete list of all the local government areas, their constituencies and wards were obtained from the lagos state government. the target population for this study were male and female adults (18 years and above) who consume fish in lagos state. the multistage random sampling procedure was employed in data collection as shown in figure 1. a total of three hundred and thirty (330) questionnaires were administered to both male and female fish consumers and a quota of 55 questionnaires were administered per ward to ensure uniformity. in total, information from 300 fully completed questionnaires (50 questionnaires per ward) was used to obtain the data used for this analysis. informed consent was obtained from all respondents by seeking their approval before proceeding with the questionnaire survey. to satisfy the inclusion criteria for participation in the survey, the respondents were asked whether they consume fish and if they were 18 years and above. on responding in the affirmative, the respondents in the selected buildings/houses were included in the study population. in cases of plural eligibility in a building, all the eligible respondents were selected. visual aids in the form of pictures were incorporated in the interview process for easy identification of the listed fish by-products. statistical analysis the data collected for this study were analyzed using descriptive (i.e. frequency distribution and percentages) and inferential statistics (i.e. chi-square). chi-square (x2) test was used to check for statistical significance (p<0.05) in the relationship between the respondents’ age, sex, income, education, and the by-products they regard as waste; discard and consume. results socio-demographic characteristics of respondents the results of the socio-demographic characteristics of the respondents are shown in table 1. two-thirds of the respondents were female and about one-third were male. majority of the respondents (42%) were within the age group 25-35 years. all the respondents had a form of formal education. only 5% had a masters’ degree while 54% of the respondents had tertiary education (ond/hnd and bachelors’ degree). the distribution of respondents by occupation shows that about 82% of the respondents had a source of livelihood. the results further indicate that majority (31%) of the respondents were involved in entrepreneurship. in addition, very few people (1%) were civil servants. even though all the respondents had formal education and many had a means of livelihood, only about 35% earn above ₦ 50, 000. figure 1. multi-stage random sampling procedure used in data collection. 31research paper b. egbedi, and a. o. osibona consumers response on fish by-products fish by-products regarded as waste: the results of respondents’ responses on the various by-products they regard as waste is shown in figure 2. although there were varying responses from the respondents on the by-products they regard as waste; the results indicated that the scales were the by-products largely considered to be a waste by the respondents while the skin was the by-product least considered to be a waste. fish by-products discarded by respondents: as shown in figure 3, the scales were the by-products mostly discarded as reported by 96% of the respondents. following the scales; the gut, fins and gills were the by-products largely discarded by more than 80% of the respondents. the skin was the least discarded by-product. distribution of consumers’ responses fish by-products consumed by respondents: as shown in figure 4, the skin was the most consumed by-product. the gut was the least consumed by-product followed by the scales. the respondents’ reasons for discarding the various fish by-products are shown in figure 5. the three major reasons which influenced the respondents’ choice for discarding these by-products were because they found them uneatable (54%) of no use to them (30%) and a waste (24%). the respondents also listed other factors which influenced their attitude towards fish by-products consumption some of which include preference, beliefs, family upbringing and other social factors. the fish species consumed by the respondents are shown in figure 6. atlantic mackerel (locally called titus) was the fish species mostly consumed by the respondents. inferential statistics chi-square test was used to check for significant differences and to gain a deeper understanding of the relationship between the socio-demographic characteristics: age, sex, income and education (re-categorized) of the respondents and the by-products they discard, consume and regard as waste. there was no statistically table 1. percentage distribution of respondents by socio-demographic characteristics. variable frequency (n) percentage (%) sex male female age groups 18-24 years 25-35 years above 35 years highest level of education ssce ond/hnd bachelor’s degree master’s degree others occupation entrepreneur/business men professional services artisans students sales representatives/executives civil servants clerical workers unemployed monthly income (₦) less than 20,000 20,000-50,000 above 50, 000 98 202 89 125 86 116 77 83 15 9 94 58 53 52 32 4 4 3 96 100 104 33 67 30 42 29 39 26 28 5 3 31 19 18 17 11 1 1 1 32 33 35 figure 2. percentage frequency of fish by-products regarded as waste. 32 squ journal of agricultural and marine sciences, 2022, volume 27, issue 2 fish by-products consumption and discard pattern in nigeria significant relationship (p>0.05) between the respondents’ age and the by-products evaluated. there was a statistically significant relationship (p<0.05) in the sex of respondents and certain by-products they discarded and regarded as waste. the chi-square analysis in table 2 also shows a statistically significant relationship (p<0.05) between respondents’ income and their response to whether they discarded the fins and considered it a waste. their response to the other listed by-products were not statistically figure 3. percentage distribution of respondents who discard fish by-products. figure 4. percentage distribution of respondents who consume fish by-products. 33research paper b. egbedi, and a. o. osibona significant (p>0.05). there was no association between the education of respondents and the by-products they discarded but a statistically significant (p<0.05) relationship was observed in their views on whether they regarded the bone as waste and whether they consumed the fins, skin and bones. discussion knowledge of fish by-products consumers regard as waste; discard and consume is essential if these resources are to be harnessed and utilized effectively. in this study, the term waste and discard refer to two different terms. the scales were the by-products largely regarded as waste followed by the gut, fins, gills bone, head and skin as shown in figure 2. a similar trend was observed figure 5. respondents’ reasons for discarding fish by-products fish species consumed. figure 6. fish species mostly consumed by respondents inferential statistics . 34 squ journal of agricultural and marine sciences, 2022, volume 27, issue 2 fish by-products consumption and discard pattern in nigeria in the by-products discarded by the respondents. as shown in figure 3, 96% of the respondents discarded the scales, thus making it the most discarded by-products followed by the gut (89%), fins and gills (85%). the skin (3%) was the least discarded by-product. a possible reason why the respondents in this study discarded certain by-products such as the scales, gut, gills and fins more than the bone, head and skin may be because they regard them as inedible and worthless. this was further confirmed from the distribution of responses on the factors influencing the discard of by-products as shown in figure 5. where the most discarded by-products were those considered uneatable, of no use or a waste. this finding is in agreement with caruso (2016) who reported that more than 50% of fish by-products were discarded because they were considered a waste. malaweera and wijesundara (2014) also reported that certain by-product, such as the scales are discarded because they are largely considered to be worthless. these by-products: scales, gut, gills, fins, bones, head, and skin are not worthless or a waste because they have potential applications in various industries such as the food, feed and pharmaceutical industries owing to their nutritional or chemical composition. fish scale is a rich source of collagen, the most abundant protein in the body of animals and one which has a vital role in the formation and maintenance of various parts of the body like the bones, ligaments, hair, nails and skin (jonsson and vidarsson, 2016). collagen can be utilized in cosmetic and skin care products owing to its moisturizing, regenerating and film-forming properties (sionkowska et al., 2020). type i collagen obtained from the scales of sea bream were used in the hydrolysate form and it demonstrated angiotensin converting enzyme (ace) inhibitory activity, which can be further used in the treatment of hypertension (fahmi et al., 2004). kandyliari et al. (2020) recorded varying concentrations of proteins, lipids, fatty acids, and minerals in the head, skin, bones, trimmings, gut and gills of large gilthead seabream. when compared to the skin and head, the most consumed by-products in our study, kandyliari et al. (2020) found out that the bones had a higher mineral or ash value. the gills (37.46%) and intestines (43.19%) proved to be good sources of lipids and their values were higher than the lipid content in the head (37.08%) and bones (30.56%). all the by-products had high protein values greater than 30% thus, they can be considered as potential sources of bioactive peptides and for use in the development of functional foods. falkenberg et al. (2014) recorded radical scavenging activity in gill extracts from salmon fish. the skin of cod fish has been used in the development of wound patches and tissue regeneration solutions (jonsson and vidarsson, 2016). research on the production of enzymes from fish intestines are being carried out for potential use in food, pharmaceutical, cosmetic, health and industrial applications (arason, 2003). table 2. chi-square test result on the socio-demographic characteristics and the by-products respondents regard as waste, discard and consume. statements age sex education income by-products regarded as waste head gills fins gut scales skin bones by-products discarded head gills fins gut scales skin bones by-products consumed head gills fins gut scales skin bones 4.968 8.471 4.235 2.854 0.324 4.827 0.097 7.643 0.793 6.159 1.937 6.791 1.585 3.290 6.828 0.933 0.622 1.940 3.316 2.408 0.401 2.478 14.116** 6.895* 11.775** 9.345** 1.472 8.111* 0.636 7.222* 10.589** 0.498 3.178 4.926 5.737 1.069 2.772 2.312 2.870 1.498 5.178 2.606 1.557 2.629 5.868 1.134 2.614 2.375 7.462* 4.903 0.098 4.237 1.854 3.116 2.192 2.809 2.338 0.532 8.316* 4.433 0.984 9.129* 15.136** 2.804 4.428 11.282* 1.124 8.738 3.806 1.146 6.042 2.172 10.378* 4.055 5.811 1.498 0.687 8.184 6.341 8.638 2.524 6.085 6.321 1.538 note: *= significant at 5% (p<0.05) and ** = significant at 1% (p< 0.01) 35research paper b. egbedi, and a. o. osibona the results of the by-products consumed by the respondents indicated that the by-products least consumed were those frequently discarded and regarded as waste. olsen (2004) opined that taste (positive effect), distaste (negative effect) and nutrition are factors that influence consumers preference for particular foods. certain attributes, beliefs and social norms may also contribute to the negative effect of food attitudes. social norms or factors which can be defined as the expectations from people in one’s family, locality or immediate social circle, play a role in determining fish consumption among people all over the world (olsen, 2004; rozin, 1995). during the field survey, the respondents in this study further expressed certain social bias which influenced their consumption of by-products. according to them, social factors such as family upbringing (i.e. watching their mothers discard certain by-products), beliefs (i.e. bones can choke a person to death; gills and guts contain a lot of dirt), social norms (such as the cutting off of the fins of fish by fish mongers in the markets even without being asked to do so) positively contributed to why a large proportion of certain by-products such as the scales, gut, gills and fins were considered uneatable. the social bias stated by respondents in this survey was similar to the findings of gomna and rana (2007). the authors observed that women in various households in niger and lagos state nigeria, could not give certain by-products such as the head and tails to their husbands to consume. according to the women, serving their husbands these by-products to consume may embarrass them owing to the ‘perceived societal expectations’, which saliently infer that consumption of certain parts of fish, indicate the poverty level of a person. the fact that more than 50% of the respondents consumed the skin, head and bone showed that these by-products were considered edible by many nigerians. this can explain why majority of the respondents did not regard the skin, head and bone as waste nor discard them as shown in figures 2 and 3 respectively. jonsson and vidarsson (2016) affirmed that dried cod heads in iceland are mostly exported to nigeria. this is in agreement with the findings of this study where the head of fish was the second most consumed fish by-product among the respondents. the kind of fish species may also influence consumers’ attitude toward by-products. this may be the reason why few respondents agreed that the various by-products (i.e. bone, head, gut, fins, gills and scales) may not always be consumed, discarded or regarded as waste. if the fish is of low value, it is also possible that its by-products may not be regarded as valuable hence, may be discarded and/or regarded as waste. the hypothesis that the kind of fish species may play a role in determining the consumption and discard pattern of its by-products was affirmed by the findings of falch et al. (2006) who reported that liver and roe from relatively large cod (gadus morhua) are the by-products utilized for human consumption in northern europe. according to jonsson and vidarsson (2016), cod is the most important species in iceland and its salted by-products, such as the tongues and cheeks from big cod heads are the most sought after in southern europe. although the fish species consumed by the respondents was not correlated with their response on the by-products they regard as waste, discard and consume; the results in figure 6 show that atlantic mackerel (a frozen fish locally called titus) was the most consumed fish species followed by catfish (clarias gariepinus). the result is in agreement with the findings of oluwaniyi and dosumu (2009) who reported that scomber scombrus (atlantic mackerel) and two other forms of frozen fish namely clupea harengus (herring) and trachurus trachurus (horse mackerel) were the most consumed and readily available marine fish species in south-western nigeria. dauda et al. (2016) also reported that atlantic mackerel was the most preferred frozen fish in kastina state, nigeria. according to oluwaniyi and dosumu (2009) atlantic mackerel being one of the most imported fish species in nigeria; is one of the major sources of animal protein for the average individual and family in nigeria because it is readily available and affordable. the reason for the lower consumption of catfish when compared with atlantic mackerel may be because of its relatively high cost. this is in agreement with oyewole and amosu (2012) who observed that the consumption of catfish in many parts of nigeria was often regarded as a delicacy for the upper class. the texture of the by-products in each fish species may also contribute to whether their by-products can be consumed or not. this is in agreement with oyewole and amosu (2012) who observed that 47.1% of respondents in south-western affirmed that the texture of catfish (clarias gariepinus) which they considered too soft and sometimes nauseating made them averse to catfish consumption. according to malde et al. (2010), bone structure in fish varies between species. the head and fins of mackerel are soft thus can be chewed safely without the fear of the bones choking or wounding the buccal cavity of consumers. the soft texture of its by-products such as the head and bones may be the reason why more than 50% of the respondents in this study consume the head and bones. the chi-square analysis of the socio-demographic characteristics of the respondents show that only sex, education and income were found to be statistically significantly (p<0.05) related to the by-products respondents regarded as waste and those discarded. the chi-square analysis in table 2 show a statistically significant (p<0.05) relationship between the sex of respondents and certain by-products regarded as waste (gills, fins, gut, scales and bone) and those discarded (gills and fins). the results further indicated that the female respondents regarded the gills, fins, gut, scales and bone as waste when compared to the male respondents. the same pattern was also observed in their discard of gills and fins. in nigeria, females are more directly involved in the preparation of 36 squ journal of agricultural and marine sciences, 2022, volume 27, issue 2 fish by-products consumption and discard pattern in nigeria meals in the family and as a result, by-products which they do not consume or those they regard as waste may be discarded. if this happens, such by-products may never be consumed by other members of their household. this may be the possible reason for the variation in responses between the male and female respondents. the findings from this study showed that education was the sole socio-demographic characteristic which was observed to have a statistically significant (p<0.05) relationship in the by-products (fins, skin and bone) consumed by the respondents. respondent’s knowledge of the nutritional benefits of certain by-products may also have an influence on the by-products they consume. this may explain why the respondents who had a tertiary education consume the fins and bones more than those having lower educational degrees (as shown in appendix 2). the positive relationship observed between education and the by-products consumed by the respondents implies that an improvement in the educational status of nigerians on the health benefits of these by-products may lead to an increase in their consumption. this is in agreement with dauda et al. (2016) who observed a positive correlation between education and fish demand among consumers. income plays a role in shaping consumer’s food choices (dauda et al. 2016). the result of the inferential statistics as shown in table 2 indicate that there was a statistically significant (p<0.05) relationship between the respondents’ income and whether they discard and/or regard the fins as waste. in this study, it was surprising to note that a higher number of respondents who earned the least (below ₦ 50, 000) regarded the fins as waste and discarded them when compared to respondents who earned above ₦ 50, 000. the findings in this study therefore contradicts those of adeniyi et al. (2012) who reported that an increase in income, result in a shift of consumers preference towards more expensive sources of animal protein. consumer preference for certain by-products may be the reason why respondents with higher incomes (above ₦50, 000) consumed the fins when compared with those with lower incomes. this is in agreement with albert and tasie (2016) who observed that the consumption of frozen fish among respondents in rivers state, nigeria, was solely dependent on their preference and not their income. attitudes and preference are suggested to play a major role in explaining food consumption behavior in humans (olsen, 2001). food consumption pattern of humans is an extremely complex issue, and it varies significantly across countries, cultures, families, and individuals. it is influenced by many interrelating factors such as the food’s quality, sensory attributes, and availability; consumers preference, personality, knowledge (olsen, 2004), social norms and socio-demographic characteristic of the respondents (verbeke and vackier, 2005). the result in this study indicates that several interrelating factors, such as social factors, type of fish species and socio-demographic characteristics determine the by-products respondents in the study area regard as waste; discard and consume. conclusion the results of this study have shown that the scales, gut, gills and fins are the by-products mostly discarded and underutilized in the three lgas used in this study; while the skin, head and bones are the most consumed by-products. there is a need to educate the public on the benefits of utilizing these by-products to reduce the deleterious effects their discard will have on the environment. to prevent their discard, further research on ways these by-products can be developed into value-added products for both economic and environmental benefits as well as for the realization of a sustainable circular economy is needed. it is hoped that the findings of this study will be of interest to policy makers, research institutions, fish companies, current and future importers of fish by-products and all concerned about attaining the united nations sustainable development goals (sdgs) especially those which deal with ending hunger, poverty and promoting the conservation and sustainable utilization of fisheries resources. acknowledgement the authors would like to thank mr. femi olowu for helping in the analysis and interpretation of some of the data. funding this research did not receive any specific grant from funding agencies in the public, commercial, or not-forprofit sectors. references adeniyi or, omitoyin sa, ojo oo. 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(2005). individual determinants of fish consumption: application of the theory of planned behaviour. appetite 44(1): 67-82. 39research paper b. egbedi, and a. o. osibona appendix 1: percentage distribution of socio-demographic characteristics (sex) and by-products discarded and regarded as waste. socio-demographic characteristics percentage responses (%) percentage responses (%) it is not a waste it is not always a waste yes, it is a waste i do not discard i do not always discard yes, i discard sex head male female gills fins gut scales skin bone 72.4 77.2 13.3 12.4 14.3 9.4 12.2 4.0 9.2 2.0 87.8 92.1 50.0 59.9 17.3 10.9 16.3 4.0 13.3 5.9 17.3 9.9 5.1 3.0 7.1 4.5 30.6 16.3 10.2 11.9 70.4 83.7 72.4 84.7 70.4 86.1 85.7 95.0 5.1 3.5 19.4 23.8 66.3 70.8 5.1 6.9 7.1 7.4 1.0 1.5 1.0 3.5 85.7 93.1 41.8 54.5 15.3 12.9 15.3 5.9 15.3 4.5 11.2 8.9 3.1 1.0 10.2 4.0 33.7 21.8 18.4 16.3 79.6 87.1 77.6 88.1 87.8 89.6 95.9 95.5 4.1 3.0 24.5 23.8 appendix 2: percentage distribution of socio-demographic characteristics (education) and by-products consumed. socio-demographic characteristics percentage responses (%) i do not eat i do not always eat yes, i eat education head ssce and others tertiary education gills fins gut scales skin bone 20.8 20.0 84.8 81.7 90.4 77.7 84.8 88.6 96.8 95.4 4.8 5.7 30.4 14.3 12.8 19.4 10.4 12.0 6.4 14.9 12.8 11.4 2.4 2.3 1.6 10.3 14.4 28.0 66.4 60.6 4.8 6.3 3.2 7.4 2.4 0.0 0.8 2.3 93.6 84.0 55.2 57.7 40 squ journal of agricultural and marine sciences, 2022, volume 27, issue 2 fish by-products consumption and discard pattern in nigeria appendix 3: percentage distribution of socio-demographic characteristics (income) and by-products discarded and regarded as waste. socio-demographic characteristics percentage responses (%) percentage responses (%) it is not a waste it is not always a waste yes, it is a waste i do not discard i do not always discard yes, i discard income head less than ₦ 20,000 ₦ 20,000–₦50,000 above ₦ 50, 000 gills fins gut scales skin bone 79.2 77.8 70.5 17.7 11.1 9.5 8.3 10.1 14.3 8.3 5.1 6.7 0.0 7.1 5.7 88.5 93.9 89.5 60.4 54.5 55.2 10.4 13.1 15.2 6.3 7.1 10.5 2.1 9.1 13.3 13.5 12.1 11.4 3.1 2.0 5.7 5.2 5.1 5.7 17.7 22.2 22.9 10.4 9.1 14.3 76.0 81.8 80.0 89.6 80.8 72.4 78.1 82.8 81.9 96.9 90.9 88.6 6.3 1.0 4.8 21.9 23.2 21.9 75.0 72.7 61.0 6.3 6.1 6.7 6.3 5.1 10.5 3.1 0.0 1.0 1.0 2.0 4.8 91.7 90.9 89.5 53.1 48.5 49.5 9.4 13.1 18.1 12.5 7.1 7.6 3.1 7.1 13.3 10.4 10.1 8.6 2.1 3.0 0.0 5.2 7.1 5.7 25.0 25.3 26.7 15.6 14.1 21.0 81.3 86.9 85.7 90.6 87.9 76.2 86.5 89.9 90.5 96.9 94.9 95.2 3.1 2.0 4.8 21.9 26.3 23.8 research paper journal of agricultural and marine sciences 2023, 28(1): 16–29 doi: 10.53541/jams.vol28iss1pp16-29 received 13 feb 2022 accepted 16 april 2022 evaluation of several chromatographic resins on the separation of dates sugar and their impact on other compounds in dates al-shaaibi sihama, al-alawi ahmeda,*, and wesonga ronaldb al-alawi ahmed( ) ahmed543@squ.edu.om, adepartment of food science and nutrition, college of agricultural and marine sciences, sultan qaboos university, muscat 123, sultanate of oman, bdepartment of statistics, college of science, sultan qaboos university, muscat 123, sultanate of oman introduction one of the major concerns on dates’ industry is the loss of freshly harvested dates during pick-ing, storage, and processing stages (parn et al., 2015). approximately, two million tons per year of dates are abandon as wastes (mrabet et al., 2017). low-quality dates are not consumed by humans but rather discarded or combined in animal feed (parn et al., 2015) due to their hard texture, insect infestation or fungus contamination (abbès et al., 2011; mrabet et al., 2017). the discarded dates was found to have similar characteristics compared with high grade dates especially in sugars, dietary fibers and safety (besbes et al. 2009). therefore, the low quality dates can be utilized into new products like biomass production or metabolites (abbès et al. 2011). the gross economic loss in discarding low quality dates is believed to be much higher when the economic value of dates’ bioactive compounds are considered (elleuch et al., 2008). bioactive compounds in dates waste or low-quality dates products could be extracted and used as value-added constituents. therefore, high value-added products could be prepared from low-quality dates (abbès et al., 2011). however, there are limited studies are reported on the dates’ product development (ahmad & abu bakar, 2018). the main dates’ product used in the food industry is molasses (i.e. syrup) (bedeir, 2014). dates’ molasses can be consumed directly or as an ingredient in many food products (abbès et al., 2011), such as jams, ice cream, bakery products, confectioneries and concentrated beverages (abbès et al., 2011; al-mamary et al., 2014; be تقييم فعالية عدد من الراتنجات الكروماتوجرافية يف فصل سكر التمر و أتثري ذلك على املركبات األخرى املوجودة يف التمر سهام الشعييب، أمحد العلوي، ويسوجنا روانلد abstract. dates are one of the most important food commodities in the middle east countries, including the sultanate of oman. the fruit is regarded as a highly nutritious and healthy food. however, there are two million tons per year of dates that are abandoned waste worldwide. the objective was to establish an optimized method to separate sugars from dates using chromatographic resins and know the effect of those resins on the other ingredients. fard date and three strong-cation gel-type resins (dow-ca, pcr-ca and pcr-na) were used in this study. the free-sugar extracts were analyzed by hplc-ms method to quantify sugars and polyphenols. most of the sugars were adsorbed by all of the tested resins with a higher selectivity towards fructose compared to glucose and sucrose. dow-ca had the lowest sugar adsorption compared to the others. minerals profile by icp detected a sharp reduction in potassium content, which was the main mineral found in fard dates. polyphenols content showed drastic decrease after treatment. overall, the project succeeded in defining a method to remove sugar from dates and extend the loss of minerals and polyphenols in the process. for future work, it is recommended to evaluate the efficiency of other chromatographic resins in sugar separation. keywords: resins, sugar, dates, hplc-ms, bioactive compounds. امللخص:تعتــر التمــور مــن أهــم الســلع الغذائيــة يف دول الشــرق األوســط مبــا يف ذلــك ســلطنة عمــان حيــث اهنــا تعتــر غــذاء صحــي ومغــذي للغايــة. ومــع ذلــك فــان هنــاك فاقــد كبــر، حيــث يتــم التخلــص مــن مليــوين طــن مــن التمــور ســنواي يف مجيــع أحنــاء العــامل. اهلــدف مــن هــذه الدراســة هــو إنشــاء طريقــة حمّســنة لفصــل الســكرايت عــن التمــر ابســتخدام الراتنجــات الكروماتوجرافيــة ومعرفــة أتثــر هــذه الراتنجــات علــى املكــوانت األخــرى. ومت اســتخدام متــر الفــرض كمثــال للتمــور يف هــذه الدراســة كمــا مت اســتخدام ثــالث راتنجــات مــن النــوع اهلالمــي قــوي الكاتيــون وهــي د.ا.و-كالســيوم و ب.ســي.ركالســيوم و ب.ســي.ر-صوديوم. مت حتليــل املســتخلصات الناجتــة مــن عمليــة فصــل الســكرايت جبهــاز الفصــل الكروماتوجــرايف الســائل عــايل األداء املــزود بكاشــف مطيــاف الكتلــة لقيــاس الســكرايت والبوليفينــول. أظهــرت النتائــج امتصــاص معظــم الســكرايت بواســطة مجيــع الراتنجــات املختــرة مــع انتقائيــة أعلــى جتــاه الفركتــوز مقارنــة ابجللوكــوز والســكروز. كان د.ا.و-كالســيوم أقــل امتصــاص للســكر مقارنــة ابلراتنجــات األخــرى. كمــا كشــف اختبــار حتليــل املعــادن بواســطة جهــاز البالزمــا عــن اخنفــاض حــاد يف حمتــوى البواتســيوم، وهــو املعــدن الرئيســي يف متــور الفــرض، كنتيجــة لعمليــة الفصــل. كمــا أظهــر حمتــوى البوليفينــول اخنفاًضــا حــاًدا بعــد فصــل الســكر. بشــكل عــام جنــح املشــروع يف حتديــد طريقــة إلزالــة الســكر مــن التمــور وحتديــد درجــة امتصــاص الراتنجــات الكروماتوجرافيــة للمعــادن والبــويل فينــول املوجــودة يف التمــر. وللعمــل املســتقبلي يوصــى بتقييــم كفــاءة راتنجــات كروماتوجرافيــة أخــرى يف فصــل الســكر. الكلمات املفتاحية: الراتنجات، السكر، التمور، جهاز الفصل الكروماتوجرايف السائل عايل األداء املزود بكاشف مطياف الكتلة، املركبات احليوية النشطة . 17research paper al-shaaibi, al-alawi, wesonga deir, 2014). the syrup is rich in essential nutrients and contains high sugar content which provides rapid energy to the human body (abbès et al., 2011). the syrup consists mainly of moisture, fructose, glucose, and small amounts of sucrose, pectin, protein and calcium (mostafazadeh et al., 2011). dates’ type (mostafazadeh et al., 2011) and processing methods (abbès et al., 2013) affect the date syrup components. besides that, dates’ syrup contains high amount of antioxidants that could reduce progression of many diseases, oxidative stress and inhibit macromolecules oxidation. antioxidants such as phenolic acid, carotenoids, flavonoids, and ascorbic acid has been identified in dates (abbès et al., 2013). the functional ingredients in dates that are biologically beneficial to human health (bedeir, 2014) are greatly enhance dates’ uses in nutraceutical businesses (abu-reidah et al., 2017). additionally, phytochemicals substances enhance date fruit’s organoleptic and nutritional properties (baliga et al., 2011). epidemiological studies demonstrated that routine intake of fruits and vegetables could decrease the risk of several chronic diseases due to their dietary antioxidants content (abu-reidah et al., 2017). therefore, dates’ syrup was recommended to be used as a functional food due to its biological components, e.g. antioxidants activity (abbès et al., 2011). however, there is a concern of regular consumption of high amount of dates with high level of sugar, especially for non-communicable diseases (ncd) patient. fortunately, with modern food technology, bioactive compounds in dates could be extracted individually or collectively. on most dates, glucose and fructose are found in equal quantity whereas sucrose is at is lower level (mostafazadeh et al., 2011). due to the structural similarity of glucose and fructose, their isolation is difficult. there are several methods suggested to extract and purify sugars from sugar cane and beets including enzymatic breakdown, sugar-binding protein; lectins, fractional freezing techniques, and carbonation (buchele, 2010). each method has disadvantages such as high cost, undesirable breakdown, toxicity and strong bound complexes. other studies had used toxic solvent to separate sugar from the media (e.g. juice), such as methanol, chloroform and acetonitrile. also, there are chromatographic granular applied in the sugar refining process, which was found to be safe. chromatographic carbohydrate separation mechanism is based on hydrophilic or hydrophobic interactions, ion exchange, size exclusion and ligand exchange (gramblička & polakovič, 2007; nobre et al., 2009). the resins of sulfonated polystyrene-co-divinylbenzene (ps-dvb) are largely used in sugar industry due to their higher selectivity and capacity and they are chemically inactive (luz et al., 2008). generally, resins are classified into two major groups; macroporous and gel-type. resins are functionalized with cations to form complexes with sugar hydroxyl group and according to the orientation of this group a selective adsorption occur. therefore, cation and sugar conformation limits the cation-sugar affinity and distribution coefficient. in addition, number of oh groups have a major effect on cation-sugar complex stabilities (tiihonen et al., 2002). moreover, the formed adsorption forces between resins and sugars are weak forces and thus are easily broken by hot water (buchele, 2010). calcium gel-type resins are the mostly used resins in food industry for fructose-glucose separation (luz et al., 2008). nevertheless, sodium and potassium cation resins are recommended for these sugar separation (nobre et al., 2009). several patents were registered that documented the use of chromatographic resins in producing sugar-free juice (blase & thomas, 2008; buchele, 2010; pease and pu, 2016). baikenov et al. (2020) published a work describing the optimal parameters for the separation of glucose, fructose, and oligosaccharides from glucose-fructose syrup using chromatographic resins. in the case of dates, mostafazadeh et al. (2011) implemented the same approach to separate sugars from date syrup. however, all the aforementioned methods aimed to optimize and model sugar separation process without studying the effect on the other important compounds such as polyphenols and minerals. therefore, the objective of this study was to study the efficiency of different chromatographic resins (calcium and sodium resins) in removing dates’ sugars and their impact on other important compounds that exist in dates. the final aim was to produce date products. materials and methods materials and chemicals date sample of fard variety in fully ripe stage (tamar stage) was purchased from the local market. all reagents and standards were of analytical grade and were obtained from sigma-aldrich unless otherwise stated. methanol lc-ms grade from fisher scientific (uk), acetonitrile lc-ms grade from bdh chemicals (germany), nitric acid for trace metal analysis from bdh (germany) and ammonium acetate hplc grade from j. t. baker (germany). the resins used were dowex™ monosphere™ 99ca/320 (dow-ca) (dow chemical, usa), pcr641ca 3282q/18/2 (pcr-ca) and pcr642na mr7-916 (pcr-na) (purolite®, usa). specifications of the used resins are shown in table1. table 1. resins characteristics resin type ionic form volume diameter functional group dow-ca strong acid cation, gel ca++ 300 330 μm sulfonate pcr-na strong acid cation, gel na+ 315 ± 20 μm sulfonic acid pcr-ca strong acid cation, gel ca++ 310 ± 10 μm sulfonic acid 18 squ journal of agricultural and marine sciences, 2023, volume 28, issue 1 evaluation of several chromatographic resins on the separation of dates sugar and their impact on other compounds in dates sugar separation sample preparation: the chart in figure 1 illustrates sample preparation steps for sugar extraction. sugar extraction was done similarly to the method described by myhara et al. (2000) with some modifications. briefly, 100 g of pitted dates were homogenized with 70% or 75 or 80% (70 oc) ethanol in a ratio of 1:4 (w: v) by ultramixer homogenizer (ultra-turrax, t-25 basic) at a speed of 13,000 rpm till a homogeneous slurry was produced. then, the solution was sonicated in a water bath at 70 oc for 15 minutes. after that, the solution was centrifuged at 10,000 rpm, at 30 oc for 10 min. the supernatant was collected and filtered using glass microfiber filter paper (a, whatman) while the residue was extracted again by ethanol solution following the same procedure used above. the extraction step was repeated thrice for complete removal of sugar. only the first extract was used in the subsequent analysis. then, the residue was dried in an oven (carbolite, uk) at 85 oc for 6 h, milled and stored in a freezer (20oc) till further analysis. sugar concentration of the filtered supernatant was measured by an automatic refractometer (hi 96802, hanna instruments inc., romania) then diluted by 70% or 75 or 80% ethanol to produce 10% and 15% ethanolic sugar solution. summary of the sample preparation steps are shown in figure 1. resin conditioning: three different types of resins were used for sugar extraction; dow-ca, pcr-ca and pcr-na. the resins were conditioned before their use as per the manufacturer instructions with minor modification. briefly, the resin was soaked in deionized water in 1:4 (v/v) ratio for 5 min. then, the water was decanted and 70% or 75% or 80% ethanol was added to the conditioned resin in a ration 1:4 (v/v) and left for 5 min to ensure complete water removal. then the ethanolic solution was decanted. sugar extraction: the diluted ethanolic sugar solution; 10% and 15% were sonicated for 5 min to remove gasses that could interfere sugar adsorption by resin as suggested by the resin manufacturer. then, 50 ml of the conditioned resin was mixed with the diluted ethanolic sugar solution in different ratio (1:1, 1:2 and 1:3, resin: solution) in a reagent bottle. two temperatures (20 oc and 40 oc) were used in this experiment that was adjusted using water bath. sugar brix was measured by an automatic refractometer (hi 96802, hanna instruments inc., romania) at different time intervals; 1, 10, 20, 30 and 40 min. the mixture was caped and kept under continuous mixing using low speed in a magnetic stirrer plate throughout the experiment. after 40 min, the ethanolic sugar solution was decanted carefully from the resin and collected in a separate beaker. the resin was washed and conditioned before another cycle of extraction. an aliquot (5 ml) of the ethanolic sugar solution was taken for further analysis and the rest was subjected to another extraction cycle using the same resin after it is being washed and conditioned using the same procedure used in cycle 1. the various experiment parameters are summarized in table 2. resin washing: to release the adsorbed sugar from the resin before moving to the second extraction cycle; resins were washed using hot water as per the instructions of the manufacturer. prior to the washing step, the resins were soaked in 100 ml de-ionized water (i.e. at room temperature, rt) for 5 min to remove any residual ethanol and then the water was discarded. then, hot deionized water (70 oc) in a ratio 1:2 was added. the mixture was kept under continuous stirring using a magnetic stirrer in a hot plate. brix was measured continuously till no further change in the reading; then water was removed and a new hot deionized water was added. the washing step was repeated three times. after washing, the resin was re-conditioned again by ethanol (70% or 75 or 80% depending on the starting ethanol solution) to remove any remaining water before starting a new extraction cycle. figure 1. summary chart of sample preparation 19research paper al-shaaibi, al-alawi, wesonga sample concentration: samples collected from first and second extraction cycles as well as from dates’ stock solution were dried by vacuum concentrator (concentrator plus, eppendorf, usa) at 30 oc. dried samples were stored at -60 oc until further analysis. ash determination samples were ashed using a muffle furnace (carbolite, uk) at 550 oc for 18 h (aoac 2000, method p). few drops of hydrogen peroxide were added to samples that had carbon. samples that showed persistent black spots were suspended in a deionized water and filtered through an ashless filter paper (whatman no. 541). the filtrate was dried in an oven and the filter paper with the black materials were ashed using the same conditions used initially. minerals profile by induc tively coupled plasma (icp) sample preparation: some of the ashed samples were used to determine minerals profile by icp, including date fruit, date residue, sugar extract and 15% (1:3) first cycle according to (en act oct1, 2017) method with slight modification. the ashed sample was digested by adding 2 ml concentrated nitric acid hno3 and kept in a hot plate at 250 oc until it was dissolved. then drops of deionized water were added to cool the solution, thereafter, transferred to 10 ml volumetric flask and diluted with deionized water to the mark. after that, the solution was filtered using ashless filter paper (whatman #541) and then stored in a fridge at 2 oc until it was injected to icp. icp conditions: perkin elmer-optima 8000 icp-oes with spectral range 165-900 nm and resolution < 0.009 nm @ 200 nm was used. the detector was uv-sensitive, dual backside-illuminated charge-coupled device (ccd) array detector with two photosensitive segments containing 176 by 128 pixels. the detector is cooled to -8 °c using a single-stage integrated peltier cooler. the rf coil power was 1500 w and the peristaltic pump flow rate was 1 ml/min. the plasma gas was argon with flow rate of 8 l/min and the shear gas was compressed air. the tested elements were arsenic, zinc, lead, cobalt, cadmium, nickel, iron, boron, mercury, manganese, chromium, copper, aluminum, sodium, potassium, magnesium and calcium. sugar and polyphenol quantification by hplc-ms sugar and polyphenols were quantified using nexera-x2 lc instrument (shimadzu corporation, japan) composed of lc-30ad pump, sil-30ac autosampler and mass-spectrometer lcms-2020 following the manufacture recommendation. the column used was imtakt unison uk-amino column (250×3 mm, 3 µm) maintained at 37 oc by the unit cto-20ac. the ionization mode interface was duis (esi and apci) and dl temperature was 250 oc and heating block at 300 oc. nitrogen was used as nebulizing gas and drying gas at a flow rate of 1.5 l/min and 15 l/min, respectively. four events were used, two for scan (positive and negative) and the other remaining two events were sim positive and negative according to m/z ± (h+) or + (ch3cooh-). interface voltage was 3.5 kv, dl voltage, quarry dc and rf voltage were sat at default. scan speed was 10000 u/ sec from 100 m/z until 1000 m/z with event time 0.1 s. the mobile phase consisted of lc-ms grade acetonitrile (mobile phase a) and 100 mm ammonium acetate (mobile phase b). the gradient for mobile phase b was programmed as follows, 5%-100% (0-15 min), then 100% for 5 min then 0% for 6 min. the concentrated samples were dissolved in 1 ml methanol and filtered into vials using 0.22 µm nylon syringe filter (alwsci group, china). sample injection volume was 1 µl and flow rate was 0.3 ml/min. statistical analysis the statistical analysis was carried out using microsoft excel 2021 (version 16.57,© 2021 microsoft ) to calculate one-way analysis of variance (anova) to test significance of the means of the samples. the significance of the difference between the analyzed group parameters was analyzed by student’s ttest. also, r program (version 4.1.1 (r core team, 2021)) used to test parameters correlations by tukey test, regression test and anova interaction plots. p<0.05 was considered statistically significant. the collected data were expressed as mean ± standard deviation (sd). results optimization of separation condition many tests were performed before finalizing sample preparation and extraction procedure. in reference to table 2. experimental parameters for sugar separation parameters conditions sample sugar % 10% 15% temperature 20oc 40oc extraction cycle 1 2 resin dow-ca pcr-ca pcr-na solvent conc. 70% 75% 80% ratio (resin: sample) 1:1 1:2 1:3 time 1 min 10 min 20 min 30 min 40 min 20 squ journal of agricultural and marine sciences, 2023, volume 28, issue 1 evaluation of several chromatographic resins on the separation of dates sugar and their impact on other compounds in dates the sample preparation, deionized water was compared with ethanol to check the best solvent for sugar solubilization that will facilitate sugar adsorption by the resin. it is noteworthy that mostafazadeh et al. (2011) used deionized water to solubilize dates’ sugars. also, mode of process was evaluated by comparing column (separatory funnel) to batch under vacuum (conical flask). the results (not shown) found that resins adsorbed more sugar (higher capacity) when ethanolic solution was used. moreover, ethanol offered many other advantages such as lower solubility of minerals and precipitation of water-soluble polysaccharides such as pectin. with regard to mode of separation, batch separation was better than column extraction due to longer contact time between resin and sugar molecules. vacuum was not critical factor on the experiment since the solution was degassed. furthermore, use of refractometer to measure sugar content in ethanolic solutions was a challenge as ethanol itself gives a reading. this problem was solved by spiking the different ethanolic solutions (70%, 75%, 80%) with sugars to construct a calibration curve to normalize effect of ethanol on brix readings. standards were prepared by dissolving glucose (10% w/w) and fructose (10% w/w) in the different ethanolic solutions to produce 20% stock ethanolic sugar solution. then, the solution was diluted into several concentrations. the curve equation for each ethanolic solution (70%, 75%, 80%) was used to determine sugar concentration in all the solutions afterwards. date sugar in this study, glucose, fructose and sucrose were quantified in fard dates using hplc. the analysis was found to be the most important factor that affects resin chromatographic separation (baikenov et al., 2020). the results of sugar content and types are shown in figure 2. this information was used to adjust dates’ sugar-ethanolic extract to the desired concentration. as per the obtained data, in 100 g of dates, glucose and fructose level was ~ 35 g individually whereas sucrose was ~1.6 g. level of ethanol (70-85%) was not significant in sugar extraction from fard fruit. parameters of the separation method interactions of the method parameters: the aim of this work was to find an effective method to separate sugars from dates’ extract. several factors and variables were tested to reach to the optimum separation conditions. these factors were adsorbent (resin) type, sugar concentration, solvent concentration, resin to sample ratio, extraction temperature, experiment time and number of extraction cycle. through r program, the variations between these factors with respect to sugar concentration readings after each treatment were tested by tukey multiple comparisons of means. table 3 illustrates the results of this test for extraction cycle 1 and table 4 for extraction cycle 2. interaction of experimental time and resin types in extraction cycle 1 and extraction cycle two showed no significant differences as it is clear in figures 3 and 4. however, there was a significant difference (p <0.05) between sample to resin ratio (1:1, 1:2, 1:3) within time in extraction cycle 1 (figure 5) and extraction cycle 2 (figure 6). secondly, temperature (temp) did not show an effect (20°c vs. 40°c) in sugar separation in the extraction cycle 1 (figure 7). however, in extraction cycle 2 the time interval from 20 min to 40 min was signififigure 2. effect of ethanol concentration on extraction of sugar from fard dates. 21research paper al-shaaibi, al-alawi, wesonga cantly different (p <0.05) in brix readings between 20°c and 40°c (figure 8). moreover, there was a significant difference (p <0.05) between the two tested concentrations (15% and 10%) according to brix readings with experiment time interval in extraction cycle 1 (figure 9) and extraction cycle 2 (figure 10). resin-sugar holding capacity: due to the differences in the functional group and cation in the used resin, holding capacity was different as illustrated in figures 11-13. pcr-ca was the highest sugar adsorbent (99%) followed by pcr-na, however, the differences between the two resins was not significantly different (p<0.05). dow-ca resin showed the lowest adsorption capacity towards sugar; maximum adsorption was towards fructose (94%). as it’s clear from figures 11-13, sugar holding capacity is proportional with resin:solution ratio. also, 80% ethanol concentration enhanced sugar absorptivity by resin compared to the other concentrations (70% and 75%). table 3. analysis of variance for cycle 1 parameter df sum sq mean sq f value pr(>f) resin 2 4.4 2.2 1.990 0.138 temp. 1 0.0 0.0 0.005 0.944 de.conc 1 1597.9 1597.9 1432.704 < 2e-16 *** ssratio 2 967.9 483.9 433.910 < 2e16 *** time.interval 4 1358.7 339.7 304.559 < 2e16 *** residuals 529 590.0 1.1 de.conc: dates extract concentration (10 %& 15%), ssratio: solution: resin ratio, signif. codes: ‘***’ = 0.0 table 4. analysis of variance for cycle 2 parameter df sum sq mean sq f value pr(>f) resin 2 5.5 2.8 2.618 0.07391 temp. 1 13.0 13.0 12.305 0.00049 *** de.conc 1 435.4 435.4 411.591 < 2e-16 *** ssratio 2 2286.0 1143.0 1080.457 < 2e-16 *** time.interval 4 724.7 181.2 171.266 < 2e-16 *** residuals 529 559.6 1.1 de.conc: dates extract concentration (10 %& 15%), ssratio: solution: resin ratio, signif. codes: ‘***’ = 0.0 figure 3. correlation between resin types and time in cycle one 22 squ journal of agricultural and marine sciences, 2023, volume 28, issue 1 evaluation of several chromatographic resins on the separation of dates sugar and their impact on other compounds in dates resin-sugar affinity: all of the tested resins adsorbed most of the sugars in the sample, especially pcr-na and pcr-ca compared to dow-ca. however, fructose was adsorbed more than both glucose and sucrose. resin washing: as mentioned earlier, sugar separation in this study was based on an adsorption cycle followed by a desorption cycle (nobre et al., 2009). in the desorption cycle, sugars separated from resin by washing using hot water. according to the washing procedure, it involved three cycles of washing by hot deionized water. in each cycle, brix was measured to check efficiency of the desorption process. the sum of brix readings for each washing cycle is illustrated in figure 14. at washing cycle 1, most of the adsorbed sugars was released, > 60% of the total adsorbed sugar. dow-ca resins discharged the highest amount of sugars followed by pcr-na then pcr-ca. in cycle three, all of the tested samples recorded less than 1 g/ml of sugar. this makes the resin reusable for further sugar removal cycles. sugar content glucose, fructose and sucrose were determined in the resin-treated ethanolic solution. the main findings are illustrated in figure 15. hplc-ms results were supporting figure 4. correlation between resin types and time in cycle two figure 5. dates solution ratios with time in cycle 1 23research paper al-shaaibi, al-alawi, wesonga brix readings at the separation experiment. from figure 15 we can conclude that ca resins, dowand pcr-ca, were more selective to fructose than glucose and sucrose. similar observation was also reported by baikenov1 et al. (2020). while na-resin (pcr-na) had no sugar selectivity towards any of the sugars (i.e. glucose and fructose). thus, calcium resins made the solution rich in glucose than sucrose and fructose. however, na-resin produced sucrose rich solution. overall, sugar content in the resulting extract from exposure to the various types of resins was very low compared to the original sugar content in dates. this illustrates that the experiment succeeded in removing sugars from dates’ ethanolic extract. ash content and minerals profile ash contents: all three used resins in this study adsorbed most of the ash during the first extraction cycle (about 98%). figure 16 illustrates the main minerals in the 75% ethanolic solution extract after treatment with the different resins (1:3 resin to sample ratio). resins with the same cation have similar properties; dowand pcr-ca. calcium became the main mineral followed by sodium and potassium in solutions treated by dow and pcr-ca resins. however, sodium content was not affected in the solution treated by pcr-na resin. figure 6. dates solution ratios with time in cycle 2 figure 7. temperature effect in brix reading with time in cycle 1 24 squ journal of agricultural and marine sciences, 2023, volume 28, issue 1 evaluation of several chromatographic resins on the separation of dates sugar and their impact on other compounds in dates polyphenol contents: dates fruits are rich in polyphenols content as many studies proved. in this study, the free polyphenols content was determined using lc-ms. total of 18 compounds were detected in fard date samples as shown in figure 17. caffeic acid and the gallic acid were the dominant polyphenols. similar to the observation with whole fard dates fruits, 18 free polyphenols were identified in the treated extract but with different proportions. this is because the resins had adsorbed some of the polyphenols. polyphenols’ adsorption varied with the resin type as shown in figure18. figure 18 displays the profile of polyphenols in the sugar ethanolic solutions resulted from treatment by the three different resins. it is very evident that pcr-na and pcr-ca resins adsorbed mainly sugars along with other compounds including free polyphenols. the percentage range of polyphenols hold by pcr-na and pcr-ca were 75% 100% and 89% 100%, respectively, depending on the type of the polyphenol. for example, m-coumaric acid was the lowest polyphenol adsorbed by pcr resins, whereas dow-ca resin adsorbed 95% of m-coumaric acid present initially in the solution. figure 8. temperature effect in brix reading with time in cycle 2 figure 9. sample concentration with time in cycle 1 25research paper al-shaaibi, al-alawi, wesonga discussion carbohydrates are the major component in dates fruit; around 70%-80% (dw) (bedeir, 2014). glucose and fructose are the main simple reducing sugars in dates along with the disaccharide sucrose (al-harrasi et al., 2014). al-farsi et al. (2005) reported that fard dates contain 28 g/100g (fw) glucose and the same for fructose while the total sugar was 56.7 g/100g (fw). however, for the same variety, myhara et al. (1999) found that 100 g (dw) contains 43.6 g glucose, 42 g fructose and 0.53 g sucrose. al-harrasi et al., (2014) determined the total carbohydrates in fard dates which were 79 g/100 g (dw). the differences are attributed to moisture content, sample preparation and quantification methods. in this study, fard dates was found to contain ~82% sugars which is in line with what was reported earlier for the same variety (myhara et al., 1999). furthermore, as it is clear in the figures 2 and 3, there was no significant differences in the extraction power of glucose or fructose or sucrose content (p <0.05) by different ethanol concentration (70%, 75% and 80%). this means either solution can be used for this step (sugar extraction step) to prepare sugar ethanolic solution. sugars exhibit high solubility in ethanolic solution and the percentage of solubilization decreases with the decrease in water percentage (bockstanz et al., 1989). ethanol offers many advantages over other organic solvents, such as safety and re-usability while eliminates extraction of other ingredients (such as pectin) that could complicate the subfigure 10. sample concentration with time in cycle 2 figure 11. dow 99 ca sugar holding capacity figure 12. pcr642 na sugar holding capacity 26 squ journal of agricultural and marine sciences, 2023, volume 28, issue 1 evaluation of several chromatographic resins on the separation of dates sugar and their impact on other compounds in dates sequent treatments (rayo-mendez et al., 2019). during resin treatment, ethanol was unfavorable medium for sugars, thus sugar migrated into the polar resins. other tested parameters were significantly (p >0.05) affected in sugar adsorption at extraction cycle 1, except type of resin and temperature. however, in extraction cycle 2, resin type and waiting time (20-40 min) did not affect the separation significantly. a previous study employed na+ and k+ cation resins for similar separation at 25 °c and 40 °c concluded that in mono-component sugar mixture higher temperature decreased adsorption while sugar adsorption increased with increased temperature in multi-component sugar mixtures (nobre et al., 2009). overall, the tested parameters had different effect on sugar adsorption. temperature and the used resin types were not significantly effective variables in sugar adsorption. while sample concentration and resin:sample ratio were significantly effective (p >0.05) in sugar extraction within the different variables used. figure 13. pcr641 ca sugar holding capacity figure 14. sugar concentration in each washing cycle for each resin figure 15. fructose, glucose and sucrose ratio in sugar-free dates extract 27research paper al-shaaibi, al-alawi, wesonga pcr-ca was the highest in adsorbing sugar (99%) with no significant differences (p <0.05) within sugar type. however, dow-ca resin was the lowest in sugar adsorption. cation type had effect in sugar adsorption and affinity. as proved by this study, the solution treated by calcium resins contained more glucose than sucrose and fructose. however, na-resin-treated-solution contained higher sucrose. this result is supported by mostafazadeh et al. (2011) findings where they used pcr-ca to separate fructose from date syrup. moreover, this finding was also observed elsewhere with other resins; potassium geltype and sodium macroporous resins (nobre et al., 2009). additionally, sugar selectivity was found to be unaffected by temperature. work done by nobre et al. (2009) on na resins reported similar results to our findings. this was attributed to the similarity in molecular weight of sugars. however, fructose/sucrose selectivity was higher anticipated to fructose-resins strong adsorption. also, gel-type resins are higher selective than macroporous resin towards fructose (gramblička & polakovič, 2007; nobre et al., 2009). moreover, tiihonen et al. (2002) showed that higher ethanol content are better suited for sugar separation by ca2+ column than na+ and la3+ columns. whereas water sugar mixture is best for la3+ columns. the main mineral in fard dates was potassium which had declined after exposure to the three tested resins. also, the main free polyphenol in fard dates fruits were caffeic and gallic acids. this finding is somehow different than other studies that reported gallic acid the main free polyphenol in omani dates (ahmed et al., 2013; al harthi et al., 2015). however, after exposure to the resin, rutin figure 16. main minerals in 75% ethanolic solution extract after treatment with 1:3 resin:sample ration figure 17. polyphenols compounds extracted by different ethanol concentration from fard dates 28 squ journal of agricultural and marine sciences, 2023, volume 28, issue 1 evaluation of several chromatographic resins on the separation of dates sugar and their impact on other compounds in dates and procyanidin b2 became the highest in the samples treated by dow-ca resin. for samples treated by pcr resins, m-coumaric acid and vanillic acid became the highest in pcr-na and pcr-ca treatments, respectively. conclusion the method presented in this work showed that resins had different power and selectivity towards different sugars. pcr-ca had the highest adsorbing power towards sugar (99%) followed by pcr-na and dow-ca, respectively. calcium based resins had more affinity towards glucose, whereas sodium based resin had more affinity towards fructose. furthermore, all resins adsorbed minerals and polyphenols along with sugars. temperature was found to be not critical. references abbès f, bouaziz ma, blecker c, masmoudi m, attia h, besbes s. (2011). date syrup: effect of hydrolytic enzymes (pectinase/cellulase) on physico-chemical characteristics, sensory and functional properties. lwt-food science and technology 44(8): 1827–1834. abbès f, kchaou w, blecker c, ongena m, lognay g, attia h, besbes s. (2013). effect of processing conditions on phenolic compounds and antioxidant properties of date syrup. industrial crops and products 44: 634–642. abu-reidah im, gil-izquierdo á, medina s, ferreres f. (2017). phenolic composition profiling of different edible parts and by-products of date palm (phoenix dactylifera l.) by using hplc-dad-esi/msn. food research international 100: 494–500. ahmed j, almusallam a, al-hooti sn. (2013). isolation and characterization of insoluble date (phoenix dactylifera l.) fibers. lwt food science and technology 50(2): 414–419. ahmad sz, abu bakar ar. 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(2008). juice processing. united states patent application, patent no. us 20080044531 a1. figure 18. the main polyphenols (%) in resin treated sugar-ethanolic solution 29research paper al-shaaibi, al-alawi, wesonga bockstanz gl, buffa m, lira ct. (1989). solubilities of alpha anhydrous glucose in ethanol-water mixtures. journal of chemical and engineering data 34(4): 426–429. broumi m, ali l. (2014). nutritional assessment and antioxidant analysis of 22 date palm (phoenix dactylifera) varieties growing in sultanate of oman. asian pacific journal of tropical medicine 7(s1): s591–s598. buchele wn (2010). sugar extraction process. united states patent application, patent no. us 20100068373 a1. elleuch m, besbes s, roiseux o, blecker c, deroanne c, drira ne, attia h. (2008). date flesh: chemical composition and characteristics of the dietary fibre. food chemistry 111(3): 676–682. gramblička m, polakovič m. 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(2000). sensory and textural changes in maturing omani dates. journal of the science of food and agriculture 80(15): 2181–2185. myhara rm, karkalas j, taylor ms. (1999). the composition of maturing omani dates. journal of the science of food and agriculture 79(11): 1345–1350. nobre c, santos mj, dominguez a, torres d, rocha o, peres am, rocha i, ferreira ec, teixeira ja, rodrigues lr. (2009). comparison of adsorption equilibrium of fructose, glucose and sucrose on potassium gel-type and macroporous sodium ion-exchange resins. analytica chimica acta 654(1): 71–76. parn oj, bhat r, yeoh tk, al-hassan aa. (2015). development of novel fruit bars by utilizing date paste. food bioscience 9: 20–27. pease s, pu g. (2016). chromatographic separation of sugars using blend of cation exchange resins. united states patent application, patent no. us 9441280 b2. r core team (2021). r: a language and environment for statistical computing. r foundation for statistical computing, vienna, austria. rayo-mendez lm, gómez av, tadini cc. (2019). extraction of soluble sugars from banana puree to obtain a matrix rich in non-starch polysaccharides. food chemistry 294: 539–546. tiihonen j, markkanen i, paatero e. (2002). complex stability of sugars and sugar alcohols with na+, ca2+, and la3+ in chromatographic separations using poly(styrene-co-divinylbenzene) resins and aqueous organic eluents. chemical engineering communications 189(7): 995–1008. research paper journal of agricultural and marine sciences vol. 24 : 51– 62 doi: 10.24200/jams.vol24iss1pp51-62 reveived 3 dec 2018 accepted 14 mar 2019 improving solanine production in in vitro cultures of solanum nigrum l. using different chemical and physical factors *mu,ad a. alkiyyam1, rida a. shibli*2, reham w. tahtamouni3, tamara s. alqudah4, bashaer b abu-iramaileh4 introduction plant cell and tissue culture technologies have been established from different explant types, such as plant leaves, stems, roots, and meristems under sterile conditions for the production of secondary metabolites besides micropropagation purposes. recently, successful production of many elite chemical compounds from plant cell suspension cultures has been التحكم ببعض الظروف الزراعية يعزز من إنتاج السوالنني يف مزارع السويقات :.solanum nigrum l النباتية والكالوس واملعلقات اخللوية لنبات املغد األسود نبات طيب بري معاذ أ. القيام ورضا أ. شبلي ورهام و. هتتموين ومتارة س. القضاة وبشائر ب. أبو الرمايلة abstract. solanum nigrum l. is a medicinal plant of solanaceae family with distinguished therapeutic properties. traditionally, s. nigrum. had been used as an anti-tumorgenic, antioxidant, hepatoprotective, diuretic, and antipyretic agent. the most important alkaloid member in this plant is solanine. therefore, this study was conducted to utilize tissue culture techniques for the enhancement of solanine production in the in vitro grown cultures of this promising neglected plant. for callus growth and development experimental part, the highest callus growth parameters (callus diameter (21.4 mm) and callus fresh weight (2202.4 mg) were obtained in callus grown on murashige & skoog ms media supplemented with 2,4-dichlorophenoxyacetic acid (2.0 mg·l-1) plus 1.5 mg·l-1 thidiazuron. similar trend was also obtained in cell suspension culture experiment, as maximum growth was recorded at similar hormone combination. moreover, high-performance liquid chromatography analysis revealed that, solanine was affected by growth regulator type and concentration. the highest solanine levels were obtained when the explants were treated with 6-benzylaminopurine at level of 2.0 mg·l-1, as solanine content reached up to (2.61, 1.53 mg.g-1) for callus and cell suspension, respectively, while, microshoot contained the highest solanine (4.52 mg.g-1 dw) at 6-benzylaminopurine level of 1.6 mg.l-1. additionally, carbon source had positively affected solanine level, where 0.2 m sucrose resulted in production of the highest amounts (3.13, 2.03 and 1.20 mg.g-1 dw) of solanine in microshoots, callus and cell suspension, respectively. also, exposing microshoots and callus to light intensity of (100 µmol.m-2s-1) yielded the highest solanine content (4.03 and 1.26 mg.g-1 dw, respectively),while the lowest solanine levels (1.50 and 0.48 mg.g-1 dw) were observed in plant material exposed to the lowest light intensity treatment (25 µmol.m-2s-1). our results were promising for production of solanine especially in the microshoot (4.52 mg.g-1 dw) using 1.6 mg.l-1 of ba, as compared with previous studies which maximized production of solanine only up to 2.33 mg. g-1 dw using 0.5 mg.l-1 of cholesterol in solanum lyratum. keywords: callus; carbon source; cell suspension; light, solanin. املســتخلص: املغــد األســودsolanum nigrum l. نبــاٌت طــيٌّ ينتمــي للعائلــة الباذجنانيــة ويتميــز خبصائصــه العالجيــة املميّــزة، فقــد اســتخدم تقليديــاً كعامــل مضــاد لــألورام ومضــاد لألكســدة ومضــاد للســمية الكبديــة، وكمــدر للبــول وخافــض للحــرارة. يعــد الســوالنني القلويــد األكثــر أمهيــة يف هــذا النبــات. لذلك أجريت هذه الدراسة مستخدمة تقنيات الزراعة النسيجية لتعزيز إنتاج السوالنني يف هذا النبات الواعد واملستحق للمزيد من االهتمام وباستعمال مــزارع النمــو املختربيــة. لوحــظ يف القســم التجريــي املتعلــق بنمــو الكالــوس وتطــوره أّن القيــم األعلــى لنمــو الكالــوس املــزروع )قطــر الكالــوس: 21.4 مــم، 2,4-dichlorophenoxyacetic مضافــاً لــه محــض ms ووزنــه الرطــب: 2202.4 مــغ( قــد مت احلصــول عليهــا باســتعمال وســط موراشــج وســكوج 2( مــغ.ل1-( وthidiazuron )1.5 مــغ.ل1-(. كمــا مت التوصــل إىل تأثــر مماثــل يف جتربــة زراعــة املعلــق اخللــوي، حيــث ُســجلت أقصــى قيمــة للنمــو باســتعمال املزيــج اهلرمــوين ذاتــه. عــالوة علــى ذلــك، كشــف التحليــل اللــوين الســائل عــايل األداء أن الســوالنني قــد تأثــر بنــوع وتركيــز منظــم النمــو، فقــد مت تســجيل أعلى مســتويات للســوالنني عندما عوجلت العينات النباتية بـ)2.0 مغ.ل1-( من benzylaminopurine-6، حيث وصل حمتوى الســوالنني إىل )2.61، 1.53 مــغ.غ1-( يف كل مــن الكالــوس واملعلــق اخللــوي، علــى التــوايل، يف حــني احتــوت الســويقات النباتيــة علــى أعلــى مســتوى مــن الســوالنني )4.52 مــغ.غ1مــاء مقطــر( عنــد إضافــة )1.6 مــغ.ل1-( مــن benzylaminopurine-6. كمــا كان ملصــدر الكربــون أثــر إجيــايب يف مســتوى الســوالنني، حيــث أدى اســتعمال 0.2 مــول مــن الســكروز إىل إنتــاج كميــات أعلــى مــن الســوالنني )3.13، 2.03، و1.20 مــغ.غ1 مــاء مقطــر( يف كل مــن الســويقات النباتيــة والكالــوس واملعلــق اخللــوي علــى التــوايل. وكذلــك فــإن تعريــض الســويقات النباتيــة والكالــوس لشــدة الضــوء البالغــة )100 ميكرومول.مــر2ثانيــة 1-( قــد حقــق أعلــى حمتــوى مــن الســوالنني )4.03 و1.26 مــغ.غ1مــاء مقطــر) علــى التــوايل، بينمــا لوحظــت أدىن مســتويات للســوالنني )1.50 و0.48 مــغ.غ1مــاء مقطــر( يف املــواد النباتيــة عنــد تعرضهــا ألدىن معاجلــة مــن شــدة الضــوء )25 ميكرومول.مــر2 ثانيــة 1-(. الكلمات املفتاحية: الكالوس، مصدر الكربون، املعلق اخللوي، الضوء، السوالنني. 52 squ journal of agricultural and marine sciences, 2019, volume 24, issue 1 improving solanine production in in vitro cultures of solanum nigrum l. using different chemical and physical factors reported in various medicinal plants by exposing the cultured explants to different growth conditions in vitro such as, using different types of culturing media, growth regulators, sugars and manipulating some physical environmental factors, such as, temperature, moisture and light (robbins et al., 1996; shibli and ajlouni, 2000; chawla, 2002; jasmin et al., 2011). solanum nigrum l. (black nightshade) (fig. 1a) is an annual herbaceous plant of 30-90 cm height with a green, smooth and semi-climbing stem. this plant grows wild in wet woods, near river, waste land, old field, ditches roadside and cultivated land (pronob and islam, 2012). despite of being considered as a noxious weed that grows in many agro-climatic regions (sundari et al., 2010), s. nigrum has been recently classified as a medicinal plant with distinguished therapeutic properties (rajani et al., 2012). traditionally, s. nigrum had been used in oriental systems of medicine for various purposes as, an anti-tumorgenic, antioxidant, hepatoprotective, diuretic, and antipyretic agent (lee et al., 2003 ; raju et al., 2003). solanine is considered the most important alkaloid produced in the green fruits of s. nigrum and many studies have confirmed solanine activity as a cardiac antiaccelerating agent (cham; 1994). this is in addition to its use as an antimicrobial agent against many strains of bacteria and fungi (roddick, 1996). moreover, solanine is recently recommended as a new therapy for treatment of many cancer cell lines (cham, 2008; ji et al. 2008; sutkovic et al., 2011). solanine can be found in the wild plants at high concentrations; but if we want to study how secondary metabolites are produced in plant cells in details we must adopt the tissue culture approach where the interference of all other factors such as, environmental factors is excluded. moreover, wild plants in general are not effective sources to study secondary metabolites, as most medicinal wild plants are subjected to heavy loss due over collection; climate fluctuations; grazing ;urbanization , etc. tissue culture is a potent technique that is used to enhance massive plant in vitro propagation and huge plantlets production under controlled conditions in few times and all around the year (vinod and dipali , 2013). furthermore; in vitro culture permits better understanding of the mechanism by which plant cells synthesize secondary metabolites and the factors the can maximize their production by optimizing the cultural conditions of plant cells (dicosmo and misawa, 1995; saito and mizukami, 2002; jasmin et al. 2011). additionally, in vitro propagation of medicinal plants with enriched medicinal compounds and cell culture methodologies for selective metabolite production was found to be highly useful for commercial production of medicinally important compounds, as tissue culture techniques guarantee sustainable supply of true to name plants with high purity of the medicinally important compounds by excluding environmental factors and any possibility of genetic drift due to outcrossing (hussain et al., 2012). large-scale plant tissue culture is found to be an attractive alternative approach to traditional methods of plantation as it offers controlled supply of biochemirida a. shibli*2 ( ) mu,ad a. al-kiyyam1, department of plant production and protection, faculty of agriculture, jerash university, jordan. rida a. shibli*2, department of horticulture and agronomy, faculty of agriculture, university of jordan, jordan, email: r.shibli@ ju.edu.jo. reham w. tahtamouni3, department of applied sciences, princess alia university college, al-balqa applied university, jordan. tamara s. alqudah4, hamdi mango center for scientific research (hmcsr), university of jordan, jordan. bashaer b abu-iramaileh4, hamdi mango center for scientific research (hmcsr), university of jordan, jordan. table 1. effect of plant growth regulators type and level on callus fresh weight and diameter of in vitro grown s. nigrum in combination with (2.0 mg.l-1) 2,4-d, except for (c & 0.0) concentrations. plant growth regulator concentration (mg.l-1) tdz callus weight (mg) callus weight (mg) 0.0 551.7z f 6.3 d cx 613.4 e 6.9 d 0.5 679.8 d 7.0 d 1.0 1729.2 b 16.1 b 1.5 2202.4 a 21.4 a 2.5 1229.5 c 10.9 c kinetin 0.0 551.7 d 6.3 a 0.5 589.8 c 6.8 a 1.0 623.3 a 7.0 a 1.5(cx) 613.4 ab 6.9 a 2.5 601.9 b 6.9 a bap 0.0 551.7 d 6.3 d cx 613.4 c 6.9 c 0.5 809.9 b 8.1 b 1.0 1137.8 a 10.2 a 1.5 615.9 c 7.0 c 2.5 605.5 c 7.1 c x c (control treatment) represents callus establishment media consisted of ms solid media plus 2.0 mg.l-1 2,4d and 1.5 mg.l1 kinetin. z means within columns for each growth regulator having different letters are significantly different according to tukey hsd at p≤0.05. 53research article kiyyam, shibli, tahtamouni, al-qudah, abu-iramaileh of (5.0 mm) and weight of (500 mg) were subcultured into a hormone free ms medium (hf-ms) for one week to remove the carry-over effects of plant growth regulators (pgrs.). later, the calli were sub-cultured into fresh ms media supplemented with (2.0 mg·l-1) 2, 4-d in combination with different levels (0.0, 0.5, 1.0, 1.5 or 2.5 mg·l-1) of kinetin, 6-benzylaminopurine (bap) or tdz. control treatment was consisted of solid ms media plus (2.0 mg·l-1) 2, 4-d in combination with 1.5 mg·l-1 kinetin (callus establishment media). data were obtained after 8 weeks for callus diameter and weight. cell suspension cultures approximately 1.0 g of friable callus, which was still in its active growth phase (i.e., after the 15th day of subculture) was placed in 250 ml jar containing 50 ml liquid ms medium (murashige and skoog, 1962). the culture media used in this experiment were as follows: hormone free ms solid media , ms media plus hormone combination which was found to be optimum for maximum callus growth in callus multiplication experiments (2.0 mg·l-1 2,4-d + 1.5 mg·l-1 tdz) (control) or ms media plus (0.1 or 0.25 mg·l-1) bap in combinations with (0.1 or 0.25 mg·l-1) 2,4-d. cultures were incubated in complete darkness at 25ºc on a horizontal shaker at 100 rpm for 15 days. growth of cells was determined by measuring packed cell volume (pcv) described by allan (1996) under sterile conditions at 7and 15 days of which was expressed as ml cell pellet per culture. for pcv measurements, which were repeated three times per treatment, the cell suspension in flasks was gently shaken and then 10 ml aliquots were transferred into 15ml graduated conical centrifuge tubes followed by centrifugation at 200 g for 5 min using a swing-out rotor (allan, 1996) in order to determine the best hormonal combinations that can give the maximum cell suspension culture weight. cal’s independent of plant availability (sajc et al., 2000). therefore, this study was conducted to investigate the possibility of improving solanine production in s. nigrumin in vitro grown cultures by manipulating some tissue culture growth conditions (chemical and physical factors). materials and methods establishment and multiplication of plant material microshoots mature seeds of s. nigrum were collected from the mother plants grown in wild in jerashjordan (n: 32.27372, s: 35.89464).then the seeds were surface sterilized before being subcultured into full strength ms (murashige and skoog, 1962) solid media at concentrations of 4.4 g.l-1 and supplemented with 1.0 ml.l-1 ms vitamin mixture (sigma aldrich murashige and skoog vitamin powder 1000x) pluse 0.1 m sucrose. seeds were cultured and kept up in the growth room under a daily temperature of 24±1 °c under a 16/8 (light/dark) photoperiod of 45–50 μmol m-2s-1 irradiance, until germination. for shoot multiplication, a prelimenary experiment was conducted to determine which growth regulatores would result in best shoot multiplication (data not shown), and based on the obtained results nodal segments (2 cm) from the germinated seedlings were subcultured into ms media supplemented with (1.2 mg·l-1) thidiazuron; 1-phenyl-3-(1,2,3-thiadiazol-5-yl (tdz) plus 0.1 mg·l-1alpha-naphthalene acetic acid free acid (naa) (media that was found to be best for shoot proliferation). the cultures were kept under growth room conditions described earlier. callus callus was successfully established from excised in vitro grown leaf discs subcultured into callus establishment media (ms solid media supplemented with 2.0 mg·l-1 of 2,4-dichlorophenoxy acetic acid (2,4-d) and 1.5 mg·l-1 of kinetin) and kept under complete dark condition for 8weeks. after callus establishment, calli with diameter table 2. effect of different combinations of bap and 2,4-d on growth rate of cell suspension cultures of s. nigrum within different periods. days growth regulator 0.0 cx bap 0.1 mg.l-1+ 2,4-d 0.1 mg.l-1 bap 0.1 mg.l-1 + 2,4-d 0.25 mg.l-1 bap 0.25 mg.l-1 + 2,4-d 0.1 mg.l-1 bap 0.25 mg.l-1 + 2,4-d 0.25 mg.l-1 7 11.5dz 39.9 a 19.5 c 19.7 c 18.7 c 27.5 b 15 37.7d 88.5 a 44.9 d 59.2 c 56.1 c 68.7 b x c (control treatment) represents callus multiplication media consisted of liquid ms media plus 2.0 mg.l-1 2,4 d + 1.5 mg.l-1 tdz. zmeans having different letters are significantly different according to tukey hsd at p≤0.05. cell suspension culture growth expressed as % packed cell volume (pcv) 54 squ journal of agricultural and marine sciences, 2019, volume 24, issue 1 improving solanine production in in vitro cultures of solanum nigrum l. using different chemical and physical factors effect of chemical factors and light intensities on the in vitro production of solanine effect of cytokinins microshoots were grown in ms media supplemented with 0.1 m sucrose, 0.1 mg·l-1 naa in addition to different concentrations of different cytokinin growth regulators: bap, kinetin or 6-(gamma, gammadimethylallyl amino) purine (2ip) at levels of 0.0, 0.4, 1.0, 1.6 or 2.0 mg·l-1. the subcultured microshoots were kept under normal growth room conditions. for callus and cell sspenssion, a part of plant material was treated with the different cytokinin types and levels mentioned before and kept under dark, while the other part was cultured on a media consisted of ms media plus best hormone formula resulted in the callus multiplication experiments (2.0 mg·l-1 2,4-d and 1.5 mg·l-1 tdz) and maintained under complete dark conditions. after 8 weeks, plants material (microshoots, callus and filtered cell suspension) from each experiment were collected, dried in the oven (35 ºc for 2 days). next, the dried plants material were grounded in a mortar and pestle, and pooled before being analyzed for alkaloids quantification (extraction and analysis), and the results were compared with those obtained from wild mother plant from jerash grown in green house at faculty of agriculture/ university of jordan, amman -jordan. effect of carbohydrate sources microshoots of s. nigrum (1.0 cm long) were subcultured into a hormone free ms medium for one week to remove the carry-over effects of plant growth regulatores (pgrs). next , the microshoots were transferred into hormone free ms media supplemented with elevated concentrations of sucrose, glucose and fructose (0.05, 0.1, 0.15 and 0.2 m). for the callus and cell suspension, plant material were subcultured into callus multiplication media described earlier and supplemented with the different sugar types as mentioned above and kept under dark. after 8 weeks, the plant materials were dried and grounded as described earlier before being analyzed for alkaloids quantification (extraction and analysis) and the results were compared with those obtained from wild mother plant. effect of different light intensities microshoots and callus samples were kept at different light intensities (25, 50, 75 or 100 μmol. m−2.s−1) irradiance for 8 weeks. the plant material was collected, dried and grounded as described earlier before being analyzed for alkaloids quantification (extraction and analysis), and the results were compared with those obtained from wild mother plant from jerash grown in green house at faculty of agriculture, university of jordan, amman -jordan. determination of alkaloids content using high performance liquid chromatography(hplc): alkaloids extraction samples (3 g) from each powdered plant material taken from each experiment, in addition to samples taken from the wild plants collected from the five different places in jordan (including the wild mother plant from jerash) were extracted thrice with 200 ml of 5% aqueous acetic acid and its ph was adjusted to 11 with ammonium hydroxide before being vacuum filtered. the alkaline extract was partitioned with water-saturated butanol and evaporated to dryness, purified and the residue was weighed and dissolved in acetonitrile and analyzed. preparation of solanine stock solution and working standards solanine stock solution at concentration of 20 ppm was prepared by weighing 2.0 mg of solanine in 100ml volumetric flask, dissolved and completed up to volume by methanol hplc grade .the prepared stock solution was stored at 4ºc in dark. working solutions were prepared by serially diluting stock solutions using the mobile phase at concentrations of 0.5, 1, 2.5, 5 or 10 ppm. fresh working standards were prepared daily. about 2.0 mg (±0.01mg) of solanine reference standard was dissolved into a 100 m1 volumetric flask and about 100 ml of acetonitrile until complete dissolve. four points were constructed for the calibration curves ( fig. 2) and hplc chromatogram (fig. 3) for solanine was obtained before starting chemical analysis. chromatographic conditions chromatographic separation was carried out on hplc shimadzu system (japan), equipped with (lc-10 at) pump, a manual injector, a system control (scl-10a),a uv/vis detector (spd-10a), and an analytical column – c18 (250 4.6 mm i.d. 5 µm, merck, germany). the software, shimatzu class-vp (v6.14 sp1) chromatography data system was used as the data acquisition system. an ultrasonic cleaner (jeiotechus) , a vm300 vortex (germany industrial corp), an electronic balance (precisa 410am-fr, switzerland), a supra 30k (hanil science industrial co., ltd., germany) ultra-centrifuge, a microfiltration unit (advantec, mfs, inc) with a rotary pump (rocher 300) were used in sample treatment. the alkaloids were analyzed using hplc apparatus consisting of shimadzu lc-10a system equipped with a model lc-10at pump, an spd-10a variable wavelength detector, a cbm-10a interface module with class lc-10 hplc software using a merck c-18 column (250×4.6, i.d., 5 μm particle size). 55research article kiyyam, shibli, tahtamouni, al-qudah, abu-iramaileh solanine identification test the basic method for solanine identification followed in this research was that set by mohy-ud-din et al., (2010). after conditioning the column and reaching equilibrium with the mobile phase, 20 μl of each of the solanine standard solution was injected at 0.5ml/min flow rate and tested at the range of detection wavelength 204 nm in order to determine solanine peak. method development when the basic solanine identification method was applied, no separation between solanine peak and a matrix impurity peak was achieved. therefore, it was necessary to develop this method, to improve the separation of solanine from the peak of impurity in plant extract matrix. the best separation of solanine was achieved on the following detection conditions: mobile phase: 25 acitonitrile (acn), 75 potassium dihydrogen phosphate and 5ml triethylamine at ph 7.5, the flow rate was 0.5 ml/ min and uv detector wavelength set at 204 nm. experimental design and arrangement all treatments in each experiment were arranged in a completely randomized design (crd) and consisted of five replicates with 4 explants /replicate. meanwhile, in alkaloids content determination experiment each treatment consisted of 3 replicates with 3 samples /replicate and sample dry weight of (3.0 g). the collected data were statistically analyzed using spss analysis system and analysis of variance (anova) was used to analyze the obtained results, and mean was separated with probability level of 0.05 according to the tukeys hsd. results and discussion callus induction and multiplication: effect of tdz in callus multiplication experiments, the combination of 2,4,d (2.0 mg·l-1) plus tdz resulted in increasing callus growth in terms of fresh weight and diameter at all tdz levels compared to control (c) and 0.0 mg·l-1 (table 1). similar results were reported by sajid and faheem (2009) who investigated the effect of thidiazuron (tdz) on in vitro micropropagation of solanum tuberosum and they reported that, tdz promoted callus induction and multiplication due to its biological activities in inducing the synthesis and accumulation of endogenous cytokinins which would direct cell division and callus clumps formation. the highest callus diameter (21.4 mm) and callus fresh weight (2202.4 mg) (table 1) were recorded in callus grown in hormone combination of 2,4-d (2.0 mg·l-1) plus 1.5 mg·l-1 tdz. improving callus growth using different combinations of 2, 4-d and tdz of was also reported to be efficient in stephania tetrandra, as it was found that, best callus growth and multiplication resulted on ms media plus 1.0 mg·l-1 2, 4d and 0.5 mg·l-1tdz (chao et al., 2011). however, increasing tdz level to 2.5 mg·l-1 resulted in decreasing callus fresh weight and diameter (table 1), which might be attributed to the high tdz concentration that might had inhibitory influence on callus growth and development. effect of kinetin callus fresh weight and diameter increased significantly with increasing kinetin level in the media up to 1.5 mg·l -1 (table 1). the maximum values for both tested figure 1. a: solanum nigrum plant. (http://www.homeredies.com/solanum-nigrum-medicinal-uses-and-images). b: chemical structure of solanine (nino et al. 2009). b 56 squ journal of agricultural and marine sciences, 2019, volume 24, issue 1 improving solanine production in in vitro cultures of solanum nigrum l. using different chemical and physical factors parameters were obtained in the combination of 1.0 mg·l-1 kinetin and 2.0 mg·l-1 2, 4-d as it yielded the highest callus fresh weight (623.3 mg) and diameter (7.0 mm) as shown in table (1). generally, kinetin performance was poor in terms of callus growth compared to the results obtained in tdz treated explants. this contrasted the results reported about callus induction and multiplication of securinega suffruticosa and viola uliginosa, as they were maximized when their explants were grown on media supplemented with 2,4-d plus kinetin (raj et al., 2015; slazak et al., 2015; respectively). this might refer to the fact that, plant responses to the different types and combinations of the growth regulators are species dependent. effect of bap adding bap in combination with 2,4-d improved callus growth significantly up to bap level of 1.0 mg·l1 compared to the results recorded in control (c and 0.0 mg·l -1) (table 1). the maximum callus weight (1137.8 mg) and diameter (10.2 mm) were obtained in bap level of 1.0 mg·l-1 (table 1). these results agreed with those reported by sridhar and naidu (2011), sheeba and palanivel (2013) and sheeba et al., (2013) through their investigation on callus induction procedure of s. nigrum, solanum surattense and physalis minima, respectively. the obtained results from callus multiplication experiment can lead to a conclusion that, tdz (1.5 mg·l-1) and 2,4, d (2.0 mg·l-1) was the best combination that gave the maximum callus fresh weight and diameter of s. nigrum. cell suspension culture the obtained results indicated that, adding 2.0 mg·l-1 2,4-d plus 1.5 mg·l-1 tdz (callus multiplication hormonal combination (c)); to the culture medium had yielded the maximum cell growth rate compared to the other treatments (table 2). meanwhile, for bap and 2,4d combination treatments, the highest cell growth rate (68.7%) was recorded in bap (0.25 mg·l-1) and 2,4-d (0.25 mg·l-1) treatment (table 2), this agrees with song et al., (2002) results, as they reported that the media containing high bap (0.25 mg·l-1) and 2,4-d (0.25 mg·l-1) produced greater rates of cell division in sugar beet (beta vulgaris) than either medium with lower bap (0.1 mg·l1) and 2,4-d (0.1 mg·l-1) levels or the control (hormone free ms liquid media). this agrees with kshirsagar et al. (2015) findings in their study on swertia lawii burkill; as the maximum growth of cells suspension cultures (fresh weight = 2.8 g and dry weight 0.6 g) was observed after 15 days of culture in ms liquid medium supplemented with 2, 4-d (2.0 mg l−1) and bap (2.0 mg l−1). similarly, maximum growth of cells in suspension were observed between 10–15 days were reported in passiflora alata using similar combination of growth regulators (2, 4-d and bap) (pacheco et al., 2012). effect of chemical factors and light intensities on the in vitro production of solanine calibration curve a calibration curve of alkaloids (solanine) reference standard solution was prepared (fig. 2) in order to calculate solanine content in the microshoots, callus and cell suspension of s. nigrum and comparing the results to solanine content in the wild type plant as mentioned above. figure (2) explains how solanine contents was determined and calculated in the samples (a quantification method) using different quality control points includes different concentrations of the solanine standard to build up the calibration curve of solanine. alkaloids table 3. effect of cytokinine type and concentration on solanine % (mg.g-1) dry weight (dw) in microshoots, callus and cell suspension of in vitro and wild (in green house) grown s. nigrum. concentration (mg.l-1) bap kinetin 2ip microshoot w* 4.92 az 4.92 a 4.92 a cy 1.82 d 1.82 d 1.82 e 0.4 2.20 c 2.00 d 2.16 d 1.00 3.93 b 2.60 c 3.00 c 1.6 4.52ab 3.83 b 3.87 b 2.0 3.77 b 4.00 b 3.43 bc callus w 4.92 a 4.92 a 4.92 a cy 0.73 d 0.73 d 0.73 e 0.4 0.95 d 1.97 c 1.10 d 1.00 1.62 cd 2.13 c 1.53 c 1.6 2.01 c 2.21 c 1.62 c 2.0 2.61 b 2.82 b 2.55 b cell suspension w 4.92 a 4.92 a 4.92 a cy 0.43 c 0.43 d 0.43 c 0.4 0.63 c 0.50 d 0.42 c 1.00 1.00 bc 0.50 d 0.76 b 1.6 1.11 bc 0.98 c 1.01 b 2.0 1.53 b 1.33 b 0.86 b w*: represents mother plant collected from jerash. cy: control treatment for microshoots consisted of hormone free solid ms media. cy: control in callus experiment consisted of callus multiplication media (ms solid media + 2.0 mg.l-1 2, 4-d + 1.5 mg.l-1 tdz ). cy: control for cell suspension cultures experiment consisted of ms liquid media plus 2.0 mg.l-1 2,4-d + 1.5 mg.l-1 tdz. zmeans within columns having different letters for each growth regulator type are significantly different according to tukey hsd at p≤0.05. 57research article kiyyam, shibli, tahtamouni, al-qudah, abu-iramaileh compounds were eluted at 6.26 min for solanine, and (fig. 3) represents the peak of solanine, areas and linear calibration curve (r²= 0.9999) as they were measured in the range of 12.5-12800 µg.ml-1 (ppm or mg·l-1). solanine was determined based on figure 2 (calibration curve) using the following equation provided by the calibration curve: y = ax + b where: y = area, a = constant, x = solanine concentration and b = constant effect of plant growth regulator on solanine content effect of bap the obtained data in bap experiment revealed that, solanine percentage in microshoots had increased remarkably in response to bap level in the media to reach a maximum level of (4.52 mg.g-1 dw) at bap concentration of 1.6 mg·l-1 compared to (1.82 mg.g-1 dw) recorded in the control treatment (c) (table 3). this means that bap level of (1.6 mg·l-1) was able to enhance solanine production in the microshoots to reach a level which was very close to solanine content obtained in jerash mother plant grown in the greenhouse. meanwhile, solanine tended to decrease (3.77 mg.g-1 dw) at higher bap level (2.0 mg·l-1).these results fully agreed with yogananth et al., (2009) and bhat et al., (2010), where bap enhanced the solanine accumulation in s. nigrum shoots. also, jayabalan et al., (2014) studied improve solasodine (another important alkaloid in solanacea family) accumulation in vitro solanum trilobatum using different concentration of bap, and they concluded that 2.0 mg·l-1 of bap was the best levels that gave the maximum solasodine percentage. additionally, al-hawamdeh et al., (2013) reported the effect of bap on the content of silymarin compounds in silybum marianum, as they found that silybin, silydanin, and silymarin content increased as bap concentration increased compared with the control. in callus experiment, solanine was recorded to increase with increasing bap level to reach a maximum concentration (2.61 mg·l-1 dw) at 2.0 mg·l-1 of bap (table 3). moreover, solanine was positively influenced by bap level in the samples taken from the cell suspension, but in lower percentages than those obtained in the microshoots and callus cultures (table 3), as the maximum level of solanine recorded in the cell suspension was only (1.53 mg.g-1 dw compared to 3.77 and 2.61 mg.g-1 dw) extracted from the microshoots and callus; respectively at similar bap level (table 3). this could be attributed to high water content in the cells cultured in the liquid ms media, as high water content in the cell was always reported to have a negative impact on the production and accumulation of secondary metabolites including alkaloids (morales et al., 1993; tahtamouni et al., 2016). effect of kinetin in kinetin experiment, the results showed that, increasing kinetin concentration positively affected solanine percentage (mg.g-1 dw) in shoots, callus, and cell suspension at all levels. (table 3). similar to the results trend obtained in bap experiment, the highest solanine level were recorded in the microshoots (4.00 mg.g-1 dw) and callus culture (2.82 mg.g-1 dw) while the lowest values were recorded in the cell suspension cultures at all kinetin levels (table 3). the positive impact of kinetin on alkaloids production was also reported by al-hawamdeh et al., (2013) as kinetin enhanced the content of silymarin compounds in silybum marianum shoots at 1.6 mg·l-1 kinetin. moreover, effects of kinetin on biosynthesis of vindoline and other indole alkaloids in catharanthus roseus callus cultures was investigated by jian et al., (2001) and table 4. effect of charbohydrate type and concentration on solanine % (mg.g-1 dw) in microshoots, callus and cell suspension of in vitro grown s.nigrum, in addition to wild (in green house) grown s. nigrum. concentration (mg.l-1) sucrose glucose fructose microshoot w* 4.92 az 4.92 a 4.92 a 0.05 0.90 e 0.43d 1.68 c 0.1 (cy) 1.82 d 2.67 c 1.85 c 0.15 2.43 c 3.00 b 2.13 bc 0.2 3.13 b 2.00 c 2.40 b callus w 4.92 a 4.92 a 4.92 a 0.05 0.21 e 0.58 c 0.58 c 0.1 (cy) 0.73 d 0.85 b 0.61 c 0.15 1.50 c 1.03 b 0.93 b 0.2 2.03 b 0.48 c 1.05 b cell suspension w 4.92 a 4.92 a 4.92 a 0.05 0.10 d 0.33 c 0.13 d 0.1 (cy) 0.43 c 0.38 c 0.26 c 0.15 1.16 b 0.56 b 0.50 b 0.2 1.20 b 0.40 c 0.66 b w*: represents wild mother plant from jerash. cy: for microshoots control treatment is consisted of hormone free ms media + 0.1 m of each carbohydrate types. cy: control in callus experiment consisted of callus multiplication media (ms solid media+2.0 mg.l-1 2,4d+ 1.5 mg.l-1 tdz ) + 0.1 m of each sugar types. cy : control in cell suspension cultures experiment consisted of ms liquid media plus (2.0 mg.l-1 2,4-d + 1.5 mg.l1 tdz) ) + 0.1 m of each sugar types. zmeans within columns having different letters for each sugar type are significantly different according to tukey hsd at p≤0.05. 58 squ journal of agricultural and marine sciences, 2019, volume 24, issue 1 improving solanine production in in vitro cultures of solanum nigrum l. using different chemical and physical factors they reported that, indole alkaloids increased as bap increased, which was attributed to enhanced peroxidase activity, reflected the pattern of alkaloid biosynthesis under the same culture conditions. effect of 2ip the obtained data in 2ip experiment concluded that, solanine percentage in the microshoots had increased significantly in response to 2ip level in the media to reach a maximum level of (3.87 mg.g-1 dw) at 2ip concentration of 1.6 mg·l-1 compared to (1.82 mg.g-1 dw) recorded in the control treatment (table 3). meanwhile, solanine in microshoots tended to decrease (3.43 mg.g-1 dw) at higher 2ip level (2.0 mg·l-1). in callus experiment, solanine was observed to increase with increasing 2ip level to reach a maximum concentration (2.55 mg.g-1 dw) at 2.0 mg.l-1 of 2ip (table 3). in cell suspension experiment, solanine content increased as 2ip concentration increased; 1.6 mg·l-1 of 2ip gave the highest solanine content (1.01 mg.g-1 dw) in cell suspension after that solanine content decreased to (0.86 mg.g-1 dw). al-hawamdeh et al., (2013) studied the effect of 2ip on the content of silymarin compounds in silybum marianum shoots and they reported that silybin, silydanin, and silymarin content increased as 2ip concentration increased compared with the control, and the maximum percentages for both silybin (0.76%) and silydanin (0.24 %) were obtained at 1.0 mg·l-1 2ip and 0.1 mg·l-1 naa, while higher concentrations of 2ip ( more than 1.0 mg·l1) was reported to reduce the production of all silymarin compounds. karolak et al., (2015) explained that cytokinin significantly suppresses the transport of macronutrients such as nitrate, ammonium, sulfate and phosphate, while nitrate regulates the expression of genes involved in the phenylpropanoid and flavonoid pathways. on the other hand, the concentrations of solanine in the control (c) treatments were lower compared to solanine concentrations found in the plant materials treated with the growth regulators (2ip, bap, kinetin) (table 3). this could refer to the fact that, c media was designed for each explants type to be optimum for cell division and growth which would direct all plant cell resources towards cell division and primary metabolites (proteins, carbohydrates ...etc) synthesis rather than production of secondary metabolites, which was very obvious in the results obtained in callus and cell suspension cultures where cell division is the predominant task for the cells (table 3). meanwhile, the obtained data revealed that, the highest values for solanine in this experiment were those extracted from mother plant (w) collected from jerash. effect of carbohydrates sources on solanine content sucrose different levels (0.05, 0.1, 0.15 and 0.2 m) of sucrose were investigated for their impact on the solanine content of s. nigrum microshoots, callus and cell suspension. as sucrose level increased in the media, higher solanine in the microshoots than control (c) and the maximum solanine content (3.13 mg.g-1 dw) at sucrose level 0.2 m (table 4). similarly, solanine content in the callus cultures increased significantly with increasing sucrose level in the media and 2.0 m sucrose treatment resulted in production of the highest solanine content (2.03 mg.g-1 dw) (table 4). however, solanine content table 5. effect of different light intensities on solanine % (mg.g-1) in microshoots and callus of in vitro grown s. nigrum, in addition to wild (in green house) grown s. nigrum. light intensity (µmol/m -2 s-1) solanine (mg.g-1) microshoot w* 4.92 az 25 1.50 b 50 (cy) 1.82 b 75 3.53 a 100 4.03 a callus w* 4.92 a 25 0.48 d 50 (cy) 0.73 cd 75 0.93 bc 100 1.26 b *w: represents mother plant from jerash grown under ordinary light intensity (50 ( µmol.m -2 s-1) . yc: control for microshoots, was microshoots grown in ms solid media + 0.1 m sucrose under normal growth room light intensity. for callus control (cy) represents callus grown in callus multiplication media + 0.1 m sucrose under normal growth room light intensity. z means within columns having different letters are significantly different according to tukey hsd at p≤0.05. 0e+00 1e+07 2e+07 3e+07 4e+07 5e+07 0 5000 10000 15000 solanin concentration (ppm) a re a y = 3770.9 x + 58818.4 r2 = 0.9999 figure 2. standard calibration curve of solanine. y: area, r2: retention time. 59research article kiyyam, shibli, tahtamouni, al-qudah, abu-iramaileh in cell suspension culture was less than those obtained in microshhots and callus experiments, as the maximum solanine content was only (1.20 mg.g-1 dw) obtained at the highest sucrose level (0.2 m) (table 4). this agrees with another research, where sucrose (60% = 0.2 m) was found to improve alkaloid content in callus culture of catharanthus roseus (ashutosh et al., 2012). also, in cell suspension cultures of gymnema sylvestre, different sugars types were tested, and sucrose was found to be the perfect carbohydrate source for biomass accumulation (11.56 g.l-1 dw) and gymnemic acid production (9.95 mg.g -1 dw) (nagella et al., 2011). high sucrose concentrations was reported as a technique for inducing osmotic stress in plants which forces plant cell to produce more electrolytes and secondary metabolites inside the cell as a defense mechanism to increase osmolarity and to decrease water loss from the cells (shibli et al., 2006), which might explain the increase in solanine level resulted in our experiments. glucose adding elevated levels of glucose had improved solanine content in all of the experimented explants types, and 0.15 m glucose produced the highest solanine content in microshoots, callus and cell suspension culture, respectively (3.0, 1.03 and 0.56 mg.g-1 dw) (table 4). al-hawamdeh et al., (2013) investigated the effect of glucose on the content of silymarin compounds in silybum marianum shoots and they reported that, these compounds increased as glucose concentration increased to reach the maximum at 0.1 m of glucose, while exceeding this concentration led to the reduction of secondary metabolites production. similarly, wang and weathers, (2007) investigated the effect of equal concentrations (0.1m) of carbohydrates types such as sucrose, glucose, or fructose on artemisinin production from the in vitro grown of artemisia annua, and they concluded that a dramatic increment in the production of artemisinin in the medium treated with glucose compared with other sugar types. fructose solanine content of in vitro grown s. nigrum was significantly and positively affected in microshoots, callus and cells suspension culture (table 4). maximum solanine content (2.40, 1.05 and 0.66 mg.g-1 dw) were obtained in micoshoots, callus and cell suspension; respectively, treated with 0.2 m of fructose as shown in (table 4). this agrees with al-hawamdeh et al., (2013) who reported that, silybin, silydanin, and silymarin content increased as fructose concentration increased up to 0.15 m of fructose. in general, the result obtained from our study indicated that solanine content responded positively to increasing the concentration of sucrose, glucose and fructose. however, based on current study sucrose was for the solanine production in all the tested plant materials. for all sugar types; wild collected plants from jerash; produced the highest solanine contents. effect of light intensity on solanine content solanine content in the microshoots and callus increased significantly with increasing light intensity compared to the results obtained in c plant materials which cultured on the ordinary light intensity of 50 ( µmol/m-2 s-1) (table 5). beside that wild plant gave the highest content of solanin at ordinary light intensity of 50 ( µmol/m-2 s-1) . exposing both plant materials types to light intensity of (100 µmol/m-2 s-1) yielded the highest solanine content in shoot and callus (4.03 and 1.26 mg.g-1 dw, respectively) (table 5). meanwhile, the lowest solanine level was observed in explants exposed to the lowest light intensity treatment (25 µmol/m-2 s-1) for both microshoots (1.50 mg.g-1 dw) and callus (0.48 mg.g-1 dw)(table 5). this might be justified by the fact that, solanine biosynthesis in tissues is highly dependent on the presence of active chloroplast (moreira et al., 2010). additionally, high light intensities might resulted in building a strong stress on the cultures that might cause cell dehydration 3.558 4.443 4.583 4.892 5.133 5.792 6.392 6.775 7.075 7.233 9.167 0.00 0.01 0.02 0.03 0 1 2 3 4 5 6 7 8 9 10 time (min) vo lts peak of solanin standard figure 3. hplc chromatogram for the solanine content from in vitro grown plantlets of s. nigrum. 60 squ journal of agricultural and marine sciences, 2019, volume 24, issue 1 improving solanine production in in vitro cultures of solanum nigrum l. using different chemical and physical factors and yet increasing cell osmotic potential as a defense response, which shifted cell mission from division and production of primary metabolites into production and accumulation of secondary metabolites ( lenore et al., 1985) many studies investigated the influence of light on alkaloids production, for example, lenore et al. (1985) concluded that the light increased the alkaloids of heimius alicifolia , and they explained that there was a positive correlation between chlorophyll content and lupine alkaloid formation, and suggested that the lysine branch of the biosynthesis of the heimia alkaloids might also be influenced by light. similar findings were reported by karimi et al., (2013) as they reported that, the maximum production of flavonoids and phenolic compounds were achieved at high light intensity (630 μmol m−2s−1 ) as increasing light intensity increases primary photosynthate, which leads to an increase in phenolic concentration in the plant (warren et al., 2003). moreover, effects of light on the biosynthesis of vindoline and other indole alkaloids in catharanthus roseus callus cultures was studied by jian et al., (2001) and they reported that light enhance all alkaloid biosynthesis in the callus, especially vindoline and serpentine about 3–4 folds higher than that in the dark. conclusion based on the outcomes of this study, it was found that manipulating some tissue culture growth conditions (chemical and physical factors) enhanced the production of solanine in microshoots, callus and cell suspension cultures of solanum nigrum l. the highest solanine level (4.52 mg.g-1) dw was obtained when the plant material were treated with bap at level of 1.6 mg·l-1; this results were remarkable if compared to other previous studies on the production of solanine in vitro using other techniques. for example; in solanum lyratum the addition of cholesterol at a concentration of 0.5 mg/l increased the synthesis of solanine (2.33 mg/g dw) compared to those extracted from the control (1.32 mg/g dw) (lee et al., 2007) which were less than solanine level obtained in our study. also, our data revealed that carbon source had positively affected solanine level, especially in plant material grown in media supplemented with 0.2 m sucrose. moreover, exposing microshoots and callus to light intensity of (100 µmol/m-2s-1) yielded the highest solanine content compared to the other light intensities treatments. however, other culture growth conditions need to be under research for better enhancement of solanine production in solanum nigrum l. in vitro. acknowledgement authors would like to thank the university of jordan, the deanship of academic research, for granting this research fund project. further thanks are extended to hamdi mango center for scientific research, the faculty of agriculture: the department of horticulture and crop sciences at the university of jordan. references ahmad s, esam s, fawaz c (2013) qualitative and quantitative steroidal alkaloids of solanum species distributed widely in syria by tlc and hplc. international journal of pharmaceutical sciences review and research 23(2): 23-27. al-hawamdeh fm, shibli ra, al-qudah ts (2013) in vitro production of silymarin from silybum marianum l. medicinal and aromatic plants 1(1):2167 0412 allan e (1996) plant cell culture. in stafford a, warren g, ed, plant cell and tissue culture. chichester: john wiley and sons, 1-23. ashutosh kv, singh rr, seema s (2012) improved alkaloid content in callus culture of catharan thusroseus. botanica serbica 36 (2):123 -130 bhat ma, mujib a, junaid a, mahmood u (2010) in vitro regeneration of solanum nigrum l with enhanced solasodine production. biological plantarum 54: 757760. cham b.e. 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(2013). in vitro clonal propagation of solanum nigrum l. research journal of chemical and environmental sciences. vol. 1(2): 32-33 wang y, weathers p (2007) sugars proportionately affect artemisinin production. plant cell report 26:1073–1081 warren mj, bassman j, fellman jk, mattinson ds, eigenbrode s (2003) ultraviolet-b radiation of populustricho carpata leaves. tree physiology 23: 527-535 yogananth n, bhakyaraj r, chanthuru a, parvathi s, palanivel s (2009) comparative analysis of solasodine from in vitro and in vivo culture of solanum nigrum l. kathmandu university. journal of science, engineering and technology 5: 99103. review article journal of agricultural and marine sciences 2021, 26(2): 24–34 doi: 10.24200/jams.vol26iss2pp24-34 reveived 16 july 2020 accepted 24 nov 2020 a review on the novel discoveries of begomoviruses in oman m. s. shahid* and a. m. al-sadi m. s. shahid ( ) mshahid@squ.edu.om, department of plant sciences, college of agricultural and marine sciences, sultan qaboos university, al-khod 123, oman, orcid: m. s. shahid : https://orcid. org/0000-0002-3550-0000 introduction geminiviridae is a family of plant pathogens char-acterized by geminate (twin) icosahedral parti-cles containing a circular single stranded dna (ssdna) genome. based on variability in their genome organization, insect vectors and host range, they are divided into nine different genera: mastrevirus, curtovirus, topocuvirus, begomovirus, capulavirus, eragrovirus, becurtovirus, turncurtovirus and grablovirus (zerbini et al., 2017). among all genera, begomovirus is the largest genus in the geminiviridae, having more than 200 species vectored by whiteflies (bemisia tabaci, gennadius) (zerbini et al., 2017). begomoviruses are known to cause severe damage to many dicot plants in temperate, subtropical, and tropical agroecosystems. the genome of begomoviruses is either bipartite, consisting of two (dna a and dna b) genomic components, approximately 2.6-2.8 kb in size or monopartite (dna a) consisting of a single component ranging from 2.6 to 2.8 kb in size. the bipartite begomoviruses frequently occur in the new world (nw), which includes central america and south america, while the monopartite begomoviruses are commonly found in the old world (ow), which consists of australia, japan, china, indian subcontinent, africa, mediterranean and european region (zerbini et al., 2017). the dna a component of begomoviruses originating from the ow consists of genes that encode six proteins (rep, trap, ren, cp and v2 and c4). in the ow, the majority of monopartite begomoviruses are associated with betasatellites (family tolecusatellitidae, genus betasatellite) (briddon et al., 2018; zhou et al., 2013), which are circular ssdna molecules استعراض االكتشافات اجلديدة لفريوسات البيجوموفريوس يف عمان حممد شفيق شاهد و عبدهللا بن حممد السعدي abstract. begomoviruses (family; geminiviradae) consist of single-stranded (ss) and circular genome particles. they are transmitted by whiteflies, and represent a major constraint to agricultural crops in different parts of the world. in oman, they have been causing huge losses to crops (tomato, cucumber, watermelon and beans). research on begomoviruses in oman over the last years focused on molecular characterization, phylogenetic relationship, recombination analysis, pathogenicity test on model and host plants and the development of transgenic plants with resistance. some studies focused on the association of dna satellites (alphasatellite and betasatellite) molecules with begomoviruses. this review highlights the latest developments in begomovirus and associated dna satellites discoveries in oman over the last three decades. this period encountered changes in agricultural practices and developments in virus detection technologies from morphological to the application of genome diagnostics to the emergence of high throughput dna sequencing, capable to sequence multiple and diverse dna molecules in parallel, enabling of millions of dna molecules to be sequenced at a time. in addition, several tomato cultivars bearing different ty genes having resistance to tylcd complex were developed. keywords: viruses, whitefly, transmission امللخص:تتكــون فريوســات البيجوموفــريوس والــي تنتمــي اىل عائلــة اجلمنيفرييــداي مــن جزيئــات جينــوم أحاديــة ودائريــة و تنتقــل عــن طريــق الذاببــة البيضــاء. متثــل هــذه الفريوســات عقبــة رئيســية أمــام احملاصيــل الزراعيــة يف أجــزاء خمتلفــة مــن العــامل، كمــا تســبب خســائر فادحــة يف عــدة حماصيــل يف ســلطنة عمــان، منهــا الطماطــم واخليــار والبطيــخ والفــول. ركــزت األحبــاث الــي أجريــت علــى فريوســات البيجوموفــريوس يف عمــان علــى مــدى الســنوات املاضيــة علــى التوصيــف اجلزيئــي ، والعالقــة التطوريــة ، وحتليــل إعــادة الرتكيــب ، واختبــار اإلمراضيــة علــى النبــااتت، وتطويــر نبــااتت معدلــة وراثيــا ذات مقاومــة لألمــراض. كمــا ركــزت بعــض الدراســات علــى ارتبــاط جزيئــات االلفاســاتاليت والبيتاســااتاليت ابلفريوســات. تســلط هــذه الورقــة الضــوء علــى آخــر األحبــاث علــى الفــريوس يف الســلطنة علــى مــدى العقــود الثالثــة املاضيــة، وهــي الفــرتة الــي شــهدت تغــريات يف املمارســات الزراعيــة وتطــورات يف تقنيــات الكشــف عــن الفريوســات مــن االعتمــاد علــى الشــكل املورفولوجــي إىل تطبيــق تشــخيص اجلينــوم وحتليــل تسلســل احلمــض النــووي وإدخــال أصنــاف الطماطــم الــي حتمــل جينــات ty املختلفــة الــي هلــا مقاومــة لســالالت الفــريوس. الكلمات املفتاحية: الفريوسات، الذاببة البيضاء، االنتقال. 25review article shahid and al-sadi of ~1350 nucleotides (nt) in size. betasatellites depend on a helper virus (the main virus dna genome) for replication, movement, and transmission between plants (briddon et al., 2002, 2001; saunders et al., 1999; 2004; 2008). however, they have no sequence similarity to their helper begomoviruses, except the hairpin structure, which has resemblance to the region of geminiviruses replication which contains the nonanucleotide (taatattac) sequence (briddon et al., 2003). many begomovirus strains and associated satellites have been identified in oman on various plants, including vegetable, legume, medicinal, weed and fruits crops. contemplating the significance of begomoviruses to omani agriculture, the significant research accomplishments on begomoviruses in oman over the last three decades are presented in this review. agriculture in oman being a non-agricultural country as well as its geographical location, oman has historical trade relations with various countries around the globe, particularly with asian and african countries. agricultural commodities in oman are particularly imported from iran, india, pakistan, egypt, lebanon and from various other countries. the agricultural produce of oman, mainly in winter season, is grown primarily for local consumption except for certain export to some neighbouring countries like uae. al batinah north and dhofar in the south are the main agricultural cultivation areas in oman. according to maf (2015) (www.maf.gov.om), the total area under cultivation in oman is 67,000 ha, though most of planting material is imported from different countries. the import of planting material for commercial farms or via travellers and workers has led to the introduction of different begomoviruses into oman. the exchange of planting material among farmers as well as local propagation of imported planting material that is infected with viruses helped spread viruses locally. begomovirus research in oman over the past few years, extensive work has been carried out on the detection and characterization of begomoviruses in oman (originated from different countries) (figure 1). studies on begomoviruses utilized polymerase chain reaction (pcr), rolling circle amplification (rca), cloning, restriction endonuclease analysis, and the application of next generation sequencing technology (ngs). extensive research has been done on begomoviruses on their sequence analysis, phylogeny, pathogenicity, plant-virus interactions, pathogen-derived transgenic resistance as well as characterization of dna satellites. until now different begomoviruses and dna satellites have been discovered from 16 different agricultural crops in oman (table 1). this review outlines the main crops affected by begomoviruses in oman. tomato (lycopersicon esculentum) tomato is a leading vegetable crop, which is cultivated mainly in the al-batinah. begomoviruses are the major biotic factor limiting tomato production in oman (fig. 4c). tomato leaf curl disease (tolcd) plants showing variable symptoms (yellow, upward curling, stunting and bushy appearance) were observed by the maf in the early 1990s. however, the causal organism of the disease was characterized late in 2004. tomato plants displaying symptoms of tolcd were collected from tomato fields during the winter season of 2004-2005. nucleic acid was extracted and used in rolling circle amplification (rca). sequence analysis showed 91% nt identity with the iranian strain of tomato yellow leaf curl virus (tylcv). similarly, sequence analysis of associated betasatellite showed 88.5% nt identity with tomato leaf curl betasatellite (tolcb) reported from pakistan. this study was the first to report tylcv and tolcb causing tolcd in oman (khan et al., 2008). in 2011, a complex of tylcv and a recombinant species of tomato leaf curl oman virus (tolcomv) associated with an alphasatellite and tolcb were discovered. the alphasatellite shared maximum nt identity with ageratum yellow vein singapore alphasatellite (ayvsga), which is unusual dna-2-type alphasatellite that is rarely associated with monopartite begomovirus complex. the pathogenicity study was also done using agrobacterium-mediated inoculation and it was found that in the coinfection with begomovirus complex, ayvsga ameliorate the symptoms developed by the tylcv and tolcb (idris et al., 2011; shahid et al., 2020a). afterward, a recombinant begomovirus of an african origin, tomato leaf curl sudan virus (tolcsdv), was identified near the yemen border. surprisingly, no betasatellite was detected from the tomato plants harbouring tolcsdv. infectivity was achieved through infectious constructs in n. benthamiana and tomato plants. however, effort to find the interaction of tolcsdv with tolcb in model host plant was not successful (khan et al., 2012a). later, different begomovirus strains such as chilli leaf curl virus (chilcv), tomato leaf curl al-batinah virus (tolcabv) and tomato leaf curl barka virus (tolcbv) were also reported to infect tomato in oman. to avoid further tomato production losses, resistant tomato lines (provided by the world vegetable centre, taiwan) were screened under natural conditions in two different locations. during data recording, tolcd symptoms were observed on few lines, and the infected leaves were collected and processed for virus identification. surprisingly, a recombinant begomovirus, showing the maximum levels of identity (92.9-93%) to the newly reported cotton leaf curl gezira virus (clcugev) in the uae was detected (kj939446; idris et al., 2014). based on the 91% criteria for begomovirus strain identification by the ictv (brown et al., 2015), the name “al batinah” for clcugev was proposed. the identified clcugev-ab 26 squ journal of agricultural and marine sciences, 2021, volume 26, issue 2 a review on the novel discoveries of begomoviruses in oman begomovirus is a recombinant strain which evolved through intraspecific and interspecific recombination from the “sudan” strain of clcugev (kj939446) and oman strain of clcugev (hf536716) (figure 3a). the interspecific recombination events showed the presence of a dna fragment from an african cassava mosaic virus (acmv), discovered from burkina faso (figure 3b). recently, tolcd caused by mixed infection was identified using ngs technology, where mixed infection was identified from tomato plants infected with tylcv-ir strain, tolcb and a legume infecting bipartite begomovirus, mungbean yellow mosaic india virus (mymiv). the biological activities of the whole virus complex were also studied in n. benthamiana (a model host) and tomato (natural) host plants (shahid et al., 2019b). cassava (manihot esculenta) oman has long relations with zanzibar in africa, where many omanis brought cassava tubers back into oman. although, the cultivation of cassava is at a limited scale in oman, cassava mosaic disease (cmd) was observed during a begomovirus survey in a’seeb, muscat. a single bipartite begomovirus, east african cassava mosaic zanzibar virus (eacmzv), has been identified as the causative agent for cmd in oman (khan et al., 2013a) (figure 3b). this virus has narrow geographical distribution as it was only reported from zanzibar and kenya. this suggests that eacmzv has been imported through cassava tubers into oman. the bemisia tabaci population was also noticed on infected cassava plants in oman, yet their contribution in cmd dissemination has not been studied. since cassava is grown at a small scale in oman, which is very isolated from the major cassava cultivation regions of the world, so it should be easy to wipe out cmd in the country by the establishment of virus-free cassava tubers, subject to proper quarantine measures to avoid future incursions. however, the emergence of cmd in oman emphasizes how the human activities can disseminate plant pathogens, as reported for other crops (phytophthora. ramorum in northern california) (cushman et al., 2008). cucurbits watermelon chlorotic stunt virus (wmcsv), a middle eastern virus, and squash leaf curl virus (slcv), having a new world origin, are two bipartite begomoviruses that cause severe economic losses to cucurbitaceae plants throughout the middle east and the world. the first molecular characterization of wmcsv was from squash (cucurbita moschata) plants in oman. the c. moschata plants exhibiting begomovirus symptoms were observed (figure 4g) in an experimental field in the agriculture experimental station (aes), sultan qaboos university oman. sequence analysis revealed the highest nt identity with dnaa and dna b components of wmcsv isolates of iran (khan et al., 2012b; shafiq et al., 2020). pathogenicity of the virus was confirmed using agrobacterium mediated inoculation into n. benthamiana model host plants. n. benthamiana plants did not show any visible symptoms following inoculation with dna a only. however, n. benthamiana plants produced obvious symptoms after 15 days of inoculation when inoculated with dna a and dna b (khan et al., 2012b). watermelon (citrullus lanatus) is an essential summer food crop in oman. in 2015, c. lanatus plants displaying yellow, leaf curling, and crumpling symptoms with a disease incidence of 70%-80% were observed at squ, oman. the genomic components verified to be the monopartite begomovirus chilcv and tolcb infecting watermelon plants (shahid et al., 2017b; 2020b). cucumber (cucumis sativus) is another greenhouse crop extensively grown in oman. recently, c. sativus figure 1. the world depicting possible origin and migration routes of begomoviruses identified in oman, mainly from east and north africa (purple and green arrows), middle east (brown arrow), mediterranean (blue arrow) and indian subcontinent (dark blue arrow). 27review article shahid and al-sadi plants showing yellow mosaic and crumpling, symptoms typical of begomovirus infection were observed (figure 4b). also, medium to high density of whitefly population was observed on cucumber plants in barka farms. the whitefly is a complex of more than 40 crypitc species, or biotypes, including the widespread middle east-asia minor 1 (meam1 or b biotype) and mediterranean (med or q biotype). transmission of begomoviruses solely depends on their interaction with b. tabaci, where begomoviruses have to cross the certain barriers situated in the whitefly where some of the proteins bind with the coat protein (czosnek et al., 2017; fiallo-olivé et al., 2019). after cloning and sequencing analysis, it was confirmed the mymiv is associated with the cucumber disease (shahid et al., 2018). squash leaf curl virus (slcv) is a nw begomovirus, but according to few reports, it has been identified from many middle eastern countries like jordan, israel and egypt. recently, squash plants showing severe symptoms typical of begomovirus infection were observed on squash plants (fig. 4e). in molecular analysis, viral genome dna a and dna b components were produced and sequenced. sequence analysis confirmed that the squash plants are infected with a bipartite begomovirus slcv, which has highest similarity with an slcv isolate reported from israel (issq-c2; kt099165, rosario et al., 2015) (figure 3b). slcv is the first nw begomovirus infecting squash in oman (shahid et al., 2020c) (table 1). since, different exotic monopartite begomoviral strains have been discovered to infect agricultural crops in oman and the introduction of another bipartite begomovirus may cause extra risk through interaction with the former begomoviral strains. legumes yellow mosaic disease (ymd) is a vast spread disease of legumes in south asia. ymd was first identified during 1960 in india (nariani, 1960), infecting blackgram (vigna mungo) and mungbean (v. radiata) and resulted in huge losses to legume production. among legumes, kidney bean (phaseolus vulgaris) is a commonly grown vegetable crop in oman. during a field visit in 2015, foliar mosaic, yellow, and crumpling symptoms, with whitefly population, was observed on kidney bean plants. genomic dna isolation followed by begomovirus identification using pcr and rca was done. sequencing and sequence analysis confirmed mixed infection by mungbean yellow mosaic india virus (mymiv), which was associated with tolcb. sequence analysis of dna a sequences indicated 99% nt sequence identity (figure 2b), which confirms that a single begomovirus species is involved in the disease. in recombination analysis, dna a sequence showed potential intraspecific genome recombination with mymiv-pk and mymiv-in strains as the major and minor parents, respectively. the sequence of the homolog dna b of myniv showed 97.8% nt sequence identity with mymiv-in isolate, which was further verified by phylogenetic analysis (table 1). the mymiv oman demonstrated the greatest levels of nt identity to the isolates reported in southeast asia (shahid et al., 2017). mymiv are member of “legumoviruses” which are very unique among other bipartite begomoviruses discovered in the ow and phylogenetically they have a diverse group of begomoviruses (ilyas et al., 2009) (fig. 2b). mymiv is common in india, pakistan, nepal, indonesia and china (tsai et al., 2013). oman is far away in west, where the mymiv has been reported. the isolates of the virus reported in oman have high identity to isolates identified from india from cowpea plants. this possibility leads to indicate that this unusual mymiv has been possibly imported from the south asian county (india). okra (abelmoschus esculentus) okra (abelmoschus esculentus) is an extensively cultivated vegetable crop, and it is believed to be originated from western africa. it is widely cultivated during winter season from small to large scale in different regions of oman. okra leaf curl disease (olcd) is a main problem in okra cultivation. olcd is characterized by curling, distortion, yellowing, mottling, mosaic, and stunted growth (figure 4h). in oman olcd is caused by a begomovirus and associated betasatellites and alphasatellites (akhtar et al., 2014). the analysis of sequences confirms that the begomovirus has maximum identity (85%) with clcugev (figure 2a). since the nt sequence identity of virus was lower according to the criteria set for species demarcation by international committee on taxonomy of viruses (ictv), hence it was discovered as a new virus species which was named as okra leaf curl oman virus (olcomv). further sequence analysis showed that the olcomv has evolved through different recombinant events among clcugev and tylcv-om. the sequence analysis of dna satellite revealed that betasatellite seemed to be of african origin, known as okra leaf curl betasatellite (oklcb) and the okra leaf curl alphasatellite (oklca) of middle east origin. although several begomovirus and dna satellites complexes have been identified from okra plants globally, however in oman a single monopartite begomovirus complex has been reported. this monopartite begomovirus complex infecting okra possibly provides an environment for mixed infection, which leads to the evolution of recombinant viruses and satellites through mutation and genomic components exchange. papaya (carica papaya) papaya (carica papaya) belonging to the caricaceae family and it is a dicot woody plant, native to mexico, america (central and south) but now adapted to almost all tropical regions (https://www.arabnews.com/ node/344838). due to its dietary benefits and demand, its production has been significantly increased over the last few decades in different countries. papaya is a wide28 squ journal of agricultural and marine sciences, 2021, volume 26, issue 2 a review on the novel discoveries of begomoviruses in oman ly grown fruit in salalah, and as a minor crop in other regions of oman, with an approximately 20 tons of fruit production annually. symptomatic papaya plants were collected from quriyat (figure 4f ). the viral dna was pcr amplified, cloned and sequenced. genome analysis revealed that the amplified virus components showed 83.3%-95.1% nt identity to clcugev genome (figure 2a). further analysis confirmed that the clcugev has recombination with tylcv-iran strain as a major parent (khan et al., 2012a). different begomovirus species have been reported to infect papaya plant from southeast asian countries, but so far, a single begomovirus infecting this crop has been identified in oman. however, there are ongoing studies on the geographical distribution and genetic diversity of plant viral strains infecting papaya crop in the country. chillies (capsicum annuum l.) chillies are an extensively grown vegetable crop after tomato in open fields during winter in oman. chili leaf curl disease (clcd) causes main losses to the chili crop across the old world and is caused by several begomoviruses (monopartite and bipartite). clcd was first documented in india during the 1960s (dhanraj and seth, 1968). later this disease spread into the neighbouring countries. in oman, leaf curl disease of chilli was investigated using rca and agrobacterium mediated inoculation approaches. in extensive surveys during 2010-2011, virus and betasatellite genomes were produced and sequenced completely. according to the sequence analysis with the accessions in the genbank, they showed the maximum nt identity between 88.0% and 91.1% to the isolates of “pakistan” strain of chilcv, indicating a different strain of chilcv for which the name as chilcv-oman strain (chilcv-om) was proposed. on the other hand, the betasatellite genome sequences exhibited the highest nt identity to a an earlier identified tolcb (khan et al., 2013b; 2013c). infectious clones were produced, and infectivity analysis confirmed the biological role of chilcv and tolcb in disease development in n. benthamiana and tomato plants. however, efforts to infect chilli plants with chilcv-om or with tolcb were not successful through agrobacterium mediated inoculum, nevertheless under natural field conditions virus and satellite can transmit the disease through the vector (b. tabaci). radish (raphanus sativus) radish, family brassicaceae, is an essential and widely grown winter vegetable crop in oman. it is usually grown as a mix crop along with cabbage, carrot, lettuce and squash. in an earlier study, reddish plants exhibiting typical symptoms of begomovirus infection were observed in al-batinah, with severity ranging from 50‒80%. the infected leaves were collected to investigate the pathogen. molecular analysis proved that the disease is due to mixed infections of tylcv and chilcv (al-shihi et al., 2018a). the begomovirus strains identified from radish showed 99% identity to the isolates of tylcv and chilcv (table 1). the agrobacterium mediated inoculation assays suggested mixed infection as evident from different viral symptoms compared with the single virus infection in n. benthamiana plants, which were further confirmed by southern hybridization and real time pcr analysis (al-shihi et al., 2018b). after individual inoculation of tylcv or chilcv to n. benthamiana plants, typical begomovirus infections were produced. however, in co-inoculation with tylcv and chilcv, the symptom severity has been enhanced. southern hybridization and real-time qpcr confirmed that both viruses interact synergistically where virus load and copy number increased in co-inoculation experiments compared with single virus inoculation (al-shihi et al., 2017). figure 2. species demarcation tool analysis of monopartite begomoviruses (a) and bipartite begomoviruses (b). 29review article shahid and al-sadi tobacco (nicotiana tabacum) tobacco is grown in oman in limited farms. in 2015, tobacco plants showing leaf curling (downward), yellowing, swelling of veins and stunting were noticed on tobacco plants in suhar (figure 4a). rca was employed to augment the full genome of begomovirus and betasatellite. full-length genome sequences of virus and betasatellite were determined and after analysis, it was found the variants of chilcv and tolcb were linked with the leaf curl disease of tobacco (shahid et al., 2019a). moreover, pathogenicity of chilcv and tolcb was verified by agrobacterium-mediated inoculation into three nicotiana host plants (shahid et al., 2019). different begomoviruses have been identified from the tomato crop, however, chilcv is the only begomovirus infecting tobacco, along with the first detection of tolcb in tobacco in oman. basil (ocimum basilicum) basil (ocimum basilicum l.), family: lamiaceae is a medicinal annually grown plant with purple-white flowers (danechian et al., 2009). basil is frequently utilized in cooking cosmetics a well as in traditional drugs (klimánková et al., 2008). due to its economic value basil is cultivated extensively and consumed as fresh, dried as a cooking spice and domestic use. due to the rich source of antioxidant and active ingredient properties, basil is consumed for stomach aches as well as for skin diseases. during a field visit in 2014 in al-seeb, basil plants showing yellowing, curling and leaf crinkling symptoms were observed and collected. after the application of molecular tools, it was verified that the induction of symptoms in basil plants were due to the mixed infection by three monopartite begomoviruses tylcv-om, tolcabv, and chilcv. pairwise sequence analysis of complete gefigure 3. neighbour-joining phylogenetic trees with 1000 bootstrap iterations and pairwise identity matching with aligned full-length genome sequences of selected begomoviruses with the genbank accessions, representing different species of monopartite begomoviruses (a) and betasatellites (b). figure 4. different plant species infected by diverse begomoviruses and associated dna satellites; tobacco (a), cucumber (b), tomato (c), pumpkin (d), squash (e), papaya (f), watermelon (g), okra (h). 30 squ journal of agricultural and marine sciences, 2021, volume 26, issue 2 a review on the novel discoveries of begomoviruses in oman nome sequences of tylcv-om, tolcabv and chilcv showed 98%, 99% and 100% nt identity, respectively, with the previously identified begomovirus strains in oman. it was further confirmed that these viruses also harbour tolcb, which exhibited 95% nt identity with an isolate of tolcb (ammara et al., 2015) (table 1). weed a weed (senna italica mill) showing yellowing and stunting symptoms suspected to begomovirus infection with a moderate density of whiteflies was observed near an infected tomato field in khasab, musandam, oman. molecular analysis and phylogenetic analysis using species demarcation tool (sdt) confirmed the association of chilcv with tolcb with s. italica plants (salma et al., 2020 unpublished) (figure 2a). s. italica is the first weed host in oman co-infected with chilcv and tolcb (table 1). mint mint belongs to genus mentha (family: lamiaceae). it is a valuable herb that has been grown and used for food as well as for medicinal purposes since centuries. during a survey in 2016 in salalah, oman, begomovitable 1. list of all monopartite and bipartite begomoviruses and dna satellites infecting different crops in oman. disease virus(es) identified suggested origin acronym symptoms produced host detection method strain in oman association of satellite(s) references(s) monopartite begomoviruses tomato leaf curl disease tomato yellow leaf curl virus middle east and/ or mediterranean tylcv y, lc, s tomato, basil, radish pcr/rca tyl-cv-om tolcb khan et al. (2008) aummar et al. (2016) al-shihi et al. (2018) bean yellow mosaic disease tomato yellow leaf curl virus middle east and/ or mediterranean and indian subcontinent tylcv ym, lc, cr common beans rca tyl-cv-ir tolcb shahid et al. (2018) leaf curl disease chili leaf curl virus indian subcontinent chilcv y, lc, s tomato, pepper, watermelon, basil, radish, mint, tobacco, urtica incisa pcr/rca chil-cv-om tolcb khan et al. (2013a) shahid et al. (2017a, 2017b, 2019a, 2019d) al-shihi et al. (2018) tomato leaf curl disease cotton leaf curl gezira virus north africa clcugv sc, vt, vd papaya, tomato rca clcugv tolcb khan et al. (2012a) okra leaf curl disease okra leaf curl virus north africa olcv vc, y, rla, rfz okra pcr/rca olcv-om olcb and olca khan et al. (2013b) tomato leaf curl disease tomato leaf curl sudan virus north africa tolcsdv vc, s, y tomato pcr/rca tolcsdv-om tolcb khan et al. (2014a) tomato leaf curl disease tomato leaf curl al-batinah virus middle east and/ or indian subcontinent tolcabv vc, s, y tomato, basil rca tolcabv tolcb khan et al. (2013b) aummar et al. (2016) tomato leaf curl disease tomato leaf curl barka virus middle east and/ or indian subcontinent tolcbrv vc, s, y toma-to rca tolcbrv tolcb khan et al. (2013b) tomato leaf curl disease tomato leaf curl liwa virus middle east and/ or indian subcontinent tolclwv y, vc, s, tomato, basil pcr/rca tolclwv tolcb and ayvsga idris et al. (2011) amara et al. (2016) 31review article shahid and al-sadi rus-like symptoms (leaf yellowing and stunting growth) of mint plants were seen. young symptomatic leaves of mint plants were collected for begomovirus detection. the complete genome sequences of begomovirus analysis by using ncbi-blast tool http://blast.ncbi.nlm.nih. gov/blast.cgi) verified the yellow and stunting symptoms of mint were due to the infection by a chilcv strain, which is different from the one reported earlier from tomato and pepper. the sdt evaluation of chilcv sequences with available begomovirus sequences showed mint begomovirus to have high levels of nucleotide sequence similarity to isolates of the “oman” strain of chilcv-om, showing maximum nt identity 94.9% (muhire et al., 2014) (figure 2a). this conclusion was further supported by phylogenetic analysis, which proved that mint begomovirus to be segregated along with chilcv isolates and is divergent from other chilcv strains (table 1). the chilcv was also associated with betasatellite infection in mentha (shahid et al., 2019c). the sdt analysis showed 98.2% nt identity with tolcb isolate (kx452232) recently reported from phaseolus vulgaris (shahid et al., 2017a). in a phylogenetic study, tolcb grouped with earlier tolcb isolates identified from arabian peninsula, which are distinctive from south asia isolates. factors affecting begomovirus distribution and spread in oman whitefly vector plays a crucial part in the transmission of begomoviruses. in oman only b tabaci meami is reported, which can travel to limited distances, yet possibly, it contributes actively to the distribution of diverse virus species. however, we cannot ignore agriculture trade activities among countries either through land, sea, or air as they may help disseminate the insect vector into different geographical locations. another bipartite begomoviruses cassava mosaic disease east african cassava mosaic zanzibar virus east africa eacmzv ym cassava rca eacmzv tolcb khan et al. (2013a) mungbean yellow mosaic disease mungbean yellow mosaic india virus indian subcontinent mymiv y, lc, s, ym tomato, bean pcr/rca/ ngs mymiv tolcb shahid et al. (2019c, 2019d) watermelon leaf curl disease watermelon chlorotic stunt virus middle east and/ or africa wmcsv lc, c, s squash, cucumber rca/pcr wmcsv tolcb khan et al. (2012b) shahid et al. (2019c) squash leaf curl disease squash leaf curl virus middle east and/ or mediterranean slcv sc, y, s squash rca slcv tolcb shahid et al. (2020) dna satellites tomato leaf curl disease tomato leaf curl betasatellite middle east tolcb vc, s, y tomato pcr/rca/ ngs tolcb shahid et al. (2019) okra leaf curl disease okra leaf curl oman middle east and/ or indian subcontinent olcb vc, y, rla, rfz okra pcr olcomb sohail et al. (2014) tomato leaf curl disease ageratum yellow vein singapore alphasatellite south east asia and/or indian subcontinent ayvsga y, vc, s tomato rca ayvsga idris et al. (2011) okra leaf curl disease okra leaf curl oman alphasatellite middle east olca vc, y, rla, rfz okra rca olcoma sohail et al. (2014) * yellowing (y), leaf curling (lc), chlorosis (c), yellow mosaic (ym), crumpling (cr), stunting (s), severe curling (sc), vein thickening (vt), vein deformation (vd), vein clearing (vc), reduction leaf area (rla), reduction fruit size (rfz). ** polymerase chain reaction (pcr), rolling circle amplification (rca), next generation sequencing (ngs) 32 squ journal of agricultural and marine sciences, 2021, volume 26, issue 2 a review on the novel discoveries of begomoviruses in oman contributing factor is human movement, which also contributes to the spread of viruses. however, there are other reasons including virus mutation, recombination, polyphagous nature of the vector, rigorous agricultural procedures like growing of single crop or cultivation of a single plant cultivar, cultivation of susceptible cultivars and the world-wide transport of agricultural goods are thought to increase the emergence and proliferation of viruses. hence, begomoviruses form a major risk to the worldwide food security. policies must be designed to prevent continuous crop failures due to plant infecting viruses and avoid the transport and spread of these lethal pathogens into new places (where environmental factors are suitable to enhance the population density of the whitefly vector). environmental factors play a key role in plant-virus interaction, where an optimal temperature can influence disease development, disease severity and/ or incidence. for instance, papaya ringspot virus can multiply, infect, and transmit virus to papaya plants ideally between 26 °c to 31 °c (mangrauthia et al., 2009). in cassava plants, cassava mosaic virus (genus; begomoviruses family; geminiviradae), enhanced symptoms and viral titres at 25 °c, compared to 30 °c (chellappan et al., 2005). banana bunchy top virus, which is vectored by an aphid (pentalonia nigronervosa), can actively develop and has lowest mortality at 25 °c (robson et al., 2007). heat and drought have also an impact on the severity of viral diseases. such as, in arabidopsis heat, drought and turnip mosaic virus synergistically reduced the plant growth than the individual factor (prasch et al., 2013). conclusion and prospects despite the existence of diverse viruses and dna satellites that have their origin out of oman, there is no indication that these begomoviruses are spreading out from oman. however, to restrict the movement of these pathogens, trade products could be regulated by improved phytosanitary measures. for instance, for different import commodities arriving at sohar port, hard quarantine should be applied to kill the insect vectors, particularly in containers importing wood products. similar precautionary measures should be applied for the imports through airports and road border (uae, saudi arabia and yemen). the propagative plant materials/ nursery stocks should be given special attention when inspecting diseases or insect pests. for example, oman has introduced approximately one million tons of propagative plant material in 2012, which could have harboured vectors and diseases, including begomoviruses. one latest example is the introduction of begomovirus disease of cotton in china, which is believed to be due to the negligence of quarantine material in import of ornamental plants (sattar et al., 2013). additionally, we cannot ignore the emergence of new and recombinant begomoviruses and dna satellite strains that could evolve in one place and spread out through the same trade routes, which are believed to bring the pathogens initially into the country. hence, to avoid further trade of geminiviruses, oman requires to set-up a phytosanitary facility equipped with the latest virus detection and discovery technologies. acknowledgement the funds were provided by sultan qaboos university to m.s. shahid, under internal and research fund grants. references akhtar s, khan aj, singh as, briddon rw. 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(2013). advances in understanding begomovirus satellites. annual review of phytopathology 51: 357-381. research paper journal of agricultural and marine sciences 2022, 27(2): 41–49 doi: 10.53541/jams.vol27iss2pp41-49 received 5 december 2021 accepted 25 april 2022 cooked sesame meal in the diet of african catfish clarias gariepinus (burchell 1822): effects on haematology, liver and kidney histology w. a. jimoh1,*, o. a. fagbenro2 and e. o. adeparusi2 w. a. jimoh1,*( ) jimoh.wa@unilorin.edu.ng, 1department of aquaculture and fisheries technology, university of ilorin, pmb 1515, ilorin, kwara state, nigeria, 2department of fisheries and aquaculture technology, federal university of technology, pmb 704 akure, ondo state, nigeria. introduction plant and animal products, especially by-prod-ucts of processing plants, make up the majority of traditional fish feed ingredients. these items are also consumed by humans (socas-rodríguez et al., 2021). soybean meal, which is the best plant protein feedstuff used in fish feeds, could potentially replace a large portion of fish meal (hodar et al., 2020). however, ever-increasing demand for human consumption and other animal feed industries make it difficult to use soybean protein sources for fish feed sustainably (jimoh et al., 2020c ; siddhuraju & becker, 2001 ; arru et al., 2019). this has lowered the viability of the fish farming industry in many developing countries, necessitating the quest for alternative protein sources for the development of low-cost feeds that can substitute these convenوجبة السمسم املطبوخة يف النظام الغذائي لسمك السلور األفريقي: )clarias gariepinus (burchell 1822 التأثريات على أمراض الدم والكبد وأنسجة الكلى جيموه1،*، فاجبينرو2، أديباروسي2 abstract. haematological and histological alterations are strong pointers to the health status of farmed fish, farm animals and even humans. these provide dependable information on metabolic disorders and deficiency. the haematological and histological changes in african catfish clarias gariepinus (burchell 1822) fingerlings fed cooked sesame (sesamum indicum) seed meal was examined in a 56-day feeding trial. three batches of sesame seeds were cooked for 10, 20 or 30 min, dried, milled, and mechanically defatted using a screw press. cooked seed meals (csm) were substituted for defatted soybean meal in the diets of african catfish at 15, 30, and 45 per cent. the highest haemoglobin content (hb) was found in catfish fed the control diet (ctr), while the lowest hb levels were found in catfish fed the csm345 diet. the haemoglobin content of catfish fed different dietary treatments varied significantly (p<0.05). hb values of catfish fed ctr diet and test diets csm115, csm215, csm315, and csm130 were not significantly different (p>0.05). other haematological parameters of the fish fed various dietary treatments showed a similar trend as rbc. dietary replacement of soybean meal by differently cooked sesame seed meal in clarias gariepinus diet did not affect haematology of the fish at lower inclusion levels for the different cooking times employed in the study (15% and 30% inclusion level for 10 min cooked sesame-based diets; 15% inclusion level for 20 and 30 min cooked sesame-based diets). although, there was marked vacuolation of hepatocytes in catfish subjected to various dietary treatments, however these did not relate to dose-dependent dietary treatments. keywords: haematology, histology, sesame, packed cell volume, clarias gariepinus. هــذه توفــر البشــر. وحــى املزرعــة وحيــواانت املســتزرعة لألمســاك الصحيــة احلالــة علــى القويــة املؤشــرات مــن والنســيجية الدمويــة التغــرات تعــد املســتخلص: املؤشــرات معلومــات ميكــن االعتمــاد عليهــا حــول اضطــراابت التمثيــل الغذائــي ونقــص. مت فحــص التغــرات الدمويــة والنســيجية يف إصبعيــات الســلور األفريقــي clarias gariepinus (burchell 1822)2 الــي تتغــذى علــى وجبــة بــذور السمســم املطبــوخ )sesamum indicum( يف جتربــة تغذيــة مدهتــا 56 يوًمــا. حيــث مت طهــي ثــاث دفعــات مــن بــذور السمســم ملــدة 10 أو 20 أو 30 دقيقــة ، وجتفيفهــا وطحنهــا وإزالــة الدهــن ميكانيكيًــا ابســتخدام مكبــس لولــي. مت اســتبدال وجبــات البــذور املطبوخــة )csm( بدقيــق فــول الصــواي منــزوع الدهــن يف وجبــات مســك الســلور األفريقــي بنســبة 15 و 30 و 45 يف املائــة. مت العثــور علــى أعلــى حمتــوى مــن اهليموجلوبــن )hb( يف مســك الســلور الــذي مت تغذيتــه علــى النظــام الغذائــي )ctr( ، بينمــا مت العثــور علــى أدىن مســتوايت اهليموجلوبــن يف مســك الســلور الــذي مت تغذيتــه علــى النظــام الغذائــي .csm345 أظهــرت النتائــج عــن وجــود اختــاف واضــح و متبايــن)p >0.05( يف حمتــوى ctr اهليموجلوبــن يف مســك الســلور الــذي مت تغذيتــه علــى معاجلــات غذائيــة خمتلفــة. و علــى النظــر مل تكــن قيــم اهليموغلوبــن يف األمســاك الــي تغــذت علــى نظــام والوجبــات الغذائيــة االختباريــة csm115 و csm215 و csm315 و csm130 خمتلفــة بشــكل كبــر )p< 0.05( . أظهــرت معامــات الــدم األخــرى لألمســاك الــي تتغــذى علــى معاجلــات غذائيــة خمتلفــة اجتاًهــا مشــاهبًا لكــرات الــدم احلمــراء. مل يؤثــر االســتبدال الغذائــي لوجبــة فــول الصــواي عــن طريــق وجبــة بــذور مسســم مطبوخــة بشــكل خمتلــف يف نظــام clarias gariepinus الغذائــي علــى الــدم يف األمســاك عنــد مســتوى اســتبدال أقــل )أي وقــت طهــي خمتلــف مســتخدم يف الدراســة ؛ 15٪ و 30٪ مســتوى اســتبدال ملــدة 10 دقائــق مطبــوخ علــى أســاس التغذيــة املعتمــدة علــى السمســم؛ 15٪ مســتوى اســتبدال ملــدة 20 و 30 دقيقــة يف تغذيــة السمســم املطبوخــة(. علــى الرغــم مــن وجــود فجــوة ملحوظــة يف خــااي الكبــد يف مســك الســلور اخلاضــع للعاجــات الغذائيــة املختلفــة ، إال أن هــذه مل تكــن هلــا عاقــة ابلعاجــات الغذائيــة املعتمــدة علــى اجلرعــة. clarias gariepinus ، الكلمات املفتاحية: أمراض الدم ، علم األنسجة ، السمسم ، حجم اخلااي املعبأة 42 squ journal of agricultural and marine sciences, 2022, volume 27, issue 2 cooked sesame meal in the diet of african catfish clarias gariepinus (burchell 1822): effects on haematology, liver and kidney histology tional feedstuffs. in addition, the high phytate content of soybean meal demands supplementing with inorganic phosphorus sources in monogastric animals. excessive dietary phosphorus is excreted into the environment, where it forms pollution (hussain et al., 2021). phytate has an adverse effect on fish development and body composition. in fish, phytate forms a phytate-phosphorus combination with phosphorus, leaving it unavailable to the fish. in addition, phytate forms complexes with cations such as calcium, iron, copper, magnesium, and others, lowering mineral bioavailability. phytate binds to trypsin and prevents the protein from being digested (kumar et al., 2012). furthermore, soybeans are deficient in sulphur-containing amino acids, particularly methionine and lysine (jannathulla et al., 2019). other legumes are less costly protein sources that have the potential to reduce the cost of fish feed when used as supplementary ingredients to fulfil the nutritional needs of fish (dorothy et al., 2018 ; pelletier et al., 2018). thus, the quest for less expensive and more reliable protein sources becomes a priority. the majority of the studies focused on underutilized plant proteins in fish diets. the reported studies on the use of other oilseed residues in warm water fish feeding, such as sesame meal, is minimal (davies et al., 2000 ; jimoh, 2020a ; jimoh, 2020b). sesame seed (sesamum indicum) is one of the world’s most valuable annual oil crops. they contained nutrients that are comparable to soybean meal and other conventional legumes quantitatively and qualitatively (hossain and jauncey, 1990 ; jimoh et al., 2011 ; vera et al., 2020). their dietary protein sources in the fish diet is well established for clarias gariepinus (jimoh & aroyehun, 2011 ; fagbenro et al., 2010 ; jimoh, 2021) and common carp (hossain & jauncey, 1989a ; hossain & jauncey, 1989b ; hossain & jauncey, 1990). the protein-rich meal leftover from oil extraction can be used as feed ingredients in aquafeed manufacture (jimoh, 2021). furthermore, sesame seed cake is considered to be high in methionine and tryptophan (saleh, 2020; jimoh et al., 2014); amino acids that are missing in most plant protein feedstuffs. it’s use in fish diets has received little attention. sesame is palatable and has a high digestibility coefficient and its apparent nutrient digestibility coefficients in clarias gariepinus fed various timed wet-heat-treated sesame seedmeal based were comparable to those reported for fish fed with control diets (jimoh, 2021; jimoh et al., 2014). since they provide dependable information on metabolic disorders and deficiency, haematological and histological alterations are strong pointers (bahmani et al., 2001; ferreira et al., 2007). in the light of this consideration, an attempt was made to investigate the effect of feeding diets containing cooked sesame (sesamum indicum) seed meal and their effects on the haematology and histology of the liver and kidney of african catfish clarias gariepinus (burchell 1822) fingerlings. materials and methods sesame seeds were collected from a farm in kebbi, nigeria and other feedstuffs were purchased from commercial sources in nigeria. they were milled separately, and screened to fine particle size (250 µm). three batches of sesame seeds were dried, milled in a hammer mill, and mechanically defatted using a locally made screw press. after that, the triplicate samples of the cake’s proximate composition were determined (aoac, 2010). the gross energy content of the samples was determined using the physiological values of 5.61 kcal/g protein, 9.50 kcal/g lipid, and 4.11 kcal/g carbohydrate (tacon, 1999). based on the composition of protein in the feedstuff, a control diet and nine test diets (40 per cent crude protein, 12 per cent crude lipid, and 18.45 mj/kg gross energy) were made (table 1). soybean meal, which produced 50% of total protein, was included in the control diet (ctr). each of these differently processed seed meals was used in nine test diets at three different levels of soybean meal replacement: 15, 30, and 45 per cent (table 2). the feedstuffs were ground, and hot water was added to assist binding before being fed into a hobart-200t pelleting and mixing machine. it was then created to a homogeneous mass, which was then minced into 0.8 mm (long) 2 mm (diameter) pellets and immediately sun-dried (30-32oc). after drying, the diets were kept frozen in a refrigerator (-4oc) and samples were taken for proximate and amino acid analysis. three replicated samples were considered. before the feeding trial, clarias gariepinus fingerlings were acclimated to experimental conditions for 7 days. aquaria with 60 litre size rectangular plastic tanks were stocked with 15 catfish fingerlings (3.38±0.015g). for 56 days, each diet was fed to the catfish in triplicate tanks twice a day (at 9.00 am, 4:00 pm) at 5% body weight. the total fish weight in each tank was calculated every two weeks, and the amount of diet was changed to match the new weight. haematological examination of the fish after euthanization in 100 ml/l clove oil, fish (n=6) from each replicate were removed for blood analysis. a 2 ml disposable heparinised syringe treated with ethylenediaminetetraacetic acid (edta) as an anticoagulant was used to extract 3 ml blood per treatment from a cardiac puncture on the fish. the blood analysis was performed according to the procedure of jimoh (2020b). histological examination of catfish three fish per treatment were sampled for histological examination at the end of the experiment. the test organisms were euthanized in 100 ml/l clove oil and then dissected kidney and liver were taken out. the organs were fixed in 10% formalin for three days, and then the tissue was dehydrated for three days in graded levels of 50%, 70%, 90%, and 100% alcohol to enable paraffin 43research paper jimoh, fagbenro, adeparusi wax to penetrate into the tissue. melted wax was used to embed the organs. using a rotatory microtome, the tissue was sectioned into thin parts (5-7 µm) and stained for ten min with harris hematoxylin-eosin (h&e) stain according to the procedures of jimoh (2020a). each section was cleared by immersing it in warm water (38°c), and placed it on a clean slide, and heating it at 58°c for 30 min to melt the wax. sections of the stained slide were analyzed under a light microscope at 400x magnification. the sections were interpreted at the university of ibadan, department of veterinary anatomy, nigeria. ethics approval the care and use of laboratory animals were done following standard procedure for animal welfare during transportation, housing and termination. animal research: reporting of in-vivo experiments (arrive) guidelines were followed (kilkenny et al., 2010). statistical analysis using spss 17.0, all data were expressed as mean ± standard deviation and subjected to a one-way analysis of table 1. proximate composition (g/100 g dry matter) and essential amino acid profile of feedstuff (g/100 g protein). proximate composition csms10 csms20 csms30 fishmeal soybean meal corn meal moisture crude protein crude lipid crude fibre ash nfe 9.1 40.39 11.90 5.38 11.28 22.02 8.97 38.36 12.83 6.22 10.38 22.02 9.28 35.83 12.58 5.41 12.28 24.62 7.59 69.76 8.82 13.83 8.92 42.81 18.56 5.63 6.01 18.07 9.21 8.89 1.49 29.78 3.81 46.82 amino acid profile * * * lysine histidine arginine threonine cystine valine methionine isoleucine leucine tyrosine phenyalanine 3.66 2.72 11.68 2.98 1.95 4.80 3.42 2.32 3.62 2.33 3.68 3.22 2.88 11.72 3.21 2.02 4.92 3.47 3.76 8.12 2.96 3.34 3.04 3.06 12.01 3.10 1.82 5.08 3.71 3.91 5.22 2.18 4.81 4.96 1.47 4.41 2.82 0.82 3.31 1.84 2.98 4.78 2.0 2.50 3.10 1.26 3.41 1.92 0.63 2.53 0.72 2.92 4.02 1.72 2.45 0.28 0.29 0.48 0.4 0.25 0.5 0.19 0.39 1.37 0.43 0.54 *values obtained from nrc (1993) what is nrc? csm 10: sesame seeds cooked for 10 minutes csm 20: sesame seeds cooked for 20 minutes csm 30: sesame seeds cooked for 30 minutes table 2. gross composition (g/100 g dry matter), of experimental diets at varying replacement levels of differently cooked sesame seed meals ctr csm 115 csm 130 csm 145 csm 215 csm 230 csm 245 csm 315 csm 330 csm 345 fishmeal soybean meal cooked sesame corn meal fish oil *vit/min premix starch 27.24 46.71 11.25 5.09 5.00 4.71 27.24 39.71 7.42 11.25 5.09 5.00 4.29 27.24 32.70 14.86 11.25 5.09 5.00 3.86 27.24 25.70 22.80 11.25 5.09 5.00 2.92 27.24 39.71 7.86 11.25 5.09 5.00 3.85 27.24 32.70 15.72 11.25 5.09 5.00 3.00 27.24 25.70 23.58 11.25 5.09 5.00 2.14 27.24 39.71 8.37 11.25 5.09 5.00 3.34 27.24 32.70 16.75 11.25 5.09 5.00 1.97 27.24 25.70 25.12 11.25 5.09 5.00 0.60 * specification: each kg contains: vitamin a , 4,000,000iu; vitamin b, 800,000iu; vitamin e, 16,000mg, vitamin k3,800mg; vitamin b1, 600mg; vitamin b2, 2,000mg; vitamin b6, 1,600mg, vitamin b12,8mg; niacin,16,000mg; caplan, 4,000mg; folic acid, 400mg; biotin, 40mg; antioxidant 40,000mg; chlorine chloride, 120,000mg; manganese, 32,000mg; iron 16,000mg; zinc, 24,000mg; copper 32,000mg; iodine 320mg; cobalt,120mg; selenium, 800mg manufactured by dsm nutritional products europe limited, basle, switzerland. 44 squ journal of agricultural and marine sciences, 2022, volume 27, issue 2 cooked sesame meal in the diet of african catfish clarias gariepinus (burchell 1822): effects on haematology, liver and kidney histology variance (anova) test. when anova showed a significant difference (p<0.05) and duncan’s multiple range test was used to determine the significant differences between treatments (p<0.05). results the proximate composition and amino acids of experimental diets are shown in the tables 3 and 4. there was no significant difference (p>0.05) in the crude protein, crude lipid, and energy contents of the experimental diets, indicating that they were isonitrogenous, isolipidic, and isocaloric. c.gariepinus’ dietary requirements for protein, energy, and lipids. throughout the feeding trial, the fish in each dietary treatment successfully fed on the experimental diets. haematological examination table 5 indicates the haematological parameters of c. gariepinus fed cooked sesame meal-based diets. the fish fed ctr had the highest primary haematological value (hb, pcv, and rbc), which was significantly different (p<0.05) from the fish fed the other dietary treatments except for the test diets csm115, csm215, csm315, and csm130. between the control and fish-fed test diets, there was no significant difference in white blood cell count or mchc (p>0.05). the esr of fish fed with the control diet and those fed with the test diets csf115, csf130, csf215, and csf315 did not vary significantly (p>0.05). discussion the reduction in haematological parameters observed in c. gariepinus fed cooked sesame diets might be connected to the decrease in the nutritional quality of the seedmeal as as the cooking time increased (table 1). this agrees with the report of jimoh et al. (2020b). the nutritionally deficient diets can cause haemoglobin concentration, haematocrit, and red blood cell count to decrease. physiologically, haemoglobin is essential for fish survival since it is directly linked to blood’s oxygen binding ability. given that the values are within the usual range reported for african catfish. the reduction observed in this study may not have harmed c. gariepinus. furthermore, the hb, pcv, rbc, and wbc values recorded in this study were all within the normal range table 3. proximate composition (%) and gross energy (kcal/100 g) of experimental diets at varying replacement levels of differently cooked sesame seed meals. ctr csm 115 csm 130 csm 145 csm 215 csm 230 csm 245 csm 315 csm 330 csm 345 moisture protein lipid fibre ash nfe energy (kcal/100g) 9.43±0.35 40.53±.22 12.30±0.25 5.25±0.29 6.56±0.38 25.93±0.57 450±5 9.55±0.18 40.61±0.29 12.25±0.10 5.48±0.16 6.63±0.47 25.47±0.92 448±2 9.72±0.40 40.50±0.29 12.21±0.13 5.36±0.17 6.50±0.19 25.71±0.77 448±1 9.79±0.06 40.41±0.34 12.39±0.22 5.38±0.05 6.36±0.20 25.67±0.50 449±1 9.36±0.21 40.69±0.27 12.29±0.28 5.36±0.14 6.53±0.34 25.77±0.33 450±3 9.65±0.33 40.60±0.41 12.39±0.38 5.34±0.35 6.38±0.18 25.64±1.19 450±1 9.57±0.16 40.48±0.27 12.41±0.18 5.39±0.23 6.44±0.23 25.71±0.32 450±2 9.46±0.25 40.29±0.34 12.40±0.15 5.30±0.36 6.76±0.07 25.78±0.29 449±3 9.57±0.31 40.33±0.45 12.52±0.13 5.63±0.11 6.46±0.24 25.48±0.46 449±1 9.33±0.15 40.05±0.80 12.20±0.11 5.36±0.41 6.74±0.14 26.31±1.05 448±2 nfe: nitrogen free extracts table 4. amino acid profile (g/100g protein) of experimental diets at varying replacement levels of differently cooked sesame seed meals. ctr csm 115 csm 130 csm 145 csm 215 csm 230 csm 245 csm 315 csm 330 csm 345 lysine histidine arginine threonine cystine valine methionine/tsa isoleucine leucine tyrosine phenyalanine/taa 3.15 1.02 2.85 1.71 0.55 2.14 0.86 2.22 3.33 1.40 1.89 2.89 1.08 3.28 1.80 0.65 2.32 1.06 2.19 3.32 1.45 1.99 2.94 1.14 3.70 1.88 0.75 2.50 1.27 2.16 3.31 1.50 2.10 3.01 1.21 4.18 1.99 0.86 2.70 1.49 2.14 3.31 1.57 2.21 2.87 1.21 3.31 1.83 0.66 2.35 1.08 2.31 3.69 1.51 1.98 2.90 1.40 3.78 1.95 0.78 2.56 1.30 2.40 4.05 1.62 2.07 2.94 1.60 4.24 2.06 0.89 2.77 1.53 2.49 4.40 1.73 2.16 2.87 1.18 3.37 1.84 0.65 2.39 1.11 2.34 3.49 1.50 2.12 2.91 1.33 3.89 1.96 0.76 2.64 1.38 2.47 3.65 1.52 2.35 2.91 1.49 4.40 2.09 0.87 2.88 1.64 2.59 3.80 1.58 2.58 4.8 1.2 3.6 2.8 2.4 2.4 2.0 3.5 4.0 taa: total aromatic amino acid tsa: total sulphur-containing amino acids 45research paper jimoh, fagbenro, adeparusi table 5. haematological profile of blood of clarias gariepinus fed cooked sesame meal based diets experimental diets. ctr csm 115 csm 130 csm 145 csm 215 csm 230 csm 245 csm 315 csm 330 csm 345 hb pcv wbc rbc mchc mcv mch esr 10.11±0.10a 30.55±0.17a 6600±141.42 3.30±0.04a 33.09±0.14 92.72±.48f 30.68±0.03d 3.52±0.04a 10.03±0.08a 30.14±0.26ab 6450±212.13 3.18±0.04ab 33.27±0.02 94.92±0.23e 61.58±0.11bc 3.48±0.03a 9.75±0.25ab 29.28±0.75ab 6375±106.07 3.04±0.08bc 33.30±0.01 96.48±0.01bc 32.13±0.02abc 3.39±0.09ab 8.84±0.13c 26.57±0.35c 6300±141.42 2.74±0.04d 33.27±0.05 97.13±0.01b 32.33±0.05a 3.07±0.04c 10.01±0.06a 30.05±0.18ab 6450±70.71 3.18±0.02ab 33.29±0.01 94.64±0.05e 31.51±0.01bc 3.47±0.02a 9.55±0.17b 28.73±0.57b 6350±141.42 2.98±0.06c 33.25±0.06 96.58±0.16bc 32.10±0.11abc 3.32±0.06b 8.71±0.03c 26.51±0.26c 6250±141.42 2.70±0.01d 32.86±0.22 98.17±0.46a 32.25±0.06ab 3.02±0.01c 10.00±0.04a 30.05±0.16ab 6400±141.42 3.15±0.01ab 33.27±0.06 95.38±0.09de 31.73±0.03abc 3.47±0.01a 9.55±0.11b 28.75±0.31b 6337±194.45 2.99±0.06c 33.22±0.04 96.16±0.78cd 31.94±0.23abc 3.32±0.04b 8.55±0.31c 26.06±1.47c 6330±141.42 2.69±0.17d 32.83±0.66 96.90±0.64bc 31.81±0.85abc 2.97±0.11c row means with different superscripts are significantly different (p<0.05) hb: haemoglobin content (gm/100 ml) pcv: packed cell volume ( % ) wbc: white blood cell count (104mm3) rbc: red blood cell count (106 mm3 ) mchc: mean corpuscular haemoglobin concentration ( % ) mcv: mean corpuscular volume (µ3) mch: mean corpuscular haemoglobin (ρg) esr: erythrocyte sedimentation rate (mm/h) figure 1. photomicrographs (h&e stained, 5µm section, x400 magnification) of the liver of clarias gariepinus fed. (a) ctr: there was diffuse vacuolation of the hepatocytes; (b) csm115: there was very mild, diffuse vacuolation of the hepatocytes; (c) csm145: there was very mild, diffuse vacuolation of the hepatocytes; (d) csm215: there very moderate diffuse vacuolation of the hepatocytes; (e) csm230: there was diffuse vacuolar degeneration of the hepatocytes; (f) no visible lesion was seen in the livers of fish fed csm130, csm245, csm315 and csm330 (g) csm345: there was mild central venous and portal congestion 46 squ journal of agricultural and marine sciences, 2022, volume 27, issue 2 cooked sesame meal in the diet of african catfish clarias gariepinus (burchell 1822): effects on haematology, liver and kidney histology of a healthy fish (jimoh et al., 2020c; myburgh et al., 2008). the rbc values found in this study were similar to those found in clarias lazera (zaki et al., 2011), clarias gariepinus (omitoyin, 2006), heteropneustes fossilis (khan and abidi, 2010; khan and abidi, 2011). usually, an erythrocyte count of more than 1×106/mm3 is considered high and this indicates that the blood has a high oxygen-carrying capacity. this is typical capability of aerial respiration and high activity (fagbenro et al., 2013). haniffa and mydeen (2011) found a value of hb for channa striatus was higher than the value found in this study. the hb values for hybrid catfish fed a control diet reported by osuigwe et al. (2002) for hybrid catfish (heterobranchus longifilis x c. gariepinus) were similar to those found in this study. the haematocrit values for fish were also within the usual range of 2038 per cent (erondu et al., 1993; adeyemo et al., 2014). increased production of leucocytes in the haematopoietic tissue of the kidney and possibly the spleen is responsible for the rise in wbc as observed in the fish fed with cooked sesame diets (fazio et al., 2015). antibodies are produced by lymphocytes, which act as a powerful defence against infection (hua and hou, 2020). according to akinwande et al. (2016), immunity of fish is measured by the number of white blood cells it produces. the increased number of white blood cells seen in this study indicated that the fish had a high level of disease resistance (shen et al., 2018) and it may be caused a rise in the rate of haemoglobin destruction or a reduction in its productivity or synthesis (srivastava and reddy, 2020). it would be observed that haemoglobin concentration reduced in the fish fed with the test diets as compared to control. similar observations were recorded by jimoh et al. (2020c) when oreochromis niloticus was fed with diets containing toasted jatropha curcas seed meal and clarias gariepinus was fed withdiets containing luffa cylindrica seed meal (jimoh et al., 2020b). other researchers recorded a decrease in haematocrit and haemoglobin with increased ingredient levels (blom et al., 2001; jimoh, 2020a; jimoh, 2020b). furthermore, the histology of the kidney and liver of fish fed with the sesame diets appeared unaffected. similar findings were reported by mérida et al. (2010) when sunflower meal was used as a partial substitute in the case of juvenile sharp snout sea bream (diplodus puntazzo) diets. pereira et al. (2002) observed in the case of rainbow trout fed with partial substitution of brassica by-products. hansen et al. (2006) made a similar observation when gut and liver histology was examined in a cod fed diet containing various inclusion of plant protein. the results of this study showed marked vacuolation of hepatocytes and did not link to dose-dependent figure 2. photomicrographs (h&e stained, 5µm section, x400 magnification) of the kidney of clarias gariepinus fed (a) ctr: the tubular epithelium was completely eroded; (b) csm230: there was diffuse degeneration of the tubular epithelium; (c) no visible lesion was observed in the kidneys of fish fed csm115, csm130, csm145, csm215, csm245, csm315, csm330 and csm345. 47research paper jimoh, fagbenro, adeparusi dietary treatment. olukunle (2011), jimoh et al. (2020c) and jimoh et al. (2020b) made the similar observation. mild to moderate vacuolation of the hepatocytes were recorded in the livers of fish fed cooked jatropha-based diets as compared to the soybean-based control diet (jimoh et al., 2020a). the high vacuolation of the liver may be due to the organ’s high lipid content, which can be traced back to high lipid diets. the existence of numerous and voluminous lipid droplets in hepatocytes is a physiological response to dietary lipid excess or increased lipogenesis (martins et al., 2007; valente et al., 2011; gatta et al., 2011). conclusion dietary replacement of soybean meal by differently cooked sesame seed meal in clarias gariepinus diet did not affect haematology of the fish at lower inclusion level. the addition of 15% and 30% inclusion level for 10 min cooking time; and 15% inclusion level for 20 and 30 min cooking time had similar profile with control. although, there was marked vacuolation of hepatocytes in catfish subjected to various dietary treatments, and this was not related to dose-dependent dietary treatments. this indicated that the health of clarias gariepinus fed cooked sesame seed meal diets did not put stress on the fish. references adeyemo bt, obande ra, solomon sg. 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(2011). phenol toxicity affecting hematological changes in cat fish (clarius lazera) mona. life science journal 8: 244-248. research paper journal of agricultural and marine sciences 2020, 25(1): 09–19 doi: 10.24200/jams.vol25iss1pp09-19 reveived 05 nov 2019 accepted 21 jan 2020 use of soil-structured capillary barrier can mitigate the impact of saline-irrigation water on marigold grown under field condition mohammed s. al-mazroui1*, rashid a. al-yahyai1*, said s. al-ismaily2, anvar r. kacimov2, hamed al-busaidi2 mohammed s. al-mazroui1*( ) mohammed3039@hotmail.com 1department of crop sciences, sultan qaboos university, po box 34, al khoud 123, sultanate of oman .2department of soils, water and agricultural engineering, sultan qaboos university, po box 34, al khoud 123, sultanate of oman. introduction salinity is a major abiotic factor limiting agricul-tural production in the world and particularly in arid and semi-arid regions. soil salinity has affected about 952 million hectares (7%) of land around the world (al-mulla, 2010). it is estimated that globally 20% of total the cultivated area and 33% of the irrigated agricultural lands are affected by high salinity. also, more than 50% of the arable land would be saline by 2050 (jamil et al., 2011). ghassemi et al. (1995) estimated that the annual loss of income from the salinization of irrigated lands is about us$ 12 billion worldwide. soil salinity in oman is considered a serious threat to the sustainable use of two of the most important natural resources in the country, which are soil and water. the estimated values for salt-affected lands in oman are approximately 44% of the total geographical area and 70% of the arable agriculturally suitable land (al-rawahy et al., 2010). salinity stress induces several biochemical and physiological changes in plants (nemoto and sasakuma, 2002). it can cause osmotic effect, ion toxicity, nutritional imbalance leading to a reduction in photosynthetic efficiency and other physiological disorders. the major inhibitory effects of salinity are quantified via plant استخدام الحاجز الشعري املركب للرتبة للحد من تأثري مياه الري املالحة عىل نبات املاريجولد املزروعة تحت الظروف الحقلية محمد املزروعي*1 و راشد اليحيايئ*1 و سعيد االسامعييل2 و أنفار كاسيموڤ 2 و حمد البوسعيدي2 abstract. capillary barriers (cbs) as engineered porous composites is novel and promising technology for mitigating salinity and drought stress of plants. this study aimed to imitate a naturally formed cb structure recently discovered in the reservoir bed of al-khoud dam at the governorate of muscat in northern oman and to test the impact of this unique cb on mitigating the salinity stress of marigold plants grown under an open field condition. a plot was constructed and divided into “structured” (engineered cascade cb design) and “unstructured” soils and planted with marigold (tagetes erecta) plants that were subjected to four salinity treatments (control with eci ≈ 0.6 ds m -1 ; 3 ds m-1; 6 ds m-1; and 9 ds m-1). plant physiological, vegetative, and reproductive growth parameters were measured in each treatment. the results showed that the structured soil significantly saved irrigation water and reduce salts accumulation. structured soil improved all vegetative and reproductive plant parameters measured and helped in reducing the effects of salinity stress on the growth and production of the marigold under arid-climate field conditions. the results also showed the capability of structured soil in water saving and improving water use efficiency. this study substantiates a novel method in mitigating salinity problem and in water saving in arid and semi-arid regions, in particular in oman. further studies are required to test the use of the engineered cascade cb design with different crops and with alternative (e.g. subsurface) irrigation methods. keywords: soil; capillary barrier; structured soil; soil moisture; salinity; plant growth; arid-climate. امللخــص: تعتــر الحواجــز الشــعرية للرتبــة احــدى التقنيــات الجديــدة الواعــدة التــي تخفــف مــن تأثــري االجهــاد امللحــي والجفــاف عــىل النباتــات. تهــدف هــذه الدراســة اىل محــاكاة الحواجــز الشــعرية والتــي أكتشــفت حديثــا ومتشــكلة طبيعيــا يف ســد الخــوض الواقــع يف واليــة الســيب مبحافظــة مســقط شــامل ســلطنة عــامن، واختبــار تأثــريه عــىل تخفيــف اإلجهــاد امللحــي لنبــات املاريجولــد واملزروعــة تحــت ظــروف حقليــة يف تربــة مهيكلــة. ــري ــة غ ــمل ترب ــة تش ــة( والثاني ــعريية متتابع ــز ش ــون حواج ــة لتك ــة )مهندس ــة مهيكل ــمل ترب ــن األوىل تش ــىل معاملت ــمل ع ــع يش ــاء موق ــم انش ت ds 6 1 و-ds m 3 1( و-ds m 0.6( مهيكلــة، ومتــت زراعــة نبــات املاريجولــد يف كالهــام، حيــث تــم ريهــا بأربعــة مســتويات مــن امللوحــة: الشــاهد ــج أن ــرت النتائ ــة. أظه ــات يف كل معامل ــيولوجية النبات ــر فس ــي ومعاي ــري واالنتاج ــو الخ ــر النم ــن معاي ــد م ــاس العدي ــم قي m-1 و ds m 9-1. وت الرتبــة املهيكلــة ســاعدت عــىل تقليــل كميــات ميــاه الــري وتراكــم األمــالح يف الرتبــة. كــام أن الرتبــة املهيكلــة حســنت بشــكل كبــري جميــع العوامــل النباتيــة الخريــة واالنتاجيــة املقاســة وســاعدت يف الحــد مــن آثــار اإلجهــاد امللحــي عــىل منــو وإنتــاج املاريجولــد يف الظــروف الجويــة الجافــة يف الحقــل. كــام أظهــرت النتائــج أيضــا قــدرة الرتبــة املهيكلــة عــىل توفــري امليــاه وتحســن كفــاءة الــري، مــام يعــزز مــن قدرتهــا عــىل التخفيــف مــن تأثــري امللوحــة وخصوصــا يف املناطــق الجافــة وشــبه الجافــة وبينــت قــدرة الرتبــة املهيكلــة عــىل تعزيــز كفــاءة اســتخدام ميــاه الــري، مــام ينتــج عنــه وفــرة امليــاه وتخفيــف حــدة امللوحــة يف مناطــق جافــة وشــبه جافــة مثــل ســلطنة عــامن. ويقــرتح املزيــد مــن الدراســات عــىل محاصيــل مختلفــة وطــرق، ري مختلفــة، ملعرفــة مــدى، تأثــري، الرتبــة، املهيكلــة عليهــا. 10 squ journal of agricultural and marine sciences, 2020, volume 25, issue 1 use of soil-structured capillary barrier can mitigate the impact of saline-irrigation water on marigold grown under field condition growth and yield descriptors (ashraf et al., 1991; khan et al., 1995). under high salinity levels, crop growth, leaf surface expansion, and primary carbon metabolism are negatively affected due to osmotic effects, water deficit, nutritional imbalance, and oxidative stress (kim et al., 2008). marigold (tagetes erecta l.) is an herbaceous annual plant belonging to the family asteraceae. marigold is used for ornamental and medicinal purposes. it is also used in cosmetic and perfume industry due to its aromatic nature and essential oil contents (regaswamy and koilpillai, 2014). in oman, marigold is a major seasonal flowering plant grown in the public parks, gardens, and roadside throughout the year. marigold is known to grow well under saline conditions (escalona et al., 2012). however, salinity can affect negatively on the growth and production of marigolds. sayyed et al. (2014) found that dry biomass, chlorophyll a, chlorophyll b and carotenoids content are reduced under high salinity (150, and 200 mm nacl) of the irrigation water. an increase of more than 100 mm in salt concentrations significantly reduced the shoot fresh weight (koksal et al., 2016). salinity of 100 mm nacl decreased marigold flower weight, plant fresh and dry biomass, plant height and had a negative effect on physiological processes such as stomatal closure and chlorophylls content decrease (chrysargyris et al., 2018). several techniques are implemented to mitigate adverse effect of salinity on plants such as increasing organic matter in soil, selecting salt-tolerant crops, using irrigation system with uniform water application, high efficiency of irrigation (e.g. drip irrigation and mini-sprinklers) and frequent irrigation with lower doses of water, among others. these techniques aim to lower the levels of salinity in the plant root zone and to improve drainage and to enhance salts leaching (abrol et al., 1988; machado and serralheiro, 2017; qadir et al., 2000). capillary barrier (cb) is one of the engineering techniques used to maximize crop production by improving soil moisture conditions in the root zone. a traditional cb is a composition of two soil layers having distinct differences in texture and, therefore, hydraulic characteristics. the classical way of creating soil cb is by adding a mulch layer. recently, there is an increase in cbs studies, especially, by researchers of arid zone soils (kacimov et al., 2017). a recent novel design of the cb soil substrate involves 3-d structures of soil composites of coarse and fine zones with variable vertical and lateral hydraulic properties (al-ismaily et al., 2013; al-maktoumi et al., 2014). this cb soil structure optimizes the root zone conditions for cultivating crops under harsh climatic environment such as high temperature (kacimov et al., 2017), drought (al-ismaily et al., 2013; al-maktoumi et al., 2014), salinity and poor quality irrigation water (ityel et al., 2012). in arid and semiarid countries like oman, the use of cb can be beneficial because it minimizes fresh (irrigation and rainfall) water percolation to deep saline aquifers and evaporation losses. as a result, plant roots get properly aerated by the abundance of air provided in the coarse zones of cbs. a naturally formed cb structure was discovered in the reservoir bed of the al-khoud dam at the governorate of muscat in northern oman (al-ismaily et al., 2013). this cb consists of fine (silt) blocks (which can be geometrically approximated as rectangular parallelepipeds) and cracks between these blocks filled with a coarse “proppant” sand. having this uniquely structured cb allowed the soil to capture a large quantity of water during a relatively short ponding period (less than 1 month) and to conserve this water for long time (over six months) in the cascade of silty blocks at a depth of 0.5 to 2.5 m, despite the high topsoil temperature and lack of rainfall during most part of the year (al-ismaily et al., 2013; al-maktoumi et al., 2014), resulting in lush wild vegetation emerging in several areas of the reservoir bed. normally, salts move with water, for example, during water evaporation, salts get advected by ascending moisture fluxed and accumulate in the top of the soil profile. during infiltration events, these accumulated salts are leached downward. when the soil has layers of contrasting texture (a discontinuity of the soil properties across the interfaces), the vertical fluxes of moisture and solutes become more intricate as compared with homogeneous soils. it has been found that 3-d structured soils conserve water and reduce water evaporation even more than unstructured (homogeneous) soils (al-maktoumi et al., 2014). thus, the cb structured soils conserve water through reducing the evaporation rate, our hypothesis is that the structured soil will be able to minimize salt accumulation in the plants’ root zone. in this study, we have investigated the influence of cb structured soils on mitigating salinity stress of marigold grown under field conditions of an arid climate of oman. materials and methods site preparation the experiment was conducted in an open field at the agricultural experiment station (aes) (23°37’n, 58°10’e), sultan qaboos university (squ), al-khoud, seeb, muscat, oman. an experimental plot made of a concrete block raised bed was constructed. the plot had a total area of 23m×8.5m and a boundary wall of 80 cm height. half of the plot (11.5m×8.5 m) was filled with a homogeneous fine-textured soil (silty loam) brought from the reservoir of al-khoud dam. the remaining half of the plot was engineered to resemble the cb structure discovered by al-ismaily et al., (2013). aluminum frame templates, having the size of 175 cm in length, 45 cm in width, and 30 cm height, were designed and manufactured to create the cb structure (figure 1); where 11research paper al-mazroui, al-yahyai, al-ismaily, kacimov, al-busaid the (a) spaces were filled with a fine-textured soil and the fractures of a small aperture (b) were filled with a sand (coarse-textured soil, also collected from the wadi which feeds the al-khod dam; the same sand was found in the natural prototype of the 3-d cb structure of the reservoir (al-ismaily et al., 2013). the elementary cell of the periodic 3-d structure in figure 1 geometrically and hydraulically replicates the parallelepipeds of blocks and “proppant” sheaths in al-ismaily et al. (2013) and al-maktoumi et al. (2014). figure 2 represents a side view of the experimental plot showing the structured or cb plot as compared to the unstructured or homogenous plot. the structured and unstructured plots were prepared and filled with soil in the following manner: for the ‘unstructured soil’ plot, the area was filled with a fine-textured soil (silty loam) up to 60 cm in height (figure 2). the other half of the plot was designated as a ‘structured soil’ plot, and it consisted of two layers (top and bottom) having fine soil surrounded by the sandy fingers (figure 2). filling of the structured soil area was as following; (1) a thin layer (≈5 cm) of sand was placed at the bottom of the plot area; (2) aluminum frame templates were used to fill the first (bottom) structured layer at about 30 cm; (3) another thin layer (5 cm) of sand was placed over the bottom structured layer; and (4) the top layer was filled in the same way using the same aluminum frame templates. the top structured layer was placed in a way it overlapped with the bottom structured layer as shown below in figure 2. the frames in the top structured layer were filled up to 20 cm in height, i.e. the top layer is “thinner” than the bottom layer (figure 2). when the top structured layer was completed, a thin layer (2 cm) of mulch made of sand was placed over it. the total height of the engineered structured soil was about 60 cm, i.e. same as the height of the unstructured soil in the other half of the plot. soil properties soil texture was determined by using the hydrometer method (bouyoucos, 1962). the percentages of sand, silt, and clay of the soil used for the unstructured soil and in the blocks of the structured soil were 22%, 53%, and 26%; the soil texture was silty loam. the soil water retention curve (figure 3) was determined using the pressure plate apparatus from four suction values (1, 3, 5, and 15 bar) and corresponding volumetric moisture content. these values were plotted in retc software (van genuchten et al., 1991) and the retention curve was constructed using parametric models of brooks-corey and van genuchten. the soil retention curve shows that the saturation point was about 0.42 cm3cm-3, field capacity was around 0.32 cm3cm-3, and the permanent wilting point of –15 bars was about 0.11 cm3cm-3. the measured soil salinity (ece) and ph were 1.4 ds m-1 and 8.4, respectively (rhoades, 1996; soil survey staff, 2014). treatments marigold (tagetes erecta) ‘taishan orange’ was used as a model plant in this study due to its extensive use as ornamental and medicinal plant in arid climates and refigure 2. side view (a vertical cross-section) of the structured soil (top panel) and unstructured soil (bottom panel). figure 3. soil water retention curve of soil used in unstructured area and blocks of structured area predicted by retc software (water conent: cm3 cm-3) figure 1. illustration of the templates used for filling the structured soil 12 squ journal of agricultural and marine sciences, 2020, volume 25, issue 1 use of soil-structured capillary barrier can mitigate the impact of saline-irrigation water on marigold grown under field condition sponded well to cb studies under controlled conditions (al-mazroui et al., 2019) three-weeks-old marigold seedlings were transplanted and grown in both structured and unstructured soil areas. initially, all plants in the two areas were irrigated with freshwater (desalinated, ecw ≈ 0.6 ds m-1) for three weeks. then, plants were subjected to three salinity levels of irrigation water (eci= 3 ds m-1, 6 ds m-1, and 9 ds m-1), in addition to the control (desalinated water, eci ≈ 0.6 ds m-1). the irrigation system consisted of three saline stock solutions of ec= 100 ds m-1 and three dosatron injectors (non-electric proportional liquid dispenser) (d3; dosatron international, bordeaux, france). the injectors were used to pump 1m (100 ds m-1) nacl salt solution to the freshwater (ecw = 0.6 ds m-1). the injectors were set to inject the salt solution into the freshwater in ratios that resulted in the required eci= 3, 6, and 9 ds m-1 of irrigation water. sixty seedlings of marigold were planted in each treatment divided into three lines (20 seedlings in each line). a total of 480 seedlings were planted in the two sections, 240 seedlings for each of the structured and unstructured soils. the inter-plant distance was 50 cm, and the inter-row distance was 50 cm whereas the boundary between the treatment plots was 1 m. irrigation and fertilization inbuilt drip irrigation system (pressure-compensating drip emitters with flow rates of 4 l h–1) was installed and used to irrigate the plants. each treatment had a solenoid valve (electrical valve) connected with an irrigation controller (hunter’s controller). the irrigation controller was programmed to irrigate each treatment separately. the amount of irrigation water given to the plants was based on the field capacity. they were irrigated with approximately 50% depletion of available water capacity (awc). all plants were fertilized with npk (20:20:20+te) initially through the irrigation system by dissolving 4 kg npk in 4000 l of desalinated water in the tank. after that, the plants were fertilized through spraying method every two weeks. soil moisture content and electrical conductivity measurements sensors (5te, decagon device, pullman, wa, usa) were placed at two depth levels to measure soil moisture content (θv) and ec (figure 2). in the structured soil, six sensors were placed in each treatment (3 sensors at the bottom structured layers and 3 sensors at the top structured layers). thus, a total of 24 sensors were placed in the structured soil area. in the unstructured soil area, also 24 sensors were used. six sensors were placed for each treatment. three sensors were placed at 40 cm depth (the same depth of the bottom layer in the structured soil), and three sensors were placed at 10 cm depth (the same depth of the top layer in the structured soil). the total number of sensors in the whole plot were 48. sensors were connected with data loggers and programmed to read the moisture content and ec every hour. at the end of the experiment, the ece of the two layers in the structured soil area and the corresponding soil depth (10 cm and 40 cm) in unstructured soil were measured using electrical conductivity meter (oakton waterproof/pcstestr35ph/conductivity/tds/salinity tester, oakton, usa). plant growth and production measurements vegetative, reproductive and physiological measurements included: shoot height, shoot width (canopy), number and size of flowers, leaf area, fresh and dry weight of shoots and roots, chlorophyll content and chlorophyll fluorescence. chlorophyll content was measured using chlorophyll meter spad 502 (minolta, japan) whereas chlorophyll fluorescence was measured using fluor pen fp100 (photon systems instruments, brno, czech republic). water use efficiency (wue) we define wue as the ratio of the yield of a crop (y) to the total amount of water used in the field per day. wue of each treatment was computed using the following formula (sinclair et al., 1984): wue=y/wr (1) where, wue = water use efficiency (g/l), y = vegetative or reproductive biomass (g), wr = amount of water applied for a plant per day (l). figure 4. time series of θv in the top (a) and bottom (b) layers of the structured soil and unstructured soil 13research paper al-mazroui, al-yahyai, al-ismaily, kacimov, al-busaid statistical analysis the data were analyzed using the analysis of variance (anova) procedure (proc anova) of the sas version 9.4 (sas, 2018). results soil moisture content and electrical conductivity (ec) the time series of the soil θv of both structured and unstructured soil at the two selected depths (10 cm and 40 cm) in unstructured soil, and (top and bottom layers) in the structured soil are presented below (figures 4 a and b). the high θv at the beginning of the experiment was because the soils were watered to allow them to settle down mechanically and also to check the irrigation system. the θv of the top layer in the structured soil and at 10 cm depth in the unstructured soil was maintained within the field capacity of the soil (0.20 – 0.25 cm3cm-3). the bottom layer in the structured soil showed a continuous decrease in θv whereas almost a constant (θv = 0.21) was obtained for unstructured soil at 40 cm. this was the case during the whole experiment period. the amount of water used to irrigate marigold plants was measured in both soil substrates using a water meter. the amount of the daily water applied to irrigate a single plant of marigold was about 0.75 l in the unstructured soil and 0.22 l in the structured soil. in other words, the structured soil required more than three times less water to maintain the targeted moisture conditions of the root zone. the results showed that in all salinity treatments, the ece of the topsoil was significantly higher in the unstructured soil than in the structured soil (figure 5-a). the difference in ece between the structured and unstructured soils was more significant at higher salinity level of irrigation water, viz. at eci= 6 ds m-1 (4.05 and 7.35 ds m-1 for structured and unstructured soil, respectively) and 9 ds m-1 (5.74 and 8.70 ds m-1 for structured and unstructured soil, respectively). the same was with the bottom soil except in control salinity level (irrigation with freshwater) where there was no significant difference between the structured and unstructured soil (figure 5-b). unlike the top layer of the structured soil, the bottom part showed no increase in ece as the salinity of irrigation water increased from control (1.37 ds m-1) to 9 ds m-1 (1.46 ds m-1). vegetative growth table 1 shows a significant decrease in all marigold vegetative parameters measured in the unstructured soil as the salinity level increased. on the other hand, there was no reduction in marigold vegetative parameters measured in the structured soil as the salinity level increased. there were no significant differences between control and 3 ds m-1 salinity level in the vegetative growth parameters except in the root fresh weight in both structured and unstructured soil. at 6 ds m-1 salinity level, there was a reduction by 5.6% in shoot height, 10.1% in shoot width, 28.8% in leaf area, 30.7% in the shoot fresh weight, 24.6% in the dry shoot weight, 54.4% in the roots fresh weight, and 69.8% in the roots figure 5. the ece of the topsoil in the structured and unstructured soil at different salinity treatments (a), and the ece of the bottom soil in the structured and unstructured soil at different salinity treatments (b) 14 squ journal of agricultural and marine sciences, 2020, volume 25, issue 1 use of soil-structured capillary barrier can mitigate the impact of saline-irrigation water on marigold grown under field condition dry weight in comparison to control. the effect of 6 ds m-1 salinity level was much less on the marigold in the structured soil where the shoot height, shoot width, leaf area, shoot fresh weight, shoot dry weight, root fresh weight, and root fresh weight decreased by 3.0%, 6.7%, 16.9%, 1.5%, 7.4%, 50.8%, and 63.2%, respectively. at 9 ds m-1 salinity level, all vegetative traits measured were significantly less in the unstructured soil where the shoot height, shoot width, leaf area, shoot fresh weight, shoot dry weight, root fresh weight, and root fresh weight decreased by 10.6%, 21.6%, 46.0%, 47.2%, 30.3%, 60.4%, 75.5% respectively (table 1). in contrast, there was no significant effect of 9 ds m-1 salinity level on measured vegetative parameters (except for shoot width and leaf area) of marigold grown in the structured soil. the shoot height, shoot width, leaf area, shoot fresh weight, shoot dry weight, root fresh weight, and root fresh weight in structured soil decreased by 4.4%, 10.9%, 27.6%, 2.3%, 4.4%, 21.6%, and 27.4% respectively. table 1 also shows a comparison between the structured soil and unstructured soil, with respect to the effects of salinity stress on marigold vegetative parameters. at control and 3 ds m-1 salinity levels, there were no significant changes in all vegetative parameters, except in the shoot width at 3 ds m-1 salinity level, whereas shoot width of marigold in the unstructured soil was higher than in the structured soil. at 6 ds m-1 salinity level, the shoot height and shoot width were significantly higher in the structured soil than in the unstructured soil (by 5.3% and 14.3%, respectively). at 9 ds m-1 salinity level, the shoot height, shoot width, and shoots fresh weight were significantly higher in the structured soil than in the unstructured soil (by 10.7%, 24.2%, and 40.3%, respectively). overall, the structured soil resulted in significantly higher shoot height, shoot width, and leaf area. reproductive growth table 2 depicts the effect of different salinity levels on the reproductive growth of marigold plants grown in the structured and unstructured soil. the number of flowers, their size and weight decreased as salinity level increased in the unstructured soil. however, there was no significant effect of salinity on the marigold flowering traits in the structured soil. the unstructured soil, at eci= 3 ds m-1, indicated a significant reduction in the size of the flowers (by 4.1% compared to control). at eci= 6 ds m-1, showed a reduction by 18.8 % in the number of flowers, 8.7% reduction in the flower diameter, 28.9% in the flowers’ fresh weight, and 10% in the flowers dry weight. in contrast, the reductions in the structured soil were only by 6.3% in the number of flowers, 2.3% reduction in the flower diameter, 3.7% in the flowers fresh weight, and 2.3% in the flowers dry weight. at eci= 9 ds m-1 salinity level, the number of flowers, flower diameter, flower fresh weight, and flower dry weight were decreased by 31.3%, 9.9%, 56.5%, 35.6%, respectively in the unstructured soil and by 6.3%, 2.6%, 8.2%, and 1.3%, respectively in the structured soil. although all marigold reproductive parameters declined significantly in the unstructured soil, the reduction in the structured soil was not significant. table 2 also compares the structured soil and unstructured soil in the effect of salinity stress on marigold reproductive paramfigure 6. water use efficiency for fresh flowers (a) and shoot biomass (b) in the structured and unstructured soil at different salinity levels 15research paper al-mazroui, al-yahyai, al-ismaily, kacimov, al-busaid eters. at control salinity level, there was no significant difference between the structured and unstructured soil in all reproductive parameters. at eci= 3 ds m-1, the flower diameter in the structured soil was significantly bigger than that in the unstructured soil, whereas there were no critical differences in the number of flowers and their fresh and dry weight. at eci= 6 ds m-1, the number of flowers produced by the marigold in the structured soil was statistically higher than that of the unstructured soil. also, the structured soil resulted in a larger flower diameter than the unstructured soil at the same salinity level. at eci= 9 ds m-1, all reproductive parameters were significantly higher in the structured soil than in the unstructured soil. taken together, the structured soil showed a significantly higher number of flowers, bigger flowers, and higher flowers’ dry weight. physiological parameters the experiments showed a significant decrease in the marigold leaf chlorophyll content and chlorophyll fluorescence with increasing levels of salinity in the unstructured soil whereas no significant changes were table 2. effect of different salinity levels on reproductive growth parameters on marigold plants grown in the structured and unstructured soil design salinity level soil shoot height shoot width leaf area shoot fresh weight control structured 15aa±0.61 6.18aa±0.06 87.90aa±2.68 21.94aa±1.09 unstructured 15aa±1.06 6.06aa±0.06 100.17aa±3.57 20.03aa±1.26 3 ds m-1 structured 15aa±0.81 6.05aa±0.05 82.09aa±2.71 21.27aa±0.77 unstructured 16aa±1.26 5.80bb±0.06 92.73aa±4.75 22.33aa±1.16 6 ds m-1 structured 15aa±0.66 6.07aa±0.06 84.63aa±7.65 21.43aa±2.16 unstructured 11abb±0.82 5.53cb±0.06 71.25ba±4.23 17.84aa±0.82 9 ds m-1 structured 16aa±0.92 6.21aa±0.05 80.65aa±6.57 22.66aa±1.33 unstructured 13bb±1.38 5.46cb±0.08 43.56cb±5.01 12.90bb±1.90 average of structured 15a 6.13a 83.82a 21.83a average of unstructured 14b 5.71b 76.93a 18.28b values (means ± se) in the same column with the same uppercase letters indicating no significant difference of the structured and unstructured soil separately at different salinity levels. same lowercase letters in the same column indicating no significant difference between structured and unstructured soil at each salinity level at p≤0.05. table 1. effect of different salinity levels on vegetative growth parameters on marigold plants grown in the structured and unstructured soils salinity level soil shoot height shoot width leaf area shoot fresh weight shoot dry weight root fresh weight root dry weight control structured 36.67aa±0.47 24.67aa±0.68 19.03aa±0.64 70.41aa±2.47 11.95aa±0.54 5.00aa±0.30 2.77aa±0.55 unstructured 35.67aa±0.62 24.67aa±0.67 19.25aa±0.94 77.83aa±8.42 11.99aa±1.22 7.70aa±1.95 3.51aa±0.97 3 ds m-1 structured 35.11aa±0.43 23.56ab ±0.65 17.61aba±1.14 63.15aa±4.50 10.38aa±0.52 2.34ba±0.27 1.03aa±0.14 unstructured 34.56aba±0.56 25.22aa±0.32 16.75aba±1.38 68.37aa±5.56 11.52aa±1.04 4.00ba±0.68 1.81aba±0.44 6 ds m-1 structured 35.56aa±0.46 26.44aba±0.65 15.81bca±0.67 71.49aa±7.44 11.06aa±0.73 2.46bb±0.07 1.02aa±0.06 unstructured 33.67bb±0.62 22.67bb±0.55 13.71bca±0.91 53.87aba±0.38 9.04aba±0.17 3.51ba±0.12 1.06ba±0.09 9 ds m-1 structured 35.72aa±0.54 26.11ba±0.51 13.78ca±0.84 68.76aa±3.17 11.43aa±0.71 3.92aba±0.95 2.01aa±0.84 unstructured 31.89cb±0.42 19.78cb±0.91 10.40ca±1.89 41.06bb±5.91 8.36ba±0.84 3.05ba±0.46 0.86ba±0.22 average of structured 35.77a 25.20a 16.56a 68.45a 11.21a 4.57a 1.81a average of unstructured 33.95b 23.09b 15.03b 60.28a 10.23a 3.43a 1.72a values (means ± se) in the same column with the same uppercase letters indicating no significant difference of the structured and unstructured soil separately at different salinity levels. same lowercase letters in the same column indicating no significant difference between structured and unstructured soil at each salinity level at p≤0.05. 16 squ journal of agricultural and marine sciences, 2020, volume 25, issue 1 use of soil-structured capillary barrier can mitigate the impact of saline-irrigation water on marigold grown under field condition observed in the marigold leaf chlorophyll content and chlorophyll fluorescence with increasing salinity level in the structured soil (table 3). the unstructured soil showed a reduction in the chlorophyll content by 5.28%, 12.17%, and 18.23% at eci= 3 ds m-1, 6 ds m-1, and 9 ds m-1, respectively, compared to the control. on the other side, the structured soil showed only 2.27%, 1.63%, and 3.04% reduction at eci= 3 ds m-1, 6 ds m-1, and 9 ds m-1, respectively, compared to the control. chlorophyll fluorescence decreased significantly in the unstructured soil at eci= 6 ds m-1, and 9 ds m-1 by 1.5% and 3.13%, respectively, whereas the structured soil showed no significant reduction in the chlorophyll fluorescence as salinity level increased. there were no significant differences between the structured and unstructured soils in the marigold chlorophyll content and chlorophyll fluorescence for the control and the eci= 3 ds m-1 treatment, however, at eci= 6 ds m-1 and 9 ds m-1 salinity level, the chlorophyll content and chlorophyll fluorescence were significantly higher in the structured soil than in the unstructured soil (table 3). overall, the structured soil had significantly higher chlorophyll contents and chlorophyll fluorescence. plant mortality at the end of the experiment, the number of dead plants in each treatment for both structured and unstructured soil was counted. the mortality percentages in the unstructured soil were 58.3%, 8.3%, 0%, 0% at eci= 9 ds m-1, 6 ds m-1, 3 ds m-1 and control, respectively. in contrast, the mortality percentages in the structured soil were 15%, 1.6% , 0%, 0% at eci= 9 ds m-1, 6 ds m-1, 3 ds m-1 and control, respectively. the mortality of marigold plants in the structured soil was less by five to four times compared to the unstructured soil when irrigated with eci= 6 ds m-1 and eci= 9 ds m-1, respectively. water use efficiency the wue, which was based on the marigold fresh flower and shoot biomass to the daily irrigation water applied, is presented in figure 6. wue for shoot biomass varied from 328.85 g/l (in the structured soil at eci= 6 ds m-1) to 54.79 g/l (in the unstructured soil at eci= 9 ds m-1). the wue for flowers varied from 404.34 g/l (in the structured soil at control salinity level) to 58.12 g/l (in the unstructured soil at eci= 9 ds m-1). there was a decreasing trend in wue for both shoots and flowers biomass as the salinity level increased. this decrease in wue was more obvious in the unstructured soil than in the structured soil. wue for flower biomass in the unstructured soil at control was 66.9% less than in the structured soil, and the differences increased with salinity. the difference was 67.2%, 75.6%, and 84.3% at eci= 3 ds m-1, 6 ds m-1, and 9 ds m-1, respectively. also, the wue for shoot biomass in the unstructured soil at control was 67.9% less than in the structured soil, and the differences increased with the salinity. the difference was 68.6%, 78.1%, and 82.7% at eci= 3 ds m-1, 6 ds m-1, and 9 ds m-1, respectively. discussion structured soil on water saving and salts accumulation smartly structured soil substrate designed in this study showed a high capacity to save water and reduce salts accumulation compared to unstructured soil. the amount of water used to irrigate marigold plants in the unstructured soil was more than three times, as compared with that in the structured soil. the key reason for this huge table 3. effect of different salinity levels on physiological parameters on marigold plants grown under structured and unstructured soil configurations salinity level (eci) soil chlorophyll content (spad readings) chlorophyll fluorescence (fv/fm) control structured 63.84aa±0.87 0.65aa±0.00 unstructured 63.69aa±0.65 0.64aba±0.01 3 ds m-1 structured 62.20aa±0.80 0.65aa±0.00 unstructured 60.33ba±0.94 0.66aa±0.01 6 ds m-1 structured 63.23aa±0.59 0.65aa±0.00 unstructured 55.94cb±0.95 0.63bcb±0.01 9 ds m-1 structured 61.90aa±0.74 0.64aa±0.00 unstructured 52.08db±1.62 0.62cb±0.01 average of structured 62.79a 0.65a average of unstructured 58.01b 0.64b values (means ± se) in the same column with the same uppercase letters indicating no significant difference of the structured and unstructured soil separately at different salinity levels. same lowercase letters in the same column indicating no significant difference between structured and unstructured soil at each salinity level at p≤0.05. 17research paper al-mazroui, al-yahyai, al-ismaily, kacimov, al-busaid water saving is the presence of the unique 3-d cb in our structured soil. our smart composite prevents or retards moisture movement from the pores of the silt blocks to sand. the engineered soil architecture reduces both the upward moisture movement during evaporation and downwards water seepage during infiltration (al-ismaily et al., 2015; al-saqri et al., 2016). therefore, structuring the soil allows the root zone to hold more “productive” water than in homogeneous soils and to prevent it from evaporative-percolation losses. thus, water is depleted at a slow rate through favourable transpiration rather than evaporation and deep percolation (al-maktoumi et al., 2014). water resources in the arid and semi-arid zones of the arabia are very scarce. thus, saving irrigation water is of paramount importance for agriculture, urban landscaping and – in general – for national economies of mena countries. in terms of salt accumulation, the ece of the top and bottom structured soil was significantly less than the ece of the unstructured soil at all salinity levels of irrigation water (figures 5a and 5b). the difference in ece between the structured and unstructured soils was more significant at higher salinity levels of irrigation water, viz. at eci= 6 ds m-1 and 9 ds m-1. this is again due to higher evaporation rates in the unstructured soil compared to the structured soil (al-maktoumi et al., 2014). during evaporation, salts move with water to accumulate at the soil surface and shallow sub-surface (goosen and shayya,1999). therefore, due to the higher water evaporation (and high norms of irrigation with saline water in the unstructured soil), there was much more salt accumulation in the unstructured soil. effect of salinity on the vegetative and reproductive growth and physiology of marigold grown in the structured and unstructured soils increasing water salinity level in this study was much correlated with the reduction in vegetative, reproductive and physiological parameters of marigold grown in the unstructured soil compared to structured soil (tables 1-3). plant parameters were significantly better in structured soils compared to unstructured soils including shoot height, canopy width, leaf area, number of flowers, flower diameters, and floral dry weight (tables 1 and 2), and plant physiological parameters (table 3). this may have been attributed to the lower salts accumulated in the structured soil than in the unstructured soil (figures 5a and 5b). marigold vegetative characteristics such as shoot height, root length, no of leaves, fresh and dry biomass of marigold exhibited reduction under high concentration of nacl (150, and 200 mm nacl) (sayyed et al., 2014). furthermore, chrysargyris et al., 2018 found that salinity of 100 mm nacl decreased marigold flower weight, plant fresh and dry biomass, plant height and had a negative effect on physiological processes such as stomatal closure and chlorophylls content decrease. in the present study, structured soil was so effective in mitigating salinity stress of marigold plants. our results are in agreement with cude et al., (2018) who reported that a standard (layered) cb led to reductions or smaller increases in salinity than in treatments without a cb. also, ityel et al., (2012) showed that the bell pepper plants grown above a cb yielded 24% higher biomass than control plants, particularly, under saline condition. furthermore, rooney et al., (1998) reported that placing a cb under the root zone was effective to prevent salinization from underlying sources by stopping the capillary rise. plant mortality the mortality percentage of the marigold in the unstructured soil was 58.3% at eci=9 ds m-1 and 8.3% at eci=6 ds m-1 whereas in the structured soil it was only 15% at eci=9 ds m-1 and 1.7% at eci=6 ds m-1. the higher mortality in the marigold grown in the unstructured soil is because of higher concentrations of salts accumulated in the unstructured soil than in the structured soil. high soluble salts in the soil lead to osmotic stress, specific ion toxicity and ionic imbalances (munns, 1993) and, as a result, plants grown under these intolerable saline conditions die (rout and shaw, 2001). ozturk et al. (2004) showed that all seedlings of melissa officinalis died at 6 ds/m. also, increasing soil salinity with nacl salt up to 3000 ppm, corresponding to 5.7 ds m-1, resulted in the complete death of sage plants (hendawy and khalid, 2005). thus, our 3-d cb structured soil composites reduce salinity stress on the plants. water use efficiency structured soil showed a great impact on improving wue, viz. about 66.9% improvement in the wue for flower biomass and 67.9% for shoot biomass at control salinity level comparing with unstructured soil. the difference in wue between the structured soil and unstructured soil was greater at higher salinity levels. there was 67.2%, 75.6%, and 84.3% improvement in the wue at eci= 3 ds m-1, 6 ds m-1, and 9 ds m-1, respectively for flower biomass and 68.6%, 78.1%, and 82.7% at eci= 3 ds m-1, 6 ds m-1, and 9 ds m-1 salinity level, respectively for shoot biomass. the higher wue for both flowers and shoot biomass in the structured soil than in the unstructured soil was due to less amount of water required to irrigate the marigold plants grown in the structured soil compared to the unstructured soil. soil with even 1-d cb store more water than those without cb (bruch, 1993; zornberg et al., 2010; huang et al., 2011). the cb can improve wue by minimizing water loss and/or increasing the crop yield. several studies have shown the capability of the cb in improving wue. an experiment conducted in greenhouses during cultivation of a horticultural crop by ityel et al. (2012) found that the installation of a cb increased 60% the soil water content and 25% the fruit yield for green peppers, and increased the 18 squ journal of agricultural and marine sciences, 2020, volume 25, issue 1 use of soil-structured capillary barrier can mitigate the impact of saline-irrigation water on marigold grown under field condition matric head by 80% and the biomass yield by 36% for lettuce. a numerical study by wongkaew et al. (2018) demonstrated the role of a cb in improving the root zone conditions and maximizing wue. moreover, sadegh-zadeh et al. (2009) indicated that cb can increase the water holding capacity and soil water content in layered soils. conclusion & recommendations marigolds were grown in two soil configurations: structured and unstructured soils. in each soil treatment, marigolds were subjected to four salinity levels of irrigation water. the results showed the ability of the structured soil, through its silty soil sandwiched by a sand-filled maze of horizontal and vertical fingers, to conserve the soil moisture more than three times, as compared with the unstructured soil. the wue for both marigold flower and shoot biomass were much higher in the structured soil than in the unstructured soil. the wue in the unstructured soil was 66.9% less than in the structured soil for flowers biomass, and 67.9% less for shoot biomass at control salinity level and the differences increased with salinity. also, the structured soil significantly reduced salt accumulation in the roots zone where the ece of the structured soil was significantly higher than the ece of the unstructured soil. moreover, marigold in the structured soil substrate showed better growth and flower production than the marigold in the unstructured soil, especially, at higher salinity levels. the physiological, vegetative and reproductive parameters of marigold in the unstructured soil significantly decreased with salinity of irrigation water. there were no significant changes due to irrigation with saline water in most physiological, vegetative and reproductive parameters of marigold in the structured soil compared to unstructured soil. therefore, our study explored and substantiated a novel method in mitigating salinity problem, water-saving, and improving roots zone conditions and thereby improving crop production and wue especially under the harsh conditions of desertic farming. further studies are needed to evaluate this smart-design soil with different plants including fruits, vegetables and ornamental plants of different root systems and growth patterns and under different irrigation systems. acknowledgment the authors acknowledge the financial support from sultan qaboos university (squ) and the sultan qaboos higher center for culture and science – diwan of royal court and the research council of oman (trc) [rc/agr/ swae/17/01]. the technical help by the agricultural experiment station (aes) staff is highly appreciated. references abrol ip, yadav jsp, massoud fi. 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(2010). geosynthetic capillary barriers: current state of knowledge. geosynthetics international 17(5): 273–300. review article journal of agricultural and marine sciences 2021, 26(2): 10–23 doi: 10.24200/jams.vol26iss2pp10-23 received 19 dec 2020 accepted 21 jan 2021 gis and remote sensing techniques in controlled environment agriculture: a review asma m. al-maimani 1, abdulrahim m. al-ismaili 2,*, yassine charabi 2,3 abdulrahim m. al-ismaili 2,*( ) abdrahim@squ.edu.om; ams.ismaili@gmail.com, 1department of soils, water and agricultural engineering, sultan qaboos university, sultanate of oman, 2department of geography, sultan qaboos university, sultanate of oman, email: yassine@squ.edu.om, 3 center for environmental studies and research, sultan qaboos university, sultanate of oman introduction in arid and semi-arid regions, high temperatures and water scarcity are the two major constraints for ag-riculture development and sustainability (al-ismaili and jayasuriya, 2016). greenhouses are considered a sustainable option for crop production in harsh climatic conditions (helmy et al., 2013; kumar et al., 2009) through providing favourable microclimate for plants, extending the cropping season and achieving year-round production. controlled environment agriculture (cea) term refers to a group of agricultural systems including screenhouses, greenhouses, shade-houses and aquaponics (al-ismaili et al., 2017). the total area under plastic greenhouse covers has rapidly grown to reach more than 500,000 ha around the world (agüera and liu, 2009). تطبيقات نظم املعلومات اجلغرافية و اإلستشعار عن بعد يف الزراعة احملمية: مراجعة أمساء م. امليمين1، عبدالرحيم م. اإلمساعيلي 2،*، ايسني شرعيب 2،3 abstract. geographic information system (gis) and remote sensing (rs) are useful tools in environmental monitoring, evaluation and analysis for various sectors including agriculture. this paper reviews the applications of gis, rs and the integration of both techniques in the agricultural field, in general, and controlled environment agriculture (cea), in particular. more emphasis is given to their applications in arid areas and oman is taken as a case study. gis techniques have been used in the mapping of soil and water quality, spatial assessment for water quantity stress, land suitability, pest and disease distribution of crops as well as delineating and generating database management systems (dbms) for protected cultivations. in oman, gis was only employed to analyse the spatio-temporal dynamics of land use changes as affected by external factors and greenhouses as an example in northern part. rs was also utilised to map the changes in land cover and their uses, detect and map soil salinity, and monitor agricultural droughts. in cea, rs was utilised for mapping, detection and classification of greenhouses through aerial images and satellites. in oman, negligible study was documented on the use of rs techniques in the cea field. the integration of both techniques has proven its capability in mapping, evaluating and managing natural resources and greenhouse distribution and generating database management system in agriculture and cea fields. sophisticated geostatistical analysis models based on multi-criteria analysis using fuzzy-logic and analytic hierarchy process could be a good platform for trade-off analysis for land suitability analysis and optimal location of cea in challenging agriculture like oman. keywords: gis; remote sensing; greenhouse; database management system امللخص: تعد تقنيات نظم املعلومات اجلغرافية )gis( واإلستشعار عن بعد )rs( من األدوات املفيدة يف املراقبة البيئية والتقييم والتحليل ملختلف القطاعــات مبــا يف ذلــك الزراعــة. تســتعرض هــذه الورقــة تطبيقــات نظــم املعلومــات اجلغرافيــة و اإلستشــعار عــن بعــد ودمــج كلتــا التقنيتــني يف اجملــال الزراعــي بشــكل عام والزراعة احملمية )cea( على وجه اخلصوص. مت الرتكيز بشــكل أكرب على تطبيقاهتم يف املناطق القاحلة ويتم أخذ عمان كدراســة حالة. مت اســتخدام نظــم املعلومــات اجلغرافيــة يف رســم خرائــط الرتبــة وجــودة امليــاه ، والتقييــم املــكاين إلجهــاد كميــة امليــاه ، ومالءمــة األراضــي ، وتوزيــع اآلفــات واألمــراض للمحاصيــل وكذلــك حتديــد وإنشــاء نظــام إدارة قواعــد البيــاانت )dbms( للزراعــة احملميــة. يف ُعمــان، مت اســتخدام نظــم املعلومــات اجلغرافيــة فقــط لتحليــل الديناميكيــات املكانيــة والزمانيــة لتغــرات اســتخدام األراضــي والبيــوت احملميــة كمثــال يف اجلــزء الشــمايل. كمــا مت اســتخدام اإلستشــعار عــن بعــد لرســم خريطــة التغــرات يف الغطــاء األرضــي واســتخداماته ، واكتشــاف ملوحــة الرتبــة ورســم خرائــط هلــا ، ورصــد حــاالت اجلفــاف الزراعــي. يف الزراعــة احملميــة، مت اســتخدام اإلستشــعار عــن بعــد لرســم خرائــط واكتشــاف وتصنيــف الزراعــة احملميــة مــن خــالل الصــور اجلويــة واألقمــار الصناعيــة. يف عمــان ، مل يتــم توثيــق أي دراســة واحــدة حــول اســتخدام تقنيــات االستشــعارعن بعــد يف جمــال الزراعــة احملميــة . أثبــت تكامــل كلتــا التقنيتــني قدرتــه علــى رســم خرائــط وتقييــم وإدارة املــوارد الطبيعيــة وتوزيــع الزراعــة احملميــة وإنشــاء نظــام إدارة قواعــد البيــاانت يف جمــاالت الزراعــة والزراعــة احملميــة. ميكــن أن تكــون منــاذج التحليــل اإلحصائــي املتطــورة القائمــة علــى التحليــل متعــدد املعايــر ابســتخدام عمليــة التسلســل اهلرمــي التحليلــي واملنطــق الضبــايب منصــة جيــدة لتحليــل املقايضــة لتحليــل مالءمــة األرض واملوقــع األمثــل للزراعــة احملميــة يف مــكان تتواجــد بــه التحــدايت الزراعيــة مثــل عمــان. الكلمات املفتاحية: نظم املعلومات اجلغرافية، اإلستشعار عن بعد، البيت احملمي، نظام ادارة قواعد البياانت. 11review article al-maimani, al-ismaili and charabi however, this rapid growth of cea should be monitored and mapped for better understanding and planning for the development and management of natural resources, which could be achieved using geographic information system (gis) and rs (remote sensing) techniques. gis is a professional computer system that manipulates spatial and non-spatial data to present them in a simple illustrative manner on the map (soomro, 2015). it links the tabular (database) information with their respective locational (spatial) coordinates for better visualization. in addition, it has a unique capacity with spatial data in terms of collection, storage, management, conversion, analysis, modelling and display as it performs these functions in a very organised way (davis, 1996). gis tools and techniques are very helpful and beneficial in several fields including geography, computer science, environmental science, agriculture, forest, food, entertainment, banking, health services and manufacturing (soomro, 2015). rs is an art of acquiring information about an object or event on earth’s surface, ocean or atmosphere using remote sensors (e.g. special cameras, radars and digital scanners) (bhatta, 2011; wang and weng, 2013). buildings, soils, water and vegetation are examples of sensing/observing objects at distant (remote) places which are investigated by scientists (campbell and wynne, 2011). rs has several distinguished advantages, such as observation of a broad area at one time (spatial) as well as observing the areas for long periods (temporal). another advantage is the possibility to collect data from places that are geographically or politically inaccessible without any distortions (bhatta, 2011; wang and weng, 2013). the user can benefit from the results of rs in a variety of applications such as ecosystems, natural landscapes, hydrology, urban planning and agriculture. usery et al. (1995) mentioned that advanced technologies such as gis and rs are used to collect and handle spatially referenced data, perform spatial analysis and decision-making for factors related to geography in order to solve problems in planning and management (parthasarathy, 2010; soomro, 2015). using interrelationships between geography, location and people in gis makes it possible to take decisions aiming to improve the living on earth (soomro, 2015). rs and gis are very beneficial techniques to store, operate and quantitatively evaluate the soil sustainability and capability for various practices (saleh et al., 2015). applications of gis in agriculture in agricultural field, gis can be used for a small scale areas like a single farm to a large scale areas like the globe (wilson, 1999). the basic of success and profitability of any farm is to balance between inputs and outputs (parthasarathy, 2010). gis tools are beneficial to owners of agricultural farms by visualising the environmental parameters and workflows within their farms. these tools enable them to handle the agricultural spatial data, which are collected through mobile devices, in investigating their farm conditions and evaluating their effects on the wellbeing of their farms (soomro, 2015). jayasuriya et al. (2014) presented the use of gis in mapping the levels of soil compaction by heavy-load vehicles and the moisture content distribution of rhodes grass to reach the best tillage and irrigation management. results showed an inverse relationship between rhodes grass growth and soil compaction levels. sadat-noori et al. (2014) worked on gis and water quality index (wqi) to assess and examine the spatial distribution of ground-water quality of saveh-nobaran aquifer in iran. the major cations and anions (ca, mg, na, hco3, so4, cl, and tds), ec, ph and hardness of ground-water samples were analysed and documented. using gis, maps of the aforementioned parameters were created using kriging method. figure 1 shows the wqi map of the selected aquifer. for the wqi assessment, they reported that 65% of samples were under three categories of drinking water qualities; very poor, poor and unsuitable. the amalgamation of gis and wqi method was very effective and can help for better decision making. in another study, knowledge-base model was built in gis environment to assess the supplementary irrigation in rain-fed agricultural watersheds in india (reshmidevi et al., 2010). the model used the empirical information of land suitability for crops, irrigation practices and the hydrological models to improve the supplementary irrigation in the watershed. it was found that this model could be implemented to estimate the irrigation requirements based on rainfall conditions. land suitability analysis is necessary for agricultural planning and sustainability. gis can also aid farmers to determine the preference areas for crop cultivation as well as to manage pests and increase the profit during harvesting (soomro, 2015). bhagat et al. (2009) used gis to analyse land suitability for cereal production in himachal pradesh, india. the geo-referenced data (climate, elevation, soil and land cover) with potential production were fed to gis. the resulted maps delineated suitable lands for growing cereals in the study area. for agricultural sustainability, gis showed that small agricultural lands can be merged efficiently together. in turkey, a study of land suitability for fruit growing using gis was done by yarilgac (2012). similarly, chiranjit and kishore (2016) reviewed gis applications on land suitability evaluation for agricultural crop selection using different approaches such as fuzzy logic, multi-criteria evaluation (mce) and analytic hierarchy process (ahp) within gis environment. the mce approach is one of the land assessment tools used for selecting the proper factors from a large number of factors and thus, giving the best solutions and finding alternatives for decision making (gastli and charabi, 2010; hedia and elkawy, 2016; olaniyi et al., 2015). the combination of mce within gis environment gives a strong support for decision makers and researches. hedia and elkawy (2016) 12 squ journal of agricultural and marine sciences, 2021, volume 26, issue 2 gis and remote sensing techniques in controlled environment agriculture: a review studied the assessment of land suitability for agricultural uses in egypt by means of mce within gis. (chivasa et al., 2019) evaluated the land suitability for maize production (zea mays l.) with aid of gis, ahp and mce in zimbabwe. different thematic maps such as rainfall, soil type and slope were ovleraid in gis environment. results found that there was a significant posituve correlation between maize yield and classes of land suitability (r2= 0.63-0.85). this method was effective and recommended to use it as a tool for decision making for maize placement in the country. many researches have used the integration of ahp with gis to assess land suitability (mishra et al., 2015; romano et al., 2015; uyan, 2013) manyong et al. (2008) described the benefits of gis techniques in disease and pest control particularly in predicting, monitoring and managing the spread of xanthomonas wilt (bxw) in banana (musa spp.). similarly, a study on the spatial analysis of lettuce downy mildew were conducted in usa (wu et al., 2001). in another application, gis was employed to map the agricultural plastic waste in greece (hiskakis et al., 2007). in oman, the use of gis in agricultural-related applications was recently introduced. to date, several studies were conducted to measure the soil and water qualities using gis. jamrah et al. (2008) evaluated ground-water vulnerability using drastic method in arcgis. drastic stands for seven parameters; d: depth to groundwater, r: net recharge, a: aquifer media, c: hydraulic conductivity of the aquifer, s: soil media, i: impact of vadose zone and t: topography or slope. this study covered the period between 1994 and 2004 for barka, north al-batinah governorate. a number of seven drastic layers were generated and the resulted maps revealed that the northern and central parts of baraka were highly affected by contaminants compared to the southern part (fig. 2). al-barwani and helmi (2006) studied seawater intrusion for the coastal aquifers between as’ seeb and as’ suwaiq cities for the years 1984-2005 (figure 3). using gis, geographical locations of wells and their water salinity (ec) values were created on the map. the ec data were recorded from regular field measurements undertaken by the ministry of regional municipalities and water resources. the salinity zones were delineated for all areas between the two cities. results showed a 7% decrease in land with suitable water for agricultural purposes between 2000 and 2005. also, they reported that seawater intrusion in barka city has moved 12 km inland over the same period. gis techniques have been used also for spatial assessment of water quantity stress across the sultanate of oman (al-awadhi and mansour, 2015). results presented significant variations in water quantity stress across the governorates. also, seasonal variations in water supply and drought severity were the most important predicators for water quantity risk. in another study, behrendt et al. (2015) investigated the distribution and diversity of banana (musa spp.) in wadi tiwi, oman. the spatial distribution of different banana cultivars is depicted in figure 4. al-habsi (2015) studied gis-linked computer simulation model for wheat seed emergence predication in oman. the study showed the best locations for wheat production in oman through linking simulation model with numerical weather predication model (nwpm) in gis environment. the model was used to predict time of emergence based on soil temperature, water potential and planting depth (figure 5). in renewable energy sector, a study was done to investigate the best locations to build large photovoltaic system (pv) using mca (multi-criteria analysis) in gis environment in al-batinah farms, oman (gastli and charabi, 2010). this will be beneficial to exploit the solar energy in oman and implement large pv plants. it can be source of energy inside farms. figure 1. the spatial distribution of water quality index (wqi) in saveh-nobaran aquifer in iran (sadat-noori et al. 2014). 13review article al-maimani, al-ismaili and charabi applications of gis in cea very few studies were reported on the applications of gis in the field of controlled environment agriculture (cea). matsuoka et al. (2015) studied the use of gis and developed monte carlo method to simulate the collection of catch crops (e.g. dent corn) from greenhouses to collection stations in kochi prefecture in japan. the study also estimated the yield production and carbon emissions from the transportation of catch crops. using the results from the above investigations, potential ways to reduce groundwater contamination and conserve agricultural resources were explored. results revealed that the total collected fresh weight of catch crops was 67,900 tons and 70% of production came from central plains of the study area where the cluster of greenhouses was more. gis maps clearly illustrated that eggplant was the dominant crop in the eastern part and cucumber was the dominant crop in the western part (figure 6). the combination of the developed method and gis were easy and multilateral in solving collection and transportation problems. crifasi et al. (2002) reported the use of gis as a data base management system (dbms) for protected cultivations in marsala town, western sicily, italy. the study covered an area of about 3,588 ha having 2,607 greenhouses (figure 7). the distribution of greenhouses and their floor area were recorded. the study emphasised the capability of gis to precisely determine greenhouse sizes and to handle, organise and administer large amounts of data in a quick and simple manner. in oman, there was only one study on the use of gis in cea. deadman et al. (2016) studied the spatio-temporal dynamics of land use changes affected by external pressures and considered greenhouses as an example in northern oman. this study considered gps coordinates of greenhouses for five years; 2001, 2002, 2003, 2004 and 2009. results revealed that greenhouse density was figure 2. drastic values for barka in 2004 (jamrah et al.. 2008). figure 3. salinity zones in as’ seeb (al-barwani and helmi 2006). figure 4. geographical locations of musa spp. in the study area (behrendt et al., 2015). 14 squ journal of agricultural and marine sciences, 2021, volume 26, issue 2 gis and remote sensing techniques in controlled environment agriculture: a review increasing with increasing distance from the coastline (i.e. decreasing groundwater salinity). barka city was the most affected by the increase in groundwater salinity and so, 57.8% of all abandoned farms in al-batinah governorates were in barka (figure 8). new and large farms were developed away from high levels of groundwater salinity and away from urbanised areas. because this study did not cover the whole country, a more comprehensive study is necessary to investigate the factors affecting the spatio-temporal distribution of greenhouses in oman. applications of rs in agriculture remote sensing (rs) is progressively used in a variety of agricultural applications such as soil salinity which is a severe environmental problem particularly in arid and semi-arid regions (sahoo et al., 2015). rs techniques are professional, more informative and faster than traditional methods used in detecting soil salinity (al-mulla, 2010; allbed and kumar, 2013). additionally, they have a capability in delineation, mapping and assessment of this problem. alavipanah and goossens (2001) studied the relationship between soil salinity and data obtained from landsat tm and mss. in another study, allbed et al. (2014) described the use of ikonos satellite imageries to assess the soil salinity using vegetation and soil salinity indices in a region dominated with date palm trees in al-hassa oasis, saudi arabia. three sites were selected within the study area and field measurements were under taken. remotely sensed data were used to extract the soil-adjusted vegetation index (savi) and 12 soil figure 5. a raster map shows the time (days) of emergence at 25 mm planting depth (al-habsi, 2015). figure 6. the cultivated area in proportions with four produced catch crops (matsuoka et al., 2015). figure 7. distribution of greenhouses by area (m2) (crifasi et al., 2002). figure 8. : barka map displays levels of groundwater salinity related to active, abandonment ground cover and urban area (deadman et al., 2016). 15review article al-maimani, al-ismaili and charabi salinity broadband indices. results showed that soils of al-hassa oasis were highly saline (ec >16 ds/m). this salinity level was indicated with a higher spectral response in the visible and nir range compared to the other salinity levels (figure 9). however, other levels of soil salinity differed within the three sites due to human-induced or environmental factors such as: poor quality of irrigation water, unbalanced agricultural practices and poor drainage. the most beneficial indices for assessing soil salinity in areas dominated by date palm were savi, ndsi and si-t that were extracted from the ikonos. a similar study was done using ikonos satellite images and landsat multi spectral scanner (mss) to detect crop reflectance, soil salinity levels and salinity impact on crop yield (elhaddad and garcia 2006). in another study, alhammadi and glenn (2008) studied savi to detect the health of date palms and greenness change of vegetation in the eastern part of united arab emaciates. savi was examined from landsat thematic mapper (tm) and enhanced thematic mapper plus (etm+) images for three different sites: fujairah, hatta and kalba in 1987 and 2000. additionally, field measurements were taken for ground-truthing. results revealed that in hatta, there was a reduction in vegetation greenness and healthy conditions yet the overall agricultural land area increased (fig. 10). salt-affected soils were identified using the savi values which decease with the rise in soil salinity. the study confirmed that a special attention should be given in monitoring and managing soil salinity problem to keep date palm trees productive. rs is also used to detect vegetative covers in forest vegetation using vegetation indices, vi (jinguo and wei, 2004). dawbin and evans (1988) reported some rs techniques for digital crop classification using landsat data for australian environment. for arid and humid regions, rhee et al. (2010) proposed a new drought index called scaled drought condition index (sdci) which is based on temperature data for land surface, normalized difference vegetation index (ndvi) and precipitation data from selected satellites for monitoring agricultural drought. on the other hand, tenkorang and lowenberg-deboer (2008) reviewed the potential of using rs to improve farm profits such as optimizing the use of fertilizers and pesticides. in oman, al-mulla (2010) highlighted the use of rs in mapping soil salinity. he mentioned that salinity is a dynamic process which affected large areas in oman. the vegetation abundance in the vicinity of sultan qaboos university in muscat was studied using rs by rajendran et al. (2016). on the other hand, harris (2003) evaluated agricultural land changes using landsat mss in 1978 and landsat enhanced thematic mapper (etm) data in 2001 (fig. 11). the study was conducted in khaburah and sohar cities on the coastal line of al-batinah. field work was done to support earth observation data for 1979 and 2001. the change in agricultural lands was estimated from environmental change maps that were derived from supervised and unsupervised classifications. the study concluded that the change in agricultural areas was clear and considerable in the study period due to the growing income since 1970, i.e. fast urbanization. applications of rs in the cea in recent years, rapid growth of plastic greenhouses took place and the total land area under plastic greenhouses reached more than 500,000 ha worldwide (agüera and liu, 2009). mapping and detection of greenhouses by means of rs could be a challenging task (aguilar et al., 2014; aguilar et al., 2015; tarantino and figorito, 2012). aguilar et al. (2014) studied the classification of greenhouses in cuevas del almanzora of almeria, spain, using object-based image analysis (obia) for two high resolution stereo images of geoeye-1 (ge1) and worldview-2 (wv2), (figure 12). in the eastern part of almefigure 9. soil spectral reflectance of al-hassa oasis (allbed et al., 2014). 16 squ journal of agricultural and marine sciences, 2021, volume 26, issue 2 gis and remote sensing techniques in controlled environment agriculture: a review ria, spain, another mapping of plastic greenhouses was produced using texture analysis to improve per-pixel classification from other high resolution satellite images which were quickbird and ikonos (figure 13), (agüera et al., 2008). similarly, mapping of plastic covered vineyard using true colour aerial data (very high spatial resolution) was examined in the apulia region (italy) (tarantino and figorito, 2012). the object-based classification method from aforementioned data were developed for testing eight locations in the study area. the overall accuracy of the method used for mapping areas was about 90%. in another study, yang et al. (2017) developed a new spectral index for mapping plastic greenhouses through medium spatial resolution satellite images in china. rs approaches were also utilized to study the spatial and temporal patterns of greenhouses and the factors driving these changes between 2000 and 2015 in shouguang city, china (yu et al., 2017). arcidiacono and porto (2010a) investigated the classification of crop-shelter using rgb aerial images. similar study was done for the classification of crop shelter through processing of digital images in italy (arcidiacono and porto, 2007). aguilar et al. (2015) identified, for the first time, the horticultural crops that were grown under figure 10. false colour composite images (red, layer 4; green, layer 3; and blue, layer 2) for hatta area for 1987 (top) and 2000 (bottom). red colour represents vegetation (alhammadi and glenn, 2008). figure 11. supervised classifications in sohar, (a) landsat mss in 1978 (b) landsat etm in 2000 (harris, 2003). 17review article al-maimani, al-ismaili and charabi plastic greenhouses of almeria in spain. eight images were acquired between may and november 2013 from landsat 8 operational land imager (oli) where obia and decision tree (dt) classifier applied to these images. in addition, a single wv-2 multi-temporal satellite imagery was applied as a data source. both types of images were utilized to derive spectral information, vegetation indices (vi) and textural features which were already being segmented to detect the most popular crops cultivated in greenhouses of the study area (pepper, tomato, aubergine and cucumber). the overall classification accuracy was 81.3% for the whole series of landsat 8 oli imageries. in another study, the accuracy of rs reached 95.9% in mapping greenhouses with landsat tm imagery in qingzhou, china (geng-xing et al., 2004). in oman, the number of greenhouses increased by almost 40% annually between 2001 and 2005 (al-kiyumi, 2009; al-sadi et al., 2007). however, no studies have been done in utilizing rs techniques for identifying and mapping greenhouses or studying the temporal distribution of cea and the external factors affecting such distribution such as groundwater salinity in the sultanate. therefore, a need for such a study is essential to update the status of cea and all relevant aspects. applications of gis and rs in agriculture rs and gis data are widely utilized in mapping and managing natural resources and building environmental models (sajjad et al., 2015). for instance, saleh et al. (2015) evaluated land resources (e.g. soil quality and water availability) for potential agricultural practices using rs and gis techinques in el-galaba basin, eygpt. similarly, another study used rs and gis in the assessment of land cover and soil quality (obade and lal, 2013). shalaby and tateishi (2007) investigated land cover and land use changes in egypt. rs and gis were also used to detect changes of forest cover in tehsil barawal, pakistan for 2000 and 2012 (figure 14) (sajjad et al., 2015). in another study, jha et al. (2007) conducted a review for using rs and gis tools for the development and management of groundwater. jiménez-bello et al. (2012) used rs and gis tools for irrigation management of citrus trees in southwest europe. another study presented the use of landsat method (which combines gis and rs) to estifigure 12. nine classes assigned for all objects based on aerial pnoa (spanish programme of aerial ortho-photography) ortho-image (aguilar et al., 2014). figure 13. study area from two different satellites: quickbird (top) and ikonos (bottom) (agüera et al., 2008). 18 squ journal of agricultural and marine sciences, 2021, volume 26, issue 2 gis and remote sensing techniques in controlled environment agriculture: a review mate the exposure of agricultural pesticides on human health in usa (vopham et al., 2015; ward et al., 2000). in oman, gis and rs techniques have been used to map the temporal changes of soil salinity for 1991 and 2005 in al-rumais area, barka (al-mulla and al-adawi, 2009). in this study, two satellite imageries were re-projected and geo-referenced and thus, soils affected with salinity were identified and classified. results showed a high potential of utilizing gis and rs techniques due to their accuracy, labour saving and cost effectiveness. alrawas and valeo (2011) investigated quality of groundwater and pollution sources in as’ seeb area by means of rs, gis techniques and spatial data analysis. in this study, 335 water samples were collected from the study area. levels of nitrate (no3), acidity (ph) and electrical conductivity (ec) were analysed and compared to the omani standards (moci, 2006) and who standards for drinking water. results revealed that all water wells were unsuitable for drinking (beyond omani standards) because ec values were greater than 4000 ms/cm in farms close to sea because of over pumping (figure 15) yet, ph values were within standards (6.5 – 8). the percentage of samples that exceeded the allowable concentration levels of no3 (>50 mg/l) was 23.28%. these levels were originated from populated areas and near to the drainage system which is affected by landfill location of as’ seeb area. the presence of septic tanks and proximity to the landfill were the two major reasons for the increase of no3. the study is beneficial in providing an overview of the spatial assessment of groundwater quality in as’ seeb city. in another study, gis and rs techniques were utilized to identify the vegetative cover using satellite imageries in dhofar, oman (al-awadhi et al., 2011). three approaches were studied: ndvi, supervised classification and unsupervised classification. results reaveled that large variations in calcuating the total areas of vegeation among the three approaches. yet, ndvi was the best approach compared to other approaches since it was closer to visual comparsions. applications of gis and rs in cea rs satellites have the capability of recording environmental information at a fast rate and economical scale for various purposes. gis can combine these data with other spatial data (e.g. maps) and non-spatial data (e.g. text or tables) to simplify new forms of analyses (ehlers, figure 14. classified images for the two years: 2000 (above) and 2012 (below) (sajjad et al., 2015). figure 15. map of interpolated ec values (ms/cm) (alrawas and valeo, 2012). 19review article al-maimani, al-ismaili and charabi 1996). the integration of gis and rs becomes very helpful (merchant and narumalani, 2009). sönmez and mustafa (2006) conducted a study to generate a new database system for greenhouses using gis and rs techniques of antalya, turkey, as an effort to determine and register the agricultural resources for the european union common agricultural policy (eucap). pan-sharpened ikonos satellite image was used to determine the type of greenhouses (e.g. glass or plastic greenhouses). within gis environment, the database management system (dbms) was created for each greenhouse in the region including position, number, area and type of greenhouses, information about owner, production input and amount of production (figure 16). results concluded that the accuracy of using gis and rs technologies was high (97% for plastic greenhouses and 96.1% for glass greenhouses). also, dbms provided a reliable source for statistical data. both technologies were capable in creating databases which were reliable with european union and other international standards. in another study, gis and rs techniques were utilized to determine the negative environmental effects on air, water cycle and agricultural soil under plastic protected cultivation and also to determine the aesthetic distortion in rural areas along the coast of jonian sea, southern italy (picuno et al., 2011), (figure 17). the analysis was carried on multi-temporal landsat tm images with supervised classification, image processing, gis tools and vectorialization. results revealed a method of auto-detection for the plastic covers used in cea. furthermore, a concept of “threshold” limit of the quantity of plastic covers was suggested. the possible adjustment of colour and texture of the cladding material was also evaluated. similar study was done for the environmental effects of crop-shelter by utilizing landscape indicators, rs imageries and gis analysis (arcidiacono and porto, 2010c). moreover, arcidiacono and porto (2010b) built a model figure 16. an example of dbms for a greenhouse, (sönmez and mustafa, 2006). figure 17. a view of plastic film that covered the agricultural land (picuno et al., 2011). 20 squ journal of agricultural and marine sciences, 2021, volume 26, issue 2 gis and remote sensing techniques in controlled environment agriculture: a review for managing the spatial development of crop-shelter using rs imageries, gis and spatial indicators in italy. in oman, the agricultural census is taking place every 10 years to provide updated statistical data on the agricultural sector components (maf, 2013). although the number of greenhouses keeps on growing at rapid rates, there has been no single study that integrated the use of gis and rs in cea. so, there is a need for similar studies integrating the use of rs and gis in order to acquire a consistent statistical data about cea and all relevant aspects. consequently, such information may help to increase the income of farmers and food security of oman. conclusion in this review, an attempt has been done to highlight the previous inventory work done by scientists and researchers. gis is one of the powerful techniques in capturing, storing, retrieval, displaying and analysing spatial data. it has a capability of mapping, solving problems, planning, managing, and taking decisions and predications. gis was utilized in many studies within agricultural fields. in oman, it has been used only to study the greenhouse distribution and the spatio-temporal dynamics of land use changes affected by external pressures in northern oman. rs is another useful technique utilized progressively in a variety of agricultural applications around the world. regarding the cea in oman, no studies have been done in utilizing rs techniques for identifying and mapping greenhouses or studying the temporal distribution of cea and the external factors affecting such distribution such as groundwater salinity. the integration of gis and rs is very helpful and their data are widely utilised in mapping, managing natural resources and building environmental models. in cea, satellite imageries and gis tools were used for generating dbms, mapping and identifying greenhouses. in oman, there has been no single study that applied the integration of both techniques. so, a need for a similar study is necessary to acquire a consistent statistical data about cea and all relevant aspects. this could probably help increasing the income of farmers and food security of oman. multi-criteria evaluation in gis environment could provide a trade-off analysis for cea land planning with high ecosystem service value. this platform of trade-off analysis for land suitability analysis 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(2017). spatial patterns and driving forces of greenhouse land change in shouguang city, china. sustainability 9(3): 359-374. research paper journal of agricultural and marine sciences vol. 23 : 29 – 39 doi: 10.24200/jams.vol23iss1pp29-39 reveived 15 sep 2015 accepted 30 sep 2017 circle hook versus j-hook: a case study of the sultanate of oman 1 ibrahim a. al-qartoubi,2 shekar bose,3 hussein s. al-masroori, 3 anesh govender 3*al-masroori, hussain ( ) department of marine science and fisheries, college of agricultural and marine sciences, sultan qaboos university, p.o. box 34, postal code 123, sultanate of oman, email: masroori@squ.edu.om. 1ministry of agriculture and fisheries, p.o. box 427, postal code 100, sultanate of oman. 2department of natural resource economics, college of agricultural and marine sciences, sultan qaboos university, p.o. box 34, postal code 123, sultanate of oman. introduction with rising concerns over conservation and sustainable utilization of fishery resources, there is a global impetus to mitigate harmful impacts of fishing gear on the marine environment and to improve harvest efficiency through modifications or the design of new fishing gears, and through technological innovation (glass et al. 2007). following the ‘code of conduct for responsible fisheries’ developed by the food and agriculture organization of the united nations (fao, 1995), bjordal (2002) characterized the ideal fishing gear by using criteria such as high selectivity of target species, relatively low impact on non-target species and habitat, cost efficiency and product quality, amongst others. in this context, research on fishing gear it is evident from the past research that the performance of circle hooks is better than that of j hooks (prince et al. 2002; kerstetter & graves, 2006; pacheco et al. 2011; andraka et al. 2013; huang et al. 2016). for example, a study by prince et al. (2002) evaluated the performance of circle and j hooks with the aid of indicators such as fishing success, hook location, physical damage and trauma on mainly atlantic and pacific sailfish. it was found that in terms of fishing success (fish hooked/ bite), hook location (minimized deep hooking and foul hooking) and physical damage (minimize hook-related bleeding) circle hooks performed better than of j hooks. in a comparative performance evaluation of circle hook اخلطاف الدائري مقابل اخلطاف طويل الساق: دراسة حالة يف سلطنة عمان 1إبراهيم عبداهلل القرطويب و2 شيكار بوز و3 حسني مسح املسروري و3 أنيش جوفندر abstract. improvement of harvesting efficiency and mitigation of undesirable environmental impacts of fishing gears are of considerable importance for achieving long term economic and environmental sustainability in fisheries. this paper analyses the operational efficiency and economic performance of the circle hook and the j-hook, commonly used by traditional fishers in the demersal longline fishery of the sultanate of oman. a longline experiment was conducted at three fishing locations at masirah island of al-sharqiyah governorate. a total of 6,120 baited j-hooks and circle hooks were deployed over a 17-day period. the findings from this experimental research suggest that the overall performance (measured under various operational yardsticks such as hooking status and location, catch composition and quality, catching efficiency, and time and cost efficiency) of the circle hook is better than its counterpart. the results also indicate that the use of circle hooks has the potential to yield better financial returns. it is acknowledged that the reliance on three fishing locations may restrict the scientific generalizations. however, it is hoped that the results from this study will provide insight into the design of future experiments to ensure the validity of the present results and design effective management measures which will promote ecosystem-based approach to fishery management advocated by the fao code of conduct for responsible fisheries. keywords: operational efficiency; economic performance; longline fishery; traditional fishery املســتخلص: إن لتحســن كفــاءة االنتــاج والتخفيــف مــن اآلثــار البيئيــة الضــارة لبعــض معــدات الصيــد أمهيــة كبــرة علــى مصايــد األمســاك لتحقيــق االســتدامة االقتصاديــة والبيئيــة علــى املــدى الطويــل، وقــد مت يف هــذه الدراســة حتليــل الكفــاءة التشــغيلية واألداء االقتصــادي للخطــاف الدائــري واخلطــاف طويــل الســاق الذيــن يشــيع اســتخدامهما مــن قبــل صيــادي األمســاك التقليديــن يف مصايــد األمســاك باخليــوط الطويلــة يف ســلطنة عمــان، حيــث مت إجــراء جتربــة صيــد باخليــوط الطويلــة يف ثاثــة مواقــع لصيــد األمســاك يف جزيــرة مصــرة مبحافظــة الشــرقية مــن خــال رمــي مــا جمموعــه 6120 خطــاف مــن النوعــن ملدة 17 يوًما. أشــارت نتائج هذه الدراســة إىل أن األداء العام )الذي يتم حســابه حســب مقاييس التشــغيل املختلفة مثل مكان الصيد وحالة املصيد، ومكونــات ونوعيتــه املصيــد، وكفــاءة الصيــد، وكفــاءة الوقــت والتكلفــة( للخطــاف الدائــري أفضــل مــن أداء اخلطــاف طويــل الســاق، كمــا أشــارت النتائــج أيًضــا إىل أن اســتخدام اخلطافــات الدائريــة ميكــن ان حيقــق عوائــد ماليــة أفضــل، مــع التأكيــد علــى أن االعتمــاد علــى مواقــع صيــد األمســاك الثاثــة قــد يقيــد تعميــم النتائــج العلميــة، ومــع ذلــك فإنــه مــن املأمــول أن توفــر نتائــج هــذه الدراســة إســتبصار يف تصميــم التجــارب املســتقبلية لضمــان صحــة النتائــج احلاليــة وتصميــم تدابــر اإلدارة الفعالــة الــي ســتعزز النهــج القائــم علــى النظــام اإليكولوجــي إلدارة مصايــد األمســاك الــذي تدعــو إليــه مدونــة الســلوك ملنظمــة األغذيــة والزراعــة للصيــد الرشــيد. الكلمات املفتاحية: الكفاءة التشغيلية، األداء االقتصادي، مصايد اخليوط الطويلة، املصايد التقليدية 30 squ journal of agricultural and marine sciences, 2018, volume 23, issue 1 circle hook versus j-hook: a case study of the sultanate of oman and j hook using performance indicators such as catch composition, catch rates, hooking location, and status at release in a commercial atlantic ocean pelagic longline fishery. pacheco et al. (2011) suggested that the use of circle hooks, in comparison with j hooks, has the potential to reduce fishing mortality of by catch species with minimal effects on the target species catch. in analyzing the performance of circle hooks in relation to j hooks and tune hooks based on the hooking rates of target and non-target species in the artisanal longline fisheries of ecuador, panama, and costa rica, andraka et al. (2013) noted that sea turtle hooking rates were lower in case of circle hooks. based on a review of recent research huang et al. (2016) pointed out a potential conservation value as the shape of circle hooks contributes to the minimization of foul-hooking and injury to both fishes and bycatch species. in a study on the u.s. atlantic coastal pelagic longline fishery that involves target (tuna and swordfish) and non-target species (billfish and sea turtles) kerstetter & graves (2006) noted that the use of circle hooks not only improved the survival of the non-target species but also had minimum effects on the catches of target species. the present paper evaluated this hypothesis for the case of a traditional small-scale fishery using hook status, catch composition and quality, hooking location, time and cost efficiency as performance indicators. it also extended this hypothesis by adding an economic indicator (i.e., gross economic benefits) and hypothesize that the use of circle hooks has the potential to yield better financial returns to fishers compared to j hooks. considering this significance of research on fishing gear and designs, the main objective of this study is to analyse the operational efficiency, and economic performance of the j-hook and the circle hook used in the demersal longline fishery of oman. in the context of oman, there is a dearth of research on this subject matter and the basic information on such fishing practices is limited. therefore, an appraisal of various aspects of operational efficiency of the selected fishing gear should provide vital information to the process of recommending environmentally friendly fishing gear, enhancing fishing efficiency through refinements, improving catch quality, and making informed management decisions for effective management of fisheries resources. longline fishing and related elements fisheries is an integral part of the traditional way of life in oman and the traditional sector that refers to groups of small-scale fishermen employing a variety of traditional fishing gear and vessels (al-masroori et al. 2004) has been the dominant both in terms of total landings and value (about 86% in 1985-2013). in addition, the traditional sector provides direct employment (both full and part-time) of 44,521 fishermen (maf, 2013). in oman, longline fishing has been divided into two categories namely, traditional and industrial longlining. the industrial fishing by pelagic longliners began in oman in 1989 and is mainly used to catch tuna and swordfish. these are steel vessels that can range in length from 40 to 60 m, and they fish in the high seas at distances of more than 20 nautical miles offshore. as part of the traditional category, demersal longlining (locally termed as alshakah) is practiced by traditional fishers (maf 2002) and the subsequent catch typically comprises of grouper (epinephelus sp., cephalopholis sp.), emperor (lethrinus sp.), snapper (lutjanus sp.), thicklip (plectorhinchus sp.), and sea bream (argyrops sp., acanthopagrus sp.), amongst other species. the demersal longline consists of a mainline, branchlines and hooks in between two floats. the mainline is usually several hundred metres in length, with a diameter commonly ranging from 0.5  cm to 1  cm and is made of various types of multifilament (cotton, nylon, polyester or polypropylene) and monofilament (polyamide, nylon) materials. the most common hooks used in omani demersal longline fisheries are the j-hook and the circle hook. however, it is noted that the circle hook has gained popularity despite a comparatively higher cost (2-3 times higher) associated with its use1 . this popularity of circle hook could be due to a higher catch rate and better catch quality experienced by fishers compare to the traditional j-hook (stengel and al-harthy, 2001). the demersal longline fishing is mostly carried out with the use of fiberglass reinforced plastic (frp)-fishing boats. fishers use mackerel, sardine, cuttlefish and squid as bait which may be fresh, frozen or salted. the hook is central to longline fishing which consists of a shank, bend, point, barb and an eye (or ring) for attaching it to the branch line. the hook performs two functions: catching the fish and retaining it until it is safely landed on board the boat. the catching efficiency of a longline is defined as the proportion of target or commercial fish that are caught per unit number of baited hooks set. the daily catch (c) of a longline is therefore defined by the number of hooks that are set and hauled per day and can be expressed by the following equation (bjordal & lokkeborg 1996): eq (1) where, n=number of hooks set and hauled per day, a1= proportion of hooks leaving the vessel with bait on, a2= proportion of hooks with bait loss caused by sea birds, a3=proportion of hooks with bait loss due to seabed scavengers, a4=proportion of hooks with bait loss due to small fish or non-target species that eat the bait without being hooked, a5=catching (hooking and retention) probability of target fish, and w=average weight of target fish. 1a box of 100 mustad size 6 common longline j-hook, costs approximately omr 3 (depending on the number and location of purchase) while the same quantity of equivalent sized number 6/0 circle hooks might cost from omr 6 to 9 (1 rial =us $ 2.58). 31research article al-qartoubi, bose, al-masroori, govender various factors influence the catching efficiency namely, hook spacing and density of target species (bjordal & lokkeborg 1996; skud & hamley 1978), bait type, quality and size (bach et al. 2000; johannessen et al. 1993), hook design (radcliffe 2005), size of the hook, which is measured by gap width, shank length and wire dimension (garry et al. 1999; bjordal and lokkeborg 1996), material of the hook (iron, stainless steel), shape of the point, hook finish (colour and coating), and environmental factors such as tide, current, light, moon phase and the nature of the sea bed (ices 1977). martian and mccracken (1954) found that bait size had a significant effect on catching efficiency, and longline experiments have demonstrated very different rates of effectiveness of squid, mackerel and herring for catching demersal fish. halliday and kenchington (1993) concluded that since the power of attraction is directly related to the size of the bait, it is important in selectivity studies to use a standard bait size. the wide gap hook with a very fine turned in point may be more successful in penetrating the inner mouth parts than a more conventional hook. research done by skud (1978), lokkeborg and bjordal (1992) and bjordal and lokkeborg (1996) found that smaller hooks give higher catch rates than larger hooks. in comparison with other frequently used fishing gear, the popularity of demersal longlining as mentioned in the literature, was due to economic efficiency labelled as lower cost per unit effort (cai et al. 2005), catching effectiveness (he et al. 1997), delivery of better quality products (lokkeborg & bjordal 1992), less fuel consumption (bjordal 1988), good species selective properties through the selection of hook type, bait type and fishing depth and ground (clarke et al. 2002), and little or no destructive impact on bottom habitats (hareide 1995). materials and methods a longline fishing experiment was carried out at ra’s abu rasas, south of masirah island (see figure 1 for study location) from 2-23 december, 2004. the fishing ground ra’s abu rasas, was chosen for the experiment on the basis of familiarity gained by the first author through previous fishing experience, and access to local fishermen knowledge about the fishing ground which is essential for a successful deployment of the gear. other variables such as depth, distance between locations, and proximity were also considered in selection. the experiments were conducted on-board a small frp (fibre reinforced plastic) fishing boat, measuring 9 m long × 2.5 m wide × 0.8 m draft, propelled by two 60 hp outboard mariner engines. on-board fish finder and global positioning system (gps) were used to decide on the fishing locations within ra’s abu rasas for deployment of the fishing gear. three locations (1, 2 and 3), 2 to 4 nautical miles (nm) apart from each other, were selected with average depths of 50, 22 and 10 m respectively (figure 1). the the seabed was characterised by patches of rocks, sand and coral (stengel and al-harthy, 2001). given their close proximity and similar seabed characteristics, it was assumed that the three locations were similar with respect to fish abundance. each location was given a number from one to three and a location was randomly selected every day. for all three locations the same fishing gear was engaged throughout the study period. a total of six demersal longlines were used daily in the experiment. each longline consisted of a 124 m polyester (pes) multifilament main line with a diameter of 0.4 cm. sixty monofilament branch lines were connected to each mainline via a number 2/0 swivel to prevent the fish rotating and tangling the branch line and the mainline. the length of each branch line was 80 cm with a 0.1 cm diameter. each branch line was attached to the mainline 2 m apart and hence, hook spacing was also 2 m. at the end of each branch line there was either a circle hook or a j-hook, thus a total of 60 hooks per basket were used in the experiment. the features of the hooks used in the experiment are as follows: the j-hook size no. 6 (mustad, ref: 2335dt, key brand, made in norway) and the circle hook size no. 6/0 (mustu hooks, maruto fish hook works, quality no. 350, superior steel, eagle wave brand, made in japan). these types of hooks are commonly used by the traditional fishers to catch demersal n arabian sea sea of oman 26 e 24 e 22 e 20 e 18 e 58 e52 e 60 e56 e54 e sultanate of oman masirah island figure 1. map of sultanate of oman including with the sampling (masirah island) (source: mne. 2004). 32 squ journal of agricultural and marine sciences, 2018, volume 23, issue 1 circle hook versus j-hook: a case study of the sultanate of oman species in oman. the j-hook was 5.3 cm in length with a 1.9 cm wide gap and the circle hook was 3.5 cm in length with a 1.4 cm wide gap. a 25 m polyethylene (pe) buoy line with a diameter of 0.8 cm was used. around 3 kg of weight was used as a sinker at each end of the main line. a total of 3,060 j-hooks and 3,060 circle hooks were deployed over 17 days. each morning, 180 j-hooks and 180 circle hooks were deployed from six baskets in the selected location. across all three fishing locations an equal number of circle and j-hooks were randomly deployed each day. over the duration of the study 41.2% of the total number of hooks was deployed at location 1 and 29.4% were deployed at each of locations 2 and 3. each of the six baskets was given a number from one to six along with hook types for ease of identification. each day of the experiment, the basket was selected in a random manner to avoid hook-selection bias. frozen cuttlefish (sepia spp.) was used as bait weighing about 10g. each evening the hooks were baited for the following day’s fishing experiment, and the baited longline was then refrigerated overnight. the longline set was deployed and hauled by hand in the direction of the prevailing tides. it was assumed that the bait-plume from one longline would not influence the attractiveness of any adjacent longline within the same fishing location. the experiments were usually conducted between 07:25 am and 12:00 noon, which is the normal operation time for coastal fishing boats at masirah island. the demersal longlines were set in the morning and the soak times for all experiments were two hours (a typical soak time for the coastal boats in omani waters). when a longline was hauled, each caught fish was recorded in terms of weight (kg), total length (cm), species (common and scientific name) and hook location. information on hook status (e.g. hooks missing, damaged), gear condition (e.g. main line and branch line loss or damaged) and bait condition (loss, return) was also recorded for each set. hooking locations were designated using the following terminology: corner of the mouth, jaw (upper and lower), gill, gut, eye and body. additional information was also recorded such as fishing location (longitude, latitude, depth, and bottom characteristic), weather conditions, and operation time (deployment and hauling time). experimental data gathered from the three locations were analysed for individual location and for all location as a group. total catches were standardized to daily catch per unit of effort (cpue), defined as the number of fish caught per 100 hooks retrieved (no. of fish/100 hooks retrieved). appropriate test statistics (i.e. χ2 test, f-test, tukey’s post hoc test) and analytical methods (i.e., ancova) were used to examine various relevant hypotheses using the spss software. considering the catch composition and species current market status, only for commercial species and dominant family category cases were statisticaly results this section provides both location-specific and combined analytical results where relevant with particular reference to yardsticks used namely hook status, catch composition, hooking location, catch efficiency for total, commercial and dominant family species, gross financial returns from commercial species catch, and time efficiency. hook status: retrieval and loss of the total number of hooks deployed, approximately 10% of the gear involving both hook types was lost. about 5% of the total loss was assigned to missing sections of the mainline, while 24% was due to broken branch lines and the remainder was due to missing hooks. due to gear loss or damage, 90% of the circle hooks and 89% of the j-hooks were retrieved. a significant difference in hook status by hook types is noted (χ2=123.698, df =2, p<0.001), with more circle hooks retrieved with fish and less circle hooks with bait attached. figure 2 depicts the hook retrievals by hook types with fish, bait, and without fish and bait. the proportion of hook status was comparatively higher for empty category for both hook types (fig. 2). in addition, statistical differences in the proportion of hooks with regard to hook status (i.e. empty, bait only, or fish) was detected among fishing locations (χ2=502.376, df 4, p<0.001). the proportion of retrieved hooks with bait attached was more for both hook types in location 2 and the proportion of empty hooks was less for both hook types at the same location. the highest proportion of retrieved circle hooks with fish attached (14.8%) was recorded in location 3. it is noted that hook losses figure 2. hook status by hook type. hook status describes a retrieved hook either with fish (commercial and non-commercial) attached, only bait attached or empty (bait removed). the arrows indicate the outcome of chisquare analysis of hook status where the observed number of hook was less (down arrow) or more (up arrow) than expected. 33research article al-qartoubi, bose, al-masroori, govender were similar among the three fishing locations and no significant difference was observed between locations (χ2=4.363, df 4, p=0.359). catch composition there were total of 18 (14 commercial and 4 non-commercial) species in the observed catch consisting of 11 families (7 commercial and 4 non-commercial) (table 1). circle hooks caught 9 families whereas the j-hook caught all 11 families. catches with both types of hooks were dominated by family lethrinidiae and three species namely, lethrinus microdon, lethrinus nebulosus and lethrinus lentjan. these 3 species together accounted for 53% and 62% of the total commercial catch by weight and number respectively. catches of both hook types were dominated by lethrinus microdon, which accounted for 38% and 48% of the total catch by weight and number respectively. hooking location of the total catch of commercial and non-commercial fish by both hook types, 65% of the fish were hooked in the corner of the mouth, 19% were hooked in the jaw, 11% were hooked in the gill, and 5% were hooked in the gut (fig. 3). there was a significant difference in hooking location for the total catch between hook types (χ2 = 291.338, df =3, p<0.001). approximately 90% of the total catch caught by the circle hook was hooked in the corner of the mouth and 21% were hooked in the similar position by j-hooks. the proportion of fish hooked in the jaw table 1. catch composition by hook type. s.no family name scientific name common name fish number commercial species j-hook circle hook 1 arridae arius bilineatus roundsnot sea catfish 3 0 2 haemulidae plectorhinchus pictus trout thicklip 13 22 3 haemulidae plectorhinchus gibbosus dusky thicklip 1 5 4 hemigaleidae paragaleus sp. arabian weasel shark 44 4 5 lethrinidae lethrinus microdon spangled emperor 68 188 6 lethrinidae lethrinus nebulosus smalltooth emperor 16 23 7 lethrinidae lethrinus lentjan redspot emperor 26 38 8 lutjanidae lutjanus coeruleolineatus bluelined snapper 0 13 9 lutjanidae lutjanus russelli russell’s snapper 1 3 10 serranidae epinephelus stoliczkae epaulet grouper 8 8 11 serranidae epinephelus areolatus areolate grouper 1 8 12 serranidae epinephelus diacanthus spinycheek grouper 0 1 13 sparidae argyrops spinifer king soldier bream 13 30 14 sparidae rhabdosargus sarba gold striped seabream 1 0 non-commercial species 1 balistdae sufflamen frarnatus bridled triggerfish 7 9 2 diodontidae diodon hystrix porcupine fish 2 2 3 muraenidae siderea flavocula palenose moray 6 14 4 stegostomatidae stegostoma varium zebra shark 3 0 figure 3. the observed number of fish caught in each hooking location by hook type. the arrows indicate the outcome of chi-square analysis where the observed number of fish was less (down arrow) or more (up arrow) than expected. 34 squ journal of agricultural and marine sciences, 2018, volume 23, issue 1 circle hook versus j-hook: a case study of the sultanate of oman and gill using the j-hook was 38% and 29% respectively. there was a significant difference (χ2=15.708, df=6, p<0.015) in hooking location for the total catch with respect to fishing location, with a greater number of fish being hooked in the gill by both hook types at location 1 and a greater than expected number being hooked in the jaw at location 2. with respect to commercial species, there was a significant difference (χ2=248.49, df =3, p<0.001) in the hooking location by hook type but no significant difference was found (χ2=12.05, df=6, p<0.061) in hooking location with fishing locations. with respect to the dominant family (lethrinidae), there was a significant difference in hooking location by hook types (χ2=153.896, df =3, p<0.001), with a greater number of catch being hooked in the corner of the mouth by the circle hook and a greater than expected number being hooked in the gut by the j-hook. over 97% of the total catch of lethrinidae by the circle hook was hooked in the corner of the mouth, but only 29% were hooked in this same position by the j-hook. of the total catches of lethrinidae by both hook types, around 71% were hooked in the corner of the mouth, 11% were hooked in the jaw, 13% were hooked in the gill and less than 5% were hooked in the gut. a significant difference (χ2=16.318, df=6, p<0.012) was also found in hooking location for the lethrinidae catch by fishing location. in relation to the dominant species (lethrinus microdon), a significant difference (χ2=89.807, df= 3, p<0.001) was noted in the hooking location for lethrinus microdon by hook type but the same does not hold for fishing location (χ2=9.54, df 6, p<0.145). catching efficiency total catch the average catching efficiency (± standard error) measured by equation (1) for the circle hook and the j-hook was 17.1±2.0 kg and 16.7±3.0 kg per 100 hooks retrieved, respectively. there was no significant difference in the mean catching efficiency of the total catch between hook type ( anova: f value = 0.001, df=1, 96, p<0.976). also, the difference in mean catching efficiency between hook type and location was not significant (anova: f(hook type*locations)=0.002, df=2, 96 p<0.998). however, there was a significant difference in the mean catching efficiency for the total catch between the three fishing locations (anova: f = 4.367, df=2, 96, p<0.015). furthermore, the tukey’s hsd showed that this difference was significant between locations 1 and 2 (p<0.013). a total of 581 fish were caught by the j-hook and circle hook with a combined total weight of 924.3 kg. the circle hook caught 50.7% of the total catch weight and 63% of the total catch number (table 2). there was a significant difference in the total catch weight by hook type (ancova: f = 16.312, df =1, 574, p<0.001). the average catch per day was not affected by the difference in fishing days among the locations (ancova: f = 0.181, df 1, 574, p = 0.670) and the difference in average catch per day between hook type and location was not significant (ancova: f(hook type*location) = 0.278, df =2, 574 p <0.757). there was no significant difference (ancova: f = 0.694, df =2, 574, p<0.500) in the total catch mean weight by fishing locations. there was a significant difference in length frequency distribution of the total catch between the two hook types (χ2= 67.229, df =4, p<0.001), with fish > 60 cm more likely to be caught using the j-hook than the circle hook and the circle hook more likely to have caught more small fish. there was also a significant difference (χ2 = 32.240, df =8, p<0.001) in length frequency distributions for the total catch among the fishing locations, with more small fish (<31 cm) caught by both hook types at location 1 and more than expected large fish (>91 cm) caught at location 2. commercial catch there was no significant difference in the mean catching efficiency of total commercial catch by hook type (anova: f = 0.001, df=1, 96, p<0.975). also, the difference in mean catching efficiency between hook type and location was not significant (anova: f (hook type*locations) = 0.004, df=2, 96, p<0.996). however, there was a significant difference in the mean catching efficiency for the total commercial catch between the three fishing locations (anova: f = 8.004, df=2, 96, p<0.001). furthermore, the tukey’s post hoc test showed that this difference was significant between locations 1 and 2 (p <0.001) and location 1 and 3 (p<0.007). however, there were no significant differences noted in mean catch between location 2 and 3. the commercial catch comprised 88% by weight and 92.6% by number of the total catch. there was a significant difference in catch weight by hook type (ancova: f = 8.800, df=1, 531, p<0.003). the circle hook caught 94.7% by weight and 93.2% by number of the total combined catch (commercial and non-commercial). the difference in the number of fishing days among the locatable 2. total combined catch weight and number (+/se) at each fishing location by hook type. location hook type number of fish weight (kg) weight (%) average weight se 1 j-hook 93 184.4 40.5 2.0 0.35 circle hook 157 181.5 38.7 1.2 0.08 2 j-hook 46 97.9 21.5 2.1 0.17 circle hook 93 134.4 28.7 1.4 0.13 3 j-hook 74 173.4 38.1 2.3 0.52 circle hook 118 152.6 32.6 1.3 0.09 total j-hook 213 455.7 100.0 2.1 0.23 circle hook 368 468.5 100.0 1.3 0.10 35research article al-qartoubi, bose, al-masroori, govender tions did not affect the average catch per day (ancova: f = 1.644, df =1, 531, p<0.200). the difference in average total commercial catch per day between the two hook types was the same at all locations (ancova: f (hook type*location) = 2.395, df =2, 531, p<0.092). there was no significant difference (ancova: f=2.646, df =1, 531, p <0.072) in the total commercial catch weight by fishing locations. the circle hook caught 54.5% by weight and 63.8% by number, of the total combined commercial catch. in all three fishing locations and for both hook types, 60% of the commercial catch measured between 31 60 cm, 26% were < 31 cm and 14% were > 60 cm (figure 4). between hook types the length frequency distributions of the commercial catch were significantly different (χ2 =70.880, df =4, p<0.001). circle hooks caught more than expected fish in the 31-60 cm size class. fish larger than 60 cm were more likely to be caught using the j-hook than the circle hook and the circle hook caught more of the smaller fish. dominant family (lethrinidae) there was no significant difference (anova: f = 0.001, df =1, 96, p<0.982) in the catching efficiency of the lethrinidae by hook type. also, the difference in average catching efficiency between hook type and location was not significant (anova: f (hook type*locations) = 0.001, df= 2, 96, p<0.999). in addition, there was no significant difference in catching efficiency of the lethrinidae catch among the three fishing locations (anova: f = 2.366, df =2, 96, p<0099). there was a significant difference in the average total catch weight of lethrinidae by hook type (ancova: f = 12.931, df= 1, 352, p<0.001). the circle hooks caught on average 36.3% by weight and 46.3% by number of the total combined catch. the lethrinidae catch accounted for 59.6% by weight and 66.7% by number of the total combined catch (commercial and non-commercial). in all three locations and for both hook types, 63% of the total lethrinidae catch were in the range of 31 60 cm, table 3. average price, catch weight, and gross value of species caught using j-hook and circle hook at different locations. ave. price locaton 1 location 2 location 3 total species j-hook circle hook j-hook circle hook j-hook circle hook j-hook circle hook omr wt. (kg) value (r.o) wt. (kg) value (r.o) wt. (kg) value (r.o) wt. (kg) value (r.o) wt. (kg) value (r.o) wt. (kg) value (r.o) wt. (kg) value (r.o) wt. (kg) value (r.o) l. microdon 0.49 55.2 27.0 71.0 34.8 34.5 16.9 68.2 33.4 16.7 8.2 61.3 30.0 106.4 52.1 200.5 98.2 l. nebulosus 0.49 27.5 13.5 16.7 8.2 18.5 9.1 24.0 11.8 6.5 3.2 22.7 11.1 52.5 25.7 63.4 31.1 p. pictus 0.55 9.0 5.0 22.0 12.1 19.0 10.5 13.1 7.2 8.5 4.7 20.2 11.1 36.5 20.1 55.3 30.4 a. spinifer 0.50 11.5 5.8 14.8 7.4 10.5 5.3 18.0 9.0 7.5 3.8 19.7 9.9 29.5 14.8 52.5 26.3 l. lentjan 0.49 21.3 10.4 22.8 11.1 0.0 0.0 1.6 0.8 10.0 4.9 7.2 3.5 31.3 15.3 31.5 15.4 p. gibbosus 0.55 0.0 0.0 6.0 3.3 3.5 1.9 0.0 0.0 0.0 0.0 8.0 4.4 3.5 1.9 14.0 7.7 a. bilineatus 0.13 4.5 0.6 0.0 0.0 0.0 0.0 0.0 0.0 7.5 1.0 0.0 0.0 12.0 1.6 0.0 0.0 e. stoliczkae 0.59 1.5 0.9 1.1 0.6 0.7 0.4 0.2 0.1 1.3 0.8 2.4 1.4 3.5 2.1 3.7 2.2 e. areolatus 0.59 0.5 0.3 6.1 3.6 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.5 0.3 6.1 3.6 l.coeruleolineatus 0.67 0.0 0.0 2.5 1.7 0.0 0.0 2.0 1.3 0.0 0.0 2.0 1.3 0.0 0.0 6.5 4.4 r. sarba 0.50 1.0 0.5 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.0 0.5 0.0 0.0 l. russelli 0.67 0.0 0.0 0.0 0.0 0.0 0.0 0.1 0.1 0.3 0.2 0.2 0.1 0.3 0.2 0.3 0.2 e. diacanthus 0.59 0.0 0.0 0.2 0.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.2 0.1 total 132.0 64.0 163.2 82.9 86.7 44.0 127.2 63.7 58.3 26.8 143.7 72.8 277.0 134.6 434.0 219.6 price per kg 0.48 0.51 0.51 0.50 0.46 0.51 0.49 0.51 figure 4. length frequency of the commercial catch by hook type. the arrows indicate length frequency where the observed numbers were less (down arrow) or more (up arrow) than expected. 36 squ journal of agricultural and marine sciences, 2018, volume 23, issue 1 circle hook versus j-hook: a case study of the sultanate of oman 30% were < 31 cm, and only 7% were > 61 cm in length. between the hook types the length frequency distribution of lethrinidae was significantly different (χ2= 22.783, df =2, p<0.001), with fewer small fish (< 31 cm) caught by the j-hook and the circle hook caught more than expected lethrinidae 31-60 cm. with respect to lethrinidae larger than 61 cm, both hook types caught similar numbers. gross financial benefits from the commercial catch the total catch value of the commercial catch (excluding the protected (shark)paragaleus sp. (ducrocq 2004)) from both hook types was omr 354 or 0.500 omr/kg (1 omani rial (omr) = us $2.58, see table 3 for details) and the share of the circle hooks is about 62% which is significantly different from the j-hooks (χ2=7.501, df =2, p<0.024). the total catch value of lethrinidae from both hook types was omr 237.9 or 0.49 omr/kg. by hook type the value of the catch of lethrinidae was significantly different at all three locations (χ2=8.032, df 2, p<0.018). at locations 2 and 3 the catch value for the circle hook was greater than that of the j-hook. the total value of the catch taken by the circle hook was 61%, however on a value per kg basis there was little difference between hook types. lethrinus microdon was by far the most dominant commercially valuable species caught by both hook types with a total catch value of omr 135.4 (table 3). there was no significant difference across all three locations in the catch value of lethrinus microdon by hook type (χ2 = 5.186, df =1, p<0.075). the total catch of lethrinus microdon from the circle hook accounted for 65% of the total catch value of this species. by location, the total catch value of this species, caught by the circle hook, was higher at all three locations. time efficiency in relation to ‘setting times’ no significant difference was found in the time for either hook type (anova: f = 0.397, df =1, 32, p<0.533) or between fishing locations (anova: f = 0.629, df =2, 48, p<0.537). for both hook types at each location, the average setting time (± standard error) was 6.8 ± 0.2 minutes. there was no significant difference in the time required to haul a longline of either hook type (anova: f = 2.269, df =1, 32, p<0.141) or between fishing locations (anova: f = 0.632, df =2, 48, p<0.536). for both hook types at each location the average hauling time (± standard error) was 14.3 ± 0.4 minutes. discussion the results suggest that circle hook performs better than its counterpart in relation to various yardsticks. while the locational difference noted with regard to hook status, the overall finding from this study is in favour of circle hook as more circle hooks retrieved with fish. this is consistent with the results obtained by willey et al. (2016). willey et al. (2016) found that circle hooks performed better than j hooks with regard to both hooking and capture rate. the economic implication of this finding is that circle hook has the potential to fishing success involving commercial species as indicated by the results of catch composition which can improve returns from fishing operations, other things being equal. the proportion of retrieved j-hooks with bait attached was almost double the proportion of circle hooks with bait. this, perhaps, suggests that the baited j-hook may have been less attractive to fish because the shank of the hook is longer and more exposed. there was no indication of bait loss to seabirds, turtles or sea mammals. it is possible that small fish or crustaceans could have eaten the bait without being hooked. also, this could be a result of the lack of experience of the crews in correctly baiting circle hooks, which may have resulted in poorer bait retention on the hook. during the experiment both hook types were lost on occasion because of missing mainline section, missing branch lines, or missing hooks only. compared to the j-hook, the circle hook had a relatively low proportion of gear loss which has direct bearing on the cost of fishing. one of the reasons for losing branch lines and hooks might relate to the characteristics of fishing locations, which are characterised by patchy regions of coral reefs and rocks. in contrast to the circle hook, the j-hook has an exposed point which may increase its potential for fouling on rocks and coral. the other reason might be related to sea conditions, which were unpredictable and fluctuated between calm and rough and thus resulted in high current tension on the gear. although this study was conducted after the monsoon season, generally regarded as a good fishing season, the numbers of commercial and non-commercial fish caught by both hook types at all three fishing locations were relatively lower than that from normal commercial fishing operations. the reasons for this low catch rate could be related to several factors including environmental factors (e.g. wind, current, temperature and depth), biological factors (e.g. species diversity, fish habitat preference), engineering factors (e.g. fishing gear constructions), and human factors (e.g. skill and experience of the skipper and crew) (bjordal & lokkeborg 1996). with regard to the total catch, where the commercial catch is significantly higher than the non-commercial catch, the effectiveness of the circle hook is significantly higher than the j-hook. the implication of this finding is that in the absence of any limit on output (that is, total allowable catch) in the fishery and given equal soak time for both hook types, the circle hooks are financially more desirable to fishers than j-hooks. this is, perhaps, one of the main reasons of circle hook increased popularity among traditional fishers in recent years. 37research article al-qartoubi, bose, al-masroori, govender the significant difference in hooking location indicates that circle hooks cause less hooking damage than the j-hooks because a majority (98%) of the fish caught by the circle hook were hooked in the corner of the mouth and jaw. findings from other studies (for instance, see (grover et al. 2002, lukacovic & uphoff 2002, skomal et al. 2002). there are a number of claims in support of circle hooks with particular reference to hooking status, injuries (cooke & suski 2004) and mortality (muoneke & childress 1994). the circle hook increases survival because circle hooks predominantly catch in the jaw, whereas the j-hook catches more fish in the gut (trumble et al. 2002). for example, in a study on red drum by thomas et al. (1997), it was found that the hooking mortality rate for the circle hook was 3% and for the j-hook was 7%. in investigating the capture efficiency and injury rate of walleyes circle jones (2011) found that the strike-specific injury rate of circle hooks (0.12 injuries/ strike) was significantly lower than that of j hooks (0.27 injuries/strike). in assessing the role of circle hooks in conservation and fisheries management based on case studies and literature review cooke & suski (2004) observed that the incidence of hooking mortality was considerable lower for circle hooks than j hooks. in a quantitative review of literature with particular reference to commercial and recreational hook-and-line fisheries serafy et al.(2009) noted that higher rates of mortality, deep hooking and bleeding were associated with j-hooks relative to circle hooks. because of relatively minimum injuries and less mortality rates (including incidence of bleeding and ease of hook removal) associated with circle hooks, the use of circle hooks was promoted as a potential conservation tool for both target and non-target species (cooke et al. 2003; kerstetter & graves, 2006; andraka et al. 2013; huang et al. 2016) the economic implication is that fish caught with less physical damage by the circle hook remain fresh and are more likely to command a better market price (hareide 1995) and hence better financial returns for traditional fishers. kerstetter & graves (2006) argued that by reducing the catch of non-target and bycatch species the use of circle hook may also increase time efficiency by saving crew time and hence vessel operation costs. the management implication of this result is that the use of circle hooks may be encouraged by the management authority through a regulatory measure for conservation of fisheries resources that involve both target and non-target species. andraka et al. (2016) mentioned that circle hooks have been proposed in nine eastern pacific ocean countries as a way to mitigate the problem of sea turtles by-catch. the present study involves only three locations, and replication of this experiment is recommended to ensure the validity of the results and thus make effective management decisions. the catching efficiency of the total catch (commercial and non-commercial) for both hook types was 16.9 kg per 100 hooks retrieved and the difference in catching efficiency between the circle hook (17.1 kg/100 hooks retrieved) and the j-hook (16.7 kg/100 hooks retrieved) was not statistically significant. these figures are considerably higher than those reported by pajot & weerasooriya (1980) in sri lanka (4.6 kg per 100 hooks) and by kihedu et al. (2001) in tanzania (5.8 kg per 100 hooks). the total catch (commercial and non-commercial) weight for circle hook was relatively higher than that of the j-hook. although no significant difference methods found in total catch number among the two hook types, the same is not true for the total catch weight. this implies that, other things being equal, the higher catch weight offers higher revenue for fishers. with regard to the total catch value of the commercial catch the circle hook performed better than the j-hook. the average unit (kg) price was also higher for the catch of the circle hook because more highly valued species where caught with this hook and fish were less damaged thus circle hook has the potential of generating higher financial benefits to fishers. a comparative study by özgül et al. (2015) on circle hook (kahle hook) and j-hook baited with sardine in the pelagic longline fishery of turkey, it was found that the overall catch-per-unit-effort (cpue) for all fishes involving circle hook was about two-times higher than that of j-hook. conclusion this paper examines the performances of the circle hook and the j-hook generally used by the traditional omani fishers for demersal longline fishing. the results from this experimental research suggest that the overall performance – measured with various operational yardsticks (i.e. hooking status and location, catch composition and quality, catching efficiency, and time and cost efficiency) of the circle hook surpasses that of its counterpart. the results also indicate that the use of circle hook has the potential to yield better financial returns which is in harmony with one of the strategic goals -‘to increase traditional fishers’ income’of the sector as stipulated in the 7th five-year plan (mne, 2007). it is acknowledged that reliance only three fishing locations may restrict the scientific generalizations. replication of this experimentation may help ensure the validity of the results and thus make effective management decisions. also, there is a need to gather more evidence through further trial by varying the parameters of interest such as hook size and shape, bait type and size, water columns, location, and season to evaluate the efficiency and selectivity of longline gear. at the same time, here is an opportunity to involve local fishers in such research activities which has the potential to play an important role in generating community awareness about the possible benefits of this type of research and in fostering community responsibility. 38 squ journal of agricultural and marine sciences, 2018, volume 23, issue 1 circle hook versus j-hook: a case study of the sultanate of oman references al-masroori h, al-oufi h, mcilwain jl, mclean e. 2004. catches of lost fish traps (ghost fishing) from 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unpublished report. thomas rg, boudreaux c, lightner j, lear e, hebert v. 1997. hook release mortality of red drum and spotted sea trout. abstract in the 1997, southern division american fisheries society midyear meeing, san antonio, tx. trumble rj, kaimmer sm, williams gh. 2002. a review of the methods used to estimate, reduce, and manage bycatch mortality of pacific halibut in the commercial longline ground fish fisheries of the northeast pacific, in: lucy ja, studholme al, editor. 2002. catch and release in marine recreational fisheries, american fisheries society symposium 30: 88-96. willey, a.l., barker, l.s. and sampson, m., 2016. a comparison of circle hook and j hook performance in the recreational shark fishery off maryland. fishery bulletin, 114(3), pp.370-373. review paper journal of agricultural and marine sciences 2020, 25(2): 1–12 doi: 10.24200/jams.vol25iss2pp1-12 received 13 april 2020 accepted 25 july 2020 role of grapevine rootstocks in mitigating environmental stresses: a review muhammad mumtaz khan1,*, muhammad tahir akram2, rashad waseem khan qadri2, rashid al-yahyai1 muhammad mumtaz khan1,*( ) mumtaz@squ.edu.om, 1department plant sciences, college of agricultural and marine sciences, sultan qaboos university, p.o. box 34, al-khod 123, sultanate of oman. 2institute of horticultural sciences, university of agriculture faisalabad, pakistan introduction grape (vitis vinifera l.) is one of the top fruit crops of the world that are grown for liquid (juice, vinegar, spirits), dry fruit (raisin) and fresh fruit consumption. at present, climate change is one of the major global concerns affecting viticulture (sara et al., 2018) and adversely impacting grapevines growth and development, thus affecting its yield and quality (dinis et al., 2018). the use of appropriate rootstock is a longterm strategy in changing climatic conditions (fraga et al., 2016; cramer et al., 2011). hence, the grapevine rootstocks have their significant importance as they can mitigate environmental stresses by adapting to adverse soil and climate conditions. an ideal rootstock should have abilities to withstand drought, heat, salinity, cold, insect and pest resistance with the ability to adopt a wide range of soils (ollat et al., 2015). besides, a rootstock should have abilities of early bearing and high yield attributes, however, it is seldom that single rootstock possesses all desirable traits (theodore and stephen, 1997). before selecting and propagating a grapevine rootstock, a number of its attributes and characteristics are evaluated. traits such as its compatibility, vigor, yield, rooting ability, and propagation technique (pedersen, 2006), adaptation to the soil, and climate are taken into consideration (pavloušek, 2011). moreover, these rootstocks should have tolerance against salinity and drought with the ability to resist soil-borne pathogens. in grapes, there is the problem of graft incompatibility, which occurs over the time (gökbayrak et al., 2007). this دور أصول العنب يف تخفيف الضغوط البيئية: مراجعة محمد ممتاز خان 1 *، محمد طاهر أكرم 2 ، راشد وسيم خان قادري 2، راشد اليحيايئ1 abstract. viticulture is one of the most important crop industries in the world and its cultivation is on the upward trend globally. global water and soil resources continued to decline sharply and rampant extreme weather conditions are becoming a serious threat to sustainable agriculture and food security. further, the changes in climatic conditions are increasingly becoming favorable for rearing certain harmful biotic organisms, which are hostile to sustained grape cultivation. the environmental changes have shown a projected negative impact on viticulture by increased biotic and abiotic stresses. range of strategies can be employed to mitigate such scenarios, however, integration of rootstocks to combat such challenges is a sustainable nature. grape rootstocks have exhibited their role in mitigating the problems raised due to a variety of environmental stresses. for example, certain vitis species are used as rootstock against phylloxera and other harmful pests of grapes. similarly, there are certain rootstocks developed which have their tolerance against salinity, drought, cold, and iron chlorosis. with ever-changing environmental conditions, it is not essential that one rootstock perfors better at a specific place may perform well in another place. this article reviewed several grape rootstocks which have their specific resistance or tolerance features against a variety of stresses, including pests, disease, salinity, and drought. consistent endeavors in grapevine rootstock improvement and utilization are critical for the sustainability of the grape industry, in particular during the ever-increasing environmental stresses. keywords: drought; phyloxera; salinity, rootstocks; viticulture; stress. املســتخلص:تعترب زراعــة الكــروم واحــدة من أهم الصناعــات املحصولية يف العامل وزراعتها يف االتجاه التصاعدي عىل مســتوى العامل. واصلت موارد املياه والرتبة العاملية انخفاضها الحاد وانتشــار األحوال الجوية القاســية ، وأصبحت تشــكل تهديًدا خطريًا للزراعة املســتدامة واألمن الغذايئ. عالوة عىل ذلك ، أصبحــت التغــريات يف الظــروف املناخيــة مواتية بشــكل متزايد لرتبية بعــض الكائنات الحية الدقيقة الضارة ، املعادية لزراعة العنب املســتدام. أظهرت التغــريات البيئيــة تأثــريًا ســلبيًا متوقًعــا عىل زراعة الكروم من خــالل زيادة الضغوط الحيوية وغري الحيوية. ميكن اســتخدام مجموعة من االســرتاتيجيات للتخفيــف مــن مثــل هــذه الســيناريوهات ، ومع ذلك ، فإن تكامل الجــذور ملكافحة هذه التحديات هو طبيعة مســتدامة. أظهرت جذور العنب دورها يف التخفيــف مــن املشــاكل التــي أثــريت بســبب مجموعــة متنوعة من الضغــوط البيئية. عىل ســبيل املثال ، يتم اســتخدام بعض أنــواع vitis كجذر ضد phylloxera واآلفــات الضــارة األخــرى للعنــب. وباملثــل ، هنــاك بعض الجذور التي تــم تطويرها والتي تتســامح ضد امللوحة والجفــاف والربد والحديد الكلــور. مــع الظــروف البيئيــة املتغــرية باســتمرار ، ليــس مــن الــروري أن يعمــل الجــذر األســايس بشــكل أفضــل يف مــكان معني بشــكل جيــد يف مكان آخــر. يف هــذه املقالــة ، تــم اســتعراض العديد من جذور العنــب التي لها خصائص مقاومة أو تحمل محددة ضد مجموعــة متنوعة من الضغوط ، مبا يف ذلــك اآلفــات واألمــراض وامللوحــة والجفاف. تعترب املســاعي املتناســقة يف تحســني جذور العنب واالســتفادة منها حاســمة الســتدامة صناعــة العنب ، ال ســيام خالل الضغوط البيئية املتزايدة باســتمرار. لكلامت املفتاحية: الجفاف ، phylloxera ، امللوحة ، الجذور ، زراعة الكروم ، اإلجهاد 2 squ journal of agricultural and marine sciences, 2020, volume 25, issue 2 role of grapevine rootstocks in mitigating environmental stresses: a review incompatibility results in poor vascular bundle development and causes phloem degeneration (cookson et al., 2013). this problem resulted an uneven distribution of water and nutrients with poor plant performance (pina et al., 2009). in vineyards establishment, identification of the most suitable rootstock choice is one of the key factors for its success (loreti et al., 2006). the rootstocks of grapes play a key role in dividing plant biomass between trunk, root, shoot, and fruit (köse et al., 2014). the carbohydrates stored in canes are responsible for plant health and vigor of earlier year growth. similarly, the carbohydrates stored in the plant roots are responsible for root and shoot development. it also increases stem growth, initiates flower bud induction, and fruit setting (göktürk et al., 2005). besides, rootstocks are responsible for controlling the scion flowering and fruiting. it also affects the quality of the fruit (reddy et al., 2003). moreover, grapes rootstocks have exhibited the ability to withstand biotic stress like phylloxera and abiotic stresses including drought, salinity and flooding (satisha et al., 2007). at present, climate change is of great concern as erratic environmental conditions are making agriculture difficult to sustain, because of heavy rain, flood or drought, soil and water salinity, and a range of extreme weather conditions. the grapes grown under (light and water) stress conditions resulted in low yield as compared to grapes grown under ideal environments (akram et al., 2019). most of the grape rootstocks are developed from north american vitis species. approximately 90% of grape rootstocks that exist in the world were developed from ten rootstock cultivars (keller, 2010). the genetic origin of grape rootstock used broadly in the world is shown in (figure 1). in viticulture, it is essential to understand the behavior of rootstocks as the success of viticulture depends upon various factors including soil, climate, biotic-abiotic factors and rootstock -scion combinations. any change in these factors can entirely change the scenario. there are certain rootstocks in grapes that are capable of overcoming the biotic and abiotic stresses at large. therefore, it is essential to find such rootstocks in grapes that carry the desirable traits to withstand the ever-increasing environmental stress. thus, the objectives of this study were to review the current literature on the role of grapes rootstocks in mitigating environmental stresses in sustainable viticulture production. response of grape rootstocks to biotic stresses phylloxera the “phylloxera” species is one of the most destructive pests of grapes. it consists of several species. in the 1880s, its first species (phylloxera vitifoliae fitch.) appeared and it was a root parasite (coombe, 1999). it severely affected the grapes growing areas. then in 1930, grapes first rootstock was developed to tolerate the attack of “phylloxera”, which in the 19th century destroyed several european vineyards (granett at al., 2001). the use of rootstock in viticulture was initiated due to this pest. to cope with phylloxera, the grapes rootstock from north american vitis species were selected and european varieties were grafted (vrsic et al., 2016). later grape hybrids were used to solve this problem. but the phylloxera species (daktulosphaira vitifoliae fitch) became a dynamic and more aggressive strain, which destroyed several vineyards of europe. american rootstocks showed their resistance against this pest. after the 1990s, the european rootstocks were replanted again and were grafted on “borner” rootstock (becker, 1989). this rootstock has shown strong resistance against phylloxera and since it is used commercially (blank et al., 2009). this rootstock was a hybrid figure 1. the genetic origin of some rootstocks used worldwide [adapted from dry (2007)] 3review paper khan, akram, qadri, al-yahyai al., 2004). in the black foot, several species of cylindrocarpon are involved, namely c. destructans, c. obtusisporum, c. macrodidymum and c. fasciculare. but the most destructive one was the c. destructans (halleen et al., 2004). recently this disease is also reported with fungal species of genera “dactylonectria” and “neonectria” (lombard et al., 2013). it is called “black foot” as it causes brown to black streaks or black discoloration at the main base of the rootstock. the damage caused by this disease on grapevine rootstock is presented in figure 2. this disease causes contraction in root biomass with deep necrotic lesions on root hairs (agustí-brisach and armengol, 2013). it also affects plants aerial parts by weakening vegetation, bud breaking, uneven wood maturity and interveinal chlorosis (larignon, 2004). this disease is most common around the coastal area where it is known as “aka young vine decline”. it affects the roots of mature and young vines (bleach et al., 2007). this disease can be controlled by planting the resistant rootstock against this disease or by controlling the disease management practices at the nursery level. in grapes rootstock, the least susceptible rootstock reported against this disease was 101-14 while the most susceptible rootstock to this disease was riparia gloire (brown et al., 2013). the other resistant rootstocks reported against this disease are ‘o39-16’ and ‘freedom’, which were taken from the species vitis riparia (gubler et al., 2004). while in the coastal areas, the rootstock a x r1 (aramon rupestris ganzin no. 1) showed the highest resistance against this disease as compared to 140r and 039-16 (battany, 2015). petri disease petri disease is the most destructive disease of newly established vineyards, especially which have less than ten years’ lifespan. this disease is reported by several countries around the world (chicau et al., 2000; crous that was obtained by the crossing of two grape species “vitis riparia 183 gm × vitis. cinerea arnold” (ambrosi et al., 1994). at present, several rootstocks are being developed in europe, which showe their resistance against phylloxera (arrigo and arnold, 2007). the highest resistance against phylloxera has been observed in american species, but its mechanism of resistance is still not clear. the american species that showed resistance against phylloxera includes: vitis rupestris, vitis riparia and vitis berlandieri. most of the grapevine rootstocks are developed from these species show a very less genetic variability among them. serra et al. (2013) reported that about 90% of grape genotypes are grafted on ten rootstocks, which shows that the grapes are at huge risk and these rootstocks can lose their significance with time being due to less genetic diversity. for example, a × r1 californian rootstock which was the combination of vitis vinifera ×vitis rupestris has lost its root system significance and it is further not effective (corso and bonghi, 2014). until now, the most resistant hybrids against phylloxera developed from vitis rupestris, vitis riparia and vitis berlandieri species are 101-14, 196.17 castel and schwarzmann (grant and matthews, 1996). similarly, another grapevine rootstock so4 (selection oppenheim 4) showed its highest resistance against phyloxera (schmid et. al., 1998). however, there is always a great need to develop more rootstock against this pest. black foot disease in 1961, black foot disease was recorded for the first time in france (maluta and larignon, 1991). after that, this disease was observed in the vineyards of tasmania (sweetingham, 1983), portugal (rego et al., 2000) and the usa (gugino and travis, 2003). the causal organism isolated for this disease was cylindrocarpon species, which was a soil-borne pathogen (francois et al., 2006) and this affects the roots of grapes (brayford et figure 2. the cross-section of rootstock infected by black foot disease (a), cross-section of the root (b) and longitudinal-section of a young grapevine infected with cylindrocarpon spp. (c) [adapted with the permission from halleen et al. (2007)]. 4 squ journal of agricultural and marine sciences, 2020, volume 25, issue 2 role of grapevine rootstocks in mitigating environmental stresses: a review and gams, 2000). this disease is also called young vine decline or black goo decline (gubler et al., 2004). it is a fungal disease and is mostly associated with p. phaeoacremonium spp. (gramaje and armengol, 2011), and with other fungi cephalosporium and acremonium (larignon, 2012). this disease shows both external and internal symptoms. the affected plant has undersized trees, having less vegetation and chlorotic leaves with necrotic borders. while internally, it causes brown necrosis and results in the formation of phenolic compounds, gums and tyloses around the xylem tissues (gramaje and armengol, 2011). the sap flux appears during necrosis and it is known as “black goo” (larignon, 2012). the pathogens associated with this disease are soil-borne pathogens, and it is directly affecting the roots of the plant. the incidence of this disease varies with rootstocks susceptibility. the rootstock “freedom”, “1103” and “so4” are highly susceptible to this disease while the rootstocks “salt creek”, “st george”, “harmony”, “110r”, “3309c”, “schwarzman” and “a x r1” and proved least susceptible to petri disease (eskalen et al., 2001). in another finding, the rootstock “golia” showed its highest resistance against petri disease. while the rootstocks “so4”, “riparia glorie” and “1103” were moderately tolerant, whereas the rootstock “iac 572” was highly susceptible to this disease (ferreira et al., 2018). crown gall crown gall is one of the most destructive diseases of grapes and it limits the grape production worldwide (burr et al., 1997). the causal organism of this disease is bacteria “agrobacterium vitis”. this pathogen affects the main trunk and canes of the grapevine. this pathogen induces small galls on the infected part of the vine. the incidence of the disease started with the mechanical or with the frost injury at the sites. after the injury, small galls start to form on the infected parts. with disease severity, the galls start to enlarge. in most destructive cases, the pathogen disturbs the graft union, internal disturbance of the plant systematic system, or even death is seen in grape growing regions. the disease incidence is normally reduced by good cultural practices along with effective bio-control and using tolerant rootstock. in grapes, vitis raparia is considered as a tolerant species against this disease (süle and burr, 1998). other rootstocks (i.e. ramsey, 110-r and 1613-c) are tolerant against this disease (davut et al., 2018). the incidence and variability of the disease vary with the climate of a region and rootstocks used. for example, “chardonnay” and “riesling” showed resistance in chile, while these two genotypes were found susceptible in different regions of the usa (burr et al., 1997). similarly, the rootstock “ramsay” was found highly resistant to this disease in turkey, while it was found susceptible in south africa (davut et al., 2018). in another finding, the rootstocks “kober 5 bb” and “ramsey” were found moderately tolerant to crown gall disease (demir et al., 1998). table 1. grapevine rootstocks tolerance reported to different biotic stresses (phylloxera, black foot disease, petri disease, crown gall and nematodes) rootstocks phylloxera black foot disease petri disease crown gall nematodes references 196.17 castel high corso and bonghi (2014) schwarzmann high low high medium corso and bonghi (2014); eskalen et al. (2001) 101-14* high brown et al. (2013) a x r1** low high high battany(2015); eskalen et al. (2001) riparia gloire medium high medium high corso and bonghi (2014); ferreira et al. (2018) freedom medium high low high corso and bonghi (2014) 1103 paulsen medium low medium medium m corso and bonghi (2014); ferreira et al. (2018) o39-16 high high low gubler et al. (2004) ramsey high high high davut et al. (2018) 110-r high high davut et al. (2018); eskalen et al. (2001) so4*** high low low medium schmid et al. (1998); ferreira et al. (2018) kober 5 bb medium high medium demir et al. (1998) *full name of rootstocks: 101-14* (101-14 millardet et de grasset); a x r1** (aramon rupestris ganzin no. 1); so4*** (selection oppenheim 4) 5review paper khan, akram, qadri, al-yahyai nematodes in grapevine, root-knot nematode is another common destructive pest. in america, this pest reduces 20% of the total yields of grapevines and these nematodes are becoming a serious problem of australian viticulture (nicol et al., 1999). there are several common nematode species available in vineyards, such as meloidogyne incognita, m. arenaria, pratylenchus vulnus and m. javanica (mckenry and safdar, 2006). all nematodes species can penetrate deeply into the root of a plant for taking their nutrients. there are two types of nematodes, endoparasitic and ectoparasitic. some species are endoparasitic nematodes entered into the root of the plant and consume nutrients from the root, while the ectoparasitic nematodes live outside the plant root and consume nutrients from outer tissues of the roots. in grapes, the most common and destructive rootknot nematodes belong to the genus meloidogyne. these nematodes are sedentary endoparasites, which hatch eggs at the second stage of juvenility and then migrate from soil towards the root of grapevine roots. after penetration in the roots, they form giant cells where it completes its next juvenile stages. a single gall or giant cell can consist of one to several females which can lay up to 1500 gelatinous matrix eggs (brown et al., 1993). the best way to control nematodes is the use of resistant rootstock. in australia, ramsey rootstock is specifically used to control meloidogyne species nematodes, while the rootstocks, v. champini, v. longii and v. cinerea have their resistance against root-knot other nematodes species (nicol et al., 1999). normally a single rootstock has resistance against single species, but now several developed rootstocks show their resistance against more than one nematode. recently developed rootstocks rs-3, rs9, usda 6-19b, usda 10-17a and usda 10-23 band have their resistance against more than one nematode species (anwar and mckenry, 2006; gu and ramming, 2005). recently, five grape rootstocks ucd grn1, ucd grn2, ucd grn3, ucd grn4 and ucd grn5 are developed, which show their resistance against paratylenchus hamatus, mesocriconema xenoplax, tylenchulus semipenetrans and pratylenchus vulnus nematodes (ferris et al., 2012). the specific rootstocks have their specific tolerance against each biotic stress (phylloxera, black foot disease, petri disease, crown gall and nematodes) and these are shown in table 1. response of grapes rootstocks to abiotic stresses salinity salts are present in the form of minerals and these are required for the growth of plants. these salts are readily available in soil and water. every plant species has its specific potential to tolerate salt. the capacity of a plant to withstand or endure excessive salt in its root zone is called “salt tolerance” (adnan, 2004). deficiency or toxicity of minerals, both are harmful to plants. the excessive salts present in the soil are called “salinity”. saline soils contain excessive amounts of salts (na+ and cl-) present in the soil that are harmful to grape growth and yield (corso and bonghi, 2014). in grapes, high salinity level causes disturbance in water and minerals uptake (ismail et al., 2012). grape genotypes are moderately tolerant of saline conditions however prolonged exposure to salt stress especially the chloride ions are highly damaging. these ions disturb the co2 assimilation and show effects on the stomatal conductance of grapes by its osmotic pressure (cramer et al., 2007). grapes growing in semi-arid irrigated areas are highly affected by this problem. the saline area of the world is increasing day by day and around 40% of world arable land is under saline conditions (nabati et al., 1994). several factors are affecting soil salinity. it includes water or irrigation systems, the climate of a particular area, soil of grapes cultivated area and the genotypes, especially the rootstock–scion combination used for commercial cultivation. it is also reported that grapes rootstocks are more affected by clions as compared to na+ (cramer et al., 2007). the grapes rootstocks have great variability in taking up of these ions and their accumulation concentration varies with the selected rootstocks (fisarakis et al., 2001). the wild species grapes (i.e. vitis rupestris) have the maximum strength to exclude clions. similarly, the grapevine’s other rootstocks vitis cinerea and vitis champini tolerate saline conditions. for the good production of grapes, the combination of scion and rootstock is very essential. vitis berlandieri had great strength to withstand salt but when vinifera scion was used. it reduces the strength of na+ and clexpulsion. for example, a hybrid 41b which was the combination of vitis berlandieri × vitis vinifera lost its ability to exclude ions. other reported grapes rootstocks (ramsey and two hybrids, 1103 paulsen and r2) showed a positive response towards salinity and increased the weight and bunches number (walker et al., 2002). while southey and jooste (1992) recommended 101-14 mgt and 143-b mgt rootstocks against salinity. in a comparison of 101.14 and m4 as commercial rootstocks, m4 showed greater capacity to tolerate saline and drought stress by maintaining the physiological processes and photosynthetic activity (meggio et al., 2014). scion/rootstock grafting interaction showed that a sensitive variety (i.e. syrah) grafted onto a moderately tolerant rootstock (i.e. 1103p) resulted in enhanced tolerance levels against salt stress as compared to a moderately tolerant variety (i.e. muscat d’italie), which was grafted on a sensitive rootstock (so4) (hanana et al., 2015). drought stress climate change is one of the major threats and an increase in temperature on the landmass is causing the 6 squ journal of agricultural and marine sciences, 2020, volume 25, issue 2 role of grapevine rootstocks in mitigating environmental stresses: a review problems of drought and water scarcity. among abiotic factors, drought is one of the main factors that directly affect the yield and productivity of a crop (tsago et al., 2014). based on climate models and weather predictions, it is assumed that there is an increase in arid land in the future (dai, 2013). the solution to this problem is to use such genotypes that are greatly water efficient. this is one of the breeding key strategies for the improvement of genotypes (marguerit et al., 2012). in grapes, there are certain rootstocks, which use water more efficiently. hence, the rootstock can play an effective role in drought by improving water efficiency. the efficacy of rootstock depends upon several factors, such as scion, vigor, stomatal conductance, aquaporin proteins and their combinations. in water stress conditions, stomatal conductance plays an effective role in water regulation and first organelles to respond to drought (damour et al., 2010). moreover, during stress conditions, a plant releases an abscisic acid hormone, which accumulates in grape leaves and this retards the plant cellular growth (serra et al., 2013). this hormone is immediately released by the plant when it is in stress and the accumulation of abscisic acid in leaves causes closure of stomata. it is also observed that in water stress conditions, there is a production of aquaporin genes, which controls the water use efficiency of plants and these genes are more in drought-tolerant rootstocks. considering drought conditions, the rootstocks are divided into two categories: (i) the rootstocks having higher vigor and drought tolerance mechanism, (ii) rootstocks having least vigor and drought tolerance. the rootstocks exhibit higher vigor; they develop rapid roots growth in a later season, especially during wet conditions while rootstocks having less tolerance and develop roots in the early growing season without prevailing any wet conditions (serra, 2013). in grapes rootstocks, it is essential to find both drought tolerance mechanisms to cope with water-scarce conditions. plants may suffer metabolic changes due to exposure of abiotic stresses and these result in the decline of quality and productivity of grapevine. rootstock integration approach can be used to mitigate such harmful impacts due to their abilities to enhance the drought tolerance mechanism during the scion. under deficit water regimes, the grafter grapes rootstocks (i.e. mgt 101-14 and 1103 paulsen) showed significant alterations in grape technological maturity. the primary metabolism was not noticed in the rootstocks, while the accumulation of phenolic compounds in berries (e. g. anthocyanins) was very distinct. plants under water stress and normal water regimes showed a significant difference in the gene and mirna expressions. results conferred that the rootstocks can modulate water stress effects on grapes through regulating the secondary metabolism (zombardo et al. 2020). several grapevine rootstocks showed their variability in drought tolerance. in grapes, the highest drought tolerance was shown by v. champinii species (padgett-johnson et al., 2003). early 1935, two rootstocks ‘riparia’ and ‘101-14mgt’ were commonly used against drought (dry and coombe, 2005). after another rootstock “ramsey” of v. champinii became very famous and was widely used in australian vineyards due to its highest drought tolerance (walker and clingeleffer, 2009). the other grapevine rootstocks (i.e. kober 5bb, 140 ruggeri, lider 116-60, 1103 paulsen and richter 110) showed their tolerance towards drought (flexas et al., 2009). m4 rootstock planted at water-deficient and salt stress soil showed its tolerance towards salt stress and water stress. it also maintains its photosynthetic activity. in another finding, the rootstock ‘110r’ showed the highest drought tolerance while ‘101-14mgt’ showed the medium tolerance, whereas ‘riparia’ showed the least tolerance to drought (ollat et al., 2015). similar results were reported by pouget and delas (1989) and it showed that ‘riparia’ and ‘101-14mgt’ were low in drought tolerance as compared to ‘110r’. in other studies, it was reported that the level of aquaporin genes was different in grapes roots and leaves. the concentration of this gene was less in leaves where it reduced the transpiration rate, while its concentration was more in roots and it promotes roots elongation for water uptake (galmés et al., 2007). in a hot and dry climate, rootstocks having vigor extends greater as compared to less vigorous rootstocks. similarly, the grapevines grafted on 1103p rootstock showed a deep root system for water uptake during water stress as compared to 10114 rootstock and it showed less depth during summer (alsina et al., 2011). in grapes, certain hybrid rootstocks were developed with the combination of grapes xerophylic species v. rupestris. it was observed that the combination of v. berlandieri × v. rupestris was highly drought-tolerant (tramontini et al., 2013). similarly, the scions grafted on drought-tolerant rootstocks showed good evaporation, transpiration, carbon assimilation and water conductance (alsina et al., 2011). low temperature stress low temperature is one of the major environmental constraints affecting grape production. most cultivars growing in different geographical parts of the world belonging to european origin showed poor cold resistance (yu et al., 2017). low temperature disturbs the physiological and biological function of plants. in extreme cases, low temperature causes problems like crown gall or in severe situations, it may kill the whole grapevine. in grape genotypes, there is a minute difference in temperature of 1 to 2°c for cold tolerance, but this small difference is essential for vine survival. because each genotype has a certain capacity to tolerate freezing temperature, especially in dormant seasons. in low temperatures, grapes cane showed cytoplasmic desiccation, bud freezing, and primordial death, especially in late winter (anne, 2004). the grapes rootstocks have their direct effect on freezing tolerance and scion biochemistry, whereas it 7review paper khan, akram, qadri, al-yahyai has an indirect effect on vine size (striegler and howell, 1991). the grapevine rootstocks are made up of genus ‘vitis’ having several species. each species has its specific cold tolerance. in laboratory conditions, v. rotundifolia tolerated -20 to -23°c, whereas in field conditions it can tolerate up to -13°c freeze (clark and watson, 1998). in grapes, couderc 3309 (c3309), kober 5bb (5bb) and selection oppenheimer no. 4 (so4, v. spp.) are widely used rootstocks of cold regions as they can tolerate the low temperature. however, the performance of scion grafted on these rootstocks varies with the individual rootstock (anne, 2004). in field conditions, the rootstock “c3309” acclimated more rapidly as compared to others, while rootstock “5bb” was least acclimatized rootstock (miller et al., 1988). similarly, another rootstock used in eastern us is 3309 couderc (c-3309). it is the combination of v. riparia and v. rupestris. it is a cold-hardy rootstock having tolerance against phylloxera and acidic soils as well (hoover et al., 2002). the temperate region fruit rootstocks must contain the character of winter or cold hardiness (nimbolkar et al., 2016). iron chlorosis the calcareous soils usually have iron (fe) deficiency, leading to grapevines grown on calcareous soils having iron chlorosis. the grapevines are also sensitive to the calcareous soils, especially when these are rich in bicarbonates compounds. in grapevines, iron chlorosis causes stunted growth of the vine with low yield. further, it also affects plant longevity and productivity (covarrubias and rombolà, 2013). during iron chlorosis, the production of fe-reductase enzyme increases in grapevines and the plant excretes organic compounds and protons in its roots, thus resulted in increased fe solubility and lowered ph. this condition of the plant is known as a strategy i (jiménez et al., 2007). in response to iron chlorosis (calcareous soils), grape rootstock (140 ruggeri) is proved more efficient as it has not shown signs of iron deficiency. the high tolerance against iron deficiency was observed in this rootstock due to fe (iii)-reductase activity in its root. moreover, this rootstock releases toxic phenolic compounds to the soil when planted in calcareous soils (ksouri et al., 2006). the fercal rootstock in france and 140 ru (vitis berlandieri × vitis rupestris) rootstock in italy, showed its highest tolerance against lime chlorosis (fregoni and bavaresco, 1986). the scion and rootstock combination is also necessary when planted at calcareous soils. the grape rootstocks 3309c showed a positive response when pinot blanc cultivar was grafted on it (bavaresco and lovisolo, 2000). similarly, the rootstock so4 showed its medium tolerance against iron chlorosis (bavaresco and lovisolo, 2000). nowadays, mostly hybrid rootstocks are used against chlorosis. the hybrids showed the highest tolerance against chlorosis when a combination of vitis riparia, vitis cinerea and vitis berlandieri were used. the hybrid rootstocks developed from the combination of vitis rupestris and vitis amurensis showed medium tolerance towards chlorosis. for example, the hybrid (binova × börner) showed its medium resistance towards lime chlorosis, whereas the rootstock hybrid developed with the combination of teleki 5c × börner and [binova × (binova × teleki 5c) × börner] showed their highest tolerance towards lime chlorosis (pavlousek, 2009). the specific rootstocks have their specific tolerance against table 2. grapevine rootstocks tolerance reported to different abiotic stresses (salinity, drought, iron chlorosis, low-temperature stress) rootstocks salinity drought iron chlorosis low temperature references 196.17 castel high high corso and bonghi (2014) schwarzmann medium medium corso and bonghi (2014) 101-14* low medium low alsina et al. (2011) riparia gloire medium low low corso and bonghi (2014); ollat et al. (2015) 101-14mgt high medium low ollat et al. (2015); southey and jooste (1992) freedom low medium low medium gubler et al. (2004) 110r high ollat et al. (2015) 1103 paulsen high high medium corso and bonghi (2014) o39-16 high corso and bonghi (2014) ramsey high medium medium flexas et al. (2009) 3309c high high hoover et al. (2002) so4** medium low bavaresco and lovisolo (2000) kober 5 bb low medium high flexas et al. (2009) *full name of rootstocks: 101-14* (101-14 millardet et de grasset); so4** (selection oppenheim 4) 8 squ journal of agricultural and marine sciences, 2020, volume 25, issue 2 role of grapevine rootstocks in mitigating environmental stresses: a review each abiotic stress (salinity, drought, iron chlorosis, and low-temperature stress) as shown in table 2. conclusion globally, climate change is one of the major threats to sustainable grape production since it has shown to have a profound impact on the proliferation of several biotic and abiotic environmental stresses. rootstocks have demonstrated the abilities to mitigate such stresses through their peculiar evolving plant traits. several grape rootstocks are developed from vitis and each species of vitis has its specific characteristic and tolerance mechanism against specific ranges of stress. grape rootstock responses to biotic and abiotic limiting factors are multifaceted which involves several ecological, physiological, molecular and genomic mechanisms. many of these mechanisms have been discussed earlier where several plant traits related to such mechanisms and genomic areas have previously been recognized at the scion and rootstock levels. however, a better understanding of the specific role of alleles in these areas can benefit from manipulating the plant materials to handle the increased risk of biotic or abiotic stresses. in this article, several grapevine rootstocks with their specific resistance or tolerance features against a variety of stresses, including pests, disease, salinity and drought were reviewed. prolongation of grapevine rootstock improvement through conventional and molecular breeding, extensive evaluation and crop management research is critical for the sustainability of the grape industry as new biotic and abiotic stress factors continued to emerge. acknowledgment we acknowledge greatly the academic support of sultan qaboos university, oman. we are also thankful to haleen f. for allowing us to reproduce images of their work. references adnan ay. 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(2017). vaerd15, a transcription factor gene associated with cold-tolerance in chinese wild vitis amurensis. frontiers in plant science 8: 297. zombardo a, mica e, puccioni s, perria r, valentini p, 12 squ journal of agricultural and marine sciences, 2020, volume 25, issue 2 role of grapevine rootstocks in mitigating environmental stresses: a review mattii gb, cattivelli l, storchi p. (2020). berry quality of grapevine under water stress as affected by rootstock–scion interactions through gene expression regulation. agronomy 10: 1-25 (article 680). research paper journal of agricultural and marine sciences vol. 23 : 11– 23 doi: 10.24200/jams.vol23iss1pp11-23 reveived 15 jun 2017 accepted 19 sep 2018 overview of decadal ecosystem changes in the western arabian sea and the occurrence of algal blooms 1paul j. harrison, 2*sergey piontkovski, and 2khalid al-hashmi 2*sergey piontkovski ( ) spion@squ.edu.om. 1dept. earth & ocean sciences, univ. british columbia, vancouver, bc, canada v6t 1z4. 2college of agriculture & marine science, sultan qaboos university, al-khod 123, oman introduction most areas of the ocean are already responding physically and biologically to anthropogeni-cally induced impacts. some of the small scale impacts such as eutrophication have occurred more quickly and are easier to understand and quantify in small scale coastal zone studies. however, the dual impacts of increased co2, which acidifies the ocean as well as warms the atmosphere and surface ocean are much more complex since they are large scale, evoke relatively slow changes and involve atmospheric as well as oceanic changes and impacts. our review aimed to synthesize our current understanding of the relationship between long term ecosystem changes and the occurrence of algal blooms as well as other climatic changes that are occurring in the sea of oman and the western arabian sea. how the western arabian sea ecosystem functions about 50 years ago, the international indian ocean expedition was launched to explore one of the last great frontiers in the ocean. yet 50 years later, the indian ocean remains one of the most poorly studied and نظرة شاملة للتغريات الِعقدية يف النظام البيئي لغرب حبر العرب وحدوث ظاهرة ازهرار الطحالب بول ج هاريسون وسريجي بوينتكوفسكي وخالد اهلامشي abstract. gradual decadal changes have taken place in the western arabian sea over the last 50 years. here we syntheses available evidences and reveal the trends pronounced in directly measured and remotely sensed parameters. we show that decadal changes have affected wind speeds, atmospheric and sea surface temperature, thermohaline stratification, shoaling of the oxycline, and dust/iron inputs. a decrease in nitrate supply of the photic layer have caused an increase in annual frequency of harmful algal blooms and fish kills. along with that, a decrease in diatom biomass and a shift from red noctiluca to green noctiluca during the northeast monsoon was observed during the last two decades, even though these are the same species they have very different nutritional modes. the red one is a heterotroph with a preference for grazing diatoms, while the green one has a symbiont and thus it is a mixotroph. recent results suggest that this shift may be caused by the shoaling oxycline since the green noctiluca grows better under low oxygen because the symbiont produces oxygen for its host. the western arabian sea is temporally and spatially complex. with the recent advances in remote sensing of the ocean, a further understanding of the mesoscale spatial-temporal variability of noctiluca blooms can be gained through analyzing frequent images with opportunistic ground-truthing. keywords: sea of oman; western arabian sea; monsoons; upwelling; nutrients; habs املســتخلص: لقــد طــرأت تغــريات عقديــة )كل عشــر ســنوات( تدرجييــة علــى غــرب حبــر العــرب علــى مــدى اخلمســن ســنة املاضيــة. هنــا نقــوم بتجميــع األدلــة املتاحــة وكشــف أكثــر االجتاهــات وضوحــا يف املتغــريات البيئيــة الــي مت قياســها مباشــرة وعــن بعــد. نوضــح هنــا أن التغــريات العقديــة قــد أثــرت علــى ســرعة الريــاح ، ودرجــة حــرارة الغــاف اجلــوي ودرجــة حــرارة ســطح البحــر, وطبقــات امللوحــة ودرجــة احلــرارة ، وضحالــة الطبقــة املنخفضــة األكســجن , وعلــى كميــة امــدادات الغبــار / احلديــد. وقــد تســبب االخنفــاض يف امــدادات النيــرات للطبقــة الضوئيــة يف زيــادة التكــرار الســنوي الزهــرار الطحالــب الضــارة ونفــوق األمســاك. باألضافــة اىل اخنفــاض يف الكتلــة احليويــة للداياتومــات وحتــول ازهــرار النكتيلــوكا مــن اللــون االمحــر اىل اللــون االخضــر اثنــاء الريــاح املومسيــة الشــمالية الشــرقية خــال العقديــن املاضيــن . علــى الرغــم مــن أهنا)النوكتيلــوكا( هــي نفــس النــوع اال انــا لــدى كل واحــدة منهمــا وســائل غذائيــة خمتلفــة جــدا. فــذات اللــون األمحــر تكــون غرييــة التغذيــة مــع تفضيــل الدياتومــات ، يف حــن أن ذات اللــون األخضــر فتحتــوي بداخلهــا علــى طحالــب تعايــش ، وبالتــايل تكــون خمتلطــة التغذيــة. تشــري النتائــج األخــرية إىل أن هــذا التحــول قــد يكــون نامجًــا عــن ضحالــة طبقــة املــاء املنخفضــة االوكســجن حيــث أن النوكتيلــوكا اخلضــراء تفضــل النمــو فــو وســط منحفــض األكســجن بســبب ان الطحالــب التعايشــية تقــوم بانتــاج األكســجن ملضيفهــا. إن غــرب حبــر العــرب معقــد مــن الناحيــة الزمانيــة واملكانيــة ولكــن مــع التطــورات احلديثــة يف تقنيــات االستشــعار عــن بعــد للمحيطــات فانــه ميكــن احلصــول علــى مزيــد مــن الفهــم للتقلبــات الزمانيــة واملكانيــة الزهــرار النوكتيلــوكا مــن خــال حتليــل الصــور املتكــررة والنتائــج املأخــوذه مــن البحــر مباشــرة الكلمات املفتاحية: حبر عمان, غرب حبر العرب, الرياح املومسية, التيارات الصاعدة,املغذيات, ازهرار 12 squ journal of agricultural and marine sciences, 2018, volume 23 overview of decadal ecosystem changes in the western arabian sea and the occurrence of algal blooms overlooked regions in the world’s ocean (hood et al. 2015). since the arabian sea is a relatively small basin in the northwest corner of the indian ocean bounded by oman and somalia on the west and india on the east it should be possible to intensify international efforts in the future (fig. 1). the arabian sea (as) is one of the world’s most productive oceanic areas, yet it is one of the least studied large marine ecosystems (lems) (naqvi et al. 2010; hood et al. 2015; piontkovski and queste 2016). therefore, it is difficult to obtain historical records of decadal time series of various parameters in order to assess climate change impacts. oceanographic research in the indian ocean has lagged the atlantic and pacific oceans. yet, the as has many unique characteristics such as intense upwelling, high productivity, predicable monsoon winds with reversing pattern, the world’s largest scale hypoxia in deep waters and large dust inputs that deliver iron that make it ideal for testing various hypotheses. wiggert et al. (2005; 2006) provide an excellent comprehensive historical review of the evolution of our understanding of monsoon-driven biogeochemical processes in the as. navqi et al. (2010) provide a summary of the biogeochemical processes during the late southwest monsoon (swm) and smith (2001) provides a summary of the 1994-96 joint global ocean flux study (jgofs) for the arabian sea region. a small section of the northwest corner of the as is called the sea of oman (or gulf of oman) (fig. 1). geographically, it is a strait connected to the arabian gulf (persian gulf ) on the west and the western as to the east and south. during the northeast monsoon (nem) in winter (from december to march), surface waters are dominated by oceanic water which flows in along the iranian coast accompanied with some upwelling. in contrast, in summer (in june to september), during the southwest monsoon (swm) high salinity, low oxygen arabian gulf water flows out, producing a strong salinity front where this water meets the less saline surface water of the sea of oman and eddies are also produced (piontkovski et al. 2012a). a frontal zone forms near the eastward promontory of the ras al hadd in summer and roughly separates the sea of oman from the larger as (fig. 1). the as reverses its geostrophic circulation seasonally, due to the reversing monsoon wind which drives highly energetic currents and the formation of mesoscale eddies. the strength of the monsoon winds is regulated by the thermal gradient that develops from the differential heating of the land and ocean. during the swm in summer, the heating of the eurasian land mass produces a low pressure area and an accompanying high pressure over the ocean which gives rise to southwesterly winds which blow off somalia, yemen and oman. these very strong winds are known as the findlater jet and they produce intense upwelling off the central and southern coast of oman. in addition to coastal upwelling, processes such as wind-mixing, lateral advection, ekman pumping, mesoscale eddies and filaments also play an important role in supplying nutrients to the euphotic zone during summer (piontkovski and nezlin 2012; piontkovski and al-jufaili 2013). the ekman transport can transport chlorophyll offshore along with eddy formation. the most powerful current feature in the as during the sw monsoon is an extension of the northward flowing somali current. at the eastern most point of oman (ras al hadd), this current veers abruptly offshore, forming the ras al hadd jet or front (fig. 1). at the northern boundary of a large anti-cyclonic eddy north of the ras al hadd jet/front, a cyclonic eddy forms and it has higher concentrations of nutrients and chlorophyll (piontkovski et al. 2012a, b: piontkovski and nezlin 2012). the counter-clockwise eddies are figure 1. top panel: map of the arabian sea as a small nw section of the indian ocean, bounded by oman and somalia on the west and indian on the east (from etopo 2 bathymetry data from noaa ngdg . bottom panel: the system of currents and water mass transport along the omani coast. background image: three-dimensional bathymetric map (www.earth.google.com). two parallel lines: (1) demarcate the location of the ras al hadd frontal zone formed by the confluence of currents (3 and 4). arrows (2-4) indicate direction of the main currents in summer through the fall period. (2): inflow of the indian ocean water mass, (3): outflow of the arabian (persian) gulf water mass, and (4): oman coastal current. 13research article harrison. piontkovski, al-hashmi associated with offshore transport, while the clockwise eddies may transport blooms onshore. the injection of nutrients into the surface waters produce the highest chlorophyll concentrations during the year which gives rise to a rich fishery of small pelagics, in particular myctophids that escape predation by hiding in the oxygen minimum one during the day (piontkovski et al. 2013). in winter, the eurasian land mass cools and produces a high pressure area and consequently a switch to northeast winds. there is considerable interannual variability in the strength of the winds because when there is more snow cover, the pressure gradient between the land and the ocean increases and the winds are stronger (goes et al. 2005). these cool dry winds are not as strong as the sem winds, but the accompanying cooling of the surface waters promotes deep convective mixing of nutrients from depth and a subsequent increase in chlorophyll, but about 50% less than during the summer months (piontkovski et al. 2011) during the spring inter-monsoon (march–may) these waters are largely oligotrophic with very low chlorophyll concentrations, whereas the fall inter-monsoon (september–november) represents the tapering phase of the very high summer chlorophyll concentrations (piontkovski et al. 2011). decadal changes in ecosystem drivers over the last several decades, the parameters that influence the functioning of the ecosystem have been changing. the as is experiencing a regional climate shift, with substantial warming especially after about 1995. surprisingly, sarma et al. (2013) observed that the warming was more rapid off the southern omani coast than in the 0.25 0.50 0.75 1.00 1.25 1960 1970 1980 1990 2000 2010 year w in d s pe ed (m /s ) wind component meridional wind zonal wind 16 20 24 0 100 200 300 temperature (ºc) d ep th (m ) period 1960−1970 1970−1980 1980−1990 1990−2000 2000−2010 0 1 2 3 4 0 100 200 300 dissolved oxygen (ml/l) d ep th (m ) period 1960−1970 1970−1980 1980−1990 1990−2000 2000−2010 10 20 0 100 200 300 nitrates (ml/l) d ep th (m ) period 1960−1970 1970−1980 1990−2000 0.3 0.4 0.5 0.6 0.7 1960 1980 2000 year c hl or op hy ll a (m g. m − 3 ) a b c e d figure 2. environmental changes in the western arabian sea during the swm. upper left panel: interannual changes in wind speed with zonal (zw) and meridional (mw) components. upper right panel: vertical profiles of summer temperature averaged over 5 decades. bottom left panel: decadal change in dissolved oxygen vertical profiles over 5 decades. bottom central panel: decadal changes in annually averaged nitrate profiles (number of stations per decade; for 60-70, n = 145; for 70-80, n = 18; for 90-2000, n = 305). bottom right panel: decadal change in chlorophyll in the surface layer. dotted line = 95% confident limits (from piontkovski and queste 2016). 14 squ journal of agricultural and marine sciences, 2018, volume 23 overview of decadal ecosystem changes in the western arabian sea and the occurrence of algal blooms sea of oman from 1961 to 2010. there has been a 5-fold increase in intense cyclones (kumar et al. 2007, 2010). even though the as has not been as well studied as many other areas, piontkovski and queste (2016) were able to find a relatively large amount of historical data. they obtained over 29,000 vertical profiles from mainly usa and uk cruises and determined many significant decadal changes over the last 50 years (1960-2010). they found that a decline in wind speed was influenced by the reduction in the siberian high atmospheric anomaly (fig. 2a). the increase in the atmospheric temperature caused an increase in the sea surface temperature (sst) of about 0.2oc/decade or 2.3oc from 1950 – 2010 and an increase in salinity in the top 300 m (fig. 2b). this increase in thermohaline stratification due to surface warming resulted in a shoaling of the oxycline (fig. 2c). the 1 ml l-1 oxygen concentration shoaled from 145 to 80 m (banse et al. 2014; piontkovski and queste 2016). in addition, the arabian gulf water that enters the sea of oman at 150 to 300 m has less oxygen than in previous decade. the nitracline has shoaled and nitrate in the surface waters decreased by 30% (fig. 2d). changes in these physical and chemical parameters led to a decrease in chlorophyll fig. 2e), a reduction in primary productivity, and a decline in sardine landings (piontkovski and queste 2016). lower oxygen, partially due to warmer water, caused a nearly a 3 times increase in fish kills and likely some habitat compression due to the shoaling of the oxycline (piontkovski et al. 2011; harrison et al. in press). there was an increase in acidification, especially in the deeper waters, in part due to the decrease in ph of the deep water flowing in from the arabian gulf (piont1 2 3 4 5 1 2 3 4 5 6 7 8 9 10 11 12 month c hl or op hy ll a (m g. m − 3 ) location masirah oman sea open sea 2 4 6 1 2 3 4 5 6 7 8 9 10 11 12 month c hl or op hy ll a (m g. m − 3 ) mf a m j a s o dnjj 2 0 4 3 1 c hl or op hy lla (m g m -3 ) month c b a figure 3. (a) seasonal change in chlorophyll determined from seawifs data from 1998-2008. gom = gulf (sea) of oman; os = open sea region; ms = missirah (see fig. 1). (from piontkovski et al. 2011). (b) interannual variability in the seasonal cycle of remotely sensed seawifs chlorophyll from 1998-2007 for the western arabian sea (mean is darker) and (c)averaged chlorophyll seasonal cycle (from piontkovski and nezlin 2012). 30 1 0.6 0.5 0.4 0.3 0.2 0.1 0.080.72.510 10 16 28 n 22 10 16 28 n 22 chlorophyll a (μg/l) june – september 1999 58 64 70 7652 e january – march 1999 58 64 70 7652 e a b figure 4. satellite average chlorophyll concentrations for the months of (a) june to september (swm) and (b) january to march (nem) (from piontkovski et al. 2013). 15research article harrison. piontkovski, al-hashmi kovski and queste 2016). since nitrate has shown a significant decadal decrease, it is possible that silicate may be decreasing also. wyrtki (1971) noted that surface silicate concentrations were low compared to other oceans. morrison et al. (2001) also suggested that si may be limiting since n:si ratios in the swm water were often >2:1, whereas a 1:1 ratio indicates balance availability of n and si. similarly n:p ratios were frequently <16:1 suggesting that n availability was less than p, possibly because the intense oxygen minimum zone is a major sink for nitrate via denitrification. because of the interest in denitrification in the arabian sea, the main focus of nutrient measurements has been on nitrate and nitrite and much less effort on si (naqvi et al. 2010; ward et al. 2009; banse et al. 2014). therefore, more n and si measurements are needed to determine if n and si play a dual role in the regulation of diatom blooms. unfortunately, piontkovski and queste (2016) did not determine decadal changes for silicate along with nitrate. silicate is supplied by the intense summer upwelling over a 200 km band off the omani coast and is taken up diatoms, the main group of primary producers during the summer upwelling season. however, silicate is exported more rapidly out of the photic zone than nitrogen due to its slower regeneration rate. nair et al. (1989) reported that biogenic silica collected in moored sediment traps in the northern arabian sea, contributed up to 40% of the particle flux in july, primarily as frustules of guindardia (rhizosolenia). in contrast, in the eastern basin off india, the sediments are relatively devoid of diatom frustules, suggesting that si may be limiting in this area perhaps due to less intense upwelling. modeling and measurements of silicate during the jgofs expedition in the 1990s, also indicated potential silicate limitation, mainly in the eastern basin east from ~66oe to the western coast of india (young and kindle 1994). another driver of productivity is iron that is delivered to the ocean as dust (wiggert and murtugudde 2007). the canonical thinking that the northern arabian sea is invariably iron replete is now being challenged by both model results and recent observational studies (wiggert and murtugudde 2007; moffett et al. 2015). results indicate that the low iron concentrations (0.3 to 0.5 nm) are strongly modulated by the specific composition of the aeolian mineral deposition. thus, climate and/or land use influences dust mobilization and composition and may explain the large interannual variability in algal blooms that is frequently observed (moffett et al. 2015). dust-enhanced blooms result in a more pronounced shift toward netplankton, and an increase in export flux of up to a 20% during the swm monsoon and possible regulation of diazotrophic blooms such as trichodesmium which could be a source of new nitrogen (moffett et al. 2015) moffett et al. (2015) found that the fe concentration is relatively high in the eastern as due to the oxygen minimum zone where the reduced form of iron, fe(ii), is dominant. in contrast, in the western arabian sea, fe is low and often limiting during the swm. the upwelling of nutrients and subsequent advection offshore during the swm and accompanying fe addition by dust can represent a large scale fertilization event with increased production up to 1000 km from the coast. in fe enrichment incubations at sea, chlorophyll increased up to 6-fold for some areas in the central arabian sea (but there were no fe additions for the western as) with rapid growth of the flagellate phaeocystis, thus confirming fe limitation for these areas (moffett et al. 2015). the enhanced depletion of si relative to n is one of the diagnostics of si limitation (takada et al. 2005). nutrient concentrations during the swm showed preferential depletion of si relative to n during the advection of the upwelled water further offshore (morrison et al. 1999). takeda et al. (1995) determined that at the beginning of the northwest monsoon (nwm), phytoplankton were co-limited by fe and nitrogen. as the nwm continues, nitrate builds up and the phytoplankton become fe-limited and therefore, a dust storm could stimulate bloom formation. since dust storms and their delayed effects on productivity are difficult to detect due to ship-scheduling uncertainties, various types of satellite data may provide daily information on chlorophyll as well as dust storms. although episodic dust events are more prevalent in the summer because of the high winds, cloud cover limits satellite observations. therefore, banerjee and kumar (2014) focussed on the winter nwm when nutrients are entrained by convective cooling and deepening of the mixed layer. however, during the nwm, the dust levels are lower than the swm period, but some dust deposition can still occur in winter due to the shamal nw winds. they tracked 45 dust storms during the nwm from 2002-2011 and found that only 8 storms produced enhanced chlorophyll. wiggert and murtugudde (2007) examined satellite images from the central arabian sea (cas) and concluded that even though the cas supports low levels of chl biomass during the winter, the influence of episodic events like dust depositions that supply dfe can periodically turn the cas into a productive system and account for a large part of the interannual variability within this region. kumar et al. (2010) examined both summer and winter monsoons and they found little increase in chlorophyll during the summer, but during sept to the winter, the increase in chlorophyll was more pronounced. barnali and mishra (2013) examined satellite data from 2002 to 2012 from modis aqua and tera and seawifs and found that after most dust storm events there was an increase in chlorophyll and thus an indication of fe limitation by phytoplankton in various areas of the as. so in general, the strength of dust storms might be considered as one of potential drivers of productivity in the region. 16 squ journal of agricultural and marine sciences, 2018, volume 23 overview of decadal ecosystem changes in the western arabian sea and the occurrence of algal blooms decadal chlorophyll responses to environmental changes there are several major upwelling areas in the global oceans that were investigated by the jgofs program. the as was a relatively unique site for jgofs’ biogeochemical investigations because of its predictable reversing monsoon winds, intense upwelling, deep convective mixing and their subsequent effect on algal blooms during these two seasonal monsoon periods (barber et al. 2001; marra and barber 2005). the jgofs group concluded that primary productivity during the swm off oman was controlled mainly by mesozooplankton grazing and secondarily by episodic nitrogen limitation and that fe and light were not limiting. as expected, the swm period was the most productive at ~123 mmol c m-2 d-1, but did not reach its capacity because of the active grazing that kept chl at ~3 mg m-3, nevertheless the chlorophyll-specific productivity was high at >10 mmol c mg chl-1 d-1. the northeast monsoon (nem) productivity was higher than expected at 112 mmol c m-2 d-1. the spring intermonsoon productivity was also surprisingly high at 86 mmol c m-2 d-1, considering the more oligotrophic conditions and the dominance of picoplankton such as synechococcus and prochlorococcus. in 1995, the annual mean primary productivity was 111 mmol c m-2 d-1 and was about equal to the north atlantic spring bloom (barber et al. 2001). more recent studies in the coastal upwelling area of the western as near massirah island, found that the seasonal cycle of chlorophyll has two peaks, high concentrations in aug-sept and a lesser peak in feb-mar which corresponds the end of the swm and nem respectively (fig. 3) (piontkovski et al. 2011; piontkovski and nezlin 2012). in the sea of oman, the highest chlorophyll peak of >2 mg m-3 occurred during the convective mixing of the nem, while a smaller peak of 1 mg m-3 occurred in the swm (fig. 3) (al-azri et al. 2010; piontkovski et al. 2011). in the western arabian sea, satellite images of chlorophyll clearly show the higher spatial variability during the swm (piontkovski et al. 2013; also see their table 1) due to upwelling, eddies and filaments compared to the nem with much less pronounced spatial variability (fig. 4). goes et al. (2005) suggested that the arabian sea was becoming more productive due to the warming of the eurasian landmass due to the decrease in the snow cover in the tibetan-himalayan plateau due to a general warming trend. this was linked to a strengthening of the swm winds and a subsequent increase in upwelling, increased nutrients and an increase in phytoplankton blooms in the western as (gomes et al. 2008; 2010). the increase in chlorophyll reported by goes et al. (2005) was partially ascribed to a large increase in the abundance of green noctiluca scintillans (n. miliaris is no longer the accepted name: see worms website). the increase in chlorophyll was based on a correlation between the increase in sea surface temperature (sst) and chlorophyll during the swm between 1997 and 2004. however, goes et al. (2005) only selected a 5o square region (52-57oe, 5-10on), which is only a small section (~1%) of the whole arabian sea. their report stimulated prakash and ramesh (2007) to determine if there was a similar increase in chlorophyll in the eastern part of the arabian sea between 1997 and 2005, by deriving chlorophyll from monthly sst data. they did not find an increase in the eastern as and suggested that the increase reported by goes et al. (2005) was not due to global warming and the heating of the eurasian land mass. they concluded that any change in the monsoonal intensity because of a contrast in land-sea temperature should affect the ne arabian sea more strongly because of its closer proximity to the himalayan region compared to the southwest as. in a follow up to the prakash and ramesh (2007) analysis, piontkovski and claereboudt (2012) analyzed the sst, chlorophyll, and wind speeds during 1997-2009 (12 years) for the whole as by sub-dividing it into 61, two degree grids. on a basin-wide analysis, chlorophyll did not show the increase that was observed in the single 5o region in the southwest as that was reported by goes et al. (2005). this basin-wide analysis agreed with the findings of prakash and ramesh (2007) for the northeastern basin of the as that there was no significant increase in chlorophyll, but there was more interannual variability in the chlorophyll concentration compared to the eastern region (piontkovski and claereboudt 2012). the finding of goes et al. (2005), has stimulated other satellite oriented investigations for the same period and to consider the effect of the 1998 el niño and the 1999 la niña. liao et al. (2014) found that chlorophyll was lower during the el niño because of surface warming, increased rainfall and a decrease in winds which weaken ekman pumping and transport offshore, leading to reduced nutrient supply. examining data after 2000, naqvi et al. (2010), prakash and ramesh (2007) and liao et al. 0.000 0.025 0.050 0.075 0.100 1998 2000 2002 2004 2006 year b io m as s (m g. m −3 ) figure 5. interannual change in diatom biomass in the sea of oman from noaa ocean biogeochemical model (from piontkovski et al. 2012a). 17research article harrison. piontkovski, al-hashmi (2012) all found a decrease in winds and hence no increase in chlorophyll in the oman upwelling area during 2004-09, in disagreement with goes et al. (2005) who found an increase in chlorophyll after 1997. patra et al. (2007) suggested that the anomalous ne winds during the decline of el niño reduced the atmospheric input of dust/fe which could have reduced chlorophyll. roxy et al. (2016) examined a larger area that included more open ocean (50-65oe and 5-25on) than goes et al. (2005) who examined a smaller more coastal area (47-55oe and only 5-10on) and found a 20% decrease in chlorophyll over the last 6 decades due to surface warming and increased stratification. decadal changes in harmful algal blooms (habs) due to environmental changes piontkovski et al. (2012a) observed a decrease in diatoms and an increase in dinoflagellates (not shown) from 19972006 in the sea of oman (fig. 5) and this change occurred about the same time as the decrease in red noctiluca. more habs have been observed to occur along the northern area adjacent to the gulf of oman possibly because more research has been conducted in this area (thangaraja et al. 2007; al-azri et al. 2012; al-gheilani et al. 2012). another plausible explanation is that bloom development is initiated in the arabian gulf and then cells are exported into the gulf of oman where further growth occurs. it is not surprising that hab occurrences peak during the ne and sw monsoon periods due to the injection of nutrients into the surface during the convective mixing in winter and upwelling in summer. the annual frequency of habs have increased from 1970s to 2010 along with fish kills (fig. 6). there are more than a dozen habs and they are mostly dinoflagellates, but two habs, red and green noctiluca scintillans and the ichthyotoxic dinoflagellte cochlodinium polykrikoides, make up the bulk of the reports (al-azri et al. 2012). there was a huge longlived cochlodinium bloom in 2008 that caused extensive fish kills, closure of desalination plants and a reduction in tourism in the western arabian gulf and the sea of oman (richlen et al. 2010; piontkovski et al. 2011; al-azri et al. 2014). it is surprising that since 2008, large blooms of this species have not re-occurred. this is similar to korean waters where large annual blooms of cochlodinium occurred from 1995 to 2007 and since 2008 there has been a sharp decrease in blooms of this species for unknown reasons (lee et al. 2013). occasionally the large nitrogen-fixing cyanobacterium trichodesmium erythraeum, the dinoflagellates, karenia selliformis and prorcentrum arabianum and some diatoms also contribute to the blooms (al-gheilani et al. 2012). red noctiluca is a neritic, heterotrophic dinoflagellate that can often replace copepods as the primary grazer on phytoplankton and has a preference for diatoms, small copepods and even fish eggs (harrison et al. 2011). noctiluca is less harmful than most hab species, and any fish kills are usually due to low oxygen during the decomposition of the bloom. noctiluca does have relatively high intercellular nh4, ranging from 8 nmol per cell (pithakpol et al. 2000) to 20 mm (nawata and sibaoka (1976), but when the bloom decomposes, the nh4 concentration in the ambient waters ranges from 36 to 80 µm (montani et al. 1998; pithakpol et al. 2000), but only in a very thin 5 cm surface layer which is not toxic for most organisms. hence, previous claims that noctiluca is toxic because of its high intracellular nh4 concentrations are unfounded. red noctiluca is generally considered a temperate to sub-tropical species and its optimum temperature range is 17-25oc. previous to the mid-1990s, the red form of the dinoflagellate noctiluca was abundant and formed frequent blooms in the sea of oman and western as (al-azri et al. 2007). red noctiluca has been observed in the arabian sea in the indus shelf region of pakistan (saifullah and chaghtai, 1990) and on both the east and west coasts of india (subrahmanyan, 1954) and it geographically overlaps with green noctiluca, but they appear in different seasons (e.g. red n. scintillans in winter) or in different water masses as discussed below. in the coastal waters of the northern part of the arabian sea bordering pakistan, red noctiluca occurs during a short period in late winter (feb and mar) when water temperatures are 22-24oc. compared to the baluchistan shelf west off karachi, the blooms are more frequent off the indus delta shelf due to eutrophication and the subsequent higher productivity and more algal biomass (food supply) in this area (saifullah & chaghtai, 1990). the distribution of green noctiluca appears to be much more restricted and is limited mainly in tropical asian waters and parts of the as, sea of oman and the red sea. in the late 1990s, green noctiluca became dominant off the omani coast, while red noctiluca declined in abundance (al-azri et al. 2012). even though they are the same species, green noctiluca has a sym0 10 20 30 1971−1980 1981−1990 1991−2000 2001−2010 year in ci de nc e pe r d ec ad e incidence fish kill hab figure 6. decadal frequency and relationship between hab occurrences and fish kills in the sea of oman (from piontkovski et al. 2012a). 18 squ journal of agricultural and marine sciences, 2018, volume 23 overview of decadal ecosystem changes in the western arabian sea and the occurrence of algal blooms biont inside called pedinomonas noctiluca, belonging to the class prasinophyceae (sweeney 1976). it has its optimum growth rate at a ph of 4.5 to 5.5, which is the intracellular ph of noctiluca. noctiluca has unusually high intracellular nh4 concentrations (furuya et al. 2006a; harrison et al. 2011) and therefore it is not surprising that as a unialgal culture, growth of pedinomonas in the laboratory is fast on nh4. the amount of the symbiont inside noctiluca varies (hansen et al. 2004). when the symbiont is abundant, noctiluca is mainly autotrophic and its growth rate in laboratory cultures is lower (~ 0.2 µ d-1), compared to the more mixotrophic/heterotrophic ‘feeding strain’ that has a higher growth rate of > 0.3 µ d-1 (furuya unpubl. results). these growth rates of green noctiluca fall well below the maximum for most phytoplankton species and its temperature optimum is ~30oc, compared to ~25oc for red noctiluca. while the appearance of green noctiluca was relatively rapid along the omani coast, coastal waters of pakistan (chagntai and saifullah 2006), and the western as (katti et al. 1988; prakash et al. 2008; gomes et al. 2008) in the early 2000s, there were similar reports of its relatively sudden appearance in other tropical/sub-tropical areas. green noctiluca was first discovered in the gulf of thailand in the early 1970s (sweeney 1976), but in the early 1990s it appeared as massive blooms in manila bay, philippines and in the gulf of thailand (lirdwitayaprasit et al. 2006). in manila bay, it replaced the two previously dominant habs, pyrodinium bahamense and gymnodinium catenatum and since 2001, it has persisted (azana and miranda 2001; furuya et al. 2006b). in the gulf of thailand, there are massive blooms of green noctiluca along with ceratium at the north end of the gulf (furuya et al. 2006b). it is unknown why massive blooms of green noctiluca appeared in the early 2000s in these three geographically separated areas, but it suggests that there could be a common factor among these three widely separated areas, such as surface warming. in manila bay and the gulf of thailand, excessive eutrophication may play a role in algal bloom development (furuya et al. 2006b), but obvious eutrophication impacts are less pronounced along the omani coast. vertical distribution of habs: the overlooked dimension in their distribution many algal blooms are only noticed due to marked coloration of the surface waters and then often subsequently sampled to determine the species. similarly in hong kong waters, the government counts the hab (‘red tides) occurrences by confirming fishermen’s reports of coloured surface water. of course this leads to under reporting since sub-surface populations are not detected and in addition, some habs occur in relatively low concentration at the surface and go undetected (harrison et al. 2010). george et al. (2013) and ravichandran et al. (2012) observed a deep chlorophyll maximum at 40-80 m in the as and suggested that cells in this layer could seed the surface layer along with nutrient enrichment when mixing occurs during the convective overturn during nem. recent field surveys using sea gliders deployments showed that noctiluca dominated the biomass in the subsurface algal blooms at 25-55 m, which persists throughout inter-monsoon seasons. they may form a seed population and therefore link the chlorophyll maximum to algal blooms that are subsequently initiated during the sw and ne monsoons (piontkovski et al., submitted). sampling this subsurface bloom showed a net decrease in noctiluca cell size that is indicative of an actively growing population and illustrated a shift towards a deep chlorophyll maximum adapted community, but no increase in its endosymbiont. therefore, while habs may not ‘bloom’ in the chlorophyll maximum, they do provide a viable seed population that can account for subsequent blooms when they are mixed to the surface during the monsoon periods. the arrival of new habs and environmental changes the most dramatic new arrival is green noctiluca. until about the mid-1990s, the red heterotrophic noctiluca was dominant, but there has been a gradual shift from the early 2000s to dominance of green noctiluca, a mixotroph with a photosynthetic symbiont called 50 75 100 125 1970 1980 1990 2000 2010 year o xy ge n sa tu ra tio n (% ) b a 0 1 2 3 5 6 4 2 3 a bu nd an ce (l og c el ls / l) a bu nd an ce (l og c el ls / l) diatoms noctiluca scintillans figure 7. abundance of noctiluca scintillans and diatoms from 1965 to 2010 in the section of the arabian sea from 19-23on to 64-69oe. b) percent o2 saturation in upper 40 m. bars represent +/10% s.e. (from gomes et al. 2014). 19research article harrison. piontkovski, al-hashmi pedinomonas noctilucae (i.e. carbon fixation plus prey ingestion). during peak blooms, chlorophyll reached 25 mg-3 and c-fixation rates of 2 g c m-3 d-1 at the surface and 12 g c m-2 d-1 (gomes et al. 2014). in some large blooms, green noctiluca has replaced the traditional diatom-dominate bloom during the nem (fig. 7a). as discussed previously, there are many factors that have changed in the last few decades such as changes in atmospheric pressure, wind speed, warming of the sst, increased stratification, n and especially si availability/limitation, and iron deposition by dust. gomes et al. (2008) hypothesized that cyclonic cold core eddies bring up nutrients and low oxygen during the nem and these factors are responsible for promoting green noctiluca blooms. they observed, along with others that the oxycline was shoaling and thus o2 was lower in near surface waters figs. 2c & 7b) (gomes et al. 2014, banse et al. 2014; piontkovski and al-oufi 2015; piontkovski and queste 2016). in a series of laboratory experiments, gomes et al. (2014), tested if noctiluca’s symbiont p. noctilucae could fix carbon more efficiently under low o2 than other phytoplankton. in shipboard experiments, these authors observed that green noctiluca had significantly higher c-fixation rates in low o2 water than other phytoplankton in the size class of <100 µm (see fig. 4 in gomes et al. 2014). gomes et al. (2014) also tested green noctilca’s dual nutrition strategy of photosynthetic c-fixation and facultative heterotrophy (i.e. prey ingestion). they found that growth rates via photosynthetic c-fixation were greater than by phagotrophy (food ingestion in the dark) (fig. 8). hence, phagotrophy is a reserve/supplemental mode of nutrition when nutrients and/or light are limiting. since phagotrophy involves a preference for the ingestion of diatoms, the combined results of faster growth at low o2 and phagotrophic ingestion of diatoms may explain how noctiluca has been able to replace the previously dominant diatom blooms. therefore, capturing a symbiont has the dual advantage of having its own organic carbon factory (hansen et al. 2004) that can operate efficiently under low o2 because the photosynthetic symbiont can produce o2 and hence green noctiluca is not as sensitive to low ambient o2 concentrations as the red noctiluca. a similar symbiont strategy is used by the large diatom guiardia (rhizosolenia) to cope with oligotrophic conditions in the equatorial pacific by hosting a cyanobacteria that fixes n2 and subsequently providing ammonium for this very large diatom (villareal 1998). the massive bloom of the ichthyotoxic dinoflagellate cochlodinium polykrikoides in the sea of oman and western as in 2008 was unexpected since it had not been previously observed in the area (al-azri et al. 2014). it had been a regular problem for fish farms off the coast of korea in the 1990s and early 2000s, in a different temperate environment vs. the tropical sea of oman. kudela et al. (2008) suggested that it appears to be expanding globally. in the sea of oman, it was able to outcompete the regularly occurring noctiluca. it has many of the ideal characteristics that allow it to outcompete other phytoplankton. it swims, produces cysts in order to survive adverse conditions, grows slowly (reduced nutrient demand), is a mixotroph (prefers nh4 and utilized dissolved organic nitrogen), tolerates high temperatures up to ~30oc and it is not readily grazed (kudela et al. 2008; richlen et al. 2010; kudela and gobler 2012: koch et al. 2014; al-azri et al. 2014). the suggested environmental conditions that promoted the bloom was the much stronger than normal upwelling (much lower sst) along the iranian and omani coasts during the swm in late summer accompanied by elevated inorganic and organic nutrients. in late october, the discharge of unusually warm surface water that enhanced stratification and setup the optimum conditions for the bloom to form (al-azri et al. 2014; al-hashmi et al. 2015 ) and with its mixotrophic capacity, the bloom lasted for many months. anti-cyclonic eddies have been suggested to have concentrated the bloom by pushing it closer to the shore in the sea of oman due to the reversal of the wind direction during the nem. it is likely that c. polykrikoides was able to outcompete noctiluca because it can tolerate temperature to ~30oc compared to ~25oc for noctiluca. conclusions the as is a large physically and biogeochemically complex area to attempt to monitor short and long term changes over large spatial scales. fortunately, rapid advances have been made in satellite technology and have made it cost-effective to monitor winds, sea surface temperature and a estimation of nutrient inputs from upwelling and mixing, sea surface height anomalies (eddies), aerosols (dust), and chlorophyll (with an estimation of primary productivity) with ground-truthing carried out by hplc and microscopy (parab et al. 2006). 0.0 0.1 0.2 0.3 f f+n nf nf+n treatment s pe ci fic g ro w th ra te (d −1 ) irradiance dark light figure 8. specific growth rates of noctiluca scintillans incubated for 96 h with food (f) and no food (nf), with or without nutrients (n) in the light and dark. bars = +/1 sd and n = 3 to 8. (from gomes et al. 2014). 20 squ journal of agricultural and marine sciences, 2018, volume 23 overview of decadal ecosystem changes in the western arabian sea and the occurrence of algal blooms imaging from space offers great potential for determining environmental conditions that trigger algal blooms. these images can complement local in situ measurements (ground-truthing) and provide larger spatial and temporal coverage. the coastal zone color scanner (czcs) (banse and english 2000) and seawifs (banzon et al. 2004) provided images from the late 1970s to 2010. further advances have been made and moderate resolution imaging spectroradiometer (modis)-aqua and terra and well as medium resolution imaging spectroradiometer (meris) provide better resolution of blooms down to 300 m (zhao et al. 2015). recently, cochlodinium blooms have been distinguished from diatoms, noctiluca and trichodesmium blooms using the integration of meris fluorescence and particle backscattering data in the arabian gulf and the sea of oman (zhao et al. 2015) and tholkapiyan et al. (2014) and dwivedi et al. (2015) detected the green noctiluca bloom along the west coast of india. however, phytoplankton biomass and estimates of the as productivity may be greater than estimated previously through remote sensing observations due to the persistence, intensity, and vertical extent of the deep chlorophyll maximum layer which cannot be accurately measured remotely. autonomous instruments such as argos profiling floats and/or gliders with physical, chemical and biological sensors have been used to obtain information over large spatial, temporal and vertical scales (george et al. 2013; ravichandran et al. 2012) and may be necessary for ground-truthing satellite measurements and assessing vertical chlorophyll distribution. the most intriguing change in habs has been the shift from red to green noctiluca that forms a massive bloom in the western as during the nem. it has been suggested that this shift may be due to the shoaling oxycline. further studies on long-term succession of the phytoplankton community are needed since keystone species like noctiluca scintillans play an important role in the formation of the trophic structure of a pelagic ecosystem in this region. acknowledgement this work was supported by the squ/uaeu collaborative research program grant # cl/squ-uaeu/18/04 and squ grant # ig/agr/fish/17/01. reference al-azri a, al-hashmi k, goes j, gomes h, ahmed i, al-habsi h, al-khusaibi s, al-kindi r, al-azri n. 2007. seasonality of the bloom-forming heterotrophic dinoflagellate noctiluca scintillans in the gulf of oman in relation to environmental conditions. international journal oceans oceanography 2: 51–60. al-azri ar, piontkovski sa, al-hashmi ka, goes ji, gomes hr, glibert pm. 2014. mesoscale and nutrient conditions associated with the massive 2008 cochlodinium polykrikoides bloom in the sea of oman/ arabian gulf. estuaries coasts 37: 325–338. al-azri ar, piontkovski sa, al-hashmi ka, al-gheilani h, al-habsi h, al-khusaibi s, alazri n. 2012. the occurrence of harmful algal blooms (habs) in omani coastal water. aquatic ecosystem health management society 15: 56–63. al-azri ar, piontkovski sa, al-hashmi k, goes jg, gomes hdr. 2010. chlorophyll a as a measure of seasonal coupling between phytoplankton and the monsoon periods in the gulf of oman. aquatic ecology 44: 449–461. al-gheilani hm, matuoka k, al-kindi ay, amer s, waring c. 2012. fish kill incidents and harmful algal blooms in omani waters. agriculture and marine science 16: 23-31. al-hashmi k, smith, sl, claereboudt m, piontkovski sa, al-azri ar. 2015. dynamics of potentially harmful phytoplankton in a semi-enclosed bay in the sea of oman. bulletin of marine science 91: 141-166. azanza r v, miranda, l n. 2001. phytoplankton composition and pyrodinium bahamense toxic blooms in manila bay, philippines. journal of shellfish research 20: 1251–1255. banerjee, p, kumar sp. 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26 nov 2020 accepted 17 may 2021 إنتاج القمح يف عمان: اخلربات والتحدايت والفرص حممد فاروق، أمان هللا، صاحل اهلنائي، سليم قاسم نداف، عبد هللا حممد السعدي، صفاء حممد الفارسي، وسيف علي اخلميسي. wheat production in oman: experiences, challenges and opportunities muhammad farooq1,*, aman ullah1, saleh al-hinai2, saleem k. nadaf3, abdullah m. al-sadi1, safaa mohammed al-farsi1,2, and saif ali alkhamisi2 muhammad farooq( ) farooqcp@squ.edu.om, 1department of plant sciences, college of agricultural and marine sciences, sultan qaboos university, al-khoud 123, oman, 2directorate general of agriculture and livestock research, ministry of agriculture, fisheries and water resources, p.o box 50, al-seeb 121, oman, 3oman animal and plant genetic resources centre, the research council, oman. introduction bread wheat (triticum aestivum l.) is the lead-ing staple and strategic food crop in the sul-tanate of oman. it is grown under irrigated conditions, however, in the musandam region, rainfed wheat is also cultivated (maf, 2019). the wheat is used for making omani bread resembling thin papery sheets locally known as ‘khubz’ or ‘karam’ besides its use in ‘omani halwa’ (a local popular sweet). the national wheat production can meet less than 1% of the domestic requirements. historically, wheat grown in oman had been sufficient to fulfill the domestic requirement. therefore, there was no wheat import in the country from 1961 to 1980. after the 1980s, a continuous increase in the wheat import in oman has been noted (figure 1) to meet the domestic requirements. total arable land in oman is about 2.2 m ha which is 7% of the total area of oman (31.4 m ha) (maf, 2010). however, the actual cropped area in the sultanate is 62,000 ha, which is 2.8% of the total arable land and 0.2% of the total area of the country. due to continuous efforts to achieve food security in the country, an increase of 7.9% in the cultivated land area was noted during the year 2018. during 2018-19, 3, 579 tons of wheat were produced from an area of 472.28 ha in the country (figure 2). this area under wheat is spread in different parts of the country (figure 3). during 201819, the wilayat ibri recorded the highest production of 293.8 tons, followed by 142.3 tons in the wilayat bahla, 99.2 tons in the wilayat dhank, 93.2 tons in the abstract. bread wheat (triticum aestivum l.) is the leading staple and strategic food crop in the sultanate of oman; however, the national wheat production can meet less than 1% of the domestic requirements. the balance is met through imports from australia, canada, russia, and argentina. however, reliance on imported wheat alone may put oman at risk in the event of wheat export bans. therefore, wheat production needs to be enhanced to ensure national food security. nonetheless, water deficits, salinity, prolonged droughts, unavailability of stress resilient genotypes, and heatwaves challenge this notion. in this review manuscript, the current status, constraints, and opportunities to improve wheat production in the sultanate of oman have been discussed. the major opportunities to improve the wheat production include crop improvement (i.e. development of short duration, high yielding, disease resistant and climate resilient varieties), efficient irrigation system, adoption of conservation agriculture to conserve the resources, strengthening system of certified seed distribution, seed enhancements, and development and dissemination of site-specific production technologies. keywords: grain yield, abiotic stresses, water efficient genotypes, seed enhancement امللخص:قمــح اخلبــز )triticum aestivum l( هــو احملصــول الغذائــي الرئيســي واالســراتيجي يف ســلطنة عمــان. ومــع ذلــك ، فــأن إنتــاج القمــح الوطــي يلــي أقــل مــن 1٪ مــن األحتيــاج احمللــي و يتــم حتقيــق هــذه األحتياجــات مــن خــال الــواردات مــن أســراليا وكنــدا وروســيا واألرجنتــن. علمــا أبن االعتمــاد علــى القمــح املســتورد وحــده قــد يعــرض الســلطنة للخطــر يف حالــة حظــر تصديــر القمــح. لذلــك ، حيتــاج إنتــاج حمصــول القمــح إىل التطويــر لضمــان األمــن الغذائــي الوطــي. ومــع ذلــك ، فــإن عجــز امليــاه ، وامللوحــة ، واجلفــاف لفــرات طويلــة ، وعــدم توفــر األمنــاط اجلينيــة احملليــة مــن القمــح املقاومــة لإلجهــاد ، وموجــات احلــرارة تتحــدى هــذه الفكــرة. ويف خمطوطــة املراجعــة هــذه متــت مناقشــة الوضــع احلــايل والقيــود والفــرص املتاحــة لتطويــر إنتــاج القمــح يف ســلطنة عمــان حيــث تضمنــت الطــرق الرئيســية لتحســن إنتــاج القمــح و احملاصيــل )أي تطويــر أصنــاف قصــرة األجــل وعاليــة األنتاجيــة ومقاومــة لألمــراض ومقاومــة للظــروف املناخيــة ( كمــا اشــنملت علــى نظــم ري وطــرق زراعــة فعالــة للحفــاظ علــى املــوارد وتعزيــز نظــم توزيــع البــذور احملســنة املعتمــد ونشــر تقنيــات اإلنتــاج اخلاصــة ابملواقــع. الكلمات املفتاحية: أنتاجية احلبوب ، الضغوط الاأحيائية ، الراكيب اجلينية ذات الكفاءة املائية ، حتسن البذور. 2 squ journal of agricultural and marine sciences, 2022, volume 27, issue 1 wheat production in oman: experiences, challenges and opportunities wilayat yanqul, and 55.1 tons in the wilayat nizwa. the low national food production dictates the increase in imports and a rise in prices. in addition to a decrease in area under wheat, the average wheat yield is also very low (figure 2). the major reasons for low wheat yield in oman include moisture deficit, high temperature, soil, and water salinity, growing of low yielding varieties and landraces, and unavailability of climate-resilient wheat genotypes. moreover, policy-related bottlenecks as the non-existence of effective extension services to transfer site-specific production technologies, unavailability of skilled farm labour, lack of efficient water management strategies, and non-adoption of modern farm machinery also cause a decrease in wheat production and average yield. furthermore, the area under wheat has been substituted with fodder and vegetable crops due to better returns. in the current climatic conditions, there is potential to increase wheat production through the introduction of climate-resilient and high-yielding wheat genotypes, the application of an efficient irrigation system, and a site-specific suit of production technology. in this review, the history of wheat research and associated challenges are discussed. furthermore, pragmatic options to enhance wheat productivity and production, and food security are proposed. brief history of field crop research in oman there were two agricultural research stations earlier in the 1970s located at sohar and nizwa where the research on fruit, vegetable, field, and forage crops was initiated (maf, 1970). in the year 1971, two more research stations were established at rumais (welayat barka) and wadi quriyat (welayat bahla). a separate section of field crop research, with the headquarter at wadi quriyat and regional offices at rumais and salalah was established with a mandate of research on various aspects of cereal, grain legumes, oilseed and forage crops (maf, 1971). at rumais, experiments were conducted during 197273 and 1973-74 on a limited scale (maf, 1973-74). from 1975-77, a detailed program of research on field crops was initiated at rumais and salalah with the appointment of the research staff at these locations (maf, 1978). at wadi quriyat, the location was shifted in 198283 from the old farm to the present date farm location and research was initiated at welayat al-kamil in the sharqiya governorate (maf, 1983). in 1990, all activities of field crops were shifted from wadi quriyat to jimah (welayat bahla) (maf 1991, 93). during 1973 to 1990, comprehensive experiments on crop improvement and management were conducted at wadi quriyat. during 1995-96, the activities were extended to other agriculture research stations located at sohar and al-kamil (maf, 1995-96). the research materials for field and forage crops were received from ‘the international center for agricultural research in the dry areas’ (icarda), aleppo, syria, ‘the international crops research institute for the semi-arid tropics’ (icrisat), hyderabad, india, ‘the international institute of tropical agriculture (iita)’, ibadan, nigeria, ‘the international maize and wheat improvement center (cimmyt)’, mexico, ‘the arab center for the studies of arid zones and dry lands (acsad)’, syria, ‘the international center for biosaline agriculture (icba)’, dubai, united arab emirates, ‘the international atomic energy agency’, vienna, austria, and from many private companies especially in case of vegetables and fruit crops besides forage crops like rhodes grass and alfalfa (maf, 1994, 2000). meanwhile, agricultural research activities at the establishment of the college of agricultural and marine sciences at the sultan qaboos university were as part of an educational program or independent research programs under the projects by the staff and faculty through institutional, national and international funding on the problems faced by the farming community in the field, vegetable, fruits and forage crops (squ, 2020). figure 1. area and production of wheat during last six decades in the sultanate of oman (source: www.fao.org/faostat) 3review paper farooq, aman ullah, al-hinai, nadaf, al-sadi, al-farsi, alkhamisi the research on field crops, in oman, was focused on: (i) identification of high yielding genotypes under local conditions, (ii) development of the package of production practices for the field crops, (iii) research on emerging biotic and abiotic problems in field crops, (iv) identification of crop genotypes tolerant to drought, salinity, and heat stresses, and (v) dissemination of package of production practices for the cultivation of field crops (akhtar and nadaf, 2001). the research on wheat was initiated in the 1970s with the start of experiments on field crops in oman. the research activities were, in general, focused on identification and selection of suitable high yielding elite genotypes under oman conditions, and optimization of crop husbandry practices including planting date, planting method, planting density, and plant nutrition, etc. (akhtar and nadaf, 2001). subsequently, research orientation was tuned to address the problems faced figure 2. wheat production, import, and total requirement of sultanate during last six decades (source: www.fao.org/faostat) figure 3. major wheat production areas in the sultanate of oman 4 squ journal of agricultural and marine sciences, 2022, volume 27, issue 1 wheat production in oman: experiences, challenges and opportunities by the local growers such as breeding for high yielding and better-quality wheat genotypes tolerant to diseases. experiences introduction and screening of high yielding genotypes adapted to local conditions during the 1970s, local landraces of wheat viz. sarraya, missani, cooley, hamira, walidi, shwaira and greda were very popular among the growers (maf, 1970). two varieties viz. 31-1 and gamanneya were introduced from rajasthan, india, and australia, respectively in the late 1960s. the variety 31-1 was resistant to rust whereas the variety gamanneya was an awnless and tall statured with rust escape potential. as mentioned in the earlier section, agricultural research station was established at wadi quriyat in the early 1970s, with a focus on wheat varietal improvement. the research station in collaboration with the icadra, the cimmyt, and the food and agriculture organization (fao) started screening wheat varieties provided by these institutions. later, wheat genotypes provided by acsad were evaluated for adaptability to local conditions. at the same time, some varieties were introduced from other countries e.g., mexipak from pakistan, kalyansona, s. 227 and hd series from india, and sannine from lebanon. out of these varieties, mexipak, kalayansona, and sannine were released for commercial farming in oman. the variety kalyansona had a resemblance with mexipak as both of these were developed from the breeding lines provided by cimmyt (with one common parent) (maf 1971, 1994-96). the varieties mexipak and sanine are still being grown in selected wheat-growing areas of the sultanate (maf 1971, 1994-96). two wheat varieties wqs 151 and wqs 160 (wqs after the name of wadi quriat research station), with the yield potential of 3.1 and 3.2 t ha-1, respectively, table 1. agronomic characters and disease reaction of improved varieties released for cultivation during 1970-2019 sr. no. selection name source year of release days to heading days to maturity plant height (cm) grain yield (t/ha) reaction to leaf rust reaction to stem rust 1 wqs 151 icarda 85/86 65 120 80 3.10 1 1 2 wqs 160 icarda 85/86 75 122 75 3.20 2 1 3 wqs 302 icarda 96/97 65 120 65 4.00 0 0 4 wqs 305 icarda 93/94 68 120 85 4.01 1 0 5 wqs 308 mexico 92/93 75 120 85 3.67 1 0 6 jimah 1* cimmyt 96/97 75 120 75 3.20 1 0 7 jimah 2* cimmyt 96/97 75 121 85 3.95 1 0 8 jimah 101 icarda/ cimmyt 97/98 69 112 90 3.25 1 0 9 jimah 102 icarda/ cimmyt 97/98 62 108 86 3.30 1 0 10 jimah 103 icarda/ cimmyt 97/98 58 105 82 3.10 1 0 11 jimah 107 icarda/ cimmyt 98/99 73 114 84 4.9 12 jimah 110 icarda/ cimmyt 98/99 77 121 84 4.4 13 jimah 125 icarda/ cimmyt 99/2000 69 108 74 5.2 14 jimah 132 icarda/ cimmyt 99/2000 69 108 81 4.0 15 wqs 226 icarda 2008/2009 60 108 103 4.0 1 1 16 wqs 225 australia 2008/2009 69 113 88 4.9 0 0 17 wqs 227 acsad 2016/2017 78 118 85 4.5 18 jibreen 1 maf** 2018/2019 65-70 105-110 85-90 3.9 19 nizwa 1 maf** 2018/2019 65-70 105-110 85-90 3.5 20 bahla 1 maf** 2018/2019 65-70 105-110 85-90 3.6 21 nejd 1 maf** 2018/2019 65-70 105-110 85-90 4.1 check cooley local 1970 71 140 110 1.96 3 2 * the names have been changed from jimah to wqs with the same code number; not assessed. **national crop improvement program through plant breeding 5review paper farooq, aman ullah, al-hinai, nadaf, al-sadi, al-farsi, alkhamisi were released for general cultivation in 1985-86. subsequently, wqs 161 was released in 1985-86, wqs 308 in 1992-93, wqs 305 in 1993-94, and wqs 302 in 1996-97 (maf, 1992, 98). as the research station was shifted to its current location at jimah, the varieties released later had the name of this station. for example, two promising varieties jimah 1 and jimah 2 were selected and released during 1998-99 for seed multiplication program for later distribution of seeds to wheat growers. three promising varieties jimah 101, jimah 102 and jimah 103 were also selected and released. selection of wheat from institutional nurseries, observational nurseries, and regional trials of specific traits like salt and heat tolerance started in 1973-1974. the varieties and breeding lines were selected from the trials following the standard protocols. subsequently, besides the icarda, the acsad started sending advanced breeding trials for mild winter for initial screening and evaluation and selection for release of high yielding lines for general cultivation (maf, 2000; table 1). crop breeding for improving local omani bread wheat varieties the sultanate of oman has an ancient history of cultivation of bread wheat because of its position at the eastern edge of the ‘arabian peninsula’ (hammer et al., 2009; filatenko et al., 2014). wheat landraces constitute the prime genetic resource of cultivated wheat not only in oman but also in several other middle east and north african (mena) countries (al-khanjari et al., 2005, 2007; jaradat and shahid, 2014). indigenous landraces have the potential to use in crop improvement programs owing to a considerable morphological variation among and within landraces (al-maskri et al., 2003). many wheat landraces have been collected from different parts of oman during collecting missions in the 1980s and 1990s after oman’s inclusion in worldwide activities for the collection of plant genetic resources under the fao program (guarino, 1990). although the wealth of the omani landraces has been emphasized (filatenko et al., 2008) on the morphological variation, tolerance to abiotic and biotic stresses, and quality traits, these aspects have been not significantly exploited (jaradat and shahid, 2014; ahmad et al., 2014) as the information on the extent and pattern of genetic variation in these omani wheat landraces is not available. the omani farmers prefer local wheat landraces, such as cooley, hamira, sarraya, and missani to cultivate but these local cultivars are low yielding, tall-statured, and susceptible to rust and smut diseases. hence, the crop improvement program through conventional breeding was undertaken from 2001 to 2014 involving landraces to develop high yielding genotypes with the desired characteristics of local varieties such as better bread-making quality, tolerance to heat, and diseases (rust and smuts). the local varieties sarraya, missani, and cooley (female parent) were crossed with exotic wheat varieties wqs-110, wqs-125, wqs-225 and wqs-302 (male parent). from the above crosses to get f2 seeds, seeds of the f1 generation were grown in the winter season of 2001-2002. during winter 2002-03, seeds of the f2 generation were grown and selection of f2 plants was based on plant height (short, medium, and tall), the number of tillers per plant (equal or higher than 7 tillers), time to heading and maturity (early, medium, and late), other relevant agronomic characters, and resistance against insect pests and diseases. in the f2 populations, pedigree method of breeding, and a higher selection intensity (0.05) was applied on a single plant basis (maf, 2004-05). subsequent final selections from 12 crosses led to the identification of 36 outstanding advanced high yielding f7 lines. these advance lines were grown during winter 2007-08 along with three standard local check varieties at agriculture research station, jimah (al-dakhiliyah governorate) and agriculture research station, al-kamil & al-wafi (south al-sharqiya governorate). the results of the trials at both locations showed significant differences among the lines. based on multi-location results the 10 promising lines were selected for early maturity, high yield, disease resistance, and baking quality. further, these 10 lines were tested at on-farm trials in three different governorates (al-sharqiya, al-dakhiliyah, and al-batinah). four lines belonging to the crosses cooley × wqs125, cooley × wqs 302, sarraya × wqs302, and sarraya × wqs 125 were released for commercial cultivation with the names jibreen 1, nizwa 1, najd 1, and bahla 1, respectively. the lines were selected for early maturity (at least 110 days), high yield (with at least 15% superiority), and better bread-making quality. the superiority percentage of these 4 varieties (sarrya × wq125, sarrya × wq302, cooly × wq125, and cooly × wq302) for grain yield was 52, 37, 32, and 28%, respectively over their local parents (table 1; arsj, 2016). the variety nejd 1 produced the highest grain yield (4.1 t ha-1) followed by variety jibreen 1(3.9 t ha-1), bahla 1 (3.6 t ha-1), and nizwa 1 (3.5 t ha-1) (table 1; arsj, 2016). these new varieties have merits of their earliness to save water for irrigation with all required bread-making quality traits of their local parents (cooley and sarraya) over, which they were evolved and developed. the seed of these four improved bread wheat varieties was multiplied during 2016 and the varieties were released for general cultivation in 2018-19 cropping season with the distribution of seeds among the farmers in the different agro-climatic regions. these four varieties were also registered with the ‘international union for the protection of new varieties of plants’ (upov) system with the information of uniformity, distinctness, and stability (uds) tests. crop husbandry practices the experiments, involving different sets of wheat genotypes, were conducted on planting dates at wadi quri6 squ journal of agricultural and marine sciences, 2022, volume 27, issue 1 wheat production in oman: experiences, challenges and opportunities yat and salalah from the 1970s to onwards. the 3rd week of november was found as the best time of planting at wadi quriyat, while the last week of october was ideal for wheat planting in the salalah region. the varieties also differed for their responses to different planting dates. the late-maturing variety cooley yielded more when sown in early november, whereas early maturing varieties like mexipak yielded better when planted in late november (maf, 1971-74). the experiments conducted at jimah, during 1992-93 and 1993-94, showed that the wheat planting during mid-november yielded better compared to early or late plantings (maf, 1992-94). different experiments on planting density were conducted at al-dakhliyah (wadi quriyat) and salalah, during the 1970s and 1980s. the seed rate of 125 kg ha-1 at wadi quriyat, (for mexipak) and salalah (for cooley) yielded the best. these studies conducted at wadi quriyat during 1988-89 indicated the highest yield of the variety sannine was harvested using seed rates of 100 kg ha-1, while at jimah during 1991-92, 160 kg ha-1 was the best seed rate for the variety wqs 160. there was no difference between broadcast and line sowing in the experiments conducted during 1985 (maf, 1985). however, the studies conducted during 1988-89, using the variety sannine, showed that line sowing is better than the broadcast (both for grain and straw yield) (maf, 1989). within line sowing, the highest grain yields were recorded where wheat was planted in 20 cm rows whereas the highest straw yields were obtained from wheat planting in at 25 cm spaced rows (maf, 1989). weeds were not an issue for wheat in the al-dakhiliyah governate because of a shift in cultivation (maf, 1985). therefore, controlling weeds, by chemical means or hand weeding did not show any yield benefit compared with weed check (maf, 1987). the only experiment carried out in 1980 on cropping systems indicated that for line sowing wheat can be intercropped with chickpea, radish, and safflower, however, for broadcasting, it can only be mixed with chickpea (maf, 1980). the experiment conducted at wadi quriyat during the 1980s on the response of n-nitrogen, p-phosphorus, and k-potassium on both tall-statured and dwarf-statured wheat varieties indicated differential response for the n application. the tall-statured varieties like cooley responded better to lower dose (66 kg n ha-1) than the dwarf-statured varieties, whereas the dwarf-statured variety mexipak yielded better at the higher dose (88 kg n ha-1). at salalah, the fertilizer application at 80:60:40 kg ha-1 npk produced the highest yield (2363 kg ha-1) with no difference between methods of application. in another study conducted at wadi quriyat, the highest grain yield was obtained with 90 kg n ha-1 and irrigated at 7 days intervals (maf, 1980). during 1988-89, the experiment was conducted at wadi quriyat to evaluate the response of seven wheat varieties to four nitrogenous fertilizer levels under sprinkler irrigation; it was concluded that n fertilization of 150 kg ha-1 in the split with four doses – (¼ at the time of sowing, ¼ at 10 days after sowing, ¼ at the heading stage and the remaining at milky grain stage) was the best strategy to harvest highest benefits (maf, 1989). in another experiment, conducted at wadi quriyat, during 1988-89, the response of seven wheat varieties was evaluated against four p levels under sprinkler irrigation, and maximum yield was recorded at 90 kg p ha-1 (maf, 1989). tolerance against drought and salinity stresses drought and salinity (both soil and water) are a serious problem of present-day agriculture in oman and elsewhere too. since the mid-1990s, several studies have been conducted on salinity tolerance in wheat. for example, in a study, the response of 12 known salt-tolerant wheat genotypes introduced from egypt was evaluated to five levels of saline irrigation viz. control (2 ds -1), 4, 8, 12, and 16 ds m-1 during winter 1996-97 and 1997-98. the years, genotypes, salinity levels, and the effects of their interactions were significant for most of the studied traits viz. days to flowering, leaf length, plant height, number of leaves, number of tillers plant-1, spike length, grain yield plant-1, tissue k+, na+, cland k+/na+ ratio. there was no significant difference in response of genotypes for most of the characters between control (2 ds m-1) and 4 ds m-1 while the genotypes varied in their performance under higher salinity levels (nadaf et al., 2001 a, b). in another study, six local wheat landraces/ varieties viz. sarraya, wq110, missani, sannin, cooley, and humaira were screened for salinity during 2011-13. the preliminary results for the total grain weight of the cultivars under the different treatments showed that missani, sannin, cooley, and humaira were tolerant to 6 ds m-1 (maf, 2012-13). in another study, based on water conservation 7 local landraces of wheat (both bread & durum wheat) were evaluated for stem structural and specific leaf features. the tested wheat landraces were ranked as s-24 > j-305 > sarraya > senain > cooley > mh-97 > missani>hamira > shwairaa based on shoot fresh and dry weights, and degree of tolerance to drought and salinity stresses. the succulence in leaf and stem, a high degree of sclerification, pubescence on the leaf surface, and low resistance to water conductance in vascular tissue contributed to the water conservation. a high proportion of chlorenchyma and intensive sclerification in stem structure, dense pubescence on the leaves, and well-developed bulliform cells were recorded in drought and salt tolerant cultivar s-24. in other omani wheat landraces like shwairaa and hamira, these modified features were poorly developed, which were less tolerant to salinity and drought (al-maskri et al., 2014). to improve crop growth in saline soils the excess salts need to be leached below the root-zone and should not be allowed to come up. in a field study conducted at agriculture research station, rumais, the effects of saline irrigation water with three levels viz. 3, 6, and 9 ds m-1 were evaluated based on yield and leaching. 7review paper farooq, aman ullah, al-hinai, nadaf, al-sadi, al-farsi, alkhamisi with the increase in salinity of the irrigation water (and consequently soil), the corresponding decrease in the yield components and grain yield was noted. however, with 35% leaching application a significant increase in yield and yield components was recorded. likewise, the leaching × saline irrigation water was significant for grain yield and yield components. increases in grain and straw yield were associated with increases in the leaching to a certain limit. a leaching fraction of 35% was preferable if the salinity of irrigation water was less than 9 ds m-1. the saline irrigation water could be used in combination with leaching fraction as an alternative and less expensive technique to irrigate crops like wheat, to improve the grain yield and the agricultural economy of salt-affected areas (maf, 2002). use of treated wastewater for wheat production in the arid regions, the irrigation of crops with reclaimed sewage water can contribute to the saving and conservation of water resources. around the globe, many countries in the north africa, middle east, and sub-saharan africa are facing serious water shortages. during 201011, different field studies were conducted to evaluate the yield response of other and wheat crops grown in rotation with reclaimed water in comparison to the ground and desalinated water. the growth, grain yield, and water productivity of wheat were improved with reclaimed irrigation water (al-khamisi et al., 2017). during the winter seasons of 2008-09 and 2009-10, a similar study was conducted at agricultural research station, rumais to evaluate the response of fresh and treated wastewater on the performance of 3 different wheat varieties wqs 110, wqs 302, and wqs 308. the maximum grain yield of 3.85 t ha-1 was recorded in variety wqs 302 irrigated with treated wastewater followed by wqs 110 (3.70 t ha-1) and wqs 308 (3.46 t ha-1). there was no difference in n contents in the genotypes except water treatments as plants irrigated with treated wastewater had more n content than freshwater treatment. however, there were no significant differences in fresh and treated waste water and between the varieties for the concentrations of different heavy metals (maf, 2010-11). expansion of wheat to other governorates the traditional wheat-growing areas in oman are the governorates of al-dakhiliyah and al-dhahirah. the yield potential of field crops depends on the genetic make-up of genotypes and the environmental conditions where they are grown (ali et al., 2010). the adaptation of different wheat varieties in different governorates of oman is generally related to temperature and humidity. either of these factors influences the grain yield and grain quality. during the 1980s, the first experiment was conducted to evaluate the released varieties under very low temperature conditions of jabel akhdar (maf, 1981-83). two varieties of wheat viz. sannine and cooley were planted at jabel akhdar in early january and early march. both varieties yielded well when planted in january producing 4.6 t ha-1 (sannine) and 3.0 t ha-1 (cooley) as compared to march planting (sannine-2.25 t ha-1; cooley-1.0 t ha-1) (maf, 1984). since mid-2000, the area under wheat expanded to al-batinah governorate under changed humid conditions due to climate change. the results of previous trials indicated that the grains of variety wqs 110 cultivated in the al-batinah governorate were smaller than the grains of the same variety planted in the al-dakhiliyah governorate possibility due to the weather variability. the five wheat varieties (viz. wqs 110 interior, wqs 110 batinah, wqs 101 interior, wqs 308 interior, and wqs 302 interior) were planted during winter 2007-2008 at two locations (viz. jimah, al-dakhiliyah, and sohar, north ai-batinah) to compare their responses for yield and grain quality. there were significant differences among the varieties and between the locations. the varieties wqs 110 (interior) and wqs 110 (batinah) produced the highest grain yield than the other varieties. there were significant differences among the varieties and between the locations. the grain yield at jimah (4.0 t ha-1) was almost double than in sohar (2.22 t ha-1) (maf, 2011-15). the newly developed wheat varieties, resistant to heat and diseases, are being evaluated. in the wilayat of adam, 2.30 tons seed of different wheat types was distributed among 16 farmers. the cultivated area expanded from 9.7 ha to 17 ha in 2018-19. however, the cultivation of wheat in the wilayat of adam faced some challenges, the most important of which is the lack of water and insufficient experience of workers in this field. the ministry of agriculture, fisheries and water resources provided technical support to grow the wheat crop from the start of cultivation in november/december until the harvest in april. the crop is harvested in april with the use of modern combine harvesters. water resources to meet the increasing water demands of economical, industrial, and social developments the government of the sultanate of oman is exerting great efforts to develop water resources. several programs on water resources development have been implemented, these include construction of dams and rainwater harvesting. two types of dams are being constructed viz. recharge dams and flood protection dams. the recharge dams are constructed to enhance groundwater recharge through the use of valleys flood water which is often wasted in sea and desert. during 1985-2001, 39 recharge dams that have been constructed. about 14 flood protection dams are being constructed in musandam and muscat governorate to protect occupants of downstream areas from flood risks and can be used for recharge whenever possible (https://omanwires.com). 8 squ journal of agricultural and marine sciences, 2022, volume 27, issue 1 wheat production in oman: experiences, challenges and opportunities extension services the weak agricultural extension system is also a serious problem in getting the required production targets (maf, 2015). to attain self-sufficiency in food production, several projects were financed by the agricultural and fisheries development fund (afdf). the afdf has spent more than omr 1.0 million in three stages to develop the cultivation and production of wheat in the sultanate from 2006 to 2018 given of the importance of wheat crop to oman. the main objective was to expand the area under wheat cultivation to decrease the wheat import in the country. the afdf also provided support, guidance, high quality seed, and training to farmers in wheat cultivation to boost production. in addition to this, the basic tools and farm machinery were also provided to the farmers. advisory services are also provided on the use of machines (for sowing and harvesting). currently, the extension services in oman have introduced modern irrigation systems. with the sprinkler system, significant progress has been made in the expansion of crop cultivation and production. the ministry of agriculture, fisheries, and water resources has also issued a regulation to prohibit the use of agricultural lands for other purposes. challenges water scarcity water scarcity is a major problem in wheat production in oman. oman is an arid country as the mean annual rainfall is < 100 mm and pattern of rainfall are irregular from year to year and most of the months remain dry throughout the year (ahmed et al., 2013). however, in different parts of the country rainfall varies between 50 to 300 mm and salalah is the only area where monsoon rains occur. the country is divided into very dry and dry parts (hussain, 2005). many regions in oman are still characterized by a considerable year by year variability (e.g., central, northern, and southern areas, and south-eastern coast). in several regions, the monsoon climate and rainfall seasonality strengthen the impacts and effects of climate change. along the south-eastern coast, the recorded rainfall in autumn-winter is three times higher than the spring-summer. however, the summer and spring rainfall is equal to half of the autumn-winter rainfall. generally, in the central and northern regions, the distribution of rainfall throughout the year is more evenly spread. the irrigated areas in oman have been limited due to challenging climate mainly water scarcity (zhou et al., 2010). moreover, the environmental conditions are more unfavourable where human activities, vegetation, and grazing affect local environmental conditions. indeed, the status of the natural resources as soil, vegetation, and water resources has been changed owing to production activities and increase in aridity. moisture deficit stress affect wheat growth at all stages and cause yield losses, however, flowering and grain-filling phases are more critical. the reduction in grain yield occurs as drought stress causes a decrease in net photosynthesis due to limitations in metabolic activities, stomatal closure, oxidative damage, and poor grain development (farooq et al., 2014). in the country, crop production depends on wells (126 thousand ha) and aflaj (19 thousand ha) for irrigation (maf, 2013). the total water requirement of the country is 1430.2 million cubic meters, while available water is 1048.9 million cubic meters with the addition of 30 million cubic meters from sewage treatment annually and 8 million cubic meters from desalinization on daily basis contribute to the water need of the country. however, there is a short fall of 381.9 million cubic meters of the total water requirement (mrmwr, 2013). the most common irrigation technique is the traditional surface irrigation system covering 80% of the irrigated areas (fao, 2008). high temperature in summer, in the coastal areas, oman has a hot and humid climate, while the interior part has a hot and dry climate. the mean temperature in june in oman is usually 31-45°c, while in january temperature is mostly 20-25°c (https://weather-and-climate.com/average-monthly-rainfall-temperature-sunshine-in-oman). however, the temperature during the wheat sowing (15th-november to10th-december) is usually higher than 25°c. the optimum temperature for anthesis and grain filling in wheat ranged between 12-22°c and temperature above this optimal range significantly reduced the grain yield (farooq et al., 2011) owing to reduction in individual grain weight (prasad and djanaguiraman, 2014), which is due to leaf senescence and decreased grain filling duration (asseng et al., 2011; lobell et al., 2012). moreover, a high temperature decreased floret fertility by affecting pollen and pistil morphology (prasad and djanaguiraman, 2014). as the temperature increases, the solubility of carbon dioxide decreases which reduced carboxylation and enhances production of electrons to form reactive oxygen species and photorespiration (farooq et al., 2011). salinity salinity (both soil and groundwater) is another major bottleneck in successful wheat production in oman. of the total geographical area, 44% is salt affected and 70% of the agriculturally suitable land. the high temperature with little rainfall is main cause of salt accumulation in soil. the second cause of salt accumulation is the persistent use of saline groundwater by increased pumping (higher in batinah region-productive area for agriculture). the intrusion of saline seawater. in south al-batinah, 50% of the area is affected with slight to moderate salinity (ec > 4 ds m-1). in north al-batinah, about 50% of the total cultivated area is irrigated with water having ec > 3 ds m-1 and 38% with 9review paper farooq, aman ullah, al-hinai, nadaf, al-sadi, al-farsi, alkhamisi ec > 5 ds m-1 (maf and icba, 2012)). the country’s agriculture completely depends on irrigation and due to the absence of surface water bodies all irrigation occurs with groundwater drawn from sedimentary aquifers (springs). the use water level of the country now exceeds the long-term recharge (omezzine and zaibet, 1998; al-ajmi and abdel-rahman, 2001) which caused a decline of groundwater tables and intrusion of saline water into aquifers of the batinah and salalah coastal plains (victor and al-farsi, 2001; weyhenmeyer et al., 2002). in wheat, salinity stress reduced the growth and yield by decreasing the germination, photosynthesis, and transpiration rate along with an increase in sodium (na+) and cl-1 which disturbs the normal metabolic activities (jafar et al., 2014; tabasssum et al., 2017). during germination, salinity causes osmotic stress which imbalance the hormonal and enzymatic activities in seed reserves (jafar et al., 2014) leading to poor germination. under salinity stress, oxidative stress causes the production of reactive oxygen species as hydrogen peroxide, superoxide, and singlet oxygen which cause cellular damage to nucleic acid, proteins, and lipids in wheat (afzal et al., 2013; victor and al-farsi, 2001). low yielding varieties the cultivation of low yielding local landraces and varieties is one of the major reasons for the low yield of wheat in oman. in the past, the wheat varieties grown in the country had low yield potential and the first wheat variety cooley which was released in 1970 had a yield potential of 1.96 t ha-1. the potential yield of different wheat varieties (released from 1970-2019) varies between 1.96 to 5.2 t ha-1 (table 1). unavailability of climate resilient wheat genotypes as the climate of oman is harsh, therefore the climate resilient crops perform well under these climatic conditions. in the case of wheat, the climate resilient genotypes as tolerant to drought, salt, and heat stresses are not available. for salinity tolerance, a little work on the screening of wheat genotypes was done in 1990s. however, till now there is no wheat genotype reported which have been developed in oman for abiotic stress tolerance traits. lack of rainwater harvesting and water storage bodies there are 31 major recharge dams in the country since 1985 along with many small, structured dams which retain water at peak flows and are intended for groundwater recharge (fao, 2008). however, to the best of our limited knowledge, there is no water reservoir for rainwater harvesting and storage for use in crop production. lack of skilled farm labor most of the farming in the sultanate is subsistence farming where production is taken according to the family size or need. many farmers cultivate small areas using a channel for water in aflaj and the mountains. most of the farmers, use family labour or hired labour which is mostly not skilled. the labour, working in different farms, is mostly non-skilled who cannot identify the critical stages of the crop to save it from stresses/ losses as a critical stage of irrigation, fertilization, weeding, plant protection and harvesting. there is no regular training of the labour working on the farms. the use of skilled labour at the peak crop seasons (sowing, weeding, and harvesting) can help to increase crop production. modern farm machinery modern farm machinery is an important component of present-day agriculture to ensure food security. farm machinery covers all the machinery which is used in farming from start to end user of the output. however, the unavailability of modern farm machinery for wheat in the country is also a problem in fulfilling the national wheat requirement. according to the agricultural census of 2012-13, the equipment used by farmers are tractors, hand plough, and combine harvester (maf, 2013). the modern farm machinery e.g., seed drills, fertilizer drills, seed-cum fertilizer drills, bed planter, sub-soiler, boom sprayers, drip irrigation, mechanical weeder, and harvesters are not commonly available. substitution of wheat with fodder and vegetable crops about 89% of the farms contain less than 2 ha where mainly alfalfa and annual grasses and vegetables are grown which occupy 24.6% of the total arable land (maf, 2014). in 2015, the total fodder production was 1.77 mt, and more than half (53%) was in the form of perennial fodder crops. the rhodes grass was major fodder with 500,000 t (due to salt and drought tolerance) followed by alfalfa (278, 037 t), and sorghum (57,000 t). there was 54% increase in land area under fodder production between 2013 and 2105 with rhodes grass (60%) and alfalfa (56%) (oxford business group, 2020). in the case of vegetables, an increase of 19% was noted in 2015 than the last year. tomato was the leading vegetable crop with 116, 408 t production along with a 40% increase in area than 2014 (from 1296 ha to 1798 ha). the area under potato increased from 206 ha to 875 ha (oxford business group, 2020). however, a 30% decrease in the area (from 5600 ha in 2013 to 3910 ha in 2015) under field crops (wheat, barley, and maize) was noted (oxford business group, 2020). farm size another major factor in low wheat production in the sultanate is small landholding (< 2 ha) owing to the urbanization of different regions for residential colonies, infrastructure, and industrial purposes. the farm areas are shrinking due to population increase and conversion of farm areas to residential houses. as the 90% land10 squ journal of agricultural and marine sciences, 2022, volume 27, issue 1 wheat production in oman: experiences, challenges and opportunities holding size is < 2.02 ha and the landholding of > 4.05 ha are 5% (maf, 2013). moreover, the small landholder farmers cannot invest in farming due to less purchasing power for agricultural inputs, and competition with imported agricultural commodities. opportunities rainwater harvesting and storage rainwater harvesting is on-site accumulation of rainwater instead of running off that water. this can be collected from the roof tops or rivers/valleys. the construction of dams for rainwater harvesting and storage to collect the rainwater and to use that for wheat production can increase wheat production in the long run. the dams as small retention dams, cisterns, and quarry pits can be used to harvest rainwater. in the center and north of oman, the rainfall is received during winter season (november‒april), while in south of the country (dhofar), the summer monsoon (june‒september) rainfall (300 mm) is received (fao, 2008). this 300 mm rainfall water can be collected and stored for later use in wheat production. efficient irrigation system the use of traditional irrigation systems like wells and aflaj causes heavy losses of water due to leakage and high evaporation. however, water losses can be reduced in modern irrigation systems and increase the availability of groundwater (al-mamary and al-kalabani, 2010). efficient irrigation systems as drip irrigation and sprinkler irrigation systems are more productive in saving water and increasing crop production. according to the agricultural census of 2015-16, the 25 thousand ha (18%) of the total agricultural lands are irrigated with the modern irrigation system (maf, 2015-16). however, there is still sufficient potential to increase this area to modern irrigation systems. according to the ministry of agriculture and fisheries, the use of modern irrigation systems can improve farmers’ household income, crop availability in markets, and reduce water consumption (maf, 2011). however, the adaption rate of efficient irrigation systems is low which can be increased by subsidies and awareness campaign from the government. development of climate resilient and high yielding wheat genotypes the 50% of water in wheat is lost with evaporation which reduces water use efficiency, which causes a decrease in grain yield and total biomass (lopez-castaneda and richards, 1994). in instituto nacional, de investigaciones forestales, agrícolas y pecuarias (inifap) in mexico, the wheat breeding program had developed water efficient high yielding genotypes which are also rust resistant (solis et al., 2008), by the introduction of such varieties the wheat production in sultanate can be improved. moreover, the resistant wheat genotypes produce good yield under arid environmental conditions. in a screening study of 96 wheat genotypes under drought stress, the 15 genotypes (lm03, lm04, lm15, lm22, lm23, lm27, lm29, lm31, lm35, lm44, lm71, lm77, lm85, lm96, and lm100) performed very good under drought stress for yield production (mwadzingeni et al., 2016). the wheat genotypes tolerant to drought and heat stress are developed by cimmyt’ which are sm04, sm07, sm15, sm19, sm29, sm30, sm32, sm45, sm50, sm73, sm75, sm84, sm94, sm96, and sm97 (mkhabela et al., 2019), which can be grown in the country to get self-sufficiency in wheat production. the early maturing and high yielding climate resilient wheat genotypes produce higher yields under both optimal and suboptimal conditions. as in a study, mondal et al. (2016) evaluated the progress in breeding for early maturing and heat tolerant cimmyt wheat, adaption, and grain yield and found that early maturing and heat tolerant germplasm had higher grain yield than local check. the increase in grain yield in the genotypes varied between 104‒116% compared to the local check. under high temperature stress, early maturity is an excellent crop adaption mechanism in those regions where there is continuous high temperature (joshi et al., 2007; mondal et al., 2013). similarly, the screening of diverse wheat genotypes under the environmental conditions of sultanate oman can benefit similar results and the best performing genotypes can be further used in breeding programs. in our field adaption trial of 218 diverse wheat genotypes (collected from different parts of the world) conducted during 2019-2020 at agricultural experiment station, sultan qaboos university, oman, we found that out of these 218 wheat genotypes, 150 genotypes performed excellent regarding grain yield under the natural conditions of oman along with no disease attack (farooq et al.; unpublished data). breeding wheat genotypes for higher intercellular co2, photosynthesis, and water use efficiencies can increase grain yield and tolerance to drought and heat stress (ullah et al; unpublished data). the genetic potential of the existing national gene pool is very low as the genotypes developed from 1970 to 2019 have a yield potential of 1.96 to 5.2 t ha-1. this potential can be increased by crop improvement (breeding), through screening of diverse wheat genotypes and by regional adaptability of these diverse genotypes. there is a need to screen diverse wheat genotypes for adaptability different parts of the country. the elite genotypes can be used in the national breeding programs to further improve the wheat genotypes. for instance, in india, the introduction of improved wheat varieties has increased the grain yield by 27% (sonune and mane, 2018). in the sultanate, various wheat varieties are grown, locally known as a’sara’eea, al kuli, al hamira, al maysani, al walidi, al jareeda, and a’shuweira. these varieties are well-adapted to the local conditions. however, these varieties mature late, have low productivity, 11review paper farooq, aman ullah, al-hinai, nadaf, al-sadi, al-farsi, alkhamisi and are susceptible to diseases. the use of introduced wheat varieties, like wadi quriyat 110, a’sannin, wadi quriyat 226, wadi quriyat 302, and wadi quriyat 308 have shown good results for yield. the ministry of agriculture, fisheries and water resources distributed > 10 new varieties (as wadi quriyat 226, a’sannin, and wadi quriyat 308) to farmers in all governorates in the wheat growing season of 2018-2019. use of modern farm machinery in the success and adoption of a crop, the farm machinery is one of the key factors (ullah et al., 2020). farm mechanization is a tool to enhance the crop productivity and profitability (verma, 2006). the modern farm machinery as laser land leveler, seed drills, fertilizer drills, seed-cum fertilizer drills, bed planters, tractor mounted tillage implements, boom sprayers, drip irrigation, mechanical weeder, and combine harvester, etc. can help boost the wheat productivity. the use of precision agriculture tools can also help improve the wheat productivity by optimizing the input use (european agricultural machinery, 2020 ). there exists a huge potential to enhance wheat production in oman through use of modern farm machinery and precision agriculture tools. development and dissemination of site-specific package of production technologies the development and dissemination of site-specific production technologies package can boost wheat production in the country. for instance, late sowing of wheat causes a delay in germination, results in a sub-optimal plant population with a slower growth rate ends with a low grain yield due to sub-optimal temperature at sowing and at the reproductive stage. similarly, selecting a wrong variety (not well-adapted), subor supra-optimal seed rate, imbalanced fertilizer use, overor under use of irrigation water, lack of plant protection measures, and poor harvesting measures caused significant yield reduction. developing, disseminating and adopting of a site-specific package of production technology can help increase grain yield significantly. for example, a 33% increase in wheat grain yield was recorded in a production technology transfer study of wheat in faizabad district of uttar pradesh, india (singh et al., 2016). therefore, the development and dissemination of site-specific wheat production technology should be prioritized to increase wheat production in the country. seed enhancements seed enhancement is the application of nutrients, fertilizer, microbes, and other chemicals through seed to improve the performance, yield, and quality of crops (farooq et al., 2012). the poor plant population is one of the major reasons for low wheat yield in many situations. . adverse field and environmental conditions, like soil salinity, above than temperature and soil moisture deficit, may affect the crop stand establishment that then affects the crop growth and yield. under such circumstances, seed enhancement (priming and coating) is a cost-effective option to improve the germination, quality of seed and grain yield. seed priming improves germination through earliness, uniformity, and better seedling emergence (farooq et al., 2019). moreover, seed priming with zn and plant growth promoting rhizobacteria (pgpr) enhanced the grain yield in wheat (rehman et al., 2018 a, b). similarly, seed priming with mn increased the grain yield of wheat (ullah et al., 2018). seed coating is an application of growth regulators, nutrients, and pesticides at the surface of seed through some stick material (farooq et al., 2012). the increase in grain yield in many field crops as wheat, rice, chickpea, and cowpea through seed coating has been reported (masuthi et al., 2009; rehman and farooq, 2016; ullah et al., 2017, 2018; farooq et al., 2018). the application of zinc seed coating (1.25‒1.50 g zn kg-1 seed) in wheat improved the emergence, grain yield, and quality of grains (rehman and farooq, 2016). conclusion the production of bread wheat in oman is less than 1% of the domestic requirements. water deficits, salinity, heatwaves, prolonged droughts, unavailability of high yielding and stress resilient genotypes, and small and fragmented landholdings are major challenges of wheat production in oman. crop improvement programs should be initiated to develop high yielding, disease resistant and climate resilient wheat varieties well adapted to local conditions. high efficiency irrigation, principles of conservation agriculture, and seed enhancements may be included in the development and dissemination of site-specific packages of production technology. strengthening the system of certified seed distribution and effective extension services may help farmers improve wheat productivity and profitability. acknowledgements the financial support received to conduct this study from ‘his majesty trust fund’ sultan qaboos university (sr/agr/crop/19/01) is acknowledged. references afzal i, basra sma, cheema ma, farooq m, jafar mz, shahid m, yasmeen a. 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(2006). impact of agricultural mechanization on production, productivity, cropping intensity income generation and employment of labour. status of farm mechanization in india 2006: 133-153. victor r, al-farsi aa. (2001). water quality and invertebrate fauna of farm wells in an area affected by salinization in oman. journal of arid environments 48(3): 419-28. 15review paper farooq, aman ullah, al-hinai, nadaf, al-sadi, al-farsi, alkhamisi weyhenmeyer ce, burns sj, waber hn, macumber pg, matter a. (2002). isotope study of moisture sources, recharge areas, and groundwater flow paths within the eastern batinah coastal plain, sultanate of oman. water resources research 38(10): 1184. zhou, y., yang, h., mosler, h. j., & abbaspour, k. c. (2010). factors affecting farmers’ decisions on fertilizer use: a case study for the chaobai watershed in northern china. consilience. journal of sustainable development, 4(1), 80-102. https://doi.org/10.7916/ d8c24wt5. img058 img059 img060 img061 img062 img063 img064 img065 img066 img196 img197 img198 img199 img200 img206 img207 img208 img209 img210 img211 img212 img213 research paper journal of agricultural and marine sciences vol. 22 (1): 67-74 doi: 10.24200/jams.vol22iss1pp67-74 received 20 mar 2016 accepted 25 dec 2016 effect of sugar replacement with date paste and date syrup on texture and sensory quality of kesari (traditional indian dessert) chandini s. kumar1, annamalai manickvasagan1* and zaher h. al-attabi2 1* a. manickavasagan ( ) sultan qaboos university, college of agricultural and marine sciences, dept. of soils, water and agricultural engineering, box 34 al-khod 123, sultanate of oman. email: manick@ squ.edu.om. 2dpt. of food science and nutrition. box 34, al-khod 123. sultanate of oman. introduction kesari is a popular semolina-based sweet which is commonly included in many varieties of south indian meals. it is also consumed in north india as ‘sheera’ and ‘sooji’ halwa. a different version of this sweet is also common in nepal, bangladesh, pakistan, afghanistan and other countries like albania, azerbaijan, bulgaria, cyprus, greece, montenegro, macedonia and turkey. kesari is generally made with wheat semolina, sugar and ghee. also dry fruits, nuts and saffron are often added in different regions (banu et al., 2013). sugar is an important ingredient in the preparation of enumerable sweets. it has many functional properties in foods such as bulking agent, preservative, texturizer, humectant, dispersing agent, stabilizer, fermentation substrate, flavor carrier, browning agent and decorative agent (pai, 2006). in the recent years there has been a lot of concern about the excessive consumption of sugar, and its effect on health. scientific evidence demonstrates that excessive added sugar increases the risk of overweight, obesity, cardiovascular diseases, dyslipidemia, high blood pressure, tooth decay, nutrient deficiencies, and may cause hypoglycaemia and hyperactivity in children and in sensitive people (lustig et al., 2012). the world health organization recommends limiting added sugar intake to <10% of total energy (world health organization, 2003). the food guide from the united states department of agriculture (usda) recommends consumption of added sugar in the range of 6 to 10% of total energy. to minimize the intake of added sugar, and enjoy the delicious sweet taste, the natural sugar from the fruits would be the ideal solution. fruits in its various forms have the potential to blend with the ingreأتثري استبدال السكر بعجينة التمر والدبس على امللمس واجلودة احلسية للحلوى اهلندية التقليدية )كيساري( تشانديين س. كومار1 وأنامالي مانيكافاسجان1* وزاهر العطايب1 abstract. in this study, a popular indian dessert, kesari, was reformulated by substituting refined sugar at various levels (0%=control, 25%, 50%, 75% and 100%) with date past and syrup, and changes in instrumental texture profile, l*a*b* colour values and sensory properties were determined. the hardness of date syrup kesari was higher than that of date paste kesari. however, there were no differences in hardness among various levels of replacement. there were no differences between syrup vs paste products or among various levels of replacements in cohesiveness, springiness, gumminess, adhesiveness and chewiness of kesari. the developed kesari scored 5.5 to 7.5 on a 9 level hedonic scale (like slightly-like moderately) in all sensory attributes. replacement of sugar at 75% and 100% levels, significantly lowered the scores for most of the sensory attributes. around 50% of the panellist in informed sensory, selected 50% replaced products (paste or syrup) as their first choice. keywords: date paste; date syrup; texture; sweetness; colour; kesari. امللخــص: يف هــذه الدراســة، مت تغيــر مكونــات حلــوى هنديــة شــعبية يطلــق عليهــا كيســاري، عــن طريــق اســتبدال الســكر املكــرر بنســب خمتلفــة )٪0، 25٪، 50٪، 75٪ و 100٪( بعجينــة التمــر والدبــس، مت حتديــد التغــرات يف امللمــس، واللــون l * a * b * واخلصائــص احلســية. وجــد أن صالبــة حلــوى الكيســاري املضــاف إليهــا الدبــس كان أعلــى مــن تلــك املنتجــة بإضافــة عجينــة التمــر. ومــع ذلــك،مل تكــن هنــاك اختالفــات يف صالبــة املنتــج بــن خمتلــف النســب املضافــة. كذلــك مل تكــن هنــاك اختالفــات بــن تلــك املنتجــة بإضافــة الدبــس أو عجينــة التمــر أو بــن النســب املختلفــة منهمــا يف التماســك، واملرونــه، وااللتصــاق واملضــغ. وقــد ســجلت احللــوى املطــورة معــدل 5.5 إىل 7.5علــى مقيــاس هيدونيــك 9 )أفضلــه قليــال أفضلــه معتــدل( يف مجيــع الســمات احلســية.إن اســتبدال الســكر بنســبة 75٪ و 100٪ ، خفضــت بشــكل كبــر القيــم ملعظــم الصفــات احلســية. وجــد أن حــوايل ٪50 مــن املشــاركن يف التقيــم احلســي والذيــن مت اطالعهــم عــن املنتــج مســبقا، اختــاروا املنتــج )عجينــة أو دبــس( الــذي بــه نســبة اســتبدال تقــدر بـــ 50٪ مــن بقيــة املنتجــات كخيارهــم األول. الكلمات املفتاحية: عجينة التمر; الدبس، امللمس ; طعم حلو; اللون، كيساري 68 squ journal of agricultural and marine sciences, 2017, volume 22, issue 1 effect of sugar replacement with date paste and date syrup on texture and sensory quality of kesari dients of many products both at home-preparation and industry level. there are abundant opportunities to use fruit concentrate, dried fruits and fruit powder in various food preparations to replace added sugar and add sweet taste with several healthy bioactive compounds. dates are ideal fruits to substitute added sugar in foods. in the present study sugar was replaced by date syrup and paste in the development of kesari. date is a delicious fruit with sweet taste and fleshy mouth feel. dates consist of about 70% sugar (sucrose, glucose, and fructose) and are rich in dietary fibre, phenolic compounds and vitamins. scientific studies have shown that dates and their aqueous extracts have demonstrated the free radical scavenging activity, inhibition of free radical-mediated macromolecular damages, antimutagenic, and immunomodulatory activities (vayalil, 2002; al-farsi and lee, 2012; saafi et al.,2009). traditionally, dates have been considered as the staple food in the arab gulf regions. they are mainly consumed fresh or dried. in the processed form, they are consumed as paste, syrup, pickles, jams, jellies, and are used in many bakery and confectionary products together with chocolate, coconut, honey, vinegar, and others (al-hooti et al., 1997; besbes et al., 2009; manickavasagan et al., 2012, benmeddour, et al., 2013; abessa et al., 2013). manickavasagan et al. (2013) added date paste, syrup and chopped dates in idli preparation by substituting dates with sugar as an accompaniment. manickavasagan et al. (2014) substituted sugar with date paste and syrup in the fermentation of appam batter. eullech et al. (2014) improved halva quality using date fiber from date pulp. aboubacar et al. (2010) used date syrup to replace sugar in muffin. sidhu et al. (2003) used dates to substitute sugar in pan bread. however, there are no reports using dates in any of the traditional indian desserts. the objective of the present work was to substitute sugar with date paste and syrup in kesari preparation and determine their effect on the texture, colour and sensory quality. materials and methods materials semolina (approximate particle size of 300-700 µm; dahabi, oman flour mills company, muscat, sultanate of oman), ghee (almarai, almarai company, riyadh, kingdom of saudi arabia), date fruit (khalas variety, procured from local market), date syrup (national dates, national united manufacturing company llc, sultanate of oman) and sugar were purchased from a supermarket in muscat, sultanate of oman. methods preparation of date paste to make paste, the date fruits (pitted) were soaked in warm water (40°c) for 1h to soften the flesh. the flesh was ground in a mixer grinder (m/s panasonic, model mx-ac2105, panasonic corp., india) until a smooth homogenous paste was obtained (sanchez-zapata et al., 2011). preparation of kesari bath control kesari: semolina with 5 g of ghee was roasted at 140°c for 3 min. to 15 g of melted ghee, water was added (semolina to water ratio, 1:6 (w/w)). to the boiling water and ghee mixture roasted semolina was added gradually, while stirring continuously. once semolina was cooked, sugar was added (semolina to sugar ratio, 1:1 (v/v)). an additional 15 g of ghee were added and stirred. reformulated kesari: similar to control, kesari bath was prepared using date syrup and paste as sweetening agent using the same raw materials and procedures except the white sugar was replaced by increasing proportion of date syrup and paste (25, 50, 75 and 100%) . the amount table 1. textural attributes of kesari prepared with date paste and syrup (n=3). product hardness cohesiveness springiness gumminess adhesiveness chewiness control (100:0) 4.44 ± 2.73 0.13 ± 0.01 0.30 ± 0.09 0.95 ± 0.15 0.23 ± 0.08 0.25 ± 0.09 75:25 4.57 ± 2.30 0.11 ± 0.01 0.404 ± 0.09 0.73 ± 0.44 0.24 ± 0.02 0.27 ± 0.09 50:50 4.69 ± 2.84 0.13 ± 0.01 0.343 ± 0.11 0.87 ± 0.44 0.27 ± 0.06 0.27 ±0.08 25:75 4.78 ±3.66 0.15 ± 0.01 0.314 ± 0.14 1.34 ± 0.71 0.30 ± 0.07 0.36 ± 0.06 0:100 4.82 ±2.99 0.47 ± 0.05 0.274 ± 0.08 1.44 ± 0.41 0.33 ± 0.03 0.19 ±0.04 date paste kesari 75:25 4.57 ± 0.89 0.11 ± 0.01 0.35 ± 0.04 0.50 ± 0.12 0.25 ± 0.09 0.17 ± 0.04 50:50 4.64 ± 1.03 0.11 ± 0.03 0.32 ± 0.05 0.37 ± 0.06 0.30 ± 0.07 0.12 ± 0.02 25:75 4.67 ± 0.95 0.11 ± 0.05 0.30± 0.05 0.82 ± 0.18 0.51 ± 0.10 0.24 ± 0.05 0:100 4.15 ± 0.57 0.10 ± 0.01 0.29 ± 0.03 1.62 ± 0.61 1.50 ± 0.53 0.73 ± 0.64 69research article kumar, manickavasagan, al-attabi of date syrup and paste added was calculated based on the sugar content of dates (70%.) the entire experiment was done in triplicates (n=3). texture measurement a texture analyzer (model ta xt2i, stable micro systems, surrey, england) was used to measure the forcetime curve using the two-cycle compression test (rahman and al-farsi, 2005). a plate (diameter 7.5 cm) compressed the kesari cube (10 mm × 10 mm × 10 mm) placed on a mounted fixed table. the load cell was calibrated with a 5 kg weight. the equipment was set to zero automatically lowering the plate until the bottom surface of the plate just contacted the table before each experiment. then the crosshead was allowed to descend at the rate of 2 mm/s to a total deformation 3 mm (70% compression). when the compression stroke was completed, plunger abruptly reversed its direction and started upward stroke at 5 mm/s. then a second (down and up) cycle was run on the same sample. all operations were automatically controlled by the texture analyzer. the compression depth was held constant at 3 mm in all experiments. the instrument automatically recorded the force-displacement or force-time curve. the experiment was conducted in triplicates (n=3). colour measurement colour of kesari samples was measured using hunter lab colour measuring system (labscan xe, hunter associates laboratory, reston, usa). values were measured in terms of l* (lightness), a* (+a* : red, -a* : green), and b* (+b* : yellow, -b* : blue) values. sensory analysis evaluation sheet the samples were evaluated on a 9 level hedonic sensory scale (1like extremely, 2 – like very much, 3 – like moderately, 4 – like slightly, 5 – neither like nor dislike, 6 – dislike slightly, 7 – dislike moderately, 8 – dislike very much, 9 – dislike extremely). the panellists were asked to test 9 attributes of the products and give a score on the hedonic scale. the attributes were: appearance (colour, surface smoothness), mouth feel (softness, chewiness, solubility, sweetness, taste), aroma and overall acceptability. the panellists were also asked to select their first choice among the given products. panel and sensory the untrained panellists were randomly selected from a pool of undergraduate students and employees at sultan qaboos university (n=40). two types of sensory tests (informed and blind) were conducted in four batches (10 people in each batch; total 20 blind and 20 informed). the panellists were within the age range of 19 to 50. for blind sensory evaluation, no product information was provided to the panellists, and coded samples were given, whereas in the informed sensory evaluation, the panellists were explained about the ingredients of these products. the actual names were given to the samples in informed sensory evaluation. this study was conducted at the ‘‘sensory and food preparation laboratory’’ of the college of agricultural and marine sciences at sultan qaboos university. statistical analysis the effect of date type and replacement level on individual attribute of instrumental texture and sensory quality was studied by analysis of variance (anova) using factorial design models with the general linear model (glm) procedure using statistical analysis system software (sas, version 8.02, sas institute, inc., cary, nc). two factorial model (2 date products (date paste * date syrup) × 5 replacement levels (0% * 25% * 50% * 75% * 100%)) for texture analysis and three factorial model (2 date products (date paste * date syrup) × 5 replacement levels (0% * 25% * 50% * 75% * 100%) × 2 sensory type (blind * informed)) for sensory analysis were used. in each textural and sensory attribute, the differences within levels was tested at 95% confidence interval (α= 0.05) by the least significant difference (lsd) method of comparison of mean. the colour values of the reformulated products were compared with control and each other using t – test at 5% significance level. table 2. mean values (standard deviation) of hunter colour determinant (l*, a*, b*) of kesari prepared with date paste and syrup (n=3). l* a* b* control (100:0) 75. 02 a (2.56) -2.47a (0.20) 11.74 a (0.69) date syrup kesari 75:25 55.71 be (0.69) 0.97b (0.08) 11.92a (0.52) 50:50 53.07 be(3.46) 1.32 c (0.11) 11.88ab (1.81) 25:75 44.08 c (4.58) 2.43dg (0.32) 12.99 ab (0.02) 0:100 42.77 c (0.56) 3.30e (0.22) 13.77b (0.04) date paste kesari 75:25 66.60 d (2.56) 0.68f (0.07) 11.13a (0.52) 50:50 63.99 d (0.94) 2.28d (0.04) 11.88a (0.58) 25:75 61.65 d (2.14) 2.63g (0.14) 11.82a (0.83) 0:100 57.24de(2.69) 3.09he (0.19) 13.06b (0.82) 70 squ journal of agricultural and marine sciences, 2017, volume 22, issue 1 effect of sugar replacement with date paste and date syrup on texture and sensory quality of kesari results and discussion instrumental texture profile texture attributes of kesari as affected by replacement of sugar with date syrup and paste at various levels (0, 25, 50, 75 and 100%) are given in table 1. the values were 4.15-4.82 n, 0.10-0.47, 0.27-0.40, 0.37-1.62, 0.231.50, 0.12-0.73 for hardness, cohesiveness, springiness, gumminess, adhesiveness and chewiness, respectively. the hardness of the reformulated kesari with date syrup was significantly higher than that of date paste. otherwise, there were no differences in any other texture figure 1. visual aspect of kesari prepared with different concentrations of date paste and syrup as replacement for white sugar. table 3. mean value (standard deviation) of sensory scores given by 20 panellists during a blind test. values correspond to a 9 -level hedonic scale from 1: like extremely to 9: dislike extremely. appearance mouth feel sugar (%) colour surface smoothness softness chewiness sweetness solubility taste aroma overall acceptability control (100:0) 7.55 (1.28) 7.20 (1.20) 7.00 (1.26) 7.05 (1.47) 7.00 (1.30) 6.8 (1.64) 7.15 (1.31) 6.60 (1.57) 7.10 (1.12) date syrup kesari 75:25 7.15 (0.93) 7.25 (1.12) 6.70 (1.56) 6.85 (1.46) 6.10 (1.12) 6.45 (1.57) 6.50 (1.36) 5.95 (1.43) 6.50 (1.19) 50:50 7.05 (1.10) 7.15 (1.09) 6.90 (1.17) 7.00±1.45 6.90 (1.33) 6.65 (1.50) 6.70 (1.53) 5.95 (1.19) 7.00 (1.30) 25:75 7.15 (1.27) 6.90 (1.12) 7.00 (1.41) 6.85 (1.46) 6.70 (1.81) 6.50 (1.54) 7.00 (1.59) 6.60 (1.35) 7.00 (1.56) 0:100 7.25 (1.02) 7.00 (1.41) 7.05 (1.19) 7.00 (1.17) 6.80 (1.20) 6.40 (1.60) 6.80 (1.28) 6.40 (1.23) 6.80 (1.28) date paste kesari 75:25 6.80 (1.28) 6.6 (1.35) 6.60 (1.10) 6.05 (1.47) 6.50 (1.47) 6.75 (1.21) 6.70 (1.30) 6.15 (1.14) 6.90 (1.12) 50:50 7.15 (1.04) 6.55 (0.94) 6.60 (0.99) 6.35 (1.42) 6.55 (1.28) 6.50 (0.83) 6.80 (1.28) 5.85 (0.88) 6.85 (1.04) 25:75 6.55 (0.60) 6.50 (0.95) 6.90 (1.07) 6.30 (1.66) 6.65 (1.81) 6.60 (1.23) 6.50 (1.15) 6.15 (1.27) 6.70 (1.13) 0:100 6.45 (0.94) 6.20 (1.54) 6.75 (1.25) 6.20 (1.70) 6.20 (1.74) 6.20 (1.36) 6.05 (1.43) 6.40 (1.43) 6.30 (1.59) 71research article kumar, manickavasagan, al-attabi attribute between date types (paste vs syrup) or within replacement levels. this indicates that date paste or syrup can be used to replace sugar without affecting the texture profiles of kesari. hashim et al. (2009) fortified yogurt with date fiber, and reported that it was harder than control yogurt. instrumental colour the l*a*b* colour values of the reformulated kesari with date paste and syrup are shown in table 2. addition of date paste and syrup affected the colour of kesari. significant reduction in the l* value in reformulated products from the control was observed. in date paste kesari, there were no differences in l* values between replacement levels, however, it decreased with increasing replacement levels in syrup kesari. melanins in dates are responsible for the dark colour (roufegari-nejad, 2002). an increase in dark colour may also be associated with increase in the antioxidant potential (anese et al., 1999). the ‘a’ value increased with replacement levels in both paste and syrup products. the red index (+a) could be related to the tannins that develop dark colour due to non-enzymatic millard reaction that takes place during postharvest storage and handling (roufegari-nejad 2002). hashim et al. (2009) reported that addition of date fiber in yogurt decreased l* and increased a* values. the ‘b’ value in 100% replaced syrup and paste kesari products were significantly higher than the remaining products (without any difference among them). sensory characteristics the effects of replacement of sugar with date syrup and paste on the sensory characteristics of kesari are presented in tables 3 and 4. the sensory type (blind vs informed) did not have significant effect on the sensory scores of individual attribute except aroma. similarly, the date product (paste vs syrup) did not affect the sensory attributes except surface smoothness. appearence the sensory scores for the colour attribute varied between 6.5 and 7.6 representing like moderately to like very much for all the samples. there were no differences in colour among all levels of replacement and control except 100% products. the 100% replaced products scored significantly lower colour value than other products. similar trend was observed by aboubacar et al. (2010) in muffins prepared with date syrup did not affect the colour up to 50%, but scored lower than control muffin while adding more syrup. the traditional colour of the kesari normally varied based on regions. in some areas, it is prepared without any colourant, and the product looks white; whereas in other places some food colourants (yellow to orange) are added. the surface smoothness score for kesari was in the table 4. mean value (standard deviation) of sensory scores given by 20 panellists during an informed test. values correspond to a 9 level hedonic scale from 1-like extremely to 9-dislike extremely. appearance mouth feel sugar (%) colour surface smoothness softness chewiness sweetness solubility taste aroma overall acceptability control (100:0) 7.55 (1.28) 7.20 (1.20) 7.00 (1.26) 7.05 (1.47) 7.00 (1.30) 6.80 (1.64) 7.15 (1.31) 6.60 (1.57) 7.10 (1.12) date syrup kesari 75:25 7.15 (1.14) 6.85 (1.27) 6.55 (1.54) 6.90 (1.07) 6.95 (1.00) 6.35 (1.42) 6.75 (1.16) 6.60 (1.27) 6.95 (1.32) 50:50 7.75 (1.02) 7.15 (0.81) 7.00 (1.08) 6.80 (1.06) 7.35 (1.18) 6.85 (1.18) 7.60 (1.14) 6.90 (1.25) 7.40 (0.94) 25:75 7.20 (0.89) 6.65 (0.75) 6.60 (0.94) 6.50 (1.05) 6.50 (1.61) 6.30 (1.03) 6.55 (1.47) 6.35 (1.18) 6.60 (1.39) 0:100 6.15 (1.95) 5.80 (1.36) 6.20 (1.24) 5.60 (1.35) 5.75 (1.83) 5.55 (1.32) 5.55 (1.73) 6.05 (1.50) 5.65 (1.84) date paste kesari 75:25 6.95 (1.27) 6.70 (1.54) 6.85 (1.07) 7.05 (1.00) 6.55 (1.42) 6.85 (1.16) 6.45 (1.27) 6.90 (1.32) 6.90 (1.12) 50:50 7.10 (0.81) 7.30 (1.08) 7.20 (1.06) 7.85 (1.18) 7.00 (1.18) 7.95 (1.14) 7.20 (1.25) 7.60 (0.94) 6.85 (1.04) 25:75 6.85 (0.75) 6.95 (0.94) 6.70 (1.05) 7.20 (1.61) 6.80 (1.03) 7.15 (1.47) 6.75 (1.18) 6.85 (1.39) 6.70 (1.13) 0:100 5.90 (1.36) 6.00 (1.24) 6.10 (1.35) 5.90 (1.83) 5.45 (1.32) 5.55 (1.73) 6.40 (1.50) 5.50 (1.84) 6.30 (1.59) 72 squ journal of agricultural and marine sciences, 2017, volume 22, issue 1 effect of sugar replacement with date paste and date syrup on texture and sensory quality of kesari range of 5.8 to 7.3. the score was lower for the products blended with paste than that of syrup. this may be due to the presence of dark specs of dates skin and fibre in the product (fig. 1). products blended with dates (syrup and paste) up to 50% did not differ from the control products. but 75% and 100% products scored significantly lower than control products. manickavasagan et al. (2013) also noticed dark specs in idlis prepared with chopped dates, which scored lower than control. in general, kesari is expected to be smooth, free from any charred or burnt particles and lumps. mouth feel softness. the kesari products with 100% sugar replacement had significantly lower score for softness than control and other products (no difference among them). in another study while replacing white sugar with date syrup, aboubacar et al. (2010) determined that up to 50% replacement of white sugar with date syrup produced similar texture and acceptance rating to that of control muffins. chewiness. the chewness score for kesari were in the range of 5.6 to 7.2. the products blended with 75% and 100% dates scored significantly lower than control and other produtcs. replacement of sugar with dates up to 50% did not affect the chewiness of kesari. sweetness. the sweetness scores of kesari ranged between 5.8 to 7.4. kesari prepared with 100% dates perceived as less sweeter than other products (no diffences between control and other levels of replacements). gouhari et al. (2005) investigated the possibilities of using date syrup to replace sucrose in ice cream at various levels of substitution (0 to 100%) and determined that up to 50% replacement did not affect the sensory properties. solubility. the scores given by the pannellists for solubility of kesari was in the range of 5.5 to 7.0. the kesari blended with 100% dates scored significantly lower than remaining products. taste. the score for the taste was from 5.6 to 7.2 during sensory evaluation. similar to other attributes, 100% replacement kesari scored lesser value than other products. aroma. the aroma of the kesari products were from 5.9 to 7.2. the score was significantly higher in the informed test than blind sensory evaluation. this indicates that panellists with prior information on the the ingredients prefer the aroma of dates. also there was no difference in aroma of reformulated products at all levels and control. the overall acceptability of kesari products were between 5.5 and 7.6. the acceptability score was significantly lower for 100% replaced products than other products. therefore, it may not be possible in kesari products to make complete replacement of sugar with dates. however, in some products, 100% replacement of sugar with dates are achievable. for example, sidhu et al. (2003) used date syrup to replace sucrose in pan bread formulations (0 to100% replacement), and determined that in spite of lower score in crumb colour of date syrup pan bread, there were no significant differences in texture and overall acceptability of control and date syrup pan breads. in blind sensory evaluation, the first choice (most preferred product) was spread to almost all products except 25% replaced products. less than 5% of the panellists prefered 25% replacement products (paste and syrup) category (fig 2). however, during informed evaluation, around 50% of the panellists opted 50% replacement products (syrup or paste) as their first choice. it is eveident that the product information and their health benefits must be clearly informed to the people to promote healthy products. bowar and saadat (1998) stated that blind sensory evaluation alone cannot reflect the real food selection, evaluation and acceptance, thus product label information must be provided in this type of studies 0 10 20 30 40 control 25% 50% 75% 100% date syrup/paste addition p re fe re nc e (% )− b lin d te st type paste syrup figure 2. first choice chosen by panellists in blind (left) and informed (right) sensory tests with n=20 panellists for each test. 0 10 20 30 40 50 control 25% 50% 75% 100% date syrup/paste addition p re fe re nc e (% )− in fo rm ed te st type paste syrup 73research article kumar, manickavasagan, al-attabi conclusion although substitution of sugar with dates in kesari did not affect most of the instrumental textural attributes, the colour values were greatly affected even at 25% replacement level. the sensory attributes were not affected up to 50% replacement level in both date syrup and paste. in informed sensory, the explanation about ingredient information and their health benefits before sensory test significantly affected the panellist’s selection of the first choice product. further research must be carried out on the reformulation of various traditional desserts with dates and other fruits. similarly industries should investigate the potential of new products with fruits as sweetener. it may not be possible to replace 100% added sugar in certain products; however it is still better to launch new products with partial replacements. it is also important to create awareness among people to include the fruit based products in their diet. acknowledgements this study was supported by squ internal grant no. ig/agr/ swae/14/01 (nutrification of traditional desserts with omani dates). the authors thank sawsana al-rahbi for her assistance in texture analysis and srirangu rayar for his assistance in sensory analysis. references al-hooti s., sidhu j.s., qabazard h. 1997. physicochemical characteristics of five date fruit cultivars grown in the united arab emirates, plant foods for human nutrition, vol.50, kluewer academic publisher, netherland, issn:0921-9668, pp.101–113. al farsi, m. and young, l.c., 2012. dates-production, processing, food and medicinal values, crc press, london, chapter no.25, pp. 351. aboubacar, a., hashim, i.b. and afifi, h.s. 2010. quality characteristics of muffin containing date syrup as sweetener. poster presented in fourth international date palm conference (fidpc), march 15 – 17 abu dhabi, uae. abbèsa, f., kchaoua, w., bleckerb c., ongenac, m., lognayd, g., attia, h. and besbesa, s. 2013. effect of processing conditions on phenolic compounds and antioxidant properties of date syrup, industrial crops and products, vol.44, elseivier science, london, issn:0926-6690, pp.634– 642. anese, m., manzocco, l., nicoli, m., lerici, c.r. 1999. antioxidant properties of tomato juice as affected by heating, journal of the science of food and agriculture, vol.79, jhon wiley & sons, new york, issn: 1097-0010, pp.750-754. arya, s.s., thakur, b.r. 1986. instant halwa (kesari bath) mix-storage stability and packaging requirements, indian food industry, vol.5, afst(i), india, issn: 0975-8402, pp.119-121. banu, h.n.i., 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polishing of rice on quality parameters of idli. journal of sensory studies, 20: 397-409. elleuch, m., bedigian, d., maazoun, b., besbes, s., blecker, c. and attia, h. 2014. improving halva quality with dietary fibres of sesame seed coats and date pulp, enriched with emulsifier. food chemistry, 145: 765–771. gouhari, a.a., habibinajafi, m.b. and hadad, k.m.h. 2005. effect of date syrup as a substitute for sugar on the physicochemical and sensory properties of soft ice cream. iranian food science and technology research journal, 1: 3-32. hashim, i.b., khalil, a.h. and afifi, h.s. 2009. quality characteristics and consumer acceptance of yogurt fortified with date fiber. journal of dairy science, 92: 5403-5407. lustig r., schmidt l.a.and brindis c.d. 2012. the toxic truth about sugar. nature, 482: 27-29. manickavasagan a. 2012. dates-production, processing, food and medicinal values, crc press, london, chapter 22, pp. 351. manickavasagan, a., teena, a.m., al-attabi, z.h. and al-zakwani, i.m. 2013. dates as substitute for added sugar in traditional foods – a case study with idli. emirates journal of food and agriculture, 25: 899906. manickavasagan, a., chandini, s.k., sivakumar, a. and pratibha r. 2014. effect of dates on fermentation of appam batter. journal of pure and applied microbiology, 8: 1-7. martín-sánchez, a.m., ciro-gómez, g., sayas, e., 74 squ journal of agricultural and marine sciences, 2017, volume 22, issue 1 effect of sugar replacement with date paste and date syrup on texture and sensory quality of kesari vilella-esplá, j., ben-abda, j.j. and pérez-álvarez ,a. 2013. date palm by-products as a new ingredient for the meat industry: application to pork liver pâté. meat science, 93: 880-887. pai, j.s. 2006. traditional indian foods: physico chemical aspects, bulletin pfndai (protein foods and nutrition development association of india), india, pp.1-2. rahaman, m.s. and al-farsi, s.a. 2005. instrumental texture profile analysis (tpa) of date flesh as a function of moisture content. journal of food engineering, 66: 505-511. roufegari, n. 2002. the examination of colored compounds from date syrup and their elimination, master degree thesis, food science and technology department, faculty of agriculture tabriz, iran. saafi, e.b., el-arem, a., issaoui, m., hammami, m.and achour, l. 2009. phenolic content and antioxidant activity of four date palm (phoenix dactylifera l.) fruit varieties grown in tunisia. international journal of food science and technology, 44: 2314–2319. sidhu, j.s., al-saqer, j.m., al-hooti, s.n. and al-othman a. 2003. quality of pan bread made by replacing sucrose with date syrup produced by using pectinase/ cellulase enzymes. plant foods for human nutrition, 58: 1–8. vayalil, p.k. 2002. antioxidant and antimutagenic properties of aqueous extract of date fruit (phoenix dactylifera l. arecaceae), journal of agriculture and food chemistry, 50: 610–617. world health organization (who). 2003. food and agriculture organization of the united nations, expert consultation, diet, nutrition and the prevention of chronic diseases. who technical support series no. 916, chapter no. 4, pp.30, world health organization, geneva, switzerland. research paper journal of agricultural and marine sciences 2023, 28(1): 47–61 doi: 10.53541/jams.vol28iss1pp47-61 received 20 july 2022 accepted 22 august 2022 evaluation of the intestinal bacterial community of local omani and cobb 500 broiler chickens raised in an open-sided house using 16s rdna-based analysis mai a s al-balushi1, yasmin el tahir1, muhammad n asi1, hani m. el-zaiat1,2, mohammed a al-abri1, kaadhia al-kharousi1 and waleed al-marzooqi1,* waleed al-marzooqi1,*( ) walmar@squ.edu.om,1department of animal and veterinary sciences, college of agricultural and marine sciences, sultan qaboos university, muscat, sultanate of oman, 2department of animal production, faculty of agriculture, university of alexandria, alexandria, egypt. introduction local chicken production has contributed signifi-cantly as sources of protein, food security and source of income in communities with limited resources (al-jumaili et al., 2020). local chicken production is among the farming activities in the rural communities of oman that provides opportunities for food security and income for many rural families (maf, 2013). the cobb 500 broiler chickens are the world’s foremost broiler breed, adapting well to warmer weathers; has the best growth rate and an ability to thrive on low density and less costly diets (dessie et al., 2017). however, cobb 500 broiler chickens has become very popular in oman where feed costs are inflated saving poultry farmers a fortune. an improvement in local chicken productivity would be highly valuable in the enhancement of the socioeconomic and nutritional status of farmers. several studies have shown the beneficial effect of the microbial community in the gastrointestinal tract of the host and their important contributions in many roles such as in nutrient absorption, feed digestion, and immune system (gong et al., 2002). chickens’ gastrointestinal (gi) tracts are home to a rich and complex microbiota that aids in digestion and nutrition absorption, as well as immune system development and pathogen exclusion (shang et al., 2018). the symbiotic relationship between the host and the microbiota is critical for the health and production of chickens. the age of the chickens and their position in the digestive tract have a big impact on the diversity of their gut تقييم اجملتمع البكتريي املعوي للدجاج العماين احمللي ودجاج الكوب 500 الالحم 16s rdna الذي مت تربيته يف منزل مفتوح ابستخدام التحليل القائم على مي أ س البلوشي1، ايمسني الطاهر1، حممد ن عاصي1، هاين م الزايت1، 2، حممد العربي1، كاذية اخلروصي1، وليد املرزوقي1،* abstract. little is known about how the intestinal bacterial microbiota differs among different strains of chickens raised in an open sided house, predominantly those with lower growth rates, such as indigenous chickens. ninety-oneday-old chicks of each strain of chickens were raised in an open-sided house system and fed a conventional corn-soybean meal diet from day 0–35 days of age. the objective of this study was to assess the relative abundance of bacteria microbiota identified in the intestinal tract of local omani and cobb 500 broiler chickens raised in an open-sided house system using 16s rdna-based analysis. the results obtained showed the diversity of bacterial populations in different intestinal regions of two chicken strains. bacilli were found in higher numbers and reached 98.8% of the bacteria in the duodenum on day 5 in cobb 500 versus 72.5% in the omani chickens. local omani chickens had significantly higher numbers of clostridia at an early age period. on day 5 clostridia comprised 13.1% of the bacteria in the duodenum of local omani chickens, versus only 0.062% in the cobb 500. the relative abundance of the bacterial microbiota differed significantly (p <0.05) across different intestinal segments of the two strains of chickens, suggesting that each region generated its bacterial community with different relative abundances. keywords: omani, chicken, 16s rdna, intestine, microbiota, house. امللخــص: ال يعــرف ســوى القليــل عــن كيفيــة اختــاف امليكــروابت البكترييــة املعويــة بــني ســاالت خمتلفــة مــن الدجــاج الــي تــرىب يف منــزل مفتــوح ، يف الغالــب تلــك الــي لديهــا معــدالت منــو أقــل ، مثــل الدجــاج احمللــي. مت تربيــة واحــدا وتســعني مــن الكتاكيــت البالغــة مــن العمــر يومــا مــن كل ســالة مــن الدجــاج يف نظــام منــزل مفتــوح اجلانــب وتغذيــة نظــام غذائــي تقليــدي لوجبــة الــذرة وفــول الصــواي مــن اليــوم 0-35 يومــا مــن العمــر. كان اهلــدف مــن هــذه الدراســة هــو تقييــم الوفــرة النســبية للميكــروابت البكترييــة الــي مت حتديدهــا يف األمعــاء للدجــاج العمــاين احمللــي ودجــاج cobb 500 الاحــم الــذي مت تربيتــه يف نظــام منــزل مفتــوح اجلانــب ابســتخدام التحليــل القائــم علــى 16s rdna. أظهــرت النتائــج الــي مت احلصــول عليهــا تنــوع اجملموعــات البكترييــة يف مناطــق معويــة خمتلفــة مــن ســالتني مــن الدجــاج. مت العثــور علــى العصيــات أبعــداد أكــرب ووصلــت إىل ٪98.8 مــن البكتــرياي يف االثــي عشــر يف اليــوم 5 يف كــوب 500 مقابــل ٪72.5 يف الدجــاج العمــاين. كان لــدى الدجــاج العمــاين احمللــي أعــداد أكــرب بكثــري مــن كلوســريداي يف فــرة مبكــرة مــن العمــر. يف اليــوم اخلامــس ، شــكلت كلوســريداي ٪13.1 مــن البكتــرياي يف االثــي عشــر مــن الدجــاج العمــاين احمللــي ، مقابــل ٪0.062 فقــط يف cobb 500. اختلفــت الوفــرة النســبية للميكــروابت البكترييــة اختافــا كبــريا )p <0.05( عــرب شــرائح معويــة خمتلفــة مــن ســالتني مــن الدجــاج ، ممــا يشــري إىل أن كل منطقــة لديهــا جمتمعهــا البكتــريي اخلــاص هبــا بوفــرة نســبية خمتلفــة. الكلمات املفتاحية: عماين، دجاج، 16s rdna، أمعاء، ميكروبيوات، منزل. 48 squ journal of agricultural and marine sciences, 2023, volume 28, issue 1 evaluation of the intestinal bacterial community of local omani and cobb 500 broiler chickens raised in an open-sided house using 16s rdna-based analysis microbiota. normal gut morphology and integrity are important in the maintenance of intestinal microbial homeostasis in the prevention of infection and promoting digestion and absorption of nutrients (jimoh et al., 2017). evaluation of the microbial diversity and intestinal development of different strains of chickens has become widely recognized (glendinning et al., 2019; richards-rios et al., 2020). however, there is a limited information about the effect of house type on the composition and succession of intestinal microbial communities in birds raised in open-sided housing systems. the majority of small and medium scale farmers in middle east countries, such as oman uses an open-sided housing system to grow their chickens. a greater understanding of the chicken gut function and microbiology can provide an opportunity for the improvement of chicken’s health and production especially those with various growth rates, such as the local omani chickens. the use of modern high-throughput sequencing approaches, that involve analyzing the structure of bacterial communities by determining the characteristic features of the microbial dna extracted from the community samples, are a powerful tool that has led to important new insights into the biological and ecological roles of the gi microbiota (shang et al., 2018; mclaren et al., 2019). the objective of this study was to assess the relative abundance of bacteria microbiota identified in the intestinal tract of local omani and cobb 500 broiler chickens raised in an open-sided house system from 0 to 35 days of age using 16s rdna-based analysis. materials and methods ethical approval all experimental work was conducted at the poultry research unit at the agricultural experiment station in accordance with the experimental unit policy on animal welfare and the requirements of the procedures involving animals/birds and their care were conducted in conformity with international laws and policies at sultan qaboos university. birds housing, diets and sample collection one hundred and fifty 1-day-old chicks of two strains of chickens: local omani and cobb 500 broiler chicken were obtained from commercial hatcheries at barka. on arrival, all chicks were scrutinized to ensure that they were free of abnormalities and early signs of sickness. before the trial, open-sided house unit, cages, feeders, and drinkers were disinfected through fumigation. in addition, strict hygiene and biosecurity measurements were implemented. the open-sided house was built from a galvanized iron shed with profiled steel shed roofing which was naturally ventilated. chicken mesh panels were put on all sides, along with one-meter-high block work protection. to assist circulate the air, four sets of electric wall fans were used. shade cloth were used to screen direct sunrays during midday. there were 15 replicates for each strain of chicken with each replicate cage containing six birds (a total of 90 birds/strain). birds per replicate combinations were randomly allocated. chicks of both strains were fed a nonmedicated conventional corn-soybean meal diet from day 0–35 days of age. the composition of experimental diet is as described by al-marzooqi et al. (2019). feed was available ad libitum. the house temperature maintained at 33 °c on day 1 and reduced by 3 °c each week to reach a constant 22 °c. the lighting program was 23l: 1d. at 5, 15, 25, and 35 days of age, one bird per cage for each strain of chicken was randomly selected. birds with the body weight closest to the average from each cage were selected, marked, and kept in their cage until being euthanized. then, the selected bird was injected with a mixed dose of ketamine 10% and xylazine 20% intramuscularly to put the bird into a deep sedation and anaesthesia. after dissection, intestinal tracts were removed from the carcasses immediately and luminal contents of the duodenum, jejunum, ileum and cecum were aseptically collected into a labeled sterile 15-ml tube. the entire process of collecting intestinal contents was performed on a thoroughly cleaned workbench and required less than 30 min. samples were placed on ice and immediately transported to the laboratory and stored in −80 °c freezer until analysis. dna extraction, 16s rdna gene amplicon production and high-throughput sequencing total dna was extracted from contents of each luminal content samples (duodenum, jejunum, ileum, and cecum) using a qiaamp dna stool mini kit (qiagen, ca, hamburg, germany) according to the manufacturer’s instructions. the dna concentration was evaluated by measuring optical density using nano-drop 2000 (thermo electron corporation, waltham, ma, usa) at a wavelength of 260 and 280 nm. the integrity of the dna extracts was assessed visually using 1.0% agarose gel (containing ethidium bromide) electerophoresis. the variable regions v3-v4 of the 16s rdna gene were amplified and sequenced. the pcrs were performed in triplicate in a total volume of 20 μl containing 5 μm of each primer, 10 ng of dna template, 4 μl 1× fastpfu buffer, 2.5 mm dntps, and 0.4 μl of fastpfu polymerase (transgen biotech, beijing, china). pcr conditions were as follows: initial denaturation at 95 °c for 2 min; followed by 25 cycles of denaturation 94 °c for 30 s, annealing at 55 °c for 30 s, and extension at 72 °c for 30 s and then, a final extension at 72 °c for 5 min. pcr products were separated on 2% agarose gels, and purified using the dna gel extraction kit (axygen scientific inc., union city, ca, usa). amplicons produced form different intestinal luminal content samples were sent to a commercial company (bgi genomic lab, tai po industrial zone, new territories, hong kong, china) for sequencing on the illumina misequencing platform. 49research paper al-balushi , el tahir, asi, el-zaiat, al-abri, al-kharousi, al-marzooqi sequencing analysis all the raw sequences obtained from illumina miseq were firstly filtered for quality control to get operational sequences. the quality control and analysis of the sequences were performed using the software quantitative insights into microbial ecology (qiime, v1.8.0) (caporaso et al., 2010). the paired-end reads from the dna fragments were merged using flash (magoc and salzberg, 2011). sequences data was treated by read trimming and identification of v3-v4 sequences and set of sequences with ≥97% identity were defined as an operational taxonomic unit (otu). the uclust (edgar, 2010), clustering method was used to cluster operational taxonomic units. the defined otus were assigned to different taxonomic levels (phylum, class, genus and families) at a cutoff of 97%. the clustered otus were also used to construct the rarefaction curves and calculate the shannon and simpson diversity indices, abundance-based coverage estimators (ace), chao 1 richness, and coverage percentage by good’s method. bioinformatics and statistical analysis bioinformatics and statistical analyses were performed using the qiime and r package (v3.1.1). the alpha-diversity indices (chaol, ace, shannon diversity index, and simpson index) were calculated to establish the relative abundance and diversity of the sequences. beta diversity was determined using unweighted unifrac distance metrics to evaluate the structure and distribution of the microbial genetic communities among the samples. differences in the unifrac distances for pairwise comparisons among groups were calculated using student’s t-test and the monte carlo permutation test with 1000 permutations. metastats and r package (v3.1.1) (james et al., 2009) were used to compare and determine which taxonomic groups were significantly different between groups of samples based on intestinal segments and age period. the differences were considered to be significant at p < 0.05. the obtained p-value was adjusted by a benjamini–hochberg false discovery rate correction (function ‘p.adjust’ in the stats package of r (v3.1.1)). results bacterial taxonomic composition of duodenum bacteria were classified according to their respective phylum and class, found in the duodenum of broiler chickens at different age periods, are presented in table 1. seventeen bacterial florae at the class level were detected in the duodenum. of the 30248 detected sequences, the most abundant class was bacilli, at 93.4 % of the total sequences. clostridia accounted for 2.9 % out of the total detected sequences. actinobacteria and proteobacteria sequences represent 1.01 % and 0.694 %, respectively of the total sequences. across different age periods bacilli were considered the dominant group with 98.9 % at day 5, 94.6 % at day 15, 89.9 % at day 25 and 88.7 % at day 35 of sequences. clostridia sequences fluctuated from 0.062 % at day 5, 1.78 % at day 15, 4.61% at day 25, and 6.00 % at day 35. chloroplast were detected at very small percentage across all age periods except at day 25 of age was detected at 3.39 %. both actinobacteria and proteobacteria group-related sequences were detected at smaller percentage across all age periods. bacterial taxonomic composition of the jejunum bacteria were classified according to their respective phylum and class, found in the jejunum of broiler chickens at different ages are presented in table 2. seventeen bacterial florae at the class level were detected in the jejunum. of the 28678 reads, bacilli were the most abundant, at 79.6 % of the total sequences. clostridia accounted for 7.61% of the total sequences. actinobacteria and proteobacteria sequences represented 4.46 % and 4.44%, respectively of the total sequences. across different age periods bacilli were the dominant group, representing 86.4 % at day 5, 93.3 % at day 15, 91.5 % at day 25 and 40.1 % at day 35 of sequences. clostridia sequences varied from day 5: 4.20%, day 15: 4.33%, day 25: 0.859% and day 35: 23.60%. actinobacteria sequences were day 5: 2.33%, day 15: 0.318%, day 25: 0.109%, and day 35: 17.4%, while sequences related to gammaproteobacteria were day 5: 0.015%, day 15: 0.625%, day 25: 4.94%, and day 35: 12.0%. bacterial taxonomic composition of the ileum bacteria were classified according to their respective phylum and class, found in the ileum of broiler chickens at different ages are presented in table 3. seventeen bacterial florae at the class level were detected in the ileum. of the 31007 reads, bacilli were the most abundant, at 96.1 % of the total sequences. only few of clostridia (0.239%) related to the total sequences were detected. actinobacteria and proteobacteria represented a very small percentage of 0.893% and 0.232%, respectively, of the total sequences. across different age periods bacilli were the dominant group, representing 91.1 % at day 5, 99.0 % at day 15, 99.6 % at day 25 and 95.2 % at day 35 of sequences. clostridia sequences fluctuated from 0.565% at day 5, 0.140% at day 15, 0.107% at day 25, and 0.050% at day 35. proteobacteria group-related sequences were detected at smaller percentages across all age periods. bacterial taxonomic composition of the cecum bacteria were classified according to their respective phylum and class, found in the cecum of broiler chickens at different ages are presented in table 4. seventeen bacterial florae at the class level were detected in the cecum. of the 28035 reads, clostridia were the most abundant, at 63.4 % of the total sequences. bacilli were detected at 13.1% of the total sequences. actinobacteria and proteobacteria sequences represented 6.01% and 50 squ journal of agricultural and marine sciences, 2023, volume 28, issue 1 evaluation of the intestinal bacterial community of local omani and cobb 500 broiler chickens raised in an open-sided house using 16s rdna-based analysis 1.75%, respectively of the total sequences. across different age periods clostridia were the dominant group, representing 40.8% at day 5, 73.5% at day 15, 75.0% at day 25 to 62.6% at day 35 of the sequences. bacilli sequences fluctuated from 16.3% at day 5, 21.0% at day 15, 11.8% at day 25, and 2.32% at day 35. actinobacteria sequences were day 5: 22.0%, day 15: 0.809%, day 25: 1.18%, and day 35: 0.0%. proteobacteria group-related sequences were detected at smaller percentages across age periods. table 1. abundance of bacterial 16s rdna sequences (n=30248) identified from the duodenum flora of 500 cobb broiler chicken. abundance of sequence (no. of sequence [%]) at day: phylum class day 5 day 15 day 25 day 35 actinobacteria actinobacteria coriobacteriia thermoleophilia 43 (0.531) 0 (0) 0 (0) 191 (2.32) 3 (0.036) 0 (0) 46 (0.531) 0 (0) 0 (0) 0 (0) 15 (0.285) 0 (0) bacteroidetes cyanobacteria firmicutes proteobacteria tenericutes thermi total bacteroidia 4c0d-2 chloroplast bacilli clostridia erysipelotrichi alphaproteobacteria betaproteobacteria deltaproteobacteria epsilonproteobacteria gammaproteobacteria mollicutes deinococci other 0 (0) 0 (0) 34 (0.420) 8005 (98.9) 5 (0.062) 0 (0) 5 (0.062) 1 (0.012) 0 (0) 3 (0.037) 0 (0) 0 (0) 1 (0.012) 0 (0) 8097 0 (0) 0 (0) 20 (0.243) 7777 (94.6) 146 (1.78) 2 (0.024) 36 (0.438) 27 (0.328) 0 (0) 11 (0.134) 5 (0.061) 3 (0.036) 3 (0.036) 0 (0) 8224 0 (0) 2 (0.023) 293 (3.39) 7785 (89.9) 399 (4.61) 0 (0) 25 (0.289) 6 (0.069) 0 (0) 84 (0.970) 6 (0.069) 0 (0) 11 (0.127) 0 (0) 8657 8 (0.152) 175 (3.32) 0 (0) 4675 (88.7) 316 (6.00) 42 (0.797) 0 (0) 0 (0) 1 (0.019) 0 (0) 0 (0) 32 (0.607) 0 (0) 6 (0.114) 5270 note: values in the parentheses are abundance of sequence (no. of sequence [%]) at day table 2. abundance of bacterial 16s rdna sequences (n=28678) identified from the jejunum flora of cob 500 broiler chickens. abundance of sequence (no. of sequence [%]) at day: phylum class day 5 day 15 day 25 day 35 actinobacteria actinobacteria coriobacteriia thermoleophilia 154 (2.33) 0 (0) 0 (0) 27 (0.318) 0 (0) 0 (0) 8 (0.109) 0 (0) 0 (0) 1090 (17.4) 0 (0) 0 (0) bacteroidetes cyanobacteria firmicutes proteobacteria tenericutes thermi total bacteroidia 4c0d-2 chloroplast bacilli clostridia erysipelotrichi alphaproteobacteria betaproteobacteria deltaproteobacteria epsilonproteobacteria gammaproteobacteria mollicutes deinococci other 0 (0) 0 (0) 427 (6.45) 5718 (86.4) 278 (4.20) 0 (0) 38 (0.574) 5 (0.076) 0 (0) 0 (0) 1 (0.015) 0 (0) 0 (0) 0 (0) 8584 0 (0) 0 (0) 64 (0.755) 7906 (93.3) 367 (4.33) 13 (0.153) 38 (0.448) 10 (0.118) 0 (0) 0 (0) 53 (0.625) 0 (0) 0 (0) 0 (0) 7872 0 (0) 0 (0) 175 (2.39) 6705 (91.5) 63 (0.859) 1 (0.014) 16 (0.218) 0 (0) 0 (0) 0 (0) 362 (4.94) 0 (0) 0 (0) 0 (0) 7582 0 (0) 0 (0) 0 (0) 2504 (40.1) 1475 (23.6) 429 (6.87) 0 (0) 0 (0) 0 (0) 0 (0) 751 (12.0) 0 (0) 0 (0) 0 (0) 7217 note: values in the parentheses are abundance of sequence (no. of sequence [%]) at day 51research paper al-balushi , el tahir, asi, el-zaiat, al-abri, al-kharousi, al-marzooqi differences of bacterial communities among samples from different intestinal segments the p-value distribution of 16s rdna gene sequence libraries used to compare the quantitative differences of microbial communities among samples from different intestinal segments of broiler chickens are presented in table 5. statistical comparisons of the libraries showed that the composition of the duodenum-jejunum, duodenum-ileum, cecum-duodenum, cecum-ileum cecum-jejunum bacterial microbiota differed significantly (p < 0.05), implying that each region established its own bacterial community. the number of actinobacteria, alphaproteobacteria, bacilli, bacteroidia, betaproteotable 3. abundance of bacterial 16s rdna sequences (n=31007) identified from the ileum flora of cobb 500 broiler chicken. abundance of sequence (no. of sequence [%]) at day: phylum class day 5 day 15 day 25 day 35 actinobacteria bacteroidetes cyanobacteria firmicutes proteobacteria tenericutes thermi total actinobacteria coriobacteriia thermoleophilia bacteroidia 4c0d-2 chloroplast bacilli clostridia erysipelotrichi alphaproteobacteria betaproteobacteria deltaproteobacteria epsilonproteobacteria gammaproteobacteria mollicutes deinococci other 220 (2.44) 0 (0) 0 (0) 3 (0.033) 0 (0) 466 (5.16) 8222 (91.1) 51 (0.565) 1 (0.011) 55 (0.610) 4 (0.044) 0 (0) 0 (0) 1 (0.011) 0 (0) 0 (0) 0 (0) 9023 56 (0.655) 0 (0) 0 (0) 2 (0.023) 0 (0) 7 (0.082) 8458 (99.0) 12 (0.140) 0 (0) 5 (0.059) 3 (0.035) 0 (0) 0 (0) 1 (0.012) 0 (0) 0 (0) 0 (0) 8544 1 (0.013) 0 (0) 0 (0) 0 (0) 0 (0) 17 (0.227) 7467 (99.6) 8 (0.107) 0 (0) 1 (0.013) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 7494 0 (0) 87 (1.46) 0 (0) 40 (0.673) 7 (0.118) 0 (0) 5659 (95.2) 3 (0.050) 137 (2.30) 0 (0) 0 (0) 0 (0) 0 (0) 2 (0.034) 11 (0.185) 0 (0) 0 (0) 5946 note: values in the parentheses are abundance of sequence (no. of sequence [%]) at day table 4. abundance of bacterial 16s rdna sequences (n=28035) identified from the cecum flora of cobb 500 broiler chicken. abundance of sequence (no. of sequence [%]) at day: phylum class day 5 day 15 day 25 day 35 actinobacteria actinobacteria coriobacteriia thermoleophilia 1535 (22.0) 25 (0.359) 1 (0.014) 57 (0.809) 21 (0.298) 2 (0.028) 93 (1.18) 0 (0) 0 (0) 0 (0) 114 (1.85) 0 (0) bacteroidetes cyanobacteria firmicutes proteobacteria tenericutes thermi total bacteroidia 4c0d-2 chloroplast bacilli clostridia erysipelotrichi alphaproteobacteria betaproteobacteria deltaproteobacteria epsilonproteobacteria gammaproteobacteria mollicutes deinococci other 35 (0.502) 12 (0.172) 1103 (15.8) 1134 (16.3) 2839 (40.8) 24 (0.344) 165 (2.37) 78 (1.12) 0 (0) 0 (0) 11 (0.158) 0 (0) 5 (0.072) 0 (0) 6967 32 (0.454) 13 (0.185) 92 (1.31) 1480 (21.0) 5177 (73.5) 24 (0.341) 63 (0.895) 58 (0.824) 1 (0.014) 0 (0) 22 (0.312) 1 (0.014) 0 (0) 0 (0) 7043 2 (0.025) 0 (0) 855 (10.9) 925 (11.8) 5902 (75.0) 2 (0.025) 83 (1.05) 5 (0.064) 0 (0) 0 (0) 1 (0.013) 0 (0) 0 (0) 0 (0) 7868 2010 (32.65) 27 (0.439) 0 (0) 143 (2.32) 3851 (62.6) 6 (0.097) 0 (0) 0 (0) 5 (0.081) 0 (0) 0 (0) 1 (0.016) 0 (0) 0 (0) 6157 note: values in the parentheses are abundance of sequence (no. of sequence [%]) at day 52 squ journal of agricultural and marine sciences, 2023, volume 28, issue 1 evaluation of the intestinal bacterial community of local omani and cobb 500 broiler chickens raised in an open-sided house using 16s rdna-based analysis bacteria, clostridia and erysipelotrichia differed significantly across different intestinal segments (p < 0.05). bacilli were the dominant 16s rdna sequences in the duodenum, jejunum, and ileum libraries, whereas clostridia were the dominant 16s rdna sequences in the cecum libraries. table 5. p-value distribution of 16s rdna gene sequence libraries compared the abundance differences of microbial communities among samples from different segments for cobb 500 broiler chicken. p-value class duodenumjejunum duodenum-ileum jejunumileum caecum-duodenum caecum jejunum caecum ileum 4c0d-2 actinobacteria alphaproteobacteria bacilli bacteroidia betaproteobacteria chloroplast clostridia coriobacteriia deltaproteobacteria epsilonproteobacteria erysipelotrichi flavobacteriia gammaproteobacteria lentisphaeria mollicutes sphingobacteriia verrucomicrobiae 0.270 0.921 0.575 0.901 0.026 0.191 0.327 0.512 0.828 0.501 0.479 0.726 0.233 0.699 0.124 0.328 0.483 0.581 0.797 0.724 0.673 0.051 0.153 0.203 0.826 0.542 0.778 0.289 0.108 0.427 0.124 0.614 0.447 0.682 0.745 0.630 1.000 0.879 0.737 0.543 0.514 0.322 0.684 0.603 0.236 0.405 1 0.485 0.507 0.029 0.303 0.000 0.011 0.018 0.218 0.002 0.058 0.192 0.270 0.003 0.069 0.096 0.146 0.403 0.074 0.415 0.015 0.025 0.000 0.007 0.042 0.142 0.002 0.071 0.183 0.600 0.004 0.501 0.096 0.107 0.103 0.463 0.052 0.108 0.000 0.029 0.005 0.083 0.002 0.070 0.285 0.766 0.003 0.362 0.098 1 0.117 table 6. p-value distribution of 16s rdna gene sequence libraries compared the abundance differences of microbial communities among sample from different ages period for cobb 500 broiler chickens. p-value class day 5-day 15 day 5-day 25 day 5 day 35 day 15-day 25 day 15day35 day 25day 35 4c0d-2 actinobacteria alphaproteobacteria bacilli bacteroidia betaproteobacteria chloroplast clostridia coriobacteriia deltaproteobacteria epsilonproteobacteria erysipelotrichi flavobacteriia gammaproteobacteria lentisphaeria mollicutes sphingobacteriia verrucomicrobiae 0.005 0.054 0.678 0.299 0.165 0.027 0.871 0.130 1 0.592 0.501 0.123 0.342 0.342 0.247 0.046 0.235 0.924 0.317 0.158 0.746 0.875 0.226 0.288 0.035 0.758 0.621 0.497 0.347 0.347 0.198 0.004 0.036 0.914 0.344 0.051 0.283 0.854 0.290 0.171 0.069 0.511 0.111 0.249 0.676 0.499 0.299 0.226 0.016 0.112 0.669 0.750 0.614 0.031 0.848 0.733 0.342 0.043 0.652 0.501 0.556 0.475 0.361 0.361 0.199 0.748 0.178 0.695 0.738 0.532 0.147 0.806 0.659 0.248 0.080 0.907 0.501 0.217 0.228 0.369 0.561 0.337 0.191 0.012 0.304 0.913 0.678 0.922 0.464 0.856 0.556 0.660 0.193 0.648 0.332 1 0.347 1.000 0.760 53research paper al-balushi , el tahir, asi, el-zaiat, al-abri, al-kharousi, al-marzooqi differences of microbial communities among samples the p-value distribution of 16s rdna gene sequence libraries comparing the quantitative differences of microbial communities among samples from broiler chickens at different age groups are presented in table 6. statistical comparisons of the libraries revealed that there were no significant differences (p > 0.05) between the microbial compositions at different age groups: day 5–15, day 5–25, day 5–35, day 15–25, day 15–35, and day 25–35. the results of the statistical evaluation at certain age groups revealed that the percentage of bacterial microbiota of actinobacteria, alphaproteobacteria, chloroplast and epsilonproteobacteria varied significantly (p< 0.05). the average percentage of actinobacteria detected at day 5 (6.83%) of age was significantly higher (p < 0.05) than at day 15 (1.03%), at day 25 (0.458%) and at day 35 (4.35%) of age. the average percentage of alphaproteobacteria was detected at significantly higher level (p < 0.05) at day 35 (0.904%) of age than at day 5 (0.458%) of age. the average percentage of chloroplast detected at day 15 (0.598%) was significantly lower (p< 0.05) than at day 25 (4.23%) of age. the average percentage of epsilonproteobacteria at day 25 (0.243%) was significantly higher (p < 0.05) from those of the other age groups. taxonomic composition distribution of the bacterial community in intestinal segments percentage of relative abundance of bacterial community of cobb 500 broiler chickens determined from diffigure 3. percentage of relative abundance of bacterial community of cobb 500 broiler chickens determined from different intestinal segments at different age periods from 16s rdna libraries. 54 squ journal of agricultural and marine sciences, 2023, volume 28, issue 1 evaluation of the intestinal bacterial community of local omani and cobb 500 broiler chickens raised in an open-sided house using 16s rdna-based analysis ferent intestinal segments at different age periods from 16s rdna libraries are presented in figure 1. from figure 1, it can be seen that the diversity of the bacterial community in the intestinal segments of broiler chickens changed from one age period to the next. species that exhibited an abundance less than 0.5% in all samtable 8. abundance of bacterial 16s rdna sequences (n=31255) identified from the jejunum flora of local omani chickens. abundance of sequence (no. of sequence [%]) at day: phylum class day 5 day 15 day 25 day 35 actinobacteria bacteroidetes cyanobacteria firmicutes lentisphaerae proteobacteria tenericutes thermi total actinobacteria coriobacteriia bacteroidia flavobacteriia sphingobacteriia 4c0d-2 chloroplast bacilli clostridia erysipelotrichi lentisphaeria alphaproteobacteria betaproteobacteria deltaproteobacteria epsilonproteobacteria gammaproteobacteria mollicutes verrucomicrobiae 200 (2.33) 4 (0.047) 1 (0.012) 2 (0.023) 0 (0) 0 (0) 1578 (18.4) 6484 (75.5) 215 (2.50) 3(0.035) 0 (0) 92 (1.07) 4 (0.047) 0 (0) 0 (0) 1 (0.012) 0 (0) 0 (0) 8584 2 (0.025) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 18 (0.229) 7616 (96.8) 225 (2.86) 9 (0.114) 0 (0) 1 (0.013) 0 0 (0) 0 (0) 1 (0.013) 0 (0) 0 (0) 7872 49 (0.646) 1 (0.013) 0 (0) 0 (0) 0 (0) 0 (0) 268 (3.53) 7092 (93.5) 101 (1.33) 0 (0) 0 (0) 29(0.382) 11 (0.145) 0 (0) 23 (0.303) 8 (0.106) 0 (0) 0 (0) 7582 109 (1.51) 1 (0.014) 0 (0) 0 (0) 0 (0) 1 (0.014) 178 (2.47) 6889 (95.5) 10 (0.139) 0 (0) 0 (0) 25 (0.346) 3 (0.042) 0 (0) 0 (0) 0 (0) 0 (0) 1 (0.014) 7217 note: values in the parentheses are abundance of sequence (no. of sequence [%]) at day table 7. abundance of bacterial 16s rdna sequences (n=33443) identified from the duodenum flora of local omani chickens. abundance of sequence (no. of sequence [%]) at day: phylum class day 5 day 15 day 25 day 35 actinobacteria bacteroidetes cyanobacteria firmicutes lentisphaerae proteobacteria tenericutes thermi total actinobacteria coriobacteriia bacteroidia flavobacteriia sphingobacteriia 4c0d-2 chloroplast bacilli clostridia erysipelotrichi lentisphaeria alphaproteobacteria betaproteobacteria deltaproteobacteria epsilonproteobacteria gammaproteobacteria mollicutes verrucomicrobiae 213 (2.55) 6 (0.072) 2 (0.024) 0 (0) 4 (0.048) 0 (0) 502 (6.00) 6065(72.5) 1096 (13.1) 6 (0.072) 0 (0) 419 (5.01) 39 (0.466) 1 (0.012) 0 (0) 9 (0.108) 0 (0) 0 (0) 8362 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 3 (0.037) 8023 (97.7) 150 (1.83) 10 (0.122) 0 (0) 4 (0.049) 2 (0.024) 0 (0) 0 (0) 8 (0.097) 15 (0.183) 0 (0) 8215 21 (0.235) 2 (0.022) 2 (0.022) 0 (0) 0 (0) 2 (0.022) 23 (0.257) 8667 (97.0) 121 (1.35) 2 (0.022) 0 (0) 11 (0.123) 11 (0.123) 1 (0.011) 71 (0.795) 1 (0.011) 0 (0) 0 (0) 8935 144 (1.82) 0 (0) 3 (0.038) 0 (0) 0 (0) 5 (0.063) 50 (0.630) 7618 (96.1) 29 (0.366) 1 (0.013) 0 (0) 15 (0.189) 12 (0.151) 0 (0) 15 (0.189) 0 (0) 39 (0.492) 0 (0) 7931 note: values in the parentheses are abundance of sequence (no. of sequence [%]) at day 55research paper al-balushi , el tahir, asi, el-zaiat, al-abri, al-kharousi, al-marzooqi ples were classified into “others”. the intestinal segments of duodenum, jejunum, and ileum had a higher relative abundance of bacilli, and as the birds aged, the percentage of bacilli decreased, whereas the cecum had a higher relative abundance of clostridia and as the birds aged, the percentage of clostridia increased. table 9. abundance of bacterial 16s rdna sequences (n=31337) identified from the ileum flora of local omani chicken. abundance of sequence (no. of sequence [%]) at day: phylum class day 5 day 15 day 25 day 35 actinobacteria bacteroidetes cyanobacteria firmicutes lentisphaerae proteobacteria tenericutes thermi total actinobacteria coriobacteriia bacteroidia flavobacteriia sphingobacteriia 4c0d-2 chloroplast bacilli clostridia erysipelotrichi lentisphaeria alphaproteobacteria betaproteobacteria deltaproteobacteria epsilonproteobacteria gammaproteobacteria mollicutes verrucomicrobiae 116 (1.29) 1 (0.011) 1 (0.011) 0 (0) 0 (0) 0 (0) 2170 (24.1) 6531 (72.5) 26 (0.289) 3 (0.033) 0 (0) 144 (1.60) 9 (0.100) 0 (0) 0 (0) 2 (0.022) 0 (0) 0 (0) 9003 2 (0.026) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 192 (2.49) 6814 (87.0) 471 (6.01) 1 (0.013) 0 (0) 3 (0.038) 2 (0.026) 0 (0) 0 (0) 349 (4.45) 0 (0) 0 (0) 7834 12 (0.155) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 16 (0.206) 7674 (98.9) 57 (0.734) 0 (0) 0 (0) 0 (0) 1 (0.013) 0 (0) 3 (0.039) 0 (0) 0 (0) 0 (0) 7763 147 (1.72) 2 (0.023) 1 (0.012) 0 (0) 1 (0.012) 33 (0.387) 768 (9.00) 7090 (83.1) 398 (4.66) 2 (0.023) 0 (0) 70 (0.820) 7 (0.082) 4 (0.047) 9 (0.105) 5 (0.059) 0 (0) 0 (0) 8537 note: values in the parentheses are abundance of sequence (no. of sequence [%]) at day table 10. abundance of bacterial 16s rdna sequences (n=31337) identified from the ileum flora of local omani chicken. abundance of sequence (no. of sequence [%]) at day: phylum class day 5 day 15 day 25 day 35 actinobacteria bacteroidetes cyanobacteria firmicutes lentisphaerae proteobacteria tenericutes thermi total actinobacteria coriobacteriia bacteroidia flavobacteriia sphingobacteriia 4c0d-2 chloroplast bacilli clostridia erysipelotrichi lentisphaeria alphaproteobacteria betaproteobacteria deltaproteobacteria epsilonproteobacteria gammaproteobacteria mollicutes verrucomicrobiae 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 657 (9.33) 5417 (76.9) 222 (3.15) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 745 (10.58) 0 (0) 0 (0) 7041 0 (0) 31 (0.397) 1320 (16.9) 0 (0) 0 (0) 0 (0) 0 (0) 29 (0.371) 6361(81.5) 45 (0.576) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 22 (0.282) 0 (0) 0 (0) 7808 0 (0) 21 (0.336) 695 (11.1) 0 (0) 0 (0) 0 (0) 0 (0) 17 (0.272) 4953 (79.2) 143 (2.29) 1 (0.016) 0 (0) 0 (0) 31 (0.496) 7 (0.112) 354 (5.66) 0 (0) 30 (0.480) 6252 0 (0) 98 (1.36) 2187 (30.4) 0 (0) 0 (0) 119 (1.65) 0 (0) 471 (6.54) 4191 (58.2) 57 (0.792) 2 (0.028) 0 (0) 0 (0) 11 (0.153) 0 (0) 2 (0.028) 0 (0) 60 (0.834) 7198 note: values in the parentheses are abundance of sequence (no. of sequence [%]) at day 56 squ journal of agricultural and marine sciences, 2023, volume 28, issue 1 evaluation of the intestinal bacterial community of local omani and cobb 500 broiler chickens raised in an open-sided house using 16s rdna-based analysis bacterial taxonomic composition of the duodenum of local omani chickens across age periods bacteria classified according to their respective phylum and class, found in the duodenum of local omani chickens at different ages are presented in table 7. eighteen bacterial microbiota at the class level were found in duodenum. of the 33443 reads, bacilli were the most abundant, at 90.8% of the total sequences, while sequences related to clostridia accounted for 4.17% of the total sequences. actinobacteria and chloroplast represented a very small percentage of 1.13% and 1.72%, respectively of the total sequences. across different age periods bacilli were the dominant group, representing 72.5 % at day 5, 97.7 % at day 15 and 97.0 % at day 25 and 96.1 % at day 35 of the sequences. clostridia sequences fluctuated from 13.1% at day 5, 1.83% at day 15, 1.35% at day 25 and 0.366% at day 35. both actinobacteria and bacteroidia related sequences were day 5: 2.55%, day 15: 0.0%, day 25: 0.235% and day 35: 1.82% and day 5: 0.024%, day 15: 0.0%, day 25: 0.022%, and day 35: 0.038%, respectively. proteobacteria group-related sequences were detected at smaller percentages across age periods. bacterial taxonomic composition of the jejunum of local omani chickens across age periods bacteria classified according to their respective phylum and class, found in the jejunum of local omani chickens at different ages are presented in table 8. eighteen bacterial microbiota at the class level were found in jejunum. of the 31255 reads, bacilli were the most abundant, at 89.84% of the total sequences. chloroplast represented 6.53% of the total sequences. clostridia accounted for 1.76% of the total sequences. actinobacteria and gammaproteobacteria represented a small percentage of 1.15 % and 0.032 %, respectively of the total sequences. and chloroplast were 6.53%. across different age periods bacilli were the dominant group, representing 75.5% at day 5, 96.8% at day 15, 93.5% at day 25 to 95.5% at day 35 of the sequences. clostridia sequences fluctuated from 2.50% at day 5, 2.86% at day 15, 1.33% at day 25, and 0.139% at day 35. chloroplast sequences were 18.4% at day 5, 0.229% at day 15, 3.53% at day 25 to 2.47% at day 35 of the sequences. actinobacteria sequences were day 5: 2.33%, day 15: 0.025%, day 25: 0.646%, and day 35: 1.51%, while gammaproteobacteria sequences were day 5: 0.012%, day 15: 0.013%, day 25: 0.106%, and day 35:0.0%. bacterial taxonomic composition of the ileum of local omani chickens across age periods bacteria classified according to their respective phylum and class, found in the ileum of local omani chickens at different ages are presented in table 9. eighteen bacterial microbiota at the class level were found in ileum. of the 31337 reads, bacilli were the most abundant, at 84.8% of the total sequences. chloroplast accounted for 9.49% of the total sequences. clostridia and gammaproteobacteria represented a small percentage of 2.87% and 1.07%, respectively of the total sequences. only a few actinobacteria (0.88%) related sequences were detected. table 11. p-value distribution of 16s rdna gene sequence libraries compared the abundance differences of microbial communities among samples from different segments for cobb 500 broiler chicken. p-value class duodenumjejunum duodenum-ileum jejunumileum caecum-duodenum caecum jejunum caecum ileum 4c0d-2 actinobacteria alphaproteobacteria bacilli bacteroidia betaproteobacteria chloroplast clostridia coriobacteriia deinococci deltaproteobacteria epsilonproteobacteria erysipelotrichi gammaproteobacteria mollicutes thermoleophilia unclassified 0.881 0.374 0.467 0.485 0.831 0.918 0.037 0.753 0.863 0.564 1 0.497 0.681 0.228 0.194 1 0.514 0.352 0.885 0.900 0.390 0.048 0.068 0.820 0.283 0.646 1 0.556 0.080 0.606 0.094 0.500 0.680 0.119 0.635 0.767 0.320 0.318 0.765 0.901 0.394 0.851 0.538 0.619 0.505 0.495 0.208 0.670 0.006 0 0.314 0.038 0.019 0.002 0.045 0.268 0.239 0.347 0.075 0.566 0.138 0.512 0.347 0.212 0.823 0.039 0 0.318 0.218 0.009 0.002 0.046 0.174 0.141 0.263 0.070 0.464 0.087 1 0.370 0.203 0.611 0.055 0 0.299 0.027 0.018 0.001 0.010 0.324 0.162 0.324 0.068 0.768 0.126 0.324 57research paper al-balushi , el tahir, asi, el-zaiat, al-abri, al-kharousi, al-marzooqi proteobacteria sequences represented 1.72% of the total sequences. across different age periods bacilli were the dominant group, representing 72.5% at day 5, 87.0% at day 15, 98.8% at day 25 to 83.1% at day 35 of the sequences. clostridia sequences fluctuated from 0.289% at day 5, 6.01% at day 15, 0.734% at day 25, and 4.66% at day 35. chloroplast sequences were day 5: 24.1%, day 15: 2.49%, day 25: 0.206%, and day 35: 9.0%, while actinobacteria sequences were day 5: 1.29%, day 15: 0.026%, day 25: 0.155%, and day 35: 1.72%. proteobacteria group-related sequences were detected at smaller percentages across all age periods. bacterial taxonomic composition of the cecum of local omani chickens across age periods bacteria classified according to their respective phylum and class, found in the cecum of local omani chickens at different ages are presented in table 10. eighteen bacterial microbiota at the class level were found in cecum. of the 28299 reads, clostridia were the most abundant, at 73.9% of the total sequences. bacteroidia and gammaproteobacteria accounted for 14.9 % and 3.97 %, respectively of the total sequences. bacilli and erysipelotrichi represented a small percentage of 4.15% and 1.65%, respectively of the total sequences. across different age periods clostridia were the dominant group, representing 76.9% at day 5, 81.5% at day 15, 79.2% at day 25 to 58.2% at day 35 of the sequences. bacilli sequences fluctuated from 9.33% at day 5, 0.371% at day 15, 0.272% at day 25, and 6.54% at day 35. bacteroidia sequences were day 5: 0.0%, day 15: 16.9%, day 25: 11.1%, and day 35: 30.4%, while erysipelotrichia sequences were day 5: 3.15%, day 15: 0.576%, day 25: 2.29%, and day 35: 0.792%. differences of microbial communities among samples from different intestinal segments of local omani chicken the p-value distribution of 16s rdna gene sequence libraries used to compare the quantitative differences of microbial communities among samples from different intestinal segments of local omani chickens is presented in table 11. statistical comparisons of the libraries showed that the composition of the duodenum-jejunum, duodenum-ileum, cecum-duodenum, cecum-ileum cecum-jejunum bacterial microbiota differed significantly (p < 0.05), suggesting that each region established its own bacterial community. the number of alphaproteobacteria, bacilli, betaproteobacteria, chloroplast, clostrdia and coriobacteriia differed significantly across different intestinal segments (p < 0.05). bacilli were the dominant 16s rdna sequences in the duodenum, jejunum, and ileum libraries, whereas clostridia were the dominant 16s rdna sequences in the cecum libraries. differences of microbial communities among samples from local omani chickens of different age groups the p-value distribution of 16s rdna gene sequence libraries comparing the quantitative differences of microbial communities among samples from local omani chickens at different age groups are presented in table 12. statistical comparisons of the libraries revealed that there were no significant differences (p > 0.05) between table 12. p-value distribution of 16s rdna gene sequence libraries compared the abundance differences of microbial communities among samples from different segments for cobb 500 broiler chicken. p-value class day 5-15 day 5-25 day 5-35 day 15-25 day 15-35 day 25-35 4c0d-2 actinobacteria alphaproteobacteria bacilli bacteroidia betaproteobacteria chloroplast clostridia coriobacteriia deinococci deltaproteobacteria epsilonproteobacteria erysipelotrichi gammaproteobacteria mollicutes thermoleophilia unclassified 0.315 0.343 0.736 0.925 0.347 0.746 0.669 0.839 0.185 0.068 1 0.159 0.574 0.052 0.259 0.347 0.442 0.875 0.850 0.933 0.511 0.337 0.812 0.929 0.598 0.119 0.494 0.264 0.681 0.483 0.624 0.376 0.688 0.481 0.057 0.599 0.328 0.128 0.094 0.868 0.144 0.681 0.485 0.163 0.934 0.215 0.335 0.111 0.386 0.277 0.271 0.620 0.911 0.213 0.575 0.742 0.779 0.277 0.634 0.066 0.277 0.021 0.872 0.121 0.248 0.287 0.092 0.230 0.285 0.129 0.388 0.188 0.554 0.112 0.244 0.121 0.057 0.494 0.065 0.555 0.344 0.080 0.143 0.860 0.717 0.373 0.201 0.661 0.123 0.536 0.107 58 squ journal of agricultural and marine sciences, 2023, volume 28, issue 1 evaluation of the intestinal bacterial community of local omani and cobb 500 broiler chickens raised in an open-sided house using 16s rdna-based analysis the microbial compositions at different age groups: day 5–15, day 5–25, day 5–35, day 15–25, day 15–35, and day 25–35. the results of the statistical evaluation at certain age groups revealed that the percentage of bacterial microbiota of 4c0d-2 varied significantly (p< 0.05). the average percentage of 4c0d-2 was detected at significantly higher level (p < 0.05) at day 35 (0.529%) of age than at day 15 (0.0%) of age. taxonomic composition distribution of the bacterial community in intestinal segments at the class-level of local omani chickens from figure 2, it can be seen that the diversity of the bacterial community of intestinal segments of local omani chickens changed from one age period to the next. species of that exhibited an abundance less than 0.5% in all samples were classified into “others”. the intestinal segment of duodenum, jejunum, and ileum had a higher abundance of bacilli, and as the birds aged, the percentage of bacilli decreased, whereas the cecum had a higher abundance of clostridia, and as the birds aged, the percentage of clostridia increased. discussion the aim of this study was to generate a phylogenetic diversity census of bacteria identified in the intestinal segments (duodenum, jejunum, ilium and cecum) of local omani and cobb 500 broiler chickens raised in open-sided house from 0 to 35 day of age using 16s rdna-based analysis. however, little is known about the figure 4. percentage of relative abundance of bacterial community of local omani chickens.and determined from different intestinal segments at different age periods from 16s rdna libraries. 59research paper al-balushi , el tahir, asi, el-zaiat, al-abri, al-kharousi, al-marzooqi intestinal bacterial community composition and succession for birds especially those with various growth rates such as the indigenous chickens raised in naturally ventilated open-sided house system. the open-sided house is widely practiced by a majority of small and medium scale farmers in the developing countries. a greater understanding of the chicken gut function and microbiology will enhance chicken’s health and productivity raised in naturally ventilated open sided house system. the data obtained in the study revealed the heterogeneity of bacterial populations found in different intestinal segments as derived from molecular detection and bioinformatics analysis. as a result, the current study’s findings have been confined to the most quantitatively significant bacterium classes. therefore, this study focused solely on bacilli and clostridia, the two most common groups in the firmicutes phylum. the statistical analyses of microbial community libraries within each breed among samples from different intestinal segments at different age groups revealed no significant differences (p > 0.05) in the current investigation. quite the contrary, the bacterial microbiota of each breed differed significantly (p<0.05) across distinct intestinal segments, suggesting that each region established its bacterial community with different relative abundances. it is anticipated that diverse bacteria will emerge in various intestine segments as each segment’s function and environmental circumstances differ from one another (rehman et al., 2007; wise and siragusa, 2007). in the current study the most reflective differences in the microbial population in the intestinal segments of the two breeds was detected between day 5 to 25. one possible explanation is that at early age periods, immediately after hatching, is the most critical period in the life of the chick. during this early age period, there is the transition from yolk to oral nutrition associated with major physical and functional development of the digestive tract and organs (ravindran, 2003) resulting in unstable environmental conditions of the digestive tract’s microecosystem. different studies observed similar results that the microbial community structure varies with age and the microbial community structure was impartially stable and is replaced by a stable bacterial community once the rate of the intestinal development lessened (mackie et al., 1999; xu et al., 2003; amit-romach et al., 2004). the unique microbial community at 3-5 days of age suggests that the early bacterial community is relatively transient and is replaced by a stable bacterial community later in life (lumpkins et al., 2010; glendinning et al., 2019). in the current study, our data showed that bacilli was the most dominant class in the duodenal flora of cobb 500 at a younger age than local omani breed (cobb 500: day5 98.9 %; local omani: day5 72.5 %). clostridia was the second most abundant class in the duodenum. their levels were high in local omani than in cobb 500 at an early age (local omani: day5 13.1 %; cobb 500: day5 0.062 %, respectively). it is well documented that the chicken cecum and its mucosal tissue are dominated by clostridia related species (bjerrum et al., 2006; gong et al., 2007; lund et al., 2010). clostridia are mainly involved in fermentation and can ferment a wide variety of substrates including monosaccharides and polysaccharides (jones and woods, 1986). the larger number of clostridia in the duodenum of local omani chickens during early intestinal development possibly have no or limited function in nutrient absorption and subsequently the duodenum functions at a lessened level when compared to that of cobb 500 chickens. according to al-marzooqi et al. (2020) the higher abundance of clostridia that are associated with fermentation act in an inhibitory fashion for nutrient absorption in the intestine of the local omani chickens and the villus development is slowed down. the morphological analysis in a study by al-balushi (2021) showed that villus height to villus width ratio in cobb 500 broilers was significantly higher compared to the local omani chickens (14.18 versus 9.74, respectively p < 0.01). it is assumed that an increased villus height is paralleled by an increased digestive and absorptive function of the intestine due to increased absorptive surface area, expression of brush border enzymes, and nutrient transport systems (amat et al., 1996). enterocyte enzymatic activity and structure are two of the most important features of the intestinal mucosal physiology (caspary, 1992). al-marzooqi et al., (2019) concluded that villus development has a profound effect on the growth performance of the chickens. many studies proved that variations in bacterial population between certain broiler lines might be attributed to differences in villi height, which could result in a wider distance between the crypt and the lumen with increased villus height, creating a niche for specific bacteria (suau et al., 1999; salzman et al., 2002; lumpkins et al., 2010). as a result, villi height might be referred as a contributing element to the bacterial community’s habitat. conclusion the dynamics of the gut microbial community or microbial balance are still far from fully understood. however, the future development of the local omani chicken breed for rapid growth production requires a further selection of lines that should take in consideration the intestine’s overall developmental rate. in addition, future studies will need to look into histological alterations related to intestinal function. it is essential to establish baseline values for production parameters of local omani chickens and characterize the overall performance of local omani chickens. future research should be focused by identifying gut bacteria that can be associated with improved/poor chicken growth performance. moreover, future studies need to be directed towards development of diets, such as the utilization of probiotics to increase the development of bacilli during early intestinal development and subsequent better utilization of nutrients in the local omani chickens. 60 squ journal of agricultural and marine sciences, 2023, volume 28, issue 1 evaluation of the intestinal bacterial community of local omani and cobb 500 broiler chickens raised in an open-sided house using 16s rdna-based analysis acknowledgement this study was financially supported by the sultan qaboos university research fund [number: ig/agr/ anvs/19/01]. references al-jumaili as, boudali sf, kebede a. 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(2003). development of digestive function in neonatal poultry: physiological limitations and potential. proceeding australia poultry science symposium 15: 1–7. rehman hu, vahjen w, awad wa. (2007). indigenous bacteria and bacterial metabolic products in the gastrointestinal tract of broiler chickens. archive animal nutrition 5: 319–335. 61research paper al-balushi , el tahir, asi, el-zaiat, al-abri, al-kharousi, al-marzooqi richards-rios p, fothergill j, bernardeau m, wigley p. (2020). development of the ileal microbiota in three broiler breeds. frontiers in veterinary science 7: 1-18 (article 17). salzman nh, de jong h, paterson y, harmsen hjm, welling gw, bos na. (2002). analysis of 16s libraries of mouse gastrointestinal microflora reveal a large new group of mouse intestinal bacteria. microbiology 148: 3651-3660. shang y, kumar s, oakley b, kim wk. (2018). chicken gut microbiota: importance and detection technology. frontiers in veterinary science 5: 1-11 (article 254). suau a, bonnet r, sutren m, gordon jj, gibson gr, collins md, dore j. (1999). direct analysis of genes encoding 16s rrna from complex communities reveals many novel molecular species within the human gut. applied environmental microbiology 65: 4799-4807. wise mg, siragusa gr. (2007). quantitative analysis of the intestinal bacterial community in one to threeweek-old commercially reared broiler chickens fed conventional or antibiotic-free vegetable-based diets. journal of applied microbiology 102: 1138–1149. xu zr, hu chm, xia s, zhan xa, wang mq. (2003). effects of dietary fructooligosaccharide on digestive enzyme activities, intestinal microflora and morphology of male broilers. poultry science 82: 1030-1036. review article journal of agricultural and marine sciences 2022, 27(1): 16–37 doi: 10.53541/jams.vol27iss1pp16-37 received 3 jan 2021 accepted 27 june 2021 biotic and abiotic stresses of major fruit crops in oman: a review rashid a. al-yahyai1*, latifa m. al-kharusi2, mumtaz m. khan1, ali o. al-adawi3, ali m. al-subhi1, basim s. al-kalbani1,3, abdullah m. al-sadi1 rashid a. al-yahyai1*( ) alyahyai@squ.edu.om,department of plant sciences, college of agricultural and marine sciences, sultan qaboos university, al-khod, sultanate of oman. introduction the sultanate of oman is situated on the south-eastern coast of the arabian peninsu-la, having a semi-arid to an arid climate. it’s a unique country that lies within two geographic regions, the south-central part of the country is desert, having its resemblance with africa (16-26° n and 51-59° e), while the northern part is mountainous which resembles continental asia (20-40° n and 40-50° e), in its climatic conditions, while dhofar governorate in the south of oman has tropical monsoon climate (al-khafaji et al., 2017). oman receives less than 100 mm of annual average rainfall which is 10 times less than the average evapotranspiration rate. about 75% of its total area is desert while the remaining is highly diverse within its topographic and climatic conditions, which allowed the cultivation of various tropical to subtropical fruits (al-yahyai et al., 2014). among the agricultural commodities, الضغوط احليوية والالحيوية حملاصيل الفاكهة الرئيسية يف عمان: مراجعة راشد اليحيائي، لطيفة اخلروصي، ممتاز حممد خان، علي العدوي، علي الصبحي، ابسم الكلباين، عبد هللا السعدي abstract: oman is located in an arid region of the world that is characterized by adverse climatic conditions, including heat and drought. in recent years, it has also been affected by climate turbulence and the occurrence of severe weather, such as cyclones and heat/cold waves affecting large agricultural areas of the country. fruit cultivation area represents 31% of the total cultivated area (97,239.58 ha) in the country. however, the production share is only 17% of the total crop production in the country (2.6 million tons). about 90% of the fruit cultivation area is dominated by date palm, banana, lime, and mango. in addition to the abiotic stresses, such as drought, heat, and salinity, major fruit crops have declined in recent years due to various biotic stressors, primarily insect pests, and diseases. for several decades, the date palm has suffered from the dubas bug and in recent years from red palm weevil. lime has been infected with witch’s broom disease of lime (wbdl) caused by ‘candidatus phytoplasma aurantifolia’ that has led to the decline of production to 25% from its peak in the nineties. banana is oman`s second-largest fruit crop in production and export. it has also been the subject of studies due to losses incurred by farmers during pre-and post-harvest stages, in addition to several pests and diseases that affect bananas in oman. mango is another major fruit crop that is primarily cultivated in northern oman. severe infection with mango decline has led to the eradication of mango orchards from many regions of oman, particularly in batinah coast, where increased salinity has led to a decline in mango yield. research conducted in oman has investigated several aspects of these challenges. this review paper summarizes the outcome from studies conducted in the country and proposes directions towards resolving current and future challenges to the fruit industry. keywords: date palm, lime, mango, banana, fruit trees, climate change, abiotic stress امللخص:تقــع ســلطنة عمــان يف منطقــة قاحلــة مــن العــامل تتميــز بظــروف مناخيــة قاســية تشــمل شــدة احلــرارة واجلفــاف، ويف الســنوات األخــرة أتثــرت أيًضــا ابالضطــراابت املناخيــة مثــل األعاصــر وموجــات احلــرارة والــرودة الــي أثــرت علــى مناطــق زراعيــة واســعة مــن البــاد، ومتثــل مســاحة زراعــة الفاكهــة مــا نســبته 31٪ مــن إمجــايل املســاحة املزروعــة )97،239.58 هكتــار( يف الســلطنة ومــع ذلــك ، فــإن حصــة اإلنتــاج ال تتجــاوز 17٪ مــن إمجــايل إنتــاج احملاصيــل الزراعيــة يف الســلطنة )2.6 مليــون طــن(، ويهيمــن النخيــل واملــوز والليمــون العمــاين واملاجنــو علــى 90٪ مــن مســاحة زراعــة الفاكهــة، ابإلضافــة إىل الضغــوط الاأحيائيــة ، مثــل اجلفــاف واحلــرارة وامللوحــة ، تراجعــت حماصيــل الفاكهــة الرئيســية يف الســنوات األخــرة بســبب الضغوطــات احليويــة املختلفــة وعلــى رأســها اآلفــات واألمــراض. ولعــدة عقــود، عانــت خنيــل التمــر مــن حشــرة الــدوابس ويف الســنوات األخــرة مــن سوســة النخيــل احلمــراء. كمــا أصيــب الليمون مبرض مكنسة الساحرة والنامجة عن )candidatus phytoplasma aurantifolia( مما أدى إىل اخنفاض اإلنتاج إىل 25٪ من ذروة االنتــاج يف التســعينيات. ويعتــر املــوز اثين أكــر حمصــول فاكهــة يف ســلطنة عمــان انتاجــا وتصديــرا وابإلضافــة اىل الدراســات املختلفــة عــن اإلنتــاج، أقيمــت دراســات عــن اخلســائر الــي يتكبدهــا املزارعــون خــال مرحلــي مــا قبــل وبعــد احلصــاد، ابإلضافــة إىل العديــد مــن اآلفــات واألمــراض الــي تصيــب املــوز يف عمــان. وحيــث أن املاجنــو هــو حمصــول رئيســي آخــر يــزرع بشــكل أساســي يف مشــال عمــان فقــد أدت اإلصابــة الشــديدة مبــرض تدهــور املاجنــو إىل فقــدان العديــد مــن بســاتني املاجنــو يف الســلطنة وخاصــة يف ســاحل الباطنــة، حيــث ســامهت زايدة امللوحــة كذلــك إىل اخنفــاض انتــاج حمصــول املاجنــو. وتلخــص ورقــة املراجعــة هــذه نتائــج الدراســات الــي أجريــت يف الســلطنة واملتعلقــة إبنتــاج الفاكهــة وتقــرح حلــول توجيهيــة للتحــدايت احلاليــة واملســتقبلية. الكلمــات املفتاحيــة: خنيــل التمــر، الليمــون العمــاين، املاجنــو ، املــوز ، أشــجار الفاكهــة ، تغــر املنــاخ ، اإلجهــاد الاأحيائــي. 17review article al-yahyai, al-kharusi, m. khan, al-adawi, al-subhi, al-kalbanim, al-sadi fruit crops are the main agricultural products that have been traditionally cultivated for thousands of years. while this climatic and geographic diversity helped cultivate a variety of fruit crops in a subsistence manner, there have been many challenges that increased over time as the agricultural sector adopted more modern approaches to cultivation. these challenges include biotic, largely caused by the emergence of pests and diseases, while others are abiotic, including heat, drought, and salinity. future challenges include the shift to the modernization of agriculture, climate change, and declining water and land resources. these challenges were the main research focus in oman. this review article was aimed to present the status of research and major outcomes that can develop future research directions towards resolving some of these challenges. current status of fruit production in oman a large percentage of the cultivated area in oman is used to produce a variety of tropical, subtropical, and deciduous fruit crops. fruit cultivation area represents 31% of the total cultivated area (97,239.58 ha) in the country. however, the production share is only 17% of the total crop production in the country (2.6 million tons) (figure 1). this indicates that there are several challenges in fruit production at the pre-harvest and postharvest levels. however, despite the great potential of fruit crop production, the sector remains an unattractive alternative to fodder crops that use plenty of water resources. the topographical and climatic variations in the country provided fruit growers. the high-altitude mountains in northern oman, al-jabal al-akhdar at 2000 m above sea level, is characterized by low temperatures that are adequate to meet the chilling requirements of several deciduous fruit species, the most common being pomegranates, pome and stone fruits and nut crops such as walnuts (figure 2). the southern plains of salalah are characterized by summer rainfall due to annual drifts from the indian ocean monsoon, are characterized by the cultivation of several tropical fruit crops, most prominently coconut, bananas and papayas. whereas, the rest of the country largely features hot summers, suitable for the cultivation of the most dominant fruit crop, the date palm. other important fruit crops that are suitable for many of oman’s regional climatic zones include mango, lime, guavas and annona. according to the latest national agricultural census that was conducted in 2012/2013, the number of date palms declined slightly by 3.8% totaling 7,563,279 palms compared to 7,859,443 in the 2004/2005 census. this decline may be attributed to the continued loss of agricultural land to salinity and desertification, in addition to extreme weather events caused by climate change, in date palm cultivation areas. however, other fruit crops have increased in numbers by larger percentages, which may also indicate a replacement of date palms with a more profitable crop. lime has increased by 11% (390,218 trees), mango by 8.5% (434788 trees), and coconut by 11.5% (159,527 palms) in 2012/2013 census, compared to 2004/2005 census (maf, 2017). it is noteworthy, that oman has initiated a project to plant one million date palms in 2009, of which 600, 000 palms have already been planted to date. the major fruit crops in oman are date palm, bananas, lime and mangoes, constituting 83%, 6%, 3%, 3% of fruit production areas in the country, respectively (table 1). over the past few years, there has been an increase in fruit production in oman, despite a slight decline in the cultivated area (figure 3), which may be attributed to improved cultural practices and the introduction of high-yielding cultivars, such as the case for mangoes. the increase in fruit production is driven by increasing figure 1. production and cultivated area of crops in oman in 2017 (maf, 2017). 18 squ journal of agricultural and marine sciences, 2022, volume 27, issue 1 biotic and abiotic stresses of major fruit crops in oman: a review demand, as the country’s import of fruits continues to increase, driven by health consciousness and an increase in economic prosperity. nonetheless, the increase in fruit production over the past few years varied from year to year, due to several factors, including climate anomalies, pests and diseases, and availability of resources, adverse abiotic conditions such as salinity and drought, and human factors related to labor, energy and the economy. challenges in fruit production cultural practices one of the major challenges to developing fruit production as an economic sector is the traditional means of cultivation and cultural practices followed by the less cost-effective resource and time-consuming methods. these traditional methods have been reported for various fruit crops, including date palm (al-yahyai and khan, 2015), lime (al-yahyai et al., 2012), mangoes (al-jabri and al-yahyai, 2017; al-yahyai et al., 2013) and pomegranates and deciduous crops (al-yahyai et al., 2009; alsaid et al., 2013; al-yahyai et al., 2014). this has resulted in decreased yield and selling price of locally produced fruits. experiments have shown that several techniques can be followed to enhance the quality of fruit production, including management of irrigation water by utilizing deficit irrigation for date palm (al-yahyai and khan, 2015) and bananas (al-harthi and al-yahyai, 2009), and improved storage (al-yahyai and al-kharusi, 2012) and marketing strategies (al-yahyai, 2007). utilization of post-harvest technology can lead to enhanced marketability of major fruit crops, such as date palm (al-yahyai and manickavasagan, 2012 a,b) and bananas (opara et al., 2013, opara et al., 2012). abiotic stresses affecting fruit production in oman drought, heat, salinity and climate change are major abiotic factors worldwide that limit fruit crop productivity and sustainability by disturbing their growth and productivity (zörb et al., 2019). generally, plants are highly susceptible to abiotic stresses due to their sessile nature, as these stresses limit their capability. it is reported that 90% of arable lands are suffering from one or more of the mentioned abiotic stresses and are causing about 70% yield losses (reis et al., 2012; mantri et al., 2012). oman figure 2. distribution of deciduous fruit crops cultivated at various altitudes in oman. (source: basim al-kalbani, unpublished). 19review article al-yahyai, al-kharusi, m. khan, al-adawi, al-subhi, al-kalbanim, al-sadi fruit industry suffers from drought, aridity, salinity and water scarcity problems (ahmed and choudri, 2012). also, more changes in environmental conditions may cause huge economic losses. due to climate change, the semi-arid regions are predominantly affected by abiotic stresses, resultant drought and soil salinization have been increased on agricultural lands. in arid and semi-arid regions, there is a natural phenomenon of high evapotranspiration and sea water entry in coastal areas, which causes salt accumulation around the plant rhizosphere (sobhanian et al., 2020). drought and salinity stresses have been increased due to global warming and anthropogenic activities such as improper irrigation and drainage. besides, global warming, the changing rainfall pattern has also increased the evapotranspiration rate, which has ultimately increased the drought severity (dai, 2011). drought due to environmental changes, the agriculture sector is greatly affected by drought stress, which seriously influences plant vegetative and reproductive stages (chaves and oliveira, 2004). water is essential for all physiological functions occurring in plants. in drought, plants undergo complex anatomical mechanisms to regulate water in their body and inappropriate conditions stimulate fundamental changes in plant morphology, physiology and biochemistry of water-deficient organs (anjum et al., 2011; jarvis and jarvis, 1963). to minimize water loss by transpiration, plants modify their anatomical characteristics like the closing of stomata, production of cuticle wax, reducing leaf area, besides it includes certain changes in plant physiological mechanism including a reduction in photosynthetic rate, changes in gene expression and increase in osmotic stress (hadley and smith, 2011; munné-bosch and alegre, 2004; chaves et al., 2003). in drought, the creation of drought-resistant varieties is a strategy to ensure proper food supply. the response of drought-tolerant species is different from the susceptible species. plants adapt to drought stress in different ways, such as by changing their growth patterns, morphology and defense mechanism (zandalinas et al., 2018). during drought, one of the most common mechanisms adopted by plants is the remobilization of prestored carbohydrates from stems to overcome drought (schnyder, 1993). the other cellular and subcellular mechanism induced by plants during a drought include photosynthesis, antioxidative response, energy metabolism, osmotic adjustment, lipid metabolism, ion homeostasis and gene expression regulation (sobhanian et al., 2020). therefore, evaluation of drought-resistant cultivars, throughput analysis of plant genomics, proteomics and transcriptomics is required (peng et al., 2009). effects of drought on fruits trees horticultural crops are perishable and require a large amount of water for sustained growth and yield, whereas drought or water-deficient conditions adversely affect crop yields and quality. in fruit crops, the drought timing, duration, intensity, and species determine its hazardous effects. date palm (phoenix dactylifera l.) is the top fruit crop of oman, which contributes about 80% to total fruit crops grown in the country (al-yahyai and khan, 2015). it is considered tolerant to drought and salt stress and provides a significant contribution to the food security of the arid regions. however, recent threatened its productivity (hazzouri et al., 2020). the date palm has various anatomical characteristics that enable it to tolerate drought stress, including thick pinnate compound leaves having waxy cuticles and spines on them. besides, it has a deep root system, which enables it to maximize water uptake, while all other leaf traits help in minimizing figure 3. fruit area and production in oman (2000-2018) (source: faostat, 2020). 20 squ journal of agricultural and marine sciences, 2022, volume 27, issue 1 biotic and abiotic stresses of major fruit crops in oman: a review evapotranspiration rate (sané et al., 2005; ramoliya and pandey, 2003). despite having drought-tolerant properties, it requires a lot of water for commercial productivity. dates suffering from drought have reduced productivity and fruit quality (hussain et al., 2012). similar findings were observed by other researchers who stated that long-term drought negatively affects date palms by reducing their growth, productivity and quality (elshibli et al., 2016; alhammadi and kurup, 2012). arab et al. (2016) reported that 2-year-old date palm seedlings subjected to drought and heat showed a reduced concentration of antioxidants, e.g. ascorbate and glutathione in leaves. the fatty acid composition under drought was changed but it remained unchanged under heat environment, which shows that date palms may have independent metabolic systems to deal with drought and heat stresses. proline accumulation occurs in plants due to multiple stresses; high proline contents were observed in date palms in response to drought and salinity, proline can be used as a possible marker in date palm to improve drought and salinity tolerance (yaish, 2015). the date palm (cv. khalas) fruit chemical quality changes as a result of decreased water regimes, and overall the drought effects on fruit quality were significant (al-yahyai and al-kharusi, 2012). the ministry of agriculture and fisheries reported that climate change and environmental constraints are major causes of date palm production instability in oman. however, kheiry (2017) used the stochastic model to analyze and identify the sustainable date palm farming systems in oman. he argued that al-batinah is the most risk efficient region and recommended awarding economic incentives to growers for sustainable date palm varieties plantation and diversification which can minimize the sustainability risks of date palm production in oman. al-yahyai (2018) reported multifaceted challenges that growers are confronting in date palm production in oman. he argued that farmer participation, training and extension agent’s role can help in monitoring the crop limiting factors and mitigating such anomalies for the improvement of date palm cultivation and production of export-quality dates in oman. it has been claimed that the date palm distribution in oman will be changed due to ever-changing climate conditions. they used the basic climex software package to see the climate responses and later this was further integrated to demonstrate date palm possible distribution with two global climate models (gcms) including csiromk3.0 and miroc-h. the earlier results showed that some regions may become unsuitable for date palm cultivation in oman by 2100 (shabani et al., 2015). historically, banana has been one of the most domesticated crops of the arabian peninsula and the gulf ports of oman have played a major role in the exchange of banana genetic resources between africa, china, the indian subcontinent and the arabian peninsula, despite being arid and unfavorable climatic conditions for its cultivation (al-busaidi, 2013). bananas are highly sensitive to drought, as they have large leaves with large air pockets inside; the annual evapotranspiration rate of bananas varies from 1200 to 2690 mm (robinson and alberts, 1986). musa species show differences in stomatal conductance based on leaf age, climatic conditions and soil water relation (ravi and vaganan, 2016). in water stress, the flowering stage is highly affected as it is sensitive to drought, the lowest yield was observed in banana genotype “elakki” when drought was given at the flower differentiation stage (murali et al., 2005). similarly, the lowest yield was observed in genotype “robusta” when water stress was applied after the flower set (hegde and srinivas, 1989). ravi and vaganan (2016) stated that the genotypes, “rasthali”, “robusta” and “karpuravalli” showed a reduction in bunch weights when stress was applied. mango (mangifera indica l.) is the third-largest fruit crop of oman after date palm and banana (al-yahyai et al., 2013). due to the huge diversity of this crop, it has limited the outbreak of mango decline disease in oman (al-adawi et al., 2006). in oman drought conditions, mangoes showed a very little response in leaf visual parameters and leaf potential by adjusting their physiological functions according to drought. mango growth comes in flushes, in drought, the mango vegetative flushes growth is reduced significantly, and it also lessens the leaf water contents, leaves in flush and flush length (laxman and bhatt, 2017). water stress has a significant effect on mango reproductive growth, and it has been observed that drought stress for a longer time delayed flowering time (tahir et al., 2003). however, drought for a lesser time enhanced flowering in mango (scholefield et al., 1986). similar findings were observed by schaffer et al. (1994) who stated that drought has an inhibitory effect on vegetative flushes, but it promotes reproductive flushes. drought can lead mangoes towards a decline in terms of yield and quality as well (wei et al., 2017). drought reduces fruit size by decreasing cell size and number and it also enhances fruit drop in mangoes (singh, 2005). the variation in water requirement not only affects mango fruit size and yield but also affects fruit quality attributes like titratable acid, total soluble solids (tss), starch and ascorbic acid contents (wei et al., 2017). lime (citrus aurantifolia) is one of the main citrus species cultivated in oman, which represents about 3.44% of all fruit crops grown in oman. however, in recent decades, the production of lime and its cultivated area is greatly reduced in oman. this decline has been largely attributed to a combination of biotic and abiotic factors that negatively affected lime tree growth and yield (al-yahyai et al., 2012). in lime, abiotic stresses are of great concern as its key production countries such as india, mexico and the middle east are highly suffering from water scarcity and salinity (donkersley et al., 2018). in citrus, irrigation and soil conditions are the important factors of its quality enhancement (levy 21review article al-yahyai, al-kharusi, m. khan, al-adawi, al-subhi, al-kalbanim, al-sadi and syvertsen, 2004). well-managed and precision irrigation increases citrus economic production and profit (ruiz-sanchez et al., 2010). however, drought or water stress in citrus resulted in poor vegetative growth, yield and fruit quality, besides increasing pathogens susceptibility (levy and syvertsen, 2004). similar findings were observed by other researchers who stated that water stress increased the incidence of disease development and has greatly influenced lime growth and yield (syvertsen and levy, 2005; blodgett et al., 1997). grape (vitis vinifera l.) is one of the most cultivated crops in the world. in 2005, drought severely affected grape yield and processing in south africa, which resulted in an agricultural income loss of about 3.7 million dollars (johnston, 2009). the family of muscat grapes consists of more than 200 varieties; its name is associated with muscat the governorate of oman and these are planted at jabal akhdhar where the temperature is highly suitable for their production. muscat grapes are known globally for their peculiar aroma (ebuen, 2019). grape is drought tolerant fruit as compared to other fruit crops and can endure stress conditions; however, it goes through certain morphological, anatomical and physiological changes during water stress conditions. grapes have large xylem vessels as compared to other fruits, which enables them to tolerate water stress or drought (serra et al., 2014). during adequate water supply its roots remain on the upper topsoil while during drought, roots move deep in the soil (bauerle et al., 2008), leading to its increased root length but decreased shoot length (hardie and martin, 2000). a higher number of new roots were observed in grapes during drought for water uptake (serra et al., 2014). water stress causes stomata closure which limits photosynthesis and reduces dry mass production and yield (berdeja et al., 2014). however, little drought stress at maturity increases sugar and phenolic contents in grapes (van-leeuwen et al., 2009). papaya (carica papaya l.) is a drought-tolerant crop, however, to achieve its productive yield, sufficient water is required (campostrini and glenn, 2007). drought drastically reduces papaya plant growth, nutrient uptake, transpiration, photosynthesis, chlorophyll contents and leaf abscission in papaya (mahouachi et al., 2006; slattery et al., 2017). water stress conditions limit the physiological performance of papaya (mahouachi et al., 2007), besides there is the highest accumulation of proline, abscisic acid and jasmonic acid during drought (mahouachi et al., 2012). masri et al. (1990) reported a 50% reduction in leaves, 86% in flowers and 58% in fruit, the growth and development of papaya fruit was highly reduced during drought. guava (psidium guajava l.) is a dicotyledonous, evergreen plant that has tolerance against drought and saline conditions (akram et al., 2017), however, various biotic and abiotic factors affect its growth. in guava, several morphological and physiological characteristics were affected by salinity (bezerra, 2018). salinity was also found to increase catalase, polyphenol oxidase, carotenoids, proline, but sodium chloride treatment decreased peroxidase and chlorophyll (a, b, and total) (ghalati et al., 2020). besides photosynthesis, drought severely affects certain biochemical and physiological functions (estrada-luna et al., 2000). similarly, in coconut (cocos nucifera) water deficit greatly affects the growth, productivity, and physiology of plants (gomes and prado, 2007; passos et al., 2005). pomegranate (punica granatum l.) is being grown in several parts of oman, however, the green mountains (al jabal al akhdar) are the top areas where quality pomegranates are produced due to suitable climatic conditions, and is also a good source of income for growers (al-said et al., 2013; al-harthi, 2011). in oman, harvesting of pomegranate local cultivars (‘hamedh’, ‘malasi’, ‘helow’, ‘qusum’) is done based on fruit size shape and color due to prevailing climatic conditions (al-yahyai et al., 2009). pomegranate is popular due to the presence of antioxidants and phenolic compounds, while these contents vary with maturation, ripening and abiotic stresses (labbé et al., 2016; zarei et al., 2011). in pomegranate, khattab et al. (2011) observed a decrease in chlorophyll contents with a decrease in irrigation. similar findings were observed by tavousi et al. (2015) who stated that it is highly susceptible to dehydration while it has resistance against salinity. pourghayoumi et al. (2017) examined pomegranate cultivars under drought conditions and found increased proline contents in all cultivars except ‘ghojagh’, while the cultivar ‘rabab’ showed high contents reactive oxygen species (ros) scavenging mechanism in drought conditions, besides these genotypes, showed good tolerance against drought as well. salinity salinity is one of the major problems in arid and semi-arid regions (foster et al., 2018). more than 800 million hectares of land or over 6% of world soil surfaces are affected by this problem (munns and tester, 2008). global annual losses in crops due to salinity are more than us $12 billion (shabala, 2013). the first signs of salinity and its effects are osmotic effects, whereby the presence of high sodium chloride (nacl) levels in soil inhibits water uptake leading to osmotic stress, which causes slow growth. moreover, when the salt stress becomes severe, oxidative stress is induced and eventually causes death particularly in sensitive plants (munns and tester, 2008; munns, 2002; shabala, 2017). in the sultanate of oman, salinity has affected a large area of agricultural lands (al-yahyai, 2006). however, some fruit trees withstand harsh salinity conditions and thrive very well under salinity, such as date palms. in the sultanate, date palm accounts for more than 200 cultivars (al-yahyai and khan, 2015; al-yahyai, 2011). it is a dioeciously sustained fruit tree that can withstand salinity, drought, and temperature conditions (hazzouri et al., 2020; alhammadi and kurup, 2012) it is a salinity tolerant fruit crop (dowson, 22 squ journal of agricultural and marine sciences, 2022, volume 27, issue 1 biotic and abiotic stresses of major fruit crops in oman: a review 1982; yaish and kumar, 2015; sperling et al., 2014; levy and syvertsen, 2004; furr and armstrong, 1975). date palm is a pivotal agriculture crop in oman (al-yahyai and khan, 2015; al-yahyai and al-khanjari, 2008), and the largest date palm yield is produced from the al-batinah region, the northern part of oman (al-yahyai, 2011). according to fao, the total date production in oman is 8.5 mt in 2018 (fao, 2019). date palm growth and development decrease under environmental stress conditions. reduction in date palm under salinity is well documented in different countries (tripler et al., 2007; tripler et al., 2012; chao and krueger 2007; serret et al., 2020; al-qurainy et al., 2020; al mansoori et al., 2006) and in oman (jana et al., 2019; yaish et al., 2015; al-yahyai, 2006; al-harrasi et al., 2020; alrasbi et al., 2010; haplogypsids et al., 2006; erskine et al., 2004; al-yahyai and manickavasagan, 2012a,b; al kharusi et al., 2017); however, the degree of reduction varies within the cultivars. recently, several researchers in the country reported that salinity has affected the growth of some susceptible cultivars of date palm (al kharusi et al., 2017; patankar et al., 2019, al-rahbi, al-mulla and jayasuriya, 2020; al-harrasi et al., 2020). these cultivars can withstand low-moderate salinity, however, more energy is required to perform normal metabolism. additionally, in date palm, there are some inappropriate irrigation practices such as using saline water, which is pumped from wells (yaish et al., 2017) and has changed the groundwater recharge rates resulting in sea-water intrusion into the groundwater leading to soil salinization (yaish et al., 2015) . therefore, a significant cause of soil salinity may be owing to the use of poor-quality water for crop irrigation (munns and tester, 2008). besides, other factors may have contributed to the reduction of date yields such as high evapotranspiration rates and low rainfall amount. on the other hand, some tolerant cultivars, when exposed to high salinity metabolize normally without showing any damage symptoms (al kharusi et al., 2017b). in general, salt stress can reduce date palm growth and development through different aspects such as osmotic effects, ion toxicity, inadequate nutrients (al-qurainy et al., 2020; hazzouri et al., 2020). aljuburi (1992) studied the effects of salt stress on the growth of four date palm cultivars, lulu, khalas, boman and barhee. he found that the cultivar lulu was more susceptible to salinity than other cultivars. salinity tolerance, which involves several complex mechanisms, protects plants against the harmful effects of salinity. date palm cultivars differ in their salinity tolerance capacities (marashi et al., 2017; al-khateeb et al., 2019; abdulwahid 2017; djibril et al., 2005; ibraheem et al., 2011; el-khawaga, 2013; yaish et al., 2015). in the sultanate of oman, some date palm cultivars (i.e., manoma, umsila, fard nagal and barni) can thrive in saline conditions (al kharusi et al., 2017; alrasbi et al., 2010). despite some of these cultivars are considered not good quality and used as animal feed (al-yahyai and khan 2015; al-yahyai, 2006), are capable to adapt and mitigating the environmental impacts in their growing zones such as salinity stress. these cultivars possess various mechanisms that allow their roots, leaves and trunk tissues to cope with high salt availability where they are grown (satisha et al., 2020; patankar et al., 2019; hazzouri et al., 2020; al kharusi et al., 2019; youssef and awad 2008; kurup et al., 2009; al mansoori et al., 2006). salinity adaptation mechanisms in omani date palm osmotic adjustment mechanism the osmotic adjustment mechanism is a pivotal adaptation in date palm surviving under salinity because it helps to maintain turgor and cell volume amide salinity soil (shabala and shabala, 2011; munns and tester, 2008). recently, an osmotic adjustment mechanism was reported in some omani date palm cultivars (al kharusi et al., 2017) via an efficient photosynthetic system as indicated by the higher quantum yield, stomatal conductance, membrane stability and the excessive photochemical energy diverted to various pathways. also, an osmotic adjustment mechanism was reported in another omani cultivar (al-harrasi et al., 2020), where salt ions are then regulated and transported across the cell membrane via the proton motive force (pmf ) (wegner and shabala, 2020) and pumped by the date palm gene (pd6nhx) into the vacuole of transgenic arabidopsis plants (al-harrasi et al., 2020), followed by electrochemical gradients. then the gradients are balanced by the synthesis of high hydration organic metabolites and compatibles. these metabolites were indicated in recent research in omani date palm cultivar as an adaptation mechanism under salt stress (al kharusi et al., 2019b), including sugars, nitrogenous compounds (proline and glycine-betaine) in the cytoplasm. these solutes are capable to stabilize the cytoplasmic enzymes on the cellular membranes, thereby protecting them against inactivation by salt ions (smirnoff and stewart, 1985), where they play a pivotal role in mitigating nacl-induced potassium k+ efflux (shabala et al., 2012), and these have a direct protective role for membrane integrity as osmoprotectants under salt stress and other environmental stresses (zhang et al., 2010; he et al. 2010; yaish, 2015). they also have an indirect protective role through participating in signal transduction pathways (kumar et al., 2018). similarly, effects of high salinity irrigation on growth, gas exchange, and photoprotection on young date palms (cv. medjool) were reported by sperling et al. (2014), where photosynthetic efficiency and potentially were preserved through osmotically driven stomatal closure. furthermore, another omani date palm (cv. umsila) was reported as a saline tolerant cultivar and can adapt to salinity by better maintenance of plant-water relations (al kharusi et al., 2019). however, the synthesis of sufficient osmoprotectant is metabolically expensive 23review article al-yahyai, al-kharusi, m. khan, al-adawi, al-subhi, al-kalbanim, al-sadi and energy exhaustive in plant tissues (chen and jiang, 2010). however, date palms have proven to accumulate high energy primary and secondary metabolites such as antioxidants, vitamins, growth regulators, sugars and nitrogenous compounds (al-kharusi et al., 2009; abdulwahid, 2012; al kharusi, al yahyai and yaish, 2019a, jana et al., 2019, daoud et al., 2019). ion homeostasis mechanism salt inclusion vs. exclusion some of the physiological and molecular basis of salt tolerance in omani date palm cultivars were reported (al kharusi et al., 2019b; al-harrasi et al., 2020; alrasbi, hussain and schmeisky, 2010; jana et al., 2019; yaish et al., 2015; al-yahyai and manickavasagan 2012a,b; patankar et al., 2016). besides the production of organic osmo-regulators, date palm tissues also possess an alternative mechanism to accumulate high levels of ions, such as k+ and calcium ca2+ and more other ions from the external soil medium (al kharusi et al., 2019b). date palms can take up low amounts of na+ in the leaves tissues and accumulate high amounts of k+ (al-rahbi et al., 2020; al kharusi et al., 2017a,b; patankar et al., 2019a,b), with low energy demand. in a recent study on the salinity tolerance mechanism on omani date palm (cv. khalas), it was proven that overexpression of one of the date palm aquaporin genes (pdpip1;2) confer salinity tolerance and implicated in na+ and k+ transportation (patankar et al., 2019a). in addition, it was found that accumulation of this gene in the date palm leaves under different stress conditions (e.g. drought) could also have a role in photosynthesis efficiency (patankar et al., 2019a). another study on omani established young date palm seedlings (cv. umsila) reported that significant accumulation of enzymatic and non-enzymatic antioxidants are pivotal and have caused a significant increase in the xylem loading of k+, which then is translocated to the leaves (assaha et al., 2017) as a result of higher k+/ na+ ratio balance. additionally, this study revealed that both leaves and roots tissues maintained higher chlorophyll content indicating better photosynthesis capacity and high proline content and subsequently decreased reactive oxygen species (ros), which confer salinity tolerance (al kharusi et al., 2019). another recent study on omani date palm revealed that a cloned date palm gene (pdmt2a) improved drought and salinity stress tolerance in transgenic arabidopsis plants and showed a higher k+/na+ ratio (patankar et al., 2019b). salt tolerance in date palm is associated with lignin accumulation (al kharusi et al., 2019b) and the formation of casparian strips (jana et al., 2019). increased deposition of lignin in the steel was reported in omani date palm salt-tolerant cultivar (al kharusi et al., 2019), as lignification was observed in the root endodermal vascular tissues in response to salinity. on the other hand, increased deposition of casparian band was reported in two omani date palm cultivars (al kharusi et al., 2019b; jana et al., 2019). casparian strip enhances selective ion and water movements across the root cell membranes and maintains a balanced na+/k+ ratio and antioxidant defense as well (garcía-caparrós et al., 2018). also, casparian strips enhance the apoplastic barriers and regulate hydraulic conductivity in roots and therefore, prevent the non-selective apoplastic bypass of na+ into the stele tissues, which helps increase salinity tolerance (zimmermann et al., 2000; karahara et al., 2004). it was also proposed that maize, cotton and beans tend to accelerate the growth of the exoand endoderm cells in response to salinity (karahara et al., 2004; reinhardt and rost, 1995; schreiber et al., 2005). also, the effects of high salinity irrigation on the growth of young date palms (cv. medjool) was reported by sperling et al. (2014), where toxic sodium ions were excluded from the leaves of the young seedlings through the exclusion method. accumulation of global metabolomics and differential metabolites mechanism salt tolerance mechanisms are yet to be puzzled out in date palm, since specific metabolites may be associated with salinity tolerance. a study aimed to decipher the salinity tolerance mechanism in date palm based on the information encoded by the metabolomics profiles of the omani date palm salt-tolerant cultivar revealed the presence of natural metabolites, potent antioxidants, growth regulators and essential vitamins under salt conditions. these metabolites may help to improve the membrane capacities to control water and ion flow, as well as modification of the lignin and casparian strip constituents, which may assist in better salt exclusion. in addition, the enhancement of the accumulation of various antioxidants, which act as reactive oxygen species (ros) scavengers, may help to reduce the oxidative damage caused by salinity. therefore, these metabolites could represent a key mechanism for salt tolerance in date palms. also, this study showed another adaptation mechanism through the accumulation of some membrane and cell-wall constituents that were altered in response to salinity in date palms such as phospholipids, antioxidants, and vitamins. the phosphatidylethanolamine (lysope), a plant growth regulator, is among the phospholipid metabolites and was found exclusively accumulated in the leaves of the salt-tolerant cultivar (cv. umsila) when exposed to salinity. this metabolite is involved in the growth-promoting activity (cowan, 2009). another accumulation of glycolipids was noted from this study; monogalactosyldiacylglycerol (mgdg) increased by 5.8-fold and digalactosyldiacylglycerol (dgdg) were exclusively detected in the leaf tissues of ‘umsila’ when exposed to salinity. the abundance of these two glycolipids in the membrane determines the stability and physical properties of the thylakoid membrane of the chloroplast, which may influence salinity tolerance (quartacci et al., 2000). this study also reported various 24 squ journal of agricultural and marine sciences, 2022, volume 27, issue 1 biotic and abiotic stresses of major fruit crops in oman: a review antioxidants, which were identified using the lc-ms technology and were mapped to the flavonoid synthesis pathways that usually result in the production of antioxidants metabolites and potential free radical scavengers (figure 4). these metabolites included catechin, epicatechin, and eriodictyol. epicatechin and catechin, which are flavonoids that perform antioxidant and iron-chelating functions (morel et al., 1993, koch et al., 2017). these compounds accumulated in salinity-treated ‘umsila’ seedlings. this study also revealed the importance of vitamin b9 in date palm under salinity stress, as it was found that metabolites such as 5, 10-methenyltetrahydrofolic acid, l-glutamic acid, methionine, cysteine, and other antioxidants were involved in vitamin b9 synthesis. these metabolites were differentially accumulated in cv. ‘umsila’ upon exposure to salinity. previous studies have also shown that vitamin b9 is involved in abiotic stress tolerance in plants, with susceptible plants unable to maintain a reasonable level of this vitamin under abiotic stresses (hanson et al., 2016). biotic stresses affecting fruit production in oman several biological challenges affect fruit production in oman. biotic stresses are important due to the economic losses that cause to fruit growers. several studies have identified, major issues with fruit crops, most notably dubas bug on date palm, phytoplasma in lime, viral & fungal diseases in citrus, and mango sudden wealth in mangoes, are the most common causing major challenge to the main fruit crops in the country. dubas bug (ommatissus lybicus de bergevin) is a major pest that causes major damage to date palm and reduces its growth and productivity (al-kindi et al., 2018) and requires large chemical input to control this pest. studies have been conducted to investigate the potential of natural enemies such as pseudoligosita babylonica viggiani, aprostocetusnr beatus, and bocchus hyalinus to control the dubas bug (al-kindi et al., 2018). further research on the impact of dubas bug distribution throughout oman and the environmental and climatic factors that affect the distribution of dubas. studies have predicted that the north of oman is presently at great risk of dubas bug invasions and will remain high in 2050 and 2070 (shabani et al., 2018). mango wilt disease in oman mango is an important fruit crop in oman with a cultivation area of 1,269 ha, representing 3.39% of the total figure 4. the involvement of differentially accumulated metabolites in response to salinity in the flavonoid pathway and the production of antioxidants. the pink boxes indicate the differentially accumulated metabolites in date palm as a result of salinity. 25review article al-yahyai, al-kharusi, m. khan, al-adawi, al-subhi, al-kalbanim, al-sadi fruit cultivated area with a production of 10.9 thousand tons (table 1). mango wilts disease, caused by ceratocystis manginecans (al adawi et al., 2006; van wyk et al., 2007), is the most serious threat to the production of mango in the country. the disease killed thousands of mango trees in oman since its first report in 1998 (al adawi et al., 2006). the bark beetle hypocryphalus mangiferae vectors the pathogen from diseased to healthy hosts, which helps spread the disease (al adawi et al., 2013a). data from the agriculture census in 2004/2005 estimated the death of over 210,000 mango trees during 2000–2005 in the al batinah region alone (maf, 2002; 2003; 2004; 2006). the disease is more severe in trees propagated from local seed sources and on exotic cultivars grafted on the rootstock of omani cultivars (al adawi et al., 2006). mango wilt disease management includes chemical treatments that are expensive and effective only for short periods of time. the selection of resistant cultivars is a long-term effective control of this disease. c. manginecans inoculation trials in oman showed that the cultivar ‘pairi’ and local mango cultivars were highly susceptible. on the other hand, the cultivars ‘hindi besennara’, ‘sherokerzam’, ‘mulgoa’, ‘baneshan’, ‘rose’, and ‘alumpur baneshan’ were relatively resistant (al adawi et al., 2013b). witches’ broom disease of lime (wbdl) acid lime has been a major commercial crop in oman for decades. however, acid lime production has been seriously hampered over the last forty years due to witches’ broom disease of lime (wbdl). in oman, lime production has declined by 75% due to wbdl and now it stands at an average 6.68 thousand tons representing 1.79% of fruit production in the country (table 1). about 80% of the mature acid lime crops are infected with wbdl and most of them either have been killed or removed from the orchards (khan, 2000; al-yahyai et al., 2012). affected acid lime trees show witches’ broom, small leaves, production of several branches and reduction in flower and fruit production from symptomatic branches of infected trees (al-yahyai et al., 2015). wbdl has been worsened by biotic stresses that include citrus tristeza virus and citrus viroids (al-sadi et al., 2017) and abiotic conditions caused by drought and salinity. the disease is caused by ‘candidatus phytoplasma aurantifolia’ (16srii-b) (zreik et al., 1995; al-subhi, 2018). wbdl has also been reported in the uae, iran, saudi arabia, india and brazil (bove et al., 2000; alhudaib et al., 2009, queiroz et al., 2016; ghosh et al., 1999). infected acid lime trees from southern oman, saudi arabia and brazil do not show typical witches’ broom symptoms (al-subhi, 2018). environmental conditions may influence symptom expression (al-ghaithi, 2017). other citrus species like citron, lemon, c. macrophylla and rough lemon have been reported as hosts of the ‘ca. p. aurantifolia’ in oman (al-subhi, 2018, al-subhi et al., 2019, al-yahyai et al., 2012). wbdl phytoplasmas can be transmitted by different means including insect vectors, grafting and seeds. there is evidence that wbdl phytoplasma can be transmitted via seeds (al-shanfari, 2000; al-amri, 2006). the main means of spread of phytoplasma diseases in the fields is by phloem-feeding insect vectors in the families cicadellidae (leafhoppers), fulgoridea (planthoppers) and psylloidae (psyllids). two hemipteran species, leafhoppers and psyllids were recorded as vectors of wbdl phytoplasma in oman (queiroz et al., 2016). citrus tristeza virus (ctv) citrus tristeza virus (ctv) resulted in extreme losses in citrus in different parts of the world. the first report of ctv epidemics was in the early 20th century in south africa where millions of citrus trees grafted on sour orange rootstocks collapsed (eppo, 2004). subsequently, millions of citrus trees were lost in argentina and brazil in the 1930s (bar-joseph et al., 1989). also, over 40 million trees declined progressively in spain in 1957 (cambra et al., 2000). ctv causes different symptoms, the most severe of which are rapid decline (tristeza) and stem pitting. the first causes the decline of trees grafted on sour orange, where grafted trees start collapsing in a few weeks. trees affected with ctv stem pitting strain can show variously sized pits or grooves on twigs or trunks (brlansky, 2002). stem pitting symptoms are common in lime, pummelo, grapefruit and sweet orange (lee and bar-joseph, 2000). other symptoms include leaf chlorosis, stunting and a reduced root system. ctv dispersal can be either by the propagation of virus-infected buds that can cause an introduction of ctv to a new area (bar-joseph and lee, 1989) or by vector transmission. in oman, the first detection of ctv was reported in 1986 in grapefruit, mandarin and lemon seedlings shipped from india (bove, 1995). aphis gossypii, which is one of the important vectors of ctv, was reported in oman in 1984 (moneem, 2005). the ministry of agriculture (ma) surveyed the sultanate in 2007 and 2008. they found that ctv is associated with acid lime and is distributed in muscat, dhofar and al batinah regions (ma, 2009). a subsequent study by al-sadi et al. (2012) in 2009 and 2010 showed that ctv is present in acid lime farms in barka, alrustaq, shinas, sohar, alsuwaiq, boushar, alseeb, quarayat, dhank, yanqul, ibri, mahadha, bahla, nizwa, samael, dibba, madha, ibra, almudhaibi, and salalah. the incidence ranged from 3 to 63%. in addition, ctv was detected in citrus seedlings/budlings imported from different countries. management options of the disease should include strict quarantine measures and eradication programs (navarro et al., 1984; frison and taher, 1991). all citrus-growing counties should have certification programs to ensure that ctv is not spread with budwood 26 squ journal of agricultural and marine sciences, 2022, volume 27, issue 1 biotic and abiotic stresses of major fruit crops in oman: a review or seedlings (navarro et al., 1988). it is also important to avoid grafting trees on sour orange rootstocks as they make trees more vulnerable to the decline disease. fusarium wilt disease of banana banana is the second most important fruit crop oman. over 2.3 thousand hectares of agricultural land in the sultanate are grown with the banana crop of various varieties producing an annual average of 30.74 tons, which represents 8.25% of all fruits produced in oman (table 1). the north and south al batinah governorates come first in terms of cultivated area, with an area of 4,197 faddan (1762.74 ha), followed by dhofar governorate with 960 faddan (403.2 ha), then sharqyia governates with an area of 81 faddan (34.02 ha) (maf, 2014). banana varieties grown in oman include dwarf cavendish (local known as malindi bananas), al-barshi, somali, al-fard, and williams (viswanath, et al., 2000, de langhe, 2002, al-hosni et al., 2010; al-saady et al., 2010). many diseases limit banana production in the world like fusarium wilt (panama disease), moco disease, black segatoka, bunchy top virus disease (ploetz, et al., 2003). banana fusarium wilt disease caused by fusarium oxysporium f.sp cubense (foc) is a soil borne disease and pathogen persist in the infected area for decades. the pathogen initially infects banana plants through roots then moves through the plant into the vascular system within the pseudo-stem and blocks vascular tissue and causes plant death. infected banana plants exhibit yellowing of older leaves and discoloration of vascular tissues. the disease became most destructive in many banana-growing countries. the disease was firstly reported during 1874 in australia and later race1 of the pathogen foc was reported in central american countries (ecuador and panama) wiping gross michel banana cultivar from these areas and south america. consequently, the gross michel cultivar was replaced with the cultivation of cavendish cultivars which was resistant to foc race 1, and cavendish cultivars dominated the market (ploetz, 2005). during the early 1990s, a new race of foc called tropical race 4 (tr4) was reported southeast asia causing a serious problem for cavendish cultivars plantations in this region (ploetz, 2006a &b). the new race tr4 spread around the world and reported threatening banana cultivation in many countries in asia, africa and recently in south america (damodaran et al., 2019, o’neill et al., 2016, ordóñez et al., 2016, ploetz, 2015, ploetz, et al., 2015). in oman, symptoms resembling that of fusarium wilt disease of banana were first observed in northern governates. samples from diseased banana plants were collected from infected farms and isolated pathogen identified as foc race tr4 using molecular diagnostic marker (dita et al., 2010). integrated disease management options of fusarium wilt of banana should be considered as until now there is no known effective chemical or biological control measures for this serious disease. strict quarantine measures are important to prevent the spread of the disease from infected area to new healthy banana plantations and oman has table 1. area and production of major fruit crops in oman (2000-2018) (source: faostat, 2020). area (ha) production (tons) year all fruits dates bananas limes mangoes all fruits dates bananas limes mangoes 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 42,485.00 40,758.00 40,672.00 40,198.00 42,463.00 37,173.00 36,580.00 38,521.00 37,239.00 36,947.00 38,468.00 39,136.00 35,526.00 39,434.00 41,218.00 29,832.00 29,576.00 32,126.00 32,805.00 35,508.00 33,919.00 33,869.00 33,848.00 35,532.00 31,353.00 31,353.00 32,746.00 31,353.00 31,353.00 31,353.00 31,348.00 30,615.00 34,195.00 36,255.00 24,120.00 24,120.00 24,617.00 25,125.00 2,633.00 2,716.00 2,610.00 2,520.00 2,856.00 2,225.00 2,225.00 2,435.00 2,435.00 2,436.00 3,720.00 4,374.00 2,500.00 1,400.00 1,421.00 1,421.00 1,421.00 1,564.00 1,560.00 1,678.00 1,620.00 1,690.00 1,440.00 1,210.00 1,242.00 1,242.00 1,231.00 1,231.00 1,233.00 1,233.00 1,236.00 710.00 1,200.00 1,208.00 1,208.00 1,207.00 1,302.00 1,399.00 1,507.00 1,510.00 1,510.00 1,500.00 1,470.00 1,070.00 1,071.00 1,071.00 1,071.00 1,071.00 1,071.00 1,071.00 610.00 1,490.00 1,019.00 1,496.00 1,496.00 1,505.00 1,506.00 359,353.00 383,465.00 320,298.00 295,395.00 320,275.00 324,012.00 315,090.00 325,544.00 345,560.00 327,379.00 382,421.00 376,587.00 382,491.00 391,497.00 386,583.00 416,832.00 427,567.00 495,765.00 505,114.00 280,030.00 298,006.00 238,611.00 219,770.00 231,000.00 247,331.00 258,738.00 255,871.00 267,000.00 258,572.00 276,405.00 268,011.00 281,000.00 308,400.00 317,400.00 344,690.00 355,332.00 360,917.00 368,808.00 32,150.00 33,680.00 32,915.00 28,750.00 34,000.00 26,720.00 25,955.00 28,892.00 29,000.00 28,890.00 56,686.00 61,584.00 56,790.00 19,970.00 18,184.00 16,578.00 16,578.00 18,397.00 18,265.00 8,210.00 8,560.00 8,385.00 6,830.00 5,875.00 6,159.00 5,916.00 5,983.00 7,440.00 6,354.00 6,354.00 6,503.00 6,340.00 6,250.00 5,943.00 6,199.00 6,199.00 6,340.00 7,112.00 10,874.00 10,945.00 10,910.00 10,910.00 8,700.00 7,743.00 6,882.00 6,373.00 10,000.00 10,199.00 10,199.00 8,949.00 8,600.00 12,969.00 9,496.00 15,673.00 15,673.00 15,924.00 15,847.00 average 37,429.32 31,188.53 2,340.63 1,290.53 1,269.21 372,696.21 286,099.58 30,736.00 6,681.68 10,887.68 % of total 83.32 6.25 3.44 3.39 76.76 8.25 1.79 2.92 27review article al-yahyai, al-kharusi, m. khan, al-adawi, al-subhi, al-kalbanim, al-sadi established strict quarantine measures in banana production regions to prevent the spread of diseases. furthermore, tissue culture banana plant materials should be the sole source for planting banana in an area free of foc tr4 and avoid using sucker planting material as it could be a source of new inoculum of the pathogen to an area free of the disease. several banana cultivars were found to be moderately resistant to foc tr4 including giant cavendish tissue culture variants (gctcv), which was developed in taiwan and two of these variants including gctcv 218 & gctcv 219 were used in several countries to reduce the impact of the disease in the infected area. furthermore, several hybrids developed through a breeding program at fundacion hondurena de investigacion agricola (fhia) in honduras such as fhia 1, fhia 2, fhia 3, fhia 18 and fhia 25 were found slightly susceptible to foc tr4. however, all the above-mentioned bananas were not acceptable in the market, compared with world-known cavendish cultivars such as william and grand nain (ploetz, 2015a &b). many of these developed cultivars of banana are being evaluated in the banana gene banks at research centers of al batinah and dhofar in oman. climate change globally, climate change is of major concern (thomas et al., 2004). due to this climate change, oman has been ranked at 40th position by german watch, based on data available at global climate risk index (harmeling, 2010). according to ipcc (intergovernmental panel on climate change) findings, oman has been declared at higher risk due to climate change and the increasing temperature, sea level, erratic rainfall pattern and their combination is leading oman towards desertification by affecting its coastal regions and ecosystem (ipcc, 2007). the climate of a particular area affects its various environmental aspects and climate change greatly reduces agricultural productivity and stability, by changing cropping patterns and loss of agricultural land (waqas et al., 2019). climate change is one of the major concerns of 21st century, anthropogenic activities have increased the carbon dioxide level in the atmosphere which has resulted in very high or low temperatures and irregular rainfall patterns. due to these climatic changes, stresses occur in plants which severely affect agriculture production and are key constraints to the food supply, as climate change disturbed the cropping season, pattern, duration, and production intensity (harmeling, 2010). oman is at high risk of these vulnerable climate changes, for example, there is an increase in average temperature, sea level, desertification, and irregular rainfalls. besides in 2007 and 2010, oman suffered from two cyclonic storms that caused adverse effects on agriculture production and plant genetic resources (al-khafaji et al., 2017). it is also speculated that recent harmful algal bloom outbreaks along the oman coast are due to climate change (al-azri et al., 2010). cold stress and heat stress, both are related to temperature, any of these stresses during plant development stages severely affect crop production (zhou et al., 2018). the temperature stress in plants reduces their biochemical and physiological functions by tempering their molecular mechanism (takahashi and shinozaki, 2019). high-temperature stress increases plant growth and reduces crop duration (lobell et al., 2011). it greatly affects plant reproductive growth by reducing pollen viability, pollen fertility, flower abortion, and pistil tissues (djanaguiraman et al., 2018; talwar et al., 1999). it has also been reported that heat stress or high temperature causes premature another development, restricted cell proliferation and induces male sterility in plants (oshino et al., 2007; abiko et al., 2005). likewise, cold temperature stress affects the cropping season and yield as well, according to geographical distribution one-degree drop on average can reduce the yield of summer field crop up to 40% (larcher, 2003). cold temperature affects plants at various stages including the early stage, acclimatization phase, developmental stage, and fruit maturity stage. cold stress at any stage of plants highly disturbs its biochemical and physiological functions. potential impact of climate change climatic factors such as temperature and precipitation affect the quality and production of fruits (akram et al., 2020). in oman, high temperature is of great concern as it disrupts various plant physiological processes. during the photosynthesis process, high temperature causes carbon fixation in dry matter, disturbs plant parts during its various stages of development (laxman and bhatt, 2017). generally, in fruit plants, it causes sunburn of various plant parts like leaves, branches, twigs and stems. besides, it retards shoot and root growth, leaf senescence and fruit discoloration (wahid et al., 2007). it also disrupts plant normal cell functioning and reproductive stages. the date palm can tolerate a wide range of climatic conditions, it can tolerate frost and is well adapted to heat as well. temperature widely affects date growth, flowering, fruit setting and fruit production. due to high temperatures, early bloom in dates was also noticed (darfaoui and assiri, 2009). dates require prolonged summer to mature fruit, however, rainfall and humidity at fruit maturity cause fruit cracking and attract fungal diseases (burt, 2005). date palm can tolerate temperature up to 50oc under irrigation and as low as 0oc, however, growth is restricted below 7oc and above 40oc and it also affects the quality of date production (al-yahyai, 2018). the date palm biodiversity is on a steady decline in oman due to certain biotic and abiotic factors. however, realizing the vulnerability of in-situ gene banks of date palm, newer approaches for preserving local varieties are being investigated. detailed studies on date palm in oman are under way at the date palm horticulture research laboratory, jimmah (maf, 2006). it has been 28 squ journal of agricultural and marine sciences, 2022, volume 27, issue 1 biotic and abiotic stresses of major fruit crops in oman: a review argued that oman is prone to climate change effects and farming and precious plant genetic resources are under threat due to ever-changing climate, population influx, urbanization, and other factors along with environment are playing substantial roles in agricultural activities and plant genetic resources (hameed et al., 2017). in mango, temperature determines vegetative and flowering flushes. high temperature induces vegetative flushes (laxman and bhatt, 2017), temperature below 16 °c induces floral induction (schaffer et al., 1994). panicles that emerged below low temperature have more male flowers (singh et al., 1974). the sudden variability in climate change may influence the vegetative and reproductive growth of mango by affecting its production. recently extreme weather scenarios such as gonu in 2007 and phet in 2010, and torrential rains-caused flooding have damaged the date plantation. events related to climate change may be the next challenge to date palm sustainable cultivation in oman. the government helped in replacing date palms destroyed by climatic catastrophes like cyclones and storms (al-yahyai and khan, 2015). each grape cultivar performs well in a suitable range of temperatures and changes in temperature of climate its physical and biochemical parameters (akram et al., 2020). in grapes, the adaptability of genotypes of a particular region enables it to produce fruit efficiently (akram et al., 2019). high-temperature effects sugars, acids and antioxidant compounds in grapes, besides it may affect the aroma and color of grape vines (de-orduna, 2010). in grapes, high temperatures lead plants towards prematurity due to which berry size does not develop properly. due to climate change, frost and storms have changed the citrus phenology which has increased the risk factor (fitchett et al., 2014). the global increase in temperature has increased the distribution and behavior of citrus insects. for example, the incidence of pathogens candidatus and diaphorina citri is highly increased with an increase in temperature (lópez-arroyo et al., 2009). likewise, rainfall distribution highly affected the natural distribution of citrus black spot disease (martı´nez-minaya et al., 2015). in coconut, the high temperature reduces the pollen production and promotes male flowers induction (burke et al. 2004), besides high temperature and excessive rainfall cause flower and fruit abortions (nainanayake et al. 2008). likewise, in banana, growth is also affected by high temperature and it was observed that leaf emergence and fruit production was highly reduced beyond 33.5°c and 35°c, respectively (thornton and cramer, 2012). in pomegranate, the ideal temperature for fruit growth is from 17 and 26°c, the high temperature at the fruit maturity increases oxidative stress by increasing peroxidase activity (fischer et al., 2013). high temperature also varies antioxidant, anthocyanin, and the chemical composition of pomegranate fruits (fernandes et al., 2015). conclusion the potential for expanding fruit crop production in oman is great, especially since the country has the requirements, including diverse climatic conditions, educated labor force, market chains, industrial infrastructure, and logistical needs. knowledge and cumulative experience that is based on research is also growing and aims to address fruit crop cultivation challenges. this review paper has highlighted the latest research on major challenges to fruit production in oman, which include abiotic and biotic stress factors. in recent years, oman witnessed a drastic change in climatic patterns and severe weather attributed to climate change, and existing adverse conditions, such as heat, salinity, and drought. fruit production constitutes a large percentage of the total agricultural cultivated area in oman, and almost 90% consists of date palm, banana, lime, and mango. in addition to the abiotic stress, major fruit crops have declined in recent years due to various biotic stressors, primarily pests and diseases including dubas bug and red palm weevil. furthermore, lime has been infected with witch’s broom disease of lime (wbdl) caused by ‘ca. phytoplasma aurantifolia’, and large areas of mangoes have been lost to sudden wilt. several solutions have been proposed to address these challenges, however, further research is still needed as the challenges will continue to grow. furthermore, applied research is still lacking in the areas of fruit production 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(2019). salinity and crop yield. plant biology 21: 31-38. zreik l, carle p, bové jm, garnier m, (1995). characterization of the mycoplasma like organism associated with witches’-broom disease of lime and proposition of a candidatus taxon for the organism, ‘’candidatus phytoplasma aurantifolia”. international journal of systematic bacteriology 45: 449-453. img036 img037 img038 img039 img040 img041 research paper journal of agricultural and marine sciences vol. 24 : 30– 33 doi: 10.24200/jams.vol24iss1pp30-33 reveived 18 nov 2018 accepted 14 nov 2019 variations in consumer’s acceptability and proximate composition of yellow croaker (larimichthys polyactis) with processing methods a. a. ayeloja1, f.o.a. george, w. a. jimoh, s. a. abdulsalami a. a. ayeloja1( ) ayeloja2@gmail.com, department of aquaculture and fisheries, university of ilorin, pmb 1515 ilorin, kwara state, nigeria introduction consumers have become increasingly interested in fish as a source of dietary protein due to the rising cost of meat protein foods (emere and dibal, 2013). fish as a whole, has a lot of food potential and can therefore be expected to provide relief from malnutrition, especially in developing countries (ashraf et al., 2011). it constitute about 60% of the total protein intake in adults especially in rural areas (adeleye, 1993). foran et al. (2005) pointed that fish is a highly protein containing food consumed by a larger percentage of population because of its availability and palatability. in nigeria, fish is eaten fresh, preserved or processed (smoked) and form a much-cherished delicacy that cuts across socio-economic, age, religious and educational barriers (adebayo-tayo et al., 2008). however, the gap between demand and supply of fish is widening due to increase in population, poor postharvest handling, lack of processing and storage facilities and utilization of unconventional fish species (ogbonnaya and ibrahim, 2009). different fish processing and preservation methods are used to slow down spoilage resulting in fish that are both be safer for consumption and with an increased shelf-life. researchers have also studied the effect of processing methods on the nutritional qualities of different fish species. nutritive and organoleptic changes of nigerian traditionally-processed freshwater fish species were studied by afolabi et al. (1984). the effect of traditional drying processes on the nutritional values of fish was studied by eves and brown (1993). changes in chemical composition and nutritional quality of fried sardine (clupea pilchardus) produced by frozen storage and microwave reheating were reported by castrillon et al. (1997). ayeloja et al. (2013) reported the effect االختالفات يف قبول املستهلكني والرتكيب الكيمائي للكروكر األصفر )larimichthys polyactis( مع طرق التصنيع أيلويا ا.ا. وجورج ف.و.ا. وجيموح و.ا. وعبداللسالمي س.ا. abstract. the effect of processing methods on the proximate composition and consumer’s acceptability of yellow croakers were investigated. the experiment followed a completely randomized design with several processing methods. frozen yellow croaker fish of 12 kg were purchased, cut into chunks, divided into 4 groups of 3 kg each, each group was salted and then subjected to different processing methods including: air drying in the sun, deep-frying, solar drying and smoking. after processing, the products were subjected to organoleptic assessment using an hedonic scale while the proximate composition was determined using standard experimental procedures. the results of this study indicated that the odour and flavour of smoked fish product were significantly (p < 0.01) preferred by consumers. solar dried fish product had highest percentage crude protein (71.45 kg/100 kg sample) followed by smoked fish product (70.43 kg/100 kg sample) while smoked fish product had the highest crude ash (10.73 kg/100 kg sample). the study suggested that it was better to process quality yellow croaker using solar dryers and smokers to attract customers. keywords: consumers; proximate composition; processing methods; yellow croaker. املســتخلص: مت دراســة تأثــر طــرق التصنيــع علــى الرتكيــب الكيميائــي وقبــول املســتهلك لســمك الكــرور األصفــر. وقــد إتبعــت التجربــة تصميًمــا إحصائيــا عشــوائًيا متاًمــا مــع طــرق التصنيــع املســتخدمة. مت شــراء أمســاك الكروكــر الصفــراء اجملمــدة بــوزن 12 كجــم ، مقطعــة إىل قطــع ، مقســمة إىل 4 جمموعــات كل منهــا 3 كجــم ، ومت إضافــة امللــح علــى كل جمموعــة مث تعريضهــا ألســاليب تصنيــع خمتلفــة مبــا يف ذلــك: التجفيــف اهلوائــي الشمســي ، القلــي العميــق ، التجفيــف بالطاقــة الشمســيه والتدخــن . بعــد عميلــة التصنيــع ، مت دراســة املنتجــات بإســتخدام طــرق التقييــم احلســي باســتخدام مقيــاس هيدونيــك وكذلــك دراســة الرتكيــب الكيميائــي باســتخدام التجــارب القياســية. أشــارت نتائــج هــذه الدراســة إىل أن رائحــة ونكهــة منتــج الســمك املدخــن مــن قبــل املســتهلكن كانــت مفضلــة بدرجــة كبــرة )p>0.01(. حيتــوي منتــج األمســاك اجملففــة بالطاقــة الشمســية علــى أعلــى نســبة مــن الربوتــن اخلــام )71.45 كجــم / 100 كجــم عينــة( يليــه منتــج الســمك املدخــن )70.43 كجــم / 100 كجــم عينــة( بينمــا حيتــوي منتــج الســمك املدخــن علــى أعلــى نســبة رمــاد خــام )10.73 كجــم / 100 كجــم عينــة(. أشــارت الدراســة إىل أنــه مــن األفضــل إســتخدام جمففــات الطاقــة الشمســية و التدخــن للحصــول علــى منتــج ذات جــودة عاليــة مــن مســك الكروكــر األصفــر جلــذب املســتهلكن. الكلمات املفتاحية: املستهلكون ، الرتكيب الكيميائي ، طرق التصنيع ، الكروكر األصفر 31research article ayeloja, jimoh, abdulsalami of processing methods on the nutritive value of catfish (clarias gariepinus). however, there is little information on the effect of processing methods on the nutritional quality of yellow croaker, thus the need for this study. schiffman and graham (2000) reported that taste and smell played an important role in developing appetite, making food choices, and nutrient intake for the following reasons: (1) these chemosensory signals prepare the body to digest food by triggering salivary, gastric, pancreatic, and intestinal secretions, which are termed cephalic phase responses, (2) they enable us to detect and discriminate among foods in the face of fluctuating nutritional requirements. taste and smell enable selection of a nutritious diet as there are associations between a food taste or smell and its post-ingestion effects as taste enable the consumer to modulate food intake in anticipation of its nutritional consequences. thus, taste sensations serve as an indicator of a particular food nutritional value. in addition, taste and smell signals initiate, sustain and terminate ingestion, and hence play a major role in the quantity of food that is eaten and the size of meals. taste sensations induce feelings of satiety and are primary reinforced by eating. thereby, justifying the use of texture, odour and flavour (which is a combination of taste and odour) in determining consumers’ acceptability of various food, in this case differently processed yellow croaker. materials and methods the experiment followed a completely randomized design where the treatments were the various processing methods employed. twelve (12 kg) frozen yellow croaker fish was purchased from the cold room of atlantic shrimpers limited, ring road, near challenge roundabout, ibadan oyo state, nigeria. these were transported within 17 minutes to the fish processing unit of federal college of animal health and production technology (fcah & pt) moor plantation, where these were cut into chunks and then divided into 4 groups of 3 kg each. each chunk was washed, salted and then subjected to different processing methods including: air drying in the sun (sun drying), deep-frying, solar drying (in a solar oven) and smoking. sun drying was done for 4 days using locally constructed sun drying rack with appropriate screen, which protected the product from direct contact with insects. the average ambient temperature during the period of the experiment was 27oc ± 3oc. deep-frying was performed in vegetable oil in a pot on a hot flame with occasional flipping in order to achieve even frying. frying was achieved within 21 minutes at a temperature of about 240ºc. solar drying was achieved in 4 days using locally constructed solar dryer with appropriate screen, which protected the product from direct contact with insects. smoking was done at the temperature of 90oc ± 10oc for 42 hours using niomr (nigeria institute for oceanography and marine research) smoking kiln installed in the fish processing unit of the fisheries technology department, federal college of animal health and production technology (fcah & pt) moor plantation ibadan oyo state nigeria. charcoal was used to generate heat and smoke. the various processed fish products were subjected to sensory quality evaluation using descriptive test based on 5-point hedonic scale modified from tobor (1994) and eyo (2001). odour, flavour and texture were the sensory attributes examined. the following grades were allotted depending on their qualities: 8 – 10 = excellent, 6 – 8 = very good, 4 – 6 = good, 2 – 4 = bad and ≤ 2 = worst. twelve trained panelists from the federal college of animal health and production technology ibadan were used for the assessment. the proximate composition of the fish samples was determined using table 1. effect of processing methods on the perceived physical attributes (hedonic scale) of yellow croaker. fish products odour kruskal–wallis (c2) p-value flavour kruskal–wallis (c2) p-value texture kruskal–wallis (c2) p-value sun dried 25.65 36.836** 0.01 20.59 40.705** 0.01 36.76 3.932 0.27 fried 53.38 52.68 28.56 solar dried 16.47 18.53 31.85 smoked 42.50 46.21 40.82 **kruskal wallis test (c2) is significant between rows at p < 0.05 figure 1. effect of processing methods on texture of processed yellow croaker 32 squ journal of agricultural and marine sciences, 2019, volume 24, issue 1 varations in consumer’s acceptability and proximate compostion of yellow croaker with processing methods the standard methods of aoac (1994). statistical analysis data collected on descriptive organoleptic assessment using hedonic scale were subjected to nonparametric test (kruskal wallis test) and data collected on proximate composition were subjected to analysis of variance (anova) to determine significance between means. duncan multiple range test (dmrt) was used to compare differences among means. significant level was chosen at p < 0.05. results and discussion there was a significant difference between the odour of differently processed yellow croaker (c2=36.836, p<0.01) with fried product, rated as having the best odour followed by smoked fish product (table 1). there was also a significant difference between the flavour (c2=40.705, p<0.01) of the various processed fish products with fried yellow croaker rated as having the best flavour followed by smoked product (table 1). ayeloja et al. (2013) reported similar result in their study of the effect of processing methods on nutritive value of catfish (clarias gariepinus). the result of this study also agrees with the opinion of jang et al. (2009). in their study of food attributes as reported that the satisfaction levels of ethnic foods varies depending on diverse food attributes such as taste, fresh, colorful, uniqueness and healthiness. in related veins, lin (1991) observed that oyster consumption was mainly influenced by five food attributes, including taste, nutritional value, freshness, cost and safety. however, there was no significant difference (c2 =3.932, p > 0.05; table 1) in the perceived texture of the various fish products although there was a small preference for smoked fish, (29%) over sundried fish product (27%) and fried fish (21%) (fig.1). the results of the effect of processing methods on proximate composition of yellow croaker (table 2) indicated that processing methods showed effect on the proximate composition of processed yellow croaker. ogbonnaya and ibrahim (2009) also reported that different drying methods affected the proximate compositions of catfish. the moisture content of the various fish products was significantly different (p<0.05) with fried fish having the highest moisture content (30.44 +0.04 g/100 g sample). a similar trend was observed for percentage lipid composition with fried fish product had the highest percentage of lipids (18.58+0.02 g/100 g sample). however, solar dried fish product had the highest crude protein (71.45+0.02%) which was significantly different (p<0.05) from the protein content of the other fish products, which suggests that proteins in solar dried fish product were retained and less denatured by processing method employed than in other processed fish products. fried fish had the lowest percentage protein. this is in accordance with the findings of gokoglu et al. (2004), tao and linchun (2008). there was a significant difference (p<0.05) in the percentage ash of the various fish products with smoked fish product having the highest ash content (10.73 + 0.01 g/100 g sample). oyero et al. (2012) expressed a similar opinion that smoked fish products showed significant higher levels of ash content, which was as a result of inorganic matter which remains on it after the organic matter burnt. this signifies that the smoked fish products had high levels of mineral contents. conclusion this study indicates that consumers prefer the odour and flavor of fried fish product above others followed by that of smoked fish product. on the other hand, solar-oven dried fish had the highest crude protein followed by smoked fish. smoked fish had the highest percentage of ash which probably resulted from the burnt organic matter; this signifies that the smoked fish products had high levels of mineral matter. it is therefore better to process yellow croaker fish using solar oven or smoking as fish preserved using these preservation methods have better protein content. consumers also preferred the odour and flavour of smoked fish above others; this additional value could increase the economic value of smoked fish and in turn increase the income of fishers. references adebayo-tayo, b.c., onilude, a.a. and patrick, u.g. (2008): mycoflora of smoke dried fishes sold in uyo, table 2. effect of processing methods on proximate composition yellow croaker fish products moisture + sd (g/100 g sample) crude protein + sd (g/100 g sample) lipid + sd (g/100 g sample) ash + sd sundried 15.39 + 0.02c 69.05 + 0.05c 6.42 + 0.02b 8.15 + 0.02b fried 30.44 + 0.04a 47.08 + 0.04d 18.58 + 0.02a 3.55 + 0.01d solar dried 14.13 + 0.03d 71.45 + 0.02a 4.43+ 0.03c 5.70 + 0.02c smoked 16.03 + 0.05b 70.43 + 0.03b 2.72 + 0.02d 10.73 + 0.01a values with different letter within each column are significantly different (p<0.05) sd: standard deviation 33research article ayeloja, jimoh, abdulsalami eastern nigeria. world journal of agricultural science. 4(3): 346 – 350. adeleye, o.a. (1993). conservation needs of fisheries resources and reorientation for sustainable captive and culture practices. in proceedings of the 10th annual conference fisheries society of nigeria (fisson), 16-20 november, 1992, abeokuta, nigeria. pp: 230-234. afolabi o.a., o.a. arawomo and o.l. oke, (1984). quantity changes of nigeria traditional processedfreshwater species: nutritive and organoleptic changes. j. food technol., 19: 333-340. association of official analytical chemists (1994). official methods of analysis of the association of official analytical chemist, vols. i and ii, association of analytical chemist, arlington. 1298pp. ashraf, m. a.; zafar, a.; rauf, s.; mehboob and. qureshi, n. a. (2011). nutritional values of wild and cultivated silver carp (hypophthalmichthys molitrix) and grass carp (ctenopharyngodon idella). int. j. agric. biol., 13: 210–214. ayeloja, a. a.; george, f.o.a.; akinyemi, a. a.; jimoh, w. a.; dauda, t. o. and akinosho, g. a. (2013). effect of processing methods on nutritive value of catfish (clarias gariepinus).journal of food science and quality management. 11: 31 – 38. castrillon, a.m., navarro, p. and alvárez-pontes, e. (1997). changes in chemical composition and nutritional quality of fried sardine (clupea pilchardus) produced by frozen storage and microwave reheating. j. sci. food and agric. 75: 125-132. emere, m. c. and dibal, d. m. (2013). a survey of the methods of fish processing and preservation employed by artisanal fishermen in kaduna city. journal of food science and quality management. 11: 16 – 22. eyo, a. a. (2001). fish processing technology. in the tropics. published by university of illorin press, nigeria. eves, a. and r. brown, (1993). the effect of traditional drying processes on the nutritional values of fish. tropical sci., 33: 183-189. foran, j.a.; carpenter, d. o.; hamilton, m.c.; knuth, b.a. and schwager, s.j., (2005).riskbased consumption advice for farmed atlantic and wild pacific salmon contaminated with dioxins and dioxinlike compounds. journal of environmental health perspective. 33:552-556. gokoglu, n.; yerlikaya, p. and cengiz, e. (2004). effects of cooking methods on the proximate compositionand mineral contents of rainbowtrout (oncorhynchus mykiss). journal of food chem., 84: 19-22. jang. s. s. c., ha, a., and silkes, c. a. (2009). perceived attributes of asian foods: from the perspective of the american customers. international journal of hospitality management, 28 (1), 63–70. lin, j. (1991). consumer food attribute perceptions and consumption behavior.consumer interests annual 1991. ogbonnaya, c. and ibrahim, m. s. (2009). effects of drying methods on proximate compositions of catfish(clariasgariepinus). world journal of agricultural sciences. 5 (1): 114-116. oyero j.o.; sadiku, s. o. e. and eyo, a. a. (2012).the effect of various smoking methods on the quality ofdifferently salted oreochromis niloticus. international journal of advanced biological research. 2(4): 717 – 723. schiffman, s. s. and graham, b. g. (2000) taste and smell perception affect appetite and immunity in the elderly. european journal of clinical nutrition. 54 (3): 54 – 63. tao, w. and linchun, m. (2008). influences of hot air drying and microwave drying on nutritional andodorous properties of grass carp (ctenopharyngodon idellus) fillets. journal of food chem., 110 (3): 647-653. tobor, t. g. (1994). fish production and processing on nigeria. niomr tech. paper. review article journal of agricultural and marine sciences 2023, 28(2): 01–06 doi: 10.53541/jams.vol28iss2pp01–06 received 13 november 2022 accepted 1 may 2023 استخدام الكركم )curcuma longa( يف تغذية الدواجن رافع حممد طاهر خليل use of turmeric (curcuma longa) in poultry nutrition: a review rafea mohammedtaher khulel rafea mohammedtaher khulel( ) rafhkhulel@uomosul.edu.iq, animal production dept./college of agriculture and forestry/university of mosul /iraq introduction medicinal plants and herbs have been used to treat many health problems in poultry, which reflects in their health, due to their antibacterial and antifungal effects, and these natural medicinal plants can also promote growth, improve the intestinal environment and immunity. the crude protein content of dried turmeric is 6.3%, ether extract 5.1%, ash 3.5%, carbohydrate 69.5%, moisture 13.1%, essential oils 5%, and tetrahydrocurcuminoids 5%. curcumin, dimethoxy curcumin and bismethoxy curcumin are the active compounds of turmeric (eevuri and putturu, 2013; li et al., 2011). curcuma longa, also known as turmeric, is a tropical medicinal plant and used for its antifungal, immunomodulatory, antioxidative, and antimutagenic effects (nisar et al., 2015). linnaeus classified turmeric c. longa, and it belongs to the following taxonomic group: order zingiberales, family zingiberaceae, class liliopsida, subclass commelinids, genus curcuma species curcuma longa, also known as turmeric. protein, lipid, mineral, carbohydrate, and moisture content of turmeric is 6.3%, 5.1%, 3.5%, and 69% and 13.1%, respectively. rhizome steam distillation yields 5.8 % essential oil that contains 1 % α-phellandrene, 1% cineol, 0.6 % sabinene, 25% zingiberene, 1% borneol and 53% sesquiterpines. the yellow colour comes from curcumin (diferuloylmethane), which is 3–4 % (sotiboldieva et al., 2020). the chemical components of turmeric (curcuma longa l.) tissues has been widely researched (li et al., 2011). it has been found that the species contains at least 235 compounds, including 22 diarylheptanoids and diarylpentanoids, 8 phenolic compounds, 68 monoterpenes, and 109 sesquiterpenes, 5 diterpenes, 3 triterpenes, 4 sterols, and 2 alkaloids, as well as 14 other compounds. according to fascina et al (2012), use of phytogenic additions increases the secretion of pancreatic and intestinal enzymes, synthesis of bile salts, and activity of pancreatic and intestinal lipase, all contribute to improve nutrient metabolism. al-asmary et al. (2014) mentioned that curcuma longa used in traditional medicine in saudi for loss of appetite, liver problems, jaundice, arthritis, and gall bladder disorders. it is due to its active components, like curcumin, demethoxycurcumin, and bis-demethoxycurcumin. curcuma extracts showed anabstract. turmeric (curcuma longa) is a plant used in herbal medicine that has been used to treat many health problems in poultry, as antibacterial, and antifungal, promoting growth and improving the intestinal environment and immunity. the aim of this article was to review the research focused on using turmeric (curcuma longa) in rations of broilers and layers on performance, carcass characteristics, blood parameters, egg production, and egg quality characteristics. most research indicated that turmeric addition to broiler rations improved productive traits (i.e. body weight, weight gain, feed intake and feed conversion), increased livability and had insignificant effects on carcass traits (i.e. dressing percentage, carcass cuts percentages), abdominal fat, edible giblets, cooking loss and water holding percentage). there were different results of turmeric addition on blood parameters; some indicated that it had positive effects, and indicated negative effects, while others found insignificant effects on blood characteristics. most researchers found a decrease in feed consumption when turmeric was added to layer rations, while different results were observed on laying performance and egg quality traits. keywords: turmeric, broiler, layers, performance, carcass, blood امللخــص: الكركــم )كركمــا لوجنــا( هــو نبــات يســتخدم يف طــب األعشــاب وقــد مت اســتخدامه لعــاج العديــد مــن املشــاكل الصحيــة يف الدواجــن ، كمضــاد للبكتــراي والفطــرايت ، ممــا يعــزز النمــو وحيســن البيئــة املعويــة واملناعــة. اهلــدف مــن هــذه املقالــة هــو مراجعــة األحبــاث الــي تركــز علــى اســتخدام الكركــم )كركمــا لوجنــا( يف تغذيــة فــروج اللحــم ودجــاج البيــض علــى األداء وخصائــص الذبيحــة ومعايــر الــدم وإنتــاج البيــض والصفــات النوعيــة للبيــض . تشــر معظــم األحبــاث إىل أن إضافــة الكركــم إىل عائــق التســمن أدت إىل حتســن الصفــات اإلنتاجيــة )وزن اجلســم ، الــزايدة الوزنيــة ، اســتهاك العلــف ، ومعامــل التحويــل الغذائــي( ، واحليويــة ، ومل يكــن هلــا أتثــر معنــوي علــى صفــات الذبيحــة )نســبة التصــايف ، نســب قطــع الذبيحــة(. دهــون البطــن ، االحشــاء املأكولــة ، نســبة الفقــد أثنــاء الطبــخ ، نســبة االحتفــاظ ابملــاء(. كانــت هنــاك نتائــج خمتلفــة إلضافــة الكركــم علــى صفــات الــدم. أشــار البعــض إىل آاثره اإلجيابية ، والبعض اآلخر أشار إىل آاثر سلبية ، يف حن وجد البعض اآلخر آاثرًاغر معنوية على خصائص الدم. وجد معظم الباحثن اخنفاًضا يف اســتهاك العلــف عنــد إضافــة الكركــم إىل عائــق البيــاض ، بينمــا كانــت هنــاك نتائــج خمتلفــة يف صفــات وضــع البيــض والصفــات النوعيــة للبيــض. الكلمات املفتاحية: الكركم ، االداء ، فروج اللحم ، دجاج البيض ، صفات الدم 2 squ journal of agricultural and marine sciences, 2023, volume 28, issue 2 use of turmeric (curcuma longa) in poultry nutrition: a review tidiabetic qualities similar to commercial drugs and may even be more effective in people in some instances (priyangga et al., 2021). broiler performance abd al-jaleel (2012) studied the effect of turmeric addition to ross broiler ration at ratios of 0, 0.25, 1.0, and 1.5 %. he found that 0.25, 0.5%, additions had a significant (p≤0.05) improvement in final body weight at 42 days. ration of 0.5% was significantly higher than 0.25, 1 and 1.5%. abd el-hakim (2009) found insignificant effect of 0.2% curcuma longa addition to the cobb broiler’s low protein diet (i.e. 18%) on the weight gain, feed conversion ratio, dressing percentage, liver, gizzard, abdominal fat, total edible parts, and edible giblets percentages. the nitrogen content of feces and nitrogen retention were insignificantly different between curcuma longa treatment and control. mehala and moorthy (2008) indicated that 0.1 or 0.2% tumeric addition to control ration did not affect body weight, weight gain, feed intake, feed conversion ratio and livability. ürüşan and bölükbaş (2017) studied the effect of turmeric addition by 0, 2, 4, 6 ,8 ,10 g/kg showed significantly lower weight gain compared to 0, 2, 6, 10 treatments, 10 g/kg treatment was highest feed intake and 2 g/kg showed best feed conversion. nayaka et al. (2013) did not find a significant effect when the addition of 0.2% turmeric to the control ration on live body weight at 6 weeks or feed conversion and livability. widodo et al. (2021) found insignificant effect of adding 1, 2, or 3% white curcuma (curcuma zedoaria) to broiler basal diet on digestibility (i.e. dry matter, crude fat, protein biological value, and nitrogen retention). hussein (2013) found that 7 g/kg addition of turmeric powder to the starter and finisher rations of broilers improved body weight and weight gain, feed conversion, and decreased feed intake significantly (p≤0.05). he attributed this effect to turmeric’s active compounds (i.e. curcuminoids and curcumin) and it improved feed utilization efficiency leading to better growth. turmeric’s antimicrobial properties inhibited chicken pathogens. another study conducted by rajbit et al. (2012) on broilers used 0, 100, 150, and 200 mg/kg of turmeric.their results showed a significantly increased body weight at 42 days of age for the 3rd and 4th treatments (i.e. 150 and 200 mg/kg) and in feed conversion for the 200 mg/ kg treatment, but there was an insignificant difference in feed intake between all treatments. islam (2018) found that adding 0.25, 0.5, and 0.75 gm/kg turmeric to broiler rations improved body weight significantly (p≤0.05) in the 0.5 and 0.75 treatments, but there was an insignificant difference in feed consumption and feed conversion between all treatments. wang et al. (2015) studied the effect of turmeric rhizome extract at levels of 0, 100, 200, and 300 mg/kg during 2–12 weeks of wenchang broiler age. the results indicated that there was an insignificant difference between treatments in final body weight at 12 weeks. control was significantly less weight gain during 9–12 weeks. addition of 300 mg/ kg showed a significant decrease in feed intake compared to other treatments in the total period of 2–12. addition of 100 and 300 mg/kg showed better feed conversion than control. urusan and bolukbasi (2017) studied the effects of adding 2, 4, 6, 8, 10 g/kg of turmeric powder on broiler performance to 42 days of age and found that turmeric addition had an insignificant effect on final body weight at 42 days of age, a significant increase in weight gain, a significant decrease in feed intake in the 10 g/kg treatment, and a significant improvement in feed conversion in the 2 g/kg treatment. hussien (2013) found that 7 g/kg turmeric addition showed a significant improvement in body weight, weight gain, feed conversion and a significant decrease in feed intake when compared to 0 and 9 g/kg treatments. arslan et al. (2017) found that adding 1 to 1.5% turmeric powder improved body weight and weight gain (p≤ 0.05), decreased feed consumption, and improved feed conversion. adding 0.5% turmeric improved (p≤ 0.05) body weight, weight gain, and feed conversion. ahmed et al. (2018) found that the addition of 1 g/kg turmeric powder to broiler diets led to improvement in body weight, feed consumption, and feed conversion. widjastuti et al. (2020) found that adding red ginger and turmeric mixture (1/1) to broiler ration decreased protein consumption, increased body weight gain, and improved protein conversion and meat protein conversion. choudhury et al. (2018) found that a 0.75% addition of turmeric powder in the broiler ration showed a significant increase in final body weight at 6 weeks compared to 0 and 0.25% levels but did not differ with 0.5% turmeric, and this treatment showed the best feed efficiency and broiler performance efficiency index. olabode et al. (2018) found that adding 1.5% turmeric to broiler ration reduced significantly final body weight, weight gain, and feed intake at 42 days old. sadeghi et al. (2012) compared the effect of replacing drinking water (control) with cinnamon, thyme, and turmeric infusions on broiler performance. the control group showed significantly better body weight at 21 days of age, which did not affect weight gain, feed intake, or feed conversion significantly, adding red ginger and turmeric mixture (1/1) to the broiler ration at 0.5 and 1.5% decreased protein consumption significantly, and that 0.5 and 1.5% treatments increased body weight gain and improved protein conversion and meat protein conversion significantly. carcass characteristics widjastuti and andriani (2010) did not find a significant effect of 3.5, 4.5, and 5.5% addition of turmeric zedora to the control diet of broiler on the percentage of abdominal fat, while significantly decreased broiler meat cholesterol in 3.5, 4.5, and 5.0% treatments. pur3review article khulel wanti et al. (2018) did not find a significant effect of 2.5% turmeric extract addition to the basal diet on the ph, % cooking loss, tenderness, juiciness, and acceptability of broiler meat, while there was a significant decrease in water holding capacity from 22.65 to 18.88%, which was comparable to control. negari and nurwantoro (2014) studied the effect of administration of turmeric exctract to the broiler diet by 100, 200, 300, and 400 mg/ kg of body weight on the carcass characteristics of the broiler, where they found that there was an insignificant decrease in water holding capacity, tenderness of meat, and a significant decrease in ph for the 100, 300, 400 treatments as 6.04, 6.08, and 5.98 compared to control (6.46). ashayerizadeh et al. (2009) compared the effects of supplemented broiler ration with 0.2% prebiotic, 0.1% garlic, and 0.1% turmeric powder on the internal organs of broiler. there was an insignificant difference in heart, liver, and gizzard weight, but abdominal fat was decreased significantly in prebiotic and garlic treatments compared to turmeric and control treatments. al-noori et al. (2011) found that turmeric powder addition by 0.5 and 1% to the broiler ration did not affect dressing percentage, heart, liver, gizzards, or spleen percentage significantly. singh et al. (2018) investigated 3 levels of turmeric in broiler rations (0.5, 1, and 1.5%), and he found that treatments did not affect carcass parameters such as dressing yield, giblet weight, cooking loss, ph, shear force, or proximate composition, although separable fat and meat cholesterol levels were reduced (p≤ 0.05) in broiler chickens fed a ration supplemented with 1.0 or 1.5% turmeric powder. the sensory qualities of the carcass were unaffected by dietary treatments. mondal et al. (2015) found that using turmeric powder by 0.5, 1, and 1.5% in broiler chick rations increased carcass characteristics such as average weight of liver, heart, and gizzard, but the effects were not significant. in chickens fed turmeric-supplemented diets, there was a substantial decrease (p<0.01) in abdominal fat pad and a significant rise (p≤0.05) in dressing percentage. al-mashhadani (2015) did not find a significant effect by the addition of 0.2, 0.4, 0.6% in dressing percentage, breast, thigh, wing, back, neck, heart, liver, spleen, bursa of fabricius percentages. wang et al. (2015) found that the addition of 100, 200, 300 mg/kg turmeric rhizome extract to the wenchang chicken ration did not affect the dressing percentage, thigh weight, or percentage, while significantly increased breast muscle weight and decreasing abdominal fat percentage. sadeghi et al. (2012) studied the effect of replacement drinking water (control) with cinnamon, thyme, and turmeric infusions on broiler performance. there was an insignificant difference in relative weight of carcass, heart, liver, pancrease, bursa, and abdominal fat, but gizzard and proventiculus in the thyme treatment were significantly heavier than others. blood parameters riasi et al. (2012) indicated that addition of 0.5, 1, 1.5, and 2 g/kg of turmeric powder to layers’ diet decreased triglycerides, total cholesterol, ldl-cholestrol, compared to control, and increased hdl-cholestrol significantly except for 2 g/kg treatments. we did not find a significant effect when we added 1 g/kg turmeric powder to the broiler ration on blood total protein, albumen, globulin, glucose, cholesterol, triglycerides, hdl, ldl, and vldl. akbarian et al. (2012) found that the 0.5 g addition of turmeric powder to the diet reduced alanine aminotransferase (alt) activity but had no effect on aspartate aminotransferase (ast) or lactate dehydrogenase (ldh) activity, or serum concentrations of low density lipoproteins (ldl), high density lipoproteins (hdl), cholesterol, or triglycerides. the addition of turmeric rhizome powder lowered serum chloride and overall electrolyte balance, but sodium and potassium concentrations remained stable. muliani (2015) found that turmeric extract given to arbor acres males at 200, 300, or 400 mg/ kg/day had no effect on blood cholesterol levels. qasem et al. (2016) studied the effect of 10, 12, 14, 16, 18, 20 gm/ kg of turmeric powder in the broiler ration affected significantly: serum glucose concentration (mg/dl), serum albumin concentration (g/dl), serum globulin concentration (g/dl), blood urea nitrogen (bun), serum total bilirubin concentration (mg/dl), serum alt enzyme activity (iu/l), serum lactic dehydrogenase concentration activity (iu/l), but serum total protein concentration (g/dl) and serum creatine kinase activity (u/l) did not differ significantly. olabode et al. (2018) stated that addition of 1% turmeric lead to a significant decrease in packed cell volume (%), hemoglobin (g/d), red blood cell (×1012/l), white blood cell (×10 9/l) and packed cell volume (%), compared to control and 0.5, 1.5% turmeric treatments. wang et al. (2018) found that turmeric rhizome extract increased superoxide dismutase and glutathione peroxidase enzyme activities and decreased malondiadehyde levels compared to the control group. widhowati et al. (2017) indicated that turmeric as a feed supplement enhanced the number of heterophil and basophil cells, as well as had an immunostimulatory impact against the avian influenza vaccination in layer chickens. sadeghi et al. (2012) discovered that replacing drinking water (control) with cinnamon, thyme, and turmeric infusions had no effect on hemocrit percent, but cinnamon had a significantly higher antibody titer than other treatments, implying that cinnamon significantly improved birds’ immune response to the ndv vaccine. ramadan et al. (2021) investigated the effect of 0.5% turmeric addition to broiler ration under heat stress and discovered that turmeric addition resulted in a significant decrease in hgb, pcv, albumin, serum t3 and t4, rbcs, total protein, whereas increased h/l, triglycerides, uric acid, cholesterol, ast, alt , ldl-cholesterol, alp, tbil, dbil, and creatinine significantly. 4 squ journal of agricultural and marine sciences, 2023, volume 28, issue 2 use of turmeric (curcuma longa) in poultry nutrition: a review layers riasi et al. (2012) found that the addition of 1.5 and 2 g/ kg tumeic powder to layers’ diet at the age of 100 weeks in the second production cycle for four weeks had decreased feed intake significantly (p≤0.05). treatment of 2 g/kg increased egg mass significantly compared to 1.5, 1, 0 g/kg treatments and improved feed conversion significantly compared to 0 and 1.5 g/kg treatments. there was an insignificant difference in egg quality traits including specific gravity, egg shell thickness (mm), egg shell weight (g), and egg shell weight/egg weight between all treatments (egg weight) between all treatments (egg weight), while yolk color improved significantly when 2 g/kg added compared to 0 and 1 g/kg. samia et al. (2018) indicated that the addition of 6 g/kg turmeric poweder to golden montazah layers’ basal diet during 29–40 weeks of age improved significantly (p<0.01): egg number, egg weight, egg mass, decreased feed intake, improved feed conversion, increased shell weight, decreased albumin weight, while it did not affect body weight gain, yolk weight, yolk index, or shell thickness. azouz et al. (2019) discovered that adding 0.25% turmeric powder to sinai layers aged 59-74 weeks had no significant effect on egg number/hen, laying rate (%), egg weight (g), egg mass (g/ hen), feed intake, feed conversion ratio, yolk index, yolk (%), albumen (%), shell (%), haugh unit, net return, or economic efficiency. gumus et al. (2018) found insignificant effect of adding 0.5% turmeric powder to the basal diet on final body weight, feed consumption, feed conversion ratio, egg production, albumen index, yolk index, haugh unit, or yolk color in his study of lohman brown layers at 30-36 weeks of age. chauhan et al. (2018) studied the effect of 1.5, 3, 4.5, and 6% turmeric powder inclusion in layer rations from 32–40 weeks of age and indicated that the addition of 4.5 g turmeric powder/kg feed improved the performance of birds by 53.60% as compared to the initial value of egg production (p≤0.05), but feed intake, egg weight, and egg shell quality did not differ between treatments. malekizadeh et al. (2012) did not find a significant effect of turmeric rhizome powder (i.e. 0, 1 or 3%) on egg production, egg mass, egg weight and feed efficiency, but 1% turmeric showed a significant decrease in feed consumption compared to control (0 and 3%). park et al. (2012) looked at the effects of adding 0, 0.10, 0.25, or 0.50 percent to the feed of laying hens for seven weeks on egg production. they found that there was no significant difference in egg production or feed intake, but adding 0.5% increased egg weight significantly. they also found that the daily egg mass of the turmeric treatments was significantly higher than that of the control group. there was no difference in shell strength, shell thickness, or haugh unit, but the 0.5% treatment shaowed a significant increased. conclusion the addition of turmeric to the broiler rations led to an improvement in the performance, and had insignificant effect on carcass traits. there were different results of adding turmeric to blood traits. add liitle more on blood traits? most researchers found a reduction in feed consumption when turmeric was added to egg-laying rations, while there were varied results in egg-laying and egg-specific qualities. references abd al-jaleel ra. (2012). use of turmeric (curcuma longa) on the performance and some physiological traits on the broiler diets. the iraqi journal of veterinary medicine 36(1): 51-57. abid el-hakim asa, cherian g, ali mn. (2009). use of organic acid, herbs and their combination to improve the utilization of commercial low protein broiler diets. international journal of poultry science 8(1): 14-20. ahmed i, el-rayes t, ahmed ai. (2018). assessment of dietary supplementation of turmeric (curcuma longa) as a phytobiotic on broiler performance and bacterial count. egyptian journal of nutrition and feeds 21(2): 519-528. akbarian, a, golian a, kermanshahi h, gilani a, moradi s. (2012). influence of turmeric rhizome and black pepper on blood constituents and performance of broiler chickens. african journal of biotechnology 11(34): 8606-8611. al-asmari ak, al-elaiwi am, athar mt, tariq m, al eid a, al-asmary sm. (2014). a review of hepatoprotective plants used in saudi traditional medicine. evidence-based complementary and alternative medicine 2014: 1-22 (article 89084). al-mashhadani h e.(2015). effect of different levels of turmeric (curcuma longa) supplementation on broiler performance, carcass characteristic and bacterial count. al-anbar journal of veterinary science .8:2:12-19. al-noori ma. (2011). the effect of dietary curcuma longa powder (turmeric) supplementation on some blood parameters and carcass traits of broiler chickens. al-anbar journal of veterinary science 4: 69-74. arslan m, haq a, ashraf m, iqbal j, mund md. (2017). effect of turmeric (curcuma longa) supplementation on growth performance, immune response, carcass characteristics and cholesterol profile in broilers. veterinaria 66(1): 1-5. azouz hm. (2019). effects of dietary turmeric and hot pepper powder supplementation on productive performance of local laying hens. egyptian poultry science journal 39(4): 935-951. choudhury d, mahanta j, sapcota d, saikia b, islam r. (2018). effect of dietary supplementation of turmeric (curcuma longa) powder on the performance of commercial broiler chicken. international journal of livestock research 8(7): 182-191. 5review article khulel eevuri tr, putturu r. (2013). use of certain herbal preparations in broiler feeds-a review. veterinary world 6(3): 172-179. fascina vb, sartori jr, gonzales e, carvalho fbd, souza imgpd, polycarpo g dv, pelícia vc. (2012). phytogenic additives and organic acids in broiler chicken diets. revista brasileira de zootecnia 41(10): 2189-2197. gumus h, oguz mn, bugdayci ke, oguz fk. (2018). effects of sumac and turmeric as feed additives on performance, egg quality traits, and blood parameters of laying hens. revista brasileira de zootecnia 47: 1-7. hussein sn. (2013). effect of turmeric (curcuma longa) powder on growth performance, carcass traits, meat quality, and serum biochemical parameters in broilers. journal of advanced biomedical and pathobiology research 3(2): 25-32. li sy, deng g, wang p, yang p, aggarwal b. (2011). chemical composition and product quality control of turmeric (curcuma longa l.). pharmaceutical crops 2: 28-54. malekizadeh m, moeini mm, ghazi s. (2012). the effects of different levels of ginger (zingiber officinale rosc) and turmeric (curcuma longa linn) rhizomes powder on some blood metabolites and production performance characteristics of laying hens. journal of agriculture science technology 14: 127-134. mehala c, moorthy, m. (2008). effect of aloe vera and curcuma longa (turmeric) on carcass characteristics and biochemical parameters of broilers. internatioanal journal of poultry science 7(9): 857-861. muliani h. (2015). effect of turmeric (curcuma domestica vahl.) extract on broiler blood cholesterol levels. jurnal sains dan matematika universitas diponegoro 23: 107-111. nayaka hs, umakantha b, ruban sw, murthy hnn, narayanaswamy hd. (2013). performance and hematological parameters of broilers fed neem, turmeric, vitamin e and their combinations. emirates journal of food and agriculture 25(6): 483-488. nisar t, iqbal m, raza a, safdar m, iftikhar f, waheed m. (2015). turmeric: a promising spice for phytochemical and antimicrobial activities. american-eurasian journal of agricultural and environmental science 15(7): 1278-1288.‏ olabode ad, adetutu is, agu ci, ugwuowo lc, ojuoloruntaye t j, okelola oe. (2018). growth performance and haematological characteristics of starter broilers fed diets supplemented with turmeric (curcuma longa) meal. nigerian journal of animal production 45(5): 79-83. park ss, kim jm, kim e j, kim hs, an bk, kang cw. (2012). effects of dietary turmeric powder on laying performance and egg qualities in laying hens. korean journal of poultry science 39(1): 27-32. priyangga kta, sagita cp, yuliati l. (2021). a narrative review of curcuminoids from various curcuma species in indonesia as potential antidiabetic agents. longhua chinese medicine 4(9) :1-15 purwanti s, zuprizal z, yuwanta t, supadmo s. (2019). physical and sensory quality of broiler meat as influenced by dietary supplementation of turmeric (curcuma longa), garlic (allium sativum) and in combinations as a feed additive. animal production 20(1): 61-69. qasem maa, alhajj ms, jer el nabi ar, al-mufarrej si. (2016). effects of dietary supplement of turmeric powder (curcuma longa) on blood biochemistry parameters and antioxidant activity in chickens. south african journal of animal science 46(2): 204-213.‏ rajput n, muhammah n, yan r, zhong x, wang t. (2012). effect of dietary supplementation of curcumin on growth performance, intestinal morphology and nutrients utilization of broiler chicks. journal of poultry science 50: 44-52. ramadan oesa, samia el, samy m, el-gharib a, mohamed fz. (2021). the protective role of curcuma longa (turmeric) on broilers exposed to chronic heat stress. alfarama journal of basic & applied sciences 2(2): 194-202. riasi a, kermanshahi h, mahdavi ah. (2012). production performance, egg quality and some serum metabolites of older commercial laying hens fed different levels of turmeric rhizome (curcuma longa) powder. journal of medicinal plants research 6(11): 2141-2145. sadeghi gh, karimi a, padidar jahromi sh, azizi t, daneshmand a. (2012). effects of cinnamon, thyme and turmeric infusions on the performance and immune response in of 1-to 21-day-old male broilers. brazilian journal of poultry science 14(1): 15-20. samia mm, rizk am, el-sayed oa. (2018). effect of supplementing diet with spirulina platensis algae or turmeric on productive and reproductive performance of golden montazah layers. egyptian poultry science journal 38(1): 109-125. singh pk, kumar a,tiwari dp, kumar a, palod j. (2018). effect of graded levels of dietary turmeric (curcuma longa) powder on performance of broiler chicken. indian journal of animal nutrition 35(4): 428-435.‏ sotiboldieva di, mahkamov tx. (2020). component composition of essential oils curcuma longa l. (zingiberaceae) introduced in uzbekistan. american journal of plant sciences 11(8): 1247-1253. vürüşan h, bölükbaşı şc. (2017). effects of dietary supplementation levels of turmeric powder (curcuma longa) on performance, carcass characteristics and gut microflora in broiler chickens. journal of animal and plant sciences 27(3): 732-736. wang d, huang h, zhou l, li w, zhou h, hou g, hu l. (2015). effects of dietary supplementation with turmeric rhizome extract on growth performance, carcass characteristics, antioxidant capability, and meat quality of wenchang broiler chickens. italian journal of animal science 14(3): 344-340. 6 squ journal of agricultural and marine sciences, 2023, volume 28, issue 2 use of turmeric (curcuma longa) in poultry nutrition: a review widhowati d, hidayah n, yunani r, malia m. (2017). the effect of turmeric as immuno-stimulator against avian influenza (ai) vaccine. advances in social science, education and humanities research (assehr) 98: 293-295. widjastuti t, andriani l. (2010). the use of curcuma zedoaria, rosc meal to reducabdominal fat and meat cholesterol in broiler. universitatea de ştiinţe agricole şi medicină veterinară iaşi 53: 126-129. widjastuti t, garnida d, tanwiriah w, balia rl. (2018). mixed red ginger (zingiber offinale var rubrum) with turmeric (curcuma longa) as feed additive to improve conversion meat protein broiler. the journal of agricultural sciences – sri lanka15 (2): 244-249. img086 img087 img088 img089 img090 research paper journal of agricultural and marine sciences 2023, 28(1): 62–69 doi: 10.53541/jams.vol28iss1pp62-69 received 7 july 2022 accepted 4 september 2022 دراسة مقارنة للمالحظات فوق اهليكلية على خالاي الدم للدجاج احمللي العماين والالحم كوب 500 شذى خ. العويف1، هيثم علي1، هاين م. الزايت21، كاذية اخلروصي1، سلمى ر. العدواين1، ايمسني الطاهر1، عبدالرمحن النبهاين3، حممد أ الكندي، وليد املرزوقي1،*3 comparative study of ultrastructural observations on blood cells of local omani and cobb 500 broiler chickens shadha k. al-aufi1, haytham ali1, hani m. el-zaiat1,2, kaadhia al-kharousi1, salma r. al-adwani1, yasmin el tahir1, abdulrahman al nabhani, mohamed a. al kindi and waleed al-marzooqi1,* waleed al-marzooqi1,*( ) walmar@squ.edu.om, 1department of animal and veterinary sciences, college of agricultural and marine sciences, sultan qaboos university, muscat, sultanate of oman, 2department of animal production, faculty of agriculture, university of alexandria, alexandria, egypt, department of pathology  college of medicine and health sciences, sultan qaboos university, oman. introduction the local chicken is considered an essential part of human livelihood, and it contributes to the food security of low-income families as a significant source of meat and eggs in more than 80% of poor households in the developing regions around the world (shaat and al-habsi, 2016). cobb 500 is superlatively suitable to the middle east region, adapting well to warmer climates with integrators benefiting from the breed’s efficiency right through the production chain. one of the main characteristic of cobb 500 broiler breed is the great feed conversion and there for that make it the best choice in broilers breed selection (hult, 2015). many farmers in oman raise local chickens for meat and egg production. to ensure an enhanced production of local breed chickens, it is important to assess their health performance first (shaat and al-habsi, 2016). the immune system is built up by many lymphoid tissues, molecules and leukocytes, which defend the body from infectious agents, such as viruses, bacteria, parasites and fungi. besides protecting the body from pathogens, the immune system plays a role in maintaining body hemostasis by restoring and removing damaged endogenous tissues and cells. leukocytes are produced predominantly in the bone marrow. after differentiation and maturation, leukocytes migrate to the blood, lymabstract. the local omani chicken represents a long-established indigenous chicken breed in the sultanate of oman. many farmers in oman raise local chickens for meat and egg production. therefore, to ensure an enhanced production of local breed chickens, it is important to assess their health performance. the present study was conducted to describe the comparative ultrastructural details of the blood cells of omani and cobb 500 chickens. twenty apparently healthy 35-old birds (10 per strain) of either sex reared at the poultry research unit at the agricultural experiment station, sultan qaboos university. the blood was collected from wing vein into tubes containing edta as anticoagulant. the blood was further processed for transmission electron microscopic study. the results obtained showed that all blood cells of both cobb 500 and omani chicken were similar. the heterophil nucleus had a multi-lobed nucleus. the number of nuclei lobes ranges from 2 to 3. the eosinophil had a distinctive appearance and mostly had a lobulated nucleus. basophil was round in appearance and had four types of granules (dense granules, mottled granules, web or net granules and myelin granules) which can be seen clearly. the lymphocytes were the smallest leukocytes and it was characterized as small round cell with few cytoplasmic process. the monocytes were round in shape with kidney-shaped or indented nucleus. the nucleus had more heterochromatin patches compared to euchromatin. the thrombocytes were distinguished from other cells by their dense nucleus and the large vacuoles found in the cytoplasm. in conclusion, this study shows great similarities in the ultrastructure of all blood cells composition between local omani and cobb 500 broiler breeds. keywords: blood cells, cobb 500, omani local chicken, ultrastructure. امللخــص: ميثــل الدجــاج العمــاين احمللــي ســالة دجــاج حمليــة راســخة يف ســلطنة عمــان. يقــوم العديــد مــن املزارعــني يف عمــان برتبيــة الدجــاج احمللــي إلنتــاج اللحــوم والبيــض. لذلــك ، لضمــان تعزيــز إنتــاج الدجــاج احمللــي ، مــن املهــم تقييــم أدائهــم الصحــي. أجريــت هــذه الدراســة لوصــف التفاصيــل للمقارنــة فــوق اهليكليــة خلــااي الــدم يف الدجــاج العمــاين والدجــاج الاحــم كــوب 500. عشــرون طائــرا يبــدو بصحــة جيــدة يبلــغ عمرهــا 35 عامــا )10 طيــور لــكل ســالة( مــن كا اجلنســني تــرىب يف وحــدة حبــوث الدواجــن يف حمطــة التجــارب الزراعيــة جبامعــة الســلطان قابــوس. مت مجــع الــدم مــن الوريــد اجملنــح إىل أانبيــب حتتــوي علــى edta كمضــاد للتخثــر. متــت معاجلــة الــدم بشــكل أكــر للدراســة اجملهريــة اإللكرتونيــة لارســال. أظهــرت النتائــج الــي مت احلصــول عليهــا أن مجيــع خــااي الــدم لــكل مــن cobb 500 والدجــاج العمــاين كانــت متشــاهبة. كان للنــواة غــر املتجانســة نــواة متعــددة الفصــوص. يــرتاوح عــدد فصــوص النــوى مــن 2 إىل 3. كان للحمضــات مظهــر مميــز وكان هلــا يف الغالــب نــواة مفصصــة. كان البازوفيــل مســتديرا يف املظهــر وكان لديــه أربعــة أنــواع مــن احلبيبــات )حبيبــات كثيفــة ، حبيبــات مرقشــة ، حبيبــات شــبكية أو صافيــة وحبيبــات املايلــني( والــي ميكــن رؤيتهــا بوضــوح. كانــت اخلــااي الليمفاويــة أصغــر الكــرايت البيــض ومتيــزت أبهنــا خليــة مســتديرة صغــرة مــع عــدد قليــل مــن العمليــات الســيتوبازمية. كانــت اخلــااي الوحيــدة مســتديرة الشــكل مــع نــواة علــى شــكل الكلــى أو املســافة البادئــة. كان لــدى النــواة بقــع غــر متجانســة أكثــر مقارنــة ابليوكروماتــني. مت متييــز الصفيحــات الدمويــة عــن اخلــااي األخــرى مــن خــال نواهتــا الكثيفــة والفجــوات الكبــرة املوجــودة يف الســيتوبازم. يف اخلتــام ، تظهــر الدراســة أوجــه تشــابه كبــرة يف البنيــة الفائقــة جلميــع .cobb 500 تكويــن خــااي الــدم بــني ســاالت العمانيــة احملليــة و الدجــاج الاحــم الكلمات املفتاحية: خااي الدم، كوب 500، دجاج عماين حملي، بنية فائقة. 63research paper al-aufi, ali, el-zaiat, al-kharousi, al-adwani, el tahir, al-marzooqi phatic system and peripheral tissues to perform their different immunological functions (hult, 2015). avian leukocytes include mononuclear cells (monocytes and lymphocytes), granulocytes (basophils, eosinophils and heterophils) and thrombocytes (jones, 2015). in recent years, transmission electron microscopy has become necessary to study biological and molecular ultrastructures. however, very little electron microscopy in chicken blood cells have been reported, and no survey on local omani chicken has been done so far. the main aim of this study was to compare the ultrastructural observations of the blood cells of local omani and cobb 500 broiler chickens raised under intensive management. material and methods ethical approval this study was approved in 2019 by the animal research ethics board at sultan qaboos university. resource population this study was conducted on both cobb 500 broilers (n=10) and local omani chickens (n=10) that were apparently healthy of age 35 days old of either sex reared at the poultry research unit at the agricultural experiment station, sultan qaboos university. feed and water were provided ad libitum. sample processing blood samples were obtained using disposable syringes needles (23 gauges) from the wing vein. samples were collected into tubes containing ethylenediamine teraacetic acid (edta). the samples were kept on ice and transported to the electron microscopy lab in the college of medicine, immediately after collection to prevent any cells ultrastructure alteration. the identification and classification of blood cells were achieved using the transmission electron microscopy (tem). samples for electron microscopy were prepared as previously described (johnson et al., 2020). briefly, to obtain a buffy coat layer, samples were centrifuged at 400 g for 20 minutes within 90 minutes of collection. the plasma was removed, and the buffy coat was coated with karnovsky’s fixative (2 percent glutaraldehyde in 2.5 % paraformaldehyde in 0.2 m phosphate buffer, ph 7.38) on top. the fixative was withdrawn and the buffy coat layers were peeled off and dissected into 2 × 1 × 1 mm blocks and placed in a petri dish containing fresh karnovsky fixative for an additional 90 minutes after overnight refrigeration. a tissue processor from leica electron microscopy was used to process the blocks. spurr’s epoxy resin embedding media was used to embed tissues, which were polymerized overnight. light microscopy was used to examine sections stained with 1 % toluidine blue in 1% borax. ultra-sectioning with an ideal thickness of 60–90 nm and staining with uranyl acetate and reynold’s lead citrate were used to identify locations with the highest concentration of lymphocytes. a jeol jem-1230 transmission electron microscope with an 80 kv volt-age was used to examine sections on grids. msc si0031 gatan ccd camera and digital micrograph (tm) 1.85.1535 software were used for digital imaging and acquisition. prior to screening samples, images were automatically gain-corrected using gain and dark standards and calibrated using a carbon grating replica (robinson, geraci, sonnenblick, & factor, 1988). results the ultrastructural observations of omani local chicken and cobb 500 brioler chickens were examined. in general, we found that the ultrastructural features of blood cells of both strains were similar and are therefore described together. heterophils the heterophil nucleus was surrounded by a nuclear membrane. in most cells, the nucleus has a higher quantity of heterochromatin than euchromatin. mature polymorphonuclear cells have a multi-lobed nucleus. the number of nuclei lobes ranges from 2 to 3 (figures 1a and 1b). different organelles were detected in the cytoplasm such as mitochondria, vesicles, centrioles and central body. in addition, pseudopodia were seen frequently in the heterophil peripheral cytoplasm. in addition, two types of intracellular granules were seen; dense granules and less dense granules. dense granules can be either oval or spherical. they are cytoplasmic membrane-bounded electron dense granules. the size of these granules ranges from 120-575 nm. multiple numbers were demonstrated. less dense granules (specific granules) are lighter than dense granules and smaller in size. they are membranous granules. their size ranges from less than 200-270 nm. eosinophil eosinophils had a distinctive appearance and showed small pseudopodia (figures 2a and 2b). mostly they had a lobulated nucleus. heterochromatin and euchromatin were in equal quantities. the nucleus often was located in the center of the cell. major structures were detected in both broiler cobb 500 and omani chicken were golgi apparatus. invaginations resembling vacuoles in the granules are seen approximately a quarter the size of the granule and different sizes of dense granules surrounding with a membrane were present in this cell. basophil basophils are round in appearance. small pseudopodia were detected (figures 3 and 4). the single nucleus showed indentation. heterochromatin and euchromatin were distributed equally in cobb 500 breed. in the omani breed, the euchromatin distribution was more 64 squ journal of agricultural and marine sciences, 2023, volume 28, issue 1 comparative study of ultrastructural observations on blood cells of local omani and cobb 500 broiler chickens prominent than heterochromatin. nucleoli were present in some cells. in both breeds, the mitochondria could be seen. four types of granules (dense granules, mottled granules, web or net granules and myelin granules) could be seen (figures 5 and 6). dense granules were darker granules, and some of them had a little internal structure which can be seen. they range from 100-280 nm in cobb 500 chicken and 100-250 nm in omani chicken. mottled granules, they are less dense than the first granules. in cobb 500 chicken they range from 150-200 nm and from 200-250 nm in local chicken. web or net granules, looser than mottled granules and had ability to break down. they range from 80-100 nm in both breeds. myelin granule, these granules size was 250 nm in cobb 500 and 120 nm in omani chicken. figure 1. transmission electron micrograph of (a) cobb 500 broiler and (b) omani local chicken. in both panel (a and b), a heterophil showing bi-lobed nucleus (n), heterochromatin (hc), euchromatin (ec) and nuclear membrane (arrow) were observed. the cytoplasm includes dense granules (dg), less dense granules (lg), centriole (c), golgi apparatus (ga) mitochondria (m), dissected central body (cb), pseudopodia (p) and vesicles (v) figure 2. transmission electron micrograph presenting eosinophil from (a) cobb 500 broilers and (b) omani local chicken. nucleus (n), nucleolus (n), heterochromatin (hc), euchromatin (ec) and nuclear membrane (nm). this cell also shows centric nucleus and various sized of dense granules (dg). pseudopodium (p) is also detected 65research paper al-aufi, ali, el-zaiat, al-kharousi, al-adwani, el tahir, al-marzooqi lymphocyte in both chicken breeds’ peripheral blood, lymphocytes were the smallest leukocytes. lymphocyte was round in shape (figure 7a and 7b). the nucleus was located in the center of the cell and showed a higher nucleus to cytoplasm ratio. the nucleus was round in shape, and it contained an equal quantity of euchromatin and heterochromatin. different structures were observed in the cytoplasm, such as different sizes and number of mitochondria. in some cells, there were up to six mitochondria. in addition, multi-vascular body, few short endoplasmic reticulum strands, beta-glycogen granules and less than 0.1 µm measures small clear vesicles were detected. monocyte monocyte can be easily identified due to their kidney-shaped or indented nucleus (figures 8 and 9). monocyte contained less heterochromatin compared to euchromatin even though monocyte heterochromatin were not as dense as lymphocyte. heterochromatin was always found towards the edge of the nucleus. the identification of the nuclear membrane was better in monocyte compared to other leucocytes. both cobb 500 and omani breeds had a similar shape and structure. in the majority of monocyte cells, a single layer of rough endoplasmic reticulum surrounded the other nuclear membrane. there was no smooth endoplasmic reticulum detected. many mitochondria of different sizes were frequently observed in each cell. some of the mitochondria were small and round with a dense matrix, and others were larger with more prominent cristae and lighter matrix. golgi apparatus was detected more often in this cell than in other leukocytes. many cells contain lysosomes with different densities. large empty vesicles were seen in the cytoplasm. pinocytotic vesicles were also detected. pseudopodium was seen in the majority of the cell. figure 3. transmission electron micrograph of cobb 500 breed basophil showing a single central nucleus (n), nucleolus (n), heterochromatin (hc), euchromatin (ec), vessel (v) and mitochondria (m) four different types of granules: (1) dense (2) mottled (3) web or net form (4) myelin figure also can be seen figure 4. higher magnification of figure-3 showing dense (1), mottled (2), web or net form (3) granules figure 5. transmission electron micrograph of omani breed basophil showing single central nucleus (n), nucleolus (n), heterochromatin (hc), euchromatin (ec) and pseudopodia like structures (p) 66 squ journal of agricultural and marine sciences, 2023, volume 28, issue 1 comparative study of ultrastructural observations on blood cells of local omani and cobb 500 broiler chickens thrombocyte thrombocyte was distinguished from other cells by their dense nucleus and the large vacuoles found in the cytoplasm. heterochromatin was predominating over euchromatin, and that made the nuclei detection easier. in many cells, the nucleolus was irregular, large and dense (figures 10 and 11). the primary cell structure detected in in the cytoplasm of the thrombocyte cells in both breed was vacuoles. there were two types of vacuoles; large vacuoles were around 1 µm. the majority of large vacuoles were empty except from one or two dense granules measuring 50-100 nm. small vacuoles can be detected all around the cytoplasm, measuring less than 250 nm. pinocytotic vesicles, mitochondria and myelin figure was also detected. erythrocyte erythrocytes in both breeds were similar under transmission electron microscopy. the cytoplasm is moderately dense because of hemoglobin content, without notable organelles. the erythrocytes have a narrower, more elongated, elliptical shape. artifactual separation of the nucleus from the cytoplasm is evident (figures 12a and 12b). discussion chicken heterophil is a multilobulated oval or round cell with rod-like eosinophilic granules. cobb 500 and omani chickens had similar heterophil traits. euchromatin was detected in the nucleus center region, while heterochromatin was found in patches around the perimeter, similar to the findings of mohd et al. (2016). single beta granules were always recognized as glycogen. there was evidence of the golgi apparatus, and mitochondria were frequently spherical and tiny. other bird species with similar traits include ducks, geese, turkeys, pigeons, quail, and guinea-fowl (maxwell, 1973). the goose and duck heterophils, on the other hand, lacked the small, spherical, dense, membrane bound granules seen in chickens. heterophil possesses two types of granules: dense cytoplasmic granules (primary granules) and short round or oval less dense granules (secondary granules) figure 6. higher magnification of figure-8 showing the nucleus (n) of the basophil with 4 different types of granules: (1) dense (2) mottled (3) web or net form (4) myelin figure. mitochondria (m) also can be seen figure 7. transmission electron micrograph presenting lymphocyte from cobb 500 (a) and omani local chicken (b). nucleus (n), heterochromatin (hc), euchromatin (ec), mitochondria (m), pinocytotic vesicle (pv), multi-vascular body (mvb), dense electron granules (g), small empty vesicles (v), beta-glycogen granules (gl) and myelin figure (mf) 67research paper al-aufi, ali, el-zaiat, al-kharousi, al-adwani, el tahir, al-marzooqi in chicken. the dense granules contain a central body that play an important role during phagocytosis (mohd et al., 2016). heterophil central body was also reported in duck, goose, turkeys and pigeons (maxwell, 1973). dense granules of both cobb 500 and omani breed were measured and there were no significant differences in dense granules of both breed. cobb 500 chicken dense granules measurements were within the range reported previously (mohd et al., 2016), which were 400-1600 nm in length. similar observations have been observed in duck and goose, with lengths ranging from 260 to 300 nm in turkey and pigeon (maxwell, 1973). no obvious ultrastructure differences were observed in the lymphocyte cells between cobb 500 breed and the omani breed examined. except for the cytoplasm to nucleus ratio, which was lower than monocytes, they had a similar diameter to monocytes. this was in line with maxwell’s (1973) and mohd et al.’s results (2016). the nucleus of a medium-sized lymphocyte featured one to two nucleoli, which were encircled by a chromatin rim. despite the fact that it shares some characteristics with both tiny lymphocytes and monocytes, medium sized lymphocytes were previously overlooked as a unique cell type in avian peripheral blood. however, granules detected in the medium-sized lymphocytes of the two chicken strains studied were comparable to those seen in six bird species including domestic fowl (maxwell, 1973; mohd et al., 2016). figure 8. transmission electron micrograph of cobb 500 breed monocyte with a kidney shaped nucleus (n). this cell shows a distinct double nuclear membrane (nm), heterochromatin (hc) and euchromatin (ec). mitochondria (m), endoplasmic reticulum (er), golgi apparatus (ga), dense lysosome (ly), beta-glycogen granules (gl), pinocytotic vesicles (pv) and empty vesicles (v) can also be seen. pseudopodia (p) can also be detected figure 9. transmission electron micrograph of omani breed monocyte showing kidney shape nucleus (n), this cell shows a distinct double nuclear membrane (nm), heterochromatin (hc) and euchromatin (ec). mitochondria (m), endoplasmic reticulum (er), golgi apparatus (ga), dense lysosome (l), beta-glycogen granules (gl), myelin figure (mf) and empty vesicles (v) can also be seen. pseudopodia (p) can also be detected figure 10. transmission electron micrograph of cobb 500 breed thrombocyte showing a single nucleus (n), heterochromatin (hc) and euchromatin (ec). small dens granules (dg) attached to large vacuoles (lv), small vacuoles (sv), beta glycogen granules (gl), pinocytotic vesicle (pv) and mitochondria (m) can be detected 68 squ journal of agricultural and marine sciences, 2023, volume 28, issue 1 comparative study of ultrastructural observations on blood cells of local omani and cobb 500 broiler chickens the cell surface of lymphocyte was spherical, with few cytoplasmic structures visible. the nucleus was eccentric, occupying the majority of the cytoplasm in the form of a rim, which is consistent with earlier observations (gupta and singh, 2008; mohd et al., 2016). the nuclei of turkey, geese, pigeon, duck, guinea fowl, and quail small lymphocytes were found to have an equal quantity of heterochromatin and euchromatin, small clear vacuoles, and multi-vascular structures (maxwell, 1973), which were similar to the findings of this study. however, tyretrack like structure was not seen in any cell examined in the current study. one of the most intriguing features was the significant proportion of euchromatin in the nuclei of the majority of the monocytes studied. nuclei with more euchromatin and less stainable material are metabolically more active than those with coarse bulk of highly stained heterochromatin (maxwell and trejo, 1970). the presence of rough endoplasmic reticulum, which was more visible in monocytes than other white blood cells in this investigation and was consistent with prior observations, is likely associated to the high activity state according to maxwell and trejo (1970) and mohd et al. (2016). as observed in the current study, the nucleus of the monocyte was kidney or bean-shaped this finding was in accord with the gupta and singh (2008) who reported that monocytes from guinea fowl have a kidney-shaped nucleus with a distinct nuclear membrane. furthermore, mitochondria, lysosomes of various sizes, and dense multi-vesiculated bodies were assessed in this study, were consistent with earlier findings (maxwell and trejo, 1970; salakij et al., 2014). similar to prior studies, the eosinophil nucleus was sometimes solitary and often bilobed, with peripheral heterochromatin and central euchromatin patterns (maxwell and trejo, 1970; mohd et al., 2016). the cytoplasmic granules were spherical and thick, and they were dispersed throughout the cytoplasm. these findings were comparable to those of the uttara fowl eosinophil, which showed circular and oval granules; nevertheless, elongated granules were identified in other bird species, such as ducks, geese, and guinea fowl (maxwell et al., 1972; mohd et al., 2016). figure 11. transmission electron micrograph of omani breed thrombocyte showing nucleus (n), heterochromatin (hc) and euchromatin (ec). myelin figures (mf), beta glycogen granules (gl), pinocytotic vessel (pv) and a large empty vacuole (v) with peripheral dense granule (dg) can be seen figure 12. transmission electron micrograph presenting erythrocyte from cobb 500 (a) broiler and omani local chicken (b). nucleus (n), heterochromatin (hc) and euchromatin (ec). the cytoplasm is moderately dense because of hemoglobin content, without notable organelles. the erythrocytes have a narrower, more elongated, elliptical shape. 69research paper al-aufi, ali, el-zaiat, al-kharousi, al-adwani, el tahir, al-marzooqi when compared to eosinophil, basophil has more granules, whereas heterophil has almost the same quantity. the majority of avian species had granules of smaller than 0.1-0.8 m in diameter (maxwell and robertson, 1998), which is similar to the findings of this study. furthermore, chicken basophil had four types of granules, but other species such as goose, turkey, duck, japanese quail, guinea fowl, and pigeons had three types of granules (maxwell and robertson, 1998). the first type of granules was electro-dense oval or elongated granules. the second type was mottled granules which is the most appendant granules. this type of granules has stippled internal structure. the third granules have a honeycomb arrangement. these three types of granules were also previously reported by (maxwell, 1973; maxwell and robertson, 1998; maxwell and trejo, 1970; mohd et al., 2016). the fourth type of basophil granules resembles a myelin-like according to mohd et al. (2016). similar to earlier findings in kadaknath fowl by (yadav, 2012), the thrombocytes examined in this study displayed both oval and elongated cells with oval to round shaped eccentrically or centrally nuclei and peripherally scattered heterochromatin. there were two forms of glycogen granules in the investigated thrombocytes alfa and beta. similarly, it was reported that beta glycogen granules were observed are in the cytoplasm of the thrombocyte (maxwell and trejo, 1970). however, erythrocytes in this study were oval or elliptical in shape and the cytoplasm was homogeneously stained with no cell organelles which in agreement previous studies (mohd et al., 2016; yadav, 2012). conclusion the present study revealed that hematological parameters for local breed are similar to those of cobb 500. this indicates that these parameters can be used as performance indicators for both breeds. the present work could contribute to understanding pathophysiological changes relevant to chicken performance. acknowledgement this study was financially supported by the sultan qaboos university research fund [number: ig/agr/ anvs/19/01]. references gupta v, singh i. 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(2016). current status of animal genetic resources in oman-pearl research journals. journal of agricultural science and food technology 2: 139-146. sweeny pr, carlson hc. (1968). electron microscopy and histochemical demonstration of lysosomal structures in chicken thrombocytes. avian diseases 12: 636–644. yadav gc, ishwar s. (2012). cytochemical studies on the blood cells of kadaknath fowl. indian journal of veterinary anatomy 24: 113–114. img054 img055 img056 img057 research paper journal of agricultural and marine sciences 2022, 27(2): 59–65 doi: 10.53541/jams.vol27iss2pp59-65 received 16 june 2021 accepted 04 dec 2021 antifungal activity of shirazi thyme (zataria multiflora boiss.) essential oil against hypomyces perniciosus, a causal agent of wet bubble disease of agaricus bisporus yumna juma rashid al-balushi1, abdullah mohammed al-sadi1, issa hashil al-mahmooli1, majida mohammed ali al-harrasi1, jamal nasser al-sabahi2, alaa khamis sulaiman al-alawi1, khalid al-farsi3 and rethinasamy velazhahan1,* rethinasamy velazhahan( ) velazhahan@squ.edu.om, 1department of plant sciences, college of agricultural and marine sciences, sultan qaboos university, p.o. box 34, al-khoud, muscat 123, sultanate of oman, 2central instrumentation laboratory, college of agricultural and marine sciences, sultan qaboos university, p.o. box 34, al-khoud, muscat 123, sultanate of oman, 3oman botanic garden, muscat, oman. introduction mushroom farming is becoming a popular agro-based business worldwide. over 8.99 million tons of mushrooms are produced annually worldwide (kumla et al., 2020). white button mushroom [agaricus bisporus (lange) imbach] is the most popular and widely cultivated edible mushroom globally (sanchez, 2004). diseases are serious constraints in the commercial production of button mushrooms. several fungal diseases including wet bubble (hypomyces perniciosus), dry bubble (lecanicillium fungicola), cobweb (cladobotryum mycophilum) and green mold (trichoderma aggressivum) are reported to significantly reduce the yield and quality of mushroom crops (gea et al., 2021). wet bubble disease (wbd) caused by the ascomycetes fungus hypomyces perniciosus magnus [mycogone perniciosa (magnus) delacroix] was reported to cause yield reductions ranging from 15 to 30% in مضادات نشاط فطر hypomyces perniciosus املسبب ملرض الفقاعة الرطبة على فطر األبيض )املشروم( ) zataria multiflora boiss.( إبستخدام الزيت العطري من الزعرت الشريازي agaricus bisporus ميىن بنت مجعة بن راشد البلوشي1 و عبدهللا بن حممد السعدي1 و عيسى بن هاشل املهمويل1 و ماجدة بنت حممد بن علي احلراصي1 و مجال بن انصر الصباحي2 واآلء بنت مخيس بن سليمان العلوي1 وخالد الفارسي3 و ريثيناسامي فيالزهاهن1 abstract. wet bubble disease (wbd) caused by hypomyces perniciosus is a major constraint of button mushroom (agaricus bisporus) cultivated worldwide. a few synthetic chemical fungicides are used to control wbd. in our study, the potential of essential oil (eo) from zataria multiflora in inhibition of h. perniciosus was evaluated as an alternative to chemical fungicides. an isolate of h. perniciosus was isolated from wet bubble diseased a. bisporus and pathogenicity of the mycoparasite was determined under artificially inoculated conditions. the mycoparasitic fungus was identified using sequences of the internal transcribed spacer (its) region of ribosomal dna. the eo was extracted from the aerial parts of z. multiflora by microwave extraction method and evaluated in vitro for its antifungal activity against h. perniciosus. the eo of z. multiflora (zeo) at the tested concentrations (50% and 100%) inhibited the growth of h. perniciosus in the agar diffusion test. the minimum inhibitory concentration (mic) of zeo was 0.04% as assessed by the poisoned food technique. the chemical composition of zeo was determined by gas chromatography-mass spectrometry analysis. a total of 23 compounds were identified. among them, the most abundant compounds were linalool (20.3%) and bornyl acetate (15.5%). linalool at the tested concentrations of 0.25% and 0.125% completely inhibited the mycelial growth of h. perniciosus in an in vitro assay. these results suggest that zeo can be exploited for control of wbd. keywords: : agaricus bisporus; antifungal; essential oil; mycogone perniciosa; wet bubble disease; zataria multiflora. agaricus( هو أحد املعوقات الرئيسية لفطر األبيض hypomyces perniciosus الناجم عن )wbd( امللخص:مرض الفقاعة الرطبة bisporus( املــزروع يف مجيــع أحنــاء العــامل. يســتخدم عــدد قليــل مــن مبيــدات الفطــرايت الكيميائيــة األصطناعيــة للتحكــم يف wbd. يف دراســتنا، مت تقييــم إمكانيــة الزيــت العطــري مــن zataria multiflora يف تثبيــط h. perniciosus كبديــل ملبيــدات الفطــرايت الكيميائيــة. مت عــزل h. perniciosus مــن الفطــر االبيــض a. bisporus مصــاب بـــ الفقاعــة الرطبــة وبعــد ذلــك مت إختبــار هــذه العزلــة و حتديــد اإلمراضيــة للطفيــل الفطــري لتســبب هــذا املــرض علــى فطــر أبيــض ســليم حتــت ظــروف مناخيــة معلومــة. مت تعريــف الطفيــل الفطــري إبســتخدام التصنيــف اجليــي يف تسلســل وحــدة الريبوســومات املوجــودة علــى فواصــل النســخ الداخلــي )its( مــن محــض النــووي الريبوســومي .مت إســتخراج الزيــت العطــري eo مــن .h. perniciosus بطريقة اإلستخالص ابمليكروويف ومت تقييمه يف املخترب لنشاطه املضاد للفطرايت ضد z. multiflora األجزاء العلوية لـ أعــاق eo لـــ zeo(p( z. multiflora برتكيــزات خمتــربة )50٪ و 100٪( منــو h. perniciosus يف إختبــار خلــط الزيــت ابألجــار. كان احلــد األدىن للرتكيــز املثبــط )mic( لـــ zeoهــو 0.04٪ الــذى مت تقييمــه بواســطة تقنيــة الغــذاء املســموم. مت حتديــد الرتكيــب الكيميائــي لـــ zeo عــن طريــق حتليــل كروماتوجرافيــا الغــاز لقيــاس الطيــف الكتلــي. كذلــك ، مت حتديــد إمجــايل 23 مركبًــا. مــن بينهــا ، كانــت املركبــات األكثــر وفــرة linalool )20.3٪( و bornyl acetate )15.5٪(. قــام linalool برتكيــزات خمتــربة بنســبة 0.25٪ و 0.125٪ بتثبيــط منــو الغــزل .wbd للتحكــم يف zeo متاًمــا يف إختبــار يف املختــرب. تشــر هــذه النتائــج إىل أنــه ميكــن إســتغالل h. perniciosus )الفطــري )امليســيليوم الكلمــات املفتاحيــة: agaricus bisporus، مضــاد للفطــرايت، زيــت العطــري، mycogone perniciosa، مــرض الفقاعــة الرطبــة، zataria multiflora 60 squ journal of agricultural and marine sciences, 2022, volume 27, issue 2 antifungal activity of shirazi thyme (zataria multiflora boiss.) essential oil against hypomyces perniciosus, a causal agent of wet bubble disease of agaricus bisporus. button mushroom (wang et al., 2016; zhou et al., 2016; li et al., 2019; shi et al., 2020). deformation of basidiome, appearance of white cottony growth of the mycelium, exudation of brown coloured liquid and appearance of flocculent mycelia on the substrate are the common symptoms of wet bubble disease (fletcher et al., 1995; fu et al., 2016). since the mycoparasite directly affects the formation of caps the yield losses to the mushroom industry due to this disease is very high. in general vegetative mycelium of a. bisporus was not affected by h. perniciosus, whereas the morphogenesis of its fruiting bodies was severely affected (zhang et al., 2017). this fungus is also known to infect pleurotus citrinopileatus (zhang et al., 2017). the contaminated casing soil has been reported as the main source of inoculum of the fungus (fletcher and gaze, 2008). pathogen also spreads through air, contaminated tools and operators (gea et al., 2021). wbd can be prevented by good hygiene, sanitation and application of fungicides without affecting the growth of mushrooms (gea et al., 2021). fungicides such as benomyl (bollen and fuchs, 1970), iprodione and prochloraz-mn (gea et al., 2010; potocnik et al., 2010), thiabendazole, fludioxonil, diniconazole, fenbuconazole and imazalil (shi et al., 2020) were found to be effective in controlling h. perniciosus. the use of natural products for the control of foodborne pathogens has been considered a safe and environmentally friendly approach. the inhibitory effect of essential oils (eos) of a few plant species including lippia citriodora and thymus vulgaris (regnier and combrinck, 2010), crithmum maritimum (glamoclija et al., 2009), origanum majorana (tanovic et al., 2009) against h. perniciosus was reported. these essential oils are aromatic and volatile liquids extracted from plants through steam distillation process. in the course of screening of omani traditional medicinal plants for in vitro antifungal activity, we observed that the essential oil of zataria multiflora boiss. (lamiaceae) completely inhibited the growth of aspergillus flavus, a common contaminant and major aflatoxin producer in a wide range of agricultural commodities (unpublished data). considering the best knowledge of the authors, the antifungal activity of z. multiflora essential oil (zeo) against h. perniciosus has not been studied. in this study, the inhibitory effect of zeo and its major constituent linalool on h. perniciosus was determined. materials and methods plant material zataria multiflora boiss. (lamiaceae) (accession number 201100114) plants were obtained from oman botanic garden, muscat, sultanate of oman. mycoparasite isolation agaricus bisporus fruiting bodies showing symptoms of wet bubble disease were collected from the mushroom cultivation demonstration trials at the department of plant sciences, sultan qaboos university. a small piece of tissue was cut with a sterile surgical scalpel from the infected mushroom and surface sterilized with 1% sodium hypochlorite for 1 min. the tissue was then rinsed in sterile distilled water (sdw) and placed on potato dextrose agar (pda) (oxoid ltd., uk) medium in a petri dish. the plate was kept at 27°c for 3-5 days. a pure culture of the fungus was obtained by hyphal tip culture method. molecular identification mycelia were collected from 7-day-old pda culture plate. dna was extracted from approximately 80 mg of mycelium according to lee and taylor (1990). the dna quantity and quality was checked using a nanodrop 2000 spectrophotometers (thermo scientific, usa). polymerase chain reaction (pcr) was performed in 25 μl reaction volume using its4 and its5 primers (white et al., 1990) with puretaq ready-to-go pcr bead (ge healthcare, uk) according to al-rashdi et al. (2020). an aliquot (5 μl) of the pcr product was analyzed by 1.2% (w/v) agarose gel electrophoresis and amplified product (~600 bp) was sequenced at macrogen inc. (seoul, korea). the dna sequence from this study was compared with reference sequences of fungal species in the ncbi database (www.ncbi.nlm.nih.gov) using blast search. testing pathogenicity polyethylene bags (25×30 cm) were filled with approximately 1 kg of phase iii compost spawned with a. bisporus (obtained from gulf mushroom products company, barka, oman). casing soil (obtained from gulf mushroom products company) was applied as a layer (30-40 mm) on the surface. ten ml of spore suspension (1×104 spores/ml) of h. perniciosus was mixed with the casing soil. the bags were kept at 25°c for 2-3 weeks and checked for the disease development. extraction of essential oil one kg of z. multiflora leaves and stem was transferred to a glass reactor followed by the addition of 1.5 l of distilled water. the essential oil (eo) was extracted using ethos x microwave extraction system (milestone inc., shelton, ct, usa). the essential oil was stored in small amber glass vials in a freezer at -20°c. testing antifungal activity the antifungal activity of the eo of z. multiflora against h. perniciosus was tested using agar diffusion assay (al-maawali et al., 2021). briefly, sterile filter paper discs (6-mm diameter) were placed on the surface of pda medium in petri dishes and 10 μl of eo (50% and 100%) was 61research paper al-balushi, al-sadi, al-mahmooli, al-harrasi, al-sabahi, al-alawi, al-farsi, velazhahan applied on the discs. then a 7-mm mycelial disc obtained from a 7-day-old h. perniciosus culture was placed in the center of the petri dish and incubated at 27°c for 5-7 days. the formation of inhibition zone around the filter paper discs was observed. the assay was conducted in triplicate. minimal inhibitory concentration (mic) the mic of zeo was determined according to kiran et al. (2016). briefly, calculated quantity of the zeo was diluted in 0.5 ml of 5% tween-20 and mixed with 19.5 ml of molten pda and poured into sterile petri dishes to obtain the final concentrations of 0.1-1.0 μl/ml. in the center of the petri dish, a 7-mm mycelial disc obtained from a 7-day-old h. perniciosus culture was placed. the petri plates were incubated at 27°c for 5-7 days and observed for the mycelial growth inhibition and mic (the lowest concentration that causes no visible growth of the fungus). petri plate containing pda amended with 0.5 ml of 5% tween-20 alone was used as negative control. four replications were maintained per treatment. the data were analyzed using sas v8, (sas institute, nc, usa) and the values were compared by “duncan’s multiple range test, dmrt” at p ≤ 0.05. purified linalool (≥ 95.0%) (fluka, sigma-aldrich chemie gmbh, switzerland) was diluted in ethanol and mixed with pda medium to obtain final concentrations of 0.25% and 0.125% and evaluated for its antifungal activity against h. perniciosus as described above. analysis of essential oil shimadzu gc-2010 plus gas chromatography machine fitted with rtx-5ms capillary column (30 m × 0.25 mm; 0.25 μm), coupled to a gcms-qp2010 ultra ms was used for analysis of z. multiflora essential oil (hanif et al., 2011). the data were obtained by collecting the fullscan mass spectra with the scan range of 40-550 amu. figure 1. agaricus bisporus showing symptoms of wet bubble disease, 14 days after artificial inoculation with hypomyces perniciosus. figure 2. inhibition of mycelial growth of hypomyces perniciosus by essential oil of zataria multiflora. 62 squ journal of agricultural and marine sciences, 2022, volume 27, issue 2 antifungal activity of shirazi thyme (zataria multiflora boiss.) essential oil against hypomyces perniciosus, a causal agent of wet bubble disease of agaricus bisporus. the total run time was 63.5 min. the national institute of standards and technology (nist) v.2.3 and wiley 9th edition mass spectrum libraries were used for identification of the compounds. results and discussion hypomyces perniciosus was isolated from agaricus bisporus showing the symptoms of wbd and pure culture was obtained. the fungus was identified based on the analysis of pcr-amplified its regions. the fungal isolate showed 100% identity to sequences of over 30 strains of hypomyces perniciosus stored in the genbank database. the sequence of the fungus was deposited in the genbank under the accession number mz149255. the pathogenicity of the fungus was confirmed by artificial inoculation of casing soil with the spore suspension of h. perniciosus. the mycoparasite induced typical symptoms of wbd on the emerging mushrooms approximately 14 days after inoculation (figure 1). the eo extracted from z. multiflora (zeo) aerial parts had a very strong antifungal activity and completely stopped the growth of h. perniciosus at the tested concentrations (50% and 100%) in agar diffusion test, whereas the control recorded 4.8 cm diameter growth after 7 days of incubation (figure 2). the mic value of zeo was 0.4 μl/ml as assessed by poisoned food technique (table 1). antifungal activities of eos of a few plants against m. perniciosa have been reported in previous studies (regnier and combrinck, 2010; glamoclija et al., 2009). glamoclija et al. (2009) demonstrated that the eo of critmum maritimum and its major components viz., limonene and α-pinene effectively inhibited the growth of m. perniciosa. preventive application of eos of lippia citriodora and thymus vulgaris at a concentration of 40 μl/l was demonstrated to control the development of wbd in a simulated commercial trial (regnier and combrinck, 2010). different modes of action of eos on fungi have been reported. cox et al. (2000) while studying the mode of action of essential oil on yeast (candida albicans) and bacteria (staphylococcus aureus and escherichia coli) reported that the eo of melaleuca alternifolia suppressed the respiration and augmented the permeability of plasma membranes of yeast and cytoplasmic membranes of bacteria. tian et al. (2012) demonstrated that eo of anethum graveolens induced morphological alterations in aspergillus flavus cells and reduced the ergosterol content and activities of atpase and dehydrogenase and increased the mitochondrial membrane potential and production of reactive oxygen species. chaudhari et al. (2020) reported that the eo of pimenta dioica completely inhibited the growth of a. flavus and the production of aflatoxin b1. the oil caused reduction of methylglyoxal, a signaling molecule that can trigger aflatoxin biosynthesis gene aflr, increased ions leakage from the cells and ergosterol content of fungal plasma membrane, suggesting plasma membrane of fungi as the action site. the inhibition of mycelial growth of m. perniciosa by zeo as observed in this study might be due to the presence of antifungal compounds in zeo (nazzaro et al., 2017). phytochemical profile of zeo by gc-ms analysis in table 1. minimum inhibitory concentration of zataria multiflora essential oil against hypomyces perniciosus. concentration of zeo (μl/ml) diameter of mycelial growth (cm) 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 5.3 a 2.5 b 1.8 c 1.2 d 0 e 0 e 0 e 0 e 0 e 0 e 0 e values followed by the same alphabetical letter, do not differ significantly (p = 0.05; duncan’s multiple range test). figure 3. gas chromatogram of zataria multiflora essential oil. 63research paper al-balushi, al-sadi, al-mahmooli, al-harrasi, al-sabahi, al-alawi, al-farsi, velazhahan this study identified 23 compounds (figure 3). among these, linalool (20.3%) and bornyl acetate (15.5%) were the major components (table 2). antimicrobial effect of linalool, an acyclic monoterpene (park et al., 2012) has been reported earlier (peana et al., 2002). bornyl acetate has been identified as the major component of eo of tetraclinis articulata that showed antibacterial activities (rabib et al., 2020). several reports indicated the chemical composition of eo of z. multiflora (shafiee and javidnia, 1997; moosavy et al. 2008; mahboubi and bidgoli, 2010; raeisi et al., 2016). carvacrol (71.20%), γ-terpinene (7.34%) and α-pinene (4.26%) were reported as the major components of zeo (moosavy et al. 2008). mahboubi and bidgoli (2010) reported thymol (38.7%), carvacrol (15.3%) and p-cymene (10.2%) as the major components in zeo. in another study, carvacrol (63.2%) and thymol (15.1%) were reported as the main constituents of zeo (raeisi et al., 2016). saleem et al. (2004) reported higher thymol concentration in fresh plant (73.21%) and carvacrol in dry plant (62.87%) tissues. the difference in the composition of zeo might be due to plant samples collected at varying growth stages, geographical locations, prevailing climatic conditions and habitat (ruiz-navajas et al., 2012; abd-elgawad et al., 2019). the results of this study also revealed that linalool, one of the major components of zeo also inhibited the growth of h. perniciosus even at a concentration of 0.125% under laboratory conditions (figure 4). the inhibitory effect of zeo on h. perniciosus in this study could be attributed to the presence of linalool. figure 4. inhibition of mycelial growth of hypomyces perniciosus by linalool. table 2. chemical composition of essential oil of zataria multiflora. s.no. name of the compound rt (min) area % calculated ki nist ki 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 camphene trans-.beta.-ocimene .beta.-pinene 3-octanone .(-)-limonene .gamma.-terpinene linalool 1,5,7-octatrien-3-ol, 3,7-dimethyl2,6-dimethyl-1,3,5,7-octatetraene, e,eisoborneol terpinen-4-ol .alpha.-terpineol 2,6-dimethyl-3,5,7-octatriene-2-ol, ,e,elinalyl acetate bornyl acetate thymol (-)-.beta.-elemene caryophyllene .gamma.-elemene humulene germacren d-4-ol .alpha.-cadinol shyobunol 7.83 8.24 8.99 9.23 10.41 11.24 12.53 12.57 12.96 14.26 14.49 14.84 15.07 16.43 17.31 17.37 19.53 20.00 20.54 22.28 23.98 25.62 26.43 6.195 10.703 1.454 0.727 1.593 0.954 20.332 2.567 2.169 10.696 1.209 2.518 4.368 3.043 15.564 2.269 0.858 0.720 2.611 1.393 1.289 1.323 5.434 941 956 984 993 1036 1066 1113 1114 1129 1177 1185 1198 1207 1260 1294 1296 1385 1404 1428 1504 1581 1659 1793 935 958 970 962 1020 1047 1081 1115 1134 1146 1161 1172 1187 1236 1269 1262 1377 1424 1425 1456 1570 1641 1709 64 squ journal of agricultural and marine sciences, 2022, volume 27, issue 2 antifungal activity of shirazi thyme (zataria multiflora boiss.) essential oil against hypomyces perniciosus, a causal agent of wet bubble disease of agaricus bisporus. conclusion z. multiflora is commonly used as a flavor ingredient in foods and has a wide range of biological and medicinal properties including antibacterial, antiseptic, anesthetic, antioxidant and immunomodulatory activities. this study demonstrated the antifungal activities of zeo and its major constituent linalool against h. perniciosus. the results of this study suggest that zeo is a safe, environmentally friendly natural product for control of wbd. however, further research is required to investigate the inhibitory effect of zeo on a. bisporus. acknowledgement we thank the gulf mushroom products company, barka, oman for providing phase iii compost and casing soil and oman botanic garden for providing zataria multiflora plants. references abd-elgawad am, elshamy ai, al-rowaily sl, el-amier ya. 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(2016). genetic diversity analysis of mycogone perniciosa causing wet bubble disease of agaricus bisporus in china using srap. journal of phytopathology 164: 271-275. research paper journal of agricultural and marine sciences vol. 23 : 68– 75 doi: 10.24200/jams.vol23iss1pp68-75 reveived 4 feb 2018 accepted 03 oct 2018 the importance of the intertidal area for the mullet liza klunzingeri 1 adel alsaffar, abdulrahman bin hassan, talal dashti, ali taqi, ali al-mousawy, adnan al-alawi 1*alsaffar, adel ( ) asaffar@kisr.edu.kw, ecosystem-based management of marine resources program, environment and life sciences research center, kuwait institute for scientific research, p.o. box 24885, 13109 safat, kuwait. introduction around 243 species of bony fishes inhabit ku-wait’s waters and includes the commercially im-portant mullet species, locally known as maid. mullets ranked third after that of “newaiby” (otolithes ruber) and “sha’em” (acanthopagrus latus) in all finfish species based on the average landings for the last ten years. formerly, maid were identified as liza carinata, but more recently, the species has been identified as liza klunzingeri (carpenter et al., 1997). adult mullets range between 15 and 25 cm in length (abou-seedo and al-khatib, 1995; dadzie et al., 2005) and occupy a variety of marine habitats, form schools, and are probably an important link between primary producers and secondary consumers in the marine trophic ecosystem. mullets are caught by gillnet, intertidal stake traps (hadrah) and as a by-catch of shrimp trawlers operating in shallow waters. current catches of mullet are mainly by gillnet, and the minimum allowable marketable size of this species is 14 cm.the central statistical bureau (csb) generates the annual data on kuwait’s fishery landings and routinely records the landings volume of 22 species of finfish, including mullet. from 2000 to 2012, landings of finfish declined to 50%, from about 4,500 tons to 2,200 tons (fig. 1). the decline in mullet landings was 90%, from about 750 tons to only 78 tons, for the same period. small mullets, 8 cm or less in length, are actually juveniles and locally called zorie. juveniles have no commercial value but are occasionally used as a fresh bait for sport fishing. zorie are often found very close to the shores, particularly on a rising tide during spring. the shallow areas along kuwait’s coastline are reported to provide a nursery habitat for l. klunzingeri (abou-seedo and dadzie, 2004; dadzie et al., 2005). a project was conducted to assess kuwait’s mullet (liza klunzingeri) stock status, estimate the potential harvest volume, and formulate a management plan for a liza klunzingeri أمهية منطقة املد واجلزر لسمكة امليد عادل الصفار وعبدالرمحن بن حسن وطالل دشيت وعلي تقي وعلي املوسوي وعدنان العلوي abstract. the mullet liza klunzingeri, locally known as maid, is an important commercial species in kuwait and accounts for up to 16% of the total finfish landings. to determine the seasonal and spatial distributions of juvenile mullet, a small-mesh seine net was employed monthly at seven selected coastal sites during the period from november 2013 through october 2014. semicircular sweeps of the 30 m long, two-meters high seine covered an area of approximately 1,400 m2. juvenile maid were captured at most of the sampling sites during the entire investigation period, but mainly in spring and summer, indicating a wide coastal distribution of this species. the highest catches of juveniles occurred in may with an average of 30.2 kg per sweep, corresponding to a density of 22 g/m2. catches of juveniles from sampling sites in or just south of the kuwait bay, near prime maid fishing grounds, were much higher than those from more southerly sampling sites. the captured maid ranged in total length (tl) from 18 to 179 mm, with a high peak at 41 to 50 mm. by-catch included thirty species, with hasoom (sillago sihama), imchawah (diplodus sargus kotschyi), and yowaff (nematalosa nasus) being the most common. the by-catch consisted mostly of juveniles with lengths less than100 mm tl, showing the importance of the intertidal and coastal waters for many species. keywords: juveniles; nursery grounds; biomass; distribution املســتخلص: تعتــر مسكــة liza klunzingeri واملعروفــة حمليــا بامليــد مــن األنــواع التجاريــة املهمــة يف الكويــت، وأعلــى تقديــر هلــا يصــل إىل 16 % جملمــل كميــات األمســاك الزعنفيــة يف األســواق. ولتحديــد التوزيــع املومســي واملــكاين ليوافــع امليــد مت اســتخدام شــبك طــاروف ذو فتحــات صغــرة، عنــد ســبعة مواقــع ســاحلية خمتــارة، شــهريا مــن نوفمــر 2013 ولغايــة أكتوبــر 2014. وكانــت عمليــة املســح علــى شــكل نصــف دائــرة بشــبك طولــه 30 مــر وارتفاعــه مريــن، وكانــت املســاحة املغطــاة 1400 مــر مربــع. ومت صيــد يوافــع امليــد يف معظــم املواقــع خــالل فــرة البحــث وباألخــص يف الربيــع والصيــف، ممــا يــدل علــى التوزيــع الواســع هلــذا النــوع مــن األمســاك علــى الســواحل. وكان أعلــى مصيــد لليوافــع يف شــهر مايــو مبتوســط 30.2 كيلــو جــرام لــكل عمليــة مســح، تعــادل كثافــة 22 جــرام لــكل مــر مربــع. وكان مصيــد اليوافــع مــن املواقــع يف جــون الكويــت أو يف جنوبــه القريــب، بالقــرب مــن مناطــق صيــد امليــد الرئيســية، أكثــر بكثــر مــن نظــره مــن املواقــع الســاحلية األكثــر جنوبــا. وتــراوح الطــول الكلــي للمصيــد مــن امليــد مــن 23 إىل 145 مليمــر مــع كــون املنــوال عنــد 41 و45 مليمــر. وضــم املصيــد املــرادف ثالثــن نوعــا، وأكثرهــا شــيوعا احلاســوم )sillago sihama( واجملــوة )diploddus sargus kotschyi( واليــواف )nematalosa nasus(. ويتكــون املصيــد املــرادف مــن يوافــع بطــول أقــل مــن 100 مليمــر للطــول الكلــي، ممــا يبــن أمهيــة مناطــق املــد واجلــزر وامليــاه الســاحلية للعديــد مــن األنــواع البحريــة. الكلمات املفتاحية: الراكم احليوي على األسطح املغمورة، 69research article alsaffar, bin hassan, dashti, taqi, al-mousawy, al-alawi long-term sustainable mullet fishery. part of this study included a nursery ground survey for mullet juveniles along kuwait’s coastal waters. here, we present the results of the nursery ground survey. materials and methods to conduct the nursery ground survey, most of the kuwait’s coastline was examined for suitable sampling sites and seven locations were selected (fig. 2). these sites are characterized by gradually sloping bottom; prominent rocks and debris were removed before the start of the survey to allow smooth, uninterrupted sweeps with a seine net. small-mesh seine net was employed for the juvenile mullet survey. small mesh seines were obtained from an usa-based company. the nets were received with the following measurements: length, 30 m; height, 1.8 m; and square mesh opening about 7×7 mm. at 45 and 30 cm intervals, the net was supported with floats at the top and lead weights at the bottom, respectively. a bamboo pole was tied to each end of the net to facilitate seining. the operation of the net was conducted as follows: on a rising tide, the two poles were positioned 30 m apart at the water’s edge. keeping one pole fixed, the other pole was swept into the rising tide making a 30-m radius semicircle, sweeping an area of 1,400 m2 in the process (fig. 3, fig. 4a, b). this operation required from 5 to 20 min, depending on weather, water current and (or) the amount of seagrass and seaweed that interfered with the operation (fig. 4c). separating the catch, however, took 15 to 45 min, especially if considerable seaweed was collected in the net (fig. 4d). the catch was returned to the laboratory and separated by species when possible. for the mullet catch, the total length to the nearest millimeter and the weight to the nearest gram of all (less than 25) or about 25 individuals were measured. for the rest of the mullet catch, the number was counted and the total weight was measured. for other species, only the total length was measured to the nearest millimeter for all (less than 25) or about 25 individuals and the total weight of the catch were recorded. for a very large catch, a sample was taken and the number and the weight measured were calculated for the total catch. results and discussion table 1 summarizes the monthly juvenile survey catches. no sampling was carried out in the month of july. the highest catches of juveniles occurred in may with an 0 1000 2000 3000 4000 2000 2002 2004 2006 2008 2010 2012 year la nd in gs (t on s) species mullet other finfish figure 1. landings of mullet (liza klunzingeri) and other finfish in kuwait. figure 2. location of the 7 sampling sites (black stars) of the nursery ground survey of liza klunzingeri in kuwaiti waters. land sea swept area : 1400 m2 fixed polenet water edge moving pole moving direction 30 m figure 3. schematic illustration of the operations carried out for the nursery ground survey. 70 squ journal of agricultural and marine sciences, 2018, volume 23, issue 1 the importance of the intertidal area for the mullet liza klunzingeri average of 30.2 kg per sweep, corresponding to a density of 22 g/m2. juvenile mullet length-frequency the length-frequency data for the juvenile mullet captured in the nursery ground survey showed that the mullet ranged from 1.8 to 17.9 cm with a high peak at 4.1 to 5.0 cm and a low peak at 8.6 to 9.5 cm (fig. 5). the monthly length-frequency for juveniles showed the moving of towards right indicating its seasonal growth (fig. 6). biomass and distribution the abundances (number and weight per squared kilometer) of juvenile mullets in the surveyed nursery grounds were estimated using the catch rate and the swept area (1,400 m2) (table 2). juveniles were caught at all sampling sites especially during spring and summer seasons indicating a wide distribution of juveniles in the coastal waters of kuwait over a prolonged period (figs. 7 and 8). a large number of juveniles occurred from march through june particularly along the kuwait bay’s southern coast (sampling site 3), just south of kuwait bay (sampling site 4), at sampling site 5, and at sampling site 6 (fig. 2). the average number of juveniles per square kilometer in these sampling sites exceeded two million (table 2). the paucity of juveniles caught at sampling site 7 is an indication that kuwait’s southern coastal waters are not as important a nursery area as the northern waters. juveniles were most abundant in april and may, which supports the view that april and may are the major months of recruitment (dadzie et al., 2005).according to the interviews with the fishermen, mullets were most abundant in the shallow areas in kuwait bay, areas around failakah island, and areas east and south of boufigure 4. (a) the seine net at the beginning of the operation, which required three to four persons for deployment. (b) the seine net deployment at the end of a sweep. (c) the seine net operation in the presence of abundant benthic algae and (d) separating the catch from the macroalgae required considerable effort. 71research article alsaffar, bin hassan, dashti, taqi, al-mousawy, al-alawi byan island (fig. 9). the by-catch species are listed in table 3. the most commonly caught species numerically was sillago sihama (hasoom), followed by diplodus sargus kotschyi (imchawah) and nematalosa nasus (yowaff ). the sizes of the by-catch were small and most were juveniles with lengths less than 100 mm and individual mass of a few grams. the nursery ground survey found large quantities of juvenile mullet mainly in april and may along the kuwait bay’s southern coast (sampling site 3), just south of kuwait bay, at sampling site 4, at sampling site 5, and at sampling site 6 (fig. 2). for example, the highest estimated number of juveniles per square kilometer exceeded twenty million at sampling site 4 in may (table 2). a closed season from april through may in these areas may be necessary to protect the juveniles table 1. estimated juvenile abundances of l.klunzingeri (number and weight per squared kilometer) based on the catch rates and swept areas. month st.1 st.2 st.3 st.4 st.5 st.6 st.7 total average dec-13 no.(×1000) 2.9 0.0 32.9 0.0 nc nc nc 36 8.9 wt. (kg) 2.0 0.0 24.3 0.0 nc nc nc 26.3 6.6 jan-14 no.(×1000) nc 0.0 84.3 21.4 nc 0.0 nc 106 26.4 wt. (kg) nc 0.0 80.9 12.4 nc 0.0 nc 93.2 23.3 feb-14 no.(×1000) 3.6 0.0 0.0 0.0 nc 64.3 0.0 68 11.3 wt. (kg) 3.8 0.0 0.0 0.0 nc 54.5 0.0 58.2 9.7 mar-14 no.(×1000) 21.4 522.9 130.0 0.0 nc 4025.1 0.0 4699 783.2 wt. (kg) 17.0 606.2 288.5 0.0 nc 3329.6 0.0 4241.3 706.9 apr-14 no.(×1000) 0.0 460.0 13577.4 3786.5 8085.9 17269.6 0.0 43179 6168.5 wt. (kg) 0.0 291.1 20409.3 6465.5 10440.0 20944.4 0.0 58550.4 8364.3 may-14 no.(×1000) 1.4 8.6 9708.8 20144.7 8145.2 5137.2 0.7 43147 6163.8 wt. (kg) 80.7 84.7 45375.0 79395.4 14292.1 11590.7 0.7 150819.3 21545.6 jun-14 no.(×1000) 2465.8 17.1 370.0 21.4 18.6 75.0 0.0 2968 424.0 wt. (kg) 27580.1 43.7 2890.3 102.3 56.9 410.7 0.0 31084.0 4440.6 aug-14 no.(×1000) nc 6.4 85.7 132.1 37.1 101.4 0.0 363 60.5 wt. (kg) nc 91.0 913.3 923.6 179.0 1075.1 0.0 3182.1 530.4 sep-14 no.(×1000) 10.0 5.0 7.9 56.4 323.6 0.0 0.0 402.9 57.6 wt. (kg) 178.3 50.3 147.6 678.9 5459.3 0.0 0.0 6514.4 930.6 oct-14 no.(×1000) 5.7 0.0 0.0 8.6 0.0 2.1 0.0 16.4 2.3 wt. (kg) 208.0 0.0 0.0 157.0 0.0 45.9 0.0 411.0 58.7 nov-14 no.(×1000) 0.0 0.0 78.6 5.0 3.6 45.9 0.0 133.0 19.0 wt. (kg) 0.0 0.0 945.0 98.6 27.1 45.9 0.0 1116.6 159.5 total no.(×1000) 2511 1020 24075 24176 16614 26721 1 95118 13726 wt. (kg) 28070.0 1167.0 71074.2 87833.7 30454.6 37496.7 0.7 256096.9 36776.2 average no.(×1000) 279.0 92.7 2188.7 2197.8 2373.4 2672.1 0.1 8647.1 1247.8 wt. (kg) 3118.9 106.1 6461.3 7984.9 4350.7 3749.7 0.1 23281.5 3343.3 nc= not carried out, st. =sampling site n = 1082 0 50 100 150 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 length (cm) fr eq ue nc y figure 5. length-frequency data of the juvenile mullets captured in the nursery ground survey. 72 squ journal of agricultural and marine sciences, 2018, volume 23, issue 1 the importance of the intertidal area for the mullet liza klunzingeri november october september august june may april march february january december 5 10 15 0 20 40 60 0 20 40 60 0 20 40 60 0 20 40 60 0 20 40 60 0 20 40 60 0 20 40 60 0 20 40 60 0 20 40 60 0 20 40 60 0 20 40 60 sizes fr eq ue nc y figure 6. monthly length-frequency data of the juvenile mullets captured in the nursery ground survey. 0 1 2 s1 s2 s3 s4 s5 s6 s7 station p op ul at io n de ns ity (i nd .m −2 ) figure 7. spatial variation of the abundance of juvenile mullet. 0 2 4 6 dec jan feb mar apr may jun na aug sep oct nov month p op ul at io n de ns ity (i nd .m −2 ) figure 8. temporal variation of the abundance of juvenile mullet. figure 9. mullet fishing areas (hatched area) as indicated by fishermen during interviews. 73research article alsaffar, bin hassan, dashti, taqi, al-mousawy, al-alawi table 2. juvenile mullet abundance, weight and by-catch catches (no. org/1400m2) at 7 selected sampling sites . month st.1 st.2 st.3 st.4 st.5 st.6 st.7 total average dec-13 no. 4 0 46 0 nc nc nc 50 12.5 wt. (g) 2.8 0.0 34.0 0.0 nc nc nc 36.8 9.2 by-catch wt.(g) 6.3 0.0 1.3 0.0 nc nc nc 7.7 1.9 jan-14 no. nc 0 118 30 nc 0 nc 148 37 wt. (g) nc 0.0 113.2 17.3 nc 0.0 nc 130.5 32.6 by-catch wt.(g) nc 0.8 2.3 22.4 nc 233.7 nc 259.2 64.8 feb-14 no. 5 0 0 0 nc 90 0 95 16 wt. (g) 5.3 0.0 0.0 0.0 nc 76.3 0.0 81.5 13.6 by-catch wt.(g) 127.1 7.1 55.6 0.0 nc 4.9 1846.0 2040.7 340.1 mar-14 no. 30 732 182 0 nc 5635 0 6579 1097 wt. (g) 23.9 848.7 403.9 0.0 nc 4661.4 0.0 5937.8 989.6 by-catch wt.(g) 1055.2 218.3 481.3 187.1 nc 2.0 1372.0 3315.8 552.6 apr-14 no. 0 644 19008 5301 11320 24177 0 60450 8636 wt. (g) 0.0 407.6 28572.5 9051.535 14615.7 29321.6 0.0 81968.9 11709.8 by-catch wt.(g) 7855.0 8592.4 17231.5 2248.5 5384.3 19678.4 299.0 61289.1 8755.6 may-14 no. 2 12 13592 28202 11403 7192 1 60404 8629 wt. (g) 113.0 118.5 63523.7 111151.4 20008.5 16226.6 1.0 211142.8 30163.3 by-catch wt.(g) 1161.5 2859.3 17542.2 13296.7 591.5 20784.4 1023.7 57259.2 8179.9 jun-14 no. 3452 24 518 30 26 105 0 4155 594 wt. (g) 38611.4 61.1 4046.4 143.2 79.7 574.9 0.0 43516.7 6216.7 by-catch wt.(g) 2536.0 2674.9 2071.9 588.3 849.9 2709.8 279.1 11709.9 1672.8 aug-14 no. nc 9 120 185 52 142 0 508 85 wt. (g) nc 127.4 1278.6 1293.0 250.6 1505.1 0.0 4454.9 742.5 by-catch wt.(g) nc 5154.6 1083.8 1543.9 396.2 109.9 38.9 8327.4 1387.9 sep-14 no. 14 7 11 79 453 0 0 564 81 wt. (g) 249.6 70.4 206.6 950.5 7642.9 0.0 0.0 9120.0 1302.9 by-catch wt.(g) 248.6 2931.7 637.3 895.4 235.0 1358.0 226.7 6532.8 933.3 oct-14 no. 8 0 0 12 0 3 0 23 3 wt. (g) 291.2 0.0 0.0 219.8 0.0 64.2 0.0 575.3 82.2 by-catch wt.(g) 449.2 2457.3 254.7 1956.1 803.8 1077.6 1136.0 8134.7 1162.1 nov-14 no. 0.0 0.0 110.0 7.0 5.0 0.0 0.0 122 17 wt. (g) 0.0 0.0 1323.0 138.0 38.0 0.0 0.0 1499.0 214.1 by-catch wt.(g) 66.8 2204.3 74.5 1138.4 170.1 1049.6 311.0 5014.8 716.4 total no. 3515 1428 33705 33846 23259 37344 1 133098 19206 wt. (g) 39297.2 1633.7 99501.9 122964.8 42635.5 52430.1 1.0 358464.2 51476.5 by-catch wt.(g) 13505.7 27100.7 39436.5 21876.8 8430.9 47008.3 6532.3 163891.3 23767.4 average no. 390.6 129.8 3064.1 3076.9 3322.7 3734.4 0.1 12099.8 1746.0 wt. (g) 4366.4 148.5 9045.6 11178.6 6090.8 5243.0 0.1 32587.7 4679.7 by-catch wt.(g) 1500.6 2463.7 3585.1 1988.8 1204.4 4700.8 725.8 14899.2 2160.7 nc= not carried out 74 squ journal of agricultural and marine sciences, 2018, volume 23, issue 1 the importance of the intertidal area for the mullet liza klunzingeri table 3. overall species composition of the by-catch (abundance and biomass) from all samples (in decreasing order) rank scientific name catch in no. catch wt.(g) total lenght range (mm) 1 sillago sihama 10203 62060.0 21 to 242 2 diplodus sargus kotschyi 9479 19483.3 26 to 174 3 nematalosa nasus 5992 24130.6 62 to 132 4 herklotsichthys lossei 1980 4118.2 51 to 79 5 acanthopagrus latus 1408 6426.4 21 to 160 6 aphanius dispar 982 3787.5 25 to 71 7 hypoatherina temmincki 883 5974.5 21 to 129 8 herklotsichthys quadrimaculatus 662 855.7 38 to 85 9 hemiramphus sp. 622 10616.0 100 to 242 10 gerres filamentosus 456 3041.7 20 to 216 11 strongylura leiura 447 13072.3 230 to 443 12 pentaprion longimanus 185 892.3 35 to 164 13 pomadasys stridens 139 339.1 43 to 84 14 rhabdosargus haffara 87 223.1 30 to 93 15 scomberoides commersonnianus 83 1631.0 60 to 165 16 liza subviridis 82 5046.8 90 to 247 17 metapenaeus stebbingi 81 94.2 100 to 150 18 trachinotus mookalee 31 76.2 41 to 60 19 thryssa whiteheadi 26 743.8 165 20 leiognathus bindus 17 110.3 28 to 102 21 solea stanalandi 12 32.8 52 to 76 22 gerres oyena 8 13.8 37 to 69 23 crab sp. 7 4.6 18 to 35 24 ilisha compressa 7 51.0 83 to 125 25 pseudotriacanthus strigilifer 6 69.1 52 to 190 26 sparidentex hasta 5 60.4 53 to 152 27 upeneus tragula 5 80.4 90 to 122 28 gnathodon speciosus 4 0.5 21 to 24 29 sepia pharaonis 1 1011.0 235 30 lutjanus ehrenbergii 1 0.3 26 31 terapon puta 1 2.1 54 32 scatophagus argus 1 29.5 89 33 sea cucumber sp. 1 31.1 97 75research article alsaffar, bin hassan, dashti, taqi, al-mousawy, al-alawi references abou-seedo f. s., h. y. al-khatib. 1995. a histological and macroscopic study of ovarian development in the grey mullet, liza carinata (valenciennes 1836). journal of the university of kuwait (science) 22: 239-254. abou-seedo f., s. dadazie. 2004. reproductive cycle in the male and female grey mullet, liza klunzingeri in the kuwait waters of the arabian gulf. cybium 28(2):97-104. carpenter k. e., f. krupp, d. a. jones, , u. zajonz. 1997. living marine resources of kuwait, eastern saudi arabia, bahrain, qatar, and the united arab emirates. food and agriculture organization of the united nations, fao species identification guide for fishery purposes, rome, italy. dadzie s., j.o. manyala, f. abou-seedo. 2005. aspects of the population dynamics of liza klunzingeri in the kuwait bay. cybium 29(1):13-20. research paper journal of agricultural and marine sciences 2023, 28(2): 18–27 doi: 10.53541/jams.vol28iss2pp18-27 received 19 december 2022 accepted 30 april 2023 تقييم مصايد الباطنة فيما يتعلق ابلتنمية املستدامة بيئياً ابستخدام هنج القرار متعدد املعايري هدى السيايب1,* وحسني املسروري2 an assessment of al batinah fishery with respect to ecologically sustainable development using multi-criteria decision analysis approach huda al siyabi1,* and hussain al masroori2 huda al siyabi1,* ( )hudakhalfan@hotmail.com, 1economic and development sector, a’shura council, sultanate of oman, 2 department of marine science and fisheries, college of agricultural and marine sciences, sultan qaboos university, sultanate of oman. introduction the recognition of the concept of sustainability is a critical need in order to manage any sector including fisheries (michael et al., 2014). it had a notable discussion during the last few decades since it concerns the principles of conserving all natural resources for the current and future generation needs. fisheries management’s thoughts raised globally as a result of the growing of fishery sector importance for human life in providing food, employment, income etc. therefore, several frameworks were developed to assess the progress toward sustainable development (coll et al., 2013; fao, 1999; fletcher et al., 2005; levrel et al., 2009). one of these frameworks is the ecologically sustainable development (esd) framework, which is used in this study. esd framework structure is similar to the general sustainable development framework which reflects the human and environmental components (fao 1999). it represents the effects of fishing activities on human and abstract. globally, sustainable development is considered as a vital need to fisheries sector that integrated both human and environmental well-beings. this issue was recognised by the omani government therefore, it started to promote the fishery management system by establishing new fisheries development plans and management policies to achieve the sustainable development goals. this study aimed at assessing the progress of al batinah fishery towards sustainable development using ecologically sustainable development (esd) framework and multi-criteria decision analysis approach (mcda) from 2008 to 2017. a consultation review was conducted to identify all possible components (criteria) of the esd framework. progress of each component toward sustainability and sensitivity analysis were conducted to identify strengths and weaknesses of components. attainment toward sustainability in al batinah fishery progressed a positive trend. scores increased from 50 points (on 100 points scale) in year 2009 to 81 points in year 2016. specifically, the progress toward sustainability in the human well-being was better. the scores increased from 55 points in year 2009 to 95 points in year 2016 indicating excellent progress. however, the progress toward sustainability in the environmental well-being was minimal. the scores increased from 42 points in year 2008 to only 67 points in the last three years 2015 to 2017 indicating a slow and a below average progress. the results indicated that the year 2016 had the best attainment toward sustainability and the management measures and/or practices adopted in 2016-favoured socio-economic development more than conserving the environment. sensitivity analysis confirmed that year 2016 was the most preferred year and provided different strengths and weaknesses to improve both human and environmental well-beings and consequently improving the progress toward sustainability. the management authority is therefore advised to adapt conservative measures to promote and protect the environment. in the long-term, such preferences of human well-being over environment might threaten the whole fishery. keywords: fisheries sustainable development, sensitivity analysis, esd framework, al batinah fishery امللخــص: علــى الصعيــد العاملــي، تعتــر التنميــة املســتدامة حاجــة حيويــة لقطــاع مصايــد األمســاك الــذي يدمــج الرفــاه البشــري والبيئــي. مت إدراك هــذه القضيــة مــن قبــل احلكومــة العمانيــة، لذلــك بــدأت يف تعزيــز نظــام إدارة مصايــد األمســاك مــن خــال وضــع خطــط جديــدة لتنميــة مصايــد األمســاك، وسياســات اإلدارة لتحقيــق أهــداف التنميــة املســتدامة. هدفــت هــذه الدراســة إىل تقييــم التقــدم احملــرز يف مصايــد الباطنــة حنــو التنميــة املســتدامة ابســتخدام إطــار التنميــة املســتدامة بيئيًــا)esd( وهنــج حتليــل القــرار متعــدد املعايــر )mcda( مــن 2008 إىل 2017. مت إجــراء مراجعــة استشــارية لتحديــد مجيــع املكــوانت )املعايــر( املمكنــة إلطــار )esd(. مت إجــراء تقييــم التقــدم حنــو االســتدامة وحتليــل احلساســية لــكل مكــون لتحديــد نقــاط القــوة والضعــف يف املكــوانت. أظهــر التقــدم حنــو االســتدامة يف مصايــد الباطنــة اجتاهــا إجيابيــا. زادت الدرجــات مــن 50 نقطــة )علــى مقيــاس 100 نقطــة( يف عــام 2009 إىل 81 نقطــة يف عــام 2016. علــى وجــه التحديــد، كان التقــدم حنــو االســتدامة يف رفاهيــة اإلنســان أفضــل. ارتفعــت الدرجــات مــن 55 نقطــة يف عــام 2009 إىل 95 نقطــة يف عــام 2016 ممــا يشــر إىل تقــدم ممتــاز. ومــع ذلــك، كان التقــدم حنــو االســتدامة يف الرفــاه البيئــي ضئيــًا. ارتفعــت الدرجــات مــن 42 نقطة يف عام 2008 إىل 67 نقطة فقط يف آخر ثاث ســنوات )2015-2017( مشــراً إىل تقدم بطيء وأقل من املتوســط. أشــارت النتائج إىل أن عــام )2016( حقــق أفضــل املكاســب حنــو االســتدامة وأن تدابــر اإلدارة و / أو املمارســات املعتمــدة يف عــام 2016 كانــت لصــاحل التنميــة االجتماعيــة واالقتصاديــة أكثــر مــن احلفــاظ علــى البيئــة. أكــد حتليــل احلساســية أن عــام 2016 كان العــام األكثــر تفضيــًا وقــدم نقــاط قــوة ونقــاط ضعــف خمتلفــة لتحســني رفاهيــة اإلنســان والبيئــة وابلتــايل حتســني التقــدم حنــو االســتدامة. لذلــك، تُنصــح الســلطة اإلداريــة بتكييــف تدابــر حتفظيــة لتعزيــز البيئــة ومحايتهــا. حيــث أنــه وعلــى املــدى الطويــل، قــد هتــدد تفضيــات رفاهيــة اإلنســان علــى البيئــة املصايــد أبكملهــا. الكلمات املفتاحية: التنمية املستدامة ملصايد األمساك، حتليل احلساسية، إطارالتنمية املستدامة بيئياً، مصايد الباطنة 19research paper al siyabi, al masroori environment. in addition, esd framework establishes the hierarchy structure of components, in which each component in the framework can be subdivided further into several criteria or indicators (fao 1999). multi criteria decision analysis (mcda) is used to provide a method of scoring alternative decision in term of their importance of various preferences (stoycheva et al. 2018). moreover, mcda provides an overall ordering options, from the most preferred to the least preferred option (communities 2000). these options are differing in the extent and they achieve the objectives and no option will be the best in achieving all objectives (communities 2000). mcda methods involve several theories; one of them is called analytical hierarchy process (ahp) that is adopted in this study. oman is characterized as poor fisheries data available (al masroori and bose, 2016; 2021), mcda can deal with incomplete data and uncertain information to give the overall trend of sustainability. in addition, the hierarchical structure provided by ahp method will facilitate the comparison between the ecological aspects with socio economic ones at the same framework (mendoza and martins 2006). hiview software (catalyze 2003) is also used in the current study to solve large and complex mcda problems (communities 2000). it allows the value tree to be visually created and edited. the top of it called the root node, where all data in the model is collated. out of the root node there are branches that represent the objectives. the criteria are structured under the nodes: effects on human and effects on environment (catalyze 2003; al masroori 2008). further information can be found in the reference by catalyze (2003). in the current study, hiview software is hired to assess the progress of each component toward sustainability and to conduct sensitivity analysis in order to identify strengths and weaknesses of all identified components that contribute positively or negatively to the progress of both human and environmental well-beings toward sustainability. all components were weighted equally. thus, the two main categories of the framework had been given a weight of 50%. each component under the main category had given a weight also. then, for each indicator a preferred score was selected and the standardize index was calculated for each component. thus, the weight summation for any component is the average of its critefigure 1. esd hierarchical structure for al batinah fishery generated by hiview software 20 squ journal of agricultural and marine sciences, 2023, volume 28, issue 2 an assessment of al batinah fishery with respect to ecologically sustainable development using multi-criteria decision analysis approach ria weight. then, the weight summation was determined for each component for the two main categories (chesson et al 1999). therefore, the same weight was given for each criterion under the same component assuming an equal consideration toward human and environmental well-being. this software analysis provides some signs about the criteria sensitivity for weight change. the aim of this study was to assess the sustainability progress of al batinah fishery using mcda. the sultanate of oman is a coastal country with a long coastline that stretches about 3126 km long. therefore, fishing is an old and important occupation in oman’s communities and contributes to the public economy and fishermen income especially as oman is considered one of the largest fish producers and exporters in the region (fao 2019). oman’s fisheries produced around 840,000 tons of fish in 2020 and exported around 283,000 tones out of the total landing. moreover, fishing sector plays a vital role in providing a food source, employing people and contributing to the country’s gross domestic product (gdp). fishing activity in oman depends fundamentally on marine capture, which provides around 94% of the total landing produced by traditional fishery (maf 2020). on the other hand, fishing sector’s contribution to the country’s gdp is still weak. it did not exceed 0.9% only in 2019 (maf 2020) and it is obvious that this sector needs an advance management and assessing the sustainability of the traditional fishery in oman and it should be a prime concern for the fisheries authority. in this regard, this paper takes al batinah governorate as a case study due to the availability of data compared to other governorates and for its contribution to the omani artisanal fishery landing. among all other eleven governorates, al batinah came in the fourth place after al wusta, sharqiah and dhofar according to its contribution (10%) to the total landing (maf2020). it has more than (14,500) fishermen working on about 6300 boats (maf 2020). the most important fishes caught in al batinah are yellowfin tuna, longtail tuna, sardine and anchovy (maf 2020). furthermore, al batinah has a unique characteristic, which are the artificial reefs. they were deployed in 2003 as a trial to boost the declined fisheries sector and enhance the ecosystem in the region. methodology to assess the progress of al batinah fishery toward sustainability, a modified version of the esd framework developed by chesson and clayton (1998) was followed. the modification was done through a consultation review was designed and discussed with the stakeholders. consulting key stakeholders to identify the issues of the base esd framework is a vital step to ensure that the context of the esd framework tree would be functional within al batinah fisheries sector. the consultation helped in identifying all possible components of the hierarchical structure, maximizing consistency and minimizing the chance of missing any issues or impacts (positive or negative) and gaining the acceptance of all stakeholders. the modified esd framework was distributed and explained personally with 19 experts covering different levels of fisheries stakeholders; 8 academics, 6 managers and 5 researchers in the field with a response rate of 58%. as shown in the figure 1, framework has two main components, namely the effects on human and the effects on environment. these two components were further divided into subcomponents, which were identified through the consultation meetings with stakeholders. the specified objectives and indicators with their preferred trends and reference points developed by al masroori and bose (2009; 2014), following fao (1999) technical specifications, were used as basis in this study (tables 1 and 2). the objectives were specified with respect to the national regulations and international legislation and conventions in the sultanate. data was obtained from fisheries statistical books from maf (2008 – 2017), the statistical department in maf, the directorate general of fisheries in al batinah and the national centre for statistics and information (tables 3, 4 and 5). in addition to that, the weighted summation method (al masroori, 2008) was followed to evaluate the progress toward sustainability over the study period 2008 to 2017). for the current study, the same weight was given for each criterion under the same component assuming an equal consideration toward human and environmental well-being. the best value given for each indicator was depending on the objective specified for it. the score for any component of the esd tree was determined to be as the weight sum of the sub-components belongs to it using the following formula (chesson and clayton 1998): (1) where: j represents esd component, i represents time, wj the weight for component j, ujj is the score for component j in year i. as mentioned earlier, all components were weighted equally. thus, the two main categories of the framework had been given a weight of 50%. each component under the main category had given a weight also. then, for each indicator a preferred score was selected and the standardize index was calculated for each component. thus, weight summation for any component is the average of its criteria weight. then, weight summation was determined for each component for the two main categories (chesson et al. 1999). for each component in the esd framework, weight average for each year of the study period was calculated using 21research paper al siyabi, al masroori table 1. indicators used for each component of the effects of al batinah fisheries on human during the period (2008 – 2017) component objective indicator required data food • total catch in al batinah per year nutrition enhancement of food security from fishing sector fish per capita (kg) • total population in oman variety increase the number of species come from al batinah fishery total number of species caught in al batinah (mt) • annual total number of species caught in al batinah marketed domestic increase the local consumption of al batinah fishery production total amount of al batinah fishery consumed locally (mt) • annual percentage of al batinah fishery production consumed locally export decrease the exported amount of al batinah fishery production total amount of al batinah fishery exported (mt) • annual percentage of al batinah fishery production exported income individual increase fishers’ income annual income of al batinah local fishers (or) • annual catch value gained by local fishers national improve country income annual contribution of al batinah fishery to the country gdp (or) • fishers licenses fees • boats licenses fees • tracks licenses fees • fishing institutions fees • fishing gear fees • artificial reef fees • technicians on vessels fees life style fishers enhancement of fishers’ lifestyle number of boats owned by fishermen • number of boats owned by fishermen each year community enhancement of communities’ lifestyle number fishing tracks in al batinah • annual number of fishing tracks in al batinah employment direct increase the number of al batinah local fishers total number of local fishers in al batinah • annual total number of al batinah local fishers figure 2. a) nutrition criterion data (kg), b) preference values of nutrition criterion for food component, and c) weight scores and contributions of food component 22 squ journal of agricultural and marine sciences, 2023, volume 28, issue 2 an assessment of al batinah fishery with respect to ecologically sustainable development using multi-criteria decision analysis approach hiview software. the results were examined using hiview software © version 3.2.0.9 (a multi-criteria decision analysis tool) to evaluate the progress of al batinah fishery toward sustainability (2008 – 2017). mcda approach is used to reduce the complexity of data in this study using the hiview software. in addition, microsoft excel software was used for some basic calculations. for further investigation of the overall results, sensitivity analysis was used to determine the most sensitive criteria for weight change. this type of analysis could help decision-makers to predict the future scenario for the current situation and consequently, they can change their actions to maintain the suitable status of the fishery. for the current study, sensitivity analysis was carried out to investigate the preferred year within the study period and its strength and weakness. more details about sensitivity analysis can be obtained in (al masroori, 2008). results and discussion the esd framework of al batinah fishery was developed and analyzed following the steps addressed by chesson and clayton (1998) and communities (2000). the final framework used in this study is shown in figure 1 as built by the hiview. it is worth noting that some components in the esd hierarchical structure were eliminated from the analysis due to the unavailability of representative data such as pollution, seascape, fish biodiversity and post-harvest indicators. this is considered as a limitation to this study and hence the concerned authoritable 2. indicators used for each component of the effects of al batinah fisheries on environment during the period (2008 – 2017) component objective indicator required data primary commercial species abundance of target species control the target species catch to preserve them against over-exploitation landings (mt) total catch of target species per year nontarget species discard minimize the amount of discarded fish in al batinah annual amount of discarded fish in al batinah (mt) • total annual amount of discarded fish in al batinah other aspects artificial reef enhancement of fish biodiversity in al batinah number of artificial reef units deployed in al batinah • annual total number of artificial reef units deployed in al batinah table 3. data and preferred score of effect on human component indicators year 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 preferred score nutrition (kg) per capita fish consumption 3.528 3.072 3.830 3.345 4.248 4.338 4.778 4.808 4.796 5.288 5.288 food variety (h) shannon diversity index 87.51 96.57 100.00 93.98 93.93 95.72 97.85 98.48 98.18 98.96 100.00 domestic market (mt) catch consumed locally 19197.1 18727.7 20592.2 21370.1 29840.9 33101.9 36213.7 35098.8 41910.5 48229.2 48229.2 export (mt) catch exported outside the governorate 1444.9 1195.4 1083.8 1124.8 1570.6 1023.8 2725.8 5713.8 1296.2 984.3 984.3 individual income (000 omr) catch value gained by local fishers 14 19 19 24 37 42 47 43 51 56 56 national income (omr) contribution of al batinah fisheries to the country gdp 38488.9 33717.5 55164.9 39597.3 49743.9 63901.2 40289.6 39540.5 68107.5 74687 74687 fishers lifestyle (boat) number of boats owned by local fishers 4704 4080 4796 4852 5025 5294 5754 5996 6087 6144 6144 community lifestyle (licenses) number of tracks licences issued for fish transporting and marketing 470 500 557 575 601 629 719 780 1636 897 1636 direct employment (omani) number of local fishers 12036 8764 10028 10887 11943 12675 13166 13546 13834 14216 14216 23research paper al siyabi, al masroori ties are recommended to start gathering such important information. tables 1 and 2 show the criteria, objectives, indicators and required data used for the case study analyses (al masroori and bose, 2009). food component will be taken as an example to explain the process of analyzing. as shown in table 1, food component was classified into three sub-components: nutrition, food variety and marketed which were divided further into: domestic market and export. per capita fish consumption was used as an indicator for nutrition sub-component. the table 4. data and preferred score of effect on environment component indicators year 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 preferred score primary commercial species (mt) total catch of primary commercial species 20642 19923 21676 22495 31411 34126 38939 40813 43207 49213 49213 discard (mt) total discarded fish 206.42 199.23 216.76 224.95 314.11 341.26 389.39 408.13 432.07 492.13 0 artificial reef (unit) total number of artificial reef 1374 1874 2374 4774 5174 5294 5294 5358 5358 5358 5358 table 5. total catch and the amounts of total catch consumed locally and exported (mt) (2008 – 2017) year 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 total catch (mt) 20642 19923 21676 22494.842 31411.442 34125.657 38939.454 40812.603 43206.676 49213.499 amount used in domestic market (mt) 19197.06 18727.62 20592.20 21370.10 29840.87 33101.89 36213.69 35098.84 41910.48 48229.23 amount export (mt) 1444.9 1195.4 1083.8 1124.742 1570.572 1023.7697 2725.7618 5713.7644 1296.2003 984.2699 number of species 36 37 37 37 36 36 38 37 38 37 figure 3. weight scores and criteria contributions of effect on; a) human component, b) environmental component and, c) from both human and environment components 24 squ journal of agricultural and marine sciences, 2023, volume 28, issue 2 an assessment of al batinah fishery with respect to ecologically sustainable development using multi-criteria decision analysis approach trend for the nutrition sub-component indicator is preferred to be positive. figures 2a and 2b show standardized data and scoring process relative to the preferred value of the nutrition sub-component. it is clear from figure 2 that the highest score 100 was assigned to the year 2017 with the value of 5.288 kg. all other preference values were relative to 2017. on the other hand, the lowest score (58.094) which assigned the value (3.072) was recorded in 2009. more explanation about figures reading can be found in (al masroori and bose, 2014). all other sub-components of food component were analyzed following the same way and then, weighted summation method was applied for all food’s sub-components. as it was mentioned earlier, all food criteria have the same weight so, no preference of one criterion over another. figure 2c represents the data, weight scores and the contribution of each criterion for each year. it is clear that the best food trend was achieved in 2017 when most of the food sub-components achieved the peak. the year 2017 was characterized by the higher level of total catch during the study period, which affects all food components positively. the same steps were followed in analyzing all other components in the esd framework to examine the progress toward sustainability. overall results as shown in figure 3a, year 2016 scored the highest preferred value of 95 for the effect on human. while year 2009 scored the lowest as 55. on the other hand, figure 3b shows that the years 2015 (with 2016 and 2017) scored the highest preferred value as 67 for the effect on environment and 2008 scored the lowest value of 42. a similar trend (increasing) is almost happening in both dimensions. this is supported by the overall comparative assessment between human and environment components, where year 2016 scored the highest preferred value of 81, with a major contribution from the human components (figure 3c). generally, the results of this study indicated that higher priority was given by the government toward the human benefits in 2016 and the management policies applied favored what is considered as a short-term benefit. in general, all human components were improved from 2008 to 2017 due to the concentration of the government on the sector as one of the promising economic sectors in the country. it is allocating 500 million omr to support the strategic plan for the development of the fishing sector from 2013 to 2020, which has been implemented by the ministry of fishery (maf). it is obvious that all the national fisheries development strategy from 2013 to 2020 are concentrated toward human benefits. by 2020 the total landing in oman was around 840,000 tonnes (maf, 2020) and there were around 60 fish markets and 26 harbors (maf, 2020) around the country to meet the national strategy objectives. although no single objective has been related to the environmental protection or stocks conservation in the strategy. environmental well-being was also figure 4. most preferred year (sensitivity down) 25research paper al siyabi, al masroori progressing in an increasing trend but not as well as in human well-being (figure 3). this study shows a similar trend of favoring the human wellbeing over the environmental wellbeing that was also found in al masroori and bose (2021) for an industrial fishery. this indicates a similarity in the management strategies for traditional and industrial fisheries and a little change in the management structure. sensitivity analysis based on the overall results shown in figure 3c, the most preferred year was 2016 followed by 2017. figure 4 confirms this by sensitivity down analysis. the figure lists the criteria at the middle and different coloured bars indicate which criteria are the most sensitive for weight change. figure 4 shows that 2017 could override year 2016 if the weights of food variety, fishers’ lifestyle and artificial reefs are increased by more than 15 points. also, it is clear that 2017 could override the year 2016 if the weights of direct employment, export, nutrition, individual income and national income are increased between 5-15 points. on the other hand, the same figure shows that 2017 can override the year 2016 if the weights of domestic market and primary commercial species are increased by less than 5 points and the weights of community lifestyle and discards are decreased by less than 5 points. figures 5a and 5b are called sort graphs that are used usually to compare the performance of two options (years) and examines the strengths and weaknesses in any options. figure 5a shows the weakness of the most preferred year 2016. it is clear that most of the weak components of year 2016 are in the environmental sector especially in discards and primary commercial species. discard component contributed a lot to the weakness of the most preferred year. on the other hand, it gained its strength from both environmental sides in artificial reefs and primary commercial species along with human components dominated by direct employment, lifestyle component, income component, and nutrition and food variety of the food component (figure 5 b). generally, it can be stated that the year 2016 was stronger in human sides and short-term benefits than conserving the environment. a similar further analysis was done to investigate the human component using sensitivity up analysis, figure 6a shows that the year 2016 is the most preferred year for the effect on human component and it is very clear that decreasing the weight to almost 0% will only change the year to 2017. sensitivity analysis was also applied for environmental component as shown in figure 6b. it can be seen that 2016 is also the most preferred year for the effect on environment component and only year 2017 can override the year 2016 if the weight of the effect of environment component is increased to almost 100% as shown by the shaded area in figure 6b. these trends (the dominance of the year 2016 over all other years indicate that the management measures practiced in year 2016 figure 5. a) weaknesses and b) strength of the most preferred year (2016) 26 squ journal of agricultural and marine sciences, 2023, volume 28, issue 2 an assessment of al batinah fishery with respect to ecologically sustainable development using multi-criteria decision analysis approach were the best among the investigated year. conclusion the progress of al batinah fishery toward sustainability showed a positive trend. the results revealed that the year 2016 had the best attainment toward sustainability. generally, the above results indicated that the management measures practiced in 2016 were the best in terms of human components and short-term benefits (food, income, lifestyle and employment) rather than conserving the environment. this give an indication that the management authority was preferring the human well-being over the environmental well-being, which means it is progressing away from sustainable development. sensitivity analysis confirmed that year 2016 was the most preferred year in the assessment between year 2008 and 2017 and the year 2017 could override it if some criteria weights have been changed. recommendations based on the main findings and limitations encountered in this research, the following recommendations are proposed to promote the sustainable development of the fisheries sector in oman in general: (i) accurate and specific data representing fishery indicators like: post-harvest data, pollution, sea scape etc in the sector is a critical need for better assessment. (ii) the qualified fishery indicators such as fish biodiversity are important to be considered by the fishery authority. (iii) more attention needs to be applied to the environmental well-being like: preserving stocks, reduce pollution level and minimize the destruction of marine habitats in preparing the future fisheries strategic plans. (iv) establishing a unit to organize and coordinate the joint work between maf and ea (environment authority) might strengthen the environmental protection and therefore enhance the sustainability. references al-masroori hs. (2008). an assessment of the commercial trawl fishery of the sultanate of oman using the ecologically sustainable development framework; an evaluation study, phd thesis, university of tasmania, australia. al-masroori hs, bose s. (2009). developing indicators for the assessment of sustainability of an industrial fishery: a case study in the sultanate of oman. egyptian jornal of aquatic research 35(2): 189–197. al-masroori hs, bose s. (2014). towards developing index for the assessment of sustainable development: a case study of the sultanate of oman. in proceeding of the seventeenth biennial conference of the international institute of fisheries economics and trade (iifet), pp. 7-11. al-masroori hs, bose s. (2016). anchoring to determine negotiated catch limits: a case study of an industrial fishery in oman. african journal of marine figure 6. sensitivity up of effect on; a) human component and b) environment component 27research paper al siyabi, al masroori science 38(1): 101-109. al-masroori hs, bose s. (2021). fisheries sustainability assessment and sensitivity analysis: an illustration. environment, development and sustainability 23: 16283-16303. catalyze. (2003). hiview 3: enabling effective decisions (starter guide) catalyze ltd. chesson j, clayton h. (1998). a framework for assessing fisheries with respect to ecologically sustainable development. bureau of rural sciences, canberra, australia. chesson j, clayton h, whitworth b. (1999). evaluation of fisheriesmanagement systems with respect to sustainable development. ices journal of marine science 56(6): 980-984. coll m, libralato s, pitcher t, solidoro c, tudela s. (2013). sustainability implications of honouring the code of conduct for responsible fisheries. global environmental change 23: 157–166. communities. (2000). multi-criteria analysis manual. uk. national economic research association. fao. (1999). indicators for sustainable development of marine capture fisheries. fao technical guidelines for responsible fisheries, rome. fao. (2019). fishery and aquaculture country profiles, the sultanate of oman. retrieved from http://www. fao.org/fishery/facp/omn/en fletcher wj, chesson j, sainsbury kj, hundloe tj, fisher m. (2005). a flexible and practical framework for reporting on ecologically sustainable development for wild capture fisheries. fisheries research 71(2): 175–183. levrel h, kerbiriou c, couvet d, weber j. (2009). oecd pressure–state–response indicators for managing biodiversity: a realistic perspective for a french biosphere reserve. biodiversity and conservation 18(7): 1719–1732. maf. (2020). annual statistics report for 2020. ministry of agricultural and fisheries wealth, muscat, oman. arabic. mendoza g, martins h. (2006). multi-criteria decision analysis in natural resource management: a critical review of methods and new modelling paradigms. forest ecology and management 230: 1–22. michael fl, noor zz, figueroa mj. (2014). review of urban sustainability indicators assessmentâ�”case study between asian countries. habitat international 44: 491–500. stoycheva s, marchese d, paul c, padoan s, juhmani a, linkov i. (2018). multi-criteria decision analysis framework for sustainable manufacturing in automotive industry. journal of cleaner production 187: 257–272. img115 img116 img117 img118 img119 img120 img121 img098 img099 img100 img101 img102 research paper journal of agricultural and marine sciences vol. 24 : 39– 43 doi: 10.24200/jams.vol24iss1pp39-43 reveived 12 dec 2018 accepted 23 dec 2019 activation of apoptotic cell death by skin mucus from asian swamp eel (monopterus albus) against human lung cancer cell line ayah rebhi hilles1*, syed mahmood2,3*, mohd arifin kaderi1, ridzwan hashim1 *ayah rebhi hilles ( ) *ayah.hilles90@gmail.com,*syedmahmood@ ump.edu.my.1department of biomedical sciences, kulliyyah of allied health sciences, international islamic university malaysia, 25200 kuantan, pahang, malaysia.2department of pharmaceutical engineering, faculty of engineering technology, university malaysia pahang, 26300 gambang, pahang, malaysia.3centre of excellence for advanced research in fluid flow (cariff), university malaysia pahang, 26300 gambang, pahang, malaysia. introduction asian swamp eel (monopterus albus) belongs to the family of synbranchidae under syn-branchiformes order (cheng et al., 2003). asian swamp eel skin mucus is secreted by the epidermal goblet cells in the epidermis which composed from inorganic salts, immunoglobulins, lipids and gel-forming macromolecules such as mucins, and other glycoproteins suspended in water (bragadeeswaran and thangaraj, 2011), which gives the mucus lubricating properties (pearson and brownlee, 2005). there are two main mechanisms describing the cell death in eukaryotic cells, apoptosis and necrosis. apoptosis is a process with well-defined key steps that mark the progress of the process in individual cells. cells undergoing apoptosis possess distinctive morphological, biochemical and molecular features including sequence of chromatin margination and aggregation, nuclear and cytoplasmic condensation, cellular shrinkage, budding and fragmentation through the partition of cytoplasm and nucleus into the apoptotic body (eriksson et al., 2008). these apoptotic bodies immediately recognized and phagocytized by macrophages or adjacent epithelial cells. hence, there is no inflammatory response is elicitتنشيط موت اخلالاي املربمج ابملخاط اجللدي من ثعبان األنقليس اآلسيوي )monopterus albus( ضد خط خالاي سرطان الرئة البشرية آية رحبي حلس1* وسيد حممود2,3* وحممد عارفني قادري1 ورضوان هاشم1 abstract. asian swamp eel (monopterus albus) is a freshwater fish which distributed widely in the east of india mainly across malay peninsula and indochinese peninsula, it is also broadly distributed in the southern areas of east asia including, southeastern china, western japanese archipelago, and korean peninsula. it lives in muddy places, rice paddies, and slow-flowing currents areas. it has a unique morphological elongated body which is similar to snake and covered with a thick layer of mucus. the objective of this study is to screen the cytotoxic activity of eel skin mucus extracts and to evaluate the mechanism of cell death apoptosis or necrosis based on caspases activity assays. for this purpose eel skin mucus was collected from healthy fresh eels to prepare aqueous and methanol extracts. preliminary cytotoxicity study was demonstrated against non-small-cell lung carcinoma cell line (a549) using cell viability assay which revealed that methanol extract was more potent than aqueous extract based on the response of esm methanol and aqueous extracts to the relevant ic50 concentrations as ic50 values were 621±0.09 µg/ml and 845 ± 0.25 µg/ml respectively. subsequently cell death was induced through triggering apoptosis by the activation of caspase-3/7, 8 and 9. in conclusion, the present study has revealed the cytotoxic potentials of eel skin mucus which may lead to the development of new anticancer agents. keywords: monopterus albus; cytotoxic activity; apoptosis; caspases. املســتخلص:أنقليس املســتنقعات اآلســيوية )monopterus albus( هــو مــن أمســاك امليــاه العذبــة الــي يتــم توزيعهــا علــى نطــاق واســع يف شــرق اهلنــد بشــكل رئيســي عــر شــبه جزيــرة املاليــو وشــبه جزيــرة اهلنــد الصينيــة ، كمــا أهنــا موزعــة بشــكل واســع يف املناطــق اجلنوبيــة مــن شــرق آســيا مبــا يف ذلــك ، جنــوب شــرق الصــني ، أرخبيــل غــرب اليابــان ، و شــبه اجلزيــرة الكوريــة. تعيــش يف األماكــن املوحلــة وحقــول األرز ومناطــق التيــارات بطيئــة التدفــق. وهلــا تركيبــة جســم فريــدة مــن نوعهــا والــي تشــبه فيهــا الثعبــان وتغطــى بطبقــة مسيكــة مــن املخــاط. اهلــدف مــن هــذه الدراســة هــو فحــص النشــاط الســام علــى اخلاليــا ملســتخلصات خمــاط جلــد ثعبــان األنقليــس ولتقييــم آليــة مــوت اخلليــة ســواء كان مــوت اخلاليــا املرمــج أو النخــر علــى أســاس اختبــارات نشــاط الكاســبيزس. هلــذا الغــرض؛ مت مجــع خمــاط جلــد ثعبــان البحــر مــن ثعابــني طازجــة صحيــة إلعــداد مســتخلصات املــاء وامليثانــول. مت إجــراء دراســة أوليــة للســمية اخللويــة ضــد اخلاليــا غــر الرئويــة لســرطان الرئــة )a549( باســتخدام اختبــار قابليــة اخلليــة الــي أظهــرت أن مســتخلص امليثانــول أقــوى مــن املســتخلص املائــي حيــث أن قيــم ic50 كانــت 621 ± 0.09 ميكروجــرام / مــل و 845 ± 0.25 ميكروجــرام / مــل علــى التــوايل. ويف وقــت الحــق ، فــإن آليــة مــوت اخلليــة تســبب املــوت اخللــوي مــن خــالل التســبب يف مــوت اخلاليــا املرمــج عــن طريــق تفعيــل الكاســبيز 7/3 و 8 و 9. يف اخلتــام ، كشــفت الدراســة احلاليــة عــن إمكانــات اخلاليــا الســامة للخاليــا ملخــاط ثعبــان البحــر ممــا قــد يــؤدي إىل تطــور جديــد. وكالء مضــاد للســرطان. الكلمات املفتاحية: monopterus albus ، النشاط السام للخاليا ، موت اخلاليا املرمج ، الكاسبيزس. 40 squ journal of agricultural and marine sciences, 2019, volume 24, issue 1 activation of apoptotic cell death by skin mucus from asian swamp eel against human lung cancer cell line ed (fadok et al., 2000). however, in vitro, the apoptotic bodies and residual cell fragments swell and lyse (chang and yang, 2000). the morphologic features that characterize apoptotic cells are the consequence of several biochemical features, which are stimulated by proteolytic destruction of cytoskeletal and metabolic proteins. activation of the effector caspases 3 and 7 is a common step in both intrinsic and extrinsic apoptotic signal pathways, which accomplish the characteristic changes in the nuclear morphology and biochemistry, including chromatin condensation and dna fragmentation (fan et al., 2005). methodology materials cell lines the cell lines used in the study include human nonsmall lung carcinoma (a549, atcc ccl-185) and normal mouse embryonic fibroblast (3t3-l1, atcc crl3242). the cell lines were obtained from biomedical science department, kulliyyah of allied health sciences, international islamic university malaysia. chemicals phosphate buffered saline (pbs), fetal bovine serum (fbs), dulbecco`s modified eagle medium (dmem), penicillin-streptomycin were purchased from gibco invitrogen co. (scotland, uk). paclitaxel (taxol®) and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (mtt) were purchased from merck kgaa, germany. caspase-3/7, caspase-8, caspase-9 kits were purchased from promega, madison, wi, usa. methods sample collection and extraction the eel skin mucus (esm) was collected from healthy eels by gently scraping the surface of the eel skin and then it was homogenized with 2 volumes of distilled water using homogenizer, followed by centrifugation at 13,000 rpm for 30 min, the supernatant was freezedried for 5 days. the dried substance was weighed and dissolved in distilled water to form aqueous extract and in methanol to form methanol extract, after that, the dissolved substance was filtered using 0.22 µm syringe filter to be ready for use. the extraction procedure was carried out according to the method previously described by sadakane et al. (2007) with a slight modification. cell viability test (mtt-based cytotoxicity assay) the antiproliferative effect of aqueous and methanol extracts of esm on growth of two human cancer cell lines, i.e. human non-small lung carcinoma (a549) and normal mouse embryonic fibroblast (3t3-l1), were evaluated by mtt assay. approximately 5 × 10⁴ of cells were seeded into 96-well plates. after the cells reach the confluency level, they were treated with different concentrations of esm aqueous and methanol extracts from 200 to 1000 μg/ml for 24 hrs. then, 20 μl of mtt was added to each well and the plates were further incubated for 24 hrs. after that, 100 μl of dmso was added to each well table 1. caspase-3/7 activity after treatment of a549 cells with esm methanol and aqueous extracts along with positive control (taxol) and negative control (untreated cells) for 24 hrs. treatment od1 od2 od3 average sd fold change methanol 0.301 0.339 0.322 0.320* 0.019 3.340* aqueous 0.236 0.202 0.229 0.222* 0.017 2.344* taxol 0.351 0.332 0.347 0.343* 0.010 3.597* control 0.091 0.098 0.093 0.094 0.003 0.094 caspase-3/7 activities were determined using the caspace® system. mean ± sd (n = 3 wells/treatment). *p < 0.05 compared with the untreated cells. fold changes was calculated based on the control/untreated cells. od is optical density. table 2. caspase-8 activity after treatment of a549 cells with esm methanol and aqueous extracts along with positive control (taxol) and negative control (untreated cells) for 24 hrs. treatment od1 od2 od3 average sd fold change methanol 0.380 0.371 0.295 0.348* 0.046 3.233* aqueous 0.197 0.229 0.215 0.213* 0.016 2.216* taxol 0.153 0.202 0.197 0.184* 0.026 1.790* control 0.103 0.109 0.115 0.109 0.006 0.109 caspase-8 activities were determined using the caspace® system. mean ± sd (n = 3 wells/treatment). *p < 0.05 compared with the untreated cells. fold changes was calculated based on the control/untreated cells. od is optical density. 41research article hilles, mahmood, kaderi, hashim a549 which is required to reduce 50% of cell viability (ic50) was calculated and it was recorded as follows; 621 ± 0.09 µg/ml for methanol extract, 845 ± 0.25 µg/ml for aqueous extract and 43.12 ± 0.6 µg/ml for taxol. effects of esm aqueous and methanol extracts on caspase 3,8 and 9 activities a549 cells-treated with the esm extracts exhibited a sharp increase in the activities of caspases 3, 8 and 9. the activities of the individual caspases were expressed as fold increases with respect to the untreated control. fold change is defined as the ratio between different values, the fold change of caspase 3,8 and 9 was higher for esm methanol extract than aqueous extract compared to the control (untreated a549 cells) as shown in table 3.1,2,3. the activities of 3, 8 and 9 caspases were increased significantly in a549 cells-treated with 600 μg/ml of esm methanol extract and 800 μg/ml of esm aqueous extract compared to untreated cells (the concentration of methanol and aqueous extracts was chosen based on the nearest concentration to ic50 value which was 621 ± 0.09 µg/ml for esm methanol extract and 845 ± 0.25 µg/ml for esm aqueous extract. discussion treatment of esm aqueous and methanol extracts significantly inhibited the growth of a549 cell line compared to the normal cell line. this result agrees with what has been reported about the anticancer activities of amphibian skin mucus (kawasaki and iwamuro, 2008). the present results showed that esm extracts treatments activated 3, 8 and 9 caspases compared to the control (untreated cells), indicating that they induced a549 cell death via apoptosis as caspases test one of the biochemical markers which can be used to distinguish the mechanism of cell death, as it activated in the case of both intrinsic and extrinsic apoptotic signals (fan et al., 2005). however, necrotic cell death does not involve caspase activation (mansilla et al., 2006). activation of caspases consider a hallmark of apoptosis and there are two pathways included; death receptor pathway which based on caspase-8 activation and mitochondrial pathway which based on caspase-9 activation (leong et al., 2016). accordingly, activities of the caspases 3, 8 and 9 and incubated for 4 hrs. then, the absorbance was measured at 570 nm using a microplate reader. the percentage of cell survival rate was calculated using to the cell viability formula: percentage of cell viability = (mean of experimental absorbance / mean of control absorbance) × 100 (villarroel et al., 2007). pbs was used as a negative control while 1 μg/ml of taxol was used as a positive control as it is a chemotherapy medication used in the treatment of non-small-cell lung cancer (nsclc) such as a549 cell line. determination of the mechanism of cell death by measuring of caspase 3, 8 and 9 activities caspase 3, 8 and 9 are members of the cysteine aspartic acid-specific protease (caspase) family which play key roles in apoptosis induction. the test was conducted according to the instructions of the kits. a549 cells were cultured in 96-well plates at the density of 1 × 104 cells per well overnight. the adherent cells were further incubated for 24 hrs with 100 μl media containing ic50 values of esm aqueous and methanol extracts. after the treatment, the cells were harvested and centrifuged then the pellets were washed with pbs and lysis in chilled lysis buffer. the mixture was left on ice for 10 min then centrifuged at 2000 rpm for 5 min at 4°c. then the supernatant was used for the determination of caspase activities. the results were read on a microplate reader at 405 nm (abdullah et al., 2015). results cell viability assay the results showed that the reduction in cell viability of a549-treated with esm extracts was significant compared with the untreated cells. at 200 µg/ml which was the lowest concentration used, the cell viability of esm aqueous and methanol was recorded as 87. 61% and 76.29% respectively whereas at 1000 µg/ml of esm aqueous extract the cell viability was recorded as 46.58% while for methanol extract was 38.19%. the cell viability of esm aqueous and methanol extracts against 3t3l1 at 1000 µg/ml was 79.24% and 63.65% respectively while at 200 µg/ml was 92.53% and 89.21% respectively. the inhibitory concentrations of esm extracts against table 3. caspase-9 activity after treatment of a549 cells with esm methanol and aqueous extracts along with positive control (taxol) and negative control (untreated cells) for 24 hrs. treatment od1 od2 od3 average sd fold change methanol 0.442 0.450 0.447 0.446* 0.004 3.937* aqueous 0.299 0.318 0.271 0.272* 0.023 2.725* taxol 0.541 0.519 0.528 0.529* 0.011 4.625* control 0.019 0.012 0.017 0.033 0.003 0.033 caspase-9 activities were determined using the caspace® system. mean ± sd (n = 3 wells/treatment). *p < 0.05 compared with the untreated cells. fold changes was calculated based on the control/untreated cells. od is optical density. 42 squ journal of agricultural and marine sciences, 2019, volume 24, issue 1 activation of apoptotic cell death by skin mucus from asian swamp eel against human lung cancer cell line were measured in a549 cells-treated with esm aqueous and methanol extracts as well as taxol which is a chemotherapy drug use for apoptosis induction (hu et al., 2005). conclusion the activation of caspase (3, 8 and 9) only occurs as a result of apoptosis not necrosis and this parameter has been considered as one of the most reliable biochemical parameters to differentiate between apoptotic and necrotic cell death, therefore, the current study revealed that esm extracts activate cell death via apoptosis. acknowledgement this work was financially supported by a research grant (project no. rdu 180371) from universiti malaysia pahang (www.ump.edu.my), for which the authors are very grateful. references abdullah, a. s. h., mohammed, a. s., rasedee, a., mirghani, m. e. s., & al-qubaisi, m. s. (2015). induction of apoptosis and oxidative stress in estrogen receptor-negative breast cancer, mda-mb231 cells, by ethanolic mango seed extract. bmc complementary and alternative medicine, 15(1), 45. bragadeeswaran, s., & thangaraj, s. (2011). hemolytic and antibacterial studies on skin mucus of eel fish, anguilla anguilla linnaeus, 1758. asian journal of biological sciences, 4, 272-276. chang, h. y., & yang, x. (2000). proteases for cell suicide: functions and regulation of caspases. microbiology and molecular biology reviews, 64(4), 821-846. cheng, h., guo, y., yu, q., & zhou, r. (2003). the rice field eel as a model system for vertebrate sexual development. cytogenetic and genome research, 101(3-4), 274-277. eriksson, d., riklund, k., johansson, l., & stigbrand, t. (2008). radiation induced cell deaths. in stigbrand t., carlsson j. and adams g. p. (eds.). targeted radionuclide tumour therapy (pp. 215-248), springer. fadok, v. a., bratton, d. l., rose, d. m., pearson, a., ezekewitz, r. a., & henson, p. m. (2000). a receptor for phosphatidylserine-specific clearance of apoptotic cells. nature, 405 (6782), 85-90. fan, t.-j., han, l.-h., cong, r.-s., & liang, j. (2005). caspase family proteases and apoptosis. acta biochimica et biophysica sinica, 37 (11), 719-727. hu, h., jiang, c., ip, c., rustum, y. m., & lü, j. (2005). methylseleninic acid potentiates apoptosis induced by chemotherapeutic drugs in androgen-independent prostate cancer cells. clinical cancer research, 11(6), 2379-2388. kawasaki, h., & iwamuro, s. (2008). potential roles of histones in host defense as antimicrobial agents. infectious disorders-drug targets (formerly current drug targets-infectious disorders), 8(3), 195-205. leong, k. h., looi, c. y., loong, x. m., cheah, f. k., supratman, u., litaudon, m., ... & awang, k. (2016). cycloart-24-ene-26-ol-3-one, a new cycloartane isolated from leaves of aglaia exima triggers tumour table 4. caspase-8 activity after treatment of a549 cells with esm methanol and aqueous extracts along with positive control (taxol) and negative control (untreated cells) for 24 hrs. treatment od1 od2 od3 average sd fold change methanol 0.380 0.371 0.295 0.348* 0.046 3.233* aqueous 0.197 0.229 0.215 0.213* 0.016 2.216* taxol 0.153 0.202 0.197 0.184* 0.026 1.790* control 0.103 0.109 0.115 0.109 0.006 0.109 caspase-8 activities were determined using the caspace® system. mean ± sd (n = 3 wells/treatment). *p < 0.05 compared with the untreated cells. fold changes was calculated based on the control/untreated cells. od is optical density. table 5. caspase-9 activity after treatment of a549 cells with esm methanol and aqueous extracts along with positive control (taxol) and negative control (untreated cells) for 24 hrs. treatment od1 od2 od3 average sd fold change methanol 0.442 0.450 0.447 0.446* 0.004 3.937* aqueous 0.299 0.318 0.271 0.272* 0.023 2.725* taxol 0.541 0.519 0.528 0.529* 0.011 4.625* control 0.019 0.012 0.017 0.033 0.003 0.033 caspase-9 activities were determined using the caspace® system. mean ± sd (n = 3 wells/treatment). *p < 0.05 compared with the untreated cells. fold changes was calculated based on the control/untreated cells. od is optical density. 43research article hilles, mahmood, kaderi, hashim necrosis factor-receptor 1-mediated caspase-dependent apoptosis in colon cancer cell line. plos one, 11(4), e0152652. mansilla, s., priebe, w., & portugal, j. (2006). mitotic catastrophe results in cell death by caspase-dependent and caspase-independent mechanisms. cell cycle georgetown tex, 5 (1), 53-60. pearson, j., & brownlee, i. a. (2005). a surface and function of mucosal surface. colonization of the mucosal surface, nataro jp, asm press, washington dc. e-isbn:978.1555817019 sadakane, y., konoha, k., nagata, t., & kawahara, m. (2007). protective activity of the extracts from japanese eel (anguilla japonica) against zinc-induced neuronal cell death: carnosine and an unknown substance. trace nutrients research, 24: 98-105. villarroel, f., bastías, a., casado, a., amthauer, r., & concha, m. i. (2007). apolipoprotein ai, an antimicrobial protein in oncorhynchus mykiss: evaluation of its expression in primary defence barriers and plasma levels in sick and healthy fish. fish and shellfish immunology, 23(1), 197-209. research paper journal of agricultural and marine sciences vol. 22 (1): 42-47 doi: 10.24200/jams.vol22iss1pp42-47 reveived 15 feb 2016 accepted 25 oct 2016 in-situ colour correction for digital images acquired under non-standard lighting conditions p. m. k. alahakoon2 and annamalai manickavasagan1* 1* a.manickavasagan ( ) department of soils, water and agricultural engineering, college of agricultural and marine sciences sultan qaboos university, p.box 34, pc 123, sultanate of oman. 2department of agricultural engineering, faculty of agriculture, university of peradeniya, sri lanka. introduction computer vision techniques have been successful-ly used in various pre-harvest and post-harvest applications of agricultural and food products. due to the common availability of digital imaging equipment and image processing software, many have been encouraged to develop their own techniques which are more inexpensive and easy to use (o’neal et al., 2002) than depending on commercially available equipment. further, the developments in digital imagery have opened many new trends in plant and food applications. digital cameras in combination with computers and appropriate software can be used to image and evaluate the objects for their many surface qualities with relative ease and at an affordable cost. however, the researchers are compelled to acquire images under laboratory conditions, by illuminating the test sample under standard lighting conditions in order to achieve a consistent colour interpretation which is a must for the success of subsequent analyses. the selection of the illumination source must be done carefully which may drastically change the outcome (luo et al., 1997; brown and timm, 1992; manickavasagan et al., 2008). due to this reason, most of the image related studies inevitably use either a laboratory تصحيح الصور الرقمية امللتقطة ابملوقع حتت ظروف اإلضاءة غري القياسية أالحكون2 ومنيكافا سجان أنامايل1* abstract. computer vision techniques using colour images are becoming popular in food and agriculture sector. need of a standard illumination source is an important criterion in this approach to determine various attributes based on rgb values of the objects. in general, under laboratory conditions with standard lighting, an imaging system performs with high consistency in digitizing colour. however, in field conditions where the availability of a standard light source cannot be guaranteed, the colour interpretations may not yield accurate results. the objective of this study was to develop a simple algorithm to compensate for the variations in rgb values due to varying light conditions. it is intended to be useful in situations where taking digital images of objects without standard light sources is essential for a particular purpose. a set of quadratic transformation algorithms were developed to transform the rgb values of the images acquired under five different lighting conditions. the mean variance in rgb values of the image of a colour palette (with 6 different colours) taken under five lighting conditions were in the range of 277 – 548. after implementing the developed algorithm, this was reduced to 34 – 142. similarly, this variance was reduced from 180 – 294 to 63 – 128 in the test conducted with a plant material. this algorithm can be easily adopted in all computer vision applications where variations in colour interpretations due to nonstandard lighting sources are common. keywords: colour balancing; illumination; image correction; computer vision. امللخــص: أصبحــت تقنيــات الرؤيــة احلاســوبية باســتخدام الصــور امللونــة شــائعة يف جمــاالت الغــذاء والزراعــة. تعتــر احلاجــة إىل مصــدر ضــوء قياســي يف اســتخدام هذه التقنية معيارا مهما للتعرف على خمتلف الســمات لألشــياء اعتمادا على قيم األلوان الثالثة األمحر األخضر واألزرق )rgb( بشــكل عــام، وحتــت الظــروف املعمليــة وباســتخدام إضــاءة قياســية يســتطيع نظــام الرؤيــة احلاســوبية التعــرف علــى األلــوان بدرجــة عاليــة مــن التناســق. يف املقابــل، يف الظــروف الفعليــة ومــع عــدم ضمــان توفــر مصــدر للضــوء القياســي فــإن التعــرف علــى األلــوان باســتخدام هــذا النظــام قــد ال يعطــي نتائــج صحيحــة. اهلــدف مــن هــذه الدراســة هــو تطويــر خوارزميــة بســيطة حلــل مشــكلة التبايــن يف قيــم األلــوان )rgb ( والــذي تســببه تأثــرات اإلضــاءة املتغــرة. تكمــن أمهيــة هــذه اخلوارزميــة عنــد احلاجــة إىل التقــاط صــور لشــيء مــا بــدون اســتخدام مصــدر إضــاءة قياســي. مت تطويــر جمموعــة مــن اخلوارزميــات التحويليــة مــن )rgb( للصــور امللتقطــة حتــت مخــس ظــروف خمتلفــة للضــوء. وجــد أن متوســط التبايــن يف قيمــة األلــوان )rgb( الدرجــة الثانيــة لتحويــل قيــم األلــوان املأخــوذة عــن لوحــة األلــوان والــي حتــوي ســتة ألــوان خمتلفــة حتــت ظــروف اإلضــاءة اخلمــس كانــت يف حــدود 277-548. بينمــا وبعــد اســتخدام اخلوارزميــة املطــورة مت ختفيــض هــذا التبايــن ليصــل إىل 34-142. باملثــل، مت تقليــص التبايــن مــن 180-294 إىل 63-128 يف جتربــة مت تنفيذهــا علــى جــزء مــن نبتــة. ميكــن اســتخدام هــذه اخلوارزميــة يف كل تطبيقــات الرؤيــة احلاســوبية حيــث أن التبايــن يف التعــرف علــى األلــوان يعتــر شــائعا بســبب ظــروف اإلضــاءة غــر القياســية واملتغــرة. الكلمات املفتاحية: موازنة اللون؛ اإلضاءة؛ تصحيح الصورة؛ الرؤية احلاسوبية 43research article alahakoon, manickavasagan setup to acquire images under controlled lighting conditions or use a commercially available flat bed scanner to scan the objects for obtaining their images in the case of flat objects such as plant leaves (murakami et al., 2005). some of the light sources used are circular fluorescent lights (paliwal et al., 2003; majumdar and jayas,1999), fluorescent tube lights (manickavasagan et al., 2008), incandescent lights, and infrared lights (halogen lamps) in special situations (hehn and sokhansanj, 1990; liu et al., 2005). digital imaging is very much dependent on the light source and the resulting interpretation of colours in rgb coordinates or as gray levels. however, in agriculture like many other natural science fields, there are many instances where the sample or the object needs to be imaged in the natural environment. in field conditions, the plant materials such as leaves, fruits and flowers have to be imaged without removing from the plant. also in food handling and in supply chain applications, there are several situations where the background lighting cannot be made standard all the time. one of the challenges faced by researchers in taking digital images under such non-standard lighting situations that may also change from one picture to another, is to maintain closeness in the representative colours in the images. even though there are white balancing options included into many modern digital cameras used today in order to provide a close approximation to the actual colours present in the scene, capabilities in the camera alone are not sufficient to yield the same ‘digital’ colours for an object imaged under different lighting situations. even though professional software packages provide excellent improvement in colour and contrast, the resulting colours may not yield the same rgb values for the same object imaged under different environments and lighting situations. on the other hand, since the colour of the sample or its specific regions of interest are represented as an rgb value, the researcher must be able to ensure that the acquired digital image does contain rgb values very close to the actual if not exact. the expected actual rgb values are the ones that will be obtained for a lighting situation that will provide 0, 0, 0 for black and 255, 255, 255 for white regions in the same scene. therefore, it is essential that the digital images acquired are properly preprocessed in such a way that rgb values are closer to the actual as that will assist in proper diagnosis and drawing conclusions on the image properties, especially in food and agriculture related work which involves field images. as can be seen in some applications, measurement of different colour patches is important in making decisions in a large number of studies (o’neal et al., 2002). shahin and symons (2003) developed an algorithm to adjust the colours recorded by digital scanners in order to establish uniform interpretation of colours in the event of using more than one scanner for scanning grains for research purposes. chang and reid (1996) presented a method for correcting for the variations in rgb values caused by vision system components used in acquiring the image. different types of error sources have been identified and modeled in order to correct for the errors. weng et al. (2006) proposed a new algorithm for automatic white balancing of digital images which provided more visually appealing high contrast images compared to some of the existing methods such as gray world method, perfecto reflector method, fuzzy rule method, and chikane’s method. conversely, chikane and fuh (2006) also presented an improved algorithm that can be incorporated into the image processing software in digital cameras, showing that white balancing is a prime requirement of all image acquisition operations. in order to carry out manual white balancing, a more artistic operation, it is necessary to acquire pictures in the raw format, and use professional software customized to post-adjust the rgb components of the image based on the information recorded by the camera at the time of acquisition. in situations where raw image acquisition and the use of professional graphics processing software is limited, especially in industrial visits, and acquisition of images in agricultural fields, this approach posed limitations in use, thus justifying an attempt to develop techniques to address this issue. takemura and ishii (2011) presented a neural network based approach for determination of actual colour of objects for robot vision systems. due to its very sophisticated and demanding computational power requirement, normal users find it difficult to adopt such to their work. besides, the calibrations performed are camera specific and may not be applicable for different cameras used under different conditions. li et al. (2006) developed a specific colour adjustment system to obtain close to true colour representations of colposcopic images used in auto diagnosis of cervical cancer and also in telemedicine related applications. since the diagnosis is primarily based on the colour of the tissue observed under artificial light sources, they have found that variations in the light source provided different colours in the digital image acquired, which may obstruct reaching a clear and fast diagnosis. development of a simple algorithm that can be applied for each image would be highly beneficial to utilize in computer vision techniques for food and agricultural applications where huge variations in lighting conditions are inevitable. therefore the objective of this study was to develop an algorithm to correct the rgb values of an image based on the rgb values of three standard colour cards imaged under the same lighting condition. 44 squ journal of agricultural and marine sciences, 2017, volume 22, issue 1 in-situ color correction for digital images acquired under non-standard lighting conditions methodology standard colour cards black, gray and white standard colour cards (dgk colour tools, boston, massachusetts, usa) were used as the basis for correcting the rgb values of different regions of the images acquired under different lighting situations. the homogeneous rgb values of these colour cards were (0, 0, 0), (128, 128, 128) and (255, 255, 255) for black, white and gray, respectively. colour palette a flat colour palette comprising of 6 different colour regions along with the 3 standard colour cards was assembled by using uniform colour sheets as shown in (fig. 1). the colours were selected by taking 3 stronger shades (blue, green and red) and three lighter shades (yellow, light green and pink) to test the effectiveness of the algorithm. image acquisition a digital colour camera (resolution: 4608 × 3456; model: wb850f; samsung electronics company ltd., uk) was used to acquire images. the developed colour palette was imaged under five non-standard lighting conditions in order to simulate real field conditions: (1) shade of a building; (2) fluorescent tube lighting (inside the laboratory; (3) natural cloudy (outside); (4) in a dark corridor (imaged with built-in flash); and (5) focused fluorescent lighting (test bench). field test to investigate the performance of the developed algorithm, a simulated field experiment was conducted by taking images of a plant leaf under the same lighting situations. in this experiment, the plant leaf was imaged along with the three standard colour cards in all lighting conditions. results and discussion algorithm development with standard colour cards the colour palette, comprising of 6 different colour squares and 3 standard colour cards were used together and exposed to 5 lighting situations. rgb values extracted from the standard colour cards were used to develop a quadratic transformation algorithm for each image using the least squares method, so that the rgb values for the three cards would be translated to (0,0,0), (255, 255, 255), and (128, 128, 128), respectively for black, white, and gray, as prescribed by the manufacturers. all the mathematical operations related to algorithm development and numerical computations were done in ms excel environment. the algorithm development is briefly described by considering the matrices [y], [x] and [h], where [y] containing the expected gray levels for the standard colours [0 128 255], [x] containing the actual measured rgb values representing each colour, placed as [r2 r1] for the equation for the r component, and [h] matrix being the coefficients required as the solution for each equatable 1. variance observed in the rgb values among the images acquired under 5 different lighting conditions before and after correction. red green blue card colour before after before after before after red 817 0 80 285 61 101 yellow 868 0 595 11 0 0 green 398 117 390 78 122 605 light green 336 42 525 12 366 27 blue 68 42 504 218 511 64 pink 798 3 600 111 604 57 mean 548 34 449 119 277 142 figure 1. image of the developed colour palette (first column represents 3 standard colour cards). 45research article alahakoon, manickavasagan tion developed. y⎡⎣ ⎤⎦ = x⎡⎣ ⎤⎦ h⎡⎣ ⎤⎦ h⎡⎣ ⎤⎦ = x tx⎡⎣ ⎤⎦ −1 x⎡⎣ ⎤⎦ t y⎡⎣ ⎤⎦ (1) the coefficients thus derived by solving for [h] as shown in equation 1, provided the algorithm for transforming a colour component r, g, or b. the same operation was repeated for the 3 colour components. the set of 3 functions developed were then used to transform the colour values of the other colour squares that represent different objects in the same image in order to obtain a colour adjusted image. the final rgb values for each colour region were compared to estimate the variance among images obtained under different lighting situations. as a final measure to fine tune the algorithm, the gray level corresponding to the gray card region (128) was adjusted to bring the total variance computed among rgb values of the new images to a minimum. rgb correction on colour palette regions the image of the colour palette with 3 standard colour cards and 6 refernce colours are shown in fig. 1. the derived equations were used to correct the rgb values of the 6 colour regions in the colour palette. a sample set of such transformation functions derived for one lighting setting is given in eqn 2-4. r new = −0.003108r old 2 +2.1102r old −46.8914 (2) g new = −0.002983g old 2 +2.0802g old −46.2674 (3) b new = −0.003705b old 2 +2.2362b old −48.2317 (4) where r, g, bold are the rgb values in the original image and r, g, bnew are the rgb values of the corrected image. in order to simulate and represent the field situations, some of the pictures were taken under natural light outside as well as in the shade. the rgb values pertaining to 10 different points in the white, gray, and black regions were sampled and recorded together with those sampled from the other 6 colour regions. the variance values computed for each of the colour components r, g, and b, of selected regions representing each colour palette before and after the colour adjustment are given in this table 1. the high variance values before adjusting the colours indicate that a colour is represented by significantly different rgb values depending on the lighttable 2. variances observed in the rgb values among the images of a plant leaf acquired under 5 different lighting conditions before and after correction. red green blue card colour before after before after before after region 1 189 161 210 38 291 62 region 2 226 4 247 159 0 0 region 3 11 7 446 200 247 166 region 4 533 79 402 83 42 94 region 5 97 0 354 228 183 35 region 6 246 129 105 59 315 164 mean 217 63 294 128 180 87 figure 2. example of the rgb values representing three standard colour cards (white, gray, black) used under one lighting condition). 46 squ journal of agricultural and marine sciences, 2017, volume 22, issue 1 in-situ color correction for digital images acquired under non-standard lighting conditions ing source under which it is imaged. after adjustment of colour values, the mean variances show a significant reduction. the only exception being with the rgb values pertaining to green colour imaged under fluorescent lighting. this could be attributed to the unbalanced nature of spectral distribution in fluorescent light, which may significantly alter the r and b components compared to the g component. rgb correction on plant leaf regions the colours extracted from the plant leaf were transformed using the new algorithms derived from the rgb values sampled from the standard colour cards included in the same image. the analyses showed that the algorithms derived in following the developed approach were capable of transforming the image rgb values to new values giving lower variance among the same colours in different images. the variance values computed for each of the colour components r, g, and b, of selected regions of different colour patches on the plant leaf before and after the colour adjustment procedure are shown in table 2. pixel value averaging was used in both these representations to minimize any variations within the selected representative region, in each lighting situation. the variance among the adjusted colour regions appear to be lower than that before adjustment, indicating the success of the method tested herein. the algorithm as well as the procedure to acquire images was expected to be relatively easy to implement on general purpose software platforms and in-situ image acquisition work, and present more flexibility in deciding on the gray level that corresponds to the level of gray used in the image compared to other commercially available image editing software, and reduce the inter-image variability in the final colours obtained after the transformation. flexibility of the algorithm there were several advantages in the new approach compared to the use of traditional colour balancing methods for rgb values of acquired images. the developed algorithm corrected rgb values by taking into account 10 representative regions distributed over the whole image representing the three colour pallets in the image. this undoubtedly makes the algorithm more robust and representative of the existing rgb values, since a close examination of the standard colour regions would reveal that there are variations in rgb values among the pixels regardless of the effort to provide uniform lighting at the time of taking the image. further, an additional ‘tuning’ operation was also built into the new algorithm whereby the rgb value of the gray colour card could be adjusted in a manner that would provide minimum variance among the same colour regions pictured under different lighting situations, after subjecting them to the colour transformations. conclusion the developed algorithm for colour adjustment of images provided less dispersed rgb values for a certain colour pictured under different lighting situations, compared to the original image. this made it possible to use images acquired in the field with minimal colour variations for subsequent image analyses and feature recognition steps. it was however necessary to acquire the image all the time with the three standard colour cards in the frame of the image together with the subject, to carry out this colour adjustment procedure. acknowledgements we thank the research council (trc) of the sultanate of oman for funding this study (project no. rc/agr/ swae/11/01-development of computer vision technology for quality assessment of dates in oman). references brown, g. k.and timm, e. j., 1992. lighting for fruit and vegetable sorting. asae paper no. 936069, st. joseph, mi, usa. chang, y., reid and j. f., 1996. rgb calibration for color image analysis in machine vision. ieee transactions on image processing. 5, 1414-1422. chikane, v.and fuh, c., 2006. automatic white balance for dgital still cameras. journal of information science and engineering. 22, 497-509. hehn, j. l. and sokhansanj, s. 1990. canola and mustard seed identification using mackintosh based imaging system. asae paper no. 903534, st. joseph, mi, usa. li, w., thompson, m. s., xiong, y. and lange, h. 2006. a new image calibration technique for colposcopic images. medical imaging 2006: image processing, edited by joseph m. reinhardt, josien p. w. pluim, in proceedings of spie. 6144, 227-239. liu, z., cheng, f., ying, y. and rao, x. 2005. identification of rice seed varieties using neutral network. journal of zhejiang university science. 6b, 10951100. luo, x., jayas, d. s., crowe, t. g. and bulley, n. r. 1997. evaluation of light sources for machine vision. canadian agricultural engineering. 39, 309-315. majumdar, s. and jayas, d.s. 1999. classification of bulk samples of cereal grains using machine vision. journal of agricultural engineering research. 73, 35-47. manickavasagan, a., sathya, g. and jayas, d.s. 2008. comparison of illuminations to identify wheat classes using monochrome images. computers and electronics in agriculture. 63, 237-244. murakami, p. f., turner, m.r., van den berg, a. k. and schaberg, p. g. 2005. an instructional guide for leaf color analysis using digital imaging software. gen. 47research article alahakoon, manickavasagan tech. rep. ne-327. newtown square, pa: u.s. department of agriculture, forest service, northeastern research station. 33 p. o’neal, m., landis, d. a.and isaacs, r. 2002. an inexpensive, accurate method for measuring leaf area and defoliation through digital image analysis. journal of economic entomology. 95, 1190 – 1194. paliwal, j., visen, n. s., jayas, d. s. and white, n.d.g. 2003. cereal grain and dockage identification using machine vision. biosystems engineering. 85, 51-57. shahin, m. a. and symons, s. j. 2003. color calibration of scanners for scanner-independent grain grading. cereal chemistry journal. 80, 285-289. takemura, y, and ishii, k. 2011. auto color calibration algorithm using neural networks and its application to robocup robot vision. international journal of artificial intelligence. weng, c., chen, h. and fuh, c. 2006. a novel automatic white balance method for digital still cameras. journal of communication engineering. 12. img201 img202 img203 img204 img205 img026 img027 img028 img029 img030 img031 research paper journal of agricultural and marine sciences 2020, 25(2): 22–29 doi: 10.24200/jams.vol25iss2pp22-29 received 30 march 2020 accepted 19 may 2020 in vitro antagonistic potential, plant growth-promoting activity and indole-3-acetic acid producing trait of bacterial isolates from button mushroom (agaricus bisporus) spent substrate shima nasser hamed al-mamari1, abdullah mohammed al-sadi1, s. p. sathish babu2, issa hashil al-mahmooli1, rethinasamy velazhahan1,* التأثري املضاد، والنشاط املعزز لنمو النبات وميزة إنتاج األندول 3حمض األسيتيك يف املخترب من العزالت البكتريية من السامد املستهلك )كمبوست( )agaricus bisporus( بعد إنتاج فطر املرشوم الدائري شيامء بنت نارصبن حمد املعمرية1، عبدالله بن محمد السعدي1، ساثيش بابو2، عيىس بن هاشل املهمويل1 و راثيناسمي فيالزهاهن1* abstract. spent mushroom substrate (sms) is widely used as a fertilizer and to control plant diseases. the microorganisms surviving in sms play a crucial role in plant growth promotion and biocontrol activity. in this study, an effort was made to isolate and characterize the bacterial species present in the sms of agaricus bisporus and to study their antagonistic potential, plant growth-promoting ability and indole-3-acetic acid (iaa) producing trait. six different bacterial isolates exhibiting morphological variabilities were obtained from the sms by serial dilution technique. on the basis of 16s rrna gene sequences, these isolates were identified as staphylococcus epidermidis (sh1 and sh3), s. aureus (sh2), bacillus albus (sh4), delftia lacustris (sh6) and comamonas aquatica (sh7). these bacterial strains were assayed for their antagonism against pythium aphanidermatum, a phytopathogenic oomycete. the results of in vitro dual culture assay revealed that all the 6 bacterial isolates showed low levels of suppression of p. aphanidermatum and recorded less than 5 mm inhibition zone. among the bacterial isolates, s. epidermidis sh3 recorded the maximum inhibition zone of 4.2 ± 0.5 mm. plant growth promotion test using roll paper towel method revealed that c. aquatica sh7, b. albus sh4, d. lacustris sh6 and s. epidermidis sh3 caused a significant increase in seedling vigour of cucumber compared to control. the seeds treated with the bacterial isolate c. aquatica sh7 showed the maximum seedling vigor (2018 ± 255). assessment of in vitro production of iaa by the bacterial isolates revealed that the bacterial isolates highly varied (ranging from 0.28 to 9.25 mg l-1) in their potential for production of iaa. the maximum amount of iaa was produced by c. aquatica sh7 (9.25 ± 0.02 mg l-1). further studies are required to assess the possibility of using the iaa-producing bacterial isolates identified in this study or their metabolites to promote plant growth or to enhance growth and yield of mushrooms. keywords: button mushroom; spent compost; iaa production; agaricus bisporus; antagonistic activity; plant growth promotion. املســتخلص:خالصة: يســتخدم الســامد املســتهلك )كمبوســت( بعــد إنتــاج فطــر املــرشوم بشــكل واســع كســامد وأيضــا يف مكافحــة الفطريــات املمرضــة للنباتــات. ــف ــزل وتوصي ــا بع ــة قمن ــذه الدراس ــي. يف ه ــة البيولوج ــاط املكافح ــات ونش ــو النب ــز من ــاًم يف تعزي ــامد دوًرا حاس ــذا الس ــش يف ه ــي تعي ــة الت ــة الدقيق ــات الحي ــب الكائن تلع ــو ــيط من ــات وتنش ــض الفطري ــو بع ــط من ــى تثبي ــا ع ــا قدرته ــة أيض ــر agaricus bisporus ولدراس ــاج فط ــتخدم يف إنت ــذي يس ــت ال ــذا الكمبوس ــودة يف ه ــا املوج البكتريي ــي ــف التسلس ــة التخفي ــتخدام تقني ــا بإس ــول عليه ــم الحص ــة ت ــة مختلف ــات ظاهري ــا ذات صف ــن البكتريي ــزالت م ــت ع ــيتيك. س ــض األس ــدول 3حم ــاج اإلن ــات وإنت النبات ــى ــك )s1٦( ع ــض الريبونيوكلي ــى حم ــودة ع ــومات املوج ــدة الريبوس ــل وح ــي يف تسلس ــف الجين ــتخدام التصني ــا بإس ــف البكتريي ــم تصني ــت. ت ــز الكمبوس ــوى تركي يف محت و delftia lacustris )shو)٦ bacillus albus )s4h(hو s.aureus )sh2( و staphylococcus epidermidis )sh 3 و 1sh( إنهــا ــرت ــرضpythium aphanidermatum . أظه ــكاذب املم ــر ال ــو الفط ــط من ــى تثبي ــا ع ــم تجربته ــة ت ــالالت البكتريي ــذه الس )comamonas aquatica )sh٧. ه النتائــج التــي أجريــت يف املختــرب بعــد وضــع كل مــن أوميســيتس p. aphanidermatum مــع جميــع العــزالت البكترييــة الســتة مســتويات تثبيــط منخفضة وســجلت منطقة تثبيــط أقــل مــن ٥ مــم. مــن بــن العــزالت البكترييــة، ســجلت b. و c. aquatica shــة أن ٧ ــل الورقي ــات املنادي ــة لفاف ــتخدام طريق ــات باس ــو النب ــار من ــف إختب ــم. كش ــط 4,2 ± ٠,٥ م ــة تثبي ــى منطق s. epidermidis sh3 أق albus sh4 و d. lacustris sh٦ و. epidermidis sh 3 تســببو يف زيــادة معنويــة كبــرية يف قــوة إنبــات بــادرات الخيــار مقارنــة بالشــاهد. أظهــرت البــذور املعالجــة البكتريية بالعزلة c. aquatica sh٧ قــوة قصــوى للشــتالت )2٠1٨ ± 2٥٥(. كشــف تقييــم إنتــاج اإلنــدول 3حمــض األســيتيك iaa يف املختــرب مــن قبــل العــزالت البكترييــة أن c. aquatica ــطة ــن iaa بواس ــدر م ــرب ق ــاج أك ــم إنت ــاج iaa. ت ــى إنت ــا ع ــر( يف قدرته ــرام / ل ــن ٠,2٨ إىل ٩,2٥ ملج ــراوح م ــوع )ت ــديدة التن ــة ش ــزالت البكتريي الع ــة أو ــذه الدراس ــددة يف ه ــة لـــ iaa املح ــة املنتج ــزالت البكتريي ــتخدام الع ــة إس ــم إمكاني ــات لتقيي ــن الدراس ــد م ــة إىل مزي ــاك حاج ــر(. هن ــرام /ل sh٧ )٩,2٥ ± ٠,٠2 ملج نواتجهــم لتعزيــز منــو النبــات أو لتعزيــز منو وإنتــاج الفطر. 23research paper al-mamari, al-sadi, babu, al-mahmooli, velazhahan rethinasamy velazhahan1,*( ) velazhahan@squ.edu.om, 1department of plant sciences, college of agricultural and marine sciences, sultan qaboos university, p.o. box 34, al-khoud, muscat 123, sultanate of oman. 2 central analytical and applied research unit, college of science, sultan qaboos university, al-khoud, muscat 123, sultanate of oman. introduction m ushroom farming has gained recognition in the recent years and has emerged as a prom-ising agro-based business. malaysia, china, india and ireland are the world’s leading edible mushrooms producers (hanafi et al., 2018). several edible mushrooms including button mushroom (agaricus bisporus), shiitake mushroom (lentinula edodes), paddy straw mushroom (volvariella volvacea), oyster mushroom (pleurotus spp.) and enoki mushroom (flammulina ostreatus) are being cultivated commercially worldwide (feeney et al., 2014). agaricus bisporus is cultivated commercially in oman. mixtures of agricultural/poultry/industrial wastes are commonly used as substrates for mushroom cultivation. the mushroom industry discharges huge quantities of spent mushroom substrate (sms) after harvest. the sms usually contains mycelia and remnants of fruiting bodies of mushrooms, and the substrate used for cultivation of mushrooms (kang et al., 2017). a wide variety of biologically active compounds such as extracellular enzymes, antimicrobial compounds and secondary metabolites that are mainly produced by mushrooms are present in the sms (kwak et al., 2015). the potential of sms in large-scale enzymes production, plant diseases control, bioremediation, fertilizer, vermicomposting and for feeding animals has been documented (inagaki and yamaguchi, 2009; ahlawat et al., 2011; parada et al., 2011; parada et al., 2012; kwak et al., 2015; roy et al., 2015). several reports indicated the effectiveness of sms in plant disease management (yohalem et al., 1996; uzun, 2004; goonani et al., 2011; riahi et al., 2012). riahi et al. (2012) demonstrated that the extract of sms inhibited the growth of lecanicillium fungicola, the causal fungus of dry bubble disease of a. bisporus. kang et al. (2017) reported that aqueous extract prepared from sms of lentinula edodes suppressed the growth of phytophthora capsici, reduced the phytophthora blight and enhanced the growth of pepper. the antagonistic microorganisms present in the sms were attributed to the disease suppression (riahi et al., 2012). the objectives of the present study were to isolate and characterize the bacterial species present in the spent mushroom substrate of a. bisporus in oman and to study their in vitro antagonistic potential, plant growth-promoting trait and iaa producing ability. materials and methods sms collection and bacterial isolation spent mushroom substrate of a. bisporus was obtained from the department of plant sciences, cams, sultan qaboos university. bacteria from the sms were isolated by employing serial dilution plate technique. briefly, 1 g of sms was suspended in 99 ml of sterile water and kept on a rotary shaker (150 rpm) for 30 min. later, the suspension was serially diluted at 1:10 ratio with sterile water. an aliquot (100 μl) from 10−4 to 10−7 dilutions was gently spread over the nutrient agar (na) (oxoid, uk) with a sterile spreader and then the petri plates were incubated at 30 °c for 48 h. the bacterial colonies with varying morphological features were selected and transferred to fresh na plates. figure 1. enhancement of cucumber growth by seed bacterization with comamonas aquatica sh7 isolated from spent mushroom substrate of agaricus bisporus الكلامت املفتاحية: الفطر الدائري، السامد املستهلك، إنتاج iaa، agaricus bisporus، نشاط تثبيط، تعزيز منو النبات 24 squ journal of agricultural and marine sciences, 2020, volume 25, issue 2 in vitro antagonistic potential, plant growth-promoting activity and indole-3-acetic acid producing trait of bacterial isolates from button mushroom (agaricus bisporus) spent substrate molecular identification of bacterial isolates the 16s rrna gene sequence analysis was employed for identification of the bacterial isolates. the bacterial isolates were grown individually on a shaker in nutrient broth (nb) medium (100 ml) at 30°c for 48 h. the bacterial cultures were centrifuged at 14000 g for 15 min and the bacterial cell pellets were collected. dna was extracted from the bacterial pellet using a commercial foodproof starprep two dna extraction kit (biotecon diagnostics, germany). the universal primers 27f (5’-agagtttgatcmtggctcag-3’) and 1429r (5’-tacggytaccttacgactt-3’) were used for amplification of bacterial 16s rrna gene by pcr as described by al-hussini et al. (2019). the pcr amplified products were sequenced at macrogen inc., seoul, korea. a database search of homologous sequences was carried out using national center for biotechnology information (ncbi) blastn program (http://www.ncbi. nlm.nih.gov). test pathogen a virulent isolate of pythium aphanidermatum, the cucumber damping-off pathogen (al-shibli et al., 2019), was used in this study. the oomycete pathogen was multiplied on potato dextrose agar (pda) (oxoid, uk) at 25 ± 2 °c. bacterial isolates screening against p. aphanidermatum the bacterial isolates were screened for their inhibitory effect on p. aphanidermatum using an in vitro dual culture method as described by al-hussini et al. (2019). briefly, a mycelial plug (7 mm diameter) of p. aphanidermatum was placed aseptically on one end of the petri plate (9 cm diameter) containing pda. the bacterial isolate was streaked on the other side of the petri plate (~ 1 cm away from the margin). the inoculated plate was incubated at 27 °c for 3-5 days. after incubation, the inhibition zone was measured. petri plates inoculated with p. aphanidermatum discs alone were used as control. four replications were maintained for each bacterial isolate. figure 2. hplc chromatograms showing iaa produced by bacterial strains from spent mushroom substrate of agaricus bisporus 25research paper al-mamari, al-sadi, babu, al-mahmooli, velazhahan plant growth promoting activity of bacterial isolates each bacterial isolate was cultured in nb medium (100 ml) in 250 ml conical flask on a shaker (200 rpm/min) at 30°c for 48 h, and then the bacterial suspension was centrifuged at 3000 rpm for 10 min. the bacterial cell pellet was collected and re-suspended in sterile distilled water and the concentration of the bacterial cells was adjusted to 4×108 cfu ml-1. cucumber seeds (cv. jabbar, f1; us agriseeds, usa) were immersed in the bacterial suspension for 3 h at room temperature (25±2 °c), while the control seeds were soaked in sterile distilled water. the roll paper towel method (shifa et al., 2015) was used to test the effect of bacterial strains on the growth of cucumber. the percentage of cucumber seed germination, seedling shoot length and root length were recorded 12 days after treatment and vigor index was calculated by multiplying the germination percentage of seeds with the total of seedling root length and shoot length. four replicates of 10 seeds each were used for each treatment. analysis of iaa production the bacterial isolates were cultivated in nb medium supplemented with 5 mm tryptophan in a shaker (200 rpm) for 72 h at 30°c. the cultures were centrifuged at 14000 g for 10 min at 4°c and the culture supernatants were collected. the iaa content in the cell-free bacterial culture supernatants was analyzed by high-performance liquid chromatography (hplc) (szkop and bielawski, 2013). analysis of iaa was performed using a hplc system (agilent-1200 infinity series), equipped with a high performance autosampler (g4226a), quaternary pump (g4204a), thermostatted column compartment (g1316c) and a diode array detector (dad) (g4212a). the separation was achieved with waters symmetry c8 (5 µm, 3.0×150 mm) column. the mobile phases consisted of a (2.5% acetic acid with a ph 3.8) and b (80% acetonitrile). the mobile phase began with eluent a: eluent b at 80:20 and changed to 50:50, 0:100, 80:20 in 15, 16, and 16.5 min, respectively, and maintained in 80:20 for 1.5 min with a flow rate 1 ml per min. the detection wavelength was set at 280 nm. peaks in the sample were identified and quantified by comparing with the standard rt. statistical analysis the experimental design used was completely randomized design. the data on mycelial growth inhibition, percent seed germination and seedling growth of cucumber and iaa production by bacterial isolates,were analyzed by one-way anova (minitab 17, state college, pa, usa). the data on % seed germination was analyzed after arcsine transformation of values to ensure homogeneity of variance. results isolation and characterization of bacteria from sms a total of 6 morphologically different bacterial isolates were obtained from the sms of a. bisporus. on the basis of 16s rrna gene sequences, these bacterial isolates were identified as staphylococcus epidermidis (sh1), s. aureus (sh2), s. epidermidis (sh3), bacillus albus (sh4), delftia lacustris (sh6) and comamonas aquatica (sh7) (table 1). the 16s rrna gene sequences of these bacterial isolates were deposited in the genbank database with the accession numbers mt002750, mt002751, mt002756, mt002776, mt002777 and mt002779. antagonistic activity of bacterial isolates the antagonistic abilities of these bacterial isolates were determined against p. aphanidermatum using an in vitro dual-culture assay. the results indicated that none of the bacterial isolates showed considerable level of inhibition of mycelial growth of p. aphanidermatum. all the bacterial isolates recorded less than 5 mm inhibition zone (table 2). of the 6 bacterial isolates evaluated, s. epidermidis sh3 produced the maximum inhibition zone of 4.2 mm. plant growth promoting activity of bacterial isolates the bacterial isolates were tested for plant growth promotion effects on cucumber using a roll paper towel table 1. identification of bacterial isolates from spent mushroom substrate of agaricus bisporus by 16s rdna sequence analysis bacterial isolate genbank accession number hit in the ncbi database % identity sh1 mt002750 staphylococcus epidermidis (kx348319.1) 99.87 sh2 mt002751 staphylococcus aureus (cp045468.1) 100 sh3 mt002756 staphylococcus epidermidis (lc499612.1) 100 sh4 mt002776 bacillus albus (mn793202.1) 100 sh6 mt002777 delftia lacustris (mf457528.1) 100 sh7 mt002779 comamonas aquatica (mn216294.1) 100 26 squ journal of agricultural and marine sciences, 2020, volume 25, issue 2 in vitro antagonistic potential, plant growth-promoting activity and indole-3-acetic acid producing trait of bacterial isolates from button mushroom (agaricus bisporus) spent substrate technique. the results revealed that seed bacterization with c. aquatica sh7, b. albus sh4, d. lacustris sh6 and s. epidermidis sh3 resulted in a significant (f=9.57, df=6, p<0.05) increase in seedling vigour compared to control (table 3). among the various treatments, seeds treated with c. aquatica sh7 showed the highest seedling vigor (figure 1). no significant (p<0.05) difference in the % seed germination among the treatments was observed. iaa production all the 6 isolates of bacteria tested produced iaa between 0.28±0.02 and 9.25±0.02 mg l-1 in tryptophan-amended growth medium (table 4; figure 2). the maximum (9.25 mg l-1) and minimum (0.28 mg l-1) production of iaa was recorded with c. aquatica sh7 and s. epidermidis sh1, respectively. discussion the existence of a broad range of bacterial species in the sms has been documented (ntougias et al., 2004; watabe et al., 2004). ntougias et al. (2004) reported the presence of bacterial genera arthrobacter, brevibacterium, bacillus, comamonas, carnobacterium, desemzia, microbacterium, paenibacillus, exiguobacterium, sphingobacterium and staphylococcus in the spent mushroom compost of agaricus spp. by using dna sequence typing, several bacterial species including, bacillus subtilis, bacillus licheniformis, paenibacillus lentimorbus, pseudomonas mevalonii, stenotrophomonas sp., klebsiella/enterobacter sp., microbacterium sp. and sphingobacterium multivorum have been reported in the spent mushroom compost (watabe et al., 2004). the type of substrates used in the compost preparation and their pasteurization conditions are known to influence the diversity of bacterial communities in sms (ntougias et al., 2004). choudhary (2011) isolated acinetobacter sp., pseudomonas sp. and sphingobacterium sp. from the casing material for agaricus bisporus. zhu et al. (2014) found comamonas serinivorans sp. nov. in wheat straw compost. silva et al. (2009) reported the presence of bacillus, paenibacillus spp. and streptomyces in a sugarcane bagasse and cynodon dactylon straw compost used for a. brasilienses cultivation. gbolagade (2006) reported the presence of pseudomonas aeruginosa, enterobacter aerogenes, micrococcus roseus, bacillus subtilis, b. cereus, b. polymyxa, b. licheniformis, escherichia coli, clostridium perfringens and citrobacter freundii in the compost used for cultivation of lentinus squarrosulus and pleurotus tuber-regium. in the present study, staphylococcus epidermidis (sh1 and sh3), s. aureus (sh2), bacillus albus (sh4), delftia lacustris (sh6) and comamonas aquatica (sh7) were detected in the sms of a. bisporus. the primary source of these bacteria might be the casing material or compost or water used for cultivation of mushrooms (rainey et al., 1990; choudhary, 2011; kertesz and thai, 2018; cao et al., 2019). several bacteria isolated from compost are reported to have ability to suppress the growth of plant pathogenic fungi (boulter et al., 2002; suarez-estrella et al., 2007; sreevidya and gopalakrishnan, 2017) and to promote plant growth (chin et al., 2017; sreevidya and gotable 2. inhibition of mycelial growth of pythium aphanidermatum by bacterial isolates from spent mushroom substrate of agaricus bisporus bacterial isolate inhibition zone (mm) staphylococcus epidermidis sh1 3.0 ± 0.8abc staphylococcus aureus sh2 4.0 ± 0.8ab staphylococcus epidermidis sh3 4.2 ± 0.5a bacillus albus sh4 2.0 ± 0.8c delftia lacustris sh6 3.0 ± 0.0abc comamonas aquatica sh7 2.5 ± 0.6c data are mean of four replications ± standard deviation. values in the column with the same letter are not significantly different from each other at p<0.05 table 3. effect of bacterial isolates from spent mushroom substrate of agaricus bisporus on cucumber seed germination and seedling vigor bacterial isolate % germination* shoot length (cm) root length (cm) vigour index** staphylococcus epidermidis sh1 75.0 ± 5.8 6.3 ± 1.5b 14.8 ± 3.8ab 1583 ± 293bc staphylococcus aureus sh2 72.5 ± 5.0 6.1 ± 1.5b 16.1 ± 2.1a 1612 ± 156bc staphylococcus epidermidis sh3 75.0 ± 5.8 7.0 ± 1.8b 15.3 ± 1.9ab 1671 ± 185b bacillus albus sh4 75.0 ± 5.8 8.0 ± 1.2ab 16.6 ± 3.2a 1844 ± 294ab delftia lacustris sh6 75.0 ± 5.8 8.0 ± 0.9ab 16.1 ± 1.9a 1805 ± 152ab comamonas aquatica sh7 77.5 ± 5.0 9.1 ± 1.6a 17.0 ± 2.5a 2018 ± 255a control 72.5 ± 5.0 6.4 ± 1.5b 12.1 ± 2.0b 1343 ± 160c * non-significant (p<0.05) . **vigor index was calculated by multiplying the % germination of seeds with the sum of shoot length and root length. data are mean of three replications ± standard deviation. values in the column with the same letter are not significantly different from each other at p<0.05 27research paper al-mamari, al-sadi, babu, al-mahmooli, velazhahan palakrishnan, 2017). riahi et al. (2012) identified three bacterial species viz, bacillus subtilis, b. licheniformis and b. amyloliquefaciens from the extract of leached spent mushroom compost that showed antagonistic effect towards lecanicillium fungicola, the causal agent of dry bubble disease of button mushroom. in the present study, none of the bacterial isolates showed substantial level of suppression of growth of p. aphanidermatum and all the bacterial isolates recorded less than 5 mm inhibition zone. however, plant growth promoting effect of these bacterial isolates was observed. although no significant difference in % seed germination was observed, seed bacterization with c. aquatica sh7, b. albus sh4, d. lacustris sh6 and s. epidermidis sh3 resulted in a significant increase in seedling vigor of cucumber compared to control and c. aquatica sh7 treated seeds showed the maximum seedling vigour. several reports indicate the beneficial effects of bacteria present in the substrates used for cultivation of mushrooms (rainey et al., 1990; straatsma et al., 1994; ahlawat and vijay, 2010). the bacteria such as alcaligenes faecalis and pseudomonas putida which are surviving in casing layer are reported to influence the growth and morphogenesis of a. bisporus by producing growth inducing compounds, which stimulate initiation of pinheads (rainey et al., 1990). straatsma et al. (1994) demonstrated that the thermophilic fungi present in mushroom compost enhanced the growth rate of agaricus mycelium up to two fold. inoculation with bacillus megaterium or staphylococcus has been shown to enhance mushroom production and early cropping (ahlawat and vijay, 2010). the increase in seedling vigor of cucumber in the present study could be as a result of production and release of growth promoting compounds like iaa by the bacterial isolates. iaa is a common auxin and is a product of l-tryptophan metabolism of microorganisms. in bacteria, iaa is primarily synthesized via the indole-3-pyruvic acid pathway (gomes et al., 2017). iaa produced by plant growth-promoting rhizobacteria (pgpr) is known to enhance root growth (persello-cartieaux et al., 2003) and the growth of root hairs (desbrosses et al., 2009). asghar et al. (2002) observed a significant relationship between in vitro auxin production by pgpr and yield of brassica juncea. deepa et al. (2010) demonstrated that enterobacter cloacae and enterobacter aerogens strains, which produced iaa, exhibited growth-promoting effect in vigna unguiculata. in addition to the effects of iaa produced by beneficial bacteria on plants, the growth and yield of mushrooms also reported to be influenced by iaa (maniruzzaman et al., 2008; ramachela and sihlangu, 2016). maniruzzaman et al. (2008) demonstrated that the culture media amended with iaa (5 ppm) caused rapid proliferation of oyster mushroom mycelia. ramachela and sihlangu (2016) reported that auxins promoted the cap size of pleurotus ostreatus. in the present study, all the 6 bacterial isolates produced iaa in vitro and the production levels varied between 0.28 and 9.25 mg l-1. among the bacterial isolates tested, c. aquatica sh7 showed the highest production of iaa (9.25 mg l-1). the same bacterial isolate displayed the highest plant growth promoting activity. these results suggest that iaa produced by this bacterial isolate might have involved in enhancing vigor of cucumber seedlings. an interesting observation in our study is that the bacterial isolate b. albus b4, which is producing low amounts of iaa in vitro, enhanced the growth of cucumber. these results suggest that other mechanisms of action might have been involved in plant growth promotion by this bacterium. however, schwachtje et al. (2012) reported that the non-growth promoting bacterial strains pseudomonas sp. wcs417r and g53 isolated from the rhizosphere of arabidopsis showed the highest levels of iaa production. conclusion this study demonstrated the existence of different bacteria in sms of agaricus bisporus in oman. these bacterial isolates displayed low levels of antagonism against p. aphanidermatum and produced less than 5 mm inhibition zone. however, these bacterial isolates enhanced the plant growth as demonstrated by increased seedling vigor of cucumber compared to control. the level of production of iaa by these bacterial isolates varied among isolates. among the bacterial isolates tested, comamonas aquatica sh7 showed the highest production of iaa as well as plant growth promoting activity. further studies are required to evaluate the potential of these bacterial isolates or their cell free culture filtrates in promoting growth of edible mushrooms and in enhancing plant growth under in vivo conditions. acknowledgements this work was supported by the squ research grants ig/agr/ crop/18/01 and rc/rg-agr/crop/19/02. we thank the central analytical and applied research unit, squ for hplc analysis. table 4. production of iaa by bacterial isolates from spent mushroom substrate of agaricus bisporus bacterial isolate iaa (mg l-1) staphylococcus epidermidis sh1 0.28 ± 0.02e staphylococcus aureus sh2 1.07 ± 0.01c staphylococcus epidermidis sh3 0.77 ± 0.01d bacillus albus sh4 0.33 ± 0.00e delftia lacustris sh6 7.57 ± 0.07b comamonas aquatica sh7 9.25 ± 0.02a data are mean of four replications ± standard deviation values in the column with the same letter are not significantly different from each other at p<0.05 28 squ journal of agricultural and marine sciences, 2020, volume 25, issue 2 in vitro antagonistic potential, plant growth-promoting activity and indole-3-acetic acid producing trait of bacterial isolates from button mushroom (agaricus bisporus) spent substrate references ahlawat op, vijay b. 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(2014). description of comamonas serinivorans sp. nov., isolated from wheat straw compost. international journal of systematic and evolutionary microbiology 64: 4141-4146. img214 img215 img216 img217 technical notes journal of agricultural and marine sciences 2021, 26(1): 53–56 doi: 10.24200/jams.vol26iss1pp53-56 reveived 11 may 2020 accepted 30 nov 2020 microbiological assessment of locally dried fish in oman: technical note aaisha k. al-saadia, abdulrahim m. al-ismaili a,*, mohammed al-ruzeikib, ismail m. al-bulushib abdulrahim m. al-ismailia,*( ) abdrahim@squ.edu.om; abdrahim@ hotmail.co.uk, adepartment of soils, water and agricultural engineering, sultan qaboos university, 123, al-khoud, sultanate of oman, bdepartment of food science and nutrition, sultan qaboos university, 123, al-khoud, sultanate of oman introduction fish is the main foodstuff around many countries in the world because of its high protein content and nutritional value. however, in the hot climates, fish perishes quickly and it is common to increase their shelf life using different techniques such as drying, smoking and salting (sultana et al., 2010). in the gulf region, oman is the largest fish producer (fao, 2019) and it has more than 150 kinds of fish and crustaceans (belwal et al., 2015). most of the fish in oman are sold fresh (93%) and the remaining 7% is sold after being dried, salted or smoked (fao, 2019). in 2018, the total fish production of oman was about 553 thousand tons which was 59% more than the production in the previous year (maf, 2018). in the same year, fish export constituted 44% of the total production (about 245 thousand tons). the traditional drying process of fish causes the loss of 30-40% of dried fish due to eating by dogs, birds, cats, and rats, especially during winter when drying takes about a week (sablani et al., 2002). indeed, this factor causes a reduction on the revenue of dried fish, which also suffers from the contamination by sand particles. it was reported that sand contamination causes high concentration of ash in the dried fish (al ghabshi et al., 2012). in addition, sun-dried fish may become unhealthy التقييم امليكروبيلوجي لألمساك اجملففة حملًيا يف عمان: مالحظة فنية عائشة الساعدي1، عبد الرحيم اإلمساعيلي1،*، حممد الرزيقي2، إمساعيل البلوشي2 abstract. the presence of microorganisms is one of the major factors affecting the quality of dried fish. in this project, a number of analytical tests were used to verify the presence of biochemical contamination in dried fish, as well as to propose an engineering solution to reduce the incidence of these contaminations. two types of fish samples (anchovy and shark) were collected from two local markets (buraimi and seeb). the analyzed parameters included total fungal count (tfc), total viable count (tvc) and enumeration of escherichia coli (e. coli), staphylococcus aureus and coliforms species in dried fish. the results indicated that the anchovy collected from seeb market had the highest tvc and tfc (tvc= 5.59×105 cfu/ ml, tfc= 3.60×104 cfu/ml) compared to all other samples. it could be recommended to dry fish under more hygienic conditions using solar drier instead of direct drying on beach sands. keywords: solar drying, fish drying, fish contamination, dried fish, microbial assessment الدراســة هــذه ويف اجملففــة، األمســاك جــودة علــى تؤثــر الــي الرئيســية العوامــل أهــم أحــد الدقيقــة احليــة الكائنــات وجــود يعتــر املســتخلص: هندســي حــل اقــراح مت وكذلــك حمليــاً، اجملففــة األمســاك يف البيلوجيــة امللــواثت وجــود مــن للتحقــق التحليليــة األختبــارات مــن عــدد اســتخدام مت حمليــا )تســمى والقــرش األنشــوجة ومهــا األمســاك مــن لنوعــن عينــات مجــع مت فقــد ذلــك أجــل ومــن امللــواثت، هــذه وجــود تقليــل علــى يعمــل والعــدد )tfc( للفطــرايت الكلــي العــدد التاليــة: العوامــل وجــود حتليــل مت وقــد والســيب، الرميــي ومهــا حمليــن ســوقن مــن العــوال( و القاشــع اجملففــة. األمســاك يف الكوليفــورم وبكتــراي staphylococcus aureus بكتــراي و e-coli بكتــراي وتعــداد )tvc( احليــوي الكلــي الــي األنشــوجة يف (g3.60×104 cfu/ml ) احليــوي الكلــي والعــدد (g5.59×105 cfu/ml ) للفطــرايت الكلــي العــدد أن النتائــج أظهــرت وقــد مت مجعهــا مــن ســوق الســيب كان أكثــر منهــا يف العينــات األخــرى. وبنــاء علــى وجــود هــذه امللــواثت يف األمســاك اجملففــة فإننــا نوصــي بتجفيــف الشــاطىء. رمــال علــى املباشــر التجفيــف مــن بــدال الشمســية اجملففــات اســتخدام علــى ونشــجع أفضــل، صحيــة ظــروف يف األمســاك الكلمات املفتاحية: التجفيف الشمسي ، جتفيف األمساك ، تلوث األمساك ، األمساك اجملففة ، التقييم امليكروبيلوجي. 54 squ journal of agricultural and marine sciences, 2021, volume 26, issue 1 microbiological assessment of locally dried fish in oman: technical note when it is attached by insects and larva. it was found that some fishermen apply insecticides to avoid this kind of attacks (bala & mondol, 2001). the presence of microorganisms affects the quality of dried fish. some studies showed that bacteria, molds, and yeasts are potential microorganisms that usually contaminate dried fish (akwuobu et al., 2019). therefore, it is important to determinate the microbiological quality of dried fish. the aim of this study was to verify the presence of microbiological contamination in dried fish collected from selected local markets; and to propose an engineering solution to reduce these contaminations. methodology two common types of traditionally dried fish in oman were collected namely; anchovy and shark (locally called owal) from two different places; buraimi and seeb fish markets. the anchovy samples were collected from packaged and unpackaged conditions from the two places. about 500 g was purchased from each place. they were placed in zipped bags and transported to the food microbiology laboratory at the college of agricultural and marine sciences, squ for analysis. media preparation all media were prepared according to al bulushi (2017) and each test was prepared using the media as mentioned in table 1. after preparing the media for each test, it was mixed with distilled water. then, each mixture was poured in a bottle and autoclaved at 121ºc for 2-2.5 h. after autoclaving, 15 ml of the agar media was placed in petri dishes and cooled at room temperature to solidify the media (al bulushi, 2017). total fungal count and total viable count from each sample, 25 g was placed in a sterile stomacher bag, and 225 ml of maximum recovery diluent was added in the stomacher bag (interscience/france) to achieve 1/10 (10-1) dilution. then, 10-2 and 10-3 dilutions were prepared. for plating, 0.1 ml (100 µl) was transferred from each tube of the 10-1, 10-2, and 10-3 dilution mixtures to duplicate plates of the potato dextrose agar (pda) plate aseptically. then, the mixture was spread using alcohol flamed spreading from the highest dilution to the lowest dilution (i.e. 10-3 to 10-1). all plates were incubated aerobically at an ambient temperature of nearly 23ºc for 3-5 days. after that, the colonies on plates were counted and reported (cfu/g) using equation 1. for total viable count, all procedures were the same as total fungal count except the differences with the type of agar used (spca), temperature (35ºc) and period of incubation of the plates (48 h). enumeration of bacteria the samples were stored in a freezer at -40ºc until used for the microbial analysis. then, the samples were analyzed for 3 types of bacteria; e. coli, staphylococcus aureus and coliforms as total colony-forming units (cfu/ml) using different agar media, as explained below. enumeration of e. coli, staphylococcus aureus and coliforms for e. coli, about 50 g of fish sample was taken, cut into small pieces and mixed together. then, a stomacher bag was placed in a beaker and only 25 g of the mixed pieces were placed in the bag. after that, 225 ml of diluent was added to the stomacher bag and blended for 1 min to achieve a homogenized mixture at 10-1 dilution. then, dilutions of 10-2 and 10-3 were prepared. for plating, 0.1 ml from each tube of the 10-1, 10-2, and 10-3 diluents were transferred to duplicate plates of tryptone bile x-glucuronide agar (tbxa) plate aseptically. then, the mixture was spread using alcohol flamed spreading from the highest dilution to the lowest dilution (i.e. 10-3 to 10-1). finally, incubation was done for all plates aerobically at 35ºc for 24 h and only blue or green colonies were counted and reported (cfu/g) using equation 1. for staphylococcus aureus, the diluents were prepared as explained earlier for the enumeration of e. coli in dried fish. for plating, molten baird-parker agar were used instead of molten tbx agar. finally, black colonies were counted and reported (cfu/g) using equation 1. for coliform species, the diluents were prepared as explained earlier for the enumeration of e. coli in dried fish. for plating, 1 ml from each diluent was transferred to sterile petri dishes. for each dilution, two plates were used. over a period of 15 min, approximately 12 ml of molten vrb agar at 44-47ºc was added. the medium with the inoculum was carefully mixed by horizontal movements (pour plate method) and the medium was allowed to cool down. finally, the dishes were incubated for 24±2 h at 35ºc and only pink colonies were counted and reported (cfu/g) using equation 1. moisture content and water activity the moisture content was determined by oven-drying the samples at 105oc for 24 h (ullah et al. 2016). the water activity (aw, unit less) of the sample was determined using a water activity meter. the correlation of moisture content and water activity with the analyzed microbial counts was studied using stata 13.0 (statacorp, usa) at α = 0.05. 55technical notes k. al-saadi, m. al-ismaili, al-ruzeiki, m. al-bulushi results and discussion microbial contamination the anchovy collected from seeb market had the highest tvc and tfc (5.59×105, 3.60×104 cfu/ml, respectively) as compared to all other samples (table 1). in addition, the presence of 3 species of bacteria; e. coli, staphylococcus aureus, and coliforms was detected in anchovy samples more than in shark samples as collected from the two markets. previous studies reported that anchovy had more contamination than the allowable levels (aliya et al., 2018; kumar et al., 2017). it was observed that the moisture content and water activity of the shark from buraimi market were the highest among all samples (30.37% and 0.74, respectively). in the case of dried fish storage, bala and mondol (2001) stated that microbial growth was inhibited when the moisture content was reduced to 25% and particularly mold growth could be avoided when the moisture content was not more than 15%. however, this was not the case in this study, as reported in table 2, which could be related to the types of contaminations present in the samples used in this study. although, the moisture content of anchovy was lower than 15%, large values of tvc and tfc were observed. the detected microbes in the analyzed samples could have come from several sources, namely, unhygienic handling of fish during drying and storage, and birds and animals’ droppings. in addition, long time opensun drying under high humidity environments enhances the growth of microorganisms (sablani et al., 2002). in general, major sources of contamination include polluted coastal water and soil, dust and unhealthy treatment practices (ginigaddarage et al., 2018). placing the fish directly on the sand is more susceptible to the contamination by dust, insects, and sand (bremner, 2002). in addition, the stability of microbial growth in dried fish depends on how much moisture they contain during processing and storage stages (logesh et al., 2012). rain and humid conditions hamper sun-drying by increasing the moisture content of dried fish and made them susceptible to blowfly larvae attacks (kleih et al., 2003). techniques to avoid the contamination the presence of microbes in dried fish presents a health hazard that needs to be prevented. to avoid the contamination of sand, dirt, and animals, the process of drying has to be done quickly using drying shelves, which can help to keep dried fish away from these sources of contamination (ward & beyens, 2015). solar dryers, like greenhouse tunnel dryers and forced convective solar dryers can also help to avoid physical and atmospheric-driven contamination and they can accelerate the drying process (sahu et al., 2016; seerangurayar et al., 2019). these types of solar dryers are highly recommended as they protect dried fish from many sources of contamination like rain, humid environment, dust, insects and animals as well as increase the drying rate. conclusion in this article, we verified the presence of microbiological contamination in two types of dried fish (anchovy and shark) available in local markets (seeb and buraimi). the major issue that affects the quality and safety of dried fish is the contamination caused by bacteria and fungi. results from this study evidenced the presence of fungi and three species of bacteria; e. coli, staphylococcus autable 1. the media used for each biological test. tests media manufacturer/country total fungal count potato dextrose agar (pda) sigma-aldrich/usa total viable count standard plate count agar (spca) sigma-aldrich/usa the diluent maximum recovery diluent sigma-aldrich/usa enumeration of e. coli tryptone bile x-glucuronide agar (tbxa) sigma-aldrich/usa enumeration of staphylococcus aureus baird parker agar (bpa) sigma-aldrich/usa enumeration of coliforms species violet red bile agar (vrba) sigma-aldrich/usa table 2. results obtained from different tests. fish type (market) xm (%) aw tvc=apc (cfu/ml) tfc (cfu/ml) e. coli (cfu/ml) s.aureus (cfu/ml) coliforms (cfu/ml) shark (seeb) 23.66 0.64 1.05×103 2.50×102 0 6.96×103 0 shark (buraimi) 30.37 0.74 1.05×104 2.00×103 0 1.33×104 0 anchovy (seeb) 14.54 0.69 5.59×105 3.60×104 4.77×102 1.64×106 1.78×103 anchovy (buraimi) 14.15 0.65 1.29×105 3.70×103 6.00×102 2.27×105 2.82×102 56 squ journal of agricultural and marine sciences, 2021, volume 26, issue 1 microbiological assessment of locally dried fish in oman: technical note reus and coliforms. the microbial contamination in anchovy samples was more than in shark samples collected from the two local markets. to avoid the contamination mentioned above, we recommend using solar dryers for fish drying instead of open-sun drying, as they protect the dried fish from different types of contamination and speed up the drying process. references akwuobu ca, antiev ws, ofukwu ra. (2019). fungal contaminants of smoke-dried fish sold in open markets in makurdi, benue state, north-central nigeria. food and nutrition sciences 10(3): 290-297. al bulushi im. (2017). the handbook of food microbiological analytical methods. nova science publishers, inc. al ghabshi a, al-khadhuri h, al-aboudi n, al-gharabi s, al-khatri a, al-mazrooei n, sudheesh ps. (2012). effect of the freshness of starting material on the final product quality of dried salted shark. advance journal of food science and technology 4(2): 60-63. aliya a, sudheesh ps, nasser aa, umkalthoum ak, wafaa ae, humaid ak, mahmood am, alia az, waleed ar, mahmood am. (2018). microbiological, chemical and nutritional quality and safety of salted cured fishery products from traditional dry fish processing plants in the sultanate of oman. food research 2(3): 279-86. bala bk, mondol mr. (2001). experimental investigation on solar drying of fish using solar tunnel dryer. drying technology 19(2): 427-436. belwal r, belwal s, al jabri o. (2015). the fisheries of oman: a situation analysis. marine policy 61: 237-248. bremner ha. (2002). safety and quality issues in fish processing. woodhead publishing and crc press, new york. fao. (2019). fishery and aquaculture country profiles. [http://www.fao.org/fishery/facp/omn/en (accessed 11 october 2020) ginigaddarage ph, surendra ih, weththewa wk, ariyawansa kw, arachchi gg, jinadasa bk, hettiarachchi ks, edirisinghe em. (2018). microbial and chemical quality of selected dried fish varieties available in sri lankan market. sri lanka journal of aquatic sciences 23(1). kleih, u., alam, k., dastidar, r., dutta, u., oudwater, n., & ward, a. (2003). livelihoods in coastal fishing communities, and the marine fish marketing system of bangladesh. synthesis of participatory rural appraisals in six villages, and assessment of the marketing system (nri report no. 2712). kumar gp, xavier km, nayak bb, kumar hs, venkateshwarlu g, balange ak. (2017). effect of different drying methods on the quality characteristics of pangasius hypophthalmus. international journal of current microbioly and appllied science 6: 184-195. logesh ar, pravinkumar m, raffi sm, kalaiselvam m. (2012). an investigation on microbial screening on salt dried marine fishes. journal of food resource science 1(1): 15-21. maf. (2018). statistical book on fishery. ministry of agriculture and fishery, oman. sablani ss, rahman ms, mahgoub o, al-marzouki a. (2002). sun and solar drying of fish sardines. proceedings of the international drying symposium, p 1662-1666. sahu tk, jaiswal v, singh ak. (2016). a review on solar drying techniques and solar greenhouse dryer. iosr journal of mechanical and civil engineering (iosrjmce) 13: 31-37. seerangurayar t, al-ismaili am, jeewantha lj, al-habsi na. (2019). effect of solar drying methods on color kinetics and texture of dates. food and bioproducts processing 116: 227-239. sultana n, hossain mt, siddique mp, uddin mi, dina ma, farhana z. (2010). microbial quality of dried fish of different areas chittagong and mymensingh districts of bangladesh. international journal of bioresearch 2(8): 1-5. ullah n, hazarika p, handique pj. (2016). biochemical quality assessment of ten selected dried fish species of north east india. international advanced research journal in science, engineering and technology 3(1): 30-33. ward a, beyens y. (2015). fish handling, quality and processing: training and community trainers manual. smartfish working papers. 001. port louis, commision del’ocean indien, mauritius. research paper journal of agricultural and marine sciences vol. 22 (1): 87–91 doi: 10.24200/jams.vol22iss1pp87-91 reveived 15 aug. 2016 accepted 19 dec. 2016 increasing water productivity enhances water saving for date palm cultivation in oman y. a. al-mulla1* and h. m. al-gheilani2 *1 yasseen al-mulla ( ) 1department of soils water and agricultural engineering, p.o. box 34, al-khod 123, college of agricultural and marine sciences, sultan qaboos university, sultanate of oman. email:yalmula@squ.edu.om. 2ministry of agriculture and fisheries, p.o. box 467, al-khwair 113, muscat, sultanate of oman introduction one total area of the sultanate of oman is 30.95 million hectares, where around 4.8%, i.e. 1.5 million hectares, of this area is considered suitable for growing crops. only 4.4% of these available arable lands, i.e. 0.21% of the total country area, are currently cultivated covering an area of 65967 hectares (world bank, 2015; maf, 2014). there are 7.6 million date palm trees currently planted in the farms in oman covering an area of 23241 hectares or 35% of total agricultural area in the sultanate in addition to 0.9 million palm trees planted in homes or for landscaping in public parks and beside the roads. hence, date palm is considered as plant number one in the country. the total production of date palm trees in 2014 was 317 million kg of dates. around 54% of these dates (fig. 1) were consumed by people locally whereas 24% and 19%of the dates were used for industry and as forage for animals, respectively, and 3% of them were exported outside the country (maf, 2015). the total production of date palm trees and the production per tree in the sultanate from 1998 to 2014 are زايدة إنتاجية املياه يعزز من توفري املياه من زراعة أشجار النخيل يف سلطنة عمان ياسني بن أمحد املال و محد الغيالين abstract. the total amount of water consumption needed to irrigate the cultivated lands in the sultanate oman is 1487 mm3. there are 7.6 million date palm trees currently planted in the farms in oman covering an area of 23241 hectares or 35% of total agricultural area in the sultanate in addition to 0.9 million palm trees planted in homes or for landscaping in public parks and beside the roads. hence, among all cultivated crops in oman, date palms are the major water consuming plants. they consume 558 mm3 that is 38% of total irrigation water and 31% of groundwater recharge that suffers an annual water deficit estimated at 316 mm3. these findings framed the main objectives of this study: (1) to describe the current status of date palm tree cultivation in the sultanate; (2) to suggest solutions to reduce high consumption of water while improve dates production; and (3) to explore how irrigation water can be saved through increasing water productivity through alternative date palm cultivation and irrigation practices. the water saving recommendation in this study was based on the collected from different sources in addition to the investigation on the water loss during irrigation practices. we found that it is possible to save a total of 396 mm3 of irrigation water by for instance reducing the cultivation of low quality/value date palm varieties and switching to modern over traditional irrigation systems. it is also important to determine the quality and value of the date palm cultivars to be planted in the proposed reduced area which will then contribute to an increased financial return for the farmers and thus to the country through increasing the water productivity by 64% of these new plots. keywords: water productivity; irrigation water; economical return; date palm trees; oman. امللخــص: امجــايل كميــة امليــاه الالزمــة لــري األراضــي املزروعــة يف ســلطنة عمــان هــو 1487 مليــون مــر مكعــب. ويبلــغ عــدد أشــجار النخليــل املوزرعــة يف عمــان حاليــا 7.6 مليــون شــجرة خنيــل تغطــي مســاحة قدرهــا 23241 هكتــار أي 35٪ مــن إمجــايل املســاحة الزراعيــة يف الســلطنة باإلضافــة إىل 0.9 مليــون شــجرة خنيــل مزروعــة يف البيــوت و احلدائــق العامــة وجبــوار الطــرق . وبالتــايل، مــن بــني مجيــع احملاصيــل املزروعــة يف عمــان، تعتــر النخيــل هــي النباتــات األكثــر اســتهالكا للميــاه. إهنــا تســتهلك 558 مليــون مــر مكعــب مــن امليــاه أي 38٪ مــن إمجــايل ميــاه الــري و 31٪ مــن امليــاه اجلوفيــة الــي تعــاين مــن عجــز مائــي ســنوي يقــدر بـــ 316 مليــون مــر مكعب.علــى ضــوء هــذه الــدالالت مت تأطــر األهــداف الرئيســية هلــذه الدراســة: )1( لوصــف الوضــع الراهــن لزراعــة شــجرة النخيــل يف الســلطنة. )2( لوضــع اقراحــات مــن شــأهنا تســاهم يف اجيــاد احللــول للحــد مــن اســتهالك الكميــات الكبــرة مــن امليــاه مــع حتســني إنتاجيــة التمــور. و )3( إلستكشــاف آليــة متكــن مــن ترشــيد ميــاه الــري مــن خــالل زيــادة إنتاجيــة امليــاه عــن طريــق اجيــاد بدائــل أخــرى ملمارســات زراعــة النخيــل وعمليــات ري هــذه األشــجار. اســتندت هــذه الدراســة علــى بيانــات مت مجعهــا مــن مصــادر خمتلفــة باإلضافــة إىل اســتقصاءات حــول فقــدان امليــاه مــن خــالل ممارســات الــري املختلفــة. لقــد وجدنــا أنــه مــن املمكــن توفــر مــا جمموعــه 396 مليــون مــر مكعــب مــن ميــاه الــري مــن خــالل علــى ســبيل املثــال احلــد مــن زراعــة أصنــاف النخيــل املنخفضــة اجلــودة / القيمــة والتحــول إىل أنظمــة الــري احلديثــة. ومــن املهــم أيضــا حتديــد األصنــاف اجليــدة مــن النخيــل ذات القيمــة العاليــة لزراعتهــا يف املســاحات املقرحــة والــذي سيســاهم يف زيــادة العائــد االقتصــادي ألصحــاب املــزارع والدولــة بشــكل عــام مــن خــالل زيــادة إنتاجيــة امليــاه بنســبة 64٪ مــن امليــاه املســتخدمة لــري هــذه النباتــات. الكلمات املفتاحيه: :إنتاجية املياه، أشجار النخيل، مياه الري، العائد االقتصادي، عمان 88 squ journal of agricultural and marine sciences, 2015, volume 19, issue 1 increasing water productivity enhances water saving for date palm cultivation presented in (fig. 2) (kamoonpuri, 2014; maf, 2014, maf; 2010, maf, 2007; maf, 2004a; maf, 1999) whereas (table 1) presents the annual production of top cultivars of date palm trees. these cultivars produce 44% of total dates production in oman (maf, 2010, 2013, 2015). from this table, it can be noticed that the five most productive date palm trees in the sultanate are “neghal”, “khesab”, “fard”, “khalas”, and “um silla”, with production percentages of 12%, 9.8%, 7.6%, 7.3%, and 7.1% of total dates production. each hectare planted with date palm trees produce an average of 6075 kg of dates with an average income of 1065 omr. the water recharge in the sultanate of oman is estimated at 1267 million m3 per year. additional water recharge comes from treated wastewater with amount of 42 million m3 and from desalination with an amount of 196 million m3. from the available water resources 1487 million m3 is used for agricultural purposes, whereas, 158 million m3 is used for domestic, commercial, municipal, and industrial purposes (al shibli, 2014, aljabri, 2013, fao, 2009, al-hattaly, 2005 and mcdonald, 2004). the water deficit in oman, however, is estimated at 316 million m3 i.e. 31% of total recharge because of groundwater out flowing due to storage depletion and sea water intrusion (al shibli, 2014, fao, 2009). the total amount of water consumption needed to irrigate the cultivated lands in the sultanate is 1487 million m3. wells are the dominating source of irrigation providing 1204 million m3 followed by aflaj (single falaj, which is an ancient canal based water distribution system) providing 164 million m3 and springs providing 119 million m3 of irrigation water (fluet et al., 2009; almamari, 2001; maf, 2014). around 907 million m3 of the irrigation water is consumed by the farming practices applying traditional irrigation systems whereas around 580 million m3 of water is consumed by modern irrigation systems (maf, 2014). among all cultivated crops in oman, date palms are the major water consuming plants followed by rhodes grass and alfalfa and then by other fruits and vegetables. the date palm trees consume 558 million m3 (fig. 3) that represent 38% of total irrigation water and 31% of groundwater recharge for an annual water deficit estimated at 316 million m3. rhodes grass and alfalfa on other hand consume 457 and 117 million m3 of irrigation water respectively while the remaining water for irrigation around 342 million m3 is used to irrigate the other fruits and vegetables (maf 2014, maf, 2015; al-hattaly, 2005, mcdonald, 2004). besides the fact of predominating the irrigation water consumption, 84% of date palm trees are irrigated by flooding an irrigation export food forage industry 0 20 40 date consumption (%) s ec to r figure 1. dates consumption in 2014 by different sectors in oman. 0 100 200 300 2000 2005 2010 2015 year a nn ua l d at e p ro du ct io n (k to n) figure 2. annual dates prodution (mkg) in oman. table 1. date cultivars annual production (mkg) in oman. date cultivar 2008 2009 2010 2011 2012 2013 2014 naghal 24.6 24.9 24.1 28.0 29.7 33.3 37.8 khussab 27.9 25.4 26.4 26.2 26.1 27.9 30.9 fardh 20.5 15.8 20.9 16.4 16.9 20.9 24.1 khallass 12.7 16.9 20.5 20.3 22.4 24.8 23.0 um silla 35.2 27.5 29.1 26.3 28.9 31.0 22.4 mabsali 31.2 19.4 14.7 19.4 19.9 19.5 18.9 shahel 12.6 16.9 19.7 16.6 17.4 19.1 18.4 khunaizi 11.3 15.8 15.8 13.7 15.6 17.2 14.9 qash na 8.3 9.9 7.0 8.5 9.1 7.8 89research article al-mulla , al-geilani system that causes a loss of half of supplied water (maf, 2004b). based on the fact that the water productivity of the date palm trees (table 2) does not go beyond 0.57 kg of yield/m3 of consumed water and 0.23 omr revenue/ m3 of consumed water (maf, 1999; maf 2014). there are around 300 varieties of date palm trees in oman (alal-ruqaishi, 2009) but some of these trees are of low quality and give very low production yet they are planted in large areas while others which are of high quality, are planted in small areas but give high production. other planted date palms trees in oman are not productive at all due mainly to salinity problems and also some of them are male type of trees. although people in oman prefer khalas dates they also consume other good quality dates like nighal, khessab, khenaizi and others while the consumption of low quality dates is almost negligible. these ground based information have led to a fact that only one half of planted date palm trees are producing high value dates (al-yahyai and khan, 2015; al-mamari, 2001). these findings focused the main objectives of this study which were (1) to evaluate the current status of date palm tree cultivation in the sultanate; (2) to suggest solutions for reducing high consumption of water and improving dates production at same time; and (3). to explore how irrigation water can be saved through increasing water productivity by finding alternative date palm cultivation and irrigation practices. methodology all data related to date palm trees in the sultanate of oman were collected and used as a base for this study. these data included scientific studies that determine the country’s groundwater recharge amount according to fao (2009), al-hattaly (2005) and mcdonald (2004). we also included data from agricultural census conducted by the ministry of agriculture and fisheries wealth which determined the date palm trees planted areas, water consumption, total and per tree production, and their different cultivars (maf, 2014; maf, 2004a). another data set used were those related to dates production per hectare of land in addition to the technical and economical returns of these dates and water productivity (maf, 2004b), historic date production data (maf, 2015; maf, 2013; maf, 2004a and maf, 1999) and data related to different cultivars of date palm trees in the sultanate and what are the most productive cultivars among them (maf, 2015; maf, 2000). the dataset indicated that only 50% of planted date palm trees were producing high value dates. hence, water consumption of the other 50% of lower quality date palm trees can be considered as water loss and removing these types of trees will result in water saving by 50% of total date palm water consumption which is 38% of total irrigation water. furthermore, 84% of date pam cultivations are under traditional irrigation systems which consume around 468 million m3 of irrigation water. according to reported water saving using modern irrigation systems over traditional methods (e.g. reilly, 2005), around 50% of the water cunsumption could be saved if switching to modern irrigation systems. water productivity of the proposed changes on date palm cultivations is based on above data and analysis that is calculated in terms of the drop per crop (yield) and the economic return (revenues) using the following two equations: wp y = y w (1) wp e = r w (2) where wpy is the water productivity based on yield (crop per drop) in kg·m-3, wpe is water productivity based on economic return in omr·m-3 , y is date palm tree yield in kg, w is amount of irrigation water consumed to irrigate the palm tree in m3 , and r is the revenue in omani rials (omr). results and discussion as mentioned earlier date palm trees consume 38%, i.e. 558 mm3 of the irrigation water in oman, hence, the water loss due to planting of low value date palm trees accounts for (0.5 x 38 = 19%), i.e. (0.5 x 558 = 279 million m3) of irrigation water. this means that out of 1487 million m3 of total irrigation water, only 279 million m3 will be used to irrigate the date palm trees while the remaining 279 million m3 could be saved for other water usage after removing low quality types of date palm trees. by replacing the traditional irrigation systems which are applied in 84% of the proposed reduced date palm cultivation, this means about (0.5 x 0.84 x 279 =117) an 0 200 400 alfalfa date palm rhodes grass vegetables crop w at er c on su m pt io n ( m m 3 yr −1 ) figure 3. dates consumption in 2014 by different sectors in oman. 90 squ journal of agricultural and marine sciences, 2015, volume 19, issue 1 increasing water productivity enhances water saving for date palm cultivation additional 117 million m3 of irrigation water could be saved for other water consumption purposes and only (279 117 =) 162 million m3 will actually be needed to irrigate the high quality types of date palm trees. by combining both practices of avoiding planting low quality date palm trees and introducing modern irrigation systems, the total water saving can reach up to (279 +117 = 396) 396 million m3 that can be used in reducing the groundwater recharge deficit and increasing water productivity. these practices will encourage planting other types of crops of high quality and value which will contribute in increasing the economical return to the farmers and to the country. the water productivity, after introducing the proposed changes mentioned above of the cultivation and irrigation practices of date palm trees, can be calculated using equations 1 and 2. we showed above that the total production of date palm trees in 2014 was 317 million kg of dates and that only 50% of planted dates tress should be kept to account for high quality and production trees while the other 50% should be removed as it consists of low quality, low productive, or non-productive types of date palm trees. if we we assume that high quality and yield dates have contributed to total production in 2014 by as much as 80%, i.e. with a production of (0.8 x 317 =), the production of these “good quality” trees was 253.6 million kg. we also showed above that by replacing traditional irrigation with modern systems would reduce irrigation water consumption to 162 million m3 to irrigate the high quality types of date palm trees. if we consider that the average price of dates was 0.400 omr per kg, the water productivity based on economic return can be obtained as [(0.400 omr x 253.6m kg) / 162m m3] = 0.63 omr/m3, while the water productivity based on yield (crop per drop) can be obtained as (253.6m kg / 162m m3 = 1.56 kg/m3). therefore, introducing the above mentioned changes of the cultivation and irrigation practices of date palm trees will increase the water productivity by 64% from 0.57  kg·m-3 to 1.56  kg·m-3 and from 0.23  omr·m-3 to 0.63 omr·m-3. conclusion date palm trees consume 558 million m3 that is 38% of total irrigation water and 38% of groundwater recharge. the water saving recommendation in this study was based on the above mentioned data in addition to the investigation on the water loss during irrigation practices. it is shown in this study that changing cultivation practices and converting irrigation system to modern system would increase the water productivity by 64% which should contribute in increasing the economical return for the farmers and so the country. references al-hattaly, s.a.s. 2005. water resources assessment and management practices in the sultanate of oman. the international workshop in public participation, awareness, and information exchange for water resources development and management. p. 1-13. al-jabri, i.o. 2013. water situation in oman. in: proceedings of the 1st meeting of the comcec agriculture working group. comcec coordination office, ankara, turkey al-mamary, s. 2001. the importance of modern irrigation systems and how to increase its performance. the gcc water week: scientific symposium. ministry of agriculture and fisheries. muscat, sultanate of oman. al-ruqaishi, i. 2009. the current status of date palm biotechnology in oman. qatar university life science symposium on date palm research, biotechnology and conservation perspectives, 15-16 december, doha, qatar. al shibli, s. 2014. sultanate of oman’s strategy for securing water resources. oral presentation. wsta 11th gulf water conference. muscat. 20-22 october. al-yahyai, r., m. khan. 2015. date palm status and perspective in oman. in: date palm genetic resources and utilizatio. editors: jameel am al-khayri, shri mohan jain, dennis v johnson. springer, pp.207-240 fao (food and agriculture organization of the united nations). 2009. groundwater management in oman. draft synthesis report. food and agriculture organization of the united nations, room fluet, m.j., vescovi, l. and bokoye, a.i., 2009. the united nations world water development report–n° 3-2009–water and climate change (citizen mobilization, a source of solutions). unesco. kamoonpuri, h. 2014. love dates? go to nizwa today. oman daily observer newspaper (monday 13th, october 2014). mcdonald m. 2004. master plan for the water sector: main report. ministry of economy. muscat, sultanate of oman. maf. 1990. the general map for development. ministry of agriculture and fisheries. muscat, sultanate of oman. maf. 1999. a study on the investment opportunities in the field of agricultural production in the sultanate of oman. ministry of agriculture and fisheries. muscat, sultanate of oman. maf. 2000. national strategy in developing the production of date palm trees. ministry of agriculture and fisheries. muscat, sultanate of oman. maf. 2004a. the sultanate dates production (2003 -2004). department of statistics and information. 91research article al-mulla , al-geilani ministry of agriculture and fisheries. muscat, sultanate of oman. maf. 2004b. agricultural census. ministry of agriculture and fisheries. muscat, sultanate of oman. maf. 2007. annual book for 2007 agricultural census. ministry of agriculture and fisheries. muscat, oman maf. 2010. annual book for 2010 agricultural census. ministry of agriculture and fisheries. muscat, oman maf. 2013. annual book for 2013 agricultural census. ministry of agriculture and fisheries. muscat, oman maf. 2014. agricultural census for years 2012-2013. volume 1. ministry of agriculture and fisheries. muscat, oman maf. 2015. agricultural and fisheries sectors performance: productivity and economic indicators between 2011 and 2014. directorate general of planning and development. ministry of agriculture and fisheries, muscat, oman reilly, j. 2005. drip irrigation: a water conserving solution. irrigation & green industry network, a division of isg communications, inc, usa worldbanck. 2015. oman: the world bank. available at: http://data.worldbank.org/country/oman. accessed april 2015. img005 img006 img007 img008 img162 img163 img164 img165 img166 img167 img168 img169 img091 img092 img093 img094 img095 img096 img097 perspective papers journal of agricultural and marine sciences 2021, 26(1): 62–65 doi: 10.24200/jams.vol26iss1pp62-65 reveived 09 sep 2020 accepted 30 nov 2020 effect of covid-19 pandemic situation on the teaching of graduation projects and internship type courses in undergraduate degree programs hemanatha p. w. jayasuriya hemantha p. w. jayasuriya ( ) hemjay@squ.edu.om, department of soils, water and agricultural engineering, college of agricultural and marine sciences, sultan qaboos university, muscat, oman perspectives the covid-19 pandemic has been denominat-ed as a public health crisis by the world health organization (who) (who covid-19, 2019). without discrimination, the virus has affected all countries, developed and developing, including the span of different societal levels. the pandemic has had a monumental effect on the livelihood of people resulting in all gatherings being prohibited including the sectors pertaining to education. the effect on education at all levels has become one of the main concerns for academic institutions at primary, secondary and tertiary levels. one positive is various new technological developments emerged with online or distance teaching, however there are significant components such as; laboratory practical’s, field work, field visits, projects, internships, and co-op type training coming under secondary and tertiary education that must not be compromised in order to avoid any detriment to the students education. the impediments due to the pandemic on tertiary education may have an adverse effect as some of the online teaching and evaluation techniques utilized are grossly violating the stipulated accreditation requirements in some college degree programs. identification of effective teaching methods in light of the covid-19 pandemic is in continuous discussion amongst academics and educational institutions. the uses of e-learning techniques and computer-based innovations have largely answered some of the prevailing areas of concern (hetsevich, 2017; parashchenko, 2020; rosel, 2020). however, there are obstacles to be met for أتثري حالة جائحة covid-19 على تدريس مشاريع التخرج والتدريب امليداين يف برامج درجة البكالوريوس هيمانثا جاايسرياي abstract. the covid-19 pandemic has negatively impacted all aspects of social life all over the world. it has also significantly affected the global education system from primary to tertiary levels. the effect on college education has likely to be substantial, as some specializations and academic activities have undergone severe setbacks by virtue of the need for the presence of dynamic, face to face student-teacher interactions to provide effective teaching delivery. this article pinpoints the evident setbacks from a quality assurance perspective, when considering selected components such as graduation projects, internships, laboratory and field work in certain degree programs. keywords: covid-19 pandemic, accreditation criteria, student learning outcomes, teaching delivery, graduation projects, internships املســتخلص:أثرت جائحــة covid-19 ســلًبا علــى مجيــع جوانــب ومناحــي احليــاة االجتماعيــة يف مجيــع أحنــاء العــامل لــكل مــن البلــدان املتقدمــة والناميــة. كمــا أثــرت بشــكل كبــري علــى نظــام التعليــم العاملــي مــن املرحلــة االبتدائيــة إىل املراحــل اجلامعيــة املتقدمــة. ولقــد كان التأثــري علــى مرحلــة التعليــم اجلامعــي كبــريًا ، حيــث تعرضــت بعــض التخصصــات واألنشــطة األكادمييــة النتكاســات شــديدة بســبب احلاجــة إىل وجــود تفاعــل ديناميكــي وجهــاً لوجــه بــن الطــاب واحملاضريــن لتقــدمي تعليــم فعــال. حتــدد هــذه املقالــة النكســات الواضحــة مــن منظــور ضمــان اجلــودة مــن خــال اختيــار عناصــر للتقييــم مثــل مشــاريع التخــرج، والتدريــب امليــداين، والعمــل املخــربي وامليــداين لعــدد مــن الربامــج أالكادمييــة. الكلمات املفتاحية: جائحة كوفيد-19، معايري االعتماد، خمرجات التعليم، طرق التدريس، مشاريع التخرج، التدريب العملي. 63perspective papers hemantha p. w. jayasuriya courses with a specific nature that relies on active interactions to meet particular teaching objectives such as courses with projects, fieldwork and, laboratory components. in addition to that, the execution of internships widely used in engineering, science and technology education at college level that needs hands-on experiences were notably affected. this article has taken a few examples to provide an overview of the challenges encountered due to the pandemic in the teaching delivery of capstone courses, graduation projects and the execution of internship programs embedded in the study plan of the agricultural engineering degree program at sultan qaboos university, oman. the course outlines of these courses are adhered to the abet (accreditation board for engineering and technology) accreditation criteria and the teaching objectives, continuous and final assessments are aligned with abet specified student learning outcomes (slos). during the course teaching delivery in capstone-graduation projects, students are expected to engage with real-world, meaningful projects that are low-cost and use appropriate-technology. as a part of creative thinking process with direct interactions by the instructor, the project topic identification is given as a prominent brain-storming task and follows an area of national or regional importance that is feasible for a small group of students to carry out. in capstone project type courses, students are required to select a project, design and develop, prototype fabrication, performance evaluation, and provide reports and oral presentations defending the outcomes of their project for assessment. consequently, evaluations are based on the accomplishment of slos; such as the application of engineering principles, use of a creative thinking approach, and adoption of appropriate strategies and standard procedures for solving design problems, engagement in life-long learning, team work for interpretation and presentation of project outcomes are also of significance (abet criterion 3, 2019). before this pandemic situation, student teaching evaluations were on the high end (above 3.5/4.0) and with highly positive comments under open-ended questions, such as “satisfaction on achievements of making something workable solving a identified problem”, “success due to teamwork and continuous instructor interaction” etc. some of the prototypes developed by student groups won competitions (trc/occ awards, 2019; al watan, 2019), and were submitted for patents and commercialization programs, and some extended for postgraduate research studies (al-hinai and jayasuriya, 2020; al-hinai et al., 2019; jayasuriya et al., 2018). before covid-19, the teaching delivery of these courses could be considered as high-impact teaching practice making it a captivating learning approach for students. however, under the influence of this pandemic, teaching delivery of these courses has become a serious challenge along with the need to satisfy the accreditation and quality assurance requirements. considering the importance of not delaying the graduation of students, alternative online teaching and assessment methods have been identified by academic institutions and relevant authorities around the globe. having stated the possibilities of online teaching with new technologies, there are components of teaching that cannot be compromised and compensated by this online approach, illustrating the harsh effects of the covid-19 pandemic. two such areas in undergraduate programs are internships and graduation projects (shown in figure 1); both are considered essential components of any undergraduate curriculum. when it comes to the internship component, undergraduate students are supposed to undergo training with career-guidance professionals at relevant work establishments where they are given status as trainee employees. due to the pandemic, some institutions and programs have initiated online internship programs; however, the success of these approaches will be program-specific or depend on the nature of the degree program, but would not be properly replicated. similarly, for the graduation project component, undergraduate students individually, or in small groups should engage in realistic projects relevant to their field of study under the supervision of an academic or professional in the same specialization. these projects enable them to accomplish some of the slos stipulated by the degree program objectives under the accreditation process. such slos include the; application of scientific or engineering principles, a creative thinking approach, the use of appropriate strategies and standard procedures for solving realistic problems, engagement in life-long learning, team work and brain-storming for acquiring solutions, and finally the successful interpretation and presentation of the project outcomes. the above-mentioned learning outcomes are specified as requirements by abet (abet criterion 3, 2019). project based learning (pbl) method (pbl, 2020) is currently one of the recommended approaches that facilitates online delivery of teaching and instructions for successful completion of specific project type tasks such as graduation projects to some extent. however, the projects of development and validation nature that fall under engineering and technology areas will not be completely successful without having the necessary student-teacher interactions and hands-on activities. conclusion as the pandemic seems to continue for the present and until uncertain future, there are major challenges for the academics in these specific areas to find alternative active teaching delivery methods to overcome possible learning deficiencies that may impact their graduates during the pandemic period. as a short-term alternative, degrees can be awarded pending completion of such components once the cessation of the pandemic situation. 64 squ journal of agricultural and marine sciences, 2021, volume 26, issue 1 effect of covid-19 pandemic situation on the teaching of graduation projects and internship type courses in undergraduate degree programs unfortunately, an enormous level of uncertainty lies ahead due to uncontrollable fluctuations in covid-19 infections with multiple waves appearing in some countries. it is time for academic institutions and potential employers around the globe to create internationally acceptable guidelines on accreditation and quality assurance standards for the graduates completing their degrees during the covid-19 global pandemic. moreover, there is a dire need for innovating and developing new teaching delivery methods to mitigate abovementioned deficiencies as long-term solutions, not only for covid-19, but also for any future pandemic situation. references abet criterion 3. (2019). https://www.abet.org/accreditation/accreditation-criteria/criteria-for-accrediting-engineering-programs-2019-2020/#gc3 al-hinai a, jayasuriya h, al-adawi s, al-mahdouri a. (2019). ergonomic performance evaluation of date stripping process, advances in intelligent systems and computing, springerbook series (aisc), volume 789, p. 74-84. al-hinai a, jayasuriya, h. (2020). development of a stripper machine for al-mabsili dates and evaluation of human interactions and performances, advances in intelligent systems and computing, springer book series (aisc), volume 1018, p. 737-742. trc/occ awards. (2019). sawsan al-khanbashi won the best project idea in the first phase of the innovation room award for a project “designing a dried lime pulp extraction machine” the research council and oman chamber of commerce awards 2019, oman tv, september 16, 2019. al watan. (2019). “anfal al hamdani wins a project related to a dried lime extraction machine at qatar foundation competition”, al watan newspaper, oman, november 11, 2019. jayasuriya hpw, al-hinai, a, al-adawi s, al-mahdouri, a. (2018). comparison of ergonomic performance evaluation in mechanized and traditional date stripping processes, asabe library paper no. 1800790, asabe annual international meeting 2018 (doi:10.13031/aim.201800790.. hetsevich i. (2017). advantages and disadvantages of e-learning technologies for students. https://www. joomlalms.com/blog/guest-posts/elearning-advantages-disadvantages.html (accessed 20 october, 2020) parashchenko t. (2020). the undeniable benefits of e-learning in the education industry. https://huskyjam.com/blog/what-are-the-benefits-of-e-learning/ (accessed 18 october, 2020) pbl (2020). pbl works. https://www.pblworks.org/ what-is-pbl (accessed 15 october, 2020) figure 1. examples of graduation projects (a and b) and internship activities (c) with essential hands-on practice needed for creative thinking and skills development in undergraduate studies 65perspective papers hemantha p. w. jayasuriya rosel, c. d. (2020). advantage of e-learning. blog cae. https://www.cae.net/advantage-of-elearning/ (accessed 15 october,2020) who covid-19. (2019). coronavirus disease (covid-19) https://www.who.int/emergencies/diseases/novel-coronavirus-2019 (accessed 10 october, 2020). research paper journal of agricultural and marine sciences vol. 23 : 76– 80 doi: 10.24200/jams.vol23iss1pp76-80 reveived 13 mar 2018 accepted 7 oct 2018 bacterial infection in farmed barramundi juveniles, lates calcarifer buthaina al-khaziri, azhar al-busaidi, adil al-sulimani, najla al-mandhari,*gilha yoon *1dr. gilha yoon( ) ghyoon@squ.edu.om. department of marine science and fisheries, college of agricultural and marine sciences, sultan qaboos university, p.o. box 34, al-khod 123, sultanate of oman introduction barramundi, lates calcarifer is a catadromous fish of the family latidae and the order of per-ciformes. this species is widely distributed from the indo-west pacific region to papua new guinea and northern australia. barramundi has been one of the most important cultured finfish in asian countries. this fish has become the second highest potential species for freshwater aquaculture after tilapia in the sultanate of oman. due to the recent introduction of barramundi aquaculture in oman, there has been an interest to study this species. however, as any other cultured fish species; a significant economic damage has been reported in farmed barramundi due to various infectious pathogenic bacteria around the world. bacterial infections of several species are being identified as the major cause of losses in the aquaculture industry (bromage et al. 1999). a gram-positive coccus of the species lactococcus garvieae has been recorded as a zoonotic pathogen that has been identified as one of the major causative agents of aquaculture pathogenic problems worldwide (chen et al. 2001). the gram-negative aeromonas sobria has also been identified as a primary pathogenic causative agent of many fish species (jurajmajtán et al. 2012). many of modern and effective drugs and antibiotic are synthesised from traditional folk of medicine (natarajan et al., 2003). therapeutic efficacy of many different plants has been discovered in the traditional medicine practices (al maqbool et al.1985). the healing attribution of henna leaves has been known for centuries and it is a subject of scientific studies (azaizeh et al. 2003). this plant is scientifically known as lawsonia inermis that belongs to the family lythraceae (abdulmoneim 2007). henna leaves contain lawsone (2-hydroxy-1, 4-napthoquinone) components that are red orange in colour. (abdulmoneim 2007). the chemical data of the henna leaves prompted to investigate its antibacterial دراسة العدوى البكتريية ألمساك الرباموندي املستزرعة بثينة اخلزيري وأزهار البوسعيدي وعادل السليماين وجنالء املنذري وجيلها يوين abstract. in 2016, barramundi, lates calcaifer juveniles imported from thailand to the aquaculture station at sultan qaboos university exhibited remarkable external clinical signs of losing scales, severe muscle necrosis, and ascites. fin rot was also observed in the diseased fish. the mortality reached more than 90% and it was assumed that some bacterial species were associated with the diseased fish. the objective of the present study was to investigate the infection route of disease, revealing the causative agent and finding the most effective antibiotic treatment. the suspected pathogen vehicle was mosquito larvae in the outlet of the culture tank as bacterium was isolated inside the mosquito larvae. primary, traditional phenotypic tests and the vitek test confirmed that the bacteria were pathogenic aeromonas sobria and lactococcus garvieae. eight of the most commonly used antibiotics in the aquaculture industry was used for antibiotic susceptibility test. it showed that that gentamycin was the most effective antibiotic while the most effective environmentally friendly source was effort of henna, lawsonia inermis, at a concentration of 10%. keywords: barramundi, lates calcaقifer, mortality, antibiotic, aeromonas sobria, lactococcus garvieae, henna. املســتخلص: عام 2016، أظهرت أمساك الرباموندي املســتوردة من تايالند إىل حمطة اإلســتزراع الســمكي يف جامعة الســلطان قابوس عالمات ســريرية خارجيــة ملحوظــة كفقــدان الزعانــف، خنــر العضــالت احلــاد، واالستســقاء. كمــا لوحــظ تــآكل الزعانــف يف األمســاك املريضــة. بلغــت نســبة الوفيــات أكثــر مــن 90% وقــد أفــرض أن عــدوى بكترييــة كانــت الســبب يف هــذه الوفيــات. اهلــدف مــن هــذه الدراســة هــو البحــث يف طريقــة العــدوى البكترييــة، كشــف العامــل املســبب هلــا، وإجيــاد املضــاد احليــوي األكثــر فعاليــة. الناقــل املشــتبه هلــذه العــدوى هــي يرقــات البعــوض املوجــودة يف خــزان تفريــغ امليــاه مــن أحــواض اإلســتزراع الســمكي، حيــث مت عــزل البكترييــا مــن داخــل الريقــات. أكــدت التحليــالت التقليديــة األوليــة، وحتليــل vitek أن البكترييــا املســببة للمــرض هــي aeromonas sobria وlactococcus garvieae . مت اســتخدام مثانيــة أنــواع مــن املضــادات احليويــة األكثــر اســتخداما يف االســتزراع الســمكي يف اختبــار احلساســية للمضــادات احليويــة. أظهــرت الدراســة أن gentamycin كان املضــاد احليــوي األكثــر فعاليــة ضــد البكترييــا املســتخلصة، يف حــن أن أوراق احلنــاء lawsonia inermis هــي املضــاد احليــوي الصديــق للبيئــة بركيــز %10. الكلمات املفتاحية: الرباموندي، ليتس كالكريفر، املضادات احليوية، إيروموناس سوبريا، الكتوكوكوس غارفيي، احلناء. 77research article al-khaziri, al-sulimani, al-mandhari,yoon activity. as disease prevention and control is fundamental to the success of aquaculture, therefore, the present study aimed to investigate the infection route of diseased barramundi, to reveal the causative agent that causes mass mortality and to find the most effective antibiotic treatment and finally to screen environmentally-friendly treatment methods derived from omani herbs. materials and methods different tests like primary, traditional phenotypic and experimental challenge tests were applied to identify the pathogenic vehicles that cause such a mass barramundi mortality. an antibiotic susceptibility test was also applied to find the most effective treatment. fish history of samples in august 2016, barramundi juveniles were imported from thailand to the aquaculture station at sultan qaboos university. there was an observed increase in the morbidity and mortality of the fish, where more than 90% of fish died in that period. the fish showed remarkable external clinical signs of scales losing, severe muscle necrosis, ascites, and fin rot (figure 1, a and b). isolation of bacteria the suspected pathogen vehicle (mosquito larvae) were collected from the outlet of the culture tank and grouped according to their different life stages. the bacteria were isolated from each stage and cultured in tryptone soya agar (tsa). the cultured bacteria were incubated at 37oc for 24 hours. each colony of the cultured bacteria was cultured again in separated tsa plates. the plates were incubated at 37oc for 24 hours. identification of bacteria primary test gram staining was used for the isolated bacteria to identify the group of bacteria; whether they were gram-positive or negative. secondary test a 3% koh solution was used for a primary test to divide the groups of bacteria into gram positive and gram negative. a densichek plus was used to measure the density of the bacteria used: a saline solution was added to the samples to make the density between 0.03 to 0.5 mg/ml. an identification machine (vitec ltd.) was used to identify the bacterial species, within 24 hours automated. table 1. the eight antibiotics used and their average inhibition zone for the aeromonas sobria species. antibiotics disk potency (µm) diameter of zone of inhibition (mm) average inhabited zone (mm) susceptible intermediate resistant oxytetracycline (ot 30) 30 ≥ 23 19-22 ≤ 18 24 ± 0.1 ciprofloxacin (cip 5) 5 ≥ 21 16-20 ≤ 15 24 ± 0.1 erythromycin (e 15) 15 ≥ 21 16-20 ≤ 15 25 ± 0.2 chloramphenicol (c 30) 30 ≥ 21 18-20 ≤ 17 21 ± 0.1 gentamycin (cn 10) 10 ≥ 15 13-14 ≤ 12 22 ± 0.2 tetracyclin (te 30) 30 ≥ 28 25-27 ≤ 24 25 ± 0.2 nitrofurantoin (f 300) 300 ≥ 17 15-16 ≤ 14 21 ± 0.1 ampicillin (a 10) 10 0 figure 1. remarkable external clinical signs ofthe infected fish: scale loss, severe muscle necrosis ad fin rot. 78 squ journal of agricultural and marine sciences, 2018, volume 23, issue 1 bacterial infection in farmed barramundi juveniles, lates calcarifer experimental challenge test to identify the causative agent of the mass mortality, an experimental challenge test was performed by infecting healthy barramundi juveniles by the suspected bacteria extracted from the mosquito larvae. the fish were kept and treated under the same conditions as the cultured ones, where the control fish were treated in a similar manner without bacteria. the infected fish were examined for the clinical signs of disease. treatments susceptibility test of commercial antibiotics the antibiotic susceptibility test was carried out using eight of the most commonly used antibiotic in the aquaculture industry (oxytetracycline, ciprofloxacin, erythromycin, chloramphenicol, gentamycin, tetracyclin, nitrofurantoin, and ampicillin). iso-sensitest agar (oxoid) was used in this test. the diameter of the inhibition zones of the antibiotics were measured (mm) and compared with the antibiotic standard table from oxoid. environmentally-friendly treatment alcohol based extraction was applied for two different omani herbs (henna, lawsonia inermis and zamuta). the henna and zamuta leaves were grounded and mixed with 100% ethanol for about 24 hours. the extracts were filtered to separate any solids and mixed with iso agar plates with 5 different concentrations of 10%, 5%, 2.5% 1% and 0.5%, respectively. a pure culture of the bacteria was diluted with pbs (phosphatebuffered saline) and inoculated in each plate. the plates were incubated at 37oc for 24 hours. the same concentrations of the henna extract were tested for their antibacterial activity using the spectrophotometer device. results identification of bacteria the isolated pathogenic bacteria were aeromonas sobria and lactococcus garvieae. these bacteria have been reported to cause loss of scales, severe muscle necrosis, and ascites or to cause fish mortalities in some cases. experimental challenge test the challenge test was applied to fulfil the causative agent of the mortality and compare the clinical signs of the killed fish. the fish died within 24 hours after infection, and they displayed darkened, and with some losing scales, severe muscle necrosis, and fin rots. in the control fish tank, no mortality occurred. antibiotic test commercial antibiotics tables 1 and 2 show the results of the eight different antibiotics used for the two species of bacteria (aeromonas sobria, and lactococcus garvieae). the most effective antibiotic for the lactococcus garvieae and aeromonas sobria was gentamycin (cn 10) with an average inhabited zone of 22 ±0.2 mm and 24 ± 0.3 mm respectively. generally, both lactococcus garvieae and aeromonas sobria were resistant against ampicillin (a 10). henna extract showed more bio-activity against bacteria in at the concentrations of 10% and 5%, while it shows low bio-activity at the concentration of 2.5% and no activity against bacteria at the lower concentrations. for the zamuta extracts, the bio-activity was low at the concentration of 10%, while it shows no activity at the lower concentrations (fig. 2). discussion table 2. the eight antibiotics used and their average inhibition zone for the lactococcus garvieae species. antibiotics disk potency µm diameter of zone of inhibition (mm) average inhabited zone (mm) susceptible intermediate resistant oxytetracycline (ot 30) 30 ≥ 23 19-22 ≤ 18 25 ± 0.1 ciprofloxacin (cip 5) 5 ≥ 21 16-20 ≤ 15 23 ± 0.1 erythromycin (e 15) 15 ≥ 21 16-20 ≤ 15 26 ± 0.1 chloramphenicol (c 30) 30 ≥ 21 18-20 ≤ 17 21 ± 0.2 gentamycin (cn 10) 10 ≥ 15 13-14 ≤ 12 24 ± 0.3 tetracyclin (te 30) 30 ≥ 28 25-27 ≤ 24 27 ± 0.2 nitrofurantoin (f 300) 300 ≥ 17 15-16 ≤ 14 20 ± 0.1 ampicillin (a 10) 10 0 79research article al-khaziri, al-sulimani, al-mandhari,yoon bacterial identification and experimental challenge test both pathogenic aeromonas sobria and lactococcus garvieae have been reported to infect and kill fish in the aquaculture industry (chen et al. 2001, majtán et al. 2012). in both cases the infected fish from the farm and from the challenge test, the clinical signs are similar. it also assumed that the pathological findings are similar within the visceral cavity. lactococcus garvieae infection in fish causes lesions in the vascular endothelium, hemorrhages, swollen abdomens, and accumulation of ascitic fluid that mainly affect the spleen, liver, brain, gut, kidney, and heart (vendrell et al. 2006). the pathogenic aeromonas sobria has been reported to cause hemorrhages and bleeding of skin lesions (majtán et al. 2012). aeromonas sobria and lactococcus garvieae may act as a primary pathogen and a potential risk factor for barramundi with mosquito larvae acting as potential reservoir for the pathogens. antibiotic test commercial antibiotics both of the isolated bacteria only showed resistance against ampicillin, whilst gentamycin was the best at killing or inhibiting the growth of these bacteria. environmentally-friendly alcoholic based extraction henna plant has been known for their healing attribute that considered as an active agent against bacteria and fungi (abdulmoneim 2007). since henna shows a high biological antimicrobial activity, it can be used for any microbial infection without any side effects or bacterial resistance (abdulmoneim 2007). henna leaves contain glycosidic compounds like lawsone (2-hydroxy-1,4-naphthoquinone) which also known as hennotannic acid, gallic acid, α-d-glucose and tannic acid (ostovari 2009). these compounds have been also proved for their effective antimicrobial activity against human bacteria (abdulmoneim 2007). however, zamota leaves did not show high antimicrobial activity against the isolated bacteria. conclusion it is suggested that aeromonas sobria and lactococcus garvieae can act as a primary pathogen for barramundi that cause a risk of mass mortality. the clinical signs for both bacterial species were lesions in the vascular endothelium, hemorrhages, swollen abdomens, accumulation of ascitic fluid, and bleeding from skin lesions. the most effective antibiotic against these pathogenic bacteria was gentamycin while henna extract from screened herbs proved to be also highly effective against these bacteria. acknowledgement the authors would like to thanks to ig/agr/fish/16/01, sultan qaboos university for financial support of this study. refrences abdulmoneim ma. 2007. evaluation of lawsonia inermis linn. (sudani henna) leaf extracts as an antimicrobial agent. research journal of biological sciences 2 (4), 419-423. almaqbool az, bashir, ak, farouk, a, salih, akm. 1985. antimicrobial activity of certain sudanese plants used in folkloric medicine screening for antifigure 2. the bio-activity for both a henna, (lawsonia inermis) and b (zamuta) extracts against bacteria at different concentrations. 80 squ journal of agricultural and marine sciences, 2018, volume 23, issue 1 bacterial infection in farmed barramundi juveniles, lates calcarifer microbial activity (iv). fitoterapia, 56: 331. azaizeh h, fulder s, said k, khalil o. 2003. ethno-botanical knowledge of local arab practitioners in the middle eastern region. fitoterapia, 74: 98-108. barramundi. (november 16 2017). retrieved november 18, 2017, from https://en.wikipedia.org/wiki/barramundi. bromage es, owens l. 2002. infection of barramundi lates calcarifer with streptococcus iniae: effects of different routes of exposure. discipline of microbiology and immunology, james cook university, townsville, queensland 4811, australia, diseases of aquatic organisms 52, 199–205. hittino ec. 1999. actococcus garvieae and streptococcus iniae infections in rainbow trout oncorhynchus mykiss: similar, but different diseases. diseases of aquatic organisms 36, 227–231. majtán j, černy j, ofúkaná a, takáč p, kozánek m. 2012. mortality of therapeutic fish garra rufa caused by aeromonas sobria. asian pacific journal of tropical biomedicine, 2(2), 85-87. natarajan mr, lalithankumar d. 1987. leaf extracts of lawsonia inermis as antifungal agent. current science 56:1021-1022. ostovaria a, hoseinieha sm, peikaria m, shadizadehb sr, hashemia sj. 2009. corrosion inhibition of mild steel in 1 m hcl solution by henna extract: a comparative study of the inhibition by henna and its constituents (lawsone, gallic acid, α-d-glucose and tannic acid). corrosion science, 51(9), 1935-1949. vendrell d, balcázar lj, ruiz-zarzuela i, de blas i, gironés o, múzquiz jl. 2006. lactococcus garvieae in fish: a review. comparative immunology, microbiology and infectious diseases, 29 (4), 177-198. img050 img051 img052 img053 img054 img055 img140 img141 img142 img143 img144 img145 img014 img015 img016 img017 img018 img019 research paper journal of agricultural and marine sciences vol. 23 : 24– 28 doi: 10.24200/jams.vol23iss1pp24-28 reveived 15 aug. 2016 accepted 25 feb 2017 impact of the domestic labor market on sustainability of agriculture in oman *1hemesiri kotagama and 1hanam al farsi *hemesiri kotagama ( ) assistant professor and student, respectively at the department of natural resource economics, college of agricultural and marine sciences, sultan qaboos university, sultanate of oman. corresponding author: hemkot@squ.edu.om. introduction oman being highly dependent on oil revenue since the 1970’s, has recently adopted a policy of revenue diversification, in which the agricultural sector is expected to contribute prominently. however, the substantial exodus of omani labor from agriculture to non-agricultural employment poses a challenge to sustainable improvement of agriculture and national food security. according to agricultural census of oman in 2013 only 16% of households in the agricultural sector have reported farming as the main occupation and 53% have reported government employment as the main occupation, whilst the balance is employed in the private and nonformal sectors (maf 2013). this may be due to the distorted labor market; where government legislated, higher remuneration in the non-agricultural sector vis-a-vis agricultural sector, influences أتثري سوق العمل احمللي على استدامة الزراعة يف عمان حيميسريي كوتاجاما*1 وحنان الفرسي1 abstract. in 2013, only 16% of households in oman have reported agriculture as the main occupation and 53% have reported non-agricultural government employment as the main occupation, whilst the balance is employed in the private and non-formal sectors. this situation is hypothesized to be related to the labor market; where government legislated higher remuneration in the non-agricultural government sector vis-a-vis agricultural sector, influences omani farmers to move to non-agricultural employment, causing reduced cultivated area and farm production. the study uses operations research methods to quantify the impact of labor market policies on agricultural employment, farm gross income and land use intensity. in an national average farm of 0.9 ha with 1.33 persons of family labor available, only 75% land use intensity is achieved, with a gross income of 1061 omr/year/household, which is below legislated minimum income for low skilled employment in the non-agricultural government sector (4632 omr/year/household). the household gross income would increase to 5304 omr/year/household with non-agricultural employment of 1 person and 0.33 persons in agricultural employment, which explains low employment of omani’s in agriculture. farms of 2.1 ha (5 feddans), with availability of 1.33 family labor earns a gross return of 2502 omr/year/household, which is again less than the salary in the non-agricultural government sector. however, with the current government policy of allowing to hire 1 expatriate laborer per 2.1 ha with 1 omani person in non-agricultural employment and 0.33 family labor in agricultural employment, gross income increases to 6414 omr/year/household and further if temporary labor hiring is allowed at peak farm labor requirements, gross income could be increased to 6632 omr/year/household. the current policy on hiring 1 expatriate labor per 2.1 ha along with non-agricultural employment of omani labor is in the short-run optimal. keywords: labor market; agriculture; oman; government policies املســتخلص: يف عــام 2013 ، مت اإلشــارة إىل أن 16٪ فقــط مــن األســر يف ســلطنة ُعمــان تعمــل يف الزراعــة باعتبارهــا املهنــة الرئيســية و 53٪ أفــادوا بــأن الوظائــف احلكوميــة غــري الزراعيــة هــي املهنــة الرئيســية هلــم، يف حــن يعمــل البقيــة يف القطاعــن اخلــاص وغــري الرمســي. ويفــرض أن تكــون هــذه احلالــة مرتبطــة بســوق العمــل ؛ حيــث قامــت احلكومــة بتشــريع أجــور أعلــى يف القطــاع احلكومــي غــري الزراعــي مقابــل القطــاع الزراعــي ، ممــا دفــع املزارعــن العمانيــن لالنتقــال إىل الوظائــف غــري الزراعيــة ، وهــذا بــدوره ســبب اخنفــاض املســاحة املزروعــة واإلنتــاج الزراعــي. تســتخدم الدراســة أســاليب أحبــاث العمليــات لتحديــد تأثــري سياســات ســوق العمــل علــى العمالــة الزراعيــة ، والدخــل اإلمجــايل للمزرعــة وكثافــة اســتخدام األراضــي. يف املزرعــة الوطنيــة البالغــة 0.9 هكتــار مــع 1.33 شــخص مــن العمالــة العائليــة املتاحــة ، ال يتــم حتقيــق ســوى 75٪ مــن اســتخدام األرض ، مــع دخــل إمجــايل يبلــغ 1061 لاير عمــاين لــكل ســنة ، وهــو أقــل مــن احلــد األدىن مــن الدخــل القانــوين للعاملــن بالوظائــف الــي تتطلــب مهــارات منخفضــة يف القطــاع احلكومــي غــري الزراعــي )4632 لاير عمــاين لــكل ســنة(. وســيزيد الدخــل اإلمجــايل لألســر إىل 5304 لاير عمــاين يف الســنة بوجــود شــخص يعمــل يف الوظائــف غــري الزراعيــة و 0.33 شــخص يف العمالــة الزراعيــة ، ممــا يفســر اخنفــاض العمالــة العمانيــة يف الزراعــة. . املــزارع الــي تبلــغ 2.1 هكتــار )5 فــدان( ، مــع توفــر 1.33 مــن عمالــة األســرة ، تبلــغ إمجــايل العائــدات 2502 لاير عمــاين لــكل ســنة ، وهــو أقــل مــرة أخــرى مــن الراتــب يف القطــاع احلكومــي غــري الزراعــي. ومــع ذلــك ، مــع السياســة احلكوميــة احلاليــة املتمثلــة يف الســماح بتعيــن عامــل وافــد واحــد لــكل 2.1 هكتــار مــع شــخص عمــاين واحــد يف العمالــة غــري الزراعيــة و 0.33 مــن العمالــة العائليــة يف العمالــة الزراعيــة ، يرتفــع إمجــايل الدخــل إىل 6414 لاير عمــاين لــكل ســنة، وأكثــر مــن ذلــك إذا مت الســماح بتوظيــف العمالــة املؤقتــة يف أوقــات ذروة متطلبــات العمــل الزراعــي ، حيــث أن إمجــايل الدخــل ســيزيد إىل 6632 لاير عمــاين يف الســنة . إن السياســة احلاليــة بشــأن توظيــف العمالــة الوافــدة لــكل 2.1 هكتــار إىل جانــب التوظيــف غــري الزراعــي للعمالــة العمانيــة يعتــر يف املــدى القصــري هــو األمثــل. الكلمات املفتاحية: الراكم احليوي على األسطح املغمورة، 25research article kotagama, al-farsi farmers to move labor to non-agricultural employment. theoretically, undistorted factor markets are a prerequisite for efficient allocation of resources and a growth in production. this study with the use of operations research methodology quantifies the impact of distorted labor markets on farm revenue, farm land use intensity (proxy of production) to examine the role of labor markets in sustaining domestic agricultural production and national food security in the sultanate of oman. literature review apergis et al. (2014) based on a study conducted on middle east and north african countries, for the period of 1970 to 2011 concluded that the boom in the oil sector have had an adverse effect on the agricultural sector. this effect has been attributed to the well-known “dutch disease” phenomenon, where in particular, the economic boom in the oil sector would increase real wages in the oil related non-agricultural sector, siphoning labor out of the relatively low waged agricultural sector (reed 2012). the labor allocation between agricultural (on-farm) and non-agricultural (off-farm) sectors has been widely examined and reviewed (donnellan and hennessy 2012) and most empirical studies have examined and established the factors causing households to allocate labor from agricultural to non-agricultural employment. these factors include endogenous factors such as intra-household joint decision making between spouses, family size, educational status of individuals, farm income risk, the type of farming system in terms of size and enterprises, and exogenous factors such as labor market considerations, transaction cost of transfer from agricultural to non-agricultural employment, rates of urbanization, government subsidies to different sectors, government payments to non-agricultural labor (donnellan and hennessy 2012). most of the studies are based on the seminal theoretical model proposed by becker (1965) on household labor allocation and have used econometric methods to establish causative reasons on the shift of agricultural to non-agricultural employment. in contrast, studies examining the effect of non-agricultural employment on agricultural production and productivity are few (nasir and hundie 2014). non-agricultural employment may have both positive impacts on farm productivity through supply of finance (mathenge and tschirley 2007) and/or negative impacts of moving labor out of agriculture and constraining its availability to agricultural production (nasir and hundie 2014). the studies suggest that the net impacts of labor shift from agriculture to non-agricultural employment may impinge adversely on local food production and food security. in oman, as table 1 indicates, in 2012 the main employment (by income) of omani “farmers” has been mostly in the non-agricultural government sector (52.9%), whereas agricultural employment has been only 15.9% (maf 2013). thus the indications are that omani farmers are leaving agriculture and opting for non-agricultural employment and expatriate labor is substituting omani agricultural labor. the causes and implications of this phenomenon on farm production have not been empirically examined to date and are undertaken by this study. methodology the hypothesis of this study is that the shift of agricultural to non-agricultural employment of omani labor is caused by labor market conditions of relative remunerations of agricultural and non-agricultural sectors, which households consider in labor allocation decision making. becker (1965) proposed that households maximize utility, which is a function of consumption of commodities and time allocated between work and leisure. becker’s proposition could be used to model farm household decision making where the household is considered to maximize utility, over consumption (with income as a proxy) generated through agricultural production and its sales and allocation of labor between agricultural, non-agricultural labor and leisure (singh, squire and strauss 1986; huffman and lange 1989; gould and saupe 1989; and weersink, nicholson and weerahewa 1998). a farmer is considered to maximize utility (u) which is function of consumption (c) and leisure time (l), as expressed by equation (1) subject to constraints of time (t) and household budget. t is finite and is allocated between leisure (l), off-farm (nonagricultural) labor (o) and on-farm (agricultural) labor (f) as expressed by equation (2). consumption of commodities (c) is dependent on returns to labor and commodities purchased at price pc. c is constrained by the budget (equation 3) where c at its extreme is considered to be equal to income and income is dependent on agricultural labor (o) and its wage (w), and the agricultural profit. the agricultural profit is the product of price of farm products (pf) and volume of production (yf) less the cost of production, which is the product of cost of farm inputs (if) including labor that could be hired and volume of inputs (xf). the non-agricultural wage (w) depends on labor market conditions. the farmer in maximizing utility table 1. farmer’s main employment main employment farmers % of total agricultural 9595 15.9 government sector 31821 52.9 non-agricultural private sector 7387 12.3 other 1360 2.3 unknown 10005 16.6 total 60168 100.0 source: maf (2013) 26 squ journal of agricultural and marine sciences, 2018, volume 23, issue 1 impact of the domestic labor market on sustainability of agriculture in oman (equation 1) would allocate time between agricultural labor, non-agricultural labor and leisure, constrained to available labor (t) and consumption possibilities that are dependent on income derived of agricultural production and non-agricultural income. the farmer in the constrained maximization of utility, at optimum would equate the marginal utilities of time allocated of labor between agricultural, non-agricultural and leisure. maximize: u= f (c, l) eq.(1) subject to constraints of: t= l + o + f eq.(2) c.pc= w.o + (pf.yf if.xf) eq.(3) the theoretical model elicited above on household labor allocation, is applied in this study, with simplified assumptions of considering a single household decision maker, maximizing utility on monetary gain, and ignoring many other complexities and realities (as reviewed in section 2). the structure of the theoretical model is applied to a farm context using linear equations and solved using a linear programming algorithm. the proxy for utility is considered income derived from agricultural production and non-agricultural income, which is maximized constrained to agricultural production and labor availability (family and hired labor) and labor market conditions. agricultural production of crop and livestock, is dependent on, resource availability and technology of production. the farm linear programming model is given below as equations (4) to (7). the model considers annual farm production, as non-agricultural employment is considered to be annually fixed. two seasons of vegetable and forage crop cultivation is considered with annual crop extent that is fixed. maximize: π f (σ pi.yi + σ pa.aa + wo.o – wh.h) eq.(4) subject to constraints of: σ cij.yi + σ cij.ai ≤ xj eq.(5) σ cil.yi + σ cil.ai + 1o – 1h ≤ xl eq.(6) yi ≥ 0 eq.(7) where: π is gross margin (omani rials, omr/year), pi are gross margins (omr) per ha of land of ith crop, yi are ha of land of alternative i crops, pa is the price (omr) of a farm animal a, aa is the number of farm animals sold per year of a; wo is the non-agricultural wage (omr/person/year), o is persons of non-agricultural labor allocation (persons/year), wh is wage of hired labor (omr/person/year), h is persons of hired labor, cij are input-output coefficients of land, water and labor on production of crops and animals, xj are available input levels of land (ha), water (cu.m./year), xl is available family labor (persons/year) and hired labor is unlimited but at a cost of wh (omr/person/year). the data were obtained from published sources, namely: the agricultural census of oman (maf 2013), report on cost of crop and livestock production in oman (maf 2008), and a study on profitability analysis of selected farms in the batinah region of oman (al said et al. 2007). the sustainability of farming systems in oman is analyzed by simulating the impact of labor allocation changes caused by non-agricultural labor wages on: household income (omr/year/household) and land use intensity. the land use intensity is estimated as: (land cultivated during spring + summer/ land owned*2)*100. land use intensity is considered as a proxy of domestic food production which relates to food security. more than 70% of the farms in oman are less than 0.42 ha (1 feddan) and these farms account for only 7.0% of the total cultivated area. about 75% of the farms by area cultivated are larger than 2.1 ha (5 feddans). farm land ownership is such that 90% farmers own 25% land area vs 10% farmers own 75% of land. the national average farm size is of 0.9 ha. the government of oman has stipulated a legal limit of hiring 1 expatriate laborer per 2.1 ha. based on the nature of farm size and ownership and legal conditions of hiring expatriate labor, two scenarios are analyzed viz; small farms of 0.9 ha and large farms of 2.1 ha. the minimum wage of non-agricultural employment is considered as 386 omr/month as legislated by the government (royal decree 2013) on standardized grades and salaries schedule for omani civil employees of the state. the wage of hired expatriate labor is considered as 60 omr/month excluding provision of food, accommodation and other associated fixed cost of recruiting expatriate labor. results and conclusion the optimization results of a national average size 0.9 a farm (scenario 1), with different labor allocation possibilities, are given in table 2. in oman a family is classified as poor if it spends more than 60% of the household expenditure on food (mne, 2010). accordingly the poverty line is approximately 300 omr/month/household for an average household size of 8.5 members (mbaga and kotagama 2010). it is observed in table 2 row (1) that the gross revenue from a 0.9 ha farm is 1061 omr/ year/household which is far below the national poverty threshold defined above which is 3600 omr/year/ household. as mentioned above 70% of the farms are less than .42 ha (1 feddan). further farm income which is only 88 omr/month/household is substantially lower than the minimum wage offered to unskilled labor by the non-agricultural government sector, which is 386 omr/month/person. thus, there is a compulsive incentive to move away from agricultural to non-agricultural 27research article kotagama, al-farsi employment to improve household income. the full extent of 0.9 ha is not cultivated and only 75% land use intensity is achieved. of a total availability of 1.33 persons/ year of family labor, only 0.55 persons/year is used in farming. as evident in row (2) of table 2 a single family member employed in non-agricultural sector increases the income to 5304 omr/year/household. however the land use intensity decreases by 11% (from 75% to 61%) resulting to a decrease in farm production. the decrease in land use intensity is caused by scarcity of family labor. hiring labor for farms below 2.1 ha is illegal. however, if hypothetically the farm is allowed to hire 1 person/ year permanent labor, that would increase land use intensity but the farm income would decrease to 4973 omr/year/household (row 3 in table 2) and only 0.55 persons/year of hired labor would be used in the farm. hence it is not rational to hire permanent labor to small farms for farming activities only. hired permanent labor if allocated to farm and other household work may be rational and would also increase land use intensity thus farm production. the farm optimization results for a 2.1 ha farm are given in table 3 (scenario 2). as evident from line (1) use of only family labor achieves only 75% land use efficiency. it is also that the gross revenue is 2502 omr/ year/household which is below the national poverty line which is 3600 omr/year/household. thus there is an incentive for omani labor to move to non-agricultural employment and as evident in line 2 with non-agricultural employment of 1 omani labor household income increases 2 fold to 5320 omr/year/household. however land use intensity decreases to 28% with resulting decrease in farm production, due to labor scarcity. the shadow price of labor (marginal value product of labor) is estimated as 102 omr/month/person and compared to the wage for hired expatriate labor 60 omr/month/ person, justifies hiring of labor. with employment of 1 expatriate labor per 2.1 ha (5 feddans) as per government labor legislation, the gross revenue increases to 6414 omr/year/household and achieves a land use intensity of 75%. however it is found that labor constraints prevail during planting and harvesting periods and allowing for temporary labor employment for those periods, increases the gross revenue to 6632 omr/year/ household and land use intensity to 94% resulting to increased farm production. in conclusion, income from an average 0.9 ha farm that uses family labor is below the national poverty line of a household, providing strong incentives for farmers to fetch for non-agricultural employment with legislated higher income. oman has thus been experiencing a movement of labor from agriculture to non-agricultural sector at the cost of reduced land use intensity and thus reduced local food production. on the other hand, relatively larger farms of 2.1 ha too do not generate enough income, to be above the poverty line. this is the incentive for family labor to move out of agricultural to the non-agricultural employment to increase household income. as a consequence farm land is abandoned resulting to low land use intensity and reduced local crop production (scenario 2). thus the current policy of legislatively allowing employment of 1 expatriate labor per 2.1 ha is optimal in terms of increasing omani household income and agricultural land use intensity. land use intensity could be further improved by allowing temporary employment of labor during labor peak requirements of the farm. the current government policy intervention in the labor market through legislatively determining wage rates in the non-agricultural sector and the low productivity of the farm sector provides and incentive to omani farm labor to leave agriculture. as a result farm production is reduced. the current policy of allowing the employment of 1 expatriate labor per 2.1 ha (5 feddans) farm is optimal with allowing for hiring temporary labor during peak labor demanding periods. the gross income and land use intensity of farms could too be improved with allowing for employment of temporary expatriate labor to substitute the omani labor that moves to non-agricultural labor. a flexible labor market policy of allowing temporary labor hiring will improve omani household income and local farm production. however the implications of non-omani management of farms and the long-run feasibility of hiring expatriate labor for farming need to be examined to ensure sustainable farming and food security in oman. in the long run agricultural protable 2. farm optimization results for 0.9 ha farm (scenario 1) labor allocation gross revenue (omr/year/household) land extent cultivated (hectares) land use intensity (%) labor use (persons) omani expatriate spring sumer family non agricultural hired family labor 1061 0.66 0.66 7.5 0.55 0 0 family labor + non-agricultural 5304 0.58 0.49 61 0.33 1 0 family labor + non-agricultural + hired labor 4973 0.66 0.66 75 0 1 0.55 28 squ journal of agricultural and marine sciences, 2018, volume 23, issue 1 impact of the domestic labor market on sustainability of agriculture in oman ductivity need to drastically improve to retain omanis in agriculture with simultaneous removal of labor market distortions. references al said f, zekri s, khan ia. 2007. profitability analysis of selected farms in the batinah region of oman, agricultural and marine sciences, 12:1-12. apergis s, el-montasser g, sekyere e, ajmi an, gupta r. 2014. dutch disease effect of oil rents on agriculture value added in middle east and north african (mena) countries, energy economics, 45, 485-490. becker g. 1965. a theory of the allocation of time, economic journal, 75, 493-517. donnellan t, hennessy t. 2012. the labor allocation decisions of farm households: defining a theoretical model, comparative analysis of factor markets for agriculture across member states, working paper, www.factormarkets.eu, isbn 978-94-6138-238-2. gould bw, saupe we. 1989. off-farm labor market entry and exit, american journal of agricultural economics, vol. 71, issue 4, 960-969. huffman we, lange md. 1989. off-farm work decisions of husbands and wives: joint decision making, the review of economics and statistics, vol. 71, no. 3, 471-480. mathenge mk, tschirley d. 2007. off-farm work and farm production decisions: evidence from maize-producing households in rural kenya, paper submitted for the csae conference 2007 on ‘economic development in africa’, st. catherine’s college, university of oxford, uk: march 18-20, http:// www.csae.ox.ac.uk/conferences/2007-edia-lawbidc/papers/408-mathenge.pdf (01/07/2015). maf. 2008. report on results of a study on cost of production of crops and livestock in the sultanate of oman (2007-2008), agricultural and fisheries development fund, ministry of agricultural and fisheries (maf), sultanate of oman. maf. 2013. agricultural census of oman, ministry of agricultural and fisheries (maf), sultanate of oman. mbaga m, kotagama h. 2010. food demand survey: indicative demographic trends, a consultancy report submitted to grm international, 15 may 2010, https://www.researchgate.net/publication/264895677_food_demand_survey_indicative_ demographic_trends_a_consultancy_report_submitted_to_grm_international_15_may_2010. mne. 2010. the important result of household expenditure and income survey results from 20 /5 /2007 to 19 /5/ 2008, ministry of national economy (mne) sultanate of oman, directorate general of social statistics. nasir m, hundie b. 2014. the effect of off farm employment on agricultural production and productivity: evidence from gurage zone of southern ethiopia, journal of economics and sustainable development www.iiste.org issn 2222-1700 (paper) issn 22222855 (online) vol.5, no.23:85-98. reed m. 2012. specific food security concerns in oman, keynote presentation at the international conference on food security in arab countries, sultan qaboos university, mind over matter, 2:42-44. royal decree. 2013. http://www.muscatdaily.com/archive/oman/royal-decree-on-standardised-salaries-grades-schedule-issued-2syn#ixzz4vr79x4ts. singh i, squire l, strauss j. 1986. agricultural household models; extensions, applications and policy, the world bank, http://documents.worldbank.org/curated/en/621291468739297175/pdf/multi-page.pdf weersink a, nicholson c, weerahewa j. 1998. multiple job holdings among dairy farm families in new york and ontario, agricultural economics, vol. 18, issue 2, 127-143. table 3. farm optimization results for 2.1 hectare farm (scenario 2) labor allocation gross revenue ( o m r / ye a r / h o u s e hold) land extent cultivated (hectares) land use intensity (%) labor use (persons) omani expatriate spring sumer family non agricultural hired family labor 2502 1.60 1.54 75 1.3 0 0 family labor + non-agricultural 5320 0.58 0.58 28 0.33 1 0 family labor + non-agricultural + hired labor 6414 1.60 1.54 75 0.33 1 1 temporary labor 6632 1.97 1.97 94 0.33 1 1 research paper journal of agricultural and marine sciences 2022, 27(1): 99–111 doi: 10.53541/jams.vol27iss1pp99-111 received 17 may 2021 accepted 08 oct 2021 risks in the sri lankan banana supply chain: analysis through an interpretive structural modeling shanaka rajakaruna1,*, alge wattage wijeratne2 shanaka rajakaruna1,*( ) shanaka.rajakaruna@gmail.com, 1dalian maritime university, transportation engineering college, no:1 linghai road, dalian, china, 2department of agribusiness management, sabaragamuwa university of sri lanaka introduction banana (musa acuminata l.) is one of the favourite fruit crops grown in sri lanka covering an area of 72,010 hectares with an annual average production of 864,120 tons (agstat, 2019). it is also known as one of the staple foods that helps the food security of many tropical countries (ghag & ganapathi, 2017). out of the 1000 varieties available around the world, sri lanka grows 29 of these varieties (ratnasinghe, 2003). these are mainly divided into four main groups namely; sour, seeni, kolikuttu and anmalu (agstat, 2018). sri lanka is geographically located in a favourable position to grow banana. additionally, the soil and other climatic conditions are also useful to the growth of the crop (perming, 2013). due to these facts, there is a potential to increase the harvest and income of farmers. however, irrigation problems, weather patterns, cost of inputs, pests and diseases, political impacts, and climate changes, are seen as the crucial impediments to planting and growing banana in sri lanka (perming, 2013). there is always a struggle among farmers to continue agriculture due to the low income. due to the shorter yield time, low cost of replanting and low overheads, more farmers grow banana as perennial crop (arvanitoyannis and mavromatis, 2009). although, there is a املخاطر يف سلسلة توريد املوز السريالنكي: التحليل من خالل النمذجة اهليكلية التفسريية شاانكا راجاكاروان1* , اجلي وااتج وجيرياتين abstract. although banana is an important fruit in sri lanka that gives a good income to farmers. researchers have indicated that the majority of the crop is damaged from the farm gate to the consumer table. accordingly, this research was addressed ‘to find the risks of the banana supply chain in sri lanka. the interpretive structural modeling (ism) approach was used in this research to find the risks in the banana supply chain of sri lanka. according to the literature survey and data analysis, several risks such as human and personal, production, financial, land prices, biological and environmental, information, political, weather-related, management and operational, agricultural policy, logistics and infrastructure, country’s economic cycle, price or market and input risks can be encountered in the banana supply chain. these risks were categorized into different levels according to the influence they provide to the supply chain. identifying these risks on a hierarchical model was significant to the administrators, managers and farmers to minimize them effectively to manage the supply chain. the analysis in this study further indicated that production, financial, biological and environmental, weather-related events, political situations, and logistics and infrastructure were the most significant risks. dealing with these risks can minimize the effect of other risks, improve the income of the farmers and maximize consumer choice. keywords: agriculture, banana, interpretive structural modeling (ism), risks, sri lanka, supply chain. امللخص:علــى الرغــم مــن أن املــوز يعتــر فاكهــة مهمــة يف ســريانكا حيــث يوفــر دخــًا جيــًدا للمزارعــن، إال أن الباحثــن أشــاروا إىل أن غالبيــة احملصــول يبــدأ ابلتلــف منــذ خروجــه مــن بوابــة املزرعــة وحــى طاولــة املســتهلك. وفًقــا لذلــك، تنــاول هــذا البحــث خماطــر سلســلة توريــد املــوز يف ســريانكا. يف هــذا البحث مت اســتخدام هنج النمذجة اهليكلية التفســريية )ism( للعثور على املخاطر يف سلســلة توريد املوز يف ســريانكا. وفًقا للمصادر العلمية وحتليل البيــاانت، هنــاك العديــد مــن املخاطــر مثــل املخاطــر البشــرية والشــخصية واإلنتاجيــة واملاليــة وأســعار األراضــي واملخاطــر البيولوجيــة والبيئيــة واملعلوماتيــة والسياســية واملخاطــر املتعلقــة ابلطقــس واإلدارة والتشــغيل والسياســة الزراعيــة واللوجســتيات والبنيــة التحتيــة والــدورة االقتصاديــة للبلــد و خماطــر األســعار أو الســوق كل هــذه املدخــات ميكــن مواجهتــا يف سلســلة توريــد املــوز. مت تصنيــف هــذه املخاطــر إىل مســتوايت خمتلفــة وفًقــا للتأثــري الــذي حتدثــه يف سلســلة التوريــد. إن حتديــد هــذه املخاطــر علــى منــوذج هرمــي ســيكون مهًمــا للمســؤولن واملديريــن واملزارعــن لتقليــل هــذه املخاطــر بشــكل فعــال وإلدارة سلســلة التوريــد. وقــد أشــارت نتائــج هــذه الدراســة إىل أن اإلنتــاج، واألحــداث املاليــة والبيولوجيــة والبيئيــة، واألحــداث املتعلقــة ابلطقــس، واألوضــاع السياســية، واخلدمــات اللوجســتية والبنيــة التحتيــة كانــت مــن أهــم املخاطــر. إن التعامــل مــع هــذه املخاطــر قــد يــؤدي إىل تقليــل أتثــري املخاطــر األخــرى، وحتســن دخــل املزارعــن وزايدة خيــارات املســتهلك. الكلمات املفتاحية: الزراعة ، املوز ، النمذجة اهليكلية التفسريية )ism( ، املخاطر ، سريانكا ، سلسلة التوريد. 100 squ journal of agricultural and marine sciences, 2022, volume 27, issue 1 risks in the sri lankan banana supply chain: analysis through an interpretive structural modeling relatively higher turnaround of income from planting banana, full benefit of the yield is not received by farmers due to various problems in the supply chain. the yield of sri lankan banana has increased without a major increase in the harvested area. although the prices of the various crops of banana have increased from 20 to 30 per cent from 2016 to 2017, the wholesale prices have only increased from 10 to 20 per cent (agstat, 2018) during the same period. this indicates that there is a decrease of profit from farmer to wholesaler. researchers have indicated that the state of the insubstantial and non-standard transportation methods from each point in the supply chain have made a significant quantity of the crop being perished during transportation (wasala et al., 2014). the supply chain always encourages a system-wide approach that helps identify the commonalities and the differences in separate segments (king and venturini, 2014). as described by jaffee, et al. (2010), banana supply chain in sri lanka also covers various activities, such as raw materials with equipment and technology; production methodology adopted for harvesting. in addition, post harvesting methods such as re-plantation and crop rotation; processing the harvest by diversifying the product range; promoting the product by carrying out marketing campaigns; and distribution of the products throughout the country to the consumers affected the supply chain. there is a physical financial information flow occurs in this supply chain as in the case of others (partane et al., 2020). the major attraction of growing banana to the farmers is the economic gain. a shorter life cycle and ease of planting also contribute to the growth (kudagamage et al., 2002). however, 30% of the crop is damaged during the journey from the ‘farm to fork’ (ekanayake and bandara, 2002). researchers indicated that improper handling, bad packaging, and excess use of pesticides, mechanical damage and various other problems throughout the supply chain as the reasons for this loss (hathurusinghe et al., 2012). additionally, the involvement of middle vendor by double handling the product contributes to these post-harvest losses and reduces the level of profits of farmers. although there was no increase in the cultivated land, crop yield has increased between 2014 and 2017 (indexmundi, 2020; agstat, 2018). due to the various factors, the advantage of production growth has not reached farmers (ratnasinghe, 2003). additionally, the relationship between income and profitability depends on the cost of cultivation. such a decreasing trend in profitability may have various associated reasons. having an effective supply will leverage the firms and improve profitability (salvia, 2020). this research, therefore, was focused on identifying the risks that affect the banana supply chain to propose strategies to minimize such risks that would contribute to increase the profit of the sector. many programs have been launched by the governmental and non-governmental sector to reduce the negative effects on banana supply chains. there has been previous research conducted to find the effectiveness of the banana industry (ekanayake and bandara, 2002), factors affecting the transport chain (abeysekera & abeysekera, 2008), methods of increasing the yield (ekanayake and bandara, 2002), supply chain issues (sarananda, 1999) and packaging (wilson, 1996) of banana in sri lanka. the risk will restrict the efficient function of the supply chains (crouhy et al., 2006). a large number of risks have been studied by previous researchers concerning agriculture supply chains (jaffee et al., 2010). managing these risks is also necessary to increase efficiency and effectiveness. however, in this research, we considered the factors with a holistic view of the supply chain. although different types of risks are agreed upon by different researchers, they may differ from situation, sector, time and type of operation (crouhy et al., 2006). risk management is also a prominent factor in agriculture (jaffee et al., 2010). although the concept of risk management in agriculture is less-known in sri lanka, it is being practiced in other regions. risk management in the agriculture supply chain can also be explained as “managing the most demanding events” (jaffee, et al., 2010) that negatively affect the financial and information flows in the supply chain. it is difficult to mitigate all the risks to the lowest level. however, trying to minimize such risks will positively affect the collective impact of the whole supply chain (hathurusinghe et al., 2012). it did not mention what risks are the most significant in banana supply chains. a holistic approach to agricultural supply chain risks is not deemed practical due to the diverse nature of each crop and the other aspects such as region and country that may affect the supply chain (dolgui, et al., 2020). the situation is the same with sri lankan banana industry. thus, the main objective of this study was to identify the risks in the banana supply chain of sri lanka and rank them according to their severity. these findings will enable the regulators to mitigate them depending on the impact of each risk. we used interpretive structural modeling (ism) to analyze the data. subsequently, this research will enable administrators and farmers to minimize the likelihood and the consequences of risks in the banana industry. this will enable a smoother efficient flow of product, finances and information. this is the intial study carried out to find the risks in the banana supply chain in sri lanka. additionally, initial study to apply ism in the sri lankan banana industry. thus, this research can open a new paradigm in the agriculture supply chain of sri lanka. methodology in this study, firstly we researched journal articles to find various risks in the banana industry as published by 101research paper rajakaruna, wijeratne the previous researchers. number of journal sites were used for this search. accordingly, we found 312 articles with the term ‘agriculture supply chain’ and ‘risks’ in the publication title. thereafter, this search was further refined to find the words ‘agriculture’, ‘risk’ and ‘banana industry’ in the abstract and/or key words of each article; 21 articles qualified the criteria. having gone through the articles, it was revealed that 8 of those 21 articles do not contain any direct relevance to agricultural risk in the banana industry. finally, we established 16 risks that have a relationship to ‘agriculture risks’ and ‘banana industry’ and thirteen articles was finally selected. secondly, we discussed the existence of these 16 risks in the sri lankan banana industry with a randomly selected sample of government agriculture officers, farmers and vendors. the sample consisted of 10 government agriculture officers, 30 small, medium and large scale farmers and 15 vendors. we requested the sample to rank the risks according to their knowledge and experience. the sample represented all banana growing districts in sri lanka. thirdly, we introduced interpretive structural modeling (ism) as the principal method of data analysis in this research. accordingly, we provided these initially agreed 16 risks to a focus group consisted of six academics and administrators in the field of agriculture. considering the socio-economic conditions as well as with relevance to the banana industry in sri lanka, the focus group agreed on fourteen most relevant risks that are suitable to the sri lankan banana supply chain. the focus group decided to drop marketing risk since it is already including in the price or market risk. additionally, institutional risk was also dropped since it is already a part of management & operational risk. consequently, the following fourteen risks were considered for the ism analysis considering their relevance to the sri lankan economic and agricultural situation: (i) human & personal risk, (ii) production risk, (iii) financial risks, (iv) risk of increase in land prices, (v) biological & environmental risk, (vi) information risk, (vii) political risk, (viii) weather-related risks, (ix) management & operational risk, (x) agricultural policy risk, (xi) logistics & infrastructure risk, (xii) country’s economic cycle, (xiii) price or market risk, and (xiv) input risk. we use ism to study the hierarchy of these risks. this method enables to convert poorly expressed models to more detailed and defined models that can be further tested with the use of data. ism can also be used for many other purposes, such as finding the interrelationships among variables, to identify and rank the variables, ease of educating the public and critically analyse the results for improvements (sushil, 2012) however, the interrelationship of the factors can be considered as the most important (attri et al., 2013). the method is interpretive since the judgment of a group decides the relationship among different variables. modelling methodology in ism facilitates to develop a diagraph that showed the direction and order in the variables (attri et al., 2013). ism has several advantages as an analysis tool. all possible pairwise elements are selected through a literature survey was further purified by the respondents’ recommendations. the use of such transitive inferences can reduce the required rational queries making the process efficient (sushil, 2012). ism also helped to record complex issues efficiently and systematically. the structural model generated through ism graphically presented a complex problem. this graphical representation could depict the problem where interdisciplinary and interpersonal communication can be effectively. thenceforth, ism served as a tool to develop a deeper understanding when identifying, analyzing and taking actions to each element (kumar et al., 2018). every effort was made to reduce the negative effects of ism in this research. as having a larger number of variables may increase the complexity of methodology, this research was only considered the most significant risks factors in the banana supply chain with the assistance of expert opinion. discussions were carried out among the researchers and the focus group on the driving and the dependence power effect variables. ism was used across many research fields such as information technology (pfohl et al., 2011), supply chain (khan and rahman, 2017), agriculture (gardas et al., 2017), and quality management (muruganantham et al., 2018). risk identifications and analysis was the core of these research. thus, it was proved that ism was a realistic analysis tool in identifying risks. although agricultural risks was identified in previous research (gardas et al., 2017; sudarshan et al., 2013), there is a deficiency of literature on banana supply chains, particularly in the asian region. this research deemed significant considering factors, such as the income of banana farmers, nutritious value in the food, improvement of export income and diversification of the agricultural sector in sri lanka. steps were taken according to the ism methodology when developing and identifying the risks to the banana supply chain. step one listing of variables most of the research published in various sources was discussed and the variables that relate to the banana supply chain were indicated in table 1. step two establishing a contextual relationship among variables contextual and pairwise relationship among variables were identified in this step. the consultation and assistance of an expert panel consisted of researchers, academics and practitioners were used initially to nominate the variables and to find the pairwise relationship among them whilst removing the transitive links. as indicated previously, the opinion of experts from various spheres in the agricultural field was used to identify the relationship of these risks to one another. afterwards, this appropriate relationship and significance were further 102 squ journal of agricultural and marine sciences, 2022, volume 27, issue 1 risks in the sri lankan banana supply chain: analysis through an interpretive structural modeling examined. the relationship among variables was shown in the ssim as below: v= i will achieve j. a= j will achieve i. x= i and j will achieve each other. o= i and j are unrelated. where i and j are variables in the banana supply chain and ψ indicates the relationship among the variables. structural self interaction matrix (ssim) is a comparison that was based on pairwise relationships. thus, ssim was obtained by asking a question of whether ‘variable i’ influenced the ‘variable j’. this was described in figure 1. step three structural self interaction matrix (ssim) development table 1. structural self-interaction matrix (ssim) of the causal factors of risks in banana supply chain: source research data variable j risk parameter 14 13 12 11 10 9 8 7 6 5 4 3 2 1 variable i 1 2 3 4 5 6 7 8 9 10 11 12 13 14 human & personal risk production risk financial risks risk of increase in land prices biological and environmental risk information risk political risk weather-related risks management & operational risk agricultural policy risk logistics & infrastructure risk country’s economic cycle price or market risk input risk x v v x v a v v a v v a a v v v v v a v v a v o a v v v v v v v v a v v a a o a o a o o o a a v v a v a v v o o v v v v x v v o v v a x a o o v v a o o v o v v v a v v a x o v a a a note. where the driver is v= element i will help to achieve element j where the driver is a= element j will help to achieve element i where the driver is x=element i and j will achieve each other where the driver is o= i and j are unrelated accordingly, the decision of the expert panel was considered to develop the ssim in table 2. figure 1. structural self interaction matrix (ssim). 103research paper rajakaruna, wijeratne ssim was established for all variables to identify the pairwise relationship for the research area of the banana supply chain of sri lanka. step four initial binary reachability matrix (ibrm) development the previously created ssim reachability matrix was used to form the irm, and this was also further analysed for transitivity. transitivity was an assumption that defined the relationship among factors such as if ‘a’ was related to ‘b’ and also ‘b’ was related to ‘c’ then we hypothesized that ‘a’ was also related to ‘c’. the ssim developed in the previous step was converted to a binary matrix. the v, a, x, and o was converted to 1’s and 0’s. ibrm is presented in table 2. the 1’s and 0’s were replaced according to the following rule: • if i,j entry is v then it becomes a 1 and the corresponding j, i entry be a 0. • if i, j entry is a then it becomes a 0 and the corresponding j, i entry be a1. • if i, j entry is x then it becomes a 1 and the corresponding j, i entry also be a 1. • if i, j entry is o then it becomes a 0 and the corresponding j, i entry also be a 0. step fivedeveloping a final reachability matrix (frm) after considering the transitivity as indicated in step four, frm was developed. the frm was developed by considering transitivity. accordingly, the reachability matrix’s transitivity was analysed with equations 1 and 2 according to huang et al. (2005): i. rm = ssim+u1 ii. rm*= rmx= rmx+1 +1,x> 12 according to the above equation, u is the unit of matrix and x indicates the power. also rm* is the reachability matrix. boolean multiplication and addition system was used (lin et al., 2010) in determining the transitivity values. this suggests us: 1.1=1;1+1= 1;1.0= 0;1+0= 0+1= 1;1.0 = 0.1 = 0. step six carrying out level partitions level partitions were checked to identify the rank of each element. reachability and the antecedent sets were used to identify such hierarchy. reachability and antecedent sets were found from the frm as used to develop the level partitions. these assisted to identify the elements in a ranked pattern (suhil, 2012). this can be expressed as: r(di)= r(di) ∩ a(di) accordingly, di is element and all the other elements that help to attain, r(di) is reachability set with the element as well as all other elements that help to attain it, and a(di) is antecedent set that consists of the subjective element and all other elements to achieve it. step seven – creating a diagraph a direct graph (diagraph) was created using the final reachability to present the relationship among variables. previously, different levels of drivers in the banana supply chain were identified to develop a diagraph. step eight micmac analysis impact matrix cross-reference multiplication applied to a classification (micmac) analysis was performed to find the driving and dependence power of each variable. table 2. initial binary reachability matrix: parameter variable j 1 2 3 4 5 6 7 8 9 10 11 12 13 14 variable i 1 2 3 4 5 6 7 8 9 10 11 12 13 14 1 1 1 1 1 0 0 0 0 1 1 0 0 1 0 1 1 0 0 0 0 0 0 0 1 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 1 0 1 1 1 0 1 1 0 1 1 0 0 1 0 1 1 0 1 0 0 1 0 0 0 0 0 0 1 0 1 1 1 1 0 1 1 1 1 0 1 1 0 1 1 0 0 0 1 0 0 0 0 0 0 0 0 1 1 0 1 0 0 1 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 0 0 1 1 1 0 1 1 0 1 0 1 1 0 1 1 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 1 1 0 1 1 1 1 1 0 1 1 1 1 1 1 1 1 1 1 0 1 1 0 1 0 0 1 1 1 1 1 1 1 0 1 1 0 1 1 0 0 1 source – survey data 104 squ journal of agricultural and marine sciences, 2022, volume 27, issue 1 risks in the sri lankan banana supply chain: analysis through an interpretive structural modeling results and discussion as described previously, several risks related to the banana supply chain from the ‘farm to fork’ was explored in this research. identifying such risks can enable us to undertake the most vital risk that can have a trickledown effect to minimize other related risks. such action can, therefore, reduce the cost and effort of tackling each risk independently. this can create a cost and benefit advantage for the farmers and vendors as well as the government to attain an effective banana supply chain in sri lanka. all such risks researched previously were selected by the expert panel and these were used in this research. types of risk risk of country’s economic cycle domestic crop production can be greatly influenced the economic cycle and governmental policies to promote agriculture. research has showed that the economic crisis can positively affect agriculture since more people can turn to agriculture due to increasing unemployment (ogboru et al., 2018). moreover, the elasticity variance of agriculture was low during different economic periods from a recession to an expansion (contre and goldin, 1990). however, the sustainability of agriculture has a concern on economic, social and ecological sustainability (ghag and ganapathi, 2017). price or market risk: due to the nature of demand and supply pattern in agriculture, there is always a risk involved in market price. however, the price or market risk can vary from product to product (rosch, 2018). banana being a short-term crop and can help the subsistence farmers in sri lanka, since there is always a price variation. from 2015 jan 2019 monthly banana prices have increased by 65% (indexmundi, 2020). this did not consider the monthly variations that were almost 15% in the year 2017 (for ambul only) (cbsl, 2018). risk of increase in land price: land prices in the cofigure 2. ism model for banana supply chain risks. 105research paper rajakaruna, wijeratne lombo district have increased by 18% compared to 2017 (cbsl, 2019). central bank (2019), report further indicates that ‘three sub-indices of land price index, namely ‘residential, commercial and industrial have contributed’ to this increase. it can be claimed that this has a trickle-down effect on the increase in land prices in other districts. growth in population and improvement of roads and infrastructure has also contributed to this de-urbanization (rosch, 2019: ogboru, et al., 2018). as a result, harvesting of banana did not increase from 2014 to 2017 (agstat, 2018). input risk: banana farmers face a shortage of approved tissue cultured nursery plants due to minimum research carried out in sri lanka (perming, 2013). the situation about the labor, pesticides and the special planting and yielding equipment were also the same (hanson et al., 2004). researchers indicated that 2% of the yield was damaged due to bad handling at the farm gate since the right equipment was not available (wasala et al., 2014). moreover, most of the banana plantations on the island were organic (sarananda, 1999), thus required knowledge and the inputs to develop popular organic farming were also in short supply. biological and environmental risk: researchers have classified biological and environmental risks in agriculture to two areas namely, dependent and independent from the business activities (zakharchenko, 2017). the growth of agriculture including farming and animal husbandry harms the environment (jaffee et al., 2010). heavy use of fertilizer can deteriorate the quality of the topsoil and deplete the groundwater sources (zakharchenko, 2017). since the farmers lack knowledge on scientifically grounded crop rotation methods, problem of soil and groundwater contamination has worsened. also, the continuously deteriorating environment due to deforestation and extreme climatic conditions can be negatively contributed. although, there was much less use of fertilizer in the banana plantations in sri lanka (sarananda, 1999), other factors did not affect biological and environmental risk. logistics and infrastructure risk climacteric and the perishable nature of banana make them highly vulnerable to postharvest losses (wasala et al., 2014). the available transportation and storage conditions can also deteriorate the situation further. as indicated in figure 2, banana supply chain in sri lanka has many transportation loops and storage points. this can make it vulnerable to more postharvest losses during transit and it was calculated that this loss amounts to 30% of the yield (ekanayake and bandara, 2002). political risk: to develop an efficient and resilient agriculture mechanism in any country, innovative experimentation and research are needed (bennett et al., 2014). also, there should be a ‘holding hands’ approach between the farmers and the authorities to develop a winning supply chain. since all governmental issues are politically driven, it is difficult to have the expected sustainability in agriculture (ghag and ganapathi, 2017). this has a direct impact on the agriculture policy risk that can be discussed next. however, other factors are influenced by political risks, such as land availability, supply chain effectivity and agricultural decentralization (dolgui et al., 2020). these can be influenced by the prevailing political regime. such short-termism approach of the politicians had negatively influenced the agriculture industry including the banana supply chain (contre and goldin, 1990). considering the influence that the political risk can bring to the banana supply chain (ekanayake and bandara, 2002), it can be included as a major risk. agricultural policy risk: as described previously, the government agricultural mechanism can waste resources and efforts in practices that are ineffective and does not provide adequate opportunities for innovation (de silva and kawasaki, 2018). as a reason, the farming community is unable to reap the benefits of such governmental efforts. presently, it is provided by the local agricultural advisers and this does not have an end to end process where a crop can be looked after by the governmental mechanism from seed to yield (abeysekera and abeysekera, 2008). additionally, the policy of various governments changed time to time ad these could also slow down the growth. weather-related risk: agriculture contributes 7.5% of the total gdp of sri lanka in the year 2018 (cbsl, 2019). that said, there is a correlation between weather-related activities and agriculture productivity (de silva and kawasaki, 2018). natural disasters are increasing due to climate change. therefore, whenever there is a climatic change, there is a risk of the banana crop being damaged. financial risk: managing the costs incurred through planting to consumption, availability of various financing methods, and the knowledge of the farmers to manage the cash flows are known as the highest risks in agriculture (komarek et al., 2020). there is a lack of knowledge in cash flow management throughout the farming communities of sri lanka (kiriveldeniya and rosairo, 2020) since there is a shortage of awareness in sound financial control due to the illiteracy of the farming communities (wanigasundera and atapattu, 2019), objective nature of farming could not be achieved. whilst the fact that the role of the government to improve the financial acumen of the farmers are not being negated, there is still much the farming communities can also do in reducing the financial risk by way of cooperatives and other cartels (kiriveldeniya and rosairo, 2020). production risk: production risk involves all the risk factors that help production from inputs, process, weather, biological and environmental factors (shahzad and abdulai, 2019). although some of these risks were discussed previously, we highlighted production risk also as a separate risk phenomenon due to the significance. since there are other contributory factors such as pests, disease and machinery efficiency and these did 106 squ journal of agricultural and marine sciences, 2022, volume 27, issue 1 risks in the sri lankan banana supply chain: analysis through an interpretive structural modeling not include previously. the food and agriculture organisation (fao) of the united nations have claimed that there is “20 to 40 percent of crops that are lost due to pest” (fao, 2020). these pest problems have affected the food security of various countries. although there are no statistical data, this must-have affected the sri lankan agriculture sector too. the recent locust attacks on the plantations in kurunagala district in sri lanka can be one of the examples (shivantha, 2020). human and personal risk: there are various human and personnel risks that the agriculture industry faces every day in sri lanka (cbsl, 2019). among them a scarcity of labor force (karunagoda, 2004), inadequate health and safety systems (weerasinghe et al., 2020), non-effective training to farmers including the partners of the banana supply chain (kiriveldeniya and rosairo, 2020), non-availability of pension schemes (perera and weerakkody, 2018) and ill health among farming communities (dcs, 2017) are the most aggravating factors that affect human and personal health. operational risk: operational risk is defined as something that might happen and its effect(s) on the achievement of objectives (iso, 2018). when considering the banana supply chain, there may be numerous objectives including growth, expansion profitability and resilience. the ministry of agriculture has laid down policy objectives and road maps for the whole industry. however, there is a lack of proactive planning to have a first and second-line defense model to minimize or to eradicate the consequences and likelihoods of problems that may encounter when reaching these strategic objectives (nisansala et al., 2020). additionally, the changes in the policy and political environment can also affect the drive towards the set strategic objective. information risk: information has become a significant requirement in our everyday life. thenceforth, it is also vital to the development of the banana supply chain (bo et al., 2014). accordingly, the right mandate and figure 3. micmac analysis diagram, banana supply chain risks. 107research paper rajakaruna, wijeratne infrastructure were set by the authorities to have a free flow of supply chain-wide information availability. the banana supply chain can achieve many advantages by effectively employing costly inputs (dolgui et al., 2020). even though, the government has taken several steps there are still gaps in the system. lack of knowledge and the ability of the farmers, lack of information sources, unreceptive attitude of the authorities and slow flow of information are some problems, and these have to be resolved to have a sound information regime (gardas et al., 2017). considering the impact that information has on the development of the banana supply chain, information risk can be judged as risk as identified in this research. the final binary reachability matrix is presented in table 3. according to the results, financial risks takes the highest rank of the set of drivers followed by production risks. this implies that policy-level initiatives must be in place to reduce both financial and production risks as a priority. the third rank is taken by biological and environmental risks that should be handled separately. when the dependence power is examined the top rank is taken by price or market risks. this signals that price regulation and access to market price and market place timely may help reduce such dependency. models the results of level partitions are presented in table 4. thus, the element which has the highest number of intersections and antecedents were considered as the first level partition. this application was continued until all variables were removed. these partitions were then used to develop the diagraph and the ism model at the later stage. thenceforth, the frm achieved is shown in table 4 indicating the driving and dependence power as well as the transitivity of the banana supply chain risks in sri lanka. this further indicates the role of financial risks and logistic and infrastructure risks in the overall context of the banana supply chain in sri lanka. results of diagraph and formation of ism-based model shows the graphical representation of the relationships of the elements according to different hierarchy. according to the diagraph, it can be seen that “logistics & infrastructure risk (driver 11)” and “financial risks (driver 3)” can be considered as the most significant risks to affect the others in the banana supply chain. therefore, these risks need to be dealt with at the outset. however, management and operational risk are at the top of the diagraph. this indicates that treating this risk can greatly influence all the other risks. accordingly, the final model of the diagraph after removing the transitivity is presented in figure 2. results of micmac analysis helps to understand the driving and dependence power of the risks in the banana supply chain. there are four groups in this analysis. namely, autonomous, dependent, linkage and independent. these were also numbered as region one to four respectively in figure 3 (kumar et al., 2018). there were no risks in the banana supply chain that falls into the autonomous region which is also called region one. the dependence cluster which is named as region two had information risk (6),” “country’s economic cycle (12),” “price or market risk (13),” and “management & operational risk (9)”. these risks had high dependence and low driving power. the region three (linkage) had, “human & personal risk (1),” “risk of an increase in land prices (4),” “input risk (14),” and “agriculture policy risk (10)”. this indicates that action taken to minimize these risks can affect other risks. risks such as “production risk (2),” “financial risk (3),” “biological & environmental risk (5),” “weather-related risks (8),” “political risk (7),” and “logistics infrastructure table 3. final binary reachability matrix: source – survey data. drivers variable j 1 2 3 4 5 6 7 8 9 10 11 12 13 14 driving power rank 1 2 3 4 5 6 7 8 9 10 11 12 13 14 human & personal risk production risk financial risks risk of increase in land prices biological & environmental risk information risk political risk weatherrelated risks management & operational risk agricultural policy risk logistics & infrastructure risk country’s economic cycle price or market risk input risk dependence power rank 1 1 1 1 1 0 0 1# 0 1 1 0 0 1 9 v 0 1 1 0 0 0 0 0 0 0 1 0 0 0 3 ix 0 0 1 0 0 0 0 0 0 0 0 0 0 0 1 x 1 1# 1 1 1 0 1 1 0 1 1 0 0 1 10 iv 0 1 1 0 1 0 0 1 0 0 0 0 0 0 4 viii 1 1# 1 1 1 1 0 1 1 1 1 0 1 1 12 ii 0 1 1 0 0 0 1 0 0 0 0 0 0 0 3 x 0 1 1 0 1 0 0 1 0 0 1# 0 0 0 5 vii 1# 1 1 1 1 1 1 1 1 1# 0 1 1 1 13 i 0 1 1 0 1 0 1 1 0 1 1 0 0 0 7 vi 0 0 0 0 0 0 1 0 0 0 1 0 0 0 1 x 1 1 1 1 1 1 1 1 0 1 1 1 1 1 13 i 1 1 1 1 1 0 1 1 0 1 1# 0 1 1 11 iii 1 1 1 1 1 0 0 1 0 1 1 0 0 1 10 iv 7 12 13 7 10 3 7 10 2 8 10 2 4 7 v ii i v iii vii v iii viii iv iii viii vi v note. 1# entries indicate the transitivity 108 squ journal of agricultural and marine sciences, 2022, volume 27, issue 1 risks in the sri lankan banana supply chain: analysis through an interpretive structural modeling table 4. drivers to risks in banana supply chain partition. drivers(di) reachability r(di) antecedent a(di) intersection r(di) ∩ a(di) level i 1 2 3 4 5 6 7 8 9 10 11 12 13 14 1,4,6,9,12,14 1,2,4,5,6,7,8,9,10,12,13,14 1,2,3,4,5,6,7,8,9,10,12,13,14 1,4,6,9,12,13,14 1,4,5,6,8,9,10,12,13,14 6,9,12 4,7,9,10,12,13,14 1,4,5,6,8,9,10,12,13,14 6,9 1,4,6,9,10,12,13,14 1,2,4,6,8,10,11,12,13,14 9,12 6,9,12,13 1,4,6,9,12,13,14 1,2,3,4,5,8,10,11,14 2,3,11 3 1,2,3,4,5,7,8,10,11,14 2,3,5,8 1,2,3,4,5,6,8,9,10,11,13,14 2,3,5,7 2,3,5,8,11 1,2,3,4,5,6,7,8,9,10,13,14 2,3,5,7,8,10,11 7,11 1,2,3,4,5,6,7,8,10,11,12,13,14 1,2,3,4,5,7,8,10,11,13,14 1,2,3,4,5,7,8,10,11,14 1,4,14 2 3 1,4,14 5,8 6,9 7 5,8 6,9 10 11 12 13 1,4,14 level ii 1 2 3 4 5 6 7 8 10 11 12 13 14 1,4,6,13,14 1,2,4,5,6,7,8,10,13,14 1,2,3,4,5,6,7,8,10,13,14 1,4,6,13,14 1,4,5,6,8,10,13,14 6 4,7,10,13,14 1,4,5,6,8,10,13,14 1,4,6,10,13,14 1,2,4,6,8,10,11,13,14 12 6,13 1,4,6,13,14 1,2,3,4,5,8,10,11,14 2,3,11 3 1,2,3,4,5,7,8,10,11,14 2,3,5,8 1,2,3,4,5,6,8,9,10,11,13,14 2,3,5,7 2,3,5,8,11 2,3,5,7,8,10,11 7,11 1,2,3,4,5,6,7,8,10,11,12,13,14 1,2,3,4,5,7,8,10,11,13,14 1,2,3,4,5,7,8,10,11,14 1,4,14 2 3 1,4,14 5,8 6 7 5,8 10 11 12 13 1,4,14 level iii 1 2 3 4 5 7 8 10 11 13 14 1,4,13,14 1,2,4,5,7,8,10,13,14 1,2,3,4,5,7,8,10,13,14 1,4,13,14 1,4,5,8,10,13,14 4,7,10,13,14 1,4,5,8,10,13,14 1,4,10,13,14 1,2,4,8,10,11,13,14 13 1,4,13,14 1,2,3,4,5,8,10,11,14 2,3,11 3 1,2,3,4,5,7,8,10,11,14 2,3,5,8 2,3,5,7 2,3,5,8,11 2,3,5,7,8,10,11 7,11 1,2,3,4,5,7,8,10,11,13,14 1,2,3,4,5,7,8,10,11,14 1,4,14 2 3 1,4,14 5,8 7 5,8 10 11 13 1,4,14 level iv 1 2 3 4 5 7 8 10 11 14 1,4,14 1,2,4,5,7,8,10,14 1,2,3,4,5,7,8,10,14 1,4,14 1,4,5,8,10,14 4,7,10,14 1,4,5,8,10,14 1,4,10,14 1,2,4,8,10,11,14 1,4,14 1,2,3,4,5,8,10,11,14 2,3,11 3 1,2,3,4,5,7,8,10,11,14 2,3,5,8 2,3,5,7 2,3,5,8,11 2,3,5,7,8,10,11 7,11 1,2,3,4,5,7,8,10,11,14 1,4,14 2 3 1,4,14 5,8 7 5,8 10 11 1,4,14 109research paper rajakaruna, wijeratne risk (11)” fell into region four (also known as an independent). these risks therefore considered as the most significant risks in the banana supply chain since they drive the other risks. this phenomenon was also evident in the ism model in figure 2 where these risks were in the lower layers of the risk model. we consider that this would help the administrators to take necessary measures to minimize the risks in the banana supply chain. it shall be emphasized that administrators, practitioners and farmers must take the required action to reduce these risks to improve the banana supply chain and increase the profit as well as the benefits to the customers. also, the structural model we introduced can show the hierarchy of action needed to improve the performances of the banana by undertaking each risk considering the interrelationship among each risk as shown in figure 3. since there were no risks that fall into ‘region one’, none of the risks shown in the research can be disconnected. therefore, the authorities should look into all risks that are identified from a holistic point of view. additionally, the risks that are in ‘region three’ are high independence and driver power, therefore minimizing these risks can reduce the effect on them as well as the other risks such as the ones in ‘region two’ which can be influenced by them. additionally, the risks that are in ‘region four’ of the micmac analysis diagram lie on the lower part of the ism model (figure 3). therefore, minimizing such as production risk (2), logistics & infrastructure risks (11) and the financial risk (3), affect the whole banana supply chain. moreover, administrators and managers can minimize these risks as the basis of all other risks. this research explored the risks that are in the sri lankan banana supply chain. however, there were some limitations encountered during the research due to time and financial restraints. accordingly, we could not compare the results of ism against other available models such as structural equation modeling (sem), pareto analysis or failure mode and effects analysis (fmea). additionally, there may be other risks that affect the banana supply chain. we call for future research in these areas. although this research was only towards the banana supply chain, this model could be applied to other areas in agriculture in sri lanka as well as in other regions. finally, we hope that the productive potential of the banana supply chain can be increased by minimizing these risks. conclusion this study was initiated to find the risks that are available in the sri lankan banana supply chain. accordingly, various agricultural risks were found through a literature survey and these were forwarded to a randomly selected sample of farmers, vendors and government-appointed agricultural officers. these represented all banana growing districts of sri lanka. once the sample agreement was obtained, these risks were presented to a focus group to carry out the pairwise relationship among them whilst removing the transitive links. afterwards, the data were analyzed through ism according to their driving and dependence power. it was revealed that four risks are more significant than others. minimizing or eradicating these four risks can influence other risks. level v 2 3 5 7 8 10 11 2,5,7,8,10 2,3,5,7,8,10 5,8,10 7,10 5,8,10 10 2,8,10,11 2,3,11 3 2,3,5,8 2,3,5,7 2,3,5,8,11 2,3,5,7,8,10,11 7,11 2 3 5,8 7 5,8 10 11 level vi 2 3 5 7 8 11 2,5,7,8 2,3,5,7,8 5,8 7 5,8 2,8,11 2,3,11 3 2,3,5,8 2,3,5,7 2,3,5,8,11 7,11 2 3 5,8 7 5,8 11 level vii 2 3 11 2 2,3 2,11 2,3,11 3 7,11 2 3 11 level viii 3 11 3 11 3 7,11 3 11 110 squ journal of agricultural and marine sciences, 2022, volume 27, issue 1 risks in the sri lankan banana supply chain: analysis through an interpretive structural modeling the administrators can take necessary action to discuss a methodology to minimize them throughout the supply chain. this study is significant to sri lankan banana supply chain since there is a 30% wastage of the crop from ‘farm to fork’. this was the initial study carried out in sri lanka regarding agriculture using ism methodology. this study can also be used in other countries in the region with the necessary adaptations. references abeysekera t, abeysekera s. 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(1996). supply chain management: a case study of a dedicated supply chain for bananas in the uk grocery market. supply chain management: an international journal 1(2): 28-35. zakharchenko o. 2017. ecological risks in agriculture: problem-oriented approach. business, management and accounting 3(1): 12-18. img110 img111 img112 img113 img114 img081 img082 img083 img084 img085 img038 img039 img040 img041 img042 img043 img044 img045 img188 img189 img190 img191 img192 img193 img194 img195 research paper journal of agricultural and marine sciences vol. 22 (1): 58– 62 doi: 10.24200/jams.vol22iss1pp58-62 received 15 aug. 2016 accepted 19 feb 2017 development of a decision support system for precision management of conjunctive use of treated wastewater for irrigation in oman hemanatha p. w. jayasuriya*1, ahmed al-busaidi 1 and mushtaque ahmed 1 * 1 hemanatha p.w. jayasuriya ( ) , sultan qaboos university, college of agricultural and marine sciences, dpt. of soils, water and agricultural engineering, box 34, al-khod 123, sultanate of oman. email: hemjay@squ.edu.om . introduction as in any country or region with arid environ-ment, water is scarce in oman. yet the agri-culture is a common and traditional practice in oman in which more than 50 percent of the arable lands are located in the northern coastal belt of al-batinah region (alahakoon et al., 2013; maf, 2013; maf, 2015). the country with average annual rainfall around 100 mm, has limited natural freshwater resources and has been facing the serious problem of seawater intrusion into the scarce gw reserves due to undisciplined excessive pumping of gw for irrigation from aquifers. farmers are allowed to use gw with a quota system developed by the two ministries: the ministry of agriculture and fisheries and the ministry of water resources (maf, 2013; mott macdonald and mrmwr, 2013a; mott macdonald and mrmwr, 2013b; maf, 2014; maf, 2015). however, gw over pumping has been undisciplined and is a common practice among some farmers causing seawater intrusion and salinity issues in the region with most arable lands (norman et al., 1998; prathapar et al., 2005; zekri, 2008; alahakoon et al., 2013). there are problems with the crop selections and rotations as the farmers make own decisions on that issue without considering the water saving efforts. some of the crops that have higher crop to water demand are grown by using inefficient irrigation methods (fao, 1998; fao, 2010; somarathna and ahmed 1999; ensink et al., 2004). the researchers, with the support of the relevant ministries, have been looking for alternative options to minimize the use of irrigation water by over pumping of gw (zekri, 2008; alahakoon et al., 2013; mott macdonald and mrmwr, 2013a; mott macdonald and mrmwr, 2013b) and more efficient irrigation techniques (zekri, 2008; alahakoon et al., 2013; تطوير نظام دعم القرار إلدارة دقيقة الستخدام مياه الصرف الصحي املعاجلة واملخلوطة بعمان مهاناثا جاياسوريا*1و امحد البوسعيدي1و مشتاق امحد1 abstract. this research aimed at finding alternative options for conjunctive use of treated wastewater (tw) with groundwater (gw) minimizing the irrigation water from aquifers in the al-batinah region with the assistance of a decision support system (dss). oman is facing a three-facet problem of lowering of gw table, wastewater over-production and excess tw. approved guidelines for use of tw with tertiary treatments are of two classes: class-a (for vegetables consumed raw), class-b (after cooking). the developed dss is comprised of four management subsystems: (1) data management in excel, (2) model and knowledge management by macro programming in excel, (3) with linear programming (lp) optimization models including transportation algorithms, and (4) user interface with excel or visual basic (vb). the results are based on two extreme scenarios: zero tw excess, and zero gw used for irrigation. the dss could predict water balance for number of crop rotations, and based on adjustable cost variables farmer profit margins could be created. crop selections and rotation could be done using lp optimizations while transportation algorithm could organize best locations and capacities for treatment plants and the wastewater collection and transportation to farming areas via treatment plants. the developed dss will be very useful as a water management, optimization and planning tool. keywords: decision support; precision irrigation management; conjunctive use; treated wastewater; groundwater. امللخــص: يهــدف البحــث لتحســن إدارة امليــاه اجلوفيــة وميــاه الصــرف الصحــي املعاجلــة عــن طريــق اســتخدام نظــام دعــم القــرار. تواجــة عمــان ثــاث حقائــق مائيــة وهــي اخنفــاض مســتوى امليــاه اجلوفيــة واإلنتــاج الزائــد مليــاه الصــرف الصحــي املعاجلــة مــع تزايــد كمياهتــا مــع مــرور الزمــن. يتكــون نظــام دعــم القــرار مــن إدارة األعــداد، اإلدارة املعرفيــة للربامــج، اإلدارة اخلطيــة للربامــج املســخدمة واســتخدام التداخــل العــددي يف الربامــج. اعتمــدت النتائــج علــى تصوريــن ومهــا االســتخدام الكلــي للميــاه املعاجلــة وعــدم اســتخدام امليــاه اجلوفيــة يف الزراعــة. تنبــأ النظــام بكميــات امليــاه املطلوبــة لعــدة حماصيــل منتجــة أثنــاء الســنة والــذي يدعــم ربــح املــزارع. مــن خــال النظــام قــد يكــون هنــاك تنبــوأت بنوعيــة احملاصيــل وتدويرهــا ممــا يتناســب مــع كميــة امليــاه املنتجــة واملنقولــة. النظــام اجلديــد ســيكون مفيــدا إلدارة امليــاه وعمــل املخططــات املســتقبلية. الكلمات املفتاحية: دعم اختاذ القرار، إدارة الري الدقيق، االستخدام املشرتك، مياه الصرف الصحي املعاجلة واملياه اجلوفية 59research article jayasuriya, al-busaidi and ahmed alessandra, 2014) including precision irrigation (zekri, 2008; alahakoon et al., 2013). a consistent deficit of gw has been experienced due to irrigation use, and annual deficit of gw in the agricultural region al-batinah along was 315×106 m3 in 2013 (zekri, 2008; alahakoon et al., 2013; mott macdonald and mrmwr, 2013a; mott macdonald and mrmwr, 2013b). due to people migration to cities, city expansions and industrial growth have created excess production of wastewater. as per the statistics, there is a steep growth rate of wastewater production. current daily wastewater produced in muscat governorate is 94 000 m3 and predicted to be four fold in 2025 (somaratna and ahmed, 1999; prathapar et al., 2005; mott macdonald and mrmwr, 2013a; mott macdonald and mrmwr, 2013b). wastewater treatment plants have been established around the city with tertiary treatment levels, standard processes and quality; however there is not much effort made to use the water for consumable crop irrigation. even after applying for various needs, there is a significant excess production of tw and handling this has become a challenge as there are restrictions for recharge (david and williams, 1979; berry et al., 1980; harvey, 1997; mohammad and mazahareh, 2003; fluet et al., 2009; bedbabis et al., 2010; abdelrahman et al., 2011; al khamis et al., 2011). rationale the objective of this research was to find solutions for oman’s three-facet problems of lowering of gw table (al-batinah gw deficit 315×106 m3 in 2013), increasing daily wastewater production (94 000 m3/day in 2015) and how to handle excess tw after reuse (prathapar et al., 2005; zekri, 2008; mott macdonald and mrmwr, 2013a; mott macdonald and mrmwr, 2013b). the developed dss can find potential solutions to all above-mentioned problems. a couple of key variables are kept in the system in order to maintain flexibility and adjustments. following critical points and constraints were taken into consideration when developing the dss for the use of tw for irrigation. points considered on development: • it is important to find alternative options for replacing the irrigation water used by over pumping gw with the assistance of technology and planning. • the seawater intrusion, soil salinity, land degradation hinder agricultural production. • use of tw for irrigation is one of the best options, and the cheapest option in oman to save gw. constraints on implementation: • acceptance by society to use in agriculture and agro industry; farmers, consumers, managers and the scientists. many sensitive issues, need to be addressed. • no storage facilities at sewage treatment plants (stps) to store bulk of tw exit from the plant, transportation network should be efficient with just-in-time basis or dump in somewhere (in the ocean). objectives the main objective of the study was to find alternative options for replacing the irrigation water used by over pumping gw (zekri, 2008; alahakoon et al., 2013, mott macdonald and mrmwr, 2013a; mott macdonald and mrmwr, 2013b) with the assistance of a dss. the specific objectives of the study were to see the feasibility of maximizing the use of tw replacing gw use for irrigation and to minimize the unused tw excess, optimize the land use for different crop combinations and rotations with tw use while optimizing the farmers’ profit, optimize the tw distribution network; determine the feasibility for locating stps minimizing transportation (tw) cost for farmers, and develop a dss for managers to conduct feasibility studies for better planning and management of tw use. methodology an excel and visual basic based decision support system (dss) was developed to select options for conjunctive use of treated waste water (wt) and ground water (gw) for irrigation in oman. the developed system targeted managers and farmers as users and the system was with necessary simplicity and flexibility. the system architecture utilized is illustrated in (fig. 1). it comprised of four management subsystems; data management in excel, model and knowledge management by macro programming in excel, with linear programming (lp) optimization models including transportation algorithms all in excel, and user interface optional with excel or vb mode. graphical results could also be retrieved in the vb mode two critical threshold levels were considered in the figure 1. architecture used in developing the decision support system. 60 squ journal of agricultural and marine sciences, 2015, volume 19, issue 1 development of a decision support system for the management of treated wastewater irrigation analysis considering the two scenarios shown in (fig. 2). threshold levels were: (1) zero excess tw and (2) zero use of gw based on the prevailing conditions in oman. the main decision variable of the systems is the volume of daily production of tw in 106 m3. in addition, there are other variables in the system applicable for different management modules (fig. 1). as an example, for the cost analysis, prices of tw and gw (including transportation costs) are auxiliary variables. once all the variables are entered, the results including graphical results will appear (fig. 3). crop and meteorological data are based on the experimental farming by the moaf oman. results figure 3 shows a sample view of excel-based decision support system and results with graphics obtained under given data and applied decision variables. table in (fig. 3) shows the three crop rotations and two extreme scenarios of zero excess tw and zero gw use. extended portion of the table shows the cost of excess tw or the opportunity cost. the bottom left section shows the cells for decisions variables used in the computations: daily tw production costs for tw and gw ,etc. the bottom area shows the cost analysis results in graphical form. decision makers can observe the simulation results and select the appropriate crops and cropping enterprises leading to profit maximization while maintaining the optimum conjunctive use of tw and gw. figure 2. the two extreme scenario considered : (1) zero gw use, i.e. the peak of treated water production is considered as the peak of irrigation water requirements and (2) zero tw excess, the minimal requirements for the different crops is provided by treated water and additional gw is used when necessary. figure 3. a sample view of excel-based dss on farmer profit maximization condition. 61research article jayasuriya, al-busaidi and ahmed figure 4 shows a sample view of the vb interface window which provides the results in tabular form with cells having decision variables for adjustments. the upper row of the table shows option buttons (summery, rotations, profits, lp, lp-transportation etc.), through which corresponding programs could be executed in excel and results could be obtained in the vb window. the cells in the upper rows provide the main decision variables for necessary adjustments and tables show the corresponding results. the graphical results (bar charts) obtained in excel could also be retrieved in the vb mode. the system provided greater simplicity and flexibility, and with a short training the users will be able to operate the system. conclusion and recommendations • the developed dss could simulate best options with conjunctive use of tw and gw for scheduling seasonal irrigation in oman. • the developed dss could simulate potential solutions for the oman’s three-facet problems; reduce the use of gw lowering the stress on gw table, maximize the use of tw without dumping in sea, and system could be used to plan the locations for treatment plants and two-way transportation network with quantities. • the developed dss is very simple, flexible and user-friendly. it can be further improved with extensions incorporating leaching fraction, soil/water salinity fractions etc. acknowledgements the authors wish to acknowledge the financial support given by the usaid-fabri program through the mena research network and the facilities provided by the sultan qaboos university (squ), haya water llc and dr. saif al khamisi of ministry of agriculture and fisheries, oman for the valuable contributions by providing field data. references abdelrahman, h. a., alkhamisi, s., ahmed, m., and ali, h. 2011. effects of treated wastewater irrigation on element concentrations in soil and maize plants. communications in soil science and plant analysis. 42: 2046-2063. alahakoon, m., jayasuriya h.p.w., slim zekri, riadh zaier, al-busaidi, h. 2013. design of a database and wireless data retrieval systems for monitoring irrigation in al-batinah region in oman. in proceedings of the international conference on agricultural engineering, feb 24-26, 2013, sultan qaboos university, oman. al-ajmy, i. 2002. wastewater in the sultanate and its effects on environment (arabic), in: international conference on wastewater management and its effect on the environment in hot and arid countries, 21-23 oct., 2002. al-khamisi, s. a., abdelrahman, h. a., ahmed, m., and. goosen, m.f.a. 2011. assessment of reclaimed water irrigation on growth, yield, and water-use efficiency of forage crops. appl. water science. 1: 57-65. bedbabis .s, giuseppe. f, bechir. b. r, and makki, b. 2010. effects of irrigation with treated wastewater on olive tree growth, yield and leaf mineral elements at short time. horticulture science. 126: 345-350. berry, w.l., wallace, a. and lunt, o.r. 1980. utilization of municipal wastewater for culture of horticultural crops, horticulture science, 15, p. 169-171. david, d.j and williams, c.h. 1979. effects of cultivation on the availability of metals accumulated in agriculture and sewage treated soils, prog. water technol. 11, p.257264. ensink, j.h.j., mahmood, t., van der hoek, w., raschid-sally, l. and amerasinghe, f.p., (2004). a nation-wide assessment of wastewater in pakistan: an obscure activity or a vitally important one? water policy, 6,197 – 206. fao. 2010. groundwater management in oman. draft synthesis report. food and agriculture organization of the united nations, rome. fao. 1998 . fao corporate document repository. crop evapotranspiration guidelines for computing crop water requirements fao irrigation and drainage paper 1998, 56. http://www.fao.org/docrep/x0490e/ x0490e00.htm fluet, m.j., vescovi, l. and bokoye, a.i. 2009. the united nations world water development report–n° 3-2009–water and climate change (citizen mobilization, a source of solutions), unesco. figure 4. a sample view of visual-basic interface of the dss on crop rotation optimization. 62 squ journal of agricultural and marine sciences, 2015, volume 19, issue 1 development of a decision support system for the management of treated wastewater irrigation haruvy, n. 1997. agriculture reuse of wastewater: nationwide cost-benefit analysis. agriculture, ecosystem & environment, 66 (2), p.113-119. maf. 2013. oman salinity strategy. ministry of agriculture and fisheries, sultanate of oman.(http:// maf.gov.om/download.ashx?file=fckupload/file/ books/main.pdf ). maf. 2014. agricultural census for years 2012-2013. volume 1. ministry of agriculture and fisheries. muscat, oman. maf. 2015. agricultural and fisheries sectors performance: productivity and economic indicators between 2011 and 2014. directorate general of planning and development. ministry of agriculture and fisheries, muscat, oman. mohammed, m. j. and mazahareh, n. 2003. changes in soil fertility parameters in response to irrigation of forage crops with secondary treated wastewater. communications in soil science and plant analysis, 34 (9/10), p, 1281-1294. mott, macdonald and mrmwr, (2013a). water balance computation for the sultanate of oman. final report – executive summary, mott macdonald and company llc and ministry of regional municipalities and water resources, sultanate of oman. mott, macdonald and mrmwr, (2013b). water balance computation for the sultanate of oman. final report, mott macdonald and company llc and ministry of regional municipalities and water resources, sultanate of oman. norman, w. r., shayya, w. h. , algafri, a.s. and mccann, i. r. 1998. aflaj irrigation and on farm water management in northern oman. irrigation and drainage systems, 12: 35-48. prathapar s.a, jamrah, a. ,ahmed, m , al adawi, s., al sidairi, s. and al harassi, a. 2005. overcoming constraints in treated greywater reuse in oman. desalination, 186/2:177-186. scardigno, a. 2014. improving water-efficient irrigation: prospects and difficulties of innovative practices, j. agricultural water management, elsevier, 146: 84– 94. somaratne, n. m. and ahmed, m. 1999. opportunities and problems of wastewater re-use. in water management, purification and conservation in arid climates. technomic publishing co. inc. pennsylvania u.s.a (isbn 1-56676-771-7). zekri, s., 2008. using economic incentives and regulations to reduce seawater intrusion in the batinah coastal area of oman. agricultural water management, 95(3): 243-252. research paper journal of agricultural and marine sciences vol. 24 : 19– 23 doi: 10.24200/jams.vol24iss1pp19-23 reveived 1 jan 2019 accepted 24 may 2019 gillnet selectivity of the indian oil sardine sardinella longiceps fished in the sea of oman govender, anesh* and al-oufi, hamed** govender, anesh* ( ) department of marine and fisheries science, college of agricultural and marine sciences, sultan qaboos university, p.o. box 34, al-khoud 123, sultanate of oman ** ministry of agriculture and fisheries, sultanate of oman, p. o. box 427, muscat, postal code 100 *corresponding author: govender@squ.edu.om introduction gillnet selectivity is the quantitative measure of the amount of fish caught within a size range that is retained by the net and it is a function of the probability of the fish encountering the net, the chance of being caught and the intensity of the fishing. generally, one length class will be sampled most efficiently with efficiency decreasing symmetrically to zero both above and below this length class. because gillnets are highly selective for fish of certain sizes, knowledge of the selection is necessary for both population assessment and management of the fishery (carlson and cortés, 2003). selection curves can be used to set a mesh size that can restrict the size of fish captured and hence, limit the catch of immature fish or reinforce minimum landing size regulations. in this study we describe the selection curve of the indian oil sardine (sardinella longiceps) harvested in the sea of oman. the indian oil sardine is found in the north and west indian ocean ranging from the horn of africa, along the arabian sea, sea of oman and aden (excluding the red sea and arabian gulf ) and then eastward to the southern coasts of india and sri lanka (al-abdessalaam, 1995). small pelagic fish, including s. longiceps, occur in abundance in omani waters. this species forms an important component of the marine food web because it comprises the bulk of the forage for large fish and other predators (al-barwani et al., 1989). the indian oil sardine and other sardines also contribute significantly to the omani marine fishery. in 2013 about 52544 tonnes of sardines were landed along the coast of oman, of which 8320 (16%) tonnes were s. longiceps (anonymous, 2013). this species, as well as other sardines, is exploited sardinella( إنتقائية الشباك اخليشومية ألمساك السردين الزييت اهلندي longiceps( املصطادة يف حبر عمان أنيش جوفيندر* ومحد العويف** abstract. the size selectivity of drift gill-nets for sardinella longiceps was investigated in the sea of oman using a range of 5 nets between 3.3 and 5.7 cm stretched mesh size. all nets had a hanging ratio of 0.5. a total of 1211 indian oil sardines were caught in the 5 experimental nets, the majority of which were retained by the 3.3, 3.8 and 4.5 cm mesh nets. peak selectivity was reached at 14.9 cm fl for the 3.3 cm mesh size increasing to 16.9 cm for the 3.8 cm mesh size. the estimated and observed length frequency distributions were unimodal. a log-normal selection function indicated that the highest selectivity was obtained when the length class to mesh size (l:m) ratio was 4.4. sardinella longiceps’s relative abundance was estimated to be the highest at 16.4 cm fl, with numbers decreasing beyond this peak. this would indicate that selectivity by gilling is optimal with a mesh size of 3.8 cm with nets having a hanging ratio of 0.5. this mesh size appears to satisfy two criteria: high catch efficiency and protection of juveniles. keywords: sardine; gillnet selectivity; model; sea of oman. املســتخلص: مت البحــث يف إنتقائيــة حجــم الشــباك اخليشــومية العائمــة ألمســاك الســردين )sardinella longiceps( يف حبــر عمــان باســتخدام 5 شــباك يــراوح حجــم فتحــات عيوهنــا بــن 3.3 و 5.7 ســم، وبإســتخدام معامــل تعليــق واحــد )0.5(. مت إصطيــاد مــا جمموعــه 1211 مسكــة مــن أمســاك الســردين الزيــي اهلنــدي يف الشــباك التجريبيــة اخلمســة، حيــث أصطيــدت غالبيتهــا مــن خــال الشــباك ذات الفتحــات 3.3 و 3.8 و 4.5 ســم. ومت الوصــول إىل أفضــل إنتقائيــة عنــد طــول شــوكي 14.9 ســم بالشــبكة ذات حجــم 3.3 ســم والــي إرتفعــت إىل 16.9 ســم بالشــبكة ذات حجــم 3.8 ســم. ووجــد أن توزيعــات تــردد األطــوال املقــدرة واملاحظــة كانــت أحاديــة الوســائط. وأشــارت دالــة التحديــد اللوغاريتمــي املعتــدل إىل أنــه مت احلصــول علــى أعلــى انتقائيــة عندمــا كانــت نســبة فئــة الطــول إىل حجــم الشــبكة تســاوي 4.4. ومت تقديــر الوفــرة النســبية األعلــى ألمســاك الســردين الزيــي اهلنــدي )sardinella longiceps( عنــد 16.4 ســم، مــع اخنفــاض األرقــام إىل مــا بعــد هــذه الــذروة. وقــد يشــر هــذا إىل أن االنتقائيــة اخليشــومية مثاليــة مــع الشــبكة ذات حجــم 3.8 ســم ومعامــل تعليــق 0.5. حيــث يبــدو ان هــذا احلجــم الشــبكي يلــي معياريــن ومهــا: كفــاءة الصيــد العاليــة ومحايــة صغــار األمســاك. الكلمات املفتاحية: السردين، إنتقائية الشباك اخليشومية، منوذج، حبر عمان 20 squ journal of agricultural and marine sciences, 2019, volume 24, issue 1 gillnet selectivity of the indian oil sardine sardinella longiceps fished in the sea of oman primarily by cast nets, beach seines and gillnets. as they require little investment in manpower and equipment, and are efficient in catching pelagic fish, gillnets are widely used by traditional omani fishermen. because of the decline in large pelagics (e.g. scomberomorus commerson (govender et al., 2006), human consumption of sardines has increased, resulting in increased market prices. these issues will likely result in over-exploitation of sardines which may lead to a decrease in abundance in the future. based on late 1980s data, (dorr, 1991) already observed that sardines were caught at near optimum levels. although fluctuations in sardine abundance are largely regulated by the environment (kawasaki, 1991), intensive fishing in coastal waters may reduce fish productivity. seeing as the indian oil sardine is considered one of the key species in the oman fishery, selectivity estimates are potentially of great value in management and research. therefore, the main objective of this study was to determine the gillnet selection parameters of the indian oil sardine gillnet using nets of different mesh sizes fished simultaneously on the same population. materials and methods sampling was carried out monthly between september 2001 and july 2003 on board the rv al-jamiah, a 17.5 m (overall length) multipurpose fishing boat. green polyamide (nylon) gillnets of similar thickness (pa 210d × 6 plays) and of mesh sizes 3.3, 3.8, 4.5, 5.0 and 5.7 cm (stretched mesh) were used. for each mesh size a gillnet was constructed with 0.5 hanging ratio; thus 5 experimental nets of similar fishing power were constructed and joined together as a gang. for all nets, a similar hanging ratio was used for the float line and the lead line to restrict fish being tangled. all nets were made to the same finished length of 25 m, giving a total length of 125 m and a fishing height of 3 m. the nets were rigged with a 6 mm pe (polyethylene) float line fitted with several pvc floats (113 g buoyancy) regularly distributed to give a float line buoyancy of around 135 g/m, while the sinking force employed for the lead lines had a force of 50 g/m. the order of mesh panels was randomized at the beginning of the experiment. the nets were joined together with a 2 m gap between adjacent nets. this design was chosen to avoid the effect of larger fish being led by smaller mesh-sized nets into neighboring nets of a more suitable mesh size (hovgård, 1996; madsen et al., 1999). each net was coded to enable identification on hauling. fishing stations were selected in shallow waters in the muscat (23º 37’ n, 58º 35 e’) area. one end of the net series remained attached to the boat by a rope and both the net and boat was set to drift with the current. fishing was carried out a few hours before sunrise and the net series was hauled-in after sunrise giving an average fishing time of 4 hours. the total number of valid sets was 34. catches were sorted by species and fork length (fl) was measured to the nearest cm and the weight to the nearest gram. girth measurements at the snout, behind the head and at maximum girth (before the dorsal fin) were also recorded for each fish. although girth measurements were taken for all fish, fork length was used to construct the selectivity curves because length is closely related to mesh size as is girth (reis and pawson, 1999). gilled or wedged fish were used in the analysis while tangled fish were excluded from the analysis as tangling of fish is not a function of net selectivity. selectivity modeling hamley (1975) provided a review of the approaches to estimate gillnet selection curves and more recently hovgård and lassen (2000) provided an updated review of all methods, including new statistical approaches that are based on general models for the selection process. eq. 1 the parameters for the selection curves in this study were obtained using maximum likelihood (ml) (kirkwood and walker, 1987; millar, 2000). assuming that fishing effort and fishing power are constant, the selection equation (hovgård and lassen, 2000) is written as eq. 2 where-?-is the predicted catch in length class l for mesh size m, q is the catchabilty co-efficient (assumed constant for each l and each m), n is the number of available fish and s is the selectivity function. we assumed that the selectivity function followed a log-normal distribution i.e. eq. 3 and that the error was poisson distributed i.e. where c is the observed catch, k is the predicted ratio of (l/m) that has the maximum selectivity and σ is the dispersion factor around k. table 1. estimates and their 95% confidence intervals for the parameters of the selection equation for three mesh sizes (3.3, 3.8 and 4.5 cm stretched mesh) with a hanging ratio = 0.5. the negative log-likelihood (log l) = -4345.944. parameter value 95% confidence interval k 4.4 4.3 – 4.5 σ 0.124 0.117 – 0.133 21research article govender, al-oufi eq. 4 the estimates of the parameters k and σ were obtained by minimizing the negative of the log-likelihood (log l), with constant values removed. the 95% confidence intervals for the parameters k and σ were obtained using the likelihood ratio test (lebreton et al., 1992). results a total of 1211 indian oil sardines were caught in the 5 experimental gillnets, the majority of which were retained by the 3.3 (454), 3.8 (438) and 4.5 cm (301) nets. because catches obtained with the 5.0 (17) and the 5.7 cm (1) meshes were small, these data were not included in the analysis. almost all s. longiceps caught (gilled or wedged) were observed to have meshes stretched tight across their bodies in the region behind the gill cover to the maximum girth. some were observed to have twine caught in their mouth (snagged) and some others were entangled. only the first category was included in the analysis, although the other two categories do not appear to affect their size selection as length distributions were similar for all three categories of entrapment in the nets. as expected, the mode of the length frequency distribution of s. longiceps for different mesh sizes increased with mesh size (fig. 1). the observed peak length for the 3.3, 3.8 and the 4.5 cm mesh gillnets were 16.1, 16.5 and 18.0 cm, respectively. the size range of fish caught by the 3.3 cm mesh size was 13-18 cm, compared with 14-19 cm for the 3.8 cm and 14-20 cm for the 4.5 cm mesh size (fig. 1). the length distributions were unimodal except for the 3.3 cm mesh size which showed a second minor mode at 14 cm fl (fig. 1) gill net selectivity the estimated selectivity curves for s. longiceps appeared bell-shaped (fig. 2), which is to be expected for fish that are gilled or wedged, as was confirmed during fishing trials. peak selectivity was reached at 14.9 cm fl for the 3.3 cm mesh size, increasing to 16.9 cm for the 3.8 cm mesh size. the results indicated that the 3.3 and 3.8 cm mesh size had an equal selectivity for fish of 15.8 cm in length, whereas the 3.8 and the 4.5 cm mesh sizes had an equal selectivity for fish of 18.3 cm length (fig.  2). the estimated parameter values and their 95% confidence intervals are given in table 1. maximum selectivity was achieved at an l:m ratio of 4.4 (table 1). the small confidence intervals indicate that the parameters are well estimated (table 1). discussion there has been no previous attempts to estimate gillnet selectivity parameters for the indian oil sardine and hence, comparisons cannot be made. the unimodal nature of the selection curve is linked to the catching process, namely gilling or wedging, whereas maxillae enmeshing or entangling, which would have resulted in either a sigmoid-shaped or a bimodal curve, was shown to have been of little importance. since the indian oil sardine has no spines or any other projections on its body which could result in entanglement the shape of the selection curve is therefore influenced by fish girth alone. girth being directly proportional to fish length justifies the latter being used as a proxy for girth since fish length is easier and quicker to measure. these findings are in agreement with those of reis and pawson (1999) and santos et al. (1998), although both these studies were investigating other fish species; they had similar body shapes to s. longiceps. in contrast, several studies have used bimodal selection curves with two distinct modes that are linked to two different catching processes, wedging and entangling (madsen et al., 1999). millar and fryer (1999) used a bimodal selection curve to describe plaice catch data in a trammel net experimesh_size: 4.5 cm mesh_size: 3.8 cm mesh_size: 3.3 cm 13 14 15 16 17 18 19 20 0 50 100 150 200 0 50 100 150 200 0 50 100 150 200 fork length class midpoint (cm) n um be rs o f f is h figure 1. observed (bars) and predicted (lines) numbers of sardinella longiceps caught with gillnets of varying mesh sizes. 22 squ journal of agricultural and marine sciences, 2019, volume 24, issue 1 gillnet selectivity of the indian oil sardine sardinella longiceps fished in the sea of oman ment while madsen et al. (1999) used it for sole, plaice and cod and hovgård (1996) used it for cod catch data. while our data did showed a minor mode for the 3.3 cm mesh net we regarded it as negligible for the model fitting process. previous studies have indicated that s. longiceps reaches first maturity at 15.93 cm total length in the sea of oman (siddeek et al., 1994). this total length was transformed to a fork length using the equation: tl=1.075fl+0.72 eq. 5 r2=0.96(h. al-oufi, unpubl. data). length at first maturity for this population is therefore equal to 14.1 cm fl. the length at first maturity is slightly lower than the optimal catch size computed for the 3.3 cm mesh size. in catches of the 3.3 cm gillnet, individuals under the length at first maturity made up slightly more than 11% of the catch, whereas this was around 2% for the 3.8 cm gillnet and was virtually zero for the 4.5 cm mesh. although, a minimum landing size has not yet been set for s. longiceps in the omani fishery, the results of this study show that in the interests for sustainable fishing of s. longiceps it can be suggested that gillnets with stretched mesh of 3.8 cm (with a hanging ratio = 0.5) should be used. this would certainly increase the average size caught when compared to the 3.3 cm net. catches obtained with the 4.5 cm gillnet were always small, confirming that the large mesh size targeted only the larger individuals of the indian oil sardine population in the sea of oman. the 3.8 cm mesh size gillnet appears to satisfy two criteria: high catch efficiency and protection of juveniles. the use of smaller mesh sizes in this experiment may have resulted in a better match between the overall selectivity of the gang of nets and the relative indian oil sardine population abundance. however, it was considered more important to include those mesh sizes that have direct applicability to gillnets used by local fishers. construction details of nets used in this study, such as twine diameter and hanging ratio, is similar to that used by the local fishers (stengel and al harthy, 2002). the shape of the selectivity curve depends on several characteristics of the fish and the net. gray et al. (2005) reported an overall reduction in mean catch associated with an increased hanging ratio, although the results were not significant. of particular importance are the physical properties of the twines used, such as extensibility and elasticity (klust, 1982). low extensibility and elasticity result in the loss of captured fish which ultimately will influence the estimated selectivity. the twines used to construct the experimental gillnets were polyamide continuous filaments, which has high extensibility coupled with high elasticity. reported elasticity was above 96% (klust, 1982) which means that these twines are almost completely elastic, a property that is needed to hold the gilled fish securely while the gear is in the catching process and during hauling (klust, 1982). other factors, such as sex, ripeness and amount of food in the gut, would also influence the girth of the fish and hence the shape of the selectivity curves. to minimize variation caused by reproduction and gut contents, (salvanes, 1991) proposed pooling samples for months when food availability and temperature are the lowest. this could not be achieved in this study as this would have reduced sample sizes to unacceptably low numbers. márquez-farias et al. (2005) added oceanographic currents as a possible factor affecting selectivity; since strong currents can distort the shape of the meshes and therefore select for fish sizes not captured under conditions of a mild current. this effect was considered negligible in this study. there are limitations to this study. the study was limited to the muscat area (for logistic reasons) and since sardines generally school and migrate in similar age/ length classes it is quite possible that smaller/younger or larger/older classes were not available for capture. this research need should be accounted for in future research. acknowledgement the authors express sincere thanks to prof. anton maclachlan, former dean of the college of agricultural and marine sciences, sultan qaboos university who kindly reviewed the manuscript and to dr. michel claereboudt of sultan qaboos university who assisted with the ml model and provided many comments and suggestions. sincere thanks to mr khamis al-riyami, saleh al_mashari, manolito c. barte and mohamed alghithy who assisted during the fishing operations. this study was funded by sultan qaboos university (project number: ig/agr/fish/00/03) references al-al-abdessalaam, t.z.s., 1995. marine species of the sultanate of oman. muscat: marine science and fisheries centre, ministry of agriculture and fisher0.00 0.25 0.50 0.75 1.00 10 11 12 13 14 15 16 17 18 19 20 21 length class midpoint (fl, cm) s el ec tiv ity mesh_size m3.3 m3.8 m4.5 figure 2. selectivity curves for various mesh sizes for sardinella longiceps. the plotted lines have been smoothed. 23research article govender, al-oufi ies. 412 p. al-barwani m, prabhakar a, dorr j, al-manthery m., 1989. studies on the biology of sardinella longiceps (valenciennes) in the sultanate of oman, 1985-1986. kuwait bulletin of marine science 10,201-209. anonymous, 2013. annual fisheries statistical year book for 2013. muscat: ministry of agriculture and fisheries resources. carlson, j.k., cortés e. 2003. gillnet selectivity of small coastal sharks off the southeastern united states. fish res 6,:405-414. dorr, j.a., 1991. small pelagics final report for the contract for technical services for staffing the marine science and fisheries center. project no 272-01011-1. gray, c.a., broadhurst, m.k., johnson, d.d., young, d.j., 2005. influences of hanging ratio, fishing height, twine diameter and material of bottom-set gillnets on catches of dusky flathead platycephalus fuscus and non-target species in new south wales, australia. fish sci 71,1217-1228. hamley, j., 1975. review of gillnet selectivity. j fish res board can 32,1943-1969. hovgård. h., 1996. a two-step approach to estimating selectivity and fishing power of research gill nets used in greenland waters. can j fish aquat sci 53,10071013. hovgård, h, lassen, h. 2000. manual on estimation of selectivity for gillnet and longline gears in abundance surveys. rome: fao. kawasaki, t. 1991. long-term variability in the pelagic fish population. in: kawasaki, t., tanaka, s., tola, y., taniquiche, a., editors. the long-term varaiability of pelagic fish populations and their environment. new york: pergamon press. kirkwood, g.p., walker, t.i. 1987. gill net mesh selectivities for gummy shark, mustelus antarcticus günther, taken in south-eastern australian waters. aust j mar freshw res 37,689-697. klust, g. 1982. netting materials for fishing gear. rome: fao. 175 p. lebreton, j.d., burnham, k.p., clobert, j, anderson, d.r., 1992. modeling survival and testing biological hypotheses using marked animals: a unified approach with case studies ecol monogr 62,67-118. madsen, n., holst, r., wileman, d., moth-poulsen, t., 1999. size selectivity of sole gill nets fished in the north sea. fish res 44,59-73. márquez-farias, j.f., corro–espinosa, d., castillo– géniz, j.l., 2005. observations on the biology of the pacific sharpnose shark (rhizoprionodon longurio, jordan and gilbert, 1882), captured in southern sinaloa, méxico. journal of northwest fishery science 35,107-114. millar, r.b., 2000. untangling the confusion surrounding the estimation of gillnet selectivity. can j fish aquat sci 55,1328-1337. millar, r.b., fryer, r.j., 1999. estimating the size-selection curves of towed gears, traps, nets and hooks. rev fish biol fish 9, 89-116. reis, e.g, pawson, m.g., 1999. fish morphology and estimating selectivity by gillnets. fish res 39,263-273. salvanes, a.g.v., 1991. the selectivity for cod (gadus morhua) in two experimental trammel-nets and one gillnet. fish res 10,265-285. santos, m.n., monteiro, c.c., erzini, k., gerard, l., 1998. maturation and gill-net selectivity of two small sea breams (genus diplodus) from the algarve coast (south portugal). fish res 36,185-194. siddeek, m.m., al-habsi, h.n., al-jufaily, s.m., al-ghafry, i.n., 1994. spawning cycle, recruitment patterns and maturity length of indian oil sardine at al-aziba, the sea of oman. in: chou, l.m., munro, a.d., lam, t.j., chen, t.w., cheong, l.k.k., ding, j.k., hooi, k.k., khoo, h.w., phang, v.p.e., shim, k.f., tan, c.h., editors. the third asian forum. manila, philippines: asian fisheries society. stengel, h., al harthy, a., 2002. the traditional fishery of the sultanate of oman (fishing gear and methods). muscat: ministry of agriculture and fisheries, directorate general of fisheries resources, marine science and fisheries center. 147 p. research paper journal of agricultural and marine sciences vol. 23 : 48– 51 doi: 10.24200/jams.vol23iss1pp48-51 reveived 27 feb 2018 accepted 05 apr 2018 second gcc marine biotechnology conference: emerging opportunities and future perspectives sergey dobretsov *sergei dobretsov ( ) department of marine science and fisheries, college of agricultural and marine sciences and center of excellence in marine biotechnology, sultan qaboos university, box 34, al-khod, 123. email: sergey@squ.edu.on introduction the oceans cover 71 percent of the earth’s surface and contain a large diversity of abiotic and biotic marine resources. in spite of this great potential of marine resources, these remain largely unexplored and unused. marine biotechnology or “blue biotechnology” exploits the enormous genetic, biochemical and taxon biodiversity found in oceans and seas for the benefit of mankind (allen and jaspars 2009). due to the development of novel engineering, molecular and genetic technologies marine biotechnology has experienced a rapid growth in the recent years. it is estimated that marine biotechnology will have a global annual growth rate of 4-5% with a total market value of 3.5 billion euro by 2018 (global industry analysis 2013). in europe only through the horizon 2020, blue growth strategy, the eu provided a budget of 145 million euro for the development of marine biotechnology (greco and cinquegrani 2016). the sultanate of oman has a coastline of more than 3000 km with highly productive waters and diverse marine bio-resources (al-belushi et al. 2015). living marine resources are oman’s major renewables and have a remarkable potential for commercial exploitation beyond the traditional fisheries industry. development of marine biotechnology in oman can help and generate new materials, isolate bioactive compounds and describe biochemical systems and processes regulations that will have applications for human health, nutrition and future supplies of energy (al-belushi et al. 2015). marine biotechnology can create new job opportunities and thus provide new sustainable sources of income for the sultanate of oman. in recognition of the marine biotechnology potential of the sultanate, the “second gcc marine biotechnology conference: emerging opportunities and future perspectives” was organized by the centre of excellence in marine biotechnology, sultan qaboos university, 31 october – 1 november 2017. the conference was held in al-faham stage, sultan qaboos university (squ), muscat. this is the second conference in this field organized in the region. the first marine biotechnology symposium took place at squ in november 2013 and 100 participants representing fifteen different countries came to share their ideas and knowledge (goddard et al. 2015). the main aim of this 2nd gcc marine biotechnology conference was to provide a stage for marine biotechnology, aquaculture and fisheries scientists from the region and other countries to exchange ideas, build املؤمتر الثاين للتقنية احليوية البحرية لدول جملس التعاون اخلليجي: الفرص الناشئة ووجهات النظر املستقبلية سرجي دبرتسوف abstract. the second gcc marine biotechnology conference was held at sultan qaboos university from the 31 october to 1 november 2017. the conference was organized by the center of excellence in marine biotechnology, squ and focused on four major themes: (1) genetics and biodiversity, (2) marine biofouling and its prevention, (3) marine natural products, and (4) aquaculture and fisheries. in total, 160 delegates from 23 countries were registered for this conference and 106 delegates attended the conference. in addition to a plenary lecture and three keynote addresses, 39 oral and 30 poster presentations were made. the final session reviewed national and regional issues and identified some of the main challenges in marine biotechnology in the region. keywords: oman; marine biotechnology; aquaculture; biofouling; genetics; biodiversity املســتخلص: أقيــم املؤمتــر الثــاين للتقنيــة احليويــة البحريــة لــدول جملــس التعــاون اخلليجــي جبامعــة الســلطان قابــوس مــن 31 أكتوبــر اىل 1 نوفمــر 2017. مت تنظيــم املؤمتــر مــن قبــل مركــز التميــز للتقنيــة احليويــة البحريــة جبامعــة الســلطان قابــوس وركــز علــى أربــع حمــاور رئيســية: )1( علــم اجلينــات والتنــوع احليــوي، )2( الرتاكــم احليويــة لألســطح املغمــورة والوقايــة منــه، )3( املنتجــات البحريــة الطبيعيــة، )4( االســتزراع الســمكي وعلــوم األمســاك. يف اجملمــل، مت تســجيل 160 شــخص مــن 23 دولــة كمشــرتكني يف هــذا املؤمتــر و106 أشــخاص كانــوا مــن احلضــور. باإلضافــة اىل احملاضــرة العامــة والثــاث حماضــرات الرئيســية، مت عــرض 39 عــرض شــفهي و 30 ملصــق. اســتعرضت اجللســة اخلتاميــة القضايــا الوطنيــة واالقليميــة ومت حتديــد بعــض التحديــات يف جمــال التقنيــة احليويــة البحريــة يف املنطقــة. الكلمات املفتاحية: التقنية احليوية البحرية، االستزراع السمكي، الرتاكم احليوي على األسطح املغمورة، علم اجلينات، التنوع احليوي 49research article dobretsov up new collaborations, and strengthen existing ones between institutes, centers and industries. the objectives of the conference were to assess and promote the development of marine biotechnology in the region. this holds in particular for the prevention of biofouling, the search for marine natural products for various industrial purposes, and screening the genetic and molecular biodiversity of marine organisms for a sustainable aquaculture. conference the 2nd gcc marine biotechnology conference focused on four major themes: 1. genetics and biodiversity; 2. marine biofouling and its prevention; 3. marine natural products; 4. aquaculture and fisheries. these topics were selected based on current and planned research activities in oman and elsewhere in the gulf region. squ and the office of naval research global (usa) provided the funding of the conference. overall, 160 delegates from 23 countries were registered and 106 delegates attended the conference (fig. 1). in addition to one plenary lecture and three keynote addresses from world leading scientists, delegates presented 39 oral and 30 poster presentations. the organizers of the conference awarded the best student poster and student oral presentation prizes (table 1). additionally, the european society for marine biotechnology (esmb) gave three special awards to deserving young marine biotechnologists who presented their work at the conference. during the conference, all speakers emphasized that the sultanate of oman and other oil-rich countries needed to diversify their economy. marine biotechnology can provide possible solutions for such economic diversification. it was emphasized that the collaborative studies between biologists, chemists, and engineers are urgently needed and can result in novel marine biotechnological applications and products. additionally, it is important to close the gap between research and industry. this can be done through academia/industry cooperation such as joint research projects of university scientists with their counterparts in the industry. the keynote speakers prof. claire hellio (brest university, france) and prof. grant burgess (newcastle university, uk) presented several successful stories of such collaborative projects between industry and academia. as proof of the benefits of such partnership, several industrial partners sponsored the participation at this conference of several presenters. the challenging part of such joint research between industry and academia is the possible conflicts of interests. this holds particularly true when confidentiality is required by the industry, while dissemination of scientific results is required by the academic research. it was highlighted that open innovation is a useful tool for biotechnology. this will be of benefit for the sultanate of oman and other developing countries. several models of open innovation have been developed, tested, and presented at the conference. high biodiversity of marine organisms is at the base for chemical and genetic diversities that can be used to create new products and processes to benefit humanity. several speakers highlighted that we do not know enough about the species of marine organisms living in the arabian gulf and the sea of oman, such as microalgae, bacteria, corals, bryozoans and other invertebrates. only fish and mollusks, the groups relevant for direct exploitation, have received sufficient attention. many other invertebrate taxonomic groups, which are essential for the development of a marine bio-prospecting effort, were only superficially investigated and local expertise in many cases is minimal. this holds particularly for their molecular and genetic information, which is untapped as yet. several presenters clearly identified the array of genetic tools as one of the main mechanisms to study biodiversity and the physiological variability in organisms. the keynote speaker dr. roger huerlimann (james cook university, australia) emphasized the importance of environmental dna (edna) for the identification of footprints of marine organisms. by the identification of edna through next generation sequencing technology it is meanwhile possible to determine the presence of particular species or communities, such as invasive, biofouling, commercially important, endangered and species of other interest. such approaches also provide challenges. some closely related species cannot be separated or identified using these modern techniques yet as in many cases, specific markers have not yet been developed. environmental factors such as temperature, ph, or uv radiation affect the stability of edna and limits its applicability over time as is the lack of reference material, particularly for local species. the plenary speaker prof. grant burgess (newcastle university, uk) and several other researchers provided evidence that edna can play an important role in biofilm and particle formation and stability. it has been shown that enzymes that inhibit production or cleave edna can be used for biofilm removal. in combination with antibiotics they can provide a suitable tool to counter microbial infections and to prevent biofouling. the keynote speaker prof. claire hellio (brest university, france) highlighted the importance of sufficient supplies of bioactive compounds from marine organisms for the growing and diverse demands of the industry. she demonstrated that the production of bioactive substances from marine organisms in their natural environment could vary with time, locations, and physiological conditions. as it is possible to control the production of bioactive compounds from bacteria and microalgae in the laboratory, it makes these organisations a more predictable source of marine natural products. synthetic chemistry could be another solution where natural 50 squ journal of agricultural and marine sciences, 2018, volume 23, issue 1 second gcc marine biotechnology conference: emerging opportunities and future perspectives compounds could serve as lead substances in diverse biotechnological applications. fish and crustacean waste were proposed as potential sources of novel antifouling agents as well as forms of food preservatives. for example, chitosan and chitosan nanocomposites were successfully used to extend the shelf life of some vegetables. subsequent presentations, demonstrated the high potential of photocatlytic zno nanoparticles and nanorods for the prevention of biofouling in the laboratory and field experiments. toxic risks assessments of nanomaterials are demanded. a study conducted in iran suggested that higher temperatures, such as that observed as a result of global climate change, altered the composition, the growth rate, and the biomass of biofouling communities. among future challenges, it was mentioned that the process of biofouling is complex and requires interdisciplinary research by biologists, chemists, and others. additionally, there are currently limited links between the industry and academia to exchange ideas and develop innovative antifouling coatings. the keynote speakers dr. stephen goddard (water farmers, belgium) and dr. lee wee (temasek polytechnic, singapore) highlighted that due to human population growth the global need for food and clean water is steadily increasing. the long-term sustainability of traditional fisheries resources became a problem. aquaculture in re-circulating water is a possible solution that addresses these problems, and provide food security, create value added products, and generate knowledge and sustainable employment. aquaculture is not a farming approach anymore but became a food production industry, demanding diverse management skills. freshwater and marine aquaculture can produce among other products, animal and plant food, nutraceuticals and pharmaceuticals, as well as bioenergy and extact nutrients from wastewater treatment. at the same time, there are avoidable negative issues associated with aquaculture, such as natural habitat destruction, increased risks table 1. list of conference awards for the best student and young marine biotechnology presenters. name/affiliation category awarded by emily claereboudt, university of liege, belgium best student oral presentation organizers jalila al-hadrami, sultan qaboos university, oman best student poster presentation organizers surendraraj alagarsamy, kuwait institute for scientific research, kuwait best young marine biotechnology presenter european society for marine biotechnology muna al hinai, sultan qaboos university, oman best young marine biotechnology presenter european society for marine biotechnology cassy bakshani, newcastle university, uk best young marine biotechnology presenter european society for marine biotechnology figure 1. participants of the 2nd gcc marine biotechnology conference 51research article dobretsov of invasive species, and the possible spread of infectious diseases. speakers presented examples of novel approaches that could overcome such problems. these include aquaponic, bio-flock and integrated multi-trophic aquaculture management systems. such novel approaches reduce the overall amount of used water, minimize waste and chemicals usage, as well as allow the production of multiple species, such as fish, shrimps, mussels and agricultural crops. aquaculture could benefit from recirculating aquaculture systems with reduced or no water discharge. “waste” from aquaculture can be reused for other purposes. presenters gave few examples for such approaches. “fish dew”®, a fertilizer made of fish waste can provide a revenue higher than the value of the fish that produce it. another example is chitosan, which is produced from shrimp exoskeleton, and can be used in food, biomedical, and agricultural applications. urban aquaculture saves space and brings fresh products, such as fish, seafood, seaweed or vegetables, from aquaponic enterprises to the consumers by saving transport efforts. the conference also identified some of the main challenges in developing a marine biotechnology particularly in the arab region: lack of collaborative efforts, a very small pool of existing biotechnology industries, a limited sharing of know-how, logistic and financial resources. most countries in the gcc region are small and only recently embraced scientific research at a global scale. the region also suffers from a basic scientific infrastructure, a legislation offering often only an incomplete protection of the intellectual property, a still developing framework for fostering international cooperation and are industry-academia collaborations. all participants agreed on the need to organize a workshop between academia, policy makers and the private sector in order to discuss problems and find possible solutions in the future. acknowledgement we would like to acknowledge financial and logistic support of the conference by sultan qaboos university and the office of the naval research global. we also thank the european society for marine biotechnology for the awards to young marine biotechnologists who presented their work at the conference. references al-belushi, k., s.m. stead, j.g. burgess. 2015. the development of marine biotechnology in oman: potential for capacity building through open innovation 2015. marine policy 57: 147-157. allen, m.j., m. jaspars. 2009. industrial biotechnology 5(2): 77-83. goddard, s., m. delghandi, s. dobretsov, h. al-oufi, s. al-habsi, and j.g. burgess. 2015. the first gcc marine biotechnology symposium: emerging opportunities and future perspectives. marine biotechnology 17: 285-289. global industry analysts inc. 2013. marine biotechnology, global strategic business report. http:// www.slideshare.net/globalindustryanalystsinc/marine-biotechnology-a-global-strategic-business-report (accessed on 27 february 2018). greco, gr, m. cinquegrani. 2016. firms plunge into the sea. marine biotechnology industry, a first investigation. frontiers marine science doi.org/10.3389/ fmars.2015.00124. research paper journal of agricultural and marine sciences 2021, 26(1): 21–26 doi: 10.24200/jams.vol26iss1pp21-26 reveived 06 july 2020 accepted 01 dec 2020 subclinical mastitis in camels in oman: a pilot study muhammad nadeem asi, waleed al-marzooqi, yasmin eltahir, al ghaly, al toobi, sara al raisi, haytham ali, elshafie i. elshafie, eugene h. johnson muhammad nadeem asi( ) asi@squ.edu.om, assistant professor, department of animal & veterinary sciences, college of agricultural & marine sciences, sultan qaboos university, 123 oman introduction camels are a mainstay of rural communities in oman as elsewhere in arid and semi-arid zones in the middle east and africa, by virtue of their endurance and productive potential under such agro-ecological environments. in oman, as in the arab world, camel (camelus dromedaries) is akin to culture and subsistence livelihood in rural areas where camel is an important source of milk (barlowska et al., 2011; zibaee et al, 2015), which is generally acclaimed for its nutritive and health benefits (mullaicharam, 2014). moreover, camel’s milk has recently been gaining wider consumption and a place in the market of dairy products. relevant to that is the relatively substantial population of camel in oman, estimated at 273,000 (ncsi, 2019), with significant contributions to livelihood of the owners and economy. however, one of the major problems إلتهاب الضرع حتَت السَّريِريَّ يف اإلبل يف عمان: ِدراَسة ِإْرتَِياِديَّة حممد ندمي عاصي ، وليد املرزوقي ، ايمسني الطاهر ، الغالية الطويب ، سارة الرئيسي ، هيثم علي ، الشفيع إبراهيم الشفيع ، يوجني هاربر جونسون abstract. camels are important and multipurpose animals in many parts of the world including middle east. camel milk may harbor different bacteria. centuries old tradition of consumption of raw camel milk is still a common practice in oman. this study was carried out to conduct a microbiological analysis of camel milk samples with subclinical mastitis in the region of muscat, sultanate of oman. a total of 61 camel (camelus dromedarius) milk samples were collected from various animal holdings in and around muscat. onsite california mastitis test (cmt) revealed 18 (29%) camels positive for subclinical mastitis. positive milk samples were subjected to routine microbiological workup for bacterial isolation and identification. a total of 7 (47%) enterobacter cloacae isolates, 4 (27%) escherichia. coli, 3 (20%) coagulase negative staphylococci spp. (cns) and 1 (7%) micrococcus spp. were identified out of 15 milk samples. three milk samples did not yield any growth after two repeat attempts. isolates belonging to enterobacteriaceae were further subjected to antimicrobial sensitivity testing. all e. cloacae samples 7 (100%) were found to be resistant to penicillin, ampicillin, amoxicillin-clavulanic acid, first generation cephalosporins, and the macrolide group of antibiotics whereas 3 (43%) e. cloacae isolates were found to be intermediately resistant to the phenicol group of antibiotics. all four e. coli (100%) isolates were found resistant to penicillin, ampicillin, amoxicillin-clavulanic acid, first generation cephalosporins, and 2 (50%) showed resistance to macrolides, whereas 1 (25%) isolate was found to be resistant to tetracyclines. in this study, enterobacteriaceae were the most common group of bacteria isolated from camels with subclinical mastitis. enterobacter cloacae and e. coli were the predominant organisms. keywords: raw camel milk, enterobacter cloacae, e. coli, resistance املســتخلص:تعترب اإلبــل حيــواانت مهمــة ومتعــددة األغــراض يف أجــزاء كثــرة مــن العــامل مبــا يف ذلــك الشــرق األوســط. قــد حيتــوي حليــب اإلبــل علــى أنــواع خمتلفــة مــن البكتــراي. ال يــزال تقليــد اســتهالك حليــب اإلبــل اخلــام ممارســة شــائعة يف عمــان منــذ قــرون. أجريــت هــذه الدراســة إلجــراء حتليــل ميكروبيولوجــي لعينــات حليــب اإلبــل املصابــة ابلتهــاب الضــرع حتــت السَّــريرِيَّ يف منطقــة مســقط ، ســلطنة عمــان. مت مجــع 61 عينــة مــن حليــب اإلبــل )camelus dromedarius( مــن خمتلــف حيــازات احليــواانت يف مســقط وحوهلــا. أظهــر اختبــار كاليفورنيــا إللتهــاب الضــرع )cmt( أن 18 )29٪( مــن اإلبــل كانــت إجيابيــة لإلصابــة إبلتهــاب الضــرع حتــت الســريري. مت إخضــاع عينــات احلليــب املوجبــة للفحــص امليكروبيولوجــي الروتيــي لعــزل وتعريــف البكتــراي. أظهــرت النتائــج 7 )47٪( عــزالت مــن اأَلْمعائِيَّــُة َكيَــّـَرة مــن أصــل 15 عينــة ُ ْذَرِقيَّــة ، 4 )27٪( مــن اإِلْشــريِكيَُّة القولونِيَّــة ، 3 )20٪( مــن املكــورات العنقوديــة الســلبية املخثــرة و 1 )7٪( مــن جنــس البكــراي امل َ امل حليــب. ثــالث عينــات مــن احلليــب مل تســفر عــن أي منــو بكتــري بعــد حماولتــني متكررتــني. مت إجــراء إختبــار احلساســيه للعــزالت الــي تنتمــي إىل اأَلْمعائِيَّــات ملضــادات ْذَرِقيَّــة كانــت مقاومــة للبنســلني، األمبيســلني، محــض أموكسيســيلني-كالفوالنيك، اجليــل األول َ امليكــروابت. أظهــرت النتائــج أن مجيــع عينــات 7 )100٪( اأَلْمعائِيَّــُة امل ْذَرِقيَّــة ذات مقاومــة متوســطه جملموعــة الفينيكــول مــن َ مــن السيفالوســبورينات، وجمموعــة املاكروليــد مــن املضــادات احليويــة، بينمــا 3 )43٪( مــن عــزالت اأَلْمعائِيَّــُة امل املضــادات احليويــة. مت العثــور علــى عــزالت اإلشــريكية القولونيــة األربعــة )100٪( مقاومــة للبنســلني واألمبيســلني ومحــض أموكسيســيلني كالفوالنيــك واجليــل األول مــن السيفالوســبورين و 2 )50٪( مقاومــة للماكروليــدات ، بينمــا وجــدت عزلــة واحــدة )25٪( مقاومــة للتراســيكلني. يف هــذه الدراســة ، كانــت البكتــراي اأَلْمعائِيَّــُة هــي ْذَرِقيَّــة و اإِلْشــريِكيَُّة القولونِيَّــة هــي الســائدة. َ اجملموعــة األكثــر شــيوعا مــن البكتــراي املعزولــة مــن اإلبــل املصابــة إبلتهــاب الضــرع حتــت الســريري. كانــت بكــراي اأَلْمعائِيَّــُة امل ْذَرِقيَّة ، اإِلْشريِكيَُّة القولونِيَّة ، املقاومة. َ الكلمات املفتاحية: حليب اإلبل اخلام ، اأَلْمعائِيَُّة امل 22 squ journal of agricultural and marine sciences, 2021, volume 26, issue 1 subclinical mastitis in camels in oman: a pilot study impacting camel milk production and health is mastitis, though there is lack of reports in oman. mastitis, both clinical and subclinical, has been reported in gulf countries neighboring oman, uae and saudi arabia, in addition to iraq, kuwait, pakistan, india, somalia, sudan, kenya and more (toroitich et al., 2017). subclinical mastitis does not seem to show clear clinical signs but pathogenic microorganisms are harbored in intramammary tissue and are secreted in the milk. however, milk from an animal positive for subclinical mastitis may appear normal with normal total somatic cell count. this does raise public health concern considering the tradition of consumption of raw and unpasteurized milk in these regions, besides its bearing on camel health and losses in milk yield. however, unpasteurized milk is not recommended for its safety issue. our literature search indicated that there is lack of studies on subclinical mastitis in camels in oman. therefore, the aim of this study was to investigate the status of subclinical mastitis by conducting microbiological analysis of milk of camels to ascertain the extent of positive cases. a number of studies investigated subclinical mastitis in camel with successful application of california mastitis test (cmt) (saber et al., 2010, ali et al., 2019). assessment of milk samples by cmt and somatic cell count (scc) was shown to tie significantly regarding the detection subclinical mastitis in camels (abdulrahman, 1996), together with a good correlation of cmt to milk leukocyte count (obeid, 1983). applying cmt and scc to screen for subclinical mastitis in a group of camels led to revealing the predominance of gram-positive bacteria including streptococci spp. and staphylococci spp (saleh, 2011). moreover, a similar study in camels revealed the predominance of enterobacterium spp., staphylococcus spp. and streptococcus spp. in cases of subclinical mastitis (al-sailihi, 2017). diverse bacterial species were reported to be implicated in subclinical and clinical mastitis in camel. this is apparently related to a location as well as hygiene conditions and their management. a study of subclinical mastitis in camels in a district in iraq showed that the main isolates involved were coagulase negative staphylococci followed by streptococcus spp. and e. coli and micrococcus spp. were in a lesser extent (al-rammahi et al., 2018). in another location, ali et al. (2019) investigated subclinical mastitis in the two districts in pakistan and observed the high prevalence of s. aureus. in a habitat with close resemblance to oman, such as that of uae, isolates from subclinical as well as clinical mastitis of camel were identified to be mainly staphylococcus spp. trailed by streptococcus spp. and enterobacterium spp. (al-jaboori et al., 2013). materials and methods study area in this study, a total of 61 milk samples from healthy she-camels (camelus dromedaries) located in various holdings in and around muscat, sultanate of oman were considered. ethics statement in this study, verbal consent of camel’s owners was obtained prior to the collection of milk samples from their animals. animals were used just once for milk collection by professional veterinary technologists at the department of animal & veterinary sciences. this work was not an experimental research on animals and hence approval by the ethical committee at sultan qaboos university was not obtained. milk samples collection milk sampling was done by hand stripping just prior to milking using sterile screw caped 50 ml falcon tubes (kartell s.p.a and cellstar tubes, germany). milk sample (10 ml) was collected from each quarter in a sterile tube and labeled as per guidelines. (national mastitis council., 1990). california mastitis test (cmt) milk samples were subjected to onsite cmt test. cmt was carried out using the methods as described by schalm and noolander (1957). the cmt solution was obtained from immucell (portland, usa). equal volume of milk and cmt working solution were mixed in corresponding testing paddles. the mixture was gently rotated in horizontal position and results were recorded as negative, weak positive (+), distinct positive (++) and strong positive (+++). milk samples positive for onsite cmt test were transported to the laboratory in an ice box and processed for bacteriological examination within two hours of collection. animals with history of mastitis or recent treatment with antimicrobials were excluded from this study. bacteriological examination bacteriological examination of the samples was carried out following the standard methods as described by quinn et al. (1999). for microbiological analysis, each milk sample (0.1 ml) was streaked on blood agar (oxoid, basingstoke, england) and macconkey’s agar (oxoid, basingstoke, england) and subjected to incubation at 37oc for 24-48 hours in both aerobic and anaerobic conditions. in the case of no growth, corresponding milk sample was cultured again to obtain growth. the plates with growth were examined for growth colony morphology, hemolysis, and pigment production. 23research paper asi, al-marzooqi, eltahir, al ghaly, al toobi, al raisi, haytham ali, i. elshafie, h. johnson identification of bacterial isolates all isolates were subjected to gram staining, catalase, and oxidase tests. micrococci spp. and staphylococci spp. were identified using mannitol salt agar (oxoid), and coagulase test using both slide and tube methods along with catalase and oxidase testing. all biochemical tests were done according to standard procedures (nccls, 2000). analytical profile index test gram-negative isolates with oxidase negative and catalase positive reactions were subjected to api® 20e (biomérieux, france) and were further confirmed using vitek2 gram-negative (gn) test cards (biomérieux, france) in an automated vitek® 2 instrument. all isolates were kept in viabank tm tubes at -70°c for further use. gram-positive cocci isolates with positive catalase reactions were subjected to api® staph (biomérieux, france). staphylococci isolates were subjected to coagulase test using the tube coagulase method (quin, 1998). antimicrobial sensitivity test antimicrobial susceptibility and minimum inhibitory concentrations (mics) were determined using automated vitek® 2 instrument with ast cards (biomérieux, france). breakpoints used as recommended by the national committee for clinical laboratory standards (nccls, 2000). results california mastitis test and bacteriological examination analysis a total of 61 camels were examined for subclinical mastitis. out of 61 animals, 18 (29%) camel milk samples were found to be positive for subclinical mastitis using california mastitis test (cmt), whereas only 15 isolates yielded growth during microbiological analysis. three samples positive for cmt, did not yield any growth even after second culture. out of 15 positive growths, 7 (47%) isolates were confirmed as e. cloacae, 4 (27%) e. coli whereas 3 (20%) coagulase negative staphylococci and 1 (7%) isolate was confirmed as micrococcus spp. antimicrobial sensitivity test analysis antimicrobial sensitivity analysis revealed that all e. cloacae (100%) isolates were resistant to penicillin, first generation cephalosporins, and macrolide group of antibiotics, whereas 3 isolates (43%) shown intermediate resistance to phenicols. all four e. coli (100%) isolates exhibited resistance to penicillin, ampicillin, and amoxicillin, 2 (50%) isolates were resistant to erythromycin and tylosin, 3(75%) were resistant to first generation cephalosporins whereas only 1 (25%) isolate was found resistant to tetracycline. discussion the present study shows the presence of subclinical mastitis in camels in oman based on cmt and bacterial culture of milk samples. they also reflect a high correlation between cmt and cultural isolates. enterobacteriaceae e. cloacae and e. coli were found as the predominant bacteria with few coagulase negative staphylococci and micrococcus sp. e. cloacae isolated in this study belongs to the microbiota in the surrounding environment. this is a common commensal in animal digestive tract and is a common member of the human microbiome (keller et al., 1998). our results are in slight discrepancy with other reports since we report enterobacteriaceae e. cloacae and e. coli as dominant causative agents in subclinical mastitis in camels. reports on isolates from camel cases from neighboring countries implicate staphylococcus and streptococcus spp. as dominant ones in clinical and subclinical mastitis (al-jaboori et al., 2013; al-rammahi, 2018), in agreement with other reports (hadel et al., 2018). though al-jaboori et al. (2013) identified enterobacterium spp. from subclinical mastitis in camels in the uae, yet the dominant ones were staphylococcus and streptococcus spp. considering rural management practice, it is likely that cross-infection was established in camels since management and the level of hygiene is not optimal. to best of our knowledge this is the initial investigation to report subclinical mastitis in camels in oman, and that the coliform is the dominant type. not a single camel owner interviewed during sampling was aware of the concept of subclinical mastitis in camels or use of california mastitis test (cmt) screening. camel milk is obtained via hand milking without any pre or post milking dipping. it was even observed camel owners drinking milk right from camel teats using hands, although it is not recommended for safety. e. cloacae is a biofilm forming organism and this secretes a number of cytotoxins deemed important for its pathogenicity (mezzatesta et al., 2012). more importantly, due to expression of extended spectrum β-lactamases (esbl) and carbapenemases, it has turned into third broad spectrum enterobacteriaceae specie causing nosocomial infections along with k. pneumoniae and e. coli (potron et al., 2013). in last few decades, e. cloacae have been added to the list of most worrying microorganisms due to their ability to acquire resistance. in humans, e. cloacae are known to cause septic arthritis, endocarditis, and skin, urinary, respiratory and abdominal infections. it is contracted via skin and gastrointestinal tract (sanders et al., 1997, lee et al., 2002). coliform mastitis is also the most common form of clinical mastitis in cattle in different parts of the world. among coliforms, e. coli is most commonly isolated from animals with mastitis and primary source of these bacteria are cow feces, environment and infections via teat canal (sumathi et al., 2008, lipman et al., 1995). 24 squ journal of agricultural and marine sciences, 2021, volume 26, issue 1 subclinical mastitis in camels in oman: a pilot study in the present study, enterobacteriaceae was observed to be the predominant isolates from camels with subclinical mastitis. this is in line with other studies conducted in cows with mastitis (bengtsson et al., 2009, saidi et al., 2014). however, a study done in subclinical mastitis in camels in saudi arabia, streptococcus spp., staphylococcus aureus and other staphylococci spp. were found to be the predominant organism (77%) whereas only 12.9% isolates were identified as e. coli. (saleh & faye, 2011). in another study conducted on subclinical mastitis in camels, the authors found coagulase negative staphylococci (cns) to be the predominant isolates (35%) and only (10.72%) were confirmed as e. coli (leyla et al., 2017). a study (al-rahmmahi et al., 2018) carried on in al-najaf on 82 camels, the researchers found coagulase negative staphylococci to be the predominant (17.68%) followed by streptococcus spp. (12.92%). the authors also reported staphylococcus aureus (10.2%), e. coli (8.16%) and micrococcus (4.08%). in our study we found 3 isolates (20%) of cns and 1 isolate of micrococcus. in the present study, all e. cloacae (100%) isolates were found to be resistant to penicillin, first generation cephalosporins, macrolides and 43% were intermediately resistant to phenicols. currently, there is a lack of consensus regarding exact definition of multidrug resistant organisms in veterinary medicine. in human medicine, for an organism to be reckon as multidrug resistant, it should be resistant to at least one agent in at least three antimicrobial classes. however, according to criteria for assessment of multidrug resistance in bacteria (food.gov. uk), these organisms cannot be considered multi-drug resistant as e. cloacae harbors intrinsic resistance to penicillin, first generation cephalosporins and cephamycins. in our study, all e. coli (100%) isolates were resistant to ampicillin, amoxicillin, 3 (75%) were resistant to the first generation cephalosporins, 2 (50%) resistant to macrolides whereas 1 (25%) were found resistant to tetracyclines. similar trends have been reported in cows with mastitis (saidi et al., 2014) and camels with subclinical mastitis (saleh and faye, 2011). camel milk if consumed raw can be a source of infection for humans. a case of e. cloacae sepsis has been reported in a preterm infant feeding on mother’s milk. same pathogen was cultured from milk samples obtained from mother over the period of 7 days. however, mother’s milk could not be established as a direct cause of e. cloacae infection in infant as other sources of infection could not be ruled out (weem et al., 2015). further studies warranted to establish the link between consumption of raw camel milk and human infections. all of the isolates (100%) were found to be resistant to macrolide antibiotics including erythromycin and tylosin. macrolides have shown good activity especially against gram-positive cocci organisms. however, these antibiotics have limited efficacy against enterobacteriaceae in general. enterobacteriaceae may acquire resistance against macrolide in a variety of mechanisms described elsewhere (leclercq, 2002; ojo et al., 2004) identification of enterobacter cloacae establishes the fact that the organism is ampc producer that yields the inducible chromosomal ampc β-lactamase and therefore it is not necessary to detect ampc production in these isolates (gupta et al., 2014). coagulase negative staphylococci (cns) are opportunistic pathogens that may cause infection due to improper teat disinfection. cns are commonly isolated from bovine milk samples as these organisms are part of normal skin flora and contamination of milk is common. however, infections are usually subclinical in nature. raw milk contamination with enterobacteriaceae can occur during milking process, contamination of milk with animal feces or mastitis (dahmen et al., 2013). as camel milk is obtained exclusively by hand-milking, washing hands and udder of the animal, post milking teat dipping, pasteurization of milk and prevention of contamination during transport of camel milk can help in control of these organisms. the best way forward is the education of camel owners about dangers of drinking raw camel milk that can lead to infection with variety of bacteria and importance of pasteurization to avoid infections. consumption of raw camel milk is commonly practiced in middle east including oman; therefore, it is important to evaluate the microbiological quality of the camel milk. more number of camels could not be included in the study due to various factors including overall low camel population in the study area as compared to other parts of oman, noncompliance of camel owners to provide milk samples, small holdings (one or two camels commonly kept along with other livestock animals), and non-availability of camels for sampling at holdings due to long overall grazing time period. it is concluded that camel owner education programs are required to improve the udder health of the camels, regular screening of camels for subclinical mastitis using cmt, and educate them regarding hazards of using raw camel milk. conclusion and recommendation this is the initial investigation to report subclinical mastitis in camels in oman, and that the coliform is the dominant type. in the present study, enterobacteriaceae was observed to be the predominant isolates from camels with subclinical mastitis. this is the initial report of isolation of e. cloacae and e. coli from camel milk samples positive for subclinical mastitis in oman. in the present study, all e. cloacae (100%) isolates were found to be resistant to penicillin, first generation cephalosporins, macrolides and 43% were also intermediately resistant to phenicols. in this study, we could conclude that camel owner education programs are required to improve the udder health of the camels, regular screening of camels for subclinical mastitis using cmt, and educate them regarding hazards of using raw camel milk. 25research paper asi, al-marzooqi, eltahir, al ghaly, al toobi, al raisi, haytham ali, i. elshafie, h. johnson acknowledgement this work was supported by deanship research fund, project number: rf/agr/anvs/18/01. special thanks go to the ministry of agriculture & fisheries camel owners’ community for facilitating the sample collection and cooperating with the team during sample collection. all authors declare no conflict of interest. references al-rammahi hm, hatem aa, al-atabi ac (2018). diagnostic study of she camel subclinical mastitis in al-hyadia district – al-najaf province. advances in animal and veterinary sciences 6(6): 1-3. al-salihi, ka, sahab a, lifta a, habib l. (2017). epidemiological study of clinical and subclinical mastitis in she-camel in samawah desert al muthanna governorate. mirror of research in veterinary sciences and animals 6: 11-24. barłowska j, szwajkowska m, litwińczuk z, król j. (2011). nutritional value and technological suitability of milk from various animal species used for dairy production. comprehensive reviews in food science and food safety 10: 291– 302. bengtsson b, unnerstad he, ekman t, artursson k, nilsson-ost m, waller kp. (2009). antimicrobial susceptibility of udder pathogens from cases of acute clinical mastitis in dairy cows. veterinary microbiology 136: 142-149. dahmen s, métayer v, gay e, madec jy, haenni m. (2013). characterization of extended-spectrum beta-lactamase (esbl)-carrying plasmids and clones of enterobacteriaceae causing cattle mastitis in france. veterinary microbiology 162(2-4): 793–99. gupta g, tak v, mathur p. (2014). detection of ampc β lactamases in gram-negative bacteria. journal of laboratory physicians 6(1): 1-6. hoffmann h, roggenkamp a. (2003). population genetics of the nomenspecies enterobacter cloacae. applied and environmental microbiology 69: 5306–5318. keller r, pedroso mz, ritchmann r, silva rm. (1998). occurrence of virulence-associated properties in enterobacter cloacae. infection and immunity 66: 645–649. leclercq r. (2002). mechanisms of resistance to macrolides and lincosamides: nature of the resistance elements and their clinical implications. clinical infectious diseases 34: 482–92. lee so, kim ys, kim bn, kim mn, woo jh, ryu j. (2002). impact of previous use of antibiotics on development of resistance to extended-spectrum cephalosporins in patients with enterobacter bacteremia. european journal of clinical microbiology and infectious diseases 8: 577–581. leyla h, aggad h, hamad b. (2017). bacterial causative agents with subclinical mastitis in dromedary she-camels in southeaster algeria. jordan journal of biological sciences 11: 209-214. lipman lja, de nijs a, lam tjgm, gaastra, t. (1995). identification of eschericia coli strains from cows with clinical mastitis by serotyping and dna polymorphism patterns with rep and eric primers. veterinary microbiology 43:13-19. lj t. (1965). role of milk and milk products in nutrition in tropical and subtropical countries. journal of dairy science 48: 1547– 50. mezzatesta ml, gona f, stefani s. (2012). enterobactercloacae complex: clinicalimpactandemergingantibioticresistance. future microbiology 7: 887–902. national center for statistics & information (ncsi), ministry of oman, oman (2019). https://data.gov. om/search?query=camel&pageindex=&scope=&term=&correct= (accessed: 1 march 2020). national committee for clinical laboratory standards. (2000). methods for disk susceptibility tests for bacteria that grow aerobically, 7th ed. nccls document m2-a7. wayne, usa. national mastitis council (1990). microbiological procedures for the diagnosis of bovine udder infection. national mastitis council, arlington, va, usa. table 1. percentage resistance of 11 enterobacteriaceae species from camel positive for subclinical mastitis. enterobacteriace strains to tal number of resistant isolates (percentage resistance) pen. cet amp amc. tim str. enr. ery. tyl. tet. ffc. cfp. fur. ipm. gen. neo. flu. enr. mar. sxt. lex. e. cloacae 7 7(100) 7(100) 7(100) 0(0) 0(0) 0(0) 7(100) 7(100) 0(0) 3(43) 0(0) 0(0) 0(0) 0(0) 0(0) 0(0) 0(0) 0(0) 7(100) 7(100) e. coli 4 4(100) 4(100) 4(100) 0(0) 0(0) 0(0) 2(50) 2(50) 1(25) 0(0) 0(0) 0(0) 0(0) 0(0) 0(0) 0(0) 0(0) 0(0) 3(75) 3(75) total 11 11(100) 11(100) 11(100) 0(0) 0(0) 0(0) 9(82) 9(82) 1(9) 3(27) 0(0) 0(0) 0(0) 0(0) 0(0) 0(0) 0(0) 0(0) 10(90) 10(90) pen: penicillin; amp: ampicillin; amc: amoxicillin + clavulanic acid; tim: ticarcillin/clavulanic acid; str: streptomycin; enr: enrofloxacin; ery: erythromycin; tyl: tylosin; tet: tetracycline; ffc: florfenicol; cfp: cefoparazone; fur: ceftiofur ; imp: imipenem ; gen: gentamicin; neo: neomycin; flu: flumequine ; enr: enrofloxacin ; mar: marbofloxacin ; sxt: trimethoprim/sulfamethoxazole; lex: cefalexin; cet: cefalotin; 26 squ journal of agricultural and marine sciences, 2021, volume 26, issue 1 subclinical mastitis in camels in oman: a pilot study obeid ai, bagadi ho. (1996). mastitis in camelus dromedarius and the somatic cell count of camel’s milk. research in veterinary science 61: 55-58. ojo kk, ulep c, van kirk n, luis h, bernardo m, leitao j. (2004). the mef(a) gene predominates among seven macrolide resistance genes identified in gram-negative strains representing 13 genera, isolated from healthy portuguese children. antimicrob agents chemotherapy 48: 3451–3456. potron a, poirel l, rondinaud e, nordmann p. (2013). intercontinental spread of oxa-48 beta-lactamase producing enterobacteriace over a 11-year period, 2001 to 2011. eurosurveillance 18(31): 1-14 (article 20549). quinn pj, carter me, markey b, carter gr. (1999). clinical veterinary microbiology wolf publishing, london, england. p. 327. quinn pj, carter me, markey bk, carter gr. (1998). clinical veterinary microbiology. 2nd ed. mosby publishing, london, uk. saber k, mohammed s, ahmed a. (2010). sanitary conditions of lactating dromedary she-camel environment with special reference to milk quality and subclinical mastitis monitoring. emirates journal of food and agriculture 22(3): 207-215. saleh sk, faye b. (2011). detection of subclinical mastitis in dromedary camels (camelus dromedaries) using somatic cell counts, california mastitis test and udder pathogen. emirates journal of food and agriculture 23(1): 48-58. sanders we jr, sanders cc. (1997). enterobacter spp. pathogens poised to flourish at the turn of the century. clinical microbiology reviews 10: 220–241. schalm ow, noorlander dd. (1957). experiments and observations leading to development of california mastitis test. journal of the american veterinary medical association 130: 199–204. sumathi br, veeregowda bm, amitha gr. (2008). prevalence and antimicrobial profile of bacterial isolates from clinical mastitis. veterinary world 1: 237-238. weem mf, dereddy nr, arnold sr. (2015). mother’s milk as a source of enterobacter cloacae sepsis in a preterm infant. breastfeeding medicine 10(10): 503-504. zibaee s, hosseini sm, yousefi m, taghipour a, kiani ma, noras mr. (2015). nutritional and therapeutic characteristics of camel milk in children: a systematic review. electronic physician 7: 1523–1528. research paper journal of agricultural and marine sciences 2020, 25(2): 39–45 doi: 10.24200/jams.vol25iss2pp39-45 received 02 dec 2019 accepted 13 june 2020 farmers’ perceptions on the influence of inter-communal conflicts on the agricultural land in share/tsaragi communities, kwara state, nigeria issa zubair busari2*( ) maikangu@gmail.com,1department of agricultural extension and rural development, university of ilorin, nigeria. 2department of environmental conservation, abuja environmental protection board, nigeria. 3department of agricultural technology, yaba college of technology, epe, lagos, nigeria. introduction t he study of peace and conflict has become a glob-al imperative due to the mere fact that the two relate to the condition that defines and shape human existence and wellbeing in the present world (best, 2004). according to donohue et al. (1992), conflict is a situation in which people in social interaction express differences in the process of achieving their goals and need. it is inherent in all kinds of social, economic and political settings that are characterized by ethnic, religious, cultural and other forms of pluralism. the west africa sub-region, particularly nigeria, has experienced significant upsurge of inter-communal conflicts which are characterized by: (i) the inter-dependence and inter-communal relations between two or more communities, (ii) the proximities of each community to the other bringing them to share a common boundary, (iii) the presence of scarce resources that each of the communities have claim of ownership and (iv) the prioritization of win-lose perspective in which the goal of each party is to secure a winner takes all advantage (olabode and ajibade, 2004). oboh and hyande (2006) described the communal conflict as involving two or تصورات املزارعني عن تأثري النزاعات الطائفية عىل األرايض الزراعية يف مجتمعات شري/ تساراجي ، والية كوارا ، نيجرييا فيليكس أوالينكا أوالديبو، عيىس زبري بصاري، عبدالرزاق كامل دودو، أوالوايل سمسون سيلييس abstract. inter-communal conflicts have plagued rural communities which produce the bulk of agricultural produce in nigeria. one such conflict is share/tsaragi inter-communal conflict. the objective of the study was to assess perceptions of farmers on the influence of inter-communal conflicts on the agricultural production in share and tsaragi communities in edu and ifelodun local government areas (lgas) of kwara state, nigeria. a three-stage random sampling procedure was used to select 120 respondents for the study. data were collected using an interview schedule technique. a likert-type five-point continuum scale was used to rank farmers’ perceptions with five (5) as the most and one (1) as the worst check. the results showed that 68% of the respondents were above forty (40) years of age and 70% have resided in the communities for more than ten (10) years. respondents perceived that conflict of resource which bordered on the boundary issue, claim of ownership of fertile land at fejewe area, conversion of leased land to personal property among others are causes of the conflicts within the two communities. the results equally revealed the perceptions of respondents on the effects of conflicts in the area to include scarcity of arable land, displacement of farmers, destruction of lands and crops, scarcity of food and destruction of stored produce among others. the study showed the relationship between selected socio-economic characteristics and perception. this study concludes that there should be a clear delineation of the boundary within the two communities, the lift of the ban on some arable lands seized by the government and the promotion of other secondary occupations to relieve pressure on the land. keywords: conflict; farmers; perception; kwara state; share; tsaragi. املســتخلص:ابتليت املجتمعــات الريفيــة التــي تنتــج معظــم املنتجــات الزراعيــة يف نيجرييــا بالرصاعــات الطائفية. أحد هــذه الرصاعات هــو الرصاع بني tsaragi و share حيــث تــم تقييــم تصورات املزارعني حول تأثري النزاعات بني الطوائف عىل اإلنتاج الزراعي يف مجتمعات . share/tsaragi طائفتــي يف مناطــق الحكــم املحــي edu و ifelodun يف kwara . أخــذت العينــات بطريقــة عشــوائية مــن ثــاث مراحــل الختيــار 120 شــخصا للدراســة. تــم جمــع البيانــات مــن خــال مقابلتهــم . تــم اســتخدام مقياس ليكرت من خمــس نقاط لرتتيب تصــورات املزارعني مع خمســة )5( كأعىل اســتجابة و )1( كأقــل اســتجابة. أوضحــت النتائــج أن 68٪ مــن املجيبــني هــم فــوق 40 ســنة وأن 70٪ يقيمــون يف املجتمعــات املحليــة ألكــر مــن 10 ســنوات. أدرك املجيبــون أن تضــارب املــوارد الــذي يحــد مــن قضيــة الحــدود ، واملطالبة مبلكيــة األرايض الخصبــة يف منطقــة fejewe ، وتحويل األرايض املســتأجرة إىل ممتلــكات شــخصية مــن بــني أمــور أخرى هي أســباب النزاعــات داخل املجتمعني. وكشــفت النتائج بالتســاوي تصــورات املجيبني حول آثــار النزاعات يف املنطقــة لتشــمل نــدرة األرايض الصالحــة للزراعــة ، وترشيــد املزارعــني ، وتدمــري األرايض واملحاصيــل ، ونــدرة الغــذاء وتدمــري املنتجات املخزنــة وغريها. أظهرت الدراســة العاقة بني الخصائص االجتامعية واالقتصادية املختارة والتصورات .وتخلص هذه الدراســة إىل أنه يجب أن يكون هناك ترســيم واضح للحــدود داخــل الطائفتــني ، ورفــع الحظــر املفــروض عىل بعــض األرايض الصالحــة للزراعة التي اســتولت عليها الحكومــة وتعزيز املهــن الثانوية األخرى لتخفيــف الضغــط عــىل األرض. share, tsaragi ،لكلامت املفتاحية: الرصاع، املزارعون، تصور، والية كوارا 40 squ journal of agricultural and marine sciences, 2020, volume 25, issue 2 farmers’ perceptions on the influence of inter communal conflicts on the agricultural land in share/tsaragi communities, kwara state, nigeria. more communities engaging themselves in disagreement or act of violence over issues such as claims for land ownership, religious and political differences leading to loss of lives and destruction of properties. communal violence (sometimes inter-communal violence) is a situation where violence is perpetrated across ethnic lines, and victims are chosen based upon ethnic group membership (horowitz, 2000). inter-communal conflicts have plagued rural communities which produce the bulk of agricultural produce in nigeria. one of such conflicts is share/tsaragi inter-communal conflicts. the inter-communal existence of yoruba of share and nupe of tsaragi in kwara state, nigeria, was dated back when rampaging war brought them together at their present location (alao, 2012; gazette of ilorin, 1921). the communities had been living together peacefully until when resources were becoming scarce to satisfy the need of the two communities and when the ifelodun local government area (lga) was created in 1976. the two communities started to identify their cultural differences and began exercising authority and control over farmland and water resources. more so, the boundary between the two communities was not well defined during the reorganization exercise which ceded nine villages to tsaragi (memorandum submitted to tsaragi, ref: tseada/tsg/02/vol1/5, 2010). the earlier friction occurred in 1948 among women as a result of the denial of access to water sources and claiming of ownership by the two communities. also, when ifelodun lga was created in 1976, owing to the preponderance of yoruba in the lga, the nupes (tsaragi) started agitating to be merged to nupe dominated lga. in the year 2000, these resilient communities clashed over farmland in the surrounding area of fejewe, which claimed many lives and property worth millions of naira. again in 2008, another violent clash occurred over ethnic identity and non-implementation of the recommendation of inquiry committee (alao, 2012; abdulwahab, 2008). in december 2015, another violent clash occurred between the two communities which claimed many lives and many properties destroyed. this news was reported by major newspapers in nigeria (see the nigeria vanguard 20/12/2015 and january 10 2016; the nation 19 & 20/12/2015 and 2nd february 2016). the impacts of all these clashes were the destruction of lives and properties worth millions of naira, displacement of indigenes of both communities and destruction of farmland and farm produce. many research works have been carried out on inter-communal conflicts in nigeria (akinteye et al., 1999; albert, 1999; best et al., 1999; olabode & ajibade, 2004; alao et al., 2012). these research works laid emphasis on historical antecedent to the conflict, its progression into crisis and possibilities of conflict resolution. however, not much focus was given to the influence of the conflict on agricultural production. the new dimension on-farm-related conflicts has been recognised to be a threat to national peace and stability as well as food security in nigeria. therefore, there is an urgent need for the identification and analysis of the influence of these inter-communal conflicts on agricultural production in the study area. as a result of the preceding, this study was designed to assess perceptions of farmers on the influence of inter-communal conflicts on agricultural production in share and tsaragi communities of kwara state, nigeria. the specific objectives were to describe the socio-economic characteristics of the farmers in the study area, identify the causes of inter-communal conflicts in the study area, and examine the effects of these conflicts on food production in the study area. in this table 1. socio-economic characteristic of respondents characteristic frequency percentages age 24-39 38 31.7 40-55 42 35.0 56-71 34 28.3 >72 6 5.0 gender male 84 70.0 female 36 30.0 year of residence in the area < 3 13 18.8 4-9 23 19.2 10-15 25 20.8 16-21 38 31.7 >21 21 17.5 educational attainment no formal education 18 15.0 adult education 12 10.0 primary education 31 25.8 secondary education 35 29.2 tertiary education 24 20.0 farming system crop farming 93 77.5 animal husbandry 11 9.2 mixed farming 16 13.3 religion christianity 37 30.8 islam 78 65.0 others 5 4.2 source: field survey, 2018 41research paper oladipo, busari, daudu, selesi za sativa), cassava (manihot esculenta), yam (dioscorea alata), maize (zea mays), guinea corn (sorghum vulgare cv. durra), groundnut (arachis hypogaea), cowpea (vigna unguiculata) okra (abelmoschus esculentus) and various kind of leafy vegetables (kwadp, 2015). sampling technique and sample size the population of this study consists of all farmers in share and tsaragi communities of kwara state. threestage random sampling procedures were used to obtain one hundred and twenty (120), respondents. in the first stage, two local government areas that experienced conflicts were purposively selected. in the second stage, one community that is involved in the inter-communal clash was selected from each lga. then sixty (60) farmers were purposively selected from each community to give a total of one hundred and twenty (120) respondents. data were collected with the aid of a well-structured questionnaire using interview schedule technique to elicit information from the respondents on socio-economic characteristics such as age, marital status, years of residence in the community, educational level, perceived causes of the conflicts and perceived effect of the conflicts on agricultural production. perceived causes and effects were measured on a five-point likert-type response scale of strongly agreed (sa), agree (a) disagree (d), undecided (ud), disagree (d), and strongly disagree (sd). study, it was hypothesized that: (i) there is no significant relationship between the frequency of inter-communal conflicts and socio-economic characteristics of the farmers in the study area, and (ii) there is no significant relationship between the inter-communal conflicts and availability of land for agricultural production. materials and methods study area this study was carried out in kwara state, nigeria. the state has a land area of about 32,500 km square, and a population of about 2,371,089 based on the national population census (2006). it is situated between latitude 7°45’n and 9° 30’n and longitude 2° 30’e and 6° 25’ of the equator. the state has sixteen local government areas (lgas) with administrative capital in ilorin. share and tsaragi are located in ifelodun and edu local government areas of kwara state respectively. the two communities are located on latitude 4° and 8° n and longitude 8° and 9° east of the equator. the area is characterized by wet and dry seasons with rainfall ranging between 1000 mm and 1500 mm, and average temperature varies between 30°c and 35°c, while relative humidity ranged from 35% to 60%. the primary source of livelihood of both communities is farming with emphasis on cultivation of crops such as rice (orytable 2. perceived causes of share/tsaragi inter-communal conflicts variables mean sd rank perceptions of farmers agreeing boundary issue 4.70 1.68 1 claim of ownership of fertile farmland at fejewe 4.32 1.61 2 conversion of leased land to personal property 4.19 1.58 3 competition for land for arable crop production 4.16 1.56 4 poverty and unemployment 4.14 1.57 5 incompatible values 3.58 1.46 6 perceptions of farmers undecided poor governance 3.23 1.39 7 support from external interest 3.08 1.36 8 lack of equal opportunity 2.78 1.29 9 poor social interaction 2.78 1.25 10 government involvement 2.68 1.26 11 competition on land for grazing 2.57 1.24 12 perceptions of farmers disagreeing language barrier 2.45 1.21 13 non-implementation of committee of inquiry recommendation 2.32 1.18 14 source: field survey, 2018 42 squ journal of agricultural and marine sciences, 2020, volume 25, issue 2 farmers’ perceptions on the influence of inter communal conflicts on the agricultural land in share/tsaragi communities, kwara state, nigeria. data analysis data collected were analyzed using descriptive analysis such as percentage, frequency counts, while pearson correlation analytical tool was used to test the hypotheses set up for the study. farmers’ perception on the influence of conflict on agricultural production in the study area were evaluated by asking the respondents to indicate the extent of their agreement with each indicator using 5-point likert-type continuum of the scale of sa, ag, ud, d, sd with a weight loading of 5, 4, 3, 2 and 1 for the statements. for each variable a weighted mean was obtained as follows: wm={(fsa*5) + ( fag*4) + (fud*3) + (fd*2) + (fsd*1)}/n where wm is weighted mean, f is frequency, values 5, 4, 3, 2, 1 is attached weights, n is total number of statements. this study adopted joshua et al. (2014) perception analysis, the means of all indicators were categorized as follows: 4.50-5.00 = sa, 3.504.49 = ag, 2.50-3.49 = ud, 1.50-2.40 = d, 1.00-1.49 = sd results and discussion socio-economic characteristic of respondents the socio-economic characteristic of respondents (table 1) shows that 66.7% is between 24-55 years old while the average age was 46.6 years. this indicated that they were at the active economic age and that the respondents were old enough to understand the conflict between share and tsaragi concerning the causes, implication and effects on agricultural production within the two communities. the majority of the respondents (i.e. 70%) were male. this suggests that the male was predominant farmers in the study area. the result equally shows that the majority (i.e. 70%) of the respondents have been residing in the area for more than ten (10) years. in terms of educational attainment, 84% of respondents have one form of education ranging from adult to tertiary education. the higher level of education has been known to widen one’s exposure. therefore, it may be affirmed that the majority of the respondents had adequate exposure to the inter-communal conflicts between the two communities. they are equally small-scale farmers as 53% of them had farm size between 1-10 acres as 76% engaged in crop farming. this indicates that crop farming is the predominant occupation of the two communities. perceived causes of share/tsaragi inter-communal conflicts fourteen indicators/variables (as shown in table 2) on the various causes of conflicts between share and tsaragi were evaluated after farmers’ responses. their perceptions were calculated by obtaining a weighted mean of the response and later ranked accordingly. the overall result showed the number of variables agreed upon by the respondents as the causes of conflicts was 43%, disagreed on 43% and undecided on 14% (figure 1). findings shows that respondents perceived the conflict between the two communities to be over resource use which bordered on boundary issue which was ranked highest, followed by claim of ownership of fertile farmland at fejewe, conversion of leased land to personal property (contested ownership), competition for arable land for crop production, poverty and unemployment, and incompatible values in that order (see table 2). this indicates that land which is a major factor of production in agriculture especially crop production was at the center of the conflicts between the two communities. this confirms the earlier results by ani et al. (2015) and which showed that conflicts were caused as a result of boundary issues and contested ownership. however, respondents were undecided on six varitable 3. perceived effects of inter-communal conflicts on agricultural production variables mean sd rank perceptions of farmers agreeing scarcity of arable land 4.32 1.60 1 displacement of farmers 3.97 1.54 2 destruction of farm crops 3.71 1.49 3 scarcity of food 3.70 1.48 4 destruction of stored produce 3.66 1.47 5 perceptions of farmers undecided problems of transporting farm produce 3.38 1.42 6 scarcity of hired labour 3.08 1.36 7 problems of accessing farm inputs 3.07 1.35 8 decline in animal annual yield 2.93 1.32 9 source: field survey, 2018 43research paper oladipo, busari, daudu, selesi ables (see table 2), which include poor governance, support from outside interest, lack of equal opportunity, weak social interaction, government non-interference and competition on land for grazing. these were ranked 7th-12th in the table. this indicates that respondents perceived that there is no strong reason to link these variables and conflicts in the study area. according to them, no external influence/ interest on their land and people had intermarried between the two communities which made them interact freely when there were no issues. only two of the variables were out-rightly disagreed with by the respondents (i.e. 14%). these are the language barrier and non-implementation of committee recommendations. this shows that language was not a problem among the people of the study area as the majority of them can speak yoruba even among the nupes. moreover, the respondents may not be aware of what recommendations were submitted to the government for implementation. perceived effects of inter-communal conflicts on agricultural production nine indicators/variables were listed on effects of the conflicts on agricultural production in the study area (table 3). the perception of respondents was calculated as above and then ranked. the result shows that five variables were agreed upon as the effects of the conflicts representing 56% while 44% was undecided. the result reveals (table 3) that respondents perceived scarcity of land as the most felt effect of the conflicts between the two communities partly because of an outright ban of cultivation on some of the disputable arable lands in the area by the government. farmers were displaced during and after every clash in the area; farms and crops were destroyed which later led to the scarcity of food even as stored produce was not left out during the conflicts. this indicates that the conflicts have very adverse effects on human development and should be handled carefully to avert unnecessary famine and food insecurity in the state and particularly in the study area. respondents were, however, undecided on problems of transporting farm produce, scarcity of hired labor, problems of accessing farm inputs, and decline in annual animal yield. this imtable 4. correlation between respondents socio-economic characteristic and inter-communal conflict. variable r-value p-value educational level -0.847** 0.000 secondary occupation -0.871** 0.004 year of residence in the area -0.274** 0.006 ave. monthly income 0.131 0.153 (**) significant at 5% level table 5. perceived effect of inter-communal conflict on non-availability of farmland variable r-value p-value perceived effect of inter-comm. conflict availability of arable farmland 0.983** 0.005 (**) significant at 5% level figure 1. categorized perceptions on the causes of conflicts between share and tsaragi communities 44 squ journal of agricultural and marine sciences, 2020, volume 25, issue 2 farmers’ perceptions on the influence of inter communal conflicts on the agricultural land in share/tsaragi communities, kwara state, nigeria. plies that though these are problems respondents could not link them to the effects of the conflicts. test of hypotheses pearson product multiple correlation was used to test the hypotheses set up for the study. the result in table 4 shows that there was a significant but inverse relationship between educational level, secondary occupation and conflicts. it can, therefore, be deduced that farmer’s education could contribute to the reduction of inter-communal conflicts in the area as this will give them exposure on how to manage conflict and diversify their source of income. this is in agreement with the observation of mccafferey (2005), who noted that peace and conflict resolution at the community level could be facilitated through increased education. similarly, secondary occupations with negative loading imply that if respondents were encouraged to take up other occupations in the area, there might be a gradual reduction of the conflicts between the two communities as this will reduce pressure on land and get them to engage in other nonfarm activities. year of residence equally shows a significant but inverse relationship which can be inferred that the more the respondents stayed in the area, the more they will be able to understand the dynamics of the conflicts and able to resolve or evade its consequences/effects. conversely, the second correlation (table 5) shows a positive relationship between perceived effects and no availability of arable farmland. this implies that the conversion of arable farmland to the buffer zone which makes the farmland inaccessible to farmers, contributes to the frequency of conflicts in the study area. this is consistent with the findings of dohrn (2008) as insecure land tenure impedes fair resource management which could lead to conflict. conclusion and recommendations this study has shown that the conflicts in the two local governments were as a result of inadequate farmland for agricultural purposes, which may substantially affect food security if not urgently handled. furthermore, sustainable development goals (sdg) one, two and three which aimed at ending hunger, poverty and ensuring healthy lives and promote well-being for all at all ages might be a mirage. below are the recommendations of the study: (i) the government should, as a matter of urgency, lift the ban on some of the arable farmlands seized from the farmers and share equitably between the two communities, (ii) set up a peace committee among the two communities to resolve any issue before it gets out a hand, (iii) the head of each community or his representative, should be part of the committee, (iv) members of the communities should be encouraged to engage in off-farm activities to lessen competition for agricultural land and thereby reduce the deleterious effects of conflict, (v) proper boundary delineation should be carried out to douse future tension. references abdulwahab t. 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(2006). impact of communal conflict on agricultural production in oye community of oju lga in benue state. in: conflicts in benue valley. gyuse tt, ajene o. eds. benue state university press, makurdi. olabode o, ajibade s. (2004). environment induced conflict and sustainable development. a c a s e study of fulanifarmers’ in oke-ero lga, kwara state, nigeria. tsaragi, ref: tseada/tsg/02/vol1/5, 2010. report of the kwara state technical committee on location of boundary as at 1976 submitted to the kwara state government on january 13, 2010. research article journal of agricultural and marine sciences 2021, 26(2): 56–63 doi: 10.24200/jams.vol26iss2pp56-63 received 11 nov 2020 accepted 08 april 2021 anti-diabetic potential properties of two edible omani wild plants (pteropyrum scoparium and oxalis corniculata) iman r. s. al-qalhati, mostafa i. waly*, lyutha al-subhi, zaher al-attabi mostafa i. waly*( ) mostafa@squ.edu.om, department of food science and nutrition, college of agricultural and marine sciences, sultan qaboos universit y, p. o. box 34 -123, sultanate of oman introduction diabetes is a major health concern due to its high incidence coupled with complications includ-ing cardiovascular problems, renal failure, and compromised immune system that in turn contribute to the increased mortality rate in adults (waly et al., 2010). oxidative stress has been involved in the etiology of various human chronic diseases including diabetes (suresh et al., 2017), and more than 1200 plant species have been suggested for the treatment of these diseases (krishnaiah et al., 2011). recent studies have declared the effectiveness of some therapeutic plants and herbal preparations in the improvement of hyperglycemia (petrovska, 2012). edible wild plants are considered as natural therapeutic agents due to their antioxidant properties, minimum side reactions, and low cost (petrovska, 2012). the traditional use of plants as medicine precedes اخلصائص احملتملة املضادة ملرض السكري الثنني من النبااتت الربية العمانية: السيداف )oxalis corniculata( و احلُمَّْيض )pteropyrum scoparium( إميان القلهايت و مصطفى وايل* و ليوثة الصبحي و زاهر العطايب abstract. the use of plants for medicinal purposes has a long history worldwide. there is a lack of research that identifies the antidiabetic effect of edible omani wild plants. oxidative stress mediates the pathogenesis of diabetes and it has been suggested that natural antioxidants might be considered as an effective intervention for combating diabetes. this study aimed to assess the anti-diabetic and antioxidant potential properties of two edible omani wild plants (pteropyrum scoparium and oxalis corniculata) or their mixture in streptozotocin (stz)-induced diabetic rats. thirty-seven male sprague dawley rats, weighing 250–300 g, were allocated into 5 groups: non-diabetic (9 rats/group), diabetic group (7 rats/group), and three diabetic groups that received oral feeding of either pteropyrum scoparium, oxalis corniculata, or their mixture (7 rats/group). diabetes was induced by a single intraperitoneal injection dose of stz drug, 50 mg/kg body weight. at the end of the experimental trial, after 8 weeks, all rats were fasted overnight and sacrificed; blood glucose was measured, meanwhile, pancreatic tissues were dissected and homogenized for the biochemical assessment of oxidative stress markers (glutathione, gsh, and total antioxidant capacity, tac). stz resulted in hyperglycemia and oxidative stress (gsh depletion and tac impairment) in the diabetic group as compared to the non-diabetic group. meanwhile, the concomitant treatment of diabetic groups with the two wild edible omani plants or their mixture has shown a protective effect against the stz-induced hyperglycemia, but with no effect on oxidative stress. it was noted that for the final body weight, the improvement was not significant. histopathological examination of the pancreatic tissues showed that the stz injection leads to pathological changes associated with diabetes in the pancreatic tissues of all diabetic groups. pteropyrum scoparium and oxalis corniculata combated the stz-induced hyperglycemia with no effect on oxidative stress. there was no synergistic effect of pteropyrum scoparium and oxalis corniculata on hyperglycemia or oxidative stress. keywords: diabetes, pteropyrum scoparium, oxalis corniculata, oxidative stress امللخــص:إن اســتخدام النبــااتت لألغــراض الطبيــة لــه اتريــخ عريــق يف مجيــع أحنــاء العــامل، اال ان هنــاك نقــص يف األحبــاث الــي حتــدد أتثــر النبــااتت الربيــة العمانيــة الصاحلــة لــألكل ضــد مــرض الســكري. يتســبب اإلجهــاد التأكســدي يف تغــرات فيزيولوجيــة مرتبطــة مبــرض الســكري، وتعتــرب مضــادات األكســدة الطبيعيــة مــن التدخــات الفعالــة لتخفيــف درجــة األكســدة الناجتــة عــن مــرض الســكري وابلتــايل التحكــم بــه. هدفــت هــذه الدراســة إىل تقييــم خصائــص مضــادات األكســدة الثنــن مــن النبــااتت الربيــة العمانيــة الصاحلــة لــألكل وفعاليتهــا لضبــط مــرض الســكري، وهــي الســيداف pteropyrum scoparium واحلُمَّْيــض oxalis corniculata يف اجلــرذان املصابة بداء السكري اثر حقنها مبركب السرتبتوزوتوسن )stz(. ولقــــد اشــــتملت التجربــــة علــــى سبعة وثاثن ذكرا مــــن جرذان ســــالة ســــرباغ داويل ، بوزن 250300 جــرام ، مقســمة كاأليت: اجملموعــــة الضابطــــة )9 جــرذان ( و اجملموعــــة املصابــة مبــرض الســكري بعــد حقنهــا مبركــب stz )7 جــرذان ( بينمــــا تلقــــت اجملموعــــات الثاثــة األخــرى )7 جــرذان / جمموعــة( مســــتخلصات أوراق الســيداف أو احلميضــة أو خليطهمــا بعــد حقنهــم مبركــب stz . اســــتمرت التجربــــة ملــــدة 8 أســابيع و بعدها مت التضحية ابجلرذان و مت قياس مستوى اجللوكوز يف الدم ؛ كما مت تقييم مؤشرات اإلجهاد التأكسدي يف أنسجة البنكرايس جلميع اجلرذان . وقد أظهــرت نتائــج هــــذه الدراســــة زايدة ملحوظة يف نســبة جلوكوز الدم يف اجلرذان املصابة مبرض الســكري و كذلك نقص حاد يف مســتوى مركب اجللواتثيون ) gsh( و القدرة اخللوية اإلمجاليــة املضــادة لألكســدة )tac( وكذلــك أظهــر الفحــص النســيجي ألنســجة البنكــرايس أن حقــن اجلــرذان مبركــب stz أدى إىل تغــرات مرضيــة مرتبطــة مبــرض الســكري يف أنســجة البنكــرايس جلميــع جمموعــات داء الســكري. ومــن جانــب اخــر، أظهــر كأل مــن الســيداف واحلُمَّْيــض علــى حــدى أتثـيـــراً خافضــا جللوكــوز الــدم دون أتثر على اإلجهاد التأكســــدي املرتبــــط مبرض الســكري، إال أن خليط هذه النبااتت مل يظهر أي أتثر آتزري ســواء على مســتوى جلوكوز الدم أو االجهاد التاكســدي. الكلمات املفتاحية: مرض السكري ، اإلجهاد التأكسدي ، النبااتت الربية العمانية )السيداف و احلُمَّْيض(. 57research article al-qalhati, waly, al-subhi, al-attabi modern medicine throughout the world (world health organization, 2009). according to the world health organization, almost 80% of the people in the world used medicinal plants for their primary health care (world health organization, 2009). there are many natural products that have been isolated from plants such as flavonoids, phenolics, curcuminoids, tannins, coumarins, xanthones, terpenoids, and lignans (jeong et al., 2004). in addition, synthetic antioxidants like butylated hydroxytoluene (bht), tert-butylhydroquinone (tbhq), and butylated hydroxyanisole (bha) are manufactured chemically and used in the food industry because they are more effective and cheaper than natural antioxidants (lourenco et al., 2019). but, the use of synthetic antioxidants as food additives has raised some concerns related to their potential health problems and toxicity as tbhq, bha and bht might be carcinogenic and had been banned in several western countries (lourenco et al., 2019). therefore, there is a lot of potential commercial use of natural antioxidants from plant extracts as an alternative for artificial synthetic ones. there are numerous edible indigenous plant species in the gulf region, but there are limited studies about the health aspects of these plants in the daily food supply chain (al-attabi et al., 2015). oxalis corniculata is a cosmopolitan weed spreading with a slim stem covered with rounded tipped hairs (brown, 1989). it is commonly known as “sour grass” (pickering et al., 2008). it grows in shady moist places and traditionally, was used for treating wounds and certain diseases (pickering et al., 2008). pteropyrum scoparium grows mainly in february after the rainy season in december. it is used in the traditional food in which it is mixed with dried anchovies. the leaves were used medicinally for blood purification and the treatment of indigestion (al-badi, 2011). streptozotocin (stz) is a potent diabetic-inducing agent commonly used in rats; the stz effect is mediated by oxidative stress in pancreatic cells (al-maskari et al., 2012). stz induces diabetes in experimental animals via a mechanism that is mediated by glutathione (gsh) depletion and impairing total antioxidant capacity in pancreatic cells of rats (al-maskari et al., 2012). gsh is a tripeptide and acts as a part of the defense system against oxidative stress compounds like reactive oxygen and nitrogen species (waly et al., 2015). gsh acts as antioxidants since it is a carrier for the active thiol group, and has a direct antioxidant effect through interacting with electrophiles, reactive oxygen, or nitrogen (waly et al., 2015). oxidative stress in pancreatic tissue is a condition under which gsh and antioxidant enzymes (glutathione peroxidase, superoxide dismutase, and catalase) are not counterbalancing ros, and subsequently, induce pancreatic cellular damage (unuofin and lebelo, 2020; matough et al., 2012). oman region is rich in medicinal plants with antioxidant properties, therefore understanding the biological aspects of these plants in relation to oxidative-stress mediated diabetes might be considered as an effective dietary intervention in the primary prevention of diabetes. in the current study, we aimed to assess the biochemical significance of two edible omani indigenous plants (pteropyrum scoparium and oxalis corniculata) using an in vivo experimental model for diabetes. methods plants preparation the two edible omani wild plants, pteropyrum scoparium and oxalis corniculata, were freshly collected in october 2014 from two areas, nizwa and sur, and were identified by a specialized botanist from the crop sciences department at the college of agricultural and marine sciences, sultan qaboos university. the leaves of the collected plant were separated from the undesirable materials. then the leaves were washed and rinsed by distilled water and dried by free zone 6-liter benchtop freeze dry system (labconco, usa) at -40 ºc. the dried leaves were powdered by an electrical grinder (philips, hr2027). one gram of the dried powder was mixed with 50 ml distilled water. at the end, the mixture was stored in airtight container at -40 ºc until used for later experiments. experimental animals thirty-seven adult sprague dawley male rats weighing approximately 250-300 g were used in this study. animals were adapted to the animal house conditions for one week before starting the experiment. animals were housed in standard laboratory room conditions at 23±2 ºc, with a 12 h light/dark cycle, relative humidity of 55±10 % and were maintained with free access to standard diet and tap water. the standard diet was acquired from oman flour mills company (muscat, oman). all the animal procedures were implemented accordingly to the “guide for the care and use of laboratory animals” published by the national institutes of health. an ethical approval from university animal research ethics committee was obtained (squ/aec/2010-11). experimental design and diabetes induction the thirty seven rats were randomly allocated into five groups as follow: non-diabetic control rats (n=9) that fed standard diet, diabetic control rats (n=7) that were injected with stz and fed standard diet, diabetic rats (n=7) that were injected with stz and fed standard diet and an oral dose of pteropyrum scoparium extract (5 ml/week), diabetic rats (n=7) that were injected with stz and fed standard diet and an oral dose of oxalis corniculata extract (5 ml/week), diabetic rats (n=7) that were injected with stz and fed standard diet and an oral dose of a mixture of the extracts of both plants (10 ml/ week). the oral dose supplementations were carried out in the same day and time on weekly basis for all groups. the experiment was carried out for 8 weeks. throughout the experimental period, all rats were weighed once a 58 squ journal of agricultural and marine sciences, 2021, volume 26, issue 2 anti-diabetic potential properties of two edible omani wild plants (pteropyrum scoparium and oxalis corniculata) week, using a laboratory scale (electronic balance kern; pcb 6000-0) to the nearest gram. the allocated diabetic groups were injected with a single intra peritoneal injection of stz (50 mg/ kg body weight) while the non-diabetic group received a single intra peritoneal injection of 0.1 m citrate buffer solution. stz was purchased from sigma-aldrich chemical company (product number s0130), and dissolved in a freshly prepared 0.1 m citrate buffer (ph 4.5). diabetes was confirmed after three days of the stz injection by measuring blood glucose. briefly, the diabetic rats were fasted overnight and the distal part of each rat’s tail was lightly snipped; the first blood drop was discarded and the second drop was absorbed by a test strip inserted in a portable glucose meter (one touch ii; johnson & johnson, milpitas, ca, usa).the blood glucose level for all rats in the diabetic groups was ≥ 200 mg/dl. animals sacrifice and pancreatic tissue homogenization after eight weeks of the experiment, all rats were fasted overnight and blood samples were taken from the tails to measure blood glucose level. then all rats were anesthetized with a lethal dose of a mixture of ketamine (1 mg), xylazine (5 mg) and acepromazine (0.2 mg). the pancreas was dissected and removed. small pieces of the pancreatic tissues were placed in 10% of formalin for histopathological examination. the rest of pancreas samples (2 g) were homogenized in 0.1 m phosphate buffer and centrifuged at 4000 rpm at 4°c for 5 minutes. the resulting supernatants were used for protein content measurement using the lowry’s method (lowry et al., 1951) and for biochemical measurements of glutathione and total antioxidant capacity. biochemical measurements the glutathione (gsh) was measured using the gsh assay kit from biovision company (kit number; k251). the assay uses a dye that forms an adduct with glutathione which is monochlorobimane (mcb). the unbound mcb is mainly non fluorescent, while the dye fluoresces blue when bound to glutathione. this reaction is catalyzed by glutathione s-transferase. the assay identifies both reduced and oxidized glutathione. total antioxidants capacity (tac) was estimated using assay kit from biovison company (kit number; k274), which can measure both the small molecule antioxidants and proteins or small molecules alone in the presence of protein mask. cu²+ ion is converted to cu+ by both small molecule and protein. the protein mask prevents cu²+ reduction by protein, enabling the analysis of only the small molecule antioxidants. the reduced cu+ ion is chelated with a colorimetric probe giving a broad absorbance peak around 570 nm, relative to the total antioxidant capacity. histopathological examination pancreatic tissues saved in 10% formalin at room temperature were used to study their histological structures. the fixed specimens were dehydrated in graded ethanol, cleared in xylene and embedded in paraffin wax. tissue blocks were sectioned into 10 μm thickness using rotary microtome (thermo scientific stp120, thermo fisher scientific uk ltd.). the sections were stained by hematoxylin and eosin (h&e) to examine the pancreatic tissues under conventional light microscope by a pathologist. statistical analysis the statistical analysis was performed using one-way analysis of variance (anova) followed by tukey’s test using graphpad prism (version 5.03; graphpad software inc. san diego, ca). p<0.05 is considered as statistically significant. the results are expressed as means ± standard error of means (sem). results final body weight the effect of the treatment with pteropyrum scoparium, oxalis corniculata or their mixture on body weight in all groups is presented in figure 1. the results exhibited that the diabetic control group showed a significant reduction in the final body weight as compared to the non-diabetic group, p< 0.05. diabetic groups treated with pteropyrum scoparium, oxalis corniculata or their mixture showed an improvement in the final body weight, although the differences were not significant (p> 0.05) fasting blood glucose levels after animal’s sacrifice figure 2 illustrates the effect of pteropyrum scoparium, oxalis corniculata and their mixture on the fasting blood glucose level. stz injection induced a significant increase in fasting blood glucose level of all diabetic groups as compared with the non-diabetic group, p<0.05. feeding diabetic groups with pteropyrum scoparium, oxalis corniculata or their mixture positively ameliorated the elevation of blood glucose level as compared to the diabetic control group, but not significantly (p>0.05). pancreatic tissue antioxidants markers table 1 presented the potential effect of pteropyrum scoparium, oxalis corniculata or their mixture on the cellular antioxidants markers (gsh and tac). in all diabetic groups (treated and untreated), there was a depletion in the gsh level compared to the non-diabetic control group (p<0.05). there was a significant impairment of tac level of the diabetic groups treated with the extracts of pteropyrum scoparium, oxalis corniculata and their mixture as compared to control non-diabetic group. 59research article al-qalhati, waly, al-subhi, al-attabi histopathological examination figure 3 shows the histological appearance of the pancreatic islet cells of all experimental groups. the pancreatic section from the non-diabetic control group showed the normal histological structure of pancreatic cells with increased size and cellularity of the cells (figure 3.a). on the other hand, microscopic examination of the pancreatic sections of the diabetic control rats revealed decreased size and number of lymphocytes of β-cells of islets of langerhans (figure 3.b). figures 4c-e represents the pancreatic sections of the diabetic rats that were treated with pteropyrum scoparium, oxalis corniculata and their mixture, respectively. a mild to chronic lymphocytic infiltration is noted between acini in figure 3.c; cystic dilatation of pancreatic duct was detected in figure 3d and a congestion of pancreatic blood vessel was observed in figure 3e. discussion there is an increasing effort in searching for plants products possessing anti-diabetic activity with fewer side effects. diabetes is a challenging metabolic disease that affects the population worldwide (pradeepa et al., 2013). the total number of people with diabetes in the globe is estimated to increase sharply in the future (abdul sani et al., 2014). several treatments were used to cure diabetes mellitus, yet these treatments have limitations and undesirable effects (pradeepa et al., 2013). therefore, there was an increasing effort in searching for plant products possessing anti-diabetic activity with fewer side effects (habibuddin et al., 2008). the recent scientific studies as the traditional practices believed that the combination of many plants will be more efficient than using a single plant (ogbonnia et al., 2008). few studies revealed the effect of oxalice corniculata in diabetic animal models (agila, 2012), while there is no study conducted with pteropyrum scoparuim or the combination of these two plants. the present study has been undertaken to assess the effect of pteropyrum scoparuim, oxalice corniculata and their mixture in stz-induced diabetic model. in the present study, the diabetic control group showed a significant decrease in the final body weight compared with non-diabetic group. the obtained findings were in agreement with a previous reported that the injection of stz has been related with body weight loss because of the elevation in protein catabolism and muscle wasting. moreover, the lack of insulin secretion leads to unavailability of carbohydrate which is a source of energy resulting in the observed body weight loss among the diabetic groups. this finding is consistent with what was reported earlier that administration of 50 mg /kg of stz resulted in a significant reduction in the body weight of diabetic animals (suresh et al., 2017; waly et al., 2015). there were no previous studies to verify the effect of supplementation with pteropyrum scoparium, oxalis corniculata or their mixture on the body weight of stz-diabetic rats. our results showed an improvement trend in the final body weight of all three treated diabetic groups compared to the untreated diabetic control group. however, the obtained results were not significant and this may be due to the size of the dose used which might have not been enough to relief the weight loss resulting from the diabetes insult. in our study, stz-induced diabetic control rats showed a significantly elevation in the fasting blood glucose level when compared with the control non diabetic group, p<0.05. a similar result was reported earlier which stated that stz in a dose of 50 mg/kg induced diabetes in the experimental animals (suresh et al., 2017). diabetes mellitus is characterized by a disturbance of glucose homeostasis and adversely affects carbohydrates, fat, and protein metabolism due to lack of insufigure 1. final body weight in the rat groups aall the diabetic groups had significantly lower body weight than the non-diabetic group, p< 0.05. 60 squ journal of agricultural and marine sciences, 2021, volume 26, issue 2 anti-diabetic potential properties of two edible omani wild plants (pteropyrum scoparium and oxalis corniculata) lin (waly et al., 2015). the increase in the blood glucose level is attributed to the cytotoxic effect of stz on pancreatic cells (waly et al., 2015). in addition, stz leads to destruction of β-cells of islets of langerhans and malfunctioning of the pancreas resulting in the blood glucose elevation (sung et al., 2019; agila and kavitha, 2012). furthermore, our study revealed amelioration in the fasting blood glucose levels of all the treated diabetic groups. in contrast to our findings with respect to oxalis corniculata, it was demonstrated that a single daily oral administration of an aqueous extract of oxalis corniculata (100 mg/kg body weight) caused a significant reduction in the blood glucose in alloxan-induced diabetic mice when treated for a period of ten days (do prado et al., 2020). the results observed in our study are based on a different dose and feeding duration. on the other hand, there were no studies to compare the results obtained from treating diabetic animals with pteropyrum scoparium or the mixture of two plants. long term of untreated hyperglycemia in diabetes is asfigure 2. fasting blood glucose measurements in the rat groups. all the diabetic groups treated with pteropyrum scoparium, oxalis corniculata or their mixture positively ameliorated the elevation of blood glucose level as compared to diabetic control group, but not significantly, p>0.05 a, bsimilar superscripts are not significantly different. figure 3. histopathological examination of the pancreatic tissues of rat groups (h&e stain x 400). section a: pancreatic tissue of the non-diabetic group consisting of acini; ducts and islets of langerhans with no evidence of inflammation and necrosis. section b: pancreatic tissue of the diabetic group; the islets are small (atrophic) and a few lymphocytes (black arrow) are noted. section c: diabetic + pteropyrum scoparium; occasional islets show moderate chronic inflammatory cells infiltrate (black arrow) and necrosis (red arrow) with mild lymphocytic infiltration noted between acini (black arrow). section d: diabetic + oxalis corniculata; show dilated and congested blood vessels (black arrow). section e: diabetic + pteropyrum scoparium & oxalis corniculata; show moderate number of lymphocytes (black arrow), occasional single cell necrosis (red arrow) and dilated ducts (large black arrow). no improvement in the stz-mediated pathological effects were seen in any of the three treated groups. 61research article al-qalhati, waly, al-subhi, al-attabi sociated with oxidative stress generating from glucose autoxidation, protein glycation and glycoxidation leading to tissue injury and damage (do prado et al., 2020). induction of stz generates h2o2 and increased the production of free radicals in vitro as well as in vivo increasing the oxidative stress level (balaji et al., 2020). those reactive free radical species generated by stz contribute to dna fragmentation and induce other damaging changes in the cells. the formation of superoxide anions could be a result of stz action or/ and an increased activity of xanthine oxidase on mitochondria (hassanzadeh et al., 2019). thus high blood glucose level induces a damage to the body by many mechanisms that lastly leads to cellular stress (jakus, 2000). in the present study, stz-induced diabetic rats showed a depletion trend in the glutathione level. similar results were observed in the three treated diabetic groups. such a finding could be due to hyperglycemia which causes osmotic stress to cells by increasing the movement of glucose through polyol pathway and the production of sorbitol that consumes dihydronicotine amide adenine dinucleotide phosphate causing depletion in intracellular glutathione (pradeepa et al., 2014). it was reported that the best solvents of extracting the flavonoid from oxalis corniculata are the polar solvents such as methanol and water (al qalhati, 2016). moreover, the polar solvents like the ethanolic extract of pteropyrum scoparium showed better free radical scavenging activity indicating that the pteropyrum scoparium is a rich source of some antioxidants constituents like epicatechin-3-o-gallate (al qalhati, 2016). in the present study the plants extracts were aqueous-based, and the results obtained in our study showed a significant impairment of total antioxidants capacity in the three treated groups. stz as a diabetic insult is causing specific cytotoxicity to β-cells of the pancreas (waly et al., 2015). it generates high level of free radicals causing dna fragmentation of ß cells and cells necrosis which leads to decreasing the level of insulin and increasing the blood glucose level (suresh et al., 2017). the microscopic examination of the pancreatic tissue of the diabetic control group is in conformity with what was reported earlier that atrophy of β-cells of islets of langerhans, necrosis along with cystic dilatation of pancreatic duct, reduction in cells size, decrease cellularity, and congestion of pancreatic blood vessels (kakkar et al., 1998). these changes in pancreatic cells can be attributed to the stz cytotoxicity causing a destruction of β-cells of the pancreas (khattab et al., 2013). also, this effect may be explained by generation of h2o2 in the pancreatic β-cells by induction of stz causing dna fragmentation. in addition, the hyperglycemia stimulates the production of free radicals causing cell dysfunction and damaging the pancreatic cells (singab et al., 2014). the microscopic examination of the pancreatic tissues of the treated diabetic groups showed no histopathological changes indicating that treatment with pteropyrum scoparium, oxalis corniculata or their mixture have any effect on the pancreatic tissues. this may be due to the increase in the oxidative stress (srikanth et al., 2012). conclusion in conclusion, our study demonstrated that stz induced diabetes and oxidative stress in the experimental rat model. in addition, it indicated that pteropyrum scoparium, oxalis corniculata, and their mixture improved the stz-induced hyperglycemia and the final body weight but not significantly. neither the two plants nor their mixture has an effect on the cellular antioxidant markers or the histopathological changes in pancreatic tissues. there was no significant synergistic effect of the two plants (pteropyrum scoparium and oxalis corniculata) on stz-induced diabetes and oxidative stress. further research is needed to investigate the dose and time-dependent attributes of pteropyrum scoparium and/or oxalis corniculata in relation to diabetes. table 1. . biochemical measurements of glutathione (gsh) and total antioxidant capacity (tac) in the rat groups. antioxidant marker group gsh (ng/mg protein) tac (ng/mg protein) non-diabetic 1.24 ±0.17 251.16 ±64.11 diabetic *0.89 ± 0.24 *143.71 ± 34.15 diabetic + pteropyrum scoparium 0.70 ± 0.16 82.23 ± 20.41 diabetic + oxalis corniculata 0.75 ± 0.13 73.4 ± 11.13 diabetic + pteropyrum scoparium & oxalis corniculata 0.72 ± 0.09 68.10 ± 5.44 *significantly lower than non-diabetic group, p< 0.05. in all diabetic treated and non-treated groups there was depletion in the gsh level compared to the control non-diabetic group but this depletion was not significant p>0.05. meanwhile, a significant impairment of tac level of diabetic groups treated with pteropyrum scoparium, oxalis corniculata or their mixture was observed as compared to control non-diabetic group. 62 squ journal of agricultural and marine sciences, 2021, volume 26, issue 2 anti-diabetic potential properties of two edible omani wild plants (pteropyrum scoparium and oxalis corniculata) references abdul sani nf, belani lk, pui sin c, abdul rahman sna, das s, zar chi t,yusof yam. 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(2013). biochemical evaluation of antidiabetic properties of pithecellobium dulce fruits studied in streptozotocin induced experimental diabetic rats. international journal of herbal medicine 1(4): 21-28. pradeepa s, subramanian s, kaviyarasan v. (2014). antioxidant role of pithecellobium dulce fruit pulp extract in ameliorating hyperglycemia induced oxidative stress studied in streptozotocin induced experimental diabetic rats. journal of pharmacy research 8(3): 377-384. qihui l, shuntian d, xin z, xiaoxia y, zhongpei c. (2020). protection of curcumin against streptozocin-induced pancreatic cell destruction in t2d rats. planta medica 86(2): 113-120. 63research article al-qalhati, waly, al-subhi, al-attabi singab an, youssef fs, ashour ml. (2014). medicinal plants with potential antidiabetic activity and their assessment. med aromat plants 3(1): 151-156. srikanth m, swetha t, veeresh b. 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(2020). antioxidant effects and mechanisms of medicinal plants and their bioactive compounds for the prevention and treatment of type 2 diabetes: an updated review. oxidative medicine cellular longevity 2020: 1-36 (article 1356893). waly mi, ali a, essa mm, al-shuaibi y, al-farsi ym. (2010). the global burden of type 2 diabetes: a review. international journal of biological medical research 1(4): 326-329. waly mi, guizani n, suresh s, rahman ms. (2015). ginger extract attenuates preliminary steps of streptozotocin-mediated oxidative stress in diabetic rats. international journal of nutrition, pharmacology, neurological diseases 5: 151-158. world health organization. (2009). the use of herbal medicines in primary health care, technical report, 2009, pp1-66. https://apps.who.int (accessed 2 january 2020). research paper journal of agricultural and marine sciences vol. 23 : 52– 57 doi: 10.24200/jams.vol23iss1pp52-57 reveived 1 mar 2018 accepted 18 may 2018 integrated aquaculture in arid environments 1stephen goddard, 2fatma s. al-abri *1stephen goddard, ( ) stephen@waterfarmers.ca water farmers, rue de libin, hatrival, belgium 6870. 2fatma saif al-abri, centre of excellence in marine biotechnology, box 50, sultan qaboos university, al-khod 123, sultanate of oman. introduction global population growth, coupled with increas-ing water demands, present a major challenge in the provision of future food security. it has been predicted that by 2050 50% more food will be needed to feed a world population exceeding 9 billion (godfray et al., 2010). this will necessitate intensification of food production, sustainable practices and more efficient use and protection of natural resources. aquaculture plays a key role in eliminating hunger, promoting health and creating economic benefits and expanded at an average annual rate of 5.8% in the period 2005-2014, to a total of 73.8 million tonnes (fao, 2016). inland aquaculture is a major sector although its development in desert and arid regions faces considerable obstacles, particularly with regard to feed and water supplies. the combined production of fish and vegetable crops in integrated systems, with multiple use of water and other resources, holds the potential to increase food productivity in such regions ( crespi and lovatelli, 2011). aquaponics whilst aquaponics may have ancient antecedents it was likely first developed in its modern form in the mid1970’s by scientists researching methods for treating recycled water in fish culture systems (love et al., 2015). in these studies edible plants, including tomatoes and االستزراع السمكي املائي املتكامل يف البيئات القاحلة ستيفن جودرد¹ وفاطمة العربي² abstract. around one third of the globe is classified as desert or arid (<200 mm rain annually) and most such regions lack food security. traditional freshwater aquaculture is often a marginal activity and competes with agriculture for limited water resources. developing technologies offer new opportunities to increase farm productivity through integration with vegetable production in aquaponic systems and to reduce water requirements through the application of biofloc technology. aquaponic systems combine aquaculture and hydroponic plant production and are integrated within a re-cycled water system. fish waste metabolites provide the nutrients for plants grown in soil-less, hydroponic systems. biofloc fish production systems operate with minimum or zero water exchange. suspended biofloc particles develop in fish tanks under conditions of full aeration and controlled carbon to nitrogen ratios. they comprise algae, bacteria, protozoa and particulate organic matter held in a loose matrix. they provide in-situ treatment of harmful fish metabolites, are protein rich, contain essential fatty acids, vitamins and minerals and supplement the diets of filter-feeding farmed species. the integration of fish culture with vegetable production provides new opportunities for small and medium enterprises. integrated farms occupy a small footprint, optimise the use of resources and can be built close to population centres. this paper reviews current developments in aquaponics, including recent research into the incorporation of biofloc technology in aquaponics, against the background of food security needs in arid regions. keywords: water conservation; food security; aquaponics; bioflocs املســتخلص: يصنــف حــوايل ثلــث الكــرة األرضيــة علــى أهنــا صحــراء قاحلــة او شــحيحة املــاء )>200 مــم مــن االمطــار ســنويا( وتفتقــر معظــم هــذه املناطــق إىل األمــن الغذائــي. غالبــاً مــا يكــون االســتزراع الســمكي التقليــدي للميــاه العذبــة نشــاطاً ويتنافــس مــع الزراعــة حمدوديــة ملــوارد امليــاه. حيــث ان التكنولوجيــا املتقدمــة توفــر فرًصــا جديــدة لزيــادة اإلنتاجيــة الزراعيــة مــن خــال نظــام املتكامــل مــع إنتــاج اخلضــروات يف أنظمــة االســتزراع الســمكي املائــي وتقليــل متطلبــات املــاء مــن خــال تطبيــق التقنيــة احليويــة الــي جتمــع بــن تربيــة األمســاك وإنتــاج النباتــات املائيــة يف نظــام إعــادة تدويــر امليــاه. حيــث اهنــا توفــر مــن خملفــات األمســاك العناصــر املغذيــة للنباتــات الــي تــزرع يف النظــام املائيــة مــن دون تربــة. كمــا ان خملفــات األمســاك املوجــودة يف خــزان األمســاك حتــت ظــروف التهويــة الكاملــة والكربــون املتحكــم فيهــا يتحــول إىل عنصــر النيرتوجــن. وكمــا ان الطحالــب والبكترييــا والكائنــات األوليــات واجلســيمات للمــواد العضويــة املوجــودة يف خــزان األمســاك تنتــج خملفــات ســامه وغنيــة بالربوتــن حيــث اهنــا تتحــول هــذه املخلفــات إىل مســاد مغــذي للنباتــات وهــذا ممــا يوفــر مثــن التســميد كمــا ان النباتــات تنقــي امليــاه مــن خملفــات األمســاك الــي قــد تضــر هبــا، حيــث اهنــا حتتــوي علــى األمحــاض الدهنيــة األساســية والفيتامينــات واملعــادن املتكاملــة يف النظــام الغذائــي لتغذيــة النباتــات. كمــا ان هــذا النظــام يعــد متكامــل الــذي يدمــج بــن تربيــة األمســاك وإنتــاج اخلضــروات ويوفــر فرًصــا جديــدة للمؤسســات الصغــرية واملتوســطة. ويشــجع هــذا النظــام علــى اســتغال املســاحات الصغــرية والــي ميكــن بناؤهــا بالقــرب مــن اجملمعــات الســكانية. تســتعرض هــذه الورقــة التطــورات احلاليــة واملســتجدات يف النظــام االســتزراع الســمكي مــع النباتــات، مبــا يف ذلــك البحــوث األخــرية الــي تدمــج التكنولوجيــا يف االســتزراع الســمكي مــع الزراعــة املائيــة بــدون تربــة، والــذي يتماشــى مــن احتياجــات األمــن الغذائــي يف املناطــق القاحلــة. الكلمات املفتاحية: احملافظة على املاء، االمن الغذائي، الزراعة التكاملية بن األمساك والنبات 53research article goddard, al-abri lettuce, were used to remove waste products from carp and tilapia production tanks (naegel, 1977). early pioneering work on aquaponics was pursued by various university research groups, most noteably the group led by james rakocy at the university of the virgin islands in the usa. aquaponics combines the benefits of fish production (aquaculture) with the soil-less production of plants (hydroponics) using the same water. it operates within a closed-loop system where fish feed provides most of the nutrients required for healthy plant growth. these nutrients, excreted directly by the fish, or generated by the microbial breakdown of organic wastes, are absorbed by growing plants. research is generally aimed at refining methods for improved output (rakocy, 2006). the use of soil-less culture techniques and water re-cycling provide considerable benefits for long-term sustainability (bernstein, 2013). water consumption is less than 10% of normal levels for horticultural production and can be provided from potable supplies or pathogen-free groundwater (somerville, 2015). there are no direct mineral or fertilizer costs since the primary mineral source is the fish feed provided to support fish growth. some small additions of alkaline salts, to maintain a stable, neutral ph and ferrous salts, to maintain the necessary iron content, are the only mineral additives used in aquaponics. the intensive nature of aquaponic production greatly reduces the amount of land necessary for commercial production units and there is no requirement for arable land. water recirculation technology has seen significant progress in recent years with some standard methods emerging and equipment supplies becoming more available and cost efficient (martins et al., 2010; bregnballe, 2015). the combination of aquaponics with water recirculation technology has opened the way for aquaponic developments on large commercial scale. further possibilities exist to conserve water through the application of biofloc technologies. these are zero or minimum water exchange systems production systems in which the carbon nitrogen ratios are adjusted to provide optimal conditions for the growth of bioflocs: small aggregates (<1 mm) of waste food, fecal material, phytoplankton, zooplankton and bacterial communities (hargreaves, 2013). in well balanced systems the bacterial communities take up the nitrogenous compounds, which are otherwise harmful to fish, and produce microbial protein, lipids, vitamins and minerals. fish production, using biofloc systems, linked to hydroponic plant production in aquaponic systems holds the potential to minimise water use and to reduce feeding costs through improved food conversion ratios. initial trials have demonstrated the availability of minerals from bioflocs in integrated fish and vegetable production (chappell and brown, 2010) and the potential to develop aquaponics, based on fish production in biofloc systems, is being researched, with positive results (pinho et al., 2017). figure 1. al-arfan farms, oman. a commercial aquaponics farm operating in a hot arid environment. the farm is protected by a shade house and the fish unit produces 4-5 tonnes of nile tilapia each year. a wide variety of vegetables, fruits and culinary herbs are grown throughout the year in a combination of deep water culture and media filled beds. picture credit: arvind venkataraman 54 squ journal of agricultural and marine sciences, 2018, volume 23, issue 1 integrated aquaculture in arid environments vegetable production a wide range of vegetables and fruits are grown in aquaponic systems, including include lettuce, chard, pak choi, spinach, kale, basil, tomatoes, peppers and micro-greens. three systems are available for hydroponic plant production. these are described in detail by somerville et al., (2014) and are summarised below. nutrient film systems (nft) these are based on conventional hydroponic systems in which plants grow in long narrow channels. water flows down each channel, providing plant roots with water nutrients and oxygen. nft systems must also include tanks for settlement of solids and a bio-filter for the breakdown of ammonia. the systems are prone to blockage with circulating organic materials and are less commonly used in aquaponics than deep water culture and media-filled systems. media-filled systems in these systems crops are produced in shallow growbeds (50 cm), using media to provide support for root systems. expanded clay balls or graded gravel are commonly used. the system is typically operated with a flood and ebb system controlled by a bell siphon, where each bed is filled with nutrient-rich water and drained 2-3 times each hour. the media provides large surface area which promotes biological filtration, reducing ammonia to nitrite and nitrate. the media also provides support to plant root systems and enables relatively tall plants to be grown. all of the organic waste is broken down in the grow beds and worms are often added to enhance the breakdown. the overall productivity of plants is generally less than in nft and floating raft systems, although a greater variety of plants can be grown. deep water culture systems this method is used for smaller plants such as herbs and salads, which grow floating in a styrofoam raft. the plants are initially contained in small coir pots and receive their necessary minerals from the fish tank via the water which circulates around their exposed roots beneath the floating rafts. the fish are held in a separate tanks and water from the fish tank circulates continuously through the system. beneficial bacteria live throughout the system and the extra volume of water in the grow beds provides a buffer for fish, reducing stress and potential water quality problems. deep water culture and media-bed systems are most commonly used in aquaponics. they may be used singly or in combination. deep water culture methods are commonly used in large commercial units for the production of large quantities of mono-crops, such as lettuce, salad greens and culinary herbs. fish production a limited range of freshwater fish species is grown in aquaponics. tilapia (oreochromis spp) is most commonly grown since it is hardy, readily available, grows rapidly under optimal conditions and is familiar to consumers (bernstein, 2013). other warm-water species include asian seabass, catfish and carp, including ornamental varieties of koi carp. the volume and value of food fish grown in aquaponics is small in comparison with plant production. plants reach harvest faster, which permits multiple plantings and have higher value per unit weight than fish. typically, profits are gained on plant yield rather than fish production and fish are primarily used as a source of bio-available plant nutrients. water re-use and treatment the essential requirements for treatment of recycled water depend primarily on the plant growing system selected. small scale, media-filled grow beds will remove solids and function as biofilters. in contrast deep water culture systems require additional solids separation and biofiltration. water flows from the fish tanks in a cycle through solids separation equipment, followed by biofilters and then through the plant grow beds. it is then collected in a sump and pumped back to the fish tanks. air, generated by blowers and delivered through fine bubble diffusers, is applied directly in the fish tanks and in deep water culture beds. more efficient oxygenation using oxygen generators or stored liquid oxygen is necessary for fish cultured at high stocking densities. solids removal separating solids from fish tank effluent is a key part of water management in commercial deep water culture aquaponics. accumulation of solids in the water can cause irritation and gill damage in most fish species and within the hydroponic system can accumulate around the root systems of growing plants impairing the uptake of water and dissolved nutrients. a range of sizes of solid particles are excreted by feeding fish and various systems are available to separate the various solid fractions (table 1). settleable and supra-colloidal solids form the bulk of solids excreted by fish and can be removed by gravitational devices and micro-screens. circular fish tanks with flat bottoms are generally used in large installations. water circulates uniformly and centripetal forces transport solid wastes to the centre from where they can be table 1. solids waste in fish tank effluent solids type size (µm) treatment dissolved < 0.001 ozone colloidal 0.001 – 1 foam fractionation supra-colloidal 1 – 100. screen filter or sand/bead filters settleable > 100 swirl filters or radial flow settlers 55research article goddard, al-abri separated in a small separate drain pipe from the main flow of cleaner water. additional suspended solids can then be removed by a combination of swirl separators, radial flow filters or rotating drum filters fitted with micro-screens (40-100 µm), depending on the nature and volume of solids to be removed. biofiltration the finest particles will pass through separators and micro-screens along with dissolved compounds, such as phosphorus and nitrogen. nitrogen in the form of nitrite and free ammonia (nh3) is toxic to fish and is oxidised by nitrifying bacteria growing in films on the biofilter surface to harmless nitrate, which is then available for plant growth. biofilters units are designed to contain as large a surface area as possible to support the growth of bacterial films. light, plastic media giving a high specific surface area (ssa, m2/m3) is commonly used (harwati and jo, 2011). biofilters can be configured in varioius ways and many designs are currently used in aquaponics (table 2). the size of biofilters is calculated based on various parameters. these include the total ammonia-nitrogen (tan) released by the fish, hydraulic loading, water flow rates and the relative surface area of the selected filter media. tan calculations are based on the nitrogen content of the fish feed, daily food consumption, digestibility and nitrogen content of protein. calculating biofilter size should also take into account the available surface areas of the grow beds and styrofoam floats which will be in contact with water and will also support the growth of bacterial films. metrics based on feed use are fundamental to aquaponics. determination of the quantity and quality of food used daily are used to calculate both scope of water treatment necessary and the scale of hydroponic plant growth which can be supported by the treated effluent from fish tanks. routine monitoring of water chemistry is vital to maintain a balanced water re-use system (colt, 2006). recycled systems accumulate acidity which must be adjusted by base additions to maintain optimal ph for fish, bacteria and plant growth growing in the same system. safety food safety is a critical component of food production and aquaponic farmers should follow codes of good practice and apply biosecurity protocols for both aquaculture and horticulture components. food safety and levels of food safety indicator organisms from both produce and water in aquaponic systems have been examined (chalmers, 2004; fox et al., 2012; goddard et al., 2015). the bacterium escherichia coli is the most widely studied potential contaminant in aquaponics. this bacterium is found in the intestines of warm-blooded animals, including birds and cattle, and has been used in developing human health-based regulatory standards as a common indicator of fecal contamination and microbial water quality in agricultural water systems. indicator microbes and pathogenic bacteria, such as e. coli and salmonella spp., if present in aquaponic systems, most probably originate from warm-blooded animals, such as birds, since these enteric bacteria are transient in fish gut microflora (sugita et al., 1996). as in all crop production systems cross-contamination is possible, but the risk in aquaponics is greatly reduced when compared with field crops (sirsat and neal, 2013). studies from oman (goddard et al., 2015), usa (fox et al., 2012) and canada (chalmers, 2004) have reported negative tests across numerous aquaponic farms for e. coli and salmonella spp. biofloc farming systems the application of biofloc technology in intensive aquaculture is in its early stages (avinmelech, 2007). the technology is based on waste nutrient recycling, particularly nitrogen into microbial biomass. this biomass can be used directly by filter feeding species such as tilapia, carp, catfish, marine shrimp and freshwater prawns (bossier and ekasar, 2017). on a dry matter basis, microbial biomass has been shown to contain 20-45% crude table 2. characteristics of 4 biofilter types used in aquaponic systems type ssa (m2/m3) characteristics trickle filter 200 water enters from an overhead spray pipe and cascades through a media column (e.g. corrugated plastic sheets) where nitrification occurs. relatively inexpensive and simple to construct and operate. they self-aerate and de-gas excess co2 rotating bio-contactor 200 filter media comprises circular plates or discs attached to a horizontal shaft. the media is half submerged in the fish tank or a separate container. as the filter rotates the media is alternately submerged and exposed to the air. passive aeration and co2 degassing occurs and head loss is low. simple to operate and can powered by a small motor or air-lift. higher initial purchase and maintenance cost than trickle filters but more compact. moving bed biofilm reactor 500 filter media (small plastic spheres with surface sculpting) is held in an open tank (50% water and 50% media). the bottom of the tank is fitted with an air distribution system designed to give continuous turnover and aeration of the submerged media. head loss is low. various adaptations of this filter are commonly used in aquaponics on both small and large-scale. bead filter 3000 filter media (tiny glass beads) is held in a pressurised vessel through which the water is pumped. combines solids removal and nitrification. automatic backwash. compact but high initial cost. 56 squ journal of agricultural and marine sciences, 2018, volume 23, issue 1 integrated aquaculture in arid environments protein, 1-5% lipids and various bioactive compounds including essential fatty acids, carotenoids, vitamins and minerals (kuhn et al., 2009). the availability of in situ nutrients has opened the way for reformulation of special aquafeeds for use in biofloc systems. protein content can be reduced and fish meals can be replaced with plant meals. this both improves sustainability and reduces cost (martinez-cordova et al., 2015). in practice biofloc tanks or ponds must be continuously mixed and aerated and the carbon nitrogen ratio (c:n) carefully maintained (12-20:1) to support the formation and stabilisation of a heterotrophic microbial community (perez-fuentes et al., 2016). carbon content is balanced using available carbohydrate sources such as molasses or grain pellets. total suspended solids content is monitored throughout the fish production cycle and maintained at optimal levels of 100-300 ppm. excess biomass can be harvested and processed into feed ingredients (kuhn et al., 2009). biofloc farming systems operating with zero or minimum water exchange offer greatly enhanced biosecurity, which is particularly valuable for shrimp farmers in the control of transmissable viral diseases. the role of natural probiotics and immunostimulants on survival and growth have also been reported from studies on the microbial ecology of bioflocs (rani et al., 2017) planning and economics a detailed review of planning, construction, operation and economics of small-scale aquaponic farms has been provided by fao (somerville et al., 2014). capital costs can be high in relation to income and a recent survey suggest that the majority of aquaponic farms operate on small commercial scale (love et al., 2015). farm design should be optimised for the targeted production levels and fish species (limited choice) and plant varieties (wide choice) should be selected based on local and regional consumer demand and value. some failures of large projects have been reported where profits could not match the demands of initial investment plans (somerville et al., 2015). aquaponics in urban environments is taking the lead in large-scale developments. disused industrial space, including rooftops, is attracting developments in many european and north american cities. they are typically based on the use of a temperature and light-controlled greenhouse structures designed to support year-round production and incorporate space-saving stacked and vertical horticulture systems (kyaw and ng, 2017). capital and operating costs are high but operators benefit from a large consumer base and demand for organically produced fresh products from local suppliers. urban projects also play an important role in education and public awareness. future prospects aquaponic developments hold great potential to contribute to food security and support sustainable development goals in hot arid and regions. they benefit from efficient water use, high productivity and low environmental impact. in these regions costly heating systems and greenhouse structures are not necessary and solar energy can be used to generate electricity supplies for water pumps, aerators and other equipment. this reduces capital and operating costs and supports the development of aquaponic enterprises as small or medium enterprises or ever large commercial ventures. integration of aquaponics with biofloc technologies has the potential to reduce the costs of water treatment, improve feeding efficiency and scale-up fish production. early research indicates the bio-availability of plant nutrients in biofloc tanks and ponds. systems will however require modification for efficient handling of solids waste and excess biofloc. further potential exists to apply aquaponic techniques in arid regions, where salinization of ground water restricts traditional agriculture. many commonly-farmed fish species are tolerant of low to medium water salinities and their production can be combined with growing salt tolerant varieties of traditional crops at low salinities (goddard et al., 2010) or edible halophytes at higher salinities (pantanella and bhujel, 2015). references avnimelech y. 2007 feeding with microbial flocs by tilapia in minimal discharge biofloc technology ponds. aquaculture 264: 140-147. bernstein s. 2013 aquaponic gardening. saraband, glasgow. bossier p, ekasar j. 2017. biofloc technology applications in aquaculture to support sustainable development goals. microbial biotechnology 10: 1012-1016. bregnballe j. 2015. a guide to recirculation aquaculture. fao/eurofish, rome,fao, 95pp. chalmers, ga. 2004. aquaponics and food safety. lethbridge, canada. 74pp. colt j. 2006. water quality requirements for reuse systems. aquaculture engineering 34:143 156. chappell ja, brown wt. 2008. a demonstration of tilapia and tomato culture utilising an energy efficient integrated system approach. in 8th international symposium on tilapia in aquaculture. eds. elghbashy h, fitzsimmons k, and diab as. october 12-14, cairo, egypt. crespi v, lovatelli a. 2011. global desert aquaculture at a glance. in crespi v and lovatelli a. aquaculture in desert and arid lands: development constraints and opportunities. fao technical workshop. 6–9 july 2010, hermosillo, mexico. fao fisheries and aquaculture proceedings no. 20. rome, fao. pp. 25–37. fao. 2016. the state of world fisheries and aquacul57research article goddard, al-abri ture. rome, fao. 91pp. available at http//www.fao. org fox bk, tamaru cs, hollyer j, castro lf, fonseca jm, jay-russel m, and low t. 2012. a preliminary study of microbial water quality related to food safety in recirculating aquaponic fish and vegetable production systems. food safety and technology fst51, college of tropical agriculture and human resources, university of hawaii. goddard s, al-busaidi as, al-kendi ukh. 2010. fish culture and hydroponics at low salinities. in: a monograph on management of salt-effected soils and water for sustainable agriculture. ds. ahmed, m., al-rawahy, s.a. and hussain, n. pp 89-94. sultan qaboos university press, muscat, oman. goddard s, al-abri w, al-abri f, bose s. 2015. design and testing of an aquaponics fish/hydroponic plant) production system for use in a hot arid environment. project report eg/dvc/mbio/13/01. agricultural and fisheries development fund, ministry of agriculture and fisheries, oman. 42pp. godfray hcj, beddington jr, crute ir, haddad l, lawrence d, muir jf, pretty j, robinson s, thomas sm, toulmin c. 2010. food security: the challenge of feeding 9 billion people. science 327: 812-818. hargreaves ja. 2013. biofloc production systems for aquaculture. southern regional aquaculture center, srac publication no. 4503. stoneville, usa. harwati d, o sy, jo jy. 2011. comparison of nitrification efficiencies of three biofilter media in a freshwater system. fisheries and aquatic sciences 14: 363-369. kuhn d, boardman g, lawrence, a, marsh l, flick g. 2009. microbial floc meal as a replacement ingredient for fish meal and soybean protein in shrimp feed. aquaculture 296: 51 57. kyaw ty, ng ak. 2017. smart aquaponics for urban farming. energy procedia 143: 342-347. love dc, fry jp, ximin l, hill es, genello l, semmens s, thompson re. 2015. commercial aquaponic production and profitability: findings from an international survey. aquaculture 435: 67-74. martins cim, eding eh, verdegem mcj, heinsbroek ltn, schneider o, blancheton jp, roque d’ordcastel e, verreth jaj. 2010. new developments in recirculating aquaculture systems in europe: a perspective on environmental sustainability. aquaculture engineering 43:83-93. martinez-cordova lr, emerancian m, miranda-baeza a, martinez-porchas m. 2015. microbial based systems for aquaculture of fish and shrimp: an updated review. reviews in aquaculture 7(2): 131-148. naegel, lca. 1977. combining production of fish and plants in recirculating water. aquaculture 10: 17-24. pantanella e, bhujel rc. 2015. saline aquaponics, potential players in food, energy production. global aquaculture advocate jan/feb 42-43. perez-fuentes ja, hernandez-vergara hp, perez-rostro ci, fogel i. 2016. c:n ratios affect nitrogen removal and production of nile tilapia raised in a biofloc system under high density cultivation. aquaculture 452: 247-251. pinho sm, mollinari d, demello gl, fitsimmons km, emerenciano gc. 2017. effluent from a biofloc technology (bft) tilapia culture on the aquaponic production of different lettuce varieties. ecological engineering 103: 146-153. rani am, verma ak, maqsood m. 2017. biofloc technology: an emerging avenue in aquatic animal healthcare and nutrition. aquaculture international 25: 1215-1226. rakocy je, masser mp, losordo tm. 2006. recirculating aquaculture tank production systems: aquaponics integrating fish and plant culture. southern regional aquaculture center, srac publication no. 454. stoneville, usa. sirsat sa, neal ja. 2013. microbial profile of soil-free versus in-soil grown lettuce and intervention methodologies to combat pathogen surrogates and spoilage microorganisms on lettuce. foods 2: 488-498. somerville c, cohen m, pantanella e, stankus a, lovatelli a. 2014. small-scale aquaponic food production. integrated fish and plant farming. fao fisheries and aquaculture technical paper no. 589. rome, fao. 262pp. sugita h, shibuya k, shimooka h, deguch y. 1996. antibacterial abilities of intestinal bacteria in freshwater cultured fish. aquaculture 145: 195-203. research paper journal of agricultural and marine sciences 2022, 27(1): 112–117 doi: 10.53541/jams.vol27iss1pp112-117 received 30 jan 2021 accepted 01 july 2021 rehydration ability of native dried date (phoenix dactylifera l.) fruits soaked in orange juice messaid habiba, ait-ameur lamia, benamara salem* benamara salem*( ) sbenamara2001@yahoo.fr, research laboratory in food technology, faculty of engineering sciences, university m’hamed bougara, boumerdès, 35000, algeria introduction preservation of genetic diversity of date palm (phoe-nix dactylifera l.) tree needs valorization of date fruits (dfs) having low commercial value (acourene et al., 2007). native dry df varieties like mech-degla are known to be a sugar-rich material, attributing to the fruit pulp a sweet taste and non-juicy consistency. rehydration is a unit operation widely used in food processing (amami et al., 2006). this is a complex process aimed at the restoration of the food properties, including thermophysical properties (vega-gálvez et al., 2009). many works have been devoted to rehydration process of different fruits, including dfs, using distilled water as soaking media: hot air-dried dfs (falade and abbo, 2007), freeze-dried pineapple, mango, guava, acerola and papaya (marques et al., 2009), softening of over dried ‘deglet nour’ dates and impact of rehydration on the dried products (boubekri et al., 2010), osmotic pre-dehydrated, hot-air and microwave-vacuum dried strawberry and apples (kowalska et al., 2018) , etc. however, to our knowledge, little research has been reported on the rehydration using fruit juices as soaking media. the present paper reports on the rehydration ability of algerian native dry dfs (phoenix dactylifra l., var. mech-degla) using orange juice as soaking liquid. the orange juice could add specific physicochemical, nutritional and organoleptic characteristics to new infused fruit. it is worth pointing out that the possibility of obtaining dried date fruits infused in syrup was initially reported by amellal et al. (2007) and benamara et al. (2008). preservation of fruits in syrup is well known traditional method (tindall, 1994). (phoenix dactylifera l.) قدرة مثار النخيل اجملفف على الرتطيب عن طريق نقعها يف عصري الربتقال مسيد حبيبة ، آيت عامر ملياء ، بن عمارة سامل abstract. algerian date (phoenix dactylifera l., dried variety mech-degla) fruits (dfs) are of low commercial value. to our knowledge, research on the rehydration of dfs by soaking in citrus or other fruit juices is limited. the present paper reports on the soaking process of naturally dried dfs in orange juice (oj). the df rehydration ability was analyzed by applying two levels factorial design with three responses (df weight gain, oj °brix and df breaking strength) and three factors (soaking temperature “x1”, soaking time “x2” and oj volumetric fraction “x3”). the optimal experimental conditions (x1 = 5 °c, x2 = 24 h and x3 = 0.1) allowed to achieve weight gain ~ 0.5, °brix ~ 16 °bx and breaking strength of 0.6 n (i.e. against 3.7 n for the initial dfs). in addition, the resulting syrup-infused dfs showed a good heat treatment capability in terms of texture retention. the soaking of dried dfs in citrus juice like oj could be an alternative to valorize such products. keywords: dried date fruit, orange juice, rehydration, soaking, syrup امللخص:تعتــر التمــور اجلزائريــة )phoenix dactylifera l( مــن النوعيــة اجلافــة )mech-degla( ذات قيمــة جتاريــة منخفضــة. و علــى حــد علمنــا، فــإن البحــوث العلميــة يف معاجلــة )ترطيــب( التمــر عــن طريــق النقــع يف عصائــر احلمضيــات أو الفواكــه األخــرى حمــدودة. تشــر املقالــة احلاليــة إىل عمليــة نقــع هــذه التمــور اجلافــة طبيعيــا يف عصــر الرتقــال. متــت دراســة قــدرة ترطيــب التمــر مــن خــال تطبيــق التصاميــم التجريبيــة )تصميمــات عاملــة كاملــة( ذو مســتوين دون تكــرار مــع األخــذ بعــن االعتبــار لثاثــة متغــرات اتبعــة )زايدة وزن التمــر ، brix° لعصــر الرتقــال ، وقــوة كســر x1=5( الظــروف التجريبيــة املثلــى . )»x3« نســبة عصــر الرتقــال »x2« مــدة النقــع ، »x1« التمــر( وثاثــة متغــرات مســتقلة)درجة حــرارة النقــع درجــات مئويــة ، x2 =24 ســاعة و x3 =0.1 ( مكنــت بتحقيــق زايدة يف وزن التمــر تقــدر ابلنصــف ، قيمــة brix ~ 16° درجــة وقــوة االنكســار n 0.6 ) مقابــل n 3.7 للتمــور الغــر معاجلــة(. ابإلضافــة إىل ذلــك، فقــد أظهــرت التمــور املشــبعة ابلعصــر قــدرة جيــدة علــى املعاجلــة احلراريــة مــن حيــث االحتفــاظ ابمللمــس. ميكــن أن يكــون اذن نقــع التمــور اجملففــة يف عصــر احلمضيــات مثــل عصــر الرتقــال بديــًا لتثمــن هــذه التمــور. الكلمات املفتاحية: التمور اجلافة، عصر الرتقال، النقع، شراب مركز، تصميمات عاملة كاملة دون تكرار. 112 squ journal of agricultural and marine sciences, 2022, volume 27, issue 1 rehydration ability of native dried date (phoenix dactylifera l.) fruits soaked in orange juice materials and methods plant materials algerian date (phoenix dacylifera l., dried variety mech-degla) fruits (dfs) were harvested in the region of biskra (south-eastern algeria) and purchased from the city of constantine (north-eastern algeria). they were characterized by high sugar content of 64% (wb), low water content of 14% (wb) and relatively high ph of 6.3 as already highlighted by noui (2007) and messaid (2008). these are the three most important parameters because they are likely to have a direct influence on the mass transfer and texture. the fruits were sorted and cleaned, then packaged in a polyethylene bag at 6 °c. before rehydration, the fruits were washed, dried by absorbent paper and then cut longitudinally into two halves. the orange juice (oj) used as soaking media was from fruits of late variety valencia cultivated in the region of blida (50 km west of algiers). the oranges were cleaned, washed and dried by absorbent paper. the oj was extracted immediately prior to use, by manual pressing of orange halves using lemon squeezers. after extraction, oj was filtrated and centrifuged. rehydration by soaking in orange juice the rehydration of dfs by soaking in diluted oj was studied using two-level full factorial design as described by goupy (1996). for this, three factors (variables) were considered, namely temperature of oj used as soaking media (x1, level (-) = 5 °c and level (+) = 45 °c), soaking time (x2, level (-) = 0.5 h and level (+) = 24 h) and volumetric fraction of oj in the soaking aqueous solution (i.e. mixture of distilled water and natural oj) (x3, level (-) = 0.1 and level (+) = 0.9). the temperature was controlled using a refrigerator equipped with a thermostat (i.e. 5° c) and a thermostatically controlled water bath (i.e. 45° c). three responses were taken into account, namely, df weight gain (weight fraction, with reference to the initial weight), oj °brix and df breaking strength (n). the df halves:soaking oj ratio was 1:3 (w/v), corresponding to 20 g date pieces/60 ml diluted oj. data modeling was performed using xlstat software. instrumental texture analysis it is well established that the texture of foods, together with color and flavor, is one of the most important quality criteria, which determines the consumer acceptability (andrés-bello and barreto-palacios, 2013). the measurement of the breaking force (expressed in n) was carried out on dfs before and after soaking, using the texture analyzer ta lloyd (ar2000 ta plus lloyd instrument, ametek, uk) with drip tray. fundamentally, it consisted of three modules, namely drive system, test cell and force measuring and recording system. the plunger used was cylindrical shape with a flat base 12.7 mm in diameter, moving with a speed of 1 mm/s. several parameters were measured but only the breaking strength, indicative of the df firmness, is presented. for comparison purpose, commercial syrup-infused pineapple and papaya were subjected to the same analysis. pasteurization this test consisted essentially to check the ability of the processed date fruits to maintain texture during thermal pasteurization. preliminary, time needed to reach the desired temperature at the center of df pieces was determined, using a thermocouple (type j blindi), a heat generator (lauda type) and a temperature recorder (type servogor 210/goerz). the dfs soaked in the oj syrup were packaged in a glass jar, which was first sealed with a screw cap and then immersed in a thermostatically controlled heating bath. the pasteurization temperature was kept constant at 78 °c during pre-determined heating time of 4 min. results and discussion the results of rehydration ability are summarized in table 1. as it can be seen from the table, the test 3 was the most interesting based on: i) the maximum date fruit (df) weight gain ~ 0.5, ii) brix value ~ 16 °bx, corresponding to a syrup of light type (fao, 2003), and iii) appreciated df texture with a tensile strength of 0.64 n (against 3.66 ± 0.6 n for the initial fruits) (i.e. close to that of commercial syrup infused fruits, 0.63 and 1.2 n for papaya and pineapple, respectively). the breaking force of 0.64 n was chosen because among all the values obtained for the breaking force, it was the closest to 0.63 n (i.e. commercial infused papaya). none of the values did show as close to the firmness (1.2 n) of pineapple (i.e. commercial infused fruit). to our knowledge, there was negligible numerical data on the firmness of other infused fruit species. regarding dfs, soft and chewy moist fruits are commonly preferred (barreveld, 1993). globally, the rehydration ability and firmness of processed dfs seemed to be close to those (2-50% and 0.4 to 2 n, respectively) of infused blueberries (rodrigues et al., 2015). infused fruits generally refer to the process of osmotic dehydration. in this present work, the process of soaking of dfs in orange juice (oj) was visualized as compared to other two processes of rehydration and osmotic dehydration (figure 1). the observed enhancement in the texture of rehydrated df pieces can be attributed to absorbed water (stanley and aguilera, 1985). in addition, various substrates, ions and enzymes in oj can interact with dfs during soaking and heat treatment (andrés-bello and barreto-palacios, 2013). the color change may also be influenced by the ph value (andrés-bello and barreto-palacios, 2013). the rehydration ability of df varieties can be depended on sun-drying of fruits on the tree. such drying is relatively different from post-harvest drying. in fact, the high temperature of drying involves 113research paper messaid, ait-ameur, benamara a more rigid structure, which can lead to a lower rehydration rate (ramallo and mascheroni, 2012). models obtained with the coded variables are given as follows, using xlstat software (goupy, 1996): weight gain: y = 0.357 + 0.010x1 + 0.146x2 + 0.007x3 (1) °brix : y = 15.19 + 1.50x1 + 6.55x2 + 3.40x3 + 1.18x1x2 +0.35x1x3 – 0.40 x2x3 + 0.23x1x2x3 (2) breaking strength: y = 1.37 – 0.35x1 – 0.835x2 + 0.08x3 + 0.13x1x2 (3) the measured and predicted values are shown in figure 2. for the “weight gain” response (eq. 1), the factor time table 1. experimental design related to soaking of native dried dates soaked in orange juice no x1 x2 x3 weight gain °brix* breaking strength, n 1 0.211 4.63 2.58 2 + 0.224 5.03 1.63 3 + 0.499 16.63 0.64 4 + + 0.521 20.83 0.28 5 + 0.195 12.00 2.78 6 + + 0.215 12.90 1.81 7 + + 0.483 21.50 0.86 8 + + + 0.507 28.00 0.35 level (-) 5°c ±3 0.5 h 0.1** level (+) 45 °±3 24 h 0.9*** * expressed as fraction, based on the initial weight; **10 % (v/v) pure orange juice; ***90 % (v/v) pure orange juice; x1: temperature of soaking juice; x2: soaking time, and x3: volumetric fraction of orange juice. figure 1. diagrams of rehydration in water (a), osmotic dehydration (b), and soaking date fruit in orange juice (c). the arrows of different sizes indicate the direction and, for general guidance, the intensity of the corresponding mass transfers. 114 squ journal of agricultural and marine sciences, 2022, volume 27, issue 1 rehydration ability of native dried date (phoenix dactylifera l.) fruits soaked in orange juice (x2) has a positive main effect and it seems to be the most influential factor. in the case of “°brix” (eq. 2), time and oj concentration have a positive effect and both factors seem to be more influential than temperature. regarding the “breaking strength” (eq. 3), the soaking time and temperature have a negative main effect and they seem to be more influential as compared to the oj concentration. moreover, there is a synergistic interaction between orange juice temperature and soaking time. the internal and external surface of df halves at different stages of treatment are shown in the figure 3. sugars as essential components of dfs promote water uptake by plant tissue, whereas the fruit minerals could improve the texture firmness of the final product, and potassium being frequently associated with the fruit firmness (guedes et al., 2013; cromey, 2012; watson and lom, 2008; neumann 1972). it should be noted that preliminary tests showed that the rehydration of dried dfs figure 2. predicted by the model and measured values of weight gain (a), °brix (b) and breaking strength (c), (see table 1 for units). 115research paper messaid, ait-ameur, benamara by soaking in water was not convenient because of the disintegration of the fruit texture (results not presented here), whereas the citrus juices produced a firm texture. conclusion naturally dry date fruits (dfs) showed a good ability to rehydration when they were soaked in orange juice. in addition, the thermal pasteurization improved the rehydration ability and surface structure of infused dfs. these findings confirm the possibility of obtaining a new df product. additional studies are needed to improve the modeling and optimization of rehydration and pasteurization processes. references acourene s, allam a, taleb b, tama m. (2007). inventaire des différents cultivars de palmier dattier (phoenix dactylifera l.) des régions de oued-righ et de oued-souf (algérie). sécheresse 18(2): 135-142. amami e, fersi a, khezami l, vorobiev e, kechaou n. (2007). centrifugal osmotic dehydration and rehydration of carrot tissue pre-treated by pulsed electric field. lwtfood science and technology 40: 1156-1166. amellal h, ait-ameur l, benamara s, noui y. (2007). treatment of mech-degla date by immersion in the citrus juices, in: lazos es, eds, proceeding of 5th international congress of food technology, v.1, thessaloniki, greece, 2007, pp. 647−652. andrés-bello a, barreto-palacios v. (2013). effect of ph on color and texture of food products. food engineering reviews 5: 158-170. barreveld wh. (1993). whole dates. in: date palm products: fao agricultural services bulletin no. 101. benamara s, gougam h, amellal h, djouab a, benfigure 3. images of pitted dried date fruits halved longitudinally: a) before soaking, b) after soaking, according to test no 3 (see table 1), and c) after soaking followed by pasteurization at 78°c during 4 min. on the left: date fruit external side; on the right: date fruit internal side. 116 squ journal of agricultural and marine sciences, 2022, volume 27, issue 1 rehydration ability of native dried date (phoenix dactylifera l.) fruits soaked in orange juice ahmed a, noui, y. (2008). some technologic proprieties of common date (phoenix dactylifera l.) fruits. american journal of food technology 3 (2): 79-88. boubekri a, benmoussa h, courtois f, bonazzi c. (2010). softening of over dried ‘deglet nour’ dates to obtain high-standard fruits: impact of rehydration and drying processes on quality criteria. drying technology 28 (2): 222-231. cromey, d. w. (2012). digital images are data: and should be treated as such. in cell imaging techniques (pp. 1-27). humana press, totowa, nj. falade ko, abbo es. (2007). air-drying and rehydration characteristics of date palm (phoenix dactylifera l.) fruits. journal of food engineering 79: 724-730. fao. (2013). directives pour les milieux de couverture des fruits en conserve, cac/gl51-2003. food and agricultural organization, rome, italy. goupy j. (1996). la methode des plans d’expériences. dunod, paris, 303 pp. guedes mns, de abreu cmp, maro lac, pio r, de abreu jr, de oliveira jo. (2013). chemical characterization and mineral levels in the fruits of blackberry cultivars grown in a tropical climate at an elevation. acta scientiarum biological sciences 35 (2): 191-196. kadam su, tiwari bk, o’donnell cp. (2015). improved thermal processing for food texture modification. in: modifying food texture, volume 1: novel ingredients and processing techniques, pp. 115-131. kowalska h, marzec a, kowalska j, ciurzyńska a, samborska k, bialik m, lenart a. (2018). rehydration properties of hybrid method dried fruit enriched by natural components. international agrophysics 32: 175-182. marques lg, prado mm, freire jt. (2009). rehydration characteristics of freeze-dried tropical fruits. lwt food science and technology 42 (7): 1232-1237. messaid h. (2008). optimisation du processus d’immersion-réhydratation du système dattes sèches-jus d’orange. mémoire de magister, faculté des sciences de l’ingénieur, université m’hamed bougara, boumerdès, algérie, 96p. neumann hj. (1972). dehydrated celery: effects of predrying treatments and rehydration procedures on reconstitution. journal of food science 37: 437-441. noui y. (2007). caractérisation physico-chimique comparative des deux principaux tissus constitutifs de la pulpe de datte mech-degla. mémoire de magister, faculté des sciences de l’ingénieur, université m’hamed bougara, boumerdès, algérie, 112p. ramallo la, mascheroni rh. (2012). quality evaluation of pineapple fruit during drying process. food bioproducts processing 90 (2): 275–283. stanley dw, aguilera jm. (1985). a review of textural defects in cooked reconstituted legumes-the influence of structure and composition. journal of food biochemistry 9 (4): 277-323. tindall hd. (1994). sapindaceous fruits: botany and horticulture. in j. janick (eds), horticultural reviews, volume 5, john wiley & sons, pp. 143-196. vega-gálvez a, notte-cuello e, lemus-mondaca r, zura l, miranda m. (2009). mathematical modelling of mass transfer during rehydration process of aloe vera (aloe barbadensis miller). food and bioproducts processing 87 (4): 254-260. watson fl, lom b. (2008). more than a picture: helping undergraduates learn to communicate through scientific images. cbe—life sciences education 7: 27-35. research paper journal of agricultural and marine sciences 2021, 26(1): 27–36 doi: 10.24200/jams.vol26iss1pp27-36 reveived 11 may 2020 accepted 13 aug 2020 biological efficiency and control of a membrane bioreactor and conventional activated sludge process for treating municipal wastewater buthaina mahfoud al-wahaibi1, 2, abdullah al-mamun1, *, mahad said baawain1, ahmad sana الكفائة و التحكم البيولوجي يف مفاعل حيوي غشائي و عملية احلمأة املنشطة التقليدية ملعاجلة مياه الصرف الصحي البلدية بثينة الوهييب1 ، 2 ، عبدهللا املأمون1 ، * ، حماد سعيد ابعوين1، أمحد سنا abstract. the performance of a membrane bioreactor (mbr) was compared to a conventional activated sludge (cas) process and it was aimed to identify the best technological option for a municipal sewage treatment plant (stp). the mbr system was fed by the diluted sewage coming from the main municipal sewer network, which contained an averagely lower concentration of organics, inorganics and biological pollutants. while the cas system was fed by a concentrated sewage coming from household septic tanks, contained averagely high concentration of organics, inorganics and biological pollutants. cas showed a higher removal efficiency of biochemical oxygen demand (bod), chemical oxygen demand (cod), total suspended solids (tss), volatile suspended solids (vss), fat-oil-grease (fog), nitrogen, phosphorous, helminths ova (ho), and pathogenic bacteria compared to the mbr. nevertheless, the removal efficiencies of nitrogen, ho and pathogenic bacteria in the case of cas were lower than mbr due to the high concentration of those parameters in the influent fed to cas. however, both the efficiency and the amount of removal for phosphorous in the case of cas was quite higher than that of mbr due to extended aeration in cas. the pathogenic bacteria and ho were removed almost 99.97% by the mbr, whereas the cas removed 91±5% of the pathogenic bacteria and ho. therefore, the effluent of the cas system required additional disinfection for the reduction of pathogens and ho. in terms of biological efficiency and influent flexibility, both the systems can satisfy the national standards. overall, the data suggested that cas possessed a higher capacity of treating concentrated sewage for removing all pollutants to satisfactory limits except complete removal of pathogenic bacteria and ho. it was obvious that mbr possessed a membrane barrier to retain the pathogens and ho; therefore, they could be removed up to very low levels. however, further investigation is necessary to verify the mbr performance using the same concentrated sewage as cas. keywords: membrane bioreactor; conventional activated sludge; municipal wastewater treatment; removal efficiency; sewage treatment plant; national standards. املســتخلص:متت مقارنــة أداء مفاعــل غشــائي حيــوي )mbr( بعمليــة احلمــأة املنشــطة التقليديــة )cas( وذلــك لتحديــد اخلياراألفضــل التكنولوجــي حملطــة معاجلــة ميــاه حمطــة صــرف الصحــي بلديــة. متــت تغذيــة املفاعــل احليــوي الغشــائي مــن ميــاه الصــرف الصحــي املخفــف القادمــة مــن شــبكة الصــرف الصحــي ابملناطــق احلضريــة الرئيســية، الــي حتتــوي علــى معــدل تركيــز أقــل مــن املــواد العضويــة، غــر العضويــة وامللــواثت البيولوجيــة. يف حــن متــت تغذيــة نظــام املنشــطة التقليديــة مــن ميــاه الصــرف الصحــي املركــزة القادمــة مــن خــزاانت الصــرف الصحــي املنزليــة،و الــي حتتــوي علــى متوســط تركيــز عــاٍل مــن املــواد العضويــة وغــر العضويــة وامللــواثت البيولوجيــة. أظهــرت نظــام احلمــأة املنشــطة التقليديــة علــى كفــاءة إزالــة أعلــى مــن الطلــب البيوكيميائــي األكســجن )bod( ، الطلــب علــى االكســجن الكيميائــي )cod( ، إمجــايل املــواد الصلبــة العالقــة )tss( ، املــواد الصلبــة املعلقــة ،)vss( ، املركبــات الدهنيــة )fog( ، النيرتوجــن ، الفوســفور، بويضــات الديــدان)ho( ، و البكتــراي املســببة لألمــراض، مقارنــة ابملفاعــل الغشــائي احليــوي. ومــع أن كفــاءة إزالــة النيرتوجــن ، بويضــات الديــدان، والبكتــراي املســببة لألمــراض يف حالــة نظــام احلمــأة املنشــطة التقليديــة كان أقــل مــن املفاعــل الغشــائي احليــوي بســبب الرتكيــز العــايل مــن هــذه العوامــل يف النظــام املغــذي للحمــأة املنشــطة التقليديــة. ومــع ذلــك، فــإن كال مــن كفــاءة وكميــة إزالــة الفوســفور يف نظــام احلمــأة املنشــطة التقليديــة كان أعلــى جــدا مــن ذلــك يف املفاعــل الغشــائي احليــوي بســبب التهويــة املمتــدة يف نظــام احلمــأة املنشــطة التقليديــة. متــت إزالــة البكتــراي املســببة لألمــراض و بويضــات الديــدان بنســبة 99.97٪ تقريبًــا بواســطة املفاعــل الغشــائي احليــوي ، يف حــن أزالــت نظــام احلمــأة املنشــطة التقليديــة 91 ± 5٪ مــن البكتــراي املســببة لألمــراض و بويضــات الديــدان. لذلــك ، يتطلــب تدفــق نظــام احلمــأة املنشــطة التقليديــة تطهــرًا إضافيًــا لتقليــل مســببات األمــراض و بويضــات الديــدان. مــن حيــث الكفــاءة البيولوجيــة ومؤثــر املرونــة ، فــإن كال النظامــن ميكــن أن يلــيب املعايــر الوطنيــة. وعمومــا، تشــر البيــاانت إىل أن نظــام احلمــأة املنشــطة التقليديــة ميتلــك قــدرة أعلــى علــى معاجلــة ميــاه الصــرف الصحــي املركــزة إلزالــة مجيــع امللــواثت إىل حــدود مرضيــة ابســتثناء إزالــة كاملــة للبكتــراي املســببة لألمــراض وبويضــات الديــدان. كان مــن الواضــح أن املفاعــل الغشــائي احليــوي وضــع حاجــزًا غشــائًيا لالحتفــاظ مبســببات األمــراض و بويضــات الديــدان ؛ وابلتــايل، فإنــه ميكــن إزالتهــا إىل أدىن املســتوايت. ومــع ذلــك، فانــه مــن الضــروري إجــراء املزيــد مــن البحــث للتحقــق مــن أداء املفاعــل الغشــائي احليــوي ابســتخدام نفــس ميــاه الصــرف الصحــي املركــزة مثــل نظــام احلمــأة املنشــطة التقليديــة. الكلمات املفتاحية: املفاعل احليوي، نظام احلمأة املنشطة التقليدية، الصرف الصحي، كفائة االزالة، نظام الصرف الصحي، املعاير الوطنية 28 squ journal of agricultural and marine sciences, 2021, volume 26, issue 1 biological efficiency and control of a membrane bioreactor and conventional activated sludge process for treating municipal wastewater introduction the growing scarcity of water resources in arid re-gions, like the sultanate of oman, has extensive-ly increased the necessity to preserve the current resources for drinking purposes (oliver et al., 2008; zanetti et al., 2010). to do so, municipal wastewater plants have been established to treat wastewaters and support the sustainable development of the country (baawain et al., 2020; 2019a; 2019b; iglesias et al., 2010; papa et al., 2016). wastewater is often treated by a conventional activated sludge (cas) process, which includes the steps of biological, physical and chemical treatment. the physical treatment during the cas process, such as conventional solids settling and sand filtration, cannot remove all the contaminants up to the desired level. therefore, subsequent chemical or physical treatment steps, such as chlorination and/or uv ray treatment are required. the implementation of such chemical treatments already has identified as risks and threats to the environment and public health as it discharges chemicals and chemicals by-products as effluent into aquatic systems (chitrakar et al., 2019; al-mamun, 2017; baawain et al., 2017; zanetti et al., 2010). in order to improve the effluent quality before final disposal, membrane-based technology can be better alternatives for removing tiny solid particles and pathogenic microbes without any usages of eco-threatening chemical treatment steps (chlorination or ozonation) (jafary et al., 2018; 2020a, 2020b, al lawati et al., 2019). in sewage treatment plants (stps), a microporous membrane for filtration purposes combined with a biological wastewater treatment known as a membrane bioreactor (mbr) is utilized (collivignarelli et al., 2017; melin et al., 2006). over the last decades, mbr has proven to be a valuable alternative for cas plants (van den broeck et al., 2010). because, mbr has some major advantages than that of the cas, including small footprint, superior quality effluents (no chemicals and chemical by-products), and sludge reduction (drews, 2010; jeison and van lier, 2007; judd, 2010; tewari et al., 2010). for example, the mbr processed water from an integrated process in germany provided a water quality that fully meets the requirements of a washing process (hoinkis and panten, 2008). however, the mbr has the drawback of membrane fouling, leading to an increased energy demand due to increased trans-membrane pressure and influenced the removal efficiencies and nitrous oxide emission (van den broeck et al., 2012; mannina et al., 2017). for this reason, an upgraded version of mbr with microbial fuel cell (mfc) for sewage treatment is quite essential for combined removal of organics and nitrogen, and recovery of electrical energy (ryue et al., 2020; lefebvre et al., 2008a; 2008b; 2009; 2010; al-mamun and baawain, 2015). however, this up-gradation can be feasible only by exploring the cost-effective materials and appropriate reactor designs with combined mbr-mfc system (al-mamun et al., 2016; 2017a; 2017b; chung et al., 2020). recent studies have revealed some insight on comparing cas to mbr process in a variety of industrial wastewater systems, such as a winery (valderrama et al., 2012), tannery (munz et al., 2008), textile factory (malpei et al., 2003), or municipal sewage (de luca et al., 2013; liu et al., 2009; zanetti et al., 2010). however, the biological efficiency of mbr and cas processes in the municipal wastewater industries has not been carried out extensively. the review of previous studies revealed that selected polar pollutants in municipal wastewater, the mbr removal efficiency in laboratory studies was significantly greater than that of the cas, while no improvement has been recorded for other pollutants (weiss and reemtsma, 2008). the pilot mbr resulted in higher removal of chemical oxygen demand (cod) (i.e. 93%), suspended solids (>99%) and microorganisms as well as a color abatement. while, the chemical removal efficiency was very variable and it was particularly amongst the different classes of organic contaminants (gerbersdorf et al., 2015). in other words, the mbr system has demonstrated consistent performance in treating high-strength and fluctuating strength wastewater in pilot scales (chang et al., 2008). in recent decades, advanced wastewater treatment technologies, such as mbr, are of particular attention, because of the thorough removal efficiency of the suspended and dissolved chemical and biological components from wastewater (petrović et al., 2003; barua et al., 2018; 2019). however, the experimental efforts to compare the removal efficiency of different components in real plants have been lacking. this is due to the fact that it is not feasible to acquire statistical rigorous data from a full-scale treatment plant. thus, the available comparative studies have normally been limited to only a few pilot-scale cases, which make it extremely problematic to generalize the results on a global scale with any sort of assurance. therefore, in order to gain an understanding of the removal efficiencies of organics, inorganics and biological pollutants from a full-scale treatment plant, a case study of municipal wastewater treatment comparing the mbr and cas technologies was carried out. the samples were collected from three different locations, which were influent raw sewage (rs), biological aeration tank and treated effluent. the emphases of this study were to characterize the strength of influent rs, distinguish the concentration load in the biological treatment tank, calculate the removal performance of each parameter, and compare the quality of treated effluents to the ministry of environment and climate affairs (meca) standards in muscat, sultanate of oman. furthermore, abdullah al-mamun1,*( ) aalmamun@squ.edu.om, 1department of civil and architectural engineering, sultan qaboos university, po box 33, pc 123, muscat, sultanate of oman. 2al-ansab sewage treatment plant, haya water, po box 1047, pc 133, muscat, sultanate of oman. 29research paper al-wahaibi, al-mamun, baawain, sana the performance of the current cas and mbr systems were compared with respect to the measured parameters. this study allows a technological recommendation for the optimization of the stps in the municipal wastewater treatments. materials and methods process description of old al-ansab stp old al-ansab stp, located in south muscat (figure 1), was commissioned in 1990 and then handed to haya water in 2006. the old stp was designed to treat annual average flow of 12,000 m3 day-1 with a peak flow of up to 24,000 m3 day-1. the old stp consists of five main units, including tanker discharge area, pre-treatment facilities, secondary biological treatment, filtration, and chlorination. the plant was designed to treat the wastewater by the cas process at solids retention time (srt) of 21 days. process description of the new al-ansab stp the new al-ansab stp is an integral part of the muscat wastewater scheme project (mbr based technology) with a plant average capacity of 55,000 m3 day-1 . the new plant was commissioned in 2010 to serve the bausher catchment. the treatment process consisted of six main units, which were preliminary treatment, biological treatment and solids separation, treated effluent storage, sludge dewatering, chemical storage/dosing and odor control system. the mbr process included flat sheet membrane panels (kubota submerged membrane unittm, spc400, japan) housed in units. the flat sheet table 1. wastewater characteristics at al-ansab stp parameter units minimum maximum biochemical oxygen demand (bod5) mg l-1 350 400 chemical oxygen demand (cod) mg l-1 600 900 total suspended solids (tss) mg l-1 350 500 volatile suspended solids (vss) mg l-1 280 400 vss/tss ratio % 75 85 total kjeldahl nitrogen (tkn) mg l-1 50 70 ammonia nitrogen (nh3-n) mg l-1 35 45 total phosphorous (tp) mg l-1 9 15 total alkalinity (as caco3) mg l -1 100 200 oil and grease mg l-1 na 200 ph [-] 6.0 8.0 temperature °c 20 35 membrane was made of chlorinated polyethylene with maximum (nominal) pore size of 0.4 μm (average: 0.2 μm) which blocks most microorganisms in the activated sludge. the submerged membrane panel was aerated by a coarse bubble system underneath each unit, which was necessary to prevent rapid membrane fouling and microbial degradation of the pollutants. the flat plate configuration kept enough space between the membranes so that the debris accumulation was minimum. in-situ chemical cleaning was the only maintenance typically required for such system. the chemical cleaning was done using the standard protocol supplied by the manufacturer (sánchez, 3013). sampling procedure the sampling procedure consisted of sampling locations, sample types, sample equipment and sample collection. influent rs, biological aeration tank and treated effluent locations were selected as the sampling points. to ensure good mixing and minimization of settled solid samples were collected near the center of the flow channel at approximately 40 to 60% of the water depth, where the turbulence was at a maximum level. however, the most desirable locations were not accessible all the time. sample collection was carried out from january to march 2014 and the reported values demonstrated the average values of different experiments (n = 24) with their standard deviations. design characteristics plant design condition for rs: wastewater arrives at the al-ansab stp from the sewage pumping stations and by tanker trucks, which are mainly from domestic sources (residential, commercial, and institutional). the combined influent wastewater was analyzed in accordance with the standard methods for the examination of water and wastewater. table 1 shows the characteristics of the rs. detailed discussion in this regard has been provided elsewhere (baawain et al., 2014). analytical methods a set of analytical methods was implemented to understand the performance of the cas and the mbr process. total suspended solids (tss) and volatile suspended solids (vss) were determined by applying the standard method (method 2540) and the gravimetric method was carried out using a glass-fiber filter. the measurement and analysis of nitrogen are important because it is the building block in the synthesis of organic matters. total nitrogen (tn) was calculated from the major form of nitrogen as comprised of organic nitrogen, ammonia, nitrite and nitrate. the following equation shows the determination of tn from its elements (sawyer et al., 1994). tn = organic n + nh3-n + no2-n + no3-n (eq. 1) 30 squ journal of agricultural and marine sciences, 2021, volume 26, issue 1 biological efficiency and control of a membrane bioreactor and conventional activated sludge process for treating municipal wastewater the organic nitrogen and total kjeldahl nitrogen (tkn) were determined analytically according to the standard method for examination of water and wastewater (method 4500-n) (eaton, 1995). tkn is the total amount of organic and ammonia nitrogen. depending on the ph of wastewater, ammonia nitrogen exists in aqueous solution as either the ammonium ion (nh4 +) (dominant at ph<7) or ammonia gas (nh3). nitrate and nitrite were measured by using ion chromatography method. total phosphorus was determined in the wastewater matrix using hach/lange test cuvettes. the intensity of the blue color was measured using a spectrophotometer. the procedure is suitable for the concentration of 0.05 to 20 mg l-1 of po4 3--p. the respirometric method covers the determination of biochemical oxygen demand (bod) of water and wastewater within a 5-day incubation period (bod5). the test analysis was based on the standard methods for the examination of water and wastewater (method 5210) (eaton, 1995). besides, the cod was determined by the spectrophotometric method (method 5220). the oil and grease were identified by infrared spectroscopy according to the standard method 5520. determination of fecal coliform (fc) in water and wastewater was carried out by using multiple tube fermentation (method 9221) as explained by eaton (1995). helminths ova (ho) were measured by the standard provided here (astm, 2004). results and discussion the performance analysis of cas and mbr systems was achieved by investigating different biochemical parameters in influents and effluents of the two systems. the results were compared with the meca standards (a and b), which indicated the national requirements of the final effluent for irrigation applications or sea-disposal. rs characteristics in order to quantify the performance in cas and mbr systems, the characteristics of rs has in terms of physicochemical and biological parameters of wastewater. figure 2 showed the average concentration of rs parameters during the study period. the rs influent showed the physicochemical parameters with low or even trace concentration of fog, nitrogen, phosphorus, and ho compared to the other biological parameters. as shown in figure 2, the differences between the other sewage parameters (bod, cod, tss, and vss) were significant. this was due to the fact that the mbr was fed by a large quantity of diluted municipal wastewater through domestic sewer network; while, the cas system was fed with concentrated wastewater from household septic tanks, commercial and light industries through tankers. the average values of bod5 and cod are presented in figure 2. according to metcalf and eddy (2004), the average values of bod5 in rs were categorized as high strength for cas (491.81 mg l-1); whereas, it was classified as a medium-strength concentration (229.44 mg l-1) for mbr. simultaneously, the average values of cod for the cas and mbr were 808.42 mg l-1 and 607.82 mg l-1, respectively. this might be related to the introduction of some industrial organic pollutants that were received by tankers at cas. the higher concentrations of degradable cod required a large-volume aeration basin, more oxygen transfer facilities and greater sludge production. in order to save cost and time, it was also useful to know the relation between bod5 and cod in each sampling location. the rs bod5/cod ratios for cas and mbr were measured as 0.61 and 0.38, respectively. these ratios were within the typical range of 0.30 to 0.80 for rs as reported by metcalf and eddy (2004). moreover, the values indicated that the rs was mainly composed of domestic wastewater without any toxic elements. the absence of toxic elements in rs was favourfigure 1. areal map of al-ansab stp showing the location of the treatment units and facilities. 31research paper al-wahaibi, al-mamun, baawain, sana able to decompose the organic matters easily. besides, in the cas system, bod concentration in the aeration tank rose slightly by 260 mg l-1 compared to those of the mbr. such increment of bod in the aeration tank of cas system was within the limiting value of stp’s design criteria, where the moderately concentrate microbial community (mix liquor suspended solid, mlss) could oxidize the organics load in a longer retention time. solids in stps were analyzed by using gravimetric method. as shown in figure 2, the average tss was about 442.21 mg l-1 and 137.76 mg l-1 for cas and mbr, respectively. based on metcalf and eddy (2004), rs influent of the cas and mbr plant could be classified as high strength and medium strength, respectively. such an amount of tss could be attributed to the high load of solids received by the tankers. the average vss concentrations in the rs were 214.61 and 55.06 mg l-1 for cas and mbr plant, respectively. from the obtained values of tss and vss, the vss/tss ratios in influent were 0.49 and 0.40 for cas and mbr plants, respectively. the rests were fixed inorganic suspended solids that remained even after ignition at 550 °c. tn and tp data could be used to evaluate the treatability of wastewater by biological processes. the results in figure 2 showed that the major parts of the tn compounds were ammoniacal and only small parts were nitrate. it was worth to mention that the ammoniacal nitrogen (nh3-n) served as substrates of the nitrifying microbes. the cas plant received a denser concentration of nutrients (n and p) than that of the mbr, which was classified as a high strength influence according to metcalf and eddy (2004). the tp fed to the cas system was approximately double the concentration that fed to the mbr. this might be due to the partial mixing of septic tank sewage with the light industrial wastewater in the case of cas. the higher concentration of tp was due to the mixing of industrial wastewater as it contained a higher concentration of phosphorus. overall, the tp concentration in the mbr influent was reasonably low. removal performance similar to influent, the physicochemical and biological parameters of the treated effluent from two systems, cas and mbr, were measured and analyzed. the analytical results of the treated effluent parameters are shown in figure 3. in order to check the suitability of the treated wastewater for irrigation purposes or discharge to the sea, the compliance of treated water was identified by comparing it with the meca standards. figure 3 illustrates that the bod5 quality of the treated effluent for cas and mbr were within the acceptable range defined by meca standards (7.38 mg l-1 and 3.28 mg l-1, respectively). for cod, the treated effluents were in compliance with the meca standards with the values of 36.78 mg l-1 and 15.14 mg l-1, respectively; where the meca standards were defined as 150 mg l-1 and 200 mg l-1 for the upper and lower limits. in addition, no standard had been reported for vss by meca. the tss and vss values for the cas process were obtained after a sand filter and before chlorination, while in the mbr process, the samples were taken after filtration. in practice, the high percentage of tss from the cas process could be due to improper mechanical screening. moreover, negligible primary sedimentation tank had been installed in both stps that allowed the heavy solids to settle down. the concentration level of fog was almost negligible from both systems. the effluent concentrations of nitrogen and tp were found in a reasonable range, except for tkn and nh3-n. the concentration level of tkn at old stp was about 24.11 mg l-1, which was above the limit of meca standards (5 and 10 mg l-1, respectively). the concentration of tkn, nh3-n, and no3-n of the mbr were within the standard limits, where the measured values were 0.86, 0.26, and 5.96 mg l-1, accordingly. furthermore, the concentration limits of tn for both processes were obtained satisfactorily. figure 2. raw sewage characteristics of the cas and mbr processes. 32 squ journal of agricultural and marine sciences, 2021, volume 26, issue 1 biological efficiency and control of a membrane bioreactor and conventional activated sludge process for treating municipal wastewater the concentration of nh3-n slightly exceeded from the standard value, which was the same as tkn. this could be due to an insufficient amount of dissolved oxygen supplied by very old aerators as well as a lack of adequate air diffusers installed at the bottom of the tank. removal efficiency the physicochemical and biological parameters as discussed in influent and effluent, the removal performances (in removal percentages) of the similar parameters from the two systems are shown in figure 4. organics in terms of bod5 and cod were removed by more than 95% in the mbr as well as the cas treatment system. particles in the form of tss were removed up to 98% in the mbr and 97% in the cas system. regarding the vss, the mbr performed slightly better as up to 96.8% removal compared to 94.7% in the cas system. fogs were removed by greater than 99% in both the systems. regarding the nitrogen and ho removal, the mbr showed a better performance compared to that of the cas. the mbr was able to remove up to 99% of nh3-n and approximately 83% of the tn, whereas the cas was only able to remove approximately 55% of tn. besides, tkn and nh3-n removal in the case of mbr was greater than 98%, while such values for the cas system were 61% and 80%, respectively. the results of the nitrogen and ammonia removal from the mbr system were similar to the reported studies for municipal wastewater (côté et al., 1997; mohammed et al., 2008), where gonzález et al. (2007) found similar results in a poorly performing cas system in terms of ammonia removal. the remaining nitrogen (organic nitrogen) had a complex structure that made it difficult to degrade. the unacceptable removal efficiency of nitrogen in cas had a negative impact on the system performance by growing algae inside the facilities. hence, the mbr system showed a better performance, which could be due to the fact that the old aeration equipment in the cas system supplied oxygen to nitrifying microbes and this did not meet the demand to achieve full nitrification. however, figure 3. effluent characteristics of the cas and mbr processes. figure 4. treatment efficiency of the cas and mbr processes in percentage (%). 33research paper al-wahaibi, al-mamun, baawain, sana in the mbr system nitrates were formed probably due to incomplete denitrification, which effectively increased the concentration of nitrate. an additional denitrification step would be necessary for complete nitrate removal. in the cas system less nitrogenous compounds, e.g., ammonia and organic nitrogen, were removed and therefore less nitrates were formed because of relatively poor aeration equipment. cas system still showed a better performance in the case of tp removal compared to that of mbr. the tp was removed by 88% in cas, while 54% in mbr. mbr system showed almost 99.97% removal of ho. this higher removal efficiency of ho in mbr was due to the physical separation of particulate matters by membrane barriers, while the cas removed only 91±5% of ho through the sedimentation of other biomasses. pore sizes of the mbr system were small enough to separate solids and microbes from the bulk volume of settling water by almost 100%. the presence of ho in the effluent of cas could be due to incomplete sedimentation of it in the sand filter. however, the removal performance of biological pollutants using the mbr technology was more reliable than that of membrane filtration, because it removed particles more reliably than a settling basin (de luca et al., 2013). however, both the values were satisfied by meca standards. in both cases, the effluent concentration of ho was below the limits set by the national standards, deeming the treated effluent suitable for irrigation applications. the removal performance of fcs was exceptional in both systems (>99%). this fact was attributed to the smaller pore size of membrane sheets that did not allow the bacteria (greater than 0.04 µm) to permeate. on the other hand, the discharged fcs of cas was very small compared to that of the inlet coliform in rs. the resultants bacteria before disinfection by sodium hypochlorite and before discharging to the network were decreased to less than 1000 mpn/100 ml and 200 mpn/100 ml as per standard b and a of meca. thus, additional disinfection was required for the reduction of pathogens and ho in the cas process. removal amount figure 5 shows the removal amount instead of removal efficiency. with the current load, cas showed a higher amount of removal in the case of bod, cod, tss, vss and even fog. in the case of nitrogen, although the removal amounts were similar, the removal efficiency (figure 4) was different. this was because of this fact that the influent concentration of nitrogen in the case of cas was higher than that of mbr. in other words, the cas system was responsible for treating concentrated wastewater from household septic tanks, commercial and light industries, which was more concentrated than the diluted municipal wastewater through the domestic sewer network to the mbr. the results in figure 5 suggested that the cas system presented superior performance to the mbr in almost all of the investigated criteria, except for nitrogen removal as in this case the cas system underperformed due to the unsuitable aeration equipment. in order to achieve full comparability of the two treatment process plants, further investigation is necessary to examine if the mbr performs equally under the same conditions as of the cas. conclusion this study investigated the biological and physical removal performances of two existing municipal wastewater treatment systems as cas and mbr in muscat, sultanate of oman. diluted sewage from the municipal network was being treated in mbr, whereas the concentrated wastewater from household septic tanks and light industries was being treated in cas. on average, both the systems performed more than 95% removal of bod, cod, tss, vss, and fog up to the national stanfigure 5. treatment efficiency of the cas and mbr processes in amount (mg∙l-1) 34 squ journal of agricultural and marine sciences, 2021, volume 26, issue 1 biological efficiency and control of a membrane bioreactor and conventional activated sludge process for treating municipal wastewater dards of the country. this leads to the conclusion that both systems showed stable and robust performance (removal percentage) with varying influent qualities. specifically, the removal of nitrogenous compounds by mbr was quite superior (34% higher) to that by the cas system. while the amount of phosphorus removal by cas was quite higher than that of mbr due to extended aeration in cas. for ho and pathogenic microbes, the mbr system was to be preferred due to its almost complete solid retention by the membrane, which eliminated the necessity of subsequent disinfection process as compared to cas. however, the removal amounts (mg l-1) for all the biological parameters by cas were quite higher than that by the mbr indicated that the cas system possessed the handling capabilities of concentrated sewage. therefore, further investigation is needed to ensure whether the mbr is flexible enough to achieve similar removal capabilities as the cas has for concentrated sewage under similar operating conditions. acknowledgement the authors wish to extend their appreciation to the research council (trc) and sultan qaboos university (squ), muscat, oman, for the financial 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(2010). performance of a full-scale membrane bioreactor system in treating municipal wastewater for reuse purposes. bioresource technology 101(10): 3768-3771. research paper journal of agricultural and marine sciences 2020, 25(1): 27–38 doi: 10.24200/jams.vol25iss1pp27-38 reveived 05 nov 2019 accepted 31 dec 2019 consumers’ preference and behaviour pattern towards fresh and smoked catfish in ilorin metropolis, nigeria w. a. jimoh*, a. a. ayeloja, e. t. agboola, a. abdullahi *w. a. jimoh ( ) department of aquaculture and fisheries, university of ilorin, pmb 1515, ilorin, kwara state, nigeria. email: jimoh.wa@unilorin.edu.ng introduction t he fisheries sector plays significant role in the economic development of many countries as it contributes to employment generation, income augmentation, addressing food and nutritional security concerns and foreign earnings (sabater et al., 2008). nigerians, on realization that there existed a wide gap between demand and supply of animal protein in the 1990s, invested heavily in fish production (jimoh et al., 2013). today nigeria is a leading catfish producer in the sub saharan africa. catfish production in nigeria represents more than half of the total production volume with an estimation of 13.3 kg annual per capita fish consumption in 2013 (fao, 2017). in order to avoid wastage and economic loss, fresh catfish is hot smoked to keep its quality at a high level (ayeloja et al., 2017). with increasing demand for fish as per capital income, and high prices of alternative sources of animal protein, there has been a shift to the consumption of fish. these are mostly in fresh and smoked forms. due to the increase in aquaculture production and nigeria’s population, there is a need to study the consumers’ preference and consumption pattern so that investors can determine the product that are preferred; thereby witnessing sustained fish demand. in general, consumers’ buying of any product largely depends upon their perception about the product (kazmi, 2012). hansen (2006) stated that consumer preferences for products differ depending on the nature of a product as well as the social and economic status of the consumer. consumers purchasing decisions are determined by cultural, social, personal and psychological factors (lautiainen, 2015). solomon (2010) opined that a consumer’s occupation, income level and purchasing power influences their purchasing decisions and buying behavior. research into consumers’ preference and behavior is necessary for the development of the consumers’ products to secure sustained consumer demand and to maximize profit (costa and jongen, 2006). various strategies are used in collecting information on consumers’ behavior and preference on a product in order to witness sustained consumer demands of the products تفضيل املستهلكني وسلوكهم تجاه سمك السلور والسمك املدخن كام هو موضح يف دراسة إليورين ، نيجرييا جيمو أ ، ايلوجا أ ، أجبووال ت ، عبدالله أ abstract. consumers’ preference study allows industries to tailor the supply towards the preference of consumers so that market could be optimized for their turn-over and profits. this study investigated consumers’ preference of fresh and smoked catfish in ilorin metropolis. a total of 225 questionnaires were administered adopting multi-stage techniques to elicit information from the respondents. the obtained data were subjected to descriptive and inferential statistics. the results showed that majority of the respondents in this study preferred smoked catfish irrespective of their socio-economic profile. the majority of the respondents agreed with the factors used in this study for the preference of fish (i.e. types) and their frequency of eating as their preferred fish. this study showed that only tribe of the respondents showed significant effect (p<0.05) on the respondents’ preferences for whole or chunk fish; and family size, age and religion had significant effect on the frequency of their preferred fish. keywords: catfish, preference; principal component analysis; consumption behavior; scree plot. امللخــص: إن دراســة مــا يفضلــه املســتهلكني، تســمح للقطــاع الصناعــي بإمــداد الســوق باملنتجــات التــي يفضلونهــا حيــث أن ذلــك يســاعد عــى تحســن الســوق و زيــادة األربــاح. ولذلــك تــم إجــراء هــذه الدراســة ملعرفــة مــا يفضلــه املســتهلكني مــن ســمك الســلور ســواء الطــازج واملدخــن يف مدينــة إليوريــن. حيــث تــم توزيــع 225 اســتبيان إلســتخالص املعلومــات مــن عينــة الدراســة. وقــد خضعــت البيانــات التــي تــم الحصــول عليهــا اىل إحصــاءات وصفيــة واســتنتاجية. حيــث أظهــرت النتائــج أن غالبيــة املشــاركني يف هــذه الدراســة يفضلــون ســمك الســلور املدخــن بغــض النظــر عــن وضعهــم االجتامعــي و االقتصــادي. كذلــك وافــق غالبيــة املشــاركني عــى أن العوامــل التــي تــم دراســتها هــي املســؤولة عــن تفضيلهــم لنــوع معــني مــن االســامك وتكــرار اســتهالك تلــك االســامك. باالضافــة اىل ذلــك أظهــرت هــذه الدراســة أن القبيلــة فقــط لهــا تأثــري كبــري )p<0.05( عــى تفضيــل األســامك كاملــة أو كقطــع كبــرية ؛ وكان لحجــم األرسة والعمــر والديــن تأثــري كبــري عــى تكــرار اســتهالك تلــك األســامك املفضلــة لديهــم. الكلامت املفتاحية: سمك السلور ، التفضيل ، تحليل املكون الرئييس ، سلوك املستهلكني ، التمثيل البياين. 30 squ journal of agricultural and marine sciences, 2020, volume 25, issue 1 consumers’ preference and behaviour pattern towards fresh and smoked catfish as studied in ilorin metropolis, nigeria (nijssen and lieshout, 1995). information that affects consumers’ preference and behavior for a particular product, such as demographic, sociocultural, socioeconomic information, are collected by the food industry to maintain their products competitive in the markets or to develop products that could satisfy the preference of the consumers (stewart-knox and mitchell, 2003). socio-cultural factors which include ethnic composition, education, and lifestyles have been reported to influence consumers’ preference and buying pattern (meulenberg and viaene, 2005). religious composition also plays influential role in consumers’ preference (solomon, 2010). household size, age and gender distribution was also reported to have influence on the demand for a particular product (hoek et al., 2004). the evaluation of consumers’ preference for fresh and smoked-dried fish products can be used to prepare production planning and distribution of fish across the country (adeniyi et al., 2012). figure 1. socio-economic profile and their preference for part of chunk preferred (legends are shown in figure 2) 31research paper jimoh, ayeloja, agboola, abdullahi it gave a better understanding of the relationship that existed with the actual consumption or purchase (honkanen et al., 2004; olsen, 2004). the most closely studied relations in consumer economics is the association between personal preferences, consumption and demand curve (myrland et al., 2000). preference is considered to be the major factor influencing general food consumption behavior (myrland et al., 2000). fish consumption is mostly affected by tradition, and habit; it can be enhanced by nutritional awareness (pieniak et al., 2008). although many researchers have studied consumers’ preferences for fresh and smoke-dried catfish products (jimoh et al., 2013; sabater et al., 2008), there is a paucity of information on consumer’s acceptability of fresh and smoked-dried catfish, thus this research was planned. this study therefore examined consumers’ preference and behavior for fresh and smoked catfish sold within ilorin, nigeria. materials and methods this study area was ilorin the capital of kwara state. it is located on latitude 8˚30’n and longitude 4˚35’e, in north western nigeria. ilorin city has a population of 847,582 and it is a confluence of cultures, populated by yoruba, fulani and other tribes. its town has about three local government areas including ilorin east, ilorin west and ilorin south. the population comprises different fish mongers and consumers within ilorin. primary data were collected with the use of scheduled interview using structured questionnaire. primary data for this study were collected using multistage sampling techniques. the first stage involved the selection of three (3) wards under each of the three local government areas selected using simple random technique, which gave a total of nine (9) wards. the second stage involved selection of five (5) communities under each ward using simple random technique, which gave a total of forty-five (45) communities. the third stage involved the selection of 5 respondents comprising of 2 fish mongers and 3 fish consumers from each community selected using simple random techniques, which resulted in a total of 225 respondents. however, the response rate was 88.9%, which resulted 200 respondents as the sample size. the reliability of items in the questionnaire was measured using cronbach’s alpha method of examining reliability. the cronbach alpha offered a measure of the infigure 2. socio-economic profile and their preference for part of chunk preferred 32 squ journal of agricultural and marine sciences, 2020, volume 25, issue 1 consumers’ preference and behaviour pattern towards fresh and smoked catfish as studied in ilorin metropolis, nigeria ternal consistency of a scale or test, expressed as number between 0 (completely unreliable test) and 1 (completely reliable test). an alpha score above 0.75 is generally taken to indicate a scale of high reliability, 0.5 to 0.75 is generally accepted as indicating a moderately reliable scale, while a figure below this generally indicates a scale of low reliability. data analysis the reliability of items in the questionnaire was measured using cronbach’s alpha method of examining reliability. scale statistics was done using a measure of central tendencies. the data collected were processed using both descriptive and inferential statistics. the descriptive analysis was mainly in terms of percentage and frequency of distribution to show the socio-economic profile of the respondents and factors that guide the respondents in their preference of fish in the study area. bar charts were used to depict the socio-economic profile of the respondents and their preference for certain parts of fish or the other. inferential statistics (chi-square statistics) were used to test the significance of the effect of some socio-economic profile of the respondents on their preference for the type or part of fish or the frequency of eating their preferred fish. principal component analysis (pca) was used to select variable of importance in the factors that guide the preference for certain types or part of fish and their frequency of eating (i.e. their preferred fish) using eigenvalue. the percentage of variance as indices after the data was subjected to kaiser-meyer-olkin (kmo) measure as the sampling adequacy and bartlett’s test of sphericity. all the analysis were conducted using spss version 17 (spss, 2008). results reliability analysis of the questionnaire the reliability value of items in the questionnaire was 0.645, indicating a moderate reliability (table 1). table 1. reliability analysis of the questionnaire reliability statistics cronbach's alpha 0.688 cronbach's alpha based on standardized items 0.645 number of items 29 scale statistics mean 77.54 variance 99.250 std. deviation 9.962 number of items 29 socio-economic profile of the respondents personal information of the respondents using frequency counts and percentage are shown in table 2. respondent were almost equally distributed across genders with 50.5% of the respondents being male and 49.5% of the respondents being female; 43.5% fell within the age group 31-40 years as compared to 8% of the respondents fell within the age group of 50 years and above. the majority of the respondents practice christianity and islam (46%) as compared to 8% are traditional worshippers. the majority of the respondents (43%) were married while 5% were widow/widower. the majority of the respondents: 60.5% were yoruba tribe, while hausas had the lowest percentage (10%). most of the respondents had formal education and only 11.5% of the respondents were not educated. respondents (37 %) were civil servants, 33% were traders and 30% of the respondents were artisans. spending capacity of the responds were: 41% spent below ₦15,000, 33.5% spent ₦15,000 ₦30,000 while 8% of the respondents spent above ₦45,000 on fish every month. based on house hold size, this study showed that majority of the respondents 43.5% fell within the house hold size of 5-8 people, while 15% were 9-12 people, respectively. figure 3. scree plot showing the eigen value of the studied variables 33research paper jimoh, ayeloja, agboola, abdullahi socio-economic profile of the respondents and their preference for fresh or smoked fish table 3 shows the cross tabulation (chi-square test of independence) of the demographic factors of the respondent against their preference for fresh or smoked fish. the socio-economic profile did not show significant effect (p>0.10) on the preference of respondents for fresh or smoked fish except religion. socio-economic profile of the respondents and their preference for whole or chunk fish table 4 shows the cross tabulation (chi-square test of independence) of the demographic factors of the respondent against their preferred type of fish, either whole or table 2. socio economic profiles of the respondents variables parameters frequency percent sex male 101 50.5 female 99 49.5 age range less than 30 57 28.5 31.40 87 43.5 41-50 40 20 above 50 16 8 religion christianity 92 46 islam 92 46 traditional 16 8 marital status single 52 26 engaged 52 26 married 86 43 widow/widower 10 5 tribes hausa 20 10 igbo 21 15.5 yoruba 121 60.5 other tribes 28 14 educational attainment no formal education 23 11.5 primary school 30 15 secondary school 47 23.5 university 100 50 occupation civil servant 74 37 artisanal 60 30 trader 66 33 monthly expenditure below n15,000 82 41 15,000-30,000 67 33.5 30,000-45,000 35 17.5 above 45,000 16 8 family size below 4 66 33 5-8 87 43.5 9-12 30 15 above 13 17 8.5 chunk of fish. the table shows that only tribe of the respondents had significant effect (p<0.05) on the respondents’ preference for whole or chunk fish, while other socio-economic profile had no significant effect (p>0.05) on the respondents’ preference for whole or trunk fish. socio-economic profile and their preference for part of chunk preferred the bar chart in the figures 1 and 2 show that majority of the respondents with the family size regardless of sex, occupation or tribe of respondents preferred to eat the trunk part of fish. also, respondents aged 50 or less prefer eating trunk fish although those above 50 years of age prefer to eat tail of fish. the bar chart also shows that the majority of the respondents practice islam and 34 squ journal of agricultural and marine sciences, 2020, volume 25, issue 1 consumers’ preference and behaviour pattern towards fresh and smoked catfish as studied in ilorin metropolis, nigeria table 3. socio economic profiles of the respondents socio-economic factors types of preferred fish total χ2-value significance fresh smoked family size < 4 27 39 66 0.137 ns 5-8 39 48 87 9-12 11 18 29 >12 12 05 17 total 89 110 199 sex male 47 53 100 0.306 ns female 42 57 99 total 89 110 199 age (years) <30 29 27 56 0.512 ns 31-40 35 52 87 41-50 19 21 40 >50 06 10 16 total 89 110 199 religion christianity 46 46 92 0.093 * islam 40 51 91 traditional 03 12 15 total 89 110 199 tribe hausa 07 12 19 0.143 ns igbo 10 21 31 yoruba 62 59 121 others 10 18 28 total 89 110 199 marital status single 23 28 51 89 110 engaged 20 31 51 married 21 45 86 widow/widower 05 06 11 total 89 110 199 educational attainment nfe 12 11 23 0.183 ns primary 09 21 30 secondary 18 28 46 tertiary 50 50 100 total 89 110 199 occupation civil servant 36 38 74 0.675 ns artisans 23 37 60 trader 30 35 65 total 89 110 199 financial status <15,000 42 40 82 0.229 ns 16,000-30,000 25 41 66 31,000-40,000 13 22 35 >45,000 09 07 16 total 89 110 199 ns: not significant (p<0.1) nfe: no formal education *: significant 35research paper jimoh, ayeloja, agboola, abdullahi table 4. socio-economic profile of the respondents and their preference for whole or chunk fish. socio-economic factors types of preferred fish total χ2-value significance fresh smoked family size < 4 35 31 66 0.678 ns 5-8 48 39 87 9-12 14 16 30 >12 7 10 17 total 104 96 200 sex male 55 46 101 0.288 ns female 49 50 99 total 104 96 200 age (years) <30 29 28 57 0.630 ns 31-40 48 39 87 41-50 21 19 40 >50 06 10 16 total 104 96 200 religion christianity 49 43 92 0.309 ns islam 50 42 92 traditional 05 10 15 total 104 95 199 tribe hausa 09 11 20 0.011 * igbo 10 21 31 yoruba 74 47 121 others 11 17 28 total 104 96 200 marital status single 30 21 51 4.06 ns engaged 27 25 52 married 44 42 86 widow/widower 03 07 10 total 104 95 199 educational attainment nfe 08 15 23 0.105 ns primary 14 16 30 secondary 22 25 47 tertiary 60 40 100 total 104 96 200 occupation civil servant 39 35 74 0.746 ns artisans 32 28 60 trader 33 33 66 total 104 96 200 financial status <15,000 41 41 82 0932 ns 16,000-30,000 37 30 67 31,000-40,000 18 17 35 >45,000 08 08 16 total 104 96 200 *: significant (p <0.05) ns: not significant 36 squ journal of agricultural and marine sciences, 2020, volume 25, issue 1 consumers’ preference and behaviour pattern towards fresh and smoked catfish as studied in ilorin metropolis, nigeria table 5. socio-economic profile and frequency of eating their preferred fish socio-economic factors frequency of eating preferred fish total χ2-value significance daily weekly monthly festive period family size < 4 28 25 10 03 66 0.000 * 5-8 27 40 17 03 87 9-12 10 03 13 04 30 >12 04 03 06 04 17 total 69 71 46 14 200 sex male 35 34 24 8 101 0.920 ns female 34 37 22 6 99 total 69 71 46 14 200 age (years) <30 23 21 10 03 57 0.014 * 31-40 32 34 20 01 87 41-50 11 12 11 06 40 >50 03 04 05 04 16 total 69 71 46 14 200 religion christianity 41 32 13 06 92 0.007 * islam 27 35 24 06 92 traditional 01 04 08 02 15 total 69 71 45 14 199 tribe hausa 04 06 10 0 20 0.000 * igbo 10 12 08 1 31 yoruba 49 47 19 6 121 others 06 06 09 7 28 total 69 71 46 14 200 marital status single 21 18 09 03 51 0.069 ns engaged 15 27 08 02 52 married 29 25 25 07 86 widow/widower 03 01 04 02 10 total 68 71 46 14 199 educational attainment nfe 07 05 07 04 23 0.190 ns primary 11 09 10 0 30 secondary 13 19 12 03 47 tertiary 38 38 17 07 100 total 69 71 46 14 200 occupation civil servant 30 20 18 06 74 0.608 ns artisans 18 26 14 03 61 trader 21 25 14 05 65 total 69 71 46 14 200 financial status <15,000 27 31 18 06 82 0.430 ns 16,000-30,000 24 27 13 03 67 31,000-40,000 11 11 11 02 35 >45,000 07 02 04 03 16 total 69 71 46 14 200 *: significant (p<0.05) ns: not significant 37research paper jimoh, ayeloja, agboola, abdullahi christianity, and they preferred eating the trunk part of fish. the traditionalists preferred the tail of fish except those who have no formal education whose majority prefer eating the tail of fish, the majority of educated respondents irrespective of their educational attainment preferred eating trunk of fish. the majority of the other socio-economic factors under this study preferred eating trunk of fish. socio-economic profile and frequency of eating fish table 5 shows the cross tabulation (chi-square test of independents) of the social-economic profile of the respondents against the frequency of their preferred fish. it shows that family size, age and religion had significant effect on the frequency of eating fish. factors guiding preference for fish consumption table 6 shows the factors guiding preference for fish consumption. the mean score on the 5-point likert scale for all the variables under consideration were above 2.5, which is the average of the 5-point likert scale. majority of the respondents agreed with the studied variables as factors responsible for their preference of certain type or part of fish and their frequency of eating fish. the confidence interval estimated for all the studied variables were all very highly significant (p<0.0001). factor analysis table 7 shows the results of kaiser-meyer-olkin (kmo) measure of sampling adequacy and bartlett’s test of sphericity as conducted prior to pca. the kmo test was 0.708 with bartlett’s test of sphericity being significant (p<0.05). the kaiser-meyer-olkin measure of sampling adequacy (kmo) was calculated using correlations and partial correlations to test whether the variables in our sample are adequate to correlate, it was calculated to identify whether variables were so highly correlated and cannot be distinguished between them (multicollinearity). a general rule of thumb is that a kmo value should be greater than 0.5 for a satisfactory factor. the higher the value is considered better. the kmo value in this study was 0.708, showing the data can be used for pca. the results of the bartlett’s test of sphericity shows table 7. kmo and bartlett’s test kaiser-meyer-olkin (kmo) measure of sampling adequacy 0.708 bartlett’s test of sphericity approx. chi-square 1034 df 120 significant 0.000 table 6. factors guiding preference for fish variables sd d u a sa mean sd cie 1. fish is highly nutritive 22(11%) 16(8%) 07(3.5%) 71(35.5%) 84(42%) 3.89 1.34 3.70-4.00*** 2. it is less costly 10(5%) 26(13.1%) 14(7%) 97(48.7%) 52(26.1%) 3.78 1.12 3.62-3.94*** 3. it is more delicious 11(5.5%) 14(7%) 21(10.5%) 106(53%) 48(24%) 3.83 1.05 3.68-3.98*** 4. it has sweet aroma 14(7%) 16(8%) 10(5.1%) 108(54.3%) 51(25.6%) 3.83 1.11 3.68-3.99*** 5. it is easy to cook 09(4.5%) 13(6.5%) 22(11%) 97(48.5%) 59(29.5%) 3.92 1.03 3.78-4,06*** 6. packaging 14(7%) 32(16%) 29(14.5%) 87(43.5%) 38(19%) 3.52 1.17 3.35-3.68*** 7. size of fish 09(4.5%) 27(13.6%) 36(18.1%) 82(41.2%) 45(22.6%) 3.64 1.11 3.48-3.79*** 8. does your age affect choice 18(9%) 53(26.5%) 44(22%) 62(31%) 23(11.5%) 3.10 1.18 2.93-3.26*** 9. does your health status influence your choice 18(9%) 62(31.2%) 35(17.6%) 59(29.6%) 25(12.6%) 3.64 1.22 2.99-3.23*** 10. physical features of fish 17(8.5%) 43(21.5%) 42(21%) 77(38.5%) 21(10.5%) 3.21 1.15 3.05-3.37*** 11. psycho-social issues 17(8.5%) 49(24.5%) 46(23%) 60(30%) 28(14%) 3.16 1.19 3.00-3.33*** 12. level of disposable income 12(6%) 49(24.5%) 46(23%) 60(30%) 28(14%) 3.58 1.12 3.42-3.74*** 13. fish size requirement 17(8.5%) 25(12.5%) 38(19%) 85(42.5%) 40(20%) 3.60 1.17 3.44-3.77*** 14. availability 17(8.5%) 19(9.5%) 20(10%) 110(55%) 34(17%) 3.62 1.13 3.47-3.78*** 15. family background 27(13.5%) 58(29%) 30(15%) 64(32%) 21(10.5%) 2.97 1.26 2.79-3.15*** 16. cultural background 39(19.5%) 46(23%) 34(17%) 49(24.5%) 32(16%) 2.94 1.38 2.75-3.14*** d: disagreed; sd: strongly disagreed; u: undecided; a: agreed; sa: strongly agreed sd: standard deviation ; cie: confidence interval estimate, *** significant difference 38 squ journal of agricultural and marine sciences, 2020, volume 25, issue 1 consumers’ preference and behaviour pattern towards fresh and smoked catfish as studied in ilorin metropolis, nigeria table 8. communalities showing percentage of the variability in variables that is explained by the extracted factors s/n variables initial extraction 1. fish is highly nutritive 1.000 0.638 2. it is less costly 1.000 0.683 3. it is more delicious 1.000 0.637 4. it has sweet aroma 1.000 0.534 5. it is easy to cook 1.000 0.407 6. packaging 1.000 0.617 7. size of fish 1.000 0.417 8. age 1.000 0.785 9. health 1.000 0.762 10. physical feature of fish 1.000 0.549 11. psycho-social issues 1.000 0.637 12. level of disposable incomes 1.000 0.472 13. fish size requirement 1.000 0.509 14. availability 1.000 0.520 15. family background 1.000 0.608 16. cultural background 1.000 0.619 whether there is a relationship between the variables. if no relationship is found then there is no point in proceeding with the factor analysis. a p-value less than 0.05 indicated that it was necessary to continue with the factor analysis. since the p-value obtained in this study was significant (p <0.001) it can be concluded that there were relationships between variables considered in this study, hence the data generated can be used for factor analysis. extraction method: principal component analysis table 8 explains the percentage of the variability in the variables that is explained by the extracted factors. the results showed greater than 50% of the variation in each variable were explained by extracted factors except for variable 5 and 12 that were below 50%. table 9 reveals that four components (or factors) have been produced with eigenvalues greater than 1 accounting for 58.71% of the variance in the data. if more than 5% variance is to be selected, then first 13 factors would be selected. the scree plot is presented in figure 3. discussion the cronbach’s alpha value obtained in this study depicted the items in the questionnaire to have moderate reliability as the total scores of the questionnaire. the respondents score was 77.54 (mean) with a variance of 99.25, and a standard deviation of 9.96. the small standard deviation indicated that variations in the scores of our respondents was small for the overall total score on the questionnaire, thus indicating moderate reliability of the questionnaire. chi-square test of independence was used to show whether significant difference existed between the socio-economic profile of the respondent and the factors guiding their choice of catfish type and part. this test showed that there was no significant difference between the socio-economic profile of the respondents and their preference for smoked or fresh catfish except religion. this study showed that only tribe played significant role in the association between the socio-economic profile of the respondent and their choice for whole or chunk fish. van trijp and steenkamp (2005) observed similar trend in their study of the influence of cultural factors on consumer buying behavior (i.e. a case study of pork). sethi and chawla (2014) also stated that tribal, social, cultural and psychological factors were some of the major factors that influenced the buying behavior of consumers. tribe, culture, subculture and social class had profound influences on people’s behavior because they were powerful drivers in the formation of attitudes, beliefs and values, this explained why certain consumption behavior was hard to change once developed (blythe, 2008a, b). socio–cultural factors have been reported to have impact on fish consumption preference (myrland et al., 2000). the result of this study also indicated that religion also had a significant effect on the type of catfish preferred and frequency of consumption of their preferred fish. religion was a major component of culture, it has strong influence on people’s lives and behavior (cwiertka, 2005; kumar et al., 2008; wandel et al., 2008). ijewere and odia (2012) and lawan and zanna (2013) opined that religion exerted the great influence on the thinking, perception and behavior of many people in the world. that was a key element of culture which influenced both behavior and purchasing decisions, it therefore influenced what to buy and in what form it should be bought. this study equally established that family size and age have significant association between socio-economic profile and the frequency of their consumption of preferred fish, while others had no significant association. can et al. (2015) also observed that age group had significant influence on fish consumption preference among people leaving in antakaya community in turkey. palash (2004) also observed that family size have significant influential role on consumption pattern and consumer behavior of fish in dhaka city. most of the respondents agreed with the variable listed as factor affecting consumers’ preference on fresh and smoked fish. kumar et al. (2008) reported that perceived quality of fish such as taste, health benefits, nutrition, price and availability are factors that could influence consumers’ preference. family size, age and religion had significant effect on the frequency of their preferred fish in this study. this was in consonance with the reports of meulenberg and viaene (2005) and costa and jongen (2006), as the size of families and households and demand for a food product. also, hoek et al. (2004) reported that demographic factors, such as household size and age could be used as indices of food preference and 39research paper jimoh, ayeloja, agboola, abdullahi demand. greater percentage of our respondents are educated and readily agreed that level of education constituted one of the factor guiding their preference of fresh or smoked fish. they were the nutrition-conscious consumers. this study showed that respondents who had low level of educational did not consume as much fish as the respondents who were educated. the increased education level lead to produce and consume healthy food as educated consumers are nutrition-conscious (brody and lord, 2007; kearney, 2010; senauer et al. 1991). conclusion fish consumption is influenced by many factors. these factors mainly determine the consumers’ preference for fish. the present study indicated most of the respondents’ preferred smoked catfish irrespective of their socio-economic profile. the majority of the respondents agreed with the studied variables (e. g. price, packaging, age) as the factors responsible for their preference of certain type or part of fish and their frequency of eating. this study showed that only tribe of the respondents had significant effect on the respondents’ preference for whole or chunk fish. the family size, age and religion had significant effect on the frequency of their preferred fish. it is recommended that the consumers should be educated more on nutritional value of fish because this study showed that respondents who had low level educational attainment do not consume as much fish as the educated ones. acknowledgement the authors appreciate prof abdulkadri olabode abdullah for editing of the manuscript prior to being sent for publication and also mr musa mustapha for translation of the manuscript title and abstract section into arabic language. references adeniyi or, omitoyin s, ojo o. 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(2015). fish consumption preferences and factors influencing it. food science and technology 35, 339-346. table 9. total variance explained initial eigenvalues extraction sums of squared loadings component total % of variance cumulative % total % of variance cumulative % 1. 4.186 26.162 26.162 4.186 26.162 26.162 2. 2.244 14.026 40.189 2.244 14.026 40.189 3. 1.708 10.673 50.861 1.708 10.673 50.861 4. 1.255 7.845 58.706 1.255 7.845 58.706 5. .998 6.236 64.942 6. .901 5.634 70.576 7. .852 5.325 75.901 8. .664 4.149 80.050 9. .598 3.739 83.789 10. .566 3.538 87.327 11. .476 2.973 90.300 12. .400 2.502 92.801 13. .349 2.180 94.981 14. .314 1.961 96.942 15. .287 1.792 98.734 16. .203 1.266 100.000 40 squ journal of agricultural and marine sciences, 2020, volume 25, issue 1 consumers’ preference and behaviour pattern towards fresh and smoked catfish as studied in ilorin metropolis, nigeria costa, a. i., jongen, w. 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(2010). consumer behaviour: a european perspective. pearson education, uk. spss, (2008). spss statistics for windows, version 17.0. chicago: spss inc. stewart-knox, b., mitchell, p. (2003). what separates the winners from the losers in new food product development? trends in food science & technology 14, 58-64. van trijp, j., steenkamp, j. (2005). consumer-oriented new product development: principles and practice. innovation in agri-food systems 87-124. wandel, m., råberg, m., kumar, b., holmboe-ottesen, g. (2008). changes in food habits after migration among south asians settled in oslo: the effect of demographic, socio-economic and integration factors. appetite 50, 376-385. research paper journal of agricultural and marine sciences 2021, 26(1): 47–52 doi: 10.24200/jams.vol26iss1pp47-52 reveived 21 april 2020 accepted 22 nov 2020 protective effect of oxalis corniculate and pteropyrum scoparium leaf extracts against azoxymethane-induced oxidative stress and colon carcinogenesis mostafa i. waly*, mohammed al-khusaibi, nejib guizani mostafa i. waly*( ) mostafa@squ.edu.om, department of food science and nutrition, college of agricultural and marine sciences, sultan qaboos university, muscat, oman introduction oman has around 1200 species of wild plants, many of which are reported to be used in tradi-tional medicine (divakar et al., 2016). however, less than 10% of these plants have been screened for their medicinal use (waly et al., 2014). among the important wild plants of oman are two edible plants (oxalis corniculate, commonly known as hamd, and pteropyrum scoparium, commonly known as sidaf) which have therapeutic properties based on their bioactive constituents (al attabi et al., 2015). oxalis corniculate is short-lived perennial plant growing only 5 – 10 cm tall but spreading at the roots to form a mat of growth 30 cm or wider, and it is harvested from the wild for food, medicine and various other commodities (divakar et al., 2016). pteropyrum scoparium has been used for generations as an additive to omani traditional dishes; it is considered as التأثري الوقائي ملستخلص أوراق النبااتت الربية العمانية ) السيداف و احلميضة( ضد اإلجهاد التأكسدي الناجم عن تسرطن القولون يف حيواانت التجارب مصطفى وايل*, حممد اخلصييب, جنيب قيزاين abstract. oxalis corniculate and pteropyrum scoparium are two edible wild omani plants with known preventive effects on various human diseases, yet their therapeutic role in colon cancer has not been studied yet. azoxymethane (aom) is a common oxidizing agent that induces colon cancer in experimental animal models. in the current study, the protective effect of oxalis corniculate and pteropyrum scoparium leaves extracts against aom-induced cancer and oxidative stress in rat colon was examined. sixty sprague-dawley rats were randomly divided into 6 groups (10 rats/group). control group was fed a standard diet; the aom-treated group was fed a standard diet and received an intraperitoneal injection of aom at a dose of 30 mg/kg body weight for each rat. the other four groups received an intra-gastric intubation of pteropyrum scoparium or oxalis corniculate leaves extracts (0.1 mg extract/1 ml water/ day) in the absence or presence of aom injection. after 8 weeks, all rats were sacrificed and the colon tissues were dissected for aberrant crypt foci (acf) enumeration of cancer lesions development, and for measurements of glutathione (gsh), total antioxidant capacity (tac), and dna oxidative damage. the results in this study showed that the aom-injected rats showed significant increased level of dna oxidative damage, lower levels of gsh and tac, and higher acf as compared to the control group. oxalis corniculate and pteropyrum scoparium leaf extracts significantly suppressed the oxidative damage associated with aom injection and mitigated its carcinogenic effect in rat colon. both oxalis corniculate and pteropyrum scoparium leaf extracts acted as potent antioxidants and combat the aom-associated oxidative stress and colon carcinogenesis. the data from this study suggest that dietary supplementation of these two wild plants might be applied as a therapeutic agent for colon cancer treatment. keywords: antioxidants, colon cancer, omani wild plants, oxidative stress املســتخلص:النبااتت العمانيــة )الســيداف pteropyrum scoparium( و )احلميضــة oxalis corniculate( هــي نبــااتت تنمــو يف الربيــة و صاحلــة لــأكل و أيضــاً هلمــا آاثر وقائيــة معروفــة ضــد العديــد مــن األمــراض املزمنــة ، ومــع ذلــك مل يتــم دراســة دورمهــا العالجــي يف ســرطان القولــون حــى اآلن. فمــن املعــروف أن العوامــل املؤكســدة تســبب مــرض ســرطان القولــون لذلــك يف الدراســة احلاليــة ، مت فحــص التأثــر الوقائــي ملســتخلصات أوراق النبــااتت العمانيــة ضــد الســرطان الناجــم عــن اإلجهــاد التأكســدي يف قولــون الفئــران كنمــوذج حليــواانت التجــارب. ولقــد اشــتملت التجربــة علــى ســتون فــأراً مــن ســاللة ســرباغ داويل ومقســمة إىل 6 جمموعــات )10 فئــران / جمموعــة( كاأليت: اجملموعــة الضابطــة و اجملموعــة املعاجلــة بســرطان القولــون )الــي تلقــت حقنــة مــن مركــب aom جبرعــة 30 جمــم / كجــم مــن وزن اجلســم لــكل فــأر( بينمــا تلقــت اجملموعــات األربــع األخــرى مســتخلصات أوراق نبــات الســيداف أو احلميضــة يف غيــاب أو وجــود مركــب aom . اســتمرت التجربــة ملــدة 8 أســابيع ، و بعــد هــذه املــدة مت التضحيــة جبميــع الفئــران ومت تشــريح أنســجة القولــون مــن أجــل رصــد تطــور األورام الســرطانية يف القولــون ، ومت ايضــاً قيــاس مركــب اجللواتثيــون )gsh( ، والقــدرة اإلمجاليــة ملضــادات األكســدة )tac( ، وكذلــك أضــرار أكســدة احلمــض النــووي يف مجيــع أنســجة القولــون جلميــع الفئــران. ولقــد أظهــرت نتائــج هــذه الدراســة أبن الفئران احملقونة بـ aom أظهرت زايدة ملحوظة يف مســتوى ضرر أكســدة احلمض النووي ، واخنفاض مســتوايت gsh و tac ، وارتفاع نســبة األورام الســرطانية ابلقولــون مقارنــة ابجملموعــة الضابطــة. بينمــا أظهــرت النبــااتت العمانيــة املســتخدمة أتثــر دفاعــي ضــد الضــرر التأكســدي املرتبــط حبقــن aom وخففــت أيضــاً مــن التأثــرات املســرطنة يف القولــون. ختامــاً فــإن كاًل مــن أوراق نبــات الســيداف و احلميضــة تعمــل كمضــادات أكســدة قويــة وتكافــح اإلجهــاد التأكســدي املرتبــط بـــسرطان القولــون. و تشــر البيــاانت الــواردة مــن هــذه الدراســة إىل أن هــذه النبــااتت الربيــة العمانيــة ميكــن اســتخدامها كمكمــل غذائــي عالجــي ملكافحــة مــرض ســرطان القولــون. الكلمات املفتاحية: مضادات األكسدة ، سرطان القولون ، النبااتت الربية العمانية ، اإلجهاد التأكسدي 48 squ journal of agricultural and marine sciences, 2021, volume 26, issue 1 protective effect of oxalis corniculate and pteropyrum scoparium leaf extracts against azoxymethane-induced oxidative stress and colon carcinogenesis an important herbal drug for treating various diseases, such as diabetes, fever, skin diseases and inflammation (divakar et al., 2016). colon cancer is the third most common type of cancer in terms of incidence and the fourth in cause of death world-wide (who, 2020). clinical studies continue to support the notion that oxidative stress is involved in the etiology of colon cancer (afshari et al., 2019). oxidative stress is a condition in which oxidants level is counterbalancing the antioxidant-dependent cellular defense mechanisms and contributes among other factors to the pathogenesis of cancer (monteiro et al., 2020). it has been suggested that higher intake of antioxidants is associated with a lower risk of oxidative stress-mediated colonic carcinogenesis (waly et al., 2014). azoxymethane (aom) induces cancer in the colon and rectum of animal models by causing oxidative damage to dna and its associated gene mutation and adductions (waly et al., 2015). glutathione (gsh) is the major intracellular antioxidant which scavenged oxidants, and accordingly an increase in its level is crucial to combat oxidative stress-mediated colon carcinogenesis (padmanabhan et al., 2019). total antioxidant capacity (tac) reflects the cellular redox status (enzymatic and non-enzymatic systems), and tac impairment activity was reported in animals’ models for colon cancer (waly et al., 2016). there are negligible published reports that identify the in vivo antioxidant potential properties of oxalis corniculate and pteropyrum scoparium in relation to colon cancer pathogenesis. therefore, this study was undertaken to evaluate these two omani plants for their phytochemical contents and antioxidant properties in an experimental model of colon cancer. methods chemicals aom (catalogue # a5486) and sodium chloride physiological solution (catalogue# 52455) were purchased from sigma-aldrich co. (st. louis, missouri, usa). plant collection and identification three kg of each plant (oxalis corniculate and pteropyrum scoparium) were collected from their natural habitat and immediately washed of dust and impurities using tap water. the plants were kept at room temperature under shade until they are completely dried, and the leaves of each plant were ground to fine powder by use of electric grinder (moulinex ar1043-uk0). the powdered samples were macerated in aqueous methanol, and the filtrates were then evaporated using rotary evaporator. the resulting crude extract (50 g dry solids) was stored at 40 ºc till use for subsequent experiments. phytochemical contents of plants leaves extracts folin-ciocalteu assay was used to determine the total phenol content (suresh et al., 2016). the total phenolic content of samples was expressed as mg gallic acid equivalents (mg gae/100 g sample). the total flavonoids content was determined using catechin as standard, and the results were expressed as mg catechin (mg of cae/100 g sample). (suresh et al., 2016). evaluation of the free radical scavenging capacity of plant leave extracts the capacity of each one of the two plants leaves extract to scavenge 1,1-diphenyl-2-picrylhydrazyl (dpph) free radical was performed by a spectrophotometric methodology. briefly, each plant leave extract at different concentrations (10 100 µg/ml), were mixed with stable dpph radical in methanolic solution (0.3 ml of dpph radical solution 0.5 mm in 3 ml ethanol). when dpph reacts with an antioxidant compound, which can donate hydrogen, it is reduced. the changes in color (from deep violet to light yellow) were read [absorbance (abs)] at 517 nm after 30 min of reaction using a uvvis spectrophotometer (du 800; beckman coulter, fullerton, ca, usa). controls contained all the reaction reagents except plant leaves extracts or 2,6-di-tert-butyl-4-hydroxytoluene (bht), the positive control. the free radical scavenging capacity of different samples were expressed as %dpph inhibition, a higher %free radical scavenging activity value indicates a higher antioxidant activity and it was calculated as follows: % dpph inhibition = [(absorbance of control–absorbance of sample)/ absorbance of control] x 100 animal and experimental design the protocol used in this study was conducted in accordance with international laws and policies and approved by the animal ethics committee at the sultan qaboos university (squ/aec/2019-2020/8). sixty male sprague dawley rats weighing 150 ± 5 gm were obtained from the animal breed at the animal house facility, sultan qaboos university, muscat, oman. the rats were housed in individual cages at standard conditions, and they were fed a standard diet and given water ad-libitum. the rats were randomly divided into 6 groups (n=10 rats/group). control group was fed a standard diet and also received a single intraperitoneal injection of 0.9% physiological saline in week one; aom-injected group was fed a standard diet and a single intra-peritoneal dose of aom (30 mg/kg body weight) dissolved in 0.9% physiological saline in week one. the other four groups were fed a standard diet and received intra-gastric intubation of 1 ml of either oxalis corniculate or pteropyrum scoparium leaves extracts (100 µg extract/ml sterile distilled water/day) in the presence or absence of aom injection. the therapeutic dose used effective doses for the 49research paper waly, al-khusaibi, guizani two plants leaf extracts were determined based on the results of dpph assay. the plant leaf extracts were given on daily basis at the same timing early morning, throughout the 8 weeks study period. body weight was recorded weekly for the entire duration of the experiment. animal sacrifice after 8 weeks, the rats were fasted overnight, anesthetized with a lethal dose of a cocktail containing ketamine (1 mg), xylazine (5 mg), and acepromazine (0.2 mg) and then sacrificed. the colon tissue of each rat was excised for histo-pathological examination of any cancer lesions development, and for biochemical measurements of oxidative stress indices. colon preparation the colons were carefully removed from rats and were kept on a glass plate in ice jackets. the colons were then opened longitudinally, rinsed with ice-cold physiological saline, and sectioned longitudinally into two equal halves. the first half was fixed flat in 10% buffered formalin (fisher scientific, fair lawn, nj) between two filter papers for one week before aberrant cypt foci (acf) enumeration. meanwhile, the other half was rinsed with ice-cold physiological saline and was immediately homogenized in 10 ml of 100 mm potassium phosphate buffer (ph 7.2) by a glass-teflon homogenizer with an ice-cold jacket and centrifuged at 6,000 g at 4°c for 60 minutes. the resulting supernatant was used for determination of protein, gsh and tac measurements. aberrant cypt foci (acf) enumeration fixed colons were stained with 0.2% methylene blue in kreb’s ringer bicarbonate buffer for 20 minutes in a petri dish and rinsed with physiological saline. after staining, the colons were placed with the mucosal surfaces up on a slide, to be examined with a light microscope under 40x magnification and scored for acf. in brief, the acf were distinguished from normal crypts by their darker stain, enlarged and slightly elongated size, thick epithelial lining, slightly elongated cryptal opening and often slit shaped. the total number of acf was recorded for all examined colons (waly et al., 2014). protein content analysis the protein content of colon tissues was assayed by the method of lowry et al. (1951) using bovine serum albumin as standard and protein content was expressed as mg/ml of sample. gsh measurements aliquots of supernatant (100 µl) were transferred to fresh eppendorf tubes and 2 µl of monochlorobimane (25 mmol/l) and 2 µl of glutathione-s-transferase reagent were added, as provided by a commercial kit (biovision, mountain view, ca, usa, catalog # k251). after 30 minutes of incubation at 37oc, the samples and standards were read in a fluorescence plate reader at 380/460 nm. gsh content was determined by comparison with values from a standard curve using freshly prepared gsh and normalized to the protein content of the assayed colon tissue homogenates. total antioxidant capacity (tac) measurements a colorimetric method (randox assay kit, randox laboratories ltd, uk) was used to measure the tac. the assay is based on the incubation of samples with 2, 2’-azino-di-[3-ethylbenzthiazoline sulphonate (6)] diammonium salt (abts) with a peroxidase (metmyoglobin) and hydrogen peroxide to produce the radical cation abts+ which has a relatively stable blue-green color that is measured at 600 nm. antioxidants present in the assayed colonic mucosal tissue homogenate samples inhibit the oxidation of abts to abts+ (cause suppression of the color production) to a degree that is proportional to their concentration. the assay results were normalized to the protein content of the assayed colon tissue homogenates. dna oxidative damage assay the dna was isolated from the colon tissues homogenates and the dna oxidative damage was measured using 8-oxo-7,8-dihydro-20-deoxyguanosine (8-oxodguo) assay as described earlier (suresh et al., 2017). the 8-oxodguo and 2dg in the dna were detected using an esa coulochem ii electrochemical detector in line with a uv detector. statistical analysis the results are expressed as means ± standard deviation (sd). the statistical analysis was performed using oneway analysis of variance (anova) followed by tukey’s test and a p value of less than 0.05 was considered significant (graphpad prism version 5.03; graphpad software inc. san diego, ca). results polyphenols and flavonoids oxalis corniculate leaf extract had as higher total polyphenol contents as compared to that of pteropyrum scoparium leaf extracts (320±13 and 252±10 mg gae/100 g sample, respectively, p < 0.05). a similar significant difference in the flavonoid contents was observed for both oxalis corniculate and pteropyrum scoparium leaves extracts (245±9 and 117±8 mg of cae/100 g sample, respectively, p < 0.05). dpph as presented in figure 1, the oxalis corniculate and pteropyrum scoparium leaves extracts inhibited dpph 50 squ journal of agricultural and marine sciences, 2021, volume 26, issue 1 protective effect of oxalis corniculate and pteropyrum scoparium leaf extracts against azoxymethane-induced oxidative stress and colon carcinogenesis formation in a dose-dependent manner (10-100 µg/ml), and it was observed that oxalis corniculate leaves extract exhibited a higher inhibition rate as compared to the pteropyrum scoparium leaf extracts, p < 0.05. the plateau of the effective doses for both extracts was 50100 µg/ml. therefore, the effective dose, 100 µg/ml, was used for subsequent animal in vivo studies. body weight gain of animals no mortality occurred in any group, and the body weight for each rat was recorded weekly for the whole duration of the experiment and as demonstrated in figure 2. the body weight increased gradually throughout the experimental period for all the groups. however, all rats in the aom-injected group showed a consistent decrease in body weight throughout week 2 to week 8 as compared to control groups, p < 0.05. it was notable that the supplementation of aom-injected group with either oxalis corniculate or pteropyrum scoparium leaves extracts compensated for the weight loss due to aom injection, p < 0.05. acf enumeration all the aom-injected rats developed the acf; meanwhile the concomitant supplementation of aom-injected groups with oxalis corniculate or pteropyrum scoparium leaves extracts has abrogated the acf production, p < 0.05. the histopathological examination of colonic tissues of rats supplemented with oxalis corniculate, or pteropyrum scoparium leaves extracts displayed the normal architecture of colon tissue as compared to the control group and did not show any acf development (figure 3). aom-associated oxidative stress it has been observed that the oxalis corniculate, or pteropyrum scoparium leaves extracts supplementation to the aom-injected group resulted in combating the observed aom-induced oxidative stress by restoring the level of depleted gsh to a level that is comparable to the control group, p > 0.05 (figure 4). the same trend was observed for the protective effects of the plants extracts supplementation on abrogating the aom-mediated effect on tac, (figures 5). as illustrated in figure figure 1. scavenging effect of effects of oxalis corniculate and pteropyrum scoparium leaves extracts and 2,6-di-tert-butyl-4-hydroxytoluene (bht) against 1,1-diphenyl-2-picrylhydrazyl (dpph) free radical formation. *significantly higher as compared to pteropyrum scoparium leaves extracts, p< 0.05. figure 2. changes in body weight of rats supplemented with oxalis corniculate and pteropyrum scoparium leaves extracts in the presence or absence of azoxymethane (aom) carcinogen. animals in the six groups were examined for the changes in their body weight every week for 8 weeks. *significantly lower as compared to control group, p< 0.05. values without superscript are not significantly different as compared to control group. figure 3. effects of oxalis corniculate and pteropyrum scoparium leaves extracts on aberrant crypt foci (acf) development in control and azoxymethane (aom)-injected groups. *significantly higher than the control group, p<0.05. **significantly lower than aom-injected group, p<0.05. values without superscript are not significantly different as compared to control group, p>0.05. 51research paper waly, al-khusaibi, guizani 6, aom caused oxidative damage to the dna in the colon tissues of rat injected with aom and the difference was significantly higher than the control group, p<0.05, meanwhile, the plants extract supplementation showed a significant reduction in the dna damage in the aom-injected group, p < 0.05. discussion aom injection acted as a colon cancer inducing agent in a mechanism that involves oxidative stress as evidenced by the significant reduction of the intracellular gsh level, impairment of tac, and increase in the level of dna oxidative damage as compared to control non-treated group. the present study elucidated the role of oxalis corniculate and pteropyrum scoparium leaves extracts in alleviating aom-induced oxidative stress and its associated colon carcinogenesis. we reported that rats injected with aom developed oxidative stress in the colon tissues as evidenced by gsh depletion, reduction of tac and increased dna oxidative damage, as well as histo-pathological changes which manifested carcinogenic effect in the examined colonic tissues. this is consistent with previous reports from our research group which indicated that aom injection in rats resulted in a reduction in the colonic redox cellular status (waly et al., 2014). however, oxalis corniculate and pteropyrum scoparium supplementation has suppressed the oxidative damage associated with aom injection and mitigated its carcinogenic effect. these findings suggested that these two omani wild plants can have a colon-protective effect against aom-induced oxidative stress and its associated colon carcinogenesis. the findings in this work are consistent with the well documented role of natural plants in the treatment and prevention of chronic diseases, including cancer (wang et al., 2020). in particular, oxalis corniculate and pteropyrum scoparium have wide medicinal applications, as previous studies have shown that oxalis corniculate and pteropyrum scoparium are rich in phytonutrients and figure 4. glutathione (gsh) measurements in colonic tissue homogenates of rats supplemented with oxalis corniculate and pteropyrum scoparium leaves extracts in the presence or absence of azoxymethane (aom) carcinogen.*significantly lower as compared to control group, p<0.05. **significantly higher than aom injected group, p<0.05. values without superscript are not significantly different as compared to control group, p>0.05. figure 5. total antioxidant capacity (tac) measurements in colonic tissue homogenates of rats supplemented with oxalis corniculate and pteropyrum scoparium leaves extracts in the presence or absence of azoxymethane (aom) carcinogen. *significantly lower as compared to control group, p<0.05. **significantly higher than aom injected group, p<0.05. values without superscript are not significantly different as compared to control group, p>0.05. figure 6. dna oxidative damage (8-hydroxydeoxyguanosine, 8-ohdg) in colonic tissue homogenates of rats supplemented with oxalis corniculate and pteropyrum scoparium leaves extracts in the presence or absence of azoxymethane (aom) carcinogen. *significantly lower as compared to control group, p<0.05. **significantly higher than aom injected group, p<0.05. values without superscript are not significantly different as compared to control group, p>0.05. 52 squ journal of agricultural and marine sciences, 2021, volume 26, issue 1 protective effect of oxalis corniculate and pteropyrum scoparium leaf extracts against azoxymethane-induced oxidative stress and colon carcinogenesis prevent generation of cellular oxidative stress and inflammation, hence offers a novel therapeutic approach to prevent oxidative stress-induced pathogenesis (al-attabi et al., 2015). our study documented that oxalis corniculate and pteropyrum scoparium scavenged the oxidative stress-induced colon carcinogenic effect in the used experimental model, these results address the primary prevention of oxidative stress in relation to colon cancer. conclusion aom administration resulted in oxidative stress and increased acf formation in the examined colon tissues in rats. oxalis corniculate and pteropyrum scoparium are rich in total phenolic and flavonoid compounds, and their supplementation have significantly abrogated the aom-mediated oxidative stress, and combated the aom-induced afc formation. our study suggests that dietary supplementation of these two wild plants might be applied as a therapeutic agent for prevention against colo rectal cancer rather than its treatment as abberant crypt foci are more of premalignant lesions and dysplasia, however it is essential to conduct further studies to evaluate the colon-protective effect of these two omani wild plants in human-based clinical trials. acknowledgment the authors declared no conflicts of interest. this research was supported by a grant obtained from the college of agricultural and marine sciences, sultan qaboos university, muscat, oman (ig/agr /food /20/01). an oral presentation of this manuscript was presented at the 21st isanh middle east world congress in muscat, sultan qaboos university on march 4-5, 2019. the presentation entitled: medicinal plants from chemoprevention to identification of potential biomarkers for colon cancer. references afshari k, haddadi ns, haj-mirzaian a, farzaei mh, rohani mm, akramian f, naseri r, sureda a, ghanaatian n, abdolghaffari ah. (2019). natural flavonoids for the prevention of colon cancer: a comprehensive review of preclinical and clinical studies. journal of cell physiology 234(12): 21519-21546. al-attabi z, almamri r, al abdaslam k. (2015). antioxidant potential properties of three wild omani plants against hydrogen peroxide-induced oxidative stress. canadian journal of clinical nutrition (2): 16-22. divakar mc, al-siyabi a, varghese ss, rubaie ma. (2016). the practice of ethnomedicine in the northern and southern provinces of oman. oman medical journal (4):245-52. lowry oh, rosebrough nj, farr al, randall rj. (1951). protein measurement with the folin phenol reagent. journal of biological chemistry. 193(1): 265-75. monteiro hp, rodrigues eg, amorim reis akc, longo ls jr, ogata ft, moretti ais, da costa pe, teodoro acs, toledo ms, stern a. (2019). nitric oxide and interactions with reactive oxygen species in the development of melanoma, breast, and colon cancer: a redox signaling perspective. nitric oxide 89: 1-13. omara t, kiprop ak, ramkat rc, cherutoi j, kagoya s, moraa nyangena d, azeze tebo t, nteziyaremye p, nyambura karanja l, jepchirchir a, maiyo a, jematia kiptui b, mbabazi i, kiwanuka nakiguli c, nakabuye bv, chepkemoi koske m. (2020). medicinal plants used in traditional management of cancer in uganda: a review of ethnobotanical surveys, phytochemistry, and anticancer studies. evidence based complementary alternative medicine 2020: 1-26 (article id 3529081). padmanabhan s, waly mi, taranikanti v, guizani n, ali a, rahman ms, al-attabi z, al-malky rn, al-maskari snm, al-ruqaishi brs, dong j, deth rc. (2019). folate/vitamin b12 supplementation combats oxidative stress-associated carcinogenesis in a rat model of colon cancer. nutrition cancer 71(1):100-110. suresh s, waly mi, rahman ms, guizani n, al-kindi mab, al-issaei hka, al-maskari snm, al-ruqaishi brs, al-salami a. broccoli (brassica oleracea). (2017). reduces oxidative damage to pancreatic tissue and combats hyperglycaemia in diabetic rats. preventive nutrition and food science 22(4): 277-284. waly mi, al-ghafri br, guizani n, rahman ms. (2015). phytonutrient effects of date pit extract against azoxymethane--induced oxidative stress in the rat colon. asian pacific journal of cancer prevention (8): 3473-3477. waly mi, al alawi aa, al marhoobi im, rahman msh. red seaweed (hypnea bryodies and melanothamnus somalensis) extracts counteracting azoxymethane-induced hepatotoxicity in rats. asian pacific journal of cancer prevention 2016 dec 1; 17(12): 5071-5074. waly mi, al-rawahi as, al riyami m, al-kindi ma, al-issaei hk, farooq sa, al-alawi a, rahman ms. (2014). amelioration of azoxymethane induced-carcinogenesis by reducing oxidative stress in rat colon by natural extracts. bmc complementary alternative medicine 14: 1-10. wang j, seyler bc, ticktin t, zeng y, ayu k. (2020). an ethnobotanical survey of wild edible plants used by the yi people of liangshan prefecture, sichuan province, china. journal of ethnobiology and ethnomedicine 16: 1-27. who. 2020. world health organization report on cancer: setting priorities, investing wisely and providing care for all. isbn 978-92-4-000129-9 (electronic version). isbn 978-92-4-000130-5 p. 28-30. research paper journal of agricultural and marine sciences 2023, 28(1): 70–76 doi: 10.53541/jams.vol28iss1pp70-76 received 9 june 2022 accepted 15 october 2022 دراسة التخزين هلريس اخلضار املركب من الطماطم واليقطني والزجنبيل r.g. الكمايل1، سيناراتنا 2s. m. a. c.، k. برمياكومارs. m. m ،1.أفرين1 storage study on tomato, pumpkin, and ginger composite vegetable squash r. g. lakmali1, s. m. a. c. u. senarathna2, k. premakumar, * s. m. m. s. afreen1 afreen s. m. m. s1,*( ) afreen0899@gmail.com, 1departent of agric chemistry, faculty of agriculture, eastern university of sri lanka, sri lanka, 2 food research unit, department of agriculture, gannoruwa, sri lanka. introduction sri lanka produces approximately 1,167,141 tons of vegetables every year over an area of 84,191 hect-ares (hamangoda and pushpakumar, 2019). hence, postharvest loss of vegetables ranges from 16 percent to 40 percent of total production (vidanapathirana et al., 2018) in turn creates scarcity for the vegetables at the local markets followed by cropping seasons of maha and yala. therefore, intake of vegetables decreased, in turn increases demand for those. as vegetable prices have risen, make the people unwilling to purchase them. in sri lanka, per capita consumption of vegetable is 33.76 kg/person/year, meanwhile the nutritional requirement of vegetables is 75 kg/person/year. to close this gap and enhance sri lankans’ vegetable consumption, production of vegetable-based instant foods seems to be better solution. the price of vegetables is low during the high-production season, and it can be used to manufacture value-added items, like beverages. a beverage is a food product that is made specifically for human consumption and serves to quench thirstiness. vegetable beverages are widely available in the global market. the beverages are available under a number of names, including fruit drink, nectar, squash, spice squash, readyto-serve (rts) (kumar et al., 2013). amongst, squashes are becoming more popular than synthetic beverages, abstract. sri lanka has a vast variety of vegetables. although the nutritional and medicinal properties of pumpkin and tomato are acknowledged, their consumption as beverage is limited due to their lack of taste. blending these vegetables with spice extracts is considered a more nutritious alternative when added to beverages. an effort was completed to determine the storage stability of vegetable squash made using different proportion of tomato, pumpkin and ginger. considering the findings of several preliminary studies, five formulations in various mixes of tomato and pumpkin, were chosen. the highest scores for all the sensory parameters and chemical characters were obtained by formulation (t1) 50% tomato + 50% pumpkin followed by (t2) 75% tomato +25% pumpkin. the best combination was improved using 1 % ginger to form t3 (50% tomato+ 50% pumpkin+ 1% ginger). the most three promising treatments (t1, t2 and t3) were chosen for a storage experiment at 30°c and 70-75% relative humidity. compositional analysis and sensory assessments were done. in chemical analysis, it was found that variances in the scores of ph, ascorbic acid, titratable acidity, total sugar and reducing sugar were significant (p< 0.05). squash formulations showed an increasing trend in titratable acidity (0.43 % -0.64 %), ph (3.37 – 4.08), total sugar (11.78 % 37.04 %), reducing sugar (4.42 % -31.96 %) and a decreasing trend in ascorbic acid (308.23 mg/100 ml – 79.97 mg/100 ml) and total soluble solids (25.05 -24.3o brix) as a function of storage time. sensory analysis revealed significant differences (p<0.05) across formulations for organoleptic characteristics, such as aroma, taste and overall acceptability. the composite vegetable squash t3 was chosen as the best formulation based on the findings of physicochemical and sensory attributes. it could be stored for 12 weeks without any significant variations and prolonged shelf life. keywords: ginger extract, physico chemical analysis, sensory attributes, shelf life املســتخلص: ســريالنكا لديهــا جمموعــة متنوعــة مــن اخلضــروات. علــى الرغــم مــن اخلصائــص الغذائيــة والطبيــة لليقطــن والطماطــم، إال أن اســتهالكهما كمشــروابت حمــدود بســبب مذاقهمــا. يعتــر مــزج هــذه اخلضــار مــع مســتخلصات التوابــل بديــاًل مغــذًي أكثــر عنــد إضافتــه يف املشــروابت. مت حتديــد فــرة ختزيــن اهلريــس النبــايت املركــب مــن نســب خمتلفــة مــن الطماطــم واليقطــن والزجنبيــل. ابلنظــر إىل نتائــج العديــد مــن الدراســات األوليــة، مت اختيــار مخســة تركيبــات مــن خليــط خمتلــف مــن الطماطــم واليقطــن. ومت احلصــول علــى أعلــى التقديــرات جلميــع املتغــرات احلســية واخلــواص الكيميائيــة عــن طريــق الركيبــة )t1( 50٪ طماطــم + 50٪ يقطــن تليهــا الركيبــة )t2( 75٪ طماطــم + 25٪ يقطــن. مت حتســن أفضــل تركيبــة ابســتخدام 1٪ زجنبيــل لتشــكيل t3 )50٪ طماطم + 50٪ قرع + 1٪ زجنبيل(. مت اختيار أكثر ثالث معاجلات واعدة )t1 وt2 و t3( لتجربة التخزين عند 30 درجة مئوية ورطوبــة نســبية تــراوح بــن 70-75٪. مت إجــراء التحليــل الكيميائــي والتقييمــات احلســية. يف التحليــل الكيميائــي وجــدت فروقــات ملحوظــة يف درجــات األس اهليدروجيــي ومحــض األســكوربيك ومحوضــة املعايــرة والســكر الكلــي والســكر املختــزل. )p <0.05( أظهــرت تركيبــات هريــس اخلضــار املركــب اجتاهاً متزايداً يف احلموضة القابلة للمعايرة )0.43٪ -0.64٪( ، ودرجة احلموضة )3.37 4.08( ، وإمجايل الســكر )٪11.78 ٪37.04( ، والســكر املختزل )4.42٪ -31.96٪( واجتاه تنازيل يف محض األســكوربيك )308.23 جمم / 100 مل 79.97 جمم / 100 مل( واملواد الصلبة )p <0.05( كدالــة لوقــت التخزيــن. كشــف التحليــل احلســي عــن فــروق ذات داللــة إحصائيــة )الذائبــة الكليــة )25.05 24.3 درجــة بريكــس ابلنســبة للخصائــص احلســية، مثــل الرائحــة والطعــم والقبــول العــام. مت اختيــار تركيبــة هريــس اخلضــار t3 كأفضــل تركيبــة بنــاًء علــى نتائــج اخلصائــص الفيزيئيــة والكيميائيــة واحلســية. حيــث ميكــن ختزينهــا ملــدة 12 أســبوًعا دون وجــود أي اختالفــات كبــرة وفــرة صالحيــة طويلــة. الكلمات املفتاحية: مستخلص الزجنبيل ، التحليل الكيميائي الفيزيئي ، الصفات احلسية ، فرة التخزين. 71research paper lakmali , senarathna, premakumar, afreen owing to their flavor, taste, nutritional content, and storage stability. fruit juice, sugar, citric acid, and preservatives are common constituents in squash beverages (maciel et al., 2013). tomatoes (solanum lycopersicum) are one of the world’s most frequently grown vegetable crops. it is a specie of the solanaceae family of nightshades. tomatoes contain an exceptional amount of vitamin c and beta-carotene, as well as a decent amount of the mineral manganese and a good amount of vitamin e (aldrich et al., 2010). cucurbita pepo (pumpkin) is a commercially important cucurbitaceae family member. it is a rich source of naturally active substances and is advised to consume for diseases including arthrosclerosis and diabetes, as well as controlling cholesterol (dhiman et al., 2017). in 2018, tomatoes were grown on 6712 hectares in sri lanka, with a production of 101,404 tons meanwhile pumpkins were grown in 7301 ha with the annual pumpkin output level of 81,200 tons. (hamangoda & pushpakumar, 2019). ginger is the subterranean rhizome of the plant zingiber officinale, which belongs to the zingibeaceae family. in 2018, sri lanka produced 14,208 tons of ginger for 1999 hectares (hamangoda and pushpakumar, 2019) . ginger has been extensively used as a spice and a natural preservative. despite having strong nutritious properties, the use of vegetables for the preparation of various processed products is limited due to excessive acidity, astringency, bitterness, and other features in the vegetables. as a result, blending different vegetables and spices can improve the juice’s storability as well as inhibit microbiological growth (bhardwaj and pandey, 2011). thus, the current research was conducted to generate squash from tomato, pumpkin, and ginger, as well as to assess its quality during storage. materials and methods the experiment was conducted at the food science lab of the food research unit in gannoruwa, sri lanka. fresh and high-quality tomato, pumpkin, and ginger were procured from cargills food city in kandy, sri lanka; while sugar was obtained from a nearby shop in gannoruwa. the most preferred composite squash formulations from our previous study were selected for storage study and they are 50% tomato and 50% pumpkin (t1) and 75% tomato and 25% pumpkin (t2) (table 1). these formulations were prepared as described in our previous study (begum et al., 2018) and stored at an ambient temperature of 27°c and 70-75 % rh. hence, the formulation t1 was improved with 1% ginger extract and named as t3 (50% tomato and 50% pumpkin and 1 % ginger) to investigate the potentiality of ginger extract on the improvement of storage of composite squash formulation (table 1). the prepared blends were kept in glass bottle with three replications under ambient conditions. sensory evaluation a panel of 20 un-trained panelists evaluated the formulated composite squash for organoleptic features, such as color, aroma, taste, nature, and overall acceptability at the end of storage. the panelists were chosen from different social status. three digits numbers were selected and assigned to each treatment sample. prepared tomato-pumpkin squashes were presented simultaneously for the panelist and serving order was randomized. the panelists were not allowed to communicate during evaluation. the hedonic rating test was used to determine the acceptability. the panelists rated their acceptability of the product on a 5-point hedonic scale. the scale was arranged liked that 5 = extreme like, 4 = like moderately, 3 = neither like nor dislike, 2 = dislike moderately and 1=extreme dislike. the sensory assessment was performed within 9.00 am and 12.00 pm. each panelist was given a set of samples to assess at random. physico-chemical analysis of squash the physico-chemical properties of the stored squash were assessed using aoac-recommended standard techniques (horwits and latime, 2005). a hand-held refractrometer was used to measure the total soluble solids (tss) and expressed as obrix (model atago-s28e). a digital ph meter was used to determine the ph (model hanna hi 98130). 5 ml squash was homogenized with 45 ml of distilled water for 1min at 20ºc to measure the ph. the titratable acidity of the juices was measured by titrating them with standard sodium hydroxide (naoh) and expressed the results in percent citric acid. the indophenol dye method was used to determine vitamin c content, while the lane-eynon method was used to determine total sugar in all squash formulations. during the analysis, each parameter was replicated three times. statistical analysis to evaluate the significance at p < 0.05, the results of the sensory evaluation and chemical analysis were statistically evaluated using anova and the computer-aided sas statistical software was used. standard errors were calculated using minitab 14 statistical package. comparison of means of sensory evaluation and chemical analysis were done by tukey’s standardized range test (tsrt) and duncan multiple range test (dmrt) respectively. results and discussion ph changes in ph of stored composite vegetable squashes of tomato, pumpkin and ginger are presented in the table 2. as per the table 2, the highest ph value (4.31) was recorded in formulation t1, while lowest (4.08) in the t3 at the end of storage. the findings of this study are 72 squ journal of agricultural and marine sciences, 2023, volume 28, issue 1 storage study on tomato, pumpkin, and ginger composite vegetable squash expected because the phenolic components and organic acids (i.e. malic acid and oxalic acid) in ginger extract can release h+ ions, and ph was reduced (faiqoh et al., 2021). at room temperature, there were significant variations (p<0.05) in ph among squash formulations and it gradually increased during storage. this might be due to the use of acids in the presence of metal ions to produce hexose sugars from polysaccharides and non-reducing sugars during storage and the same behaviors were observed in sapota squash (relekar et al., 2013). table 1. experimental plans treatments tomato (% w/w) pumpkin (% w/w) ginger (% w/w) t1 50 50 00 t2 75 25 00 t3 50 50 01 total soluble solids (tss) changes of tss in stored composite vegetable squashes of tomato, pumpkin and ginger are shown in table 3. at the end of storage, it shows that tss value was the highest (26.1) in t2 formulation and the lowest in the t3 formulations (24.3). it could be because the ginger juice inhibited microbial development, which could advance metabolic rates and ginger extract’s phenolic compounds, such as gingerole, and shagoal. these may trap sucrose, hexoses, and other constituents, thus preventing it to contribute in the soluble components (bhardwaj and mukherjee, 2011; hariharan and mahendran, 2016). tss of all formulations was reduced as storage time increased, possibly due to chemical interactions between the squash’s organic constituents (inthuja et al., 2019). as vitamin c is water soluble and prone to oxidation, it progressively reduced; this is the fundamental reason for the decrease in acidity and tss (mikdat simsek, table 2. changes in ph of stored composite vegetable squashes of tomato, pumpkin and ginger storage periods (weeks) t1 t2 t3 2 4.04 ± 0.0a 4.02 ± 4.02a 3.37 ± 0.08b 4 4.04 ± 0.01a 4.03 ± 0.00a 3.80 ± 0.01b 6 4.00 ± 0.0b 4.17 ± 0.00a 3.91 ± 0.01c 8 4.00 ± 0.0a 4.16 ± 0.05c 3.90± 0.00b 10 4.32 ± 0.01a 4.13 ± 0.00c 4.07 ± 0.01b 12 4.31 ± 0.0a 4.13 ± 0.01c 4.08 ± 0.00b t1: treatment 1, t2: treatment 2, t3: treatment 3 the values are the means of three replicates ±standard error. values shown with different letters are different significantly (p<0.05) table 3. experimental plans storage t1 t2 t3 2 26.10 ± 0.10a 26.15 ± 0.45a 25.05 ± 0.05a 4 25.50 ± 0.50a 25.60 ± 0.00a 25.05 ± 0.05a 6 25.75 ± 0.25a 25.90 ± 0.10a 24.15 ± 0.15b 8 25.75 ± 0.10a 25.90 ± 0.20a 24.15 ± 0.05b 10 24.20 ± 0.20b 26.10 ± 0.10a 24.40 ± 0.00b 12 26.05 ± 0.05a 26.10 ± 0.10a 24.30 ± 0.10b t1: treatment 1, t2: treatment 2, t3: treatment 3 the values are the averages of three replicates ± standard error. means with the same letter in the column are not significantly different from each other (p>0.05). figure 1. changes in ascorbic acid of tomato, pumpkin, and ginger composite vegetable squashes 73research paper lakmali , senarathna, premakumar, afreen 2011). the results are similar to the finding of a low-calorie herbal aonla-ginger beverage (gaikwad et al., 2012). ascorbic acid figure 1 explains that the maximum average value of vitamin c was 79.97 mg/100 ml in t3 (pumpkin 50 % + tomato 50 % + ginger 1 %), while the mean minimum value was 35.35 mg/100 ml in t1 (pumpkin 50 % + tomato 50 %). during the whole storage time under ambient conditions, a gradual decline in ascorbic acid was seen in composite squash formulations. the rate of decrease was low in the case of t3 because ginger extract could reduce the oxidation process of ascorbic acid (bhardwaj and mukherjee, 2011). the breakdown of ascorbic acid to dehydro ascorbic acid or the unstable nature of ascorbic acid was due to the influence of heat, light, and air (herbig and renard, 2017). the current findings are consistent with those of squash from wild prickly pear fruits (chauhan et al., 2019), mulberry squash (thakur and hamid, 2017) and sweet orange squash (syed et al., 2012). titratable acidity figure 2 shows the changes in titratable acidity of stored composite vegetable squashes of tomato, pumpkin and ginger. at the end of storage the formulation t3 had the highest titratable acidity value (0.65 %) whereas the formulation t1 had the lowest (0.35 %) (figure 2). during storage, titratable acidity was increased significantly in all formulations. this could be associated with the presence of microbes and the breakdown of sugar, but also might be acid production, oxidation of reducing sugars, polysaccharide degradation, or the breakdown of uronic acid and pectin components ( bhardwaj and pandey, 2011; kesavanath et al., 2015). blend of pineapple, carrot and orange juices revealed a similar result (jan and masih, 2012). total sugar content figure 3 shows the changes in total sugar content of stored composite vegetable squashes of tomato, pumpkin and ginger. t3 (tomato 50 % + pumpkin 50 % + ginger 1 %) had the highest mean value (37.04 %) for total sugars after the storage. throughout twelve weeks of storage table 4. sensory evaluation of tomato, pumpkin, and ginger composite vegetable squashes at the end of 12 weeks formulations weeks colour aroma taste nature overall acceptability t1 0 12 4.62 ± 0.18a 4.69 ± 0.13a 3.92 ± 0.24a 4.46 ± 0.22a 4.46 ± 0.24a 2.77 ± 0.30a 2.93 ± 0.33ab 3.08 ± 0.29a 2.38 ± 0.14a 3.00 ± 0.28ab t2 0 12 4.00 ± 0.28ab 3.85 ± 0.27b 3.31 ± 0.37ab 3.69 ± 0.21b 4.08 ± 0.21ab 2.78 ± 0.31b 2.62 ± 0.21abc 2.08 ± 0.21c 2.08 ± 0.14a 2.00 ± 0.16c t3 12 2.76 ± 0.26a 2.08 ± 0.27c 2.62 ± 0.29abc 2.38 ± 0.24a 3.46 ± 0.27a t1: treatment 1, t2: treatment 2, t3: treatment 3 values are the averages of 20 replicates ± standard error means of the columns with the same letters are not significantly different (p<0.05) five-point hedonic scales were used to assess sensory characteristics figure 2. changes in titratable acidity of stored composite vegetable squashes of tomato, pumpkin and ginger 74 squ journal of agricultural and marine sciences, 2023, volume 28, issue 1 storage study on tomato, pumpkin, and ginger composite vegetable squash under ambient conditions, total sugars in squash formulations increased gradually (figure 3). this could be due to the hydrolysis and conversion of polysaccharides from other components, such as pectin, cellulose, starch (hariharan and mahendran, 2016). similar increase in the total sugars was recorded in orange-based blended rts beverages (malav et al., 2014), seabuckthorn squash (ali et al., 2011) and sapota squash (relekar et al., 2013). reducing sugar figure 4 shows the changes in reducing sugar content of stored composite vegetable squashes of tomato, pumpkin and ginger. figure 4 displays the data reducing sugars as affected by storage of formulated squash. at the end of storage, t3 reported the mean highest value (31.96 %) for reducing sugars, while t1 showed the mean minimum value (19.97 %). during storage, the reducing sugar content of each sample increased gradually. this could also be due to starch breakdown into sugars. as well as the hydrolysis of non-reducing sugars into reducing sugars and the conversion of complex polysaccharides into simple sugars (thakur and hamid, 2017). in an orange-based blended rts beverage, a similar increase in reducing sugars was shown during storage (malav et al., 2014). sensory quality table 4 shows sensory evaluation of tomato, pumpkin, and ginger composite vegetable squashes at the end of 12 weeks. the sensory evaluation result revealed that the color, aroma, taste, nature, and overall acceptability scores of squash gradually declined as the storage period progressed. color is a prominent factor of visual perception. reduced oxygen in the headspace can increase carotenoid breakdown via oxidation, thus resulted the development of off-color (gliemmo et al., 2009). the aroma scores of various squash samples differed significantly (p<0.05). it was probably due to the loss of aroma (i.e. volatile aromatic components) (thakur and hamid, 2017). the taste of several squash samples differed significantly (p<0.05). the loss of the sugar-acid combination of squash after storage could be explained by the decline in taste (chauhan et al., 2019).the drinking ability of a drink is nature. the difference in nature score between squash samples was not significant (p>0.05) at the end of twelve weeks. treatment t3 had the highest mean nature (2.38) while treatment t2 had the lowest mean nature (2.08). according to statistical analysis, the overall score of various squash samples differed significantly (p<0.05). squash’s overall acceptability scores could be declined over storage due to the changes in appearance, flavor components, product uniformity (ullah et al., 2015). during storage, sensory qualities in papaya blended pineapple rts beverage (sindhumathi and premalatha, 2013) and box myrtle squash (thakur et al., 2016) showed a considerable decrease. when compared with other squash samples, t3 (50 % tomato+ 50 % pumpkin+1 % ginger) was favored. conclusion according to the compositional study, ph, titratable acidity, total sugar, and reducing sugar of all formulations increased with storage time ( 12 weeks), while total soluble solid and ascorbic acid declined marginally and the sample t3 (50 % tomato + 50 % pumpkin + 1 % ginger composite vegetable squash) obtained higher ascorbic acid, titratable acidity, total sugar and reducing sugar content. although all the squash samples were acceptable, the formulation t3 proved to be the more superior to other when examined over a period of 12 weeks. tomato, pumpkin, and ginger have enormous potential for creating a healthy squash. this may, if properly exploited, provide a healthier alternative to the sugar intensive drinks. this may also be a better technique to preserve the products and reduce spoilage and vegetable waste. figure 3. changes in total sugar content of stored composite vegetable squashes of tomato, pumpkin and ginger 75research paper lakmali , senarathna, premakumar, afreen references aldrich ht, salandanan k, kendall p, bunning m, stonaker f, külen o, stushnoff c. 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(2018). safety issues in fresh fruit and vegetable supply chains in sri lanka: a review. hector kobbekaduwa agrarian research and training institute.colombo,sri lanka. research paper journal of agricultural and marine sciences vol. 22 (1): 8-17 doi: 10.24200/jams.vol22iss1pp8-17 received 15 may 2016 accepted 19 feb 2017 moisture and temperature in a proppant-enveloped silt block of a recharge dam reservoir: laboratory experiment and 1-d mathematical modelling anvar kacimov1 , ali al-maktoumi*, said al-ismaily1, and hamed al-busaidi1 * 1 ali al-maktoumi ( ) , sultan qaboos university, college of agricultural and marine sciences, dpt. of soils water and agricultural engineering. box 34, al-khod 123. sultanate of oman. email: ali4530@ squ.edu.om introduction layering, i.e. vertical alternation of textures with distinct interfaces between layers, is the backbone of soil sciences in applications to agronomy and ecohydrology (see e.g. connolly, 1998, noy-meir, 1973). in soil physics, water upward-downward fluxes (evaporation-infiltration-redistribution) are usually considered as 1-d steady or transient phenomena, with effective water conductance-capillarity properties derived by conjugation of individual layers of the soil profile (see e.g., assouline et al., 2014, fehmi and kong, 2012, gardner and fireman 1958, hillel and talpaz, 1977, khan, 1988, ripple et al., 1970, willis, 1960, warrick and yeh, 1990, wuest and schillinger, 2011, zhu and warrick, 2012). مستوى الرطوبة واحلرارة يف الكتل الطمية املغلفة ابلرمل يف حبرية سد التغذية: جتربة معملية ومنذجة حتليلية أحادية البعد أنفر كاسيموف1 وعلي املكتومي*وسعيد االمساعيلي1 ومحد البوسعيدي1 abstract. mosaic 3-d cascade of parallelepiped-shaped silt blocks, which sandwich sand-filled cracks, has been discovered in the field and tested in lab experiments. controlled wetting-drying of these blocks, collected from a dam reservoir, mimics field ponding-desiccation conditions of the topsoil layer subject to caustic solar radiation, high temperature and wind, typical in the batinah region of oman. in 1-d analytical modelling of a transient richards’ equation for vertical evaporation, the method of small perturbations is applied, assuming that the relative permeability is averyanov’s 3.5-power function of the moisture content and capillary pressure is a given (measured) function. a linearized advective dispersion equation is solved with respect to the second term in the series expansion of the moisture content as a function of spatial coordinates and time. for a single block of a finite thickness we solve a boundary value problem with a no-flow condition at the bottom and a constant moisture content at the surface. preliminary comparisons with theta-, tdrprobes measuring the moisture content and temperature at several in-block points are made. results corroborate that a 3-d heterogeneity of soil physical properties, in particular, horizontal and vertical capillary barriers emerging on the interfaces between silt and sand generate eco-niches with stored soil water compartments favourable for lush vegetation in desert conditions. desiccation significantly increases the temperature in the blocks and re-wetting of the blocks reduces the daily average and peak temperatures, the latter by almost 15°c. this is important for planning irrigation in smartly designed soil substrates and sustainability of wild plants in the region where the top soil peak temperature in the study area exceeds 70°c in summer but smartly structured soils maintain lash vegetation. the layer of dry top-blocks acts as a thermal insulator for the subjacent layers of wet blocks that may host the root zone of woody species. keywords: soil capillary barrier; soil heterogeneity; hydropedology; soil moisture content; linearized richards’ equation. امللخــص: خــال دراســة التغيــرات يف تربــة ســد اخلــوض مت العثــور علــى تشــكيله فريــدة للرتبــة الطميــة ذات النمــط الكتلــي ذو األســطح املتعــددة واملغلفــة بالرمــل، والــي تشــكلت بفعــل عوامــل عديــدة منهــا طوبوغرافيــة الســطح وترســبات الطمــي والرمــل مليــاه الفيضانــات ذات الســلوك غــر املنتظــم. مت دراســة ســلوك املــاء واحلــرارة يف هــذه الكتــل خمربيــا وباســتخدام النمذجــة التحليليــة. صممــت التجربــة لكــي حتاكــي الوضــع يف ســد التغذيــة وذلــك بالتحكــم يف دورات الرطوبة واجلفاف للكتل الطمية وتعريضها لإلشــعاع الشمســي ودرجات احلرارة املرتفعة. كما مت اســتخدام معادلة ريتشــارد اخلطية حلســاب معدل البخــر العمــودي باعتبــار ثابــت أفرنيانــوف لرطوبــة الرتبــة هــو 3.5 وأمــا ثابــت الضغــط الشــعري فتــم قياســه أيضــا. مت مقارنــة نتائــج التجــارب املعمليــة مــع نتائــج النمذجــة التحليلــي وأثبتــت النتائــج تأثــر احلواجــز الشــعرية للرتبــة خاصــة لألســطح البينيــة للطمــي والرمــل، والــي أدت إىل االحتفــاظ بـــماء الرتبــة كحويصــات توفــر امليــاه لألعشــاب والشــجرات يف البيئــة الصحراويــة، وأدى جفــاف الرتبــة إىل رفــع درجــة حــرارة الكتــل الطميــة كمــا أن إعــادة ترطيــب الرتبــة ســاعد علــى خفــض معــدالت درجــة احلــرارة اليوميــة وخفــض الدرجــة القصــوى مبعــدل 15 درجــة مئويــة. لقــد أوجــدت طبقــات الرمــل احمليطــة بالكتــل الطميــة حاجــزا حراريــا وهيدرولوجيــا يعيــق خــروج املــاء مــن الكتــل إىل طبقــات الرمــل وبالتــايل أعــاق عمليــة التبخــر، ممــا أدى إىل بقــاء املــاء يف الكتــل الطميــة والــذي يعــد مهمــا للــري ودميومــة الزراعــة يف بيئــة تصــل درجــة حــرارة تربتهــا إىل 70 درجــة مئويــة يف فــرتة الصيــف. الكلمات املفتاحية: معادلة ريتشارد اخلطية، حمتوى رطوبة الرتبة، هيدروبيدولوجي، الرتبة الغر متجانسة، احلواجز الشعرية للرتبة 9research article kacimov, al-maktoumi, al-ismaily, al-busaidi spatially patchy, i.e. 2-d and time-wise persistent distributions of the volumetric moisture content (vmc) in a seemingly homogeneous topsoil have been discovered and described on the scale of a mini-watershed/cultivated field and attributed to soil aggregates (guber et al., 2003, pachepsky et al. 2005), i.e. a 3-d composite with a size of an elementary cell (aggregate) of several millimeters, which is superior in terms of soil water dynamics as compared to unstructured soils (see e.g. sawiñski et al., 2011). lehman and or (2009, 2013) studied a similar phenomenon of 2-d patchy textural pattern of the soil (macroscale) and pore bundles (microscale), which conduct and evaporate moisture in a spatially mosaic way. al-ismaily et al., (2013), discovered an essentially 3-d and temporarily very stable patchiness of the soil-structure, which is not detectable by standard on-surface measurements of the moisture content or evaporation rate i.e. by such common instruments as theta-probes, surface-mounted tensiometers or evaporimeters. hereafter this structure is called a “smart design”. this patchiness becomes evident either in pedons of 1.5-2.0 m deep or by observing distinct ecotones of emerging vegetation. the vegetation, as a proxy-indicator of structural heterogeneity, serves as a footprint, with high transpiration detectable by sapflow meters. the cascades of silty blocks of sizes of 30-40 cm and cracks of apertures of up to several cm (fig. 1a) were found in pedons dug inside the reservoir of the al-khod recharge dam in oman. the cracks were filled with a medium-size sand, which, by analogy with fracking in reservoir engineering, is called a “proppant”. consequently, the whole cascade of the soil structure is a triple-periodic composite, with sharp contrasts of hydraulic and thermal properties between texturally contrasting components (blocks and filled fractures). al-ismaily et al., (2015), al-maktoumi et al. ( 2014), al-saqri et al. (2016) studied further hydrological and geotechnical applications of natural “smart design” patterns. in arid regions such as oman, both the natural and cultivated vegetation relies on the soil substrate as an eco-refuge, in the hostile ambient atmospheric conditions (brown, 1974, lambers et al., 2008) of annual precipitation of about 100 mm and air average temperature of about 30°c. the water deficit conjugated with heat stress and, in case of poor irrigation practices, ensued secondary soil salinization (see e.g geng and boufadel, figure 1. smart block-fracture structure in the field and experimental replicate: (a) silt blocks in a pedon dug in the reservoir area of the al-khod dam (left panel); (b) surface view of the site (right panel), (c) silt block (light colour) collected from the reservoir and trimmed to fit the blue plastic box. sheaths of loose sand (proppant) have darker colour, and d) measurements of vmc-temperature after the first ponding. a c b d 10 squ journal of agricultural and marine sciences, 2017, volume 22 issue 1 moisture and temperature in a proppant-envelopped silk block 2015), are eco-constraints in hot deserts, which were prognosticated to amplify in the so-called global warming scenarios (see e.g., clair and lynch, 2010). these constraints are mitigated by plants’ adaptation in texturally heterogeneous soils, as noy-meir (1973) elucidated. since his seminal paper, the temporal and spatial soil water dynamics (swd) in hydraulically-thermally commingled soil compartments (aggregates and layers) became a topic of intensive studies in hydropedology and hydroecology (see e.g. lin et al., 2006, porporato and rodriguez-iturbe, 2002). as is evident from (fig. 1a), right photo, woody species (e.g. castor oil plants) thrive on the “smartly designed” substrate. the top-most blocks are deadly dry and hot but starting from the second layer of blocks (see the pedon in fig. 1a) the moisture content is amazingly high, despite a continuous transpiration by the plant roots. temperature distributions and heat fluxes in heterogeneous soils in temperate and relatively humid climates (arkhangelskaya, 2012, goncharov and shein, 2006, physics, 1963), where plants’ cultivation is impeded by the deficit of solar radiation, are controlled by agroengineering techniques (e.g. reducing the albedo of the soil surface, its mechanical undulations, mulching, etc.) such that the topsoil serves as a heat condenser. in oman and other arid tropics the situation is opposite: plants’ roots suffer from excessive heating and, consequently, tillage, mulching, increasing albedo, subsurface irrigation and other soil-water management techniques (see e.g. lipiec et al., 2013) serve for thermal insulation against conductive heat transfer from an extremely hot soil surface (peak temperature of which in june reaches 72-73°c in the study area) to the root zone. the discovered “smart design” of the soil structure was replicated in an on-farm experiment and showed an excellent water saving efficiency for crop cultivation in oman (al-maktoumi et al., 2014) and in growing ornamental plants as passive thermal coolers of building envelopes (kacimov et al., 2010). the objective functions in the agroengineering design and optimization included biomass, yield and leaf-area index. structural patchiness of the edaphic factor, band-type distribution of the plant roots and ensued transpiration and swd was discovered and discussed in geotechnical applications by kacimov and brown (2015). in this paper, we elaborate on the effect of the soil texture and structure on swd and soil temperature. we report the results of natural evaporation and heating of one isolated silt block, collected from a reservoir site, shown in figure 1a, and sheathed by texturally the same “proppant” (wadi sand) as in al-ismaily et al., (2013). the main purpose was to understand how the top-most blocks of silt in (fig. 1a) dries out and how temperature varies inside the block during this post-ponded desiccation. for this purpose, we had to quantify the capillary properties of the blocks in controlled wetting and drainage conditions. the average saturated hydraulic conductivity, ks=0.023 m/day, of the blocks was well known from the previous experiments conducted by double-ring and tension infiltrometers and laboratory permeameter tests. in the field ks variations within the al-khod dam area were reported for silt blocks in comparisons with regular soils in the off-reservoir area (alsaqri et al., 2016). moreover, ks is, generally speaking, varies vertically within any silt block because of textural variation during stokes’ sedimentation (al-ismaily et al., 2013). in this paper, ks is a constant (apparent or effective) quantity and its variability is not considered in the physical and mathematical models. the parameters of the unsaturated conductivity and water-holding capacity of silt were parametrically involved in mathematical modelling, in which we used linearization of richards’ equation (kulabukhova and polubarinova-kochina, 1959, abbreviated hereby as kpk-59). 3-d distributions of a transient moisture content within the block and “proppant”, obtained from probes and modelling of 1-d flow, are important for assessing the capillary barrier phenomenon (impedance of water drainage from a wet silt to dry sand) and enhanced counter-evaporation properties of the “smart design” in (fig. 1). both in the field of “smartly designed” soil substrate and in our lab replication, a detailed 3-d moisture content and temperature distributions require a network of monitoring probes. in our experiment, there were only 3 functioning probes that is, of course, a serious hindrance in validation of the mathematical model. imbibition-desiccation experiment a silt block was collected from the first layer of a 4-layered cascade of similar blocks (two layers separated by a thin layer of wadi sand are shown in figure 1a) from a site of the dam reservoir, which is unique from pedological, hydroecological, sedimentological and hydrological viewpoints (al-ismaily et al., 2013, 2015). the block was tooled into a rectangular parallelepiped to fit a plastic box. between the box walls-bottom and the five sheathed faces of the block we put a coarse sand (see figure 1b), also collected from a wadi which crosses the figure 2. sketch of the experiment in figure 1c . 11research article kacimov, al-maktoumi, al-ismaily, al-busaidi dam reservoir. the upper face of the block was open to the atmosphere. consequently, the experiment in (fig. 1b)models the topmost blocks of (fig. 1a) experimental design a system of cartesian coordinates oxyz is selected as depicted in (fig. 2). the sizes of the block and sand sheath in (fig. 1b) as well as the loci of the probes, placed in the xoz plane of the block, are shown in (fig. 2) wired sensors, connected to a data logger (5tm sensor – decagon em50), were inserted into the silt and sand. a data logger, port 4 recorded information (vmc and temperature) from the sheath, port 2 – from the block centre and port 1 – from the sensor close to the silt-sand interface (fig. 2). probe 2 defaulted for a short time as indicated in (fig. 3a). the experiment started with an instantaneous ponding i.e. full saturation of the dry block and the sheath. during this imbibition phase water was added and its temperature eventually equilibrated with that of the soil. after that, measurements started on march 20, 2014 at 3:40 pm. the probes recorded vmc and temperature in °c every 20 min. the first desiccation cycle lasted till april 12, 2014. on that day the system was ponded again, the block and sheath “proppant” re-saturated for two days. the second desiccation cycle started on april 16, 2014 and continued until the three vmc-curves (sand, block centre and periphery close to the silt-sand interface, see fig. 2) figure 3. vmc (a) and temperature (b) as a function of time during the imbibition-dessication experiment. 12 squ journal of agricultural and marine sciences, 2017, volume 22 issue 1 moisture and temperature in a proppant-envelopped silk block reached almost horizontal asymptotes on may 10, 2014. figure 3a and 3b illustrates vmc and temperature curves during the two cycles of the experiment. vmc curves (fig. 3a) have periodic blips, which reflect diurnal variations of the moisture content due to sorption-desorption of air humidity, as we witnessed in the farm experiments (al-maktoumi et al., 2014). as is evident from the temperature curves in (fig. 3b), the temperature diurnally fluctuates with a general trend of an increasing daily average temperature during one post-wetting desiccation cycle. this trend is obviously caused by progressively decreasing latent heat losses due to gradually decreasing evaporation from the block surface. the thermal gradient between the block and “proppant” becomes more pronounced as the vmc becomes low. for example, considering the period at the end of the first desiccation cycle (7th april 2014 -13th april 2014), when the vmc of 0.2 for the block and of 0.05 for the sand were recorded, the temperature difference between two points is 3-5°c while when the vmc is at saturation for both the silt and “proppant” (after rewetting on 15th april 2014), the difference in temperature is about 1°c only and less as the soil temperature equilibrates with that of the added water. the difference in vmc becomes high because the sand loses moisture faster compared to the fine textured soil of the block. correspondingly, the difference in temperature reaches about 6°c when the difference in vmc is 0.224, considering the data of mid-day of 23rd april 2014. as the soil desiccates the temperature difference between sand and silt becomes small (around 2°c). the thermal gradient between the block and the sand sheath reverses at night time (fig. 4). figure 4 plots the difference in temperature readings by the two sensors for the period from 15/4/2014 at 10:45 am to 24/4/2014 at 4:00 am. the sand is observed to cool faster during the night than the block and heated-up faster during the day. this could be attributed to variation in heat conductance as to the soil texture or to the effect of the walls through which the whole box in (fig. 1a) loses or gains heat. kpk-59 mathematical model of swd evaporation from initially saturated soil massifs is a 3-stage, two phase (moisture and vapour), non-isothermal and transient transport of mass and energy, with complex exchanges between the top soil, atmospheric boundary layer and plant roots and periodic intervention of irrigators who induce periodic imbibition-drainage-redistribution cycles (deol et al., 2014, philip, 1991, van wijk, 1963, shein and goncharov, 2006). taking into account complexity of evaporation, in this section we model isothermal swd inside the blocks. hysteresis of soil hydraulic properties, although evident from the two imbibition-drainage cycles in (fig. 3a), is ignored in the kpk-59 model. as our focus is on the desiccation phase indicated in (fig. 3), we disregard drainage of the sand and, consequently, do not conjugate flow in silt and sand. in other words we study swd within the block only. figure 4. difference in temperature (°c) between the sheath and the centre of the block for selected period between 1/5/2014 12:00 pm and 11/5/2014 12:00 am (after re-wetting). 13research article kacimov, al-maktoumi, al-ismaily, al-busaidi geometrically, the experimental block in (fig. 1b) mimics an elementary cell of the triple-periodic (in the domain -∞ < x < ∞ , -∞ < y < ∞ and 0 < z < ∞ , see fig. 2) cascade of blocks and “proppant”-filled cracks (fig.1a). physically, the natural blocks in the reservoir bed, as compared with one in (fig. 1b), have slightly different conditions at all faces but the upper one. namely, the side and bottom faces of the natural block are less heated than that in (fig. 1b), which is exposed to extra heating from the four faces of the plastic box and from a hot ground surface. another peculiarity of our experiment was in relating it to the so-called “coupled” flow of lehman and or (2009). the richards’ equation for a 3-d distribution of vmc, w(x,y,z,t) [unitless], and pressure head, p(x,y,z,t) [m], inside the silt block reads: ∂w ∂t = ∂ ∂x k(w) ∂p ∂x ⎛ ⎝⎜ ⎞ ⎠⎟ + ∂ ∂y k(w) ∂p ∂y ⎛ ⎝⎜ ⎞ ⎠⎟ + ∂ ∂z k(w) ∂p ∂z ⎛ ⎝⎜ ⎞ ⎠⎟ − ∂k(w) ∂z , (1) where t is time, k(w) is the unsaturated hydraulic conductivity and p(w) is the capillary pressure function (see e.g. warrick, 2003). swd described by eqn.(1) is isothermal. both constituting relations, k(w) and p(w), are basic hydrophysical properties of the silt. we assumed k(w) to obey the following empiric averyanov’s relation (see kpk-59) k(w)= k s w−w 0 m−w 0 ⎛ ⎝ ⎜ ⎞ ⎠ ⎟ n = k s wn (2) where w is a normalized phase saturation, w0 is irreducible moisture content of silt, m is porosity and n is an exponent (usually assumed to be equal 3.5, see e.g. kpk-59, or pore-scale models in al-maktoumi et al., 2015, kacimov and kayumov, 2002). for p(w) the van-genuchten, averyanov, brooks-corey or other empiric functions can be used. pore-scale models can be also involved in derivations of both the capillary pressure function (yang and lu, 2012) and thermal conductivity of unsaturated soils (youngs and kacimov, 2007) . kpk-59 linearized the nonlinear parabolic pde (1) in the following manner. the phase saturation in eqn.(2) was expanded as a series: w =w 0 (x , y,z,t)+ λw 1 (x , y,z,t)+ λ2w 2 (x , y,z,t)+…, (3) where λ is a parameter and w0, w1, w2, are functions to be found. we assume that w0=const, which is the initial normalized full saturation of the block in the second desiccation cycle of (fig. 3a). the series in (3) is truncated and only the first two terms are retained. the corresponding truncations of (2) and capillary pressure curve give: k(w)= k s w 0 n + λnk s w 0 n−1w 1 (x , y,z,t), p(w)= p w 0( )+ λ ′p w0( )w1(x , y,z,t), (4) in the first line of eqn.(4) only the first term is retained, i.e. the unsaturated conductivity expansion is truncated as k(w)≈ksw0 n . this is actually the averyanov unsaturated conductivity function at n=3.5 (although mathematically n can be an arbitrary positive number), which is plotted elsewhere (see e.g. polubarinova-kochina, 1977). the first derivative p’(w0) is a constant which, as we shall show below, is readily calculated from the selected capillary pressure function. taking into account eqns. (3) and (4), eqn.(1) for the first-order term in the expansion is reduced to: ∂w 1 ∂t = d ∂2w 1 ∂x2 + ∂2w 1 ∂y2 + ∂2w 1 ∂z2 ⎛ ⎝ ⎜ ⎞ ⎠ ⎟ −u ∂w 1 ∂z , (5) where d= k s w 0 n ′p w 0( ), u= nksw0n−1 (6) are two constants. obviously, eqn. (5) is a linear advective dispersion equation (ade), in which the parameter d is “diffusivity” and u is the “convective” (“velocity”) term. eqn.(5) should be solved in the domain −a/2< x <a/2, −b/2< y <b/2, 0< z <c (7) where for our physical model in (fig. 2)a=0.3 m, b=0.21 m and c= 0.17 m. the boundary conditions for ade (5) reflect a physical set-up. in arid climates, the top-soil surface z=0 dries out quickly and evaporation is controlled by soil conditions (philip’s, 1991 phase 2 of evaporation). therefore, w=constant condition (called dirichlet’s condition) can be imposed there. in other cases, a given flux (newman’s condition) is satisfied at z=0. on the vertical and bottom faces of the block prior to the desiccation phase (see fig. 3) for a coupled flow (i.e. within both silt and “proppant” subdomains, see lehman and or, 2009) the boundary condition is of the 4th type that reflects the uptake of water from the sand sheath to the block (capillary siphoning). this requires conjugation of the pressure-vmc fields in both silt and sand. our focus is on the desiccation stage in (fig. 3a), which is most important for agronomic and hydroecological applications (al-ismaili et al., 2013, al-maktoumi et al., 2014) because the blocks, isolated by the capillary barriers, do not drain, i.e. serve as excellent storage compartments of soil water, which in the field is consumed by the plant roots. so, we consider the stages demarcated by two vertical lines in (fig. 3 a), which indicate inception of desiccation of the blocks when the phase saturation of sand is almost constant, i.e. the lehman-or (2009) coupling stops but vmc in the block keeps dropping. apparently, the only way for water to escape is to evaporate, prev14 squ journal of agricultural and marine sciences, 2017, volume 22 issue 1 moisture and temperature in a proppant-envelopped silk block alently from the z=0 face of the block (side faces of the block also evaporate but much less than the upper face). 1-d evaporation in the block as is evident from (fig. 3a), soon after the inception of the desiccation phase, the difference in vmc between the centre of the block and its side face becomes negligible (the blue and red curves almost coincide). this signifies the inception of a purely 1-d ascending evaporation, for which eqn.(5) is reduced to: ∂w 1 ∂t = d ∂2w 1 ∂z2 −u ∂w 1 ∂z , (8) an analytical solution to eqn. (8) for a half-space was obtained in kpk-59 by the laplace transform method. here we use wolfram’s (1991) mathematica, the ndsolve routine to solve eqn.(8) with the initial and boundary conditions: w 1 0,t( )=1, w1 z,t( )0=1, w z,0( )=w0 d ∂w 1 c,t( ) ∂z −uw 1 c,t( )=0 (9) clearly, the boundary-value problems (8)-(9) describes redistribution of vmc by pure evaporation, with no infiltration. for our experiment in (fig. 1c) we had w(0,t)=0.18, w(z,0)=0.42, n=3.5 and ks=0.0226 m/day. the most difficult soil characteristic is indeed, all standard capillary pressure curves (brooks-corey, van genuchten, fredlund, or others) as functions p(w) have almost vertical segments at very small phase saturations and at almost full saturations. the latter limit falls within the tension saturated conditions when a standard pressure plate apparatus or penn state method for measuring p(w) are vulnerable to mistakes in determinations of the phase saturation w. in order to get p’(w0) we used a pressure plate apparatus and obtained the capillary pressure p=ρ g [bar] (ρ = water density, g = gravity acceleration), which is shown in (fig. 5) as a function of vmc (triangles). we selected two points retrieved from (fig. 4): p(0.36)=3 m and p(0.28)=9 m. then we calculated a finite difference between these two points and calculated an approximate (extrapolated) value of p’(0.42)=50 m. this value was used in the computer algebra code. the results are shown in (fig. 6) as w(0.1,t) (curve 1, time in days). for sensitivity analysis we also selected p’(0.42)=100 m (curve 2) and p’(0.42)=1000 m (curve 3). curve 1 qualitatively matches the trend in (fig. 3). for example, vmc at port 2 of (fig. 2) in 3 days drops from 0.42 to 0.25 as shown on (fig. 3a). figure 6 modelled vmc as a function of time (in days) at the middle of the block. unfortunately, we did not have a probe above probe 2 close to the soil surface that would give us the real rather than “extreme” (absolute dryness) moisture content at z=0. summary and conclusion in hot deserts, and oman is a typical example of this, low organic matter in sandy soils and limited fertilization of natural and cultivated vegetation are secondary bio-impeding factors, as compared with low vmc and high temperature in the root zone. our experiments with green roofs prove this for extreme conditions, with no fertilization of the soil substrate for 5+ years and “smart irrigation” schemes. this paper studied an elementary cell of a 3-d cascade of a “smartly designed” soil, viz. a silt block with a sand sheath (“proppant”) in contact with five faces of the block and its upper face open to solar radiation. the conducted experiments with measurements of vmc within a block confirm that desiccation from full, post-ponding saturation to 3+ bars of capillary pressure is relatively rapid (within a month) during april-may in the muscat area of oman. a mathematical model of 1-d evaporation, based on the kpk-59 linearized transient richards equation, gives qualitatively similar results. for advancement of the preliminary work in this paper we figure 5. water retention curve of block soil. figure 6. modelled vmc as a function of time (in days) at the middle of the block. 15research article kacimov, al-maktoumi, al-ismaily, al-busaidi plan to measure the 3-d distribution of moisture content and temperature within desiccating blocks, using a dense network of probes. this will allow validation of the mathematical model. this “normal” desiccation of the top-most blocks corroborates our hypothesis that the edaphic factor in general and “smart heterogeneity” of the soil substrate in particular are major controls of swd and of hydroecology of natural and engineered plant environment in arid climates. results of this study prove that a 3-d heterogeneity of soil physical properties, in particular, horizontal and vertical capillary barriers emerging on the interfaces between silt and sand generate eco-niches with stored soil water compartments favourable for lush vegetation in desert conditions. the desiccation regime of the silt blocks is also important for local geotechnical engineering and catchment-scale management of water resources. indeed, the soil making the studied block is a bed of a hydraulic structure (dam), which is one of the largest managed aquifer (mar) recharge projects in oman. when flash floods fill the dam reservoir, infiltration into the blocks is controlled by the degree of their dryness. therefore, we can conclude that if the summer floods recur less frequently than once a month (this is just the case in oman), then the mar efficiency will not be affected by the “residual” wetness of silt in the top-most blocks. desiccation significantly increases the temperature in the blocks and re-wetting of the blocks reduces the daily average and peak temperatures, the latter by almost 15°c. this is extremely important for planning irrigation in smartly designed soil substrates and sustainability of wild plants in the region where the top soil peak temperature in the study area exceeds 70°c in summer but smartly structured soils maintain lash vegetation. obviously, the layer of dry top-blocks already acts as a thermal insulator for the subjacent layers of wet blocks, which host the root zone of woody species. these plants cool the soil by both transpiration and shading, with minimal evaporation from the dry silty block surface. the details of temperature distribution in the blocks and heat fluxes there are needed to assess the thermal stress on the herbaceous species growing in the reservoir area, rooted in the top-most blocks in our system and perishing due to the soil dryness/extreme temperature and inability of the roots to penetrate to deeper wet block layers of the cascade in the heterogeneous pattern presented in this paper. from the agronomic view point, the “smartly designed” soil substrate amalgamates the advantages of the fine and coarse texture but on a larger than usually perceived scale. moreover, what is commonly illustrated as “cracked desiccated soil surface” in fear-mongering of desertification and propaganda of global warming can —with a smart engineering design—be an excellent agronomic technique leading to drastic increases of water use efficiency. the recipe is very simple: backfill the cracks by a coarse “proppant” and make a cascade of 3-d elementary cells as presented in this paper. natural soils in oman are mostly sandy and correspondingly, the natural vegetation is ecologically adopted to the adverse ambient conditions through drought deciduousness, reduced size of the leafs and limited biomass production. this is not suitable for desert farming and shading of tropical buildings by ornamental plants. juxtaposition of structurally contrasted blocks and sandwiched “proppants” solves the problem: with limited water resources for irrigation, the block-“proppant” composite of relatively rapidly infiltrates the irrigation water (common in sandy soils) and, on another hand, minimizes intensive evaporation (common in silty-clayey soils). the temperature regime within the silty blocks, even of the topsoil array in the “smart” cascade remains tolerable for the plants, until this array gets dry. some of the results in this paper were presented to the 10th international conference on thermal engineering: theory and application held in muscat on february 26-28, 2017 as kacimov, a., al-maktoumi, a., al-ismaily, s., obnosov, y. and al-busaidi, a. evaporation and heat convection through a “smartly designed” structured topsoil. acknowledgements the authors acknowledge the financial support through the grant ig/agr/swae/10/02 from the sultan qaboos university, oman. support of the department of soils, water, and agricultural engineering in the college of agricultural and marine sciences at sultan qaboos university, and from the ministry of regional municipalities and water resources – oman is appreciated. authors are most 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pedosphere, 22(1): 103–111. youngs, e.g. and kacimov, a.r. 2007. conduction through spherical particles at low liquid сontent. international j. heat and mass transfer, 50 (1-2): 292302. willis, w.o. 1960. evaporation from layered soils in the presence of a water table. soil science society of america journal, 24(4), pp.239-242. zhu, j. and warrick, a.w. 2012. unsaturated hydraulic conductivity of repeatedly layered soil structures. soil science society of america j., 76 (1): 28-35. research paper journal of agricultural and marine sciences vol. 22 (1): 27-35 doi: 10.24200/jams.vol22iss1pp27-35 received 5 jun 2016 accepted 19 oct 2016 agricultural resources management through a linear programming approach: a case study on productivity optimization of crop-livestock farming integration hemanatha, p. w. jayasuriya1* and romy das2 *1 hemanatha p.w. jayasuriya ( ) sultan qaboos university, college of agricultural and marine sciences, dpt. of soils, water and agricultural engineering, box 34, al-khod 123, sultanate of oman. email: hemjay@squ.edu.om. 2agricultural systems and engineering program, asian institute of technology, klong luang, pathumthani 12120, thailand. introduction the diverse climatic conditions of nepal has en-abled its people to practice various forms of agri-cultural activities. farming takes place from the terai region to the permanently cultivated land above 4000 msl (schroeder, 1985). at higher altitude, livestock plays the most prominent role in the livelihood and people are mostly pastoralist, whereas in fertile plains, the emphasis is on crop production. in the broad band between high hills and lower mountains area, farmers mostly rely on the century’s old tradition of integrated and diversified mixed crop-livestock farming (sumberg, 2003; bell and moor, 2012). crop-livestock integration is thus the established characteristics of the hills of nepal. the role of livestock as nutrient recyclers, source of income and draft power obligates farmers to keep large number of livestock leading to high livestock population in the country. mid hilly region of the country has approximately two third of the country’s livestock population. livestock density in nepal is the highest among south asian countries. it has been estimated to be 6.52/ ha, which is higher than 3.99 ha, the density in bangladesh, where similar climatic and economic conditions exists (fao, 1990). excessive grazing on natural forests due to high livestock population in the hills has resulted into severe deterioration in the growth of shrubs and trees. the ground cover to limit soil erosion is either at a minimum or has vanished. the higher livestock population is not only a pressure on the resources but has also negative impact on the productivity (anderson, 1997; bell and moor, 2012). the majority of the livestock in the hill districts of nepal suffers from low nutrition. even though the animals are of high genetic potential, poor nutrition negatively affects production (regmi 1992). the mid hills of nepal have tremendous potential for dairy production, but its productivity remains vulnerable due to diminishing availability of feed resources and growing number of unproductive animals. إدارة املوارد الزراعية من خالل الربامج اخلطية: حالة دراسية للتكامل الزراعي يف حتسني إنتاج احملاصيل والثروة احليوانية مهاناثا جاياسوريا1* ور. داس2 abstract. the crop-livestock integrated farming system practiced in most developing countries depends to a greater extent on the ecosystem as a whole. the importance of animals as an agent of nutrient recycle, sources of rural energy in terms of draft power and fuel as well as major contributor of the farm economy, has resulted into increased population of ruminant stock in these regions creating threats to the sustainability and productivity of land resources. this casestudy research attempted to formulate optimum herd size compatible to different resource holding farm categories within the sub watershed in mid hills region of nepal. the research was conducted by classified data collection in nepal and analysis using linear programming (lp) techniques. the lp analysis revealed that the farmers of large, medium and small categories of farms can optimize their livestock holding with combination of 3 livestock units (lu) buffaloes and 4 lu goats, 2 lu buffaloes and 4 lu goats and 1 lu buffaloes and 4.4 lu goats with maximum return to the farm family without exerting pressure on the fragile natural resources. keywords: livestock unit; land resources; optimum herd size; total digestive nutrient supply امللخــص: يعتمــد التكامــل الزراعــي يف الــدول الناميــة بشــكل عــام علــى النظــام البيئــي، إن للثــروة احليوانيــة أمهيــة كبــرة يف تدويــر مغذيــات الرتبــة وإنتــاج الطاقــة وكذلــك إســهامها يف حتســن دخــل املزارعــن، ممــا أدى إىل تزايــد أعدادهــا والــذي قــد يشــكل ضغــط مباشــر علــى املــوارد الطبيعيــة. أن هــذا البحــث حيــدد األعــداد التوافقيــة للثــروة احليوانيــة للوصــول إىل اســتدامة بيئيــة ملنطقــة النيبــال باســتخدام الربامــج اخلطيــة. أظهــرت النتائــج بــأن أصحــاب املــزارع الكبــرة عليهــم اختــاذ 3 وحــدات حيوانيــة مــن اجلامــوس و4 وحــدات مــن املاعــز. يف حــن أن املزارعــن املتوســطن عليهــم اختــاذ وحدتــن مــن اجلامــوس و4 وحــدات مــن املاعــز. أمــا يف املــزارع الصغــرة فعليهــم اختــاذ وحــدة واحــدة مــن اجلامــوس و 4.4 وحــدات مــن املاعــز، حيــث أن هــذا التقســيم ســوف يقلــل الضغــط علــى املــوارد الكلمات املفتاحية: وحدة الثروة احليوانية، موارد األراضي، إمجايل اجلهاز اهلضمي للعناصر الغذائية 28 squ journal of agricultural and marine sciences, 2017, volume 22, issue 1 agricultural resources management trough linear programming high livestock population pressure on the natural resource base as well as on agricultural land is the result of farmers’ poor decisive ability regarding herd size (price and hacker, 2009; bell and moor, 2012). rural farmers are mostly confronted with the problem of properly allocating scarce land and labor resources in a crop and livestock mix farming system (minh et al. 2007). reaping maximum benefits from available resources necessitates proper farm planning to utilize the resources more effectively for crop and livestock production without exerting additional pressure on natural resources (millar and badgery, 2009). efficient farm planning regarding livestock holding will further contribute to the economic and sustainable development of the watershed (agrawal and heady, 1972; beneke and winterboer, 1973; igwe et al., 2011; andreea and adrian, 2012). although an assessment of carrying capacity in terms of livestock unit is a useful tool for planning as well as policy formulation, it is unable to infer directly the number and the composition of livestock in the farmers’ household (robertson et al., 2009; govindrao and kabeer, 2011). in fact, livestock rearing not only depends upon the feed available but also on the labor availability because livestock rearing is labor intensive. in this context, it is important to formulate the optimum livestock number based on the available resources to the farmers. tulachan (1989) signified the importance of livestock to enhance the farm income of the rural farmers with the recommendation of various herd size suitable for different farm categories. minh et al., (2007) showed the feasibility of optimizing the crop-livestock integration with an additional component of crop-residue-dung compost fertilizer use. similarly, regmi (1992) carried out an economic analysis of the farming system and formulated optimum farm plan with equal focus on crop and livestock as enterprises. but both of these studies were conducted in terai and did not represent the conditions of mid-hills where the livestock raising contributes significantly to the farm economy. therefore, this study attempted to formulate the optimum livestock number and its composition, which gives high income to farm family with variable resources, using lp technique. methodology site election the study was conducted in kumpur subwatershed of dhading district. the watershed covers an area of 66.2 ha, which occupies 3.45% of the total area of the district. it comprises kumpur village development committee completely, sunaula bazaar and kalleri partially. the sub watershed constitutes four micro-watersheds covering major tributaries as adam, bijuli, sakura and thopal khola of trishuli river. the elevation within kumpur sub watershed varies approximately from 446 m near the trishuli river to approximately 1570 m at the north-eastern corner of the study area. due to variation in the altitude, a wide range of farming systems can be found even within small sub watershed. data collection the outcome of the research is based on primary as well as secondary data collected in kumpur sub watershed of dhading district. the methods of primary data collection were household survey, group discussion and field observation. similarly, secondary data were collected from annual reports of district livestock service centre, district soil conservation office, district forest office, locally based ngos and vdc profile. similarly, publications of international centre for integrated mountain development, articles from international journals and textbooks served as important sources of secondary data. collected data were analyzed using spss (statistical package of social science). farm plans for three categories of farmers were formulated using linear programming tools. data analysis the linear programming (lp) technique farmers in hilly region of the country possess very limited resources particularly land, labor and capital. in case of poor resources holding at their own, as well as dwindling supply from common pool resources, it is essential to estimate the best combination of available farm resources to maximize the net farm income. the overall goal of farmers to maximize the farm income with optimum resource allocation allows the use of the lp technique as an appropriate decision making tool in the analysis (agrawal and heady, 1972; beneke and winterboer, 1973; hillier and liberman, 2001; minh et al., 2007; soltani et al., 2011; govindrao and kabeer, 2011). using the shadow prices and sensitivity analysis, ranking of livestock components was done allowing farmers to select the best among several options considering the sociological and economical factors. mathematically, a linear programming (lp) model can be expressed as follows: table 1. farm categorization of the sampled households farm categories land holding no. of farm household small farm <0.5 ha 58 medium farm 0.5<1 ha 57 large farm >1 ha 45 29research article jayasuriya and das z max = c i x i i=1 j ∑ (1) subjected to resources constraints a ij x i ≤b j j=1 m ∑ i=1 n ∑ (2) and non-negative constraints x i ≥0 (3) where z = the objective function x j = the level of the jth decision variable c j = gross margin of unit of the jth activity a ij = the quantity of the ith resource required to produce 1 unit of jth activity m= the number of resources m= the number of possible activities b i = the amount of the ith resource available i =1,2,…m; j =1,2,…n farm classification farmers of the study area differed in resource availabilities. resource holding in terms of land, family labor and livestock number were the main basis for farms categorization for the lp analysis. however, land holding size served as a major criterion for farm categorization in the model. livestock master plan (1993) also categorized the farm families into large, medium and small farm based on their land holding size. farmers of the study area were also classified into three groups based on the above criteria. the total 160 sample households were categorized into three groups as given below. the average value of resources such as land, labor, nutrient availability and livestock holdings of sampled farm household were used to construct a representative of three farm categories and linear programming model was run for each representatives farms. assumptions made in lp model (1) crop residues or crop by-product used as main sources of animal feeds for livestock production. the use of crop residue, such as rice straw, maize stover was considered as transfer activities in the integrated farming system. rice straw was produced in the winter season and stored as feed for rest of the year. crop residue, as feed sources were considered without their opportunity cost in the model. similarly, manure production from livestock was considered to be used in the crop production as farm yard manure (fym). (2) return from the bullock was calculated based on the number of days, they are placed for work. since their use was seasonal, it was assumed that a pair of bullock is used approximately for 180 days in cropping activities. tulachan (1989) adopted the same method to calculate the return from the draft power use of bullock. (3) family labor and use of own bullock was considered without their labor cost. for crop production, cost of hired labor was included. however, it was assumed that livestock production is entirely performed through family labor. returns received from the linear programming solution were return to farm labor, family owned bullock and land. capital cost of each type of livestock in the model was considered using market price and current interest rates. (4) the main economic animals considered for the models were milking buffaloes, milking cows, draft bullocks and goats. the model only considered adult animals which gives economic return. (5) livestock were assumed to be raised with two different feeding management systems. the existing farm plan had taken into account maintenance ration only whereas improved feeding with maintenance and production rations was considered in the improved farm plan. decision variables used in linear programming model a. cropping activities rice and maize were the major cereal crops used as staple food in the study area. additionally, these were the major sources of crop residues for livestock feed. therefore, these two crops had been taken as only cropping activities in the model. production cost per unit was deducted from the per unit output value of each cropping activities to get the gross return. b. livestock enterprises each type of livestock unit (lu) was considered as a separate activity in the model. balancing the livestock carrying capacity (=lu) for each type of livestock, based on tdn requirement, 4 goats were considered as one lu. since the main objective of the model was to determine the optimum stocking for each farm categories, the number and type of livestock was selected based on available feed resources. milk production was considered as a major output from cattle and buffaloes. similarly, draft power use during working periods was considered for the calculation of return from bullock. return from goat indicated the economic value of meat produced per year. return from livestock activities was estimated without including the cost of feeds except concentrate. due to improved feeding, comparatively higher return from buffalo milk production was considered in improved farms plans than the existing plan. c. fodder plantation grazing a large flock of goats was difficult under the community sanction of common pool resources in the study area. moreover, considering the negative effects of the browsing nature of goats on vegetation cover, increased number of goats might require increased farm 30 squ journal of agricultural and marine sciences, 2017, volume 22, issue 1 agricultural resources management trough linear programming fodder production. therefore, to minimize the dependency on external sources, certain proportion of upland area was considered under fodder tree plantation in all improved farm plans so that stall-feeding of large number of goats can be possible and grazing in common pool resources can be minimized. since fodder tree occupies certain area under cultivated land, it was considered as a separate activity in the improved farm model. the economic return from fodder tree was calculated with respect to the total digestive nutrient (tdn) value of crop residue. farm resources and constraints used in lp model a farmer has to take decisions regarding cropping and livestock activities within the boundary of resources available to the farm household. the major resources that a farmer owns are the land, family labor and the capital. these resources are limited for the family therefore, they demand efficient use. the resources considered in the model are discussed as follows. a. land resources land is a scarce resource for the hill farmers of nepal. efficient allocation of land is an important factor to be considered in increasing whole farm income. table  2 presents the land holding of three farm categories. the cultivated land holding was categorized into upland (unirrigated land) and lowland (irrigated land) in each farm category. rice is grown in the irrigated land therefore the total available irrigated land was considered as land constraints under rice cultivation. since there was hardly any option for further increasing the landholding and land type of the farm household, no attempt was made to increase land area under rice and maize in the model. maize is usually grown in the upland of the area; therefore, bari land (unirrigated land) was taken as constraints for the area under maize. fodder trees are grown on the riser and bunds and occupy a certain area of the bari land. fodder trees are rarely cultivated in khet land due to its shading effect on the crop yield. according to lrmp (1986), about 17.4% of gross cultivated area in kavrepalanchowk district of nepal is under riser and bunds. the same figure was assumed in the study area as well. therefore, the upland area with same figure was allocated under the fodder tree as an equality constraint in the improved farm model. b. labor resources labor is the most important resource for crop as well as livestock activities. cropping activities are seasonal table 2. cultivated land holding of farm categories. farm category total land holding (ha) upland holding (ha) lowland holding (ha) large farm (n=45) 1.75 1.25 0.5 medium arm (n=57) 0.8 0.52 0.28 small farm (n=58) 0.43 0.26 0.17 source: household survey, primary data table 3. cultivated land holding of farm categories. age category heads labor equivalent estimated ld/month ld/month in farming ld/year for labor hours available for farming large farm <0-15yrs 2.42 0.5 15 3 72 576 16-59 yrs 3.23 1 30 25 900 7200 >60yrs 0.44 0.5 4 19.2 153.6 total 7929 medium farm <0-15yrs 2.47 0.5 15 3 72 576 16-59 yrs 2.86 1 30 25 900 7200 >60yrs 0.37 0.5 15 4 14.4 115.2 total 7891 small farm <0-15yrs 1.81 0.5 15 3 72 576 16-59 yrs 3.02 1 30 25 900 7200 >60yrs 0.28 0.5 15 4 9.6 76.8 total 7852 source: household survey, primary data 31research article jayasuriya and das and required to be performed within a specified period of time. delay in one of the activities may affect the other. in contrast, livestock activities are neither seasonal nor they have sequential effect upon each other. therefore, the later activities are usually carried out by family labor. livestock management in the study area was found as a full time job for one family member of a household in the study area. forest fodder collection and grazing were the most time consuming activities for the livestock management. crop production consumed family as well as hired labor but livestock production mostly depended upon the family labor. farmers reported that family labor was not enough during the peak period of crop cultivation. therefore, hired labor was essential to perform several activities in time. table 3 shows family labor calculation in three farm categories. it was calculated according to the labor-days available in the farming activities. the same method of family labor calculation was adopted by regmi (1992). labor-days (ld) available for farming activities per month was calculated based on the age and health condition of the each member. finally, labor per month was converted into annual labor hour available for farming. c. livestock and feed resources livestock contributes significantly to the sustainability as well as household income of a farming family. therefore, it has been considered as a major resource of the farm. the major ruminant animals reared by the farmers of study area were milking cow, buffalo, bullock and goats. they receive high income from milk and meat trading. therefore, milking cow, buffalo, draft bullock and goats were considered as source of economic return in the farm model. the livestock used in the model were of local breads. table 4 shows the number and types of livestock reared by the three farm categories. livestock in the study area were mainly reared on crop residue, cropby products, tree leaf fodder from farm land as well as supply from common property resources and wasteland through grazing, cut grasses/weeds and leaf fodder. furthermore, they were fed with the home produced maize flour and by-products such as rice bran as concentrate feed. improved fodder grasses and forage crops plantation was not common in general. table 5 shows feed supply from various sources, which were considered as maximum feed supply in the farm model. feed supply has been considered in term of total digestive nutrient (tdn). results and discussion optimization of livestock holding using lp method the study attempted to formulate the optimum number and combination of livestock that should be reared by the households with different resource holdings. to formulate the optimum number and composition of livestock in crop-livestock integrated farming system, the study used linear programming as a main analytical tool. using the shadow prices of decision variables and the sensitivity analysis, different combination of livestock number, which gave maximum income to the farm household, were selected as optimum herd size. since the livestock population of subwatershed was above the carrying capacity of resources, optimum herd size was formulated without significantly increasing their existing herd size (table 6). optimum livestock holding for small farm size the representative of small farm size in the study area consisted of six members with an average of 2 members under age group 0-15 years and 3 members belonging to 16-59 years. the small farm size had annual family labor of 7852 hours (981 mandays). in an average a farm household in this category collected 3.8 mt/yr tdn from different sources. the total cultivated land holding size of small farm category was 0.43 ha out of which irrigated land is 0.17 ha and unirrigated land 0.26 ha. rice was mainly grown in lowland (irrigated) areas whereas maize was grown in upland area (unirrigated). besides crop production, the farmers under small farm category, reared in on average 1 milking cow, 1 milking buffalo, 1 bullock and 6 goats. with the existing resources, this farm category received 40133 nrs per year (table  7). table 4. livestock holding by farm categories types of livestock large farm (n=47) medium farm (n=57) small farm (n=58) mean std. mean std. mean std. cow 1.5 1.47 1.4 1.4 1.2 0.84 bullock 1.72 0.87 1.61 1.03 1.38 0.92 cattle calves 0.33 0.79 0.21 0.64 0.28 0.61 buffalo 1.72 1.16 1.19 0.98 1.43 0.77 buffalo calves 0.82 0.76 0.52 0.61 0.48 0.89 goat 5.88 3.10 5.08 4.00 5.55 2.18 source: household survey, primary data 32 squ journal of agricultural and marine sciences, 2017, volume 22, issue 1 agricultural resources management trough linear programming the lp analysis revealed that the small farm categories with the above resources holding can optimize their herd size with 1 lu of buffalo and 4 lu of goat with 32% increase in gross income and 45% return in family labor optimum livestock holding for medium farm size medium farm family in the study area has total cultivated land holding of 0.83 ha with irrigated and unirrigated land 0.28 and 0.55 ha respectively. the household within the medium land holding consists of an average of 2 members belonging to age group 0-15 years and 3 members within age group, 15-59 years. the total annual family labor availability for farming activities is 7891 hrs (986 man-days). on an average, a farm household in this category collects 4.5 mt/yr of tdn from different source. the medium category of farm possess one lu of milking cow, one lu buffalo, 2 lu bullock and 1.5 lu goats (6 goats) and receives annual gross return of 49,158 nrs per year under the above mentioned crop and livestock activities whereas 2 lu of milking buffalo and 3.5 lu goats (14 goats) has been found as optimum livestock holding for medium farm family with the maximum use of above-mentioned land, labor and tdn supply. medium farm family can increase their gross income with 35% and return at family labor by 49% with optimum herd size. table 6. optimum herd sizes for three categories of farm households. decision variable small farm medium farm large farm gross return (nrs) 53059.50 66711.84 91830.58 cropping activities (ha) rice 0.17 0.28 0.5 maize 0.22 0.5 1 fodder plantation (ha) 0.04 0.08 0.2 optimum herd size (lu) cow buffalo 1 2 3 bullock goat 4 (16 goats) 4 (16 goats) 4 (16 goats) contribution of livestock (nrs*) 47516 (86%) 54956 (82%) 99884 (72%) return over family labor (nrs) 170 173 195 * there is no indication table 5. tdn supply from various sources of feed (kg/year). types of livestock large farm (n=45) medium farm (n=57) small farm (n=58) mean std. mean std. mean std. rice straw 480.25 410 329.02 273.45 245.69 296.56 millet straw 34.94 52 40.89 79.84 29.39 43.67 wheat straw 4.26 11 4.77 17.0 4.18 12.5 maize stover 293 185 236.88 183.7 248.0 200.0 maize cob 14.83 15.6 9.72 10.78 10.41 11.4 pulse residue 3.56 0.88 3.8815 1.14 3.60 1.140 maize flour 1036.11 1867 685.45 419.67 585.42 278.8 rice bran 95.86 195 58.46 120.67 16.2 62.5 farm grass 1711.90 361.6 310.24 321.4 285.30 457.7 fodder tree 480.24 1138 310.24 178.6 285.30 222.6 forest fodder 1175.82 494.7 1958.742 690. 1819.96 641.7 grazing supply 274.68 158.43 268.26 133.5 269.72 164.0 total 5606 4506 3803 source: household survey, primary data 33research article jayasuriya and das optimum livestock holding for large farm size large farm size in the study area possessed comparatively higher resources than the other two farm categories. it has total cultivable land holding of 1.75 ha with 1.2 ha irrigated (khet land) and 0.55 ha of irrigated upland (bari land). households in large farm size category consists of two members belonging to age group 0-15 years, three members between age 16-59 years and one elder member of more than 60 years of age. the total family labor availability in large farm size is 7929 hrs/yr (991man-days/yr). on an average, a farm household in this category collects 5.6 mt/yr of tdn from different sources. a farm household receives annual gross return of nrs 76745 per year with 0.5 and 1.2 ha of land altable 7. comparison of system economics of current and simulated for all farm categories and three optional plans with respective gross returns to choose farm category decision variables existing farm plan improved farm plans (lp simulated) plan 1 plan 2 plan 3 cropping activities (ha) rice 0.17 0.17 0.17 0.17 maize 0.26 0.22 0.22 0.22 fodder 0.04 0.04 0.04 small livestock activities (lu) cow 1 1 buffalo 1 1 1 1 bullock 1 1 1 goat 1.5 (6 goats) 2 (8 goats) 2.8 (11 goats) 4 (16 goats) gross return (nrs) 40 132 13 432 47341 53060 contribution of livestock (nrs) 74% (36 2012) 76% (37 658) 78% (42 898) 82% (54 956) cropping activities (ha) rice 0.28 0.23 0.23 0.23 maize 0.55 0.5 0.5 0.5 fodder 0.08 0.08 0.08 medium livestock activities (lu) cow 1 1 buffalo 1 1 1 2 bullock 2 2 2 goat 1 (4 goats) 1.3 (5 goats) 2 (8 goats) 4 (16 goats) gross return (nrs) 49 158 50 526 54 653 66 712 contribution of livestock (nrs) 74% (36 212) 76% (37 658) 78% (42898) 82% (54956) cropping activities (ha) rice 0.5 0.5 0.5 0.5 maize 1.2 1 1.0 1.0 fodder 0.2 0.2 0.2 large livestock activities (lu) cow 1 1 buffalo 2 2 2 3 bullock 2 2 2 goat 1.5 (6 goats) 1.7 (7 goats) 2 (8 goats) 4 (16 goats) gross return (nrs) 76 745 75 414 78 552 91 831 contribution of livestock (nrs) 67% (48 826) 66% (50 310) 68% (53 606) 72% (66 884) for goats 1lu=4 adult goats 34 squ journal of agricultural and marine sciences, 2017, volume 22, issue 1 agricultural resources management trough linear programming located for rice and maize respectively as well as from livestock activities. livestock herd in this farm category is composed of a pair of buffaloes, a pair of bullocks, one cow and six goats. since the large farm category has comparatively higher resources holding than other farm categories, they are able to rear up to 3 lu of buffalo. thus the large farm categories can optimize their livestock holding up to 3 lu of buffalo and 4 lu of goats (16 goats) with 19% increase in gross return and 40% increase in return at family labor. other optional crop-livestock plans in addition to the constraints on economic and direct resources for crop-livestock activities, other sociological and agro-ecological aspects can be incorporated in the system by proper modelling and mathematical conversions of such linear functions. as an example, farmers in some systems can have a milking cow for family nutrient supply or a bullock for land preparation and transportation by sacrificing a little reduction in optimum economic return. table 7 shows the optimum crop-livestock combinations under three such plans compared with the current systems, in which farmers can chose the appropriate plan considering their conditions and requirements. respective optimum economic returns under each plan and crop-livestock optimization was based on sensitivity analyses conducted in the program. smaller farms show the highest livestock contribution contrarily by large farms. three plans shows increasing trend of livestock contribution, the plan iii showing the optimal condition. some additional benefits due to increase in livestock number were not taken in to the analysis such as soil nutrition improvement by the increased dong manure generation etc. conclusion findings of the linear programming revealed that with the current feed resources capacity, farmers in the study area could maximize their farm income from crop-livestock system without creating excessive pressure on the land resources and contribute towards sustainability of resources at the same time. since the resources holding of farmers varies among each other, livestock carrying capacity at the household level also varies with farmers with different resources capacity. farmers in the large, medium and small farm categories can raise livestock up to 3 lu buffaloes and 4 lu goats, 2 lu buffaloes and 4 lu goats and 1 lu buffalo and 4.4 lu goats respectively according to their resources capacity. farmers of these farm categories can maximize their benefit up to 19%, 34% and 32% from the improved farm plan with high return at the family labor than the existing farm plan. in all proposed farm plans i to iii, contribution of livestock in gross return was found higher in small and medium farm categories than in the large. it indicates that a livestock enterprise in the study area is most profitable for low resource holding farmers. among the herd composition, buffalo and goat rearing have proven more promising than cattle in terms of profit maximization. furthermore, high return to the farm household labor shows potential for solving the problem of unemployment and under employment. gross margin analysis in all improved farm plans showed high return at family labor reflecting better employment opportunities of the farm labor in all farm categories. considering the sociological factors as well as household requirements, farmers have to sacrifice their economic return in substantial amount. references agrawal, r. c. and heady, e.o. 1972. operational methods for agricultural decisions. iowa state university press, ames. anderson, b. 1997. testing livestock feeds for beef cattle, dairy programme. study of global change. human dimension of global environment change programme, stockholm and geneva. raluca, a.i. and adrian,t.r. 2012. linear programming in agriculture: case study in region of development south-mountenia. international journal of sustainable economies management, 1(1), 51-60, doi: 10.4018/ijsem.2012010105. bell l. w., and moore, a.d. 2012. integrated crop–livestock systems in australian agriculture: trends, drivers and implications. agricultural systems 111: 1–12. beneke, r.r. andwinterboer, r. 1973. linear programming applications to agriculture. ames: the iowa, state university press. fao 1981. report of the seventh session of the fao regional commission on farm management for asia and far eastern. held in jog jakarta, indonesia. 24-29 august 1981. govindrao, s. r. and kabeer, s. j. 2011. linear programming problem (lpp) and geographic information systems (gis): a joint venture to optimize land utility. journal of statistics and mathematics, 2(2): 59-62, issn: 0976-8807. hillier, f.s. and lieberman, g.j. 2001. introduction to operation research. mcgraw–hill publishing company, new york. hmg/n. 1993. livestock master plan. his majesty’s government of nepal. igwe, k.c., onyenweaku, c.e. and nwaru, j.c. 2011. application of linear programming to semi-commercial arable and fishery enterprises in 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(1986). agriculture and forestry report. land resource mapping project kathmandu. kenting earth sciences, canada and department of topography. hmg/nepal. millar, g.d. and badgery, w.b. 2009. pasture cropping: a new approach to integrate crop and livestock farming systems. animal prod. sci. 49, 777–787. minh thai thi, ranamukhaarachchi s. l., and jayasuriya, h. p. w. 2007. linear programming-based optimization of the productivity and sustainability of crop-livestock-compost manure integrated farming systems in midlands of vietnam. science asia 33: 187-195. price, r.j. and hacker, r.b. 2009. grain and graze: an innovative triple bottom line approach to collaborative and multidisciplinary mixed-farming systems research, development and extension. animal prod. sci. 49, 729–735. regmi, p. p. 1992. economic analysis of the farming system of shivnagar village, nepal: a linear programming approach. unpublished ait thesis no.hs-92-26. bangkok, thailand. robertson, m.j., bathgate, a., moore, a.d., lawes, r.a. and lilley, j.m. 2009. seeking simultaneous improvements in farm profit and natural resource indicators: a modelling analysis. animal prod. sci. 49: 826–836. schroeder, r. f. (1985). himalayan subsistence systems indigenous agriculture in rural nepal. mountain research and development. 5 (1): 31-44. soltani, j., karbasi, a. r. and fahimifard, s. m. 2011. determining optimum cropping pattern using fuzzy goal programming (fgp) model. african journal of agricultural research vol. 6(14), pp. 3305-3310, doi: 10.5897/ajar11.585. sumberg, j. 2003. towards a dis-aggregated view of crop-livestock integration in western africa. land use policy 20: 253–264. tulachan, p.m. 1989. potential contribution of livestock sector development to farm income and employment in the chitwan valley of nepal. unpublished ph.d. dissertation. cornell university, usa. research article journal of agricultural and marine sciences 2021, 26(2): 35–41 doi: 10.24200/jams.vol26iss2pp35-41 received 15 dec 2020 accepted 13 mar 2021 characterization of genetic diversity in dhofari wild gazelles ahmed jashool1, alya al ansari2, waleed al marzooqi2, othman alqaisi3, mansour al gahdhami3, mohammed a al-abri2,* mohammed a al-abri2,*( ) abri1st@squ.edu.om,2department of animal and veterinary sciences, college of agriculture and marine sciences, sultan qaboos universit y, 1office of the conservation of environment, royal court affairs, 3department of biology, college of science, sultan qaboos universit y introduction the genus gazelle belongs to family bovidae. ac-cording to the international union of conser-vation of nature, iucn, there are eleven different gazelle species (mallon and kingswood, 2001). in oman, two known gazelle species have been documented. namely, gazella arabica and gazella subgutturosa marica. gazella arabica is a vulnerable gazelles species found in the arabian peninsula (iucn, 2017; massolo et al., 2008). in oman, gazelles are found in protected areas and are scattered in various the wild areas around the country. the numbers of gazelles in the wild are estimated to be 1737 animals in jabal samhan and nejed areas of dhofar governorate (al hikmani et al., 2015). توصيف التنوع اجليين للغزال الربي مبحافظة ظفار أمحد جشعول، علياء األنصاري، وليد املرزوقي، عثمان القعيسي، منصور اجلهضمي وحممد العربي abstract. wild gazelles are scattered in most arid and semi-arid areas in the sultanate of oman particularly in valleys, mountains and sandy zones of rub’ al khali desert. recently, however, gazelles’ numbers have been declining in oman mainly due to the loss of habitat. consequently, a gradual loss of their genetic diversity is inevitable. however, little is known about the status of the genetic diversity of the omani wild gazelles. this study aimed to determine the extent of inbreeding, population structure and genetic diversity in the omani gazelles’ populations in dhofar region. samples from four different locations namely gara, stom, solot and ayon were collected. dna belonging to 74 gazelles’ fecal samples was extracted using the human stool dna extraction protocol. following extraction, four microsatellite nuclear markers were used to calculate the levels of inbreeding, population differentiation and genetic diversity. pcr inhibitors were significantly removed using bovine serum albumin (bsa) and dimethyl sulfoxide (dmso). the mean inbreeding for the population was 0.228 for all loci with a standard error of 0.09. it is therefore postulated that dhofari gazelles are generally undergoing gradual inbreeding, which may lead to lack of fitness in future generations. the genetic differentiation (fst) ranged between 0.071 (between gara and stom) and 0.231 (between gara and ayon). on the other hand, the fst estimate between solot (most distant) versus other dhofari gazelles populations (pooled together) was 3.7%. principle components analysis (pca) clustered ayon and gara populations apart from one another and closer to stom while placing solot further than all other populations, which is in agreement with the fst results and the geographical distribution. in conclusion, the results of this preliminary study provides an insight towards the conservation of wild gazelles in dhofar in oman. it provides an initial report on the status of the genetic diversity of dhofari wild gazelles and serves as a reference point for future studies assessing their genetic diversity and variability. keywords: noninvasive samples, microsatellite, inbreeding, genetic diversity, population structure. امللخص:تنتشــر الغــزالن الربيــة يف معظــم املناطــق القاحلــة وشــبه القاحلــة مــن ســلطنة عمــان وخاصــة يف الــوداين واجلبــال واملناطــق الرمليــة مــن صحــراء الربــع اخلــايل، ويف اآلونــة األخــرة ، تواجــه الغــزالن إخنفاًضــا يف أعدادهــا، األمــر الــذي قــد يــؤدي اىل فقــدان التنــوع اجليــي تدرجييــا ممــا قــد يتســبب يف انقراضهــا مــن الربيــة، ويعتــرب الفقــدان التدرجيــي للتنــوع اجليــي خســارة ألحــد املقومــات الرئيســية الــي قــد حتمــي مــن األنقــراض، وحــى االن ال ُ يعــرف ســوى القليــل عــن حالــة التنــوع الوراثــي للغــزالن العربيــة الربيــة يف حمافظــة ظفــار. هــدف هــذا املشــروع إىل حتديــد أفضــل الطــرق ألخــذ عينــات روث الغــزال وحتليلهــا والتعــرف علــى أفضــل بروتوكــول إلســتخاص احلمــض النــووي الريبــوزي )dna( والتحســن مــن أداء تفاعــات سلســلة البوليمــرز )pcr(. ويعتــرب إســتخاص احلمــض النــووي مــن الــروث مــن أفضــل البدائــل للحيــواانت الربيــة وهــو بديــل عــن إســتخاصه مــن الــدم والــذي قــد يتطلــب ختديــر احليــوان ممــا يعــد عمليــة مضنيــة وخطــرة علــى احليــواانت الربيــة، أمــا األهــداف الثانويــة فهــي تطويــر فهــم مســتوايت زواج األقــارب و نوعيــة الرتكيبــة اجلينيــة والتنــوع الوراثــي لــدى جمموعــات الغــزالن الربيــة، وقــد إســتنتج أن أفضــل بروتوكــول إلســتخراج احلمــض النــووي مــن عينــات الــروث هــو الربوتوكــول الــذي يســتخدم يف اســتخراج احلمــض النــووي للــرباز البشــري، وبعــد اســتخراج احلمــض النــووي مــن هــذه العينــات مت اســتخدام أربعــة عامــات وراثيــة مــن نــوى اخلــااي اجلســمية يف حتديــد مســتوى زواج األقــارب والتنــوع اجليــي يف الغــزالن، ولقــد حتســنت هــذه )dmso( وثنائــي ميثيــل سلفوكســيد )bsa( وذلــك عــن طريــق إضافــة مــادة املصــل البقــري الــزااليل pcr القياســات بعــد أن متــت إزالــة مثبطــات تفاعــل سلســلة البوليمريــز وأظهــرت النتائــج أبن متوســط زواج األقــارب هــو 0.228 جلميــع عينــات حمافظــة ظفــار وبنســبة خطــأ قياســي )se( قــدره 0.09، حيــث يشــر ذلــك أبن الغــزالن متــر مبرحلــة مبكــرة مــن التــزاوج الداخلــي التدرجيــي، أمــا فيمــا يتعلــق ابلتنــوع الوراثــي اجليــي فقــد إعتمــد علــى حســاابت fst املتبعــة بــن جمموعتــن مــن الغــزالن مثــل نتائــج fst الــي تصــل اىل 3.7٪ بــن جمموعــة غــزالن منطقــة صولــوت solot و ابقــي الغــزالن املضمنــه يف الدراســة، وأمــا قياســات ال fst لباقــي الغــزالن الربيــة فهــي تــرتاوح مــا بــن 0.071 )بــن وادي غــارة ووادي ســتوم( و 0.231 )بــن وادي غــارة ووادي عيــون(، ولقــد حللــت اخللفيــة اجلينيــة بطريقــة حتليــل املكــوانت الرئيســية للمجموعــات األربــع مــن الغــزالن الربيــة املوجــودة يف أربــع وداين رئيســية وأشــارت النتائــج عــن بعــد غــزالن عيــون عــن غــارة جينيــا وتبعــد عنهــا بقليــل غــزالن وادي ســتوم وأمــا غــزالن منطقــة صولــوت فقــد كانــت األبعــد عــن غــزالن املناطــق األخــرى، وتتفــق هــذه النتائــج الfst وواقــع التوزيــع اجلغــرايف ملواقــع مجــع العينــات، ويف اخلتــام ، تعــد نتائــج هــذه الدراســة هــي األوىل مــن نوعهــا يف دراســة إمكانيــة إســتخاص احلمــض النــووي مــن عينــات الــروث يف الغــزال يف الســلطنه وهــي ذات أمهيــة يف معرفــة الرتكيبــة اجلينيــة للغــزالن الربيــة يف ســلطنة عمــان وميكــن اســتخدام نتائجهــا كمرجــع للدراســات املســتقبلية املعنيــة ابلتنــوع اجليــي يف الغــزال العــريب يف الســلطنة. 36 squ journal of agricultural and marine sciences, 2021, volume 26, issue 2 characterization of genetic diversity in dhofari wild gazelles the first action taken by the omani government to protect wild gazelles was to set up several sanctuaries that encompassed gazelles. these sanctuaries include ras al shagar protected area, al wusta wildlife reserve, and jabal samhan protected area, established in 1982, 1994 and 1997 respectively. together, these sanctuaries have greatly attributed to the protection of gazelles’ population in oman although several populations are still struggling to survive due to habitat destruction (as a result of highways construction and urban sprawl), pouching and reduction of pastures due to lack of rainfall (ministry of environment and climate affairs, sultanate of oman, personal communication). other areas where wild gazelles have been reported including al saleel natural park, al hajar mountain, and southern coastal plain of mirbat and sadah. additionally, few separated individuals have been reported throughout dhofar nejd areas (ministry of environment and climate affairs, sultanate of oman, personal communication). unfortunately, gazelles population are continuously declining due to illegal hunting and animal capturing (al hikmani et al., 2015; massolo et al., 2008). gazelles are a main dietary component for some wild species, such as the arabian leopard panthera pardus nimr (commonly found in dhofar mountains) which (judas et al., 2006). in addition, gazelle’s juveniles are considered one of the opportunistic mammalian preys for the scavenger white vulture’s (considered an endangered species by the iucn, 2017) which relies on gazelles juveniles as feed for its hatchlings (margalida et al., 2012). in addition, habitat degradation and population fragmentation also threaten arabian gazelles. the presence of various kinds of flora in many valleys in oman is a primary source of feed for many wildlife species. however, plants destruction along valleys due draught or weather conditions is common. an example of conditions is the floods caused by the tropical cyclone gonu in northern oman in 2007, and more recently, the destructive cyclone (mekunu) and the cyclone (luban), which impacted dhofar governorate in 2008. these cyclones could diminish the numbers of wild gazelles and the types of plants that they feed on in addition to threatening their livelihood as gazelles become unable to adapt to sudden habitat and environmental catastrophes (ministry of environment and climate affairs, sultanate of oman, personal communication). another challenge facing the gazelle populations is the construction of road networks across gazelles habitats separating gazelles herds smaller herds, which could increase inbreeding and reduce fitness. for instance, the road between qurayyat and sur wilatats splits the wild gazelles population into two herds (groups) of gazelles with little interbreeding between both populations. the pouching of adult gazelles in various parts of oman remains a continuous threat the gazelles’ population. non-invasive sampling is advantageous and it is easier and cheaper than invasive sampling (taberlet et al., 1999) and is also in line with ethics and conservation strategies for wild animals. nevertheless, there are some drawbacks associated with in non-invasive sampling. for instance, in fecal samples, there is a chance of cross contamination of feces belonging to different individuals. this can be avoided by properly selecting the pellets exactly from the top of the fecal colony to get fecal pellets belonging to only one individual. the challenge associated with fecal dna is its degradation because of the sun’s uv light (king et al., 2018). the fecal moisture is yet another concern as it enhances the attachment of the soil to the feces and increase the inhibitors from the soil, which in turn prevents proper amplification of dna. thus, gathering fresh fecal samples and preserving them in very dry and low temperature is essential for successful dna amplification (murphy et al., 2007). the feces of both nubian ibex and domestic goats is occasionally confused with the gazelles scats and this could affect the accuracy of the results of genetic diversity studies. in such cross-species contamination of fecal samples, the alleles obtained for the analysis could give false genotyping results resulting in allelic dropout or multiple alleles. in order to avoid such complications, developing basic knowledge of differentiation between species fecal samples becomes essential. the separation between individual gazelles fecal samples is also important in assessing the level of genetic diversity of the species. collecting scat samples from a spot scat of different gazelles are found and it is assumed that it belongs to one individual could result in higher estimates of heterozygosity. although the threats of gazelle populations in oman are continuous, the impacts of these threats on the fitness and genetic variation of these populations had not been assessed. it is therefore a matter of importance to assess the status of the genetic variation in the omani gazelle population. such assessment is not only important to guide policy makers to take appropriate actions today, but can be a reference point helping future researchers compare today’s genetic variation with their future findings. monitoring the genetic diversity of omani gazelles is crucial as it helps us to predict their future fitness, disease susceptibility and the levels of inbreeding (hedrick and garcia-dorado, 2016; szulkin et al., 2013). therefore, genetic diversity assessment is required for shaping policies in gazelles’ protection. the aim of this project was to determine population structure and genetic diversity of the arabian gazelles in dhofar using microsatellite dna markers. we utilized a non-invasive sampling approach in which we extracted dna from gazelles’ scat samples. our approach is the initial of its kind in assessment of genetic diversity in gazelles’ populations in oman. 37research article jashool, al-ansari, al-marzooqi, alqaisi, al-gahdhami, al-abri materials and methods collection and grading of faecal samples for dna extraction in this project, 110 gazelles’ feces specimens were collected from 69 locations from four different valleys in dhofar governorate stom, gara, ayon and solot (table 1). gazelles scat samples were located by tracing gazelles toe prints. gazelle toes prints are small footprints shaped like a longitudinal symmetrical cross section of an apple with clear med-line as shown in figure 1. the diameter of a scat pellet’s area is roughly 30 cm. in collection zones, different pellets from different gazelles usually exist in the same spot. therefore, in a cluster of feces, old or fresh samples can be found. however, only fresh scat pellets were sampled carefully from the top of any scat colony in order to best ensure they belong to the same individual. although we took this measure, it is still imperative to indicate that the samples number is not always reflective of the individuals’ number in a certain site since an individual can defecate at more than one spots within a location. we graded the gazelle’s faecal sample based on their color on a scale of a (fresh gazelle’s feces) to d (at least 5 days old feces). the colors of grades a to d samples ranged from dark black to white respectively as shown in figure 2. the difference in color is attributed to evaporation of moisture table 1. collection of scat samples in gazelles habitats for dhofar governorate. population valleys locations samples 1 solot 25 38 2 wadi ayon 11 14 3 wadi gara 18 29 4 wadi stom 15 29 total 69 110 and physicochemical changes the difference of plants species that gazelles graze on in different locations. the physical characteristics and grading of scat samples of various colors are given in table 2. samples collection was conducted in the same day and in any given location to limit the collection of scat from the same herd twice. this mitigated the chance of double sampling of the same individual as gazelles could migrate from one location to another especially during lack of water resources and competitions for pasture. the fecal samples were collected in plastic bags, labeled and preserved in a cool box and later frozen at -80°c until dna extraction. dna extraction pre-dna extraction, crusting of fecal samples was performed using sterile and disposable blades into 4 ml eppendorf tubes. for the extraction protocols in this project, we crusted the outer layer of 11 pellets from each sample for a total weight of 0.18 g to 0.22 g. in total, 913 pellets belonging to 83 fecal samples were crusted for dna extractions. dna extraction was performed using the qiaamp® human stool dna extraction protocol following the manufacturer’s procedure. dna concentration and purity were assessed using a nano-drop. polymerase chain reaction (pcr) fecal samples carry some compounds that inhibit pcr reactions. these compounds came from the soil, bile salts, complex polysaccharides, collagen, heme, humic acid, and urea. to overcome pcr inhibitors, 50% dmso and 10% bsa were used in an amount 2.5µl of total pcr volume. the composition of the master mix was used for amplifying various gazelle molecular markers. these were performed in 25 µl of total volume (1x) containing on average 25 ng/µl of dna, 200 µm of each dntp, 2 µm mgcl2, 5 pmol of each primer, 1-unit hot start polymerase, 2.5 µl of the same amount of both 50% dmso and 10% bsa. finally, 7.8 µl nuclease free water were added to complete the total pcr volume. the phases of pcr cycles started with 94°c for 7 min and ended with 72°c for 7 min and in-between cycles were as follows: (i) dna denaturation at 94°c for 30 s, (ii) primers annealing phase for 30 s (at a temperature chosen to be the lowest annealing temperature amongst both primers), and (iii) dna extension took place at 72°c for 30 s in presence of (taq) polymerase enzyme. fragment analysis a size standard “rox 400” (abi) (internal lean standard) was run concurrently in each capillary to create the standard curve. three markers (fam, hex and tamara) labeled with different dyes, were used to label the product of the 9 microsatallite markers shown in table 4. the markers were run in groups of three (a<b and c) according to the melting point, to reduces the required consumables and duration of analysis. the used composition of the master mix for each run is given in table 3. 10.1µl of the total volume were loaded in 96 figure 1. an image showing gazelles toe print on the soil. 38 squ journal of agricultural and marine sciences, 2021, volume 26, issue 2 characterization of genetic diversity in dhofari wild gazelles plate and centrifuged 500 rpm for 1 min. then, the plate was incubated at 95°c for 5 min and kept on ice for 1min before being centrifuged at 500 rpm for 1 min before genotyping using the abi genetic analyzer (model 3130xl). measures of genetic diversity and population structure the fixation index (f), inter-population differentiation (fst), hardy weinberg equilibrium (hwe) and principle component analysis (pca) were calculated using genalex v.6.51 (peakall & smouse, 2012). results fragment analysis out of the 110 dna samples extracted in this study, 74 samples yielded enough dna for successful genotyping and only four polymorphic microsatellite markers (bm4505, texan19, inra40, and bm415) were successfully amplified. for these markers, four population gara, solot (area between merbat and sadah), stom, and ayon were investigated. stutter peaks were carefully evaluated to avoid mistakes in allele sizing. genetic diversity a chi-square test of the hwe was performed at a α=0.05 with the null hypothesis (ho) that the distribution of sample markers followed hwe. the results indicated that there was no significant deviation from hwe in markers frequencies in two populations, gara and ayon. however, three markers in solot, and two in stom showed a significant deviation from hwe at α=0.05 as illustrated in table 5. although not all the loci were in hwe, we decided to include which are not at hwe due to the limitation of small sample size and the few markers used in this study. therefore, all four loci were used to evaluate the genetic diversity of the four population. the fixation index (f), mean and standard error (se) of sample size (n), no. alleles (na), effective alleles (ne), table 2. physical characteristics of fecal samples as graded in this study. grade a b c d color black/ green brown/black black/brown white moisture moist dry dry dry mucus presence yes no no no soil presence soil (crystals) sometimes no no scattered combined somewhat scattered very scattered table 3. composition of the master mix used. master mix 1x(µl) formamide 9.2 internal lean standard, rox dye 0.3 dna form three dilution mixes of labeled dyes of pcr results (2:2:3 or 2:2:4) 0.6 total volume 10.1 figure 2. gazelle fecal samples grades a (fresh) to d (oldest). 39research article jashool, al-ansari, al-marzooqi, alqaisi, al-gahdhami, al-abri observed heterozygosity (ho), and expected heterozygosity (he) and the genetic differentiation values (fst) for all the populations are presented in the tables 6 and 7, whereas the pca is shown in figure 3. table 4. multiplexes a, b, c: primer names, primers sequences, dye name and melting temperatures of various primers used in the study. # loci primer sequence (´5-> 3´) forward reverse dye tm c° a bm302 f-gaattcccatcactctctcagc r-gttctccattgaaccaacttca 5´ hex 58.4 sr-crsp6 f-catagttcattcacaatatggca r-catggagtcacaaagagttgaa 5´ fam 57.5 eth10 f-gttcaggactggccctgctaaca r-cctccagcccactttctcttctc 5´ tamra 66.4 b texan6 f-aggcagttaccatgaacctacc r-atcctggtgggctacagtctac 5´ fam 62.1 bm4505 f-ttatcttggcttctgggtgc r-atcttcacttgggatgcagg 5´ hex 58.4 texan19 f-ctgaaaccctcttattcaaattgtg r-tgcagagtcagataaaaatccc 5´ tamra 58.4 c oarfcb304 f-ccctaggagctttcaataaagaatcgg r-cgctgctgtcaactgggtcaggg 5´ fam 66.8 inra40 f-tcagtctccaggagagaaaac r-ctctgccctggggatgattg 5´ tamra 59.4 d bm415 f-gctacagcccttctggtttg r-gagctaatcaccaacagcaag 5´ tamra 59.4 table 5. summary of chi-square tests for hardy-weinberg equilibrium. the markers names, degree of freedom (df), chi-square value (chisq) and its probability are shown. population locus df chisq prob. gara bm4505 15 20.160 0.166 gara texan19 28 39.020 0.081 gara inra40 1 0.194 0.659 gara bm415 1 0.000 1.000 solot bm4505 3 6.000 0.112 solot texan19 36 56.525 0.016 solot inra40 21 67.089 0.000 solot bm415 3 20.989 0.000 solot bm4505 15 30.000 0.012 solot texan19 36 73.229 0.000 solot inra40 21 30.238 0.087 solot bm415 6 11.194 0.083 ayon bm4505 3 4.160 0.245 ayon texan19 28 48.333 0.010 ayon inra40 15 22.440 0.097 ayon bm415 1 0.141 0.708 table 6. mean and standard error (se) of sample size (n), no. alleles (na), no. effective alleles (ne), observed heterozygosity (ho), expected heterozygosity (he), and fixation index (f) for the populations. pop mean/ se n na ne ho he f gara mean 7.250 4.500 2.863 0.519 0.563 0.030 se 0.479 1.500 0.708 0.086 0.122 0.075 solot mean 21.250 5.500 3.127 0.248 0.617 0.595 se 6.223 1.500 0.651 0.118 0.106 0.152 stom mean 13.000 6.500 4.172 0.663 0.740 0.067 se 2.415 1.041 0.611 0.111 0.048 0.222 ayon mean 8.500 4.750 2.494 0.357 0.505 0.219 se 1.555 1.377 0.713 0.070 0.119 0.143 table 7. gazelle populations pairwise population fst values. gara solot stom ayon gara solot 0.000 stom 0.073 0.000 ayon 0.104 0.133 0.000 fst values below diagonal. fst=0 (panmixis), fst=0.01 (moderate diversity), fst<0.2 (high diversity). 40 squ journal of agricultural and marine sciences, 2021, volume 26, issue 2 characterization of genetic diversity in dhofari wild gazelles discussion the largest allele number obtained was in solot (21.25) followed by stom (13) and lowest sample size observed was in gara (7.25). however, the number of alleles only increased slightly as the sample size increased. the observed heterozygsity did not depart largely from the observed heterzygosity except for solot and ayon. the results of the fixation index (table 6) showed some degree of inbreeding in all the locations. however, it was the highest in solot (0.595) and lowest in gara (0.030). the fst values showed the presence of a clear population differentiation in our data with no panmixic populations (lower that 1%). the fst value between solot and stom populations was 7.3%, which indicates that the two populations are genetically close. this is also an indication that the two populations are near panmixia and might be undergoing random mating. the fst value between gara and ayon (23.1%) is a relatively higher genetic differentiation compared to that between other populations. this suggests that there was little interbreeding or migration between the two populations. the fst value between gara and stom was 7.1%, which was moderate and similar to the value between solot and stom (7.3%), while that between ayon and solot was 10.4%. however, the genetic diversity between gara and solot, was 14.5%, which was higher than ayon and solot. altogether, our results indicated a moderate to high genetic diversity in wild dhofar gazelle’s populations. in contrast, computing fst pairwise between two gazelles population (solot versus remaining populations) gives 3.7% of genetic diversity. taken together, our results show that all populations had a moderate genetic differentiation from one another. however, the levels of genetics differentiation found in this study are considered within the range reported for gazelle populations. in a previous study on wild gazelles of the southern levant, the pairwise fst between dorcas gazelles (arava) and acacia gazelles was found to be 30.9 % which is a relatively high genetic differentiation (hadas et al., 2015). principle components analysis of pc 1 vs pc 2 shown in figure 3a agreed with fst results and showed that gara and stom (lowest pairwise fst) were closer to each other compared to the rest of the populations. it also placed gara and ayon distantly from one another (highest pairwise fst). conclusion there was a low to moderate inbreeding levels and moderate to high genetic diversity in wild gazelles populations included in this study, which indicated higher within population mating and lower between populations mating. our genetic differentiation (fst) analysis showed that the highest differentiation was between gara and ayon (23.1%). the pca was in agreement with the genetic differentiation analysis and clustered gara and ayon further away from one another. in addition to that, the pca analysis clustered the populations according to their geographical distribution in the map with solot being further away from the other sampling locations. our study illustrates the successful utilization of noninvasive sampling in assessment of genetic diversity in wild gazelle populations in oman. nevertheless, additional markers and a larger sample size are required in order to get accurate estimation of population genetics parameters in future studies. alternatively, utilization of modern genotyping techniques such as genotyping by snps would ultimately yield more markers and increase the confidence and reliability of the results compared to microsatellites. figure 3. clustering of gazelle populations using principal coordinates analysis a (pc1 vs pc2), b (pc2 vs pc3) and c (pc1 vs pc3). 41research article jashool, al-ansari, al-marzooqi, alqaisi, al-gahdhami, al-abri acknowledgment we would like to thank the office for conservation of the environment, sultanate of oman for funding this study. we would also like to thank the following individuals for assisting this project: from the office for conservation of the environment: yasser al-salami, salim al-rabei, zaher al-alawi, mosleem al-amri, khalid al-hakmani, nasser zabanoot, suhail bait said and ali al-rasbi. from the ministry of environment and climate affairs: hamed al-wihaibi, mohammed al-sherieqi. from the minister of agriculture and fisheries, zaken, korea. references al hikmani h, zabanoot s, al shahari t, zabanoot n, al hikmani k, spalton a. (2015). status of the arabian gazelle, gazella arabica (mammalia: bovidae), in dhofar, oman. zoology in the middle east 61(4): 295–299. hadas l, hermon d, boldo a, arieli g, gafny r, king r, bar-gal, gk. (2015). wild gazelles of the southern levant: genetic profiling defines new conservation priorities. plos one 10(3): 1-18 (article e0116401). hedrick pw, garcia-dorado a. (2016). understanding inbreeding depression, purging, and genetic rescue. trends in ecology and evolution 31(12): 940-952. iucn. (2017). gazella arabica. http://dx.doi.org (accessed 5 july 2020). judas j, paillat p, khoja a, boug a. (2006). status of the arabian leopard in saudi arabia. cat news, iucn species survival commission, 1, 1–9. http://www. catsg.org (accessed 15 march 2020). king srb, schoenecker ka, fike ja, oyler-mccance sj. (2018). long-term persistence of horse fecal dna in the environment makes equids particularly good candidates for noninvasive sampling. ecology and evolution 8(8): 4053–4064. mallon d, kingswood s. (2001). global survey and regional action plans, antelopes, part 4: north africa, the middle east and asia. iucn publications services unit. margalida a, benitex jr, sanchez-zapata ja, avila e, arenas, r, donzar ja. (2012). long-term relationship between diet breadth and breeding success in a declining population of egyptian vultures neophron percnopterus. ibis 154(1): 184–188. massolo a, spalton a, al-lamki f. (2008). notes on the status and conservation of the reem gazelle gazella subgutturosa marica in the sultanate of oman. italian journal of zoology 75(3): 305–309. murphy ma, kendall kc, robinson a, waits lp. (2007). the impact of time and field conditions on brown bear (ursus arctos) faecal dna amplification. conservation genetics 8(5): 1219–1224. peakall r, smouse pe. (2012). genalex 6.5: genetic analysis in excel. population genetic software for teaching and research—an update. bioinformatics 28(19): 2537–2539. szulkin m, stopher kv, pemberton jm, reid jm. (2013). inbreeding avoidance, tolerance, or preference in animals? trends in ecology & evolution 28(4): 205–211. taberlet p, waits lp, luikart g. (1999). noninvasive genetic sampling: look before you leap. trends in ecology & evolution 14(8): 323–327. research paper journal of agricultural and marine sciences 2022, 27(2): 19–27 doi: 10.53541/jams.vol27iss2pp19–27 received 31 october 2021 accepted 16 february 2022 analysis of shoreline change along the coast of the wadi al ma’awil watershed, oman, using the digital shoreline analysis system amna al ruheili* amna al ruheili*( ) alruheli@squ.edu.om, department of plant sciences, college of agriculture and marine science, sultan qaboos university, muscat, oman. introduction the coastal zones provide both environmental and economic assets for a country. coastal regions are dynamic systems that undergo key changes because of natural and anthropogenic factors. to maintain a coastal zone, regular sediment input for the deltas is necessary because the sediment maintains the deltas’ surface elevation, thereby contributing to reduced salinization, erosion, and flooding. failure to transport sediment to the coastal plains and deltas increases the vulnerabilities that arise from sediment starvation and the land sinking (wang et al., 2018). more than 95% of ocean sediments come from water streams (syvitski, 2003). the sediments carried by the water streams lead to the formation of deltas and development of coastal zones (rao et al., 2010). however, deltas can be threatened by the changes in land use in upstream catchments and reservoir construction. these developments can impact the fluvial sediment inputs downstream and result in sediment starvation (dunn et al., 2018; kondolf, rubin and minear, 2014). bird (1985) reported that most of the beaches in the world (about 70%) experience erosion because construction of reservoirs and dams in rivers prevent 20% of the global sediment from reaching the coast (syvitski et al., 2005; li et al., 2018). a study conducted by syvitski et al. (2009) showed that in recent decades, construction of reservoirs has prevented 20 to 100% of the global sediment from reaching the deltas. moreover, there has also been a huge fall in river sediment loads in about 50% of the world’s rivers and dams. this is probably an important factor that determines sediment fluctuations between land and ocean حتليل تغري اخلط الساحلي على طول ساحل مستجمعات مياه وادي املعاول،عمان، ابستخدام نظام حتليل اخلط الساحلي الرقمي أمنة الرحيلية* abstract. in an arid climate, lack of water constitutes a challenge. one solution can be to use storage dams as a tool to facilitate groundwater recharge and provide water for various uses. however, dams cannot be constructed without affecting the environment of the coastal shoreline and its ecological habitats. this study investigated the structural changes (i.e. accretion or erosion) of the coastline along the wadi ma’awil watershed. the wadi ma’awil watershed was dammed in 1991, providing a 10m m3 dam capacity. satellite images were obtained for 1972, 1984, 1994, 2008, 2014, and 2018, and coastlines were digitized. for this research, we employed the digital shoreline analysis system (dsas) to calculate the rate of coastline movement and the changes arising from dam construction or anthropogenic changes to the beach. the results showed that from 1972 to 2018, the shoreline experienced erosion of up to -0.70 m/yr for 56% of the watershed coast. this loss could result in remarkable coastal change. this study can be used by urban planners as support for the importance of preserving natural resources and ecological habitats. keywords: coastal erosion, ma’ awil watershed, dam, accretion. املستخلص:يشــكل نقــص امليــاه يف مناطــق املنــاخ اجلــاف يشــكل حتــدًي كبــرا. وتعتــر ســدود التخزيــن مــن أحداحللــول املســتخدمة لتســهيل إعــادة تغذيــة امليــاه اجلوفيــة وتوفــر امليــاه لالســتخدامات املختلفــة. ومــع ذلــك ، ال ميكــن بنــاء الســدود دون وجــود أتثــر علــى بيئــة الشــواطئ الســاحلية ومواردهــا البيئيــة. اســتقصت هــذه الدراســة التغــرات الــي تتمثــل يف عمليــات الرتاكــم أو التعريــة للخــط الســاحلي علــى طــول مســتجمعات امليــاه يف وادي معــاول. حيــث مت بنــاء ســد مســتجمعات املياهاجلوفيــة يف وادي معــاول يف عــام 1991 ، ممــا وفــر 10 مليــون مــرت مكعــب مــن امليــاه كمخــزون يف الســد. اســتخدمت هــذه الدراسة عددا من صور األقمار الصناعية لألعوام 1972 و 1984 و 1994 و 2008 و 2014 و 2018 ، ومت رقمنة اخلطوط الساحلية ملنطقة الدراســة. واســتخدم هــذا البحــث حتليــل اخلــط الســاحلي الرقمــي )dsas( حلســاب معــدل حركــة اخلــط الســاحلي والتغــرات الناشــئة عــن بنــاء الســدود أو التغيــرات البشــرية علــى الشــاطئ. أظهــرت النتائــج أنــه مــن عــام 1972 إىل عــام 2018 ، شــهد اخلــط الســاحلي آتكاًل يصــل إىل -0.70 م / ســنة لـــ 56 ٪ مــن ســاحل مســتجمعات املياه.حيــث ميكــن أن تــؤدي هــذه اخلســارة الــي نتجــت مــن حجــب وصــول الرواســب اىل اتمناطــق الســاحلية إىل تغيــر يف اخلــط الســاحلي بشــكل ملحــوظ.و ميكــن اســتخدام نتائــج هــذه الدراســة مــن قبــل املخططــن احلضريــن كأداة تدعــم التخطيــط العمــراين كصديــق للبيئــة و تعزيــز االهتمــام و احلفــاظ علــى املــوارد الطبيعيــة واملــوارد البيئيــة. الكلمات املفتاحية: آتكل الساحل , مستجمع وادي املعاول , السد , الرتاكم. 20 squ journal of agricultural and marine sciences, 2022, volume 27, issue 2 analysis of shoreline change along the coast of the wadi al ma’awil watershed, oman, using the digital shoreline analysis system (li et al., 2018; syvitski and milliman, 2007). sediment load plays an important role in assessing the quality of the environment, and it allows researchers to evaluate the level of potential impact on the ecosystem (khanchoul et al., 2012). sediment is known to play a very important role in maintaining and developing coastal habitats and their ecosystems, which include wetlands, lagoons, coral reefs, mangrove swamps, dunes, and sand barriers (kotti et al., 2018). the construction of large dams has increased scholars’ debate about the environmental impact of such structures because such dams decrease the rates of sediment delivery downstream, indirectly enhancing coastal erosion and decreasing habitat heterogeneity (chang and chuang, 2018; rao et al., 2010; syvitski, 2003; tealdi et al., 2011). according to a study by vorosmarty et al. (1997), about 30 to 40% of the sediment that would have been taken to the areas along the coast through the river systems was retained by man-made structures. the changes downstream were obvious and clearly arose from the shift in sedimentation deposits, which affected the morphology of the fluvial system (ma et al., 2012). in another example, the mekong river delta shoreline showed acceleration in erosion that was related to human-induced modifications such as dam constructions (besset et al., 2016; li et al., 2017; anthony et al., 2015; van manh et al., 2015). since the construction of the aswan dam on the nile, moreover, the coastal area lost 98% of its sediment input and showed an increased erosion that impacted its coastal ecosystem (giosan et al., 2014; kim and sultan, 2002; syvitski, 2003; syvitski et al., 2009). moreover, the construction of the three gorges dam led to 65% of the sediment load in the yangtze river being lost (yang et al., 2014). in tunisia, inspection carried out after the mejerda dam was built showed an alarming narrowing of waterbeds downstream from the dam (zahar et al., 2008). furthermore, the amazon river basin showed environmental and ecological distress resulting from the dam construction upstream. this construction resulted in a lack of sedimentation input that changed the downstream area (latrubesse et al., 2017). satellite images and gis data are important because they give us early estimates of shoreline change. both these sources give us a good database for digitizing shoreline positional information which helps researchers to calculate the rates of historical change at the selected sites. the statistics estimated the speed of shoreline change gave us a cumulative summary of the processes that had affected the coast (dolan et al., 1991). varying sets of data can be used to assess coastal changes. the importance of this data depends on the way in which it was obtained (dolanetal., 1991; polk and eulie, 2018). this study used end point rates (epr) and net shoreline movement (nsm) to calculate the speed of change of the coastline (thieler et al., 2012). the study objectives were: (i) to find the definitions of the accretion and erosion areas, and (ii) to evaluate the speed at which shoreline was changing. materials and methods study site the research area is situated in northern oman in the al batinah region along the oman sea. the coastal plain is narrow in shape at the northwestern and southeastern ends, and widens in the middle to a breath of around 50 km (hayes and baird, 1993). the geology of al batinah coastal region is composed of a tectonically emplaced late paleozoic and mesozoic continental margin and tethys deep sea sediments known as samail ophiolites (robertson et al, 1990). the local winds rarely exceed 10 knots at 10 m height with upwelling appearing as short irregular events (vic et al., 2015). the coast of al batinah is mesotidal and tide-dominated. it has low wave energy and a limited littoral drift of less than 100,000 m3/ year (kwarteng et al., 2016). the coastal plain has alluvial fans that have undergone the process of sedimentation that varies from gravel, coarse sands to fine sands and silt near the coast (al hatrushi et al., 2014). as a result, the plains along the coast are known for their high fertility, and that has resulted in heavy urbanization including agriculture and fishing activities (al-hatrushi, 2013). the coastal shore of the wadi ma’awil watershed is located south of the coastal town of barka. this area has small periodic (tidal) currents and a stronger flow (more relevant for sediment transport) occurs during a-periodic events that last several days (bruss et al, 2018). the watershed has many wadis that flowed directly into the coastal area before they were dammed. the mean tidal range is 3.65 meters (m) (onho, 2018). the amount of yearly discharge of the catchment is estimated at 21.1 mm3/yr (wilson, n.d.). the ma’awil dam was constructed in 1991 as a ground water recharge dam with a capacity of 10 mm3 (mrmwr, 2012) as shown in figure 1. the study area coastline stretches for about 25 km and has a gentle foreshore slope that ranges between 0.6 and 0.7%. study approach this study went through three phases. first, various satellite images from different years were obtained (see table 1). second, the band combination shortwave infrared: near infrared: red was used to emphasize the difference between land and water, after which the coastline was digitized, followed by determination of shoreline rates of change. historical shoreline analysis the information on changing shoreline was based on satellite images (1972, 1984, 1994, 2008, 2014, 2018) spanning a period of 46 years (see table 1). the images were obtained from the usgs global visualization viewer (http://glovis.usgs.gov) with their multicolored bands with a resolution of 30m×30m for pixel size, except for 21research paper al ruheili sentinel at 15×15m pixel size. all the image data used were geometrically corrected based on the universal transverse mercator (utm) projection system—zone 40n using arcgis software 10.5.1 to attain less than 20 m accuracy of absolute planimetric (fossi-fotsi et al., 2019). there are numerous possible errors involved in deriving shoreline data and such errors can affect the accuracy of the computed rates in the modeling. many studies have come up with estimates of the typical measurement errors that can happen during using mapping methods and shoreline digitization (anders and byrnes, 1991; moore, 2000; mortonetal., 2004). shoreline extraction requires geo-referencing maps and subsequently interpreting and digitizing a shoreline position. this study implemented fossi-fotsi et al. (2019) approach in measuring the uncertainty in coastal extraction with some modifications to calculate the annualized error (table 2). the band combination of infrared: near infrared: red is used to best display the contrast between land and water boundaries to identify the shoreline in satellite images. the band combinations were done in arcgis 10.5.1. the purpose of using the band combination was to optimize the difference between land and water to facilitate digitization. the shorelines were manually and visually checked and reviewed to reduce errors. digital shoreline analysis system (dsas) for the purpose of this study, we used the digital shoreline analysis system (dsas) version 4.4, developed by the united states geological survey (usgs), to evaluate the speed of shoreline changes. the dsas can be added as extension to arcgis 10.5 software. the dsas can compute the rate of change statistically from multiple historical shoreline positions. the dsas multiple statistical approaches, including the end point rate (epr), net shoreline movement (nsm), and linear regression rate (lrr), were all used to calculate the shoreline change (thieler et al., 2012). the lrr was used to measure rate of shoreline change because it is widely believed that it is the most statistically robust quantitative method while dealing with a limited number of shorelines (addo et al., 2008). after the completing the digitization of the coastline of the wadi al ma’awil watershed, the dsas was used to calculate the speed of coastline change and erosion. the analytical process involved four steps: (i) shoreline preparation represented by vectors data extracted from satellite images; (ii) baseline creation, onshore or offshore; (iii) transect generation; and (iv) computation of the speed of shoreline change (thieler et al., 2012). the software gave us transects along the shoreline which were cast perpendicular to the baseline with spetable 1. list of used satellite images satellite year path/row landsat 1-5 mss october 22, 1972 170/44 landsat 4-5 tm october 8, 1984 158/44 landsat 4-5 tm october 20, 1994 158/44 landsat 5 tm november 11, 2008 158/44 landsat 8 oli tirs october 11, 2014 158/44 sentinel-2a october 23, 2018 tile #: t40qem figure 1. study site, (a) oman boundary, (b) wadi channels of al ma’awil watershed. 22 squ journal of agricultural and marine sciences, 2022, volume 27, issue 2 analysis of shoreline change along the coast of the wadi al ma’awil watershed, oman, using the digital shoreline analysis system cific spacing measurements that are chosen by the user. after that, the points where the transect shoreline intersected with the baseline were used to calculate the speed of change statistics. during the course of this research we found that the dsas program generated 3,816 transects with a 25 m spacing and 900 m length. these were perpendicular to the baseline located offshore at an 870 m length along the coast figure 2. rate of shoreline change the end point rate (epr), the least median of squares (lms), and the net shoreline movement (nsm) were utilized to calculate the shoreline changes. the epr measured through the distance division of the moved shoreline between the earliest and latest measurements at each transect by the elapsed time. the lms was calculated by using the median value of the squared residuals instead of the mean in the lrr model to determine the best-fit equation for the line to all shoreline points for a specific transect. the nsm was associated with the dates of only two shorelines and it reported the distance between the oldest and youngest shorelines for each transect. the lrr was determined by fitting a least squares regression line to all the comparable shore points of different periods for a particular transect, using a confidence interval of 95.0% (thieler et al., 2012). positive values of epr and lrr stand for sediment accretion through shoreline movement towards the sea, while negative values indicate erosion and shoreline movement towards the land. results and discussion in coastal areas, the shoreline is very dynamic as it undergoes rapid changes. waves and currents are the primary causes that lead to sediment re-suspension (rajaee et al., 2009). the coastal areas provide a wide range of ecosystems that are critical to coastal resiliency and to economic development (polk and eulie, 2018). both natural coastal processes and human interference are the main factors affecting shoreline change (sheik, 2011). frequent monitoring to detect shoreline changes is therefore important if we want to understand the processes and dynamic features of coastal areas. the speed of change along the shoreline was calculated using the dsas software and three different statistical techniques: end point rate (epr), the least median of squares (lms), and the linear regression rate-ofchange (llr). the most significant changes were observed between 1972 and 1984, and between 2014 and 2018, when the shoreline was retreating at a rate of 1.6 m/year. the change between the period 1972 and 1984 could be attributed to the starting of development in oman, and the country movement toward urbanization and modernity. while the period between 2014 and 2018 were subjected to various cyclones and storms events that could contributed to higher erosion. a summary of the statistics for the rate of change are given in table 3. about 600 transects were used to evaluate the rate of shoreline change along the coastline of the wadi al ma’awil watershed for a short distance of 25 km. this has been shown in figure 2. the epr, lms and llr measured the rate of shoreline change based on differences between shoreline positions across time. the reported rates were expressed as meters of change along transects per year. the values of epr and llr for the research area from1972 to 2018 are presented in figure 3. the dsas rate-of-change models for 1972–1984, 1994– 2008 and 2014–2018 are represented in figure 4. the table 2. shorelines estimated and annualized error variables 1972 1984,1994 2008,2014,2018 digitizing error 15.3 6.3 planimetric error (ep) 35 25 20 total error (et) 40.3 29.3 21 table 3. statistics for the rate of change year variables 1972–1984 1994–2008 2014–2018 epr mean mobility shoreline change (m/year) -1.60 0.60 0.66 erosion trend (m/yr) -2.59 -1.77 -0.72 & % 73 % 28 % 93 % accretion trend (m/yr) 1.24 1.52 0.20 & % 27 % 72 % 7 % total transects that record accretion 183 478 68 total transects that record erosion 490 86 594 b. dist. from coastline (m) 230 237 400 23research paper al ruheili epr-model and the lrr-model show the shoreline point data that has the most confidence, with transects running perpendicular to the shoreline. it is clear that the positive and negative rates of change in figure 4 show that both accretion and erosion are taking place on the coast. table 2 gives us a summary of the speed of shoreline change as averages of all the changes, including both erosion (shown by the negative numbers) and accretion (shown by the positive numbers), and as averages of only the erosion values and only the accretion values. it would appear that some coastal area is being lost. this could be due to natural changes in the coastal system, or caused by human activities such as agriculture, irrigation and the building of dams. for example, dam construction could trap sediments in the upstream area in which obstruct the natural movement of sediments to the downstream area resulting in less nourishment for the coastal area (al-ismaily et al., 2013). figure 2. shoreline of the study area. figure 3. variations in the rates of shoreline change (in meters) calculated using the dsas program, alternating between erosion and accretion 24 squ journal of agricultural and marine sciences, 2022, volume 27, issue 2 analysis of shoreline change along the coast of the wadi al ma’awil watershed, oman, using the digital shoreline analysis system the coast of the wadi al ma’awil watershed was studied at various intervals in the years 1972-1984, 1994-2008, and 2014-2018. in 1972 through 1984, the net speed of erosion averaged over 490 transects was -2.59 m/yr. the accretion trend was around 1.24 m/yr for 183 transects. in the period 1994–2008, 86 transects accounted for an1.77m/yr erosion rate, and a 1.52 m/yr accretion rate was present for 478 transects. for 2014-2018, the coastal erosion rate was found to be -0.72 m/yr and the speed at which accretion was taking place was 0.20 m/ yr. these smaller numbers could be related to the shorter period span. the movement of building recharge dams in oman have contributed to shoreline changes. as stated by al-ismaily et al. (2013), dam construction in al khoud had limited coastal plains enrichment with silt and sediments that the wadies carry downstream to the valley. other study carried by graf (2006) indicated dam effect on river discharge, and sediment load that resulted in a quasi-equilibrium state of the river, altering the channel form. therefore, the transposition of sediment and its redistribution play a major role in determining the geology, biology, and chemistry of fluvial ecosystems and coastal area. overall, this research clearly showed that erosion and accretion have led to structural changes at the coastal shoreline of the wadi al ma’awil watershed. the results also indicated that during 1972–1984 and 2014–2018, shoreline erosion increased. the highs and lows recorded are given in table 3. the shoreline experienced the greatest shoreline changes, with an nsm of 429 m, during the period 1994–2008. the sudden and rapid rate of shoreline change during this period may be due to beach nourishment activities and building of the port at barka. moreover, in 2007, a major cyclone hit the area and contributed to coastal accretion. in fact, all along al batinah coast the most severe erosion and sediment deposition occur during major storms events (kwarteng et al., 2016). shoreline changes for the period between 1972 and 1984 were more variable, with most of the coastline being affected by erosion and only a few areas being stable. it was observed that between 1994 and 2008 the shoreline accreted in comparison with the period between 1972 and 1984, and also the period between 2014 and 2018 and this could be attributed to coastal nourishment activities. however, beach nourishment along louisiana beach, usa, showed a temporal ability in serving as a beach barrier, but due to, wave and current action the shoreline retreated and the coastal vulnerability has increased (cohen et al., 2021). the research area had an average epr of -1.60 m/yr and an nsm average of -18.6 m between 1972 and 1984. however, the period of 2014–2018 also showed that erosion was taking place, with an epr of -0.66 m/yr and an nsm average of -44 m, the coastal erosion could be attributed to cyclone phet in 2010. for example, there are some studies indicated the impact of natural hazards and cyclone on beach erosion (al ruheili and boluwade, 2021). this only happened for four years, and it is anticipated that the average epr can increase with longer spans. it should be noted that, during the coastal nourishment that related to coastal development, huge amounts of sediments were discharged along coastfigure 4. dsas rate of change models in meters (a, b, c) epr-model; (d, e, f) lms-model for 1972–1984, 1994–2008 and 2014–2018, respectively. 25research paper al ruheili al areas. the fast changes or the variations in shoreline change rate show that the dynamics of shoreline are being shaped by both natural processes and man-made activities along the wadi mawil shoreline. conclusion many researchers have studied the consequences that the naturaland human-induced activities cause on shoreline change. change can be the result of natural processes. waves, currents, geology, variations in sea level, and storms can all contribute to shoreline changes (zhu et al., 2018). in addition, human interference can also contribute to coastal erosion through by constructing dams, or urbanizing the beaches and thus changing the hydrological cycles (bheeroo et al., 2016). coastal geology also has a very important role in changing shorelines. the wadi mawil coastal area is marked by various coastal landforms, such as bays, beaches, and sand dunes. this study shows that the coastal area of wadi mawil is vulnerable to coastal erosion due to low-lying sandy beaches and dunes. the sediment transport depended on natural process and climatic factors that influence the nature of waves. the strength of these waves contributed to the amount of sediment transported, to erosion, and to accretion, all of which result in shoreline changes (manjulavani et al, 2017). the sedimentation brought to the coastal area by wadis, rivers, tides, and winds through natural processes can be the most important factor in determining the shape of the coastline (van rijn, 1993). the amount of the sediment deposited on the coast determines its appearance, creating sand dunes and beaches, mangrove swamps, and mudflats (storlazzi and field, 2000). most studies, to date, have indicated that the growth of the coastal region is associated with sedimentary processes which contribute to the coastal geomorphology (pranzini et al., 2013). for example, islands in the indian ocean have eroded due to a shortage of sediment on the shoreline (mujabar and chandrasekar, 2011). during the period from 1994-2008, north oman experienced cyclone gonu (2007) and that resulted in accretion due to the abnormally high quantity of sediment discharged through the wadi and storm surge. however, now the coastal area is showing signs of erosion, due to a shortage of sediment that could be related to disruption of the natural process. sediment discharges from wadis have been reduced due to various factors such as dam construction, coastal developmental and encroachments. this makes the rest of the sandy beaches in the area more susceptible to erosion. the changing shoreline is very important to efforts to calculate the spatial dynamics of the wadi al ma’awil coastal system. the al ma’awil coastline is threatened by erosion that may contribute to ecological and economic loss along its coastal zone. human factors, such as sand extraction from beaches, reclamation of land for agricultural use, and the damming of wadis, have modified the system flows and have contributed to coastal erosion. reduced sediment supply caused by damming the wadi flow has also led to more loss and damage of coastal habitats, including beaches and mangrove swamps. the sediment supply to the coastal area has been trapped by the dams that have been constructed. this research shows that the wadi mawil watershed is being eroded due to this impediment of the natural process and as a result of the modification of the hydrological processes that occurred in the study area after the dam was constructed in 1991. the wadi mawil coast now faces an additional, urbanization problem as new port and tourism developmental projects take place along the coast. building artificial barriers increases erosion along the wadi mawil coast. accurate coastline identification conducted using landsat and sentinel satellite images is a useful approach given the moderate spatial resolution and good spectral resolution provided by these tools, which helped in defining the shoreline. coastal accretion was most significant in the period 2008–2014, possibly because of the ports that were being constructed during that time. coastal erosion was also dramatically apparent in some parts of the study area in 1972–1984 and 2014–2018. erosion was observed at 73%, 28%, and 93% for 1972–1984, 1994–2008, and 2014–2018, respectively. the coastline is deteriorating at an average rate of -2.59 m/year, -1.77 m/year, and -0.72 m/year, respectively. the overall average of the epr for the entire coast is accreting at the rate of 0.50 m/year. the research area has natural as well as economic importance for agriculture and drainage, but damming the wadi modified the watershed regime and contributed to coastal change. the dsas shoreline change analysis showed that erosion was taking place in the area being studied. natural processes as well as human interference have changed the shoreline of the study area through erosion and accretion. the coastal zones of the wadi mawil watershed, have accretion due to sediment deposition during the 2007 cyclone gonu storm surge and wadi flash flooding. however, dams have stopped the transportable 4. shoreline highs and lows at wadi al ma’awil variables nsm (max) nsm (min) nsm (avg) epr (avg) 1972–1984 54.53 -400 -18.6 -1.60 1994–2008 429 -332 8.3 0.60 2014–2018 46.65 -749 -44 -0.66 26 squ journal of agricultural and marine sciences, 2022, volume 27, issue 2 analysis of shoreline change along the coast of the wadi al ma’awil watershed, oman, using the digital shoreline analysis system tation of sediments which in turn led to erosion in the coastal areas. this research clearly shows that proper beach filling and nourishment should be made along the coast to protect the coastal area from severe hazards. this can also help restore the area. it further explicates that local managers and decision-makers should take into consideration the impacts of dams on shoreline erosion. it is clear that such construction significantly contributes to changing the ecosystems and the habitats of the coastal zone. the study also documents that the dsas can come up with important data which can help us in determining shoreline erosion and accretion. conflict of interest this research has no conflict of interest. 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(2018). properties of suspended sediment concentrations in the yellow river delta based on observation. marine georesources & geotechnology 36(1): 139-149. research paper journal of agricultural and marine sciences 2020, 25(1): 39–47 doi: 10.24200/jams.vol25iss1pp39-47 reveived 07 oct 2019 accepted 01 mar 2020 fish consumption and knowledge of chemical pollutants among a sample of new mothers in tripoli, libya thuraya a. abuhlega1,*, huria m. maamar1 thuraya a. abuhlega1,*( ) t.abuhlega@uot.edu.ly, food science & technology dept., fac. of agric., university of tripoli, tripoli, libya, 1 food science and technology dept., faculty of agriculture, university of tripoli, libya introduction the presence of fish in the diet is very important be-cause it is a source of proteins, vitamins, minerals and unsaturated essential fatty acids, especially omega-3 fatty acids. omega-3 fatty acids have activity against cancer and prevent heart disease and atherosclerosis (abuhlega and hassan, 2017). the amount of polyunsaturated fatty acids consumed during pregnancy is associated with the reduced preterm delivery, low risk of under development within the womb, and high blood pressure during pregnancy (dovydaitis, 2008). omega-3 fatty acids also play an important role in the growth of the embryos, especially docosahexaenoic acid, which is an important component of the neural and retinal membranes and accumulates in the brain during pregnancy and the postpartum period (cetin and koletzko, 2018). on the other side, fish may be a source of various استهالك األسامك واملعرفة بامللوثات الكيميائية لدى عينة من األمهات الجدد يف طرابلس ، ليبيا ثريا احمد ابوحليقة و حورية مسعود معمر abstract. fish and fish products are important sources of nutritional elements, especially iodine and unsaturated fatty acids (omega-3). these are essential for pregnant women and their embryos during a pregnancy period. however, women and their embryos may be exposed to chemical pollutants when they consume fish. therefore, this study aimed to assess the consumption pattern of fish during pre-pregnancy, pregnancy and post-pregnancy periods, and explore the awareness on the chemical pollutants in fish among the women who recently gave birth in tripoli city, libya. this study targeted 370 women randomly in tripoli city and collected data through a face to face questionnaire. the questionnaire consisted of three parts: characteristics of new mothers; consumption of fish, crustaceans, mollusks and canned fish; and knowledge on the importance and risks of eating fish and fish products. the results showed that eating fish, crustaceans, and mollusks once a month was the highest proportion in the three periods with a percentage of 38, 38 and 41%, respectively. sardine, sea bream and mackerel were the most fish common consumed by new mothers during the three periods. more than half of the mothers did not change the pattern of their consumption of fish, crustaceans and/or mollusks during pregnancy as compared to the pre-pregnancy period and after the birth of their children as compared to the pregnancy period. the canned tuna was the most canned fish consumed by respondents (93%). more than half of mothers realized that eating fish is important for health in general and for pregnant women with a percentage of 58 and 59%, respectively. the results of this study showed that there was a great need to raise the awareness of new mothers about chemical pollutants in fish. furthermore, effective programs should be adopted by the competent authorities to educate mothers about what types and amounts of fish they should consume during pregnancy and the types that should be avoided. keywords: pregnancy; mothers; environmental pollutants; libya; seafood امللخــص: تعتــر األســامك واملنتجــات الســمكية مــن املصــادر الهامــة للعنــارص الغذائيــة، وخاصــة اليــود واألحــامض الدهنيــة غــر املشــبعة )أوميغــا 3(. التــي تعتــر رضوريــة للنســاء الحوامــل وأجنتهــن خــالل فــرة الحمــل. ومــع ذلــك، قــد تتعــرض النســاء وأجنتهــن للملوثــات الكيميائيــة عندمــا يســتهلكن األســامك. لذلــك، تهــدف هــذه الدراســة إىل تقييــم منــط اســتهالك األســامك خــالل فــرات مــا قبــل الحمــل والحمــل ومــا بعــد الحمــل، واستكشــاف الوعــي حــول امللوثــات الكيميائيــة يف األســامك بــن النســاء الــاليئ ولــدن مؤخــراً يف مدينــة طرابلــس، ليبيــا. اســتهدفت هــذه الدراســة 370 امــرأة بشــكل عشــوايئ يف مدينــة طرابلــس وجمعــت البيانــات مــن خــالل اســتبيان وجهــاً لوجــه. يتكــون االســتبيان مــن ثالثــة أجــزاء: خصائــص األمهــات الجــدد؛ اســتهالك األســامك والقرشيــات والرخويــات واألســامك املعلبــة؛ واملعرفــة بأهميــة ومخاطــر تنــاول األســامك واملنتجــات الســمكية. أظهــرت النتائــج أن تنــاول األســامك والقرشيــات والرخويــات مــرة واحــدة يف الشــهر كان أعــى نســبة يف الفــرات الثــالث بنســبة 38 و 38 و 41 ٪ عــى التــوايل. كانــت أســامك الرسديــن والوراتــة واملاكريــل أكــر األســامك التــي تســتهلكها األمهــات الجــدد خــالل الفــرات الثــالث. مل تغــر أكــر مــن نصــف األمهــات منــط اســتهالكهن لألســامك والقرشيــات و / أو الرخويــات أثنــاء الحمــل مقارنــًة بفــرة مــا قبــل الحمــل وبعــد والدة أطفالهــن مقارنــًة بفــرة الحمــل. كانــت أســامك التونــة املعلبــة أكــر األســامك املعلبــة التــي تســتهلكها االمهــات )93٪(. أدرك أكــر مــن نصــف األمهــات أن تنــاول الســمك مهــم للصحــة بشــكل عــام وللحوامــل بنســبة 58 و 59٪ عــى التــوايل. أظهــرت نتائــج هــذه الدراســة أن هنــاك حاجــة كبــرة لرفــع وعــي األمهــات الجــدد بامللوثــات الكيميائيــة يف األســامك. عــالوة عــى ذلــك، ينبغــي اعتــامد برامــج فعالــة مــن قبــل الســلطات املختصــة لتثقيــف األمهــات بشــأن أنــواع وكميــات األســامك التــي يجــب أن يســتهلكنها أثنــاء الحمــل واألنــواع التــي ينبغــي تجنبهــا. 40 squ journal of agricultural and marine sciences, 2020, volume 25, issue 1 fish consumption and knowledge of chemical pollutants among a sample of new mothers in tripoli, libya chemical pollutants that can cause harmful effects on human health especially pregnant women and their embryos. the chemical pollutants include persistent organic pollutants, including mercury, polychlorinated biphenyls and dioxins (costa, 2007; mdh, 2012; and jacobs jr et al., 2014). mercury is mainly found in the organic form methylmercury (mehg). the mehg can have neurotoxic effects if ingested in sufficient quantities and accumulated in fish from contaminated aquatic environments (balshaw et al., 2007 and strain, 2014). it is a strong neurotoxin that is known to impair infant neuronal growth (strain, 2014). fetal exposure is associated with maternal exposure (dariush mozaffarian and rimm, 2006). the fetus is susceptible to the toxic effects of mercury because of its possible transmission from the placenta (taylor et al. 2018). it was found that mothers who highly consume fish during pregnancy may be exposed to mehg, which may negatively affect the development of the fetal brain (strain, 2014). in the 1950s, children developed neurodevelopmental abnormalities, because their mothers ate highly contaminated fish containing 10-30 ppm of mehg caught from industrially polluted minimata bay, japan (dariush mozaffarian and rimm, 2006). environmental pollution is the main source of mercury in aquatic organisms and its concentration in fish tissues depends on the type and age of fish (dariush mozaffarian and rimm, 2006). the tissues of large and long-lived predatory fish such as swordfish, and shark contained higher concentrations of mehg while small and short-lived fish such as shellfish, salmon contained lower concentrations (dariush mozaffarian and rimm, 2006). many studies have been conducted to evaluate the mercury level in fish and aquatic environments in libya. banana et al. (2016) found that the fish at farwa lagoon is heavily contaminated with hg2+ and hg2+ concentrations exceeded the levels provided by international standards (0.34-3.13 μg/g). similarly, al-asadi (2018) found that the concentration of total mercury in fish muscle ranged from 0.176 and 3.586 μg/g as a result of industrial wastes of the chlorine-alkali plant at abo-kamash area, west of libya. the state of libya is located on the southern shore of the mediterranean with a coastline of about 2000 km. tripoli is the most important city overlooking it and its population gets fish from local fishing as well as from imported fish. the estimated per capita fish consumption in libya 21.4 kg/year (abuhlega and hassan, 2020). several countries have provided guidance regarding the types of fish that a pregnant woman should consume during pregnancy and the types that should be avoided, ensuring that the fetus gets omega-3 fatty acids and harmful effects of mercury element on the neurodevelopment of the fetus can be avoided (verger et al., 2007; oken & bellinger, 2008 taylor et al., 2018 and epa & fda, 2019). the epa and fda advised women and young children as followed: (i) do not eat shark, swordfish, king mackerel, or tilefish, because they contain high levels of mercury, (ii) eat up to 12 ounces (2 average meals) a week of a variety of fish and shellfish that contains lower mercury, such as shrimp, canned light tuna, salmon, pollock, and catfish (aep and fao, 2019). pregnant women need to raise awareness and guidance on fish consumption in terms of increased fish intake and reduced exposure to mehg (connelly et al., 2013). however, intensive recommendations confirming that fish are a source of mehg and it is contributed to the reluctance of pregnant women to eat fish despite their high nutritional value. therefore, awareness of the risks and benefits of fish consumption should be raised using different communications with the pregnant women and should advise them to help choosing the safer fish based on scientific evidence (starling et al., 2015). it was mentioned that pregnant women reduced fish consumption including tuna, dark meat fish, and white meat table 1. characteristics of the responding mothers characteristics of the sample number percentage age <18 1 0.30 18-22 37 10.0 23-27 98 26.5 28-32 101 27.3 33-37 80 21.6 38-42 46 12.4 > 42 7 1.90 educational level uneducated 3 .8 basic education 35 9.5 secondary education 91 24.6 university education 237 64.0 ma / phd 4 1.1 most recent pregnancy was the first yes 95 25.7 no 275 74.3 type of baby feeding breastfeeding 175 47.3 bottlefeeding 65 17.6 breastfeeding and bottlefeeding together 130 35.1 the period of time after the last birth ‹ a month 44 11.9 › a month-two months 38 10.3 › two months-3 months 26 7.0 › 3 months-4 months 19 5.1 › 4 months-5 months 22 6.0 › 5 months-6 months 54 14.6 › 6 months-12 months 167 45.1 41research paper a. abuhlega, m. maamar fish after the dissemination of federal recommendations (oken et al., 2003). as a result of the lack of previous studies on the pattern of consumption of fish and fishery products by new mothers in tripoli, libya, and the mothers’ cultural level on the health benefits of fish and fishery products, needs to be explored. in addition, very negligible study was available on how to avoid their risks. therefore, the objectives of the study were: (i) to assess the pattern of fish consumption (pre-pregnancy, pregnancy, and post-pregnancy); (ii) to determine the most important factors affecting this pattern; and (iii) to explore the knowledge of chemical pollutants in fish among the new mothers in tripoli, libya. table 2. number times of eating fish, crustaceans and/or mollusks of new mothers in pre-pregnancy, pregnancy and post-pregnancy periods number of times of fish eaten periods pre-pregnancy % (n)* pregnancy % (n)* post-pregnancy % (n)* none 27.0 (100) 28.4 (105) 27.3 (101) once/month 38.4 (142) 38.1 (141) 40.5 (150) twice/month 18.6 (69) 17.3 (64) 16.5 (61) once/week 5.4 (20) 5.4 (20) 5.7 (21) twice/week 7.6 (28) 7.8 (29) 7.6 (28) 3-6 times/week 1.6 (6) 1.4 (5) 1.6 (6) daily 0.3 (1) 0.5 (2) 0.0 (0) do not know 1.1 (4) 1.1 (4) 0.8 (3) *numbers of new mothers table 3. types of fish eaten by new mothers in pre-pregnancy, pregnancy and post-pregnancy periods before, during, and after pregnancy conmen name periods pre-pregnancy % (n)* pregnancy % (n)* post-pregnancy % (n)* shrimp 12.5 11.4 12.72 seafood 13.2 12.5 12.72 cuttlefish 16.1 14.0 16.36 octopus 7.5 7.0 6.90 mackerel 37.1 37.6 37.45 sea bream 51.8 52.4 52 red mullet 9.6 9.2 9.81 red porgy 10 10.3 9.81 sardine 72.1 73.1 72.36 grouper 11.9 12.5 12 sepia 0.0 0.0 5.09table 4. changes in the amount of fish, crustaceans and/or mollusks meals eaten by new mothers during pregnancy compared to pre-pregnancy statement percentage respondents (n)* did not eat fish before and during pregnancy 25.1 (93) ate a lot more fish 2.4 (9) ate a little more fish 1.4 (5) ate the same amount of fish 66.2 (245) ate a little less fish 1.9 (7) ate a lot less fish 1.4 (5) stopped eating fish 1.6 (6) *numbers of new mothers figure 1. types of canned fish consumed by new mothers 42 squ journal of agricultural and marine sciences, 2020, volume 25, issue 1 fish consumption and knowledge of chemical pollutants among a sample of new mothers in tripoli, libya methodology data collection the face to face questionnaire was designed based on a study conducted by connelly et al. (2013) and it was presented to the new mother in the arabic language. the observational cross-section study targeted 370 new mothers at public hospitals, public health centers, and private clinics across the five municipalities in the city of tripoli (suk alguma, tripoli center, abusleem, hai al andulas, and tajoura). the researcher explained to the women targetted in this study and assured that the confidentiality of women’s responses will be maintained. then, they were asked for their voluntary participation in this study. women who exceeded more than 12 months after giving birth, were excluded from this study to ensure accurate answers. the survey was conducted between february and november (2018). the questionnaire consisted of three parts: part 1: characteristics of a new mothers sample (5 questions); part 2: consumption of fish, crustaceans, mollusks and canned fish (6 questions), and part 3: knowledge about importance and risks of eating fish and fish products (5 questions). the new mothers were interviewed within 20 minutes. data analysis data collected from the survey were coded and filled in an excel table (microsoft office excel 2016). then, data were entered into spss (statistical package for social sciences, version 22) and were subjected to descriptive analyses. fisher’s exact test was used to verify possible associations between the education level of new mothers and fish consumption patterns, canned fish consumption patterns, and new mothers’ knowledge of fish. the significance of difference was tested with the 5% level of the confidence interval. table 5. changes in the amount of fish, crustaceans and/or mollusks meals eaten by new mothers after pregnancy compared with the pregnancy period statement percentage respondents (n)* did not eat fish during and after pregnancy 23.5 (87) ate a lot more fish 1.9 (7) ate a little more fish 2.2 (8) ate the same amount of fish 65.6 (243) ate a little less fish 2.2 (8) ate a lot less fish 2.2 (8) stopped eating fish 2.4 (9) *numbers of new mothers table 6. the number of times of eaten of canned tuna fish, whether in the form of sandwiches, pizza, salad, pasta or others by new mothers in pre-pregnancy, pregnancy and after pregnancy number of times of eating canned tuna periods pre-pregnancy % (n)* pregnancy % (n)* post-pregnancy % (n)* none 6.2 (23) 7.6 (28) 7.3 (27) once/ month 9.5 (35) 9.5 (35) 9.2 (34) twice/ month 5.4 (20) 5.4 (20) 5.1 (19) once/ week 12.2 (45) 11.6 (43) 11.9 (44) twice/ week 18.1 (67) 17.8 (66) 18.4 (68) 3-6 times/ week 30.5 (113) 30.0 (111) 29.2 (108) daily 17.8 (66) 17.6 (65) 18.1 (67) do not know 0.3 (1) .5 (2) .8 (3) *numbers of new mothers figure 2. knowledge of the importance of eating fish for health in general and for pregnant women 43research paper a. abuhlega, m. maamar questionnaire validity and reliability a pilot study carried out by presenting the questionnaire forms to 25 women and filled to ensure the validity and reliability of the questionnaire. these respondents were not included in the final data collection for this study. after the pre-testing, some questions were reformulated, as some respondents encountered difficulties with some of the questions in the questionnaire. results characteristics of the new mothers table 1 shows the characteristics of the sample of new mothers. the age of the sample ranged from <18 to > 42 and the age of 28-32 represented the highest age category of respondents (27.3%). the majority of respondents (64.1%) had received a university education. for the majority of women (74.3%), their most recent childbirth was not their first pregnancy. breast feeding was the most common method used by mothers, followed by breast feeding and bottle feeding together, and then bottle-feeding with a percentage of 47%, 35%, and 18%, respectively. table 1 also shows that the period of time after the last birth of the mothers when the interview was conducted. the duration ranged from a month to 6 months and 12 months. the time period (6-12 months) represented the highest percentage of mothers, while (3-4 months) was the lowest percentage. consumption of fish, crustaceans, and mollusks in pre-pregnancy, pregnancy, and post-pregnancy periods table 2 shows the frequency of eating fish, crustaceans and/or mollusks in pre-pregnancy, pregnancy, and post-pregnancy periods by new mothers. the results show that eating fish, crustaceans, and mollusks once a month was the highest eating rate in three periods before, during and after pregnancy with a 38, 38 and 41%, respectively. the percentages of new mothers who eat fish, crustaceans, and mollusks once/week or twice/ week before, during and after pregnancy were 13, 13 and 13 %, respectively. the results of the statistical analysis (fisher’s exact test) revealed that no significant association between the three periods of eating fish before (p=0.41), during (p=0.51) and after pregnancy (p=0.71) and education level. table 3 displays the various fish that were eaten by new mothers. sardine, sea bream and mackerel were the most common fish types that were eaten by new mothers before, during, and after pregnancy. the results of this study showed that more than half of the sample (66%) did not change their consumption figure 3. received information about the types and quantity of fish that should be eaten to maintain the health of the mother and her baby by new mothers figure 4. main information source of the new mothers on the types and quantity of fish that should be eaten to maintain the health of the mother and her baby 44 squ journal of agricultural and marine sciences, 2020, volume 25, issue 1 fish consumption and knowledge of chemical pollutants among a sample of new mothers in tripoli, libya pattern of fish, crustaceans and/or mollusks during pregnancy compared to the pre-pregnancy period (table 4). by the fisher exact test, no significant association was found between the change in the amount of fish, crustaceans and/or mollusks meals consumed during pregnancy as compared to pre-pregnancy and the education level of new mothers (p=0.062). similarly, table 5 shows that more than half of the sample (66%) did not change the pattern of their fish, crustaceans and/or mollusks intakes after the birth of their children as compared with the pregnancy period. using the fisher’s exact test, it was observed that there was no significant association between change in the amount of fish eaten after birth as compared with the pregnancy period and the education level of new mothers (p=0.077). consumption of canned fish pre-pregnant, pregnancy and post-pregnancy types of canned fish consumed by new mothers are illustrated in figure 1. the results showed that canned tuna was the most common canned fish consumed by respondents (93%) followed by a canned sardine, anchovy, and mackerel with a percentage of 29, 0.5 and 0.5%, respectively. the frequency of canned tuna fish consumption in the form of sandwiches, pizza, salad, pasta or others during pre-pregnancy, pregnancy and post-pregnancy periods is shown in table 6. the results revealed that a high percentage of new mothers ate canned tuna 3-6 times a week with a percentage of 31, 30 and 29% followed by twice a week with the percentages of 18% and then daily with percentages of 18% before, during and after pregnancy, respectively. there was a significant association between frequency of canned fish-eating in three periods before (p=0.001), during (p=0.006) and after (p=0.00001) pregnancy and new mothers’ education level. new mothers’ knowledge on the benefits and risks of fish consumption results in figure 4 shows that 29% of the mothers reported that the internet was the main source that provided them with information about importance of eating fish for their health and their babys’ health followed by society (22%), obstetrician (21%), tv (18%) and personal study (11%). the mothers did not receive any information about eating fish from newspapers and radio. new mothers were tested to explore their knowledge about chemical pollutants in fish through eight statements as shown in table 7 (four generally true, two generally false, and one for self-assessment of knowledge of the mothers). slightly less than a third of the mothers agreed with statements that some chemical contaminants from eating fish build up in their body over time. older fish generally have more chemical contaminants than younger fish. the amount of chemical contaminants in predatory fish is higher than that of herbivorous fish and children’s health can be harmed more than adult’s health by chemical contaminants in fish with percentage of 33, 32, 31 and 35%, respectively. while the percentage of new mothers who disagree with generally false statements (i.e. most of the mercury is found in the fat of fish and, smaller fish generally have more chemical contaminants in them than larger fish) was 19 and 37%, respectively. more than half of new mothers (57%) disagreed with the statement that “i know predatory fish and herbivorous fish”. the statistical analysis revealed that there was a significant association between some statements and education level of new mothers that were some chemical contaminants from eating fish build table 7. knowledge of new mothers about chemical pollutants in fish statements strongly agree agree neutral strongly disagree disagree some chemical contaminants from eating fish build up in my body over time (generally true). 3.8 28.9 44.1 4.6 18.6 older fish generally have more chemical contaminants in them than younger fish (generally true). 4.0 27.6 47.8 3.8 16.8 most of the mercury is found in the fat of fish (generally false). 4.3 27.2 49.7 3.8 15.0 amount of chemical contaminants in predatory fish is higher than that of herbivorous fish (generally true). 3.2 27.6 49.2 15.4 4.6 i know predatory fish and herbivorous fish. 14.1 24.3 4.3 3.0 54.3 smaller fish generally have more chemical contaminants in them than larger fish (generally false). 1.9 10.3 51.3 26.8 9.7 children’s health can be harmed more than adults’ health by chemical contaminants in fish (generally true). 7.0 28.2 46.1 15.2 3.5 45research paper a. abuhlega, m. maamar up in my body over time (generally true) (p=0.00001), older fish generally have more chemical contaminants in them than younger fish (generally true) (p=0.017), smaller fish generally have more chemical contaminants in them than larger fish (generally false) (p=0.009) and children’s health can be harmed more than adults’ health by chemical contaminants in fish (generally true) (p=0.0035). while no significant association was found between other statements and education level of new mothers that included most of the mercury is found in the fat of fish (generally false) (p=0.10), amount of chemical contaminants in predatory fish is higher than that of herbivorous fish (generally true) (p=0.82), “i know predatory fish and herbivorous fish” (p=0.061). discussion characteristics of the new mothers it is worthy to focus on two important points. the educational level of the majority of respondents was university level, which indicated the possibility of success of any educational program before and during pregnancy if offerred by competent authorities. breastfeeding was the most common way of feeding a baby among respondents, which indicated the importance of what the mother eating for her child’s health. breastfeeding is the best source of infant nutrition. however, it may also be a source of environmental pollutants (björnberg et al. 2005). consumption of fish, crustaceans, and mollusks during pre-pregnancy, pregnancy, and post-pregnancy periods the results showed that less than a quarter of new mothers ate fish once/week or twice/week before, during and after pregnancy. while a lower percentage ate fish 3-6 times/week in the three periods. the percentage was lower in this study as compared to anderson et al. (2004). they observed nearly 10% of the women consumed two or more fish meals per week. slightly better results were obtained in this study as compared to godala et al. (2012), when 1/3 of pregnant women consumed fish several times a week. from the point of view of nutritionists, pregnant women should consume three to four oil-rich fish meals a week (simopoulos et al., 1999). the type and quantity of fatty acids and chemical pollutants varied in fish and shellfish (guldner et al., 2007). the new mothers in this study did not consume fish predatory species, which are prevented by many countries and agencies that include shark, swordfish, marlin, orange rough and escolar (taylor et al., 2018). more than 65% of new mothers did not change the pattern of their intake of fish, crustaceans and/or mollusks during pregnancy as compared to the pre-pregnancy period and after the birth of their children as compared with the pregnancy period. this reflects that they did not receive an effective program to increase their knowledge on the importance of eating fish. in a similar study conducted by connelly et al. (2013), it was found that 29.4% of women did not change the pattern of fish consumption during pregnancy as compared to before pregnancy and also 43.9% did not change the pattern of fish consumption after pregnancy as compared to pregnancy. consumption of canned fish during pre-pregnancy, pregnancy and post-pregnancy periods in the recent decades, libyan society has been characterized by the consumption of canned tuna. hosseini et al. (2015) reported that countries including libya, the united states of america, portugal, saudi arabia, turkey, and iran consumed canned fish regularly. the majority of the new mothers ate canned tuna, while a low proportion of them ate canned sardines, anchovies and mackerel. similarly, abuhlega and hassan (2017) found that canned tuna was the highest consumption by pupils/students for both males and females with a percentage of 78% and 81%, respectively. also, abuhlega and hassan (2020) found that canned tuna was the most consumed canned fish by respondents with a percentage of 94.4%. the highest percentage of new mothers ate canned tuna 3-6 times a week. there was a significant association between the number of times of eating canned tuna fish and the level of education of new mothers. it is very important to mention there is a need to raise the awareness level of mothers about the importance of eating canned sardine, anchovies and mackerel due to their high nutritious value as a source of omega-3 and as well as these types of fish are not a source of mercury. this is due to their high nutritious value as a source of omega-3 and as well as these types of fish are not a source of mercury. sardine, anchovy and mackerel fish are considered the best choice for pregnant women as guided by fda (2017). new mothers’ knowledge on the benefits and risks of fish consumption many countries provide detailed advice to pregnant women about the types of fish that should be reduced during pregnancy and those that should be avoided completely. this advice varies from country to country. the advice mainly focuses on the content of mercury in fish in order to maintain the health of the pregnant woman and the health of her fetus (taylor et al., 2018). it is worthy to mention that there are no programs in the state of libya at present for advising for pregnant women. similarly, guneri et al. (2017) reported that pregnant women didn’t receive education about food safety. however, a high percentage of new mothers (74 and 76%) realized that eating fish is important for health in general and for pregnant women. there was a significant association between the education level of new 46 squ journal of agricultural and marine sciences, 2020, volume 25, issue 1 fish consumption and knowledge of chemical pollutants among a sample of new mothers in tripoli, libya mothers and the importance of fish in general and for pregnant women. the result is in the line of musaiger and, al rumaidh (2005), who found that 76% of individuals disagreed with a statement that eating pregnant women of fish is harmful. despite no significant association was found between agreeing with this belief and education level. the internet was the main source of getting information on the types and quantity of fish that should be eatten by pregnant women, followed by society, obstetrician, tv, and studying. the internet and society information may not be correct and accurate. therefore, the obstetrician should play a role in raising the awareness of pregnant women. bloomingdale et al. (2010) concluded that the advice of obstetricians could affect pregnant women and make them eating more fish. it is worthy to mention that although 70% of new mothers reported that they received information about eating fish, and their knowledge of chemical pollutants in fish was low. the knowledge of new mothers on chemical pollutants in fish varied. slightly less than a third of the mothers knew that some chemical contaminants from eating fish build up in my body over time; older fish generally have more chemical contaminants in them than younger fish, amount of chemical contaminants in predatory fish is higher than that of herbivorous fish and children’s health can be harmed more than adult’s health by chemical contaminants in fish. on the contrary, anderson et al. (2004) found that most women (71%) were aware of mercury’s toxicity to the development of a child. this study is in line with a related study conducted by gliori et al. (2006), who found that roughly one-third of women were aware that older fish and predatory fish have the highest levels of mercury. there was a significant association between the level of education of new mothers and four statements: (i) some chemical contaminants from eating fish build up in my body over time (generally true), (ii) older fish generally have more chemical contaminants in them than younger fish (generally true), (iii) smaller fish generally have more chemical contaminants in them than larger fish (generally false) and (iv) children’s health can be harmed more than adults’ health by chemical contaminants in fish (generally true). the education level was strongly related to the knowledge of fish chemical contaminants (connelly et al., 2013). the results of this study showed that there is a great need to raise women awareness through an integrated program supported by the government sector, private sector, and occupational organizations in the country. conclusion based on the findings of this study and for the purpose of raising the level of safe consumption of fish by pregnant women, it is recommended the following: (i) adopting programs to educate mothers by the competent authorities through provision special publications and distributing them in maternity centers and clinics as well as by programs in the available media such television to increase amount and number of times of eating safe fish in a week; (ii)the role of obstetrician should include advising mothers about what they should eat particularly fish consumption ; (iii) replicate similar surveys regularly, at least every five years; (iv) use this study as a reference to monitor behavioral changes in fish consumption habits by mothers; (v) more comprehensive studies on the role of fish in the diet and the actual quantity of consumption by mothers at the country level should be conducted rather than on annual fish statistics that do not provide sufficient indication. acknowledgement the researchers extend thanks and appreciation to prof. tawfik m. hassan for reviewing the questionnaire in terms of the relevance of the questions to the libyan society and the grammar of the arabic language. references al-asadi mkk. (2018). evaluation of marine pollution by mercury from petrochemical hot spot, west of libya. mesopotamian journal of marine science 33(1): 49-56. abuhlega t, hassan t. (2017). consumption trend of canned fish in a sample of pupils/ students of basic and secondary education in tripoli, libya. arab journal of food and nutrition 17(39): 79-91 (arabic). abuhlega t, hassan, t. 2020. evaluation of the consumption pattern of fish in the city of tripoli-libya and the extent of awareness of their importance and nutritional value. the libyan journal of agriculture (in press). anderson ha, hanrahan lp, smith a, draheim l, kanarek m, olsen j. (2004). the role of sport-fish consumption advisories in mercury risk communication: a 1998-1999 12-state survey of women age 1845. environtal research 95(3): 315-324. balshaw s, edwards j, daughtry b, ross k. 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(2015). fish intake during pregnancy and foetal neurodevelopment-a systematic review of the evidence. nutrients 7(3): 2001–2014. strain j. (2014). eating fish for two. nutrition bullelin 39(2): 181–186. verger p, houdart s, marette s, roosen j, blanchemanche s. (2007). impact of a risk-benefit advisory on fish consumption and dietary exposure to methylmercury in france. regulatory toxicology and pharmacology 48: 259-69. research article journal of agricultural and marine sciences 2021, 26(2): 42–50 doi: 10.24200/jams.vol26iss2pp42-50 received 14 sep 2020 accepted 27 jan 2021 physical and chemical fruit quality attributes of two pomegranate cultivars grown at varying altitudes of al-hajar mountains in oman basim s. al-kalbani1,2*, rashid a. al-yahyai1, abdullah m. al-sadi1, al-ghaliya h. al-mamari2 basim s. al-kalbani 1,2,*( ) basem87alkalbani@gmail.com, 1department of plant sciences, college of agricultural and marine sciences, sultan qaboos university, al-khod, sultanate of oman, 2directorate general of agriculture and livestock research, ministry of agriculture, muscat, sultanate of oman introduction fruit quality of pomegranate is affected by climat-ic and cultural variables, especially for cultivars that are grown in marginal lands, such as those cultivated in al-hajar mountains of oman (al-said et al., 2009). pomegranate is one of the main fruit crops grown in the northern oman in al-hajar mountain at an altitude of 2000-3000 m above sea level (al-said et al., 2009; al-yahyai et al., 2009). omani pomegranates have a special economic significance in the growing regions of oman and have attracted customers worldwide, primarily tourists and residents from neighboring gulf cooperation council (gcc) countries leading to a great demand of fruits during harvesting time in september every year and huge potential for expansion of cultivated area (al-said et al., 2013). pomegranate is one of the most important fruit crops that gained interest in recent years and currently produced widely around the world. india, iran, turkey, china and usa are the leading pomegranate producers and more than 76% of the pomegranate fruits world export is from these countries (martínez-nicolás et al., 2019). pomegranate fruit quality is important to increase the profits of producers. اخلصائص الفيزايئية والكيميائية جلودة صنفني من فاكهة الرمان يزرعان على ارتفاعات خمتلفة يف جبال احلجر يف عمان ابسم الكلباين , راشد اليحيائي , عبدهللا السعدي , الغالية املعمري abstract. the present study investigated the differences in fruit physical and chemical quality characteristics of two popular local pomegranate cultivars, namely helow and malasi, as influenced by the altitudinal microclimates. three sites of varying altitudes were selected for this study at al-hajar mountains in northern oman that included, high (2019 m, saiq), mid (1876 m, sograh) and low altitudes (1540 m, wakan). the results showed that at lower altitudes of wakan, the malasi cultivar had better color attributes than helow cultivar. malasi also had more lightness (l), yellowness (b) and color intensity (chroma) but less greenness (a), while in mid-altitude, helow had better color compared with malasi cultivar. furthermore, helow colors was developed as evidenced in terms of brightness, skin and arils redness at higher altitude compared to the two lower altitude sites. physical fruit qualities were also investigated and the results indicated that in most measured parameters, the malasi fruit quality was better in both locations (sograh and wakan) than helow cultivar, while helow cultivar had superior fruit quality at higher elevation in saiq. additionally, malasi had higher juice volume (jv), total soluble solid (tss) and titratable acidity (ta) than helow in wakan. helow fruits in saiq showed better performance and higher results for juice volume (jv), total soluble solid (tss) and maturity index (mi) as followed by those in sograh and wakan. our study showed that the fruit physical and chemical quality attributes of local pomegranate cultivars are strongly influenced by growing location and altitude. keywords: pomegranate, physical and chemical quality, altitudes, microclimates امللخص:حبثــت الدراســة احلاليــة يف االختالفــات يف خصائــص اجلــودة الفيزايئيــة والكيميائيــة للفاكهــة لصنفــني حمليــني شــائعني مــن الرمــان ومهــا احللــو و املالســي، حيــث أهنمــا يتأثــران ابملنــاخ احمللــي املرتفــع. مت اختيــار ثالثــة مواقــع ابرتفاعــات متفاوتــة للدراســة يف جبــال احلجــر يف مشــال عمــان والــي تضمنــت ارتفــاع )2019 م ، ســيق( ، منتصــف )1876 م ، الســوجرة( واالرتفاعــات املنخفضــة )1540 م ، وكان(. أظهــرت النتائــج أنــه يف االرتفاعــات املنخفضــة مــن وكان ، وكان للصنــف املالســي صفــات لونيــة أفضــل مــن الصنــف حلــو. وكان لــدى املالســي أيًضــا خفــة أكثــر يف اللــون )l( و اصفــرار )b( وكثافــة )chroma( ولكــن أقــل خضــرة )a( ، بينمــا يف االرتفــاع املتوســط ، كان احللــو يتمتــع بســمات لونيــة أفضــل مــن الصنــف املالســي. عــالوة علــى ذلــك ، تطــورت ألــوان احللــو بشــكل جيــد للغايــة مــن حيــث الســطوع وامحــرار القشــرة واحلــب علــى ارتفاعــات أعلــى مقارنــة ابملوقعــني املنخفضــني. كمــا مت فحــص الصفــات الفيزايئيــة للفاكهــة وأظهــرت النتائــج أنــه يف معظــم املتغــرات الــي مت قياســها كانــت جــودة مثــار املالســي أفضــل يف كال املوقعــني )الســوجرة ووكان( مــن الصنــف احللــو ، بينمــا كان الصنــف حلــو يتمتــع جبــودة مثــار أعلــى يف املرتفعــات العاليــة يف ســيق. ابإلضافــة إىل ذلــك ، كان لــدى املالســي كميــة عصــر أعلــى )jv( ، وإمجــايل مــواد صلبــة قابلــة للــذوابن )tss( ومحوضــة قابلــة للمعايــرة )ta( مــن احللــو يف وكان. أظهــرت مثــار احللــو يف ســيق أداًء أفضــل ونتائــج أعلــى يف كميــة العصــر )jv( وإمجــايل املــواد الصلبــة الذائبــة )tss( ومؤشــر النضــج )mi( تليهــا تلــك املوجــودة يف الســوجرة ووكان. أظهــرت دراســتنا أن مســات اجلــودة الفيزايئيــة والكيميائيــة للفاكهــة ألصنــاف الرمــان احملليــة تتأثــر بشــدة مبوقــع النمــو واالرتفــاع. الكلمات املفتاحية: الرمان ، اجلودة الفيزايئية والكيميائية ، االرتفاعات ، املناخ. 43research article al-kalbani, al-yahyai, al-sadi, al-mamari fruit physico-chemical qualities plays an important role in defining price structure of pomegranate fruits (alsaid et al., 2009). high demand of pomegranate fruits in the world is because of its health benefits from the juice, arils, dehydrated seeds, rind and other parts of the fruit (melgarejo et al., 2013). the local cultivars grown in oman, are helow, qusum, malasi and hamedh. the helow cultivar is the most popular with the sweetest taste which occupies the largest cultivated area (al-yahyai et al., 2009). undesirable characteristics of the other cultivated cultivars like qusum having hard seeds malasi smaller in size smoother skin being more susceptible to bruising. similarly, hamedh is a wild cultivar that usually grows on the edges of farms, has highly acidic taste and small fruit size with undesirable eating quality (al-said et al., 2009). pomegranate quality depends on the factors, such as climate, cultivar, growing conditions, maturity and cultural practices. it is important to select suitable climatic conditions to cultivate the best cultivar of pomegranate with desirable quality fruit (el-salhy et al, 2019). there is variability in performance of these cultivars in different agro-climatic conditions (el-salhy et al., 2019). despite its great international success, ‘wonderful’ is one of commercial pomegranate cultivar which has not done well in pomegranate growing regions of oman. mphahlele et al. (2016) conducted a study which showed that ‘wonderful’ pomegranate quality and the maturity stage affected its biochemical and aroma volatile attributes under different agro-climatic locations (altitudes). like pomegranates, naryal et al. (2019) showed that the fruit sugar contents and sugar profiles of dried apricot (prunus armeniaca l.) affected when cultivated at different altitudes. further, boussaa et al. (2020) found that physical properties of pomegranate, such as bioactive compounds, and antioxidant activity also changed with altitude. peng et al. (2020) grouped 37 varieties of pomegranate in china into three categories based on cluster analysis after analysis of fruit physico-chemical quality parameters. in al-hajar mountain, fruits cultivars differ with different elevations. in saiq (altitude, 2019 m above sea level), helow cultivar is the dominant among cultivars as compared to malasi which is dominant in wakan at (altitude, 1540 m) and sograh (altitude, 1876 m). this present study investigated the effects of growing at different altitudes on pomegranate fruit and aril physical and chemical quality characteristics of two major cultivars (i.e. helow and malasi). materials and methods sample collection three locations in al-hajar mountain were selected from al-jabal al-akhdar and wadi mastel where pomegranate is commonly cultivated as the primary fruit crop. two locations in al-jabal al-akhdar namely; saiq (23.0872618 latitude, 57.6938060 longitude and 2019 m altitude) and sograh (23.144504 latitude, 57.672766 longitude and 1876 m altitude) were used. other location from wadi mastel, wakan, (23.1421282 latitude, 57.7340133 longitude and 1540 m altitude) was used. fruits were harvested from farmers’ field during two years 2018 and 2019. fruits were hand-picked at skin color change (maturity index) commercial ripening time. fruits were harvested during the month of september. in wakan and sograh, two pomegranate cultivars ‘helow’ and ‘malasi’ were selected for the study and one cultivar ‘helow’ from the 3rd site, i.e. saiq. ten ‘malasi’ and five ‘helow’ trees were selected for fruit harvest, due to the limited number of representative trees. five mature fruits per tree were collected for physical and chemical quality measurements. analysis of fruit physio-chemical characteristics color: color measurements were performed using a colorimeter (model cr 200, minolta, milton keynes, uk). fruit color (fc) measurements were taken along the equatorial axis of three selected fruit. three readings of each color index (l* a* b) were taken per fruit, given a total measurement per fruit sample, where l is difference in lightness/darkness value. negative (l) values indicate darkness and higher positive (l) values indicate lightness. on the other hand, negative (a) values indicate green and higher positive (a) values indicate red color. higher positive (b) values indicate a more yellow skin color and negative (b) indicate a blue color. these values were then used to calculate hue degree, where 0° = red-purple, 90° = yellow, 180° = bluish green, and 270° = blue, and (chroma), which indicates the intensity or color saturation (selcuk and erkan, 2015). chroma and hue were calculated as follows: chroma = √(a*²+b*²) (1) hue = arctan (b*/a*) (2) also arils color was measured with the same colorimeter from tow fruit sample per tree and three readings from each fruit. physical quality parameters of fruits and arils: the length and diameter of the fruit and arils were determined with a digital venire caliper while the weight was determined using a weighing balance. three mature fruits from each tree were taken from helow and malasi cultivars. fruit total length (fl2), fruit total length excluding the calyx (fl1), calyx diameter (fd2), fruit equatorial diameter (fd1), and fruit skin thickness (ec). arils maximum width (sw) and arils length (sl) were measured. three arils were used from each fruit sample. also the seeds of the arils were used to determine width (w), length (l) and weight of woody portion (wpw). fruits were weighed using a balance of exactitude of 0.001 g. fresh weights (fw) were taken for three fruits per tree. rind weight plus weight of capillary membranes (pcmc), aril weight (aw) and weight of woody portion (wpw) inside the aril were measured. number of carpels (nc) 44 squ journal of agricultural and marine sciences, 2021, volume 26, issue 2 physical and chemical fruit quality attributes of two pomegranate cultivars grown at varying altitudes of al-hajar mountains in oman in each fruit were also counted. the arils were removed from the fruit and arils fresh weight or arils yield (rs) were determined (rs= fwpcmc). chemical quality parameters of fruits: the fruits were peeled and the skin covering the arils was removed. the juice was extracted from pomegranate arils using a juice extractor. the juice was used to determine juice volume (jv) and the chemical properties of each individual fruit and replicated according to the type of measurements. total soluble solids (tss) (brix) were determined on three fruit samples per tree using a temperature compensating hand-held refractometer. juice acidity was measured using three samples per fruit. percentage of titratable acidity (ta), expressed as percent citric acid, was determined using a 10 ml homogenized extracted juice sample. the juice sample was added to 10 ml distilled water. aliquot of 20 ml were titrated with 0.1m naoh until the color changed to pink as indicated by phenolphthalein indicator (aoac, 2000). three homogenized samples per cultivar were analyzed for ta. statistical analysis the experimental design used was a completely randomized design (crd). statistical analysis was done by sas software using duncan’s multiple range test (sas institute, cary, n.c.). treatment means were compared using duncan’s multiple range test at p ≤ 0.05. results effect of locations and cultivars on color parameters effects of location on the color parameters of helow and malasi cultivars and difference among the cultivars (helow or malasi) in different locations are shown in table 1. all cultivars showed significant differences between locations in fruit and arils color parameters except malasi, which showed no significance different between different locations in arils color. in the lower altitude, wakan, malasi cultivar showed higher values in all fruit color parameters than helow cultivar, where malasi had more brightness (l), yellowness (b), intense (chroma) and less greenness (a). hue values from fruits in wakan showed that both cultivars were from red to purple, as degree near to zero. in the middle altitude, sograh, helow cultivar had more brightness, greenness and yellowness while malasi was more intensely red. arils color in wakan and sograh showed that helow cultivar had brighter color and yellower than malasi, which had more intensely red color. hue was same as in wakan that both cultivars were from red to purple as degree near to zero. in the higher altitude, saiq, helow cultivar was dominantly cultivated. helow cultivar in saiq showed higher red (a), less yellowness (b) and less intense (chroma) in fruit color than sograh and wakan. aril color of helow fruits was brighter, yellower and less intensely red at lower altitudes (wakan and sograh) than at highest altitude (saiq). on the other hand, fruit color of malasi cultivar was brighter, yellower and more intense at lower altitudes (wakan). malasi cultivar showed more red in color in sograh than wakan. arils color of malasi cultivar had same brightness, yellowness and intensely same in lower and middle altitudes. fruit and aril differences among cultivars and locations in color are shown in figure 1. fruit and aril color development varies among growing altitudes and between cultivars. color of helow cultivar was more affected by location compared with malasi. helow cultivar in lower altitudes (wakan) showed lower brightness (l), less red and intensely in color comparing to helow and malasi cultivars in same, middle (sograh) and higher (saiq) altitudes in fruits and arils color parameters. malasi in wakan was brighter and yellower in fruit color. malasi arils in wakan and sograh higher red in color comparing to the cultivars in the other altitudes. effect of locations and cultivars on physical and chemical quality parameters the effects of locations and cultivars on fruit quality properties were tested by comparing fruit weight (fw), total fruit length (fl), fruit length without calyx (fl1), calyx length (cl), fruit diameter (fd), calyx diameter (cd), number of carpels (nc), rind weight plus weight of capillary membranes (pcmc), skin thickness (ec) and arils yield (rs) of helow and malasi cultivars in saiq, sograh and wakan (table 2). all physical and chemical quality parameters between locations were significantly different except for the number of carpels (nc), skin thickness (ec) and arils yield (rs). also cultivars were significant different (p<0.05) in all parameters except number of carpels (nc). starting with wakan, the results showed malasi cultivar was significantly better than helow in fruit weight (fw), total fruit length (fl), fruit length without calyx (fl1), fruit diameter (fd) and rind weight plus weight of capillary membranes (pcmc) (table 2), while helow cultivar had higher calyx diameter (cd). in sograh, there was no significance different in fruit weight (fw) between malasi and helow cultivars but malasi had more total fruit length (fl), fruit length without calyx (fl1), fruit diameter (fd), calyx diameter (cd) and rind weight plus weight of capillary membranes (pcmc). however, sograh showed same results when comparing between helow and malasi cultivars as wakan which was illustrated previously. over all, malasi cultivar performed better in wakan and sograh than helow cultivar. helow in saiq was the best in all fruit physical quality parameters than the other locations. it was higher in fruit weight (fw), total fruit length (fl), fruit length without calyx (fl1), calyx length (cl), fruit diameter (fd), calyx diameter (cd) and rind weight plus weight of capillary membranes (pcmc). helow cultivar in wakan had calyx length (cl) and calyx diameter 45research article al-kalbani, al-yahyai, al-sadi, al-mamari (cd) similar to helow in saiq. however, there was no significant difference between saiq and wakan in calyx length (cl) and calyx diameter (cd) but there was a significant difference from helow in sograh, which was lower. also there was no significance different between helow in saiq and sograh in fruit diameter (fd), total fruit length (fl), fruit length without calyx (fl1) but there was a significant difference from helow in wakan which was showed lower on previous parameters. results clearly indicated that fruit weight (fw) and rind weight plus weight of capillary membranes (pcmc) were significantly higher (p<0.05) in saiq than sograh followed by wakan. over all malasi cultivar quality performed better in sograh and wakan, while helow cultivar was better in higher elevation in saiq. there was no interaction between cultivars and locations in all fruit physical quality parameters as showed in table 2. the effects of locations and cultivars on fruit quality properties (physical and chemical of fruit quality parameters) were tested by comparing arils width (sw), arils length (sl), aril weight (aw), juice volume (jv), total soluble solid (tss), titratable acidity (ta), maturity index (mi), seed width (w), seed length (l), woody portion weight (wpw) and woody portion index (wpi) of helow and malasi cultivars in saiq, sograh and wakan (table 3). location effects were significantly different with respect to all arils and chemical parameters while cultivars were significantly different with all except arils length (sl), woody portion weight (wpw) and woody portion index (wpi). firstly, comparing malasi and helow cultivars in wakan, the results showed that malasi had more aril weight (aw), juice volume (jv), total soluble solid (tss), titratable acidity (ta) and seed width (w) while helow had higher arils length (sl), maturity index (mi) and seed length (l). malasi had better aril quality than helow in wakan. secondly, malasi showed higher chemical quality parameters [juice volume (jv), total soluble solid (tss), titratable acidity (ta) then helow which showed higher physical quality parameters (arils length (sl), aril weight (aw), maturity index (mi), seed width (w) and seed length (l)]. comparing malasi cultivars between wakan and sograh, it was found that there was no significance different in juice volume (jv), total soluble solids (tss) and seed length (l). wakan had higher arils width (sw), aril weight (aw) and seed width (w) while in sograh, malasi cultivar showed higher arils length (sl), titratable acidity (ta), maturity index (mi), woody portion weight (wpw) and woody portion index (wpi). on the contrary, comparing helow cultivar in the three locations it was observed that higher arils width (sw), arils length (sl), aril weight (aw), titratable acidity (ta) and seed width (w) were found in sograh but there was no significance different between sograh and saiq in aril weight (aw) and sograh and wakan in titratable acidity (ta). there was no significant difference between the three locations in seed length (l). saiq showed higher results for juice volume (jv), total soluble solids (tss), maturity index (mi), woody portion weight (wpw) and woody portion index (wpi), followed by sograh and after that wakan. overall, helow cultivar performed better at higher altitude in saiq, compared with sograh and the least was for lowest altitude which was wakan. as the elevation decreased the physical and chemical quality parameters of helow cultivar decreased. in malasi there was not much difference between sograh and wakan in physical and chemical quality parameters, which was not commonly grown in high elevation areas like saiq as has been reported by farmers. interaction between locations and cultivars also was illustrated in table 3. arils physical quality properties showed no significant interaction except in arils weight which showed higher arils weight (aw) in helow cultivar in saiq while helow in wakan was the lowest. there was no significant difference between helow in saiq and sograh and also between malasi in sograh figure 1. fruits and arils of helow and malasi cultivars in saiq, sograh and wakan. 46 squ journal of agricultural and marine sciences, 2021, volume 26, issue 2 physical and chemical fruit quality attributes of two pomegranate cultivars grown at varying altitudes of al-hajar mountains in oman and wakan. in seed, physical quality properties there was no interaction except width of the seeds, which was higher in malasi than helow in wakan. the difference in arils weight (aw) and seed width (w) was not high because it differs (0.1 mg) in arils weight and (1.0 mm) in seed width. arils chemical quality properties highly interact between locations and cultivars. helow in saiq had higher juice volume (jv) followed by helow and malasi of sograh. also there were no significant differences between malasi in sograh and wakan and helow of wakan where it was the least. malasi showed higher (tss) and (ta) than helow cultivars in all locations. malasi in sograh was the highest followed by malasi of wakan then helow of saiq followed by helow of sograh, where helow of wakan were the lowest. it was clearly seen that in helow cultivar, tss decreased as the elevation decreased. titratable acidity (ta) also was higher in malasi of sograh than wakan followed by helow of wakan. helow of wakan and sograh showed no significant difference with helow in sograh and saiq, which was the lowest. maturity index (mi) decreased as elevation decreased in helow cultivar, which was higher than malasi cultivar. there was no significant difference between malasi in wakan and sograh in (mi). discussion experiment on physical and chemical description of pomegranate fruits effect of locations and cultivars on color parameters: color parameters of helow and malasi cultivars of pomegranate fruits grown in saiq, sograh and wakan were significantly different. fruit brightness as determined by l value at cielab scale, showed that the lower altitude wakan fruits were brighter in color than mid-elevation sograh in malasi cultivar, and lowest in helow cultivar than sograh followed by saiq. fruit brightness (l) indicated how light colors developed in the fruit at the time of harvest and can be attributed to many variables, including the development of other colors (such as tallow background, green, and red colors). in fruits, gonzález et al. (2011) suggested that the change in l value may be attributed to genetic variability among genotypes, which is evident when comparing two cultivars grown in the same location. the increase of l values may be related also to degradation of chlorophyll as fruits turn red with a differential susceptibility to degradation of chlorophylls among genotype (kumari et al., 2019). in terms of red color of fruits, a* value results showed as the elevation increase red color also increased while yellowness b* increased inversely with elevation which was observed for both cultivars. different trees gown at different elevations are exposed to different microclimatic conditions (such as temperature and relative humidity), which highly influence the coloration of the fruits. this was observed in the color development of deciduous fruits such as in the case of skin color of apple by increasing the carotenoids because of the temperature factor (gonzález et al., 2011). in peach the high-altitude improved skin red blush intensity june gold cultivar (karagiannis et al., 2016). environmental factors like day/night temperature, solar radiation wave lengths or a mixture of these factors can control fruit ripening and the variances between these environmental factors growing with altitude, and it determined the fruit quality at harvest (kumari et al., 2019). nour et al. (2015) found that the red color was the product of chlorophyll degradation and synthesis of lycopene and other carotenoids, as chloroplasts converted into chromoplasts (bilalis et al., 2018). hue value which was indicated in table 1 showed that the fruits ranged from red to purple color as the degree ranged from (0 to 90). also intensity of color (chroma) was higher in malasi then helow and as elevation increased intensity decreased and that because of increased in temperature as elevation decreased as found in fruit color tomato by nour et al. (2015). higher mean air temperature in the fruiting stage during the second year of the study resulted in more reddish tomato fruits because color saturation increases during the ripening of tomato fruits (bilalis et al., 2018). also in arils, our finding showed that cultivars varied in size of fruits and fruit and aril color at maturity stage (al-said et al., 2009). so different elevations lead to different climate conditions (light intensity, temperature and relative humidity) which effect on the color parameters of fruits. effect of locations and cultivars on physical and chemical quality of pomegranates: the effects of locations and cultivars were significantly different in all fruits and arils physical and chemical quality parameters as shown in tables 2 and 3. the results indicated that variations between locations and cultivars was expected because each location (elevation) differs in microclimate (light intensity, temperature and humidity), which leads to variation in fruits and arils physical and chemical quality parameters. fruit weight (fw) was not significantly different between helow and malasi cultivars. the helow and malasi fruit weight decreased as elevation decreased. helow scored the highest mean for fruit weight (fw) in saiq and the lowest in wakan. solarte et al. (2014) found that altitude influenced fruit weight of different guava genotypes. regional roja and guavatá victoria guava genotype in the lower altitude had a higher fruit weight while regional blanca and ráquira blanca guava genotype reversely affected in higher altitude because of variations between day and night temperatures and higher radiation at lower altitudes that changes the balance between sugar accumulation and degradation resulting in increased fruit weight (kumari et al., 2019). most of the fruits physical quality parameters were influenced by elevation and these increased in both cultivars as elevation increased like total fruit length (fl), fruit length without calyx (fl1), fruit diameter (fd) and rind weight plus weight of capillary membranes (pcmc). 47research article al-kalbani, al-yahyai, al-sadi, al-mamari orazem et al. (2011) stated that the fruit size was stimulated by genotype in peach fruit (kumari et al., 2019). in rosehip fruits, physio-chemical features showed significant differences, and these differences were affected by type, genotype and ecological conditions (eroğul et al., 2018). skin thickness (ec) and arils yields (rs) were significant between malasi and helow cultivars and this was expected since they were different. the similar findings of al-said et al. (2009) showed that cultivars vary in fruit and aril color, and size at maturity which was also observed in by hamid et al. (2018). porterville fruit had low aril yield regardless of their fruit weight. this might be excused by climatic conditions, which possibly favor the growth of membranes more than arils (opara et al., 2013). measured physical and chemical quality parameters of arils of malasi and helow cultivars showed variable response to elevation, particularly in aril length (sl) and width (sw) and weight (aw). differences in aril and seed physical quality parameters were similarly observed by opara et al. (2013). in the present study, total soluble solids (tss) was found to increase with increasing altitudes which is in line with kumari et al. (2019) in their study on physical and biochemical attributes of three indian apples (malus demostica borkh.) cultivars as affected by elevation and genotype. titratable acidity (ta) was also found to decrease as elevation decreased in helow cultivar, while malasi showed no difference in this character between locations. higher juice volume (jv) was observed in helow cultivars than malasi except in wakan, where it was found lowest in helow which was expected because of the lowest fruit weight. malasi was higher in titratable acidity (ta) than helow and also it was higher in sograh than in wakan while in helow cultivar, it was higher in wakan and lower in saiq. thus, different cultivars responded differently to elevations, which had different microclimates (opara et al., 2013). maturity index (mi) was lower in malasi cultivars than in helow and also for high titratable acidity (ta) was found in malasi cultivars (26.6 and 22.9) in sograh and wakan, respectively. seed width was different between locations and cultivars while seed length was no significant between locations but significant between cultivars. al-said et al. (2009) observed that cultivars varied in fruit and aril color, and size at maturity and this finding was confirmed our results which showed woody portion weight (wpw) and woody portion index (wpi) of helow and malasi cultivars decreased as the elevation decrease. table 1. effects of locations on the color parameters of the cultivars and interaction between location and cultivars. location cultivar fruit color arils color l a b hue chroma l a b hue chroma wakan helow 66.50 b c -3.29 b c 42.96 b a -1.50 b c 43.13 b a 76.07 aa -0.14 bc 30.17 a a -0.15 bc 30.19 b b malasi 83.54 a a -0.08 a b 46.67 a a -0.02 a b 46.70 a a 59.77 b ns 41.78 a ns 18.68 b ns 0.42 a ns 45.81 ans sograh helow 82.48 a a -0.33 b b 38.15 a b -0.27 b b 38.17 b b 76.89 a a 5.31 b b 29.08 aa 1.39 a a 29.61 bb malasi 73.23 b b 29.54 a a 30.73 b b 0.81 a a 42.94 a b 59.36 b ns 42.25 a ns 18.91 b ns 0.42 bns 46.34 a ns saiq helow 75.31 b 8.91 a 33.32 c 1.31 a 34.56 c 70.43 b 17.61 a 27.07 b 0.99 b 32.36 a p values cultivar <.0001 <.0001 <.0001 <.0001 <.0001 <.0001 <.0001 <.0001 0.0282 <.0001 location <.0001 <.0001 <.0001 <.0001 <.0001 <.0001 <.0001 <.0001 <.0001 <.0001 cultivar*location <.0001 <.0001 <.0001 0.0265 0.1406 0.2815 <.0001 0.1003 <.0001 0.2172 cultivar*location fruit color arils color l*** a*** b*** hue* chroma ns l ns a*** b ns hue*** chroma ns helow saiq 75.31 c 8.91 b 33.32 d 1.31 a 34.56 70.43 17.61 c 27.07 0.99 b 32.36 helow sograh 82.48 ab -0.33 cd 38.15 c -0.27 d 38.17 76.89 5.31 d 29.08 1.39 a 29.61 helow wakan 66.50 e -3.29 e 42.96 b -1.50 e 43.13 76.07 -0.14 e 30.17 -0.15 e 30.19 malasi sograh 73.13 d 29.46 a 30.81 e 0.80 b 42.97 59.36 42.25 a 18.91 0.42 c 46.34 malasi wakan 83.54 a -0.08 c 46.67 a -0.02 c 46.70 59.77 41.78 ab 18.68 0.42 cd 45.81 values marked with different letters in the same column indicate significant differences (p < .05); ns=not significant. the capital letters in the tables illustrate the difference of cultivars in same location while the small letters illustrate the difference of the same cultivar in different locations. where l difference in lightness/darkness value. negative (l) values indicate darkness and higher positive (l) values indicate a lightness. on the other hand, negative (a) values indicate green and higher positive (a) values indicate a red color. higher positive (b) values indicate a more yellow skin color and negative (b) indicate a blue color. these values were then used to calculate hue degree, where 0° = red-purple, 90° = yellow, 180° = bluish green, and 270° = blue, and (chroma), which indicates the intensity or color saturation (selcuk and erkan, 2015). chroma was calculated using formulas chroma = (a2 + b2)1/2 and hue = arctan (b*/a*). 48 squ journal of agricultural and marine sciences, 2021, volume 26, issue 2 physical and chemical fruit quality attributes of two pomegranate cultivars grown at varying altitudes of al-hajar mountains in oman table 2. effect of locations and cultivars on fruit physical quality parameters. location cultivar mean fruit dependent variable fw (g) fd (mm) cd (mm) fl (mm) fl1 (mm) cl (mm) nc ns pcmc (g) ec (mm) ns rs (%)ns wakan helow 261.49 bc 80.15 bb 23.04 aa 68.53 bb 82.89 bb 14.36 a 6.10 112.79 bc 4.31 b 55.55 a malasi 347.60 ab 94.79 ab 21.22 ba 86.39 ab 99.87 ab 13.48 6.10 170.72 ab 5.06 a 49.70 b sograh helow 392.83 b 90.30 ba 18.86 ab 83.53 ba 93.29 ba 9.76 b 6.47 172.63 bb 4.71 a 55.30 a malasi 407.50 a 108.45 aa 17.89 ab 102.86 aa 114.92 aa 12.06 6.04 212.34 aa 5.09 a 48.78 b saiq helow 464.72 a 93.10 a 23.15 a 81.89 a 97.11 a 15.22 a 6.52 207.24 a 4.40 55.38 malasi p values year 0.6424 0.1462 <.0001 0.005 0.1374 0.0042 0.0257 0.0322 0.0014 <.0001 location <.0001 0.0001 0.2051 <.0001 <.0001 0.0002 0.2244 <.0001 0.7176 0.9996 cultivar 0.0082 <.0001 <.0001 <.0001 <.0001 0.4399 0.1422 <.0001 0.0328 0.0024 location*cultivar 0.0676 0.4478 0.4206 0.9303 0.4116 0.1416 0.0418 0.3175 0.3125 0.9010 values marked with different letters in the same column indicate significant differences (p < .05); ns=not significant. the capital letters in the tables illustrate the difference of cultivars in same location while the small letters illustrate the difference of the same cultivar in different locations. fruit weight (fw), total fruit length (fl), fruit length without calyx (fl1), calyx length (cl), fruit diameter (fd), calyx diameter (cd), number of carpels (nc), rind weight plus weight of capillary membranes (pcmc), skin thickness (ec) and arils yield (rs). table 3. effect of locations and cultivars on arils physical and chemical quality parameters. location cultivar mean seed aril physical properties aril chemical properties seed physical properties sw (mm) sl (mm) aw (mg) jv (ml) tss (obrix) ta mi w (mm) l (mm) wpw (mg) wpi % wakan helow 5.80 b 9.34 ab 0.19 bb 68.87 bc 12.20 bc 6.10 ba 2.08 ac 2.64 bb 6.79 aa 0.03 c 0.53 c malasi 6.04 a 8.50 bb 0.26 aa 105.75 aa 16.23 aa 22.94 ab 0.82 bb 3.63 aa 6.28 ba 0.03 b 0.50 b sograh helow 6.50 a 10.52 aa 0.29 aa 120.03 ab 14.12 bb 5.88 ba 2.52 ab 3.20 aa 6.84 aa 0.04 b 0.60 b malasi 5.82 b 9.39 ba 0.25 bb 109.64 ba 16.41 aa 26.65 aa 0.66 ba 2.66 bb 6.32 ba 0.04 a 0.62 a saiq helow 5.92 b 9.56 b 0.30 a 134.10 a 15.65 a 4.75 b 3.96 a 2.70 b 6.64 a 0.041 a 0.74 a p values location <.0001 <.0001 <.0001 <.0001 <.0001 0.0002 <.0001 0.0021 0.0215 <.0001 <.0001 cultivar 0.1937 <.0001 0.0345 <.0001 <.0001 <.0001 <.0001 0.0023 <.0001 0.0331 0.2056 location*cultivar <.0001 0.9059 <.0001 <.0001 <.0001 <.0001 0.004 <.0001 0.4567 0.9485 0.8425 cultivar*location aril physical properties aril chemical properties seed physical properties sw (mm) ns sl (mm) ns aw *** jv (ml)*** tss*** ta*** m1** w (mm) ns l (mm) ns wpw ns wpi ns helow saiq 5.92 9.56 0.30 a 134.10 a 15.65 c 4.745cde 3.96 a 2.70 c 6.64 0.04 0.74 helow sograh 6.50 10.52 0.29 ab 120.03 b 14.12 d 5.88 cd 2.52 b 3.20 b 6.84 0.04 0.60 helow wakan 5.80 9.34 0.19 e 68.87 e 12.20 e 6.10 c 2.06 c 2.64 cde 6.79 0.03 0.53 malasi sograh 6.03 9.65 0.25 cd 112.30 bc 16.76 a 26.92 a 0.64 de 2.69 cd 6.43 0.03 0.58 malasi wakan 6.04 8.50 0.26 c 105.75 cd 16.23 b 22.94 b 0.82 d 3.63 a 6.28 0.03 0.50 values marked with different letters in the same column indicate significant differences (p < .05); ns=not significant. the capital letters in the tables illustrate the difference of cultivars in same location while the small letters illustrate the difference of the same cultivar in different locations. arils width (sw), arils length (sl), aril weight (aw), juice volume (jv), total soluble solid (tss), titratable acidity (ta), maturity index (mi), seed width (w), seed length (l), woody portion weight (wpw) and woody portion index (wpi). 49research article al-kalbani, al-yahyai, al-sadi, al-mamari conclusion the results led to conclusion that helow cultivar performed better in saiq which was at the highest elevation as compared to those grown at mid-elevation in sograh and at lower altitude in wakan in terms of fruit color, fruit and aril physical and chemical quality parameters. as the elevation decreased the fruit and aril quality of helow cultivar also decreased. however, quality measurements of malasi cultivar showed no differences between sograh and wakan in fruit and arils color, physical and chemical quality parameters. traditional pomegranate farmers by their inherited experience, rarely grow malasi cultivar at higher elevations and they know for certain that the quality could not be the same as when it was grown at lower elevation. however, helow, a highly popular cultivar, showed the opposite and quality was best at higher altitudes. the effect of micro-climate (light intensity, temperature and humidity) on the quality of pomegranate cultivars need to be studied with a wide range of cultivars and also on different deciduous fruit crops to determine their impact on fruit physical quality (such as color development) and edible chemical qualities, such as tss & ta. this could help growers to select suitable cultivars for each elevation and predict the future of pomegranate cultivation in marginal mountainous regions of the world, as temperature might change due to global warming. the results of this study contributed to adaptation mechanisms of mitigating the impact of climate change, particularly rising temperatures, which has significant importance in the conservation of local genotypes of deciduous fruit crops grown in al-hajar mountain of oman. references aoac. 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(2011). identification and quantification of phenols, carotenoids, and vitamin c from papaya (carica papaya l., cv. maradol) fruit determined by hplc-dad-ms/msesi. food research international 44(5): 1284-1291. selcuk n, erkan m. (2015). changes in phenolic compounds and antioxidant activity of sour–sweet pomegranates cv. ‘hicaznar’during long-term storage under modified atmosphere packaging. postharvest biology and technology 109: 30-39. solarte me, melgarejo lm, martínez o, hernández ms, fernández-trujillo, jp. (2014). fruit quality during ripening of colombian guava (psidium guajava l.) grown at different altitudes. journal of food, agriculture & environment 12(2): 669-675. research paper journal of agricultural and marine sciences 2023, 28(1): 7–15 doi: 10.53541/jams.vol28iss1pp7-15 received 9 september 2021 accepted 24 february 2022 effect of intermittent frying on the stability of vitamins a and d in commercially fortified oils seham al-amri, m. shafiur rahman, nasser al-habsi, and mohammed al-khusaibi* mohammed al-khusaibi*( ) mohamedk@squ.edu.om, department of food science and nutrition, college of agricultural and marine sciences, sultan qaboos university. p.o.box 34, alkhoudh 123, muscat, oman introduction malnutrition due to micronutrients deficiency is a major global concern, which is also af-fecting middle east countries. according to world health organization (who, 2010), deficiencies reported in the middle east include calcium, iodine, iron, and zinc, folate, vitamin a, and vitamin d. intervention strategies have been adopted to reduce the deficiencies among populations; including fortification of food with micronutrients (allen et al., 2006). vegetable oils have been proposed as a vehicle for fat-soluble vitamins in food fortification strategies. however, fat-soluble vitamins are not stable during processing and their retention is questionable especially at high processing temperatures (hrncirik, 2010). the exposure of vegetable oils to high frying temperatures in the presence of أتثري القلي املتقطع على ثبات فيتامني )أ( وفيتامني )د( يف الزيوت املدعمة سهام العامري، حممد شفور الرمحن، انصر احلبسي، حممد اخلصييب * abstract. fat-soluble vitamins and fatty acids are very sensitive to high temperature and oxidation. in this study, stability of vitamins a and d, and physiochemical changes were investigated in two types of oils, palm olein (po) and a blend of po and sunflower oil (ob). the intermittent frying was performed at two different temperatures 160 and 190 °c. batches of french fries (500 g) were fried in a deep-fat fryer for 5 cycles, a cycle per day. in each cycle, food was fried every 15 min with a total frying time of 5 h per day. oil samples were taken at the end of each heating cycle to measure vitamins a and d concentration, free fatty acid (ffa), peroxide value (pv) and color. in po, vitamin a was reduced by 96.7% after 25 h of frying at 160 °c and it was completely depleted after 15 h at 190 °c. in ob, the vitamin was reduced by 72.2% after 25 h of frying at 160 °c; and it was completely depleted at 190 °c at the end of frying cycles. vitamin d was less stable, its content in po decreased by 67.0% and 80.0% at 160 °c and 190 °c, respectively, after 5 h of frying. in ob, it was reduced by 50.0% and 67.0% at 160 °c and 190 °c, respectively, after 5 h of frying. it was found that both types of oil and frying temperatures showed significant effect on vitamin a concentration, while they did not show any effect on vitamin d. red color increased linearly with frying time in both oils, while fried at two frying temperatures. the change in color was significantly associated with the vitamin a depletion. a low, but significant, association was found between color changes and depletion of vitamin d. in conclusion, the stability of these vitamins depended on the types of oil and temperature of frying. these were more stable in ob compared to po, and similar stability was observed in the cases of ffa and pv. keywords: frying, vitamin depletion, vitamin a, vitamin d, retinol, cholecalciferol, fat-soluble vitamins. املســتخلص: تعتــر الفيتامينــات الذائبــة يف الدهــون واألمحــاض الدهنيــة حساســة جــًدا لدرجــات احلــرارة املرتفعــة واألكســدة. يف هــذه الدراســة، مت قيــاس ثبــات فيتامينــات )أ( و )د( والتغــرات الفيزيوكيميائيــة يف نوعــن مــن الزيــوت، زيــت النخيــل وخليــط مــن زيــت النخيــل وزيــت عبــاد الشــمس )يســمى الحقــا ابخلليــط(. مت اســتخدام الزيــوت يف القلــي املتقطــع علــى درجتــن حــرارة خمتلفتــن: 160 و190 درجــة مئويــة. مت قلــي دفعــات مــن البطاطــس )500 جــرام( يف مقــاة عميقــة ملــدة إمجاليــة بـــخمس دورات، دورة واحــدة يف اليــوم. يف كل دورة، مت قلــي دفعــة مــن البطاطــس كل 15 دقيقــة حيــث كان وقــت )ffa( األمحــاض الدهنيــة احلــرة ،)القلــي الكلــي 5 ســاعات يف اليــوم. مت أخــذ عينــات مــن الزيــت يف هنايــة كل دورة لقيــاس تركيــز الفيتامينــات )أ( و )د ، قيمــة البروكســايد )pv( واللــون. وجــد أن فيتامــن )أ( نقــص بنســبة 96.7٪ بعــد 25 ســاعة مــن القلــي يف زيــت النخيــل عنــد 160 درجــة مئويــة، ونفــد متاًمــا بعــد 15 ســاعة عنــد 190 درجــة مئويــة. أمــا يف اخلليــط، فقــد اخنفــض الفيتامــن بنســبة 72.2٪ بعــد 25 ســاعة مــن القلــي عنــد 160 درجــة مئويــة. ونفــد متاًمــا عنــد 190 درجــة مئويــة يف هنايــة دورات القلــي. كان فيتامــن )د( أقــل ثبــاات، حيــث اخنفــض حمتــواه يف زيــت النخيــل بنســبة ٪67 و80٪ عنــد 160 درجــة مئويــة و190 درجــة مئويــة، علــى التــوايل، بعــد 5 ســاعات مــن القلــي. أمــا يف اخلليــط، اخنفــض بنســبة 50٪ و67٪ عنــد 160 درجــة مئويــة و190 درجــة مئويــة، علــى التــوايل، بعــد 5 ســاعات مــن القلــي. وجــد أن كا مــن نــوع الزيــت ودرجــات حــرارة القلــي هلمــا أتثــر ذو داللــة احصائيةعلــى تركيــز فيتامــن )أ(، بينمــا مل يكــن هلمــا أتثــر علــى فيتامــن )د(. زاد اللــون األمحــر خطًيــا مــع وقــت القلــي يف كا الزيتــن، بينمــا قــل عنــد درجــي حــرارة القلــي. ارتبــط التغيــر يف اللــون بشــكل كبــر بنضــوب فيتامــن أ. مت العثــور علــى ارتبــاط منخفــض، ولكــن ذو داللــة احصائيــة، بــن تغــرات اللــون ونضــوب فيتامــن د. يف اخلتــام، يعتمــد اســتقرار هــذه الفيتامينــات علــى أنــواع الزيــت ودرجــة حــرارة القلــي حيــث كانــت أكثــر اســتقرارًا يف اخلليــط مقارنــة بزيــت النخيــل حيــث لوحــظ اســتقرار مماثــا لألمحــاض الدهنيــة احلــرة وقيمــة البروكســايد. الكلمات املفتاحية: القلي، استنفاد الفيتامينات، فيتامن أ، فيتامن د، ريتينول، كوليكالسيفرول، الفيتامينات الذائبة يف الدهون. 8 squ journal of agricultural and marine sciences, 2023, volume 28, issue 1 effect of intermittent frying on the stability of vitamins a and d in commercially fortified oils oxygen and moisture (i.e. deep-fat or shallow frying) results in several chemical changes. these changes resulted in the decline of oil quality and acceptability (al-khusaibi and rahman, 2021). the peroxide value (pv) measures the concentration of hydroperoxides formed due to oxidation reactions, while free fatty acids % (ffa) measures the concentration of free fatty acids formed due to hydrolysis of triglycerides. it has been reported that peroxide value increased with the increase in frying time (park and kim, 2016; arsalan et al., 2017). park and kim (2016) reported an increase in the pv after 100 frying cycles (10 cycles per day for 10 days). they found that the degree of change in pv was associated with the type of oil (canola oil, soybean oil, lard and palm olein). the highest percentage change was found in lard and the least change was in palm olein. the increase in pv due to thermal oxidation was also reported (moh et al., 1999; gotoh and wada, 2006). ffa was approved as an index of oil degradation by the 28th session of the codex committee on methods of analysis and sampling held in budapest, hungary in 2005 (gotoh and wada, 2006). the ffa concentration increased with the increase on frying cycles (sohu et al., 2020; garg et al., 2021). codex alimentarius has set a limit for ffa in oils extracted from quick frozen french fried potatoes to be 1.5 % (codex 2019). different countries have set different maximum limits of ffa%. in general, it is in the range of 0.5-2.5% depending on each country’s legislations (dobargarnes et al., 1998; firestone, 1993). there have been extensive studies on the stability of different vitamins either in food samples or in vegetable oils during frying. examples are vitamin e (hou et al., 202; hu et al., 2020; adu et al., 2019; santos et al., 2018b), vitamin c (islam et al., 2021; santos et al., 2018a), vitamin k (omotosho 2015). the vitamins retention in different food samples during differing food preparation methods was reviewed in several review, such as leskova et al. (2006); and fillion and henry (1998). several studies were conducted to study the stability of vitamin a during different cooking methods, such as boiling and baking and shallow frying (hrncirik, 2010), storage (favaro et al., 1991; silalahi et al., 2017; ikram et al., 2021), extrusion (ribeiro et al., 2021; sharma et al., 2020), heat treatments (namely pasteurization, boiling and sterilization) (sachdeva et al., 2019), boiling and repeated deepfat frying (favaro et al., 1992), heating at 180°c for 5 min with no food samples. rady et al. (2019) studied the degradation of vitamin c and β-carotene during frying of sweet potato in soybean oil. their sample preparation included two steps of frying (one cycle), par-frying for 60 s and finish frying for 3 min, both at 180°c. they reported 49% and 70% decreased in vitamin c and β-carotene, respectively. simonne and eitenmiller (1998) studied the stability of vitamin a, in the form of retinyl palmitate, during simulated deep-fat frying (using cotton balls) at 185 °c for 30 h of frying. they reported higher stability in palm olein than in soybean or corn oil. favaro et al. (1991) reported high retention of vitamin a in rice and beans cooked by boiling for 40 min. however, 42% depletion was found in soybean oil subjected to four pan-frying at 115-117 °c. riaz et al. (2009) reported high losses of vitamin a and d during extrusion. several studies have been conducted on the stability of vitamin d during different cooking methods, such as boiling and baking and shallow frying (hrncirik, 2010), fortification and storage (silalahi et al., 2017; moeller et al., 2018), pasteurization/sterilization and storage (kaushik et al., 2014), drying (sławińska et al., 2016). in some studies, using frying as a processing method, the concentration in the food was measured instead of oil (omotosho, 2015; ložnjak et al., 2018). zareie et al. (2019) studied the stability of vitamin d3 in fortified canola oil heated in an oven at different temperatures (100 180 °c) for several times (5 30 min). the retention of the vitamin was temperature and initial concertation dependent. the highest loss was at 180 °c (67% depletion). loznjak et al. (2018) measured the content of vitamin d2 and d3 in sunflower oil after pan-frying for 1 minute at a temperature described as “high level” without measuring the oil temperature. the vitamin retention was 70% and 72% for vitamin d2 and d3, respectively. however, there is a lack of literature on its stability during deep-fat frying. the available literature discusses the stability of vitamin d during shallow frying (jakobsen and knuthsen, 2014; hrncirik, 2010), which is expected to have less detrimental effect compared to deep-fat frying. for example, the concentration of polymerized triglycerides in oil used for shallow frying was less than 1.3%, which was negligible and it did not show excessive use of the oil as in the deep-fat frying (jakobsen and knuthsen, 2014). adu et al. (2019) showed that changes in vitamins levels of vegetable oils was greatly influenced by the nature of food being fried. most of the studies that investigates the stability of vitamins a and vitamin d included the retention of vitamins at storage conditions and cooking, e.g. pan-frying. in addition, studies that investigated the retention at high frying temperatures did not mimic the industrial repeated frying cycles. both factors (i.e. high temperature and repeated frying cycles) could result in higher rate of oil oxidation, which can negatively affect the stability of vitamins. the aim of this study was to determine the effect of intermittent frying on the stability of vitamins a and d in two vegetable oils, and to correlate the depletion of the vitamins with the physico-chemical parameters related to the quality. materials and methods samples refined bleached and deodorized palm olein (po) and a blend of the palm olein and sunflower oil in a ratio of 40:60 (ob) were provided by areej vegetable oil and 9research paper al-amri, m. rahman, al-habsi, al-khusaibi derivatives company (saoc). both oils were fortified by the manufacturer with vitamins a and d3. par-fried french fries were purchased from the local market (mccain alimentaire s.a., harnes, france). the french fries were stored at -18 ºc until used for frying. frying intermittent frying was done by frying a batch of 500g of french fries every 15 min interval for 5 h daily for 5 days (i.e. 0, 5, 15, 20, 25 h). the sample took 7 min to get fried and 8 min were idle time until the next batch of frying. the frying was done in a 12 l deep fryer (frymaster, model no. h117-2blcsc, u.s.a) at two temperatures (i.e. 160 and 190 °c). at the end of each 5 h of frying cycle, oil samples were collected in amber bottles and kept at -18 °c until further analysis. free fatty acid and peroxide value analysis free fatty acids (ffa) were measured by titration to the american oil chemists’ society (aocs) official method ca 5a-40. recommended oil sample size according to the method was mixed with hot neutralized 95% ethyl alcohol and phenolphthalein indicator, and the mixture was titrated with naoh of recommended strength. the ffa % was calculated according to the following equation: equation (1) peroxide value (pv) were measured according to aocs official methods cd 8b-90. recommend sample size was mixed with 50 ml of 3:2 acetic acid-isooctane solution. after adding 0.5 ml of ki solution and allowing the mixture to stand for 1 minute, it was titrated with 0.1n sodium thiosulfate. titration was carried out until the disappearance of yellow color. then 0.5 ml of starch indicator solution was added. titration was carried out until the disappearance of blue color. a blank determination was conducted with reagents without sample. pv value was measure by the following equation: peroxide value (milliequivalents peroxide/1000 g sample) equation (2) where, s is the volume of sodium thiosulfate from sample titration (ml); s is the volume of sodium thiosulfate from titration of blank; and n is the normality of sodium thiosulfate solution. all measurements were in triplicate and the mean value ± standard deviations are reported. vitamin a and d analysis vitamin a was measured according to aoac official method 2001.13 using high performance liquid chromatography (hplc, agilent technologies, germany) with zorbax e clipse plus c18 column. two grams of sample were weighed in erlenmeyer flask, added 50 mg of pyrogallic acid and added 40 ml of ethanol. then 20 ml of 50 % koh were added and saponified for 45 min. after saponification, 10 ml of acetic acid were added and the sample was kept at room temperature. this was made up to 100 ml with diluent tetrahydrofuran (ethanol, 50:50) and then 20 ul was injected in hplc. the mobile phase used was acetonitrile:water (70:30). the results were expressed as µg/g using the following formula: equation (3) where rf is the response factor for vitamin a; pkht is the total test sample peak height or area of all trans and 13-cis retinol; and w is the weight of test portion (g). vitamin d was analyzed following the aocs official method 2002.05 hplc (agilent technologies, germany) with lichrosorb 5 rp18 column. the normal phase was zorbax rx-sil (4.6x250 mm, 5 micron) from restek, usa. sample was prepared by mixing 2 gm of sample, 500 mg of ascorbic acid, 50 ml of 95% ethanol and 2 ml vitamin d2 as internal standard. the mixture was saponified for 30 min with 50% koh. after saponification, 50 ml of distilled water was added through the condenser, solution was transferred to separating funnel and 100 ml of 40% ethanol was added. the vitamin was extracted by the addition of 75 ml of hexane. after phase separation, layer of hexane was removed and collected into a 250 ml separatory funnel. this was done twice and the separated layers were combined. the combined phase was washed once with 50 ml of 1m koh, twice with 50 ml of 40% ethanol and with water for 4 times, consecutively. a pinch of butyl hydroxy toluene (bht) and 15 ml ethanol were added and the hexane was evaporated at 45 °c. after evaporation, 2 ml of mixture of cyclohexane and n-heptane were added. the extract was injected in hplc with normal phase and vitamin d2 and d3 was collected. the collected sample was dried and then 0.5 ml of acetonitrile-methanol (80:20) was added and the solution was injected in hplc in reverse phase. vitamin d3 content was calculated using the following equation: equation (4) where ad3 is the peak area for vitamin d3; ad2 is the peak area for vitamin d2; md2 is the weight of vitamin d2 added to the test portion (µg); ms is the weight of test portion (g); and f is the response factor (d3/d2) at 265 nm. color analysis the color of oils was measured using a lovibond tintometer, uk (seial no: 16352 and 12435) with a 5¼’’ cell. the measurement was done as per the manufacture instructions. the cell was filled with oil sample and placed in the meter. the lamp was switched on and the viewing tube was focused until a sharp image of the aperture was observed. a set of standard color filter was adjusted to match the sample color. when both sample and standard color matched, the value of red color was noted. 10 squ journal of agricultural and marine sciences, 2023, volume 28, issue 1 effect of intermittent frying on the stability of vitamins a and d in commercially fortified oils statistical analysis analysis of variance (anova) was used to compare between means of different independent variables followed by least significant difference (lsd) using spss (ibm spss statistics 2020). a significance probability value of 0.05 was used. results and discussion changes in free fatty acids and peroxide value the changes in the free fatty acids (ffa) of palm olein (po) and oil blend (ob) are shown in figure 1. this figure clearly shows linear increase (r2 > 0.99) in the concentration of ffa with the oil usage time. this increase was higher in the po as compared to the ob at both frying temperatures (i.e., 160°c and 190 °c). the increase in ffa was well documented during deep fat frying (warner, 2004; tyagi and vasishtha, 1996). from the change in the ffa, it appeared that ob degraded at lower rate as compared to po, which indicated better stability at the frying temperatures (i.e. 160°c and 190°c). the change in ffa content during frying process could depend on many factors including frying temperature, number of frying cycles, the food being fried, and replenishment of oil during frying (karimi et al., 2017). arsalan et al. (2017) showed different ffa in different oil blends exposed to the same frying conditions (170°c, 10 h of frying with 30 min interval). at the end of the frying process, the values of ffa ranged from 0.84 to 1.13. the figure 1. the change in free fatty acids (ffa) in palm olein (po) and oil blend (ob) at a: 160 °c and b: 190 °c figure 2. the change in peroxide value (pv) in palm olein (po) and oil blend (ob) at a: 160 °c and b: 190 °c 11research paper al-amri, m. rahman, al-habsi, al-khusaibi difference in the ffa formation due to the type of oils was also reported by azimah et al. (2017). karimi et al. (2017) reported different values in the oil discarded by restaurants and street vendors in kenya. the final ffa content ranged from 0.68 to 3.95. the maximum accepted level of ffa varied from one country to another and ranged from 0.5 to 2.5% (dobargarnes et al., 1998; firestone, 1993). peroxide value (pv)increased significantly as a function of frying temperature, frying time and types of oil. ob had lower changes in pv during frying, which was in accordance to the ffa results. baltacıoğlu et al. (2017) reported that change in pv during frying is significantly influenced by oil type and frying temperature. with the variation of frying parameters such as the number of frying cycles and frying temperature, pv values in the range 9.65 20 (baltacıoğlu et al., 2017; marinova et al., 2012). paunović et al. (2020) reported 75 and 78% increase in peroxide value in sunflower oil and palm olein, respectively. degradation of vitamin a the initial vitamin a content was around 11 µg/g in po and 13 µg/g in ob. table 1 shows the change in the concentration of vitamin a in po and ob at 160 and 190 °c frying temperatures. after 25 h of frying cycles at 160 °c, content of the vitamin in po decreased to 0.36 µg/g, which represented 97% reduction of the initial content. at 190 °c, the vitamin was completely destroyed after 15 h, which can be attributed to the higher temperature of frying. simonne and eitenmiller (1998) reported higher retention of vitamin a in palm olein followed by corn oil and least in soybean oil exposed to simulated frying at 185°c for 30 min. omotosho (2015) reported that vitamin a was greatly reduced in cocoyam fried in table 1. change in vitamin a concentration (µg/g) in palm olein and oil blend used for frying at 160 °c and 190 ° c frying time (h)/temperature palm olein oil blend 160 °c 190 °c 160 °c 190 °c 0 11.05 ± 0.04a 11.03 ± 0.01a 13.07 ± 0.09a 10.01 ± 0.07a 5 5.06 ± 0.04b 1.05 ± 0.01b 9.15 ± 0.05b 4.6 ± 0.24b 10 1.69 ± 0.05c 0.32 ± 0.02c 6.9 ± 0.09c 2.43 ± 0.35c 15 0.86 ± 0.02d nd 5.83 ± 0.11d 1.31 ± 0.17d 20 0.42 ± 0.00e nd 4.59 ± 0.06e 0.68 ± 0.03e 25 0.36 ± 0.00e nd 3.63 ± 0.06f nd values are expressed as mean ± sd of triplicate readings values with different superscript letters in a column are significantly different at p = 0.05 table 2. the effect of oil type, temperature, and their interaction on vitamin a depletion. source type iii sum of squares df mean square f sig. oil 115.55 1 115.55 8.296 0.005 temperature 120.93 1 120.93 8.682 0.004 oil*temperature 36.28 1 36.28 2.605 0.111 table 3. change in vitamin d concentration (µg/g) in palm olein and oil blend used for frying at 160 °c and 190 ° c. frying time (h)/temperature palm olein oil blend 160 °c 190 °c 160 °c 190 °c 0 0.054 ± 0.001a 0.054 ± 0.006a 0.063 ± 0.002a 0.057 ± 0.001a 5 0.024 ± 0.002b 0.006 ± 0.001b 0.030 ± 0.002b 0.018 ± 0.001b 10 0.011 ± 0.001c nd nd nd 15 0.004 ± 0.001d nd nd nd 20 nd nd nd nd 25 nd nd nd nd values are expressed as mean ± sd of triplicate readings values with different superscript letters in a column are significantly different at p = 0.05 12 squ journal of agricultural and marine sciences, 2023, volume 28, issue 1 effect of intermittent frying on the stability of vitamins a and d in commercially fortified oils canola oil (0.034 µg/g) and was completely lost when the product was fired in soya or vegetable oils. silalahi et al. (2017) reported 49% reduction of vitamin a concentration when fortified po was heated at 180 °c for 5 min. fat-soluble vitamins are sensitive to heat and oxidation, therefore these can be partially or completely lost during food processing. the vitamins depletion was influenced by several factors, such as high cooking temperature, exposure time, and presence of oxygen (hrncirik, 2010; silalahi et al., 2017). extreme of these factors are present in the deep-fat intermittent frying. the rate of depletion of vitamin a in ob was lower than that in po. after 25 h of frying cycles at 160 °c, content of the vitamin decreased from 13 µg/g to 4 µg/g representing 72% decline. the effect of high temperature of frying (i.e. 190 °c) was evident and complete depletion of the vitamin was detected after 25 h of frying cycles. similar to the free fatty acids and peroxide values, it can be seen that po had higher increase in ffa and pv. this may explain the higher rate of vitamin depletion in the oil. pignitter et al. (2016) compared the stability of vitamin a in soybean oil and palm oil and they found better stability in the palm oil. this was attributed to the superior oxidative stability of palm oil compared to soybean oil, which was also supported in this work as evidenced in the changes of ffa and pv. a two-way anova examined the effect of frying temperature and oil type on vitamin a depletion (table 2). vitamin a depletion was significantly influenced by oil type (p = 0.005) frying temperature (p = 0.004). degradation of vitamin d table 3 shows the concentration of vitamin d during the 25 h frying cycles in both oils. the vitamin d content of po decreased by 67% after 5 h of frying at 160°c and 80% at 190 °c. after 20 h of frying cycles, vitamin d content was completely depleted. at 160 °c, vitamin d was more stable in po than the ob. while 100% depletion was found after 10 h of frying in the blend, around 80% decrease was detected in the po. in both oils, vitamin was completely lost after 5 h of frying at 190 °c. compared to vitamin a depletion, vitamin d was less stable and 100% depletion was detected after 10 h of frying cycles. it must be noted that studies on the vitamin d retention in food staff during cooking are limited; especially during frying. hrncirik (2010) reported 40% decrease in vitamin d content after shallow frying in fortified liquid margarine at 180 °c. on the other hand, 70% retention of the vitamin was reported in sunflower oil followed by pan-frying at “high-level temperature” as described by table 4. the effect of oil type, temperature, and their interaction on vitamin d depletion. source type iii sum of squares df mean square f sig. oil .012 1 .012 3.595 0.064 temperature .010 1 .010 2.846 0.098 oil*temperature .012 1 .012 3.611 0.063 table 5. correlation between red color of oils and vitamins a and d content vitamin pearson correlation p-value a 0.814 < 0.001 d 0.250 0.034 figure 3. the change in red color in palm olein (po) and oil blend (ob) at a: 160 °c and b: 190 °c 13research paper al-amri, m. rahman, al-habsi, al-khusaibi the authors without measuring the exact value (ložnjak and jakobsen, 2018). mattila et al. (1999) reported high vitamin d3 retention in baked fish (78-100%) and vitamin d retention in pan-fried mushrooms (80-100%). the effect of cooking parameters on vitamin d retention was influenced by the heating conditions and the type of food being cooked (jakobsen & knuthsen, 2014; ložnjak, & jakobsen, 2018). table 4 shows the effect of oil type and frying on vitamin d depletion. oil type and frying temperature did not show any significant effect on vitamin d depletion. it must be noted that this might be due to the limited number of data resulting from the fast depletion of the vitamin. color analysis red color has been always reported as an indicator of the degradation of frying oils (jurid et al., 2020; fauziah et al., 2000). the red color was initially high in fresh palm olein (≈ 2.6 units) compared to the blended oil (≈ 0.8 units). po has been reported to have higher values than other oils and the values reported in this study are in agreement with literature (fauziah et al., 2000; low et al., 1998; tarmizi et. al., 2016). after the 5 days frying cycles, the red color changed by 182% in plam olein and by 250% in the oil blend at frying temperature of 160 °c. although the change in color in palm olein has been reported to be relatively faster than sunflower oil (razali et al., 1999), this may not be true in the case of blended oil. it can be noticed that the change was observed higher in the ob compared to the po (figure 3). pearson’s correlation was calculated to measure the association between vitamin content and red color change (table 5). a strong negative association (r = -0.814, p < 0.001) can be noticed between vitamin a content and red color. low association (r = 0.250, p = 0.034) was found between vitamin d content and red color (-0.250). conclusion the intermittent frying used in this study caused linear increase in the free fatty acids content (ffa) and peroxide value, which showed the deterioration of oil by frying protocol. the depletion of vitamin a was time, temperature and oil type dependent. vitamin a showed higher stability compared to vitamin d, which depleted completely after 15 h of frying time in po at 160 °c. the red color of oils was negatively associated with vitamin a concentration, while the association with vitamin d concertation was not significant. the strategies of oil fortifications as an intervention method need to be reassessed in order to make sure that the goals of intervention could be achieved. based on the maximum limit of ffa, frying in the oil blend at 160 °c resulted in the least depletion of vitamin a. on the other hand, frying in palm olein at 160 resulted in the least depletion of vitamin d. kinetics of vitamins a and d depletion needs to be studied for the possible predicting of depletion of vitamins as a function of time, temperature and oil type. acknowledgement authors would like to thank sultan qaboos university for funding this work (ig\agr\food\19\02) and areej vegetable oils and derivatives company for providing the oil used in the study. the language editing support provided by the editing refinery, md, usa is highly acknowledged. references arslan fn, şapçı an, duru f, kara h. 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(1998). retention of vitamin e and added retinyl palmitate in selected vegetable oils during deep-fat frying and in fried breaded products. journal of agricultural and food chemistry 46(12): 5273-5277. sławińska a, fornal e, radzki w, skrzypczak k, zalewska-korona m, michalak-majewska m, parfieniuk e, stachniuk a. (2016). study on vitamin d2 stability in dried mushrooms during drying and storage. food chemistry 199: 203-209. tarmizi aha, ismail r, kuntom a. (2016). effect of frying on the palm oil quality attributes–a review. journal of oil palm research 28(2): 143-153. tyagi v, vasishtha a. (1996). changes in the characteristics and composition of oils during deep-fat frying. journal of the american oil chemists’ society 73(4): 499-506. warner k. (2004). chemical and physical reactions in oil during frying. frying technology and practices. p. white b, w. k. and m. k. gupta, aocs publishing. who (2010). world health organization. regional committee for the eastern mediterranean regional strategy on nutrition 2010–2019. http://applications.emro.who.int. zareie m, abbasi a, faghih s. (2019). thermal stability and kinetic study on thermal degradation of vitamin d3 in fortified canola oil. journal of food science 84(9): 2475-2481. review article journal of agricultural and marine sciences 2021, 26(2): 1–9 doi: 10.24200/jams.vol26iss2pp1-9 received 25 oct 2020 accepted 22 march 2021 a review on solar drying of fish nasreen s. al-mahruqi and abdulrahim m. al-ismaili* abdulrahim m. al-ismaili*( ) abdrahim@squ.edu.om; ams.ismaili@ gmail.com, department of soils, water and agricultural engineering, sultan qaboos university, oman introduction oman is considered one of the largest fish pro-ducers and consumers in the gulf cooperation council (fao, 2015). fish is a very popular food due to its high protein and nutrients content. however, the due to the high moisture content in fish (tiwari et al., 2009), spoilage is a critical issue facing fish producers. because of the high spoilage rate of fish (jain and pathare, 2007), ghaly et al. (2010) found that 30% of fish is lost every year. therefore, several techniques have been practiced to preserve fish in order to increase their shelf life and to maintain their texture, flavour and nutritional value (ghaly et al., 2010). smoking, drying, chilling, brining and freezing are among the commonمراجعة على التجفيف الشمسي لألمساك نسرين س. احملروقية ، عبدالرحيم م. اإلمساعيلي * abstract. oman is one of the major fish producers in this region. fish is highly perishable, therefore different preservation techniques, such as smoking, drying, chilling, brining and freezing are being used. solar drying is one of the most popular technique due to its simplicity and low cost as compared to other techniques. this study aimed to review the different types of solar drying techniques and highlighted the quality measures of solar dried fish. solar drying techniques can be divided into three types: open-sun drying, direct and indirect solar drying. the open-sun drying is the most adoptable method because it is the cheapest preservation technique. however, this technique has several drawbacks, such as the uncertainty of weather, large implementation area, required time, poor drying rate, high labor costs, possible attack by insects, microorganism and birds, and contaminated with dust and foreign materials. solar dryers, on the other hand, overcome the most of drawbacks associated with open-sun drying. they have shorter drying time and higher drying rate, and at the same time these enhance the physical properties of dried fish. for better understanding of the drying processes many regression models were used and the exponential model was found to be the best fitted model describing the drying behavior. fish possesses good nutritional value due to higher amount of proteins, lipids and ash contents. for higher shelf life, fish has to meet certain characteristics with respect to ph, water activity, microbial load, total volatile base nitrogen (tvb-n), trimethylamine nitrogen (tma-n) and enzymatic autolysis. for a very good quality, the ph must be ranged from 6.0-6.9 and the water activity must be lower than 0.6. the tvb-n and tma-n are the indicators of spoilage and their upper acceptable limits are 10-15 mg/100g and 35-40 mg/100g, respectively. total plate count (tpc) and total fungal count (tfc) are two attributes used to assess the microbiological quality of fish products. the autolysis changes in the fish lead to spoilage as a result of the production of biogenic amines and microbial growth. studying the health aspect of dried fish is very important for the human body to obtain a greater proportion of proteins and important substances away from the harmful chemicals that may appear in traditional draying technique. keywords: solar drying techniques, fish, quality امللخص:عمــان هــي واحــدة مــن أكــر منتجــي األمســاك يف هــذه املنطقــة، وألن األمســاك قابلــة للتلــف بدرجــة كبــرة فإنــه يتــم اســتخدام تقنيــات خمتلفــة حلفظهــا؛ مثــل التدخــن والتجفيــف والتريــد والتخمــر والتجميــد، ويعــد التجفيــف الشمســي مــن أكثــر التقنيــات شــيوًعا نظــرًا لبســاطته وتكلفتــه املنخفضــة مقارنــة ابلتقنيــات األخــرى. ولقــد هدفــت هــذه الدراســة إىل مراجعــة األنــواع املختلفــة لتقنيــات التجفيــف الشمســي وإبــراز مقاييــس اجلــودة لألمســاك اجملففــة مشســيا. وميكــن تقســيم تقنيــات التجفيــف الشمســي إىل ثالثــة أنــواع: التجفيــف الشمســي املفتــوح، والتجفيــف الشمســي املباشــر وغــر املباشــر داخــل اجملففــات الشمســية، ويعتــر التجفيــف حتــت أشــعة الشــمس املفتوحــة هــو األســلوب األكثــر اســتخداًما ألنــه أرخــص تقنيــة للحفــظ، ولكــن هــذه التقنيــة هلــا العديــد مــن العيــوب؛ مثــل تقلبــات الطقــس، واملســاحة الكبــرة الــي حتتاجهــا، وطــول الوقــت املطلــوب للتجفيــف، وبــطء معــدل التجفيــف، وتكاليــف العمالــة املرتفعــة، وتعرضهــا للحشــرات والكائنــات احليــة الدقيقــة والطيــور، واحتماليــة التلــوث ابلغبــار واملــواد اخلارجيــة. ولقــد وجــد أن اجملففــات الشمســية تتغلــب علــى معظــم العوائــق املرتبطــة ابلتجفيــف حتــت أشــعة الشــمس املفتوحــة وذلــك ألن اجملففــات الشمســية حتتــاج لوقــت جتفيــف أقصــر وهلــا معــدل جتفيــف أعلــى، ويف نفــس الوقــت فإهنــا حتســن مــن اخلصائــص الفيزايئيــة لألمســاك اجملففــة، ولفهــم عمليــات التجفيــف بشــكل أفضــل قــام الباحثــون ابســتخدام العديــد مــن منــاذج االحنــدار، ووجــد أن النمــوذج األســي هــو أفضــل منــوذج مالئــم يصــف ســلوك التجفيــف. ومــن انحيــة أخــرى؛ فــإن األمســاك متتلــك قيمــة غذائيــة جيــدة بســبب احتوائهــا علــى كميــات كبــرة مــن الروتينــات والدهــون وحمتــوايت الرمــاد، وللحصــول علــى عمــر ختزيــي أعلــى فإنــه جيــب أن تفــي األمســاك خبصائــص معينــة فيمــا يتعلــق بدرجــة احلموضــة والنشــاط املائــي واحلمــل امليكــرويب وإمجــايل النيرتوجــن األساســي املتطايــر )tvb-n(، والنيرتوجــن ثالثــي ميثيــل األمــن )tma-n( واالحنــالل الــذايت األنزميــي، وللحصــول علــى جــودة جيــدة جــًدا جيــب أن يــرتاوح الرقــم اهليدروجيــي بــن 6.0-6.9 وأن يكــون نشــاط املــاء أقــل مــن 0.6. ويعــد tvb-n و tma-n مهــا مؤشــرا التلــف وحدودمهــا القصــوى املقبولــة هــي 10-15 جمــم/100 جــم و 35-40 جمــم/100 جــم علــى التــوايل، وأمــا عــن إمجــايل عــدد الصفائــح )tpc( وإمجــايل عــدد الفطــرايت )tfc( فهمــا مستــان تســتخدمان لتقييــم اجلــودة امليكروبيولوجيــة ملنتجــات األمساك. وتؤدي تغرات التحلل الذايت يف األمساك إىل تلفها نتيجة إنتاج األمينات احليوية والنمو امليكرويب. وتعتر دراسة اجلانب الصحي لألمساك اجملففة أمرًا مهًما جــًدا لصحــة اإلنســان مــن أجــل احلصــول علــى نســبة كبــرة مــن الروتينــات واملــواد املهمــة بعيــًدا عــن املــواد الكيميائيــة الضــارة الــي قــد تظهــر يف تقنيــة التجفيــف التقليديــة. الكلمات املفتاحية: طرق التجفيف التقليدية، األمساك، اجلودة. 2 squ journal of agricultural and marine sciences, 2021, volume 26, issue 2 a review on solar drying of fish ly-practiced techniques for fish preservation (ghaly et al., 2010). however, fish drying is the most popular technique (jain and pathare, 2007; sahu et al., 2016), which is achieved using different approaches such as solar, electrical, spray and mechanical drying methods (prakash and kumar, 2014; singh et al., 2017). due to the increase in the prices of fossil fuels, solar drying became the most widely-used drying method as it uses a renewable source of energy and does not rely on fossil fuel (bala and janjai, 2009; prakash and kumar, 2014). the objectives of this article were to review the different types of solar drying techniques and to highlight the quality measures of solar dried fish. solar drying techniques solar energy is the most abundant source of energy on the earth and consequently, it is used in many processes. solar drying is a traditional drying process that harnesses solar energy to speed up the drying process. there are three types of solar drying techniques, which are open-sun drying, direct and indirect solar drying (sahu et al., 2016). the most popular technique is drying by the direct exposure to sun which is considered the cheapest technique as it does not demand a significant infrastructure and operational costs (jain and pathare, 2007) (figure 1). when the product is exposed to sun, its temperature increases due to heat absorption, which in turn leads to moisture reduction, i.e. drying. in the direct solar drying technique, the product is placed inside a structure that is covered with a transparent material, such as plastic and glass (figure 2). this kind of structure traps the solar heat (greenhouse effect) as it allows shortwave radiation to pass and captures the longwave radiation (singh et al., 2017), i.e. causing higher air temperatures and thus, faster drying (sahu et al., 2016). in this technique, drying rate can be additionally increased by the use of fans to bring dryer air over the products and this technique is known as “forced convective” direct drying (singh et al., 2017). in the indirect drying techniques (figure 3), products are not exposed to direct sun light but instead, ambient air is heated by solar radiation via a solar collector and then the hot air flows over the products. the air is circulated in this technique either by natural convection (i.e. indirect dryer under passive mode) or by the use of exhaust fans. in the former, ambient air enters to the solar collector through a lower vent and then the hot air leaves to the drying chamber through a higher vent, i.e. thermosyphic effect (prakash and kumar, 2014). in the latter, exhaust fans located at the outlet vent are used to move the air stream and this technique is known as forced convection indirect solar drying (sahu et al., 2016). the forced convection dryer is more suitable for products with high moisture content while natural convection is suitable for low moisture products (sahu et al., 2016; singh et al., 2017). prakash and kumar (2014) found that the convective mass transfer coefficient in the forced convection mode was double than that in the natural convection mode. as illustrated in figures 2 and 3, the structure of direct and indirect solar dryers is similar to the structure of greenhouses, which may explain the reason why these dryers are also called “greenhouse dryers”. the efficiency of solar dryers is enhanced by the integration with photovoltaic (pv) systems. the use of pv-integrated solar dryers is very practical if forced convection is to be implemented in the areas where electricity is not available or not affordable (sahu et al., 2016). in terms of solar drying performance, the greenhouse dryer is considered the best alternative to sun drying. bala and janjai (2009) reported that pv-integrated greenhouse solar dryers can reduce the drying time by almost 50%. the shape of the greenhouse is another factor affecting the drying process. it was reported by charters et al. (2017) that the dome shape (hemispherical) can offer the maximum utilization of solar radiation and the even-span shape is utilized for proper air mixing. figure 1. solar drying by direct sun exposure for (a) red chili pepper (walters and jha, 2016), and (b) fish (ochieng et al., 2015). 3review article al-mahruqi and al-ismaili advantages and disadvantages of solar drying solar radiation is an abundant, eco-friendly and inexhaustible source of energy (ghaly et al., 2010). hence, it represents the cheapest way to preserve food (jain and pathare, 2007). nevertheless, there are many disadvantage related to open-sun drying method, such as the uncertainties of weather, requirement of large implementation area, time-consuming, poor drying rate, high labour costs, attacking by insects, microorganism and birds, and mixing with dust and foreign materials (jain and pathare, 2007; al rawahi et al., 2013; martunis, 2013; sontakke and salve, 2015). mansur et al. (2013) found that, during open-sun drying, some fish samples contained a large amount of debris from the poor quality underlying material and the dried samples have undergone surplus drying or inappropriate drying and handling. however, some of these limitations, e.g. time-consuming, insect attacks and dust contamination, can be eliminated by the use of greenhouse dryers (charters et al., 2017; sontakke and salve, 2015). solar fish drying in many coastal areas, fish is considered a main source of food and income (belwal et al. 2015). however, fish products are highly perishable and thus, have a short shelf life (bala and mondol, 2001). drying is the most widely-used preservation technique used to overcome the spoilage problem. because of their high market value and availability, several fish species such as ribbon fish, golden anchovies, croker, prawns, paplet and surmai are dried using solar drying techniques (sengar et al., 2009). in oman, due to the high fish production and consumption, traditional sun drying techniques are widely practiced to dry a variety of fish types such as sardine, anchovy and jake mackerel (al bulushi et al., 2013; al rawahi et al., 2013). sardine fish alone represents 80% of the total oman small fish catching and the annual amount of dried sardine is 23000 tons, which is mainly used as a livestock feed (al-jufaili and al-jahwari, 2011; basunia et al., 2011). open-sun drying of fish is an old method used worldwide to dry a variety of fish types. in oman, as an example, sardine fish (figure 4) are traditionally dried by dispersing the fish on sandy beaches for 7 days in low ambient temperatures and 4-5 days in high temperatures (basunia et al., 2011). this method, although widely-accepted, is associated with a substantial loss of almost 30-40% of the total dried amount due to a variety of reasons that include rain, wind, dust and contamination and consumption by animals, birds and rats (al rawahi et al., 2013). other solar drying techniques such as greenhouse dryers are implemented to overcome the drawbacks of open-sun drying. for instance, sengar et al. (2009) used a low cost passive (natural convection) multi-shelf greenhouse solar dryer (figure 5) to dry prawns. the fish dried inside the solar dryer were found better than the fish dried in open-sun in terms of drying time, texture and color. in a similar study, silver jewfish was dried by a natural convection solar tunnel drier in bangladesh (bala and janjai, 2009). the solar dried products had better quality with a significant reduction in drying time as compared with open-sun drying. in another study, a low cost passive solar tunnel dryer (figure 6) was developed in oman to dry sardine, skater bream and jake mackerel (al rawahi et al., 2013). on the other hand, an active (forced convection) greenhouse solar dryer was used in indonesia for drying anchovy fish (figure 7) (martunis, 2013). in a similar study, jewfish was dried in a hybrid solar drying system and it was found that the drying time took only 8 h to reduce the moisture content from 64 to 10% (singh et al., 2017). all of the abovementioned dryers managed to reduce the drying time with increased water loss. several studies focused on the calculation of drying time, drying rate and the final moisture content of the figure 2. direct solar dryer (singh et al., 2017). figure 3. indirect forced convection solar dryer; 1: vent , 2: exhaust fan , 3: heating chamber, 4: drying chamber and 5: glass cover with fibre (singh et al., 2017). 4 squ journal of agricultural and marine sciences, 2021, volume 26, issue 2 a review on solar drying of fish dried fish products. for example, the drying time to reduce the initial moisture content of prawns from 75 to 16.4% in open-sun drying and to 16.5% in a low-cost passive solar dryer was 11 and 8 h, respectively (sengar et al., 2009). similarly, abraha et al. (2017) found that open-sun drying of anchovy took 5 days and inside a solar tent drier, it took only 3 days. using a natural convective solar drier, it was found that the drier was able to reduce the initial moisture content of bayad fish flakes from 78.67% to a final moisture content of 11.41% (babiker et al., 2014). mustapha et al. (2014) studied five different solar driers and found that black stone-inserted glass drier showed the fastest drying rate in comparison to the plastic drier, mosquito net drier, glass drier and aluminum drier for drying african catfish and nile tilapia. martunis (2013) reported that the drying rate of fish using a force convection greenhouse was 3.29% per hour in a total drying time of 11 h while the same amount of fish took 2 days to dry in the sun. using a parabolic-dish solar collector (figure 8), solomon et al. (2016) found that salted prawn and unsalted prawn required 8 h and 15 h to dry, respectively which highlights the effect of salting on the drying time. in all drying processes, the drying time increased with increasing humidity in the ambient air (bala and janjai, 2009). in general, the drying rate starts high at the beginning of the drying process and decreases with the reduction in moisture content (jain and pathare, 2007). the solar drying technique has a great effect on the physical properties of dried fish. under open-sun drying, (mansur et al., 2013) compared three physical characteristics, namely, color, odor and texture, of three types of fish; labeo, channa and wallago attu. the results showed that labeo and channa fish had better quality than wallago fish which developed bitter taste, rancid odor and soft and fibrous texture. however, all three fish had brown color as compared to the fresh fish which have cream color. in a similar study the channa fish showed good physical quality as compared with wallago and glossogobius fish (majumdar et al., 2017). islam et al. (2012) reported differences in the physical properties of dried mola fish in a solar tunnel. the final color of the dried fish was ranging from white to light brown and the texture was firm and flexible with good odor. the overall quality of the dried mola fish was excellent as compared with the traditionally dried mola fish, where the color was brown and the texture was soft with off-odor. in general, mustapha et al. (2014) found that the physical parameters of open-sun dried fish was the least acceptable among the fish dried in five other solar driers. abraha et al. (2017) reported that the physical properties, such as color, flavor, appearance, texture and odor was superior for fish dried in a solar tent drier to fish dried in open-sun. for instance, anchovy fish dried in a greenhouse dryer undergone no color change during the drying process (martunis, 2013). sengar et al. (2009) figure 4. traditional open-sun drying of sardine, (a) sardine fish dispersed on a sandy beach and (b) animals eating from the dried sardine (al-jufaili and al-jahwari, 2011). figure 5. low cost passive solar dryer (sengar et al., 2009). 5review article al-mahruqi and al-ismaili found that the color and texture of salted fish inside a low cost dryer were better as compared with unsalted fish, but the dried fish in open-sun was the least accepted one. in a similar study, the addition of salts in the dried fish affected positively the physical (organoleptic) properties, such as aroma, taste, texture and general acceptability. solomon et al. (2016) observed good taste and total acceptability of salted fish were superior to those of unsalted fish when both were dried in a solar drier. therefore, direct and indirect solar drying techniques provide better quality fish than open-sun drying and salted fish gave better physical properties than unsalted fish. for better understanding of the behavior of drying processes, regression models were extensively used. to optimize the drying process, accurate simulation-models can be to predict the performance of the product to be dried (belessiotis and delyannis, 2011). non-linear regression models were used to best-fit experimental drying curves with the closest matching models. the drying rate could be either constant (fixed) or falling (decreasing), however the falling rate prevails (toujani et al., 2013) because in most biological products, the constant rate does not exist (bellagha et al., 2002). in the drying process, the moisture is removed rapidly at the beginning then it decreases slowly as the drying progresses. this is because at the beginning moisture evaporates from the surface of the fish and then moisture moves by diffusion inside the fish material toward the surface (toujani et al., 2013). this behavior is described using different regression models such as exponential, logarithmic, diffusion-approximate, two-term and many others. hubackova et al. (2014) found that the appropriate models describing the natural convection solar drying kinetics of five species of fish were as follows; logarithmic model for climbing perch and nile tilapia fish; diffusion-approximate model for swamp eel and walking catfish; and two-term model for channa fish. in another study, the drying kinetics of sardine muscle were well-fitted using two models, namely, exponential and page (djendoub et al., 2009). figure 9 illustrates the exponential drying curve of tilapia fish (kituu et al., 2010). on the other hand, a logarithmic regression model was used to describe the drying rate of prawn and chelwa fish under open-sun drying (jain and pathare, 2007). in electric oven-drying, the most appropriate model for all fish species is the modified page1 because of the uniform drying conditions except for channa fish where the exponential model showed the best-fit. all mentioned models can help in predicting the drying kinetics of fish using different drying techniques. health aspects of solar-dried fish the quality of dried fish has to meet certain characteristics with respect to protein, lipid and ash content. recent studied proved that dried fish with high amount of protein, ash and fat content have very good nutritional value (siddique et al., 2012). proteins control the metabolism in the nerves and bones and control blood sugar level by producing peptides (jónsson et al., 2007). the protein content in dried fish is higher compared to fresh fish, which is a desirable characteristic. the protein is an important factor that helps in the quality assessment of dried fish (hazarika et al., 2016). lipids and ash are two important sources of energy for the body. it was found that the amount of lipids is affected by the drying technique where it was reported that lipid content of open sun dried fish is less than that in fish dried with other drying methods (anh et al., 2015). commonly, ash content of dried fish is higher than that of fresh fish. however, it could be less in the dried fish because the ash content comes from inorganic matter, i.e. a residue that remains after drying, where water content and organic matter are reduced (oladipo and bankole, 2013). when the values of protein, lipids and ash content were analyzed for 10 fish species dried under open sun, they ranged 28.63-53.84, 4.42-16.52 and 8.96-30.30 g/100 g, figure 6. fish drier diagram (al rawahi et al., 2013). figure 7. force convection greenhouse solar dryer (martunis, 2013). 6 squ journal of agricultural and marine sciences, 2021, volume 26, issue 2 a review on solar drying of fish respectively (hazarika et al., 2016). in a similar study, islam et al. (2013) reported that the protein, lipids and ash content for 4 fish types, namely, amblypharyngodon mola (mola), puntius spp. (punti), channa punctata (taki) and glossogobius giuris (bele), dried under opensun amounted to 32.02-41.38 g/100 g (channa punctatus had the highest value), 3.21-14.03 g/100 g (channa punctatus had the lowest value) and 20.14-24.40 g/100 g. sultana et al. (2008) compared the protein, lipids and ash content of fresh silver jew fish, bombay and duck ribbon fish with the dried samples in a solar tunnel dryer. the protein content of fresh fish ranged from 65.9071.60 g/100 g, lipids ranged from 13.42 to 21.30 g/100 g and ash content from 11.27 to 12.44 g/100 g whereas after drying they ranged 71.9-80.52, 8.05-19.18 and 9.47-10.24 g/100 g, respectively. similarly, babiker et al. (2014) found that the protein, fat and ash content of dried bayad fish flakes using a natural convective solar drier were 69.19, 0.23 and 30.68 g/100g of product, respectively while, the fresh fish contained 92.51, 0.22 and 7.27 g/100 g of product, respectively. across the developing countries, dried fish is considered a widespread delicacy. therefore, extending the shelf life of dried fish is necessary for long time storage. to achieve this, dried fish has to meet certain characteristics such as ph, water activity, microbial load, total volatile base nitrogen (tvb-n), trimethylamine nitrogen (tma-n) and enzymatic autolysis which differ due to the fluctuations in processing conditions (al bulushi et al., 2013). lower ph values of dried products offer more enhancement in microbial inhibition and consequently, increase the shelf life of dried fish by preventing endogenous proteases activities (majumdar et al., 2017). dried fish under a ph range of 6.0-6.9 are considered to be of very good quality (kakati, 2017). this implies that the loss of fish quality can result from the increase in ph. in literature, puntius sophore, setipinna phasa, amblypharyngodon mola, pseudeutropius atherinoides, pseudambassis ranga and corica soborna fish were dried under open-sun drying where the ph was 6.2-6.6 (kakati.b, 2017). in another study, noemacheilus beavani, chanda ranga, barilius tileo, amphipnous cuchia, anabas testudineus, amblypharyngodon mola, channa punctatus, tor putitora, puntius chola and conta elongate fish were also dried under open-sun drying where most of these fish types were within the good-quality ph range and only four of them, viz. amblypharyngodon mola, channa punctatus, tor putitora and conta elongate, were outside the range (hazarika et al., 2016). the second characteristic is the water activity, which is the ratio of vapor pressure of water in the fish product to the vapor pressure of pure water at the same temperature (labuza, 1980). the water activity is considered as a criterion and a measure of microorganism development and toxin release of enzymatic and non-enzymatic browning development. it was found that water activity greatly affects fresh fish endogenous microflora (al bulushi et al., 2013). there is a water activity limit for each food product below which the microorganism stop growing (belessiotis and delyannis, 2011). most molds maintains their growth at a minimum water activity of 0.7 (oparaku et al., 2017) and many bacteria sustains the growth at 0.9, while some biogenic amines, such as e. cloacae, need water activity of 0.48 (al bulushi et al., 2013). majumdar et al. (2017) found that when moisture content of dried fish is less than 15%, no microbe can grow. this is because with the increase in water absorption from the surronding, the water activity increases, causing an increase in microbial growth and reduction of shelf life of dried products. further reduction in the water activity limits the spoilage and microbial growth. the microbial quality of fish products is affected by the drying method and the proper handling anoxic conditions (hygienic conditions) (al bulushi et al., 2013; oparaku et al., 2017). developing countries produce low microbiological quality products which could be loaded with staphylococcus aureus, clostridium spp. and fecal streptococcus spp. pathogens (al bulushi et al., 2013). to assess the microbiological quality of fish products, total plate count (tpc), which uses plate count agar, and total fungal count (tfc), figure 8. parabolic-dish solar collector (solomon et al., 2016). figure 9. exponential drying curve of tilapia fish (kituu et al., 2010). 7review article al-mahruqi and al-ismaili which uses potato dextrose agar by apha, are used as microbial parameters. immaculate et al. (2012) observed that tpc and tfc were high in open-sun dried sardine but absent in the sardine dried in a solar drier. they also reported the presence of e. coli pathogens in open-sun samples, however other pathogens such as salmonella and vibrio were absent in both methods. total volatile base nitrogen (tvb-n) and trimethylamine nitrogen (tma-n) are signs (indicators) of spoilage which are correlatated strongly with the bacterial activity, endogenous enzymes and thus, the rate of spoilage (kakati, 2017). they can be determined from trichloroacetic acid removal by micro diffusion from the sea product (fish). the recommended acceptability upper limit of these indicators for human consumption is 10-15 mg/100g for tma-n and 35-40 mg/100g of tvb-n in dried fish (immaculate et al., 2013). the quality of dried fish with respect to tvb-n can be classified into very high quality at tvb-n value of 25 mg/100g or less, good quality at 26-30 mg/100g, limit of acceptability at 30-35 mg/100g and spoilt quality above 35 mg/100g (jinadasa, 2014). however, in previous studies, the acceptablity limit for tvb-n was considered to be 100 mg/100g (connell, 1980), which is much higher than the recent classifications. accordingly, hossain et al. (2017) found that tma-n and tvb-n values of open-sun dried silver pomfret and open-sun dried perch fish were within the human acceptablity levels. the tma-n and tvb-n values for perch dried-fish were 8.21±0.12 and 46.97±1.00 mg/100g, respectively and for silver pomfret, the values were 9.41±0.37 and 85.68±1.60 mg/100g, respectively. in another study, the tvb-n value were found to be acceptable for human consumption for mola fish dried in a solar tunnel dryer (15.68 mg/100g) and in open-sun (20.36 mg/100g) (islam et al., 2012). similarly, sultana et al. (2008) repoted that in a solar tunnel dryer, the tvb-n values of dried ribbon fish, silver jew fish and bombay duck were ranging from 15.46 to 19.21 mg/100g. the last cause of fish spoilage is the autolytic changes (oparaku et al., 2017) which denotes the biological and chemical changes occurring because of quality losses at early stage of fresh fish (ghaly et al., 2010; oparaku et al., 2017). major fish molecules undergo enzymatic breakdown and as a result of autolysis of fish muscle proteins peptides and free amino acids can be produced which cause fish meat spoilage as a result of production of biogenic amines and microbial growth (ghaly et al., 2010). for instance, open sun dried anchovy fish was reported to contain biogenic amines that can cause scombroid-poisoning (al bulushi et al., 2013). the scombroid poisoning can also be caused by the increase in the level of histamine in the fish product so it is also called histamine fish poisoning (hungerford, 2010). bulushi et al. (2009) found that biogenic amines could be involved in the formation of nitrosamines at a high significant level when biogenic amines are present at a high concentration in fish products. it was reported, in the same study, that impure salts enhance the formation of nitrosamine whereas, pure salts (sodium chloride) inhibit nitrosamine formation. conclusion a review on solar drying of fish was done, several points can be concluded from this the study: (i) open-sun draying is the most popular preservation technique of food products, (ii) the drawbacks of open-sun drying can be overcome by implementing other solar drying techniques such as greenhouse tunnel dryers, (iii) solar dryers have shorter drying time and higher drying rate, and the physical properties of dried fish are enhanced, (iv) many regression models were used for better understanding of the drying processes, (v) fish have very good nutritional value due to their high amount of proteins, lipids and ash contents, and (vi) some characteristic, such as ph, water activity, microbial load, total volatile base nitrogen (tvb-n), trimethylamine nitrogen (tma-n) and enzymatic autolysis analyzes, are used to assess the quality of dried fish to achieve longer shelf life. references abraha b, samuel m, mohammud a, habte-tsion hm, admassu h, al-hajj, nqm. (2017). a comparative study on quality of dried anchovy (stelophorus heterolobus) using open sun rack and solar tent drying methods. turkish journal of fisheries and aquatic sciences 17(6): 1107-1115. c-5: al-jufaili s, al-jahwari os. (2011). the omani coastal traditional sardine fishery 1994-2007: a review. journal of agricultural and marine sciences 16: 1-12. al bulushi im, guizani n, dykes ga. (2013). effect of ambient storage on the microbial characteristics of traditional dried anchovies (encrasicholina punctifer). african journal of microbiology research 7(28): 3575-3581. al rawahi zna, munusami a, kaithari dk. (2013). performance analysis of solar drying system for marine product of oman. international journal of students’ research in technology & management 1(6): 610-613. anh ntn, nhi nt, van hoa n. (2015). effect of different drying methods on total lipid and fatty acid profiles of dried artemia francis-cana biomass. can tho university journal of science 1: 1-9. babiker amo, ismail ia, osman oe, salih za. (2014). effect of solar drying using a natural convective solar drier on bacterial load and chemical composition of bayad (bagrus bayad) fish flakes. international journal of multidisciplinary and current research 2: 2321-3124. bala b, janjai s. (2009). solar drying of fruits, vegetables, spices, medicinal plants and fish: developments and potentials. international solar food processing con8 squ journal of agricultural and marine sciences, 2021, volume 26, issue 2 a review on solar drying of fish ference, indore, india, january 14-16. bala b, mondol m. (2001). experimental investigation on solar drying of fish using solar tunnel dryer. drying technology 19(2): 427-436. basunia ma, al-handali hh, al-balushi mi, rahman ms, mahgoub o. (2011). drying of fish sardines in oman using solar tunnel dryers. journal of agricultural science and technology b 1: 108-114. belessiotis v, delyannis e. (2011). solar drying. solar energy 85(8): 1665-1691. bellagha s, amami e, farhat a, kechaou n. (2002). drying kinetics and characteristic drying curve of lightly salted sardine (sardinella aurita). drying technology 20(7): 1527-1538. belwal r, belwal s, al jabri o. (2015). the fisheries of oman: a situation analysis. marine policy 61: 237-248. bulushi ia, poole s, deeth hc, dykes ga. (2009). biogenic amines in fish: roles in intoxication, spoilage, and nitrosamine formation—a review. critical reviews in food science and nutrition 49(4): 369-377. charters w, macdonald r, kaye d, xiaoren s. (2017). passive greenhouse type solar dryers and their development. international energy journal 11(2): 51-60. connell jj. (1980). control of fish quality ii, vol. 12, fishing news books ltd.: 7-129. djendoubi n, boudhrioua n, bonazzi c, kechaou n. (2009). drying of sardine muscles: experimental and mathematical investigations. food and bioproducts processing 87(2): 115-123. fao. (2015). fishery and aquaculture country profiles. oman. http://www.fao.org (accessed 7 march 2018). ghaly ae, dave d, budge s, brooks m. (2010). fish spoilage mechanisms and preservation techniques. american journal of applied sciences 7(7): 859. hazarika p, ullah n, handique pj. (2016). assessment of biochemical quality of ten selected dried fish products of north east india. assessment 3(3): 183-186. hossain m, jamil m, mia m, uddin m, mansur m. (2017). studies on the proximate composition, quality and heavy metal concentration of two sun-dried marine fish (sun-dried silver pomfret and sun-dried perch) of cox’s bazar district of bangladesh. journal of environmental science and natural resources 10(1): 25-32. hubackova a, kucerova i, chrun r, chaloupkova p, banout j. (2014). development of solar drying model for selected cambodian fish species. the scientific world journal 2014. vol. 2014.10.1155 hungerford jm. (2010). scombroid poisoning: a review. toxicon 56(2): 231-243. immaculate j, sinduja p, jamila p. (2012). biochemical and microbial qualities of sardinella fimbriata sun dried in different methods. international food research journal 19(4): 1699-1703. immaculate k, sinduja p, velammal a, patterson j. (2013). quality and shelf life status of salted and sun dried fishes of tuticorin fishing villages in different seasons. international food research journal 20(4): 1855-1863. islam m, hossain m, mian s. (2012). nutritive value of dried and heat processed mola fish (amblypharyngodon mola) products. international journal of natural sciences 2(2): 43-48. islam mt, ahmed s, sultana ma, tumpa a, flowra fa. (2013). nutritional and food quality assessment of dried fishes in singra upazila under natore district of bangladesh. trends in fisheries research 2(1): 2319-4758. jain d, pathare pb. (2007). study the drying kinetics of open sun drying of fish. journal of food engineering 78(4): 1315-1319. jinadasa b. (2014). determination of quality of marine fishes based on total volatile base nitrogen test (tvb-n). nature and science 12(5): 106-111. jónsson á, finnbogadóttir ga, þorkelsson g, magnússon h, reykdal ó, arason s. (2007). dried fish as health food. matis-food research. innovation & safety report 5: 1-22. kakati bk, sharma p, goswami uc. (2017). quality evaluation of dried fish products commerce in assam, india. international journal of advanced biological research 7(3): 465-469. kituu gm, shitanda d, kanali c, mailutha j, njoroge c, wainaina j, silayo v. (2010). thin layer drying model for simulating the drying of tilapia fish (oreochromis niloticus) in a solar tunnel dryer. journal of food engineering 98(3): 325-331. labuza tp. (1980). the effect of water activity on reaction kinetics of food deterioration. food technology 34(4): 36-41. majumdar bc, afrin f, rasul m, khan m, shah a. (2017). comparative study of physical, chemical, microbiological and sensory aspects of some sun dried fishes in bangladesh. brazilian journal of biological sciences 4(8): 323-331. mansur ma, rahman s, khan mna, reza ms, uga s. (2013). study on the quality and safety aspect of three sun-dried fish. african journal of agricultural research 8(41): 5149-5155. martunis m. (2013). performance of a forced-convection greenhouse dryer for fish drying. rona teknik pertanian 6(1): 426-430. 9review article al-mahruqi and al-ismaili mustapha mk, ajibola tb, salako af, ademola sk. (2014). solar drying and organoleptic characteristics of two tropical african fish species using improved low-cost solar driers. food science & nutrition 2(3): 244-250. ochieng ob, oduor opm, nyale mm. (2015). biochemical and nutritional quality of dried sardines using raised open solar rack dryers off kenyan coast. journal of food resource science 4(2): 33-42. oladipo i, bankole s. (2013). nutritional and microbial quality of fresh and dried clarias gariepinus and oreochromis niloticus. international journal of applied microbiology and biotechnology research 1: 1-6. oparaku nf, mgbenka bo, eyo je. (2017). proximate and organoleptic characteristics of sun and solar dried fish. animal research international 7(2): 1169-1175. prakash o, kumar a. (2014). solar greenhouse drying: a review. renewable and sustainable energy reviews 29: 905-910. sahu tk, jaiswal v, singh ak. (2016). a review on solar drying techniques and solar greenhouse dryer. iosr journal of mechanical and civil engineering 13: 31-37. sengar s, khandetod y, mohod a. (2009). low cost solar dryer for fish. african journal of environmental science and technology 3(9). siddique m, mojumder p, zamal h. (2012). proximate composition of three commercially available marine dry fishes (harpodon nehereus, johnius dussumieri and lepturacanthus savala). american journal of food technology 7(7): 429-436. singh p, shrivastava v, kumar a. (2017). recent developments in greenhouse solar drying: a review. renewable and sustainable energy reviews 82: 3250-3262. solomon s, okomoda v, egwumah a. (2016). design and performance of a pioneering solar collector using parabolic dish for fish processing. jordan journal of agricultural sciences 12(2): 581-590. sontakke ms, salve sp. (2015). solar drying technologies: a review. international journal of engineering science 4: 29-35. sultana s, hossain m, shikha f, islam m, kamal m. (2008). quality assessment of rotating and solar tunnel dried marine fish product. bangladesh journal of fisheries research 12(1): 121-128. tiwari g, das t, chen c, barnwal p. (2009). energy and exergy analyses of greenhouse fish drying. international journal of exergy 6(5): 620-636. toujani m, hassini l, azzouz s, belghith a. (2013). experimental study and mathematical modeling of silverside fish convective drying. journal of food processing and preservation 37(5): 930-938. walters sa, jha ak. (2016). sustaining chili pepper production in afghanistan through better irrigation practices and management. agriculture 6(4): 62-71. research paper journal of agricultural and marine sciences vol. 23 : 02– 10 doi: 10.24200/jams.vol23iss1pp2-10 reveived 15 aug. 2017 accepted 19 feb 2018 effect of grafting on resistance to vine decline disease, yield and fruit quality in muskmelon cv. sawadi 1,2*q.s. al mawaali,2a. al-sadi, 2f.a. al-said,3m.s. rahman,3i. al-zakwani, 3a. ali, 1m.al-yahyai, 2m.l.deadman 1*mike deadman( ) directorate general of agricultural & livestock research, ministry of agriculture and fisheries, p o box 50, alseeb 121, oman. 2department of crop sciences, sultan qaboos university, p o box 34, al khoud 123, oman. 3department of food science and nutrition, sultan qaboos university, p o box 34, al khoud 123, oman. introduction muskmelon (cucumis melo l.) is one of the most economically important and widely cul-tivated crops in many parts of the world. in 2012, china, turkey, iran, egypt and usa are the main producer of melons (fao, 2013). in oman, muskmelon occupied approximately 410 ha of land, with a total production of 12,500 tons in 2012 (fao, 2013), making it among the top horticultural crops in production in the country. production levels notwithstanding, yield in oman is limited by several biotic and abiotic factors. vine decline disease is the major biotic factor limiting its production, with losses exceeding 90% in several farms (al-mawali et al., 2013; al-rawahi et al., 1998; al-sa’di et al., 2008; martyn, 2008). the fungus monosporascus أتثري التطعيم على مقاومة مرض تدهور الشمام و كمية االنتاج وجودة الثمار لصنف الشمام سوادي قيس بن سيف املعويل1,2* وعبد اهلل بن حممد السعدي2 وفهد بن اجللندى ال سعيد2 وحممد شفور الرمحن3 وانتصار الزكواين3 وأمانات علي3 ومنري اليحيائي1 ومايكل ديدمان2 abstract. a study was conducted to evaluate graft success, resistance to vine decline disease and effect of grafting on quality and yield of muskmelon. two field experiments, conducted in oman, showed that muskmelon cv. sawadi grafted on six cucurbit rootstocks gave high grafting success: 97.6-99.1% (avg. 98.6%) and 92.4-96.9% (avg. 95.3%) under field conditions in fall 2012 and spring 2013 respectively. no significant differences were observed between seasons among the six treatments and a non-grafted control in consumer preference for odor and firmness, fruit shape, flesh vitamin c, micronutrient content and tss (sucrose %) or ph in spring 2013 (p > 0.05). the concentration of phosphorus and sodium significantly decreased in both seasons in all treatments in comparison to the control (p > 0.05). in both seasons potassium content significantly increased when rsscih7458 and mubyeongjangsoo rootstocks were used (p < 0.05). strong tosa rootstocks showed zero graft failure, high resistance to vine decline disease, high yield production and higher tss (sucrose %) as compared to other rootstocks. strong tosa and tetsukabuto rootstocks showed significantly higher consumer acceptance for rind color, flesh color and overall consumer acceptance in spring 2013 and was also less affected by seasonal changes. results suggested that by grafting muskmelon cv. sawadi some quality attributes may be improved in addition to the increased level of resistance to disease. however, additional trials are required to make final recommendations for the farming community. keywords: melon; grafting; soil-borne diseases; fruit quality املســتخلص: لقــد أجريــت هــذه دراســة لتقييــم جنــاح التطعيــم، ومقاومــة األصــول ملــرض تدهــور و مــوت حمصــول الشــمام وتأثــري التطعيــم علــى كميــة االنتــاج و جــودة الثمــار.مت تنفيــذ التجــارب يف حقلــن منفصلــن يف ســلطنة عمــان، و أظهــرت النتائــج أن صنــف الشــمام ســوادي املطعــوم علــى ســتة أصــول مــن القرعيــات أعطــى جناحــا كبــريا يف التطعيــم: حيــث تراوحــة نســبة التطعيــم بــن 97.6-99.1٪ )98.6٪( و ٪96.9-92.4 )٪95.3( يف ظــل ظــروف احلقــل يف خريــف عــام 2012 وربيــع 2013 علــى التــوايل. مل تظهــر النتائــج وجــود فــروق معنويــة بــن الســتة معامــات والشــاهد )الشــمام الغــري مطعــوم( مــن حيــث اختبــار تفضيــل املســتهلكن للرائحــة وصابــة وشــكل الثمــار و فيتامــن c وحمتــوى املــواد الصلبــة الذائبــة )الســكروز٪( أو الرقــم اهليدروجيــي يف ربيــع p( 2013< 0.05(. وأشــارت النتائــج اىل اخنفــاض تركيــز الفوســفور والصوديــوم بشــكل ملحــوظ يف الثمــار لــكا املومســن يف rsscih7458 0.05(. كمــا زاد حمتــوى البوتاســيوم زيــادة كبــرية يف الثمارعندمــا مت اســتخدام أصلــي >p( مجيــع املعامــات باملقارنــة مــع الشــاهد و مــويب ينــج ســو )p >0.05(. وأظهــرت النتائــج أن أصــل الســرنج تــوزاء أعطــى نســبة0٪ لفشــل التطعيــم ، وأظهــر مقاومــة جيــدة ملــرض تدهــور حمصــول الشــمام وكميــة إنتــاج جيــدة وحمتــوى مرتفــع مــن املــواد الصلبــة الذائبــة )الســكروز٪( باملقارنــة مــع غــريه مــن األصــول. كمــا أشــارت النتائــج أن أصلــي الســرنج تــوزاء و تيتســوكابوتو حصــا علــى أعلــى قبــول الختبــار تفضيــل املســتهلكن مــن حيــث لــون القشــرة واللــون اللحــم والقبــول العــام الختبــار تفضيــل املســتهلكن يف ربيــع عــام 2013، وكانــا أيضــا أقــل تأثــرا بالتغــريات املومسيــة. عمومــا ميكــن أن نقــول أن التطعيــم علــى االصــول املقاومــة المــراض الربــة أدى إىل حتســن بعــض مســات جــودة الثمــار باإلضافــة إىل زيــادة مســتوى املقاومــة لألمــراض لصنــف الشــمام ســوادي. ومــع ذلــك، هنــاك حاجــة إىل عمــل جتــارب إضافيــة لتأكيــد النتائــج ولتقــدمي التوصيــات النهائيــة للمزارعــن. الكلمات املفتاحية: الراكم احليوي على األسطح املغمورة، 3research article al mawaali, al-sadi, al-said, rahman, al-zakwani, ali, al-yahyai, deadman cannonballus is the main causal agent of melon vine decline in oman as well as in us, spain, japan and many other countries. other pathogenic fungi including macrophomina phaseolina, fusarium spp., monosporascus cannonballus, phoma spp., pythium spp., phytophthora drechsleri, rhizoctoina solani, acremonium cucurbitacearum and verticillum dahliae have also been implicated in disease etiology (aegerter et al., 2000; al-mawali et al., 2013; al-sa’di et al., 2008; pivonia et al., 1997; zitter et al., 1996). the use of grafted plants for controlling soil-borne diseases has been established since the 1920s in many countries in the world including japan and korea (lee, 1994). in 1990 in japan for example, 59% of the total production area of watermelon, melon, cucumber, tomato and eggplant was associated with grafted crops (oda, 1993, 1999). the primary purpose of grafting was originally to overcome soil-borne diseases and increase the yield of grafted crops. objectives of grafting later expanded towards increasing tolerance to low-temperature, salt and soil wetness; improving water and nutrient uptake, increasing the plant vigor and extending harvest duration (lee, 1994; lee and oda, 2003). although in oman grafting cucumber plants on cucurbit hybrid rootstock varieties titan and hercules has been shown to reduce damping-off and vine decline of cucumber (al-mawaali et al., 2012), commercial utilization of the technology is still in its infancy. it is also not clear whether grafting could form part of an integrated strategy to reduce vine decline of muskmelon in the country. no prior research exists on the effects of grafting on the quality of muskmelon fruit in oman. the main objective of this study was to characterize the level of resistance of different rootstocks to vine decline disease of muskmelon in oman. specific objectives included: (1) to test the compatibility of six selected cucurbit rootstocks with muskmelon cv. sawadi; (2) to evaluate resistance of the rootstocks against vine decline disease; (3) to examine the effect of these rootstocks on yield and fruit quality of muskmelon cv. sawadi. knowledge in these areas will help in future management programs for vine decline disease and in improving the quality and yield of muskmelon in oman and elsewhere. methodology plant growth and yield the field experiment was conducted at the agricultural experiment station (aes) of sultan qaboos university, muscat, oman (23.35on, 58.9oe). the first trial was between october 2012 and january 2013; the second trial from february to may 2013. tongue approach grafting was done under greenhouse conditions 12-16 days after sowing, following the method of oda (1999). a total of 900 plants of muskmelon cv. sawadi (scion) were grafted on six rootstocks. graft success was recorded for all rootstocks. treatments were distributed in the field as a completely randomized design. soil of the field was sandy loam with ph 8.2 and soil ec 2.05 ds m-1. the treatments were repeated four times with 15 seedlings in each replication. the spacing was 1m between plants, 2m between treatments and 2 m between rows. irrigation was controlled by a maxicom2 central control system (rain bird, ca, usa) and the water ph was 7.6 and ec was 0.3 ds m-1. npk (20:20:20) fertilizer (kristalon, hungary) was applied at a rate of 0.6 g per plant twice a week for the first month; thereafter 12:12:36+te fertilizer (kristalon, hungary) was applied at 1.2g per plant twice a week until the end of the season (maf, 2007; maf, 2009). all fertilizer applications were via the irrigation system. minimum and maximum temperatures during october, november, december 2012 and january 2013 were 20.2 to 39.9oc, 18.9 to 34.9oc, 13.5 to 33.4oc, and 13.1 to 31.3oc, respectively. corresponding temperatures were 14.1 to 31.5oc in february, 17.8 to 36.1oc in march, 19.8 to 42.9oc in april and 20.6 to 44.8oc in may 2013. non-grafted muskmelon seedlings (cv. sawadi) were transplanted in the field as a control. vegetative growth was assessed 50 days after transplanting using 5 plants from each replicate, for each sampling event (yetisir and sari, 2003). stem diameter of scion (cm) was recorded after the first node. leaf chlorophyll was measured using four fully expanded leaves from the apex of the main stem (yetisir and sari, 2003). flowering time was expressed as the percentage of plants flowering at the time when 50% plants in the treated plots had started flowering (yetisir and sari, 2003). fruits were harvested at maturity; each fruit was measured and total yield (kg) per plant was recorded. at leaf senescence, which occurred 30 to 45 days after pollination. , the effect of different rootstocks on marketable muskmelon fruits shape was analyzed by taking table 1. initial graft success and graft failure in the field of selected rootstocks with sawadi muskmelon cultivar scion. rootstock c graft success %a graft failure %b trial#1 trial#2 trial#1 trial#2 titan 98.5 96.9 8 6.7 tetsukabuto 97.6 96 9.3 0 mubyeongjangsoo 98.7 96.8 0 1.7 rsscih7458 97.9 92.4 0 5 strong tosa 99.1 93.3 0 0 ezra 99.5 96.3 20 10 a graft success in nursery. b graft failure in field c rootstock: titan (hybrid) ramiro arnedo, spain, tetsukabuto (hybrid squash) national seeds production company l.t.d japan, mubyeongjangsoo (hybrid squash) seminis® china, rsscih7458 (hybrid squash) seminis® korea, strong tosa (f1 hybrid) syngenta seeds – china and ezra f1 (squash) nickerson-zwaan, holland. 4 squ journal of agricultural and marine sciences, 2018, volume 23, issue 1 effect of grafting on resistance to vine decline disease, yield and fruit quality in muskmelon cv. sawadi fruit length and width; the circle ratio was obtained by subtracting width from length. response to vine decline disease the response of grafted plants to vine decline disease was assessed by determining the percentage of plants developing typical vine decline symptoms (al-mawali et al., 2013). observations on vine decline disease were taken starting 15 days after transplanting and thereafter at 15 days interval to the end of each season. the estimated inoculum density in the first trial were (1.8 ascospores g-1 soil, 5.5 cfua g-1 soil and 6.4 cfua g-1 soil) and in the second trial were (2.8 ascospores g-1 soil, 7.1 cfua g-1 soil and 9.5 cfua g-1 soil) respectively for m. cannonballus, r. solani and pythium spp. fruit quality and consumer preference consumer preference of fruit quality attributes was performed for flavor, odor, juiciness, firmness, flesh color, rind color and overall acceptance using a 9-point hedonic scale from 19 with 1 = dislike extremely and 9 = like extremely (society of sensory professionals, 2013). in the cases of flavor, odor and juiciness, participants in panel testing were instructed to place the melon cubes between molars and to perform chewing. they assessed and recorded their score before swallowing. firmness was assessed by applying force on the cubes between tongue and palate. they scored the preference of force required. color was assessed by visual observation. ninety panelists consisting of omani students and faculty in the university completed the test in three sessions (one hour between each), six different samples of fresh fruits were used for each session. for each completed test preferences were recorded for flavor and odor (first session), juiciness and firmness (second session) and rind color, flesh color and overall acceptance (christakou et al., 2005; lester and shellie, 1992). panelists were instructed to wash the mouth once between assessments. all sessions were conducted in a climate-controlled sensory analysis booth (i.e. 22oc room temperature, positive air pressure) and under white florescent lighting. the consumer preference test was repeated using fruits from the second field trial. influence of grafting on quality of muskmelon fruits marketable fruit total soluble solid (tss: sucrose) was determined from 3 mature fruits from each replicate using a refractometer for sucrose (0-32%, eclipse brix, uk, esr 027540). immediately after harvest, color of rind and flesh (hunter color value parameters brightness (l), redness (a), and yellowness (b)) of marketable fruits were measured (minolta colorimeter cr-310, minolta, japan) (crinò et al., 2007). the pureed samples of fruit flesh were frozen at -20 co prior to nutrient content analysis (lee and oda, 2003; yetisir and sari, 2003). values for sugar concentration, vitamin c (mg/100g) content, n, p, k, ca, mg, na and soluble protein (g/100g) content, fe, mn, zn and cu (mg/kg) content of fruit flesh were performed according to the methods of aoac (2000). all experimental data were analyzed using anova with tukey’s studentized range test to compare individual means (sas v8, sas institute, cary, nc, u.s.a). table 2. field evaluation of the tolerance/resistance of 6 selected rootstock against vine decline disease and its effect on scion flowering, fruit number, fruit weight, leaf chlorophyll and stem diameter of sawadi muskmelon cultivar at squ in the fall 2012 and in the spring 2013. rootstock b incidence of vine decline (%)a flowering (%)a fruit no. (1000 ha-1)a fruit weight (ton ha -1)a chlorophyll content a stem diameter (cm)a trial#1 trial#2 trial#1 trial#2 trial#1 trial#2 trial#1 trial#2 trial#1 trial#2 trial#1 trial#2 ezra 66.9a 51.7a 44b 8.1c 10.6b 8.9c 8.1c 9.7b 48.7a 47.4b 0.82a 0.71c tetsukabuto 16b 15b 80a 38.5a 42.6a 21.4a 38.5a 31.9a 52.7a 52.4a 1.02a 0.99a titan 13.4b 13.3b 88a 33.1ab 38.6a 19.1ab 33.1ab 31.8a 54.6a 52.6a 0.95a 1a mubyeongjangsoo 9.4b 13.3b 97.3a 38.3a 43.3a 17.3abc 38.3a 28.7a 54.8a 52.1a 1a 0.97ab rsscih7458 4b 10b 97.3a 24.7ab 10.6b 11.7 bc 24.7ab 13.4b 51.7a 52a 0.9a 0.84 bc strong tosa 2.7b 5b 86.7a 42.6a 43.3a 20ab 42.6a 33.7a 50.6a 51.5a 1.02a 1.03a control 12b 16.7b 94.7a 43.5a 48.5a 22.2a 43.5a 32.8a 53.4a 50.5ab 1.03a 1.08a a values with the same letter in the same column are not significantly different from each other at p > 0.05(tukey’s studentized range test) b rootstock: titan (hybrid) ramiro arnedo, spain, tetsukabuto (hybrid squash) national seeds production company l.t.djapan, mubyeongjangsoo (hybrid squash) seminis® china, rsscih7458 (hybrid squash) seminis® korea, strong tosa (f1 hybrid) syngenta seeds china, ezra f1 (squash) nickerson-zwaan, holland and control (non-grafted sawadi muskmelon cultivar) tawoos farm, oman. 5research article al mawaali, al-sadi, al-said, rahman, al-zakwani, ali, al-yahyai, deadman results plant growth and yield greenhouse-assessed grafting success was high for all rootstocks, ranging from 97.6 to 99.1% (avg. 98.6%) in fall 2012 and 92.4 to 96.9% (avg. 95.3%) in spring 2013. field-assessed graft failure varied for rootstocks between 0-20% (avg. 6.2%) in fall 2012 and 0-10% (avg. 3.9%) in spring 2013. all rootstocks except strong tosa showed some graft failure (table 1). the six rootstocks exhibited variations in flowering between seasons. there were differences in earliness of flowering for the treatments. in fall 2012, flowering in ezra rootstock plants was significantly delayed relative to other treatments; in spring 2013 all treatments with the exception of mubyeongjangsoo were delayed relative to the non-grafted control. plants grafted onto ezra rootstocks had significantly lower chlorophyll content compared to grafted treatments in spring 2013 and ezra and rsscih7458 showed significantly smaller stem diameter compared to the non-grafted sawadi control in spring 2013 (table 2). fruit harvesting was earlier for non-grafted sawadi plants than for any grafted plant. in fall 2012 harvesting began 52 days after sowing, 7 days before all grafted plants with the exception of those with ezra rootstocks where harvesting started on day 66. in spring 2013 mature fruits were harvested from sawadi plants 54 days after sowing, compared with day 63 for other grafted plants except those with ezra rootstocks for which the harvesting started on day 65. plants grafted onto ezra and rsscih7458 showed significantly lower fruit number (p < 0.05) compared to the non-grafted sawadi control in fall 2012 and in spring 2013 (table 2). fruit weight of control was the highest in fall 2012 and strong tosa was the highest in spring 2013 although significantly different (p < 0.05) only from ezra in fall 2012 and from ezra and rsscih7458 in spring 2013 (table 2). response to vine decline disease disease incidence for all rootstocks ranged from 2.7%– 66.9% (average 18.7%) in fall 2012 and 5-51.7% (average 18.1%) in spring 2013 (table 2). only three rootstocks maintained disease levels below control treatment strong tosa, rsscih7458 and mubyeongjangsoo (2.7%, 4% and 9.4% in fall 2012 and 5%, 10% and 13.3% in spring of 2013, respectively) (table 2). ezra was apparently susceptible to highly susceptible to vine decline disease with a significant difference in incidence compared to the control in both seasons (p < 0.05). there was a significant, negative correlation between disease incidence and stem diameter in fall 2012 (r = 0.4405, p < 0.05) and spring 2013 (r = 0.4157, p < 0.05); between disease incidence and chlorophyll content in fall 2012 (r = 0.5671, p < 0.05) and between disease incidence and yield in spring 2013 (r = 0.741, p < 0.05). there was a significant, positive, correlation between yield and flowering in fall 2012 (r = 0.5885, p < 0.001) and in spring 2013 (r = 0.652, p < 0.001), and between yield and stem diameter in fall 2012 (r = 0.720, p < 0.001) and in spring 2013 (r = 0.567, p < 0.001). there was no correlation between disease incidence and any of the other parameters studied. pythium aphanidermatum, monosporascus cannonballus and rhizoctonia solani were isolated from diseased non-grafted sawadi plants and from plants grafted on squash ezra f1. only r. solani was isolated from diseased plants with other rootstocks. fruit quality and consumer preference tss levels were not affected by grafting but varied between seasons (table 3). only the plants grafted with rootstock titan showed a significant (p < 0.05) higher table 3. effect of grafting on scion fruit ph, sucrose % and fruit shape of sawadi muskmelon cultivar at squ in the fall 2012 and in the spring 2013. rootstock b ph a sucrose (%)a fruit shape a trial#1 trial#2 trial#1 trial#2 trial#1 trial#2 titan 5.7a 5.7a 14.6a 10.2a 0.6b 2.3a rsscih7458 5.6ab 5.6ab 13.6a 11a 0.9ab 1.7a strong tosa 5.3bc 5.3bc 13a 11.3a 1.5ab 2.1a mubyeongjangsoo 5.2c 5.2c 12.4a 10.5a 1.3ab 1.6ab tetsukabuto 5.5abc 5.5abc 11.9a 11.9a 1.8a 1.9a ezra 5.3bc 5.3bc 10.8a 9.6a 1.5ab 1a control 5.3bc 5.3bc 12.7a 11.3a 1.9a 2.2a a values with the same letter in the same column are not significantly different from each other at p > 0.05 (tukey’s studentized range test) control is non-grafted sawadi muskmelon cultivar b rootstock: titan (hybrid) ramiro arnedo, spain, tetsukabuto (hybrid squash) national seeds production company l.t.djapan, mubyeongjangsoo (hybrid squash) seminis® china, rsscih7458 (hybrid squash) seminis® korea, strong tosa (f1 hybrid) syngenta seeds china, ezra f1 (squash) nickerson-zwaan, holland and control (non-grafted sawadi muskmelon cultivar) tawoos farm, oman. 6 squ journal of agricultural and marine sciences, 2018, volume 23, issue 1 effect of grafting on resistance to vine decline disease, yield and fruit quality in muskmelon cv. sawadi ph and different fruit shape in fall 2012 (table 3). hunter color values (brightness (l), redness (a), and yellowness (b)) of fruit (rind and flesh) showed seasonal variations. rind brightness (l), redness (a), and yellowness (b) showed a significant (p < 0.05) difference between control and titan rootstock in the fall 2012. rind brightness (l) and redness (a) showed a significant (p < 0.05) difference between control and tetsukabuto rootstocks in the fall 2012. flesh brightness (l) and yellowness (b) was not significantly different (p > 0.05) between fruits from non-grafted control and fruits from grafted plants in both seasons(table 4). odor and firmness were not affected by grafting and showed no significant differences (p > 0.05) between fruits obtained from non-grafted controls and others in either fall 2012 or spring 2013. consumer preference values were significantly (p < 0.05) higher for rind color and flesh color of fruit from strong tosa and tetsukabuto rootstock grafted plants compared to fruits from control plants in spring 2013 (table 4). the ratings for flavor of fruits from titan and juiciness of fruits from titan and strong tosa rootstock grafted plants was significantly (p < 0.05) lower than the ratings for fruits from sawadi plants in fall 2012. fruits from tetsukabuto rootstock grafted plants showed significantly (p < 0.05) higher ratings for overall acceptance in spring 2013 compared to fruits from all other treatments (table 4). significantly, positive correlations were found between consumer preference scores for juiciness and firmness in fall 2012 (r = 0.6889, p < 0.01) and spring 2013 (r = 0.4729, p < 0.01), between rind color and flesh color in fall 2012 (r = 0.7328, p < 0.001) and spring 2013 (r = 0.5835, p < 0.001), rind color with overall acceptance in fall 2012 (r = 0.5125, p < 0.01) and spring 2013 (r = 0.5483, p < 0.01) and flesh color with overall acceptance in fall 2012 (r = 0.5143, p < 0.01) and spring 2013 (r = 0.5243, p < 0.01). hunter color values for flesh brightness (l) were positively and significantly related to consumer preference ratings for flesh color in fall 2012 (r = 0.5165, p < 0.01) and spring 2013 (r = 0.401, p < 0.05). none of the other quality attributes were significantly related. mineral and nutritional analysis showed some variation between seasons for some of the parameters. the seasonal effect was very clear in the case of some macroelements (n, ca, mg) and protein content of analyzed table 4. effect of grafting on scion fruit ph, sucrose % and fruit shape of sawadi muskmelon cultivar at squ in the fall 2012 and in the spring 2013. rootstock hunter color values c consumer preference rating d rind color flesh color l* a* b* l* a* b* rind color flesh color flavor odor juiciness firmness overall acceptance trial 1a control 63.9a 7.6a 27.9ab 80.7ab -2.7ab 22.1a 6.1a 6.5a 7.3a 6.7a 7.2a 6.4a 6.9a strong tosa f1 64a 7.4a 32.4a 83.1a -5.1a 23.7a 6.7a 7a 6.3a 5.9a 6.1bc 5.6a 6.7a mubyeongjangsoo 56.4ab 7.1a 29.7a 82.3ab -2.7a 21.1a 6.8a 7.1a 7.1a 6.3a 7.2a 6.3a 7a rsscih7458 57.7a 6.5a 29.9a 83.2a -3.9ab 20.4a 6.5a 7.3a 6.6a 6a 7.18a 6.5a 7.2a tetsukabuto 49.4bc 3.8b 24.9bc 77b -4.8b 22.3a 6.6a 6.8a 7.3a 6.5a 7.7a 6.7a 6.7a titan 47.7c 3.3b 20.9c 78.3ab -4ab 21.2a 7.2a 7.2a 5b 5.4a 5.98c 5.9a 6.9a trial 2a control 77.4a 8.2a 28.1ab 81.7a -8.3b 28.7a 6b 6.2b 6.3ab 5.9a 6.8a 6.8a 6.3b strong tosa f1 78.4a 7.5a 30.4ab 84.1a -6.6ab 28a 7.3a 7.1a 6.7ab 6a 6.6a 6.6a 6.9ab tetsukabuto 77.7a 8.3a 33.7a 83.6a -5.8ab 28.6a 7.1a 7.2a 6.8ab 6.4a 6.8a 6.6a 7.3a titan 76a 6.9a 34.4a 86.3a -6.5ab 27.3a 6.8ab 7.1a 5.9b 5.9a 6.5a 6.2a 6.3b rsscih7458 75.1a 7.4a 31.7ab 84.8a -7.5b 28.5a 6.6ab 6.7ab 6b 6.4a 6.9a 6.6a 6.7ab mubyeongjangsoo 70a 8.1a 25.5 b 85.3a -4.4a 27.8a 7ab 7ab 7.2a 6.5a 6.5a 6.8a 7ab a values having on letters in common are significantly different (p > 0.05) according to tukey’s studentized range test b rootstock: titan (hybrid) ramiro arnedo, spain, tetsukabuto (hybrid squash) national seeds production company l.t.djapan, mubyeongjangsoo (hybrid squash) seminis® china, rsscih7458 (hybrid squash) seminis® korea, strong tosa (f1 hybrid) syngenta seeds chinaand control (non-grafted sawadi muskmelon cultivar) tawoos farm, oman. c hunter color values (parameters l* brightness, a* redness, and b* yellowness). d preference ratings based on a scale when 1= dislike extremely, 2= dislike very much, 3= dislike moderately, 4= dislike slightly, 5= neither like nor dislike, 6= like slightly, 7= like moderately, 8= like very much & 9= like extremely. source: (society of sensory professionals, 2013) 7research article al mawaali, al-sadi, al-said, rahman, al-zakwani, ali, al-yahyai, deadman fruits (table 5). the vitamin c and micromineral (fe, zn, mn and cu) contents appeared not to be affected by grafting treatment and showed no significant (p > 0.05) differences in comparision to the control across seasons (table 5). fruit phosphorus and sodium concentrations were reduced in all grafted treatments and showed significant differences in comparision to fruits from control plants in both seasons except that phosphorus concentration was significantly (p < 0.05) higher in fruits of rsscih7458 rootstock grafted plants compared to the control in spring 2013 (table 5). grafting significantly (p < 0.05) increased fruit potassium content relative to non-grafted controls for plants grafted onto rsscih7458 and mubyeongjangsoo rootstocks in both season (table 5). discussion there are many reported reasons why rootstock selection affects yield and scion fruit quality. taxonomic affinity plays an important role in the success of grafting. studies on graft compatibility have shown that many cucurbit rootstock species or cultivars, with some significant exceptions, could be used for many types of cucurbit scions (davis et al., 2008; lee and oda, 2003). different rootstocks showed varying effects on grafted plants and the difference in diameter of cucurbita rootstock and cucumis scion has been related to the survival rate of grafted plants (traka-mavrona et al., 2000). incompatibility between rootstock and scion can affect undergrowth or overgrowth of the scion, leading to decreased water and nutrient flow through the graft union, causing vine decline or wilting of the grafted plant. incompatibility can be affected by the environment, phytohormones, growth stage of rootstock and scion, physiological and biochemical characteristics and tissue and structure differences (davis et al., 2008). andrews and marquez (1993) reported that graft incompatibility can be measured through failure to unite into a strong union, failure of the grafted plant to grow in a healthy manner, or premature death after grafting. physiological incompatibility can be measured by the lack of cellular recognition, wounding responses, growth regulators, or incompatibility toxins. in the present study, grafted sawadi muskmelon scions showed high graft success with all tested rootstocks indicating a good affinity between the selected rootstocks and sawadi muskmelon scion. this could be related to fortuitous selection of rootstock although many cucurbit rootstocks can be used for many different types of cucurbit scions yet taxonomic affinity does play an important role in grafting success (traka-mavrona et table 5. effect of grafting on scion fruit vitamin c, protein content, macroelements (n, p, k, ca, mg, na) and microminerals (fe, zn, mn and cu) of sawadi muskmelon cultivar commenced at squ in the fall 2012 and in the spring 2013(amount per 100g fresh product). rootstock b squ trial 1a vit-c mg/100g microminerals (mg/100g) macroelements (mg/100g) fe mn zn cuc n p k ca mg na protein control 5.3a 0.02a 0.001a 0.02a te 58b 26a 215b 17c 5.8ab 4.8a 362b strong tosa f1 5.4a 0.02a 0.0012a 0.01a te 59b 10b 190c 20ab 4c 1.6bc 369b mubyeongjangsoo 5.5a 0.03a 0.0014a 0.01a te 73a 11b 230a 23a 4.8bc 1.9b 456a rsscih7458 5.3a 0.03a 0.0012a 0.02a te 71a 15b 230a 20ab 5.3ab 1.5c 443a tetsukabuto 6.1a 0.02a 0.0014a 0.01a te 74a 12b 220ab 17c 6.3a 1.5c 463a titan 5.5a 0.02a 0.0013a 0.02a te 69a 12a 210b 19.5bc 6.3a 1.1d 431a squ trial 2a control 6.6a 0.03a 0.001ab 0.01a te 84a 23b 240b 16ab 8d 3.4a 525a strong tosa f1 6.3a 0.02a 0.0007b 0.01a te 76bc 17cd 219c 14c 13a 1.6c 475ab mubyeongjangsoo 9.5a 0.02a 0.002a 0.02a te 80abc 19c 250a 16.3a 8d 2.3b 500ab rsscih7458 6.9a 0.04a 0.001ab 0.02a te 73c 29a 260a 14.5bc 12b 3.1a 456b tetsukabuto 7.8a 0.03a 0.002a 0.01a te 73c 14d 216c 17a 10c 1.5c 456b titan 6.5a 0.03a 0.002a 0.02a te 83ab 18c 220bc 12d 14a 1.6c 518ab a values having on letters in common are significantly different (p > 0.05) according to tukey’s studentized range test b rootstock: titan (hybrid) ramiro arnedo, spain, tetsukabuto (hybrid squash) national seeds production company l.t.djapan, mubyeongjangsoo (hybrid squash) seminis® china, rsscih7458 (hybrid squash) seminis® korea, strong tosa (f1 hybrid) syngenta seeds chinaand control (non-grafted sawadi muskmelon cultivar) tawoos farm, oman. c trace elements-specifically copper 8 squ journal of agricultural and marine sciences, 2018, volume 23, issue 1 effect of grafting on resistance to vine decline disease, yield and fruit quality in muskmelon cv. sawadi al., 2000; lee & oda, 2003). however, after transplanting into the field some graft failure was observed in both seasons, mainly with the ezra rootstock. in contrast the strong tosa rootstock showed zero graft failure. davis et al. (2008) have reported that after transplanting some graft failure could be related to environmental factors or poor grafting technique. rsscih7458, mubyeongjangsoo and strong tosa rootstocks maintained average disease levels in both seasons, below average disease levels of the non-grafted control whereas ezra rootstocks showed significantly higher disease levels in both seasons as compared to control plants. in pervious assay, this phenomena could be related to root structure that have a well-developed, vigorous root system and fast replacement of dead or infected root for withstanding vine decline (martyn, 2008; lee and oda, 2003). c. maxima, c. maxima x c. moschata, and c. moschata x c. moschata rootstocks showed efficacy in reducing monosporascus root rot vine decline disease levels in israel (cohen et al., 2007; edelstein et al., 1999). isolations made during the current study showed the association of p. aphanidermatum, m. cannonballus and r. solani with declining non-grafted sawadi plants and from plants grafted on squash ezra f1. similar result was found by al-mawali et al. (2013) when isolation from declining muskmelons followed by pathogenicity test provided evidence that m. cannonballus, p. aphanidermatum and r. solani, were pathogenic to muskmelon in oman. this result may reflect the weakness of infected plant that don’t have fast replacement of dead or infected root for withstanding vine decline (martyn, 2008 and lee and oda, 2003). however, some rootstocks with appropriate architectural traits are susceptible to infection by m. cannonballus and therefore could aid in the potential build-up of inoculum in the soil even though they typically do not support extensive perithecia development on the roots (martyn, 2008). only r. solani was isolated from diseased plants with other rootstocks. in the current study, there was a clear effect of grafting on fruit maturity in both seasons. harvesting from non-grafted sawadi plants was faster in both seasons compared to grafted treatments. this could be attributed to the enhancement of undesirable physiological disorders by the rootstock such as vigorous vegetative growth, uneven maturity, and internal breakdown of fruit caused by unbalanced uptake of nitrogen and calcium into the fruit (lee and oda, 2003). farmers frequently express a desire for rootstocks with less vigorous root systems, rather than the vigorous interspecific hybrid rootstocks, to obtain earlier harvests and better quality rather than higher yields (lee and oda, 2003). in the present study, all rootstocks used showed lower fruit number and fruit weight with the exception of strong tosa which gave higher fruit weights than the control in spring season 2013. this could be related to early harvesting (52-54 days) in the non-grafted control that could escape from or reduced vine decline stress on fruiting plants whilst the delay in fruit maturation (59-63 days) in grafted plant lead to increased disease stress on fruiting plants. disease symptoms were evident in the field 62 days after transplanting grafted plants in both seasons. strong tosa was highly resistant to vine decline with high yield production in both seasons and should therefore be tested further with other muskmelon scions to improve production per area of cultivation. in the present study tss was not affected by grafting but showed variation between seasons except in the case of the tetsukabuto rootstock grafted plants. the tss levels of non-grafted sawadi plants and strong tosa rootstock grafted plants were very high relative to other treatments. however, the tss levels from ezra rootstock grafted plants were exceptionally low in both seasons. this could be related to factors such as susceptibility to vine decline disease and low content of chlorophyll in leaf tissues which could result in a decrease in photosynthesis and thus a decrease in yield and fruit quality (xu et al., 2006; zhu et al., 2006). this result reflect the significant, negative correlation between disease incidence and chlorophyll content in fall 2012 and between disease incidence and yield in spring 2013. similarly rivero (2003) indicated that differences in the uptake and translocation of nutrients depend on the vigor of the aerial parts of the plant whilst as total phosphorus content in the foliar tissues of grafted plants increased there was an accompanying increase in carbohydrate content. consumer preference and hunter color values of fruit (rind and flesh) showed some variation between seasons. seasonal effects were clear in fruits from plants with the titan rootstock in terms of the consumer preference (flavor and juiciness) and the hunter color values (rind brightness and redness). previous study suggest that abnormal fruit quality has been reported in grafted melon fruit as a reduction in fruit soluble solids, persistent green color in the suture stripe, fruit fermentation, fibrous flesh and off-taste (davis et al., 2008). odor and firmness were not affected by grafting and there were no significant differences between non-grafted control fruits and grafted treatments in either season. this finding is interesting since bartoshuk and klee (2013) pointed out that flavor quality of many fresh fruits available to consumers today certainly contributes to poor flavor. a large part of the problem is the challenge of breeding for and accurately assessing such a complex, multi-genic trait in a natural product such as a fruit. davis et al. (2008) noted that fruit firmness could be decreased due to grafting. in the current study, consumer preferences for rind color and flesh color were significantly higher for strong tosa and tetsukabuto rootstock grafted fruits than for the non-grafted control in spring 2013. this was mainly due to the higher than expected preference matching with color, flavor and odor as shown in table 4. fruits from tetsukabuto rootstock grafted plants showed the highest overall ac9research article al mawaali, al-sadi, al-said, rahman, al-zakwani, ali, al-yahyai, deadman ceptance rating in spring 2013 which reflect the positive effect of the rootstock on fruit of grafted muskmelon plant. the uptake and translocation of ions, photosynthesis, plant hormones and alkaloids can be influenced by rootstocks or the grafting method used. vigorous rootstocks can show an increase in the uptake of water and minerals as compared to own rooted plants. the increase in water absorption in grafted plants may cause a dilution of ion concentration in xylem sap that affects the absorption and translocation of ions such as phosphorus, nitrogen, magnesium and calcium and microelements including iron and boron (lee and oda, 2003). rivero (2003) reported that differences in the foliar n and na content can lead to differences in yield. in the present study, nutrient content showed some variation between seasons for some parameters. this may have been caused by unbalanced uptake of water and minerals such as nitrogen and calcium into the fruit. seasonal effects were also very clear for some macroelements (n, ca, mg) and protein content of fruit. vitamin c, ph and microminerals (fe, zn, mn and cu) were not affected by grafting and showed no significant differences between treatments in either season. phosphorus and sodium concentrations were reduced in all grafted treatments and showed significant differences with the non-grafted control plants in both seasons. the potassium content of grafted sawadi fruits increased when rsscih7458 and mubyeongjangsoo rootstocks were used and showed significant differences with non-grafted controls in both season that is good for human due to increase the nutritional value of muskmelon fruit. conclusion all rootstocks used with the sawadi scion showed high graft success. strong tosa rootstocks showed zero graft failure, high tolerance or resistance to vine decline disease, with significantly higher yield production and higher tss values compared to other treatments in both seasons. titan rootstock grafted plants were highly affected by seasonal changes and gave variable results across seasons for many of the assessed parameters. the use of ezra rootstocks should be approached with some caution as they appear to be susceptible to infection by m. cannonballus and could therefore increase inoculum in the soil even though they typically do not support extensive perithecia development on the roots. strong tosa and tetsukabuto rootstocks showed significantly higher consumer acceptance for rind color and flesh color and tetsukabuto showed significantly higher rating for overall consumer acceptance in spring season. strong tosa and tetsukabuto are recommended for further testing with other muskmelon scions to improve yield and fruit quality. acknowledgment financial support to the study through the strategic project sr/agr/crop/10/01 is acknowledged. references aegerter bj, gordon tr, davis rm. 2000. occurrence and pathogenicity of fungi associated with melon root rot and vine decline in california. plant disease 84: 224-230. al-mawaali qs, al-sadi am, khan aj, al-hasani h, deadman ml. 2012. response of cucurbit rootstocks to pythium aphanidermatum. crop protection 42: 64-68. al-mawali q.s., al-sadi a.m., al-said f.a., deadman m.l. 2013. etiology, development and reaction of muskmelon to vine decline disease under arid conditions of oman. phytopathologia mediterranea 52: 457-465. al-rawahi a.k., zouba a.a., al-maqbaly y.m. 1998. first report of pythium deliense as a causal agent of watermelon and muskmelon sudden collapse disease in oman. squ journal scientific research; agricultural science 3: 126. al-sa’di a.m., deadman m.l., al-said f.a., khan i., al-azri m., drenth a., aitken e.a.b. 2008. first report of pythium splendens associated with severe wilt of muskmelon (cucumis melo) in oman. plant disease 92: 313-313. andrews pk, marquez cs. 1993. graft incompatability. horticultural review 15: 183-232. aoac. 2000. association of official agricultural chemists, (a.o.a.c). official methods of analysis, (17th ed), williams horowitz. washington. d.c. usa. bartoshuk lm, klee hj. 2013. better fruits and vegetables through mini review sensory analysis. current biology 23: 374-378. christakou ec, arvanitoyannis is, khah em, bletsos f. 2005. effect of grafting and modified atmosphere packaging (map) on melon quality parameters during storage. journal of food agriculture and environment 3, 145-152. cohen r., burger y., horev c., koren a., edelstein, m. 2007. introducing grafted cucurbits to modern agriculture. the israeli experience. plant disease 91: 916923. crinò p, lo bianco c, rouphael y, colla g, saccardo f, paratore a. 2007. evaluation of rootstock resistance to fusarium wilt and gummy stem blight and effect on yield and quality of a grafted inodorus melon. horticultural science 42: 521-525. davis ar, perkins-veazie p, sakata y, lópez-galarza s, maroto jv, lee s-g, huh y-c, sun z, miguel a, king 10 squ journal of agricultural and marine sciences, 2018, volume 23, issue 1 effect of grafting on resistance to vine decline disease, yield and fruit quality in muskmelon cv. sawadi sr, cohen r, lee j-m. 2008. cucurbit grafting. critical reviews in plant science 27: 50-74. edelstein m, cohen r, burger y, shriber s, pivonia s, shtienberg d. 1999. integrated management of sudden wilt in melons, caused by monosporascus cannonbollus, using grafting and reduced rates of methyl bromide. plant disease 83: 1142-1145. fao. 2013. faostat-agriculture. http://faostat.fao. org/site/567/default.aspx#ancor. lee jm. 1994. cultivation of grafted vegetables: current status, grafting methods, and benefits. horticultural science 29: 235-239. lee j.m., oda m. 2003. grafting of herbaceous vegetable and ornamental crops. horticultural rev. 28, 61-124. lester g.e., shellie k.c. 1992. postharvest sensory and physicochemical attributes of honey dew melon fruits. horticultural sci. 27, 1012-1014. maf. 2007. agricultural and livestock research annual report. directorate general of agriculture and livestock research. ministry of agriculture and fisheries (maf). oman. 432 pp. maf. 2009. agricultural and livestock research annual report. directorate general of agriculture and livestock research. ministry of agriculture and fisheries (maf). oman. 334 pp. martyn rd. 2008. late-season vine declines of melons: pathological, cultural or both? phytoparasitica 36: 309-312. oda m. 1993. present state of vegetable production using grafted plants in japan. agriculture horticulture 68: 442-446. oda m. 1999. grafting of vegetables to improve greenhouse production. osuku prefecture university, japan. pivonia s., cohen r., kafkafi u., ben-ze’-ev i.s., katan j. 1997. sudden wilt of melons in southern israel: fungal agents and relationship with plant development. plant disease 81: 1264-1268. rivero r. 2003. role of grafting in horticultural plants under stress conditions. journal of food agriculture and environment 1: 70-74. society of sensory professionals (2013). the 9-point hedonic scale. https://www.sensorysociety.org/knowledge/sspwiki/pages/the%209-point%20hedonic%20 scale.aspx. traka-mavrona e, koutsika-sotiriou m, pritsa t. 2000. response of squash (cucurbita spp.) as rootstock for melon (cucumis melo l.). horticultural science 83: 353-362. xu cq, li tl, qi hy. 2006. effects of grafting on development, carbohydrate content, and sucrose metabolizing enzymes activities of muskmelon fruit. acta horticultura sinica 33: 773-778. yetisir h, sari n. 2003. effect of different rootstocks on plant growth, yield and quality of watermelon. austral. journal of experimental agriculture 43: 12691274. zhu j, bie zl, huang y, han xy. 2006. effects of different grafting methods on the grafting work efficiency and growth of cucumber seedlings. china vegetables 9, 24-25. zitter t.a., hopkins d.l., e. t.c. 1996. compendium of cucurbit diseases. aps press, st. paul, minnesota, usa. img312 img313 img314 img315 img316 img317 img323 img324 img325 img326 img327 img328 img329 research paper journal of agricultural and marine sciences 2022, 27(2): 1–9 doi: 10.53541/jams.vol27iss2pp1-9 received 3 november 2021 accepted 16 february 2022 benefits of value addition in agricultural produce on land, water and labor productivities under arid agriculture: case of dates in oman alaa al hinai*1, hemanatha jayasuriya1, pankaj b. pathare1, talal al shukeili1, ibtisam al abri2 alaa al-hinai ( ) s81455@student.squ.edu.om, alaa.w.alhinai@ gmail.com, 1 department of soils, water and agricultural engineering, 2department of natural resources economics, college of agricultural & marine sciences, sultan qaboos university, oman. introduction agricultural practices of most middle eastern countries have not been impressive in devel-oping sustainability and achieving food security (baumer, 1983; brief, 2010; mizyed 2013). arid and semi-arid regions of the middle east suffer from water scarcity and land mismanagement which causes an obstacle to achieve agricultural sustainability (ahmed et al., 2001; mizyed, 2013; namara et al., 2007; rahman, 1996). one of the important ways to improve sustainability and food security is to reduce postharvest losses (kiaya, 2014). from another perspective, the impact of postharvest losses extends to the environment through attrition in the use of lands, water, energy and labors in producing non-consumable products (fao, 2013). the importance of utilizing postharvest losses is to raise incomes for many farms, combat hunger and poverty, فوائد إضافة القيمة يف اإلنتاج الزراعي على إنتاجية األرض واملياه والعمالة يف الزراعة اجلافة: حالة التمور يف عمان آالء اهلنائي*1، هيمااناث جاايسوراي1، ابنكاج ابثري1، طالل الشكيلي1، وابتسام العربي2 abstract. oman is an arid country in the middle east with water scarcity, and hence land and labor management issues hindering agricultural sustainability and food security. value addition can minimize food wastes, which is crucial to achieve sustainability by improving the land, water and labor productiveness. this study aimed to evaluate and quantify the improvements in land, water and labor productivities through value addition in date cultivated under arid conditions in oman. five date factories and different value-added products of the most popular date varieties, khalas and fardh were selected for this study. the comparisons were made between productivity improvements of the value-added products and the raw products. khalas dates value-added with nuts had the highest productivity ratio of 540%, the same for fardh was 360% while the lowest were in khalas value-added with flavors with 111% and in fardh date paste with 129%. in khalas, the best improvement by the value addition in average land, water and labor productivities from the base-values of 6.93 ton ha-1, 0.57 kg m-3, and 0.82 kg h-1 of the raw date were 25.05 ton ha-1, 2.06 kg m-3, and 2.95 kg h-1 in date with nuts, respectively; while in the fardh, these were 18.82 ton h-1, 1.55 kg m-3, and 2.21 kg h-1 respectively of the same value-added product. the variations in productivity improvement of selected value-added products could be due to the availability and cost of the raw dates, cost of the value addition, market options and selling price. value addition showed high potential for improving productivities under arid conditions and is worth making adoption efforts for achieving agricultural sustainability goals. keywords: arid region, postharvest losses, productivity, sustainability, value addition, dates. امللخص:تعتــرب عمــان مــن الــدول القاحلــة يف الشــرق األوســط الــي تعــاين مــن نــدرة امليــاه، وابلتــايل فــإن املشــاكل املتعلقــة إبدارة األراضــي الزراعيــة والعمالــة فيهــا تعيــق اســتدامة الزراعــة واألمــن الغذائــي. إن إضافــة قيمــة للمنتجــات الزراعيــة ميكــن أن تقلــل مــن فاقــد الغــذاء، والــذي مــن املمكــن أن يكــون مفتاحــا لتحقيــق االســتدامة مــن خــالل تطويــر إنتاجيــة األرض وامليــاه والعمالــة. هدفــت هــذه الدراســة إىل تقييــم وتقديــر التحســينات يف إنتاجيــة األرض وامليــاه والعمالــة مــن خــالل إضافــة قيمــة للتمــور املزروعــة يف ظــل الظــروف اجلافــة يف ســلطنة عمــان. مت اختيــار مخســة مصانــع للتمــور للدراســة وحتديــد خمتلــف املنتجــات ذات القيمــة املضافــة مــن أصنــاف التمــور األكثــر شــهرة وهــي اخلــالص والفــرض. مت إجــراء املقــارانت بــن التحســينات اإلنتاجيــة للمنتجــات ذات القيمــة املضافــة واملنتجــات اخلــام. كانــت أعلــى نســبة إنتاجيــة للتمــور ذات القيمــة املضافــة هــي التمــور مــع املكســرات لــكال الصنفــن اخلــالص والفــرض بنســبة 540% و 360% علــى التــوايل، بينمــا األدىن مــن متــور اخلــالص هــي التمــور ابلنكهــات بنســبة 111% ومعجــون التمــر مــن متــور الفــرض بنســبة 129%. يف صنــف اخلــالص، أفضــل حتســن يف متوســط إنتاجيــة األرض وامليــاه والعمالــة مــن حيــث القيــم املضافــة مقارنــة ابلقيــم األساســية مــن املــواد اخلــام البالغــة 6.93 طن/هكتــار، 0.57 كجــم/م3 ، و 0.82 كجم/ســاعة كانــت 25.05 طن/هكتــار، 2.06 كجــم/م3 ، و 2.95 كجم/ســاعة يف التمــور مــع املكســرات، بينمــا يف الفــرض كانــت 18.82 طن/هكتــار، 1.55 كجــم/م3 ، و 2.21 كجم/ســاعة علــى التــوايل مــن نفــس املنتــج ذي القيمــة املضافــة. ميكــن أن ترجــع االختالفــات يف حتســن اإلنتاجيــة للمنتجــات ذات القيمــة املضافــة املختــارة إىل توفــر التمــور اخلــام وتكلفتهــا، تكلفــة القيــم املضافــة، خيــارات الســوق وســعر البيــع. أظهــرت القيــم املضافــة إمــكاانت عاليــة لتحســن اإلنتاجيــة يف ظــل الظــروف القاحلــة وتســتحق بــذل اجلهــود لتطبيقهــا يف حتقيــق أهــداف االســتدامة الزراعيــة. الكلمات املفتاحية: املنطقة اجلافة ، فاقد ما بعد احلصاد ، اإلنتاجية ، االستدامة ، القيمة املضافة ، التمور. 2 squ journal of agricultural and marine sciences, 2022, volume 27, issue 7 benefits of value addition in agricultural produce on land, water and labor productivities under arid agriculture: case of dates in oman spacing and region specific or cultivar specific planting arrangements. the uses of local dates, with a determination of their quantity and the proportion of their use, are indicated in table 3 (maf, 2019b). the date palm is considered as the most water-consuming crops, with total consumption of 558 mm3 (al-mulla and al-gheilani, 2017) using scarce water resources (al-yahyai, 2006). al-mulla and al-gheilani (2017) estimated the water consumption for date palm of about 38% of the total water used for irrigation in oman and around 31% of groundwater that facing about 316 mm3 of water deficit annually. table 4 shows the comparison of the percentage water use with the percentage of cultivated area for open field crops. the percentage of cultivated area and the percentage water use for date palm are 30.2% and 42.5%, respectively (maf, 2011b). therefore, improving the water use efficiency in irrigation and water productivity has become a vital matter (hamdy et al., 2003). the ministry of agricultural, fisheries and water resources indicated that the annual water productivity of 6.930 tons of dates is about 2045 m3 in one hectare (maf, 2011b). fao (2008a) reported the annual water productivity of date palm in the range 0.150-0.210 kg m-3 as shown in table 5. al-mulla and al-gheilani (2017) reported that water productivity can be increased from 0.570 to 1.560 kg m-3 with an average date price of 0.400 omr, and in economic basis, the water productivity is increased from 0.230 to 0.630 omr m-3. moreover, other studies indicated that the date water productivity is about 1 kg m-3 (al wahaibi, 2018), 0.350 kg m-3 (joseph 2017), 0.440 kg m-3 (chapagain and hoekstra, 2008) and 0.489 kg m-3 (maf, 2011b) and these discrepancies in productivity values may be due to the climate change, date palm characteristics, type of soil and other factors. the average number of labors used for different cultivated crops, their annual labour hours and annual cost are shown in table 6. dates are categorized as trees table 1. the top ten cultivated date varieties in oman (maf 2019a) date variety date production (ton) percentage of production (%) naghal 37,167 9.86 khisab 35,504 9.42 khalas 35,225 9.35 al-mabsili 32,708 8.68 umm al-salla 30,151 8.00 fardh 24,847 6.59 khunizi 21,152 5.61 shahal 19,850 5.27 abu da’an 11,116 2.95 madluki 10,877 2.89 contribute to the global markets and raise the standard of living (kiaya, 2014). the decline in farm income due to intense competition in global markets has led to consideration for agricultural product development by incentivizing farmers to introduce value-added activities into their products to sustain in this competition (evans, 2012). value addition can contribute to offset the poor positioning of any agricultural product in the market, building up the quality and branding, improving the income and increasing employment (choudhary et al., 2015). it is defined as an activity that agricultural producers may process to produce a new commodity outside the traditional frame to obtain higher returns (evans, 2012). oman is one of the middle east countries that encompasses an arid climate (ampratwum and dorvlo, 1999). agriculture has represented the first source of life in omani history (maf, 2017) although climate change, water depletion, soil salinization and poor labor productivity pose weaknesses and threats in agricultural productivities (sarads, 2016). date palms and other fruits are considered as the permanent crops that cover huge cultivating lands with other vegetable crops (fao, 2008b; moi 2015). on the other hand, there is a high percentage of postharvest losses that may reach an average of 28% in fruits and 30% in vegetables (al-lawati et al., 2016). the ministry of agriculture, fisheries and water resources has initiated several programs toward enhancing agricultural productivity per unit area, improving the quality and preserving the agricultural products especially the dates (maf, 2011a). therefore, this study was aimed to evaluate and quantify the improvements in land, water and labor productivities through value addition in date products cultivated under arid conditions in oman. date palm is one of the main cultivated crops in oman with around 50% of the total cultivated crops and 80% of other cultivated fruits and with over 250 varieties (al-yahyai and khan, 2015; ali, 2010). oman is the eighth largest producer of dates in the world with about 377,000 tons annual productions in 2019 (al-yahyai and khan, 2015; maf, 2019b). date palm trees cover about 35,000 hectares of agricultural land in oman, which contains more than eight million trees (ali, 2010; ishag, 2017). the top ten date varieties in oman are shown in table 1 (maf, 2019a). the land productivity of dates in oman has shown different statistics by deferent sources. al-mulla and al-gheilani (2017) reported that average date yield is about 6075 kg, on average, per one hectare with an average income of 1065 omr. the ministry of agricultural, fisheries and water resources indicated that about 6.930 tons of date are produced per one hectare (maf, 2019b). faostat (2019) estimated the statistics of date production and land productivity from 2015-2019 as shown in table 2. this contradiction may be due to over 200 varieties having different yields, use of different tree 3research paper al hinai, jayasuriya, pathare, al shukeili, al abri and average labour productivity can be estimated as 0.815 kg h-1 (maf, 2011b) of 6930 kg ha-1 of the average date production. materials and methods selected dates factories involved in value addition located in different areas of oman were visited and the completed questionnaires were collected from the stakeholders. the questionnaire contained two main sections, firstly questions about raw dates, and secondly questions about the value-added products of different date varieties. subsequently, five-date factories were selected for the study and the two most popular date varieties were considered for studying the value-added process. two varieties mostly used for value addition by the factories were khalas and fardh. moreover, the selected value-added products of different varieties were compared among the five factories to determine the range of the data variation. the details of the selected factories, date varieties and type of value-added products are shown in table 7 (al hinai and jayasuriya, 2021). the land, water and labour productivities of the selected value-added products are calculated using the following equations (cai et al., 2011; hamdy et al., 2003; karamanos et al., 2005) to compare it with the productivities of raw date: (1) where, agricultural benefit (crop production) (kg), land use (m2). table 2. the production and land productivity statistics of date in oman from 2015-2019 (faostat 2019). 2015 2016 2017 2018 2019 production (tons) 344690 355332 360917 368808 372572 area harvested (ha) 24120 24120 24617 25125 25382 land productivity (tons ha-1) 14.291 14.731 14.661 14.679 14.679 per palm yield (kg palm-1) 114.3 117.2 117.3 117.4 117.4 table 3. the quantity and percentage of date consumption in oman (maf 2019b). consumption distribution quantity (ton) percentage (%) share total production 377,000 100.00 human consumption 198,000 52.52 export 21,000 5.57 processed dates 15,000 3.98 available for industry 144,000 38.20 table 4. comparison of the percentage water use with the percentage of cultivated area for open field crops (maf 2011b). crop cultivated area (%) water use (%) field crops 3.9 1.2 vegetable crops 17.6 13.3 fruit crops 40.9 53.7 fodder crops 37.6 31.8 table 5. annual water productivities of date palm and associated crops for different middle east countries (fao 2008a). countries annual gross water use (m3 palm-1) annual gross water use (m3 ha-1) productivity (kg m-3 of water) egypt 86-124 10,280-14,880 2.28-3.31 saudi arabia 150-350 18,180-42-600 0.15-0.37 iran 102164 12,270-19,720 0.21-0.34 algeria 43-210 5,200-25,400 0.14-0.67 oman 183-240 21,950-29,320 0.15-0.21 libya 183-240 7,200-29,700 0.15-0.21 tunisia 100 12,000 0.28 morocco 105-200 12,600-23,900 0.21-0.40 united arab emirate 130-173 15,500-20,740 0.20-0.26 yemen 130-173 15,500-20,740 0.13-0.16 4 squ journal of agricultural and marine sciences, 2022, volume 27, issue 7 benefits of value addition in agricultural produce on land, water and labor productivities under arid agriculture: case of dates in oman (2) where, agricultural benefit (crop production) (kg), water use (m3). table 6. average number of labors used, their annual labor hours and annual cost (maf 2011b). number of labour number of months average monthly wage (omr) average annual labour hour (h) average annual labour cost (omr) cultivation of field crops (ha) 3.89 7.87 70 8,963 2,143 fodder cultivation (ha) 4.02 9.19 70 9,262 2,586 open cultivation of vegetables (ha) 5.52 7.59 76 12,718 3,184 the trees (ha) 3.69 9.70 70 8,502 2,506 single greenhouse cultivation 3.36 8.79 75 7,741 2,215 double greenhouse cultivation 3.38 7.19 75 7,788 1,823 table 7. data collection of date factories, date varieties and value-added products (al hinai and jayasuriya 2021). factory code (location) date variety type of value addition a (samail) khalas cleaned dates with packaging date with nuts fardh cleaned dates with packaging date with nuts syrup b (bahla) khalas cleaned dates with packaging date with nuts syrup paste date halwa fardh cleaned dates with packaging date with nuts syrup paste date halwa c (nizwa) khalas cleaned dates with packaging date with nuts dates with saffron, hill and cinnamon fardh cleaned dates with packaging date with nuts syrup d (barka) khalas cleaned dates with packaging date with nuts paste fardh cleaned dates with packaging date with nuts e (ibri) khalas cleaned dates with packaging date with nuts paste halwa fardh cleaned dates with packaging date with nuts 5research paper al hinai, jayasuriya, pathare, al shukeili, al abri (3) where, agricultural benefit (crop production) (kg), annual labour hour (h). the benefit of value-added products is calculated using the following equation (lewbel 2003): net income=selling price (value added)-purchase price (raw)-value addition cost (4) where, selling price, purchase price and value-added product (omr ton-1). the net profit based productivity ratio is calculated using the following equation (farooq et al., 2001): (5) the key data of land, water and labor productivities of the raw date products estimated from the literature reviews and they are as follows: date palm planting density 125 palms h-1 (kotagama et al. 2014), on average, raw date price 0.400 omr (al-mulla and al-gheilani 2017) land productivity 6.930 ton ha-1 (maf 2011b), water productivity 0.570 kg m-3 and the water productivity based on economics 0.630 omr m-3, and average labor productivity 0.815 kg h-1 (maf 2011b). table 8. the summarized results of the two most used date varieties from the five factories in oman (al hinai and jayasuriya 2021). value-added product cost for the raw product (omr ton-1) cost of value-added product (omr ton-1) the selling price of value-added product (omr ton-1) net income (omr ton-1) productivity ratio (net profit basis) (%) khalas dates cleaned date with packaging 400-500 100 6001,500 100-900 125-280 date with nuts 500-800 400-626 1,500 – 3,200 500-2,200 183-540 syrup 2,400 100 5,000 2,500 204 paste 500-600 100-300 850-1,200 150-400 130-180 date halwa 600 850-900 2,000-3,000 500-1,550 183-358 date with different flavour; saffron, hill, and cinnamon 800 615.4 1,500 85 111 fardh dates cleaned date with packaging 300-600 100 600-1,500 225-900 138-280 date with nuts 400-800 350-872 1,500-3,200 400-834 183-360 syrup 4,200-4,800 100 5,000-7,500 400-2,600 109-180 paste 700 100 1,000 200 129 date halwa 700 872 2,000 428 161 table 9. the improvements in land, water and labor productivities due to value addition in dates. value-added product land productivity improvement from 6.930 (ton ha-1) water productivity improvement from 0.570 (kg m-3) labour productivity improvement from 0.815 (kg h-1) khalas dates cleaned date with packaging 8.660 – 19.400 0.713 1.596 1.019 2.282 date with nuts 12.680 – 37.420 1.043 – 3.078 1.491 – 4.401 syrup 14.140 1.163 1.663 paste 9.010 – 12.470 0.741 – 1.026 1.060 – 1.467 date halwa 12.680 – 24.810 1.043 – 2.041 1.491 – 2.918 date with different flavour; saffron, hill, and cinnamon 7.690 0.633 0.905 fardh dates cleaned date with packaging 9.560 – 19.410 0.787 1.596 1.125 – 2.282 date with nuts 12.680 – 24.950 1.043 – 2.052 1.491 – 2.934 syrup 7.550 – 12.470 0.621 – 1.026 0.888 – 1.467 paste 8.940 0.735 1.051 date halwa 11.160 0.918 1.312 6 squ journal of agricultural and marine sciences, 2022, volume 27, issue 7 benefits of value addition in agricultural produce on land, water and labor productivities under arid agriculture: case of dates in oman results and discussion the productivity results of the two selected date varieties from the five-date factories in oman are summarized in table 8 (al hinai and jayasuriya, 2021) that shows the selected value-added product, cost of the raw date, cost of the value-added product, net income of the value-added product, and the productivity ratio through the value-added product. the results of the value-added productivity ratio of the two date varieties in table 9 were used to determine the improvements in land, water and labour productivities from the base values 6.930 ton ha-1 (maf, 2011b), 0.570 kg m-3 (al-mulla and al-gheilani, 2017) and 0.815 kg h-1 (maf, 2011b) respectively as shown in table 9. the results showed that khalas, fardh varieties are the most widely used by the selected five factories for value addition process. this is due to the availability, relatively higher production, variation in sugar content (fardh has less sugar content than khalas), low purchase cost, more economic value, and the good texture for forming and filling with different nuts and flavors during the value addition process. in khalas variety., date with nuts has the highest productivity ratio that may reach up to 540% because there is a considerable difference between the selling price and the production cost (raw date cost and value-added cost) for about 3,000 omr/ton that makes the net income higher as shown in table 8. the second highest productivity ratio was date halwa 358%, followed by a cleaned date with packaging 280%, date syrup 204%, date paste 180% and finally, date with saffron and other flavours 111%. in fardh variety., consistent with khalas variety., date with nuts has the highest productivity ratio that may reach up to 360% but it is less than the productivity ratio of khalas variety. due to the high cost of the value-added operations as shown in table 8. cleaned date with packaging is the second-highest productivity ratio 280%, followed by date syrup 180%, date halwa 161% and finally, date past 129%. factories are not making value-added products of fardh dates with saffron and other flavors. date with nuts value-added products of the two date varieties got the highest productivity improvement compared to the other value-added products because of the highest productivity ratio. table 9 shows that the date with nuts in khalas and fardh has about 37.42 and 24.95 ton ha-1 maximum value in land productivity improvement from the 6.93 ton ha-1 of the raw date products respectively. besides, the improvement of water productivity in date with nuts is up to 3.078 kg m-3 in khalas and 2.052 kg m-3 in fardh compared to the water productivity of the raw date 0.57 kg m-3. moreover, the maximum value of the improvement in labor productivity of date with nuts is about 4.401 kg h-1 in khalas and 2.934 kg h-1 in fardh compared with the 0.815 kg h-1 labor productivity of the raw date. the average improvement productivities of the value-added products of the two varieties comparison prior value addition dates are summarized in figure 1. in general, the variation of the land, water and labour productivities of the selected value-added products of two date varieties (khalas and fardh) are mainly due to the cost of the raw dates (before value addition), cost of the value-added process and selling price of the value-added products. the cost of the raw date is varied among the five selected factories in different regions of oman. in addition, differences in dates selling prices can be explained by the retail sale from suppliers and the quality of dates. the cost of the value-added process was also varied among the factories and this was because of the types of machines used (machine type and capacity), labour cost and other manufacturing processes. these two main costs of production (raw and value-added processing) lead to variation in the selling prices of the different value-added products at different factories to achieve the desired net income. conclusion oman is one of the arid countries in the middle east, its agriculture sector is suffering from scarcity of arable lands, water and labour resources which has not been supportive in achieving sustainability and food security. value addition can be one of the best options to achieve sustainability goals, minimize food wastes and improve product quality and exports by improving the land, water and labor productivities. the government of oman aims to increase agricultural production, improve the quality and preserving the agricultural products especially the dates, which is most grown crop in oman. therefore, different value-added products from five different date factories in oman were selected for the study with considering two date varieties, khalas and fardh. results revealed that the improvement of land, water and labor productivities can be achieved through value addition. among the most common value-added date products, date with nuts achieved the highest productivity improvement (540%) especially in khalas variety followed by date halwa, cleaned date with packaging, syrup, paste, and date with saffron and different flavours. moreover, in fardh variety., date with nuts also obtained the highest productivity improvement (360%) followed by a cleaned date with packaging, syrup, date halwa and paste. the improvements in land, water and labor productivities were compared from the base values obtained 6.930 ton ha-1, 0.570 kg m-3 and 0.815 kg h-1 respectively and similar trend were observed as the productivity ratios developed. the variations in the productivity ratio of the selected value-added products are mainly due to the cost of the raw date, cost of the value-added process and selling price of the value-added products that may take into consideration for the future improvement in productivity. 7research paper al hinai, jayasuriya, pathare, al shukeili, al abri figure 1. the average productivity improvement of land, water and labour at different value-added date products of two varieties (a) land productivity improvement in kg m-3 (b) water productivity improvement in kg m-3 (c) labour productivity improvement in kg h-1. 8 squ journal of agricultural and marine sciences, 2022, volume 27, issue 7 benefits of value addition in agricultural produce on land, water and labor productivities under arid agriculture: case of dates in oman references ahmed m, ai-rawahy s, al-handhaly j, ai-saadi sn, al-ajmi h. 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(2003). calculating compensation in cases of wrongful death. journal of econometrics 113(1): 115–128. maf. (2011a). agriculture and livestock five-year research strategy 2011-2015. directorate general of agriculture & livestock research. ministry of agricultural and fisheries. 52 pp. http://extwprlegs1.fao. org/docs/pdf/oma152793.pdf. maf. (2011b). assessing returns to support investments in the two agricultural development projects (icarda & maf (eds.)). muscat: international center for agricultural research in the dry areas, ministry of agricultural and fisheries. 200 pp maf. (2017). about agricultural sector. ministry of agricultural and fisheries. h t t p : / / w w w . m a f . g o v . o m / p a g e s / a b o u t . a s p x ?id=100&lang=ar&i=104199&did=0&cid=0&cmsid=800245. maf. (2019a). date production book 2019. muscat: ministry of agricultural and fisheries. 50 p. maf. (2019b). the yearbook of agricultural statistics 2019. issue 47. ministry of agricultural and fisharies. 359 pp. https://www.ncsi.gov.om/elibrary/pages/librarycontentdetails.aspx?itemid=ls%2fmy%2fxay%2fnsxicl9denma%3d%3d. mizyed nr. (2013). challenges to treated wastewater reuse in arid and semi-arid areas. environmental science and policy 25: 186–195. moi. (2015). the total area of cultivated land in the sultanate is 164 thousand feddans in 2014 and production is more than one million tons. ministry of information. https://omaninfo.om/option.php?action=pdf&id=1287. namara re, hussain i, bossio d, verma s. 2007. innovative land and water management approaches in asia: productivity impacts, adoption prospects and poverty outreach. the journal of the international commission on irrigation and drainage 56(2-3): 335–348. rahman haa. (1996). traditional systems and application of modern irrigation techniques in the sultanate of oman. agricultural mechanization in asia, africa and latin america 27(1): 41–45. sarads. (2016). sustainable agriculture and rural development strategy towards 2040. sarads. https:// andp.unescwa.org/plans/1210. research paper journal of agricultural and marine sciences 2022, 27(2): 66–73 doi: 10.53541/jams.vol27iss2pp66-73 received 5 december 2021 accepted 6 march 2022 evaluation of physical and chemical properties and total phenolic content in baker’s yeast obtained from grape juice sawsan mahmood*1, ali ali2, ayhem darwesh3, wissam zam4 sawsan mahmood*1( ) sawsanmahmood480@gmail.com,1phd student at the department of food technology, faculty of technical engineering, tartous university. 2professor at faculty of technical engineering, tartous university. 3professor at faculty of technical engineering, tartous university. 4professor at faculty of pharmacy, alwade university. introduction fermentation is the process of using microorgan-isms to produce valuable products, such as an-tibiotics, industrial enzymes, food, and chemicals. microorganisms which multiply predominantly by budding are collectively called “yeasts” (saranraj et al., 2017). phaff (1990) gave the definition for yeasts as unicellular eukaryotes, which at some stage in their life cycle, divide by budding. the known organisms is the strain of saccharomyces cerevisiae used in the brewing and baking industries. if the term “yeast” is not further specified, saccharomyces cerevisiae is the commonly referred organism. this strain of yeast has been extensively studied and applied widely both in the laboratory and in industry. baker’s yeast (saccharomyces cerevisiae) is one of the oldest products of industrial fermentation. it is still one of the most important fermentation products based on the volume of sales and its use for bread making, a stable food for large section of world population. the baker’s yeast saccharomyces cerevisiae has been associated with human beings for more than 6000 years due to its use in food production, baking, wine and beer (saranraj et al., 2017). saccharomyces cerevisiae was the first eukaryotic organism to be sequenced in 1996 (goffeau et al., 1996), and is clearly the most ideal eukaryotic microorganism for biological studies. the impact of baker’s yeasts on the production, quality and safety of foods and beverages is intimately linked to their ecology and biological activities. recent advances in understanding the taxonomy, ecology, physiology, biochemistry and molecular biology of baker’s yeasts have stimulated increased interest in foods and beverages. this has led to a deeper understanding of their roles in the fermentation of established products, such as bread, beer and wine. as the food industry develops new products and processes, yeasts present new challenges for their control and exploitation. food safety and the linkage between diet and health are the issues of major concern to the modern conتقييم اخلواص الفيزايئية والكيميائية واحملتوى الفينويل الكلي يف مخرية اخلبز املأخوذة من عصري العنب سوسن حممود * ١ ، علي علي ٢ ، أيهم درويش ٣ ، وسام زم ٤ abstract. baker`s yeast is mainly produced from molasses in various parts of the world, and other sources, including grape juice. in this study, the grape juice was chosen. this study aimed to produce a biomass from dry baker`s yeast. its physical and chemical properties was evaluated. the biomass from baker’s yeast s. cerevisiae was equal to 41.50±0.01 g/l. the following fermentation conditions, i.e. temperature (30.1oc), ph (4.75), sugar concentration (158.36 g/l), ratio of carbon to nitrogen (11.9), and initial concentration of yeasts (2.5 g/l) were used. the fermentation was carried out for a period 12 h. grape juice was subjected to four different heat treatments as follows: pasteurized grape juice at (65, 70, and 75oc) for 10 min, and sterilized grape juice in the autoclave at 121oc for 20 min. the effect of each treatment was determined on inhibition of the enzyme polyphenol oxidase present in grape juice. the total phenolic content was determined in the yeast. heat treatments gave the best phenolic content in the resulting yeast. the heat treatments of the juice succeeded in reducing the activity of the enzyme polyphenol oxidase and autoclave heat treatment gave the best phenolic content in the yeast. keywords: : baker`s yeast, grape juice, fermentation, phenolic content. امللخص:يتــم إنتــاج اخلمــرة املســتخدمة يف املخابــز بشــكل أساســي مــن دبــس الســكر يف أجــزاء خمتلفــة مــن العــامل ، ومصــادر أخــرى ، مبــا يف ذلــك عصــر العنــب. يف هــذه الدراســة مت اختيــار عصــر العنــب. وعليــه كان اهلــدف مــن هــذه الدراســة هــو إنتــاج كتلــة حيويــة مــن مخــرة املخابــز اجلافــة. حيــث مت تقييــم اخلــواص الفيزايئيــة والكيميائيــة للخمــرة. فقــد كانــت الكتلــة احليويــة مــن مخــرة اخلبــاز s. cerevisiae تســاوي ٤١.50 ± 0.0١ جــم / لــر. وقــد مت اســتخدام ظــروف التخمــر التاليــة ، درجــة احلــرارة )٣0.١ درجــة مئويــة( ، و درجــة احلموضــة )٤.75( ، وتركيــز الســكر )١58.٣6 جــم / لــر( ، ونســبة الكربــون إىل النيروجــن )١١.9( ، والركيــز األويل للخمائــر )٢.5 جــم / لــر(. مت إجــراء التخمــر ملــدة ١٢ ســاعة. تعــرض عصــر العنــب ألربــع معامــات حراريــة خمتلفــة علــى النحــو التــايل: عصــر العنــب املبســر عنــد )65 ، 70 ، 75 درجــة مئويــة( ملــدة ١0 دقائــق ، وعصــر العنــب املعقــم يف جهــاز التعقيــم عنــد ١٢١ درجــة مئويــة ملــدة ٢0 دقيقــة. مت حتديــد أتثــر كل معاملــة علــى تثبيــط إنــزمي بوليفينــول أوكســيديز املوجــود يف عصــر العنــب و حتديــد حمتــوى الفينــول الكلــي يف اخلمــرة. أعطــت املعاجلــات احلراريــة أفضــل حمتــوى فينــويل يف اخلمــرة الناجتــة. جنحــت املعاجلــات احلراريــة للعصــر يف تقليــل نشــاط إنــزمي بوليفينــول أوكســيديز وأعطــت املعاجلــة احلراريــة جبهــاز التعقيــم أفضــل حمتــوى فينــويل يف اخلمــرة. الكلمات املفتاحية: مخرة املخابز ، عصر العنب ، التخمر ، حمتوى الفينول. 67research paper mahmood, ali, darwesh, zam sumer and baker’s yeasts are emerging in this context (saranraj et al., 2017). on the positive side, there is increasing interest in using baker’s yeasts as novel probiotic and biocontrol agents, and for the nutrient fortification of foods (gelinas, 2006; prem kumar et al., 2015a). baker’s yeast, saccharomyces cerevisiae, is still one of the most important biotechnological products because of its several industrial applications. baker’s yeast as a commercial product has several formulations that can be grouped into two main types: compressed yeast, called fresh yeast, and dried yeast (beudeker et al., 1990). compressed yeast is the traditional formulation of baker’s yeast and is ready for immediate use. dried yeast is available in two forms: active dry yeast (ady) and instant dry yeast (idy). active dry yeast (ady) is normally sold in airtight packages, vacuum seal or filled with an inert gas such as nitrogen. it is not a problem to maintain quality, but it should be rehydrated before use. unlike ady, instant dry yeast (idy) does not have the cell damage during rehydration. idy is the most expensive among the three type of baker’s yeast. baker’s yeast is marketed in two ways, either as compressed cakes or as a dry powder, however there is also a saleable intermediate of the process known as ‘cream yeast’ (gill et al., 2013). yeast are a unicellular fungi or plant-like microorganism that exists in or on all living matter i.e. water, soil, plants, and air. they are microbial eukaryote, associated with ascomycetes and are rich in protein and vitamin b (dunn et al., 2015). as a living organism, yeast primarily requires sugars, water and warmth to stay alive. in addition, albumen or nitrogenous material is also necessary for yeast to thrive. there are hundreds of different species of yeast identified in nature, but the genus and species most commonly used for baking is saccharomyces cerevisiae. the scientific name saccharomyces cerevisiae, means a mold which ferments the sugar in cereal (i.e. saccharo-mucus cerevisiae) to produce alcohol and carbon dioxide. yeasts are usually spherical, oval or cylindrical in shape and a single cell of s. cerevisiae is around 8 μm in diameter. each cell has a double-layered wall, which is permeable to certain substances and food material is taken into the cell and metabolites (slonimski et al., 2013). cell division or cell reproduction generally takes place by budding. in the budding process, a new cell forms as a small outgrowth of the old cell, the bud gradually enlarges and then separates. although, most yeast reproduce only as single cells, under some conditions some yeasts can form filaments (madigan et al., 2003; sivasakthivelan et al., 2014). yeasts flourish in habitats where sugars are present, such as fruits, flowers and bark of trees. however, commercial yeasts of today are quite different from wild strains due to genetic manipulation, allowing them to grow in previously unsuitable conditions (liti et al., 2009; prem kumar et al., 2015b). yeasts are of great economic importance. yeasts, especially different strains of saccharomyces cerevisiae have long been used for the production of alcoholic beverages, solvents and other chemicals. in the modern bakery, yeasts are used for manufacturing of different kinds of bread and confectionaries. it is responsible for leavening the dough and imparting a delicious flavor to the product (warringeret al., 2011). molasses is the most used raw material in the production of baker’s yeast, and it may be sourced from sugar beet, or sugar cane, and it contains about 50-55% of fermentable sugars, and some vitamins and minerals. these are important in cell proliferation containing fermentable sugars, such as date and grape juices (gelinas et al., 2000). yeasts have a positive image with consumers, as they are considered a safe source of ingredients and additives for food processing (boze et al., 1992; bekatorou et al., 2006; tsunatu et al., 2017). preparations of baker’s and brewer’s yeasts have been available for many years as dietary, nutrient supplements because of their high contents of b vitamins, proteins, peptides, amino acids and trace minerals. yeasts are often considered as an alternative source of protein for human consumption (buzzini et al., 2005; chaucheyras-durand et al., 2008; pienaar et al., 2012). many products are now derived from yeasts and, according to abbas (2006), about 15–20% of the global industrial production of yeasts is used for this purpose. the production of antioxidants, aromas, flavors, colors and vitamins could be done by yeasts. interest in food phenolics has increased, because of their antioxidant and free radical scavenging abilities (lugasi and hovari, 2003), metal chelators and enzyme modulators (dulger et al., 2002). many phenolics can exhibit antioxidant activity as their extensive, conjugated electron systems allow ready donation of electrons, or hydrogen atoms, from the hydroxyl moieties to free radicals. however, the antioxidant efficacy, in terms of reaction stoichiometry and reaction kinetics may vary considerably (lugasi et al., 2003). this is dependent on structural features, such as the number and positions of the hydroxyl moieties on the ring systems, and the extent by which the unpaired electron in the oxidized phenolic intermediate can delocalise throughout the molecule. thus, most phenolics, especially flavonoids are very effective scavengers of hydroxyl and peroxyl radicals. phenolics are chelators of metals and inhibit the fenton and haber-weiss reactions abilities (lugasi et al., 2003; dulger et al., 2002), which are important sources of active oxygen radicals. phenolic compounds inhibited the development of cancerous tumours, reduce a risk for cardiovascular disease, and have showed antibacterial, anti-inflammatory, antispasmodic and anti-diarrheic properties (abdoul-latif et al., 2012). fermentation is a good technology with great potential for application on the production or extraction of antioxidant active compounds from natural sources. new bioactive compounds could be found during fermentation. moreover, modification of fermentation process could be tailored to increase the bio accessibility of bio68 squ journal of agricultural and marine sciences, 2022, volume 27, issue 2 evaluation of physical and chemical properties and total phenolic content in baker’s yeast obtained from grape juice active compounds. production of bioactive compounds yet remains a quite unexplored potential, which could be accomplished by utilizing new fermentation process. therefore, in the future, it can be anticipated that fermentation could be used to design food with health effects. some fermentation processes are available on the applications of production of antioxidant activity compounds (shahat, 2017). however, the underlying mechanisms affecting anti-oxidative activity during fermentation are varied, and the production of antioxidant active compounds during fermentation (hur et al., 2014). some of the most compelling evidence of a protective effect of diets against cancer, in recent years, is the evidence on the intake of fruits and vegetables (block et al., 1992; fokou et al., 2017). epic (european prospective investigation into cancer and nutrition) is an important study that indicates that these retrospectively obtained results, at least respecting to cancer, might have been somewhat overestimated, however, still a significant reduction of consumption of fruits and vegetables on colorectal cancer (bouayed0 et al., 2010). polyphenols can further act by inhibiting cell proliferation, which is deregulated in cancer. this inhibition has been demonstrated in vitro in many tumor cell lines. although the anti-proliferative effects of polyphenols in general and in particular of flavonoids and iso-flavonoids in cell cultures seems well established, there are relatively few data regarding the in vivo anti proliferative activity, and virtually nothing is known about the clinical relevance of this bioactivity (birt et al., 2001). this anti-proliferative effect suggests that polyphenols may have an effect via regulating the cell cycle or inducing apoptosis in tumor cells. in fact, many studies have shown the effect of polyphenols on the cell cycle of tumor cells in cultures in in vitro assays. therefore, in this presented study, grape juice was selected as the sole source of carbon for producing dry biomass from yeast due to its richness in phenolic compounds. then the phenolic content of the yeast obtained from grape juice was evaluated. this study distinguished from previous studies using an organic medium, while previous studies used commercial media to obtain dry yeast with good phenolic content (shaha, 2017). it is known that grapes contain a good amount of the enzyme, polyphenol oxidase, which causes oxidation of phenolic compounds and reduces their quantity. it also causes enzymatic browning, which may negatively effect of the final product quality. in this study, the effect of heat treatment on the activity of the enzyme polyphenol oxidase was evaluated at different temperatures with the aim of choosing the best heat treatment in reducing the enzyme activity and thus maintaining a good phenolic content in the resulting yeast. materials and methods commercial materials all materials used in these experiments are collected from himeda company, mumbai, india. glucose and vitamin solutions were sterilized by filtration and added to the autoclaved medium. origin and reactivation of the yeast s. cerevisiae dried powder yeast form of s. cerevisiae (atcc20408/ s288c) was used in this study. it was produced by the biomatric-the biostability company. the yeast was reactivated on agar plates containing ypga medium composed of yeast extract 10 g/l, peptone 10 g/l, glucose 20 g/l, agar 20 g/l with a ph 6, incubated at 30oc for 24 h. preparation of grape juice baladi grapes (figure 1), which is one of the white grape varieties, originating in spain were used. it is known as cayetana grape. baladi grapes are among the varieties available in syria. its yield is up to 20%. it is a domestic variety characterized by the size of its large mass and has a single conical shape. the grains are spherical in shape, large size, yellowish-white in color, and the peel is thin and light pink in color. the pulp is flaky, has a good taste, has a characteristic flavor, it is a late-ripening variety. it is a popular and luxurious table variety, suitable for remote transportation and long winter storage. baladi grape samples were collected from the sheikh badr area in the countryside of tartous city in syria. the grape berries were removed from their clusters, cleaned and washed with warm water. the juice was extracted by breaking and pressing in doubly folded cloth. figure 1. the baladi grape 69research paper mahmood, ali, darwesh, zam thermal treatment for grape juice the heating effect on the grape juice was pasteurized at (65, 70 and 75oc) for 10 min, while fourth treatments was sterilized grape juice in the autoclave at 121 oc for 20 minutes. then the effect of each heat treatment on inhibiting the activity of the enzyme polyphenol oxidase in grape juice was determined by estimating the phenolic content in the yeast. preparation of culture medium based on grape juice and inoculums the method cited by kocher and uppal (kocher et al., 2013) was used with minor modifications. the obtained grape juice from the above preparation was supplemented by mineral salts: magnesium sulfate 0.44 g, urea 12.70 g, and ammonium sulfate 5.30 g. finally, the medium was distributed in an erlenmeyer of 250 ml with a ratio of 100 ml per flask and sterilized at 120 oc for 20 min. the pre-culture was obtained by inoculating two colonies of the yeast s. cerevisiae in 250 ml shake flasks containing 100 ml of grape juice, mentioned above. the pre-culture was incubated at 30 oc for 3 h, and used further as inoculums for the yeast biomass production. fermentation process the fermentation was carried out within a biological fermenter with a capacity of 6 liters with an engineering design and initial volume of the fermentation medium (i.e. grape juice) was 3 liters. the initial conditions for the fermentation process were: temperature (30.11 oc), ph (4.75), sugar concentration (158.36 g/l), ratio of carbon to nitrogen (11.9), initial concentration of yeasts (2.5 g/l), stirrer speed (630 r.p.m), air flow (20 min/l), and period fermentation was 12 h. the temperature of the fermentation medium was set at the required degree using the cooling and heating coils in the biological fermenter. the ph was also adjusted by pumping appropriate quantities of 10 % (w/v) naoh and 10% (v/v) h2so4 as needed into the fermentation medium. biomass concentration the measurement of biomass was followed by estimation of cell dry weight, expressed in g/l. one ml of yeast culture was centrifuged at 5000 rpm for 5 min. the supernatant obtained was washed twice with water and dried by incubation at 105 oc until at a constant weight (jiménez-islas et al., 2014). total phenolic content (tpc) in the yeast biomass total phenolic content of yeast extracts obtained from grape juice medium was estimated using the folin-ciocalteu reagent method (kahkonen et al., 1999; ainsworth and gillespie, 2007). one ml of each sample extracts were mixed with 250 μl of 10% (v/v) folin-ciocalteu reagent, followed with the addition of 500 μl saturated sodium carbonate (10%, w/v aqueous solution) after 2 min of incubation at room temperature. the mixture was placed in the dark for 1 hour. absorbance was then measured at λ750 nm. the concentration of total phenols was calculated based on a calibration curve using gallic acid. the phenol content was expressed as gallic acid equivalent (gae), which reflects the phenol content, as the amount of gallic acid units in liter of extract (mg gae l-1). three replicates were used for total phenolic content. physicochemical characteristics of the obtained yeast proximate composition: total protein, nitrogen, moisture, dry matter and ashes were determined in accordance with the aoac procedures (1975; 1990). total carbohydrates were determined through the colorimetric method from dubois et al. (1958). total lipids were extracted through the procedure of blight et al. (1959) and determined gravimetrically. fibers were quantified through the method from asp et al. (1983). density, ph and energy of dry yeast were determination with the cofalec (2012): general characteristics of dry baker’s yeast. test for dispersibility in water: weigh 5 g of dry baker’s yeast or 20 g of fresh baker’s yeast into a 400 ml beaker and add 50 ml of distilled water at 40 oc. leave the product undisturbed for 5 min and thereafter, stirred for 2 min. take into a one liter graduated cylinder, 900 ml of distilled water at 40 oc in the case of dry baker’s yeast and at 30 oc for fresh baker’s yeast. pour the slurry from the beaker into the water in the graduated cylinder. wash the beaker with 50 ml of distilled water, poured it into the cylinder and left it undisturbed for 5 min. checked for any deposits at the bottom of the cylinder. if no deposits appeared at the bottom of the cylinder, the material shall be considered to have passed the test (rad et al., 2017). dough raising capacity fresh baker’s yeast (4 g) or 1.0 g of dry baker’s yeast with 100 g of wheat flour were mixed. sucrose (1.0 to 1.5 g) was added to a suitable quantity of water (about 55 ml). these were mixed by knead well press into a glass beaker until formed a dough. the level of the dough by means of a scale, from the bottom of the beaker was noted. it was kept covered for one h at 27 oc. at the end of this period, level was recorded again. the product shall be deemed to have satisfied the test if the level was at least 80 percent of the original for dry baker’s yeast and 110 percent for fresh baker’s yeast (rad et al., 2017). yeast survivability was determined as cfus per gram of dry matter. a microbial test can be used to measure the viability and survivability of yeast cells. twenty-five grams of yeast was mixed with 175 ml of water. the viability of the suspensions was checked by plate counting. yeast cell suspensions were counted on yeast extract glucose-chloramphenicol (ygc) agar (ygc agar, merck) after 5 days of incubation at 25 oc. logarithmic dilutions were carried out in saline, and diluted suspensions were 70 squ journal of agricultural and marine sciences, 2022, volume 27, issue 2 evaluation of physical and chemical properties and total phenolic content in baker’s yeast obtained from grape juice cultured on ygc agar and incubated at 25 oc for 5 days (rad et al., 2017). statistical analysis experiments were performed in three replicates and all results were expressed as mean ± standard deviation (sd) using windows software, version 7.0 (origin lab, 2010). results and discussion biomass from baker’s yeast s. cerevisiae in grape juice medium was determined as a sole carbon source, and it was equal to 41.5±0.01 g/l at the fermentation conditions of temperature (30.11oc), ph (4.75), sugar concentration (158.36 g/l), ratio of carbon to nitrogen (11.9), initial concentration of yeasts (2.5 g/l) and a period of fermentation (12 h). similarly, nancib et al. (1997) obtained biomass from baker’s yeast s. cerevisiae was 40 g/l, when date fruit byproducts were used. khan et al. (2017) used six different strains of s. cerevisiae in fermentation medium containing date extract (with 60% sugars), 2 g/l ammonium sulfate and 50 mg/l biotin. their results showed that the theoretical yields were about 42.8%. in addition, al obaidi et al (1986) studied two substrates (i.e., date syrup and molasses) for the propagation of baker’s yeast strain s. cerevisiae on a pilot plant scale. the results showed that higher productivity of baker’s yeast was observed when date extract was used. in fact, the optimal biomass production (6.3 g/l) was depicted at 24 h using saccharomyces cerevisiae div13z087c0vs on a medium containing sweet cheese as a sole carbon source (boudjema et al., 2015). on the other hand, the production of baker’s yeast from apple pomace gave a yield of 0.48 g/g (bhushan et al., 2006). therefore, it was concluded from these studies that the medium containing the grape juice as a sole carbon source is an excellent fermentation medium for baker’s yeast production. the total phenolic content was estimated by folin-ciocalteu method using gallic acid as the standard reference (figure 2). total phenolic content in the yeast extract were 1275.39±0.01, 1623.3±0.01, 1739.17±0.01, and 2087±0.01 mg/l at thermal treatment of grape juice 65, 70, 75, and in autoclave at 121oc, respectively. it was noted that the heat treatment of the juice succeeded in reducing the activity of the enzyme polyphenol oxidase by about 50% at temperature 65oc, 70% at temperature 70oc, 75% at temperature 75 oc, and 90% at temperature 121oc, respectively. the best heat treatment was observed in the case of autoclave, as it helped to maintain the best phenolic content in the resulting yeast. shahat (2017) were determined for four commercial mediums after sterilized in the autoclave at 121 °c for 20 min. the phenolic contents were 1387±0.01, 1990±0.01, 1129±0.01 and 982±0.01 mg/l for the yeast-peptone-dextrose medium, corn meal, oat meal and sugar cane medium, respectively. the best result was with corn meal, and was close to the result of this current study at 121 °c for 20 min. consequently, the yeast produced from grape juice can play an important part in the human health and nutrition due figure 2. standard calibration urve for galic acid at a wavelength of 765 nm 71research paper mahmood, ali, darwesh, zam to its biological effectiveness and its antioxidant and anticancer activities. the results of physico-chemical characteristics of yeast are shown in table 1 with the corresponding values according to the cofalec (2012). dry yeast cells was dispersed in water as required and no yeast cell was deposited. the level of dough became 80 percent of the original as required , and yeast cells have satisfied the test. colony counting of the samples showed that the number of cfu/mg yeasts was 15×1010 cfu per milligram in the dry matter of yeast. according to the cofalec (2012), coliform count was below 1000 cfu/g, thus the yeast produced from grape juice was acceptable. conclusion this study showed that the heat treatments of the juice reduced the activity of the enzyme polyphenol oxidase and autoclave heat treatment gave the best phenolic content in the yeast. it is clear that the use of grape juice can be possible as the sole source of carbon in order to produce bread yeast. it demonstrated a good yield of dry biomass from bread yeast and these could be used by food industries, and it contained high level of phenolic content. it can also make a nutritional supplement and could beneficial to human health. references abbas ca. 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(2017). antioxidant and anticancer activities of yeast grown on commercial media. international journal of biological and chemical sciences. 11(5): 2442-2455. sivasakthivelan p, saranraj p, sivasakthi s. (2014). production of bioethanol by zymomonas mobilis and saccharomyces cerevisiae using sunflower head wastes–a comparative study. int. j. microb. res. 5(3): 208-216. slonimski pp. (2013). adaptation in microorganisms. third symposium of the society for general microbiology, cambridge university press, p.76. tsunatu dy, atiku kg, samuel tt, hamidu bi, dahutu, di. (2017). production of bioethanol from rice straw using yeast extracts paptone dextrose. nigerian journal of technology 36(1): 296 – 301. warringer j, cubillos fa, zia a, gjuvsland a. (2011). trait variation in yeast is defined by population history. plan genetics. 7: 102-111. research paper journal of agricultural and marine sciences 2020, 25(2): 46–57 doi: 10.24200/jams.vol25iss2pp46-57 received 16 mar 2020 accepted 14 may 2020 dynamics of physical capital in artisanal fisheries and policy implications shekar bose1, hussein samh al-masroori2*, salim darwish salim al-hasani3 hussein samh al-masroori2*( ) masroori@squ.edu.om, 2department of marine science and fisheries, college of agricultural and marine sciences, sultan qaboos university. 3ministry of agriculture and fisheries, sultanate of oman. 3gibbon street, woolloongabba queensland, 4102, australia. introduction the twin problems of over-investment and excess harvesting capacity are of major concerns for fish-eries in both developed (zhang et al., 2018; kirkley et al., 2002; kirkley and squires, 2003) and developing countries (pomeroy, 2012; purcell and pomeroy, 2015). these problems are essentially linked to both physical and natural capital (nøstbakken et al., 2011). the role of physical capital as a produced means of production is well established in economics in general (hulten, 1991), and in natural resource industries like fisheries in particular (clark et al., 1979). frequent occurrence of conflicts in fisheries due to excess capacity (ahmed et al., 2006), threats to long term sustainability due to capital stuffing (kirkley and squires, 1998), and poor economic returns associated with over-investment are some of the legitimate justifications for the need to address the concerns of over-investment and excess capacity in smalland/or large-scale fisheries. this calls for effective management of overcapitalization in fisheries which is crucial for ensuring sustainability in fisheries and the flow of benefits to the society in the long run (kirkley and squires, 1998). furthermore, recognizing the role of small-scale fisheries in development (de melo alves damasio et al., 2016), the financing of small-scale fisheries whether by public or private funds has received attention of policy-makers in recent years both locally (diffey et al., 2009; setlur and arbuckle, 2015) and globally (heck et al., 2007; holmes et al., 2014). however, a lack of knowledge about the status of physical capital engaged in fishing will not only undermine effectiveness of management but also introduce uncertainty to the future investment planning for the sector. hulten (1991) emphasized that an estimate of capital, however imperfect, is crucial to understand the ديناميات رأس املال املادي يف مصايد األسامك الحرفية واآلثار املرتتبة عىل السياسات شيكار بوز1 وحسني سمح املرسوري2* وسامل درويش الحسني3 abstract. the dynamics of physical capital stock and net investment in artisanal fisheries of al-seeb, a coastal fishing town of muscat governorate, were examined covering the period 2004-2013. data was gathered from two sources namely the ministry of agriculture and fisheries and field survey. a hedonic regression model was used to examine the influence of boat characteristics on the boat acquisition prices and then to derive the growth rate of physical capital stock. boat characteristics comprising of ‘age’, ‘horsepower (hp)’ and ‘length (vl)’ were found to be statistically significant at the 5% level and carry sign consistent with the economic theory of depreciation and cost respectively. while inter-annual fluctuation of net investment was observed, a positive trend in cumulative investment with an average growth rate of 7.63% was experienced in the fishery during 2004-2013. a crude assessment of the operating costs and the gross revenue of surveyed boat-owners in 2015 showed that on average monthly economic profit of 571±169 sd omr was received by individual boat-owner, which complements the positive trend in cumulative investment. these findings have important management and policy implications in relation to the effective management of harvesting capacity as well as attract investment in the fishery. finally, some limitations of the study are discussed along with the indication of potential future research. keywords: sultanate of oman, al-seeb, capital stock, investment, hedonic model, fishing fleet. املســتخلص:تم يف هــذه الدراســة فحــص ديناميــات مخــزون رأس املــال املادي وصايف االســتثامر يف املصايد الحرفية يف والية الســيب مبحافظة مســقط يف الفــرتة 2004-2013 وذلــك بإســتخدام بيانــات جمعــت مــن وزارة الزراعــة والــروة الســمكية وعــن طريق املســح امليداين، وقد أســتخدم منــوذج إنحدار املنفعــة لفحــص تأثــر خصائــص القــارب عىل أســعار اقتنائه ثم إلشــتقاق معدل منــو رصيد رأس املال املــادي. وقد وجد أن خصائص القــارب التي تتكون مــن العمــر والقــوة والطــول كانــت ذات داللــة إحصائية عند مســتوى 5٪ وتحمل عالمــة تتوافق مع النظريــة االقتصادية لإلهالك والتكلفــة عىل التوايل، وبينــام وجــد تذبــذب ســنوي يف صــايف االســتثامر لوحــظ وجــود اتجــاه إيجــايب يف االســتثامر الرتاكمــي مبتوســط معــدل منــو 7.63٪ يف مصايــد األســامك خــالل الفــرتة 2004-2013، وقــد أظهــر تقييــم تكاليــف التشــغيل واإليــرادات اإلجامليــة ملالــي القــوارب الذيــن شــملهم االســتطالع يف عــام 2015 أن مالــك القــارب الفــردي حصــل يف املتوســط عــىل أربــاح اقتصاديــة شــهرية تبلــغ 571 ± 169 ريــال ُعــامين، وهــو مــا يؤكــد االتجــاه اإليجايب يف االســتثامر الرتاكمــي، ولهــذه النتائــج تداعيــات إداريــة وسياســية مهمة فيام يتعلــق باإلدارة الفعالة لقــدرة الحصاد وجذب االســتثامر يف املصايــد، ويف نهاية الورقة متت مناقشــة بعض قيود الدراســة مع اإلشــارة إىل البحوث املستقبلية املحتملة. الكلامت املفتاحية: سلطنة عامن، السيب، رصيد رأس املال، اإلستثامر، منوذج املنفعة، أسطول الصيد 47research paper bose, al-masroori, al-hasani process of economic growth. in economics, the description of the term capital has been conceived as deferred consumption, as a stock of durable goods, or as a flow of factor services (hulten, 1991). in case of fisheries as argued by squires (1988) that the quantity of capital measured as the flow of services from the number of boats (i.e. physical capital stock) operating in a fishery. the economic theory of capital in fisheries, differentiates three types of capital namely physical (e.g. boat, equipment), natural (fish stock), and human (crews, skills and expertise). the interdependencies of natural and physical capital (boyce, 1995; burt and cummings, 1970) under various conditions such as functional form of investment costs (boyce, 1995) and degree of malleability (clark et al., 1979) were studied in fisheries. it was argued that favorable condition of growth in natural capital and other form of economic incentives (e.g. subsidy) leads to investment decisions by fishers and entry and exit behavior of fishers, other things being equal (le floc’h et al., 2011). however, it is important to note that exit from fisheries may be difficult due to lack of alternative employment opportunities (bose et al., 2013; ikiara and odink, 1999). eisenack et al. (2006) argued that for a developing fishery, a time gap existed between the growth of physical and natural capital, and due to partial substitutability between these two forms of capital the growth in physical capital continues even after decline of the natural capital. in general, while the conservation and management of natural capital are the primary objectives of management authorities, the regulatory environment is likely to exert influence on fishers’ investment decisions relating to physical capital (nøstbakken et al., 2011). the capital market imperfections in relation to the borrowing and lending constraint which has particular relevance to small-scale fisheries in oman where collateral is needed by the financial institutions (diffey et al., 2009). other factors affecting investment decision include boat age and size, future revenues, operating costs (e.g. fuel, and labour), stock status of the main target species, and the impact of management measures (e.g. mesh size restrictions) and fleet size (tidd et al., 2011). the main objective of this case study were three-fold considering the above-mentioned strategic importance of small-scale fisheries sector in oman. first, the extent of influence of basic boat characteristics on the acquisition price of boat. second, an empirical assessment of the dynamics of physical capital stock and net investment in artisanal fisheries during 2004-2013. third, ascribing importance to the view of ‘fishing costs’ as a key driver of fishers’ investment decisions, among others, and the scarcity of such cost information (lam et al., table 1. descriptive statistics of sample used for hedonic regression year boat boat length (ft) boat price (omr) engine (hp) engine price (omr) no. mean sd cv (%) mean sd cv (%) mean sd cv (%) mean sd cv (%) 2004 9 22.89 5.49 23.98 1614.53 971.31 60.16 102.78 92.4 89.90 1938.98 1383.32 71.34 2005 8 23.37 5.66 24.22 1537.87 839.75 54.60 109.37 96.49 88.22 2058.91 1382.51 67.15 2006 8 21.62 4.24 19.61 1361.36 704.28 51.73 88.12 86.89 98.60 2164.27 1842.41 85.13 2007 8 21.62 4.24 19.61 1474.83 803.87 54.51 88.12 86.89 98.60 1697.81 1056.14 62.21 2008 6 21.17 4.21 19.89 1429.34 772.88 54.07 70.83 76.77 108.39 1517.64 1101.61 72.59 2009 6 21.17 4.21 19.89 1676.81 784.26 46.77 70.83 76.77 108.39 1506.67 934.74 62.04 2010 4 22.75 4.57 20.09 1825.53 517.31 28.34 93.75 90.12 96.13 2194.17 1308.22 59.62 2011 4 24.50 4.51 18.41 2142.88 954.55 44.55 143.75 98.1 68.24 2882.25 1189.67 41.28 2012 2 27.00 2.83 10.48 na na na 140 84.85 60.61 4053.75 1773.07 43.74 figure 1. map of oman and study location 48 squ journal of agricultural and marine sciences, 2020, volume 25, issue 2 dynamics of physical capital in artisanal fisheries and policy implications and the harvesting function is well established in fisheries literature, and the dynamic behaviour of physical capital stock is used for explaining the rate of investment associated with fisheries resource use. therefore, research on capital-stuffing and investment behavior of fishers is valuable as it may provide necessary signal for investment incentives (or dis-incentives) to the private sector which is one of strategic objectives of the sector. the existence of capital market imperfections in relation to the borrowing and lending constraints (diffey et al., 2009) further rationalizes the importance of the present research to identify market constraints and thereby, enhance the knowledge of the relevant actors to formulate appropriate marketing strategies to accommodate the market dynamics of foreign origin. case study profile fisheries are an integral part of oman’s economy and have occupied an important place in the national policy agenda as the ‘oman vision 2020’ a long-term development plan, reflects the country’s desire to achieve food security, enhance fishers’ income, and maximize socio-economic benefits from the sector (bose et al., 2010; mne, 2007). the superior economic performance of the sector is a prerequisite for the achievement of these strategic objectives. small-scale artisanal fisheries in oman have been the dominant both in terms of landings and value. during the past decade or so, the sector’s contribution to gross domestic product (gdp) has remained stable around 0.6% (at 2000 constant prices) (bose et al., 2010; al-subhi et al., 2013). with the advent of economic diversification policy guided by ‘the vision for oman’s economy-2020’ the fisheries sector has attracted renewed 2011). this study aimed to provide a crude estimate of monthly average operating costs and revenue per boat experienced in 2015. due to time and resource limitations, the cost estimate was produced using the logbook information obtained from ten owner-operators participated in the study. from an academic perspective, this study can provide a wider relevance to artisanal fisheries sector in developing countries as this type of quantitative assessment is relatively limited in fisheries literature. in addition, the authors are unaware of any empirical work available or devoted explicitly to address the matter at hand in oman. more importantly, the lack of knowledge about the existing fleet capacity and the extent of their utilization has been highlighted as major issues, among others, confronting the management of fisheries sector in oman (setlur and arbuckle, 2015; al-siyabi and bose, 2018). in the absence of such information fisheries managers may have the tendency to use the number of operating boats as a measure of capital stock and investment in the traditional fisheries sector. however, such measure would not be adequate as it ignores changes in the quality of such capital over time (kirkley and squires, 1998; kendrick, 1961). so far, there is negligible attempt to collect and compile statistics on either the capital stock or the level of investment in the sector. this study also contributes to the practical realm, as it provides policy makers and investors with knowledge that has the potential to assist in designing effective strategic actions with regard to investment in fisheries. therefore, this case study not only fills the existing knowledge gap but also complements the existing global literature by adding country-specific information. the link between aggregate physical capital stock 0 20000 40000 60000 80000 100000 120000 140000 160000 180000 0 50000 100000 150000 200000 250000 300000 v al ue (t ho us an d o m r ) l an di ng s (m t) year landings (mt) value (omr 1000) figure 2. landings and value of artisanal fisheries, oman 49research paper bose, al-masroori, al-hasani interest and accordingly the authority has been promoting public-private partnerships to attract private investment in the sector. recently, efforts have been directed to, amongst others, (i) modernize fishing operations and improve fleet performance, (ii) initiate effective fisheries governance mechanisms; (iii) ensure sustainable use of fisheries resources; and (iv) optimize socio-economic benefits from the sector. the present study conducted in al-seeb area which is a coastal fishing town located in the northwest part of the muscat governorate. the selection of the study site is influenced by several factors, such as, time and costs, information availability and geographical proximity. it is envisaged that the replication of this study would be useful for generating insights into the pattern of fishery investment and subsequently the design of effective management policies in relation to the future investment in the fishery. muscat governorate is one of the seven coastal governorates of oman (see figure 1). muscat governorate has six wilayah (province) namely muscat (capital city), qurayyat and al-seeb, bawshar, al-amrat and mutrah. figures 2, 3, and 4 exhibit the performance of total fish landings and gross value at the national (oman), governorate (muscat) and wilayah (al-seeb) level respectively covering the period 2004-2015. from these figures, it can be noted that at the national level showed a distinct positive trend during the study period, while the same pattern was not evident at the governorate and wilayah level. however, a resemblance was observed in the behavioral pattern of landings and gross value at the governorate and wilayah level. further comparative analysis comprising landings, gross value, fishing boats, and number of fishers are provided in the results section. methodology data ideally, the economic value of capital services should be reflected in rental price. in the absence of such rental market the imputed price of capital services consists of two cost elements, namely the opportunity cost and the depreciation cost associated with the investment and the capital equipment respectively (jorgenson, 1974; cited by squires, 1988). there is negligible published database on actual transaction prices of new boats and, therefore, the factory quotation prices for new boats available for the period 2004-2013 were used in this analysis. in the absence of price information for other capital items, such as fishing gears, electrical equipment, and consistent price index series for heavy machinery, the nominal prices of tangible assets such as boats and engine along with the corresponding quality attributes age, boat length, and engine horsepower are considered in this study. data were collected from two sources. first, the price quoted by omani companies submitted to the ministry of agriculture and fisheries during 2004-2013 for 53 boats of various sizes (ranging from 16ft to 33ft) and engine types were collected. the acquisition prices were not available. second, data on registered fishing boats operating in al-seeb coastal water along with their characteristics, such as size, engine power, and boat age were collected from the local ministry office. it was noted that the quoted prices for the same boat size and engine power from different companies differ in a given period due to different technical specification of boats and add-ons (such as warranty condition, and insurance period) coming with the deals. the average value was used to represent such cases. as mentioned earlier, a 0 5000 10000 15000 20000 25000 30000 0 5000 10000 15000 20000 25000 30000 35000 v al ue (t ho us an d o m r ) l an di ng s (m t) year landings (mt) value (omr 1000) figure 3. landings and value of artisanal fisheries, muscat governorate 50 squ journal of agricultural and marine sciences, 2020, volume 25, issue 2 dynamics of physical capital in artisanal fisheries and policy implications simple logbook was prepared (in arabic) to collect information on basic operation costs. ten owner-operators nominated by the local office of the ministry were engaged during february-april 2015 to record costs per trip incurred by individual fisher for two weeks (14 trips per fisher). in fisheries, boats are treated as a durable but depreciable asset. in estimating physical capital stock and net investment in the new england commercial fisheries (kirkley and squires, 1988) followed hedonic regression method and used data on boat characteristics, such as gross registered tonnage (grt), length, and engine power. the basic idea behind the hedonic approach is to consider a fishing boat as a bundle of characteristics, such as length, age, engine horsepower (hp) and to generate estimate of the missing prices when quality changes. empirical model the basic model adopted in this study is mainly drawn from the study by kirkley and squires (1988). it involves two steps. first, a hedonic model was estimated, and second step growth rate of capital stock was derived by making use of the estimates of implicit price from the first step. broadly speaking, the hedonic approach hypothesizes that the price of a commodity is influenced by its characteristics (rosen, 1974). kirkley and squires (1988) have argued that the hedonic approach offers an attractive characteristic for estimating capital stock in fishing industries such that it incorporate changes in the quality of capital over time which should be reflected in boat acquisition prices. to represent this, the following cobb-douglas functional form was employed. c=constant.(age)α.(vl)β.(hp)γ.(exp)u eq.(1) where, c is the list price or acquisition price of boat, age is age of the boat, vl is boat length, hp is engine horsepower, and u is white noise error term. from a theoretical standpoint, the relationship expected between the price and the characteristics are as follows: α<0,β>0,and γ>0. the hedonic approach is adopted because there is no market information available for used or rented boats. the application of hedonic regression on the available data provides implicit prices of the chosen quality dimensions which would also provide signal to the cost of fishing effort. the age of a boat, was counted from the year the boat was first registered in the boat registry of the ministry. size (measured as boat length) and capacity (measured as horsepower) are two important characteristics of fishing boats as they are routinely used for fishing effort measures. the stability of the estimated coefficients obtained from the hedonic regression model would not be tested due to lack of enough observation for each expected period. in empirical analysis, a linear, semi-logarithmic, and log linear form of the model is frequently used. as there is no a priori reason to assume that price and quality behave in a particular fashion, a box-cox transformation was applied to decide whether linear or log-linear functional form of the model fit the data best as follows: eq.(2) parameter ‘λ’ which was determined by the data defines the functional form as: if λ=1, it represents linear speci 0 1000 2000 3000 4000 5000 6000 7000 0 2000 4000 6000 8000 10000 12000 v al ue (t ho us an d o m r ) l an di ng s (m t) year landings (mt) value (omr 1000) figure 4. landings and value of artisanal fisheries, al-seeb 51research paper bose, al-masroori, al-hasani fication, and if λ=0, it reduces to log-linear specification. each observation of the dependent variable (i.e. boat price) was first divided by the geometric mean (gm = 3118.32) of the dependent variable and two versions (with and without taking log of the dependent variable) of the regression model (equation 1) was run. the values of residual sum squares (rss) were used to conduct a chi-square test to decide between the linear and log-linear functional forms. the test result (see the result section) supported a log-linear version of the model. as the model is in log-linear form, the resulting regression coefficients can be interpreted as partial price elasticity with respect to the variable concerned, other things being equal. following grillches (1961), a semi-logarithmic form of the model (equation 1) with respect to the age variable was also experimented to accommodate the possibility of geometric patterns of depreciation of boat value with age. the first data set was used to estimate the parameters from the two versions of equation 1. at the second-stage, the parameter estimates from equation 1 were used to generate estimate of capital stock per boat per year based on the second data set that include physical characteristics of the registered boats that have been operating in the al-seeb fisheries. the estimated capital stock per boat was then summed for all boats in a year to obtain the estimate of total capital stock. it was assumed that the value of all capital services was the sum of the values of individual capital services (squires, 1988). net investment was then calculated as the change in total capital stock per unit of time (i.e. year). results some relevant comparative statistics are also calculated from the data presented in the figures 1-3. during 20042015, the average growth rate of total landings in oman was about 5.65% per annum whereas muscat governorate and al-seeb were witnessed negative growth rate of -4.08% and -0.09% respectively. however, during the same period, the positive trends in total value were observed for oman, muscat governorate and al-seeb, was observed the average growth rate of 9.71%, 4.90% and 7.31%, respectively. furthermore, for muscat and alseeb, a downward trend was observed for total landings around mid 2000-2012 and then a positive trend after 2012. the sharpest decline in landings appeared to take place in 2008. with reference to number of fishers and boats positive trends were observed for oman, muscat and al-seeb but differed in extent, with the average growth rates of 3.40%, 1.60% and 2.41% for number of fishers and 2.03%, 1.61%, and 2.11%, respectively. the variation in total landings as measured by the coefficient of variation (cv) for al-seeb was the highest (45.47%) followed by muscat governorate (32.94%) and oman (24.92%). on the other hand, the variation observed in total value was the highest for oman (37.18%) followed by al-seeb (33.49%) and the governorate (22.91%). the descriptive statistics of the sample used for hedonic regression model are presented in table 1. it was mentioned earlier that a box-cox transformation was followed to decide between the two conventional versions namely the linear and the log-linear models. the estimated χ2 test value (38.25, 8 df ) supported the log-linear specification of the model. table 2 provides the empirical results of the hedonic regression mod -60000 -40000 -20000 0 20000 40000 60000 n et in ve st m en t ( o m r) year figure 5. net investment in the fishery during 2004-2013 52 squ journal of agricultural and marine sciences, 2020, volume 25, issue 2 dynamics of physical capital in artisanal fisheries and policy implications el specified in equation 1 in two forms (log linear and semi-log with respect to age) along with the summary statistics and diagnostics. the potential ‘non-linearity’ in variable was also experimented by including square root term for each variable in to the model but failed to generate any theoretically convincing results. some important results can be noted from table 1. the average boat length was more or less similar across the years, which indicated the degree of homogeneity in small-scale fisheries with respect to boat size. however, the results of boat power exhibited relatively greater degree of heterogeneity in the sample as reflected in the coefficient of variation (cv) estimate. this was because of the fact that some boats were using twin-engine. this was also reflected by the fact that the average price of engine is higher than that of boat except for 2009. furthermore, the variability (as indicated by cv estimates) of average boat price was lower than engine power and engine price which to some extent consistent with the homogeneity in boat size as mentioned earlier. apart from higher capital cost (i.e. fixed cost), the use of twin-engine also exerted influence on variable costs due to recent rise in fuel price. it is noted that a limited number of quality dimensions explain a very large fraction of the total variability of the list price as measured by r2 value. the coefficient of the variable ‘age’ carries an expected sign as expected from the economic theory of depreciation and the associated t-value suggests that the variable is statistically significant at the 5% level. the coefficient of age in model 1 is the elasticity, which is the predicted average proportionate change in boat list price due to proportionate change in boat age, holding other qualities constant. on the other hand, semi-log form the coefficient of age can be interpreted as the percentage change in the boat list price due to a unit change in age, other things being equal. the variables ‘horsepower (hp)’and ‘length (vl)’ are statistically significant at the 5% level with expected sign that is consistent with the theory of cost which predicted that the boat cost should increase with the increase in the characteristics of power and size. these results are in line with kirkley and squires (1998). furthermore, it is important to note that boats engine power and length have the highest influence on the acquisition price of boats, which is consistent with the descriptive statistics presented in table 1. to demonstrate the empirical validity of the model a series of diagnostics has been applied and the results are presented in table 2. it can be seen that in all cases, the results from the econometric diagnostics do not exhibit any deviations from the classical linear regression properties. the j-b lm test was used to examine the normality of the residuals at the 5% level (jarque and bera, 1980). the test statistic follows a χ2 (with 2 df ) distribution and the value of the test statistic indicates that the null hypothesis of normality cannot be rejected. the b-p-g test was used to test the null hypothesis of homoscedasticity of the residuals at the 5% level (breusch and pagan, 1979; godfrey, 1978). the test statistic follows a χ2 (with 2 df ) distribution and the test value was insignificant at the 5% level thereby the null hypothesis of homoscedastic error variances cannot be rejected. the lagrange multiplier (lm) test statistic with two lags was used to test the null hypothesis of no autocorrelation at the 5% level. the test result supported the null hypothesis of no autocorrelation. comparing the output of summary statistics, forecast performance, and model selection criteria, it can be 0 200 400 600 800 1000 1200 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 cu m ul at iv e in ve st m en t ( 10 00 o m r) year figure 6. cumulative investment in the fishery: 2004-2013 53research paper bose, al-masroori, al-hasani seen that model 1 performs only marginally better than model 2. therefore, it was decided to use the parameter estimates of model 1 in the second stage. at the second-stage the parameter estimates from equation 1 were used to generate estimate of capital stock per boat per year based on the second data set that include physical characteristics of the registered boats that have been operating in al-seeb water. the net investment was calculated as the change in total capital stock per unit of time (i.e. year) for the period 20042013 and it is presented in figure 5, which exhibits inter-annual fluctuation in net investment in the fishery. despite this year-to-year fluctuation, the cumulative of net investment in the fishery experienced a positive trend during 2004-2013 as depicted in figure 6. table 3 presents the descriptive statistics of boat characteristics, engine and gear price, maintenance costs, and operating costs per trip per boat gathered from the logbook survey data. it is noted that the boats involved in cost analysis ranging in length from 22 feet to 25 feet with an average horsepower of about 104 hp. these figures are within the range presented in table 1. furthermore, the largest variability with regard to engine price is consistent with the result presented in table 1. on average, the fishing trip lasted for about 8 hours. the operating costs include fuel, oil, food bait and ice, and the average cost per trip for individual fisher was estimated to be about 15 omr. on average, fuel cost has the highest share (about 53%) followed by the bait cost (28%) in the total trip cost. this information is of important use for future research in this area. the highest share of fuel cost has important cost implication for boats that are using twine-engine as stated earlier. to get an idea about the extent of economic benefits generated from fishing activities, crude estimates of the average monthly net value earned per boat are presented in table 4 based on the survey data and the data from the statistical yearbook. the gross value is evaluated at farm gate prices of fish species. in the calculation of monthly operational costs per boat, it was assumed that individual boat makes 20 trips per month. therefore, the estimate was conservative in nature. fishers’ physical access to market can improve their table 2. empirical results of the hedonic regression model model 1 (log-log) model 2 (semi-log w.r.t. age) variable coefficient t-value variable coefficient t-value ln(age) -0.23 -4.61 age -0.03 -4.50 ln(hp) 0.49 9.97 ln(hp) 0.49 9.85 ln(l) 0.47 2.26 ln(l) 0.49 2.37 constant 4.98 10.49 constant 4.71 10.12 summary statistics: r2 0.95 0.94 residual sum square (rss) 0.78 0.81 log likelihood 37.20 36.82 f statistics (joint test) 287.50 283.16 (p = 0.00) (p = 0.00) regression diagnostics: normality: lm test(χ22 df ) 2.23 (p = 0.33) 2.27 (p = 0.32) serial correlation: durbin watson (d-w) lm test (χ22 df ) 2.06 2.05 1.52 (p = 0.47) 0.98 (p = 0.38) heteroscedasticity: b-p-g test (χ23 df ) 0.10 (p = 0.96) 0.11(p = 0.95) forecast performance: rmse 0.121 0.122 mae 0.102 0.103 mape 1.274 1.288 model selection criteria aic -1.23 -1.22 sc -1.08 -1.07 h-q -1.17 -1.16 table 3. descriptive statistics of boat operation costs, al-seeb item min max mean sd boat size (feet) 22 25 23.9 1.2 engine power (hp) 60 200 103.5 43.5 engine price (omr) 1500 5000 2604.1 1240.6 fishing gear (units) 10 83 38.7 25.4 fishing gear price (omr) 525 5350 2215.9 1471.7 maintenance cost (omr) 150 1250 517.8 332.6 fishing trip (hours) 2 19 8.1 3.8 cost/trip/boat (omr) fuel 1 67 8.1 9.6 oil 0.7 23.5 2.4 2.5 food 0.2 33.5 2.7 3.4 bait 0.5 15 4.3 3.2 ice 0.5 8 1.5 1.1 total 4 75.9 15.4 14.3 source: field survey 54 squ journal of agricultural and marine sciences, 2020, volume 25, issue 2 dynamics of physical capital in artisanal fisheries and policy implications profitability, as the prevailing market price was higher than that of farm gate. one of the reasons for the establishment of the central wholesale market in oman in april 2014 was to give fishers access to market and address pricing inefficiency (al-busaidi et al., 2016; al-jabri et al., 2015). furthermore, the extent of profitability was also influenced by the economic value of species caught, which differed from species to species. the monthly net revenue figures ranged from 297 in july (summer month) to 842 in february (winter month). on average, the monthly net revenue per boat was about 571 ± 169 omr. the findings indicates the fact that fishing has been a profitable profession and this is reflected in the estimates of cumulative net investment. personal discussion with fishers also revealed the same. however, upto-date, comprehensive, and quality economic data are required to convey precise assessment of the economic situation of the sector. expenditure figures presented in table 4 are only a part of the costs involved in fishing operations. the cost of the boat in the form of depreciation allowance needs to be accounted. in addition, the opportunity costs of capital and the owner’s labor and management have to be accounted for in order to arrive at the results of this economic activity. discussion the degree of homogeneity in relation to boat length and the degree of heterogeneity to engine power are consistent with the findings by al-siyabi and bose (2018). at least two important implications of these findings are as follows: (i) the homogeneity aspect may help reduce the conflicts, which arise from unequal catch share between large and small boats, and (ii)) the apparent heterogeneity to engine power along with the highest share of fuel cost (on average 53%) has important economic implications as the use of twin-engine exerts influence on operating costs. in addition, the recent rise in fuel price as noted by al-siyabi and bose (2018) exerted upward pressure on the operation costs. higher fuel costs may discourage fishers’ future investment decisions in the sector as it could reduce net gain unless it is compensated by the revenue earned through either increase in fish price or increase in total landings, or a combination of both (tidd et al., 2011). tidd et al. (2011) found a statistically significant influence of fuel prices on vessel entry and suggested that the vessels would enter at lower costs of subsidized fuel. the highest degree of variation in total landings measured by the coefficient of variation (cv) and its sharpest decline experienced in 2008 for the study area signal the level of uncertainty in generating revenue from fishing. this is reflected by the variability in fishers’ income as shown in table 3. the authority may promote diversification rather than specialization of fishing portfolio through fishers’ participation in additional or more diverse fisheries to mitigate seasonal variation in their income. this approach is common in fisheries. anderson et al. (2017) proposed such strategy to buffer against income variability due to seasonality in fisheries. in a local context, alternative strategic initiatives such as aquaculture development (al-siyabi and bose, 2018) and fishing tourism (al-busaidi et al., 2016) are also suggested to enable fishers to choose related but alternative profession. this type of approach would also help reducing fishing pressure and if economically viable would encourage relatively inefficient fishers to exit from harvesting operations. the results of the hedonic model in relation to boat age, length and horsepower are consistent with the theoretical predictions and have important management implications. the statistical significance of the variable boat ‘age’ can be related to operational efficiency of the fleet as older vessels are expected to be less efficient than the newer one. tidd et al. (2011) argued that older vessels are more likely to exit the fishery. the statistical significance of the variables ‘horsepower (hp)’ and ‘length (vl)’ predicted that the boat cost would increase with the increase in the characteristics of power and size. the results are also consistent with other empirical studies (tidd et al., 2011). the implication of these results is that boat size and horsepower together with the high table 4. crude estimates of the average monthly net value earned per boat in al-seeb number of boats 521 number of fishers 1201 cost (omr)/trip/boat 15.366 cost (omr)/boat/month * 307.320 month value (omr) value (omr)/boat income (omr)/boat january 593000 1138.2 830.9 february 599000 1149.7 842.4 march 448000 859.9 552.6 april 321000 616.1 308.8 may 447000 858.0 550.6 june 370000 710.2 402.9 july 315000 604.6 297.3 august 439000 842.6 535.3 september 467000 896.4 589.0 october 535000 1026.9 719.6 november 500000 959.7 652.4 december 457000 877.2 569.8 total 5491000 10539.3 6851.5 * assuming that a boat will make 1 trip per day and work for 20 working days a month. source: field survey and maf data. 55research paper bose, al-masroori, al-hasani fuel costs may affect stock status and the economic viability of fishers, which in turn discourage future investment in fisheries. with regard to the parameter estimates of the model, one may argue that the use of list prices of boats and engines introduces bias in estimates depending on the extent to which they deviate from the actual acquisition price. furthermore, prices of used boats or rental market were not available. due to a lack of sales data (new or used), validity of parameter estimates with specific reference to boat age could not be checked. it should also be noted that the boat acquisition price series were not inflation adjusted due to a lack of suitable (e.g., price index for equipment) and consistent price index for the study period. however, this may not undermine the results. it is argued that available machinery and durable equipment price index failed to incorporate quality changes adequately (griliches, 1961), and therefore the process of deflation can introduce errors in measurement of price variable (hulten, 1991). usher (1980) mentioned the choice of price index reflects the equivalent performance of the old and new capital goods which is contrary to the real situation. the estimated parameters may be upward bias due to the use of quoted price rather than the acquisition price. however, this upward bias may be partly compensated as other components of capital costs, which are not included in the present analysis. while inter-annual fluctuation in net investment in the fishery is observed, the cumulative investment trend was positive. the negative net investment could be influenced by various factors. for example, disinvestment in 2011 may be due to negative growth in landings as depicted in figure 4 and social upheaval experienced in the country (valeri, 2015). on the other hand, the positive net investment was influenced by the influx of new entrant. for instance, 25 new boats added to the registry in 2005. the positive trend in cumulative net investment for the period 2004-2013 reflects the overall dynamics of physical capital. therefore, a convincing case can be made to support government investments and develop infrastructure. the positive trends in relation to number of fishers and boats were observed for oman, muscat and al-seeb signal economic potential of fisheries. in a recent case study, al-siyabi and bose (2018) noted the existence of under-utilized fishing capacity and the presence of technical inefficiency in the utilization variable inputs (i.e. crews and fishing time) in small-scale fisheries. based on these findings, al-siyabi and bose (2018) argued that there was potential for improving production without having to incur any additional physical capital costs. therefore, this signal of economic potential can be used as a tool to attract private investment in the sector, which is one of the strategic goals of the sector as mentioned earlier. however, a precautionary approach needs to be adopted and any effort to increase investment must strike a balance with the stock status. otherwise, the call for public-private partnership can inevitably be limited. while the findings in this study have important strategic implications with regard to future course of actions in the context of investment in small-scale fisheries, there are a number of limitations of this paper that need to be mentioned. first, a variety of potential variables such as fishing gear and equipment, and shore-based tangible assets like cars and buildings, are not considered as the data for such variable are not readily available. second, the estimate of capital stock is based on the registered fishing boats in the local office, which is different from the number of boats as published in the yearbook. this discrepancy is due to the time lag in license renewal requirements. third, estimates generated in this study used registered boats of al-seeb fisheries only, therefore, it should not be treated as an indication of net investment in the overall fisheries sector of oman. conclusion this case study uses a hedonic approach for examining the dynamics of physical capital stock and net investment in al-seeb artisanal fisheries. in spite of the above-mentioned limitations, the study has identified important information gaps in this area of research, set the groundwork for a more complete research study in the future, and form the basis for generating insights into the pattern of fishery investment and subsequently the design of effective management policies in relation to the future investment in the fishery. while the present case study has provided useful information, the robustness of empirical data and conclusions needs to be verified with further studies to a point where generalization of results can be accomplished. there is a great deal of room for further research particularly in the area of inclusion of physical assets other than boat and engine, inclusion of add-on characteristics in the quoted price, larger samples covering the whole sector, and improved method of inferring depreciation rates of boats. they could provide the authority with essential indicators/estimates which could be used in promoting and making investment decisions. furthermore, it could motivate the data collection agencies to create a database and provide a better basis for making informed decisions. references ahmed m, salayo nd, viswanathan kk, garces lr, pido md. 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(2015). sustainable management of the fisheries sector in oman : a vision for shared prosperity. the world bank report no.: 110678. 44 pp. squires d. (1988). index numbers and productivity measurement in multispecies fisheries: an application to the pacific coast trawl fleet. noaa technical report nmfs 67, noaa/national marine fisheries service, usa. tidd an, hutton t, kell lt, padda g. (2011). exit and entry of fishing vessels: an evaluation of factors affecting investment decisions in the north sea english beam trawl fleet. ices journal of marine science 68(5): 961–971. usher d. (1980). introduction to “the measurement of capital.” in: the measurement of capital. national bureau of economic research. nber book series studies in income and wealth. p. 1–22. valeri m. (2015). simmering unrest and succession challenges in oman. carnegie endowment for international peace, washington dc, usa. zhang d, sikveland m, hermansen ø. (2018). fishing fleet capacity and profitability. marine policy 88: 116–121. img032 img033 img034 img035 img036 img037 img337 img338 img339 img340 img341 img361 img362 img363 img364 img348 img349 img350 img351 img352 img353 research paper journal of agricultural and marine sciences vol. 24 : 2– 18 doi: 10.24200/jams.vol24iss1pp2-18 reveived 5 may 2019 accepted 18 august 2019 co-management feasible in achieving fisheries sustainability? a case of oman’s lobster fishery shekar bose*1, abdullah hilal al balushi 2, ahmed al-haddabi3, ruqaiya al-bulushi4 dr. shekar bose*1 ( ) associate professor, department of natural resource economics, college of agricultural and marine sciences, sultan qaboos university, p.o box 34, al-khod 123, sultanate of oman email: sbose@squ.edu.om. 2oman animal and plant genetic resource center, box 515, pc123, muscat oman. 3director of fisherie development, ministry of agriculture and fisheries. muscat, oman. 4fisheries management division, ministry of agriculture and fisheries, muscat, oman. introduction the 2018 food and agriculture organization of the united nations (fao) report on the state of world fisheries and aquaculture highlighted the critical importance of fisheries and aquaculture sector to the global economy and well-being of coastal communities through providing employment, food and nutritional security, and income and livelihoods (fao, 2018). it is also well-recognized that small-scale fisheries (ssf) that predominate in developing countries constitute a significant part of the global fisheries sector and are critical for socio-economic well-being and food security of the world’s most vulnerable communities (schuhbauer and sumaila, 2016; jentoft, 2014; teh et al. 2011). for instance, teh & sumaila (2013) estimated that ssf employ about 22 million fishers (i.e. about 44% of all fishers) engaged in harvesting sector. in a consultative meeting organized by fao in co-operation with the ministry of agriculture and fisheries (hereafter, maf) held in muscat, oman, march 26-28, 2012, attainment of sustainability in small-scale fisheries in the near east and north africa region was highlighted with the purpose of bringing together responsible fisheries and social develهل االدارة التشاركية جمدية لتحقيق استدامة املصايد: دراسة حالة ملصايد الشارخة يف سلطنة عمان شيكار بوز*1 وعبداهلل هالل البلوشي2 وامحد اهلدايب3 ورقية البلوشي4 abstract. this study assesses the feasibility of co-management arrangements in managing scalloped spiny lobster (panulirus homarus) fishery in the sultanate of oman. the appraisal is conducted using various indicators involving pre-implementation phase and institutional characteristics and substantiated by findings of the review of relevant local and global literature and the results of a structured questionnaire survey conducted during 9-28 june, 2013 with 536 randomly selected fishers from three governorates namely al-sharqiyah south, al-wusta, and dhofar. the former method helps identifying suitable assessment criteria and provides indication of readiness while the later method helps determining primary stakeholders’ perceived views on various aspects of regulatory measures and co-management arrangements. while findings related to fishers’ commitments, willingness to support government decisions, willingness to participate in co-operative research, and preference for co-operative decision-making are promising, institutional weaknesses identified under the category of ‘interactive organization’, ‘resource ownership and control’, ‘existence of planned process’, and ‘diversity’ should be of major concerns for policy-makers in moving towards co-management arrangements. based on the findings some policy implications are also discussed. keywords: co-management; fisheries sustainability; lobster fishery; oman. املستخلص: تقّيم هذه الدراسة جدوى اإلدارة التشاركية يف إدارة مصايد شارخة الصخور )panulirus homarus( يف سلطنة عمان. مت إجراء التقييــم باســتخدام العديــد مــن املؤشــرات مشلــت مرحلــة مــا قبــل التنفيــذ وخصائــص املؤسســة مًدعمــة مبخرجــات الدراســات املرجعيــة احملليــة والعامليــة ذات الصلــة ونتائــج اســتبيان أجــري خــالل الفــرة مــن 9 اىل 28 يونيــو 2013 مــع 536 صيــاداً مت اختيارهــم عشــوائياً مــن ثــالث حمافظــات هــي: جنــوب الشــرقية، والوســطى، وظفــار. ســاعدت املنهجيــة االوىل يف حتديــد معايــر التقييــم املناســبة كمــا وفــرت مؤشــرًا علــى مــدى االســتعداد، بينمــا ســاعدت املنهجيــة الالحقــة يف حتديــد وجهــات نظــر أصحــاب املصلحــة الرئيســيني حــول اجلوانــب املختلفــة للتدابــر التنظيميــة وترتيبــات اإلدارة التشــاركية. وعلــى الرغــم مــن أن النتائــج املتعلقــة بتًقيــد الصياديــن، والرغبــة يف دعــم القــرارات احلكوميــة، والرغبــة يف املشــاركة يف البحــوث التعاونيــة، وتفضيــل اختــاذ القــرارات بصــورة تعاونيــة هــي قضايــا واعــدة، اال ان الضعــف املؤسســي احملــدد حتــت فئــة »املؤسســة املتفاعلــة«، و »ملكيــة املــوارد والتحكــم هبــا »، و »وجــود خطــة للعمليــات« و »التنــوع« جيــب ان تكــون أكــر اهتمامــات صانعــي السياســات يف االجتــاه حنــو ترتيبــات اإلدارة التشــاركية. يف ضــوء املخرجــات مت ايضــاً مناقشــة بعــض اآلثــار املرتبــة علــى السياســات. الكلمات املفتاحية: اإلدارة التشاركية، استدامة املصايد، مصايد الشارخة، عمان 3research article bose, al-balushi, al-haddabi, al-bulushi opment (fao, 2012). however, ssf in developing countries including the sultanate of oman (hereafter, oman) are usually characterized by the problems of overfishing, overcapacity, non-compliance, weak enforcement, economic inefficiency (al siyabi & bose 2018; fao 2017; pomeroy, 2012; salas et al. 2007). in oman, the socio-economic significance of the fisheries sector in the country’s economic diversification policies and sustainable development drive is well-echoed in the national policy agenda (mne, 2007a; mne, 2007b; bose et al. 2010). for instance, to enhance achievement of economic diversification policy objectives. the fisheries sector has been identified as one of the five promising sectors in the 9th five-year plan (2016-2020) and the sector is expected to achieve an average growth rate of 6.5% (in constant prices) and the share in gdp is expected to rise from 0.5% to 0.6% (scp, 2016). accordingly, considerable efforts have been directed by government agencies in oman to ensure sustainable utilization of fisheries resources and to maximize socio-economic benefits from the sector (mne, 2007b). despite such efforts, some challenges such as overfishing of high value commercial species such as kingfish (al-oufi et al. 2004; al-balushi et al. 2016) and lobster (al-haddabi, 2010), inefficiency in fishing operations (al-siyabi and bose, 2018), weak enforcement and the presence of non-compliance (al-subhi et al., 2013; bose et al., 2017) etc. are still confronting the sector and adversely impacting on the progress towards sustainability in fisheries. to address these challenges the implementation of co-management approach to effectively manage ssf has been advocated since the late 1980s by the scholars in the field (jentoft, 1989; pomeroy, 1995; sen and nielsen, 1996; mccay & jentoft, 1996; pomeroy & berkes, 1997; jentoft, et al. 1998; jentoft, 2004; al-habsi, 2012; kalikoski & franz, 2014; to name a few). it is noted that routinely ascribed characteristics such as undemocratic, unfair, and ineffective to the top-down-management approach to fisheries management (i.e. command-and control approach) form the basis for joint action or co-management (fiorino, 1990; berkes, 2009). co-management has been touted in fisheries management with the expectation to: 1) encourage democratic participation of resource user-groups in regulatory decision-making that helps advancing equity, legitimacy and efficiency (nielsen et al. 2004; al-balushi et al., 2016), 2) improve rule compliance and hence regulatory effectiveness (pomeroy & berkes, 1997; al-subhi et al. 2013), 3) empower local community (nielsen et al. 2004) and boost fishers’ competence by upgrading their skills through training and through the formation of social capital (for example, fishers’ social networks) (rydin & pennington, 2000; schusler, et al. 2003; nenadovic & epstein, 2016), 4) foster mutual respect and hence cooperation (bose & cress-morris, 2009), 5) minimize transaction costs (abdullah et al. 1998), 6) provide basis for the integration of scientific knowledge with fishers’ knowledge and hence improved management (mackinson, 2001; bergmann et al. 2004; hartley & robertson, 2009), and 7) help broaden decision makers’ understanding of user-groups’ perceptions and attitudes that improves regulatory effectiveness and the successful implementation of policies (mackinson, 2001; jentoft & mccay 1995). recognizing these potentials, al-oufi (2002), al-habsi (2012), al-subhi et al. (2013), al-balushi et al. (2016) and bose et al. (2017) advocated the approach to local fisheries management. the encouragement and development of fisheries co-management approach in managing fisheries resources in oman is also echoed in the development of long-term strategic direction and policy recommendations for the sector by international experts (wb & maf, 2015). although, community-based management approach in the form of traditional committee (locally termed as ‘sunat al-bahar’ committee) has existed in oman, the functioning of such committee has diminished over time.(al-oufi et al. (2000); al-subhi et al.2013). the top-down management approach is more evident in oman and fishers’ participation in decision-making is not well-articulated. while, research on co-management in fisheries was conducted with geographical intent (al-oufi, 2002, al-habsi, 2012), the feasibility of such management approach has not received adequate attention. given this background and considering the strategic importance of the fisheries sector, the main objective of this case study was to assess the feasibility and desirability of co-management approach to the management of the scalloped spiny lobster (panulirus homarus) fishery in oman. the main reasons for considering lobster fishery are two-fold: first, the fishery has been experiencing a prolonged period of high fishing pressure (fig. 2). the decline in total landings has caused legitimate concern among policy makers, scientists, and fishers about its possible socio-economic consequences. second, lobster is one of the high-valued species in oman and the fishery provides significant employment and income opportunities to the traditional fishing communities. this research has significance in terms of academic, industry and policy perspectives. while various country-specific studies have been conducted on this approach, however, research on this topic in oman is scarce, and to this end, this paper not only fills the existing knowledge gap in local research but also complements the existing global literature by adding country-specific case study. the documentation and dissemination of country specific experience have been encouraged by nielsen et al. (2004) to guide others. furthermore, by presenting barriers and opportunities for moving towards partnership approach this study contributes to the practical realm as well, as it provides policy makers and fishery managers of local and global 4 squ journal of agricultural and marine sciences, 2019, volume 24, issue 1 is co-management feasible in achieving fisheries sustainability? a case of oman’s lobster fishery resources called ‘collective’ or ‘public good’ (ostrom, 1990). interested readers are referred to plummer & fitzgibbon (2004) for further details on a conceptual framework developed through blending theory and practice on co-management. despite these potential benefits, some limitations of co-management approach are also documented in the literature. it is argued that no self-interested individuals would join a collective effort when there are incentives generated by externally enforced rules (address free-rider problem) (ostorm, 2000). another is the dilemma for legitimacy when representatives have fixed mandates and a system based on personal representation that is, fishers’ cooperatives may represent only members’ interests (jentoft, 2000). next is the accountability and motivation, which are related to human dimension (grafton, 2007). it is worth mentioning that in reviewing fisheries governance mechanisms involving countries from south east asia and southern africa, nielsen et al. (2004) provided evidence of mixed results of co-management approach. similar view of mixed results is also recognized in cinner et al. (2012). case study background in oman, the lobster fishery is located in three governorates namely al-sharqiyah south, al-wusta, and dhofar (see figure 1). the governorate dhofar was dominant in terms of landings (67.8%) followed by al-wusta (25.8%) and al-sharqiyah south (6.4%) (maf, 2012). origins with knowledge that has the potential to assist in designing effective strategies. co-management: pros and cons co-management was initially considered as a power-sharing arrangement between the management authority and a community of resource users and the concept has been evolved over time with the experience from the field (sen & nielsen, 1996; pomeroy & berkes, 1997). for instance, berkes (2009) branded co-management as a process/mechanism of determining power sharing, building institutions, building trust and social capital, solving problems, and as people-centered governance approach. the emerging interest in the co-management of natural resources has a sound theoretical basis as it has deep roots in public-choice and social-choice theories (sen, 1995; ostrom, 1998; jentoft, et al. 1998). the contrast between these two theoretical postulates is that the former is based on individual rationality where as ‘homo economicus’—individual behaviour is based on self-interests, while the later promotes an integrated social preference from diverse individual preferences (sen, 1995). fisheries managers and policy makers are already aware of the problems caused by biological and economic overfishing, stock depletion, and user-group conflicts associated with open access fisheries (gordon, 1954; seabright, 1993). however, with regard to the effective management of common property resources like fisheries (gordon, 1954) a dichotomy of opinion prevails in the existing literature. one group advocated government ownership or privatization to sustain commons. for instance, to sustain commons hardin (1968) suggested for some sort of mutually agreed upon coercion involving the government to solve ‘the tragedy of commons’. linked to this proposition, economists argue that adoption of private property rights would results in conservation and economically efficient use of common property resources as the internal benefits and costs accrue to the owner (schlager & ostrom, 1992; ostorm, 2003). however, opponents (mostly anthropologists and social scientists) argued that this proposition is not cross-culturally valid and have promoted effective local institution by resource users as a way to avoid the ‘tragedy’ (acheson, 1989; ostrom, 1990; agarwal, 2001). by drawing a distinction between ‘common-property’ and ‘communally owned resources’ and citing a number of cases, acheson (1989) pointed out that communally owned property is not necessarily subject to overexploitation as property owned communally does have an owner after all. here lies the idea of collective action or co-management as local level management system can co-exist with the centralized institution involving government and avoid ‘tragedy’ of commons. it is argued that under some circumstances local-level communities can generate institutions and rules to manage their figure 1. map of the sultanate of oman with study sites 5research article bose, al-balushi, al-haddabi, al-bulushi the fishery is regulated under the marine fishing and living aquatic resources protection law and its executive regulations. besides other relevant articles, article 14 of the marine fishing and living aquatic resources protection law that is specific to the lobster fishery includes the following elements: 1) prohibition of lobster catching during the breeding and reproduction season, 2) harvesting lobster shall be by lobster traps with specifications determined by the competent authority, 3) prohibition of catching or handling egg bearing lobster, and lobster with carapace length less than 80 mm, 4) prohibition of processing or dealing in lobster during the breeding and reproductive seasons, and 5) amount of lobsters in possession must be registered at the end of each season with the competent authority. since 1986, a number of ministerial decisions were issued related to the fishing season in the lobster fishery (al-haddabi, 2010). non-compliance with the regulations includes penalties such as fine (fixed amount and doubled with recurrence of offense), imprisonment, confiscation of catch, gear, boat and license (for a period or permanently) based on court’s decisions (al-haddabi, 2010). artisanal fishers have been using lobster trap, gillnets and tangle nets to harvest lobster with nets being the dominant fishing gear. this suggests that the regula0 500 1000 1500 2000 1986 1989 1992 1995 1998 2001 2004 2007 2010 2013 2016 year la nd in gs (t on s) figure 2. total landings of lobster (mt) from 1988 to 2017. 0 1000 2000 1986 1989 1992 1995 1998 2001 2004 2007 2010 2013 2016 year va lu e (1 00 0 o m r ) figure 3. gross value (‘000 omr) of lobster landings during 1991-2017. 6 squ journal of agricultural and marine sciences, 2019, volume 24, issue 1 is co-management feasible in achieving fisheries sustainability? a case of oman’s lobster fishery tory measure involving fishing gears as stipulated in the marine fishing and living aquatic resources protection law as ‘harvesting lobster shall be by lobster traps with specifications determined by the competent authority’ has not been enforced. in addition, there is no special license requirement for harvesting lobster. the data from the present study suggests that a considerable number of part-time fishers are involved in the lobster fishery. according to data on landings collected by the maf, the lobster landings dropped from 1936 mt in 1988 to 339 mt in 2017, an average growth rate of -5.83% during the period of 1988-2017 (fig. 2) with most of the drop during in the first decade. the gross value of lobster catch has shown the similar pattern (but to a lesser extent), an average growth rate of -1.54% during 19912017 (fig. 3). however, it is interesting to note that the unit value of lobster has shown a positive growth (2.12%) during the 1991-2017 (see figure 4). this indicates an economic potential that can be achieved if the sustainable utilization of the resources was adhered to. as shown in figure 2, the fishery has experienced a considerable decline in total landings. during the period table 1. assessment criteria with explanatory note for co-management feasibility. criteria explanatory note pre-implementation phase initiator of the idea of co-management how and by whom the idea of co-management is conceived? conditions and driving force issues and conditions (i.e. drivers) in fisheries that led to the idea of co-management community willingness to support the idea extent of fishers willingness to support the idea of co-management communicative process comprising participation, preparation, reflection and adaptation existence of mechanisms for regular exchange of management information with fishers, fishers’ access and willingness to take part in management meetings, active participation of fishers in the preparation of co-management plan institutional characteristics interactive organization this promotes institutional flexibility not only in terms of space and time but also in terms of process/functions, and structure. it also embraces the presence of advisory organization that represents fishers’ interests. it also points out institutional fitness to accommodate effectively geographically oriented fishing communities. resource ownership and control this includes access and withdrawal rights, collective choice rights (management rights, exclusion rights, enforcement rights, and transfer rights). existence of planned process existence of the process of preparing co-management plans with clear objectives, and functions and responsibilities of each institutional actor. diversity comprises equity (i.e. fairness in the representation of the range of interests, and participatory democracy), fisheries contribution to economic development, and fisheries sustainability. source: noble (2000), chuenpagdee & jentoft (2007), cinner et al. (2012). 4000 6000 8000 1986 1989 1992 1995 1998 2001 2004 2007 2010 2013 2016 year va lu e (o m r /to n) figure 4. gross value (omr/mt) of lobster landings during 1991-2017. 7research article bose, al-balushi, al-haddabi, al-bulushi 1988-2017, the fishery experienced changes in management measures related to fishing season including its duration and timing through the issuance of a number of ministerial decisions. for instance, a two months period (december-february) fishing season was first introduced in 1992 and subsequently changed to the period october 15-december 15 in 2002. prior to 1992, fishing season was six months period (october-march). in 2009, the fishery was technically inoperative due to a decision on the shift in fishing season (from 15th october -15th december to 1st marchlast day of april). the indicators of severity of exploitation of lobster resources are identified in various studies as follows 1) the catch is dominated disproportionately by younger size group (mehanna et al. 2012; maf, 2012; rogers, 2002), and 2) the dramatic decline in catch over the period (fig. 2). in addition, a large proportion of egg bearing females in the catch, as pointed out by mehanna et al. (2012) and rogers (2002) harms the reproductive potential of the population. there is also a substantial indication of fishers’ non-compliance with the regulations specific to the lobster fishery as stated above (roger 2002, al-haddabi, 2010; mehanna et al. 2012; maf, 2012) which undermines the effectiveness and legitimacy of regulations. materials and methods selection of criteria for assessment prior to addressing the research objective and to provide specificity to the subject-matter at hand, some relevant criteria were selected from the literature for evaluative purpose. table 1 presents the selected criteria with brief explanation. in appraising the pre-implementation stage of co-management, chuenpagdee & jentoft (2007) have identified some key criteria that include: i) how and by whom the idea of co-management is conceived, ii) conditions and driving force that led to the idea, iii) community willingness, iv) communicative process, v) participatable 2. respondent’s profile. item al-sharqiyah south (n= 68) * al-wusta (n= 106) * dhofar (n=362) * no. % no. % no. % boat owner 67 98.5 82 96.5 298 83.5 crew 1 1.5 3 3.5 59 16.5 participation full-time 63 92.6 25 23.8 225 62.2 part-time 5 7.4 79 75.2 137 37.8 experience in fishing ≤ 10 years 6 8.0 16 15.2 78 21.8 above 10 years 61 91.0 89 84.7 279 78.2 educational status ≤ elementary & preparatory 61 92.4 64 62.7 91 25.4 above elementary & preparatory 5 7.6 38 37.3 267 74.6 is (was) your father a fisher? 68 100.0 105 100.0 235 65.1 community dependency on fisheries 68 100.0 67 63.2 295 81.5 is (was) your father a fisher? 68 100.0 105 100.0 235 65.1 age of respondent (average years) 44.3 31.2 37.2 proportion of annual income from fishing (%) 90 51 46 * for each question the percentage figure is calculated based on the total number of responses rather than the overall sample size (n). all figures have been rounded to nearest decimal place. 8 squ journal of agricultural and marine sciences, 2019, volume 24, issue 1 is co-management feasible in achieving fisheries sustainability? a case of oman’s lobster fishery tion and preparation, and vi) reflection and adaptation. similar thematic criteria were also used by cinner et al. (2012) in analyzing transitions towards co-management involving three african countries. from an institutional perspective, noble (2000) has added some institutional criteria (along with sub-criteria) that are prerequisites to effective co-management namely: i) the extent of interactiveness in organization, ii) the extent of resource ownership and control by community, iii) level of community support, iv) presence of planned process, and v) diversity. furthermore, the following important observations are made from a brief review of literature. first, driving forces that led to the introduction of co-management initiatives were not common across countries that provide justification for the case study at hand. for instance, conflicts over fisheries resources that popularized co-management in south east asia (nielsen et al. 2004), is relatively uncommon in oman. second, while the factors of influence differ in their extent across countries, the overall objective of resource sustainability had been the main attraction to co-management approach. third, the deliberation of co-management approach helps create a bridge between the two theoretical postulates namely public and social choice theories. to facilitate the process of assessment, this paper draws evidence from studies on co-management of local and global origins, and elicits fishers’ views on various aspects such as, socio-economic, technical, and regulatory aspects of the fishery, awareness of co-management requirements, willingness to participate in management decision-making, monitoring and research, and sharing management responsibilities, etc. a field survey based on face-to-face interviews with a structured questionnaire was conducted during june 9-28, 2013 with randomly selected 536 lobster fishers from three governorates namely al-sharqiyah south south, al-wusta, and dhofar. prior to the design of the questionnaire for the field surveys, a pilot field visit was made to al-sharqiyah south (march 17, 2013) and discussions were held with local officials and fishers to gain a clear understanding of the key issues and challenges faced by the fishery. following the field visit and based on the review of existing literature, a questionnaire was developed. in the absence of any specific register for lobster fishers to draw samples from, the interview was carried out by asking whether the respondent has involvement in lobster fishing. the sampling approach relied on a stratified sampling based on the number of boats involving 11 coastal villages from al-sharqiyah south, al-wusta, and dhofar governorates. the participation in the survey was voluntary and to avoid any inappropriate use of survey information the respondents were kept anonymous according to the code of conduct of the ministry of agriculture and fisheries (maf). on average it took about 40 minutes to complete the questionnaire in the field. survey data were processed using excel and spss. a workshop comprising the data collectors was held on june 5, 2013 to reduce potential ‘interviewer bias’, and to discuss the interview protocol and the structured interview questions. during the workshop data collectors were given opportunity to review the questionnaire and to clarify any question if arises. it can be noted from table 2-9 that survey questions are both binary and scale-based in nature. the scale-based questions were measured on a five-point scale. results this section presents respondents’ background profile, some economic fundamentals, and the assessment of the feasibility of co-management arrangements in the lobster fishery under the selected criteria presented in table 1. respondent’s profile and some economic fundamentals table 2 presents respondent’s profile. majority of the respondents in all study sites were boat owners and had more than 10 years of fishing experience. the number of full-time fishers in al-sharqiyah south was comparative higher than that of the other study sites. overall, a majority of the respondents had low educational attainment with the average age profile ranged from 31.2 years to 44.3 years. it was perceived by the respondents that fisheries are an important part of community livelihoods and the average proportion of fishing income (generated from all fishing activities) out of overall household income ranged from 46% to 90%. the crude estimates of average catch, average price, average gross earnings, and average operating costs per table 3. crude estimates of average catch, average price, and gross earnings. governorates average catch (kg)/ boat average price (omr)/ kg average gross earning (omr)/ boat/ trip average operating costs (omr)/ trip* al-sharqiyah south 7 7.4 51.80 7.00** al-wusta 36.56 5.5 201.08 30.32*** dhofar 21.03 4.8 100.94 67.60 ( for trap)*** 38.15 ( for net)*** * the average operating costs per fishing trip for the fiberglass boats engaged in harvesting kingfish was estimated to be omr 6.87 (al-oufi et al., 2004). ** excluding labor cost. *** including labor cost. 9research article bose, al-balushi, al-haddabi, al-bulushi trip for the boats engaged in lobster fishing are provided in table 3. the price (omr/kg) of lobster during the 2013 season ranged from 4.8 omr in dhofar to 7.4 omr (al-sharqiyah south). in al-sharqiyah south and al-wusta, lobster is sold predominantly to retailers and truckers respectively, while retailers, truckers, and companies are engaged in buying lobster in dhofar governorate. the average (gross) earning of the respondents from al-wusta was about four and two times higher than that of the respondents from al-sharqiyah south and dhofar respectively. during the pilot visit fishers and the local officials reported that lobster catch had always been high during the earlier part of the season and declined gradually towards the end of the season during which fishers divert their fishing efforts to catch other species. in al-sharqiyah south and al-wusta nets were used for harvesting lobster, however, in dhofar, both traps and nets were used. on average, the crew members per boat ranged from 2 to 3. the trip duration per day ranged from 5 hours (dhofar) to 11 hours (al-sharqiyah south), and trip numbers ranged from 5 to 6 times per week. criteria-based assessment of co-management feasibility initiators of the idea of co-management it was evident from a number of local studies that the present-day concept of co-management was embedded in the currently operated sunat al-bahar committee at coastal wilayat level headed by the wali and that includes member from fishing community and the maf. the ‘sunat al-bahar’ (meaning the ‘code of the sea’) historically encompassed rules and person with extensive knowledge. the task of the committee is to study fisheries related decisions of the ministry, help in solving conflicting issues, and communicate fisheries issues with fishers and the management authority. (al oufi et al. 2000; al-balushi et al. 2016; al-subhi et al. 2013). however, local studies also pointed out the diminishing role of the traditional committee (al oufi et al. 2000, al-subhi et al. 2013) and recommended the revitalization of the function of traditional institution to enhance community attitudes to resource use and rule compliance (al-balushi et al. 2016; al-subhi et al. 2013). recently, the 2040 strategy developed for the sector by the world bank (wb) has placed a greater emphasis on table 4. effect of charbohydrate type and concentration on solanine % (mg.g-1 dw) in microshoots, callus and cell suspension of in vitro grown s.nigrum, in addition to wild (in green house) grown s. nigrum. item fishers compliance al-sharqiyah south (n=68)*** al-wusta (n=106)*** dhofar (n=362)*** no. % no. % no. % compliance with fisheries regulations ≤ 50% 34 50.0 68 64.1 236 65.6 greater than 50% 34 50.0 38 35.8 124 34.4 violation of lobster fishery rules ≤ 50% 42 61.8 72 67.9 238 67.0 greater than 50% 26 38.2 34 32.1 117 32.9 enforcement item (measuring scale used: 1=strongly agree and 5=strongly disagree) al-sharqiyah south (n=68) al-wusta (n=106) dhofar (n=362) k-s test (df =2) mean hfs* mean hfs mean hfs adequacy of enforcement at sea 2.87 4 1.66 2 2.67 2 53.78** adequacy of enforcement at landing sites 2.76 4 2.44 2 2.52 2 2.65 self-enforcement 3.63 5 2.50 2 3.46 5 36.32** * hfs represents highest frequency score. **the kruskal-wallis (k-s) test results indicate that the results are significant at the 1% level (critical value is 9.21). *** for each question the percentage figure is calculated based on the total number of responses rather than the overall sample size (n). all figures have been rounded to nearest decimal place. 10 squ journal of agricultural and marine sciences, 2019, volume 24, issue 1 is co-management feasible in achieving fisheries sustainability? a case of oman’s lobster fishery consultation with stakeholders to improve communication necessary for effective fisheries management (wb & maf, 2015). therefore, it appears that local and international experts have been the initiator of the idea of co-management. conditions and driving force the primary driver of the recent co-management appeal resulted from overfishing of certain high valued species (al-balushi et al. 2016), extent of non-compliance (al-subhi et al. 2013), weak enforcement (bose et al. 2017) in general and the catch of undersized lobster in particular (bose et al. 2017). to address this situation, local researchers recommended the implementation of partnership approach as a tool to revitalize the role of traditional committee, and to enhance awareness, mutual trust and legitimacy (bose et al. 2017; al-subhi et al. 2013). with regard to the case in hand, inadequacy of enforcement and non-compliance with regulations (table 4), lack of fair market price, decline in stocks (table 9), etc. pose threats to both biological and economic viability of the fishery which have been major concerns to both fishers and fishery managers. the decline in lobster stock (fig. 2), and lack of enforcement and compliance were of common concerns to respondents. a majority of the respondents from al-sharqiyah south in particular viewed that fisheries enforcement at sea and at landing sites was inadequate. the extent of compliance with fisheries regulations in general and lobster regulations in particular perceived by respondents is consistent with enforcement inadequacy (see table 4). it is noted that ‘self-enforcement’ is not a practical option at the current stage and there was a significant difference in views across the governorates. co-operative decision-makings involving fishers and the management authority were preferred by a majority of the respondents across all governorates and the non-parametric test results did not show any significant difference in their views (table 6). community willingness and support with regard to community willingness and support, the results are positive as respondents acknowledged the resource threats and a relatively high proportion of respondents from al-sharqiyah south and dhofar expressed their high level of commitment to co-management. furthermore, respondents’ were willing to: 1) participate in decision-making, 2) provide fishery-related information, 3) take part in monitoring and enforcement activities, and 4) take part in cooperative research. respondents were prepared to assist the authority by supporting decisions (table 7). when asked if they would like to form a local committee, a majority of respondents agreed to form a local committee involving relevant stakeholders for effective management of the lobster fishery. it is also noted that a relatively high proportion of respondents from al-wusta and dhofar showed low level of willingness to take full management responsibility (table 7). this is, perhaps, because they felt they would be unable to manage the fishery on their own and hence co-operative decision-making was preferred by a majority of the respondents across all governorates as mentioned above. while a generational transfer of fishing profession was observed in case of al-sharqiyah south and al-wusta governorates, involvement of new generation fishers (34.9%) was noted in case of dhofar (table 2). when asked ‘whether they would encourage their next generation to choose fishing as profession’ 85% and 43.9% of the respondents from al-wusta and dhofar respectively responded negatively. table 5. views on management regulations. item (measuring scale used: 1=strongly agree and 5=strongly disagree) al-sharqiyah south (n= 68) al-wusta (n= 106) dhofar (n=362) k-s test (df =2) mean hfs mean hfs mean hfs which of the following general tools of fisheries management do you feel are most effective in reducing fishing pressure? size limit 3.13 4 2.26 1 2.84 4 18.92* closed season 3.03 4 2.82 1 2.49 1 9.05** market control 1.84 2 1.97 1 1.59 1 35.96* gear restrictions 2.01 2 2.02 2 1.61 1 41.52* closed area 3.07 4 3.36 4 3.15 5 2.08 *the kruskal-wallis (k-s) test results indicate that the results are significant at the 1% level (critical value is 9.21). ** the kruskal-wallis (k-s) test results indicate that the results are significant at the 5% level (critical value is 5.99). 11research article bose, al-balushi, al-haddabi, al-bulushi of effective co-management that involves, among others, concept clarity, capacities of fishers (i.e. technical expertise, administrative skills, and social cohesion), provision of protection from outsiders, provision of legislative support, credible commitments and accountability from both parties, mutual trust, refraining from opportunistic behaviour etc. (charles, 2008; singleton, 2000) was found to be low among respondents across the sampled areas. resource ownership and control while fishers having valid fishing and boat licenses have the legal right to access the fishery and harvest lobster, they do not possess collective choice rights that include management rights, exclusion rights, enforcement rights, and transfer rights. furthermore, private property rights for individual fishers or communities in the form of individual quota (i.e. individual/community harvest rights) do not exist in the fishery. there is no clear evidence of power delegation or transfer (i.e. decentralization) of management functions to the traditional community organization to manage and control lobster resources. furthermore, the scope of delegation and decentralization is diminished by the absence of fishers’ technical capacities and lack of awareness about the essentials of co-management approach. the diminishing role of traditional institution within fishing communicommunicative process to the best of authors’ knowledge no planned process exists at present in connection with the preparation of co-management plan, and therefore, the contemplation of the criteria such as ‘participation and preparation’ and ‘reflection and adaptation’ mentioned by chuenpagdee & jentoft (2007) was not possible. furthermore, mechanism for exchange of management information with fishers is unclear and information exchange is irregular in nature. interactive organization the low level of fishers’ participation in traditional institution (i.e. sunat al-bahar committee) undermines its continued existence, operational effectiveness and the advisory role of traditional organization in fisheries management (table 7). furthermore, it weakens the representative voice of fishing communities. responses with regard to the occurrences and level of awareness of consultation meeting, participation in ministry meetings in case of al-sharqiyah south and dhofar, proper acknowledgement of fishers’ views raised, extent of fishers’ involvement in traditional committee, and level of fishers’ representation (particularly in al-sharqiyah south), undermine the basic characteristics of interactive organization (table 7). the level of awareness of the ‘terms and conditions’ table 6. views on management regulations. questions al-sharqiyah south (n= 68) ** al-wusta (n= 106) ** dhofar (n=362) ** χ2 test (df=6) yes % yes % yes % do you agree with having a lobster closed-season? 27 39.7 32 30.2 284 78.5 108.11* do you agree with the minimum size restrictions? 52 76.5 44 41.5 306 84.5 88.80* do you agree with the restrictions on gear that can be used? 49 72.1 82 77.4 338 93.4 46.05* do you agree with the restrictions on taking lobster with eggs? 53 77.9 91 85.8 348 96.1 41.43* do you respect lobster closed-season? 67 98.5 92 86.8 342 94.5 11.76 do you catch lobster during closed season? 3 4.4 16 15.1 13 3.6 53.86* do you get lobster as bycatch during closed season? 18 26.5 60 56.6 213 58.8 33.42* should the ministry, the fishermen or both make decisions on managing the lobster fishery? χ2 test (df=4) ministry 1 1.5 6 5.8 9 2.5 5.48 fishermen 5 7.4 2 1.9 5 1.4 both 62 91.2 95 92.2 348 96.1 * the results are significant at the 1% level (critical values for 6 and 4 dfs at 1% level are 16.81 and 13.28 respectively. ** for each question the percentage figure is calculated based on the total number of responses rather than the overall sample size (n). all figures have been rounded to nearest decimal place. 12 squ journal of agricultural and marine sciences, 2019, volume 24, issue 1 is co-management feasible in achieving fisheries sustainability? a case of oman’s lobster fishery ties, perhaps, influenced by the ever-changing nature of fisheries issues involving resources and user-group (nielsen et al. 2004). across all governorates, a relatively high proportion of respondents (>50%) raise fisheries issues through the sunat al-bahar committee (table 9), however, the traditional committee have no legal rights to impose any regulatory measures. as discussed earlier the lobster fishery is managed through the implementation of regulatory measures such as closed season, gear restrictions, and size limits, by the management authority. although the respondents respect the measure of closed season, less than 50% of the respondents from al-sharqiyah south and al-wusta agreed with the measures. with regard to ‘minimum size’ a similar pattern was observed in case of al-sharqiyah south. a significant difference in the views of the respondents on their agreement with the regulatory measures was observed across the sampled areas (table 5). while prohibition of catching egg bearing females, market-based control, and gear restrictions were viewed as effective management measures by a majority of the respondents across the sampling areas, the extent of disagreement reflected through the perceived views on ‘closed season’ and ‘minimum size’ indicate the site-specific diversity that require specific attention from the authority (table 6). both functional and territorial characteristics should also be taken into consideration to promote equity through participatory democracy. existence of planned process there is no evidence of common priority-setting efforts with participation from both sides. lack of efforts in this regard reflects organizational inertia undercutting the progress to improve the situation. based on the findings it can, perhaps, be suggested that interviewed fishers may not wish to maintain the status quo as the table 7. awareness, participation, membership and representation. item a l s h a r q i y a h south (n= 68) ** al-wusta (n= 106) ** dhofar (n=362) ** yes (%) no (%) yes (%) no (%) yes (%) no (%) awareness of consultation meeting for making regulations 13.2 85.3 34.0 63.2 47.8 51.7 participation in ministry meetings (2011-2013) 11.8 88.2 50.9 45.3 37.3 62.7 recognition of views raised in meetings (if participated) 51.5 (n=47) 17.6 16.0 (n=38) 26.4 19.3 (n=201) 36.2 membership in sunat al-bahar committee 7.4 91.2 12.3 84.9 3.9 96.1 do you feel that sunat al-bahar committee represents you? 41.2 58.8 81.1 16.0 62.7 36.2 way of helping the authority al-sharqiyah south (n= 68) ** al-wusta (n= 106) ** dhofar (n=362) ** k-s test (df =2) yes (%) no (%) yes (%) no (%) yes (%) no (%) supporting decisions 76.5 17.6 52.8 46.2 94.5 4.1 119.18* participating in decision-making 79.4 14.7 72.6 26.4 92.0 4.1 46.02* sharing management responsibilities 45.6 48.5 58.5 39.6 71.3 21.3 26.02* providing information 61.8 32.4 71.7 26.4 84.5 13.5 19.10* monitoring and enforcement 86.8 7.4 58.5 39.6 92.8 5.5 81.93* participating in research project 61.8 32.4 30.2 67.0 76.2 15.5 97.14* taking full management responsibility 42.6 52.5 21.7 76.4 49.4 39.8 32.64* formation of a local stakeholder committee to better manage 67.6 32.4 75.5 22.6 82.0 16.3 9.73* * the kruskal-wallis (k-s) test results indicate that the results are significant at the 1% level (critical value is 9.21). ** for each question the percentage figure is calculated based on the total number of responses rather than the overall sample size (n). all figures have been rounded to nearest decimal place. 13research article bose, al-balushi, al-haddabi, al-bulushi current bio-economic situation (such as stock status, fishing costs, lack of local market outlets, competition etc.) affecting the livelihood of fishers (see tables 4 and 5). majority viewed that creating awareness and market opportunity through government initiative would help mitigating such concerns. this signal is conducive to the introduction of partnership arrangements. it is also noted that the existing institutional environments are not unfavorable either as there has been a long tradition of community organization (i.e. sunat al-bahar committee) and partnership in the sector. however, as noted from the responses (see table 8), the delegation of responsibilities that suits the capacity of the local committee should be decided upon carefully. al-balushi et al. (2016) argued that the authority could take essential steps to reform the traditional institution by establishing clearly defined roles for and responsibilities of the committee in relation to fisheries management. this action will not only provide an opportunity for the management authority to raise community awareness of fisheries issues, but also help reduce any communication gaps between the authority and the primary stakeholders. it is important to note that such approach focuses on disseminating conservation ethics through awareness programs and helps reduce local opposition to regulations. of course, the effective solutions to the prevailing issues are likely to emerge over time through a learning process, however, inclusion and transparency in decision-making and, persistent dialogue with community leaders and members could help gain support from the local community. diversity there is no evidence of the existence of well-articulated process that supports equity in relation to fishers’ participation in decision-making. with regard to fisheries contribution to economic development, the existing conditions identified above will not only weaken the sector’s contribution to national food security and community well-being but also fail to ensure access of new generation of fishers to lobster resource. in addition, this study identified some key challenges for the fishery including overfishing, decline in economic returns, market inefficiency, ineffective management measures, lack of enforcement and compliance, amongst others that need to be addressed to protect stock and achieve longterm sustainability. discussion and policy implications the results associated with boat-ownership, average age profile and the proportion of income from fishing indicate that the livelihoods of those owner operators and younger fishers are linked to the long-term sustainability of the fishery. the results with regard to the dependency on fishing income are consistent with the proportion of part-time fisher in the respective governorate. the lowest proportion of annual income generated from fishing in case of dhofar is consistent with al-marshudi & kotagama (2006) who reported that fishers from dhofar have other jobs along with fishing. the low level of educational attainment particularly in al-sharqiyah south and al-wusta not only limits fishers’ choice of profession as pointed out by bose et al. (2013), but also fishers’ ability to contribute to co-management arrangements. furthermore, if fishers’ unwillingness to encourage their next generation to take fishing as profession is true it may inspire short-term interests of fishers which is not conducive to long term sustainability. it should be noted that the existing regulatory measure of closed-season was not agreed upon by the majority of the respondents from al-wusta and al-sharqiyah south. consequently, the existing management approach will be ineffective and, therefore, will not be able to deliver the desired results. the disagreement table 8. factors of co-management. factors al-sharqiyah south (n= 68) al-wusta (n= 106) dhofar (n=362) k-s test (df =2) mean hfs2 mean hfs mean hfs awareness of ‘terms & conditions’ of co-management1 1.2 1.0 2.1 1 1.9 1 28.33* willingness to take responsibility 3.1 5.0 2.6 3 2.1 1 32.95* ability to manage lobster resource 3.2 5.0 2.7 3 2.2 1 29.53* level of commitment 4.1 5.0 2.8 3 3.1 5 32.60* 1‘terms and conditions’ of effective co-management involves, among others, concept clarity, capacities of fishers (i.e. technical expertise, administrative skills, and social cohesion), provision of protection from outsiders, provision of legislative support, credible commitments and accountability from both parties, mutual trust, refraining from opportunistic behaviour etc. (charles, 2001; singleton, 2000). 2 hfs denotes ‘highest frequency score’. * the kruskal-wallis (k-s) test results indicate that the results are significant at the 1% level (critical value is 9.21). 14 squ journal of agricultural and marine sciences, 2019, volume 24, issue 1 is co-management feasible in achieving fisheries sustainability? a case of oman’s lobster fishery with regard to the existing closed-seasons may be influenced by the genetically different stock structures of scalloped spiny lobster (panulirus homarus) as observed by al-breiki et al. (2018). roger (2002) pointed out that if the priority is resource conservation then it is important to determine the reasons behind the non-preference of the existing closed-seasons by initiating a cooperative research. although a majority of the respondents agree with the gear restrictions, the findings indicate that the use of traps as required by the regulation was not popular among fishers and consequently not followed by the majority of the respondents from al-sharqiyah south and al-wusta. presence of significant diversity between governorates with regard to views and perceptions of fishers should be taken into consideration and evaluated appropriately prior to developing partnership arrangements. the ‘one-size-fits-all’ approach would not be conducive as the findings indicated significant differences in respondents’ preference structures with regard to the extent of participation in co-management. the driving force behind the move towards co-management for the case in hand was found to be from local scientists and international experts which is in contrast with the findings from cinner et al. (2012) where move towards co-management in case of kenya, tanzania, and madagascar was mainly driven by donor ideology and subsequent support. however with regard to conditions that led to the development of co-management idea, the present finding is in line with the case of ssf of lake chiuta where circumstances such as environmental degradation and overexploitation of fish stocks led to the government initiated development of co-management in the early 1990s (donda, 2017). yang & pomeroy (2017) mentioned that to prevent the increasing rate of deterioration of ssf resources in the philippines and due to poor performance of the other management system government actively promoted the development of community-based fisheries management (cbfm). they argued that the cbfm approach improved equity in the fishing community with regard to community participation in fisheries management, control of resource use pattern, the level of bargaining power over decision-making, fair allocation of operational rights and family income. respondents’ unwillingness to take full management responsibility should not hinder the possibility of co-management approach. noble (2000) argued that even if fishers are not capable or not willing to take full responsibility of resource management, they can activetable 9. raising issues, fishery concerns, and government support. item* al-sharqiyah south (n= 68)* al-wusta (n= 106)* dhofar (n=362)* no. (%) no. (%) no. (%) approach to raise fisheries concerns: local fisheries office 10 14.7 2 1.9 44 12.2 sunat al-bahar committee 62 91.2 86 81.1 268 74.0 wali’s office 4 5.9 48 45.3 142 39.2 peers 20 29.4 50 47.2 98 27.1 list of major concerns about the lobster fishery: fishing season nil 0.0 nil 0.0 174 48.1 decrease in stock 51 75.0 26 24.5 250 69.1 non-compliance 37 54.4 50 47.2 216 59.7 market price 39 57.4 11 10.4 1 0.3 lack of enforcement 32 47.1 82 77.4 236 65.2 government support: (yes) 67 98.5 65 61.3 341 94.2 type of support from the government management 21 30.9 5 4.7 166 45.9 administration 53 77.9 0 0.0 230 63.5 training 39 57.4 8 7.5 145 40.1 research 18 26.5 1 0.9 141 39.0 creating market opportunity 48 70.6 34 32.1 196 54.1 creating awareness 58 85.3 4 44.3 229 63.3 * for each question in the table, the percentage figure was calculated based on the total number of responses rather than the overall sample size (n). all figures have been rounded to nearest decimal place. 15research article bose, al-balushi, al-haddabi, al-bulushi ly participate in planning and decision-making through properly planned co-management arrangements. in addition, noble (2000) pointed out that a full institutional restructuring is not always necessary to make partnership arrangements possible. despite respondents’ unwillingness to take full responsibility of resource management (particularly in dhofar and al-wusta) their high level of commitment (al-sharqiyah south and dhofar) and full support for the co-operative approach signify the fact that the approach is demand (fishers)-driven. the management authority should take advantage of this signal and initiate a plan and capacity building efforts through the design of co-operative research projects which may provide opportunities for both parties to collectively arrive at more effective solutions to overfishing and non-compliance problems. tightly constrained fishery budget make it all the more crucial to reduce management and enforcement costs. furthermore, the finding with regard to fishers’ willingness to take part in cooperative research provides support to design a knowledge-based planning process through the integration of socio-cultural and economic characteristics of local community and ecological knowledge of fishers. non-compliance has also been viewed as one of the key factors responsible for overfishing of lobster stock which is in line with the observation by rogers (2002). the capacity to detect non-compliance is of utmost importance, not only to gain better information for stock assessment purpose but to protect stock and ensure the integrity of management measures and sustainability of lobster resources. as the majority of the respondents are ready and willing to support the authority (see table 7), local officials and fishers can join together under a partnership arrangement to become stronger and more effective in enforcement monitoring and of rules and regulations. to cite an example, cinner et al. (2012) pointed out that the enforcement of regulation banning beach seine nets was effective through the establishment of beach management unit (bmu) – a formal organization of fishers and other stakeholders in kenya. for the present case, the establishment of an integrated compliance program will be critical to the effectiveness of fisheries management. donda (2017) examined the impacts of co-management arrangements in case of lake chiuta, malawi and observed that such arrangements benefited government in terms of reduced enforcement costs and creating positive image for establishing a sustainable fishery through fostering user participation, and benefited fishers in terms of getting government protection from outsiders, increased income, employment and improved livelihoods. the recent report by the world bank and maf mentioned that the commitment to increase stakeholder input and participation in the fisheries sector is an important step toward maximizing voluntary compliance (wb & maf, 2015). with regard to respondents’ low level of educational attainment and lack of awareness about the ‘terms and conditions’ of co-management indicate that intervention to augment fishers’ capacity through the development of technical and administrative skills and strengthening traditional institutions through appropriate awareness program may prove beneficial in the long-run and may be the key for resolving local level fisheries issues. in stressing the gender issue in traditional fisheries in oman and low educational attainment of fisherwomen involved in shellfish fisheries, bose et al. (2013) also recommended a ‘target group’based approach to skill development programs to equip fisherwomen with generic skills that are easily transferable to other occupations. the ‘fisheries extension department’ should play a significant role not only in delivering various extension services but also promoting awareness among fishers about their roles and responsibilities in achieving sustainability in the fishery. fisheries extension program must strive to educate fishers on the association between overfishing and its impact on the resources on which many of the fishers depend for their livelihoods. capacity building efforts, if they are to be sustained, must include provisions of long-term support from the authority. however, the ultimate success of any co-management initiatives would depend upon their ability to influence fishers’ attitudes towards resource sustainability. however, extension officers should receive appropriate training to deliver intended services to fishers effectively. the details of such a partnership arrangement with respect to its type, selection of members, functions, responsibilities etc. need to be worked out. considering the fishery situation, an arrangement of participatory management should be considered involving the key stakeholder groups and strived for broad consensus on the management measures to ensure the protection and conservation of the lobster resources. this approach will enhance trust, legitimacy and encourage voluntary compliance and reduce enforcement expenditures. the evolution of co-management institution for pacific northwest salmon fisheries as reported by singleton (2000) illustrates the fact effective partnership approach is possible despite the historical adversarial relations between the state and the american indian tribes as they were engaged collectively in collecting and analyzing data and implementing other initiatives. in a canadian case davis (2008) found that incentive to participate, consensus decision-making and independent facilitation were essential to ensure fairness and effectiveness of the planning process. the process can be developed through the issuance of ministerial decision that will not only provide the legal mandate but also help attracting community and industry attention to the fishery. examples of such decisions can be found in al-balushi et al. (2016). the study by al-balushi et al. (2016) exemplifies that a co-operative management plan could be developed and differences in interests could be accommodated with impressive rating on the compre16 squ journal of agricultural and marine sciences, 2019, volume 24, issue 1 is co-management feasible in achieving fisheries sustainability? a case of oman’s lobster fishery hensiveness of such plan. development practitioners argue that property rights institutions should be designed to be beneficial, flexible, socio-culturally sensitive, politically encouraged, legally and socially recognized, enforceable by a legitimate authority, and conducive to local conditions in order to effectively conserve resources and protect community interests (acheson, 1989; seabright, 1993; agarwal, 1994; ostrom, 2003). conclusion this case study focuses on the feasibility of co-management in the lobster fishery of oman and highlights some strengths and weaknesses related to the feasibility and desirability of such management approach. while findings related to fishers’ commitments, willingness to support government decisions, willingness to participate in co-operative research, and preference for co-operative decision-making are promising, institutional weaknesses identified under the category of ‘interactive organization’, ‘resource ownership and control’, ‘existence of planned process’, and ‘diversity’ should be of major concerns for policy-makers in moving towards co-management arrangements. although the results are dependent on the limited indicators used in the feasibility assessment, it is believed that the incorporation of additional indicators in the assessment process would not alter the basic thrusts of the conclusion. if continuity and long-term sustainability of the fishery is a priority, then fishers’ commitment in running an economically viable and environmentally sustainable fishing should be secured through a partnership approach. therefore, without successfully addressing these impediments, any co-management initiatives will not live up to their full potential. the real challenge is to create mechanisms that facilitate coordination between both parties. genuine attention from the management authority to the subject matter would not only demonstrate the ‘sense of moral duty’, but would also be in harmony with the national policy direction on the inclusion of key stakeholders in socioeconomic development programs. acknowledgement we would like to thank all those who participated in the survey. we would also like to thank the reviewer for the comments on an earlier version of the manuscript. the usual disclaimer applies. references abdullah, nmr., kuperan, k., & pomeroy, rs. 1998. transaction costs and fisheries co-management. marine resource economics, 13(2), 103-114. acheson, jm. 1989. management of common property resources. in s. plattner (ed.), economic anthropology (pp. 351–378). stanford, ca: stanford university press. agarwal, b. 2000. conceptualizing environmental collective action: why gender matters. cambridge journal of economics, 24(3), 283–310. al-balushi, ah, bose, s, & govender, a. 2016. stakeholders’ views on management arrangements: a case of kingfish fishery in the sultanate of oman. natural resources, 7(05), 251-264. al-breiki, r. d., kjeldsen, s. r., afzal, h., al hinai, m. s., zenger, k. r., jerry, d. r., ... & delghandi, m. 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gallo et al., 2021; kumar et al., 2021) تقييم حمتوى األفالتوكسني b1 والفطرايت املنتجة ألفالتوكسني يف السلع الغذائية املستوردة يف مسقط بسلطنة عمان اآلء بنت سليمان بن مخيس العلوية١ و عهد بنت امحد سعيد املنذرية١ و ماجدة بنت حممد بن علي احلراصية١ و عيسى بن هاشل املهمويل١ و امساعيل البلوشي١ و عبدهللا بن حممد السعدي١ و راثينامسي فيالزهاهن١* abstract. aflatoxins, mainly produced by aspergillus flavus and a. parasiticus are considered as serious food safety and human health issues due to their hepatotoxic effects. in the present study, the occurrence of aflatoxin b1 (afb1), the most potent human liver carcinogen, and prevalence of toxigenic isolates of aspergillus spp. were assessed in 140 food commodities in muscat markets, oman, and the 95 quarantined imported food commodities. these samples consisted of rice, corn, peanut, red chilli powder, soybean, dried dates and tree nuts. afb1 was analyzed using competitive elisa/lc-ms and the aflatoxigenic fungi were detected using plating technique followed by molecular identification. no afb1 was detected in 89 (63.6%) samples collected from local markets, while 44 (31.4%) samples contained 1-5 ppb and the remaining 7 (5%) samples (red chili powder) contained 6-10 ppb. none of the samples exceeded the maximum permissible limit of 10 ppb set for foods by oman legislation. of the 95 quarantined samples, only 17 (17.9%) samples were positive and contained afb1 at concentrations ranging from 1-3.4 ppb. four isolates of aspergillus pp. were isolated from the collected samples and were identified as aspergillus flavus (a14, a16 and a23) and a. chevalieri (a46) on the basis of internal transcribed spacer (its) sequences of ribosomal dna. among them, a. flavus strain a14 alone produced afb1 (7.6 ppb), while a16, a23, and a46 were non-toxigenic. this is the first detailed report on the occurrence of afb1 in food commodities imported into oman. keywords: aflatoxin b1; aflatoxigenic fungi; aspergillus flavus; food-borne mycotoxins املســتخلص: تعتــر األفالتوكســينات و الــي تنتــج بشــكل رئيســي مــن اســراجليس فالفــوس و اســراجليس ابراســيتيكس، مــن املشــاكل اخلطــرة لســالمة األغذيــة وصحــة اإلنســان بســبب آاثرهــا الســامة علــى الكبــد. يف هــذه الدراســة ، مت حتديــد األفالتوكســن b1 (afb1)1 مــن نــوع االســرجليس ، املسبب لسرطان الكبد البشري واشدها فعالية ومنتجة للسموم يف ١40 سلعة غذائية يف أسواق مسقط بسلطنة عمان و 95 سلعة غذائية مستوردة خاضعة للحجر الصحي. اشــتملت هذه الســلع على األرز والذرة والفول الســوداين ومســحوق الفلفل األمحر وفول الصواي والتمور اجملففة واملكســرات. afb1 ابســتخدام التقنيــة احلديثــة يف املقايســة األمتصاصيــة املناعيــة لالنــزمي املرتبــط و الكروماتوجرافيــا الســائلة املقرتنــة مبطيــاف الكتلــة مت حتديــد lc-ms elisa / ومت حتديــد الفطــرايت املنتجــة للســموم ابلتعريــف اجلزيئــي. مل يوجــد afb1 يف 89 (63.6٪( عينــة مت مجعهــا مــن األســواق احملليــة ، بينمــا احتــوت 44 (3١.4٪( عينــة علــى ١-5 جــزء يف البليــون ، واحتــوت 7 عينــات )5٪( املتبقيــة )مســحوق الفلفــل األمحــر( علــى ١0-6 جــزء يف البليــون. مل تتجــاوز أي مــن العينــات احلــد األقصــى املســموح بــه لألغذيــة حســب التشــريعات العمانيــة وهــو ١0 أجــزاء مــن البليــون. مــن 95 عينــة حمجــورة ، كانــت ١7 (١7.9٪( عينــة فقــط إجيابيــة واحتــوت علــى afb1 برتكيــزات تــرتاوح بــن ١-3.4 جــزء يف البليــون. مت عــزل أربــع انــواع مــن االســراجليس مــن العينــات الــي مت مجعهــا ومت حتديدهــا علــى أهنــا اســراجليس فالفــوس )a14، a16 و a23( و )a46( واســراجليس شيفاليري على اساس منطقة التمييز احلمض النووي )its( للحمض النووي الريبوزومي. من تلك االنواع ، أنتجت ساللة a14 من اسراجليس فالفــوس وحدهــا afb1 يف حــدود 7.6 جــزء يف البليــون ، يف حــن أن a16 و a23 و a46 كانــت غرمنتجــة للســموم. هــذا هــو أول تقريــر مفصــل عــن وجــود afb1 يف الســلع الغذائيــة املســتوردة يف عمــان. الكلمات املفتاحية: االفالتوكسن b1، الفطرايت املنتجة للسموم، اسراجليس فالفوس ، السموم الفطرية الي تنقلها األغذية. 2 squ journal of agricultural and marine sciences, 2023, volume 28, issue 1 assessment of aflatoxin b1 content and aflatoxigenic molds in imported food commodities in muscat, oman currently 20 different forms of aflatoxins have been characterized among which aflatoxin b1, b2, g1 and g2 are commonly found in agricultural commodities (kumar et al., 2017). among the aflatoxins, afb1 is the most ubiquitous and threatening mycotoxin to humans and considered as one of the most potent naturally occurring hepato-carcinogens known. when cow, camel, goat or other lactating animal consumes aflatoxins b1 contaminated feed, aflatoxin m1 will be formed as a result of the metabolic process in the liver of animals and excreted in milk (sharma et al., 2020). aflatoxin m1 in camel milk samples collected from jeddah, saudi arabia (bokhari et al., 2017) and abu dhabi, united arab emirates (saad et al., 1989) was reported, whereas, the presence of afb1 in the meat and eggs of poultry birds fed with aflatoxin-contaminated feed has been reported (trucksess et al., 1983). ingestion of food or feed contaminated with excessive levels of aflatoxins leads to the disease called “aflatoxicosis” in humans and animals (williams et al., 2004; ogodo and ugbogu, 2016; sarma et al., 2017). the world health organization (who) ranked the aflatoxicosis as the 6th among the top 10 important health risks to human beings (williams et al., 2004). the international agency for research on cancer (iarc) classified aflatoxins as class i human carcinogens (international agency for research on cancer, 2002). in humans, acute and chronic exposures to aflatoxins cause a variety of clinical symptoms including liver damage, pulmonary edema, haemorrhage and in some cases death (wu et al., 2014; sarma et al., 2017). the existence of aflatoxins in the food chain threatens people’s livelihood, their health and food security (kumar et al., 2017). hence, over 100 countries enforce aflatoxin tolerance levels in foods (van egmond et al., 2007). the food and drug administration (fda) of the united states of america fixed an aflatoxin tolerance limit of 20 parts per billion (ppb) for foods. the sultanate of oman has fixed the maximum permissible level of aflatoxin b1 in foodstuffs at 10 ppb (agenda item 11, codex committee on contaminants in foods, eleventh session, rio de janeiro, brazil, 3-7 april 2017). oman imports most of the food grains from international markets (mbaga, 2013). however, information on the aflatoxin contents, precisely the carcinogenic type afb1, in food commodities in oman is limited. in this study corn, peanut, red chilli powder, rice, soybeans, dates and tree nuts samples collected from local markets, super markets and quarantine department, ministry of agriculture, fisheries and water resources, sultanate of oman were assessed for the presence of afb1. furthermore, the prevalence of aflatoxigenic strains of aspergillus spp. in the collected samples was determined. materials and methods sample collection a total of 140 samples (100-1000 g) were collected from the retail shops and supermarkets in oman in 2020. the collected samples consisted of raw peanuts (15), roasted peanuts (5), walnuts (15), raw pistachios (18), roasted pistachios (5), raw almonds (14), roasted almonds (3), rice (8), corn (8), red chili powder (16), dried dates (6), cashew (16), roasted cashew (8), hazelnut (1), peacon (1) and brazil nut (1). these food commodities were precisely selected due to their high frequency consumption in most arabian gulf countries including oman. the collected samples were kept in sterile bags and stored at 4 °c until analysis. another 95 imported food commodities were collected from the quarantine department, ministry of agriculture, fisheries and water resources, sultanate of oman during july august 2021. these samples consisted of rice, peanut, almonds, pistachios, cashew and soybeans. the collected samples were kept in sterile bags and stored at 4°c until analysis. quarantined foods were selected to tackle the source of afb1. determination of aflatoxin b1 the samples were ground into fine powders by using a blender and 5 g of powdered sample was added with 25 ml of 70% methanol and mixed well by vortexing. the homogenate was centrifuged at 10000×g for 10 min at room temperature (25±2°c) and the supernatant was collected. the supernatant was diluted with distilled water (1:1, v/v) and afb1 content in the samples were analyzed using a commercial enzyme-linked immunosorbent assay (elisa) kit (ridascreen aflatoxin b1; r-biopharm ag, darmstadt, germany) according to the manufacturer’s instructions. isolation of aspergillus spp. aspergillus spp. were isolated from the collected samples on potato dextrose agar (pda) (oxoid, uk) medium under laboratory conditions (karthikeyan et al., 2009). molecular identification of aspergillus spp. genomic dna was isolated from the 7-day-old fungal mycelia as described by karthikeyan et al. (2009). the internal transcribed spacer (its) regions of the fungal rdna were amplified by pcr by using the extracted dna and its4 and its5 primers (white et al., 1990) as described by halo et al. (2018). the pcr products of the expected size were sequenced (macrogen, korea) and the sequences were subjected to blast searches using the national center for biotechnology information (ncbi) database (http://www.ncbi.nlm.nih.gov). 3research paper al-alawi, al-mandhari, al-harrasi, al-mahmooli, al-bulushi, al-sadi, velazhahan assessment of toxigenic potential of aspergillus spp. the mold cultures were grown in 250 ml conical flasks containing 100 ml of smky medium (200 g sucrose, 0.5 g mgso47h2o, 0.3 g kno3 and 7 g yeast extract in 1l of distilled water) at 25±2 °c for two weeks. at the end of incubation period, the culture filtrates were collected by filtration using whatman no. 1 filter paper. the culture filtrate (500 μl) was extracted with chloroform (1:1 v/v) and the chloroform fraction was fully evaporated using a water bath at 60°c. the residue was dissolved in 20 μl of hplc-grade methanol and analyzed by agilent lc/ ms/ms, equipped with high-performance autosampler (g4226a), quaternary pump (g4204a), thermostatted column compartment (g1316c) and 6460 triple quad ms detector. chromatographic separations were performed with symmetry c8 5 µm, 3 mm × 150 mm column (waters). the column was maintained at 45ºc. the injection volume was 5 µl. the mobile phase used was acetonitrile (eluent a) and water (eluent b), both with 0.1% formic acid under gradient condition (eluent a 1070% in 0-1 min, 70-95% in 1-2 min, hold at 95% for 4 min (2-6 min), 95-70% in 6-7.5 min, 70-10% in 7.5-8 min and hold at 10% for 1 min) with a flow rate of 0.3 ml per min. the following ms detector parameters were used for the analysis: gas temperature 300ºc, gas flow 3 l min-1, nebulizer pressure 50 psi, sheath gas heater 375ºc, sheath gas flow 10 l min-1, capillary voltage 3500 v, scan range 100 to 3000 m/z and positive polarity. mass spectra data were acquired and processed by agilent masshunter workstation and agilent masshunter qualitative analysis software, respectively. results and discussion out of 140 food commodities from local markets and supermarkets analyzed, afb1 has detected in 51 (36.4%) samples (table 1). however, afb1 content in all the food samples was below the maximum tolerance limit (10 ppb) set by oman legislation. the levels of afb1 in 7 red chilli powder samples exceeded the maximum tolerance limit of 5 ppb set by the european union for chilli (ezekiel et al., 2019; gallo et al., 2021). the low levels of afb1 contamination in agricultural commodities might be due to good agricultural and storage practices. reasonably high afb1 content (above 5 ppb) in red chilli powder suggests that the contaminated red chilli may be a major source of consumer exposure to aflatoxins in oman. chilli is considered as one of the favourable substrates for the growth of many agronomically important molds including a. flavus and toxin production (supriya et al., 2015). the presence of mycotoxins such as aflatoxins, ochratoxin a, fumonisins, zearalenone and patulin in capsicum has been documented (costa et al., 2019; chuaysrinule et al., 2020). moreover, iqbal et al. (2010) reported that more than 50% of chilli pepper samples from punjab region of pakistan contained above 5 ppb of afb1. chuaysrinule et al. (2020) reported that 96.7% of dry chilli pods and 86.7% of chilli powder collected from markets in thailand were contaminated with molds; among them aspergillus section flavi were predominant. kiran et al. (2005) reported that chilli pods kept in cold storage were contaminated with aflatoxin b1 to the extent of 5.5 ppb. paterson (2007) recorded up to 93 ppb of afb1 in dry chilli samples obtained from markets in pakistan. ezekiel et al. (2019) reported that 69% of the chili pepper samples collected from local markets and farmers’ stores in nigeria were contaminated with aflatoxins with an average of 8.9 ppb. of the 95 food samples obtained directly from the quarantine department and evaluated, 17 samples were found to be positive for afb1 but the levels were below 5 ppb (1-3.4 ppb) (table 2). this is probably due to adoption of strict plant quarantine regulations and phytosanitary measures. the water content of chilli at the time of harvest is usually between 65% and 80% [water activity (aw) 0.995]. in order to minimize mold growth and mycotoxin production, the water content of the harvested chilli should be reduced quickly to 13% (aw 0.50) by drying (toontom et al., 2012; sanzani et al., 2016). as the dried chilli is highly hygroscopic, they need to be properly packed soon after drying (costa et al., 2019). at retail markets, rehydration of dried chilli may favour growth of molds and mycotoxin production. sahar et al. (2015) observed a direct relationship between aflatoxin content in red chilli and moisture content, thus drying of chilli to less than 10% moisture content to prevent mold growth and to minimize aflatoxin contamination was recommended. hence, proper drying and storage of dry chilli in retail shops may help in preventing mold growth and aflatoxin production. of the 235 samples tested, only 4 samples viz., a14 (from cashew), a16 (from peanut), a23 (from peanut) and a46 (from corn) collected from local shops showed the presence of aspergillus spp. none of the samples obtained from the quarantine department showed the presence of aspergillus sp. the mold isolates were found to be a. flavus (a14, a16, a23; 100% identity) and a. chevalieri (a46; 100% identity) based on the sequences of the its regions of rdna. the sequences were deposited to the genbank with the accession numbers mw386304; mw386306; mw386307 and mw386308. the natural occurrence of aflatoxin-producing molds in chilli has been reported (jeswal and kumar, 2015; chuaysrinule et al., 2020). the absence of aflatoxin-producing molds in other samples in this study does not guarantee that those are free of aflatoxins (pitt et al., 2000). for instance, the 7 red chilli samples that showed afb1 above 5 ppb were free from aspergillus spp. this might be due to removal of toxigenic fungi from red chilli during postharvest processing or disappearance of molds after secretion of the toxins in the substrate. among the 4 strains evaluated for in vitro production of afb1, a. flavus strain a14 was found to be capable of producing afb1 and the amount of afb1 produced 4 squ journal of agricultural and marine sciences, 2023, volume 28, issue 1 assessment of aflatoxin b1 content and aflatoxigenic molds in imported food commodities in muscat, oman was 7.6 ppb, while a16, a23, and a46 were non-toxigenic. the contamination of red chilli depends on the virulence and toxigenic potential of the aspergillus spp. strains. several studies found no correlation between the level of afb1 in foods and the population of a. flavus as toxin production is governed by genetic make-up of mold species, availability of nutrients in the substrate, water activity, temperature, etc. (paterson, 2007; santos et al., 2011). though a. flavus strain a14 (aflatoxigenic) was isolated from cashew in this study, no afb1 was detected in this sample. elshafi et al. (2002) found that 9 out of 20 (45%) isolates of a. flavus isolated from spices in oman produced aflatoxins (50-90 ppb). jeswal and kumar (2015) reported that 56% of a. flavus isolated from red chilli were toxigenic and produced aflatoxins. gherbawy et al. (2015) while studying the mycobiota of chilli products in saudi arabia reported that some aspergillus strains did not produce aflatoxins, though they had the gene clusters for aflatoxin biosynthesis. conclusion in this work, we found that afb1 content in all the food samples commercialized in muscat, oman, was within the permissible limit set by oman regulations. only red chilli powder samples (5%) were found contaminated with afb1 above 5 ppb, the maximum tolerance limit fixed by the european union. such aflatoxins contaminated chilli may be a potential route of exposure of local people to aflatoxins. the levels of afb1 in the food commodities obtained directly from the port of entry through the quarantine department were less than 5 ppb. the occurrence of an aflatoxigenic strain of a. flavus in one of the samples indicates a possible risk of aflatoxin production in foods especially if stored under improper conditions. our results suggest that proper storage practices need to be followed in the retail shops/processing units to prevent mold growth and afb1 contamination. further studies are needed to increase sampling table 1. aflatoxin b1 content in food commodities in muscat markets, oman food commodities total number of samples number of samples and afb1 concentration range (ppb) 0 1-5 6-10 11-15 16-20 above 20 raw peanuts 15 9 (0) 6 (1.0-4.4) roasted peanuts 5 4 (0) 1 (1.8) walnuts 15 3 (0) 12 (1.0-4.8) raw pistachios 18 13 (0) 5 (1.0-1.6) roasted pistachios 5 5 (0) raw almonds 14 12 (0) 2 (1.0-1.4) roasted almonds 3 3 (0) rice 8 6 (0) 2 (1.6-2.4) corn 8 6 (0) 2 (1.2-2.0) red chilli powder 16 9 (2.8-4.8) 7 (7.4-9.8) dried dates 6 6 (0) cashew 16 14 (0) 2 (1.2) roasted cashew 8 6 (0) 2 (1.0) hazelnut 1 1 (0) pecan 1 1 (3.8) brazil nut 1 1 (0) total 140 89 44 7 5research paper al-alawi, al-mandhari, al-harrasi, al-mahmooli, al-bulushi, al-sadi, velazhahan size and analyze other food-borne mycotoxins, such as afb2, afg1, afg2 and ochratoxin a in the chilli samples. to our knowledge, this is the initial detailed report on the levels of afb1 contamination in foods in oman. acknowledgement the authors thank dr. saif al-yaqoobi, director of food monitoring, food safety and quality center, oman for providing food samples and central analytical and applied research unit (caaru), squ for lc-ms analysis of afb1. this study was supported by a research grant (ig/agr/crop/21/03) from sultan qaboos university. references adeyeye sa. (2016). fungal mycotoxins in foods: a review. cogent food & agriculture 2: 1213127. benkerroum n. (2020). chronic and acute toxicities of aflatoxins: mechanisms of action. international journal of environmental research and public health 17: 423. bokhari f, aly m, al-kelany a, rabah as. (2017). presence of aflatoxin m1 in milk samples collected from jeddah, saudi arabia. iosr journal of pharmacy 7: 49-52. chanda a, roze lv, linz je. (2010). a possible role for exocytosis in aflatoxin export in aspergillus parasiticus. eukaryotic cell 9: 1724-1727. chuaysrinule c, maneeboon t, roopkham c, mahakarnchanakul w. (2020). occurrence of aflatoxin-and ochratoxin a-producing aspergillus species in thai dried chilli. journal of agriculture and food research 2: 100054. costa j, rodríguez r, garcia-cela e, medina a, magan n, lima n, battilani p, santos c. (2019). overview of fungi and mycotoxin contamination in capsicum pepper and in its derivatives. toxins 11: 27. elshafie ae, al-rashdi ta, a-bahry sn, bakheit cs. (2002). fungi and aflatoxins associated with spices in the sultanate of oman. mycopathologia 155: 155-160. ezekiel cn, ortega-beltran a, oyedeji eo, atehnkeng j, kossler p, tairu f, hoeschle-zeledon i, karlovsky p, cotty pj, bandyopadhyay r. (2019). aflatoxin in chili peppers in nigeria: extent of contamination and control using atoxigenic aspergillus flavus genotypes as biocontrol agents. toxins 11: 429. gallo p, imbimbo s, alvino s, castellano v, arace o, soprano v, esposito m, serpe fp, sansone d. (2021). contamination by aflatoxins b/g in food and commodities imported in southern italy from 2017 to 2020: a risk-based evaluation. toxins 13: 368. gherbawy ya, shebany ym, hussein ma, maghraby ta. (2015). molecular detection of mycobiota and aflatoxin contamination of chili. archives of biological sciences 1: 223-234. halo ba, al-yahyai ra, al-sadi am. (2018). aspergillus terreus inhibits growth and induces morphological abnormalities in pythium aphanidermatum and suppresses pythium-induced damping-off of cucumber. frontiers in microbiology 9: 95. international agency for research on cancer – iarc. 2002. some traditional herbal medicines, some mycotoxins, naphthalene and styrene (iarc monographs on the evaluation of carcinogenic risks to humans, no. 82). lyon: iarc. pmid: 12687954. iqbal sz, paterson rrm, bhatti ia, asi mr. (2010). survey of aflatoxins in chillies from pakistan produced in rural, semi-rural and urban environments. food additives and contaminants 3: 268-274. jeswal p, kumar d. 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(2009). genetic variability and aflatoxigenic potential of aspergillus flavus isolates from maize. archives of phytopathology and plant protection 42: 83-91. table 2. aflatoxin b1 contamination in food commodities imported (from july 2021 to august 2021) in oman food commodities total number of samples number of samples and afb1 concentration range (ppb) 0 1-5 6-10 11-15 16-20 above 20 almond 1 1 (0) pistachios 1 1 (0) cashew 3 2 (0) 1 (1.0) rice 71 58 (0) 13 (1.0-3.4) soybean 17 14 (0) 3 (1.0-1.8) peanut 2 2 (0) total 95 78 17 6 squ journal of agricultural and marine sciences, 2023, volume 28, issue 1 assessment of aflatoxin b1 content and aflatoxigenic molds in imported food commodities in muscat, oman khan r, ghazali fm, mahyudin na, samsudin nip. (2021). aflatoxin biosynthesis, genetic regulation, toxicity, and control strategies: a review. journal of fungi 7: 606. kiran dr, narayana kj, vijayalakshmi m. 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(2016). mycotoxins in harvested fruits and vegetables: insights in producing fungi, biological role, conducive conditions, and tools to manage postharvest contamination. postharvest biology and technology 122: 95-105. sarma up, bhetaria pj, devi p, varma a. (2017). aflatoxins: implications on health. indian journal of clinical biochemistry 32: 124-133. sharma h, jadhav vj, garg sr. (2020). aflatoxin m1 in milk in hisar city, haryana, india and risk assessment. food additives & contaminants: part b 13: 59-63. supriya s, kannan k, ragupathi n, velazhahan r. (2015). evaluation of chilli (capsicum annuum l.) genotypes for resistance to aspergillus flavus infection and aflatoxin production. biochemical and cellular archives 15: 465-468. toontom n, meenune m, posri w, lertsiri s. (2012). effect of drying method on physical and chemical quality, hotness and volatile flavour characteristics of dried chilli. food research international 19: 1023-1031. trucksess mw, stoloff l, young ky, wyatt rd, miller bl. (1983). aflatoxicol and aflatoxins b1 and m1 in eggs and tissues of laying hens consuming aflatoxin contaminated feed. poultry science 62: 2176-2182. van egmond hp, schothorst rc, jonker ma. (2007). regulations relating to mycotoxins in food. analytical and bioanalytical chemistry 389: 147-157. white tj, bruns t, lee s, taylor j. (1990). amplification and direct sequencing of fungal ribosomal rna genes for phylogenetics. in: innis ma, gelfand dh, sninsky jj, white tj, editors. pcr protocols: a guide to methods and applications, academic press, san diego, usa, p. 315-322. williams jh, phillips td, jolly pe, stiles jk, jolly cm, aggarwal d. (2004). human aflatoxicosis in developing countries: a review of toxicology, exposure, potential health consequences, and interventions. the american journal of clinical nutrition 80: 1106-1122. wu f, groopman jd, pestka jj. (2014). public health impacts of foodborne mycotoxins. annual review of food science and technology 5: 351-372. img009 img010 img011 img012 img013 img006 img007 img008 img306 img307 img308 img309 img310 img311 img046 img047 img048 img049 img013 img014 img015 img016 img017 img018 img019 img020 img020 img021 img022 img023 img024 img025 img024 img025 img026 img027 img028 pdf995, job 6 _________________ *corresponding author. 9 agricultural sciences, 7(2):9-15 (2002) © 2002 sultan qaboos university natural attenuation of volatile hydrocarbons in unsaturated soil zone p. grathwohl* and u. maier university of tübingen, department of applied geology, sigwartstr. 10, d-72076 tübingen, denmark abstract: scenario-specific numerical simulations were performed in order to assess the diffusive spreading of volatile fuel constituents and their biodegradation in the unsaturated soil zone. this is especially important in arid regions where the groundwater table is far below the surface and groundwater recharge is limited. the model results compare well with data from a controlled outdoor test with an emplaced source of kerosene. modelling results illustrate that the overall biodegradation rates depend mainly on properties of the fuel constituents such as henry’s law constant, on the individual degradation rate constants, the soil water content and temperature. the contaminant transfer rates into groundwater can be determined provided the spreading processes in the unsaturated zone are understood. keywords: attenuation, volatile hydrocarbon, unsaturated soil, biodegradation, henry’s law, groundwater, risk assessment. ontaminated land poses a serious problem with respect to soil quality and the risk of spreading of pollutants into other compartments of the environment. a major concern at most contaminated sites is the risk of groundwater pollution by organic and inorganic compounds. since the remediation of all of the contaminated sites is economically not feasible in many countries, groundwater risk assessment procedures are needed for the ranking of sites, decision making on further use and remedial actions. of special interest is monitored natural attenuation (wiedemeyer, 1999), that thus far, is mainly applied in polluted aquifers and only to a very limited extent in the unsaturated zone. at sites where petroleum products are handled or stored, contamination of the unsaturated soil zone is frequently found. hydrocarbons can reach the groundwater by transport with percolating water and by spreading in soil-gas. degradation processes can limit the spreading in the unsaturated soil zone and, in the best case, restrict the contamination to the unsaturated zone. the objective of this study was to use numerical experiments to elucidate the processes/parameters which are relevant in contaminant spreading and thus for groundwater risk assessment. the results are compared to data from a well controlled field test performed at the værlose airforce base, denmark (christophersen et al., 2002). sensitivity analyses were performed accounting for physical-chemical properties of volatile fuel constituents and properties of the soil. model the numerical model min3p (mayer, 1999) uses the finite volume method and allows for the calculation c ! !"#$%&'()*+(!,)-&'(./(0)123-%&'(4256,)789:12;<&(."*#3&'(=>6&'( !"#$%&'()(%*(+,)!-%!./0% ! (!?? !"%1%%%%%%%%%%%%%%%%%%%23456')%!/7%20!.')%&8%9::;<(%!"#=.6')%>+?+')% #5.!)%"//#.'%2$#%%&#'+" #(/)'%2/*+#" %,-#*6!%.)!*-/%"*<%0 %%%%%%%%%%%1')%2#/6')%3/4%28#1')%56#(6')%&8%2$#%%2/6'7%"//#.')%)8'%9*).:"(%%%%2"8;.')%<>(=;$(%<!/4>%?#6@7%a:@%2/8+%0%=#'( %%%%%% #6!)=')%&8%b/c(!/:')%d)=e.c#0%2/:#;')%f #1.')%b$%<##.)6')%&#!#/4')%g$%<!/4>%2*='%&*+#"!')%,-+6(*')%50#*=<h%0 %%%%i!('%j+!#?%k0#l>%m%>+?+')%n)+%%a:@%#c#c7%=6.3<%o:;.')%&#>%j7%pq#.(')%r*++<(%s%t+.)$(%o:;.')%o$#3$%k0#,( )%%%%%%%%%< )!*;')%&#*>(%20!.*')%&*8%20+6!*'%0%%%%% #5.!u)%&#/:6@%"v8%=(@%2/8+1')%2#/6')%&8%&#,+:6')%2>!4%="=;<%j#:$w)%&8( 23456')%!/7%20!.')%&8%28'0% grathwohl and maier 10 of vapour phase transport and unsaturated flow in the vadose zone. groundwater transport processes and mass transfer across the capillary fringe can be simulated as well and a variable number of geochemical reactions such as biodegradation processes can be handled (mayer, 1999). density driven gas advection was not included in the simulations. it is often considered a significant transport process for compounds with very high vapour pressures in highly permeable materials such as coarse gravel. hughes-conant et al. (1996), however, showed that in sandy material, density induced advection is of only minor importance. the base scenario for the model was adapted to a well controlled field test in denmark, where a small volume of a multicomponent napl (non-aqueous phase liquid) was buried and monitored over a time period of one year (christophersen et al., 2002). site characteristics with respect to, for example, grain size distribution, geochemistry, and permeability, were implemented in the model as precisely as possible. the site had a vadose zone of 3.5 meters thickness, consisting of sandy and not too heterogeneous material. the source was emplaced in the subsurface at 1 m depth. the synthetic hydrocarbon mixture consisted of 13 volatile to semi-volatile kerosene compounds and one tracer (freon). volatilization and vapour phase diffusion were investigated by reckhorn et al. (2002). biodegradation processes were analyzed by höhener et al. (2002). monitoring of the contaminant spreading in soil air and groundwater samples in a one-year measurement campaign allowed a comparison to modelled data. a compilation of model input parameters is given in table 1, and a vertical cross section of the model domain is shown in figure 1. to reduce computational time, several sensitivity analyses were performed in 1d and 2d, whereas the model was fitted to field data in 2d and 3d. results and discussion the contaminant spreading at the field site and the interactions of 13 kerosene compounds and the tracer could be reproduced reasonably well already by the non table 1 compilation of important parameters of the field site model. porosity 35% volumetric soil water content 7 % (unsaturated zone) and 10.5 % (top soil 50 cm) temperature 15°c (averaged value), and daily measured data, resp. groundwater flow velocity 0.15 m day-1 biodegradation pseudo first order; rate constants from pasteris et al. (2001). diffusion coefficients 8.10-10 m2 s-1 (aqueous) and 7.3.10-6 m2 s-1 (air) napl composition 13.6 l of kerosene with 13 compounds and 1 tracer (freon cf113) calibrated model (pure forward prediction solely based on field and compound parameters). no depletion of o2 was observed even at the source location, which coincides well with the field measurements. ageing of the napl source results in the enrichment of the lower volatile compounds at the expense of the components with higher vapour pressure, which escape to the atmosphere. the transient evolution of the composition of the napl source is shown in figure 2, which can be regarded as a typical example of kerosene ageing during one year after spill. after 350 days only 5 compounds remain in the residual phase in significant amounts: xylene, tri-methyl-benzene, n-octane, n-decane, n-dodecane and methyl-cyclohexane. the contaminant flux into groundwater is very small compared to volatilisation of source constituents to the atmosphere. as already observed in previous studies (klenk, 2000; pasteris et al., 2001) the results show that for vocs most of the contaminant mass will be degassing to the atmosphere or is subject to biodegradation, whereas only a small fraction diffuses across the capillary fringe into the groundwater (as long as the surface is not sealed). groundwater aquitard cover organic rich top soil monitoring well kerosene spill shallow groundwater plume ? soil gas plume figure 1: conceptual model used for sensitivity analysis in numerical simulations. natural attenuation of volatile hydrocarbons in unsaturated soil zone 11 time [days] m as s [m o l] 0 100 200 300 0 2 4 6 8 10 12 14 16 benzene toluene m-xylene 1,2,4-tmb hexane octane decane dodecane 3-meth-pentane iso-octane cyclo-pentane mcp mch cf113 mass of the kerosene compounds remaining in the napl phase, figure 2: change of kerosene composition during first year as simulated in 3d model. sorted in compound classes, from top to bottom, initially: benzene, toluene, 1,2,4-tri-methyl-benzene, hexane, octane, decane, 3-methyl-pentane, iso-octane, cyclo-pentane, methyl-cyclo-pentane, methyl-cyclo-hexane, and the tracer freon cf113 (only in very small fraction). recharge is a significant contaminant pathway only in soils with high water content (reduced vapour phase diffusion) and for compounds with low henry’s law constants (e.g. mtbe in silt or clay). maximum transport rates into groundwater occurred for the 2 most volatile and soluble compounds toluene and cyclo-pentane. even in this case only about 0.2% of the total mass of each compound was transported into the groundwater. the flux to the atmosphere was most pronounced for the tracer (freon 113), the light alkanes (n-, isoand cyclo-alkanes) due to their low biodegradation rate constants. biodegradation was most important for the aromatic compounds (low henry’s law constant) and the heavier n-alkanes (high biodegradation rate constants). according to the model a total mass of 5 kg o2 was consumed during one year of the experiment leading to production of co2 and water (oxidation of hydrogen contained in the hydrocarbons). a view of a vertical cross-section through a 2d model domain is shown in fig. 3 for the concentration of iso-octane, which is most concentrated in the original napl, at the time of its maximum concentration at the source location. the concentration decreases rapidly from the source zone. significant contamination extends only in an area of 5 m in diameter due to biodegradation and volatilisation to the atmosphere. x [m] d ep th [m ] 0 5 10 15 20 0 1 2 3 iso-oktan 50 20 2 1 0.2 0.02 0.002 0.0002 t_j, t = 3.000e+01 days mg/l soil air figure 3: vertical cross section through model domain for 2d scenario and compound iso-octane 30 days after source installation (time of maximum concentration in source). grathwohl and maier 12 degradation rate constant [s-1] m as s in % o fi n iti al 10-6 10-5 10-4 10-3 0 10 20 30 40 50 60 70 80 90 100 toluol iso-oktan mch toluol iso-oktan mch henry = 0.25 (toluene) henry = 4.23 (mch) henry = 132 (iso-octane) biodegradation degassing to atmosphere fate of contaminant depending on biodegradation rate constant 2d numerical experiment, napl mixure degradation degassing figure 4: relation of degassing rate to atmosphere compared to biodegradation rate for three selected compounds with different henry’s law constant h. sensitivity analyses to evaluate the importance of soil and meteorological parameters for the contaminant behaviour, sensitivity analyses on biodegradation rate constants, henry’s law constant h, aqueous saturation concentration csat for the different compounds, temperature, soil water content and possible anaerobic conditions were conducted in 1d and 2d. the overall biodegradation rate depends strongly on henry’s law constant. highly volatile compounds are slowly degraded (see iso-octane, figure 4) compared to low h compounds such as btex (see toluene in figure 4), because biodegradation takes place only in the aqueous phase. the ratio of the atmospheric escape to biodegraded mass versus h at a constant degradation rate constant (pseudo first order) is shown in figure 5. it demonstrates that low h compounds degrade more efficiently. this can be explained by the large fraction of such compounds occurring in the aqueous phase. henry [-] 25°c % o fi n iti al m as s 100 101 102 0 10 20 30 40 50 60 70 80 90 100 degradation % degassing to atmosphere % toluene h = 0.25 hexane h = 75 iso-octane h = 132 mch h = 4.23 mcp h = 15 fate of contaminant in % of initial napl mass; degr. rate 10 -̂5 s-1 figure 5: fate of organic contaminants in relation to henry‘s law constant. a uniform pseudo-first order biodegradation rate constant =10-5 s-1 was applied for all contaminants. gracosværløse 2d scenario (14 compound mixture), depth of contaminant source 1 m. henry’s law constants from pasteris et al. (2001). natural attenuation of volatile hydrocarbons in unsaturated soil zone 13 de g radatio n rate c o ns tant [s -1] m as s in % of in iti al 1 0-6 10 -5 1 0-4 1 0-3 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 0 10 0 m-xyle ne bio de g rada tio n de g as s ing to atmo s phe re mas s s till pre s e nt figure 6: fate of m-xylene in relation to pseudo first order biodegradation rate constant. gracosværløse 2d scenario (14 compound mixture), depth of contaminant source 1 m. depletion of the napl phase can be accelerated by rapid biodegradation. this is because the evaporation of the napl constituents is enhanced due to steep concentration gradients which are maintained by biodegradation (figure 6). increasing soil water contents reduce the degassing to the atmosphere and thus slightly increase the fraction biodegraded as long as no oxygen limitation occurs. higher temperatures enhance the volatilisation of the napl constituents in general and therefore lead to both, more rapid degassing to the atmosphere and faster biodegradation. the significance of oxygen depletion at the napl source and possible anaerobic degradation scenarios were also tested using the model. three different anaerobic scenarios can be distinguished: (1) degradation by electron acceptors such as nitrate and sulphate, (2) reduction of iron oxide or manganese oxide containing soil minerals and (3) methanogenesis. nitrate and sulphate reduction (1) can be neglected due to the low concentrations in rain (scheffer and schachtschnabel, 1992). reduction of oxides (2) can occur e.g. in iron oxide rich soils, but is kinetically limited. methanogenesis (3) is often observed in heavily contaminated soils if the oxygen supply is restricted. the scenarios required to establish anaerobic conditions were evaluated further as described below. in a 1d scenario there is no lateral possibility for oxygen supply and anaerobic conditions can develop quickly, but this scenario is not very realistic for a field case. in a 2d model, the values required for methanogenesis at the field site are constant volumetric water content larger than 14 % (with a porosity of 35 %, a benzene fermentation rate constant of 7.8 x 10-6 mg l-1s-1 (zero order), a methane oxidation rate constant of 10-5 s-1 (pseudo first order), and an inhibition threshold of 0.03 mg/l oxygen). the napl source in this scenario contained only benzene, which is highly soluble and fast degassing, i.e. rapidly consuming oxygen (figure 7). under this condition, small concentrations of methane gw flow direction [m] de pt h [m ] 0 5 10 15 0 1 2 3 4 ch4(g) 1.02e-03 8.49e-04 6.81e-04 5.14e-04 3.46e-04 1.78e-04 1.00e-05 methane partial gas pressure [atm] 0.1 % 0.001 % g_i, t = 5.000e+01 days figure 7: methane concentration at maximum, 20 days after source installation in 2d simulation. grathwohl and maier 14 time [days] pa rt ia lg as pr es su re [a tm ] 0 100 200 3000 0.0025 0.005 0.0075 0.01 0.0125 0.015 0.0175 0.02 co2(g) 3d model co2(g) værløse field data g_i, volume = 4914, located 1 m below center of napl source, x = 0.0 m y = 0.0 m z = 2.3 m depth component partial gas pressures in atm, 3d model figure 8: a first comparison of measured and simulated carbon dioxide concentrations at a sampling port 1 m below the centre of the kerosene source. (< 1 % vol.) occur at the capillary fringe below the napl source. if soil water contents approach saturation, then the zone of methane formation moves closer to the napl source due to faster oxygen. for the kerosene composition used in the field experiment, however, oxygen depletion was neither predicted by the model nor observed at the field site. thus, anaerobic conditions can only be expected for fine grained material with high water content or very large, extended napl sources, especially if they are deep or close to the groundwater table. calibration the numerical simulations demonstrated that in the scenario investigated most of the contaminant mass in the unsaturated zone will either be transported to the atmosphere or be subject to biodegradation. only a very small fraction will diffuse across the capillary fringe and end up in the groundwater. parameters, which are not measured independently have to be fitted in the model. this will occur most likely for the biodegradation rate constants in the unsaturated zone. after the contaminant spreading in the vadose zone is quantified, mass transfer to groundwater can be evaluated by realistic estimates of transverse vertical dispersion and diffusion in the capillary fringe (see klenk and grathwohl, 2002; eberhardt and grathwohl, 2002; gaganis et al., 2002). if the model accounts for a depth and timedependent temperature field (lower vapour pressures in the winter months), then the agreement with measured data improves significantly compared to constant temperature simulations as shown in figure 8. a temporally variable unsaturated flow field due to infiltration events results in elevated concentrations of co2 during longer precipitation periods. this can be explained by higher pore water saturation in the top soil which diminishes the diffusive transport of the biodegradation product to the atmosphere. figure 8 shows good agreement of field observations with pure forward-modelling. the field experiment is ongoing and more data will be provided in future papers. conclusions measured data at the controlled field experiment of a kerosene spill at v!rløse field test site, on natural attenuation in the unsaturated zone can be reproduced with the numerical model min3p. modelling results illustrate that the overall biodegradation rates depend mainly on distribution parameters such as henry’s law constant of the fuel constituents, on the biological degradation rate constant, on the soil water content, and on the temperature. the contaminant transfer into groundwater depends on all of these properties and can be determined after quantification of the processes in the unsaturated zone. results of the field investigations allow the validation of the model, that can then be used to quantify the risk of groundwater contamination for a variety of different scenarios. references christophersen, m., m. broholm, and k. kjeldsen. 2002. migration and degradation of fuel vapours in the vadose zone. in: groundwater risk assessment at contaminated sites. halm and grathwohl (eds.). proceedings of the 1st gracos workshop, tübingen 22./23.02.02, 83-87. eberhardt, c. and p. grathwohl. 2002. time scales of pollutants dissolution from complex organic mixtures: blobs and pools. invited paper for special issue of j. cont. hydrol. on site remediation (in print). gaganis, p., e.d. skouras, m. theodoropoulou, and v. burganos. 2002. modelling contaminant emission across the capillary fringe. in: groundwater risk assessment at contaminated sites. halm & grathwohl (eds.). proceedings of the 1st gracos workshop, tübingen 22./23.02.02, 119-124. natural attenuation of volatile hydrocarbons in unsaturated soil zone 15 grathwohl, p. and i. klenk. 2000. groundwater risk assessment at contaminated sites (gracos). in: contaminated soil 2000 (12):831-834, w. harder et al., (eds). leipzig: thomas telford. höhener, p., n. dakhel, d. werner, and g. pasteris. 2002. biodegradation of volatile organic compounds in the unsaturated zone. in: groundwater risk assessment at contaminated sites. halm & grathwohl (eds.). proceedings of the 1st gracos workshop, tübingen 22./23.02.02, 88-93 . hughes-conant, b, r.w. gillham, and c.a. mendoza. 1996. vapor transport of trichlorethylene in the unsaturated zone: field and numerical modeling investigations. water resources research 32(1): 9-22. klenk, i.d. 2000. transport of volatile organic compounds (voc’s) from soil-gas to groundwater. phd dissertation, tga, c55, geological institute, tübingen. klenk, i.d. and p. grathwohl. 2002. transverse vertical dispersion in groundwater and the capillary fringe. j. cont. hydrology 58 (1-2):111-128. reckhorn, s.b.f., g. wang, and p. grathwohl. 2002. volatilization rates of organic compounds in the unsaturated zone. in: groundwater risk assessment at contaminated sites. halm & grathwohl (eds.). proceedings of the 1st gracos workshop, tübingen 22./23.02.02, 101-107. mayer, k.u. 1999. a multicomponent reactive transport model for variably saturated media. phd-thesis at the university of waterloo, department of earth sciences, waterloo, ontario, canada. pasteris, g., d. werner, k. kaufmann, and p. höhener. 2001. vapor phase transport and biodegradation of volatile fuel compounds in the unsaturated zone: a large scale lysimeter study. environ. sci. technol. submitted. scheffer, f. and p. schachtschabel. 1992. lehrbuch der bodenkunde. 13. auflage, stuttgart, 491 p. wiedemeyer, t.h., h.s. rifai, c.j. newell, and j.t. wilson. 1999. natural attenuation of fuels and chlorinated solvents in the subsurface. john wiley and sons, new york. _________________________________________ received september 2002. accepted november 2002. img033 img034 img035 img036 img037 img038 img039 img040 research paper journal of agricultural and marine sciences 2023, 28(2): 07–13 doi: 10.53541/jams.vol28iss2pp07–13 received 6 february 2022 accepted 22 february 2023 استجابة املعاملة املسبقة بنقع بذور الفجل الكرزي ).raphanus sativus l( يف حملول كلوريد الصوديوم على حتمل منو النبات حتت ظروف اإلجهاد امللحي إدريس أمحد اجلهاين 1 * ، سامي علي العشييب 1 ، طاهر حممد حممد 1 ، عبد احلكيم سعد بين 2 influence of seed pretreated in sodium chloride on the salt tolerance of cherry radish (raphanus sativus l.). idress a. al gehani1* sami a. alasheebi1 taher m. mohammed1 and abdulhakim s. banni2 idress a. al gehani1* ( ) idress.algehani@uob.edu.ly, 1department of plant production, faculty of agriculture, university of benghazi, benghazi, libya, 2department of botany, faculty of arts and sciences (almarj), university of benghazi, libya. introduction salinity in soil or water is one of the major abiotic stresses that are widespread in the world (ibra-him, 2016), as about 20% of the world’s cultivated land and half of the irrigated land are affected by salinity (kasim et al., 2016). thus, it is considered a main factor reducing crop productivity in arid and semi-arid areas (cayuela et al., 2001). salinity may occur as a result of over-irrigation, irregular drainage, and imbalanced application of fertilizers (ayyub et al., 2016). salt stress affects all major plant processes such as growth, photosynthesis, protein synthesis, and metabolism of amino acids and organic acids (kasim et al., 2016) through the osmotic effect induced by water deficit. the salinity of the soil solution reduces the ability of plants to absorb water or is influenced by the specific effect of excessive amounts of absorbed salts, especially na+ and cl-. in addition to their toxic effects on plants, they reduce the absorption of nutrients, as well as ionic imbalance (moabstract. this study was conducted to evaluate the effect of sodium chloride (nacl) seed soaking on seed germination and plant growth of cherry radish (raphanus sativus l.) under saline conditions. seeds were pretreated by soaking in nacl solutions at concentrations of 0, 1500, 3000 and 4500 ppm. the pretreated seeds were divided into two groups: the first group was germinated in petri dishes, and the second group was sown in pots. both groups were irrigated with different concentrations of salinity (tap water, 1000, 2000 and 3000 ppm nacl). the results indicated that the salinity of the irrigation water decreased the seed germination percentage and leaf chlorophyll content under a salinity level of 3000 ppm. on the other hand, pretreatment of seeds with nacl solution led to a gradual increase in germination percentage and total chlorophyll content of leaves. pretreatment with 4500 ppm nacl gave comparable values to the effect of control treatment under irrigation conditions with 1000 and 2000 ppm salinity. however, pretreatment of seeds with nacl led to a gradual decrease in germination percentage, reaching 60% under a salinity level of 3000 ppm, and no obvious effect was seen on the leaf chlorophyll contents. pretreatment of seeds by nacl solutions increased the root and shoot fresh and dry weights, while shoot and root weight gradually decreased with the increasing salinity of irrigation water and regardless of the effects attributed to seed pretreatment. the increase in irrigation water salinity also led to a decrease in leaf area, and root length and root diameter, as well as root water contents. in contrast, the salinity led to a gradual increase in leaf specific weight, while the value of leaf number and leaf water contents were not affected. therefore, the increased specific leaf weight as a result of the salinity of the irrigation water gave an indication that soaking the seeds in saline solutions increased the plant tolerance to salinity that lead to better plant growth. keywords: soaking seeds, salinity, salt tolerance, radish امللخــص: بــذور فجــل كــرزي ).raphanus sativus l( اســتنبتت يف أطبــاق بــري يف حــن زرعــت جمموعــة أخــرى يف أصــص لدراســة أتثــر املعاملــة املســبقة بنقــع البــذور يف حماليــل كلوريــد الصوديــوم )nacl( بركيــزات 0، 1500، 3000 و 4500 جــزء يف املليــون علــى إنبــات ومنــو النبــات حتــت ظــروف امللوحــة ابلــري بركيــزات خمتلفــة مــن امللوحــة )مــاء الصنبــور،1000، 2000 و 3000 جــزء يف املليــون(. أشــارت النتائــج إىل أن الــزايدة يف ملوحــة ميــاه الــري أدت إىل اخنفــاض نســبة إنبــات البــذور )gp( وإمجــايل حمتــوى األوراق مــن الكلوروفيــل حتــت مســتوى ملوحــة بلــغ 3000 جــزء يف املليــون. حيــث أدت املعاجلــة املســبقة للبــذور مبحلــول nacl إىل زايدة تدرجييــة يف gp وحمتــوى الكلوروفيــل الكلــي لــأوراق. مــن الواضــح أن املعاجلــة املســبقة بـــ 4500 جــزء يف املليــون مــن nacl أعطــت قيمــاً مماثلــة لتأثــر معاملــة املقارنــة حتــت ظــروف الــري مــع ملوحــة 1000 و 2000 جــزء يف املليــون. مــن انحيــة أخــرى، أدت املعاجلــة املســبقة للبــذور nacl إىل اخنفــاض تدرجيــي يفgp وصــل إىل %60 حتــت ظــروف الــري مبســتوى ملوحــة 3000 جــزء يف املليــون، ومل يالحــظ أي أتثــر واضــح علــى حمتــوى الكلوروفيــل. أدت املعاجلــة املســبقة للبــذور عــن طريــق النقــع يف حماليــل nacl إىل زايدة الــوزن الطــازج )fw(والــوزن اجلــاف )dw( لــكل مــن اجملمــوع اخلضــري واجلــذري. بينمــا اخنفــض وزن اجملمــوع اخلضــري واجلــذري تدرجييــاً مــع زايدة ملوحــة ميــاه الــري وبغــض النظــر عــن التأثــرات املنســوبة إىل املعاملــة املســبقة للبــذور. أدت الــزايدة يف ملوحــة ميــاه الــري أيًضــا إىل اخنفــاض مســاحة الورقــة )la(، وطــول )lr( وقطــر )dr( اجلــذور، وحمتــوى املــاء )wc( للجــذور. يف املقابــل، أدت امللوحــة إىل زايدة تدرجييــة يف الــوزن النوعــي لــأوراق )slw(، بينمــا مل تتأثــر قيمــة عــدد األوراق )ln(وحمتواهــا املائــي )wc(. لذلــك، فــإن زايدة slw نتيجــة مللوحــة ميــاه الــري، ممــا يعطــي مؤشــرا علــى أن نقــع البــذور يف احملاليــل امللحيــة يزيــد مــن قــدرة حتمــل النبــات لظــروف اإلجهــاد امللحــي، ممــا يــؤدي إىل منــو وتطــور أفضــل للنبــات. الكلمات املفتاحية: نقع البذور، ملوحة، حتمل امللوحة، فجل. 8 squ journal of agricultural and marine sciences, 2023, volume 28, issue 2 influence of sodium chloride seed soaking pretreatment on salt tolerance of cherry radish (raphanus sativus l.) hamed and gomaa, 2012). salinity decreases the co2 assimilation rate, and the excess of light absorbed that is not used by the plant can lead to an increase in reactive oxygen species production and, consequently, oxidative stress (ma et al., 2020). these stressful conditions cause a change in the hormonal balance of plants, such as a decrease in auxins and gibberellins and an increase in abscisic acid in plant tissues (ibrahim, 2016). the radish plant is a root vegetable, and it belongs to the cruciferous family. its roots are consumed fresh and sometimes in pickling, and it has several therapeutic benefits. due to the importance of this crop and the consumer demand for it, this led to an increase in the spread of its cultivation, but it faced the problem of salinity, which led to a decrease in production. the researchers indicated that salinity reduced the percentage and rate of germination of radish seeds (jamil et al., 2007; kaymak et al., 2009). several studies have shown that salinity reduces plant height, leaf area, and the fresh and dry weight of the shoot and root of the radish plant (mohamed and gomaa, 2012; chaparzadeh and hosseinzad-behboud, 2015; jasim et al., 2016). it was also found by de sousa basílio et al. (2018) that salinity reduced the number of leaves and the diameter of the root of radish plants. in addition, salinity has decreased the root length, shoot length, and fresh weight of the shoot and root parts (jamil et al., 2007). salinity reduced the percentage of chlorophyll (yildirim et al., 2008; chaparzadeh and hosseinzad-behboud, 2015; jasim et al., 2016) and relative water content of radish plant leaves (yildirim et al., 2008). whereas jamil et al. (2007) discovered that salinity decreased the content of chlorophyll in leaves while having no effect on the water content of radish leaves. on the other hand, mohamed and gomaa (2012) indicated that the content of chlorophyll a, b, and total as well as the content of iaa and ga3 have decreased. in contrast, the content of abscisic acid has increased. based on the increased risks of salinity and the need for better salinity-tolerant crops (esmaielpour et al., 2006), and to reduce the effect of salinity on the growth and production of crops, many treatments are carried out on plants, such as seed soaking with antioxidants, growth regulators, and salts (gebreegziabher and qufa, 2017). soaking the seeds is one of the beneficial physiological methods by which plants can adapt to saline conditions, and it is an easy, low-cost, and safe technique that is used to overcome the salinity problem in agricultural lands (ibrahim, 2016). seed soaking or pretreating with nacl is considered a successful method because it not only reduces the effect of salt stress during germination but also increases the salinity tolerance during the plant growth stage (sivriepe et al., 2005). for instance, treating maize seeds in nacl solution increased the percentage and speed of germination, plant height, length of branches, and yield under salt stress conditions (gebreegziabher and qufa, 2017). esmaielpour et al. (2006) also reported that pretreating cucumber seeds with nacl increased the percentage and rate of germination, dry weight, and length of roots under saline stress conditions. on the other hand, it decreased the percentage of na+ and increased the content of k+, ca+2, and proline in plants. bajehbag (2010) found that treating sunflower seeds with nacl increased the percentage of germination and reduced the time required for germination. it also increased root length, plant height, plant dry weight, and the number of leaves. in another study, sivritepe et al. (2005) reported that treating watermelon seeds with nacl increased the dry matter of leaves, leaf area, number of leaves, and plant height as well as chlorophyll content. in tomato, seed treatment with nacl increased plant biomass, fresh and dry weight of shoots and root dry weight, decreased na+ and cl-content, and increased k+ in the plant (cayuela et al. 2001). seed pretreatment has proved to be an effective technique to improve the germination performance, seedling growth, and seed yield of maize (tian et al., 2014). cao et al. (2018) indicated that seeds soaked with nacl could remarkably enhance antioxidant metabolism, thereby decreasing the accumulation of reactive oxygen species and membrane lipid peroxidation during germination under water stress. therefore, due to the dependence of the benghazi plain region in libya on groundwater for irrigating crops, and this source having a relatively high salt content, that would negatively affect agricultural production in this region. based on the previously mentioned benefits of pretreatment of seeds before sowing and its positive effect in facing the problems of high salinity levels, this study aims to know the effect of soaking seeds in solutions of sodium chloride salt on the growth and development of the radish plant under salt stress conditions. materials and methods plant material, growth conditions and treatments the experiment was carried out by planting the cherry radish variety (raphanus sativus l.) at the research station of the faculty of agriculture-university of benghazi, libya during the winter seasons of 2018 and 2019. the seeds were pretreated by soaking in solutions of different concentrations of sodium chloride (nacl) at 0, 1500, 3000, and 4500 ppm at room temperature for 24 h. one group of pretreated seeds (20 seeds) were placed in each petri dish to calculate their germination percentage at 19°c (wilcox and pfeiffer, 1990). another group of pretreated seeds (4 seeds) was sown in a silty clay soil mixed with sand and compost (1:1:1 vol.) in a 3-l pot (20×20 cm diameter × height), two seedlings were maintained in each pot. soil composition was 1.27% organic matter, 20% calcium carbonate, ph 7.56, ec 0.98 dsm−1, available p 10.4 ppm and total n 0.11%. throughout the experiment, the plants were fertilized by modified hoagland solution as a complete nutrient solution with irrigation. 9research paper al gehani, alasheebi, mohammed, banni the full nutrient solution contains (mmol l-1) 5 kno3, 5 ca(no3)2•4h 2o, 2 mgso4•7h2o, 1 kh2po4, mixture of 0.02 feso4•7 h2o; 0.02 na2edta; 2 h2o; 0.045 h3bo3; 0.01 mncl2•4 h2o, and (in μmol/l) 0.8 znso4•7 h2o, 0.4 na2moo4•2 h2o, and 0.3 cuso4•5 h2o. seedlings were grown under a plastic canopy for protection from rain at 10 h photoperiod, photosynthetic active radiation reached a daytime peak value of 800 µmol m-2 s-1, the temperature and relative humidity were 17/9 °c and 70/89% during day/night periods, respectively. treatments began with the sowing of pretreated seeds, followed by irrigation with various concentrations of salty water. the irrigation was carried out daily with 4 levels of salt water: tap water (the concentration of salts is about 500 ppm), 1000, 2000, and 3000 ppm, prepared by adding 0, 500, 1500, and 2500 ppm of nacl to tap water, respectively. the amount of irrigation was added according to the needs of the plant and the change in the daily temperature. with respect to the increase in the size of the plant in terms of the gradual increase in the amount of irrigation water needed by the plant to reach the field capacity at each irrigation. treatments continued till 45 days until achieving the economic stage of cherry radish roots. germination and vegetative stage measurements the germination percentage (gp) was calculated as (the number of seeds germinated/the total seeds×100). ten seedlings for each treatment were used to measure and count the fresh weight (fw) of shoots and roots, the leaf number and leaf area (ln and la), as well as the length and diameter of roots (rl and rd) at the end of the experiments. the plants were dried for 72 hours in an oven at 65 °c (until there was no decrease in weight) for the determination of dry weight (dw) and percentage of water content (wc) of shoots and roots. according to morgan (1984), the wc was calculated as wc={(fw-dw)/fw}*100 the specific leaf weight (slw) was determined by dividing values of leaf dry weight by leaf area (lei zhang et al., 2012). the total chlorophyll content of the leaves was calculated on a fresh weight according to moran (1982). a fully developed leaf was selected from the middle section of shoots on each plant. ten leaf discs were punched and immersed in 10 ml of n,n-dimethylformamide (moran and porath, 1980). the samples were stored in darkness at 4°c for 24 h. the absorbance of the pigment extract was determined photometrically at 603 nm, 647 nm, and 664 nm. experimental design and statistical analysis the data represents the mean values of two independent experiments for each season. the experiments were conducted using 5 replicates for each treatment (each figure 1. effect of seed soaking pretreatment in nacl solution and salinity of irrigation on germination percentage (gp) of radish seeds. bars represent standard errors. different letters indicate a significant difference between treatments by duncan’s multiple range test at 5% level. 10 squ journal of agricultural and marine sciences, 2023, volume 28, issue 2 influence of sodium chloride seed soaking pretreatment on salt tolerance of cherry radish (raphanus sativus l.) replicate consisted of 20 seeds in one petri dish for germination stage measurement and two plants in each pot for vegetative stage measurements). a factorial experimental 4×4 in a completely randomized design was used with the treatments of soaking seeds pretreatment and salinity of irrigation treatment. data were subjected to analysis of variance using a two-way anova test and means were compared by duncan’s means test (p<0.05) using the sas glm procedure (sas institute, cary, nc). result the results indicated that increasing the salinity of the irrigation water led to a gradual decrease in the germination percentage (gp) of radish seeds from 97% with the control treatment to 81% with the 3000 ppm treatment (figure 1). the total chlorophyll decreased from 31.6 to 22.6 (mg/100g fw) with 3000 ppm treatment (figure 2.). whereas the pretreatment of the seeds with nacl solutions led to a gradual increase in the gp and the content of leaves from total chlorophyll, which was accompanied by an increase in the concentration of the used solution. obviously, the pretreatment with 4500 ppm of nacl results in comparable value to the effect of the control treatment under the condition of irrigation with 1000 and 2000 ppm of salinity (figures 1 and 2). on the other hand, the pretreatment of the seeds with nacl led to a gradual decrease in the gp, reaching 60% under the condition of irrigation at a salinity level of 3000 ppm (figure 1), and no clear effect was shown on the amount of chlorophyll (figure 2). pretreatment of the seeds by soaking in nacl solutions increased the fresh weight (fw) and dry weight (dw) of both shoots and roots. the shoot was from 16.9 and 1.3 to 23.4 and 1.9 g, respectively, and the root was from 7.46 and 0.6 to 12.8 and 0.9 g, respectively (tables 1 and 2). while the shoot and root weight were gradually decreased with increasing the salinity of the irrigation water, regardless of the effects attributed to the pretreatment of the seeds. the increase in the salinity of the irrigation water also led to a decrease in the leaf area (la) (table 1), the length (lr), diameter (dr) and water content (wc) of the roots (table 2), and in contrast to a gradual increase in the specific weight of the leaf (slw), while the value of the number of leaves (ln) and their water content (wc) were not affected (table 1). discussion salt stress caused significant decrease in the germination and growth of radish. the decrease was attributed to the increased salts in the irrigation water led to a rise in the osmotic pressure of the soil solution, which led to an increased in the viscosity of the soil solution (kaymak et al., 2009; bajehbaj, 2010). on the other hand, the figure 2. effect of seed soaking pretreatment in nacl solution and salinity of irrigation on chlorophyll content of radish leaves. bars represent standard errors. different letters indicate a significant difference between treatments by duncan’s multiple range test at 5% level. 11research paper al gehani, alasheebi, mohammed, banni toxic effects of na+ and clions may cause the seeds to die or delay their germination, which led to a decrease in the gp. it was indicated that pretreatment by soaking the seeds in a nacl solution increased the gp of radish seeds, as reported by gebreegziabher and qufa (2017). perhaps the reason is that pretreatment by soaking the seeds in saline solutions may cause hardening of the seeds and a physiological change in the internal components of the seed. subsequently, which results in an increased ability of the seed to absorb water and an increased tolerance to the toxic effects of salts, which helped it to grow and developed in saline conditions. indeed, the high level of water irrigation salinity led to reducing the fw and dw of the shoot part and la of the plant (table 1). similar results were reported by mohamed and gomaa (2012) and jasim et al. (2016). the decrease in vegetative growth measurements was due to the increased salinity of the irrigation water could reduce the amount of water absorbed by the roots. this event could be attributed to the increase in the osmotic pressure of the soil solution and the accumulation of salts with toxic effects on the root growth zone. increasing the plant’s absorption of some elements, such as na and cl ions reduced the availability of some nutrients necessary for plant growth, such as nitrogen, phosphorous and potassium. subsequently, it negatively affected the efficiency of the photosynthesis process and caused a decrease in all vital processes (ma et al., 2020), thus reduced plant growth. in fact, the increase in the salinity of the irrigation water led to a decrease in the total chlorophyll content in the leaves (figure 2). this was previously noted, whereas there was a decrease in the plant’s ability to absorb the necessary nutrients, some of which enter into the formation of the chlorophyll molecule, such as nitrogen and magnesium, or have an important role in its formation processes, such as iron (mohamad and gomma, 2012). this decrease was due to the unavailability of these nutrients as a result of high soil ph or the replacement of harmful salts such as na+ in the exchange sites in the soil. in contrast, the increase in the total chlorophyll content in the leaves can be explained as a result of the plant’s adaptation to growth in saline conditions. additionally, the absorption of water and nutrients has been achieved with a higher efficiency state, which is in agreement with results mentioned by sivritepe et al. (2005). whereas, the pretreatment of seeds with nacl solution increased the vegetative growth of the plant such as the fw and dw of the shoots, ln, la and slw (table 1), which is consistent with results mentioned by many researchers (cayuela et al., 2001; sivritepe et al., 2005; bajehbaj 2010). the increase in plant growth may be due to the physiological changes that occurred in the plant as a result of seed pretreatment, which led to a high osmotic pressure of the plant cells and thus an increase in water absorption through the roots. this can be due to increase in table 1. effect of seed soaking pretreatment in nacl solution and salinity of irrigation on fresh weight (fw), dry weight (dw), leaf number (ln), leaf area (la), specific leaf weight (slw) and water content (wc) of radish shoots treatments measurements conc. of seed socking solution (nacl ppm) salinity of irrigation (ppm) fw (g/shoot) dw (g/shoot) ln (leaf ) la (cm2) slw (g/cm2) wc (%) 0 500 1000 2000 3000 16.98b-f 11.24g-h 9.94h 9.56h 1.36a-e 0.80de 0.70e 0.86c-e 6.20e 6.20e 6.25e 6.20e 131.93ab 69.20de 47.79e 43.61e 0.144h 0.165d-h 0.177d-g 0.186c-f 91.82b-f 92.56a-d 92.48a-d 91.01e-g 1500 500 1000 2000 3000 23.46a 19.22bc 16.82b-f 13.26e-h 1.96a 1.38a-e 1.58a-c 1.24a-e 8.00a 7.60ab 6.60de 6.75de 136.85ab 123.25a-c 107.27b-d 67.22de 0.145h 0.156gh 0.158f-h 0.212bc 91.95b-f 92.77a-c 90.90fg 91.10e-g 3000 500 1000 2000 3000 20.30ab 17.20b-e 15.24c-g 13.72d-h 1.34a-e 1.22b-e 1.47a-d 1.36a-e 6.27e 6.80c-e 7.40a-c 6.80c-e 135.07ab 127.00a-c 136.20ab 62.50de 0.170d-h 0.175d-g 0.188c-e 0.230ab 93.38a 92.95ab 90.48g 91.82b-f 4500 500 1000 2000 3000 20.20ab 17.68b-d 12.98f-h 13.72d-h 1.70ab 1.42a-e 1.12b-e 1.28a-e 7.00b-d 6.60de 6.20e 6.33e 157.71a 128.67a-d 83.66c-e 57.37e 0.145h 0.160e-h 0.194cd 0.242a 91.34d-g 92.18b-f 91.62c-g 91.10e-g means followed by the same letter in each column are not significantly different by duncan’s multiple range test at 5% level. 12 squ journal of agricultural and marine sciences, 2023, volume 28, issue 2 influence of sodium chloride seed soaking pretreatment on salt tolerance of cherry radish (raphanus sativus l.) the proportion of important nutrients, such as potassium and calcium, and thus an increase in the efficiency of vital processes such as photosynthesis, building plant tissues, and the transpiration process. these processes greatly affected the absorption of water by opening and closing stomata. indeed, the prior treatment may increase the proportion of some amino acids, such as proline, which accumulate when a plant was stressed to try to recover from the damage caused by it. therefore, since the prior treatment with nacl salt increased the wc of the plant tissue (table 1. and 2.) and the content of chlorophyll in the leaves (figure 2), all these factors increased the efficiency of the photosynthesis process and increased plant growth. indeed, the decrease in the growth measurements of the roots (table 2) is due to the negative effects of salinity on the vegetative growth stage of the plant, the chlorophyll content of the leaves, the efficiency of the photosynthesis process, and all the vital processes related to the high osmosis, including ec and ph in the soil solution. eventually, this led to a decrease in the fw and dw of the root, as well as the lr and dr of the root (jamil et al., 2007; jasim et al., 2016; de sousa basílio et al., 2018). indeed, there are many studies that agree with our findings, as the pretreatment of seeds by soaking them in nacl solution reduces the negative effect of the salinity of irrigation water (cayuela et al., 2001; esmaielpour et al., 2006; tian et al., 2014). on the contrary, it increased the fw and dw of the root and the lr and dr of the root (table 2). this effect was due to the increase in the adaptability and tolerance of the plant to the conditions of salt stress as a result of soaking the seeds in nacl solution. moreover, which led to an increase in the vegetative growth of the plant and an increase in the concentration of pigments involved in the photosynthesis process. subsequently, this reflected positively on the growth of the root system and the increased in the wc of the root due to the prior treatment of seeds. finally, it indicated that the plant has adapted to the surrounding conditions and increased its ability to absorb water more efficiently, which increases plant growth. a decrease in the wc of the root system with an increase in the salinity of the irrigation water may be attributed to the inability of the plant to absorb a sufficient amount of water. plant deficiency may be due to the high osmotic pressure of the soil solution due to the increase in the amount of salt dissolved in it (yildirim et al., 2008). in contrast, the pretreatment of the seeds slightly increased the wc of the shoot and root system, which may be due to the increase in the osmotic pressure of the plant, thus enabling it to absorb more water through its roots. conclusion the salinity of the irrigation water caused significant decrease in plant growth, seed germination and chlorophyll content of leaves. soaking of seeds in nacl solution imtable 2. effect of seed soaking pretreatment in nacl solution and salinity of irrigation on fresh weight (fw), dry weight (dw), length (lr), diameter (dr) and water content (wc) of radish roots. treatments measurements conc. of seed socking solution (nacl ppm) salinity of irrigation (ppm) fw (g/root) dw (g/root) lr (cm) dr (cm) wc (%) 0 500 1000 2000 3000 7.46bc 4.24c-f 2.88ef 2.70f 0.63d-g 0.43h 0.25h 0.26h 2.48b-f 1.78f 1.90ef 1.71f 2.06c-g 1.64e-g 1.45fg 1.42g 93.16ab 92.81a-c 91.13b-e 89.55e 1500 500 1000 2000 3000 12.86a 13.12a 6.20c-e 6.80cd 0.84a-d 0.82a-d 0.70c-f 0.62d-g 3.42a 2.40b-f 2.44b-f 2.32b-f 2.66a-c 3.13a 2.00c-g 1.80d-g 93.96a 93.91a 91.12b-e 89.77de 3000 500 1000 2000 3000 10.83ab 13.55a 7.07cd 4.88c-f 0.67d-g 0.79b-e 0.96ab 0.56e-g 2.58b-e 2.36b-f 2.96ab 2.44b-f 2.26b-f 2.43a-d 2.16c-g 1.81d-g 93.56ab 94.20a 91.31b-e 89.44e 4500 500 1000 2000 3000 10.88ab 12.80a 7.00cd 3.95d-f 0.93a-c 1.05a 0.85a-d 0.47f-h 2.38b-f 3.00ab 2.48b-f 2.18c-f 2.53a-d 3.03ab 2.33a-d 1.66e-g 92.20a-d 93.33ab 90.28de 90.53c-e means followed by the same letter in each column are not significantly different by duncan’s multiple range test at 5% level. 13research paper al gehani, alasheebi, mohammed, banni proved the germination, chlorophyll content, and fresh and dry weight of shoot and root under salinity conditions. acknowledgments thank you to everyone who collaborated with us to make this work a success, and also to the employees of the research farm of the faculty of agriculture at the university of benghazi for their assistance. references ayyub cm, shaheen mr, raza s, yaqoob ms, qadri rwk, azam m, akhtar n. (2016). evaluation of different radish (raphanus sativus l.) genotypes under different saline regimes. american journal of plant sciences 07(06): 894-898. bajehbaj aa. (2010). the effects of nacl priming on salt tolerance in sunflower germination and seedling grown under salinity conditions. african journal of biotechnology 9(12): 1764-1770. cao y, liang l, cheng b, dong y, wei j, tian x, peng y, li z. (2018). pretreatment with nacl promotes the seed germination of white clover by affecting endogenous phytohormones, metabolic regulation and dehydrin-encoded genes expression under water stress. international journal of molecular science 19: 1-15 (article 3570). cayuela e, estañ mt, parra m, caro m, bolarin mc. (2001). nacl pre-treatment at the seedling stage enhances fruit yield of tomato plants irrigated with salt water. plant and soil 230(2): 231-238. chaparzadeh n, hosseinzad-behboud e. (2015). evidence for enhancement of salinity induced oxidative damages by salicylic acid in radish (raphanus sativus l.). journal of plant physiology & breeding 5(1): 23-33. de sousa basílio ag, vieira de sousa l, da silva ti, de moura jg, de melo gonçalves ac, de melo filho js, jardelino dias t. (2018). radish (raphanus sativus l.) morphophysiology under salinity stress and ascorbic acid treatments. agronomía colombiana 36(3): 257-265. esmaielpour b, ghassemi-golezani k, khoei fr, gregoorian v, toorchi m. (2006). the effect of nacl priming on cucumber seedling growth under salinity stress. journal of food agriculture and environment 4(2): 347-349. gebreegziabher bg, qufa ca. (2017). plant physiological stimulation by seeds salt priming in maize (zea mays): prospect for salt tolerance. african journal of biotechnology 16(5): 209-223. ibrahim ea. (2016). seed priming to alleviate salinity stress in germinating seeds. journal of plant physiology 192: 38-46. jamil m, lee kj, kim jm, kim hs, rha es. (2007). salinity reduced growth ps2 photochemistry and chlorophyll content in radish. scientia agricola 64(2): 111-118. jasim ah, al timmen wma, abid as. (2016). effect of salt stress on plant growth and free endogenous hormones of primed radish (raphanus sativus l.) seeds with salicylic acid. international journal of chemtech research 9(6): 339-346. kasim waea, saad-allah km, hamouda m. (2016). seed priming with extracts of two seaweeds alleviates the physiological and molecular impacts of salinity stress on radish (raphanus sativus l.). international journal of agriculture and biology 18(3): 653-660. kaymak hç, güvenç i̇, yarali f, dönmez mf. (2009). the effects of bio-priming with pgpr on germination of radish (raphanus sativus l.) seeds under saline conditions. turkish journal of agriculture and forestry 33(2): 173-179. lei zhang zz, zhang g, meng y, chen b, wang y. (2012). monitoring the leaf water content and specific leaf weight of cotton (gossypium hirsutum l.) in saline soil using leaf spectral reflectance. european journal of agronomy 41:103–117. ma y, dias mc, freitas h. (2020) drought and salinity stress responses and microbe-induced tolerance in plants. frontiers in plant science 11: 1-18 (article 591911). mohamed hi, gomaa ez. (2012). effect of plant growth promoting bacillus subtilis and pseudomonas fluorescens on growth and pigment composition of radish plants (raphanus sativus l.) under nacl stress. photosynthetica 50(2): 263-272. moran r, porath d. (1980) chlorophyll determination in intact tissues using n, n-dimethylformamide. plant physiology 65: 478-479. moran r. (1982). formulae for determination of chlorophyllous pigments extracted with n, n-dimethylformamide. plant physiology 69(6): 1376-1381. morgan jm. (1984). osmoregulation and water stress in higher plants. annual review of plant physiology 35: 299-319. sivritepe hö, sivritepe n, eriş a, turhan e. (2005). the effects of nacl pre-treatments on salt tolerance of melons grown under long-term salinity. scientia horticulturae 106(4): 568-581. tian y, guan b, zhou d, yu j, li g, lou y. (2014) responses of seed germination, seedling growth, and seed yield traits to seed pretreatment in maize (zea mays l.). the scientific world journal 2014: 1-8 yildirim ertan, turan metin, donmez mf. (2008). mitigation of salt stress in radish (raphanus sativus l.) by plant growth promoting rhizobacteria. roumanian biotechnol letter 13: 3933-3943. wilcox ge, pfeiffer cl. (1990) temperature effect on seed germination, seedling root development and growth of several vegetables. journal of plant nutrition 13(11): 1393-1403. pdf995, job 6 23 agricultural sciences, 7(2):23-28 (2002) © 2002 sultan qaboos university maintaining fresh-water aquifers over saline water in coastal aquifers e.g. youngs institute of water and environment, cranfield university, silsoe, bedford mk45 4dt england abstract: seepage analysis is used to investigate the location dependence of fresh-water inputs and outputs in maintaining the depth of the fresh water over the saline water intruding from the sea in coastal aquifers in steady state conditions. examples are given that show that maximum depths occur when the inputs are in the vicinity of the watershed and the outputs are near the coast. keywords: saline water intrusion, coastal aquifers, steady state, ghyben-herzberg lens, groundwater abstraction, seepage. resh-water aquifers overlying saline water near coasts are maintained by water supplied by surface infiltration or by injection into wells. relatively small rates of fresh water can maintain large bodies of freshwater and limit the amount of sea-water intrusion. however, exploitation of the freshwater aquifer reduces the depth of freshwater and can result in brackish water supplies from pumped wells. analyses of the movement of the fresh water under given conditions give the depth of the fresh-water lens at a given position. a complete analysis must consider the non-steady-state situation of the changing position of the interface between fresh-water and saline water regions considering also the movement of the saline water to and from the sea. here we consider the simpler steady-state situation when the interface remains stationary with no movement of saline water, to give an insight into the extent of the fresh-water region. examples using steady-state theory show the dependence of the depth of the fresh-water lens above the saline water on the location of inputs and outputs. steady–state analysis of fresh-water aquifer in the analysis of the so-called ghyben-herzberg lens of fresh water overlying saline water intruding from the sea in coastal aquifers (childs, 1969; bear, 1972), the assumption is made that no mixing takes place between the saline water and fresh water so that a sharp interface exists between the fresh-water region above and the saline water below in communication with the sea (fig.1). the upper boundary of the fresh-water aquifer is a water table where the soil-water pressure is atmospheric and the lower is the boundary between fresh and saline water where the pressure in the fresh water is the same as the pressure in the saline water. if z is the vertical coordinate of the interface measured from sea level, sρ the density of the saline water, and g the acceleration due to gravity, the soil-water pressure at the interface is gzp sz ρ−= . f ! !"#$%&'(!)*!+'#,'(!-#,'(!./*!01*/2'(!0345'(!6#1,'(!"#$%7!89:!0;*#<,'( 019=#>'(!01*/2'(! !"#$%&!'()*')! ! !0?? !"!+!!!!!!!!!!,-.!/01!2-345)!678905!:7;$<)!('7=>*!'()%>!?8-!2 !45)!"#$;5!%&'5)!(80$)!*)+,;-)!./)!678905!*0!5)!1945)!27 !!!!!!!!!!!!!!!!!!!!!!!!!!!!!34!2805765)!284%#5)!67895)!177'>!34!2/-345)!678/95)!8/>!2/$5795)!678/95)!(/9)+)!:/'#)*!;57/95)!27/95)!<7,=/7!>%/4 !!!2;-7?5)!@*#a5)!b!%=,5)!>791c)!de-!;f%)!2-)(+5)!63g!34!h7i495)!20?>c)j!k#,57-!(+=95)!d%l&!7>+'1!7m5%n*!?l9&! %95)*!3o795)!p%$5)!?>!(5765)!:$7#-!'(!b! youngs 24 figure 1. fresh water overlying saline water in coastal regions (not to scale). seepage analysis (youngs, 1965, 1966, 1986) gives the component of horizontal seepage of fresh water, qx, at position (x,y) in the x-direction as (youngs,1971a): zd x h kq h z x ! ∂ ∂ −= (1) where k is the hydraulic conductivity of the soil (assumed uniform here although the seepage analysis allows k to vary with depth), h = p/!fg +z the hydraulic head at a height z where the soil-water pressure is p, !f the density of freshwater, and h and z the water-table height and the level of the interface between fresh and heavier saline water at position (x.y), both measured from sea level. thus: x z g kp zd g kp x zd x p g k q f z h z f h z f x ∂ ∂ ρ − ρ∂ ∂ −= ∂ ∂ ρ −= !! (2) since p = 0 at z = h at the watertable and p = pz at z = z at the interface, pz = z!sg, so that: x g qx ∂ ∂ −= (3) where g is the seepage potential defined by: ! ρ ρ − ρ = h z f 2 s f 2 zk zd g pk g (4) similarly, the horizontal seepage qy in the y-direction is: y g q y ∂ ∂ −= (5) in steady-state conditions, if the vertical downward flux of fresh water through the watertable at (x,y) is q(x,y): )y,x(q y q x q yx = ∂ ∂ + ∂ ∂ (6) so that g is described by poisson’s equation: )y,x(q y g x g 2 2 2 2 −= ∂ ∂ + ∂ ∂ (7) at the coast where fresh water seeps into the sea, g = 0 and at a watershed where there is no horizontal seepage, .0g =∇ from equation 4, the value of g is an indication of the thickness of the fresh-water lens. if we assume the dupuit-forchheimer approximation of horizontal flow with head constant with depth, we have: 2 kz )1()( 2 kh )1( )( g 2 fsfs 2 fs fs −ρρρρ= −ρρ ρρ ≈ (8) so that the thickness t of the fresh-water lens is: k g2 )1( )( zht fs fs −ρρ ρρ =−= (9) fresh-water lens maintained by uniform infiltration with uniform steady infiltration q over a coastal strip of width l and with no water abstraction, all the water supplied over the area by infiltration drains to the sea. g at any distance x from the watershed is then obtained by solving the one-dimensional form of equation 7 with dg/dx = 0 at x =0 and g = 0 at x = l, giving: 2)xl(qg 22 −= (10) so that g0, the value of g at the watershed at x = 0, is ql2/2. the seepage analysis (youngs, 1965, 1966) allows estimates of water-table heights to be made within calculated limits. for this situation of uniform steady infiltration over a coastal strip, youngs (1971a) fresh saline interface (z = z) water table (z = h) infiltration sea well soil surface z x capillary rise maintaining fresh-water aquifers over saline water in coastal aquifers 25 figure 2. the variation of lh 0 and lz 0− with q/k as given by equations 11 and 12. argued that streamlines at the watershed diverged so that the hydraulic head gradient decreased with depth, leading to: )kq1)(/( )kq1/(kq( l h / )1/(kq( fs fs0 fs fs −ρρ +−ρρ << ρρ −ρρ (11) and )kq1/)(/( )kq1(kq l z )1/)(/( kq fsfs 0 fsfs +−ρρρρ − > − > −ρρρρ (12) where 0h and 0z are the values of h and z at x = 0. as shown in figure 2, the upper values of h0 and –z0 given by equations 11 and 12 are about 10% above the lower values at q/k = 0.005 and less for smaller values of q/k. the first terms in equations 11 and 12 are the expressions given by applying the approximate dupuit-forchheimer analysis to the problem (equation 8). thus, this approximate analysis provides a good estimate of the thickness t of freshwater at the watershed for small steady infiltration rates, as given by equation 9. due to the relatively small difference in density between fresh and saline water, a large thickness of fresh water, most of which is below sea level, can be obtained with only a small continuous supply from above. the shape of the fresh-water lens calculated from equation 10 assuming dupuitforchheimer approximations is shown in figure 3 in dimensionless variables. distributed input of fresh water the fresh-water aquifer in coastal regions is usually supplied by water non-uniformly over the area, not by uniform infiltration as considered above. the seepage analysis allows a consideration of the effect of location of the freshwater supply on the fresh-water region. we consider infiltration supplied at a rate q through a surface strip parallel to the coast between l’ and l” measured from the watershed with no abstraction of fresh water from the fresh-water aquifer. solving equation 7, we obtain the value of g, 0g , at the watershed at x = 0, as: ]2)ll(l[q]2)ll(l)[ll(qg s0 ′′+′−=′′+′−′−′′= (13) where qs is the seepage of fresh water per unit width draining to the sea, which is equal to the total amount of water being supplied per unit width over the strip. equation 13 shows that g0 is greatest when the infiltration is concentrated in the vicinity of the watershed and is least when concentrated near the sea. thus, from equation 9, it follows that the thickness of the fresh-water lens is also greatest when the infiltration is supplied in the vicinity of the watershed. the fresh-water aquifer can also be maintained by water supplied by injection into wells. for a series of m wells in a coastal aquifer with the nth well located at a distance ln from the watershed being injected at a rate qn, from seepage analysis and the mean value theorem of potential theory (youngs, 1970) (gav)0, the mean value of g along the watershed, is given by: " # $ % & ' −= ( = m 1n nn0av q)ll(b1)g( (14) where b is the length of the coastal strip. as with the case of infiltration through the soil surface, equation 14 indicates that maximum thickness of the fresh water lens is obtained when the injection wells are located near to the watershed. youngs (1971b) applied -7 -6 -5 -4 -3 -2 -1 0 1 0 0.5 1q/k h* z* z* h* figure 3. the dupuit-forchheimer estimate of the freshwater lens with uniform steady infiltration, shown as )qk()lh(*h = and )qk()lz(*z = as functions of lx . 0 0.2 0.4 0.6 0 0.005 0.01q/k -z 0/l h 0/l x10 z 0 h 0 df df youngs 26 methods used in potential theory to investigate optimum pumping conditions to avoid the upconing of saline water below the well providing an output of brackish water. the analysis allows values of gat any position (x,y) to be obtained and shows that for maximum supply of fresh water wells should be sunk to sea level and pumped with the level of water in them negligibly small. abstraction of fresh water water abstraction from the fresh-water lens can occur either from pumped wells or by capillary rise to supply surface evaporation. a fresh-water lens can be maintained with given fresh-water inputs and abstractions so long as dg/dx < 0 at x = l. if the loss is sufficiently large, then dg/dx > 0 at x = l and seawater intrusion will result. the rate of fresh-water seepage towards the sea between wells at distances lp and lp+1 from the watershed in a coastal strip is described generally by: 1pp x 0 p 1n n av lxl,qb1xd)xq( dx dg + = <<−′′−= ! ( (15) where gav is the mean value of g at distance x from the watershed. the surface flux distribution, q(x), is negative when there is capillary rise and qn is positive for injection and negative for abstraction. since g = 0 along x = l, integration of equation 15 yields: " " " " " # $ % % % % % & ' +−−− −−− +′′= " " " " " # $ % % % % % & ' −++− +−+− + +′′= +′′= ( ( !! (( (( !! !(!! = ++ ++++ = = + = ++ + = ++ = + = m 1n nmm3p3p 2p2p1p1p p 1n nl x x 0 m 1n nm 2p 1n n2p3p 1p 1n n1p2p p 1n n1p l x x 0 l x p 1n n l x x 0 av qlql.....ql qlqlqx b1xdxd)x(q q)ll(....q)ll( q)ll(q)xl( b1 xdxd)x(q xdqb1xdxd)x(qg which reduces: " " " # $ % % % & ' −−−+′′= ((!! == p n nn m n nn l x x av qlxqllbxxxqg 110 )()(1dd)( (16) equation 16 gives the mean value of g at a distance x from the watershed for a surface infiltration distribution q(x) and for injection and abstraction from a system of wells. it is seen that the result is dependent on the distribution of the sources and sinks. in the following examples we employ the analysis given here to a variety of situations where water is supplied by infiltration and injection wells and abstracted by capillary rise with loss of water through evaporation and pumped wells. example 1: q (x) = q, 0 < x l!; q (x) = -e, l!"< x < l. this is the situation where there is uniform infiltration over a strip adjacent to the watershed and capillary rise with loss of water through evaporation over the remaining area. equation 16 gives the uniform value of g along x = 0 as: 2/e)ll(q)2/ll(lg 20 ′−−′−′= (17) since it can be argued that the streamlines near x = 0 diverge with depth, equations 11 and 12 apply and the thickness of the fresh-water aquifer here is known within limits. for small values of q/k it is given to a good approximation by equation 9. if all the water supplied by infiltration is equal to that abstracted by the evaporation so that ql! = e (l-l!), , no water seeps into the sea and dg/dx = 0 along x = 0; then: 2/e)ll(l2/qllg 0 ′−=′= (18) the variation of g with the distance x from the watershed, both shown in dimensionless units, for various values of e/q when l! = 0.5, is shown in figure 4. 0 0.1 0.2 0.3 0.4 0 0.5 1 x/l g/ql2 0.5 0 1.0 infiltration capillary rise figure 4. the variation of g/ql2 with x/l or l’ =0.5 for three values of e/q shown by the curves. maintaining fresh-water aquifers over saline water in coastal aquifers 27 example 2: line of injection wells at x = li, total supply rate qi over length b of coastal strip, and a line of abstraction wells at x = la, total abstraction rate qa. for a line of wells at distance li from the watershed injecting water at a rate qi into the freshwater aquifer and another line of wells at distance la abstracting water at a rate qa, figure 5 illustrates the variation of gav with distance x given by equation 16. the value of gav at the watershed, (gav)0, is: b/]q)ll(q)ll[()g( aaii0av −−−= (19) equation 19 shows the advantage of supplying water near the watershed and abstracting water from the fresh-water region as near the coast as possible to obtain maximum depth of fresh water. example 3: infiltration at a rate q, l! < x < l!!, line of abstraction wells at x = la, total abstraction rate qa over length b of coastal strip. figure 6 illustrates the maintenance of the freshwater lens by infiltration over a region when water is abstracted by wells, as obtained from equation 16. again calculations of equation 16 show the importance of the location of the sources and sinks with maximum depth of fresh water occurring when the water is supplied in the vicinity of the watershed and abstracted near the sea, with values of (gav)0 given by: bq)ll(q]2/)ll(l)[ll()g( aa0av −−′+′′−′−′′= (20) example 4: line of injection wells at x = li, total supply rate qi over length b of coastal strip, evaporation from capillary rise at rate q = e, l! < x l!!. results calculated from equation 16 for this situation are illustrated in figure 7. maximum depth of fresh water results when water supply is in the vicinity of the watershed and abstraction is near the sea, as in previous examples. in this case (gav)0 is given by: e]2/)ll(l}[ll(bq)ll()g( ii0av ′+′′−′−′′−−= (21) discussion theoretical analyses show that the ghybenherzberg lens of fresh water in coastal aquifers can extend to great depths when maintained by a relatively small input of fresh water. however, exploitation of the fresh water aquifer for domestic, agricultural and industrial uses causes the saline water below to cone upwards into the fresh-water region at the positions of abstraction, and capillary rise with loss of water by evaporation considerably reduces the depth of fresh water. fresh-water inputs and abstractions are generally intermittent and hence non-steady state theory needs to be used to obtain an accurate estimate of the changing figure 5. the variation of g* = gavb/qil with x/l when there are injection wells at x = li and abstraction wells at x = la for qa/qi = 0.5. curves 1, 2, 3 and 4, li/l = 0; curves 5, 6, 7 and 8, li/l = 0.5; curves 1 and 5, la/l = 0; curves 2 and 6, la/l = 0.25; curves 3 and 7, la/l =0.5; and curves 4 and 8, la/l = 0.75. 0 0.1 0.2 0 0.2 0.4 0.6 0.8 1 x/l g* 1 2 3 4 5 6 figure 6. the variation of g* = gav/ql 2 with x/l when there is infiltration at a rate q on to a surface strip l! < x l# and abstraction from wells at x = la at a rate qa. curves 1, 2 and 3, l!/l = 0, l#/l = 0.5; curves 4, 5 and 6, l!/l = 0.5, l#/l = 1.0; curves 1 and 4, la = 0.25; curves 2 and 5, la = 0.5; and curves 3 and 6, la = 0.75:qa/blq = 0.1. figure 7. the variation of g* = gav/el 2 with x/l when water is injected into wells at x = l at a rate qi and there is capillary rise with loss of water due to evaporation at a rate e between l’ < x < l”. curves 1, 2 and 3, l’/l = 0, l”/l = 0.5; curves 4, 5 and 6, l’/l = 0.5, l”/l = 1.0; curves 1 and 4, li = 0.25; curves 2 and 5, li = 0.5; and curves 3 and 6, li = 0.75:qi/ble= 1.0. 0 0.2 0.4 0.6 0.8 1 0 0.2 0.4 0.6 0.8 1 1 2 3 4 5 6 8 7 x/l g* 0 0.2 0.4 0.6 0.8 0 0.2 0.4 0.6 0.8 1 x/l g* 1 2 3 4 5 6 youngs 28 depth of the fresh-water region, taking into account the movement of saline water to and from the sea as well as the movement of fresh water. however, if the intermittent pattern of water input and abstraction is regular with time, average rates used in simpler steadystate analyses should give an estimate of the average extent of the fresh-water region. seepage analysis (youngs, 1965, 1966) has been used to investigate the steady horizontal seepage of fresh water in the ghyben-herzberg lens (youngs, 1971a; 1971b). this shows that the dupuitforchheimer analysis provides a good estimate of the depth of fresh water overlying saline water intruding from the sea in coastal regions for small steady-state uniform infiltration rates over the surface area. in situations where the surface input is not uniform over the whole coastal area, the distribution of the seepage potential defined by equation 4 can be calculated over the coastal area for the given distribution of inputs and outputs. if this is assumed to relate to the dupuitforchheimer estimate of the depth of fresh water through equation 9, it provides a means of comparing different distribution patterns of inputs and outputs for maintaining fresh-water coastal aquifers. the various examples given in this paper show how the seepage potential varies in a coastal strip with different distributions of infiltration and capillary rise as well as for different distributions of input and abstraction wells. maximum values of the seepage potential occur when water input is in the vicinity of the watershed and abstraction takes place near the coast thus it can be inferred that this pattern of input and abstraction would maximise the depth of the fresh-water lens for given input and abstraction rates. references bear, j. 1972. dynamics of fluids in porous media. new york, elsevier. childs, e.c. 1969. the physical basis of soil water phenomena. london, john wiley. youngs, e.g. 1965. horizontal seepage through unconfined aquifers with hydraulic conductivity varying with depth. j. hydrology 3: 283-296. youngs, e.g. 1966. exact analysis of certain problems of groundwater flow with free surface conditions. j. hydrology 4: 277-281 youngs, e.g. 1970. a mean value theorem in potential theory. water resources research 6: 1792. youngs, e.g. 1971a. seepage through unconfined aquifers with lower boundaries of any shape. water resources research 7: 624-631. youngs, e.g. 1971b. optimum pumping conditions for wells located in unconfined coastal aquifers. j. hydrology 13: 63-69. youngs, e.g. 1986. the analysis of groundwater flows in unconfined aquifers with nonuniform hydraulic conductivity. transport in porous media 1:399-417. received august 2002. accepted november 2002. img318 img319 img320 img321 img322 pdf995, job 6 ______________ *corresponding author. 1 agricultural sciences, 7(2):1-7 (2002) © 2002 sultan qaboos university modeling residual napl in water-wet porous media r.j. lenhard1*, a.r. kacimov2, a.m. tartakovsky1, and h. abdelrahman2 1idaho national engineering and environmental laboratory (ineel), idaho falls, id, usa, 83415-2025 2department of soil and water sciences, college of agricultural and marine sciences, sultan qaboos university, po box 34, al-khod 123, muscat, sultanate of oman abstract: a model is outlined that predicts napl which is held in pore wedges and as films or lenses on solid and water surfaces and contributes negligibly to napl advection. this is conceptually referred to as residual napl. since residual napl is immobile, it remains in the vadose zone after all free napl has drained. residual napl is very important because it is a long-term source for groundwater contamination. recent laboratory experiments have demonstrated that current models for predicting subsurface napl behavior are inadequate because they do not correctly predict residual napl. the main reason for the failure is a deficiency in the current constitutive theories for multiphase flow that are used in numerical simulators. multiphase constitutive theory governs the relations among relative permeability, saturation, and pressure for fluid systems (i.e., air, napl, water). in this paper, we outline a model describing relations between fluid saturations and pressures that can be combined with existing multiphase constitutive theory to predict residual napl. we test the revised constitutive theory by applying it to a scenario involving napl imbibition and drainage, as well as water imbibition and drainage. the results suggest that the revised constitutive theory is able to predict the distribution of residual napl in the vadose zone as a function of saturation-path history. the revised model describing relations between fluid saturation and pressures will help toward developing or improving numerical multiphase flow simulators. keywords: porous media, advection, groundwater contamination, multiphase flow, constitutive theory, vadose zone. !"#$%&!'()*+!,(-!.)&#/%&!0+!'(1234%&!'(45%&!'67489:;<=>!? #%&!!"! 4%&!!+*/! !"#$%&'()*+',#-*./012/3+43*+'540/%&-*62",748*+25&-*9+4:;%*<$=-+** ! !'##$%&*>********************+2?%&* ,!4"*$,#*$!&20%&*!"* ,%&('"%&* ,%"/%&*()2'%%*4%*+2"5* %)+2%&*,-%.*/%*23012345***<4"40"%4=* ?(3$"%&* ***************-.*6* =$'%&-*74"%&*8?79*:;)* ,<#9*-9* &,)+*<4&(%=* >%,.*:%;)*?2%/3*.%'%&-* ,;,@%7a&*b.403*c* ,&('"%&* ,"/%&*, ******** ,"40"%&*d=4;"%&*.1*$!&20%&*e$f3* ,;")*.1*g***********.1*:&(3*4:5h1*6*e$f'3*c*$!&20%&*,-.*!"* ,&('"%&* ,"/%&*?9*4"=**************:%i*j#/5*')*e$f';%* ;=4&%&*<4,"/%&*?2/3*?9*'k=* ,&('"%&* ,"/%&*,-.*?2/'%3-*$%l2=*!%"/%* =$'%;%* ,"4%0"%&*d=4;%"%& *****d%")9*d=4;%"*g********* ,%&('"%&* ,%"/%&*,-%.*$(%'k30***4.$m%n*b%#+*1************,4,"%&*o2;'%*&+'p"*?2/3*?9*!/"l*4%:5q*r$,%(8* ,%".9*<&+ *****',k(%&*s'"%&*:;)* ,12t%&*g*** ,148*j0,%*$!&20%&*,-.*e2;7*()2'%* ,%4f%&*u+4";%&*?9*r$,vq&* ,;"k"%&*w+4t'%&*<$:x9 ****y(%;'3*c-=*8,fp%&*$/<%4=*e2;0%&*&-:*g0,!$%&*z(0%&*?i* l$.2t%&*<4l$[;%&*$<1*.1*!"/l*u+4";%&*,-.*$<1*7&+-*. ************* l9'k%&*<484f"%&*.1*$"k'0l*\-%&-*+&2=q&*9'k'%"%&*d1''%;%* ,%%4f%&*g******.'%&*..*+&2=q&*r9'k'"%&* l$.2t%&* l$[;%&*?i ****$!&20%&*]m^-*((<'%&-* ,(0;%&* l+4@;%&*!,=*<4%)_k%&*b%/f30,!4"*$,#*$!&20%&-*6*74"*6*7&2.*`*\9+2?%&* *g*1*,-.*ab;3 *********** ,%4f%&*+&2=q&*r9'k'"* l$.2t%&* l$[;%&*("*c*4"9&*!/"l*.'%&-*$!&20%&*]m^-*((<'%&*!,=*<4)_k%&*dpl*4*+2"5* )+2%& ************$!&20%&*,-.*!%"*.%&('"%&*e4%p"9&-*dl$%p3-*()2'%%*6**g********()23*:;)*r+94)* ,;l2/'%&* l$.2t%&* l$[;%&*?y=*f!4';%&*ab;3***,-.*e4p"9&*(%lg23**********((<'%&*+40"*:;)* %&'8*74"%&*:%i* 14^a4=*$!&20%&**g******\-%&-*(*&$"%&*u+2";%&*(t<3* 7&+'%&*,-. **************************** l9'k%&*<484f"%&*$l2?3*:;)*')4%0,7*,+-'%=*\-%%&-*$!&2%0%&*]m%^-*((%<'%&* &?;%"*.%1*w$'%%&*!%,=*<4%)_k%&*d%pl *+&2=q&*9'k'"*d1';%* ;0f"%&g* lenhard et al. 2 he contamination of groundwater by fuel and industrial chemicals occurs throughout the world. a major class of contaminants is nonaqueous phase liquids (napls). the risk that they pose to public health and the environment can be severe because many of these compounds are known or suspected carcinogens. several cases of napl migration to groundwater have been reported in the sultanate of oman. a leak at a british petroleum gasoline station in al kamil contaminated the vadose zone as well as the groundwater. discovery of petrol compounds in groundwater wells located several tens of meters from the leak source initiated a series of actions, including construction of an air-sparging system (mwr, 2000). contamination of groundwater close to major roadways is another environmental concern in the sultanate of oman. during dry periods, napls (principally petroleum products) become emplaced along roadways because of improper disposal and leaks from automobiles. the napl will occupy soil-pore wedges and small pores, because the water content in sandy soils is very low. the napl will be held in the vadose zone against gravity because it is immobile. during brief rainy periods, which include torrential rain, compounds from the napl will dissolve and move downward with the water to the groundwater, effectively delivering a pulse of contaminants to the groundwater. the migration of napls toward groundwater is a complex process. in addition to the physical movement of napl, volatile and soluble components of the napls can move toward groundwater in the gas and aqueous phases. once in contact with groundwater, these components can partition into groundwater. napls less dense than water (lnapls) will accumulate above the water table and may depress the water-saturated region. napls more dense than water (dnapls) can penetrate below the water table. fuel compounds, such as hydrocarbons, are lnapls and industrial solvents, such as trichloroethylene and carbon tetrachloride, are dnapls (fetter, 1993). as napl migrates downward through the unsaturated zone (vadose zone) toward groundwater, some of the napl remains in the vadose zone. that portion which remains likely resides in pore wedges and as thin films or lenses on water surfaces. as such, this napl is relatively immobile (or negligibly mobile). the negligibly mobile napl that does not drain from the pore spaces in the vadose zone is referred to as residual napl and can be continuous or discontinuous throughout the pore spaces. residual napl can serve as a long-term source for groundwater contamination. because of its persistent nature, residual napl needs to be considered when developing plans for site characterization and cleanup strategies and technologies. modeling has been recognized as a scientific method to help cost-effectively manage subsurface contamination. to predict multiphase flow, a set of nonlinear partial differential equations needs to be solved. a solution can be obtained for given boundary and initial conditions only if the constitutive relations are known. for multiphase flow, constitutive relations are the relationships among relative permeability (k), saturation (s), and pressure (p), i.e., k-s-p relations. a deficiency in current constitutive theory is its inability to predict residual napl (oostrom et al., 2003). the commonly used constitutive theory predicts that napl will completely drain from the vadose zone over time, which is contrary to laboratory and field observations. in a controlled experiment by hofstee et al. (1998), a residual napl saturation ranging to 20% was measured, but computer simulations failed to accurately predict the behavior of the residual napl. in another investigation by oostrom and lenhard (2002) that included sand and porous media high in calcium carbonate, numerical simulations using common constitutive theory were unable to satisfactorily predict the measured residual napl saturation in the experiment. improvements in constitutive theory are needed to accurately predict the subsurface behavior of napls in the vadose zone. in this paper, we will describe improvements to commonly used constitutive theory that allow residual napl to be predicted using numerical simulators. the improvements are based on the work of lenhard et al. (2003). also in this paper, we will apply the revised constitutive theory to a scenario involving napl imbibition and drainage and water imbibtion and drainage. unfortunately, we will not be able to present the detailed revised constitutive theory proposed by lenhard et al. (2003) or discuss other recently proposed modifications to current constitutive theory (wipfler and van der zee, 2001; van geel and roy, 2002) due to space constraints. model description probably, the most commonly used constitutive theory for air-napl-water flow is that published by parker et al. (1987), parker and lenhard (1987), and lenhard and parker (1987). the work by parker et al. (1987) pertains to nonhysteretic k-s-p relations. the works by parker and lenhard (1987) and lenhard and parker (1987) pertain to hysteretic k-s-p relations. in the latter work, the concept of an apparent saturation is introduced and entrapment of napl and air are modeled. both models are for strongly water-wet t modeling residual napl in water-wet porous media 3 porous media where water is the wetting fluid and napl and air are nonwetting fluids, in which the napl is more wetting than air. the improvements presented in this paper are modifications to the hysteretic k-s-p relations. the key modifications are 1) redefining the total-napl saturation, 2) proposing an equation to predict the residual-napl saturation as a function of saturation-path history, and 3) calculating entrapped air in the residual napl. major aspects of these modifications will be presented below as well as major components of the hysteretic k-s-p relations. for a more detailed description of the modifications, the readers are referred to lenhard et al. (2003). before presenting the model, we want to inform the readers about the terminology that we will employ to describe fluid saturations. we define trapped fluid as that which becomes discontinuous and occluded by more wetting fluids. since trapped fluids are discontinuous, they are immobile in sandy or finer porous media at normal fluid flow conditions. we define residual fluid as that which is either immobile or negligibly mobile and not occluded by another fluid. we believe residual fluid can be either discontinuous or continuous. residual fluid that is contained in pore wedges or in lenses on water surfaces (nonspreading liquids) may be discontinuous or continuous, depending on the direction of fluid movement and the fluid saturation. residual fluid that is a thin film on water surfaces is likely to be continuous (spreading liquids). we believe that discontinuous residual fluid is immobile and continuous residual fluid is negligibly mobile. this definition differs than that is typically used in the petroleum industry with regard to residual napl. what we call trapped napl, petroleum engineers call residual napl. to avoid confusion between residual water and residual napl, we have adapted the above definitions. we define free fluid as that which is continuous and mobile. s-p model the apparent water saturation is defined as: )1( rw rwatwotw w s1 ssss s − −++ = where sw is the water saturation, sot is the trapped-napl saturation occluded by the aqueous phase, satw is the trapped-air saturation occluded by aqueous phase, and srw is the residual-water saturation, which is assumed to be negligibly mobile and the value of which is independent of the water saturation-path history. satw also includes the trapped air in the trapped napl that is occluded by the aqueous phase. the apparent total-liquid saturation is defined as: rw rwatow t s1 ssss s − −++ = )2( where so is the total-napl saturation and sat is the total trapped-air saturation. note that sat is the sum of trapped-air saturations occluded by the aqueous phase and the napl: atoatwat sss += (3) where sato is the trapped-air saturation occluded by the napl. the terms sot, satw, and sat in equations (1) and (2) are functions of the water and total-liquid saturation-path histories [see lenhard (1992) for descriptions]. the first modification to the constitutive theory involves redefining the total-napl saturation. in the hysteretic s-p model described by parker and lenhard (1987) and lenhard (1992), the total-napl saturation consisted of two components: free napl and trapped napl. the modification is defining the total-napl saturation to consist of three components: free napl, trapped napl, and residual napl. correspondingly, the total-napl saturation (so) is defined as: (4)rootofo ssss ++= where sof is the free-napl saturation and sro is the residual-napl saturation. to determine so, each component needs to be calculated based on the totalliquid and water saturation-path histories and the napl-water and air-napl capillary pressures. note that so does not approach zero as sof approaches zero. the second modification involves developing an equation to predict the residual-napl saturation as a function of saturation-path history. based on arguments given in lenhard et al. (2003), the predictive equation is: )5(5.1w 5.0 w max tromrot )s1()ss(ss −−= )7( )6( rw rom rom rw atrro rot s1 s s s1 ss swhere − = − + = in which rots is the apparent residual-napl saturation, roms is the effective maximum residual-napl saturation, maxts is the historic maximum apparent total-liquid saturation, and satr is the trapped-air saturation in the residual napl. rots is composed of lenhard et al. 4 sro and satr. an effective nonwetting fluid saturation, such as the effective maximum residual-napl saturation, is determined accordingly: )8( rw x x s1 s s − = where sx is the nonwetting fluid saturation. the third modification involves modeling entrapped air in the residual napl. because the trapped air in the residual napl is occluded only by the napl (i.e., it will never also be occluded by water such as trapped air in trapped napl), it is a component of sato [see equation (3)]. therefore, sato consists of two components: trapped air in free napl (satof) and trapped air in residual napl (satr): )9(atratofato sss += furthermore, the trapped air in the residual napl consists of two components, depending on the saturation-path history, which are defined as: )10(atroatrwatr sss += where satrw is the trapped-air saturation in the residual napl that resulted from advancing air-water interfaces and satro is the trapped-air saturation in the residual napl that resulted from advancing air-napl interfaces. both satrw and satro and their corresponding scaled values (effective saturations) are determined from the saturation-path history. to calculate satrw and satro, the smallest pores where air-water and air-napl interfaces occupied relative to those indexed by rotw ss + need to be considered. the smallest pores that possessed air-water interfaces are indexed by ∆ s w aw , and the smallest pores that possessed air-napl interfaces are indexed by mins . for the saturation paths in which rotw ss + is greater than aw ws∆ , air trapped in residual napl may have resulted from either advancing air-water or air-napl interfaces. the condition where mints is larger than or equal to rotw ss + means that all trapped air in the residual napl resulted only from advancing air-water interfaces. )12(0s )11( s1 s,smaxss ss ssss ss atro aw w aw wwrotw atrwatrw rotw min t aw wrotw andfor = − −+ = +≥>+ ! " ! # $ ! % ! & ' ( ) *+ , ∆ ∆ ∆ the condition where mints is smaller than rotw ss + means that the air trapped in the residual napl may have resulted from either advancing airwater or air-napl interfaces. the amount of air trapped in the residual napl by advancing air-napl interfaces can be determined from )13( s1 ssmaxss ss sss ands ssfor min t min t,wrotw aroatro rotw min t aw wrotw ! " ! # $ ! % ! & ' − ( ) * + , -−+ = +<>+ ∆ to determine the amount of air trapped in the residual napl by advancing air-water interfaces for this saturation path, mints is compared to .s aw w ∆ )14( s1 s,smaxs,smax ss ss aw w aw www min t arwatrw aw w min t ! ! " !! # $ ! ! % !! & ' ( ) *+ , ∆ ∆ ∆ − (( ) * ++ , − = > )15(0s ss atrw aw w min t = ≤ ∆ for the saturation paths where rotw ss + is less than or equal to awws∆ , any air trapped in residual napl resulted only from advancing air-napl interfaces. depending on the value of mints , there may be no air trapped in the residual napl. )17( )16( 0s 0s sssandsssfor atro atrw rotw min t aw wrotw = = +≥≤+ ∆ modeling residual napl in water-wet porous media 5 )19( s1 s,smaxss ss )18(0s sssandsssfor min t w min trotw aroatro atrw rotw min t aw wrotw ! " ! # $ ! % ! & ' − ( ) *+ , -−+ = = +<≤+ ∆ in equations (11)-(19), aros and arws are the maximum effective trapped-air saturations for the given saturation-path history, awws∆ is the effective water saturation at the drying-to-wetting reversal from the main drainage s-p path, and mints is the historic minimum apparent total-liquid saturation. aros is the maximum effective trapped-air saturation that results from advancing air-napl interfaces, and arws is the maximum effective trapped-air saturation that results from advancing air-water interfaces. all air trapped in a three-phase fluid system is a function of aros , and all air trapped prior to initiation of a three-phase fluid system is a function of arws . readers are referred to parker and lenhard (1987) and lenhard (1992) for descriptions of how aros and arws are determined. discussion a computer program was written to calculate apparent, actual, trapped, and residual saturations for inputted capillary pressures, incorporating the above sp modifications. a saturation-path scenario involving napl and water imbibition and drainage was used to test the revised s-p constitutive model. table 1 lists the parameters that we used to generate the fluid saturations as functions of the capillary pressures. the parameters, which are all defined in parker and lenhard (1987) and lenhard and parker (1987) except srom, reflect a sandy porous medium. the hypothetical saturation-path scenario begins with water drainage, yielding a two-phase air-water fluid system. water drains until an air-water capillary pressure of 80 cm and a water saturation of 0.356. all fluid saturations unless otherwise noted are actual saturations (not scaled). the next condition, which we call path-2, involves napl imbibition. the total-liquid saturation increased to 0.751. we simulated a slight decrease in the water saturation (i.e., 0.005 saturation units) as the napl front passed. during napl imbibition, air will become trapped in napl by advancing air-napl interfaces. the residual-napl saturation will increase as maxts increases, and there is no entrapped napl because water is on the main drainage path. path3 involves napl drainage, while the water saturation table 1 parameters used to calculate saturations corresponding to the hypothetical saturation-path scenario. parameter value parameter value parameter value dα 0.05 cm-1 aoβ 1.80 aro i s 0.20 iα 0.10 cm-1 owβ 2.25 arw i s 0.25 n 2.0 roms 0.20 or i s 0.25 rws 0.15 increased only slightly. a rebound was simulated in the napl-water capillary pressure as the napl front passed (napl drained), which caused the water saturation to increase from 0.351 to 0.353 – thus causing very minor napl entrapment in water. the residual-napl saturation remains constant until the water saturation increases. inspection of equation (5) shows that as long as maxts and ws are constant, rots will not change. maxts obtained its highest value during napl imbibition (i.e., maxts = 0.751). air that was trapped during napl imbibition is now being released as napl drains from the larger pore spaces, except the trapped air which remains in the residual napl. path4 involves water imbibition (e.g., water table elevation increased). the napl saturation was held near 0.136, while the water saturation increased from 0.353 to 0.610. during water imbibition, free and residual napl will become occluded by water (trapped napl). the entrapped air saturation will also increase as the air-napl interfaces move into larger pore spaces. in the last saturation path (path-5), the totalliquid saturation continually decreases. early in the saturation path, water drains at a constant napl saturation of 0.136, and later in the saturation path, napl drains at a constant water saturation of 0.315. in the final stage of path-5, all of the napl became residual napl. results are shown in figures 1 and 2. figure 1 shows the saturations for path-2 and path-3. figure 2 shows the saturations for path-4 and path-5. note that figure 1b is a continuation of figure 1a, figure 2a is a continuation of figure 1b, and figure 2b is a continuation of figure 2a. the changes in saturations are shown as a function of the air-napl capillary pressure. by inspecting figure 1 for path-2, it can be seen that as the total-liquid saturation increases, both residual and free napl increase. when the difference between the total-liquid and water saturations is small, the relative amount of residual napl to the total napl is greater than for free napl; however, there is some free napl even at low total-napl saturations. lenhard et al. 6 figure 1. total-liquid, water, residual-napl, free-napl, and trapped-napl saturations as a function of the air – napl capillary pressure for a) path-2 and b) path-3. free napl first appeared when the total-napl saturation was only 0.015. the total-napl saturation at which free napl appears will be a function of the apparent water saturation. as the total-napl saturation increases, the relative amount of free napl increases. for path-3, the total-napl saturation decreases while the water saturation is relatively constant. the decrease in the free-napl saturation corresponds to the decrease in the totalnapl saturation, because the predicted residual-napl saturation remains constant. further investigations are warranted to determine if the residual-napl saturation should remain constant for the saturation-path conditions of path-3. since it is very difficult to measure residualand free-napl saturations simultaneously, the best approach to investigate this issue figure 2. total-liquid, water, residual-napl, free-napl, and trapped-napl saturations as a function of the air-napl capillary pressure for a) path-4 and b) path-5. is to compare numerical simulations to transient airnapl-water flow experiments. in figure 2 for path-4, the water saturation increased while the total-napl saturation was constant. this caused the total-liquid saturation to increase. as the water moved into larger and larger pores, some of the residual and free napl became trapped napl in water. the free-napl saturation decreased as the water saturation increased. the residual napl was not mobilized; it became trapped in water along with some free napl. eventually, all of the napl became entrapped (the residualand freenapl saturations are zero). when the apparent totalliquid saturation was equal to the apparent water saturation (all napl is entrapped), water drainage from the porous medium was simulated. as water modeling residual napl in water-wet porous media 7 drained, trapped napl was released and became residual and free napl. initially, most of the trapped napl that was released became residual napl. shortly thereafter, most of the released napl became free napl. the amount of residual napl relative to free napl is different depending on whether water is imbibing (figure 2a) or draining (figure 2b). the reason for this is because the saturation-path history is different for path-4 conditions and path-5 conditions. the water saturation decreased until all of the trapped napl was released. at this stage, the residual-napl saturation is predicted to be greater than the free-napl saturation. during the later periods of path-5, the water saturation was held constant while the free napl was allowed to drain. eventually, the freenapl saturation became zero (all of the napl was residual napl). when air-napl capillary pressure was further increased, the model would not allow further drainage of napl and the total-liquid and water saturations remained constant. comparing figures 1 and 2, one can observe that the calculations of residual-, trapped-, and free-napl saturations for path-4 and path-5 yield very different results compared to path-2 and path-3. the predicted trapped-, residual-, and free-napl saturations can have complex patterns even though the total-liquid and water saturation increase or decrease in a smooth, monotonic manner. conclusions the revised s-p constitutive relations proposed by lenhard et al. (2003) were tested. a hypothetical saturation-path scenario was developed from which apparent, actual, trapped, free, and residual saturations were predicted. analyses of the results suggest that the revised constitutive theory is able to predict the distribution of residual napl in the vadose zone as a function of saturation-path history. the revised model describing relations between fluid saturations and pressures will help toward developing or improving numerical multiphase flow simulators. however, further investigations are warranted to fully evaluate the constitutive relations. in particular, the revised constitutive relations need to be incorporated in numerical simulators and tested against transient airnapl-water flow experiments. acknowledgment appreciation is extended to the laboratory directed research and development program at the idaho national engineering and environmental laboratory (ineel) for funding this work. the ineel is operated for the us department of energy (doe) by bechtel bwxt idaho, llc under doe idaho operations office contract de-ac0799id13727. references fetter, c.w. 1993. contaminant hydrogeology. macmillan publishing company, new york. 458pp. hofstee, c., r.c. walker, and j.h. dane. 1998. infiltration and redistribution of perchloroethylene in partially saturated, stratified porous media. j. contam. hydrol. 34:293-313. lenhard, r.j. 1992. measurement and modeling of three-phase saturation-pressure hysteresis. j. contam. hydrol. 9:243-269. lenhard, r.j., m. oostrom, and j.h. dane. 2003. a constitutive model for air-napl-water flow in the vadose zone accounting for residual napl in strongly water-wet porous media. submitted for publication j. contam. hydrol. lenhard, r.j. and j.c. parker. 1987. a model for hysteretic constitutive relations governing multiphase flow, 2. permeability-saturation relations. water resour. res. 23:21972206. ministry of water resources (mwr). 2000. report on the hydrocarbon contamination in willayat al-kamil. report number n756. ministry of water resources, sultanate of oman. oostrom, m. and r.j. lenhard. 2002. flow behavior in unsaturated hanford caliche material: an investigation of residual napl. submitted for publication vadose zone j. oostrom, m., c. hofstee, r.j. lenhard, and t.w. wietsma. 2003. flow behavior and residual saturation formation of liquid carbon tetrachloride in unsaturated heterogeneous porous media. j. contam. hydrol. (in press). parker, j.c. and r.j. lenhard. 1987. a model for hysteretic constitutive relations governing multiphase flow, 1. saturationpressure relations. water resour. res. 23:2187-2196. parker, j.c., r.j. lenhard, and t. kuppusamy. 1987. a parametric model for constitutive properties governing multiphase flow in porous media. water resour. res. 23:618-624. van geel, p.j. and s.d. roy. 2002. a proposed model to include a residual napl saturation in a hysteretic capillary pressuresaturation relationship. j. contam. hydrol. 58:79-110. wipfler, e.l. and s.e.a.t.m. van der zee. 2001. a set of constitutive relationships accounting for residual napl in the unsaturated zone. j. contam. hydrol. 50:53-77. ________________________________________ received september 2002. accepted november 2002. sultan qaboos university journal for scientific research agricultural and marine sciences, 10(1):27-31 (2005) ©2005 sultan qaboos university 27 * corresponding author handling practices during distribution of kinnow-mandarins (citrus nobilis x citrus nobilis x citrus nobilis citrus deliciosa) used for preparation of fresh-squeezed juices and their effects on microbiological safety m. ghosh, a. ganguli* and m. kumar department of biotechnology and environmental sciences, thapar institute of engineering and technology, patiala-147004, punjab, india تأثیر طرق توزيع الیوسفي نوع كینو لغرض تحضیر العصیر الطازج على السالمة من األحیاء المجھرية أ. جانجولي من كعصیر تحضیره عند المجھرية باألحیاء اإلصابة من الیوسفي سالمة لتقییم ھو الدراسة ھذه من الھدف إن الخالصة: قبل الباعة في الشارع. لقد تم جمع 150 نموذجا من ھذه الفاكھة من عدة أماكن خالل سلسلة توزيع نفس الشحنة، حیث من كعصیر تحضیره عند المجھرية باألحیاء اإلصابة من الیوسفي سالمة لتقییم ھو الدراسة ھذه من الھدف إن الخالصة: قبل الباعة في الشارع. لقد تم جمع 150 نموذجا من ھذه الفاكھة من عدة أماكن خالل سلسلة توزيع نفس الشحنة، حیث من كعصیر تحضیره عند المجھرية باألحیاء اإلصابة من الیوسفي سالمة لتقییم ھو الدراسة ھذه من الھدف إن الخالصة: التلوث من المتأتي وكذلك الكلي الكولیفورم الستافیلوكوكاس، الھوائیة، البكتريا مجموع لمعرفة مخبريا وتحلیلھا غسلھا تم قبل الباعة في الشارع. لقد تم جمع 150 نموذجا من ھذه الفاكھة من عدة أماكن خالل سلسلة توزيع نفس الشحنة، حیث التلوث من المتأتي وكذلك الكلي الكولیفورم الستافیلوكوكاس، الھوائیة، البكتريا مجموع لمعرفة مخبريا وتحلیلھا غسلھا تم قبل الباعة في الشارع. لقد تم جمع 150 نموذجا من ھذه الفاكھة من عدة أماكن خالل سلسلة توزيع نفس الشحنة، حیث بالفضالت، السالمونیال، والشیجال. وقد تبین انه ومع عدم وجود أية زيادة ملحوظة في مجموع البكتريا الھوائیة والكولیفورم بنوعیه، التلوث من المتأتي وكذلك الكلي الكولیفورم الستافیلوكوكاس، الھوائیة، البكتريا مجموع لمعرفة مخبريا وتحلیلھا غسلھا تم بالفضالت، السالمونیال، والشیجال. وقد تبین انه ومع عدم وجود أية زيادة ملحوظة في مجموع البكتريا الھوائیة والكولیفورم بنوعیه، التلوث من المتأتي وكذلك الكلي الكولیفورم الستافیلوكوكاس، الھوائیة، البكتريا مجموع لمعرفة مخبريا وتحلیلھا غسلھا تم فأن نسبة الستافیلوكوكاس قد ارتفعت بصورة إحصائیة مھمة (p < 0.05) خالل عملیة التوزيع على محالت البیع. لقد وجد إنزيم بالفضالت، السالمونیال، والشیجال. وقد تبین انه ومع عدم وجود أية زيادة ملحوظة في مجموع البكتريا الھوائیة والكولیفورم بنوعیه، فأن نسبة الستافیلوكوكاس قد ارتفعت بصورة إحصائیة مھمة ( بالفضالت، السالمونیال، والشیجال. وقد تبین انه ومع عدم وجود أية زيادة ملحوظة في مجموع البكتريا الھوائیة والكولیفورم بنوعیه، كوأجیولیز المنتج من الستافیلوكوكاس في 72 نموذج وكان 23 منھا قد أنتجت انتیروتوكسین نوع c, b. ولم يتم التعرف على ) خالل عملیة التوزيع على محالت البیع. لقد وجد إنزيم كوأجیولیز المنتج من الستافیلوكوكاس في 72 نموذج وكان 23 منھا قد أنتجت انتیروتوكسین نوع ) خالل عملیة التوزيع على محالت البیع. لقد وجد إنزيم فأن نسبة الستافیلوكوكاس قد ارتفعت بصورة إحصائیة مھمة ( كوأجیولیز المنتج من الستافیلوكوكاس في 72 نموذج وكان 23 منھا قد أنتجت انتیروتوكسین نوع فأن نسبة الستافیلوكوكاس قد ارتفعت بصورة إحصائیة مھمة ( أية مصادر للسالمونیال والشیجال في أي نموذج، بینما وجدت أعداد كبیرة من مصادرenterotoxigenic s aureus نتیجة للتداول كوأجیولیز المنتج من الستافیلوكوكاس في 72 نموذج وكان 23 منھا قد أنتجت انتیروتوكسین نوع enterotoxigenic s aureusأية مصادر للسالمونیال والشیجال في أي نموذج، بینما وجدت أعداد كبیرة من مصادر كوأجیولیز المنتج من الستافیلوكوكاس في 72 نموذج وكان 23 منھا قد أنتجت انتیروتوكسین نوع الیدوي غیر الصحي لدى الباعة من الطبقة المتوسطة وفي الشارع. يتبین نتیجة ھذه الدراسة مدى رداءة وسائل الوقاية من التلوث المیكروبي لفاكھة الیوسفي واحتمال حصول ھذا التلوث أثناء عملیات التوزيع وكذلك بسبب قلة وسائل النظافة لدى الباعة الیدوي غیر الصحي لدى الباعة من الطبقة المتوسطة وفي الشارع. يتبین نتیجة ھذه الدراسة مدى رداءة وسائل الوقاية من التلوث المیكروبي لفاكھة الیوسفي واحتمال حصول ھذا التلوث أثناء عملیات التوزيع وكذلك بسبب قلة وسائل النظافة لدى الباعة الیدوي غیر الصحي لدى الباعة من الطبقة المتوسطة وفي الشارع. يتبین نتیجة ھذه الدراسة مدى رداءة وسائل الوقاية من في الشارع. ولذا فأننا نرى ضرورة اتخاذ اإلجراءات الالزمة والمالئمة للتأكد من سالمة العصیر وخلوه من التلوث وبالتالي تقديم التلوث المیكروبي لفاكھة الیوسفي واحتمال حصول ھذا التلوث أثناء عملیات التوزيع وكذلك بسبب قلة وسائل النظافة لدى الباعة في الشارع. ولذا فأننا نرى ضرورة اتخاذ اإلجراءات الالزمة والمالئمة للتأكد من سالمة العصیر وخلوه من التلوث وبالتالي تقديم التلوث المیكروبي لفاكھة الیوسفي واحتمال حصول ھذا التلوث أثناء عملیات التوزيع وكذلك بسبب قلة وسائل النظافة لدى الباعة عصیر طازج سلیم صحي. abstract: the objective of this study was to assess the microbiological safety of kinnow-mandarins (citrus nobilis x citrus deliciosa) used for preparation of fresh squeezed juices by street vendors. one hundred and fifty kinnow mandarin samples were collected from different points in the distribution chain from the same lot, washed and aliquots of the wash samples were analyzed for total aerobes, staphylococcus, total and fecal coliforms, salmonella and shigella. although, there was no notable increase in the total aerobic, total or fecal coliform counts, total staphylococcal counts increased significantly (p<0.05) during distribution to street vendors; seventy-two samples from the street vendors showed the presence of coagulase positive staphylococcus aureus, twenty-three of these produced enterotoxins b and c. salmonella and shigella were not detected in any of the samples. sources of high numbers of enterotoxigenic s. aureus were traced to unhygienic manual handling by middle level buyers and by street vendors. the results of our study demonstrate the poor microbiological quality of kinnow-mandarins, the possible entry points of contaminants in the distribution chain of these fruits and unhygienic vending practices. appropriate intervention measures are needed to ensure safe fresh squeezed juices for consumers. keywords: india, distribution chain, enterotoxigenic staphylococcus aureus. introduction outbreaks associated with fresh produce have emerged as an important public health concern and documented illnesses following consumption of raw produce or related products have been linked to bacteria, parasites and viruses (harris et al., 2001). fresh produce can be contaminated with pathogens not only in the field, but also from many post-harvest sources such as wash and rinse water, unhygienic human handlers, transport vehicles, cross contamination, improper storage, processing and packaging (cdr, 1991). the low sanitation standards, especially during postharvest handling, and increased consumption of raw produce and produce related products (e.g. fresh ghosh, et al. 28 squeezed fruit, vegetables juices etc) has generated heightened concerns for food safety (chalmers et al., 2000; mcmahon and wilson, 2001; roberts, 1997) in developing countries. kinnow–mandarins (citrus nobilis x citrus delicosa) are important products in india, especially during the months of october to march, and enjoy high consumer acceptance on account of their taste and nutritional benefits. kinnow-mandarins are, however, preferred as fresh-squeezed juices. although citrus juices are assumed to be safe, the consumption of unpasteurized juices may be dangerous since they could be a potential source of bacterial pathogens (ryu et al., 1998; uljas et al., 1998; zhuang et al., 1995). outbreaks of food poisoning caused by biological hazards have been traced back to the consumption of unpasteurized citrus juices (cdc, 1998). in an earlier study mudgil et al. (2003) reported the incidence of bacterial pathogens in street vended fresh-squeezed carrot and kinnow-mandarin juices in patiala, a principal city of punjab, where approximately 94% of the population, including tourists of all ages and income groups, consume fresh squeezed juices. although no documented outbreaks related to the consumption of juices exist in india, unofficial reports confirm that such incidents have actually increased. contamination of produce may be minimized prior to consumption if suitable interventions are developed. however, one of the keys to the selection of appropriate intervention steps to reduce populations of pathogenic microorganisms on kinnow-mandarins would be the identification and elimination of the sources of contamination as affected by post-harvest practices. we hypothesized the distribution chain of kinnow-mandarins to be a major source of contamination with bacterial pathogens. the objective of this study was therefore, to assess the microbiological quality of kinnow-mandarins at each stage of this chain up to preparation of fresh-squeezed juices by street vendors. the potential sources and vending practices contributing to such contamination were also investigated. materials and methods one hundred kinnow-mandarin samples (whole fruits) were collected from each point of the distribution chain. all kinnow–mandarin samples were packed individually in sterile whirl-pack bags (fischer scientific) using sterile latex gloves. the samples were maintained on ice packs during transportation and processed within 2 hours after arrival in the laboratory. to each bag, 100ml sterile 0.1% peptone water were added and samples were hand massaged for 2 min to dislodge the surface microbial population (burnett and beuchat, 2001). part of the wash samples were further diluted in peptone water and appropriate dilutions were used for enumerating total aerobic counts, s. aureus, total and fecal coliforms. the rest of the samples were enriched for detecting salmonella and shigella. aerobic plate count (37 oc, 24h) was performed using plate count agar (himedia, mumbai, india); total coliform count was done using violet red bile agar (himedia, mumbai, india) (37 oc, 24h). presence of fecal coliforms was determined using brilliant green lactose bile broth (himedia, mumbai, india) (44.5 oc, 48h), followed by confirmation of gas positive tubes using eosin methylene blue agar (himedia, mumbai, india). for enumeration of staphylococcus aureus, 1.0 ml wash samples were divided among three plates (0.3, 0.3, and 0.4 ml) of baird–parker agar (himedia, mumbai, india) supplemented with egg yolk tellurite enrichment suspension (himedia, mumbai, india) and spread-plated. plates were incubated at 37 oc for 48 hr, typical s. aureus colonies (jet-black, glistening, circular with clear zones) were counted and numbers calculated (log cfu/ml or g). the isolates were identified and confirmed by biochemical tests (brackett and splittoessar, 1992), coagulase positive strains of s. aureus were tested for the production of enterotoxins using a reversed passive latex agglutination based kit (set rpla, oxoid, basingstoke, uk). salmonella were isolated based on the protocol described by the u.s food and drug administration in the bacteriological analytical manual; 10 ml of wash samples were enriched in universal preenrichment broth for 24 h at 37 oc; 0.1 ml of the preenriched culture was inoculated in semisolid rappaport vassiliadis agar (himedia, mumbai, india) and incubated at 42 oc for 24 h. a loop full of agar was then streaked on xylose–lysine deoxycholate agar (himedia, mumbai, india) and incubated at 37 oc for 24-48 h (usfda, 2000). presumptive colonies were sent to national centre for escherichia and salmonella, central research institute, kasauli, india for further confirmation. shigella was selectively enriched by incubating 10 ml peptone suspension in shigella broth at 37 oc for 24 h, colonies were isolated on xylose–lysine–desoxycholate agar; presumptive handling practices during distribution of kinnow-mandarins 29 colonies were streaked on tsi (triple sugar iron media) (himedia, mumbai, india) and motility agar slants (himedia, mumbai, india), incubated at 37 oc and observed after 24 and 48 h. an unpaired students t-test was used to identify any significant differences in population proportions of total staphylococcal counts (α = 0.05) between middle level vendors and samples hand wiped by the street vendors. statistical analysis of data was performed with spss software (spss inc, chicago, ill). results in patiala, local farmers around the city bring mandarins from farms to a central distribution site or ‘mandi’. kinnow-mandarins are purchased in bulk by middle level buyers (about ten in numbers) from the central distribution site and sold to about one hundred street vendors, who use kinnow–mandarins for preparing fresh squeezed juices, the distribution chain through which this fruit proceeds prior to being available to consumers as fresh-squeezed juices. the total aerobic counts (table 1) of kinnow-mandarin samples did not differ significantly (p > 0.05) from its course from mandi to the carts or street vendors (4.2 to 4.88 log cfu/g). no significant increases of total and fecal coliforms were observed in samples during transit from the central distribution site to street vendors. total staphylococcal counts increased significantly from 3.5 cfu/g to 6.7 log cfu/g. seventytwo samples from the street vendors showed the presence of coagulase positive staphylococcus aureus, twenty three of these produced enterotoxins b and c. table 2 shows the handling practices adopted by the middle level buyers and street vendors. neither salmonella nor shigella was detected. table 1. microbiological analysis of kinnow–mandarins (citrus nobilis x citrus deliciosa) in the distribution chain. microbial counts in each case are means of three replicates. sampling locations* bacterial counts (log cfu/g) apc (range) tsc (range) tc (range) tfc (range) central distribution site 4.2b ± 0.5 (3.3 – 5.8 ) 3.5b ± 0.3 (3.0 – 5.0 ) 4.8b ± 0.3 (2.0 – 6.3) 2.0b ± 0.4 (2.2 – 3.0) middle level buyers 4.8b ± 0.4 (4.8 – 5.7) 4.9b ± 0.5 (2.5 – 6.1) 4.8b ± 0.4 (2.0 – 4.9) 2.3b ± 0.5 (2.0 – 3.3) street vendors 4.9b ± 0.5 (5.0 – 6.6) 6.7b ± 0.5 (6.4 – 8.0) 5.2b ± 0.7 (2.0 – 6.0) 2.7 ± 0.3 (3.2 – 5.2) street vendorsa 5.9b ± 0.6 (3.1 – 6.4)(3.1 – 6.4) 5.0b ± 0.6 (4.5 – 7.8)(4.5 – 7.8) 3.8b ± 0.4 (2.1 – 4.7)(2.1 – 4.7) 3.0b ± 0.5 (2.0 – 3.3)(2.0 – 3.3) *100 kinnow-mandarin samples were collected from each point in the distribution chain. abacterial counts from samples after ‘cleaning’ by street vendors. b mean bacterial counts + s.d. table 2. handling practices adopted at different levels in the distribution chain of kinnow-mandarins. levels in distribution chain handling practices middle level buyers unhygienic storage space, remixing of damaged fruits, use of unpotable water, unwashed cloths used for cleaning fruit surfaces. street vendors unpotable water stored and used for multiple purposes, soaps or detergents not used, use of hands for wiping fruits, dilution of juices with water, frequent use of physically-damaged fruits. ghosh, et al. 30 discussion prior to sampling, we identified the distribution chain for kinnow–mandarins and studied the practices involved during different stages of handling. the distribution of kinnow-mandarin proceeds prior to being processed for fresh squeezed juices for consumers as follows: central distribution site →middle level buyers → street vendors→consumers kinnow-mandarins are usually purchased by the middle level buyers from a common central distribution site and transported by carts or vans to the shops. manual handling at this stage is relatively low. after reloading, the fruits are remixed by these buyers according to their quality, e.g. those having minor physical damage during transport are sold at lower prices. the storage space for dumping and remixing are unhygienic and the handling personnel involved during these operations are unskilled and totally unaware of hygienic practices; the increase in total staphylococcal counts, especially coagulase positive s. aureus in the stages prior to procurement of kinnow-mandarins by street vendors, may be traced to this high degree of unhygienic handling and cross contamination during remixing of the fruits. earlier studies have shown the presence of s. aureus on fresh produce and ready–to–eat vegetable salads (vishwanathan and kaur, 2001). high numbers of coagulase positive s. aureus were also detected in freshly pressed carrot juice (mudgil et al., 2003). unhygienic handling therefore could be regarded as the primary determinant for contamination of kinnowmandarins till this stage of distribution. following receipt of kinnow-mandarins, the middle-level buyers usually wiped the fruits using pieces of cloth that were moistened with water (unpotable). the same cloth was used for wiping several other fruits, the slight increase in total and fecal coliforms may be attributed to this practice. use of contaminated cloth has been shown to aid both survival and transfer of the bacterial pathogens to foods or produces (beuchat, 1998). the significant increase in total staphylococcal counts (p<0.05) in the same lots of kinnow-mandarins following receipt by the street vendors, may be attributed to the practice of cleaning the outer surface of the fruits by hand. we noted that none of the street vendors used soaps for cleaning their hands either before handling the fruits or during preparation of juices; furthermore the vendors used stored water for diluting the juices. the practice of using stored water for multiple uses was found to be fairly consistent among the vendors, most of whom had limited access to clean, running water. the levels of fecal and total coliforms were reasonably high in water samples analyzed during the study (results not shown). while washing, fresh produce can reduce most microbial contamination on the surface of fruits and vegetables, reusing processing water may result in the buildup of microbial loads, including pathogens from the produce. these pathogens may be transferred to subsequent lots or batches of produce (beuchat, 1998), in this case directly to the juices and thence to consumers. the presence of fecal and total coliforms and high levels of coagulase positive s. aureus, especially enterotoxigenic s. aureus, in kinnow-mandarins destined for juicing is clearly unacceptable. although we could not detect salmonella or shigella spp. in the kinnow-mandarin samples, the presence of fecal contamination implies the possible presence of enteric pathogens; the entry of such pathogens subsequently to freshly squeezed juices could be facilitated if damaged or partially damaged kinnow-mandarins are used. in our studies approximately 87% of kinnowmandarins procured by the street vendors were found to be partially damaged. overall, our study demonstrates the poor microbiological quality of kinnow-mandarins, which are used for preparing fresh squeezed juices. the results obtained during this study can be correlated to our earlier findings (mudgil et al., 2003) where fresh squeezed kinnow-mandarin juices samples (18) were found to contain coagulase positive s. aureus, high total viable counts (6 log cfu/ml) and total fecal coliform counts (5 log cfu/ml). handling practices observed in this study during the movement of kinnow-mandarins through the distribution chain is important in terms of safety to consumers. recent food-borne disease outbreaks emphasize the importance of screening various vegetables and fruits, especially those that are vulnerable to contamination and those which are ready to eat, or used for products not undergoing any processing steps (endley et al., 2003). the possible sources of contamination at various stages of distribution may be important, since adoption of proactive measures (e.g. use of running water supply, use of clean cloth or washed cloth handling practices during distribution of kinnow-mandarins 31 for wiping fruits, blanching the fruits in hot water) could lead to reduced final contamination of kinnowmandarins. it is crucial for government agencies to educate the vendors about food safety, hygienic practices and to set adequate standards for pathogen prevention from field to the plate. acknowledgement the authors wish to thank the coordinator, center of relevance and excellence in agro and industrial biotechnology, department of biotechnology and environmental sciences, for providing adequate facilities and the technology information and development council (tifac), department of science and technology, government of india, for financial support. references beuchat, l.r. 1998. surface decontamination of fruits and vegetables eaten raw: a review. food safety issues.who/fsf/fos98.2. food safety unit. world health organization, geneva. brackett, r.e. and d.f. splitsstoessar. 1992. fruits and vegetables. in: compendium of methods of microbiological examination of foods, c. vanberzont and d.f. splittstoesser (editors), pp.919-927. apha, washington, d.c. burnett, a.b. and l.r. beuchat. 2001. comparison of sample preparation methods for recovering salmonella from raw fruits, vegetables, and herbs. journal of food protection 64:1459-1465. cdc (centers for disease control). 1998. salmonella surveillance: annual tabulation summary. atlanta, georgia: u.s department of health and human services. cdr. 1991. melon associated salmonellosis. communicable disease report weekly 36:161. chalmers, r., m.g. nichols and r. rooney. 2000. food borne outbreaks of cyclosporiasis have arisen in north america. is the united kingdom at risk? communicable diseases to public health 3:50-55. endley, s., l. lu, e. vega, m. hume and s. pillai. 2003. male specific coliphages as an additional contamination indicator for screening fresh carrots. journal of food protection 66:88-93. harris, l.j., l.r. beuchat, m.t. kajs, t.e. ward and c.h taylor. 2001. efficacy and reproducibility of a produce wash in killing salmonella on the surface of tomatoes assessed with a proposed standard method for produce sanitizers. journal of food protection 64:1477-1482. mcmahon, m.a. and i.g. wilson. 2001. the occurrence of enteric pathogens and aeromonas species in organic vegetables. international journal of food microbiology 70:155-162. mudgil, s., d. aggarwal and a. ganguli. 2003. microbiological analysis of street vended fresh carrot and kinnow–mandarin juices in patiala city, india. internet journal of food safety 3:1-3. roberts, r. 1997. emerging pathogens associated with infectious diarrhea. brazilian journal of infectious diseases 1:153-176. ryu, j.h. and l.r. beuchat. 1998. influence of acid tolerance responses on survival, growth and cross protection of escherichia coli o157:h7 in acidified media and fruit juices. international journal of food microbiology 45:185-193. uljas, h.e. and s.c. ingham. 1998. survival of escherichia coli o157:h7 in synthetic gastric fluid after cold and acid habituation in apple juice or trypticase soy broth acidified with hydrochloric acid or organic acid. journal of food protection 61:939-947. usfda (united states food and drug administration). 2000. bacteriological analytical manual: aoac international, arlington, va, usa. vishwanathan, p. and r. kaur. 2001. prevalence and growth of pathogens on salad vegetables, fruits and sprouts. international journal of hygiene environmental health 203:205-213. zhuang, r.y., l.r. beuchat and f.j. angulo. 1995. fate of salmonella montevideo on and in raw tomatoes as affected by temperature and treatment with chlorine. applied environmental microbiology 61:2127-2131. received: december 2004 accepted: june 2005 microsoft word jamsy2003v08n01content-arabic.doc agricultural and marine sciences, 8(1):41-46 (2003) © 2003 sultan qaboos university ___________________ *corresponding author. 41 salinity–ph relationships in calcareous soils a.s. al-busaidi* and p. cookson department of soil and water sciences, college of agricultural and marine sciences, sultan qaboos university, p.o. box 34 al-khod 123, sultanate of oman abstract: soil ph is the most commonly requested analysis undertaken during farm advisory work. determination of ph assists in understanding many reactions that occur in soil. variations in ph between soils have been related to a number of other soil parameters. in this study thirty different soils were collected from agricultural areas to have a wide range of ph, salinity, and texture. the objective was to study the relationship between soil ph and salinity. a negative relationship was found between soil salinity and ph. the main factor contributing to this relationship was probably the presence of soluble ca2+ ion in soil. variations in soluble ca2+ ion concentrations between soils were negatively related to soil ph and positively related to soil salinity. other soil properties that may affect ph, including cec, caco3, clay content, gypsum and sodium adsorption ratio (sar), were also determined. keywords: electrical conductivity, sodicity, ph, alkaline soil, caco3. alinization and sodiciation are important processes in arid regions which often reduce crop yields. salinity is the concentration of soluble mineral salts present in soils on a unit volume or weight basis (page et al., 1982), and sodicity is the concentration of na+ ions in soil. soil salinity and sodicity can affect nutrient movement to plants, soil properties, and various soil chemical reactions including ph. in alkaline soils, ph usually increases with an increase in salinity due to the presence of sodium-bicarbonate carbonates (gupta et al., 1989). however, tan (1993) reported that increasing sodicity in soil does not necessarily yield a rise in ph. many sodic soils are neutral in reaction, whereas some are even acid in reaction. the strongly alkaline reaction (ph around 10) of most sodic soils is caused by alkalinization during which sodium carbonate and bicarbonate are formed. under less alkaline conditions, i.e. where calcium carbonate dominates the soil mineralogy, soil ph has been shown to drop with an increase in salinity (lai and stewart, 1990). several reasons have been proposed for this behavior, including common ion effects (mcgeorge, 1938), sulphate complexation (clark, 1964), variation in ionic strength of soil solutions and junction potential (mahrous et al., 1983). in calcareous soils, statistical studies suggest a strong inverse relationship between the concentration of soluble ca2+ ions and ph (cresser et al., 1993). since ph is a routinely measured property of cultivated soils, it is essential for soil advisory work that reliable reasons for soils to have a particular ph are understood. the commonly held belief that a reduction in ph of an alkaline soil is beneficial to crop growth may not be entirely suitable for regions where carbonitic soils vary in salinity. oman is one of many countries experiencing soil salinity problems (maf, 1993). since salinity-ph relationships have not been previously reported from oman, this paper attempts to determine the nature of this relationship in cultivated calcareous soils. s !"#$%!&'()*+,%!,-.(*%/01234516*+%7"-*8%%!19(:*+% !"#$%#%!&'()!*!+,(-.#/01!,234! ! %!;;<#=!5!!!!!!!678(9*:,(;01!<=&701!&/7'->? !!"!!!!!!!!!!!!!!#$)&'01!$)#%&!<((''0!()&*#+!,->!6'01!./(%001!<7)4!172!3)&'740!!#;*!,5($> !6745!!!!!!!!!!!!!!!!!#$)&'01!67*!7,78+!67'01!9:5(;'701!172!&(7<%!<7;*!30*!!!6*!=>#9#201!&?(8-01!@4'02!a2!$;4'02!9(=:5!$)&'01!b!6* !!!!!!c:c!a29!!<+!#$.1:,01!de7)!!!!!!!!!645!f#%840!"(2-)!=>#9#201!$(51:g01!h&'01!@4'02!12!$8(5!1(!!!!!!<=&01!i,2!6*!a.*4!f(-2! !!!$73#4201*!678(9*:,(;01!b!!!!!,>,8+!#)!$.1:,01!de)!172!67$(/&01!j,7;01$3#4201*!1(9*:,(;01!<=&01!1()!=>#9#201!$=:-01b !!!!!!!$7.1:,01!de7)!67*!!!!k(87)!"4!l7m+1!!!!!!!!68(9*:,(;01!<=&01!*!$)&'01!$3#42!1()!$($n5!$=:5!!b!!6*!<)($201!6$(/&01!o2(-01 !!!1!de7)!17>#n+!*4!:#7;p!!!! +e01!q#($0(n01!"#>4!>#9*!#7)!$7=:-030!a2!$()(->r!$=:5!*!68(9*:,(;01!<=&01!!a2!$($n5!$=:5! !!$)&'01!$73#42!b!!!!,>,8+!<+!,=*!!!!$)&'40!i&&s1!./(%001!!68(9*:,(;01!<=&01!645!=&ct2016u#>s1!&(v'01!$-.!o<2*!$3#4201!!*! q#($0(n01!9(u#)&%b!! al-busaidi and cookson 42 table 1 descriptive statistics for whole data. non-saline saline soil properties minimum maximum mean std. deviation minimum maximum mean std. deviation ec1:1 (ds/m) 0.29 2.15 0.9259 0.5205 4.50 34.75 10.9804 9.6378 ecsp (ds/m) 0.67 3.70 1.7205 0.8819 4.01 86.80 26.5684 24.5684 sar 2.66 9.53 6.0437 2.3739 7.31 52.10 20.4657 11.6653 phwa (1:1) 8.39 8.93 8.6109 0.1587 7.88 8.64 8.1832 0.2340 phwa (1:2.5) 8.67 9.25 8.8845 0.1799 8.03 8.96 8.4037 0.2710 phca (1:1) 7.75 8.13 8.0164 0.1108 7.78 8.25 8.0079 0.1629 phca (1:2.5) 7.96 8.29 8.1209 0.1021 7.95 8.36 8.1432 0.1404 phk (1:1) 7.72 8.40 7.9282 0.2091 7.68 8.37 7.9805 0.1816 phk (1:2.5) 7.94 8.73 8.1964 0.2448 7.88 8.63 8.2011 0.1944 phba (1:1) 7.95 8.33 8.1182 0.1073 7.82 8.39 8.0584 0.1701 phba (1:2.5) 8.05 8.56 8.2136 0.1466 8.00 8.44 8.1847 0.1444 na (mmol/l) 5.44 21.74 12.8450 6.0867 27.17 565.22 156.1797 146.7047 ca (mmol/l) 1.25 6.25 5.7955 1.5076 6.25 100.00 37.8289 28.0650 mg (mmol/l) 2.08 8.33 3.0301 1.9463 4.17 166.67 70.2852 63.6767 caco3 (g/g) 0.33 0.60 0.4327 0.0755 0.28 0.58 0.4129 0.0646 caso4(cmol/kg) 1.00 1.00 1.0000 0.0000 1.00 10.00 2.0105 2.4644 cec (cmol/kg) 1.96 16.30 9.3673 5.5536 2.17 21.74 9.2905 5.9732 % clay 6.00 35.00 16.0909 8.9045 4.00 30.00 11.5789 7.1594 materials and methods soil sampling and preparations: thirty surface (010 cm) and subsurface (10-20 cm) agricultural soils were sampled from the batinah (barka) and interior (adam) regions of oman. soils were selected from cultivated areas to have a wide range of ph, salinity and textures. all samples were air dried at 25oc and passed through a 2-mm sieve. soil ph determination: soil ph was determined for each sample in distilled water (phwa), 0.01m cacl2 (phca), 1m kcl (phk) and 0.01m bacl2 (phba) electrolyte solutions. soil/solution ratios of 1:1 and 1:2.5 (w/v) for each electrolyte were used. the soil/electrolyte suspensions were shaken manually every 10 minutes for 30 minutes. values of ph were recorded after 1 minute of stirring. all ph determinations were performed at room temperature (20 ± 2oc) using jenway 3020 ph meter and philips combined glass/calomel electrode (type ce1), that had previously been calibrated at ph 7.0 and 9.0. the meter was recalibrated, when necessary, to ensure accuracy. soil electrical conductivity determination: soil salinity was assessed by measuring the electrical conductivities in saturated paste extracts (ecsp) and 1:1 (w/v) soil/water suspensions. after adding distilled water and mixing saturated soil pastes were left for 1h to stand and then filtered under vacuum. for each soil/solution ratio, the soil-solution suspensions were shaken automatically for 1h, and ec values of filtered extracts recorded. measurement of ec in pastes and extracts were performed by using a calibrated jenway 4020 conductivity meter connected to a conductivity electrode. determination of soluble cations and sodium adsorption ratio (sar): concentrations of na+, ca2+, and mg2+ in saturated paste extracts were measured by using an atomic absorption spectrometer (pye unicam sp9). the sar for each soil was calculated by using the equation of miller (1990): 2/1]2/)2mg 2(ca of millimoles[/na of millimoles sar −+++ += statistical analyses: analysis of variance (anova) was used to determine the significance of differences in phwa, phca, phk, phba and ec values between soils. the general linear model (glm) procedure was used to test for least significant differences between means, and for significance of regression equations. statistical analyses were performed using statistical analysis system (sas) statistical package. results and discussion soil properties: individual soils within the suite analyzed were classified as saline if the ecsp was more than 4.0 ds/m or non-saline if less than 4.0. minimum and maximum values and variances for each property measured are given in table 1 for saline and non-saline soils separately. saline soils were characterized by relatively high sar values, ranging from 7.31 to 52.10. values of sar in non-saline soils ranged from 2.66 to 9.53, suggesting that non-saline soils were also nonsodic. in general, soils were dominated by calcium carbonate, with contents ranging from 28 to 60%. gypsum contents were low in all soils. the particle size fraction was dominantly sand with clay contributing on average 13.5%. salinity – ph relationships in calcareous soils 43 ! ! figure 1. mean ph values of saline and non-saline soils under different electrolytes. electrolyte effect: anova revealed that the mean ph of non-saline soils was 8.36, being significantly higher (p<0.05, f 1,695 = 224.48) than the mean for saline soils, i.e. 8.20. figure 1 shows that the difference in ph between non-saline and saline soils was greater in the absence of added electrolytes than following their addition. the addition of bacl2 also resulted in significantly lower ph in saline than non-saline soils (p<0.05, f 1,695 = 76.56). in the presence of cacl2 or kcl the differences in ph between non-saline and saline soils were not significant. in general, readings from the ph electrode from non-saline soils tended to fluctuate more than when readings were taken from saline soils. however, ph readings from saline soils in different electrolytes also fluctuated but not to the same extent as in non-saline soils. electrolytes appeared to suppress fluctuations in ph readings, probably due to, both, reducing the liquid junction effect (especially in water) and minimizing alkaline errors. the reduction in fluctuation between ph values in non-saline and saline soils supports the use of electrolytes especially in non-saline soils. soil salinity, sodicity and ph relationships: sodic soils conditions are believed to occur when the sar soil extracts exceed 15. in oman, soil salinization is frequently associated with addition of irrigation water high in sodium to soil. consequently, non-saline sodic soils are rare in cultivated soil of oman. soils, in the collection under study, belong mostly to either non-saline/non-sodic, or saline-sodic categories. figure 2 shows the relationship between ecsp and sar for all the soils under investigation. the linear regression line (sar = 0.464 ec + 7.077, r2 = 0.83) fitted to the data collection is highly significant (p<0.001), suggesting that the cause of salinity in these soils was a high concentration of sodium ions. 0 10 20 30 40 50 60 0 25 50 75 figure 2. ec – sar (saturated paste) relationship. figure 3 shows the relationship between phwa and log ec (1:1) for all soils studied. the linear regression equation is given in equation 1 below. the negative relationship between phwa and salinity was significant (p<0.001), for saline and non-saline soils analyzed separately. in both groups, soils with lower phwa tended to be more saline, than those of higher phwa values. it can be concluded that phwa values in the calcareous soils in investigation were inversely related to salinity. the inverse relationship between ph and salinity was less apparent when ph was measured in different electrolyte solutions. however, ph measured in electrolyte solutions were considerably less closely related to ec (1:1) values than when measured in water. it appears that measurements of ph in water are highly sensitive to differences in soil salinity whereas the measurements of ph in electrolyte solutions are indicative of electrolyte-soil interactions which are not similar to soil-water interactions. figure 3. soil ec – ph relationship. 7.6 7.8 8 8.2 8.4 8.6 8.8 9 ca ba k wa ph ns s ec (ds/m) s a r 7.5 7.7 7.9 8.1 8.3 8.5 8.7 8.9 9.1 -0.7 -0.2 0.3 0.8 1.3 1.8 ph w a log ec (ds/m) electrolytes al-busaidi and cookson 44 the calculated regression relationship between ph and ec (1:1) is given in equation 1: )1(0.77r,1):(10.4881ogec8.81waph 2 =−= this equation is not entirely supported by other published research. according to gupta et al., (1989) sodium ions react in calcareous soils to form sodium carbonate and bicarbonate, which by hydrolyzing at ph values more than of 8.8, leads to a direct relationship between soil salinity and ph. in the absence of concentrations of sodium ions, soil ph has also been found to decrease as salinity increases. since the inverse ph-salinity relationship depends on the absence of high concentrations of sodium ions in soil then in the present study, where soils were both saline and saline-sodic, no direct relationship between the two variables was expected. however, finding an inverse relationship suggests that sodium, as either carbonate or bicarbonate, were either not present in the soils or did not hydrolyze rapidly enough, during ph measurement, to have an appreciable effect on ph. many factors have been found to contribute to phsalinity relationships in calcareous soils. among these, the following are relevant to the present study of arid soils: in the presence of sodium ions, ph of calcareous soils often exceeds 8.5 and may reach as high as 12. this situation was not encountered in the present study since the ph value of the most saline-sodic soil was only 8.2, suggesting that formation of sodium carbonate and bicarbonates from the reaction between calcium carbonate and sodium did not occur in the soils. soil aeration can influence co2 exchange in soils. high ph values are rarely attributed to caco3 in aerated soils. when the aeration is poor, as in many alkali soils, and carbon dioxide is absent, then caco3 may produce ph values of 8.5 or higher (foth and ellis, 1988). in oman, soils are mostly light textured, rarely poorly aerated and appear to experience generally free exchange of carbon dioxide with the atmosphere. hence co2 consumes oh ions, and thus restrains the rise of ph [oh + co2 " hco3 -]. in addition to that, the presence of caco3 in the soil is also a major source of gaseous co2, through the reaction with carbonic acid: (2)2hcocacohcaco 3 2 323 −+ +↔+ calcareous soils were highly buffered with respect to calcium. when calcium ions are present on exchange sites and in sufficient quantity in the soil solution, calcium carbonate will precipitate. as long as calcium dominates the cation exchange complex rather than sodium, the soil ph is buffered and unlikely to rise above 8.5. the buffering effect of calcium leads to precipitation of calcium carbonate through the following reaction: (3)o2h2co 2ca2h(calcite)3caco ++ +↔++ figure 4: ph of water at 1:2.5 dilution ratio with log ca. under more acid conditions, the equilibrium will start to move from left to right, effectively increasing soil ph. conversely, if hydroxide ions are generated they will react with hydrogen ions thus forcing the equilibrium to the left (figure 4). the equilibrium relation between ph and the partial pressure of co2 (i.e. pco2) in the air for the system caco3-h2o-co2 can be expressed as follows: (4)k1og2pco1/21og1/21og(ca)ph +−−= where k is an equilibrium constant. the relationships between soil ph, salinity, caco3 and ca2+ in a heterogeneous system, such as a calcareous soil, can be represented by equations 5, 6 and 7. the calcium hydroxide activity is fixed by pco2 but the individual ionic activities of calcium and hydrogen may increase or decrease as influenced by soluble salts and exchange reactions (5)ohnah)soil(cao2hna)soil(ca −+++−−↔+−− (6)2oh2cana)soil(2ho22hna)soil(ca −+++−−↔+−− (7)o2h3caco2co2oh 2ca +→+−++ if sufficient calcium comes into solution at high ph, calcium carbonate will precipitate. through the reaction presented in equation (3), h+ are liberated passing from right to left, which neutralizes the hydroxide ion produced by the hydrolysis reaction in equation 5. displacement of na+ by hydrolysis liberates hydroxide, which remains in solution, thus raising the solution ph. increases in soil ph above 8.5 are associated with high concentrations of exchangeable sodium ions (sar > 15%), and low ec (< 4 ds/m). a high concentration of sodium chloride in the soil solution suppresses the displacement of exchangeable sodium by hydrogen (equation 6) as a consequence of the ratio law (cresser et al., 1993). 7.8 8 8.2 8.4 8.6 8.8 9 9.2 9.4 0 0.5 1 1.5 2 ph w a log ca (mmol/1) salinity – ph relationships in calcareous soils 45 in the case of accumulation of sodium ions in soil, calcium and magnesium can be displaced by sodium. however, the calcium and magnesium thus replaced are not converted into soluble calcium and magnesium salts, but probably precipitated principally as carbonates, and a lesser extent as silicates. consequently, the leaching process may not remove any significant amount of calcium and magnesium from the soil. reducing soluble sodium salts by leaching gives an opportunity for calcium minerals to react with sodium exchange complex. consequently, sodium is gradually replaced by calcium with the formation of na2co3 and nahco3 as follows: (8)conaclay)(cacacoclay)(na 323 +−↔+− sodium carbonate and bicarbonate formed by these reactions have to be leached into the subsoil and lost to drainage. soil solution salinity and ionic strength effects on soil ph. mcgeorge (1935) showed that phwa decreases with increasing concentrations of nacl. he speculated that the ph of the soil increased as the salt concentration of the soil solution was reduced because of an increase in the hydrolysis of the sodium clay complex. no definite relationship could be found between soluble salts concentration in soil and phwa, probably due to the wide variation in the composition of the salts present in different soils (mcgeorge, 1938). salinity increases the ionic strength of the soil solution and consequently suppresses the activity coefficient of ions in solution. this would result in increasing the ph values, but increasing ionic strength mainly decreases the ph values because salinity decreases the junction potential. garrels and christ (1990) found a direct relationship between calcite solubility and ionic strength under the influence of sodium chloride. the following factors sulfate complexing, the absence of equilibrium conditions, and the presence of more soluble forms of calcium carbonate may account for the differences between ph values of different calcareous soils (clark, 1964). presence of gypsum in soil can reduce ph and affect sodium solubility. generally, gypsum is found only in arid soils where leaching is restricted. application of gypsum to sodium-affected soils in the ph range of 8.5 to 10 raises soluble ca2+ above that of the calcite and leads to the precipitation of calcite with the release of hydrogen ions as presented in equation (3). the ph then drops to the range of 7.5 to 8.0 where gypsum and calcite can coexist. in this way soluble ca2+ is restored to approximately 10-2.5 m, keeping the soil colloids flocculated and predominantly calcium saturated. displaced na+ can then be leached from the soil as drainage is supplied (suhayda et al., 1997). the common-ion effect on ca solubility (i.e. the addition of ca to soil solutions from sources other than caco3 or exchange sites) can lead to an increase in the concentration of ca that supersaturates the solution and causes precipitation. this is the case when caco3 precipitates in the presence of ca2+ ions from a combination of caco3 and caso4 sources. precipitation continues until the product of ca2+ and co3 2ion activities is reduced to the equilibrium constant (of 10-10). in this case, reactions 9, 10 and 11 occur, with the formation of ca2+ ions. (9)10k(aq)co(aq)ca(s)caco i. 1023 2 3 −−+ =+↔ )01(24so 2ca4(s)caso ii. −++↔ kcaco3 = aca 2+ . aco3 2 where aca2+ and aco3 2are activities of ca 2+ and co3 2 ions, respectively. then10kif 10−! (11)(aq)23co(aq) 2ca(s)3cacoiii. −++→ conclusions soils in oman are mostly calcareous, and might, at first, be expected to vary little in terms of their ph value. however, this study showed that statistically significant differences in ph are found between soils. the soils investigated varied from being virtually non-saline to being excessively saline. soil extract was negatively related to ph in all electrolytes, especially to phwa (r 2 = 0.77). a possible reason for the negative relationship was that soils were influenced by increased solubility of ca2+ ions in saline conditions under ambient atmospheric co2 concentrations that lead to a release of hydrogen ions. other soil parameters such as caco3, gypsum and clay contents were also studied but their influence on soil ph did not appear to be as prominent as the concentration of soluble ca2+ ions. the ph of calcareous soils has not generally been studied extensively because soil scientists once believed that the presence of a powerful buffer, such as calcium carbonate, would prevent significant changes in ph. however, it is becoming to be recognized that the behavior of carbonate and bicarbonate anions of different elements, including major soil cations such as ca2+, mg2+, and na+, can cause significant changes in ph. the present study should be considered only as a commencement of the work needed in order to fully understand ph behavior in the soils of oman. finally, more research is needed on the chemical reactions in calcareous soils in general, especially on ph dependent reactions. a comparison between ph dependent reactions in calcareous and acidic soils would help in highlighting areas of differences in soil behavior. al-busaidi and cookson 46 references clark, j.s. 1964. an examination of the ph of calcareous soils. soil science 98(3):145-151. cresser, m., k. killham, and t. edwards. 1993. soil chemistry and its applications. soil ph, 65-117. cambridge university press. new york. foth, h.d. and b.g. ellis. 1988. soil fertility. soil ph and its management, 36-59. wiley, new york. garrels, r.m. and c.l. christ. 1990. solutions, minerals and equilibria. carbonate equilibria, 77-131. jones and bartlett publishers, boston. gupta, r.k., r.r. singh, and i.p. abrol. 1989. influence of simultaneous changes in sodicity and ph on the hydraulic conductivity of an alkali soil under rice culture. soil science 147(1): 28-33. lai, r. and b.a. stewart. 1990. soil degradation. salt–affected soils, 224-247. springer–verlag. new york. ministry of agriculture and fisheries (maf). 1993. south batinah integrated study. directorate general of agricultural research, ministry of agriculture and fisheries, sultanate of oman. mahrous, f.n., d.s. mikkelsen, and a.a. hafez. 1983. effect of soil salinity on the electro-chemical and chemical kinetics of some plant nutrients in submerged soils. plant and soil 75:455-472. mcgeorge, w.t. 1935. the measurement and significance of hydroxyl-ion concentrations in alkaline-calcareous soils. arizona agricultural experimental station technical bulletin 57:239-271. mcgeorge, w.t. 1938. factor contributing to the reaction of soils and their ph measurement. arizona agricultural experimental station technical bulletin 78:95-126. miller, r.w. 1990. soils. (6th ed) salt–affected soils and their reclamation, 308-319. prentice hall international editions, usa. page, a.l., r.h. miller, and d.r. keeney. 1982. methods of soil analysis, chemical and microbiological properties. 2nd ed. soil ph and lime requirement, 199-223. madison, wisconsin usa. sas. 1985. user’s guide (5th ed). sas institute inc. cary, north carolina. suhayda, c.g., l. yin, r.e. redmann, and j. li. 1997. gypsum amendment improves native grass establishment on saline– alkali soils in northeast china. soil use and management 13:43-47. tan, h.k. 1993. principle of soil chemistry. 2nd ed. soil reaction, 255-278. marcel dekker, new york. ______________________________________________________ received may 2001. accepted february 2003. sultan qaboos university journal for scientific research agricultural and marine sciences, 10(1):13-19 (2005) ©2005 sultan qaboos university 13 * corresponding author prediction of composition of broiler chicken excreta using near-infrared reflectance spectroscopy i. t. kadim*, w. al-marzooqi, o. mahgoub and k. annamalai department of animal and veterinary sciences, college of agricultural and marine sciences, sultan qaboos university, po box 34, al-khod, pc 123, muscat, sultanate of oman التنبؤ بالمكونات الكیمیائیة لفضالت الدواجن بأستخدام جھاز معامل االنعكاس باالشعة تحت الحمراء عصام توفیق كاظم الجافة المادة بمحتوى للتنبؤ المطیاف باستخدام الحمراء تحت باألشعة االنعكاس معامل جھاز معايیر تطوير تم الخالصة: فضالت من عینات في والفوسفات والكالسیوم الكلیة والطاقة والحوامض القواعد في الذائبة واأللیاف والدھون والنیتروجین الدجاج الالحم. ثم تحلیل التكوين الكیمائي لبراز الدجاج الالحم بطرق التحلیل الكیمیائیة التقلیدية بالمختبر ومقارنتھا بنتائج جھاز المطیاف تم تجفیف اثنان وسبعون عینة من برا فضالت الدجاج الالحم بدرجة حرارة 60 درجة مئوية تم تحلیلھا لتحديد مستوى المادة الجافة والنیتروجین والدھون واأللیاف الذائبة في القواعد والحوامض والطاقة الكلیة والكالسیوم والفوسفات وكانت قراءات المتوسط العام ومعامل اإلنحراف القیاسي كاآلتي :للمادة الجافة 31.46±7.65 (المدى: 44.51-19.14) والناتروجین 2.88±5.85 (المدى: 1.99±16.7: الحامضیة المحالیل في الذائبة وااللیاف )1.99-0.88 (المدى: 0.25±1.37 4.85-7.00)والدھون )تامدى 0.99±15.27 الكلیة: والطاقة (30.21±22.03 (المدى: 1.63±26.26 القفاعدية المحالیل في الذائبة االلیاف و (19.97-12.11 ثم .(2.11-1.41 (المدى: 0.15±1.79 الفوسفات: و (3.01-2.16 (المدى: 0.22±2.57 والكالسیوم: (16.11-14.52 (المدى: فحصت العینات باستخدام المطیاف موديل 5000 وحدد الخط الطیفي لكل عینة. طورت معادالت المعايرة وقیم التنبؤ لعینات براز الدجاج الالحم كما تم تطوير أنظمة البرنامج لحساب التراجع التربیعي االقل التي تعتبر اكثر مالئمة للمنتجات الطبیعة. وكانت فحصت العینات باستخدام المطیاف موديل 5000 وحدد الخط الطیفي لكل عینة. طورت معادالت المعايرة وقیم التنبؤ لعینات براز الدجاج الالحم كما تم تطوير أنظمة البرنامج لحساب التراجع التربیعي االقل التي تعتبر اكثر مالئمة للمنتجات الطبیعة. وكانت فحصت العینات باستخدام المطیاف موديل 5000 وحدد الخط الطیفي لكل عینة. طورت معادالت المعايرة وقیم التنبؤ لعینات براز r) والخطأ المعیاري المتوقع لعینات من فضالت دجاج االحم للمادة الجافة 0.97 و 1.27وللناتروجین 0.95 و 0.72 الدجاج الالحم كما تم تطوير أنظمة البرنامج لحساب التراجع التربیعي االقل التي تعتبر اكثر مالئمة للمنتجات الطبیعة. وكانت r) والخطأ المعیاري المتوقع لعینات من فضالت دجاج االحم للمادة الجافة 0.97 و 1.27وللناتروجین 0.95 و 0.72 الدجاج الالحم كما تم تطوير أنظمة البرنامج لحساب التراجع التربیعي االقل التي تعتبر اكثر مالئمة للمنتجات الطبیعة. وكانت 2 معامل التقدير( وللدھون 0.92 و 0.07 و لاللیف الذائبة في الحوامض 0.87 و 0.78 و لاللیاف الذائبة في القواعد 0.88 و 0.72 و للطاقة الكلیة 0.89 و 0.24 و للكاسیوم 0.96 و 0.06 و للفسفور 0.93 و 0.09 باتتابع. أشارت نتائج ھذا البحث إلى امكانیة استخدام معیار المطیاف وللدھون 0.92 و 0.07 و لاللیف الذائبة في الحوامض 0.87 و 0.78 و لاللیاف الذائبة في القواعد 0.88 و 0.72 و للطاقة الكلیة 0.89 و 0.24 و للكاسیوم 0.96 و 0.06 و للفسفور 0.93 و 0.09 باتتابع. أشارت نتائج ھذا البحث إلى امكانیة استخدام معیار المطیاف وللدھون 0.92 و 0.07 و لاللیف الذائبة في الحوامض 0.87 و 0.78 و لاللیاف الذائبة في القواعد 0.88 و 0.72 و للطاقة الكلیة 0.89 للتنبؤ بمكونات فضالت الدجاج الالحم. abstract: near-infrared reflectance spectroscopic (nirs) calibrations were developed for the prediction of the content of dry matter (dm); nitrogen (n), ether extract (ee), neutral detergent fibre (ndf), acid detergent fibre (adf), gross energy (ge), calcium (ca) and phosphate (p) in broiler excreta samples. the chemical composition of broiler excreta was determined by the conventional chemical analysis methods in the laboratory and compared with nirs. excreta samples (n = 72) were oven dried (60 oc) and analyzed for dm, n, ee, ndf, adf, ge, ca and p. the determined values (mean ± sd) were as follows: dm: 31.46 ± 7.65 (range:19.14 44.51), n: 5.85 ± 2.88 (range: 4.85 -7.00), ee: 1.37 ± 0.25 (range: 0.88-1.99), adf: 16.71 ± 1.99 (range: 12.11-19.97), ndf: 26.26 ± 1.63 (range: 22.03-30.21), ge: 15.27 ± 0.33 (range: 14.52-16.11), ca: 2.57 ± 0.22 (range: 2.16-3.01), p: 1.79 ± 0.15 (range: 1.41-2.11). the samples were then scanned in a nirs model 5000 analyzer and the spectra obtained for each sample. calibration equations and prediction values were developed for broiler excreta samples. the software used modified partial least square regression statistic, as it is most suitable for natural products. for broiler excreta samples, the coefficient of determination (r2) and the standard error of prediction (sep) was dm = 0.97, 1.27, n = 0.95, 0.72, ee = 0.92, 0.07, adf = 0.87, 0.78, ndf = 0.88, 0.72, ge = 0.89; 0.24, ca = 0.96, 0.06, p = 0.93, 0.09, respectively. the results indicate that it is possible to calibrate nirs to predict major constituents in broiler excreta samples. keywords: spectroscopy, broiler, excreta, calibration, oman. introduction poultry manure, which is a pollutant in soil and water, is produced in large quantities by the poultry industry. an accurate and fast analytical procedure to detect poultry manure components is becoming more critical in areas with intensive poultry production (reeves, 2001). in some countries, restrictive manure management guidelines have been adopted, which kadim et. al. 14 need a quick, easy and reliable method for determining excreta composition to assist those abiding by and enforcing regulations. to manage these pressures, it is necessary to collect as much information as possible on raw materials, which depend on analytical laboratory techniques. traditionally, chemical reference methods are laborious, time consuming and generate hazardous wastes. near-infrared reflectance spectroscopy (nirs) has been widely used as a rapid and accurate method for measuring some constituents of materials without requiring extensive sample preparation (norris et al., 1976). components successfully measured include nitrogen, moisture, fibre, starch, individual sugar, amino acids, and fat (foley et al., 1998; fontaine et al., 2002; smith et al., 2001; valdes and summers, 1986), the principle of nirs is the selective absorption of electromagnetic radiation from 800 to 2500 nm in accordance with the characteristic vibration frequencies of functional groups (de boever et al., 1994). it has the capability to measure ch, nh, oh bonds, which form the functional groups in moisture, protein, amino acids, fibre, sugar and fat in biological samples. although organic complexes may be detected (shenk et al., 1992), no absorption bands for minerals exist in the near-infrared region. every biological substance has a unique nirs composite spectrum, depending on their characteristic functional groups; the nirs spectrum of a sample is the composition of all the physical and chemical information of the sample (de boever et al., 1994; murray and williams, 1987). the objectives of the current study were to calibrate nirs spectrometer equations and to evaluate their accuracy to predict chemical composition, moisture, nitrogen, ether extract, neutral detergent fibre, acid detergent fibre, gross energy, calcium and phosphorus in broiler excreta. materials and methods seventy-two broiler excreta samples (500 g) were randomly collected from a broiler feed evaluation project. the excreta samples were dried in a forced air oven at 60 oc until no decrease in weight occurred. all samples were then left on the laboratory bench for over 48 h to equilibrate with atmospheric moisture. the samples were ground in a cyclotech 1093 sample mill with a 0.5-mm screen and were stored in plastic bags until analysis. laboratory analysis excreta samples were analysed for dry matter (dm) by drying in an oven at 60 oc until no decrease in weight occurred, and for organic matter (om) and ash by ashing dry samples at 450 oc for 12 h in a muffle furnace (aoac, 1990). triplicate samples of approximately 2 g each were freeze-dried for 4 days for ether extraction (ee) by petroleum ether in a soxhlet apparatus. nitrogen (n) was determined by the kjeldahl method. neutral detergent fibre (ndf) was determined by using sodium sulphite and sodium lauryl sulphate as a neutral detergent extracting solution as described by van soest et al. (1991). acid detergent fibre (adf) was determined using table 1. values for chemical analysis in 72 broiler excreta samples used for the near-infrared reflectance equation .and validation. variable mean sd range sec secv r2 1-vr dry matter (%) 31.46 7.65 19.14-44.51 1.18 1.27 0.97 0.97 nitrogen (%) 5.85 2.88 4.85-7.00 0.64 0.72 0.95 0.93 ether extract (%) 1.38 0.25 0.88-1.99 0.07 0.07 0.92 0.91 acid detergent fibre (%) 16.72 1.99 12.11-19.97 0.71 0.78 0.87 0.85 neutral detergent fibre (%) 26.26 1.63 22.03-30.21 0.55 0.72 0.88 0.81 gross energy (mj/kg) 15.27 0.33 14.52-16.11 0.22 0.24 0.89 0.47 calcium (%) 2.57 0.22 2.16-3.01 0.04 0.06 0.96 0.92 phosphorous (%) 1.79 0.15 1.41-2.11 0.08 0.09 0.93 0.61 sd: standard deviation, sec: standard error of calibration, secv: standard error of cross validation, r2: coefficient of determination, 1-vr: 1variance ratio. prediction of composition of broiler chicken excreta using near-ir reflectance spectroscopy 15 cetyl trimethyl ammonium bromide and 1n h2so4 as described by roberston and van soest (1981). calcium (ca) and phosphorus (p) were measured with an atomic absorption spectrophotometer (philips model pu9100, single beam) according the procedures of aoac (1990). gross energy (ge) was measured using a bomb calorimeter. analysis for all items was done in triplicate on a dry matter basis. near-infrared reflectance spectroscopy analysis samples were divided into calibration and prediction sets, which consisted of 72 and 40 samples, respectively. prediction samples were randomly selected from the calibration samples. all calibration samples were analysed by conventional chemical methods in the laboratory and then scanned in the nirs for comparison. a feed and forage foss nirs systems model 5000 reflectance transport model analyzer was used for scanning samples and collecting spectra. the software used was winisi ii version 1.50. interpretation of nirs spectra was done by calibrating with reference values obtained from laboratory analysis of the sample and correlating them to nirs measurements of these samples. the reference laboratory data and the sample spectra were used to develop predictive equations. samples were uniformly mixed and loaded in the nirs sample cups. about 5-6 g of ground sample were placed in sample cup to about 8 mm depth, then covered to be processed on the holder gently. consistency in sample preparation and packing is important for accuracy. the nir spectrum for each sample was recorded as log 1/r (reflectance) for each wavelength in the nirs range. calibration the mathematical relationship between chemical reference values and the nirs spectral data was analysed by linear regression. calibrations were made using reference values on a dry matter basis, so the nirs predicted results are also expressed on a dry matter basis. spectra of 72 broiler excreta samples were collected in the nirs region (800-2800 nm). calibration equations were computed for dm, n, ee, adf, ndf, ge, ca and p using modified partial least squares regression using the winisi ii software. the program calculates the mathematical relationship between the spectral data from the scanned sample and its reference values obtained by standard chemical procedures. the program then calculates the cross validation errors for each component, and the modified partial least square statistics was determined. the program repeats this process for each component and upon completion, the nirs equation was developed to predict the constituents in the product. statistically, the equation was evaluated using the monitor results program, which performs a statistical comparison between chemical reference values and nirs predicted values for the data set. it also provided tabular and graphical comparison of the two values. model performance was reported as the coefficient of determination (r2), standard error of prediction (sep), and linear regression of components reference method against predicted values (slope) (hurschka, 1987). results and discussion the descriptive statistics for the different constituents of broiler excreta are summarized in tables 1 and 2. there was a considerable variation in the composition, table 2. near-infrared transmission calibration and validation statistics for broiler excreta. variable mean sd range sep bias r2 slope dry matter (%) 31.20 7.44 20.93-42.81 1.56 0.188 0.96 1.01 nitrogen (%) 5.97 2.59 5.22-6.80 0.77 0.125 0.93 1.04 ether extract (%) 1.38 0.27 0.86-1.91 0.10 0 0.88 1.01 acid detergent fibre (%) 17.20 1.41 14.06-19.32 1.07 0.053 0.65 1.05 neutral detergent fibre (%) 26.50 1.47 22.37-29.51 0.83 0.048 0.73 0.94 gross energy (mj/kg) 15.20 0.22 14.77-15.63 0.31 0.043 0.85 0.99 calcium (%) 2.57 0.19 2.22-2.97 0.07 0.004 0.89 0.97 phosphorous (%) 1.79 0.11 1.52-2.01 0.11 0.023 0.91 0.82 sep: standard error of prediction. kadim et. al. 16 figure 1. the relationship between near-infrared reflectance spectroscopy (nirs) predictions and determined percentage dry matter values of 72 broiler excreta samples. figure 2. the relationship between near-infrared reflectance spectroscopy (nirs) predictions and determined nitrogen values (%) of 72 broiler excreta samples. as shown by the wide range of values. it is essential for any calibration procedure to ensure that a range of spectral variation found in the whole population is represented in the samples selected for calibration development (foley et al., 1998). calibration and validation statistics are shown in tables 1 and 2, respectively. the range of excreta parameters of dm, n, ee, ndf, adf, ge, ca and p in the calibration set are similar to the corresponding ranges in the prediction set. limited studies have been conducted utilizing nirs to analyse the chemical composition of poultry manure or excreta (reeves, 2001; smith et al., 2001). contradictory conclusions have been reported by these authors on the suitability of the nirs to estimate the mineral contents. the findings of reeves (2001) indicated that nirs was not suitable for the determination of minerals (p, ca, etc.) in poultry manure. this may be attributed to the nature of the samples being used. however, smith et al. (2001) attempted to calibrate an nirs to predict the ca and p contents of chicken excreta. they obtained an r2 of 0.86, an sep of 0.14 for ca and r2 0.93 and an sep of 0.13 for p. they concluded that nirs was a good predictor for ca and total p content of chick excreta. there are no absorption bands for minerals in the near-infrared region, but organic complexes and chelates may still be detected (de boever et al., 1994). studies have shown that ca and p may exist in forms detectable by nirs, at least in some grasses and legumes (clark et al., 1987; saiga et al., 1989). the calibration values obtained for p in forages were figure 3. the relationship between near-infrared reflectance spectroscopy (nirs) predictions and determined fat values (%) of 72 broiler excreta samples. figure 4. the relationship between near-infrared reflectance spectroscopy (nirs) predictions and determined gross energy values (%) of 72 broiler excreta samples. prediction of composition of broiler chicken excreta using near-ir reflectance spectroscopy 17 found to be acceptable by clark et al. (1987) but were not acceptable in similar studies by vasquez aldana et al. (1995). de boever et al. (1994) reported that p of feedstuffs could be predicted by nirs with an r2 of 0.94 to 0.96 and sep of 0.08. in grass samples, dealdana et al. (1995) found that ca could be predicted with an r2 0.73 to 0.92 and an sep 0.15 to 0.22. the estimation of mineral elements by nirs is generally dependent on the occurrence of these elements in organic or hydrated molecules (clark et al., 1987; vasquez de aldana et al., 1995), or mineral levels may simply be correlated to some organic material that the nirs can easily measure. the findings of the present study confirm previous reports that nirs is a good predictor for ca and p with an r2 of 0.89 and 0.91, respectively. similarly, high coefficients of determination and relatively low sep were obtained in the present study for dm (r2, 0.96, sep, 1.56) (figure 1), n (r2, 0.93, sep, 0.77) (figure 2), fat (r2, 0.88, sep, 0.10) (figure 3), ge (r2, 0.85, sep, 0.31) (figure 4), adf (r2, 0.65, sep, 1.07) (figure 5), ndf (r2, 0.73, sep, 0.83) (figure 6), ca (r2, 0.89, sep, 0.07) (figure 7) and p (r2, 0.91, sep, 0.11) (figure 8). there have been some studies utilizing nirs to analyse the moisture and n content of excreta samples. smith et al. (1999) reported an r2 of 0.97 with an sep of 0.91 for determining the n content of rooster excreta and an r2 of 0.92 with an sep of 0.13 for ge determination. smith et al. (2001) reported an r2 of 0.93 with an sep of 0.34 for moisture and an r2 figure 5. the relationship between near-infrared reflectance spectroscopy (nirs) predictions and determined acid detergent fibre values (%) of 72 broiler excreta samples. figure 6. the relationship between near-infrared reflectance spectroscopy (nirs) predictions and determined neutral detergent fibre values (%) of 72 broiler excreta samples. figure 8. the relationship between near-infrared reflectance spectroscopy (nirs) predictions and determined phosphorous values (%) of 72 broiler excreta samples. figure 7. the relationship between near-infrared reflectance spectroscopy (nirs) predictions and determined calcium values (%) of 72 broiler excreta samples. kadim et. al. 18 of 0.99 with an sep of 0.19 for n contents of chicken excreta, thus supporting the findings of the present study. conclusions the current study has indicated that determination of the composition of broiler excreta by nirs is feasible with high accuracy. therefore, nirs may be routinely used to predict excreta constituents. it may also be useful in monitoring environmental contamination by the poultry industry. with the inclusion of more samples in the calibration set to cover a broader range of constituents as well as some more refinement in the sampling technique, it would likely seem that more robust calibrations could be developed. nirs requires no consumables, it is environment friendly, has no operational cost, needs no sample preparation (only drying and grinding to uniform size) and is cost effective and reproducible. once the initial calibration and equation model for the excreta sample has been established, nirs may be used to replace wet chemistry in quantifying many compositional parameters of poultry excreta samples to an acceptable level of accuracy,. references aoac. 1990. official methods for analysis, 15th ed. association of official analytical chemists, arlington, va, pp 69-90. clark, d.h., m.h. ralphs and 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the agricultural and food industries, 17-34. american association of cereal chemists, inc., st paul, mn, usa. windham, w.r., k.c. lawrence and p.w. feldner. 2003. prediction of fat content in poultry meat by near-infrared transmission analysis. journal of applied poultry research 12:69-73. received: october 2004 acceptted: october 2005 sultan qaboos university journal for scientific research agricultural and marine sciences, 10(1):1-4 (2005) ©2005 sultan qaboos university 1 * corresponding author habitat variation and its effect on the morphological characters of three wild plant species in el-riyadh city w.k. taia1* and h.a. el-olyan2 1 alexandria university, faculty science, botany department, alexandria, egypt, 2 girl`s college of education, el-riyadh, kingdom of saudi arabia تغیر البیئات وتأثیرھا على صفات الشكل الخارجي لثالث أنواع نباتیة منتشرة في مدينة الرياض ھیفاء العلیان الخالصة: ھذه الدراسة تتناول مدى تأثیر الظروف البیئیة المحیطة على الصفات التصنیفیة للنباتات. ولذا فقد تم إختیار ثالث أنواع نباتیة منتشرة بمدينة الرياض وھم francoeuria crispa, rumex vesicarius, zilla spinosa. وجمعھم من ثالث بیئات مختلفة. وقد روعي جمع 25 عینة نباتیة من كل نوع وكل موقع. ومن النتائج المتحصل علیھا وجدنا أن الحالة العامة للنبات تتأثر بالبیئة النالمي بھا وكذلك طوله ولون سیقانه ومرحلة التزھیر واألثمار. ومن التحلیل المرتبط التبادلي للبیئات وجدنا أن صفات األوراق ال وقد روعي جمع 25 عینة نباتیة من كل نوع وكل موقع. ومن النتائج المتحصل علیھا وجدنا أن الحالة العامة للنبات تتأثر بالبیئة النالمي بھا وكذلك طوله ولون سیقانه ومرحلة التزھیر واألثمار. ومن التحلیل المرتبط التبادلي للبیئات وجدنا أن صفات األوراق ال وقد روعي جمع 25 عینة نباتیة من كل نوع وكل موقع. ومن النتائج المتحصل علیھا وجدنا أن الحالة العامة للنبات تتأثر بالبیئة تتأثر يصورة معنوية تبعا للتغیر في البیئات. ولذا فأننا نوصي باإلعتماد علیھا في التصنیف وعمل العالقات بین النباتات. النالمي بھا وكذلك طوله ولون سیقانه ومرحلة التزھیر واألثمار. ومن التحلیل المرتبط التبادلي للبیئات وجدنا أن صفات األوراق ال تتأثر يصورة معنوية تبعا للتغیر في البیئات. ولذا فأننا نوصي باإلعتماد علیھا في التصنیف وعمل العالقات بین النباتات. النالمي بھا وكذلك طوله ولون سیقانه ومرحلة التزھیر واألثمار. ومن التحلیل المرتبط التبادلي للبیئات وجدنا أن صفات األوراق ال abstract: fourteen taxonomic characters have been studied in three wild plant species in el-riyadh city; francoeuria crispa, zilla spinosa and rumex vesicarius; collected from three different habitats. the results of this study revealed that the habitats have insignificant effect on the leaf characters in spite of the slight effect on the general status, fruiting stage and color of the plants. cross correspondence analysis between the habitats revealed that the variations were within the confidence limits. it is concluded that leaf characters can be used as an effective selection criterion for classification. keywords: introduction morphological changes in response to environmental disorders are known as phenotypic plasticity, whereas internal changes are considered adaptation. taxonomists have to be accurate in deciding whether the studied characters are according to environment or specified to that plant. radford (1986) stated that evidence from plant morphology provided the basic language for plant characterization, identification, classification and relationships. thus, vegetative, morphological characters, especially that of the leaf, have been employed as a basis for classification since the early days of taxonomy. in fact, vegetative characters can be unreliable because of the similarity between unrelated species, but even so davis and heywood (1973) deplored the neglect of morphological characters as one of the most serious errors which delay the achievement of a natural system. schlichting and levin (1984), schlichting (1986), sultan (1987), pianka (1988) and grime (1994) have indicated the response of plants to environmental changes which may be under genetic control or may evolve under selection. in the last case, new traits evolved which allowed species to adjust to new environments (mazer and gorchov, 1996). dunn and sharitz (1991) and mazer and wolfe (1992) have found differences in plant biomass, shoot length and even reproductive growth in murdannia keisak grown murdannia keisak grown murdannia keisak in different populations. taxonomists need to be precise in choosing the characters they rely on it. this work deals mainly, with the study of fourteen phenotypic characters in three wild species; francoeuria crispa, zilla spinosa and rumex vesicarius. these species are widely distributed in taia and el-olyan 2 el-riyadh city, saudi arabia. the aim of this work was to investigate the most stable characters which can be of use in taxonomy. meanwhile, we have to know the limits of morphological alteration according to environmental changes. materials and methods the materials were collected from three different habitats in el-riyadh city; 1 el-nargis district, north el-riyadh, in which the soil is dry, hard, with high salt contents and covered with rocks, 2 the beginning of el-riyadh elkharj road, south east el-riyadh, in which the soil is calcareous, loamy and affected by the nearby factories and 3 wadi hanifa, south el-riyadh, in which the soil is sandy with a high water content. these habitats are completely different in their soil characteristics (taia and el-ghanem, 2001). at least 20 specimens from each species per location were used. all the specimens were collected during the middle of february 2002. the first three characters were measured in the field, while the rest were studied in the laboratory at el-riyadh. for plant moisture contents 100 grams of the shoot system was dried at 95 ºc overnight. the data obtained from each species/location were summarized using a chandat computer programme. then a cross correspondence analysis for the summarized data was carried out to evaluate the effect of the habitats on the studied characters. results table 1 summarizes the studied characters and their status in the different species gathered from the three habitats. f. crispa in the first location (el-nargis district) is more widely distributed than in the other two locations. but, in spite of its abundance it was dry, short, the colour of the plant was whitish green and it was sparsely branched. in the second location (el-riyadhel-kharj road) the density of the plant was low but it was flourishing and was taller, although it table 1. characters studied and their status in three habitats. location/habitatlocation/habitat el-nargis districtel-nargis district el-riyadhel-kharjel-riyadhel-kharj wadi hanifawadi hanifa sp. char. f.crispaf.crispa z.spin.z.spin. r.vesi.r.vesi. f.crispaf.crispa z.spni.z.spni.z.spni.z.spni. r.vesi.r.vesi. f.crispaf.crispa z.spin.z.spin. r.vesi.r.vesi. densitydensity 3 3 3 1 1 2 2 2 1 appearance 1 2 3 1 2 2 3 3 1 sh.syst.l. 20-30 70-85 10-22 40-62 65-72 10-15 80-110 95-150 6-10 color 1 2 2 1 2 2 3 4 4 branches 2 2 2 2 3 2 4 4 1 leaf color 3 1 3 3 1 3 3 4 2 leaf marg. 2 1 1 3 1 1 2 1 1 leaf apex 1 1 1 1 1 1 1 1 2 leaf length 1.7-2.2 2.05 1.1-1.5 1.4 4.5-5.2 4.97 2.2-2.5 2.38 1.6-2.3 2.05 3.0-4.0 3.2 2.0-2.2 2.14 1.5-1.8 1.61 2.5-4.0 3.2 leaf width 0.3-0.4 0.38 0.2-0.3 0.27 2.5-2.9 2.75 0.3-0.5 0.42 0.3-1.0 0.6 2.0-3.5 2.8 0.4-0.5 0.45 0.4-0.5 0.41 2.0-3.2 2.8 leaf shape 1 1 3 1 2 4 1 1 4 moisture 62.5 60.6 85.62 73.1 76.8 88.62 69.5 69.6 87.18 fruit 0 2 2 0 1 1 0 1 0 fruit shape 0 2 1 0 2 1 0 2 0 characters: density 1 = low, 2 = moderate, 3 = dense; appearance 1 = dry, 2 = slightly flourished, 3 = flourished; shoot system length in cm.; colour of the shoot system 1 = whitish green, 2 = green, 3 = bright green 4 = olive green; density of branches 1 = unbranched, 2 = branched, 3 = densely branched, 4 = very densely branched; leaf colour 1 = pale green, 2 = green, 3 = olive green, 4 = dark green; leaf margin 1 = entire, 2 = undulated, 3 = sinuated; leaf apex 1 = acute, 2 = rounded; leaf length in cm.; leaf width in cm.; leaf shape 1 = lanceolate, 2 = ovate-lanceolate, 3 = obovate, 4 = broadly-obovate; plant moisture content (percentage); fruit 0 = absent, 1 = present, 3 = dense; fruit shape 0 = absent, 1 = flat, 2 = globular. figures in parenthesis are mean values. habitat variation and its effect on the morphological characters of three wild plant species 3 was still whitish green and the branches were few. in wadi hanifa f. crispa was moderately abundant and the plants were flourishing, being tall, bright green and with many branches. in the three habitats there were neither fruits nor flowers. zilla spinosa is widely distributed in the first location, and its status was very good. it was flourishing, being tall and green in color but the branches were few. the distribution of z. spinosa in the second location was sparse, but even so its status was very good as in the first location. this species was moderately abundant in wadi hanifa and indicated its good status with many branches. the plants were in the fruiting stage in the three locations, but the density of the fruits was higher in the first location. the data obtained for r. vesicarius were completely different from that of the previous two species. its presence in wadi hanifa was less than in the other two habitats. at the same time, plants found in wadi hanifa were dry, short, olive green, not branched and without any fruits, whereas in the first two locations it was dense and flourishing, slightly taller, green in color, with few branches and in the fruiting stage. leaf characters for the three species were more fixed, whereas the moisture contents of the plants differed slightly according to the location. these results are demonstrated in figures 1, 2, and 3. the cross correspondence analysis between each pair of habitats shows that the differences between the habitats were within the confidence limits. accordingly the effect of the habitats on the studied characters were insignificant. discussion the effect of habitat type on vegetation has recently been discussed (el-demerdash et al.,1995; taia and el-ghanem, 2001). but how much the variations in the soil characters and the surrounding environment affect the phenotypic characters of the same species has gained less attention. schlichting and levin (1984) have noticed the effect of environmental conditions on the morphology of annual phlox. dunn and sharitz (1991) found that the water available to the plant, besides the light intensity and temperature, altogether can have a direct effect on the phenotypic characters of m. keisak, especially the shoot length. this corresponds with our data, as the three chosen habitats have different soil types, water contents and chemical constituents (taia and el-ghanem, 2002). even so, the changes in the morphological characters in the studied species were insignificant. the observable changes were only in the color of the figure 3. variation in r. vesicarius growing in the three habitats. figure 1. variation in f. crispa growing in the three habitats. figure 2. variation in z. spinosa growing in the three habitats. taia and el-olyan 4 plant, its status, degree of branching and fruiting stage. these characters can be due to the water available to the plants, which differ according to the habitats and the soil salt contents. mahmoud et al. (1985) pointed to the effect of environmental conditions, especially soil salinity, on the structure of the vegetation and degree of speciation. meanwhile, they neglected the effects of environmental changes on morphology. our results show that the main factor affecting the plant is water availability and this may be due to the studied species allocated under the same climatic factors. alawi and abulfatih (1996) have found that the taxonomic characters in calotropis procera grown in two altitutidinal ranges were uniform and this is what we found in the results obtained. our data reveal that the change in habitats which completely differ in their soil structure and constituents (taia and el-ghanem, 2002) has little effect on the phenotypic characters of the plants. the cross correspondence analysis between habitats revealed that the habitats have insignificant effect on the morphological characters and accordingly we can rely on these in taxonomic works. references alawi, h.m. and h.a. abulfatih. 1996. uniformity of morphological characteristics of calotropis procera found in two altitudinal ranges in saudi arabia. arab gulf journal of scientific research 14:169-176. davis, p.h. and v.h. heywood. 1973. principles of angiosperm taxonomy. robert e. krieger publishing co., huntington, new york. dunn, c.p. and r.r. sharitz. 1991. population and phenotypic plasticity in murdannia kiesak (commelinaceae). american journal of botany 78:1712-1723. el-demerdash, m.a., a.k. hegazy and a.m. zilay 1995. vegetation-soil relationships in tihamah coastal plains of jazan region, saudi arabia. journal of arid environments 30:161-174. grime, j.p. 1994. the role of plasticity in exploiting environmental heterogeneity. in exploitation of environmental heterogeneity. m.m. cadwell and r.w. pearcy (editors), pp2-19, academic press, new york. mahmoud, a. a.m. el-sheikh and f. isawi. 1985. ecology of the littoral salt marsh vegetation at rabigh on the red sea coast of saudi arabia. journal of arid environments 5:3542. mazer, s.j. and l.m. wolfe. 1992. density influences the expression of genetic variation in seed mass in wild radish (raphanus sativus:wild radish (raphanus sativus:wild radish ( brassicaceae). american journal of botany 79:1185-1193. mazer, s.j. and d.l. gorchov. 1996. paternal effects on progeny phenotype: distinguishing genetic and environmental causes. evolution 50: 44-53. nicotra, a.b., r.l. chazdon and c.d. schlochting. 1997. patterns of genotypic variation and phenotypic plasticity of light response in two tropical piper (piperaceae) species. american journal of botany 84:1542-1553. pianka, e.r. 1988. evolutionary ecology, 4th. ed. harper and row, new york. radford, a.e. 1986. fundamentales of plant systematics. harper and row, new york. schlichting, c.d. 1986. the evolution of phenotypic plasticity in plants. annual review of ecology and systematics 17: 667-693. schlichting, c.d. and d.a. levin. 1984. phenotypic plasticity of annual phlox: test of some hypotheses. american journal of botany 71:252-260. sultan, s.e. 1987. evolutionary implications of phenotypic plasticity in plants. evolution biology 21:127-178. sultan, s.e. 1995. phenotypic plasticity and plant adaptation. acta botanica neerlandica 44:363383. taia, w.k. and w.m. el-ghanem. 2001. city vegetation analysis of three habitats at el-riyadh. bulletin of pure and applied sciences 20b:53-63. taia, w.k. and w.m. el-ghanem. 2002. comparative ecological studies on the natural vegetation of three different transects within el-riyadh region. ph.d. thesis, girl`s college of education, el-riyadh, saudi arabia.. received: october 2003 approved september 2005 agricultural and marine sciences, 13:1-6 (2008) ©2008 sultan qaboos university 1 *corresponding author. e-mail: alnahdi22@hotmail.com a first record of whip lobsters puerulus sewelli from oman with notes on size, condition and length-weight relationships abdullah al-nahdi*1, abdulaziz al-marzouqi1, johan c. groeneveld1 and ahmed al-hosni2 1 marine science and fisheries centre, p.o. box 227 pc 100, muscat, sultanate of oman 2 ministry of fisheries wealth, p.o. box 427 pc 100, muscat, sultanate of oman abstract: arabian whip lobsters puerulus sewelli were for the first time reported from the waters of oman in 2007, extending its known range along the southeastern coast of the arabian peninsula by ~ 200 km northeastwards from its previous boundary at ras fartak in yemen. the lobsters were caught in exploratory trawls at 230–787 m depth. the size of 67 lobsters ranged from 51–87 mm cl (31.4–161.7 g whole weight, ww). females were larger than males. the size distribution was bimodal, showing recent recruits and post-recruits. female tail weight (tw) became progressively heavier than male tw, relative to increasing, but equivalent cl or ww-values. of the females, 8% were soft-shelled, 19% carried external eggs, and 77.7% had maturing or ripe gonads. الحجم، الحالة في مالحظات مع عمان سلطنة في العربیة السوط األول لشارخة التسجیل بالوزن الطول والعالقات الحوسني وأحمد جرونفلید جوھان ، المرزوقي عبدالعزیز النھدي، عبداهللا ٢٠٠٧ عام في المیاه العمانیة في األعماق شارخة العربیة (puerulus sewelli) أو السوط لشارخة ظھور أول الخالصة: تم تسجیل رأس عند السابقة حدودھا من الغربي الشمال باتجاه كیلومتر ٢٠٠ حوالي العرب بحر شرق جنوب المعروف تواجدھا ویمتد . م عمق یتراوح ما بین على بالجرف صید استكشافیة رحالت خالل االستكشافیة المصائد بواسطة الشارخة اصطیاد تم الیمن. فرتك في أكبر اإلناث أن وتبین الكلي). ١٦١,٧ جرام للوزن ٣١,٤) الدرع لطول مم ٨٧ ما بین ٥١عینة ٦٧ حجم تراوح مترا. ٢٣٠-٧٨٧ األعماق. شارخة لكبار وأخر الشارخة لصغار اإلمدادات یبین ثنائي منحنى ھناك أن یوضح األطوال توزیع أن كما الذكور، من حجما كانت اإلناث من ٪ ٨ نسبتھ ما أن أیضا العینات خالل اتضح من نسبیًا. لدى الذكور منھا أثقل اإلناث الذیل لدى وزن إلى أن باإلضافة ناضجة. مبایض لدیھا ٪٧٧,٧ و خارجیا بیضا تحمل ٪١٩ و ناعمة قشرة ذات keywords: puerulus sewelli, size, oman. introduction the arabian whip lobster, puerulus sewelli ramadan, 1938 (family: palinuridae) (fig. 1) has patchy distribution in the indian ocean region especially in the waters of somalia, the gulf of aden, yemen, pakistan, and sw coast of india and the gulf of mannar (fischer and bianchi, 1984, holthuis, 1991). in the present paper, the occurrence of p. sewelli in the waters of oman is reported for the first time. the lobsters were caught during an exploratory demersal trawl survey conducted in october and december 2007 at depths between 230 and 787 m. puerulus sewelli has been of considerable interest to fisheries (holthuis, 1991). in 1974–1977 and 1983 it was commercially fished off eastern somalia (johnsen, 1985), and in the gulf of aden experimental trawling returned average catches of 10–129 kg/h. off sw india rich fishing grounds were found and in the gulf al-nahdi and others 2 3 a first record of whip lobsters from oman of mannar it was available in varying quantities along the depth belt of 150-500 m (see www.fsi.gov.in). off yemen, a trawl fishery in the 1970s landed between 112 and 428 t annually, but this fishery seems to have collapsed by 1993 (sanders, 1981; anon., 2004), and no catches were reported for 2000–2002. biological information on puerulus sewelli is scattered among various unpublished reports (sanders, 1981; johnsen, 1985) and fisheries survey bulletins (see www.fsi.gov.in). notably, it inhabits a substrate of coarse sand, hard mud and shells, reaches a maximum total body length of about 200 mm (average of 150 mm), grows fast, and has a mean lifespan of 3 years while in the exploited phase (sanders, 1981; holthuis, 1991). the aims of this study were to report on the geographical range extension, and provide information on the size, composition, length-weight relationships, and the reproductive condition of p. sewelli in a sample taken in oman. materials and methods exploratory trawls at depths >230 m were executed during daylight on the 10th of november (2 trawls) and the 8th of december 2007 (1 trawl), in the region between mirbat and the yemen border. a trawl net with an 18 mm mesh in the codend was used, and the start and end points of each trawl that caught p. sewelli, depth range, trawl speed, distance between trawl doors and duration of trawls are shown in table 1. ctd drops were made at the end of each trawl to determine bottom temperature. captured lobsters were frozen on-board and transferred to the msfc laboratory. after defrosting, the total length (tl ± 1 mm; from the ridge between the eyes to the tip of the uropod) and carapace length (cl ± 1 mm; ridge between the eyes to the posterior edge of the carapace) of each lobster were measured using vernier calipers, and the whole weight (ww ±1 g) and tail weight (tw ± 1 g) determined. linear regressions were fitted to cl versus tl, and ww versus tw, and non-linear regressions to cl versus tw and cl versus ww using a least-squares algorithm in microsoft excel. gender was determined from external characteristics, and female gonads were categorized into one of four groups based on colour: stage 1 or immature – white; stage 2 or developing – yellow to very light orange; stage 3 or maturing – orange; and stage 4 or ripe – red (groeneveld and melville-smith, figure 1. p. sewelli collected off oman. 5 cm table 1. gps readings at the start and end of three exploratory trawls, depth, trawl speed, and duration of trawls and the distance between trawl doors and lobster catch. start trawl end trawl depth (m) trawl speed (knots) distance between trawl doors (m) duration of trawl (min) lobster catch (kg) 16°44′68n 53°57′41e 16°44′04n 53°58′43e 253–399 3.5 110.45 19 <1 16°43′73n 53°59′10e 16°42′79n 54°00′07e 442–787 3.5 116.30 30 1.8 16°44′72n 53°57′18e 16°44′02n 53°58′32e 230–410 3.3 95.85 20 6.4 al-nahdi and others 2 3 a first record of whip lobsters from oman 1994). the proportions of females with ovaries in stages 2-4 per 2-mm size class were fitted to a logistic equation of the form p=1/(1+exp(a-btl) where p is the proportion of mature females in each length class and a and b are constants, and the cl at 50% maturity determined. results and discussion the easternmost point at which p. sewelli was previously recorded on the southeastern arabian continental slope was off ras fartak in yemen (15°35’ n 52°12’ e (sanders, 1981). the exploratory trawls in oman encountered the species up to 16°42’ n 54°00’ e, thus extending its known range by approximately 200 km northeastwards. the depth range covered in the exploratory trawls off oman (230–787 m) was similar to the 200–600 m range where p. sewelli was most often fished in yemen (sanders, 1981). bottom water temperatures in oman were 12.6°c, 12.4°c and 13.6°c for the three trawls, and the trawlable area (i.e. soft substrate without significant reefs) was small, based on acoustic data collected during the survey using the vessel’s hull-mounted 38 khz transducer. additional data on bycatches and ctd information are stored on the survey database under oma0701, for station numbers 318–321, and oma0702, station numbers 379 and 380. table 2. comparison of average (± s.d.), minimum and maximum cl, tl, ww and tw of male, female and all p. sewelli caught in exploratory trawls in 2007. sample size shown in parenthesis. variable gender average ± s.d. minimum maximum cl (mm) all (67) 69.7 ± 8.8 51 87 f (37) 72.0 ± 9.0 52 87 m (30) 66.8 ± 7.8 51 77 tl (mm) all 159.6 ± 18.6 119 195 f 166.8 ± 18.7 124 195 m 151.2 ± 14.9 119 172 ww (g) all 83.7 ± 28.8 31.4 161.7 f 91.9 ± 31.1 31.4 161.7 m 73.2 ± 21.7 34.0 112.4 tw (g) all 26.6 ± 10.5 11.1 53.6 f 31.6 ± 11.1 11.9 53.6 m 20.5 ± 5.2 11.1 32.5 figure 2. size frequency distribution (cl, mm) of male and female p. sewelli caught in oman in 2007. al-nahdi and others 4 5 a first record of whip lobsters from oman figure 3. al-nahdi and others 4 5 a first record of whip lobsters from oman a total of 67 lobsters, 37 females and 30 males (a ratio of 1:0.81) (6.4 kg), were collected from the trawl made on 8th december, the size of specimens ranged from 51 – 87 mm cl (119–195 mm tl), with an average of 69.7 ± 8.8 (s.d.) mm cl (159.6 ± 18.7 mm tl) (table 2). the average cl of females (71.9 ± 9.0 mm) was larger than that of males (66.8 ± 7.8 mm), and 38% of females were larger than the maximum size of 77 mm cl measured for males (fig. 2). this result is consistent with that of sanders (1981) from yemen, where females grew to a “considerably larger length than males”. the largest length class from somalia was 215 mm tl (johnsen, 1986) and in yemen the largest individual measured was 205 mm tl (sanders, 1981). the size frequency distribution suggests two modes, at 54 mm and 72 mm cl respectively (fig. 2), very similar to modes at 52.8 mm and 72.4 mm cl reported by sanders (1981) for a sample taken in december 1972 (the same month as in the present study) in yemen. the latter author suggested that the smaller lobsters (recruits) moved into the fishery in autumn, and that the larger lobsters (post-recruits) consist of cohorts recruited in the spring of the same year, and earlier. the linear regressions of cl versus tl for males and females respectively fitted the data well, with high coefficients of variation (r2>0.91; fig. 3a). for sexes combined, the equation was tl = 2.0238×cl + 18.352 (r2 = 0.93), and this equation was used above to convert data from yemen (given in tl in sanders, 1981) to cl for comparisons with the present data from oman. the linear regressions of ww versus tw fitted the data well (r2 = 0.85 for males and 0.93 for females; fig. 3b), showing that the tw proportion of females increase faster than that of males as lobsters increase in ww. this is a common occurrence in many lobster species (groeneveld, 1996). regressions of cl versus ww and cl versus tw are useful for raising the length composition of biological subsamples to reflect that of total catches in biomass calculations. the non-linear regressions of cl versus ww are shown for males (r2 = 0.89) and females (r2 = 0.88) in fig. 3c. similar regressions of cl versus tw are shown for males (r2 = 0.87) and females (r2 = 0.92) in fig. 3d, and the latter regressions confirm that the tw of females becomes progressively heavier than that of males as cl increases. three females were soft-shelled (8%), indicating that they had recently moulted, but none of the males were soft. based on the visual examination of 36 excised female gonads, 8.3% were immature (ave. cl = 53 mm), 13.8% were developing (75.6 mm), 55.5% were maturing (73.7 mm) and 22.2% were ripe (72.6 mm). seven females (19%) carried external eggs, and this percentage was much lower than the 76.5%– 92.3% found in december 1975 in yemen (sanders, 1981). given that only a december sample existed from oman, no further inferences could be made on reproductive seasonality. the smallest egg-bearing female had a cl of 74 mm, and the l50 estimated from the logistic curve, based on gonad stages, was 54 mm. sanders (1981) reported a smallest egg-bearing female of 57 mm cl. the lower value obtained from the oman sample is based on a very small sample size in the smallest size classes, and is likely an underestimate. the range extension shown for p. sewelli into the waters of oman is perhaps not surprising, given that it inhabits the continental slope of the arabian sea off yemen, and that a similar deeper-water environment extends northeastwards to ras al hadd. possibly, its presence off southern oman remained unknown because the steep and often rocky continental slope between the yemen/oman border and mirbat is not exploited by trawlers. the potential commercial value of p. sewelli off oman should be further investigated through experimental fishing. acknowledgement the research was based on data collected during the fish resources assessment survey of the arabian sea coast of oman. we are grateful to dr. hamed aloufi (under-secretary, ministry of fisheries wealth) and dr. ahmed al-hosni (dg for fisheries research and extension) for commissioning the survey and supporting the associated research projects. we thank the crew and scientists aboard the survey vessel almustaqila for providing the samples. references anon. 2004. fisheries statistics book (2003) for the republic of yemen. general department for planning and statistics, ministry of fish wealth, sana’a. 224 pp. fischer, w. and g. bianchi. 1984. fao species identification sheets for fishery purposes. western indian ocean (fishing area 51). prepared and printed with the support of the danish international development agency (danida). rome, food al-nahdi and others 6 and agricultural organization of the united nations, vols. 1-6:pag.var. groeneveld, j.c. 1996. morphometric relationships of palinurid lobsters palinurus delagoae and p. gilchristi and a scyllarid lobster scyllarides elisabethae caught in traps off the south and east coasts of south africa. south african journal of marine science, 17: 329-334. groeneveld, j.c. and r. melville-smith. 1994. size at onset of sexual maturity in the south coast rock lobster, palinurus gilchristi (decapoda: palinuridae) from south african journal of marine science, 14:219-223. holthuis, l.b. 1991. fao species catalogue. 13. marine lobsters of the world. an annotated and illustrated catalogue of species of interest to fisheries known to date. fao fisheries synopsis, 125(13), 292 pp. johnsen, t. 1985. commercial trawling for fish and deep sea lobster (puerulus spp.) off somalia. fao, rome, raf/79/065/wp/13/84. 42 pp. www.fao.org/docrep/field/255099.htm. sanders, m.j. 1981. preliminary stock assessment for the deep sea lobster puerulus sewelli taken off the coast of the people’s democratic republic of yemen. fao, rome, rab/77/008/18. 48pp. pdf995, job 6 _________________ *corresponding author. 61 agricultural sciences, 7(2):61-67 (2002) © 2002 sultan qaboos university effect of groundwater pumping on seawater intrusion in coastal aquifers m.m. sherif1* and v.p. singh2 1civil engineering department, college of engineering, united arab emirates university, p.o. box 17555 al-ain, uae 2civil and environmental engineering department, faculty of engineering, louisiana state university, baton rouge, la 70803-6405 abstract: many aquifers around the globe are located in coastal areas and are thus subjected to the seawater intrusion phenomenon. the growth of population in coastal areas and the conjugate increase in human, agricultural, and industrial activities have imposed an increasing demand for freshwater. this increase in water demand is often covered by extensive pumping of fresh groundwater, causing subsequent lowering of the water table (or piezometric head) and upsetting the dynamic balance between freshwater and saline water bodies. the classical result of such a development is seawater intrusion. this paper presents a review for the seawater intrusion phenomenon in coastal aquifers. the effect of pumping activities on the seawater intrusion in the nile delta aquifer of egypt is investigated. it was concluded that any additional pumping should be located in the middle delta and avoided in the eastern and western sides of the delta. keywords: seawater intrusion, groundwater pumping, coastal aquifer, recharge, upcoming, nile delta aquifer, sutra, watertable. eawater intrusion phenomena are of main concern in almost all coastal aquifers around the globe. the problem is more severe in arid and semi-arid regions where the groundwater constitutes the main freshwater resource. a 3% mixing of seawater with the freshwater in a coastal aquifer would render the freshwater resource unsuitable for human consumption. therefore, groundwater resources in coastal aquifers should be carefully studied to maintain the dynamic balance between the fresh and saline water bodies. the shape and degree of the seawater intrusion in a coastal aquifer depend on several factors. some of these factors are natural and cannot be controlled while others are manmade and could, thus, be managed. these factors, include among others, the type of the costal aquifer (confined, phreatic, leaky, or multi-layer) and its geology and geometry, water table and/or piezometric head, seawater concentration and density, natural rate of flow, capacity and duration of water withdrawal or recharge, rainfall intensities and s !"#$%&'()*+%,-'()./)012'()3%"4)56(78)9#:)!"/;<'()3%"-'()=>)? 7!4)0""#8) !"#$%&'()*$+,-.$/012$ ! !$%&6$3$$$$$$$$$$$$$$$$$$$$$$$$$4&(2$56789$:-;&<=$&>?,$&!2$"$#($%&0=7$&'&"!=7$()$)=& =7$*+%$#()+'=7$4&(!=7$,&-.'$/2$8,8 =7$/-9 -1.=7$0$$$$$$$$$$$)$:1&,2=7*$#($%&0=7$&'&"!=7$()$3&40=7$+!5$6-)$8-=*$$$$$$$$$78,7272$&.$'$#,-8.=7*$#(97:2=7*$#(9&";=7$,&'&8"=7$( $$$$$$$&'&"!=7$4<;$5=2$()$>< =7$?&!$=$0$$$$$$$$$$$$$$4&(!$=$/07!=7$@a=&b$3&(%c7$d$ef$()$4&(!=7$g$9$d$h=7$()$:1&,2=7$4<;$ghi9* $$$$$$$$$$$$$$$$$$$$$$7$4&(2*$#b< =7$4&(!=7$/(b$(4(2&",8=7$3j7+7=&b$5k,*$4&(!=7$>+0"2$6&lk5&b$&-%m$d.07,$&!2$"$#()+'=7$$$%<=7*$"$-1.= $$$$$$$$$$$$$$$$$#b< =7$4&(!=7$&'&"2$()$-1.=7$4&(2$56789$g=n$#,&>"=7$()$%1o,$0$$$$$$$$$$$/2$-1.=7$4&(2$56789$:-;&p$#q:+=7$4<;$6709 $$$$$$$$$$$$$$$$$$$$$$$#-.'$()$56787=7$:-;&p$g$9$#()+'=7$4&(!$=$@a=7$,&'&85$-rf$/2$&-179$&!s$"$#($%&0=7$&'&"!=7$()$#b< =7$4&(!=7 $$$$$$-;2$()$#()+'=7$&7=8=7$0t$k705*$$$$$$$$$$$$$$$$$$$$# q7*$3+49$3f$d',$&7=8=7$()$4&(!$=$#()&?n$@?$*&!9f$#,f$3f$g=n$#q:+=7$4<;$/2$ $4&(!$=$u-6f$@?$,&($!9$%c$&>"2$#(b-i=7*$#(q-8=7$&'&"!=7$d"'9$d',$&!s$"$&>"2$gh#+=7$#-h"!=7$()0$ sherif and singh 62 frequencies, evaporation rates, physical and geometric characteristics of the porous media, geometric and hydraulic boundaries, tidal effects, variations in barometric pressure, earth tides, earthquakes and other vibrational effects, water wave actions, and chemical changes. the depth of the aquifer at the seaside through which the seawater intrudes inland and pumping and recharge rates and locations are the most critical factors to be considered. seawater intrusion problems can be simulated both analytically and numerically. each method has its own advantages and disadvantages as compared to the other. analytical models are generally simpler in formulation and application and do not require detailed input parameters (data). they provide accurate results when applied to small-scale problems, e.g., upconing phenomenon below pumping wells. however, analytical models often require simplified assumptions and idealized domains. numerical models are relatively adaptable and flexible and could be applied to heterogeneous systems and irregular domains. many well-developed and verified numerical codes are already available and can be easily employed to almost every case. the main disadvantage of numerical methods is the need for detailed field data in space and time that might not be available. analytical solutions are often employed to verify numerical models for idealized domains, flow and boundary conditions. this paper presents an overview for the mechanism of seawater intrusion in coastal aquifers. the problem is simulated in the horizontal view of the nile delta aquifer of egypt. different scenarios are made to investigate the effects of pumping activities on the seawater intrusion problem. the usgs model, sutra (voss, 1984), was employed. mechanism of seawater intrusion consider the idealized leaky system shown in figure 1. the aquifer is recharged by freshwater entering from the landward boundary and by leakage through the upper clay cap (aquitard) in parts where the free water table is higher than the aquifer piezometric head (before the point of the intersection, hinge point, between the free water table and the aquifer piezometric head). in some cases, the free water table may be higher than the piezometric head all over the upper clay cap, therefore the system will be recharged by the freshwater through out the entire upper boundary as well as the land side boundary. an unconfined (phreatic) aquifer will be recharged by freshwater through infiltration of precipitation. a confined aquifer will be recharged only by freshwater from the boundary at the land side. at the seaward boundary, there will be an influx of seawater into the system which, because of its greater density, will migrate to the bottom of the aquifer and displace the freshwater. upward leakage of mixed water will also take place through the aquitard in parts where the free watertable is lower than the piezometric head (near the seaside). the rest of the mixed water will find its way out of the system through the window at the seaside. this discharge through the window and the upward flux through the aquitard cause a loss of salt from the system which is replenished by new seawater moving in from the seaward boundary. the bottom boundary is impermeable. the flux of water and salt ions through this boundary is therefore equal to zero. figure 1. mechanism of seawater intrusion in coastal aquifers. effect of groundwater pumping on seawater intrusion in coastal aquifers 63 if the boundary conditions remain constant, a state of dynamic equilibrium will eventually be attained by the system. at equilibrium, the total fluid mass entering at both ends of the aquifer plus the leakage influx, will be balanced by the upward leakage through the aquitard plus the flux out through the window on the sea side. likewise, the salt mass entering at the seaward will be balanced by the salt mass swept out from the system with the mixed water through the aquitard and the window at the seaward boundary. the nile delta aquifer the nile delta and its fringes occupy at total area of 22000 km2 (figure 2). the level of the delta land ranges between +17 m above sea level at the south boundary to less than one meter at the north boundary (farid, 1985). the nile delta aquifer is naturally bounded northward by the mediterranean sea and eastward by the suez canal. the western boundary extends well into the desert. at the south, the aquifer demises and seems to be isolated from the aquifer of upper egypt by an aquiclude approaching the clay cap near cairo. many studies have been conducted to assess seawater intrusion in the nile delta aquifer using numerical techniques. the simulations have been mainly two-dimensional either in the vertical cross section or in the horizontal view. some studies were based on the sharp interface approach, while others accounted for the dispersion zone and density variation in the vertical direction. previous investigations that adopted the sharp interface approach include wilson et al. (1979), amer and farid (1981), and farid (1980 and 1985). contour lines for the freshwater thickness in the aquifer were outlined. sherif et al. (1988, 1990), amer and sherif (1995), sherif and singh (1997), and sherif (1999) conducted various investigations to study the seawater intrusion problem in the nile delta aquifer using the dispersion zone approach. based on numerical simulations, equiconcentration and equipotential lines were drawn to characterize the flow pattern and salinity distribution. hydraulic parameters and pumping activities field and laboratory experiments were carried out to determine the hydraulic parameters for the nile delta aquifer. based on field data, an isotropic hydraulic conductivity of 100.0 m/day and a storativity of about 10-4 to 10-3 were considered representative of the regional values of the aquifer. farid (1980) reported different values for hydraulic conductivity and storativity at various locations. the hydraulic conductivity of the figure 2. the nile delta aquifer in egypt. aquifer decreased toward the south and west. an effective porosity of 0.3 was considered to represent the aquifer medium. the clay cap takes different profiles along the shore of the mediterranean sea. generally, it is divided into two layers. the first layer is the upper clay cap that acts as an aquitard, about 20 m thick. the second layer is the lower clayey sand layer, a few meters in thickness, with a higher permeability than the former. the thicknesses of the upper clay cap (aquitard) and the clayey sand layer are well defined at many locations in the delta. their thicknesses are mostly less than 20 m and 15 m, respectively. only along the mediterranean shore, the thickness of the clay cap may reach 70 m. the vertical movement of water through the upper semipervious layer affects, to a great extent, the water balance of the system. the downward movement of water occurs in two different stages. the first is the downward infiltration of irrigation water from the ground surface to the subsoil water table through the unsaturated zone of the clay cap. the velocity of this movement is defined by the downward infiltration velocity. the second is the movement of the subsoil water from the water table to the groundwater in the aquifer through the saturated zone of the clay cap. the velocity of the flow in this zone is defined by the seepage velocity and can be evaluated from darcy's law. the vertical hydraulic conductivity, kcv, for the clay layer in the nile delta has an average value of 2.5 mm/day. based on similar studies, the longitudinal dispersivity, !l, and lateral dispersivity, !t, for the nile delta aquifer are set equal to 100 m and 10 m, respectively. the free watertable is measured at various locations. when this information is missing it is generally assumed to be 1.0 m below the ground surface. the piezometric head is measured periodically through an intensive-monitoring network. records for water levels and piezometric heads are available in the sherif and singh 64 database of the groundwater research institute (gwri), national water research center (nwrc), egypt. pumping activities from different governorates are monitored by the gwri in egypt. total pumping from the nile delta is estimated at 2.3 billion m3/year. selected pumping scenarios to examine the response of the nile delta aquifer to pumping activities and define the best locations for additional groundwater pumping, six different scenarios of pumping were selected and compared with the current pumping (basic run). the simulation was preformed via sutra to reflect the intrusion behavior in the aerial view. these scenarios were chosen after many preliminary simulations with coarser grid systems. the delta was divided into three main zones for pumping activities; the middle zone, the eastern zone, and the western zone. the following scenarios were thus considered: basic run: this scenario represented current pumping activities (2.3 billion m3/year) from the various governorates in the nile delta. scenario 1: the current pumping was redistributed in the eastern and western sides of the delta without any pumping from the middle of the delta. the 2.3 billion m3/year were distributed among the nodal points in the eastern and western delta only. scenario 2: the 2.3 billion m3/year were pumped from the middle delta only without any pumping in the eastern and western sides. scenario 3: in this scenario, the current pumping was doubled; 4.6 billion m3/year were pumped from the same governorates. the share of each node, as calculated in the basic run was thus doubled. scenario 4: in this scenario, 4.6 billion m3/year were pumped from the eastern and western sides of the delta. no pumping takes place in the middle delta. scenario 5: the distribution of the current pumping (2.3 billion m3/year) was maintained, while additional pumping of 1.5 billion m3/year in the eastern delta and 0.8 billion m3/year in the western delta were considered. the total pumping was thus equal to 4.6 billion m3/year. scenario 6: in this scenario, an additional pumping of 2.3 billion m3/year was considered in the middle delta only, while the distribution of the current pumping was maintained. results and discussion the usgs model, sutra, was employed to simulate the seawater intrusion behavior under the selected scenarios. to initiate the numerical calculation, for the basic run, a fresh water concentration and a hydrostatic pressure distribution between cairo and the mediterranean sea were assumed through the entire domain. for the other scenarios (1 through 6) the concentration and pressure distribution resulting from the basic run were considered as initial conditions. the convergence criterion for both the concentration and the pressure was set equal to 10-3. the model was first run under transient conditions for both water flow and transport of salt. the time step was set equal to 3.65 days. hundreds of years were required to reach steady state conditions through the transient procedure. results of the concentration distribution and piezometric heads were stored after every 1000 time steps (10 years) and compared to each other after every 2000 time steps. overlapping the equiconcentration lines indicated that the rate of seawater intrusion migration or retardation under any of the proposed scenarios was relatively small, in the range of 10 to 40 m/year. a movement of 1.0 km of any equiconcentration line would require between 25 and 100 years, according to the proposed scenario. figure 3 shows the equiconcentration lines under the current pumping activities at the steady state conditions. equiconcentration line 31.5 (31,500 ppm) intruded inland to a distance of 41.0 km measured along latitude 31° 00' from the shore boundary, while equiconcentration line 17.5 intruded to a distance of 61.5 km along the same latitude measured from the sea side boundary. equiconcentration line 3.5, representing 0.1 of the maximum concentration, intruded inland to a distance of 84 km. although no exact measurements for the concentration distribution in the nile delta aquifer are available, yet the above concentration resulted from the simulation of the current conditions is quite consistent with the observations recorded from production wells in the region. for example, the salinity of groundwater figure 3. equiconcentration lines under the current pumping activities. effect of groundwater pumping on seawater intrusion in coastal aquifers 65 at kafr el-sheikh, 53 km from the shore line, is equal to the seawater salinity at a depth of less than 100 m. on the other hand, the groundwater at tanta, 92 km from the shore line, is mostly fresh up to a depth of about 250 m. to the south of tanta, the groundwater has a salinity of less than 1000 ppm throughout the entire depth of the aquifer. it should also be noted that while areal simulation of seawater intrusion in the nile delta aquifer is very useful in testing intrusion behavior under various scenarios of pumping, it does not provide accurate values for concentration distribution. the salinity may vary in the vertical direction, at the same point, from fresh water concentration to seawater concentration. this variation can not be included in the areal simulation. the concentration of groundwater at a specific point in the plane is not indicative unless the depth of that point is defined. under scenario 1, where the current pumping is redistributed to the eastern and western zones of the delta, less intrusion was encountered in the middle and more intrusion is found in the eastern and western parts. equiconcentration lines in the eastern zone were slightly affected. in the middle, all equiconcentration lines retreated to the sea side. under scenario 2, where current pumping (2.3 billion m3/year) is only considered to take place in the middle delta, less intrusion is found as compared to the basic run. in the middle delta, all equiconcentration lines retreated backward to the sea side within a few kilometers (1 to 4 km), while they retreated by some tens of kilometers (20 to 30 km) in the eastern parts. this may be attributed to the proximity of the nile river to the pumping areas and the high recharge rate resulting from intensive irrigation. under scenario 3, the current pumping was doubled from the same locations. at steady state conditions, various equiconcentration lines advanced by considerable distances as compared to the current conditions (basic run). the eastern parts of the delta were much more affected than the others. under scenario 4, 4.6 billion m3, were pumped annually from the eastern and western zones only. equiconcentration lines in the western area advanced inland considerably. compared to the basic run, equiconcentration line 31.5 advanced by a distance of 17 km measured along latitude 30° 30', while equiconcentration line 3.5 advanced 3.5 km along the same latitude. in the middle delta, all equiconcentration lines retreated to the sea side, while more seawater intrusion was observed in the eastern delta. in scenario 5, where additional pumping of 1.5 and 0.8 billion m3/year were considered from the eastern and western delta, respectively, the seawater traveled inland in the entire domain with the exception of a limited area in the far east. under scenario 6, an additional pumping of 2.3 billion m3/year was considered in the middle delta. limited additional intrusion was seen as compared to the basic run. at steady state conditions, maximum inland migration of 4.0 km was encountered in the middle delta. equiconcentration lines in the western delta moved inland by variable distances between 1 and 3 km. in the eastern delta, equiconcentration line 3.5 retreated to the sea side by about 8.0 km, while equiconcentration line 31.5 was not affected as compared to the basic run. figures 4a through f compare equiconcentration lines 31.5 and 3.5 in the various scenarios with those in the basic run (representing the current conditions). solid lines represent the basic run, while dashed lines represent various scenarios as indicated. the distance between the former two equiconcentration lines may be considered to indicate the width of the dispersion zone. scenarios 1 and 2, consider current pumping but with different allocation to pumping area. figures 4a and b reveal that both of these two scenarios are actually better than the current policy for groundwater pumping as regard to seawater intrusion. although the same amounts of water were pumped, yet less intrusion was encountered. scenario 1 reduces the intrusion in the middle considerably with an additional slight inland intrusion in the east and more intrusion in the west. scenario 2 reduces the intrusion throughout the delta with much more effect in the eastern parts. scenarios 3, 4, 5, and 6 represent seawater intrusion under various policies of pumping an additional amount of 2.3 billion m3/year. figures 4c through f reveal that scenarios 4 and 6 are causing less impact. in scenario 4, figure 4d, although the pumping from the entire delta was doubled yet less intrusion was found in the middle delta. on the other hand, equiconcentration line 3.5 advanced inland by a distance of about 21 km and 7.5 km in the western and eastern parts, respectively. under scenario 6, where additional pumping of 2.3 billion m3/year is considered from the middle delta only, equiconcentration line 3.5 advanced inland by a limited distance in the middle and western delta and retreated slightly in the eastern delta as shown in figure 4f. scenario-6 is thus more relevant and has nominal impact on the groundwater quality. conclusions the nile delta aquifer is severely subject to the problem of saltwater intrusion from the mediterranean sea. this has a serious environmental impact. groundwater resources should thus be carefully managed and developed. sherif and singh 66 a. basic run versus scenario 1. b. basic run versus scenario 2. c. basic run versus scenario 3. d. basic run versus scenario 4. e. basic run versus scenario 5. f. basic run versus scenario 6. figure 4. comparison between equiconcentartion lines of the basic run and other scenarios. effect of groundwater pumping on seawater intrusion in coastal aquifers 67 to examine the response of the nile delta aquifer under different pumping activities, six scenarios were considered and the resulted intrusion was compared with the original one under current pumping conditions. two alternatives for the amount of groundwater pumping were thus examined; 2.3 and 4.6 billion m3/year. for the two alternatives different locations for pumping were checked and the resulted seawater intrusion was assessed for the different cases and compared with the intrusion under the current pumping conditions. for the first alternative, scenario 2 is the best. all equiconcentration lines were retreated throughout the entire delta with much more effect in its eastern and western parts. for the second alternative, where 4.6 billion m3/year were pumped, scenario 6 has the least impact amongst the tested scenarios. all tested scenarios indicated that any additional pumping should be practiced from the middle delta and minimized in the eastern and western parts of the delta. acknowledgement this study was sponsored by the binational fulbright commission in egypt. several constructive ideas and remarks were made by members of the fulbright commission during the course of the study. the uaeu provided the support and facilities to complete this paper. references amer, a. and m. sherif. 1995. behavior of seawater intrusion in the nile delta under different conditions. working paper series no. 32-1, srp, nwrc-mpwwr, cairo, egypt. amer, a. and m.s. farid. 1981. about sea water intrusion phenomenon in the nile delta aquifer. proceedings of the international workshop on management of the nile delta groundwater aquifer, cu/mit, cairo. farid, m.s. 1980. nile delta ground water study. m sc. thesis, faculty of engineering, cairo university, cairo. farid, m.s. 1985. management of groundwater system in the nile delta. ph. d. thesis, faculty of engineering, cairo university, cairo. sherif, m.m. 1999. the nile delta aquifer, chapter 17. seawater intrusion in coastal aquifers: concepts, methods and practices, bear et. al. (eds). book series theory and application of transport in porous media, vol. 14, pp. 559-590, kluwer academic publishers, netherlands. sherif, m.m. and v.p. singh. 1997. groundwater development and sustainability in the nile delta aquifer. final report, binational fulbright commission, egypt. sherif, m.m., v.p. singh, and a.m. amer. 1988. a two-dimensional finite element model for dispersion (2d-fed) in coastal aquifers. j. hydrol. 103:11-36. sherif, m.m., v.p. singh, and a.m. amer. 1990. a sensitivity analysis of (2d fed), a model for sea water encroachment in leaky coastal aquifers. j. hydrol. 103:11-36. voss, c.i. 1984. a finite element simulation model for saturatedunsaturated, fluid density-dependent ground-water flow with energy transport or chemically-reactive single-species solute transport. water resources investigation report 84-4369, usgs, usa. wilson, j., h. townley, and a. sada casta. 1979. mathematical development and verification of a finite element aquifer flow model aquifem-1. technology adaptation prpgram report no. 792, mit, cambridge. ___________________________________________ received september 2002. accepted november 2002. microsoft word jamsy2003v08n01content-arabic.doc ___________________ *corresponding author. 15 agricultural and marine sciences, 8(1):15-20 (2003) © 2003 sultan qaboos university control of varroa mite (varroa destructor) on honeybees by aromatic oils and plant materials a. al-abbadi1 and i.k. nazer2* 1department of bioagricultural technology, faculty of agricultural technology, al-balqa’ applied university, al-salt, jordan. 2department of plant protection, faculty of agriculture, university of jordan, amman, 11942, jordan. abstract: the effect of several volatile plant oils, plant materials and fluvalinate (apistan®) strips on the control of the mite varroa destructor on honeybee (apis mellifera l.) colonies was studied. the volatile oils were: clove, lavender, peppermint, sage, and thyme. the plant materials were: cumin fruits, eucalyptus leaves, and worm wood flowers. for each tested material, three treatment periods were carried out. each period lasted for 24 days followed by eight days no-treatment. within each treatment period, an average of three to six treatments were applied. dead mites were counted one hour before and after each treatment. an increase in dead mites was recorded for the three treatment periods. it indicated that worm wood flowers, peppermint oil and clove oil treatments gave the best results in the control of varroa mites but not significantly different than the control. the overall increase in the dead mites was 3.92, 3.62 and 3.34 fold, respectively. keywords: varroa mite, honeybees, aromatic oils, weeds, jordan. eekeeping is an important part of agriculture. there are thirty thousand modern hives in jordan and about six hundred traditional clay hives (ministry of agriculture, 1997). honeybee colonies are subject to infestation by insects, mites and diseases. the parasitic mite varroa jacobsoni oud. renamed as varroa destructor (anderson and trueman), (anderson and trueman, 2000) is considered one of the most serious pests to beehives, causing great economic loss to the beekeeping industry (baker and peng, 1995). this mite can be found on adult bees, on the brood, and in hive debris. in a heavy infestation, pupae may not develop into adult bees. the adults that do emerge may weigh less than healthy bees (shimanuki and knox, 1991). advanced infestations cause considerable damage to honeybee populations (baker and peng, 1995) resulting in a reduction of the quantity and quality of the colonies available for honey production and pollination (spivak, 1997). in one apiary in the usa, out of 245 colonies only 28% (67 colonies) survived. it appeared that the b !"#$%& ' "!() *!+,%.!/012231!4567289732:;<='"!;,>!?) !!!!="!#"$%&'%" !+(),)'"!*%+ ,"#!+-./='"!01-2'"! !"#$%&'()*+',-."/%&'012&-34' ' !+33456'5678+9":%&'0;<'=>?" )'!?'""#$13&'%1#)'&'&-(+'=17"#/%&')&*+,&+'=--.$%&'/0-*%&'1$3'-1237'=4&9!''&5678897' :;<=8>?=98@''a'bc;d'($$%&'(>@efg<'h;iigj;87'kl'l5678=1%"#%&'=--.$%&'/0-*%&'-1237''=4&9!''5'8-m+'(:a-n%&'8-m&'+'9%/?o '''8c-m%&''''''8c-m'+'p"/c$/%&'''''8c-m+'=1c)-16%&''''''''''67'%n?'=17"#/%&')&*c+q%'=#c$/%"3'"c)*'r-#cd*8''''"06 %&'9"62'-1237'=4&9!''+'''"/1 %&'s&9+* '''''''''&+9"c:%&'0c;<'bc;d'&1ct%&'9"c2m*+'l'''''-#c?'(cu'/-6#c4&'''v%6%'vwx'''y0-'''=d0##)3'v-#:y"-&'=1a"62'3=;)"$)'"+%'l'v-#?'(u'z[\ '''''''''][2'^)'v!"6%&'=?"_4'8c67'=c;)"$)b%4'=;)"$6%&'p0a'`$<'/&-)'84''l'=#16%&'&+9":%&'0;<'!&%d*'(1a$7'07'=d"4'%/d '''v%c<&+''(#cb''%c$3+=;)"$6%&l67'8[c%&'=;)"$6%&'/&-#?'z[\'=#16%&'0;>%&'!&%d*'v!"-m'=d<[)'=2l''%b+/[)"$)'e'"#a'8b0:7 ''''''''''''(:a-cn%&'8c-m+'p"/c$/%&'8c-m'+'&1ct%&'9"c2m*'''%2"t%&'f)'=a9"n6%"3'=-0/$)'/"b+-:%&'^ 7'0%'^ %+'&+9":%&'0;<'!c?'0 >#c;% 'v!"-*%&'z%$)'""u'g1<'=1; %&'=#16%&'&+9":%&'!&%d*'!?hliw'+'hljw'+'hlhx!%&0#%&'b;d'k":$_'l' al-abbadi and nazer 16 death was caused by varroa (putman and cochise, 1996). in jordan, varroa mite inflicted heavy damage in 1986. this led to the loss of 15,000 hives representing 50% of modern hives and most of the traditional ones (ministry of agriculture, 1986). the ministry imported the acaricide sencor and distributed it to jordanian beekeepers in order to address the varroa problem. since then, beekeepers have used several acaricides e.g. bromopropylate, coumaphos, flauvalinate, amitraz and formic acid. in other countries beekeepers used different acaricides like amitraz, coumaphos, and fluvalinate (ruijter, 1994). due to the widespread misuse of chemical treatments, several cases of resistance have been reported (elzen et al., 1998). since varroa mite has developed resistance to certain acaricides, it is of fundamental concern to look for new control agents (dufol et al., 1991; kraus et al., 1994; lindberg et al., 2000). in this research we investigated the possibility of using volatile plant oils and local plant materials for the control of varroa mite on bees. these natural materials generally have no side effects on honeybees and are less hazardous to beekeepers. materials and methods experimental honeybee colonies: two experiments were carried out. the first was conducted in amman governorate at three locations (na’ur, yajouz and albaqa’) in the summer of 1997. the second one was in al-salt governorate at three locations (al-magareeb, alaksam and wadi-al-salt) in the summer of 1998. both experiments had the same number of colonies, treatments and replications. thirty colonies of hybrid italian honeybees, apis mellifera were used each summer, ten in each location were considered as a replicate. the chosen infected colonies were similar with approximately the same number of brood frames, each of one honey and pollen frames and headed by a one-year old queen. in each of the two experiments, the treatments were arranged in a randomized complete block design (rcbd). treatments: five volatile oils: clove (syzigium romaticum), lavender (lavandula coronopofolia), peppermint (mentha piperita), sage (salvia triloba) and thyme (origanum syriacum) were tested for the control of varroa mite. in addition, three plant materials: cumin fruits (cuminum cyminum), eucalyptus leaves (eucalyptus camadulentis) and worm wood flowers (artemisia herba-alba) were tested for the control of varroa at the same time. at each location, there were two colonies. one of them was treated with fluvalinate, apistan strips®, and the other was left untreated for comparison. during each summer, there were three treatment periods, 24 days each for a total of 72 days. during each treatment period, the number of applications varied according to the tested material. before each period, there was an eight day period with no treatment application to count the number of the dead mites in each colony. the number of fallen mites was counted two times (four day interval) for each colony in each apiary during that period. the treatments of colonies were carried out from 19 june to 30 september and from 15 may to 27 august in the summer of 1997 and 1998, respectively. the difference in timing was governed by infestation of colonies with the varroa mite. methods of application: treatment with volatile oils application of concentrated volatile oils was made three times during each treatment period, eight days apart as applied by amrine et al. (1996). florist foam blocks, were utilized as a carrier for the oils (calderone and spivak, 1995). a sample, 25 ml, of concentrated volatile oil was applied, which was enough to saturate four florist blocks (2x2x2 cm). the blocks saturated with the test material were distributed between the brood combs, inside the hive on the bottom board of the colony. after eight days, they were removed and replaced with new ones. treatment with plant materials i. eucalyptus leaf-smoke one colony out of ten in each replication was treated with eucalyptus leaf-smoke. the colony was exposed to the smoke of ten grams of eucalyptus leaves as carried out by shalaby et al. (1996). the leaves were placed in a lighted smoker with burlap, and fifteen puffs were blown inside the hive through the entrance. the entrance was blocked for fifteen minutes, and the colony was completely closed from all sides. the treatment of eucalyptus leaf-smoke was repeated every four days with six applications during each treatment period (24 days). ii. worm wood and cumin fifty grams of cumin fruits and 50 g of worm wood flowers were ground using a grinding machine as described by abu-zeid and ghoniemy (1993). the powders for each of the two materials were placed on four pieces of porous cheese cloth and tied. the four samples were placed inside on the bottom board of the colony between the brood combs. in each location, one colony received worm wood flowers and one colony received cumin fruits. after eight days of application the tested material was removed and replaced with a new one. three applications were made in each treatment period. apistan strips one colony in each replicate was treated with apistan®, which was used at the rate of one strip/five control of varroa mite varroa destructor on honeybees by aromatic oils and plant materials 17 brood combs (bach, 1995). the strip was inserted between the brood combs. one application of these strips per colony was made every 24 days, with a total of three applications in each summer. mite collection device: mite collection devices were locally made, and consisted of a rectangular wooden frame of 40.5 cm length, 25 cm wide and 2 cm high. in the open space of the frame, a movable wooden board was placed on which a piece of rigid white paper was fixed by pins and smeared with a thin layer of vaseline to capture the fallen mite (colin, 1990). a wire mesh (2 mm) screen was placed on the upper part of this device, to allow the dead mites to fall through onto the movable wooden board. this screen would not allow bees to pass through and thus prevented them from removing the dead mites outside the colony (calderone and spivak, 1995). the vaseline-treated paper was taken every four days to count the number of fallen mites, and was replaced with new vaseline smeared paper. the mite collection device was fixed at the lower of the hive after removing the bottom base of the hive. the fixing and removable side of the wooden frame in each hive was at the back of the hive, to avoid honeybee’s disturbance. number of fallen dead varroa mites to evaluate the effectiveness of the control agents, the number of mites captured by the collecting device was counted and recorded for each colony. the number of fallen mites was counted every four days. statistical analysis the number of the dead (fallen) mites was used to calculate the folds of dead varroa. results were statistically analyzed using duncan’s multiple range test (dmrt). the folds of dead varroa after treatment that determined which treatment was superior over other treatments during each treatment period in each summer, were calculated. the average number of fallen mites for the pretreatment period was divided by the average number of fallen mites during one treatment period (tables 1 and 2). the most effective application period of treatment to control varroa was calculated by taking the total number of fallen mites collected during one treatment period, divided by the total number of fallen mites collected in each reading (each four days), multiplying by 100%. this equation gave the percent mortality of varroa (tables 3 and 4). results effectiveness of tested materials: results presented in table 1 show that in the first treatment period (ftp), there were no significant differences among table 1 means of folds of fallen varroa mites for each of three treatment periods during summer of 1997. treatments first* second third clove oil 2.61a ± 1.62** 0.78b ± 0.49 5.32a ± 3.83 lavender oil 1.77a ± 0.46 0.70b ± 0.21 2.18a ± 0.61 peppermint oil 3.83a ± 1.87 0.79b ± 0.15 2.79a ± 2.18 sage oil 3.21a ± 1.38 0.79b ± 0.43 0.85a ± 0.49 thyme oil 2.79a ± 0.88 0.58b ± 0.16 1.07a ± 0.32 cumin fruit 1.58a ± 0.46 0.59b ± 0.34 4.07a ± 1.92 eucalyptus leaves 1.72a ± 0.61 0.58b ± 0.06 1.88a ± 0.59 worm wood flowers 3.85a ± 1.82 1.00b ± 0.41 4.67a ± 2.23 apistan strips 3.18a ± 1.40 1.03b ± 0.55 1.35a ± 0.25 control 1.43a ± 0.21 3.40a ± 2.30 3.43a ± 2.94 * each treatment period lasted for 24 days, with six readings. ** means within columns with the same letters are not significantly different according to dmrt at 5 % level. table 2 means of folds of fallen varroa mites for each of three treatment periods during summer of 1998. treatments first* second third clove oil 3.77ab**± 0.07 1.50ab ± 0.63 6.07a ± 1.22 lavender oil 4.38ab ± 1.74 0.91ab ± 0.25 3.69a ± 0.92 peppermint oil 5.62a ± 1.56 2.15ab ± 0.60 2.96a ± 1.68 sage oil 2.22ab ± 0.85 3.38ab ± 1.68 3.93a ± 1.22 thyme oil 4.39ab ± 1.22 3.68a ± 1.40 2.74a ± 0.70 cumin fruit 3.70ab ± 1.29 2.12ab ± 1.47 1.95a ± 0.53 eucalyptus leaves 1.19b ± 0.22 1.13ab ± 0.71 3.95a ± 1.71 worm wood flowers 5.62a ± 2.32 2.04ab ± 0.89 6.38a ± 3.55 apistan strips 5.16ab ± 1.51 3.50ab ± 0.58 6.82a ± 3.34 control 1.69ab ± 0.99 0.69b ± 0.07 3.10a ± 1.55 *each treatment period lasted for 24 days, with six readings. **means within columns with the same letters are not significantly different according to dmrt at 5 % level. table 3 comparison of means of folds of fallen varroa mite for all treatments during summers of 1997 and 1998. means of means of folds of fallen mites for three treatment periods* treatments summer 1997 summer 1998 clove oil 2.90a** ± 1.38 3.78ab ± 0.77 lavender oil 1.55a ± 0.32 2.99ab ± 0.78 peppermint oil 2.47a ± 0.94 3.58ab ± 0.86 sage oil 1.62a ± 0.59 3.18ab ± 0.69 thyme oil 1.48a ± 0.43 3.60ab ± 0.76 cumin fruit 2.08a ± 0.78 2.59ab ± 0.51 eucalyptus leaves 1.40a ± 0.32 2.09ab ± 0.61 worm wood flowers 3.17a ± 1.01 4.68ab ± 1.42 apistan strips 1.85a ± 0.56 5.16a ± 1.77 control 2.75a ± 1.13 1.83b ± 0.69 *means for the three treatment periods with six readings for each period. **means within rows with the same letters are not significantly different according to dmrt at 5 % level. the treatments. there was a 3.18 fold increase in the dead mites after treatment with apistan® compared to a 1.43 fold increase in the control treatment. several al-abbadi and nazer 18 table 4 means of three treatment periods of mortality of varroa mite for each of six readings obtained at four day intervals for summer 1997. mortality means (%) ± se treatments reading (1) (2) (3) (4) (5) (6) clove oil 15.54a* ± ! 4.55 12.48a ± 2.89 19.97a ± 3.36 15.39a ± 2.29 16.79a ± 2.87 19.90a ± 5.13 lavender oil 7.33c ± !1.33 12.61bc ± 2.60 14.68abc ± 1.98 23.70a ± 6.01 19.46ab ± 2.62 24.14a ± 4.69 peppermint oil 15.88a ±! 4.51 16.91a ±! 3.96 18.14a ± 3.37 13.74a ± 2.72 13.00a ± 3.40 11.22a ± 2.90 sage oil 14.07a ± 2.60 16.46a ± 2.36 17.74a ± 2.67 18.50a ± 2.46 19.72a ± 2.55 13.48a ± 2.57 thyme oil 15.49a ± 4.17 16.67a ± 2.82 17.13a ± 2.51 14.73a ± 2.48 19.24a ± 3.47 15.56a ± 2.62 cumin fruit 17.03a ± 3.39 23.29a ± 3.82 15.36a ± 2.72 14.46a ± 2.85 13.57a ± 2.51 16.27a ± 3.92 eucalyptus leaves 11.13c ± 1.99 13.79cb ± 2.21 14.60bc ± 2.20 17.62abc ± 2.33 18.79ab ± 2.59 24.08a ± 2.52 worm wood flowers 20.42a ± 6.64 17.94a ± 3.85 19.98a ± 6.13 14.88a ± 4.46 13.00a ± 4.28 13.77a ± 4.63 apistan strips 11.80b ± 2.60 20.87a ± 3.03 16.84ab ± 1.70 16.63ab ± 2.09 20.17a ± 1.96 13.70ab ± 2.43 control 13.98ab ± 1.81 13.61ab ± 2.92 15.53ab ± 1.73 24.72a ± 5.63 20.63ab ± 5.35 11.47b ± 3.57 *means within rows with the same letters are not significantly different according to dmrt at 5 % level. table 5 means of three treatment periods of mortality of varroa mite for each of six readings obtained at four day intervals for summer 1998. mortality means (%) ± se treatments reading (1) (2) (3) (4) (5) (6) clove oil 22.69a* ±! 1.93 25.22a ± 1.91 24.06a ± 2.46 14.62b ± 2.05 7.90c ± 0.83 4.99c ± 0.62 lavender oil 23.04a ±! 2.78 25.30a ± 1.76 23.37a ± 3.15 12.36b ± 0.67 8.93b ± 1.80 7.31b ± 1.11 peppermint oil 23.10a ± 1.45 22.77a ± 2.03 22.78a ± 2.92 13.04b ± 1.40 10.17b ± 1.29 12.00b ± 1.68 sage oil 21.16ab ± 3.57 18.54abc ± 1.19 24.14a ± 3.22 15.36bc ± 1.73 12.90cd ± 0.91 7.93d ± 0.96 thyme oil 21.21ab ± 2.11 23.30a ± 2.41 17.28bc ± 1.35 15.07cd ± 1.64 12.52cd ± 1.82 10.51d ± 2.07 cumin fruit 25.17a ± 2.14 23.55a ± 2.14 23.59a ± 2.79 12.53b ± 1.10 7.97bc ± 1.49 6.32c ± 1.44 eucalyptus leaves 23.57a ± 3.87 22.24a ± 2.52 23.69a ± 5.30 11.76b ± 1.85 10.46b ± 1.97 8.10b ± 1.64 worm wood flowers 18.67ab ± 2.07 23.92a ± 3.34 26.39a ± 6.17 12.52bc ± 1.28 09.88bc ± 1.37 8.50c ± 2.17 apistan strips 22.12a ± 2.28 20.86a ± 0.88 25.41a ± 3.64 13.06b ± 0.90 11.30b ± 1.54 8.13b ± 1.64 control 22.03a ± 2.87 21.50a ± 3.38 15.93ab ±! 0.89 13.98b ± 1.37 14.28b ± 2.20 12.33b ± 1.77 *means within rows with the same letters are not significantly different according to dmrt at 5 % level. treatments were better but not significantly different than apistan®. worm wood flowers, peppermint oil and sage oil gave 3.85, 3.83, and 3.21 folds, respectively over the control (1.43). the other treatments gave better results than the control. in the second treatment period (stp), mortality in the control was significantly higher than all other treatments (table 1). in the apistan® and worm wood flower treatments, the trend of dead mites did not change after treatment. during this period, the applied agents showed lower apparent effects on varroa, as compared to control treatment that could be attributed to the build up of the varroa population at this period. this was due to the fact that the colonies were not treated with any control agent. in the third treatment period (ttp), no significant differences were found. however, clove oil, worm wood flowers and cumin fruit treatments resulted in 5.32, 4.67, and 4.07 folds of dead mites, respectively as compared to the control treatment (3.43 folds). all treatments gave better results than apistan! except for sage and thyme oil. comparison among the means of folds of the three treatment periods for summer 1997 (table 3) resulted in no significant differences among the treatments. however, worm wood flowers and clove oil gave the highest folds of dead mites after treatment, 3.17 and 2.90 folds, respectively. the peppermint oil and cumin fruits treatment resulted in 2.47 and 2.08 folds of dead mites, respectively. however, this increase was lower than the control treatment (2.75), but higher than apistan! (1.85) (table 3). the results for summer 1998 (table 2) indicated that in the ftp, peppermint oil and worm wood flower treatments significantly increased the dead mites as compared with eucalyptus leaves, but they were at the same level of significance with all other treatments. in the stp, thyme oil was significantly superior (3.68) over the control treatment (0.69) in the dead fallen mites, but it was similar to other treatments. in the ttp, there were no significant differences. the folds of dead varroa were approximately the same in the case of apistan!, worm wood flower and clove oil treatments, 6.82, 6.38 and 6.07, respectively. the means of folds of the treatment periods (table 3) indicate that treatment with apistan! was control of varroa mite varroa destructor on honeybees by aromatic oils and plant materials 19 superior but not significantly different than cumin fruits, eucalyptus leaves and the control treatment. however, the other treatments were significant, as apistan!, in their effectiveness for killing mites. during the three periods of treatments, the means of folds obtained from the control treatment was 1.83. the effective period of application: results for summer 1997 (table 4) indicated that the percent mortality means of mites for clove oil, peppermint oil, sage oil, thyme oil, cumin fruits and worm wood flower treatments were not significantly different among all readings. however, in case of the lavender oil treatment the fourth and the sixth readings were significantly superior over the first and the second readings, but they were at par with the other levels. treatment with eucalyptus leaf-smoke showed the highest percent mortality means of mites after the sixth application, which was significantly superior over the first, second and third readings. however, they were at par with the other readings. the second and the fifth readings of the percent mortality means of mites for apistan! treatments were significantly superior over the first reading, but they were at par with other readings. according to the time of application, the result of comparison of each two readings in each application indicated that the second reading of the percent mortality means of mites was higher than the first one in the case of lavender oil, peppermint oil, sage oil, thyme oil, cumin fruits, eucalyptus leaves and apistan! strips. results from summer 1998 (table 5) showed that the first, second and the third readings of the percent mortality means of mites were significantly superior over the other readings in case of clove oil, lavender oil, peppermint oil, cumin fruits, eucalyptus leaves and apistan! strips treatments. however, results of sage oil treatment indicated that the third reading of percent mortality means of mites was significantly superior over the fourth, the fifth and sixth readings. on the other hand, with thyme oil, the second reading of percent mortality means of mites was significantly superior over all other readings except the first one. treatment with worm wood flowers showed that the second and the third readings of the percent mortality means of mites were significantly superior over the fourth, the fifth and the sixth readings, but they were at par with the first reading. with regards to the time of application (i.e. first, second or third application), the results indicated that the second reading of the percent mortality means of mites was higher than the first one for clove oil, lavender oil, thyme oil and worm wood flowers. however, for all treatments, the third reading of the percent mortality means of mites was higher than the fourth one, and the fifth reading was higher than the sixth one. discussion according to baker (1988), the infestation rate of varroa depends on climate, the physiological stage of honeybee and varroa mite, presence or absence of drone cells and the hive itself. the efficiency of any control agent depends on it’s activity and on the conditions prevailing inside the hive at the time of application. during ftp (june 27 to july 21, 1997), there was a higher number of younger bees and drones, which are usually preferable to varroa than other honeybee stages and castes (winston, 1995). at the same time, the temperature was high enough (30°c) to hasten varroa to leave the brood cell to the adult bees. this is in agreement with szabo and walker (1996). these conditions caused a higher number of the infested bees to be exposed to the control agents, which resulted in a higher number of fallen mites (table 1). during the stp (july 29 to august 22), the applied agents showed lower apparent effects on varroa compared to that of the ftp (table 1). however, in the control treatment there was a continuous increase in the number of dead varroa during the four day interval reading (tables 1 and 4) and reached a mean of 3.40 folds. this increase could be attributed to the buildup of the varroa population at this period. this was due to the fact that the colonies were not treated with any control agent. moreover, during this period (stp), there was a high number of open brood cells, which were ready for capping. this provided a suitable chance for varroa to escape the injuries of the control agents by entering these cells (shalaby et al., 1996). these results indicate that the control agents could not penetrate the brood capping. in other words, their effects were mainly on the adult mite attached to adult bees. during the ttp (august 30 to september 23), the means of increased folds of the fallen mites for the applied control agents, showed better results than ftp and stp. during the ttp, the temperature decreased to 17°c and honeybees formed clusters with a lack of brood, a condition which was observed through the pattern of varroa falling on the sticky paper. this was not random. the fallen mites were concentrated directly beneath the clustered bees. similar results were reported by shalaby et al. (1996). all previous described conditions provided a suitable environment to expose varroa mites directly to the volatile oils and plant materials. comparing the results obtained during each of the three periods (table 1) indicates that some of the tested volatile oils and plant materials showed better results at certain periods but not through the three periods. this could be attributed to the life cycle of the honeybee and mite. worm wood flowers, peppermint oil and sage oil treatments gave better results during the ftp, where as al-abbadi and nazer 20 clove oil, worm wood flowers and cumin fruit gave better results during the ttp (table 1). conclusions from the results obtained from this work, it can be concluded that worm wood flowers, clove oil and peppermint oil can be considered promising agents for the control of varroa destructor. good results can be obtained when the above materials are used two to three times each month during the infestation period. effective time of application depends on the mite level of infestation and the life cycle of the mite. the natural control agents used in this work, seem to have no adverse effects on bees. acknowledgments the authors wish to thank the deanship of scientific research at the university of jordan for partial financial support. thanks are also due to beekeepers for their cooperation. special thanks go to prof. f. al-mohammady for his help in the statistical analysis. references abu-zied, m. j. and h.a. ghoniemy. 1993. evaluation the role of two natural substances for the controlling of varroa jacobsoni infesting honeybee colonies. egypt journal of applied sciences 8(20):295300. amrine, j.w., j.r. terry, a. stasny, and r. skidmore. 1996. new mite controls investigated. american bee journal 136(9):652-653. anderson, d. l. and j.w.h. trueman. 2000. varroa jacobsoni (acari: varroidea) is more than one species. entomology abstracts 31(10): 9507-z31. bach, j. 1995. don’t abuse apistan. bee culture 123(10):590-593. baker, m.d. 1988. variability and biotypes of varroa jacobsoni oudemans. american bee journal 128(8):567-568. baker, m.d. and c.y.s. peng. 1995. varroa jacobsoni and tropilaelaps clareae: a perspective of life history and why asian bee mites preferred european honeybees. american bee journal 135(6):415-420. calderon, n.w. and m. spivak. 1995. the successful management of the parasitic mite, varroa jacobsoni in colonies of the honeybee, apis mellifera, with natural products. wisconsin badger bee, usa. colin, m.e. 1990. essential oils of labiatea for controlling honeybee varroosis. journal of applied entomology 110:19-25. dufol, m.f., a.m. viuales, and c.s. acedo. 1991. comparative tests of fluvalinate and flumethrin to control varroa jacobsoni oud. journal of apicultural research 30(2):103-106. elzen, p.j., f.a. eischen, j.b. baxter, j. pettis, g.w. elzen, and w.t. wilson. 1998. fluvalinate resistance in varroa jacobsoni from several geographic locations. american bee journal 138(9):674676. kraus, b., n. koeniger, and s. fuchs. 1994. screening of substances for their effect on varroa jacobsoni; attractiveness, repellency, toxicity and masking effects of ethereal oils. journal of apicultural research 33(1):34-43. lindberg, c.m., a.p. melathopoulos, and m.l. winston. 2000. laboratory evaluation of miticides to control varroa jacobsoni (acari: varroideae), a honeybee (hymenoptera: apidae) parasite. journal of economic entomology 93(2):189-198. ministry of agriculture. 1986. a yearly survey of apiary conditions in jordan. amman, jordan. pp.2. ministry of agriculture. 1997. a yearly survey of apiary conditions in jordan. amman, jordan. pp.2. putman, m.b. and a.z. cochise. 1996. mites and bees. bee culture 124(6):328. ruijter, a.d. 1994. issues in the control of varroa infestation. in: new perspective on varroa, a. matheson (editor), 24-26. international bee research association. cardiff (uk). shalaby, a.a., s.i. yousif-khalil, s.m.a. el-shakaa, and e.z. matter. 1996. efficiency of some control agents against varroa mites infesting honeybee colonies. zagazig journal of agricultural research 23(6):113-130. shimanuki, h. and d.a. knox. 1991. diagnosis of honeybee diseases. usda, washington d.c., usa. spivak, m. 1997. honeybee hygienic behavior as a defense against varroa jacobsoni mites. resistant pest management 9(2):22-24. szabo, t.i. and c.r. walker. 1996. rate of infestation of honeybee colonies by varroa jacobsoni. american bee journal 136(6):447-448. winston, m.1995. pesticide resistance. bee culture 123(7):389-390. _________________________________________ received july 2002. accepted november 2002. sultan qaboos university journal for scientific research agricultural and marine sciences, 11 s.i., 29-36 (2006) ©2006 sultan qaboos university 29 water demand analysis for tree crops in spanish mediterranean farms maria angeles fernández-zamudio1*, maria dolores de-miguel2 and pedro caballero1 ¹departamento de economía y sociología agrarias, instituto valenciano de investigaciones agrarias, apartado oficial s/n. 46113 moncada (valencia), spain. ²departamento de economía de la empresa, universidad politécnica de cartagena, paseo alfonso xiii, 44. 30203 cartagena (murcia), spain. طلب المیاه لألشجار المثمرة بمنطقة فالنسیا بإسبانیا ماریا أنجلز فرنندز-زامودیو وماریا دولورس دي میجال وبادرو كابایارو الخالصة: تمثل أشجار الزیتون والعنب واللوز أھم المغروسات الزراعیة الغیر مسقیة بالمنطقة الواقعة على البحر األبیض المتوسط في أسبانیا. ویساھم الدخل المتأني من ھذه المنتجات من اإلبقاء على الحركة اإلقتصادیة في المناطق الریفیة والتقلیص من ھجرة السكان. ومن خصائص الزراعات المطریة في البحر األبیض المتوسط أن جزءًا صغیرًا فقط من المساحة الكلیة یكون خاضعًا للري. وبما أن المنطقة تتمیز بشح كبیر في المیاه فإن ھذه الورقة تھدف إلى دراسة التأثیرات من ّجراء إدخال تعریفة للمیاه كما تنص علیھ التوجھات األوروبیة إلدارة المیاه. ولھذا الغرض وقع إستعمال نظریة البرمجة المتعددة األھداف للحصول على معادلة الطلب على المیاه. و وقع التركیز على ضیعة واحدة تمثل خاصیات المنطقة لدراسة تأثیر السیاسة السعریة على الوضع اإلجتماعي واإلقتصادي والبیئي للمنطقة حسب مدى تطور المیكنة فیھا. تظھر النتائج أنھ في حالة إدخال تعریفة للمیاه فإن الحل الوحید الممكن لإلبقاء على النشاط الزراعي في المنطقة ھو التركیز على تطویر المكینة. abstract: olive, vine and almond in rainfed farming systems are the most traditional crops in the large inland extensions of the spanish mediterranean. their economic contributions enable farming activities to be maintained meaning that the villages remain inhabited. in the rainfed-farms in the mediterranean regions it is possible to find only a certain proportion of the farms with some type of irrigation system. given the water scarcity, the aim of this work is to determine the impact that an irrigationwater pricing policy would have on these regions, as outlined in the european water framework directive. after analysing the direct effect water price would have on the net margin in these crops, demand functions have been obtained, applying the multiattribute utility theory. the calculations, with reference to a farm that is representative of these regions, have been applied to two model scenarios, each with a different level of mechanization. results show the impact on economic, social and environmental aspects of the pricing policy under the current water allotment. the work is completed by analysing the different contexts of irrigation-water availability on the farm. the study leads to the conclusion that increasing mechanization may be the most straightforward strategy to ensure the survival of these farms in the short to medium term if the current trend of increasing irrigation-water prices is consolidated. keywords: mediterranean agro-systems, multiattribute utility theory, demand functions of irrigation water, olive, vine, almond. introduction mediterranean rainfed-farming is predominant in the inland parts of spain. the most traditional and characteristic crops are the olive (olea europea l.), the vine (vitis vinifera l.) and the almond (prunus l.) and the almond (prunus l.) and the almond ( dulcis mill.) combined in different proportions on the * corresponding author. e-mail: economia@ivia.es zamudio, de-miguel and caballero 30 majority of farms. the three woody species are grown extensively and frequently with minimal management; in other words, with semi-abandonment in which these three tree crops are left to survive at the mercy of the climate. these crops have helped in maintaining the countryside, which is one of the landmarks of the cultural identity of these regions, in protecting the soil from erosion, and they can also be considered an important promoter of human activity. although agriculture has traditionally supplied the main income to the population, socioeconomic changes have led to transformation of the farming communities in the mediterranean inland regions. the industrial and the service sectors continue to put strong pressure on labour resources, especially among young people giving little incentive to continue farming activities which limits generational take-over and leads to the disappearance of family farms. in the arid regions of the mediterranean, agriculture is strongly influenced by the irregularity of rainfall. the most important natural resource is water, which is in short supply and of the greatest value. the availability of water for irrigation considerably increases yield, assures a greater regularity in harvest and decreases the economic risks in farming. on the other hand, the current european water framework directive proposes an irrigation water pricing policy to improve the efficient use of this resource. however, high water prices would reduce the profitability of the farms and could affect the continuity of this type of agriculture. the present paper is conceived with the general goal of determining the impact that an irrigation-water pricing policy would have in the arid mediterranean regions. the work starts off by calculating the direct effect of water cost on the net margin and goes on to determine the demand functions of water by applying multiattribute utility theory for different contexts of the irrigation-water availability on the farm. direct impact of irrigation water on incomes a first approach to assessing the impact of irrigation water on incomes can be obtained by observing the reduction in the net margin of each crop according to the increase in the price of this resource (castrocoelho et al., 2005). in this section we are going to analyse the effect of water price on incomes from olive, vine and almond in a representative region in the spanish inland l’alcoià, in the province of alicante. we have only taken the five main activities that receive some kind of irrigation. table 1 shows the average productions and the usual volume of irrigation. two net margins have been calculated. the net-1 margin is according to the average price of the harvest received by the farmers in the zone analysed over the last five years. the net-2 margin corresponds to a price 15% lower than the first, to simulate the effect if the clear downward trend in the prices of these three species continues. these crops display high irrigation efficiency. their production increases notably even when the volumes applied are very low. the greatest problem is the low profit, especially given the trend of decreasing prices received table 1. crop-growing activities: description, annual water supply and net margin for two production prices. species olive almond vine varieties grossal comuna group monastellauthochthonous authochthonous tube irrigation irrigated relief irrigated irrigated relief irrigated relief irrigated variable 0-lr 0-l a-lr v-lr v-l annual water supply (m3/ha) 700.00 1500.00 700.00 1100.00 1500.00 production (kg/ha) 3000.00 5000.00 1400.00 7000.00 1000.00 price-1 (euros/kg) 0.66 0.66 0.66 0.35 0.35 net margin-1 (euros/ha) (*) 1075.00 2056.00 264.00 1219.00 2138.00 price-2 (euros/kg) 0.56 0.56 0.56 0.30 0.30 net margin-2 (euros/ha) (*) 778.00 1560.00 125.00 853.00 1615.00 source: own calculations.source: own calculations.s (*) net margins of zero value of irrigation water. water demand analysis for tree crops in spanish mediterranean farms 31 by the farmers for the harvest; thus any increase in the costs could reduce their profitability even more. in order to observe the direct effect of the price of irrigation water on the net margin, we present figures 1 and 2. for the almond, negative margins start to occur at a price of 0.37 euros/m3 (to price-1) and of only 0.17 euros/m3 at price-2, which implies a reduction of 54 % in growing capacity to face the cost of water. for the vine, the negative net margins are found for water prices of 1.11 or 1.13 euros/m3 (for price -1), and 0.77 or 0.85 euros/m3 if the harvest is sold at price-2, which implies a reduction of 25 or 31 %. finally, the olive would have a negative net margin if the water costs 1.53 or 1.36 euros/m3, but if the olive is paid for at price-2 the margin would be negative when the water costs 1.11 or 1.04 euros/m3. this implies a reduction of 23 or 27 % when dealing with the species that has the greatest margin to offset the high water prices. the price levels of irrigation water that this agriculture could withstand can be determined more thoroughly via demand curves, which are presented in the following section. figure 1. crops net margin changes according to irrigation water price. (data for net margin-1). figure 2. crops net margin changes according to irrigation water price. (data for net margin-2). zamudio, de-miguel and caballero 32 irrigation water demand functions on approving the water framework directive (directive 2000/60/ec), the european parliament set a number of actions regarding water policy at the community level (official journal, 2000). this directive, with a clear environmental focus, established the convenience of using pricing as an economic tool to increase the efficient use of water, proposing the achievement of full-cost recovery of water by 2010. it is difficult to find an appropriate method to achieve this objective directly, but it is possible to find an approximation of farmers’ response in the event of applying a water-pricing policy by using the neoclassical economic theory, and especially the multiattribute utility theory (maut). several previous workers pointed out the suitability of using the multiattribute utility theory to derive demand functions, (berbel and gómez-limón, 2000; gómezlimón and riesgo, 2004). the work by keeney and raiffa (1976) is a starting point of maut. later edwards (1977), farmer (1987) and huirne and hardaker (1998) went on to perfect it. we have followed the framework developed by sumpsi et al. (1996) and amador et al. (1998). the objective is to find the utility function, u, separable, u, separable, u additive and linear for each attribute, fi fi f (x), which once normalized would be: where wi are the weights obtained previously, fifif * is the * is the * ideal value for each objective and fifif * worst or anti-ideal, * worst or anti-ideal, * which are extracted from the pay-off matrix. we determined the utility function of a farm representative of the region under study. a series of simulations are made with rising prices of irrigation water, in such a way that each price is a new scenario in which utility is maximized, and from which we derive a cropping plan with a specific demand for irrigation water. the simulation models are applied to two scenarios related to the degree of mechanization on-farm. in the “manual-scenario”, low-powered mobile equipment was used together with traditional harvesting and hand-picking. in the “mechanized-scenario” we consider higher-powered mobile equipment, together with the use of pre-pruners, harvesting with integral grape-collectors in the vines, and automatic vibrators with mechanized picking and fruit loading systems for the olives and the almonds. the most expensive figure 3. demand functions for irrigation water for the two scenarios. (data for a family farm of 32 hectares). water demand analysis for tree crops in spanish mediterranean farms 33 machinery is always considered to be rented, so that its high amortization does not prevent farmers with less available capital from adopting its use. the decision variables are the surface area in exploitation for each crop-growing activity. olive and almond (an autochthonous variety and a new variety) and vine (in tube or espalier) have been introduced. in total, 16 decision variables are considered, the main difference being the amount of irrigation water applied. we contemplate the option of complementary irrigation and, in the case of the vine and olive ,conventional drip irrigation is also possible, with greater and more continuous flow. figure 4. repercussions derived from the application of a water pricing policy. (data for 32 hectares). manual scenario. figure 5. repercussions derived from the application of a water pricing policy. (data for 32 hectares). mechanizedscenario. zamudio, de-miguel and caballero 34 the following objectives are considered: maximization of the net margin of the farm and minimization of the total workforce. a number of restrictions have been taken into account, and have been considered equally in both scenarios: [1] crop area (a total of 32 hectares are available on the farm). [2] marginal management (at maximum 30 % of the available surface area). [3] the maximum surface area of each species is limited to its present situation (32 % in olive, 8 % in almond and 60 % in vine) since we are dealing with tree crops and the models under consideration are static. however, changes in variety within a species, changes in the type of irrigation, or for this to pass to marginal management are allowed. [4] irrigated surface area: only 10 % of the available surface area can receive some kind of irrigation, according to the criteria of the experts consulted. [5] manual labour and family labour is fixed at an agricultural work unit (2,160 hours a year), and hired labour is limited to complement what cannot be covered by family on a three-monthly basis. demand functions: results and discussion with respect to the availability of irrigation, water supplied cannot exceed 600 m3 monthly for the whole farm, and the total amount allotted to the farm is 5,000 m3 annually. the demand curve obtained is shown in figure 3. in the “manual scenario” there is a first range of maximum demand, between 0 and 0.51 euros/m3. this continues with a drop to half the demand for tariffs of 0.52 a 0.55 euros/m3 and ends up with cropping plans in completely rainfed-farming when the water costs over 0.56 euros/m3. in the “mechanized scenario” the demand is constantly at maximum until it reaches 0.91 euros/m3, at which point the chosen cropping plan changes to strict rainfed-farming. the different response must be looked for in the different degree of mechanization. technology improves management and enables farmers to substitute the labour requirements that arise from irrigated crops more effectively. this limitation is accentuated if the work, especially harvesting, is carried out manually. for this reason, the mechanized farms are more able to pay higher water prices. cropping plans are obtained for each water price simulated. each of them generates a net margin on the farm, labour requirements and water consumption. it is also possible to calculate another indicator from the surface area of land necessary to achive a minimum income, for example 21,500 euros. all these indicators help in understanding the economic, social, and environmental repercussions of a hypothetical irrigation water pricing policy in these regions. figures 4 and 5 show the variation in the same area for six price levels that are higher than the current ones, taking into account that the usual cost of irrigation water in this region is 0.15 euros/m3. for the “manual scenario” (figure 4), in line with the increase in water prices, there is a decrease in the income, water consumption and the manual labour figure 6. water demand function for different water allotment and prices, “manual-scenario”. (data for 32 hectares). water demand analysis for tree crops in spanish mediterranean farms 35 demanded. for a price above 0.24 euros/m3, an income below the minimum is obtained, and over 0.51 euros/ m3 a totally rainfed cropping plan is adopted. without irrigation, the net margin of the farm is 18,810 euros, employing an average of 100 hours manual work annually per cultivated hectare. at the present price of water, the minimum income is obtained by cultivating 31.3 ha, but 36.6 ha are needed if cultivation is totally rainfed. in figure 5 we can observe the effects on a farm for the “mechanized scenario”. the cropping plan includes irrigation until the price of irrigation water is lower or equal to 0.91 euros/m3. above that price the farm plan converts to rainfed cultivation. the income decreases gradually with the rise in the cost of water, and the minimum income is not assured if the price of water is over 0.4 euros/m3. with the present price of water, the minimum income is obtained by cultivating 30 ha, but in the case of the strict rainfed cultivation 37 ha are necessary to ensure the minimum income. the high stability in manual-work requirements is notable, which is practically 80 hours annually per hectare for all water prices. the analysis of irrigation-water demand is completed by evaluating, in addition to the present context, different scenarios of resource availability on the farm. in the usual scenario the farm has 600 m3 monthly and 5,000 m3 annually. these reference values are denominated as “usual (100 100)”. three drought scenarios are evaluated, in which there can be a monthly or annual reduction, in terms of the percentage with respect to the habitual, named as “drought-1 (75100)”, “drought-2 (66,5 96)” and “drought-3 (42 60)”. finally, we contemplate the possibility of having a reservoir on the farm, with which the monthly availability would increase, although not annually. this would be “reservoir (133 100)”. the demand curves obtained in new contexts of water availability on the farm show the differences between both initial model scenarios. in the “manual scenario” (figure 6), several different cropping plans are generated, ranging between the situation consuming the whole water allotment and that chosen for rainfed cultivation. for the “mechanized scenario” (figure 7), the same cropping plan is obtained if water is available . only when the price of irrigation becomes too high (0.87 €/m3) does the cropping plan change to total rainfed cultivation. these results confirm how mechanization reinforces in its turn the efficiency of irrigation. the fact that the same activities are figure 7. water demand function for different water allotment and prices, “mechanized-scenario”. (data for 32 hectares). zamudio, de-miguel and caballero 36 chosen, independently of water price, is because the good level of mechanization enables a choice of the most productive varieties, although they demand more manual labour. on the other hand, in conditions of drought, the model shows that farmers will be willing to pay more for the water. this is observed graphically, for example, in the “manual scenario” (figure 6), at 0.56 euros/m3 rainfed farming would be the option; on moving to the availability corresponding to drought-3, irrigation is continued up to a price of 0.74 euros/m3. nevertheless, this affirmation should not lead to overvaluing the capacity of this agrarian system, since the increase in price that the farm can face is not proportional to reduction in supply that it is subjected to. for a reduction of 58 % in the monthly water allotment and 40 % in the annual one, between the “manual scenario” and that of drought-3, the difference in price is only 32 %. similar conclusions can be drawn from the “mechanized scenario”, even though the most efficient activities are chosen from the first moment. in this case, a situation of extreme drought will not generate enough income to compensate higher costs of machinery, and therefore the crop plan will be totally rainfed for water prices over 0.87 €/m3 (drought-3), or over 0.91 €/m3 (in drought-1 and drought-2). conclusion in evaluating the direct impact of water price on the net margins the olive tree is the species that can justify higher irrigation water prices. with respect to the different demand functions derived, results show that the effect of water price on the farmers’ income is that a higher degree of mechanization is necessary in order to face the high irrigation-water prices. the current price of water is 0.15 euros/m3 and it could increase. however, to ensure a minimum income for the farm of 21,500 euros annually, water price cannot exceed 0.24 euros/m3 on a manual farming system, or 0.4 euros/m3 if the farm is mechanized. in situations of drought, the farming system cannot proportionally face a reduction in the allotment with higher irrigation-water prices. in any event, to ensure the survival of the farms in the spanish rainfed farming system increasing mechanization is the most straightforward strategy. this is to guarantee the viability of this agriculture if the current trend of increasing irrigation-water prices continues. mechanization should be on a rent basis and not on an ownership basis to make it affordable. acknowledgements the present paper forms part of research project agl 2002-04251-c03-01, financed by the spanish ministry of finance and technology and feder funds. references amador, f., j.m. sumpsi and c. romero. 1998. a non-interactive methodology to assess the farmers’ utility function: an application to large farms in andalusia, spain. european review of agricultural economics 25:95-109. berbel, j. and j.a. gómez-limón. 2000. the impact of water-pricing policy in spain: an analysis of three irrigated areas. agricultural water management 43:219-238. castro-cohelo, j., l.m. silva, m. tristany and p. pinto. 2005. planning cropping systems for the new irrigation areas under the influence of the alqueva dam. the case study of the odivelas irrigation scheme. new mediterranean 3:3-11. edwards, w. 1977. use of multiattribute utility measurement for social decision making. d.e. bell, r.l. keeney, r.l. and h. raiffa (editors), decisions. john wiley & sons, new york. farmer, p.c. 1987. testing the robustness of multiattribute utility theory in an applied setting. decision sciences 18:178-193. gómez-limón, j.a. and l. riesgo. 2004. water pricing: analysis of differential impacts on heterogeneous farmers. water resources research 40:w07s05. huirne, r.b.m. and j.b. hardaker. 1998. a multiattribute model to optimise sow replacement decisions. european review of agricultural economics 25:488-205. keeney, r.l. and h. raiffa. 1976. decisions with multiple objectives: preferences and value trade offs. john wiley & sons, new york. official journal. 2000. framework for community action in the field of water policy. edition l, 327 of 22.12.2000. available from url [accessed 1 nov 2005]: http://europa.eu.int/scadplus/leg/en/lvb/ l28002b.htm sumpsi, j.m., f. amador and c. romero. 1996. on farmer’s objectives: a multi-criteria approach. european journal of operational research 96: 64-71. sultan qaboos university journal for scientific research agricultural and marine sciences, 11 s.i., 47-54 (2006) ©2006 sultan qaboos university 47 simulating groundwater charges for the moroccan drâa river basin claudia heidecke* and arnim kuhn institute for food and resource economics, university of bonn, nusßallee 21, 53115 bonn, germany abstract: agricultural production in the six oases in the drâa region in southern morocco is highly dependent on irrigation using mainly traditional irrigation channels or pumps. the basin has been suffering enormously from a continuing drought during recent years. declining rainfall and high evapotranspiration rates in the semi-arid region lead to lower flow in the drâa river. aggravating this situation, farmers increasingly pump groundwater with motor pumps, leading to a rapidly drop in the aquifer. however, agricultural production is economically inefficient and based on subsistence farming. the income a farmer gets by selling a share of his production on the local markets hardly covers the variable costs for fertilizers and irrigation water. farmers do pay only the pumping cost estimated at 0.58 dh/m3. to prevent a further drop in the groundwater table, and hence to conserve water resources, the introduction of a water charge is evaluated with the mivad river basin model (rbm). this shows that imposing a water change of 0.42 dh/m3 leads to stable groundwater table, but with a drop in cropped area by 50%. keywords: water pricing, subsistence farming, income, groundwater. * corresponding author. e-mail: claudia.heidecke@ilr.uni-bonn.de introduction charging farmers for scarce irrigation water use is increasingly regarded as a means of encouraging efficient water allocation (cornish et al., 2004). in this context, water pricing regimes have been established for most irrigation perimeters in morocco in order to meet the needs for operation and maintenance of irrigation systems as well as to encourage investments in water-saving irrigation technologies. the drâa valley is the only river basin where this national strategy has not yet been implemented (serghini, 2002). but, as a consequence of a continued drought during recent years, the supply of centrally distributed river water has become ever more unreliable, pushing farmers to increasingly rely on groundwater. this has inevitably led to declining groundwater tables تقییم ضریبة على المیاه الجوفیة في منطقة الدرع جنوب المملكة المغربیة كلودیا ھایدك وأرمین كھون الخالصة: تعتمد الزراعة في الواحات الستة في منطقة الدرع جنوب المملكة المغربیة على المیاه الجوفیة. تشتكي المنطقة من جفاف متواصل خالل السنوات األخیرة. نقص األمطار مع زیادة نسبة التبخر نتج عنھا نقصان في میاه وادي الدرع. إضافة إلى الظروف المناخیة إزدادت نسب ضخ المیاه الجوفیة باإلستعمال الغیر المراقب لمضخات المیاه. تتمیز المزارع بصغر حجمھا وھذا یزید من ضعف اإلنتاجیة زیادة على أن المنتجات في معظمھا تذھب إلى اإلستھالك العائلي. لذلك فإن المداخیل التي یتحصل علیھا المزارعون تفي بتغطیة مصاریف األسمدة وتكلفة ضخ میاه الري فحسب. تقدر كلفة ضخ المیاه بـ 0.58 درھم للمتر المكعب والتي تقع على كاھل المزارع. ال یدفع المزارعون أي أداء أخر للدولة مقابل ضخ المیاه الجوفیة. تظھر نتائج ھذه الدراسة أن أحد الحلول للحد من إستنفزاف المیاه الجوفیة ھو إرساء ضریبة تقدر بـ 0.42 درھم/م3. غیر أن إرساء مثل ھذه الضریبة سینتج عنھ تقلیص المساحة المزروعة بنسبة 50 بالمائة. heidecke and kuhn 48 table 1. irrigation rates and o&m costs for different agricultural regions in morocco. ormva current water charges (dh/m³) o&m costs (dh/m³) moulouya 0.19 0.34 0.22 0.57 haouz 0.17 0.14 0.22 loukkos 0.40 0.46 0.66 souss_massa 0.38 0.50 0.25 0.89 tadia 0.17 0.09 0.14 doukkala 0.18 0.25 0.12 0.23 doukkala 0.34 0.41 0.33 0.37 gharb 0.19 0.40 0.24 0.44 source: tsur et al. (2004) note: irrigation costs for large scale irrigation systems rate of exchange to us$: 1moroccan dirham ~ 0.12 us$ (april 2006). figure 1. the drâa catchment area. source: www. impetus.uni-koeln.de and their salinization. this paper aims at identifying a groundwater charge sufficiently high to substantially curb the drop of groundwater tables. for this purpose, the effects of pumping costs in the current situation as well as additional groundwater water charges on farm income and sustainable water availability in the region are simulated using an integrated river basin model (rbm). empirical information on water costs and cropping profitability were obtained from a farm survey. the paper is organised as follows. first, a brief overview of water pricing in other watersheds in morocco is provided. then the drâa river basin water management policies are described. after a description of the research methodology the alternative water charges for agriculture in the drâa valley are compared, followed by conclusions. the results presented are based on interdisciplinary research carried out by the impetus project (www.impetus.uni-koeln.de) which aims at an integrated assessment of the water cycle as well as water management alternatives for the region. irrigation and water pricing in morocco in 1969 the ministry of rural development passed the agricultural investment code (cia) including a framework for the introduction of water prices for irrigation water in morocco. except for the drâa basin, all other watersheds in morocco have adopted water pricing schemes in recent years. investment costs of irrigation water are shared between the general budget (60% and the beneficiaries (40%), i.e. the farmers who simulating groundwater charges for the moroccan drâa river basin 49 are organised in newly established water user groups. the cia determines the water charges in order to recover all costs of operation and maintenance (o&m) as well as depreciation. table 1 shows the level of water charges in the different watersheds in morocco. on top of the volumetric water charges, farmers with more than five hectares of land are obliged to pay a fixed charge of 1500 dirham per hectare and year. however, 80 % of moroccan farmers are not relevant to this category. altogether the moroccan pricing system has contributed to the notorious underfinancing of irrigation schemes (serghini, 2003). it can be seen that in most cases actual water prices are lower than needed to recover o&m (tsur et al., 2004). moreover, it is an open question whether the design and levels of the water charges are sufficient to ensure sustainable use of surface and groundwater resources by farmers. study area: the drâa river basin the drâa river basin (fig. 1) is one of morocco’s smaller river basins, located close to the algerian border in the south-eastern part of the country. its location between the high atlas mountains and the saharan desert is characterized by low rainfall, ranging from about 54 to 106 mm per year. during recent years droughts have seriously afflicted the region. along the drâa valley there is a belt of six oases (fig. 2) characterised by the cultivation of palm trees, cereals, different kinds of vegetables, and alfalfa and barley for animal forage. most farms are of small size and are basically subsistence farms (ouhajou, 1996). the continuing drought has lead to a decrease in farm incomes with the result that young men migrate to the large moroccan cities or to foreign countries. numerous families in the oases heavily rely upon the remittances from these emigrated relatives for support. in 1972 a large water reservoir was built near the provincial capital ouarzazate, gathering the river inflows from the mountainous areas (fig. 2). since then, surface water distribution has been managed in a centralized manner where water is released periodically from the reservoir. beyond its function as a buffer against shorter droughts and the production of hydropower, another purpose for the reservoir was n figure 2. belt of the six oases included in the survey. heidecke and kuhn 50 to distribute water more evenly across the oases from north to south, giving the southern oases the chance to use water for irrigation first, while the northern oases had the advantage that their groundwater storage was recharged (ouhajou, 1996). nevertheless, since 1990 river basins south of the atlas mountains were characterised by negative hydrologic balances and these are likely to worsen further until 2020 (debbarh, 2002). until the beginning of the drought of the mid nineties this centralized water management helped to stabilize irrigation water supply. but due to declining rainfall and high evapotransipration rates, water releases from the reservoir are becoming more and more scant and irregular, and are mainly supposed to fill up groundwater levels of the aquifers below the oases. consequently, extraction of groundwater has increased considerably in the form of digging private wells and installing motor pumps. nowadays an average farmer owns two wells with motor pumps which run almost 12 hours per day during the cropping season, according to survey data. as a result the groundwater table has declined and salinization has increased during recent years (fig. 3). to evaluate the impact of a water pricing scheme it is necessary to look at the farmer’s income to see whether they are able to cope with the increasing costs, in a short as well as in a long-term perspective. table 2 illustrates gross margins for alfalfa and wheat with local prices and total production costs per hectare. gross margins for date palms are difficult to determine since variable costs were difficult to identify. gross profits are assumed to amount to approximately 200 dirham per tree according to the survey results. taking into account that farmers cultivate for self-consumption, the low level of the gross margins appears to be realistic, resulting in low remuneration for family work, but not leading to ‘visible’ monetary losses. however, with increased water costs, the negative gap widens. many farmers, particularly those who do not cultivate date palms as cash crops, will find it difficult to pay for additional water charges. as farmers will not stop the over-exploitation of groundwater until the aquifers are either depleted or salinized to an extent which makes water use for irrigation impossible, charging prices for groundwater use might be an option to curb the depletion of the common resource. however, as this price would have to be paid for from the already narrow agricultural profits, it is unlikely that water prices would leave the current size structure and performance of farms unchanged. table 2. gross margins and production costs for wheat and alfalfa in the drâa basin. wheat alfalfa yields (kg/ha) 1912 735 price per kg (dh) 4 2 total irrigation cost (dh/ha) 762 540 machinery cost (dh/ha) 878 647 cost for seeds (dh/ha) 679 581 fertilizer cost (dh/ha) 1037 275 total variable costs (dh/ha) 3356 2043 gross margin per ha 4292 -573 source: farm survey, 2005 and own calculations note: labor costs have not been taken into account. moreover, it is assumed that irrigation costs are all variable costs (predominantly fuel) as farmers usually do not take the depreciation of motor pumps or other irrigation technologies into account. average gross margins are not weighted for individual farm sizes. rate of exchange to us$: 1 moroccan dirham ~ 0.12 us$ (april 2006). figure 3. problem of salinization in the drâa region as perceived by farmers. source: own farm survey, october 2005 note: data according to farmers own assumption of salinization; measurements of electronic conductivity have been conducted in some cases for verification. simulating groundwater charges for the moroccan drâa river basin 51 methodology: the mivad model the following section is investigating two questions: which price level would preserve groundwater resources and thus enable oasis farming in the longer perspective, and which changes regarding the extent cropping activities would this price level require? both questions can be answered by simulating alternative water costs with the mivad model (modèle integrée du vallée du drâa), an integrated hydro-agro-economic river basin model (rbm, see also rosegrant et al., 2000) for the drâa region. mivad is an economic optimization model which simultaneously maximizes agricultural and hydropower generation profits as well as consumers’ utility from drinking water consumption (equation 1). the objective function of mivad is subject to a variety of constraints, represented by bounds and balance equations related to hydrology (river, groundwater and reservoir balances), agronomy (crop yield response, area and cropping mixes) and general technological aspects (hydropower, pumping by public and private agents), all of which have to be taken into account. agricultural production is represented as an lp exercise involving six stylised oasis farms. the response of crop yields to water stress is modelled by a modified penman-monteith function (allen et al., 1998). spatial relationships are represented in a node network representing different inand outflows, reservoirs and water demand sites. water distribution is modelled between the nodes. the network of the drâa river basin actually starts with the inflow node that defines the reservoir inflow exogenously for each month. the model is run over several years as a recursivedynamic model, with each year divided into twelve months, which are solved simultaneously. mivad is written and executed using gams (general algebraic modelling system). data used in the model have been mainly obtained from public official data sources and from the impetus database. in addition, data from an agro-economic survey covering 60 farmers with different resource endowments (conducted in autumn 2005 in the six oases along the drâa river), were used to round off the database of the model in the near future. currently they contribute to the validation of the model results. simulating alternative groundwater charges three water cost scenarios are simulated against a common background, a sequence of five years with low precipitation in the high atlas and thus low water flows into the mansour edahbi reservoir. the magnitude of inflows was chosen as the average of the five driest years during the recent twenty years. it is further assumed that the reservoir is already running at its minimum fill rate of 30 %. the next important step is to identify appropriate groundwater pumping costs and additional water charges. costs for pumping water are fairly high in the drâa region compared to the free surface water from the drâa river. farmers need up to one and a half litres of diesel fuel per hour, depending on the condition of the motor pump. furthermore, lubricant oil needs to be changed regularly to ensure the reliability of the pump. operation and maintenance costs of pumps account for 500 moroccan dirham on average per pump per year. on average, farmers in the drâa region manage to pump approximately 14 to 22 cubic meter of water per hour, depending on the type of motor pump and the amount of water in the well (as measured by klose and reichert, 2006). this amounts to variable pumping costs of 0.58 moroccan dirham per cubic meter of irrigation water, depending on the capacity and efficiency of the motor pump as well as local petrol prices. the fixed costs of groundwater pumping (mainly the maintenance and replacement of pumps) are more difficult to measure. moreover, it is not certain whether fixed costs are well known to the farmers and if these influence their decisions regarding groundwater use. the farm survey results indicate that the use of inputs is often not oriented at profitability only, but also at keeping up a certain production level for subsistence. this is possible because the increasing share of remittances in local incomes enables an implicit subsidisation of the households’ farming activities. in general, remittances are an important contribution to moroccan household incomes (sorensen, 2004). it is likely that farmers take variable, instead of full pumping costs into account when deciding on (1) heidecke and kuhn 52 years figure 4. simulated groundwater tables in meters at water costs of 0.58 dirham/m3 groundwater use. therefore, scenarios for pumping costs of 0.58 dirham (the variable pumping costs according to the survey data) as well as costs of 1.00 dirham per cubic metre, have been simulated. the aim is to increase the economic scarcity of water, such that groundwater use becomes more sustainable within a five-year period of drought. groundwater pumping is significantly lower at total pumping costs of 1.00 dirham per cubic meter. however, this means that less than half of the available land resources would be cropped, and that agricultural profits would contribute less to household incomes (table 3). water use has become much more efficient, which is reflected in higher average shadow water prices, i.e. the marginal value of water. moreover, the agricultural profit produced by 1 m3 of irrigation water – the average value of water – increases from 0.36 to 0.50 dirham. figures 4 and 5 show the development of the groundwater levels in the different aquifers belonging to the oases. with the actual pumping costs of 0.58 dh/m³, a depletion of groundwater resources occurs within five years for all aquifers except one, which is big enough to supply enough water for the farmers. by contrast, a water charge of 0.42 dh per m3 leads to stable groundwater levels since in such a case the total cost to the farmer becomes 1 dh. however, this water charge would require the installation of water meters on each of the wells, and an administrative mechanism to monitor water use and the collection of charges. years figure 5. simulated groundwater tables in meters at water costs of 1.00 dirham/m3 simulating groundwater charges for the moroccan drâa river basin 53 figure 6 depicts the increase of shadow prices over a period of five years, depending on costs for irrigation water. due to the increasing irrigation costs, water resources become scarcer economically. farmers pump less water due to an increase in costs and change their cropping patterns to achieve greater water efficiency. this process is reflected by an increase in the marginal value of water, the so called agricultural water shadow price. with pumping costs of 1 dirham per cubic meter the agricultural water shadow price remains most stable with values of under one dirham. for pumping costs of 0.58 dirham the marginal value of water is nearly as high as the direct pumping costs that farmers pay already at the moment. shadow prices increase in the course the simulation period, reflecting the depletion of groundwater resources as shown in figure 4. conclusions although the agricultural investment code has not yet been implemented in the drâa river basin, this does not mean that the use of irrigation water has been free of costs for the farmers in this region during recent last years. the survey shows that, on the one hand, direct costs for groundwater pumping exist and are even higher than prices farmers are charged in other basins. on the other hand, if only variable costs at these levels are taken into account in the farmers’ decision-making, they are unlikely to work as an effective constraint to excessive groundwater pumping. the simulation results, which only take variable costs into account, display a quick depletion of groundwater resources, which matches quite closely the developments of recent years in the drâa valley. this means that, at least from a perspective solely oriented at resource sustainability, it would be justified to complement these costs with a water charge. according to the simulation results, it can be shown that groundwater tables can be stabilised by introducing charges. with an additional charge of 0.42 dirham, the current (variable) costs of 0.58 dirham would reach a total cost of 1.00 dirham per cubic meter. this ‘sustainable’ water charge, however, would be four to five times higher than the water prices charged in the other irrigation perimeters in morocco. that indicates that the question of charging for irrigation water needs to be treated with considerable care as farmers already operate on the edge of subsistence. in a situation where huge families have to be fed, drought conditions squeeze farm incomes such that the migration of the young men is often the only way to ensure the livelihood of those family members who stay in the drâa valley. introducing water charges without considering the depressed economic situation of farms would put an end to most of the small farm entities in the region. water pricing should therefore not be introduced as an isolated solution, but should rather be embedded in a broader approach towards rural development in the region, aimed at both poverty reduction and resource conservation. acknowledgement the research carried out in this paper has been funded by the interdisciplinary project impetus (integrated management project for the efficient use of water resources in west africa) carried figure 6. development of shadow prices under different water costs over the 5-year simulation period. years heidecke and kuhn 54 out by the universities of cologne and bonn (see: www.impetus.uni-koeln.de). the authors are grateful to ridouane oumouch and hamd el mansouri for their great support in morocco. helpful input has also been received from the other impetus colleagues. references allen, r. g., l.s. pereira, d. raes and m. smith. 1998. crop evapotranspirationguidelines for computing crop water requirements. fao irrigation and drainage paper no. 56, pp. 6586. debbarh, a. 2002. l’irrigation au maroc: un choix stratégique pour le développement agricole et la sécurité alimentaire. in : agridocrevue thématique 4 :10-20-21. cornish, g., b. bosworth, c. perry and j. burke. 2004. water charging in irrigated agriculture an analysis of international experience. fao water reports no. 28. rome, pp.5. klose, s. and b. reichert. 2006. groundwater management in the middle drâa-river basin (south-morocco). paper presented at the isco conference, 14-19th may 2006. marrakech. www.tucson.ars.ag.gov/isco ouhajou, l. 1996. espace hydraulique et société au maroccas des système d’irrigation dans la vallée du drâa. faculté des lettres et des sciences humaines. thèse et mémoire. agadir, pp. 74-76. rosegrant, m.w., c. ringler, d.c. mckinney, x. cai, a. keller and g. donoso. 2000. integrated economic-hydrologic water modelling at the basin scale: the maipo river basin, eptd discussion paper no. 63. ifpri. washington, d.c. serghini, m. 2002. l’eau, ressource de l’avenir. in: new mediterranean 2:60-64. serghini, m. 2003. la tarification des services de l’eau au maroc. in: new medit 1:5-13. in: new medit 1:5-13. in: new medit sorensen, n.n. 2004. migrant remittances as a development tool: the case of morocco. working paper series no. 2. international organization of migration, pp.5. tsur, y., t. roe, r. doukkali and a. dinar. 2004. a microeconomic analysis of pricing in morocco, china, mexico south africa and turkey. in: pricing irrigation waterprinciples and cases from developing countries. resources for the future. washington d.c. pp. 8789. review article journal of agricultural and marine sciences 2022, 27(1): 38–61 doi: 10.53541/jams.vol27iss1pp38-61 received 02 march 2021 accepted 01 sep 2021 إستخدام احملسنات العضوية للرتبة يف عمان خالل الــ۲٥ عاما املاضية: مراجعة روندا جانكي, دانيل بالكبرين, ممتاز حان, أمحد البوسعيدي, وليد البوسعيدي, علي اهلنائي, مشتاق أمحد a 25-year history of the use of organic soil amendments in oman: a review rhonda janke*1, daniel blackburn2, mumtaz khan1, ahmed al busaidi2, waleed al busaidi1, ali al hinai1 and mushtaque ahmed2 rhonda janke*1( ) rhonda@squ.edu.om, 1department of plant sciences, 2department of soil, water and agricultural engineering, college of agricultural and marine sciences, sultan qaboos university, po box 34, al koud, 123 muscat, oman. introduction since the beginning of agriculture, humans have found ways to enrich the soil, and thus benefit from healthier crops and better yields. (price and gebauer, 1996). with the advent of processed fertilizer production, the manufacture and mining and concentration of the minerals required by plants has become more convenient, but not without cost to soil quality, if soil carbon enrichment is neglected. different farming systems around the world use various methods and combinations of materials to add this soil carbon, including the addition of livestock manures, composts, green manure legume cover crops, adding abstract. organic soil amendments have been used in oman since prehistoric agriculture began and are still being used today. recently, interest in certified organic farming, and the use of organic soil amendments to enhance soil quality has motivated more research on traditional and new diverse soil amendment products. in addition, the arid climate of oman combined with sandy soils benefit from non-traditional soil amendments and nutrient sources, such as treated human waste and wastewater. these two are not allowed in certified organic farming but offer sustainable solutions to building soil health for non-certified crops. this review will cover studies of soil quality in oman related to the comparison of these various amendments, including manures, composts, organic mulch materials, biochar, ash, and others. in general, most of these amendments improve the soil by adding organic carbon, increasing the water holding capacity, improving infiltration rate, and stimulating or providing habitat and food sources for diverse soil microbiological communities. some amendments can also help crops overcome some of the stresses of agriculture in oman, such as soil salinity, heat and drought. most also provide macro and micronutrients for crop growth. some anti-quality factors may be present however, such as a high carbon to nitrogen ratio in some mulches, or high heavy metal content, human pathogens, and pharmaceutical residues in treated waste or wastewater. biochar may have a positive or negative effect on soil microbes, depending on the source material and temperature of combustion can result in byproducts that inhibit microbes. the value of soil microorganisms has been shown in organic cropping systems, and several new species have been discovered in oman. some of these provide possibilities for biocontrol of pathogens, and increased salt tolerance in crops like tomato. though much valuable research has been done in oman and the rest of the world, there is much left to be done to determine the effects of these organic amendments over the long term, and also the interactions among various amendments, soil conditions, soil microbes, and on crops grown with different irrigation methods and cropping systems. keywords: organic farming, soil quality, microbial diversity, biochar, soil fertility. امللخــص:مت اســتخدام احملســنات العضويــة للرتبــة يف عمــان منــذ أن بــدأت الزراعــة يف عصــور مــا قبــل التاريــخ ومــا زالــت تســتخدم حــى اليــوم. يف اآلونــة األخــرية، أدى اإلهتمــام ابلزراعــة العضويــة املعتمــدة وإســتخدام احملســنات العضويــة مــن أجــل حتســن جــودة الرتبــة إىل حتفيــز املزيــد مــن البحــث حــول املنتجــات احملســنة يف الرتبــة التقليديــة واجلديــدة املتنوعــة. ابإلضافــة إىل ذلــك ، فــإن املنــاخ اجلــاف يف عمــان مــع الرتبــة الرمليــة أدى اىل اإلســتفادة مــن حمســنات الرتبــة غــري التقليديــة ومصــادر املغــذايت ، مثــل النفــاايت البشــرية املعاجلــة وميــاه الصــرف الصحــي. ل ُيســمح هبذيــن الثنــن يف الزراعــة العضويــة املعتمــدة ولكنهمــا يقدمــان حلــوًل مســتدامة لصحــة الرتبــة للمحاصيــل الغــري معتمــدة يف الزراعــة العضويــة. ســتغطي هــذه املراجعــة دراســات جــودة الرتبــة يف ُعمــان فيمــا يتعلــق مبقارنــة هــذه احملســنات املختلفــة، مبــا يف ذلــك الســماد الطبيعــي، الســماد العضــوي، مــواد الغطــاء العضويــة، الفحــم احليــوي، الرمــاد، وغريهــا. بشــكل عــام، تعمــل معظــم هــذه احملســنات علــى حتســن الرتبــة عــن طريــق إضافــة الكربــون العضــوي، زايدة القــدرة علــى الحتفــاظ ابمليــاه، حتســن معــدل الرتشــيح، حتفيــز أو توفــري مصــادر الغــذاء و بيئــة للمجتمعــات الكائنــات الدقيقــة للرتبــة املتنوعــة .كمــا ميكــن لبعــض احملســنات أن تســاعد احملاصيــل يف التغلــب علــى بعــض ضغــوط الزراعــة يف عمــان، مثــل ملوحــة الرتبــة واحلــرارة واجلفــاف. أيًضــا توفــر معظمهــا العناصــر الغذائيــة الكــرى والصغــرى لنمــو احملاصيــل. ومــع ذلــك، قــد توجــد بعــض العوامــل املؤثــرة علــى اجلــودة، مثــل ارتفــاع نســبة الكربــون إىل النيرتوجــن يف بعــض األغطيــة، أو احملتــوى العــايل مــن املعــادن الثقيلــة، مســببات األمــراض البشــرية، وخملفــات األدويــة يف النفــاايت املعاجلــة أو ميــاه الصــرف الصحــي. قــد يكــون للفحــم احليــوي أتثــري إجيــايب أو ســليب علــى ميكــروابت الرتبــة، اعتمــاًدا علــى مصــدر املــادة ودرجــة حــرارة الحــرتاق وعليــه ميكــن أن يــؤدي إىل تشــكل منتجــات جانبيــة متنــع امليكــروابت. مت توضيــح قيمــة الكائنــات احليــة الدقيقــة يف الرتبــة يف أنظمــة احملاصيــل العضويــة، كمــا مت اكتشــاف العديــد مــن األنــواع اجلديــدة يف عمــان. بعضهــا يكــون قــادر علــى مكافحــة مســببات األمــراض حيــواي، وزايدة حتمــل امللوحــة يف احملاصيــل مثــل الطماطــم. علــى الرغــم مــن إجــراء الكثــري مــن األحبــاث القيمــة يف ُعمــان وبقيــة العــامل، إل أنــه ل يــزال هنــاك الكثريمــن مــا يتعــن القيــام بــه لتحديــد آاثر هــذه احملســنات العضويــة علــى املــدى الطويــل، وكذلــك نتائــج التفاعــالت بــن احملســنات املختلفــة، وحــال الرتبــة، ومــا حتتويــه مــن ميكــروابت، وعلــى احملاصيــل املزروعــة بطــرق الــري وأنظمــة الزراعــة املختلفــة. الكلمات املفتاحية: الزراعة العضوية، جودة الرتبة، التنوع امليكرويب، الفحم احليوي، خصوبة الرتبة. 39research paper janke, blackburn, khan, al busaidi, al busaidi, al hinai, ahmed mulch to the surface of the soil, by leaving the residue from high biomass crops, and rotation between annual and perennial crops. oman has a unique combination of climate, sandy soils, and limited fresh water for agriculture. both perennial and annual crops are grown, in multi-layered mixtures on traditional farms, and monocultures with high tillage inputs on more recent contemporary farms (gaube and gangler, 2012). there are trade-offs among various cropping systems and methods; some enhance soil quality, and some deplete it, jeopardizing future agriculture on some sites. the purpose of this review is to summarize what we know about soil quality in oman, both from research conducted within the country, and to combine it with what we know about similar research around the world. the review will start with a brief summary of the current situation in oman, some historical aspects, and the relationship among farming practices, soil quality, water quality and quantity, and other contextual factors. then we summarize commonly used soil fertility amendments, and then move on to recent research on novel, less traditional amendments such as biochar. the role of microbial activity and diversity within these cropping systems are discussed, with special emphasis on studies for the future related to soil organic matter and soil quality, as well as the way that bacteria and fungi can protect plants from biotic and abiotic stresses. in addition, new ways of recycling human waste, as sludge, compost, and wastewater are considered as partial solutions to the need to improve soil quality and conserve water resources in an arid climate. methodology the goal of this literature review was to summarize all the research that could be located in the topic areas just described for oman. the 25 year time-frame corresponds to the 25 year history of the journal of agricultural and marine sciences at sultan qaboos university. the authors of this paper have all been publishing in their respective areas of expertise and used the multiple scholarly data-bases available through the library system, the internet, and also harder to locate published data in ministry of agriculture annual reports and surveys. in some cases, graduate student thesis and dissertation data was cited if the work has not been yet submitted to a journal. the oman data was then put into context by also citing well-known, recent, or review papers from world-wide refereed journals. this review is not a quantitative summary, using only certain key-words, but qualitative; sifting through what is known, and what is not yet known about soils in oman. through this iterative process of comparing what is known in oman and studies in other countries, gaps in our understanding and fruitful areas for future research could be identified. history of farming, the soil survey, and irrigation systems in oman context oman has a long history and tradition of agriculture, with some of the irrigation systems, or aflaj, dating back 3000 years. “this oasis culture, formed thousands of years ago, represents a symbiotic unity of lifestyle and environment” (gaube and gangler, 2012). traditional farming systems are often planted with multiple species of crops in the same area, and contain more biological diversity, including both weeds and also medicinal plants, than modern monoculture date palm plantations (al yahyai and al hashmi, 2017). date palm and pomegranate are traditional perennial fruit crops (al said et al., 2013; al-yahyai and khan, 2015), along with annual crops like wheat, barley and garlic, and forages such as alfalfa. at least 30 different crops have landraces and local varieties that have been recognized and are being conserved in oman (al-lawati et al., 2017). in an example traditional oasis farming communities, 66 different crop species are under cultivation in the mountain village, balad seet (gaube and gangler, 2012), including traditional crops, as well as more recently introduced species. about half of the cropped area was planted to alfalfa and barley, to be used as forage crops for ruminants. the manure from the approximately 200 goats or sheep, and up to 30 cattle were applied to the crops, both with and without additional chemical fertilizers, or sometimes fertilizer alone was applied. rates of up to 380 kg n, 30 kg p, and 400 kg k per ha, were applied and varied across crops and seasons (gaube and gangler, 2012). a soil survey of oman was completed in 1990 (map, 1990) and classified the soils according to international soil taxonomy standards into 61 different mapping units, belonging to 3 soil orders: entisols, inceptisols, and aridisols (cookson, 1996). entisols are soils that show little profile development or diagnostic horizons, and are basically unaltered parent material. inceptisols are recently formed soils, show more horizon development than entisols, but do not have any accumulation of clays, iron oxide, aluminum oxide, or organic matter. aridisols form in arid and semi-arid climates, and make up about one third of the earth’s land surface. in addition to the presence of rocks and steep slopes, the soils of oman have other limitations for agriculture such as gypsum accumulation, calcium carbonate accumulation, and soil and water salinity. about 2,000,000 ha of the total land area is categorized as class 1 or 2, which is highly/moderately, or marginally suitable for agriculture, which is about 6.5% of all soils. only 800,000 ha are in the class 1 category, or only 2.59% of the soils of oman (cookson, 1996; maf, 1990). between 1988 and 1997, more detailed soil surveys of the agricultural regions were carried out in the salalah region/governate of dhofar (maf, 1992), in south al batinah (maf, 1993) and in north al batinah, in 3 ar40 squ journal of agricultural and marine sciences, 2022, volume 27, issue 1 a 25 year history of the use of organic soil amendments in oman: a review eas; sohar, liwa and shinas (maf, 1997a; maf 1997b; maf 1997c). the salalah detailed soil survey covered an area of about 4,200 ha (about 0.04% of the total land area of dhofar). from this study area about 60 percent of the topsoil was coarse loamy (loam or sandy loam) and about 7 percent was fine loamy (heavy loam or sandy clay loam). available water holding capacity was conducted and found that about 56 percent was high or moderate, and about 42 percent were low and very low. infiltration rate of the study area was generally low to moderately low (71%), moderate (13%) and moderately high to very high (14%). soil ph was generally slightly to moderately alkaline. most soils of the study area were none to slightly saline (83%), moderately saline (14%) and strongly saline (2.5%) as measured by electrical conductivity (ec). the average topsoil cations exchange capacity (cec) was low. calcium followed by magnesium were the main cations while potassium content was moderate. organic matter was higher than in other areas in the sultanate but it was classified as low by international standards. the average of available phosphorus was moderate to high (9.6 ppm) (maf, 1992). the soil survey of south al-batinah was conducted between 1988 and 1992. it covered an area of 65,900 ha of willayats of barka, masanaa, and suwayq. about 3,200 soil samples were collected for general chemical and physical analysis. infiltration and permeability tests were also conducted by using of double rings infiltrometers. the soils of the study area developed mostly on alluvium derived from the hajar mountains. in the study area the topsoil, it was mostly coarse textured; about 80% sandy or coarse loamy, and 20% fine textured. the infiltration rate for 60% of soils was moderately to very rapid, and only about 9 % had slow permeability. the average topsoil calcium carbonate content was higher in barka compared to masanaa and suwayq. the soil ph was generally moderately to strongly alkaline. in addition, about 50 % of the soils of the area were not saline. however, 30 % were strongly affected by salinity, due to inadequate salt leaching and saline irrigation water. the average topsoil cation exchange capacity was generally low. calcium followed by magnesium were the main cations in the soil while potassium content was moderate. in addition, soil organic matter and nitrogen content were low while available phosphorus was generally moderate (maf, 1993). in the north al-batinah soil survey, the soil surveys for sohar, shinas and liwas were conducted between 1995 and 1997. soil samples were analyzed for ph, ec, and carbonate content, cec and extractable bases, organic carbon and available phosphorus contents on the topsoil samples. in addition, triplicate double-ring infiltration tests was carried out (maf, 1997a; maf, 1997b; maf, 1997c). results were similar to the south al batinah study. salinity, partly due to seawater intrusion, is a limitation to much of the coastal farmlands in both north and south al batinah, with an estimate that overall, 52% of the soils in these governates are affected to some degree by salinity, with an ec level greater than 3.0 dsm-1 (hussain, 2005). the most recent agricultural survey (maf 2015) shows that at present, only 0.48% of the land of oman is in agriculture, and that only 0.23% is cropped (table 1). this is quite a bit lower than the 6.5%, or even the 2.59% of soils that are suitable for farming according to the soil survey. the difference between cropped and agricultural lands is that some land is used for buildings, grazing, and other livestock holdings or fallow. the other limitatable 1. land area in agriculture, cropped land, and percent ag land treated with pesticide, chemical fertilizer, non-processed organic fertilizer and processed organic fertilizer (maf 2015). governate total area in ha total agricultural land area (ha) percent of total area in agricultural land cropped area (ha) percent of total area in cropped land percent of ag area that is cropped # holdings (with land) percent of total ag area treated with pesticide percent of total ag area treated with chemical fertilizer percent of total ag area treated with non-processed organic fertilizer (manures) percent of total ag area treated with processed organic fertilizer (compost) al batina north al batinah south ad dakhiliyah dhofar ash sharqiyah north adh dahirah ash sharquiyah south al buraimi muscat musandam al wusta total 790,000 532,000 3,180,000 9,910,000 2,110,000 3,590,000 1,200,000 746,000 380,000 162,000 8,250,000 30,850,000 35,750 20,574 19,208 27,687 11,560 13,984 6,387 6,772 4,853 1,362 969 149,105 4.53% 3.87% 0.60% 0.28% 0.55% 0.39% 0.53% 0.91% 1.28% 0.84% 0.01% 0.48% 24,875 10,838 7,547 7,467 5,687 4,963 3,280 3,154 2,601 911 163 71,488 3.15% 2.04% 0.24% 0.08% 0.27% 0.14% 0.27% 0.42% 0.68% 0.56% 0.00% 0.23% 69.6% 52.7% 39.3% 27.0% 49.2% 35.5% 51.4% 46.6% 53.6% 66.9% 16.9% 47.9% 21,777 19,532 31,293 11,498 24,284 15,406 12,861 4,504 8,354 3,871 630 154,010 49.5% 47.9% 70.5% 80.7% 49.0% 56.9% 43.9% 66.6% 55.0% 41.8% 85.6% 59.3% 71.9% 63.8% 64.7% 53.2% 49.4% 56.7% 40.7% 50.5% 50.2% 18.4% 27.6% 59.4% 83.9% 83.6% 92.2% 92.3% 93.0% 88.8% 92.5% 92.5% 92.8% 68.9% 93.1% 88.6% 47.9% 56.0% 39.2% 49.1% 46.4% 38.1% 36.8% 23.7% 38.3% 11.4% 37.2% 44.8% 41research paper janke, blackburn, khan, al busaidi, al busaidi, al hinai, ahmed tion to agriculture in oman besides soil suitability is the availability of water, which is why these numbers are fall below the potential based on soil suitability. oman is categorized as a country of “extreme water scarcity” by the fao, and yet it has a thriving agricultural sector, with an estimated 50% self-sufficiency rate for vegetable crops, and a 70% self-sufficiency rate for fruit (mbaga, 2014). however, this production comes at the expense of water use, which was estimated in a 1999 study to exceed sustainable re-charge by 25% (national water resources master plan, 1999). a follow-up study in 2013 also confirmed that oman continues to have a net water deficit of 315 mm3 per year (ministry of regional municipalities and water resource, 2013). both traditional aflaj methods of irrigation (usually flood) and drip irrigation from wells are used, but in different ratios in different parts of oman (figure 1). of the total water used for agriculture of 1546 mm3, about two-thirds, or 1060 mm3 are groundwater extracted by wells/pumping, and 486 mm3 flow through the aflaj systems (ministry of regional municipalities and water resource, 2013). wells are the primary irrigation sources for both north and south al batina, which account for 50% of all of the cropped land in oman. in these two governates, agriculture makes up 2 to 3% of the total land area. ad dakhiliyah and dhofar are 3rd and 4th place in number of cropped ha, but only have 0.24 and 0.08% of their total land area in crops respectively (table 1). farms in the governate of ad dakhiliyah have access to a mix of aflaj and groundwater/wells (figure 1), while in dhofar, the only source is groundwater. al wusta has the lowest amount of land in agricultural production (table 1), even though some soils are suitable, due to the lack of any easily accessible water source (figure 1). moving towards drip irrigation on many vegetable farms has improved water use efficiency (wue), but much of oman farmland continues to be watered by flood/alfaj system. flood irrigation is the most used system for fruit/date farms, while vegetables are primarily grown using drip/modern irrigation (figure 2). drip irrigation has the advantage of only irrigating in the crop row, but a disadvantage of possible salt accumulation on the surface. flood irrigation is less efficient for a single crop, but is used in oman to irrigate multiple crops in the same field, and has the advantage of leaching salts. carbon, nitrogen, and phosphorus cycling dynamics are likely to be quite different in these two systems, and both types of farming systems have been studied in oman, but to our knowledge, there are no studies with direct comparison of carbon or nutrient cycling. in both irrigation systems, due to the coarse/sandy texture of most soils of oman, leaching of nutrients is an issue, and virtually all cropped land in oman receives irrigation in one form or another, due to the low annual rainfall. perennial forages are grown using both systems, while field crops are more often planted in the traditional aflaj irrigated areas of oman, and may be planted as monoculture, or as understory crops within a planting of perennial fruit trees. the tradition of integrated crop and livestock farming has carried into the present, in terms of recommended fertilization practices, and actual use of fertilizers and manures on cropped soils. though chemical fertilizers are used on an average of 59% of agricultural land (table 1, statistics from maf 2015), there is an estimated 88% of land receiving non-processed organic fertilizer/ manure. in addition, about 45% of land also receives processed organic fertilizer (compost). the percentage of land receiving fertilizer is slightly higher in north and south al batina, which are heavily cropped with vegetables and forages (72 and 64% respectively), but these lands still receive non-processed organic fertilizer on about 84% of the land. the percentage of land receiving organic fertilizer goes up in governates such as ad dakhiliya and dhofar to 92%. pesticides are used on approximately 59% of agricultural land, on average. in addition to tradition and the presence of livestock on farms in most regions of oman, the ministry of agriculture specialists recommend annual fertilization with non-processed manures at rates ranging from 10 to 60 kg per tree for crops such as mango and coconut (hameed and habees, 2014; al jabri, 2003), depending on the tree age and size. organic manure is also recommended at fairly high rates for crops like sorghum, alfalfa and rhodes grass (table 2) (ghabeshi, 2005), but at lower rates for most vegetable crops (table 3)(anon, 2011). the application of mineral fertilizers is also recommended, in addition to the nutrients that will be released from organic matter. table 2. recommended rates of organic manures and fertilizer products for example field crops in oman (ghabishi 2005)1 and rates applied according to a survey of small, medium and larger vegetable farms in oman (al salmi, 2020)2. recommended rates (kg/ha per season)1 rates applied by small, medium and large farms in oman (kg/ha per season)2 recommended for sorghum recommended for alfalfa recommended for rhodes grass small farm (less than 5 feddan) medium farm (5 to 20 feddan) large farm (more than 20 feddan) organic manure npk (balanced) urea fertilizer (46% n) other fertilizer triple super phosphate (46% p2o5) potassium sulfate (48% k2o) 14,286 357 238 238 14,286 60 238 119 14,286 714 238 476 1,919 369 221 76 4,302 567 888 55 5,588 490 329 174 42 squ journal of agricultural and marine sciences, 2022, volume 27, issue 1 a 25 year history of the use of organic soil amendments in oman: a review a recent survey of 198 farms in the al batinah governates, north sharqiyah and ad dakhiliyah, conducted between february 2018 and april 2019 allows us to compare recommendations and actual farm practices (al salmi, 2020). the applied rates of urea fertilizer are in the range of the recommended rates (table 2, recommended rates from ghabishi, 2005) and will depend on the crop grown. for example, lower rates would be recommended for nitrogen fixing crops like alfalfa. the rates of p2o5 and k2o are difficult to compare, because the survey only recorded the use of balanced fertilizer, which would likely be a 10-10-10 or 20-20-20 mix of n, p and k. the organic manure applied by farmers is lower than the recommended rates for forage crops, but is still substantial, at between 2 and 5.6 metric tons per ha for small, medium and large farms. the rate of organic manure recommended to farmers is much lower for vegetable crops such as eggplant, tomato and okra (table 3, recommendations from anon, 2011), at only 110 kg per ha, as compared to 2.6 to 3 tons per ha reported as applied by the surveyed farms (al salmi, 2020). when the estimated nutrient values in this manure are converted to n, p and k equivalent values, the rates applied by farmers are similar to recommendations for both oman, and for sandy soils in florida, usa. in general, we see the farmers might be over-applying nitrogen to all 3 crops. this may be due to the slow release nature of nitrogen from the organic matter source, or to compensate for leached nitrogen due to constant irrigation, whether it is drip or flood. table 3. recommended rates of organic manures and fertilizers for selected vegetable crops in oman (anon. 2011)1, rates applied according to a survey of vegetable farms in oman (al salmi 2020)2 and recommended for sandy soils in florida (ref: maynard and hochmuth. 2007)3 rate applied (kg/ha per season) recommended for eggplant (oman)1 applied to eggplant2 recommended for eggplant (u of fl)3 recommended for tomato (oman) applied to tomato (oman) recommended for tomato (u of fl) recommended for okra applied to okra recommended for okra (u of fl) organic manure n p2o5 k2o 1071 192 82 143 2,8572 319 124 168 224 1683 179 107 274 82 171 3,095 332 148 196 224 168 168 107 219 82 114 2,619 327 110 151 135 168 168 notes: 1the amount of npk in the oman organic manure was small (less than 3 kg/ha) and so was not added to the npk totals. 2the estimated npk value for the organic manure was added into the total nutrient values by using the average manure values of npk from sheep, horse and feedlot (from table 4.3 pg 151 in maynard and hochmuth, 2007, which was 2.53% n, 1.20 % p2o5, and 2.73% k2o). 3the recommended rates for the university of florida are for sandy soils with very low soil p tests. if there is more soil p, the recommended rates would decrease from these values (source: table 4.32 pg 225 in maynard and hochmuth, 2007) figure 1. agricultural abstraction of water from groundwater and falaj flow by city/region from northern oman to southern oman (reference: ministry of regional municipalities and water resource, 2013). 43research paper janke, blackburn, khan, al busaidi, al busaidi, al hinai, ahmed trials with fertilizers and organic amendments though manures and composts are widely used in oman, fertilizer is also used, both alone, and in combination with organic inputs. the ministry of agriculture & fisheries (maf) has conducted some field trials to determine optimal nutrient needs of many crops. there is some risk of under-fertilization, and under-yielding of crops, but also the risk of over-fertilization, especially in fields with a history of manure use, and also in the now widely used and intensively cropped greenhouse production systems. in addition, different types and qualities of organic amendments are sold by suppliers or by plant nursery stores with a lack of knowledge in terms of their behavior in soil and plant systems (al-ismaily, 2011). in oman, there are now also 3590 greenhouses with a total area on 344 feddan, and 238 shade-houses on 188 feddan (maf, 2015). these tend to be intensively cropped and fertilized, and are at risk of over-fertilization. for example, one grower in oman was instructed by their input supplier to put 72 bags of compost for a new planting of tomatoes in one greenhouse (pers. comm. one of the authors). if one does the math, based on the average size of bag and % nitrogen in compost, that is equivalent to 41,143 kg of compost per ha, or 823 kg/ha of nitrogen. this is far above the recommended levels (table 3), and could result in high soil ec levels, reduced plant growth, and reduced fruiting of tomato due to too much n. it also makes the plants more susceptible to disease. there are also hydroponic greenhouses in oman, which have some sustainability characteristics such as water savings. however, since they have no soil, and are not allowed under european organic certification guidelines, they are not covered in this review. some of the experiments described in this section only look at the rate of mineral fertilizer applied, but most use some combination of mineral fertilizers and compost or manure, and some also include a salinity treatment. examples of fertilizer response trials in oman include those on bananas (al harthi and al-yahyai, 2009; al busaidi, 2013). in a trial conducted at the agricultural research center in rumais, oman, banana yield after 18 months was lower in the high salinity plots as compared to the low salinity treatment. however, there were no significant differences among the other treatments which included two fertilizer treatments, three compost+mulch treatments and a dairy manure treatment (al busaidi, 2013). the fertilizer was applied at a rate of 400 g/plant nitrogen as urea, split over 7 application times, and the manure and compost applied at rates of 39 and 22.2 kg/plant at the time of planting, respectively. phosphorus, potassium and micronutrients were also applied to the fertilizer treatments. an experiment with in salalah compared zero, 300, 600 and 900 g/plant split into 5 applications over 12 months (al harthi and al yahyai, 2009). in addition, 20 kg of organic compost was added to each plant twice, and all plants received micronutrient foliar spray 3 times. results showed that the optimal treatment of 600 g n/plant was significantly higher than the other treatments. yields were reduced at the 900 g n/plant level. there was no figure 2. comparison of area supplied by drip vs. flood irrigation systems by type of crop in oman (maf, 2015). 44 squ journal of agricultural and marine sciences, 2022, volume 27, issue 1 a 25 year history of the use of organic soil amendments in oman: a review significant difference between the control and the 300 g n/plant treatment. an experiment in salalah with forage sorghum over two years compared 4 levels of urea nitrogen (0, 17, 34 and 69 kg/feddan), three levels of super phosphate and three levels of potassium sulfate (anon, 2013c). there were no significant differences between the potassium and phosphorus level treatments, but the nitrogen applications were significantly different, with the highest yield at the highest level of urea application. the plots were watered with treated municipal wastewater, which would have resulted in the equivalent of 200 kg of nitrogen and 100 kg of phosphorus application per year in addition to the fertilizers. in an on-going experiment with date palm seedlings, variety ‘khalas aldahirah,’ transplants from tissue culture propagation, planted in 2011 are receiving annual rates of 0, 250, 350, 500 and 650 g n/plant in the form of organic amendments. so far results show that the rate of 500 g n is optimal, with the lowest yield for the 0 n, and the second lowest from 650 g n (anon, 2018). replicated experiments in farmer’s fields with garlic at 3 rates of fertilization found that the lowest rate gave the best yield (anon, 2013a). there was no “control” check plot, and fertilizers were chemical formulations at rates of 9776-83, 129-101-110 and 161-127-138 kg/feddan npk blends. it was not reported if organic amendments were also applied during or prior to the experiment. nutrient studies on tomatoes with fertilizers as compared to organic manure/compost vs. a combination found that the combination was the optimal treatment (al-ismaily et al., 2014), especially when subjected to salinity treatments of 6 or 9 dsm-1. fertilizer was applied at rates of 238 kg/ha for n, p and k, but the npk value in the manure treatment was 333, 52, and 338 kg/ha for npk respectively. this experiment was conducted on land that had previously been fallow for 15 years and started with low levels of all nutrients. generally, the n in manure is slowly available, and should have been applied at a 2x rate, assuming only half would be available in the first year, but in this experiment was only 1.4x the fertilizer n rate. the half-fertilizer and half-manure rates combined the best properties of both materials, with some n quickly available at the beginning of the experiment, but some also released later from the manure source. organic farming promotes the use of manures, composts, cover crops, and mulches, but in moderation (brinton 2001; barker 2010). the benefits of compost are well known, and may be especially helpful on saline soils (oo et al., 2015; ouni et al., 2013). compost quality is an area deserving of more research however, as different composts from different feedstocks have different properties (al-ismaily, 2011). international standards for compost have been proposed (brinton, 2001), but have had limited implementation in most parts of the world, including oman. in a greenhouse experiment at sultan qaboos university with broccoli and okra, two commercial composts were compared. one was a plantbased compost, and other included livestock waste. there was no significant difference in the performance of the composts on plant growth or soil properties, but there was a significant benefit of compost as compared to the no-compost control (al busaidi, 2017). the compost significantly increased the soil organic matter levels, but also raised the ec, so again, should be used in moderation and in conjunction with soil testing. previous nitrogen and carbon studies conducted in oman found that though significant amounts of nitrogen are lost through volatilization, both carbon and nitrogen can accumulate in vegetable crop rotations with organic amendments instead of fertilizer (siegfried et al., 2011; jordan et al., 2015). studies in the us have documented that carbon and nitrogen cycling are different in organic cropping systems, especially during the transition years (liebhardt et al., 1989) and the use of organic amendments can reduce carbon and nitrogen losses from cropping systems as compared to fertilizer (drinkwater et al., 1998). cover crops like sesbania can also add significant carbon and nitrogen to soils, especially at the beginning of a long term crop rotation (al-maskri et al., 2018)., even though in the context of omani agriculture, the cost of the water to grow the cover crop would need to be considered. salalah has the potential to grow more of oman’s fruits and vegetables, based on the availability of land and water, and more moderate climate as compared to the al batinah region (prathapar et al., 2014). much of the agricultural land in dhofar is devoted to animal based agriculture at this time, and only 27% of the 27,687 ha of agricultural land in dhofar is currently cropped. a study of the nutrient status of soils and plant nutrient status for some horticultural crops in salalah found that in general, phosphorus concentrations were nearly sufficient in all locations, potassium was deficient in about 50% of the crops, and nitrogen was deficient in most of the crops, as measured by leaf tissue samples (el fouly and shaban, 1999). a range of crops were sampled including the fruit crops banana, papaya, grapes, lime, other citrus and coconut, and the vegetables tomato and pepper. soil samples showed that ph is generally high (average 8.4), ec is medium (average 2.37 mmhos/cm) and organic matter with one exception was low (average 1.81%). the soil texture was classified as a sandy loam, with 52% sand, 30% silt and 19% clay content. the calcium carbonate levels of the soil were very high, which agrees with the soil survey data for salalah (maf, 1992). soil levels of phosphorus varied from medium to high, and soil potassium levels were low to very low. when farmers were asked about the fertilizers they used, it was difficult to get accurate information, but in general, nitrogen and phosphorus fertilizers were being used, but very little potassium or micronutrients. high amounts of organic manure were being used on the vegetables, 45research paper janke, blackburn, khan, al busaidi, al busaidi, al hinai, ahmed along with intensive use of pesticides. in summary, the fertility needs of each type of crop may be different, and the cropping and fertilization history for each site is different. there is a need to do these trials based on site specific conditions, and to report both the current and previous additions of organic matter that could make a difference in the nutrient release during the experiment, and also the recommended rates based on the experiments. organic amendment sources and compost quality may also be different, and there may also be interactions between irrigation practices and soil fertility which should be studied. experiments with municipal waste and wastewater though not allowed for certified organic production systems, treated municipal (human) waste, waste-based compost, and treated wastewater offer other strategies for soil improvement and nutrient application in oman. recent reviews suggest that all of these can be used safely, though attention needs to be paid to government standards, regulations, and policies for use (hussain et al., 2019; khaliq et al., 2017a). in oman, there are currently 400 wastewater treatment facilities in the country (husain et al., 2019), and much of the wastewater, especially in the municipality of muscat, the largest city, it is being used to water landscape plants for city beautification, parks, and ornamental gardens. research is being done to evaluate the safety for use on crops on some test farms. one of the risks of using treated wastewater is the presence and accumulation of heavy metals, which can be avoided by keeping them out of the seawater source stream, or by growing plants that do not take up heavy metals, and monitoring accumulation in the soil. another risk factor is the presence of human pathogens. these can be reduced or eliminated by using tertiary water treatment systems, or by growing crops not destined for human consumption. however, two new risks have emerged with the use of treated wastewater; pharmaceuticals and personal care products (al farsi et al., 2018a; al farsi et al., 2018b). in an experiment with both low levels and spiked samples with pharmaceuticals, two were not detected in soil or plant samples, one antibiotic accumulated in radish roots, and a second antibiotic was translocated into the radish plant (al farsi et al., 2018a). a review of the literature for the uptake of personal care products from wastewater found that more than 100 have been studied in several countries, and that the uptake depends on the chemical nature of the product and also the plant (al farsi et al., 2018b). many of these have the potential to reach and accumulate in plant tissue. the research on risk and its possible impact on human health is still unknown. a study on the use of grey water for home gardening, collected from a newly built home in oman, combined with kitchen effluent supplied nutrients to plants and did not show any harmful chemical or biological contamination (al ismaili et al., 2017). in the same study, cost of the greywater treatment system was calculated and found to be technically, environmentally and economically feasible. the system installed included a collection tank, a sand filter, and final treatment with chlorine prior to use in the garden. the water was tested on tomatoes and eggplant in a garden setting. heavy metals in the treated greywater were negligible, and the coliform and e. coli levels were zero due to the chlorine treatment. in contrast, a survey of urban residents in al seeb, oman, found that many were not aware of the risks of using untreated waste or wastewater from septic tanks on their gardens (shaharoona et al., 2019). in addition to the survey of 75 households, 7 soil pedons were excavated; 5 near garbage sites and 2 away from garbage sites, and were analyzed for heavy metals and microbial analysis. the questionnaire found that many gardeners were irrigating with untreated wastewater (25% untreated black water, 13% untreated greywater). water samples were then collected from three wells and one septic tank. the soil samples showed that of the heavy metals, only cadmium was at an elevated level for 2 samples, but it was below the us and eu environmental standards. however, they found that garden soils irrigated with untreated black water were contaminated with a large number of pathogenic bacteria, including e. coli, staphylococcus, salmonella, shiglla, and fecal coliforms. in contrast, no pathogenic bacteria were detected in control soils only a few meters away. only fecal coliform were found in soils irrigated with untreated greywater. none of the urban growers surveyed had ever tested their soil for nutrient levels or contamination. some of the gardeners were using farm yard manure, some were using chemical fertilizers, and 19% were not using any fertilizer at all. one of the reasons gardeners gave for using septic tank waste to water the garden, in addition to a source of nutrients, was to save money on purchasing water from the municipality, but also to save money on having the septic tank pumped, which can be expensive if done on a monthly basis. when treated wastewater is used, some of these risks can be avoided. date palms leaves, fruits and soil were sampled from areas irrigated with treated wastewater for at least 7 years and compared to dates watered with groundwater. results showed that heavy metals in the groundwater and treated wastewater were within international standards, and that heavy metals were at acceptable levels in the soil, plants and fruits (al busaidi et al., 2015). wastewater only has the potential to add nutrients, and to replace some or all of the irrigation water that would have been required. municipal sludge and/or compost has the additional benefit of improving the soil through the addition of organic matter (khaliq et al., 2017a). in one experiment white radish and green beans were grown with either chemical (npk) fertilizer or kala compost (from municipal waste) and watered with either groundwater or wastewater (khaliq, 2017b). 46 squ journal of agricultural and marine sciences, 2022, volume 27, issue 1 a 25 year history of the use of organic soil amendments in oman: a review results showed that the yield and chlorophyll contents of both were higher with kala compost as compared to the npk fertilizer. analysis of the soil and plants did not show any risk of heavy metal accumulation. the treated wastewater in this experiment did not show any statistically significant differences from watering with groundwater. the kala compost resulted in higher soil total organic carbon levels as compared to the fertilizer. experiments in barka and hamra looked at the effect of kala compost on cucumbers in commercial greenhouse production systems (al busaidi et al., 2017). high levels of nutrients were found in the soils after application, and also high ec levels at the start of the experiment, which were lowered during the course of the experiment through leaching by irrigation water. most heavy metals were low in both soil and plants, though nickel was high in some of the plant samples, but not in the soil. it was concluded that the kala compost is safe to use, and one of the greenhouses had applied kala compost for 5 consecutive years. in a third experiment in oman, kala compost was compared to inorganic npk fertilizer or a mix of the two in open field plots with the crops cucumber, tomato, cabbage, lettuce, carrot and potato (al busaidi and ahmed, 2016). the soil had sufficient amount of nutrients for good crop growth in all treatments, though yields were generally higher with the kala compost as compared to the nkp treatment. no adverse chemical or physical plant or soil problems were noted. chemical analysis of plant samples did not show any accumulation of heavy metals, and all measured elements were within the safe limit for human consumption. kala compost is manufactured in a highly controlled process that combines the treated sludge from the muscat municipal waste treatment plant with chipped wood and yard waste. the nutrient value of the kala compost used in the trial was 3.17% n and 1.4% p, potassium was not measured, and fecal coliform levels were zero. in the experiment, the soil organic matter levels were highest with the kala compost treatment. an experiment conducted on tomatoes comparing kala compost and al mukassab (commercial, animal waste-based compost) at two rates found no significant difference between the rates used and the two products for tomato production (anon, 2013b). the tomatoes were field grown during the 2012-2013 growing season, the composts had identical nitrogen concentrations (2.5%), and the rates of 10 and 20 ton/ha were compared. carbon added to soil as mulch or biochar even though it is documented that manures and composts are used in farming systems in oman, there is still much farm-generated biomass goes to waste through off-farm disposal or burning. much of this waste could be a valuable resource and be used as mulch or made into biochar. only weeds and diseased plants should be excluded. date palm prunings and mango wood could be utilized at the farm level with minimal processing (al busaidi et al., 2017). the benefits of mulches from date palm leaves on saline soils in oman has been documented for tomatoes (wahaibi et al., 2007) and also for sorghum (al-rawahy et al., 2011). the tomato experiment included date palm mulch, plastic mulch, and bare ground control, at 2 irrigation salinity levels; ec 3 and 6 ds/m. date palm mulch resulted in higher tomato fruit yield, lower soil temperature and lower soil ec levels (wahaibi et al., 2007). a similar result was found in the sorghum experiment, which also included date palm mulch, black plastic mulch, and control at the same two irrigation salinity levels (al rawahy et al., 2011). again, the date palm mulch resulted in better yields, lower soil salinity levels. it was also noted that soil temperature was lower, and soil moisture was higher with the date palm mulch. other experiments have noted benefits of organic mulches on saline soils. municipal solid waste and date palm mulch both improve the soil carbon and nitrogen levels, as well as microbial biomass and several soil enzymes that were measured under saline conditions (ouni et al., 2013). two recent reviews on soil salinity and organic wastes note that waste recycling of farmyard manures, industrial byproducts, and other organic materials provide an effective way to restore soil quality in salt affected soils (diacono and montemurro, 2015; ahmed et al., 2013). farm generated waste or biomass could further enhance soil quality if used as biochar, which is the burning or pyrolysis of a carbon source without oxygen, to retain most of the carbon and not release it as co2. recent reviews have shown that biochar can improve crop productivity by increasing nutrient content, nutrient use efficiency and water holding capacity (hussain et al., 2016; aon et al., 2015). generally, soil carbon levels increase with increasing amounts of added biochar. the effect on crop yield will vary, depending on the quality and source material of the biochar, which affects the nutrient content and carbon/nitrogen ratio of the product. application of biochar to fertile soil often results in less effect on plants than application to nutrient poor soils. the effect of biochar on microbial communities has shown both positive and negative effects (palansooriya et al., 2019). biochar can increase the amount of carbon and increase the surface area/micropores for microbial growth in the soil, but the carbon is not always readily available to the microbes. under some condition, the pyrolysis process can produce aromatic hydrocarbons, which can be toxic to microbes. in an experiment in oman, activated charcoal and tannins were added to compost and to soil in an effort to reduce the leaching and volatilization of nutrients. tannins applied directly to the soil reduced n2o emissions and nh3 volatilization (jordan et al., 2015). however, emissions of all gases increased in the compost and charcoal amended soils, but the organic soil carbon 47research paper janke, blackburn, khan, al busaidi, al busaidi, al hinai, ahmed levels also increased with these compost and charcoal as well. in a second experiment, tannins and charcoal were either added to the soil with goat manure, or fed to the goats, and then the enriched manure was applied to a sweet corn-radish crop rotation (ingold et al., 2015). all of the treatments increased the soil organic carbon levels as compared to the npk control plot, and also increased the soil microbial respiration. in this study, there were no additional measurable effects of the charcoal or the tannin addition to the manure, as compared to the manure alone. in two trials in oman with cucumber seedlings under growth chamber conditions, the addition of biochar resulted in higher soil organic matter levels, higher levels of water soluble potassium and sodium bicarbonate (olsen method) extraction of phosphorus, and in one of the two experiments, greater plant biomass (al toobi, 2018). the plants grown with biochar had decreased levels of sap no3 and increased sap k, but showed no change in sap sodium (na). a greenhouse experiment with corn and cucumber with biochar added at 5 or 10% by mass, found no effect on plant height, biomass, or chlorophyll content (khan et al., 2018a). the soil ph did not change, but soil ec increased with increasing rates of biochar. in a second greenhouse experiment with okra and broccoli, ec levels were initially higher with biochar, but the same as the control at the end of the experiment (al busaidi, 2017). the ph was not affected by biochar, but the soil organic matter levels and water holding capacity were higher. in this experiment, plant height, chlorophyll levels and plant biomass were not affected. in all three experiments, biochar was made on site from mango wood prunings, using a home-made burning apparatus (al busaidi et al., 2017). in another greenhouse experiment, local wood biochar, (maerua crassifolia) was compared to wood ash, and also to biochar and ash made from local wild grass, saccharum kajkaiense (al kindi et al., 2018; khan et al., 2018b). currently, many types of biomass from farms is burned and the ash applied to fields, and the biochar might be an alternative to ash. both the wood and the grass biochar increased the soil organic matter levels, and the wood ash increased the levels of soil potassium. soil ec levels were increased by wood ash, but not the biochar; soil sodium levels were unaffected by biochar or ash. neither the biochar nor the wood ash resulted in an increase in plant biomass, but the grass ash resulted in higher okra plant dry weight. experiments conducted in saudi arabia with biochar from date palm residue found that biochar produced at lower pyrolysis temperatures (300 and 400 c) were most effective at promoting wheat growth, but only when applied with fertilizer (alotaibi and schoenau, 2019). water retention in the soil was also improved with the low temperature biochar, especially when combined with incubation in the soil for up to 60 days. soil bulk density was decreased, and soil porosity increased more with the higher temperature biochar (up to 600 c). organic matter and cec was increased as compared to the control only for the biochar at 300c; ph and ec was not significantly different among all treatments. biochar also has the potential to be of benefit in soils affected by abiotic stress such as salinity and drought. an investigation of biochar derived from rice straw and the effects on plant growth and certain metabolic activities of salt-stressed cowpea (vigna unguiculata l.) showed significant plant growth reduction under the salinity treatment compared to control (osman et al., 2019). seed germination was enhanced with the application of rice straw-derived biochar. further, biochar increased the photosynthetic pigments and ascorbic biosynthesis. their results found the highest growth rate and plant physiological traits at 75% npk combined with the biochar amendment. they concluded that the rice straw-derived biochar reduced the extra use of chemical fertilizer up to 25%. biochar combined with microbial inoculation can also have benefits. the combined application of bacillus amyloliquefaciens and biochar was more effective in mitigating the drought stress in wheat and enhanced the its productivity compared to the control. however, plant growth promoting rhizobacteria (pgpr) application alone did not show any significant increases in leaf chlorophyll contents (zafar-ul-hye et al., 2019). it has been shown that under drought conditions biochar can increase the soil water holding capacity and its biological and physical properties. biochar has shown decreased na uptake under salt stress conditions and increased k uptake by the plants. biochar may assist in lessening the drought and salt stress effects on plants (ali et al., 2017). it has also been shown that biochar increases soil water holding capacity and plant productivity even under low water conditions (zong et al., 2016). moreover, it can reduce the trace element uptake in plants and enhance soil properties to reduce metal movement in the soil (abbas et al., 2017). effect of organic farming methods and carbon amendments on soil microbiology organic farming, in general, is a low external input farming system with a high reliance on healthy soil to sustain plant growth. high amounts of organic fertilizers are used in substitution for synthetic industrial fertilizers to sustain crop production (hartmann et al., 2015; liao et al., 2018). in addition, synthetic pesticides (herbicides, insecticides, fungicides, etc) are not allowed in organic farming, but ‘alternative’ pesticides, usually plant or mineral based, with low biotoxicity are used in substitution, in addition to preventative measures such as crop rotation, crop diversity, cover crops (lupatini et al., 2017; zarb et al., 2005). these changes in inputs are associated with complex responses of the soil microbial community diversity and function (hartmann et al., 2015), leading to what is often described as better soil 48 squ journal of agricultural and marine sciences, 2022, volume 27, issue 1 a 25 year history of the use of organic soil amendments in oman: a review health and quality (doran and parkin, 2015; lori et al., 2017; yadav et al., 2018). although these terms are loosely described, organic farming systems aim at, and relies on, improving ecosystem health and sustainability (lupatini et al., 2017). it has been suggested that organic farming systems not only lead to higher microbial biomass, activity and functional diversity, but they are also dependent on these microbial communities for nutrient cycling, plant nutrient uptake and crop yields (liao et al., 2018). in organic farming systems, nutrient availability to plants is primarily achieved through the mineralization of plant and microbial organic compounds in soils (araújo and melo, 2010) and the conservation of an active soil microbiota through mulching, erosion control and organic matter inputs (lori et al., 2017). the mineralization of soil organic matter is carried out by soil heterotrophs, which accounts for the overwhelming majority of microbial species and also the majority of the soil microbial biomass. although this is true for both organic and conventional farming systems, in organic farming, a significantly large soil microbial biomass represents an essential pool of rapidly cycling and readily available nutrients (araújo and melo, 2010; hartmann et al., 2015; liao et al., 2018). soils on organic farms may contain nearly twice as much microbial biomass carbon, microbial biomass nitrogen, total phospholipid fatty-acids than conventional systems (lori et al., 2017). this microbial biomass acts not only as a plant nutrient reservoir, but also as the source the biological processes or functions related to plant nutrient uptake, such as the production of extracellular enzymes involved in the soil organic matter decomposition e.g. carbohydrases, dehydrogenases, ureases and proteases (lori et al., 2017). soil microbes regulate not only the carbon cycle processes, but nitrogen fixation, nitrification and denitrification, and nearly all the soil sulfur oxidation-reduction reactions (yadav et al., 2018). symbiotic diazotrophs (rhizobium), rhizosphere bacteria and mycorrhizal fungi are considered to play a crucial role in mediating plant access to essential nutrients in organic farming (zarb et al., 2005). organic farming systems show a more complex fungal network with higher abundance of keystone mycorrhizae from the orders glomerales, paraglomerales, and diversisporales than other farming systems (banerjee et al., 2019). many recent studies have documented the effect of cropping systems on the response of microbial communities. on a global scale, soil microbial biomass, diversity and activity are higher in organic farming systems than under conventional farm management (liao et al., 2018; lori et al., 2017; yadav et al., 2018). when organic farming systems are involved, these effects are often separated into the following components: a) organic fertility inputs and the cycling of soil organic matter, including crop residues and the use of legume-based cover-crops and green manures; b) the effect of controlling plant pathogens with ‘alternative’ and ‘environmentally-friendly’ pesticides; c) the effect of management practices such as tillage (depth, frequency) and crop rotation); and d) bioaugmentation of the soil with beneficial microorganisms (lupatini et al., 2017; zarb et al., 2005). in comparison to organic amendments, crop protection inputs (application of pesticides) has a significantly lower impact on soil microbes (hartmann et al., 2015; zarb et al., 2005). other factors such as climate, soil management, type and life cycle of the crop also impact the microbial responses to organic amendments (lori et al., 2017). there are numerous studies that document the significant influence of both quantity and type of organic farming fertility inputs on soil microbial biomass size, activity, function and taxonomic diversity (araújo and melo, 2010; hartmann et al., 2015; liao et al., 2018). in general, the amount of the microbial biomass tends to increase with higher inputs of organic fertility amendments. soil organic matter is also widely postulated as one of the key drivers of soil microbial diversity (tsiknia et al., 2014), since chemo-organo-heterotrophs are predominant in all soils. in summary, organic fertility amendments increase soil microbial species richness, diversity, heterogeneity, dominance, and results in a different microbial community structures in comparison to the use of mineral fertilization (hartmann et al., 2015; lupatini et al., 2017). organic inputs, and organic farming management as a whole, increase the amount and diversity of keystone soil microbial species that are directly beneficial to plants (banerjee et al., 2019; liao et al., 2018; yadav et al., 2018). organic inputs create a less selective environment, allowing for a higher taxonomic diversity, whereas systems that do not receive organic inputs are dominated by oligotrophic organisms (hartmann et al., 2015; lupatini et al., 2017). this higher microbial biomass and taxonomic diversity are generally assumed to lead to a higher microbial functional redundancy, ecosystem stability, productivity and resilience (torsvik and øvreås, 2002). background soil properties such as soil texture, moisture regime, alkalinity and salinity condition the extent in which organic amendments will be effective in shaping a healthy soil microbial community. among these, soil salinity is especially relevant for omani farms. on the one hand, organic farming management may help to decrease salinization-related land degradation, and on the other, it will reduce the capacity of organic farming practices to sustain crop yields and a diverse and functional soil microbiome (daffonchio et al., 2015; lozupone and knight, 2007; rietz and haynes, 2003). soil bacterial communities are more prone to be affected by salinity than any other soil environmental conditions (lozupone and knight, 2007), tending to be enriched by halophilic actinobacteria (o’brien et al., 2019), proteobacteria and firmicutes (das et al., 2019). soil salinity decreases microbial biomass, respiration, enzymatic ac49research paper janke, blackburn, khan, al busaidi, al busaidi, al hinai, ahmed tivities, diversity and increases the microbial metabolic quotient (wasserstrom et al., 2017; zhang et al., 2019). the metabolic quotient (an indicator of stresses) is usually unaffected by organic farming systems (lori et al., 2017). the abundance of heterotrophic diazotrophic bacteria, essential for nutrient management in organic farming systems, are expected to be significantly decreased by soil salinity (moradi et al., 2011), even though some research shows that high additions of organic matter can reduce the effect of salinity on plants. soil microbiology studies specific to oman in terms of research specific to oman, one of the earliest studies of soil microbiology documented the economically important fungal diseases (waller and bridge, 1978). this has been updated, as a more general list of fungi found in oman (maharachchikumbura et al., 2016). surveys of the biological soil crusts have previously been one of the least explored areas for fungal diversity. however, in oman 226 fungal isolates were recovered from both free-living and lichen-forming fungal communities in non-cultivated areas (abed et al., 2012). these fungi were classified using dna pyrosequencing, and the authors conclude that the desert crusts of oman harbor a large diversity of fungal communities, and that the presence of lichens in these crusts improves soil characteristics. studies of date palm plantations and natural vegetation have found a large number of unique arbuscular mycorrhizal fungal communities (al-yahya’ei et al., 2011). spore abundance and species richness was higher under date palms than native vegetation. overall, 25 morphospecies were detected across both habitats, some of which seemed to be site specific. two of the most globally abundant species (glomus intraradices and glomus moseae) were not detected. in addition, the study found four previously undescribed morphospecies and a considerable degree of molecular diversity seems to make these sites unique. in a follow-up study in north-central oman using both morphological and molecular identification techniques, researchers recovered four species of arbuscular mycorrhizal fungi that had previously been described for the arabian peninsula, but are reported for the first time in oman (symanczik et al., 2014a). in a second study of the same region of north-central oman, three new species of arbuscular mycorrhizal fungi were discovered and reported for the first time; two from non-cropped areas and one from a date palm plantation (symanczik et al., 2014b). the authors conclude that further work is needed to understand the functional significance of these new taxa for conservation efforts and for agriculture. the effect of a newly discovered endophytic fungus, talaromyces omanensis, was studied on tomatoes subjected to drought-stress under greenhouse conditions (halo et al., 2020). the presence of the fungus resulted in improved tomato characteristics under drought, such as shoot dry weight, root length, the number of flowers and fruit weight, as compared to the non-inoculated control. even without the effect of drought, the inoculated plants performed better than the control. the inoculation lead to some interesting anatomical and chemical changes in the plants, such as increased phloem and cortex width, improved chlorophyll fluorescence, and higher concentration of gibberellic acid, which may enhance drought tolerance. both endophytic fungi and bacteria may help plants with other biotic stress, such as salinity, and the plants may also affect the rhizosphere. date palm seedlings were inoculated with soil from existing date palms growing at the sultan qaboos university campus, and half were subjected to saline growing conditions (yaish et al., 2016). dna extraction and barcoding revealed that 30% of bacterial and 8% of fungal species had statistically different abundance when subjected to the salinity treatment. some of the endophytes identified in this study were previously isolated from saline and marine environments. the authors suggested that there may have been a buffering effect by the host plant on the colonized root environment. the microbes in the environment may also affect each other, and respond differently to moisture or other soil conditions. when four arbuscular mycorrhizal fungal (amf) species from the arabian desert were added to the crop, sorghum bicolor, as the host plant in a microcosm experiment, they responded differently when an invasive species (rhizophagus irregularis) commonly found in commercial inoculant was introduced (symanczik et al., 2015). three watering regimes were used. in the well-watered plants, hyphal length density was slightly higher, but not significantly different than when the commercial inoculant was added. however, the drought stressed treatment had the opposite result, with more hyphal length density in the native only (no commercial) inoculant treatment. sorghum root and shoot dry weight were similar in both inoculant treatments in the watered treatment, but lower in the drying cycle and drought stressed treatment with the commercial inoculant. other researchers have found that commercial introduced species sometimes do not survive when in competition native fungi (hamel, 1996) or simply do not have any effect under field conditions, and when not in a sterile lab situation. a similar response can be seen with bacteria that were used as a manure inoculation. a native phytase-producing bacterium had significant reduction in abundance after only 6 days of incubation after inoculation (menezes-blackburn et al., 2016). in another experiment, e. coli survival time was reduced when introduced to soil with high microbial diversity, as compared to low diversity (xing et al., 2019). many crops commonly grown in oman benefit from mycorrhizal associations. citrus, for example, are strongly mycorrhizal dependent (ortas, 2012). bananas with amf benefit from enhanced plant nutrition and reduced 50 squ journal of agricultural and marine sciences, 2022, volume 27, issue 1 a 25 year history of the use of organic soil amendments in oman: a review nematode lesions (jaizme-vega and pinochet, 1997), some protection from fusarium wilt disease (castillo et al., 2019), but there can be significant differences between colonization and benefits from the amf that are different among different banana cultivars (jefwa et al., 2012). compost can be a rich reservoir of beneficial fungi. an organic compost product originating from oman made from green waste, wood, cow and buffalo manure, processed for 60 days, was sampled using direct plating methods on potato dextrose agar, and also through dna extraction and identification (al-mazroui and al-sadi, 2016). pyrosequencing detected 94 species, belonging to 6 phyla and 12 classes. sixty-seven of the identified fungi are reported in oman for the first time. only 5 species were identified using direct plating. though composts in the past had been considered potential sources of pathogenic fungi, this experiment found that the organic compost sample was dominated by saprophytic fungi and fungi with biocontrol characteristics. the three dominant fungi revealed by direct plating were aspergillus, trichoderma and penicillium. pathogenic species such as fusarium and phoma occurred at very low levels (less than 1% of the total species). in a similar experiment, 72 compost, organic fertilizer and potting media samples were compared from 14 countries. fungal diversity analysis found high fungal diversity, especially in products from the netherlands. again, trichoderma, aspergillus and penicillium predominated in most samples. saprophytic fungi and fungi with biocontrol characteristics dominated in general, but fusarium spp. were recovered at high frequencies in some samples (al-mazroui and al-sadi, 2015). when both local and imported potting soils were compared to cultivated (farmed) and uncultivated soils of oman, a surprising number and diversity of trichoderma species were found in the uncultivated soils (al-sadi et al., 2015). thirteen isolates, representing four species, were collected from 65 uncultivated soil samples with no known history of prior cropping. however, some samples were collected from dams, where soil that may have washed from farms upstream had accumulated. fifteen isolates representing five species were obtained from 45 samples collected from farms growing crops such as date palm, cucumber, tomato, bean, alfalfa, pepper and potato. twenty four isolates were obtained from 84 potting media samples produced in oman, the netherlands, estonia, germany, finland, latvia or the uk. nine species were identified from the potting media isolates. on a percentage basis, the cultivated soils resulted in a higher frequency of both isolates and species per sample collected (33 and 11% respectively), but the authors were surprised by the number of species found in uncultivated soils, including t. harzianum, which is often used as a fungal inoculant. the percent genetic variation among the populations of t. harizianum obtained from the potting media, cultivated and uncultivated soil was very low, indicating high gene flow among these three sources. the authors also note that the high level of fungal diversity found on farms in oman is a sign of soil health and makes it possible to find and select isolates with high antagonistic properties. three species identified in this study had not been before reported in oman. fungal diversity can vary between organic farms and conventional farms. a non-organic semi-oasis farm in oman growing date palm, acid limes and cucumber was compared to an organic farm growing cucumber and tomato (kazeeroni and al-sadi, 2016). the three crops on the non-organic farm had been fertilized using animal manures, but the cucumber also received conventional fertilizer and soil fungicide for the past 5 years. the organic farm crops only received organic fertilizer and had never received soil fungicide. species richness estimates showed that the two organic farm samples were significantly higher than the three samples from the non-organic farm. the shannon diversity values indicated that soils from date palm and lime have higher fungal diversity than cucumber on the non-organic farm, but that the organic cucumber and tomato soils had higher diversity than the non-organic cucumber. the diversity values were likely high for two crops on the non-organic farm, because manures are applied to the dates and limes, and there was no known use of fungicide. however, the cucumber on the non-organic farm had received fertilizers, and also soil fungicide, and both may have played a role in the lower fungal diversity. in this study, the soil organic carbon was highest under the date palm, probably due to repeated applications of manure, but not significantly different among the other crops, though it was slightly lower for the non-organic cucumbers. indigenous rhizobacteria can also have very specific plant protective properties. thirty-eight native bacterial isolates from the rhizosphere soil of muskmelon and cucumber were screened for antagonism against monosporascus root rot and vine decline disease in muskmelon. five isolates showed antagonism grown on media in the lab, and one of the isolates, pseudomonas resinovorans, reduced the incidence of vine declined by 93% relative to an infected control when used as a seed treatment or soil application (al-dagjaro et al., 2020). native bacteria isolated from compost can suppress pythium and fusarium-induced damping off in cucumber (et al., 2020). seven bacterial isolates from compost were screened, and two showed a significant level of antagonism. both isolates were identified as pseudomonas aeruginosa soil application of this bacterial were effective in controlling damping-off of cucumber. plants can also benefit from endophytic bacteria isolated from wild plants. endophytic bacteria live inside the plant, and can improve plant growth by improving plant nutrient uptake, modulating growth and stress related phytohormones, and improve plant health by targeting pests and pathogens with antibiotics, hydrolytic enzymes and by priming plant defenses (afzal 2019). in 51research paper janke, blackburn, khan, al busaidi, al busaidi, al hinai, ahmed oman, an experiment was conducted by first isolating endophytic bacteria from leaves of the mangrove tree, avicennia marina (ali et al., 2017a). from 28 bacterial isolates obtained, nine different genera were identified using dna sequencing, and from these, two salt tolerant species (bacillus pumilus and exiguobacterium sp.) were chosen for further study on tomato. tomatoes grown in a non-soil substrate were subjected to salinity stress and treated with these two strains of bacteria as a liquid inoculant. the inoculated tomatoes had significantly higher biomass, photosynthetic rate and pigment accumulation as compared to controls. the authors conclude that endophytic bacterial strains play a regulatory role in salinity stress, and possible mechanisms such as reducing oxidative stress by regulating antioxidants and related enzymes are discussed. the type of crop and the growing conditions can also lead to different results when looking at the effect of microbial association benefits. for example, on tomatoes inoculated with trichoderma harzianum and subjected to salt stress, the inoculated tomatoes without salt benefited from the inoculation in both fertilized and unfertilized experiments. however, once salt stress was introduced, only the non-fertilized tomatoes showed enhanced growth from the effect of the inoculation (rubio et al., 2017). the type of crop can also make a difference, as well as the diversity of fungi in the inoculum. wheat, barley, corn, and sorghum were compared in their response to either a single or a mix of four am fungi. wheat was unresponsive to any fungal treatment, and barley responded positively to the mix of four species, but only under low p conditions. the corn and sorghum responded positively to fungal inoculation, but only the sorghum responded to the increased fungal diversity and had higher colonization rates (frew, 2019). most of the papers reviewed in this section focus on the species of microorganisms found in the soil, or the effect they have on the plant, whether it is to stimulate growth, protect from abiotic or biotic stress. some of the species occur naturally in the soil or compost, and some have been introduced as inoculants, sometimes after being isolated from natural sources. in some organic farming literature, these broad categories of organisms and their effects are lumped together, along with others known for nitrogen fixation in a category called “biofertilizer” (venkateswarlu, 2008). this is not a very precise term, and can mask the actual mode of action or mechanism responsible for the various effects. however, this term did not come into use by accident, but rather as a response to efforts to commercialize, patent, and sell microbial inoculants (harman, 2010). as noted in the diverse studies covered in this section, some microoransims have more than one effect on a plant, including both protection and growth promotion. if a company in the us or other country wants to bring a product to market as a “biopesticide,” it can take as long as 6 years and up to $8 million for toxicology and efficacy testing, patenting, production and formulation in addition to identifying an effective organism. to register a product as a “biofertilizer, inoculant or plant strengthening agent” requires some of those same steps but can usually be accomplished in only 1 to 2 years and $1.8 million (harman et al., 2010). other models proposed that are even less expensive include government sponsored production, or community-based local production. the local model has been successfully used for strawberries in costa rica and in other countries, but quality control mechanisms must be in place to be sure that the final product is efficacious and not contaminated, but can be a cost-effective solution, with local production in close proximity in time and space to the end-users so that shelf-life of the product is not an issue. on organic farms, including in oman, some farmers purchase biological inoculants, especially trichoderma, and add it to the potting soil mix for both plant stimulation and protection from root disease. however, for the trichoderma or any other inoculant to work in the real world, the soil system must be conducive to growth. this effect is sometimes called “biostimulation,” and is usually achieved by adding organic matter compounds such as manures or composts. this brings us back to the beginning of this review, where it was noted that many farmers in oman are already adding both unprocessed and processed manures and composts. future research in oman should look at both the organisms, and the soil environment into which they are found or introduced, to better understand these processes as a whole system. application of organic matter to the soil, especially composted crop, animal manures and mulches is also a recommendation in the “strategic plant for combating water and soil salinity in the sultanate of oman” (hussain, 2005). cropping systems research and organic farming over the years, long term cropping systems studies have made a significant contribution to our understanding of organic agriculture; especially in terms of nutrient and carbon cycling (drinkwater et al., 1998), and also yield and pest management during the conversion to organic (liebhardt et al., 1989). most current textbooks on organic farming emphasize the need for a systems approach (e.g. lockeretz, 2007; francis, 2009; barker, 2010). in a systems approach, organic treatments are not simply removing an input such as a synthetic fertilizer, but designing a diverse crop rotation with organic fertility amendments, non-chemical pest control, and different methods of planting, tillage, and mulching as compared to conventional monoculture systems. understanding soil processes and differences between conventional and organic systems is key, especially when these are understood and studied as agro-ecosystems (drinkwater, 2009). much relevant research has been conducted in oman, in short term focused studies. for example, carbon and 52 squ journal of agricultural and marine sciences, 2022, volume 27, issue 1 a 25 year history of the use of organic soil amendments in oman: a review macro-nutrient balances were studied in organic vegetable systems within a crop rotation over a 2-year period in northern oman (siegfried et al., 2011). tools such as genetic/molecular identification of beneficial soil microorganisms such as trichoderma are also increasing our understanding of presence of these microorganisms in both cultivated and uncultivated soils in oman (al sadi et al., 2015a), and fungal diversity in potting media and fertilizers used in organic systems (al sadi et al., 2015b). this level of detail is needed to explain the sometimes apparently contradictory results in the literature. for example, that trichoderma can induce systemic resistance in host plants for a variety of plant diseases (hoitink et al., 2006), but that the effect depends on whether the potting mix contains compost. these complex details can be best studied in side-byside replicated long term research plots, where complete control over soil conditions is established and monitored every year. trials such as these have been conducted in the us since the early 1980’s. a review of lessons learned from six of these experiments demonstrate accumulation of soil carbon, nitrogen, and other measures of improved soil health over the long term under organic management (delate et al., 2015). competitive economic returns are also realized from these cropping systems, but sometimes only after organic price premiums are considered. diverse crop rotations along with organic amendments were key to good crop production, but also the level of experience of the farm manager made a difference in terms of the success of organic weed control. a review of 132 long-term studies of long-term experiments (greater than 10 years) world-wide also found that the application of manure resulted in gains in soil organic matter and olsen p, but not always equivalent yields to treatments with inorganic fertilizer or manure plus fertilizer (chen et al., 2018). the authors concluded that adding fertilizer to plots with organic amendments resulted in more resilience, especially if the crops were grown under tropical conditions or the inherent fertility of the soil was low. in contrast, a long-term experiment from the netherlands, summarized after 13 years found less variability (lower coefficient of variation) in yields or the organic as compared to conventional systems with fertilizer, after initially finding lower yields in the organic plots in the first few years (schama et al., 2018). soil properties showed significantly higher soil organic matter, soil aggregates, nutrient availability, and soil biota in the organic systems. the organic system also resulted in lower groundwater nitrate concentrations and fewer plant parasitic nematodes. an analysis of 14 long term field trials in the us and the uk, ranging from 20 to 120 years, was used to compare the effect of fertilizers and manures (edmeades, 2003). manured soils had higher contents of organic matter and soil microfauna, and were also higher in p, k, ca and mg in the topsoil, and nitrate n in the subsoil. they also had lower bulk density, higher porosity, hydraulic conductivity and aggregate stability as compared to fertilized soils. this experiment cautioned that over-application of manures over a long period of time can lead to excess p and the potential leaching of nitrate if not applied in moderation, and it recommended to match the rates of application to the nutrient needs of the crops. long-term in-ground greenhouse production systems (also called high tunnels), can also result in changes in soil properties over time as compared to field plots (knewtson et al., 2012). after eight years of organic production the total carbon and particulate organic matter (readily available carbon) were both increased in the organic high tunnel and open field plots, but not in conventionally managed/fertilized high tunnels or field plots, with a vegetable crop rotation. soil salinity increased slightly in the high tunnels as compared to the field in both systems but was not high enough to be detrimental to crop growth. organic farming in oman benefits and potential in addition to soil improvement, other benefits of organic farming have been well documented in terms of environmental quality, and also human health. in oman, over-fertilization has been found to contribute to high levels of nitrate in groundwater supplies (ahmed et al., 2001). mis-use of both legal and illegal pesticides in oman has also been documented in a farmer survey (al zadjali et al., 2014), and pesticide testing for shipments of fruits and vegetables going into and out of oman has become mandatory, due to un-safe levels of pesticide residue detection on some shipments. several reviews have revealed links between human pesticide exposure and certain forms of cancer (bassil et al., 2007), and also links between pesticides and other negative non-cancer health impacts (sanborn et al., 2007). organic food has been demonstrated to have lower levels of pesticide residues than non-organic foods (smith-spangler et al., 2012), though similar levels of nutrient content (dangour et al., 2009). however, other research found higher levels of anti-oxidants and other beneficial phytochemicals in organic foods (zhao et al. 2006). children who eat diets of organic food consistently for 2 weeks have less pesticide metabolites in their urine than the control group (curl et al., 2003; lu et al., 2006), so less pesticide in the diet can translate into less pesticide in the body. but does eating organic food can also lead to a lower risk of cancer? two extensive, long term co-hort studies have been conducted in france (baudry et al., 2018) and in the uk (bradbury et al., 2014). participants were asked to report their consumption of organic foods, and data were controlled for other risk factors such as smoking, age, and gender then co-horts were followed over a period of years. the study in france over 7 years included 68,946 participants and found links to several 53research paper janke, blackburn, khan, al busaidi, al busaidi, al hinai, ahmed types of cancer in the non-organic consumption group. the uk study included 623,080 individuals over 9 years and found a statistically significant reduction in the incidence of non-hodgins forms of leukemia for the group that consumed organic foods. globally, organic food and drink sales have been growing at a rate of about 20% per year for at least 2 decades, and has reached $97 billion usd. the land classified as “certified organic” has increased from 11.0 to 69.8 million ha from 1999 to 2017 (willer and lernoud, 2019). in addition, there is probably much land that is being managed organically but is not certified. the certification process is expensive, and requires registration with a certification organization, annual fees and inspections, in addition to documentation and records showing that only the allowed inputs are being used on the farm. certification is usually only pursued by farmers with markets that will pay a premium price for organic products, or allow the farm to achieve product differentiation or distinction in the market. attitudes towards organic farming in oman seem to be generally positive. a recent survey conducted at a farming conference in oman found that 50% of the farmers preferred to use organic compost, 30 % preferred organic non-composted manures, and only 6% preferred to use chemical/synthetic fertilizers (al toubi, 2015). she also found that when asked about the possibility to adopt organic farming systems in oman, 68% believed it is possible, while 19% thought it isn’t possible due to pest and/or soil fertility issues. neighboring countries such as the uae and saudi arabia have recently developed organic agricultural policies and certification schemes, demonstration farms, and also dedicated organic research plots (hartmann et al., 2012). al toubi (2015) concludes her thesis by suggesting that long-term research is needed to address the future research questions for organic farming in oman, while a general case was made by drinkwater (2009) for long term ecological studies to move the science of organic farming forward. understanding the soil food web, especially the microbial component, can help us design cropping systems for the future that are more resilient to drought (de vries et al., 2012). benefits of improved soil in oman a note about audience for this research; there are 154,010 land-holding farms in oman (maf, 2015) on 315,011 feddan (a feddan is 0.42 ha). of these, 90% of them are 2 feddan in size or smaller (figure 3). the 10% of farms that are larger than 2 feddan are potentially selling product in the marketplace. similar percentages are seen in the marketing statistics (maf, 2015), as the census of agriculture shows that 88% of farms are growing primarily for family consumption, 9.5% to sell at markets in oman, and 0.5% is sold into the export market. the remainder is unknown or sold for processing. research on soil quality, and the results from the research needs to be disseminated to both market and non-market oriented farms, of various size categories, in addition to farms on different soil types, crops, and using different irrigation systems described in the earlier sections. urban home gardeners are also an important recipient of this information, as many are growing fruits and vegetables for home consumption (al mayahi, 2019). many small farms/gardens may already be using primarily organic practices, and may not care about certification, but could be encouraged to continue to use their soil and water resources wisely. a recent survey of 125 households in a suburban area in muscat oman, found that 57% of them had home gardens. of those that had a garden, 75% were growing fruit crops, and 48% vegetable crops, in addition to ornamental plants and grass (al-mayahi et al., 2019). in terms of soil fertility inputs, only 17% were using fertilizer alone, 54% were using only organic sources (compost, green manure and livestock manure) and 25% used a combination of fertilizer and manure. about 4 % didn’t use any soil amendment or fertilizer, but the majority of the gardeners brought in new soil every year from an outside source (66%). most were applying their fertilizer only once a year. in most cases, family members, or family members along with a gardener or a housemaid were caring for the garden, but in 27% of the gardens, the care was left up to either the housemaid or gardener. sources of information for the gardeners in the survey area were the internet, family, friends, social media, neighbors and the plant nursery, in that order (al-mayahi et al., 2019). in the farm survey (al salmi, 2020), the farm planting decisions were primarily made by the owner (85%), but with workers (8%), a farm manager (5%), or family (2%) also making the decisions on some farms. sources of information for the farms include [note, survey respondents could select more than one answer] parents (82%), neighbors (65%), and extension agent (45%). less mentioned sources were the internet/newspaper (32%), vegetable traders/processors (31%), consumers (25%) and input suppliers (14%). conclusion this review has summarized the research on a wide variety of organic soil amendments used in agriculture, with a focus on the research that has been done in oman. there are many benefits to using these amendments, ranging from increased organic carbon, improved water holding capacity, better habitat for soil microbial diversity and function, resulting in better nutrient mineralization, plant protection, and crop yield. amendments vary from organic mulches, compost, manures, and municipal biosolids and wastewater. municipal biosolids and wastewater are not allowed in certified organic farming, but have beneficial effects on the soil and its properties, and are good for the environment as long as the anti-quality factors that may be present are either 54 squ journal of agricultural and marine sciences, 2022, volume 27, issue 1 a 25 year history of the use of organic soil amendments in oman: a review controlled at the source, or tested and only applied to crops not for human consumption. the audience for this research varies from home gardeners, to family farms with small plots for home use, to larger scale farms that grow for both domestic and international export markets. crops range from forages, grains, fruits and vegetables, and irrigation systems include both drip from well water and flood irrigation from springs/aflaj. the soils suitable for agriculture in oman are limited to only 6.5% of the total land area, and are further limited by soil and water salinity and the availability of water. however, the papers summarized in this review show that organic matter added to the soil can help soils conserve water and reduce the effects of salinity. the most recent oman agriculture census data shows that 88% of agricultural land received non-processed manures from some source, and 45 % received processed manure, or compost, which is positive. in addition, many of the ministry recommendations for soil fertility for a range of crops include organic sources. organic farming is a trend that continues to grow world-wide at a rate of about 20% per year, and farmers who choose to get the organic certification usually enjoy a price premium for their products. long term experiments on organic cropping systems show that it is possible to get the same yield using organic methods as compared to conventional npk fertilizer and pesticides, but it requires excellent management, long-term application of organic fertility sources, and in some cases, cultural and biological control of some insect and disease pests. as the research in these areas progress, organic farming will become more feasible in the future, and is prepared to feed the anticipated 9 billion people. continuous farming with only npk fertilizer degrades land, contributes to the salt index, does not build organic matter, and has no long-term benefits. in addition, fertilizers and pesticides can leach into groundwater and are associated with higher rates of cancer. on the other hand, organic farming methods lead to increased organic matter in the soil, which can be achieved by using both traditional and non-traditional carbon sources. this increased soil organic matter is also associated with higher microbial biomass, diversity, and can result in enhanced crop growth and successful biological control of plant pathogens. this review has covered a wide range of topics, which are all inter-linked, and we hope this will provide a road map for future research in these areas including long-term systems studies on both farms and experiment stations. figure 3. number of farms and area by size class in oman (maf, 2015). 55research paper janke, blackburn, khan, al busaidi, al busaidi, al hinai, ahmed acknowledgement the authors would like to thank sultan qaboos university and the sultanate of oman for funding numerous research projects and graduate students over a several-year period, including, but not limited to the dean’s research fund, internal grants, research council grants and his majesty trust fund research grants. references abed rm, al-sadi am, al-shehi m, al-hinai s, robinson md. 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(2016). acidity, water retention and mechanical physical quality of a strongly acidic ultisol amended with biochars derived from different feed stocks. journal of soils and sediments 16: 177-190. sultan qaboos university journal for scientific research agricultural and marine sciences, 10(1), 41-47 (2005) ©2005 sultan qaboos university 41 effect of the nitrate reductase genes (nia) on the quality of different lettuce genotypes for low nitrate content k.n. al-redhaiman plant production and protection department, college of agriculture and veterinary medicine, al qassim university, buraidah, p.o. box 1486, saudi arabia تأثیر الجین المسؤول عن نشاط أنزيم اختزال النترات على جودة التراكیب الوراثیة للخس من حیث خفض محتواھا من النترات خالد بن ناصر الرضیمان الخالصة: درست االختالفات الوراثیة بین سالالت الخس التي تنتمي إلى أربعة مجموعات ھي (مجموعة الخس ذات األوراق الدھنیة , مجموعة الرومین , مجموعة ذات األوراق الخشنة و مجموعة الخس الساقي) بالنسبة لمحتواھا من النترات وعالقتھا الساللة أن النتائج وأظھرت النترات. اختزال إنزيم نشاط عن المسؤول مجموعة 'lobjoit's green' بالجین إلى تنتمي التي الدھنیة , مجموعة الرومین , مجموعة ذات األوراق الخشنة و مجموعة الخس الساقي) بالنسبة لمحتواھا من النترات وعالقتھا الساللة أن النتائج وأظھرت النترات. اختزال إنزيم نشاط عن المسؤول مجموعة 'lobjoit's green' بالجین إلى تنتمي التي الدھنیة , مجموعة الرومین , مجموعة ذات األوراق الخشنة و مجموعة الخس الساقي) بالنسبة لمحتواھا من النترات وعالقتھا 'augusta and kennedy' الرومین كانت اقل تركیز للنترات في األوراق (4877.7 ) و سجل أعلى تركیز للنترات في أوراق سالالت الساللة أن النتائج وأظھرت النترات. اختزال إنزيم نشاط عن المسؤول مجموعة 'lobjoit's green' بالجین إلى تنتمي التي 'augusta and kennedy' الرومین كانت اقل تركیز للنترات في األوراق (4877.7 ) و سجل أعلى تركیز للنترات في أوراق سالالت الساللة أن النتائج وأظھرت النترات. اختزال إنزيم نشاط عن المسؤول مجموعة 'lobjoit's green' بالجین إلى تنتمي التي و التي إلى 'little gem' التي تنتمي إلى مجموعة الخس ذات األوراق الدھنیة. و كان تركیز النترات عالیا في جذور الساللة الساللتین جذور في كذلك و الرومین األوراق 'augusta and merveille des quatre saisons' مجموعة مجموعة إلى التي الدھنیة. و كان تركیز النیتروجین في السالالت التي تنتمي الي مجموعة الخس ذات األوراق الدھنیة و مجموعة الخس ذات األوراق الخشنة أعلي من السالالت التي تنتمي الي مجموعتي الرومین و الخس الساقي. و أيضا كانت ھناك عالقة معنوية جدا الدھنیة. و كان تركیز النیتروجین في السالالت التي تنتمي الي مجموعة الخس ذات األوراق الدھنیة و مجموعة الخس ذات األوراق الخشنة أعلي من السالالت التي تنتمي الي مجموعتي الرومین و الخس الساقي. و أيضا كانت ھناك عالقة معنوية جدا الدھنیة. و كان تركیز النیتروجین في السالالت التي تنتمي الي مجموعة الخس ذات األوراق الدھنیة و مجموعة الخس ذات (0.82) بین تركیز النترات في االوراق و تركیز النیتروجین. وكشف عن وجود الجین المسؤول عن نشاط إنزيم اختزال النترات في ambassador, bath, merveille des quatre, romain de benicardo, colona سالالت الخس حیث وجد الجین في سالالت and chinese stem باستخدام دلیلین جزيئین متخصصین و كانت ھذه السالالت منخفضة في تركیز النترات في األوراق مقارنة التي تنتمي "salddin" التي تنتمي إلى مجموعة الخس ذات األوراق الدھنیة و الساللة "augusta and kennedy" بالسالالت الي مجموعة الخس الخشن. وبناء عن ھذه النتائج، يمكن استنتاج إلى أن الجین المسؤول عن نشاط إنزيم اختزال النترات يفید .في حصر التراكیب الوراثیة للخس لخفض محتواھا من النترات abstract: genotypic variation in nitrate concentrations of different lettuce genotypes belonging to four types (butterhead, cos/romaine, crisphead, and stem lettuce) and its relationship to nitrate reductase genes (nia)cos/romaine, crisphead, and stem lettuce) and its relationship to nitrate reductase genes (nia)cos/romaine, crisphead, and stem lettuce) and its relationship to nitrate reductase genes ( for low nitrate concentrations of leaves was investigated. the results showed that the romaine genotype ' lobjoit's green' exhibited the lowest leaf nitrate concentration (4877.7 mg/kg dry weight). the highest nitrate levels were recorded in the butterhead genotypes 'augusta and kennedy'. nitrate concentrations in the roots were significantly higher in the romaine genotype ' little gem' and the butterhead genotypes 'augusta and merveille des quatre saisons' than the other lettuce genotypes. total n concentrations were higher in the butterhead and crisphead genotypes than in the romaine and stem lettuce genotypes. a significant positive association (r = 0.80, p > 0.01) was observed between leaf no concentrations and total n concentrations. moreover, gene-specific primer pairs for amplification of nitrate reductase revealed the presence of the gene (niagene-specific primer pairs for amplification of nitrate reductase revealed the presence of the gene (niagene-specific primer pairs for amplification of nitrate reductase revealed the presence of the gene ( ) in butterhead type (ambassador, bath, merveille des quatresaisons), cos/ romaine type (romain de benicardo genotype), crisphead type (colona genotype), and stem lettuce type (chinese stem genotype). these genotypes showed lower leaf nitrate concentrations than the other butterhead genotypes "augusta and kennedy" and crisphead genotype "salddin" which did not amplify with the nia gene. based on these results, it is concluded that the gene-specific primer pairs for amplification of nitrate reductase gene (nia(nia( ) might be useful in screening lettuce breeding material for low leaf nitrate content. introduction concerns about high nitrate levels in vegetable production have led to the introduction of limits on nitrate concentrations in some salad crops (anon., 2001; escobar-gutierrez et al., 2002). among vegetable crops, lettuce, along with spinach, is routinely ranked as one of the highest accumulators of nitrate no (lorenz, 1978; al-redhaiman, 2000). keywords: low nitrate concentrations, lactuca sativa, pcr, saudi arabia. al-redhaiman 42 differences in the capacity to accumulate no among lettuce types (crisphead, butterhead, romaine, leaf) and their respective genotypes and cultivars are well documented (reinink and groenwold, 1988; reinink, 1991). it has been shown that crisphead cultivars contain higher no than other lettuce types (maynard et al., 1976). escobar-gutierrez et al. (2002) found that nitrate concentration showed not only great variability between cultivars in general, but also between the main lettuce types and between cultivars within the butterhead type as well. genotypic and species differences in accumulation may be related to differences in various physiological processes of nitrogen metabolism in plants, including uptake, reduction/assimilation, and translocation/partitioning (al-redhaiman, 1996). cultivars can vary in efficiency of nitrogen assimilation, and accumulation of may be associated with a reduced capacity for reduction and a low nitrate reductase activity (nra) (goodman, 1979). . . . . . . . . . materials and methods seeds of eleven lettuce genotypes belonging to the types butterhead (ambassador, augusta, bath, kennedy, and merveille des quatre saisons), cos/ romaine (little gem, lobjoit's green, and romaine de benicardo), crisphead (colona and salddin), and stem lettuce (chinese stem) were introduced from horticulture research international, wellesbourne, warwick cv35 9ef, uk. seeds of each genotype were germinated in a mixture of peat moss and vermiculite (1:1 v/v) at the greenhouse of the college of agriculture and veterinary medicine, al-qassim university, saudi arabia. the seedlings of each genotype were produced in mesh pots supported by the pot rims, in pvc channels approximately 14 days after germination. plants were spaced at 19 cm within the rows. 25 liters of aerated nutrient solution were used for supplying two channels in which the nutrient solution was re-circulated. four re-circulating hydroponics systems were used as replicates. the nutrient solution consisted of ca (no ) , 0.575; kno , 0.331; mg (no ) .7h o, 0.219; kh po , 0.0828 and k so , 0.1466 (g/l). the micro nutrients were supplied to this solution as fe-eddha 16; mnso .7h o, 2.44; h bo , 0.68; znso .7h o, 0.176; cuso .5h o, 0.156 and (nh ) 6mo o , 0.148 (mg/l). the nutrient solution was changed weekly. the level of solution no was monitored daily, and was replenished back to its original concentration with kno when the concentration of no fell below one-half of its initial level. the ec of nutrient solution was about 2.5 ds/m. the ph of the solution was maintained between 5.8 and 6.2 by adjustments with nitric and phosphoric acids (3:1 v/v). after 75 days of growth, three plants of each genotype were randomly chosen from each replicate. the samples of leaves and roots were oven dried at 70oc then ground in a blender and stored in glass vials for no and total n determinations. nitrate contents of leaves and roots of each genotype were determined by nitration of salicylic acid (cataldo et al., 1975) and the results expressed as mg no -, per kg dry weight. tissue total n was determined using a modified microkjeldahl digestion procedure (nelson and summers, 1980). total genomic dna of lettuce genotypes was extracted using the cetyltrimethyl-ammonium bromide (ctab) method described by hoisington et al. (1994). each sample (0.5 g) of leaf tissue was transferred to a tube containing 10 ml of extraction buffer (1.5 m nacl, 100mm tris-hcl ph 8, 20 mm edta, 1% ctab). the samples were incubated for 2 hours at 65oc with occasional mixing. following incubation, 5 ml of chloroform/isoamylalcohol (24:1) was added to effect of nitrate reductase genes (nia) on the quality of different lettuce genotypes 43 the tubes, mixed, and centrifuged at 2600 g for 10 min. the aqueous phase was removed to a fresh tube and an equal volume of ice-cold isopropanol was added, followed by centrifugation as above to precipitate the dna. the pellet was washed in 70% ethanol and dissolved in te buffer (10mm tris-hcl, ph8.0, 0.1mm edta). gene-specific primer pairs for amplification of the nitrate reductase gene (nia) were as follows: forward primer, 5'-ggtaggcgattggctaaca ttgtctgc-3'; and reverse primer 5'-gagacac caacagtctttcctctgcg-3' (sherameti et al., 2002). amplification was carried out in 25 µl reaction volumes, containing 1x taq polymerase buffer (50 mm kcl, 10mm tris, ph 7.5, 1.5 mm mgcl2) and 1 unit of taq polymerase (pharmacia biotech, germany) supplemented with 0.01% gelatin, 0.2 mm of each dntps (pharmacia biotech, germany), 25 pmol primer, and 50 ng of total genomic dna. amplification was performed in a thermal cycler (thermolyne amplitron) programmed for 1 cycle of 30s at 94oc; and 40 cycles of 1 min at 94oc, 1 min at 63oc, and 1 min at 72oc; followed by 5 min at 72oc. an aliquot of 10 µl from each reaction product was resolved by electrophoresis on 1.5% agarose gel in 1x tae buffer, stained with ethidium bromide, and visualized with uv light. data were statistically analyzed by using a randomized complete block design with four replicates through student-keul's test according to sendecor and cochran (1980). the least significant differences were used to compare means at the 5% level. linear association between total n of plant tissue and leaf nitrate concentrations was determined. results and discussion leaf nitrate concentrations showed significant differences (p < 0.05) among lettuce genotypes (fig. 1). the romaine genotype 'lobjoit's green' exhibited the lowest leaf nitrate concentration (4877.7 mg/kg figure 1: no3concentrations in leaves of eleven lettuce genotypes. vertical bars show standard errors of four replicates. al-redhaiman 44 dry weight). the stem genotype 'chinese stem', the buterhead genotype 'bath', and the romaine genotypes 'romaine de benicardo' and 'little gem' also showed lower nitrate concentrations than other genotypes. the highest nitrate levels were recorded in the butterhead genotypes 'augusta and kennedy'. it was recognized that lettuce genotypes can differ in nitrate accumulation (behr and wiebe, 1988; reinink, 1992; belligno et al., 1996). regarding within butterhead genotypes, 'bath' showed a lower nitrate concentration than the other butterhead genotypes. therefore, for nitrate concentration a high variability was found, not only among genotypes in general, but also between the lettuce types, and among genotypes within the butterhead group (escobar-gutierrez et al., 2002). in the roots of lettuce genotypes, the romaine genotype 'romaine de benicardo' exhibited the lowest nitrate concentration (4000 mg/kg dry weight) (fig. 2). nitrate concentration in the roots was significantly higher in the romaine genotype 'little gem' and the butterhead genotypes 'augusta and merveille des quatre saisons' than other lettuce genotypes. it may be noted that the romaine genotype 'little gem' showed a low nitrate concentration in the leaves. this might indicate that the romaine genotype 'little gem' can store a large portion of absorbed material in the roots thus translocating less no to leaves. al-redhaiman (2000) reported that lettuce genotypes can accumulate no to different levels due to their differential translocation or partitioning characteristics. significant differences (p < 0.05) in total nitrogen concentrations as a percentage among lettuce genotypes were found (fig. 3). in general, total n concentrations were higher in the butterhead and crisphead genotypes than in the romaine and stem lettuce genotypes. this confirms the findings of alredhaiman (1996) that total n concentrations were higher in the butterhead cultivars than in the romaine type. correlation analysis was performed for the overall dataset to establish whether there was a significant relationship between total n concentrations of plant tissues and leaf nitrate concentrations. a significant (p < 0.01) positive association (r = 0.80, p < 0.01) was observed between leaf no concentrations and total n concentrations. genotypes such as lobjoit's green and chinese stem were characterized by the lowest genotypes of leaf nitrate concentrations and total n concentrations. on the other hand, the butterhead genotypes 'augusta and kennedy' were characterized by the highest genotypes of leaf nitrate concentrations and total n concentrations. a positive and significant correlation between leaf no concentrations and total figure 2: no3concentrations in roots of eleven lettuce genotypes. vertical bars show standard errors of four replicates. effect of nitrate reductase genes (nia) on the quality of different lettuce genotypes 45 n concentrations was also reported by al-redhaiman (1996) and gent (2003). in general, total n in the plants results from accumulated n uptake. therefore, variation in leaf nitrate concentrations in lettuce genotypes may be attributed to differences in nitrate uptake (behr and wiebe, 1992; al-redhaiman, 2000). the nitrate reductase gene (niathe nitrate reductase gene (niathe nitrate reductase gene ( ), which is responsible for the nitrate reductase activity, was amplified from butterhead type (ambassador, bath and merveille des quatre saisons genotypes), cos/ romaine type (romain de benicardo genotype), crisphead type (colona genotype), and stem lettuce type (chinese stem genotype). the amplification of the nia gene of these genotypes yielded one fragment of approximately 800bp (fig. 4). on the other hand, the nia gene was not amplified in pcr from other genotypes. it was interesting to note that the butterhead genotypes 'ambassador, bath and merveille des quatre saisons' had the nitrate reductase gene (nia) and showed low leaf nitrate concentrations. however, the other butterhead genotypes 'augusta and kennedy' exhibited the highest leaf nitrate concentrations and did not amplify with the nia gene. moreover, the romaine genotype 'romaine de benicardo' was amplified with the nia gene and showed low nitrate concentrations in the leaves and roots. therefore, the low nitrate content in lettuce might be due to the nitrate reductase gene (niareductase gene (niareductase gene ( ). al-redhaiman (1996) suggested that genotypic differences in no accumulation in lettuce are not exclusively the result of cultivar differences in no uptake and reduction, but may also involve other factors related to no metabolism, such as nitrate reductase activity. the total nitrate reductase activity is regulated comparably to the expression of the nitrate reductase genes (sharameti et al., 2002). curtis et al. (1999) concluded that the presence of the nitrate reductase gene (niathe nitrate reductase gene (niathe nitrate reductase gene ( ) in transgenic lettuce was confirmed by nitrate reductase enzymatic assay, a reduction in the nitrate content of leaves and by southern hybridization. figure 3. nitrogen percent in plant tissues of eleven lettuce genotypes. vertical bars show standard errors of four replicates. figure 4. agarose gel of amplified nitrate reductase gene (niagene (niagene ( ) from eleven lettuce genotypes (left to right) ambassador (l1), augusta (l2), bath (l3), romaine (l8), colona (l9), kennedy (l4), little gem (l6), lobjoit's green (l7), saladin (l10), merveille (l5), and chinese stem (l11). al-redhaiman 46 the work presented in this paper illustrates that sensitive specific pcr assays represents a valuable and a new tool for screening lettuce breeding material for low nitrate content which will be a major objective in lettuce breeding programs to limit nitrate concentration 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electron effect of nitrate reductase genes (nia) on the quality of different lettuce genotypes 47 transport determines nitrate reductase gene expression and activity in higher plants. journal of biological chemistry 277:46594-46600. snedecor, g.w. and w.g. cochran. 1980. statistical methods. sixth edition, iowa state university press, ames, iowa. wilkinson, j.q. and n.m. crawford. 1991. identification of the arabidopsis chl3 gene as the nitrate reductase structural gene nia2. plant cell 3:461-471. wilkinson, j.q. and n.m. crawford. 1992. identification and characterization of a chlorate resistant mutant of arabidopsis with mutations in both nia1 and nia2 nitrate reductase structural genes. molecular and general genetics 239: 289-297. yu, x., s. sukumaran and l. marton. 1998. differential expression of the arabidopsis nia1 and nia2 genes. plant physiology 116:1091-1096. received: january 2005 accepted: april 2005 pdf995, job 6 39 !"#$%&!'(!)*+,-.*/%&!)0123&,!4&-/567/%&!89:!;-<=/%&!)*>? !*"%&!4?*9/5%& !-*#!'$?7/%&%&1/%&! !"#$!%&$'! !)''()*!(!!!!!!!!!!!!!!!!!!!!!!!!!!!)*+,-./0$!)123450$!673/80$!"9:;<!=:*!3:>'3? !!"#3:$%#!) 5-:0$!&3*3:.*!"9:$<!%:'!(:4+)0$!"9;-:0$!!%:;?4 !!!!!!!!!!!!!!!!&3 #5*1/0$!++$9<!,-3*!!.:/0!)1:#341120$!&$5:34/0$!53:6*-7$#!):7$"+0!):498!):?''!9!&$:3:;0$#!<#$9:.0$!=9/:7!>3:-3)/0 !!!3?<3@3:6&#!a!!!!!b9-.*!c32,&$!de3:$4#!!<#3.0$!,1 !%);.0$!+60$!b9-.*!%'!&$51;<!f3/03 !%*3./0$!g790$!=h6<! !!!!!!!!!!!!!,0!i<3&!%*1&3*1*!!g;2!!j$+ek#!9!!<#3.0$#!:3;0$!"36-&$!l03.*!51;<#!!)1#3/0$!,@$9/0$!l*2<!%:'!dh:.-4!3:/*!"3,h:0$# !!!!!!!!!!!!!m3./0$!b9-.*!./0!)45?60$!)1n3,0$!dh. !5?o/0$!<#3.0$!p;7#!f3/0$!&3oh:@!a!"31-%$!q<#!!!!!5$8?0$!qre!,1 !)8s?0$! !!!!!!!!!!!!!!!!!!!!t91)0$!63-&u$!>'3410!)1#341120$!&$12)/0$!v560!)0#3)*!%'!)1 #5*1/0$!>5/?-./0$!qre#!,1?*!g;2!,:0!i<38:0$!<#3:.0$ !!!!)1::*1&3*1/0$#!)1::03o-&w$!x::$#3$,0!)r1::-&!l:07#!&3 #5*1::/0$!,::@$9*!51::;<!%::'!$"#'!f3:;;0$!$y::>!d::?/4#!9!%::+"3,0$!f3:;;/0 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habitats and activity in unsaturated porous media d. or department of civil and environmental engineering university of connecticut, storrs, ct 06269-2037, usa abstract: recent advances in soil pore space visualization and geometrical characterization coupled with improved models for liquid and gaseous behaviour provide the impetus for examination of physical influences on microbial habitats and activity. desaturation of a porous medium is accompanied by marked changes in liquid-vapour interfacial configurations, which result in confinement and fragmentation of aquatic habitats, alteration of liquid and gaseous diffusion pathways, and introduction of mechanical stresses exerted by films and receding menisci. at the pore scale, we examine relationships between liquid element size (at a given potential) and typical organism or colony size, in an attempt to explain physical triggers for enhanced biological production of extracellular polysaccharides (eps) coating. the role of eps in habitat alteration is deduced from its structural, mechanical and transport characteristics. the interplay between increasing liquid-vapour interfacial area and decreasing liquid diffusion pathways with decreasing water content can be formulated as a function of pore space geometry. such relationships are potentially important for optimal biological control of various bioremediation activities taking place at the soil profile scale. interactions between microorganisms and solid surfaces are investigated in the context of adhesion and formation of biofilms. in such prevailing microbial communities, eps forms complex three-dimensional structures that facilitate efficient transport processes and support a rich spatial arrangement of microorganisms with different affinities to oxygen and various nutrients. effects of microbial activity on properties of solid surfaces including weathering and wettability, and structural stabilization of the solid matrix by biological products are examined. keywords: microbial, unsaturated, porous media, organism, eps, bioremediation, biofilm, bio-filter, bacteria, diffusion, hydraulic conductivity, soil structure. review of soil physics and hydrologic literature reveals that despite remarkable advances in soil characterization and sophisticated physical process modeling, the role of microbiological activity in controlling microand macro-scale fluxes and its potential impact on soil structural and transport a or 40 properties is largely ignored. as gardner (1993) stated: “soil flora and fauna may be inconvenient for the soil physicist, but even we should be taking them seriously and be thinking and writing sensibly about them.” similarly, the microbiological literature is plagued with oversimplified depiction of natural environments and physical processes affecting microbial activity in unsaturated soils. considering the importance and ubiquity of microbiological processes, the increasing reliance on biological processes to remedy polluted soils, and the use of the unsaturated zone of agricultural soils as an active bio-filter for wastewater reuse, bridging these gaps is a timely and necessary undertaking. recent improvements in modeling pore-scale liquid and gaseous behavior have altered some of the oversimplified concepts of static (tuller et al., 1999; or and tuller, 1999) and dynamic (friedman, 1999) interfacial processes. concurrent advances in biological microsensors, confocal microscopy, and in fluorescent in-situ hybridization (fish) methods offer a potential for analyzing complex in situ microbial community structure and function without traditional bias of cultivation methods (okabe et al., 1999; lipski et al., 2001). this review is aimed at elucidating primary physical processes influencing microbial habitats and activity in unsaturated agricultural soils by focusing on the fragmentation of aquatic habitats with concurrent changes in liquid and gaseous diffusion pathways during desaturation. these physical changes trigger an array of biological responses including enhanced production of extracellular polysaccharides (eps) that form the biofilm matrix and serve as a protective coating for the embedded bacterial cells (roberson and firestone, 1992; chenu and roberson, 1996). the reduction in contiguous liquid volumes affects substrate and gaseous diffusion, and reduces mobility of bacteria and microbiovorous grazers (savin et al., 2001). the largest impact of liquid reconfiguration is on diffusion; a key process in most aspects of bacterial biology (koch, 1990). the reduction in aqueous continuity and reduced liquid film thickness as soils dry reduces nutrient (and toxic excretion) diffusion rates to/from bacterial communities. in contrast, liquid-vapor interfacial area and gaseous phase continuity increase with decreasing water content, resulting in enhancement of gaseous diffusion and improved exchange with the atmosphere. the interplay between increasing liquid-vapor interfacial area and decreasing liquid diffusion pathways with decreasing water content (skopp, et al., 1990) is potentially important for biological control of wastewater reuse and for bioremediation activities taking place in a soil profile (huesemann, 1994). desaturation affects diffusion processes at a continuum of scales ranging from diffusion within individual microbial colonies to diffusion at the soil profile scale. discrepancies between successful laboratory experiments and failures under field conditions can be attributed to incomplete consideration of physical constraints operating at the various scales; diffusion processes in particular. diffusion constrains the spatial arrangement of microbial colonies in soil pore spaces, their size and thickness, and internal arrangement of bacterial strains within a bacterial community. such spatial distributions can affect transport and mechanical properties of soils as will be discussed below. in a recent review of microbial biofilms davey and o’toole (2000) stated that: “our perception of bacteria as unicellular life forms is deeply rooted in the pure-culture paradigm”. observations in a variety of natural habitats have established that microbes persist attached to solid surfaces within structured biofilms and not free floating. since an individual bacterium is unable to modify its environment they aggregate and form a community that provides a certain degree of shelter and homeostasis. a key component of such microbial micro-environments is the surrounding extrapolymeric matrix (eps, protein, and other substances). eps forms complex three-dimensional structures that facilitate efficient transport processes and support a rich spatial arrangement of microorganisms with different affinities to oxygen and various substrates (watnick and kolter, 2000; okabe et al., 1999). microbial colonies or biofilms can significantly reduce the pore space available for water flow, resulting in a reduction in the hydraulic conductivity, termed biological clogging (avnimelech and nevo, 1964; okubo and matsumoto, 1979; baveye et al.,1998). reduction in saturated hydraulic conductivity up to four orders of magnitude has been observed. experiments in bioclogging of unsaturated soils under controlled laboratory conditions are virtually non-existent; hence it is unclear whether the presence of immersed biofilms will accentuate the highly nonlinear decrease in unsaturated hydraulic conductivity. under unsaturated conditions the role of biofilms is likely to be dependent on spatial arrangement and extent, and their intrinsic transport properties. the lack of a coherent conceptual framework is coupled with rapid progress and emergence of highly specialized jargon that not only form disciplinary barriers, but also hamper efforts to assemble a more realistic picture of the complex interactions described above. thus progress in these areas requires interdisciplinary and collaborative effort. the objective physical processes affecting microbial habitats and activity in unsaturated porous media 41 of this work is to provide an overview of primary physical processes and constraints affecting microbial habitats and microbial activity in unsaturated soils at the pore scale, and highlight implications for behavior at the soil profile scale. aspects of microbial activity and response on soil pore space, soil structure, and soil transport and water retention properties will be discussed. overview of physical and microbial processes in unsaturated soils diffusion processes and microbial activity in unsaturated soils: the reduction in conducting liquid pathways as soil dries reduces liquid and nutrient diffusion rates at all scales, particularly at the microscale of individual bacterial communities and within a biofilm. macroscopically, the primary effect is on gaseous diffusion and convective supply of substrates. as water content decreases soil air content and liquid-vapor interfacial area increase resulting in enhancement of gaseous diffusion and improved gaseous exchange (with atmosphere) at both the microand macroscale. the interplay between the increase in liquid-vapor interfacial area and the decrease in liquid diffusion pathways with decreasing water content can be formulated as a function of pore space geometry and water status. skopp et al., (1990) analyzed this interplay focusing on macroscopic diffusion coefficients to identify an “optimal” water content that maximizes microbial activity at soil sampleor profile-scales (figure 1). at the microscale, both, structure and position of a bacterial colony within the soil pore space are likely to play an important role in the onset of diffusional constraints for different liquid configurations. under “dry” conditions soil water is primarily in the form of films held by surface forces. the thickness of the liquid film coating solid surfaces, and hydraulic connectivity between the liquid-filled crevices, play a primary role in determining substrate diffusion rates (mills and powelson , 1996). rivkina et al. (2000) show data from siberian permafrost (figure 2) suggestive of diffusional constraints on amounts of 14c-lable acetate incorporation imposed by thin liquid films (film thickness is a function of ambient temperature). for relatively dry soils, the relationships between soil water potential and film thickness are readily available according to tuller et al. (1999). even at the biofilm scale, dramatic changes in diffusion rates are experienced as soil dries (chenu and roberson, 1996; holden et al., 1997). attempts to quantify such effects on microbial activity have focused on individual processes, such as effects of figure 1. (a) a conceptual sketch of (aerobic) microbial activity as a function of water content; and (b) comparison with data for yolo soil (skopp et al., 1990). figure 2. incorporated 14clabeled acetate by native bacterial population in siberian permafrost (cpm) vs. measured amounts of unfrozen soil water (% mass) and estimated film thickness (nm) (rivkina, et al., 2000). or 42 matric potential on diffusion through the eps coating (chenu and roberson, 1996), effects of matric vs. solute potentials on nitrification (stark and firestone 1995), and effects of pore space heterogeneity on nutrient acquisition. a unifying theory is clearly needed, as crawford et al. (1993) state: “it is clear from the order of magnitude considerations presented above that to understand the dynamics of soil microbial population it is necessary to have a quantitative framework which encapsulates soil structure”. by corollary, it will require detailed consideration of liquid organization as well. effects of microbial activity on soil hydraulic conductivity and water retention: the formation and growth of microbial biofilms, and their extent and spatial arrangement almost certainly affect soil transport, retention, and structural properties. effects on hydraulic conductivity: microscopic observations in bioclogging studies indicated that in some cases a continuous biofilm covering the grains had developed (cunningham et al., 1991), while in other cases discrete microcolonies were detected (vandevivere and baveye, 1992). observations made in a twodimensional glass network micromodel study indicated that the biomass accumulated both as biofilms covering the pore walls and discrete aggregates clogging the pore throats (kim and fogler, 2000). this study also revealed that changing from nutrient to starvation conditions resulted in partial biofilm sloughing and permeability recovery (figure 3). estimates of biofilm thickness were in the range of 15 µm (for 0.12mm sand grains) to 150 µm (for 0.7mm sand grains), which could explain the significant porosity and permeability reductions. rittmann (1993) claimed that the most important factor determining bacterial deposition patterns is substrate supply rate and proposed a normalized surface loading criterion, which is defined to be the actual substrate flux (i.e. rate of removal per unit surface area) divided by the minimum flux capable of supporting a deep biofilm. when this number is larger than 1, a continuous biofilm develops, and when less than 0.25 patchy biofilms develop, mostly in pore throats. additional geometrical (pore size) (vandevivere and baveye, 1992), and hydrodynamic factors (nevo and mitchel, 1967) also affect the spatial arrangement of bacterial populations. modeling efforts for bioclogging effects on permeability reduction were based on different approaches to describe the saturated hydraulic conductivity of the clean bed: a single cylindrical capillary model (okubo and matsumoto, 1979), cut-andrejoin bundle of capillaries models (taylor et al., 1990; figure 3. dynamics of bioclogging in a glass micromodel (kim and fogler, 2000). vandevivere et al., 1995) and the kozeny-carmen equation (taylor et al., 1990; vandevivere et al., 1995). in all the above models a uniform narrowing of the pore space by the continuous developing biofilm was assumed, which is highly unlikely. a more realistic assumption is that biofilms develop preferentially in larger pores with larger water flow (substrate supply, toxic compound removal), whereas for discrete colonies, a probable location for initial bacterial deposition is at pore constrictions and near grain contacts. such microscopic biofilm thickening and single bacterial deposition patterns are characterized by different macroscopic permeability-porosity relationships along the bio-clogging process. another physical processes affecting microbial habitats and activity in unsaturated porous media 43 figure 4: changes in (a) water potential, and (b) water content during 14 h of drying in sand with and without eps added (roberson and firestone, 1992). bioclogging mechanism in saturated porous media is gas (e.g., methane) release and consequent pore blockage due to entrapped bubbles (sanchez de lozada et al., 1994). effects on water retention properties: under unsaturated conditions with fragmented aquatic habitats it is likely that bacteria will form discrete colonies where a biofilm is discontinuous, thin, and covers only a fraction of soil mineral surfaces. consequently, the different wettability properties of such organic “spots” on mineral surfaces will produce soil water retention characteristic that exhibit a fractional wettability behavior (bradford and leij, 1996; ustohal et al., 1998). in the presence of appreciable amounts of eps, soil water-holding capacity increases (figure 4), as demonstrated by roberson and firestone (1992) and chenu (1993). the increased water retention during drying is attributed to both the direct addition of eps with its very high water holding capacity (up to > 50g/g) and also to creation of a more open pore space and separation between solid particles with a fibrous network attached to clay particles (chenu, 1993). however, upon rewetting of kaolinite-eps complexes, a decrease in the amount of water absorbed was observed (chenu, 1993), probably due to irreversible structural changes in eps during drying (holden et al., 1997), and perhaps due to changes in clay wettability. figure 5. eps scleroglucen adsorbed on kaolinite particles (w.c. 1.5 g/g) (chenu and tessier, 1995). effects of microbial activity on soil structure: formation of microbial colonies adhered to solid surfaces has an important effect on soil structural properties primarily through the formation of polymer bridges that bind soil particles (chenu and guerif, 1991; chenu, 1993). the microbial enmeshing of soil particles shown in figure 5 has a dual role in forming microaggregates, and more importantly their stabilization (oades, 1993). the spatial arrangement of microbial activity (hence microbial debris) likely plays an important role in the structural efficiency of such stabilizing agents. moreover, we expect that the soil strength (and structural stability) acquired by accumulation of microbial debris would be strongly correlated to the mechanical properties of eps forming the bacterial colonies (thwaites and mendelson, 1991). as clearly illustrated in figure 5, the presence of eps helps maintain an open structure among clay particles (and at an aggregate bed scale). such an open structure is favorable for soil transport properties. hadas et al. (1994) attributed the increase in aggregate size and strength one week after plant residue addition to reinforcement by fungi hyphae, whereas changes appearing after the sixth week were attributed to bacterial secretions. following intense colonization of wheat rhizosphere by eps-producing bacteria, amellal et al. (1998) observed significant soil aggregation and concluded that p. agglomerans plays an important role in soil water regulation by improving aggregation. or 44 morphological and functional adaptation of microbial colonies during soil drying: studies have shown that under drying conditions bacterial colonies respond by enhanced production of eps (roberson and firestone, 1992). additionally, dehydration of non-submerged biofilms will cause collapse of the open structure and affect transport properties of the biofilm (holden et al., 1997). an illustration of the morphological changes in the eps 3d structure is shown in figure 6. in contrast to the fibrous and open structure on the left (wet soil), the eps becomes dense and amorphous. it was hypothesized that such a change reduces rates of water loss and possibly traps nutrients within the dense protective coating thereby assisting bacteria to survive desiccation (chenu, 1993). an important aspect of such changes is the mechanical response of eps to changes in its hydration status. it has been observed with similar biopolymers (thwaites and mendelson, 1991) that the tensile strength and the young’s modulus increase by several orders of magnitude as the relative humidity (or water potential) decreases from near saturation. moreover, the biopolymer changes from soft and ductile at high humidity to stiff and brittle at low humidity. knowledge concerning these mechanical changes could help explain the role of eps in providing mechanical and diffusional protection for bacterial biofilms during desiccation. a related issue is the marked increase in soil strength with decreasing soil water content. it would be interesting to obtain estimates of the proportion of observed increase in soil strength attributable to the increase in the strength of eps as a bonding agent. conclusions rapid changes in liquid and interfacial configurations in unsaturated soils present various constraints to activity of microbial communities thereby triggering an array of biological responses to changes in ambient conditions. an important constraint highlighted in the present review is the dramatic change in diffusion pathways of substrates and gases. as the energy state of soil water (matric potential) decreases, the physico-biological adjustment of microbial communities becomes more evidenced by the enhanced production of eps. the review provides a starting point for quantitative modeling of interactions between physical (a biotic) processes and microbial adaptation in a given pore space. ongoing research focuses on pore scale interplay between solution and gaseous exchange in angular pores, and on understanding of the physical consequences of enhanced eps production on microand macro-scale processes and on soil macroscopic properties. references amellal, n., g. burtin, f. bartoli, and t. heulin. 1998. colonization of wheat roots by an exopolysaccharide-producing pantoea agglomerans strain and its effect on rhizosphere soil 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terrace, adelaide sa 5001, australia and university of lethbridge, alberta, canada. abstract: australia has aggressively pursued water markets as an integral part of water policy reforms. compared to most other countries, relatively active water markets have therefore emerged. consequently, australia provides an unique opportunity to study how markets have been introduced and adopted and their role in managing demand and scarcity. this paper discusses: a) how water markets have evolved in australia, b) prices paid and volumes traded in water markets, and c) the increase in market participation. during periods of drought, scarcity is the main driver of price and market participation. irrigators do not buy water in order to maximize their profits due to good commodity prices. farmers with significant investments in long-term assets purchase water to protect their assets against long-term losses due to inadequate watering. this behavior drives prices to levels where no other agricultural users can compete. the price of water entitlements fluctuates with the price of water allocations, but irrigators do not capitalize scarcity-driven short-term increases in allocation prices into the price of entitlements. once the region is out of this period of drought further research should be conducted to establish the water price/commodity price relationship during periods of more normal supply. keywords: water trading, australia, market drivers, demand management. introduction since the early 1990s, the use of economic instruments to manage demand for water within an environment of scarcity has been increasingly promoted by international organizations. australia has aggressively implemented market policies since 1994. compared to most other countries, markets in water allocations (the right to short term use of water) have developed to a high level of maturity, whereas markets for water entitlements (the long term right to access water) email: henning.bjornlund@unisa.edu.au أسواق المیاهأدوات لمعالجة شح المیاه ھانین بجورنالند الخالصة: إتبعت أسترالیا سیاسة جریئة في إدخال أسواق المیاه ضمن خطط إصالح السیاسات المائیة. فبالمقارنة لبلدان أخرى فإن أسواق المیاه في صدد التطور. لھذا فإن أسترالیا تعتبر فرصة جیدة لقراءة جدوى التصرف على الطلب في ضوء شح المیاه. تطرح ھذه الورقة النقاط الثالثة التالیة: كیف تطورت أسواق المیاه في أسترالیا تطور األسعار وكمیات المیاه المتبادلة تطور المشاركة في األسواق المائیة تظھر النتائج أنھ خالل فترات الجفاف ترتفع األسعار وتكثر المشاركة في األسواق. یقبل المزارعون الذین إستثمروا أموالھم على المدى البعید (تربیة أبقار أو غراسة األشجار) على شراء المیاه في فترة الجفاف رغم غالء األسعار لحمایة ضیعاتھم من اإلتالف. غیر أن أسعار حقوق المیاه لم تتأثر بطریقة خطیة مع أسعار المیاه في المدى القصیر. نتائج ھذه الدراسة مرتبطة جدًا بظروف الجفاف المدى البعید (تربیة أبقار أو غراسة األشجار) على شراء المیاه في فترة الجفاف رغم غالء األسعار لحمایة ضیعاتھم من اإلتالف. غیر أن أسعار حقوق المیاه لم تتأثر بطریقة خطیة مع أسعار المیاه في المدى القصیر. نتائج ھذه الدراسة مرتبطة جدًا بظروف الجفاف المدى البعید (تربیة أبقار أو غراسة األشجار) على شراء المیاه في فترة الجفاف رغم غالء األسعار لحمایة ضیعاتھم من اإلتالف. غیر السائدة في المنطقة حالیًا. نترقب رجوع األمطار إلى حالتھا العادیة للتمكن بخروج بنتائج یمكن تعمیمھا. أن أسعار حقوق المیاه لم تتأثر بطریقة خطیة مع أسعار المیاه في المدى القصیر. نتائج ھذه الدراسة مرتبطة جدًا بظروف الجفاف السائدة في المنطقة حالیًا أن أسعار حقوق المیاه لم تتأثر بطریقة خطیة مع أسعار المیاه في المدى القصیر. نتائج ھذه الدراسة مرتبطة جدًا بظروف الجفاف bjorlund 12 have been more subdued. analyses of water market prices to establish the factors impacting irrigators’ willingness to pay and accept prices are few and far between. this is due in part to the paucity of water pricing data (brookshire et al., 2004), the thin markets in many areas, the private nature of price information and the relatively short time period during which active markets have existed. thirteen years of pricing and market data are now available for water markets in the goulburn-murray irrigation district (gmid) in victoria, australia, on the basis of which crosssectional and time series analysis can be conducted. australia provides an unique opportunity to analyze water market data to identify what factors influence market prices and markets’ ability to manage scarcity. this paper first discusses the evolution of water markets in australia. it then outlines the methods and data used for the analysis. the following four parts discuss the outcome of analyses of prices and volumes traded in the allocation and entitlement markets based on papers previously published by the author. the final two parts provide previously unpublished findings regarding the impact of allocation markets on water use and the increase in farm businesses’ participation in water markets. the evolution of water markets in australia in australia, markets for water entitlements and allocations first emerged formally in south australia in 1983 without any direct legislative provisions. this was provoked by early scarcity, created by a moratorium on new licenses and a reduction in existing but unused or underused licenses in the 1970s. when demand started to increase from new high value users, such as horticulture and viticulture, in the early 1980s, the pressure was on to create alternative means to provide water for these ventures. trading in allocations was introduced in new south wales (nsw) the same year, and in victoria the first trial allocation markets were introduced in 1987. markets for entitlements were introduced by legislation in both these states in 1989, but in victoria the regulations controlling trading were not passed until september 1991 and the first trades were not registered until january 1992. informal water trading was taking place earlier than this, during periods of severe scarcity, by allowing transfers between entitlements in the same ownership, through the purchase and amalgamation of irrigated land. in some instances water authorities allowed water bailiffs to redirect water between neighbors (turall et al., 2005). water markets were made compulsory in all states as part of the new water policy reform initiated by the council of australia governments (coag) in 1994. initially, trading in both markets was thin (turall et al., 2005; bjornlund, 2003a). irrigators soon became familiar with the allocation market, whereas the use of the entitlement market has, for a number of reasons, remained low (bjornlund, 2004a). for a discussion of how irrigators have used markets to manage supply risk and the process of structural change see bjornlund (2002, 2004b, 2006a). as the use of the allocation market increased, irrigators demanded more efficient market mechanisms to allow them to purchase water instantly when factors of supply and demand changed. consequently, in 1998, a weekly water exchange was introduced in the gmid to ease the administrative pressure on the authorities and to facilitate faster and cheaper transactions (bjornlund, 2003b). in 2003, coag reviewed the 1994 reform program and found that good progress was being made, but that the existing market mechanism still prevented water markets from achieving their most beneficial outcomes. in 2004, coag therefore introduced a new national water initiative. among other things it aimed to improve the operation of water markets and the emergence of markets in more sophisticated derivative water products by providing: a) better specified and nationally compatible water entitlements, defined as shares of the available resource rather than in volumetric terms; and b) secure water entitlement registers. the policy process of evolving more efficient and sophisticated water markets is still ongoing and the ambitions of establishing derivative markets in order to achieve the potential efficiency gains experienced from such markets in other commodities are in their infancy (acil tasman, 2003). methods and data the analyses in this paper are based on thirteen years of market data from the gmid. data related to the price paid for water in the market for water allocations and in the market for water entitlements were collected. allocation prices were obtained from plan right, the largest water broker in the district, for the period 1991-98 and from watermove, the water exchange that operates on a weekly basis, for the period 1998water markets economic instruments to manage scarcity 13 2004. entitlement prices were obtained from surveys conducted by the author for the period 1992-96 and from plan right for the period 1997-2004. data related to volumes of water traded on a monthly basis were obtained from the records of goulburn-murray water (gmw), the authority that manages the gmid. the data has been analyzed using time series analyses of mean monthly prices and monthly volumes traded, as well as by cross sectional regression and correlation analyses also using mean monthly prices and monthly volumes traded as dependent variables and measures of scarcity, commodity prices and macro-economic factors as independent variables. the objectives of these analyses were to identify: 1) trends in water prices and volumes traded; 2) factors determining irrigators’ willingness to pay and accept prices for water; 3) factors determining volumes traded in the market; and 4) the relationship between prices paid in the allocation and entitlement markets. the outcome with respect to the allocation market has been published in bjornlund and rossini (2005a); the outcome with respect to the entitlement market in bjornlund and rossini (2006), and the comparison of the allocation and entitlement prices in bjornlund and rossini (2005b). the discussions in the next two sections are based on this literature and the reader is referred to these papers for a comprehensive discussion of the actual equations, statistical details, and full discussions of the outcomes. this paper will concentrate on discussing aspects of the analyses which assist our understanding of how water markets have been used as an economic instrument to manage water scarcity and how scarcity has driven prices and activities in water markets. the last part of the paper draws on an analysis of the water entitlement and water trading registers, as well as water use data from the gmid, to establish how farm businesses have adopted water markets over the first 13 years of operation and how this relates to water scarcity. increases in water trading based on volumes traded have previously been reported in papers such as turall et al. (2005) and bjornlund (2004b), but a proper analysis of the extent to which farm businesses have adopted water trading has not previously been conducted. to facilitate the most meaningful analysis, water entitlements were first consolidated into farm businesses. this was done by sorting the entitlement register by surname and address, and then consolidating all entitlements in the same ownership into one farm business. this process reduced the original number of 17,125 service numbers in the entitlement register to 14,384 farm businesses. next, farm businesses without a tradable water entitlement were eliminated. this reduced the number of farm businesses to 10,011. the trading registers were then merged with the entitlement register to identify which farm businesses participated in which kind of trading during each of the 13 irrigation seasons and identifying which farm business had participated in some kind of trading from the start of trading to the end of each season. results and discussion the market for water allocations – factors driving market prices initial expectations were that the allocation market would allow irrigators to adjust to short-term fluctuations in supply and demand for water as well as in commodity prices. analyses of prices and volumes traded in the allocation market suggest that the main driver of market activities and prices is scarcity, resulting in an annualized growth in allocation prices of 30.85% (bjornlund and rossini, 2005a). most commodity prices have a significant but negative correlation with allocation prices. it is noteworthy that this is the case for dairy products since historically, in the gmid, the dairy industry has been the main high value water user and the main buyer of water allocations and entitlements. this suggests that increased allocation prices during the study period are not a result of irrigators buying additional water in pursuit of opportunities of increased profit due to higher commodity prices. in a way this could appear to be counterintuitive. however, it is also exactly what we expect the market to do – facilitate a reallocation of water during scarcity to minimize the negative impact of the drought – in this case to allow high value users to stay in business. the main concern of these businesses during this period of scarcity is to minimize their losses, which is the best possible economic outcome for them in the short term. further research is needed to see how market prices react once the region is out of this period of extreme scarcity. hedonic analyses show no significant causal relationship between the price of dairy products and the price of water allocations. however, there is clear evidence that when the price of feed for dairy bjorlund 14 cattle rises, the willingness to pay for water to grow grass increases. this supports anecdotal evidence that, during periods of drought and when the price of water allocation is high, dairy farmers to some extent substitute buying water to grow grass with buying feed (bjornlund, 2003b). it was also found that when seasonal allocations are low the price of allocations goes up. the seasonal allocation is set by gmw as a percentage of entitlement at the beginning of each season depending on water availability in the reservoirs and is then revised fortnightly depending on inflows into the storages (that is dependent on precipitation in the catchment). seasonal allocations go down due to low precipitation in the catchments of the major reservoirs. this decreases the supply to irrigators and therefore increases demand in the allocation market, resulting in a higher willingness to pay for water allocations. finally, it was found that as evaporation increases the price of water allocations go up. this is because more evaporation increases water use, as irrigators need to apply water not only to support plant growth but also to replace the loss of soil moisture due to evaporation. this in turn results in higher demand in allocation markets and higher market prices. in conclusion, prices in the allocation market have been driven by scarcity rather than by commodity prices. irrigators’ willingness to pay is driven by their effort to reduce losses due to inadequate watering. when prices on the allocation market have increased to a$500/ml, this has been driven by horticultural farmers protecting their long-term investments in plantings, and at prices up to around a$300/ml by dairy farmers protecting their long-term investments in dairy herd and milking equipment. if farmers are unable to feed dairy cattle they will be forced to sell at a time where the market is depressed and cattle prices are low. it also takes many years to build up a dairy herd to be productive. further, if cattle are sold off, or sent out to pastures in areas not affected by drought, milking volumes will decrease, reducing farmers’ ability to service their debt. in short, they pay more for water than is profitable in order to stay in business. there is anecdotal evidence of banks supporting this approach by lending money to farmer to buy water at loss-making prices. during this period of extreme scarcity due to drought and policy changes, the allocation market has played an important role in enabling high value water users to protect their assets and stay in business in the long term. in the short-term they have had to accept increasing allocation prices relative to commodity prices and therefore have experienced decreasing profits (bjornlund, 2006b). the market for water allocations – factors driving market activity hedonic analyses using monthly volumes of water traded as the dependent variable also show that it is scarcity that drives market activity. this is true both immediately and as a delayed reaction. first, if evaporation is high during a given month, the level of trading is also high as irrigators need to apply more water to keep meeting plant requirements. second, as the deficit between precipitation and evaporation accumulates over a three-month period, the volume of water traded increases. this deficit represents the volume of water that the irrigators have to apply to accommodate plant needs. this finding supports anecdotal evidence (bjornlund, 2003b). irrigators receive their seasonal allocation at the beginning of the season and there is no rule that they have to space their use of the water. they can use it all in the beginning of the season and then rely on buying water later in the season. it has therefore been reported that some irrigators do not buy when scarcity first sets in; initially they use the part of their allocation that they know they will need later in the season. this is especially the case if prices in the allocation market are high. they hope that prices will decrease so that they can buy cheaper later, that it will rain later in the season so that demand will decrease, or that inflows to the reservoirs in the catchments increase and allocations therefore go up eliminating the need to purchase water. it was also found that during the months of january to march, which covers the hottest and driest part of the year, the volume of water traded is significantly higher than during any other period. this reflects that irrigators have different management responses to scarcity. some risk-averse farmers, with the financial ability to buy water, purchase what they need for their planned crops based on the opening allocation, providing them with peace of mind during the season. others are more risk-takers, or do not have the ability to pay for water at the beginning of the season. they water markets economic instruments to manage scarcity 15 postpone buying water until they have used up their seasonal allocation and then find that the crop still needs water. they do this in the hope that prices will be lower later in the season [this has historically proven to be the case during most seasons (bjornlund, 2003b)] or that rains come early so that they do not need to buy water to finish their crops (bjornlund, 2004c). finally, it was found that as the price of allocations increase the volume of water traded decreases. this indicates that as scarcity drives prices up, irrigators buy smaller volumes to accommodate their cash flow; and in the hope that further purchases can be avoided due to rain or increased allocation, or that prices might go down again. the market for water entitlements – factors influencing price the activities in the entitlement market show less direct impact of seasonal scarcity caused by fluctuations in evaporation and rainfall. this is as expected, since the price of entitlements should reflect the long-term impact of scarcity rather than withinseason fluctuations. it was also found that the price increase over the study period has been only half that of water allocations, with an annualized increase of 15.41% (bjornlund and rossini, 2006). reflecting scarcity, two main factors determine the price of water entitlements. first, the allocation level: since 1996 seasonal allocations have been drifting lower in response to scarcity due to drought and policies, such as water trading, increased environmental entitlements and capping of water use in the murray-darling basin. as allocations have decreased, prices of water entitlements have increased in response to increased demand in the market as many irrigators wanted to offset lower seasonal allocations by purchasing more entitlements rather than buying more seasonal allocations (see also the discussion in the following section). in a sense this is illogical as lower allocations mean that the entitlements yield less allocation each season; something which should result in a lower willingness to pay. second, as the price of allocations increases, so does the price of entitlements. this is supported by a comparison of the cyclical factors for allocation and entitlement prices (bjornlund and rossini, 2005b). the two cyclical factors are almost synchronized. however, when extreme scarcity during 2002/03 caused a substantial increase in allocation prices, irrigators did not capitalize this increase into the price of entitlements. it was also found that although the cyclical factors are almost perfectly synchronized, their magnitude is very different with the allocation factor being twice as high as the entitlement factor. this suggests that entitlement prices are far more stable than are allocation prices, and that irrigators do not capitalize extreme fluctuations in allocation prices into the entitlement price. irrigators are aware when changes in allocation prices are due to short-term fluctuations in the underlying fundamentals rather than long-term factors. the market for water entitlements – factors influencing market activity the analysis of factors influencing market activities in the entitlement market was not nearly as conclusive as the previously discussed analyses. the level of unexplained variability in volume traded was very high. however, some of the findings are of interest: 1) when the price of water entitlements increases, the volume traded declines. 2) when the price of water allocations increases, the volume of water traded in the entitlement market also increases. this supports clear anecdotal evidence that, while prices in the allocation market were low and water was readily available, there was a trend among many irrigators to rely on purchases of water allocations (bjornlund, 2003b). however, since the price of water allocations has gone up and scarcity has caused increased competition in the allocation market, many irrigators have showed an increased interest in buying water entitlements to provide a greater level of certainty of supply during periods of scarcity. 3) as the price of dairy products increases, dairy farmers become more confident and therefore are willing to buy more water entitlements despite the fact that there is a negative correlation between the price of water allocation and the price of dairy products. the impact of allocation markets on total water use this section analyzes water use data and total volume of water traded on the allocation market. table 1 shows how big a proportion of total water use was generated by the allocation market since 1995 in the two main supply systems of the gmid: the murray and the goulburn systems. as can be seen from the table, the murray system recently has had a higher allocation level than the goulburn system. irrigators bjorlund 16 in the gmid have a very high level of supply security. their entitlements are designed to be delivered in full in 96 out of 100 years. in addition, irrigators in most years get access to additional water when the reservoirs contain more water than is needed for the current and next season. in many years allocations are well in excess of 100% of entitlement. however, this excess has declined considerably over the last 20 years from consistently being 200 percent or more to consistently being at 100% and in one season well below. this has caused scarcity among many irrigators because they have developed their properties to rely on the historically high allocations. it is apparent from table 1 that the allocation market has succeeded in transferring water among competing users in periods of scarcity. when allocations are at 200%, trading accounts for only 8% or less of water use; this level of trade reflects irrigators buying water to benefit from good commodity prices or high demand for their commodities. as scarcity increases, trade accounts for a higher proportion of water use, up to about 20% with 100% allocations and as much as 24% when the allocation dropped to 57% in the goulburn system (also the total volume traded that season was higher than during any other season). it is clear that trading in the murray system did not accelerate until allocations in that system declined to close to 100%, something that occurred for the first time in 1997/98 and then consistently for the three seasons from 2002 to 2005. it is apparent from these data that the allocation market has had a significant impact on irrigators’ ability to cope with scarcity, allowing high value producers with capital investments in plantings, herds and equipment to protect their investments and stay in business by paying low value producers not to use their water (bjornlund 2004b,c; 2003a,b). increase in market participation and scarcity this section analyses how farm businesses in the gmid have adopted water markets and how this adoption rate has been influenced by scarcity. figure 1 shows the proportion of farm businesses that participated in any kind of water trading during each season. that is, they bought or sold water in either the allocation or entitlement markets. the figure shows a significant increase in market participation over time. during the first six years, when allocations in both systems were in excess of 200% (except during 1995/96 when it was only 150% in the goulburn system) the participation rate mainly stayed below 10%. the exceptions are that the participation rate: 1) peaked during 94/95 as trading rules were relaxed and trading was introduced between irrigation district irrigators and private diverters; 2) remained high in the eastern part of the goulburn system as the allocation dropped to 150%; and 3) increased to about 30% in the western part of the goulburn system. this last event happened because this area has the highest proportion of low-value broad acre cropping, grazing and mixed production farms with lower value water uses as well as large areas with significant soil degradation problems. this area therefore had the greatest potential table 1. relationship between seasonal allocations and extent of trade. season goulburn system murray system allocation (%)1 % of trade2 allocation (%)1 % of trade2 1995/96 150 7 200 3 1996/97 200 4 200 3 1997/98 120 9 130 13 1998/99 100 13 200 5 1999/00 100 14 200 8 2000/01 100 16 200 2 2001/02 100 18 200 5 2002/03 57 24 129 16 2003/04 100 16 100 18 2004/05 100 18 100 22 source: goulburn–murray water’s records 1 maximum seasonal allocation. 2 total water trade for season as percentage of total water use. water markets economic instruments to manage scarcity 17 for beneficial trade-offs between irrigators with high and low value crops and productive and unproductive soils. the level of market participation increased to almost 40% in both systems during 1997/98 when allocations were low (table 1). following that year, allocations remained low in the goulburn system, resulting in steadily increasing market participation. the allocation level in the murray system returned to 200% and the participation rate declined to 10-20% until allocation levels dropped again during 2002/03. at that time the participation rate in that system figure 1. percentage of farm businesses trading annually. figure 2. accumulated percentage of farm businesses which have traded. bjorlund 18 reached the same level as in the goulburn system, with 60% of all farm businesses participating in trading during that and the following season. over the 13 year period (1991-2004) market participation has increased from less than 10% of farm businesses per year to about 60%. figure 2 reveals the proportion of farm businesses that have participated in any kind of water trading from the beginning of trade to the end of each season. the figure reveals the same three jumps in market participation. it first increases from around 8% to 21% in 1994/95 when 13% of new farm businesses had their market debut. the next jump in the participation rate, to about 42%, took place in 1997/98 when allocations dropped in both systems (table 1) with another 21% of farm businesses entering water markets for the first time. finally, the participation increased considerably, to 80-90%, during 2002/03 and 2003/04, with about another 43% of farm businesses entering the market. at the present time, fewer than 15% of farm businesses have not participated in any kind of market activity. water trading now seems to be an instrument that farmers use routinely to manage scarcity. in drawing this conclusion it has to be recalled that there is a substantial difference in the way the entitlement and allocation markets have been adopted by irrigators. whereas around 60% of farm businesses are buying and/or selling allocations each year, only 2.5% are selling and 2% are buying entitlements. conclusions in the goulburn-murray irrigation district in australia there is clear evidence that water markets have been widely adopted during the first 13 years of their operation. the major driver of the increase in activity and willingness to pay during this period has been scarcity due to a prolonged period of drought and policy changes. during this period, high value users have been willing to pay increasing prices for water relative to the prices paid for the major commodities produced. the allocation market has played an important role in enabling irrigators to manage scarcity by allowing high value water users with substantial capital investments in plantings, dairy herds and milking equipment, to buy water to retain their herds and to keep their permanent plantings alive. in this process, they compensated the low value producers selling their water by offering prices in excess of what these farmers could make from using it. once the region is out of this period of drought, further research should be conducted to establish the water price/commodity price relationship during periods of more normal supply. during the worst drought years, 60% of all farm businesses were active in the market and almost a quarter of all the water used was purchased in the allocation market. there is, however, still widespread reluctance to adopt the use of entitlement markets due to uncertainty over the long-term security of entitlements. initially, farmers preferred to buy water seasonally in the form of water allocations if they needed it. however, a couple of seasons with exceptionally low allocations caused allocation prices to reach unviable levels and at times it was difficult for high-value irrigators to secure enough water when they needed it. this caused increased activities in the entitlement market as more viable farmers sought to ease their reliance on seasonal purchases. when new jurisdictions consider introducing markets it is important that the issue of resource availability is addressed first, and that the volume of water available for consumptive use is capped at that level. when introducing markets, it is also important to maximize market flexibility by allowing trading to take place within a large geographical area and between as many different user categories as possible, while respecting hydrological, environmental and social constraints of catchments. acknowledgement this research is part of a larger project funded by the australian research council and six industry partners: murray-darling basin commission, department of natural resources in new south wales; department of sustainability and environment in victoria, goulburn-murray water, department of water, land and biodiversity conservation in south australia and upmarket software services. references acil tasman. 2003. water trading in australia – current and prospective products. acil tasman, canberra. bjornlund, h. 2002. the socio-economic structure of irrigation communities – water markets and the ructural adjustment process. rural society 12: 123–145. water markets economic instruments to manage scarcity 19 bjornlund, h. 2003a. farmer participation in markets for temporary and permanent water in southeastern australia. agricultural water management 63:agricultural water management 63:agricultural water management 57–76. bjornlund, h. 2003b. efficient water market mechanisms to cope with water scarcity. the international journal of water resources development 19:553–567. bjornlund, 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outcomes in markets for permanent water – an australian case study. proceedings from the 12th annual conference of the pacific rim real estate society, auckland, new zealand, january. available at www.business. unisa.edu.au/prres bjornlund, h. 2006a. can water markets assist irrigators managing increased supply risk? some australian experiences. water international 31:water international 31:water international 221-232. bjornlund, h. 2006b. the monitoring of, and reporting on, water trading within the goulburnmurray irrigation district, industry partner report no. 2. arc linkage grant ‘water scarcity and rural social hardship – can water markets alleviate the problems?’. adelaide, university of south australia. for a copy contact henning.bjorl und@unisa.edu.au brookshire, d.s., b. colby, m. ewers and p.t. ganderston. 2004. market prices for water in the semiarid west of the united states. water resources research 40, w09s04. turall, h.n., t. etchells, h.m.m. malano, h.a. wijedasa and p. taylor. 2005. water trading at the margin: the evolution of water markets in the murray-darling basin. water resources research 41, w07011. microsoft word jamsy2003v08n01content-arabic.doc ___________________ *corresponding author. 27 agricultural and marine sciences, 8(1):27-34 (2003) © 2003 sultan qaboos university maximizing toxicity of certain insecticides against tribolium castaneum (herbst) a.h. mansee1* and m.r. montasser2 1department of pesticide chemistry, faculty of agriculture (el-shatby), university of alexandria, egypt. 2central lab of pesticide, agricultural research center (sabahia), alexandria, egypt. abstract: effects of temperature and light exposure on the toxicity of deltamethrin, chlorpyrifos-methyl, and malathion against tribolium castaneum were extensively studied using the residual film method. results revealed that mortality increased proportionally with an increase in temperature, where the optimum temperature for the three tested insecticides was 30°c. toxicity of the tested insecticides could be arranged in the following descending order: chlorpyrifos-methyl >deltamethrin >malathion. moreover, light exposure obviously enhanced toxicity of the three investigated insecticides compared to dark exposure. piperonyl butoxide (pb) acted as an oxidase inhibitor, when mixed with each of the three insecticides, increased the toxicity ratio by about four fold in both dark and light. joint toxic effects between deltamethrin and the two tested op as esterase inhibitors, showed that mixing chlorpyrifosmethyl with deltamethrin increased deltamethrin toxicity by 152.7 and 137.12 fold in dark and light, respectively. finally, deltamethrin + chlorpyrifos-methyl + pb blend was found to possess maximum efficiency, which increased deltamethrin toxicity by 679.05 fold under exposure to light conditions. thus, modification of deltamethrin toxicity by increased temperature; light exposure and detoxification inhibitors maximized its toxicity to tribolium castaneum, reduced insecticide rate, and thus reduces both the environmental stress, and the resistance pressure. keywords: maximizing toxicity, deltamethrin, organophosphorus, tribolium castaneum. hemical control of stored grain pests requires adequate and continuous attention to the storage rooms, during transportation, and to silo cells (storey et al., 1984). annual losses of stored grains caused by insects are estimated to be over 15% of the total stored grains produced in egypt (essa, 1995), and up to 9% of the world’s production (gifap, 1989). the red flour beetle, tribolium castaneum (herbst) is one of the major insect pests of stored grain products in warm and tropical regions of the world (semple, 1986). it is the most abundant and injurious pest in flour mills, bulks of grains, oilseeds and warehousing facilities (zettler, 1991). application of protectant insecticides is an integral part of the c !"#$%&'()*$%+,-./*$012)$3*4&2')*$%+567)*$48$9-(:;<$=&>4)*$9*5'7)*$ !"#$%&'()%*+,()%-./()% % $%?? !<%012%34567%-89:2%;</=5%>,?67% 65-!"5%*%-89:2%#-$/"5% %,&'"%()*%38"4%+,%!)%!#--8),/"."5%/01#-8260)3"5* 4+8-8)%5089<""5*%.&% -67%%,'1(=%889."5%%5-"!"5%:5.;/4,2%3<#-=%1)81"5%&<>/""5?%.9*%@!&*$%ab,/("5% 7,#c%38"4% %>5.8d>""5%% ->d/;""5%e,126,2%3?67% 65-!"5%.9*%@f,,%3?67% 65-!"5%()-""5%>5.8>")"%3).;/'""5%&g%3456."5%&h%ijk:?% %.d9*%%5,d,%%ld82-2%%>5.8d>""5%%!d)%m87%38"'"5%&",/",,0%/01#-8260)3"54+8-8)%!#--8),/"."5%5089<""5?% *<*%)*(%n"o%5pg% %#-$/d"5%%%0dq)"%%.d9%%-drs$%% 7,d#c%3!&5*%&g%189%38"'"5%38>'("5%>5.8>")"%39<-"5% ->/;""5%3f6,<)%r/8"'2,%@!2%;*-s% :<st5?%,",%5$%3g,&u%v6()%"5+8f*->>%.8',02082%("u%+,%!)%>5.8>""5%3).;/'""5%.9%w7$%("u% 7,#c%38"'"5%38>'("5% %65.d<"2%%&d"507%%xd26$%%;,$d&$%%nd"o*%%@d!2%%;*-ds%% %,d&t5%%:<dst5*?%%.d9*%%>-drs$%%3d4567%%+d$1"5%%:,d'"5%%y-/d6""5%.8>""% %!d#--8),/"."5%x)%>5.8>""5%3#601401"5% ->/;""5%5$%v)=%/01#-8260)3"54+8-8)%x)%!#--8),/"."5%.9%w7$%("u% 7,#c%38"'"5% %38>d'("5%%3df6,<)%%.8d>"2%%!d#--8),/"."5%%z7-d1"2%%nd"o*%%65.d<"2%%[\]?^%*%[i^?[]%%_$d&%%@d!2%%-ds;*%:<st5% %,&t5*%()*% %&d"50/"5?%%5-8d=$*`%.<g%@!&*$%3456."5%5$%+qg$%3a)=%12%,r)5.;/45%@a*$%()*$%-89:2%.&% -6!"5% ->/;""5%&h%v)=% %!d#--8),/"."5%%xd)%%/01#-8d260)3"54%+8d-8)%%xd)%%+8df*->>"5%%.8d',02082%%@d!2%%;*-ds%#-$/"5%%0q)"%m87%@f,,%3"89%38"'"5% %38>d'("5%%&dh%b^c?j\%_$&%f6,<)3%!#--8),/".",2%z7-1"2%@!2%d1f%;*-e"5?%n"f"%!3"#%!8'!2% %,13"5%3#7,2t5%.8>""% %!d#--8),/"."5%%nd"o*%% 7,#gd2%%3d?67% 65-!"5%n"f,*%#-$/"5%%0q)"%,q#$*%:5.;/4,2%>,a>-)%3"5cu%38"'"5?%h7i#%+,%n"o%("u% %xdg6% %,1,%.8>""5%.&% -6!"5% ->/;""5%5fr2*%!3"#%+8)<2%>j.$""5%.;/'""53)%!)%.8>""5%&",/",2*%k1=%6,a=$%l0)/"5% &m8>"5%n"f,*%k1=%31n%3)*,<""5% -6!)"%>5.8>")"?! mansee and montasser 28 management of this pest (bengston et al., 1991). malathion has been used extensively for nearly 30 years as a grain protectant to control this pest, but now, it is losing its effectiveness due to insect resistance (horton, 1984). among the op pesticide, chlorpyrifosmethyl is a possible substitute for malathion as a stored grain protectant for the malathion-resistant species particularly the t. castaneum (collins et al., 1993). since the grain insect pests are notorious for developing resistance to insecticides (champ, 1986), and recently because there is a desire to reduce op chemical residues on grains, alternatives to the op have been sought by the grain protection industry. most important of such alternatives are the α-cyanophenoxy benzyl cyclopropanecarboxylate pyrethroid derivatives, particularly deltamethrin synergised with pb (arthur, 1994 a&b). however, high levels of resistance to pyrethroid insecticides have been reported in t. castaneum (collins, 1990). therefore, with two protectants being applied to grain, there is a potential for synergism between them (daglish, 1998). synergism between pyrethroids and organophosphorus insecticides has been demonstrated (daglish, 1998 and richter et al., 1998). however, the use of chemical treatment to control stored insects has been limited by the risk of insecticide resistance, cost, and consumer obstruction to using toxic chemicals on food or food products. this has resulted in reducing the maximum residue limits (armitage et al., 1994). the aforementioned reasons have placed increasing reliance on the development of low-cost, low chemical input, and integrated pest management storage strategies that must be capable of guaranteeing the same degree of freedom from pests as chemical strategies. an integrated package of physical and chemical techniques had been recommended (armitage et al., 1994). the interaction between physical factors such as temperature and moisture may be used to minimize the required dose of protectant (shawir and mansee, 1997). the effect of photo-period has also been considered (montasser, 1999). thus, different pesticides or pesticide combinations could be selected depending on the ambient environmental conditions under which the grain is to be stored. the present investigation estimated the effects of light exposure and temperature, on the toxicity of deltamethrin, chlorpyrifos-methyl and malathion against t. castaneum. in addition, synergistic and joint toxic effects of tested insecticides after light exposure were evaluated against the tested insect pest. the final aim of this study was to investigate the management toxicity of tested insecticides against t. castaneum by using physical parameters. specifically, it was observed whether mixtures and conditions could be exploited to increase the toxicity with a reduction in the application rates for the control of stored product insects. materials and methods insects: adults of red flour beetle, t. castaneum (herbst) were laboratory cultured, and reared on sterilized whole meal flour (12 % moisture content) in glass jars. beetles were cultured at 25±2 °c and 70% ±5 r.h. the adults tested were 3-4 weeks old. chemicals: deltamethrin [(s)-α cyano3-phenoxybenzyl (1r,3r)-3-(2,2-dibromovinyl)-2,2 dimethylcycloproanecarboxylate], technical grade (≈98% a.i.); chlorpyrifosmethyl [ o,odimethyl o-(3,5,6trichloro-2-pyridinyl] phosphorothioate, 99.2% purchased from chemservice inc. usa.; malathion [o,o-dimethyl-5-(1,2-dicarbethoxymethyl) phosphorodithioate], technical grade (99.5% a.i.); and piperonyl butoxide [5-{[2-(2-butoxy ethoxy) ethoxy]methyl}-6-propyl-1.3-benzodioxolie], as an oxidase inhibitor, was purchased from same source. bioassay of tested insecticides: effects of light on insecticide toxicity at different temperatures using a 1 ml pipette, a 0.5 ml sample of diluted insecticide solution (diluted with acetone), at the selected concentrations, was applied on a whatman no. 1 filter paper (7cm i.d.), placed in a petri dish to ensure even chemical distribution (shawir and mansee, 1997). the filter paper was allowed to dry for approximately half hour. twenty normally active adult beetles were transferred to each petri dish, confined by plastic rings, and incubated at 15, 20, 22, 25, and 30°c. dishes were kept in continuous light (14 w light source) in an incubator (okiwelu et al., 1998). another group of petri dishes was kept under continuous dark conditions for comparison. beetles were examined after 5 days of exposure and the mortality counts were recorded. each group included seven concentrations and a control, each in three replicates. the lc50 values expressed as µ g/cm2 were calculated according to finney (1971). synergism and joint toxic effect of tested insecticides synergism of tested insecticides: piperonyl butoxide (pb) was mixed, as an oxidase inhibitor, with each tested insecticides at the ratio of 1:5. blends were tested against t. castaneum using the residual film method as previously mentioned, and were incubated at 30°c for tested insecticides, under continuous darkness or light. toxicity and synergistic effect were computed according to the method of metcalf (1967). joint toxic effects of synthetic pyrethroid, deltamethrin: series of deltamethrin concentrations were mixed with malathion or chlorpyrifos-methyl at the ratio of 1:5 to evaluate the joint toxic effects between insecticides according to bengston et al. (1987). the residual film application method as previously described was followed and treated insects were kept at the optimum maximizing toxicity of certain insecticides against tribolium castaneum (herbst) 29 temperature degree, 30°c (shawir and mansee, 1997). the joint toxic effect was studied by mixing deltamethrin with the op insecticide, chlorpyrifosmethyl, as an esterase inhibitor, and piperonyl butoxide, as an oxidase inhibitor. deltamethrin was mixed with chlorpyrifos-methyl and piperonyl butoxide at the ratio of 1:4:8 respectively according to bengston et al. (1983). the residual film application, as previously described, was used against t. castaneum at 30°c under continuous darkness or light for 5 days to evaluate the joint toxicity action. the 95% fiducial limits of the lc50 values were used to test for the statistical significant differences in toxicity between different treatments (koziol and witkowski, 1982). results and discussion role of temperature and light exposure on insecticide toxicity: influences of temperature as well as exposure to source of light, on the toxicity of tested insecticides, deltamethrin, chlorpyrifos-methyl and malathion, against adults of t. castaneum, were extensively investigated. results are presented in figure 1 a, b, and c, as toxicity ratios of tested insecticide, under continuous darkness or light conditions at different temperatures. toxicity ratio was calculated by dividing the lowest toxicity value (lc50 of malathion treatment in darkness at 30°c, as 5.717 µg/cm2), with lc50 values of each treatment. the duncan test was used to test for the statistically significant differences in toxicity ratio among different temperature levels (herzberg, 1983). present results show that the toxicity of tested insecticides against t. castaneum after exposure to the light is higher than those of the corresponding toxicity in dark at each examined temperature. in addition, the data showed that the toxicity of tested insecticides to t. castaneum increased with a temperature increase, either in light or in dark, except in the case of deltamethrin. the toxicity ratio of deltamethrin treatments at 20, 22, and 25°c under continuous light or dark against t. castaneum seems to be negatively correlated with temperature. the present study also revealed a margin of temperature range at which deltamethrin exerts a negative temperature-toxicity correlation. the optimum temperature was found to be 30°c for insecticides against t. castaneum under light or dark exposure. moreover, chlorpyrifos-methyl was more toxic than deltamethrin or malathion at all temperatures under light or dark exposure. the toxicity ratios of chlorpyrifos-methyl values were calculated to be 6.381 and 12.138 folds at 30°c under darkness and light treatments, respectively against t. castaneum. the current investigation revealed that synthetic pyrethroid, deltamethrin toxicity ratios at 20, 22, and 25°c, were negatively correlated with temperature. this is in agreement with the findings of longstaff and desmarchlier (1983) who reported that the toxicity of figure 1. a. effect of temperature on toxicity of deltamethrin against t. castaneum. b. effect of temperature on toxicity of chlorpyrifos-methyl against t. castaneum. c. effect of temperature on toxicity of malathion against t. castaneum. toxicity ratio values for a given temperature followed by a common letter are not significantly different as duncan test. deltamethrin to s. oryzae decreased with increasing temperature. however, watters et al., (1983) reported that the toxicity of the pyrethroid insecticides cypermethrin and fenvalerate to t. castaneum was significantly higher at 20oc than at 10oc or 30oc. 0 5 10 15 15°cc 20°cb 22°cab 25°cab 30°ca dark light 0 5 10 15 15°cc 20°cb 22°cab 25°cab 30°ca dark light 0 5 10 15 15°cb 20°cab 22°cab 25°ca 30°ca dark light temperature degree temperature degree temperature degree t ox ic ity r at io (f ol ds ) t ox ic ity r at io (f ol ds ) t ox ic ity r at io (f ol ds ) a. b. c. mansee and montasser 30 moreover, shawir and mansee (1997) reported that toxicity of the tetrahalo-pyrethroid tralomethrin to s. oryzae and t. castaneum using residual application was higher at 25oc than at 35oc or 15oc. they also reported that deltamethrin was more toxic at the higher temperature (35oc) for residual exposure against s. oryzae and t. castaneum. in other words, very low or very high temperature might have a severe effect on the biological and physiological activities of the insect that in turn may affect insect susceptibility to pyrethroids. the same trend of temperature-toxicity interaction was observed by montasser (1999). also, it was cited that the pyrethroid insecticide permethrin expressed a higher effect at 20oc than at 30, or 15oc to both tested insects. the present investigation showed that the toxicity of two tested op’s, malathion and chlorpyrifos-methyl, increased by increasing temperature. toxicity also increased as a result of light exposure rather than dark conditions. desmarchelier (1977) indicated the effect of lower temperature and supported these findings in reducing toxicity of organophosphorus, dichlorvos, malathion, fentriothion and pirimiphos-methyl against tribolium and sitophilus species. in addition, tyler and binns (1982) mentioned that the effectiveness of malathion and pirimiphos-methyl against the examined susceptible stored product insects was greater at 25oc than at 17.5oc and was markedly lower at 10oc. montasser (1999) added that tested organophosphorus insecticides, pirimiphos-methyl and malathion were more toxic at higher temperature against s. oryzae and t. castaneum. in contrast, longstaff and desmarchlier (1983) showed that the pirimiphos-methyl was shown to have opposite relationships with temperature to s. oryzae. the present results show that the three tested insecticides could be arranged in a descending order according to their toxicity to t. castaneum at all examined temperatures as chlorpyrifos-methyl, deltamethrin and malathion. the present investigation also showed that light exposure plays an important role in the toxicity of each of the tested insecticides against t. castaneum. however, the toxicity of these insecticides was increased when exposed to light at the same temperature. it can also be concluded that light exposure increases the toxicity ratio compared to darkness by 280, 190.2, and 235.03% for deltamethrin, chlorpyrifos-methyl and malathion treatments respectively, at optimum temperature (30°c). previous work emphasized that the effects of exposure to light on the toxicity of pesticides especially for stored product insects are few. fernandez and randolph (1966) mentioned that the photoperiodic rearing conditions affect the susceptibility of houseflies to a given dosage of insecticides. it could be explained according to the assumption of pittendrigh (1961), who found that the photoperiod could exert effects on other fundamental aspects of insect physiology. el-sebae and moustafa (1970) studied the effect of three photoperiodic treatments such as continuous illuminating, 12 hours periodic light and dark and continuous darkness on the life cycle and susceptibility of m. domestica to ddt. they concluded that continuous illumination increased the activity of the insects. this might render the insects more vulnerable to ddt poising. okiwelu et al. (1998) added that the photoperiod affects some aspects of the biology of the merchant grain beetle, oryzaephilus mercator. montasser (1999) supported the present findings and concluded that the toxicity of permethrin, pirimiphosmethyl and malathion after exposure to light, was higher than the corresponding toxicity in absence of light against both s. oryzae and t. castaneum. influence of pb on synergism of tested insecticides: synergistic effects of the oxidase inhibitor, piperonyl butoxide (pb) on the toxicity of insecticides at their optimum temperature (30°c) against t. castaneum, under continuous darkness or continuous light, are presented in table 1. the lc50 values for given treatments were compared. the significant differences between lc50 values were detected by using the 95% fiducial limits (koziol and witkowski, 1982). the results show that addition of the oxidase inhibitor (pb) to deltamethrin, chlorpyrifosmethyl and malathion resulted in a remarkable synergism against t. castaneum under both exposure operations. in addition, synergistic ratios in the continuous light treatment were higher than those under darkness treatment for all tested insecticides. the toxicity of chlorpyrifos-methyl +pb blends against t. castaneum after exposure to light was the most toxic than all other tested insecticide blends, showed 0.115 µg/cm2 and 4.09 folds as lc50 and synergistic ratio, respectively. furthermore, mixing pb with malathion resulted in the highest synergism, against t. castaneum. the values were calculated as 4.84 and 4.49 folds for darkness and light treatments conditions, respectively. mixed function oxidase (mfo) plays a significant role in degradation of pyrethroid insecticides (yamamoto, 1973) or organophosphorus insecticides (attia and frecker, 1984). however, using piperonyl butoxide, well known as an mfo inhibitor, could be classified as an active synergist with all tested insecticides (wilkinson, 1971). thus, inhibition of these types of enzymes by pb is a possible explanation for the high level of synergism (lloyd, 1973). adding pb to the three tested insecticides, in the present investigation, resulted in a remarkable synergism against t. castaneum. this result can be supported by the report of bengston et al. (1983), who indicated that deltamethrin + pirimiphos-methyl + pb blend completely controlled s. oryzae (l.), t. castaneum, t. confusum and r. dominica. marei et al. (1994) added that pb synergized the toxicity of deltamethrin against s. oryzae (l.). on the other hand, wanas et al. (1982) maximizing toxicity of certain insecticides against tribolium castaneum (herbst) 31 table 1 effects of oxidase inhibitor, piperonyl butoxide (pb), on insecticides toxicity to t. castaneum using residual film method at 30ºc. treatments in dark in light insecticides lc50("g/cm 2) (95% fiducial limits) toxicity ratio** (fold) lc50("g/cm 2) (95% fiducial limits) toxicity ratio** (fold) without pb 2.00 0.713 (1.72-2.40) (0.64-0.79) + pb 0.625* 3.2 0.166* 4.3 deltamethrin (0.57-0.68) (0.14-0.19) without pb 0.896 0.471 (0.82-0.97) (0.40-0.54) + pb 0.228* 3.93 0.115* 4.09 chlorpyrifos-methyl (0.20-0.26) (0.10-0.13) without pb 4.442 1.89 (4.1-4.82) (1.76-2.03) + pb 0.918* 4.84 0.421* 4.49 malathion (0.84-0.99) (0.39-0.45) *lc50 values followed by asterisks are significantly greater than without pb based on the 95% fiducial limits. **relative to the toxicity of insecticide without synergism (pb). reported that pb could be used successfully as a synergist for malathion and other organophosphorus insecticides against s. oryzae. moreover, bengston et al. (1983) mentioned that pirimiphos-methyl + pb controlled common field strains of s. oryzae and r. dominica. the addition of pb to malathion was also attempted to increase the toxicity of this organophosphorus against o. surinamensis (attia and frecker, 1984). montasser (1999) mentioned that mixing of pb with permethrin, pirimiphos-methyl and malathion resulted in a synergistic effect of toxicity against both s. oryzae and t. castaneum. the tested insecticide-synergist mixtures can be arranged in the following descending toxicity order: pirimiphos-methyl + pb at 30oc > permethrin + pb at 20oc > malathion + pb at 30oc. influence of esterase inhibitors on toxicity of deltamethrin: organophosphorus insecticides when mixed with pyrethroids used to play a role as an esterase inhibitor, which result in increasing the toxicity of pyrethroids (marei et al., 1982). thus the joint toxic effects of chlorpyrifos-methyl and malathion, as an esterase inhibitors when mixed with deltamethrin, were extensively evaluated against t. castaneum at 30°c in continuous light or darkness (table 2). the results show that inhibitors, when mixed with deltamethrin, significantly enhance its insecticidal toxicity against the tested insect in light and darkness conditions. however, when deltamethrin was mixed with chlorpyrifos-methyl, the blend was more toxic than the deltamethrin-malathion mixture under dark or light conditions. the lc50 of the mixture (deltamethrin-chlorpyrifos-methyl) against t. castaneum under continuous dark treatment was 0.0131 µg/cm2 with toxicity ratio of 152.7 folds, while in continuous light treatment the values were 0.0052 µg/cm2 and 137.12 folds, respectively. meanwhile, the two tested deltamethrin-organophosphorus mixtures, showed more toxicity under light treatment than under dark treatment. organophosphorus compounds were classified as exceptionally potent pyrethroid esterase inhibitors (marei et al., 1982). the esterase enzymes play an important role in detoxification and degradation of pyrethroid insecticides. the inhibition of these enzymes by op compounds enhanced pyrethroids persistence (mansee, 1992). the organophosphorus compounds, chlorpyrifosmethyl and malathion as esterase inhibitors, showed an effect on the insecticidal activity when used in mixtures with pyrethroid insecticide (deltamethrin) against the adults of t. castaneum (herbst). current findings may table 2 effects of esterase inhibitors on deltamethrin toxicity against t. castaneum using residual film method at 30ºc. treatments in dark in light insecticides lc50("g/cm2) (95% fiducial limits) toxicity ratio* (fold) lc50("g/cm2) (95% fiducial limits) toxicity ratio* (fold) deltamethrin 2.00a 0 0.713b 0 (1.72 – 2.40) (0.64 –0.79) deltamethrin + malathion 0.16c (0.14 –0.18) 12.5 0.0174d (0.013 –0.023) 41 deltamethrin +chlorpyrifos methyl 0.0131d (0.0081-0.013) 152.7 0.0052e (0.0042-0.0063) 137.12 *relative to the toxicity of deltamethrin alone. lc50 values for a given treatment followed by a common letter are not significantly different at the 5% level of probability based on the 95% fiducial limits. mansee and montasser 32 table 3 joint toxic effects of deltamethrin toxicity against t. castaneum using residual film method at 30ºc. treatments in dark in light insecticides lc50("g/cm2) (95% fiducial limits) toxicity ratio* (fold) lc50("g/cm2) (95% fiducial limits) toxicity ratio* (fold) deltamethrin 2.00a 0.713b (1.72 – 2.40) (0.64 –0.79) deltamethrin + pb 0.625b (0.57-0.68) 3.2 0.166c (0.14-0.19) 4.3 deltamethrin + chlorpyrifos methyl 0.013d (0.0081-0.013) 152.7 0.0052e (0.00420.0063) 137.12 deltamethrin + chlorpyrifos methyl + pb 0.0056e (0.0046-0.0069) 357.14 0.00106f (7.9e4-1.41e3) 679.05 *relative to the toxicity of deltamethrin alone. lc50 values for a given treatment followed by a common letter are not significantly different at the 5% level of probability based on the 95% fiducial limits. also be supported by carter et al. (1980) who found that chlorpyrifos-methyl, pirimiphos-methyl or fenitrothion in combination with permethrin resulted in potentiation for control of stored product insect pests. bengston et al. (1983) added that pirimiphos-methyl + permethrin controlled s. oryzae (l.) and r. dominica, and completely prevented progeny production in t. castaneum, t. confusm and in e. cautella. conversely, a mixture of permethrin and pirimiphos-methyl was less effective against p. truncatus and s. zeamis (richter et al., 1998). marei et al. (1994) found that mixing profenfos with deltamethrin resulted in enhancement of permethrin toxicity against the rice weevil, s. oryzae (l.). also, the toxicity of pyrethroids to stored product insects was increased when mixed with other organophosphorus insecticides such as chlorpyrifos-methyl (daglish, 1998). montasser (1999) concluded that the addition of the organophosphorus, tocp, malathion and pirimiphosmethyl resulted in potentiation of the insecticidal toxicity of permethrin against the adults of s. oryzae (l.) and t. castaneum (herbst). this is in agreement with our investigation. the toxicity of the mixtures against insects can be arranged in the following descending order: permethrin+ pirimiphos-methyl > permethrin + malathion > permethrin + tocp > permethrin alone. effects of esterase and oxidase inhibitor combination on deltamethrin toxicity: to study the joint toxic effect against t. castaneum, deltamethrin was mixed with chlorpyrifos-methyl and pb, at the ratio of 1:4:8 and kept at 30°c under continuous darkness and light conditions. the mixture gave lc50 and toxicity ratio values of 5.6 x 10-3 µg/cm2 and 357.14 folds under continuous darkness and 1.06 x 10-3 µg/cm2 and 679.05 folds in continuous light, respectively (table 3). this mixture exhibited the most significant synergistic effect among all tested mixtures or deltamethrin alone. the activity of deltamethrin, chlorpyrifos –methyl, and pb mixture showed an obvious effect over the activity of deltamethrin alone against t. castaneum. generally, the relative toxicity of this mixture proved the highest ratio in the present study either in darkness or light conditions against tested insects. the toxicity of the different mixtures with deltamethrin against stored-product insects could be arranged in the following descending order: deltamethrin plus chlorpyrifos-methyl plus pb > deltamethrin plus chlorpyrifos-methyl > deltamethrin plus pb > deltamethrin. in addition, all tested treatments showed a better effect to t. castaneum under light than under darkness condition. comparing insecticide toxicity under different conditions with recommended application rate: the results showed that the used unit of malathion in dark at 25°c was 100 µ g/cm2, while at 30°c, the same value was 88.84 µ g/cm2 (table 4). both chlorpyrifosmethyl and deltamethrin, when tested in darkness at 30°c, showed increased toxicity against t. castaneum compared with malathion (used units was 17.36 and 40 µ g/cm2, respectively). the suggested blend of deltamethrin + chlorpyrifos-methyl + pb in dark at 30°c, increased the toxicity value by decreasing the units used (0.112 µ g/cm2). the toxicity values were expressed as 20 times of each lc50 (µg/cm 2). the lc50 multiplied by 20 times, to simulate the dose of malathion recommended to control empty silos in egypt (suggested by the egyptian ministry of agriculture, 1997) as 100 µg/cm2 of malathion at 25°c, which equal to 20 times of its lc50 at the same conditions in the present study. all the previous treatments when tested under light condition, increased the toxicity value of the treatment compared to the recommended application. the same table showed how much the treatments and blends save or decrease the amounts of insecticides used as compared to the recommended application by the ministry. table 4 comparative toxicity of tested insecticides under different conditions with special reference to the recommended application. units used ("g/cm2) units saved (%) treatments in dark in light in dark in light malathion (25ºc) 100.00* 38.30 61.70 malathion (30ºc) 88.84 37.80 11.16 62.20 chlorpyrifos-methyl (30ºc) 17.36 9.42 82.64 90.58 deltamethrin (30ºc) 40.00 14.26 60.00 85.74 deltamethrin+chlorpyrifos methyl + pb (30ºc) 0.11 0.02 99.88 99.98 *recommended dose of malathion in empty silos in egypt at 25ºc according to the egyptian ministry of agriculture (1997), which is equal to 20 times of lc50’s malathion at 25ºc in dark. maximizing toxicity of certain insecticides against tribolium castaneum (herbst) 33 it can be concluded that exposure to light saves more than 60% of the malathion dose, while in the case of chlorpyrifos-methyl and deltamethrin, savings reached 90% and 85%, respectively. the suggested blend in the present study might be used as an alternative to malathion. this will help to save about 99% of malathion units used in the regular recommendation. conclusions light exposure increases the toxicity of the tested insecticides against t. castaneum, compared to darkness exposure at all examined temperatures. the toxicity value increased proportionally with an increase in temperature. the optimum temperature level for the three examined insecticides was 30°c. both oxidase and esterase inhibitors, when mixed with deltamethrin, increased the toxicity values in darkness and light. moreover, modification of deltamethrin toxicity by temperature, light exposure and inhibitors resulted in an increase in the toxicity, thus 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(ed.). 1983. principles of statistics. york university, john wiley and sons, u.s.a. horton, p.m. 1984. evaluation of south carolina field strains of certain stored-product coleoptera for malathion resistance and pirimiphos-methyl susceptibility. journal of agricultural entomology 1(1):1-5. koziol, f.s. and j.f. witkowski. 1982. synergism studies with binary mixtures of permethrin plus methyl parathion, chlorpyrifos, and malathion on european corn borer larvae. journal of economic entomology 75(1):28-30. lloyd, c.j. 1973. the toxicity of pyrethrins and five synthetic pyrethroids to tribolium castaneum (herbst) and susceptible and pyrethrins-resistant sitophilus granarius. journal of stored products research 9(1):77-92. longstaff, b.c. and j.m. desmarchelier. 1983. the effects of the temperature-toxicity relationships of certain pesticides upon the population growth of sitophilus oryzae (l.) 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the effects of photoperiod on some aspects of biology of oryzaephilus mercator (fauvel) (coleoptera: silvanidae). journal of stored products research 34(2/3):189-193. mansee and montasser 34 pittendrigh, c.s. 1961. on temporal organization in living systems. harvey lectures series 56:93-125. richter, j., a. biliwa, and s.h. helbig. 1998. efficacy of dust formulated insecticides in traditional maize stored in west africa. journal of stored products research 34(2/3):181-187. semple, r.l. 1986. problems relating to pest control and use of pesticides in grain storage: the current situation in asean and future requirements. in: pesticides and humid tropical grain storage system: aciar proceedings no. 14, b.r. champ and e. highley (editors), 45-75.aciar, canberra, australia. shawir, m.s. and a.h. mansee. 1997. the influence of temperature on the residual toxicity of deltamethrin and tralomethrin to sitophilus oryzae and tribolium castaneum. alexandria journal of agricultural research 42(3):207-215. storey, c.l., d.b. sauer, and d. walke. 1984. present use of pest management practices in wheat, corn, and oats stored on the farm. journal of economic entomology 77(2):784-788. tyler, p.s. and t.j. binns. 1982. the influence of temperature on the susceptibility to eight organophosphorus insecticides of susceptible and resistant strains of tribolium castaneum, oryzaephilus surinamensis and sitophilus granarius. journal of stored products research 18(1):13-19. wanas, e.m., g.a. tantawy, a.e. khamis, f.i. moustafa, and m.i. zeid. 1982. the toxicity of certain insecticides against the rice weevil sitophilus oryzae (l). research of bulletin 500:1-10. watters, f.l., n.d.g. white, and d. cote. 1983. effect of temperature on toxicity and persistence of 3 pyrethroid insecticides applied to fir plywood for the control of the red flour beetle tribolium castaneum (coleoptera:tenebrionidae). journal of economic entomology 76 (1):11-16. wilkison, c.f. 1971. insecticide synergists and their mode of action. proceedings of the 2nd international iupac congeries of pesticide chemistry 2:117-159. yamamoto, i. 1973. pyrethroid insecticides and the synergists action and metabolism. journal of agricultural science. tokyo nogyo diagaku 17:273-313. zettler, j.l. 1991. pesticide resistance in tribolium castaneum and t. confusum (coleoptera: tenebrionidae) from flour mills in the united states. journal of economic entomology 89(3):763-767. ______________________________________________________ received december 2001. accepted march 2003. img009 img010 img011 img012 img330 img331 img332 img333 img334 img335 img336 agricultural and marine sciences, 16:41-50 (2011) ©2011 sultan qaboos university 41 __________________________________________ *corresponding author. e-mail: carp12@naver.com the in vitro activity of a range of natural bioflavonoids against five species of pathogenic fish bacteria gil ha yoon1,2*, sarah al jufaili2, aliya al ghabshi2, and nashwa al mazrooei2 1,2 department of marine science and fisheries, college of agricultural and marine sciences, sultan qaboos university, p.o. box 34, al-khod 123, muscat, sultanate of oman 2 fishery quality control center, ministry of agriculture and fisheries wealth p.o. box 427, p.c. 100, muscat, sultanate of oman البكتيريا من انواع خمسة على الطبيعية البيوفالفونات بعض أثر مخبرية حول دراسة االسماك ألمراض املسببة املزروعي ونشوى الغبشي وعالية اجلفيلي وسارة يون ها قل السمكية والثروة – وزارة الزراعة األسماك جودة ضبط مركز البكتيريا من انواع على منو خمسة النباتات من املستخرجة و للجراثيم القاتلة املركبات نشاط بعض دراسة مخبرية مت ظروف اخلالصة: حتت درجة ٢٢ درجة حتت ساعة ٧٢ مقدارها زمنية في فترة تاردا) أ. و وايدوارسيال اكتلوري سوربيا وا. وا.ساملونسيديا هايدروفيال ( ارمونوس املائية (ابيجنني احلمضي التركيب ذات البيوفالفينات مركبات من ستة فعالية اثبات مت املركبات. لهذه املعد االجار لوح باستخدام وذلك مئوية، ١٠ بني ما تتراوح بتراكيز املركبات استخدام هذه اعاله عند املذكورة اجلراثيم منو على كورسيتني) و ومورين ونارينجني وهيسبريدين وكاتيشني جزء ١٠٠٠ مقدارها جرعة اضافة مت املستهدفة، للبكتيريا النمو ديناميكية على املركبات هذه فعالية من وللتأكد املليون. من جزء ١٠٠٠ الى فعالية التجربة هذه من تبني البكتيريا. هذه منو في اليومية مراقبة التغيرات متت ثم ومن بكتيري مستزرع الى البيوفالفينات من من املليون ما البكتريا أنواع جميع على فعالية ذو املورين مركب ان اتضح كما الدراسة، هذه شملتها التي البكتيريا ضد جميع انواع الكوسرتني مركب ايضا لنموها مثبط و قاتل للبكتيريا كعامل يعمل انه وجد فقد الهيسبيدين، ملركب بالنسبة اما سوربيا). أ. و (ا.هايدروفيال هما اثنني عدا مركب تواجد عند انه الدراسة اثبتت كما الدراسة عليها شملت التي البكتيريا انواع جميع حيال ضعيفا االبيجني مركب تأثير كان في حني الدراسة وخلصت ضعيفا. ايرموناد بكتيريا تاثيرهما على كان لكن و البكتيريا منو تثبيط الى يؤديان فانهما النارينجني مع مركب الكاتيشني تعمل انها قد كما االسماك ألمراض املسببة البكتيريا انواع ضد بعض لديها فعالية النباتات من املستخرجة بعض املركبات اخملبرية إلى أن املزيد إلى حتتاج الدراسات هذه اجملال، إال أن هذا في تستخدم التي الكيميائة املواد لتحل مكان يؤهلها مما قد البكتيريا هذه على تثبيط منو احلية. الكائنات على جتربتها ينبغي و املتابعة من abstract: the in vitro antibacterial activity of thirty two plant-derived compounds (26 crude herbal extraction and 6 pure citrus-based bioflavonoids) were tested on five different species of aquatic bacterial pathogens (aeromonas hydrophila, a. salmonicida, a. sobria, edwardsiella ictaluri, and e. tarda) over a period of 72 hours at 22 oc. from the agar diffusion test, six pure citrus-based bioflavonoids (apigenin, catechin, hesperidin, morin, naringin and quercetin) appeared to impact on growth when used at concentrations ranging from 10 ppm 1000 ppm. to confirm their effect on the growth dynamics of each bacteria, a 1000 ppm dose of the appropriate bioflavonoid was added to a bacterial culture and daily changes in culture growth were measured. quercetin was found to be bacteriocidal against all the bacterial strains. morin was found to be bacteriocidal against only 4 out of 6 strains while hesperidin was found to affect the growth of all the tested bacterial strains, working both as a bacteriocidal and as a bacteriostatic agent. apigenin performed poorly and had no effect on the growth of any bacterial strain while catechin and naringin were found to be generally bacteriostatic in action but had little impact on the growth of the aeromonad strains. from the current in vitro work, it was concluded that certain plant extracts do have an impact on the growth dynamics of select bacteria and show potential as alternatives to the use of antimicrobials, but further research is required to assess their performance in vivo. keywords: fish disease, bioflavonoids, bacteria, aeromonas, edwardsiella. introduction bioflavonoids are a biologically active group of natural compounds that are present in a wide range of plants (twigs, leaves, bark, roots, spices, herbs, nuts, seeds, vegetables, flowers, fruits and buds) (formica and regelson, 1995; peldt et al., 2001). the bioflavonoids and essential oils extracted from many plants have been used in traditional oriental medicine for thousands of years but it is only recently that they have been shown to possess a broad range of activities. recently, there has been increased interest in the activity of certain plant-derived oils and flavonoids and in the possibility that they might represent antimicrobial activity against bacterial diseases affecting fish species. categorised as "alternative medicines" rather than as first line treatments, little research has been done to explore the potential of using 42 ha yoon and others 43 the in vitro activity of a range of natural bioflavonoids against five species of pathogenic fish bacteria bioflavonoids as antimicrobials (roth, et al., 1993; hart et al., 1997) due to the increased awareness and concern over antibiotic residues within farmed fish species new health management approaches which are complementary to existing management strategies are being investigated (martin et al., 1998; mayer and hamann, 2002). natural products such as the citrus derived bioflavonoids may have positive effects as antimicrobials against a number of bacterial fish pathogens. pyrethrum, extracted from the flower heads of chrysanthemum cinerariaefolium and c. coccineum, and the synthetic pyrethroid insecticides derived from them (e.g. cypermethrin and deltamethrin) have been used to control the ectoparasitic crustacean copepods lepeophtheirus salmonis krøyer, 1837 and caligus elongatus von nordmann, 1832 on atlantic salmon, salmo salar l. both have shown to be efficacious (roth, 2000; boxaspen and holm, 2001). the aims of the current study were, therefore, to investigate the antimicrobial efficacy of a number of naturally-occurring bioflavonoids, particularly those from within the citrus bioflavonoids (e.g. hesperidin, naringin and quercetin). the discovery of effective biocides for the treatment of fish pathogens would, therefore, have the potential to make a significant contribution to the health management strategies currently employed in the control of certain fish diseases. materials and methods plant extract preparation the bacteriocidal activity of twenty-six crude plant extracts, seven pure bioflavonoids and a synthetic compound were assessed, in vitro, against cultures of five bacterial pathogens using an agar diffusion method (table 1). the seven commercially produced bioflavonoids (catechin c15h14o6, hesperidin c28h34o15, morin c15h10o7, quercetin c15h10o7 and rutin c27h30o16, apigenin c15h10o5 and naringin c27h32o14 from sigma-aldrich, poole, uk) were prepared by dissolving 1g of the pure bioflavonoid in 5ml 0.25m naoh before diluting them to the appropriate concentration for testing (10 ppm – 100 %). quercetin was prepared in distilled water. crude plant extracts were prepared by grinding 10 g of each dried plant product in a pestle and mortar and then adding the ground fraction to 200 ml of distilled water and boiling the mixture until the volume had reduced to 100 ml. where fresh plants were available for study, 20 g of each fresh plant was homogenized using a hamilton beach model no. 909s blender with 100 ml distilled water. the collected liquid fraction was then filtered through 20 µm plastic mesh. the filtrate was regarded as 100 % and lower concentrations were prepared as required. selection of bacterial species and in vitro assessment by agar diffusion five bacterial species were purchased from the national collection of industrial bacteria (ncimb) and pure cultures were used for this study. the bacterial species used were aeromonas hydrophila (ncimb 1134), a. sobria (ncimb 12065), a. salmonicida (ncimb 13161), edwardsiella ictaluri (ncimb 13272) and e. tarda (ncimb 2074). all cultures were grown on general purpose tsa (tryptone soya agar, oxoid u.k.) at the appropriate temperatures. single colonies were identified following the techniques described by frerichs and millar (1993). for each bioflavonoid, a range of concentrations were tested (10 ppm – 100 %) in triplicate, by mixing 10 ml of the appropriate bioflavonoid concentration with 10ml of isa (iso-sensitest agar, difco uk) media on each plate. for inoculation, a sub-sample of each pure cultured test bacteria was resuspended in 5 ml tsb (tryptic soy broth, oxoid) and incubated for 24 hrs prior to their inoculation onto isa-flavonoid plates using a denley multi-point inoculator. a series of control plates were also included in the study. all the inoculated plates were then maintained at 22 °c for 48-72 hrs after which table 1. details of the plant extracts, pure bioflavonoids, bioflavonoid complexes and synthetic compounds used in the current study. scientific name common name tested concentration i) crude plant extracts (%) allium cepa onion 1-5 angelica gigas angelica 1-5 allium sativum garlic 2-100 bambusicola thoracia chinese bamboo 1-5 capsicum annuum chili 2-100 cinnamomum verum cinnamon 2-100 citrus aurantiifolia lime seed 2-100 cnidium officinale cheonkung 2-100 codonopsis pilosula deng shen 2-100 digitalis purpurea common foxglove 2-100 dioscorea opposite yam 2-100 glycyrrhiza glabra liquorice 2-100 lavandula angustifolia lavendar 2-100 lippa alba alba 2-100 maximowiczia typica omija 2-100 mentha spicata spearmint 2-100 ocimum basilicum basil 2-100 paeonia obovata white peony 2-100 panax ginseng ginseng 2-100 pimpinella vulgare aniseed 2-100 poria cocos hoelen 2-100 rosmarinus officinalis rosemary 2-100 petroselinum crispum parsley 2-100 wasabia japonica wasabi 1-5 yucca spp. yucca 1-5 zingiber officinale ginger 2-100 ii) purified bioflavonoids (ppm) apigenin 10-1000 catechin 10-1000 hesperidin 10-1000 morin 10-1000 naringin 10-1000 quercetin 10-1000 rutin 10-1000 iii) synthetic biocides (ppm) ddq 10-1000 42 ha yoon and others 43 the in vitro activity of a range of natural bioflavonoids against five species of pathogenic fish bacteria the growth of each bacterium against each concentration of bioflavonoid was recorded and compared against the control series of plates. bacterial colony growth on each plate was scored as either (-) no growth, (+) weak growth, (++) medium growth or (+++) strong growth. scores were given after three researchers gave their results based on comparing the growth patterns with the control plates. bacteriocidal assessment of the most efficacious bioflavonoids following the preliminary in vitro assessment of the selected bioflavonoids by the agar diffusion method, the most efficacious compounds were characterised further to establish whether their mode of action was bacteriocidal or bacteriostatic. to test this, a 1000 ppm dose of the most efficacious compounds identified from the disc diffusion assay: apigenin, catechin, hesperidin, morin, naringin and quercetin were added individually to each species of bacteria cultured in tsb (oxoid uk) media. each bacterial culture had a control (tsb + bacteria only) and cultures dosed with 5 ppm ddq (di-n-decyldimethylammonium chloride) (mackie pharmaceuticals, uk) were employed as s a positive control. ddq, a synthetic compound, appeared to be effective against all the bacteria species that were used in the in vitro testing when used at doses of 10 ppm. the culture broth tubes were then maintained at 22 °c and the turbidity of each tube was measured daily for a period of 8 days using a spectrophotometer at 610 nm wavelength (triplicate readings for each culture on each day) to estimate bacterial growth. results efficacy of the selected bioflavonoids by in vitro agar diffusion against bacterial fish pathogens the efficacy of each bioflavonoid over the range of concentrations is presented in tables 2 and 3. catechin was also effective against different species of aeromonas but at varied concentrations; 10 ppm against a. salmonicida, 1000 ppm against a. sobria and yet apparently totally ineffective against a. hydrophila. the most effective bioflavonoid against e. tarda and e. ictaluri was 100 ppm of catechin (table 3). bacteriocidal assessment of the most efficacious bioflavonoids from the agar diffusion trial (tables 2 and 3), it appeared that the six pure bioflavonoids, apigenin, catechin, hesperidin, morin, naringin and quercetin were the most efficacious compounds in inhibiting bacterial growth in vitro. the synthetic compound, ddq, was found to be effective at concentrations of 10-1000 ppm (table 3) against all the bacteria that were used in the agar diffusion trial and was tested alongside the pure bioflavonoids but at a lower dose of 5 ppm. the growth of the bacteria was measured daily spectrophotometrically and the data are presented in figures 1-5. by comparing the results obtained for this aspect of the study with those obtained from the agar diffusion trials, it can be seen that a 1000 ppm dose of quercetin had the broadest activity demonstrating a bacteriocidal effect against all bacteria that were tested. hesperidin was also found to display broad activity, more so than was detected by the agar diffusion method and notably in its action against a. sobria (figure 3). from the agar diffusion trials, higher doses of 1000 ppm had an impact on both species of edwardsiella. incubation with apigenin did not affect the growth of any of the bacterial species tested (table 3; figures 4 and 5). a lower dose of ddq, likewise, failed to impact on the growth and survival of any of the bacterial species over the test period. a 1000 ppm dose of morin was also found to have broad bacteriocidal activity except against a. hydrophila and a. sobria. the performance of catechin and naringin was lower and essentially bacteriostatic when used at 1000 ppm. of the bacteria tested, a. hydrophila, was less affected by the pure bioflavonoids compared with the other bacterial species. discussion this study set out to investigate the efficacy of 26 crude plant extracts and 6 pure bioflavonoids in their ability to affect the growth of several pathogenic species of aquatic bacteria. the bacterial species selected are pathogenic in a wide range of fish species of economic importance within global aquaculture. of the plant compounds tested by agar diffusion, it appeared that it was the synthetic compound ddq and the pure bioflavonoid compounds that gave the most efficacious results. when these were tested further in broth culture, the flavonols quercetin and morin, and the flavone glycoside hesperidin, emerged as the most effective, in terms of their bacteriocidal activity. paradoxically, quercetin which displayed efficacy against a. salmonicida only in the agar diffusion trial, displayed the broadest activity in broth culture, and interestingly, was the only water soluble, pure bioflavonoid that was tested. while the lipid solubility of certain products, notably the essential oils, might be improved through the use of detergents, the medium in which the compounds are assessed may also impact on the true activity of the compounds under test. a study by remmal et al. (1993), for example, suggested that the activity of certain essential oils, in particular clove and oregano oils, were significantly reduced when added to agar as opposed to ethanol or tween-80. from the results presented here, it appears that certain compounds, notably quercetin, perform differently when assessed in different media. interestingly, though, high doses of quercetin did not have an effect against the two edwardsiella species in this study a 1 % solution prepared from a crude extract of onions (a. cepa), known to be one of the richest sources of quercetin (284-486 mg/kg; hertog and feskens, 1993) reduced growth of both bacterial species. morin is a ubiquitous secondary metabolite found in plants (harborne and williams, 2000) and although 44 ha yoon and others 45 the in vitro activity of a range of natural bioflavonoids against five species of pathogenic fish bacteria table 2. the efficacy of the crude plant extracts were tested against five pathogenic bacterial species found in fish. the data for each compound and concentration represents the average result obtained from two replicate plates except the control which is based on the average results of multiple plates. the growth of bacteria on each plate is scored as either: (+++) strong growth, (++) medium growth, (+) weak growth or (-) no growth. compound (%) aeromonas hydrophyla aeromonas salmonicida aeromonas sobria edwardsiella ictaluri edwardsiella tarda a. cepa 1 ++ ++ +++ + + 2 ++ ++ +++ + + 5 ++ ++ +++ + + a. gigas 1 +++ ++ +++ + + 2 +++ ++ +++ + + 5 +++ ++ +++ + + a. sativum 2 +++ ++ +++ + + 5 +++ ++ +++ + + 100 b. throracia 2 +++ +++ +++ +++ +++ 5 +++ +++ +++ +++ +++ 100 +++ +++ + ++ ++ c. annuum 1 +++ +++ +++ +++ +++ 2 +++ +++ +++ +++ +++ 5 +++ +++ +++ +++ +++ c. aurantiifolia 2 +++ ++ ++ ++ + 5 ++ +++ + 100 c. officinale 2 +++ ++ +++ + + 5 +++ ++ +++ + + 100 +++ ++ +++ + + c. pilosula 2 +++ ++ +++ ++ ++ 5 +++ ++ +++ ++ ++ 100 +++ ++ +++ ++ ++ c. verum 2 +++ +++ +++ ++ ++ 5 +++ +++ +++ ++ ++ 100 d. opposite 2 +++ ++ +++ + + 5 +++ ++ +++ + + 100 +++ ++ +++ + + d. purpurea 2 +++ ++ +++ + + 5 +++ ++ +++ + + 100 ++ ++ g. glabra 2 +++ +++ +++ +++ +++ 5 +++ +++ +++ +++ +++ 100 +++ +++ +++ +++ +++ l. alba 2 +++ +++ +++ + + 5 +++ +++ +++ + + 100 ++ + + + + 44 ha yoon and others 45 the in vitro activity of a range of natural bioflavonoids against five species of pathogenic fish bacteria table 2 . . . . . . compound (%) aeromonas hydrophyla aeromonas salmonicida aeromonas sobria edwardsiella ictaluri edwardsiella tarda l. angustifolia 2 +++ +++ +++ +++ +++ 5 +++ +++ +++ +++ +++ 100 +++ +++ +++ +++ +++ m. spicata 2 +++ +++ +++ +++ +++ 5 +++ +++ +++ +++ +++ 100 +++ +++ +++ +++ +++ m. typica 2 +++ ++ +++ + + 5 +++ ++ +++ + + 100 o. basilicum 2 +++ +++ +++ +++ +++ 5 +++ +++ +++ +++ +++ 100 +++ +++ +++ +++ +++ p. cocos 2 +++ ++ +++ + + 5 +++ ++ +++ + + 100 +++ ++ +++ + + p. crispum 2 +++ +++ +++ +++ +++ 5 +++ +++ +++ +++ +++ 100 +++ +++ +++ +++ +++ p. ginseng 2 +++ +++ +++ ++ ++ 5 +++ +++ +++ + + 100 +++ +++ +++ + + p. obovata 2 +++ ++ +++ + + 5 +++ ++ +++ + + 100 +++ ++ +++ + + p. vulgare 2 +++ +++ +++ +++ +++ 5 +++ +++ +++ +++ +++ 100 r. officinalis 2 +++ +++ +++ +++ +++ 5 +++ +++ +++ +++ +++ 100 +++ +++ +++ +++ +++ w. japonica 1 ++ ++ +++ + + 2 ++ ++ +++ + + 5 ++ + ++ ++ + yucca spp. 1 ++ ++ +++ ++ ++ 2 ++ ++ +++ ++ ++ 5 z. officinale 2 +++ +++ +++ +++ +++ 5 +++ +++ +++ +++ +++ 100 +++ +++ +++ +++ +++ (tsa+dh 2 0)1 +++ +++ +++ +++ +++ (tsa+naoh)2 +++ +++ +++ +++ +++ 143 replicates used 212 replicates used 46 ha yoon and others 47 the in vitro activity of a range of natural bioflavonoids against five species of pathogenic fish bacteria table 3. the efficacy of seven pure bioflavonoids and a synthetic compounds against five pathogenic bacteria, the genera aeromonas and edwardsiella. the data for each compound and concentration represents the average result obtained from two replicate. the growth of bacteria on each plate is scored as either: (+++) strong growth, (++) medium growth, (+) weak growth or (-) no growth. compound (ppm) aeromonas hydrophyla aeromonas salmonicida aeromonas sobria edwardsiella ictaluri edwardsiella tarda apigenin 10 +++ + +++ + + 100 +++ + +++ + + 1000 +++ + +++ catechin 10 +++ ++ +++ + + 100 +++ ++ +++ 1000 +++ ddqtm 10 +++ +++ 100 + 1000 hesperidin 10 +++ ++ +++ + + 100 +++ ++ +++ + + 1000 +++ + +++ morin 10 ++ +++ ++ + 100 ++ +++ ++ + 1000 ++ +++ ++ naringin 10 +++ ++ +++ + + 100 +++ ++ +++ + + 1000 +++ ++ +++ + + quercetin 10 ++ +++ ++ + 100 ++ +++ ++ + 1000 ++ +++ ++ + rutin 10 +++ ++ +++ + + 100 +++ ++ +++ + + 1000 +++ + +++ (tsa + dh 2 0)1 +++ +++ +++ ++ ++ (tsa + naoh)2 +++ +++ +++ ++ ++ 46 ha yoon and others 47 the in vitro activity of a range of natural bioflavonoids against five species of pathogenic fish bacteria � figure 1. the growth of aeromonas hydrophila in the presence of six different bioflavonoids, each at a concentration of 1000ppm, against time (days). the broth turbidity are measured against a control (bacteria + media) and 5ppm ddq (a synthetic drug shown to be effective at doses of 10ppm). � figure 2. the growth of aeromonas salmonicida in the presence of six different bioflavonoids, each at a concentration of 1000ppm, against time (days). the broth turbidity are measured against a control (bacteria + media) and 5ppm ddq (a synthetic drug shown to be effective at doses of 10ppm). � figure 3. the growth of aeromonas sobria in the presence of six different bioflavonoids, each at a concentration of 1000ppm, against time (days). the broth turbidity are measured against a control (bacteria + media) and 5ppm ddq (a synthetic drug shown to be effective at doses of 10ppm). 48 ha yoon and others 49 the in vitro activity of a range of natural bioflavonoids against five species of pathogenic fish bacteria � � figure 4. the growth of edwardsiella ictaluri in the presence of six different bioflavonoids, each at a concentration of 1000ppm, against time (days). the broth turbidity are measured against a control (bacteria + media) and 5ppm ddq (a synthetic drug shown to be effective at doses of 10ppm). figure 5. the growth of edwardsiella tarda in the presence of six different bioflavonoids, each at a concentration of 1000ppm, against time (days). the responses are measured against a control (bacteria + media) and 5ppm ddq (a synthetic drug shown to be effective at doses of 10ppm). this flavonol displayed mixed results in the agar diffusion trial conducted within this study, a high dose (1000 ppm) appeared bacteriocidal to all but two strains of aeromonas spp. (a. hydrophila and a. sobria) when tested in broth culture. the flavone glycoside hesperidin is an antioxidant and a predominant flavonoid commonly found in citrus fruits. while the actions of quercetin and morin were largely bacteriocidal in action against the bacterial species and strains under assessement, the responses to hesperidin were mixed showing both bacteriocidal and bacteriostatic effects. mixed responses were also observed for catechin, hesperidin and morin against aeromonas spp. and for hesperidin and naringin against edwardsiella spp. of the pure bioflavonoids that were tested in broth culture, only the flavone apigenin, failed to elicit any effect on any of the bacterial species. the agar diffusion tests suggested that a 1000 ppm dose of apigenin might affect the growth of both edwardisella species while a 1000 ppm dose of catechin might restrict the growth of a. sobria. at 1000 ppm, these were the highest doses that were tested and while these were ineffective in broth culture, the culture medium may play a role in affecting their efficacy. this suggests that higher doses are possibly required to exert an effect. the performance of ddq in broth culture was disappointing and none of the results observed in the agar diffusion trial were mirrored in the broth culture trial. 48 ha yoon and others 49 the in vitro activity of a range of natural bioflavonoids against five species of pathogenic fish bacteria anthony, j.p., l. fyfe, and h. smith. 2005. plant active components a resource for antiparasitic agents? trends in parasitology 21:462-468. boxaspen, k. and j.c. holm. 2001. the development of pyrethrum-based treatments against the ectoparasitic salmon lice lepeophtheirus salmonis in sea cage rearing of atlantic salmon salmo salar l. aquaculture research 32:701-707. burt, s. 2004. essential oils: their antibacterial properties and potential applications in foods – a review. international journal of food microbiology 94:223-253. formica, j.v. and w. regelson. 1995. review of the biology of quercitin and related bioflavonoids. food and chemical toxicology 33:1061–1080. frerichs, g.n. and s.d. millar. 1993. manual for the isolation and identification of fish bacterial pathogens. 55pp. pisces press. u.k. harborne, j.b. and c.a. williams. 2000. advances in flavonoid research since 1992. phytochemistry 55: 481-504. hart, j.l., j.r.m. thacker, j.c. braidwood, n.r. fraser, and j.e. matthews. 1997. novel cypermethrin formulation for the control of sea lice on salmon (salmo salar). veterinary record 140:179-181. hertog, m.g.l. and e.j.m. feskens. 1993. dietary antioxidant flavonoids and risk of coronary heart disease: the zutphen elderly study. lancet 342:10071011. magi, e., h. talvik, and t. jarvis. 2005. in vivo studies of the effect of medicinal herbs on the pig nodular worm (oesophagostomum spp.). helminthologia 42:67-69. martin, t., l. villaescusa, m. gasquet, f. delmas, c. bartolome, a.m. diaz-lanza, e. ollivier, and g. balansard. 1998. screening for protozoocidal activity of spanish plants. pharmaceutical biology 36:56-62. nijveldt, r.j., e. van nood, d.e.c. van hoorn, p.g. boelens, k. van norren, and van p.a.m. leeuwen. 2001. flavonoids: a review of probable mechanisms of action and potential applications. the american journal of clinical nutrition 74:418-425. park, i.k., j.y. park, k.s. choi, i.h. choi, c.s. kim, and s.c. shin. 2005. nematicidal activity of plant essential oils and components from garlic (allium sativum) and cinnamon (cinnamomum verum) oils against the pine wood nematode (bursaphelenchus xylophilus). nematology 7:764-774. remmal, a., t. bouchikhi, a. tantaoui-elaraki, and m. ettayebi. 1993. inhibition of antibacterial activity of essential oils by tween 80 and ethanol in liquid medium. journal de pharmacie de belgique 48:352356. roth, m. 2000. the availability and use of chemotherapeutic sea lice control products. contributions to zoology 69:109-118. roth, m., r.h. richards, and c. sommerville. 1993. current practices in the chemotherapeutic control of sea lice infestations in aquaculture a review. journal of fish diseases 16:1-26. veal, l. 1996. the potential effectiveness of essential oils as a treatment for head lice, pediculus humanus capitis. complementary therapies in nursing and midwifery 2: 97-101. the broth culture experiment, however, was significantly more sensitive in identifying bioflavonoids that exerted an effect on the different bacteria under test. therefore, future tests may use the agar diffusion assay as a pre-screening method to evaluate the general activity of potentially useful compounds. these should then be followed up using the broth culture method which appears to be more sensitive, thus providing more accurate data. crude extracts taken from garlic (allium sativum), cinnamon (cinnamomum verum), lime seed (citrus aurantiifolia), omija (maximowiczia typica), aniseed (pimpinella vulgare) and yucca (yucca spp.) and to a lesser extent common foxglove (digitalis purpurea) displayed broader antibacterial activity. most of these were effective only when used in their crude extracted form although lower concentrations of yucca (<5 %) appeared to effect growth. of these, garlic and its active components allicin and ajoene, is arguably the best known since it displays a broad spectrum of activity against a range of bacteria, viruses and parasites (ankri and mirelman, 1999; zenner et al., 2003; anthony et al., 2005; magi et al., 2005; park et al., 2005). similarly, cinnamon oil has been effectively used against, among others, intestinal flagellates and phthirapteran lice (veal, 1996; zenner et al., 2003; anthony et al., 2005). given that the agar diffusion trials have been successful in highlighting compounds which when tested further have been found to be efficacious, suggests that there is value in further evaluating the plants listed above shown to have a broad activity. the results from this study indicated that some of the compounds tested had potential antimicrobial activity by reducing bacterial growth. it is not intended that natural compounds replace the need for antibiotics to treat bacterial disease outbreaks. it may be that the role of the naturallyderived products could be a complementary addition to the existing health management practices applied within a wide range of fish-farming systems. the natural products may be able to lower the bacterial loading of opportunistic pathogens within the water column, thus reducing their ability to cause disease. this in turn could lower the prevalence and spread of opportunistic pathogens within the production system resulting in fewer applications of antibiotics. this study has demonstrated the efficacy of certain bioflavonoids against a range of bacteria commonly causing infections within fish in vitro, the next phase of research must focus on evaluating the efficacy of the best performing compounds in vivo. while the results from the agar diffusion tests and broth cultures provided an indication of effective doses of bioflavonoid, the minimum inhibitory concentration (mics) of the bioflavonoids in vitro may require a greater magnitude in diets (burt, 2004). references ankri, s. and d. mirelman. 1999. antimicrobial properties of allicin from garlic. microbes and infection 1:125-129. 50 ha yoon and others zenner, l., m.p. callait, c. granier, and c. chauve. 2003. in vitro effect of essential oils from cinnamomum aromaticum, citrus limon and allium sativum on two intestinal flagellates of poultry, tetratrichomonas gallinarum and histomonas meleagridis. parasite journal de la societe francaise de parasitologie 10: 153-157. received: may 26, 2010 accepted: september 19, 2010 img354 img355 img356 img357 img358 img359 img360 sultan qaboos university journal for scientific research agricultural and marine sciences, 11 s.i., 77-84 (2006) ©2006 sultan qaboos university 77 temporary water markets in oman slim zekri*, hemesiri kotagama and houcine boughanmi department of agricultural economics and rural studies college of agricultural and marine sciences sultan qaboos university p.o. box 34, al-khod 123, muscat, sultanate of oman abstract: market vis-à-vis command and control approaches have been widely adopted in natural resource and environmental management since the 1980s. adoption of markets in managing irrigation water resources is also emerging. it has been argued that markets are ineffective in managing the demand for irrigation water due to very low price elasticity. most studies have been based on mathematical models simulating water markets and not on observed prices and quantities in real water markets since such data are rarely available. in oman, perhaps in response to the extreme scarcity of water, elaborate water demand management institutions emulating markets have evolved and have been used for centuries. water entitlements are leased based on prices through a community auction. the traded quantities of water and related prices have been recorded. this study uses this unique data set to estimate the elasticity of irrigation water. a log function on quantity and price of irrigation water is used with dummy variables on time and type of irrigation system. the price elasticity varies from -0.10 to -0.28, depending on the specifications of the econometric model. these estimates are higher than most estimates reported in past studies,, indicating the efficacy of the indigenous market-based irrigation water management institution adopted in oman. keywords: water market, price elasticity, price analysis, falaj. introduction the advantage of market-based approaches in improving efficiency over command and control approaches in resource management has been theoretically established (randall, 1987). there is substantial literature evaluating the successes and failures of the adoption of market based policy instruments in natural resource management (sterner, * corresponding author. e-mail: slim@squ.edu.om أسواق میاه الري في سلطنة عمان سیري كوتاجاما وحسین البوغانميسلیم زكري و ھمسیري كوتاجاما وحسین البوغانميسلیم زكري و ھمسیري كوتاجاما وحسین البوغانمي الخالصة: منذ مطلع الثمانینات من القرن العشرین وقع اعتماد األسواق وسن القوانین والمراقبة إلدارة الموارد الطبیعیة والمشاكل البیئیة وبدأ كذلك اعتماد األسواق كأداة إلدارة المیاه في النمو. لقد اعتبر أن األسواق غیر فعالة للتصرف و إدارة میاه الري نظرا لضعف المرونة السعریة لطلب میاه الري. عدم توفر البیانات من أسواق المیاه جعل معظم الدراسات تركز على طرق غیر مباشرة لتقییم المرونة السعریة. شدة الجفاف في سلطنة عمان جعلت أسواق المیاه منتشرة ومزدھرة منذ عدة قرون، حیث أن حقوق المیاه یقع تبادلھا عن طریق المزایدة مرة في األسبوع في كل فلج ویتم تدوین كمیات المیاه المتبادلة واألسعار في دفتر المحاسبات. یرتكز ھذا البحث على دراسة وتحلیل أسعار میاه الري المتبادلة لتقییم مدى تفاعل المزارعین مع تغیر العرض وازدیاد األسعار باستعمال معادلة " اللوغریتم" بین كمیات المیاه واألسعار ومتغیرات نوعیة أخرى تأخذ بعین االعتبار الزمن ونظام الري. تظھر نتائج الدراسة أن مرونة األسعار تتراوح بین0.10 و 0.28 حسب تغییر طریقة التقییم. تعتبر ھذه النتائج أعلى من النتائج التي تم نشرھا في بحوث عالمیة متعددة وتدل على أن أسواق المیاه في سلطنة عمان فعالة. zekri, kotagama and boughanmi 78 2003). the choice of appropriate policy is dependent prmaily upon understanding potential policy response, which is empirically estimated as elasticity. since the early 1990s, market based volumetric pricing has been proposed to manage demand for irrigation water (de charlotte and perry, 2002; schoengold et al., 2005). water price would be an incentive for efficient use of water, to recover the cost of water supply and enable further investments. a primary requirement for water pricing, to induce water saving behavior, is that the price of irrigation water be sufficiently elastic to generate a response from water users. appels et al. (2004) provide a comprehensive review of other requirements for use of markets for irrigation demand management. there are several factors that may render the use of markets ineffective in water management such as high implementation costs, externalities, generation of inequities and social non-acceptance. it has been argued that water pricing is an ineffective means of managing water because elasticity (α) is low, due to the low substitutability of water in agriculture. it has also been found that α is low,low,low,, particularly at reduced water prices and where the cost for water is negligible (molle and turral, 2004). the α also depends on a host of other factors such as the mix of crops. the α is low in perennial cropping systems and tends to vary over space and time (appels et al., 2004). despite the policy significance and conceptual simplicity, there are few empirical studies that have estimated α (appels et al., 2004: schoengold et al., 2005). the major reason for the lack of such studies is due to the paucity of data on observed market prices and quantities of water traded (appels, 2004; brookshire et al., 2004). therefore, most studies have used simulated data in estimating α (appels, 2004; schoengold et al., 2005) and are not based on observed farmers’ behavior. appels et al. (2004) comprehensively reviewed studies undertaken between 1986 and 2004 on responsiveness of demand for irrigation water. all studies based on simulated prices obtained through mathematical models and water shadow prices rather than observed data on quantity and price of irrigation water. the estimated α, based on reviewed studies ranges from 0.00 to –3.80, with an extreme estimate of –14.10. the α is higher in the long run than the short run. further the α is low at low water prices and increases with increasing water prices. the α also varies depending on the type of function/model used in the estimation. schoengold et al. (2005), based on a panel study of water demand, have estimated the α as –0.40. it is claimed that this estimate is higher than most previous estimates, indicating the potential to use water pricing to manage irrigation water demand. this estimate of α is the same as residential water use elasticity. in a meta-analysis of residential water use elasticity was found to be –0.41 (dalhuisen et al., 2003). this study estimates the irrigation water demand elasticity based on market prices and quantities as observed in small community-managed irrigation systems in oman. the following section provides a brief description of the irrigation water management institutions in oman. the subsequent section presents the analytical methodology, followed by results. finally the implications of the results on the potential use of markets in managing water demand are discussed. water management institutions in oman oman relies on groundwater and desalinated water. desalinated water is used exclusively for urban and industrial purposes. of the ground water, 93% is used in the agricultural sector. water pumping through wells represents 67% while the traditional irrigation (aflaj, singula falaj) share is 33% of total groundwater use. this study is based on data collected from aflaj systems. aflaj irrigation systems are a long-established indigenous engineering method and a social heritage of oman. aflaj is a network of man-made underground galleries conveying groundwater to a community for domestic and irrigation uses. there are three aflaj types in oman. daudi aflaj are usually located in plains, derive water from alluvial aquifers and are characterized by relatively stable water flow rate throughout the year. ghaili aflaj involve a diversion of a quasi-perennial flow in the surface gravels of a wadi (river) into a channel (wilkinson, 1977); since these aflaj depend on water collected in pools that form in depression areas of wadis, they tend to dry up during drought years. finally, aini aflaj consist of one or more natural springs diverted through a channel (mrmew, 2002). this study is based on data collected from daudi and ghaili afalaj. the community has managed the aflaj for centuries. a general belief is that large numbers of temporary water markets in oman 79 small farmers may find it difficult to cooperate and manage irrigation systems successfully. the large number of small irrigated farms translates into high transaction costs precluding collective action. besides the transaction costs, difficulties arise in arriving at consensus-based decisions on water sharing too, due to the large number of farmers (shah et al., 2002). this problem of collective action is overcome in irrigation water management in oman by the falaj institution. two types of water rights prevail in the falaj; these are private rights and common rights. the private water rights are explicit rights with property licenses owned by individuals and recognized by courts. the common water rights are created by pooling together a set of private water rights based on a percentage of individual shares. these rights are mainly established to generate income for falaj maintenance and operating expenditures. the common water rights are auctioned weekly, semi-annually, or on an annual basis (zekri and al-marshudi, 2006). the income raised from the sale of common water rights finances the operating and management costs of the systems. the manager of the falaj is a person legally authorized to manage the affairs of the falaj’s commonly owned water rights. he is elected among the community of water rights’ owners. aflaj managers’ main roles are auctioning common water rights and deciding on expenditures on operation and maintenance of the falaj. he reports to falaj shareholders on returns and expenses on a yearly basis. in cases where water auction income does not cover operating and maintenance costs, shareholders pay the difference proportionately to the water rights owned. the manager receives 5 to 7% of water auction income for his services. farmers are price-takers and cannot strategically affect water market prices given the large number of farmers. a bidding process for common water rights generates a weekly water price. each water right is leased to the farmer offering the highest price. different water shares are auctioned, with a minimum timing for any share from half an hour up to six hours. the total shares offered for bidding add up to 24 hours. any farmer from the community can participate in the auction. prices are regularly registered in the falaj book. each water share is registered with its corresponding price and time-share. the ministry of regional municipalities, environment and water resources (mrmewr) monitored a sample of aflaj for water flow and quality. the availability of flow measures allow the transformation of time shares into volumetric measures (in cubic meters) which are used in this study. methods the prices and quantities of water auctioned weekly in four aflaj representing two falaj types over the years 1994 to 2003 were used in this study (table 1). the water quantities and prices are based on records maintained by aflaj managers and mrmewr. the four aflaj considered in this study are situated in the region of samail, in oman, within a radius of about 15 km. the same climate and soil type prevail in the area. average rainfall is 81 mm/year, occurring in the form of sparse and irregular winter storms that result in large run-off flows through wadi (rivers). most of the water infiltrates to the aquifers linked to the aflaj (al-qurashi, 2002). winter is mild with temperatures ranging from 15 to 28 °c. summer, lasting from april until mid of october, is hot with temperatures varying between 33 and 46 °c and humidity reaching up to 90% during summer. date palms are the major crop cultivated in the aflaj command areas. vegetables are intercropped under the palm trees during the winter season. the main vegetables cropped are tomato, cucumber, and lettuce. alfalfa and rhodes grass are also cultivated. table 1. summary of features of the aflaj studied. name of falaj type irrigated area ha average flow l/sec flow/irrigated area l/sec/ha period for which data is available al-farfara daudi 40.2 13 0.33 2001-2003 mehaidath daudi 28.4 106 3.72 1997-2003 al-balfai ghaili 17.1 32 1.87 1997-2003 al-samdi ghaili 80.0 74 0.94 1994-2003 zekri, kotagama and boughanmi 80 water demand functions have been generally estimated using linear, log-log or log-linear functional forms (hanemann, 1998; quoted by schoengold, 2005). the best fit for the data in this study was given by a log-log function. hence, elasticity was estimated using a log-log function of quantity and price as given below. estimations were made by adding control variables of the falaj (4 aflaj) and year (1994 to 2003) to represent space and time variations. ln qif = α if = α if 0 + α 1 ln pif + α if + α if 2 df + α f + α f 3 dy + eif where, qif = quantity of water auctioned (cubic meter x 100) at the ith auction and fth auction and fth auction and f falaj. pif = price of water at the i th auction and fth auction and fth auction and f falaj. df = dummy on 4 aflaj. dy = dummy on years. eif = error term of the i th auction and fth auction and fth auction and f falaj. α = intercept (α 0 ) and coefficients (α 1 … α 4 ) results figures 1(a) and 1(b) show the trends in quantity of water traded and the prices over years. the negative relationship between quantity of water traded and price is clearly observed. the quantity of water traded has decreased by 42% and water prices have increased by nearly 132% over the years of study. table 2 shows the average quantity of water traded weekly and the average price of the 4 aflaj and 2 aflaj types. the quantities supplied differ among falaj according to the falaj’s natural flow. the higher the flow the higher the quantity auctioned and supplied. the water trade consists of renting a 24 hours water time share owned by the falaj community on a weekly basis. thus the common water share leased represents 1 out of 7 days or 14.3% of total falaj water. the supply, in terms of time share, is thus fixed and does not vary from one week to another, except for variation due to the falaj’s flow. the prices of water are shown in column 4 of table 2 and are expressed in baisa/m3 as well as in $us/m3. on average, prices vary from a low of 5.27 baisa/m3 for mehaidath to 25.02 baisa/m3 for al-balfai. the average price for the four falaj is 17.59 baisas/m3 or us$ 0.046/m3. since the same climate, soil and socio-economic conditions prevail it table 2. statistics of quantities of water traded and prices by falaj and falaj types. falaj quantity of water auctioned and supplied weekly (m3) price of water baisa/m3 ($us/m3) mean standard deviation mean standard deviation al-farfara (n = 163) 1138 363 22.95 (0.060) 7.76 mehaidath (n = 324) 9753 3171 5.27 (0.014) 11.11 al-balfai (n = 294) 2694 1640 25.02 (0.065) 33.81 al samdi (n = 397) 5018 1754 19.97 (0.052) 33.19 daudi falaj type (n = 487) 6870 4826 11.19 (0.029) 13.11 ghaili falaj type (n = 691) 4041 2069 22.12 (0.058) 33.53 pooled (n=1179) 5208 375 17.59 (0.046) 27.54 note: 1 omani riyal = 1000 omani baisa = 2.6 us$. temporary water markets in oman 81 figure 1 (a). trend of quantity of water traded over time. figure 1 (b). trend of mean price over time. zekri, kotagama and boughanmi 82 table 3. estimates of water demand functions based on pooled data (4 falaj and over time 1994-2003). independent variable model 1 model 2 model 3 1. intercept 5.19 (89.65) 5.11 (47.28) 4.17 (47.81) 2. ln ptj -0.20 (-24.64) -0.28 (-22.45) -0.10 (-10.48) 3. falaj dummy (base is al-samdi) i. al-farfara -126.00 (-34.94) -1.11 (-30.42) ii. mehaidath 0.28 (8.66) 0.41 (12.16) iii. al-balfai -0.68 (-23.04) -0.74 (-25.58) 4. year dummy (base is year 2003) i. 1994 0.55 (5.07) 0.34 (4.93) ii. 1995 0.43 (4.79) 0.23 (3.77) iii. 1996 0.77 (7.14) 0.48 (6.99) iv. 1997 0.56 (6.76) 0.71 (13.23) v. 1998 0.61 (8.29) 0.65 (13.71) vi. 1999 0.54 (7.52) 0.56 (12.11) vii. 2000 0.42 (6.18) 0.40 (9.13) viii. 2001 0.36 (5.67) 0.45 (10.92) ix. 2002 0.19 (3.44) 0.20 (5.98) adjusted r2 0.80 0.55 0.84 note: the numbers within parenthesis are the t values. all the coefficients are significant at 95% level of confidence. the blanks indicate that the variable was not included in the model. is surprising to find a great difference in water price, particularly between mehaidath and the other 3 falaj. however, mehaidath has a substantially higher water flow/ha, which explains the low price. water prices should not converge, as there is no water transfer between aflaj, due to the absence of infrastructure for such a purpose. the estimates of the demand models based on 1179 observations of the pooled data (over years and the 4 falaj) are given in table 3. all the estimated models have reasonably high adjusted r2. model 3 has the highest r2 of 0.84 with all coefficients significant at 95% level of confidence. the signs of coefficients, particularly of the price variable, are consistent with expectations. the individual falaj has a significant impact on the quantity of water traded. it is also revealed that a significant difference exists in the quantity of water traded over years. the α1 temporary water markets in oman 83 ranges between -0.10 (model 3) and -0.28 (model 2). these estimates of α1 are consistent and fall within the range of estimates reported in previous studies; in congruence with schoengold et al. (2005), the α1 estimates in this study are reasonably high, though less than one. these estimates are high in relation to the expectation of low α1 estimates for perennial crops such as date palms. the present study indicates that water price could be used as a tool to manage irrigation water demand efficiently as farmers’ response to price is tangible. the traditional aflaj irrigation water management institution emulates markets effectively. it shows the possibility of using indigenous traditional institutions to meet present day expectations of using market-based approaches in irrigation water demand management. it also needs to be recognized that, even if the elasticity of demand is considered to be low, and given the high quantity of water used for agricultural purposes, the water savings will be substantial. the irrigation water prices in the study area have increased substantially in response to water supply decrease. such adjustments are made systematically via the market without the need for any government intervention. the water market prices are proving to be an excellent signal to farmers regarding the quantities leased. the development of institutions, such as defining water rights and introducing trading mechanisms to use the market processes, is generally difficult, since it may be costly and may not be socially accepted (de charlotte and perry, 2002). the advantage in oman is that such institutions are already in place and thus should be preserved and encouraged. conclusions since the 1980s there has been an interest in using market-based approaches to manage irrigation water demand. the feasibility of such an approach depends, among other factors, on the elasticity of water demand. it has generally been believed that the elasticity of water demand is very low, particularly at low water prices. few studies have empirically estimated the elasticity of water demand. these studies have mostly used simulated data to analyze (on an ex-ante basis) farmers’ reactions to changes in water prices. such models were used because of the lack of real observed prices and quantities in operational water markets. this study uses observed data on prices and quantities of aflaj irrigation systems in oman to estimate α1. the community, ingeniously emulating the markets, manages the aflaj irrigation systems. the water price elasticity estimated in this study was found to be within the range of previous studies and is reasonably high, despite the low water prices that had prevailed in the past and the cultivation of perennials. it also establishes the potential to use market-based approaches to manage demand for irrigation water. follow-up studies need to be done on the nature of adaptations at the farm level to increasing water prices over time, such as land use and cropping systems and technological adoption in the long run. references al-qurashi, a.m. 2002. effects of rainfall and wadi flows on aflaj. paper presented at the oman international conference on the development and management of water conveyance systems. ministry of regional municipalities, environment and water resources, 18-20 may 2002, muscat. sultanate of oman. pp 193-207. appels, d., d. robert and d. gavan. 2004. responsiveness of demand for irrigation water: a focus on the southern murray-darling basin. staff working paper, australian government, productivity commission. 82 pages. brookshire, d.s., b. colby, m. ewers and p.t. ganderston. 2004. market prices for water in the semi-arid west of the united states. water resources research 40:1-8. dalhuisen, j.m., r.j.g.m. florax, h.l.f. de groot and p. nijkamp. 2003. price elasticity of residential water demand: a meta analysis. land economics 79:292-308. de charlotte, f. and c. perry. 2002. why is irrigation water demand inelastic at low price ranges? paper presented at the conference on irrigation water policies: micro and macro considerations, international water management institute, agadir, morocco, 15-17 june 2002. pp 1-20. molle, f. and h. turral. 2004. demand management in a basin perspective: is the potential for water saving overestimated? paper presented at the international water demand management conference, dead sea, jordan, 30 may 3 june 2004. zekri, kotagama and boughanmi 84 mrmewr (ministry of regional municipalities, environment and water resources). 2002. aflaj in the sultanate of oman. international printing press, sultanate of oman. randall, a. 1987. resource economics: an economic approach to natural resource and environmental policy, second edition, john wiley and sons. schoengold, k., d.l. sunding and g. moreno. 2005. panel estimation of an agricultural water demand function, http://are.berkeley.edu/-sunding/ workingpapers/water. pp 1-23. shah, t., b.v. koppen, d. merry, m. lange and m. samad. 2002. institutional alternatives in african smallholder irrigation: lessons from international experience with irrigation management transfer. iwmi, research report no. 60. sterner, t. 2003. policy instruments for environmental and natural resource management. resources for the future. the world bank, swedish international development cooperation agency. wilkinson, j.c. 1977. water and tribal settlement in southeast arabia. oxford research studies in geography,geography,geographygeography . clarendon press. oxford. zekri, s. and a. al-marshudi. 2006. a millenarian water rights system and water markets in oman. wsta seventh gulf water conference, 19-23 november 2005. water international (under review). img021 img022 img023 pdf995, job 6 ______________ *corresponding author. 53 !"#$%&'()!*+&%,&!-./$!0123&4567!489!1#:)! !"#$%&'()*+,-(./01(2+%3,-(!"4(.567( ! !1;;<=>(8((((9'1":;(<0"$/'+;(=>? %/'1(9!1*"1(#*.$(.$-(+%&!1*1(&$/'(=7+6(;(1.6.%'(+&'1>%)1(*+,1"'-./(0,-(*+%14(2"&$,( 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((((((((((((((((((2"8'1(f"%8,(g$a(<67++s%$1(>&+;1.'(:+x1(g+$a((&+i>%'1(g+'q(9+w+/'1(h"+:$'(.(<_>4/'1(d&#`'(<3$+n,(+k65(c/'(.$((((((((((((((((((v&:,(9_(2+/a(<n`$)(g$a(+&'1>%)1(9_(9!1*"1(&$/'(=*17q(r,+e>;(?6x(0,(<#8%1/'1(<&e1.&/'1-(<&/$4'1(#1>#+z'1(<0"$/'1(<$13,.( agricultural sciences, 7(2):53-60 (2002) © 2002 sultan qaboos university landscape salinisation and management: an australian perspective d. hoey 1*, m. ahmed 2, m. littleboy 3 1department of land and water conservation, po box 2185, dangar, nsw, 2309 australia 2department of soil and water sciences, sultan qaboos university, al-khod 123, po box 34, sultanate of oman 3department of land and water conservation, po box 189, queanbeyan, nsw, 2620 australia abstract: australian landscapes are facing an increasing salinisation threat. it is estimated that 2.5 million hectares are affected by land salinisation, and this area is expected to triple by 2050. federal and state governments have jointly developed a policy framework to address this issue, with each state refining their own salinity management strategies within this framework. scientific assessment and modelling underpin these salinity management strategies, though socio-economic considerations are also important. landscape salinity assessment techniques used in the australian context are outlined, and examples of salinity hazard and recharge mapping at the landscape scale described. current developments in both recharge assessment, and groundwater flow modelling in australia are described, and the use of these models in underpinning state salinity strategic planning discussed. the salinity management ‘toolkit’ is discussed. the progression from initially applying engineering solutions to deal with the symptoms of salinisation; to dealing with the causes of salinisation; to developing an integrated catchment management approach; to including a stronger emphasis on market-based economic measures; and the importance of over-arching catchment blueprints, is described in detail.the application of knowledge and experience gained through the management of australian land salinisation to other countries is discussed in the context of the salinity problem in the sultanate of oman. keywords: salinisation, recharge, australia, integrated catchment management, mdbc, lwmp, flowtube, hydrological modeling, evaporation basin, desalination, batinah, salinity strategy. ustralia has critical salinity and water quality problems demanding urgent attention. it is estimated that 2.5 million hectares are affected by land salinisation (agriculture, fisheries and forestry – australia. 2002) and this area is expected to triple by 2050. this applies to all states of the commonwealth. in western australia 1.8 million hectares are affected at present, and this could double within 20 years (and a hoey, ahmed, and littleboy 54 double again before equilibrium is reached), and over half the state’s surface water is already saline, brackish or of marginal quality. in south australia, all agricultural district show some degree of dryland salinity, and at least 20% of surface water resources are above desirable salinity limits for human consumption. in victoria, there are extensive impacts in western and central regions. in new south wales and the act, as much as 7.5 million hectares could be affected in the future as groundwater rises. even in relatively less intense areas such as queensland severe salting affects 10,000 hectares, and in tasmania, about 18,000 hectares (two percent of cleared agricultural land) is affected by salinity (csiro, 2002). one third of australian rivers are in extremely poor condition, partly attributable to increasing salinisation. salinity also affects urban areas, with infrastructure (mainly buildings and roads) being severely damaged in a number of urban centres. salinisation costs are significant, and this is expected to increase considerably in the future. while some actions have been developed across the country in response to local problems, it has been widely recognised that a co-ordinated approach to dealing with salinity is required. accordingly, a national action plan for salinity and water quality has been developed by the australian federal and state governments to address this issue. natural resource management is a state responsibility in australia, and each state has also developed its own salinity management strategies within this framework. this paper will draw on the large amount of work that has been done to date in dealing with salinisation across australia. scientific assessment and modelling approaches will be briefly outlined, and approaches to salinity management will be described. the murray region land and water management plans provide an example of how a range of salinity control measures can be integrated through community action. the hunter saline water remediation project demonstrates technology working within a policy framework that encourages to innovation. salinity assessment and modelling salinity mapping techniques can be divided into direct measurement of salinity outbreaks; indirect measurement; modelled (current) outbreaks; modelling of future areas at risk generated by salinity hazard assessment; and use of process models to predict future outbreaks (please et al., 2002). direct salinity assessment, based on aerial photograph or satellite imagery interpretation and soil landscape mapping in the field, is the basis for most salinity assessment. while field assessment is considered most reliable (depending on the soil surveyors skills), it is time consuming, and there is only limited coverage of soil landscape maps across the country. indirect assessment using a range of geophysical techniques, such as radiometrics, electromagnetic induction and magnetics, can cover larger areas more quickly, but still require calibration. the signal from electromagnetic induction, for example, is a function of salinity, moisture content, soil mineralogy (williams and hoey, 1987) at a depth which depends on induction coil orientation. gamma ray spectrometry measures the natural radiation from potassium, thorium and uranium in the upper 30 cm of the soil surface (wilford et al., 2001) is used for regolith mapping. again, large areas can be covered relatively cheaply, but ground truthing is required for calibration and verification (george et al., 1998). terrain-based models and their derivatives, such as fuzzy landscape analysis using gis (flag) (summerell et al., 2001) use topographical information to predict where water will accumulate across the landscape (areas of ‘wetness’ and ‘dryness’). this has been used in nsw to predict salt discharge areas. it can be quite effective in undulating country, but has limited value in flat terrain. determining areas at risk from salinisation (‘salt hazard maps’) are being used increasingly in planning at the catchment scale. before the widespread use of geographical information systems (gis), shaw et al. (1986) listed criteria indicating ‘intake areas’ for land susceptible to salting in queensland. these indicators were based on vegetation types, geomorphology, geology, soil, and landholder information. this approach has been further developed as information technology has improved. for example, salinity ‘indicators’ (such as groundwater salinity) have been used to predict relative salinity hazard for the northern territory (ticknell, 1994) and gis and expert systems have been applied to predict recharge and discharge areas in a small catchment in south australia (kirkby and kurzel, 1993). geology, soils, rainfall, vegetation, groundwater and landform information were used at 1:2,500,000 scale, with a ‘weights of evidence’ approach to determining salinity hazard across nsw (bradd and gates, 1996). this was based on comparing attributes such as geology and slope (the ‘predictor’ variables) with a ‘response’ map (the dryland salinity occurrence map). weights were then calculated, by statistical bestfit, for each selected attribute. each weighted attribute was then overlain on the gis, to predict broad-scale salinity hazard assessment across the state. a similar approach has been used in southeast queensland, where 13 natural resource information landscape salinisation and management: an australian perspective 55 layers were combined using an additive, weighted model to assess salinity hazard for 100m grid cells (searle and baillie, 1998). the separate data layers were individually weighted based on knowledge of salinity processes, then combined using arc/info, and validated against community-derived ‘saltwatch’ data. humphries (2000) used a lumped parameter model to assess salinity hazard for each sub-catchment within the bogan-castlereagh catchment (nsw) in effect producing 37 irregularly shaped cells (subcatchments), with a single output for each cell. this approach is being developed to produce recharge maps of new south wales by linking existing biophysical simulation modelling with statewide data sets of soils, climate, land use and topography. the data used to compile these maps will be dependent on simulation modelling. however, there has been little quantitative validation in the nsw environment, though detailed recharge validation is now in progress at four sites across nsw. however, a review of 36 models used in australia for catchment modelling (marston et al., 2002) concluded that there was little standardisation of model development. similar conclusions led the murraydarling basin commission to produce a ‘best practice’ guideline for groundwater flow modelling (middlemis et al., 2001). a review of models used in land and water management plans (lwmp) (milner and woolley, 1999) noted problems in integration of surface water and groundwater (and different aquifer systems), extent of available data, and relevance of timesteps used. however, models still provide a valuable means of assessing a range of management scenarios, and there is a current emphasis on integrating a range of models to examine not only the environmental effects of hydrologic change, but also socio-economic issues. economic models have been developed, and linked into hydrologic process models to attempt to integrate salinity management measures. for example, apsim was used to provide estimates of recharge and runoff. flowtube used this as input to calculate hydrological and salinity implications, and smac, an economic model, was used to fine-tune land-use and farm income estimates (evans, 1998). catchment scale hydrological modelling is essential to give spatial expression to optimisation results, including areas for implementing recommended land use changes. engineering solutions engineering solutions focus on reclamation of saline or poorly drained areas. horizontal drainage techniques include: large scale landforming; shallow open drains (on poorly drained flat heavy clays); deep open drains on more permeable soils; shallow mole drains (with or without perforated plastic liners); tile drainage (to depths of 2 metres); and deep ‘agpipe’ drainage (up to 3 metres depth). vertical drainage configurations include: single wells (‘tubewells’, and ‘production wells’); multiple single wells as part of a well field; spearpoints (multiple wells connected by a common header line); relief wells (which rely on artesian or sub-artesian pressure to ‘bleed’ the aquifer); and airlift pumping (particularly useful for low yield aquifers and highly aggressive saline water). engineering solutions generally produce saline effluent, which needs to be managed. approaches have included: controlled (and uncontrolled) discharges to rivers or wetlands (which will often have environmental and economic consequences); using receiving waters to dilute discharges to acceptable limits; use of innovations such as serial biological concentration (to irrigate progressively salt tolerant crops and trees); and detention and evaporation basins. evaporation basins themselves may require a range of engineering solutions to control seepage. saline effluent is often considered a pollutant or waste. however, changing the paradigm to ‘saline resource’ opens up a number of opportunities to recover some of the costs in dealing with ‘reject brines’ (ahmed et al., 2000). opus, the ‘options for productive use of salinity’ database (ndsp, 2001) provides a number of contact points for use of saline effluent in agriculture, forestry, fauna and algae production minerals and energy production. in nsw, this has been applied by department of state and regional development to facilitate business opportunities (department of state and regional development, 2002). the involvement of this department highlights the importance of integrating engineering and socio-economic considerations. engineering solutions can also be used in a preventative manner. examples include seepage control along irrigation supply channels, by channel lining or using techniques such as bentonite grout curtains. there is also considerable interest in piping irrigation water supplies to reduce seepage. engineering options such as desalination of both water supplies, and drainage water is also being seriously re-examined, due to improvements in technology and the increasing value of water. a review of over 200 examples of engineering approaches to dealing with dryland salinity (sinclair knight mertz, 2001) noted recurring problems of effluent disposal, poor economics and funding difficulties, technical difficulties, and ‘negative perceptions of the engineering option’. however, the hoey, ahmed, and littleboy 56 ‘social issues’ are also important. successful implementation of schemes depends on getting the support of all stakeholders (particularly local landholders adjacent to disposal areas). it is precisely the potential lack of support by a range of beneficiaries that led to a broadening of the engineering approach, to also include non-engineering solutions. non-engineering solutions some of these issues associated with engineering solutions (notably cost, ownership, and effluent disposal) have led planners to focus more on dealing with the causes, rather than the symptoms, of salinisation. the nsw salinity strategy (nsw government, 2000) takes this broader view by focusing on eight key tools for salinity management. these involve setting end-of-valley salinity targets (to force an outcome-based focus on salinity control and address the drainage discharge issue), and developing marketbased solutions and ‘environmental services investment’. it also includes promotion of business opportunities (such as commercial salt production), better-targeted government regulations and advice. improving information systems (such as improving community access to government salinity assessments) is linked to the scientific knowledge program. finally, planning systems at the catchment level aim to integrate salinity management and other natural resource issues. in nsw, integration and direction is provided by catchment blueprints. these are drafted by the community, through catchment management boards made up of natural resources users, primary producers, conservation representatives, local government, indigenous representatives and state government agencies. catchment management boards operate using a collaborative community/government partnership, using a ‘consensus’ approach to decisionmaking, rather than “majority voting” to make joint decision. they advise the minister for land and water conservation as to appropriate natural resource management targets for their catchment. this represents a significant change of approach, from government driven reclamation and remediation, to government providing a more supportive role for regional communities to lead change themselves. the establishment of the cooperative research centre for plant based solutions to dryland salinity in 2001 has provided a focus for research into the use of vegetation for recharge management on a catchment scale, as well as looking at the social and economic impacts of changing farming systems (walker et al., 1999 and stirzaker et al., 2000). market-based measures include assigning property rights, taxes and fines (and their counterparts incentives and subsidies) (economic and social commission for asia and the pacific, 1998) property rights already exist for land and water, but are now also being developed for ‘pollutant rights’ such as salinity credits and ‘green offsets’. the hunter river salinity trading scheme has developed from load-based licensing concepts and tradeable property rights to become an effective means of lowering river salinity, while still allowing some saline discharge. it is underpinned by transparency and currency of information (usually real-time due to extensive telemetry systems which is provided by government, but paid for (on a user-pay basis) by industry). catchment blueprints are the primary integrating mechanism for all natural resource planning for investment in a broad range of management actions in each catchment, over a ten year planning horizon. they set overarching natural resource priorities for the catchment, and provide direction and investment guidance. components include water management plans and regional vegetation management plans. case study – murray land and water management plans examination of a productive agricultural area which has been affected by salinity and drainage shows how both engineering and non-engineering solutions can be combined to tackle these problems. the murray irrigation districts consist of 750,000 hectares of government-sponsored irrigation (now privately operated) located north of the murray river and centred on the town of deniliquin. deniliquin is approximately 300 km north of melbourne, and 700 km west of sydney. the districts cover a range of soil types, ranging from well draining sandy soils to poorly draining heavy clays. average rainfall is 400 mm/yr, with average evaporation rate of 1500 mm/yr. the 2300 farm holdings which make up murray irrigation limited generally use a total of about 1.6 gl/yr of irrigation water, mainly for pasture for livestock, and rice. irrigation has increased the hydraulic loading on the landscape, not only in the direct application of irrigation to crops, but also through the impact of clearing native deep rooting vegetation for farm layout, and the associated irrigation infrastructure. the 3000 km of supply channels crossing the landscape can interfere with the limited natural drainage that exists in such a flat (1:2000 grade) area, and roads and other development all contribute to a disrupted natural drainage system. landscape salinisation and management: an australian perspective 57 the geomorphic characteristics of the region compound these problems. the districts are part of a large alluvial plain and are underlain by a number of aquifer systems which strongly influence surface conditions. within 20 years of irrigation commencing at wakool, waterlogging and salinisation had become significant in the district. the problem was further compounded by high groundwater salinity (averaging 30 ds/m), and the fact that the shallow aquifers are affected to some extent by high piezometric levels in the deeper formations. salinity and waterlogging affect landholders directly by reducing agricultural productivity. it also indirectly impacts on infrastructure (e.g. road damage repair) and on downstream communities, through additional salt and nutrient loading in natural streams. engineering solutions were originally developed to deal with these problems, with government sponsored surface drainage and subsurface drainage works installed. to a large extent, this provided an expensive means of maintaining the agricultural status quo, as landholders continued with the same agricultural practices which contributed to causing the initial problem. it was soon realised, however, that engineering solutions had to be combined with on-farm management and landuse change, and a reassessment of institutional arrangements (e.g. water pricing structures, water transferability, etc.) to be fully effective, and encourage a strong land stewardship ethos. this led to the development of integrated land and water management plans (lwmp) (berriquin land and water management plan working group, 1995; denimein lwmp working group, 1995; cadell land and water management plan working group, 1995; and wakool land and water management plan working group, 1995), with its strong emphasis on community involvement and a more holistic view to landscape management (murray and murrumbidgee catchment management committees, undated and murray and murrumbidgee catchment management committees, 1993). while initially based on salinity and drainage control, the plans have developed a much wider charter. the objective of the berriquin plan is ‘to manage land salinity, high watertables and waterlogging in the berriquin irrigation district in order to ensure the social well being, agricultural productivity and environmental sustainability of the district’. the wakool plan’s aim is simply ‘to make our community a better place to live by improving the management of our natural resources’. these visions of the future were developed through extensive consultation with all stakeholders. the extent of the problem is considered and recognised by the community, with background reports commissioned. community-based committees then oversight investigations by technical staff in both government and private agencies, following an investigation and implementation project plan they have helped develop. technical groups periodically report to the community groups. this allows integration of each option as it is developed, usually after lengthy debate. for berriquin, options were based on surface drainage, sub-surface drainage, on-farm works, infrastructure development and institutional arrangements, formally linked by economic, environmental and hydrologic modelling, but linked by provision of progress reports to the berriquin steering committee. however, each district is different, and so each land and water management plan has developed its own distinctive characteristics. this is crucial in retaining relevance to the community particularly important as these plans will be setting the environmental agenda for the next 30-40 years. over the last few years, a dramatic shift in community involvement in decision-making in natural resource management issues has occurred. in the murray irrigation districts, major salinity and drainage problems, and social issues such as privatisation forced the issue, but the district land and water management plans became a major vehicle for change. case study – hunter regional groundwater management for salinity control the hunter catchment is located north of sydney. the valley is an important agricultural, mining and industrial centre for nsw. salinity has been recognised as a significant land degradation issue: mapping within the hunter catchment indicates that 25,000 hectares are affected by land salinisation (thomas, 2000). a recent salinity audit (beale et al., 2001) noted the increasing trend of groundwater levels across the catchment, and the impact this will have on future river salinity hunter river salinity. this has important implications for both agriculture and industry in the region. part of the river salinity issue is addressed by the hunter river salinity trading scheme (hrsts) (environmental protection authority, 1994). this combines load based licensing concepts with tradeable pollution rights which can be accessed under certain river flow conditions. under this scheme, approximately 11,000 tonnes of salt have been discharged each year since 1995 while still keeping hunter river salinity below set targets. twenty coalmines and two power stations are currently participating in the hrsts. proposed changes to the hrsts will reduce the window of opportunity for hoey, ahmed, and littleboy 58 discharges, and require greater on-site storage of saline water (or greater trading). however, most of the salt content in the hunter river is due to diffuse sources. one way of dealing with this is to develop regional-scale groundwater management schemes to control saline groundwater. control sites can be optimised using groundwater models, but disposal of saline groundwater will continue to be an issue. while controlled river disposal has been considered ‘best practice’ in the past, improvements in technology, changing economic and social values, and the development of a more flexible institutional framework have created new opportunities for dealing with salinity. given that average groundwater salinity is only around 5ds/m, desalination begins to look attractive particularly where high-value uses for desalinated water produced are located close to the desalination site, and desalination is linked with a process for recovering resources from the saline concentrate. desalination coupled with resource recovery from saline effluent has been successfully tried in urban salinity control at two sites in nsw, and this approach may also be applicable on a larger scale in the hunter, if the desalinated water and the salts produced can be utilised locally. this is particularly so if local synergies can be further developed through regional industrial and agricultural development. this is currently being investigated, requiring further assessment and modelling, then linking with market forces for water and salinity credit trading and for salt products. it will also require strong community consultation, a detailed benefit-cost assessment of the project, and a partnership between government, industry and researchers to encourage innovation in creating opportunities from problems. land salinisation in oman and the application of australian experience for its management land salinisation is a serious problem in oman especially in the batinah coastal plain. this is the most important agricultural study region encompassing 80,000 ha of cultivated land (cookson and lepiece, 2001). a ministry of agriculture and fisheries study (maf, 1993) conducted in south batinah concluded that 50% of the cultivated land could be classified as saline (from slightly to extremely saline). the cause of soil salinity in batinah can be directly attributed to high levels of salt in irrigation water. groundwater is used for irrigation and without irrigation cultivation is not possible as average rainfall is less than 125 mm/yr and potential annual evapo-transpiration is twenty times higher. saline water intrusion in coastal aquifers supplying irrigation water has resulted in elevated levels of salinity in groundwater. saline water intrusion is the result of the farmers abstracting groundwater at rates much higher than annual groundwater recharge. efforts have been made to combat soil salinity in batinah. individual as well as comprehensive wellplanned government efforts have been made. government actions, reflecting the recommendations contained in the south batinah integrated study (maf, 1993) include controlling digging of new wells and rehabilitation of older wells, construction of recharge dams, reduction of cultivated land, and developing incentives for modern irrigation systems. the main effort has been to reduce water abstraction to maintain overall water balance in the aquifers supplying irrigation water so as to prevent further saline water intrusion. government efforts have been made with a view to making farming environmentally sustainable, economically viable and socially sustainable. in the absence of any comprehensive evaluation, it is difficult to say whether government efforts have made any significant gain to combat soil salinity. there are similarities between the salinity situation in oman and australia. agricultural practices have resulted in soil salinity, salinity has caused severe hardships for farmers, and the process has been relatively rapid (very fertile land becoming saline within a span of 10-20 years). however, there are also dissimilarities. these include physical drivers (elevated groundwater level is the main reason for salinity in australia whereas in oman it is due to application of saline groundwater) as well as social elements. the latter include the small size of omani farms compared to australian farms, and large differences with regards to application of modern technology in farming, economic and educational levels of farmers. the presence of large number of non-arabic speaking expatriate farm workers in oman is also different to rural australia (which tends to have fairly homogeneous social groups), and has important implications for communication and technology transfer. the land and water management plan concept applied in australia could be a useful model for managing soil salinity in oman if it is adjusted to meet local requirements for socio-economic and cultural reasons. in such plans, scientific assessments and modelling, linked to socio-economic considerations, are the basis for developing salinity management strategies for long-term environmental sustainability. partnership between government and private enterprise underpins these plans. lessons learned in australia with regards to development and implementation of land and water management plans could bring large benefits to the farmers in batinah. ‘technology transfer’ and scientific landscape salinisation and management: an australian perspective 59 exchange would be a valuable first step in this process. this is not to say that the land and water management process has all the answers by any means. the process of development and implementation of the plans in australia was relatively long, and testament to the difficulties encountered. however, it is certainly worth investigating as to whether such an approach is indeed suitable for oman. conclusions landscape salinisation is an increasing problem in australia. different salinity assessment techniques have been developed, with varying degrees of cost, accuracy and repeatability. the use of geophysical techniques such as electromagnetic induction, radiometrics and magnetics has improved coverage and cost-effectiveness, but must always be validated on the ground. rapid developments in information technology have blurred the boundary between assessment and modelling, and assisted scenario testing for salinity management at the catchment scale. a range of non-engineering measures now complement the more ‘traditional ‘engineering solutions such as surface and sub surface drainage. policy initiatives such as the nsw salinity strategy, catchment blueprints, and close involvement of affected communities help ensure the integration of these measures. in fact, the biggest challenge is not necessarily in technology, but in the integration of all elements (including issues of socio-economic change) to ensure long-term environmental and economic sustainability. the salinity problem continues to grow in australia, but much has been learned, and this is reflected in the increasing integration of measures used, and the strong partnerships that are being developed to address this problem. references agriculture, fisheries and forestry – australia. 2002. national action plan for salinity and water quality http://www.napswq.gov.au/publications/vital_resources,html [accessed 12/9/02]. ahmed, m., a. arakel, d. hoey, and m. coleman. 2000. integrated power, water and salt generation: a discussion paper. desalination 134 (2001):37-45 beale, g., r. gilmore, m. simmons, s. realica, and n. nandakumar. 2001. nsw coastal rivers salinity audit: predictions for the hunter valley, dlwc, oct 2001. berriquin land and water management plan working group, 1995. berriquin land and water management plan. echuca december 1995 bradd, j. and g. gates. 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variability of the salt and clay contents of soils. australian journal of soil research 1987, 25, 21-27. _________________________________________________ received august 2002. accepted november 2002. agricultural and marine sciences, 16:75-81 (2011) ©2011 sultan qaboos university 75 رافع محمد طاهر خليل الصفات اإلنتاجية و للذبائح الكيميائي التركيب بني العالقة احمللي الرومي الدجاج في العراق املوصل/ جامعة والغابات/ الزراعة كلية احليوانية/ الثروة قسم على تغذيتها بعد احمللي الرومي للدجاج اإلنتاجية والصفات للذبائح الكيميائي التركيب ما بني عالقة إليجاد الدراسة هذه أجريت امللخص: فردية أقفاص في وتربيتها اإلناث عن الذكور فصل مت أسابيع ٨ عمر عند كالوري/كغم. و٢٩٥٠ كيلو ٣٠,٢٪بروتني على حتتوي بادئ عليقة الرطوبة (نسبة للذبيحة الكيميائي للتركيب التنبؤ معادالت إليجاد للذبائح الكيمياوي التحليل وإجراء الطيور ذبح مت أسبوع. ١٦ عمر لغاية عند النهائي اجلسم ووزن (غم) أسابيع ٨ عمر عند االبتدائي اجلسم وزن مثل اإلنتاجية الصفات بعض من بيانات الدهن) البروتني ، ، ،الرماد اليومي البروتني واستهالك الغذائي التحويل وكفاءة اليومي(غم) العلف استهالك و (غم) اليومية الوزنية والزيادة (غم) أسبوع عمر١٦ بني والدهن، البروتني نسبة وكل من الرطوبة بني نسبة معنوي ارتباط وجود النتائج أظهرت التصافي٪. ونسبة البروتني حتويل وكفاءة (غم) التصافي، ونسبة والدهن والرماد الرطوبة نسبة وكل من البروتني نسبة بني التصافي، ونسبة والدهن البروتني من نسبة الرماد وكل نسبة البروتني حتويل وكفاءة الغذائي التحويل وكفاءة احلي اجلسم ووزن البروتني ونسبة الرماد ونسبة الرطوبة نسبة من وكل الدهن بني نسبة على تعتمد الرطوبة لنسبة التنبؤ معادلة بان الدراسة هذه أظهرت التنبؤ، ملعادالت التحديد معامل صغر من التصافي.بالرغم ونسبة التصافي نسبة على ونسبة الدهن تعتمد ونسبة البروتني الرماد نسبة من التنبؤ لكل معادلة بينما الغذائي، التحويل .كفاءة التنبؤية ،املعادالت اإلنتاجية الصفات التركيب الكيميائي، احمللي، الرومي الكلمات:الدجاج .مفاتيح relationship between body composition and performance of local turkey rafh mohammed taher khuleel animal resources department, faculty of agriculture and forestry university of mosul, republic of iraq abstract: this study examined the relationship between carcass composition and performance traits of local turkey fed starter diet (30.2% protein, 2950 kcal/kg me). at 8 week of age, male and female chicks were separated and reared in individual cages until 16 weeks of age. at the end of the experiment, the birds were slaughtered and carcasses were analyzed for chemical composition to predict chemical composition (moisture, ash, protein and fat) from performance traits such as initial body weight (g) at 8wk, final live body weight (g) at 16wk, daily weight gain (g), daily feed intake (g), feed conversion ratio, daily protein intake (g), protein conversion ratio, dressing-out percentage. there were significant correlations between moisture, protein and fat; between ash, protein, fat and dressing-out percentage; between protein, fat and dressing-out percentage; between fat, moisture, ash, protein, live body weight, feed conversion ratio, protein conversion ratio and dressing-out percentage. although the coefficient of correlation (r2) for prediction equations was not high, the moisture content equation depends on feed conversion ratio while for ash, protein and fat depends on dressing-out percentage. املقدمة املواد حتويل في العالية ذات الكفاءة احليوانات الدواجن من تعتبر طيور الرومي وتربى قيمة غذائية عالية. ذات إلى حلوم العلفية مجد غير يعتبر البيض من إنتاجها أن حيث اللحم إلنتاج أساسا كبيض الستهالكه اقتصاديا بني أن العالقة إلى ( de وآخرون (2003 lange وقد أشار مائدة. اللحم حليوانات الكيميائي التركيب و املستهلكة الغذائية العناصر ولغرض والعوامل الوراثية. والبيئة التغذية عوامل منها بعدة تتأثر هذه من متثيل البد احليوانات وإنتاجية نوعية اللحوم في التحكم حسابية. معادالت العالقة في key words: local turkey, chemical composition, productive traits, prediction equations. __________________________ e-mail: rafh_moh@yahoo.com 76 بئذخ ف ٙ ر ٛ ٛى ان ًٛ خ ان زائٛ خ ف ٙ انؾٕٛاَ بد ؿشٚ خ انكًٛٛبئٙٚذذ انزؾهٛم ٔثغجت أٌ انـ ش انكًٛٛبئٛ خ انًزجذ خ يض م ؿشٚ خ .انضساعٛخ ٔيُٓب انذٔاعٍ كه ذال نز ذٚش انج شٔرٍٛ ٔانغٕكغ هٛذ نز ذٚش ان ذٍْ رؾز بط إن ٗ انكضٛ ش ي ٍ يً ب رُ زظ عُٓ ب ئٛخانغٓذ ٔانٕقذ إػبفخ إنٗ أَٓب رغزهضو اعزخذاو يٕاد كًٛٛب ٔ يؾ بٔالد عذٚ ذح الع زُجبؽ ؿ ش أع ٓم دف ذ ع ش ،غ بصاد ع بيخ أثخ شح and اع زخذو ٔ .( 1995ٔآخشٌٔ eduardo)انكًٛٛبئٙ نز ذٚش انزشكٛت pesti bakalli (1997 ) ( ان ٕصٌ انُ ٕعٙ نه زثبئؼspecific gravity ) ( 1972)ٔآخشٌٔ jacksonاعزخذو كًب ، نٓب انكًٛٛبئٙنهزُجؤ ثبنزشكٛت نهزثٛؾ خ ؽٛ ش ٔع ذ أٌ انكًٛٛ بئٙ انخـ ٙ انًزذ ذد نهزُج ؤ ثبنزشكٛ تاالَؾ ذاس ك بٌ غٛ ش كبفٛ ب ٔأٌ إػ بفخ َغ جخ انشؿٕث خ ف ٙ انزثٛؾ خ إن ٗ رشكٛ ت انذهٛ خ eitan and suller ٔق ذ رك ش . ٚؾغٍ يٍ دقخ انزُج ؤ انؾغبثٛخانًذبدالد (1985 ) ٍ ب أي .أٌ ُْب عالقخ قٕٚخ ثٍٛ انضٚ بدح ف ٙ ان ٕصٌ ٔرشع ٛت ان ذْ kubena ٌٔأٌ صٚبدح اعزٓال انجشٔرٍٛ ٚ ؤد٘ ٔاف ذ ركش( 1972 )ٔآخش إن ٗ صٚ بدح اجَغ غخ انذؼ هٛخ ثًُٛ ب صٚ بدح اع زٓال انـبق خ ٚ ؤد٘ إن ٗ صٚ بدح خبط خ ،ٚز ثصش أٚؼ ب ثو شٔل انجٛئ خ انكًٛٛ بئٙ ٌ انزشكٛتأٔ ،رشعٛت انذٍْ ش ي ٍ رغ زخذو َغ جخ اكج سدانج ب ـ ظ دسعخ انؾشاسح ؽٛ ش أٌ انـٛ ٕس ف ٙ ان ٍ johnson أي ب . انـبق خ نزذفئ خ انغغ ى ٔرشع ت َغ جخ أق م ي ٍ ان ذْ farrell and (1988 ) انشؿٕث خ أَ ّ ًٚك ٍ انزُج ؤ ثُغ جخ اف ذ ٔع ذ إن ٗ أَ ّ ( 2002)ٔآخ شٌٔ etis, ثًُٛ ب أ بس ٔانج شٔرٍٛ ي ٍ ٔصٌ انغغ ى ًٚك ٍ انزُج ؤ ثُغ جخ انج شٔرٍٛ ٔان ذٍْ انًزشع ت ي ٍ اع زٓال انج شٔرٍٛ % ي ٍ 20ـ 15أٌ ارك ش ف ذ ( kiraz and ) sensül 2005 قخ أيبٔانـب % ف ٙ 15انٕصٌ انكهٙ فٙ فشٔط انهؾى ْٕ عجبسح ع ٍ دْ ٌٕ رز ٕصع ثُغ جخ ٔ .ٔانغه ذ ٔانذؼ الداجؽش بء انذاخهٛ خ % ف ٙ ث ٛ خ اجعؼ بء يض م 85ان ذو إن ٗ أَ ّ ًٚك ٍ ر ذٚش كًٛ بد انج شٔرٍٛ ( 1972)ٔآخ شٌٔ veluٔقذ أ بس chambers andرك ش ، كً ب نزثٛؾ خ ي ٍ يؾز ٕٖ انشؿٕث خ ٔان ذٍْ ف ٙ ا fortin(1984 ) ٍ ًْٚك ٍ أٌ اجؽش بء انذاخهٛ خ انزثٛؾ خ ٔدْ ٍ أٌ أٔصاٌ د .نهغغى انكًٛٛبئٙهزشكٛت عٛذح ن إيكبَٛخ انزُجؤ ثظٕسحرذـٙ نهغغ ى ف ٙ ئٙٚٓذل ْزا انجؾش إن ٗ دساع خ إيكبَٛ خ انزُج ؤ ثبنزشكٛ ت انكًٛٛ ب فبد اإلَزبعٛ خ خ الل فز شح ٍ ثٛبَ بد ثذ غ انظ انشٔي ٙ انًؾه ٙ ي ان ذعبط أعجٕع(. 16ـ8يٍ انًُٕ ) اد والطريقةوالم ٍ أعشٚ ذر ى انؾظ ٕل عه ٗ ثٛبَ بد ْ زِ انذساع خ ي ٍ رغشث خ عه ٗ قـٛ ع ي ف شؿ ثذً ش ٚ ٕو ٔاؽ ذ ر ى انؾظ ٕل 384انشٔيٙ انًؾهٙ ٚزكٌٕ يٍ انذعبط .بع خ انزشثٛ خ غشف خ انؾؼ بَخ داخ م ق إنٗخشٚفٛخ ؽٛش َ هذ ف غّعهٛٓب يٍ ٔقذ كبَذ ْزِ ان شفخ يضٔدح ثكبفخ يغزهضيبد انزشثٛ خ ي ٍ فش خ ي ٍ َش بسح انجالع زٛكٛخ انً هٕث خ ٔانًغ بقٙانخش ت ٔع ذد ي ٍ ط ٕاَٙ انذه ا ٔانؾبػ ُبد ان بصٚ خ نز ٕفٛش دسع خ انؾ شاسح انًـهٕث خ ٔيفشغ بد انٓ ٕاء عه ٗ ف شاؿ اجٔق ذ ر ى رشثٛ خ ْ زِ انؾ شاسح. نًزبثذخ دسعخ ٔيؾبس ٚشنهزٕٓٚخ ٔق ذ .عٛثبأع 8يٍ عًش ٕٚو ٔاؽذ ن بٚخ عًش خالل يشؽهخ انجبدا اجسػٛخ ثبدئ خ عهٛ ّعه ٗ ((ad libitumكبَ ذ انز زٚ خ عًبعٛ خ ٔؽغ ت انشغج خ ٍ 30.2٘ ؿبق خ يًضه خ/ك ى ٔ كٛهٕكبنٕس 2950رؾزٕ٘ عهٗ عُ ذ .% ث شٔرٛ ي ٍ خ الل ٔصٌ انغغ ى اإلَ بسيك ٍ رًٛٛ ض ان زكٕس ع ٍ أ عبثٛأع 8عً ش 36ٔاخزٛ بس اإلَ بس ؽٛش رى فظم انزكٕس ع ٍ ،انشأطٔانضائذح انهؾًٛخ فٙ ع ى 70×50×50 ثئثذ بد فشدٚ خ ؽذٚذٚ خ أقفبصيٍ كم عُظ ٔػذذ داخم ٚؾز ٕ٘ عه ٗ فزؾ بد رغ ًؼ ثزُ بٔل انذه ا اإليبؤكم قفض يضٔد ثجبة يٍ ثئثذ بدٔق ذ ر ى رذهٛ يذه ا يذ ذَٙ يغ زـٛم .ٔانً بء ي ٍ خ بسط ان ف ض ٔٔػ ع يغ ٗ ثالع زٛكٙ ي ه ٕة ث ٍٛ ك م ،ى نك م قف ض ع 15×10×20 (أع جٕع 16 – 8انـٛ ٕس خ الل فز شح انًُ ٕ ) أعـٛ ذ قفظٍٛ نزُبٔل انًبء . ٘ 3000رؾزٕ٘ عهٗ ؿبقخ يًضه خ ثًذ ذل ًَٕ عهٛ ّ ؿبق خ يًضه خ كٛهٕك بنٕس ٔك بٌ ٚ زى ٔصٌ انذه ا فشدٚ ب نك م ؿٛ ش ٔؽغ بة .%19/ك ى ٔثشٔرٍٛ خبو انـٛ ٕس ٔانذه ا انًغ زٓهك أٔصأٌرى قٛبط .ٕعٛبأعجكًٛخ انذها انًغزٓهك ف ذ ك بٌ اإلػ بءحَو بو أي ب. غ ى 1ثبع زخذاو يٛ ضاٌ كٓشث بئٙ رٔ ؽغبع ٛخ ى ر .ي ٍ انذً ش اجٔن ٗانضًبَٛ خ اجع بثٛعع بعخ خ الل 24يغ زًشا نً ذح ٗ اعزخذاو َوبو االػبءح انـجٛذٛ خ ي ع ركًه خ ع بعبد االػ بءح خ ع بع 16 إن انظ ؾٛخ اإلع شاءاد كبف خ ارخزد (.أعجٕع 16 – 8ٕ )ٕٚيٛب خالل فزشح انًُ اجخٛ ش ٔفٙ انٕٛو .انًـهٕثخ ثظٕسح يٕؽذح انز ٛؾبدانـٕٛس كبفخ ٔإعـبء انـٛ ٕس يغ بءا ن شع أي بو انغبدط عشش رى عؾت انذها يٍ اجعجٕعيٍ إن ٗٔف ٙ انظ جبػ انز بنٙ ر ى َ م انـٛ ٕس .انٓؼ ًٛخرفشٚ م يؾزٕٚ بد ان ُ بح ع شٖ رث ؼ انـٛ ٕس ٚ ذٔٚب ٔف زؼ ان زثبئؼ ٔاع زخشاط ان ُ بح يك بٌ ان زثؼ ؽٛ ش ص ى قـذ ذ ،ش ٚ ذٔٚبان شٚ إصان خٔرُوٛفٓ ب ي ٍ يخهف بد ان زاء ثذ ذ انٓؼ ًٛخ ي ٍ انجالع زٛك ٔؽفو ذ رؾ ذ انزغًٛ ذ أكٛ بط ٔرى رذجئخ انـٕٛس فٙ اجسعم ر ى اع زخشاط ان زثبئؼ ٔ ،انكًٛٛ بئٙانزؾهٛ م إع شاءو نؾ ٍٛ °20-عه ٗ دسع خ ص ى ع شٖ ر ـٛذٓ ب إلراثزٓ ب سعخ ؽ شاسح ان شف خ نذ ذح ع بعبد ٔرشكٓب عهٗ د صى .انذاخهٛخ ٔاجؽشبءكٓشثبئٛخ كجٛشح يع انذوى يبكُٛخ فٙقـع ط ٛشح إنٗ aٙ ٔؽغ ت ئانزؾهٛ م انكًٛٛ ب إع شاء عُٛ بد ي ٍ ك م رثٛؾ خ ن شع أخزد .o.a .c (1984 ) ثٕاع ـخ ثشَ بيظ إؽظ بئٛب . ر ى رؾهٛ م انجٛبَ بدsas ( ؽٛ ش يضه ذ stepwiseط االَؾ ذاس انخـ ٙ انًزذ ذد ) ؽغت ًَٕر 1985 ًز ٛ شاد كف ٙ انغغ ى ك م ي ٍ َغ جخ انشؿٕث خ ٔانشي بد ٔانج شٔرٍٛ ٔان ذٍْ ٙ يغ ز هخ زثبئؼانًذزً ذح ف ذ كبَ ذ ٔصٌ ان انًز ٛ شاد أي ب ،عه ٗ انز ٕان ، أع جٕع 16ٌ انغغ ى انؾ ٙ عُ ذ عً ش ٔصٔ، عٛثبأع 8االثز ذائٙ عُ ذ عً ش ٙ ٔ، انٕٛيٛ خيذ ذل انضٚ بدح انٕصَٛ خ ٔ كف بءح ٔ، يذ ذل اع زٓال انذه ا انٛ ٕي يذ ذل اع زٓال ٔ، (ٔصَٛ ّغ ى صٚ بدح \عه ا يغ زٓهك غ ى )انزؾٕٚ م ان زائٙ غ ى \يغ زٓهك ث شٔرٍٛغ ى ، كف بءح رؾٕٚ م انج شٔرٍٛ غ ى )انج شٔرٍٛ انٛ ٕيٙ .(%)َغجخ انزظبفٙ ٔ،(ٔصَّٛصٚبدح 77 النتائج والمناقشة انذهٛب ٔانذَٛب ان ٛبعٙ ٔان ٛى( يزٕعؾ ٔاالَؾشال 1ٕٚػؼ عذٔل سقى ) ( ٚجٍٛ يذبيالد االسرجبؽ ثٍٛ 2ثًُٛب عذٔل سقى ) ،نهظفبد انًذسٔعخ انزشكٛت انكًٛٛبئٙ نهزثٛؾخ ٔانظفبد انًذسٔعخ. ؽٛش ٚالؽظ ٔعٕد اسرجبؽ يذُٕ٘ عبنت ثٍٛ َغجخ انشؿٕثخ ٔكم يٍ يغزٕٖ انجشٔرٍٛ ٔانذٍْ رؾذ ٔقذ كبَذ قٛى يذبيم ( عهٗ انزٕانٙ. p<0.05ٔp<0.01يغزٕٖ ) فٙ دساعزّ solvyns and pym (1978)االسرجبؽ ْزِ اقم يًب ٔعذِ ( عهٗ انزٕانٙ ، ٔرزف يع 0.50 -، 0.97-عهٗ فشٔط انهؾى ؽٛش كبَذ ) يٍ أٌ انذالقخ ثٍٛ َغجخ chambers fortin and (1984)يب ٔعذِ ٌٔ ٔآخش bregendahlانشؿٕثخ ٔانذٍْ عكغٛخ ٔيع يب ٔعذِ كم يٍ (2002 ٔ ، )velu ( ٌٔ1972ٔآخش ، )wolynetz sibbald and ٌ انذالقخ ثٍٛ َغجخ انًبدح انغبفخ ٔانذٍْ انخبو يٕعجخ ، ثًُٛب ايٍ (1990) ؽٛش نى ركٍ (bregendahl 2002 (رخزها ْزِ انُزبئظ يع يب ٔعذِ ع يُْب عالقخ يذُٕٚخ ثٍٛ َغجخ انًبدح انغبفخ ٔانجشٔرٍٛ انخبو ، كًب رزف ٌ انذالقخ ثٍٛ َغجخ انشؿٕثخ يع اعزٓال ا( يٍ 1984)friars يب ٔعذ غى عها يغزٓهك \)غى صٚبدح ٔصَّٛ انذها ٔانضٚبدح انٕصَٛخ ٔكفبءح انز زٚخ 0.07-، 0.31-كبَذ عكغٛخ نكٍ قٛى يذبيم االسرجبؽ كبَذ يخزهفخ ) ٌ يفٕٓو ؽغبة كفبءح انز زٚخ )غى صٚبدح ج( عهٗ انزٕانٙ. َٔوشا 0.28-، غى عها يغزٓهك( ْٕ عكظ كفبءح انزؾٕٚم ان زائٙ )غى عها \ٔصَّٛ غى صٚبدح ٔصَّٛ(. فئرا كبَذ انذالقخ ؿشدٚخ يع اؽذًْب فٓٙ \يغزٓهك يع اجخشٖ. ٔر بسة قٛى يذبيم االسرجبؽ فٙ دساعزُب ثٍٛ َغجخ عكغٛخ فٙ رثبئؼ فشٔط انهؾى ؽٛش friars (1984 )يب ٔعذِ يعانشؿٕثخ ٔانذٍْ ( ،كًب p<0.01( رؾذ يغزٕٖ يذُٕٚخ )0.84-كبَذ قٛى يذبيم االسرجبؽ ) يٍ عذو ٔعٕد عالقخ pesti bakalli and (1997)رزف يع يب ٔعذِ َغجخ انشؿٕثخ ٔٔصٌ انغغى ؽٛش كبَذ قًٛخ يذبيم االسرجبؽ يذُٕٚخ ثٍٛ إنٗ ٔعٕد اسرجبؽ يذُٕ٘ ثٍٛ دَبِ(. رشٛش انُزبئظ فٙ انغذٔل أ0.224-) ( ٔيع َغجخ p<0.01َغجخ انشيبد يع َغجخ انجشٔرٍٛ انخبو رؾذ يغزٕٖ) ( ٔقذ p<0.05( ٔيع َغجخ انزظبفٙ )p<0.01انذٍْ انخبو رؾذ يغزٕٖ ) إنٗ ٔعٕد عالقخ عكغٛخ ثٍٛ fortin chambers and (1984 )أ بس أٌ يذبيم االسرجبؽ friars(1984)َغجخ انشيبد َٔغجخ انذٍْ ثًُٛب ٔعذ ثٍٛ َغجخ انشيبد ٔكم يٍ انضٚبدح انٕصَٛخ ٔاعزٓال انذها ٔكفبءح انز زٚخ أظٓشد انُزبئظ أٚؼب ( عهٗ انزٕانٙ.0.17-، 0.36-، 0.19 -كبَذ ) ٔعٕد اسرجبؽ يذُٕ٘ عبنت ثٍٛ َغجخ انجشٔرٍٛ يع َغجخ انشؿٕثخ ٔانشيبد ( عهٗ انزٕانٙ،p<0.05 ،p<0.01 ،p<0.01ٔانذٍْ رؾذ يغزٕٖ ) bakalli and pesti، ٔقذ أ بس ثًُٛب نى ركٍ ان ٛى اجخشٖ يذُٕٚخ نؾٙ َٔغجخ( ثٍٛ ٔصٌ انغغى اp<0.01) إنٗ ٔعٕد عالقخ يذُٕٚخ( 1997) friars( ٔٔعذ0.305-انجشٔرٍٛ ؽٛش كبٌ يذبيم االسرجبؽ ثًُٛٓب ) إٌ قٛى يذبيم االسرجبؽ ثٍٛ َغجخ انجشٔرٍٛ انخبو ٔكم يٍ انضٚبدح ( 1984) (1972ٔآخشٌٔ ) veluٔرزف ْزِ انُزبئظ يع يب ٔعذِ انٕصَٛخ ٔاعزٓال انجشٔرٍٛ انخبو َٔغجخ انشؿٕثخ.( ثٍٛ َغجخ p<0.01يٍ اسرجبؽ يذُٕ٘ ) اَخفبػب morrison and leeson (1978)ٔيٍ َبؽٛخ أخشٖ ف ذ ٔعذ عُذ رؾغٍٛ (p<0.05)رؾذ يغزٕٖ يذُٕٚب فٙ َغجخ انجشٔرٍٛ انخبو انًزٕعؾ ٔاالَؾشال ان ٛبعٙ ٔان ٛى انذهٛب ٔانذَٛب نهظفبد انًذسٔعخ.( 1جدول ) اجقم اجعهٗ االَؾشال انًذٛبس٘ انًزٕعؾ انذذد ان ٛبعبد انشؿٕثخ % انشيبد % انجشٔرٍٛ انخبو % يغزخهض االٚضش % انٕصٌ االثزذائٙ غى ٔصٌ انغغى انؾٙ غى انضٚبدح انٕصَٛخ انٕٛيٛخ غى اعزٓال انذها انٕٛيٙ غى كفبءح انزؾٕٚم ان زائٙ اعزٓال انجشٔرٍٛ انٕٛيٙ غى كفبءح رؾٕٚم انجشٔرٍٛ َغجخ انزظبفٙ % 72 72 72 72 72 72 72 72 72 72 72 72 66.35 4.38 17.07 12.21 913.01 2465.0 26.48 113.34 4.47 21.12 0.83 67.75 1.97 0.46 1.04 2.11 170.20 523.87 6.88 17.49 1.01 4.39 0.18 2.42 70.95 5.89 20.34 17.84 1207 3603 39.48 150.04 9.33 30.30 1.45 72.82 60.64 3.60 15.02 7.03 625.0 1363 10.23 74.45 3.13 13.88 0.56 61.77 78 ( أٚؼب إٌ يذبيم االسرجبؽ ثٍٛ 2ٕٚػؼ انغذٔل سقى ) انضٚبدح انٕصَٛخ. َغجخ انذٍْ انخبو ٔكم يٍ َغجخ انشؿٕثخ َٔغجخ انشيبد كبٌ يذُٕٚب عبنجب ( ٔيع كم يٍ َغجخ انجشٔرٍٛ انخبو َٔغجخ انزظبفٙ p<0.01رؾذ يغزٕٖ ) ؾٙ ٔكفبءح انزؾٕٚم ( ٔيع كم يٍ ٔصٌ انغغى انp<0.01رؾذ يغزٕٖ ) إنٗ friars(1984)ٔقذ أ بس (p<0.05ان زائٙ ٔكفبءح رؾٕٚم انجشٔرٍٛ ) ٌ يذبيم االسرجبؽ ثٍٛ َغجخ انذٍْ ٔكم يٍ انضٚبدح انٕصَٛخ ٔاعزٓال أ ( عهٗ انزٕانٙ. كًب 0.24، 0.44، 0.02انذها ٔكفبءح انز زٚخ كبَذ ) رؾذ يغزٕٖ عالقخ قٕٚخpesti bakalli and (1997 )ٔعذ (p<0.001ْثٍٛ َغجخ انذ ) يذبيم أٍ ٔانشؿٕثخ ٔانجشٔرٍٛ. كًب ٔعذ ٌ lin. ٔ قذ ٔعذ 0.915االسرجبؽ ثٍٛ ٔصٌ انغغى انؾٙ َٔغجخ انذٍْ كبَذ (1981) suller eitan and (1985 ) ٙعالقخ قٕٚخ ثٍٛ انضٚبدح ف morrisonانٕصٌ ٔ رشعٛت انذٍْ. ٔ ال رزف ْزِ انُزبئظ يع يب ٔعذِ and leeson 1978) ٍيٍ اسرفبع يذُٕ٘ فٙ َغجخ انذٍْ يع رؾغ ) ( ي1983ٍٔآخشٌٔ ) chambersانضٚبدح انٕصَٛخ ثًُٛب رزف يع يب ٔعذِ نٕصٌ االثزذائٙعذو ٔعٕد اسرجبؽ يذُٕ٘ ثٍٛ َغجخ انذٍْ ٔكم يٍ ا ٔال رزف يع يب ٔعذِ َفظ انجبؽش يٍ ٔعٕد اسرجبؽ ،ٔانضٚبدح انٕصَٛخ ( ثٍٛ َغجخ انذٍْ انخبو ٔكم يٍ اعزٓال انذها ٔكفبءح p<0.01ُٕ٘ )يذ انز زٚخ . (يذبدالد االَؾذاس نهظفبد انًذسٔعخ عهٗ 3ٔ4ٔ5ٔ6رٕػؼ انغذأل ) كم يٍ َغجخ انشؿٕثخ ٔانشيبد ٔانجشٔرٍٛ ٔانذٍْ فٙ انغغى عهٗ انزٕانٙ ، انخـٕح ؽٛش ظٓش إٌ أفؼم يذبدنخ رُجؤٚخ ًٚكٍ انؾظٕل عهٛٓب ثـشٚ خ ( فٙ ؽبنخ َغجخ انشؿٕثخ ْٙ ثبالعزًبد عهٗ كفبءح stepwiseخـٕح ) انزؾٕٚم ان زائٙ. إال أٌ ْزِ انذالقخ نى ركٍ يذُٕٚخ ،كًب إٌ قًٛخ يذبيم انًُٕرط كبَذ ط ٛشح ( انز٘ ٚذجش عٍ دقخ رًضٛم r2انزؾذٚذ ) نشيبد(، أيب انذالقخ ثٍٛ انظفبد انًذسعخ ٔكم يٍ َغجخ ا0.058) ٌ أفؼم يذبدنخ رُجؤٚخ ًٚكٍ انؾظٕل عهٛٓب أٔانجشٔرٍٛ ٔانذٍْ ف ذ ٔعذ ْٙ ثبالعزًبد عهٗ َغجخ انزظبفٙ ؽٛش كبَذ انذالقخ يذُٕٚخ رؾذ يغزٕٖ (p<0.05 ،p<0.01 ،p<0.01 عهٗ انزٕانٙ، ٔقذ كبَذ قٛى يذبيم ) ( عهٗ 0.1333، 0.094، 0.074انزؾذٚذ نٓزِ انًذبدالد أفؼم قهٛال ) ٚزؼؼ يٍ ْزِ انذساعخ اَّ يٍ انظذٕثخ االعزًبد عهٗ انظفبدٕانٙ. انز يذبيالد االسرجبؽ ثٍٛ انزشكٛت انكًٛٛبئٙ نهغغى ٔانظفبد انًذسٔط( 2جدول ) %شيبدان %دٍْ %ثشٔرٍٛ %انشؿٕثخ ان ٛبعبد 0.05382 **0.81058* 0.272931.00000 انشؿٕثخ % 1.00000 ***0.42408** 0.32021 0.05382 انشيبد % **0.32021 **0.307561.00000 *0.27293انجشٔرٍٛ % ***0.420481.00000 **0.30756***0.81058انذٍْ% 0.03647 0.00497 0.037400.00600 انٕصٌ االثزذائٙ )غى( 0.05879*0.23284 0.074980.19620ٔصٌ انغغى انؾٙ )غى( 0.053710.21780 0.052670.19305انضٚبدح انٕصَٛخ انٕٛيٛخ )غى( 0.03350 0.08341 0.052090.06958اعزٓال انذها انٕٛيٙ )غى( 0.16128 *0.248300.00617 0.22541 كفبءح انزؾٕٚم ان زائٙ 0.00692 0.11051 0.00183 0.12094جشٔرٍٛ انٕٛيٙ )غى(اعزٓال ان 0.15206 *0.232490.01734 0.20471 كفبءح رؾٕٚم انجشٔرٍٛ *0.27214**0.36516 **0.302280.16850َغجخ انزظبفٙ % >p 0.001*** يذُٕ٘ رؾذ يغزٕٖ ، >p 0.01** يذُٕ٘ رؾذ يغزٕٖ ، >p 0.05* يذُٕ٘ رؾذ يغزٕٖ 79 ههغغى ئ يذبدالد رُجؤٚخ نهزشكٛت انكًٛٛبانًذسٔعخ انًشبس إنٛٓب فٙ إٚغبد فٙ انشٔيٙ انًؾهٙ ٔقذ ٚذٕد ْزا إنٗ ٔعٕد اخزالفبد كجٛشح فٙ أداء عالنخ انشٔيٙ انًؾهٙ ال ٚذذانذعبط انـٕٛس يٍ ؿٛش إنٗ أخش, كٌٕ عٛخ, إػبفخ إنٗ ٔعٕد اخزالفبد كجٛشح فٙ ان بثهٛخ اإلَزبعٛخ ثٍٛ انزكٕس قٛب ٔاإلَبس فٙ عًٛع انظفبد انًذسٔعخ كًب أ بسد إنٗ رنك كضٛش يٍ ( ٔ ٚؾٛٗ 1988( ٔ ثـشط ٔٚؾٛٗ )1986انذساعبد انغبث خ ثـشط ) (1978. ) 3 pr> ff valuemean squaresum of squaredfsource 0.0569 ns 3.7514.01913 3.74135 14.01913 261.89474 275.91386 1 70 71 model error corrected total y2=64.36853+ 0.44199x5 r2 = 0.0508 ns .يذبدنخ خؾ االَؾذاس نظفخ َغجخ انشيبد فٙ انغغى( 4جدول ) pr> ff valuemean squaresum of squaredfsource 0.0207 * 5.601.09280 0.19518 1.09280 13.66278 14.75558 1 70 71 model error corrected total y2=7.84637 – 0.05123x8 r2 = 0.0741 0.05p< 80 .شٔرٍٛ فٙ انغغى( يذبدنخ خؾ االَؾذاس نظفخ َغجخ انج5جدول ) pr> f f value mean square sum of square df source 0.0099 ** 7.04 7.03735 0.99969 7.03735 69.97845 77.01580 1 70 71 model error corrected total y3 = 25.87291 – 0.13001x8 r2 = 0.0914 >p 0.01يذُٕ٘ رؾذ يغزٕٖ .َؾذاس نظفخ َغجخ انذٍْ فٙ انغغىيذبدنخ خؾ اال( 6جدول ) pr> ff valuemean squaresum of squaredfsource 0.0016 ** 10.7742.21192 3.91940 42.21192 274.35797 316.56989 1 70 71 model error corrected total y4 = -9.35850 + 0.31841x8 r2 = 0.1333 0.01p< مراجعال (. رثصٛش اعزخذاو يغزٕٚبد يخزهفخ يٍ 1986ثـشط ، ٕٚعا ٚذ ٕة. ) انجشٔرٍٛ فٙ عهٛ ّ انًُٕ نهشٔيٙ انًؾهٙ عهٗ ثذغ انظفبد اإلَزبعٛ خ 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purchase behavior of consumers for seafood products n. al-mazrooei1, g.v. chomo2, and a. omezzine3* 1quality control center, ministry of agriculture and fisheries, p.o. box, 467, muscat, sultanate of oman 2escwa, beirut, lebanon 3ministry of agriculture and fisheries. p.o. box 467, pc 113, muscat, sultanate of oman abstract: fish consumption is a key component in production and marketing decisions. fish consumers play a key role because fishermen and distributors recognize their purchase choices as a determinant to their operation. consumers make buying decisions according to market conditions and to various attributes of the product, namely the specie, the form, the place of purchase, the size and the quality. this study is aimed at providing information on oman consumers’ attitudes and preferences for fish purchase form and market outlets using an information-processing model. it identifies factors for predicting changes in market demand for fish products and services as a result of changes in consumers attributes. results indicate that on-shore fish markets are the most preferred outlets for the coastal population while retailers and oman national fisheries company are the commonly used outlets. results also show that whole fish is the most preferred form of purchase for both rural and urban medium to low-income consumers while a large proportion of high-income consumers in urban regions prefer mainly sliced fish. market development efforts should focus on the organization of on-shore fish markets in coastal regions, and retailers and oman fisheries company’s outlets in the inland areas. forms other than whole fish may be promoted for sale in supermarkets and specialized shops for the urban high-income consumers group.. keywords: fish products, consumers behavior, sultanate of oman lthough fish products have always been an important dietary food item, fish consumption in countries such as oman has increased remarkably. consumption in this country has reached an annual average of more than 60,000 metric tons (t) during the last five years with a peak of about 28 kilogram (kg) per capita in 1999 (maf, 1999). there are over 300 fish species in oman but only less than 120 among them are commercially exploited. local markets are the most important outlets for all these species although seafood exports have increased during the last ten years (omezzine, 1998). due to the importance of the local market, consumers’ buying behavior is a significant determinant of production and marketing decisions made by the private and public sectors (houston et al., 1996). survey data (houston et al., 1996) show that omani consumers react to many different attributes of fish products. they make a !"#$%&'(!)*+,-.'(!/012,3.'!/4($5'(!6713'(! !"#$%&'(&)%*+,-&./.01&2"3.456-&7,-3#8$%&9.0:& & !"889:;&;&&&&&<2=>.? &!/&".#-2$4"&%&:(&'=(&32$4$%&-&!")2=?$%&<%3%*+&76&,2=-=.3&,%3-)&/"*0+$%&<2$418$%&.52&4-/&342" &&&&&&&&&5).6$$%&-&7%*60$%&"265/-&8560$%&-&916?$2#&/:24468$%&;4618$%&<&*6&"&&7:284$%&=2&4-8$%&>.2?&/?%3)&@$a&'0+$%&%bc&d &&&&&&&&&&&>28?e$&f.%*g&*1,&f:".-1&bh1/-&850$%&'=(&!/&;46182$&f1%32=64 a-&<&&&&&&&@2,&i%#:j%&!+%.8#&k%.?l%&"m#&;.241$%&*=01 &&&&&&&&&&&&>28?l%&/n*g-&k*h8$%&k%.?(&8o681&2816=#&/=2(26-$%&pq2168$%&"256-$&86rh8$%&76-=.*$%&bh168$%&8o681&sq%.60$% &/=6:284$%&&&&/=662 %*$%&pq2168$%&"256-$&,t284466?a&*o6nl%&bh168$%&&<&&&&&-&/=66h"*$%&pq2168$2#&!=52&46-8$%&"(&,266r"(&;.2461$%&!6=+1&&&&&&&&&&&&&&&&&&&&&&&>28?l%&7%*g&!h1*68$%&86 *$%&u-v&".52&46-8$%&86rh"&2816=#&!=6w:1&"-*6#&/62/2n&>286?l%&7%*6g&".26rh"&/"*6r0$% &&&&&&&&&&5)*446/&i256g(&@62,&/64w:8$%&-&5#6c2$$%&<&&&&&#=n*4#&/?%3*$%&76>.1&&k%.?l%&*".w1&@2,&/=58-$%&k%.?l%&/=811&).&x &&&&&&&&&&&&&&&&2&#&/=?2?l%&/=1+$%&!=-01-&/=2 %*$%&pq2168$2#&k*6h8$2#&!=6+$%&k%.6?(-&i%#6:j%&!6+%.8#&&<&&&&&!=#&b621/&*".w4#&7>.1&28n !h1*8$%&8 *$%&u-v&!=52&4-8$%&32q&/=+24$&/??y48$%&<z08$%&-&[n32/&*#.-$%&8o/&5#&$8$%&>28?l%<& al-mazrooei et al. 2 decisions on the species, the form, place of purchase, and quality based on product prices, disposable income and other consumption factors. moreover, consumers’ preferences are affected by their demographic, socioeconomic and attitudinal characteristics. successful fish traders respond to consumers’ preferences. fishermen, investors, and distributors recognize the key role of consumers, their buying behavior, and their preferences in the development of market outlets, and the supply of products in the desired form and quality. previous studies of seafood demand and marketing have focused heavily on consumer attitudinal factors and their impacts on choices between species, form, and quality (hanson et al., 1995; houston et al., 1996; gempesaw et al., 1995; herrmann et al., 1994). most studies include traditional determinants of demand, namely product prices, consumers’ tastes, habits, income, and preferences. however, consumer behavior and choice attitude have significant bearing on market development. consumers are generally believed to formulate their attitudes from available information and experience. these attitudes are of interest because they influence the choice of a given product, quantity, and quality. the operative mode of this framework is consistent with the “attitude-before-behavior” paradigm used to depict the effects of advertising in situations that exhibit high consumer involvement (ray, 1974). attitudes may be affected by both endogenous and exogenous factors. the informationprocessing model recognizes the importance of consumer perceptions and attitudes as they relate to behavioral intention in the decision-making process within a simultaneous framework (huang, 1993). many approaches have been developed in the field of consumers’ attitudes and purchase choice. these were aimed primarily at identifying how behavioral factors might affect market dimensions and development. they differed from traditional demand analysis that focus on explaining the relationships between quantity demanded and its determinants such as consumer income, taste, and prices and aimed primarily at determining consumer response to income and price changes. houston et al. (1996) conducted a study of fish consumers’ preferences in oman with respect to species choice and product nature. they addressed the role of consumers’ attitudes with respect to four common fish species (kingfish, shrimp, cuttlefish, and tuna) and the product nature (fresh, frozen, canned, and sliced). their results provided valuable information to assist market and product development. houston et al. (1996) contended that freshness is the primary concern of omani consumers, with little regard for “quality or product differentiation”. they contended that the market could be expanded if consumers accepted frozen and processed fish products. extending the market is beneficial to consumers by increasing fish availability in the diet, to fishermen by increasing the value of their catch, and to fish processors and traders by raising their revenues from a higher volume and better quality of fish products. however, it is essential to determine exactly how the market can be extended by analyzing all details of consumer preferences for fish products. the present study focuses specifically on product form and market outlet as they influence consumer attitudes and preferences for fish products in oman. this study recognizes the importance of thorough market analysis to assist in market development and improvement of revenues from the fish resources. the specific objective of the study is to generate information regarding the primary factors affecting consumers’ choices between different purchase forms of fish (whole, fillet, and sliced) and, between the various market outlets available to consumers in oman on-shore market, oman national fisheries company (onfc), supermarkets, specialized fish shops, and retailing outlets near the on-shore fish market. furthermore the study separates out consumer characteristics such as income, market preference, education, urban versus rural, etc., to clarify preferences for product differentiation and market outlet. it is anticipated this study will identify factors for predicting changes in market demand for fish products and services in line with income growth, rural to urban population drift, and continued improvements in education. results are expected to contribute to product and market development and differentiation. overview of fish consumption and market setting in oman fresh and frozen fish are the most commonly forms sold in both the domestic and export markets. the local market is very important, as average per capita consumption of fish has been increasing and reached around 28.5 kg in year1999 (maf, 1999). previous studies (omezzine, 1998; maf, 1999) indicate that the marketing system for fish in oman is dominated by on-shore fresh fish direct sale from fishermen to consumers in the coastal regions and dispersed retail sale outlets in the inland regions. a few other sale outlets have evolved during the last few years as a result of changes in life-styles and social conditions of consumers together with the increasing demand from high income expatriates working in the country. the development of these new outlets has been viewed to be slow as demand for them has been judged still below promoters’ expectations. officials believe that the domestic market is still underdeveloped and offers slower growth than the potential purchase behavior of consumers for seafood products 3 might indicate (maf, 2002). consumer behavior and consumption habits are the most important factors affecting the development of these markets. field observations and prior studies of omani dietary habits stated that consumers prefer fresh vegetables, fresh fruit, fresh meat, and fresh fish. moreover, consumers seem to prefer large fish rather than small. consumers treat favorably large fish as determined by name, appeal, recognition and appearance. frozen fish have a very thin market in oman (ingvarsson, 1988). whole fish is a common form of sale except for very large species. other forms of fish sale have evolved with new sale outlets during the last few years. however, the market for these new forms such as sliced fish, fillets, smoked and dried remains very limited. research methodology model specification: the logistic regression procedure is the most frequently used method to study consumer perceptions and attitudinal behavior (gempesaw et al., 1995). it allows the analyst to measure the effects of relative price perceptions and socio-economic and demographic characteristics on household choices of forms of products and market outlets. according to demarris (1995) a logistic regression is a logical choice for modeling consumer choice behavior because the error term is not normally distributed due to the nature of the data used. when data are generated from a survey using questions based on the likert five-point scale, responses are clumped and truncated at either side of the distribution. that is, more positive or negative responses are expected rather than responses being normally distributed. the error term has a logistic distribution and, therefore, the appropriate analytical technique is the logistical regression. a choice model is specified with a dichotomous dependent variable representing the consumer’s final choice to be explained by a set of variables such as demographic factors, socio-economic factors, perception, experience, and preferences. the logit model transforms the problem of predicting probabilities within a (0,1) interval to the problem of predicting the odds of an event occurring within the range of the entire real line. this model takes the following form: choice = f (explanatory variables) the analytical form of the logit model is based on the cumulative logistic probability function where the probability (pi) that a consumer will make a certain choice (i) given his attributes (x1) is specified as follows (pindyck and rubinfeld, 1981): (1) )i!x("e1 1 ize1 1 )i!xf(")if(zip +− + =− + =+== pi is the probability that an individual will make a certain choice, given knowledge of xi. in the fish purchase choice, pi would represent the probability that a consumer will choose a certain form or an outlet given an income (education level, etc.) equal to xi. f is the cumulative probability function and zi is a theoretical index, which is determined by an explanatory variable xi; " and ! are constants. the model to be estimated is derived from equation (1) pindyck and rubinfeld, 1981). )2(i!x"iz ip1 iplog +== ! ! " # $ $ % & − the dependent variable in equation (2) is the natural logarithm of the odds (the ratio of expressing the probability) that a particular choice will be made (pindyck and rubinfeld, 1981; judge et al., 1982). the estimated coefficients " and ! reflect the effect of a change in an independent variable xi on log )).ip/(1i(p − the slope of the cumulative logistic distribution is greatest at p = ½. this implies that changes in the independent variables xi will have their greatest impact on the problem of choosing a given option at the midpoint of the distribution. in the case of purchase choice, the model presumes that an increase in income for example will increase the probability of choosing a certain form of outlet. however, it may have no significant effect on low-income individuals who are unlikely to alter their choice under any conditions. likewise, it may have very slight impact on highincome individuals who are very likely to have made their choice before the increase in income. pi is approximated through i i i n r p = ! where ri is the number of times an alternative is chosen by consumers with the same xi; ni is the number of consumers choosing the same xi and choosing the same alternative. then log ! ! " # $ $ % & − = − ip1 p log ip1 )i(p ! al-mazrooei et al. 4 .iix!" izin irlog in iz1 in iz log ip1 p logthen ∈+∗+∗= − = − = ! ! " # $ $ % & − ! ! .x!x!x!! p-1 p log :asestimatedbewillmodellogitthe termerror inn22110 ∈++++= ∈= "! ! the parameters do not indicate the increase of the probability of the event occurring, given a one unit increase in the corresponding independent variable. the amount of change in probability depends on the original probability and thus, on the initial values of all the dependent variables and their coefficients. specifically, (3) )e(1 e! idx idp 2zi i iz+ = the interpretation of the estimated parameters must be done with care since the left-hand side of the equation is the logarithm of the odds of choice and not the actual probability (pindyck and rubinfeld, 1981). the change in the logarithm of the odds of choice can be determined as follows: (4) ix !# ip1 iplog# = ' ' ( ) * * + , − for example, to interpret the effect of a change in xi on the probability of choosing a given form of fish we use equation (2) as follows: i#xi! ip1 iplog# = − ( ) ip#)ip(1ip 1 ip# ip1 1 ip 1 ip1 )i(plog# − = − −= − ! ! " # $ $ % & + ()ip(1ipi!ip# 1isix#if −= → then a one-unit change in xi will result in [ ])p-(1 p! p iiii =∆ change in the probability that a choice will be made given a value of xi. data and survey procedure: data for this paper was gathered from a cross-sectional survey (bulmer, and warwick, 1983) executed in the sultanate of oman. some 124 households were selected and interviewed using a pretested questionnaire according to the principles described in nachmias and nachmias, (1996). the survey instrument contained ordered responses that follow the likert five-point scale (simon and burstein, 1985), as well as close-ended questions consisting of “yes” or “no” stated items. all statistical treatments employed sassoftware (statistical analysis system; sas/stat, 1993). the reliability of the questionnaire was tested through a pilot study. the same instrument was used on the same subjects twice. the questionnaire was then revised to incorporate suggestions and clarify ambiguous questions or deal with omitted items that may have bearings on consumers’ attitudes and attributes. the final questionnaire was then conducted on 124 households. a convenience sampling procedure was used to assign consumers from urban coastal and rural inland regions of oman. it was not possible to reach a larger group of potential respondents because of the unavailability of respondents and budget constraints to cover a larger geographic area. questions were addressed to the person responsible for the purchase of seafood for household consumption. while the sample was randomly selected, demographic characteristics of the country were represented to a large extent. however, because of difficult access to households the resulting sample was slightly skewed towards higher education level and urban consumers respondents. this, in our opinion, will not affect seriously the conclusions of the study as fish market development may potentially target the educated and urban strata of the population. meanwhile, the sample was also skewed towards male respondents. in many countries of the world women are primarily responsible for food purchase. this is not the case for oman. although no official records exist on this issue it is well known that men are responsible for food purchase, and even more so for fish. women are present in outlets where prices are fixed such as supermarkets, but are seldom found in food outlets where prices are negotiated or auctioned. this is the case of fish markets. it is a matter of culture that women cannot stand in a crowd to negotiate prices or participate in an auction with men. model estimation: to analyze the survey data, two models were specified. the first deals with decision purchase behavior of consumers for seafood products 5 table 1 dependent variable names, definitions, and coding values. form of purchase whole fish 1 = whole fish, 0 = otherwise fillets 1 = fillets 0 = otherwise slices 1 = slices 0 = otherwise place of purchase on-shore market 1 = on-shore markets 0 = otherwise fisheries company 1 = company 0 = otherwise frozen fish sold by retail outlet of fisheries co. supermarket 1 = supermarket 0 = otherwise chilled or frozen or iced fisheries sold fish shop 1 = shop 0 = otherwise specialized shop selling chilled or frozen fish retailer 1 = retailer 0 = otherwise small fish dealers in markets or truckers, jobbers selling fish to consumers table 2 independent variables, names, and coding. hhsze household size measured in numerical values; edu education of respondents measured by number of years of education; age the respondent’s age measured in years; ncom the respondent’s income measured in ro. as reported by respondent and grouped as follows: in ro. = 1,200 if 0 < income < 2,400; = 4,200 if 2,400 < income < 6,000; = 8,000 if 6,001< income < 10,000; = 15,000 if 10,001< income. this variable is introduced as a dummy and was given values from 1 to 4 for the different categories of income, respectively. urbru whether respondent is urban or rural. it is equal to 1 if rural and 0 if urban; incomri income increase in the future (expectation). equals 1 if an increase of income would increase purchase of fish, and 0 otherwise; prceexp price expectation. equals 1 if a future price decrease would increase purchase of fish and 0 otherwise; price the price of fish. equals 1 if very important or important in decision of fish purchase and substitution and 0 otherwise; odor fish odor measured in the likert five-point scale with 5 = very good, 4 = good, 3= medium, 2 = satisfactory, 1 = unsatisfactory; textr fish texture measured in the likert five-point scale with 5 = very good, 4 = good, 3= medium, 2 = satisfactory, 1 = unsatisfactory; moistnss fish moistness measured in the likert five-point scale with 5 = very good, 4 = good, 3= medium, 2 = satisfactory, 1 = unsatisfactory; flavor fish flavor measured in the likert five-point scale with 5 = very good, 4 = good, 3= medium, 2 = satisfactory, 1 = unsatisfactory; overall fish overall attractiveness measured in the likert five-point scale with 5 = very good, 4 = good, 3 = medium, 2 = satisfactory, 1 = unsatisfactory; availbl availability of fish in place of residency measured in the likert five-point scale with 5 = very good, 4 = good, 3 = medium, 2 = satisfactory, 1 = unsatisfactory; spouse spouse contribution to fish purchase measured in the likert five-point scale with 5= always,..., 1= never choice on form of purchase and the second with market outlet. in both models the choice variables were converted into binary variables with 0 and 1 values. selected purchase forms considered in the choice include whole fish, fillet, and sliced. specific market outlets included in the choice are on-shore market, oman national fisheries company (onfc), supermarket, fish shop, and retailer. in the purchase form model, the purchase decision of a particular form takes the value of 1 if the respondent’s answer is “yes”, and 0 “otherwise". in the place of purchase model the decision on a particular outlet takes the value of 1 if the respondent’s answer is “yes", and 0 "otherwise”. both choice models included a set of explanatory variables as indicated below: choice = "0 + hhze "1 + edu "2 + urbu "3 + age "4 + income "5 + incmri "6 + prceex "7 + price "8 + odor "9 + textr "10 + moistnss "11 + flavor "12 + overall "13 + availbl "14 + spouse "15 + markt "16 + fishcom "17 + sprmkt "18 + shop "19 + retail "20 + e. tables 1 and 2 represent the dependent and independent variable names, definitions, and their coding, respectively. al-mazrooei et al. 6 results and discussion descriptive statistical analysis of consumers’ preferred forms and place of purchase was performed first to determine the importance of each form and market outlet in the consumers’ choices. the logit model was then estimated using the maximum-likelihood estimation procedure (sas, 1988). the results are presented for both choice variables in tables 3 and 4. all measures of model goodnessoffit indicate that the estimated models for both choice decisions fit the data with high percentages of correct predictions ranging from 69% to 94% for the purchase choice model, and 80% to 96% for the market outlet model. the purchase form choice model: results of descriptive statistics analysis on consumers fish preferred indicate that whole fish is the most frequently purchased form. about 92% of the respondents answered “yes” when they were asked if whole fish was their preferred form of purchase, while only 60% of respondents said “yes” for sliced fish. fillet is the least preferred with about 21% of “yes” responses. table 3 shows the estimated coefficients and the asymptotic t-ratios for the purchase form decision model. results suggest that the logarithm of the odds that an individual consumer will choose whole fish as a form of purchase is higher if the respondent buys from an on-shore market and ranks the perceived flavor of that particular fish specie “very good” to “good”. consumers who buy from the on-shore market are more likely to buy whole fish. however, the probability that consumers prefer whole fish decreases with income and overall actual attractiveness of a particular form. actual attractiveness is dependent on what the product in a particular form looks like and how it is packed, handled and presented to the buyer. there is no doubt that those who place importance on attractiveness are more likely to choose fillets and sliced fish rather than whole fish from the on-shore markets. consumers with lower income are also more likely to buy whole fish. this negative relationship between purchase form and income is consistent with observed buying attitudes. on the other side, observed attitudes show that often high-income consumers prefer to buy their fish supplies from higher service market outlets where fish slices and fillets are available. this inference is confirmed in the place of purchase choice model where high-income consumers prefer supermarkets and fish shops that provide them the form and attributes they desire. the negative relationship between the likelihood of whole fish purchase choice and overall attractiveness of fish table 3 omani consumer behavior survey, parameters of choice models for normally purchased form. independent variable whole fish fillet slice constant 0.098 -3.100 2.220 (0.018) (-1.177) (1.057) household size -0.144 0.132 -0.086 (-0.942) (1.235) (-0.864) education 0.133 0.078 -0.122** (1.242) (1.167) (-2.320) rural/urban 0.481 -0.172 0.138 (0.365) (-0.267) (0.263) age -0.035 -0.042 0.003 (-0.631) (-1.238) (0.101) income -0.255e03* 0.141e03** 0.120e03** (-1.862) (2.030) (2.007) income increase 0.364 -0.807 -0.042 (0.326) (-1.141) (-0.083) price expectation -0.100 0.283 1.079* (-0.079) (0.394) (1.795) market 2.903* 0.150 -0.373 (1.675) (0.177) (-0.471) fisheries co. 0.505 -0.385 -0.693 (0.316) (-0.440) (-1.082) supermarket 0.096 0.307 -0.961 (0.073) (0.371) (-1.474) fish shop -0.271 0.844 0.278 (-0.227) (1.384) (0.518) retailer 0.684 1.009 -0.562 (0.367) (1.121) (-0.710) odor 0.843 -0.002 -0.814* (0.924) (-0.003) (-1.795) texture -0.256 -0.128 0.134 (-0.165) (-0.186) (0.255) moistness -0.499 -0.549 -0.095 (-0.417) (-1.031) (-0.229) flavor 2.281* 0.979 -0.281 (1.826) (-0.231) -(1.626) overall -1.791* 0.979* -0.281 (-1.774) (1.856) (-0.667) spouse decision 0.174 -0.309* -0.024 (0.579) (-1.810) (-0.169) cragg-uhler r2 0.392 0.242 0.191 number of observations 124 124 124 observations at zero (answers no) 10 97 49 likelihood ratio 22.817 21.187 18.829 % of correct predictions 94.4 84.7 69.3 number in parentheses are asymptotic t-values. *indicates significance at p= 0.10. **p= 0.05 level. __________________ *corresponding author. 7 table 4 omani consumer behavior survey, parameters of choice model for place of purchase. independent variable on-shore market fisheries co. supermarket fish shop retailer constant 4.505 -2.461 2.449 1.323 -0.176 (1.019) (-0.735) (0.789) (0.584) (-0.028) household size -0.069 -0.446** -0.229 -0.214 -0.290 (-0.399) (-2.262) (-1.286) (-1.573) (-1.125) education 0.167** -0.098 -0.166* 0.033 0.420** (2.026) (-1.067) (-1.805) (0.556) (2.087) rural/urban 0.312 1.734* -3.029** 0.060 3.445** (0.269) (1.949) (-2.337) (0.106) (2.206) age 0.036 0.029 -0.001 0.023 0.046 (0.782) (0.720) (0.034) (0.741) (0.0694) income -0.198e03* +0.115e03* +0.354e04* -0.435e04* -0.355e03* (-1.682) (1.147) (0.384) (0.658) (-1.841) income increase 0.824 1.030 -1.656 -0.324 -0.444 (0.765) (1.379) (-1.496) (-0.518) (-0.346) price expectation 0.712 0.366 0.778 -0.063 2.010* (0.811) (0.523) (1.007) (-0.116) (1.844) market -0.211 -0.463 -1.969** -8.962*** (-0.189) (-0.295) (-2.139) (-3.735) fisheries co. -0.186 -0.441 -0.121 0.776 (-0.154) (-0.351) (-0.165) (0.493) supermarket 0.374 -0.521 -0.857 1.046 (0.270) (-0.387) (-0.945) (0.462) fish shop -2.456** 0.209 -1.229 -6.003** (-2.452) (0.272) (-1.196) (-2.558) retailer -6.358*** -2.969* 1.565 -2.931** (-4.731) (-1.776) (0.947) (-2.605) odor 0.932 -1.530* 0.646 0.185 -0.516 (1.067) (-1.858) (0.838) (0.369) (-0.419) texture -2.160* 2.854** -0.256 -1.329** -3.229*** (-1.989) (2.203) (-0.325) (-2.586) (-3.070) moistness 0.271 1.312* 1.323 0.670 0.698 (0.355) (-1.912) (1.606) (1.441) (0.606) flavor 0.790 0.113 -1.951** 0.455 3.047** (0.904) (0.142) (-2.080) (0.801) (2.047) overall -0.470 1.327* 0.914 0.360 -1.860 (-0.579) (1.844) (1.092) (0.691) (-1.479) spouse decision -0.564* 0.066 0.237 -0.065 -0.254 (-1.847) (0.306) (0.890) (-0.419) (-0.734) cragg-uhler r2 0.718 0.345 0.375 0.238 0.807 number of observations 124 124 124 124 124 observations at zero (answers no) 30 108 109 94 95 likelihood ratio 81.269 25.491 27.035 21.495 94.875 % of correct predictions 88.7 88.7 91.9 79.8 96.0 number in parentheses are asymptotic t-values. *indicates significance at p=0.10. **p= 0.05 level. *** p= 0.01 level. __________________ *corresponding author. 8 products indicates that the higher the consumer perception of overall attractiveness, the lower is their purchase of whole fish. this may mean that whole fish as a form of purchase does not exemplify much attractiveness and that consumers preferring whole fish are looking for other characteristics such as freshness or low per unit price, rather than attractiveness. the variables that have a significant effect on consumer’s choice of fillet as a form of purchase were income, overall attractiveness, and spouse. results suggest that high-income consumers are more likely to prefer fillets than lower income consumers. this is very consistent with the previous interpretation of the negative relation between the market outlet as a choice of place of purchase and income. the higher the income the more consumers prefer to buy from fish shops and supermarkets where fish are sold in different forms including fillet and slice. consumers who place more importance on overall attractiveness are more likely to buy fillet. the logarithm of the odds that a consumer will choose fillet is higher if the consumer thinks that overall attractiveness is important in making his choice of form of purchase. the probability that consumers consider fish fillet in his form-evoked set will decrease if spouse contribution in purchase decision is important. respondents whose spouses contribute very often to the fish purchase decisions are less likely to buy fillet. however, since less than 25% of spouses are responsible for fish purchase in oman, this result implies that the market for fish in the form of fillets may be promoted. the factors for the odds of choosing sliced fish include education, income, price expectation, and odor. the logarithm of the odds that an individual consumer will choose slice as a form of purchase increases for higher consumer income, and more important the price is in substituting fish for other products. consumers with a higher level of education and those who rate natural fresh fish odor as very important in their purchase decision are less likely to buy fish in slices. the negative relationship between price and slice form of purchase is consistent with the law of demand. the lower the price of sliced fish, the greater is the probability of consumers buying fish in the form of slices. likewise, the positive relationship between income and slices is consistent with income elasticity of normal goods. the probability of buying fish in slices increases for higher consumer incomes. highincome consumers do not buy whole fish, preferring higher per unit price slices because they are consistent with their attitudinal attributes. the market outlet choice model: descriptive statistical analysis of survey data on market outlet choice revealed that the on-shore market is by far the most preferred outlet. about 76% of the respondents indicated that the on-shore fish market is their exclusive source of supply. these markets provide a variety of fish products in the most preferred forms and quality to omanis and foreign nationals residing in oman. fish is not sold per weight but by unit, case, or string of many pieces together. sales take place in an open area on the seashore where fish is displayed on the ground as landed. all other outlets are deemed less important in the consumers’ market choice. about 24% of respondents prefer fish shops and retailers while only 13% have a preference to onfc and supermarkets. results of estimated parameters and asymptotic t-values of the market outlet choice model are presented in table 4. education, income, fish shop, retailer, texture, and spouse variables significantly affect on-shore fish market choice. the model estimates indicate that consumers with higher education levels are more likely to choose on-shore market for buying fish. fish shops and retail outlets are marked substitutes for on-shore markets. moreover, the more important the fish texture to consumers’ choice the less they buy from the onshore market. likewise, the more the spouse contribution is important in the purchase decision, the less they buy from the on-shore market. finally, income is found to have negative impact on the probability of buying from on-shore markets. highincome people are less likely to use on-shore markets because on-shore markets are inconvenient and don’t offer the form and services they desire. although other market outlets appear more popular, some variables are found to have a significant effect on consumers’ choice of onfc, retailers, fish shops and supermarkets. results indicate that the probability of choosing onfc as a place of purchase decreases for large sized households, when odor and moistness are important criteria in the purchase decisions, and finally when retail outlets are important in consumers’ evoked set. in contrast, the probability of onfc purchase increases for rural consumers, and with favorable views of texture, and availability. the level of education, consumers’ origin, and flavor significantly affects the choice of supermarket. the probability of using supermarkets as the preferred place of purchase increases in urban areas with lower level of education and when flavor is an important factor in fish purchase. results indicate that rural consumers are less likely to use supermarkets as their preferred place of fish supply. results also indicate that the logarithm of the odds that a particular consumer will choose a fish shop is lower if this same consumer specified the onshore market or retailer in his choice evoked set and if texture is very important in his decision of purchase. on-shore fish markets and retailers are the most competitive outlets to the fish shop. purchase behavior of consumers for seafood products 9 the choice of retailer is significantly affected by the level of education, the origin of consumers, income, future price, texture, flavor and other market outlets, namely the on-shore market and the fish shop. results show that the probability that an individual consumer will have “retailer” in his evoked set of fish market outlets is higher with a higher level of education, if he lives in a rural area, belongs to the medium to low income group and considers price very important in substitution of fish for other products, and texture is less important in making his purchase decision. rural consumers are more likely to choose retailers than are urban dwellers. this is consistent with their geographical location with respect to on-shore markets. rural inland consumers are far from the seacoast. on the other hand, consumers who consider price as important in their spending decision on food and other products are more likely to choose retailers as their preferred outlets. the on-shore markets and the fish shops are found to be very competitive for retailers conclusions this study has focused on consumers’ attitudinal behavior with respect to fish product form and market outlet. it has generated information regarding the potential factors affecting consumers’ choices between different purchase forms and between the various market outlets. results indicate that on-shore fish markets are the most popular outlets of fish purchase in the coastal regions. they provide a variety of fish products in the most preferred form and quality. retailers and fish shops are primarily important in the rural inland areas. whole fish is the most preferred form of purchase for both rural and a large proportion of urban consumers. sliced fish is highly preferred by higher income households in urban regions. these preferences are the result of the effects of consumer demographic, socio-economic, and attitudinal characteristics as well as product attributes. income is a significant determinant of the probability that consumers buy whole fish at on-shore markets. this suggests that higher income consumers do not use the on-shore markets because they prefer to buy their fish in other forms. on the other hand, price seems to have no significant impact on fish purchases from onshore markets. this suggests a highly inelastic demand for fish in the on-shore fish markets at the current market prices. however, price is an important factor in the substitution of fish for other products. it has a significant effect on consumers' decisions only when buying fish in slices or fillet consumers’ perceptions of product characteristics are very important in the purchase decision of form and place. results indicate that the higher the consumers’ perception of overall acceptability, odor, flavor, and moistness, the lower the probability of choosing whole fish and on-shore fish markets. this indicates that consumers preferring whole fish and on-shore markets do not consider these product attributes as important, but may have higher perception of other attributes provided in fish products sold directly by fishermen on landing sites. high-income consumers are found to prefer fresh fish in processed slice and fillet forms. they place high importance on attractiveness that is not available in other forms of fish. for this reason they are more likely to buy in other outlets than on-shore markets. yet, high income people prefer to shop in one-stop outlets to buy all food items or in specialty shops where they think they are served better. moreover, their diet and cooking habits may differ from lower income households for that they are significantly attracted by forms other than whole fish. the consumers’ education is another significant factor to affect choices of place and form of purchase. results indicate evidence of positive relationship between the level of education and the preference for whole fish and on-shore market. a significant proportion of the highly educated consumers are found to have preferences for whole fish from on-shore markets. yet, this preference does not imply that the educated group will sacrifice the other good attributes of freshness, flavor, attractiveness and natural odor. the product form and market place they prefer are not provided in other market outlets. moreover, another explanation for this inconsistent relationship between the level of education and preference for whole fish and on-shore markets is the lack of evidence of a correlation between high income and education in a yet young population. strict education level is not an indicator of income. these results have considerable implications on production and marketing decisions as well as consumption planning and forecasting in light of economic development in the country and continued growth in income, education, and urbanization. it is expected that economic growth and continued improvement in income and education will prove significant in developing new product forms and purchase places at supermarkets and specialty shops. market development efforts in oman should consequently focus on the organization of on-shore fish markets in coastal regions and retailing outlets in the inland areas. the promotion of fish selling in supermarkets and specialized shops for other forms of fish would necessarily target urban high-income areas references bulmer, m. and d.p. warwick. 1983. research strategy. in: social research in developing countries: surveys and censuses in the third world, m. bulmer and d.p. warwick (editors), 27-40. john wiley and sons, inc., new york. al-mazrooei et al. 10 gempesaw, c., j.r. bacon, c.r. wessells, and a. manalo. 1995. consumer perceptions of aquaculture products. american journal of agricultural economics (77):1306-1312. hanson, g.d., g.p. rauniyar, and j.m. dunn. 1995. seafood counters in grocery stores and store characteristics. paper presented at the world aquaculture society annual meeting, san diego, ca., january 1995. herrmann, r.o., g.p. rauniyar, g.d. hanson, and g. wang. 1994. identifying frequent seafood purchasers in the northeastern united states. agricultural and resource economics review (23):226-235. houston, j., n. al-mazrooei, and c. huang. 1996. the role of consumers in fisheries product market development in oman. paper presented in marrakesh, morocco symposium, june 1996. huang, c.l. 1993. simultaneous equation model for estimating consumer risk perceptions, attitudes, and willingness-to-pay for residue-free produce. the journal of consumer affairs (23):377-396. kinnucan, w., r.g. nelson, and j. hiariey. 1993. united states preferences for fish and seafood: an evoked set analysis. marine resource economics 8:273-91. judge, g.g., r.c. hill, w.e. griffiths, h. lutkepohl, and t.c. lee. 1982. introduction to the theory and practice of econometrics. john wiley & sons. new york. ministry of agriculture and fisheries (maf). 1999. report for five year plan 2000-2001. oman. unpublished document. nachmias, c.f. and d. nachmias. 1996. research methodology in the social sciences (5th ed), london, arnold. omezzine, a. 1994. fish markets in oman. paper presented in the department of fisheries science and technology. seminar series. college of agriculture, sultan qaboos university. omezzine, a. 1998. on-shore fresh fish markets in oman: a descriptive analysis. journal of international food and agribusiness marketing 10(1):53-69. pindyck, r. and d. rubinfeld. 1981. econometric models and economic forecasting.(2nd ed). mcgraw-hill book co, new york. ray, m.l. 1974. consumer initial processing: definitions, issues and applications. in: buyer/consumer information processing, d. huges and m.l. ray (editors) 145-156. chapel hill, university of north carolina press, north carolina. simon, j.l. and p. burstein. 1985. some principles of measurement. new york. random house. statistical analysis system (sas). 1988. sas/ets users guide version 6 (1st ed). sas/stat (1993). users guide, 2(6), cary, nc. __________________________________________________ received july 2002. accepted january 2003. agricultural and marine sciences, 18:31-35 (2013) sultan qaboos university 31 ____________________________________________ *corresponding author/e-mail: rashid99@squ.edu.om a serological study on foot and mouth disease in cattle from the dhofar governorate of oman rashid m. al-busaidi1*, ahmed al -jassasi2, and eugene h. johnson1 1department of animal and veterinary sciences, college of agricultural and marine sciences, sultan qaboos university, p.o. box 34, al-khod -123, sultanate of oman 2ministry of agriculture and fisheries, p.o. box 467, muscat 113, sultanate of oman في األبقار في القالعية مرض احلمى انتشار عن مصلية دراسة عمان ظفار بسلطنة محافظة جونسون ه. ويوجني اجلساسي راشد البوسعيدي وأحمد البلدان في احليوانية والثروة االقتصادي االنتاج على كبير تأثير وله واالنتشار العدوى شديد فيروسي مرض القالعية احلمى اخلالصة: انتشار حتديد بهدف 2004 ومارس 2003 أغسطس بني في الفترة عمان في سلطنة ظفار منطقة الدراسة في هذه إجراء مت املتضررة. استخدام وقد مت قرى ظفار من قطيع 19 في بقرة 395 مجموع من مصلية عينات جمع و مت األبقار الظفارية في القالعية احلمى مرض 40.5% للعترة بواقع (206 = ٪ (العدد 52.1 القالعية احلمى ملرض العام املصلي االنتشار كان العينات. لفحص اختبار االليزا (o) و %11.6 العترة (a) للعترة (395).وشكلت العينات إجمالي والعترة (o) من %77 ,7 نسبته (a) ما اإليجابية. 22,3% العينات إجمالي من معدالت ارتفاع الى اجتاه هناك كان ولكن والسن للجنس تبعا املصلي االنتشار معدل في كبير تباين وجود لعدم الدراسة أشارت عترة من قالعية حمى وجود الدراسة هذه أوضحت ذلك إلى باإلضافة العمر. في احليوان تقدم مع االصابة a ظفار o و منطقة في .oو a العترة ، عمان ، األبقار ، القالعية احلمى كلمات مفتاحية: abstract: foot and mouth disease (fmd) is a highly contagious viral disease that has a significant impact on the economy and livestock productivity of affected countries. based on unpublished reports, serotype o has been incriminated as the sole serotype present in oman. the present study was conducted in the dhofar region of the sultanate of oman between august 2003 and march 2004 with the objective of determining the seroprevalence against fmdv in dhofari cattle. sera samples were collected from 395 cattle in 19 different herds. sera underwent screening using a liquid phase blocking elisa to determine the antibody response to the serotypes o, a, c, asia 1, sat1, sat 2, and sat 3. the overall seroprevalence of fmd was 52.1% (n=206). of the seropositive animals, 77.7% were positive for type o and 22.3% for type a. there was no significant variation in seroprevalence among different sex and age groups; however, there was a tendency towards a higher incidence of seropositive in older animals. this study confirmed that fmdv is widespread in the dhofar region. furthermore, it is the first report of serotype a and an animal testing seropositive for o and a in the sultanate of oman. keywords: foot and mouth disease, cattle, oman, serotypes o and a. introduction foot and mouth disease (fmd) fmd is the most contagious disease of cloven-hoofed domestic animals, such as cattle, sheep, goats and pigs (brown, 2003). the disease is of great concern to veterinarians, farmers, and animal product traders, because of three main factors: its highly contagious nature, its ability to persist in carriers, and the fact that there is no cross protection between the serotypes of the virus (alexandersen et al., 2003). there are 7 immunologically and serologically distinct types of fmdv: a, o, c, and south african territories (sat) 1, sat 2, sat 3 and asia 1. within each serotype there are several subtypes (alexandersen et al., 2003; sanson, 1994). infection with one type does not cross-protect against infection with the other types (aggarwal and barnett, 2002; davies, 2002; sanson, 1994). in 1987, an epidemiological study was carried out by the central diagnostic laboratory and revealed that fmd was endemic in the sultanate of oman (anonymous, 2004). virus type o was the only serotype documented (unpublished data). representative outbreaks of fmd in the sultanate of oman indicate an incidence of the disease of over 100 cases per year since 1995. dhofar is located in the southern region of the sultanate of oman and is one of the main cattle rearing areas in the country. it has a large animal population due to presence of extensive areas of green pastures. nearly two thirds of the population depends on animal husbandry for their livelihood. fmd presents a serious problem for dhofari farmers due to 32 al-busaidi et al. 33 a serological study on foot and mouth disease in cattle from the dhofar governorate of oman its devastating effect on the overall income of farmers. therefore, the present study was an endeavor to determine the seroprevalence of fmd in cattle in the dhofar region of oman, and to ascertain what serotypes they have been exposed to. materials and methods animals a total of 395 dhofari cows of both sexes (males n=121, (31%), females n=274 (69%) of different ages were used in this study. the animals were randomly selected from 19 farms from different regions of dhofar during the period from august to march 2004. none of the farms selected for this study had any vaccination program for their animals. the animals were sorted according to age groups. group 1: aged less than one year (n=21), group 2: 12 years (n=29). group 3: 23 years (n=150), group 4: 34 years (n=152) and group 5: 4-7 years of age, respectively (n=43). cows were from the following areas of dhofar: dalkot, keron herety, tawy ater, tetam, madenat alhaq, kastwt, kabrart, hgeef, krdhat, shaba saib, gadu, gorokub, alsan, sehlanoot, sadah, gahnen, al deharez, zeeq and mqorah. cattle were fed crop and orchard residues, dates, dried sardines and barley, rhode grass, agricultural residues and by-products. the cows were maintained in shaded houses and partially closed pens. samples blood samples were collected from the jugular vein in plain vacutainer tubes for serum isolation. the samples were transported to the laboratory in an icebox (4°c). all serum samples were aliquated and frozen at -20°c. liquid phase blocking elisa liquid phase blocking elisa tests, using 96-well polystyrene microtiter plates were conducted following the procedure described by the manufacturer [the institute for animal health (iah), pirbright laboratory, united kingdom]. the assay is based on specific blocking of a defined amount of fmdv antigen by antibodies in the test sample during the liquid phase. after the test serum is allowed to react with specific fmdv antigen, the test serum/antigen mixture was transferred to an elisa plate coated with fmdv serotype specific trapping antibodies. the presence of antibodies to fmdv in the serum sample results in the formation of immune complexes and consequently reduces the amount of free antigen trapped by the immobilized rabbit antisera. briefly, elisa plates were coated with 50 µl/well rabbit antisera o 1 monisia, a 22 and asia 1 , and left overnight in a humid chamber at 4°c. the elisa plates were washed three times with phosphate buffer saline (pbs). in u-shape 96 multiwell plates, 50 µl of a duplicate, control and test serum were prepared at dilution 1/16, resulting in 20 test sera for every serotype/plate. to each well, 50 µl of a constant dose of homologous viral antigen was added and the mixtures were left overnight in a humid chamber at 4°c. subsequently, 50 µl of the serum/antigen mixtures (liquid phase) were transferred from the carrier plate to the rabbit-serum coated elisa plate and incubated at 37°c for 1 hour on a rotary shaker. after washing, 50 µl of guinea-pig antiserum homologous to the viral antigen used in the previous step was added to each well. the plates were then incubated at 37°c for 1 hour on a rotary shaker. the plates were washed and 50 µl of rabbit anti-guineapig immunoglobulin conjugated to horseradish peroxidase were added to each well. the plates were incubated at 37°c for 1 hour on a rotary shaker. the plates were washed again and 50 µl of the substrate (orthophenylene diamine containing 0.05% h 2 0 2 ) were added to each well. the reaction was stopped after 15 minutes by the addition of 50 µl of 1.25 m sulphuric acid to each well. the plates were read at 492 nm on a spectrophotometer. the diagnostic threshold for this assay was set at 50 % inhibition (50 pi). if both replicate pi values of a test serum fell below 50 pi then that test serum was considered to be negative. if either, or both replicate pi values of a test serum fell above 50 pi then that test serum was considered to be positive. statistical analysis the data obtained from this study was analyzed by analysis of variance and least square (ls) mean were used to evaluate the effect of age and sex on the persistence of fmdv infection in dhofari cows. all of the statistical analysis was performed using the statistical analysis system for windows (sas, 1993). results serological results the results of the serological analysis of the tested animals are given in table 1. 40.5% of the tested sample of cows were positive for fmdv serotype o, 11.6% were positive for serotype a, and 47.9% were negative for all seven serotypes of fmdv (strain o, strain a, strain c, asia1, sat 1, sat 2, and sat 3) . from the total number of positive samples (n= 206), 160 (77.7%) and 46 (22.3%) were reactive against o and a, respectively (table 2). effect of age the results of the serological comparison of different age groups revealed that there were no significant differences (p>0.05) between the groups. however, there was a tendency for older animals to exhibit a greater number of seropositive results (table 3). effect of sex there was no significant difference (p>0.05) in seropositivity between males and females (table 4). 32 al-busaidi et al. 33 a serological study on foot and mouth disease in cattle from the dhofar governorate of oman serological response to multiple antigens one animal had a positive serological response to both type a and type o serotypes. discussion this study confirms that fmd is endemic in the dhofar region of oman. a total of 395 cattle serum samples were collected from 19 farms, 52% exhibited seropositive responses to one or more fmd viral antigens. the endemic nature of this disease may be due to the husbandry practices of farmers who increase their herd sizes by buying new animals from different markets without quarantining them (bronsvoort et al., 2004). this practice tends to increase the risk of infection (esayas et al., 2009). also, it was noticed that farmers tend to underplay the significance of fmdv as a threat to their herds. this may be due to the farmers’ experiences with the less adverse effects of fmdv in the local cattle breed. this attitude towards fmd was also observed in uganda among local farmers (clavijo and kitching, 2003). tomasula and konstance (2004) and balinda et al. (2009) reported that fmdv was shed into the milk before dairy cattle show any clinical signs of the disease and therefore, there is opportunity for raw milk to act as a factor contributing to the spread of the disease from farm to farm. in dhofar, most farmers keep mixed herds especially with sheep and goats. barnett and cox (1999) and esayas et al. (2009) reported on the relationship between mixed herds and the prevalence of fmd among cattle. they found that small ruminants are important reservoirs for fmdv but do not show clinical signs and can remain carriers for long periods of time. it can also not be ruled out that wild animals might be reservoirs of infection for cattle. indeed, potential sources of infection need to be studied in oman, as this is absolutely essential in order to develop effective control measures in the sultanate. unpublished results from the ministry of agriculture have concluded that serotype o was the only serotype found in the sultanate. however, the results obtained from the present study confirmed the incidence of serotypes a and o in the dhofar region with type o accounting for 77.7% and a for 22.3% of the seropositive responses, respectively. the emergence of serotype a may be due to the illegal importation of ruminants across borders with neighboring countries such as yemen, uae and saudi arabia where fmdv type a exists (shimshony and economides, 2006). further studies are needed to monitor the occurrence of fmdv among illegally and legally imported animals, and the probability of the entrance of other strains of fmdv. the cattle in this study were categorized according to age. there was no significant difference in the infection rates among these age groups. however, it was noticed that there was a tendency to observe a higher incidence of seroprevalence among animals aged 3 to 7 years old compared to those between 1 to 3 years of age, which is in agreement with the findings of esayas et al. (2009), molla et al. (2010), and sarker et al. (2011), who found table 1. serological response of sera collected from 395 cattle to fmdv serotypes. serotypes o a c sat 1 sat 2 sat 3 asia 1 seropositive (%) 40.5 11.6 0 0 0 0 0 number of positive sample (n=160) (n=46) (n=0) (n=0) (n=0) (n=0) (n=0) table 2. percentage of positive serological responses from the total number of positive samples. serotypes o a seropositive (%) 77.7 ( n=160) 22.3 ( n=46) table 3. the relationship between different cattle age groups and seropositivity against fmd serotypes o and a. age (yrs) number of samples number of seropositive animals percent (%) 1 21 10 47.6 12 29 14 48.3 23 150 77 51.3 34 152 86 56.6 4 7 43 25 58.1 table 4. comparison of seropositive response to o and a fmd serotypes among male and female cattle. serotypes males (n=121) females (n=274) o+ a 60 (49.6%) 146 (53.3%) a 15 (25%) 32 (21.9%) o 45 (75%) 114 (78.1%) 34 al-busaidi et al. 35 a serological study on foot and mouth disease in cattle from the dhofar governorate of oman an increasing number of seropositive animals in older animals. this may be due to the farming practices that confine younger animals and prevent them from grazing with older ones, hence decreasing their exposure to fmdv. this would be in agreement with the findings of rufael et al. (2008) and sarker et al. (2011). also there is a tendency for older cattle to follow seasonal movement patterns in search of good pastures and water where they go for long distances and cover large areas of land, thus giving them a greater opportunity to be exposed to fmd infected animals (broonsvoort et al., 2004). this study also showed no significant differences in the response to infection between males and females. this is consistent with the findings from other studies that have shown no differences between males and females (esayas et al., 2009; mekonen et al., 2011). however, a study by mazengia et al. (2010) reported a significantly higher incidence of fmd in females. the author proposed that this might be the result of higher physiological stressors such as estrus, pregnancy and lactation factors documented to affect resistance to infection. the results of the present study showed that one animal aged above 4 years of age was seropositive for both a and o. molla et al. (2010) also found infections with two different serotypes in the same animals. he suggested that this may be due to the fact that animals above 4 years of age have a greater probability of being infected with more than one serotype since they have more likely been exposed to multiple serotypes. this finding draws light on the need for the continuous monitoring of all imported animals to prevent entrance of new strains that do not yet exist in oman. in conclusion, the present study provides evidence that exposure to fmdv is widespread in dhofari cattle. furthermore, in contrast to unpublished reports of the ministry of agriculture, serotype a, in addition to serotype o, is prevalent in oman. these findings underscore the widespread nature of fmdv in dhofar and the necessity of establishing appropriate control measures. studies need to be undertaken to assure that vaccine strategies presently employed in the sultanate provide adequate protection against clinical outbreaks of the disease. it is obvious from this study that vaccines employed against fmd in oman should contain serotypes a and o, and all animals in oman should be targeted for vaccination programs and regular monitoring for development of fmdv infections. furthermore, this study indicates the need for more efforts to fully characterize isolates of fmd virus from outbreaks in oman, and to undertake seroprevalence studies in other regions of the country. references aggarwal, n. and p.v. barnett. 2002. antigenic sites of foot-and-mouth disease virus (fmdv): an analysis of the specificities of anti-fmdv antibodies after vaccination of naturally susceptible host species. journal of general virology 83:775-782. alexandersen, s., z. zhang, a.i. donaldson, and a.j. garland. 2003. the pathogenesis and diagnosis of foot-and-mouth disease. journal of comparative patholology 129:1-36. anonymous. 2004. ministry of agriculture, central veterinary laboratory, annual report, oman. balinda, s.n., k. tjornehoj, v.b. muwanika, a.k. sangula, f.n. mwiine, c. ayebazibwe, c. masembe, h.r. siegismund, and s. alexandersen. 2009. prevalence estimates of antibodies towards foot-and-mouth disease virus in small ruminants in uganda. transboundary and emerging disease 56:362-371. barnett, p.v. and s.j. cox. 1999. the role of small ruminants in the epidemiology and transmission of footand-mouth disease. veterinary journal 158:6-13. bronsvoort, b.m., k.j. sorensen, j. anderson, a. corteyn, v.n. tanya, r.p. kitching, and k.l. morgan. 2004. comparison of two 3abc enzyme-linked immunosorbent assays for diagnosis of multipleserotype foot-and-mouth disease in a cattle population in an area of endemicity. journal of clinical microbiology 42:2108-2114. brown, f. 2003. the history of research in foot-and-mouth disease. virus research 91:3-7. clavijo, a. and p. kitching. 2003. the nature and diagnosis of foot-and-mouth disease. clinical microbiology newsletter 25:81-88. davies, g. 2002. foot and mouth disease. research veterinary sciences 73:195-199. esayas, g., a. gelagay, a. tsegalem, and a. kassahun. 2009. seroprevalence of foot and mouth disease in bench maji zone, southwestern ethiopia. journal of veterinary medicine and animal health 1:5-10. mazengia, h., m. taye, h. negussie, s. alemu, and a. tassew. 2010. incidence of foot and mouth disease and its effect on milk yield in dairy cattle at andassa dairy farm, northwest ethiopia. agricultural and biology journal of north america 5:969-973. mekonen, h., d. beyene, t. rufael, a. feyisa, and f. abunna. 2011. study on the prevalence of foot and mouth disease in borana and guji zones, southern ethiopia. veterinary world 7:293-296. molla, b., g. ayelet, y. asfaw, y. jibril, g. ganga, and e. gelaye, e. 2010. epidemiological study on foot-andmouth disease in cattle: seroprevalence and risk factor assessment in south omo zone, south-western ethiopia. transboundary of emerging disease 57:340-347. ott, l. 1993. an introduction to statistical methods and data analysis. duxbury press, california. rufael t., a. catley, a. bogale m. sahel, and y. shiferaw. 2008. foot-and-mouth disease in the borana pastoral system, southern ethiopia and implications for livelihoods and international trade. tropical animal health and production 40:29-38. sanson, r.l. 1994. the epidemiology of foot-and-mouth disease: implications for new zealand. new zealand veterinary journal 42:41-53. 34 al-busaidi et al. 35 a serological study on foot and mouth disease in cattle from the dhofar governorate of oman sarker, s., s. talukder, m.h. haque, m.h. islam, and s.d. gupta. 2011. epidemiological study on foot and mouth disease in cattle: prevalence and risk factor assessment in rajshahi, bangladesh. wayamba journal of animal science 71-73. issn: 2012-578x. shimshony, a. and p. economides. 2006, disease prevention and preparedness for animal health emergencies in the middle east. review science technology 25:253-269. tomasula, p.m. and r.p. konstance. 2004. the survival of foot-and-mouth disease virus in raw and pasteurized milk and milk products. journal of dairy science 87: 1115-1121. received: september 15, 2012 accepted: december 3, 2013 img070 img071 img072 img073 img074 agricultural and marine sciences, 12:1-12 (2007) ©2007 sultan qaboos university 1 *corresponding author. e-mail: slim@squ.edu.om profitability analysis of selected farms in the batinah region of oman fahad a. al said1, slim zekri2* and iqrar a. khan1 1department of crop sciences / 2department of agricultural economics and rural studies, college of agricultural and marine sciences, sultan qaboos university, p.o. box 34, al-khod 123, muscat, sultanate of oman abstract: the agricultural sector of oman represents less than 2% of the total gdp and uses 88% of the fresh water. several decision makers are questioning whether the agricultural activity in the sultanate of oman can be sustained and if so what type of crops should be encouraged. more than 53% of the agricultural cropped area is situated in the batinah coastal area where farming is exclusively based on groundwater pumping. a sample of 49 market-oriented farms from the batinah region was surveyed during 2006. four types of farms were considered. results showed that the most profitable farms are mixing fodder crops and vegetables with a net margin of 1,412 ro/ha/year. the less profitable farms are based on tree crops and vegetables with a net margin of 847 ro/ha/year. for vegetables the most profitable crop is tomato with an average net margin of 2,580 ro/ha/year with a standard deviation of 2,043 ro/ha/year and the least profitable crop is cabbage with 113 ro/ha/ year with a standard deviation of 182 ro/ha/year. the net margin of crops grown under drip irrigation is higher than that for crops under furrow irrigation, with a difference of 548 ro/ha/year. farms equipped with such modern irrigation systems tend to irrigate almost the same area in winter as in summer, while farms under furrow irrigation crop less than one percent of their cropped area during summer compared to winter. consequently and contrary to expectations, modern irrigation systems tend to increase, rather than reduce, groundwater pumping given the financial incentives for farmers to grow summer vegetables instead of only winter vegetables. even so, the net water use efficiency is greater for vegetable production under drip irrigation بسلطنة عمان الباطنة، في منطقة مختارة لمزارع تحلیل ربحي خان زكري وإقرار سلیم سعید و آل فھد الریفیة والدراسات الزراعي قسم االقتصاد / المحاصیل علوم قسم والبحریة الزراعیة العلوم كلیة الماء من ھذا القطاع %88 المحلي، بینما یستخدم الناتج إجمالي من % 2 من اقل في سلطنة عمان یمثل القطاع الزراعي الخالصة: تشجیعھا. یجب التي المزروعات وماھیة عمان سلطنة في النشاط الزراعي استدامة حول القرار صناع من البعض یتساءل وقد العذب. وخالل وحدھا. الجوفیة المیاه على یعتمد المزارعون حیث الباطنة، ساحل في المزروعة تقع األراضي إجمالي من %53 من أكثر إن أنواع أربعة االعتبار في اخذ وقد الباطنة، في منطقة الھدف تجاریة المزارع الصغیرة أصحاب من مزارعا 49 تم استبیان 2006 عام أما ریال/ھكتار). 1412 صافي الربح والخضار( األعالف تنتج التي ھي جدوى المزارع أن اكثر أوضحت النتائج من المزروعات. الدراسة الخضار وجدت لمزارع وبالنسبة ریال/ھكتار). 847 الربح والخضار(صافي األشجار مزارع فكانت جدوى األقل المزارع 113 (صافي الربح جدوى األقل ھو الملفوف كان بینما ریال/ھكتار) 2580 الربح (صافي جدوى األعلى المنتج ھو إن الطماطم بالغمر للمزروعات التي تروى الربح صافي التقطیر كانت أعلى من للمزروعات التي تروى بنظام الربح صافي كما أن ریال/ھكتار). المزروعة المساحة نفس تروي الحدیث الري نظام تستخدم التي المزارع بان ھنا /ھكتار. تجدر اإلشارة ریال 548 مقداره باختالف المزروعة المساحة من % 2 عن تقل نسبة الشتاء فصل في تستغل الغمر نظام تستخدم التي المزارع بینما الصیف، و الشتاء فصلي في على زراعة المحاصیل المزارعین بتشجیع الجوفیة ضخ المیاه إلى زیادة یؤدي الحدیث الري نظام أن ذلك یتضح من الصیف. في منھا أعلى الخضروات في الحدیث الري بنظام استخدام المیاه كفاءة أن إال على فقط. الشتویة زراعة المحاصیل عن عوضا الصیفیة تم التي إلى المحاصیل مالیة بالنسبة جدوى ھي ذات في منطقة الباطنة أن الزراعة على في المتوسط وتدل المؤشرات األعالف. في إلى الفرق ھذا ویعزى المختلفة. المحاصیل وبین المزارع وبعضھا في األرباح بین كبیر فرق وجود مع الدراسة، ھذه في إعتبارھا في األسعار. االختالف واالقتصادیة الناتجة عن المحاصیل، إنتاجیة في الكبیر التباین خالل من التقنیة وذلك األسباب al-said, zekri and khan 2 3 profitability analysis of selected farms in the batinah region of oman introduction the climatic and ecological diversity in oman offers an opportunity to grow high-value, off-season vegetable crops, which have a ready market in the region as well as in distant markets. off-season vegetable cultivation is feasible because of the mild winter climate. exports of agricultural products reached 12.5% of oman’s non-oil exports in 2005 (ministry of national economy, 2007) and over 160,000 omanis are fully or partially employed in the agricultural and fisheries sectors (ministry of agriculture and fisheries, 2006). despite these achievements the agricultural sector’s performance remains unsatisfactory. in this article we consider improving the efficiency of water use and shifting to high-value vegetable crops in order to improve the productivity of the agricultural sector. more than 53% of the cropped area in oman is situated in the batinah region and is totally dependent on groundwater (ministry of agriculture and fisheries, 2006). excessive water mining has caused seawater intrusion into the aquifer, leading to salinity problems in many locations. the soil salinity in the batinah region ranges between 2 ds/m to 20 ds/m; salinity is one of the most serious constraints in crop production. worldwide, over two billion people suffer from deficiencies of micronutrients in their diets (gardner and halweil, 2000). such malnutrition prevents much of the world’s population from reaching their full mental, physical and financial potential. it also contributes to higher rates of deaths caused by heart disease, stroke and cancer (khaw et al., 2001). this situation can, in part, be remedied by increasing the supply and consumption of vegetables. it is important that the quantity and quality of vegetables used are of the highest possible standard. the diet in oman is dominated by rice and is thus potentially deficient in vitamin a; this suggests that greater research and extension efforts need to be applied to vegetable production and supply (dellapenna, 2001). previous research in this field includes analysis of the demand for, and marketing of, vegetables in oman (omezzine et al., 1998); studies on some aspects of salinity and fertilization of potatoes and tomatoes (rehmatullah, 1996; satti et al., 1995). however, studies that consider the profitability of both crops and farming systems are missing. the present paper attempts an assessment of the profitability of farms specializing in vegetable production and compares the results to profitability figures for other forms of agriculture in the same region of oman. the paper also analyzes the impact of the adoption of modern irrigation systems and farmers’ awareness of the problem of groundwater salinization. it provides a baseline for future analysis of the profitability of the farming sector. the paper concludes with a discussion on the possible implications for vegetable growers of a new policy on the production of fodder crops. methodology gross margins and net margins are used as indicators to estimate crop and farm profitability. calculations are based on observations of farmers’ inputs and production of outputs. the gross margin (gm) is defined as follows: gm = yield *price variable costs where, yieldi = output in kg/ha for crop i; pricei = price of output i in omani ro/kg; variable costsi = cost of seeds, fertilizers, agrichemicals, occasional labor and transport to market for crop i in omani ro/ha. the weighted average gross margin per crop and group of farms is defined as follows: wgm = ∑∑a *gm /∑a where, aif = area of crop i at farm f in group g; gmif = gross margin of crop i at farm f in group g. the net margin (nm) at farm level is the return to land, capital and management and is defined as follows: nm = ∑wgm permanent labor cost energy cost dcmis than it is for fodder production. the figures show that, on average, farming in the batinah is financially profitable for the types of farm considered in this study. however, profitability varies widely between different farms and crops. the reasons for these differences are technical, as observed in the big differences in yield among crops, and economic because the prices received by farmers differ significantly. keywords: vegetables, oman, salinity, irrigation, fodder crops, yields, profitability. al-said, zekri and khan 2 3 profitability analysis of selected farms in the batinah region of oman where, energy costf = the cost of electricity or fuel used for pumping groundwater at farm f; dcmisf = depreciation cost of the modern irrigation system at farm f. the net margin should not be interpreted as a net return because the cost of management, cost of capital and the opportunity cost of land are not accounted for. data collection a survey was run in the batinah area of farms of over two hectares in size to determine crop mix, crop yields, and input use. more than 150 farms were visited but only 54 farmers were willing and able to answer the detailed questionnaire about input use and output. the total number of farms larger than two hectares in the batinah region is 8,587 (maf, 2006). the final number of farms retained for statistical analysis was 49 only, due to incoherent data in five surveys, which were removed from the sample. the sample thus represents only 0.6% of total farms larger than two hectares. this is due to the fact that most farmers do not keep any records related to input use and output marketing. although the sample is statistically not representative the paper gives an overview of farming profitability in the batinah region and focuses on farms with available information. the farms were divided into four different groups according to the major types of crops grown. these groups are defined as follows: table 1. survey sample and farm characteristics. all farms group 1 2 3 4 vegetables tree crops and vegetables fodder and vegetables mixed number 49 23 17 5 4 total area (ha) 394 262 91 18.1 19 cropped area (ha) 289 207 54 14 14 cropped area (%) 73 79 59 76 73 average farm size (ha) 8.03 11.39 5.37 3.62 4.82 average cropped area (ha) 5.90 9.00 3.18 2.76 3.49 area occupied by vegetables (%) 68 100 46 21 43 area occupied by trees (%) 25 0 54 0 23 area occupied by fodder (%) 7 0 0 79 33 • group 1: farms growing vegetables only. • group 2: farms growing mainly perennial crops (e.g, dates, mangoes, citrus fruit), with some vegetables. • group 3: farms growing mainly fodder crops, with some vegetables. • group 4: mixed farms growing vegetables, fodder crops and perennials (dates, etc.). table 1 shows some characteristics of the surveyed farms. the average farm size is eight hectares. on average the cropped area represents only 73% of the total area with farmers in group 1 cropping 79% of the total area and farmers in group 2 cropping only 59% of the area. seventy five percent of the farms are individually owned, with 25% of the farms owned by two or three siblings. farming is the sole source of income for 37% of the farmers interviewed. the remaining farmers are either retired from previous occupations (15%) or are part-time farmers with their main activity in the government or private sector (48%). despite the small size of the farms, 60% of them employ permanent laborers and 40% of the farms use occasional labor. on average a permanent employee is paid 60 ro/month plus food, housing, health insurance and travel costs. for the occasional labor, employees are paid 4 ro/day in most cases. results the results are presented on a crop-by-crop basis for each of the four groups of farms. subsequently, group performances are compared. al-said, zekri and khan 4 5 profitability analysis of selected farms in the batinah region of oman group 1: farms growing only vegetables the average number of crops grown per farm in this group is six. the relatively large number of crops grown with respect to the small area denotes the absence of specialization despite the fact that farms are market oriented. the most important crops in terms of area are watermelon and melon with 31% and 27% of the cropped area respectively, followed by tomato (25%) and cabbage (8%). comparing all crops, the highest average yield is observed in potato with 48 t/ha (table 2). melon and watermelon registered average yields of 14 and 16 t/ha, respectively. yields for cabbage and tomato were 4 and 38 t/ha, respectively. yield differences among farms are very high, as is shown by the calculated standard deviations. thus, for example, for melon and water melon the standard deviations were 7 t/ha for both crops and for tomato 26 t/ha. these high standard deviations indicate that there are large possibilities for yield improvements in the batinah region by the appropriate planning of extension programs for vegetable growers, focusing on the best management practices. the available data could serve as a basis for the selection of the best farmers for collection of further details on best management practices. on average the variable costs for this type of farm are 1,662 ro/ha, with the highest cost observed for potato at 3,955 ro/ha. the last figure might explain why only one single farmer produced potatoes. in terms of profitability, the highest gross margin (gm) is obtained for tomato with 3,105 ro/ha and the least profitable crop is cabbage with only 560 ro/ha. the weighted average gm at farm level is 1,674 ro/ha. at farm level, the net margin (nm) or the return to land, capital and management is estimated at 1,253 ro/ha of cropped land. given an average cropped area of nine hectares for this group then the average return to land, capital and management is 10,689 ro per farm or 890 ro/month. this figure does not represent the net economic return since the cost of management, cost of capital and the opportunity cost of land are not subtracted. since vegetables are produced during both the winter (planted in fall) and summer (planted in march onwards) seasons, it is necessary to analyze the profitability on a per season basis. the comparison is important because water is scarce in oman and crops grown in the summer require more water. in terms of area, almost the same cropped area is observed in winter and in summer with only a 2% reduction of table 2. yields, total costs and profitability of crops in group 1 farms. crop cropped area (%) yield operating cost gross margin net margin average t/ha standard deviation average ro/ha standard deviation average ro/ha standard deviation average ro/ha standard deviation tomato 25 38 26 2,166 1,296 3,105 1,998 2,627 2,018 eggplant 1 8 2 2,774 696 2,839 1,115 1,392 145.000 pepper 5 15 10 1,870 1,161 1,897 1,097 1,415 1,112 cauliflower 1 15 18 1,440 587 1,112 500 821 635 watermelon 31 16 7 1,272 667 1,235 679 938 552 potatoes 1 48 0 3,955 3,019 1,769 794 1,402 493 lettuce 1 9 4 1,472 960 658 384 321 253 melon 27 14 7 1,662 595 1,217 968 854 1,029 onion 1 17 0 2,015 1,434 1,456 1,425 345 235 cucumber 0.1 24 24 2,611 1,399 365 parsley 0.1 2 2 283 660 431 cabbage 8 4 1 818 355 560 210 204 84 bitter gourd 1 6 1 1,895 760 1,087 228 407 176 total 100 1,662 1,674 1,253 al-said, zekri and khan 4 5 profitability analysis of selected farms in the batinah region of oman area during summer. the crop mix differs between seasons: crops such as cauliflower, cucumber, lettuce, coriander and potatoes are grown only in the winter. seventy five percent of the cropped area in winter is occupied by tomato, cabbage and watermelon. the most important crops grown in the summer are musk melon and water melon, together taking up 89% of the cropped area. yields are higher in winter than in summer for all crops grown in both seasons except for watermelon, for which the yield in winter was 14 t/ha and in summer 16 t/ha. a comparison of the net margins for vegetables in winter and in summer is shown in figure 1. the nm is much higher in winter than in summer for tomato, pepper and melon but cabbage and watermelon are more profitable when grown in summer. the average nm of winter vegetable crops is 1,655 ro/ha, almost double the nm for summer vegetables of only 882 ro/ha. because water is the major constraint in crop production in oman the return to water should be considered as an indicator for water-management policy. given that nms are lower in summer and that crop water requirements are higher in summer, then the return to water from summer vegetables is lower than the return to water from winter vegetables. consequently, growing vegetables in the summer should be discouraged. n et m ar gi n (r .o ./h a) crops figure 1. main vegetable crops and their profitability per season. most farms in group 1 are irrigated using modern irrigation systems, mainly the drip system. comparison of profitability at farm level, after subtracting the depreciation and variable cost of the drip irrigation system (estimated to be 412 ro/ha), shows that it is more profitable to use drip irrigation than furrow irrigation. the average nm for crops using the drip irrigation system is 956 ro/ha, compared to 408 ro/ ha for those watered by furrow irrigation. comparing farms, the nm of farms irrigating more than 80% of their land by the drip system is 1480 ro/ha, while the nm for farms using furrow irrigation on more than 80 % of their land is 670 ro/ha. however it should be made clear that farms equipped with drip irrigation systems irrigate almost the same area in summer as in winter, while those using the furrow irrigation system irrigate less than 1% of the land cropped in winter in the summer. these figures illustrate clearly that, although modern irrigation systems use water more efficiently, they tend to increase water demand by allowing vegetable crops to be grown in the summer, since they provide a continuous flow of water responding to crop requirements. thus, contrary to expectations, modern irrigation systems tend to increase, rather than reduce, groundwater pumping given the financial incentives for farmers to grow summer vegetables as well as winter vegetables. however, the double cropping of tomato pepper watermelon melon cabbage farm al-said, zekri and khan 6 7 profitability analysis of selected farms in the batinah region of oman vegetables irrigated by drip systems still uses water more efficiently than does the cultivation of fodder crops and tree plantations (perennials). the production potentials of vegetables are observed in the top ten percent of farms in group 1. these farms have an average gross margin of 3,108 ro/ha and an average net margin of 2,580 ro/ha, double the average nm of group 1 as a whole, and have an average water salinity of 1,082 µs/cm. on these best performing farms drip irrigation covers 87% of the cropped area and the average monthly electricity bill is18 ro, triple the average consumption for farms in group 1. the two most important crops are tomato and watermelon with yields of 66 t/ha and 14 t/ha, respectively. group 2: farms growing perennials and vegetables more than 50% of the cropped area for farms in this group is occupied by date palm, mango and citrus trees. the remaining area grows vegetables. table 3 shows the yield and profitability of the different crops grown by farms in group 2. the prevailing vegetables are cucumber and tomato, with cucumber giving the highest yield at 27 t/ha. the average variable cost per farm in group 2 is 1,351 ro/ha, with the variable cost of growing cucumber being the highest, at 5,354 ro/ ha. the average gross margin per farm is estimated at 1,522 ro/ha, with potatoes having the highest gm at 5,048 ro/ha followed by cucumber with 4,301 ro/ha. the average nm per farm is 847 ro/ha. finally, a comparison of the profitability of vegetables and that of tree crops shows that vegetables are more profitable, except for lettuce, which is less profitable than tree crops. a comparison of the average net margins of groups 1 and 2 shows that group 1 is significantly the more profitable with a nm of 1,253 ro/ha, while the nm of group 2 is only 847 ro/ha, a difference of 406 ro/ha. group 3: farms growing fodder crops and vegetables in this group of farms vegetable crops represent only 21% of the cropped area. as shown in table 4 the most important vegetable crop, in terms of area, is onion with eight percent of the area. the average variable cost is 738 ro/ha at farm level and the crop with the highest cost is potato with 2,100 ro/ha. in terms of profitability the highest gm is obtained for garlic with 3,167 ro/ha; the lowest gm is observed for onion with 706 ro/ha; and the highest gm for any fodder crop is for alfalfa, with 2,948 ro/ha. fodder crops are usually sold as green fodder. at farm level the weighted average gm is 1,876 ro/ha which is higher than the gms obtained for farms in groups 1 and 2. table 3. yields, total costs and profitability of crops in group 2 farms. crop/plant cropped area (%) yield operating cost gross margin net margin ave. t/ha ave. ro/ha standard deviation ave. ro/ha standard deviation ave. ro/ha standard deviation potatoes 1 19 2,161 5,048 3,553 cucumber 8 27 5,354 4,568 4,301 3,237 2,197 2,151 pepper 3 17 2,649 1,954 2,712 1,934 1,637 1,171 tomato 5 22 2,642 1,850 2,691 1,901 1,049 1,406 onion 3 14 2,216 2,311 1,704 1,231 1,704 1,231 watermelon 1 7 1,182 915 246 bitter gourd 1 6 1,855 1,721 819 67 502 3 lettuce 0.4 2 213 333 168 dates 52 3 575 791 1,222 1,700 742 1,699 mango 18 7 1,216 2,266 777 1,154 385 883 orange 1 7 1,018 240 1,228 223 476 251 lime 6 5 690 562 913 640 289 531 total 100 1,351 1,522 847 al-said, zekri and khan 6 7 profitability analysis of selected farms in the batinah region of oman table 4. yields, total costs and profitability of crops in group 3 farms. crop/plant cropped area (%) yield (t/ha) total cost (ro/ha) gross margin (ro/ha) net margin (ro/ha) ave. standard deviation ave. standard deviation ave. standard deviation ave. standard deviation garlic 3 5 1,605 3,167 2,348 potatoes 3 29 2,100 3,512 2,185 onion 8 18 1,518 706 268 tomato 5 8 3 1,173 503 1,046 570 351 36 alfalfa 40 71 50 622 319 2,948 1,985 2,493 1,561 maize 34 1 294 630 420 baffle grass 11 71 41 792 728 1,592 911 994 626 rhodes grass 13 7 471 522 243 total 105 738 1,876 1,412 the average nm is 1,412 ro/ha, which is the highest nm found in any of the four groups of farm and which appears to show that the highest level of farm profitability is linked to fodder production. since this study used only prices for 2005/06, this result should be considered with some care due to price variations from year to year. group 4: farms growing a mixture of crops this group is composed of farms growing vegetables (38%), tree crops (or perennials) (44%) and fodder crops (18%). the average farm size is 3.37 ha and on average a farm grows eight crops (table 5). the most important vegetable crop is tomato representing 16 % of the area, followed by watermelon and muskmelon with 8 and 5% of the area, respectively; the most important fodder crop is rhodes grass, taking 13% of the cropped area; and the most important perennial (or tree crop) is dates, with date palms taking 33% of the cropped area. on average, variable costs are 701 ro/ ha with cucumber having the highest variable costs at 6,638 ro/ha and mango the lowest at only 155 ro/ha. among vegetables the highest gm is obtained for tomato with 3,854 ro/ha. the average gm per farm is 1,559 ro/ha and the average nm is 1,187 ro/ha, which is the second best nm among the four groups. comparisons of farm performance in this section we compare the profitability of the four groups of farms. the highest average gross margin per group is obtained by farms in group 3, producing fodder crops and vegetables as shown in figure 2. the highest average net margin per group at 1,412 ro/ha is also found in group 3; thus the most profitable type of farming appears to be a mixture of fodder crops and vegetables. the second highest average nm is found among farms in group 1 at 1,253 ro/ha, which is only 160 ro/ha less than the average nm for group 3 farms. the average nm of all farms is 1,179 ro/ha with a standard deviation of 889 ro/ha, and a coefficient of variation of 76% between farms. for group 1 farms the standard deviation is 936 ro/ha, with a coefficient of variation of 75%. the highest coefficient of variation is observed among group 2 farms at 83% and the lowest coefficient of variation, 55%, is found among farms in group 3. this may indicate that a mixture of fodder crops and vegetables is the least risky type of farming. these figures indicate that in all groups profitability variation among farms of the same group is very high. this may be due to the absence of organization and communication among farmers, which may hold back diffusion of the best management practices. since all these farms experience similar environmental conditions, the reasons for the wide discrepancies among farms are most likely to be related to the way these farms are managed, though the availability and quality of irrigation water might also explain part of the profitability differences among farms of a given group. table 6 shows the water salinity levels per farm group. the average salinity level of the surveyed farms is 1642 µs/cm. most of the farms (84%) have a al-said, zekri and khan 8 9 profitability analysis of selected farms in the batinah region of oman table 5. yields, total costs and profitability of crops in group 4 farms. crop/plant cropped area (%) yield (t/ha) operational cost (ro/ha) gross margin (ro/ha) net margin (ro/ha) ave. standard deviation ave. standard deviation ave. standard deviation ave. standard deviation eggplant 1 7 1,263 3,150 2,308 cucumber 1 38 6,638 2,919 981 tomato 16 36 1,030 230 3,854 1,414 3,434 1,493 pepper 1 18 1,394 3,019 2,177 watermelon 8 27 29 1,503 453 1,641 1,027 878 894 melon 5 14 1,556 2,159 1,302 garlic 2 4 5 262 94 848 875 666 829 parsley 2 2 751 654 440 onion 2 3 375 123 378 77 197 123 dates 33 3 3 181 67 974 1,102 814 1,094 lime 5 3 1 514 558 1,052 1,196 864 1,169 mango 4 4 2 155 84 441 218 286 302 orange 2 2 0 202 152 229 81 74 165 alfalfa 3 36 942 1,657 843 baffle grass 1 89 1,892 2,165 340 maize 1 4 371 2,844 2,629 rhodes grass 13 12 520 418 195 total 100 701 1,559 1,187 moderate salinity level and only 2 % of the farms have a low level of salinity with less than 300 µs/cm. group 3 and group 4 have the highest percentages of farms with water salinity exceeding 2500 µs/cm. observation of farms in group 1 shows that melon, watermelon and cucumber are not grown in farms with high salinity. differences in yield vary from crop to crop when farms with moderate salinity are compared to farms with high salinity. for instance, for tomato the average yield for farms with moderate salinity was 37 t/ha but for those with high salinity the yield was 31 t/ha; for pepper the yield dropped more markedly from 14 t/ha to only 6 t/ha. the average gm was 1,804 r/ha for farms having moderate salinity compared to a gm of 1,171 r/ha for farms with high salinity. these figures are merely indicative and should not be generalized as the sample was not large enough to address specifically the salinity problem. besides, the use of inputs varies between farms, which also causes gm differences. in other words, differences in gross margin among the farms with moderate salinity and those with high salinity could not be attributed to the water salinity variable alone. farmers’ awareness and groundwater salinization given the scarcity of water and its quality degradation farmers were interviewed about water management, the reasons for increasing salinization and possible remedies. table 7 shows well depth in 2005 and decisions to deepen wells in that year. on average the well depth was 39.2 meters. in 2005 twenty seven percent of farmers deepened their wells by an average of 11.8 meters. those farmers who deepened their wells were all looking for more water and 23% of farmers were looking for lower salinity levels. since wells are not equipped with water-flow meters the consumption of electricity is used as a proxy for water use. on average, farms are spending 9.735 ro/month/ha on electricity. given that the depths of the wells vary between the four groups of farms, the monthly cost of electricity/ha/meter of well depth was estimated to allow comparison. the figures vary between a low of 0.208 ro/ha/month/meter for farms in group 3 and a high of 0.389 ro/ha/month/meter for group 4 farms. surprisingly, for group 1 farms, all of which grow only vegetables, the average electricity al-said, zekri and khan 8 9 profitability analysis of selected farms in the batinah region of oman consumption is 0.230 ro/ha/month/meter while for group 3, in which farms produce fodder crops and vegetables, the consumption of electricity and hence water is the lowest of all. the cultivation of fodder crops in the batinah is thought to require the greatest amount of water and figure 2. gross and net margins per farm group and standard deviations. group of farms table 6. irrigation water salinity level per farm group. average salinity (µs/cm) max salinity (µs/cm) min salinity (µs/cm) low salinity (< 300 µs/ cm) (%) moderate salinity (300< >2500 µs/ cm) (%) high salinity (>2500 µs/ cm) (%) all farms 1642 11330 242 2 84 14 group 1: vegetables 1994 11330 622 0 85 15 group 2: tree crops and vegetables 1245 3010 242 6 88 6 group 3: fodder and vegetables 1827 3240 322 0 67 33 group 4: mixed 1436 3480 580 0 75 25 r ia ls /h a/ ye ar is thus identified as an important cause of the overabstraction of groundwater. our results show that the type of farms using the highest quantity of electricity, and hence the highest volumes of water, are those in groups 2 and 4 where tree crops occupy 54% and 23% respectively of the cultivated area. the average al-said, zekri and khan 10 11 profitability analysis of selected farms in the batinah region of oman table 7. wells: depth, management and electricity consumption. average well depth (m) farms increasing well depth during 2005 (%) average increase in depth (m) looking for better quality water (%) looking for more water (%) monthly cost of electricity (ro/ha) ratio of monthly cost of electricity to well depth (ro/ha/meter) all farms 39.2 27 11.78 23 100 9.735 0.248 group 1: vegetables 26.6 26 3.21 33 100 6.111 0.230 group 2: tree crops and vegetables 62.3 29 25.88 0 100 23.605 0.379 group 3: fodder and vegetables 40.0 40 2.262 50 100 8.318 0.208 group 4: mixed 27.2 0 0 0 0 10.588 0.389 electricity bill for farms in group 2 is nearly four times higher than the average bill for farms in group 1, which would indicate excess water application to tree crops. however, for cultural reasons, it is hard to implement any policy to reduce the area of plantations mainly occupied by date palms. when farmers were asked about the salinization of the groundwater, 47% said that they were concerned by this problem. eighty seven percent identified overpumping as the reason for the salinization problem. this high percentage shows the awareness of farmers about the main cause of the problem. farmers were then presented with four options to reduce the overpumping of groundwater: the results are presented in figure 3. the most frequently chosen option was to ban irrigation during the summer season (47% of the responses); 39% of respondents chose banning the production of fodder crops; 11% of farmers chose increasing electricity prices; the least popular option was establishing water quotas, chosen by only 3 % of farmers. farmers were also asked what solutions they would propose to reduce groundwater over-pumping (see figure 4). twenty seven percent proposed a ban on growing fodder crops; 20% suggested using desalinated water for irrigation; 13% proposed increasing well depth and another 13% proposed introducing modern irrigation systems; 7% proposed the use of treated wastewater; while 13% still think that greater rainfall in the future will solve the problem of salinization. these suggestions contradict the result in the paragraph above where 87% of the farmers recognized that over-pumping is the main cause of seawater intrusion and hence salinization. actually, most of the farmers considered that the salinity problem was caused by “others”. many farmers still appear to believe that the limits of water pumping have not been reached, because they proposed increasing well depth. not a single farmer proposed cooperation between farmers and common management of water resources as a solution to the problem. finally, 20% of farmers proposed that the government desalinates water for agricultural uses; thus implying that farmers expected someone else (the government) to solve the problem they (the farmers) are causing and at a cost higher than the benefit for society. these results suggest the need for an extension program for farmers focussing on the necessity for a reduction in groundwater pumping and the mechanisms by which this might be achieved. possible implications of banning the cultivation of fodder crops in the batinah one of the policy options being considered by the government is a ban on the cultivation of fodder crops al-said, zekri and khan 10 11 profitability analysis of selected farms in the batinah region of oman on batinah farms larger than 13 ha and the transfer of cultivation of these crops to the nejed area. the main objective of this policy is the reduction of groundwater pumping to minimize seawater intrusion. the current area of fodder crops in the batinah is 9,687 ha while the total area of vegetables is only 4,070 ha (maf, 2006). such a ban would seem to present the opportunity to expand the area of vegetable crops, since most fodder growers are likely to shift to vegetables, largely because vegetables are seasonal crops with immediate profitability. but fodder producers would first need to figure 3. farmers’ opinions about measures to control groundwater extraction. figrue 4. farmers’ suggestions to circumvent the water salinization problem. taxing car washers, 7%use treated wastewater, 7% rely on more rain, 13% increase well depth, 13% ban growing fodder, 27% use mis, 13% use desalinated water, 20% establish water quotas, 3% increase electricity prices, 11% ban irrigation during may to sept, 47% ban fodder production, 39% upgrade their irrigation systems from sprinklers to the drip system; this could apply to over 5,000 ha. one immediate consequence of such a switch from fodder to vegetable production would be an increase in supply and a subsequent fall in price, unless more vegetables are exported. however, in the short run it is unlikely that greater exports could be achieved since there are no farmers’ boards and farmers lack organization. in addition, it is hard to believe that farmers more used to producing fodder crops could, in the short run, produce the high quality vegetables demanded by international markets. in terms of the demand for water, a comparison of vegetable farms with farms producing fodder, shows that the former use slightly more water, as shown by the demand for electricity (see table 7). consequently, banning the cultivation of fodder crops will not allow water saving. from a financial point of view, current vegetable farmers as well as farmers who switch to growing vegetables would suffer a fall in income. the former will lose as a consequence of an excess supply of vegetables, at least in the short run. incomes in the latter group would fall for two reasons, the first is that vegetable cropping is less profitable than fodder production and the second is that vegetable prices would fall, as mentioned above. another issue concerns the shortage of agricultural labor due to restrictions on the number of visas for laborers from neighboring countries. most fodder production is mechanized, but al-said, zekri and khan 12 vegetable production is labor intensive and would thus become much more costly. conclusions in this paper a sample of 49 small-scale farms in the batinah has been studied, using interviews with farmers and surveys. yields, variable costs and profitability were estimated. we observed that vegetable yields differ significantly among farmers, as is indicated by the high standard deviations. these yield gaps might be reduced by extension programs for vegetable growers, which focus on the best management practices. in financial terms farming in the batinah is a profitable activity, with even the lowest average net margin per group being 847 ro/ha/year in 2005 this was for the fruit and vegetable farms forming group 2. against expectations, the highest average net margin of 1,412 ro/ha/year was obtained for group 3, in which farms produce fodder crops and vegetables. though all four groups’ average net margins are high enough, the standard deviations point to large variations in profitability between farms. this implies that the full potential of economic productivity has not yet been reached. the top 10% of vegetable farms growing only vegetables (group 1) registered a net margin of 2,580 ro/ha, double the average net margin of the whole group. however, these top farms operate in an environment characterized by moderate salinity, which is not the case for all farms in the batinah. even if better water quality does explain part of the high net margins obtained by some farmers, there are technical deficiencies as well as economic barriers that should be looked at to improve farmers’ returns in the region. from a purely technical point of view, yields are still lower than can be found in other countries. one example is tomato where the highest observed yield was 66 t/ha, far from the widespread 100 t/ha achieved in several developed and less developed countries; similarly, the yields reported for cabbage are particularly low. from an economic point of view, helping farmers to get organized and work together should be considered in order to reduce production costs, improve marketing and increase prices received. the crop mix in all farm groups shows a large number of crops being cropped at a time. the farms considered in this study are market oriented. the mix of several crops is an indication of absence of specialization, but it is also a mean of reducing risk. the high variation of yields among farmers for the same crop calls for diffusion of the results obtained in several research projects. the expected ban on growing fodder crops in the batinah area, and the transfer of such cultivation to the nejed area, might lead to an increased supply of vegetables in the local market and a subsequent price fall for farmers in the short run. however, the expected expansion of vegetables in the batinah is an excellent opportunity to promote best management practices and increase productivity in the years to come. acknowledgments this research was funded by his majesty’s strategic research project (sr/agr/plnt/04/01) awarded to dr. iqrar khan. the authors are grateful to murei albarhi for his assistance with this investigation. references dellapenna, d. 2001. nutritional genomics. science 285:375-379. gardner, g. and b. halweil. 2000. underfed and overfed: the global epidemic of malnutrition. worldwatch paper 150. worldwatch institute. washington, dc, u.s.a. khaw, k., s. bingham, a. welch, r. luben, n. wareham, s. oakes, and n. day. 2001. relation between plasma ascorbic acid and mortality in men and women in epic-norfolk prospective study: a prospective population study. the lancet 357: 657-663. ministry of agriculture and fisheries. 2006. agricultural census 2004/2005. ministry of agriculture and fisheries. sultanate of oman. ministry of national economy. 2007. economic development strategy and the growth of the agricultural sector. workshop on the agricultural sector sustainable development and labor market. 10-12 february, 2007. ministry of national economy, samail, sultanate of oman. omezzine, a., g.v. chomo and o. al-jabri. 1998. demand analysis of selected fruits and vegetables in oman. squ journal of scientific research agricultural sciences 3:19-26. rehmatullah, x. 1996. diagnostic criteria for fertilizing irrigated potatoes on entisols under arid climate of oman. pakistan journal of soil sciences 12:45-50. satti, s.m.e., m. lopez and s.a. al-rawahi. 1995. effect of saline nutrient solutions on growth and accumulation of mineral elements in some tomato cultivars. communication in soil and plant analysis 26:21. received: june 2007 accepted: november 2007 img054 img055 img056 img057 img058 img059 img029 img030 img031 img032 agricultural and marine sciences, 17:45-52 (2012) ©2012 sultan qaboos university 45 ____________________________________________ *corresponding author. e-mail: sdewaal@gmail.com habitat preferences of juvenile abalone (haliotis mariae wood, 1828) along the dhofar coast of oman and implications for conservation schalk willem petrus de waal*, mohammed balkhair, ali al-mashikhi, and salem khoom fisheries research centre-salalah, ministry of agriculture and fisheries wealth, p.o. box 33, salalah, p.c. 217, sultanate of oman abstract: surveys were conducted along the eastern dhofar coast of oman to investigate densities and habitat preferences of juvenile haliotis mariae (< 3 cm sl). average density was 0.62 m-2 (sd 0.56); average urchin density was 3.4 urchins m-2 (sd 3.9). relationships between juvenile abalone densities and small boulders (<30 cm in diameter (ø)) tested significant (p = 0.049), as did those between juvenile abalone and urchin densities (p = 0.031). selectivity (w) and standardized (b) ratios quantifying the relative probability of selection by juvenile abalone for different categories of resource available were calculated. for the studied area b values tested significantly different for (p = 0.004) the different habitats, urchins, boulders <30 cm, 30> <50 cm, and >50 cm ø, respectively. b values were highest for urchins (6 times that for small boulders), and for boulders <30 cm ø (double that for boulders 30> <50 cm ø). b values for boulder habitats decreased as boulder size increased. urchin utilisation by juvenile abalone as shelter ranged between geographic areas from a minimum of 15.5% to a maximum of 47.6%. the proportion of total habitat that is preferred by more than 97% of juvenile abalone found, including urchins and boulders < 50 cm ø, comprises 29% of surveyed substratum. while the role urchins play on wild juvenile h. mariae has not proved vital, it is definitely significant. although juvenile densities are low and are not currently limited by the availability of suitable habitat, it is crucial to identify and conserve those microhabitats that support recruitment of h. mariae. the abundance of these areas should be among the criteria used in selecting protected conservation areas. محافظة في الشواطئ طول على الصفيلح صغار بواسط البيئات تفضيل حمايته على ذلك وأثر ظفار وعلي املشيخي وسالم اخلوم بلخير ومحمد فال بيتروس دي ويليم شالك تفضلها التي البيئات وطبيعة كثافة على للوقوف عمان سلطنة في ظفار حملافظة الشرقي الساحل طول على مسوحات إجراء مت اخلالصة: فيما بلغ ،( (٢ sd م-٠,٥٦ ٠,٦٢ الصفيلح كثافة بلغ متوسط سم). ٣ من صدفة أكثر (بطول (haliotis mariae) صغار الصفيلح العماني الصخور الصفيلح وبني صغار بني كثافة ومؤثرة عالقة كبيرة وجود املسوحات أظهرت . ( (sd قنفذ٣,٩ ٢ ٣,٤مالبحر قنافذ كثافة متوسط p =) البحر وكثافة قنافذ الصفيلح صغار كثافة بني مماثلة عالقة وجود وكذلك ,(p=٠,٠٤٩) ٣٠سم من أكثر قطرها يبلغ التي الصغيرة واملقاييس القيم بتحويل وذلك احمليطة بها واملوارد االمناط مختلف (w) انتقاء على الصفيلح صغار قدرة الدراسة حساب هذه في ومت ,(٠,٠٣١ التي والصخور الصغيرة القنافذ وبني احمليطة البيئة بني ( p معنوي (٠,٠٠٤= احصائية داللة (b) القيم اظهرت حيث .(b) ثابتة نسب الى من أعلى أضعاف ٦) البحرية للقنافذ قيمة أعلى (b) القيم وسجلت . من٥٠سم أكبر ,٣٠سم<>٥٠سم, ٣٠سم من أكثر قطرها يبلغ قيم وتتناقص سم٣٠<>٥٠سم), للصخور التي قطرها القيم (ضعف <٣٠سم قطرها الصغيرة التي يبلغ وللصخور الصغيرة) الصخور اجلغرافية االماكن في للحماية البحرية القنافذ الصفيلح صغار تستغل الصفيلح. صغار وجود بيئة في الصخور حجم زاد كلما (b) في التواجد تفضل الصفيلح من صغار ٪٩٧ ان استنتاج الصفيلح مت بيئة تواجد كل الى بالنسبة كحد أعلى. ٪١٥,٥٪-٤٧,٦ من بنسبة أن الدراسة اثبتت املمسوحة. املنطقة أجمالي ٢٩٪ من ذلك ٥٠ سم, شمل من أكثر قطرها صغيرة بحرية وصخور قنافذ بيئة بها محيط محصورة وليست كثافة صغار الصفيلح قليلة ان بالرغم مؤكدة. ذو داللة ولكنه حيوياً الصفيلح ليس صغار بيئة في البحرية القنافذ دور املناطق ان حتديد .h. mariae الصفيلح واستقرار لوجود الداعمة البيئة على واحلفاظ التعرف األهمية من فإنه ، املناسبة بوجود البيئة حالياً بالصفيلح مستقبالً. اخلاصة احملميات إلختيار املثلى اآللية في وضع يسهم سوف الصفيلح املفضلة لصغار البيئة بها توجد التي عمان. ، حماية املوطن ، اإلختيار حتاليل البيئات، ، تفضيل الصفيلح صفار كلمات مفتاحية: keywords: juvenile abalone, habitat preferences, selectivity analyses, habitat conservation, oman. introduction the wild abalone fishery along the eastern dhofar coast of oman has formed part of traditional fishing culture for decades, and as a valuable commercial species contributes substantially to the livelihoods of coastal dwelling fisher folk (al hafidh, 2006). the fishery takes place in the winter months, usually between october and december, when the seas are relatively calm and sea water temperatures are in excess of 20º c (al hafidh, 2006; sanders, 1982). haliotis mariae is the only abalone species occurring in oman. it is endemic in the dhofar region of the arabian sea (al hafidh, 2006). currently, it inhabits a rocky coastal 46 de waal et al. 47 habitat preferences of juvenile abalone along the dhofar coast of oman and implications for conservation zone between mirbat and hassik, approximately 100 km in length (fig. 1). prior to 2008 the species range extended approximately 80 km further east from hassik to ras sharbithat (al-hafidh, 2006). however, an extreme episode of harmful toxic algal blooming by the species cochlodinium polykrikoides during 2008 and 2009 (al gheilani, 2009) wiped out virtually all the abalone in the ras sharbithat region. as a result of the commercial importance of the species, worth approximately or 8.2 million in 2012 (fishery statistics, 2012), extra consideration is being given to the management of the fishery. the annual abalone survey now includes juvenile specific surveys to broaden the investigation into the dynamics of the species. the lifecycle of abalone in general can be considered complex. juvenile abalone are sensitive to bright light (heasman et al., 2007) and as a result cryptic by nature. they generally inhabit under-boulder habitats, cracks and crevices (roberts et al., 2007; dixon et al., 2006), becoming emergent as they mature. abalone, specifically juveniles have a wide range of predators from which they need to seek refuge. these include sea stars, moray eels, lobsters, crabs, some species of fish, and octopus. many of these predators inhabit the same general habitat, under-boulder, cracks and crevices, as the abalone themselves, making it crucial for juvenile abalone to find suitable shelter. in this study, we have investigated juvenile abalone up to 30 mm in sl (shell length), i.e. the cryptic juvenile phase. these animals differ in diet and behavior from adult animals. h. mariae is considered generally to become emergent at approximately 60-mm sl moving onto exposed sites on reefs or boulders. adult h. mariae are grazers as well as trappers of a range of drift seaweed species, with the choice of species depending on the area and the abundance and diversity of seaweeds present (al-hafidh, 2006). juveniles, on the other hand, have been shown to be grazers, the epithelial layer of the encrusting corallines figure 1. the main centres for the existing abalone fishery along the dhofar coast of oman. 46 de waal et al. 47 habitat preferences of juvenile abalone along the dhofar coast of oman and implications for conservation on which the recruits are found, together with benthic diatoms, are a source of nutrition for recruits and small juveniles (al-rashdi and iwao, 2008). the association between urchins and abalone is well documented for various abalone species worldwide. however, this association is not always simple, in some cases urchin and abalone numbers are inversely related due to their competition for food (tarr et al., 1996; andrew and underwood, 1992). recruits from some species that grow to the juvenile stage have been found predominantly under sea urchins (goodsell et al., 2006, de waal, 2005, day and branch, 2002, 2000). although urchins are considered a source of shelter for juvenile abalone the relationship between h. mariae recruits and urchins has not yet been investigated (al-hafidh, 2006). adult abalone generally occupy habitats less hidden than that of juveniles. it is crucial however that the habitat requirements of juvenile abalone are met if recruitment is to be successful. part of understanding the ecology of the species includes an understanding of the habitat requirements of wild juvenile h. mariae. this understanding will also play a crucial part in providing information that can be used to select suitable conservation areas for the species. this study investigates habitat preferences of wild juveniles along the dhofar coast with the aim of quantifying the relationship between substratum structure, urchins and wild juveniles. it was conducted with a number of questions in mind: (1) are there specific physical substratum limitations in effect in the distribution of wild juvenile abalone? (2) is the availability of habitat a limiting factor with respect to recruitment, how much habitat is being utilized by juvenile abalone? (3) what is the relationship between wild juvenile abalone and the sea urchin? (4) are there findings that impact on potential conservation of this species? materials and methods quantitative wild juvenile surveys between march and early april 2012, juvenile specific surveys were conducted in four abalone fishery areas: mirbat, sadah, hadbin and hassik (fig.1). abalone smaller than ≈ 3 cm (sl) were classified as juvenile. the survey comprised 35 separate 10x1 m transects, totalling 350m2, placed randomly in areas considered to be prime abalone fishing areas. transects were placed both parallel and perpendicular to the beach and did not exceed an average depth of 6 m. in each transect a destructive invasive search was conducted; all boulders, stones and urchins were lifted and searched, cracks and crevices were searched where possible (rogers-bennet et al., 2002). in addition to an abalone and urchin count, average depth was recorded in each transect. an estimate was made of the physical substratum in the following categories (de waal, 2002): (1) percent area exposed. this is defined as open reef, bedrock or sand, area that does not provide any shelter for juvenile abalone. exposed reef does not necessarily have to be flat and open; many exposed areas have a high degree of rugosity (southwest region protected resources division, 2011; mccormick, 1994) and may be complex in features including outcrops, pockets, and ridges. while not providing under-boulder habitat these areas may provide anchor opportunities for sea urchin species which in turn offer shelter to juvenile abalone. (2) boulders with diameter (ø) greater than (>)50 cm. (3) boulders with ø between (><)30 and 50 cm. (4) boulders with ø less than (<)30 cm. all juvenile abalone and urchins in each transect were counted. for each juvenile the exact position was recorded in the categories described above, in addition to being found under an urchin. data analyses abalone densities and urchin densities were calculated for each transect. proportional distribution of each habitat category and the proportional utilization of each category, including urchins, by juvenile abalone were calculated (table 1). the following statistical analyses (using statistixl software) were conducted: (1) non parametric kruskal-wallis tests were conducted to test for differences in habitat composition between the four areas. (2) linear regression analyses to test for relationships between number of juveniles found and habitat composition in the categories listed above including depth and number of urchins per transect. (3) selectivity analyses of juvenile abalone for substratum habitat categories including urchins for shelter: the selectivity analyses were done using manley’s formula that calculates a resource selection function w i (the relative probability of selection for the category i, formula i) for the different categories of resource available. the selection function attempts to estimate the probability that the next resource used will be of a specific type. it allows a biological interpretation of used and available resource ratios by animals, and has been used to test habitat selectivity by abalone (de waal, 2002; manly et al., 2002; day and branch, 2002, 2000). w i = u i / m i (1) w i is the selectivity ratio; m i is the number of available units in category i in a sample of available resource units; and u i is the number of units in category i in a sample of used units. a useful way of presenting selection ratios is to standardize them so that they add up to a total of 1. this leads to manly’s standardized selection ratio b i1 (with used resource units replenished or in this case constant, formula ii). b i1 = (u i /m i ) /σ(u i /m i ) (2) 48 de waal et al. 49 habitat preferences of juvenile abalone along the dhofar coast of oman and implications for conservation table 1. general data describing biological and substratum characteristics from each transect. proportional distribution of habitat categories and proportional distribution of utilization of different habitat categories by juvenile abalone from each fishing area are shown. site depth (m) abalone m-2 urchins m-2 proportional distribution (% area) habitat categories proportional distribution (%) abalone utilizing habitat categories urchins <30cm ø 30> <50 cm ø >50 cm ø exposed urchins <30 cm ø 30> <50 cm ø >50 cm ø mirbat 1 7 0.2 1.8 1.24 10 20 50 18.76 0.00 50.00 50.00 0.00 2 6 0.2 5.1 3.50 20 40 20 16.50 0.00 50.00 50.00 0.00 3 5 0.3 4.3 2.95 10 20 30 37.05 0.00 100.00 0.00 0.00 4 8 0.2 0.3 0.21 10 10 20. 59.79 0.00 0.00 100.00 0.00 5 6 0.4 0.6 0.41 10 10 10 69.59 50.00 50.00 0.00 0.00 6 9 0.3 1.2 0.82 10 20 10 59.18 0.00 0.00 100.00 0.00 7 1 0 7.2 4.95 10 10 20 55.05 0.00 0.00 0.00 0.00 8 7 0.3 0.8 0.55 0 0 40 59.45 100.00 0.00 0.00 0.00 9 5 1.2 0.2 0.14 50 50 0 0.00 25.00 58.33 16.67 0.00 10 3.5 1.3 20 13.74 0 0 10 76.26 69.23 0.00 0.00 30.77 11 6 1 2 1.37 10 20 60 8.63 10.00 50.00 40.00 0.00 12 5 0.3 1 0.69 0 0 60 39.31 33.33 66.67 0.00 0.00 13 3.5 1.4 5 3.43 10 10 55 21.57 21.43 42.86 35.71 0.00 sadh 1 3 0.7 4.8 3.30 10 10 60 16.70 0.00 57.14 28.57 14.29 2 0.5 0.5 6 4.12 10 10 70 5.88 60.00 40.00 0.00 0.00 3 3 0.9 6.8 4.67 10 20 60 5.33 11.11 11.11 22.22 55.56 4 3 0.9 2.4 1.65 20 40 40 0.00 0.00 77.78 22.22 0.00 5 3 0.7 4.8 3.30 10 10 80 0.00 0.00 42.86 57.14 0.00 6 4.5 0.2 3.8 2.61 10 10 10 67.39 100.00 0.00 0.00 0.00 7 6 1 0 0.00 40 10 50 0.00 0.00 90.00 10.00 0.00 8 4 1 3.6 2.47 10 10 20 57.53 20.00 70.00 10.00 0.00 9 2 1.1 3.8 2.61 10 20 20 47.39 54.55 27.27 18.18 0.00 10 2.5 1.8 13.3 9.14 0 0 0 90.86 100.00 0.00 0.00 0.00 11 1.5 0.1 1.8 1.24 10 10 50 28.76 100.00 0.00 0.00 0.00 12 5 0.3 1.8 1.24 0 0 60 38.76 33.33 66.67 0.00 0.00 13 3.5 1.4 1.5 3.43 10 10 55 21.57 21.43 42.86 35.71 0.00 hadbin 1 4 2.2 1.9 1.31 30 30 40 0.00 9.09 54.55 36.36 0.00 2 4 0.8 1.2 0.82 20 30 20 29.18 37.50 62.50 0.00 0.00 3 2 0 0.4 0.27 10 10 50 29.73 0.00 0.00 0.00 0.00 hassik 1 6 0 0 0.00 0 0 0 100.00 0.00 0.00 0.00 0.00 2 3 0 0 0.00 0 0 0 100.00 0.00 0.00 0.00 0.00 3 6 0.1 3 2.06 0 0 50 47.94 100.00 0.00 0.00 0.00 4 3 0 0.5 0.34 10 10 20 59.66 0.00. 0.00 0.00 0.00 5 3 0.1 3.6 2.47 20 35 35 7.53 100.00 0.00 0.00 0.00 6 3 0.7 3 2.06 25 30 40 2.94 85.71 14.29 0.00 0.00 average 0.62 3.36 2.37 11.87 14.71 34.71 36.52 32.62 32.14 18.08 2.87 sd 0.56 3.97 2.72 11.12 13.11 22.62 30.12 38.29 31.40 27.07 10.78 48 de waal et al. 49 habitat preferences of juvenile abalone along the dhofar coast of oman and implications for conservation non-parametric friedman tests were conducted on the w (selectivity ratio) and b values (standardized ratio) for each area grouped to test for differences between the four fishery areas, and on b values from all the sites for each of the different habitat categories, including urchins, grouped to test for differences in strength of preference for different habitats. results depth for all sites combined ranged from 1m to a maximum of 9 m (average 4m, sd 1.1). the average abalone density was 0.63 abalone m-2 (sd 0.37), and the average urchin density 2.8 urchins m-2 (sd 1.6). the averaged data sets calculated for each separate geographic area were too small to allow constructive testing for significance, however, general differences can be seen in table 1. there are a number of species of urchin found in the area, including diadema setosum (leske, 1778), echinostrephus molaris (blainville, 1825), echinometra mathaei (blainville, 1825), toxopneustes pileolus (lamarck, 1816), and stomopneustres variolaris (lamarck, 1816). juvenile abalone are generally associated with the shorter spine dark urchins like s. variolaris and e. mathaei. abalone densities were lowest in hassik, the most easterly of the areas, and highest in hadbin, the area just west of hassik. in both areas the number of transects surveyed were limited, 3 in hadbin and 6 in hassik (table 1). analyses showed that transects were generally similar in physical substratum structure and appearance, and no significant differences were found between the four areas with respect to the physical attributes described in the categories listed in the methods section above. depth differences between transects, however, tested significant (p = 0.017, table 2). abalone densities also tested significantly different (p = 0.019, table 2), while urchin densities did not. the utilization of urchins by juvenile abalone ranged between geographic areas from a minimum of 15.5% to a maximum of 47.6%. the area under urchins (using an average urchin ø of 9.3 cm sd 1.3) is by far the lowest compared to the area under all other categories of substratum (boulders with varying average ø, table 1). in all four fishery areas the area comprising small boulders (<30 cm ø) made up the smallest proportion of boulder habitat (table 1). in mirbat and hassik the proportion of exposed area was higher than the proportion of area under boulders, and in sadah and hadbin exposed area was less than that under boulders. it is important here to note how small the proportion of total area comprises small boulders. in this study this category of substratum is shown to be significantly important to juvenile h. mariae. seventy-six percent of wild juvenile abalone utilise 14% of the total substrate available, that is the area comprising urchins and area under boulders <30 cm ø. ninety-seven percent utilize boulders <50 cm ø, which is 29% of the available substratum. in other words, less than 30% of the total available surveyed habitat comprises substratum that can support juvenile abalone, including the area under urchins which will be variable over time. analyses (pearson correlations and anova, table 3, fig. 2) showed significant positive relationships exist between juvenile abalone densities and small boulders (< 30 cm ø, p = 0.049), and juvenile abalone densities and urchin densities (p = 0.031). the relationships between juvenile abalone densities and all categories of larger boulder tested insignificant. a negative significant correlation was shown to exist between urchin densities and depth (p = 0.037). non-parametric friedman tests showed no significant differences (p = 0.416) between the four fishery areas when using either w or b as a measure. however, the same tests showed the highly significant (p = 0.004) difference values of b for all categories of habitat when table 2. kruskal-wallace tests on all categories of habitat description including number of urchins per transect. transect characteristics (sd) df f p average depth (m) 3 4.41 0.017* average density (abalone m-2) 3.8 3.00 0.019* average density (urchins m-2) 1.80 3.00 0.41 physical substratum boulders <30 cm ø 1.10 3.00 0.35 boulders 30 > < 50 cm ø 0.80 3.00 0.51 boulders >50 cm ø 1.50 3.00 0.23 exposed area 0.90 3.00 0.41 *significant at 95% confidence limits. table 3. linear regression analyses (pearson correlation and anova) for relationships between abalone and urchin densities and substratum categories. pearson r2 anova prob. juvenile abalone no vs. boulders <30 cm ø 0.112 0.049* boulders 30> <50 cm ø 0.044 0.227 boulders >50 cm ø 0.003 0.275 exposed area 0.081 0.098 urchin density 0.134 0.031* depth 0.027 0.348 urchin no vs. boulders <30 cm ø 0.072 0.119 boulders 30> <50 cm ø 0.030 0.316 boulders >50 cm ø 0.011 0.556 exposed area 0.027 0.348 depth -0.125 0.037* 50 de waal et al. 51 habitat preferences of juvenile abalone along the dhofar coast of oman and implications for conservation the same categories are grouped from each transect. the standardized b value for urchins selected as shelter by juvenile abalone is almost 6 times higher than for small boulders (<30 cm ø). the b values for the other categories decrease as boulder size increases with a minimum for exposed areas. for boulders <30 cm in diameter b is double that for boulders 30> <50 cm diameter (table 4). discussion the survey data reflect abalone and urchin densities at a specific time of the year, and therefore must be seen in the context of growth and dispersal, since recruitment, food availability and general environmental conditions vary depending on the season. analyses were conducted on a specific size range of juveniles. observations made during other months suggest that juvenile abalone inhabit the same type of habitat throughout this lifecycle phase. densities, however, will change during the year, and this too has been observed. in this context the abalone densities observed here are relatively low when compared to those from other species, haliotis rubra (leach, 1814) juveniles for example average between 1 and 3 m-2 (roberts et al., 2007; goodsell et al., 2006). however, this is variable and must be seen in the context of the recent and current status of the abalone stocks in general together with site-specific ecological regimes and habitat characteristics (roberts et al., 2007). it is not enough to attempt to manage only emergent or adult stocks; in california for example juvenile red abalone abundance was not correlated with local adult red abalone abundance (rogers-bennett and pearse, 2001). in that study it was concluded that fishing for red urchins potentially decreased the microhabitat available for juvenile abalone. in this study a prime abalone fishing habitat was selected. however, along the entire dhofar coast suitable habitats for juvenile abalone will be relatively less abundant than in this area. due to the complex ecological requirements for successful recruitment to take place, table 4. standardized b values showing habitat preferences by juvenile abalone (all data is pooled). pooled 0 w b urchin area 0.02 0.02 0.38 19.03 0.80 <30 cm ø 0.12 0.37 3.12 0.13 30 > <50 cm ø 0.15 0.21 1.41 0.06 >50 cm ø 0.35 0.03 0.10 0.00 exposed 0.36 0.00 0.00 0.00 23.66 1.00 figure 2. significant pearson correlation analyses between abalone and urchin densities, the abundance of small boulders and depth of transects. � 50 de waal et al. 51 habitat preferences of juvenile abalone along the dhofar coast of oman and implications for conservation habitats suitable for recruitment may in fact be more limited than that available for juveniles to live in. the fact that a significant correlation is found between juvenile abalone and small boulders corresponds with findings for abalone species internationally. juvenile abalone are generally sheltered in the shallows in under-boulder habitats. in new zealand haliotis iris (gmelin, 1791) juveniles are found almost exclusively under boulders from the low water mark to several meters (roberts et al., 2007). in canada it was found that juvenile haliotis kamtschatkana (jonas, 1845) require cryptic habitats with some boulders (lessard and campbell, 2007). in california haliotis cracherodii (leach, 1814) (black abalone) juveniles up to a size of about 20 mm, black abalone are highly cryptic, occurring primarily in under-boulder habitats or in deep narrow crevices (southwest region protected resources division, 2011). it is important to note that these surveys were conducted in areas considered prime adult abalone habitats and does not therefore reflect the entire dhofar coastline. this limited portion of intertidal and sub tidal habitats is not a safe or stable area when human and natural effects are taken into account. in this habitat juveniles are vulnerable to the movement of boulders, either by natural forces or by humans during abalone fishing or collecting of other marine organisms and the clogging of under-boulder habitats by sand and shale during storms (roberts et al., 2007; maliao et al., 2004). it is also this area that is most accessible to people and pollution. for example, trash discarded by fishermen and day visitors in abalone fishery areas along the dhofar coast is a clear hazard the positive correlation between juvenile densities and urchin densities combined with the strong selectivity index b found in this study correspond with a number of international findings. in north america, field studies have shown a strong correlation between juvenile abalone and sea urchins (rogers-bennett and pearse, 2001). in south africa the same has been found with the species haliotis midae (linnaeus, 1758) [day and branch, 2002, 2000; tarr et al., 1996 with similar results in japanese species (kojima, 1981)]. it is thought that small abalone are protected by the extended spines of the urchin (goodsell et al., 2006). in 1997 along the californian coast between 30 and 45% of the juvenile haliotis rufescens (swainson, 1822) found in specific study sites in marine protected areas were located under the spine canopy of red urchins with the remainder in other microhabitats (rogers-bennett and pearse, 2001). in canada survey sites showed 7% of h. kamtschatkana <45 mm sl were found under urchins and a positive correlation was found between abalone numbers and sea urchins (tomasckik and holmes, 2003). the same authors found a negative correlation between urchin densities and abalone size, indicating that urchins may have a beneficial role in survival of smaller abalone. urchins play a significant role in supporting a large proportion (≈ 31%) of the wild juvenile abalone population in the fishery areas of the dhofar coast. while this role is significant it is not vital to juveniles because a larger proportion of juvenile abalone occupy under-boulder habitats. conclusions it is important to note that the proportion of total habitat that is preferred by more than 97% of juvenile abalone found, including urchins and boulders <50 cm ø, comprises 29% of the substratum surveyed. the proportion of total habitat that will support recruitment requires ecological factors not measured in this study, one being the presence of crustose coralline algae. in effect this additional requirement might make total habitat available for recruitment even less than this. while the role that urchins play on wild juvenile h. mariae has not proved vital it is highly significant. however, inferences cannot be made from this data about the relationship between urchins and the recruitment of h. mariae. this must be investigated in future studies. studies in california and the philippines have shown that marine protected areas result in an increase in juvenile abalone densities (maliao et al., 2004; rogers-bennett and pearse, 2001). this study shows that while juvenile densities are low they are not currently limited by the availability of suitable habitat. however, conservation of this species requires managing the entire lifecycle of the species which includes the physical substratum required. it is crucial to identify and conserve those microhabitats that support recruitment of h. mariae; shallow intertidal areas easily accessible and most prone to human activities. the distribution and abundance of these areas should be among the criteria used in selecting protected conservation areas. acknowledgements this study was financed by the oman agricultural and fisheries development fund, sultanate of oman. we appreciate the support given by the fisheries research centre-salalah, ministry of agriculture and fisheries wealth, and the directorate general of fisheries in dhofar. references al-gheilani, h.m. 2009. final report: blooms of cochlodinium polykroides along the coast of oman in 2008-2009 and their effects. internal report: marine and oceanography section, marine science and fisheries center, ministry of fisheries wealth. al-hafidh, a.s. 2006. assessment and management of abalone haliotis mariae, (1828 wood) fishery in the omani water. university of hull. hull international fisheries institute. unpublished ph.d. thesis. u.k. 137pp. al-rashdi, k.m. and t. iwao. 2008. abalone, haliotis mariae (wood, 1828), hatchery and seed production trials in oman. sultan qaboos university agriculture and marine sciences a research journal 13:53-63. andrew, n.l. and a.j. underwood. 1992. associations and abundance of sea urchins and abalone on shallow subtidal reefs in southern new south wales. 52 de waal et al. maliao, r.j., e.l. webb, and k.r. jensen. 2004. a survey of stock of the donkey’s ear abalone, haliotis asinina l. in the sagay marine reserve, philippines: evaluating the effectiveness of marine protected area enforcement. fisheries research 66:343-353. manly, b.f.j., l.l. mcdonald, d.l. thomas, t.l. mcdonald, and w.p. erickson. 2002. resource selection by animals. statistical design and analysis for field studies (2nd edition). kluwer academic publishers, boston, ma, usa, 240pp. mccormick, m.i. 1994. comparison of field methods for measuring surface topography and their associations with a tropical reef fish assemblage. marine ecological progress series 112:87-96. roberts, r.d., e.f. keys, g. prendeville, and c.a. pilditch. 2007. viability of abalone (haliotis iris) stock enhancement by release of hatchery-reared seed in marlborough, new zealand. journal of shellfish research 26:697-703. rogers-bennet, l., p.l. haaker, t.o. huff, and p.k. dayton. 2002. abalone baselines in california. estimating baseline abundances of abalone in california for restoration. california cooperative oceanic fisheries investigations 43:97-111. rogers-bennett l. and j.s. pearse. 2001. indirect benefits of marine protected areas for juvenile abalone. conservation biology 15:642-647. sanders, m.j. 1982. preliminary stock assessment for the abalone taken off the south east coast of oman. fisheries development in the gulf fi; dp/rab/80/ 015/3. fao. rome. 47pp. southwest region protected resources division, 2011. final designation of critical habitat for black abalone. final biological report. national marine fisheries service. 501 west ocean blvd., suite 4200 long beach, california 90802. 59pp. tarr, r.j.q., p.v.g. williams, and a.j. mackenzie. 1996. abalone, sea urchins and rock lobster: a possible ecological shift that may affect traditional fisheries. south african journal of marine science 17:319-323. tomascik, t. and h. holmes. 2003. distribution and abundance of haliotis kamatschatkana in relation to habitat, competitors and predators in the broken group islands, pacific rim national park reserve of canada. journal of shellfish research 22:831-838. received: october 9, 2012 accepted: january 16, 2013 australian journal of marine and freshwater research 43:1547-1559. day, e. and g.m. branch. 2000. evidence for a positive relationship between juveniles abalone h. midae and the sea urchin parechinus angulosus in the southwestern cape, south africa. south african journal marine science 22:145-156. day, e. and g.m. branch. 2002. effects of urchins (parechinus angulosus) on juveniles and recruits of abalone (haliotis midae). ecological monographs 72: 133-149. de waal, s.w.p. 2002. factors influencing the ranching of the abalone species (haliotis midae) along the namaqualand coast of south africa. university of cape town. south africa. unpublished ph.d. thesis. 240pp. de waal, s.w.p. 2005. boulders or urchins? selecting seeding sites for juvenile haliotis midae along the namaqualand coast of south africa. african journal of marine science 27:501-504. dixon, c.d., r.w. day, s.m.h. huchette, and s.a. shepherd. 2006. successful seeding of hatcheryproduced juvenile greenlip abalone to restore wild stocks. fisheries research 78:179-185. fishery statistics book, 2012. fisheries statistics and information department. general directorate of fisheries research. ministry of agriculture and fisheries wealth, sultanate of oman. goodsell, p.j., c,a.j. underwood, m.g. chapman, and m.p. heasman. 2006. seeding small numbers of cultured black-lip abalone (haliotis rubra leach) to match natural densities of wild populations. marine and freshwater research 57:747–756. heasman, m.p., w. liu, p.j. goodsell, d.a. hurwood and g.l. allan. 2007. development and delivery of technology for production, enhancement and aquaculture of blacklip abalone (haliotis rubra) in new south wales. frdc project no. 2001/033 nsw department of primary industries–fisheries final report series no. 95 issn 1449-9967. kojima, h. 1981. mortality of young japanese black abalone haliotis discus discus after transplantation. bulletin of the japanese society of scientific fisheries 47:151-159. lessard, j. and a. campbell. 2007. describing northern abalone, haliotis kamtschatkana, habitat: focusing rebuilding efforts in british columbia, canada. journal of shellfish research 26:677-686. agricultural and marine sciences, 17:9-19 (2012) ©2012 sultan qaboos university 9 __________________________________________ *corresponding author. e-mail: slim@squ.edu.om damage cost of drying of aflaj in the sultanate of oman slim zekri1*, ayoub fouzai2, ali naifer3, and tariq helmi4 1department of natural resource economics, college of agricultural and marine sciences sultan qaboos university, p.o. box 34, al-khod 123, sultanate of oman 2ecole superieure d’agriculture de mograne, university of tunis, tunisia 3scet-agri tunisie, tunisia 4ministry of regional municipalities and water resources, sultanate of oman abstract: life style changes, population and economic growth, and lack of institutional innovations are causing noticeable damage to the rural communities living in and around aflaj. the ministry of regional municipalities and water resources (mrmwr) reported more than 1,000 dried-up aflaj out of 4,112 in 1996. this paper presents an estimation of the damage caused to the rural communities due to aflaj dry-up. the production function method and the cost based method are used to estimate the direct losses incurred by farmers and the local communities. these are related to (1) losses in marketed agricultural products, (2) increase in domestic water expenditures per household and (3) capital losses related to changes in house and land values. the study considered 33 dried-up aflaj among the 1029 monitored by the mrmwr. our results show that on average each family in the dried-up falaj has lost an income equivalent of o.r 320 per month. this highlights the importance of aflaj as an income generator in the remote rural areas. live aflaj provide fresh vegetables and healthy food as well as drinking water to the rural population without the need for governmental intervention. the contribution of the supporting wells, whenever provided by the mrmwr, is estimated at o.r 1,478 per family per year. on average the annual financial loss per family due to dry-up is estimated at o.r 3,301 per year. the total damage cost of dried-up aflaj, at the sultanate level, is estimated at more than o.r 59 million per year. keywords: farmers’ income losses, domestic water, housing relocation, present value. introduction groundwater quantity and quality are declining in the arid and semi-arid regions. several externalities caused by groundwater depletion in these environments have been observed (reddy, 2005 & 2001). in many arid regions, several groundwater hydraulic structures have been used to drain out of the surface by gravity. these systems are referred to as aflaj, karez, foggara, qanat…etc. these “…ancient engineering technologies demonstrate long standing, sustainable use of water … in extremely arid desert lands” (unesco, 2007). groundwater over-exploitation, inadequate policies and the lack of maintenance of these infrastructures are causing their deterioration and consequent abandonment (hussain et al., 2008). although aflaj in oman have persisted for hundreds of years, they are facing an unprecedented degradation in recent years as confirmed by flow measurements (al-ghafri, 2006; mrmewr, 2006). a survey undertaken by the ministry of عمان سلطنة في األفالج جفاف عن الناجتة األضرار اإلقتصادية ٤ حلمي وطارق ٣ النيفر وعلي ٢ فزاعي وأيوب ١ زكري سليم اتمعات في ملحوظة أضراراً املؤسسية االبتكارات وجود وعدم والسكاني اإلقتصادي والنمو منط احلياة في التغييرات تسبب اخلالصة: ٤و١١٢ مجموع من جفت فلج قد ١,٠٠٠ من أكثر وموارد املياه أن اإلقليمية البلديات وزارة تعيش على األفالج وحولها. ذكرت الريفية التي دالة اإلنتاج أسلوب مت استخدام األفالج. جفاف بسبب الريفية باتمعات حلقت التي األضرار تقدير الورقة وتستعرض هذه ١٩٩٦م. عام في املنتجات في اخلسائر بالتالي: (١) عالقة ذات اخلسائر احمللية. هذه واتمعات املزارعون تكبدها التي املباشرة لتقدير اخلسائر التكلفة وطريقة وقيمة املنزل في بالتغييرات املتعلقة الرأسمالية اخلسائر (٣) و الواحدة لألسرة املنزلية املياه نفقات في الزيادة (٢) املسوقة، الزراعية من ٣٢٠ رياالً يعادل فقدت ما قد جاف فلج كل في لكل أسرة أن النتائج أظهرت جافاً. فلجاً ٣٣ مجموع الدراسة على متت األراضي. لزراعة املياه احلية توفر األفالج النائية. الريفية املناطق في للدخل مورداً باعتبارها األفالج أهمية على الضوء يسلط هذا الشهري. الدخل مجموع تقدر كما احلكومي. التدخل إلى احلاجة دون الريف لسكان للشرب الصاحلة املياه وكذلك الصحية واألغذية الطازجة اخلضروات اخلسائر فتقدر السلطنة مستوى على اما الواحدة. السنة في رياالً ٣,٣٠١ بحوالي الواحدة و(٣) للعائلة (٢) و (١) االقتصادية األضرار احلد تساهم في لألفالج املساعدة اآلبار أن الدراسة تظهر كما اجلافة. األفالج مجموع بعني االعتبار أخذنا إذا سنوياً رياالً مليون ٥٩ بحوالي السنة في رياالً للعائلة ١,٤١٨ يعادل ما بتوفير وذلك اخلسائر، من املالية القيمة ، املنازل نقل املنزلية، ، املياه املزارع دخل النقض مفتاحية: كلمات 10 zekri et al. 11 damage cost of drying of aflaj in the sultanate of omac regional municipalities and water resources (mrmwr, 2001) in 1996 has reported that more than 1,000 aflaj out of 4,112 have dried-up aflaj supply about 410 million m3/year, representing 38% of oman’s fresh water, which satisfies part of domestic and agricultural demand in scattered rural areas (norman et al., 1997; zekri and al-marshudi, 2008). aflaj constitute an integrated environment where thousands of people live, produce, consume and trade healthy fresh products. lifestyle changes, population and economic growth, and lack of institutional innovations are causing noticeable damages to the rural communities living in and around these aflaj. all or most aflaj are tapping the shallow alluvium aquifer, located at the open plain away from the mountainous area which constitutes the recharging area. a falaj dries up whenever the water level at the mother well is lowered below the regional groundwater table. this usually happens as a result of over pumping the aquifer regardless of the recharge. the drilling of wells to support dried-up aflaj in the affected areas, whenever possible, is a solution implemented by the government to counteract the damages to rural communities. however, long-term drought periods cause a regional lowering of the water table and negatively affect the efficiency of the supporting wells and the sustainability of the aflaj communities. to mitigate the effects of aflaj deterioration the omani government, through the mrmwr, supported 669 projects of aflaj reparation and maintenance with a total cost of o.r 5.73 million (al sulaimani et al., 2007). however, these achievements were not enough to prevent aflaj dry-up, whose major cause is groundwater over pumping. in fact, there is no scientific evidence of rainfall decline or change in rainfall intensity during the period 1974-2003 as shown by kwarteng et al. (2009) eliminating thus the assumption of drought being the cause of dry-up. although several studies have been undertaken regarding aflaj irrigation systems, water resources (alghafri, 2006) and water markets (zekri et al., 2006), the damage caused to the rural communities due to aflaj dryup has not been estimated. evaluating the damages caused to communities by aflaj dry-up helps decision makers to implement appropriate policies to remedy and/or prevent it and to support public expenditures in repairing and maintaining some of the aflaj. the objective of this paper is to estimate the losses resulting from aflaj dry-up with a focus on direct losses incurred by farmers at the local falaj community. farmers are the legal owners of the falaj water (zekri and almarshudi, 2008). the environmental as well as the social losses, are beyond the objective of this paper. literature review estimates of damage cost due to natural resources degradation have been presented in a number of studies. hussain et al. (2008) identified the benefits and costs of the karez ain-zubaida rehabilitation project in saudi arabia without a quantitative estimation. the potential benefits are recreation, preservation of cultural-heritage, ecological and energy saving from pumping. the costs refer to tube-well owner’s losses due to the reduction of pumping and the costs of rehabilitating, operating and managing the karez system. the authors stressed that rehabilitation of the karez is pre-conditioned by the ability to establish and implement a regulatory framework of water use and water rights’ system. total water pumping from private tube-wells should be halved. if this could be achieved then a sustainable direct social benefit of water estimated at o.r 16,900 per day will incur in the long term. according to hussain et al. (2008) two types of costs were related to water resources degradation in the karez systems; on the one hand, indirect costs to the society as a cultural heritage loss, adverse environment impacts, loss of employment opportunities, loss of value related to tourism and associated economic activities. on the other hand, direct costs to private owners were identified as capital cost, operating and management cost, energy pumping and water transportation cost. reddy (2005) estimated the costs of groundwater depletion in india, using the public good and externalities framework. he estimated household income as a function of groundwater depth, total land owned and level of education. he then derived the costs of degradation and the resulting losses incurred at the household level. the author considered two cost categories; direct costs and indirect costs. the direct costs are replacement costs in the form of investment made in bore wells, sunk costs: capital loss due to drying up of open wells. the indirect costs are the losses in net return per acre and losses due to cropping pattern changes. howe and goemans (2003) used an input-output model to estimate the losses of the irrigated area reduction due to water rights transfer from the south plate and arkansas basins. falls of agricultural production negatively affect agricultural input suppliers, agricultural output processors and financial institutions. the authors assumed five to ten years for reemployment of displaced labor, capital and land after water transfer has taken place. the study involved determination of the cropping pattern, crop yields and crop prices for the dried-up land, value of output losses that have been sold outside the subject areas and changes in payment to households, taxes and employment. the results were presented as net present value of losses by unit of water volume transferred, using a discount rate of five percent and assuming that the annual loss drops linearly to zero by the end of the designated study period. methodology various techniques have been developed to assess the economic impacts resulting from alterations of conditions influencing the flow of goods and services these assets provide. the literature of environmental valuation techniques provides various taxonomies of techniques developed and tested to measure the economic value 10 zekri et al. 11 damage cost of drying of aflaj in the sultanate of omac of a broad range of environmental degradation. these techniques are classified as direct techniques and indirect techniques; (i) the direct techniques measure the monetary value of environmental services by looking to a surrogate market to infer individuals’ preferences or by asking individuals to express their preferences. the travel cost method, hedonic price method and contingent valuation method are considered as a direct approach (garrod and willis, 1999); (ii) indirect techniques do not directly measure individual preferences. the indirect techniques don’t provide accurate valuation information and welfare measures. production function method and cost based valuation method are usually included in this technique. the production function method values physical changes in production, caused by environmental change, using market prices for inputs and outputs. changes in productivity are based on the relationship between environmental attributes and the output level of an economic activity. the money value estimates obtained with this approach should not be interpreted as the true value measure, but a proxy of the environmental change’s ultimate welfare impacts. cost based methods measure the value of an environmental asset by the costs incurred in avoiding negative environmental impact. costs are easy to quantify because they are based on market prices and use actual expenditures. however, the results may underestimate the true effects due to non-use value and nonmaterial damages being excluded. under this estimation technique, three distinct approaches can be designated; the averting behavior and relocation cost approach; the cost of illness and human capital approach and the restoration cost approach. two methods were used to estimate the damage resulting from aflaj dry-up. the first one is the production function method where physical changes in production are valued using market prices for inputs and outputs. the second method is the cost based method which measures the value of an environmental asset, groundwater, by the costs incurred in avoiding negative impact of groundwater depletion. within this later method the averting behavior and relocation cost approaches are used. this paper estimates the losses resulting from aflaj dry-up with an exclusive focus on direct losses incurred by farmers. the direct losses that will be estimated are shown in table 1 and are related to (1) losses in marketed agricultural products and family consumption, (2) increase in domestic water expenditures per household, (3) capital losses related to changes in house and land values (fig. 1). the effects of aflaj dry-up on the other economic activities such as input suppliers and food processors are negligible due to the subsistence nature of agricultural production irrigated by aflaj. table 1. methodology for the damage costs computation. type of damage description methodology agricultural income loss marketed crop losses net factor income marketed livestock losses net factor income losses of household-consumption of agricultural products market prices capital losses due to life conditions degradation relocation to another house (losing falaj house and cost of new building) relocation cost value of agricultural land in falaj market prices increase water expenditures new sources of water for domestic and/or drinking purpose replacement cost total annual damage costs/family agricultural income loss capital losses due to life conditions degradation increased water expenditures income loss on figure 1. methodology for the estimation of the losses in dried-up aflaj. total annual damage costs/family 12 zekri et al. 13 damage cost of drying of aflaj in the sultanate of omac case study aflaj represent an important source of water supply to a major part of the rural population in oman. degradation of the aflaj systems influences the social and economic activities in the rural areas. the study considered 33 dried-up aflaj among the 1029 dried-up aflaj monitored by the mrmwr (2001). a survey was undertaken during the period july-november 2008. a total of 205 farmers were interviewed and only 191 questionnaires were fully answered and then used for data analysis. complementary information was obtained from local water authorities. the survey was divided into four parts; household identification; living conditions around the aflaj before and after water resource degradation; water resources in the falaj before and after resource degradation and new costs of water supply for drinking and domestic purposes; agricultural losses due to aflaj dry-up. agricultural losses estimates of losses related to the ceasing of agricultural activity caused by aflaj dry-up are based on average value of the agricultural marketed production per crop before and after the aflaj dry-up. this value does not consider the production consumed by the family. these estimated values will be shown below. in fact, farmers were asked about the value of the gross margin before and after the falaj dry-up. the gross margin implies the monetary transactions of the agricultural crops and does not include the family consumption. in some cases the government intervened by drilling tube wells, referred to as supporting wells, to support the local community, which allowed some agricultural crops to be partially grown. this required treating these two types of aflaj separately in order to be able to measure the impact of government intervention to reduce the impact of dry-up. thus, the results will be presented separately for aflaj with supporting wells and aflaj without supporting wells. the gross margin provides an estimation of the direct loss to the farmer and local community. the total value of crop losses per household is estimated using the following equations. marketed crop losses gmx i lost = gmx i after = gmx i before where, gmx i lost : average gross margin loss per hectare per year of farm x i; gmx i after : average gross margin (gm) per hectare per year of farm x i, after dry-up; gmx i before : average gross margin (gm) per hectare per year of farm x i, before dry-up. in the case of completely dried-up aflaj, gm of farm gmx i after is equal to zero, thus the agricultural losses are equal to gmx i before . however, the existence of supporting wells in some aflaj helped to maintain a few activities at the farm level. the same formula as in the case of dried-up aflaj will be applied with the difference that gmx i after ≠ 0. the aggregation of losses per falaj is estimated as follows: tgmx i lost = gmx i lost x tda j where, tgmx i lost : total loss of farm x i gm for the whole falaj; gmx i lost : average farm x i gm in sampled farms; tda j : total dried up area (hectare) of the falaj; results are presented in table 2 according to whether the falaj benefitted from a supporting well or not. results show that the average crop loss in aflaj without supporting wells is 651 o.r/ha/year and is slightly higher than the loss in aflaj with supporting wells which is estimated at 545 o.r/ha/year. based on the field findings, the small difference in losses are due to: (i) the supporting wells are usually dug quite late after the damage has already occurred, (ii) the supporting wells’ flows are considerably below the natural aflaj flow as a result of regional groundwater depletion and (iii) the cropping pattern is more oriented to forage and annual crops rather than high value crops in order to avoid the risk related to the nonreliability of water supply. marketed livestock losses the impact of aflaj dry-up on livestock was less severe than the crop losses, because in several cases farmers were still able to maintain a minimum livestock activity based on grazing and buying of animal feed and concentrates table 2. value of marketed crop losses. all aflaj (n=191) aflaj with supporting wells (n=119) aflaj without supporting wells (n=72) min avg max min avg max min avg max cropped area (ha) 0.14 2.32 18.40 0.18 2.29 15.01 0.14 2.36 18.40 gross margin crop losses (o.r/ha/yr) 108 585 1590 108 545 1538 143 651 1590 (1) (2) 12 zekri et al. 13 damage cost of drying of aflaj in the sultanate of omac mainly in the case of aflaj with supporting wells. the annual loss in net benefit of animal production is the difference between net benefit before and after dry-up, excluding the family consumption. the losses were then reported per hectare to allow aggregation of the results. a livestock gross margin for each activity was computed referring to the annual productivity, using prolificacy, mortality as well as reform rates. we proceeded by calculating the difference between the gm after and before aflaj dryup, which represents the annual livestock losses. these losses are shown in table 3 and were estimated as follows: gmls i after gmls i before = gml s i lost where, gmls i after : average gm per hectare per year of livestock activities after dry-up in surveyed farms; gmls i before : average gm per hectare per year of livestock activities before dry-up in surveyed farms; gml s i lost : average loss gm per hectare per year of livestock activities in surveyed farms. in most sampled aflaj we have observed four major animal activities; goats, sheep, cattle and camels. according to table 3, aflaj without supporting wells have higher losses in terms of gross margin per hectare, estimated at 252 /ha/yr than those with supporting wells, estimated at 201 /ha/yr. the minimal value of the losses (equal to zero) reflects either a zero loss or an absence of livestock activity in the farm. household and life conditions household consumption most of the farms around the aflaj are small-scale properties and are considered as subsistence farms. the ceasing or reduction of agricultural and livestock production have had an adverse impact on households’ vegetables, fruit and meat consumption. aflaj households typically consume a considerable part of their production. after aflaj dry-up, the households were obliged to buy the agricultural products from the market. in this section we account for that part of agricultural production which was destined for consumption and was not accounted for in the marketed agricultural production. the difference between a household’s monthly expenditure for vegetables and fruit before and after a falaj dry-up allows the researchers to estimate the family losses due to aflaj drying up. this is considered as a lower-limit estimation because when farmers were the producers their opportunity cost was the wholesale price, while after the falaj dry-up they are facing a retail price for the agricultural products. since the retail prices are higher than the wholesale prices, thus the family demand of agricultural goods is negatively affected. table 4 shows that on average a household spends o.r 551 per year to buy agricultural products that were previously produced at the farm level. cost of house changing moench (2007) reported that the changing of household location is considered as an adaptive response to drought and a strategy to mitigate the associated impacts. our survey results showed that there are two types of adaptive table 3. value of marketed livestock losses. all aflaj (n=191) aflaj with supporting wells (n=119) aflaj without supporting wells (n=72) min ave max min ave max min ave max cropped area (ha) 0.14 2.32 18.40 0.18 2.29 15.01 0.14 2.36 18.40 livestock gross margin losses (o.r/ha/yr) 0 220 1159 0 201 1120 0 252 1159 (3) table 4. farm output household consumption losses. all aflaj (n=191) aflaj with supporting wells (n=119) aflaj without supporting wells (n=72) min ave max min ave max min ave max cropped area (ha) 0.14 2.32 18.40 0.18 2.29 15.01 0.14 2.36 18.40 household consumption losses (per family/yr) 24 551 1,800 48 542 1,800 24 567 1,800 14 zekri et al. 15 damage cost of drying of aflaj in the sultanate of omac behaviour dictated by access to domestic water. in fact, if the initial house location is on the village periphery, access to domestic and drinking water is ensured through water tankers avoiding the displacement or rebuilding of another house. however, if the house is in the middle of the fields, with narrow access paths, water provisioning becomes impractical and relocation becomes a necessity. the damage cost is calculated as the sum of the lost value of the falaj house and the cost of building a new house. the damage cost is only estimated for farmers who changed their houses due to the drought and degradation of living conditions at the falaj. the first row of table 5 shows that the average loss, due to house relocation considering all aflaj samples, as estimated at o.r 31,813. however, only 16% of the families were obliged to relocate their houses, consequently the weighted average cost of housing relocation is estimated at 5,090/family. housing losses were computed as follows: hl i = f h c i + nhc i where, hl i : average housing losses for surveyed household from sampled aflaj; f h c i : average value of abandoned falaj house; n h c i : building cost of new house due to falaj dry-up. cost of water for domestic and drinking purposes in normal conditions aflaj represent the main water source for domestic and drinking purposes. after dry-up the households in aflaj turn to use multiple sources of water of different qualities. data collected from farmers have taken into account the difference between domestic and drinking purposes following verhagen and bhatt (2006). farmers were asked to provide detailed costs of the water according to the uses and the sources. four sources were considered, wells, water company, tankers and bottled water. the aggregated computation of domestic water losses due to aflaj dry-up were estimated as below: where, tdul : the total domestic water uses losses in the whole falaj after dry-up; n : total number of households leaving in sampled falaj; pwc : percentage of surveyed households using water from company to meet their domestic water uses; pwe : percentage of surveyed households using wells to meet their domestic water uses; pta : percentage of surveyed households using tankers to meet their domestic water uses; pmi : percentage of surveyed households using bottled water to meet their domestic water uses. results are shown in table 6. it is estimated that on average a family is spending a cost of o.r 328 per year for domestic water as a replacement cost against the water that was previously supplied freely by the falaj. households at aflaj without supporting wells spend 21 o.r/yr more than households at aflaj with supporting wells. ( )( ) ( )( ) ( )( ) ú ú ú û ù ê ê ê ë é ´-+ ´-+ ´= ptadotacdotac pwedowecdowec pwcdowccdowcc ntdul beforeiafteri beforeiafteri beforeiafteri (5) (4) table 5. weighted average housing relocation losses in dried-up aflaj in o.r/household. all aflaj ( n=191) aflaj with supporting wells (n=119) aflaj without supporting wells (n=72) min ave max min ave max min ave max average family size 1 11 40 1 11 40 1 11 32 housing relocation losses 9807 31813 142920 11407 34836 142920 9807 23120 55502 weight (number of houses relocated/total falaj houses) (16%) (19%) (11%) weighted housing relocation losses (per household) 1569 5090 22867 2167 6618 27155 1079 2543 6105 average falaj household number 38 45 29 aggregated housing relocation losses (per falaj) 59622 193420 868946 97515 297810 1221975 31291 73747 177045 14 zekri et al. 15 damage cost of drying of aflaj in the sultanate of omac aflaj were the only water source for agriculture, drinking and domestic purposes in the past. however, after afalaj dry-up, several water sources were needed. in most cases, two sources of water supply are observed; a good quality water for drinking purposes, and a lower quality water for domestic uses which is considerably cheaper. for this reason total water losses were presented according to their use. the average loss is estimated to about o.r 7,610 per falaj per year for the domestic uses and o.r 7,369 per falaj per year for drinking purposes. although these losses are very similar in value terms, the volumes of water consumed for drinking and domestic uses are largely dissimilar. table 7 represents the annual value of water used for drinking and domestic purposes in all dried-up aflaj (1,029) at the sultanate level. the figure shows that on an annual basis the total loss reached more than o.r 15 million. in other terms, the 1,029 dried up aflaj used to provide farmers and their families with a volume of water worth more than o.r 15 million in the form of drinking and domestic water. currently, these families who have lost their water from aflaj spend o.r 15 million to buy water for domestic and drinking purposes. the economic loss to the national community is even higher due to the fact that in most cases the water price is subsidized and does not reflect the real economic cost of water paid by the society as a whole to supply water to users. agricultural land value change in aflaj given the desert climate and low rainfall in oman, all agricultural activities depend on irrigation. consequently, aflaj dry-up should result in a loss in the value of agricultural land as it is no longer considered a productive asset. to estimate the change in value of agricultural land, we asked farmers about the land value before and after aflaj dry-up. farmers who were not involved in land transactions found some difficulty in answering the question. the damage due to aflaj dry-up is estimated as the difference between the land value before and the value after aflaj dry-up. another variable that affects land value is inflation, however until 2005 inflation in oman was very low and close to zero. thus we assume that the inflation effect on land price is negligible. another variable that does affect land price is the change of its table 6. annual drinking water and domestic water losses per family. all aflaj (n=191) aflaj with supporting wells (n=119) aflaj without supporting wells (n=72) min ave maxi min ave max min ave max average family size 1 11 40 1 11 40 1 11 32 drinking water losses (per family/yr) 24 132 540 24 133 540 24 131 384 domestic water losses (per family/yr) 24 202 600 24 191 600 36 221 540 total water provisioning losses (per family/yr) 36 328 816 36 320 816 72 341 648 table 7. annual domestic and drinking water losses in dried-up aflaj. region losses for domestic water per (falaj (/per yr losses for drinking water per falaj ((per yr total water losses per falaj (per yr) number of dried-up falaj total water losses in dried-up aflaj ((per yr al buraimi 0 11,280 11,280 --dakhliya 11,386 6,436 17,822 249 4,437,616 dhahirah 5,166 14,901 20,067 243 4,876,364 north batinah 6,924 9,499 16,424 352 5,781,131 sharqiyah 7,501 5,067 12,568 185 2,325,046 total 7,610 7,368 14,977 1,029 15,411,648 16 zekri et al. 17 damage cost of drying of aflaj in the sultanate of omac status from agricultural land to urban land. whenever agricultural land is converted to urban uses, the land value increases. in fact in some cases a falaj dry-up allowed farmers to urbanize their lands or sell it for urban uses which resulted in an increase of its value. by law, aflaj land and agricultural land could not be converted into urban land if a falaj is still flowing and agricultural activity is possible. the change in monetary value takes negative values when there is increase in the land value as it is not a damage but rather a benefit. table 8 shows that on average the net result for the agricultural land value is a loss of o.r 475 per hectare due to aflaj dry-up. for those aflaj which benefited from supporting wells the land value has actually increased as shown on the last row by o.r -2,655 per hectare. for aflaj without supporting wells the net result was a decrease in land value of o.r 5,967 per hectare. total value of losses per family table 9 summarizes the annual losses incurred by an average family due to aflaj dry-up. these losses are monetary losses that the family used to receive (crop losses, livestock losses, and agricultural employment losses) or to avoid payment (household consumption of agricultural products and cost of new sources of water for domestic uses, housing relocation cost) as well as the changes in the value of the agricultural land due to the dry-up. to be able to add together losses that occur yearly, such as the agricultural income losses and losses (or gains) that occur once in a lifetime, such as the cost of relocation to another house and the change in the land value, the concept of depreciation is used. thus, the once-in-life losses are thus converted into an annual value at an interest rate of 5% over a period of 40 years. the total annual losses per family varied between o.r 3,301 for aflaj with supporting wells and o.r 4,779 for aflaj without supporting wells. thus, the contribution of supporting wells on a yearly basis is estimated as the difference of the above figures and is around o.r 1,478 per family. the supporting wells helped reduce the damage on crop and livestock losses as well as on the household consumption. however, the supporting wells did not contribute significantly to the cost of domestic water consumption. overall, the contribution of supporting wells, undertaken by the ministry of regional municipalities and water table 8. land value changes. all aflaj sample (n=191) aflaj with supporting wells (n=119) aflaj without supporting wells (n=72) min ave max min ave max min ave max land value decrease (/ha) 0 11,279 65,238 0 10,762 42,857 0 11,880 65,238 land value increase (per ha) -54,762 -15,223 -476 -54,762 -16,071 -476 -30,952 -12,194 -1,190 net result: increase/ decrease (per ha) -54,762 475 65,238 -54,762 -2,655 42,857 -30,952 5,967 65,238 table 9. losses per family in o.r per year. all sample (n=191) aflaj with supporting wells (n=119) aflaj without supporting wells (n=72) crop losses 1,357 1,248 1,536 livestock losses 510 460 595 losses of household-consumption of agricultural products 1,278 1,241 1,338 annualized relocation costs 297 386 148 new sources of water for domestic and/or drinking purposes 328 320 341 annualized change of agricultural land value 64 -354 821 total annual loss per family 3,835 3,301 4,779 16 zekri et al. 17 damage cost of drying of aflaj in the sultanate of omac resources, is quite significant. considering the full aflaj sample, regardless of presence of supporting wells, the annual family losses are estimated at o.r 3,835 equivalent to o/r 320 per month. this figure shows the importance of aflaj in providing food, employment, drinking water and income to families located in remote areas. thus protecting aflaj, whenever possible, contributes to environmental as well as economic sustainability. total losses of dried-up aflaj in the sultanate table 10 shows the total annual losses from dried-up aflaj at the sultanate level. the total loss is estimated at o.r 59.03 million per year. region wise, the batinah region’s annual loss from dry aflaj is the highest loss and is estimated at o.r 23.1 million. figure 2 shows the distribution of the losses at the sultanate level. the highest losses are incurred by the loss of agricultural and animal production for farmers’ families consumption labeled as “household consumption losses” representing 38% of the total losses. drinking and domestic water users’ losses represent 26%, and finally, the lost gross margin from marketed agricultural products represents 15%. it is worth noting that the losses of drinking and domestic water are higher than the marketed agricultural products. this is mainly due to the fact that several families who used to live around the aflaj used to benefit from them as a source of water for domestic and drinking purposes without being owners of land next to aflaj. on average 38 families live in and around each falaj. the agricultural land value loss represents only 1% of the total loss. this is due to the fact that most of the land has been converted to urban uses thus increasing its value and compensating the loss table 10. total annual losses in dried-up aflaj. region number of dried-up falaj marketed agricultural losses household consumption losses drinking & domestic water losses annualized housing relocation cost annualized land value loss total annual losses in dried-up aflaj (o.r./yr) dakhliya 249 565,829 5,004,402 4,437,616 2,804,530 161,938 12,974,315 dhahirah 243 3,738,889 10,712,967 4,876,364 2,736,951 158,035 22,223,206 batinah 352 2,640,472 10,488,896 5,781,131 3,964,637 228,924 23,104,060 sharqiyah 185 835,745 2,750,280 2,325,046 2,083,687 120,315 8,115,073 total 1029 8,784,833 22,576,621 15,411,648 11,589,805 669,212 59,032,119 15% 38% 26% 20% 1% agricultural losses household consumption losses drinking & domestic water losses housing relocation cost annualized land value loss figure 2. annual losses in dried-up aflaj. 18 zekri et al. 19 damage cost of drying of aflaj in the sultanate of omac observed by some farmers who were unable to convert their land use. conclusions two methods have been used to estimate the damages resulting from aflaj dry-up. the first one is the production function method where physical changes in production are valued using market prices for inputs and outputs. the second method is the cost based method which measures the value of an environmental asset, groundwater, by the costs incurred in avoiding negative impact. within this latter method the averting behavior and relocation cost approach are used. three types of impacts due to aflaj dry-up have been observed and measured in this study. these are the agricultural income loss, household and life conditions degradation and finally the land value change. the study considered 33 dried-up aflaj among the 1029 dried-up aflaj monitored by the mrmwr. a survey was undertaken during the period july-november 2008. a total of 205 farmers were interviewed and only 191 surveys were used for data analysis and loss computation. complementary information was obtained from local water authorities. the results have shown that on average a family owning land next to aflaj has lost the equivalent of o.r 3,301 per year or o.r 320 per month. the monthly income from aflaj represents more than treble the social security payment provided by government to needy families. the results show that aflaj played and still play a major role as a sustainable income source in the remote rural areas and are thus a barrier against poverty. farms provide fresh vegetables and healthy food to the rural population as well as drinking water without the need for any governmental intervention, in a sustainable way. on the other hand, 16% of the families living in and around aflaj were obliged to relocate due to the dryness of aflaj and lack of water. on average each of these families has spent 31,813 o.r as a cost of building a new house and the loss due to the abandoning of the old house located next to a falaj. the total losses in all dried-up aflaj, at the sultanate level, are estimated at more than o.r 59 million/yr with the losses in drinking and domestic water estimated at o.r 15 million/yr. in fact, aflaj used to provide water for domestic purposes without the need to install a pipeline network to supply either groundwater or desalinated water from the coastal area. our estimation of the losses related to domestic water is based on the extra cost incurred by families to buy water from new sources. this figure does not take into consideration the economic losses incurred by the government to supply domestic water to remote areas. the major cause of aflaj degradation and dry-up is the lax implementation of the law protecting the mother wells and aquifer storage. some of the aflaj studied have benefited from supporting wells drilled and equipped by the mrmwr. the supporting wells were found to have a positive impact mainly by reducing the damage on crop and livestock losses as well as on household consumption. the contribution of the supporting wells is estimated at o.r 1,478 per family per year. taking into consideration the changes in land value and the cost of housing relocation those aflaj which benefitted from supporting wells have had lower damage cost. the results have shown that the supporting wells contributed to limiting the damage to the families living in and around aflaj but could not prevent it. actually, the supporting wells draw water from the same shallow aquifer as aflaj, and thus the volumes of water pumped could not provide enough relief to the population. consequently, preventing aflaj from drying up is a better solution than drilling supporting wells. traditionally, farmers have always had plans to deal with natural drought or lack of rainfall by reducing the cropped area and limiting it to the perennial crops. however, when the dryness of aflaj is caused by excess pumping, from illegal wells, farmers have to organize themselves and collaborate with the mrmwr to protect their rights. finally, in some cases, wells were drilled and the water use was diverted to other economic activities out of the aflaj areas which might have resulted in higher income than the agricultural activity. even though this might be true, the water diversion from one user to another user should have been done after agreements and payments to the farmers who own the water. economic compensation should have taken place in such circumstances instead of an illegal transfer of water from aflaj water owners to other users. acknowledgements this research was financed by internal grant, ig/agr/ econ/05/01from sultan qaboos university. the research also benefitted from strong support of the ministry of regional municipalities and water resources, sultanate of oman. the authors would like to thank especially dr. seif al-shaqai, dg hamed al-hatmi, eng. saif alamri for their support to the project. thanks also go to two reviewers and to dr. hemesiri kotagama for their comments and suggestions which helped improve the paper considerably. references al sulaimani, z.k., t. helmi, and h. nash. 2007. the social importance and continuity of aflaj use in northern oman. the 4th asian regional conference and 10th international seminar on participatory irrigation management (pim), 2-5 may 2007, tehran, iran. al-ghafri, a. 2006. aflaj’s irrigation water demand/ supply ratio: two case studies. agricultural and marine sciences a research journal 11(special issue):85-92, sultan qaboos university, sultanate of oman. garrod, g. and k.g. willis. 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christchurch, new zealand, 23 june 02 july 2007. verhagen, j. and m. bhatt. 2006. multiple use of water in urban areas a case study in bhuj, gujarat, india (final report) june 2006. zekri, s., h. kotagama, and h. boughanmi. 2006. temporary water markets in oman. agricultural and marine sciences a research journal, 11(special issue):77-84. sultan qaboos university, sultanate of oman. zekri, s. and a. al-marshudi. 2008. a millenarian water rights system and water markets in oman. water international 33:350-360. received: november 6, 2012 accepted: december 23, 2012 pdf995, job 6 73 !"#$!%&'%()*+,!%-./0,!%123456%(789:0,!%;<,!%=9.+45!%>.? %(/!"",!%# (/$#.%,!% !"#$%!&"'(! ! %(&&'2(!)!!!!!!!!!!!!!!!!!!!*+,-./0!12345%!6,785%!6%39./,:!;<=(!>?, !!<"!*+,-./0!#<$<5$%3<&!#2'(7)!;(*":!#(/%%35%!+,(&!6"(-# !!!!!!!!!!!!!!!!!!!!!!!!!!!!>.!*%"/405%!'<1!#<(."25%!#<(?,05%!3%"(45%!6"('#!#(25,-05!678(5%!9(:"5%!;<(/8#!>(.!,(&%$3"!;<(<-#$!#"$+<(05%!=(>5% !!!!45%!#<'4,(?5%!@a,8(05%!#2'(>!b!!!!!!!!!!!!!!!!!!#<$<5$%32,c5%!d/5%!@<ef#!g$02!h()i!0j!6"'.(5%!#(25,!>(.!6,78(5%!k,(2)!g( !;1'(5,:$ '4e5%!+,<05!lm%3#!!n$+!#<'4,?5%!@a,805%!g !#:,-5%!#<."25%!+,<05%!!4/!>.!o,<8-.5%$b! agricultural sciences, 7(2):73-74 (2002) short communication © 2002 sultan qaboos university dual pump recovery (dpr) system to extract freshwater in coastal aquifers c. otto csiro petroleum, private bag, po wembley, wa 6014, australia abstract: the paper describes the hydraulic theory of recovering a dense plume using a newly devised dual pump recover system (dpr) and its feasibility to half the remediation time of a contaminated unconfined aquifer in a coastal urban environment. although the dpr system was successfully applied to clean up the polluted aquifer, the hydraulic principles and techniques are also applicable to extract fresh groundwater from coastal aquifers without the risk of saltwater incursion. keywords: dual pump recovery, coastal aquifer, unconfined aquifer, saltwater intrusion, plume, freshwater, recharge, groundwater. he concept of a dpr system is simple and not new. similar techniques have been used or have been proposed to prevent upconing of the seawater wedge in coastal aquifers (underhill and atherton, 1964; zack, 1988), recovery of dense coal tar wastes (villaume et al., 1983) and recovery of light oils, which float on the water table (wisniewski et al., 1985). the principles of operating a dpr system are as follows: in essence, where there is a sharp interface between two layers in an aquifer, with distinctly different characteristics (e.g. density stratification, or even a difference in chemical composition which is insufficient to cause density stratification), each layer can be recovered separately by positioning two pumps within a single fully-penetrating screen, with the ratio of pumping in the two pumps equal to the ratio of the transmissivities in the two layers. a fully penetrating screen has the advantage that well losses are markedly reduced, thus there is minimal drawdown of both the water table and the interface in the near field of the bore. radial flow towards the bore is essentially horizontal at a small distance from the bore, and the two types of water are drawn into the screen and separated within the screen by being drawn upwards or downwards towards the control and recovery pumps, respectively. there is little or no mixing of the two types of water within the screen, because a stagnation point exists between the two pumps, i.e. a point where the net velocity is zero. dual pump receovery system a dpr system consists of a pair of "recovery" and "control" pumps that can be used to recover dense and/or contaminated groundwater in an aquifer that contains two distinct layers of water. the recovery pump is the lower pump, and the control pump is the upper pump. the role of the control pump is to balance the rate of extraction from the recovery pump, so as to ensure that contaminated water enters the recovery t otto 74 pump and relatively uncontaminated water enters the control pump. let qr be the rate of pumping in the recovery pump, and qc be the rate of pumping in the control pump. the intake of the recovery pump is located in the contaminated zone or saline interface, as close to the base of the aquifer as practicable, and the intake of the control pump is located as high as possible, perhaps limited by drawdown of the water table. an appropriate choice of pumping rates will cause contaminated water to be removed through the recovery pump and freshwater to be removed through the control pump. the efficiency of the dpr system depends on choosing a combination of pumping rates so that the capture zones of the two pumps meet at (or just below) the elevation of the interface in the far field, i.e. where horizontal flow occurs. when qc is too low the concentration in the recovery pump will be diluted by freshwater, whereas when qc is too high, the control pump will be extracting more contaminated water than necessary. local variations in flow patterns within the near field will cause the interface to move, but it is the position of interface in the far field which is most important. conventional recovery in a layered aquifer mixes the water recovered from each layer and requires all recovered water to be treated. dpr recovers two separate types of water: contaminated water from depth which must be treated, and fresh water from near the water table which is clean enough that it can be safely recharged to the aquifer a short distance away. since the water from the control pumps can be recharged, it is possible to pump at a larger total rate at each dpr site without adversely affecting the water balance of the region. as a result, the plume is recovered more quickly. furthermore, the water sent for treatment is not diluted by overlying fresh water, the volume of water to be treated is less, and water treatment costs are therefore reduced. pumping rates recovery of the contaminant is controlled adaptively by varying the ratio of pumping from the two pumps. therefore, a key issue is the appropriate selection of pumping rates. if at any stage the pumping rate of the control pump is too small, the concentration of recovered groundwater from the recovery pump will start to decrease. conversely, if the pumping rate in the control pump is too large, the concentration of groundwater in the control pump will start to increase, thus limiting re-use and perhaps requiring treatment of the control water. during the operation of a dpr system, concentrations at the pump outlets need to be monitored frequently and pumping rates must be adjusted to changes in concentrations (or elevations of the interface in the far field), so as to maximize the efficiency and the rate of mass recovery of contaminated groundwater at all times. results of field trials are described in otto and townley, 1997. conclusions the dpr system can also be used to pump fresh groundwater from a coastal aquifer near the freshwatersaltwater interface. in this case the recovery pump functions as the control pump, and the control (upper) pump is the recovery pump, which delivers the fresh water to the drinking water scheme. the saline water from the control (lower) pump can be discharged back to the marine environment. references otto, c.j. and l.r. townley. 1997. feasibility of a dual pump recovery (dpr) system to recover a dense plume of contaminated groundwater. chilton, j. et al., nottingham. balkema. 513-516. underhill, h.w. and m.j. atherton. 1964. a coastal groundwater study in libya and a discussion of a double pumping technique. j.hydrology 2:52-64. villaume, j.f., p.c. lowe, and g.p. lennon. 1983. coal tar recovery from a gravel aquifer, stroudsburg, pa. proc. asce conf on the disposal of solid, liquid and hazardous wastes. bethlehem, pennsylvania, april. wisniewski, g.m., g.p. lennon, j.f. villaume, and c.l. young. 1985. response of a dense fluid under pumping stresses. toxic and hazardous wastes, proc. 7th mid-atlantic waste conf. zack, a.l. 1988. a well system to recover usable water from a freshwater-saltwater aquifer in puerto rico. u.s. geological survey water-supply paper: 2328. _______________________________________________ received october 2002. accepted november 2002. agricultural and marine sciences, 16:23-33 (2011) ©2011 sultan qaboos university 23 ________________________________________________ *corresponding author. e-mail: asadalaqidah@gmail.com fish kill incidents and harmful algal blooms in omani waters hamed mohammed al gheilani1*, kazumi matsuoka2, abdulaziz yahya alkindi3, shehla amer4, and colin waring5 1ministry of agriculture and fisheries wealth, p.o. box 427, pc 100, muscat, sultanate of oman 2institute for east china sea research, nagasaki university, 1-14 bunkyo-machi, nagasaki, 852-8521, japan 3department of biology, college of science, sultan qaboos university, p.o. box 36, pc 123 al khodh, sultanate of oman 4nizwa university, sultanate of oman 5marine institute, portsmouth university, united kingdom العمانية املياه في الضارة الطحالب وازدهار األسماك نفوق حوادث ويرجن وكولني عامر شهلة الكندي، يحيى العزيز عبد ماتسوكا، كازومي الغيالني، محمد حمد واالقتصاد الساحلية السمكية الثروة على تأثيرات عدة إلى يؤدي طبيعيا تغيرا يعتبر الضارة الطحالب ازدهار ظاهرة أو األحمر املد اخلالصة: واالستزراع السمكية الثروة على واثر األسماك نفوق إلى أدى بعض األخيرة. السنوات االزدياد في في اخذ األحمر املد والصحة العامة. احمللي للمد املسببة البحرية العوالق أنواع حال، معظم كل على املياه. حتليه محطات على تأثيره إلى باإلضافة عام البيئة بشكل على اثر كم مت رصدها والتي وترايكوزميم، بروروسنترم ارابني مثل سامة أخرى أنواع بينما سنتلينس. مثل نكتلوكا سامة غير عمان سلطنة في األحمر لم األحمر املد أثناء اإلنسان بصحة مرتبطة مشكالت لكن األكسجني. ونقص التقليب بظاهرتي مرتبط عمان في األحمر املد مؤخرا. عمان. في تسجل abstract: red tide, one of the harmful algal blooms (habs) is a natural ecological phenomenon and often this event is accompanied by severe impacts on coastal resources, local economies, and public health. the occurrence of red tides has become more frequent in omani waters in recent years. some of them caused fish kill, damaged fishery resources and mariculture, threatened the marine environment and the osmosis membranes of desalination plants. however, a number of them have been harmless. the most common dinoflagellate noctiluca scintillans is associated with the red tide events in omani waters. toxic species like karenia selliformis, prorocentrum arabianum, and trichodesmium erythraeum have also been reported recently. although red tides in oman have been considered a consequence of upwelling in the summer season (may to september), recent phytoplankton outbreaks in oman are not restricted to summer. frequent algal blooms have been reported during winter (december to march). habs may have contributed to hypoxia and/or other negative ecological impacts. keywords: red tide, habs, fish kill, noctiluca scintillans, phytoplankton, upwelling, hypoxia. introduction throughout the world’s coastal waters, harmful algal bloom are being reported with increasing frequency and causing severe impacts on coastal resources, local economies and public health. harmful algal blooms (habs) are caused by microalgae, usually single-celled prokaryotic and eukaryotic photosynthetic organisms that live in freshwater, estuarine and marine realms. harmful and toxic incidents caused by dinoflagellates are intensifying and spreading all over the world accompanied with extensive ecological damage during the last four decades (cho, 1981; olsen et al., 1988; smayda and fofonoff, 1989; chen and gu, 1993; hallegraeff, 1993; nuzziet al., 1996; anderson, 1997; wong, 1989; kim et al.,1990, 1993; steidinger, 1993) including the coastal waters of oman (thangaraja et al., 1990, 1991, 1998, 2000, 2007; al gheilani et al., 2005, 2007; al kindi et al., 2007, unpublished; al busaidi et al., 2008; richlen et al., 2010; matsouka et al., in preparation). the reasons for the increasing red tides may be related to the global climate change, increase of human impact in coastal zones, awareness resulting from scientific research and reports of habs events. the negative effects caused by such micro-algae include the biotoxins, physical damage and the anoxia or hypoxia (al gheilani et al., 2005). however, cell densities of causative micro-algae cannot increase forever and as soon as the first critical nutrient runs out, the bloom will collapse 24 al gheilani and others 25 fish kill incidents and harmful algal blooms in omani waters (van den bergh et al., 2002). thus, for understanding hab phenomena the behavior of nutrients is one of the important subjects for research. since habs are globally distributed and integral parts of marine and brackish-water ecosystems, the main research problems can be addressed comprehensively and effectively only through international, interdisciplinary and comparative research on important questions about the dynamics of habs within their oceanographic and ecological systems (geohab, 1998). recurring algal blooms and red tides in the coastal waters of oman have been documented for nearly three decades, and some of them cause damage to the marine environment and economic losses to the fisheries industry. the other negative effects of red tides-causing dinoflagellates in omani waters include the production of biotoxins, physiological damages to fish and the anoxia or hypoxia in the environment (al gheilani et al., 2005). hence, in order to diminish fisheries damages, especially for aquaculture, adequate monitoring systems of the outbreaks are required. as habs are of national concern to oman, there is need to foster national cooperative research on habs in order to find better solutions regarding this issue. this paper intends to provide an overview of habs history, causative species and previous research activities for establishing counter measures to habs damages in the sultanate of oman. history of hab occurrences and investigations in oman early scientific records of red tide events in oman prior to 1976 were rare. the first hab / red tide incident was reported during the 4th week of august 1976 along the salalah coast between taqah and raysut, and caused a loss of about 7,000-10,000 tons of fish (barwani, 1976, unpublished report). subsequently, there were two more incidents of mass mortality of fish in muscat; one in october 1976 and the other in february 1978, and causative organisms were n. scintillans and gonyaulax sp. (zahran, 1978), respectively. since 1988, there has been regular documentation and monitoring of red tides and their impacts on the coastal waters of oman (thangaraja, 1990, 1991; thangaraja et al., 1998, 2000, 2007; al gheilani et al., 2010, unpublished). different coastal regions of oman show variation in susceptibility to algal blooms and red tides, however most of the incidents have been recorded from the muscat region (fig. 1). the red tides appear to have become more widespread and persistent since late 1980s (fig. 2). a review of different habs occurrences from 1976 to 2009 showed that about 81 red tide events have been recorded along the coastal waters of oman; of which 10 incidents have resulted in mass mortality of fish and other marine organisms (figs. 2 and 3; table 1). figure 1. distribution of red tide in omani coast. 24 al gheilani and others 25 fish kill incidents and harmful algal blooms in omani waters of the 22 identified habs causative species, 16 were dinoflagellates and most of the fish kills were caused by these dinoflagellates (thangaraja et al., 2000, unpublished report of the ministry of agriculture and fisheries wealth). red tide data (thangaraja et al., 2000, data from ministry of agriculture and fisheries; al gheilani et al., unpublished) showed that 80% of all identified algal blooms were caused by dinoflagellates singly or in combination with diatoms. noctiluca scintillans is the most important species causing more than 50% of habs in omani waters, but most noctiluca blooms (31 from 37 blooms) did not affect marine organisms. � 0 2 4 6 8 10 12 14 19 88 19 89 19 90 19 91 19 92 19 93 19 94 19 95 19 96 19 97 19 98 19 99 20 00 20 01 20 02 20 03 20 04 20 05 20 06 20 07 20 08 20 09 frequency years no�damage fish�kill figure 2. major habs event occurring in oman (70) and habs outbreaks causing fisheries damage and marine organism mortalities (22) (data: ministry of fisheries wealth). � 0 5 10 15 20 25 30 35 40 n oc til uc a� sc in til la ns co ch lo di ni um ce ra tiu m g on ya ul ax �s p. tr ic ho de sm iu m �s p. rh iz os ol en ia �s p. pr or oc en tr um �s p. d in op hy si s� sp . frequency phytoplankton�species figure 3. main habs causing species in omani waters. 26 al gheilani and others 27 fish kill incidents and harmful algal blooms in omani waters mechanism of algal blooms in oman for intensive fish mass mortality in oman, the following two scenarios are possible; 1) depletion of dissolved oxygen, and/or 2) blooms of toxic phytoplankton species. oxygen depletion the phenomenon of oxygen depletion is increasing in coastal waters of the world (kamykowski and zentara, 1990) with occurrence as permanent, seasonal and episodic features. oxygen depletion in the waters can result in hypoxic or anoxic conditions in the coastal areas. two principal factors that lead to the development of hypoxia and anoxia; 1) water column stratification that isolates the bottom water from exchange with oxygenrich surface water and followed by 2) decomposition of organic matter in the isolated bottom water that reduces oxygen levels (sarmiento et al., 1988; diaz, 2002). persistent low oxygen is evident in oxygen minimum zones (omz) defined as regions where oxygen concentrations are <0.5ml*l-1 (22µm; levin, 2003). the omz in the northern arabian sea impinges on the continental margin creating permanently hypoxic conditions in the deep coastal to baythal benthic environment (reichart, et al., 2002). on the oman continental margin, the omz extends down from about 60 m to about 1000 m deep, with gradual increasing dissolved oxygen (do) below this depth to “normal” near saturated oxygen levels by 2000-2500m (lamont and gage, 2000). bacterial oxidation in sinking organic matter typically found just below the thermocline at the depth from 50 to 100 m (morrison et al., 1999) brings highly fertile conditions for growth of phytoplankton and other photosynthetic organisms in the northern arabian sea and the oman sea. consequently, the arabian sea has one of the thickest oxygen depleted layers of ocean water found anywhere in the world (gooday et al., 2000; herring, 2002). sometimes, due to shifts in the overlying wind field, these deep oxygen-poor waters upwell to the surface indirectly leading to periodic mass fish kills. in the arabian sea the differences in oxygen concentrations between the mixed layer, thermocline and deep waters become most apparent during periods of strong thermal stratification (at the end of the summer) when mixing across the thermocline is nearly impossible. the mixed layer has temperatures ranging from 25 to 32ºc and high do content (do= 4mll-1to 6ml l-1or higher). the temperature of the thermocline is between 24ºc and 26ºc and the do concentrations are between 2ml l-1and 4ml l-1, while the deeper water has temperature below 24ºc and do concentrations below 2mll-1(morrison et al., 1999). the breakdown of stratification of water column occurs in periods of upwelling (cold water brought to the surface) and either relaxation or downwellings (surface water pushed down along the coast). during the upwelling, water masses transported from 60 or 70 m depth result in the lowering of the temperature to 23-25 ºc at the sea surface. these cool waters are also poor in oxygen but rich in nutrients. this nutrient rich water is then susceptible to table 1. massive fish kills recorded in omani waters (1976-2009). period major species area mortality august 1976 salalah 7000-1000 tons of fish september 1988 ceratium fucus c. macroceros diatom seeb to qurum mass mortality of marine organisms august to september 2000 coscinodiscus spp barka 15-30 tons of fish march 2001 sur 250 tons of fish april 2001 al sharqiya 34 tons november to december 2001 al sharqiya and al wasta 40 tons of fish 250 turtles january 2004 bander kharan 3000 tuna fish october 2005 noctiluca scintillans; prorocentrum micans and trichodesmium erythraeum masirah massive fish kill september 2006 sohar massive fish kill october 2008 to april 2009 cochlodinium polykrikoides oman and arabian sea 200 tons of fish and shellfish 26 al gheilani and others 27 fish kill incidents and harmful algal blooms in omani waters trigger the development of phytoplankton bloom (mostly harmless diatoms), at least for the few days that follow the onset of upwelling. savidge and gilpin (1999) estimated chlorophyll a concentrations and primary production to be maximal in the coastal upwelling zone in n w indian ocean during the late monsoon season. after a rapid growth, the phytoplankton produce oxygen at least in the upper layers of the water column, but during night they consume oxygen. later in the cycle, the nutrient cannot sustain any further growth of the phytoplankton and dead or dying cells start to sink or decay. in bacterial denitrification, nitrate ions are used for oxidation of organic matter, in this process they are reduced to molecular nitrogen with nitrite as an intermediate (codispoti and christansen, 1989). nitrification, the oxidation of nitrite and ammonium also occurs in these waters (ward et al., 1989). the low oxygen condition physiologically stressful for fish usually varies among taxa. the point at which various animals suffocate varies, but generally effects start to appear when oxygen drops below 2 ml l-1 or 2.8 mg l-1, for seawater, this is about 18% saturation (diaz and rosenberg, 1995). in several parts of the world, fish kills have been attributed to low dissolved oxygen levels generated by high biomass blooms and not necessarily due to toxicity. for example, from 1980–1989, at least 50% of fish kill in the gulf of mexico and 69% in the south atlantic, usa, were attributed to low dissolved oxygen (lowe, et al., 1991). similarly, the low do levels have caused fish mortality in oman. in most cases the dominant red tide causative species in the oman sea is n. scintillans (table 2). number. of occurrences impact single species noctiluca scintillans 37 fish mortality (6) no damage (31) cochlodinium polykrikoides 21 fish and shellfish mortality (21) ceratium sp. 06 fish mortality (3) no damage (3) rhizosolenia sp. 03 no damage trichodesmium sp. 04 fish mortality (1) no damage (3) gonyaulax polygramma 04 fish mortality (4) prorocentrum sp. 02 no damage coscinodiscus 01 fish mortality karenia mikimotoi 01 no damage mixed species gonyaulax, noctiluca 02 fish mortality (2) c. fusus, c. macroceros, diatoms 01 fish mortality n. scintillans, c.furca, c. macroceros, p. micans, pyrophacus holorogicum, peridinium 01 no damage rhizosolenia, pleurosigma sp., nitzschia pungens, coscinodiscus spp., fragilaria sp., triceratium sp., chaetoceros sp., ceratium sp. 01 no mortality coscinodiscus marginalis, asteromptelus spp., chaetoceros sp., rhizosolenia sp., ceratium sp. 01 no mortality dinophysis, ceratium spp. 01 fish mortality n. pungens, rhizisolenia alata, thalassisora, cyclotela, pyrocystis, gymnodium splendens, p. minimum, p. arabianum 01 fish, green turtle and bird mortality table 2. species causing habs in omani waters and their effects. 28 al gheilani and others 29 fish kill incidents and harmful algal blooms in omani waters the appearance of n. scintillans was noted in plankton samples collected within the waters of muscat from 1st february till the end of march 1988 (thangaraja, 1990). at that time red tide of this species was recorded along the coast of the oman sea from khasab to sur. n. scintillans produced many patches of orange red coloration in the waters from al-bustan to qurum on 1st, 8th, and 10th february with a peak on the 19th march, 1988. this species formed red tide blooms almost every year in the oman sea between january and may since 1988 (thangaraja, 1990). the bloom intensity of n. scintillans is increasing year by year. in 1999 a new strain of this species formed green tide in the eastern coasts in the oman sea (msfc, 19762010). phytoplankton blooms were also observed three times between february 1988 and april 1989 along the coast of muscat (latitude 23º37’n; longitude 58º36’e) (thangaraja et al.,1990). blooms occurring from 5th to 20th of september 1988 (with a peak on the 14th) caused discoloration of waters from seeb to qurum, and mass mortality of marine organisms happened in a 30 km coastal stretch. the dinoflagellates identified were ceratium fusus, c. macroceros, c. furca, prorocentrum micans, pyrophacus horologicum and protoperidinium species. however, excepting c. fusus, the other dinoflagellates were few in number. large blooms of these organisms caused first discoloration of the water and then mass mortality of marine life. low oxygen levels were recorded (2.64 ml/l and 1.87 ml/l) at water depths of 2-3 meters and 8-10 meters respectively, on 14th september 1988 at alghubrah coast. seawater temperature was 27.5°c, salinity 35.9% and ph 8.31-9.0 (thangaraja, 1990). although, ceratium spp. are not toxic, they are known to cause deterioration of the water quality (onoue, 1990). n. scintillans blooms repeatedly appeared in the muscat coasts in the plankton samples from 25th february to 5th april 1989. dense patches of discoloration were noticed about 5 km off shore on 5th april during the regular plankton survey. on 11th april the bloom developed denser than that of the previous year, the intensity of red tide started declining on 12th april. between 11th and 13th april, eight species of dead fish were found at al-bustan coast during this bloom. this was a significant record of fish kills by n. scintillans bloom (thangaraja, 1990). previous data suggest that in oman no red tide was noticed in the summer season but these events are common in winter months including january and february (fig. 4). it was observed that n. scintillans bloom affected marine ecosystems in two different ways; first depletion of oxygen and then bacterial infection. according to thangaraja (1990), in the first incident of fish kill during february to march 1988 both above-mentioned effects were recognized, but in 1989 only the depletion of oxygen was observed. the dead fish collected during 1989 bloom showed no morphological abnormalities of gills or gill clogging. the guts were in advanced stages of putrefaction and therefore their contents were not examined. thousands of the pelagic fish, atherinomorus lacunosus were killed with “fin and tail rot” disease caused by bacterial infection following the noctiluca bloom � 0 2 4 6 8 10 12 14 16 ja nu ar y fe br eu ar y m ar ch a pr il m ay ju ne ju ly a ug us t se pt em be r o ct ob er n ov em be r d ec em be r frequency months figure 4. seasonal variation of habs in omani waters. 28 al gheilani and others 29 fish kill incidents and harmful algal blooms in omani waters (thangaraja, 1990). there are several examples which show that either acute/chronic exposure to microalgal toxins or harmful mechanisms associated with habs was sufficient to increase the susceptibility of aquatic organisms to disease. during 1989-1990, a n. scintillans bloom in the pie hai sea (northern china sea) resulted in losses of about $100 millions in shrimp penaeusorientalis mariculture. poor water quality caused an increase in the susceptibility of prawns to parasitic infections, which led to disease mortalities and additional losses valued at $i million (chen and gu, 1993). most of the habs-related fish mortality events in oman have been attributed to noctiluca blooms (table 2). accumulated ammonia is produced after death, and dissolution of noctiluca cells caused fish mortalities (schaumann, et al., 1988, okaichi and nishio, 1976, suvapepun, 1989). when the bloom of noctiluca at maximum cell densities of 5.3x106m3 occurred accompanied with a mass mortality of demersal fish and benthic organisms along the east coast of jakarta bay of indonesia in july 1986, ammonia, nitrogen and phosphate levels in the seawater just after the mortality were significantly increased (adnan, 1989). in some cases, such conditions may not result in mortality but in avoidance by fish, leading to localized reductions in fisheries. noctiluca can also create a large quantity of mucus, which mechanically damages fish gills or interferes with fish respiration (subramanian, 1985). thus large blooms of heterotrophic noctiluca can consume significant amounts of oxygen and after their subsequent decay bacterial production can result in severe oxygen depletion. therefore, although not considered toxic, large noctiluca blooms can significantly contribute to deterioration of water quality, accompanied with depleted dissolved oxygen (elbrachter and qi, 1998; subramanian, 1985; suvapepun, 1989; ho and hodgkiss,1992). another major incident of phytoplankton blooms was reported in oman along seeb al-hail shores approximately 10 km from muscat during the second week of august 2000. in the last week of august 2000, another incident of fish kill was reported in barka, some 80 km from muscat. it was the consequence of a series of local upwelling of oxygen poor waters with do levels measuring less than 1-2ppm (mathews et al., 2001). analysis of water samples taken from the area revealed that large centric diatoms of the genus coscinodiscus were responsible for the bloom (claereboudt et al., 2001). however, this genus is known not to contain toxic species for the moment. non-toxic coscinodiscus caused depletion of oxygen in already oxygen poor waters (claereboudt et al., 2001). do concentrations were found to be 2.6 mg/l at 5 m depth and 0.40 mg/l at 10 m depth (thangaraja et al., 2000). analyses of nutrients off coastal waters along dhofar coasts showed that the waters had become eutrophic with nutrient levels in excess of 20µm nitrate–nitrogen and 2 µm phosphatephosphorous found between july and mid october 2000 (savidge et al., 1990). high levels of nutrients and low temperature (<20°c) accounted for dense blooms of phytoplankton (maximum>20µg chlorophyll a l-1) and the annual development of dense beds of macroalgae along the arabian sea coasts (savidge et al., 1990). as malcolm et al. (1999) also suggested that during the monsoon season, upwelling is the major influence on the nutrient supply in the surface waters of the arabian sea off the coast of oman, high nutrient such as levels of no 3 (= 18 µmol l-1) and po 4 (1.48 µmoll-1) in the close inshore coastal zone and also higher concentrations (no 3 =12.5 µmoll-1; po 4 = 1.2 µmoll-1) at the region of offshore upwelling off the shelf during september/october 1994. toxic algal blooms in oman and their impact the abnormal production of phytoplankton (diatoms, dinoflagellates and blue green algae) such as trichodesmium sp., dinophysis spp., gonyaulax spp., and ceratiums pp. led to discolouration of water and caused either environmental impacts or mass mortality of marine organisms in omani waters in 2000 (thangaraja et al., 2000). a total 109 fish species were recorded as causative organisms for massive fish kills. these species consists of the coral reef associated fish species (59%), demersal fish species inhabiting shallow coastal waters (28%), and pelagic species (13%) (claereboudt et al., 2001). the upwelling of nutrients in sw monsoon triggered blooms in march-april and november-december 2001. as a result of these habs, widespread fish and green turtle (cheloniamydas) mortalities appeared in the southern region of oman. about 284 tons of fish during march and april and 40 tons of fish along with 250 turtles, some dolphins and birds were killed during november and december, 2001 (maf and mrmewr, 2002). the taxonomic composition of the bloom showed that the bloom was dominated by diatom nitzschia pungens grunow ex cleve(=pseudo-nitzschia pungens (grunow ex cleve) hasle), n. cf. subcurvata hasle (pseudonitzschiasubcurvata (hasle) fryxell), rhizosolenia alata brightwell (=proboscia alata (brightwell) suderstom, thalassiosira spp., and cyclotellaspp. (stirn et al., 1993). the secondary succession phase appeared to be dominated by dinoflagellate such as pyrocystis sp., and potentially toxic dinoflagellates gymnodium splendens lebour(=akasahio sanguinea (hirasaka) g. hansen et moestrup) and prorocentrum minimum (pavillard) (garrison et al., 1998). an unarmored ichtyo-toxic dinoflagellates karenia selliformis haywood, steidinger et mackenzie originally described from new zealand in 2004 first occurred in water samples collected from the north and south of khaluf in concentrations of 2,492,000 cells/liter [drs. j. landberg, k. steidinger and a. haywood at the florida marine research institute, st. petersburg, florida, u.s.a. (preliminary unpublished report, 2005)]. k. selliformis is phylogenetically related to k. mikimotoi (miyake and kominami) g. hansen et moestrup and k. brevis (davis) g. hansen et moestrup (haywood et al., 2004). other species such as k. mikimotoi and karenia 30 al gheilani and others 31 fish kill incidents and harmful algal blooms in omani waters digitata yang, takayama, occurring in hong kong during march and april 1998 killed fish worth us $40,000,000 (lu and hodgkiss, 2004). although karenia spp. including k. mikimotoi has reportedly caused mass fish mortality in kuwait bay (heil et al., 2001; gilbert et al., 2002), it is not unknown in the arabian sea. the toxins produced and released by these microorganisms might be responsible for the mortality of green turtles, dolphins and birds in oman (jupp, 2001). moreover, a new species of planktonic dinoflagellate, prorocentrum arabianum was recorded during this incident in 2001 and was added to the list of hazardous species, because p. arabianum was capable of producing a cytotoxic as well as an ichthyotoxic compound (morton et al., 2002). after the major fish and marine organism mortality event in 2001, nine other red tide incidents were recorded in 2002 and six incidents were recorded in 2003. n. scintillans was identified as red tide causative species in all cases except for one. k. mikimotoi was found in the plankton samples from bloom in march 2003. however, none of these blooms caused any damage to fisheries or other marine organisms (unpublished data, ministry of agriculture and fisheries). in 2004, five algal blooms were recorded and n. scintillans was probably responsible for all blooms. fish mortality was observed in three of these incidents occurring in january, april and september 2004 (unpublished report of ministry of agriculture and fisheries wealth). recently, at the end of october 2005, extensive blooms occurred in the east of masirah island accompanied with massive fish mortality. this habs event lasted for eight days accompanied by a red-orange discolouration of the water. hydrographical surveys using satellite images revealed low temperatures due to upwelling of waters with oxygen deficient. plankton analysis revealed n. scintillans, prorocentrum micans and toxic blooms of cyanobacteria trichodesmium erythraeum (ehrenberg) (al busaidi et al., 2008). more recently, in august 2006, massive fish kills occurred in muscat. depletion of oxygen was suspected to be the reason of the demersal fish kill. also, in september 2006, a massive fish kill occurred in sohar. the levels of oxygen were within the normal range. no harmful species were reported, but the water temperature was lower than the usual condition (ministry of agriculture and fisheries, 2006). no fish kill were recorded in 2007. however, extremely large fish kills were recorded in 2008-2009 caused by blooms of cochlodinium polykrikoides. the blooms were started in the oman sea in september 2008 in musandam and al batinah coasts and ended in april 2009 in the arabian sea and the oman sea. more than 200 tons of fish and shellfish were killed. during these blooms, seventy tons of goldlined seabream were killed at an aquaculture farm in quraiat, muscat. the levels of oxygen were very low (less than 1mg/l) during cochlodinium blooms. as well as the low oxygen levels during cochlodinium blooms, damage to fish gills were also recorded (richlen et al., 2010; matsoukaet al., unpublished; al gheilani et al., unpublished). these habs events occur on a regular basis in oman and require a long-term solution. conclusion a programme for the establishment of a habs monitoring system was launched in the sultanate of oman in 1978. the system deals with monitoring of environmental conditions, including studies on red tides, and collection of data on the taxonomy of marine biota, hydrology and water quality. meteorological and oceanographic data including current, temperature, oxygen, algae and nutrients are obtained on a regular basis from different sites and positions along the coastal waters of oman. however, the quality of technology for detecting, modeling and predicting harmful algal blooms needs improvement. modeling of bloom-forming mechanisms of various causative organisms are tried in order to create a prediction system. unfortunately, this has not been very effective mostly because of incomplete data acquisition and accumulation. water quality data collection and reporting are not consistent among different agencies, reducing the effectiveness of the data for modeling of bloom-forming mechanisms. spatial and temporal monitoring of harmful algal blooms continue in oman and research is being conducted that will assist in management of the blooms. scientists and managers are making efforts to create less cumbersome, cheaper, faster and automated detection techniques, which would greatly benefit them in responding to these events more efficiently and effectively. however, vigorous efforts need to be devoted to the elucidation of the biology and ecology of red tide organisms and their blooming mechanisms, modeling and mitigation methods in the sultanate. since oman has a large mariculture operation, future research efforts need to be focused on the influence of mariculture activity in triggering hab occurrences in coastal areas to help retain a healthy marine ecosystem along the coast of oman. hence, there is also an urgent need for bloom mitigation strategies in aquaculture areas in the sultanate. acknowledgements we are grateful to the staff, scientists and researchers of the marine science and fisheries center, ministry of agriculture and fisheries wealth, sultanate of oman, for providing the data of red tides in oman. references adnan, q. 1989. red tides due to noctiluca scintillans (maccartney) ehrenb, and mass mortality of fish in jakarta bay. in: red tides, biology, environmental science and toxicology, t.d. okaichi, d.m. anderson, and t. nemoto (editors), 53-55. 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h.a. al-shaqsi. 2000. phytoplankton blooms, red tide phenomena and recorded impacts in oman. msfc annual report. ministry of agriculture and fisheries, sultanate of oman. 22pp. thangaraja, m., a. al-aisry, and l. al-kharusi. 2007. harmful algal blooms and their impacts in the middle and outer ropme sea area. international journal of oceans and oceanography 2:85-98. van den bergh, j.c., p.a. nunes, h.m. dotinga, w.h. kooistra, e.g. vrieling, and l. peperzak. 2002. exotic harmful algae in marine ecosystems: an integrated biological-economic-legal analysis of impacts and policies. marine policy 26:59-74. ward, b.b., h.e. glover, and f. lipschultz. 1989. chemoautotrophic activity and nitrification in the oxygen minimum zone off peru. deep-sea research 36:1031-1051. wong, p.s. 1989. the occurrence and distribution of red tides in hong kong – applications in the red tide management. in: red tides biology, environmental science and toxicology. proceedings of the 1st international symposium on red tides, japan, 1987, s.t. okaichi, d.m. anderson, and t. nemoto (editors), 125-128. elsevier, new york, amsterdam, london. zahran, t. 1978. red tide. almawared al tabei’eiah, (june, 1978 issue), 19-20. received: november 28, 2010 accepted: september 4, 2011 agricultural and marine sciences, 12:21-34 (2007) ©2007 sultan qaboos university 21 response of buttonwood (conocarpus erectus) trees to drought conditions ansary edris moftah* and abdul-rahman ibrahim al-humaid college of agriculture and veterinary medicine qassim university, saudi arabia p.o. box, 1482 burida, k.s.a. *corresponding author. e-mail: ansary80@yahoo.com abstract: six-month-old buttonwood (conocarpus erectus l.) seedlings were grown in containers under different soil water potentials (ψsoil). the objective of the work was: 1) to determine the minimum soil water potential at which conocarpus trees can survive and grow fairly well, 2) to study the soil-plant water relationship at different irrigation regimes, and 3) to examine the capacity of conocarpus seedlings for osmotic adjustment via solute accumulation. seedling growth was not affected significantly at soil water potential above –0.1 mpa (between 40 and 30% field capacity (fc). at lowerψsoil, plant height, leaf area and shoot and root dry weights became disrupted by water deficit. water stress decreased the osmotic potential (ψπ) of leaves and roots. leaves tended to osmoregulate their cell sap through osmotic adjustment processes as their content of soluble sugars increased. the positive survival under low ψsoil could be related to increased osmotic adjustment. ψsoil values were found to be more useful than fc values to estimate water requirements and use over an extended period of time, for plants grown under different soil types and different environmental conditions. conocarpus seedlings can withstand reasonable water stress and can survive at moderately low water potential but, in contrast to other studies, this can not be classified as a high drought tolerant or resistant species. keywords: water stress, conocarpus, growth, osmotic adjustment, osmotic potential. introduction buttonwood (conocarpus erectus l.), an evergreen tree of the family combretaceae, has been found to tolerate extreme desert heat where summer temperature may reach 47 oc and to grow in soil of very low fertility (branney, 1989). this tree deserves attention because it grows fairly rapidly and can endure the unrelenting fierce tropical sun and can survive high salinity levels if it is adequately supplied with water. it provides food and cover for wildlife, protects the soil during rainstorms and helps fix dunes against migration (popp et al., 1989). it is widely الجفاف لظروف إیریكتس) (كونوكاربس الكونوكاربس أشجار استجابة إبراھیم الحمید الرحمن وعبد مفتاح أنصاري إدریس السعودیة العربیة المملكة القصیم – جامعة البیطري والطب الزراعة كلیة المائي الجھد من مختلفة درجات تحت رملیة تربة في أشھر ستة العمر من البالغة الكونوكاربس أشجار بادرات تنمیة تم الخالصة: عند والتربة البادرات بین المائیة العالقات 2-دراسة عنده، النمو للنباتات یمكن للتربة مائي محتوى 1-تقدیر أقل وذلك بغرض للتربة والمواد على تراكم السكریات ومقدرتھ االسموزي التنظیم على الكونوكاربس مقدرة 3-اختبار المائي، الجھد من مستویات مختلفة میجاباسكال 0.1 حتى للتربة الجھد المائي عند تدني معنویا یتأثر تأثیرا لم نمو البادرات أن وقد وجد التربة. جفاف یتحمل حتى الصلبة طول النبات متمثال في البادرات، نمو فأن ذلك عن المحتوى الرطوبي للتربة نقص وعندما الحقلیة)، السعة من %30-40 بین (أي مائي محتوى عند النامیة المقارنة بنباتات بالمقارنة كثیرا تأثر قد والجذري، الخضري للمجموع الجاف والوزن األوراق ومساحة لجأت النباتات إلى والجذور، كما من األوراق األسموزي لكل الجھد تناقص إلى المائي اإلجھاد أدى وقد الحقلیة. السعة من %100 ظروف تحت النمو على مقدرتھا ذادت النباتات فأن وبالتالي فیھا الذائبة السكریات تركیز بزیادة وذلك ألنسجتھا التنظیم األسموزي المحتوى على االعتماد كثیرا من أفضل للتربة الجھد المائي قیاسات استخدام على أن أیضا النتائج دلت وجفافھا. وقد ماء التربة نقص أن الدراسة فقد أوضحت األساس ھذا أشجار الكونوكاربس، وعلى لبادرات العالقات المائیة على الجفاف تأثیر دراسة عند للتربة المائي للجفاف. المقاومة األشجار من تعتبر ال محدودة ولكنھا لفترات التربة في المناسب للماء النقص یمكنھا تحمل الكونوكاربس أشجار moftah and al-humaid 22 23 response of buttonwood trees to drought conditions planted as anornamental evergreen in yards, parking lots, streets, parks, and potted plants are used to form bonsai (gliman and watson, 1993). the wood is durable and is used to make railroad ties, posts, boats, fuel and charcoal. the bark and leaves have been used in tanneries and traditional medicine (liogier, 1990). unfortunately, there is little information on the water use and requirements of buttonwood, as the case in other isolated landscape trees. most of the information on c. erectus water use in saudi arabia, as in many other arid regions, is based on recommendations for low-water-use trees set by various organizations, such as the environmental protection agency (garbesi, 1992) and reported in the literature (levitt et al., 1995, nardini et al., 2000). information on these species is usually based on experimental observations and the plant’s native habitat, which are often not precise. usually, minimum water requirements and drought survivability, rather than actual water use (levitt et al., 1995) are studied. correspondingly, buttonwood (conocarpus sp.), for example, is reported to be highly drought tolerant (gliman and watson, 1993; stevens et al., 2001), but its actual water use and requirement are not known. most methods of estimating water use of isolated trees consist of direct gravimetric measurements, such as measuring water consumption or transpiration. soil moisture readings and potential are useful tools to determine how much water is available for the crop, when to start irrigating, and how much water to apply. the objective of this study was: 1) to determine the minimum soil water potential at which c. erectus can survive and grow fairly well, 2) to find the relationship between soil water potential and plant water potential at different irrigation regimes, and 3) to compare the variations in plant osmotic potentials and osmotic adjustment of c. erectus seedlings in response to water stress. materials and methods field experiments were conducted at the research station of the college of agriculture and veterinary medicine in al-qassim, saudi arabia, between may 2 and september 15, 2003. the weather during the experiment was characterized by sunny, hot, dry days and warm nights. the average daily maximum temperature was 37.6 oc with little variation. the daily minimum temperature during the experiment ranged from 15.6 to 28.5 oc. no rain fell during the experimental period. six-month old buttonwood (conocarpus erectus l.) seedlings were transferred from nursery soil in the greenhouse to 30-l plastic containers filled with 40 kg sandy soil each. the seedlings, averaging 75 ± 4.5 cm tall with a caliper of 2.5 ± 0.3 cm at the soil line, were grown outdoors under natural conditions in a shadefree location. containers were sunk in the ground such that the surface of the potted soil was at approximately the level of the surrounding ground surface. empty containers were used as sleeves to line the holes so that the plant-holding containers could be removed and replaced easily. the tops of the containers were covered with white polyethylene film to minimize evaporation. a completely randomized design with 10 replicates for each treatment was used in this experiment. seedlings of uniform height (one seedling per pot) were located in lines with a spacing of 2 m between lines and 1 m between pots to avoid mutual shading. the ground surface between and surrounding the trees consisted of bare soil. at the time of transplanting, all trees were fertilized with the complete water-soluble fertilizer "sangral" compound fertilizer (20n-20p20k, plus micronutrients) at the rate of 600 kg ha-1. each tree received a total of 10 g fertilizer. for the first 4 weeks, all seedlings were watered to field capacity (fc), supplying an amount of water equal to transpiration losses: pots were weighed every other day, to ensure the establishment of seedlings and to allow adaptation to field conditions before water stress was imposed. by the end of this period, pots had received an amount of water equal to 100, 80, 60, 40, 20, or 10 % of fc and were then allowed to grow for 4 more weeks. fc was determined gravimetrically and found to be 12 %. each water treatment consisted of 10 seedlings. at the time of transplanting, five seedlings identical to those used in the experiment were separated to roots, stems, and leaves, then oven-dried at 70 oc until constant weight, and weighed separately. measurements soil measurements. at each water regime treatment, soil water potential was measured using tensiometers, and soil water content was measured gravimetrically using an electronic balance (mittler eb60, hightstown, nj) as described by ranney et al. (1991). moftah and al-humaid 22 23 response of buttonwood trees to drought conditions the relation between amount of soil moisture as % of fc and soil water potential was established by the pressure plate apparatus, described by shock et al. (2002) in which, saturated soil samples were set on a plate composed of a porous membrane. the membrane was placed in a pressure cooker type chamber and sealed. the soil was then subjected to a selected series of pressures. the pressure in the chamber forced the water out of the soil through the membrane. after equilibrium was established at each pressure step, a soil sample was taken from the chamber and the amount of water in the soil determined gravimetrically. plant measurements plant water relations: predawn (ψpd) and midday (ψmd) leaf water potential was determined in eight randomly chosen leaves from each irrigation regime, using a pressure chamber (pms instrument co., corvallis, or, usa) as described by scholander et al. (1965). the sampled leaves were enclosed in a polyethylene bag just before detaching them from the plant and conserved in a thermal isolated box. the measurements were made as soon as possible using a pressure increment of 0.1 mpa per 2 or 3 seconds. osmotic pressure was determined as described by ranney et al. (1991). terminal-fully-expanded and middle leaf and root samples were collected before dawn to minimize variation in solute accumulation during the light period. roots were excised at a point where the root diameter was 5 mm and included the portion of the root system distal to the excision. excised tissue was hydrated by recutting under water and holding for 2 hours, covered with plastic, in the dark, with the cut end submerged. this method was sufficient to fully rehydrate tissues, i.e., result in a water potential of 0 mpa. osmotic potential (ψπ ) was determined on expressed sap from fully hydrated tissue after freezing and thawing. osmolality of expressed sap was determined using a vapor pressure osmometer (wescor model 5100c, logan, utah). ψπ potential of the expressed sap was then calculated for 20oc, based on the van’t hoff relation as given by nobel (1999): ψπ (mpa) = 0.002437 (m3.mpa.mol-1) × osmolality (mol.m-3) turgor potential (ψp)was calculated by subtracting ψπ from ψw and osmotic adjustment was calculated as the difference in osmotic potential at full turgor between control (100 % fc) and stressed plants (blum, 1989). soluble sugar analysis: total soluble sugars were analyzed in terminal leaves, mature leaves and roots after 30 days of the onset of the irrigation treatments. soluble sugars were determined using the phenolsulfuric acid method described by dubois et al. (1956) and developed by buysse and merckx (1993). briefly, 50 mg of dry leaf powder was extracted with 80 % (v/v) ethanol three times (20 ml). the total volume of the combined and filtered extracts was adjusted to 100 ml using deionized water. one milliliter of samples was transferred into a glass tube, and 1 ml 18 % (w/v) phenol solution was then added. immediately afterwards, 5 ml of concentrated sulphuric acid were added, the solution in the tube was mixed using a vortex mixer. the tubes were allowed to stand for 20 min, and cooled to room temperature before absorbance was measured with a spectrophotometer at 490 nm (genesys, spectronic instruments, inc., rochester, ny, usa). the contribution of soluble sugars to the osmotic potential of the expressed sap was calculated based on the relative dry weight (rdw) at saturation [dry weight/ (saturated weight – dry weight)], the solute concentration, and the van’t hoff relation. transpiration: cumulative transpiration was measured gravimetrically and water use efficiency (wue) was determined by dividing total dry matter production by the cumulative amount of water used throughout the growth period. growth analysis: shoot length, leaf area per plant (measured with a leaf area meter li-cor model 3100, lincoln, ne), and dry weight of plants were recorded at harvest. the decision to harvest any particular treatment was based on the need to do so at the beginning of death symptoms and before deaths began to occur. dry weights were determined after drying at 70 oc till constant weights. leaves dropped during water-stress treatment were included. relative growth rate (rgr) was measured according to the equation: rgr = (ln w2 – ln w1)/ (t2 – t1) where ln is the natural logarithm and w and w are total dry weight (wt) at times (t) 1 and 2, respectively. the experiment was arranged in a completely randomized design and was analyzed by analysis moftah and al-humaid 24 25 response of buttonwood trees to drought conditions of variance. all data were statistically analyzed by anova according to snedecor and cochran (1980) with the aid of costat computer program for statistics. differences among treatments were tested with lsd at 5 % level of significance. results and discussion expression of soil moisture status in terms of soil water potential reveals much more than just the amount of moisture. soil water at fc is readily available to plants and sufficient air is present for root and microbial respiration. the optimum water content for plant growth and soil microbial respiration is considered to be close to fc. thus, high growth rate is expected to occur at or near fc. data in figure 1 show that at fc, sandy soil used in this experiment was found to be holding water at a tension of about –0.015 mpa. permanent wilting and symptoms of death did not appear until soil water potential reached about –1.5 mpa, below which, plants were not able to tolerate severe drought or revive after rewatering. in contrast to gliman and watson (1993), who reported that c. erectus is a highly drought tolerant tree, the present results indicate that c. erectus seedlings can withstand reasonable soil water stress (less than –1.5 mpa) and can survive at moderately low ψsoil, but can not be classified as a highly drought tolerant or drought resistant species which can survive at a lower ψsoil, as described by kramer and boyer (1995). the differences between the early and the present studies may be attributed to the differences between environmental conditions. vapor pressure deficit (vpd) between leaves and air is highly dependent on environmental parameters that might be differing in both studies. seedling growth was not affected significantly until soil water potential was lower than –0.1 mpa (between 40 and 30 % fc), after which plant height, leaf area and shoot and root dry weights became disrupted by the interruption in water status as they were severely reduced by soil water deficit (figures 2 and 3). leaf area per plant was the growth parameter most affected by low soil-water potential, causing a considerable reduction in the rate of leaf production, which, in part, accounted for the effect of drought on leaf biomass production. the reduction in leaf area per plant was about 70% at soil water potential of –0.3 mpa (20% fc) compared to that at 100% fc (-0.015 mpa). the corresponding reduction in shoot dry weight was about 40 % at the same soil water potential. figure 1. relationship between soil water content and soil water potential (mpa). soil water content (% of fc) s oi l w at er p ot en tia l ( m p a) moftah and al-humaid 24 25 response of buttonwood trees to drought conditions reduction in plant growth is one of the most conspicuous effects of water deficit on the plant and is mainly caused by inhibition of leaf expansion and stem and root elongations when water potential decreases below a threshold which differs among species (kramer and boyer, 1995). because turgor reduction is the earliest significant biophysical effect of water stress, turgor-dependent activities, such as leaf expansion and cell elongation, are the most sensitive to water deficit. this reality is based on the fact that cell expansion is a turgor-driven process and is extremely sensitive to water deficit according to the equation gr = m(ψp – γ) where gr is the growth rate, ψp is the turgor, γ is the pressure below which the cell wall resists deformation, and m is the wall extensibility. therefore, a small decrease in plant water content and turgor can substantially decrease the relative growth rate (figure figure 2. effect of soil water potential on plant height and leaf area per plant (n = 6). vertical bars indicate standard error of the mean. p la nt h ei gh t ( cm ) le af a re a (d m 2 ) soil water potential (mpa) moftah and al-humaid 26 27 response of buttonwood trees to drought conditions 4) and slow down or fully stop growth (taiz and zeiger, 2002). moreover, water deficit episodes in field conditions are frequently associated with high radiation, thus water deficit is an important limitation factor to plant growth and production in arid and semi-arid regions (delperee et al., 2003). typically, as the water content of the plant decreases by water deficit, its cells shrink. this decrease in cell volume results in lower turgor pressure and the subsequent concentration of solutes in the cell. because growth is dependent mainly on cell turgor (leuschner et al., 2001) and turgor pressure is very sensitive to water deficit, it decreases sharply with little change in plant water content. in an early study, nilsen and orcutt (1996) pointed out that the quantity and quality of soil water potential (mpa) figure 3. effect of soil water potential on shoot and root dry weights (n=6). vertical bars indicate standard error of the mean. r oo t d w t ( g) s ho ot d w t ( g) moftah and al-humaid 26 27 response of buttonwood trees to drought conditions plant growth depend on cell division, enlargement, and differentiation, and all these parameters are affected by water deficit because all of them are dependent on turgor pressure. lowering turgor potential and consequent inhibition of cell expansion as a result of water deficit conditions was reported to slow plant growth and to reduce the number of leaves as plants became shorter (taiz and zeiger, 2002). also, root mass production decreases progressively with decreasing soil water potential (figure 3). this decrease in root growth was associated with decreased root osmotic potential and, consequently, decreases turgor pressure (figure 5). it appears that osmotic adjustment in roots occurred at soil water potential lower than –0.40 mpa (figure 5). over a range in soil water potential of –0.015 (fc) to nearly –1.0 mpa, root osmotic potential fell about 0.37 mpa (35 %) whereas p fell about 0.75 mpa (60 %). the increase in root/shoot ratio with decreasing water potential indicates the more severe reduction soil water potential (mpa) figure 4. effect of soil water potential on relative growth rate (rgr) and root/shoot ratio (n=6). vertical bars indicate standard error of the mean. r g r ( m g. g1. d1 ) r oo t/s ho ot r at io moftah and al-humaid 28 29 response of buttonwood trees to drought conditions in shoot than root growth with decreasing soil water potential (figure 4). it is frequently observed that drought increases allocation to roots (kramer and boyer, 1995). it may be that aba plays a role in inhibiting shoot growth, since it has a negative effect on photosynthesis through its effects on stomatal opening, gas exchange, and pigment formation, more than its effect on root growth (hsiao and xu, 2000). finally, the reduction in leaf growth leaves more assimilates free to go to roots (leuschner et al., 2001). water stress decreased ψπ of c. erectus leaves and roots (table 1). it is clear that fully expanded upper leaves have higher ψπ than lower (older) figure 5. effect of soil water potential on root turgor potential and root osmotic potential (mpa). vertical bars indicate estandard error of the mean (n=6 roots). soil water potential (mpa) r oo t o sm ot ic p ot en tia l ( m p a) r oo t t ur go r pr es su re ( m p a) moftah and al-humaid 28 29 response of buttonwood trees to drought conditions table 1. effect of water regime on total soluble sugar concentration (mmol.kg-1 dry wt), and calculated osmotic potential (ψπ) for fully expanding upper and lower leaves and roots of conocarpus seedlings. fc = field capacity; values represent means of 3 measurements. means followed by the same letter(s) within a column are not significantly different using lsd compraisons. water regime (% fc)1 upper leaves lower leaves roots mmol sugar ψπ (mpa) mmol sugar ψπ (mpa) mmol sugar ψπ (mpa) 100 365.3 c -0.26 c 415.2 d -0.41 d 114.5 c -0.12 d 80 410.7 b -0.53 b 488.3 c -0.75 c 165.5 b -0.14 c 60 482.7 a -0.88 a 531.5 b -0.94 b 196.2 b -0.18 b 40 513.4 a -0.92 a 622.3 a -1.22 a 250.1 a -0.21 a table 2. effect of water regime on the contribution of soluble sugars to the measured osmotic potential (ψπ) of conocarpus leaves and roots. fc = field capacity; calc. = calculated, measu. = measured; values represent means of 3 measurements. means followed by the same letter(s) within a column are not significantly different using lsd comprarisons. water regime (% fc)1 upper leaves lower leaves roots measu. ψπ (mpa)2 % calc./ measu. measu. ψπ (mpa) % calc./ measu. measu. ψπ (mpa) % calc./ measu. 100 -1.24 c 21 c -1.45 c 28 c -0.44 d 27 a 80 -1.46 b 36 b -1.77 b 42 b -0.55 c 25 b 60 -1.76 a 50 a -1.94 a 48 b -0.64 b 28 a 40 -1.84 a 50 a -1.92 a 64 a -0.83 a 25 b leaves. interestingly, when stressed, all leaves tended to osmoregulate their cell sap as leaves adjusted osmotically. as soil water potential fell from –0.015 mpa (100 % fc) to –1.0 mpa (40 % fc) the upper leaves showed the greatest decrease in osmotic potential (0.60 mpa), while lower leaves typically decreased by 0.47 mpa (table 2). the roots had substantially higher ψπ than leaves, with an osmotic potential of –0.44 and –0.80 mpa at 100 and 40 % fc treated plants, respectively. the higher osmotic potential of roots than of leaves is consistent with work done on other woody species, including juglans nigra and quercus spp. (parker and pallardy, 1988), and prunus avium (ranney et al., 1991). but it should be noted that, although ψπ is typically higher in roots than leaves, the greater elasticity of root tissue can contribute to decreased water content and increased solute concentration as tissue water potential declines, resulting in similar water potential at the turgor loss point for both leaves and roots (ranney et al., 1991). total soluble sugars increased in response to water stress in leaves and roots. estimates of the contribution of total soluble sugars to the ψπ of the expressed sap of leaves and roots showed that sugars accounted for a large percentage when plants were exposed to severe drought conditions. the contribution reached about 50-60 % in leaves and about 25 % in roots (table 2). generally, the stress-induced reduction in ψπ could be accounted for by increasing levels of soluble sugars. the capacity for osmotic adjustment via solute accumulation (including soluble sugars) has been reported for many woody plants (paker and pallardy, 1988; ranney et al., 1991). higher sugars and other solute concentrations contribute to lower tissue osmotic potential, maintenance of turgor potential, and improved tolerance of low tissue water potentials (tyree et al., 2001). in early studies, ranney et al. (1991) found that osmotic potentials of expanding terminal leaves of water-stressed apple and cherry trees, respectively, moftah and al-humaid 30 31 response of buttonwood trees to drought conditions were higher than those of older leaves. other studies have found that soluble sugars and sorbitol (a sugar alcohol) are synthesized primarily in older leaves, suggesting that osmotic adjustment in expanding leaves resulted either from increased translocation of soluble sugars and sorbitol to young leaves or from a decreased rate of the metabolism of both compounds, resulting in their accumulation in young leaves under water stress conditions without being disruptive to cell organelles, enzymes, and membrane-bound processes (taiz and zeiger, 2002; wang et al., 2003). water soluble sugars have been found to be associated with osmotic adjustment in response to water stress in some plant species (wang et al., 2003). in the present study, soluble sugar content was higher under prolonged and severe drought stress conditions than under wet conditions. barathi et al. (2001) found that increases in soluble sugar content during prolonged drought stress were accompanied by decreases in starch, protein, and nucleic acids, which indicates drought injury. data in figure 6 shows that when the soil was held close to fc (-0.015 mpa) leaf water potential (ψleaf) fell from –0.05 mpa in the morning to -0.8 mpa in the middle of the day. during drying, ψleaf progressively decreased with decreasing ψsoil to reach its minimum (-0.75 mpa ) as soil became severely dry (ψsoil = -1.45 mpa). the corresponding value of midday ψleaf was –2.8 mpa. menzel et al. (1986) reported that 85% of the variation in ψleaf could be attributed to the negative response to leaf-air vapor pressure deficit (vpd). there is not likely to be much response to soil water potential or irrigation when the air is dry. wet soil alone did not prevent development of low leaf water potential of lychee trees when the air was dry (menzel et al. (1986). in this respect, scholander et al. (1965) gave a good survey of the water potential ranges of species from different habitats. they found no values below –2.5 mpa for forest trees. richter (1997) also listed the minimal water potentials from contrasting environments for woody species from temperate regions and gave a range between –1.5 and -2.5 mpa. c. erectus showed fairly low ψleaf that reached about –2.8 mpa at midday and survived at rewatering. this low ψleaf is comparable with the minima found on chaparral shrubs (-3 to –4 mpa) figure 6. effect of soil water potential on predawn (solid line) and midday (dashes line) water potential (mpa) of conocarous plants. vertical bars indicate standard error of the mean (n=6 leaves). soil water potential (mpa) le af w at er p ot en tia l ( m p a) moftah and al-humaid 30 31 response of buttonwood trees to drought conditions as reported by bowman and roberts (1985). this means that the hydraulic conductivity of the roots can be maintained even as the soil water potential fell below –1.4 mpa during drought periods. for water stress sensitive species, total blockage of sap flow might occur at potential of –1.2 mpa (kramer and boyer, 1995). therefore, only small fluctuations of field water potential are tolerable for these species to maintain vitality. so, c. erectus may be considered as a moderately drought-tolerant species. data in figure 7 show that cumulative transpiration was reduced with decreasing ψsoil, particularly under severe drought conditions. the decrease in cumulative water loss may be attributed to the decrease in transpiration rate under water deficit (kramer and boyer, 1995). it should be understood that the water potential of the trees was kept relatively high by quite sensitive stomatal control of transpiration (vogt and losch, 1999), and this may contribute to drought survival. the suppression of transpiration at severely low ψsoil may be a reason for the diminishing differences between ψsoil and the morning ψleaf (ni and pallardy, 1991). there was a tendency for increasing values of water use efficiency (wue) with a decrease in the soil water content (figure 7). it is clear that wue increased as ψsoil decreased to –0.8 mpa followed by a decline at lower water potential. these results agree well with those reported by mielke et al. (2000) on eucalyptus grandis. under moderately drought condition it seems that c. erectus can regulate stomata without prejudicing the amount of water ultimately transpired. soil water potential (mpa) figure 7. effect of soil water potential on cumulative transpiration and water use efficiency of conocarpus (n=6). vertical bars indicate standard error of the mean. w u e ( gd w t.k g h 2o ) c um m . t ra ns p. ( kg h 2o ) moftah and al-humaid 32 33 response of buttonwood trees to drought conditions it may maintain higher stomatal conductance and this probably enables high dry matter accumulation. as the soil was allowed to dry behind a critical value, both photosynthesis and conductance decreased causing a marked decrease in wue. similar relationships were also found on quercus alba (ni and pallardy, 1991) and eucalyptus trees (li, 2000). morvant et al. (1998) found that poinsetta plants acclimated to the water limitation by increasing their photosynthetic wue. they reported that with an increase in wue, the drought-treated plants were better able to utilize internal co2 for photosynthesis. li (2000) explained the influence of wue on plant growth and stated that increasing wue could theoretically either increase or decrease biomass productivity. when water is limited, plants that use a finite water supply more efficiently would grow more rapidly. in this situation, high wue would positively affect plant growth. moreover, the partial closure of stomata increases wue and restricts photosynthesis relative to plants with fully opened stomata. this strategy would result in a negative correlation between wue and plant biomass productivity (makela et al., 1996). in the present study c. erectus followed the latter strategy, as did those in a study by tuomela (1997) and li (2000), who also found that increasing wue could decrease plant dry matter production. conclusions based on the results of this experiment, the use of soil water potential values seems to be a more useful tool than fc values for estimating water requirements and use in c. erectus seedlings over an extended period of time. c. erectus was found to tolerate a moderate soil water stress over a long period of time rather than a severe stress for a short time. growing plants at ψsoil of –0.1 to –0.2 mpa had only a slight effect on the height, the leaf area, and the dry weight of c. erectus seedlings, and the effect was quickly reversed on rewatering. severe drought caused a substantial reduction in the leaf production, which in part accounts for the effect of drought on plant biomass production. root elongation decreased progressively with decreasing ψsoil and was associated with decreased ψπ and decreased turgor pressure. osmotic adjustment occurred at ψsoil of less than -0.4 mpa. decreased ψπ in roots was caused by accumulation of osmotica, particularly 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al-shidi2, najma mahmood al-zadjali2 and yousuf mohammad al-raeesy2 1pest control division, kwality agri-farm services, deluxe colony, tolichowki, hyderabad 500 008, a.p., india 2crop protection research center, rumais directorate general of agriculture, p.o. box 50, seeb 121, ministry of agriculture, sultanate of oman abstract: regular monitoring of hemipteran hopper species (including psyllids) associated with small-fruited acid lime trees (citrus aurantifolia l.) was conducted for four years using motorized insect suction to determine the possible vectors of witches’broom disease of lime (wbdl). the study was done in two phases: monitoring was done in habra village, wilayat wadi almaawal (batinah region) for one year from june 2000 to may 2001; then monitoring was done in maharah village, wilayat almusannah (batinah region), for a period of three years from may 2001 to april 2004. twelve species of cicadellid سلطنة عمان: في الحامض اللیمون أشجار على المتواجدة النطاط أنواع مراقبة ورصد الساحرة مكنسة مرض ناقالت محاولة للبحث عن الرئیسي ویوسف الزدجالي ونجمة الشیدي وراشد رازفي سید شفط آلة باستخدام العماني اللیمون أشجار في المتواجدة حشرات النطاط أنواع مختلف تعداد مراقبة الدراسة ھذه تناولت الخالصة: الحشریة المحتملة الناقالت معرفة بھدف سنوات، أربع مدى سلطنة عمان على في الباطنة بمنطقة الدراسة ھذه أجریت ولقد الحشرات. إلى مایو 2000 م من ینایر الفترة في األولى على مرحلتین: الدراسة ولقد كانت العماني. اللیمون أشجار في الساحرة مكنسة لمرض أحد في المصنعة والیة في محارة قریة في والثانیة المعاول، وادي بوالیة الحبراء لیمون مصابة بشدة في قریة أشجار على 2001م أعراض من الشتالت خالیة حیث كل 2001م، مایو من وذلك العمر من وسنتین سنة تبلغ كثیفة أشجار لیمون على المزارع الخاصة النطاط نوع تواجد نتائج الدراسة أظھرت 2004م. أبریل نھایة سنوات حتى ثالث ولمدة اإلصابة (hishimonus phycitis) بأعداد الحبراء. قریة في ،%74.8 إلى النوع جمعھ من ھذا تم ما نسبة وصلت حیث التي تم جمعھا األخرى النطاط من باقي أنواع أعلى أكتوبر شھري خالل متوسطا و 2005م، مایو إلى أبریل ومن 2000م، سبتمبر إلى یونیو من الفترة في منخفضا التعداد وكان تذبذب حالة في األعداد كانت فقد المصنعة منطقة في أما 2001م. مارس إلى 2000م دیسمبر من الفترة في نسبیا ومرتفعا ونوفمبر على العثور ولم یتم عام. كل من مارس إلى ینایر الفترة من في كان لھ وأعلى تواجد عام، كل من مارس إلى من سبتمبر الفترة خالل النطاط ثالثة أنوع وھي: كما رصدت سبتمبر. إلى أبریل الصیف من فصل خالل حشرت النطاط toya sp النطاط و circulifera haematiceps التابعة ل النطاطات من deltacephalinae و أحد التوالي على %2.4 و 3.8 و 10.4 وبلغت نسبیا، مرتفعة بأعداد النطاط وھي النطاط من أخرى أنواع تسع تواجد تسجیل تم كما السنوات األربع. خالل جمعھا التي تم الحشرات مجموع exitianus nanus (distant) والنطاط cicadulina sp النوع emposca والنطاط storeyi (china) والنوع chinai (ghauri) من distinguenda (paoli) والنطاط amrasca biguttula (ishihara) والنطاط deltocephalus (recilia) pruthii (metcalf) والنطاطneolimnus aegyptiacus (mutsumura) نطاطات وثالث cicadellids أحدھا) deltacephaninae الثاني یقارب typhloceybinae و شكلت ما حیث جدا التسعة بتعداد منخفض النطاطات تم العثور ھذه ولقد محدد). الثالث غیر و للنطاط نشاط أقصى عند حرارة درجات وأدنى أعلى تراوحت السنوات األربع. تجمیعھا خالل التي مجموع النطاطات من %5 من h. phycitis یعتبر النسبیة. الرطوبة لدرجات یذكر تأثیر یكن ھناك لم التوالي، بینما على مئویة درجة 20 – 17 و 30 – 25 بین المبیدات h. phycitis النطاط رش یقترح العماني. لذا اللیمون في مكنسة الساحرة مرض نقل في بھ الرئیسي المشتبھ الحشري الناقل تعداد من الحد للخفض أو عام كل من مارس إلى نوفمبر من الفترة العماني خالل اللیمون على أشجار بانتظام الحشریة الجھازیة ممكنة مدة ألطول المرض انتشار تأخر أو منع بھدف الناقالت الحشریة razvi and others 54 55 monitoring of hemipteran hopper species associated with acid lime plants leafhoppers and one delpahacid planthopper species were collected, while no psyllids were found. hishimonus phycitis (distant) (cicadellidae) was the most abundant hopper (78.4 % of collected individuals). next in abundance were toya sp. (delphacidae), circulifera haematiceps? and a deltocephalin leafhopper, respectively constituting 10.4, 3.8 and 2.4 % of the total catches of the four years. nine other species made up 5% of the total collection: exitianus nanus (distant), cicadulina sp. (either chinai (ghauri) or storeyi (china)), emposca distinguenda (paoli), amrasca biguttula (ishihara), deltocephalus (recilia) pruthii (metcalf), neolimnus aegyptiacus (mutsumura) and three undetermined species (one deltocephalinae, one typhlocybinae and one undeterminable to subfamily). catches of h. phycitis were highest from november to march and lowest from may to september. there was a significant linear relationship between number of h. phycitis and maximum and mininmum temperature. relative humidity was not significantly correlated to number of h. phycitis. in maharah, young lime trees were free from wbdl but the disease incidence increased with age. h. phycitis is the best candidate vector of wbdl. the potential of toya sp., circulifera haematiceps? and an undetermined deltocephalin as candidate vectors is discussed. finally, it is suggested that regular sprayings of acid lime trees with effective systemic insecticides during november to march each year can greatly reduce the vector population and can prevent or delay the spread of the disease to a great extent. introduction the small-fruited acid lime trees (citrus aurantifolia l.) locally known as “omani lime” are grown throughout the sultanate of oman. in the sultanate these trees have been suffering from a widespread and lethal disease called witches’broom disease of lime (wbdl) caused by the phytoplasma (previously referred to as mycoplasma-like organism, mlo) candidatus phytomplasma aurantifolia (bove, 1995). the name of the disease reflects its most conspicuous symptoms: dense growth of very small pale green leaves, highly proliferated shoots, and reduction in length of inter-nodes. the disease slowly spreads to all branches and then the branches start drying. later the whole plant dries and eventually dies within five years of appearance of the first symptoms of the disease. the disease appears to have been present in oman since the 1960’s. symptoms of the disease were first clearly reported in the mid seventies from albatinah region (moghal et al., 1996). the disease was officially recognized in the early eighties, and in the mid eighties it epidemically exploded (moghal et al., 1996). the disease progressed and spread very fast in the batinah region, but other regions of northern oman have not been spared from the disease. it has already destroyed lime orchards, especially in the batinah, killing thousands of infected trees (garnier et al., 1991; bove, 1995), causing big losses to farmers. the disease is also found in the the united arab emirates and has recently been reported as destroying lime trees in iran (salehi et al., 1997). the disease has also been reported from india (ghosh et al., 1999). because of the rapid spread of the disease, an insect vector was suspected (bove, 1995). it is important to determine candidate vectors of wbdl as a first step in the process of arriving at the actual vector or vectors through transmission studies. to determine potential vectors of wbdl, we conducted regular monitoring of all the hemipteran hoppers (including psyllids) that are associated with acid lime trees in the batinah. in addition, this study on the populations of hoppers associated with lime trees is expected to provide information on the peak acitivity period of the hoppers and will hopefully help in developing a suitable strategy to manage hoppers with the greatest potential to vector wbdl. materials and methods sampling monitoring of populations of hemipteran hoppers (including psyllids), as potential vectors of wbdl, was done on acid lime trees at regular intervals at two farms in the southern batinah. the study was done in two phases. phase i: monitoring hoppers associated with wbdl in a highly infected lime orchard regular insect collections were done in an acid lime orchard highly infected with wbdl at habra village (wilayat wadi almaawal, batinah region) from june 2000 to may 2001 to provide preliminary information about the hoppers associated with wbdl. in this village the source of irrigation water was the falaj (spring water carried through ducts) and crops were flood-irrigated. lime trees were more than 8 years old, closely spaced, and all were highly infected with wbdl. keywords: pytoplasma, leafhopper, vector, witches broom disease of lime, hishimonus phycitis. razvi and others 54 55 monitoring of hemipteran hopper species associated with acid lime plants insects were collected by vacuuming 20 lime trees for one hour, twice a month. the insect collection was done using a back-pack motorized insect suction sampler (univac portable, burkard scientific company, u.k.). vacuuming of insects was done up to a height of two meters on each tree, covering the outer and inner plant canopy. all the hoppers collected were sorted, based on their morphological characters and the hoppers collected were pooled on a monthly basis. all the hopper species to be identified were numbered and preserved in 75% ethanol. phase ii: monitoring hoppers associated with a lime orchard intially free of wbdl to have a more complete assessment of the insects associated with acid lime trees, 56 young (1-2 years old) and wbdl-free (results of polymerase chain reaction (pcr) were negative) omani acid lime trees from a private farm in maharah village, wilayat musannah (batinah region) were selected in the year 2001. the plants were under wellirrigation using an irrigation line fitted with bubblers. the spacing between trees was 8 x 8.5 m and the area under the plants was cleanly cultivated. the presence of all the hoppers on these lime plants was monitored using an insect suction sampler (described above) twice a month, for one hour on each visit. on each tree, sampling was done up to a height of two meters, from both the outer and inner plant canopy. monitoring was conducted for a period of three years, from may 2001 to april 2004. collected hoppers were sorted, preserved in 75% ethanol, and unidentified forms b)a) toya sp 10.4% catches d) hishimonus phycitis 78.4% catches c) deltocepalinae 2.4 % catchescirculifera haematoceps 3.8% catches figure 1 a-d. four most abundant collected hoppers. a. hishimonus phycitis. b. toya sp. c. circulifera haematoceps. d. undetermined deltocephalinae. razvi and others 56 57 monitoring of hemipteran hopper species associated with acid lime plants were numbered. abundance of collected hoppers were recorded on monthly basis. all unknown hopper species collected during the four years study were sent to the natural history museum, london, for identification. weather data and statistical analysis data on maximum and minimum temperatures and mean relative humidity were recorded daily at the meteorological observatory, agricultural experiment station, rumais, which is the nearest observatory to maharah. these data were used to calculate corresponding monthly averages of maximum and minimum temperature and relative humidity, which were in turn tested for relationships with the catches of hoppers from maharah through correlation and regression analyses. correlation and regression analyses were done separately for each of the three years using the data analysis tool of microsoft excel. results and discussion species composition and population dynamics phase i: monitoring hoppers associated with wbdl in an infected lime orchard data on hoppers collected from habra during june 2000 to may 2001 (table 1) indicate that the most abundant hopper (81.3% of all specimens) caught on most collection dates was hishimonus phycitis (distant). this species was low in numbers during june to september 2000, with moderate numbers in october and november, and then reached peak catches from december 2000 to march 2001. with the onset of summer, the population started decreasing to low levels in april and may 2001. there were two other cicadellids, namely circulifera haematoceps and an unidentified deltocephalin, both of which were caught in relatively large numbers (respectively 8.7 and 4.2 table 1. hopper species collected from witches’broom diseased small fruited acid lime trees (citrus aurantifolia) at habra, wilayat wadi almaawal, batinah region, sultanate of oman (june 2000 to may 2001). h. p. = hishimonus phycitis. *other hoppers – 1. circulifera haematoceps, 2. deltocephalinae (cicadellid), 3. banus sp, 4. exitianus nanus (distant), 5. cicadulina sp either chinai (ghauri) or storeyi (china), 6. indeterminable (cicadellid), 7. toya sp (delphacid), 8. emposca distinguenda (paoli), 9. amrasca biguttula (ishihara), 10. typhlocybiane: empoascini (cicadellid), 11. deltocephalus (recilia) pruthii (metcalf), 12. neolimnus aegytiacus (matsumura). year/ month h.p. other hopper species collected with specimen number* total 1 2 3 4 5 6 7 8 9 10 11 12 2000 june 10 2 0 0 0 0 0 0 0 0 0 0 0 12 july 7 2 12 0 1 5 2 0 0 0 0 0 1 30 aug 10 7 0 0 0 0 0 2 0 0 0 0 0 19 sept 9 3 0 0 0 0 0 0 0 0 1 0 0 13 oct 18 0 0 0 0 0 0 0 0 0 0 0 0 18 nov 13 2 0 0 0 0 0 0 0 0 0 0 0 15 dec 49 0 0 0 0 0 0 0 0 0 0 0 0 49 2001 jan 50 0 0 0 0 0 0 0 0 0 0 0 0 50 feb 38 0 0 0 0 0 0 0 0 0 0 0 0 38 mar 35 0 0 0 0 0 0 0 0 0 0 0 0 35 april 10 5 0 3 0 1 0 0 0 1 0 0 0 20 may 3 6 1 0 0 0 0 0 1 0 0 0 0 11 total 252 27 13 3 1 6 2 2 1 1 1 0 1 310 % of total 81.3 8.7 4.2 1.0 0.3 1.9 0.6 0.6 0.3 0.3 0.3 0.0 0.3 -- razvi and others 56 57 monitoring of hemipteran hopper species associated with acid lime plants % of total catches). nine more species of hoppers constituted 5.8 % of caught specimens. these were the delphacid toya sp. and eight cicadellids, namely: banus sp, exitianus nanus (distant), cicadulina sp. either chinai (ghauri) or storeyi (china), emposca distinguenda (paoli), a typhlocybin (empoascini), amrasca biguttula (ishihara), neolimnus aegytiacus (matsumura), and a species undeterminable to subfamily. these latter nine sepcies were mostly caught in the summer months. it can be hypothesied that hoppers, especially h. phycitis, managed to build up their populations and be present throughout the year because of the optimal microhabitat in the habra orchard. this is probably due to (i) close spacing of lime trees which were shaded by tall date palms, (ii) intercropping, (iii) growth habit of wbdl-affected limes and (iv) flood-irrigation. phase ii: monitoring hoppers associated with a lime orchard intially free of wbdl 2001-2002: in addition to h. phycitis, nine other hopper species were collected during may 2001-april 2002, when the lime plants were apparently healthy and young (table 2). they were the delphacid toya sp, and the cicdaellids: banus sp, exitianus nanus (distant), cicadulina sp either chinai (ghauri) or storeyi (china), emposca distinguenda (paoli), amrasca biguttula (ishihara), deltocephalus (recilia) pruthii (metcalf), neolimnus aegytiacus (matsumura), and an unidentified deltocephalin. adult h. phycitis constituted 33.6 % of the total catches. the catches of this species in general were low but relatively high in december 2001, and in january and april 2002 (table 2). on the other hand, toya sp. numbers were exceptionally high, amounting to 55.8% of the total catches. most of these (83%) were collected in march 2002. this indicates that there was a brood of toya sp. which emerged in march 2002. the total catches of the other hoppers were very low, constituting together only 10.6% of total catches. 2002-2003: in the year may 2002 to april 2003, when the plants were 2-3 years old, the total catches of h. phycitis increased to 124 (table 3) from 38 in the previous annual period. there were no catches of h. phycitis in may to september 2002. the catches were very low during october and november 2002 and april 2003. most of the catches of this species ocurred during december 2002 to march 2003. the results obtained during this year indicated that, table 2. hopper species collected from initially healthy small fruited acid lime (citrus aurantifolia) plant at maharah, wilayat almusannah, batinah region, sultanate of oman (may 2001 to april 2002). h. p. = hishimonus phycitis. *for names of hopper species see table 1 caption. year/ month h. p. other hopper species collected with specimen number* total a n 1 2 3 4 5 6 7 8 9 10 11 12 2001 may 0 0 0 0 0 0 0 0 7 1 0 0 0 0 8 june 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 july 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 aug 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 sept 1 0 0 1 0 1 0 0 0 0 0 0 0 0 3 oct 2 0 0 0 0 0 0 0 0 0 0 0 0 0 2 nov 5 0 0 0 0 0 0 0 0 0 0 0 0 0 5 dec 6 0 0 0 0 0 0 0 0 0 2 0 0 0 8 2002 jan 7 0 0 0 0 0 1 0 3 0 1 0 1 0 13 feb 3 0 0 0 0 0 0 0 0 0 0 0 0 0 3 mar 5 0 0 0 0 0 1 0 52 0 0 0 0 0 58 apr 9 0 0 1 1 0 0 0 1 0 0 0 0 0 12 total 38 0 0 2 1 1 2 0 63 1 3 0 1 1 113 % of total 33.6 0.0 0.0 1.8 0.9 0.9 1.8 0.0 55.8 0.9 2.7 0.0 0.9 0.9 -- razvi and others 58 59 monitoring of hemipteran hopper species associated with acid lime plants table 3. hopper species collected from initially healthy small fruited acid lime plant (citrus aurantifolia) at maharah, wilayat almusannah, batinah region, sultanate of oman (may 2002 to april 2003). h. p. = hishimonus phycitis. *for names of hopper species see table 1 caption. year/ month h. p. other hopper species collected with specimen number* total a n 1 2 3 4 5 6 7 8 9 10 11 12 2002 may 0 0 0 0 0 1 0 0 0 0 0 0 0 0 1 june 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 july 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 aug 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 sept 0 0 0 0 0 0 0 0 0 2 0 0 0 0 2 oct 1 0 0 0 0 0 0 0 0 1 0 0 0 0 2 nov 5 0 0 0 0 0 0 0 0 2 0 0 0 0 7 dec 37 7 0 0 0 0 0 0 0 0 0 0 0 0 44 2003 jan 30 4 0 1 0 0 0 0 0 1 0 0 0 0 36 feb 21 1 0 0 0 0 0 0 1 0 0 0 0 0 23 march 12 0 0 0 1 0 0 0 1 2 0 0 0 0 16 april 6 0 0 0 0 0 0 0 0 0 0 0 0 0 6 total 112 12 0 1 1 1 1 0 2 8 0 0 0 0 138 % of total 81.2 8.7 0.0 0.7 0.7 0.7 0.7 0.0 1.4 5.8 0.0 0.0 0.0 0.0 --in addition to h. phycitis, six other hoper species were found on lime trees. they were the delphacid toya sp., the cicdaellids: banus sp, exitianus nanus (distant), cicadulina sp either chinai (ghauri) or storeyi (china), and emposca distinguenda (paoli) and an unidentified deltocephalin. h. phycitis was consistently seen in large number (adults and nymphs constituted 89.9% of total catches). these six other hopper species together constituted 10.1 %. among the other hoppers, emposca distinguenda was the most abundant, constituting 57% of all other hoppers caught (table 3). 2003-2004: during the period extending from may 2003 to april 2004, the trend with regard to the catches of h. phycitis remained the same. total numbers of this species increased to 178, which amounted to 93.5 % (adults and nymphs) of the total catches (table 4). the other four hopper species caught were the delphacid toya sp. and the cicadellids: emposca distinguanda, cicadulina sp., and an unidentified deltocephalin. among these other hoppers, the most abundant (3.9 % of total catches) was toya sp., which was caught only during january to march 2004. general patterns composition of hopper species pooled data of hopper species on acid limes for the four year study is presented in table 5 for comparison. no psyllids were caught during the four years. the total catch of h. phycitis was very high (581 specimens), representing 78.4 % of the total catches. twelve other hopper species were collected during the four years study. among these, three hopper species were caught in relatively large numbers: toya sp (74 specimens), followed by circulifera haematiceps (27 specimens) and undetermined deltocephalin (17 specimens) (table 5). fig.1 a-d shows the latter four most abundant hoppers. other less abundant leafhopper species were: emposca distinguenda (paoli), cicadulina sp (either chinai (ghauri) or storeyi (china)), banus sp., amrasca biguttula (ishihara), exitianus nanus (distant), neolimnus aegyptiacus (mutsumura), undetermined (cicadellid), deltocephalus (recilia) pruthii (metcalf), and undetermined typhloceybin. these latter nine species were extremely low in numbers, over a period of four years, suggesting that razvi and others 58 59 monitoring of hemipteran hopper species associated with acid lime plants they cannot be the vectors of wbdl, given the rapid rate of disease spread. possible vectors of wbdl since h. phycitis was collected in large numbers and was present on most of the collection dates, it appears that it may be the most likely vector of wbdl, as also suggested by bove et al. (1988) and koizumi (1995). furthermore, this insect was also reported as a vector of phytoplasma disease on other crops. in plants such as periwinkle (catharanthus roseus) it transmits periwinkle little leaf disease (kar and panda, 1990). in india it is known to transmit a phytoplasma disease called little leaf disease of eggplant (srinivisan and chelliah, 1978). interestingly, h. phycitis has long been known in india, and acid lime is known as one of the hosts plants on which this leafhopper is able to live and multiply (bindra and singh, 1969). thus h. phycitis is the number one candidate, but the presence of three more hopper species (toya sp, circulifera haematiceps and an undetermined deltocephalin) in significant numbers means that these species should be considered as candidates vectors no. 2, 3 and 4 for wbdl. since h. phycitis is considered as the number one candidate vector, we will focus on its population dynamics and the weather conditions during its peak population period. population dynamics of h. phycitis and effects of temperature and relative humidity the population fluctuations of h. phycitis during the four year study are depicted in fig. 2. it clearly shows that population fluctuations followed similar trends during the four years. the peak activity period was between november and march, while the population decreased to low levels between april and september. h. phycitis catches and the maximum and minimum temperatures during each of three year annual periods in maharah are plotted together in each of figs.3 a-c, which indicate that the maximum and minimum temperatures during the peak activity periods of h. phycitis ranged from 25 to 30 o c and from 17 to 20 o c, respectively. in order to determine whether there was an association between temperature and relative humidity on the one hand and h. phycitis numbers on the other hand, the monthly catches of h. phycitis during the three year study at maharah were correlated with monthly table 4. hopper species collected from initially healthy small fruited acid lime plant (citrus aurantifolia) at maharah, wilayat almusannah, batinah region, sultanate of oman (may 2003 to april 2004). h. p. = hishimonus phycitis. *for names of hopper species see table 1 caption. year/ month h. p. other hopper species collected with specimen number* total a n 1 2 3 4 5 6 7 8 9 10 11 12 2003 may 1 0 0 0 0 0 0 0 0 1 0 0 0 0 2 june 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 july 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 aug 1 0 0 1 0 0 0 0 0 0 0 0 0 0 2 sept 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 oct 1 0 0 0 0 0 1 0 0 1 0 0 0 0 3 nov 2 0 0 0 0 0 0 0 0 0 0 0 0 0 2 dec 16 3 0 0 0 0 0 0 0 0 0 0 0 0 19 2004 jan 30 11 0 0 0 0 0 0 1 0 0 0 0 0 42 feb 38 3 0 0 0 0 0 0 4 0 0 0 0 0 45 march 30 3 0 0 0 0 0 0 2 0 0 0 0 0 35 apr 27 1 0 0 0 0 0 0 0 0 0 0 0 0 28 total 146 21 0 1 0 0 1 0 7 2 0 0 0 0 178 % of total 81.7 11.8 0.0 0.6 0.0 0.0 0.6 0.0 3.9 1.1 0.0 0.0 0.0 0.0 --razvi and others 60 61 monitoring of hemipteran hopper species associated with acid lime plants ta bl e 5. h op pe r sp ec ie s co lle ct ed f ro m h ab ra ( w ila ya t w ad i a lm aa w al , b at in ah ) a nd f ro m m ah ar ah ( w ila ya t a lm us an na h, b at in ah ). * o th er h op pe r sp ec ie s : 1 . c ir cu lif er a ha em at oc ep s, 2 . d el to ce ph al in e (c ic ad el lid ), 3 . b an us s p, 4 . e xi tia nu s na nu s (d is ta nt ), 5 . c ic ad ul in a sp e ith er c hi na i ( g ha ur i) o r st or ey i ( c hi na ), 6. in de te rm in ab le (c ic ad el lid ), 7. t oy a (d el ph ac id ), 8. e m po sc a di st in gu en da , (p ao li) , 9 . a m ra sc a bi gu ttu la (i sh ih ar a) , 1 0. t yp hl oc yb ia ne : e m po as ci ni ( c ic ad el lid ), 11 . d el to ce ph al us (r ec ili a) p ru th ii (m et ca lf ), 12 . n eo lim nu s ae gy tia cu s (m at su m ur a) . l oc at io n an d pe ri od pl an t ag e (y ea rs ) pl an t co nd iti on s h . ph yc iti s o th er h op pe r s pe ci es c ol le ct ed w ith s pe ci m en n um be r* to ta l 1 2 3 4 5 6 7 8 9 10 11 12 h ab ra ju ne 2 00 0 to m ay 20 01 >8 a ll pl an ts in fe ct ed w ith w b d l 25 2 27 13 3 1 6 2 2 1 1 1 0 1 31 0 m ah ar ah m ay 2 00 1 to a pr il 20 02 23 6 ou t o f 5 6 pl an ts in fe ct ed w ith w b d l 38 0 2 1 1 2 0 63 1 3 0 1 1 11 3 m ah ar ah 20 02 to a pr il 20 03 34 11 o ut o f 56 p la nt s in fe ct ed w ith w b d l 12 4 0 1 1 1 1 0 2 8 0 0 0 0 13 8 m ah ar ah 20 03 to a pr il 20 04 45 14 o ut o f 56 p la nt s in fe ct ed w ith w b d l 16 7 0 1 0 0 1 0 7 2 0 0 0 0 17 8 to ta l 58 1 27 17 5 3 10 2 74 12 4 1 1 2 73 9 % o f t ot al 78 .4 3. 8 2. 4 0. 7 0. 4 1. 4 0. 3 10 .4 1. 7 0. 6 0. 1 0. 1 0. 3 -- razvi and others 60 61 monitoring of hemipteran hopper species associated with acid lime plants average maximum and minimum temperatures and with relative humidities. it is evident that a significant negative correlation existed between the catches of h. phycitis and maximum and minimum temperatures. the ‘r’ values for the regression of catches against maximum and minimum temperatures during the year 2001-2002 were -0.64 and -0.70 (p<0.05), respectively (table 6). the ‘r’ values for the regression of catches against maximum and minimum temperatures during the year 2002–2003 and 2003-2004 were -0.82 and 0.82 (p<0.01), and –0.68 (p<0.05) and –0.76 (p<0.01), respectively (table 6). the ‘r’ values for maximum and minimum temperatures of the three years pooled data were –0.62 and -0.66 (p<0.05), respectively. relative humidity did not show any significant correlation with numbers of h. phycitis (table 6). linear regression analysis was conducted to predict population numbers of h. phycitis from mean maximum and minimum temperatures based on pooled data from the three years of monitoring in maharah. the linear equations and regression lines are presented in figure 4. relationships between h. phycitis population and the age and disease condition of lime trees in maharah total catches of h. phycitis were low in numbers (38 ) when the plants were young (2-3 years old) and increased with age. the number of specimens caught was 124 when the plants were 3-4 years old, and increased to 167 when the plants attained the age of 4-5 years. the h. phycitis total annual catch recorded in habra (252) was relatively higher than the other 3 annual catches recorded from maharah. the habra orchard had infected plants eight years and older in age. direct comparisons cannot be made between habra and maharah. however, due to the close proximity of the two locations, the data from habra provides some support to the idea that the population of h. phycitis in maharah could have increased with n o. o f h . p hy ci tis c ol le ct ed figure 2. population fluctuations of h. phycitis on small fruited acid lime plants (june 2000 to april 2004). month razvi and others 62 63 monitoring of hemipteran hopper species associated with acid lime plants figure 3a-c. effect of temperature on the population fluctuations of h. phycitis on lime trees in maharah (al musanah wilayat) from may 2001 to april 2004. a) b) c) te m pe ra tu re o c te m pe ra tu re o c te m pe ra tu re o c n o. o f h . p hy ci tis c au gh t n o. o f h . p hy ci tis c au gh t n o. o f h . p hy ci tis c au gh t month month month razvi and others 62 63 monitoring of hemipteran hopper species associated with acid lime plants figure 4 a-b. relationship between the catches of h. phycitis and maximum and minimum temperatures in maharah (al musanah wilayat) from may 2001 to april 2004. a) relationshp with maximum temperature. b) relationship with minimum temperature. a) n o. o f h . p hy ci tis c au gh t maximum temperature oc b) n o. o f h . p hy ci tis c au gh t minimum temperature oc razvi and others 64 65 monitoring of hemipteran hopper species associated with acid lime plants table 7. appearance of witches’broom disease of lime (wbdl) in small fruited acid lime plants (citrus aurantifolia) on which hopper species were monitored (at maharah during 2001 – 2004). plant age (yrs) no. of plants showing symptoms of wbdl in the month of total no. of pants with wbdl symptoms cumulative total of wbdl infected plants % plants showing wbdl symptoms j a n f e b m a r a p r m a y j u n j u l a u g s e p o c t n o v d e c 2 all plants were free from symptoms of wbdl 0 0 0.0 3 0 0 0 0 3 0 3 0 0 0 0 0 6 6 10.71 4 0 0 0 0 0 2 2 1 0 0 0 0 5 11 19.64 5 0 0 0 0 0 0 2 1 0 0 0 0 3 14 25.00 total 0 0 0 0 3 2 7 2 0 0 0 0 table 6. correlations between catches of hishominus phycitis and weather factors at maharah (may 2001 to april 2004). *significant at α=0.05. ** significant at α=0.01. ns = not significant. year mean catches ±sd temperature o c mean relative humidity %maximum minimum mean ±sd correlation coefficient r mean ±sd correlation coefficient r mean ±sd correlation coefficient r 2001-02 3.2 ± 3.2 33.2 ± 5.3 -0.64* 23.1 ± 5.1 -0.70* 55.4 ± 8.0 -0.13 ns 2002-03 10.3 ± 15.1 33.1 ± 5.3 -0.82** 23.4 ± 5.4 -0.82** 60.8 ± 11.1 0.10 ns 2003-04 13.9 ± 17.3 32.8 ± 4.9 -0.68* 22.9 ± 5.1 -0.76** 56.4 ± 9.9 -0.11 ns pooled analysis 9.1 ± 13.7 33.1 ± 5.0 -0.62* 23.1 ± 5.0 -0.66* 57.5 ± 9.8 0.03 ns the increase in age of lime trees, possibly due to the increase of plant canopy with age. this could have provided more congenial micro-climatic conditions for the h. phycitis to build up its population. the catches of h. phycitis were very high in plants infected with wbdl in habra (table 1). it appears that this leafhopper species has a preference to feed, thrive and multiply on diseased branches. the exact reason is not known. however, the diseased branches have soft tissues, smaller leaves, and reduced internodes. this could make microenvironmental conditions more congenial for the hopper to build up its population. another explanation for the preference of h. phycitis for diseased parts of lime trees is the altered physiology of diseased host tissues, as suggested by srinivasan and chelliah (1979) and raghuraman (1968). srinivasan and chelliah (1979), while studying the biology of h. phycitis, found a significant difference in incubation period, nymphal period and adult longevity between healthy and little-leaf diseased eggplants. according to these authors the adult longevity of h. phycitis was significantly longer on diseased plants (23 days) than on healthy plants (9 days). a similar finding was made by murral et al. (1996) who reported that the aster leafhopper macrosteles quadrilineatus lived longer on aster yellow phytoplasma-diseased plants than on healthy plants. progress of wbdl in maharah all 56 plants at maharah in 2001 (start of the study) were free from wbdl. six plants started showing razvi and others 64 65 monitoring of hemipteran hopper species associated with acid lime plants symptoms of wbdl at the age of three years. as time passed more plants started showing symptoms and by 2004, 14 plants (25% of all plants) showed symptoms of wbdl (table 7). it is also interesting to note that new records of symptomatic trees were made during the hotter months (may to august) in each of three years of monitoring in maharah (table 7). practical implications of the study because h. phycitis is the predominant hopper (table 5) and was present on most collection dates (fig. 2), it is the top potential vector. it is also clear from figure 2 that during the entire four years study, the population of h. phycitis was mostly observed during november– march. it is suggested that regular applications of effective systemic insecticides during this peak population period could control the population of the vector and consequently may check the spread of wbdl. references bindra, o.s. and b. singh. 1969. biology and bionomics of hishimonus phycitis distant), a jassid vector of “little-leaf” disease of brinjal (solanum melongena l.) indian journal of agricultural science 39:912-919. bove, j.m. 1995. virus and virus like diseases of citrus in the near east region, oman (chapter 16), p. 217-238. food agriculture organisation of united states, rome pp 518. bove j.m., m. garnier, a.m. mjeni and a. kharyallah. 1988. witches’broom disease of lime trees in oman: first mlo disease of citrus. in: proceeding 10th conference. iocv, p 307– 309, riverside, university of california. garnier m., l. zreik and j.m. bove. 1991. witches’ broom a lethal disease of lime trees in the sultanate of oman and the united arab emirates. plant disease 75:546 –551. ghosh, d.k., a.k. das, shayam singh, s.j. singh, y.s. ahlawat, and s. singh. 1999. occurrence of witches’broom, a new phytoplasma disease of acid lime (citrus aurantiifolia) in india. plant disease 83:302. kar, r.k. and r.k. panda. 1990. transmission of periwinkle little leaf disease. indian journal of mycology and plant pathology 20:188 –189. koizumi, m. 1995. virus or virus like diseases of citrus in tropical and sub tropical zones. in: first international symposium in fruit production in the tropics and sub-tropics, kyoto, japan, 22 – 23 august 1994. trukuba, japan. japan international research center for agricultural sciences. international symposium series (1995) no. 3, 61–66. moghal, s.m., a.d. al-zadjali and a. al-matrooshi. 1996. studies on witches’broom disease of lime. annual report 1996 of agricultural research center, rumais, ministry of agriculture and fisheries. murral, d.j., l.r. nault, c.w. hoy, l.v. madden and s.a. miller. 1996. effects of temperature and vector age on transmission of two ohio strains of aster yellows phytoplasma by the aster leafhopper (homoptera: cicadellidae). journal of economic entomology 89:1223-1232. raghuraman, t.v. 1968. preference of the aleyrodid bemisia tabaci genn., for bhendi plants infected with yellow vein mosaic virus with particular reference to the biochemical mechanism. unpublished m.sc. (ag.) thesis, university of madras, india. salehi, m., k. izadpanah and h. rahimian. 1997. witches’broom disease of lime in sistan, baluchistan. iranian journal of plant pathology 33:3-4, 76. srinivasan, k. and s. chelliah. 1978. influence of time of planting and weather factors on brinjal eggplant little leaf incidence and its vector hishimonus phycitis (distant). south indian horticulture 26:79-80. srinivasan, k. and s. chelliah. 1979. studies on the biology of hishimonus phycitis, vector on healthy and little leaf diseased brinjal (solanum melongena l.) eggplants. madras agricultural journal coimbatore 66:395-400. received: december 2005 accepted: may 2006 editorial journal of agricultural and marine sciences vol. 20 (2015): 7 accepted 19 feb. 2015 marine biotechnology: emerging opportunities and future perspectives symposium held at sultan qaboos university, november 12-13th 2013. stephen goddard stephen goddard ( ) sultan qaboos university, center of excellence in marine biotechnology, box 50, al-khod 123. sultanate of oman. email: sgoddard@squ.edu.om the rapid growth of genetic, cellular and molecu-lar technologies is enabling scientists to explore and develop marine resources for widespread applications in the food, medical, pharmaceutical, environmental and energy industries. marine biotechnology products and services were estimated at 2.8 billion euros in 2010, with a cumulative annual growth rate of 4-5% (marine board-european science foundation, 2010) the sultanate of oman occupies a strategic geographical position and has a coastline in excess of 3000km, with the arabian sea located to the south and the sea of oman and arabian gulf to the north. these oceans have rich biodiversity and potential resources which we are only beginning to explore. based on its marine resources, coupled with a rapidly-growing educational and research infrastructure, the sultanate of oman is well positioned to take advantage of the commercial opportunities presented by marine biotechnology. in recognition of potential development an international symposium was organized by the center of excellence in marine biotechnology, sultan qaboos university. one hundred and forty eight delegates attended the meeting, representing 15 countries. in planning the symposium three major themes were identified viz. marine biofouling and its prevention, fisheries and aquaculture biotechnology and marine biodiversity and natural products. the topics were selected on the basis of current and planned research activity in oman and elsewhere in the gcc region. three keynote addresses were presented, 23 oral presentations made and a poster exhibition held. a final session reviewed national and regional issues and the delegates agreed formally on a number of future actions. full details of the symposium and the results and analysis of a post-symposium survey on the future development of marine biotechnology are given in goddard et al. (2015). the symposium was supported logistically and financially by sultan qaboos university, the research council, and the ministry of agriculture and fisheries wealth, oman. references goddard, s., m. delghandi, s. dobretsov, h. al-oufi, s. al-habsi, and j.g. burgess 2015. the first gcc marine biotechnology symposium: emerging opportunities and future perspectives. marine biotechnology 17: 285-289. marine board-european science foundation, 2010. marine biotechnology: a new vision and strategy for europe. position paper 15. التكنولوجيا احليوية البحرية: الفرص الناشئة واآلفاق املستقبلية ستيفن جودارد agricultural and marine sciences, 13:33-42 (2008) ©2008 sultan qaboos university 33 *corresponding author. e-mail: aa.marine@gmail.com reproductive season of the scalloped spiny lobster panulirus homarus along the coast of oman: management implications abstract: the spiny lobster panulirus homarus is widely distributed in the indo-west pacific. along the coast of oman it supports an artisanal fishery using traps and tangle nets. the egg-bearing incidence of females caught between 1989 and 2006 were analysed relative to month, lobster size and location of capture. the smallest female with external eggs had a carapace length (cl) of 54.6 mm, but only 9–18% of females of 60–69 mm cl carried eggs. this percentage increased significantly above 70 mm cl, and on average, 63% of individuals >90 mm carried eggs. egg-bearing increased seasonally at the onset of the sw monsoon in may and june, when wind-driven upwelling reduces inshore water temperatures and increases primary productivity. the reproductive season extended over a 9-month period up to january, with a pause in february to april. no geographical gradient in egg-bearing seasonality was observed. the prolonged breeding season with multiple broods in large females conforms with the typical pattern of tropical palinurids. the 2-month open fishing season (15th october to 15th december) falls within the breeding season, and may be more optimally placed in february to april. اإلدارة عمان: تبعات سلطنة في الساحل طول على الصخور لشارخة التكاثر موسم الحوسني وأحمد النھدي، عبداهللا جرونفلید، جوھان المرزوقي، عبدالعزیز وتتواجد الشارخة الھادي، المحیط وغرب الھندي في منطقة المحیط (panulirus homarus) الصخور شارخة الخالصة: تتوزع الحاملة اإلناث من عینات تحلیل تم الشربكة. وشباك باألقفاص صید الشارخة .ویتم سلطنة عمان بحر العرب في ساحل طول على للبیض أنثى حاملة أصغر وجد أن وقد اصطیادھا. وحجم الشارخة وأماكن للشھر بالنسبة و ٢٠٠٦م ١٩٨٩ بین أعوام ما للبیض بیضًا. تحمل مم ٦٩ إلى ٦ درعھا بین التي تتراوح طول اإلناث من فقط ٪ ١٨ إلى ٩ نسبة أن مم، ووجد درعھا ٥٤,٦ طول یبلغ درعھا طول یفوق التي العینات من ٪٦٣ فإن المتوسط وفي مم ٧٠ من أكثر درعھا طول التي لإلناث معنویًا النسبة ھذه وارتفعت عندما تؤثر ویونیو في مایو الغربیة الموسمیة الجنوبیة الریاح موسم بدخول الحاملة للبیض اإلناث أعدد وتزداد حملت بیضا. مم ٩٠ الضحلة. ویمتد في المیاه األولیة المنتجات عدد وتزداد المیاه حرارة درجة تقل حیث المائیة االنبثاقات ظاھرة محدثة البحر في الریاح ظھور لموسم توزع جغرافي أي مالحظة كما لم یتم . أبریل إلى فبرایر بین ما ویتوقف في الفترة أشھر لتسعة موسم تكاثر الشارخة صید موسم ویقع الشارخة. االستوائي لعائلة النموذج محدثًة الشارخة لكبار حاضنات بعدة التناسل موسم ویمتد البیض. حاملة اإلناث شھري بین ما الفترة في الصید مواسم یحدد أن األنسب یكون وربما التكاثر ضمن فترة دیسمبر) ١٥ (١٥ أكتوبرالحالي الشارخة وأبریل. فبرایر keywords: panulirus homarus, reproductive season, oman 1 marine science and fisheries centre, p.o. box 227 pc 100, muscat, sultanate of oman 2 ministry of fisheries wealth, p.o. box 427 pc 100, muscat, sultanate of oman abdulaziz al-marzouqi*1, johan c. groeneveld1, abdullah al-nahdi1 and ahmed al-hosni2 al-marzouqi and others 34 35 reproductive season of the scalloped spiny lobster along the coast of oman introduction the scalloped spiny lobster panulirus homarus is widely distributed in the tropical and subtropical waters of the indo-west pacific, where it occurs in coastal waters (1–90 m depth) from eastern south africa to somalia (including madagascar), along the arabian peninsula, and from india and indonesia to japan and australia (holthuis, 1991). along the arabian peninsula, it occurs in the gulf of aden, and extends into the arabian sea along the coasts of yemen and oman, up to ras al hadd (approx. 22° n), but is uncommon in the gulf of oman and absent from the arabian gulf (al-abdessalaam, 1995). panulirus homarus inhabits coral and rocky areas, where it may co-occur with other tropical and subtropical spiny lobster species, i.e. p. ornatus, p. versicolor, p. longipes and p. penicillatus (holthuis, 1991). the nearshore distribution of p. homarus along the coast of oman makes it easily accessible to traditional (artisanal) fishers using traps and tangle nets from small (4–11 m length) motorized fibreglass boats. at least 3000 boats land lobster periodically along the arabian sea coastline south of ras al hadd (a distance of approximately 1100 km), although these boats also target other fish and cephalopod species (anon., 2006). reported lobster landings from oman have declined from over 2000 t/yr in the 1980’s to between 200 and 500 t/yr (2000–2006) although these statistics almost certainly underestimate the actual catch. the declines in lobster catches reflect a general trend in the northwestern indian ocean region, and have been attributed to destructive fishing methods and overfishing (siddeek, 1999; radhakrishnan et al., 2005; al-marzouqi et al., 2007). most of the catches from oman are exported to dubai (united arab emirates) and other international markets to earn foreign exchange of approximately $us 3–5 million per year. the present lobster management regulations include a 2-month open fishing season extending from 15th october to 15th december, a minimum legal size (mls) of 80 mm carapace length, a ban on marketing egg-bearing females and a restriction of gear to governmentapproved traps, however these regulations are not strictly enforced (mohan, 1997; al-marzouqi et al., 2007). female p. homarus in the waters of oman reach sexual maturity at a size of ~65 mm carapace length approximately 2 years after settling as pueruli on the seabed, and can attain a maximum size of 120–125 mm after 8–10 years (al-marzouqi et al., 2007). the species breed repetitively during the year; four broods/year were observed off eastern south africa (berry, 1971) and captive specimens in india produced four broods on average, with a maximum of seven (vijayakumaran et al., 2005). the frequency of eggbearing and brood size increases steeply with lobster size, and large females are highly fecund (~2 million eggs/year; vijayakumaran et al., 2005). female p. homarus may carry eggs throughout the year (vijayakumaran et al., 2005), although berry (1971) showed a peak in breeding activity over the austral spring and summer in south-africa. johnson and al-abdulsalaam (1991) found that egg-bearing females in oman occurred in all months of the year for which they had data (september–february), but noted that there were distinct peaks which varied among regions. the aim of this study was to define the breeding season of p. homarus in oman based on the monthly proportions of egg-bearing females in samples collected between 1989 and 2006. the key questions asked were whether a seasonal breeding peak could be shown, and what the influence of lobster size and geographic location had on the egg-bearing proportions. the results of this study provide fisheries managers with information on which to base the timing and duration of the open fishing season. materials and methods lobsters landed by commercial fishers at landing sites between ras al hadd and dalkut (fig. 1) were sampled during the annual 2-month open fishing seasons between 1989 and 2006, and additional catches made outside of these months were sampled whenever available. data were treated separately for the 19892002 (historical) and 2003-2006 (recent) periods, because the open fishing season was moved from december/january to mid-october/mid-december in 2003. the carapace length (cl ± 0.1 mm) of female lobsters was measured mid-dorsally from the transverse ridge between the frontal spines and posterior carapace edge, and the presence / absence of external eggs on the abdomen recorded. eggs were staged visually as follows (see berry, 1971): stage 1 – freshly extruded eggs, round and bright orange with no embryonic development visible macroscopically; stage 2 – early embryonic development with egg colour becoming deep orange to brownish, eyespots faintly visible; stage 3 – well-formed embryo, eggs slightly oval and brown due to growth of embryo and al-marzouqi and others 34 35 reproductive season of the scalloped spiny lobster along the coast of oman reduction of orange yolk, eyespots conspicuous; stage 4 – eggs hatched with ovigerous setae a mass of eggstalks and empty capsules. these are detached by the female within a few days. the proportions of females carrying eggs, relative to all females caught within the length classes <60 mm, 60–69 mm, 70–79 mm, 80–89 mm and >90 mm cl, were calculated for each year, month and area. comparisons between length classes were done using a contingency table analysis for binomial distributions (χ2-tests; zar, 1984). females were grouped into month×size categories to assess seasonal egg-bearing trends. for the spatial analysis, data were available from landing sites in dhofar (dalkut, mughsayl, mirbat, sadah, shuwaimiya and hadbin), and in al-wusta (laqbi, hitam, ras madrakah and masira) (fig. 1). only data collected during the peak egg-bearing season were used (december only for 1989–2002; october–december for 2003–2006), grouped into year×month×site×size categories and compared using similar χ2-tests than shown above.. results the size of female lobsters sampled ranged from 35.0–124.1 mm (mean cl=75.4 ± 11.8 [sd] mm, n = 20 336) (table 1), and the smallest individual carrying eggs was 54.6 mm. less than 1% of females <60 mm cl carried eggs, and in the 60–69 mm length-class egg-bearing remained low at 9–18% (fig. 2). the majority of females in these length classes may still be immature (see also al-marzouqi et al., 2007), and all females <70 mm cl were therefore excluded from further analyses. the proportions of females carrying eggs increased significantly with increasing lobster size above 70 mm cl (χ2-tests, p<0.05; fig. 2). egg-bearing proportions were also significantly higher in samples collected figure 1. the sultanate of oman, showing the sampling sites along the arabian seas coastline. al-marzouqi and others 36 37 reproductive season of the scalloped spiny lobster along the coast of oman between 2003 and 2006 than in those collected between 1989 and 2002 in equivalent length classes (χ2-tests, p<0.05; fig. 2), perhaps reflecting the shift in the open fishing season (and therefore in the sampling schedule) after 2002. no monthly samples were available for july to september in any year, because no fishing takes place during these months of adverse sea conditions (fig. 3). the raw data (proportions in month×size combinations) showed relatively lower values in february to april table 1. the total number of female lobsters sampled per year (n), cl range and average cl (±s.d.) and the total number of egg-bearing females recorded. percentage egg-bearing is shown in parenthesis. year sample size (n) min cl (mm) max cl (mm) avgcl (mm) sd (mm) egg-bearing (n) (%) 1989 742 39.9 115.0 80.1 12.4 114 15.4 1991 460 36.7 104.1 76.6 12.0 55 12.0 1992 1131 46.5 109.8 76.8 10.5 204 18.0 1993 1366 41.0 115.0 78.2 11.0 414 30.3 1994 1465 36.9 115.8 79.4 12.0 605 41.3 1995 1135 46.2 116.1 78.7 11.4 511 45.0 1996 920 43.1 111.4 78.0 10.9 300 32.6 1997 609 46.4 111.8 78.0 11.4 206 33.8 1998 333 42.0 107.0 74.4 11.3 124 37.2 1999 797 44.2 119.0 78.9 11.0 275 34.5 2000 470 40.2 110.7 75.4 14.9 160 34.0 2001 709 41.3 119.1 78.8 12.8 226 31.9 2002 128 39.6 98.5 68.0 11.9 33 25.8 2003 900 50.2 116.6 75.8 8.2 373 41.4 2004 3185 35.2 124.1 74.5 13.3 1242 39.0 2005 4290 35.0 116.1 70.9 10.6 1308 30.5 2006 1696 40.6 118.0 77.3 9.2 617 36.4 figure 2. al-marzouqi and others 36 37 reproductive season of the scalloped spiny lobster along the coast of oman figure 3. p ro po rt io n w ith e gg s p ro po rt io n w ith e gg s p ro po rt io n w ith e gg s al-marzouqi and others 38 39 reproductive season of the scalloped spiny lobster along the coast of oman table 2. results of chi-square tests for the null hypothesis that egg-bearing proportions are the same for all sites within each year of sampling. n1 and n2 are the numbers of sites compared, * indicates p<0.05, and pooled values are shown. year n1 χ2 pooled eggbearing prop. sites eliminated n2 χ2 pooled eggbearing prop. 1993 6 22.02 * dalkut 5 7.05 0.38 1994 5 32.88 * dalkut, mirbat 3 4.29 0.59 1995 4 18.31 * shuwaimiya 3 4.53 0.66 1996 5 2.39 0.37 1997 4 28.69 * mughsayl 3 2.97 0.46 1999 4 1.98 0.43 2000 2 0.001 0.47 2001 4 10.28 * mughsayl 3 2.02 0.45 2003 4 4.56 0.47 2004 6 229.98 * mirbat, hitam 4 3.75 0.57 2005 3 9.36 * sadah 2 2.03 0.53 2006 3 110.4 * compared to may and june, and october to january. in january, values were scattered between zero and 0.75, suggesting particularly high interannual variability during this month. higher values were generally obtained for females >90 mm cl. combining all the data from 1989–2006 into trends suggested that fewer females bore eggs in february to april than in any other month, and that egg-bearing increased through may and june (fig. 3). although this trend was similar for all three size classes tested, females >90 mm cl had a much higher egg-bearing incidence in june, suggesting that they start carrying eggs earlier in the season than smaller females. the null hypothesis stating that egg-bearing proportions would be the same for all sites tested for the same period within each year (i.e. year×month×site×size comparisons) was accepted for four out of 12 years tested (1996, 1999, 2000, 2003; see table 2), and for an additional five years it was accepted after eliminating a single site. no sitespecific trends emerged across years (fig. 4), apart from hitam where the two lowest values (6% and 7% in 2004 and 2006) were observed. the conclusion is therefore that egg-bearing proportions are similar among sites for a given period within a year, but with some variability. of 6854 egg-bearing females, 3973 (58%) carried eggs in stage 1, followed by 1438 (21%) in stage 2, 1069 (16%) in stage 3 and 374 (5%) in stage 4. the small proportion in stage 4 possibly reflects the short time window (days only) between hatching and the detachment of spent egg-stalks and setae. stage 1 eggs were most frequent in all months except march and june, when there were more females carrying stage 2 and 3 eggs (fig. 5). the sharp increase in stage 1 eggs between march and may, followed by the large proportion of stage 2 eggs in june is noteworthy, and suggests a synchronized onset of the reproductive season, with females becoming egg-bearing in may (i.e. the highest stage 1 frequency of all months) and progressing to stage 2 by june. discussion the analysis of the aggregated database for the 1989–2006 period provided clear answers to the three questions asked at the onset of this study, namely that: a) the incidence of egg-bearing increases in may and june after low activity in february to april, and a higher incidence also occurs in october to january; b) egg-bearing is size dependent with females >90 mm cl bearing eggs more frequently than smaller individuals; and c) most sites show a similar seasonal pattern. no data were available for july to september (the later part of the sw monsoon season), and it is therefore unsure whether the higher egg-bearing al-marzouqi and others 38 39 reproductive season of the scalloped spiny lobster along the coast of oman incidence observed in may/june extends to these months. however, of 49 egg-bearing females in an additional sample taken in october 2007, 27% were in stage 4 and another 24% in stage 3. therefore a large proportion of females must have been in the early egg-bearing stages one to two months earlier (i.e. in august and september), considering that the incubation period of this species is between 20 and 37 days (vijayakumaran et al., 2005). it therefore appears as if the egg-bearing incidence is also high between august and september, and that p. homarus in oman has a protracted breeding season that stretches from figure 4. the proportions of all females sampled with eggs per site in each year (year×month×site×size combinations). data consist of all females sampled in december in 1989–2002 and all females sampled in october–december in 2003–2006, and sample sizes per site are shown. al-marzouqi and others 40 41 reproductive season of the scalloped spiny lobster along the coast of oman figure 5. the onset of breeding in oman in may/june coincides with the onset of the sw monsoon conditions in the arabian sea region. during the sw monsoon, the prevailing wind conditions generate a coastal upwelling, resulting in cool, nutrient rich coastal waters with a general northeastward flow – the oman coastal current which may extend 200 km offshore and attain a speed of 0.4 ms-1 (elliot and savidge, 1990; kindle and arnone, 2001). during this period the temperature decreases from an average of 29°c in may (26°c in june) to 21°c in september before increasing again to 26–28°c by october to november (thangaraja, 1995). we suggest that the drop in water temperature at the onset of the sw monsoon may trigger the onset of synchronous breeding, particularly in large females (see fig. 3), although the influence of other intrinsic and environmental factors are almost certainly also important. although the change in water temperature may initiate synchronous breeding in may/june, the breeding season extends throughout the cooler water sw monsoon period, and also through the warmer water intermonsoon (mid-september to october) and ne monsoon (november to mid-february) periods. the prolonged breeding season is therefore sustained by factors other than temperature alone – and an obvious candidate is the availability of food, both for adults and hatched larvae. the initial may/june to january/february (~ 9 months), with a short pause between february and april. this pattern conforms with the general pattern shown for tropical palinurids (i.e. year-round breeding or an extended reproductive period with multiple spawnings), which is facilitated by warmer water which physiologically accelerates gonadal development, and protracts the spawning period (berry, 1971; chubb, 2000; phillips and melville-smith, 2006). water temperature and seasonal progressions in day length and/or water temperature are the obvious triggers governing the onset and conclusion of breeding seasons in lobsters, although these influences have not been explored in many species (macdiarmid and sainte-marie, 2006). panulirus homarus off eastern south africa showed a similar 9-month breeding season to those in oman, extending from june/july (austral winter) through spring and summer up to autumn (march), with the highest levels when water was warmest in mid-summer months (berry, 1971). a sharp drop in egg-bearing proportions occurred when water temperatures declined in march or april (berry, 1971). conversely, in larger females first breeding activity was recorded in june/july when water temperatures were at its lowest levels. jasus edwardsii mating in new zealand also appears to be triggered by an autumnal decline in temperature (macdiarmid and sainte-marie, 2006). al-marzouqi and others 40 41 reproductive season of the scalloped spiny lobster along the coast of oman increase in nutrients and primary productivity during the upwelling of the sw monsoon is followed by an increase in zooplankton biomass in the arabian sea in september/october to february (thangaraja, 1995), and presumably the higher productivity during this period and the concomitant availability of food plays an important role in the timing and duration of the reproductive season. a similar conclusion was reached by berry (1971), who suggested that the annual reproductive cycle of south african p. homarus was geared towards production of larvae when productivity on the continental shelf off eastern south africa was at its maximum. relationships between upwelling and reproduction were also reported for spiny lobsters jasus lalandii off the west coast of south africa (kanciruk, 1980) and panulirus interruptus along the west coast of mexico (vega, 2003). the catchability of p. homarus in shallow water declines sharply in february (pers. obs. jcg), and few females caught between february and april carried eggs (see fig. 3). the scarcity of lobsters in fishing gear during this period suggests that they have migrated to deeper waters, or are not moving around and feeding as actively as before. the cause for this behavioural change is not apparent, however it does coincide with increasing water temperatures prior to the onset of the sw monsoon and generally more oligotrophic conditions in the arabian sea (thangaraja, 1995). seasonal closures, usually around the time of breeding, are a well-utilized regulatory measure in spiny lobster fisheries, and apart from reducing fishing pressure, well-timed closures can prevent disturbance to breeding populations at a critical phase in their life cycles (chubb, 2000). furthermore, the importance of egg-production in exploited lobster populations has recently been highlighted by miller (2003), who suggested that increasing the number of eggs produced by a population has the potential to increase yield manifold. although the level of egg-production by p. homarus in oman relative to pristine is not known, the size structure of populations, and therefore the abundance of large highly fecund females, has declined sharply over recent years (al-marzouqi et al., 2007). management measures to increase eggproduction are therefore pertinent, and the existing open fishing season between 15th october and 15th december falls within the peak reproductive period. the results of this study suggests that an open fishing season would be better placed in february to may, when few females carry eggs. the absence of any notable spatial variation in the reproductive season among sites indicates that a single open season for all the fishing sites along the arabian sea coast of oman would suffice, and that zonal closures (see vega, 2003) are unlikely to be advantageous. acknowledgements the agriculture and fisheries development fund of the sultanate of oman funded this study and we thank h. al-oufi, a.h. al-hosni, and i. al-busaidi for their role in securing the funding. i. anbory, h. al-waeli, e. al-rasadi, s. rabeea, m. al-hatroshi, r. a-senaidi, j. al-jafari and s. obeed are thanked for technical support and collection of data and biological samples on field trips. references al-abdessalaam, t.z.s. 1995. marine species of the sultanate of oman: an identification guide. ministry of agriculture and fisheries, marine science and fisheries centre, sultanate of oman. muscat printing press, 412 pp. al-marzouqi, a., a. al-nahdi, n. jayabalan, and j.c. groeneveld (in press). an assessment of the spiny lobster panulirus homarus fishery in oman – another decline in the western indian ocean? western indian ocean journal of marine sciences (2007). anon., 2006. fisheries statistics book (2005) for the sultanate of oman. directorate of general planning and investment promotion. statistics and information department. ministry of agriculture and fisheries, muscat, 240 pp. berry, p.f. 1971. the biology of the spiny lobster panulirus homarus (linnaeus) off the east coast of southern africa. investigation report of the oceanographic research institute of south africa, 28:1-75. chubb, c.f. 2000. reproductive biology: issues for management. chapter 14. in: spiny lobsters: fisheries and culture, 2nd edition. b.f. phillips and j. kittaka (editors), pp 245-275. fishing news books, blackwell science, oxford. elliot, a.j. and g. savidge. 1990. some features of the upwelling off oman. journal of marine and freshwater research, 48:319-333. al-marzouqi and others 42 holthuis, l.b. 1991. fao species catalogue. 13. marine lobsters of the world. an annotated and illustrated catalogue of species of interest to fisheries known to date. fao fisheries synopsis, 125(13):292 pp. johnson, d.w., and t.z. al-abdulsalaam. 1991. the scalloped spiny lobster (panulirus homarus) fishery in the sultanate of oman. the lobster newsletter, 4:1-4. kanciruk, p. 1980. ecology of juvenile and adult palinuridae (spiny lobsters). in: the biology and management of lobsters, j.s. cobb and b.f. phillips (editors), pp 59-96. academic press, new york. kindle, j.c. and r.a. arnone. 2001. a review of the surface circulation of the northern arabian sea. in: proceedings of the 1st international conference on fisheries, aquaculture and environment in the nw indian ocean. m. claereboudt, s. goddard, h. al-oufi, and j. mcilwain, (editors), pp 113-122, sultan qaboos university, muscat, sultanate of oman. macdiarmid, a.b. and b. sainte-marie. 2006. reproduction: chapter 2. in: lobsters: biology, management, aquaculture and fisheries, b.f. phillips (editor), pp 45-77, blackwell scientific publications, oxford. miller, r.j. 2003. be-all-you-can-be management targets for canadian lobster fisheries. fisheries research, 64:179-184. mohan, r., 1997. size structure and reproductive variation of the spiny lobster panulirus homarus over a relatively small geographic range along the dhofar coast in the sultanate of oman. marine and freshwater research, 48:1085-1091. phillips, b.f., and r. melville-smith. 2006. panulirus species: chapter 11. in: lobsters: biology, management, aquaculture and fisheries, b.f. phillips (editor), pp 359-384. blackwell scientific publications, oxford. radhakrishnan, e.v., v.d. deshmukh, m.k. manisseri, m. rajamani, j.k. kizhakudan, and r. thangaraja. 2005. status of major lobster fisheries in india. new zealand journal of marine and freshwater research, 39:723–732. siddeek, m.s.m. 1999. marine fisheries resources, fisheries and marine environmental management, coral reefs and marine parks in the northwest indian ocean. report of a regional workshop on fisheries monitoring, control and surveillance, pp 101-115. muscat, sultanate of oman, 24–28 october 1999. thangaraja, m. 1995. hydrobiology off oman. msfc research report 95–1. marine science and fisheries centre, muscat, oman, 153 pp. vega, a.v. 2003. reproductive strategies of the spiny lobster panulirus interruptus related to the marine environmental variability off central baja california, mexico: management implications. fisheries research, 65:123-135. vijayakumaran, m., t. senthil murugan, m.c. remany, t. mary leema, j. dilip kumar, j. santhanakumar, r. venkatesan, and m. ravindran. 2005. captive breeding of the spiny lobster, panulirus homarus. new zealand journal of marine and freshwater research, 39:325-334. zar, j.h. 1984. biostatistical analysis. englewood cliffs, n. jersey prentice-hall inc. 620 pp. sultan qaboos university journal for scientific research agricultural and marine sciences, 11 s.i., 55-69 (2006) ©2006 sultan qaboos university 55 sea water intrusion in a coastal aquifer: a case study for the area between seeb and suwaiq, sultanate of oman ahmed al barwani* and tariq helmi ministry of regional municipalities, environment and water resources, p.o. box 2575 ruwi, p c 112 ruwi, sultanate of oman تداخل میاه البحر بساحل الباطنة – حالة دراسیة للمنطقة الواقعة بین السیب والسویق (1984م – 2005م) أحمد بن سعید البرواني وطارق حلمي أبو العطا الخالصة: تقع األجزاء الساحلیة من سھل الباطنة بین سلسلة جبال الحجر الغربي والبحر على امتداد المنطقة الواقعة بین محافظة مسقط والحـدود مع دولة اإلمارات العربیة المتحدة . وھي من أكثر المناطق مالئمة لتواجد المیاه الجوفیة . تعاني األجزاء الساحلیة من سھل الباطنة، خاصة والیتي بركاء والسویق من تدھور كبیر في نوعیة المیاه الجوفیة . وتھدف ھذه الدراسة إلى مراجعة وتقییم المسوحات الحقلیة التي قامت بھا الوزارة منذ عام 1984م وحتى عام 2005م الخاصة بقیاس الموصلیة الكھربیة للمیاه الجوفیة في نطاقات وتحدید البیانات لتحلیل الجغرافیة المعلومات نظم تقنیة استخدام تم . بالباطنة الساحلیة باألجزاء تقع بئر 1000 من أكثر الملوحة حیث تم اسقاط مواقع اآلبار وقیم الموصلیة الكھربیة على خرائط ومن ثم تم حساب مساحة ھذه النطاقات ومقارنتھا بالمساحة اإلجمالیة للمستجمعات المائیة المختلفة باإلضافة إلى مقارنتھا بالمسوحات الحقلیة السابقة . أظھرت نتائج الدراسة تدھورا كبیر في جودة المیاه الجوفیة وھو ما یؤكده انخفاض مساحة األراضي الصالحة للزراعة بمقدار 7 % خالل الفترة2000 – 2005م ، وھو ما یعادل 2714 ھكتار. كما تشیر النتائج إلى استمرار تحرك أسفین المیاه المالحة باتجاه الیابسة لیصل إلى 12 كم بحوض وادي الطو في منطقة بركاء . ومما الشك فیھ أن جمیع ھذه الشواھد تشیر إلى استنزاف الخزان الجوفي الساحلي بمنطقة الباطنة ولذلك فمن الضروري االستمرار في مراقبة التغیر في جودة وكمیة المیاه. واتخاذ اإلجراءات التي تھدف إلى تطبیق أفضل لمبدأ اإلدارة المتكاملة للمصادر المائیة خاصة باألجزاء الساحلیة وھو ما یتطلب تعاون كافة المؤسسات الحكومیة واألھلیة ومستخدمي للمیاه للسیطرة على كمیات الضخ المتزایدة من الخزان الجوفي ووقف تلوثھ الحفاظ على المصادر المائیة. abstract: the batinah coastal plain, located between the hajar mountains and the sea, from muscat to the uae border, is a favorable region for groundwater occurrence in oman and the main source of fresh water in this coastal area. the coastal parts of the batinah plain, particularly barka and suwaiq, have suffered from groundwater deterioration over the past 20 years. this paper reviews the monitoring activities of groundwater electrical conductivity in the batinah coastal plain between seeb and suwaiq over the period 1984 to 2005, an area of approximately 394 km2. gis and auto-cad techniques were applied to illustrate different salinity zones as the wells coordinates and their field ec were digitized on maps with contours. zones of salinity ranges are identified and their areas were computed and compared to the total catchment area of each wadi. all samples were collected from the same upper gravel layer, ranging in depth 20-100 meters. there has been a substantial deterioration in water quality as indicated by a 7% reduction in areas of water suitable for agriculture use (2.000 – 6.000 μs/cm), reflecting a loss of 2,714 hectares of irrigated land. also, a saline interface is reported 12 km inland at wadi al taww, barka area, an indication of aquifer over-exploitation. it is therefore critical that monitoring of water quality and quantity is continued. it is recommended to improve implementation of the standard water resources management solutions to coastal aquifer saline contamination. cooperation of different organizations and water users is essential to conserve these precious water resources. * corresponding author. e-mail: asbarwan@yahoo.com keywords: groundwater, water quality, water resources management. al barwani and helmi 56 introduction the batinah coastal plain extends 270 km along the gulf of oman from muscat to the u.a.e. border, north of shinas. the area is of critical importance to the agricultural economy of the sultanate; 50% of the total agriculture area is located here. population growth and rapid industrial and agricultural development in this area, and hence the conjugate increase in different human activities, have imposed an increasing demand for fresh water. this increased demand has been met by the extensive pumping of fresh groundwater water, causing a subsequent lowering of the water table and upsetting the natural balance between the fresh and saline water body. the result is salt water intrusion. being heavier than fresh water, salt water occurs as a wedge beneath the fresh water; the two mix in a transition zone or zone of diffusion, in which the water becomes progressively more saline downwards and towards the sea. the existence of a transition zone indicates that there is a significant circulation of seawater into and out of the aquifer. a continuous movement of fresh water through the zone produces a natural barrier that prevents saline water from moving further inland. under limited pumping of water from wells, the through flow of fresh groundwater to the sea is maintained by recharge in the upper parts of the aquifers and the transition zone holds a fairly constant position. when excessive pumping alters this equilibrium, particularly near the coast, groundwater levels fall, with the flow of fresh water being reduced and the transition zone moving inland and upwards. as a result, water pumped from wells near the coast becomes progressively more saline. groundwater abstraction for irrigation in the south batinah areas is extremely high compared to the north batinah areas. therefore, groundwater recharge and abstraction are important factors controlling saline intrusion in the south batinah. preventing the saline water intrusion along the batinah coast depends on continuous recharge events from rainfall and wadi flows and also on controlling the over pumping from wells. this study focuses on monitoring of the groundwater salinity in the area between seeb and suwaiq to detect the lateral variation in salinity of the shallow upper gravel layer of the batinah aquifer. hydrogeology of al batinah the hydrogeology of the batinah is an important factor in the occurrence of groundwater. through millions of years, the plain has been formed by the effect of natural processes such as rainfall and weathering. rainfall on the mountain area has spread sediments to build up the plain and complex patterns of gravel and clay have been formed in the braided wadi channels (stanger, 1984). the batinah area can be divided into two main parts, differentiated by rock type and geological setting, namely: the mountains, composed of hard rocks mainly igneous rocks overlain by ophiolite sediments with some sandstones and conglomerates underlain by several thrust sheets of pelagic sediments and tertiary limestone; and the lowland and coastal plain, consisting mainly of coarse gravels and boulders with occasional cemented beds. the latter is the main aquifer with a total depth of more than 300m in the sohar-saham area and more than 600 m in the seeb-barka area in the south batinah. the alluvial deposits generally become finer toward the coast and the interfluve area between the systems of braided channels. these deposits form a single deep groundwater basin along the batinah containing relatively fresher groundwater inland where saline intrusion exists near the coast. they are hydrogeologically divided into upper gravels, clayey gravels and cemented gravels. low lands or piedmont zone comprise the upper gravel unit and constitute the main productive zone as the thickness increase towards the sea. although grain size, degree of sorting, and cementation with calcium carbonate affect this unit hydraulically, its storage and transmissivity are generally good, with average transmissivity values of 550 m2/day in the barka– suwaiq area (south batinah). the transmissivity in the sohar-saham area (north batinah) is 3000 m2/day or even larger (6500 m2/day), due to either higher proportion of coarser materials caused by the narrowness of the coastal plain or a greater aquifer thickness. underlying the upper gravels are the clayey gravels, marked by the appearance of brown and red marly gravels and clayey sands associated with decreased well yields and average transmissivity about 223 m2/day. located at the bottom of the clayey gravel sequence are the cemented gravels with the smallest specific capacities and biggest drawdowns, thus making them markedly poorer aquifers (mwr, 1995). groundwater quality along the batinah is extremely varied. in the mountains near the recharge source, water quality is good, with tds of less than 1500 mg/l. in the plain and lowland area, water sea water intrusion in a coastal aquifer: a case study for the area between seeb and suwaiq, sultanate of oman 57 quality decreases as groundwater dissolves many salts (calcium carbonate) on its way to the sea, with higher tds values in the range 1500 to 6500 mg/l associated with the larger settlements. in the coastal zone the freshwater aquifer is underlain by a saltwater wedge. the prevailing rainfall pattern in the area is characterized as having the wettest months from february to april, which account an average for 40% of the total annual rainfall. a second but less pronounced relatively wet period is july and august, accounting for another 23%. mean annual rainfall (mar) varies from about 55 mm at the coast to about 310 mm in the mountains. during the period covered by this study (1984-2005), three significant dry periods and four significant wet periods can be identified (mwr, 2000): dry periods are 1979-81, 1984-86, 1991-94. the five year moving mean plots for all the available long-term stations (22-years) in the area indicates that there is no particular long-term trend and there is no evidence of any statistically significant trend to suggest any climatic change is occurring in the area. materials and methods monitoring salt-water intrusion beneath the batinah coastal plain is carried out at hundreds of hand dug coastal wells. the public authority for water resources undertook three extensive surveys, covering the entire batinah coast over the period 1982 to 1984. the surveys were repeated during 1985, 1986 and 1988 for some parts of the batinah coast, and then in 1989, 1991, 1993, 1995, 1997, 2000 and 2005. the field surveys included measurements of 716 wells (90% of them being productive) located along the study area (394 km2) on both sides of the batinah coast highway: 221 wells located in the seeb area, 186 wells at wadi al taww, 113 wells at wadi al maawil, 99 wells at wadi bani kharous, and 97 wells at wadi al fara’a. water samples were collected from all productive wells and non-pumped wells were pumped using an mp1 pump with 2 inch diameter. to obtain a representative groundwater sample, it was necessary to purge the bore to remove the stagnant water from the bore water column. this was achieved by removing about three times the volume of water contained in the borehole before a sample was collected. the well depths ranged from 20 to 100 meters, tapping only the same upper gravel layer of the batinah aquifer. the well locations (coordinates) and their field ec were digitized on maps where contours were produced using auto-cad techniques. zones of salinity range were colored, their areas computed and compared to the total catchment area of each wadi, and the results plotted on the maps. these surveys were designed to provide an overall picture of coastal salinity conditions and to demonstrate that a serious saline intrusion problem existed. results and discussion present conditions indicate that fresh water discharge to the sea along the batinah coast is largely intercepted by pumping in the coastal zone. the salt-water wedge is located several kilometers inland in some places and could pose a serious threat to existing municipal well fields. the top of the interface is approximately delineated by the red colored zones with ec > 16000 mmhos/cm shown on figures 1, 2 and 3. table 1 shows a severe water abstraction from the aquifer compared to the water available, particularly in the barka area (wadi al taww, wadi al ma’awil) and the suwaiq area (wadi al fara, wadi bani kharus). the water resources master plan (mwr, 2000), reported that total deficit amounts to 92.8 mm3 which is covered by storage depletion (47 mm3) and sea water intrusion (45.8 mm3). it should be also noted that both the storage depletion and saline intrusion flow components are not in steady state and may increase or decrease as the aerial extent of the depletion zone and the hydraulic head within that zone vary in response to changes in the groundwater abstraction pattern. the 2005 salinity survey results the total study area covered 394 km2 and 716 wells, with an average spacing of 0.6 km2 per well. this study compares the 2005 survey with all the available ones since 1983. this comparison illustrates and emphasizes the extensive and serious expansion of the saline water intrusion beneath the batinah coast, particularly in the area between seeb and suwaiq. the following are the most important results of the project (figs. 4-8): • 47% of the total measured wells (537) had salinity above 6.000 μs/cm, 18% with a salinity over 16.000 μs/cm, with the highest salinity equal to 57.000 μs/cm at wadi taw. • the southern batinah areas showed progressive salinity increases during the last decade in spite of the exceptional rainfall during 1995-1997. figure 4 shows al barwani and helmi 58 the increasing trend in salinity during 1993-2005 at three selected different catchments. • there has been substantial deterioration in water quality, indicated by the 7% reduction in areas of water suitable for agricultural use (2.000 – 6.000 μs/cm), reflecting a loss of 2,714 hectares of irrigated land and indicated by the closure of 116 wells along the study area during the last five years. in general, the variation in the degree of deterioration or improvement of the upper aquifer at the coastal area is a direct response to the rate of abstraction at each catchment, rainfall periods and to the enhancement of recharge dams located at the upstream part of each catchment. for example, near seeb, wadi samail has markedly improved and the ec has decreased over large areas. al khod recharge dam is directly upstream of the area of greatest improvement. it is known that the dam has contributed many millions of cubic metres of fresh water to the aquifer. however, it is beyond the scope of this study to separate and quantify the change in salinity due to the effect of the dam from that caused by natural recharge via wadi flow and rainfall. seeb area: wadis rusayl, samail and al hayl, al maabila and al manumah these catchments (fig. 1) were highly salinized by the time of the survey in 1991. during the five years 1995-2000, the area with high salinity water (>10,000 μs/cm) that could not be used for economic cropping decreased by 53% at wadi rusayl (fig. 5). and by 37% at wadi al hayl. however, the area with potable water in wadi maabilah reduced gradually to zero in 2000, compared to 12% in 1995 and 5% in 1997 (fig. 6). in the five years, 2000-2005 there has been a general deterioration in water quality in wadi samail and a decrease in the area covered by potable water (<2000 μs/cm). also at wadi manumah there has been a notable deterioration in water quality as the area covered by the potable water reached zero in 2005, compared to 4% in 2000. barka area : wadis al taw and al maawil in both these catchments (fig. 2), the area underlain by very saline water has increased gradually since 1991. compared to 2000, the area covered by water not suitable for agriculture (6,000 µs/cm) has increased by 2000 hectares at both wadis (fig. 7). in addition, the fresh water zone (<2000 µs/cm) in both wadis has decreased from 23 km2 in 1991 to zero in 2000 and 2005. in wadi maawil the area covered by high salinity water (>16.000 µs/cm) has increased from 17% in 2000 to 32% in 2005. the continued inland movement of the saline intrusion is proceeding in connection with the steady decline in water levels below sea level. even the exceptional rainfall during 1995-1997 was not enough to prevent the saline intrusion in this area. low average rainfall and wadi flow during 1998-2004 allowed further water quality deterioration. suwaiq area: wadis bani kharous and al fara in wadi bani kharous, the water quality has deteriorated since 1991 (fig. 3). groundwater has become unsuitable for most crops at half of the wells in the area , as indicated by a steady increase in the area of very high saline water (>16000 µs/cm) since 1991 (29 % to 38 %). compared to 1997, the area of potable drinking water (<2000 µs/cm) has decreased by 2 % to reach zero in 2000 and 2005 (fig. 8). the same situation was recorded at wadi al fara; there has been an increase in the area of high table 1. water balances and areas of over-abstraction (all values in mcm). area recharge water available water consumed deficit agriculture dom/ ind/mun total seeb 52.9 53.2 45.82 9.39 55.2 -2 barkasuwaiq 71.7 83.3 173.68 0.38 174.1 -90.8 total 124.6 136.5 219.50 9.77 229.3 -92.8 source: water resources master plan (mrmewr, 2000). sea water intrusion in a coastal aquifer: a case study for the area between seeb and suwaiq, sultanate of oman 59 figure 1. groundwater salinity map for the seeb area. al barwani and helmi 60 saline water (>10.000 µs/cm) from 4% in 2000 to 8% in 2005. on the other hand, there has been a slight wadi fara. this could be a result of the recharge effect figure 2. groundwater salinity map for the barka area. sea water intrusion in a coastal aquifer: a case study for the area between seeb and suwaiq, sultanate of oman 61 figure 3. groundwater salinity map for the suwaq area. al barwani and helmi 62 figure 4. increasing trend in salinity 1993-2005 at three different catchments. saline water (>10.000 µs/cm) from 4% in 2000 to 8% in 2005. on the other hand, there has been a slight improvement in the area with potable water located in wadi fara. this could be a result of the recharge effect of al fara dam, situated upstream. in general there has been a notable water quality deterioration during the last ten years in the suwaiq area. rainfall the analysis of rainfall data in twenty nine rainfall stations, which goes back to 1990 in south batinah and muscat reveals that the annual average rainfall is 158 mm in south batinah and 100 mm in muscat. the analysis of the average rainfall at al khadrah rainfall station in south batinah shows that water years, 1990, 1992, 1994, 1995, 1997, 1999 recorded above average annual rainfall (fig. 9). the water year 1997 is considered a wet year for the sultanate in general and for the batinah specially: the total recorded cumulative rainfall was 608 mm in south batinah. this is the highest on record since 1990. figure 10 represents the departure from mean annual rainfall at muscat rainfall station for the last one hundred years. the figure shows that the area has been subjected to a severe dry period during the past seven years. effects of rainfall on groundwater levels the water levels response to recharge events along the batinah coast was variable. the levels in musannah, suwaiq and seeb have risen slightly but less in barka. although there has been a slight water table rise as a result of rainfall during the mentioned period, this is not above sea level, especially in barka and suwaiq, due to over abstraction of the aquifers and so failing to reach water balance. figure 11 illustrates how groundwater levels fluctuate with time at two wells located near the coast along wadi maawil and wadi fara. the presence of recharge dams along the batinah coast has caused some rise in water levels, resulting in slightly lowered salinity, which has been observed in some of the wadis (mwr, 1995). but unfortunately the over abstraction in recent years has led to the lowering of water levels near the coast, causing salinity intrusion inland. two main features can be distinguished: a general downward trend in water levels throughout the period of record, and a general correspondence between preceding rainfall and rises in water levels in the well. for instance, it is noticeable that the period 1990-1995 was relatively dry. this is reflected in the downward trend of water levels sea water intrusion in a coastal aquifer: a case study for the area between seeb and suwaiq, sultanate of oman 63 figure 5. salinity changes at wadis rusayl and manumah areas, 1983-2005 al barwani and helmi 64 figure 6. salinity changes at seeb area, 1983-2005 sea water intrusion in a coastal aquifer: a case study for the area between seeb and suwaiq, sultanate of oman 65 figure 7. salinity changes at barka area, 1983-2005 al barwani and helmi 66 figure 8. salinity changes at suwaiq area, 1983-2005 sea water intrusion in a coastal aquifer: a case study for the area between seeb and suwaiq, sultanate of oman 67 figure 9. yearly and average rainfall for al khadrah rainfall station. figure 10. muscat rainfall, departure from mean. during the same period. in contrast, water levels rose considerably, in 1995-1997, as result of significant rainfall at this time. generally, in most of the selected wells the rises due to the 1997-1999 rains were much less than those following other wet periods. effects of rainfall on salinity in terms of groundwater salinity, the impact of rain differs from place to place. there has been notable water quality deterioration in many catchments, such as wadi al maabila, manumah, taw, maawil, bani kharous, and al fara. despite the heavy rainfall in 1997, as shown in al khadrah station at wadi bani kharous with an average annual rainfall 254 mm, the amount was not enough to prevent groundwater deterioration in these areas. this is related to below average rainfall during 1999 – 2004 and to the over abstraction, particularly in the rumais-barka area. al khadrah rainfall station south batinah muscat rainfall departure from mean (100 mm) 1895-2004 al barwani and helmi 68 figure 11. groundwater levels in wadis al-fara’ and maawil, 1973-2003 conclusion despite exceptional natural recharge and years of water conservation, recharge enhancement and aquifer protection programmes, groundwater salinity continues to deteriorate over large areas of the batinah. rising salinity is probably the most economically devastating water resources problem facing the country at present. the groundwater reservoirs are still adjusting to the enormous increase in water consumption that occurred during the 1970s, 1980s and the early 1990s. indeed, the situation may get worse, despite the improvements that occurred during the mid 1990s. nevertheless, the situation can be addressed if all necessary actions are taken and all users behave responsibly towards this precious national resource. there is, and has been for a decade, strong evidence that tougher water resource conservation policies are required to reduce abstraction and preserve the quality of groundwater in areas where ec is consistently on the increase. recommendations based on these monitoring results, it is recommended to apply the following management solutions for coastal aquifer saline contamination: • reduce abstraction in areas of ec increase by water licensing, water tariffs, stricter control on abstraction monitoring wells at south batinah area wadi al fara’ monitoring wells at south batinah area wadi al ma’awilwadi al ma’awil sea water intrusion in a coastal aquifer: a case study for the area between seeb and suwaiq, sultanate of oman 69 by non-bona fide farmers, increased water conservation practices, improved irrigation practices, reduction of factors contributing to soil salinization, and limiting crop types according to consumption/yield. • enhance programs of awareness of conservation practices and farming of economic crops amongst farmers. • ensure all abstraction wells in problem areas are legally registered via the national well inventory project records and ground checks. abstraction at non-registered wells should be halted. • continue to investigate the feasibility of recharge dams, where economically viable, to prevent loss of flood water to the sea. • continue to develop regional management plans. • encourage the creation of local water user associations to engage in self-regulation. • change cropping patterns to low water consumption crops, stop abstraction at the amenity farms, and eliminate non economical plants. references wr (ministry of water resources). 1995. ministry of water resources, eastern batinah resources assessment. internal report, september 1995, sultanate of oman. pp. 78. mwr. 2000. national water resources master plan. internal report, october 2000, sultanate of oman. pp. 120. stanger, g. 1984. the hydrogeology of the oman mountains. phd. thesis, department of earth science, the open university, london. pdf995, job 6 _________________ *corresponding author. 17 agricultural sciences, 7(2):17-22 (2002) © 2002 sultan qaboos university measuring water transmission parameters in vadose zone using ponded infiltration techniques d.e. elrick1* and w.d. reynolds2 1university of guelph, guelph, on, canada n1g 2w1 2agriculture and agri-food canada, harrow, on, canada n0r 1g0 abstract: the flow of soil water is characterized by water transmission parameters, field-saturated hydraulic conductivity, matric flux potential and sorptivity. soil water flow is, in turn, the primary mechanism by which soil contaminants, such as excess plant nutrient, bacteria, viruses, salts, and industrial chemicals are transported. consequently, knowledge of soil water transmission parameters is essential for understanding, preventing and remediating the contamination of soil water and ground water. this paper describes steady-state and transient methods for obtaining soil water transmission parameters from ponded infiltration under constant head and falling head conditions in surface rings and shallow auger holes. also discussed are the conditions under which the various methods are most appropriate. keywords: vadose, infiltration, ponded, hydraulic conductivity, matric flux, sorptivity, contamination, steady-state, transient, falling head, darcy’s law, unsaturated. he main soil water transmission parameters include the saturated or field-saturated hydraulic conductivity, and the matric flux potential or sorptivity. the saturated/field-saturated hydraulic conductivity characterizes the saturated component of soil water flow, while the matric flux potential or sorptivity characterizes the unsaturated component of flow. in the laboratory, soil water transmission parameters are generally obtained from ponded infiltration measurements made on "undisturbed" soil cores or soil columns extracted from the field. it is much preferred to carry out these measurements in-situ, however, as soil cores and soil columns collected from the field are invariably disturbed to some extent; and perhaps even more importantly, water transmission parameters obtained from isolated soil cores and soil columns may not be adequate representations of the actual field values. in the field, soil water transmission parameters are obtained from infiltration measurements made at the soil surface using constructed ponds or rings, or below the soil surface using shallow bore holes or pits. the infiltration measurements can be made (regardless of whether they are laboratory-based or field-based) under a quasi-steady flow environment or a transient flow environment, and with constant hydraulic head at the infiltration surface or falling (declining) hydraulic head at the infiltration surface. included below is a brief discussion of water transmission theory and t ! !"#$%&'!()*+,-!.'/0%1)2!34567&'!#*8!32#%&'!9:!;)*7&'!3<=)>?! '!"!#)*$ #7%&)2! !"#$%&'(!)*+$,,!-'.$/!#0'1! ! 3&&&'("!21!3+4456'!!7448*5$/!#449:$/!;.44<,!=>44?5$/!744 +$,(#+9$/!!+44"%6$/,!#*+445$/!$44'%*0&!'/%44()!$).644$/!744<!#*+445$/!*44< !$+4"*+6,-/,!.!!!!!!!!!!!!/*0%15$/!$2.3$!$+4+8.$/!$1+5%$/!$).6$/!74<!#*+45$/!*4<1!.>466',!.!!!!!!!*<1!'/%7!$<.6,!895$/!9,!:*2!/;9$, !!!!!!!!!!!!!!!$+<%:$/!#*+5$/,!$).64$/!<%41=!$43<* ,,!$4'*53$!$).64$/!74<!#*+45$/!.,!$5'#645$/,!>.)*6$/!;.?$/!@"%$*)!a3>$/!/;b!c,*&6' !!!!!!!!!!!!!!!!!!!!!!!!.03$/,!d.46$/!"*+e!f*9g!9,!=?h65$/,!88/#$/!.5i$/!j,.k!l3=!#*+5$/!d.4=!cm7!94,!#*+45$/!$4'%*0&!'/%47!"*+4h$ $+3?4$/!.$016(5$/!;.?1$!j,.n$/!o4&p!q*h&!8=!*52.! elrick and reynolds 18 parameters, plus descriptions of several techniques for determining water transmission parameters from ponded infiltration measurements. water transmission theory and parameters the transmission of water through unsaturated soil can be described by darcy’s law: (1) h )(k h )(k q zz ∂ ∂ ψ−= ∂ ∂ θ−= where (2) z!h += and q [l3l-2t-1] is the volume flux density of water (volume of water passing per unit time through a unit cross-sectional area of porous medium perpendicular to the direction of flow), ∂h/∂z [ll-1] is the hydraulic head gradient, k(θ) [lt-1] is the hydraulic conductivity (k) versus volumetric water content (θ) relationship, k(ψ) [lt-1] is the hydraulic conductivity versus pore water pressure head relationship, h [l] is hydraulic head, ψ [l] is pore water pressure head, and z [l] is elevation or gravitational head (positive upward). when the porous medium is saturated, k(θ) = k(ψ) = constant = ks (3) where ks [lt -1] is known as the saturated hydraulic conductivity. the ks parameter is highly sensitive to porous medium texture and structure, and as a consequence, its value ranges from as high as 10-2 10-4 m s-1 in coarse-textured and/or highly structured or cracked soils, to as low as 10-8 10-10 m s-1 in compacted, structureless clay soils and landfill liners. when hydraulic conductivity is measured via ponded infiltration into initially unsaturated soil, it is often referred to as the “field-saturated” hydraulic conductivity, kfs, as some amount of air is usually entrapped in the soil by the infiltrating water. this can result in kfs ≤ ks, but it is often argued that kfs is more appropriate than ks because most natural and manmade infiltration processes result in entrapment of air in the soil. ponded infiltration (ψ ≥ 0) into initially unsaturated soil is affected not only by kfs, but also by one of several parameters that derive from the k(ψ) relationship. to illustrate this, we can conveniently use the empirical k(ψ) function of gardner (1958): k(ψ) = kfs exp[α(ψ-ψe)] ; 0 < α < +ϑ ; ψ < ψe ≤ 0 )(4a k(ψ) = kfs ; ψ ≥ ψe )(4b where α [l-1] is a slope parameter that depends primarily on soil texture and structure, and ψe [l] is the air-entry or water-entry pressure head, depending on whether the soil is draining or wetting, respectively. integrating (4a) between ψ = ψi and ψ = ψe produces, (5) " k " kk! ! k(!(!)m sise i ∗≈ − =!=φ where φm [l2t-1] is the matric flux potential, ψi [l] is the initial or background pore water pressure head in the unsaturated porous medium, and ki [lt -1] is the initial or background hydraulic conductivity corresponding to ψi . the φm parameter is an indicator of the capillary pull or “capillarity” exerted by the unsaturated porous medium on the water during an infiltration or drainage process. under saturated conditions, φm = 0 because ki = ks in (5). in most natural unsaturated soils we can assume that: (6) ! 1 ! 1 # k "" ffm fs =−=≡∗≈ where the macroscopic capillary length parameter, α* [l-1], represents the ratio of gravity to capillarity forces during infiltration or drainage and ψf [l] (negative in value) represents the effective wetting front pressure head of the green-ampt infiltration model (green and ampt, 1911). large α* values indicate dominance of gravity over capillarity, which occurs primarily in coarse textured and/or highly structured porous media. small α* on the other hand, indicate dominance of capillarity over gravity, which occurs primarily in fine textured and/or unstructured porous media. although, kfs and φm can individually range over many orders of magnitude in a porous medium, α* generally varies from about 0.01 cm-1 to 0.5 cm-1. the reduced variability of α*, along with its connection to porous medium texture and structure, make it a useful parameter in simplified single-head analyses for estimation of kfs and φm in unsaturated porous media (discussed further below, and in reynolds et al., 2002). sorptivity (s) is a measure of the ability of an unsaturated porous medium to absorb or store water as a result of capillarity. the s and φm parameters are related by (white and sully, 1987): ( ) ( ) (7) $ hk%&2 b %& s fs m h " # $ % & ' + φ = where ∆θ = (θfs θi), θfs (l3 l-3) is the field-saturated volumetric soil water content, θi (l3 l-3) is the initial volumetric soil water content, b is a dimensionless empirical constant, and h is the applied constant head measuring water transmission parameters in vadose zone using ponded infiltration techniques 19 of water. setting b = 0.55 for infiltration gives an error of less than 10% in sh. the first term in (7) gives the sorptivity, s0, for h = 0 and the second term gives the increase in sorptivity due to the positive (ponded) head, h. note that either φm or s or α* are needed along with kfs to predict and characterize ponded infiltration into unsaturated porous media. note also that under saturated conditions, sh = 0 because ∆θ = 0 in (7) (i.e. θi = θfs). determining water transmission parameters from ponded infiltration we will use the following terms to describe the infiltration process: (8) dt dq a 1 dt di iq 0z ==== where i (lt-1) is the infiltration rate, i (l) is the cumulative infiltration, a (l2) is the cross-sectional area through which water is flowing and q (l3t-1) is the volumetric intake rate (recharge) of water. ponded infiltration from a single ring: constant head methods i) one-dimensional flow assumption – transient flow one of the earliest expressions used to describe infiltration, which includes sorption and gravity, was derived by green and ampt (1911): ( ) ( ) ( ) ( ( ( ( ( ) * + + + + + , . . . . . / 0 1 1 1 1 1 2 3 .. / 0 11 2 3 ∗+ + .. / 0 11 2 3 ∗+ −= " 1 h%& ci(t) 1ln c " 1 h %& ti ck %& t fs (9) where c = 1. philip (1957,1958) showed that one-dimensional infiltration can be described by: )10($tsi(t) h= if gravity is neglected, and by: )(11at$tsi(t) h += if gravity is included. the a parameter ranges in value from 0 for early time infiltration, to approximately kfs/3 for intermediate time infiltration, to kfs at steady state (long time infiltration). ii) one-dimensional flow assumption steady-state flow green and ampt (1911) give the following expression: (12)1 l " 1 h ki f fs ( ( ( ( ) * + + + + , + . . . . / 0 1 1 1 1 2 3 ∗+ = where lf is the distance from the infiltration surface to the wetting front. at large time, steady-state is approached because lf in the denominator of (12) becomes large relative to the numerator, and consequently i → kfs. iii) three-dimensional flow assumption transient flow numerical methods are generally used to determine 3d transient flow. however, at early times before 3d flow significantly affects i(t), equations (9),(10) and (11) can be used as approximations. iv) three-dimensional flow assumption steady-state flow steady state infiltration through a ring infiltrometer can be described by (reynolds and elrick, 1990): ( ) )(131 acdc" 1 acdc h k a q i 2121 fs ( ( ) * + + , + ( ( ) * + + , +∗ + + == where h [l] is the constant depth of ponded water in the ring, d [l] is the depth of ring insertion into the soil and a [l] is the radius of the ring. the parameters, c1 = 0.316π and c2 = 0.184π are dimensionless constants which apply for d ≥ 3 cm and h ≥ 5 cm. falling head methods under falling head conditions the head, h(t), decreases with time, t. if h(0) = d, the cumulative infiltration, i(t), can then be obtained experimentally from: i(t) = r[d h(t)] (14) where r = a/a is the ratio of the cross sectional area of the falling head reservoir, a, to the cross-sectional area of the infiltrating surface, a. obviously, there are no steady-state solutions for falling head conditions, and falling head solutions are valid only for 0 < i < rd. i) one-dimensional flow assumption transient flow elrick et al. (2002) give the following expression for i(t) when gravity effects are ignored: elrick and reynolds 20 ( ) ( ) ( ) (15)%&b i(t) 1ln%&bi(t) %&k r t fs ( ) * + , .. / 0 11 2 3 −+−= where b = r (d – 'f)/%&. the corresponding equation which includes gravity was derived by philip (1992) and is given by (9) where c = 1-(∆θ)/r. ii) three-dimensional flow assumption transient flow numerical methods are generally used to determine 3d transient flow under falling head conditions. however, at early times before 3d flow significantly affects i(t), equations (9),(10) and (11) can be used as approximations. ponded infiltration from an auger hole: constant head methods i) one-dimensional flow assumption transient flow no valid approximation available. ii) one-dimensional flow assumption steady-state flow porchet and laferrere (1935) give the following solution: (16))ah2a(kq 2fs π+π= equation (16) is an early attempt to measure kfs and assumes both saturated conditions throughout the soil profile and a unit gradient (which is equivalent to gravity flow) across the combined areas of the auger hole bottom (πa2) and submerged portion of the auger hole wall (2πah). these gross approximations can lead to errors in kfs ranging from as little as a factor of 2 to more than a factor of 10. iii) three-dimensional flow assumption transient flow analyses are complex and difficult to apply as they require the use of numerical models. iv) three-dimensional flow assumption steady-state flow over the past 75 years there have been a number of approximate analytical solutions, but it was only about 20 years ago that the unsaturated component was first taken into account (stevens and neuman, 1982; reynolds et al., 1983). reynolds and elrick (1987) give the following expression: (17)a *c h2 c h2 kq 2 2 fs . . / 0 1 1 2 3 π+ α π + π = where the terms on the right hand side represent the respective contributions of pressure, capillarity and gravity. the dimensionless shape factor, c, was obtained from numerical calculations. falling head methods one of the simplest experimental procedures is to measure the rate of fall of water in an auger hole. that is probably why the percolation test (generally referred to as the "perc" test) has been used for over 75 years to determine site suitability for in-ground wastewater treatment facilities such as septic systems. this test has traditionally measured only the time required for water to fall a pre-set distance (“t–time”) and has not been used to calculate kfs. i) one-dimensional flow assumption no valid approximation available. ii) three-dimensional flow assumption an approximate solution, based on the assumption of a series of steady state solutions, can be obtained by rewriting (17) as (elrick and reynolds, 1986): ! .. / 0 11 2 3 ∗++ = dh 22 fs 2 " 2h ca2hk cdh at (18) where t is the time required for the water to fall from the initial height h = d to a given height h = h. equation (18) needs to be integrated numerically, and steady constant head infiltration should be obtained at h = d before the falling head phase is started. philip (1993) developed a solution for the falling head permeameter where the sides of the auger hole are lined and thus water infiltrates only from the base of the auger hole: )19( a3 2a arctan a3 2a arctan a 3 a 1a ln a2 3 a 1a ln a2 1 1 k8 r )h(t 33 3 fs 2 ( ( ( ( ( ( ( ) * + + + + + + + , ( ( ) * + + , .. / 0 11 2 3 + −.. / 0 11 2 3 ρ+ +.. / 0 11 2 3 ρ− − −. . / 0 1 1 2 3 ρ− − . / 0 1 2 3 + π = where a and ρ are given by (24). see philip (1993) and munoz-carpena et al. (2002) for details. discussion although the analyses described above are only a small fraction of the total number available, they are among the most widely tested and most frequently used. the best choice of methodology and analysis depends to some extent on the nature of the soil (e.g., low or high permeability) and on your objective. for example, medium and high permeability soils (e.g., kfs > 10 -6 m s-1) permit the use of relatively simple constant head procedures measuring water transmission parameters in vadose zone using ponded infiltration techniques 21 with small ponded heads, and usually require less than an hour to obtain a measurement. on the other hand, low conductivity soils (e.g., kfs < 10 -7 ms-1) are more of a challenge, often requiring a higher ponded head and the use of more complex early-time, falling head techniques. in addition, the “best” technology will differ depending on whether your objective is, for example, to intensively characterize a small, easily accessible area, or to conduct a broad survey in a remote area where simple portable equipment and low water usage are essential. measurements at or near the soil surface (e.g., < 0.5 m depth) should probably be made using a single ring method such as the pressure infiltrometer. at greater depths (e.g., > 0.5 m) a well permeameter is probably the best approach. constant and falling head techniques can be used with both the ring and well permeameter techniques; however, we recommend use of the pressure infiltrometer whenever possible because of its procedural and analytical advantages over the well permeameter. further detail on collecting and interpreting pressure infiltrometer and well permeameter data can be found in reynolds et al. (2002). detailed research investigations: detailed research investigations might require information on both the saturated and unsaturated components of k(ψ). constant head analyses for single ring pressure infiltrometers or well permeameters can be used for moderate to high conductivity soils (> 10-6 m s-1). two or more heads (h1,h2,h3,…) can be applied to obtain two or more steady state intake rates (q1,q2,q3,…) and (13) or (17) can be solved for kfs and φm (or α*). see reynolds et al. (2002) for details on procedures and calculations using the two-head or multiple-head analyses. if the soil properties change considerably within the measurement zone, or if qi is measured inaccurately, an unrealistic (e.g., negative) value can be obtained for either kfs or φm. this simply means that the two-head or multiple-head approach was inappropriate for this site and the next step is to apply the updated single-head approach to each individual head measurement for which α* is either estimated or measured independently (reynolds et al. 2002). the individual results can then be averaged to obtain overall kfs and φm (or α*) values. early-time constant head and falling head techniques can also be used for medium and low conductivity soils. for constant head procedures see elrick and reynolds (1992) and vauclin et al. (1994). for falling head procedures see elrick et al. (1995, 2002). applied engineering investigations: applied engineering investigations often require only “ball park” estimates of kfs. in this case, procedures using a single, constant head can be used where α* is either estimated or measured independently. the kfs value can then be obtained from: pressure infiltrometer: ( ) 2(ag"1h"a gq" fsk ∗++∗ ∗ = (20) well permeameter: * h22ac2h2 cq fsk α π +π+π = (21) note that g = 0.316d/a + 0.184, where d is the depth of insertion of the ring and a is the radius of the ring. the shape factor, c, is determined from a curve of c vs. h/a (reynolds et al. 2002) or from empirical expressions (zhang, 1998). tables for estimating α* are given in reynolds et al.. (2002). survey investigations extensive data collection: if portability of equipment and water conservation are essential, or if funds, time or labour are severely restricted, simplified falling head techniques for both ring and well permeameters may be an option. for example, bagarello et al. (submitted) proposed a simplified falling head pressure infiltrometer analysis of the form: ( ) ( ) ( ( ( ( ( ) * + + + + + , 4 4 " 4 4 # $ 4 4 % 4 4 & ' .. / 0 11 2 3 ∗+ − + − ∗+ − − = " 1 d%& %&1d 1ln %&1 " 1 d %& d %&1t %& k fs (22) while munoz-carpena et al. (2002) developed a simplified analysis for a lined well permeameter open only at the base: ( ( ( ( ( ( ) * + + + + + + , ( ( ) * + + , .. / 0 11 2 3 + −.. / 0 11 2 3 + +.. / 0 11 2 3 − − − . . / 0 1 1 2 3 − − . / 0 1 2 3 + = a3 2a arctan a3 2)a arctan a 3 )a 1a ln 2a 3 3)3a 13a ln 2a 1 1 8t r2( k fs (23) elrick and reynolds 22 where ( ) 1%&a 8 (a " 1 d a 2 3 3 + . . / 0 1 1 2 3 ++ = ∗ ( )%&a 3d 1)3 += (24) if α* is estimated or determined independently, then kfs can be obtained directly from either of the above equations. in both (22) and (23), t is the time required for the water level to drop from its initial maximum height, d, to either the soil surface (pressure infiltrometer) or the bottom of the well (well permeameter). the procedure of munoz-carpena et al. (2002) has been simplified to a single measurement. it should be remembered, however, that these simplified and largely untested solutions may be of reduced accuracy relative to the other methods. references bagarello, v., m. iovino, and d.e. elrick. 2002. a simplified fallinghead technique for rapid determination of field-saturated hydraulic conductivity. submitted to soil sci. soc. am. j. elrick, d.e. and w.d. reynolds. 1986. an analysis of the percolation test based on three-dimensional, saturated-unsaturated flow from a cylindrical test hole. soil sci. 142:308-321. elrick, d.e. and w.d. reynolds. 1992. infiltration from constant head well permeameters and infiltrometers. in measurement of soil physical properties: bringing theory into practice. g.c. topp and r.e. green, ed. soil sci. soc. am., madison, wi spec. pub. 30, pp 1-24. elrick, d.e., g.w. parkin, w.d. reynolds and d.j. fallow. 1995. analysis of early-time and steady-state single ring infiltration under falling head conditions. water resour. res. 31:1883-1893. elrick, d.e., r. angulo-jaramillo, d.j. fallow, w.d. reynolds, and g.w. parkin. 2002. infiltration under constant head and falling head conditions in "environmental mechanics: water, mass and energy transfer in the biosphere", ed. by raats, smiles and warrick, geophysical monograph series vol. 129, agu washington, d.c., pp 47-53. gardner, w.r. 1958. some steady-state solutions of the unsaturated moisture flow equation with application to evaporation from a water table. soil sci., 85:228-232. green, w.h. and g.a. ampt, 1911. studies in soil physics. i. the flow of air and water through soils. j. agr. sci. 4, 1-24. munoz-carpena, r., c.m. regalado, j. alvarez-benedi, and f. bartoli. 2002. field evaluation of the new philip-dunne permeameter for measuring saturated hydraulic conductivity. soil science 167:924. philip, j.r. 1957. the theory of infiltration: 4, sorptivity and the algebraic infiltration equation., soil sci 84:329-339. philip, j.r. 1958. the theory of infiltration: 6, effect of water depth over soil. soil sci. 84: 329-339. philip, j.r. 1992. falling head ponded infiltration, water resour. res. 28: 2147-2148. philip, j.r. 1993. approximate analysis of falling-head lined borehole permeameter. water resour. res. 29: 3763-3768. porchet, m. and h. laferrere. 1935. determination des characteristiques hydrodynamiques des sols en place. ch. iv. annal. mem. notes techniques 64: 5-68. reynolds, w.d., d.e. elrick, and g.c. topp. 1983. a reexamination of the constant head well permeameter method for measuring saturated hydraulic conductivity above the water table. soil science 136:250-268. reynolds, w.d. and d.e. elrick. 1987. a laboratory and numerical assessment of the guelph permeameter method. soil science 144:282-299. reynolds, w.d. and d.e. elrick. 1990. ponded infiltration from a single ring: i. analysis of steady flow. soil sci. soc. am. j. 54: 1233-1241. reynolds, w.d., d.e. elrick, e.g. youngs, a. amoozegar, h.w.g. booltink, and j. bouma. 2002. ch. 3.4, saturated and fieldsaturated water flow parameters, in methods of soil analysis, part 4. physical methods, j. dane and c. topp, ed., 82p. stevens, d.b. and s.p. neuman. 1982. vadose zone permeability tests. asce j. hydraul. div. 108:640-659. vauclin, m., d.e. elrick, j.l. thony, g. vachaud, ph. revol, and p. ruella. 1994. hydraulic conductivity measurements of the spatial variability of a loamy soil. soil tech. 7: 181-195. white, i. and m.j. sully. 1987. macroscopic and microscopic capillary length and time scales from field infiltration. water resour. res. 23:1514-1522. zhang, z.f., p.h. groenevelt, and g.w. parkin. 1998. the well shape-factor for the measurement of soil hydraulic properties using the guelph permeameter. soil tillage res. 49:219-221. received march 2002. accepted november 2002. agricultural and marine sciences, 15:41-46 (2010) ©2010 sultan qaboos university 41 ___________________________________________________ *corresponding author. e-mail: rekik.mourad@iresa.agrinet.tn live weight changes and their relationship with the ovarian status of maiden fat-tailed barbarine ewes imēne ben salem1, mourad rekik1*, mohammed ben hamouda2 and narjess lassoued3 1ecole nationale de médecine vétérinaire, 2020 sidi thabet, tunisia 2institution de la recherche et de l’enseignement supérieur agricoles, 30 rue alain savary, 2020, tunis, tunisie 3inra-tunisie, laboratoire des productions animales et fourragères, rue hédi karray, 2049 ariana, tunisia العذراء الذیل متضخم البربري الضأن إناث في المبیض بحالة وعالقتھا الجسم وزن في التغیرات حمودة و نرجس األسود بن الرقیق و م. بن سالم و مراد أ. إختیار تم الغرض ولھذا تقریبًا. واحــدة سنة عمر عند البربري نعاج عــذارى في المبیض كفاءة على الجسم وزن في التغیرات تأثیر الحالیة الدراسة قیمت الخالصة: وبحسب الجسم وزن فــي التباین ضبط تــم الــفــطــام). عند أیــام ١٩٦±١٠ العمر ومــعــدل كغم ٣,٠٧± ٣٤,٧ الجسم وزن (مــعــدل مفطومة صغیرة نعجة ١٧١ في األعلى ھو ــوزن ال نقصان معدل كــان بحیث حیوانًا ٣٤ والثالثة ٩١ والثانیة ٤٦ ــى األول في مجامیع ثــالث إلــى الحیوانات توزیع تم البیاني الرسم في اإلنــحــدار (٪٨٥,٣) الثالثة المجموعة في شبق دورة لدیھا التي اإلنــاث نسبة أن وجد شھرًا ١٣ عمر في البطني الفحص عند الثالثة. المجموعة في واألقــل األعلى المجموعة الشبق دورة تزامن إجراء بعد .(p<٠,٠٥ ،٪٦١,٥) الثانیة المجموعة من أعلى أیضًا وكانت (p<٠,٠٠١ ،٪٤٣,٤) األولى المجموعة بحیوانات مقارنة األعلى كانت بالزما في igf-i ال ھرمون مستویات في مجموعات الثالث بین معنوي إختالف ھناك یكن لم شبق، دورة لدیھا وجــد التي لإلناث البروجستجان باستخدام أیضَا مختلفة غیر اإلسترادیول معدالت كانت مایكروغرام/لتر. و٨٩,٩ و٩٠,٨ ٩٤,٢ التوال على كانت حیث اإلسفنجات، ــراج إخ بعد ساعة ٤٢ و ٦ بین الــدم تحت المداخیل المنخفضة التربیة أنظمة تحت أنھ على الدراسة ھذه دلت التوالي. على ، بیكروغرام/مل و٠,٦٧ و٠,٧٠ ٠,٧٣ كانت حیث الثالث المجموعات بین الجسم وزن ھبوط عند خاصة التناسل معدالت إنخفاض إلــى تقریبًا سنة عمر عند ــاث اإلن تضریب یــؤدي أن یمكن تونس، في الجافة وشیھ الجافة المناخ ظــروف الصیف. فصل في الحي abstract: the current study assessed the effect of the pattern of live weight change on the ovarian function of maiden barbarine ewes at approximately 1 year of age. for this purpose, a total of 171 weaned ewe lambs (mean live weight ± s.d. 34.7±3.07 kg and mean age ± sd 196±10 days at weaning) were selected for the experiment. adjustment of live weight variation was used. based on the slope of the curve, animals were grouped into three classes lwci (n=46), lwcii (n=91) and lwciii (n=34) with live weight loss being highest in lwci and lowest in lwciii. following laparoscopy at 13 months of age, the proportion of ewe lambs found cycling in lwciii (85.3%) was higher in comparison to animals in lwci (43.4%; p<0.001) and tended to be superior to those in lwcii (61.5%; p<0.05). following synchronisation with progestagen of the females found cycling, levels of plasma igf-i concentrations between 6 and 42 hrs after removal of sponges were not significantly different between the three classes of live weight, and respectively averaged 94.2, 90.8 and 89.8 µg/l for lwci, lwcii and lwciii females. levels of estradiol were also not significantly different between the three groups (0.73, 0.70 and 0.67 pg/ml for lwci, lwcii and lwciii ewe lambs, respectively). it was concluded that, in low input systems of semi-arid and arid tunisia, mating ewe lambs at the approximate age of 1 year is likely to lead to depressed reproductive performance particularly when the summer live weight-loss is elevated. keywords: maiden ewes, live weight, ovarian activity, igf-i, estradiol. introduction the main sheep-mating system in tunisia and in several other regions of west asia and north africa is the one where the ewes are mated in spring to lamb in autumn. for those ewe lambs that are selected as replacement stock, they attain puberty when they are about 10 to 12 months of age, corresponding to late summer-early autumn and then elapse into anoestrus before they are mated at 18 months for the first time (khaldi, 1984). breeding ewe lambs when they attain puberty is not a common practice in tunisia although rekik and gharbi (1999) and rekik et al. (2002) have shown that 42 salem and others 43 live weight changes and their relationship with the ovarian status of maiden fat-tailed barbarine ewes acceptable results of fertility can be obtained if ewe lambs of the autochthonous barbarine and queue fine de l’ouest breeds receive supplementary feeding to achieve higher live weights or are hormonally treated by a combination of progestagens and equine chorionic gonadotropin. in such a type of dry mediterranean production conditions, martin et al. (1999) postulated that summer losses in live weight of the animals can have a negative effect in their ability to reproduce with satisfactory rates. the hypothesis proposed is that under semi-arid conditions of central tunisia, several changes in live weight occur from the time replacement ewe lambs are selected until their attain puberty during late summer. this study therefore aimed to investigate the effect of live weight changes on the ovarian status and functioning of approximately 1 year-old barbarine ewes. materials and methods study location and animals the experiment was carried out between april and november 2005 at the office de l’elevage et des pâturages farm of jebibina (central tunisia). the region is semi-arid with an average annual rainfall of 390 mm and its latitude is 35° n. it experiences a mediterranean climate with cool winters and hot dry summers. on april the 20th 2005 (spring), a total of 171 weaned ewe lambs of the barbarine breed selected as replacement stock (mean live weight ±s.d. 34.7±3.07 kg and mean age ± s.d. 196±10 days at weaning) were kept for the experiment. from weaning until the age of 13 months the animals were run in a single flock isolated from the rams by at least 1.5 km and housed in fully open sheds. nutritional and health management throughout the experimental period, the animals were allowed to graze poor pastures of the native medicago spp. or spontaneous graminaceae in spring and fall or cereal stubbles in summer for approximately 7 hrs a day. from early june until the end of the experiment in november; the animals were supplemented with 0.2 kg/ewe lamb/day of a soybean meal-barley-based concentrate supplement containing 12.3 mj of metabolisable energy (me)/kg dry matter (dm), 156 g crude protein (cp)/kg dm and a dm concentration of 871g/kg and also received 0.8 kg hay per ewe per day (containing 6.41 mj of me/kg dm, 80 g cp/ kg dm, and 309 g crude fibre/kg dm; dm concentration: 885 g/kg). at the approximate age of 8 months, animals were drenched against internal parasites using oxfendazol at a conventional dose of 5 mg/kg body weight. live weight variation from weaning until the age of 13 months, live weight of the ewe lambs was measured every 2 weeks at 08.00 hrs before grazing. the gamma model of wood (1967) was used to describe lactation curves (sas, 1991; newtonraphson nlin procedure). in this study, the portion of the curve separating the recorded first average live weight at weaning (196 days of age) and the lowest average live weight at the end of the summer season corresponding to an average age of 395 days (13 months). the equation describing the gamma function is: yn = an be-cn where yn is the live weight on age n; a is a scaling factor to represent live weight at weaning; and b and c are factors associated with the inclining and the declining slopes of the live weight variation curve. the slope of the curve designated s and which stands for persistency in the description of the lactation curves is calculated as being s = -(b+1) ln (c), and was used here to describe the intensity of live weight loss in the declining portion of the curve. the average squared multiple correlation coefficient (r2) of the log-transformed gamma function was 0.99±0.006. average s (±s.d) as computed from the gamma function was 8.72±0.57 and higher values of s indicated lower loss of live weight. based on this parameter, the ewe lambs were grouped in three classes of live weight: lwci ewe lambs (n=46) with a value of s < mean s-s.d/2, lwcii ewe lambs (n=91) with a value of s comprised between mean s-s.d./2 and mean s+s.d./2 and lwciii ewe lambs (n=34) with a value of s > mean s+s.d./2. average respective values of s were 8.14±0.33, 8.68±0.16 and 9.58±0.52 for ewe lambs in lwci, lwcii and lwciii (p<0.001). patterns of live weight changes from weaning until the age of 13 months according to the class of live weight are shown in figure 1. reproductive characteristics at 1 year of age in november 2005, when the ewe lambs were aged 13 months, they were subjected to laparoscopy for the determination of the ovarian status. laparoscopy was carried out according to the method described by thimonier and mauléon (1969). the animals found cycling in the three classes of live weight had their oestrous cycles synchronised using intravaginal progesterone pessaries impregnated with 40 mg fluorogestone acetate and left in situ for 14 days. at pessaries removal and for the subsequent 42 hrs, blood samples were recovered in heparinised vacutainer tubes from each animal. after centrifugation (3000 rpm, 15 min.), plasma was stored at -20°c until assayed for insulin-like growth factor-i (igf-i) and estradiol. eleven days after the removal of pessaries, the ewe lambs were again subjected to laparoscopy as described above and the age of the corpora lutea (cl) was determined based on their size and colour as described by oldham and lindsay (1980). 42 salem and others 43 live weight changes and their relationship with the ovarian status of maiden fat-tailed barbarine ewes figure 1. live weight variation of ewe lambs per class of live weight. igf-i and estradiol immunoassays igf-i concentrations in plasma were assayed using a two-site immunoenzymometric kit (iema) octeia® igf-1 (immunodiagnostic systems limited, uk) which was validated for use in sheep by elmes et al. (2005). the method incorporates a sample pre-treatment to avoid interference from binding proteins. the limit of detection was 1.9 µg/l. measurement of the absorbance of each well was performed at 450 nm (reference 650 nm) using a microplate reader (multiskan ascent, thermo labsystems, finland). coefficients of variation between assays were 9% and 7% for respectively a low (52.6 µg/l) and a high controls (235.1 µg/l). the coefficient of variation within assay was 2.7%. cross-reactivity with igf-ii, insulin and proinsulin was negligible. estradiol concentrations were measured in one single assay using the spectria radioimmunoassay kit (orion diagnostic corp., espoo, finland), as described by romeu et al. (1995) and adapted for use in ovine plasma (gonzalez-bulnes et al., 2003). sensitivity for estradiol was 0.5 pg/ml and the intra-assay variation coefficient was 6.6%. statistical analyses data on igf-i and estradiol concentrations were tested by repeated-measures analysis of variance using the statistical programme sas (1991) with the class of live weight as the main effect. when the class of live weight was significant, mean treatment groups were compared according to the null-hypothesis by the least-square means option (sas, 1991). data on the proportions of ewes cycling at 13 months of age were analysed using a χ2 test. the effect of the class of live weight was considered significant when the level of probability was 5% or less. results following laparoscopy at the approximate age of 13 months, the proportion of ewe lambs found cycling in lwciii (29/34 = 85.3%) was higher in comparison to the same proportion in lwci (p<0.001) and in lwcii (p<0.05; figure 2). between lwci and lwcii, these proportions (43.4 and 61.5%) tended (p=0.07) to be different. based on the appearance of the cl at the time of laparoscopy, carried out eleven days after the removal of sponges, all the ewe lambs had ovulated and were bearing one cl each aged 6 to 7 days. levels of plasma igf-i concentrations between 6 and 42 hours after removal of sponges (table 1) were not different between animals in the three classes of live weight (p>0.05). in addition, no effect of sampling time on igf-i levels was found within lwcii. in contrast, significant differences occurred for lwci and lwciii where the lowest levels reached were respectively 85.9±5.47 µg/l at 18 hrs and 71.0±7.43 µg/l at 24 hrs after sponges’ removal. for animals in both classes, the highest level 106 µg/l was reached at 30 and 42 hrs after sponges’ removal for respectively ewe lambs in lwciii and lwci. between 6 and 42 hrs following sponge removal, mean levels of estradiol were 0.73, 0.70 and 0.67 (s.e.m. 0.09) pg/ml for ewe lambs in respectively lwci, lwcii and lwciii. estradiol levels increased sharply in animals of the lwci at approximately 30 hrs (1.60±0.32 pg/ml) and were higher (p<0.05) than the concentrations of ewe lambs in other live weight classes (figure 3). during other sampling times, changes in estradiol plasma concentrations did not reach statistical significance. 44 salem and others 45 live weight changes and their relationship with the ovarian status of maiden fat-tailed barbarine ewes discussion two main findings emerged from this study. firstly, the rate of loss of live weight during summer time and not the absolute weight is the main cause explaining the proportion of ewe lambs found cycling at approximately 1 year of age. ewe lambs that were heaviest after weaning (lwci) lost more weight throughout the summer season, were still heavier at the time of laparoscopy, but only 43.4% were found cycling. their counterparts that recorded lower rates of live weight loss (lwcii and lwciii) were sexually more mature based on the proportions of animals cycling, despite lower absolute live weights. collectively, these results stress the importance of the dynamic component of live weight on the attainment of puberty and sexual maturity in barbarine ewe lambs. while in greyface ewes under temperate british conditions, reproductive performance was dependent on both the rate of live weight change and the absolute live weight at mating (gunn and maxwell, 1989). for lwciii ewe lambs, the lower rate of figure 2. the effect of class of live weight on the proportion of ewe lambs found cyclingat 13 months of age. table 1. the effect of class of live weight on igf-i concentrations in µg/l (±± s.e.m.) at different sampling times after sponges removal. sampling time (hours) class of live weight significance (p > f) lwci (n=20) lwcii (n=56) lwciii (n=29) 6 100.2±7.25 89.2±6.49 91.9±6.84 0.52 12 91.6±5.57 87.8±4.98 94.7±5.25 0.63 18 85.9±5.47 94.3±4.89 89.4±5.15 0.52 24 90.1±7.88 89.1±7.05 71.0±7.43 0.15 30 96.1±7.49 96.4±6.70 106.8±7.06 0.48 36 89.2±6.79 86.9±6.07 84.6±6.40 0.88 42 106.7±6.80 92.2±6.09 89.6±6.42 0.17 loss of live weight could be the key signal to enhance their lh secretion as a result of a reduced negative feed-back by oestradiol (rhind and mcneilly, 1986) and this could have accelerated the chain of events leading to puberty and establishment of ovarian cyclic activity (foster et al., 1985). secondly, in the present study, the rate of live weight loss during summer time didn’t affect changes in igf-i and estradiol concentrations during the early follicular phase, the ability to re-ovulate after synchronisation with progestagens and the number of ova shed for those animals that attained puberty. in comparison to other breeds of sheep (gonzalez-bulnes et al., 2005, viñoles, 2003), obtained low concentrations of estradiol could be explained by the low age of the animals in this experiment and also by the synchronisation treatment as ovulatory follicles from sheep treated with progestagens show deficiencies in the secretion of estradiol during the preovulatory phase (gonzalez-bulnes et al., 2005). with 44 salem and others 45 live weight changes and their relationship with the ovarian status of maiden fat-tailed barbarine ewes figure 3. the effect of class of live weight on estradiol concentrations during the follicular phase after synchronization with progestagen intravaginal sponges. regard to igf-i concentrations, the absence of differences between ewe lambs in the three classes of live weight over the 42 hrs following sponge removal can be explained by the fact that all the animals ovulated after sponge removal, a finding that is consistent with previous findings by spicer et al. (1993). they showed that for lines of finnish sheep with different levels of ovulation rate, the main difference was the significantly lower igf-i plasma concentrations during the follicular phase of those animals that did not ovulate following synchronisation. however, the same authors observed a significant correlation between plasma igf-i concentrations and body weights. there was no such relationship in our study despite significant differences in live weights among animals in the three classes at the time of oestrous synchronisation and blood sampling for igf-i determination. one possible explanation could be related to the overall poor metabolic status of the animals in our study, a consequence of the negative change in live weight throughout the summer season, while the absolute weight at that stage had no influence. such a hypothesis could also be due to the fact that all the ewe lambs had invariably shed one ovum each after pessary removal. the findings also highlight the fact that for those ewe lambs of the barbarine breed that attain puberty at the end of the summer season after loosing much body mass, no further consequences of the rate of live weight loss are depicted at the ovarian level. conclusion sheep farmers in central tunisia are likely to obtain depressed reproductive results if they intend to mate barbarine females at the end of summer time around puberty particularly in low input systems where the animals are likely to loose much body mass. however, there seem to be important individual differences in the rate of losing weight; a feature that could be exploited in selecting replacement females. acknowledgements this work was supported by the international atomic energy agency (iaea) and the ministry of scientific research, technology and capacity building of tunisia under the framework of the technical cooperation project tun 5/021. the authors are also indebted to office de l’elevage et des pâturages for providing animals and farming facilities. references elmes, m., l.r. green, k. poore, j. newman, d. burrage, d.r.e. abayasekara, z. cheng, m.a. hanson and d.c. wathes. 2005. raised dietary n-6 polyunsaturated fatty acid intake increases 2-series prostaglandin production during labour in the ewe. journal of physiology 562: 583-592. foster, d.l., s.m. yellon and d.h. olster. 1985. internal and external determinants of the timing of puberty in the female. journal of reproduction and fertility 75: 327-344. gonzalez-bulnes, a., r.m. garcia-garcia, v. castellanos, j. santiago-moreno, c. ariznavarreta and v. domínguez. 2003. influence of maternal environment on the number of transferable embryos obtained in response to superovulatory fsh treatments in ewes. reproduction nutrition development 43:17-28. 46 salem and others gonzalez-bulnes, a., a. veiga-lopez, p. garcia, r.m. garcia-garcia, c. ariznavarreta, m.a. sanchez, j.a.f. tresguerres, m.j. cocero and j.m. flores. 2005. effects of progestagens and prostaglandin analogues on ovarian function and embryo viability in sheep. theriogenology 63:2523-2534. gunn, r.g. and t.j. maxwell. 1989. a note on the effect of the direction of live weight change about the time of mating on reproductive performance of greyface ewes. animal production 48:471-474. khaldi, g. 1984. variations saisonnières de l’activité ovarienne, du comportement d’oestrus et de la durée de l’anoestrus post-partum des femelles ovines de race barbarine: influence du niveau alimentaire et de la présence du mâle. thèse de doctorat d’etat. université des sciences et techniques du languedoc, académie de montpellier. martin, g.b., s. tjondronegoro, r. boukhliq, m.a. blackberry, j.r. briegel, d. blache, j.a. fisher and n. r. adams. 1999. determinants of the annual pattern of reproduction in mature male merino and suffolk sheep: modification of endogenous rhythms by photoperiod. reproduction, fertility, development 11:355-366. oldham, c.m. and d.r. lindsay. 1980. laparoscopy in the ewe: a photographic record of the ovarian activity of ewes experiencing normal or abnormal oestrous cycles. animal reproduction science 3:119-124. rekik, m. and m. gharbi. 1999. réponse des races à viande ovines locales en tunisie à la reproduction en âge précoce. tropicultura 16-17:64-69. rekik, m., n. lassoued and c. yacoubi. 2002. reproductive performances in ewe lambs of the queue fine de l’ouest breed and their d’man crosses following synchronisation. small ruminant research 45:75-78. rhind, s.m. and a.s. mcneilly. 1986. follicle populations, ovulation rates and plasma profiles of lh, fsh and prolactin in scottish blackface ewes in high and low levels of body condition. animal reproduction science 8:301-313. romeu, a., i. molina, j.a. tresguerres, m. pla and j.a. peinado. 1995. effect of recombinant human luteinizing hormone versus human chorionic gonadotrophin: effects on ovulation, embryo quality and transport, steroid balance and implantation in rabbits. human reproduction 10:1290-1296. spicer, l.j., j.p. hanrahan, m.t. zavy and w.j. enright. 1993. relationship between ovulation rate and concentrations of insulin-like growth factor-1 in plasma during the oestrus cycle in various genotypes of sheep. journal of reproduction and fertility 97:403-409. statistical analysis systems (sas) institute, inc., 1991. user’s guide, version 6.10. sas institute, inc., cary, nc, usa. thimonier, j. and p. mauléon. 1969. variations saisonnières du comportement d’oestrus et des activités ovarienne et hypophysaires chez les ovins. annales de biologie animale, biochimie, biophysique 9:233-250. viñoles, c. 2003. effect of nutrition on follicle development and ovulation rate in the ewe. doctoral thesis. swedish university of agricultural sciences, uppsala. wood, p.d.p. 1967. algebraic model of the lactation curve in cattle. nature 216:164-165. pdf995, job 6 _________________ *corresponding author. 47 agricultural sciences, 7(2):47-52(2002) © 2002 sultan qaboos university assessing risk from dnapls in fractured aquifers d.n. lerner1*, g.p. wealthall2, and a. steele1 1groundwater protection and restoration group, university of sheffield, mappin st, sheffield s1 3jd, uk 2british geological survey, keyworth, notts, uk abstract: chlorinated solvents are among the most widespread pollutants of groundwater. as dnapls (dense nonaqueous phase liquids), they can move rapidly and in complex patterns through fractures to reach and contaminate large volumes of aquifer, and then dissolve to cause significant pollution of groundwater. however, clean-up of dnapls in fractured rocks is virtually impossible and certainly expensive. risk assessment should be used to decide whether the pollution is serious enough to justify major expenditure on clean-up or containment. a key aspect of risk assessment for dnapls in fractured aquifers is to understand how deep they are likely to have penetrated through the fracture network. this paper addresses two aspects of such predictions: measuring fracture apertures in situ and the connectivity of fracture networks with respect to dnapls. fracture aperture is an in-situ field technique that has been developed and implemented to measure aperture variability and napl entry pressure in an undisturbed, water-saturated rock fracture. the field experiment also provided the opportunity to measure the wetting phase relative permeability at residual non-wetting phase saturation. the radio (radial aperture determination by the injection of oil) method employs a constant rate injection of a non-toxic napl into a fracture isolated by a double packer array. the method was applied at the field site in scotland, and measured apertures out to ~5m from the borehole. it showed that hydraulic aperture (from packer tests) was a poor estimator of the controlling aperture for dnapl movement. this is the first time such large-scale aperture measurements have been made, and the technique is the first which can provide useful aperture estimates for risk analysis of dnapl movement.network connectivity is a fundamental property of the fracture system. dnapl connectivity extends the concept to take account of the fluid properties. keywords: dnapl, fractured aquifers, chlorinated solvents, relative permeability, fracture aperture, network connectivity. !"#$%&!'()*+!,(-!'.(/0%&!1)&#2%&!3+!'45*6%&!,7*84%&!9((:;<=>? !"!#!$% !'&'()4%&!*&#+,&! !"#$%&'()*+$%,!'-$%./.01%23+"40)5%6'+% ! !'--./0%7%%%%%%%%%809:;1#%<'0=1#%>'?:* %!"#%$=%%$ %&!:*'=1#%>'()+*=1#%2)+,%-!:.1#%80/' %.00%8301'1#%4/#:21#%3.4),$%56789:;< %%%%%%%%%%%%%%%%%%%%!?%$ $%'(= %&.0(>%?#@-#%a+:*,%!?%$ $%809:;1#%b#:cd#%e1f%&:g:*1%h:i)j1#%k)9%2)i+ %4')jl$%8m.)2l%n')2=,%k))1#$ %%%%%%%%%%;1#%<'0)=1#%o:)*,%k)9%p()2))1%n$*),%%%%.0).q%4')jl%80)9:%-%%%%%%#. #%.()++%8m2r)=1#%!:sr1#%$) $%4/#:)21#%<*)"%$) %t*s))1#%6f %%%%%%%%u'0i1$%o:*)1#%v:)2 %89.+=1%4/#:21#%<*(l%o:*)1#%$m%8=-'=1#%.w's=1#%!00i,%p;+$%$=11#%x"')l%:)(9%$)' #%6#$%y04))2 %%%%%%%%%%o:*))1#%!')j)/#%z=) %$#%[0)\=,%.0)l#2)l%-%%%%%%%%%%%%%%%#%])=m%$#%v2) %89.)+ %e)1#%8)5#!21#%<*)"%^2)(,%%%%%8'(_%k9%4/#:21#%<*)"%n'0)2/ %%%%%%%%%%%%%%%%%%4/#:21#%<*(1%8(2=1'l%h:ij1#%>''(_%`l#.,$%za:=1#%k9%>'m2r)1#%8+5%b'0a%%8a!:1#%<*"%ca'=,$%8+.sr1#%%>'m2)r)1#%%%%%%%%%8+(j=1#$%8iij)=1#%!:sr1#%k9%4/#:21#%<*"%&:q"%`d%$%h:ij1#%8+5%$+'(,%b'0i1%80*ic%80=i,%]0(.,$%.+:.,%!,%2)i1 %?')=1'l%-%%%%%>2)-$#%2)i1%%%%%%%%%%%%%%%pw!%.0d1#%z(j=1#%e-:1#%2=m%pw.1#%e-:1#%8+f'3/%b'0i1%8)g.31#%')g+#%80)*i41#%8l.;))1#%-%<*"%80=i,%6f &h'+1#%$ %$0)i(.l%k=4 $%&$@+ %]_%$#%i2g%k9%u'5%.00%'(= %jl'?%&2+ %k%%e*m%4=+,%4/#:21#%-%<*"%]0(.,%!,%2i1 %%e1f%4r,%n:i?$%h:i_%b'0a%!,$%#2=*)'5#%k9%4i41#%k9%8i+..1#l!') #%%-%6'>%k'01$!20(1#%pi11#%6#%85#!21#%>.(m#%2a$ %%%%%%%"#:=1#%<*"%n'02/#%85#!"%k9%e #2s))5n%eo)w'q%!'0)+ %-%85#!21#%<*"%2+,&$#%2+,$%&.0(>%h:i_%u#2s)5'l%u:i,%85#!"% %%%%%%%%%%%=1#%.w's=1#%85#!"%k9%'( #2s)5n%4g9#%4'jl%n:i11#%8+5%.+2i,%e*m%&!"'i1#$%'(m:/%$) %e)1$d#%80)=i)1#%<*)"%$m%8=-' %%%%%4/#:)21#%<*)"%n'0)2/#%-%%%%%%%%%%%%%%%%%j+p5$%4/#:21#%<*"%80*g#:,%6#$%8iij)=1#%q'5$d#%k9%80)5'5#%80)g'q%8'()j1#%80*)g#:,%2)+, z/'=1#%$#%4/'21#%t/'rq%$=g)01%u:(3=1#-% lerner, wealthall, and steele 48 why do we care about dnapl in fractured aquifers? contamination of groundwater by dnapls, in particular the chlorinated solvents, has received much attention in recent years. although there are many sites where significant volumes of dnapl have been released (huling and weaver, 1991), their distribution in the subsurface remains uncertain. dnapls will spread in the subsurface, primarily under the influence of gravity, until the source term is depleted or the invading fluid is immobilised by capillary forces (kueper and mcwhorter, 1991; mercer and cohen, 1993). in fractured bedrock aquifers, where the dnapl is excluded from the matrix (ross and lu, 1999; wealthall, 2002), fluid movement will be limited to the interconnected fracture porosity. for many bedrock aquifers this is only 0.001-0.1% of the bulk volume of the rock mass (mackay and cherry, 1989). the underlying assumption of this work is that even a small amount of dnapl would travel along way in a fractured bedrock aquifer. dnapls dissolve to cause significant pollution of groundwater by their component chemicals. in the uk, the severity of groundwater pollution is determined by the risks to public health and the environment, and not by absolute concentrations. clean-up is only undertaken if the risks justify it. for example, a dnapl spill which only reaches shallow depths may pose risks to local receptors such as occupants of the site through vapour migration, local wells, and streams draining shallow groundwater. a spill which goes deeper will contaminate a larger volume of aquifer, and so contaminate deeper flowpaths. pollution is then likely to present risks to more distant receptors such as public supply wells and regional groundwater discharges. hence, it is important to understand the depth of penetration of dnapl spills for risk assessment. depth of penetration is controlled by the connectivity of the fracture network and fracture apertures. fracture aperture fracture aperture is a key parameter in assessing the movement of dnapls. since dnapls are usually non-wetting of rock relative to water, excess capillary pressure is required for them to displace the water and enter fractures; this excess is inversely proportional to the square of the aperture. whilst fracture network properties such as spacing and orientation can be measured in the field, there are few methods for characterising fracture apertures. hydraulic measurements of bulk permeability can be converted to hydraulic aperture (rutqvist, 1996), but require assumptions regarding the number of fractures encountered, and are not direct measurements of physical aperture. laboratory measurements of fracture aperture have been performed by injecting napls into fractures and back calculating the fracture apertures from the entry pressure required to initiate flow (jorgensen et al., 1998; hinsby et al., 1996). the objective of this study is to describe and implement an in-situ field technique to measure aperture variability and napl entry pressure in a naturally occurring, water-saturated fracture. the technique is applied in a single borehole in fractured breccia and sandstone. in situ tests have significant advantages over laboratory tests in that the fracture aperture and infills are undisturbed, and the fracture is subject to natural compressive stress conditions which are known to influence flow characteristics (reitsma and kueper 1994). the new field test technique uses a controlled injection of a non-toxic napl into a fracture isolated by a double packer array. the test is called the radio (radial aperture determination by the injection of oil) test. the resulting transient pressure signature is reverse modelled using a two-phase flow numerical model to produce an aperture profile over several metres from the borehole (steele, 2001). the radio experiment generates real two-phase flow conditions in an in situ fracture by injection of a napl into a hydraulically isolated fracture. regulatory permission was obtained for an intentional release of up to 50l of triglyceride (as sunflower oil) directly into the aquifer. sunflower oil is an excellent dnapl surrogate for pressure controlled field experiments where the density of the fluid will not significantly influence the experimental results. it is a harmless light non-aqueous phase liquid (lnapl) foodstuff with low toxicity and ecotoxicity whose degradation pathway to carbon dioxide and water is rapid and well understood. releases of hydrocarbons directly to groundwater are strictly controlled, and this is the first time that such an experiment has been permitted to the authors’ knowledge. field site: a research site has been established on the western edge of the dumfries basin in south-west scotland. the basin is of permian age, and consists of over 1000 m of sandstones and breccias. the breccia was derived from a hardened muddy flood gravel or debris flow and has little inter-granular permeability. the dumfries basin is a key water resource in scotland, and produces over 50% of the local public water supply (ball, 1997). assessing risk from dnapls in fractured aquifers 49 40 50 60 70 80 90 100 110 0 10000 20000 30000 40000 50000 60000 70000 time since start of napl injection (seconds) p nw fo r al l s im ul at io ns e xc ep t h yd ra ul ic ap er tu re ( k p a) 600 700 800 900 1000 1100 1200 p nw fo r hy dr au lic a pe rt ur e si m ul at io n on ly (k p a) field data variable aperture model match simulation 1 matched aperture + 5% simulation 2 matched aperture -5% simulation 3 volume averaged aperture simulation 5 hydraulic aperture simulation 4 (second y axis) figure 1. transient radio test results and matches. results: this experiment was the first radio experiment at the field site and tested the interval 13.76 m to 14.17 m below ground level which consisted only of breccia with no sandstone present. the interval hosted a single sub-horizontal fracture at 13.99 m with a dip of 19°. the pnw profile (figure 1) shows three distinct pressure increases during the field test which lasted 73820 seconds, approximately 20.5 hours. these pressure steps were replicated in simulation 1 using the fracas fully compositional simulator with the resultant matched aperture profile possessing three aperture constrictions. to demonstrate the accuracy of the modeled match, the results of simulations 2 and 3 are plotted on figure 1 with aperture profiles 5 % smaller and greater than the matched profile respectively. these runs clearly show that the resultant aperture profile presented is a comparatively accurate match to the field data. the smallest aperture in the matched profile is 43 µm, and it is this aperture constriction that causes the large increase in pnw at 27000 seconds, consequently controlling the injection pressures for most of experiment 1. invasion of this controlling aperture is required to allow napl to migrate across the variable aperture fracture and we therefore denote the capillary pressure value at the leading edge of the napl to be the entry pressure pe. the radio test therefore provides a field estimate of macro scale pe under natural flow, stress and infill conditions. note that 43 µm is the entry pressure aperture for distances greater than 2 m from the borehole. for distances less than 2 m, the entry pressure aperture is approximately 125 µm, illustrating clearly that the entry pressure aperture is a function of scale. the new radio test can provide a much more detailed approximation of in situ fracture aperture than conventional hydraulic testing techniques, although it is more complicated to perform and analyse. the major constraints are the assumption of radially isotropic flow in a single horizontal fracture and the use of a literature value for swr in the numerical analysis. we have shown that aperture variations up to 5 m from the borehole can be detected and the macro scale entry pressure resolved. network and dnapl connectivity description of connectivity in the literature is generally limited to the physical fracture network, defined in this study as network connectivity. a more useful approach would be to define a connectivity expression based on the fluid active fractures, which form a sub-set of the entire fracture network. this study considers the influence of capillary pressure on the connectivity of dnapls in fracture networks. it therefore addresses connectivity which is both contaminant and rock specific. the connectivity study lerner, wealthall, and steele 50 establishes a quantitative connectivity expression for dnapl pollutants in fractured rock, which may help to define those formations that are at greatest risk from a dnapl spill. a probabilistic connectivity expression, cn, is derived from multiple fracture network simulations and is based on the ratio of fractures occupied by the invading fluid to the total number of fractures in the network. the methodology has three main elements: i) simulating geometrical models by systematically varying fracture geometry, density and length in stochastically generated 3-d fracture networks; ii) calculating values of cn; and iii) comparing cn with published connectivity indices. fieldwork at the dumfries field research site involved synthesis of existing hydrogeological data and application of multi-scale fracture characterisation methods. quantitative field measurements of fracture parameters were obtained using 1-d scanline surveys, 2-d tracemaps (priest and hudson, 1981); (gillespie et al., 1993) and aperture profiling (renshaw, 1995). lithological and fracture logs from the rock core samples were compared with borehole televiewer logs to identify fracture type, intensity, orientation, dip and dip direction. packered pumping tests were used to determine vertical profiles of aquifer transmissivity and calculate hydraulic aperture (wealthall and lerner, 2000). results: the fracture network spatial geometry was reconstructed using a 3-d stochastic discrete fracture network model (dershowitz et al., 1988). the underlying principle of this approach is that fracture network statistics, measured at outcrop and in boreholes, can be used generate multiple realisations of fracture networks with equivalent statistical properties. model calibration is accomplished using an inverse approach where the model realisations are sampled using simulated, yet comparable, methods to those used in the field (boreholes or traceplanes). the simulated data are then compared to the real data and adjusted till an acceptable match with the observed data is achieved. each model realisation is just one possible representation of the fracture network from which the statistical parameters were derived. the fracture network in each realisation becomes the conductive elements for simulating fluid flow. a fully three-dimensional, macroscopic invasionpercolation model (wealthall, 2002) simulates the invasion of a dense non-aqueous liquid (dnapl) in a fractured rock aquifer. the model is used to calculate bulk retention capacity and connectivity in fracture networks generated by the discrete fracture network model. figure 2 shows an example of the results from the process, demonstrating how the dnapl connectivity of a rock mass varies with capillary pressure. the lowest value of bulk retention capacity represents the initial entry of pce dnapl in the fracture network at crmin, and continues to increase until the entire fracture network that is connected to the source term is invaded at crmax. figure 2. principal features of the connectivity ratio plot for a single model realisation. the markers on the x-axis indicate the capillary pressure increments. -0.20 0.00 0.20 0.40 0.60 0.80 1.00 100 1000 10000 100000 capillary pressure (n m-2) cr min cr max -0.20 0.00 0.20 0.40 0.60 0.80 1.00 100 1000 10000 100000 c on ne ct iv ity r at io , c r assessing risk from dnapls in fractured aquifers 51 ninety-nine models were generated with 340 fractures per realisation and, depending on individual model geometry, up to approximately 1500 fracture intersections. crmin for the bulk of the 3dip model realisations is 800 nm-1, equivalent to a fracture aperture of 106 !m. hypothetical spill volumes were applied to the bulk retention capacity distributions to define the depth of penetration (figure 3). in the absence of detailed information on the geometry of the aquifer in the region of the research site, a simple cubic shaped aquifer was defined to estimate potential dnapl penetration depth. dnapl penetration depth is inversely proportional to capillary pressure. this reflects the low storage capacity at low capillary pressures and indicates that an given volume of dnapl will travel much further in a low storage capacity rock mass than in a high storage capacity system. capillary values that are in the range between the crmin and crmax may lead to high dnapl penetration depths. these values are summarised in table 1 for the given hypothetical spill volumes of pce dnapl (outliers are not included in this table). the fracture network in this permian sandstone basin is well connected. a high capillary pressure release (30 cm pce pool height) would be able to invade 90 to 100 % of the fracture network in all model simulations, whereas the low capillary pressure release (6 cm pce pool height) would result in limited invasion of the fracture network and therefore low connectivity relative to the dnapl. the fracture network in this permian sandstone basin is well connected. a high capillary pressure release (30 cm pce pool height) would be able to invade table 1 bulk retention capacity and dnapl penetration depth ranges. low capillary pressure release high capillary pressure release capillary pressure ((n m-1) 799 3197 equivalent pce dnapl pool height (m) 5 20 bulk retention capacity (m3 m-3) 8x10-9 20 pce dnapl storage capacity (ml m-3) 0.008 2x10-5 200 l spill: dnapl penetration depth (m) 325 20 50000 l spill: dnapl penetration depth (m) 2050 146 90 to 100% of the fracture network in all model simulations, whereas the low capillary pressure release (6 cm pce pool height) would result in limited invasion of the fracture network and therefore low connectivity relative to the dnapl. discussion understanding phase occupancy in a fracture network at a given capillary pressure is critical to predicting the proportion of the fracture network that may be impacted by a dnapl release. given further information on residual saturation in individual fractures, an estimate of the volume of rock impacted by a finite volume dnapl release can be inferred. a spill of 200 litres (drum volume) would penetrate to between 23 and 325 m depth, whereas a catastrophic release of 50,000 litres (tanker volume) would penetrate to between 146 and 2,050 metres depth. both estimates assume no changes in fracture properties with depth, as this study was limited to 10 100 1000 10000 100 1000 10000 100000 capillary pres sure (n m -2) d n a p l p e ne tra tio n d e pt h (m ) 50,000 litre tank 200 litre drum figure 3. effect of hypothetical spill volume on dnapl penetration depth. lerner, wealthall, and steele 52 fracture networks that were characterised in the near subsurface. many fractured bedrock aquifer systems are developed in deep sedimentary basins, and we anticipate that connectivity and depth of penetration will vary spatially as a function of the deposition, digenesis and tectonic history of the basin. the significant findings of this study are that: • dnapl-effective apertures can be measured in the field, which will increase the confidence in forecasting dnapl migration through fractured rocks. • uncertainty, inherent in representing the fracture network, leads to a wide range of values for bulk retention capacity and dnapl penetration depth, particularly at low capillary pressures. • the inferred dnapl penetration depth is inversely correlated with capillary pressure. • capillary pressures, equivalent to pce dnapl pool heights of between 5 and 20 cm pose the greatest risk of deep dnapl penetration to the fractured bedrock aquifer in this study. • comparison of connectivity measures from synthetic and real fracture networks suggests that, at least in this study, natural fracture networks in sedimentary bedrock aquifers are well connected. • dnapls can be expected to penetrate deeply into fractured rocks, with lithological controls being the main barrier to downward migration. such deep penetration leads to a high risk of polluting large volumes of groundwater, and significant risks to health and the environment. acknowledgements funding for this work was provided by the uk engineering and physical sciences research council. dupont (uk) ltd is thanked for access at their dumfries site. the support of the environment agency and ici chemical and polymers ltd is acknowledged. fracman was used under an academic license agreement with golder associates inc. references ball, d.f. 1997. the dumfries basin aquifer: hydrogeology. in: upland groundwater, fox, i. (ed), uk groundwater forum, edinburgh, uk. dershowitz, w.s., g. lwee, j.e. geier, t. foxford, p. la pointe, and a. thomas. 1988. fracman. interactive discrete feature data analysis, geometric modeling, and exploration simulation. user documentation. gillespie, p.a., c.b. howard, j.j. walsh, and j. watterson. 1993. measurement and characterization of spatial distributions of fractures. tectonophysics 226: 113-141. hinsby, k., l.d. mckay, p. jorgensen, m. lenczewski, and c.p. gerba. 1996. fracture aperture measurements and migration of solutes, viruses, and immiscible creosote in a column of clay-rich till. ground water, 34:1065-1075. huling, s.g. and w.w. weaver.1991. dense nonaqueous phase liquids. epa/540/4-91-002, united states environmental protection agency, washington. jorgensen, p.r., k. broholm, t.o. sonnenborg, and e. arvin. 1998. dnapl transport through macroporous, clayey till columns. ground water 36:651-660. kueper, b.h. and d.b. mcwhorter. 1991. the behavior of dense, nonaqueous phase liquids in fractured clay and rock. ground water 29: 716-728. mackay, d.m. and j.a. cherry. 1989. groundwater contamination pump-and-treat remediation. 2. environmental science & technology 23: 630-636. mercer, j.w. and r.m. cohen. 1993. dnapl site evaluation, 6. c.k.smoley. crc press, inc. 200 corporate boulevard, nw., boca raton, florida 33431, boca raton, 107-163 pp. priest, s.d. and j.a. hudson. 1981. estimation of discontinuity spacing and trace length using scanline surveys. international journal of rock mechanics and mining sciences 18: 183-197. reitsma, s. and b.h. kueper. 1994. laboratory measurement of capillary-pressure saturation relationships in a rock fracture. water resources research 30: 865-878. renshaw, c.e. 1995. on the relationship between mechanical and hydraulic apertures in rough-walled fractures. journal of geophysical research-solid earth 100(b12):24629-24636. ross, b. and n. lu. 1999. dynamics of dnapl penetration into fractured porous media. ground water 37:140-147. rutqvist, j. 1996. hydraulic pulse testing of single fractures in porous and deformable hard rocks. quarterly journal of engineering geology 29:181. steele, a. 2001. dnapl migration in variable aperture fractures. phd thesis, dept of civil and structural engineering, university of sheffield, uk. wealthall, g.p. and d.n. lerner. 2000. a volume-based approach to predicting the fate of dnapls in fractured aquifers. groundwater: past achievements and future challenges. a a balkema, pp. 843846. wealthall, g.p. 2002. predicting dnapl source zones in fractured rock. phd thesis, dept of civil & structural engineering, university of sheffield, uk. ____________________________________________________ received august 2002. accepted november 2002. sultan qaboos university journal for scientific research agricultural and marine sciences, 11 s.i., 1-9 (2006) ©2006 sultan qaboos university 1 financial performance of irrigation associations: selected cases from turkey erol h. cakmak*1, faruk cenap erdogan2, mehmet cetik1 1department of economics, middle east technical university, ankara 2operation and maintenance department, state hydraulics works (dsi), ankara abstract: the objective of the study was to trace the performance of selected irrigation associations after the transfer of operation and maintenance (o&m) activities from the state to the farmers. four irrigation associations were selected according to the regional and cropping pattern diversity. the area of the selected associations made up slightly more than 5 percent of the total transferred area. the data for the different types of revenues and expenses of the associations were obtained from the annual reports of the associations to the state hydraulic works. results suggest that irrigation associations are able to fulfill irrigation tasks to a large extent using enhanced equipment. fee collection rates are at improved levels, despite delays in payments, mainly due to the mismatch of the financial and production calendars. dominant cropping patterns for cotton lead to higher and increasing o&m expenditures compared to cereals. although the transfers increased the adjustment ability of farmers to exogenous factors, the findings suggest that it is still too early to decide on the sustainability of the transfer program. keywords: irrigation, management transfer, fee collection, ex-post evaluation. introduction the legal framework allowing the transfer of management responsibility of public irrigation schemes to local control dates back to 1954. smallscale irrigation schemes which were isolated and far from the operation and maintenance (o&m) units of state hydraulic works (dsi) had been initially transferred to users in the early sixties. these gradual but pioneering steps formed the basis for the ongoing implementation of the participatory irrigation management (pim) concept in turkey. *corresponding author. e-mail: cakmake@metu.edu.tr دراسة الجدوى المالیة لعینة من الجمعیات المائیة في تركیا إرول شاكماك و فاروق إردوغان ومحمد ساتیك ویل السلطة لھا من طرف الدولة في مجال الصیانة وإدارة المنشئات المائیة. تمثل الخالصة: تھدف ھذه الدراسة إلى تحلیل الجدوى المالیة ألربعة جمعیات مائیة بعد تحویل السلطة لھا من طرف الدولة في مجال الصیانة وإدارة المنشئات المائیة. تمثل الخالصة: تھدف ھذه الدراسة إلى تحلیل الجدوى المالیة ألربعة جمعیات مائیة بعد تحویل السلطة لھا من طرف الدولة في مجال الصیانة وإدارة المنشئات المائیة. تمثل المساحة المروریة تحت سلطة ھذه األربع جمعیات نحو ٥ بالمائة من مجموع المساحة التي تم تحویل إشرافھا إلى الجمعیات. المعطیات التي تم تحلیلھا مقتبسة من التقاریر السنویة للجمعیات. تظھر النتائج أن الجمعیات قادرة على تحمل مسؤولیة إدارة المیاه وذلك بإستخدام معدات متقدمة. مساھمة المزارعین في دفع مستلزماتھم مقابل الخدمات إرتفعت مقارنة لما قبل تحویل السلطة إلى الجمعیات. لكن رغم أن تحویل السلطة یظھر تحسن تعامل المزارعین مع المعطیات الخارجیة یبقى من المبكر الحكم على ما إذا ستكون التجربة مستدیمة. cakmak, erdogan and cetik 2 the principal aim of this study was to trace the path of several indicators for four irrigation associations (ias) after the transfer. the ias were selected from different regions with diverse cropping patterns. the next section provides an overview of o&m transfers in turkey. the characteristics of the selected ias are presented in the third section. the progress in irrigation indicators is the topic of the fourth section. in the subsequent two sections, the financial flows of the ias are analyzed. the last section is reserved for the summary of findings and conclusions. transfer of irrigation schemes in turkey water user groups (wugs), formed by the farmers in the 1960s, were the major contributing factor for an easy and effective transfer of o&m. wugs had been active in 40 percent of the total dsi-controlled area before the start of the accelerated transfer program (uskay, 1999). wugs participated in minor o&m responsibilities in the schemes in return for a certain discount on water charges. the policy of dsi before 1993 focused on transferring small and isolated schemes and only 72,000 hectares (ha) were transferred until 1993 (table 1). the economic crisis in 1994, coupled with long lasting fee determination and collection problems, caused dsi to shift towards an accelerated transfer of large dsi-managed schemes. the efforts of dsi were supported by the world bank. the process continued without loosing momentum, reaching more than 90 percent of the planned transfer area, with an eventual size of 1.9 million ha by the end of 2004. the main underlying reason for the accelerated transfer program was an unsustainable financial burden of the o&m to the dsi and, eventually, to the government budget. fee collection rates were, for instance, on average at 38 percent between 1989 and 1994 (svendsen and nott, 1999). the start of the privatization era and satisfactory performance of the transferred schemes were the reinforcing factors. village legal entities, municipalities, irrigation associations and cooperatives are eligible organizations for the transfer. ias dominate in terms of total and average irrigated area, controlling 91% percent of total transferred area, with an average of 5,108 ha (table 2). the area of an ia may be as large as 30,000 ha. irrigation associations are responsible for providing all services related to operation and maintenance and for bearing the costs of providing these services. however, neither water rights nor ownership of facilities are transferred to the ias and the property rights remain with the state. table 1. transfer of irrigation schemes, 1992 – 2004 (ha). years planned modified plan realization annual cumulative total annual cumulative total annual cumulative total 1992 1,552 62,620 1993 9,422 72,042 1994 103,958 176,000 103,958 176,000 195,320 267,362 1995 140,000 316,000 282,638 550,000 711,214 978,576 1996 120,000 436,000 171,424 1,150,000 211,758 1,190,334 1997 120,000 556,000 59,666 1,250,000 88,705 1,279,039 1998 120,000 676,000 70,961 1,350,000 204,892 1,483,931 1999 120,000 796,000 66,069 1,550,000 45,523 1,529,454 2000 120,000 916,000 70,546 1,600,000 89,215 1,618,669 2001 84,000 1,000,000 31,331 1,650,000 45,061 1,663,730 2002 50,000 1,050,000 36,270 1,700,000 31,006 1,694,736 2003 50,000 1,100,000 55,264 1,750,000 131,509 1,826,245 2004 50,000 1,150,000 43,755 1,870,000 34,724 1,860,969 source: dsi, 2005. financial performance of irrigation associations: selected cases from turkey 3 general characteristics of the selected irrigation associations the selected ias have relatively large areas compared to other transferred schemes and have a better representation of the region (table 3). another critical factor in the selection process was the subjective evaluation of the quality of data in the annual reports of the ias to dsi. cotton is the dominant crop in both soke and tektek (table 4). cumra plain is the first modern irrigation scheme in turkey. cereals cover most of the total area, though with a declining share. recently, the cultivation of beans and vegetables has been increasing. tektek is in the southeast anatolia project (gap) region. kosreli is located in the cukurova region and has the possibility of obtaining two crops in one year. the cropping pattern reveals this possibility and indicates high substitutability of soybean and corn as second crops. the area covered by this study totals 85,000 hectares, constituting slightly higher than 5 % of the area covered by all ias in turkey. two main types of irrigation indicators are recorded in the annual reports of ias (dsi, 2004). the irrigation ratio simply indicates the area actually supplied with water over the area controlled by the association. however, associations may also support the irrigation of the land in the neighborhood, which is not included in their controlled area. the total irrigation ratio is the ratio of the total area irrigated by the association divided by the controlled area. both ratios are reported in table 5. all four associations were able to irrigate more than 90 % of the controlled area. in addition, two of the associations, namely soke and cumra plain were able to provide water outside the controlled area. the impact of the drought can be easily seen in the irrigation ratios in 2001, especially under the low precipitation conditions in the central anatolia, only 48 percent of the irrigable area were irrigated. on the whole, the associations were able to fulfill their irrigation responsibilities to a large extent, except in the case of drought conditions. however, it must table 3. main features of selected irrigation associations. name of ia start of operation year of transfer area (ha) region share in dsi region (%)geographic dsi soke 1981 1998 26,000 aegean xxi 100.0 cumra plain 1912 1995 24,922 central iv 42.0 tektek 1995 1998 15,841 east med. xv 13.4 kosreli 1976 1995 18,300 southeast vi 20.6 source: dsi, 2004. table 4. cropping pattern of the ias (%). year soke tektek comra plain kosreli cotton sunflower cotton cereal cereal sugar beet beans & vegetable soybean corn vegetable garden 1999 97 2 74 26 na na na na na na 2000 72 27 na na 88 12 57 19 2001 99 91 9 85 11 1 16 70 4 2002 94 5 89 11 68 12 16 56 27 6 2003 94 3 75 23 77 12 7 27 59 4 source: dsi, 2004. cakmak, erdogan and cetik 4 be borne in mind that high irrigation ratios are not solely a consequence of the transfer of o&m, because transferred irrigation associations were already recording high irrigation ratios prior to the transfers (doker et al., 2003). revenues and fee collection rates of ias the sources of revenue of the associations can be classified as: i) irrigation fees; ii) membership fees collected only once as the start-up capital of the association after the transfer; iii) revenues from the supply of goods and services, i.e. renting out machinery and equipment; and iv) and fines and interest income for the delayed fee payments. the total and per ha revenues in 1994 prices are presented in table 6 to reflect the changes in real terms. the nominal figures converted to us dollars are also provided in table 7 to provide an idea about the size of operations that the associations are involved in. table 7 provides the total revenues in us dollars. the total revenues from irrigation fees rose by about 20% in soke during the considered period. the drastic decline in 2001 was due partly to drought conditions, but mainly because of a major macroeconomic crisis, followed by a strict implementation of a structural adjustment and stabilization program backed by imf in 2001. the us dollar figures have similar implications as well, but with different rates of changes due to the floating exchange rate regime in turkey. apart from kosreli which had a lagged impact, the associations were able to recover the drop in revenues in 2001 by 2003. the association was able to recover from table 5. irrigation ratios of the ias (%). year soke cumra plain tektek kosreli irrigation ratio total irrigation ratio irrigation ratio total irrigation ratio irrigation ratio total irrigation ratio irrigation ratio total irrigation ratio 1998 96.2 98.5 92.0 128.3 69.7 n.a. 95.2 97.7 1999 96.7 133.6 96.0 138.7 100.0 109.9 93.9 96.9 2000 92.1 94.5 96.0 144.5 87.1 97.0 92.2 94.7 2001 83.0 98.6 48.2 44.2 86.7 87.0 93.6 95.7 2002 94.7 96.5 92.0 140.6 93.6 94.0 93.7 94.9 2003 100.0 102.5 92.0 150.1 93.3 94.8 92.0 93.2 ave 93.8 104.0 86.0 124.4 88.4 96.5 93.4 95.5 source: dsi, 2004. table 6. revenues of ias (in 1994 prices). year soke cumra plain tektek kosreli revenue per ha (tl 000) total revenue index revenue per ha (tl 000) total revenue index revenue per ha (tl 000) total revenue index revenue per ha (tl 000) total revenue index 1997 4.2 100.0 7.8 100.0 1998 8.4 100.0 3.7 115.6 4.2 100.0 9.0 112.2 1999 7.1 115.0 5.7 191.6 6.0 141.8 18.0 223.4 2000 12.9 148.2 5.0 177.5 8.2 184.8 11.2 136.0 2001 7.4 88.5 11.5 132.6 9.1 188.4 16.0 196.5 2002 9.1 106.8 5.9 199.0 11.3 252.7 7.5 91.9 2003 9.5 118.0 5.0 189.7 7.2 152.9 12.2 146.3 source: dsi, 2004. financial performance of irrigation associations: selected cases from turkey 5 the 2001 economic crisis in 2003. it should be noted that, in addition to the macroeconomic crisis, the longlasting drought was another factor contributing to the decline of revenues in 2001. the principal objective of the stabilization program which started in 2001 was to achieve budget discipline, and hence the budgetary expenditures were severely constrained. the implication of the program for the agricultural sector was a drastic decline of the government intervention to the agricultural markets. the associations response to the decline in commodity prices as a result of diminished government intervention was to decrease the average irrigation fee by about 15% from 1999 to 2001, (table 8). lastly, it is worth noting that the share of fines and interest income in total revenue was very low. compared to other regions, it seems that the farmers of the soke irrigation association (in the aegean county) respect the payment schedules more than those in the rest of the country. in cumra, in addition to irrigation fees, interest income and fines constitute a considerable share (up to 25%). the impact of the drought period was heavily felt in cumra, and rainfed agriculture increased in 2001. the average fee for water declined from us$ 10 to us$ 7.8 per ha. however, the recovery was quick. the total income was more than its pre-crisis level in 2002. the increase was mainly due to an increase in total irrigated land (from 12,005 ha in 2001 to 35,052 ha in 2002) and increased average fee for water (from us$7.8 in 2001 to us$ 18.7 per hectare in 2002). the effect of the economic crisis on tektek was quite limited. the association’s real income increased in 2001. in kosreli, fines and interest income had a significant share in the total revenue. revenue from the irrigation fees declined drastically from 1999 to 2000, with no significant change in total irrigated area. in contrast, the effect of the crisis seemed to be almost non-existent, since total income increased by more than 40% in 2001 (table 6). interestingly, the association experienced a loss in income in 2002, despite no significant change in total land irrigated and a real increase in average fees for water. however, total revenue recuperated in 2003. overall, irrigation fees constituted the major item in the total income. membership fees and revenues from the supply of goods and services stayed at negligibly low levels. in some associations, fines and interest income had noticeably high shares in total income, implying considerable delays in fee payments. changes in average fees for water, total irrigated land and the economic crisis have been key factors determining the amount collected as irrigation fees. yearly fee collection rates alone may be a misleading criterion by which to evaluate the table 7. total revenues of ias (us$ thousand). year soke cumra plain tektek kosreli 1997 494.7 680.5 1998 1,111.7 622.5 345.1 830.8 1999 1,126.4 908.5 431.2 1,456.4 2000 1,347.4 781.6 521.6 823.7 2001 582.4 422.6 384.9 861.3 2002 894.4 807.1 657.2 512.9 2003 1,335.1 1,039.5 537.1 1,102.5 source: dsi, 2004. table 8. average cost of irrigation water. year soke comra plain tektek kosreli tl/ha us$/ha tl/ha us$/ha tl/ha us$/ha tl/ha us$/ha 1999 8034.2 36.7 2190.2 10.0 5738.5 26.2 na na 2000 na na 2342.8 10.0 na na 5665.8 24.1 2001 6784.0 20.9 2532.8 7.8 9892.9 30.4 5976.8 18.4 2002 5782.0 22.6 4772.5 18.7 9438.5 36.9 6368.3 24.9 2003 6697.3 35.4 4835.1 25.6 6379.7 33.7 7240.0 38.3 source: dsi, 2004. cakmak, erdogan and cetik 6 performance. it should be noted that payments in the selected associations are mostly due from october to december, i.e. in one installment towards the end of the accounting year. a delay of even a couple of weeks would shift the fee payment to the new accounting year. hence, given any possible shifts of payments into the following accounting period, collection rates are further calculated by dividing all fees collected in the last two years by total fees assessed in the same two years. the results are presented in the tcr (total collection rate) column in table 9. the results for soke support the fact that some payments were postponed to the following accounting period. the selected associations reveal better performance in fee collection rates than in the preaccelerated transfer period with an average of 38% (svendsen and nott, 1999). on the other hand, collection rate averages, according to dsi staff, were generally supposed to be more than 90%, considering all associations in the country. nevertheless, the sample in this study constitutes an area of only about 5% of the total. nevertheless, further monitoring efforts regarding this issue seems to be necessary for enhanced fee collection performance. expenditures expenditure items are elaborated under three main sub-sections; operation and maintenance costs, vehicles and equipment purchases and, lastly, personnel expenditures. operation and maintenance expenditures per hectare o&m expenditures are presented in figure 1. o&m costs increased continuously and quite severely until 2001 in soke, despite an abrupt depreciation of the domestic currency in the same year. the o&m costs then declined and became fairly stable in last two years. operation costs took greater share in total o&m costs until 2001, with the opposite occurring in the last two years. the operation costs per irrigated hectare increased by almost four fold while the maintenance costs increased even faster. as a result, the share of operation costs in total o&m costs decreased from 87 table 9. irrigation fee collection rates (%). year irrigation associations soke comra plain tektek kosreli cr tcra cr tcr cr tcr cr tcr 1998 51.14 na 55.6 na 45.0 na 1999 37.8 na 10.60 63.6 65.4 80.5 0 132.1 2000 73.2 90.7 10.30 42.6 82.0 100.0 100.0 190.6 2001 80.3 102.9 15.17 93.2 79.5 100.0 44.8 209.6 2002 73.2 91.1 16.73 68.2 78.1 101.4 16.6 104.3 2003 79.9 95.2 40.00 58.8 80.4 96.4 37.7 44.0 ave 69.0 95.0 24.00 65.3 73.5 95.7 40.7 136.0 a total collection rate (tcr) for year t = (fees collected in years t-1 and t)/(fees assessed in years t-1 and t). source: dsi, 2004. figure 1. operation and maintenance expenditures per ha. source: dsi, 2004. financial performance of irrigation associations: selected cases from turkey 7 to 47%, while the share of maintenance costs increased from 13 to 53% in six years. the reversal of the shares did not show a regular trend, implying a restructuring period after the transfer process. the rise in the share of maintenance costs may be considered to be a normal process for the association towards taking over full responsibility of maintenance and repair that requires higher use of labor, machinery and equipment. it can be seen in table 10 that soke expanded its machinery and equipment availability. hence, the rise in maintenance costs in amount and share of total o&m costs can be attributed to the fact that the transfer process has been proceeding properly. however, it would be desirable to have the expansion of the maintenance costs coupled with no significant increase in operation costs to achieve a higher level of cost effectiveness in the transfer process. on the other hand, the increase in the revenue of the association was not at par with the increase in the costs. the total income of the association was about 10 times the costs of o&m in 1998, but this figure declined to 1.29 times the o&m costs in 2003. a similar trend was observed in the ratio of income over total expenses (fig. 2). operation costs in cumra decreased regularly, both in real terms and in terms of the share of total o&m expenditures, until 2001. operation costs per irrigated ha in 2003 were almost a fifth of those in 1997. in contrast, maintenance costs per irrigated ha almost doubled during the considered period; 2001 was an exceptional year for cumra since total irrigated land was merely 12,000 ha, doubling all relevant ratios. income figures for cumra displayed better performance than to soke. the ratio of income over total o&m costs showed an increasing trend in the considered period, indicating that income can cover more of the total o&m costs over time. figure 2. income over total expenses. source: dsi, 2004. table 10. vehicles and other equipment. year soke cumra plain total irrigation area (ha) heavy vehicle other vehicle computers & othera equipment total irrigation area (ha) heavy vehicle other vehicle computers & othera equipment 1998 25615 na na na 31980 1 4 8 & 35 1999 34751 1 2 1 & 32 34556 3 5 6 & 35 2000 24561 5 5 1 & 59 37020 4 8 6 & 42 2001 25735 5 5 1 & 62 12005 5 8 6 & 42 2002 25090 5 6 6 & 54 35052 5 8 8 & 42 2003 26649 5 6 7 & 54 39410 8 11 8 & 51 tektek kosreli 1998 15841 2 & 33 17870 2 5 3 & ---1999 15773 1 1 3 & 42 17739 1 8 3 & 29 2000 14987 1 2 3 & 48 17328 2 5 3 & 28 2001 13780 1 2 4 & 47 17505 2 7 3 & 28 2002 14894 1 1 4 & 47 17365 2 8 3 & 28 2003 14019 2 4 & 47 17062 2 5 3 & 28 a other equipments include two-way radio systems, motorcycles, trailer, etc. other vehicles are tractors, automobiles and lorries. source: dsi, 2004. cakmak, erdogan and cetik 8 in tektek, the share of operation costs in total o&m costs was still at a considerable level in 2002 with a value of 69%, but declined thereafter. the share of maintenance costs in total o&m costs declined until 2002, but increased in 2003. due to a tight budget, the association was not able to expand its machinery and equipment (table 10). in kosreli, maintenance cost items generally constituted above 20% of total o&m costs. kosreli did not expand its equipment, although it was able to generate sufficient funds to acquire more equipment of its own (table 10). the association has, on average, the best rate of income over total expenses and income over total o&m costs ratios (291 and 342 %, respectively). further, the association did not increase its personnel expenditures since 2000 (fig. 3). overall, the selected associations indicate generally two trends in the o&m costs. the first one, which is observed in soke and tektek, shows a continuous increase in the o&m costs, both in real terms and per irrigated hectare, but this was disturbed slightly because of the economic crisis. the second trend can be ascribed to the remaining two irrigation associations that were on a stagnant or declining path in the o&m costs; in cumra, operation costs and in kosreli, in maintenance costs declined more severely. vehicles and other equipment expenditures all associations acquired new computers over the years (table 10). soke and cumra both expanded their ownership of heavy vehicles (excavators, graders, tractors, automobiles and lorries) to cope with the tasks of lifting, transport, etc. on their own. both associations use, on average, one heavy vehicle for 5,000 ha. kosreli and tektek seem to be relatively stable in the number of vehicles and other equipment. tektek increased the number of motorcycles and radio system units, while kosreli expanded only in tractors and lorries. in general, soke and cumra tended to increase their self-maintenance capability through increasing their equipment availability, while tektek and kosreli did not choose to do so. nevertheless, the stable trend in ownership of equipment may be highly related with the relatively smaller net irrigation areas of tektek and kosreli, compared to soke and cumra. personnel expenditures the personnel expenditures per ha and the share of the personnel expenditures in total are presented in figures 3 and 4, respectively. all selected irrigation associations, except soke, increased the number of permanent staff. soke decreased the number of permanent personnel but increased the average net salary (in us$). however, the other associations increased the number of personnel and decreased the average net salary (in us$). correspondingly, soke is the most labor efficient association studied. on average, soke employs 1.25 persons per 1000 ha, excluding the year 1999, when over 400 temporary workers were employed. cumra employs 1.31 persons; tektek, 3.59 persons; and kosreli 3.08 persons per 1000 ha. overall, it can be stated that all irrigation associations are labor efficient with respect to svendsen’s (2001) calculations figure 3. total personnel expenditures (per ha). source: dsi, 2004. figure 4. total personnel expenditures over total expenses. source: dsi, 2004. financial performance of irrigation associations: selected cases from turkey 9 for 1999, which indicated that dsi and irrigation associations used 70.4 and 4.7 persons per 1000 ha, respectively. soke and cumra’s personnel policy coincided with the fact that they expanded in machinery and equipment since they employed more of qualified workers, e.g. operators, technicians. these associations were, accordingly, the most labor efficient ones. factor substitution effect was clearer in soke. in addition, soke and cumra also recorded the lowest personnel expenditure per ha (fig. 3), and the lowest share of personnel expenditure in total expenses (fig. 4). conclusions it is observed that the irrigation associations of soke and tektek revealed more or less similar trends with respect to o&m costs per ha. cumra and kosreli tended to form another group. it is clear that the relatively older cumra and kosreli experienced a lower rate of increase in maintenance costs per hectare. on the other hand, soke increased its maintenance costs per hectare more than 30 times, and tektek more than 3 times during the six-year period. this could be closely related to the cropping pattern, in addition to the age of the irrigation system. for instance, cotton is the major crop in soke and tektek and cotton cultivation requires more frequent maintenance of the irrigation and drainage canals. soke and tektek both experienced a clear upward trend in operation costs during the first years after the transfer, but eventually the operation expenditures declined. the decline in operation costs per hectare may be attributed to the learning-by-doing factor that can enhance efficiency of operation tasks in time. hence, an increase in the operation costs following the transfer could be regarded as a natural path. on the whole, selected irrigation associations have implemented the irrigation management transfer successfully so far. all associations revealed positive signs of self-management capability, considering both revenue and expenditure management. the associations were able to supply the necessary operation and maintenance activities. however, it must be borne in mind that the transfer is the first step, the second step should be achieving sustainability. accountability and appropriate governance structures will have crucial importance in testing the sustainability of the program. therefore, more emphasis should be placed on technical and financial monitoring activities. references doker, e., f.c. erdogan, h. ozlu and e. eminoglu. 2003. irrigation management transfer to local authorities in turkey, case study on decentralization, case of turkey. water demand management forum on decentralization and participatory irrigation management, 3-5 february 2003. cairo, egypt. http://wasamed.lamb.it/ project.publications/options 52.pdf. dsi (state hydraulic works). 2005. annual reports. ministry of energy and natural resources, various years, ankara, turkey. dsi. 2004. annual reports of irrigation associations. state hydraulic works. unpublished documents, from 2000 to 2004. ministry of energy and natural resources, ankara, turkey. svendsen, m. 2001. irrigation management transfer in turkey. international e-mail conference on irrigation management transfer, international network on participatory irrigation management, june-october, 2001. http://www.fao.org/ag/agl/ aglw/waterinstitutions/docs/csturkey.pdf. svendsen, m. and g. nott. 1999. irrigation management transfer in turkey: process and outcomes. edi participatory irrigation management case studies series, june. http: //files.inpim.org/documents/sve_turk.pdf. uskay, s. 1999. participatory irrigation management practices in turkey. the eleventh seminar in the development of appropriate technology, 12-19 december 1999, tokyo japan. pp 26-32. sultan qaboos university journal for scientific research agricultural and marine sciences, 10(1):21-26 (2005) ©2005 sultan qaboos university 21 * corresponding author fate of preharvest-sprayed dicofol in date fruits: residue analysis by hplc-uv s. al-rehiayani* and k.a. osman plant production and protection department, college of agriculture and veterinary medicine, al-qassem university, buraidah, p.o. box 1482, saudi arabia عالي األداء في نطاق. مصیر مبید الدايكوفول على ثمار نخیل البلح: تحلیل المتبقیات باستخدام جھاز التحلیل الكروماتوجرافي األشعة فوق البنفسجیة سلیمان الرحیاني الخالصة: تم تقدير مصیر مبید الدايكوفول على ثمار نخیل البلح من الصنف السكري و ذلك بعد رش األشجار بالمبید بمعدل 200 مللیلتر/100لتر. وقد تم تقدير المتبقیات في ثمار النخیل بعد فترات مختلفة باستخدام جھاز التحلیل الكروماتوجرافي عالي على hplc))األداء المستخدمة التحلیل طريقة وتعتمد نانومیتر. 220 موجة طول وعلي البنفسجیة فوق األشعة نطاق في كانت خطیة (قیمة معامل االرتباط أكبر من hplc استخالص المبید بواسطة خالت اإليثايل. أوضحت النتائج أن استجابة جھاز على hplc))األداء المستخدمة التحلیل طريقة وتعتمد نانومیتر. 220 موجة طول وعلي البنفسجیة فوق األشعة نطاق في كانت خطیة (قیمة معامل االرتباط أكبر من hplc استخالص المبید بواسطة خالت اإليثايل. أوضحت النتائج أن استجابة جھاز على hplc))األداء المستخدمة التحلیل طريقة وتعتمد نانومیتر. 220 موجة طول وعلي البنفسجیة فوق األشعة نطاق في 0.98) في مدى من التركیزات قدرھا 0.0-2.0 میكروجرام من الدايكوفول و أن قیم حدود التعرف وصالحیة الطريقة المستخدمة كانت خطیة (قیمة معامل االرتباط أكبر من hplc استخالص المبید بواسطة خالت اإليثايل. أوضحت النتائج أن استجابة جھاز 0.98) في مدى من التركیزات قدرھا 0.0-2.0 میكروجرام من الدايكوفول و أن قیم حدود التعرف وصالحیة الطريقة المستخدمة كانت خطیة (قیمة معامل االرتباط أكبر من hplc استخالص المبید بواسطة خالت اإليثايل. أوضحت النتائج أن استجابة جھاز تساوي 0.24 و 0.80 جزء في الملیون علي التوالي. وقد تم حساب نسبة استرجاع المبید بعد عمل تقوية لعینات ثمار النخیل غیر المعامل بمستويات قدرھا 0.25 و 0.5 و1 جزء في الملیون وكانت نسبة االسترجاع المتحصل علیھا تتراوح بین %103.6-77.2 وانحراف معیاري نسبي يتراوح بین 6.33-11.84%. ھذا وقد أوضحت النتائج أن اختفاء مبید الدايكوفول من ثمار التمر يتبع النموذج غیر المعامل بمستويات قدرھا 0.25 و 0.5 و1 جزء في الملیون وكانت نسبة االسترجاع المتحصل علیھا تتراوح بین %103.6-77.2 وانحراف معیاري نسبي يتراوح بین 6.33-11.84%. ھذا وقد أوضحت النتائج أن اختفاء مبید الدايكوفول من ثمار التمر يتبع النموذج غیر المعامل بمستويات قدرھا 0.25 و 0.5 و1 جزء في الملیون وكانت نسبة االسترجاع المتحصل علیھا تتراوح بین %103.6-77.2 ثنائي الوجه وأن تركیز مبید الدايكوفول عند زمن صفر والذي يساوي 11.22 جزء في الملیون قد تناقص لیصبح 1.90جزء في وانحراف معیاري نسبي يتراوح بین 6.33-11.84%. ھذا وقد أوضحت النتائج أن اختفاء مبید الدايكوفول من ثمار التمر يتبع النموذج ثنائي الوجه وأن تركیز مبید الدايكوفول عند زمن صفر والذي يساوي 11.22 جزء في الملیون قد تناقص لیصبح 1.90جزء في وانحراف معیاري نسبي يتراوح بین 6.33-11.84%. ھذا وقد أوضحت النتائج أن اختفاء مبید الدايكوفول من ثمار التمر يتبع النموذج الملیون بعد 7 أيام والتي تعتبر أقل من القیمة المسموح بتواجدھا على الفواكه والخضروات (2 جزء في الملیون). أيضًا وجد أن ثنائي الوجه وأن تركیز مبید الدايكوفول عند زمن صفر والذي يساوي 11.22 جزء في الملیون قد تناقص لیصبح 1.90جزء في الملیون بعد 7 أيام والتي تعتبر أقل من القیمة المسموح بتواجدھا على الفواكه والخضروات (2 جزء في الملیون). أيضًا وجد أن ثنائي الوجه وأن تركیز مبید الدايكوفول عند زمن صفر والذي يساوي 11.22 جزء في الملیون قد تناقص لیصبح 1.90جزء في t) معدل اختفاء الدايكوفول كان سريعًا في الطور األول مقارنة بالطور الثاني حیث أن فترات نصف عمر المبید الملیون بعد 7 أيام والتي تعتبر أقل من القیمة المسموح بتواجدھا على الفواكه والخضروات (2 جزء في الملیون). أيضًا وجد أن t) معدل اختفاء الدايكوفول كان سريعًا في الطور األول مقارنة بالطور الثاني حیث أن فترات نصف عمر المبید الملیون بعد 7 أيام والتي تعتبر أقل من القیمة المسموح بتواجدھا على الفواكه والخضروات (2 جزء في الملیون). أيضًا وجد أن 1/2 على أشجار ( الملیون بعد 7 أيام والتي تعتبر أقل من القیمة المسموح بتواجدھا على الفواكه والخضروات (2 جزء في الملیون). أيضًا وجد أن على أشجار ( الملیون بعد 7 أيام والتي تعتبر أقل من القیمة المسموح بتواجدھا على الفواكه والخضروات (2 جزء في الملیون). أيضًا وجد أن النخیل تساوي 1.35 و 38.52 يوم على التوالي. وتمتاز الطريقة المستخدمة في ھذه الدراسة بسرعة األداء والحساسیة العالیة 1/2 النخیل تساوي 1.35 و 38.52 يوم على التوالي. وتمتاز الطريقة المستخدمة في ھذه الدراسة بسرعة األداء والحساسیة العالیة 1/2 .وارتفاع نسبة االسترجاع مع إمكانیة تكرار النتائج abstract: the fate of pre-harvest-sprayed dicofol (dcf) on date fruits has been investigated. date palm trees, variety sukkari, were sprayed with dcf (18.5%, ec) at the rate of 200 ml/100 l. dcf residues in date fruits were determined at different time intervals using high performance liquid chromatography (hplc) with uv detection at 220 nm. the method was based on extraction with ethyl acetate. the results showed that the hplc response was linear (r2 > 0.98) for dcf in the range of 0.0 to 2 mμg. the limits of detection and quantification were 0.24 and 0.80 ppm, respectively. the method was developed by using spiked date fruits at levels of 0.25, 0.50 and 1.0 ppm. recovery percentage was satisfactory with a range of 77.2 to 103.6% and an rsd ranging from 6.33 to 11.84%. a biphasic model was assumed in order to carry out the statistical study of the loss of dcf from date fruits. the results showed that the initial deposit of dcf on date fruits was 11.22 ppm, while the residue value decreased to 1.90 ppm seven days after spraying, which is below the tolerance limit for fruits and vegetables (2 ppm). also, the data indicate that there was a faster rate of dcf loss in the first phase than the second one. this is clearly reflected in the t1/2 values, where the half-lives of dcf were 1.35 and 38.52 days, for the first and second phase model, respectively. the described method is rapid and sensitive, with satisfactory recoveries and reproducibility. keywords: date fruits, fate, dicofol, residue, limit of detection, half-life introduction pesticides are widely used in agriculture to control a variety of pernicious organisms that spoil crops. more than 600 kinds of agrochemicals are used around the world (miyake et al., 1999). they provide unquestionable benefit for agricultural production, even though, as a consequence, low amounts of some residues may persist in the food supply and could constitute a significant exposure pathway for humans. exposure to food residues has created uncertainty for potential chronic toxicity and, in some cases, acute toxicity (saunders and harper, 1994; ekström et al., 1996; osman and al-rehiayani, 2003). al rehiayani and osman 22 quantitative methods for dcf determination in agricultural products have been reported using colorimetry (rosenthal et al., 1957), ultra-violet spectrophotometry (gunther and blinn, 1957), gas liquid chromatography using an electron capture detector, (morgan, 1967; ribeiro et al., 2000) or mass selective detection (soleas et al., 2000) and high performance liquid chromatography (fernăndez et al., 2001) the difficult and crucial step in pesticide residue analysis of complex media, such as foods, is the clean-up or separation of chemicals of interest. in this study, clean-up, separation and determination of the optimum conditions for p,p--dcf analysis in date fruits were developed. also, the present study was carried out to determine the residue levels of dcf at different time intervals following field application, as well as the half-life (t1/2) on date fruits. materials and methods dicofol (dcf), [2,2,2-trichloro-1,1-bis-(4-chlorophenyl) ethanol], (18.5% ec) was purchased from hockly international company, uk, while technical dcf was provided by environmental protection agency (epa, usa) with a purity of 99%. certified hplc-grade ethyl acetate, methanol, acetonitrile (acn) and granular ar anhydrous sodium sulfate were purchased from bdh company, while florisil (60-100 mesh) was purchased from riedel-de haën (germany). deionized water of 15 mwω.cm resistivity was obtained from a water purification system (purelab option-r, elga, uk). all solvents and solutions were passed, before used, through a 0.45 mμm sterile disposable nylon filter (acrocp, gelman sciences). sukkari, the most widely grown date variety in al-qassem region, was selected for this study. date palm trees cultivated in el-soltan farm, north of elmeledia district, al-qassem area, saudi arabia, were arranged in a randomized design and sprayed at the end of may 2002 with dcf (18.5% ec) at the rate of 200 ml/100 l (37 g active ingredient, a.i./100 l) using a motorized sprayer that was calibrated to deliver 10 l/tree. treatments were done in triplicate with eight trees assigned to each replicate. untreated trees were sprayed only with water and used as analytical controls for background residues and for fortification recovery studies. date fruits were collected 0, 2 and 4 hrs and 1, 2, 4, 7, 14, 21, 28, 42 and 56 days after dcf application the use of chlorinated hydrocarbon insecticides has been sharply curtailed or banned, but they are still the active ingredients of some pest control products (moore, 1986). for example, dicofol (dcf) is used world-wide as a pre-harvest miticide on cotton, citrus, vegetable, nuts and other crops (rohm and hass, 1984; mourer et al., 1990; fernăndez et al., 2001; kitajama et al., 2003). dcf is structurally similar to ddt, which is used as the starting material for synthesis for dcf (wiemeyer et al., 2001). the us-epa became concerned about the continued use products containing dcf because they also contained ddt and related compounds (moore, 1986). dcf products marketed after may 1986 could contain no more than 2.5% ddt and related compounds and those marketed after 1988 could have no more than 0.1% ddt and related compounds. following reassessment of dietary risk, the epa has updated u.s. tolerances for dcf residues on a variety of crop commodities and described harmonization with codex mrls (u.s.-epa, 1998). al-qassem region is one of the largest agricultural areas in the kingdom of saudi arabia and much of its arable and fertile land is under date palms (phoenix arable and fertile land is under date palms (phoenix arable and fertile land is under date palms ( dactylifera l.). al-qassem community produces the majority of date fruits consumed locally and much of those exported outside the country. during the 2002 season, date fruit production was greater than 130,000 tons, of which approximately 1,092 tons were destined for export (saudi ministry of agriculture and water, 2003). expansion in date fruit production has brought about increasing pest problems. pest control has been achieved by heavy reliance on injudicious and indiscriminate use of broad-spectrum pesticides. consequently, unacceptable concentrations of pesticide residues have been found in date fruits (alrehiayani and osman, 2003). dcf is often applied to date palms in saudi arabia at a rate of 200 ml/100l to control mites. unfortunately, no data are available on dcf residues and its loss on date fruits, although it has been reported in cucumber (nazer and masoud, 1986), fish (barbera, et al., 1986), meat (yossef et al., 2003), avian eggs (krynitsky et al., 1988) and citrus (fernăndez et al., 2001; torres et al., 1996; saitta et al., 2000). because fruits of the date palm are vital components of the diet in saudi arabia, consumers are increasingly concerned about dcf residues in date fruits and their carry-over to processed products. fate of preharvest-sprayed dicofol in date fruits 23 to determine residue concentration. samples were immediately transported to the laboratory and kept at -15ºc until residue analysis. three 50-g aliquots of date fruits from each time interval were chopped and placed in a 250-ml conical flask and blended with 100 ml ethyl acetate for 2 min. the homogenate was then filtered under vacuum through whatman no. 2 filter paper. the solids were re-extracted with 100 ml ethyl acetate for another 2 min. the combined, filtered extract was passed through a funnel containing anhydrous sodium sulfate, evaporated using a rotary evaporator (38°c) to ca. 2 ml and then made up to 5 ml with ethyl acetate. the concentrated extract was passed through a glass chromatographic column (20 cm x 10 mm i.d.) packed in sequence from bottom to top, with glass wool, 10 g of activated florisil and topped with 2 g anhydrous sodium sulfate. the column was pre-washed with ethyl acetate. the extract was added to the column and eluted with 50 ml of ethyl acetate. the eluent was evaporated to dryness using a gentle stream of nitrogen and redissolved in 10 ml methanol. the final solution was filtered through a 0.45 mμm sterile disposable nylon filter prior to hplc analysis. the hplc system was standardized on the same day as the samples were analyzed by injecting 20 μl of eight solutions of freshly prepared dcf in methanol with concentrations ranging from 0.0 to 10 ppm from a stock solution of 1000 ppm. areas under the peak (uv.sec) versus concentrations (μg) were plotted and simple linear regression used to obtain an equation for the standard curve. the amount of dcf in each sample was thus calculated based on the slope of the standard curve. three 50-g aliquots of the untreated control were treated as individual replicates for a dcf fortification recovery study. spiking was done at the levels of 0.25, 0.50 and 1.0 μg/g (ppm). in addition to the spiked samples, one date fruit blank and one solvent blank were run concurrently with the extraction set. recoveries for dcf and relative standard deviation (rsd) were calculated after hplc analysis. extracts were chromatographed on a perkin elmer hplc system model 200 equipped with a degasser, quaternary lc pump model 2000q/410, 20 μl loop, spheri-5 rp-18 column (25 cm x 4.6 mm i.d., 5 μm, perkin elmer), oven column, a lc200 uv detector. the turbochrom workstation software package was used for instrument control, data acquisition, and data analysis. the column temperature was kept at 25 °c. dcf was eluted using an isocratic gradient of 78:22 v/v acn:h2o. dcf was detected by scanning the eluent at wavelengths (lλ) from 200 to 260 nm at a flow rate of 1.1 ml/min. the retention time for dcf was 10.4 min. the detection (lod) and quantification (loq) limits with this procedure were defined as the concentration of the dcf in date fruits (expressed as ppm) that gave signals of 3 and 10 times the noise, respectively, within its retention time (tr) window (falqui-cao et al., 2001). corresponding results were compared with the maximum residue limit.compared with the maximum residue limit.compared with the maximum resid the data were calculated as mean ±± s.d and analyzed using analysis of variance technique (anova). probability of 0.05 or less was considered significant. all statistical analysis was done with costat program (version 2, cohort software, 1986). results and discussion the hplc response was linear (r2 > 0.98) for dcf in the range of 0.0 to 2 microgram (μg). the lod of dcf in date fruits was 0.24 ppm or about 8.3 times lower than the maximum residue limit (mrl) of 2 ppm. in a study of dcf residues on oranges, the lod by gc-ecd analysis was also reported to be 0.24 ppm (fernăndez et al., 2001). in a multi-residue study of matrix solid phase dispersion extraction of oranges followed by detection with gc-ecd, the lod for dcf was 0.010 ppm (torres et al., 1996). the loq determined from the method validation was 0.80 ppm. interferences from co-extractives raise the loq of a method by masking the detector response to the residue or by preventing injection of the specified sample matrix without undesirable damage to the system (falqui-cao et al., 2001). additional procedures to clean the sample extract prior to determination may improve the loq by removing these interferences. column cleanup in this study was needed to remove coextractives from date extracts prior to hplc. the florisil elution system used in the present study efficiently isolated dcf from the coextractives, where a few unknown peaks appeared in hplc chromatograms due to coextractives, but did not interfere with dcf peak. results of the recoveries of spiked samples are summarized in table 1. recovery percentage was satisfactory with a range of 77.2 to 103.6% and an al rehiayani and osman 24 rsd ranging from 6.33 to 11.84%. the results are in agreement with the extraction efficiencies reported by other authors who found that the mean recoveries for dcf ranged from 77.2 to 93.8% in egg yolk (mourer et al., 1990), 78 to 104% in tea (zhu and wang, 2000) and 87 to 95% in oranges (ribeiro et al., 2000). the percentage recoveries for the present study can be considered satisfactory according to guidelines which state that any method with a proven recovery of 70% or more could be eligible for future official adoption (schuller et al., 1976). also, the low rsds indicated a high level of repeatability for the tested method. data in table 2 illustrate the levels of dcf in date fruits over a period of 56 days following one application of dcf at rate of 37 g a.i./100 l. initial dcf residues were 11.22 ppm but decreased by 78, 66, 60, 46 and 18% of the initial deposit after 2, 4, 24, 48 and 96 hrs, respectively, following application. from day 4 on, the decrease was slow with non significant differences between the residue levels of dcf. although mrls have been established for registered pesticides on agricultural commodities to guarantee their proper use and adequate control (council directive, 1990), no maximal limit of dcf residues has been established on date fruits. the residue level 7 days after dcf spraying was 1.90 ppm which is less than the maximum residue limits for fruits and vegetables of 2 ppm (fernăndez et al., 2001). also, data in table 2 illustrate that less than 9% of the initial deposit was detected during the period of 4-8 weeks after dcf application. the present results are consistent with another investigation, where dcf residues on cucumber fruits were below the tolerance level of 2 ppm and no residue could be detected 8 days after dcf application under either plastic house or plastic tunnels (nazer and masoud, 1986). the rate of loss of dcf residue from date fruits is presented in figure 1. a biphasic model was assumed in order to carry out the statistical study of the loss of dcf according to equation (1). r=a e-aαt + b-aαt + b-aαt e-bβt (1) where r is residue level at t days, a and b are the residue concentrations at t=0 and aα and bβ are the loss rate constants for the first and second phase model, table 1. mean recoveries of dcf from spiked date fruits. amount spiked (ppm) no. of determinations recovery (%) rsd (%) 0.25 3 103.6 6.33 0.50 5 77.2 11.48 1.00 3 89.6 8.98 table 2. dcf residues in pre-harvest-sprayed date fruits after different time intervals. time interval (days) dcf level (ppm) mean ±s.d* initial deposit (%) relative standard deviation (rsd) (%) 0 11.22 ± 1.53d 100.00 13.64 2/24 8.71 ± 0.72c 77.66 8.27 4/24 7.38 ± 0.42bc 65.78 5.69 1 6.69 ± 0.97bc 59.63 14.50 2 5.19 ± 0.75b 46.26 14.45 4 2.07 ± 0.14a 18.45 6.76 7 1.90 ± 0.14a 16.93 7.37 14 1.76 ± 0.14a 15.69 7.95 21 1.25 ± 0.07a 11.15 5.60 28 0.99 ± 0.01a 8.82 1.01 42 0.93 ± 0.09a 8.29 9.73 56 0.67 ± 0.09a 5.97 13.43 * results are expressed as means ± standard deviations (s.d). means in a column with different coefficients (a-d) are significantly different (p≤ 0.05 and lsd0.05 is 1.79). figure 1. dissipation curve for dcf. data are expressed as means ±± s.d (n=3). fate of preharvest-sprayed dicofol in date fruits 25 respectively. the half-life (t ) of the exponential decay was calculated according to equation (2). t = (2.303 log 2)/rate constant (2) the data indicate that there was a faster rate of dcf loss in the first phase than the second one (table 3). this is clearly reflected in the t values, where the half-lives of dcf in date fruits were estimated to be 1.35 and 38.52 days, for the first and second phase models, respectively. conclusion although dicofol disappears rapidly from date fruits where the residue level 7 days after dcf spraying was 1.90 ppm, less than the maximum residue limits for fruits and vegetables of 2 ppm, pesticide residue monitoring programs should nevertheless be implemented to ensure minimal residue levels in date fruits and to check compliance with the existing regulations. also, the described procedure is simple and less labor intensive and troublesome emulsions, such as those frequently observed in liquid-liquid partitioning, did not occur. further, these were satisfactory recoveries. the sensitivity of detection of dcf in the present study was 0.24 ppm, which is equivalent to that obtained by fernăndez et al. (2001) when dcf was analyzed by gc-ecd. references al-rehiayani, s. and k.a. osman. 2003. residual levels of preharvest-sprayed amitraz in date fruits. journal of pest control and environmental sciences 11:1-12. barbera, j.c., f.j. lopez, f. hernandez, j. medina and a. pastor. 1986. gas chromatographic determination of organochlorine pesticides; contamination of dicofol, fenson, and tetradifon in fish and natural waters of a water area beside the mediterranean sea. bulletin of environmental contamination and toxicology 36:of environmental contamination and toxicology 36:of environmental contamination and toxicology 211-218. council directive. 1990. council directive 90/642/eec of 27 november 1990 on the fixing of maximum levels of pesticide residues in and on certain products of plant origin, including fruit and vegetables. official journal of the european communities l350:71-118. costat program. 1986. version 2, cohort software. ekström, g., h. hemming, and m. palborg. 1996. swedish pesticide risk reduction 1985-1995: food residues, health hazard and reported poisoning. reviews of environmental contamination and toxicology 147:119-139. falqui-cao, c., z. wang, l. urruty, j.j. pommier and m. montury. 2001. focused microwave assistance for extracting pesticide residues from strawberries into water before their determination by spme/into water before their determination by spme/into water before their determination b hplc/dad. journal of agricultural and food chemistry 49:5092-5097. fernăndez, m., y. pico and j. manes. 2001. pesticide residues in oranges from valencia (spain). food additives and contaminants 18:615-624. gunther, f.a. and r.c. blinn. 1957. ultraviolet spectrophotometeric microdetection of the acaricide 4,4’-dichloro-alpha-(trichloromethyl) benzhydrol (sw-293). journal of agricultural and food chemists 5:517-519. kitajama, e.w., j.a. rezende and j.c. rodrigues 2003. passion fruit spot virus vectored by brevipalpus phoenicis (acari:tenuipalpidae) on passion fruit in brazil. fruit in brazil. f experimental and applied acarology 30:225-231. krynitsky, a.j., c.j. stafford and s.n. wiemeyer. 1988. combined extraction-cleanup column chromatographic procedure for determination of dicofol in avian eggs. journal of the association of official analytical chemists 71:539-542. miyake, y., k. koji, h. matsuki and r. tajima. 1999. fate of agrochemical residues, associated with malt and hops. journal of american society of brewing . journal of american society of brewing . journal of american society of chemists 57:46-54. moore, j.a. 1986. dicofol: intent to cancel registrations of pesticide products containing dicofol: denial of applications for registration of pesticide products containing dicofol: conclusion of special review. notice of final determination. u.s. federal regulations 51:19508-19525. table 3. statistical parameters of dcf dissipation from treated date fruits. statistical parameters value a0 (ppm) 7.71 b0 (ppm) 1.85 aα (days-1 0.51 bβ (days-1 0.02 t1/2a α (days 1.35 t1/2b β (days 38.52 regression coefficient 0.98 al rehiayani and osman 26 morgan, n.l. 1967. the identification and relative retention times of p,p’-kelthane and its breakdown product p,p’-dichlorobenzophenone using glc. bulletin of environmental contamination and toxicology 2:306-312. mourer, c.r., g.l. hall, w.e. whitehead, t. shibamoto, l.r. shull and s.e. schwarzbach. 1990. chromatographic determination of dicofol and metabolites in egg yolks. archives of environmental science and health 19:154-156. nazer, i.k. and h.a. masoud. 1986. residues of dicofol on cucumber grown under plastic covers in jordan. journal of environmental science and health 21:387-399. osman, k.a. and s. al-rehiayani. 2003. risk assessment of pesticide to human and the environment. saudi journal of biological sciences 10:81-106. ribeiro, m.l., j.r. amador, l. polese, e.f. jardim, e.v. minelli and o.c. de cordis. 2000. effect of a pilot washing system on dicofol levels in 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(editor), 389. schuller, p.l., w. horwitz and l. stoloff. 1976. a review of sampling plants and collaborative studies method of analysis for aflatoxin. journal of the association of official analytical chemists 59:1315-1343. soleas, g.j., yan, j.h., k., and goldberg, d.m. 2000. multiresidue analysis of seventeen pesticides in wine by gas chromatography with mass-selective detection. journal of chromatography 882:205212. torres, c.m., y. pico, m.j. redondo and j. manes. 1996. matrix solid-phase dispersion extraction procedure for multiresidue pesticide analysis in oranges. journal of chromatography 719:95-103. u.s.-epa. 1998. registration eligibility decision (red)-dicofol. epa 738-r-98-018, november 1998. wiemeyer, s.n., d.r. clarck, jr., j.w. spann, a.a. belise and c.m. bunck. 2001. dicofol residues in eggs and carcasses of captive american kestrels. environmental toxicology and chemistry 20: 2848-2851. yossef, h., a. al-qarawi, h. mousa, k.a. osman and h. abdel-rahman. 2003. organochlorine residues in carcasses of camels slaughtered in al-gassem region, saudi arabia. in: deutsche veterinärmedizinische gesellschaft 44. tagung veterinärmedizinische gesellschaft 44. tagung veterinärmedizinische gesellschaft des arbeitsgebietes lebensmittelhygiene der deutschen veterinärmedizinischen gesellschaft. garmisch-partenkirchen. zhu, m.x. and y. wang. 2000. determination of dicofol residue in tea by wide-bore capillary gas column. se pu. 18:64-66. received: december 2004 accepted: april 2005 agricultural and marine sciences, 13:73-83 (2008) ©2008 sultan qaboos university 73 *corresponding author. e-mail: asadalaqidah@hotmail.com effects of hypoxia on the behaviour, mortality and plasma electrolyte concentrations of goldlined seabream, rhabdosargus sarba 1 marine science and fisheries centre, p.o. box 227, pc 100, muscat, sultanate of oman 2 marine institute, portsmouth university, uk 3 department of biology, college of science, sultan qaboos university, sultanate of oman 4 nizwa university, sultanate of oman abstract: the behaviour, mortality rates and plasma electrolyte concentrations of goldlined seabream rhabdosargus sarba challenged with low dissolved oxygen (do) conditions was studied in an experimental setup, comprising a control (7.9 ml/l do) and two hypoxic (2 ml/l and 1 ml/l do) treatments. increased ventilation rates and decreased swimming activity were observed in hypoxic treatments, but some fish exhibited strenuous avoidance actions. no mortalities were observed after 3 h, 6 h, or 24 h, but 50% of males and 18% of females died in the 48 h treatment at 1 ml/l do. the mean size of surviving fish (305 ± 32.1 g total weight) was significantly smaller than those that died (425 ± 33.1 g). the plasma concentrations of na+, cland mg2+ did not vary significantly relative to treatment, exposure time, fish size and gender, or interactions among treatment, time and gender. ca2+ concentrations increased significantly after 48 h at 1 ml/l, but this result may be artificial because of the small sample size. the results suggest that r. sarba is comparatively tolerant of the low oxygen or hypoxic conditions that often occur in the coastal waters of oman, where seasonal upwellings and high primary productivity have in the past caused mass mortalities of demersal fishes. الوفیات ونسبة األكسجین على سلوك نقص تأثیر القابض ألسماك بالزما الدم في االیونات وتركیز عامر وشھال الكندي بن یحیى العزیز عبد ویرنج، ، كولن الغیالني محمد حمد بن في المختبر ألسماك القابض الدم في بالزما االیونات وتركیز الوفیات ونسبة سلوك على نقص األكسجین أثر دراسة تمت الخالصة: فترات في لتر) لتر/ (١ و٢ مللي األكسجین من منخفضة مستویات وعند لتر) لتر/ مللي ٨) األكسجین من الطبیعیة النسبة باستخدام لدى تعرضھا لنقص األسماك حركة بعض في وانخفاضا التنفس في زیادة الدراسة من لوحظ ٤٨ ساعة). و و٢٤ (٣ و٦ مختلفة زمنیة عند وفیات لألسماك أیة توجد ولم من األكسجین. لنفس الكمیة لدى تعرضھا حركة البعض بینما زادت بعض األسماك في األكسجین ساعة ٤٨ إلى تعرضھا بعد لتر) (١ مللي لتر/ مستوى عند األسماك بعض نفقت بینما ساعة و٢٤ و٦ ٣ بعد األكسجین تعرضھا لنقص لنقص المعرضة األسماك وزادت نسبة الكالسیوم عند الذكور. من ومعظمھا حجما نفقت كانت اكبر األسماك التي األكسجین. من نقص والمغنیسیوم والكلوراید). الدراسة (الصودیوم، األكسجین األخرى بنقص االیونات تتأثر بینما ٤٨ ساعة) : لتر لتر/ مللي ١) األكسجین المیاه األخرى. النوع في بنفس مقارنة نسبة األكسجین انخفاض مع التأقلم على في المیاه العمانیة القدرة القابض اسماك لدى أن أكدت البیئیة. بالتغیرات المرتبطة األخرى والظواھر التقلیب ظاھرة نتیجة العمانیة المیاه في لألكسجین الطبیعي النقص إلى ذلك یعود وقد keywords: behaviour, mortality, hypoxia, electrolytes, goldlined seabream. hamed m. al-gheilani*1, colin waring2, abdulaziz al-kindi3 and shehla amer4 al-gheilani and others 74 75 effects of hypoxia on the hehaviour, mortality and plasma electrolyte concentrations of goldlined seabream introduction fish challenged with reduced levels of dissolved oxygen (do), can respond by moving away (vertical or horizontal habitat changes) or by changing activity patterns to increase ventilation surfaces or decrease energy demands (kramer, 1987; dalla via et al., 1998). increases in ventilation frequency have been reported in numerous species (holeton and randall, 1967; soivio et al., 1980; soivio et al., 1981; woo and wu, 1984; thomas et al., 1988; brauner and randall, 1998; maxime et al., 2000; pichavant et al., 2002; timmerman and chapman, 2004; evans et al., 2005), as have increases in ventilation volume (smith and jones, 1982; randall, 1990). the result is an increased oxygen uptake and enhanced convective conditions for co2 removal (brauner and randall, 1998). van raaij et al., (1996a) reported on behavioural strategies of surviving and non-surviving fish during confined hypoxia exposure. non-surviving fish exhibited strenuous avoidance (or escape) reactions, and were not able to maintain homeostasis, as evidenced by elevated plasma ions, metabolic rate and stress hormones compared to the less active surviving fish. elevations in plasma ion (electrolyte) levels in response to physical disturbances such as net confinement and transport have been documented for several marine teleosts (fletcher, 1975; pawson and lockwood, 1980; soivio et al., 1980; robenston et al., 1987; waring et al., 1992; waring et al., 1996). below a species-dependent critical oxygen threshold, aerobic energy production decreases and fish mainly resort to anaerobic metabolism (dalla via et al., 1994) and sometimes metabolic depression (van waversveld et al., 1989). most of these mechanisms are under hormonal control involving catecholamines and cortisol (kinkead and perry, 1991; van raaij et al., 1996b; pichavant et al., 2002; perry et al., 2004). localized or extensive low oxygen or hypoxic conditions are common in the coastal waters of oman (ref), where seasonal upwellings of nutrient-rich and oxygen-depleted waters are driven by the summer monsoon winds. these upwellings give rise to algal blooms in the photic zone bloom collapse, bacterial decomposition and settlement on the seafloor results in an oxygen-depleted bottom-water layer below the thermocline (claereboudt et al., 2001). although generally beneficial to fisheries, phytoplankton blooms can trigger harmful algal blooms (habs or red tides), and the latter have been implicated in massive fish mortalities in both the gulf of oman (claereboudt et al., 2001) and the arabian sea (al-busaidi et al., this issue). these mortalities were attributed to asphyxia or toxins. a recent review of hab occurrences between 1976 and 2004 showed 66 red tide events in the coastal waters of oman, out of which 25 resulted in mass mortalities of fish and other organisms (al-gheilani et al., to be submitted). the importance of commercial fishing to oman and increasing likelihood of low-oxygen conditions stimulated a recent phd study on the physiology of goldlined seabream rhabdosargus sarba confronted with hypoxic conditions (al gheilani, 2007). goldlined seabream is a coastal species distributed throughout the western indian ocean, including the red sea and arabian gulf (randall, 1995). it is often encountered in small schools, reaches a maximum size of 60 cm, and feeds on bivalve molluscs, sand dollars, sea urchins and sand-dwelling crustaceans (randall, 1995). it forms part of the demersal fish assemblage of oman, which is heavily fished. the aims of this study were to examine the effects of low oxygen conditions on the behaviour, mortality rates and electrolyte balance of r. sarba under controlled laboratory conditions. particular attention was given to the influence of gender and body size on the above parameters. materials and methods trap-caught goldlined seabream with an average weight of 245.9±8.6 g and length of 23.5±1.4 mm were purchased from a local fisherman in muscat (24n˚ 58e˚). fish were kept in oxygenated seawater while on board and transferred to well-aerated tanks on land where the water temperature and salinity were kept at 21-24°c and 20-25 psu. fish were acclimatized for a total of 3 weeks during which they were fed once daily (plante, et al., 1998) with commercially-prepared fish pellets (arasco, saudi arabia). the continuous flow experimental setup consisted of three seawater reservoirs: an overhead 600 litre (l) tank, fully aerated 400 l fish acclimatization tank and a 400 l water circulation tank (see fig. 1). the circulation tank was connected to 8 experimental tanks (30×60×40 cm; 45 l; glass with 2 ports), with flow rates of 1.5 l.min-1 and water circulating through a biological filter and uv sterilizer (temperature, 22.9±0.1c˚; salinity 34.8±0.8 psu; ammonia, 2.01±0.6 µm/l; nitrite 0.23±0.04 µm/l; phosphate 0.5±0.01 al-gheilani and others 74 75 effects of hypoxia on the hehaviour, mortality and plasma electrolyte concentrations of goldlined seabream µm/l; and a 12l:12d photoperiod). the sides of the experimental tanks were covered with black paper to minimize disturbances to fish. an aqua traul oxygen monitoring and control system (dryden aqua, scotland, uk.), fitted with 8 oxygen probes (dryden aqua, scotland, u.k.) was connected to solenoid valves to regulate the oxygen and nitrogen input to the 8 experimental tanks. the aqua traul network communicates via rs 485 serial bus protocol with a standard pc and was configured using aqua traul software. feeding was stopped and fish transferred from the acclimatization to the experimental tanks (fully aerated seawater; 7.9±0.7 ml.l-¹ o2 or 100% saturation) 24 h before low oxygen trials (see lapner and perry, 2001). two levels of hypoxia, 2.0±0.9 ml.l-¹ o2 (2.8mg/l or 25% saturation) and 1.1±0.2 ml.l-¹ (1.4 mg/l or 12.5% saturation) were selected for trials and control fish were figure 1. arrangement of seawater holding and experiment tanks. a = overhead seawater holding tank b = fish acclimation tank c = water circulation tank d = pump e = biological filter f = uv sterilizer g1-g8 = experimental tank ∏ = valves al-gheilani and others 76 77 effects of hypoxia on the hehaviour, mortality and plasma electrolyte concentrations of goldlined seabream maintained at 7.9±0.7 ml.l-¹ o2. oxygen and nitrogen were purged from tanks by immersing flexible tygon tubing (id 4 mm, od 1.2 cm) attached to ceramic gas diffusers (dryden aqua, scotland, u.k.), and oxygen levels adjusted manually and via the pc by bubbling pure nitrogen / oxygen into tanks from respective cylinders. the time required to adjust the do level was 10-20 minutes. once set up, the aqua traul units continued to monitor the system, automatically opening and closing the solenoid valves to regulate the flow of oxygen and nitrogen. water samples (250 ml) were collected using niskin bottles for analysis of ammonia, nitrite and phosphorus. nutrients were measured using a 5-channel skalar flow access auto-analyzer (see strickland and parsons, 1972). fish behaviour during hypoxia exposure and time of death was monitored every 2–4 hours. after 3 h, 6 h, 24 h and 48 h individual fish in experimental tanks were netted, stunned by a blow to the head, and terminal blood samples taken. the sex, total weight (tw, g) and total length (tl, cm) were determined. the tw and tl of surviving fish were compared with those that died using student’s t-test. whole blood was allowed to clot at room temperature for 30 min and centrifuged at 11000 rpm for 5 min to obtain plasma (hishida et al., 1999). all plasma samples were immediately frozen at -80 c˚. the beckman synchron cx7 system (cx3 module) was used to determine plasma electrolytes. sodium and chloride concentrations were determined by measuring electrolyte ion activity in solution. magnesium concentrations were determined using the manufacturers reagent and a colourimetric timed-endpoint method. the calcium concentrations were determined by adding arsenazo iii calcium reagent and measuring the absorbance of the resulting coloured calcium-arsenazo iii complex at 650 nm and 700 nm. the effects on plasma ion concentrations of the variables for gender, exposure time (3 h, 6 h, 24 h and 48 h), treatment (control, 1 ml/l or 2 ml/l do), tl and tw, and the interactions of treatment×time, treatment×gender, time×gender and treatment×time×gender were analysed using a general linear model (glm) with gender and body size (cm and g) as factors, accepting p≤0.05 as significant (ref). statistical analysis was carried out using minitab. results all fish survived up to 48 h in the 2 ml/l do trials. in the 1 ml/l do trials, all fish exposed for 3 h, 6 h and 24 hours survived, but 50% of males (n = 12) and 18% of females (n = 17) died between 24 and 48 h exposure. the mortalities occurred after 26 h (3 fish), 28 h (1), 30 h (2), 36 h (2) and 40 h (1). the mean tw (305 ± 32.1 g) and tl (24.7 ± 1.0 cm) of surviving fish were significantly smaller (p<0.05) than that of the fish that died (425.1 ± 33.1 g; 28.7 ± 0.8 cm; see table 1 and fig. 2). during the hypoxia trials two distinct behaviour patterns were observed. fish that survived in the 1 ml/l table 1. the mean total length (tl, cm) and total weight (tw, g) of male and female rhabdosargus sarba used in control and hypoxia treatments. mean tl and tw of fish that died during the 48 h, 1 ml/l do treatment are also shown. sample sizes are in parenthesis. all fish female survivors male survivors female mortalities male mortalities tw (g) tl (cm) tw (g) tl (cm) tw (g) tl (cm) tw (g) tl (cm) tw (g) tl (cm) control 301.2 (16) 24.8 (16) 355.9 (10) 26.3 (10) 210.2 (6) 22.3 (6) * * * * hypoxia exposed 342.3 (29) 25.9 (29) 318.6 (14) 25.3 (14) 273.3 (6) 23.4 (6) 474.7 (3) 29.3 (3) 400.3 (6) 28.3 (6) *no control; fish dead. al-gheilani and others 76 77 effects of hypoxia on the hehaviour, mortality and plasma electrolyte concentrations of goldlined seabream do trials reduced their routine locomotor activity, and after approximately 20 h lay almost immobile at the bottom of the tanks, appearing to have increased their ventilation rates. the fish that eventually died swam upwards in the water column, sometimes at burst swimming movement, but thereafter lost their balance and sank to the bottom where they remained inactive until they died. plasma na+ concentrations ranged between 148 mmol/l in normoxic fish and a maximum of 176.6 mmol/l in control fish after 3 hours (table 2). there were no statistically significant fluctuations in plasma na+ concentrations, irrespective of treatment, exposure time, gender, fish size, or the interactions (table 3). likewise, no significant trends could be observed in either cl (range 136.8 – 160.8 mmol/l) or mg2+ (0.07 – 0.25 mmol/l) (tables 2 and 3). the ca2+ concentrations were not examined at 6 h and at 24 h for the 1 ml/l do treatment because not enough plasma was available for analysis. in the only trial with a positive result, the plasma ca2+ concentrations were significantly higher in fish exposed to 1 and 2 ml/l do for 48 h than their controls. however, given the small sample sizes used for the ca2+ determinations, and the comparatively low value for the 48 h control measurement (0.47 mmol/l) relative to the other controls (0.57–0.65 mmol/l; see table 2), the significant increase seen in ca2+ after 48 h at 1 and 2 ml/l do exposure may be artifactual. therefore we concluded that none of the plasma electrolytes measured (na+, cl-, mg2+ and ca2+) showed a significant effect relative to exposure of time, treatment, gender, tw or tl, or interactions between the boundaries tested. discussion the effects of hypoxia on fish behaviour and mortalities have been studied for several species using a variety of do levels and exposure times, and sensitivity to low oxygen appears to be species dependent, broadly ranging from 0.9 to 2.2 ml/l do (see table 4 and itazawa, 1971; gee et al., 1978; van den thilart and waarde, 1985). woo and wu (1984) found black seabream mylio macrocephalus to be at the lower extreme of the sensitivity range (no mortalities at 0.7 ml/l do in 7 h but some deaths at 0.4 ml/l do; wu and woo, 1984). conversely, atlantic cod gadus morhua and rainbow trout oncorhynchus mykiss exhibited higher mortality rates over similar time spans at do levels >0.7 ml/l (plante et al., 1998) (table 4). in our study, no r. sarba died over a short time span of up to 24 h, even at 1 ml/l do, and it therefore exhibits a relatively high tolerance to hypoxia. hypoxia elicits hyperventilation in a variety of marine teleosts (holeton and randall, 1967;; soivio et al., 1980; soivio et al., 1981; woo and wu, 1984; thomas et al., 1988; brauner and randall, 1998; maxime et al., 2000; pichavant et al., 2002; evans et al., 2005), and was also observed in r. sarba. the hyperventilation facilitates increased oxygen uptake and enhances convective conditions for co2 removal (brauner and randall, 1998). a reduction in swimming activity as an energy-saving strategy, as reported for flatfish solea solea (dalla via et al., 1998), was also observed for r. sarba. however, not all r. sarba reduced their swimming activity, with some individuals showing strenuous avoidance behaviour – the latter group with a higher mortality rate. van raaij et al. (1996a) reported a five-fold catecholamine elevation after strenuous avoidance behaviour of nonsurviving oncorhynchus mykiss – this information is unfortunately not available for r. sarba. the r. sarba that died during the 48 h trial at 1 ml/l do had a significantly larger mean size (both tl and tw) than those that survived. smaller individuals of several other fish species were also found to be more 30 25 20 15 10 5 0 500 400 300 200 100 0 surviving fish dead fish figure 2. comparisons of the tl and tw of surviving and non-surviving rhabdosargus sarba kept at 1 ml/1 do for 48 h. means and standard errors are shown. surviving fish dead fish fi sh le ng th (c m ) fi sh w ei gh t ( g) al-gheilani and others 78 79 effects of hypoxia on the hehaviour, mortality and plasma electrolyte concentrations of goldlined seabream ta bl e 2. p la sm a co nc en tr at io ns o f n a+ , c l, m g2 + a nd c a2 + o f r ha bd os ar gu s sa rb a ex po se d to n or m ox ia c on di tio ns (n or m ) c on tr ol s at 7 .9 m l/l d o (c ), 2 m l/l a nd 1 m l/l d o fo r 3 h, 6 h , 2 4 h an d 48 h . d at a re pr es en ts m ea n va lu es ± s ta nd ar d er ro rs . sa m pl e si ze s ar e in p ar en th es is . n or m e xp os ur e 3 h 6 h 24 h 48 h r c 2m /l 1m l/l c 2m l/l 1m l/l c 2m l/l 1m l/l c 2m l/l 1m l/l n a+ 14 8 ±2 .7 (1 0) 17 6. 6 ±2 .8 (1 6) 17 3 ±2 .4 (1 2) 16 9 ±3 .1 (1 0) 17 2 ±1 .7 (1 9) 16 7. 3 ±2 .5 (9 ) 17 5. 7 ±4 .4 (1 0) 17 1. 6 ±2 .6 (2 0) 17 4 ±3 .6 (9 ) 17 6 ±2 .6 (1 0) 16 8. 7 ±3 .8 (1 9) 17 1. 7 ±5 .0 (1 0) 17 0. 3 ±3 .7 (1 0) c l13 6. 8 ±2 .5 (1 0) 16 0. 8 ±3 .1 (1 6) 15 3. 3 ±2 .0 (1 2) 15 5 ±2 .4 (1 0) 15 3. 5 ±2 .7 (2 0) 14 7. 3 ±2 .0 (9 ) 14 9. 9 ±1 .3 (1 0) 14 8. 6 ±2 .1 (2 0) 15 6. 9 ±3 .9 (1 0) 14 6 ±1 .3 (1 0) 14 9. 9 ±1 .2 (1 9) 15 2. 6 ±1 .6 4 (1 0) 15 3. 2 ±3 .5 9 (1 0) m g2 + 0. 25 ±0 .0 3 (1 3) 0. 17 ±0 .0 1 (1 6) 0. 13 ±0 .0 1 (1 2) 0. 19 ±0 .0 4 (1 0) 0. 09 ±0 .0 1 (1 9) 0. 10 ±0 .0 1 (9 ) 0. 09 ±0 .0 1 (8 ) 0. 09 ±0 .0 2 (1 8) 0. 19 ±0 .0 5 (1 0) 0. 07 ±0 .0 2 (9 ) 0. 15 ±0 .0 1 (1 8) 0. 15 ±0 .0 2 (1 0) 0. 14 ±0 .0 2 (1 0) c a2 + 0. 65 ±0 .0 7 (1 0) 0. 60 ±0 .0 3 (1 2) 0. 60 ±0 .0 5 (9 ) 0. 61 ±0 .0 2 (6 ) nm nm nm 0. 57 ±0 .1 5 (2 ) 0. 47 ±0 .1 6 (3 ) nm 0. 47 ±0 .0 2 (4 ) 0. 59 ±0 .0 9 (3 ) 0. 59 ±0 .0 9 (3 ) nm no m ea su re m en ts . al-gheilani and others 78 79 effects of hypoxia on the hehaviour, mortality and plasma electrolyte concentrations of goldlined seabream tolerant of hypoxia than larger fish (smale and rabeni, 1995; burleson et al., 2001; robb and abrahams, 2003). the higher mortality rates of larger fish may be related to lower size-surface; body weight ratios in larger individuals. timmerman and chapman (2004) studied the effect of hypoxia on behavioural and physiological responses of sailfin poecilia latipinna and concluded that females were more tolerant to hypoxia than males. overli et al. (2006) reported that male fish were more table 3. the probability matrix (α = 0.05) of the effects of treatment (1 ml/l and 2 ml/l do), exposure time (3 h, 6 h, 24 h and 48 h), gender, tw and tl, and the interactions time×treatment, time×gender, treatment×gender and time×treatment×gender on plasma electrolyte concentrations of rhabdosargus sarba. tl/tw treatment time gender treatment* time treatment* gender time* gender treatment* time* gender na+ tl 0.816 0.645 0.949 0.614 0.231 0.261 0.866 0.084 tw 0.534 0.608 0.873 0.539 0.255 0.267 0.894 0.082 cltl 0.373 0.228 0.707 0.096 0.050 0.566 0.908 0.926 tw 0.594 0.222 0.456 0.075 0.049 0.591 0.912 0.944 mg2+ tl 0.749 0.522 0.816 0.505 0.866 0.553 0.749 0.893 tw 0.857 0.857 0.531 0.846 0.846 0.534 0.761 0.900 ca2+ tl 0.051 0.023 0.066 0.231 0.020 tw 0.044 0.027 0.052 0.299 0.020 table 4. the effects of hypoxia on fish mortality rates from studies at a range of exposure times and do levels. species do (ml/l) exposure time mortalities (%) reference solea solea 0.3 0.5 12 h 12 h 0 0 dalla via et al., 1994 scophthalmus maximus dicentrarchus labrax 1.7 40 days 0 pichavant et al., 2003 epinephelus akaara mylio macrocephalus 0.7 7 h 0 woo and wu, 1984 epinephelus akaara mylio macrocephalus 0.4 7 h few wu and woo, 1984 gadus morhua 0.4 0.7 1.5 7 h 7 h 7 h 100 most 0 plante et al., 1998 scophthalmus maximus 1.3 6 h 0 pichavant et al, 2002 oncorhynchus mykiss 1.5 3 h 40 van raaij et al., 1996a gadus morhua 1.3 6 h 21 claireaux and dutil, 1992 al-gheilani and others 80 81 effects of hypoxia on the hehaviour, mortality and plasma electrolyte concentrations of goldlined seabream aggressive than females, and would presumably consume more oxygen. in the present study a larger proportion of males than females died in the 1 ml/l treatment for 48 h, and although the sample size was small (12 males and 17 females), we suggest that female r. sarba may be more tolerant to hypoxia than males. the absence of significant fluctuations in plasma electrolytes (na+, cl-, mg2+ and ca2+) of r. sarba during hypoxia exposure is in accordance with the results of several other studies on marine teleosts (see table 5), where positive results were only sporadically found. woo and wu (1984) studied the effect of hypoxia on ca2+ and na+ serum levels in m. macrocephalus, and found ca2+ levels to be unchanged whilst na+ increased. they attributed the na+ elevation to impairment of branchial or renal functions. the decrease of mg2+ reported by kakuta et al. (1992) in cyprinus carpio was attributed to a selective gain of ions entering the fish from a hyperionic environment. most other studies could not, however, find a relationship between hypoxic conditions and fluctuations in plasma electrolytes (table 5). the effects of netting (or capture) stress, confinement, transport, exercise and air-exposure on marine teleost electrolyte balance have often been reported upon, and the causes for imbalances have been suggested in some cases. railo et al., (1985) reported rapid changes in the plasma electrolyte composition of even mildly stressed fish, which suggests that capture stress had profound effects on salt and water balance. imbalances in plasma na+/clratio may reflect disturbed acid-base regulation (mcdonald and wood, 1993; mazon et al., 2002), or increasing membrane permeability due to disruption of the membrane integrity of gill cells (stagg and shuttleworth, 1982; mcdonald and wood, 1993). ionregulatory disruption induced by copper was related to inhibition of branchial na+k+-atpase activity (lauren and mcdonald, 1985; pelgrom et al., 1995). knudsen and jensen (1998) reported on exercise-induced hyperkalaemia as a consequence of an efflux of k+ from skeletal muscles during their depolarization and an insufficient reuptake. farrell (1984) suggested that elevated plasma ca2+ and catecholamine levels protect the teleostean heart from acidosis which might result from stress. salm et al. (2006) found that the plasma na+ levels in pagrus pagrus increased upon netting stress, but that other plasma ions remained unchanged, and suggested a selective gain of ions from a hyperionic environment. after 2 hours of netting stress, all plasma ion levels returned to, or dropped below basal control levels, suggesting that gill permeability had returned to normal and hydromineral balance restored. acknowledgements special thanks for dr. johan for his reviewing of this paper and adding of valid ideas and corrections. this project was funded by ministry of fisheries wealth and sultan qaboos university. references al busaidi, s.s., k.m. al rashdi, h.m. al gheilani, and s. amer. 2007. massive fish mortality during table 5. the effects of hypoxia exposure on plasma electrolyte concentrations of selected fish species from the literature. no effect = 0; + = increase; – = decrease. species doml/l) e x p . time na + clca2+ mg2+ reference o. mykiss 1.5 12 h 0 0 (van raaij et al., 1996b) 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physiological responses to handling in the turbot. journal of fish biology, 48:161-173. woo, n.y.s. and r.s.s. wu. 1984. changes in biochemical composition in the red grouper, epinephelus akaara (temminck and schlegel), and the black seabream, mylio macrocephalus (basilwsky), during hypoxic exposure. comparative biochemistry and physiology, 77a(3): 475-482. microsoft word jamsy2003v08n01content-arabic.doc ! ___________________ *corresponding author. 47 agricultural and marine sciences, 8(1):47-49 (2003) short communication © 2003 sultan qaboos university effect of irrigation on within-grove distribution of red palm weevil rhynchophorous ferrugineus y. aldryhim* and s. al-bukiri department of plant protection, king saud university p.o. box 2460, riyadh 11451, kingdom of saudi arabia ! ! ! ! ! ! ! ! abstract: the red palm weevil (rpw) rhynchophorous ferrugineus (oliv.) is the most important pest attacking date palm trees. the objective of this study was to determine the effect of drip and flood irrigation on the within-grove distribution of rpw. the current study was started with the first appearance of the infestation to almost disappearance of the infestation. results showed that more infested trees were detected in plots with flood irrigation. the number of infested trees in these plots represented 89% of the total infested trees. this study suggested that irrigation management and soil moisture are key factors in the dispersion of the rpw infestation and could be used as one of the integrated pest management tools. keywords: red palm weevil, integrated pest management, irrigation, soil moisture, infestation control. he red palm weevil (rpw) rhynchophorous ferrugineus (oliv.) is the most important pest of the date palm in the middle-east (abraham et al., 1998). the insect was discovered in saudi arabia in the mid-1980s (gush, 1997; abraham et al., 1998; faleiro et al., 1999). since then it has spread over most of the date palm areas (bokhari and abuzuhira 1992; vidyasagar et al., 2000), due to the transfer of infested offshoots and palm trees. rpw infestation is lethal to date trees. this is due to a lack of early and apparent external signs of the infestation. infestation occurrs mostly in young trees of age 5-15 years (sathiamma et al. 1992; aldryhim, unpub. observation). several control methods have been applied within an ipm (i.e. integrated pest management) strategy. the main components of ipm are phyto-sanitation, which involves cutting down and burning the infested trees, use of insecticides, and use of pheromone traps for monitoring and mass trapping of adult rpws. phyto-sanitation is crucial in preventing or reducing subsequent infestations (murphy and briscoe, 1999). there have been no reports on the within-grove distribution of rpw infestations under different watering regimes. the objective of the present work was focused on the effect of the types of irrigation on the distribution of rpw infestation in date palms within a grove. materials and methods this study was conducted in a 16,000 date palm farm in al-karaj oasis, 80 km south of riyadh. it was started with the first appearance of infestation in may 1998 and ran to october 1999 when the level of rpw infestation became low and almost disappeared. the major cultivars were: nepoot seif, khalass, sagai and berhi. the age of the trees varied from 5 to 25 years. leaf pruning (takreeb) was carried out in late autumn. t "#$%&'!&()&*+,)!-"./,)!01234!04567)!859:;<!=2>1!?> !!&,)!0"#! !"#$%&'()*+,)-.+/+01#23)*++ + !0$$6%&+4+(5678+++++9:+2-;<=+>? 8+!6)*+"-#$*+&%5&=+'5(+)*&5*+)*+,?59-)*+.5!"!+&*+,?2"*6)+/++.#&7*)+.!*23)*+012+3318 ++++%&5)*+.4#&55+&?56788)*+&5*9++:?54-6)*+/=+;+8+<5=>++?+.@-5.a*+b5#c"4+5=?-/d++"=35@23)*++.@-.a*+2"1e+f/=+b(+.5!*+?/<6-1g-h6i*+/+ +j*"?k=+!#+.@-.a*+lm-#c+ng-6-)*+o+5p/*++!6)*8q/&++.@*)*+,?9-)*+2-;<=+.(r:+o9=@+s??+&*9)-@tu+v+!)-*wx+'( +++++.@-5 *)*+2-;5<y*+m35>+/+f358/+++++++++*+.4#&5+z=+<5=>+ng-65-)*+0152+)&%+++++++l&6[*)*+.?!-!y*+,(*"7)*+'(+.?p2y*+.@"5&)*+f37(/+ :*+<=>\+)*+011@+.@-.a*+2-\6x+l&.#$*+012+.+#-'*)+.=(-'6*)*+l2*ma*+"*/m=+q3?]&+-1(*396!*+''*#+^/+ aldryhim and al-bukiri !48 ! ! figure 1. outline of field showing plots and type of irrigation. d = dripping irrigation, f = flooding irrigation. numbers refer to infested trees in plot. the farm was divided into 22 plots, each contained 650 ± 50 trees, each plot was 6500 ± 500 m2 . the distance between trees in the same!row and the distance between rows was 10 m. flood (f) and drip (d) irrigation were used (fig. 1)" the rate of drip irrigation was 0.5-1 m3 per tree per week and per two weeks in the summer and in the winter, respectively. the rate of flood irrigation was 4-8 m3 per tree per week and per two weeks in the summer and in the winter, respectively. since there is no early and clear sign for infested trees, detection of the infested trees was totally depended on the scout’s efforts. once an infested tree was observed, it was cut-down and dissected to small pieces that were packed into sacks and were burned in a special incinerator. data were taken for each infested tree such as the date on which infestation was observed, plot number and type of irrigation. results infested trees were first detected in a plot with flood irrigation. rpw spread from the hot spot, where the infestation was first appeared in may 1988, to the neighboring plots with clear preference to plots with flood irrigation (fig. 1). infestations were detected in six plots with flood irrigation and three plots with drip irrigation. number of infested trees were 55, 32, 35, 5, 10, and 4 in six plots of flood irrigation and 5, 6 and 6 in three plots of drip irrigation. the number of infested trees that were detected in flood irrigation plots was 141, representing 89 % of total infested trees. whereas, 17 infested trees were detected in drip irrigation plots that representing 10 % of total infested trees (fig. 2). discussion flood irrigation created a more suitable microhabitat for rpw. it increased soil moisture contents which appears to be preferable to rpw and allows grasses to grow 0 10 20 30 40 50 60 70 80 90 100 flood drip type of irrigation % to a high density. the groves provide shade and reduce the evaporation rate of water from the soil. leefmans (1920) reported that adults of rpw seek moist harborages till they find a new host. aldryhim and kalial (unpublished data) found that rpw adults survived up to three and 39 days in dry and moist peat moss, respectively, in the absence of the food. also, they found that rpw adults could penetrate 20 cm deep in the moist peat moss; where no attempt for penetration occurred when adults were placed on dry peat moss. giblin-davis and howard (1989) found that adults of a closely related species, r. cruentatus, suffered from high mortality when placed in petri-dishes that lacked moisture" this weevil has high cuticular permeability and is susceptible to significant water loss in dry environments (weissling and giblin-davis, 1993). it chooses high relative humidity over low relative humidity in choice tests (weissling and giblin-davis, 1993) and plant tissues with minimal moisture content are significantly less attractive (giblindavis et al., 1994). conclusion the response of rpw adults to moisture is probably an important part of the insect behavioral selection but this deserves further study. it will be useful to do more research on the use of irrigation types and soil moisture as important tools in the ipm of rpw. the results obtained may help in detection of infested trees by concentrating inspection on farms that used flood irrigation.! references abraham, v.a. and g.b. pillai. 1998. red palm weevil – a dreaded enemy of coconut palm. indian farmers` digest 7(1):15-20. abraham, v.a., m.a. al-shuaibi, j.r. faleiro, r.a. abozuhairah, and p.s.p.v. vidyasagar. 1998. an integrated management approach for red palm weevil rhynchophorous ferruginseus oliv. a key pest of date palm in the middle east. journal of agricultural sciences 3:77-83. figure 2. distribution of infested trees in plots with flood and drip irrigation. 35 5 6 32 55 6 4 10 0 5 in fe st at io n effect of irrigation on within-grove distribution of red palm weevil rhynchophorous ferrugineus ! ! 49 bokhari, v.u.g. and r.a. abuzuhira. 1992. diagnostic tests for red palm weevil. rhynchophorous ferruginseus infested date palm trees. arab gulf scientific research 10:93-104. faleiro, j.r., m.a. al-shuaibi, v.a. abraham, and t. prem kumar. 1999. a technique to assess the longevity of the pheromone (ferrolure) used in trapping the date palm weevil rhynchophorous ferrugineus oliv. agricultural sciences 4(1):5-9. giblin-davis, r.m. and e.w. howard. 1989. vulnerability of stressed plants to attack by rhynchophorus cruentatus (coleoptera: curculiondae) and insecticides control of the pest. journal of economic entomology 82:1185-1190. giblin-davis, r.m., t.j. weissling, a.c. oehlschlager, and l.m. gonzalez. 1994. field response of rhynchopharus cruentatus (coleoptera: curculionidae) to its aggregation pheromone and fermenting plant volatiles. florida entomology 77:164-177. gush, h. 1997. date with disaster. the gulf today, sept. 29, p. 16. leefmans, s. 1920. de palmsnuitkever (rhynchophorus ferrugineus oliv.). meded. inst. plziekr. 43:1-90. murphy, s.t. and b.r. briscoe. 1999. the red palm weevil as an alien invasive: biology and the prospects for biological control as a component of ipm. biocontrol news and information 20(1):35-46. sathiamma, b., v.a. abraham, and c. kurian. 1992. integrated pest management of the major pests of coconut. indian coconut journal january:27-29. vidyasagar, p.s.p.v., m. hagi, r.a. abozuhairah, o.e. al-mohanna, and a. al-saihati. 2000. impact of mass pheromone trapping on the red palm weevil: adult population and infested level in date palm gardens of saudi arabia. the planter 76:347-355. weissling, t. and r.m. giblin-davis. 1993. water loss dynamic and humidity preference of rhynchoporus cruentatus (coleoptera: curculiondae) adults. environmental entomology 22:93-98. ______________________________________________________ received march 2002. accepted september 2002. agricultural and marine sciences, 14:27-34 (2009) ©2009 sultan qaboos university 27 _____________________________ *e-mail: w3.senadeera@qut.edu.au density variation of different shaped food particulates in fluid bed drying: empirical models wiji senadeera* school of engineering systems, queensland university of technology gpo box 2434, brisbane, qld, 4001, australia abstract: three particular geometrical shapes, parallelepiped, cylindrical and spherical, were selected from potatoes (aspect ratio = 1:1, 2:1, 3:1), cut beans (length:diameter = 1:1, 2:1, 3:1) and peas respectively. the density variation of food particulates was studied in a batch fluidised bed dryer connected to a heat pump dehumidifier system. apparent density and bulk density were evaluated with non-dimensional moisture at three different drying temperatures of 30, 40 and 50 oc. relative humidity of hot air was kept at 15% in all drying temperatures. several empirical relationships were developed for the determination of changes in densities with the moisture content. simple mathematical models were obtained to relate apparent density and bulk density with moisture content. keywords: apparent density, bulk density, length diameter ratio, aspect ratio. introduction drying is a major food processing operation in the food industry, which consumes large amounts of energy. it is a very complex process and involves mass and heat transfer processes simultaneously. the quality of food materials during drying depends not only on the initial quality of the raw materials, but also on the processing conditions during drying (karel, 1991). the fluidized bed drying has been recognized as a gentle and uniform drying with a high degree of efficiency (senadeera et al., 1998). this is a very convenient method for heat-sensitive food materials as it is relatively fast, and thermal damages can be reduced (gibert et al., 1980, giner and calvelo, 1987). in the process of drying, several physical and structural changes are occurring simultaneously. most of the natural food particulates for human/animal consumption are available as high moisture materials, and drying could be used to reduce the moisture content in order to avoid the microbial growth (fusco et al., 1991). natural food particles are available in different irregular shapes and sizes. during drying, shape and size of the products change appreciably, influencing their particle properties inside the drying equipment (ratti, 1994). bulk density and particle density are important physical properties in food materials, which influence final texture, quality and transport properties of the dry foods. bulk density and particle density are the main parameters in designing equipment for the food particulates. bulk density and porosity are related to flow resistance through beds, food storage and packaging of the products (madamba et al., 1994). particle density is important in heat transfer of the material. density models are empirical relations based on experimental observations: however, theoretical models are based on mass and volume (rahman and driscoll, 1994). the effect of drying methods on bulk density and particle density of banana, apple, carrot and potato were studied and simple mathematical models were correlated with moisture (krokida and maroulis, 1997). density models were developed for garlic (madamba et al., 1994) and for apple, carrot and potato cubes (zogzas et al., 1994). density models were developed for squid flesh during air drying (rahman and potluri, 1990). the effect of drying condition was assessed and models were developed for peas during air drying (medeiros and sereno, 1994). change in structure, عند أشكالھا باختالف الغذائیة المواد كثافة جسیمات تباین التجریبیة النماذج التجفیف: سینادیرا ویجي الطول (نسبة الخضراء والفاصولیا (٣:١ و ٢:١ و ١:١ للعرض = الطول (نسبة البطاطس والكرویة، من واالسطوانیة السطوح متوازیة وھي أشكال ھندسیة، اختیار ثالثة تم الخالصة: تقوم بحمل مضخة حراریة باستخدام متتالیة دفعات على التجفیف عند الغذائیة المواد (دقائق) جسیمات كثافة اختالف دراسة وتمت على التوالي. والبازالء (٣:١ و ٢:١ و ١:١ = للقطر النسبیة الرطوبة تثبیت كما تم مئویة. درجة و٥٠ ٤٠ و ٣٠ بلغت حرارة درجات عند محتوى الرطوبة باختالف والكلیة الظاھریة الكثافة تقییم وتم الساخن. الھواء الجسیمات في وتدویر تم الرطوبة. كم الكثافة باختالف محتوى في االختالف لتحدید التجارب على المبنیة العالقات من عدد استنباط تم الدراسة ھذه ومن الحرارة. درجات لمختلف عند ١٥٪ الساخن للھواء الرطوبة. بمحتوى الظاھریة والكلیة الكثافة لعالقة ریاضیة مبسطة نماذج على الحصول الطول للعرض نسبة للقطر، الطول نسبة الكلیة، الكثافة الظاھریة، الكثافة كلمات مفتاحیة: 28 senadeera 29 density variation of different shaped food particulates in fluid bed drying: empirical models density and porosity of potato during drying have also been studied (wang and brennan, 1995). the objective of this study was to investigate the change of density for different shaped food materials with varying dimensional moisture ratios and to relate these changes to moisture content using suitable models. fluidized bed drying experiments were undertaken for an initial bed height of 150 mm in a flexi-glass laboratory batch fluid bed unit connected to a heat pump system. materials and methods material preparation fresh green beans phaseolus vulgaris of labrador variety were used for producing cylindrical particles. beans were purchased from the same supplier to maximize reproducibility of the experimental results. when selecting the size of beans, care was taken to obtain batches of consistent diameter of 10 + 1 mm. size was measured using vernier callipers with an accuracy of 0.05 mm. both ends of the beans were removed and only the middle portions, which resemble a cylindrical shape, were used to produce the required samples. samples were prepared in three lengths to diameter ratios of 1:1, 2:1 and 3:1, respectively. after preparation, beans were kept in a plastic container in a cold room at 40 c for more than 24 hours in order to make uniform moisture distribution. potatoes, solanum tuberosum, of the variety sebago were purchased from the same supplier in 50 kg bags. before sample preparation, potatoes were washed and brushed to remove skin and mud. first, large cuboid shapes were cut from the whole potatoes, removing the outer portions near the skin. subsequently, those cubes were cut carefully using a sharp knife to produce parallelepipeds with a square cross-section and sides 6.5 mm wide. those slices were then pushed through a stainless steel square cutter to make parallelepipeds in a dicing machine (hobart, australia), by incorporating a cutter which makes 6.5mm x 6.5mm square cross-section. in the case of aspect ratio of 1:1, the potato cubes were pushed through the same cutter and axial length was controlled to a length of 6.5 mm by a cutting blade. according to the required aspect ratios of 3:1, 2:1 and 1:1, the particles were cut carefully to lengths of 19.5, 13 and 6.5 mm, respectively. immediately after cutting, all the samples were immersed in a sodium metabisulphite solution (0.1 % w/w) for 15 minutes to prevent browning during drying. the samples were drained on a mesh tray. then samples were placed in a plastic bag and kept in a cold room for 24 hours at 4o c in order to produce uniform moisture distribution within the sample. for the spherical model, fresh green peas, pisum sativum of bounty variety, were purchased from the same supplier in 10 kg boxes in their pods. they were shelled by hand and graded using a wire mesh. those with average diameter 10 + 1 mm were selected and stored in a cold room for 24 hours at 4oc in order to produce uniform moisture distribution. experimental design three batches were prepared at once and used for three drying temperatures. two replicate batches were prepared for cut beans (3 l:d ratios) and diced potato (3 aspect ratios). three replicate batches were prepared for peas. for beans and potato, a split unit design with two replications corresponding to processing time, with three sizes per block and three drying temperatures for each size was used. for peas, a randomized complete block design with three replications for each temperature was used. for each particulate size, one batch stored in the cold room was taken for fluidised bed drying experimentation. the fluidised bed dryer was connected to a heat pump dehumidifier system (figure 1). a schematic diagram of the connection arrangement is shown in figure 2. the drying conditions of 30, 40 and 50o c were set by the temperature controller in the heat pump dehumidifier system, and the drying setup was run for 2 hours to achieve steady state conditions of drying before material introduction. the relative humidity during drying was maintained at 15 %. initial bed height of 150 mm was used for all materials to ensure enough material was available for sample collection and subsequent drying during the entire drying period. the hot air velocity passing through the material bed was kept constant at 2.2 m/s for all drying experiments. this velocity was selected because it was within the limit of fluidisation and terminal velocity of all figure 1. fluidised bed drying experimental setup. 28 senadeera 29 density variation of different shaped food particulates in fluid bed drying: empirical models three materials and within the capability of the fan. the air-flow entering the dryer was controlled by flow control valves. samples were collected from the dryer at 30 minute intervals through the sample outlet. each time they were collected in a sealable container and immediately used for moisture determination and volume measurements. the volume of the particles was measured by the liquid displacement method using liquid paraffin (sg = 0.8787 at 30oc) as the medium. a measuring cylinder of 22 mm inside diameter and 50 ml capacity was used for liquid displacement (zogsas, 1994). paraffin was employed as it does not interact with the constituents of the sample and it has a low enough density to ensure complete submergence of the particles. for one measurement, a known number of particles were immersed in paraffin. the number of particles for volume determination was increased progressively as drying progressed in order to maintain an approximately constant volume for each sample. volume was measured by the difference of meniscus levels before and after immersion, using vernier calipers (accuracy 0.05 mm). considering the high viscosity of paraffin, care was taken to avoid formation of air bubbles and adherence of liquid to the glass walls of the cylinder above the liquid meniscus by gently dipping the samples into the liquid. an average of three readings was recorded from three replicate samples. all the measurements were taken within a minute to avoid any possibility of absorption of paraffin into the product. the vacuum oven was used to measure the moisture content of the particles according to the aoac method 934.06 (1995). weighing dishes made of aluminium, 6080 mm diameter and 25 mm deep with easily removable lids were pre-washed, dried and kept in a desiccator with silica gel for two days prior to experimentation. duplicated samples of 5-10 g in mass weighed by an electronic balance (sartorius, + 0.001g) were thoroughly homogenised and put into tared weighing dishes from the desiccator, and placed inside a vacuum oven. the metal dishes containing the samples were in direct contact with the metal shelf of the oven. moisture content was determined by measuring the loss in weight of finely chopped samples held at 70oc and 13.3 kpa vacuum for more than 24 hours. samples were transferred from the vacuum oven to a dessicator for cooling. the cooled, samples were weighed as quickly as possible to an accuracy of 0.1 mg. analysis of experimental data the data were analysed by anova to evaluate significant differences and both linear regression and non-linear regression to obtain suitable models. statistical analysis system software (sas, 1985) was used. the experimental data on shrinkage and drying were analysed for significance (anova) using the sas routine glm (general linear models), and the model parameters were estimated using sas least squares routine (glm for linear models and nlin for non-linear models). the curve which best fitted the data was taken as the model. model validity was tested using the coefficient of regression (r2) and mean absolute error percentage (mae%). figure 2. schematic of the fluidised bed drying setup. �� �� results and discussion particle density (apparent) the model was fitted using a non linear procedure nlin (sas, 1985) similar to lozano et al. (1994): � (1) where, is particle density (kg /m3), mr is moisture ratio (db), a, b, c, d are the constants. the estimated parameters are given in table 1. cylindrical food particulate green bean the particle density term used in this paper is defined as the density of the particle including externally connected pores. the green beans in general demonstrated an increased particle density with decreased moisture content, except in the case of l:d ratio of 3:1 particle density decreased at low moisture levels. particle density of the initial fresh material ranged from 943 kg/m3 (965% db moisture) to 964 kg/m3 (1035 % db moisture) and final dry material density ranged from 779 kg/m3 (3.5 � 30 senadeera 31 density variation of different shaped food particulates in fluid bed drying: empirical models db moisture) to 1393 kg/m3 (4.1% db moisture). particle density variation with moisture ratio for beans during fluidized bed drying was correlated to a non-linear model similar to the model suggested by lozano et al. (1983) for vegetables and fruits. moisture ratio was selected instead of moisture to avoid effects due to the natural variation in initial moisture content. figure 3 shows particle density variation of beans at 30oc. these parameters were tested for their statistical significance. it was found that only the b value was significantly different (p <0.05) for different drying temperatures for each size. the value b represents the rate of change of particle density in the linear region, and it is dependent on the temperature. the constant c of the exponential part of the equation appears to have a decreasing trend, decreasing as the l: d ratio increases (table 1). this indicates that towards the end of drying, the l: d ratio affects the particulate density. as the l: d ratio increased the value of c decreased from positive to negative. a positive c means an increase in particle density and negative c means a decrease in particle density. it can therefore be concluded that c is a measure of internal porosity or internal collapse. the parameter d is a measure of rate change of density in the table 1. parameters of particle density variation model [rρap = a + b mr + c exp (d mr)] for all materials in fluidised bed drying. material l:d /ar ratio temp (oc) a b c d r2 mae% 30 0.984 0.017 0.276 8.74 0.91 2.32 1:1 40 0.966 0.0353 0.523 23.2 0.96 2.17 50 0.995 -0.039 1.04 408 0.93 0.06 30 0.972 -0.022 0.219 10.5 0.93 1.53 bean 2:1 40 0.827 0.110 0.369 8.40 0.84 2.44 50 0.964 -0.023 0.144 26.6 0.99 1.12 30 0.991 -0.022 -0.137 7.26 0.88 0.70 3:1 40 0.935 0.042 -0.253 15.4 0.90 2.64 50 1.01 -0.092 -0.245 27.4 0.98 2.13 30 1.16 -0.126 -1.12 208 0.94 0.96 1:1 40 1.19 -0.178 -0.351 97.2 0.91 1.01 50 1.17 -0.125 -0.272 113 0.81 1.65 30 1.14 -0.108 -0.123 12.8 0.80 1.12 potato 2:1 40 1.11 -0.051 -1.97 316 0.97 0.52 50 1.17 -0.173 -0.467 159 0.80 1.53 30 1.14 -0.099 -0.240 64.3 0.93 0.76 3:1 40 1.14 -0.086 -0.252 75.8 0.81 1.15 50 1.12 -0.108 -0.412 236 0.90 0.91 30 1.17 -0.166 0.081 13.7 0.99 1.24 peas 40 1.13 -0.133 0.136 15.3 0.88 1.84 50 1.10 -0.098 4.89 142 0.89 1.59 � figure 3. particle density variation of beans during fluidised bed drying. ( • experimental l:d =1:1 model l:d =1:1); (o experimental l:d=2:1 -model l:d=2:1); (δ experimental l:d =3:1 … model l:d =3:1). 300c 30 senadeera 31 density variation of different shaped food particulates in fluid bed drying: empirical models non-linear region experienced at low moisture contents. the negative c value found for l: d = 3:1 indicated that internal porosity was increased. this may be due to the long axial dimension, which facilitated closing of ends and trapping of air inside voids. particle density therefore decreased. for l: d = 2:1 and 1:1 it was found that particle density increased at lower moisture contents. some form of collapse of the structure must have contributed to this increase. for l: d = 1:1 and l: d = 2:1, the general trend of particle density behavior was similar at 300c and 400c. however, at 300c, the magnitude of increase was lower than at other temperatures. in the case of l: d = 3:1, results were similar at all temperatures. parallelepiped food particulate – potato particle density variation of potato during fluidised bed drying was correlated to a non-linear model with a moisture ratio similar to the model suggested by lozano et al. (1983) for vegetables and fruits. the particle density of potato increases with decreasing moisture content. however, once the product neared its final fixed volume and shape, the reduced shrinkage resulted in increased particle density. the particle density behaviour of potatoes with respect to moisture removal was similar to the particle density behaviour of beans. similar behaviour was observed for all aspect ratios at all temperatures. materials with aspect ratio 1:1 always tended to have a higher particle density than materials at other aspect ratios. it appeared that aspect ratio 2:1 showed lower particle density behaviour at 30oc, and 40oc. however, an aspect ratio 3:1 showed decreased magnitude at 500c and an increased magnitude at 40oc. the b value was significantly different (p < 0.05) with temperature for each size. the value b represents the rate of change of particle density in the linear region. spherical food particulate green peas particle density variation of peas during fluidized bed drying is shown in fig 4 for different drying temperatures. the particle density of peas increased with decreasing moisture content until moisture was 0.15 kg/kg db and the rate of increase decreased with the drying temperature in the linear region. below this moisture value, there was a higher rate of increase of particle density at higher temperatures, so that all treatments resulted in similar final particle density. at lower moisture values, even though the structure may be tougher due to removal of moisture, it was not enough to compensate for the effect of increased internal void (porosity) and increase in temperature of the product. this resulted in collapse of the structure. this behaviour was similar to the behaviour studied for various other fruits and vegetables by lozano et al. (1983). a similar model characterising the change in particle density with change in moisture during drying for peas, was fitted by medeiros and sereno (1994). these results are similar to the earllier published reports. the parameters of the model equation given in table 1 were tested for their significance. it was found that the b and c values are significantly different (p < 0.05) with temperature for each size. the value b represents the rate of change of particle density in the linear region. bulk density the variation of bulk density of the bed of particulates at different drying temperatures and l: d ratios were correlated to moisture, using a polynomial quadratic equation of the form: � figure 4. particle density variation of peas during fluidised bed drying. (• experimental 300c model 300c ); (δ experimental 400c -model 400c); (□ experimental 500c … model 500c). � (2) 32 senadeera 33 density variation of different shaped food particulates in fluid bed drying: empirical models table 2. parameters of bulk density variation models of materials (rρb = a + b mr + c m r2) in fluidised bed drying. material l:d /ar ratio temp (o c) a b c r2 mae% 30 268.61 598.07 -370.37 0.97 3.35 1:1 40 255.70 747.27 -512.50 0.96 3.96 50 251.06 682.88 -426.24 0.97 3.34 30 225.87 621.46 -397.78 0.87 9.83 bean 2:1 40 213.11 677.39 -453.97 0.86 9.33 50 218.79 656.87 -426.37 0.91 9.06 30 233.46 537.77 -321.85 0.82 6.61 3:1 40 223.73 620.95 -405.79 0.86 9.65 50 198.15 712.02 -473.55 0.96 6.53 30 384.35 587.43 -376.17 0.94 3.28 1:1 40 380.60 630.16 -431.32 0.97 2.60 50 353.96 798.24 -568.80 0.99 1.59 30 304.68 633.78 -380.91 0.97 3.27 potato 2:1 40 314.59 638.66 -394.40 0.95 4.58 50 314.03 640.37 -391.32 0.97 3.47 30 263.10 623.35 -363.65 0.97 2.76 3:1 40 236.71 458.35 -162.42 0.97 3.69 50 257.78 504.44 -235.45 0.99 2.24 30 687.09 -23.835 -98.726 0.85 2.21 peas 40 659.93 39.805 -131.760 0.81 1.98 50 508.93 446.85 -407.826 0.80 2.40 � figure 5. bulk density variation of beans during fluidised bed drying. ( • experimental l:d =1:1 model l:d =1:1); (o experimental l:d=2:1 -model l:d=2:1); (δ experimental l:d =3:1 … model l:d =3:1). 300c surface. this contributed to the increase in bulk density as the particles could more easily pack together. however, further drying resulted in a wrinkled surface, and twisting and deformation of the shape, increasing the interparticulate airspace. this reduced the density of the bulk material. none of the parameters given in table 2 were significantly different (p < 0.05) with temperature or size. parallelepiped food particulate – potato the variation of bulk density of different aspect ratios at different temperatures were correlated to moisture using a polynomial quadratic equation as in the case of beans (table 2). none of the parameters are significantly different (p > 0.05) with the temperature. the values of a and c are significantly different (p < 0.05) with the aspect ratio. the where, a, b, c are constants, mr is moisture ratio (kg/kg db), ρb is bulk density (kg/m3). the estimated parameters of the model are presented in table 2. the general linear modelling (glm) regression procedure (sas, 1985) was used to estimate the parameters in table 2 for all the materials. cylindrical food particulate green bean the bulk density of the fresh beans for all l: d ratios at all temperatures reached a maximum early in the drying period, and then dropped as the material dried further (figure 5). the bulk density of dried material during the later stages of drying was much lower than that of the fresh material. during the early stages of drying, there was uniform shrinkage without any irregularities on the 300c 32 senadeera 33 density variation of different shaped food particulates in fluid bed drying: empirical models bulk density variation of the fresh potato with the moisture removal for all aspect ratios at all temperatures showed a similar trend to that of beans. spherical food particulate green peas figure 6 shows the bulk density variation of peas during fluidised bed drying at different temperatures. the experimental data for bulk density were correlated with moisture ratio with quadratic equations for different temperatures and are presented in table 2. the bulk density of peas increased to a maximum and again reduced as drying proceeded. the correlation coefficients of the equations in table 2 were poor. however, mae% indicated that they are sufficient to characterise the trend in change in bulk density with respect to moisture removal. a similar trend was observed for green beans with length: diameter ratio 1:1 during drying. drying peas at 50oc resulted in a less dense product. the reduced shrinkage of peas dried at 50oc would have been a major factor in this effect. generalized models particle density the generalized form of particle density variation of all three materials (beans, potato and peas) showed very poor correlation coefficients among size and temperature. bulk density as none of the parameters given in table 2 were significantly different (p<0.05) with temperature and size for beans, for generalization purposes, a single quadratic equation for the bulk density can be assumed. the general linear modeling (glm) in sas was used to obtain the generalised equation. the generalized equation can be written as: for generalisation purposes, it was assumed that a and c parameters are linearly correlated with aspect ratio. a quadratic equation for the bulk density could be written including aspect ratio. the generalised equation can be written as: the generalized form for the bulk density variation among temperatures of peas was evaluated. however, it also has a very poor correlation coefficient. conclusion in this study a correlation between apparent density and bulk density with moisture content was observed. for beans, particle density tended to increase for the whole range except for l: d = 3:1 at all temperatures. for l: d = 1:1 and 2:1. some form of collapse may have contributed for the increased in particle density at low moisture values. beans with l: d = 3:1 showed a decreased particle density due to increased internal porosity at low moisture contents. potato particle density reached a maximum value and decreased at low moisture for all aspect ratios. in the case of peas at all temperatures, particle density was increased with the decreased moisture content until moisture was 0.15 kg/kg db. below this moisture content it was observed that the rate of increase of particle density of peas was higher at higher drying temperatures. bulk density variation of beans, peas and potato with moisture ratio was correlated to similar quadratic models. the models could be further improved by considering material particle (solid) density to investigate effects of temperature and particle shapes on porosity development during drying. nomenclature a, b, c, d constants a, b, c constants figure 6. bulk density variation of peas during fluidised bed drying. � (3) � (4) � 34 senadeera l length (m) d diameter (m) ar aspect ratio ρ density (kg/m3) mr moisture ratio (db) suffixes a apparent b bulk references aoac. 1995. official methods of analysis, 16th edition. association of official analytical chemists, washington, dc. fusco, a. j., j.r. avanza, r.j. aguerre and j.f. gabritto. 1991. a diffusion model for drying with volume change. drying technology 9:397-417. gibert, h., j.l. baxerres and h. kim. 1980. blanching time in fluidized beds. in: food process engineering 1: food processing systems. p. linko, y. malkki, j. olkku and j. larinkari (editors), 75-85. applied science publishers, london. giner, s.a. and a. calvelo. 1987. modelling of wheat drying in fluidized beds. journal of food science 52: 1358-1363. karel, m. 1991. physical structure and quality of dehydrated food. in: drying ‘91. a.s. mujumdar and i. filkova (editors), 26-35. elsevier science publishers, amsterdam. krokida, m.k. and z.b. maroulis. 1997. effect of drying method on shrinkage and porosity. drying technology 15:2441-2458. lozano, j.e., e. rotstein and m.j. urbician. 1983. shrinkage, porosity and bulk density of food stuffs at changing moisture contents. journal of food science 48:1497-1502. madamba, p.s., r.h. driscoll and k.a. 1994a. shrinkage, density and porosity of garlic during drying. journal of food engineering 23:309-319. madamba, p.s., r.h. driscoll and k.a. buckle. 1994b. bulk density, porosity and resistance to airflow of garlic slices. drying technology 12(4):937-954. medeiros, g.l. and a.m. sereno. 1994. physical and transport properties of peas during warm air drying. journal of food engineering 21:355-363. rahman, s. and r.h. driscoll. 1994. density of fresh and frozen seafood. journal of food engineering 17:121140. rahman, s. and p.l. potluri. 1990. shrinkage and density of squid flesh during drying. journal of food engineering 12:133-143. ratti, c. 1994. shrinkage during drying of food stuffs. journal of food engineering 23:91-105. senadeera, w., b.r. bhandari, g. young and b. wijesinghe. 1998. change of physical properties of green beans during drying and its influence on fluidization. in: drying’98, volume bproceedings of the 11th international drying symposium, halkidiki, greece,. c.b. akitidis, d. marinos-kouris and g.d. saravakos (editors), 1139-1146, ziti editions (pub.), thessaloniki, greece. sas. 1985. user's guide: statistics, 5th edition. sas institute inc., cary, nc. senadeera, w., b.r. bhandari, g. young and b. wijesinghe. 1998. fluidization behaviour of cylindrical green beans during batch fluidized bed drying. tropical agricultural research 10:192-202. wang, n. and j.g. brennan. 1995. changes in structure, density and porosity of potato during dehydration. journal of food engineering 24:61-76. zogzas, n.p., z.b. maroulis and d. marinos-kouris. 1994. densities, shrinkage and porosity of some vegetables during air drying. drying technology 12:1653-1666. received: november 2007 accepted: april 2008 agricultural and marine sciences, 15:15-19 (2010) ©2010 sultan qaboos university 15 _________________________________________ *corresponding author. e-mail: m_salehi@asri.ir environmental factors affecting fleece traits in raeini cashmere goat mohammed salehi1*, masood asadi-fozi2, ahmad mirhadi1 and majid afshar1 1scientific members of animal science research institute of iran 2department of animal science, faculty of agriculture, shahid bahonar university of kerman, kerman, iran والكشمیر الرایني ماعز في الشعر صفات على تؤثر التي البیئیة العوامل أفشار وم. ھادي میر وأ. فوزي أسعدي م. و صالحي م. محطات في والكشمیر الرایني ماعز ألیاف صفات على اإلدارة) ونظام والعمر (الجنس البیئیة العوامل بعض تقییم الــدراســة ھــذه من الھدف كــان الخالصة: ١ بین یتراوح (عمرھا وكشمیري رایني ماعز و١٢٠ ١٥٠ من جمعھا تم والشعر الكشمیر العینات شملت التجاریة. والقطعان المترحل الرعي ظروف وتحت البافت في الــقــارد شعر ونسبة الشعر في الكشمیر ونسبة الخصلة طــول التالیة: الشعر صفات قیاس تم التوالي. على والــمــراعــي البافت محطات من ســنــوات) ٨ إلــى الشعر ونسبة الشعر ــي ف الكشمیر ونسبة الخصلة طــول مــعــدل كــان الكشمیر. شعیرة قطر ــي ف التباین ــدل ــع وم الكشمیر شعیرة قطر ومــتــوســط الشعر ٢٠,١٩±٠,١١ و ٣٣,٥±٠,٧٢ و ٦٦,٥١±٠,٧٢ و ٠,١ ± ٦,٣٥ البافت محطات في الشعیرة قطر في التباین ومعدل الشعیرة قطر ومتوسط الشعر في الحارس التوالي. على و١٧,٨٨±٠,١٩٪، مایكرون و١٩,٥٣±٠,٢١ و٣٠,٩٤±٠,٧٤ ٦٩,٠٦±٠,٧٤ و ٥,٣٢±٠,١ الرعي نظام تحت تلك كانت بینما و١٩,٥٧±٠,٢١٪ مایكرون الــذكــور فــي مھمة بــصــورة أعــلــى الكشمیر نسبة قیم كــانــت قیاسھا. تــم الــتــي الصفات لكل التربیة نظامي بین (٠,٠٥ مــن (أقـــل مھمة ــات ــروق ف ھــنــاك كــانــت (٠,١٦) الكشمیر شعیرة قطر ومعدل الخصلة طــول بین عالي ظاھري تتوافق ــود وج لوحظ الصفات. ھــذه على للعمر تأثیر ھناك یكن لم لكن اإلنـــاث، في عنھا باإلضافة اإلدارة ونظام والجنس للعمر ثابتة تأثیرات ــود وج إلــى الــدراســة ھــذه نتائج ــارت أش .(٠,١٣) الكشمیر شعیرة قطر في التباین ومعدل الخصلة طــول و والكشمیر. لماعز الرایني الوراثي التحسین برامج في إعتماده یجب والتي الشعر بین صفات عالقة وجود إلى aِbstract: the objective of this study was to evaluate some environmental factors (sex, age and management system) on fibre characteristics of raeini cashmere goats in baft stations (bs) and of raeini cashmere goats raised in nomadic conditions (nc) as commercial flocks. fiber samples including cashmere and hair were taken from 150 and 120 raeini cashmere goats (aged 1-8 years old) from bs and nc, respectively. the fleece traits measured included staple length (sl), percentage of cashmere in fleece (c), percentage of guard hair in fleece (h), cashmere's mean fiber diameter (cmfd) and the coefficient of variation of cashmere's fiber diameter (cvfd). mean sl, c, h, cmfd and cvfd in bs were 6.35 ±0.1 cm, 66.51± 0.72 %, 33.5 ± 0.72 %, 20.19 ±0.11 micron and 19.57± 0.21% and those in nc were 5.62 ± 0.1 cm, 69.06 ± 0.74 %, 30.94 ±0.74 %, 19.53±0.15 micron and 17.88 ± 0.19 %, respectively. there were significant differences (p<0.05) between the two production management systems for all traits investigated. the value for c was significantly higher in males than females (p<0.05). the results showed that the fleece traits were affected by age. however, the effect of age on these traits was not the same. significant phenotypic correlations were found between sl and cmfd (0.16) and between sl and cvfd (0.13). the results of this study indicated that the fixed effects of age, sex and management systems as well as the relationship between fleece traits should be considered in the raeini cashmere goat breeding programs. keywords: raeini cashmere goat, environmental factors, fleece traits. introduction animal fibers such as wool, cashmere and angora grow from small skin structures known as follicles. sheep and goats have two different types of skin follicles which include primary and secondary follicles, where the latter is of major importance to fine fibre production. cashmere goats are known as double coat, inner coat (or cashmere) and outer coat (or guard hairs) that are produced by secondary follicles and primary follicles, respectively (carter, 1955; petrire, 1995 ryder and stephenson, 1968). the percentage of cashmere in a fleece depends on the ratio of secondary to primary follicles. this percentage varies between different breeds of goats distributed in different environments. the percentage of cashmere in the fleece of cashmere goats (c) was reported to be 22 to 88 % in china, 20 to 60 % in india, 36 to 96 % in russia, 8 to 58 % in australia and 30 to 60 % in scottish feral goats (millar, 1985). he also reported a value of 94 % for c in russian don and volgard goats. previous studies also show that the fiber diameter and staple length varied in different environments. accordingly, a range of 12 to 18 microns and 4 to 10 centimeters had been reported for fiber diameter and staple length of cashmere, respectively. these values were 30 to 16 salehi and others 17 environmental factors affecting fleece traits in raeini cashmere goat 90 microns and 6 to 22 centimeters for the fiber diameter and staple length of the guard hair, respectively (jin and zhang, 1995). in addition, earlier studies had shown that the fleece traits including c, sl and cmfd were affected by age, sex, flock and birth type (emami mibodi et al., 1991; newman and paterson, 1996; saghi and shiri, 2004; zakheri, 1986). therefore, the variation in the percentage of cashmere in fleece, fiber diameter and staple length which have been reported in these studies could be due to different production management systems as well as breed, sex, age, birth type and other environmental factors. however, no reports were found on fleece traits in raeini cashmere goats. the main objective of this study was to investigate the effect of production management systems (semi intensive and extensive) on the quality and quantity of fibre production in raeini cashmere goats. the effects of sex and age were investigated as well. materials and methods the fiber samples (20 gram) were taken from right midside of the goats (150 and 120 raeini cashmere goats in baft rearing station (bs) and commercial flocks, respectively) following the procedure described by hopkins (1990). baft rearing station is a farm which is close to a city named baft. this city is situated in a province called kerman in the southern part of iran. this farm was used for research purposes on raeini cashmere goat under the semi-intensive system (haji mohamadi, 1990). the other flocks (commercial flocks) in our study were considered under the extensive management system. these flocks were reared in pastures around the mountain area during the summer and migrated in flat areas during the winter. fleece traits measured included the percentage of cashmere in fleece (c), the percentage of hair in fleece (h), staple length (sl), cashmere's mean fibre diameter (cmfd) and the coefficient of variation of cashmere's fibre diameter. the staple lengths were measured using a ruler with a susceptibility of 0.5 cm (brown, 1958). three or four locks were randomly chosen from different areas of each sample. locks from each sample were individually washed with hot water (45°c) and a nonionic detergent, rinsed in hot water and then dipped in a commercial solvent (dichloromethane alcohol) to remove any residual grease after washing. care was taken to avoid disturbing the staple formation of the fibers and to minimize the loss of shorter fibers in the samples. samples were then air-dried overnight. small amounts of samples were separated as sub-samples for hand dehairing. first, a visual subjective test was used to separate the fine (cashmere) and coarse (hair) fibers. the weight of different fibers was determined by weighing, using an analytical balance accuracy of 0.0001 gram. the fine fibers were prepared for measurement with the projection microscope technique in accordance with astm d213078 short–section procedure in order to determine the fibre diameter. each sample was compressed and fibers were cut at mid-staple with a heavy-duty cross-section device to provide snippets 200-300 micron in length. over one hundred fibers from each sample were measured (anonymous, 1982). the mean fiber diameter, standard deviation of fiber diameter and coefficients of variation of fiber diameter were measured. data analyses the following statistical model was used for the analysis by a general linear model (glm) using sas software package (sas / stat user’s guide, 1987). � � � � � � � � ��������������� ��������� where � is individual records on c, h, cmfd, cvcfd or sl; � is the population mean; � is the effect of ith sex; � is the effect of jth management system;� is the effect of kth age; � ��� is the interaction between sex and the management system; � is the interaction between sex and age; ��� � ��� is the interaction between the management system and age, )(��� is the interaction between sex; age and management system; and � m is the residual effects. results and discussion least-square means for the fixed effects on fleece traits and simple statistics for c and cmfd are presented in tables 1 and 2. the management system had a significant effect (p<0.05) on fleece traits. in comparison with the extensive system, the goats in the intensive system had longer staple, less c, more cmfd and more cvcfd. the maximum c (87.54 %) and the minimum cmfd (15.39 microns) belong to the extensive system (table 2). the results show that more cashmere were produced in the extensive system in comparison with the intensive system. in addition, these cashmeres were finer (19.64 microns) than those in the intensive system (20.12 microns). previous studies showed that there is a negative and high genetic correlation between cvfd and staple strength (safari et al., 2005). therefore, the cashmere produced in the commercial flocks had more strength than the bs. the values of 47.5±8.9 cm and 16.6±1.2 microns have been reported for sl and cmfd, respectively for brown and black birjandi goats (saghi and shiri, 2004). in their study, flock, sex and management systems had significant effects on fleece traits. age had a significant effect (p<0.05) on all fleece traits investigated in our study. staple length, cmfd and cvfd were increased with age while the percentage of cashmere in the fleece (c) was changed in an irregular manner. no significant differences were observed between males and females in sl, cmfd and cvfd values, while sex had a significant (p<0.05) impact on c and relatively on h. zakheri (1986) found that sl of cashmere and hair was significantly affected by sex and age. he had reported the values of 4.74 and 7.54 cm for cashmere and hair sl, respectively 16 salehi and others 17 environmental factors affecting fleece traits in raeini cashmere goat table 1. least square means and standard errors of fixed effects for sl (staple length, cm), c (percentage of cashmere in a fleece, %), h (percentage of guard hair in a fleece, %), cmfd (cashmere mean fiber diameter for cashmere, micron), cvfd (coefficient of variation of cashmere fibre diameter, %) . effects no. traits sl c h cmfd cvfd sex ns * * ns ns male 53 5.90 ± 0.16 71.7 ± 0.90 28.1 ± 0.9 19.9 ± 0.19 19.1 ± 0.36 female 217 6.03 ± 0.08 66.6 ± 0.59 33.4 ± 0.6 19.8 ± 0.10 18.7 ± 0.16 management system ** * * * * station 150 6.35 ± 0.10 66.49 ± 0.72 33.45 ± 0.72 20.12 ± 0.11 19.56 ± 0.21 rural flock 120 5.63 ± 0.10 69.05 ± 0.74 33.94 ± 0.74 19.64 ± 0.15 17.88 ± 0.19 age * * * * * yearling 12 5.61 ± 0.41 67.80 ± 2.00 32.19 ± 2.00 19.33 ± 0.50 17.88 ± 0.54 2 years 108 6.04 ± 0.11 69.33 ± 0.72 30.66 ± 0.72 19.73 ± 0.13 18.39 ± 0.20 3 years 77 6.04 ± 0.12 67.82 ± 1.05 32.18 ± 1.05 19.70 ± 0.17 18.81 ± 0.25 4 years 19 6.38 ± 0.35 66.84 ± 2.27 32.66 ± 2.30 19.98 ± 0.36 18.75 ± 0.76 5 years 27 5.92 ± 0.23 64.80 ± 1.80 35.22 ± 1.80 19.62 ± 0.40 19.94 ± 0.52 6 years 11 5.56 ± 0.31 66.01 ± 2.70 33.98 ± 2.70 20.51 ± 0.41 19.46 ± 1.01 7 years 8 5.93 ± 0.27 60.61 ± 3.17 39.38 ± 3.17 20.62 ± 0.55 19.64 ± 1.37 8 years 8 6.54 ± 0.51 63.11 ± 2.16 36.89 ± 2.16 21.01 ± 0.43 20.51 ± 0.83 sex & flock ns * * ns * sex & age ns ns ns ns ns flock & age ns ns ns ns ns sex & flock & age ns ns ns ns ns *, **: significant (p<0.05 & p<0.01). ns: not significant (p>0.05). table 2. simple statistics for c and mfdc. effects no. traits c cmfd min max min max sex male 53 55.50 87.60 16.90 22.80 female 217 41.20 86.50 15.40 23.24 management system station 150 41.61 86.48 16.09 23.25 rural flock 120 41.23 87.54 15.39 22.85 age yearling 12 56.11 78.33 16.60 22.12 2 years 108 49.60 86.50 15.40 22.40 3 years 77 41.20 85.20 16.20 23.30 4 years 19 49.70 87.60 17.07 22.60 5 years 27 49.50 85.70 15.67 22.37 6 years 11 46.55 78.70 17.70 22.70 7 years 8 46.00 71.00 18.30 23.20 8 years 8 53.60 72.40 18.50 23.00 18 salehi and others 19 environmental factors affecting fleece traits in raeini cashmere goat in male cashmere goats at yearling age and 5.02 and 7.68 cm for females of the same age. the values for sl of cashmere and hair indicated an increase of sl at two years of age (5.38 and 6.23 cm, respectively). in this study, the mean fibre diameters of cashmere in male and female goats at yearling age were 14.63 and 15.23 cm, respectively. the cmfd was increased to 16.8 microns at 2 years of age. emami mibodi, et al. (1991) also found significant differences between males and females for c, sl and mcfd. accordingly c, mcfd and sl of males and females were of 63±10 %, 20.98±2.1 microns and 6.46±1.88 cm and 68±10 %, 19.4±1.76 % and 6.48 ±1.78, respectively. the estimation of phenotypic correlation between fleece traits is presented in table 3. significant phenotypic correlations were found between sl and cmfd and also between sl and cvfd (0.16 and 0.13, respectively) which are in agreement with previous studies (hezare moghadam and salehi, 2007). the other values were estimated to be very small to negligible. conclusions the results of this study indicated that there were significant difference between the two production management systems for the fleece traits including sl, c, h, cmfd and cvcfd. accordingly, the animals in the extensive system produced more cashmere in comparison with those in bs. in addition, their cashmere is finer and has more strength. therefore, we concluded that the quality and quantity of cashmere were affected by environmental factors including the two different management systems. in this study, the environmental differences between the two groups were not investigated and should be considered in future studies. the fleece traits were also affected by sex and age. significant phenotypic correlations were found between sl and mfd and between sl and cvfd. the other estimations of phenotypic correlations between the fleece traits were very small and could be negligible. acknowledgements the authors wish to thank the farm staff at baft station for the management and care of the animals. thanks also to the technical staff of animal science research institute. references anonymous. 1982. diameter of wool and other animal fibers by micro projection. american society for testing materials (astm). d1294-79, 32:295–302. brown, sh. 1958. do-it-yourself measurement of fiber. goat note. the australian cashmere grower association. carter, h.b. 1955. the hair follicle group in sheep. animal breeding abstracts 28:101-116. emami mibodi, a., f. eftekhar shahrodi and a. nikkhah. 1991. estimation of genetic parameters of some economic traits in raeini cashmere goat. ph.d thesis. agricultural faculty. university of tehran. iran. table 3. phenotypic correlations between the fleece traits. character c h cmfd cvfd sl -0.05 0.05 0.16* 0.13* c -1.0** 0.10 0.07 h -0.10 -0.07 cmfd -0.10 *, **: significant (p<0.05 & p<0.01). figure 1. illustrated the effects of sex (a), production management system (b) and different ages (c) on staple length, cashmere and hair percentage and mean cashmere fiber diameter cvmd. (a) (b) (c) 18 salehi and others 19 environmental factors affecting fleece traits in raeini cashmere goat haji mohamadi, m. 1990. a short report on raeini goat at baft station and city. journal of pajouhesh-vasazandegi, iran, 12:66-68. hezare moghadam, r. and m. salehi. 2007. the identification of characteristics of the coating fibers of sistan and baluchestan native goats. animal science research institute. final report. iran. hopkins, h. 1990. sampling the fleece for testing. goat note. the australian cashmere gower association. australia. jin, h. and b. zhang. 1995. study of skin follicle structure and selection methods in cashmere goats. college of animal science and technology. china. millar, p. 1985. the performance of cashmere goats. animal breeding abstracts 61-01839(67-80):180-194. newman, s. and d.y. paterson. 1996. estimates of environmental effects for live weight and fleece characteristics of new zealand cashmere goat. new zealand journal of agricultural research 39:379 -386. petrire, o.j. 1995. harvesting of textile animal fibers. fao, agricultural series bulletin, 122:13, 22-70. restall, b.j. and w.a. pattie. 1989. the inheritance of cashmere in australian goats. 1. characteristics of the base population and effects of environmental factors. livestock production science 21:157-172. ryder, m.l. and s.k. stephenson. 1968. wool growth. academic press. london, 209-247. safari, e., n.m. fogarty and a.r. gilmour. 2005. a review of genetic parameter estimates for wool, growth, meat and reproduction traits in sheep. livestock production science 92:271-289. saghi, d. and a. shiri. 2004. evaluation of rearing, management system and phenotypic characters on cashmere goat of south of khorasan. the first animal and marine conference. agricultural faculty. university of tehran. iran. sas / stat user’s guide, 1987. 6.03 editions, sas institute, inc. zakheri, g. 1986. evaluation of iranian cashmere for industry. standard and industrial research institute, iran. pdf995, job 6 _________________ *corresponding author. 69 agricultural sciences, 7(2):69-71 (2002) short communication © 2002 sultan qaboos university dynamic effect in capillary pressuresaturation relationship and its impact on unsaturated flow s.m. hassanizadeh1*, m.a. celia2, and h.k. dahle3 1section of hydrology; faculty of civil engineering and geosciences, delft university of technology, p.o. box 5048, 2600ga delft, the netherlands 2environmental engineering and water resources program, department of civil and environmental engineering, princeton university, princeton, nj 08544, usa 3department of mathematics, university of bergen, johannes brunsgate 12, 5008 bergen, norway abstract: recent theories indicate that capillary pressure is perhaps not only a function of saturation but also rate of change. this is known as the dynamic effect. a comprehensive review of experiments reported in the literature is presented. the experiments provide ample evidence that a dynamic effect is observable and even quantifiable. the reported data are used to estimate the coefficient that arises in the theory. it was found that range of values of the dynamic coefficients spans about four orders of magnitude. to examine whether these coefficients have any practical effects on larger-scale problems, a continuum-scale simulator was constructed in which the dynamic effects are included. results of our simulations indicated that the dynamic effect may be important for some field situations. numerical simulators for unsaturated flow should generally include the additional term(s) associated with dynamic capillary pressure. keywords: capillary pressure, saturation, unsaturated flow, dynamic effect, porous media, wetting phase, equilibrium, relative permeability, transient, darcy's law. apillarity plays a central role in the description of multiphase and unsaturated flow in porous media. in quantitative modelling of multiphase flow, a relationship is needed to describe capillary pressure as a function of other medium properties. although the underlying processes that determine the distribution of fluid phases in porous media are extremely complicated, the main theoretical and practical tool currently used to quantify c !"#$!%&'()*!+,-!."/01!234()56!7"84)*!9:;)*!<=>-!?&!? #!5"#')*!"#/$()* .5#%)56!234%)*! !"#$%&'(#)%!&*#+!%!"#,-.+/*#0('1#234#5!6/#5# ! !<&&'>(#7####################86!9:#+;.<#+=>-?*#8 !9?'#"#$9?#86!9:#%&'#()-.#*#++ ,#-!.$?'#%/0;?'#8!01+2#(30 #4!!025'#6+.!7>0?'#6!0=8< #####$0>/9?'#!!0/9%?#:###########$0-!/+>.5?'#!!0;39?+ #<+7>0?'#'=0&#>!0..*#:#############=&#$'#8& +3?'#?,+69%?#8%/+0@#8.a'!0/#80b,)?'#0=0&#<50&c#0 #d+06+?'#:########################e"+!b#20-+.*#8074f+?+ #!0.5a#$0-!/+>.5?'#!!0;39?'#(30 #+!0'+g#f!0?(#?,+690?'#$0h.c#+0+g#:###8!%+.+?'#6+:+!#?'#(i #######,/+0.+?+ #j#0>9%?#<5k903cl#m0 +n?'#o#######8.!7>0?'#$0'#()0a)+?'#:###" ,<#2! #+/#8+!&?'#$'#p*'!9.#$-!/+>.5?'#m +n?'#(<#50a*#50&? ##6+.)903/#:###m +n?'#(+g#'qi#+0/#r0s#?##6'!!;39?'#2+;9.#$g+s/#3$:<#5&%'#t#""'*#u+h:#v%w#8!%+w#6'!!;3c#e?# $-!/+>.5?' ###8!0-!/+>.5?'#:################,&s?'#6*+4#x.#?#++=/#()-.#5b#$-!/+>.5?'#!!;39?'#(3 #4+0g+s+?'#)y+90:#6!0=8<#50&?#:#8.(5.?'#6+g+s+?'#(i '#!!;39?+ #8h#c!+?'#8!'+z['#m ')n?'#,+$c#(<#\6.#"#$+?'#!!]#^'59%?-!.$?'#%/;?'#8!1+k?#$-!/+>.5?:# hassanizadeh, celia, and dahle 70 the capillary pressure function is an empirical relationship between capillary pressure and saturation in the form (bear and verruijt, 1987): f (s)cpwpnp ==− (1) where np and wp are the average pressures of nonwetting and wetting phases, respectively, cp is capillary pressure, and s is the wetting phase saturation. this simple model is implicitly assumed to account for all effects and processes that influence the equilibrium distribution of fluids, such as surface tension, presence of fluid-fluid interfaces, wettability of solid surfaces, grain size distribution, and microscale heterogeneities. all of these effects are essentially lumped into the scp − relationship. moreover, this relationship is obtained experimentally under equilibrium conditions. thus, to obtain a drainage (or imbibition) curve, one starts with a wet (or dry) soil sample, then the capillary pressure is increased (or decreased) incrementally. at each step the water content is measured after equilibrium is reached. the time to equilibrium after each imposed pressure increment ranges from a few hours to many days, depending on the soil type and saturation degree (elrick, 1963; stephens, 1995). the typical time needed to construct a complete capillary pressure-saturation curve is in order of weeks or longer. now, the question arises whether such curves adequately describe the relationship between np and wp and s in drainage or imbibition events with a time scale in the order of hours. in fact, there is ample theoretical and experimental evidence that this simple relationship is not unique but it depends on the flow dynamics; it depends on both the history and the rate of change of saturation. the dependence of capillary pressure-saturation curves on the history of flow is known as capillary pressure hysteresis; this is a wellknown effect and has been the subject of extensive investigations. the dependence of capillary curves on the rate of change of saturation is due to dynamic effects; it is much less known and is not quantified properly. the latter effect is the subject of this study. another important parameter in the description of unsaturated flow is relative permeability, which is also considered to be a function of saturation. there are some indications that the relative permeabilitysaturation relationship also shows hysteresis effects and may depend on the rate of change of saturation. these effects, however, are less pronounced than in the case of capillary pressure. it must be noted that the dynamic effect considered in this paper is different from the flow-rate dependence of the relative permeability coefficient. it is known that relative permeability shows some dependence on capillary number (basically on the rate of fluid flow). this dependence is more significant at high capillary numbers and is present under steadystate conditions as well (ramakrishnan and wasan, 1986). however, the dynamic effect, related to the rate of change of saturation, is a transient effect that may be significant even for small capillary numbers, and is not present under steady-state flow, as discussed later. we assume that darcy’s law holds. in this work, we present a dynamic capillary pressure-saturation relationship that was obtained in the framework of a macroscopic theory of porous media flow developed by hassanizadeh and gray (1990). thus, equation (1) is replaced with: t s )s(f t scpwpnp ∂ ∂ −= ∂ ∂ −=− ττ (12) where τ[ 11tml −− ] is a material coefficient that is a measure of the dynamic effect. experiments an overview of experiments reported in the literature provides ample evidence of the significance of dynamic effects. for example, topp et al. (1967) carried out drainage experiments on a sandy soil. they determined drainage water contentcapillary head relationships by the following three methods: (i) static equilibrium, (ii) steady-state flow and (iii) unsteadystate flow. plots of water content as a function of capillary pressure head are given in figure 1. data points from equilibrium and steady-state experiments fall very close to each other. based on our theory, this result is expected because in both cases the rate of change of saturation is negligibly small ( 0t/s ≈∂∂ ) and thus dynamic effects are not present. in the unsteady-state experiments, the (dynamic) capillary pressure is significantly higher than in the case of equilibrium or steady-state runs. given the fact that in unsteady state experiments, the rate of change of saturation is negative, the results are clearly in line with the prediction of equation (2) for drainage. in general, the abnormalities in soil characteristic curves observed in various experiments can be explained by the above equation. the magnitude of the new dynamic capillary pressure coefficient is determined from available data. its value ranges from 410 to 810 kg/m.s. almost all experiments reported in the literature deal with the case of unsaturated flow. recently, we have carried out laboratory experiments involving two immiscible phases, namely water and tce. both drainage and imbibition experiments were carried out under static as well dynamic conditions. the observations are in line with the unsaturated flow experiments mentioned above. dynamic effect in capillary pressure – saturation relationship and its impact on unsaturated flow 71 figure 1. water content-pressure head data from drainage experiments of topp et al. (1967). numerical studies to examine whether these dynamic effects may be significant in practical situations, a continuumscale simulator was constructed in which equation (2) is included. this simulator was then run to determine the range of coefficients for which discernable effects occur. results from such simulations indicate that measured values of dynamic coefficients are within one order of magnitude of those values that produce significant effects in field simulations. this indicates that dynamic effects may be important for some field situations, and numerical simulators for unsaturated flow should generally include the additional term(s) associated with dynamic capillary pressure. references bear, j. and a. verruijt. 1987. modelling groundwater flow and pollution. d. reidel publ. co., dordrecht, the netherlands. elrick, d.e. 1963. unsaturated flow properties of soils. australian j. soil res. 1:1-8 . hassanizadeh, s.m. and w.g. gray. 1990. mechanics and thermodynamics of multiphase flow in porous media including interphase boundaries. adv. water resour. 13:169-186. ramakrishnan, t.s. and d.t. wasan. 1986. effect of capillary number on the relative permeability function for two-phase flow in porous media. powder technology 48:99-124. stephens, d.b. 1995. vadose zone hydrology. lewis, boca raton. topp, g.c., a. klute, and d.b. peters. 1967. comparison of water content-pressure head data obtained by equilibrium, steady-state, and unsteady-state methods. soil sci. soc. amer. proc. 31:312-314. _____________________________________________________ received september 2002. accepted november 2002. pdf995, job 6 _________________ *corresponding author. 29 agricultural sciences, 7(2):29-37 (2002) © 2002 sultan qaboos university use of short chained alkylphenols (scap) in analysis of transport behaviour of oil contaminated groundwater m. sauter* and t. licha friedrich schiller universität jena, institut für geowissenschaften burgweg 11, 07749 jena, germany abstract: shortchained alkylphenols (scap) represent a main constituent of crude oil and coal liquefaction products. due to their specific oil/water partitioning behaviour and high aqueous solubility they can be detected in oil exploitation waters and groundwaters affected by various spills near oil pipelines, oil exploitation sites and coal liquefaction plants. new efficient and powerful analytical techniques have been developed that allow the identification of all 34 individual compounds (c0-c3) without derivatisation and in complex matrices. due to the different physico-chemical properties of the scap, differential transport behaviour in groundwater can be observed, changing the relative concentrations of scap downgradient in space and time. these characteristic ratios can be employed to derive information on migration direction and the ageing of the source of contamination. a case study is presented to illustrate the use of this new tool. keywords: alkylphenols, crude oil, groundwater, partioning, plume, biodegration, toxicity, gc-ms, tar oil, anaerobic. rude oil consists of a complex mixture of organic compounds. among those alkylphenols are the main constituents. depending on the quality and origin of the fossil fuel, the concentrations of the alkylphenols may vary considerably (taylor et al. 1997). larter and aplin (1995) suggested employing short chained alkylphenols (scap) as indicators for oil quality, the extent of the source and as tracers for the petroleum migration process. the respective technique mainly relies on the specific partitioning behaviour of phenols between the water and oil phase. taylor et al. (1997) and ioppolo et al. (1992) investigated numerous crude oils for their individual scap concentrations. they confirmed that scap are ubiquitous constituents of crude oil thus making the oil quality and quantity estimation universally applicable. apart from crude oil, alkylphenols also occur in shale oils and coal liquefaction products (licha et al., 2002). c ! !"#$%&'()()$%&*%+&,-./$0%&*012!3&452$.6&'71(8$%&'!319$%&:.!8$%&;3&<= >.?$%& !"#$%&!#'()*%+#)(,%-).!/% &' !"#%0%%%%%%%%%%%%%%12#34$5%678$5%9!:;</*%=!>$5%?8<2$%!# 3#!.%! "(#/%$%! #$&5%9&(< #'%$# "%%(%%%%%)!#4$5%*'%+5(4$5%),-%./()* %%%%%%%%<$5%0!;"1%23!</*%1#48<$5%9!'+3;$5%-/%15(24$5%1#'(:$5%)!#4$5*%?8< $5%0!; "6%178! 94$5678$5*%?8%(%1#<:)%+%(4)%6)%.:$* %%%%%%+5(4$5%),;$%<(5=>$5*%1?'.@5%9!7a+4$5%$a%-b%c "#2$%d.(4; /%1 %+.b%(%+5(4$5%),;$%1#/!3:"&5%1a+7$5%1e8=/%-#4%* %%%%%%%%%%%%%%%fg($5%h /%*7 3<$5%!-i# a+)%d+# j/%k$%! #$&5%9&(< #8$%182; >4$5%1# !!#4#a(%i#8$5%l5( >2$%1:# ;"%1# '(:$5%)!# 4$5%* ' %18! 34$5*%(%*%%%%%%%%%%%fg($5%h/%!-i#a+)%--**%!;;a+8%)!:)5%1'+?4$%l5(>$5%),-%-/%d+!8;,&5%#4%(%1/.:4$5%1$!7$5%1,5.+* 1#<:;$5%),;$%1#24?$5%9!/5.>;,&5%m2b%n.)(%% sauter and licha 30 although phenols can be a very valuable tool in oil exploration, they can become a major problem during oil exploitation. the main wastes of environmental concerns associated with onshore oil and gas production are scap contaminated drilling-waste fluids or muds, drilling-waste solids and wastewater. crude pipelines are routinely cleaned. this can lead to surface oil spills. wastewater from crude oil processing can contain up to 50 mg/l of scap. probably one of the best documented and researched spill sites of crude oil from a broken pipeline is from bemidji, minnesota (usa) (bekins et al., 2001, baedecker et al., 1993). at this site the development of the contaminant plume, the organic and inorganic geochemistry as well the microbiology has been investigated for more than 16 years. in this paper we present techniques for the analysis as well as the employment of scap for the characterisation of the contamination source and the associated groundwater contamination plume. we believe that the presence of phenols in the subsurface has largely been underestimated and their biodegradation largely overestimated. although our main experience stems from sources comprising coal liquefaction products, the principles presented here also apply to contamination from crude oil and oil production waters. properties of scap and environmental relevance in this section a brief overview on the properties of short chained alkylphenols is given. particular emphasis is put on those physico-chemical properties that affect their special respective transport behaviour as well as their environmental relevance. scap are phenols for which hydrogen atoms from the benzene ring are substituted by alkyl groups with various chain length. the number of carbon atoms outside the ring is given in the form cx, where c stands for carbon and x for the number of atoms outside the ring. to clearly separate them from other alkylphenols the abbreviation scap is introduced. short chained alkylphenols are comprised of the following eight groups with their respective isomers. in total, scap include 34 short chained alkylphenols (c1-c3) and phenol itself (c0): phenol (c0), cresols (c1) with 3 isomers, dimethylphenols (c2) with 6 isomers, ethylphenols (c2), with 3 isomers, trimethylphenols (c3) with 6 isomers, ethyl methylphenols (c3) with 10 isomers, n-propylphenols (c3) with 3 isomers, and isopropylphenols (c3) with 3 isomers. figure 1 shows structural chemical formula of typical representatives of each of the above groups. data on the physical and chemical properties of scap are only reported for some isomers. in fact, no data are available for approximately 30% of all the compounds. therefore their environmental behaviour still remains uncertain. figure 1. chemical formula of representatives of each of the eight scap subgroups. scap are highly water soluble compounds, with solubilities much higher than other common organic contaminants such as btex or pak and even higher than most inorganic salts. this effect is caused by the ability of scap to participate in hydrogen bridging bond systems. the hydroxyl group in phenols forms this electrostatic bond with water molecules. if the hydroxyl group is blocked by a substituent in ortho-position (like 2-ethylphenol) the solubility should decrease. bennett and larter (1997) described this solubility influence of substituents based on oil-brine partitioning experiments. solubility data obtained by varhanickova et al. (1995) show a different behaviour. the solubility in their investigation varied between that of the individual compounds and decreases from c0 to c2 by approximately two orders of magnitude. the solubilities determined by varhanickova et al. (1995) under identical conditions (i.e. concise set of data) are presented in table 1. the reported high solubilities are the main reason for their high concentrations in groundwater, the large travel distances and a large variation in solubilities of the individual scap together with the differential transport behaviour of scap, outlined below. further, scap are weak acids, due to the deprotonation ability of the hydroxyl group in aqueous solutions. however, a significant deprotonation only occurs at ph values well above 8. this is because the acidity constants (pka) for the individual isomers range between 9.9 and 11 (taylor et al., 1997). thus, scap are in groundwater almost always in undissociated/protonated form. scap are oh oh ch3 oh ch3 ch3 phenol 2-methyl phenol o-cresol 2,4 dimethyl phenol 2,4 xylenol oh c h2 ch3 oh ch3 ch3 ch3 oh c h2 ch3 ch3 2 ethyl phenol 2,4,6 trimethyl phenol 2-ethyl-5-methyl phenol oh c h2 c h2 ch3 oh c h ch3 ch3 2-n-propyl phenol 2-iso-propyl phenol use of scap in analysis of transport behaviour of oil contaminated groundwater 31 table 1 solubilities of scap compounds at 25°c (varhanickova et al., 1995). compound solubility (g/l) compound solubility (g/l) phenol 102.1 3,5-dimethylphenol 6.7 o-cresol 26.8 2-ethylphenol 14.0 m-cresol 19.6 4-ethylphenol 8.0 p-cresol 22.0 2,3,5-trimethylphenol 0.9 2,3-dimethylphenol 6.4 2,4,6-trimethylphenol 1.4 2,4-dimethylphenol 8.2 3,4,5-trimethylphenol 1.5 2,5-dimethylphenol 3.8 4-npropylphenol 1.3 2,6-dimethylphenol 6.2 2-isopropylphenol 4.4 3,4-dimethylphenol 7.2 4-isopropylphenol 3.3 as soluble as ions but do not carry a charge in groundwater. they do not participate in ion exchange, neither do they occur as a pure phase unlike lnapls or dnapls. this raises the question to what extent common theories and general principles regarding transport behaviour derived from either insoluble organic compounds or ionic compounds may apply to organic substances readily soluble in water. since scap toxicity with respect to the human body cannot be specified yet in detail, analogies must be applied from data gained in microbial tests and from known cresol toxicities. some individual scap have been investigated for their toxicity with toxkit microbiotests, 15 minutes ec 50 (kahru et al., 1999). according to these tests, the toxicity increases in the sequence c0-c1-c2. this may be a result of the different metabolic pathways, increased lipophilic character and an increased residence time in the organism. the effect on humans, however, may be entirely different, presumably much less. scap are toxic for aquatic organisms; an environmental concern level of 0.02 µ g/l can be determined by applying the modified us epa method. adequate data on plants and terrestrial organisms are lacking. based on the above environmental concern level for water, it is reasonable to assume that aquatic organisms may be at risk in any surface or sea water contaminated with phenol. their toxicity threshold values are orders of magnitude lower than their solubilities. this fact must be of main concern when dealing with phenol contamination. the available data are summarised in table 2. it is apparent from this table that the degree of toxicity increases considerably for cresols and dimethylphenols. chemical analysis of scap a number of methods for the analysis of individual phenols have been published. a summary of those has been given by möder (2000) and lüders (1999). these include: liquid chromatography, gas chromatography and capillary zone electrophoresis. depending on the separation technique and the sample type, various sample preparation methods and detection systems were suggested. all procedures require a substantial effort in sample preparation in order to obtain a full separation of all 35 scap. the nearly full separation of all scap by gc-ms without the elaborate derivatisation step has not yet been described. in order to investigate and economically monitor those phenols in the environment, the development of a precise, robust and cost effective analytical technique has been developed by the authors. this analytical method takes advantage of the latest and commonly established developments in sample preparation and gas chromatography column technique. the solvent free extraction technique spme offers an easy way of enrichment from environmental samples. this technique has so far been successfully applied to epa phenols by buchholz and pawliszyn (1993; 1994). spme could be shown as successful for the analysis of chloroand nitrophenols even from complex matrices using a polyacrylate fibre (möder et al., 1997). the use of cyclodextrine based capillary columns in the gas chromatographic separation has been reported to be an excellent stationary phase to separate not only enantiomers but also positional isomers. in the following, the method is described in more detail. phenol standards were purchased from dr ehrendorfer as phenol mix 1, containing 50ng/µl of each compound (phenol, 3 cresols, 6 dimethyl phenols and 4 trimethyl phenols). the 3 ethyl phenols and 5 propylphenols were purchased from fluka. the internal standard d3-2,4 dimethyl phenol was supplied by promochem. spme conditions the polyacrylate spme fibre (pa of 85-µm coating) was supplied by supelco. the sample was extracted from headspace (headspace spme, hs-spme), which requires the following sample preparation steps to yield maximum sensitity. a volume of 10 ml aqueous sample was placed in a 22 ml headspace vial containing 2.5 g of table 2 toxicity of scap. compound toxicity (mg/l) compound toxicity (mg/l) phenol 97.3 2,3-dimethylphenol 41.2 o-cresol 51.8 2,6-dimethylphenol 29.0 m-cresol 83.8 3,4-dimethylphenol 6.1 p-cresol 7.7 toxkit microbiotests data from kahru et al. (1999). sauter and licha 32 naso4. this mixture was spiked with 5 µ l internal standard and 5 drops of h2so4 (96% p.a.) were added, sealed immediately and placed into the auto sampler rack. prior to the extraction step each vial was automatically agitated at 50°c for 10 min. the hsspme was then carried out at 50°c for 45 min. finally, the analytes were thermally desorbed in the split/splitless injector port of the gc at 280°c for 3 min with a splitless time of 60 s. gc-ms method a hewlett packard gc-ms instrument (gc: 6890, msd: hp5972a) was used in combination with a combipal auto sampler (ctc analytics) to perform the spme step and the following analysis automatically and simultaneously. an capillary column with an inclusion dominated separation property (α-dex 120 (supelco), 60 m × 0.25 mm i.d., 0.25 µm film thickness) was applied. helium flow rate was set at 1.8 ml/min. the gc oven program started at 50°c. the initial temperature was held for 3 minutes and was then increased at a rate of 7°c/min to 136°c. after an isothermal period of 2 minutes a temperature gradient of only 0.4°c/min was applied until 142°c was reached and held for another minute. a final ramp of 8°c/min up to a temperature of 215°c and finally held for 7 minutes end the run. consequently, each analysis requires 60 minutes. the simultaneous extraction and gc separation allows the analysis of 24 samples per day. the following separation for some selected scap is shown on a real sample in figure 2. the inclusion mechanism existing in cyclodextrin based capillary columns shows excellent selectivity for positional isomers of scap and allows their underivatised analysis in samples with complex matrices by maintaining a high separation efficiency combined with a very good sensitivity. unfortunately, the performance of such columns drops sharply in the presence of water traces. to overcome this drawback and significantly extend the life time of the column a selective virtually water free sample preparation technique was chosen in exposing the spme-fibre to the headspace of the sample. additionally, hs-spme limits the amount of analyte introduced to the column, which itself has due to the added cyclodextrin a very low analyte capacity. thus, hs-spme improves results, increases life time of the fibre and the capillary column and enables an economical application of this combined technique to a wide variety of samples. achievable detection limits using a polyacrylate spme fibre are 0.5, 0.3, 0.2, and 0.1 µg/l for c0, c1, c2 and c3 scap, respectively. by using ring deuterated 2,4-dimethylphenol as the internal standard a high reproducibility is ensured. simultaneously, internal standardisation allows an evaluation of the influence of dissolved organic matter. several studies confirm this approach (pörschmann et al., 1998). conceptual model of differential transport of scap the above described different physical and chemical properties of scap, together with the respective differences in their adsorption behaviour implies differences in the spreading of the individual scap and therefore a change in their relative composition. furthermore, the source composition will change as well as a result of the differential depletion in the various compounds with time. !!!!!!!!!!!!!!!!!!!!!!!figure 2. chromatogram of 14 scap, each 10 µ g/l in tar matrix (sim-mode). 0 100000 200000 300000 400000 500000 600000 18 20 22 24 26 28 30 32 34 36 38 40 retention time in minutes to ta l i on c ou nt ( t ic ) ! " # $ % & % '( )# * % & + '( )# * % & , '( )# * % & ./ '0 1+ # 2" 3 &, " # $ % & .4 '0 1+ # 2" 3 &, " # $ % & 5 .4 '0 1+ # 2" 3 &, " # $ % & .6 '0 1+ # 2" 3 &, " # $ % & .5 '0 1+ # 2" 3 &, " # $ % & 5 .6 '0 1+ # 2" 3 &, " # $ % & .4 ./ '7 )1 + # 2" 3 &, " # $ % & .5 ./ '7 )1 + # 2" 3 &, " # $ % & .5 .6 '7 )1 + # 2" 3 &, " # $ % & 5 .4 .6 '7 )1 + # 2" 3 &, " # $ % & use of scap in analysis of transport behaviour of oil contaminated groundwater 33 the chemical analytical technique allows a refined investigation of scap in water and sediments at contaminated sites. a transport parameter, derived from site and laboratory investigations, is suggested to account for the different adsorption data existing for the individual scap. generally, the more carbon atoms outside the benzene ring, the stronger these scap are retarded. from our experiments a factor of 10-50 for the freundlich coefficient between c0 and c3 scap was determined for sand/subbituminous coal. this partitioning parameter is termed phenol-cresol-fraction, abbreviated as pcf and defined as: ! + = [mmol/l]m [mmol/l]m [mmol/l]m pcf scap cresolsphenol the pcf can take on a value between 0 and 1. a total scap concentration of 0.0 mmol/l has no pcf by definition. pcf variations are caused by surface processes. thus, travel velocity, travel time, travel distance and surface properties are the most sensitive parameters to cause this variation. pcf values across a scap contaminated site can be used as partitioning tracers. they can furthermore indicate the type of source from where the scap originate (table 3). from the scap distribution at the site, groundwater flow and contaminant transport direction, the type (table 2) and age of contamination (figure 4-6) can be derived. the presence of organic matter in the aquifer leads to a further separation of the different scap resulting in a continuing enrichment of the plume’s tip with respect to the easily soluble and little retarded c0-c1 scap compounds. table 3 summarizes pcf-values gained from our field investigations. table 3 pcf variation with source, time and space. anaerobic input ageing source tip of plume ltc plant waters 0.75-0.85 0.30-0.60 0.90-1.00 tar contamination 0.20-0.30 0.00-0.15 0.40-0.65 the pcf, however, can only be successfully applied if it is not superimposed by other processes such as degradation, which is usually the case in anaerobic conditions. the scap differentiation across a plume and its development over time can be expressed by the pcf. figures 3 to 5 show a conceptual model for source and plume development for three different scenarios. water equilibrated with crude oil (pcf 0.8) is assumed as the scap source in all three scenarios. crude oil itself has a pcf of 0.5 but since c0-c1 -scap are much easier soluble in water, their proportion rises in the equilibrated water to a pcf of 0.8. figure 3 shows the influence of the presence of natural organic matter (nom) on scap differentiation. a pcf variation is only observed if retardation can be assumed. since c0 is virtually unretarded, the plume length is not greatly affected by the presence of nom. the percentage, distribution and type of nom in the aquifer together with the water velocity and the kinetics of the adsorption determine the degree of differentiation. from a continuously supplying source with a pcf of 0.8 a total variation in the range between 0.8 and 1.0 can be observed. continuous source anaerobic conditions retardation transport direction c c0 2 pcf = 0.9 c c0 1 pcf = 1.0 c c0 3 pcf = 0.8aquifer with nom c c0 3 pcf = 0.8 source at oil-h o-equilibrium2 non retardation aquifer without nom distance [m] original crude oil (pcf = 0.5) 0 500 c c0 3 pcf = 0.8 c c0 3 pcf = 0.8 source at oil-h o-equilibrium2 1000 figure 3. pcf variation with and without retardation. sauter and licha 34 figure 4. temporal change in pcf in a plume from a gradually depleting source. a gradually depleting source as shown in figure 4 does not have a constant pcf over time. the source gets more rapidly depleted with respect to the highly soluble c0 and c1-scap while the less soluble c2 and c3-scap remain longer in the source zone. therefore, the pcf in the source gradually decreases and in some cases may even reach zero. a pcf of 0 means that no c1-c0 scap are present. it does not give any information on how much c2-c3 scap remains, nor does it indicate a total scap concentration of zero. a decreasing pcf of the source gradually changes the boundary condition. it is therefore difficult to illustrate the development of the plume without numerical modelling. the pcf variation across the plume simultaneously increases until it eventually covers the whole range of pcf starting with 0 at the source and finishing with a value of 1 at the tip of the plume. the same, but much faster effect on the pcf, is obtained if the contamination is small and if the source disappears completely, i.e. a pulse input (figure 5). the onset of the plume is being continuously depleted with respect to the non retarded c0-c1 by the flushing effect of uncontaminated groundwater. again, the pcf variation as well as the extent of the plume depend on the groundwater velocity; the extent, type and distribution of nom in the aquifer system and the travel time. 0.5 source t1 gradually depleting source anaerobic conditions transport direction 0.8 pcf distance [m] 0 500 t0 0.850.8 0.7 0.6 1.0t2 0.5 0.4 1.0t3 0.0 0.4 0.950.7 0.6 0.7 1000 oilwater 0.4 source 0.7 pcf oilwater 0.2 source 0.5 pcf oilwater 0.0 source 0.0 pcf oilwater 0.7 0.7 use of scap in analysis of transport behaviour of oil contaminated groundwater 35 figure 5. pcf change in the plume from a short lived source. figure 6 summarises observable pcf-values in a tar oil contaminant plume depending on distance from the source and age of the source. the plot is a synthesis of theoretical considerations and field observations. the straight lines in the plot are only schematic. the relationship may not necessarily be linear. field investigation of a subsurface tar oil contamination in order to illustrate scap transport in a real aquifer and to demonstrate the potential value of scap for the assessment of the contamination potential, initial results for tar oil contaminated groundwater are presented. the site is on the premises of a former gas works which was in operation until the early 1990s producing town gas from subbituminous coal. the study area is 50,000 m2 (200 by 250 m) and located adjacent to a river. alluvial deposits such as gravel and sand dominate the contaminated subsurface aquifer. the water table is shallow (1.5 m to 3 m below ground level), the aquifer slightly confined, highly transmissive with a hydraulic conductivity of 1.4 10-4 m/s and a groundwater velocities figure 6. pcf variation across a tar contaminated site over time. of up to 1 m/d. groundwater flow direction is nnw to sse. scap contamination was found near a tar pit source and along the assumed groundwater flow path (figure 7). first sampling (11/2001) took place after an extended dry pulsed input anaerobic conditions transport direction c c3 0 c c0 3 pcf = 0.8 input at oil-h o-equilibrium2 original crude oil (pcf = 0.5) t1 t0 0.8 t2 t3 distance [m] 0 500 1000 0.7 0.75 0.85 c c2 0 0.1 c3 0.3 c c2 1 0.95 c c2 0 0.7 c c2 1 1.0 c c1 0 0.5 c c3 1 0.8 c c2 1 0.95 c c2 0 !"# !"$ !"% !"& !"' ()* fresh aged old a ged source age sauter and licha 36 ≈ 89*1:1;921%$ <89*%+#2#) <79)<,12 8000 8000 500 500 1000 50 16000 250 10 =>*#)?921%$< #&& 12"<$%<!("! =>*#)?921%$< #&& 12"<!("!<#$%& 11/2001 9,,)%&.<$)%'$( 92#) <:&% <(1)#;21%$ ?<<<)+%( pcf: 0.28 pcf: 0.44 *91& 93<*2921%$ 12"<,)%(';2<2)9$*:#) figure 7a. shallow scap contamination (µg/l) at a gasworks site after a long dry period. ≈ 89*1:1;921%$ *91& 93<*2921%$ 12"<,)%(';2<2)9$*:#) <89*%+#2#) <79)<,12 9,,)%&.<$)%'$( 92#) <:&% <(1)#;21%$ ?<<<)+%( 20000 8000 500 250 500 50 25 =>*#)?921%$< #&& 12"<$%<!("! =>*#)?921%$< #&& 12"<!("!<#$%& 01/2002 600 50 m pcf: 0.55 pcf: 0.21 figure 7b. shallow scap contamination (µg/l) at a gasworks site after a rainfall period. use of scap in analysis of transport behaviour of oil contaminated groundwater 37 period (figure 7a). the highest scap concentration was found at the tar pit with 16,000 µ g/l with a pcf of 0.28. groundwater abstracted from an observation well 50 m downgradient of the tar pit was highly contaminated. the pcf in this well was 0.44. this indicated enrichment in c0/c1 scap relative to that of the tar pit which showed a pcf as expected from typical tar contamination. the second sampling (01/2002) was carried out after a 2 month period with numerous rainstorm events (figure 7b). the highest scap concentration was now measured at the downstream well of 20,000 µg/l. this was an even higher concentration than that observed at the tar pit two months previously. simultaneously, the scap concentration at the source well near the tar pit had dropped to only 50 µg/l which approximates the target value for remediation. assuming that scap easily dissolve in the new recharge water in the area of the tar pit and with a groundwater velocity of 1 m/d it can be concluded that the water sampled in the observation well represented the recharge water that flushed the source 60 days earlier. the pcf at the tar pit dropped to 0.21 within these 60 days while the pcf at the observation well increased to 0.55. in summary, these findings indicate that c0-c1 scap can travel more or less unretarded. scap can be easily flushed from the source under the present hydrogeological conditions. one can further assume, that the dissolution process of scap from tar is slow compared to the intensive flushing during a recharge period. this implies large uncertainties in the prediction of the temporal and spatial distribution of scap contamination. conclusions alkylphenols (scap) have been somewhat neglected as a group of contaminants in the past. this is mainly due to the general belief that phenols are highly soluble and therefore easily biodegraded. our experience shows that they are available in large concentrations in crude oil and tar oil contaminated sites, and that they can travel in groundwater almost unretarded under anaerobic conditions for large distances. we developed techniques that allow for a rapid and accurate quantification of scap even in complex matrices in order to assess the extent of the plume. it could further be demonstrated that scap can offer a large potential in the identification and characterisation of a source as well as providing a tool to characterise the development stage of a plume if relative concentrations of phenols are determined along the groundwater flow direction. references baedecker, m.j., i.m. cozzarelli, r.p. eganhouse, d.i. siegel, and p.c. bennett. 1993. crude oil in a shallow sand and gravel aquifer-iii. biogeochemical reactions and mass balance modeling in anoxic groundwater. applied geochemistry, 8:569-586. bekins, b. a., i.m. cozzarelli, and e.m. godsy. 2001. progression of natural attenuation processes at a crude oil spill site: ii. controls on spatial distribution of microbial populations. journal of contaminant hydrology. 53: 387-406. bennett, b. and s.r. larter. 1997. partition behaviour of alkylphenols in crude oil/brine systems under subsurface conditions. geochimica et cosmochimica acta, 61( 20): 4393-4402. buchholz, k.d. and j. pawilszyn. 1993. determination of phenols by solid-phase microextraction and gas chromatographic analysis. environ. sci. technol., 27: 2844-2848. buchholz, k.d. and j. pawliszyn. 1994.optimization of solid-phase microextraction conditions for determination of phenols. anal. chem., 66: 160-167. ioppolo, m., r. alexander, and r.i. kagi. 1992. identification and analysis of c0-c3 phenols in some australian cride oils. geochimica et cosmochimica acta, 18: 603-609. kahru, a., l. pollumaa, r. reiman, and a. rätsep. 1999. predicting the toxicity of oil-shale industry wastewater by its phenolic composition. atla, 27: 359-366. larter, s.r. and a.c. aplin. 1995. reservoir geochemistry: methods, applications and opportunities. aus: cubitt, j. m. & england, w. a. (hrsg.): the geochemistry of reservoirs london (geological society special publications) , 5-32. licha, t.w., j. dermietzel, and m. sauter. 2002. short chained alkyl phenols (scap) in the environment chemical analysis and field studies. in: final proceedings geoproc, march 2002, bremen, in press. lüders, ch. 1999. entwicklung von analyseverfahren und referenzmaterialien für die bestimmung von phenolen in umweltrelevanten matrices. ph.d. dissertation humboldtuniversity berlin. möder, m., s. schrader, u. franck, and p. popp. 1997. determination of phenolic compounds in waste water by solid-phase micro extraction. fresenius j. anal chem, 1997, 357: 326-332. möder, m. 2000. phenols analysis in environmental samples. in: meyers, r.a. (ed.): encyclopedia of analytical chemistry: 31013124. chichester, wiley. pörschmann, j., f.d. kopinke, and j. pawliszyn. 1998. solid-phase microextraction for determining the binding state of organic pollutants in contaminated water rich in humic organic matter. j. chromatogr., a 816: 159-167. taylor, p., s. larter, m. jones, j. dale, and i. horstad. 1997. the effect of oil-water-rock partitioning on the occurrence of alkyphenols in petroleum systems. geochimica et cosmochimica acta, 61( 9): 1899-1910. varhanickova, d., w.y. shiu, and d. mackay. 1995. aqueous solubilities of alkylphenols and methoxyphenols at 25°c. j. chem. eng. data, 40: 448-451. _________________________________________ received september 2002. accepted november 2002. agricultural and marine sciences, 15:29-32 (2010) ©2010 sultan qaboos university 29 ____________________________ *e-mail: hmelhadi@hotmail.com effect of diet quality and housing on water status in sudanese desert sheep and goats hashim mohamed elhadi* department of physiology, faculty of veterinary medicine, university of khartoum, shambat, sudan السودانیة الصحروایة والماعز األغنام في الماء حالة الغذاء واإلیواء على جودة تأثیر الھادي محمد ھاشم الماء) تحول ومعدل الجسم في الماء (مجموع الماء إیض لدراسة السودان في والماعز الصحراوي الضأن فیھما استخدم منفصلتین تجربتین ــراء إج تم الخالصة: ضأن استخدام تم الثانیة التجربة في الصحراویة. شبھ المنطقة في واإلیـــواء الرعي ــروف ظ تحت الــنــووي الماء باستخدام ــك وذل الجسم ــل داخ المیاه مواعین في المناخیة الظروف تحت الماء وأیــض المستقیم من الجسم حــرارة ودرجــة الجسم وزن قیاس تم الصحراویة. الحشائش أو البرسیم علف على غذیت وماعز صحراوي الرعي حیوانات في الماعز في الجسم حــرارة إرتفعت الحظائر. في إیواؤھا تم بالتي مقارنة الطبیعیة المراعي ترعى كانت التي الحیوانات أوزان إنخفضت الحارة. على یدل مما العالي الماء تدویر بمعدل مرتبطًا الماعز في اإلرتفاع وكان (٪٦) الضأن في أقل الحرارة درجة إرتفاع كان بینما إیواؤھا تم التي في عنھا ٪٩ بمقدار الجسم وزن على إیــواؤھــا تم التي الحیوانات حافظت التبخر. طریق عن التبرید على العتمادھا الضان من الــحــرارة تحمل على أقــل مقدرة لھا الحیوانات ھــذه أن تمیزت ــذي وال (البرسیم) الغني الغذاء من أقل میاه تناول بمعدل الصحراویة الحشائش أي الفقیر الغذاء إرتبط الــحــرارة. ــات درج إرتفاع ــراض أع علیھا تظھر ولم حیوانات في منھ أقل لكنھ فقیر غــذاء على تغذت التي الحیوانات في أعلى الخلیة خــارج المجال كان أعلى. غــذاء تناول ومعدالت أعلى میاه تدویر بمعدالت حیواناتھ البرسیم. على تغذت التي الحیوانات في أعلى الخلیة داخل المجال كان الرعي. abstract: two independent experiments were carried out using sudanese desert sheep and goats to investigate water metabolism (total body water, tbw and water turnover, wto) and internal water compartments using radioactive water (tritium), under natural grazing conditions in a semi-desert area. the second trial was carried out on confined sheep, fed high (lucerne) and poor quality (desert grasses) diets. the body weights, rectal temperature and water parameters were monitored in both trials and species under the sudanese summer conditions. the grazing animal’s body weights were reduced compared to confined ones. hyperthermia was pronounced in goats (9%) compared to sheep (6%). the goat hyperthermia was associated with high water turnover, indicating the poor heat tolerance of this species of high evaporative cooling. the confined animals, however, maintained their body weights and did not show signs of hyperthermia. the poor diet (desert grasses) was associated with reduced water intake whereas the lucerne was associated with high water turnover and high feed intake. the extracelluar compartment (ecv) was higher with the poor diet but was lower than the grazing group. the intracellular compartment (icv) was higher in the lucerne group. the study indicated that sudanese desert sheep are more tolerant to high temperatures and grazing system than goats. introduction the sudan has an area of one million square miles; half of this area is desert or semi-desert in the north of the country. the average rainfall is less than 75 mm or from 75 mm to 300 mm annually, in the desert and semi desert respectably. in the desert, apart from a few shrubs and grasses which springup after the rare showers, it is almost devoid of vegetation. however, in the semi-desert areas, the rains are erratic and unreliable and confined to the months of july and august. the vegetation consists of grasses, herbs and a scattered variety of shrubs and bushes. in such arid and semi-arid areas, the maximum temperature exceeds 35 oc and values of up of 46oc are not uncommon during may and june. the solar radiation reaches 550 cal/m2, however, the relative humidity is low, ranging from 10-30 %. under such conditions, a huge area is unsuitable to livestock. however, in areas where the livestock can survive, the bulk of the sheep and goat population is maintained under nomadic husbandry systems. the migration of nomads in pursuit of water and pasture may be up to 200 km, while distances between grazing and watering points often exceed 40 km. the watering interval is 3-7 days, however f.d islander (personal communications) indicated that 11 days interval in sheep in winter, is not uncommon. the ability of animals to survive, and indeed thrive under these harsh conditions, requires an extremely efficient adaptation, which may be reflected in their water usage and metabolism. keywords : sudan, desert sheep, goats, water turnover, water space. 30 elhadi 31 effect of diet quality and housing on water status in sudanese desert sheep and goats there were approximately 51 million sheep and 43 million goats in the sudan in 2007 (faostat, 2010). desert sheep are the predominant breed in the country whereas the two major goat breeds are desert goat and nubian goat. however, despite the considerable importance of both sheep and goats to the livestock industry in the sudan, there is a lack of information concerning the water requirements and metabolism of these animals, such information is needed for successful implementation of the livestock developmental schemes in areas where water is at a premium. materials and methods approach the present study was an attempt to examine the water requirements and metabolism of sheep and goats, under the natural grazing and shaded confined conditions. the first trial was a comparison of the water and temperature parameters of sheep and goats under natural grazing practice in a semi-desert area about 10 km north of khartoum. the second trial involved the influence of dietary quality on water metabolism and body fluid volumes in sheep maintained under confined conditions. their total body water (tbw) and water turnover (wto) measurements were monitored using radioactive water (tritium–3h) and their relationship to their water intake, as measured by conventional methods. animals in the first experiment, a total of 12 animals, comprising 6 desert rams, aged 2-3 years, and 6 nubian bucks, aged 1-2 years, were used. the animals were kept in the semi-desert area (latitude 15n) for 2 weeks before the investigation commenced. the meteorological data were collected by whirling hygrometer at 06:00, 13:00 and 17:00 hours, the mean air temperature was 20.3oc, 35.7oc and 33.5oc, respectively. the relative humidity remained at 35% during the experimental period. rectal temperatures of animals were measured using a clinical thermometer. in the second experiment, twelve desert rams (weighing 23-34 kg) were divided into two groups, each group (6 sheep) was housed, in the semi-desert area, in two separate and similar semi -shaded pens. a period of 20 days was allowed for acclimatization to the feeding and watering regime followed by 10 days of collection period. each group received either 6 kg of sun-dried chopped lucerne or 6 kg of dry desert grass. the compositions of both types are given in table 1. the food and water are offered in the morning (06:00) and their refusal or orts were weighed at 17:00 hours to calculate the amount consumed. water parameters the total body water (tbw) was determined using tritiated water (3h) and the dilution principle, the animals were injected at 5 pm using 2 ml of an isotonic solution of sodium chloride, containing 600 μ ci (sheep) or 400 μ ci (goats) given by deep intramuscular injection to each animal. the animals were then weighed; food and water were suspended till the following morning when the first blood sample was collected in heparinized tubes for radioassay. subsequent blood samples were collected in the morning and evening for 10 days for the measurement of water turnover (wto), plasma samples were prepared by adding 0.5 ml to 10 ml of “instagel” (packard) and tritium was assayed in a liquid scintillation spectrometer (beckman). similar measurements were made on the standard injected solution. the (tbw) was calculated by dividing the injected radioactivity by the plasma 3h concentrations 12 hours after injection and wto was calculated by regression analysis of the plasma activities. plasma volume was determined using evans blue dye (0.4 mg /kg) and ecv fluid volume was determined using (12 mg/kg) sodium thiocyanate. the icv was calculated by difference (tbwecv) which included the rumen volume. a computerized (t-test) programme was used to test the significance of paired varieties in some parameters. results and discussion experiment 1 during the 2 weeks period, the body weight of the grazing animals decreased slightly. the desert grasses were sparse and the animals had to walk about 5 km to and from the grazing area. the mean body weights of sheep decreased form 33.5±2.2 to 32.4±2.0 kg, and that of the goats decreased form 17.5±1.2 to 16.4±1.1kg. this reduction in body weights might indicate an adaptive feature which enables these desert animals to eat below maintenance requirements at such poor pastoral conditions. similar findings in body solids changes were reported in grazing sheep (macfarlane and howard, 1970; degen, 1977). the data in table 2 indicated a diurnal variation in the body temperature of the grazing animals. although both species experienced some degree of hyperthermia, associated with increased air temperature, this was greater in goats (9%) compared to in sheep (6%), indicating that goats are more predisposed to heat stress. the goat hyperthermia was associated with high water turnover (table 3). the poor heat tolerance of the nubian goats might be a reflection of the fact that this type of goat is not a true desert ruminant, as they are usually restricted to riverain and urban areas as milk producers. table 1. nutrient composition of lucerne hay and desert grass. diet dm (%) om (%) cp (%) ash (%) energy kcal/ gm dm lucerne hay 83 78.5 18.7 24.5 4.72 desert grass 94 85.4 3.4 8.7 4.12 30 elhadi 31 effect of diet quality and housing on water status in sudanese desert sheep and goats fluids volume the findings of these measurements are given in tables 3 and 4. tbw % was 72.6±1.4 and 75.8±3 in sheep and goat, respectively. these values are slightly higher than the values reported by macfarlane et al. (1972) for these ruminants in the somali desert, using similar procedures. the relatively high value might be due to the 12-hours post injection samples; at this time of sampling, some losses of the isotope could have occurred, which may have resulted in the overestimation of tbw. since equilibrium of 3h could take 5-7 hours in this species, such losses were presumably greater in the goats, however, the difference between the two species was not significant. tbw % reported by kamal et al. (1972) for ossami rams and nubian bucks were higher than our values. this difference might indicate a better adaptive performance of our ruminants. the wto (ml/ kg 0.82 / day) was 100±11.1 and 181±18.4 in the sheep and goats respectively as shown in table 3. the goats turned over significantly more water than the sheep (p<0.01) and this was also reflected in the direct water intake. the difference in wto rate might be due to the high degree of hyperthermia which was severe table 3. tbw, wto, water intake in grazing animals (sheep and goats) and confined sheep having lucerne or desert grass (mean ± s.e). parameter grazing animals confined sheep goats sheep lucerne hay desert grass wt (kg) 17.5 ± 1.2 33.3 ± 2.2 30.4 ± 1.9 28.8 ± 1.5 tbw% 75.8 ± 3.0 72.6 ± 1.4 71.9 ± 1.9 68.7 ± 1.0 t1⁄2 (day) 5.2 ± 0.5 9.9 ± 0.8 5.0 ± 0.2 7.1 ± 0.1 water intake ml/kg of b.wt. or dm consumed/day 100 ± 9.8 49 ± 4.3 76.0 ± 1.1 57 ± 1.2 wto/kg of b.wt. or dm consumed/day 108 ± 9.6 53.0 ± 15.6 100 ± 2.5 66.0 ± 3.8 wto/ 0.82 kg/day 181 ± 18.4 100 ± 11.1 183 ± 4.2 120 ± 6.4 table 2. rectal temperature of grazing sheep and goats and confined sheep having lucerne and desert grass (mean ± s.e). time of day rectal temperature (°c) grazing animals confined sheep goats sheep lucerne hay desert grass 06:00 37.1 ± 0.1 37.9 ± 0.3 37.3 ± 0.2 37.1 ± 0.2 13:00 40.5 ± 0.1 40.3 ± 0.2 38.6 ± 0.1 38.4 ± 0.2 17:00 39.6 ± 0.2 39.8 ± 0.2 38.1 ± 0.1 37.9 ± 0.1 table 4. body weight (kg) and total body water (tbw) and its distribution in the body of grazing sheep and goats and in confined sheep having lucerne day and desert grass (mean ± s.e). parameter grazing animals confined sheep goats sheep lucerne hay desert grass wt (kg) 17.5 ± 1.2 33.3 ± 2.2 30.4 ± 1.9 28.8 ± 1.5 tbw (%) 75.8 ± 3.0 72.6 ± 1.4 71.9 ± 1.9 68.7 ± 1.0 ecv1 (%) (scn space) 31.2 ± 0.8 28.1 ± 1.8 22.6 ± 1.1 26.2 ± 3.4 pv2 (%) 5.1 ± 0.2 5.0 ± 0.3 5.6 ± 0.4 4.7 ± 0.6 isv3 (%) 26.1 ± 0.9 23.6 ± 1.8 17.0 ± 1.2 21.5 ± 2.8 icv4* (%) 44.6 ± 2.5 44.5 ± 1.6 49.7 ± 3.3 41.7 ± 4.0 1extracellular volume. 2plasma volume (t-1824 space). 3interstitial volume. 4*intracellular volume. rumen and digestive fluids are included in this space. 32 elhadi in the goats and is reflected in the high extracellular space in the goats (31.2± 02) compared to (28.1±1.8) in the sheep. this is probably the result of more evaporative cooling in the goats, associated with high water turnover. degen (1977), produced similar values for ecv % (28.6±1.09) in the grazing awassi sheep at 32oc. both species maintained similar plasma volume (pv) of 5% and intracellular volume (icv) of 44 %. (table 4). effect of feed type the lucerne-fed group consumed all the feed offered, while the desert grass group used to leave some of the feed. two sheep, in the lucerne group, suffered mild diarrhoea during the first few days of the investigation, while none of the desert-grass group showed any signs of digestive disturbances. this indicates that sheep which are normally raised under extensive management and used to dry grass feeding needed only a short time to adapt to the new diet. the lucerne group consumed 1 kg of food (0.83 kg dm / animal) and drank 2.2 liters of water, while the desert grass group consumed 0.7 kg of desert hay (0.66 kg dm / animal) and drank 1.6 liters of water. both groups maintained their body weights over the period of two weeks, indicating that both diets satisfied their maintenance requirements, since the desert grass is of low nitrogen content (table 1), it seems that these desert sheep retained more nitrogen in their bodies with a reduced amount of water intake compared to the high water consumption with the lucerne diet. table 3, indicates that both groups had similar 3h space tbw. however, the lucerne group had significantly (p<0.01) higher wto associated with higher intake, probably indicating higher nitrogen excretion by the kidneys. previous reports indicated that water restriction improved the nitrogen retention in sheep (english, 1966; topps and elliot, 1967; singh, more and sahani 1976). it is more probable that the adaptive feature of the desert sheep is that more nitrogen is retained with reduced water intake. the distribution of the 3h space (tbw) is shown in table 4, the striking feature in these results is that the extracellular space is higher in the animals eating a poor diet (26.2±3.4) compared to those on a rich diet (lucerne) (22.6±1.1). these findings are in agreement with that of macfarlane et al (1959), who found high values in sheep with poor nutrition. since these two groups of animals did not show a wide diurnal variation in their body temperature (table 2), as did grazing sheep (experiment 1), their ecv% is lower than that of the grazing sheep (table 4). both diet-groups had a similar plasma volume (pv). however, the intracellular volume (icv) of the lucerne group was 49.7% while that of grazing sheep was 44.5% (table 4) which might indicate a large rumen space in the lucerne group which consumed more feed in comparison to sheep having a poor diet; icv% is 41.7 (table 4). references degen, a.a. 1977. fat-tailed awassi and german merino sheep under semi-arid conditions. journal of agricultural science, cambridge, 88:693-698. english, p.b. 1966. water and electrolytes balance in sheep. 1. external balance of water, sodium, potassium and chloride. research in veterinary science 7:233267. faostat. 2010. food and agriculture organization of the united nations statistics. (http://faostat.fao.org/site/573/desktopdefa ult.aspx?pageid=573#ancor). kamal t.h., o, shahata and i.m. elbanna. 1972. effect of heat and water restriction on water metabolism and body fluids compartments in farm animals. in: proceedings of symposium of isotopes studies on physiology of domestic animals. 95-100 sti / pub / 309, iaea. vienna. macfarlane, w.v., r.j.h., morris, b. howard and o.e. budtz-oslen. 1959. extra-cellular fluid distribution in merino sheep. australian journal of agricultural research 10:269-286. macfarlane, w.v. and b. howard, 1970. water in the physiological ecology of ruminants. in: physiology of digestion and metabolism in ruminants. a.t. phillipson (editor), 362-374. england. oriel press. macfarlane, w.v., b. howard and g. m. o. maloiy. 1972. tritiated water in field studies of ruminants in africa. in: proceedings of isotopes studies on physiology of domestic animals. p 83, sti / pub / 309. iaea. vienna. singh, n.b., t. more and k.l. sahni. 1976. the effect of water deprivation on food intake, nutrient digestibility and nitrogen retention in sheep. journal of agricultural science, cambridge, 86:431-433. topps, j. h. and r. c. elliot. 1967. partition of nitrogen in uterine of african sheep given a variety of low protein diet. animal production 9:219-227. sultan qaboos university journal for scientific research agricultural and marine sciences, 11 s.i., 37-45 (2006) ©2006 sultan qaboos university 37 financing the urban water sector in the united states of america, with possible implementation in the sultanate of oman ghiyath nakshbendi university of maryland university college p o box 608, glen echo, md 20812, usa abstract: the world has been experiencing a change in water and sewage infrastructure ownership and management. at one end, the public sector in developing countries has been moving towards engaging the private sector in the management and operation of water and sewage sectors. in the united states, the trend is catching up, even though there has been a mixed experience in the involvement of the private sector. while most urban facilities are owned by the public entities of the concerned urban centers, striking up a balanced involvement of both sectors is gradually taking shape. the paper focuses on financing urban water and sewage sectors in selected areas of the united states. an attempt is made to assess the viability and suitability of utilizing some of these methods in the sultanate of oman. the distribution system in the sultanate of oman is managed by the public sector; like in other countries, the private sector is getting involved on a gradual basis. there is more reliance on the private sector to manage the water sector worldwide. can this happen in the sultanate of oman? the method will rely on analysis of the available data and the researcher’s work experience in the financial sector. keywords: bonds, capital markets, financing, gcc, oman, sewage, water. e-mail: gnakshbendi@sangamoregroup.com وسائل تمویل مشاریع المیاه والمجاري في الوالیات المتحدة األمریكیة ومالئمة استخدام نفس الوسائل بسلطنة عمان غیاث نقشبندي الخالصة: یتعرض العالم لتغییرات في ملكیة وإدارة قطاع المیاه والمجاري. من ناحیة نرى إن القطاع العام في الدول النامیة یتجھ نحو القطاع الخاص إلدارة وتشغیل المرافق في قطاعي المیاه والمجاري. وفي الوالیات المتحدة فان ھذا التوجھ یتسارع مع أن نتائج التجارب مازالت غیر مكتملة فیما یتعلق بمساھمة القطاع الخاص. وبالرغم من أن معظم المراكز الحضریة تمتلكھا البلدیات إال أن ھنالك محاولة لخلق التوازن بین القطاعین الخاص والعام والتي تسیر بالتدرج. ستركز الورقة على وسائل تمویل مشاریع المیاه والمجاري في مناطق منتقاة قي الوالیات المتحدة. وسیكون ھنالك محاولة لتقییم جدوى ومالئمة استخدام بعض ھذه الوسائل في سلطنة عمان . ھل ترغب األسواق المالیة في مجلس التعاون الخلیجي في المساعدة في التمویل؟ إن نظام التوزیع في سلطنة عمان یدار من قبل القطاع العام، وكما ھو في دول أخرى فان القطاع الخاص یساھم بشكل تدریجي. إن ھنالك اعتماد اكثر على القطاع الخاص في العالم إلدارة قطاع المیاه . ھل ھذا ممكن في سلطنة عمان؟ .یعتمد أسلوب البحث على تحلیل المعلومات المتوافرة وعلى خبرة الباحث في المجال المالي المصطلحات الرئیسیة: األسواق المالیة، التمویل، دول مجلس التعاون الخلیجي، عمان ، المیاه ، المجاري naksbbendi 38 introduction the world is experiencing an increase in population and a decrease in the availability of safe drinking water. a recent objective of the world community was “to halve, by the year 2015, the proportion of the world’s people whose income is less than one dollar a day and the proportion of people who suffer from hunger and, by the same date, to halve the proportion of people who are unable to reach or to afford safe drinking water” (united nations, 2005). there is an increasing need worldwide for new water infrastructure and upgrading and rehabilitating of existing infrastructure. the world is experiencing a need for rehabilitating its aging infrastructure. in the united states of america alone, by one estimate there will be a “$300 – $800 billion funding gap over the next 20 years to repair aging infrastructure at the nation’s 16,000 wastewater treatment and 40,000 drinking water facilities” (eichenscher, 2005). other countries are facing similar problems. current spending on new water infrastructure in developing and emerging countries is roughly $80 billion a year. this will have to more than double over the next 20–25 years, to around $180 billion. much of the increase will be for household sanitation, wastewater treatment, treatment of industrial effluents, irrigation and multipurpose schemes. (camdessus, 2005). most water provider companies in the world are public utilities. these utilities are subjected to the typical process of budgeting and bureaucratic procedures which add cost and time to reach resolution. identifying methods to finance water projects deserves more attention than has been given so far. in this paper an attempt will be made to identify some methods of financing water utilities in the united states of america, with a view to assessing its applicability in the sultanate of oman. the results of such assessment might provide more ideas on the acceleration of the privatization process in the utilities sector in oman. in the u.s., “. . . utilities cannot count on federal funds financing infrastructure improvement projects. therefore, there are rate increases, bond issues, capital reserves, streamlined operations, loans, grants and surcharges to fund needed water system improvements. priorities for capital projects often vary by region” (zeilig, 2005). the point to be made is that reliance on the federal government is not an option. local water providers rely on their customer base for their operation and survival. almost all of the utilities in the middle eastern countries, including oman, are publicly owned and thus rely on government appropriation for program implementation. oman is well known for its resolve and desire to improve its economy and the living standards of its people. the advancement in all sectors of the economy in the last 30 years or so is phenomenal. a closer look at the growth of gdp, life expectancy, the electricity production and the increase in internet users demonstrates strong advancement. its privatization efforts are continuing; a new law promulgated in 2004 removed limits on the share of foreign participation in privatized companies. the government divested a significant part of its shares in a petroleum company, and a second mobile telephone company was licensed in recent months (imf, 2005). the recent privatization initiative by the state in selling 30% of its stake in omantel (business and industry, 2005) is another example of its determination to follow the steps taken by other countries in their drive to promote a market economy and encourage customer’s reliance on their sources, thus reducing some government subsidies. therefore, there is a need to develop a new method to finance water projects and to rely less on government funding by encouraging more involvement of the private sector. financing the urban water sector in the u.s. the u.s. was selected due to its large number of water and sewage facilities and the presence of diversified financing methods which could be considered as a guide to other countries. a major water utility in the country was selected to be studied. its selection was based on the number of customers served and its budget. also, examples from three other states will be presented. the washington suburban sanitary commission the washington suburban sanitary commission (wssc) is a maryland public entity which was established in 1918 as a regional organization. currently, it provides water and sewer services to the 1.6 million residents (433,000 customer accounts) of maryland’s montgomery and prince george’s counties, which border washington, d.c. it is one of the 10 largest water and sewer utilities in the country. it is governed by a board of commissioners who are financing urban water sector in the usa, with possible implementation in the sultanate of oman 39 appointed by their respective county executives and confirmed by their county councils. wssc produces an average of 167.5 million gallons (634,470 m3) of water per day; its wastewater treatment is provided and operated by wssc and one plant operated by the district of columbia water and sewer authority (wasa). the two counties, montgomery and prince george’s, prepare ten-year water and sewer plans, which are updated annually (wssc, 2006). wssc is empowered to establish water consumption rates, sewer usage rates, connection charges, front foot benefit charges to repay funds borrowed by wssc for water and/or sewer main construction. the front foot benefit charges assessment is determined by multiplying property footage by the rate per foot for the appropriate property classification. wssc allows visitors to pay a fee for engaging in fishing from portions of the shorelines of reservoirs and recreational boating. finally, wssc can levy, if required, appropriate and valorem taxes (wssc, 2006). this is very important to make the utility financially independent and capable of running its operations. wssc’s annual budget in order to determine its financing needs, an annual budget is prepared, noting that the utility is self sufficient and its customers pay for all the charges, including the capital programs. the annual budget consists of operating and capital budgets. each budget includes water and sewer elements. also, the operating budget includes an interest and sinking fund, while the capital budget includes general construction bonds fund. so, each type of operating fund is associated with a corresponding bond fund. the related operating funds are responsible for the payment of the funds that were used to finance its operation. this separation allows each service to be considered as a cost center. financing methods the commission finances its operation mainly through the issuance of bonds. it issues water supply bonds (capital fund) to finance capital activities dealing with the delivery of water to customers. in the meantime, money received from customers paying their water bills is used to pay for all expenses related to water delivery, including the repayment of principal and interest of loans accumulated in the water supply bonds. the same mechanism is applied for the sewer side of the operation. i.e. there is a sewage disposal bonds (capital) fund, and payment by customers for the service, which covers repayment of principal and interest on loans. sewer use charges are generally based upon metered water use (wssc, 2006). the average interest rate on the current outstanding debt was 4.59 % as of 06/30/2005. the wssc conducts a bond sale and award the bonds to the lowest bidder (personal communication, j.d. noell, january 11, 2006). the current budget fy ‘06 the capital budget is $265 million and the operating budget is $494 million (wssc, 2006). both are going to be financed through bonds and the receipts for providing water and sewer services to the customers. from table 1, the debt service constitutes around 46 % of the operating budget for the fiscal year 2006. wssc finances its projects mostly through bonds, and the debt service covers both the principal and the interest. table 1. operating budget major expense category. ($ millions) (%) salaries and wages 78,835 16.0 utilities 16,677 3.4 regional sewage disposal 36,060 7.3 all others 136,161 27.5 debt service 226,614 45.8 total 494,347 100.0 table 2. capital budget allocations and sources. ($ millions) (%) allocation: water supply 112,678 425.0 sewage disposal 117,776 44.5 general construction 34,365 13.0 total 264,819 100.0 sources: bonds and cash 217,449 82.1 federal/state grants 2,500 1.0 system development charge/others 43,170 16.3 paid house connections revenue 1,700 0.6 total 264,819 100.0 naksbbendi 40 the capital budget listed in table 2 shows the allocation between water and sewage disposal projects in addition to the general construction. the lower part of table 2 shows that 82% of the budget is to be financed through bonds and cash. bonds issuance is more favorable and feasible than straight loans. bonds will generate more funds because a group of banks and investment houses are sharing in its syndication and spreading the risk. for investors, bonds are more attractive because the annual return is fixed for years and at maturity, in most cases, the investor will get back the original investment. what is important to note is that the existing state laws require that the water consumption rates be sufficient to meet all the designated provisions (wssc, 2006). the wssc maintained the same rate for the fy 1999-2004, but increased its rate in 2005 by an average of 2.5% for water and sewer rates. other sample cases, from the states of new york, arkansas and utah, will be presented to reflect diverse geographic locations. four small towns in the state of new york are receiving a low-interest loan for a regional water project. if the four towns agree to go ahead with the project, the new york environmental facilities corp may be able to provide financing through a 30-year loan. the first 20 years could be financed at 2% and the last 10 years at a fixed market rate, currently 5%. the cost of the project is pegged at $24.8 million (glynn, 2005). in this case the state will be providing concessionary loans to water provider utility. while the above case is a direct loan, in the state of arkansas, a more interesting option was provided. the state was considering a loan of $88 million to white river regional irrigation district (wrid) in order to finance a water project. the money will be used to design and build a system to take more than 1 billion gallons of water daily from the white river and deliver it to some 900 farms. the point is that if wrid was unable to pay back the loan with the interest, the general public in arkansas would be responsible to pay, which caused dissention in the state. the governor still has to approve the bonds (mays and carruth, 2005). this case shows the interest of the state in helping out a number of farmers with the understanding that, in case of need, the general public will be paying for the cost. this example illustrates the state’s interest in financing water projects, including non-urban projects. further, the message is that the burden of debt repayment rests with all the taxpayers in the state and not the federal government. the case of utah deserves attention because it proposes another form of financing. like all western states, utah finances much of its water infrastructure through the general fund and from sales tax. the sales tax proposal has been put forth by another task force studying how to pay for a project (baired, 2005). the case here emphasizes the need for local beneficiaries to contribute and match the state funding –a concept which establishes equity and fairness within the state. the proposal, which was still pending as of january 2006, proposes lifting the sales tax cap on money appropriated for water projects, another bill proposes using a portion of future general fund surpluses. at this point, fiscal conservatives have been critical of both bills and environmentalists question the need for the bear river project (personal communication, j. baired, january 11, 2006). the federal government the latest estimate showed that $500 $800 billion is needed over the next 20 years for maintaining and improving the existing inventory, building new infrastructure, and meeting new water quality standards (eichenscher, 2005). therefore, u.s. congress is concerned about the status of investment in the water sector. in support of the proposed bill, h.r. 1708, a seasoned water projects financier indicated that among other methods of financing, the tax exempt financing, is essential to ensure that local communities have the latitude to formulate financing strategies that can meet local needs and alleviate the financing burdens of federal mandates that local communities must comply with and ultimately pass on to the american ratepayer (howard, 2005). the importance of the tax laws and its impact cannot be minimized and it really encourages investment initiatives. therefore, congress approved the said bill, which became known as the clean water investment and infrastructure security act of 2005, to finance water quality infrastructure projects. the main premise of this act is to modify the federal tax law to make the issuance of tax-exempt bonds for water and sewerage facilities, known as exempt facility bonds or private activity bonds (pabs), exempted from the volume cap, which limited its issuance above a certain amount per year by each state. these changes made the issuance of bonds more attractive to investors. financing urban water sector in the usa, with possible implementation in the sultanate of oman 41 the act is expected to improve the financing of water projects across the country. further, congress enacted the water for the poor act of 2005, which was submitted as house of r.submitted as house of r epresentatives 1973. the act is designed to make access to safe water and sanitation for developing countries a specific policy objective of the united states foreign assistance programs (simon, 2005). financing options for new infrastructure projects can therefore be grouped as follows; each has its attraction to different investors. in a sense, investors, both private and corporate, are going to decide which investment option they are going to select based on many factors, one of which is the impact of such investment on their portfolio and the return after taxes. 1. debt tax-exempt bonds, governmental purpose bonds, private activity bonds 2. equity private equity, taxable bonds, tax-exempt private activity some water sector aspects in the sultanate of oman basic data the capital of oman is muscat, with other major cities being salalah, nizwa, sohar and sur. its population according to official statistics is 2.4 million (ministry of national economy, 2004). oman has 920,000 in the work force, 50% of whom are involved in agriculture k force, 50% of whom are involved in agriculture k and fishing (us dept of state, 2006). the agriculture and fisheries sector contributes 2.1% to the total gdp. oman’s gdp-purchasing power parity in 2004 is estimated at $38.09 billion or $13,100 per capita gdppurchasing power parity. about 55% of the population lives in muscat and the batinah coastal plain northwest of the capital (ministry of national economy, 2004). water resources, as in most economic and social commission for western asia (escwa) countries, are owned by the state, which is responsible for conserving them and ensuring that they are used jensuring that they are used jensuring that they are used udiciously. sector budget reflects the requirements of the following agencies: ministry of housing, electricity and water (mhew), ministry of regional municipalities, environment and water resources (mrmewr) and governorate of dhofar and sohar municipality. it is worth noting that the water law of 2000 consolidated the responsibility for all water resources within one ministry, with the exception of desalinated water (escwa, 2003). the development, operation, maintenance and transmission of potable and desalinated water supplies are under the jurisdiction of mhew. the distribution of potable water is under the jurisdiction of the mhew, with the exception of muscat, where it is under the jurisdiction of the governorate of muscat. the responsibility for the assessment and collection of tariffs for potable water supplies lies with the mhew (escwa(escwa(escw , 2004). water sector and its financing like in other developmental projects in oman, all water resources planning and infrastructure development is controlled by the ministry of national economy (mne). water resources planning are set out in a 20-year national water resources master plan which is being implemented in 5-year stages under the jurisdiction of the mrmewr and the mne (world bank, 2005). the government’s development plan gives priority to meeting demand for water from the domestic and industrial sectors. in the 2000-2005 development plan, the allocation was about r.o. 202 million ($525 million) to that end (mne, 2003). oman relies on a variety of strategies, including greater reliance on desalination and water from shallow aquifers (escwa, 2004), among others to make better use of its available resources. with the emphasis on desalination, long term policy in the urban water sector aims at the partial or full privatization of the production of desalinated water and wastewater treatment (world bank, 2005). developmental plans are financed from the state’s revenue and borrowing both internally and from the international markets. the omani government has implemented its sixth 5-year plan, launched in 2001, to reduce its dependence on oil and expatriate labor. the plan focused on income diversification and job creation for omanis in the private sector. currently, efforts are underway to liberalize investment opportunities in order to attract foreign capital (us fed, 2005). this will have a direct impact on many economic sectors, including the water sector. for the seventh 5-year plan (2006-2010), an estimated r.o. 20,896 million ($54,346 million) was approved, with a deficit of r.o. 2,266 million ($5,893 million). this deficit will be financed through borrowing and withdrawal from reserves. oman obtains developmental loans from regional and international lenders, such as the arab fund and the islamic development bank. one of the naksbbendi 42 plan’s emphases is on enhancing the water resources and provision of safe water. who pays for the water? in accordance with the state plans, a mega wastewater project for the capital city of muscat, at a cost of $1 billion, is being considered, with the government planning to undertake the entire financing. the proposed project will be a joint venture with an international firm. this complex project will create a wastewater system by 2025 that will treat about 200,000 m3 of water daily for reuse, covering 80% of the population by 2014 and 90 % of the population by 2017. wastewater will be collected, processed, treated and re-distributed. the project involves several parties, such as the oman wastewater services company, the muscat municipality, a private operator, project contractors and others (mne, 2003). the project is in progress. stage 1 is under implementation while stages 2 and 3 are in the design and tendering stages (personal written communication, z. al sulaimani, january 11, 2006). implementation of this project demonstrates the desire of the state to upgrade the sector and its willingness to go the joint venture route and provide for the involvement of the private sector. there is clearly an emerging interest in reducing the reliance on government funding and engaging the private sector. there are many positive aspects of this trend. there will be more funds available, more expansion will take place and more people will be connected to the distribution network. the state will allocate its budget to more needy sectors. above all, the proper management of water resources will be enhanced through the recognition of its value by the consumers. a plan in motion: new mega water project in accordance with the state plans, a mega wastewater project for the capital city of muscat, at a cost of $1 billion, is being considered, with the government planning to undertake the entire financing. the proposed project will be a joint venture with an international firm. this complex project will create a wastewater system by 2025 that will treat about 200,000 m3 of water daily for reuse, covering 80% of the population by 2014 and 90 % of the population by 2017. wastewater will be collected, processed, treated and re-distributed. the project involves several parties, such as the oman wastewater services company, the muscat municipality, a private operator, project contractors and others (mne, 2003). the project is in progress. stage 1 is under implementation while stages 2 and 3 are in the design and tendering stages (personal written communication, z. al sulaimani, january 11, 2006). implementation of this project demonstrates the desire of the state to upgrade the sector and its willingness to go the joint venture route and provide for the involvement of the private sector. there is clearly an emerging interest in reducing the reliance on government funding and engaging the private sector. there are many positive aspects of this trend. there will be more funds available, more expansion will take place and more people will be connected to the distribution network. the state will allocate its budget to more needy sectors. above all, the proper management of water resources will be enhanced through the recognition of its value by the consumers. possibilities of implementing some u.s. financing methods obstacles in water project financing based on the available options, some of the methods used in financing water projects in the u.s. could be considered for implementation in oman. the transition could take time in order to lay the grounds for its success. the tax code in the u.s. provides a major impetus for investment opportunities. there is no personal income tax and only corporate income tax in oman, thus there is no special attraction to private investors to purchase bonds. a combination of debt and equity could be used to promote the concept that users of water should pay, ultimately, the full cost of this benefit. when the financial obligations of the provider are determined by taking into consideration the interest of both the stakeholders and the creditors, then a proper tariff will be established to achieve these financial goals. also, there will be positive attempts to control the expenses. in order to have more chance of financing programs, certain issues need to be assessed and mitigated and they are related to financing water projects in general: high initial investment and long payback period low rate of return low rate of return low rate of ret foreign exchange risk sub-sovereign risk risk of political pressure contractual risk the above are some issues to wrestle with. country (sovereign) risk is also present as a general financing urban water sector in the usa, with possible implementation in the sultanate of oman 43 constraint in international finance and not limited to the water sector. very few emerging markets have investment ratings that enable them to raise funds on attractive terms. water projects have the additional disadvantage that there is a high minimum size of project finance, due to the size of legal costs and the terms for water projects. international project finance has large returns to scale because of the legal, financial and due diligence costs associated with it. many water projects may not be viable for project finance because they fall below the minimum size for it. for the above reasons, international loans and equity investment in water have been low and falling. banks and private companies are now more aware than ever of the risk-reward tradeoff (camdessus, 2005). brief survey of the gulf cooperation council countries before suggesting the possible actions in oman, a brief review of the financing mechanism in the rest of the gcc countries will be presented. the financing of infrastructure projects in general, and water projects in particular, is common among all of the gcc countries. the reliance on government funding is well understood. there are many reasons for such reliance. it is accepted that the state is responsible for those activities. in the meantime, the availability of funds allowed the states to meet the requirements within the boundaries of the annual state budget. progress was made in providing residents of those countries with water at highly subsidized prices. the latest report of the world bank showed clearly that the burden is becoming enormous. the cost of subsidies in bahrain was around $55 million, which represents 0.7% of gdp and 1.4% of oil export revenue. the subsidies in saudi arabia represent around $3,175 million, 1.7% of gdp and 7% of oil export revenue. oman’s subsidies are the lowest among the gcc at $85 million and 0.4% of gdp and 1.1% of oil export revenue (world bank, 2005). with the increase in population and the need to have more facilities, the burden is going to be horrendous. the trend towards privatization is progressing with emphasis on new projects, such as the sulaibiya wastewater plant in kuwait, the taweelah a2 in united arab emirates and the desalination company of ras laffan (escwa, 2003) in qatar. one of the major undertakings is in saudi arabia where the government is looking for independent water and power producers (iwpps) to provide a large proportion of new generating electric capacity and drinking water; the initial plan calls for four iwpps, and each is expected to cost $1 billion. the government hopes to offer a 60 percent stake in each of the four projects to private companies. it is clear that the trend is moving towards engaging the private sector in the ownership and the management of the water facilities, and less reliance is being placed on the government. oman’s possible actions financing the water sector should be examined thoroughly and a proper course(s) of action should be advanced and presented to the decision makers. in order to have more financing options, it is necessary to restructure government agencies and make them autonomous entities. then, along with other private providers, they could try to form an association and strive to get a credit rating as well. after assembling the proper ingredients for possible success, water service providers should focus on the most important element of having a tariff which should cover initially all the operating costs and ultimately reach full cost recovery. in the case of oman, subsidies should be transparent and reviewed continuously to ensure they target the intended beneficiaries. oman is moving towards a reduction in its subsidies programs (world bank, 2005). this is a good sign. still, subsidy should be provided on the basis of need. such assessment should be implemented in the short term and without delay. after assessing the sectoral requirements and taking the decision to have an equitable tariff, which is supposed to provide for cost recovery and the financing of new projects, a financing model could be identified. water providers could borrow from the local, the gcc or the international markets. anchor investors, like the pension fund and others in oman, could facilitate the process. the banking system in oman remains strong, with proper supervision and with sound lending practices, and in a healthy economy asset prices continued to strengthen. the muscat securities market index gained 24 % in 2004 and surged another 60 % in the first half of 2005 (ford, 2005). banks are making solid profits and continue to grow, both in terms of corporate and personal lending naksbbendi 44 (gcc, 2005). these indicators should provide good possibilities for borrowing locally. possibilities for borrowing locally. possibilities f oman is proceeding to have its newest independent private water project with international investors. four japanese conglomerates are considering oman’s first independent water project, being developed in the sharqiyah region. marubeni corp, mitsui & company, sojitz corp and sumitomo corp are among fifteen international companies so far expressing interest. the multi-million dollar project is expected to have a desalination capacity of 15 20 million gallons per day (ame, 2005) and is in the tendering stage. while it is premature to assess its impact on tariffs and other factors, it is clear that investors are interested in getting a market rate return on their investment. that could be achieved through a proper tariff structure. however, the actual tariff structure may be below the envisioned ones due to its negative impact on the customers. in this case, the state may provide certain incentives, subsidies, and other rewards in order to meet the expectations of the investors. the issue of security safeguards should be assessed and promoted. the security of infrastructure projects in general, and water projects in particular, should be assessed and monitored. in the case of privatized operations, the state should have direct control over that function and should be compensated for it. conclusions and recommendations population growth and the decrease in the availability of water is a worldwide phenomenon. aside from the need for building new facilities, there is a need for upgrading and rehabilitating the existing facilities. the cost is in billions of dollars. the reliance on government budgets is going to limit the implementation of such needed tasks. there is an urgent need for proper financial engineering to implement projects and not to burden and choke government budgets. the experience of the washington suburban and sanitary commission in the maryland suburb was used as a case in point, having an independent public agency taking care of 1.6 million people with proper self financing and without burdening the tax payers in the state. other cases were cited from the states of new york, arkansas and utah. these reduce to the simple premise that users should pay for the cost of having safe water. the ultimate tariff structure should cover the operating and capital cost. with proper administration the goal could be achieved. in oman, while the trend of privatization is advancing rapidly, especially in the desalination and wastewater areas, the implementation of some of the methods used in the u.s. are possible, namely, • allowing private equity participation in the operation of the water facilities, with the understanding that a suitable form of privatization is possible after a certain period. water providers could rely on borrowing, either through direct loans or through the flotation of bonds. • assessing the possibility of imposing a sales tax on certain luxury products, such as cars and jewelry, could be considered. could be considered. could • encouraging the banking system and anchor investors, such as the social security pension fund, to lead the way in making funds available to finance water projects. this is part of a proper investment strategy by which investment should be diversified to mitigate the risk. • phasing out subsidies gradually but maintaining this for the economically disadvantaged. • reducing the agricultural usage of water resources, reducing the agricultural usage of water resources, red through the mechanism of implementing block rates and limiting access to that resource, and encouraging the growing of agricultural products that require less water to grow. • maintaining a tariff structure which will ultimately cover all the operating and capital needs of the service provider in question. with sound financial planning, there will be equity in the water charges and that will provide financial stability to the service providers, which in turn, will enable them to serve more people and eventually reduce the final cost due to the economy of scale. acknowledgements i would like to thank zaher al sulaimani, slim zekri, sheila cohen, muwaffaq saqqar, mowafak al yafi and kareem nakshbendi for their valuable critique. also to joe baired and j.d. noell for their timely update of data and to the university of maryland financing urban water sector in the usa, with possible implementation in the sultanate of oman 45 university college library for its continued support and assistance. references ame. 2005. japanese on oman water. ame info me energy, august 28, 2005. baired, j. 2005. sales tax financing for water projects debated. salt lake tribune (utah), august 12, 2005. retrieved 12/27/2005 from lexis nexis. business and industry. 2005. oman to sell 30% stake in omantel. business and industry, telecomworldwire, april 14, 2005. retrieved 12/ 23/2005 from lexis nexis. camdessus. 2005. financing water for all. report of the world panel on financing water infrastructure, world water council, 3rd world water forum globak water partnership. http://ww w.worldwatercouncil.org/fileadmin/wwc/library/ publications.and reports/camdessusreport.pdf. p.5. retrieved 12/27/2005. eichenscher, t. 2005. budget cuts could spur privatepublic partnerships. natural resources, 10:9, july 25, 2005. retrieved 11/25/2005 from lexis nexis. escwa, 2003. assessment of the role of the private sector in the development and management of water supply in selected escwa member countries, escwa, october 3, 2003. p 31. escwa. 2004. the optimization of water resources management in the escwa countries: a survey of measures taken by the escwa countries during the 1990s for the optimization of water resources management and capacity-building in the water sector, new york, u.n. 2004. http.// www.escwa.org.lb/information/publications/edit/ ford, n. 2005. waiting for privatization. middle east, jan 2005 issue 352, pp. 38-39. gcc. 2005. oman attracts regional interest. in: the banker, august 1, 2005. glynn, m. 2005. low-interest loan eyed for water system. the buffalo news, january 3, 2005. retrieved 11/15/2005 from lexis nexis. howard, s. 2005. financing water infrastructure projects. federal document clearing house congressional testimony, june 14, 2005. imf. 2005. executive board concludes 2005 article iv consultation with oman, december 9, 2005, imf. retrieved 12/29/05. http://www.imf.org/ external/np/sec/pn2005/pn05165.htm. mays, r.h. and d. carruth. 2005. tax dollars used to help 900 farmers irrigate crops. arkansas democrat-gazette, 2005. ministry of national economy. 2004. general census for population, housing and establishments. http: //www.omancensus.net/english/inde.asp. mne. 2003. the sixth five year development plan 2001-2005. ministry of national economy, sultanate of oman. simon, p. 2005. water for the poor act of 2005. passed the house of representatives on november 7, 2005. 109th congress, 1st session in the house of representatives as introduced in the house, april 19, 2005. retrieved 12/15/2005 from lexis nexis. united nations 2005. millennium declaration. resolution adopted by the general assembly [(a/55/l.2)] 55/2. http://www.un.org/millennium/ declaration/ares552e.htm. (12/13/2005). us dept of state. 2006. background note: oman. www.satet.gov/r/pa/ei/bgn/35834.htm. us fed. 2005. state department issues background note on oman. us fed news february 1, 2005. world bank. 2005 a water sector assessment report on the countries of the cooperation council of the arab states of the gulf. march 31. 2005. wwsc. 2006. approved budget fiscal year 20006, july 1, 2005. retrieved 12/27/2005, from lexis nexis. http://www.wsscwater.com/budget. fy06. pdf p. 15. zeilig, n. 2005. bridge over troubled water. american city & county, june 2005. http://ww w.americancityandcounty.com/mag/government_ bridge_troubled_water/ agricultural and marine sciences, 16:13-22 (2011) ©2011 sultan qaboos university 13 __________________________________________________ *corresponding author. e-mail: moza_albusaidi@yahoo.com changes in scomberotoxin (histamine) and volatile amine (tvb-n) formation in longtail tuna (thunnus tonggol) stored at different temperatures moza abdallah al-busaidi*, poulose yesudhason, khamis saif al-falahi, adel khalifa al-nakhaili, nashwa ali al-mazrooei and saoud hamood al-habsi fishery quality control center, ministry of agriculture and fisheries wealth p.o. box 427, p.c. 100, muscat, sultanate of oman abstract: changes in histamine and volatile amine (tvb-n) formation was studied in longtail tuna (thunnus tonggol) captured in the sea of oman and stored at different temperatures. based on sensory analysis, longtail tuna maintained shelf life for 1, 4, 15 and 300 days at 0, 8, 25 and -18 oc, respectively. histamine and tvb-n increased with time, but the rate of change varied with storage temperature. histamine formation was suppressed significantly at lower than the fda limit of 5 mg/100 g at 0 and -18 oc but not at 8 or 25 oc. tvb-n did not reflect the quality index at 0 or 8 oc even though the samples were rejected by sensory evaluation. no correlation was observed between histamine and tvb-n values except at 25 oc and assessment of tvb-n was not sufficient for estimating the degree of histamine-related health hazard. poor correlation was found between sensory score and pooled tvb-n value compared to histamine, and the correlation was closer at 8 and 25 oc than at the lower temperatures. السهوة املتطايرة لسمك النيتروجنية والقواعد الهستامني تكوين في التغييرات املزروعي ونشوى علي النخيلي خليفة الفالحي وعادل سيف وخميس يشوداسون وبولوز البوسعيدي عبداهللا موزة السمكية والثروة الزراعة وزارة – جودة األسماك ضبط مركز احلبسي حمود وسعود thunnus) نوع من السهوة لسمك (tvb-n) املتطايرة النيتروجنية والقواعد الهستامني تكوين في التغييرات دراسة متت اخلالصة: األسماك احتفاظ تبني التحاليل احلسية باالعتماد على في درجات حرارة مختلفة تخزينه مت وقد بحر عمان، من اصطياده مت الذي (tonggol الهستامني كمية التوالي. على ْ م ١٨ و و٢٥ و٨ صفر حرارة درجات في يوم و٣٠٠ ١٥ بني٤،١، ما تتراوح ملدة لالستهالك بصالحيتها مادة انخفضت حيث التخزين، درجة حرارة باختالف اختلف التغيير معدل ولكن الوقت، مبرور زادت (tvb-n) املتطايرة النيتروجنية والقواعد ْم ١٨صفر و غم في درجة حرارة ملغ/١٠٠ البالغة ٥ (fda) األمريكية الغذاء والدواء إدارة معايير عن واقل ملحوظ بشكل الهستامني في درجات اجلودة دليل على تنعكس لم (tvb-n) املتطايرة النيتروجنية القواعد كمية ان كما مْ . ٢٥ ٨ ْم أو في درجة حرارة ولكن ليس ، و الهستامني بني كمية ترابط على يتم احلصول احلسي. لم بالتقييم رفضها مت قد العينات هذه ان من ْم على الرغم أو ٨ ْم صفر حرارة كافيا لتقدير يكن لم املتطايرة النيتروجنية القواعد قياس كمية أن إال ْم ، ٢٥ درجة حرارة إال في (tvb-n) املتطايرة النيتروجنية القواعد النيتروجنية املتطايرة القواعد قيم ومجموع احلسي املقياس بني معنوي ترابط على احلصول يتم ولم الصحة. على الهستامني خطورة مدى ٢٥ْم. و ٨ ْم حرارة في درجات اقرب الترابط وقد كان بالهستامني، (tvb-n) مقارنة keywords: histamine, longtail tuna, scomberotoxin, storage temperature, safety. introduction human illness resulting from the consumption of food high in biogenic amines has generally been called histamine poisoning. histamine food poisoning is one of the most frequently reported human illnesses associated with seafood (dewaal et al., 2006). the condition is often referred to as scombrotoxic fish poisoning (sfp) or scombrotoxicosis because of its common association with fish in the family scombridae. scombrotoxic fish poisoning occurs throughout the world and the highest incidence is reported in the united states, japan and the united kingdom (lehane and olley, 2000). histamine or scombrotoxic fish poisoning accounts for 5 % of all food-related illness and 37 % of all seafoodrelated illnesses reported to the cdc (noltkamper, 2006). the most common symptoms of sfp include rash, flushing and sweating, burning of the mouth, nausea, vomiting, diarrhea, stomach pain, dizziness and swelling of tongue and face (murray and hobbs, 1982). fish belonging to the families scomberesocidae and scombridae are good candidates for histamine formation because of the high concentration of free histidine in muscle tissue (ten brink et al., 1990). however, non-scombroid fish have also been implicated (bartholomew et al., 1987; steve et al., 1989). tuna (thunnus) and mackerel (scomber) have most frequently been involved, but this is partially due to the greater consumption of these fishes world-wide (taylor, 1986). in september 1982, the fda established a defect action level (dal) for histamine in fish at 20 mg/100 g and in 1995 the fda reduced the histamine dal to 5 mg/100g. the reasoning for this reduction was due to the variability in histamine concentrations from section to section in a fish. if there is a 5 mg/100 g concentration of histamine in a sample, the fda reasoned that there could be a sufficient concentration to cause illness (50 mg/100 g) in another section of the fish. the european community 14 al-busaidi and others 15 changes in scomberotoxin and volatile amine formation in longtail tuna stored at different temperatures established that the average content of histamine in fish should not exceed 10 mg/100 g and no sample may contain more than 20 mg/100 g for fish belonging to scombridae, clupeidae, engraulidae, coryphaenidae, pomatomidae and scomberesocidae families (commission regulation 2073/2005/ec). omani legislation (ministerial decision no.12/2009) has specified that histamine should not exceed 10 mg/100 g. shalaby (1996) recommended the following guideline levels for histamine content of fish: <5 mg/100 g (safe for consumption): 5-20 mg/100 g (possibly toxic); 20-100 mg/100 g (probably toxic) and >100 mg/100 g (toxic and unsafe for consumption). knowledge of the proximate composition of fish species has fundamental importance in the application of different technological processes and it is also an important aspect of the quality of raw material, sensory characteristics and storage stability (sikorski, 1994). one of the most common chemical methods used for quality evaluation of fresh seafood is the evaluation of the total volatile bases fraction (tvbn). the tvb-n includes ammonia, monoethylamine, dimethylamine along with trimethylamine (yeh et al., 1978). omani legislation (ministerial decision no.12/ 2009) has specified the tvb-n level for good quality fish is 25-35 mg/100 g. tuna and tuna-like species are important due to their global economic importance and international trade for canning and sashimi, and are mostly consumed locally as fresh, frozen or canned. longtail tuna (thunnus tonggol) is one of the popular pelagic fish and accounts for a large proportion of fish production in the sultanate of oman. although the fish has been rarely implicated in outbreaks of scombroid poisoning, there have been concerns for potential formation of histamine, since it belongs to the scombroid family, contains high level of histidine in the muscle and has high body temperature (26-30 oc). many studies have reported on the effect of storage temperature on histamine formation for various tuna species but results very often have been ambiguous with the level of histamine formation and shelf-life. (guillen-velasco et al., 2004; silva et al., 1998; guizani et al., 2005). also, there is little or no knowledge relating to histamine levels in longtail tuna under various storage conditions. histamine was measured and compared with volatile base nitrogen and sensory analysis in order to assess the effect of storage time and temperature. materials and methods sample collection and storage the fish samples used for the trials were 102 fresh longtail tuna (thunnus tonggol) caught from the sea of oman and purchased at the landing centre, muscat, sultanate of oman. fish samples were stored on ice and kept in thermocole boxes and delivered to the laboratory within 45 minutes from the landing centre. upon arrival at the laboratory, the length and weight of the fish were measured. the tuna fish were divided into four groups. one group (n=30) was stored at 0oc in ice (ice temperature). the second group (n=27) of fish was stored at 8oc (home refrigeration temperature) in a temperature-monitored refrigerator. the third group (n=6) was stored at 25 ± 2 oc (room temperature representing the winter ambient temperature of muscat and surrounding regions). the fourth group (n=36) of fish was stored at -18 oc (frozen storage temperature) using a temperaturemonitored-cooled incubator. fish were placed individually in separate clean polythene bags and stored at respective temperatures. good manufacturing practices (gmp) and good hygienic practices (ghp) were strictly followed during the handling and storage at different temperatures of raw samples in order to avoid microbial growth and post-catch contamination. during storage, melting ice was replenished everyday in order to maintain a constant storage temperatures in ice-stored samples. temperature was monitored regularly throughout the storage period with a digital thermometer. physical, chemical and sensory tests were performed on fresh longtail tuna samples prior to storage at different temperatures. sampling was carried out at predetermined time intervals depending on the temperature of storage. samples stored at 25, 8 and 0 oc were analyzed on a daily basis. however, it is known that the deterioration progresses slowly at freezing temperatures, therefore, samples stored at -18 oc were analyzed twice a week at the beginning of the storage and thereafter at two-month intervals for a period of up to 10 months. triplicate samples were used for each analysis. proximate analysis moisture, ash, fat, and protein were determined following the aoac (1993) methodologies (sec 950.46, 938.08, 960.39, and 955.04, respectively). histamine analysis histamine was determined by the method of taylor et al. (1978) with some modifications. fish muscle (10 g) was homogenized with 20 ml of 10% trichloroacetic acid (tca) using a homogenizer (nissei, japan) for 2-3 min. the homogenate was centrifuged at 3000 rpm for 5 min and 20 ml of the supernatant was filtered through a whatman membrane filter and the ph 5-7 was adjusted using a 10 % sodium hydroxide solution. twenty ml of 0.4 m acetic acid buffer was added to the ph adjusted solution and filtered through a column containing amberlite with 100 ~200 mesh size (cg50). the column was washed with 80 ml of 0.2 m acetic acid buffer and 20 ml of 0.2 n hcl. a total volume of 25 ml was collected, filtered through a whatman (0.45 µm) membrane filter and 20 µl was directly injected into the chromatograph. the analysis was performed using a waters alliance high-pressure liquid chromatography system (hplc) model 2690 equipped with a quaternary pump, an online degasser and an injection valve with a loop capacity of 20 µl. the detector used was a scanning fluorescence 14 al-busaidi and others 15 changes in scomberotoxin and volatile amine formation in longtail tuna stored at different temperatures detector model 474 with a 330 nm excitation and 430 nm emission wavelengths. the histamine compound was determined using a reverse phase shodex asahipak column model odp-50 (150 x 4.6 mm). the isocratic mobile phase (18:82) consisted of acetonitrile (sigma, 99.9 %) and 50 mm sodium tetraborate (sigma, 99 %) aqueous solution containing 1 mm o-phtal-aldehyde (opa) (gr for fluorometry, kiran light laboratory) and 1mm nac (n-acetyl-l-cysteine) was used at a flow rate of 0.5 ml/min. the histamine peaks were integrated and calculated with empower software. for each analysis, recovery samples were prepared and analysed and the mean recovery obtained was 95.5 %. also, standard reference material of fapas canned tuna fish (srm t 2711) was used to cross-check the reliability of the test. the mean value (125 ± 6.5 mg/100 g) was within the range of the assigned value (138 ± 17.0 mg/100 g) of histamine showed that the method was adequate for the analysis of histamine. total volatile base nitrogen (tvb-n) analysis tvb-n was determined using the method of damoglu (1979). fish muscle (10 g) was homogenized with 150 ml of distilled water, 2 g magnesium oxide, and 4 drops of silicon antifoam agent for 1 min. using a warring blender. the homogenate was transferred into a receiving flask and 25 ml of 2 % boric acid and 3 drops of methyl red indicator were added and the flask was placed into a buchi steam distillation unit consisting of rotavapor model r-124, vacuum controller model b-721 and water-bath model b-480 (switzerland). the mixture was steam distilled, 75 ml of the volatile component collected and the level determined by titrating with 0.05 n sulfuric acid (h 2 so 4 ). sensory evaluation sensory analysis was carried out by 7 semi-trained panelists. the panel evaluated the fish samples based on a hedonic scale with numerical scores of 7-1, 5-1 or 3-1 point scale using the assessment scheme from the tasmanian food research unit with slight modifications (bremmer et al., 1987; guizani et al., 2005). the inherent characteristics of longtail tuna such as gill colour, gill odour, round body, overall appearance, eye colour were evaluated (table 1). scores among panelists were averaged and tested statistically. statistical analysis results of physical, chemical and sensory analysis were analyzed using spss 10.0 (spss inc., chicago, il) software. descriptive statistics of means, standard deviation, one way and two-way anova, and correlation coefficient (pearson’s) were applied in analyzing the results. a significance level of 5 % was used. the regression analysis between parameters was conducted by plotting scattered graphs and calculating the r2 factors. the r2 factors higher than 0.5 were accepted to indicate a correlation between chemical and sensory parameters. results proximate composition the average length and weight were 46.18 + 2.03 cm and 1.03 + 0.125 kg, respectively. the results of the proximate composition of longtail tuna at different storage temperatures are presented in table 2. the initial values for moisture, lipid, crude protein and ash were 72.5, 2.85, 23.19 and 1.52 %, respectively. in the present study, the values reported for moisture (71.45, 71.25, 71 and 73.05 %), lipid (3.02, 3.22, 4.48 and 2.62 %), protein (23.89, 24.0, 23.15 and 23.02 %) and ash (1.38, 1.4, 1.43 and 1.30 %) in longtail tuna stored at 0, 8, 25 and -18 oc at the end of the storage are shown in table 2. significantly (p<0.05) low loss of moisture was observed for tuna stored at -18 oc, and the loss was higher at 25 oc compared to 0 and 8 oc. the final values for moisture content in all the storage temperatures were significantly lower (p<0.05) than the initial value. reduction in fat content was noticed at -18 oc, however, unlike moisture content, 25 oc resulted in a higher fat content. at the end of the storage period 0, 8, 25 and -18 oc showed significantly higher values for fat content than the initial value. protein contents did not change significantly for the longtail tuna fish at different storage temperatures. however, tuna fish stored at -18 and 8 oc showed less and more protein contents, respectively, at the end of the storage. final values for ash contents were significantly lower in all the storage temperatures than their initial value. there were only minor differences among 0, 8 and 25 oc for ash contents, however, -18 oc exhibited a significantly (p<0.05) lower ash content. changes in histamine concentration the histamine content of longtail tuna was negligible (0.2 mg/100g) at the beginning of the experiment, as shown in figure 1. histamine production was strongly suppressed at 0 oc and no increase in the histamine concentration was observed up to day 4. thereafter, the formation of histamine showed some fluctuations with time; however, increase in the histamine content was noticed from day 7 onwards, with the highest concentration of 4.808 mg/100 g on day 11. a reduction in the amount of histamine was observed at the end of the storage on day 15, reaching a value of 0.4 mg/100 g. in this study, the histamine in longtail tuna muscle during the storage at 0 oc was lower than 5 mg/100 g even at the end of the storage (fig. 1). an increase in histamine content was delayed for the longtail tuna at the refrigerated temperature of 8 oc for the first three days reaching a value of 0.984 mg/100 g, which was slightly higher than the value reported at 0 oc. however, histamine significantly increased (p<0.05) on day 7 and rapidly increased on day 8, reaching a value of 17.99 mg/ 100 g of fish and maintained until the end of the storage on day 10. the values were nearly four times higher than the value reported for longtail tuna stored at 0 oc. in contrast to the refrigeration temperature, histamine levels increased very rapidly at 25 oc, reaching 28.40 mg/100 g of tuna in 16 al-busaidi and others 17 changes in scomberotoxin and volatile amine formation in longtail tuna stored at different temperatures table 1. sensory assessment data sheet for longtail tuna (tunnus tonggol). serial no. physical characteristics feature sensory feature score 1 general appearance of surface very bright moderately bright slightly bright neither bright nor dull slightly dull moderately dull very dull 7 6 5 4 3 2 1 texture firm soft (rank between 7 and 1) 7 1 slime very clear very slimy (rank between 7 and 1) 7 1 2 eyes surface not sunken slightly sunken sunken 3 2 1 eyeball very clear moderately clear slightly clear neither clear nor cloudy slightly cloudy moderately cloudy very cloudy 7 6 5 4 3 2 1 eye bright, clear intact bloody damaged 3 2 1 3 gills color bright red deep dark red dull red pale brown bleached 5 4 3 2 1 odor seaweedy neutral slightly fishy fishy ammonia (putrid odor) 5 4 3 2 1 slime very clear very slimy (rank between 7 and 1) 7 1 4 belly condition intact burst (rank between 7 and 1) 7 1 5 overall acceptance very acceptable moderately acceptable slightly acceptable neither acceptable nor rejected slightly rejected moderately rejected very rejected 16 al-busaidi and others 17 changes in scomberotoxin and volatile amine formation in longtail tuna stored at different temperatures table 2. changes in the proximate composition in longtail tuna (tunnus tonggol) stored at different temperatures. storage days moisture(%) protein (%) fat (%) ash (%) mean ± sd mean ± sd mean ± sd mean ± sd 0 oc 0 72.50 ± 0.50 23.19 ± 0.05 2.85 ± 0.06 1.52 ± 0.03 1 74.05 ± 0.34 23.03 ± 0.04 2.37 ± 0.02 1.51 ± 0.01 3 75.30 ± 0.20 21.67 ± 0.01 2.48 ± 0.01 1.34 ± 0.01 4 73.20 ± 0.55 23.62 ± 0.41 2.41 ± 0.01 1.35 ± 0.02 7 71.05 ± 0.05 24.06 ± 0.09 3.10 ± 0.03 1.47 ± 0.01 8 73.55 ± 0.35 23.10 ± 0.58 2.61 ± 0.04 1.40 ± 0.04 9 73.15 ± 0.65 23.11 ± 0.32 2.69 ± 0.09 1.37 ± 0.01 10 71.75 ± 1.25 24.75 ± 0.14 2.80 ± 0.03 1.40 ± 0.02 11 72.05 ± 0.65 24.72 ± 0.37 2.70 ± 0.02 1.46 ± 0.32 14 71.65 ± 1.75 25.05 ± 0.02 2.84 ± 0.01 1.12 ± 0.01 15 71.45 ± 0.28 23.89 ± 0.11 3.02 ± 0.09 1.38 ± 0.02 8 oc 0 72.50 ± 0.50 23.19 ± 0.05 2.85 ± 0.06 1.52 ± 0.03 1 73.60 ± 0.10 23.33 ± 0.02 2.49 ± 0.06 1.56 ± 0.01 2 70.95 ± 0.25 23.24 ± 0.02 3.08 ± 0.02 1.49 ± 0.01 3 74.30 ± 0.10 21.82 ± 0.01 2.89 ± 0.10 1.38 ± 0.04 4 73.70 ± 0.40 23.29 ± 0.23 2.59 ± 0.03 1.37 ± 0.04 7 73.20 ± 0.28 23.12 ± 0.31 3.24 ± 0.08 1.38 ± 0.08 8 71.15 ± 0.25 24.37 ± 0.23 3.29 ± 0.06 1.41 ± 0.01 9 72.25 ± 0.25 24.21 ± 0.15 3.03 ± 0.02 1.30 ± 0.03 10 71.25 ± 0.15 24.00 ± 0.19 3.22 ± 0.01 1.40 ± 0.01 25 oc 0 72.50 ± 0.50 23.19 ± 0.05 2.85 ± 0.06 1.52 ± 0.03 1 71.90 ± 0.70 23.12 ± 0.03 3.69 ± 0.02 1.43 ± 0.01 2 71.00 ± 0.11 23.15 ± 0.26 4.48 ± 0.02 1.43 ± 0.01 -18 oc 0 72.50 ± 0.50 23.19 ± 0.05 2.85 ± 0.06 1.52 ± 0.03 1 73.00 ± 0.63 23.15 ± 0.42 2.96 ± 0.02 1.50 ± 0.01 4 72.10 ± 0.55 23.11 ± 0.25 2.86 ± 0.04 1.40 ± 0.09 7 73.30 ± 0.30 23.62 ± 0.11 2.39 ± 0.01 1.47 ± 0.03 9 73.30 ± 0.90 23.35 ± 0.80 2.55 ± 0.09 1.43 ± 0.04 14 73.70 ± 0.10 23.77 ± 0.17 2.05 ± 0.35 1.42 ± 0.06 18 73.55 ± 0.45 22.31 ± 0.01 2.46 ± 0.06 1.51 ± 0.03 30 73.30 ± 0.20 23.09 ± 0.04 2.62 ± 0.08 1.46 ± 0.01 60 73.40 ± 0.23 23.06 ± 0.14 2.93 ± 0.04 1.53 ± 0.05 120 71.65 ± 0.35 23.52 ± 0.27 3.29 ± 0.02 1.59 ± 0.06 180 72.15 ± 0.35 24.65 ± 0.12 2.82 ± 0.04 1.55 ± 0.02 240 72.50 ± 0.20 23.42 ± 0.03 3.15 ± 0.07 1.54 ± 0.01 300 73.05 ± 0.75 23.02 ± 0.61 2.62 ± 0.05 1.30 ± 0.04 18 al-busaidi and others 19 changes in scomberotoxin and volatile amine formation in longtail tuna stored at different temperatures figure 1. changes in histamine and tvb-n in longtail tuna stored at (a) 0 oc, (b) 8 oc (c), 25 oc and (d) -18 oc. one day of storage. the concentrations became 290 and 15 times higher than the histamine concentration reported at 0 and 8 oc, respectively, and reached 34.99 mg/100 g of tuna at the end of the storage on day 2. no significant changes (p>0.05) in the histamine concentrations were observed during frozen storage at -18 oc for a period of one month. thereafter, a significant increase (p<0.05) was observed during the second month reaching a level of 3.04 mg/100g and decreased up to month eight. at the end of the storage period, a slight increase in the histamine concentration was observed. safety with respect to the histamine was maintained for nearly 10 months in this experiment. total volatile base nitrogen (tvb-n) the initial tvb-n value for fresh longtail tuna was 2.741 mg/100 g of fish in keeping with the quality of very fresh fish. an increasing trend in tvb-n was noticed in all the samples with storage time but the increase was not linear except in samples stored at 8 oc (r2 = 0.880) and 25 oc (r2 = 0.968). a significant increase (p <0.05 %) in tvb-n was noticed on day 1 and the value reached 11.03 mg/100 g on day 10, thereafter, a slight decrease was observed at the end of storage period for fish stored at 0 oc. at a temperature of 8 oc, the tvb-n values increased more rapidly on day one (reaching a value of 7.35 mg/100 g) and increased slowly but fluctuated with time reaching a maximum value of 21.99 mg/100 g on day 9. at the end of the storage period the value was 16.98 mg/100 g. a slow increase in the tvb-n was observed for samples stored at -18 oc reaching a maximum value of 17.98 mg/100 g. a slight reduction in the tvb-n was observed at the end of the storage. the values were always below the level of 30-40 mg/100 g declared for good quality fish. in contrast to the refrigerated samples, the tvb-n value increased sharply on day 1 for the longtail tuna stored at 25 oc reaching a value of 12.59 mg/100 g and at the end of the storage period the value reached a level of 62.12 mg/100 g which is above the rejection limit of 40 mg/100 g set for tvb-n (directive 95/149/eec). sensory evaluation according to the sensory analysis, the initial samples were of good quality, indicated by the value for raw tuna of 6.3 ± 0.51 (fig. 2). the mean sensory score and standard deviation for overall acceptance of longtail tuna is depicted in figure 2. storage temperature significantly (p<0.05) influenced the overall acceptance and limited the shelf life of longtail tuna to 15, 4 and less than one day during storage at 0, 8 and 25 oc, respectively. the overall acceptance was nearly 10 months for longtail tuna stored under frozen storage. discussion proximate composition in the present study, the values of proximate composition were within the range reported earlier for commercial-size tuna fish in different waters (mazorra-manzano et al., 2000; begona et al., 2006). generally, storage time and temperature significantly (p<0.05) affect the proximate composition. begona et al. (2006) reported a low loss of moisture for tuna fish stored at -18 oc. histamine concentration generally, histamine production showed different patterns at the four different storage temperatures, which indicates that storage temperature may have an effect on histamine � � � � � � � m g/ �1 00 g a 0.00 5.00 10.00 15.00 20.00 25.00 0 t 1 3 4 storage tvb�n histam 7 8 9 e�time�(days) ine 10 11 14 � 15 � � � � � 0.00 5.00 10.00 15.00 20.00 25.00 0 1 2 3 4 7 8 9 10 m g/ �1 00 g storage�time�(days) b tvb�n histamine � � � � � � � � 0.00 10.00 20.00 30.00 40.00 50.00 60.00 70.00 0 1 2 m g/ 10 0g storage�time�(days) c tvb�n histamine � �� m g/ �1 00 g d 0.00 5.00 10.00 15.00 20.00 25.00 0 1 tv 4 7 9 1 stor vb�n histamin 14 18 30 60 rage�time�(days) ne 120 180 240 3 � 300 18 al-busaidi and others 19 changes in scomberotoxin and volatile amine formation in longtail tuna stored at different temperatures figure 2. changes in sensory score (overall acceptance) of longtail tuna during storage at (a) 0, 8 and 25 oc and (b) -18 oc. production. also, fluctuation with time was noticed in all the storage temperatures. silva et al. (1998) reported <0.1 mg/100 g of histamine for bigeye tuna species and skipjack tuna species at the beginning of their study. our findings agree with that study, and the concentration was well below the fda limit of 5 mg/100 mg. storage temperatures significantly inhibited the formation of histamine at 0 and 8 oc. the reduction of histamine with time of storage could be due to its decomposition once it was produced (guizani et al., 2005). sato et al. (1994) reported that the histamine formation also depends on the presence of histamine decomposition bacteria within the flora along with histamine forming bacteria. they noticed that, initially, histamine accumulated in the fish stored at 5 oc and then the levels started decreasing and disappearing when the count of histamine decomposing bacteria exceeded 106 cells/g. it could also be due to the histaminases activity in the spoilage bacteria that may be responsible for the decline observed in longtail tuna after 11 days. lopez-sabater et al. (1995) found in bigeye tuna that histamine content declined once it reached its maximum level. however, in our study, notable amounts were not detected for up to 15 days of storage in ice. safety of longtail tuna with respect to the histamine for up to four days at 8 oc agreed well with that of bigeye tuna, where four days at the same temperature were reported by lopez-sabater et al. (1995). the histamine formation was increased at a faster rate in the longtail tuna samples stored at 25 oc. increase in histamine formation is assumed to occur as a result of the growth of psychrotrophic or psychrophilic bacteria (bennour et al., 1991; vagelis et al., 2007). stratton and taylor (1991) stated that, the enteric bacteria are the most prolific histamine producers in fish when they are maintained at temperatures greater than 4 oc. also, once the enzyme histidine decarboxylase has been formed, it can be active at or near refrigeration temperatures (fda, 2001). storage at 25 oc encouraged the rapid histamine formation reaching the toxicity level within one day. this could be due to mesophiles, which are the most prolific histamine formers. in addition, histidine decorboxylase activity is favored at temperatures higher than 15 oc. lehane and olley (2000) correlated the rapid histamine formation at 20 oc with the growth of proteus morganii, which was found to grow better and to be the main histamine producer at 24-30 oc. unlike histamine decomposition at 0 oc, no decomposition took place at 25 oc, which implies that, such a high temperature might inhibit the growth of histamine decomposing bacteria (sato et al., 1994). our results agreed well with previous findings by silva et al. (1998) and guizani et al. (2005) who found rapid histamine accumulation in bigeye tuna, skip jack tuna and yellow fin tuna where safety was maintained for only one day at 22 and 20 oc, respectively. it is possible that components, chemical or enzymatic, break down the biogenic amines faster than they can be produced at these temperatures, but then the components responsible for breaking down biogenic amines are either used up, or inactivated, whereas the enzymes producing biogenic amines remain active for a longer period of time. the histamine formation was very slow for the tuna samples stored at -18 oc. storage time at frozen temperatures strongly controlled the formation of histamine. this could be due to the freezing temperature, which probably kills the freeze sensitive histamine producing bacteria (bengigirey et al., 1998). at the same time, a slight increase in histamine concentration at this temperature could be due to the retention of histidine decorboxylase activity in frozen tuna which may increase histamine on thawing. the histamine concentration in tuna at 0 and -18 oc were lower than the health hazard level of 5 mg/100 g, fixed by the fda (2001), and the legal limit of 10 mg/100 g fixed by european community and omani regulations. however, at 8 and 25 oc the histamine levels were above the allowable limit after four days and 24 hrs, respectively, and characterized as unsuitable for consumption. shakila et al. (2003) found a histamine content above the fda maximum allowable limit of 5 mg/100 g after 12 hrs in rastrelliger kanagurta and after 15 hrs in sardinella fimbriata stored at ambient temperature (32 oc). the safe shelf life of scombrotoxin forming species is dependent upon the harvesting methods, the onboard handling and the time/temperature exposures throughout the processing, transit and storage. there are several factors affecting the probability of occurrence of histamine fish poisoning and among them, post-catch � 0 1 2 3 4 5 6 7 8 0 1 4 7 9 14 18 30 60 120 180 240 300 se ns or y� ev al ua tio n� sc or es � storage�time�(days) a b � � � � � � � � � � � � 0 1 2 3 4 5 6 7 8 0 1 2 3 4 7 8 9 10 11 14 15 se ns or y� ev al ua tio n� sc or es storage�time�(days) 0�oc 8�oc 25�oc a 20 al-busaidi and others 21 changes in scomberotoxin and volatile amine formation in longtail tuna stored at different temperatures contamination, inadequate chill storage or freezing and thawing procedures can be listed (lehane and olley, 2000). in fish subjected to elevated temperatures even for shorter periods, a large population of bacteria is soon established. during subsequent refrigeration, although bacterial growth ceases, residual enzyme activity continues slowly and histamine levels can increase (stratton and taylor, 1991). in this study, tuna showed histamine concentrations defined as safe for consumption at 0 and -18 oc, possibly toxic and probably toxic when stored at 8 and 25o c, respectively. tvb-n significant differences (p<0.05) in tvb-n values were observed for longtail tuna stored at 0 and 8 oc. this was probably due to the influence of storage temperatures. among the four different storage temperatures, slow increases in the levels of tvb-n were observed for longtail tuna stored at -18 oc; followed by 0 oc. the relatively low increase in the tvb-n value could be due to the effectiveness of low temperatures on the growth of tvb-n producing bacteria. maximum amounts and rapid increase were found for the longtail tuna samples kept at 25 oc; which indicates that, ambient temperature favoured the growth of tvb-n producing bacteria. silva et al. (1998) reported 64 mg/100 g of tvb-n for skipjack tuna at 22 oc at the end of the storage period on third day. connell (1990) reported that a maximum of 35-40 mg/100 g is usually regarded as the limit of acceptability; however, in the present study tvb-n values for tuna samples were well within the suggested limit throughout the storage period, except, for samples stored at 25 oc. figure 1 shows the tvb-n values obtained during the storage period at different temperatures. tvb-n values were found to increase linearly with time at 8 (r2=0.880) and 25 oc (r2=0.968). however, an insignificant (p>0.05) increment in tvb-n values was observed with time at 0 and -18 oc, which could denote low bacterial activity. our results were in agreement with the observation made by mazorra-manzano et al. (2000) for skipjack tuna muscle during iced storage. according to our results, changes in tvb-n content during storage of tuna at 0 and 8 oc did not reflect the quality index even though the samples were rejected by sensory evaluation. sensory evaluation fish were rejected by the panel members very early even though the tvb-n value did not exceed the limit of 30-40 mg/100 g. figure 3 shows the relationship of the overall acceptability of fish by sensory evaluation with pooled values of tvb-n and histamine. poor correlation (r2=0.472) was observed between overall acceptance and pooled tvb-n value during storage at four different temperatures indicating that the fish was rejected by the sensory panel before the fish reached the stage of decomposition. at the same time, correlation (r2=0.647) was observed between sensory score and histamine formation and the correlation was greater at 8 (r2 = 0.717) and 25 oc (r2 = 0.948). however, no correlation was found at 0o and -18o c. these results agreed with guizani et al. (2005) who reported a linear relationship between sensory score and histamine for yellowfin tuna stored at the same temperature. during storage at 0 oc longtail tuna were rejected by the panelists before histamine reached a toxic level of 5 mg/100 g fish (fda, 2001). this observation agreed with the findings of guizani et al. (2005) for storage of tuna fish at 0 oc and lopez et al. (1995) for storage of tuna at 0 oc; however, at 8 oc the fish maintained its safety up to the fourth day, that was well correlated with sensory score for overall acceptance. the loss of shelf life of longtail tuna correlated with the loss of safety with respect to histamine formation of longtail tuna when stored at 8 and 25 oc. however, tuna stored at 0 and -18 oc maintained their safety throughout the storage period. this could be due to decomposition of histamine at this temperature. the optimum temperature for the majority of the histamine formers is 25 oc. regression analysis of histamine and other quality characteristics of longtail tuna revealed a correlation between histamine concentrations and sensory analysis at 8 and 25 oc; but not at 0 or -18 oc, even though the fish were rejected by the sensory panel. no correlation was observed between histamine and tvb-n formation, except, at 25 oc (r2=0.699). measurements of volatile basic nitrogen were not adequate for estimating the extent of a histaminerelated health hazard. it was found that decomposition of longtail tuna at all the storage temperatures progressed faster than histamine formation. conclusion histamine and volatile amine (tvb-n) increased progressively during storage, but the rate of change varied with temperature. histamine production was suppressed significantly (p<0.05) and lower than the fda maximum allowable limit of 5 mg/100 g at 0 and -18 oc. with regard to the histamine toxicity, histamine production was very high at 8 and 25 oc. taking into consideration public health safety, appropriate storage temperature at preferably <4o c and appropriate handling of tuna fish are necessary for delaying histamine production and preventing histamine poisoning outbreaks. also, freezing the tuna prior to processing and storage reduced the histamine production. the histamine content did not show any correlation with the tvb-n value except, at 25 oc. however, the correlation was closer with sensory changes at 8 and 25 oc. tvb-n did not indicate the degree of freshness for fish stored at low temperatures (0 and -18 oc). estimation of tvb-n was not adequate for estimating the degree of histamine-related health hazards. the refrigeration temperature during storage is very critical to reducing histamine formation and also it is necessary to determine histamine content in order to control a potential health hazard. the loss of shelf life of longtail tuna correlated with the loss of safety with respect to histamine formation 20 al-busaidi and others 21 changes in scomberotoxin and volatile amine formation in longtail tuna stored at different temperatures figure 3. relationship between (a) sensory score and tvb-n, (b) sensory score and histamine, and (c) tvb-n and histamine of longtail tuna stored at 0, 8, 25 and -18 oc. �� � � y�=��0.0973x�+�5.8435 r²�=�0.4724 0.000 1.000 2.000 3.000 4.000 5.000 6.000 7.000 0.000 10.000 20.000 30.000 40.000 50.000 60.000 70.000 se ns or y� sc or es �fo r�o ve ra ll� ac ce pt an ce tvb�n�mg/100g a� �� � � y�=��0.1335x�+�5.4309 r²�=�0.6473 0.000 1.000 2.000 3.000 4.000 5.000 6.000 7.000 0.000 10.000 20.000 30.000 40.000 se ns or y� sc or e� fo r�o ve ra ll� ac ce pt an ce histamine�mg/kg b� c� �� � � y�=�1.2245x r²�=�0.2697 0.000 10.000 20.000 30.000 40.000 50.000 60.000 70.000 0.000 10.000 20.000 30.000 40.000 tv b� n� m g/ 10 0g histamine�mg/kg c� at 8 and 25 oc; however, tuna stored at 0 and -18 oc maintained their safety throughout the storage period. acknowledgements we would like to thank mehdia al-zidjali, alia al-zidjali and nada al-abri of fishery quality control centre, oman, for their constant assistance and contribution in sample preparation and analysis during this project. references aoac. 1993. official methods of analysis,14th ed. vol. ii. association of official analytical chemists. arlington, va. chap 35:1-8. bartholomew, b.a., p.r. berry, j.c. rodhouse, r.j. gilbert, and c.k. murray. 1987. scombrotoxic fish poisoning in 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veld. 1990. occurrence and formation of biologically active amines in foods. international journal of food microbiology 11:73-84. yeh, c.p.s., r. nickelson ii, and g. finne. 1978. ammonia producing enzymes in white shrimp tails. journal of food science 43:1400-1401. received: october 3, 2010 accepted: february 20, 2011 agricultural and marine sciences, 15:1-8 (2010) ©2010 sultan qaboos university 1 __________________________________________ *corresponding author. e-mail: isam@squ.edu.om effect of transportation and low voltage electrical stimulation on meat quality characteristics of omani sheep isam t. kadim*, osman mahgoub, waleed al-marzooqi and samera khalaf department of animal and veterinary sciences, college of agricultural and marine sciences, sultan qaboos university, po box 34, al-khod 123, sultanate of oman العمانیة األغنام جودة لحوم على املنخفض اجلهد ذو الكھربائي والتحفیز تأثیر النقل خلف قاسم المرزوقي وسمیرة وولید جعفر محجوب عثمان كاظم و توفیق عصام األغنام لذبائح الكھربائي التحفیز واستخدام مئویة) ــة درج ٣٦) الحار الفصل خــالل مفتوحة بسیارة الحیوانات نقل تأثیر لــدراســة البحث ھــذا یھدف الخالصة: بسیارات ساعات لثالث األولــى المجموعة نقل تم مجموعتین: الــى بالتساوي سنة بعمر ذكــوراألغــنــام من رأســًا عشرین تقسیم تم اللحوم. ــودة ج على العمانیة عینات جمع تم ــل. واألك الماء توفیر مع الذبح قبل ایــام ثالثة لفترة المركزي المسلخ حظائر في الثانیة المجموعة إیــواء تم بینما كیلومتر, ٣٠٠ لمسافة مفتوحة نقل المختارة الذبائح من ٪٥٠ على فولت) ٩٠) الكھربائي التحفیز استخدم األجــھــاد. ھرمونات تراكیز لقیاس والــذبــح النقل عملیة قبل الحیوانات جمیع من ــدم ال ونسبة والعصاریة ــراوة ــط وال الحموضة مثل للحوم النوعیة الصفات لــدراســة العینیة العضلة مــن عینات جمعت الــذبــح. مــن دقیقة ٢٠ مــرور بعد عشوائیًا واالدرینالین الكورتزول ھرمونات تركیز في ملحوظـة ــادات زی وجــود النتائج أظھرت اللون. و العضلیة اللویفات تكسر ومقیاس العضلیة اللیفة وطــول الماء فقد وزیــادة اللحم حموضة بانخفاض ملحوظ تأثیر الكھربائي للتحفیز كان منقولة. الغیر بالمجموعة مقارنة المنقولة الحیوانات دم في الدوبامین و أدرینالین والغیر النقل لعملیة السلبیة التأثیرات كھربائیًا.كانت محفزة بالغیر مقارنة والــلــون العضلیة اللویفات تكسر ومقیاس والعصیریة ــراوة ــط وال اللیفیة العضلة ــول ط األغنام نقل بــأن الــدراســة ھــذه ــدت اك الثانیة. بالمجوعة مقارنة الــداكــن والــلــون والعصاریة اللحم وحموضة الــطــراوة بتقلیل واضحة للحوم النوعیة الصفات على للنقل. السلبیة من التأثیرات یقلل التحفیز الكھربائي استخدام وان األغنام لحوم في الصفات النوعیة تردي إلى یؤدي الحار خالل الفصل abstract: the aim of this study was to determine the effects of road transportation during the hot season (36 oc) and low voltage electrical stimulation on meat quality characteristics of omani sheep. twenty intact male sheep (1-year old) were divided into two equal groups: 3 hrs transported or non-transported. the transported group was transferred to the slaughterhouse the day of slaughter in an open truck covering a distance of approximately 300 km. the non-transported group was kept in a lairage of a commercial slaughterhouse with ad libitum feed and water for 3 days prior to slaughter. blood samples were collected from the animals before loading and prior to slaughter in order to assess their physiological response to stress in terms of hormonal levels. fifty percent of the carcasses from each group were randomly assigned to low voltage (90 v) at 20 min postmortem. muscle ultimate ph, expressed juice, cooking loss percentage, wb-shear force value, sarcomere length, myofibrillar fragmentation index and colour l*, a*, b* were measured on samples from longissimus dorsi muscles collected 24 hrs postmortem at 2-4 oc. the transported sheep had significantly (p<0.05) higher cortisol adrenaline, nor-adrenaline, and dopamine levels than the non-transported group. muscles from electrically-stimulated carcasses had significantly (p<0.05) lower ph values, longer sarcomere length, lower shear force value, higher expressed juice, myofibrillar fragmentation index and l* values than those from non-stimulated ones. transportation significantly influenced meat quality characteristics of the longissimus dorsi muscle. muscle ultimate ph and shear force values were significantly higher, while cie l*, a*, b*, expressed juice and cooking loss were lower in transported than non-transported sheep. this study indicated that pre-slaughter transportation at high ambient temperatures can cause noticeable changes in muscle physiology in sheep. nevertheless, meat quality of transported sheep can be improved by electrical stimulation post-slaughter. keywords: sheep, transportation, longissimus dorsi, electrical stimulation, shear force. introduction transportation of small ruminants in open trucks between farms and slaughterhouse is a routine practice in the sultanate of oman. transport of live animals has been recognized as a stressful event that has significant economic and welfare implications for animals (schrama et al., 1994; kadim et al., 2006). vibrations and movement of the vehicle are novel to the animals, and therefore likely to elicit a stress response (dantzer and normede, 1983). adverse climatic conditions such as high or low temperatures and high relative humidity are also additional stressors to animals during transport. animals are inevitably exposed to handling, loading and transportation. all these stressors may increase catecholamine blood concentrations, which may result in compromising cellular and humoral immune functions, reproduction, digestion, growth and other metabolic processes (dantzer and mormede, 1983; nelson and drazen, 2000). this may also cause metabolic changes that can in turn adversely affect meat quality (ashmore et al., 1972; schrama et al., 1994; 2 kadim and others 3 effect of transportation and low voltage electrical stimulation on meat quality characteristics of omani sheep apple et al., 1995; kannan et al., 2003; bond et al., 2004; kadim et al., 2006). transportation usually imposes stress on animal and can lead to depletion of muscle glycogen reserves before slaughter that subsequently increase the ultimate ph of meat, and result in low meat quality characteristics (kadim et al., 2006). meat tenderness is one of the most important quality characteristics affected by ph and temperature (marsh et al., 1981). colour is also an important physical property of meat and consumers usually use it as a quality indicator. moreover, consumers are becoming more aware of the ethics of meat production and prefer meat that has been produced from animals that have not been mistreated (warris, 1995). electrical stimulation can increase postmortem muscle metabolism and hasten the onset of rigor mortis, which might improve the quality characteristics of stressed animals. a rapid ph decline of electrically stimulated carcasses could potentially result in a brighter coloured meat (king et al., 2004). the objective of the present study was to investigate the impact of road transport and low electrical-stimulation on meat quality characteristics of omani sheep longissimus dorsi. materials and methods animals and treatments twenty omani intact male sheep (1-year-old) were randomly selected from a homogenous flock fed rhodesgrass hay and a commercial ruminant concentrate at the agricultural experiment station, sultan qaboos university. the experiment was conducted during the hot season when the average ambient temperature was 36oc. animals were equally divided into 2 groups and randomly assigned to either non-transported or transported groups. three days prior to slaughter, the non-transported animals were transferred to a pen under shade in a lairage at muscat central slaughterhouse (40 km). feed and water were provided at libitum. on the day of slaughter, the transported animals were transported in an open truck for 3 hrs for a distance of approximately 300 km. a blood sample was collected prior to loading (initial), while a second blood sample collection was taken immediately after the transportation and prior to slaughter. the two blood samples were collected from the non-transported animals at the same time as the transported animals. blood sampling and analysis blood samples were collected in vacutainer tubes containing 81 mμl of 15% edta as an anticoagulant. the plasma was separated by centrifugation at 5 oc for 10 minutes at 3000 rpm then placed in 1.5 ml eppendorf tubes and stored at –80 oc. chemiluminescence immunoassay was used for the determination of plasma hormone levels using a beckman coulter access 2 immunoassay system and reagents. (beckman coulter, inc.). for the extraction of plasma catecholamines (all reagents chromsystems gmbh), 75mg of acid washed alumina was placed in a 2.0 ml eppendorf tube and then 750 μl of extraction buffer, 750 μl of plasma, and 100 μl of dihydroxybenzoic acid (dhba) standard 12 ng/ml were added. this mixture was vortexed for 20 minutes using an autovortex and then centrifuged at 5500 rpm (alc international microcentrifuge model # 4214) for 3 minutes and then the supernatant was aspirated. the resulting pellet was washed with 1 ml washing buffer. the mixture was then vortexed as before, centrifuged for 3 minutes, and the wash buffer carefully aspirated. the washing process was repeated three times. to retrieve the catecholamines from the alumina, the pellet was eluted using 240 μl elution buffer and vortex for 7 minutes, using the autovortex, centrifuged at 11500 rpm for 5 minutes and the supernatant containing the catecholamines and internal standard was transferred carefully to a clean vial without disturbing the alumina layer. this supernatant was immediately analyzed using an hplc with an electrochemical detector (waters 600s, 464 ecd and 717 autosampler). results were acquired and processed using millenium32 software (waters). carcass electrical stimulation animals were slaughtered and dressed at the muscat municipality central slaughterhouse following halal methods. a random 50% of the carcasses within each group were electrically stimulated for 60s, 20 minutes postmortem using a low-voltage stimulator (voltage, 90 v; agresearch, v1.3-r3b. new zealand). carcasses were kept at ambient temperature (20-25 oc) until placed in a chiller (2-4 oc) at 100±5 min postmortem. meat quality evaluation the carcasses were chilled for 24 h at 2-3 oc before the longissimus dorsi muscles were removed from the left. the muscles were placed in plastic bags then frozen at –20 oc until processing. the muscles were evaluated for a range of quality characteristics including ultimate muscle ph, expressed juice, percent cooking loss, warner-bratzler shear force value, sarcomere length, myofibrillar fragmentation index and colour l*, a*, b* were determined. the ultimate ph was assessed in homogenates at 20-22 oc (using a ultra turrax t25 homogenizer) of duplicate 1.5-2 g of muscle tissue in 10 ml of neutralized 5-mm sodium iodoacetate and the ph of the slurry measured using a metrohm ph meter (model no. 744) with a glass electrode. chilled muscle samples (13 mmx13 mm cross section) for assessment of shear force by a digital dillon warner-bratzler (wb) shear were prepared from muscle samples cooked in a water bath at 70 oc for 90 min. the cooked samples were carefully dried with tissues to remove excess surface moisture and re-weighed to determine cooking losses. sarcomere length by laser diffraction was determined using procedure described by cross et al. (1980/1981). expressed juice was assessed by a filter paper method, as the total wetted area less the meat area (cm2) relatively to the weight of the sample (g). myofibrillar fragmentation index (mfi) was measured using a modification of the 2 kadim and others 3 effect of transportation and low voltage electrical stimulation on meat quality characteristics of omani sheep table 1. effects of road transportation on hormonal concentrations in plasma of omani sheep. no. samples treatment sem transported non-transported 10 10 cortisol (nmol/l) initial 20.9a 20.6 2.91 final 38.9b 21.1 2.65 sign. ** ns adrenaline (ng/ml) initial 1.61a 1.59 0.15 final 2.15b 1.60 0.34 sign. * ns dopamine (ng/ml) initial 0.72a 0.71 0.17 final 0.99b 0.71 0.13 sign. * ns nor-adrenaline (ng/ml) initial 0.19a 0.20 0.021 final 0.38b 0.21 0.027 sign. * ns sem: standard error of mean, sign. ns not significant, * p<0.05, ** p<0.01. method of johnson et al. (1990). this measured the proportion of muscle fragments that passed through a 231µm filter after the sample had been subjected to a standard homogenization treatment. a 5 g (±0.5 g) sample of diced (6 mm3 pieces) was added to 50 ml of cold physiological saline (85% nacl) plus five drops of antifoam a emulsion (sigma chemical a5758) in a 50 ml graduated cylinder, and homogenized at 1⁄4 speed using an 18 mm diameter shaft on an ultra-turrax homogenizer for 30-s periods separated by a 30-s rest period. the homogenate was poured into a weighed filter (231 x 231 µm holes). the filter typically ceased dripping after 2-3 h, at which time they were dried at 26-28 oc in an incubator for 40 h before being reweighed. the mfi values presented herein were calculated as 100 minus the percentage of the initial meat sample weight that remained on the filter. approximately 60 min after exposing the fresh surface, cie l*, a*, b* light reflectance coordinates of the muscle surface were measured at room temperature (25±2 oc) using minolta chroma meter cr-300 (minolta co., ltd., japan), with a colour measuring area 1.1 cm diameter. it was calibrated using a minolta calibration plate (l* =97.59, a* =-5.00, b* = +6.76). the l* value relates to lightness; the a* value to red-green hue where a positive value relates to the red intensity; and the b* value to the yellow-blue where a positive value relates to yellow. the average of two measurements from each sample was recorded as the colour coordinate value of the sample. statistical analysis the effect of transportation and electrical stimulation on blood serum parameters, and meat quality were analyzed using glm procedures for analysis of variance procedure (sas, 1993). the first blood sample was regarded as an initial value and the second blood sample as final value. both samples were taken from the same animal; therefore sas repeated measurement analysis was used. differences between means were assessed using the leastsignificant-difference procedure. interaction between the transportation and electrical stimulation were excluded from the model when not significant (p>0.05). results and discussion blood serum hormonal levels physiological parameters such as cortisol, dopamine, adrenaline and nor-adrenaline have been proposed as sensitive indicators of physiological stress response in 4 kadim and others 5 effect of transportation and low voltage electrical stimulation on meat quality characteristics of omani sheep animals that have been exposed to road transportation (kadim et al., 2006). in the current study, blood parameter values were compared between the transported and nontransported sheep groups to investigate the effects of road transportation on sheep at high ambient temperatures (36 oc) (table 1). the ambient temperature in the present study was above the suggested upper limit of ruminant heat tolerance (35-40 oc) (yousef, 1985; lu, 1989). according to ali et al. (2006), measurement of cortisol is a valuable tool in stressed animals due to a graduated response depending on the severity of the stressor. in the present study, cortisol concentrations were still significantly (p<0.01) higher 3 hrs after the start of transportation. a similar conclusion was reported by kadim et al. (2006). nwe et al. (1996) and kannan et al. (2000) reported that plasma cortisol concentration increased within 30 min after the beginning of transport and reached a peak value at 1 hr in goats. the omani sheep transported the same day to slaughter had significantly higher (p<0.01) plasma cortisol levels than their non-transported counterpart sheep. this indicates that 3 hrs of transportation in an open truck under omani conditions (36 oc) appears to produce stress in sheep. broom et al. (1996), al-kindi et al. (2005) ali et al. (2006) and kadim et al. (2006) examined a range of plasma stress indicators in transported sheep and found that plasma cortisol levels were higher in transported sheep during 2-3 hrs of the transportation in comparison with the non-transported animals. moreover, ruiz-de-la-torre et al. (2001) found that the level of cortisol was higher after 4 hrs on a rough journey. the lower hormone values in the non-transported sheep indicate that there was sufficient time for recovery from stress and also the shorter distance and time of transport. adrenaline, dopamine and nor-adrenaline concentrations were significantly (p< 0.05) higher in the transported than non-transported sheep (table 1). similarly, kadim et al. (2006) found that transportation of omani sheep for 2 hrs significantly increased concentrations of adrenaline, dopamine and nor-adrenaline compared to non-transported animals. adrenaline levels increased in sheep after 10 min of transportation with little change in nor-adrenaline level (parrott et al., 1994). these findings indicated that levels of these hormones stay elevated for at least 3 hrs after transportation. release of adrenaline enables animals to mobilize body resources quickly for metabolic requirements in response to stress (dantzer and mormede, 1983). meat quality an elevated ultimate ph is a consequence of low preslaughter glycogen as a result of pre-slaughter stress including road transportation (gregory and grandin, 1998; geesink et al., 2001; kannan et. al., 2003; honikel, 2004; kadim et al., 2006). meat from transported sheep had significantly (p<0.05) higher ultimate ph value than meat from sheep that were non-transported (table 2). kadim et al. (2006) also found that 2 hrs-transportation had a significant effect on muscle-ultimate ph of the omani sheep. different types of stressors may elicit varying degrees of responses in animals. ruiz-de-la-torre et al. (2001) found that transportation of sheep on a rough road for 4 hrs significantly increased ultimate ph compared to those transported on a smooth road. similarly, muscles from stressed sheep had significantly higher ultimate ph values than non-stressed counterparts (apple et al., 1995). transportation not only includes physical stress, but also emotional stress caused by loading and unloading, noise, vibration and social disruptions. the effort needed by the sheep to keep their balance while the vehicle moves is demanding in terms of energy requirements leading to table 2. effect of transportation and electrical stimulation on a range of longissimus dorsi muscle quality characteristics (least square means) of omani sheep. transported non-transported sem significance stimulated nonstimulated stimulated non stimulated transport stimulation interaction no. samples 5 5 5 5 ultimate ph 5.72b 5.86c 5.61b 5.71b 0.05 * * ns expressed juice2 26.5b 23.7a 30.0c 26.2b 1.53 * * ns cooking loss% 22.7b 20.9a 26.7c 22.8b 0.64 * * ns shear force value 5.17b 7.35c 3.63a 5.21b 0.61 ** ** ns sarcomere length (µm) 1.49a 1.67b 1.51ab 1.75c 0.07 * * ns myofibrillar fragmentation index 78.8b 76.9a 87.7d 82.9c 0.63 * * * l* (lightness) 36.7ab 36.2a 38.4b 37.5ab 0.73 ns * ns a* (redness) 14.4ab 13.8a 14.2ab 15.7b 0.58 ns ns * b* (yellowness) 5.55 5.19 5.22 5.93 0.26 ns ns * abcmeans within the same row with different superscripts were significantly different (p<0.05). 2 expressed juice = water area (cm2) / sample weight (g), 3 warner-bratzler shear force value. 4 kadim and others 5 effect of transportation and low voltage electrical stimulation on meat quality characteristics of omani sheep depletion of glycogen and consequently decreasing muscle ph (tarrant and grandin, 1993; apple et al., 1995). the ultimate ph of muscle is a major determinant of meat quality (watanabe et al., 1996) and is related to the rate of glycogen and liberation of lactic acid via glycolysis preand post-slaughter. the ph affects meat tenderness and water-holding capacity (watanabe et al., 1996). ultimate ph value of meat is the result of a combination of many factors including pre-slaughter handling, postmortem treatment, glycogen store and muscle physiology (ashmore et al., 1973; marsh, 1977; thompson, 2002). there were significant (p<0.05) differences in ultimate ph at 24 hrs postmortem between the stimulated and non-stimulated muscles of sheep (table 2). in the present study, electrical stimulation appears to increase early postmortem glycolysis in muscle samples (table 2). similarly, geesink et al. (2001) found that ultimate ph from stimulated sheep carcass was significantly lower than that of non-stimulated carcass. in contrast, bond et al. (2004) and devine et al. (2006) have found that ultimate ph of longissimus muscle was not affected by electrical stimulation. water retention of meat is primarily caused by immobilization of tissue water within the myofibrillar system (hamm, 1981). applying pressure can cause a shift of water from the intercellular into the extracellular space and then onto the meat surface as a result of structural alterations at the level of the myofilament structure. expressed juice of sheep muscle was significantly affected by transportation and low voltage electrical stimulation (table 2). samples from transported sheep had significantly (p<0.05) lower expressed juice and cooking loss than muscles from non-transported ones (table 2). decreased cooking loss percentage is a reflection of the increased water-holding capacity (decrease expressed juice) associated with meat of high ultimate ph (bouton et al., 1971). similarly, apple et al. (1995) found that muscles from stressed lambs had lower (p<0.01) cooking loss than that from non-transported animals. in contrast, bond et al. (2004) found that muscles from exercisestressed sheep were significantly higher than those from non-exercised animals. they concluded that the mechanism causing greater water loss in the muscle of exercise-stressed lambs is unknown. expressed juice was significantly higher (p<0.05) for stimulated than for non-stimulated muscle samples. the increase in myofibrillar expressed juice of electricallystimulated muscles may be partly due to denaturised sarcoplasmic proteins in the myofibrillar fraction (eikelenboom and smulders, 1986). however, whiting et al. (1981) and bond et al. (2004) found that electrical stimulation had no effect on water-holding capacity of lamb longissimus dorsi muscle. the differences between samples from stimulated and non-stimulated muscle may probably be due to shrinkage of myofibrils as the postmortem ph fall causes denaturation of protein (offer and knight, 1988). the decline in ph after slaughter was much slower in non-stimulated than stimulated longissimus dorsi muscles. moreover, the thin and thick filaments interaction (sarcomere length) significantly (p<0.05) differed between stimulated and non-stimulated muscles (table 2). muscles from non-transported sheep had a significantly lower shear force value compared to transported sheep (table 2). in agreement with the present study, kadim et al. (2006) found that meat from non-transported sheep was significantly more tender than that from transported ones. apple et al. (1995) also found that muscles from non-transported sheep had lower shear values than stressed ones. in contrast, chrystall et al. (1982) found that the muscle from sheep chased to exhaustion by dogs was tenderer than those from their non-transported counterparts. decreased glycogen reserves and increased muscle temperature during transport resulted in muscle with a ph above 6.0 (marsh, 1983), which may activate calpain proteases (koohmaraie, 1988). in accordance with the shear-value results, muscles from the transported sheep had significantly (p<0.05) shorter sarcomere lengths than those from non-stimulated animals (table 2). muscles from non-stimulated carcasses had a significantly (p<0.01) higher shear force value compared to stimulated carcasses (table 2). the most positive advantage for electrical stimulation observed in the present study was similar to reports by chrystall and hagyard (1976); riley et al. (1981); kadim et al. (1993); polidori et al. (1999); geesink et al. (2001); and devine, et al. (2006). according to kadim et al. (1993), electrical stimulation of muscles soon after slaughter improved tenderness most probably by hastening the onset of rigor mortis rather than through processes that rapidly reduce muscle ph in sheep and consequently avoid toughening effects of cold shortening and thaw shortening. shear force values of muscles chilled at different rates were significantly reduced by electrical stimulation compared with non-stimulated ones (shorthose et al., 1986). hwang et al. (2003) stated that stimulation may improve tenderness either through effects on physical alteration and/or acceleration of energy turnover during and after the stimulation. moreover, ho, et al. (1996) and luo, et al. (2008) found a relationship between myofibrillar disruption and improved tenderness of meat. luo et al. (2008) reported that stimulation resulted in ultrastructural changes in beef longissimus muscle, which lowers the resistance to shearing force (hopkins et al., 2000). in the present study, electrically-stimulated sheep longissimus dorsi muscle had significantly (p<0.05) longer sarcomere length than non-stimulated muscles. similar findings were reported by whiting et al. (1981) and geesink et al. (2001) for lambs. the longissimus dorsi muscle from transported sheep had significantly lower (p<0.05) cie l* value than nontransported counterpart (table 2). this indicates that muscles from transported sheep were darker than muscle from non-transported sheep. the lower l* values of 6 kadim and others 7 effect of transportation and low voltage electrical stimulation on meat quality characteristics of omani sheep muscle from transported sheep in the present study are similar to those reported by apple, et al. (1995) who found lower values of l* for muscle from lambs subjected to stress. the type and intensity of transportation had an effect on meat colour. ruiz-de-la-torre et al. (2001) found that redness of sheep muscle which was transported on a rough road for 4 hrs was significantly higher than for those transported smoothly. bond et al. (2004) found that the colour of meat from stressed sheep was darker than those from non-transported animals. when muscle ph increased to above 6.0, cie a* values decreased below 16.0 (apple et al., 1995). in the present study, mean a* values of the longissimus dorsi muscles from transported sheep were below 16.0, indicating that the dark colour was effectively produced by 3 hrs of transportation due to depletion of muscle glycogen reserves before slaughter (warriss et al., 1990). muscle darkness is highly related to ph change and occurs at a ph of approximately 6.0 (macdougall and jones, 1981). mitochondrion oxygen uptake is more active at ph values greater than 6.0 (lawrie, 1958). postmortem glycolysis acid formation is insufficient to prevent mitochondrial respiration, thus allowing myoglobin to be deoxygenated and causing the muscle to remain dark (egbert and cornforth, 1986). ultimate ph can influence colour independently of meat myoglobin content (ledward, 1985), which may explain differences between the transported and non-transported muscles in the present study. the color of meat is influenced by several individual factors and their interactions. there was increased muscle lightness (l*) of the longissimus dorsi muscles from the electrical stimulated carcasses (table 2). this suggested that early postmortem conditions of these muscles favored protein denaturation (warriss and brown, 1987). high muscle temperatures combined with low muscle ph values during early postmortem are associated with increased protein denaturation. however, bond et al. (2004) found that electrical stimulation of sheep carcasses did not improve muscle lightness. transportation of sheep for 3 hrs had a significant (p<0.05) effect on myofibrillar fragmentation index of the longissimus dorsi muscles (table 2). the myofibrillar fragmentation index from non-transported muscle was significantly (p<0.05) higher than those from transported one by 8.9%. significantly lower myofibrillar fragmentation index and shorter sarcomere lengths for the transported-non-stimulated sheep are consistent with the tougher meat from that group. the high myofibrillar fragmentation index in stimulated-non-transported sheep may have been caused by myofibrils easily broken into shorter segments. myofibril fragmentation index has been used as an indicator of postmortem proteolysis in various types of meat (lametsch et al., 2007) as it accounts for differences in the rate of postmortem tenderization of meat (nagaraj et al., 2005). the latter authors concluded that structural changes occurring in meat after slaughter are generally believed to be caused by interactions of myofibrillar proteins in the muscle. low voltage electrical stimulation and transportation had a significant (p<0.05) effect on myofibrillar fragmentation index of the sheep muscle (table 2). the myofibrillar fragmentation index from transported muscle was significantly (p<0.05) lower than that from non-transported one (table 2). conclusions transportation of sheep for 3 hrs in an open truck at high ambient temperatures (36 oc) led to higher blood concentrations of cortisol, adrenaline, nor-adrenaline and dopamine. meat quality characteristics were also worsened by transportation during hot ambient temperatures. low voltage electrical stimulation can be used to reduce the deleterious effects of transportation on meat quality. references ali, b.h., a.a. al-qarawi and h.m. mousa. 2006. stress associated with road transportation in desert sheep and goats, and the effect of pretreatment with xylazine 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pollination) on tomato (lycopersicon esculentum mill) production in greenhouses. bumblebees showed no problem in visiting flowers at a temperature range of 17-42°c during the day and 2-14°c at night. bumblebee pollinated plants produced a yield per plant which was significantly higher than plants treated with pgb, vibration and the control, respectively. fruit set of tomato flowers over 10 clusters was 99.1, 96.7, 76.7, and 65.7% for bumblebee treatment, pgb application, vibration and the control, respectively. in the bumblebee pollinated flowers, the quality of fruits was superior. the fruits were hard, with more seeds, and had a high specific gravity and better appearance. the average fruit weight was 100.3, 80.5, 84.1, and 70.6 g for the bumblebee, pgb, vibration and the control, respectively. the pgb treatment produced bigger sized but puffy fruits (108.4 ml). while fruit size in the vibration treatment was the highest (126.8 ml), followed by the bumblebee and the control which were 99.3 and 98.5 ml, respectively. fruit specific gravity in the bumblebee treatment was significantly higher than other treatments, with no significant differences between the pgb and the vibration treatments. the least dense fruits were in the control treatment. regarding the firmness of fruits, the bumblebee treatment gave the hardest fruits, while the pgb and the vibration treatments were intermediate and the control was the least. average seed number per fruit was 177.0, 86.5, 61.8, and 89.8 for bumblebee, vibration, pgb and the control, respectively. keywords: bumblebees, tomato, pollination, jordan, plastichouse, greenhouse. o maximize fruit set in tomatoes and other crops, plant growth bioregulator (pgb) (pak and kim,1999), plant or truss vibration, honeybees (kremen, 2001) and bumblebees (paydas et al., 2000) are frequently used. nelson and richard (1989) found that electrical vibration is not practical and also tedious. recently, a worldwide trend is to use the bumblebee as a pollinator on many crops including tomatoes due to yield increase and enhancement of fruit quality (delaplane, 1995). proporato et al. (1993) used bumblebees for the pollination of tomatoes under polyethylene tunnels and found that plants gave better yield and quality fruits. in france, bumblebees colonies were used in tomato pollination and gave more effective pollination than mechanical vibration (caudal and trapateau, 1992). ikeda and tadauchi (1995) found that tomato fruits obtained by bumblebee pollination were more uniform and contained more seeds, flesh, t !"#$%&!'()*+,-!.$/01!234!5(63/78$9:,-!;$<(=>,-!"?!! !"#$%&'()*+,'-,&./0'123*4','.5"6%&'7)8&.9:' ' !!""#$?';''''''''''<)=>?' !"",'#$9%&'.)$'(?')$"&%*%')9.$+?',$+.-&.'/80"3164,'2"63%&' *6%&')+2)*%&'0"46%&'235'68')=+.7,' '0"?"4$6%&'''''''''*8"$89'/$$)43%&'<)$=>#%&',':"$+,*+'';'''($><'="#$5:'33%&77"'>'''''?%"+@'/a')>b84'-&'*8"8?'7%''2"63%&' *6%&'''%"8@c' '77"$33%&''''*6$<''''?%&.$d'0"$-%1'',$d,&.?'''''e$)9'fgh''ijkl'''''','':&%"$m5'jhfikl'':n)$%''>'''''''*6<':"+26$4'(><&'*d&2%&'0"46>%'="#$5o&'2"$9 ''''')3$"&29'<)$=>#%&'''2"6$3%&' *6$%&''p.qc&' 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'2"6$3%&'''''''''''''''''*8"8%&'"m>0&'2"9',')3"2#4''236%&'7164','@&6#8c&')%"d'/a')9n/%&',5"9'"36)9'e%"3r%&'h>y&''>'%,z4%&'1*<'\>9', '''''''?*$d&2%&'?.3r$%&'/$afgg>]''','`v>w''','vf>`','`t>`''0n4"$$3%'''2"6$3%&' *6$%&,'''236%&'7164,''*8"8%&,'0"?"46%&'68')=+.7' </%&2#%&'(>>' al-attal, kasrawi, and nazer 22 acids and vitamin c contents than that obtained by plant growth bioregulator application. tomato (lycopersicon esculentum mill) is planted in the jordan valley under plastichouses (i.e. greenhouses) during the months of october, november and december (anonymous, 1998). therefore, fruit set, fruit development and even maturity of several clusters occur during the cool climate in winter. efficient pollination and successful fertilization of greenhouse tomato is needed to ensure maximum fruit set and the proper development of high quality fruits, specially during cool conditions (dogterom et al., 1998; ravestijin and sande, 1991). although tomato flower is self fertile, the structure of the anther core, it’s mode of dehiscence and the position of the style make some form of disturbance necessary to ensure adequate pollination in cool winter or in high summer temperatures (raymond, 1985; rylski et al., 1994). banda and paxton (1991) found that fruit setting of tomatoes grown in greenhouses is frequently poor and fruit set is very dependent on the use of mechanical aids. the objective of this research was to compare three pollinating techniques, bumblebee, pgb and vibration, with respect to fruit set, yield, and fruit quality in greenhouse tomatoes. materials and methods all treatments were performed in two neighboring greenhouses in the abu-ubiedah area in the jordan valley. no control on light, temperature or relative humidity inside the greenhouses was performed. “argenta”, a common long shelf life cultivar of greenhouse tomatoes used for exporting purposes was transplanted on the 10th of november 1996. both greenhouses were identical and were 60 m long, 8 m wide, grown with 5 raised beds of tomatoes. the width of each bed was 0.5 m. two rows were planted in each bed and the distance between the beds was 1m. the space within rows in beds was 30 cm and between rows was 20 cm. beds were covered with black polyethylene plastic mulch and plants were irrigated by drip irrigation system. the first 20 m, the last 20 m of raised beds, and beds on both sides of the greenhouse were excluded from the experimental area to decrease variation among plots. a randomized complete block design with three replicates was used. each bed (which includes two rows) was divided into three plots and each plot was randomly assigned to each treatment. in greenhouse b, the pgb, the vibration and control treatments were conducted, while in greenhouse a, the treatment was only bumblebee. in both greenhouses, the number of plants in each plot was 10. at random, from the 10 plants in each plot, 4 plants were labeled for yield measurement (productivity plants), three plants were used for quality parameter evaluation (quality plants) and three for substitution. temperature and relative humidity were recorded each day by a thermo-hygrograph and minimax thermometer. a bumblebee hive, with an estimated 80 workers, was placed inside the greenhouse (a) on 10 december and removed on 1 april with the termination of flowering clusters. the hive was placed for 24 hrs in the experimental greenhouse, then removed and returned after 48 hrs. the pgb (para-chlorophenoxyacetic acid 7 gm/l. 4-cpa) was used in the pgb application treatment. the pgb was diluted by taking the proper amount from the stock solution in one liter of tap water according to the label instructions. three ml from the stock were applied when the temperature was lower than 20°c and 2 ml when the temperature was more than 20°c. the application was done by using a hand sprayer of 1 l volume. one spray was applied on each flower cluster. spraying was carried out in synchronization with flower anthesis. twenty-one sprays were applied between 10 december 1996 and 1 april 1997. in the vibration treatment, plants were hand vibrated each day in the morning between 10-11 a.m. for 3-5 seconds. the control plants were not treated. vibration was performed between the 10th of december and the 1st of april. fruit set percentage was calculated in each flower cluster in the productivity labeled plants in each plot until the end of fruit set on the 11th cluster. at maturity, fruits of the first nine flower clusters were harvested and average fruit weight and total yield for each cluster were recorded. at harvesting, size, weight, specific gravity, firmness of fruit, and number of seeds per fruit were measured. for fruit quality, fruit numbers 1, 3, and 5 from cluster number 1,3, and 5 on each of the three quality labeled plants were assigned. fruit size was determined by the water replacement method, then the specific gravity of the fruit was computed, the total of 81 fruits was measured. seed extract was made from fruit number 3 of cluster numbers 1, 3, and 5 for each quality labeled plants. the number of seeds inside each fruit was counted. a total of 27 fruits was used to measure this parameter in each treatment. a fruit pressure tester was used to measure flesh firmness in fruit number 1 of clusters 1,3, and 5 of quality plants. testing began by removing the epidermal layer of tomato fruit with a sharp knife on the two opposite sides, then flesh firmness was measured and the average of two readings was calculated. a total of 27 fruits was tested in each treatment. results and discussion yield: bumblebee pollinated tomato flowers produced significantly the highest average fruit weight and yield per influence of pollination technique on greenhouse tomato production 23 table 1 yield per plant, fruit weight, fruit size, seed number, firmness, and specific gravity in the bumblebee, plant growth bioregulator (pgb), vibration and control treatments of greenhouse tomatoes. treatment parameter bumblebees pgb vibration control average yield per plant (g) 5132.20a* 4116.80b 3591.00c 2818.50d average fruit weight (g) 100.30a 80.50b 84.10b 70.60c average fruit size (cm3) 99.30b 108.40ab 126.80a 98.50b average seed number per fruit 177.00a 61.80c 86.10b 89.80b firmness (kg/cm2) 3015.80a 2690.00ab 2846.10ab 2464.40b average fruit specific gravity (g/ml) 1.03a 0.96b 0.983b 0.95c * numbers having same letters in the same row are not significantly different at p = 0.05 according to duncan multiple range test. plant than the other treatments. the lowest average fruit weight and the lowest yield per plant were produced from the control tomato plants (table 1) (figure 1). paxton and banda (1991) found that the bumblebee pollination is the best means of pollination regarding the tomato yield per plant. ikeda and tadauchi (1995) reported that the use of bumblebees gave a higher yield than the application of pgb. however, fiume and parisi (1994) found that pgb application is slightly better than bumblebee pollination in tomato. this yield increase is due to higher number of pollen grains that fertilize the ovules and consequently the higher number of seeds per fruit that contributed to a higher fruit weight. the temperature throughout the flowering, growth and fruit development stages ranged from 2-14oc at night to 17-42oc during the day. this high fluctuation in temperature, the low night temperature at the stage of flower formation, in addition to stigmatic elongation on hot days will lead to poor fruit set in both vibration and control treatments. this could be related to poor pollination or poor fertilization. in the bumblebee treatment, buzz-pollination will overcome stigmatic elongation. bumblebees visit a high number of flowers each day. this increases the possibility of transferring viable pollen. also, a high relative humidity in winter days makes pollen clump. as a result no transfer of pollen grain to the stigma occurs in both the control and vibration treatments. in several clusters in the pgb treatment many fruits were seedless indicating that pgb application induces fruit set. this takes place regardless of the climatic conditions. consequently these fruits will have a lower density. one or more of these factors may play a role in the difference between the effect of the treatments over each cluster. average yield and fruit set (cluster wise analysis): in general, the average cluster yield and fruit weight were significantly higher in the bumblebee treatment than the other treatments. however, in some clusters there were no significant differences via the treatments or the significance was between the treatments and the control only. figure 1. average number of greenhouse tomato flowers per plant during the flowering period. al-attal, kasrawi, and nazer 24 table 2 average fruit weight and yield per tomato plant in the bumblebee, plant growth bioregulator (pgb), vibration and control treatments cluster wise analysis. bumblebee pgb vibration control cluster average fruit average yield average fruit average yield average fruit average yield average fruit average yield 1 93.0a* 619.6a 88.2a 428.7b 91.4a 278.7bc 70.8a 192.0c 2 111.1a 630.3a 78.9ab 495.0ab 89.8ab 351.2bc 75.6c 244.1c 3 97.1a 652.3a 84.7a 463.7b 88.2a 374.2bc 71.1a 312.3c 4 93.3a 578.8a 80.0ab 483.3ab 79.8ab 516.0ab 70.3c 399.0c 5 110.0a 607.8a 82.5b 534.5ab 85.6b 590.8ab 78.3b 445.0c 6 108.2a 689.3a 76.3b 489.5ab 90.8bc 495.0b 66.2c 374.3b 7 100.6a 633.0a 73.3b 434.3b 85.6c 345.0b 64.4d 271.5b 8 94.5a 650.0a 73.6b 418.0b 70.5b 316.9b 66.8b 287.0b 9 95.1a 650.0a 86.6a 369.8b 75.6b 323.0b 71.5b 283.3b average fruit (g) 100.3a 80.5b 84.1b 70.6c average plant yield (g) 5132.2a 4116.8b 3591.0c 2818.5d * numbers having same letters in rows for the same parameter are not significantly different at p=0.05 according to duncan multiple range test. according to the climatic conditions throughout the flowering period, as in cluster four, the vibration treatment was significantly higher than the pgb (table 2) (figure 2). the overall average fruit set by the bumblebee treatment was (99.1 %) with no significant difference with that of pgb treatment (96.7 %). both bumblebee and pgb treatments gave significantly higher fruit set percentage than the vibration (76.5 %) and the control (65.3 %) (table 3). in the first, second, seventh, and eighth clusters, the average fruit set in all clusters was similar in the bumblebee and pgb treatments. both were significantly higher than vibration and control treatment. in the third cluster, there was no significant difference in fruit set among treatments, but all were higher than the control. in the fourth and ninth clusters, fruit set in all treatments was not significantly different, but the bumblebee and the pgb application gave significantly higher fruit set than the control. in the fifth and sixth clusters, there were no differences in fruit set percentage between the treatments and the control. in the tenth cluster, the bumblebee treatment and the bioregulator application were not significantly different but they gave higher fruit set than the vibration. also, the vibration was higher than the control. in the eleventh cluster, bumblebee treatment ranked first in fruit set percentage, than the pgb application and vibration while the control was the least with no significant difference between all treatments. the low fruit set in the vibration and the control treatments in the first and the second cluster may be due to poor pollination and to poor fertilization in cool nights (2-14oc) and to high day temperature (31-42oc). during the fruit set period of cluster three, the average night temperature was 12oc and day temperatures was 31oc. this gave good pollination in all treatments and the control resulting in good fruit set. in the seventh and eighth clusters the day temperature had risen to 38oc and induced stigmatic elongation. in the ninth, tenth and eleventh clusters fruit set in the vibration treatment, decreased significantly due to a high day temperature (38oc), and to the fact that in this period of growth, the plants were near the plastic sheets which cause stigmatic elongation. figure 2. the date of anthesis of tomato clusters 1-11 in 0.5 dunum greenhouse in 1996. influence of pollination technique on greenhouse tomato production 25 table 3 average fruit set percentage in greenhouses tomato pollinated bumblebees, plant growth bioregulator (pgb), vibration and control treatment. treatment cluster bumblebee (%) plant growth bio regulator (%) vibration (%) control (%) 1 100.0a* 97.8a 73.9b 63.1b 2 100.0a 98.1a 73.3b 64.6b 3 98.7a 94.0a 89.6a 70.9b 4 100.0a 98.0a 91.2ab 75.3b 5 100.0a 99.3a 89.8a 82.6a 6 100.0a 93.0a 74.1a 78.0a 7 99.5a 94.3a 54.8b 51.0b 8 94.4a 94.9a 63.9b 52.0b 9 98.5a 99.3a 75.6ab 54.1b 10 99.7a 97.8a 78.7b 61.5c 11 95.1a 86.6ab 75.6bc 71.5c average 99.1a 96.7a 76.5b 65.3c * numbers having same letters are not significantly different at p=0.05 according to duncan multiple range test. in the bumblebee treatment, it seems that the bumblebee individual usually carries viable pollen grains which gives better yields than the pgb under temperature between (2-14oc) at night and (17-42oc) during the day. quality parameters: there was a significant difference in the average fruit weight between the different treatments (table 1). regarding fruit size, there was no significant difference between the fruit size in the bumblebee, pgb and the control treatment. the largest fruit size was in the vibration treatment, 126.8 ml, followed by pgb, 108.4 ml. the bumblebee and control treatment gave the least fruit size, 99.3 ml, and 98.5 ml, respectively (table 1). fruit density in the bumblebee treatment was significantly higher than other treatments. there was no significant difference between the pgb and vibration treatments. the least dense fruits were in the control. pgb does not increase cell division in tomato, but the increase in size is related to cell elongation, that resulted in many cavities and lighter fruits. in the vibration and control treatments density was correlated with the number of seeds (table 1). regarding the firmness of the fruits, the bumblebee treatment gave the hardest fruits, while the pgb treatment and vibration gave intermediate results. the control fruits were the least firm (table 1). seed number per fruit was significantly higher in the bumblebee treatment (177.0). the lowest seed number was in the pgb treatment (61.8). there was no significant difference in the number of seeds between the control and the vibration treatments 89.8 and 86.1, respectively (table 1). the large tomato fruit size from pgb treatment was related to the effect of the bioregulator on cell elongation but with very low seed number inside the fruit. the vibration treatment produced low fruit set and lower number of fruits per cluster and plant, which may be compensated for by the larger size. the lower number of seeds per fruit was for the vibration and control treatments. the bumblebee individual has a special buzzing pollination tactic. this ensures more contact between the pollen grains on the stigma. in the control, apparently the same number of pollen grains will fertilize the ovule due to deliberate vibration to increase fruit set and to workers movement and wind circulation. this of course was not as efficient as the buzzing effect of bumblebees. paxton and banda (1991) have similar results, i.e, that bumblebees resulted in fruits with higher number of seeds, and higher weight than the vibration or the control. vecchio et al. (1996) found that the application of pgb will speed up the ripening of fruits by about one week. shape of the fruits: flowers pollinated by bumblebees gave fruits that looked better in shape and were plump without puffiness, had more seeds, and a higher specific gravity, were harder, and were uniform color. these characteristics make fruits more preferable for local and export markets. plants that were treated with pgb produced puffy, soft fruits, with relatively lower specific gravity than other treatments, and the color some times is not uniform. in the vibration treatment, the fruits are plump but usually the size was larger than the others with a lower number of seeds as compared to the fruits from the bumblebee treatment. fruits of the control were smaller than those in the other treatments. conclusions the results indicated that bumblebees could be used successfully in greenhouses for tomato plant al-attal, kasrawi, and nazer 26 pollination. bumblebee-pollinated tomatoes gave higher yield, higher number of seeds, better weight-size correlation, higher specific gravity and higher fruit firmness than other pollinating agents; plant growth bioregulator and plant vibration. acknowledgement the authors express their gratitude to the deanship of scientific research at jordan university for the partial financial support of this research. sincere thanks are extended to mr. khalil abu-ghannam for his offer to conduct this research at his farm and for his valuable suggestions and help through out the study. the comments and the revision of the article by dr. valkmar hasse is greatly acknowledged. references anonymous. 1998. department of statistics. statistical year book, (1990-1997), the hashemite kingdom of jordan. caudal, t.y. and trapateau. 1992. pollination of tomatoes, the use of bumblebee under glass. info-paris 80:43-46. delaplane, k.s. 1995. why bumblebees. american bee journal 135:459-460. dogterom, m.h. j.r., matteoni, and r.c. plowright. 1998. pollination of plastichouse tomatoes by the north american bombus vosnesenskii (hymenoptera: apidae). journal of economic entomology 91:71-75. fiume, f. and b. parisi. 1994. pgb and pollinating bombidae insects on tomato fructification (protected cultivations italy). colture protette 23:87-93. ikeda, f. and y. tadauchi. 1995. use of bumblebees as pollinators on fruits and vegetables. honeybee science 16:49-56. kremen, c. 2001. organic farming research foundation project report # 99-07 [on line]. http://www.ofrf.org/research/researchreports.html. nelson, p. and m. richard. 1989. pollination of plastichouse muskmelon by bumblebees (hymenoptera: apidae). journal of economic entomology 82:1061-1066. pak, h. and d. kim. 1999. ishs acta horticulturae [on line]. (http://www.ishs.org/pub/483.html). paydas, s., s. eti, o. kaftanglu, e. yasa, and k. derin. 2000. ishs acta horticulturae [on line]. (http://www.ishs.org/pub/513.html). paxton, r.j. and h.j. banda. 1991. pollination of plastichouse tomatoes by bees. acta horticulturae 288:194-198. porporato, m., m. pinna, a. manino, and f. marletto. 1995. pollination of sweetpepper under protected cultivation by bombus terrestris l. and apis mellifera l. apicoltore moderno 86:99112. ravestijin, w. and j. sande. 1991. use of bumblebees for the pollination of glasshouse tomatoes. acta horticulturae 288:342-345. raymond, g. 1985. solanaceae. in: vegtable seed production. 1st edition, longham house, burnt mill. harlow. rylski, l. b. aloni, l. karni, z. zaidman, k. cockshull, y. tuzel, and a. gul. 1994. flowering, fruit set, fruit development and fruit quality under different environmental conditions in tomato and pepper crops. acta horticulture. 366:45-55. _______________________________________________________ received july 2002. accepted jan 2003. microsoft word jamsy2003v08n01content-arabic.doc ___________________ *corresponding author. 11 agricultural and marine sciences, 8(1):11-14 (2003) ©2003 sultan qaboos university life cycle and survival of hyalomma dromedarii (acari:ixodidae) under laboratory conditions a.m. alahmed* and s.m. kheir college of agriculture, king saud university, p. 0. box 2460, riyadh 11451, saudi arabia ! ! abstract: the life cycle of hyalomma dromedarii koch (acari:ixodidae) on rabbits at 25 and 32ºc was compared at 85% r.h. at these temperatures, it behaved as a two-host tick and completed its life cycle in 108-146 and 80-115 days, respectively. the preoviposition, incubation and moulting periods varied significantly and were influenced by temperature. the survival periods of different developmental stages of hyalomma dromedarii at 25ºc, 32, 38, 43, and 48ºc at 85% r.h. were investigated. the eggs, engorged nymphs and engorged females died at 38ºc, and the unfed larvae died at 43ºc. the longevity of the unfed adults decreased from 90-120 days at 25ºc to7-15 days at 43ºc. they died at 48ºc. these results suggest that the survival periods of eggs, engorged nymphs and engorged females were significantly decreased with an increase in temperature. they were more susceptible to high temperature than unfed adults. the role of unfed adult in the continuity of the life cycle of the tick throughout the year is discussed. keywords: hyalomma dromedarii, life cycle, survival, laboratory conditions. he camel tick, hyalomma dromedarii koch (acari: ixodidae) is the most important tick infesting camels in saudi arabia (badawi, 1994). the ecology and the biology of the camel tick has not been fully investigated. the availability of information on the effect of temperature and humidity on the rate of development and survival of the camel tick is essential for a rational control program. the current study was carried out to assess the life cycle of h. dromedarii and its survival at different temperatures under laboratory conditions. materials and methods fully engorged females of h. dromedarii were obtained from a camel in muzahmyia area (50 km south of riyadh city) and identified as h. dromedarii according to hoogstraal (1956). they were put in an incubator at 28°c and 85% r.h. to oviposit. the emerged larvae, nymphs and adults were fed on white new zealand tick-native rabbits. five white new zealand tick-native rabbits were infested with approximately 200 larvae of h. dromedarii. t !"#$%&'!(')*!+#,-!+./(01.'23/.(!#345,6!7)89:$&'!;<!+.')=5&!#>5$=?!/! !"#$%&'($)*+,-$.-/0$ ! !!"#$$1$$$23*45-$6-!7$83"+$89(6$:;-96$<=*>$)=?5 !"#$%%"$ &'$%(&"'))$89-!+$:*96$)+0$,--9,-$./0$012$($.302$. $=4569($$$$:"7=8-$:91$:;$$$$$$$$$$$$$$$$$$<=$3>>3"+$89(6$</*?@$3>-@($ab3c5-$<b3+d$23*45-$6-!7$e@$:;-9)5-$fg$<=7d$)=?5hi9jhkl$($9ij hh1$$$$$<5-5m5-$.=/0$3=g5n$$:$$$$$$$$$$$$$$$o"75-$pq($a77$3g$8!m=$256$./0$-!"7?$-!"dr>$!ds>$89-!t5-$:*96$e@$3un@$:;-9)5-$fg$vq($)?5( ($$$$$$$$w&=8-x-$8!m==($:-3=ut5-$8!m==$$:$$$$o"75-$$pq($y=>$($$$$$:nz[mg$!"[5-$:7!"5-$($$$$:nz[m*5-$:n95t5-$($$$!"[5-($\z[m*5-$]5375-$95^5-$ $$$$$$$$$89-!=+$_3=*96$<==$\z[m=g012$$.($302$$.($392$$.($k32$$.($k92$$$$:"7=8-$:=4569($.91$;$$$$9-56,-$`za$!=*0$25=6$:=!=c*5$: $$$$$$$$<>3g$\z[m*5-$]5375-$95^5-($:nz[m*5-$_3n95t5-($o"75-$e@$:=;-9)5-$<=m7d@)+0$89-!+$:*96$392$!"[5-$_37!"5-$<>3g$3*+"4$. $m=g[$$$$$89-!+$:*96$)+0$:nzk32.:$$$$$$83"+$89(6$<ubc--$)7($$$$$$$\z[mg$!"[5-$]5375-$95^5-$$$fgdijh0i$89-!+$:*96$<t>$$.5n$012 .$$$$$.=5e$$fjh1$$$$$$)+=0$.5=n$$$$$89-!=+$:=*96k32.$($$=>3g$)=7<$$89-!+$:*96$)+=0$k92.$:$!"[5-$]5375-$95^5-$e@$gb3m+5-$`za$fg$vumn $$$$-$5=a$\z[m=g$$$$$$$$$$h-9(6$,=c/n$i=--($89-!=t/5$:=g(3?g$!j=?,$h3g3a$$$$$$$$$$$e5k>$3g)+0$l"m5-$am=$2&#$6-!?5-$83"+$89(6$:n9-!*m;-$<=$ :ubc+g$:456!5-($:"530$89-!t5-$:*96:$ alahmed and kheir 12 the engorged nymphs dropped were weighed and the mean engorged weight was determined. the larvalnymphal feeding period was calculated as from attachment of unfed larvae to detachment of engorged nymphs. the engorged nymphs dropped were collected and divided into two groups, each consisted of 50 nymphs, then incubated at 25 and 32°c, respectively at 85% rh to moult and the moulting period was determined. in a second group consisting of 5 white tick-native rabbits, each rabbit was infested with 8 adults h. dromedarii (sex ratio 1:1). the replete females were collected after their detachment, weighed separately and the time taken to engorge was recorded (from attachment to detachment) and then divided into two groups and incubated at 25°c and 32°c, respectively to oviposit. the incubated ticks were observed daily from detachment until oviposition to determine the preoviposition period. eggs were observed daily from initiation of oviposition until the eclosion of the first larva, to establish the incubation period. the weight and number of eggs laid per female as well as hatchability were recorded. the mean index of conversion efficiency (cei) was calculated as follows: cei = [weight of eggs (mg) / weight of replete female (mg)] x 100 about 500 mg of viable eggs, 100 unfed larvae, 50 engorged nymphs, 30 unfed adults (sex ratio 1: 1) and 10 engorged females of h. dromedarii were incubated at 25, 32, 38, 43, and 48°c at 85% r.h. all these developmental stages were observed daily for their survival at these conditions. eggs, engorged nymphs and engorged adults were considered as dead when they failed to hatch, moult or lay eggs, respectively. unfed ticks were considered as dead when they did not react to mechanical or physical stimuli. for statistical analysis, the student's t-test and analysis of variance (steel and torrie, 1981) were used. results life cycle of h. dromedarii: the results showed that at 25°c there was a two-host type of development during a period of 108-146 days. almost half of this period was spent for egg development. the larvae remained attached to the host and dropped as engorged nymphs. the preoviposition and incubation periods at 25°c were 5-8 and 56-68 days, respectively (table 1). the larval-nymphal feeding period was 11-16 days, and the nymphs required 14-24 days to develop into adults. the unfed females took 10-14 days to engorge on rabbits after which they dropped off to lay eggs. at 32ºc, h. dromedarri behaved as a two-host tick and completed its life cycle in 80-115 days (table 1). the larvae remained attached to the host for 11-16 days table 1 life cycle of hyalomma dromedarii on rabbits under laboratory conditions. time (days) range (x ± sd) parameter 25ºc 32ºc preoviposition period 5-8 (6.6 ± 1.1)a 3-6 (4.3 ± 0.8)b incubation period 56-68 (62.0 ± 5.0)c 34-50 (42.0 ± 5.0)d hardening 6-8 (7.0 ± 0.8)a 6-7 (6.5 ± 0.4)a nymphal feeding period 11-16 (14.0 ± 1.8)e 11-16 (13.0 ± 1.7)e moulting of nymph 14-24 (19.0 ± 4.0)f 10-15 (12.0 ± 2.0)e female engorge 10-14 12.0 ± 1.7)e 10-14 (12.0 ± 1.8)e total 108-146 127.0 ± 13)g 80-115 (96.0 ± 11)h x – mean value; sd – standard deviation means in a row followed by different letters are significantly different (p<0.05 – p<0.001). and dropped off as engorged nymphs. the nymphs required 10-15 days to moult to adults and remained for 6-7 days in the non-feeding stage. the unfed female took 10-14 days to engorge on rabbits and then dropped off to lay eggs. the preoviposition and incubation periods were 3-6 and 34-50 days, respectively. the results showed that the preoviposition, incubation and moulting periods of the tick at 25ºc were significantly longer than at 32ºc (p<0.05), while the feeding periods of the adults, nymphs and larvae on the host were not affected by temperature (p>0.05). at 25 and 32°c, the incubation periods were significantly longer than the preoviposition periods (p<0.001), larval-nymphal feeding periods (p<0.001) and adult feeding periods (p<0.001). at 25°c, the moulting period of the nymphs to adult was significantly longer than larval-nymphal feeding and adult feeding periods (p<0.05); while at 32ºc, the temperature had no effect on the length of the moulting period, larval-nymphal feeding period and adult feeding period (p>0.05). table 2 shows that the mean engorged weight of replete females at 25ºc was 981 ± 218 mg and the mean weight of egg mass laid was 588 ± 112 mg, which hatched into 8076 ± 989 eggs. the mean index of conversion table 2 feeding of hyalomma dromedarii on rabbits at 25ºc. engorged wt (x ± sd mg) 981.0 ± 218 weight of eggs (x ± sd mg) 588.0 ± 112 no. of eggs (x ± sd) 8076.0 ± 989 hatchability (%) 99.0 nymphal engorge wt (x ± sd mg) 395.0 ± 84 i.c.e. 0.6 x – mean value; sd – standard deviation i.c.e. – index of conversion efficiency. life cycle and survival of hyalomma dromedarii 13 table 3 survival of hyalomma dromedarii under laboratory conditions in days (x ± sd) at different temperatures. temperature stage 25ºc 32ºc 38ºc 43ºc 48ºc eggs 40 -59 22-31 died 50 ± 8a*1 27 ± 3b*1 unfed larvae 38-50 44 ± 4a 26-38 33 ± 6c 5-6 5.5 ± 0.4d died engorged nymphs 15-23 19 ± 3e*2 10-15 12.5 ± 2f*2 died unfed adults 90-120 105 ± 13g 40-65 52 ± 10h 20-29 25 ± 3i 7-15 11 ± 3j died engorged adults 22-30 26 ± 3k*3 14-23 18 ± 3m*3 died x – mean value; sd – standard deviation; *1 – then hatched; *2 – then moulted; *3 – then laid eggs. means in a row followed by different letters are significantly different (p<0.05 – p<0.001). efficiency was 0.6. there was a strong positive correlation between the engorged weight and weight of eggs laid (r = 0.7164) and between engorged weight and number of eggs laid (r =0.6872). table 3 shows that all life stages of h. dromedarii survived normally at 25ºc and 32ºc, but the survival period of eggs at 25 ºc (50 ± 8 days) was significantly longer than at 32ºc (27 ± 3 days) (p<0.001). they died at 38ºc. there is a progressive significant decrease in survival period of unfed larvae with an increase in temperature. their survival period decreased from 44 ± 4 days at 25ºc to 5.5 ± 0. 5 days at 38ºc (p<0.001). they died at 43ºc. the survival period of engorged nymphs at 32ºc was significantly shorter than that at 25ºc (p<0.05). the longevity of unfed adults decreased significantly from 105 ± 13 days at 25ºc to 11 ± 3 days at 43ºc (p<0.001). they died at 48ºc. the survival period of engorged females at 32ºc was significantly shorter than that at 25ºc (p<0.05). at both 25 and 32ºc, the survival periods of unfed adults were significantly longer than that of eggs (p<0.001), unfed larvae (p<0.001), engorged nymphs (p<0.001) and engorged adults (p<0.001). discussion this study has shown that temperature is an important factor affecting the duration of preoviposition, incubation and moulting periods during the development of h. dromedarii. in general, high temperature increases the metabolic rate of poikilothermic organisms (chapman, 1976), which in turn increases the rate of physiological processes involved in egg production resulting in a decrease in preoviposition and incubation period length. the results obtained in this study are similar to those reported by hagras and khalil (1988) and ouhelli (1994) using h. dromedarii; despins (1992) using dermacentor nitens; and sunder et al. (1999) using hyalomma anatolicum. the duration of developmental periods of different stages in the life cycle of h. dromedarii observed in this study are longer than those reported by delpy and gouchey (1937) and honzakova (1971) for hyalomma dromedarii. these variations are probably due to differences in rearing conditions (host and temperature). different types of developments have been reported for h. dromedarii. in our study, h. dromedarii fed on rabbits behaved as a two-host tick. das and subramanin (1972) found that h. dromedarii fed on sheep or cattle have a three-host life cycle, but 60% of the population became a two-host tick when fed on rabbits. ouhelli (1994) found that h. dromedarii was usually a three-host tick, but became a two-host tick when density on the host was high. similarly, latha et al. (1998) found that when young larvae of h. marginatum (three months old) were fed on rabbits, they behaved as a three host tick, while larvae older than four to six months behaved as a two host tick. from these studies it seems that the type of the host, rearing conditions, density and age of the larvae may influence the life cycle of the tick. in arid zones, where h. dromedarii is widespread, low relative humidity has an inhibiting effect on egg development (ouhelli, 1994). the peripheral layer of eggs shell was quite desiccated. this may help in egg development during short-lived periods of drought and stress under field condition. in this study, almost half of the life cycle was spent for egg development. this may be a survival mechanism that permits h.dromedarii to survive in arid zones. our study has revealed that eggs, engorged nymphs, and engorged females are more susceptible to high temperature than the unfed adult. similar results were reported by delpy and gouchey (1937) who found that when h. dromedarii behaved as a three-host tick, unfed larvae and unfed nymphs resist dry atmosphere more than engorged stages. in nature, the engorged female boophilus annulatus (say) (hunter and hooker, 1907) and ixodes ricinus (l) (milne, 1950) burrow a few centimeters below the ground surface to find favorable microhabitat for egg deposition and survival during dry season. in saudi arabia, probably during the dry season, the adult h. dromedarii live in burrows or burrow a few centimeters to find a favorable microhabitat that protects the eggs and emerging larvae against high temperature and low humidity. conclusions the type and duration of h. dromedarii development were largely influenced by temperature and the host. the study has shown that unfed adult ticks were more resistant to high temperature than eggs, unfed larvae, alahmed and kheir 14 engorged nymphs and engorged females. during the dry hot season the adult tick burrows a few centimeters below the ground surface to find a favorable microhabitat for its survival. control measures using acaricides should be directed towards the adult stage. the spray of infested hosts at the onset of dry season is highly recommended. further studies on the seasonal dynamics and host-vector relationship of the tick are required. references badawi, a.i. 1994. arthropods of medical and veterinary importance in saudi arabia. king saud university press, riyadh. pp 266. chapman, r.f. 1976. the insect: structure and function. elsevier, north holland, new york. das, h.l. and g. subramanian. 1972. biology of hyalomma dromedarii koch, 1844 (acari:ixodidae). indian journal of animal science 42:285-289. delpy, l.p. and s.h. gouchey. 1937. biologie de hyalomma dromedarii (koch, 1844). annals of parasitology and human comp. 15:487-499. despins, j.l. 1992. effects of temperature and humidity on ovipositional biology and egg development of tropical horse tick dermacentor (anocentor) nitens. journal of medical entomology 29(2):332-337. hagras, a.e. and g.m. khalil. 1988. effect of temperature on hyalomma (hyalomma) dromedarii koch (acari:ixodidae). journal of medical entomology 25(5):354-359. honzakova, e. 1971. development of some tick species under standard laboratory conditions. folia parasitolgica (prague) 18:357-363. hoogstraal, h. 1956. african ixodidae. 1.ticks of the sudan. u.s. naval medical research unit no 3., cairo, egypt. hunter, w.d. and w.a. hooker. 1907. information concerning the north american fever tick with notes on other species. usda bureau of entomology bulletin 72. latha, b.r , t.j. harikrishnan, and d.j. chella. 1998. variation in the life cycle pattern of hyalomma marginatum isaac reared on rabbits. indian veterinary journal 75:11. milne, a. 1950. the ecology of the sheep tick ixodes ricinus l. microhabitat economy of the adult tick. parasitology 40:14-34. ouhelli, h. 1994. comparative development of hyalomma marginatum (koch, 1844), h. detritum (schulze, 1919), h. lusitanicum (koch, 1844) and h. dromedarii (koch, 1844) under laboratory conditions. acta parasitologica 39(3):153-157. steel, r.g. and j.h. torrie. 1981. principles and procedures of statistics. mcgraw hill book company, new york . sunder, n., s. balasundaram, and r. anandan. 1999. a note on the two host life cycle pattern of hyalomma anatolicum anatolicum fed on calves. cherion 28(1-2):45-47. received july 2001. accepted november 2002. sultan qaboos university journal for scientific research agricultural and marine sciences, 10(1):33-40 (2005) ©2005 sultan qaboos university 33 identification, geographical distribution and hosts of subterranean termites in the united arab emirates arid ecosystem w. kaakeh department of arid land agriculture, college of food systems, p. o. box 17555, united arab emirates university, al-ain, united arab emirates ولید كعك ،hodotermitidae رمیتیديjالخالصة: تم تعريف ستة أنواع من النمل األبیض (األرضة) تابعة إلى خمسة أجناس وثالث فصائل (ھودو راينوترمیتیدي rhinotermitidae، وترمیتیدي termitidae) في اإلمارات العربیة المتحدة. وأنواع األرضة التي تم تسجیلھا ھي ،hodotermitidae رمیتیديjالخالصة: تم تعريف ستة أنواع من النمل األبیض (األرضة) تابعة إلى خمسة أجناس وثالث فصائل (ھودو راينوترمیتیدي rhinotermitidae، وترمیتیدي termitidae) في اإلمارات العربیة المتحدة. وأنواع األرضة التي تم تسجیلھا ھي ،hodotermitidae رمیتیديjالخالصة: تم تعريف ستة أنواع من النمل األبیض (األرضة) تابعة إلى خمسة أجناس وثالث فصائل (ھودو ،(anacanthotermes ubachi (navas و (anacanthotermes ochraceus (burmeister الالشوكیة األرضة أو الحاصدة األرضة راينوترمیتیدي rhinotermitidae، وترمیتیدي termitidae) في اإلمارات العربیة المتحدة. وأنواع األرضة التي تم تسجیلھا ھي ،(anacanthotermes ubachi (navas و (anacanthotermes ochraceus (burmeister الالشوكیة األرضة أو الحاصدة األرضة راينوترمیتیدي rhinotermitidae، وترمیتیدي termitidae) في اإلمارات العربیة المتحدة. وأنواع األرضة التي تم تسجیلھا ھي microcerotermes diversus الصغیرة الشمعیة واألرضة ،(psammotermes hypostoma (desneux الثغرية الرمل وأرضة ،(anacanthotermes ubachi (navas و (anacanthotermes ochraceus (burmeister الالشوكیة األرضة أو الحاصدة األرضة microcerotermes diversus الصغیرة الشمعیة واألرضة ،(psammotermes hypostoma (desneux الثغرية الرمل وأرضة ،(anacanthotermes ubachi (navas و (anacanthotermes ochraceus (burmeister الالشوكیة األرضة أو الحاصدة األرضة ،(heterotermes aethiopicus (sjostedt واألرضة ، (microtermes najdensis (harris الدقیقة النجدية واألرضة ،((silvestri وباستثناء النوع h. aethiopicus، فإنه تم تسجیل األنواع الخمسة األخرى للمرة األولى في اإلمارات العربیة المتحدة. وتعیش كل األنواع تحت األرض وتصل إلى مصادر الغذاء الخشبیة من خالل أنظمة األنفاق الطینیة. وقد وجدت األرضة في مناطق مختلفة من وباستثناء النوع h. aethiopicus، فإنه تم تسجیل األنواع الخمسة األخرى للمرة األولى في اإلمارات العربیة المتحدة. وتعیش كل األنواع تحت األرض وتصل إلى مصادر الغذاء الخشبیة من خالل أنظمة األنفاق الطینیة. وقد وجدت األرضة في مناطق مختلفة من وباستثناء النوع h. aethiopicus، فإنه تم تسجیل األنواع الخمسة األخرى للمرة األولى في اإلمارات العربیة المتحدة. وتعیش كل الدولة والتي تتمیز باختالف ظروفھا المناخیة وغطاءھا النباتي ونوع تربتھا. وتفضل األرضة التغذية على العوائل الحیة أو المیتة أو األنواع تحت األرض وتصل إلى مصادر الغذاء الخشبیة من خالل أنظمة األنفاق الطینیة. وقد وجدت األرضة في مناطق مختلفة من الدولة والتي تتمیز باختالف ظروفھا المناخیة وغطاءھا النباتي ونوع تربتھا. وتفضل األرضة التغذية على العوائل الحیة أو المیتة أو األنواع تحت األرض وتصل إلى مصادر الغذاء الخشبیة من خالل أنظمة األنفاق الطینیة. وقد وجدت األرضة في مناطق مختلفة من a. ochraceus المتعفنة، باإلضافة إلى المواد غیر السیلیلوزية. ومن أكثر أنواع األرضة توزيعًا في اإلمارات العربیة المتحدة ھي الدولة والتي تتمیز باختالف ظروفھا المناخیة وغطاءھا النباتي ونوع تربتھا. وتفضل األرضة التغذية على العوائل الحیة أو المیتة أو a. ochraceus المتعفنة، باإلضافة إلى المواد غیر السیلیلوزية. ومن أكثر أنواع األرضة توزيعًا في اإلمارات العربیة المتحدة ھي الدولة والتي تتمیز باختالف ظروفھا المناخیة وغطاءھا النباتي ونوع تربتھا. وتفضل األرضة التغذية على العوائل الحیة أو المیتة أو وتتبعھا كل من p. hypostoma وm. diversus. وقد اختلف توزيع األنواع الستة ضمن كل إمارة، ولكن وجدت كل األنواع في أكبر a. ochraceus المتعفنة، باإلضافة إلى المواد غیر السیلیلوزية. ومن أكثر أنواع األرضة توزيعًا في اإلمارات العربیة المتحدة ھي وتتبعھا كل من p. hypostoma وm. diversus. وقد اختلف توزيع األنواع الستة ضمن كل إمارة، ولكن وجدت كل األنواع في أكبر a. ochraceus المتعفنة، باإلضافة إلى المواد غیر السیلیلوزية. ومن أكثر أنواع األرضة توزيعًا في اإلمارات العربیة المتحدة ھي إمارتین وھما أبوظبي ودبي. وتتبعھا كل من p. hypostoma وm. diversus. وقد اختلف توزيع األنواع الستة ضمن كل إمارة، ولكن وجدت كل األنواع في أكبر إمارتین وھما أبوظبي ودبي. وتتبعھا كل من p. hypostoma وm. diversus. وقد اختلف توزيع األنواع الستة ضمن كل إمارة، ولكن وجدت كل األنواع في أكبر abstract: six termite species, belonging to five genera and three families (hodotermitidae, rhinotermitidae and termitidae) were identified in the united arab emirates (uae). termite species recorded were the harvester termites anacanthotermes ochraceus (burmeister) and anacanthotermes ubachi (navas), the sand termite psammotermes hypostoma (desneux) and the small waxy termites microcerotermes diversus (silvestri), heterotermes aethiopicus (sjostedt), and microtermes najdensis(sjostedt), and microtermes najdensis(sjostedt), and (harris). except for a previous record of h. aethiopicus, the other five species were recorded for the first time in the uae. all species were subterranean in habitat and reach wood sources through earthen gallery systems. termites were available in areas with varied conditions of climate, vegetation and soil types. termites showed host preference for dead, living, or decaying plant materials and non-cellulose materials. the dominant termite species recorded was a. ochraceus, followed by p. hypostoma and m. diversus. the distributions of the six termite species varied in each of the seven emirates. all species were present in the two largest emirates of abu dhabi and dubai. introduction termites have become increasingly important pests of crops and buildings in the united arab emirates (uae), where desert and marginal lands are irrigated for agriculture. uae also imports many kinds of woods and wood products to meet the needs of industry, new buildings, construction and furniture. two termite foraging strategies are adopted in the uae ecosystem: species are either nocturnal or they construct protective soil tunnels within which they are shielded from heat and desiccating effects of the sun. termites feed on living, dead or decaying plant material. some species are capable of reducing wooden structures to dust and may cause serious damage to buildings. several records pertaining to termites in the arabian gulf countries, especially in saudi arabia, have been made (nasr et al., 1978; badawi et al., 1982, 1986; chhotani and bose, 1982 and 1991). the termite fauna of the arabian peninsula comprise 22 species (badawi et al., 1986; chhotani and bose, keywords: anacanthotermes ochraceus, psammotermes hypostoma, arabian region, termite distribution, isoptera, rhinotermitidae, hodotermitidae. kaakeh 34 1991). no study of the termite fauna in the uae has previously been made; the only record for uae is a colony of heterotermes aethiopicus (sjostedt) infesting a house in al-ain city in abu dhabi emirate (boocock, 1979). the objectives of this study were to conduct a general survey for identifying subterranean termites, to determine the geographical distribution of all termite species in all seven emirates, and to determine termite livingor dead-hosts. materials and methods field sampling of termites from different regions of the uae were conducted from march 2000-may 2002 (figure 1). a total of 64 field trips were made in all emirates (35 in abu-dhabi, 10 in dubai, 8 in sharjah, 4 in ajman, 2 in al fujayrah, 3 in umm al qaywayn, 2 in ras al khaymah emirate). a total of 224 sites (live or dead plant host or other infested materials) were inspected for termite presence: 115 in abu-dhabi, 46 in dubai, 25 in sharjah, 12 in ajman, 14 in al fujayrah, 6 in umm al qaywayn, 12 in ras al khaymah emirate. the number of field trips was consistent with the size of the each emirate. direct collection of termites was made from all infested plants and materials. termite specimens were mostly workers or nymphs, and to a lesser extend winged termites. winged adults of most species were collected after their swarming periods (during a humid day or at night at the beginning of the spring). soldiers and winged castes were only collected during the spring season at the time of termite swarming. specimens were kept in 70 % alcohol, each in a separate glass vial for each site in each emirate. preliminary identification of the collected termites was made using the available termite keys (snyder, 1949; harris, 1967; fontes, 1985; sands, 1998). the confirmation of termite identification was made by sending specimens to the british museum of natural figure 1. map of the united arab emirates. each circle symbol, in each emirate, represents 1-3 inspected sites in each location. geographical distribution and hosts of subterranean termites in the uae arid ecosystem 35 te rm it e e m ir at e (n um be r of s it es ) f am ily sp ec ie s a bu d ha bi (1 15 ) d ub ai (4 6) sh ar ja h (2 5) a jm an (1 2) a l f uj ay ra h (1 4) u m m a l q ay w ay n (6 ) r as a l k ha ym ah (1 2) h od ot er m iti da e a na ca nt ho te rm es o ch ra ce us (b ur m ei st er ) 45 (3 9. 1) * 13 (2 8. 3) 14 (5 6. 0) x 8 (5 7. 1) 5 (8 3. 3) 3 (2 5. 0) a na ca nt ho te rm es u ba ch i (n av as ) 6 (5 .2 ) 3 (6 .5 ) x x 6 (4 2. 9) 1 (1 6. 7) x r hi no te rm iti da e p sa m m ot er m es h yp os to m a (d es ne ux ) 35 (3 0. 4) 20 (4 3. 5) 6 (2 4. 0) 7 (5 8. 3) x x 5 (4 1. 7) h et er ot er m es a et hi op ic us (s jo st ed t) 4 (3 .5 ) 2 (4 .3 ) x x x x 1 (8 .3 ) te rm iti da e m ic ro ce rt ot er m es d iv er su s (s ilv es tr i) 19 (1 6. 5) 6 (1 3. 1) 4 (1 6. 0) x x x 3 (2 5. 0) m ic ro te rm es n aj de ns is (h ar ri s) 6 (5 .3 ) 2 (4 .3 ) 1 (4 .0 ) 5 (4 1. 7) x x x *n um be r o f i ns pe ct ed s ite s (p er ce nt ag e in p ar en th es is ) i n w hi ch e ac h te rm ite s pe ci es w as fo un d in e ac h e m ir at e. ta bl e 1. g eo gr ap hi ca l d is tr ib ut io n of id en tif ie d te rm ite s pe ci es fr om th e se ve n em ir at es o f t he u ni te d a ra b e m ir at es . n um be r o f s ite s w ith te rm ite s; fi gu re s in b ra ck et s in di ca te th e pe rc en ta ge o f a ll si te s vi si te d. kaakeh 36 history (uk). data on the geographical distribution and hosts (plants and other materials) attacked by various termite species, was collected. results and discussion termite species table 1 shows all identified termite species in each emirate. a total of six termite species, belonging to 5 genera and 3 families, were identified. termite species were the harvester termites: anacanthotermes ochraceus (burmeister) and anacanthotermes ubachi (navas), the sand termite psammotermes hypostoma (desneux), the small waxy termites microcerotermes diversus (silvestri), heterotermes aethiopicus (sjostedt), and microtermes najdensis (harris). except for the only record of h. aethiopicus in the uae (boocock, 1979), the other five species had not previously been reported in the uae. all species were subterranean in habitat and reach wood sources through earthen gallery systems. workers of most species forage in the open from late afternoon to early morning. soldiers appeared to form a small proportion of the termite colonies. identification and geographical distribution the dominant termite species found in the uae were a. ochraceus, followed by p. hypostoma and m. diversus. the distributions of the six termite species in each emirate were as follows: a. ochraceus was found in all emirates, except in ajman; a. ubachi was found in abu dhabi, dubai, al fujayrah and umm al qaywayn; p. hypostoma was found in all emirates except in al fujayrah; h. aethiopicus was found in abu dhabi, and ras al khaymah; m. diversus was found in four emirates of abu dhabi, dubai, sharjah, and ras al khaymah; and m. najdensis was found in abu dhabi, dubai, sharjah and ajman. all identified species were present in abu dhabi and dubai emirates. a. ochraceus, p. hypostoma, and m. diversus were found in 39.1, 30.4, and 16.5% of the inspected sites in abu dhabi and 28.3, 43.5 and 13.5 % of the inspected sites in dubai. in sharjah, a. ochraceus, p. hypostoma, m. diversus, and m. , and m. , and najdensis were found. in ajman, only p. hypostoma and m. diversus were found. a. ochraceus and a. ubachi were found only in al fujayrah and umm al qaywayn emirates. in ras al khaymah, a. ochraceus, p. hypostoma, h. aethiopicus, and m. diversus were found. hosts subterranean termites in the uae are considered pests because of the extent of damage they cause to various sorts of living hosts structural materials. termites showed host preference as follows: termites and residences and historical buildings: damage to wood in residences and historical buildings was inflicted by all identified species in all emirates, except in the case of m. najdensis where there was no record of infestation in buildings. a. ochraceus and p. hypostoma were found attacking and destroying roofs of historical buildings and causing damage to constructional timbers and furniture. in many cases these species had removed the straw from mud bricks used in the construction of rural residences, especially in dubai and abu dhabi emirates. kassab et al. (1960) reported that a severe infestation by a. ochraceus resulted in the abandoning of a village in egypt. the damage caused to wood in residences and historical buildings in abu dhabi and dubai emirates, mainly by a. ochraceus and p. hypostoma, justify the application of chemical preservatives and other chemical control strategies such as pressure injection treatments, barrier treatments, and the use of baits. termites and fruit trees: termites in uae are considered to be pests of fruit trees. live citrus trees, citrus sp., were infested by a. ochraceus and p. hypostoma in ras al khaymah, and m. najdensis in ajman. date palm trees, phoenix dactylifera, were affected by all identified species at various levels of infestation. live date palm trees were affected by four species: a. ochraceus in abu dhabi, dubai and al fujayrah; p. hypostoma in abu dhabi; m. diversus in abu dhabi and sharjah; and m. najdensis in abu dhabi, dubai and ajman. roots and trunks of dead palm trees in all emirates (except ajman) were infested by all identified species except m. najdensis. the most common form of attack by termites was the hollowing-out of the palm roots, which may be followed by yellowing and death of palm trees, especially young trees and offshoots. termites in woodland: several forest trees were affected by termite damage: sidr or nabak (zizyphus spina-christi), samur (acacia tortilis), samur (acacia tortilis), samur ( ghaf (prosopis ghaf (prosopis ghaf ( geographical distribution and hosts of subterranean termites in the uae arid ecosystem 37 cineraria), arabean gum (acacia arabica arabean gum (acacia arabica arabean gum ( [=nilotica]), ethel or tamarisk (tamarix sp.), arak or arakh (salvadora persica). woodland trees grown in abu dhabi emirate were infested by all identified species except a. ubachi. a. ochraceus was the only species infesting woodland trees in dubai emirate. termites and vegetable crops: tomato (lycopersicon esculentum), (lycopersicon esculentum), ( okra (abelinoschus okra (abelinoschus okra ( esculentus), pepper (capsicum annum) and cauliflower (brassica oleracea botrytis)(brassica oleracea botrytis)( were the vegetable plants most affected by a. ochraceus in abu dhabi; p. hypostoma in abu dhabi, dubai and ras al khaymah; and m. diversus and m. najdensis in abu dhabi. a. ochraceus was collected from the soil surface of dry grass and vegetable debris in the field. this feeding habit gives the anacathotermes group their alternative name of harvester termites (harris, 1967). termites and agricultural weeds: the only termite species infesting agricultural weeds in date palm plantations, field crops, and dry lands were a. ochraceus and p. hypostoma in abu dhabi emirate. the main weeds affected by termites were: amaranthus viridis, convolvulus arvenis, cornulaca monacantha, crotalaria aegyptiaca, cucumis prophetarum, cyperus rotundus, halopyrum mucronatum, halyoxylon persicum, phragmites australis, setaria verticellata, and zilla spinosa. termites and non-cellulose products: noncellulose items, such as carpets, leather and rubber were affected by all identified species in abu dhabi emirate. a. ochraceus and p. hypostoma also fed on non-cellulose items in dubai and sharjah emirates. termites and paper: paper was infested by a. ochraceus in all emirates except ajman; a. ubachi emirate termite species*termite species* anacantho-anacanthotermes ochraceus (burmeister) anacantho-anacanthotermes ubachi (navas) psammotermes hypostoma (desneux) heterotermes aethiopicus (sjostedt) microcerotermes diversus (silvestri) micro termes najdensis (harris) abu dhabi aw, dp, fs, lp, nc, pp, rs, wd, vg dp, nc, pp, rs, wd aw, dp, fs, lp, nc, pp, rs, wd, vg dp, fs, nc, pp, rs, wd dp, fs, lp, nc, pp, rs, wd, vg fs, lp, nc, wd, vg dubai dp, nc, pp, rs, wd rs, wd dp, nc, pp, rs, wd, vg rs, wd dp, pp, rs, wd lp, wd sharjah dp, nc, pp, rs x dp, nc, rs, wd x lp, nc, rs, wd wd ajman x x pp, rs, wd x x ct, lp, wd al fujayrah dp, lp, pp, rs dp, pp, wd x x x x umm al qaywayn dp, pp, rs wd x x x x ras al khaymah ,ct, dp pp, rs x ,ct, dp, rs wd, vg rs, wd dp, rs, wd x *abbreviations of termite hosts: aw = agricultural weeds; ct = citrus; dp = dead date palm, fs = forest trees; lp = live date palm; nc = non-cellulose products; pp = papers; rs = residences; wd = wood; vg = vegetable field crops; x = species not present. table 2. primary hosts of termite species identified from each of the seven emirates of the united arab emirates. kaakeh 38 was also found in abu dhabi and al fujayrah; p. hypostoma and m. diversus in abu dhabi and dubai and h. aethiopicus in abu dhabi. termites and wood: wood in storage and wood products, such as furniture, were affected by all identified species in all emirates. the seven emirates of the uae enclose a total area of about 83,000 km2 lying at the southwestern tip of the arabian peninsula between 20 and 26 ºn and 51 and 56 ºe. apart from the mountains, the landscape is dominated by geologically recent sands overlying limestone sediments plus marls, shale deposits and evaporates. folded sediments occasionally protrude through the sands as isolated hills. the uae has two coastlines, one to the west and one to the east. the climate is characterized by low rainfall and high temperatures, ideal for termite growth and development. rainfall, atmospheric temperature, humidity, vegetation and soil type are the major ecological factors influencing the abundance, distribution and dispersal of termites. the annual rainfall is highly variable. all recorded termite species occur in abu dhabi and dubai, where less than 100 mm rainfall is usually recorded. only in those areas where man has a direct influence, as in towns, villages, farms and beside roads, has there been any significant alteration to the desert environment in recent years (western, 1989). there is a wide-scale attempt to create woodland in parts of the uae which will increase the range of micro-habitats suitable for subterranean termites, especially a. ochraceus, p. hypostoma, and microcerotermes diversus. nests of termite species recorded in all emirates were of subterranean termites found in arid conditions where there was at least a proportion of clay in the soil and groundwater was enough to support sparse vegetation. nests of a. ochraceus and p. hypostoma consisted of complex systems with several interconnecting galleries. nests of other termite species consisted of diffuse systems of small cells at various depths with interconnecting galleries. a. ochraceus and p. hypostoma comprised over 70 % of the termites recorded in the largest two emirates, abu dhabi and dubai (table 2). a. ochraceus fed largely on dry grass and other vegetable debris, but it has been reported to damage rural buildings, soft timers, palm thatch and mud bricks (harris, 1967). p. hypostoma preferred non-cultivated areas with little vegetation and sandy soil through which water rapidly percolates, and where it would be possible to construct tunnels to the water table which may be at a depth of 10 m. the presence of p. hypostoma at a depth of 30-40 m has been reported (howse, 1970). the species tend to be less common in areas where the soil has a high clay fraction (harris, 1970). the nest structure and microclimate of p. hypostoma has been described by noirot (1970). the nest pattern of p. hypostoma differed greatly, particularly as to depth, in different localities (abu dhabi to ras al khaymah), presumably in relation to humidity and temperature. it is reported to replace a. ochraceus in areas of high temperature and with a sandy terrain (harris 1970). p. hypostoma fed on wood, vegetable debris and on living plants. they are found attacking and destroying roofs of historical buildings and residences in abu-dhabi and dubai emirates. the present survey was the first attempt to identify the termite fauna of the uae. future studies on subterranean termites in the uae are needed, such as population dynamics of the identified termites on their hosts, correlation of termite distribution with the type of soil and temperature, the extent of damage inflicted on local and imported woods by the identified termites and development of new control strategies to combat termite problems. acknowledgment i appreciate the assistance of all field workers in the department of agriculture and livestock in al-ain, the municpalities (al-ain, abu dhabi and dubai), and the ministry of agriculture and fisheries for collecting termites in various emirates. this research project (no. 03-6-11/00) was funded by the scientific research council of the united arab emirate university. references badawi, a., a. dabbour nd a. faragalla. 1982. a contribution to the termite fauna (isoptera) of saudi arabia. sociobiology 7:259-260. badawi, a., h. al-kady and a. faragalla. 1986. termites (isoptera) of saudi arabia, their hosts and geographical distribution. journal of applied entomology 101:413-420. boocock, d. 1979. termites. emirates natural history group bulletin 8:27-28. chhotani, o.b. and g. bose. 1982. insects of saudi arabia, isoptera. fauna of saudi arabia 4:73-83. geographical distribution and hosts of subterranean termites in the uae arid ecosystem 39 chhotani, o.b. and g. bose. 1991. isoptera from saudi arabia and kuwait, with a key to arabian species. fauna of saudi arabia 12:256-265. fontes, l.r. 1985. new genera and new species of nasutitermitinae from the neotropical region (isoptera, termitidae). review of brasilian zoology 3:7-25. harris, w.v. 1967. termites of the genus anacanthotermes in north africa and the near east (isoptera: hodotermitidae). proceedings of the royal entomological society of london (b) 36:79-86. harris, w.v. 1970. termites of the palearetic region. in: biology of termites, k. krishna and f. m. weesner (editors) 2:295-314. academic press, london. howse, p.e. 1970. termites: a study in social behaviour. hutchinson univ. library. london. kassab, a., m.i. hassan, a.m. chaarawi and a.m. shahwan. 1960. the termite problem in egypt with special reference to control. ministry of agriculture. cairo, egypt. myles, t.g. 2004. proposed taxonomy of the order isoptera. in: http://www.utoronto.ca/forest/termite/ taxon.htm. nasr, h., a. halawani, f. al-hadidi and b. yahia. 1978. survey of termite species in the western region of saudi arabia. technical report, agriculture research center, western region, ministry of agriculture and water, saudi arabia, pp46-64. noirot, c. 1970. the nests of termites. in: biology of termites, k krishna and f.m. weesner (editors), 2:73-125. academic press, london. sands, w.a. 1998. the identification of worker castes of termite genera from soil of africa and the middle east. cab international, wallingford, uk. snyder, t. 1949. catalog of the termites of the world. smithsonian miscellaneous collection 112:1-490. western, r.r. 1989. the flora of the united arab emirates: an introduction. uae university publication. al-ain, uae. received: february 2005 accepted: june 2005 research paper journal of agricultural and marine sciences 2023, 28(1): 30–46 doi: 10.53541/jams.vol28iss1pp30-46 received 6 june 2022 accepted 15 august 2022 seasonal variations of surface mesozooplankton community structure in the sea of oman and the arabian sea saud salim albusaidi1,*, michel rené claereboudt2 saud salim albusaidi1,*( ) saud.albusaidi@gmail.com, 1ministry of agriculture, fisheries and water resources, marine science and fisheries center, dpt. of marine ecology and oceanography, p.o. box 427, muscat 100, sultanate of oman, 2sultan qaboos university, college of agricultural and marine sciences, department of marine science and fisheries, p.o. box 34, al-khod 123, oman. introduction oman, in addition to the arabian/persian gulf, is open to the sea of oman (formerly known as gulf of oman) and the arabian sea. both the sea of oman and the arabia sea received considerable attention in terms of oceanographic studies in general, and zooplankton in particular. despite many scientific expeditions that explored the open water and oceanic northeastern arabian sea, the community structure of shallow water coastal mesozooplankton along the omani shelf in a spatial-temporal context was not investigated. most of these research cruises focused on the arabian sea and only rapidly passed through the sea of oman. this area should probably be considered as data deficient in terms of zooplankton. in addition, nearly all of these scientific expeditions targeted a particular season (i.e., preor post-monsoon) and rarely covered a whole calendar year. due to its characteristic location, omani seas (sea of oman and arabian sea) are affected by monsoonal التغريات املومسية يف بنية جمتمع العوالق احليوانية السطحية يف حبر عمان وحبر العرب سعود بن سامل البوسعيدي1، ميشيل رينيه كاليربودت2 abstract. the different characteristics and atmospheric forces over the sea of oman and the arabian sea are assumed to influence zooplankton seasonality and community structure. this work aimed to characterize the abundances and seasonality of coastal and surface mesozooplankton communities in the sea of oman (muscat) and the arabian sea (salalah), and the effects of environmental factors on their distribution. zooplankton samples two contrasting coastal regions; 22 in the sea of oman, and 20 in the arabian sea, were collected during 2013-2014 from the surface and analyzed. total zooplankton abundance was divided by the number of samples to obtain the monthly average abundance per meter cube (ind•m-3) of sea water. a total of 91 species were observed from all 42 samples of which 58 were copepods, among which 47 were calanoid copepods. species composition varied significantly between the two locations. the similarity between the two communities was highest (samples were closest to each other) during the winter, and showed the largest differences in composition in the summer. the seasonal changes in community structures were most significant for copepods and calanoid copepods (p= 0.0002 and p= 0.0003 respectively) and less significant for non-copepods (p= 0.0057). only few species (17 in the sea of oman and 20 in the arabian sea) represented more than 90% of the total zooplankton abundance. there was a distinct pattern of seasonal variation in the abundance of zooplankton in the arabian sea, especially copepods and meroplankton, but there was no such pattern in the sea of oman. some successful species such as temora turbinata and penilia avirostris in the sea of oman, and oithona spp. in the arabian sea seem able to exploit a wide range of prey from phytoplankton to small ciliates and thus feed through the microbial loop. keywords: mesozooplankton, copepod, abundance, arabian sea, sea of oman, northeast monsoon, southwest monsoon امللخص: من املفرتض أن تؤثر اخلصائص والرايح املومسية املختلفة على حبر عمان وحبر العرب على مومسية وبنية جمتمع العوالق احليوانية. يهدف هذا العمــل إىل وصــف وفــرة ومومسيــة جمتمعــات العوالــق احليوانيــة الســاحلية والســطحية يف حبــر عمــان )مســقط( وحبــر العــرب )صاللــة(، وأتثــر العوامــل البيئيــة علــى توزيعهــا. ُجعــت وُحللــت عينــات مــن العوالــق احليوانيــة الســطحية ملنطقتــني ســاحليتني ذوايت خصائــص متناقضــة؛ 22 مــن حبــر عمــان و20 مــن حبــر ــم إجــايل وفــرة العوالــق احليوانيــة علــى عــدد العينــات للحصــول علــى متوســط الوفــرة الشــهري لــكل مــرت مكعــب العــرب، خــالل 2014-2013. ُقسِّ )عــدد/م3( مــن ميــاه البحــر. ُصنِّــف مــا جمموعــه 91 نوًعــا مــن العوالــق احليوانيــة مــن جيــع العينــات البالــغ عددهــا 42 عينــة، منهــا 58 نوًعــا مــن جمدافيــات األرجــل، مــن بينهــا 47 نوًعــا تتبــع كاالنويــد جمدافيــات األرجــل. اختلفــت تشــكيلة األنــواع بشــكل كبــر بــني املوقعــني. كان التشــابه بــني اجملتمعــني أعلــى يف فصــل الشــتاء )كانــت العينــات األقــرب لبعضهــا البعــض(، وظهــر أكــر االختالفــات يف تشــكيلة األنــواع خــالل الصيــف. كانــت التغــرات املومسيــة calanoid( وكذلــك جمموعــة )p=0.0002( ابلنســبة جلميــع جمدافيــات األرجــل )يف بنيــة جمتمــع العوالــق خمتلفــة جــدا )أي ذات فــروق معنويــة كبــرة copepods( كاالنويــد جمدافيــات األرجــل )p=0.0003( وأقــل أمهيــة ابلنســبة لغــر جمدافيــات األرجــل )p=0.0057(. عــدد قليــل مــن األنــواع )17 يف حبــر عمــان و20 يف حبــر العــرب( مثلــت أكثــر مــن ٪90 مــن إجــايل وفــرة العوالــق احليوانيــة. كان هنــاك منــط مميــز للتبايــن املومســي يف وفــرة العوالــق احليوانيــة يف حبــر العــرب، وخاصــة جمدافيــات األرجــل والعوالــق احليوانيــة املؤقتــة )meroplankton(، ولكــن مل يكــن هنــاك مثــل هــذا النمــط يف حبــر عمــان. بعــض األنــواع الناجحــة مثــل temora turbinata و penilia avirostris يف حبــر عمــان و.oithona spp يف حبــر العــرب يبــدو أهنــا قــادرة علــى اســتغالل جمموعــة واســعة مــن الفرائــس مــن العوالــق النباتيــة إىل عوالــق حيوانيــة صغــرة كاهلدبيــات وابلتــايل تتغــذى مــن خــالل احللقــة امليكروبيــة. الكلمات املفتاحية: العوالق احليوانية، جمدافيات األرجل، وفرة، حبر العرب، حبر عمان، الرايح املومسية الشمالية الشرقية، الرايح املومسية اجلنوبية الغربية. 31research paper albusaidi, claereboudt wind patterns. oceanographic processes driven by the sea-land differential temperature over the arabian sea and the indian subcontinent (the southwest monsoon (swm) and winter (the northeastern monsoon (nem) are reflected in the characteristics of the sea of oman and the arabian sea. the sea of oman is exposed to the northeasterly winds that peak in the winter (december to february) creating the northeastern monsoon (nem), which is the prevailing atmospheric force along the sea of oman (piontkovski et al., 2013). the sea surface temperature (sst) varies throughout the year. the highest sst is usually during june-july and cools down to the minimum in february during nem. the dry and cool northeast winds over the sea of oman overturn the water column vertically (i.e., convective mixing) that pumps nutrients upward which enhances productivity (madhupratap et al., 1996b) and supports zooplankton growth. the arabian sea is subjected to annual reversal wind systems, the northeast and southwest monsoons. the energetic southwest monsoon (swm) extends from june through september, during which, a coastal upwelling develops along the southern coasts of oman (morrison et al., 1998; kidwai and amjad, 2000; uye et al., 2000; sarma, 2002). this seasonal upwelling brings nutrient-rich water from the depth that enhances the phytoplankton growth and, eventually, the fishery as well (qasim, 1982; madhupratap et al., 1996b; kazmi, 2004). the southwest monsoon (swm) has more impact on the ecosystem in general and zooplankton in particular. zooplankton biomass in the arabian sea is higher during (swm) and more pronounced inshore than offshore, further away from direct influence of the upwelling (smith et al., 1998). several copepod species such as temora turbinata, centropages tenuiremis, and a few genera belonging to family paracalanidae were linked to this upwelling areas (madhupratap et al., 1990) in the arabian sea. among the unique copepods, calanoides natalis, which was identified previously as calanoides cf carinatus (smith et al., 2020). a recent genetic study (bradford-grieve et al., 2017) concluded that throughout its geographic range this species remains near the coasts, from the bay of biscay in the atlantic all the way around africa then northwards towards the arabian sea. this species is considered a bio-indicator of upwelling areas in oman as well (smith, 1982). the contrasting characteristics of these two water masses are assumed to influence both zooplankton seasonality and community structure. this study aimed to figure 1. map of oman and the research locations (black dots) in the sea of oman (muscat) and the arabian sea (salalah). 32 squ journal of agricultural and marine sciences, 2023, volume 28, issue 1 seasonal variations of surface mesozooplankton community structure in the sea of oman and the arabian sea characterize the abundances and seasonality of coastal and surface zooplankton communities (copepods and non-copepods) in the sea of oman (muscat) and the arabian sea (salalah), and the effects of environmental factors on their distribution. material and methods samples of zooplankton were collected from two regions of the northern indian ocean contrasted by their oceanography; muscat in the sea of oman, and salalah in the arabian sea (figure 1). these two stations were chosen due to the seasonal biological and physico-chemical changes that occur in these water masses as a result of the reversal of southwest monsoon (swm) and northeast monsoon (nem). the samples were collected monthly for two years from the beginning of 2013 until the end of 2014. a plankton net of 200 µm mesh size and 60 cm ring diameter was used to collect samples. the net was towed horizontally just below the surface behind a small boat at a constant speed of 2 knots for five minutes. the boat cruised in a circular motion and the angle between the boat and the towed net is about 45 degrees. each sample was transferred to 500 ml plastic bottles and preserved with 1.5-2% formaldehyde (40-50 ml formalin 40% solution/ l). flowmeter (hydro-bios) readings before and after sampling were taken, which were then used to calculate the distance towed and the volume of filtered seawater. all the samples of 500 ml were divided into aliquots of 250 ml using a folsom plankton splitter. then, using a hensen-stempel pipette or a hensen plunger, a subsample volume of 5 ml was drawn to be examined and counted under a stereomicroscope using a bogorov chamber. the zooplankton species were identified to the lowest taxonomic level possible using the available guides (al-yamani et al. 2011a, 2011b; al-busaidi and al-aisri 2012; prusova et al. 2012). the total copepod abundances reported here included adult and copepodite stages ci-cvi. for several taxa, difficult to identify to the species or even genus level, individuals were assigned to larger taxonomic groups (eucalanidae, paracalanidae, euchaeta sp., oithona sp., copilia sp., macrosetella sp., etc.). in addition, for some taxa, the immature specimens were also grouped into a single category such as (calanoida, pseudodiaptomus sp., acartia sp., temora sp., etc.). for non-copepods, the levels of identification varied from species (penilia avirostris) to genus (e.g. lucifer, evadne, creseis, etc.), families (porcellanidae, desmopteridae, etc.) up to classes (gastropoda, stomatopoda, ostracoda, etc.) or even phyla (echinodermata). a total of 42 samples (22 from muscat and 20 from salalah) were analyzed. using filtered volume, zooplankton counts were transformed into population density (individual per cubic meter; ind m-3) following (thompson and schweigert, 2007). the total copepod abundances included both adults and copepodite stages ci-cvi. in addition to zooplankton samples, environmental variables, seawater temperature (°c), salinity (psu), dissolved oxygen concentration (mg l-1), ph, and chlorophyll-a level (mg l-1), were measured at each station at the time of sampling using a conductivity-temperature-depth (ctd) from idronaut 316 plus™. missing environmental data were compensated from satellite and argo floats data. missing sea surface temperature and chlorophyll-a concentration data were completed using giovanni’s monthly averaged data of 4 km resolution (modis-aqua modisa_l3m). whereas argo float’s data were used to fill in the gaps of missing salinity data. argo data were retrieved from esso indian national centre for ocean information services (incois), government of india. the environmental parameters were linked to zooplankton data in order to find out which of the parameters has the greatest impact on zooplankton distribution and abundance throughout the seasons at both stations. statistical analysis statistical analysis tools, such as principal component analysis (pca) and non-metric mds, were used to support and illustrate the results of the analysis. several ecological indices, such as diversity (shanon and simpson indices), richness (margalef and menhinick indices), and evenness indices were also calculated and analyzed separately (ismail and zaidin, 2015). the statistical analyses of the ecological indices were calculated using past© software (ver. 3.25; (hammer et al., 2001). to evaluate changes in community structures between seasons and locations, a 2-way non-parametric permutation multiple analysis of variance (permanova) was applied to log-transformed abundance data (to reduce the effect of the few most abundant species) using the quantitative bray-curtis similarity (legendre and legendre, 2012). the same analysis was applied to four datasets: (i) all zooplankton, (ii) copepods, (iii) calanoid copepods, and (iv) non-copepods. two factors were considered in the analysis: location (sea of oman vs arabian sea) and season (spring, summer, fall and winter) as well as their potential interaction. the differences in community structures were visualized using non-metric multidimensional scaling (nmds). table 1. monthly average abundance (ind m-3) and percentage share (% of the copepod counts) of the three main orders of copepods in the sea of oman and the arabian sea. the number between brackets in copepod groups represents the total number of taxa. copepods (ind m-3) sea of oman arabian sea calanoida (47) cyclopoida (6) harpacticoida (5) 1102 (74.85%) 363 (24.69%) 7 (0.46%) 1820 (85.98%) 290 (13.69%) 7 (0.33%) 33research paper albusaidi, claereboudt to quantify the importance of the different species as indicators of either the sea of oman or arabian sea communities, the indicator value (indval) was calculated for each species based on the fidelity and specificity of this species in relation to the community (dufrene and legendre, 1997). the test of significance for this indicator was calculated using 1000 permutations using the indval function in the r-package labdsv (roberts, 2019). results hydrographic parameters temperature: the highest sea surface temperatures in the sea of oman always coincide with the summer season during the southwest monsoon (swm) where it can reach up to 32.3°c as was recorded in june 2014. whereas, the lowest temperature was 22.8°c in february 2014 which was recorded during the northeast monsoon (nem) in the winter. on the contrary, the highest temperature in the arabian sea was in may 2013 during the spring intermonsoon (sim, 29.9°c) and the lowest was recorded during swm in july 2014 (23.0°c) (figure 2). chlorophyll-a: the peak values of chlorophyll-a in the sea of oman were recorded in february 2013 (7.25 mg l-1) and march 2014 (11.56 mg l-1) during nem. whereas in the arabian sea, the peak was in september for both years (12.50 and 4.71 mg l-1 respectively). the peak coincided with the end of swm (figure 2). salinity: the region being devoid of major rivers, the sea surface salinity values in the sea of oman vary little but were always higher than in the arabian sea during 2013-2014 (figure 2). there was a seasonality in the surface salinity values in both areas but with opposite patterns. in the sea of oman, salinity tended to increase during the summer and decrease during the winter whereas in the arabian sea surface salinity tended to progressively decrease during the sw monsoon and increase during the winter (ne monsoon) (figure 2). zooplankton community structure during this survey, a total of 91 species were observed from all 42 samples of which 58 were copepods, among which 47 were calanoid copepods. from the 33 species of non-copepods, most species were crustaceans (cirripeds, cladocerans, decapods) but also appendicularians, chaetognaths, and doliolids. copepoda: the relative monthly abundances indicated that few species represented the vast majority of the mesozooplankton (figure 3). in the sea of oman temora turbinata were by far the most common organisms (588 ind m-3 on average) whereas in the arabian sea the most common taxa were pseudodiaptomus sp. (466 ind m-3). in the sea of oman, only 17 species represented 90% of the overall abundance, whereas in the arabian sea 20 species represented 90% of the overall abundance (figure 3). some species appeared restricted to the arabian sea (e.g. calanoides natalis and undinula vulgaris) whereas others seem to be associated with the sea of oman (e.g. centropages typicus and labidocera pavo), suggesting differences in community structure between the two areas. zooplankton taxa were first divided into copepods and non-copepods. copepods were more abundant in both locations, representing 74.13% of the total zooplankton counts in the sea of oman and 76.48% in the arabian sea. in the subclass copepoda, the order calanoida was the most abundant and diverse group at both locations, whereas harpacticoida was the least abundant and diverse (table 1). in the sea of oman in particular, there were several months during which no harpacticoid copepods were observed (figure 4). the overall abundance of copepods varied irregularly and was characterized by peaks of abundances of a few species of calanoids. in the sea of oman, several peaks both in 2013 and 2014 were dominated by temora turbinata (figure 4). in november 2013, paracalanidae (622 ind m-3) and centropages orsinii (600 ind m-3) also contributed to about ⅓ of the total abundance each. in the arabian sea on the other hand, the main peak in augoct 2014 was due to a larger number of pseudodiaptomus spp. that included p. serricaudatus (aug 2014; 2079 ind m-3), p. arabicus, and pseudodiaptomus sp. (sep-oct 2014; (8744-1429 ind m-3 respectively). in addition, numerous copepodites of these species were also recorded at that time. the smaller peaks in the summer and fall of 2013 were dominated by acartia plumosa (june; 1316 ind m-3 and september; 763 ind m-3) and in 2014 by acartia amboinensis (june; 780 ind m-3). the fall peaks were in great part due to several species of paracalanidae (oct-nov 2013; 515-671 ind m-3 respectively). calanoida copepods: a total of 37 calanoid species were identified in the sea of oman and 43 taxa in the arabian sea, of which 34 were common between the two locations. the monthly average abundance (± std. dev.) in the sea of oman was 1102 ± 1340 ind m-3, whereas in the arabian sea it was 1820 ± 2306 ind m-3. table 2. monthly average abundance of cyclopoid copepods (ind m-3). the number between parentheses represents the number of months for which each species was recorded out of 22 samples in the sea of oman and 20 in the arabian sea cyclopoid copepods monthly average abundance (ind m-3) sea of oman arabian sea 1 2 3 4 5 6 oncaea sp. corycaeus sp. oithona sp. farannula sp. copilia sp. sapphirina sp. 187.3 (22) 150.1 (22) 19.3 (17) 4.3 (11) 1.8 (11) 0.7 (6) 87.3 (19) 111.1 (20) 84.9 (20) 5.7 (13) 0.5 (5) 0.2 (3) 34 squ journal of agricultural and marine sciences, 2023, volume 28, issue 1 seasonal variations of surface mesozooplankton community structure in the sea of oman and the arabian sea some species were found throughout the year and observed in all or most samples whereas most species are found only in a few samples. among copepods, only 5 species were found in more than 75% of the samples, both in the arabian sea and in the sea of oman. on the other hand, more than 20 species were only found in 25% of the samples. the 10 globally most abundant taxa made up more than 80% of the total calanoid abundance in both regions (figure 6). of these species, 5 were shared between the two locations: centropages orsinii, clausocalanus sp., canthocalnus pauper, eucalanidae, and members of the family paracalanidae (including the following genera: acrocalanus, bestiolina, calocalanus, paracalanus, and parvocalanus). five other species appeared to be associated either with the arabian sea or with the sea of oman (figure 5). the three most abundant calanoid copepods in the sea of oman during 2013-2014 were temora turbinata (53.40% of calanoid individuals), paracalanidae (15.64%), and centropages orsinii (5.45%); temora turbinata and paracalanidae constituted 69.04% of all copeptable 3. average monthly abundance of harpacticoid copepod (ind m-3). the number between parentheses represents the number of months for which each species was recorded out of 22 samples in the sea of oman and 20 in the arabian sea harpacticoid copepods monthly average abundance (ind m-3) sea of oman arabian sea 1 2 3 4 5 clytemnestra sp. euterpina sp. macrosetella sp. microsetella sp. tigriopus sp. 0.19 (2) 0.25 (3) 0.43 (2) 0.31 (3) 5.56 (3) 0.95 (2) 5.09 (14) 0.68 (5) 0.41 (3) 0.07 (1) figure 2. seasonal variation of the surface temperature (°c), chlorophyll-a (mg l-1), and salinity (psu) in the sea of oman and the arabian sea in 2013-2014. the shaded area represents the southwest monsoon (swm) period (june to september) 35research paper albusaidi, claereboudt oda. whereas, the three most abundant calanoids in the arabian sea were pseudodiaptomus sp. (28.16%), paracalanidae (18.70%), and pseudodiaptomus serricaudatus (9.04%). in terms of occurrence in the sea of oman, paracalanidae were found in all the 22 samples (i.e., 100% of the samples), temora turbinata was encountered in nearly 96% of the samples, and centropages orsinii in 68.18% of the samples. in the arabian sea, paracalanidae were found in all the samples (100%), pseudodiaptomus serricaudatus was encountered in 10 (50%) sample whereas pseudodiaptomus sp. was observed in 9 (45%) of the 20 samples. some species were found only in one location. three calanoid species were only observed in the sea of oman; labidocera kroyeri, labidocera pavo, and pontellopsis herdmani, of which the most abundant was labidocera pavo, which had a monthly average of 16 ind m-3. on the other hand, nine species were only observed in the arabian sea: acartia negligens, calanoides natalis, identified as calanoides carinatus (kroyer, 1848) in many studies, candacia catula, labidocera acutifrons, nannocalanus minor, pontellina plumata, scolecithrix danae, tortanus insularis, and undinula vulgaris. the monthly average of the two most abundant species acartia negligens and calanoides natalis were 20 and 18 ind m-3 respectively. the latter species, i.e., calanoides natalis, is considered rather unique because of its ontogenetic vertical migration characteristic of upwelling areas (smith et al., 2020). it was only found on 4 occasions, all during the swm. in august 2013, 34 ind m-3 were observed, and in 2014 there was a slight increase in the number to 45 ind m-3. in september, only one specimen was found in 2013, however, a much larger abundance was observed in 2014 with 268 ind m-3. cyclopoida copepods: cyclopoida represented the second most abundant order of copepods in both regions. it accounted for 24.69% of the copepod count in the sea of oman and 13.69% in the arabian sea. this order was represented by six genera: copilia, corycaeus, farranula, oithona, oncaea, and sapphirina. corycaeus, oncaea, and oithona were the most abundant genera within the group in both regions, but oithona was nearly 5 times more abundant in the arabian sea (table 2), whereas both coryaceus, and oncaea were more abundant in the sea of oman. oithona represented nearly 30% of the cyclopoid individuals in the arabian sea but only around 5% in the sea of oman. despite no clear pattern in the sea of oman, oithona in the arabian sea showed a seasonal increase during swm and the following fall intermonsoon (fim) before declining (figure 8). the last three genera (farranula, copilia and sapphirina) together represent around 2% of the copepod species counts (figure 7). the time series indicated large variations in the monthly abundances of all these species, without clear patterns. harpacticoida copepods: the third and least abundant group of copepods was the order harpacticoida. its percentage share among all subclass copepoda in the sea of oman and the arabian sea throughout the study was only 0.46% and 0.33% respectively. five genera from this group were found in the samples; these were clytemnestra sp., euterpina sp., macrosetella sp., microsetella sp., and tigriopus sp (table 3). in the sea of oman, tigriopus sp. constituted more than 80% of all harpacticoids records with a monthly average of 5.56 indv m-3 although this value resulted from a single sample with 110 ind m-3. euterpina was only recorded twice in the sea of oman with a monthly average of <1 ind m-3 but was the most abundant species in the arabian sea, 70.76% (5.09 ind m-3). this taxon was recorded in 14 samples (table 3). in terms of temporal occurrence in the samples, harpacticoida were found in 17 of the 20 samples in the arabian sea (mostly during the fall and winter), whereas in the sea of oman, it was only found in half the samples (10 out of 22) but without a clear temporal pattern. non-copepod zooplankton: the relative contribution of non-copepod zooplankton in the sea of oman and the arabian sea was 25.87% and 23.52% respectively. with the exception of penilia avirostris observed only in table 4. monthly average (ind m-3) of non-copepod groups. empty cells refer to taxa that were not observed. the samples were ordered by decreasing abundance in the sea of oman non-copepods monthly average abundance (ind m-3) sea of oman arabian sea penilia avirostris appendicularia evadne sp. chaetognatha doliolida cirripedia luciferidae gastropoda ostracoda fish egg brachyura creseis sp. bivalvia amphipoda siphonophorae annelida echinodermata caridea cnidaria pleopsis sp. ctenophora decapoda anomura fish larvae stomatopoda euphausiidae isopoda hemichordata porcellanidae pteropoda salpidae desmopteridae membranipora 116.10 97.02 82.60 51.89 50.99 18.83 16.48 15.87 13.46 9.45 8.40 6.57 4.17 3.58 3.09 2.84 2.28 2.22 2.13 0.93 0.86 0.86 0.83 0.56 0.56 0.43 0.19 0.12 0.12 0.06 0.06 0.07 176.36 13.04 39.39 147.98 5.57 101.25 37.62 32.94 11.27 3.80 5.03 20.44 2.24 7.40 6.38 2.85 1.22 11.14 0.27 1.49 0.07 0.20 0.07 14.26 0.41 0.27 0.34 7.81 36 squ journal of agricultural and marine sciences, 2023, volume 28, issue 1 seasonal variations of surface mesozooplankton community structure in the sea of oman and the arabian sea the sea of oman, all other groups of non-copepod zooplankton were found in both locations but with different abundances. the five most abundant groups based on their monthly average (ind m-3) that formed 80% of all non-copepod zooplankton abundance in the sea of oman were penilia avirostris, appendicularia, evadne sp., chaetognatha, and doliolida. in the arabian sea, the composition was slightly different. the most abundant non-copepod zooplankton, comprising 80% of this diverse group were: appendicularia, doliolida, luciferidae, chaetognatha, and gastropoda (table 4). the occurrence of these groups in the sea of oman samples ranged between 68.18-100% of the samples and in the arabian sea, their occurrence ranged between 75-100% of the samples. in terms of relative abundances of the different groups of non-copepod mesozooplankton, their relative abundances in the arabian sea was always slightly higher than their relative abundance in the sea of oman except for chaetognaths and cladocerans which were more abundant in the sea of oman. the ratio meroplankton/holoplankton (figure 9) appeared variable in the sea of oman without a clear temporal pattern. on the other hand, in the arabian sea, the ratio dropped during the southwest monsoon (swm). in february 2014, meroplankton constituted one-third of the whole zooplankton in the sea of oman and that was attributed to the high abundance of cirripedes (337 ind m-3). the highest peak of the meroplankton ratio in the arabian sea in december 2013 was due to the high abundance of gastropods (166 ind m-3) and bivalves (68 ind m-3). community analysis diversity index: a principal component ordination of the samples using 12 different diversity indices provides a mechanism to isolate the main components of the variability in biodiversity over time. the first axis (pc1) which was highly correlated with shannon, simpsons, and brilloins indices (combining richness and evenness) represented 67% of the variability in diversity. the second principal component (pc2) was highly correlated table 5. two-way permanova for 4 groups of zooplankton abundance (log-transformed) as a function of both location and season. the bray-curtiss similarity coefficient was used to measure similarities between samples. the groups were all zooplankton, copepods, calanoid copepods and non-copepods all zooplankton source sum of sqrs df mean square f p location season interaction residual total 0.66197 0.61505 -0.016326 3.4219 4.6826 1 3 3 34 41 0.66197 0.20502 -0.005442 0.10065 6.5773 2.037 -0.054071 0.0001 0.0001 0.1631 copepods source sum of sqrs df mean square f p location season interaction residual total 0.69736 0.65685 -0.030127 3.2276 4.5516 1 3 3 34 41 0.69736 0.21895 -0.010042 0.094928 7.3462 2.3065 -0.10579 0.0001 0.0002 0.2442 calanoid copepods source sum of sqrs df mean square f p location season interaction residual total 0.86199 0. 7475 -0.096249 4.0721 5.5853 1 3 3 34 41 0.86199 0.24917 -0.032083 0.11977 7.1972 2.0804 -0.26788 0.0001 0.0003 0.4462 all zooplankton source sum of sqrs df mean square f p location season interaction residual total 0.61519 0.59821 0.0074417 3.9144 5.1352 1 3 3 34 41 0.61519 0.1994 0.0024806 0.11513 5.3434 1.732 0.021546 0.0001 0.0057 0.1313 37research paper albusaidi, claereboudt to the number of taxa (s) and chao’s index (both indicators of species richness) and represented 22% of the overall variability. over time, the first axis of the pca had maximum values in the fall and winter and a large drop in diversity during the summer (summer monsoon) both in the sea of oman and in the arabian sea. the exact timing of the drop seemed to fluctuate from year to year. on the other hand, table 6. indicator values (indval analysis) of the zooplankton assemblages of the sea of oman and the arabian sea. species community indicator value p-value temora turbinate penilia avirostris evadne sp. labidocera pavo anomura centropages tenuiremis oithona sp. euterpina sp. calanoida acartia sp. canthocalanus pauper paracalanidae appendicularia euphausiidae cnidaria bivalvia membranipora ostracoda centropages sp. pseudodiaptomus serricaudatus acartia plumosa cosmocalanus darwinii nannocalanus minor acartia negligens calanoides natalis sea of oman sea of oman sea of oman sea of oman sea of oman arabian sea arabian sea arabian sea arabian sea arabian sea arabian sea arabian sea arabian sea arabian sea arabian sea arabian sea arabian sea arabian sea arabian sea arabian sea arabian sea arabian sea arabian sea arabian sea arabian sea 0.8103 0.6717 0.6142 0.5455 0.2915 0.6719 0.6511 0.6329 0.5956 0.5596 0.5516 0.5497 0.5488 0.5459 0.5183 0.5138 0.5000 0.4961 0.4705 0.4543 0.3741 0.3109 0.3000 0.3000 0.2500 0.001 0.001 0.003 0.001 0.029 0.001 0.003 0.001 0.001 0.009 0.048 0.017 0.022 0.001 0.049 0.035 0.001 0.034 0.005 0.004 0.004 0.026 0.008 0.009 0.019 figure 3. zooplankton species that represented 90% of total abundance in both locations. gray bars denote copepods and black bars represent non-copepod species. 38 squ journal of agricultural and marine sciences, 2023, volume 28, issue 1 seasonal variations of surface mesozooplankton community structure in the sea of oman and the arabian sea the second principal component (number of species) did not show any seasonality in its variability (figure 10). geographical and seasonal variability: on the mds based on bray-curtis similarity between samples of zooplankton (stress = 0.20910), the samples from the arabian sea were very distinct from those of the sea of oman. there was also a pattern in the similarities (bray-curtis) between the different seasons. during the northeast monsoon (nem) and the fall intermonsoon (fim), the sample points were located near the center of the plot although distinct between the arabian sea and the sea of oman. during the spring intermonsoon (sim) the samples from the sea of oman tended to show larger differences in composition (lower similarities) but the samples from the arabian sea continued to form a small cluster near that of the nem. during the summer southwest monsoon (swm), in both areas, the similarities between samples decreased as the sample dots tended to spread away from each other, indicating large variations in composition (figure 11a). when adding the correlation between the mds axis with the 3 environmental variables measured at both sampling stations, salinity appears to be well correlated with the first horizontal axis (pc1), responsible for the distinction between the two locations. using a permanova on the bray-curtis similarity between samples, the effects of both location and season were very significant (p = 0.0001 and p = 0.0001 respectively) but the interaction between the factors, although significant (p = 0.1631) was much weaker. the significant interaction likely corresponds to the difference in patterns of the two regions during the sim (table 5). when we limited the analysis to copepods only, the effects of both location and season remained very significant (p =0.0001 and p = 0.0002 respectively) but the interaction between the factors was not significant (p = 0.2442). the overall patterns, however, remained quite similar with winter (nem) and fall (fim) communities quite homogenous in both locations but spring (sim) and summer (swm) communities progressively developing large differences in compositions (table 5). salinity was still the variable that was best correlated with the axis that separated the two locations (figure 11b). if we limit the analysis to calanoid copepods only, the effect of both location and season were very significant (p =0.0001 and p = 0.0003 respectively) but the interaction between the factors was not significant (p = 0.4462) (table 5). both arabian sea communities and sea of oman communities show similar patterns; with similar communities in the fim and nem periods and progressively different communities in the sim and particularly the swm (figure 11c). salinity here is also the environmental variable that best correlates with the pattern of similarities observed between locations (figure 11c). for the non-copepod zooplankton, the effect of both location and season were very significant (p =0.0001 figure 4. abundance of copepod orders in the sea of oman (up) and the arabian sea (down). the following letters written on peak months document to most abundant calanoid species; tt: temora turbinata, pa: paracalanidae, co: centropages orsinii, ap: acartia plumosa, aa: acartia amboinensis, ct: centropages tenuiremis, ps: pseudodiaptomus serricaudatus, psp: pseudodiaptomus sp. the shaded areas indicate the southwest monsoon (swm). 39research paper albusaidi, claereboudt and p = 0.0057 respectively) but the interaction between the factors was not significant (p = 0.1313) (table 5). both arabian sea communities and sea of oman communities show similar patterns; with similar communities in the fall (fim) and winter (nem), and progressively different communities in the spring (sim) and particularly the summer (swm) (figure 11d). we see also during the swm, in the arabian sea, a movement on the mds plane towards higher chlorophyll-a values. salinity is also the environmental variable that best correlates with the pattern of similarities observed between locations (figure 11d). figure 5. monthly average abundance of calanoid copepods in the sea of oman and the arabian sea. (a) denotes the highly abundant and (b) the less abundant species 40 squ journal of agricultural and marine sciences, 2023, volume 28, issue 1 seasonal variations of surface mesozooplankton community structure in the sea of oman and the arabian sea indicator species analysis: the indicator species analysis indicated that 25 species had significant indicator values in separating the sea of oman from the arabian sea communities (table 6). most species (20) were indicators of the arabian sea. among the most significant, temora turbinata appeared characteristic of the sea of oman with penilia avirostris and evadne sp. the species most characteristic of the arabian sea communities were centropagus tenuiremis, oithona sp., euterpina sp., and acartia sp. discussion environmental variability: cool temperatures in salalah during june-september are caused by wind-driven upwelling along the arabian sea as a result of strong winds blowing from the sw. the upwelling brings up cold water from depth to the surface (madhupratap et al., 1996b). in muscat, the small dip that takes place both years in july-august resulted from the effects of a series of short and irregularly spaced coastal upwelling events along the south coast of the sea of oman (claereboudt, 2018), that raise the thermocline closer to the surface and allow some wind mixing of the surface water with much cooler water below the thermocline resulting in small changes in sst. in addition to the clear cycle of temperature, the salinity also shows a seasonal pattern. in the sea of oman, the higher salinities observed during the summer correspond likely to higher evaporation of the surface water. on the other hand, the progressive decline of salinity during the khareef (i.e., during months of the swm) in southern oman is likely the result of a progressive dilution by the rainfall and occasional river discharge combined with the upwelling of lower salinity waters (anonymous, 2022). peaks of chlorophyll-a in the sea of oman during the nem (typically december-march) are linked to a seasonal bloom of noctiluca scintillans that takes place (al-azri et al., 2007; do rosário gomes et al., 2014) and coincides with the annual drop in the sea surface temperature. in figure 6. the most abundant calanoid copepods in both locations (monthly average abundance) figure 7. relative proportions of the different species of cyclopoid copepods in the sea of oman and the arabian sea 41research paper albusaidi, claereboudt salalah, chlorophyll-a progressively increases during the swm (figure 2) as a direct response to the injection of nutrients in coastal water by the seasonal upwelling. species abundance and distribution: the calanoid copepod species temora turbinata (family temoridae) was the most abundant calanoid copepod in the sea of oman (figure 5). it was also one of the 5 species with a very high indicator value for this geographic area (table 6). this confirms previous observations in the same area (al-azri et al., 2009; fazeli and zare, 2011; piontkovski et al., 2013; fazeli et al., 2015), and the arabian sea (jemi and hatha, 2019). this planktonic and epipelagic species is widely distributed in tropical, subtropical, temperate waters (tseng et al., 2011), and lagoons (almeida et al., 2012) sometimes in high abundances. the monthly average abundance was 588 ind m-3, whereas the average abundance of females in northeastern taiwan was 606-34 ind m-3 (wang et al., 2021). if in taiwan, the abundance of t. turbinata showed a positive correlation with seawater temperature (tseng et al., 2011), in the sea of oman, this correlation with temperature was weak at best (r2 =0.184, p =0.047) and appear driven by a single high abundance count measured on a hot day in june 2014. there was no clear seasonality in the abundance of t. turbinata in the sea of oman as it was observed all year round in high abundance. this might be explained by its feeding behavior. this copepod can diversify food items to include even the smallest heterotrophic nanoflagellates (i.e., microbial loop) when the preferred diatoms become scarce (chang et al., 2014) and therefore can withstand periods of limited phytoplankton abundance. figure 8. monthly abundance distribution of oithona in the sea of oman and the arabian sea. y-axis in logarithmic scale. the shaded area denotes to southwest monsoon (swm). figure 9. ratio of meroplankton to holoplankton in the sea of oman and the arabian sea. the shaded area denotes to southwest monsoon (swm). 42 squ journal of agricultural and marine sciences, 2023, volume 28, issue 1 seasonal variations of surface mesozooplankton community structure in the sea of oman and the arabian sea figure 10. first two principal components (pc) over time. the shaded area denotes the southwest monsoon (swm). figure 11. mds representation of the 42 samples. a, referred to all zooplankton, b, copepods, c, calanoid copepods and d, non-copepod zooplankton. filled symbols correspond to the sea of oman, and empty symbols to the arabian sea. blue disks indicate (nem), green squares (sim), red triangles (swm), and black diamonds (fim). 43research paper albusaidi, claereboudt cladocerans (penilia avirostris and evadne sp.) were good indicator species that separated the zooplankton community of the sea of oman from the arabian sea (table 6). in the coastal waters of kochi, southeastern arabian sea, these cladocerans flourish in warmer environments with high sea surface temperature, particularly during high stratification periods (atienza et al., 2006). during the summer monsoon, these two cladocerans constituted up to 50% of the whole zooplankton (ezhilarasan et al., 2018). a comparison of the seasonality of p. avirostris in five different water masses (the black sea, the adriatic sea, the atlantic, the mediterranean basin, and the sea of oman) concluded that sea surface temperature played a key role in high abundance during warmer months (>22 oc). in our study, the peaks of p. avirostris corresponded with summer months in the sea of oman and support these earlier findings in the black sea, the adriatic sea, and the mediterranean basin. in an upwelling area of the north-eastern atlantic, the abundance of p. avirostris was very low arguably because the sea surface temperature was cooler (<22 oc) even during summer (piontkovski et al., 2012). this resembles the situation in the arabian sea where the abundance of cladocerans, in general, and p. avirostris, in particular, was very low in comparison to the sea of oman and this could be, also, linked to the seasonal upwelling event in the arabian sea. in addition to its association with higher water temperatures, penilia avirostris shows a diet spanning a large range of species and sizes spanning small flagellate to large diatoms, (piontkovski et al., 2012) which made this cladoceran able to thrive by grazing on many food sources regardless of their dimensions (atienza et al., 2006). the copepod centropages tenuiremis (family centropagidae) was identified as one of the indicator species of the arabian sea communities (table 6) with a monthly average abundance of 98.5 ind m-3 (only 3 ind m-3 in the sea of oman). the peak abundances of c. tenuiremis were recorded in august and september, i.e., towards the end of swm, which also corresponded with the lowest sea surface temperature. in xiamen harbor, china, c. tenuiremis is considered a dominant copepod during winter and reached a maximum abundance (80.2 ind m-3) in the spring (wang et al., 2005). this species, also, reached its highest abundance (between 50-100 ind m-3) during late swm on the southwest coast of india (jemi and hatha, 2019). c. tenuiremis may respond well to conditions of high nutrients and low temperatures similar to upwelling areas that led to the high peak during swm. cyclopoid species oithona and harpacticoid euterpina were indicators of the arabian sea samples. they seem to be associated with areas characterized by low oxygen concentrations (jyothibabu et al., 2018). meanwhile, with no clear pattern in the sea of oman, the abundance of oithona copepods in the arabian sea sharply increased with the onset of the swm and continued till the end of the fall intermonsoon (fim) before dropping. this finding was documented before (smith and madhupratap, 2005) and corresponded perhaps to the progressive exhaustion of its ciliate prey as the biomass of the summer monsoon progressively sinks below the thermocline. with its diet consisting mostly of bacteria eating ciliates, oithona was particularly well adapted to tapping into the microbial loop. calanoides natalis, although it had a low indicator value (probably because of its low abundance in surface water where the samples were collected), is typically considered a unique and characteristic species in the arabian sea upwelling area due to its ontogenetic vertical migration from deep water to the surface during the swm and, hence, is considered as an upwelling indicator species (smith et al., 2020). during seasonal surveys in 2007-2008, c. natalis populated the omani shelf from ras al-hadd to salalah in the south during the swm (piontkovski et al., 2015). it was also reported in regions of upwelling such as hadhramout coast of yemen, (mukhaysin et al., 2017), and somalia (smith, 1982) during swm. in this study, the existence of calanoides natalis near the surface is coupled with drops in sst and an increase in chlorophyll-a, which are related to the summer upwelling. a combination of strong winds and low temperatures (the typical condition of swm) are the preferred conditions for high abundances of calanoides natalis (smith et al., 2020). the sea surface temperature in the arabian sea during august-september ranged between 23.50-26.13oc, which is within the most favorable range (18-27oc) found in a study off masirah island, oman, during 2007-2016 (smith et al., 2020). the high abundance of c. natalis at the upper layers during swm was sustained by predominant diatoms (garrison et al., 1998). in a single day, this herbivorous species can ingest half the diatoms in a water column (smith et al., 2020) to the extent it can suppress diatom blooms (smith and madhupratap, 2005). meroplankton the abundance pattern of meroplankton in the arabian sea (abundant during the winter and scarce during the southwest monsoon) reflects the likely outcomes of pelagic larvae hatching during the swm: a dispersal bringing larvae towards the center of the arabian sea where appropriate benthic substrates are rare or inexistent. for instance, the abalone haliotis mariae seems to reproduce mostly in march-april, before the onset of the swm (al-hafidh, 2006). a similar reproductive period was recorded for the sea cucumber holothuria scabra, east of mahout island (al-rashdi and claereboudt, 2018). the absence of seasonality in meroplankton abundance in the sea of oman, reflects perhaps the relatively favorable conditions observed in this area. for instance, the reef scallop laevichlamys ruschenbergerii showed two periods of reproduction, one in february-march (corresponding to the spring phytoplankton bloom) and one in the fall (al-barwani, 2001). 44 squ journal of agricultural and marine sciences, 2023, volume 28, issue 1 seasonal variations of surface mesozooplankton community structure in the sea of oman and the arabian sea community structure in the sea of oman (muscat) the total number of copepod species was 50 of which 38 were calanoid copepods. in comparison, 66 species of copepods were identified in chabahar bay, iran, among which 34 were calanoids (fazeli et al., 2015), and in an earlier study (fazeli et al., 2013) among the 48 copepods recorded in the same area, 32 were calanoids. in this area of the northern sea of oman (chabahar bay), the total abundance of copepods in february (nem), may (pre-swm), august (swm), and november (post-swm) ranged 487-890, 572-1254, 613-713, and 474-594 ind m-3 respectively (fazeli and zare, 2011; fazeli et al., 2013). however, our total copepod abundances for the same periods were 1151, 412, 1092, and 2421 ind m-3 respectively. these differences in copepod abundances might be due to a combination of factors, such as environmental conditions and the geographical nature of sampling locations. the total number of copepod species in the arabian sea (salalah) was 57, of which 44 (43%) were calanoid copepods. during the john murray expedition (sewell, 1948), they observed a very similar number of copepod species (60) but the jgofs programs only identified 47 species (smith and madhupratap, 2005). in comparison to other upwelling areas, the total number of copepod species in cochin, india, was 37, where calanoids represent 21 (36%) species (jemi and hatha, 2019). however, on the hadhramout coast of yemen, the total number of copepod species was 171, of which 121 (41%) were calanoids (mukhaysin et al., 2017). the total copepod abundance during the seasonal upwelling period (swm) was 2932 ind m-3, which is close to what was recorded in cochin (3211 ind m-3) and the hadhramout coast of yemen (2660 ind•m-3). in areas of persistent upwellings, such as chile, the number of copepod species was 77 and the total abundance reached a value of 2228 ind m-3 (gonzalez et al., 2015). this variation in numbers of copepods in the samples can be affected by factors such as mesh size, towing technique (vertical, horizontal, or oblique), the nature of sampling locations (open water, semi-enclosed bay, or estuarine system), number of sampling locations, speed of the boat and number of samples. communities differ between the sea of oman and the arabian sea but also differ significantly with the season. the two communities were closest to each other in the winter and showed the largest differences in the summer. the community structure of zooplankton, in general, and copepods, in particular, were different between both locations during the summer months (swm). the sea of oman community was mainly dominated by a few species, especially temora turbinata, whereas several copepod species alternated dominance during the same period in the arabian sea (figure 4) which widened the minimum polygon of the mds plots. dominance of few species through different seasons and accounted for the majority population was also noted in previous study (madhupratap et al., 1996a). the atmospheric conditions during swm are totally different between the two basins. in the summer (during swm), the sea of oman is hot and shows intense stratification. winds are slow and, hence, mixing in the water column is weak which strengthens the stratification and prevents deep water nutrients from reaching the surface (madhupratap et al., 1996b). the upwelling phenomenon in the arabian sea, which is caused by the southwesterly winds during swm, creates an optimum condition to support the high growth of mesozooplankton (smith and madhupratap, 2005) and can affect the community structure (gonzalez et al., 2015). on the other hand, during the second half of the summer (aug-sep), local upwellings driven by high-frequency changes in the wind direction create small localized phytoplankton blooms (claereboudt, 2018) that likely drive short pulses in zooplankton production and changes in species composition. conclusion the species composition of the mesozooplankton communities varied significantly between the arabian sea and the sea of oman. the two communities were the closest in winter (nem) and showed the largest differences in composition in summer (swm). seasonal differences in the zooplankton communities were also identified in all four datasets (zooplankton, copepods, calanoid copepods, non-copepods). the seasonal changes in community structures were most significant for copepods and calanoid copepods and less significant for non-copepods suggesting that the relative abundances of the three orders of copepods responded also to seasonal 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(2021). seasonal population structure of the copepod temora turbinata (dana, 1849) in the kuroshio current edge, southeastern east china sea. applied sciences 11: 1-20 agricultural and marine sciences, 14:9-15 (2009) ©2009 sultan qaboos university 9 _________________________ *e-mail: talukder@squ.edu.om pesticide resistance in stored-product insects and alternative biorational management: a brief review farid talukder* department of crop sciences, college of agricultural and marine sciences sultan qaboos university, p.o. box 34, al-khod 123, sultanate of oman introduction it is generally accepted that settled agriculture began about 10,000 years ago and the practice of storing food grains started about 4,500 years ago as a safeguard against poor harvests and famines (saxena et al., 1988). since then, insect-pests appeared as one of the major constraints to agricultural production before harvest and during storage of crops. archaeological evidence showed that many currently available stored-products insect species (not all of them pests) of the families anobiidae, bostrichidae, braconidae, cleridae, curculionidae, dermestidae, ptinidae, pyralidae, silvanidae and tenebrionidae were found in ancient egyptian tombs (levinson and levinson, 1985). it is therefore evident that conservation of reserve food stocks and stored crops is necessary to ensure a continuous supply at stable prices more than 20,000 species of preand post-harvest pests destroy approximately one-third of the world’s food production, valued annually at more than $100 billion, among which the highest losses (43% of potential production) occur abstract: conventional pesticides are being used as the major tools for stored grain and food protection. many conventional pesticides have created problems including pesticide resistance, toxic residues in the treated products, handling hazards, health hazards to operatives and pest resurgence. among these, the incidence of pesticide resistance is a growing problem in stored product protection. problems associated with synthetic pesticides, especially pesticide resistance, have created a worldwide interest in the development of alternative biorational strategies. plant-derived materials, biological control agents, insect growth regulators, solar disinfestation systems, use of inert dusts and diatomaceous earth, etc., are potential viable alternatives. most of these alternatives have low toxicity or are not toxic to humans, making them environmentally acceptable and enabling them to be incorporated in stored product protection. keywords: stored-products, insect pests, insecticides, insecticide resistance, insecticide residues, conventional insect pest management, alternative insect pest management. in developing asian and african countries. rice and maize crops, the staple foods in many developing countries, are among those most affected (jacobson, 1982; ahmed and grainge, 1986). in the usa and canada, 20-26% of stored wheat was infested by stored-product pests (white et al., 1985). insects are the most damaging stored pests and the most difficult to control due to their small size, feeding behaviour and ability to attack grain before harvest. in india, losses caused by insects accounted for 6.5% of stored grains (raju, 1984). in ethiopia, the proportion of damaged grains due to insect pests was 29.3% at farmers’ storages (tadesse and basedow, 2004). in tropical countries, grain harvested at high ambient temperatures and delivered into storage loses heat slowly and hence provides ideal conditions for a rapid build-up of many grain insects (wallbank and greening, 1976). insect infestation of stored grain causes weight and quality losses that lead to a reduction of commercial value and seed germination. الحیویة والطریقة المخازن حشرات في المبیدات ضد المناعة موجز إستعراض إدارتھا: في المقبولة البدیلة أحمد تالوكدار فرید عدید مشاكل شكلت المستخدمة الشائعة المبیدات ھذه من الكثیر واألغذیة. الحبوب مخازن آفات مكافحة عملیات في (التقلیدیة) كجزء أساسي الشائعة المبیدات تستخدم الخالصة: على العاملین، والمخاطر الغذائیة تداول المواد وخطورة المواد الغذائیة المعاملة، في من المبیدات آثر وبقاء المبیدات، ھذه الحشرات ضد في المناعة تكون مثل لمستخدمیھا الغذائیة المواد من المشاكل المتنامیة في وقایة المبیدات ضد الحشرات المناعة لدى تعتبر و المبیدات. مع التأقلم على الحشرات وكذلك مقدرة المبیدات المتعاملین مع على الصحیة والتعفیر بالتربة والتعقیم الحراري، الحشرات، ومحكمات نمو الحیویة، والمكافحة النباتیة، المستخلصات وتعتبر المكافحة. بدیلة في حیویة طرق بالباحثین تطویر حدا المخزنة، مما في تداولھا ویمكن بیئیا مقبولة وتعتبر اإلنسان، سمي على اثر بدون أي أو قلیل سمي أثر لھا البدائل ھذه عملیات المكافحة. ومعظم في مھمة بدائل وغیرھا، تعتبر التالشي سریعة المخزنة. الغذائیة المنتجات البدیلة الزراعیة اآلفات التقلیدیة، إدارة الزراعیة إدارة اآلفات للمبیدات، األثر المتبقي المناعة، ، الحشریة اآلفات، المبیدات ، الحشرات مفتاحیة :المواد المخزنة، كلمات 10 talukder 11 pesticide resistance in stored-product insects and alternative biorational management: among the insect species causing infestations and serious damage to stored commodities, tribolium castaneum (herbst), t. confusum duval, rhyzopertha dominica (fabricius), sitophilus granarius l., s. zeamais motschulsky, callosobruchus chinensis l., c. maculatus (fabricius), oryzaephilus surinamensis (l.), acanthoscelides obtectus (say), prostephanus truncatus (horn), lasioderma serricorne (fabricius), ephestia elutella (hubner) are major pests (irshad and jilani, 1990; zettler and cuperus, 1990; sayaboc et al., 1992; talukder and howse, 1994; talukder and howse, 1995; yao and lo, 1995; benhalima et al., 2004). prostephanus truncatus and s. zeamais have been reported as the two most serious pests of stored maize in sub-saharan africa and smallholder farmers are in urgent need of guidelines for their proper management (holst et al., 2000). callosobruchus spp. are major stored product insect-pests of legume crops in the tropics and sub-tropics and cause considerable economic losses (chauhan and ghaffar, 2002). the losses of stored grains due to insect infestation is a serious problem, particularly in villages and towns in developing countries. tropical climatic conditions, poor sanitation and use of inappropriate storage facilities all encourage insect pest attack and are often highly favourable for insect growth and development (jacobson, 1982; talukder, 1995). burkholder (1977) has suggested that more effective control of storage pests in agricultural and domestic premises would immediately increase the amount of edible grain and food without any increase in agricultural productivity. the efficient control and prevention of insect pests of stored food commodities has long been the goal of entomologists throughout the world (talukder, 1995). although many methods of control are now being used, the agriculture industry is seeking safer and more economical means. in recent years, inert gases, radiation, pathogens, growth regulators and pheromones have all been used for stored-product insect control. all these can be combined with the older methods of control (resulting in integrated pest control), namely: sanitation, inspection, good packaging, good storage facilities and pesticides, etc. to provide integrated pest management (burkholder, 1977). synthetic pesticides are the major tools for stored grain protection in developed countries. they are valued for their uniform and rapid effectiveness, ease of shipment, storage, application and often relatively long-term persistence. they can be classified, according to type of formulation, into fumigants, liquid, powder etc. however, considerable problems may arise from the continued application of these insecticides, including genetic resistance of insect species, toxic residues in the treated products, handling hazards, health hazards to operatives and pest resurgence (schoonhoven, 1982; sharaby, 1988; chiu, 1989; rembold, 1989). continuous and heavy usage of synthetic insecticides results in direct toxicity to nontarget organisms such as beneficial parasitoids, predators, etc. in addition, certain chemicals may get concentrated in food chains and may cause lethal effects on the food consumers. these problems lead to rapidly rising application and marketing costs with reduced benefits. in this review, i shall focus on pesticide resistance as one of the major problems with conventional pesticides used in stored-product insect pest management and the use of alternative biorational methods as a possible solution to pesticide resistance. the pesticide resistance problem the incidence of pesticide resistance is a growing problem in stored-product protection. resistance to one or more pesticides has been reported in at least 500 species of insects and mites (georghiou, 1990). an insecticide resistance problem in different stored-product insects has been reported from many countries including australia, bahrain, canada, central african republic, china, cyprus, egypt, ethiopia, gambia, germany, greece, guyana, india, japan, kenya, malawi, malaysia, morocco, nepal, nigeria, pakistan, philippines, senegal, somalia, south africa, syria, taiwan, uganda, united kingdom, usa, zambia (dyte and halliday, 1985; prickett, 1987; rassman, 1988; irshad and jilani, 1990; zettler and cuperus, 1990; sayaboc et al., 1992; yao and lo, 1995; darp, 2003; benhalima et al., 2004). storedproduct insect pests were found to be resistant against several insecticides including bioresmethrin, carbaryl, chlorpyrifo, chlorpyrifos-methyl, cyanophos, cyfluthrin, cyhalothrin, cypermethrin, ddt, deltamethrin, diazinon, dichlorvos, ethylene dibromide, fenitrothion, lindane, malathion, methyl bromide, permethrin, phosphine, phoxim, pirimiphos-methyl, promecarb, propoxur, pyrethrins, temephos, tetrachlorvinphos (darp, 2003). the aforementioned publications documented the extent of the resistance to different groups of conventional insecticides in stored-product insect pests around the world this frustrating situation indicates the powerlessness of conventional pest management strategies against insect pests of stored products. most of the important pests of stored products have shown resistance to more than one kind of pesticide. the resistance of certain stored products pests to two of the more widely used food industry pesticides has reached the highest levels ever recorded in the usa (fehrenbach, 1991). the development of cross-resistance (to different members of the same pesticide group) and multi-resistance (to different pesticide groups) in insect strains of many important insect species is a serious concern all over the world (dyte and halliday, 1985; zettler and cuperus, 1990; chaudhry, 1997). the rapid spread of resistant insect strains through international trade is indicative of a problem likely to occur with stored products pests. white and watters (1984) reported that malathion-resistant stored grain insects enter canada primarily through international trade. table 1 shows the extent of insecticide resistance of some major stored-product insect pests. organophosphates and fumigants are two major classes of pesticides used in management of insect pests of stored-products. i will use malathion (an 10 talukder 11 pesticide resistance in stored-product insects and alternative biorational management: organophosphate) and phosphine (a fumigant), both important pesticides commonly used for the protection of stored-products, to illustrate the problem of resistance to these two major classes of pesticides. resistance to malathion currently, there are 122 insect pest species which are resistant to malathion (darp, 2003). malathion resistance in stored-product insect-pests has been reported from all over the world (rassmann, 1988; sayaboc and acda, 1990; zettler and cuperus, 1990). navarro et al. (1986) reported malathion resistance of t. castaneum, o. surinamensis, s. oryzae and r. dominica. malathion resistance in t. castaneum was reported from india by pasalu and bhatia (1983). in germany, malathion resistance was detected in s. granarius and s. oryzae (rassmann, 1988). reports showed that adult t. castaneum, in pakistan has developed a 56-fold increase in resistance against malathion, and in the philippines, red flour beetles exhibited a 57-fold increase in resistance to malathion (saleem and shakoori, 1989; gibe and motoyama, 2002). malathion resistant strains of this pest species were reported from different asian countries (irshad and jilani, 1990; dhaliwal and chawla, 1997; gibe and motoyama, 2002). irshad and jilani (1990) found that forty strains of t. castaneum, collected from various locations of pakistan, all were resistant against malathion. in the philippines, sayaboc and acda (1990) collected 61 populations of t. castaneum and r. dominica, all of which were found to be resistant to malathion. approximately one-third of o. surinamensis strains tested in u.k. during the 1984-85 harvest showed resistance to malathion (prickett, 1987). zettler and cuperus (1990) reported that from oklahama, usa, all collected strains of t. castaneum and r. dominica were resistant to malathion. in another study, zettler (1991) reported that throughout the united states, 82% of the 17 strains of t. confusum, and 93% of the 28 strains of t. castaneum were resistant to malathion. malathion-specific resistance is widespread and stable in natural populations even in the absence of pesticide exposure (arnaud and haubruge 2002). resistance to phosphine fumigation is still one of the most effective methods for the prevention of stored product losses from insect pests, but stored-product insects have been showing a slow upsurge in fumigation resistance (donahaye, 2000). lately, the availability of fumigants for insect control has dwindled drastically. only two fumigants are still in use, namely methyl bromide and phosphine. the former is suspected of leaving residues that are harmful to warmblooded animals (dansi et al., 1984). there are alarming indications of widespread resistance to phosphine in several species of stored product insects in many countries, which in some instances may have caused control failures (chaudhry, 1997). benhalima et al. (2004) investigated the phosphine resistance status of insect pests in morocco and found that, with the exception of one population of s. oryzae, all samples tested contained phosphine-resistant individuals. attia and greening (1981) reported on phosphine resistance on r. dominica, t. castaneum and t. confusum in australia. the levels of phosphine resistance in c. ferrugineus, o. surinamensis, r. dominica and t. castaneum from bangladesh are certainly higher than any previously known in any natural infestation (dyte and halliday, 1985). zettler and cuperus (1990) found a strain of t. castaneum resistant to phosphine in oklahoma, usa. zettler and keever (1994) reported phosphine resistance in l. serricorne in the usa. fumigation is still one of the most effective methods for the prevention of stored-product losses from insect pests. lately, the availability of fumigants for insect control has dwindled drastically. only two fumigants are still in use, namely methyl bromide and phosphine. however, methyl bromide is suspected of leaving residues that are harmful to warm-blooded animals (dansi et al., 1984). recently a slow increase in fumigation resistance have been observed in stored-product insects (donahaye, 2000). alarming indications of widespread resistance to phosphine have emerged in several species of storedproduct insects in many countries, which in some instances may have caused control failures (chaudhry, 1997). benhalima et al. (2004) investigated the phosphine resistance status of insect pests in morocco and found that, with the exception of one population of s. oryzae, all samples tested contained phosphine-resistant individuals. attia and greening (1981) reported phosphine resistance in r. dominica, t. castaneum and t. confusum in australia. the levels of phosphine resistance in c. ferrugineus, o. surinamensis, r. dominica and t. castaneum from table 1. insecticide resistance status of major stored-product insect pests (aprd, 2007). common name species number of insecticides resistant to red flour beetle tribolium castaneum (herbst.) 34 saw-toothed grain beetle oryzaephilus surinamensis (l.) 11 granary weevil sitophilus granarius (l.) 10 rice weevil sitophilus oryzae (l.) 08 maize weevil sitophilus zeamais motschulsky 09 lesser grain borer rhyzopertha dominica (fab.) 08 confused flour beetle tribolium confusum (duval) 05 cowpea weevil callosobruchus maculates (fab.) 02 rusty grain beetle cryptolestes ferrugineus (stephens) 01 cigarette beetle lasioderma serricorne (fab.) 01 12 talukder 13 pesticide resistance in stored-product insects and alternative biorational management: bangladesh are certainly higher than any previously known in any natural infestation (dyte and halliday, 1985). zettler and cuperus (1990) have found a strain of t. castaneum resistant to phosphine in oklahoma, usa. zettler and keever (1994) reported phosphine resistance in l. serricorne in the usa. alternative pest control methods there is an increasing dichotomy between the demands of the first world for quality food uncontaminated by insecticidal residues, and the desperate need of thirdworld populations to maintain and protect their harvested grain from the deprivations of insects, so as to maintain a minimum level of food security. the increasingly serious problems of resistance to pesticides and of contamination of the biosphere associated with the large-scale use of broad-spectrum synthetic pesticides have directed the need for development of alternative strategies, such as: 1 ) biorational chemicals which have minimal potential for development of resistance but are effective, pest specific, safe and economical; 2) biological control agents; and 3) physical and ecological methods (heyde et al., 1984; talukder and howse, 1995; hermawan et al., 1997; talukder and miyata, 2002). biorational chemicals researchers are currently seeking new classes of naturally occurring pesticides that might be compatible with newer pest control approaches. plant-derived materials have been found to be highly effective, more readily biodegradable, less likely to contaminate the environment and to have lower potential to produce resistance , making them viable alternatives to synthetic pesticides (talukder and howse, 1995; shaaya et al., 1997; talukder and miyata, 2002; park et al., 2003; khan and gumbs, 2003). talukder et al. (2004) recently reported that potential use of bioactive plant materials in storage pest management systems because they are economical and environmentally friendly. these chemicals could have lethal effects on storedproduct pests or could affect their development and reproduction. insect growth regulators (igrs), a class of biorational compounds that disrupt the normal development of insects, can be used as an alternative in stored product insect-pest protection (mondal and parween, 2000). igrs affect the biology (embryonic and post-embryonic development, reproduction, feeding, and behavior) of treated insects. unlike conventional insecticides, igrs do not exhibit quick knockdown or cause mortality, but long-term exposure to these compounds stops population growth of pests. igrs could have natural or synthesized active ingredients. many of the plant-derived bioactive chemicals have insect growth regulator properties. the screening for insecticidal principles from several medicinal herbs showed that the root bark of dictamnus dasycarpus turcz. possessed significant feeding deterrence against two stored-product insects (liu et. al., 2002). owusu (2001) suggested natural and cheaper methods for the control of stored-product pests of cereals, with traditionally useful ghanaian plant materials. plant extracts showed deleterious effects on the growth and development of insects and reduced larval, pupal, and adult weight significantly, lengthened the larval and pupal periods and reduced pupal recovery and adult eclosion (khanam et al., 1990). plant oils can play an important role in stored product protection and reduce the need for, and risks associated with, the use of conventional insecticides. the fumigant toxicity of a large number of essential oils extracted from various spices and herb plants was assessed against several major stored product insects (shaaya et al., 1997). singal and chauhan (1997) showed that pigeon pea seed treated with neem seed kernel powder or neem seed oil prevented egg laying of c. chinensis for up to 8 months. two major constituents of the essential oil of garlic (allium sativum l.), methyl allyl disulfide and diallyl trisulfide, were found to be potent contact toxicants, fumigants and feeding deterrents against s. zeamais and t. castaneum (huang et al., 2000). xie et al. (1995) reported the repellency and toxicity effects of azadirachtin and neem extracts on c. ferrugineus, s. oryzae and t. castaneum. obeng-ofori and reichmuth (1997) reported the high toxicity and protectant potential of eugenol against s. granarius, s. zeamais, t. castaneum and p. truncatus. the essential oil of artemisia annua l. was found to be toxic and repellent against t. castaneum and c. maculatus (tripathi et al., 2000). the essential oil vapours distilled from anise, cumin, eucalyptus, oregano and rosemary were reported to have fumigant properties, causing 100% mortality of the eggs of t. confusum, and ephestia kuehniella zeller (tunc et al., 2000). biological control biological control agents, such as bacteria, fungi, virus, parasitoids, predators etc. appear to be environmentally sound and potentially viable alternatives to chemical control for stored-product insect pest management. so far, only bacillus thuringiensis berliner (bt) among microbial pesticides has been approved for application against stored product insect pests (abdel-razek, 2002). the use of predators and parasitoids as biological control agents is also another alternative. trichogramma species were assessed for their suitability as bio-control agents against e. cautella (walker) and e. kuehniella, which are important pests in food manufacturing and processing facilities in australia (steidle et al., 2001). physical and ecological methods the use of kaolinite-based particle film dusts has a potential for use in stored product insect-pests management programs (arthur and puterka. 2002). inert dusts, particularly those based upon activated silicas, are finding increasing use as storage protectants in the grain industry. these materials have been used traditionally as grain protectants by small-scale farmers in the developing 12 talukder 13 pesticide resistance in stored-product insects and alternative biorational management: world (golob, 1997). more recently, materials including diatomaceous earths and silica aerogels, have been used increasingly in commercial storage in the developed world, replacing conventional chemicals. diatomaceous earth acts on insect cuticle by absorbing lipids, and perhaps by cuticular abrasion (lord, 2001). these materials have been shown to control a variety of common storage insect pests. most of them are practically non-toxic to humans and fully acceptable for the environment. as a physical or ecological alternative to conventional pesticides, chauhan and ghaffar (2002) reported that farmers in semi-arid tropical and humid tropical regions may consider using solar heating as a safe and relatively inexpensive method for disinfesting seeds of pigeon pea, as the solar heat-treated seeds remained free from bruchid damage even after 41 weeks of storage. post-harvest tobacco control is partially achieved through sanitation and insect monitoring (blanc et al., 2002). conclusions due to the current reliance on synthetic pesticides for the management of stored-product insect pests, a considerable number of problems are arising, including toxic residues in treated products, handling and health hazards, pest resurgence, and genetic resistance of insect species. the extent of the problem of resistance to pesticides in stored-product insects was discussed with reference to its geographical distribution , pest species affected, and number and types of pesticides these pest species have become resistant to. the serious problem of resistance to pesticides has created a worldwide interest in the development of alternative strategies. among the viable alternatives, the use of plant-derived materials (such as extracts, plant oils, and powders); biological control agents such as bt and trichogramma species; insect growth regulators; inert dusts and diatomaceous earth; and solar heating have been discussed. most of these alternatives were reported as having minimum toxicity to humans and the environment. to stop the increasing pressure of insecticide resistance in insect pests, and also to reduce the chances of pesticide residues in the treated stored-products, a new or alternative management strategy is necessary. among the discussed alternatives, use of a single method might not be fruitful to resolve the current pesticide resistance problem. therefore, a combination of two or more alternative control methods or a combination of conventional chemical insecticides and alternative techniques should be considered as a sustainable longterm strategy. references abdel-razek, a.s. 2002.comparative study on the effect of two bacillus thuringiensis strains of the same serotype on three coleopteran pests of stored wheat journal of the egyptian society of parasitology 32:415-424. ahmed, s. and m. grainge.1986. potential of the neem tree (azadirachta indica) for pest control and rural development. economic botany 40:201-209. aprd. 2007. arthropod pesticide resistance database. usa. web: http://www.pesticideresistance.org/ arnaud, l. and e. haubruge. 2002. insecticide resistance enhances male reproductive success in a beetle. evolution 56:2435-2444. arthur, f.h. and g.j. puterka. 2002. evaluation of kaolinite-based particle films to control tribolium species (coleoptera: tenebrionidae). journal of stored products research 38:341-348. attia, f.i. and h.g. greening. 1981. survey of resistance to phosphine in coleopterous pests of grain and stored products in new south wales. general and applied entomology 13:93-97. benhalima, h., m.q. chaudhry, k.a. mills and n.r. price. 2004. phosphine resistance in stored-product insects collected from various grain storage facilities in morocco journal of stored products research 40: 241-249. blanc, m., p. kaelin and f. gadani. 2002. bacillus thuringiensis (bt) for the control of insect pests in stored tobacco: a review. beitraege-zur-tabakforschunginternational 20:15-22. burkholder, w.e. 1977. manipulation of insect pests of stored products. in: chemical control of insect behaviour: theory & application. h.h. shorey and j.j. mckelvey, jr. 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(coleoptera: bostrichidae) in wheat. journal of economic entomology 83:16771681. zettler, l.j. and d.w. keever. 1994. phosphine resistance in cigarette beetle (coleoptera: anobiidae) associated with tobacco storage in the southeastern united states. journal of economic entomology 87:546-550. received: june 2005 accepted: november 2007 sultan qaboos university journal for scientific research agricultural and marine sciences, 11 s.i., 21-28 (2006) ©2006 sultan qaboos university 21 irrigation water pricing in tunisia: issues for management transparency chokri thabet1 and ali chebil*2 1ecole supérieure d’horticulture et d’elevage de chott mariem (tunisie) 2 institut national de recherches en génie rural, eaux et forêts de tunis2 institut national de recherches en génie rural, eaux et forêts de tunis2 تسعیرمیاه الري بتونس: مقترحات إلنجاح شفافیة التصرف في المیاه ش. ثابت و أ. شبیل خالصة: تواجھ تونس كسائر بلدان الشرق األوسط و شمال إفریقیا منافسة كبیرة بین مختلف مستعملي المیاه نظرا لتزاید السكان والنمواالقتصادي. تبرز التكھنات أن تعبئة موارد المیاه التقلیدیة تكتمل في حدود سنة 2010. لذا فإن تكلفة الفرصة البدیلة للمیاه تصاعدت والتصرف االقتصادي في المیاه بدأ یحتل مكانة ھامة. و من أجل تفادي النقص المحتمل في موارد المیاه، وضعت الدولة التونسیة خطط و سیاسات مثل برنامج اإلصالح الھیكلي للقطاع ، تحسین كفائة استخدام المیاه و إصالح السیاسة السعریة لمیاه الري. الھدف من ذلك ھو تغطیة تكالیف اإلستغالل والصیانة كمرحلة أولى و التكالیف الثابتة كمرحلة ثانیة . ولقد برز بعض الخلل من خالل دراسة المعطیات الھیكلیة لكلفة المیاه الموزعة و مقارنتھا بالكمیة المعلنة من طرف وزارة الفالحة. عندما تكون المعطیات الھیكلیة لكلفة المیاه المنتجة و الموزعة غیر شفافة، فإن إرتفاع التسعیرة یكون غیر مقبوًال من قبل الفالحین. كذلك، لما تكون المعطیات غیر دقیقة فإنھ یصعب تحدید التسعیرة. من ناحیة أخرى، لیس لدائرة المیاه معلومات دقیقة حول إنتاجیة المیاه في المستغالت الفالحیة. ونستنتج من ھذا أن خدمات قطاع المیاه بتونس تتمیز بالمعلومات الغیر متماثلة بین دائرة المیاه والفالحین. إلنجاح إصالح السیاسة السعریة، یجب أن تتوفر مجموعة من العوامل أھمھا: إصالح المحاسبة العمومیة بإدماج نقص قیمة رأس المال تقییم قابلیة الدفع لدى الفالحین بالنسبة لمیاه الري إلى جانب ذلك، فإن إحداث سوق حقوق المیاه یمكن أن یساھم في حل مشكلة عدم تناسق المعلومات وضمان النجاعة االقتصادیة. abstract: tunisia is facing increasing competition for water among users due to population and economic growth. projections show that the water resources will be fully used by 2010. as a result, the opportunity cost of water has risen significantly. in order to cope with potential water shortages, the tunisian government has undertaken a set of policies and technical measures, such as institutional reforms, improving the efficiency of water delivery network and water pricing policies reforms. it has been observed that cost estimation of water produced and delivered is not transparent. thus any increase in water price is opposed by farmers. data is not consistent, making the establishment of a water pricing scheme difficult. besides, the water authority lacks accurate information on water productivity at farm level leading to asymmetric information on the side of the authorities as well as on the side of the farmers. for a successful reform of the irrigation water pricing policy two conditions have to prevail: i) integration of the accounting system of capital costs with an analytical approach and ii) assessing farmers’ willingness to pay for irrigation water. finally, the implementation of a water rights system could be an alternative to solve the asymmetric information problem and improve the economic efficiency. keywords: water cost, accounting, cost recovery, reforms. * corresponding author.. e-mail: chebil.ali@iresa.agrinet.tn introduction the water resources in tunisia are scarce and their quality is degrading. traditionally, the water policy in tunisia was oriented much more towards supply than demand management. however, the increase of supply reached its limits and several problems emerged, such as overexploitation of the resources, increase of marginal cost, low cost recovery, interthabet and chebil 22 table 1.table 1.t water resources in tunisia (mm3). potential accessible available surface water 2700 1405 930 shallow aquifers 719 720 720 deep aquifers 1250 997 997 conventional resources total 4669 3122 2647 reclaimed wastewater 250 120 120 desalinated water 7 7 non-conventional resources total 250 127 127 total water resources 4919 3249 2774 source: ministry of agriculture, 1998. and intra-sector conflicts, misallocation and lack of efficiency. as the per capita availability of water supplies declines and the marginal costs of securing additional supplies rise, water authorities are compelled to explore new approaches to improve the management of water resources. since the nineties, international organizations (fao, 1997; world bank, 1994) and water experts (horchani, 1994; mattoussi, 2002; chohin-kuper et al., 2002) suggested a shift in policy towards water demand management taking into account the economic value of water. economic theory suggests the use of economic instruments to fulfill this target, such as water pricing, quotas and a water market. it is commonly agreed today that water pricing can be an effective tool of water demand management (johansen et al., 2002). during the last decades, volumetric pricing has been adopted wherever possible in tunisia. however, irrigation water prices have been set at very low levels for a long time and thus were disconnected from costs, mainly due to socio-economic considerations (ministry of agriculture, 1998; thabet, 2003). this resulted in an inefficient use of the resource as well as heavy subsidies that significantly contributed to the public budget deficit. these problems are likely to be aggravated by the increased demand of water by the non-agricultural sectors forecast by national planners. to cope with this situation, the tunisian government developed a water saving program including irrigation water pricing reform. the recommended annual rise in water prices was 9% in real terms, which is equivalent to 15% in nominal terms. this rate of increase has been adopted since 1990 (hamdane, 2002). public authorities aimed first to recover the variable costs related to the operation and maintenance (o&m) and later the fixed costs in the long run. as a result of this policy, farmers were dissatisfied because of the relatively high water prices, which were not accompanied by any improvement in water services. in this paper, we assess the tunisian water pricing policy and its coherence regarding the used pricing method and the pursued objectives. this will allow understanding of the reasons behind farmer’s dissatisfaction and propose measures that can be implemented for sustainable water demand management. water supply in tunisia the total potential of water resources in the country is about 4.7 billion m3 the total potential of water resources in the 3 the total potential of water resources in the , of which 2.7 billion m3 country is about 4.7 billion m 3 country is about 4.7 billion m is derived from surface water and 2 billion m3 , of which 2.7 billion 3 , of which 2.7 billion from groundwater (table 1). the water resources are unevenly distributed across the country, with 60% located in the north, 18% in the center, and 22% in the south. good quality water resources, that have a salinity below 1.5 g/l are distributed as follows: 72% of surface water resources, 8% of shallow groundwater, and 20% of deep groundwater. the nonconventional water resources (reclaimed wastewater and desalinated water) represent only 5 % of the total available resources. desalinization of brackish groundwater using reverse osmosis is under operation in the kerkenah islands and in the city of gabes, supplying 7 million m3 per year of drinking water. the water resources management and planning are outlined in the country’s five-year development plans. investments in the water sector were about 45 % of the irrigation water pricing in tunisia: issues for management transparency 23 total ministry of agriculture’s budget during the 10th economic, social and development plan (bahri, 2001). water demand and irrigated agriculture the total amount of consumed water is estimated to be 2.5 billon m3, which is distributed between users as follows: agriculture 84%, domestic use 11%, industrial sector 4% and tourism 1% (table 2). the irrigated area is presently estimated at 412,000 ha. three types of irrigation management exist (table 3): • private management applies to 40% of the total irrigated area and relates to areas irrigated with groundwater. farmers in these areas are responsible for the investment and operation costs of their individual water systems. • associative management, undertaken by water users associations (goupement d’intérêt collectifs gic), cover 36% of the total irrigated area. the collective hydraulic networks are set up through public funds, but their management is delegated to gic. • management of large irrigated schemes, which make up to 24% of the total irrigated area, is still entrusted to public agencies with financial autonomy, but under the supervision of the ministry of agriculture. farmers participate in the investment under the agricultural reform law and pay the total or part of the water o&m cost. the irrigated sector represents 7% of the agricultural area and accounts for 35% of the total agricultural value, 20% of agricultural exports and 27% of the agricultural labor force. the irrigated area produces 95% of the vegetables, 70 % of fruits and 30 % of the dairy output. the irrigated sector will inevitably face more acute competition in the near future due to the water demand increase in the service and industrial sectors, which are considered economically more competitive. water pricing in tunisia and cost recovery tunisian water pricing experiences since the promulgation of the land reform laws in 1962, measures have been prepared to make farmers table 2. water consumption by sector (mm3). irrigation domestic industry tourism total conventional water 2090 290 104 19 2503 no-conventional water 25 0 0 0 25 total 2115 290 104 19 2528 % 84 11 4 1 100 source: ministry of agriculture, 1998. table 3. irrigated areas and water sources in tunisia. private irrigated perimeters (ha) public irrigated perimeters (ha) total (ha) managed by individual farmers managed by crda managed by gic surface water 84,000 59,000 143,000 tubewells 10,000 8,000 74,000 92,000 shallow wells 145,000 145,000 springs and intermittent streams 10,000 15,000 25,000 reclaimed wastewater 5,000 2,000 7,000 total 165,000 97,000 150,000 412,000 source: dggree (2004). thabet and chebil 24 contribute to the water investments. at the beginning of the1970’s, a water pricing method was been adopted in public areas that benefited from public investments. the method was based on an arbitrary fixed tax per hectare in order to constrain users to develop irrigation and to guarantee a minimum cost recovery (ministry of the economy, 1971). during the same period, the water management authority stressed that water price should be judiciously calculated to give the users consciousness of the need to improve water efficiency (ben khelil, 1971). the four-year economic and social development plan (1973-76) was explicit on the irrigation objectives: • producing water at a minimum cost, • improving water productivity, • intensifying the mobilization of renewable water, and • basing water infrastructure development on economic criteria. in 1975 the water code was promulgated (law n°75-16), which consolidated the institutional measures and linked the allocation of water to its highest value (ministry of agriculture, 1978). during the seventies, the development office of the valley of medjerda (omvvm)) undertook several studies aimed at concretizing the pricing methods. these studies were intended to take into account the following three requirements: • those who benefit from water should pay its cost, • pricing shouldn’t compromise the irrigation development by high tariffs, and. • pricing must be conceived as an integral part of a global development strategy. other attempts at water pricing have been made, particularly in the irrigated areas of the medjerda river high valley. they differ partly from those of the medjerda lower valley by taking into account the soil quality, crop rotation and the socio-economic environment. the omvvm conceived a two-tier pricing method, which aims to promote water saving without hindering irrigation. the omvvm (1976) affirmed that the two-tier pricing method was «the most logical and equitable». it includes two terms • the first block is a fixed levy intended to finance the fixed costs that the user has to pay annually, independently of the volume of water used, and • the second term is proportional to the water volume. however, the above method caused problems as irrigation was new to farmers and was not mastered. it was then argued that the increase in the water price could hinder the financial capacity of small farmers. it was suggested that the state should pay the investment cost, at least during a transition period. the increase in water price was postponed until economic conditions improved. however, users were to be warned that at some time they would have to pay the full price of water (omvvm, 1976). the indirect advantage of the above-mentioned studies were that they contributed significantly to heighten decision makers’ awareness of the need to make users participate in financing irrigation. following this experience, several attempts at pricing have been made in other irrigated public areas. at the beginning of the eighties, the ministry of agriculture launched several studies aiming to base water pricing on farmers ability to pay relative to recovery cost. a study conducted by the national center of agricultural studies (degth, 1980) led to a pricing system as described previously (the two-tier pricing) with some modifications: • a fixed annual fee, • consideration of the agricultural development objectives regarding the strategic crops (cereal, sugar beet etc.) charged lower tariffs for water use, and • the establishment of high water prices during the high consumption periods. the application of the above pricing mechanisms was lax and resulted in low rates of cost recovery, ranging between 19 and 36% of the total water cost. according to the world bank (1980), the investment costs were not covered at all and the o&m costs were partially reimbursed. the report insisted on recommending to the tunisian government the need to recover the «greatest part possible of the investment costs». the agricultural structural adjustment program started in 1986 and constituted a new shift in the tunisian economic policy. indeed, the aap recommended coherent pricing and subsidizing policies during the implementation of the 8th and the 9th irrigation water pricing in tunisia: issues for management transparency 25 table 4. annual increase of the average irrigation water price. year water average price (td/m3) rate of water price increase (%) invoiced volume (mm3) 1995 0.060 175 1996 0.069 15.0 162 1997 0.084 21.7 186 1998 0.092 9.5 169 1999 0.098 6.5 174 2000 0.105 7.1 219 2001 0.105 0.0 197 2002 0.110 4.8 239 2003 0.110 0.0 159 mean 0.093 8.1 187 source: dggree (1995-2003). 1 td ≈ 0.76 us$ economic plans. the objective of making farmers pay for equipment renewal, in addition to the o&m costs, was clearly stated (ministry of agriculture, 1997). current water pricing nowadays, several procedures are used to measure and invoice irrigation water. when the volume of water can be measured, using meters or by the water flow and the recorded time, water is priced by volume. a fixed sum per irrigated area is used when metering is not possible. irrigation water prices are spatially and temporally variable. in 2000, they ranged between 0.116 tunisian dinars per cubic meter (td/m3) in the central coast and 0.035 td/m3 in the south (hamdane, 2002). regarding temporal variability, the applied prices have recorded a continuous rise to take into account, at a first step, the inflation rate. in the second step, the objective was to ensure cost recovery of the delivery network and o&m costs. the long term purpose of water pricing is to achieve the total cost recovery of water services, including fixed costs. this assumes that these costs are well identified and known. in the frame of the aap, the recommended annual rise in water price is 9% in real terms, which is equivalent to 15% in nominal terms, given an inflation rate of 6%. the average water price of a cubic meter, in the irrigated public areas managed by the crda, has increased from 0.060 td/m3 in 1995 to 0.110 td/ m3 in 2003, with some annual variability as reported in table 4. the average nominal annual increase of water tariffs amounted to 8.1% during 1995-2003, which is higher than the mean inflation rate during the same period (3.9%). however, the times of drought, particularly during the period 2001-2003, and concern about farmer’s capacity for payment, have made it difficult to maintain the targeted rate of water price increase. irrigation water costs in the absence of reliable cost accounting within the regional water agencies (crda), the total costs of the irrigation water, including fixed costs, are not well identified. the available information from the agricultural ministry is related to o&m cost. table 5. structure of water operating and maintenance costs at national level (1000 td). year personal energy consumableproducts others total 1995 5,663 3,198 1,592 3,399 13,853 1996 5,570 2,306 2,042 2,755 12,675 1997 5,653 2,588 1,586 4,469 14,297 1998 5,758 2,581 1,820 4,827 14,988 1999 5,828 2,339 956 5,666 14,791 2000 5,934 2,983 2,411 5,361 16,690 2001 6,030 2,821 1,658 6,153 16,663 2002 5,412 3,131 1,320 8,544 18,409 2003 5,725 2,472 729 6,245 15,172 average 5,730 2,713 1,568 5,269 15,282 percentage (%) 37.5 17.6 10.4 34.5 100 source: dggree (1995-2003). thabet and chebil 26 table 6. trend of annual average operation and maintenance costs of public perimeters managed by crda. year total water o&m costs (1000 td) invoiced volume (mm3) water o&m costs (td/ m3) 1995 13,853 175,017 0.079 1996 12,675 161,578 0.078 1997 14,297 186,371 0.077 1998 14,988 169,079 0.089 1999 14,791 174,417 0.085 2000 16,690 218,793 0.076 2001 16,663 196,706 0.085 2002 18,409 238,605 0.077 2003 15,172 158,757 0.096 total 137,541 1,679,246 0.082 source: dggree (1995-2003). table 7. trend of water subsidy regarding the o&m costs (td/m3). year water o&m costs selling price unitary subsidy* 1995 0.079 0.060 0.019 1996 0.078 0.069 0.009 1997 0.077 0.084 -0.007 1998 0.089 0.092 -0.003 1999 0.085 0.098 -0.003 2000 0.076 0.105 -0.029 2001 0.085 0.105 -0.020 2002 0.077 0.110 -0.033 2003 0.096 0.110 -0.014 average 0.082 0.093 -0.011 source : dggree (1995-2003). *the negative value of the subsidy means that the selling price is higher than the water o&m cost and covers part of the renewal costs. a study undertaken by the general director of rural engineering (hamdane, 2002), based on data received from the various crda, showed an average cost structure of irrigation water as follows: • personal costs: 37.50 % • energy costs: 17.60 % • consumables: 10.40 % • others: 34.50 % the water o&m cost structure at national level for the period 1995-2003 is reported in table 5. the shown o&m costs must be taken as indicative because they are not computed accurately. indeed, the report stresses the difficulties to allocate certain costs. the person can, for example, be employed in several irrigated public perimeters at the same time. it is the same for materials and equipment, transport equipment and heavy tools, which are used in several irrigated public areas, but no registration of the timing exist to allow the distribution of the cost among the irrigated areas. by taking into account the invoiced total water volume, the resulting average o&m cost is reported in table 6. for the period 1995-2003, the water average o&m cost was around 0.082 td/m3. however, it needs to be borne in mind that these costs don’t include the costs for heavy reparations. cost recovery problem table 7 shows that at national level, recovery of the o&m costs of irrigation water have been achieved since 1997 and part of the equipment renewal costs began to be recovered. however, it is necessary to relativize these figures because of the inaccuracies in the calculation of this cost. for example, for certain years, the income includes the late payment for unpaid former years. the variation of rate recovery is also due to the fact that during drought years, irrigation water demand increases, leading to higher recovery level and vice-versa. the examination of the rate of recovery of o&m costs reveals an inconsistency that must be emphasized. if we compare the amount of water consumed by the agricultural sector (2115 million m3) with the invoiced volume of the irrigated areas managed by the crda in 2003 (159 millions m3), it is clear that the latter represents only 8% of the total agricultural water consumption. by adding the estimated volume of water consumed by the gic (241 million m3) and the private irrigated perimeters (700 million m3), the consumption of the agricultural sector totals to 1100 million m3. hence the gap between the distributed volume for irrigation and the invoiced volume is about 1000 million m3. in this context, one should ask: what is the cost of this volume of water? the o&m costs and the unitary subsidy per cubic meter of water are calculated on the basis of the invoiced volume for all the crda and not the total distributed irrigation water pricing in tunisia: issues for management transparency 27 amount of water (see hamdane, 2002). furthermore, prices are fixed for all the irrigated areas managed by the crda according to these costs. regarding the irrigated perimeters managed by the gic, water prices are supposed to be fixed by the gic members but a recent study (treyer, 2002) has criticized the heavy supervision and direct intervention of the crda in the management of these areas and particularly in fixing water prices. if such is the case, the irrigation water subsidy estimation is thus underestimated because it depends on the invoiced water volume only. consequently, when the cost structure of water produced and delivered is not transparent, any increase in water price to farmers is not justified and can lead to dissatisfaction. furthermore, when data is not consistent, the establishment of a water pricing scheme will be difficult since the rate of subsidy is not clearly determined. finally, the water authority lacks accurate information on the productivity of water at farm level. conscious of the economic and social role that the irrigated sector plays in tunisia, farmers’ capacity to pay becomes a determinant factor in the establishment of the irrigation water price level (hamdane, 2002). hence, the water service in tunisia is characterized by asymmetric information on the side of the authorities as well as on the side of the farmers. for a long time, the accepted idea is that a regulated public agency can ensure the best water allocation if certain conditions related to production technology are met. however, this supposes that the authorities have suitable tools to determine the prices and to organize transfers between economic sectors. furthermore, cost estimation requires a good knowledge of the production costs structure. for a successful reform of the irrigation water pricing policy, some conditions need to be met: • reforming the public accounting system, which should integrate capital depreciation and an analytical approach behind invoicing; • assessing farmers willingness to pay for irrigation water; and • identifying the priority goals for the irrigation • identifying the priority goals for the irrigation • identif water pricing policy. all these elements should facilitate the implementation of a more transparent public environment, from which the reformer will be able to persuade farmers more easily. a promising alternative to be explored could be the implementation of water rights and water markets, since it solves the asymmetric information problem and improves economic efficiency. indeed, several studies have shown that markets can serve as institutional arrangements for optimal allocation of the water resources (mattoussi, 2002; bachta et al., 2004; diao and roe, 2003; zekri and easter, 2005) when transferable water rights are well-defined. this implies deep-rooted legal and institutional reforms to guarantee the efficiency of such markets. the results could be confirmed with a pilot study in a chosen region of the country. moreover, the transfer of o&m responsibilities to water users’ organizations could improve the estimation of water cost and facilitate the implementation of water markets. what is urgently needed is the devolution of the irrigation schemes to farmers to operate them themselves, instead of their current apparent and ineffective participation. conclusion irrigation water prices in tunisia have been set at low levels for a long time and were disconnected from costs, mainly due to socio-economic considerations. this situation led water users to consider water as «heaven sent» and not as a scarce resource. this resulted in high increases in water demand as well as huge subsidies that significantly contributed to the public budget deficit. to cope with this situation, a new water pricing method was adopted in the 1990’s. it consisted of increasing water prices at an annual rate of 9% in real terms. this policy aimed to recover o&m costs in the first step and some capital costs in a second step. the main difficulty encountered when implementing the new water pricing policy was acceptance by farmers of the continuous increase in water prices. examination of the cost structure of delivered irrigation water and consumed water in the agricultural sector revealed some inconsistencies. first, the water cost is calculated as a ratio of o&m costs to the invoiced volume in spite of the delivered volume. second, the fixed costs are not considered in the thabet and chebil 28 estimation. when the cost structure of water produced is not transparent any increase in water price is hardly justifiable. we argue that knowledge of the full-cost is the most important step in water policy formulation. this is crucial because the rate of subsidy of irrigation water depends on the total volume of water delivered, and the establishment of a water pricing scheme that targets the removal of these subsidies can not be implemented successfully. for successful reform of the irrigation water pricing policy, two conditions must prevail: reform of the public accounting system to integrate capital depreciation and an analytical approach behind invoicing; and assessing farmers’ ability to pay. these elements should facilitate the implementation of a more transparent public environment, providing farmers with the right information to convince them to participate. the implementation of a water rights system could be an alternative, since it solves the asymmetric information problem and improves the economic efficiency. c efficiency. c eff acknowledgement this work was funded in the frame of the research project “gestion de la demande d’eau agricole et politiques de tarification en tunisie et en espagne”. we are grateful to the spanish agency for international cooperation (aeci) and the tunisian ministry of research which have contributed funding to this research. references bachta, m.s., a. ben mimoun, l. zaibet and l. albouchi. 2004. simulation of water market in tunisia: a case stuty of gic melalsa – kairouan., modernisation de l’agriculture irriguée, 19-23 avril, rabat, morocco. pp 24-33. bahri, a. 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niveau des périmètres irrigués : diagnostic de la gestion actuelle. cnea and brl ingineering. 180 pp. ministry of agriculture. 1998. eau 21 : stratégie du secteur de l’eau en tunisie à long terme, 2030. rapport final. 400 pp. ministry of the economy, tunisia. 1971. l’eau facteur décisif d’aménagement, groupe huit. 156 pp. omvvm. 1976. etude de la tarification de l’eau d’irrigation dans la base vallée de la medjerda. office de mise en valeur de la vallée de la medjerda. ministère de l’agriculture, tunisie. pp 48. thabet, c. 2003. réforme de la politique des prix de l’eau d’irrigation en tunisie : approche en équilibre général. ph.d dissertation, ensa de rennes, france. treyer, s. 2002. analyse des stratégies et prospectives de l’eau en tunisie. plan bleu, sophia antipolis. 152 pp. world bank. 1994. la gestion de l’eau en tunisie. la gestion de l’eau dans les pays maghrébins. world bank. 150 pp. zekri, s. and w. easter. 2005. estimating the potential gains from water markets: a case study from tunisia. agricultural water management 72:61-agricultural water management 72:61-agricultural water management 175. research paper journal of agricultural and marine sciences 2023, 28(2): 38–44 doi: 10.53541/jams.vol28iss2pp38-44 received 20 november 2022 accepted 9 may 2023 إمكانية إستخدام الزيت العطري املستخرج من zataria multiflora للسيطرة على تعفن فاكهة الفراولة بعد احلصاد ماجدة بنت سعيد بن محد احلضرمية1 و زينب البلوشية1 و عيسى بن هاشل املهمويل1 و عبدهللا بن حممد السعدي1 و ريثيناسامي فيالزهاهن1* potential use of zataria multiflora essential oil to control postharvest aspergillus flavus fruit rot of strawberry majida said hamed al-hdhrami, zainab al-balushi, issa hashil al-mahmooli, abdullah mohammed al-sadi and rethinasamy velazhahan* rethinasamy velazhahan1 *( ) velazhahan@squ.edu.om, sultan qaboos university, college of agricultural and marine sciences, department of plant sciences, p.o. box 34, al-khoud, muscat 123, sultanate of oman. introduction strawberry (fragaria × ananassa duch.) is one of the popular berries in the world. strawberry fruits are preferred by consumers because of their attractive colour, aroma, taste and nutritional qualities (bhat et al., 2015). it is one of the principal fruit crops cultivated in the greenhouses in oman. strawberry fruits are rich source of fiber and several phytochemicals, such as folic acid, vitamin c and other antioxidants (chandler et al., 2012). it is being used as fresh fruit or as sliced and processed fruit (chandler et al., 2012; giampieri et al., 2012). these fruits are highly prone to attack by several fungal pathogens because of their succulent nature that can result in postharvest decay. the most common fungal pathogens that cause postharvest decay in strawberry fruits are botrytis cinerea, rhizopus stolonifer, mucor spp., colletotrichum acutatum, geotrichum candidum, penicillium expansum, cladosporium spp., alternaria spp. and aspergillus spp. (feliziani and romanazzi, 2016; ma et al., 2018; palmer et al., 2019; al-rahbi et al., 2021). a few postharvest fungal pathogens of strawberry are known to produce foodborne mycotoxins (hussein et al., 2020) and hence the quality of fruits after harvest is important for consumer’s safety. for instance, a. flavus produces aflatoxin, a naturally occurring carcinogenic mycotoxin (khlangwiset et al., 2011) and alternaria spp. produce foodborne mycotoxins including alternariol, alternariol methyl ether, tentoxin, tenuazonic acid, altenuene and altertoxins (escriva et al., 2017). postharvest diseases of strawberry can be managed by avoiding mechanical damage to fruits by following safe handling practices, cold storage of fruits, storage of fruits under modified storage atmosphere, application of chemical fungicides, biocontrol agents and natural products like plant extracts and essential oils, and physical method like uv-c treatment (feliziani and romanazzi, 2016). a. flavus is one of the most common postharvest fungal pathogens of fruits. several studies reported the inhibitory activity of essential oils (eos) from plants against a. flavus and aflatoxin production (vilela et al., 2009; kumar et al., 2010; tian et al., 2012a; kedia et al., 2014; kedia et al., 2015; kiran et al., 2016; chaudhari et al., 2020). the eos are volatile and odorous liquids extracted from plant tissues. the eos pass through the cell wall of susceptible fungi because of their lipophilic nature and cause damage to the cytoplasmic membrane, abstract. postharvest fruit rot is a major problem in strawberry production chain worldwide. aspergillus sp. is one of the major fungi associated with fruit rot of strawberry. in this study, an aspergillus flavus was isolated from a rotten strawberry fruit. based on the nucleotide sequence analysis of the internal transcribed spacer regions of rdna, the fungus was confirmed as a. flavus. pathogenicity of the isolated fungus was confirmed by artificially inoculating strawberry fruits under laboratory conditions. this strain was capable of producing aflatoxin b1 in vitro as determined by liquid chromatography-mass spectrometry analysis. postharvest dip treatment of mature strawberry fruits with zataria multiflora essential oil (zeo) (0.1%) completely suppressed a. flavus infection and prevented rotting of fruits. the results of this study suggest that zeo can be used as a sustainable and safe alternative to chemical fungicides for the control of aspergillus fruit rot of strawberry. keywords: aspergillus flavus, aflatoxin b1, essential oil, fruit rot, strawberry, zataria multiflora امللخــص: تعــد مشــكلة تعفــن مثــار الفاكهــة مشــكلة رئيســية يف سلســلة إنتــاج الفراولــة يف مجيــع أحنــاء العــامل. يعــد فطــر أســرجيلس أحــد الفطــرايت الرئيســية املرتبطــة بتعفــن مثــار الفراولــة.يف هــذه الدراســة مت عــزل عزلــة مــن فطــر أســبريجيلس فليفــس مــن مثــار فراولــة فاســدة. اعتمــادا علــى دراســة القواعــد الوراثيــة للمنطقــة املصانــة ريبوســومي للحمــض النــووي مت أتكيــد الفطــر علــى أنــه أســبريجيلس فليفــس. و مت أتكيــد القــدرة اإلمراضيــة للفطــر عــن طريــق التلويــث اليــدوي لثمــار الفرولــة حتــت ظــروف خمريــة. أظهــرت الدراســة قــدرة هــذه الســاللة علــى إنتــاج األفالتوكســن )b1( يف املختــر مــن خــالل حتليــل الكروماتوغرافيــا الســائلة الطيــف الكتلــي. كمــا أشــارت الدراســة إىل أن غمــس مثــار الفراولــة الناضجــة بعــد احلصــاد يف الزيــت العطــري للزعــر o(zeo) zataria multiflora بنسبة 0.1 % يكبح عدوى الفطر ومينع تعفن الثمار متاما. تشري نتائج هذه الدراسة إىل أنه ميكن إستخدام الزيت العطري للزعر zeo بديال آمنا ومســتداما للمبيدات الفطرية وذلك ملكافحة تعفن مثار الفراولة ابســبريجيلس. zataria multiflora ، الزيت العطري ، تعفن الثمار ، فراولة ، b1 الكلمات املفتاحية: أسبريجيلس فليفس ، أفالتوكسن 39research paper al-hdhrami, al-balushi, al-mahmooli, al-sadi, velazhahan coagulation of the cytoplasm and leakage of cellular macromolecules (hyldgaard et al., 2012; dwivedy et al., 2016). gandomi et al. (2011) reported that zataria multiflora eo induced morphological and structural changes in a. flavus including loss of turgidity, vacuolization of cytoplasm and deformation of hyphae. an increase in the generation of reactive oxygen species (ros) and mitochondrial membrane potential and decrease in atpase and dehydrogenase enzyme activities, and ergosterol content were reported in a. flavus due to the effect of anethum graveolens (dill) eo (tian et al., 2012b). chaudhari et al. (2020) demonstrated that allspice (pimenta dioica) eo caused damage to plasma membrane of a. flavus that resulted in the leakage of cellular ions. al-harrasi et al. (2021) recently reported the antifungal activity against a. flavus and aflatoxin b1-detoxification potential of zataria multiflora (lamiaceae) essential oil (zeo). in this study, a. flavus was isolated from diseased strawberry fruits and tested for its pathogenicity and aflatoxigenic potential. furthermore, the efficacy of zeo in the control of a. flavusinduced postharvest fruit rot of strawberry was studied. this is the initial study in oman describing isolation of an aflatoxigenic strain of a. flavus from rotted strawberry fruits as well as demonstrating the effectiveness of zeo in the management of a. flavus fruit rot of strawberry. materials and methods collection of fruits strawberry fruits showing fruit rot symptoms were collected from a supermarket in muscat, sultanate of oman and transferred to the laboratory in an ice box and used within 24 h after collection for isolation of fungus. isolation of fungus diseased tissues (5×5 mm, approx.) from the fruits were cut with a sterile scalpel and surface-disinfected with naocl solution (1%) for 2 min, rinsed 2-3 times with sterile distilled water (sdw), blot-dried on sterile whatman no. 1 filter paper and then placed on potato dextrose agar (pda) medium (oxoid ltd., uk) in 9-cm diameter petri dishes. the plates were sealed with parafilm and incubated at 27°c for 3-4 days. the pure culture of the fungus was obtained by single spore isolation method and the culture was maintained on pda slants at 4°c. pathogenicity test healthy strawberry fruits were surface sterilized with 70% ethanol for 5 s, rinsed twice with sdw and airdried under aseptic condition. on the surface of each fruit, minute wounds were created by using a sterile inoculation needle. twenty µl of spore suspension (1×106 spores/ml) of the fungal isolate prepared from a 5-dayold pda culture was applied on the wounded site and incubated for 7-10 days at 25°c. strawberry fruits applied with sdw served as control. disease severity was measured using a 0-8 scale developed for gray mold of strawberry, where 0 indicated no disease and 8 indicated 87.6-100% of fruit decayed (chen et al., 2018). aflatoxin b1 production by fungal isolate agar disc (6 mm diameter) of the fungus taken from a 7-day-old pda culture was transferred to 200 ml of sterile smky medium (200 g sucrose, 0.5 g magnesium sulfate, 0.3 g potassium nitrate, and 7.0 g yeast extract in 1 l of distilled water) (tiwari et al., 2022) in a 500 ml-conical flask and incubated at 27°c. after 14 days of incubation the culture was filtered through whatman no.1 filter paper and the culture filtrate was collected. in a sterile 1.5 ml centrifuge tube, 500 µl of the fungal culture filtrate and 500 µl of chloroform were added and vortexed for a few seconds. the tubes were then centrifuged at 12000 g at room temperature (25±2°c) and the chloroform layer was transferred to a new 1.5 ml tube and dried completely by using a water bath at 60°c. the residue was dissolved in 250 µl of analytical grade methanol and analyzed by liquid chromatography-mass spectrometry (lc-ms). lc-ms analysis analysis of aflatoxin b1 was performed using an agilent lc/ms/ms (agilent technologies, inc., ca, usa) system, equipped with a high-performance auto sampler (g4226a), quaternary pump (g4204a), thermostated column compartment (g1316c) and agilent 6460 triple quad mass spectrometer. the analyte separation was achieved using symmetry c18; 5 µm, 3 mm × 150 mm column (waters), with a mobile phase of water (a) and acetonitrile (b). both the eluents were with 0.1% formic acid under gradient condition (eluent a 10-70% in 0-1 min, 70-95% in 1-2 min, hold at 95% for 4 min, 9570% in 6-7.5 min, 70-10% in 7.5-8 min and hold at 10% for 1 min) with a flow rate of 0.3 ml per min. the column oven temperature was maintained at 45°c. standard aflatoxin b1 (sigma-aldrich, mo, usa) solution was used to optimize all ms parameters. the optimized ms parameter values were: gas temperature 300°c, gas flow 3 l min-1, nebulizer pressure 50 psi, sheath gas heater 375°c, sheath gas flow 10 l min-1, capillary voltage 3500 v, scan range 100 to 3000 m/z and positive polarity. ms data acquisition and analysis were performed using agilent masshunter software. molecular characterization of the fungus the genomic dna extraction from the fungal isolate was carried out using the plant/fungi dna isolation kit (norgen biotek corp., canada) as per the manufacturer’s instructions. the amplification of the internal transcribed spacer (its) regions of the rdna gene was done as suggested by karthikeyan et al. (2009). briefly, the pcr reaction was performed in a 25 µl reaction mixture consisting of a puretaq ready-to-go pcr bead 40 squ journal of agricultural and marine sciences, 2023, volume 28, issue 2 potential use of zataria multiflora essential oil to control postharvest aspergillus flavus fruit rot of strawberry (ge healthcare, uk), 1 µl each of its4 and its5 primers (white et al., 1990) and 2 µl (100 ng) of the purified dna and 21 µl of sdw. the thermal profile for pcr was as described by halo et al. (2018). the amplification was confirmed by running 5 µl of the pcr product on 1% agarose gel in tris-borate-edta (tbe) buffer followed by observation under uv light using a geneflash gel imaging system (syngene, cambridge, uk). the pcr product (~700 bp) was sequenced at macrogen, seoul, korea. a homology search of the obtained nucleotide sequence was performed using the blast program (www.ncbi. nlm.nih.gov/blast) in order to identify the fungus. efficacy of zeo in controlling aspergillus fruit rot of strawberry zeo extracted previously (al-harrasi et al., 2021) was used in this study. healthy strawberry fruits of uniform size and maturity were selected, and surface sterilized by dipping them in 1% naocl for 1 min and then washed twice in sdw. then, they were dipped in zeo (0.1% in distilled water) for 5 s and then air-dried in a laminar flow chamber for ~10 min. the fruits were then inoculated with a. flavus spore suspension as described earlier and incubated for 7 days at 25 °c. strawberry fruits applied with sdw and inoculated with a. flavus served as control. three fruits were used for each treatment and each treatment was replicated thrice. statistical analysis all experiments were performed in triplicate. the fruit rot disease severity data were expressed as mean ± standard deviation (sd). results and discussion in this study, a. flavus (isolate str10) was isolated from strawberry fruits showing the symptoms of fruit rot and pure culture was obtained (figure 1). to confirm the identity the fungus, the its region of rdna was amplified by pcr using its4 and its5 primers and the amplified product was sequenced. blast analysis of the obtained nucleotide sequence showed 100% sequence similarity with that of a. flavus strain accessions mt635198, mt509715, mn893386, mn893385, mn533904 and mn533814 in the genbank database. the nucleotide sequence of a. flavus isolate str10 from this study was deposited in the genbank with the accession number ol437469. the pathogenicity of the isolate was confirmed by artificial inoculation of strawberry fruits. the inoculated fruits exhibited the fluffy mycelial growth and symptoms of fruit rot 5-8 days after inoculation (disease severity score 6.4 ± 0.9) whereas the control fruits remained symptomless (disease severity score 0) (figure. 2). a. flavus has been reported to cause postharvest rots in several fruits including grapes (ghuffar et al., 2020), jujube (singh and sumbali, 2000), peach (michailides and thomidis, 2007), kiwi (zhu et al., 2022) and figure 1. growth of aspergillus flavus isolated from decayed strawberry fruit on potato dextrose agar medium 41research paper al-hdhrami, al-balushi, al-mahmooli, al-sadi, velazhahan lemon (kotan et al., 2009). several strains of a. flavus isolated from rotten fruits were shown to produce aflatoxins. the aflatoxins are carcinogenic, mutagenic and immunosuppressive compounds produced by a. flavus and a. parasiticus as secondary metabolites when the fungi grow on susceptible crops and food matrices under favourable conditions. among the different forms of aflatoxins, aflatoxin b1 (afb1) is considered as the most dangerous and toxic to humans and animals (velazhahan, 2017). saleem (2017) reported the production of aflatoxins by a. flavus and a. parasiticus from strawberry and the concentration of aflatoxins ranged from 23.6 to 71.1 ppb. hussein et al. (2020) reported that a. flavus was recovered from 53.3%, of strawberry samples collected from qena city, egypt and the amount of aflatoxin produced by a. flavus was 3.5 ppb. the strain of a. flavus, str10, isolated from infected strawberry fruits in this study was capable of producing aflatoxin b1 to a level of 4063 ± 993 ppb under in vitro conditions. hence, control of aspergillus fruit rot is of paramount importance to preserve the quality of harvested fruits for consumer’s safety especially if the fruits are intended to be used as dry fruits. the natural products such as plant extracts and eos have been suggested as an alternative to synthetic chemical fungicides for the control of postharvest diseases of fruits (shao et al., 2013; hosseini et al., 2020; jahani et al., 2020; raveau et al., 2020). the results of the present study revealed that postharvest dip treatment of strawberry fruits with zeo (0.1%) completely prevented a. flavus infection under laboratory conditions (figure 3). the fungal mycelium covered 65-75% of the fruit surface within 5-7 days after inoculation in the untreated control (disease severity score 6.1 ± 0.8); whereas the zeo-treated fruits showed no visible symptoms (disease severity score 0). the effectiveness of plant-derived eos in controlling postharvest fruit rots have been reported in previous studies (nikkhah et al., 2017; hosseini et al., 2020). garlic and rosemary eos have been reported to control anthracnose (colletotrichum nymphaeae) of strawberry (hosseini et al., 2020). el-mogy and alsanius (2012) reported the suppression of botrytis cinerea fruit rot of strawberry by cassia eo. alizadeh-salteh et al. (2010) demonstrated the antifungal activity of shiraz thyme eo against rhizopus stolonifer the causal agent of rhizopus rot of peach fruits. mohammadi et al. (2015) demonstrated the effectiveness of combined application of chitosan with z. multiflora or cinnamomum zeylanicum eos in the control of b. cinerea rot in strawberry. a few studies demonstrated the synergistic antimicrobial effect of eos (sharma and sharma, 2011; nguefack et al., 2012; nikkhah et al., 2017). nikkhah et al. (2017) demonstrated that pear fruits treated with cinnamon + rosemary + thyme or thyme + cinnamon eos showed higher reduction in the lesion size of rot induced by botrytis cinerea and penicillium expansum than single eo treatments figure 2. aspergillus flavus infection on artificially inoculated strawberry fruits surface-disinfected strawberry fruits were inoculated with a. flavus spore suspension (1×106 spores/ml) and incubated at 25 °c. the pictures were taken 5, 8 and 10 days after inoculation (dai). 42 squ journal of agricultural and marine sciences, 2023, volume 28, issue 2 potential use of zataria multiflora essential oil to control postharvest aspergillus flavus fruit rot of strawberry under laboratory conditions. a few essential oil-based commercial products such as promax™, sporan™, ecopcor and ecotrol are being used as food preservatives to prevent fungal contamination (dwivedy et al., 2016). conclusion the results of this study suggest that zeo can be used as a safe method for the control of aspergillus flavus fruit rot of strawberry. the u.s. food and drug administration (fda) listed a number of eos under “generally recognized as safe (gras)” category. further research is needed to test the effectiveness of zeo on other postharvest fruit rot fungal pathogens of strawberry, to elucidate the mechanisms of antifungal action of zeo and to determine if zeo affects sensory quality of strawberry fruits. acknowledgments the authors thank the central analytical and applied research unit (caaru), squ for lc-ms analysis of afb1 references al-harrasi mma, al-sadi am, al-sabahi jn, al-farsi k, waly mi, velazhahan r. 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(2022). first report of aspergillus flavus causing fruit rot on kiwifruit in china. plant disease. 106: 1990. agricultural and marine sciences, 16:65-73 (2011) ©2011 sultan qaboos university 65 ________________________ *e-mail: elmahi@squ.edu.om hematophagous flies in dhofar (sultanate of oman): a limiting factor and a potential pathogenic vector ali tigani elmahi* department of archaeology, college of arts and social sciences sultan qaboos university, p.o. box 42, al-khod 123, sultanate of oman keywords: diptera, muscidae, ceratopogonidae, trypanosomiasis, ecological zones, mountains. introduction this paper is the outcome of a field study in dhofar undertaken in 2008, which documented the traditional pastoralists’ precautionary measures against hematophagous flies. the documentation of pastoralists’ practices in this respect is to facilitate the establishment of an analogy with ancient practices and explore the possible adaptation of prehistoric pastoralists in this ecoregion (elmahi, 2010). consequently, dealing in the field with the effect of flies on the life of pastoralists and animals made it obvious that the role of flies must be addressed. for that reason, this paper aims to cast light on these flies and their role as an ecological limiting factor in dhofar. furthermore, it is to trigger awareness of the possible potential role of flies as vectors transmitting disease-producing organisms to humans and uninfected livestock. but an overriding aim is to raise alarm about a potential menace that can seriously harm a developing region in the sultanate. three hematophagous flies characterize the ecology of dhofar’s landscape: haematobia minuta bezzi (= lyperosia minuta), musca crassirostris stein, and forcipomyia (lasiohelea) whitcombei boorman (= forcipomyia lasiohelea) (mellor, 1978). the same information has been confirmed via personal communication by mr. salah ageib (ministry of agriculture and fisheries, salalah) and local informants. as the monsoonal climate shaped the characteristic ecological conditions of dhofar, the changing seasons and tropical conditions created a suitable habitat for the hematophagous flies in question. the effect of these flies on dhofari pastoralists and the ecosystem as a whole became evident during the two seasons of the field study. the flies act as an ecological limiting factor that impedes pastoralism but yet is a factor in protecting dhofar’s flora. in particular, their possible role as a vector became clearly evident during the field investigations of 2008 and 2009. however, it would be useful first to take a closer look at the geography, climate and pastoral inhabitants of dhofar. dhofar the dhofar governorate occupies the southern part of the sultanate of oman (fig. 1). the empty quarter, rub al-khali marks its northern boundary with the rest of the arabian peninsula. the arabian sea marks its southern limits and dhofar’s mountain range extends from the east to the border with yemen in the west. every year, from july to september, the seasonal southwest monsoon winds over the indian ocean cause low abstract: in dhofar, pastoralists take certain precautionary measures against hematophagous flies: haematobia minuta bezzi, musca crassirostris stein and forcipomyia (lasiohelea) whitcombei boorman. through their feeding on domesticated animals, these flies impede pasturing in certain areas during the rainy season (khareef); hence they act as a limiting ecological factor and a custodian of the flora. the possibility that these flies could be potential pathogenic vectors has not been investigated in oman, although in other parts of the world they are recognized as carriers of disease agents. the paper draws attention to this issue in dhofar. للجراثيم املمرضة وناقل محتمل محدد عامل (سلطنة عمان): ظفار في الدماء مصاص الذباب املاحي التجاني علي و ، haematobia minuta ، musca crassirostris) للدم املاص الذباب من أنواع ضد احترازية إجراءات باتخاذ في ظفار الرعاة يقوم اخلالصة: في الرعي عملية املذكورة الذباب أنواع تعرقل دماء احليوانات املستأنسة، على تغذيها خالل من .(forcipomyia (lasiohelea) whitcombei تبحث لم عمان النباتية. في للمكونات احلامي وبدور محدد بيئي بدورعامل تقوم فهي ولذا (اخلريف)، األمطار موسم خالل بعض املناطق للعوامل حاملة العالم من أخرى أجزاء في تعتبر هذه األنواع أن رغم ، املمرضة هذه ناقلة للجراثيم الذباب تصبح أنواع أن إمكانية بعد ظفار. في القضية لهذه اإلنتباه تلفت العلمية الورقة هذه لألمراض. املسببة 66 elmahi 67 hematophagous flies in dhofar, oman clouds that eventually reach the mountains of dhofar (jabal al-qamar, jabal al-qara and jabal samhan). these winds bring rain and drizzle fog to the mountain range creating a dense vegetation cover and tropical conditions. temperatures drop and humidity ranges between 80 100%. the monsoon effect results in an average annual precipitation reaching 200-500 mm in the mountains and 110 mm on dhofar’s coastal plains. this unique season is known locally as khareef, which is followed by a dry winter and summer. the landscape of southern dhofar is very much dominated by jabal al-qara in the center, jabal al-qamar in the west and jabal samhan in the east. ecological conditions on jabal al-qara are characterized by six ecological zones (fig. 2) (miller and morris 1988; ghazanfar 1992; bahit, unpublished report, department of figure 1. study areas (checkered outlines corresponding to the three main mountain ranges in dhofar, oman (after el-mahi, 2010). � figure 2. six ecological zones of jabal al-qara (after miller and morris, 1988; ghazanfar, 1992; bahit, unpublished report). jabal al-qara 66 elmahi 67 hematophagous flies in dhofar, oman across four zones namely qatan, khatam, escarpment and foothills (fig. 3) (elmahi, 2010). the flies (h. minuta, m. crassirostris) are known to use pats of cattle dung for oviposition (fig. 4) and their mature larvae pupate in the damp soil below (mellor, 1978). m. crassirostris was reported to be a serious cattle pest in india and inflicted severe bites on livestock there (patton, 1992). on the other hand, debenham (1983) describes f. lasiohelea as a similar nuisance to cattle in australia. according to reye (1964), the larvae of f. lasiohelea were found in rotten plants and damp places and they fed on fungi in decomposing plants. forcipomyia whitcombei is a true ecological limiting factor in the dhofari ecosystem. it is commonly known among local pastoralists to suck blood voraciously and cause irritation and an allergic response in man and animals. from another ecological facet, the flies protect dhofar’s flora. the lush vegetation that characterizes the landscape (fig. 5) has been protected from very early times by these flies. if it was not for them, man would have expanded and exploited the flora of the region to a greater extent. timber and perennial plants (fig. 6), excessive grazing and land use would have been the main focus of man’s exploitation (fig. 7). to illustrate, a good example is dhofar’s coastal plains and the plains (jarbib) where the main complaint by government agents is overgrazing and the degradation or disappearance of certain plant species (ageib, unpublished report in arabic). the threat caused to pastoral groups and livestock is unequivocal. on his visit to dhofar, mellor (1978) reported that these flies (h. minuta and m. crassirostris) attacked individual cattle in large numbers as high as 500. he also observed that most cattle carried ca. 5 to 200 flies at any one time (mellor, 1978). as for the effect mellor (1978) reports the following: “some animals, those pasture and range, ministry of agriculture and fisheries, sultanate of oman) in elmahi (2001). table 1 illustrates the types of vegetation in each zone. pastoralism remains a traditional occupation in dhofar and the principal animals in this ecoregion are cattle, camel and goats. interestingly, the animals and their ecological requirements have forced some sort of geographical distribution on their owners. hence, goat pastoralists seasonally occupy particular territories with characteristic ecological conditions that suit their animals’ requirements. the same holds for cattle and camel pastoralists. all in all, dhofari pastoralists are well adjusted to the environmental conditions and their pastoral management of the herds and seasonal movements are strictly traditional, which reflects their essential indigenous knowledge, ways and adaptation. the flies in august 1977, p.s. mellor from britain’s animal virus research institute at pirbright in surrey visited dhofar to investigate what is known locally as the ‘black fly’ h. minuta. the fly was reported by mellor (1978) to be a serious menace and a constant stress on livestock during the rainy season. this was the first investigation that addressed the presence and effect of bloodsucking flies in dhofar. three flies of the order diptera: h. minuta, m. crassirostris and f. whitcombei have been identified (mellor, 1978; ageib, personal communication). locally, h. minuta is known as the ‘black fly,’ m. crassirostris as ‘kieszet’ and f. whitcombei as ‘arnut.’ these bloodsucking flies are terrestrial and appear during the rainy season (khareef) between july and september in the three major areas: jabal al-qamar, jabal al-qara and jabal samhan (fig. 3). their habitat has been recorded as extending table 1. ecological zones in jabal al-qara (after miller and morris 1988; ghazanfar 1992; bahit, unpublished report). zone name of the zone characteristics of plant species 1 coastal plains low sub-shrub and grass cover: avicennia marina, acacia tortilis, zizihus teucadermis, tamarix aphylla, cadaba baccarinil, cadaba farinose, commiphora spp., caesalpinia erianthera, adenium abesum, euphorbia spp., aloe dhofarense, aole inermis. 2 foothills minimal shrubs, sparse forbs and grass cover: boscia arabica, comintphora spp., grewia spp., croton confertus and jatropha dhofarica.. 3 escarpment (with 5 minor zones) woodland: acacia senegal, commiphora spp., mytenus dhofarica, croton confertus and blepharispermum hirtum.. delonix elata. anogeissus dhofarica, sterecutia africana lanea sp. cissus quadrangularis. ficus spp, ziziphus-spina-christi and acacia nilotica trees. 4 khatam open grassland, scattered trees and steep wooded wadis: olea, anogeissus and dodonaea , euphorbia balsamifera and commiphora spp. 5 qatan short annual grass and dwarf shrubs: acacia etbalica, dracena serulata and commiphora serulata. 6 najed desert and short annual grasslow shrub land: boswellia sacra, acacia etbalica and nonorhops richiana 68 elmahi 69 hematophagous flies in dhofar, oman which looked to be in poor condition, had particularly heavy infestations. however, few overt lesions directly attributable to fly bites were seen, although one boran bull had a circular lesion about 4 cm in diameter on the left side of the hump. this area had a serosanguinous exudates and was surrounded by thickly clustered lyperosia.” pastoralists’ precautionary measures against the flies in response to the hazard and stress caused by these flies, dhofar’s pastoral groups take certain measures against them and make adjustment in their adaptation. without such measures, neither herders nor their animals would have survived in these habitats during rainy seasons. nonetheless, the measures adopted are designed to evade the flies and not to confront them. herders have no other means but to impede contact between their animals and the flies. in essence, it is an adaptation shaped by human ingenuity and culture intended to secure survival. three measures in particular are adopted by the cattle herders. the first rests on the simple fact that the flies are diurnal. accordingly, herders allow their animals to graze only at night. it is a well-observed practice that animals graze after sunset and not before. thus, the pastoralists have forced diurnal animals to become nocturnal, a triumph of culture over nature dictated by ecological stress. the second measure is to keep animals inside enclosures that are completely dark during the day. these are designed and built (of rocks and timber) to prevent any daylight getting in (fig. 8). the animals are kept in the enclosures for the whole day and are only taken out after sunset. while the animals are grazing, the herders clean the floors. during the day, they also collect all manure within the vicinity of their houses and this is divided into two portions. one is burned inside the animal enclosure, where its smoke acts as a fly repellent and the other is dried and used as bedding in the animal enclosure. mellor (1978) reports that h. minuta lay their eggs in cattle manure, where the mature larvae use the damp soil under the dung to pupate. he goes further to describe how their pupae “overwinter” under pats of animal manure, while, m. crassirostris has a life cycle similar to h. minuta, and uses cattle manure for breeding. apparently, by keeping the settlement and its surroundings clean of animal manure, herders are restricting oviposition habitats for the flies. it is clear that this measure affects the flies’ density and numbers in the vicinity of the animal enclosures and settlements. the third precautionary measure rests on seasonal movements. two types of movement are adopted by dhofari pastoral groups, namely, transhumant seasonal movements and cyclical ones. these are geared in response to the different seasons and their intensities. winter and summer impose certain conditions on the herders and their animals, while the rainy season (khareef) imposes completely different ones. these cannot be ignored or resisted by the pastoralists. table 2 illustrates the movements of each principal animal herd in response to seasonal requirements (elmahi, 2010). like all pastoral societies, dhofari pastoral groups gear their movements towards the welfare of their animals. cattle, camels and goats are moved seasonally to achieve the following objectives: (a) search for pasture, (b) avoid wet conditions caused by the khareef, and (c) avoid disturbing bloodsucking flies. elderly herders confirm that they move their animals seasonally to avoid the harmful flies. they even go further to say that their animals seem to be aware of the flies and the harm they can inflict. therefore, animals avoid areas infested by the flies (fig. 9). as stated by one of elderly informants: figure 3. close-up of study areas shown in figure 1 illustrating ecological zones in the three mountain ranges of dhofar (after elmahi, 2010). 68 elmahi 69 hematophagous flies in dhofar, oman � “there is nothing to be done, we just need to cope with it.” a limiting factor in spite of these precautionary measures, the flies are a dangerous menace in their environment and a limiting factor. in an ecological sense, a limiting factor is an environmental factor that can hamper and weaken an organism. such a limiting factor can substantially restrict its population growth and reduce its geographical distribution, range, and activity (odum, 1971). the work by krinsky (1976) and foil (1989) cast light on the animals’ productivity under the stress of bloodsucking flies and relates it to a predisposition to infection and aggravation and loss of blood which results in poor conditions and noticeable weight loss. in addition, patton (1992) reports that m. crassirostris as a pest has a bearing on the quantity of cow’s milk in india. examining a number of animals in dhofar, mellor (1978) described how some were in poor condition as a figure 4. h. minuta and m. crassirostris use pats of cattle dung to oviposit and later mature larvae pupate in the damp soil below. � figure 5. lush vegetation characterizes dhofar’s landscape during the khareef. figure 6. trees and perennial plants in dhofar. 70 elmahi 71 hematophagous flies in dhofar, oman figure 7. excessive grazing. figure 8. cattle enclosure. 70 elmahi 71 hematophagous flies in dhofar, oman figure 9. animals are aware of the flies’ boundaries. in addition to possible negative health effects on their animals, economically the pastoralists of dhofar are unable to expand either horizontally or vertically. they cannot utilize other areas of pasture and extend the range of pasture due to the fact that their animals must be protected in pitch-dark enclosures. consequently, confinement to the surroundings of the settlements leads to a limited number of animals being kept by the pastoral groups. they are aware of the carrying capacity of their surroundings and thus keep a reasonable number of animals that will balance available pasture in a limited domain. elderly informants state that increasing their cattle numbers will result in lower milk production. accordingly, it seems that the flies are limiting both cattle populations and economic expansion. potential vectors so far there is no record of h. minuta, m. crassirostris and f. whitcombei vectoring pathogens to livestock in dhofar. perhaps this can be explained by the fact that beyond mellor’s solitary study, these flies have not been comprehensively researched. another explanation is that so far no infected animals have been introduced into dhofar. on the other hand, the same flies have been reported from different parts of the world as potentially infective vectors. bellis et al. (2004) reported from australia that result of physical injury and heavy infestation. it is also possible to assume that such negative effects can equally imperil the herd’s size. it hinders productive and preproductive individuals, both of which constitute the herd’s future. viewing the landscape ecology of dhofar, one notices that pastoralists are restricted from exploiting the wide range of pastures available. they simply cannot take their animals to graze far from the enclosures which protect them from the flies during the day. therefore, their range is restricted (fig. 10). table 2. animal movement in different seasons (after elmahi, 2010). season animal area of distribution north and south of jabal al qara winter/summer cattle khatam and qatan winter/summer camels foothills and qatan winter/summer goats foothills and escarpment khareef cattle qatan, khatam, foothills and occasionally coastal plains. khareef camels coastal plains and najed khareef goats foothills, coastal plains and najed 72 elmahi 73 hematophagous flies in dhofar, oman figure 10. large grazing areas protected by the flies. bloodsucking ceratopogonid flies (of the same family as f. whitcombei) are pests that can transmit diseases and parasites to livestock. moreover, f. lasiohelea is described as a cattle-biting fly and a potential vector of animal disease (debenham, 1983). in africa, a fly survey carried out in ethiopia by shineshaw et al. (2005) refers to biting flies and mentions that kigaye and jiffar (1991) also report from the south eastern part of ethiopia ten species including h. minuta. in addition, shineshaw et al. (2005) reported that these biting pests transmit trypanosma and transmit other livestock diseases. again, mellor et al. (1975) suggests that h. minuta is a potential vector of livestock disease. now, given the presence of these flies in dhofar, to what extent is the region vulnerable? adam (veterinary laboratory, salalah hospital, personal communication) responds to this question by stressing that trypanosomiasis was diagnosed in camels twelve years ago in dhofar. in may 2008, it spread in a sporadic form among camels in wilayat mirbat. later on, it spread as an epidemic among camel herds in wilayat sadh during the first half of 2009 (fig. 1). according to adam (personal communication), no work has been carried out to determine the vector responsible for these outbreaks. dhofar’s situation is perhaps comparable to that observed in queensland, australia; and comments by reye (1964) might well be relevant. “all bloodsucking arthropods must be suspect as potential vectors of disease, and the midges are no exception. no disease transmission by midges has been proved for queensland, but elsewhere they have been proved vectors of such organisms…” despite current uncertainty, dhofar’s vulnerability cannot be ignored, especially since it is commercially and culturally linked with different parts of the world. it is also a route of many migratory birds. if pathogens transmittable to humans and animals are introduced into dhofar, the impact will certainly extend to other sectors such as public health and areas of the economy such as the tourism industry. the region’s hematophagous flies could put all these sectors at risk. conclusion given the overall situation described above, it seems obvious that dhofar is vulnerable because hematophagous insects in other regions can transmit assorted pathogens to humans, wildlife and domestic animals. but at present, there are no detailed investigations that address this issue. a priority must be to discover whether these flies can act as vectors of arboviruses to human and animal populations. further, we should ask what are the portals that can allow infected animals into the region. and how might they be monitored and scrutinized? it would be unwise to wait until cases of pathogen transmission by biting flies occur among humans and livestock on a large scale. 72 elmahi 73 hematophagous flies in dhofar, oman ghazanfar, s.a. 1992. an annotated catalogue of the vascular plants of oman and their vernacular name. scripta botanica belgica 2 meise. kigaye, m.k. and t. jiffar. 1991. a survey of ectoparasites of cattle in harar and dire dawa districts, hararghe administrative region of ethiopia. bulletin of animal health and production in africa 39:15-24. krinsky, w.l. 1976. animal disease agents transmitted by horse flies and deer flies (diptera: tabanidae). journal of medical entomology 13:225-275. mellor, p.s. 1978. biting flies attacking cattle in the dhofar province of the sultanate of oman. tropical animal health and production 10:167-169. mellor, p.s., j. boorman, and m. jennings. 1975. the multiplication of african horse-sickness virus in two species of culicoides (diptera, ceratopogonidae). archives of virology 47:351-356. miller, a.g. and m. morris, m. 1988. plants of dhofar, the southern region of oman. traditional, economic and medical uses. the office of the adviser for conservation of the environment, diwan of royal court, sultanate of oman. odum, e.p. 1971. fundamentals of ecology. w.b. sanders company, london. patton, w.s. 1992. notes on the species of the genus musca, linnaeus – part i: 411-426. http: //hbs.bishopmuseum.org/fiji/pdf/patton1922.pdf reye, e.j. 1964. the problems of biting midges (diptera: ceratopogonidae) in queensland. australian journal of entomology 3:1-6. shineshaw, a., g. abebe, and m. desquesnes. 2005. epidemiology of mechanically transmitted trypanosomosis (trpanosoma vivax) of domestic animals in three districts bordering, lake tana, ethiopia. twenty eighth meeting 28th reunion addis ababa, ethiopia, 26 september 2005. received: october 13, 2009 accepted: may 30, 2010 an immediate and in-depth investigation of this matter is recommended. it is to enhance our understanding of hematophagous flies in dhofar and establish a proper basis for coherent plans against any human and veterinary health hazards that can possibly take place in this region. acknowledgements this research project (ig/art/arch/08/01) has been fully financed by sultan qaboos university. the author is indebted to sultan qaboos university. my colleagues nasser hamd al-henahi (department of archaeology, squ), salah ageib (ministry of agriculture, salalah) and adam mohamed adam (veterinary laboratory, the veterinary hospital salalah) have been of great assistance. professor adrian roscoe (department of english, squ) kindly did the proofreading. the author is indebted to them. references bellis, g.a., l.f. melville, n.t. hunt, and m.n. hearnden. 2004. temporal activity of biting midges (diptera: ceratopogonidae) on cattle near darwin, northern territory, australia. veterinaria italiana 40:324-328. debenham, m.l. 1983. australasian species of the blood-feeding forcipomyia subgenera, lasiohelea and dacnoforcipomyia diptera: ceratopogonidae). australian journal of zoology supplementary series 31:1-61. elmahi, a.t. 2010. pastoralists adjustment to hematophagous flies in dhofar: an analogy of an ancient adaptation. adumatu 21:15-32. elmahi. a.t. 2001. traditional dhofari pastoral groups in oman: a parallel of an ancient cultural ecology. proceedings of the seminar of arabian studies 31: 131-143. foil, l.d. 1989. tabanids as vectors of disease agents. parasitology today 5:88-96. agricultural and marine sciences, 13:53-63 (2008) ©2008 sultan qaboos university 53 *corresponding author. e-mail: omanaba@yahoo.com / krashdi@maf.gov.om abalone, haliotis mariae (wood, 1828), hatchery and seed production trials in oman khalfan m. al-rashdi*1 and tsueno iwao2 1 ministry of fisheries wealth, aquaculture center, p.o. box 427, pc 100, muscat, sultanate of oman 2 japan international cooperation agency, fisheries department, japan عمان سلطنة في الصفیلح صغار وإنتاج تفریخ تجارب و ت. إواو خلفان م. الراشدي ١٩٩٩ مابین الفترة خالل مرباط بوالیة الصفیلح صغار إنتاج بمحطة العماني الصفیلح صغار وانتاج تفریخ تجارب أجریت الخالصة: االصطناعي، والتلقیح الجنسي االصطناعي، النضج والتي تشمل المستخدمة بالمحطة اإلنتاج نظم ھذه الدراسة توّضح و٢٠٠٠م. فترة ُجمعت بعد والتي اصطناعیا المكّیفة األمھات أن الجنسي النضج دراسة أثبتت وقد الصفیلح، وصغار یرقات وإدارة واإلخصاب، معّدل بأن الدراسة وأظھرت الموسمیة، األمطار قبل فترة جمعھا تم باألمھات التي مقارنة نضجا أسرع الموسمیة تصبح األمطار المظھریة والمرحلیة لیرقات التغییرات الدراسة أوضحت كما التوالي. على ٪١١ و ٪٦٣ ھو واإلناث للذكور االصطناعي التلقیح بعد بقائھا معّدل تراوح بینما ،٪٧٣،٧ ٣٥،٩٪ الى ما بین االستقرار تراوحت مرحلة قبل الصفیلح لیرقات البقاء معّدل وأن الصفیلح، والطحالب الدقیقة الخضراء الخیطیة الطحالب نمو الى العالیة للوفیات الرئیسي السبب یرجع الى ٣،٦٪. ٪١ من االستقرار مرحلة للیرقات الرئیسي الغذاء تعّد التي الدایاتومات وكمیة جودة قلة الى إضافة البالستیكیة، الصفائح سطوح على المرجانیة الحمراء تخدیر على حیث تعمل النسب للتخدیر أفضل من الكحول إیثیل مخّدر من ٪٢ نسبة بأن الصفیلح تخدیر صغار وتشیر دراسة المستقرة. ٥٢،٩ شھرا حوالي بعد ١٣ المستزرعة للصغار الصدفة طول معّدل یصل دقیقة. ١٧ خالل وعیھم واسترداد دقائق ٤ خالل الصغار الصفیلح استزراع نجاح أیضا الدراسة أثبتت التوالي. على غرام، ١،٥ و ملم ب٤،١ تقّدر شھریة وبزیادة غرام ١٩،٩ وبوزن ملم االعتبار. یؤخذ في بأن جیر أمر تجاریة مزارع وأن إقامة العماني abstract: hatchery and seed production trials for the omani endemic abalone haliotis mariae were carried out at the land-based mirbat abalone seed production station in oman between 1999 and 2000. the methods developed for broodstock conditioning, induction of spawning and fertilization, larval settlement, and the handling of small juveniles are shown. abalone collected in the post-monsoon period and held for 2 months matured faster than those collected before the monsoon and held for 6 months. spawning induction of males and females had 63% and 11% success rates respectively, and the morphology of early larval stages is shown. survival rates of veliger larvae introduced to settlement plates ranged from 35.9% to 73.7%, but the survival of post-larvae was low at 0.1% to 3.6%. the high mortality rate was attributed to invasions of filamentous green and coralline algae on settlement plates and occurrence of low quantity of diatoms as food. juveniles reacted best to 2% ethanol as anaesthetic, dropping off culture plates within 4 min and recovering within 17 min. cultured abalone reached an average shell length of 52.9 mm over 13 months, which translates to an increment of 4.1 mm.mon-1. the overall conclusion of these preliminary research trials confirms that h. mariae can be cultured successfully in oman. further studies on the standardization of the techniques would help in stock enhancement programmes and commercial farming. keywords: haliotis mariae, aquaculture, seed production, larval settlement, growth, oman introduction the abalone haliotis mariae (locally called as’sufailah) is endemic to the subtropical arabian sea coast of southern oman, where it inhabits interand subtidal rocky substrates down to 20 m depth (bosch and bosch, 1982; johnson et al., 1992). in this habitat, abalone shelter among rocks and in crevices during daytime and forage nocturnally. larger individuals al-rashdi and iwao 54 55 abalone, hatchery and seed production trials in oman occur in deeper areas than smaller animals (anon, 1984). the life cycle of h. mariae is related to the southwest monsoon driven upwelling that occurs from june to august (johnson et al., 1992), which decreases seawater temperature and increases nutrient concentrations (barratt et al., 1986). during the premonsoon (march-may) and monsoon period, the brown and red algae on which h. mariae predominantly feed are scarce or absent (barratt et al., 1984; jupp, 2002). in the post-monsoon months of september to february, abalone move into shallower waters to reproduce and feed (al-hafidh, 2006). females appear to spawn once a year with a peak spawning during december and january, and a gradual decrease during february and march as algae become scarce (al-hafidh, 2006). sea urchins appear to be a competitor for food (tripneutes gratilla) and living space (diadema spp.), and natural predators on abalone include scalloped spiny lobster (panulirus homarus), seastars (asterias spp.), octopus (octopus aegina), cuttlefish (sepia spp.) and finfishes like morays (gymnothorax spp.). a fishery for h. mariae is concentrated around sadah, with catches declining towards sharbithat in the east and mirbat to the west (fig. 1). the annual production of abalone from a two-month fishing season (table 1) was estimated at 50 t in 2006, valued at more than us$ 8 million (maf, 2007). figure 1. map of oman with important locations for abalone fisheries at dhofar region. al-rashdi and iwao 54 55 abalone, hatchery and seed production trials in oman economically, it has the highest yield per kg of all omani fisheries products. intense fishing by locals using free diving methods have led to sharp decline in catches, and abalone stock is presently regarded as overfished (al-hafidh, 2006). the aquaculture of abalone on a commercial scale has developed rapidly in several countries including the usa, mexico, south africa, australia, new zealand, japan, china, taiwan, ireland and iceland (hahn, 1989; gordon and cook, 2001). specific culture techniques need to be developed or adapted for each abalone species. the geography and subtropical climate of oman with warm clean coastal waters lends itself to aquaculture, and h. mariae furthermore has a unique yellow foot and excellent meat texture. given the high value of abalone products on international markets and the decline of wild stocks, the aquaculture of h. mariae in oman was investigated in a series of projects since 1994, the resources of which are available in several internaland unpublished reports (ogawa, 1994, 1997; iwao, 2000; al-rashdi, 2001; endo, 2005), but have not appeared in the peerreviewed literature. this paper reviews the progress of the abalone aquaculture trials in oman, with emphasis on the development of the culture facilities, hatchery and handling techniques, and constrains to the culture of h. mariae. materials and methods study site and culture system mirbat bay was selected as the site for the mirbat abalone seed production station (masps) based on several criteria. the bay is characterized as semitable 1. total catch (tons) and value (oman rial) data in the arabian abalone fishery, 1997-2006. (maf, 2007). year catch (t) value (o.r) 1997 40 2384330 1998 32 1703784 1999 29 1434116 2000 44 2249273 2001 51 2477000 2002 50 2597000 2003 56 3101000 2004 57 3146000 2005 49 2649000 2006 50 3171000 closed, opens to the arabian sea in an eastward direction, and is only moderately affected by wind and adverse sea conditions during the monsoon season. it has clean and unpolluted coastal waters. several seaweed species are available in the vicinity as abalone food, and mirbat town is close to markets and other existing infrastructure. a land-based (l-b) culture system with seawater pumped and filtered on a 24 h basis from 270 m offshore at a maximum capacity of about 120 t.h-1 (only 20 t.h-1 utilized) was installed. water was filtered to 40 µm to prevent invasion of fouling organisms. broodstock collection and conditioning h. mariae broodstock of 60–120 mm shell length (sl) were collected from the wild in may (pre-monsoon) and september (post-monsoon) by scuba diving during the daytime at depths of 5–20 m. care was taken not to damage the foot while dislodging them from the substratum. animals were transported to the hatchery within 4h using a cool box containing a wet sponge to absorb excretory products and ice to reduce temperature and metabolic rates. the total sl and weight of each abalone were measured using a vernier caliper (±0.1 mm) and electronic balance (±0.1 g). artificial conditioning trials were carried out in 1000 l capacity rectangular fiberglass tanks over 4month and 6-month periods, respectively for abalone collected before and after the monsoon period. densities in tanks were limited to 25-60 individuals per tank. inverted v-shaped glass reinforced plastic (grp) structures were placed at the bottom of the tanks as shelters. the water was filtered through three layers of sand and then recycled at an ambient temperature of 26–28oc. the water was re-circulated and re-filtered to allow microorganisms to eliminate ammonia, and aeration was provided. an artificial photoperiod (12l:12d) was maintained with a light intensity of approximately 150 lux at the bottom of the tank during the daylight hours. broodstock were fed daily with green alga, ulva fasciata, at a rate of 10% of the total body weight. a gonad maturity stage was defined by visual assessment as follows: stage (0) no gonadal development visible: stage (1) immature, with the level of the shell edge higher than the gonad coverage: stage (2) mature, with the level of the shell edge equal to the level of the gonad coverage: and stage (3) fully mature, with the shell edge lower than the gonad coverage (fig. 2). the collected broodstock had mostly immature gonads (stage 1) at the onset of conditioning. a maturity index was calculated as the average of individual gonad maturity stages in each month. al-rashdi and iwao 56 57 abalone, hatchery and seed production trials in oman spawning induction and fertilization spawning was induced following the method developed by kikuchi and uki (1975) for h. discus hannai in japan. broodstock were first exposed to the air for an hour and then immersed in filtered irradiated sea water with ultraviolet (uv) light at slightly elevated temperature (+3oc). the uv irradiation dose level used was 2400 m.w.h.l-1 at flow rates of 200 ml.min-1, distributed equally to ten 20 l aquaria. the broodstock were then left undisturbed and checked for spawning every hour for the first 3 h and then for every 30 min for a further 5 h. after spawning, eggs were siphoned out of the aquaria and filtered through a 300 µ mesh to remove unwanted particles, and the number of eggs was counted under binocular microscope by taking 5 ml sub-samples from egg water aquaria. fertilization was carried out according to hahn’s (1989) technique. eggs were maintained at the bottom of 20 l aquarium in a single layer (approximately 400,000 eggs in 2 l of water) and then fertilized with a mixture of sperms (100,000 sperm per ml) collected from several spawning males. the eggs and sperms were left for 15 min for fertilization. after all the fertilized eggs settled at the bottom, the upper water layer was decanted off and the fertilized eggs aquarium was refilled with filtered irradiated sea water. this washing process was repeated 10 times at intervals of 20 min (hahn, 1989). the fertilization rates were estimated by aliquot sampling (ebert and houk, 1984). aquaria were kept in the dark in an air-conditioned room until hatching. larval rearing the newly hatched trochophore larvae swim to the surface, leaving the egg debris and aberrant larvae at the bottom. the healthy trochophores were decanted immediately into separate sterilized aquaria to avoid bacterial contamination (hahn, 1989). the water level in the aquaria was made up to 15 l with filtered sterilized seawater. the rearing was undertaken until the larval shell was completely formed. primary film formation and larval settlement settlement and metamorphosis of h. mariae larvae were carried out on 0.33 m × 0.33 m polycarbonate transparent flat culture plates set as artificial substrates. the plates were first prepared by exposing them to a continuous through flow of sand-filtered seawater in outdoor tanks for less than 60 days. this process covers the plate surfaces with a primary film of organic material with a complex microbial community, mainly diatoms (hahn, 1989). five sets of 60 plates each were suspended vertically in two indoor rectangular fiberglass tanks (2.2 m × 1.2 m × 0.5 m) filled with filtered uv sterilized seawater, and the water level was adjusted to cover all plate surfaces. the metamorphic larvae were stocked at a density of 300 to 480 larvae per plate after which the water circulation was initiated at 300 figure 2. fully-mature abalone. a male having a milky white testis, while a female having a dark green ovary. al-rashdi and iwao 56 57 abalone, hatchery and seed production trials in oman l.h-1 through a perforated pipe along the tank bottom, and the water was aerated. changes in larval external morphology were studied by regularly cutting off small pieces of plates from 3 sets and examining the developing larvae under the microscope. after 7–15 days the settlement plates were transferred to outdoor circular tanks for further rearing. total survival was determined after one month by counting surviving juveniles. handling of juveniles and grow-out to detach thin-shelled juveniles for transfer between tanks or other purposes (hahn, 1989), 70% ethanol was diluted to concentrations of 1%, 2% and 4%, and the drop-off and recovery times of 10 juveniles (10–20 mm in size) were measured in each dilution. anova was used to compare the drop-off and recovery times between the three treatments (zar, 1996). juveniles produced at masps were maintained for 13 months at ambient temperature to assess growth rates. results and discussion the culture of abalone is a high priority project in oman, owing to the high value product and demand on international markets. wild stocks are overfished and food-limited during the monsoon season, and faster growth rates than in nature may be achievable through culture (johnson et al., 1992; shepherd et al., 1995). the maturity index of the broodstock collected in the pre-monsoon (may) increased between june and august, and all the individuals had mature gonads by the end of the period in december over a period of 6 months (fig. 3). the maturity index of breeders in the post-monsoon (september) samples increased over a shorter period and reached higher value in december over 60 days (fig. 3). after the spawning inducement in december, the samples were returned into conditioning tank and regained full maturity in february, over another 60 days (fig. 3). the postmonsoon group was collected from the wild at the onset of the reproductive season, and was presumably physiologically ready for maturation. regardless of figure 3. changes in the maturity index of h. mariae from the pre-monsoon (may) and post-monsoon (september) samples, and conditions for six months and two months, respectively, prior to spawning. al-rashdi and iwao 58 59 abalone, hatchery and seed production trials in oman the controlled conditioning methods applied in various abalone species, the result of shorter conditioning period achieved in our experiment (60 days) was better than that obtained with several abalone species (table 2). therefore, it is advantageous to collect broodstock in september, because the shorter conditioning time required will reduce costs. four spawning inducement trials were carried out successfully between december 1999 and april 2000 (table 3). spawning occurred mainly during nighttime at a temperature of 25–27°c. the pattern was similar to tropical abalone h. asinina in the philippines (capinpin and hosoya, 1995; fermin et al., 2000) and h. varia in india (najmudeen and victor, 2004). spawning in males occurred 3 h after immersion in uv-irradiated seawater; whereas, in females it was after 5 h. males spawned more frequently than females, which facilitated higher fertilization rates. the success rates of male and female spawning induction averaged about 63% and 11% respectively (see table 3). however, spawning success rate of 50% or more was obtained with female h. ruber and h. laevigata, using uv irradiation and temperature shock methods (grubert and ritar, 2005; daume, 2007). the low rate may have resulted from incorrect technique of uv stimulation (hahn, 1989) or the female broodstock not being sufficiently ripe for these stimulus (morse, 1984), thus technical modifications on female h. mariae spawning induction and further work on testing other spawning methods are required. the total number of eggs spawned in the four trials ranged from 0.59–2.8 million per female with a shell length of 60–80 mm. al-rashdi (2001) suggested that larger female h. mariae (>110 mm sl) can spawn as much as 5 million eggs. this compares well with other species: 5.2 million eggs in h. gigantea (yoo, 1989), 0.3 million in h. discus hannai (yoo, 1989), 0.2 million in h. diversicolor supertexta (chen, 1989) and 0.08 million in h. varia (najmudeen and victor, 2004). fertilized eggs were spherical and 200 µm in diameter (fig. 4). the fertilization rates varied between 72% and 98.6% (see table 3). hatching of h. mariae occurred 8 h and 25 min after fertilization at 23.6°c and 6h and 30 min at 24.7oc (ogawa, 1997), and the external morphology of larvae table 2. conditioning period of various abalone species. abalone species conditioning period (days) source haliotis mariae 60 this study haliotis discuss hannai 80 (uki and kikuchi, 1984) haliotis rufescens 90 (ault, 1985) haliotis discus 160 (kafuku and ikenoue, 1983) haliotis laevigata 90-120 (grove-jones, 1996) haliotis roei > 180 (freeman, 2001) table 3. data on the spawning success of haliotis mariae broodstock from the various trials. the number in parenthesis indicate the number of broodstock tested for each spawning trial. trial no. 1 2 3 4 date 13.12.99 16.12.99 23.01.00 01.04.00 water temperature (oc) 26 ♀ 2 (15) 25 ♀ 1 (17) 26.5 ♀ 2 (15) 27 ♀ 2 (17) no. of spawners ♂ 9 (11) ♂ 7 (12) ♂ 7(12) ♂ 6 (11) no. of eggs (104) 282 59 68.7 500 fertilization rate (%) 72.5 98.6 88.7 90.4 al-rashdi and iwao 58 59 abalone, hatchery and seed production trials in oman over the next 30 days, from hatching to plantigrade veliger stage, is shown in fig. 4. the laboratory observation of the h. mariae larval development indicated that there were no obvious differences between the external morphology of h. mariae larvae compared to h. discus hannai larvae (seki and kanno, 1977), except that h. mariae developed faster, presumably because of higher water temperatures (s.a. shepherd, personal communication). the survival rates from trochophore to plantigrade veliger figure 4. embryonic development of h. mariae from eggs to seed production {1: fertilized egg (200µm), 2: newly hatched out larva (trochophore, 210µm), 3: pre-settlement veliger larva, 4: metamorphosed larva, 5: newly settled larvae, 6: post-settlement larva with shell formation, 7: early juvenile with first respiratory pore in the shell (2.5mm, 30 days), and 8: a produced seed in the hatchery (25mm, 120 days)}. figure 5. the number of h. mariae veliger larvae and their survival rates from larval development to larval presettlement. al-rashdi and iwao 60 61 abalone, hatchery and seed production trials in oman larvae obtained from the four spawning trials and introduced to the settlement plates were low and varied between 35.9% and 73.7% (fig. 5). however, 90% has been recorded in several abalone species (hahn, 1989). it is presumed that the mortalities are due to suboptimal water management, handling methods and temperature fluctuations (hahn, 1989). at 25oc to 27oc, the trochophore larvae metamorphosed after 56 h and settled after 72 h from hatching (fig. 4). the survival of settled larvae is affected by the ingestibility and digestibility of the diatom which, in turn, depends on the species dominated in the biofilm (roberts et al., 1999). survival rates during the postsettlement period were generally low and variable (searcy-bernal et al., 1992). however, the survival of the settled larvae recorded in all our four trials ranged from 0.1–3.6% after one month (fig. 6). these low survival rates are generally a major problem in abalone seed production (ebert and houk, 1984; hahn, 1989), and were attributed to the inability to maintain the quality of diatoms (nitzschia, navicula, and cocconeis) species on culture plates for abalone settlement and subsequent feeding (mcshane, 1992; daume et al., 2004). growth of filamentous green algae and encrusted coralline algae on the culture plates and tank sides reduced diatom growth and quality in terms of space competition. similar observations have been reported in tropical species such as h. varia in india (najmudeen and victor, 2004), perhaps as a result of high light intensity (daume et al., 2004), which is also characteristic of oman. growth of juvenile abalone was enhanced at elevated temperatures, and had reached an average length of 2.5 mm.mo-1 at 26oc, in which its first respiratory pore was fully formed and visible to the naked eye (fig. 4). similarly, the first respiratory pore was visible after 27 days in h. varia at 27oc (najmudeen and victor, 2004) and 28 days in h. assinina at 27oc (singhagraiwan and sasaki. 1991), but after 8 weeks in h. rufescens at 15oc (ebert and houk, 1984) and after 43 days in h. midae (genade et al., 1988). anesthetized juveniles dropped off the culture plates after an exposure time of 10–14 min to 1% ethanol (12.5 ± 1.3 min, n = 10) but this drop-off period shortened significantly to 2–4 min at a 2% dilution (3.2 ± 0.9 min) and to 0.3-0.8 min at a 4% dilution (0.55 ± 0.15 min; anova f2,27= 476.7, figure 6. the numbers of h. mariae larvae settled, and their survival rates in each trial after one month from larval pre-settlement to larval post-settlement. al-rashdi and iwao 60 61 abalone, hatchery and seed production trials in oman p < 0.001). recovery times were 14.7 ± 1.9 min (at 1%), 10.4 ± 2.4 min (at 2%) and 9.0 ± 2.2 min (at 4%) (anova f2, 27= 35.5, p < 0.001). the later result is contrary to the expectation that recovery should take longer at higher concentrations of ethanol (hahn, 1989). nevertheless, the juveniles anesthetized with 4% ethanol did not resume feeding for three days, whereas feeding of the 2% group was apparently normal from the first recovery day. the drop-off and recovery times using 2% ethyl alcohol was similar to that found by hahn (1989), using ethyl carbonic acid, magnesium sulfate and chloral hydrate on juvenile abalone. after 13 months of rearing, juveniles reached an average size of 52.9 mm shell length (range 42–64.4 mm; fig. 7). these translate to an average growth of 4.1 mm.mo-1. stirn and al-hashmi (1996) reared abalone (<35 mm) collected from the wild in aquaria under closed water system and different diet regimens for 6 months, and obtained average growth of 4.8 mm.mo-1 with artificial diet, 3.3 mm.mo-1 with kelp. ogawa (1997) grew juveniles up to 1.5 mm.mo1 over 2 months of hatchery production. al-rashdi (2002) carried out a 1-month feeding experiment at masps using 28 mm juveniles fed with different diets, and obtained a growth rate of 6.39 mm.mo-1 with a formulated diet, 4.17 mm.mo-1 with frozen u. fasciata, and 1.17 mm.mo-1 with frozen brown alga n. zanardinii. these studies indicate that cultured h. mariae can grow fast on formulated diets, and also when fed fresh and frozen u. fasciata. conclusion artificial hatching and seed production of h. mariae have been achieved in oman, but several challenges remain, such as locating wild abalone that are ripe enough to be spawned, improving broodstock conditioning protocols, and improving spawning success particularly for females. the low survival and settlement rates during larval development are the most important impediments to large-scale commercial aquaculture, nevertheless, the preliminary research trials described in this paper confirms that h. mariae can be cultured successfully in oman. further studies on the standardization of the culture techniques would help in stock enhancement programmes and commercial farming. acknowledgements the authors would like to express their sincere thanks to joji ogawa who developed the research proposal of the masps, and to mohamed bal-khair and ali al-mishaikhi for technical participation in masps activities. thanks are also due to johan groeneveld, armando fermin and fahad al-ajmi for reading the manuscript, and to saud al-habsi for his encouragement. this study was financed by the figure 7. the average monthly the shell length (± s.d.) of cultured omani abalone, h. mariae produced at masps in 1999-2000. sample size is shown above each measurement. al-rashdi and iwao 62 63 abalone, hatchery and seed 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___________________________________________ *corresponding author. e-mail: hemkot@squ.edu.om adoption of e-commerce in the agricultural and fisheries business sector in oman zahra al-busaidi1, hemesiri kotagama1*, houcine boughanmi1, sunil dharmapala2 and john waelti1 1 department of natural resource economics college of agricultural and marine sciences, sultan qaboos university p.o. box 34, al-khod 123, sultanate of oman 2department of business statistics, college of commerce and economics, sultan qaboos university, p.o. box 20, al-khod 123, sultanate of oman abstract: small and medium businesses (smb) have substantial potential to contribute to the growth of an economy through adoption of business related information technology. the agricultural and food business (afb) sector in oman is dominated by smbs. factors influencing the adoption of e-commerce in the afb sector in oman were analyzed. the main hypothesis was that scale of the business influenced the adoption of e-commerce. data were obtained from a random sample (n = 31) of afbs in oman and was analyzed using a probit regression model. the dependent variable was whether the firm had a website, a proxy measure of adoption of e-commerce. the main independent variables were the scale of the business (measured by number of employees) and the scope of the business (international or national) and of variables related to manager’s perception of benefits of adopting e-commerce. it was found that 94% of afbs in oman used computers and about 52% of those had websites. the r-squared, of the estimated probit regression model was 0.65. the hypothesis that scale of the business influenced the adoption of e-commerce was not rejected, as the coefficient of the business scale variable was statistically significant (t = 2.5, n = 31). the likelihood of adoption increases with increased scale of the business. on the converse this suggests that the likelihood of adoption of e-commerce by small and medium businesses is lower. given the importance of small and medium businesses in the development of particularly the afb sector of oman, policy maker would have to promote and provide incentives to adopt e-commerce by smbs. keywords: e-ecommerce, adoption, agricultural and fisheries business, probit model. introduction the government of oman has embarked on a policy of economic diversification with an emphasis on improving the productivity of the agricultural and fisheries sector (international trade center, 2001). the agricultural and fisheries business (afb) sector in oman is considered to consist predominately of small and medium businesses (smb). the government of oman has recognized the potential of the smbs to contribute to development, in terms of economic growth and job creation. however, the growth of the smb has been lower than expectations (bank muscat, ud. االعمال قطاع في االلكترونیة التجارة اعتماد عمان الزراعیة والسمكیة في كوتقاما١ وھمسیري البوسعیدي زھرة والتي دھرمبال٢وجون وسونیل وحسین البوغانمي١ والمتوسطة الصغیرة المؤسسات وتمثل األعمال. إدارة في المعلومات تكنولوجیا عبر اعتماد االقتصادي النمو في للمساھمة كبیرة قدرة الصغیرة والمتوسطة الخالصة: للمؤسسات أن فرضیة من والغذائیة انطالقا الزراعیة األعمال قطاع في المعلومات تكنولوجیا تبني في المؤثرة العوامل تحلیل إلى الدراسة ھذه الزراعة واألغذیة. ھدفت قطاع في الجزء األھم بروبیت، نموذج باستعمال تحلیلھا ووقع والغذائي الزراعي القطاع في تعمل شركة تمثلت في ٣١ عشوائیة عینة الدراسة استعملت التبني. ھذا في ھاما دورا یلعب المؤسسة حجم المؤسسة صاحب إدراك محلیة) و أو ومجال العمل (عالمیة العمال) (عدد الحجم متغیرات تمثل بینما ال، أم االنترنت شبكة في موقعا تملك أن المؤسسة ھل ھو فیھ المؤثر المتغیر على الدال المعیار قیمة االنترنت. في موقعا ٥٢٪منھا تملك بینما حاسوبا تملك من المؤسسات ٪٩٤ أن الدراسة نتائج تشیر المؤثرة. المتغیرات أھم من المعلومات تكنولوجیا بمنافع بقدر تكبر المعلومات تبني تكنولوجیات إمكانیة أن على یدل وھذا المعلومات. تكنولوجیا تبني في ھاما إحصائیا مؤثرا كان الحجم متغیر أن أھم النتائج ومن .٠,٦٥ تساوي العالقة قوة ھذه على تشجیع یعملوا صانعي القرار أن على فیجب األغذیة صناعة في نسیج الطاغیة ھي الصغیرة والمتوسطة المؤسسات أن وبما بالعكس. والعكس كبیرا المؤسسة حجم كان ما المعلومات. تكنولوجیات تبني على المؤسسات بروبيت. منوذج والسمكية، الزراعية االعمال التبني، االكترونية، التجارة كلمات مفتاحية: 41 al-busaidi and others 42 adoption of e-commerce in the agricultural and fisheries business sector in oman 43 quoting a world bank study). it is argued that adoption of business related information technology (it) could provide small business companies with a competitive edge, which arises from improved management in general and linkages to global markets (al-qirim, 2004). despite the national policy emphasis to promote the adoption of it in various spheres of the economy, studies on the adoption processes of it in oman are not yet available. this study assesses the factors underlying the adoption of e-commerce in the afb sector in oman. the paper is organized into five sections. the second section presents a brief literature review on the definition of e-commerce, benefits of e-commerce and factors that influence the adoption of e-commerce in the afb sector. section three presents the conceptual framework and the analytical methodology adopted in the study. section four discusses and presents descriptive and statistical results of the analysis. section five presents the conclusion and policy recommendations emanating from the study. significance and determinants of adoption of ecommerce it is playing a significant role in promoting global economic growth. efficiency of economic activities, particularly in a market economic context, depends on access to information. access to relevant information empowers producers and consumers to make rational decisions, avoid information asymmetries thus improving market efficiency and social welfare. industrial, service and agribusiness are all pursuing to adopt it to gain competitive advantages. the major benefit of adopting ecommerce is the reduction of transaction costs in business. henderson, et al. (2000) indicated that companies could expect to reduce spending by 9% with business-tobusiness (b2b) procurement. e-commerce allows the possibility to explore a larger and more geographically diverse customer base (henderson, et al., 2000 quoting garcia, 1995). e-commerce provides consumers with more choices and more control over purchasing decisions (mcfarlane, et al., 2003). this improves the efficiency of the functioning of the market, leading to reduced prices too. it encompasses forms of technology used in accessing, creating, storing, analyzing, exchanging and presenting information. the application of it, particularly the use of the internet in businesses activities has been broadly referred to as e-business. e-commerce is considered as a subset of e-business limited to the sale or purchase of goods and services over the internet (henderson, et al., 2003). chambers, et al. (2001) defined e-commerce as any business activity that uses the internet. further, according to mcfarlane et al. (2003), these business activities could be conducted between businesses (b2b), businesses and consumers (b2c) and public sector and consumers. economic and social commission for western asia (2003) defined e-commerce as everything which relates to doing business using internet or any electronic network. luecker (2000) identified agriculture as one of the top three sectors for growth in e-commerce. despite this potential, the adoption rates of e-commerce within the agribusinesses have been relatively low vis-à-vis industrial and service businesses (henderson, et al., 2000 and 2003; mcfarlane, et al., 2003; gul, et al., 2004). the united state department of agriculture in the national agricultural resources management study has shown that 29% of farms in the united states had internet access and 15% of those had conducted some business over the internet (ehmake, et al., 2001). a survey done by intertec (1999) reported that among high-income farmers in the us, 38 % have been using the internet for e-mail, business, or to obtain information. only a small fraction (less than 5%) had made on line purchase. other research indicates that about 40 % of farm households in both canada and the us use the internet, with about 30 % of the use being specific to farming operations, and the remaining 70% for general information and entertainment purposes (intertec, 1999). hopkins and morehart (2001) reported that the use of computers on farms has grown from 38% to 55% since 1997, while internet use has grown from 13% to 43%. as reported by gregor, et al. (2002) quoting muller (2001), in germany 78% of farmers use internet for banking, 28% use it to purchase goods and 19% use it for selling goods and in australia small businesses use it for communication via e-mail (82%), to seek information about products (67%) and get research data (65%). henderson, et al. (2000) having examined adoption of e-commerce in canada concluded that the major factors that influence the adoption of e-commerce by agribusinesses are the size of the firm and the international market scope of the firm. in addition, perceived efficiency benefits in specific functions (promotion and logistics) of the supply chain are significant factors explaining the adoption of e-commerce. the perception of ability to improve inventory management and increase sales is also a factor that contributes to improved adoption of e-commerce. they have concluded that most of the ecommerce is within b2b rather than b2c. ehmke, et al. (2001) have studied the market for e-commerce services in agriculture in the state of ohio in the usa. they reported that farmers do not have sufficient human capital and the affordability to adopt e-commerce. furthermore, farmers may be resistant to change due to a commitment to tradition. they have also identified poor internet connectivity in rural areas to be constraining the adoption of e-commerce in the agricultural sector. leroux, et al. (2001) have identified 3 factors that hinder adoption of e-commerce in agribusiness. these factors relate to the change in industry structure, product complexity and the personalized nature of transactions in agriculture. the consolidation of agribusinesses leads to a reduction in electronic coordination of fragmented markets, and large businesses may create barriers to the development of transparent electronic market places. agricultural products are naturally diverse in quality and hence an adequate description is far from possible through electronic media. this complexity is further aggravated by consumer-preference changes for healthier foods, al-busaidi and others 42 adoption of e-commerce in the agricultural and fisheries business sector in oman 43 convenience, and diversity in food consumption. it has been argued that business relationships in the afb sector to be more of one to one personalized relations and this would remain to be a barrier to adoption of e-commerce with non-personalized relationships. gregor, et al. (2002) have examined the factors influencing the adoption of ecommerce in agribusiness in queensland, australia and they reported that among the reasons for the nonuse of e-commerce were the concerns about security and costs. they also reported that the primary reasons for engaging in e-commerce among australian food companies include expansion of the sales base, efficiency, and keeping up with competitors. the primary reasons that inhibit adoption of e-commerce are: lack of personal contact, the ability of people to hack into the system, the unwillingness of customers to transact through the net, the perception of customers that the are not ready for e-commerce and the lack of expertise and knowledge. in addition, gloy and akridge (2000) included age and education of farmers as important factors that determine the adoption of ecommerce in the us. according to mcfarlane et al. (2003) the lack of privacy in e-commerce transactions was a major barrier to adopt e-commerce. further firms with an international scope had a higher probability of adoption of e-commerce. the type of the product too substantially influences the adoption of e-commerce. firms that sell products such as seed, feeds, grains and crops’ inputs, and services such as consulting and financial services are more likely to adopt e-commerce. in this study the size of the firm was also found to be significantly influencing the probability of adoption of e-commerce. henderson et al. (2000) have reported similar results. driedonks, et al. (2003) have studied the economic and social factors that relate to slow adoption of electronic media in b2b in the australian beef industry. they have used two theoretical models, namely kambil and yan heck’s model of exchange process and roger’s diffusion theory. they concluded that perceived benefits of adoption have a larger influence on decision to adopt than the real economic benefits of adoption. the factors that delay the adoption of electronic markets are the loss of social capital (traditional ways of trading) and time taken for electronic market users to achieve critical mass. henderson, et al. (2003) have examined e-commerce adoption in canada. firms that perceive higher benefits from logistical and inventory management through e-commerce are more willing to adopt it. pearson and grandon (2003) upon studying perceived strategic value and adoption of e-commerce in small and medium business in usa confirmed the findings of previous researchers that the perceived benefits from e-commerce adoption is a significant factor explaining adoption rates. furthermore, they also found that other factors such as external pressure from the industry, organizational readiness to adopt are significant factors relating to adoption of e-commerce. canavari, et al. (2003) having surveyed 208 agribusiness firms in italy at all stages of the supply chain concluded that the level of adoption was low and particularly that small firms have not realized an advantage of its adoption. most firms use the internet more as a promotional tool and not as a selling and buying tool. analytical methods the main objective of this study was to establish the factors that cause adoption of e-commerce in afbs in oman. past studies suggest that adoption of e-commerce would depend on internal factors that relate to the individual (owner or manager of the business) such as perception of benefits of e-commerce; the nature of the businesses such as whether b2b or b2c; and external factors such as government policy, legal aspects and supporting public infrastructure. acknowledging the significance of small and medium business, particularly in afb sector in oman, a crucial factor that is of policy interest is the relationship of scale of the business and adoption of e-commerce. if one considers it as scale neutral, it could be expected that likelihood of adoption of e-commerce would be the same among small, medium and large businesses. henderson, et al. (2000) have presented a model to assess adoption of e-commerce which largely considered that adoption is dependent upon perceived benefits of e-commerce on supply chain functions. an objective of a business firm is to improve efficiency through reducing the transaction costs on the supply chain functions. a supply chain performs seven functions. the seven functions include; manufacturing, logistics, promotion, financing,. information, transaction and negotiation. if the use of e-commerce is perceived to be able to improve the efficiency of these functions, the likelihood of adoption of e-commerce by afbs would be high. in this framework, the level of e-commerce adoption is a function of the perceived efficiency gains from the adoption of ecommerce in any of the seven functions of the supplychain. in this study, the henderson et al. (2000) model was used with specific inclusion of the scale and scope of the business as internal factors that influence adoption of e-commerce. the external factors that influence adoption of e-commerce such as government policy, legal aspects, availability of supporting infrastructure were considered as constant.the notational representation of the above explanation is given in equation 1. ad = f (m, l, p, f, i, t, n, gb, sb) (1) where, ad is a measure of e-commerce adoption. the variables m, l, p, f, i, t and n are measures of the perceived efficiency gains in the specific functions of the supply-chain due to adoption of e-commerce. these functions represent, respectively, manufacturing (m), logistics (l), promotion (p), finance (f), information (i), transaction (t) and negotiations (n). gb is scope of business (international or national) and sb is scale of al-busaidi and others 44 adoption of e-commerce in the agricultural and fisheries business sector in oman 45 business measured as the number of employees. based on the conceptual model presented above the following specific hypotheses were formulated: (i) probability of adoption of e-commerce is higher among larger businesses than smbs; (ii) probability of adopting e-commerce is higher among business with international transactions than business with national transactions; and (iii) probability of adopting e-commerce is higher among business where managers perceive benefits in improving supply chain functions with adoption of e-commerce. since the dependent variable is non-continuous, the probit model was used to estimate the relationship between adoption and factors hypothesized as influencing adoption. firms were categorized into e-commerce users and non-users. non users are firms which did not have a website and users were firms that had a website and used e-commerce in their normal business activities such as advertising, checking the mail and other advanced features, including online ordering or online ordering and payment. perception of benefits of adoption of e-commerce was obtained based on questions that related to a change in a function on the supply chain with the adoption of e-commerce. responses were recorded on a 5-point likert scale and were used as a continuous variable in the analysis following gregor, et al. (2002). the firms were categorized based on the number of the employees following henderson, et al. (2003) and gul et al. (2004). the scope of the business was established based on whether major business activities relate to national or international markets. the probit model is an extension and an improvement of the linear probability model, which in the context of ecommerce adoption takes the following regression form: (2) where xi is a set of independent variables representing the value of attributes of the ith firm and α and β are parameters to be estimated. random error εi follows normal distribution with mean 0 and constant variance σ2. the dependent variable yi is a binary variable, which takes the value of 1, if the company has a website and 0 if the company has no website since the expected value yi, e (yi)= p (y = 1), equation 2 above can be interpreted as describing the probability p (y = 1) that a company will choose to have a website, given the information about the company’s characteristics and managers attitude and opinions. the slope of the regression line measures the effect on the probability of adopting e-commerce of a unit change in the company’s attributes. however, a weakness of the above linear probability model is that predicted values of yi may lie outside the (0, 1) range, which is not possible if they are to be interpreted as probabilities. the solution to this problem is to transform the original model in such a way that predictions will fall in the (0, 1) interval for all x. the basis of the transformation is to translate the values of the attributes x, which may range in value over all the entire real line, to a probability, which range from 0 to 1 (see griffith et al., 1992). this suggests the use of a cumulative probability function that may be presented as: (3) where f is a cumulative probability function and zi is an unobservable index related to the choice of whether to have or not have a website and which is a random variable. if the cumulative probability function is normal then we have the probit model1, which takes the following standardized form for a particular value z. (4) where z is a random variable, which is normally distributed with mean zero and unit variance. by construction, the variable pi will lie in the (0, 1) interval, representing the probability of the company‘s having a website. since this probability is measured by the area under the standard normal curve from zi, the event of having a website will be more likely to occur the larger the value of the index zi. in the probit model the conditional probability that a company will adopt-e commerce, given its attributes xi is equivalent to the probability that a standard normal variable will be less than or equal to α + βxi. the probit model is fundamentally non-linear and therefore estimating the parameters using ordinary least squares (ols) is inappropriate (judge et al., 1981). the use of ols leads to unbiased but inefficient estimators. probit models are usually estimated using maximum likelihood estimation technique, which now is routine in most modern econometric packages. ninety afb firms were randomly selected from the business directory of oman (2003). based on the business firms listed in the business directory of oman about 5% are afbs. of the afbs 39%, 18% and 42% are businesses supplying inputs in production and in marketing agricultural and fisheries products, respectively. the sample was stratified proportional to the above-mentioned types of businesses. data was obtained based on a questionnaire, which was faxed or mailed to the 90 firms. with 31 firms responding, the rate of response of the survey was 34.3%. this compares well with similar studies such as gregor et al. (2002), henderson et al. (2000), and mcfarlane et al. ��� ��� ��� �� � � � ������ � ___________________________________________________________________________________________________ 1if the cumulative probability function is logistic, then we have the logit model. al-busaidi and others 44 adoption of e-commerce in the agricultural and fisheries business sector in oman 45 (2003), which reported a response rate of 38.5%, 19.1%, and 29%, respectively. analysis descriptive analysis of the afbs that were surveyed 45.2% were involved in production and/or marketing consumer products, 16.1% were involved in marketing inputs to farms, 29.0% were marketing both farm inputs and consumer products and 9.7% provide consultancy services related to afbs. most of the firms were smbs. twenty nine percent of the firms employed up to 25 employees, 10% employed 26 to 50, 23% employed 51 to 100, 38% employ more than 100 employees. it was revealed that 19% of the firms were public, 77% are privately owned, and 1% was cooperatives and 3% had not responded. most of the firms that responded to the survey were b2c. about 80% of the firms were involved with international business activities. only 6 percent of firms did not use a computer. this compares well with the level of computer use in queensland, australia, where 95% of agribusiness are reported to have computers (gregor et al., 2002). fifty percent of the surveyed firms had a web site and adopted e-commerce. probit regression analysis as indicated earlier, the dependent variable represents whether a firm has a website (y=1) or not (y=0). the independent variables that were used are given in table 1 with their expected signs. the estimated statistics of the probit model are given in table 2. the estimated model has a reasonably high r-squared (0.65) indicating that the selected variables explain about 65% of the variation in adoption of ecommerce. among all the variables included in the model, only z1, which is the size of firm, was significant at 5% level of significance. thus the analysis suggests that the only variable that significantly influences the adoption of ecommerce is the size of the company. larger companies are more likely to adopt e-commerce than small and medium business. the small and medium afb firms in oman, which are significant contributors to growth of table 1. variables of the probit model and hypothesized signs. variable description nature of quantification hypothesized sign dependent y whether having a website or not. have =1 or no = 0 independent manager’s perception supply chain function x1 logistics e-commerce improves firm’s ability to mange inventory 1likert scale 1-5 (continuous) x2 information e-commerce enables easier access to business information. likert scale 1-5 (continuous) x3 promotion internet provides limited ability to communicate product information. likert scale 1-5 (continuous) x4 negotiation personal relationships with customers are difficult to develop over the internet likert scale 1-5 (continuous) + x5 transaction e commerce reduces security of transactions. likert scale 1-5 (continuous) + x6 promotion e-commerce makes product comparison easier. likert scale 1-5 (continuous) x7 negotiation people/customers lack the required trust to use ecommerce likert scale 1-5 (continuous) + type of business z1 size of firm (in number of employees) 2likert scale 1-5 (continuous) + z2 business scope of firm 1 = international or 0 = domestic + 1. likert scale on manager’s perception: 1= strongly agree 2 = agree 3 = unsure 4 = disagree 5 = strongly disagree 2. likert scale for size of firm: 1 = 1 to 25 employees 2 = 26 to 50 employees 3 = 51 to 100 employees 4 = 101 to 500 employees 5 = more than 500 employees al-busaidi and others 46 adoption of e-commerce in the agricultural and fisheries business sector in oman 47 the afb sector, have not been able to adopt and benefit from e-commerce despite substantial public investments on information technology. benefits of it could be best achieved only if a critical mass of business adopts the technology. hence the government of oman needs to encourage small and medium businesses to adopt ecommerce. conclusion the major variable that explains the adoption of ecommerce is the scale of the business. the findings of the study highlight the need for the government to undertake measures to promote e-commerce, among smbs, such that business productivity improves and returns to public investments on information technology is optimized. these recommendations are congruent with the recommendation by the escwa (2003) on development of e-commerce sectors in the arab region. references al-qirim, n.a.y. 2004. electronic commerce in small and medium sized enterprises: frameworks, issues and implications, idea group publishers. business directory of oman 2003. chamber of commerce, sultanate of oman. driedonks, c.f., s. gregor and a. wassenaar. 2003. economic and social analysis of the adoption of b2b electronic marketplaces. a case study in the australian beef industry. international journal of electronic commerce 9:49-72. escwa. 2003. economic and social commission for western asia secretariat. development of ecommerce sectors in the arab regions. beirut. http: //www.escwa.org.lb/wsis/conference/documents/19-ebusiness.pdf. ehmake, c., s. ernst, j. hopkins and l. tweeten. 2001. the market for e-commerce services in agriculture selected paper for the aaea annual meeting, chicago, illinois. http://www.agecon.purdue.edu/cab/research/ articles/ecommarket.pdf. goly, b.a. and j.t. akridge. 2000. drivers of internet adoption on large u.s farms and implications for agribusiness. presented at 2000 iama world food and agribuisness forum, chicago, illinois. htttp: //www.ifama.org/conferences/2000congress. gregor, s., d. menzies and j. rolfe. 2002. influences on engagement in e-commerce in agribusiness: an empirical study. itira conference, rockhampton, 27-28 august, pp285-296. http://ecocomm.anu.edu.au/ disciplines/ecom/etpaper2.pdf. griffiths, w.e., r.c. hill and g.g. judge. 1981. learning and practicing econmometrics. john wiley and sons. inc, usa, gul, a., s. mutlu and t. bal. 2004. information in food industry in cukurova of turkey. information technology journal 3(2):133-138. henderson, j., f. dooley and j. akridge. 2000. adoption of e-commerce strategies for agribusiness firms. selected paper at the american agricultral economics accosiation annual meeting, tampa, fl. http://www.agecon.purdue.edu/cab/research/articles/ ecommerce.pdf. henderson, j., dooley, f. and akridge, j. 2003. internet and e-commerce adoption by agricultural firms. paper table 2. results of the probit analysis. estimate standard error tstatistic r2 0.65321 constant -7.4998 4.3515 -1.7234 independent variables description manager’s perception x1 e-commerce improve firm’s ability to mange inventory 1.1675 0.7330 1.5927 x2 e-commerce enables easier access to business information. 1.2590 0.7700 1.6349 x3 internet provides limited ability to provide product information. -0.7015 0.4872 -1.4398 x4 e-commerce makes maintaining personnel relationship difficult. -0.7486 0.8439 -0.8870 x5 e commerce reduces security of transactions. -0.5032 0.6286 -0.8005 x6 e-commerce enables product comparison easier. -0.3122 0.5046 -0.6188 x7 people/ customers lack the required trust to use e-commerce 0.3829 0.5172 0.7403 type of business z1 size of firm (in number of employees) 1.3035 0.5201 2.5059 z2 business scope of firm 2.0168 1.5717 1.2832 al-busaidi and others 46 adoption of e-commerce in the agricultural and fisheries business sector in oman 47 presented at the rss 2003 annual meeting, montreal, c a n a d a . h t t p : / / w w w. r u r a l s o c i o l o g y. o rg / a n n u a l meeting/2003/hendersonjason.pdf. hopkins, j. and morehart, m. 2001. economic research service, united states department of agriculture. http:/ /www.ers.usda.gov/publications/agooutlook/nov2001/ ao286f.pdf. international trade center. 2001. an overview of the managerial concerns in international trade: economic and trade policy issues, a background note. paper presented as kick-off meeting, sultanate of oman, muscat. http://www.intracen.org/worldtradenet/docs/ networking/country_papers/paper_oman.pdf. intertec publishing corporation. 1999. a2k ag beyond 2000. http://www.ifama.org/conferences/2000congress/ f o r u m % 2 0 % f i n a l % 2 0 pa p e r s / a r e a % 2 0 i i i / thompson_shelly2.pdf. leroux, n., s. wortman jr. and e. mathias. 2001. dominant factors impacting the development of business to business (b2b) e-commerce in agriculture. paper presented at the international food and agribusiness management association, world food and agribusiness symposium, australia, june 27-28, 2001. http://www.ifama.org/conferences/2001conference/ papers/area%20iii/leroux_nicole.pdf. little, d. 2000. old macdonald has a web site, business week e.biz, may 15, pp83-88. mcfarlane, d., d. chembezi and j. befecadu. 2003. internet adoption and use of e-commerce strategies by agribusiness firms in alabama. department of agribusiness. alabama a&m university. paper presented at the southern agricultural economics association annual meeting, mobile, alabama. http://www.webspace.aamu.edu/ smallfarmers/agb200308.pdf. muller, r.a.e. 2 001. e-commerce and enterpreneurship in agricultural markets. american journal of agricultural economics 83:1243-1249. pacific access. 2001. yellow pages business index small and medium enterprises survey of computer technology and e-commerce in australian small and medium businesses. telstra corp, july. http://www.about.sensis.com.au/ media/pdf/sba-archive/sba/tae/_yellowpagesspecial report_ecommerce_may99.pdf. received: may 2008 accepted: march 2009 agricultural and marine sciences, 13:23-32 (2008) ©2008 sultan qaboos university 23 *corresponding author. e-mail: alnahdi22@hotmail.com length-weight relationships, maturity, and reproductive season of the fringelip mullet crenimugil crenilabis (forsskål, 1775) from the arabian sea coast of oman 1 marine science and fisheries centre, p.o. box 227 pc 100, muscat, sultanate of oman 2ministry of fisheries wealth, p.o. box 427 pc 100, muscat, sultanate of oman abstract: fringelip mullet (crenimugil crenilabis) caught at al-duqum and salalah in the arabian sea region of oman were sampled monthly between january 2001 and december 2002. the total length (tl) of mullet caught with gilland seine nets ranged from 12 to 54.5 cm (32.4 cm mean ± sd; n = 2445) but <2% of specimens had a tl<24 cm, suggesting gear selectivity. females dominated samples (1 : 0.36) and reached l50 at 32.8 cm tl (32.2 cm in males). length weight relationships were non-linear and conversion factors between tl, fork length (fl) and standard length (sl) were calculated. proportionately, most females had ripe gonads in september and october, and males in september to november. both female and male gonadosomatic indices (gsi) peaked in september and october and were lowest between may and august. the peak in reproductive activity coincides with the fall intermonsoon, when the arabian sea upwellings caused by the onshore winds of the sw monsoon season (june to august/september) retreat. during this intermonsoon period the inshore water temperatures begin to rise after reaching a minimum in august/september. some reproductive activity also occurs in other months, particularly february, when water temperatures are seasonally lower. keywords: crenimugil crenilabis, reproductive season, length-weight relationships, oman. abdullah al-nahdi*1, abdulaziz al-marzouqi1, said al-shajibi1 and ahmed al-hosni2 بحر العرب ساحل في البیاح لسمكة التكاثر وموسم التناسلي والنضج بالوزن، عالقات الطول عمان بسلطنة وأحمد الحوسني الشجیبي سعید ، المرزوقي عبدالعزیز عبداهللا النھدي، خالل شھریًا بحر العرب على وصاللھ الدقم منطقتي (crenimugil crenilabis) في البیاح سمكة عینات أخذت تم الخالصة: وشباك الخیشومیة بالشباك تصاد التي البیاح ألسماك الكلي الطول أن واتضح . 2002 دیسمبر شھر إلى 2001 ینایر من الفترة طول لھا العینات من %2 من أقل أن واتضح عینة). 2445 لعدد سم 32.4 الطول (متوسط سم 54.5 إلى 12 بین ما تتراوح الضواغي بنسبة على الذكور النوع لھذا اإلناث أعداد وسادت الصید. وسائل من النوع ھذا انتقائیة على مؤشرا یعطي سم مما 24 من أقل كلي البیاح لسمكة الطول بالوزن عالقة أن سم. تبین 32.2 وللذكور سم 32.8 إلى لإلناث تناسلي نضج عند أول الطول ویصل .(0.36:1) جنسیًا اإلناث ناضجة أغلب تكون عام والمعیاري. وبشكل الشوكي والطول الكلي بین الطول التحویل عامل إیجاد تم وقد خطیة. غیر الجنسین مرتفعا خالل لكال (gsi) النسبي التناسل وكان وزن نوفمبر. سبتمبر إلى من والذكور إلى أكتوبر سبتمبر من الفترة خالل الغربیة الجنوبیة الریاح موسم مع في نشاط التكاثر االرتفاع ویتزامن وأغسطس. مایو بین كانت األقل بینما وأكتوبر سبتمبر شھري درجة الموسمیة تبدأ الریاح فترة وخالل أغسطس/ سبتمبر. إلى یونیو من الفترة خالل للمیاه القاعي االنبعاث عندما یحدث العرب لبحر التكاثر أنشطة من بعض كذلك ویحدث وسبتمبر. أغسطس شھري في مستویاتھا أقل إلى تصل ما بعد باالرتفاع الضحلة المیاه حرارة مواسم الشتاء. في الحرارة درجة تنخفض عندما فبرایر في وخاصة أخرى في أشھر الجنسي al-nahdi and others 24 25 length-weight relationships, maturity and reproductive season of the fringelip mullet material and methods catches made by traditional fishers at al-duqum and salalah (fig. 1) were sampled by marine science and fisheries center (msfc) staff between january 2001 and december 2002. random samples from al-duqum were measured to determine lengthweight relationships and conversion factors. length measurements were made to the nearest 0.1 cm of total length and all mean values were reported ± sd. (tl; from the anterior tip of the snout to the posterior tip of the caudal fin, with the caudal fin lying straight and not in its natural position), standard length (sl; anterior tip of the snout to the anterior base of the caudal fin rays) and fork length (fl; anterior tip of the snout to the anterior margin of the fork in the caudal fin), and total weight was determined to the nearest 1 g on an electronic balance. non-linear length weight regressions (tw = atlb) were calculated for males, females and both sexes combined using a least squares fit, and regressions were compared using ancova test (zar, 1984). linear regressions of tl versus sl and tl versus fl were calculated to determine conversion factors. monthly subsamples (approximately 40 specimens, randomly selected) were collected at alduqum, and the gonads removed, sexed and weighed to the nearest 0.01 g. these gonads were classified into six macroscopically distinguishable stages for females and four stages for males (table 1). to calculate the size at which 50% of females reach sexual maturity (l50), the proportions of females with ovaries in stages 2-5 per 2-cm size class were fitted to a logistic equation of the form: p = 1 (1 + exp (a-btl) where p is the proportion of mature females in each length class, tl is total length, and a and b are constants. the best fit model was obtained by minimizing the sum of squares, and the length at 50% maturity was determined by back-calculation. the same method was used to calculate the male l50, using the grouped stages 2-4 as the mature proportion in each length class. a gonadosomatic index (gsi; mean ± sd) was calculated for females and males respectively for each month as follows: gsi = gw / tw ×100. the liver of each fish was weighed (lw ± 0.01g) and the hepatointroduction the fringelip mullet crenimugil crenilabis (forsskål, 1775) is a coastal species from the tropical waters of the indo-pacific, mainly between 32os and 32on, and shallower than 20 m depth (fischer and bianchi, 1984). single individuals or small schools occur over coral reefs and reef flats, and in lagoons with sandy or muddy substrata and harbours, and juveniles are sometimes found in tide-pools (al-abdessalaam, 1995; randall, 1995). crenimugil crenilabis is one of at least 11 mullet species known from the coastal waters of oman (al-abdessalaam, 1995), where they are caught by fishers using non-selective gilland seine nets, often from small fiberglass boats with outboard engines. government statistics show that the annual catches of mullets have increased from 123t in 2000 to 839t in 2005, however detailed catch-by-species statistics are unavailable for the mugilidae (anon, 2006). nevertheless, c. crenilabis is common in fish markets and in biological samples collected by fisheries observers at landing sites, and it therefore makes up a substantial proportion of mullet catches. of the total mullet catch from oman in 2005, 58% came from the gulf of oman and the rest from the arabian sea (anon, 2006); the latter fishery is seasonal, declining sharply over the sw monsoon period (may-august). very little information is available on the general biology of c. crenilabis in the primary literature. it attains a maximum size of 50–55 cm (al-abdessalaam, 1995; randall, 1995), and feeds on detritus containing algae and microscopic animals by scooping up the upper sand or mud layers and filtering through the gills . reproduction is oviparous and eggs are pelagic and non-adhesive (breder, and rosen, 1966). helfrich and allen (1975) observed spawning in large aggregations near the surface at night, at the beginning of an ebb tide in june. this observation was made over shallow open areas of a lagoon slope at enewetok atoll in the marshall islands. apart from the above, the basic biological parameters that are fundamental to the management of exploited fish populations are unknown for c. crenilabis in oman. the aims of this study were to determine the length-weight relationships, conversion factors among various length measurements, size composition of captured fish, size at reaching sexual maturity and reproductive season of c. crenilabis from the arabian sea coast of oman. al-nahdi and others 24 25 length-weight relationships, maturity and reproductive season of the fringelip mullet figure 1. the sampling sites along the arabian sea coastline. ar ab ia n se a al-nahdi and others 26 27 length-weight relationships, maturity and reproductive season of the fringelip mullet size of 32.4 ± 4.4 cm (s.d) (n = 2445). less than 2% of samples comprised fish < 24 cm tl, suggesting that the gear used to catch mullets select fishes above that size (fig. 1). there was no significant difference in size between females (37.3 ± 7.0 cm, n = 329) and males (36.7 ± 6.4 cm, n = 117; t = 0.79, df = 444, p>0.05) in the samples taken at al-duqum, and in these samples females dominated at a ratio of 1 female to 0.36 males (χ2 = 100.77, p<0.001). during april, june, july and december, no male individuals could be collected. table 1. macroscopically distinguishable stages of female and male gonads. sex stage characteristics female 0 immature or resting – thin, short, transparent and no eggs visible 1 developing – cream/yellow, longer in appearance, eggs not visible 2 maturing – developed, yellow to opaque eggs visible to naked eye 3 ripe and spawning – well-developed and swollen, hydrated oocytes 4 spent– translucent, pale violet with obvious blood vessels 5 post-spent – empty, shrunk, violet, flaccid male 1 developing – small, occupying about 1/3 of body cavity, transparent/pale 2 maturing – whitish/translucent, occupying about 1/2 of body cavity 3 ripe – creamy white, occupying about 3⁄4 of body cavity 4 spent/atrophied – flabby, reddish, about 1/2 of body cavity figure 2. length composition (tl in cm) of c. crenilabis caught by artisanal fishers using gill and seine nets at al-duqum and salalah during 2001. somatic index (hsi; mean ± sd) calculated as hsi = lw / tw × 100 for each month. results and discussion the largest female was 51.4 cm tl and weighed 1611 g, and the largest male was 54.5 cm, and weighed 1684 g. these measurements are consistent with the maximum size of 51 – 55 cm tl provided by randall (1995) and al-abdussalaam (1995). the tl of all fish measured ranged from 12 cm to 54.5 cm with a mean al-nahdi and others 26 27 length-weight relationships, maturity and reproductive season of the fringelip mullet this indicates that there may be segregation among sexes. however, this has to be verified by subsequent studies. the length-weight relationships were twfemales = 0.0222×tl2.801 (n = 329, r2 = 0.9499), twmales table 2. linear regressions of tl versus sl and fl for c. crenilabis females (n = 329; 14 – 52 cm tl), males (n = 117; 25 – 54 cm tl) and sexes combined, and conversion factors among length measurements. sex equation r2 f sl = 0.772 tl + 0.2284 0.964 m sl = 0.780 tl – 0.0619 0.971 all sl = 0.774 tl + 0.1732 0.966 f fl = 0.870 tl + 0.8806 0.984 m fl = 0.864 tl + 1.0546 0.982 all fl = 0.869 tl + 0.9093 0.984 = 0.0126×tl2.9441 (n = 117, r2 = 0.9473), and twboth sexes = 0.0247×tl 2.7693 (n = 446, r2 = 0.9426) (fig. 2). the log-transformed data fitted best to linear models (logtwmales = 2.9441×logtl – 1.9004 and logtwfemales = 2.801×logtl – 1.6541) and the regression slopes differed significantly between sexes (ancova, f = 1.31, p>0.05), females being slightly heavier than males of the same tl, except at the largest sizes. the linear regressions of tl versus fl and sl respectively fitted the data with r2-values > 0.96 in all cases, and the equations and conversion factors are shown in table 2. the logistic models fitted to the mature proportions of females (n = 337) and males (n = 117) resulted in minimized sums of squares of 0.18 and 0.042, respectively (fig. 3). the smallest female with a developing ovary (stage 1) had a tl of 25.5 cm, and 50% of females reached sexual maturity at figure 3. total length and total weight relationships of c. crenilabis females (a), males (b) and both sexes combined (c). al-nahdi and others 28 29 length-weight relationships, maturity and reproductive season of the fringelip mullet figure 4. the proportions of mature c. crenilabis per 2-cm tl interval and logistic curves fitted to estimate l50 values for females and males. 32.8 cm. the smallest male with a maturing gonad had a tl of 30 cm, and males reached l50 at 32.2 cm. males and females therefore reach maturity at similar sizes, comparable to that of mugil cephalus (linnaeus, 1758). male m. cephalus in south carolina first became mature at 24.8 cm tl (100% are mature at 30 cm) and females first matured at 2 years and 29 cm tl (100% were mature after 4 years at 40 cm) (mcdonough and wenner, 2000), and similar estimates were obtained from the gulf of mexico (28 cm and 29.9 cm tl respectively; ibañez-aguirre and gallardo-cabello, 1996). these values are close to our estimates for c. crenilabis. the weights of ovaries ranged from 0.21 g (at a tw = 264 g) to 73.12 g (tw = 947 g) and that of male gonads from 0.14 g (tw = 321 g) to 49 g (tw = 1200 g). of 349 ovaries sampled, 47.8% were immature and developing (stages 0 and 1), and these early stages were more prevalent in january to june (fig. 5a). active ovaries (stages 2-4, comprising 39.5% of all ovaries) were present in all months, with the highest proportions occurring in september and october, and moderately high proportions in november, december and february. post-spent ovaries (stage 5) decreased gradually between july and november (fig. 5a). these trends suggest a peak spawning season in september to october (highest ripe and lowest developing proportions), although spawning clearly continues at a lower level into november and december. the february peak may be an extension of the main spawning season, or a secondary spawning event as reported in m.cephalus from hong kong (bromhall, 1954) and gulf of mexico (stenger, 1959). nevertheless, it is clear that female reproductive activity is depressed between may and august. of 117 male gonads sampled, 32.2% were developing (stage 1), 44.8% were maturing or ripe (stages 2-3) and 23% were spent or atrophied (stage 4). ripe male gonads were present in all months. data from months with sample sizes <5 were excluded, and the remaining data suggest an increased ripe proportion in september to november, compared to january to march and may (fig. 5b). furthermore, the monthly proportions of males with developing gonads decreased gradually from august to november; these males presumably becoming ripe with the approach and onset of peak spawning. therefore, the trends in male gonad development and ripening tend to support the theory of peak spawning in september to november, with some activity in january to march. al-nahdi and others 28 29 length-weight relationships, maturity and reproductive season of the fringelip mullet figure 5. monthly proportions of (a) female c. crenilabis gonads classified as developing (stages 0 and 1), maturing, ripe and spent (stages 2-4) and post-spent (stage 5), and (b) male gonads classified as developing (stage 1), maturing and ripe (stages 2 and 3) and spent (stage 4). sample sizes were 349 females and 117 males, and monthly samples with <5 datapoints were removed. al-nahdi and others 30 31 length-weight relationships, maturity and reproductive season of the fringelip mullet f ig ur e 6. g on ad os om at ic ( a an d b) , a nd h ep at oso m at ic ( c an d d) in di ce s fo r fe m al e an d m al e c . c re ni la bi s co lle ct ed a t a ld uq um , a ra bi an s ea . m on th ly s am pl e si ze s ar e in p ar en th es is a nd s ta nd ar d de vi at io ns a re s ho w n. al-nahdi and others 30 31 length-weight relationships, maturity and reproductive season of the fringelip mullet both female and male gsi trends (fig. 6a and b) peak in september and october and were lowest between may and august. apart from the male values for december, the gsi values remain moderately high from november to april. this suggests that the peak spawning in september to october was followed by a period of spawning activity at a lower level, that was interrupted by the sw monsoon season (may to august) in the arabian sea. livers weighed between 0.4g and 40.2g, and the hsi trends of males and females peaked in april, just prior to the sw monsoon season (fig. 6c and d). a sharp decline in the hsi of females between october and november (fig. 6c) presumably reflects the metabolic energy expenditure and depletion of liver resources during spawning (busacker et al,, 1990). earlier studies on the relationships between spawning in mullets and environmental variables (mainly temperature and photoperiod) showed a tenuous linkage at best (see review by nash and shehadeh, 1980). their summary of an extensive and conflicting dataset including seven species over a wide geographical range failed to define a clear pattern, and they concluded that spawning areas of certain species of mullets were those places where optimum conditions for the incubation of eggs and the young were available. these conditions differed from region to region, influencing indigenous mullet populations. the present study suggests that peak spawning in c. crenilabis during the fall intermonsoon in the arabian sea (september and october), and thangaraja (1995) showed lowest annual but increasing temperatures (generally from <25°c to >26°) in inshore waters at several sites in august and september. the gradual warming after august and september follows on the retreat of cooler upwelled waters that are a prominent feature of this coast during the sw monsoon period (may to august/september) (kindle and arnone, 2001). we therefore tentatively suggest that low water temperatures and a gradual increase may initiate spawning in c. crenilabis in the arabian sea, but that spawning (possibly at a lower level) continues into the warming nw monsoon months. such a pattern was also shown for mugil curema along the atlantic coast of the united states, where spawning began in early spring when temperatures were rising (anderson, 1957 cited in nash and sehadeh, 1980). conversely, m. cephalus spawned when water temperatures were falling during late fall or winter (nash and sehadeh, 1980). thangaraja (1995) reported low february water temperatures (20-25°c) at 3 sites along the dhofar coast (salalah, taqah and raysut). if lower (and rising) temperatures do in fact initiate spawning in c. crenilabis (see above), these lower february temperatures may explain the larger proportion of females with ripe gonads seen in that month in fig. 6a. it should be noted that the spawning season of c. crenilabis in the arabian sea region of oman may differ from the gulf of oman, where the temperature is not as strongly affected by the sw monsoon winds and upwellings. lowest water temperatures at muscat (gulf of oman) are generally recorded during february and march (late winter; thangaraja, 1995), and based on our results in the present study we hypothesize that spawning of c. crenilabis in the gulf of oman will take place in february to march, as opposed to mainly september and october in the arabian sea. acknowledgements we are grateful to dr. h. al-oufi, under-secretary of the ministry of fisheries health, and dr. a.h. alhosni, director general for fisheries research and extension, government of sultanate of oman for their keen interest and encouragement in the preparation of this paper. we thank drs. j. groeneveld, n. jayabalan and b. human for their support in preparing the manuscript. many of the staff of the marine science and fisheries centre assisted with data collection at sea or at landing sites, and in the laboratory. funding was by the development of agriculture and fisheries fund. references al-abdessalaam, t.z.s. 1995. marine species of the sultanate of oman: an identification guide. ministry of agriculture and fisheries, marine science and fisheries centre, sultanate of oman. muscat printing press, 412 pp. anon. 2006. fisheries statistics book (2005) for the sultanate of oman. directorate of general planning and investment promotion. statistics and information department, ministry of agriculture and fisheries, muscat, 240 pp. bromhall, j.d. 1954. a note on the reproduction of the grey mullet (mugil cephalus linnaeus), hong kong univ. fish journal, 1:19-34. al-nahdi and others 32 busacker, g.p., i.r. adelman and e.m. goolish. 1990. growth. in: methods for fish biology, b. schreck and p.b. moyle, (editors), 363-387. american fisheries society, bethesda, maryland. fischer, w. and g. bianchi. 1984. fao species identification sheets for fishery purposes. western indian ocean (fishing area 51). prepared and printed with the support of the danish international development agency (danida). rome, food and agricultural organization of the united nations, vols. 1-6:pag.var. helfrich, p. and p.m. allen. 1975. observations on the spawning of mullet, crenimugil crenilabis (forskal), at enewetak, marshall islands. micronesia, 11:219-225. ibañez-aguirre, a.l. and m. gallardo-cabello. 1996. age determination of the grey mullet mugil cephalus l. and the white mullet m. curema. v. (pisces: mugilidae) in tamiahua lagoon, veracruz. ciencia marina 22:329-345. kindle, j.c. and r.a. arnone. 2001. a review of the surface circulation of the northern arabian sea. in: proceedings of the 1st international conference on fisheries, aquaculture and environment in the nw indian ocean, m. claereboudt, s. goddard, h. aloufi, and j. mcilwain (editors), 113-122. sultan qaboos university, muscat, sultanate of oman. mcdonough, c.j. and c.a. wenner. 2000. growth, recruitment, and abundance of juvenile striped mullet (mugil cephalus) in south carolina estuaries. fishery bulletin, 101:343-357. nash, c.e. and z.h. shehadeh. 1980. review of breeding and propagation techniques for grey mullet, mugil cephalus l. iclarm studies and reviews 3, 87pp. international center for living aquatic resources management, manila, philippines. randall, j.e. 1995. coastal fishes of oman. crawford house publishing pty ltd, bathurst, new south wales, australia. 439pp. stenger, a.h. 1959. a study of the structure and development of certain reproducrive tissues of mugil cephalus linnaeus. zoologica, n.y., 44: 53-68. thangaraja, m., 1995. hydrobiology off oman. msfc research report 95–1. marine science and fisheries centre, muscat, oman. 153 pp. zar, j.h. 1984. biostatistical analysis. englewood cliffs, prentice-hall, new jersey, xiv + 718p. research paper journal of agricultural and marine sciences vol. 20 (2015): 73–77 received 15 may 2014 accepted 19 feb. 2015 mortality of the abalone haliotis mariae (haliotidae: mollusca) in aquaculture a case study in oman gilha yoon1,*, hajer al-kaabi1, um kalthoum al-kindi2, salem khoom3, miyoung cho4, myong ae park4 and andrew shinn 5 *1 sultan qaboos university, college of agricultural and marine sciences , department of marine science and fisheries, p.o. box 34, alkhod 123, sultanate of oman. gilha yoon ( ) email: ghyoon@squ. edu.om 2 fishery quality control center, ministry of agriculture and fisheries, muscat, oman. 3 fisheries research center, ministry of agriculture and fisheries, salalah, oman. 4 aquatic animal health division, national fisheries research & development institute, busan, korea 5fish vet. group asia ltd. 99/386 chaengwattana building, chaengwattana road, kwaeng toogsonghong, khet laksi, bangkok, 10210, thailand introduction abalone are among the most commercially im-portant marine gastropods, valued for their high market value and nutrient content. however, natural stocks are in a serious decline because of overexploitation and the slow growth rate of populations in their natural habitat. omani abalone, haliotis mariae is the only abalone species found in oman. given the rarity of this species and its high market demand, the wild abalone fishery in the dhofar region has been regarded as a valuable source of income for the past decade (al-rashdi and iwao, 2008). dried abalone, for example, can fetch up to us$ 150 kg-1 dry weight. despite :haliotis mariae (mollusca haliotidae( نفوق رخوايت أذن البحر يف اإلستزراع السمكي يف سلطنة عمان: دراسة حالة جيلها يون1* وهاجر الكعيب 1 وأم كلثوم الكندي 2 وسامل خوم 3 وميونج شو 4 وميونج بارك واندرو شني5 abstract. the omani abalone, haliotis mariae, is the only species of abalone found in omani waters. given the rarity of this species and the high price it can fetch on the market (us$ 150 kg-1 dry weight), the wild abalone fishery in the dhofar region has been regarded as a valuable income source for the past decade. the present study was undertaken set to investigate the mortality of abalone held at the mirbat research center, through bacteriological and histopathological based investigations and challenge tests. only the adult wild abalone that had been kept for a year in the hatchery, visually, appeared to be clear of disease symptoms. infected individuals typically were swollen around the mouth, had fluid tinged with blood, bubbles in the intestines, and, very weak adhesive strength. the foot area (muscle) of diseased animals was noticeably very soft and individuals that were seen lying upside down on the bottom of the tank subsequently died. on dissection, the intestinal organs released bubbles and a foul smelling odour. identification of the isolated bacteria using various identification methods indicated that individuals were infected with staphylococcus sciuri. histopathology of infected individuals revealed spongiosis of the tissues with evident bacterial infection. neither of these histopathological conditions were seen in healthy abalone. the study concludes that the bacterium staphylococcus sciuri may be the likely cause of abalone mortalities,. keywords: املستخلص: أذن البحر العماين ، haliotis mariae هو النوع الوحيد من أذان البحر الذي يوجد يف املياه العمانية . ونظراً لندرة هذا النوع وارتفاع ســعره ، فمــن املمكــن ان يبــاع يف الســوق بـــ 150 دوالر أمريكــي لــكل واحــد كيلوجــرام مــن الــوزن اجلــاف ، فقــد كان ينظــر اىل مصائــد أذن البحــر الربيــة يف منطقــة ظفــار كـــمصدر دخــل قيــم علــى مــدى العقــد املاضــي . يعــى البحــث احلــايل بدراســة أســباب نفــوق أذن البحــر والــذي أجــري يف مركــز البحــوث يف مربــاط مــن خــال الفحــوص اجلرثوميــة والنســيجية واختبــارات التحــدي. وجــد أن أذن البحــر الربيــة البالغــة الــي ظلــت ملــدة عــام يف التفريــخ فقــط هــي الــي مل تظهــر عليهــا اعــراض املــرض. أمــا األفــراد املصابــة فقــد تورمــت حــول الفــم و قــد شــاب دمهــا ســائل كمــا وجــدت فقاعــات يف األمعــاء ، و ضعفــت قدرهتــا علــى االلتصــاق . كانــت منطقــة القــدم ) العضــات( يف احليوانــات املريضــة لينــة جــدا بشــكل ملحــوظ وقــد نفقــت اذن البحــر شــوهدت تقــف رأســاً علــى عقــب يف خــزان املــاء الحقــاً . وعنــد التشــريح ، أفــرزت االعضــاء املعويــة فقاعــات وروائــح كريهــة. وقــد أظهــر الطــرق املختلفــة للتعــرف علــى البكترييــا املعزولــة بأهنــا كانــت مصابــة باملكــورات العنقوديــة الســنجابية staphylococcus sciuri. كشــفت الدراســات النســيجية عنــد تشــريح األفــراد املصابــة عــن ظهــور أنســجة اســفنجية مــع وجــود واضــح للعــدوى البكترييــة. مل تتــم مشــاهدة أي مــن هــذه احلــاالت النســيجية املرضيــة يف اذن البحــر الســليمة. وخلصت الدراســة إىل أن بكترييا املكورات العنقودية الســنجابية staphylococcus sciuri رمبا تكون املســبب احملتمل يف نفوق أذن البحر. الكلمات املفتاحية: أذن البحر العماين، مرض بكتريي، املكورات العنقودية 74 squ journal of agricultural and marine sciences, 2015, volume 19, issue 1 mortality of haliotis mariae in aquaculture the high value of the wild abalone harvest, the industry is faced by many problems including low abundance, small harvest sizes and impacts of toxic blooms of algae (al-gheilani, 2009). for the sustainable production of omani abalone products, the government emphasized the importance of aquaculture with support for initiatives to increase the size of the wild population by funding projects to look at the habitat preferences of abalone (wall et al., 2012). currently, there is no health monitoring or surveillance of wild abalone in omani waters. a broad spectrum of disease agents have been reported to cause mortalities of both wild and cultured abalone (sawabe et al., 2007). among the causative agents, vibrios have been frequently highlighted (nishimori et al., 1998; cheng et al., 2004). vibrio parahaemolyticus and vibrio alginolyticus isolated from the haemolymph of moribund abalone have been demonstrated to cause outbreaks of vibriosis in warm water environments (liu et al., 2000; lee et al., 2001). according to muroga (2001), epizootic mortalities in juvenile black abalone, nordotis discus discus, and in ezo abalone, n. discus hannai, during seed production and the subsequent nursery stages have been occurring within several hatcheries since the early 1980s. other reports include that by moore et al. (2001) on the withering syndrome of abalone (wsa) caused by the bacterium candiatus xenohaliotis californiensis that is reported to kill most of the species of haliotis. infections are reported to infect the digestive system of abalone with a subsequent loss of body mass. the mirbat abalone hatchery research center in salalah is a unique research station which has focused on production and the stock enhancement of the omani abalone, h. mariae. when the center was initiated it began by collecting specimens from the wild. they were maintained in land based raceway tanks fed with local seaweed and a commercially formulated diet from iran. while wild abalone have been stocked in the hatchery, occasional mortality events leading to the loss of more than 50% of the stock are reported. a bacterial infection as the cause of mortality events was suspected. the aim of the present study was to investigate the mortality of abalone at mirbat research center through a comprehensive bacteriological and histopathological evaluation, with subsequent challenge tests to determine whether bacteria were the cause of mortality. materials and methods abalone collection omani abalone, haliotis mariae, used in the present study were supplied by the mirbat abalone research center. three different samples were used: 1. adult specimens from the wild supplied just before the start of the trial; 2. adults collected from the wild one year ago and then maintained on artificial and natural feed in a raceway system within the mirbat research center; and, 3. juvenile abalone originating from the hatchery. all samples were maintained in triplicate sets of tanks and the post-mortem evaluation of samples was conducted at the mirbat research center. diagnosis and bacteria culture the external and internal appearance of apparently healthy and diseased abalone were compared and features such as shell appearance and muscle appearance were documented before the abalone were dissected for bacteriology and histopathology. bacteriology samples from the muscle, intestine and the mouthparts of each abalone were inoculated on tsa + 1.5% nacl agar plates. figure 1. a direct comparison between healthy (left) and diseased (right) abalone specimens. note that the diseased animal is lighter in appearance, its tentacles and frill are not visible, and this animal has a weak or no attachment to the substrate. 75research article yoon, al-kaabi, al-kindi, khoom, cho , myong, park, shinn identification of bacteria the bacterial colonies were isolated and sub-cultured for identification. isolated pure colonies were stained with gram stain and subjected to api staph biochemical tests. results were subsequently confirmed by pcr and sequencing of the amplified products. histopathology after taking bacteriological samples, abalone were dissected. soft tissues were removed from the shell and all viscera, as well as a transverse section of the adductor muscle (foot muscle), and were placed into 10% seawater formalin to fix for at least 24 h. sections of viscera, mouth parts and foot muscle were placed into plastic cassettes and processed routinely then made 5 μm thick paraffin embedded tissue sections, which were stained with haematoxylin and eosin and cover-slipped. challenge test to confirm that the bacterium isolated from the moribund abalone was responsible for the abalone mortalities, a challenge test was performed. eighteen similar sized abalone were weighed individually and allocated to one of two 50 litre tanks (i.e. 50 cm × 50 cm × 20 cm; 9 specimens/treatment) filled with aerated 34 ppt salt water. each abalone was subsequently injected with a bacterial suspension containing 8 × 106 cfu ml/l live isolated bacteria using 1 ml sterile syringe with a 22-gauge needle. the dose administered to each specimen was adjusted to the individual weight of the abalone so that each received an equal dose. the abalone were maintained in the aerated test tanks; 50% of the tank water was replaced daily. mortalities were recorded hourly over the 72 h challenge period after which all abalone, i.e. both the mortalities and survivors, were screened for the bacteria results and discussion from the gross external and internal morphological appearance, only the adult abalone collected from the wild and maintained in the hatchery unit for a year presented clear signs of disease. the appearance of both healthy and diseased abalone is presented in figure 1. diseased individuals typically had swollen tissues around the mouth, had only a weak attachment to the substrate, produced a fluid tinged with blood and had air bubbles within their intestine which were evident before post-mortem. the foot muscle region was very soft and diseased specimens were commonly found lying upside down on the bottom of the tank; specimens displaying this behavior subsequently died. on post-mortem dissection, the intestinal organs contained bubbles and these specimens gave off a foul odour (fig. 2). the symptoms of this case were very similar to a vibrio infection of abalone described by cai et al. (2006). in this later report, the authors remarked that the diseased abalone were lethargic, had a typically white body colour and could not attach to biofilm covered substrates. the bodies of these abalone were visibly shrunken within their shells. by comparison, healthy individuals were active, dark in colour and the body tissues filled the shell space. the same bacterium isolated from the diseased abalone were also recovered from the specimens recently caught from the wild suggesting that the bacterium is ubiquitous but can become virulent when triggered by certain environmental conditions. the factors triggering this virulence though are not known at this stage and further research is required to identify potential factors or activators. the pure, dominant cultures isolated from the abalone were gram positive and the results from a standard api test (see table 1) suggested that the cultures were staphylococcus sciuri. subsequent dna sequencing of these isolates (see table 2) confirmed their identity (100% confidence). this is, figure 2. an infected abalone which has some haemorrhaging around the mouth, has shrunken muscle, a swollen intestine with bubbles inside that release a foul odour. 76 squ journal of agricultural and marine sciences, 2015, volume 19, issue 1 mortality of haliotis mariae in aquaculture to the authors’ knowledge, the first time that a staphylococcus infection has resulted in the mortality of abalone. although species belonging to the staphylococcus group are generally considered to be harmless commensals and spoilage members, nemeghaire et al. (2014), however, emphasised the ecological importance of the staphylococcus sciuri-species group which can act as a reservoir for resistance and virulence genes. the authors concluded, however, that further studies investigating the role of the s. sciuri-species group as commensal and pathogenic bacteria were required to fully assess their medical and veterinary importance since certain species belonging to this group have been found to carry multiple virulence and resistance genes including genes implicated in biofilm formation or coding for toxins responsible for toxic shock syndrome and multi-resistance. the findings from the current study lend support to the suggestions made by the latter authors that further studies investigating the potential virulence of staphylococcus species should be undertaken. histopathology of muscle samples taken from infected abalone muscle reveals numerous bacteria and spongiosis, quite unlike the densely packed tissues seen in uninfected specimens (fig. 3). the histopathology results suggest that the presence of this bacterium is the cause of the spoilage condition, i.e. a deterioration in muscle quality, air bubbles within the body organs and the production of a foul smelling odour. the response of the abalone following experimental infection by injection was pronounced, with the abalone becoming weak and losing their ability to attach to the sides of their tanks within 24  h post-infection. within 48  h, all the infected abalone had died whilst there were no losses in the control group. this result lends further support to the proposal that this bacterium was the cause of the original mortality event. conclusions this study concludes that a bacterium isolated from wild caught specimens that were maintained at the mirbat research center for a year and from recently harvested wild abalone was identified as staphylococcus sciuri following standard bacteriology tests and molecular sequencing. only specimens that had been taken from the wild were infected and exhibited the following symptoms: a swollen mouth; blood tinged fluid; air bubbles within the intestine that gave off a foul odour; softening of the foot muscle; and, very weak adhesive strength. infected animals were frequently found lying upside down at the bottom of the tank shortly before they perished. histologically, there was spongiosis of the foot muscle with an evident bacterial infection present. injection of healthy individuals with the isolated bacterium resulted in mortalities within 48 h. as the bacterium was recovered from a range of specimens taken from the wild, it would appear to be ubiquitous but the conditions triggering its virulence are not yet known. species belonging to the staphylococcus group are typically harmless commensals and spoilage members, but the findings from the present study support the suggestion that certain species may serve as a reservoir for resistance and virulence genes but this requires further study. table 1. biochemical test results of isolated bacteria from the diseased omani abalone. test response gram stain + oxidase + catalase + d-glucose + d-fructose + d-mannitol + maltose + lactose + d-trihalose + d-mannitol + xylitol d-melibiose potassium nitrate + α-methyl phosphate + sodium pyruvate raffinose xylose + saccharose + α-methyl glucoside + n-acetyl-glucosamine + arginine urea table 2. dna sequence from isolated bacteria from a diseased omani abalone. sequence tgatctacgattactagcgattccagcttcatgtagtcgagttg cagactacaatccgaactgagaataattttatgggatttgcttg gcctcgcggattcgctgccctttgtattatccattgtagcacgt gtgtagcccaaatcataaggggcatgatgatttgacgtcatccc caccttcctccggtttgtcaccggcagtcaacctagagtgccca acttaatgatggcaactaagcttaagggttgcgctcgttgcggg acttaacccaacatctcacgacacgagctgacgacaaccatgca ccacctgtcactttgtcccccgaaggggaagactctatctctag agcggtcaaaggatgtcaagatttggtaaggttcttcgcgttgc ttcgaattaaaccacatgctccaccgcttgtgcgggtccccgtc aattcctttgagtttcaaccttgcggtcgtactccccaggcgga gtgcttaatgcgttagctgcagcactaaggggcggaaaccccct aacacttagcactcatcgtttacggcgtggactaccagggtatc taatcctgtttgatccccacgctttcgcacatcagcgtcagtta cagaccagagagccgccttcgccactggtgttcctccatatctc tgcgcatttcaccgctacacatggaattccactctcctcttctg cactcaagtttcccagtttccaatgaccctccacggttgagccg tgggctttcacatcagacttaagaaaccgcctacgcgcgcttta cgcccaataattccggataacgcttgccacctacgtattaccgc ggctgctggcacgtagttagccgtggct 77research article yoon, al-kaabi, al-kindi, khoom, cho , myong, park, shinn acknowledgements this study was supported through an internal grant (project code: ig/agr/fish/13/02) from sultan qaboos university, sultanate of oman. references al-gheilani, h.m. 2009. final report: blooms of cochlodinium polykroides along the coast of oman in 2008-2009 and their effects. internal report: marine and oceanography section, marine science and fisheries center, ministry of fisheries wealth. al-rashdi, k.m. and t. iwao. 2008. abalone, haliotis mariae (wood, 1828), hatchery and seed production trials in oman. sultan qaboos university agriculture and marine sciences a research journal 13: 53-63. cai, j., y. han and z. wang. 2006. isolation of vibrio parahaemolyticus from abalone haliotis diversicolor supertexta l.) postlarvae associated with mass mortalities. aquaculture 257: 161-166. cheng, w., i.s. hsiao and j.c. chen. 2004. effect of ammonia on the immune response of taiwan abalone haliotis diversicolor supertexta and its susceptibility to vibrio parahaemolyticus. fish and shellfish immunology 17: 193-202. lee, k.k., p.c. liu and w.h. chuang. 2002. pathogenesis of gastroenteritis caused by vibrio carchariae in cultured marine fish. marine biotechnology 4: 267–277. liu, p.c., y.c. chen, c.y. huang and k. k. lee. 2000. virulence of vibrio parahaemolyticus isolated from cultured small abalone, haliotis diversicolor supertexta, with withering syndrome. letters in applied microbiology 31: 433-437. moore, j.d., t.t. robbins, r.p. hedrick, and c.s. friedman. 2001. transmission of the rickettsiales-like prokaryote “candidatus xenohaliotis californiensis” and its role in withering syndrome of california abalone, haliotis spp. journal of shellfish research 20: 867–874. muroga, k. 2001. viral and bacterial diseases of marine fish and shellfish in japanese hatcheries. aquaculture 202: 23-44. nemeghaire, s., m.a. argudin, a.t. feßler, t. hauschild, s. schwarz and p. butaye. 2014. the ecological importance of the staphylococcus sciuri species group as a reservoir for resistance and virulence genes. veterinary microbiology vetmic-d-13-8881r1/vetmic_6505. nishimori, e., o. hasegawa, t. numata and h.wakabayashi. 1998. vibrio carchariae causes mass mortalities in japanese abalone, sulculus diversicolor supratexta. fish pathology 33: 495–502. sawabe, t., s. inoue, y. fukui, k. yoshie, y. nishihara and h. miura. 2007 mass mortality of japanese abalone haliotis discus hannai caused by vibrio harveyi infection. microbes and environments 22: 300-308. wall, s.w.p., m. mohammed, a. al-mashikhi and s. khoom. 2012. habitat preferences of juvenile abalone (haliotis mariae wood, 1828) along the dhofar coast of oman and implications for conservation. sultan qaboos university agriculture and marine sciences a research journal 17: 45-52. figure 3. a-g. the histopathology results present clear differences between diseased (a-d) and healthy (e-g) abalone. note that the healthy specimen has dense muscle whilst the tissues of the diseased abalone appear sponge-like in appearance with evident bacterial growth. . research paper journal of agricultural and marine sciences vol. 20 (2015): 30-33. reveived 5 aug. 2014 accepted 19 feb 2015 microfouling on biocidal and non-biocidal antifouling coatings thirumahal muthukrishnan1* and sergey dobretsov 1 *1 thirumahal muthukrishnan ( ) sultan qaboos university, college of agricultural and marine sciences, department of marine science and fisheries. box 34, al-khod 123. sultanate of oman. email: mthirumahal@hotmail.com introduction biofouling has been a major problem in several ma-rine industries including the shipping industry. hull fouling adversely affects hydrodynamic drag الرتاكم احليوي للكائنات الدقيقة على الطالءات القاتلة وغري القاتلة املضادة للرتاكم على األسطح املغمورة ثريوحمال موثوكرشنان1* وسرجي دوبريتسوف 1 abstract. although antifouling marine paints have been used to prevent biofouling, not much is known about their effectiveness in preventing attachment of microorganisms. the current study aims at estimating the abundance of bacteria within biofilms developed on various commercial antifouling coatings in marina bandar rowdha and marina shangri la, oman. coatings tested included pettit #1863 and #1792, west marine #11046620, #5566252 and #10175206, hempel hard racing #76484, hempel olympic #86950, hempasil x3 and international yba920. all coatings were applied on clean plastic slides. slides without any coating were used as controls. microbial biofilms were harvested after 2, 7 and 14 days of biofouling. bacterial density was estimated using epifluorescence microscopy. there was a significant difference between the various treatments (coatings and control) after 2, 7 and 14 days of biofouling. although there were significant differences between both locations after 2 and 14 days of biofouling, no significant difference was observed after 7 days of biofouling at both locations. at shangri la, the lowest bacterial density was found on international yba920, pettit #1792 and hempasil x3 after 2 days, 7 days and 14 days respectively in comparison to the control treatments. however at bandar rowdha, international yba920 showed the lowest bacterial density after 2 days while west marine #10175206 showed the lowest bacterial density after both 7 days and 14 days of biofouling in comparison to the control treatment. the differential performance of tested antifouling coatings may be attributed to several factors including varying environmental conditions, difference in microfouling communities, time of exposure and physical and chemical properties of antifouling coating. keywords: coatings, antifouling, microfouling, bacteria, phototrophic. املستخلص: بالرغم من أن األصباغ البحرية املضادة للرتاكم على األسطح املغمورة تستخدم للحد من الرتاكم احليوي ، إال أنه ال يعرف الكثري عن مــدى كفاءهتــا يف احلــد مــن تعلــق الكائنــات الدقيقــة. وهتــدف الدراســة احلاليــة إىل تقديــر تواجــد البكرتيــا يف أغشــية حيويــة رقيقــة تكونــت علــى طــاءات جتاريــة خمتلفــة مضــادة للرتاكــم علــى األســطح يف مارينــا بنــدر الروضــة ومارينــا شــاجنري ال بســلطنة عمــان. الطــاءات ايل مت اختبارهــا مشلــت: 1863 ، #76484 hempel hard racing ، 10175206# و 5566252 #و west marine #11046620 ، 1792 #و pettit # international yba920 ، hempasil x3 ، #86950 hempel olympic. مجيــع الطــاءات مت وضعهــا علــى شــرائح باســتيكية نظيفــة مــع اإلبقــاء علــى بعــض الشــرائح غــري مطليــة الســتخدامها كمعاملــة مرجعيــة. ومــن مث مت مجــع األغشــية احليويــة الرقيقــة املتكونــة بعــد 2 و 7 و 14 يومــا مــن بدايــة الرتاكــم احليــوي علــى األســطح. ومت تقديــر كثافــة البكرتيــا باســتخدام تقنيــة اجملهــر الفــوق فلورســي. أظهــرت النتائــج وجــود فروقــات معنويــة كبــرية بــن املعامــات املختلفــة ) املطليــة وغــري املطليــة( بعــد 2 و 7 و 14 يومــا مــن بدايــة الرتاكــم احليــوي علــى األســطح .وبالرغــم مــن االختــاف املعنــوي يف النتائــج بــن املوقعــن بعــد 2 و 14 يومــا مــن الرتاكــم احليــوي علــى األســطح ، إال أنــه مل يكــن هنــاك فــرق يذكــر بعــد 7 ايــام مــن الرتاكــم احليــوي يف املوقعــن. ويف مارينــا شــاجنري ال، كانــت أقــل كثافــة للبكرتيــا يف املعامــات: international yba920 و pettit1792# و hempasil x3 باملقارنــة مــع املعامــات الغــري مطليــة، بعــد 2 و 7 و 14 يومــا علــى التــوايل. أمــا يف مارينــا بنــدر الروضــة فقــد أظهــر الطــاء international yba920 أقــل كثافــة للبكرتيــا بعــد يومــن مــن بدايــة الرتاكــم احليــوي علــى األســطح. بينمــا أظهــر الطــاء west marine #10175206 أقــل كثافــة للبكرتيــا بعــد7 و 14 يومــا مقارنــة باملعامــات الغــري مطليــة. إن األداء املتبايــن للطــاءات املضــادة للرتاكــم احليــوي الــي مت اختبارهــا ميكــن أن ينســب إىل عــدة عوامــل منهــا الظــروف البيئيــة املختلفــة، واختــاف جمتمعــات املرتاكمــات احليويــة الدقيقــة، ومــدة التعــرض، واخلصائــص الكيميائيــة والفيزيائيــة للطــاءات املضــادة للرتاكــم علــى األســطح. الكلمات املفتاحية: الطاءات ، مضادات الرتاكم احليوي على األسطح ، الرتاكم احليوي للكائنات الدقيقة، البكرتيا، اإلجنذاب للضوء leading to elevated fuel consumption and higher maintenance costs although the impact of biofilms is significantly less than that of macrofouling (yebra et al. 2004; schultz 2007; schultz et al. 2011). in marine environments, formation of biofilms (ie microfouling) depends on the types of fouling microorganisms, environmental factors such as current, temperature, salinity, nutrient levels and hydrodynamic conditions (wieczorek and todd 1998 ; lau et al. 2005; zhang et al. 2011) and properties of substratum (whitehead and verran 2008). mi31research article muthukrishnan, dobretsov crobial fouling communities consist mainly of numerous species of bacteria and diatoms that can positively and/ or negatively interact with each other (railkin 2003; dobretsov 2010). both bacteria and diatoms may also have a significant impact on the recruitment of invertebrate larvae and algal spores (macrofouling) by either enhancing or inhibiting their settlement (mitchell and maki 1988; maki 2002; huang and hadfield 2003; qian et al. 2007; hadfield 2011). this significantly influences the extent to which biofouling occurs in the marine environment. however bacteria have generally been accepted to be the primary colonizers on man-made surfaces in the marine environment (molino et al. 2009b). therefore it is important to study the efficiency of antifouling coatings in preventing bacterial fouling during the primary stages of biofouling in the marine environment. the objective of the current study was to estimate the abundance of bacteria within biofilms developed on various commercial antifouling coatings at two different locations in oman. the hypothesis tested was that treatments (nine commercial antifouling coatings) and location influence the abundance of bacteria within biofilms developed on commercial antifouling coatings. materials and methods coatings preparation six commercial antifouling coatings (petit # 1863, petit 1792, west marine #5566252, west marine #11046620, west marine #10175206 and international micron extra yba 920) were obtained at local boat shop (muscat, oman). three commercial antifouling coatings (hempel hard racing 76484-51170, hempel olympic 869505110 and hempasil x3) were obtained from hempel ltd. co. (muscat, oman). the nine antifouling coatings (table 1) were manually applied onto cleaned, acrylic plastic slides (75 x 25 mm) at marine science and fisheries laboratory, sultan qaboos university, oman. all coated slides were dried for several hours at ambient temperature prior to deployment. uncoated cleaned plastic slides were considered to be the control treatments. for each treatment including control, a total of 18 replicate slides were prepared. coatings deployment a total of 180 slides were randomly inserted into 6 slide cassettes (each 21 x 16 x 3 cm) such that each slide cassette contained 3 replicates of each treatment and 30 equally spaced slides in total. each slide cassette was deployed by ropes such that each slide in the slide cassette was kept vertical with respect to the surface of seawater. three slide cassettes were deployed each at marina shangri la (muscat, oman 23º 32’ 55”  n 58º 39’ 23” e) and marina bandar rowdha (muscat, oman 23º 34’ 55” n 58º 36’ 27” e). sample collection each of the three slide cassettes at marina bandar rowdha and marina shangri la were withdrawn after 2 days, 7 days and 14 days of biofouling respectively. during sample collection, all slides from the slide cassette were carefully transferred into clean plastic boxes containing formalin (3.7% final concentration) and immediately transferred to the laboratory at 4ºc for further analysis (see below). estimating abundance of bacteria the total bacterial density on the treatment surfaces was estimated by staining an area of 2 x 2 cm with 10-12  µl of 4, 6-diamidino-2-phenylindole (dapi, sigma, germany) solution for 15 minutes according to dobretsov and thomason (2011). the number of bacteria in 10 randomly selected fields of view on the ocular grid (0.001 mm2) was counted using an epifluorescence microscope (axiostar plus, zeiss, germany; magnification 1000x; λex=359nm, λem=441nm). statistical analysis factorial anova was used to test the effect of treatment and location on the total bacterial density using statistica 11 (statsoft, usa) after 2, 7 and 14 days of biofouling. post hoc hsd test was used to test for significant differences among the treatments and locations. in all cases, the threshold for significance was 0.05. results the treatments (antifouling coatings and control) significantly influenced the bacterial density in biofilms developed after 2, 7 and 14 days of biofouling (figure 1a and figure 1b; anova, hsd, p < 0.0001). although figure 1. bacterial density in biofilms developed on all treatments (coatings 1-9 and control) after 2, 7 and 14 days of biofouling at (a) marina shangri la and (b) marina bandar rowdha . data are the means + sd (n=3). 32 squ journal of agricultural and marine sciences, 2015, volume 19, issue 1 microfouling on biocidal and non-biocidal antifouling coatings both locations were found to significantly affect bacterial density after 2 and 14 days (anova, hsd, p < 0.0001) there was no significant difference between both locations after 7 days of biofouling (anova, hsd, p = 0.237). however both treatments and locations together significantly affected the bacterial density in biofilms after 2, 7 and 14 days of biofouling (anova, hsd, p < 0.01). at shangri la, the lowest bacterial density was found on international yba920, pettit #1792 and hempasil x3 after 2 days, 7 days and 14 days respectively in comparison to the control treatments (figure 1a). however at bandar rowdha, international yba920 showed the lowest bacterial density after 2 days while west marine #10175206 showed the lowest bacterial density after both 7 days and 14 days of biofouling in comparison to the control treatment (figure 1b). the differential performance of tested antifouling coatings may be attributed to several factors including varying environmental conditions and differences in the abundance of fouling bacterial communities. the variation in the concentrations of biocides in these coatings may be additional factor in influencing bacterial attachment on coatings. in particular the polishing rate behavior and biocide delivery rate behavior is known to vary for different coating types (finnie & williams 2010, bressy et al. 2010). clearly further investigations are required to study the abundance and composition of bacterial fouling communities on antifouling coatings. conclusions the current study shows that the abundance of bacteria in biofilms developed on commercial antifouling coatings is significantly influenced by the coating types and both coatings and location together after 2, 7 and 14 days of biofouling. varying environments were not found to affect the bacterial density after 7 days of biofouling although there were significant differences after 2 and 14 days of biofouling. acknowledgements this study was supported by hm sultan qaboos research trust fund sr/agr/fish/10/01. the authors thank hempel ltd. co. (muscat, oman) for providing coatings. the authors would also like to thank ms. annika vaksmaa (sultan qaboos university) for her assistance in experimental setup. references bressy, c., c., hellio, j.p., marechal, b., tanguy, and a., margaillan. 2010. bioassays and field immersion tests: a comparison of the antifouling activity of copper-free poly(methacrylic)-based coatings containing tertiary amines and ammonium salt groups. biofouling 26: 769-777. dobretsov s. 2010. marine biofilms. in: biofouling, dürr s, thomason jc, editors. wiley-blackwell, oxford (uk): 123–136. finnie aa, and d. n. williams. 2010. paint and coatings technology for the control of marine fouling. in: biofouling, dürr s, thomason jc, editors. wiley-blackwell, oxford (uk). hadfield m. 2011. biofilms and marine invertebrate larvae: what bacteria produce that larvae use to choose settlement sites. annual review of marine science 3: 453-470. huang s, hadfield mg. 2003. composition and density of bacterial biofilms affect metamorphosis of the polychaete hydroides elegans. marine ecology progress series, 260: 161-172. lau sck, v., thiyagarajan, sck, cheung, and p-y qian. 2005. roles of bacterial community composition in biofilms as a mediator for larval settlement of three marine invertebrates. aquatic microbial ecology 38: 41-51. maki js. 2002. biofouling in the marine environment. in: table 1. characteristics of the ten treatments exposed to biofouling at depth, 1m at marina shangri la and marina bandar rowdha. treatment commercial coating type of coating active ingredient 1 petit marine #1863 biocidal zinc pyrithione 2 petit marine #1792 biocidal pure zinc 3 west marine #5566252 biocidal cuprous thiocyanate 4 west marine #11046620 biocidal zinc pyrithione 5 international micron extra yba920 biocidal cuprous oxide + dichlofluanid 6 west marine #10175206 biocidal cuprous oxide 7 hempel hard racing #76484-51170 biocidal cuprous oxide 8 hempel olympic #86950-51110 biocidal copper 9 hempasil x3 non-biocidal silicone control 33research article muthukrishnan, dobretsov encyclopedia of environmental microbiology, bitton g, ed. (new york: john wiley & sons) pp 610–619. mitchell r., and js maki. 1988. microbial surface films and their influence on larval settlement and metamorphosis in the marine environment. in: marine biodeterioration: advanced techniques applicable to the indian ocean, thompson m-f, sarojini r, nagabushanam r, eds. (new delhi: oxford & ibh) pp 489-497. molino pj, s., childs, mr, eason hubbard, jm, carey, ma, burgman, and r., wetherbee. 2009b. development of the primary bacterial microfouling layer on antifouling and fouling release coatings in temperate and tropical environments in eastern australia. biofouling 25: 149-162. qian p-y, sck, lau, h-u, dahms, s, dobretsov, and t., harder. 2007. marine biofilm as mediator of colonization by marine macroorganisms: implications for antifouling and aquaculture. marine biotechnology 9: 399-410. railkin ai. 2003. marine biofouling: colonization processes and defenses. boca raton (fl): crc press. 320 pp. schultz mp. 2007. effects of coating roughness and biofouling on ship resistance and powering. biofouling 23: 331-341. schultz mp, ja bendick, er holm, and wm hertel. 2011. economic impact of biofouling on a naval surface ship. biofouling 27: 87-98. wieczorek sk, and cd todd. 1998. inhibition and facilitation of settlement of epifaunal marine invertebrate larvae by microbial biofilm cues. biofouling 12: 81118. yebra dm, s kiil, and k dam-johansen. 2004. antifouling technology: past, present and future steps towards efficient and environmentally friendly antifouling coatings. progress in organic coatings 50: 75-104. sultan qaboos university journal for scientific research agricultural and marine sciences, 10(1):5-12 (2005) ©2005 sultan qaboos university 5 * corresponding author influence of alternate bearing on leaf and fruit mineral composition at different developmental stages of date palm fruits m.o. el-mardi1*, a.e. pillay2, j.r. williams2, c.s. bakheit3, s.m. hassan2, m. al-hadabbi4 and a. al-hamdi2 1department of crop sciences, college of agricultural and marine sciences, p.o. box 34 2department of chemistry, college of science, p.o. box 36 3department of mathematics and statistics, college of science, p.o. box 36 4 department of soils and water, college of agricultural and marine sciences, p.o. box 34 sultan qaboos university, al-khod 123, sultanate of oman وثمار نخلة التمر من المعادن خالل تأثیر ظاھرة المعاومة على محتوى سعف مراحل تطور الثمار عثمان المرضي الخالصة: تم أخذ عینات السعف والثمار من نخالت الفرض تراوح عمرھا بین 15 و 16 عامًا أثناء مراحل تطور الثمار المختلفة k, )وكانت النخالت إما ذات حمل خفیف (6عذوق) أو ثقیل (8عذوق). جففت العینات ومن ثم رمدت وھضمت. تم تحديد تركیز ca, mg, na, fe, zn, cu and mn) باستخدام (icp – aes) وتركیز النیتروجین بطريقة kjeldhal. وجدت تغیرات بفروقات معنوية في تركیزات المعادن في السعف والثمار بین مرحلة الكمري (ثمار خضراء) والبسر (أحمر مصفر) تناقص تركیز (mg) و (k) في (mn و zn و fe )في الثمار وازداد في السعف. لم تظھر فروقات معنوية في تركیز (na) و (ca) السعف والثمار. كما تناقص بین مرحلتي تطور الثمار. بینما ازداد ( fe) قلیًال في السعف والثمار بین الكمري والبسر ونقص بین البسر والرطب (بداية لیونة (mn و zn و fe )في الثمار وازداد في السعف. لم تظھر فروقات معنوية في تركیز (na) و (ca) السعف والثمار. كما تناقص بین مرحلتي تطور الثمار. بینما ازداد ( fe) قلیًال في السعف والثمار بین الكمري والبسر ونقص بین البسر والرطب (بداية لیونة (mn و zn و fe )في الثمار وازداد في السعف. لم تظھر فروقات معنوية في تركیز (na) و (ca) السعف والثمار. كما تناقص الثمار). وقد وجد أن تركیز ( mg و fe و mn) كان أعلى في السعف عن الثمار بینما كانت تركیز ( k و zn و cu) أعلى في الثمار. بین مرحلتي تطور الثمار. بینما ازداد ( fe) قلیًال في السعف والثمار بین الكمري والبسر ونقص بین البسر والرطب (بداية لیونة الثمار). وقد وجد أن تركیز ( mg و fe و mn) كان أعلى في السعف عن الثمار بینما كانت تركیز ( k و zn و cu) أعلى في الثمار. بین مرحلتي تطور الثمار. بینما ازداد ( fe) قلیًال في السعف والثمار بین الكمري والبسر ونقص بین البسر والرطب (بداية لیونة تزامنت أعلى تركیزات (mg , ca) في السعف عن الثمار مع أعلى تركیز (k) في الثمار عن السعف و ظھرت فروقات معنوية في الثمار). وقد وجد أن تركیز ( mg و fe و mn) كان أعلى في السعف عن الثمار بینما كانت تركیز ( k و zn و cu) أعلى في الثمار. تزامنت أعلى تركیزات (mg , ca) في السعف عن الثمار مع أعلى تركیز (k) في الثمار عن السعف و ظھرت فروقات معنوية في الثمار). وقد وجد أن تركیز ( mg و fe و mn) كان أعلى في السعف عن الثمار بینما كانت تركیز ( k و zn و cu) أعلى في الثمار. تركیز (fe, mn, ca) في الثمار و(k, mg) في السعف بین النخیل ذات الحمل الخفیف وتلك ذات الحمل الثقیل أثناء مراحل تطور تزامنت أعلى تركیزات (mg , ca) في السعف عن الثمار مع أعلى تركیز (k) في الثمار عن السعف و ظھرت فروقات معنوية في تركیز (fe, mn, ca) في الثمار و(k, mg) في السعف بین النخیل ذات الحمل الخفیف وتلك ذات الحمل الثقیل أثناء مراحل تطور تزامنت أعلى تركیزات (mg , ca) في السعف عن الثمار مع أعلى تركیز (k) في الثمار عن السعف و ظھرت فروقات معنوية في الثمار. ولكن النمط العام أثناء مرحلة الرطب (حیث تغیر اللون إلى العســــلي مع لیونة األنسجة) يدل على أن الخوص النخیل ذات تركیز (fe, mn, ca) في الثمار و(k, mg) في السعف بین النخیل ذات الحمل الخفیف وتلك ذات الحمل الثقیل أثناء مراحل تطور الثمار. ولكن النمط العام أثناء مرحلة الرطب (حیث تغیر اللون إلى العســــلي مع لیونة األنسجة) يدل على أن الخوص النخیل ذات تركیز (fe, mn, ca) في الثمار و(k, mg) في السعف بین النخیل ذات الحمل الخفیف وتلك ذات الحمل الثقیل أثناء مراحل تطور الحمــــــل الخفیف تحتوي على تركیزات أعـــــــــلى من (mn, cu, zn, fe, mg, ca, n) عن سعف النخیل ذات الحمل الثقیل. الثمار. ولكن النمط العام أثناء مرحلة الرطب (حیث تغیر اللون إلى العســــلي مع لیونة األنسجة) يدل على أن الخوص النخیل ذات الحمــــــل الخفیف تحتوي على تركیزات أعـــــــــلى من (mn, cu, zn, fe, mg, ca, n) عن سعف النخیل ذات الحمل الثقیل. الثمار. ولكن النمط العام أثناء مرحلة الرطب (حیث تغیر اللون إلى العســــلي مع لیونة األنسجة) يدل على أن الخوص النخیل ذات بینما كانت محتويات خوص النخیل ذات الحمل الثقیل أعلى في (na, k) عن سعف النخیل ذات الحمل الخفیف. ولكن في مرحلة الحمــــــل الخفیف تحتوي على تركیزات أعـــــــــلى من (mn, cu, zn, fe, mg, ca, n) عن سعف النخیل ذات الحمل الثقیل. بینما كانت محتويات خوص النخیل ذات الحمل الثقیل أعلى في (na, k) عن سعف النخیل ذات الحمل الخفیف. ولكن في مرحلة الحمــــــل الخفیف تحتوي على تركیزات أعـــــــــلى من (mn, cu, zn, fe, mg, ca, n) عن سعف النخیل ذات الحمل الثقیل. الرطب كانت تركیزات (zn, fe, mg, ca) مماثلة لتركیزاتھا في سعف النخیل خفیفة الحمل. بینما كان تركیز (na, k) أعلى في بینما كانت محتويات خوص النخیل ذات الحمل الثقیل أعلى في (na, k) عن سعف النخیل ذات الحمل الخفیف. ولكن في مرحلة الرطب كانت تركیزات (zn, fe, mg, ca) مماثلة لتركیزاتھا في سعف النخیل خفیفة الحمل. بینما كان تركیز (na, k) أعلى في بینما كانت محتويات خوص النخیل ذات الحمل الثقیل أعلى في (na, k) عن سعف النخیل ذات الحمل الخفیف. ولكن في مرحلة ثمار النخیل ذات الحمل الخفیف عن الخوص، بینما كان (mn, cu) أعلى في ثمار النخالت ذات الحمل الثقیل عن الخوص. تدل الرطب كانت تركیزات (zn, fe, mg, ca) مماثلة لتركیزاتھا في سعف النخیل خفیفة الحمل. بینما كان تركیز (na, k) أعلى في ثمار النخیل ذات الحمل الخفیف عن الخوص، بینما كان (mn, cu) أعلى في ثمار النخالت ذات الحمل الثقیل عن الخوص. تدل الرطب كانت تركیزات (zn, fe, mg, ca) مماثلة لتركیزاتھا في سعف النخیل خفیفة الحمل. بینما كان تركیز (na, k) أعلى في النتائج على الحاجة الى أستمرارية مثل ھذا البحث. abstract: samples of leaflets and fruits at different stages were collected from 6 “on-palms” and 6 “off-palms” (15-16 years) of the fard cultivar. samples were dried, ashed and digested. macro and micronutrient concentrations of k, ca, mg, na, fe, zn, cu and mg were determined by icp-aes and n was measured by kjeldhal method. significant changes in the elemental concentrations of leaf and fruit occurred between kimri (green color) and bisir (yellowish-red color) development bisir (yellowish-red color) development bisir stages. potassium and mg concentration was reduced in leaf and fruit. calcium and na were reduced in the fruit and increased in the leaf. iron, zn and mn were not significantly different between bisir and bisir and bisir kimi. however, fe in the fruit and leaf increased between kimri and bisir and decreased from bisir and decreased from bisir bisir to rutab stages. the concentration of ca, mg, fe and mn was higher in the leaf than fruit. in contrast k, zn and cu were higher in the fruit. higher ca and mg in leaves through the developmental stages were associated with higher concentration of k in the fruit than the leaf. these variations in the leaf and fruit elemental concentration were associated with physiological and biochemical changes during fruit development. significant differences in the fruit elemental concentrations between the “on” (high yield producing) and “off” (low yield producing) palms during the developmental stages were in ca, k, mn and fe and in the leaf in mg and k. however, the general trend during rutab (honey color, soft tissue) indicates that “off-palm” leaves have higher n, ca, mg, fe, zn, cu and mn than “on-palm” leaves. potassium and na were higher in the “on-palm” leaves than “off-palm” leaves. but in the fruit, rutaband na were higher in the “on-palm” leaves than “off-palm” leaves. but in the fruit, rutaband na were higher in the “on-palm” leaves than “off-palm” leaves. but in the fruit ca, mg, fe, and zn content followed similar trends as in the “off-palm” leaves; in contrast to leaves, k and na were higher in “off-palms” fruits and cu and mn higher in “on-palm” fruits. the results indicate the need for further research. keywords: off-palm, on-palm, alternate bearing, physio-biochemical changes, sultanate of oman. el mardi et al. 6 introduction there is a growing concern about the bearing habit of some date cultivars which show fluctuations in yield, a phenomenon identified as alternate bearing. high yields of date palm in general are associated with low quality fruits, i.e. small fruit, high acidity and tannin and low sugars (nixon and crawford, 1942; al juburi, 1993; el mardi et al., 1995; mekki et al., 1998). how this phenomenon works is still not well understood, although in many cases it has been associated with depletion of carbohydrates and mineral nutrient reserves following a heavy cropping in the “on” year. alternate bearing is also influenced by several factors, including the genetic make-up of the cultivar, biotic and abiotic stresses, and improper culture techniques during the “on” year (that is a year of high yield) (jonkers, 1979; batjar and westwood, 1958). several attempts were made to minimize the effect of alternate bearing on the date palm through horticultural practices. possible regulation of alternate bearing of date cultivar through maintaining balance between vegetative and reproductive growth have been reported by many researchers (nixon, 1935 and 1936; nixon, 1940; swingle, 1925; mathes and bliss, 1942; al khateeb et al., 1993). much of such work involved nutrition, especially nitrogen fertilizers, thinning of fruits and girdling. all these relate to the balance between vegetative and reproductive growth of the tree. understanding and control of alternate bearing seems more difficult in monocotyledonous plants than dicots. in dicots some branches could be “on” while others are “off” (patrick, 1988 and 1991; goren and monselise, 1971). the alternate bearing phenomenon is controlled by growth regulators. it has been indicated that too high gibberellins in the flower bud inhibit its development. thinning by daminozide and ethephon (auxin effect) can be used to help overcome biennial bearing (faust, 1989). alternate bearing in the fard cultivar is not in regular annual cycles, the interval between “off” and “on” status could be 1, 2 or 3 years (nixon and crawford; 1942, el mardi et al., 1998). during these cycles there will always be competition between leaves and fruit for nutrients and carbohydrates. loading and mobilization of these materials is expected to be regulated by the fruit and leaf developmental stages (nixon and wedding, 1956; hassan et al., 1984; mustafa, 1993; el mardi et al., 2002). this research was intended to investigate the changes in mineral nutrients during fruit developmental stages in relation to alternate bearing in the fard date cultivar. materials and methods twelve date palms of the fard cultivar, 15-16 years old were selected randomly from those grown at sultan qaboos university campus for this study: six “onyear palms” and six “off-year palms” (“on-palm” has > 8 bunches of fruits and “off-palm” has < 6 bunches). leaflet samples were collected from the same position (leaflet number 8 from top leaflet) along the rachis of leaves in the axil of which the bunches were born. fruits were collected at three developmental stages: kimri (green), bisir (at cultivar characteristic color, yellowish-red), and rutab (honey color and softening). all samples were washed with distilled water, dried and stored at –18 °°c pending analysis. each treatment was replicated 6 times. leaf and fruit samples were digested by a dry ashing procedure (jones et al., 1991). after drying in the oven (105 °c), 1g sample was ashed in a muffle furnace (gallenkamp, size 2) at 550 °c. the ash was moistened with few drops of de-ionized water, immersed in 3 ml conc. hcl and evaporated to dryness. the residue was dissolved in 5 ml of 2 m hno , filtered through whatman filter paper #41 into a 25 ml volumetric flask and diluted to volume with millipore water. similarly, a blank sample was prepared excluding the plant specimen. concentrations of k, ca, mg, na, fe, zn, cu, and mn were determined using inductively coupled plasma – atomic emission spectroscopy (icp-aes) calibrated with spectrosol atomic absorption reference standards. nitrogen was determined using the kjeldhal method. data were statistically analyzed using spss. spearman’s rank correlation coefficients were determined and means were separated using duncan’s multiple range test (duncan, 1955). results and discussion data in table 1 shows the significant correlation coefficient for pairs of macro and micronutrients in the fruits by development stage. in bisir stage ca showed positive correlation with k (they increase or decrease together). a similar correlation was found between na and k, but fe and mn were negatively correlated (one increases the other decreases). likewise, k and na influence of alternate bearing on leaf and fruit mineral composition of date palm fruit 7 were negatively correlated in kimri stage. in rutab mg was positively correlated with k, na, zn, mn and k was positively correlated with mn. all the detected correlations were positive in the leaves during the three developmental stages, except for mn and fe which were negatively correlated. positively correlated pairs include k and mg during bisir and rutab, k and mn during kimri and rutab stagstagsta es. magnesium, fe, na and zn during bisir; cu, zn, mn and fe during kimri; and k, na, mn and mg during rutab stage. the general trend of mineral concentration indicates that, of the macronutrients, only mg and k, and ca and k were correlated positively in the fruit during the rutab and kimri and kimri and stages, respectively. whereas mg in leaf correlates to fe during bisir and to bisir and to bisir mn during rutab, k correlates with mn in kimri and rutab stages. in addition, k and mg were the main macronutrients which influenced the concentration of ca and na. potassium and mg are known to be highly soluble and move freely in the plant body (el mardi et al., 1995b) and this could be the explanation for the high correlation to other minerals within the plant body. effect of fruit developmental stages on the macro and micronutrients concentrations of the fruit and leaf table 2 shows the levels of the concentrations of the table 1. spearman’s rank correlation coefficients that are statistically significant for pairs of macro and micro nutrient elements in date fruits and leaves by stages of fruit development. stages of development bisir kimri rutab element pairs corr. coefficient (rho) pvalue element pairs corr. coefficient (rho) p-value element pairs corr. coefficient (rho) p-value fruit cak 0.811 < 0.01 k – na -0.580 <0.05 mg – k 0.825 < 0.01 na – k 0.783 < 0.01 mg – na 0.637 < 0.05 fe – mn -0.651 < 0.01 mg – zn 0.609 < 0.05 mg – mn 0.608 < 0.05 k – mn 0.832 < 0.01 leaf mg – k 0.783 < 0.01 k – mn 0.690 < 0.05 k – mg 0.797 < 0.01 mg – fe 0.615 < 0.05 cu – zn 0.793 < 0.01 k – na 0.625 < 0.05 na – zn 0.660 < 0.05 mn – fe -0.634 < 0.05 k – mn 0.937 < 0.01 mn – mg 0.720 0.01 > macro and micronutrient elements in the fruit and leaf, for the three fruit developmental stages (kimri, bisir for the three fruit developmental stages (kimri, bisir for the three fruit developmental stages ( and rutab). the concentrations of ca, mg, k and na showed a significant reduction from the kimri to the bisir fruit stages (table 2). these results are in partial bisir fruit stages (table 2). these results are in partial bisir agreement with sawaya et al. (1982), clark and smith (1990), bacha et al. (1993) and al juburi, (1995). in contrast, the present results showed a slight but not significant increase in the concentration of mg and na and a significant increase in ca and k from bisir to rutab stagstagsta es, whereas sawaya et al. (1982) and al juburi et al. (1994), showed a continuous reduction in these elements from bisir to rutab stages. similar trends for mg, and k levels were found in fruits and leaves (table 2); they were significantly higher in kimri stage than in bisir and bisir and bisir rutab stages in both samples. however, na concentration was not significantly different between these stages in the leaf, but it was significantly higher in the bisir stage bisir stage bisir of fruit. on the other hand, ca showed a significant increase from kimri to bisir stages followed by a reduction in rutab stage (table 2). these results are partially compatible with those from bacha et al. (1993) and al juburi (1995). magnesium is a component of chlorophyll, thus its concentration is expected to decrease as the fruit changes in color from the kimri stage, which is dark-green, to the reddish-yellow bisir stage. its el mardi et al. 8 concentration in the kimri fruit was about twice that in bisir (table 2). the ph of the date fruit is known to increase as the fruit develops from the kimri stage, which has higher acidity than either the bisir or rutab stage (rygg, 1946; rouhani and bassiri, 1976; el shurafa et al., 1982: el mardi et al., 1995). such an increase in rutab ph could have an inhibitory effect on k and na; thus, they are at lower levels in the rutab stage than in kimri (table 2). the high k in kimri (table 2). the high k in kimri ( kimri fruits relative to fe (1120 times) could be attributed to the higher acidity in these fruits compared to that in the later stages. titratable acidity in this cultivar is 1.25, 0.74 and 0.64 % during kimri, bisir and kimri, bisir and kimri, bisir rutab, respectively (el mardi et al., 1995). such a relationship between k and fe has also been found in apples (faust, 1989). except for fe in the fruit and leaf (table 2), none of the micronutrient elements was significantly different between stages. in fruits iron was significantly higher in bisir than in rutab and kimri. a similar trend was observed in the leaf. but fe in the fruit during rutab was significantly higher than during kimri, whereas in the leaf it was higher in the kimri than rutab stage. copper in fruit was not significantly different between stages, but it was higher in kimri and rutab than bisir. copper is an important element in the synthesis of anthocyanin, and so it is expected to be utilized for that purpose during the color development of bisir (ibrahim and khileif, 1993). insignificant differences between the concentrations of these micronutrients during the three developmental stages in leaves and fruits of date palms indicate that their ratios to macronutrients and to each other could be of more significance than their individual quantities, as indicated above by the relationship between k and fe, and k and cu. table 2 shows that during the kimri stage ca, mg, fe and mn in the leaf were higher than in the fruit, while k was higher in the fruit in the 3 stages and cu was higher in the fruit than in the leaf during the kimri and rutab stages. these results support the opinion of sink power of fruit to k to be the same as to carbohydrates, thus it accumulates in greater quantities in the fruit throughout its developmental stages (hansen, 1980). during bisir and bisir and bisir rutab, ca, mg, k, zn, cu and mn have similar trends as during kimri (leaf > fruit). however, na and fe fluctuated in the different stages. sodium was slightly higher in the fruit during kimri, but in bisir and bisir and bisir rutab it was much higher in the leaf. this is more likely related to the increase in sugar concentration during these stages causing an increase in the fruit osmotic pressure. this will cause na to concentrate more in the leaf or move from the fruit back to the leaf. iron was much higher in the leaf during kimri, but slightly lower during bisir and bisir and bisir rutab. there was mobility of fe from the leaf to the fruit at the later stages of development, as indicated by its reduced concentration in the leaf table 2. mean concentrations of macro and micro nutrient elements and sodium in the date fruit and leaf during its developmental stages (mg/kg). concentration stages of development kimri bisir rutab fruit leaf fruit leaf fruit leaf ca 1005.0a 2012.0b 548.0c 3425.0a 717.0b 2534.0b mg 1501.0a 2123.0a 805.0b 1254.0c 941.0b 1574.0b k 6723.0a 3557.0a 4365.0c 1875.0c 5458.0b 2490.0b na 173.0a 121.0a 39.0b 135.0a 70.0b 127.0a fe 6.1c 70.7b 154.8a 143.7a 92.4b 32.9c zn 2.3a 1.5a 5.4a 4.4a 3.7a 1.4a cu 2.9a 1.6a 1.6a 1.6a 2.7a 1.1a mn 4.9a 9.1a 5.2a 8.8a 2.9a 7.4a means followed by the same letter are not significantly different at .05 level, based on duncan’s multiple comparison test. influence of alternate bearing on leaf and fruit mineral composition of date palm fruit 9 and increased concentration in the fruit. results of changes in fruit na and fe concentration found here are in agreement with those obtained by sawaya et al. (1983) and ibrahim and khileif (1993). however, the concentration of fe and na during kimri was lower in the present study, which could be considered an indication of fe deficiency. there is accumulating evidence that higher ca and mg in leaves throughout the developmental stages of different kinds of fruits is consistent with lack of ca mobility in plants relative to k (batjar and westwood, 1958; pichioni et al., 1997; van goor and van lune, 1980; el shurafa, 1984). several studies have shown that k decreases in leaf during cropping while ca and mg are increasing (pichioni et al., 1997; bould,1966; diver et al., 1984; weinbaum et al., 1994). results in table 2 confirm these results. in deciduous fruit trees, such as apple and peach, leaves are annual (batjar and westwood, 1958). however, in date palms the leaf remains physiologically active for more than three years, then dries out and is pruned. evidently this difference contributes to the variable trend of the nutrient element during fruit and leaf development. when the leaves in deciduous fruit trees reach full maturity, some of the nutrient elements, especially k, mg and ca, will be transferred to the branches before the leaf fall. but in the date palm the inflorescence first appears in the axil of the mature leaf (one-year old), which is still active in nutrient uptake. thus, ca, mg, na and mn are always higher in the leaf than in the fruit. on the other hand, k, zn and cu were relatively higher in the fruit throughout its developmental stages. accumulation of ca, mg and k in the leaves amounted to 2.0x, 1.4x and 0.53x, respectively its concentration in the fruit during the kimri stage of the date palm (table 2). these ratios in pistachio during spring flush, which represent the kimri stage in dates, were: 9.5x, 5.3x and 0.80x, respectively (piechioni et al., 1997). the trend of elemental distribution is similar, i.e. ca > mg > k, but the amount accumulated in leaves of pistachio was much higher than in date palm leaves. during seed fall (representing fruit maturation) of pistachio fruit, the ratios of leaf to fruit content of these elements were: 7.7x, 3.7x and 0.62x, respectively, whereas for the bisir (representing date bisir (representing date bisir fruit maturation) they were: 6.3x, 1.5x and 0.43x, respectively. thus, the previous trend was maintained. however, the ratios of the three elements in pistachio were lower than during the spring flush period. by contrast ca and mg ratios were higher and the k was lower in the date palm during bisir than in bisir than in bisir kimri stage. these results indicate that during maturation (seed fall) there was a reduction in leaf/fruit elemental concentrations in pistachio, which had been attributed to a seasonal increase in leaf mass (marini and marini, 1983) rather than reduction in concentration. by contrast, an increase in leaf/fruit elemental concentration for ca and mg and a reduction for k were observed in the date palm. the date palm does not enter dormancy and the leaves used in this study were mature, being at least one-year old. these leaves accumulated more ca and mg with an increase in age. calcium is known to be less mobile from one organ to another relative to k, which migrates from leaf to fruit as it matures (batjar and westwood, 1958; piechioni et al., 1997). the date palm leaves tend to lose 65% of their photosynthetic efficiency after the second year (nixon and wedding, 1956); during the three stages of fruit development they tend to accumulate mg and high chlorophyll concentrations. moreover, many of the enzymes involved in carbohydrate metabolism require magnesium as an activator. effect of alternate bearing phenomenon on the mineral content of leaves and fruitsmineral content of leaves and fruitsmineral content of leaves and frui the effect of alternate bearing on fruit and leaf minerals concentrations during the three stages is shown in table 3. data in table 3 were collected during the three development stages. rutab is considered the harvestable stage of this cultivar in the study area. therefore, the concentration of minerals in these stages is more likely to influence their concentration in the next season, and they were also being influenced by their concentration in the previous season. in the fruit, ca was significantly higher in the “on-palm” than the “off-palm” during kimri, whereas, k, fe and mn during bisir, and fe during rutab were significantly higher in the “off-palm”. on the other hand, mg in the leaf was higher in the “off-palm” during rutab and k was higher in the “off-palm” during kimri. these results indicate that during the experimental season major changes occurred in minerals involved in fruit pigmentation and taste (rouhani and bassiri, 1976; rygg, 1946). however, the general trend indicates that el mardi et al. 10 the concentration of n is 13.3 % higher in leaves of the “off-palm” than “on-palm” indicating that the growth pattern in the “off-palms” was to a greater extent of a vegetative nature (data not shown in the tables). ca, fe, k and mn were slightly higher in the leaves of “on-palms” during kimri and bisir. and bisir. and but during rutab ca, mg, fe, zn, cu and mn were higher in the off-year leaves than on-year. on the other hand, in the fruit ca, mg, k, na, fe and zn during rutab were higher in the “off-year palm” than “on-year palms”, whereas, cu and mn were higher in the “on-year palm” fruits. note that “on-year palms” carried an average 8 bunches (8.0 kg/bunch) and the “off-year palms” carried 6 bunches (7.4 kg / bunch). these results are comparable to those obtained in pecan (sparks, 1977); pistachio (pichioni, 1997), citrus (monselise et al., 1983) and ‘french’ prune (weinbaum et al., 1994). the lower k concentrations in the leaves of “off-palms” in spite of their lower yield, indicate that these palms were probably deficient in this element. the concentrations of k, mn, na and cu in the fruit during rutabs showed an opposite trend than in the leaves of the same stage: k and na were higher and cu and mn were lower in the fruits of “off-palm” than those of the “on-palm”. these results indicate that alternate bearing can influence the concentration of n, k, mg, cu, fe and zn in date palms. regular fertilization with these minerals could be an effective practice to minimize the effect of alternate bearing on the date palm. but one season may not be sufficient to show the influence of alternate bearing on the mineral concentration in leaves and fruits. in this respect further study is needed for an extended period. conclusion alternate bearing showed significant effects on the concentration of ca, k, mn fe in the fruit during one or more development stages; and in the leaf only in mg and k. the results showed inconsistent variations in the minerals concentration in the fruit and leaf from “on-year” and “off-year” date palms. this indicates the need for experimentation over more than one season to verify the influence of alternate bearing on the mineral composition of the three developmental stages of the date fruit. acknowledgments the authors are greatly indebted to sultan qaboos university for supporting this project. table 3. mean concentrations of minerals in the fruit and the leaf during the three stages of development for alternate bearing years of the fard date cultivar (mg/kg). stages of development kimri bisir rutab fruit leaf fruit leaf fruit leaf bearing year bearing year bearing year bearing year bearing year bearing year on off on off on off on off on off on off ca 1041.3a 969.2b 2075.4a 1948.8a 537.1a 558.8a 3509.6a 3341.3a 709.2a 724.6a 2491.3a 2575.8a mg 1515.4a 1487.5a 2155.8a 2088.3a 765.0a 844.2a 1209.2a 1297.9a 906.3a 976.3a 1433.3b 1714.6a k 6666.7a 6779,2a 3446.7b 3666.7a 3704.2b 5025.0a 2172.1a 1576.3b 5325.0a 5591.8a 2556.7a 2424.2a na 180.5a 165.3a 116.1a 126.6a 43.4a 35.5a 136.4a 133.9a 66.4a 74.0a 132.2a 121.9a fe 6.8a 5.3a 74.1a 67.3a 6.6b 302.9a 7.5a 1.3a 8.5b 176.4a 27.9a 37.9a zn 1.7a 2.8a 1.1a 1.9a 6.0a 4.5a 7.5a 1.3a 1.2a 6.2a 0.6a 2.2a cu 2.8a 3.1a 1.5a 1.7a 2.0a 1.3a 2.0a 1.2a 3.4a 1.9a 0.4a 1.8a mn 5.2a 4.6a 9.3a 8.9a 2.2b 8.2a 9.6a 7.9a 3.7a 3.1a 7.2a 7.7a means in the same column for each stage with the same letter are not significantly different at the 0.05 level, based on duncan’s .multiple comparison test influence of alternate bearing on leaf and fruit mineral composition of date palm fruit 11 references al juburi, h.j. 1993. date palm pruning and fruit thinning in the date palm. the date palm, faculty of agricultural sciences, uae university press, al ain, pp180-192. al juburi, h.j., h. al-mesri, and m. al-banna. 1994. mineral contents of five date palm (phoenix mineral contents of five date palm (phoenix mineral contents of five date palm ( dactylifera l.) cultivars in various stages of development. bulletin faculty of agriculture, cairo university, 45:165-186. al juburi, h.j. 1995. analysis of minerals in date palm fruit under different nitrogen fertilizations. fruits 50:153-158. al khateeb, a.a., o.a. al-tahir and a. al-ghamdi. 1993. thinning stage effects on fruit size, yield and quality of date palm (phoenix dactylifera and quality of date palm (phoenix dactylifera and quality of date palm ( l.) cv “khalas”. third symposium on the date palm, king faisal university, al-hassa, saudi arabia, 17-20 january, pp231-237. bacha, m.a., m.a. shaheen and t.a. naser. 1993. study on iron and manganese contents of the fruits of some saudi date palm cultivars. third symposium on date palm, king faisal university, al-hassa, saudi arabia, 17-20 january, pp550566. batjar, l.p. and m.n. westwood. 1958. in: seasonal trends of several nutrient elements in leaves of alberta peach. proceedings of the american society for horticultural science 65:116 -126. bould, c. 1966. leaf analysis of deciduous fruits. in: nutrition of fruit crops, n.f. childers (editor), 651-684. clark, g.l and g.s. smith. 1990. seasonal changes in the composition and accumulation of mineral nutrients in persimmon fruit. scientia horticulturae 42:99-111. diver s.g., m.w. smith and r.w. mcnew. 1984. influence of fruit development on seasonal elemental concentration and distribution in fruit and leaves of pecan. communication in soil plant analysis 15:619-637. duncan, d.b. 1955. multiple range test and multi ftest. biometrics 11:1-24. el mardi, m.o., e.c. consolacion, k.m. abdelbasit., m. al-marzouqi and o.s. almantheri. 1998. evaluation of pollination method and pollen concentration on chemical characteristics of date fruit from fard cultivar. proceedings of the 1st international conference on date palm, al-ain, uae, 8-10 march, pp49-61. el mardi, m.o., h. esechie, l.m. al-kharousi and k.m. abdelbasit. 2002. effect of pollination method on changes in physical and chemical characteristics of date fruit during development. agricultural sciences 7:21-27. el mardi, m.o., s.n. labiad, e. consolacion and k.m. abdelbasit. 1995. effect of pollination method and pollen dilution on some chemical constituents of fard dates at different stages of fruit development. emirates journal of agricultural sciences 7:1-19. el mardi, m.o., s.b. salama, e. consolacion and m.s. al-shabibi. 1995. effect of treated sewage water in vegetative and reproductive growth of date palm. communication in soil plant analysis 26:1895-1904. el shurafa, m.y. 1984. annual loss of minerals from the date palm. date palm journal 3:278-290.date palm journal 3:278-290.date palm journal el shurafa, m.y., h.s. ahmed and s.e. abu naja. 1982. organic and inorganic constituents of date palm. date palm journal 1:275-284. faust, m. 1989. physiology of temperate zone fruit trees. wiley intersciences, ny, usa., pp106-227. goren, r. and s.p. monselise. 1971. effect of ripening on field of low bearing orange trees. journal of horticultural science 46:435-441. hansen, p. 1980. crop load and nutrient translocation: in: mineral nutrition of fruit trees. 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f. and d.e. bliss. 1942. the relationship of leaf area to alternate bearing in the deglet noor palm. date growers institute reports 19:3-7. mekki, m.a., a.h. hamouda and a.s. al-abri. 1998. date palm pruning and thinning in the date palm. cultural operations and maintenance. modern color press, muscat, sultanate of oman, pp 335338. monselise, s.p., e.e goldsmith, a. golomb and r. rolf. 1983. alternate bearing in citrus-long-term effect, of a single girdling treatment on individual “michal” tangerine branches. journal of the american society for horticultural science 108: 373-376. mustafa, a.a. 1993. effect of fruit thinning on yield and fruit quality of “seeway” date palm under alfayoum governorate conditions. third symposium on the date palm, king faisal university, alhassa, saudi arabia, 17-20 january, pp239-245. nixon, r.w. 1935. metaxenia in dates. proceedings of the american society for horticultural science 32:221-226. nixon, r.w. 1936. metaxenia and interspecific pollination in phoenix. proceedings of the american society for horticultural science 33: 21-26. nixon, r.w. 1940. fruit shrivel of halawy date in relation to amount and method of bunch thinning. proceedings of the american society for horticultural science 41:85-92. nixon, r.w. and c.l. crawford. 1942. quality of deslet noor date fruits as influenced by bunch thinning. proceedings of the american society for horticultural science 40:103-110. nixon, r.w. and r.t. wedding. 1956. age of date leaves in relation to photosynthesis. proceedings of the american society for horticultural science 67:263-269. patrick, j.w. 1988. control of assimilate partitioning in relation to crop productivity. hortscience 23: 33-40. patrick, j.w. 1991. control of phloem transport to the short distance transfer in sink region: an overview. in: recent advances in phloem transport and assimilate compartmentation, j.l. bonnemain, s. delrot, w.j. lucas, j. dainty (editors), 167-177. oest. edition, nates, france. piechioni, g.a., p.h. brown, s.a. weinbaum and t.t. muraoka. 1997. macronutrient allocation to leaves and fruits of mature alternate bearing pistachic trees: magnitude and seasonal pattern at the whole canopy level. journal of the american society for horticultural science 122:267-274. rouhani, i. and a. bassiri. 1976. changes in the physical and chemical characteristics of shahani dates during development and maturity. journal of the american society for horticultural science 51:489-4194. rygg, g.l. 1946. compositional changes in the date fruit during growth and ripening. technical bulletin no. 910, u.s. department of agriculture, washington d.c., pp 1-51. sawaya, w.n., h.a. khalchadarian, j.k. khalid, w.m. safri and a. al-shalhat. 1982. growth and compositional changes during the various developmental stages of some saudi arabian date cultivars. canadian journal for food science 47: 1489-1492. sawaya, w.n., j.k. khalid, m.w. safri and a. al-shalhat. 1983. physical and chemical characteristics of three saudi date cultivars at various stages of development. canadian institute of food science and technology journal 16:87-of food science and technology journal 16:87-of food science and technology journal 92. sparks, d. 1977. effect of fruiting on scorch premature defoliation and nutrient status of chickasaw pecan leaves. journal of the american society for horticultural science 103:699-673. swingle, w.t. 1925. pruning the date palm. date growers institute report 2:12-13. van goor, b.j. and p. van lune. 1980. redistribution of potassium boron, iron , magnesium and calcium in apple tree determined by indirect method. physiology plantarium 48:21-26. weinbaum, s.a., f.j. niederholzer, s. ponchne, r.c. rosecrance, r.m carlson, a.c. whittlesey and t.t. muraoka. 1994. nutrient uptake by cropping and defruited field-grown french prune trees. journal of the american society for horticultural science 119:925-930. received: december 2003 approved: september 2005 agricultural and marine sciences, 12:67-70 (2007) ©2007 sultan qaboos university 67 *corresponding author: e-mail: mdoghair@hotmail.com seasonal fluctuation of the date palm fruit stalk borer, oryctes elegans prell (coleoptera: scarabaeidae), in date palm plantations in al-qassim region, saudi arabia mohammad al-deghairi college of agriculture and veterinary medicine, qassim university, buraydah, p.o. box 1482, al-qassim, saudi arabia abstract: the date palm fruit stalk borer, oryctes elegans, is widely distributed in saudi arabia. undetected and untreated infestations by this pest result in severe losses. light trap studies to investigate seasonal population fluctuations of o. elegans were conducted in al-rajhi endowment date palm plantation in al-qassim, saudi arabia, by installing three modified robinson mercury-vapor light traps in 3 different equidistant sites. the investigation revealed that light trapping is an effective tool for the monitoring and forecasting of o. elegans infestations. the highest activity of o. elegans was witnessed from april to july, during which period 65% of adults captures were made. peak monthly activity was observed during june, when 19.4 % and 22.2% of the catches were made during 2003 and 2004, respectively. no beetle activity was observed during january and february. the highest number of beetles (56.6% of the population) was recovered in the site with relatively old and tall palms (more than 18 years old and averaging 7.5m in height). the site with shorter and younger palms received 29.6% of the beetles, whereas the uncultivated site had the lowest number of beetles (13.8% of total). keywords: oryctes elegans, date palm, light trap monitoring. منطقة القصیم في األجنحة غمدیة نخیل التمر عذوق الموسمي لحفار التذبذب السعودیة العربیة بالمملكة الدغیري عبدالعزیز محمد من oryctes boas و oryctes agamemnon arabicus و oryctes elegans مثل القرن وحیدة الخنافس تعد الخالصة: جمیع oryctes) بشكل واسع في elegans) النخیل عذوق حفار ینتشر السعودیة. العربیة المملكة في أخطر آفات نخیل التمر ضمن رصد عمل تم الدراسة ھذه في فادحة. تعامل خسائر ال أو ال تكتشف التي اإلصابات ینتج عن بالنخیل. المزروعة مناطق المملكة من أكثر یحوي والذي الراجحي أوقاف إدارة مشروع في الضوئیة المصائد باستخدام الموسمي النخیل عذوق حفار عشائر لتذبذب عملیة التقصي أوضحت متباعدة. مواقع ثالث في الضوئیة روبنسون مصیدة من ثالث مصائد معدلة وذلك بوضع نخلة ألف 200 شھر في كان نشاط لحفار العذوق أكبر العذوق. حفار عشائر أعداد زیادة وتوقع الستكشاف فعالة وسیلة تعتبر المصائد الضوئیة أن من العدد التوالي، على ،%22.2 و 19.4 تمثل 2004 2003 و عامي الشھر في ھذا في الخنافس أعداد مجموع كانت یونیو، حیث بلغت فیھا حیث للخنافس، نشاط أعلى یولیو و یونیو مایو، أبریل، أشھر وأظھرت الفترة. ھذه جمعھا خالل تم للحشرات التي الكلي النتائج أظھرت كما .2004 عام من ینایر وفبرایر شھري في للخنافس نشاط أي یكن ھناك لم بینما ،%65 المصطادة الحشرات نسبة 7.5م) (متوسط الطول طویلة نخیل بأشجار مزروعة مناطق في وضعت التي المصیدة من أتى جمعھا تم الحشرات نسبة من أعلى أن تحوي في منطقة وضعت التي المصیدة تلیھا للخنافس. الكلي العدد من %56.6 حوالي اصطیاد تم حیث عاما یفوق الـ18 وعمرھا المصیدة الكلي للخنافس. وأخیرًا العدد من %29.6 اصطیادھا حوالي التي تم الخنافس نسبة بلغت العمر حیث وأصغر في أقصر نخیال حوالي اصطیادھا التي تم الخنافس وبلغت نسبة النخیل لزراعات مالصقة و النخیل بأشجار غیر مزروعة منطقة في وضعت التي للخنافس. الكلي العدد من %13.8 al-deghairi 68 69 seasonal fluctuation of the date palm fruit stalk borer in date palm plantations introduction more than four million date palm trees are grown in al-qassim region of saudi arabia, including some of the world’s best varieties. rhinoceros beetles (coleoptera: scarabaeidae), such as oryctes elegans prell, o. agamemnon arabicus fairmaire, and o. boas fabricius, are among the most notorious pests of date palms in iraq, pakistan, iran and saudi arabia (talhouk 1984, 1991; martin, 1967, gharib, 1970; carpenter and elmer, 1978). infestations by these beetles usually remain undetected for a long period. untreated infestations result in severe losses manifested in lower yields, lower date quality, and death of trees, especially young transplants. the date palm fruit stalk borer, o. elegans is the most common oryctes species in saudi arabia (walker and pittaway, 1987) and is widely distributed throughout all date palm growing areas in the kingdom. adults feed on tender leaves, inflorescences and the fruit stalk of the fruit bunches of date palms. males and females probe and feed on bases of fronds and fruit stalks, thus sometimes causing wilting of these parts and/or production of lower quality dates due to the lower supply of nutrients and water reaching them (kadous et al., 1983; talhouk, 1984). the larvae of o. elegans (locally known as “alangara”) thrive on decomposing dung and decaying plant matter such as the stumps and trunks of dead or weak palms. larvae are also known to feed on the roots of date palms. light traps have been introduced by many researchers as means of monitoring beetle populations, as well as a method of physical control (fao, 2002; dillon and mackinnon, 2002). in this current study, light traps were used as a monitoring tool to detect the time of appearance of adult o. elegans in al-qassim date palm plantations and to provide data regarding associated adult activity (mating, egg laying), the size of the population, and the number of generations. in addition, the traps were expected to serve as a physical means of reducing densities of mating beetles (fao, 2002; dillon and mackinnon, 2002). it is anticipated that the results of this investigation will facilitate improved management of o. elegans, which will be reflected in increased yields and healthier stands of date palms. materials and methods al-rajhi endowment, the largest date palm plantation in al-qassim region, with an area of 200 ha and with more than 200,000 cultivated palm trees, was used as the site of this study. three modified robinson light traps (2 m high, supplied with mercury-vapor light, collecting funnel about 25 cm dia., and insect collection jar half filled with diesel) were installed at three different sites. light trap #1 was situated in the middle of an area in which barhi, sukari, khlas and nabtat ali date palm lines were grown. trees were 8-9 years old with an average height of 2.5 m. light trap #2 was located in an empty central area (containing stores, refrigerated rooms and other buildings) between areas in which traps # 1 and #3 were situated. light trap #3 was situated in an area under trees of the razizi, maktumi, shagra and nabtat ali lines, which were more than 18 years old, and with an average height of 7.5 m. the light traps were operated daily from sunset to sunrise, for a whole year, from june 2003 until june 2004. collected insects were removed from traps on a daily basis. catches were sorted out and positively identified o. elegans were separated out and counted. catches of o. elegans per trap were pooled monthly. results and discussion oryctes elegans was the dominant beetle, compromising more than 95% of all beetles captured in light traps during the study period. table 1 outlines the monthly catches of o. elegans adults in the three light traps. the number captured each night varied in the three light traps throughout the study period. windy and rainy conditions reduced beetle flight. however, no meteorological data were available to correlate with catches of o. elegans. the effective light range of light traps also varied substantially with the intensity of moonlight, such that on dark nights traps caught more beetles. the mean catching rate ranged from 11.8 to 85.5 beetles/trap/week, which can be considered to be indicative of a high infestation rate. the total number of oryctes beetles captured in the three traps was 5559. presuming a sex ratio of 1:1, this gives 2780 laying females. while no beetle activity at all was observed during january and february 2004, no evidence exists that al-deghairi 68 69 seasonal fluctuation of the date palm fruit stalk borer in date palm plantations o. elegans goes into hibernation in the adult stages during the winter months (from mid-december to mid-march). beetles showed up gradually in small numbers until april 2004 when a sudden outbreak was evident, the total number captured during this month in the three light traps was 804 beetles, comprising about 14.5% of the total catch of the year. april, may, june and july witnessed the highest activity of o. elegans, with 65% of the total yearly catch made during this period. peak activity of o. elegans was observed during the month of june, when 16 and 22% of the population was collected during 2003 and 2004, respectively. similar results were reported by talhouk (1982) who stated that in al-kharj and al-houfouf in saudi arabia o. agamemnon becomes active in april and reaches its peak activity from june to august. this same species was active from the end of april to the end of september in wadi qurayat in northern oman, with a peak in june (mokhtar et al., 2000). among the three trap sites, the highest number of beetles was recovered in light trap # 3, in the area under tall palms over 18 years old, where 56.6% of the total yearly catch was caught. next in percentage of catches was light trap #1 in the area of shorter and younger palms. this trap caught 29.6% of all beetles. trap #2 in the uncultivated area, caught the lowest percentage of o. elegans (13.8%). it is possible that o. elegans has a preference for older palms. in more mature plantations, decomposing organic matter and weak dying palms are expected to be more plentiful. these can be hypothesized to provide a good source of food for the beetle’s progeny and to supply good oviposition sites for adult beetles. it is documented that the eggs of o. elegans are laid in decomposing matter, and weak palm trees with decaying moist parts provide beetle larvae (martin, 1967; hussein, 1974; fao, 2002) with a good food source. another explanation for the differences in o. elegans catches among the three traps is variability in the degree of darkness among the three sites. the degree of darkness was highest in the area of light trap # 3 (tall, old palms), followed by trap # 1 (short, young palms), and then trap #2 (uncultivated field). this perhaps explains why the trap catches were consistently biased in favor of light trap # 3. acknowledgements we would like to thank the deanship of scientific research at king saud university for funding this project. also many thanks to al-rajhi endowment management at albatin, buraydah, for allowing to use the date palm plantation for this project and their endless help in maintaining and sampling the traps. references carpenter, j.b. and h.s. elmer. 1978. pests and diseases of date palm. usda agricultural handbook no. 527. dillon, m. and l. mackinnon. 2002. using light traps to suppress helicoverpa. the australian cottongrower 23:32-36. fao, 2002. date palm cultivation. a. zaid (editor). fao plant production and protection paper no. 156, rev. 1. table 1. mean number of oryctes elegans adults captured in 3 light traps during the period of june 2003 to june 2004 in a large date palm plantation in al-qassim, saudi arabia. see methods for description of sites. month number of oryctes adults captured in trap 1 trap 2 trap 3 june 2003 245 119 527 july 136 55 469 august 101 45 233 september 89 25 92 october 22 21 78 november 50 0 62 december 17 0 48 january 2004 0 0 0 february 0 0 0 march 34 0 21 april 215 97 492 may 97 130 817 june 639 273 310 total 1645 765 3149 grand total = 5559 monthly average 126.54 58.85 242.23 percent of all captures 29.60 13.80 56.60 al-deghairi 70 gharib, a. 1970. oryctes elegans prell. (coleoptera, dynastidae). applied entomology phytopathlogy (tehran) 29:10-12 (in french), 10-19 (in iranian). hussein, a. 1974. date palms and dates with their pests in iraq, 166pp. university of baghdad, ministry of higher education science research. kadous, a.a., s.m. hammad and m.m. ramadan. 1983. assessment of damage inflicted upon date palms by pseudophilus testaceus gahan and oryctes elegans prell in al-hassa oasis. in: proceeding of the 1st symposium on date palm. king faisal university, hofuf, saudi arabia. pp 698-699. martin, h. 1967. report to the government of iraq on cereal and tree pests. fao report no. ta2330, rome. mokhtar, a.m., s.s. al-nabhani and s.s. al-tamimi. 2000. seasonal abundance of the fruit-stalk borer oryctes agamemnon (burn.) (coleoptera: scarabaeidae) in date palm plantations in wadi quriyat, aldakhlyia region. annual report of entomology, jimah research station, ministry of agriculture and fisheries, sultanate of oman, pp. 44-46. talhouk, a.s. 1982. the present status of date palm pests in saudi arabia. proceedings of the first symposium on the date palm held at king faisal university, al-hassa, saudi arabia, march 23-25, 1982. talhouk, a.s. 1984. insect pests most spreading in the kingdom of saudi arabia and ways to suppress them. ministry of agriculturre and water, riyadh, saudi arabia. talhouk, a.s. 1991. on the management of the date palm and its arthropod enemies in the arabian peninsula. journal of applied entomology 111: 514-520. walker, d.h. and a.r. pittaway. 1987. insects of eastern arabia. macmillan publishers ltd., london. received: june 2005 accepted: november 2007 research paper journal of agricultural and marine sciences vol. 20 (2015): 54-61 reveived 5 aug. 2014 accepted 19 feb. 2015 gill monogenean communities on three commercially important sparid fish in omani waters gilha yoon1,*, hisham al-adawi2 and andrew shinn3 1 * sultan qaboos university, college of agricultural and marine sciences, department of marine science and fisheries, box 34, al-khod 123, sultanate of oman. gilha yoon ( ) email: ghyoon@squ.edu. om. 2 ministry of agricultural and fisheries, muscat, oman. 3fish vet group asia limited, 99/386, chaengwattana building, chaengwattana rd., kwaeng toongsonghong, khet laksi, bangkok, 10210, thailand. introduction the sultanate of oman has an extensive coast line that exceeds 3000 km in length providing a wealth of natural fishery resources, renewable sources of revenue and opportunities for the development of sustainable aquaculture enterprises. like bahrain, kuwait, qatar, saudi arabia, uae and yemen, the sultanate of oman has no extensive regions of freshwater and so much of the country’s population is distributed along its coast, with easier access to marine resources. oman’s affinity for the sea is reflected in its rich traditions and cuisine and oman’s average per capita consumption of marine fish remains among the highest in the world and surpasses that of many south-east asia countries. fishbase (froese & pauly, 2014) cites 1,018 fish species for the sultanate of oman. of these nine species belong to freshwater (four endemic, two native and three introduced species) whilst the remaining species belong to brackish and marine waters of which five species are misidentifications, 12 species are of questionable identity and three species are thought to be species that have strayed into omani waters. fao fishstatj (2013) indiجتمعات املونوجينا يف خياشيم أهم ثالثة أمساك السباريدية التجارية يف املياه العمانية جيلها يون1* وهشام العدوي2 واندرو شني3 abstract. the prevalence and intensity of polyopisthocotylean monogeneans on the gills of three commercially important species of sparid caught in omani coastal waters close to the city port of muscat were determined and compared. throughout may 2012 to april 2013, infections on bi-weekly samples of the soldier seabream, argyrops filamentosus (valenciennes, 1830), the king soldier seabream, argyrops spinifer (forsskål, 1775), and, the silver seabream, rhabdosargus sabra were evaluated. from a total of 200 specimens (standard length of 26–52 cm), caught by line angling or by traps, at least three species of gill monogenean, namely omanicotyle [bivagina] heterospina, heteromicrocotyla sp. and microcotyle sp., were commonly encountered. silver bream, which was infected by all three monogeneans, bore the highest infections (100% prevalence; mean intensity of 20.14 ± 0.92 parasites fish-1), whilst the soldier bream, which was infected only by o. heterospina had the lowest levels of infection (of the three sparids with 63.8% prevalence; mean intensity 5.8 ± 0.17 parasites fish-1). comments on the distribution of monogeneans on each host are provided but to what extent this is influenced by water current speeds passing through the buccal and opercular cavities, gill morphology, parasite size, and / or the morphology and efficiency of the parasite’s attachment apparatus requires establishing and forms the basis of ongoing investigations. keywords: gill monogenea; oman, seabreams; disease; aquaculture. املســتخلص: مت حتديــد ومقارنــة انتشــار وكثافــة الطفيليــات وحيــدة العائــل )polyopisthocotylean( يف خياشــيم ثالثــة أنــواع مــن األمســاك املهمــة إقتصاديا من فصيلة االسباريد اليت مت صيدها يف املياه الساحلية بالقرب من ميناء مسقط. خالل الفرتة من مايو 2012 إىل ابريل 2013 وملرتني كل .)argyrops filamentosus(, )argyrops spinifer(, )rhabdosargus sabra (:أسبوع مت تقييم اإلصابات يف الثالث أنواع من أمساك الكوفر وهي مــن جممــوع 200 عينــة مــن األمســاك )ذات طــول قياســي تــراوح بــني 26 إىل 52 ســم( مت صيدهــا بواســطة خيــوط الصيــد أو األقفــاص مت العثــور علــى omanicotyle )bivagina) heterospina , heteromicrocotyla ثــالث أنــواع مــن طفيليــات اخلياشــيم وحيــدة العائــل علــى األقــل بصفــة عامــة وهــي sp microcotyle sp.,. كانــت أعلــى نســبة إصابــة يف أمســاك )rhabdosargus sabra( حيــث أصيبــت جبميــع الثالثــة أنــواع مــن الطفيليــات وحيــدة العائــل بنســبة تفــش بلغــت 100% ومتوســط كثافــة 20,14 ± 0,92 نســبة طفيــل اىل الســمكة الواحــدة. بينمــا كانــت أقــل نســبة إصابــة يف أمســاك )argyrops filamentosus( حيــث أصيبــت بنــوع واحــد مــن الطفيليــات وحيــدة العائــل وهــو )o. heterospina( بنســبة تفــش 63,8% ومتوســط كثافــة 5,8 ± 0,17 نســبة طفيــل اىل الســمكة الواحــدة. مت أيضــا توثيــق مالحظــات حــول إنتشــار الطفيليــات يف العائــل، ولكــن إىل أي مــدى يتأثــر ذلــك بســرعة تيــارات امليــاه املــارة بتجويــف الفــم واخلياشــيم أو شــكل اخلياشــيم أو حجــم الطفيلــي أو فعاليــة و شــكل أجــزاء التمســك حباجــة إىل حبــث اســتقصائي مســتمر مســتقبال. الكلمات املفتاحية: طفيليات اخلياشيم وحيدة العائل، سلطنة عمان، مسك الكوفر، األمراض، االستزراع السمكي. 55research article yoon, al-adawi, shinn cates that oman wild fishery catches in 2012 were in the order of 191,563 tonnes (t) (see table 1), with over 40 species being commonly landed. collectively, this marine harvest is worth an estimated us$ 180 million. fish and fishing, therefore, remains an important part of source of income and livelihood options and is at the very heart of oman’s culture and love of eating fish. domestic fish purchases represent ~6% of the household budget and, on a national scale, fisheries represents 0.6% gdp and 34% of the agriculture sector. by comparison, aquaculture is still very much in its infancy but there is an impetus to invest in and to develop a range of aquaculture industries. the government scripted legislation regarding aquaculture in 2004 and in collaboration with fao has developed a national strategy for aquaculture development in 2007 (fao, 2011). with a national strategy for the development of aquaculture, there is also a parallel need to be aware of factors that may impact on production and to put in place management practices to either prevent or minimize their effect. the prevention and treatment of disease, for example, throughout the aquaculture industry is essential. deterioration in water quality combined with heavy losses from a variety of fish diseases has proven a major obstacle to the further development of fish aquaculture industries. the impacts that parasites can have on marine aquaculture, for example, has been recently reviewed by shinn et al. (2014). in particular, diseases caused by monogenean parasites have resulted in considerable economic damage to the aquaculture industry (buchmann et al., 1995; bondad-reantaso et al., 2005; bakke et al., 2007). in marine aquaculture, infections of heteraxine heterocerca (goto, 1894) yamaguti, 1938 and benedenia seriolae (yamaguti, 1934) meserve, 1938 on japanese amberjack, seriola quinqueradiata temminck et schlegel, 1845 as reported by kubota & takakuwa (1963) were calculated by shinn et al. (2014) to have cost the japanese industry approx. us$ 1 m at the time of the event whilst more recent figures for the collective impact of b. seriolae on s. quinqueradiata, on greater amberjack, seriola dumerili (risso, 1810), and on kingfish, seriola lalandi valenciennes, 1833, has been estimated at us$ 214 m (whittington et al., 2001; ernst et al., 2002). variable losses due to the gill polyopisthocotylean zeuxapta seriolae (meserve, 1938) on these seriolid hosts also contribute to losses throughout the industry (see shinn et al., 2014). other notable monogenean induced losses of marine aquaculture species include infections of diplectanum aequans (wagener, 1857) diesing, 1958 on european seabass, dicentrarchus labrax (l.). infections on juvenile italian stock as reported by dezfuli et al. (2007) was later estimated by shinn et al. (2014) to have caused losses worth us$ 0.925 1.85 m. yoon et al. (1997) reported that high prevalences of infection (i.e. 77.8-100%) of microcotyle sebastis goto, 1894 on korean rockfish, sebastes schlegelii hilgendorf, 1880 can lead to high parasite burdens of up to 2120 fish1 and the mass mortality of stock. estimates of loss at the time of the report are put at us$ 7,910 t-1 (shinn et al., 2014). there are also numerous reports in the literature relating to the impact of the capsalid neobenedenia [syn. girellae] melleni (maccallum, 1927) yamaguti, 1963 on a range of host fish. notable recorded losses of aquaculture stock include infections on cobia, rachycentron canadum (l., 1766) reared in taiwanese waters (lopez et al., 2002; ogawa et al., 2006) worth an estimated us$ 0.9-1.8 m (shinn et al., 2014). infections of sciaenocotyle panceri (sonsino, 1891) on meagre, argyrosomus regius asso, 1801 (see merella et al., 2009; shinn et al., 2014) and heterobothrium okamotoi ogawa, 1991 on tiger pufferfish, takifugu rubripes (temminck et schlegel, 1850) (see ogawa & inouye, 1997; ogawa et al., 2005; shinn et al., 2014) are also recorded to result in the mass mortality of stock and heavy economic loss. of the 989 valid fish species found in omani coastal waters, fishbase suggests that 45 of these may be of potential use in aquaculture (see table 2). in this study, we take the first steps to assessing the potential of some of these species as candidates for aquaculture by looking at their parasite profiles with a view to being better informed of the potential risks that some of these may pose under intensive aquaculture conditions. here we look at the communities of platyhelminth monogeneans on the gills of three commonly caught and traded species of sparid (sparidae, perciformes) in omani waters, namely the soldier seabream, argyrops filamentosus (valenciennes, 1830), the king soldier seabream, argyrops spinifer (forsskål, 1775), and the silver seabream or “tarwhine”, rhabdosargus sabra (forsskål, 1775). materials and methods sampling location and parasites collection the three species of seabream, a. filamentosus, a. spinifer and r. sabra, caught within the sea of oman off the coastal city of muscat and landed at the port of muttrah (23º 37’ 08.65” n; 58º 35’ 33.76 e) were sampled throughout the period may 2012 to april 2013. a total of 200 specimens, that were either alive or fresh dead at the time of acquisition, were screened from biweekly samples. following collection, the specimens were immediately transported to the parasitology laboratory at sultan qaboos university where the fish were measured (total length to the nearest 1 cm) and weighed (to the nearest 1 g). thereafter, the gills were excised and screened for monogenetic trematodes under an carl zeiss stemi 2000 dissecting microscope. identification of monogeneans the isolated monogeneans from individual fish were fixed and stored in 80% ethanol. the internal morphology was discerned by staining representative samples in 56 squ journal of agricultural and marine sciences, 2015, volume 19, issue 1 gill monogenean communities on three commercially important sparid fish table 1. landings from commercial fisheries in the marine waters of the sultanate of oman in 2012 ranked by tonnage. figures have been extracted from fao fishstatj (2013). common name species details tonnes % indian oil sardine sardinella longiceps valenciennes, 1847 43499 22.73 longtail tuna thunnus tonggol (bleeker, 1851) 14287 7.46 hairtails, scabbardfishes nei trichiurus lepturus l., 1758, 10878 5.68 lepidopus caudatus (euphrasen, 1788) carangids nei 21 genera, 48 species 9328 4.87 emperors nei genus lethrinus, 8 spp. 8962 4.68 indian mackerel rastrelliger kanagurta (cuvier, 1816) 8596 4.49 jacks, crevalles nei confused potentially 2 families, 4 genera, 10 spp. 7645 3.99 croakers, drums nei sciaenidae, 6 genera, 13 spp. 6863 3.58 pharaoh cuttlefish sepia pharaonis ehrenberg, 1831 6530 3.41 narrow-barred spanish mackerel scomberomorus commerson (lacepède, 1800) 5620 2.93 yellowfin tuna thunnus albacares (bonnaterre, 1788) 5582 2.91 sharks, rays, skates nei 1 20 families, 27 genera, 75 spp. 5482 2.86 sea catfishes nei 2 families, 4 genera, 6 spp. 5153 2.69 pelagic percomorphs nei 2 perciformes 66 families, 273 genera, 628 valid spp. 4814 2.51 kawakawa euthynnus affinis (cantor, 1849) 4609 2.41 queenfishes genus scomberoides, 3 spp. 4244 2.22 barracudas nei genus sphyraena, 8 spp. 4002 2.09 groupers nei 4 genera, 27 spp. 3947 2.06 demersal percomorphs nei 2 perciformes 66 families, 273 genera, 628 valid spp. 3714 1.94 anchovies, nei genera encrasicholina, stolephorus & thryssa, 11 spp. 3590 1.87 indo-pacific sailfish istiophorus platypterus (shaw, 1792) 3392 1.77 porgies, seabreams nei sparidae, 10 genera, 17 spp. 3352 1.75 mullets nei mugilidae, 6 genera, 10 spp. 3151 1.64 grunts and sweetlips gen. diagramma, plectorhinchus & pomadasys, 17 spp. 2677 1.40 threadfin and dwarf breams nei genus nemipterus, 4 spp., genus parascolpsis, 3 spp. 2337 1.22 marine fishes nei 4 1844 0.96 tuna-like fishes nei 3 scombridae, 5 genera, 5 spp. 1225 0.64 rays, stingrays, mantas nei 1 7 families, 16 genera, 28 spp. 1127 0.59 snappers, jobfishes nei lutjanidae, 8 genera, 34 spp. 1071 0.56 bullet and frigate tunas auxis rochei rochei (risso, 1810), 943 0.49 auxis thazard thazard (lacepède, 1800) spinefeet (= rabbitfishes) nei genus siganus, 4 spp. 757 0.40 penaeid shrimp nei fenneropenaeus indicus (h. milne-edwards, 1837) 742 0.39 penaeus semisulcatus (de haan, 1844) striped bonito sarda orientalis (temminck et schlegel, 1844) 501 0.26 needlefishes nei belonidae, 4 genera, 7 spp. 396 0.21 tropical spiny lobsters nei panulirus homarus (l., 1758) 243 0.13 black marlin istiompax indica (cuvier, 1832) 128 0.07 cobia rachycentron canadum (l., 1766) 128 0.07 skipjack tuna katsuwonus pelamis (l., 1758) 100 0.05 abalones nei haliotis mariae wood, 1828 54 0.03 total 191563 footnotes: 1 the species details listed for sharks, rays and skates include the general species details provided for rays, stingrays and mantas. providing precise details for each requires further detailed assessment. 2 the perciforms are large and diverse order of fish, in the absence of detailed capture fisheries data, the species found in omani waters have been grouped and not separated into pelagic and demersal species as classified by fao fishstatj. 3 does not include the other nine scombrid species listed in table 1. 4 fao fishstatj does not provide sufficient details to determine the composition of this group of fish. abbreviations: nei = not included elsewhere. 57research article yoon, al-adawi, shinn table 2. forty five species of marine and brackish fish found within omani waters that have the potential use for aquaculture as listed by fishbase (froese & pauly, 2014). scientific binomial common name local name acanthopagrus latus (houttuyn, 1782) yellowfin seabream shaam argyrosomus japonicus (temminck et schlegel, 1843) japanese meagre yanam carangoides equula (temminck et schlegel, 1844) whitefin trevally sall caranx ignobilis (forsskål, 1775) giant trevally dibsy caranx lugubris poey, 1860 black jack caranx melampygus cuvier, 1833 bluefin trevally dibsy chanos chanos (forsskål, 1775) milkfish chelon macrolepis (smith, 1846) largescale mullet anubah chelon subviridis (valenciennes, 1836) greenback mullet gutarana coryphaena hippurus l., 1758 common dolphinfish crenimugil crenilabis (forsskål, 1775) fringelip mullet eleutheronema tetradactylum (shaw, 1804) fourfinger threadfin ellochelon vaigiensis (quoy et gaimard, 1825) squaretail mullet gutarana epinephelus areolatus (forsskål, 1775) areolate grouper hamour epinephelus bleekeri (vaillant, 1878) duskytail grouper hamour epinephelus coioides (hamilton, 1822) orange-spotted grouper epinephelus lanceolatus (bloch, 1790) giant grouper hamour epinephelus malabaricus (bloch et schneider, 1801) malabar grouper hamour gnathanodon speciosus (forsskål, 1775) golden trevally bakes hippocampus kuda bleeker, 1852 spotted seahorse buzizi leiognathus equulus (forsskål, 1775) common ponyfish lethrinus nebulosus (forsskål, 1775) spangled emperor khutam lutjanus argentimaculatus (forsskål, 1775) mangrove red snapper hamra lutjanus erythropterus bloch, 1790 crimson snapper lutjanus johnii (bloch, 1792) john’s snapper khadharcha lutjanus monostigma (cuvier, 1828) one-spot snapper hamra lutjanus rivulatus (cuvier, 1828) blubberlip snapper sbetti lutjanus russellii (bleeker, 1849) russell’s snapper aglaa lutjanus sebae (cuvier, 1816) emperor red snapper hamra megalops cyprinoides (broussonet, 1782) indo-pacific tarpon muraenesox cinereus (forsskål, 1775) daggertooth pike conger asfan platax orbicularis (forsskål, 1775) orbicular batfish emad platycephalus indicus (l., 1758) bartail flathead wahar polydactylus plebeius (broussonet, 1782) striped threadfin pomadasys kaakan (cuvier, 1830) javelin grunter nagrur pomatomus saltatrix (l., 1766) bluefish tekwa protonibea diacanthus (lacepède, 1802) blackspotted croaker rachycentron canadum (l., 1766) cobia goada rhabdosargus sarba (forsskål, 1775) goldlined seabream gorgofan scatophagus argus (l., 1766) spotted scat bushami seriola dumerili (risso, 1810) greater amberjack gazala siganus canaliculatus (park, 1797) white-spotted spinefoot safi sillago sihama (forsskål, 1775) silver sillago swam terapon jarbua (forsskål, 1775) jarbua terapon yanam trachinotus blochii (lacepède, 1801) snubnose pompano suban 58 squ journal of agricultural and marine sciences, 2015, volume 19, issue 1 gill monogenean communities on three commercially important sparid fish 1% acetic carmine. identification of the monogeneans was based using a series of key morphological features, including those relating to the eggs (when present), clamp (including sclerite morphology) shape, number and configuration, shape and relative armature of the genital / vaginal atria etc. using the key of yamaguti (1963) and a recent description provided in yoon et al. (2013). data analysis from the parasitological examinations a number of basic metrics are provided and these follow those detailed in bush et al. (1997), i.e. parasite prevalence is the number of fish infected with one or more individuals of a particular parasite species divided by the number of hosts examined expressed as a percentage; and, the mean intensity is given by the total number of parasites encountered divided by the number of infected hosts. results and discussion three species of monogenean were encountered on the gills of the three sparids in the current study and the prevalence, mean intensity and distribution of these are summarized in table 3 and figure 4a-c. the microcotylid omanicotyle [bivagina] heterospina (mamaev et parukhin, 1974) yoon, al-jufaili, freeman, bron, paladini et shinn, 2013 (family microcotylidae taschenberg, 1879; subfamily microcotylinae monticelli, 1892) was encountered on the gills of all three sparids, whilst the unidentified species of microcotyle van beneden et hesse, 1863, was found on only a single species, the silver seabream, r. sabra. the species of heteromicrocotyla yamaguti, 1953 (family heteromicrocotylidae unnithan, 1961), which as yet remains to be formally identified, was found on the species of two argyrops i.e., the soldier seabream a. filamentosus, and the king soldier seabream, a. spinifer. this pattern of host infection is interesting and leads to the question of whether o. heterospina demonstrates a broad host specificity that includes other sparids found in omani waters. currently 17 species of sparid (sparidae, perciformes) classified into ten genera (acanthopagrus 5 species; argyrops 1 species; boops 1 species; cheimerius 1 species; crenidens 1 species; diplodus 3 species; lithognathus 1 species; pagellus 1 species; rhabdosargus 2 species; and, sparidentex 1 species) are documented in fishbase as occurring in omani waters (froese & pauly, 2014). interestingly though, this list does not include the soldier seabream, a. filamentosus, and suggest a need for update. although this study documents the occurrence of o. heterospina on hosts from two different genera, future studies could determine whether they occur on other sparid genera. monogeneans are generally regarded as being host-specific or having a narrow host range and different degrees of this was demonstrated by the study of rohde (1979) who from a survey of marine monofigure 1. the microcotylid monogenean omanicotyle [bivagina] heterospina was found on the gills of all three sparids: soldier bream, argyrops filamentosus, king soldier bream, argyrops spinifer, and, on silver bream, rhabdosargus sabra. 59research article yoon, al-adawi, shinn geneans found that 340 species (78%) were restricted to single host species, 388 species (89%) to one genus, 420 species (96%) to one family and 429 species (98%) to one order. similar ideas on the host-specificity of monogeneans were discussed by llewellyn et al. (1984). one observation worthy of note is that during the post-mortem dissection, the gill filaments of the silver seabream were noticeably more delicate than those of the other two hosts and this may be factor in the colonization success of polyopisthocotylean monogeneans. the distribution of monogeneans on the gills, as a community of species, is presented in figure 3. it would appear that o. heterospina, the only monogenean infecting the gills of a. spinifer, has an equal distribution across the left and right hemibranchs with no discernible preference for particular gill arches. the same situation appears to be the case of a. filamentosus which is infected by heteromicrocotyla sp. and o. heterospina. the monogeneans on the gills of r. sabra, however, favour the first gill arch and whether this is skewed by the particular habitat preferences of the species of microcotyle infecting this host is currently under investigation. buchmann et al. (1987) and buchmann (1988) suggested that the demonstrable preference by species of pseudodactylogyrus for the first and fourth gill arches on european eels (anguilla anguilla), is because of the lower flow over these gill arches. the morphology of the buccal and opercular cavities in these sparids is also under investigation and is it hoped that the data will help explain the microhabitat preferences displayed by these monogeneans on the gills of these three sparid hosts. table 3. summary of the monogeneans encountered on three commercially important species of sparid fish caught in omani coastal waters and brought in through the port of muttrah. the mean intensity is given for each followed by the prevalence in parentheses. argyrops filamentous (n= 240) argyrops spinifer (n =183) rhabdosargus sabra (n=237) heteromicrocotyla sp. 2.7 ± 0.45 (23.5%) 0 (0) 7.5 ± 0.72 (48.1%) microcotyle sp. 0 (0) 0 (0) 3.5 ± 0.39 (21.9%) omanicotyle heterospina 3.2 ± 0.72 (63.8%) 5.1 ± 0.15 (70.5%) 9.1 ± 0.21 (100%) overall prevalence 5.8 ± 0.17 (63.8%) 5.1 ± 0.15 (70.5%) 20.1 ± 0.92 (100%) figure 2. heteromicrocotyla sp. collected from the gills of soldier bream, argyrops filamentosus, and, from silver bream, rhabdosargus sabra. 60 squ journal of agricultural and marine sciences, 2015, volume 19, issue 1 gill monogenean communities on three commercially important sparid fish conclusions the polyopisthocotylean monogeneans omanicotyle heterospina, an as yet unidentified species of heteromicrocotyla, and an unidentified species of microcotyle were recovered from the soldier bream, argyrops filamentosus, the king soldier bream, argyrops spinifer, and, the silver bream, rhabdosargus sabra. the latter host was infected by all three monogeneans (100% prevalence of monogenean infection), whilst a. filamentosus was infected with o. heterospina and heteromicrocotyla sp. (63.8% prevalence of infection), and, a. spinifer by only a single species o. heterospina (prevalent on 70.5% of hosts). whilst there appears to be a fairly even distribution of monogeneans across the gills and hemibranchs on the two argyrops hosts, the monogeneans on the silver bream show a marked preference for the first gill arch. to what extent this distribution is influenced by water current speed, morphology and efficiency of the parasite’s attachment apparatus, parasite size, and / or by buccal/opercular/gill morphology is currently under investigation. acknowledgements this study was supported through internal grant (project code: ig/agr/fish/13/02) from sultan qaboos university, sultanate of oman. figure 3. heteromicrocotyla sp. collected from the gills of soldier bream, a. filamentosus, and, from silver bream, r sabra. figure 4. mean intensity of monogenean infection on each gill arch and hemibranch from each population of sparids sampled from omani waters. (a) soldier seabream, argyrops filamentosus (valenciennes, 1830); (b) the king soldier seabream, argyrops spinifer (forsskål, 1775); and (c) silver seabream, rhabdosargus sabra (forsskål, 1775). 61research article yoon, al-adawi, shinn references bakke, t.a., j. cable, and p.d. harris. 2007. the biology of gyrodactylid monogeneans: the ‘‘russian-doll killers’’. advances in parasitology 64: 161-376. bondad-reantaso, m.g., r.p. subasinghe, j.r. arthur, k. ogawa, s. chinabut, r. adlard, z. tan, and m. shariff. 2005. disease and health management in asian aquaculture. veterinary parasitology 132: 249-272. buchmann, k. 1988. interactions between the gill-parasitic monogeneans pseudodactylogyrus anguillae and p. bini and the fish host anguilla anguilla. bulletin european association of fish pathologists. 8: 98-99. buchmann, k., s. mellergaard, and m. køie. 1987. pseudodactylogyrus infections in eel: a review. diseases of aquatic organisms 3: 51-57. buchmann, k., h.c. slotved, and d. dana. 1995. gill parasites from cyprinus carpio in indonesia. aquaculture 129: 437-439. bush, a.o., k.d. lafferty, j.m. lotz, and a.w. shostak. 1997. parasitology meets ecology on its own terms: margolis et al. revisited. journal of parasitology 83: 575-583. dezfuli, b.s., l. giari, e. simoni, m. menegatti, a.p. shinn and m. manera. 2007. gill histopathology of cultured dicentrarchus labrax (l.) infected with diplectanum aequans (wagener, 1857) diesing, 1958 (diplectanidae: monogenea). parasitology research 100: 707-713. ernst, i., i. whittington, s. corneillie, and c. talbot. 2002. monogenean parasites in sea-cage aquaculture. austasia aquaculture feb./mar.: 46-48. fao. 2011. fishery and aquaculture country profiles: oman. http: //.fao.org/fishery/countrysector/fi-cp_ om/en. fao fishstatj. 2013. fisheries and aquaculture department, statistics and information service fishstatj: universal software for fishery statistical time series. copyright 2011.version 2.1.0. 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(monogenea: microcotylidae) from the gills of argyrops spinifer (forsskål) (teleostei: sparidae) from the sea of oman. parasites & vectors 6: 170-182. yoon, g.h., a.p. shinn, c. sommerville and j.y. jo. 1997. seasonality and the microhabitat of microcotyle sebastis goto 1894, a monogenean gill parasite of farmed rockfish, sebastes schlegeli hilgendorf 1880. korean journal of aquaculture 10 (4): 387-394. agricultural and marine sciences, 18:1-6 (2013) sultan qaboos university 1 ____________________________________________ *corresponding author/e-mail: ejohnson@squ.edu.om a review of observations made on select parameters of the camel immune system eugene h. johnson*, khalid r. al-habsi, and rashid m. al-busaidi department of animal and veterinary sciences, college of agricultural and marine sciences, sultan qaboos university, p.o. box 34, al-khod 123, sultanate of oman اإلبل املناعة في نظام مختارة من معلمات لبعض املالحظات عن استعراض وراشد البوسعيدي احلبسي وخالد جونسون ه. *-يوجني ويعتبر هذا احليوان. في بنظام املناعة ذات العالقة الدراسات من محدود عدد هناك أن إال ، مع البشر طويلة لفترات اإلبل بالرغم من وجود اخلالصة: تطور ولكنه ، للغاية صعبة مناخية ظروف والعيش حتت البقاء على حيوان قادر فقط إلى ليس تطورت عبر التاريخ قد اإلبل إذ أن سوء احلظ من هذا املناعة نظام اتلفة في الفاعلة املكونات فهم محاولة املهم من فإنه وبالتالي املعدية. األمراض من للعديد كبيرة بدرجة مقاوم أيضاًإلى حيوان مسببات مع التعامل حتى ميكن للحيوانات األليفة األخرى املناعة أنظمة في للتحكم ممكنة كقاعدة الستخدام أساسياتها وذلك اإلبل في الفريدة املضادة األجسام أنواع باإلضافة إلى والبلعمية عن أنظمة التكامل احلديثة اجلهود البحثية استعراض مت الكفاءة. بنفس األمراض والعالج احملتملة. التشخيص لوسائل الدور املهم مت إبراز كما احلالي. الوقت واسع في اهتمام مثار هي والتي اجلمليات في فصيلة التي توجد املناعية. ، اخلاليا احليوية املضادات املناعي، اجلهاز اإلبل ، مفتاحية: كلمات abstract: despite the camel’s long historical interaction with man there is only a limited number of studies available pertaining to the immunobiology of this species. this is unfortunate as the camel has evolved into an animal capable of not only surviving under extreme environmental conditions but also into one that is relatively resistant to a great number of infectious diseases. accordingly, it is of interest to understand the various components operative in the camel immune system, as a potential basis of manipulating the immune response of other domesticated animals to respond to disease-causing agents in a similarly effective fashion. recent research endeavors on the complement and phagocytic system, as well as the unique antibody types found in camelids that have seen an explosion of interest in recent times have been reviewed and their potential use as diagnostic and therapeutic tools highlighted. keywords: camel, immune system, antibodies, leukocytes. introduction the camel remains to a great extent an enigma shrouded in the mysteries of contemporary biology, despite centuries of man’s intensive dependence on and interaction with this species. of particular interest is the fact that not only can the camel survive under some of the most extreme environmental conditions but it also appears to have evolved into an animal with low susceptibility to a variety of diseases (fazil and hoffman, 1981). undoubtedly, studies endeavoring to elucidate the immunological mechanisms utilized by camels to fight pathogenic agents might lead to important breakthroughs in our understanding of the disease process in general, and perhaps open doors of knowledge that may enhance our ability to stimulate the immune system of man and other animals to function in a similar effective manner. the immune system is a complex network consisting of many cellular and non-cellular components which interact with each other. for simplicity, it is commonly divided into an innate (non-specific) and a specific immune system. over the last twenty years a growing body of observations and studies have been undertaken on the camel’s immune system and published in a wide spectrum of international journals. the present review is an attempt to consolidate some of the most interesting findings, in the hope that this information might encourage even more scientists to explore and exploit the immunobiology of this unique animal, and equally important, to acknowledge the fine work being undertaken by a handful of researchers in various parts of the world who are helping to bring the study of one of man’s oldest companions into vogue. the complement system the complement system is made up of at least twenty different proteins that are present in high concentrations in the blood and tissues. these proteins work together in a cascade fashion 2 johnson et al. 3 a review of observations made on select parameters of the camel immune system to destroy invading organisms, and equally important, to act as a signaling system for other elements of the immune system. in order to keep the complement system in check the individual complement components must be activated before they become effector molecules. this can be achieved by one of three ways. the first way is mediated through antibodies and is termed the ‘classical pathway of complement fixation’. the second way is termed the alternative pathway. finally, the complement system can be activated in a more recently-described fashion termed the lectin activation pathway (weiss et al., 1992). the result of all three pathways is the generation of a series of effector molecules. a generated membrane attack complex (c5bc9) causes lysis of foreign organisms. the complement system also produces proteins that serve as opsonins (ic3b, c3b, c4b), and chemoattractants (c3a, c4a and c5a) that induce acute inflammation by binding to mast cells and triggering their degranulation and subsequent release of vasoactive mediators, such as histamine. in addition, these peptides can stimulate chemokines of neutrophils, adherence to endothelial cells and enhance the respiratory burst of phagocytic cells. camels appear to have demonstrable levels of classical pathway hemolytic activity throughout their lives (olahomukani et al., 1995a) and similar to lambs (oswald et al., 1990) and calves (jain and goel, 1989) appear to acquire relatively large amounts of hemolytic complement activity via colostrum. they only exhibit higher levels of classical complement activity in their sera from 1-5 years of age (olaho-mukani et al., 1995a). similarly, it has been reported that camels between 3 months and one year of age have higher levels of alternative complement pathway activity in their sera than camels in the age group of five years and above (olaho-mukani et al., 1995b). it is unknown why the complement activity declines but it is unlikely due to the presence of conglutinins in serum, as described in cows (kakoma and kinyanui, 1974), as only low levels of these proteins have been found in the sera of camels (bhatnagar et al., 1987). interestingly, older male camels have been reported to exhibit higher levels of classical hemolytic complement activity than females of the same age group (olah-mukani et al., 1995a). although one can hypothesize that this is merely a hormone related phenomenon it does not readily explain what biological function this might serve. it would be interesting to determine whether older female camels are in any way more prone to infectious agents than similar aged male counterparts. besides for the defense against microorganisms, complement appears to be important in the control of parasitemia in camels infected with trypanosoma evansi. also, it has been suggested that the decreased levels of complement activity commonly observed in animal trypanosomiasis might result in immunosuppression (ouma et al., 1997). the neutrophil polymorphonuclear neutrophils play a crucial role in the phagocytosis and killing of invading microorganisms. they are also the predominant leukocyte type found in the peripheral blood of camels (abdurahman et al., 1992; wernery, 1995). in camels their numbers vary with age. young camels tend to have larger numbers of white blood cells and a higher percentage of neutrophils than lymphocytes (wernery et al., 1999). this is in contrast to most ruminants that have a neutrophil:lymphocyte ratio approximating 1:2. the neutrophils of camels are reported to be smaller than those from other animal species (ali et al., 1989). a unique ultra-structural observation in the camel, not found in other animal species, is the finding that the nucleus is bound by a well-defined perinuclear space (ali et al., 1989). camel neutrophils appear to have highly electron dense and less dense granules that likely correspond to the primary and specific granules reported in most other animal species (ali et al., 1989). tertiary granules have not been demonstrated. camel neutrophils exhibit an oxidative respiratory burst similar in its kinetics to that of neutrophils of other species against staphylococcus aureus (cooray et al., 1997) however, our lab has observed that neutrophils from camels exhibit a higher level of activity in their chemiluminescence response than sheep (johnson et al., 2006). the eosinophil eosinophils are most commonly associated with the ability to kill multicellular parasites and for their role in specific types of allergic reactions. however, eosinophils play an important role in regulating inflammation by modulating the function of mast cells, basophils and eosinophils (gleich and adolphson, 1986). they also produce inflammatory mediators such as leukotriene c4 (jorg et al., 1982; shaw et al., 1984), platelet activating factor (lee et al., 1984), oxygen free radicals (tauber et al., 1976) and cationic proteins (olson et al., 1977; peterson et al., 1986; peterson and venge, 1983). there is evidence that eosinophils might express major histocompatibility antigens after stimulation by granulocyte-macrophage colony stimulating factor (weller, 1992). accordingly, they might play a role in antigen presentation. neither a structural nor functional biological equivalent to ige has been found in the camel, so it is unknown whether the camel eosinophil has an fc receptor for this or any of the three camel igg subclasses. at the ultra-structural level the camel eosinophil has unique characteristics. their specific granules exhibit the basic structure of an electron-dense crystalloid core surrounded by a lighter, homogenous matrix. however, in contrast to other animal species, they are very polymorphic. the crystalloid cores are extremely variable in shape and size and often segmented and demonstrate a variety of lamellated patterns. interestingly, it is not unusual to demonstrate multiple crystalloid cores in a single granule. the extreme polymorphism of the specific granules and variety of lamellated patterns differentiate camel eosinophils from those of other species (johnson et al., 1999). camel eosinophils also appear to be especially effective killers 2 johnson et al. 3 a review of observations made on select parameters of the camel immune system of parasites and when activated commonly reveal hypersegmented nuclei (unpublished observation). it is not yet clear how these structural differences render the camel with such an apparent efficiency in killing parasites. camelid antibodies antibodies are generally described as protein molecules consisting of two pairs of proteins, termed heavy chains and light chains. the prototype antibody consists of an antigen binding region (fab), made from both heavy and light chain segments, and an fc fraction that is made entirely from the heavy chain. antibodies are generally considered to be divalent and bi-functional. divalency refers to their ability to bind two antigens at the same time. the bi-functionality is based on the ability of the antibody to not only bind to an antigen but also bind via its fc portion to specialized fc receptors found on the surface of a variety of cells such as neutrophils and macrophages. antibodies are made by b lymphocytes, which develop and mature in the bone marrow. using immunoelectrophoresis, grover et al. (1983) reported having found three types of immunoglobulins in camels, and their associated subclasses, namely igg1, igg2, iga and igm. these antibodies were also reported to be antigenically distinct from those of other farm animals and man. ten years later azawi et al. (1993) successfully separated immunoglobulins g and m from camel sera by ammonium sulfate precipitation, gel filtration and fast protein liquid chromatography. they did not however find iga antibodies. interestingly, they observed three bands in gels which reduced disulphide bonds. two of the bands corresponded to the typically observed heavy and light chain antibody molecules but the third was thought to be unique but was not further investigated. hamers-casterman et al. (1993) reported that in addition to the heterotetrameric antibodies consisting of two heavy and two light chains, described in other animal species, camelids also have a unique sub group of smaller antibodies. these were likely those observed by azawi et al. (1993) and recognized to be unique but were not further studied. hamer-casterman and his group were able to demonstrate that these antibodies consisted only of heavy chains. these antibodies are now appropriately referred to as heavy-chain antibodies (hcabs). the heavy chains, found in these antibodies, are also smaller than those of heavy chains of conventional antibodies. their smaller size is attributed to the lack of the ch1 domain which functions as the anchor for the light chains. nguyen et al. (1999) concluded that the loss of the splice consensus signal was responsible for the removal of the entire ch1 domain in camel igg2a hcabs. the variable domain is therefore joined directly to the hinge region in hcabs. hcabs correspond to the igg2 and igg3 fractions. the igg2 fraction (92 kda) binds only to protein a, whereas the igg3 (90 kda) fraction binds to protein a and protein g. by differential ph elution igg2 was shown to consist of two fractions igg2a and igg2b (muyldermans and lauwereys, 1999). igg1 consists of the classical h 2 l 2 antibodies that bind to protein a and g (de genst et al., 2006). hcabs are reported to vary but can account for upwards of 75% of their circulating immunoglobulins (nguyen et al., 1998). of particular interest is the possibility that camels have likely two lineages of b-cells, each secreting different sets of v(h) gene segments used by four and two chain immunoglobulins (ungar-waron et al., 2003). furthermore, sound evidence has been presented that the variable domains found in camel hcabs are encoded by other genes than those of four chain immunoglobulins (nguyen et al., 1998) and raises the likelihood that v(h) genes of hcabs do not arise through an ontogenic process of somatic hypermutation. camel hcabs, unlike the hcabs derived from mouse myelomas or those found in human sera have been shown to be not only functional but also have some very unique characteristics. camels for example infected with trypanosoma evansi mount an immune response with a repertoire of antibodies consisting of conventional antibodies, as well as those made up of hcabs (hamerscasterman et al., 1993). camel hcabs not only react with a wide range of antigens (muyldermans and lauwereys, 1999) but also interact with certain antigens differently than conventional antibodies. camels that were immunized with bovine red blood cell carbonic anhydrase and porcine alpha-amylase developed hcabs that acted as competitive inhibitors of these enzymes, in contrast to conventional antibodies that were incapable of binding to the enzymes’ active sites (lauwereys et al., 1998). this ability is ascribed to the difference in the antigenbinding sites of these different molecules. whereas antigen recognition in conventional antibodies results from the interaction of antigen binding sites contained within both heavy and light chains, hcab molecules have binding sites that are contained within a narrowly defined region of one molecule, the variable domain of the heavy chain (muyldermans and lauwereys, 1999). the antigen-binding site of the hcab is a single variable domain referred to as the variable domain of the heavy chain of hcabs (vhh) (muyldermans, 2001; degenst et al., 2006; deschacht et al., 2010). this finding has been a source of considerable interest as vhhs (15kda) are smaller than the antigen-binding sites of conventional antibodies. their production is easier than that of normal mammalian antibodies (alvarez-rueda et al., 2007). they can be cloned as fusion domains to effector proteins (muyldermans, 2001) and expressed in bacteria resulting in quantitative larger amounts. besides, vhh tend to retain their ability to bind to the antigens that elicited their production (roovers et al., 2007). of particular interest is that vhhs are able to recognize small antigenic sites that conventional antibodies cannot penetrate (de genst et al., 2006; paallanen et al., 2011). examples of their potential uses include their development against the epidermal growth factor receptor (omidfar, et al., 2007; 4 johnson et al. 5 a review of observations made on select parameters of the camel immune system roovers et al., 2007) and nuclear poly (a) binding protein 1 (verheesen et al., 2006). a recent study by paalanen et al. (2011) reported on the ability of vhhs to serve as both activators and inhibitors for a protein kinase. this is of particular interest as there are ten isotypes of protein kinase c (pkc). vhhs permit the elucidation of the function of the pkcs and furthermore have potential therapeutic benefits for diseases that result from abnormal pkc signaling such as patients with type ii diabetes. it has also been reported by dumoulin et al. (2003) and chan et al. (2008) that a camel antibody was able to inhibit the aggregation of lysozyme that is involved in the production of amyloid fibrils, such as those associated with the development of alzheimer’s and parkinson’s disease. a very exciting finding has been that vhhs, at least in vitro, were able to inhibit the replication of poliovirus and this raises the hope that they might serve as potential antiviral compounds (thys et al., 2010). there seems to be an inexhaustible potential for the use of camel vhhs. the dna for the binding domains can be isolated and they can be generated through bacterial engineering (arabi et al., 1997) or expressed in mouse cells (nguyen et al., 2003). other exciting prospects for these small molecules are their use in immunolabeling of targets such as tumors. they will also be more efficient at penetrating tumors and reaching their specific targets. also, the single domain antibody might be useful in the development of anti-idiotypic vaccines (muyldermans and lauwereys, 1999). there is evidence that these smaller antibodies are less antigenic and thus might not initiate significant immune responses in patients. herrera et al. (2005) reported that horse and sheep iggs had more anti-complementary activity than camel iggs. this is significant as anti-complementary activity is likely a chief mechanism leading to adverse reactions after administrations of heterologous igg preparations in humans. this would make antiserum raised in camels for use against snake or insect venom serum potentially safer than that raised for example in horses (meddeb-mouelhi et al., 2003; herrera et al., 2005; harrison et al., 2006). interesting is also the observation that camel antibodies have been reported to be less antigenic when injected into mice, and unlike horse antibodies, did not cause agglutination of human erythrocytes in vitro (herrera et al., 2005). camel vhhs have been reported to sense or induce conformational changes on different isoforms of prostatespecific antigen (psa) and it was postulated that this might be of potential benefit to study psa conformational flexibility and to differentiate different stages of 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enzymwert von gesunden und kranken rennkamelen (camelus dromedarius). tieraertzliche praxis 23:187-191. wernery, u., m.e. fowler, and r. wernery. 1999. color atlas of camelid haematology. blackwell wissenschafts-verlag. berlin. 37-43. received: march 16, 2013 accepted: november 12, 2013 agricultural and marine sciences, 17:1-8 (2012) ©2012 sultan qaboos university 1 _______________________________________________ *corresponding author. e-mail: ahmed99@squ.edu.om or albusaidiahmed@yahoo.com estimating leaching requirements for barley growth under saline irrigation ahmed al-busaidi1*, jaaman rabeea2, mushtaque ahmed1, and salim al-rawahy1 1college of agricultural & marine sciences, sultan qaboos university, p.o. box 34, al-khod 123, sultanate of oman 2directorate general of agriculture & livestock research, rumais, ministry of agriculture, sultanate of oman باملاء املالح املروي الشعير الالزمة لنمو الغسيل احتياجات تقدير الرواحي وسالم احمد مشتاق ربيع، جمعان ، البوسعيدي أحمد من للتقليل املاحلة باملياه املروية حتتاج األراض الزراعة. الزراعية مثار اهتمام كبير في لألغراض املياه الهامشية استخدام اصبح اخلالصة: ومقدار باملياه املاحلة الري تأثير لدراسة احلقلية التجربة بهذه القيام مت التصريف. أو التربة خالل عمليات غسيل من بالتربة االمالح تراكم بالتنقيط واستخدامها بالري ، دس/متر ٩ ، ٦ ، ٣ لدرجة ماحلة مياه تخفيف فلقد مت الغرض ولهذا نبات الشعير. منو على الغسيل درجة على توزيع أثرت وجودته املضاف املاء كمية بأن اوضحت النتائج املضاف. املاء من ٠,٢٥ ، ٠,٢ ، ٠,١٥ ، ٠ يعادل مبا األمالح غسيل مقدار لتوفير االمالح غسل على الغسيل زيادة ساعدت سطح التربة، ب) من بالقرب أو األعلى في االمالح وجود أ) التالي: النحو في التربة على االمالح التصريف الشعير ولكن منو على سلبية املياه بصورة ملوحة اتلفة. أثرت بني درجات الغسيل النبات في منو اختالف يالحظ وجود لم ولكن الى ٩ دس/متر) ٦و و ٣) الري مياه ملوحة زيادة أدت الغسيل. بني معدالت الفروقات وقلل من االمالح غسل على ساعد الرملية للتربة اجليد انتاج حتسني على االمالح لغسل كاف مقدار توفير مع الهامشية املياه استخدام يساعد رمبا ولكن النبات. وإجهاد منو التملح معدالت زيادة الفقيرة مائياً. املناطق في النباتات بالتنقيط الري ، الكهربائي التوصيل ، االمالح تراكم مفتاحية: كلمات abstract: the utilization of marginal water resources for agriculture is receiving considerable attention. the lands irrigated with saline water are required to reduce salt accumulations through leaching and/or drainage practices. a field experiment was carried out to investigate the effect of saline irrigation and leaching fraction on barley (hordeum vulgare l.) growth. for this purpose highly saline water was diluted to the salinity levels of 3, 6 and 9 ds m-1 and applied by drip irrigation at 0.0, 0.15, 0.20 and 0.25 leaching fractions (lf). the results of the experiment showed that both quantity and quality of water regulated salts distribution within the soil in the following manner: a) the salts were found higher near or immediate below the soil surface; b) an enhanced lf carried more salts down the soil horizon but there was no significant difference in plant yield between different treatments of leaching fractions. salinity of water significantly impaired barley growth. the good drainage of sandy soil enhanced the leaching process and minimized the differences between leaching fractions. the increment in saline treatments (3, 6 and 9 ds m-1) added more salts and stressed plant growth. however, the conjunctive use of marginal water at proportional lf could be effective in enhancing the yield potential of crops in water-scarce areas. keywords: salt accumulation, electrical conductivity (ec), drip irrigation. introduction the freshwater resources available for agriculture are declining quantitatively and qualitatively. the water demands for irrigation are projected to rise, bringing increased competition between agriculture and other users. therefore, the use of lower-quality supplies will inevitably be practiced for irrigation purposes to maintain an economically viable agriculture(oron et al., 2002). scarcity of good quality water in several regions in the world emphasizes the need to use marginal waters such as brackish water or reclaimed effluent to meet the increasing demands for water, which in turn increases the possibility of soil salinization and yield reduction (chartzoulakis et al., 2001). poor management of saline water may increase the soil salinity to a level higher than crop tolerance. therefore, the challenge is to manage poor quality water and salinized soil for sustainable agricultural production system. the soils irrigated with saline water are required to reduce salts accumulations through leaching and/or drainage practices. the amount of excess water that is applied to the crop in order to control salts is referred as the leaching fraction. in regions where the rainfall is low, a higher water fraction is added to irrigation water as drainage to lower the salt accumulation in the soil (nato, 1994). oron et al. (2002) reported that high saline water has an agricultural potential if conducted through proper irrigation management. by increasing the volume of irrigation water, the soil salinity may be reduced due to water percolation below the root zone (petersen, 1996). 2 al-busaidi et al. 3 estimating leaching requirements for barley growth under saline irrigation barley is one of the important cereal crops grown in a variety of soils, waters and climatic conditions in various parts of the world and classified as a salt-tolerant crop (shannon, 1984). the studies on the utilization and management of marginal waters on barley crop are scanty. the present study was aimed to evaluate the effects of saline irrigation water and leaching fraction on barley growth and salt accumulation in soil. more specifically the aim was to investigate the minimum leaching fraction for barley that is effective to minimize the adverse effects of different categories of saline groundwater. materials and methods in an open field at the agriculture and livestock research center, rumais, oman (21° 0' 0" n / 57° 0' 0"), a lighttextured soil was selected for this experiment and the relevant properties are shown in table 1. the soil was leveled and plots (1.5*3 m) were prepared for sowing barley (hordium vulgare l.) (fig. 1). soil samples were collected before sowing of the crop and analyzed for ec e , ph and some soluble cations. the irrigation water was also analyzed for ec, ph and some cations (table tt2). the required levels of ec of irrigation water (ec iw = 3, 6 & 9 ds m-1) were prepared through mixing of fresh and saline waters in appropriate ratios. a two meter wide buffer plot was left fallow in between treatment plots of barley to protect and keep separate the effect of different irrigation regimes. measured irrigation was applied as et c + lf. irrigation category was kept in the main plots while lf was provided in sub-plots. the drip system of irrigation was installed, and the crop water requirement was calculated by using an evaporation pan (class a). a uniform dose of fertilizer containing 180 kg ha− 1 nitrogen (n), 45 kg ha− 1 phosphorus (p), and 80 kg ha− 1 potassium (k) was applied to all plots. the crop was harvested at maturity and the physicochemical properties of the soil and plant were analyzed. this experiment continued on the same site for two years (2008 & 2009). necessary preventive measures were taken to protect plants from pests, diseases and birds during growth. data on plant height, number of tillers, leaf length and width, green and dry fodder yield of crops was measured. more than 72 soil samples were taken and on table 1. selected physicochemical characteristics of soil. property value ec e 3.06 ds m-1 ph 8.31 soluble k+ 7.00 mg kg-1 soluble ca2+ 48.70 mg kg-1 soluble mg2+ 24.90 mg kg-1 soluble na+ 30.00 mg kg-1 soluble s 4.40 mg kg-1 cation exchange capacity 2.40 mg kg-1 bulk density 1.50 g cm-3 infiltration rate (intake rate) 5.00 cm sec-1 saturated hydraulic conductivity 0.007 cm sec-1 field capacity (pf 1.8) 6 % permanent wilting point (pf 4.2) 2 % texture sand (90.68% sand, 1.21% silt, 8.11% clay) figure 1. diagram showing plots and subplots of all treatments. estimation of leaching requirements to grow barley with saline water 14 m (3 ds/m) 44 m (6 ds/m) (9 ds/m) 2 al-busaidi et al. 3 estimating leaching requirements for barley growth under saline irrigation each occasion a composite soil sample at two depths (030, 30-60) was air-dried and sieved (< 2 mm). soil texture was determined by the hydrometer method. soil salinity was measured through electrical conductivity (ec e ) of the soil saturated paste using a conductivity meter. the concentrations of ions in the soil, water and plant were determined by atomic absorption and inductive-couple plasma (icp) machines. data were analyzed statistically for analysis of variance (anova) and the means were compared at a probability level of 5% using duncan’s multiple range test. the water deficit in plants was calculated by using the formula: water deficit in plant (%) = [{(fwc-dwc)/fwc} {fwt-dwt)/fwt}] *100 (1) where fwc and dwc are fresh and dry weights of the control and fwt and dwt are fresh and dry weights of the treatments. the stress factor was calculated by using the formula: stress factor (k s ) = 1 – [(b /100 ky) (ec e ec threshold)] (mm) (2) where b is the percentage reduction in crop yield per 1 ds m-1 which is equal to 5; ky is the yield response factor equal to 1; and ec e is the soil salinity. the threshold ec value for barley is considered as 8 ds m-1 (fao, 1998). results and discussion the salt accumulation and distribution in the soil profile was affected by the amount of salts and quantity of irrigation water applied (fig. 2). usually, water uptake by plants and evaporation from the soil surface are the major causes of salt accumulation in the root zone, and salt quantities are proportional to the water volume removed by these processes. this finding was also observed by benhur et al. (2001) and bresler et al. (1982). table 3 shows that salt content in the second horizon is significantly different between all treatments, and that was the real cause for producing significant differences in plantgrowth parameters. the second horizon is commonly used to feed the plant, so salt accumulation or nutrient deficit in this horizon will affect plant growth. generally, salt accumulation depended on the soil moisture and plant root development. higher application of water leached down more salts to the deeper horizons as compared to low water fraction. soil salinity values fluctuated more under higher salinity and the reason behind that could be the proportional amount of salts added and leached by irrigation water. petersen (1996) reported low soil salinity with increased volume of irrigation water due to salt transportation below the root zone. shalhevert table 2. chemical properties of irrigation water. water type ec ph na+ ca2+ mg2+ k+ s fe salinity level ds m-1 mg l-1 3 ds m-1 2.95 6.80 358 46.5 109 5.32 46.5 0.02 6 ds m-1 6.12 6.80 677 103 244 10.40 109 0.01 9 ds m-1 9.10 6.90 965 154 367 15.30 156 0.01 0 2 4 6 8 10 12 14 s3 l0 .0 s3 l0 .1 5 s3 l0 .2 s3 l0 .2 5 s6 l0 .0 s6 l0 .1 5 s6 l0 .2 s6 l0 .2 5 s9 l0 .0 s9 l0 .1 5 s9 l0 .2 s9 l0 .2 5 treatment s oi l s al in ity (d s /m ) 0-30cm 30-60cm figure 2. salt distribution in the soil profile as affected by saline irrigation and leaching treatment (s: saline, l: leaching treatments). 4 al-busaidi et al. 5 estimating leaching requirements for barley growth under saline irrigation (1994) observed that leaching is the key to the successful use of saline water for irrigation. whereas, abu-awwad (2001) found high salt concentration on the soil surface due to evaporation. higher application of saline water caused downward flow of salts. plant parameters soil salinity is one of the principal abiotic factors affecting crop yields in the arid and semi-arid irrigated areas. plant growth was significantly affected by saline irrigation (table 4). under less salinity and a high leaching fraction, barley gave substantial biomass yield. treatment with less salinity gave the higher biomass production as compared to the high salinity. it can be seen from table 4 that plant parameters were negatively affected by an increase in saline irrigation and the reduction in growth can be seen very clearly in figure 3 especially when the plant was irrigated by saline water of 9 ds m-1. however, differences between leaching fractions was not a major factor affecting plant parameters (table 4). it seems that salt accumulation under the root zone was not very high and so did not affect root water absorption and plant growth. generally, coarse soil texture supported the leaching treatment and a relatively small amount of water was able to leach salts from the root zone. moreover, barley is a salt-tolerant crop and a small variation in salt content between each leaching fraction was not enough to reduce plant growth parameters. abu-awwad (2001) reported that saline soils with considerable soluble salts interfered with the growth of crop species. crop response to salinity usually depends on several factors including plant species, soil texture, water holding capacity and composition of the salts. during the experiment low concentrations of salts enhanced plant height, tillering and leaf length as compared to higher saline water. certainly a higher salinity profoundly impaired plant growth parameters. heakal et al. (1990) noticed that the dry matter yield of plants decreased with increasing salinity of irrigation water. al-tahir et al. (1997) found that barley grain and straw yields significantly decreased when irrigated by drainage water (ec e : i0.7~16.7 ds m-1). pal et al. (1984) concluded that barley could be grown economically with irrigation water up to ec 16 ds m-1. the greater application of water positively affected plant growth by transferring the toxic level of salts to the lower soil horizons. table 3. analysis of variance (anova) for soil and plant parameters. parameters mean square f value significance* soil ec e 0-30 cm 4.2٧e7 1.46 0.19 soil ec e 30-60 cm 6601154.78 3.16 0.00 plant height 107.28 6.17 0.00 leaf length 18.16 5.08 0.00 green yield 28488.72 3.76 0.00 dry yield 45.51 3.25 0.00 *significant at p < 0.05. salinity & leaching plant height (cm) leaf length (cm) tillers (no.) green yield (g) dry yield (200g gy) (g) s3l0.0 40.77a 20.07a 85.33a 411.41a 102.05a s3l0.15 44.47a 21.40a 113.67b 570.85b 105.77a s3l0.2 44.33a 20.87a 91.00b 441.10b 102.83a s3l0.25 47.27a 24.43b 93.67b 491.19b 102.07a average 44.21 21.69 95.918 478.64 103.18 s6l0.0 43.43b 19.20c 96.33c 329.15c 97.13c s6l0.15 37.37c 20.83c 79.67c 317.40c 94.50c s6l0.2 41.17b 21.40c 82.00c 381.49c 101.61b s6l0.25 39.80b 19.40c 85.67c 473.50d 104.37b average 40.44 20.21 85.92 375.39 98.40 s9l0.0 37.33d 19.80d 106.67d 323.72e 99.42d s9l0.15 30.37e 16.20e 98.33d 363.03e 101.84d s9l0.2 34.63d 17.63d 78.67e 295.94e 99.49d s9l0.25 32.40d 18.03d 102.33d 338.817e 94.49e average 33.68 17.92 96.50 330.38 98.81 *means in the column with same letter indicate no difference at duncan’s multiple range test at p < 0.05. table 4. plant growth parameters as affected by saline irrigation and leaching treatment. 4 al-busaidi et al. 5 estimating leaching requirements for barley growth under saline irrigation saline irrigation water also contains some plantessential elements that are beneficial for plant growth (table 3). however, those salts if present in high concentration, usually affect negatively plant growth parameters (fig. 4). the use of saline water for barley irrigation is only possible if the leaching of excess salt from the root zone is implemented. it can be seen from figure 4 that the concentration of most cations in the plant tissue are not very high and they are within the acceptable range that was published in other studies such as heakal et al. (1990). the higher increase in some cations like phosphorus is due to the application of inorganic fertilizer which contains the essential elements needed for plant growth. generally, soil salinity affects plants growth by producing an ionic imbalance or water deficit state in the expanded leaves. shani and dudley (2001) related the yield loss to reduced photosynthesis, high energy and carbohydrate expenses in osmoregulation, and interference with cell functions in saline conditions. heakal et al. (1990) reported that the dry matter yield of plant shoots decreased with the increasing salinity of water. koszanski and karczmarczyk (1985) observed that diluted or undiluted seawater reduced plant height, grain and straw yield of barley and oats. in all cases, using highly saline water for irrigation is one of the challenges in saline agriculture. table 4 shows that the best growth was with the lowest salinity treatment (3 ds m-1). however, comparing the growth of other treatments with lowest one, it can be seen from figure 5 that plant grown under treatment of 9 ds m-1 was facing a water deficit problem followed by treatment of 6 ds m-1. it seems that the plants tried to grow 0 5 10 15 20 25 30 35 plant height leaf length green yield dry yield plant parame te rs r e d u c ti o n ( % ) 6 ds/m 9 ds/m figure 3. reduction in plant parameters as affected by salinity treatments. 0 0.5 1 1.5 2 2.5 s3l0.0 s3l0.2 s6l0.0 s6l0.2 s9l0.0 s9l0.2 tre atme nt p la n t c a ti o n c o n c e n tr a ti o n ( % ) % p % k % ca % mg % na figure 4. concentration of some plant cations as affected by saline irrigation and leaching treatment. 6 al-busaidi et al. 7 estimating leaching requirements for barley growth under saline irrigation and survive under all salinity treatments but the increase in soil salinity was the main barrier for the plant to absorb the required water for growth and that led to osmotic and ion effect problems. the water deficit conditions under high salinity treatments could be directly attributed to the impaired water flow from soil to plant. yeo (1999) reported that root selectivity and transpirational water flow provide the net uptake of salts whereas the salt concentration develops with the growth rate. the greater mass flow of solution through the soil-root interface or higher magnitude of evapotranspiration would increase the salt transport in plants. thus, there is a potential risk of higher salt damage in a hot climate. within each salinity treatment, there was also a leaching-effect difference. plants which had no extra water for leaching were facing a water deficit problem (fig. 6). it was found that a leaching treatment of 0.15 was the best in terms of giving the best growth, so the deficit below that, could be due to a shortage in plant water requirements, and above that, could be due to extra salts added by saline irrigation. ghulam et al. (1997) obtained a reasonable barley yield with irrigation water (ec w ) up to 9.3 ds m-1 under 15% excess water as a leaching requirement. thus, the conjunctive use of irrigation water (ec 6.8~9.9 ds m-1) produced higher vegetative growth followed by higher grain and straw yields. stress factor (k s ) is an additional parameter to determine crop evapo-transpiration. it is an indicator of unusual plants stress such as salinity, deficit water, disease or nutrient imbalance (fao, 1998). it implies when its value decreases by less than 1 and smaller k s value means higher stress. the stress coefficient was not high and in the most treatments, the plant was growing normally (fig. 7). this happened due to the high salinity threshold value of barley and the effectiveness of sandy soil to leach salts. plots irrigated with low salinity water produced more biomass which did not decrease k s values. the lower k s 0 1 2 3 4 5 6 7 8 9 3 6 9 salinity treatment (ds/m) p la n t w a te r d e fi c it ( % ) figure 5. water deficit between salinity treatments. 0 1 2 3 4 5 6 7 0 0.15 0.2 0.25 leaching fraction p la n t w a te r d e fi c it ( % ) ec(3 ds/m) ec(9 ds/m) figure 6. water deficit between leaching treatments of 3 and 9 ds m-1. 6 al-busaidi et al. 7 estimating leaching requirements for barley growth under saline irrigation values indicated a higher accumulation of salts in the soil under the accelerated evapotranspiration due to growth conditions. in general the increment in water salinity negatively impacted the value of stress factor and plant growth. the type of soil and salt storage can affect the value of many crop factors, depending on the plant type and growth conditions. it has been reported that soil salinity, land fertility, soil management, fertilizers, soil physical condition, diseases and pests affect crop development and evapo-transpiration (fao, 1998). conclusions our study proves that salinity of irrigation waters along with the given leaching fraction affected the salts accumulation and barley biomass production. low water salinity with a medium leaching fraction produced substantially higher plant biomass. under low salinity, plants showed no stress and less water deficit as compared to high salinity. the salinity of post-harvest soil had an inverse relationship with a leaching fraction. salts were highly accumulated in the top horizons and significantly lower in the lower horizons. the salinity of soil varied with the soil profile, with the maximum salt concentration within transitional horizon of 0~30 cm. the physical parameters of sandy soil enhanced leaching and decreased the stress factor. there is a need to control the salinity of soils through sustainable use of saline water. these results confirmed that saline water could have greater agricultural potential when used with a rational fraction of leaching. this experiment indicated that when saline water is used for irrigation due attention should be given to minimize root-zone salinity. however, good management of soil and water could be a viable option for sustainable agriculture in salt affected soils. there is further need to evaluate the effect of poor water quality on different crops in arid and semi arid field conditions. references abu-awwad, a.m. 2001. influence of different water quantities and qualities on limon trees and soil salts distribution at the jordan valley. agricultural water management 52:53-71. al-tahir, o.a., y.a al-nabulsi, and a.m. helalia. 1997. effects of water quality and frequency of irrigation on growth and yield of barley (hordeum vulgare l.). agricultural water management 34:17-24. ben-hur, m., f.h. li, i. ravina, and g. shalit. 2001. water and salt distribution in a field irrigated with marginal water under high water table conditions. soil science society of america journal 65:191-198. bresler, e., b.l. mcneal, and d.l. carter. 1982. saline and sodic soils: principles-dynamics-modeling. berlin: springer-verlag, 236pp. chartzoulakis, k.s., n.v. paranychianakis, and a.n. angelakis. 2001. water resources management in the island of crete, greece with emphasis on the agricultural use. water policy 3:193-205. fao. 1998. crop evapo-transpiration. fao irrigation and drainage papers no. 56. rome. ghulam, h., a.a. al-jaloud, s.a. al-shammary, s. karimulla, and s.o. al-asawad. 1997. effect of saline irrigation on germination and growth parameters of barley (hordeum vulgare l.). agricultural water management 34:125-135. heakal, m.s., a.s. modaihsh, a.s. mashhady, and a.i. metwally. 1990. combined effects of leaching fraction salinity and potassium content of waters on growth and water use efficiency of wheat and barley. plant and soil 125:177-184. 0 2 4 6 8 10 12 14 s3 l0 .0 s3 l0 .1 5 s3 l0 .2 s3 l0 .2 5 s6 l0 .0 s6 l0 .1 5 s6 l0 .2 s6 l0 .2 5 s9 l0 .0 s9 l0 .1 5 s9 l0 .2 s9 l0 .2 5 treatment s o il s al in it y (d s /m ) 0 0.2 0.4 0.6 0.8 1 1.2 s tr es s fa ct o r (k s) ec(ds/m) ks figure 7. plant stress factor as affected by saline irrigation and leaching treatment. 8 al-busaidi et al. koszanski, z. and s. karczmarczyk. 1985. use of saline water for irrigation of spring barley and oats. zeszyty-naukowi-akademii-rolniczej-w-szczecinie, rolnictwo 36:95-105. nato. 1994. sustainability of irrigated agriculture, part five: water quality management, proceedings of the nato advanced research workshop on sustainability, vimieo, lisbon, portugal. oron, g., y. demalach, l. gillerman, i. david, and s. lurie. 2002. effect of water salinity and irrigation technology on yield and quality of pears. biosystems engineering 81:237-247. pal, b., s. singh, and h. singh. 1984. barley yield under saline water irrigation. plant and soil 81:221-228. petersen, f.h. 1996. water testing and interpretation. in: water, media, and nutrition for greenhouse crops, d.w. reed (editor), 31-49. batavia: ball. shalhevert, j. 1994. using water of marginal quality for crop production: major issues. agricultural water management 25:233-269. shani, u. and l.m. dudley. 2001. field studies of crop response to water and salt stress. soil science society of america journal 65:1522-1528. shannon, m.c. 1984. breeding, selection and the genetics of salt tolerance. in: salinity tolerance in plants, r.c. staples and a.h. toenniessen (editors), 231-254. john wiley, new york. yeo, a. 1999. prediction the interaction between the effects of salinity and climate change on crop plants. scientia horticulturae 78:159-174. received: october 24, 2010 accepted: april 3, 2012 agricultural and marine sciences, 18:7-24 (2013) sultan qaboos university 7 __________________________________________ *corresponding author/e-mail: kadim@squ.edu.om composition, quality and health aspects of the dromedary (camelus dromedarius) and bactrian (camelus bacterianus) camel meats: a review isam t. kadim1*, osman mahgoub1, waleed al-marzooqi1, samera k. khalaf1, and gulzhan raiymbek2 1department of animal and veterinary sciences, college of agricultural and marine sciences, sultan qaboos university, po box 34, muscat, sultanate of oman 2al-farabi kazkh national university, almaty, kazakhstan السنام ذات اإلبل والصفات النوعية والصحية للحوم القيمة الغذائية عام استعراض والسنامني: الواحد خلف1 قاسم وسميرة املقبالي1 وربيع املرزوقي1 وليد و محجوب1 عثمان و كاظم1 عصام توفيق قوجلان رامبوك2 و ذات املناطق في وخاصة العالية الغذائية القيمة ذو للبروتني اجليدة املصادر من السنامني أو الواحد السنام ذات اإلبل تعتبر اخلالصة: حتملها تتضمن والتي فريدة وظيفية بصفات اإلبل تتميز األخرى. املزرعة حيوانات بقاء على تؤثر سلبياً والتي البيئية القاسية الطبيعة وقلة فيها تعيش التي للمناطق القاسية والطبوغرافيا املياه توفر وقلة املباشرة الشمس واشعة املنخفضة أو العالية احلرارة لدرجات من للحيوان انتهاء العمر االنتاجي بعد كبيرة أعمار عند وتذبح الغذائية متطلباتها توفر عدم مع تقليدية اإلبل بطرق تربى النباتي. الغطاء الدهون من %17 و من العظام %26 و العضالت من %57 على عامة بصورة اإلبل ذبائح حتتوي للسباق. صاحلة تعد لم التي انتاج احلليب أو من %1.2 و الدهن من %3 و البروتني من %19 املاء و من %78 من اإلبل حلوم للذبيحة. تتكون اخللفي بالربع مقارنة االمامي الربع مع ثقل اإلبل حلوم محتوى يعتبر البشر. من تغذية العدد املتزايد في الصحية الغذائية املواد من اإلبل للحوم قلة الدهون العضلية وتعتبر األمالح صنع ميكن عضالتها. الدهون في نسبة انخفاض بسبب احليوانات حلوم بقية من مثيالتها من أعلى املعدنية واألمالح األمينية األحماض من التربية طرق حتسني على املستقبلية البحوث تتركز أن يجب لذلك الغذائية. قيمتها لزيادة حلوم اإلبل والشاورما من والنقانق الهمبيرجر ولتسويق اللحوم ومنتجاتها. اإلبل حلوم تصنيع تقنية بتحسني االهتمام مع اللحوم إنتاج لزيادة اللحوم. تصنيع ، الكيميائي التركيب القيمة الغذائية ، النوعية ، الصفات ، مفتاحية: ابل كلمات abstract: the dromedary and bactrian camels are good sources of high quality protein especially in areas where the climate adversely affects the survival of other livestock. the camel has unique physiological characteristics, including a great tolerance to high and low temperatures, solar radiation, water scarcity, rough topography and poor vegetation. camels are mostly produced under traditional systems on poor levels of nutrition and are mostly slaughtered at old ages after completing a career in work, racing or milk production. in general, camel carcasses contain about 57% muscle, 26% bone and 17% fat with fore-quarters (cranial to rib 13) significantly heavier than the hind halves. camel lean meat contains about 78% water, 19% protein, 3% fat, and 1.2% ash with a small amount of intramuscular fat, which renders it a healthy food for growing human populations. the amino acid and mineral contents of camel meat are often higher than other meat animals, probably due to lower intramuscular fat levels. camel meat has been processed into burgers, patties, sausages and shawarma to add value. future research efforts need to focus on exploiting the potential of the camel as a source of meat through multidisciplinary research into efficient production systems and improved meat technology and marketing. keywords: camel, meat quality, nutritive value, meat composition, meat processing. introduction the family camelidae include two subfamilies: camelinae (old world camelids) and laminae (new world camelids). the subfamily camelidae includes two species: camelus dromedarius and camelus bacterianus. the dromedary or the one-humped camel (camelus dromedarius) is mostly distributed in the hot arid areas of the middle east, asia and africa, whereas the bactrian two-humped camel (camelus 8 kadim et al. 9 composition, quality and health aspects of the dromedary and bactrian camel meats: a review bacterianus) is found in central asia, kazakhstan, russia and china (dorman, 1986). the new world camelids consist of the following species: the guanaco (lama guanacoe) and the vicuna (vicugna vicugna), which are wild and the llama (lama glama) and the alpaca (lama pacos),which are domesticated and mainly found in south america (murray, 1989). the camel was domesticated by secondary nomads around 5000 years ago in south arabia primarily for transport and labour (wilson, 1998). the dromedary is more abundant than the bactrian camel representing almost 90% of the genus camelus. phylogenetic analysis (micro-satellite loci) showed that camel breeds can be classified according to countries of origin (mburu et al., 2003). the camel is an important domestic animal in various countries for producing valuable food and for its adaptation to extremely harsh environments (kadim et al., 2008). it can survive on sandy terrain with poor vegetation and may chiefly consume feeds unutilized by other domestic species (tandon et al., 1988). therefore, the role of the camel as a meat producer is becoming more important due to the versatile role it plays rather than as a symbol of social prestige, which was the major role it used to play, and which has since greatly diminished (dawood and alkanhal, 1995). camel meat is described as tough, coarse, watery and sweetish in taste compared to meats from other animals. this may be partly attributed to the fact that camel meat is usually a by-product of primitive traditional systems of production where it is mainly obtained from old males and females that have become less effective in their primary roles of providing transportation, milk, or as breeding females (kadim et al., 2008). however, evidence suggests that the quality characteristics of camel meat are not much different from beef if animals are slaughtered at comparable ages (khatami, 1970; knoess, 1977; elgasim et al., 1987; tandon et al., 1988; kadim et al., 2011). although the marketing systems for camel meat are not well organised, there is evidence of a high demand for camel meat (kadim et al., 2008). camel meat could be a good source to meet the growing needs for meat in developing countries, especially for low income population groups (kadim et al., 2008). generally, camel meat is a significant source of animal protein and preferred over other meat animal species due both to the belief in it medicinal benefits and to its availability at affordable prices. this review outlines the nutritional and health value, quality characteristics and the availability of muscle bioactive compounds in dromedary and bactrian camel meats. a comparison of the nutritional properties of dromedary and bactrian camel meats with other species is also highlighted. chemical composition of camel meat camel meat composition varies according to breed, age, sex, condition and location on the carcass. however, the composition of camel meat is generally similar to meat from other species where an inverse relationship existed between the moisture and protein and fat content of the meat (table 1). composition is an important indicator of meat functionality. for instance, moisture content plays an important role in keeping and eating qualities of camel meat (kadim et al., 2008) whereas protein and fat contents dictate the manufacturing quality of meat. table 1 shows that moisture content varies widely in camel meat (67.8 to 78.9%). different muscles within the same camel carcass appear to have similar moisture contents (babiker and yousif, 1990; gheisari et al., 2009; kadim et al., 2013) as well as for the bactrian (raiymbek et al., 2012a). however, the range of moisture content of biceps femoris (74.3-78.5%) and triceps brachii (77.778.4%) muscles was higher than those from longissimus dorsi muscle (72.1-73.8%) due to the higher fat content in the longissimus thoracis muscle (kadim et al., 2013; raiymbek et al., 2012a). according to kadim et al. (2006), the moisture content of dromedary camel meat decreases with the increases in the animal age. the differences between the maximum and minimum moisture contentsof camel longissimus thoracis were 3.2, 6.4 and 12.3% for 1-3, 3-5 and 6-8 years age groups, respectively (kadim et al., 2006). this indicates that the variation in moisture content within the samples is greater in older animals. gheisari et al. (2009) found no differences in moisture content between camel meat and meat from other species at a similar age and sex. the protein content of camel meat is in the range of 17.0 to 23.7% (table 1). there are slight differences between various muscles and different age groups (elfaer et al. 1991; kadim et al., 2006, 2012; raiymbek et al., 2012a). meat from young camels has similar protein content to those found in young cattle, lamb and goat meats (elgasim and alkanhal, 1992; kadim et al., 2009b). the protein contents of six skeletal muscles (semitendinosus, infraspinatus, semimembranosus, biceps femoris, triceps brachii and longissimus thoracis) in dromedary and bactrian camels were studied by kadim et al. (2013) and raiymbek et al. (2012a). the highest protein content was found in the semitendinosus muscle in bactrian, while the semimembranosus contained the highest protein content in dromedary camel (kadim et al., 2013; raiymek et al., 2012a). total collagen content is higher in camel longissimus thoracis muscle than in semitendinosus or triceps brachii muscles, possibly due to morphological requirement for stabilizing the hump attached to the longissimus thoracis (babiker and yousif, 1990). the fat content of camel meat ranged from 1.1 to 10.6 % (table 1). differences in the fat content in various camel muscles were reported (el-faer et al., 1991; elgasim and alkanhal, 1992; kadim et al., 2006, 2008, 2009a,b; gheisari et al., 2009). an animal’s age has a great effect on the fat content, with camel meat from older animals’ containing higher fat compared with meat from younger animals (kadim et al., 2006). the ash content in the dromedary and bactrian camel meats has been reported in the range of 0.75 to 8 kadim et al. 9 composition, quality and health aspects of the dromedary and bactrian camel meats: a review 1.38% (table 1). ash content varies with muscles and between muscles (babiker and yousif, 1990; dawood and alkanhal, 1995; gheisari et al., 2009; kadim et al., 2013; raiymbek et al., 2012a). gheisari et al. (2009) found that age had a significant effect on ash content of camel meat, whereas others found no effect of age on ash content (elfaer et al., 1991; al-shabib and abu-tarboush, 2004; shehata, 2005; kadim et al., 2006, 2008). camel meat has relatively lower ash content than beef, lamb and goat meat (elgasim and alkanhal, 1992; gheisari et al., 2009; kadim et al., 2008). amino acid composition according to dawood and alkanhal (1995), the essential amino acid content of camel meat is not affected by an animal’s age. camel meat has a comparable essential amino acid contents to beef, lamb and goat meat (table 2). the amount of camel meat required to supply the daily requirements of essential amino acids for adult consumer is similar to that from lamb (based on methionine which has the lowest content in meat) but is less than the amount required from beef. table 2 shows that leucine (7.08 to 9.51% of protein) and lysine (8.33 to 9.85% of protein) are among the highest essential amino acids in camel meat. essential amino acids contents of camel meat varied slightly among different muscle locations in the carcass. the essential amino acid contents in longissimus dorsi and semitendinosus muscles differed by >2.1% with the exception of leucine, methionine and tryptophan, which differed by 18.5, 25.4 and 14.6 %, respectively (alshabib and abu-tarboush, 2004). similarly, essential amino acid contents in the infraspinatus, longissimus dorsi and semitendinosus muscles differed by > 4.2% with the exception of isoleucine, methionine, threnonine, tryptophane and valine which differed between 8 to 42% (dawood and alkanhal, 1995). on the other hand, differences in essential amino acids reported across table 1. chemical composition (%) of dromedary and bactrian camel muscles. muscle type moisture protein fat ash dromedary camel longissimus thoracis 73.8 19.0 6.2 0.85 kadim et al. (2013) infraspintus 73.2 18.2 5.3 0.96 triceps brachii 77.7 17.1 1.9 1.00 semitendinosus 75.4 18.5 3.1 0.91 semimembranosus 63.0 22.1 2.5 0.93 biceps femoris 74.3 20.8 2.5 1.00 longissimus thoracis 65.7 19.5 2.1 1.20 kadim et al. (2011) longissimus thoracis 73.8 23.7 3.6 al-bachir & zeinou (2009) biceps femoris 73.0 22.8 1.1 0.75 gheisari et al., (2009) triceps brachii 72.0 21.2 1.4 0.81 longissimus dorsi 68.3 21.5 1.6 0.69 biceps femoris 71.4 22.2 1.6 0.98 triceps brachii 70.5 20.3 2.4 1.06 longissimus dorsi 67.8 20.5 2.5 0.95 longissimus thoracis 74.8 21.1 2.8 1.34 kadim et al. (2009a) longissimus thoracis 71.7 22.7 4.4 1.10 kadim et al. (2006) longissimus dorsi 75.9 21.6 1.4 1.05 babiker and &yousif (1990)semitendinosus 75.8 21.4 1.4 1.38 triceps brachii 75.2 22.1 1.4 1.22 bactrian camel longissimus thoracis 72,1 17.0 10.0 0.9 raiymbek et al. (2012a) infraspintus 78.5 18.0 2.5 1.0 triceps brachii 78.4 17.5 3.0 1.0 semitendinosus 78.0 18.8 2.2 1.0 semimembranosus 79.0 18.2 2.0 1.0 biceps femoris 78.5 18.3 2.1 1.1 10 kadim et al. 11 composition, quality and health aspects of the dromedary and bactrian camel meats: a review different camel muscles ranged between 0.5 to 9.5% (elgasim and alkanhal, 1992; dawood and alkanhal, 1995; al-shabib and abu-tarboush, 2004). tryptophan concentration in camel meat was lower than in other meats (dawood and alkanhal, 1995). al-shabib and abutarboush (2004) reported that tryptophan concentration was 1.76% of the total amino acids, which was higher than the 1.28% reported for beef (kadim et al., 2008). the glutamic and aspartic acids, the major nonessential amino acids in camel meat ranged from 15.95 to 18.60% and from 9.30 to 10.80% of protein, respectively (table 3). similar to the essential amino acids, nonessential amino acid content also varied slightly between muscles, and larger variations are found between studies. in general, camel meat maybe a better source of nonessential amino acids than beef, lamb, and goat meats (table 3). although, elgasim and alkanhal (1992) found low alanine levels in camel meat compared to other red meats, dawood and alkanhal (1995), al-shabib and abutarboush (2004) and kadim et al. (2011) found similar concentration of alanine in camel meats and other red meats. fatty acid composition the fatty acid composition of meat is of great concern to consumers due to its important effects on human health. reduction of saturated fatty acid intake is very important to prevent obesity, hypercholesterolemia and to decrease the risk of cancer (chizzolini et al., 1999). on the other hand, diets containing lipids with a high level of monounsaturated fatty acids and polyunsaturated fatty acids have been shown to be effective in lowering serum cholesterol levels (mensink and katan, 1989). rawdah et al. (1994) identified 22 fatty acids in camel meat (table 5). major fatty acids in camel meat were also reported by al-bachir and zeinou (2009) and kadim et al. (2011). rawdah et al. (1994) reported levels of 18.93% oleic (c18:1) and 12.07% linoleic acid (c18:2) in the camel meat. however, about twice the percentage of oleic (c18: 1) and less than half the percentage of linoleic acid (c18: 2) were reported by al-bachir and zeinou (2009) and kadim et al. (2011). linoleic acid is derived entirely from the diet (wood et al., 2008) and such differences are not unexpected from studies from different regions. the major saturated, monounsaturated and polyunsaturated fatty acids in camel meat are (c16:0), (c18:1) and (c18: 2), respectively (table 4). the variation of total saturated fatty acids (51.5-53%) was small in comparison to monounsaturated (29.9 and 41.4%) and polyunsaturated (5.6% and 18.6%) fatty acids, which is in agreement with rawdah et al. (1994) and kadim et al. (2011). the fatty acid composition, total saturated, unsaturated, monounsaturated and polyunsaturated fatty acids of infraspintus, triceps brachii, longissimus table 2. essential amino acid composition in camel meat (mg/100g). amino acid1 his ileu leu lys met phe thr trp val longissimus thoracis 4.4 4.7 8.3 9.4 2.9 4.3 4.5 5.6 kadim et al. (2011) longissimus dorsi 3.4 4.2 7.1 9.1 1.6 5.6 4.8 1.6 4.7 al-shabib &abu-tarboush (2004)semitendinosus 3.4 4.3 8.4 9.1 1.3 5.5 4.8 1.9 4.6 infraspinatus 4.7 5.3 8.6 8.4 2.6 4.1 4.2 0.5 4.9 longissimus thoracis 4.3 5.4 8.3 8.6 2.2 4.4 4.7 0.7 5.3 dawood & alkanhal (1995) semitendinosus 4.5 4.9 8.3 8.3 2.5 4.2 4.2 0.6 5.4 longissimus dorsi & semitendinosus 5.6 5.9 9.5 8.9 3.6 4.7 4.8 6.3 elgasim & alkanhal (1992) camel 5.6 5.9 9.5 8.9 3.5 4.7 4.8 6.3 beef 6.2 6.5 10.7 9.1 2.7 5.7 5.5 6.6 lamb 5.9 5.8 9.6 8.5 3.3 4.9 4.2 5.9 goat 4.7 6.0 7.9 10.9 3.9 6.5 4.4 6.8 camel 3.4 4.3 7.7 9.1 1.4 5.5 4.8 1.8 4.7 al-shabib &abu-tarboush (2004) 1amino acids: his histidine, ileu isoleucine, leu leucine, lys lysine, met methionine, phe phenylalanine, thr threonine, trp tryptophane, val valine 10 kadim et al. 11 composition, quality and health aspects of the dromedary and bactrian camel meats: a review table 3.non-essential amino acid composition in camel meat (mg/100g). amino acid1 ala arg asp glu gly pro ser tyr longissimus thoracis 6.5 6.6 9.3 15.9 4.3 3.9 3.6 3.5 kadim et al. (2011) infraspinatus 6.3 7.5 9.3 17.1 6.0 5.4 3.5 3.0 dawood & alkanhal (1995)longissimus dorsi 6.2 7.1 9.3 17.3 5.9 4.9 3.8 3.4 semitendinosus 6.3 7.5 8.6 16.4 5.9 5.9 3.6 3.3 longissimus dorsi and semitendinosus 3.9 7.1 10.8 18.6 6.1 3.9 3.2 3.8 elgasim &alkanhal (1992) camel 3.9 7.1 10.8 18.6 6.1 3.9 3.2 3.8 beef 7.7 7.1 10.8 16.5 6.2 4.5 4.2 4.1 lamb 6.7 6.9 10.3 17.9 5.5 3.8 2.9 3.5 goat 4.7 7.1 10.8 15.6 5.2 3.8 3.6 5.9 camel 6.5 6.9 9.7 17.0 6.2 4.3 3.3 al-shabib & abu tarboush (2004) 1amino acid: ala alanine, argarginine, asp aspartic acid, glu glutamic acid, gly glycine, pro prolene, ser serine, tyr ttyrosine table 4. fatty acids composition (%) of the infraspinatus (is), triceps brachii (tb), longissimus thoraces (lt), semitendinosus (st), semimembranosus (sm), and biceps femoris (bf) muscles of the dromedary camel (kadim et al., 2013). muscle is tb lt st sm bf sem1 saturated fatty acid 12:0 1.71c 1.42 1.13a 1.66 1.53 1.44 0.186 13:0 1.22 1.13 1.24 1.24 1.24 1.21 0.066 14:0 7.62 7.78 7.16 7.24 7.48 7.83 0.544 15:0 2.32 2.14 2.39 2.40 2.35 2.12 0.095 16:0 27.64 27.26 26.92 25.09 26.45 26.16 2.378 17:0 2.38 2.17 2.46 2.21 2.38 2.15 2.088 18:0 8.79 8.90 9.82 8.71 8.37 8.02 2.277 20:0 0.08 0.03 0.09 0.02 0.04 0.03 0.022 21:0 0.03 0.00 0.03 0.01 0.01 0.00 0.007 22:0 0.02 0.01 0.02 0.01 0.00 0.02 0.004 mono-unsaturated fatty acids 14:1 1.63 1.62 1.35 1.73 1.63 1.62 0.112 15:1 1.04 1.03 1.01 1.01 1.03 1.02 0.051 16:1 8.88 8.56 8.25 8.79 8.66 8.57 2.233 17:1 0.16 0.14 0.14 0.15 0.11 0.11 0.039 c18:1n9 25.04 26.26 26.21 26.42 26.80 26.88 2.182 poly-unsaturated fatty acids c18:2n6 7.14 7.83 7.11 7.79 7.98 7.94 0.207 c18:3n3 0.64 0.43 0.59 0.62 0.54 0.54 0.122 c20:2 0.52 0.34 0.62 0.64 0.43 0.42 0.016 c20:3n6 0.33 0.23 0.34 0.43 0.42 0.41 0.009 c20:4n6 2.81 2.72 2.84 2.83 2.55 3.51 0.033 total saturated fa (sfa) 51.81 50.84 51.26 48.59 49.85 48.98 8.942 total unsaturated fa (usfa) 48.19 49.16 48.74 50.41 50.15 51.02 2.311 total monounsaturated fa (musfa) 36.75 37.61 37.24 38.10 38.23 38.20 2.174 total poly unsaturated fa (pusfa) 11.44 11.55 11.50 12.31 11.92 12.8 0.217 sfa: usfa 1.08 1.03 1.05 0.96 0.99 0.98 3.869 sfa: musfa 1.41 1.35 1.38 1.28 1.30 1.28 4.113 sfa: pusfa 4.54 4.40 4.46 3.95 4.18 3.82 4.120 1sem: standard error for the mean. means on the same row with different superscripts are significantly different (p<0.05). 12 kadim et al. 13 composition, quality and health aspects of the dromedary and bactrian camel meats: a review thoraces, semitendinosus, semimembranosus, and biceps femoris muscles of the dromedary was studied by kadim et al. (2013) (table 5). the fatty acid composition of the six muscles was generally similar with the exception of palmitic and oleic fatty acids. the semitendinosus muscle had lower palmitic acid than infraspintus, triceps brachii, longissimus thoraces and semimembranosus muscles. the infraspintus muscle contained lower oleic acids than other muscles. of the six muscles studied, palmitic acid is the most abundant saturated fatty acid in camel intramuscular fat, followed by stearic acid, and myristic acid. the main monounsaturated fatty acids in the six muscles were oleic acid followed by palmitoleic acid. the main polyunsaturated fatty acids in the muscles were linoleic acid and archidonic acid. the percentage of polyunsaturated fatty acids in camel meat (18.6%) was within the range reported for beef (8.8%) and buffalo (28.6%) and deer (31.4%) (sinclair et al., 1982). the ratio of linoleic and linolenic acids in camel meat is about 10.9 which is much higher than that of the meat of cattle, sheep or goat (2.0, 2.4 and 2.8, respectively) (sinclairb et al., 1982). the camel hump is commonly used as cooking oil in camel producing countries. on a fresh weight basis, the camel hump is composed of about 64.2-84.8% fat, with a very high content of saturated fatty acids of about 63.0% (rawdah, et al., 1994; kadim et al., 2002). researchers, therefore, focused on the composition of the hump (mirgani, 1977; emmanuel and nahapetian, 1980; abu-tarboush and dawood, 1993; kadim et al., 2002). palmitic acid, stearic acid and oleic acid are the most abundant fatty acids in the hump. the composition of the hump fatty acids is affected by the animal age. the highest percentage of unsaturated fatty acids and lowest percentage of saturated fatty acids were in animals of less than one year whereas an opposite trend was in animals in the 1-3 years old age group (kadim et al., 2002). mineral composition minerals are generally classified as essential elements that are required for growth and health or toxic elements, which pose health risk to animals and humans. both the deficiency and excess intake of essential elements as well as exceeding the safe limits of toxic elements can be detrimental to human health. table 6 gives essential mineral contents of various cuts of camel meat by various authors. calcium content (mg/100g fresh weight) was reported to be in the range of 4.911.48 (table 6). the level of variation reported by kadim et al. (2006; 2011), indicates that physiological factors play a major role in determining the calcium contents in camel meat. small variations in calcium content are found among different meat cuts (table 6). the calcium content between different meat cuts range from 10 to 27% (dawood and alkanhal, 1995; rashed, 2002) cobalt and chromium contents were in the range of 0.003-0.004 and 0.0080.03 (mg/100g fresh weight) (kadim et al., 2006). copper contents in camel meat ranged between 0.04 to 0.12 mg/100g fresh weight (table 6). the foreleg contains a higher copper content compared with other meat cuts (rashed, 2002). the iron content in camel meat (1.16-3.39 mg/100 g fresh meat) varied among different meat cuts (table 6) which is most probably due to the different physiological requirements of myoglobin of different muscles. as with other red meat species, meat cuts containing oxidative muscles (e.g. leg and neck) have a higher iron content than glycolytic muscles. potassium is the major element in camel meat (193.4-379.1 mg/100g fresh weight) and magnesium content in camel meat ranges between 10.4121.03 mg/100g fresh weight (kadim et al., 2009). meat cuts from the limbs have higher potassium and magnesium content compared with the loins and ribs (table 6). meat from saudi arabian camels contained similar manganese content (0.01 mg/100g fresh weight) across four different meat cuts (el-faer et al., 1991; elgasim and alkanhal, 1992). however, meat from camels in egypt appears to have higher manganese content (mg/ 100g dry matter) and the concentration varied among different meat cuts (rashed, 2002). the sodium content in table 5. fatty acid composition of the fat in camel meat. fatty acids (%) rawdah et al. (1994) al-bachir and zeinou (2009) kadim et al. (2011) saturated (s) 14:0 7.68 4.53 3.10 15:0 1.66 2.10 16:0 25.98 30.29 28.50 17:0 1.48 2.54 18:0 8.63 25.51 19.30 monounsaturated (mus) 14:1 1.0 1.60 16:1 8.06 6.30 17:1 0.94 18:1 18.93 32.01 33.50 20:1 trace polyunsaturated (ps) 18:2 6 12.07 5.13 3.20 20:2 6 0.11 18:3 3 0.52 1.20 20:3 9 0.37 20:3 6 0.30 20:4 6 2.84 1.20 22:4 6 0.10 20:5 3 0.32 22:5 3 0.48 22:6 3 0.10 p/s 0.36 0.11 total saturated 51.54 53.00 total musfa 29.90 41.40 total pusfa 18.55 5.60 3/ 6 0.092 w w w w w w w w w w w w 12 kadim et al. 13 composition, quality and health aspects of the dromedary and bactrian camel meats: a review camel meat was in the range of 40.2-87.3 mg/100g (table 7). the loin cuts had the lowest sodium content among the different meat cuts (elgasim and alkanhal, 1992; rashed, 2002; kadim et al., 2006). phosphorus is the second most abundant element in camel meat (105.6-199.0 mg/100g fresh weight) and the leg and shoulder cuts have a slightly higher phosphorus content than ribs and neck cuts (elfaer et al., 1991). the sulfur content was in the range of 54.99-136.57 mg/100g fresh weight. the sulfur content in four meat cuts varied by 17% only (el-faer et al., 1991). red meat is an important source of zinc. camel meat contains about 3.07 to 4.80 mg/100g fresh weight (table 6). the variation between different cuts was 7.6% (dawood and alkanhal, 1995) but a higher percentage of variation (47-56%) has been reported in other studies (elfaer et al., 1991; rashed, 2002). the mineral concentrations of infraspinatus, triceps brachii, longissimus thoraces, semitendinosus, semimembranosus, and biceps femoris muscles of the dromedary (kadim et al., 2013) and bactrian camels (raiymbek et al., 2012) are presented in table 7. the phosphorus magnesium, sodium, potassium and iron contents of camel muscle samples varied between muscles. the triceps brachii muscles and had the highest mean value of phosphorus, calcium, magnesium and potassium (table 7). the semitendinosus muscle in the dromedary and bactrian camels had more magnesium than infraspinatus, triceps brachii, longissimus thoracis, and biceps femoris muscles. the semitendinosus and semimembranosus muscles had more iron than other muscles in the dromedary. the longissimus thoracis muscle had a lower and the triceps brachii higher (p<0.05) potassium than other muscles (table 7). for trace elements (zinc, iron, lead, selenium, copper), there was small variation between the muscles of dromedary and bactrian camels (table 7). table 6. mineral concentrations in camel meat (mg/100g fresh weight. mineral1 factor ca co cr cu fe k mg mn mo na p s zn rump 0.004 0.12 2.5 0.04 badiei et al. (2006) intercostal 8.5 0.29 0.42 0.13 51.0 515 29.5 0.19 300.5 74.0 rashed (2002) scapula 10.0 0.35 0.32 0.21 54.5 670 51.0 0.22 225.0 58.0 sirloin 10.2 0.27 0.41 0.16 44.0 446 28.0 0.16 188.5 66.0 flank 8.4 0.32 0.33 0.12 49.0 811 49.5 0.19 223.0 69.5 front knuckle 8.4 0.26 0.42 0.25 44.5 630 37.0 0.17 299.5 73.5 front limb 9.8 0.19 0.37 0.26 50.5 548 42.5 0.19 312.5 85.5 chuck 11.5 3.2 249 17.4 73.5 3.7 dawood &alkanhal (1995) ribeye 8.1 2.9 231 16.3 67.1 3.7 leg 10.3 3.4 251 17.1 69.7 3.9 leg+loin 4.9 0.04 1.9 228 17.7 0.01 47.9 3.2 elgasim &alkanhal (1992)2 shoulder 5.1 0.01 0.07 1.2 357 20.6 0.01 69.1 196 56.1 3.5 el-faer et al. (1991) thigh 5.4 0.01 0.09 1.4 361 21.0 0.01 70.4 199 55.0 3.1 ribs 4.7 0.01 0.07 1.2 324 18.5 0.01 84.1 181 58.0 3.9 neck 5.6 0.03 0.09 1.4 338 18.5 0.01 87.3 181 64.4 4.8 effect of specie camel 5.9 0.003 0.008 193 12.9 0.08 45.3 105 kadim et al. (2009a)beef 6.2 0.003 0.009 416 20.5 0.006 51.0 162 camel 4.9 0.04 1.94 228 17.7 0.01 47.9 3.2 elgasim & alkanhal (1992)beef 6.97 0.06 2.66 277 24.8 0.02 31.2 4.1 1mineral: ca calcium, co cobalt, cr chromium, cu copper, fe iron, kpotassium, mg magnesium, mn manganese, mo molybdenum, na sodium, p phosphorus, s sulfate, zn -zinc 14 kadim et al. 15 composition, quality and health aspects of the dromedary and bactrian camel meats: a review camel blood concluded that camels could be less efficient than other ruminants in detoxifying these elements in its body (al-qarawi and ali, 2003).the monitoring of toxic material levels in camel products should pay particular attention to toxic compounds in the offal because this is consumed by low income people as a source of animal protein (faye et al., 2008). nutrition, management, breed, sex and age of animals play an important role in determining the level of various elements in the meat and the camel blood (faye et al., 2008). for instance, the calcium content in the camel the concentrations of silver, gold and nickel in five camel meats have been reported at 0.06-0.12, 0.10-0.21 and 0.05-0.38 mg/100g dry matter, respectively (rashed, 2002). the concentration of the three minerals varied among different muscles by 100, 110 and 750% (table 8). the concentrations of nickel, beryllium and vanadium increased in the dromedary camel longissimus thoracis with increasing animal age (kadim et al., 2006). the level of lead in camel longissimus thoracis was 2.5 times the concentration in beef longissimus thoracis (kadim et al., 2009). studies on the levels of trace and heavy elements in table 7. macro and micro-element levels (mg/100g) in infraspinatus (is), triceps brachii (tb), longissimus thoraces (lt), semitendinosus (st), semimembranosus (sm), and biceps femoris (bf) muscles of the dromedary (kadim et al., 2013) and bactrian camels (raiymbek et al., 2012b). dromedary bactrian muscle muscle is tb lt st sm bf is tb lt st sm bf phosphorus 6.49 7.76 5.23 6.39 7.96 6.79 3.32 3.72 2.29 3.97 3.66 3.74 calcium 0.07 0.08 0.05 0.07 0.08 0.07 0.05 0.05 0.05 0.05 0.05 0.05 magnesium 1.73 2.21 1.37 3.39 2.17 1.84 2.48 3.03 2.51 3.5 3.27 3.45 sodium 6.33 5.98 5.18 7.38 5.78 6.93 5.01 4.57 3.59 5.78 4.93 5.16 potassium 81.7 103 25.2 71.3 80.9 85.6 74.4 80.5 36.9 80.0 77.7 73.5 zinc 0.01 0.01 0.01 0.01 0.01 0.01 0.02 0.02 0.01 0.02 0.02 0.02 iron 0.02 0.06 0.03 2.42 2.52 0.05 0.06 0.08 0.05 0.08 0.12 0.08 lead 0.001 0.01 0.01 0.01 0.03 0.002 0.03 0.03 0.03 0.03 0.03 0.02 selenium 0.003 0.003 0.004 0.004 0.003 0.003 copper 0.002 0.001 0.001 0.05 0.07 0.004 0.002 0.002 0.004 0.002 0.002 0.001 1sem: standard error for the mean. means on the same row with different superscripts are significantly different (p<0.05). table 8. toxic/non-essential elements concentrations (mg/100g) of fresh weight. mineral1 factor ag al au cd ni pb sr effect of meat cut intercostal 0.07 0.11 0.24 rashed (2002) scapula 0.06 0.10 0.38 sirloin 0.11 0.19 0.05 flank 0.09 0.12 0.13 front knuckle 0.12 0.17 0.19 front limb 0.11 0.21 0.21 shoulder 0.51 0.02 el-faer et al. (1991) thigh 0.15 0.03 ribs 0.12 0.02 neck 0.58 0.03 effect of specie camel 0.003 0.025 0.015 kadim et al. (2009b) beef 0.003 0.044 0.006 1mineral: ag silver, al aluminum, au gold, cd cadmium ni nickel, pb lead, sr strontium 14 kadim et al. 15 composition, quality and health aspects of the dromedary and bactrian camel meats: a review meat reported from the same laboratory (kadim et al., 2006; 2011) or across different laboratories (dawood and alkanhal, 1995; kadim et al., 2006) supports this contention. it is worth mentioning that the biological variation of elements even within the same herd that has a similar farming background is very high (kadim et al., 2006). meat quality characteristics camel meat is often regarded as inferior to other meats. this might be attributed to the strong reluctance of camel owners to sell their young stock, and they usually slaughter older camels at the end of their productive life. most camel meat trade is of meat from old camels with a low quality, which has a direct bearing on the extent of demand for meat outside the camel herding societies. however, numerous studies have reported that meat quality characteristics from young dromedary camels are comparable to those of beef (leupold, 1968; fischer, 1975; knoess, 1977; mukasa-mugerwa, 1981; kadim et al., 2006, 2009; shariatmadari and kadivar, 2006). nevertheless, camel meat had a significantly lower level of sarcoplasmic proteins as a proportion of total proteins than beef (babiker and tibin, 1986). camels 2-4 years-old and beef 2-3 years-old had similar meat quality characteristics of the longissimus thoracis muscle (kadim and mahgoub, 2008). the camel longissimus thoracis, semitendinosus and triceps brachii muscles lose more water during cooking than beef (48% vs. 37%) while no tenderness differences were observed between the two species (kamoun, 1995a,b). in contrast, babiker and tibin (1986) reported that camel meat has less cooking losses and higher water holding capacity than beef meat. the effect of age on meat quality is discussed in order to optimize the best age for slaughtering camel for high quality meat. table 9 depicts the effect of camel age on meat quality parameters and shows that meat becomes less tender and of inferior quality with increasing animal age (kadim et al., 2006). however, kamoun (1995a,b) noted that age is not a predominant factor in meat quality, in the case of dromedarius fed the same diet and slaughtered between one and four years of age. kadim et al. (2006) suggested that the male camels should be slaughtered between one to three years of age. this is in agreement with the conclusion of dina and klintegerg (1977). at this age the animals were not yet fully grown, averaging about 60-70% of full live weight, and therefore, their meat is tender. meat quality parameters of longissimus thoracis and biceps femoris muscles inf our indian camel breeds was compared by suliman et al. (2011), and the results indicated little variation between the four breeds (table 10). the shear force values in longissimus thoracis muscles ranged from 6.45 kg in magahem to 14.32 kg in shoal, while in biceps fermoris muscles the ranges were between 19.44 kg for wodoh to 23.3 for shoal. on the other hand, various breeds exhibited a similar myofibrillar fragmentation index, ultimate ph and sarcomere length for both longissimus thoracis and biceps femoris (table 10). muscles of the loin region were tenderer than those from the leg. the eating quality of six muscles of the dromedary camel was studied by kamoun (1995b) who concluded that the vastuslateralis muscles had the highest weight and volume losses (51.1 and 47.8%, respectively) whereas psoas major muscles had the lowest (44.6 and 41.1%, respectively) (table 11). the triceps brachii and vastuslateralis muscles contained more soluble collagen than semitendinosus, psoas major, longissimus thoracis and semimembranosus muscles, possibly indicating a less thermal stable bond between collagen molecules and weaker connective tissue structures of those muscles (kamoun, 1995b). although all six muscles studied by kamoun (1995b) were ranked acceptable for tenderness, the longissimus thoracis muscle was tenderer and had less detectable connective tissue than the other muscles. the longissimus thoracis muscle had the highest juiciness score and the semitendinosus and vastuslateralis muscles were less juicy than psoas major, semimembranosus and triceps brachii muscles. ultimate muscle ph the ultimate ph of muscles is a consequence of lactic acid accumulation via glycolysis that affects meat quality characteristics (simek et al., 2003). according to laack et al. (2001), 40-50% of variation in ultimate ph is determined by glycogen concentration. it needs 0.81g/100g of glycogen to lower the ph of one kg of muscle from 7.2 table 9. effect of age on some meat quality characteristics of the dromedary camel longissimus thoracis muscle. kadim et al. (2006) kadim et al. (2009b) age group (yr) age group (yr) 1-3 3-5 5-8 1-2 8-10 ultimate ph 5.91 5.84 5.71 5.68 5.65 wbshear force value (newton) 68.4 79.5 131.9 66.1 87.3 sarcomere length (µm) 1.85 1.24 1.06 1.66 1.60 myofibrillar fragmentation index (%) 80.99 73.3 60.4 72.2 67.3 expressed juice (cm2/g) 29.6 27.36 21.26 38.1 37.4 cooking loss (%) 26.06 23.72 22.42 23.4 22.0 colour parameters l* (lightness 37.74 34.03 31.69 39.1 38.1 a* (redness 13.37 13.82 16.18 16.5 15.6 b* (yellowness) 6.09 6.78 7.26 5.58 6.29 16 kadim et al. 17 composition, quality and health aspects of the dromedary and bactrian camel meats: a review ph in camel muscles is a consequence of low muscle glycogen as a result of pre-slaughter stress, including, poor nutrition, rough handling and long transportation. the ultimate ph has an effect on several meat properties like colour, tenderness, water-holding capacity, flavor, and drip loss all of which influences consumer acceptance of camel meat. glycogen degradation speed differs between “red” and “white” muscles. red muscles have many red fibres, which contract slowly, have an oxidative metabolism and a low concentration of glycogen. white muscles contract rapidly and have a high concentration of glycogen, normally with a glucolytic metabolism and an active degradation to lactic acid (lawrie, 2006). the ultimate ph of dromedary camel meat ranges between 5.5 and 6.6 (babiker and yousif, 1990; kadim et al., 2006, 2009a,b, 2010, 2013). generally, young camels tend to produce meat with a higher ph than older camels due to lower levels of glycogen. in this respect, kadim et al. (2006) found that camels younger than three years had a ph value (5.91) which was higher than camels older than six years (5.71). the ultimate ph of longissimus thoracis muscles varied between 5.53 and 5.75 and between 5.68 and 5.80 for electrically stimulated and non-stimulated camel carcasses, respectively (kadim et al., 2009a). the breed of camels did not differ in terms of ultimate ph in longissimus thoracis and biceps femoris muscles (suliman et al., 2011). tenderness (shear force value) tenderness is the most important organoleptic characteristic and is the predominant quality determinant of meat compared to flavor and colour (koohmaraie, to 5.5 (warris, 1990). the ultimate ph of camel muscles is the result of a combination of many factors including pre-slaughter handling, postmortem treatment, glycogen storage and muscle physiology. low muscle glycogen stores at slaughter prevents the development of a desirable ph postmortem (ashmore et al., 1973). a high ultimate table 10. effect of camel breed on some meat quality characteristics of the dromedary camel longissimus thoracis and biceps femoris muscles (suliman, et al., 2011). breed magahem wodoh shoal sofor muscle1 muscle1 muscle1 muscle1 lt bf lt bf lt bf lt bf ultimate ph 5.76 5.90 5.87 5.90 5.91 5.82 6.07 6.03 wbshear force value (kg) 6.45 23.32 13.73 19.44 14.32 23.25 10.40 22.77 sarcomere length (µm) 1.69 1.68 1.68 1.66 1.64 1.69 1.65 1.67 myofibrillar fragmentation index (%) 71.6 62.4 66.2 60.9 65.4 63.0 67.0 61.2 cooking loss (%) 23.7 28.3 21.9 26.0 22.9 31.2 22.4 28.7 colour parameters l* (lightness) 31.6 30.0 33.4 28.1 31.6 31.2 31.2 29.7 a* (redness) 11.8 13.3 13.0 13.6 12.8 13.4 15.0 13.1 b* (yellowness) 4.03 4.07 4.74 3.91 4.43 4.26 4.85 3.91 1muscle: lt longissimus thoraces, bf biceps femoris. table 11. eating quality attributes of the six major muscles (kamoun, 1995b). parameter muscle1 pm lt sm st vl tb myoglobin (mg/g) 3.9 4.1 5.8 3.4 4.1 5.1 collagen (mg/g) 3.3 4.1 5.0 7.5 6.6 5.6 sensory tenderness 7.2 6.6 3.7 3.6 1.9 3.9 collagen soluble (%) 29 29 30 34 42 41 sensory juiciness 6.2 6.8 5.2 3.8 4.1 5.8 cooking weight loss (%) 45 45 49 48 51 51 cooking volume loss (%) 41 42 46 44 48 45 1muscle: pm psoas major, lt longissimus thoracis, sm semimembranosus, st semitendinosus, vl vastus lateralis, tb triceps brachii. 16 kadim et al. 17 composition, quality and health aspects of the dromedary and bactrian camel meats: a review 1988). muscle characteristics, glycogen content, collagen content, solubility, and the activities of proteases and their inhibitors are the most important physiological parameters that determine meat tenderness (hocquette et al., 2005). major variation in meat tenderness is related to the variability of muscle characteristics (renand et al., 2001). the longissimus thoracis muscle had more soluble collagen than the semitendinosus and triceps brachii muscles (kamoun et al., 1995b). the triceps brachii muscle had the highest shear force values, maximum connective tissue strength and lowest collagen solubility compared to longissimus thoracis, semitendinosus, semimembranosus, psoas major and vastuslateralis in camels, indicating that it is the toughest muscle in this group (babiker and youssif, 1990) the psoas major and longissimus thoracis muscles were the most tender and had less detectable connective tissue than other muscles. in another study, kadim et al. (2013) found that infraspinatus, triceps brachii and longissimus thoracis camel muscles had lower shear force values than semitendinosus, semimembranosus and biceps femoris muscles, which might be due to less connective tissue (table 12). raiymbek et al. (2012) reported a similar observation for bactrian camel muscles (table 12). the tenderization process starts after slaughter and it varies among individual carcasses and depends on the postmortem activity of the calpainproteolytic enzymes that include calpastatin (parr et al., 1999). the most marked difference in meat quality characteristics between camel meat and other livestock is largely believed to be tenderness (mukasa-mugerwa, 1981). camels are usually slaughtered at the end of their productive life (more than10 years) which is classified as of low quality compared with meant from other animals. average shear force value of camel meat at 5-8 years was 48% and 40% higher than those of 1-3 and 3-5 year olds, respectively (kadim et al., 2006). a number of studies have also shown that shear values of meat increase with increasing camel age (dawood, 1995; kadim et al., 2006). differences due to age may be related to changes in muscle structure and composition as an animal matures, particularly in the nature and quantity of connective tissue (asghar and pearson, 1980), significant differences (p<0.05) were found between the different ages (8, 16 and 26 months of age) and cuts (chuck, ribeye and leg) for shear force values of male nahdi camels (dawood, 1995). aging historically, meat has been aged to improve its quality characteristics because meat is often unacceptably tough immediately following rigor onset. ageing is the process that causes an improvement in tenderness, flavour, colour and texture over time and involves specific degradation of structural proteins (hwang et al., 2003; jaturasitha et al., 2004). the time required for ageing varies with the type, size, species, and age of the animal. moderate temperature table 12. meat quality characteristics of six muscles of the dromedary and bactrian camel carcasses. references kadim et al. (2013) raiymbek et al. (2012) muscle1 muscle1 is tb lt st sm bf is tb lt st sm bf age (yr) 1.5-2 2-3 ultimate ph 5.64 5.73 5.61 5.67 5.83 5.74 5.73 5.69 5.63 5.68 5.60 5.68 wb-shear force 34.8 42.1 41.8 36.8 42.4 40.2 10.8 8.9 6.0 10.0 9.8 8.6 sarcomere length (µm) 31.6 29.2 33.5 28.5 30.6 29.5 1.45 1.54 1.70 1.47 1.53 1.52 myofibrillar fragmentation index (%) 6.3 6.7 6.5 9.0 12.9 10.3 76.8 76.9 73.9 77.7 76.7 78.4 water-holding capacity 1.7 1.7 1.7 1.5 1.4 1.5 38.2 37.9 37.1 40.4 41.3 38.8 cooking loss (%) 31.6 29.2 33.5 28.5 30.6 29.5 32.7 32.6 25.1 34.3 33.9 32.1 colour l* 41.7 40.2 43.5 40.5 40.6 40.6 32.4 30.8 33.4 30.2 30.8 30.1 a* 12.7 12.6 14.0 10.5 13.6 13.3 13.2 13.1 13.8 12.8 13.8 13.5 b* 2.6 3.7 4.1 2.2 2.9 3.8 3.8 3.4 3.9 3.2 3.5 3.6 1muscle: is infraspintus, tb triceps brachii, lt longissimus thoracis, st semitendinosus, sm semimembranosus, bf biceps femoris. 18 kadim et al. 19 composition, quality and health aspects of the dromedary and bactrian camel meats: a review storage may accelerate the ageing process by keeping carcasses at temperatures of 15oc or greater (petrovic et al., 1993). the ageing processes originate within the myofibers and are responsible for degradation of cellular constituents. this resembles the method adopted by kadim et al. (2009a), where camel longissimus thoracis muscles were stored at a temperature of 2-3oc for seven days. ageing at 2-3oc for 7-days improved camel meat quality characteristics (table 13). this implies that ageing may be one of the postmortem treatments which increase camel meat tenderness that might be adopted in the camel meat industry. according to lagerstedt et al., 2008), increasing ageing time from four to seven days may cause more cooking losses in beef meat. however, kadim et al. (2009a) found no differences in cooking loss with ageing of camel longissimus thoracis muscles from two to seven days. the level of improvement in tenderness within a certain ageing time varies among different meat cuts, ages of the animal and species due to differences in the level of endogenous enzymes, contraction status and connective tissue content (george-evins et al., 2004). in general, ageing can improve quality characteristics of meats that have relatively small amounts of connective tissue and that have not cold-shortened (wheeler et al., 1999). myofibrillarfragmentation index the myofibrillar fragmentation index is a useful indicator of the extent of myofibrillar protein degradation of postslaughter camel meat (kadim et al., 2006, 2009a,b, 2011, 2013; raiymbek et al., 2012). the differences in rates of fragmentation of myofibrillar proteins may account for differences in the rate of postmortem tenderization of meat (nagaraj et al., 2005). the structural changes occurring in muscle tissue after slaughter are generally believed to be caused by alterations in and interactions of myofibrillar proteins in the tissue (nagaraj et al., 2006). claeys et al. (1994) reported that at a higher ph, proteins preferentially solublized were titin, filamin, nebulinand myosin heavy chain. except for myosin, all are preferentially degraded by calpains, which has an optimum effect atph values near neutrality. similarly, silva et al. (1999) verified that the myofibrillar fragmentation index in meat was significantly higher at ultimate ph 6.5 than at 5.7. there is a correlation between the myofibrillar fragmentation index and the tenderness of meat (veisethet al., 2001). the myofibrillar fragmentation index of camels above 6 years was lower than those of 1-3 years of age (kadim et al., 2008, 2009a). the same authors established a strong relationship between physical disruptions of the myofibrils and the tenderness of camel meat. water holding capacity (expressed juice) water retention in meat is primarily caused by immobilization of water within the myofibrillar system. applying pressure can cause a shift of water from the intercellar to the extracellular space and then onto the meat surface as a result of structural alterations at the level of the sarcomeres or of the myofilaments structure. water retention affects the retention of minerals, vitamins and volume of water (beriain et al., 2000) and is influenced by muscle ph because of the electrostatic effects of meat proteins (hamm, 1975). the dromedary and bactrian camel meats contain higher expressed juice than other camelidae such as llama and alpaca, possibly because of the lower fat content (cristofaneli et al., 2004). the amount of water loss was likely due to the ultimate ph of the muscle, composition of muscle and denaturation of proteins by the ionic strength of the extracellular fluid and oxidation of lipids which decreases the solubility of proteins (dyer and dingle, 1967). kadim et al. (2006) reported that meat table 13. effects of age and ageing on meat quality attributes of longissimus thoracis of dromedary camel (kadim et al., 2009a). age (year) 1-3 4-6 7-9 10-12 ageing 7-day ageing 2-day ageing 7-day ageing 2-day ageing 7-day ageing 2-day ageing 7-day ageing 2-day ultimate ph 5.86 5.85 5.79 5.78 5.71 5.71 5.60 5.61 expressed juice (cm2/g) 38.6 37.2 37.2 36.6 30.8 30.3 21.3 21.1 cooking loss (%) 25.7 25.0 23.9 22.7 21.3 19.8 18.9 17.8 wb-shear force (kg) 7.28 8.10 8.41 8.97 9.14 9.76 11.29 12.79 sarcomere length (µm) 1.73 1.47 1.65 1.67 1.48 1.47 1.39 1.37 myofibrillar fragmentation index 77.9 73.5 71.6 69.8 66.9 64.5 62.7 60.2 lightness (l*) 40.5 39.80 38.71 36.86 35.31 33.72 30.15 28.47 redness (a*) 15.6 15.7 16.9 16.1 18.2 19.0 19.9 19.5 yellowness (b*) 5.40 5.51 6.04 6.03 7.03 7.05 7.93 7.98 18 kadim et al. 19 composition, quality and health aspects of the dromedary and bactrian camel meats: a review from camels slaughtered at one to three years had higher water-holding capacity values than those slaughtered at five to eight years of age, probably due to variations in fat content and the binding ability of meat proteins (table 9). the water-holding capacity decreases as fat levels increase due to an increase in the ratio of moisture to fat (miller et al., 1968). dawood (1995) reported that young camel meat (eight months of age) had significantly higher waterholding capacities than meat from 26 month-old camels. the volume of the dromedary camel meat was reduced by 44.3% and weight by 48.2% after being boiled in water for 40 min (kamoun, 1995b). the longissimus thoracis and biceps femoris muscles from mature camels had 37.9 and 37.1% cooking loss which was higher than the 33.2 % cooking loss in semitendinosus muscle, which coincided with its high water-holding capacity (babiker and yousif, 1990). a higher cooking loss was observed in the longissimus thoraces muscle (33.5%) when compared to the infraspinatus (31.6%), triceps brachii (29.2%), semitendinosus (28.5%), semimembranosus (30.6%) biceps femoris (29.5%) with no significant differences between the last five muscles (kadim et al., 2013). in the bactrian camel (table 12), variation in expressed juice between infraspinatus, triceps brachii, longissimus thoracis, semitendinosus, semimembranosus, and biceps femoris muscles ranged from 37.10cm2/g (longissimus thoraces) to 41.27cm2/g (semimembranosus) cm2/g (raiymbek et al., 2012a). the variation between muscles might be due to location, activity, proportion of muscle fiber types, ph, intramuscular fat and the ratio of water to protein of individual muscles. however, suliman et al. (2011) found that biceps femoris muscles had a higher cooking loss than longissimus thoraces muscles in four different camel breeds. according to shehata (2005), young camels (10-12 months old) had a higher cooking loss than old animals. longissimus thoracis from two to three year old camels had significantly lower cooking loss (24.3%) than the values mentioned above (kadim et al., 2009a,b). the cooking loss of camel longissimus thoracis was not different from that in cattle longissimus thoracis of the same age. cooking loss is important because of its potential to change the level of nutrients in the meat once it is cooked. for example, while it generally regarded that the protein content of camel meat is similar to other red meats (elgasim and alkanhal, 1992; gheisari et al., 2009), the higher cooking loss in camel meat (33-38%), compared to beef (24.6%), will generate a more nutritionally dense cooked meat (kadim et al., 2009). colour (l*, a*, b*) meat colour is one of the most important sensory characteristics according to which consumers make judgments on meat quality. the degree of meat pigmentation is directly related to the chemical structure of myoglobin content. myoglobin concentration within a given muscle will differ according to the species or age and is dependent on muscle fibre type proportions, muscle ph, age, intramuscular fat, and muscle texture (gardner et al., 1999; lawrie, 2006). there was a negative linear relationship between colour values and ph in longissimus thoracis muscles (menzies and hopkines, 1996). postmortem protein degradation is directly related to the ultimate ph, which increases light scattering properties of meat and thereby increases l* value (offer, 1991). low ultimate ph meat samples might lead to more protein degradation resulting in higher colour values than the high ultimate ph meat samples. abril et al. (2001) reported that reflectance spectrum value for meat samples was higher for an ultimate ph above 6. postmortem glycolysis decreases muscle ph making muscle surfaces brighter and superficially wet. if the ultimate meat ph is high, the physical state of the proteins will be above their isoelectric point, and the proteins will associate with more water in the muscle and therefore, fibers will be more tightly packed (abril et al., 2001). babiker and yousif (1990) reported that dromedary camel longissimus dorsi muscles had higher lightness (l*), redness (a*) and yellowness (b*) values than semitendinosus and triceps brachii muscles. suliman et al. (2011) found that the colour of the biceps femoris muscle was not affected by breed of camels. a high redness (a*) colour component in the camel longissimus thoracis muscle was associated with a lower lightness (l*), which might be due to an increase in myoglobin content. camel muscle lightness l* values indicated that the longissimus thoraces muscle (43.5) had the lightest (p<0.05) lean colour, which was possibly due to high fat content (kadim et al., 2013). the semitendinosus muscle had the darkest coloured lean compared to infraspinatus, longissimus thoraces, triceps brachii, semimembranosus, and biceps femoris camel muscles. the longissimus thoraces, semimembranosus and biceps femoris dromedary camel muscles had higher redness (a*) values than the semitendinosus muscle, while a* value for infraspinatus and triceps brachii muscles were in between. cie a* values were similar among longissimus thoraces, semimembranosus and biceps femoris muscles (kadim et al., 2013). in camels, the highest average yellowness (b*) value was recorded in the longissimus thoraces muscle with comparable values to the triceps brachii and biceps femoris muscles. in bactrian camel, the longissimus thoraces muscle had higher lightness (l*) values and infraspinatus han triceps brachii, semitendinosus, semimembranosus and biceps femoris muscles (raiymbek et al., 2012a). the age of the camels has a significant effect on their meat colour (kadim et al., 2006). meat colour from 6-8 and 10-12 year old dromedary camels was darker (lower l*), redder (higher a*) and yellower (high b*) than 1-3 year old camels because of higher concentrations of myoglobin (kadim et al., 2006). health aspects of camel meat meat is a valuable source of food rich in many essential amino acids, minerals, vitamins and bioactive compounds 20 kadim et al. 21 composition, quality and health aspects of the dromedary and bactrian camel meats: a review such as carnosine, anserine, glutathione and essential fatty acids such as omega 3 fatty acids (williams, 2007; schonfeldt and gibson, 2008). apart from the nutritional value of meat, it provides several eating attributes and fulfilling experiences that normally are not achieved by other protein sources. beef, lamb, pork, poultry and fish are considered the major sources of animal protein worldwide. however, in africa, the middle east and some asian countries, especially in arid and semi-arid regions, camel meat is regarded as a main source of animal protein that equals and in some cases surpasses other meats in commercial importance. several epidemiological studies linked health problems such as obesity and high saturated fat and cholesterol intake to increased consumption of animal products (biesalski, 2005; chao et al., 2005). this has led to a concern that total dietary fat intake should be restricted by consuming smaller portions less frequently (schonfeldt and gibson, 2008) or replacing red meat consumption with white meat. the low cholesterol and fat contents in camel meat could potentially be considered as a better alternative to the higher fat and cholesterol contents of mutton and beef. camel meat as medicine meat in general is considered a functional food for cures of many ailments and for improved performance in many cultures around the world (migdal and živkovic, 2007). camel meat and offals such as liver are believed to have medicinal properties and are eaten raw (bin saeed et al., 2005). kadim et al. (2008) stated that somalis and indians particularly believe in the health benefits of consuming camel meat. among many african and asian countries, camel meat has traditionally been used to cure the following ailments: (1) seasonal fever, sciatica and shoulder pain, as well as for removing freckles (by placing hot camel meat slices on the freckled area); (2) camel meat soup was used to cure corneal opacity and to strengthen eyesight; (3) camel fat was used to ease hemorrhoidal pains and the hump fat was used to remove tapeworm; and (4) dried camel lungs used to be prescribed as a cure for asthma, especially if taken with honey. kurtu (2004) reported that the majority of camel meat consumers believe it is a healthier option during the dry season in which cattle are infected with various zoonotic diseases. this belief probably originated from the historical use of animals’ organs, including meat, in folklore and traditional medicine. lev (2006) cited the use of camel meat in remedial formulation by al-tabari, alkindi and al-qazwini which indicate the roots of some of the current beliefs. the camel is distinguished from other animals by the fact that the percentage of its intramuscular fat declines as the animal gets older. this quality, only found in camels, makes their meat less fatty, so its consumption is healthy and recommended for weight loss. and this quality also reduces the risk of cardiovascular disease and atherosclerosis since it lowers the percentage of cholesterol in the blood. camel meat has other medical qualities, too, such as protecting against cancerous tumors, as claimed by some researchers, because it contains unsaturated fatty acids like linoleic acid which interact with other unsaturated fatty acids taken from vegetable oils to protect against cancer. camel meat can also be used as a cure for exhaustion and fatigue because it contains energy needed by body cells. such energy comprises sugar not fat, since, a camel’s fat is concentrated in its hump whereas other animals store it in their muscles. in addition, camel meat contains glycogen, a carbohydrate which is easily absorbed and metabolized in the body, and which is converted to glucose which in turn activates nerve as well as other cells. conclusion the nutritional value of dromedary and bactrian camel meat is similar to other red meats. however, meat from young camels can be considered as a healthy option due to its low fat and cholesterol contents. the quality characteristics of camel meat are similar to beef meat quality when they are slaughtered at similar ages. according to the composition and quality parameters of camel meat, it can be successfully marketed alongside that from cattle, deer, sheep and goat. preand post mortem factors should be carefully considered to improve meat quality characteristics. references abril, m., m.m. campo, a. onenc, c. sanudo, p. alberti, and a.i. negueruela 2001. beef colour evaluation as a function of ultimate ph. meat science 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qaboos university, p.o. box 34, pc:123 al-khod. arne malzahn ( ) email: arne.malzahn@gmail.com 2alfred wegener institute for polar and marine research, ostkaje 1118, 27498 helgoland, germany 3shannon point marine center, western washington university, 1900 shannon point road, anacortes, wa 98221, usa. introduction the global yield of the capture fisheries has been stagnating at around 85 million metric tonnes per year since the mid 1980ies. since more or less the same time, aquaculture production is on an exponential rise, replacing the missing growth in capture fisheries production (fig. 1). the vast majority of the 80 million tons of aquaculture production in 2010 was made up by seaweeds and cyprinid fishes (20 and 25 million tonnes respectively) (fao). however, focussing on the value per unit the picture completely changes and next to the high value products such as abalone, shrimps and sturgeons with values between 20,000 and 50,000 us$ tonne-1 we find species such as groupers, soles and pompanos in the same price range. the main difference between the first and the latter group is that the first is relatively easy to culture and the price is based on slow growth and relatively low area based biomass production. the latter group of groupers, soles and jacks have in common that they are sought after food fish with dwindling stocks and that they are not easy to grow, reproduce and wean in captivity. one of the bottlenecks for instance in grouper culture is the larval weaning (sugama et al. 2012), and they, like many other species, rely on live feeds (lavens and sorgeloos 1996; lavens et al. 1994). this is mirrored by the still increasing number of publications on the use of live feeds in aquaculture (fig. 2). the typical succession of live feeds for very small, gape limited larvae is to start with ss-type or s-type brachionus spp., followed by larger brachionus spp. strains and eventually artemia spp. larval stages (lavens and sorgeloos 1996; lavens et al. 1994). artemia and brachionus species are not always the most suitable first feeds for marine fish larvae due to inappropriate size (pepin and penney 1997; van der meeren 1991), their swimming behaviour, which makes them less susceptible to predation (buskey et al. 1993; von herbing and gallagher 2000), and they are suspected of being of insufficient nutritional quality (støttrup and norsker 1997). calanoid copepods as live feed have been shown to improve growth and survival in groupers (doi et al. 1997), and several other species (stottrup acartia tonsa حاالت اإلستزراع وأتثريها على القيمة الغذائية للكواببودا آرين مالزان1ونيكول ابرييل مالزان2 وكاتريينا سكو1,3ومارتن بورمسا 2 abstract. live feed are still necessary for the rearing of larval stages of several fish species, especially marine ones. compared to artemia, copepods are of superior quality. this is based on a suite of traits like size, movement, and nutritional value. copepods are for example usually high in protein and fatty acids. essential fatty acid profiles reflect to a large degree the fatty acid supply, which provides the opportunity to manipulate fatty acid profiles of, amongst others, copepods. by manipulating nutrient supply of the algae rhodomonas salina we were able to double essential fatty acid concentrations in naupliar and copepodit life stages of the copepod acartia tonsa. however, this lead to growth depression rather than to increased growth rates in a series of consumer species, including larval fish. the reason for the growth depression is likely to be mineral deficiencies occurring along with the nutrient manipulation of the algae. keywords: copepod, nutritional value, live feed, aquaculture, acartia املســتخلص: تبقــى املغذيــات احليــة ضروريــة لرتبيــة الريقــات للعديــد مــن األمســاك وخصوصــا البحريــة منهــا. وتعتــر الكوبابــودا ذات جــودة عاليــة مقارنــة مــع األرتيميــا. ويســتند هــذا علــى جمموعــة مــن الصفــات مثــل احلجــم، واحلركــة، والقيمــة الغذائيــة. وحتتــوي الكوبابــودا علــى ســبيل املثــال علــى نســبة عاليــة مــن الروتــن واألمحــاض الدهنيــة. وتعكــس مالمــح األمحــاض الدهنيــة األساســية إىل حــد كبــري إمــدادات األمحــاض الدهنيــة، والــي تتيــح الفرصــة ملعاجلــة مالمــح األمحــاض الدهنيــة مــن بــن أمــور أخــرى. ومبعاجلــة التزويــد باملــواد الغذائيــة الطحلبيــة )رودومــاس ســلينا( متكنــا مــن مضاعفــة تركيــز األمحــاض الدهنيــة األساســية يف مراحــل حيــاة الكوبابــودا . إال أن ذلــك أدى إىل القصــور يف النمــو بــدل الزيــادة يف معــدالت النمــو يف سلســلة مــن األنــواع املســتهلكة مبــا يف ذلــك الريقــات. وقــد يكــون النقــص يف املعــادن ســببا مرجحــا لذلــك، نتيجــة ملعاجلــة املغذيــات اخلاصــة بالطحالــب. الكلمات املفتاحية: غراء الببتيدات، السيلوكسانات، اخلاصة بالطحالب. 41research article malzahn, aberle-malzahn, schoo, boersma 2000), and larval grouper actively select for copepod nauplii over rotifers (toledo et al. 2004). similar selectivity patterns have been reported for a suite of marine fish larvae (monteleone and peterson 1986; stoecker and govoni 1984). food quality can be expressed in many ways, such as through the concentration of polyunsaturated fatty acids (paulsen et al. 2014; paulsen et al. 2013), sterols (lee 2001), amino acids (awaiss et al. 1992) or the elemental composition (malzahn et al. 2007; shao et al. 2008) of the food item. all of the latter play a major role in fish nutrition (lavens et al. 1994), and it is crucial to find the food organisms which suits the demand best. it is very likely that marine copepods are a good match for the nutritional demands of larval fish as they are the main prey items in nature, hence an adaptation of the needs of larval fish to the main prey in supply can be assumed. wild zooplankton has been successfully used for larval rearing (otterlei et al. 1999) with growth rates superior compared to artemia larvae. however, availability of natural zooplankton is a problem, as zooplankton size spectrum (beaugrand et al. 2002; greve et al. 2004), density (beaugrand et al. 2003) and species composition (beaugrand et al. 2002; greve et al. 2004) are permanently changing. even if the supply of natural zooplankton was reliable, the nutritional value of copepods varies with species (gismervik 1997a; gismervik 1997b), life stage (villar-argaiz et al. 2002; villar-argaiz and sterner 2002) and season (villar-argaiz et al. 2002; villar-argaiz and sterner 2002) and is hence again an unreliable source of live feeds. consequently, in-house life feed production in the form of copepods seems to be a reliable way to fulfil the nutritional demand of early life stages of fish until they can be weaned on more easily accessible live feeds like brachionus and artemia or even formulated diets. this paper aims to sum up a series of experiments carried out to determine how copepod culture conditions can be manipulated to produce copepods of an elemental and biochemical composition of choice. materials and methods we conducted a series of experiments in which copepods were fed on phytoplankton which in turn was grown in nutrient manipulated growth media. the data we show here are representative for the nutrient treatments and can easily be reproduced. the phytoplankter r. salina was reared either under nutrient replete conditions using the f/2 medium following guillard and ryter figure 1. global wild fish capture and aquaculture production in million tonnes, 1950–2010. data source: fao (fao). figure 2. number of publications retrieved from web of science using the search words ‘aquaculture’ and ‘live feeds’ table 1. fatty acid concentrations and elemental ratios of phytoplankton grown on nutrient replete (f/2) and nutrient depleted (-p and –n) media. measure f/2 +/sd -n +/sd -p +/sd sum unsaturated fa (µg*µgc-1) 0.035 0.022 0.066 0.032 0.105 0.079 total fa (µg*µgc-1) 0.058 0.023 0.145 0.056 0.146 0.090 20:5n3 (epa) (µg*µgc-1) 0.009 0.007 0.011 0.006 0.016 0.011 22:6n3 (dha) (µg*µgc-1) 0.007 0.005 0.017 0.017 0.024 0.039 c:n (mol*mol-1) 7.59 0.66 10.14 2.65 8.03 1.72 c:p (mol*mol-1) 231.13 86.71 173.12 84.60 579.24 108.17 42 squ journal of agricultural and marine sciences, 2015, volume 19, issue 1 culture conditions affect the nutritional value of the copepod acartia tonsa (1962) or under nitrogen or phosphorus limitation. the phosphorus limited treatment was realized by adding all f/2 ingredients but phosphorus to sterile filtered natural seawater. this means that the phytoplankton could only use the phosphorus which was available in the seawater at the moment of filtration. adding all of the other macroand micronutrients assured a liebig/sprengel type phosphorus limitation (sprengel 1839). nitrogen limitation was realized by adding 20% of the n usually added to the f/2 medium. the addition of some nitrogen was necessary to produce enough n-limited phytoplankton to suit the experimental needs. in order to ensure constant algal quality, a new batch of algae was set up every day and cultured well into the stationary phase for the n and p limited cultures. f/2 algae were always harvested in the exponential growth phase (malzahn et al. 2007; malzahn and boersma 2012; malzahn et al. 2010). the calanoid copepod acartia tonsa was then fed on these nutrient manipulated phytoplankton for a predefined period, after which the copepods were analysed for elemental and biochemical composition as well as their developmental rates. carbon and nitrogen were analysed by means of an elemental analyser. phosphorus was analysed as orthophosphate after acidic oxidative hydrolysis with 5% h2so4 (grasshoff et al. 1999). fatty acids were analysed as fatty acid methyl esters and gas chromatography (for details see malzahn et al. 2007; malzahn and boersma 2012; malzahn et al. 2010; schoo et al. 2013a; schoo et al. 2013b). developmental rates were calculated by dividing the mean developmental stage by the age of the animals. due to the isochronal growth of a. tonsa, which means that all developmental stages are equally long (berggreen et al. 1988; miller et al. 1977) under constant growth conditions, it was not necessary to apply a weighing factor for certain developmental stages. results and discussion the different nutrient limitations the algae were subjected to resulted in significant differences in carbon-to-nutrient ratios and fatty acid profiles. phytoplankton significantly varied in their c:n and c:p ratios with respect to the nutrient treatment (fig. 3, fig. 4 and table 1). the concentrations of the limiting elements were always lower than the non-limiting elements, pointing on figure 3. c:p ratios of r. salina grown on nutrient replete (f/2) and nutrient depleted (-p and –n) conditions and a. tonsa reared on these algae. figure 4. c:n ratios of r. salina grown on nutrient replete (f/2) and nutrient depleted (-p and –n) conditions and a. tonsa reared on these algae. table 2. statistical information (one way anova followed by tukeys hsd test for unequal n) on various fatty acid measures (µg fa*µg carbon-1) from phytoplankton reared on nutrient replete (f/2) and nutrient depleted (-p and –n) conditions. measure ss df f p f/2 vs -p f/2 vs -n -n vs -p total fatty acids intercept 0.741 1 192.020 >0.05 < < n.s. treatment 0.096 2 12.449 >0.05 error 0.201 52 unsaturated fa intercept 0.258 1 101.979 >0.05 n.s. < n.s. treatment 0.046 2 9.119 >0.05 error 0.131 52 20:5n3 (epa) intercept 0.008 1 117.231 >0.05 n.s. < n.s. treatment 0.001 2 4.047 >0.05 error 0.003 52 22:6n3 (dha) intercept 0.013 1 22.242 >0.05 n.s. n.s. n.s. treatment 0.003 2 2.283 >0.05 error 0.031 52 43research article malzahn, aberle-malzahn, schoo, boersma the non-homoeostatic nature of phytoplankton growth (droop 1973; droop 1974). the concentration of fatty acids also varied significantly with nutrient limitation, showing generally higher fatty acids concentrations when grown under nutrient limitation (table 1 & table 2). similar, as well as opposing patterns, have been reported for other phytoplankton species (reitan et al. 1997). the majority of variability in fatty acid concentrations in general seems to be introduced by taxonomic group. however, the variance due to culture conditions can be substantial as well (reitan et al. 1994). this species specific behaviour of altering fatty acid production with nutrient supply enables the keen aquaculturist to tailor single species cultures or even mixes of different phytoplankton species to suit the needs of live food and subsequently the larval fish. considering fatty acids not as concentrations but as percentage of total fatty acids revealed a different picture (table 3). here we found fewer differences between the treatments, which indicate that fatty acids production might vary in quantity, but that the variation in relative proportions is less pronounced. when copepods were fed such manipulated phytoplankton we found the same pattern of increased elemental ratios and fatty acid enriched copepods as when they were fed on phosphorus limited phytoplankton (figure 3 & figure 4, table 4 & table 5). looking at the relative contribution of fatty acids to the total fatty acid pool we found no differences between the treatments (table 6), which points to the conservative nature of the propagation of fatty acids from one trophic level to the next (reviewed in dalsgaard et al. 2003). however, not only did the fatty acid concentrations change in copepods when fed on nutrient limited phytoplankton, but so did the elemental composition. we found increased c:p ratios in copepods reared on phosphorus limited phytoplankton in several experiments (malzahn et al. 2007; malzahn and boersma 2012; schoo et al. 2010; schoo et al. 2012; schoo et al. 2013a). consumers have a dome-shaped growth response to food carbon to phosphorus ratios, growth being carbon (energy) limited on the low c:p side and phosphorus limited on the high c:p side (boersma and elser 2006). high c:p ratios create problems because of the excess carbon which has to be taken up with every unit of phosphorus. the handling of the excess carbon seems to create costs high enough to significantly depress consumers’ growth. the phytoplankton in our experiments showed superior fatty acid profiles and inferior c:p ratios under phosphorus limitation, the former known to accelerate growth (dalsgaard et al. 2003; engstrom-ost et al. 2005; izquierdo et al. 2000), the latter known to depress growth (sterner table 3. statistical information (one way anova followed by tukeys hsd test for unequal n) on various fatty acid measures (expressed as %of total fa) from phytoplankton reared on nutrient replete (f/2) and nutrient depleted (-p and –n) conditions. measure ss df f p f/2 vs -p f/2 vs -n -n vs -p % sum unsaturated fa intercept 143652.115 1 541.516 >0.05 n.s. n.s. n.s. treatment 1388.279 2 2.617 0.08 error 13794.431 52 % 20:5n3 (epa) intercept 5270.416 1 243.938 >0.05 > > n.s. treatment 269.813 2 6.244 >0.05 error 1123.487 52 % 22:6n3 (dha) intercept 6571.439 1 61.112 >0.05 n.s. n.s. n.s. treatment 62.834 2 0.292 0.75 error 5591.643 52 table 4. fatty acid concentrations and elemental ratios of copepods grown on nutrient replete (f/2) and nutrient depleted (-p and –n) phytoplankton. measure f/2 +/sd -n +/sd -p +/sd sum unsaturated fa (µg*µgc-1) 0.077 0.024 0.119 0.053 0.136 0.058 total fa (µg*µgc-1) 0.013 0.006 0.024 0.011 0.036 0.016 20:5n3 (epa) (µg*µgc-1) 0.002 0.003 0.003 0.004 0.006 0.003 22:6n3 (dha) (µg*µgc-1) 0.003 0.003 0.013 0.012 0.013 0.008 c:n (mol*mol-1) 4.989 0.127 5.303 0.628 5.617 0.580 c:p (mol*mol-1) 180.912 39.585 186.018 65.281 280.917 96.898 44 squ journal of agricultural and marine sciences, 2015, volume 19, issue 1 culture conditions affect the nutritional value of the copepod acartia tonsa 1993; sterner et al. 1993; sterner and hessen 1994). the question arising from this is distinguishing which factor is more important for e.g. larval fish growth. the unique biochemical composition of the phytoplankter r. salina and the relatively strong conservation of fatty acids as well as c:p signals in the copepod a. tonsa allowed us to test this. in all of the above mentioned experiments high copepod c:p resulted in reduced growth rates in larval herring (malzahn et al. 2007), gelatinous zooplankton (schoo et al. 2010) and larval european lobster (schoo et al. 2012; schoo et al. 2013a). this finding leads to the conclusion that mineral requirements have to be fulfilled first before biochemical requirements like fatty acids can promote growth. consequently, not one single measure should be the focus when optimizing live feeds for aquaculture, but a more holistic approach will lead to better results. references awaiss, a., p. kestemont, and j. c. micha. 1992. nutritional suitability of the rotifer, brachionus calyciflorus pallas for rearing freshwater fish larvae. journal of applied ichthyology 8: 263-270. beaugrand, g., k. m. brander, j. a. lindley, s. souissi, and p. c. reid. 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83: 1899-1914. villar-argaiz, m. and r. w. sterner. 2002. life history bottlenecks in diaptomus clavipes induced by phosphorus-limited algae. limnology and oceanography 47: 1229-1233. von herbing, h. and s. gallagher. 2000. foraging behavior in early atlantic cod larvae (gadhus morhua) feeding on a protozoan (balanion sp.) and a copepod nauplius (pseudodiaptomus sp.). marine biology 136: 591-602. microsoft word jamsy2003v08n01content-arabic.doc agricultural and marine sciences, 8(1):35-40 (2003) © 2003 sultan qaboos university !!!!!!!!!!!!!!!!!!!!!!! !"!#$%&'()&!*&+,-!!!35! !"#$%&!'(#)$#!*+,-.!-+/0.(bap , iaa)!-(/,1&!234! !(+$+5-(63%!!7+85%&!9-:;%& gardenia jasminoides ! !<$=veitchii >6?$ &!>4&-*!'(+$!.!"&5;.?(#!! ! $&5#4!5+%-!&(?'("!!)+*;%&!<+*3%&!5#4+34!,&-?!5"#-#"!! !&+.(?#%&!"?8.!>+/' &"!>+4&-*%&!""30%&!>+3,!.#%&!>0#(6!1=+2!33! effect of different concentrations of growth regulators on gardenia jasminoides cv. veitchii micropropagation by tissue culture technique g. r. abdullah, a.a. al-khateeb and m. serage ! abstract: micropropagation techniques were set up for gardenia jasminoides c.v. veitchi. many plantlets were obtained by culturing shoot cuttings in ms nutrient media, 30 g/l sucrose, 7 g/l agar agar, and different concentrations of bap and iaa. the best concentration was 1mg /l bap with 0.5 mg/l iaa. this concentration gave the best sprout growth suitable for rooting in primary and secondary culture by reculturing the stuck cutting every 6 weeks and for many times. we also obtained a high rooting percentage up to 98 % of natural rooting in rooting media different from propagation media by reducing mineral salt concentration to half, sucrose to 20gm/l, and 2gm/l active charcoal, and 1mg/l iaa. plantlets were transferred to greenhous and subjected for hardening. this technique gave 22 plantlets from one cutting in one year. !#./01!2!!!!!!!345)&!&67!8.9!:.;!!<=+!>,/!? , !'?"$)!# $!)&!%'=1)&!'&?';$)!# ,(;veitchii!*(!)?;?5,)&!*(!' 5'!!!-!*$-!++/4)&!*'(,!3 4! 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'4$)!'8/,!n?5/'!#(!1;%()&a! !!!j+,.)&!'5.;+g. jasminoides!1 8,/5!ellis +!veitchii!*(! # 5-:!j&+,=&!'&',!!e!1-?8;'&!+/ !%' ":!j6"!+6!+7+*)6!%'! -,'!!!!!!'./(5+!:.%!'!5!)!!!!!!!!!!!*)6!>' ":)&!j?8;'&!+/ !* 4!89!!:%!! %&'!!!:!e!!!!!!>'=1)&!#.(<&!!8.7+!!)&6!!!# -(:!#4<&'!e'70;!>';8)&!89 !!!!!!!!*;4+!+ ?.(!>./;,(!*.(+ ,+ !!!!!!*;4!?7'?706!'(;% !*,!*'( +! !'5(;5.%!e!!!!!!!!# +$! # '/-! #4<&'+! o 5,! *+$5! #8-?=(! 2&'?70,! # /-( !!!!!!!!!'?70p)!>':?5(!' q!# +$!>r?=6!*)6!k?;.4;!?9,.')!e*)6+!!)?"'!! !!!>'&'.4%)!–!*%!!!!!!!!!!!+':;!!-5!> /)&+!< 5')&!89!!# +<.(!#."'!! !:-&'5.)&!e!!!!!*)6!?9-9'!*.'( +*%!!!!!!# +"!#5+/'!!+"+5!# +<(!#"'!! !!!!!!!!!!*(!+$,!*)6!>'&'4)&!o815!s/, !g+!# .)?-%#!!!!89!# +<(!#"'!! r?;:)&a! !s$&+$)&!#8)?1;(!?9,=!? '=1!? , !'?")&!'?&'6!:; (hetrozygous)! !!!7'?&.'6! 8./+!!!, ?5;! '+65)&! #/%&+5! ??! &&'+!?! '9h(+!?!!!!&'9,! * 5! !!!;;?,.)&!+.%,)&!e!+!!+7!!# -&'0)&!84&+,)&!*(!m+q'(!' q!a!:; !@)6) !!!!!*. ;( '/5! ? ! .$(;! ?7'?&.'6!2!!!!!++/,! *$-! #-$')?5! : -/;)?5! *)+=& !!+&(!&!+;?( ,$)!#.(+?(( g. thunbergia #$(-)?5!# ,?&)&+!a!!f67+!! !!! #( './)&!!! !?/;$&! ' q! >' .1=&!!!!!!!;;, !g+!+(,)&!r8/5!)?5,)&! *=! # !4&+)&!)?5,)&!89!)&+(,)&!*(!!+!4(!!!-!c+%a! abdullah, al-khateeb, and serage !36 !!!m."!!!!!!!!# 5:1)&!j&+,t)!#$(-)?5!%'=1)&!'?&'7&!*u5!' .'6;)& !!!.=';!# '".:)&+1!!!!!!!!*(!' 6";$)!# $5?()&!89!)?5+-/)&!*(!! !-)&! !!!!#(!1;%()&!+(-)&!#)+9'!+0.1!!e!!!!<$+(5!#/5;'()&!)?90;10)!#9?=6 !!!+.(-)&!!!!!!!!!!61,!)$+!@)6'+!?9)!# "+)+ 0 8)&!#)?4)&+!:=&!)?5,)&!*.$!+.(-)&!!e!!!!.$+* 5dumanois!!!!:?-!1( '9+!%(),!!!!+(-)&!' 6";!*u5! !!!!!!!!!!*$-!%+;4 !++$4(!89!?7!-&+$!<(,5!#=.)&!# .(()&*!!v$(!3!!*(!';) iaa !!)?5,)&!>!-?$!*(!)61,!8;)&!+(-)&!i'-!*$-!?4"?,!*' !:.)! !!!!!6!?7' 6";!#5%,!)$/+!3 4!:=&!!!!*)-'!ab!!!!!c'1,!#9"!*(+!!'w !!!!!!!!!!!!' 6";)!+&(=&!)$+)&!+7!r?;:)&!+/9!*,!*$-!* &4?5)&!*.(!!. !-)& !!#5:1;(!>/,)&!)&+(,)& watkins, 1971) !!+! (siddique, 1973!!!* %'+=&!*(!#8$;.1(!0 .'&';!:&!1;.%?5!(bose, 1977) (iba+(,)&!)?/5&(!+,!ancymidol !>!()!< '%!i /.;5!-#!!# ,?&! )' 6";)&!*$-!o '4;$(wan, 1983)a! !!!!!!!!!!!'?&'6!89!?(?7+!&' 5'!&'+!!#"%,=&!#-&'0!)? .,(;!m.-$;+ !!!!!!!!!!!89! 8&&'+)&! * ?5;)&! *-! &! -5! #(?9)&! # !?/;$g&! )?;?5,)&! *(! !. !-)& !!!!!!!!!!#'/)?5!'?&'7&!#5-/)&!)&' ":)&+!'?":=&!@)6'+!;;?,.)&!+.%,)& !!!!!!!!? , !'?")&!?9, 5!*(+!# ! .$(;)&!# '.=1)&a!!?'!!()+!*!dumanois!! !!!!!!!!!!!!:?-!89!? , !'?")&!'?&'7!#"%,=&!#-&'0!)? ,(;!:!1;.%&!*.(!++, %(),!!:!!!!!!!!#& !4)&!)&+(,)&!' 6";!89!s",!3. 4!!!+1&!!?9"?;,&!:;!8;)& !!!!!#5.%,5+!m. 5?,=&$'!b!!!>,./$)ellis!!!!!!)$+!' &u;!*(!2?./$1;(! !!!!!!o81,()&!!+!'()&!*(!?= ,+!'?&'7&!d?.",!*.$-!' 6";.)&!!#'/) ! $(;)&!'?&'7&#x!+!1$5$!*(!(lyrene,1981)!*$-!!vaccinuim ashei !+!(boulay, 1979)!*.$-!!! sequoia sempervirens! +7# 5:1)&!j&+,=&!'?&'7!#5%,)?5!&!"!#(9(!#/(,)&!f6!a! !!!!!!!!!!)?5,)&!&67!'?&'6!*$-!#"%,=&!#-&'0!:&!1;%&!'/;( !:)!*')+ !!!!5)&!: 0,,!' .;!#%&'!!+&(!@)6!*(!!-5,!*)6!m76!+5!/.(9!0&! %'+' !!!!!!!8;?5,)&!+':;)&!+4&'(!r?,&,(shen,1990)!+!!!!>!?()&!*$-!++/4)&! !!!!!!k?;,g!#.(00)&!# .;?5,)&!!>!?(!!#(!1;%()&+!!? , !'?")&!*(!* %+'')& !!!#.5./=&!8.9george et al., 1993)!y!e!z01;%&!*)6!#9?=6 !!!!!!!!!z$1;%(! #9?=6! !-5! c'1,! # 5/! )?5''(+! ++; ,?()&+! ++'.% $.)& !!!&!'?(&!0+;.''9!!!!!!!!?, !'?")&!!? 01!1 9!#-+'0()&!/%+)&!*)6!? , !'?") !!!!!?7'&?';!!*)6!)!,!8.;)&+a!!!!!!!!?(5?%!? , !'?")&!'?(&!)(!1;%&!!$+!&67! !!!!!!!!!?=('!8, /!m. 5/!+5.$!*.()0)5?9;+!)?!85/-!r%!9(+!'!( !*(4$)!*'%(+!++5$)(hayashi et al., 1992) !a! !!!!!!'?&'7&!>r?8'!* %4;!+",!*(+)!!,)&!)?;?5,)&!# -+,!!!3 4!*(!#";? !!!!!!!!# %(;)&!!,-!! ")&!+(,)&!*$-!?.9;'!$!!x!!!!!)?%&'!!@?,7!),?'!!(9!>! !!!!*.$-!!!!!!!!0?q+!''%)&!0 '';+!m 5?,=&!#0q6!:?.'46!' .&u;!!! %',!8,?& *+5'')&!!!!!!!!!!# ;&6)&!# 6.;)&!*$-!>'!?$!)?;?5,!r?/-6!*$-!# <+=)&!>!:)&+! +1&!!# %(;)&!#$4'(!+01!@)6'+!m 5?,=&! (serret et al., 1996, 1997)!!+!!!!.$!!!!)., 5!!!!)?.%&'!)&!!!!!!' q!m 5?,,!*(!#";?,)&!)?;?5,)&!*u5 !!!!!),?'!#0q7&!#.('4(!!!!!,-![?4?",!'&', %(;?9;!!!!!*(!>6+1u()&!@$;!*(! !!!!!?('!#0q7&!#'(4(!m 5?,,!!*,!!!)?; 5,)&!f69)!# <+=)&!#5?";%g&!!>$;1;! !!!!!!!:!1;.%()&!0+''.%)&!0 .'';!m.%4!x!!!!!!'!?/(!:&!1;%&!*)6!#9?=6! ! ., "+';,!!!!!!!!!>!? 0!*)6!c!,!%6)&+!%6.()&!/%+)&!89!m+?,;)?5!#8$;.1(!# !!!!!!!!!!!!? , !'?")&!*(!+'!89!#$'+()&!)&+(,)&!*(!# '51()&!#.$(-)&!# ."?;,6 !0+()&+ (george and ravishankar, 1996) a!! ! 6-#%&!7-*"!5&"#! ! !>+.(#$%&!75(#%&5!!!!!1(!89!345)&!&67!68,;!!!!!:%()!<5?;)&!#"%,=&!#-&'0!'5 !!!!89!* ;?.%5)&!!!89!+/ 9!@$()&!#-(?"5!# 6q=&+!# -&'0)&!:+$-)&!# $' !!!!!* 5!?(!#-$&+)&!>';8)&*###!–*##%:!!!!!!':-!# ?.)&!f69)!:!1;%&!3 4! !!*(!)?;?5.,g. jasminoides!!>,/!veitchii(!#-+'0!) 5!89!! !8(4(!)?9(u'89!+('!*(!#8)w(!# -&'0!#/$1!*$-!%+;4;!z/,! !! %'9,+!!!!! #5%,5! # -&'0! #5';+! i+(; 5%!2%:%!!!!!#$/&+(! <(! ?9,(! +') !!!!!!!!c'1,+!>';9!* 5!>81(!8<&6q!++$4(5!?9 'e!!!!*$-!++/4)&!>!95! !!!!!!!!!# ;?5,)&!r&0"=?5!# " %,)&!#-&'0)&!!&!(7!'(;%(!+':5!#& !4!)&+(, #(00)&!a!!!!!!!!!!r?()?5!?9$%q!:;+!:=&!)?;?5,)&!*(!#& !4)&!)&+(,)&!)$/9! !!!!! 7&!++4')?5! ?94%(! :&! %!?.-)&&!!8$ \!!0 '';$#!b!!y+!!*)6!?9/(; !!! ++/5! r&0",*5"!!!!!!!!/(9!>!4&+!>!(-!*$-!?9,(! +'! %+;4 ! :%!!!*+';) !!!89!:!1;%()&!r0.")&i %u;)&!#$4'(!!a!: (-;!:;!?7'(.5!r&0"=&!f67 !!!!!!!0 '';5!%'?";)&!i'+'+$')&!*(!++$4(!89"#!b>?=()&+!!!>!-!1) !!!!!* +;)&!*(!/?.(,\tween20!y&!!!#5%,5!>81()%!b!!>!()"'!!!:&!#( $!! !&0"=&!)$%q!!!!!!!!!30&!>!()!:(-()&+!'/(()&!r?()?5!)&'(!30&!# ;?5,)&!r >'(!+'!89!#<?$!!a! !!!!!!!!!!!'/(()&!r?()?5!?9$%q+!>'?;1()&!# ;?5,)&!r&0."=&!: .(-;!!.-5 !:.(-()&+!e(;)!!!!!!'?5;1&!m 5?,,!89!?9;-&'0!<=+5!!!!#$(-!+!-(5!8%,'! !8(+&'")&!+0-)&!0?9"!)4;!m+5,,!+'!89!>!4&+(laminar air flow hood)0'!!# )+,!#-&'!!e!?9;-&'0!!-5!m 5?,=&!f67!)-=+!:& !!!!!!!!!?7'&!((!# <+=!>!:!)4;+!#8 '(!#9'q!8.9'###!!!!>!()!i'+)!%-! !!!!! ? .(+ ! #-?.%!!! 8.9!>'&'4! #"'!!!*,±!*!!!! &'?9,! # +<(!! +**±!*!!! 0 )!# +<(!#"'!!a! !!!!!#$4'.(!8.9!?.(,!!!'?&'g&!\!# ,?&)&!#-&'0)&y!!)&+(,)&!61,!:;!!(9! !!!&'0)&!*-!#";?,)&!# '51()&!!!!!!!#( $!!# '51(!+(-!*)6!?9;<0";+!# )+=&!#!!!?9;.-&'0+!8.9!!!!!!!!!?9 $-!)4",!8;)&!# <&6.)&!+ )?4()&!*(!>! !"!/?%+,! !!!!!# .)+=&!#-&'0.)&a!!!!!!!!!!!61,!!-5!# )+=&!+(-)&!#-&'0!>!?-6!:;!* 4!8.9! !!!!!!!!!!!!!!!-&+$!!@';!!-5!! !"!*(!?7'?&'6!+,!?7' 6";)!!?9,(!#& !4)&!)&+(,.)& )&+(,)&!#& !4)&!!?9 $-!!!;)&!+!!!!:-&'5)&!*$-!%+;4;!8!!!!)?-&'0!>!-)!@)6+! !!!+'!>!4&+!>'(!+!.-(5-!'?&'p)!)?(+',!*$-!++/4)&!>!95!< 5?%,! \!# " %,!)?9(,!y+1&!!!!m 5?,=&!!!!!!!!+!: (-;)&!# $(-!'&'';!*)&!#"?4)&!*+! !*?(.=)!!!!'5',!r?/-6!!!-!!!!!!!*)6!++/+)&+!#$'+()&!#& !4)&!)&+(,)&!*(! !?/;$g&!c+!")&!+6!%'?";)&!k?;,7&# )?-)&!# a! effect of different concentrations of growth regulators ! !37 !!!";)&!#$4'(!89!?(,6!!(!1;%&!!(9!' )!!!!!!*-!#";?,)&!#& !4)&!)&+(,)&!! !!!!!+,!# )+=&!)?-&'0.)&!!'?&'g&!#$4'(!*-!!!!!!++/5!'?&'7&!)?(+',!*-!+,! !8.)&+4"!!!!'./=&!)&+(,.)&!*=!:.%!*-@)6!*+';!+!' 6";)&!#8 -=!! m-/;!?9; %(;!!*+';!+!?4?",!+$,a! !!>+/8#%&!*(9?" &5!!!!!#9?'!6 8,;!:;!!+!# )+=&!)?-&'0)&!!?9 $;!8;)&!!!!/%+!89! !!!!!!!!!!c'5')&!# ,!-()&!'/?,-)&!*.$-!%+;.4 !%6..(!!+!()!c'./)&;:&'+! !!k+'.%+(murashige and skoog, 1962)!!!!++$4(!1 .)6!?9?.=( !,. (?; 8)&)?!! (navarro et al., 1975) !*(!#8$;1(!0 '&';+!bap!\ #&#!+!!#&*'!!+!!#&'e!!%!+!%&'!+!*!!:&'"$(3';)!y!! +,iaa!!\#&#!!+! #&*'!+!!#&'!+!#&$'!+!!%!:&'."$(!3!';)y !0 '';!+=9,!<(!#''?:()?5 !!*.( bap!!+"#:&'"!3!+!0+'?'%!';)$&'!:&'"!3)/5=+!'?"4!';)! !!!#.=+(4!!!!!*$-!!/.%+)&'&'!e!!!.'?"]&!#9?=6!!-5!!!!!j0+!3 4!!'?"4 !!!!!!!i? $!'?5;1&!m 5?,,!89!%6-()&!/%+)&%'#!x!*'!!!!!!+!-(5!:(!%'!!!:(!/! !!!!8;)&+!m+5.,,!!!!!!!#/%&+5!)((-+!#9?8:!# ' ;%05!)&!&!%!#/%&+5!)($q, !!!!!!!8.<?()&!: .(-;)&!0?.9"(autoclave)!!!>'&'4!#"'!!*$-!%*%!#"'!! !>!()+!# +<(%'#( $!!a! !!!!!!!? '51(!)68,!!(9!' 6";)&!#$4'(!?(,+1&!!!!!!#< 5!*$-!%+;4;!m 5?,,! !!!!!!!!!!'/?,-)&+!>/,)&!*)6!#881()&!c'5')&!# ,!-()&!'/?,-)&!*(!#8)w(!# 6.( )&!c'./++$4(!*(!(ms)!* %'+=&!*(!#8$;1(!0 '&';!+!iaa !! \ #&#!!+!#&*'!!+!#&'!+!!#&$'!+!%!e!%&'!:&'."$(!3!';.)!y !!1)!?9!?=( !!)?, (?; 8)&!++.$4(!+5$!*(!:!1;%()&navarro et al., (1975)!+!*#! :&'"3!!!!+!0+'?'%!';)$&'!!:&'"3!'?"4!';)5!/5=+!'?",!!#=+(4)&!+!-(! !/.%+$)!!!*$-!'&'!e!-5!!!'?"4!.'?"]&!#9?=6!!!a!!!!/:,)&!:48)&!> =,!?(' !0 '';5*:&'"3)g?4)&!o-5!89!';)!a! !>+9?!.%&5!!!!!!!!!!*? 4=&!:h-(!89!? '51(!#";?,)&!)?;?5,$)!#($$=&!# $(-!+':; !!!!!!!!!#"%,=&!#-&'0!)? ,(;!:&!1;%?5!# $!)&!'?&'p)!?"'4!'&'=&!#$4'.()&!e !!!!!!!!!)6!? '51(!>'6"()&!)?; 5,)&!+(,!:;!@)6!+",!*.(+!!!!!*(!#5+/'!+$,!#< 5!* !!!@.$;!!!!!!!'5;1()&!+1&!!#8$;1()&!+4&'()&!r?,.&&!>!<?.%)&!e!!!89!)-'0!3 4 !!!!!!!*$-!# +?4)&+!+$4;$)!+5?()&+!/+.=()&!i+(; 5)&!*(!>' ../!z./, !!!!!!!!!#5%,5!) g+' (' 9+!i+(; 5!*(!#8)w(!# -&'0!#./$1%."!!!!?9( (-;!:;!! !!!!!!!!!!%,5!%'/9!!?=(!*$-!%+;4 !>81(!%6.(!++$4(5!?9 '!:&!?(5%(!!#5% !b!e!!!!!!!!6!8)+5)&!*(!#( .$'!#(5./5!?9;. /.;+&!!!!+':5!>?8:)&!o 5=&!* $ i+$?,!!!!!!!!!!!) 5)&!89!@)6+!# +")&!#5+/')&!*(!+?-!'!$!* (u;)!!!8(4()&!!-5+ !!!!!!!!!!!!!*(!>! !")&!)?;?5,)?5!# ?,-)&!#-5?;(+!r?/.)&!s;9!:; !#-&'0)&!*.(!'9.: ?("4!'5',!# ' ;%05!z/,!*)6!+(,;!:&!#49?'(+!! 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(?,)&!#(()&!c+;%(!*$-!&!"!+ $$!* , '+; %)&!0 '';!*?.9!# !!!'?&'7&!+",!*(! # $?%)&+1&!!!!!!* 5!1$5$+!m 5?,=&!okazawa,1978)!! (koda and!!m. '';!*,!!# (?,)&!#(()&!c+;%(!89!:; !* , '+; .%)&! # '6")&!e!!!!!0 '';!m$/;;!# $?%)&!#$(-)&!*?9!@)6)&!, -(!?!!!* , '+; %)&!*(! ?7'+/;)!%6.()&!/%+)&!*)6!>?=()&a! abdullah, al-khateeb, and serage !38 !!!!!!!++!")&!*(!?,)!* 5; !?.('\%!y!")&!*u5!!!5!?7'?&'6!*'( !? , !'?+!!* !!!!!!!!!!!!:&!1;%&!*,!* 4!89!#=81,(!d?",!#5%,5!*')+!* , '+; .%)&!:&!1;.%& bap!!!!!!!!!!!!!!+"+!<(!*')+!# 5,?")&!:-&'5$)!# )?-!s;8;!#5%,!*.(w !f!'.8(5! !!!!!!!!!!!!!!*(!!5g!*?'!@)6)!?9)+/+!#";?,)&!)&+(,)&!# -+,!8.9!8.,!;)&!o.-5 !! '+; %)&!'+!!>'0&w()!#''?:()?5!* %'+=&!:&!1;%&!@)6'+!'?&'7&!89!* , !!!!#";?,)&!)&+(,)&!# -+,!* .%4;!a!!!!!!!0 '&';!#%(1!@)6!+",!*(!:!1;%&!!$+ !*(iaa !87!#&#!+!#&*'!+!#&'!e!#&$'!+!%!:&'"$(!3!!+"+5+!'; ) %$(!:&'"3!*(!';)bap/%+)&!89!a! !!!!!!!++!")&!89!#,+!()&!: ()&!?,)!* 5;+\*!y1,u5!!!!!# +,-(!#+'9!!"+;!g! 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'$(/ 0(! $12 3'$() *#( 45 167 +8,9 :;<=6,'(+>'"? ! !+':)&!\%!2y#$(-)&!# !+!'(!*$-!)?-&'0)&!!!-!' &u;!#$'+()&!#& !4)&!)&+(,)&!*(! effect of different concentrations of growth regulators ! !39 ! !!!!!+'.:)&!s.=+ \*!y!!!!* %'+=&!0 '';!' &u;iaa!$-!!!*!# +<()&!#5%,)&! ' 6";$)!e+!!!';!#9?'5!* %'+=&!*u5&0 'f!!!!!!!!"+ !g!?('!!7?:)&!*$-!#+8;(! !!!!!* 0 '';)&!* 5!%+,-(!#'9#&'!!!+!#&$'!$(!:&'"3';)!a,')+!!?(9!* $+8;( !!!0 '';)&!*$-#&*'!$(!:&'"3';)!e89!4!!!* !!*,!!!# )?-)&!0 '&';)&\%!!!+!%&' (!!!:&'."$3';)!y!!!!!"+!*+!!c'1=&!0 '&';)&!*$-!#$+8;(!!!%+,-(!#'9!!+ !! ?(9, 5!e!!!!0 '';)&!*+' ! @)65+%!$(!:&'"3!!!!!+=9=&!+7!* %'+=&!*(!';) !!!!!!).$5!' 6";)&!#5%,!3. 4()&""ab!!!!!!!*$-!* %'+=&!0 '';!' &u;!?(, !!!!!!!!!!!)% )!f67+!0 '';)&!<(!2&!'/!m%?,;!!(9!'+6")&!!!.-!! !:!# /?1!> !!!!!!!!!!,$)!+(,)&!)? $(-!# !3 4!# %(;)&!# $(-!r?,&,!#/?1!# .5?" 7&!)?;?5 !>'6."()&!a!!!!!!!!# )?-)&!0 '&';)&!*$-!'+6")&!:1=;!?,h4g!?('\%!!!+!%&'! $(!:&'."3';)!y+!!!!!!!0 '';5!/:,)&!:48)&!:&!1;%&!:;!@)6)*$(:&'"3!!';)!?(( !?9 $-!# +,?&)&!'+6")&!!+"+!<(!?9(1=;!*(+!'+6")&!!!-!*(!+$$a! !>+9?!.%&5!!'5.;-;!76!!!!!!!!!+4&'(!*(!# (7,+!?"'4!'&'=&!87!#$4'()&!f !.'7&!!!!!!?7'+6"!+%q!!-5!>'6"()&!)?;?5,)&!+(,5!)(;!8;)&+!%'51()&!'?& !!!!!!!!!!!s=+(!+7!?('!#5+/')&!# )?-!>+'h!89!?9;-&'0+!0+$ ")&!*(!&! " !!!!!!!!!!!d?",)&!#5%,!),?'!3 4!''6;!)?5(-!# ,!*+!!@)6+!?(5?%%##!b!!-5 !!!+(,)&!*(!'9.:!a!!!!!!!!!!*$-!'+6")&!!!-)!' &u;!%,!!"+ !g!1,u5!?,h4g!!$+ !!'+! # %(;)&! d?",!!!?(4g!)?;?5,)&!'+/;!@)6!e!!!!!>'!()&!?9)!)?;?5,)&!*,!3 4 !!!? '51(!#$':;()&!' q!c'1,!'+6"!r?/-6!*.$-!a)?;?5,)&!f67!)$(,!:&! !!!!!!!!:"45!'5.',!z./,!*.)6%&'!!!';)!!!!:&!*(!!!!) 5)&!89!?7'+/;!)-5?; !8(4()&)?5(-!# ,!*+!+!d?",5!''6;a! ! ,(.$.?1&! ! !!!!!!!7!%'=1)&!'&?';)&!# ,(;!d?",!#%&'!)&!).;5&,!!!? , !'?")&!'?&'!a!?( 9+ !!!!!!!!!)&!) 5)&!89!# 4)&!)?;?5,)&!*(!# '51()&!#$(-)&!# !+!'(5!#$-; 8(4(!e! !!!!!!!!!!!#-+5;(!# )+=&!#$(-)&!#-&'05!%'=1)&! '?&'7&! # ,(;! :&!1;.%&! *?.9 !!!!!!!!!!*'( !'?&'7&!)?(+',!+ ':;+!>! !-!)&'.()!?9;.-&'0!>!?.-?5!*(!! !!!!!!8)&+4!*.$-!++./4)&**!!!!!!!>!4&+)&!#$(-)&!*(!84!)?5,!!!!*(!#,%!!-5 '5;1()&!89!'?&'p)!c'1,!)?(+',!*)6!#9?=6!#-&'0)&a! ! 0 20 40 60 80 100 120 0 0.25 0.5 0 .75 1 1 .5 /012 /34/567289!!:1;<=>4!?1</ ! :; <= 6,'( +;1 2' $(+ !" 3'$ 0 1 2 3 4 5 6 7 %# <= '$() *# % /!"5062 #="524!$%& ! ! !+':)&\*!y!* %'+g&!0 '0;!' &u;\iaa!y!!!-!/%+;(+!' 6";$)!# w()&!#5%,)&!*$+(,)&!89!'+6")&! ! b6&-#%&! altman, a. and r. goren. 1979. growth and dormancy cycles in citrus bud culture and their hormonal control. physiology plant 30:240–245. bose,t.k. 1977. standardization of propagation frum cutings under mist. effect of wood and size of cuttings on root formation. horticultural abstract 47, 6, 5806. boulay, m. 1979. propagation in vitro du duglas par micropropagation de germination aseptique et culture de bourgeons dormance. documents afocel n 12:67-75. dumanois, ch., b. godin, j. leboeuf, and c. bigo. 1984. 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m.i. trillas, j. matas, and j.l. araus. 1997. the effect of different closure types, light, and sucrose concentrations on carbon isotope composition and growth of gardenia jasminoides plantlets during micropropagation and subsequent acclimation ex vitro. plant-cell, tissue and organ culture 47(3):217-230. serret, m.d. m.i. trillas, j. matas, and j.l. araus. 1996. development of photoautotrophy and photoinhibition of gardenia jasminoides plantlets during micropropagation. plant-cell, tissue and organ culture 45(1):1-16. shen, h.j. 1990. studies of the peroxidase isoenzyme pattern during morphogenesis in gardenia jasminoides and dendranthema morifolium cv. xia ju. acta horticulturae sinica 17(1):65-70. abdullah, al-khateeb, and serage !40 siddique, a.m. 1973. effect of season in rooting performance of stem cutings of some shrubby flower plants of bangladesh. indian journal of horticulture 30:440-443. wan, c.k. 1983. rooting cutings of gardenia jasminoides, duranta repens, bougainvillea glabra, in ornamental horticulture, 9, 8, (abstract). watkins, j.v. 1971. growing gardenias. u.s.d.a. home and garden bulletin no. 152, 8p. received november 2001. accepted june 2002, agricultural and marine sciences, 16:35-40 (2011) ©2011 sultan qaboos university 35 ____________________________________________________________ *corresponding author. e-mail: mahmoudaly24@yahoo.com. the author also works in department of pathology, faculty of veterinary medicine, cairo university, egypt (national country). treatment of monogenic parasites in imported hybrid mono sex red tilapia fries (oreochromis spp) in the sultanate of oman aly m. mahmoud1* and adel n.z. gindy2 1department of fish quality control and extension, 2department of aquaculture, fishermen training institute, ministry of manpower, p.o.box 467, pc 113, sultanate of oman نوع البلطي من املستزرعة األسماك في العائل وحيدة بالطفيليات اإلصابة معاجلة عمان بسلطنة اجلنس وحيد األحمر عادل نصر جندى محمود على محمود*، سمكة / ٠,٢ جرام وزن مبتوسط اجلنس وحيد األحمر البلطي نوع من أسماك زريعة ١٢٠٠٠ استيراد ااخلالصة :في فبراير/شباِط، ٢٠٠٨, مت مفرخ في ِمْن استيراد األسماك مت سمكة. وقد جرام/ ٠,٥ وزن مبتوسط النيلي وحيد اجلنس البلطي نوع من زريعة ١٢٠٠٠ استيراد كما مت محافظة ِمْن كيلومترَ ٨٠ حوالي تبعد التي و بركاء مبنطقِة مزرعِة خرساني مستطيل الشكل داخل ووضعت فى حوض آسيا. شرق جنوب وحيد اجلنس األحمر البلطي نوع من الذريعة في نفوق األسماك مبعدل متزايد لوحظ باحلوض االسماك وضع من أياِم ثالثة بعد مسقط. كذلك ميل و العوم أثناء االسماك ِ في شاّذَة المعَة حركَة وجود عن لألسماك الظاهري املبدئي الفحص أوضح التربية. و لقد أحواض داخل البؤريِة. الفحُص النزفيِة باملناطِق والزعانِف اجللِد على أبيض رمادي خارجي لون وجود لوحَظ كما التربيِة. حوض بجدران لالحتكاك األسماك عند و . اجلسِم. من املناطِق هذه تُهاجُم العائل وحيدة الُطفيلية الديداِن من كبيرِة أعداِد وجود حدد واجللَد اخلياشيم من لعينة اجملهري مبنطقة اجللِد ِمْن املصابة املناطق في حاّد التهاب هيئة على جداً واضحا الطفيليات ضّد املصابة األنسجة فعل رّد النسيجي َكاَن الفحص خطة وضع مت الدراسة اخليشومِي. في هذه النسيِج ِمْن كّمي تضّخم حدوث مع للخياشيم الرقائقي في النسيج للسوائل جتمع و األدمة، وامللح امليبندازول مواد املعاجلِة نظاِم في أستخدم لقد و املزرعِة. في النافقة األسماك عدد تَقليل إلى أدت األمِد قصيرة سريعِة معاجلِة املعاجلِة، بعد املعاجلِة. أثناء املاِء نوعيِة لَتحسني متوازيِة إجراءات ومت عمل أسبوعيا. مراِت ثالث العالج وكّرر متعاقبِة أياِم ثالثة ملدة والفورمالني فحَص وعند املستخدم. العالجي النظام من بعد أسبوع واحد وتَوّقَف النفوق متاما أياِم ثالثة النافقة خالل أعداد األسماك لوحَظ نقص عدم الدراسة وأوضحت األسماك. وخياشيم على جسم متاما من الطفيلية الديدان اختفاء العملية العالجية لوحظ بعد األسماك عينات التربية. ظروف نفس حتت و املزرعة تربيتها داخل نفس من الرغم على طفيلية النيلي بأية إصابات من نوع البلطي األسماك إصابة abstract: in february, 2008, 12000 fries of monosex red tilapia hybrid (oreochromis spp) of 0.2 g and 12000 fries of monosex nile tilapia (oreochromis niloticus) of 0.5 g were imported from a hatchery in south east asia and stocked in concrete raceways at an agriculture farm in the barka region about 80 km from muscat. three days after stocking, mortality problems were observed. the preliminary inspection revealed abnormal flashing movements of the fish with body scratching against the walls. faint grayish white discoloration was observed externally on the skin and fins with focal hemorrhagic areas. examination of skin and gill biopsies demonstrated the presence of a large number of small sized monogenea parasitic worms attacking the tissue of these body regions. histopathological observations revealed tissue reactions against the parasites and demonstrated a severe dermatitis of the skin, lamellar oedema and hyperplasia of the branchial tissue. a concomitant treatment regime using mebendazole, salt and formalin was practiced for three successive days and repeated three times every week together with parallel management procedures to enhance water quality during treatment. after treatment, a reduction of mortality was noticed within three days and completely ceased after one week at which time biopsy examinations revealed the absence of any parasitic agents. there were no deaths reported among the nile tilapia, which were raised on the same farm. keywords: red tilapia, monogenic parasites, treatment, histopathology, oman. introduction as the world population has increased parallel to the increase in demand for fish, and with stable production from the sea, aquaculture has becomes one of the main sources for aquatic organisms. aquaculture continues to grow more rapidly than other animal-production sectors. recent data showed that it has grown by 8.8 % since 1970 compared to 1.2 % for capture fisheries and 2.8 % for the terrestrial-farmed meat-production system over the same period (fao, 2007). the total aquaculture production in 2006 was 51.7 million tons (without aquatic plants) with a value of 78.8 billion us$ (fao, 2008). the share of aquaculture of the total aquatic 36 mahmoud and gindy 37 treatment of monogenic parasites in imported hybrid mono sex red tilapia fries production increased from 3.9 % by weight in 1970 to 36 % in 2006. tilapia production increased from 830,000 tons in 1990 to 1.6 million tons in 2005. tilapia is among the top ten produced species in 2004 with productions of 1.7 million tons. the value of this production was 1.8 billion us$. china is the main tilapia producing country with a production of 1 million tons. egypt has a production of 200,000 tons. currently, asian countries represent about 63 % of the total tilapia production. the main tilapia species produced is nile tilapia (oreochromis niloticus). it is expected that the supply of tilapia will continue to increase in the future. currently, many new tilapia species (hybrids) have been introduced to the field of aquaculture. tilapia hybrids have been geared towards the improvement of some characteristics, such as: color, salinity resistance and weight gain (romana and eguia, 1999). thus, red tilapia is not a species of tilapia, instead it is a name used for several different manmade tilapia variants that sport attractive red coloration. these variants are the result of continuous selective breeding. many farmers prefer to cultivate red tilapia since it is very sought after in certain markets. a few examples of red tilapia variants commonly encountered in fish markets and grocery stores are florida red, jamaican red, taiwan red and nd56. unlike wild tilapia species – which tend to be black or grayish – these fish have showy red and pink colors. in this concern, lutz (2001) mentioned that, florida red tilapia is the result of blue tilapia (oreochromis aureus) mating with mozambique tilapia (oreochromis mossambicus). on the other hand, hybridization could increase fish susceptibility to some diseases such as monogenea infestation (robinson et al., 2008) . the freshwater culture of nile tilapia (oreochromis niloticus) is practiced in some private farms in oman, particular in the northern part of the country. this type of aquaculture is carried out on small farms where high levels of saline groundwater prevent or reduce normal agriculture activities. the first introduction of tilapia species to oman was originally done by the ministry of health to control mosquitoes in the natural water bodies (fao, 2008). as a result of the adaptability of this species to the environment, their numbers increased and the local people began to rear tilapia on their farms. there are very few agricultural farms, located in the north of oman that produces nile tilapia on a small commercial scale. irrigation water is used in the production process. the fishermen training institute (ministry of manpower) started an aquaculture training program in one of the tilapia farms in barka, where the fry of tilapia was imported from a hatchery in south east asia. one of the most significant problems that hinders fish farming is abnormal mortality increases especially with recently introduced fries. in this study, the aim was to investigate the cause of early mortality in the imported tilapia spp., and perform treatment regimes to minimize and control mortality rate with the object of coming up with recommendations for local authorities to take the necessary measures against importing diseases into the country. table 1. demonstrate mortality problem of red tilapia fingerlings before and after treatment given at day 4 in the farm during first 11 days of stocking. number of raceway and fish species total no. of fish/ raceway date mortality rate after stocking mortality day 1 2 3 4 5 6 7 8 10 11 (1) monosex nile tilapia 5000 number of dead fish 6 5 7 10 5 6 3 6 % 0 0.1 0 0.1 0.1 0.2 0.1 0.1 0.0 0.1 (2) monosex red tilapia 5000 number of dead fish 30 *198 600 260 162 **6 10 10 % 0 0.6 0 3.9 12 5.2 3.2 0.1 0.2 0.2 (3) monosex red tilapia 5000 number of dead fish 18 *37 185 177 12 **5 1 3 % 0 0.3 0 0.7 3.7 3.5 0.2 0.1 0.0 0.0 (4) nile tilapia 5000 number of dead fish 3 3 3 5 3 2 3 % 0 0.0 0 0.0 0.0 0.0 0.0 0 0.0 0.0 *increased mortality and treatment application. **decreased mortality after treatment. 36 mahmoud and gindy 37 treatment of monogenic parasites in imported hybrid mono sex red tilapia fries materials and methods fish source and stocking in february, 2008, 12000 fries of monosex red tilapia hybrid (oreochromis spp) of average weight 0.2 g and 12000 fries of monosex nile tilapia (oreochromis niloticus) of 0.5 g were imported from a hatchery in south east asia and stocked in concrete raceways (4×6×1 m) on a farm in the barka region, about 80 km from the muscat. the imported fish were acclimatized well prior to being released to raceways in frb tanks, which are facilitated with air and good water exchange. in raceways, fries were stocked at a density of 500 fry per cubic meter, the fish were fed 32 % crude protein commercial feed imported from saudi arabia at 7 % bw/d. mortality and clinical signs three days after stocking, deaths were observed (table 1). on primary inspection, abnormal flashing movements were observed and the fish scratched their bodies against the walls. faint grayish white discoloration was observed externally on the skin and fins with focal hemorrhagic areas. the clinical signs were suspected to be the manifestation of external parasitic infestations, so further confirmatory procedures were performed as follows: sampling: fifty fish samples in a moribund state were collected randomly from all the raceways of the farm and transported in aerated plastic bags to the fishermen training institute, el khaboura for further examination. examination: the euthanized fish samples (by cervical dislocation) were subjected to the following: skin and gill biopsies. careful external examination and biopsies were performed. skin and gill scrapings were performed by gently scraping a scalpel along the side of the body, fins and gills while the fish was restrained. the scrapings were spread onto glass slides, and evaluated carefully using an ordinary light microscope. the procedures were performed according to noga (1996). histopathological examination. tissue specimens from skin and gills were fixed in 10% neutral buffered formalin. the samples were transported in tightly closed sampling bottles for routine histopathological examinations. the fixed samples were washed in tap water overnight and exposed to ascending concentrations of ethanol (70,80,90 and 100%), cleared in xylene and embedded in paraffin. tissue slides of 5 µm thick sections were prepared and stained by hematoxylin and eosin (h&e). the histopathological preparation was performed according to bancroft et al. (1996). histopathological examination was performed in the pathology department, faculty of veterinary medicine, cairo university, egypt. samples were examined and photographed using an olympus bx 50 microscope. treatment procedures chemicals used for treatment: concomitant mass treatment of the fish in raceways was applied using the following medications: anthelmentic. mebendazole a bath of mebendazole was added at a dose of 100 mg mebendazole/liter for 10 minutes (szekely and molnar, 1987). salt. pure sodium chloride was used in the form of a bath (10 ppt), and the fish were treated for 30 minutes (scott, 1993). formalin. prolonged immersion in aquaria was performed by the addition of 15 ppm formalin/1 (hoffman and meyer, 1974). the treatment was applied for three successive days. prior to the application of the used chemicals, water levels in the all raceways were reduced to 30 cm to avoid losses of chemicals. application of the anthelmentic drug (mebendazole) was firstly added for 10 minutes followed by elevation of the water level to wash out the drug and then a salt bath was carried out for 30 minutes followed by prolonged formalin immersion. recording of mortality mortality rate before and after treatment were recorded daily (table 1). results skin and gill biopsy examination the skin and gill biopsies revealed the presence of many small-sized worms firmly attached to the skin and gill tissue in the red tilapia fish. the parasites were identified as monogeneans (fig. 1) because of their jerking or figure 1. wet mount preparation from gills of red tilapia fish showed multiple parasites (monogenea sp.) attached to branchial tissue (arrows) bar, 20 µm. 38 mahmoud and gindy 39 treatment of monogenic parasites in imported hybrid mono sex red tilapia fries caterpillar-like motion, in which the parasite repetitively stretched and recoiled and also due to presence of attaching hooks (noga, 1996). the gill and skin tissue were severely infested with these parasites. the number of the parasites on x 100 magnification revealed 4-12 parasites per microscopic field. all examined fish samples were infested with the parasites (table 2). the examined samples of nile tilapia showed absence of external parasites either on their skin or gills. histopathological examination on the skin, multiple parasitic agents were noticed on different body regions either in the anterior part attached to the eyes or in the posterior part in the tail region (figs. 2 a&b). the parasite caused spongiosis in the epidermal layer of the skin together with dermatitis manifested by mononuclear cell infiltration and dilated blood vessels. on the gills, multiple parasites were observed either free between secondary gill lamellae or attached to gill filaments. the infested branchial tissue showed lamellar oedema and diffuse hyperplasia together with mononuclear cell infiltration (fig. 2c). desquamated epithelium of the gills was prominent indicating the destructive effect of the parasite on the branchial tissue (fig. 2d). effect of treatment the treatment regime induced a dramatic positive effect on the parasites. mortalities were reduced 2 days after application of the treatment (day 6 of stocking) and completely ceased after 4 days (day 8 of stocking). at this time, examination of the skin and gill biopsies revealed absence of any parasitic agents. the percent of mortality before and after treatment is demonstrated in table 1. discussion and recommendations our study shed light on the effective concomitant treatment plans in case of parasitic infestation of red tilapia fish table 2. severity of parasite infestation of the examined red tilapia. total number of examined fish number of fish showing infestation number of parasites/ microscopic field x 100 percent 50 25 12 50 9 8 18 13 5 26 3 4 6 μ μ μ μ 38 mahmoud and gindy 39 treatment of monogenic parasites in imported hybrid mono sex red tilapia fries fries. the study also stresses problems associated with trans-boundary (introduced and transferred) fish diseases, with emphasis on parasitic diseases of tilapia fries. it has become increasingly clear that many of the human-assisted movements of fish into new areas have been responsible for the introduction, establishment and spread of pathogens and parasites into new geographic areas. hoffman (1970) and bauer and hoffman (1976) summarized the state of knowledge on the transfers of fish parasites along with host movements through human activities. hoffman (1970) documented movement and establishment on new continents of at least 48 species of parasites (5 protozoa, 31 monogenea, 3 nematoda, 5 digenea, 1 acanthocephala and 3 copepoda). because nile tilapia is considered one of the most cultured species, the possibilities of trans-boundary disease transmission are very high. in this concern, arthur (1996) noted that 50% (9 of 18) of the parasites known to infest nile tilapia in the philippines were probably introduced into the country along with the introduction of this fish for aquaculture and stocking in natural waters. the number of diseases has increased significantly with the increased ease of air travel and the recent explosive growth of the aquaculture industry. in general, fishery managers must be faulted for not giving pathogens adequate consideration when contemplating the introduction and transfer of aquatic animals. in many cases this has led to serious pathogens becoming established in new areas and hosts. once established in natural waters, such pathogens are usually impossible to eradicate. with proper planning, the introduction of many of these pathogens could have been avoided. monogenea are one of the most important parasites affecting fresh water fish causing flash movement and other characteristic signs on the fish. the detected signs in our study were in agreement with the findings of thoney (1990). the parasite can be treated using various types of anthelmentic drugs as mebenazole (szekely and molnar, 1987; thoney, 1989; thoney and hargis, 1991); also long-term exposure to suboptimal salinity may be highly effective against productivity of some monogenea as neobenedenia melleni (mueller et al., 1992) or polylabroides multispinosus (diggles et al., 1993). the use of formalin as a chemical treatment for monogenea has been recommended by langdon (1992), who stated that, freshwater or saltwater baths usually work only on small monogenean species unless followed 48 hours later by formalin or organophosphate treatment. the control requires weekly treatments for at least 3 weeks. from a pathological point of view, monogenea parasites cause severe pathological lesions either on skin and /or gills in many fish species (whittington, 1998). in our study, the observed lesions were severe on skin and gills. it appeared as dermatitis; spongiosis (intracellular oedema) and some of the parasite fragments were noticed and attached on the outer epithelial part of the skin. on gills, the lesions were prominent and characterized by destruction of the branchial epithelium and hyperplastic proliferation of the cells. our findings are in accordance with those of kearn (1998) who studied the lesions caused by monogenean parasites in several fish species. from our study, it was clear that, although red and nile tilapia were imported from the same place and reared under the same conditions, only red tilapia were affected by the parasites. in this concern, robinson et al. (2008) mentioned that, red tilapia is a hybrid of o. aureus × o. mossambicus and added that hybrid species are more sensitive to monogenean parasites than other tilapia species. the concomitant treatment regime applied in our study was a very effective means of eradicating the external parasites. recommendations to ensure absence of any parasitic agents and to avoid entrance of new pathogens to native fish, a preferable approach would be to impose a mandatory quarantine on imported fish. it is recommended that fish-health laboratories (pathology, bacteriology and parasitology laboratories) should be established and considered as a reference laboratory for oman to specify and survey different types of fish parasites and diseases. further studies should be implemented to specify the types of monogenea. acknowledgements we would like to thank all the people in the aquaculture section, fishermen training institute who assisted in this work. we also would like to thank mr. haji fakir, the director general of vocational training, ministry of manpower for his constant support; mr. al hbib sada, the former director of the institute and mr. dawood al yahaee, the director of the institute, for his support and encouragement. special thanks goes also to dr. fahad al ajmi, director of aquaculture centre, ministry of fisheries wealth for his sincere effort in reviewing the manuscript. references arthur, j.r. 1996. fish and shellfish quarantine: the reality for asia-pacific. in: health management in asian aquaculture. proceedings of the regional expert consultation on aquaculture health management in the asia and the-pacific, r.p. subasinghe, j.r. arthur and m. shariff (editors), 11-28. fao fisheries technical paper no. 360, rome, fao. 142p. bancroft, d., a. stevens, and r. turner. 1996. theory and practice of histological techniques (2nd edition). churchill livingstone, edinburgh, london, melbourne. bauer, o.n. and g.l. hoffman. 1976. helminth range extension by translocation of fish. p. 163-172. in: wildlife diseases, l.a. page (editor), 163-172. plenium publishing corp., new york, u.s.a. 40 mahmoud and gindy diggles, b.k., f.r. roubal, and r.j.g. lester. 1993. the influence of formalin, benzocaine, and hyposalinity on the fecundity and viability of polylabroides multispinosus (monogenea; microcotylidae) parasitic on the gills of acanthopagrus australis (pisces: sparidae). international journal of parasitology 23: 877-884. fao. 2007. the state of world fisheries and aquaculture 2006. food and agriculture organization of the united nations, rome, italy. fao. 2008. glimpse of global aquaculture production from the fao fishery and aquaculture database. fao aquaculture newsletter 40:42-43. fao. 2006-2008. national aquaculture sector overview oman. text by d.s. al-yahyai. in: fao fisheries and aquaculture department [online]. rome. updated 7 mar 2006. [cited 5 nov 2008]. hoffman, g.l. 1970. intercontinental and transcontinental dissemination and transfaunation of fish parasites with emphasis on whirling disease (myxosoma cerebralis). in: a symposium on diseases of fishes and shellfishes, s.f. snieszko (editor), 69-81. american fisheries society special publication no.5. hoffman, g.l. and f.p. meyer. 1974. parasites of freshwater fishes: a review of their control and treatment. tfh publications inc., neptune city, n.j., 224 p. kearn, g.c. 1998. monogeneans parasitizing the gill chambers of fishes. in: parasitism and the platyhelminths, g.c. kearn (editor), 113-140. chapman and hall, london, u.k. langdon, j.s. 1992. major protozoan and metazoan parasitic diseases of australian finfish. in: fin fish workshop. proceedings 182, post graduate committee in veterinary science, university of sydney, sydney, australia, pp. 1-26. lutz, c.g. 2001. practical genetics for aquaculture. fishing news books, blackwell sciences, oxford, united kingdom. muellwe, k.w., w.o. watanabe, and w.d. head. 1992. effect of salinity on hatching in neobenedenia melleni, a monogenean ectoparasite of seawater-cultured tilapia. journal of world aquaculture 23:199-204. noga, e.j. 1996. fish disease: diagnosis and treatment. mosby year book, inc., 201-205. robinson, r.d., n. o’connor, and r.d. steele. 2008. interaction between caged cultured hybrid tilapia and a marine monogenean, neobenedenia melleni, in jamaica. n.a.m. journal of aquaculture 70:68-73. romana-eguia, m.r.r. and r.v. eguia. 1999. growth of five asian red tilapia strains in saline environments. aquaculture 173:161-170. scott, p. 1993. therapy in aquaculture. in: aquaculture for veterinarians, l. brown (editor), 131-152. new york, pergamon press. szekely, c. and k. molnar. 1987. mebendazole is an efficacious drug against pseudogyrodactyolsis in the european eel (anguilla anguilla). journal of applied ichthyology 3:183-186. thoney, d.a. 1989. the effects of various chemicals on monogeneans parasitizing the skin of elasmobranchs. in: annual proceedings, american association of zoological parks and aquariums wheeling, w. va., the association, pp. 217-222. thoney, d.a. 1990. the effects of trichlorphon, praziquantel, and copper sulphate on various stages of the monogenean benedeniella posterocolpa, a skin parasite of the cownose ray, rhinoptera bonasus. journal of fish diseases 13:385-389. thoney, d.a. and w.j. hargis, jr. 1991. monogenea (platyhelminthes) as hazards for fish in confinement. annual review of fish diseases 1:133-153. whittington, i.d. 1998. diversity ‘down under’: monogeneans in the antipodes (australia) with a prediction of monogenean biodiversity worldwide. international journal for parasitology 28:1481-1493. received: may 16, 2009 accepted: november 4, 2009 agricultural and marine sciences, 12:35-42 (2007) ©2007 sultan qaboos university 35 evaluation of potato cultivars grown in saudi arabia by morphological characters and rapd markers abd-rahman mohamed m. al-moshileh*1, mohamed zaky el-shinawy2 and mohamed ibrahim motawei1 1department of plant production and protection, college of agriculture and veterinary medicine, al-qassim university, saudi arabia 2horticulture department, faculty of agriculture, ain shams university, shobra el-khima, cairo, egypt abstract: genetic diversity of 10 potato cultivars was investigated at the dna level with the random amplified polymorphic dna (rapd) procedure and at the phenotypic level using morphological characters. the results indicated that there were considerable variations among the different studied cultivars. cultivars victoria, frizia and safaren had the highest chlorophyll content compared to the other cultivars in both seasons. the largest leaf area and leaf dry weight were measured in cultivar safaren and mondial in both seasons. cultivars aboulx and mondia produced the highest tuber yield in both seasons. on the other hand, cultivars victoria and edward were characterized by their considerably lower yield than other studied cultivars. specific gravity varied considerably among the different potato cultivars. thirteen random decamer primers were used to amplify dna via the polymerase chain reaction and 75 rapds were generated. the rapd profiles obtained were successfully used to differentiate potato cultivars. based on the pair-wise comparison of amplification products, genetic similarity was estimated. the genetic similarity among all potato cultivars ranged from 50 to 92 %. cultivars victoria and *corresponding author. e-mail: amoshileh@hotmail.com العربیة السعودیة بالمملكة الوسطى المنطقة في النامیة البطاطس بعض أصناف تقویم (rapd) الدالئل الجزیئیة و المورفولوجیة الـصفات باستخدام مطاوع ومحمد إبراھیم الشناوي زكى محمد ، المشیلح بن محمد الرحمن عبد طریقة باستخدام وذلك (dna) على مستوى الحمض النووي البطاطس الوراثیة لعشرة أصناف من درست االختالفات الخالصة: اختالفات وجود النتائج أظھرت المورفولوجیة. الصفات باستخدام المظھري الشكل مستوى على كذلك و (rapd) الجزیئیة الدالئل الكلوروفیل من محتوى أعلى safaren و ,frizia و victoria أعطت األصناف لقد الدراسة. البطاطس تحت بین أصناف وراثیة كال للورقة في جاف وزن مساحة و أعلى mondial و safarenالصنفان أعطى و الموسمین. كال األصناف في بباقي مقارنة من أعلى كانت أنھا إال السابقین بالصنفین مقارنًة اقل kawalicو victoria للصنفین الورقیة المساحة كانت بینما الموسمین. بینما الموسمین. كال في للدرنات محصول أعلى mondial و aboulx الصنفین من كل أنتج و .aboulx edward و الصنفین المدروسة. البطاطس بین أصناف الكثافة النوعیة للدرنات. واختلفت اقل محصول edward و victoria الصنفان أنتج النووي الحامض لقطع العشوائي التكبیر طریقة واستخدمت 75 حزمة. وأعطت المتسلسل البلمرة تفاعل في جزیئیا بادئا 13 استخدم من زوجین كل بین المقارنة باستخدام الوراثي التشابھ حساب تم البطاطس. أصناف بین للتفریق بنجاح (rapd) ریبوز الدیوكسي etfadoal و victoria الصنفان 92%. وكان إلى من 50 البطاطس بین أصناف التشابھ الوراثي نسب تراوحت و الناتجة. الحزم أبعد etfadoal وكان الصنف وراثي. تشابھ درجة etfadoal أعلى و victoria الصنفان أعطى تشابھ وراثي بینما درجة أقل أساس على مجموعات ثالث إلي البطاطس أصناف وقسمت األخرى. بقیة األصناف عن الوراثي حیث درجة التشابھ من األصناف تحدید في وكذلك المختلفة البطاطس أصناف على التعرف في الطریقة ھذه استخدام یقترح لذلك .(upgma) الوراثي التحلیل البطاطس. لعشائر الخرائط الوراثیة الھامة في االقتصادیة الصفات al-moshileh, el-shinawy and motawei 36 37 evaluation of potato cultivars by morphological characters and rapd markers etfadoal presented the least similarity (0.50) while cultivars mondial and citrix had the greatest similarity (0.92). etfadoal cultivar displayed the greatest genetic diversity of all cultivars. a dendrogram was constructed using upgma analysis. on the basis of this analysis, the cultivars were grouped into three clusters. the polymorphism detected suggests that rapd markers are reliable for identification of potato cultivars and could be exploited in genetic mapping of populations to tag economically important traits. keywords: potato cultivars, fingerprint, genetic diversity, rapd markers, morphological characters. introduction potato (solanum tuberosum l.) is considered as one of the most important vegetable crops all over the world. qassim region generates about half of the potatoes produced in saudi arabia (zaag, 1991). the total production of potatoes in saudi arabia in 2002 was 315,000 tons (ministry of agriculture, 2004). potato production can be affected by several environmental factors, such as moisture, temperature, day length, light intensity, nutrient availability and genetic variation. the catalogue of potato varieties provides an indispensable source for obtaining optimum potato crops. any new variety should comply with the strict requirements of growers and users. therefore, information on the performance of varieties allows selection of the most suitable variety for any specific conditions and provides information on the latest developments in the field of potatoes (coumou, 2000). identifying plant cultivars by molecular markers procedures is becoming a practical necessity (smith and smith, 1992). the relatively narrow range of morphological traits and limited numbers of polymorphic isoenzyme systems are not sufficient to discriminate all the cultivars of any given species. furthermore, many phenotypic traits are developmentally regulated or influenced by the genotype x environment interaction. however, with the advent of dna-based genetic markers, such as restriction fragment length polymorphisms (rflp) and random amplified polymorphic dnas (rapd), the fingerprinting of plant cultivars has become more efficient, reliable, and useful (caetano-anolles et al., 1991 and nybom, 1994). rapd markers have been used successfully to identify many useful polymorphisms quickly and efficiently, and therefore the method has potential for use in cultivar identification (schneider and douches, 1996). also, rapds were shown to provide a level of resolution equivalent to rflps for determining genetic relationships among some cabbage (brassica oleracea l.) genotypes (dos santos et al., 1994) and among b. napus l. breeding lines (hallden et al., 1994). estimates of genetic similarity based on rapds have been developed for lycopersicon miller (williams and st. clair, 1993), allium cepa l. (wilkie et al., 1993), and solanum tuberosum l. (rocha et al., 2002 and collares et al., 2004). rapds have been used to investigate developmental variation in micropropagated potatoes (joyce et al., 1999) and also to correlate genetic variation observed in natural wild potato populations in the usa with a series of different ecological, geographical and reproductive variables (del rio et al., 2001). farmers and agricultural companies in saudi arabia use mainly imported potato seeds from europe. therefore, it is important to have evaluation and identification studies for potato cultivars widely grown in saudi arabia. the main objective of this study was to investigate genetic diversity among 10 potato cultivars introduced from the netherlands using morphological markers and rapd markers. materials and methods plant materials and experimental design this study was conducted at the experimental farm of the college of agriculture and veterinary medicine, al-qassim university during 2003 and 2004 fall seasons. the soil type of this farm is classified as a sandy soil. data in table 1 show specific soil characteristics. the irrigation water has a ph = 7.12 and 990 ppm total soluble salts. drip irrigation was used and the amount of 12 mm of irrigation water was applied every other day throughout the two growing seasons. each treatment was represented with three replicates and arranged in a randomized complete block design. the plot area was 3 x 6 m and contained 4 rows 75 cm apart. the planting distance was 30 cm within the row and presprouted tubers of citrix, kawalic, aboulx, spunta, mondial, victoria, safaren, edward, etfadoal and frizia cultivars were used. al-moshileh, el-shinawy and motawei 36 37 evaluation of potato cultivars by morphological characters and rapd markers these potato cultivars were introduced from hzpc holland b.v., the netherlands. the origin of potato cultivars is listed in table 2. planting dates of experiments 1 and 2 were 13th of october 2002 and 10th of october 2003, respectively. the plants in experiment 1 and 2 were harvested on 30th of january 2003 and on 1st of february 2004, respectively. a series of growth and yield parameters were measured and the data were statistically analyzed by the analysis of variance using the sas package. comparison of treatment means was performed by duncan’s multiple range test at the p = 0.05 level of significance. data were analyzed according to sendecor and cochran (1980). measurements vegetative growth parameters: three plants were randomly chosen 50 days after the planting date in 2002 and 2003 seasons, respectively, for recording the vegetative growth parameters, which included leaf area of the fifth upper leaf measured at fully expanded mature stage (cm2) using a leaf area meter, model li1300 portable area meter (stander technique no.5, usa), and also leaf dry weight (g). total chlorophyll: chlorophyll pigment was measured of the fifth upper leaf using a minolta chlorophyll meter spad –501. potato tuber yield: the number and weight of marketable tubers as well as total yield were recorded. only tubers sized 20-55 mm in diameter were considered marketable tubers. quality of potato tubers: specific gravity was measured directly after harvesting by choosing 15 marketable tubers randomly, and was calculated as follows: sg = weight of tuber in air (weight in air) (weight in water) rapd-pcr amplification total genomic dna of potato cultivars was extracted using the method described by saghai-maroof et al., (1984) for rapd analysis. twenty random primers were obtained from operon technology, usa. rapd analysis was conducted in a thermal cycler (thermolyne amplitron). the reaction mixture (25 µl) contained 1x pcr buffer with mg cl (50 mm k cl, 10 mm trishcl (ph 9.0), 2 mm mg cl and triton x-100), 200 µm each of datp, dctp, dgtp, and dttp, 30 ng template dna, 50 pm of oligonucleotide primer and 1.5 unit of taq polymerase. the mixtures were subjected to the following conditions: hold at 94˚c for 2 min, followed by 40 cycles of 94˚c for 1 min, 36˚c for 1 min and 72˚c for 2 min, and a final hold at 72˚c for 5 min. pcr products were visualized along with a dna marker on 2 % agarose gel with 1x tae buffer and detected by staining with ethidium bromide. gels were photographed on polaroid films under uv light. data handling and cluster analysis data were scored for computer analysis on the basis of the presence or absence of the amplified products for each random primer. basically, if a product was present in a genotype, it was designated "1", but if absent it was designated "0" after excluding irreproducible bands. pair-wise comparisons of cultivars, based on the presence or absence of unique and shared polymorphic products, were used to generate similarity coefficients based on a simple matching. the similarity coefficients were then used to construct a dendogram by upgma table 1. the soil mechanical features at the experimental site. mechanical analysis bulk density (g/cm3) water holding capacity (%) field capacity (%) wilting point (%)sand (%) silt (%) clay (%) 96.3 1.8 1.9 1.501 17.17 9.6 4.35 table 2. the origin of potato cultivars. cultivars parents citrix cardinal x svp 709 kawalic astarte x svp am 66-42 aboulx ostara x renska spunta bea x usda x 96-56 mondial spunta x svp ve 66295 victoria agria x ropta j861 safaren fanettex x [maris piper x inra 67.86.37] edward primura x alcmria etfadoal monalisa x hudson frizia zpc 69l 160 x am 66-42 al-moshileh, el-shinawy and motawei 38 39 evaluation of potato cultivars by morphological characters and rapd markers (unweighted pair-group method with arithmetical averages) using ntsys-pc (rohlf, 2000). results and discussion morphological characters total chlorophyll and vegetative growth: it is evident from table 3 that cultivars victoria, frizia, and safaren resulted in highest chlorophyll content compared to the other cultivars in both seasons. the lowest chlorophyll content was produced by cv. aboulx in both seasons. the leaf area and leaf dry weight varied considerably among the different potato cultivars (table 3). the highest leaf area was produced by safaren and mondial in both seasons. cultivars victoria and kawalic had a lower leaf area than cultivars safaren and mondial and higher than cultivars edward and aboulx. moreover, cultivars safaren and mondial had the highest leaf dry weight in both seasons. on the other hand, cultivar citrix had the lowest leaf dry weight in both seasons. these results could reflect the variation of vegetative growth and development among the different studied potato cultivars. similar trends of variation in potato plant development and its reflection on potato yield was observed by tibbits et al. (1992), al-moshileh and motawei (2001) and al-moshileh et al. (2003). tuber yield and specific gravity: data in table 4 clearly indicates that cultivars aboulx and mondial produced the highest tuber yield in both seasons. these two cultivars were followed by spunta, etafadoal, and frizia in both seasons. on the other hand, cultivars victoria and edward were characterized by considerably lower yield production than the other studied cultivars. table 4 indicates that specific gravity varied greatly among the different potato cultivars. aboulx, kawalic, and mondial cultivars gave the highest specific gravity in both seasons. these cultivars, except cultivar kawalic, were also characterized by the highest tuber yield. cultivars spunta and frizia gave the lowest specific gravity. in spite of the importance of the photosynthesis process, formation of carbohydrates and translocation to the tubers, tuber yield did not exactly reflect the vegetative growth. this phenomenon could indicate that yield in potatoes in this study may not only table 3. chlorophyll content (spad), leaf area and leaf dry weight of ten potato cultivars in two successive seasons. cultivars chlorophyll content leaf area (cm2) leaf dry weight (g) 2002/2003 2003/2004 2002/2003 2003/2004 2002/2003 2003/2004 citrix 38.53 38.26 44.97 44.26 0.26 0.29 kawalic 41.56 41.03 53.00 52.56 0.54 0.55 aboulx 34.10 33.93 41.46 42.83 0.60 0.58 spunta 37.63 36.43 54.51 51.90 0.35 0.30 mondial 38.30 37.86 70.94 67.73 0.75 0.61 victoria 45.16 40.76 53.20 54.96 0.41 0.38 safaren 42.36 41.40 71.48 74.20 0.62 0.61 edward 40.20 40.13 39.83 37.40 0.43 0.48 etfadoal 38.90 39.43 52.55 53.56 0.53 0.59 frizia 44.36 42.03 60.01 53.56 0.47 0.47 l.s.d at 5% 2.061 1.667 4.717 5.242 0.05 0.04 table 4. marketable yield and specific gravity of ten potato cultivars in two successive seasons. cultivars marketable yield (g/m2) specific gravity units (g/cm-3) 2002/ 2003 2003/ 2004 2002/ 2003 2003/ 2004 citrix 493.96 548.36 1.080 1.080 kawalic 595.03 660.23 1.120 1.130 aboulx 790.33 877.73 1.140 1.130 spunta 687.73 763.30 1.070 1.060 mondial 762.16 846.30 1.110 1.120 victoria 384.26 469.50 1.080 1.090 safaren 656.56 729.33 1.070 1.070 edward 431.83 476.63 1.091 1.090 etfadoal 670.30 740.73 1.111 1.110 frizia 657.33 738.73 1.041 1.040 l.s.d at 5% 15.52 15.48 0.350 0.048 al-moshileh, el-shinawy and motawei 38 39 evaluation of potato cultivars by morphological characters and rapd markers depend on leaf area and vegetative growth, but also on genotype and possibly other environmental factors (al-moshileh, 2001). rapd analysis in the rapd marker analysis, the selected primers opa05,opa07, opa08, opa09, opa11, opa12, opa14, opa15, opa16, opa17, opa18, opa19, and opa20, generated 75 amplified products, with fragment numbers varying from 3 (opa14) to 8 (opa08 and opa19) (table 5), 50 of which were polymorphic. examples of polymorphism are shown in figure 1. by means of the 13 rapd markers, all cultivars were identified and separated. collares et al. (2004) identified 27 potato genotypes using only four rapd primers. demeke et al. (1993), using the rapd technique with only two primers, identified 36 commercial potato cultivars. according to these authors, specific primers seem to produce more fragments and more dna amplified polymorphisms and are, therefore, adequate for identifying potato cultivars by the rapd technique. ghislain et al. (1999), using 12 primers, obtained 102 polymorphic table 5. the 12 selected operon primers and the number of amplified products and polymorphic fragments. primers sequence 5’ to 3’ amplified products polymorphic fragments op-a05 aggggtcttg 6 3 op-a07 gaaacgggtg 5 4 op-a08 gtgacgtagg 8 6 op-a09 gggtaacgcc 7 4 op-a11 caatcgccgt 7 6 op-a12 tcggcgatag 6 4 op-a14 tctgtgctgg 3 1 op-a15 ttccgaaccc 7 5 op-a16 agccagcgaa 4 3 op-a17 gaccgcttgt 4 2 op-a18 aggtgaccgt 4 3 op-a19 caaacgtcgg 8 5 op-a20 gttgcgatcc 6 4 figure 1. polymorphism revealed using primers op-a08 and op-a17 to amplify genomic dna purified from 10 potato cultivars. op-a08 op-a17 al-moshileh, el-shinawy and motawei 40 41 evaluation of potato cultivars by morphological characters and rapd markers markers and could discriminate 128 accessions of potato. the similarity analysis based on rapd markers showed that cultivars victoria and etfadoal presented the least similarity (0.50), whereas cultivars mondial and citrix had the greatest similarity (0.92) (table 6). the high value of genetic similarity obtained between mondial and spunta (0.81) may be due to the fact that spunta was one of the parents of cultivar mondial (spunta × svp ve66295). on the other hand, cultivar etfadoal had the greatest genetic diversity of all cultivars. these data revealed broad variability among potato cultivars. sun et al. (2003) found genetic similarity coefficients varied from 0.29 to 0.90 among cultivated potato hybrids. cluster analysis was conducted to generate a dendogram elucidating relationships among potato cultivars. the dendogram constructed with upgma analysis revealed three clusters (fig. 2). cluster i contained cultivars victorial and kawalic. custer ii contained cultivars safaren, citrix, mondial, spunta, edward, aboulx and frizia. cluster iii contained cultivar etafadoal. hosaka et al. (1994), studying the genetic relations of 73 japanese potato cultivars, reported that the patterns of rapd banding of closely related cultivars were grouped. taylor and ford (1997) were able, by means of rapd technique, to figure 2. dendrogram constructed from similarity coefficients showing the clustering of potato cultivars. table 6. simple matching coefficients of similarity determined from analysis using 75 rapd loci. cultivars v s k c ed e a f m sp victoria (v) 1.00 safaren (s) 0.69 1.00 kawalic (k) 0.69 0.63 1.00 citrix (c) 0.70 0.81 0.64 1.00 edward (ed) 0.69 0.81 0.69 0.75 1.00 etfadoal (e) 0.50 0.50 0.63 0.52 0.57 1.00 aboulx (a) 0.69 0.73 0.65 0.77 0.68 0.50 1.00 frizia (f) 0.67 0.69 0.69 0.70 0.72 0.67 0.69 1.00 mondial (m) 0.71 0.88 0.62 0.92 0.77 0.50 0.81 0.72 1.00 spunta (sp) 0.61 0.81 0.69 0.78 0.75 0.57 0.74 0.79 0.83 1.00 al-moshileh, el-shinawy and motawei 40 41 evaluation of potato cultivars by morphological characters and rapd markers differentiate closely related potato cultivars, which was not possible by morphological techniques. forapani et al. (1999), polzrova and ptacek (2000), and isenegger et al. 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2014 accepted 19 feb. 2015 identification and characterization of two amylase producing bacteria cellulosimicrobium sp. and demequina sp. isolated from marine organisms laila s.h. al-naamani*1, sergey dobretsov 1, jamal al-sabahi 1 and bassam soussi 1 1* laila s.h. al-naamani ( ) sultan qaboos university, college of agricultural and marine sciences, dept. of marine science and fisheries, box 34, al-khod 123, sultanate of oman. email: p029787@student. squ.edu.om. introduction the sea is a unique resource with a large diversity of natural products isolated mainly from inver-tebrates, such as sponges, tunicates, bryozoans and molluscs, as well as from bacteria (proksch et al., 2002). symbiotic microorganisms are often proposed as the true producers of natural products isolated from marine invertebrates. numerous examples exist in which structurally related or identical compounds have been reported from taxonomically distinct invertebrates and cultured microorganisms (moore, 1999; proksch et al., 2002). recently, research has focused on marine microorganisms as sources of many metabolites that have a potential to be used as antibiotics, antimicrobials, or antitumor agents and pharmaceuticals. marine microorganisms are a valuable source of novel enzymes with ideal characteristics because of the halophilic nature of the marine bacteria (mohapatra et al., 1998). halophiles are microorganisms that live, grow, and multiply in highly saline environments. moderately halophilic bacteria are able to grow over a wide range of salt concentrations from 0.4 to 3.5m. exoenzymes from تعريف وحتديد صفات نوعني من البكرتاي )cellulosimicrobium sp( و )demequina sp (املفرزة لألميليز مت عزهلما من كائنات حبرية ليلى النعماين1* وسريجي دوبريتسوف1 ومجال الصباحي1 وبسام سوسي1 abstract. marine sources have been known to yield novel compounds with a wide range of bioactivity with various commercial applications. in this study, the abilities of bacteria isolated from eight marine organisms to produce α-amylase were examined. all eight organisms were found to harbor amylase producing bacteria. two bacterial species isolated from the green alga ulva rigida and the sponge mycale sp. were further identified and their α-amylases were purified and characterized. the bacterial species isolated from u. rigida and mycale sp. were identified by dna sequencing as cellulosimicrobium sp. and demequina sp., respectively. cellulosimicrobium sp. obtained maximum cell growth and amylase production at 29ºc and in the presence of lactose as a carbon source. optimal cell growth and amylase production by demequina sp. was observed at 35ºc. while lactose enhanced cell growth of demequina sp., maximum amylase production was found when fructose and glycerol were the available sources of carbon. both strains grew better in the presence of tryptone, whilst peptone stimulated amylase production. maximal cell growth and amylase production by both of the strains was found at a medium salinity of 3% nacl. keywords: natural products, enzymes, amylase, bacteria. املســتخلص:تـُْعَرف املصــادر البحريــة بتوفريهــا ملركبــات جديــدة هلــا تأثــريات حيويــة واســعة النطــاق وتطبيقــات جتاريــة متعــددة. مت فحــص القــدرة علــى إفــراز األميليــز ألفــا مــن قبــل بكرتيــات مت عزهلــا مــن مثانيــة كائنــات حبريــة. وجــد أن مجيــع الكائنــات البحريــة الثمــان حتتــوي علــى بكرتيــات منتجــة لألمليــز. كذلــك مت عــزل نوعــن مــن البكرتيــا مــن الطحلــب األخضــرulva rigida ومــن األســفنجية mycale sp ومت تعريفهمــا، وتنقيــة إنزمياهتمــا cellulosimicrobium علــى أهنمــا mycale sp ومــن ulva rigida األميليزيــة وحتديــد صفاهتــا. مت تعريــف النوعــن البكرتيــن اللذيــن مت عزهلمــا مــن cellulosimicrobium حققــت البكرتيــا dna بالتــوايل، وذلــك مــن خــال تقنيــة الرتتيــب التسلســلي للحمــض النــووي demequina sp و sp sp. أقصــى منــو للخايــا و أقصــى انتــاج لألميليــز عنــد 29 درجــة مئويــة يف وجــود الاكتــوز كمصــدر كربــوين، بينمــا كان أفضــل منــو للخايــا و أفضــل إنتــاج لألميليــز لنــوع demequina sp عنــد 35 درجــة مئويــة. ورغــم أن الاكتــوز قــد حسَّــن النمــو اخللــوي ل demequina sp ، إال أن أقصــى إنتــاج لألميليــز يف هــذا النــوع قــد ُوِجــد عندمــا كان الفركتــوز واجليســرول مهــا املصدريــن املتاحــن للكربــون. ولقــد منــا النوعــان بشــكل أفضــل يف وجــود الرتيبتــون، .nacl % 3 بينما حفز الببتون إنتاج األميليز. ُوِجد أيضا أن اقصى منو للخايا وإنتاج لألميليز كان يف كلي النوعن عند مســتوى امللوحة املتوســط الكلمات املفتاحية: املنتجات الطبيعية،األنزميات، األميليز 9research article al-naamani, dobretsov, al-sabahi, soussi these microorganisms with polymer degrading ability at low water activities are of interest in many harsh industrial processes where concentrated salt solutions would inhibit many enzymatic conversions. furthermore, most halobacterial enzymes are known to be thermotolerant and remain stable at room temperature for a long time (chakraborty et al., 2008(b); mohapatra et al., 1998). free-living bacteria and bacteria attached to marine sediments usually excrete large amounts of extracellular enzymes for the hydrolysis of intractable macromolecules (mohapatra et al., 2003). the enzymes secreted by the bacteria remain associated with the cell and are released slowly to the environment to aid in the nutrition of their host. until now, researchers have isolated several enzymes such as acetylcholinesterase, amylase, urethanase, cellulase, and alginate and pectin lyases from bacteria and fungi associated with marine sponges and algae (mohapatra et al., 2003). although many microorganisms produce amylase, the ones most commonly used for industrial production are bacillus subtilis, bacillus licheniformis, bacillus amyloliquifaciens and aspergillus niger (vidyalakshmi, 2009). the sea around oman is rich in marine organisms that could be a potential source of natural products that are not yet exploited. the overall objectives of this study was to isolate bacteria associated with omani marine organisms, study their abilities to produce amylase and to investigate the optimal conditions (temperature, ph and salinity, carbon and nitrogen sources) for bacterial growth and enzyme production. materials and methods isolation of pure cultures from marine environments samples from eight marine organisms: the red sponge mycale sp., the tunicate red ascidia sp., the tunicate black ascidia nigra, the whitesponge chalina sp., the yellow sponge hemiasterella sp., the sea anemone heteractis crispa and the green alga ulva rigida and sea water were collected from bandar al khairan (depth 1-5 m), arabian gulf, sultanate of oman. the marine organisms were transferred into plastic bags immediately after collection and kept in ice until transferred to the laboratory. in the laboratory, the samples were transferred to conical flasks containing marine broth and placed in a rotary shaker at 180 rpm at 29oc for about 24 to 48 hours. after incubation, a loop full of each sample mixture was streaked onto nutrient agar and incubated for another 24 hours. the bacterial colonies were separated and subcultured several times until pure bacterial cultures were obtained. screening of amylolytic enzymes production to check the amylolytic activity of the isolated bacterial strains, each pure bacterial culture was cultured in marine broth and incubated for about 24 hours. subsequently, about 20 µl of each bacterial culture was dropped on starch agar and incubated for 24 to 48 hours. after incubation, amylase production was determined by the development of a colourless halo zone surrounding the bacterial colonies when lugol’s iodine solution (1% iodine in 2% potassium iodide w/v) was added to the plate (fig.1). the diameters of the digestion zones were measured to check the intensity of the enzyme activity of the bacteria. two of the fastest growing bacteria with largest starch digestion zones were chosen for further identification and analysis. bacterial identification the two bacterial strains were first identified by gram staining, api coryne and negative staining (tem test). then, further identification was done by dna sequencing and fatty acid analysis profile. dna sequencing the bacterial strains were identified by comparative analysis of their 16s rrna gene sequences as described in lau et al., 2002. fragments of dna sequences (about 700 bp) obtained from individual primers were assembled using the sequencher® software package (gene codes, usa). the closest match to the 16s rdna gene sequence of the respective bacteria was retrieved by comparison with data from the genbank (www.ncbi. nlm.nih.gov). bacterial fatty acids analysis the sample preparation and analysis for bacterial fatty acid determinations were performed as described by sasser, 1990 using hexane mixed with methyl tert butyl ether for the extraction of the fatty acids from the bacterial strains. figure 1. starch hydrolysis by amylase producing bacteria visualized by lugol’s-iodine coloration. 10 squ journal of agricultural and marine sciences, 2015, volume 19, issue 1 identification and characterization of two amylase producing marine bacteria gc analysis one μl of each extract of bacterial fatty acids in hexanemethyl tert butyl ether mixture was injected into a gas chromatograph (agilent 6890 n) instrument equipped with ultra-1 (crosslinked methyl silicone gum) column, hp catalogue no. 19091a-102 (25m long x 0.2mm i.d x 0.33μl film thickness). analytical conditions the injector and flame ionization detector (fid) temperatures were set at 250ºc and 260ºc, respectively. the oven temperature was programmed from 150ºc (2 minutes) to 250ºc (5 minutes) at 4ºc/min. helium was used as the carrier gas with a linear velocity of 20 cm/sec. the duration of the reaction was set for 40 minutes. data analysis retention times of the unknown bacterial fatty acids were compared to a mixture of standard bacterial fatty acid methyl esters (bame) (supelco, catalogue no. 47080). sensitivity of bacterial strains to antibiotics the bacterial strains were tested for their susceptibility to the following antibiotics: ampicillin, streptomycin, chloramphenicol, and penicillin g. concentrations of 1 mg/ml and 10 mg/ml were used for each antibiotic. the test was performed using a disc diffusion bioassay. the bacterial colonies of the two strains were evenly distributed on nutrient agar using sterile swabs. small discs (diameter = 5.5 mm and surface area = 1 cm2) containing each type of antibiotic were placed in the media inoculated with bacteria and incubated for about 24 hours. presence of clear zones around the discs correspondent to the bacterial growth inhibition was checked and their diameters were measured in millimetres with a ruler. optimization of bacterial yield and amylase production the effect of temperature, salinity and available carbon and nitrogen sources on bacterial growth was tested by measuring the optical density of the samples after incubation. amylase production was determined by the amount of maltose produced as an end product of starch hydrolysis by amylase. bacterial yield test marine broth containing different nacl concentration (0%, 3% 5%, 10% and 15% (w/v)) were prepared to test the effect of salinity. solutions containing 1% of a specific carbon source namely starch, glucose, fructose, lactose, glycerol, sucrose or maltose along with 0.1% yeast extract were prepared in sea water. solutions containing 1% peptone or tryptone as nitrogen sources were also prepared and supplemented with 0.1% yeast extract mixed with sea water. test tubes containing 10 ml of each solution was inoculated with the bacterial cultures except the blank and incubated at 29°c for 24h. to test the effect of temperature, test tubes containing 10ml marine broth inoculated with the bacterial cultures were incubated at different temperatures (5°c, 29°c, 35°c and 60°c) for 24h. after incubation, the blank control was used to zero the spectrophotometer and the absorbance at 600 nm was measured for all the samples. determination of bacterial amylase production the culture solutions prepared in the bacterial yield test, as above, were centrifuged at 10,000 rpm for 5 minutes at 15ºc to separate the bacterial cells from the broth. 1 ml of cell free supernatant of each sample was removed and added to tubes containing 1 ml of 1% starch solution. 1 ml of distilled water with 1 ml of 1% starch solution was added to the blank tube. the tubes were incubated at 37oc for 12 minutes. after incubation, 1 ml of maltose colour reagent (1% 3,5-dinitrosalicylic acid, figure 2. (a) cellulosimicrobium sp. isolated from the green alga ulva rigida after negative staining (tem test) under electron microscope at 25000x magnifications. (b) demequina sp. isolated from sponge mycale sp. after negative staining (tem test) under electron microscope at 15000x magnification. 11research article al-naamani, dobretsov, al-sabahi, soussi 0.4 m naoh, 1.06 m sodium potassium tartrate) was added to each tube and heated for 15 min at 100ºc. the heated mixtures were cooled immediately in ice. then, 9 ml distilled water was added to each tube. the blank was used to zero the spectrophotometer and the absorbance at 540 nm was measured for all the samples. results bacterial isolation and enzyme screening all eight organisms tested were found to harbour enzyme producing bacteria. more than 150 species of marine bacteria were isolated and more than 50 species were screened for enzyme production (figure 1). pure colonies have been isolated and two species among the fastest growing strains with the highest ability to hydrolyze starch were selected from the green alga ulva rigida (strain i) and the red sponge mycale sp. (strain ii). bacterial strain identification the two strains showed characteristics of being gram positive. according to api coryne test, strain i was identified from the apiwebtm identification software as cellulosimicrobium cellulans with 87.3% accuracy whereas strain ii was identified as cellulomonas spp. with 99.9% accuracy. according to partial 16s rna sequences, the two bacterial strains were identified as follows: strain i: cellulosimicrobium sp. with 98% accuracy (bacteria; actinobacteria; actinobacteridae; actinomycetales; micrococcineae; promicromonosporaceae) strain ii: demequina sp. with 98% accuracy (bacteria; actinobacteria; actinobacteridae; actinomycetales; micrococcineae; cellulomonadaceae) the tem showed the structure of the two strains under different magnifications (figure 2). gas chromatographic analysis showed that the two bacterial strains had quite similar fatty acid compositions except for the absence of three types of bacterial fatty acids in demequina sp. (table 1). this can be explained by fact that genes cellulosimicrobium and demequina are highly similar. previously demequina was re-classified from cellulomonas (yi et al., 2007; ue et al. 2011). this fact supports our api coryne test data that identified strain ii as cellulomonas sp. susceptibility to antibiotics both of the strains were highly susceptible to chloramphenicol at concentrations of 1 mg/ml and 10 mg/ml with larger inhibition zones, specifically diameters of 30±2.8 mm and 32.5±3.5 mm for cellulosimicrobium sp. and demequina sp., respectively, at a concentration of 10 mg/ml. the two bacterial isolates were inhibited by 10 mg/ml streptomycin whereas they were not affected by the same antibiotic at the lower concentration of 1 mg/ml. no inhibitory effect on the growth of both isolates was observed by ampicillin and penicillin g. the susceptibility of members of the genus cellulomonas to different antibiotics was studied by funke et al. (1995). all the clinical isolates of cellulomonas species were found to be strongly susceptible to ciprofloxacin, clindamycin, erythromycin and gentamicin. however, they were less susceptible to penicillin g, rifampin, tetracycline and vancomycin. it was found that the bacterium cellulosimicrobium cellulans grew well on standard synthetic media and was susceptible to a variety of antibiotics, including penicillin, macrolides, and glycopeptides (heym, 2005). yoon (2007) isolated cellulosimicrobium terreum from soil and found it to be susceptible to streptomycin (50 μg), chloramphenicol (100 μg) and penicillin g (20 u). susceptibility to ampicillin was observed by three clinical strains of cellulosimicrobium funkei (brown et al., 2006). all these results are totally different from what we obtained from cellulosimicrobium sp. in our study, table 1. results of gas chromatography mass spectrometry (gc-ms) analysis. bame name ret. (min) cm dq 1 methyl dodecanoate (c12:0) 17.42 0.24 1.9 2 methyl tridecanoate (c13:0) 20.05 0.31 0.0 3 methyl 2 hydroxydodecanoate (2-oh-c12:0) 20.38 0.05 0.0 4 methyl 3-hydroxydecanoate (3-oh-c12:0) 21.03 2.70 1.7 5 methyl tetradecanoate (c14:0) 22.67 8.01 4.8 6 methyl 13-methyltetradecanoate (i-c15:0) 24.32 1.22 3.2 7 methyl 12-methyltetradecanoate (α-c15:0) 24.53 0.16 0.0 8 methyl pentadecanoate (c15:0) 25.22 2.84 2.2 9 methyl 3-hydroxytetradecanoate (3-oh-c14:0) 26.22 4.82 3.7 10 methyl 14-methylpentadecanoate (i-c16:0) 26.81 1.94 0.7 11 methyl cis-9-hexadecenoate (c16:19) 27.16 39.52 29.8 12 methyl hexadecanoate (c16:0) 27.68 15.24 16.4 13 methyl 15-methylhexadecanoate (i-c17:0) 29.22 1.58 6.6 14 methyl heptadecanoate (c17:0) 30.1 1.27 1.3 15 methyl trans-9-octadecenoate (c18:19) 32.17 19.85 26.7 16 methyl octadecanoate (c18:0) 32.77 0.24 0.4 12 squ journal of agricultural and marine sciences, 2015, volume 19, issue 1 identification and characterization of two amylase producing marine bacteria since it was not affected by ampicillin and penicillin g and was susceptible to only higher concentrations of streptomycin. probably this was due to isolation of our novel strain from different environment (marine). additionally, different antibiotic susceptibility could be due to antibiotic resistance of some bacterial strains (brown et al., 2006). bacterial yield and amylase production effect of temperature the results showed optimal temperature for cell growth and enzyme production between 29ºc and 35ºc for cellulosimicrobium sp. and demequina sp., respectively (fig. 3 & 4). the two strains were inactivated at 4ºc and 60ºc which indicates the mesophilic characteristics of the two bacterial strains. this property can be related to the natural habitat of the two bacterial strains in the mesophilic sea environment. this is in accordance with what was reported by asgher et al. (2007) and kathiresan and manivannan (2006) that the influence of temperature on amylase production is related to the growth of the microorganism. effect of salt concentration the highest bacterial growth and enzyme production for cellulosimicrobium sp. and demequina sp. was obtained in the presence of 3% nacl (w/v) (fig. 5 & 6), which is the normal salinity of sea water. these results might be related to the nature of the bacterial origin since they were isolated from marine environments. there was no amylase production in the absence of nacl which clearly indicates the halophilic nature of the enzymes of both strains. cellulosimicrobium sp. retained about 9% of its growth ability at 10% salt but both strains lost their enzyme productivity at this salinity. prakash (2009b) reported that halophilic enzymes require high salt concentrations for their activity due to their adaptation to high salt concentrations while they undergo denaturation at nacl concentrations below 1m. he also suggested that halophilic bacteria can produce enzymes that can tolerate high salt concentrations 3-15% nacl. effect of carbon and nitrogen sources on bacterial yield and amylase production the maximum optical density and maltose production by cellulosimicrobium sp. in the presence of lactose was observed (figure 7). this indicated higher cell growth and amylase production, with this carbon source. this amount of cell yield and amylase production was much higher than what was obtained in the presence of starch, which is known as the general substrate for amylase production. hiller et al. (1997) demonstrated a similar enhanced cell growth and α-amylase production by bafigure 3. effect of temperature on cell yield of cellulosimicrobium sp. and demequina sp. (λ600nm). the data are the means of two replicates ± standard deviation. figure 4. effect of temperature on amylase production of cellulosimicrobium sp. and demequina sp. (λ540nm). the data are the means of two replicates ± standard deviation. figure 5. eeffect of salt concentration on cell yield of cellulosimicrobium sp. and demequina sp. (λ600nm). the data are the means of two replicates ± standard deviation. figure 6. effect of salt concentration on amylase production of cellulosimicrobium sp. and demequina sp. (λ540nm). the data are the means of two replicates ± standard deviation. 13research article al-naamani, dobretsov, al-sabahi, soussi cillus amyloliquefaciens from lactose. the lowest bacterial growth and enzyme secretion was observed in the presence of fructose. glucose was found to yield very minimum amounts of amylases from both of the bacterial strains regardless of its effect on cell growth. repression of amylase synthesis by glucose was also reported in thermophilic and alkaliphilic bacillus sp. ts-23 (lin et al., 1998), sulfolobus solfataricus (haseltine et al., 1996) and bacillus sp. isolate l1711 (bernhardsdotter et al., 2005). haseltine et al. (1996) justified that glucose prevents gene expression of α-amylase and represses its secretion. although maximum cell growth of demequina sp. was obtained in the presence of lactose, the highest enzyme production was induced by fructose and glycerol (figure 8). glycerol was reported to increase enzyme production in bacillus sp. ps-7 (tanyildizi, 2005) and bacillus sp. i-3 (goyal, 2005). higher optical density was obtained in the presence of tryptone which indicates that it enhanced the cell growth of both strains more than peptone (figure 9 & 10). however, more maltose was produced by the addition of peptone which reflected its higher stimulation of amylase production. the decrease in the amounts of maltose as the end product of starch hydrolysis in the presence of tryptone may be due to the intolerance of the bacterial strains to 0.5% tryptone. similar results were reported previously (chakraborty et al. 2008a). these authors found a decrease in amylase production by saccaropolyspora species a9 at tryptone concentrations beyond 0.4%. conclusions two amylases were isolated from the two bacterial strains cellulosimicrobium sp. and demequina sp., which were correspondingly obtained from the green figure 7. effect of carbon and nitrogen sources on cell yield of cellulosimicrobium sp. and demequina sp. (λ = 600nm). the data are the means of two replicates +1 standard deviation. figure 8. effect of carbon and nitrogen sources on amylase production of cellulosimicrobium sp. and demequina sp. (λ = 540 nm). the data are the means of two replicates +1 standard deviation. 14 squ journal of agricultural and marine sciences, 2015, volume 19, issue 1 identification and characterization of two amylase producing marine bacteria alga ulva rigida and the sponge mycale sp. maximum cell yield from the two bacterial strains was obtained at temperatures between 29ºc and 35ºc and 3% salinity, which indicate that the two strains have mesophilic and halophilic properties. addition of lactose and tryptone significantly increased the growth of both of the strains. both strains produced highest amount of amylase at temperatures between 29ºc and 35ºc, 3% salinity and in the presence of peptone. addition of lactose increased amylase production by cellulosimicrobium sp., whereas supplementation of the media with fructose and glycerol resulted in maximal amylase production by demequina sp. the present study demonstrated that all eight investigated marine organisms are promising sources of amylases producing bacteria. this finding provides the possibility to isolate more enzymes-producing bacteria and search for novel bioactive compounds from the marine environment in oman. references deeasgher, m., m. j. asad, s. u. rahman, and r. l. legge. 2007. a thermostable amylase from bacillus subtilis strain for starch processing. journal of food engineering 79: 950-955. bernhardsdotter, e. c. m. j., j. d. ng, o. k. garriott, and m. l. pusey. 2005. enzymic properties of an alkaline chelator-resistant amylase from an alkaliphilic bacillus sp. isolate l1711. process biochemistry 40:24012408. brown, j. m., a. g. steigerwalt, r. e. morey, m. i. daneshvar, l. romero, and m. m. mcneil. 2006. characterization of clinical isolates previously identified as oerskovia turbata: proposal of cellulosimicrobium funkei sp. nov. and amended description of the genus cellulosimicrobium. international journal of systematic and evolutionary microbiology 56: 801-804. chakraborty, s., a. khopade, c. kokare, k. mahadic, and b. chopade. 2008a. isolation and characterization of novel amylase from marine streptomyces. journal of molecular catalysis 10: 1-31. chakraborty, s., a. khoqade, rinbio, x.y. liu, l. zhang, k. mahadic and c. kokare. 2008b. isolation, partial purification and characterization of halophilic, alkali tolerant, thermostable, surfactant and detergent stable amylase enzyme from marine saccharoplyspora species. marine biotechnology 11:1-35. heym, b., p. gehanno, v. friocourt, m. bougnoux, m. le moal, c. husson, j. leibowitch, and m. nicolas-chanoine. 2005. molecular detection of cellulosimicrobium cellulans as the etiological agent of a chronic tongue ulcer in a human immunodeficiency virus-positive patient. journal of clinical microbiology 43(8): 4269-4271. funke, g., c. p. ramos, and m. d. collins. 1995. identification of some clinical strains of cdc coryneform group a-3 and a-4 bacteria as cellulomonas species and proposal of cellulomonas hominis sp. nov. for some group a-3 strains. journal of clinical microbiology 33(8): 2091-2097. goyal, n., j. k. gupta, and s. k. soni. 2005. a novel raw starch digesting thermostable α-amylase from bacilfigure 9. 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spp. world journal of chemistry 4: 89-91. yi, h., p. schumann, and j. chun. 2007. demequina aestuarii gen. nov., sp. nov., a novel actinomycete of the suborder micrococcineae, and reclassification of cellulomonas fermentans bagnara et al. 1985 as actinotalea fermentans gen. nov., comb. nov. international journal of systematic and evolutionary microbiology 57(1): 151-156. yoon, j., s. kang, p. schumann, and t. oh. 2007. cellulosimicrobium terreum sp. nov., isolated from soil. journal of systematic and evolutionary microbiology 57: 2493-2497. agricultural and marine sciences, 17:33-43 (2012) ©2012 sultan qaboos university 33 ______________________________________________ *corresponding author. e-mail: darbat2001@yahoo.com experimental rearing of spiny lobster, panulirus homarus (palinuridae) in land-based tanks at mirbat station (sultanate of oman) in 2009-2010 mohammed balkhair*, ali al-mashiki, and mikhail chesalin fisheries research center-salalah, ministry of agriculture and fisheries wealth, p.o. box 33, pc 217, salalah, sultanate of oman في أحواض (panulirus homarus) العمانية الشارخة لتربية دراسة جتريبية 20092010م من الفترة خالل مبرباط السمكي االستزراع بوحدة جيسالني املشيخي وميخائيل وعلي بلخير محمد مبرباط السمكي االستزراع بوحدة اليابسة على أحواض في (panulirus homarus) العمانية الشارخة تربية على جتربتني اجراء مت اخلالصة: إلى يناير من الثانية والتجربة ٢٠٠٩ ديسمبر إلى يونيو من الفترة خالل األولى التجربة نفذت بصاللة. السمكية البحوث ملركز التابعة جسم وبوزن مليمتر ٧,٤ ± ٦٤,٩ التجربة عند بدء اطوالها بلغت األولى في التجربة الشارخة من صغار ١٤ عدد تربية مت وقد .٢٠١٠ ديسمبر من بدء يوماً ١٨٧ بعد جرام ١١٤,٨ ± ووزن بلغ ٣٨٤,٠ الطول في مليمتر ٧,٢ حجم بلغ ٧١,٧± وصلت إلى بحيث جرام. ٩٨,٠ قدره ٢٩٧,٨± جرم ٣٠٤,١ والوزن مليمتر ٤,٦ ± ٤٥,٥ األولي كان الطول بحيث الشارخة، صغار من عدد ٤٥ تربية مت فقد في التجربة الثانية التجربة. أما التجربة في البقاء نسبة التوالي. ووصلت على ٪١٥٥,١ و ٪٤٥,٨ والوزن الطول من كل في الكلية بلغت الزيادة كما يوماً. ٣٣٥ فترة خالل كال التجربتني. بينما االناث في من منواً األسرع كان الذكور األشهر األولى. الستة خالل الثانية للتجربة ٪٨٦,٧ بلغت ٩٢,٩٪ بينما إلى األولى لم تكن بحر العرب، في املعروفة القيم الطبيعية املذاب األكسجني ومعدل الهيدروجيني األس ومقدار وامللوحة درجات احلرارة قيم عكست خالل مئوية درجة ٢٠ أقل من احلرارة درجات كانت بينما األلف، من جزءاً ٣٧,٥ امللوحة درجات بلغت الشارخة. لتربية باملثلى املستويات هذه الدرع طول مليمتر ٤٠-٤٥ أحجام من العمانية الشارخة استزراع و تربية إمكانية الدراسة بينت وقد (املونسون). الصيفية موسم األمطار عام خالل جرام ٣٥٠ يبلغ وبوزن الدرع طول مليمتراً ٧٠ احملدد ب القانوني واحلجم اجلنسي النضج درجات إلى جرام لتصل ١٠٠ قدره أولي وبوزن يونيو. ولغاية أكتوبر من املمتدة الفترة خالل وخصوصاً العائمة األقفاص في مستقبالً التجارب باجراء الدراسة وتوصي واحد. .panulirus homarus التغذية، االنسالخ، البقاء، معدالت النمو، نسب الشارخة، أحواض، تربية، عمان، مفتاحية: كلمات abstract: two experiments on the rearing of the spiny lobster panulirus homarus were conducted in land-based tanks at mirbat aquaculture unit from june to december 2009 and january-december 2010. in the first experiment 14 lobsters with an average size of 64.9±7.4 mm cl and weight of 297.8±98.0 g were reared to an average of 71.7±7.2 mm cl and weight of 384.0±114.8 g over 187 days. in the second experiment 45 lobsters were reared from an initial length of 45.4±4.6 mm cl and weight of 118.9 g to a length 66.0±7.1 mm cl and a weight of 304.1 g over 335 days. total length increment was 45.8% and weight increment 155.1%. the daily food ration was 3.0-8.8%. the survival rate in the first experiment was 92.9%, in the second experiment it was also high (86.7%) during the first six months. in both experiments males grew faster than females. while the water temperature, ph, salinity and dissolved oxygen reflected the ambient condition of the arabian sea, these were not optimal levels for lobsters culture. the salinity was higher (37.5 ppt), while the water temperature was low (<20oc) during the summer monsoon. the study demonstrated the possibility of cultivating sub-adult lobsters in oman from 40–45 mm cl and 100 g to maturity stage, obtaining the legal size of 70 mm cl and a weight of about 350 g over a year. it is recommended that the next experiment be conducted in floating sea cages from october to june. keywords: panulirus homarus, lobster, experiment, tanks, oman, growth, survival, molting, feeding. introduction the omani lobster fishery in the arabian sea is based mainly on the scalloped spiny lobster panulirus homarus (linnaeus, 1758). this species is one of the largest among crustaceans: the carapace length (cl) attains 14 cm and total body length 35 cm (al-abdessalaam, 1995). the spiny lobster lives along the coast, inhabiting shallow waters and tends to shelter in rocky reefs and corals. it is a subject of an artisanal fishery, fishermen catch lobsters by hand and by using traps, nets and spears. the high price of lobsters has encouraged fishermen to aggressively exploit their resources with no concern over their long-term sustainability, and as a result, more small sized lobsters were caught. according to fishery statistics, reported lobster landings from oman have sharply declined from over 2000 t.yr-1 in 1980’s to 233–478 t.yr-1 in 2000–2007 with a low of 19 t in 2009 (anonymous, 2006, 2010). an assessment of the lobster fishery in oman in 2003–2005 (al-marzouqi et al., 2007) shows that average lobster size and size at first 34 balkhair et al. 35 experimental rearing of spiny lobster in land-based tanks maturity were considerably lower in comparison with data of 1987–1989 (al-abdulsalaam, 1989) and 1994–1995 (mohan, 1997). present governmental management regulation for lobster fisheries include a 2-month open fishing season (1 march – to 30 april), a minimum legal size of 70 cm cl, gear restriction allowing only traps and a ban on the retention off egg-bearing females after capture. therefore, it is highly advisable to organize the mariculture of lobsters for both commercial purposes and stock enhancement to promote the rehabilitation of the natural resource. the first aquarium project on rearing of the p. homarus (phase i) in oman was conducted in the mirbat aquaculture unit (mau) of the fisheries research center-salalah from may to august 2007 (al-marzouqi et al., 2009). thirty-seven lobsters were placed in tanks and reared for 4 months. the initial mean length of the lobsters was 60.63 mm cl and at the end of 4-month period it was 65.06 mm cl. this paper describes the results of two experiments that were performed in mau from june to december 2009 and from january to december 2010. materials and methods phase ii of the project on experimental rearing of the scalloped spiny lobster p. homarus in aquarium tanks in mirbat was conducted over two periods: firstly, from 24 june 2009 to 27 december 2009 (187 days) and secondly, from 12 january to 13 december 2010 (335 days). in the first experiment in 2009, 14 lobsters (seven males and seven females) were reared, and in the second experiment, 45 sub-adults (23 females and 22 males). all lobsters were caught near mirbat by the fisheries research centersalalah team using traps, then placed in large polythene bags with aerated seawater and transferred rapidly upon capture to the tanks to ensure the maintenance of good condition. the lobsters were placed in fibre-reinforced plastic tanks each with a volume of 2 m3, and provided with artificial shelters (half pvc pipes). stocking density was 7–8 specimens per m2. to maintain water temperature, salinity, ph and other parameters reflecting the ambient condition of the arabian sea, a flow-through sea-water system was used with water sourced offshore. after filtering, the water passed directly to the tanks. the ph, water temperature, salinity and dissolved oxygen were measured daily with a portable probe unit (ysi 556) to study the rearing regime and its influence on growth rate. the lobsters were sexed and measured mid-dorsally from the transverse ridge between the frontal spines to the posterior carapace edge within 1 mm accuracy using a vernier caliper. total wet weight of all specimens was taken. in the first experiment lobsters were maintained in the tanks for 6 months and were remeasured and weighed each month. to eliminate disturbance in the second experiment lobsters were remeasured and weighed only at the middle stage (9 june) and at the end (13 december). the lobsters were fed daily at 17:00 h with chopped sardine. the food and remains were removed and weighed daily to study the ingestion and the food ration. the tanks were siphoned daily and cleaned thoroughly once a week. they were covered with plastic corrugated sheeting to avoid growth of filamentous green algae. important increments were calculated using the following formulae: • total length (and weight) increments = final mean carapace length (or weight) initial mean carapace length (or weight) (cl 2 cl 1 ) or (w 2 w 1 ). • total relative length (and weight) increments (%) = (final carapace length (or weight) initial carapace length (or weight)) x 100 / initial carapace length (or weight) (cl 2 cl 1 ) x 100 / cl 1 or (w 2 w 1 ) x 100 / w 1 ; • monthly length (and weight) increments = (final carapace length (or weight) − initial carapace length (or weight)) / number of months (cl 2 cl 1 ) / t or (w 2 w 1 ) / t; • daily length (or weight) increments = final carapace length (or weight) − initial carapace length (or weight) / number of days (cl 2 cl 1 ) / t or (w 2 w 1 ) / t; • specific growth rate (sgr, % of the length (or body weight) per day) = (logarithm of final carapace length – logarithm of initial carapace length) x 100 / number of days (lncl 2 lncl 1 ) x 100 / t or lnw 2 lnw 1 ) x 100 / t. an anova test was used to identify growth rate differences between males and females (zar, 1984). results water conditions the mean monthly water temperature, dissolved oxygen, salinity and ph in the rearing tanks are presented in figure 1a,b. temperature showed a seasonal trend with high values during april-june (27.1-29.1oc) and october -december (25.1-27.1oc) and low values between july and september (19.6-22.8oc) (the south-west monsoon season). salinity was relatively constant at approximately 37.53±0.24 ppt with a small decrease during the monsoon period (july-september), which corresponds to the season of rain and fog. in contrast, the concentration of dissolved oxygen increased (above 6 ml.l-1) during june-september, probably due to more wind mixing of the surface water layer. in other months it remained less saturated (4.2-5.1 ml.l-1). the ph was high, ranging between 8.0 and 10.1 (mean 8.6). it reached its maximum values of 10.1 in december 2009 and 9.8 in june 2010. growth and survival during the first experiment from june to december 2009 the mean cl of females increased from 64.5 to 70.1 cm, and weight from 290 to 367.3 g. males began with an average of cl of 65.4 cm and weight of 305.6 g. in six months they attained an average cl of 73.7 cm and weight of 403.5 g (fig. 2). 34 balkhair et al. 35 experimental rearing of spiny lobster in land-based tanks month month figure 1. water condition in the rearing tanks at mirbat over lobster husbandry during 2009 and 2010: a – temperature and salinity; b – dissolved oxygen and ph. 36 balkhair et al. 37 experimental rearing of spiny lobster in land-based tanks figure 2. growth of p. homarus males and females in tanks at mirbat from june to december 2009: a – length, b – weight. month month 36 balkhair et al. 37 experimental rearing of spiny lobster in land-based tanks the mean length increment of both sexes for six months was 6.77 mm cl (10.43%), and the mean weight increment was 84.81 g (29.96%) (table 1). monthly length increments were 0.94 mm for females and 1.39 mm for males, weight increments for both sexes was 14.37g.month-1. the daily weight increment was estimated at 0.46 g and the specific growth rate (sgr) of weight was 0.14%. males grew faster and reached 3.6 mm larger cl than females over the same period. the anova test show significant differences between the growth rate of males and females in length (f 5.12 = 6.01, p < 0.05) and weigth (f 5.12 = 7.88, p < 0.05). the survival rate of the lobsters in this experimental trial was very high; just one male died in november, so the total survival rate during 6 months was 92.9%. at the beginning of the second experiment 23 females ranged in length from 33.4 to 53.8 mm cl (mean 44.8±4.8 mm) and 22 males from 33.4 to 51.1 mm cl (mean 45.7±4.4 mm) (table 2). the total weight of all lobsters were table 1. details on growth increments of the p. homarus during tank culture in mirbat from june to december 2009 and from january to december 2010. attribute 2009 2010 both sexes females males both sexes females males total increments cl (mm) 6.77 5.62 8.31 20.7 18.3 22.5 cl 10.43 8.72 12.71 45.8 39.5 50.5 w (g) 86.22 84.81 97.92 185.1 w (%) 29.96 29.25 32.05 155.1 monthly increments cl (mm) 1.13 0.94 1.39 1.88 1.66 2.04 w (g) 14.37 14.14 16.32 16.83 daily increments cl (mm) 0.04 0.03 0.04 0.06 0.05 0.07 w (g) 0.46 0.45 0.52 0.55 sgr (%) cl (%) 0.05 0.04 0.06 0.11 0.10 0.12 w (%) 0.14 0.14 0.15 0.28 table 2. data on number (n), carapace length (cl) and standard deviation (s.d.) of the p. homarus experimental rearing in mirbat during 2010. date both sexes females males n cl (mm) s.d. n cl (mm) s.d. n cl (mm) s.d. 12.01.2010 45 45.27 * 33.4 – 53.8 4.59 22 44.83 . 33.4 – 51.1 4.82 23 45.70 . 36.7 – 53.8 4.43 9.06.2010 24 54.43 . 43.4 – 64.7 5.87 11 54.11 . 43.4 – 61.1 5.41 13 54.68 . 44.1 – 64.7 6.45 13.12.2010 7 66.0 . 54.3 – 74.2 7.11 3 63.13 . 54.3 – 70.5 8.20 4 68.15 . 60.5 – 74.2 6.48 *above the line is the average. under the line are the minimum and maximum carapace lengths. 38 balkhair et al. 39 experimental rearing of spiny lobster in land-based tanks for both sexes the equation was w= 0.0025.cl2.7932 (r2 = 0.97). molting and feeding twenty-seven molts were registered (fig. 4b) during the first 3 months of the second experiment (januarydecember 2010). the lobsters did not molt during april and may, with molting becoming more active in summer (june, july and september), when water temperature was low, with several molts noted from october to december. during the first experiments 14 lobsters were fed 150–400 g chopped sardines daily. the lobsters consumed between 150 and 228 g per day in different months, between 10.8 to 16.2 g of one lobster per day. the mean daily food ration of a lobster was 3.0–4.6% of wet body weight. in the second experiment 45 lobsters were fed 300–450 g chopped sardines daily. they consumed from 13.9 to 100% of the food (mean 74.3%). the calculated feeding rate for individuals per day increased during the experiment with lobster growth from 6.2 to 20.2 g. the mean daily food ration was 5.2–8.8% of wet body weight (fig. 5). discussion the environmental parameters in tanks during the experiments reflected the ambient conditions in this region of the arabian sea. recorded water conditions in june–december 2009 and january–december 2010 have similar trends and were also similar to the experimental 5350 g, hence the mean weight of one lobster was calculated as 118.9 g. by the middle of the year (june) the lobsters grew to an average 54.4±5.9 mm cl and weight of 200.0 g, and at the end in december they had attained a mean length of 66.0±7.1 mm cl, and a mean weight of 304±84.4 g. the largest lobster reached 74.2 mm cl and weighed 398.7 g. the size composition of lobsters at the start, middle and end of the aquarium trial is presented in figure 3. as in the previous experiment males grew faster and reached a mean cl 5 mm larger and weighed 27.6 g more in comparison with females over the same period. but an anova test did not show significant differences in this case (f 6.61 = 0.05, p < 0.05); this may be due to the small numbers of the studied individuals. the mean length increment for both sexes during 11 months was 20.7 mm cl (45.8%), and total mean weight increment was 185.1 g (155.7%) (see table 1). the mean monthly increments were 1.66 mm cl for females and 2.04 mm cl for males, the mean weight increment for both sexes was 16.8 g.month-1. the mean daily weight increment was calculated as 0.55 g and specific growth rate (sgr) of weight attained 0.28%. it is difficult to estimate the total survival rate in this experiment because 16 lobsters were lost for obscure reasons in june. in general, the survival rate was high over the first 6 months of rearing (86.7%) and low in subsequent months. in total it was registered that 22 lobsters (48.9%) died, with the highest mortality rate from june to september during the summer monsoon (fig. 4a). a total of 117 specimens were used to calculate the carapace length-total weight relationship in p. homarus, figure 3. size composition of the p. homarus at the aquarium trial in mirbat in 2010. 38 balkhair et al. 39 experimental rearing of spiny lobster in land-based tanks figure 4. mortality (a) and molting (b) of the p. homarus during experimental trial in tanks at mirbat. conditions of 2007 (al-marzouqi et al., 2009). in summary, in summer time these conditions were outside the favorable criteria for lobster culture established by phillips et al. (1980) in which water temperature must range from 28 to 32oc and the salinity should be between 30 and 34 ppt for better production. during the summer south-west monsoon (july–september) the south oman coastal surface water temperature can decrease to 17–19oc, while salinity is high and relatively stable all-year round (about 37.5 ppt). although lobsters are able to adjust to a wide range of water temperature and salinity, these fluctuations could cause environmental stress in cultured specimens. some investigations have shown that laboratory held lobsters grew faster at lower temperatures (25–26oc) than at higher temperatures (28–29oc) because of both increased molt increments and shortened intermolt periods (kulmiye and mavuti, 2005). our data confirm an increase of the molting rate in summer time when the temperature is lowered, but an increase of molting also raises the risk of lobster mortality. specifically, 17 lobsters (37.8%) died in the 2010 summer period (june–september). it is known that the lethal level of dissolved oxygen for lobster culture ranges from 0.5 to 3.0 mg.l-1 (kittaka, 1994), but such a situation was not observed during the present study. the ph was relatively high, and in some periods increased to about 10, which is not favorable for lobsters. this possibly indicates that the best period for lobster culture in omani waters of the arabian sea is from october to may-june. the calculated mean daily growth rate in the experiment held in may–august 2007 was 0.04 mm.day-1, in the experiment in june -december 2009 it was also 0.04 month month 40 balkhair et al. 41 experimental rearing of spiny lobster in land-based tanks in japan and australia have produced several hundred juveniles for several species of panulirus (yamakawa et al., 1989; kittaka and kimura, 1989; hart and van barneveld, 2000; ritar, 2001; ritar et al., 2002, 2003). the main obstacles are the extremely long development period for the phyllosoma larvae (almost 1 year), very high and changeable requirements to the environmental and feeding conditions, frequent occurrence of bacterial diseases and very low larval survival rate. it takes up to three to four years or more under optimum conditions for spiny lobsters to reach commercial size from hatching. the long culture period required for attaining market size, particularly in comparison with some cultured finfish or shrimp species, is the main constraint to commercialization of the complete cycle of lobster culture. a more effective suggested approach, alternative to hatchery production, is to capture settling wild lobster seed (pueruli or juveniles) in the sea and then allow their grow-out in tanks, ponds or in seacages (chittleborough, 1974; serfling and ford, 1975; radhakrishnan, 1994, 2004; radhakrishnan and viyayakumaran, 1990; jeffs and james, 2001; james, 2007). significant advances were made in lobster postlarval grow-out in vietnam, indonesia, taiwan, singapore, new zealand and australia. in 2006 the lobster aquaculture industry in vietnam had more than 49,000 cages producing approximately 1,900 t of product, valued at about us$90 million (hung and tuan, 2009). in indonesia more than 1,500 small-scale farm units are established and produce about 4–5 t of lobsters per month (priyambodo and sarifin, 2009). several investigations have shown that growth and survival rates of lobsters is higher in floating sea cages when compared with land-based tanks. sub-adult p. mm.day-1 and in the ones conducted in january–december 2010 it was 0.06 mm.day-1. it is known that the growth of the animals slows down over time. our experimental data show higher growth rates for the lobsters in the 45–60 mm range with decreased increments in individuals longer than 60 mm cl. as a result, it can be recommended that lobsters are reared from 40–45 mm cl to the legal size of 70 mm cl. length-weight relationship calculations show the weight of these lobsters are about 100 and 350 g, correspondingly. in all experiments males had higher growth increments and grew faster than females. the survival rate of lobsters during rearing can be high. in the 2007 experiment 32 out of the initial 37 lobsters survived (86.5%), in 2009 13 from the initial 14 specimens survived (92.9%), and during the first 6 months of the 2010 experiment 39 from the initial 45 animals survived (86.7%). to estimate outputs of the aquarium experiments at mirbat and for the purpose of future actions in the development of lobster culture in oman the current literature on life cycle and biological parameters of the p. homarus population near the coast of oman of the arabian sea and data on cultivation of these lobsters in other countries of the indian ocean was researched. the first attempts to culture spiny lobsters began in 1898 with the experimental hatching and rearing of the lobster larvae (phyllosoma) in japan by hattori and oishi (1899). for more than 110 years many studies and practical investigations have been undertaken on different species of spiny lobsters in many countries, but in spite of numerous efforts success in the large-scale larval culture has not been achieved and is unlikely to be economically viable in the foreseeable future. a limited number of laboratories figure 5. food consumption during experimental rearing of the p. homarus: 1 – mean ingested food by lobster per day, 2 – daily food ration (%). month 40 balkhair et al. 41 experimental rearing of spiny lobster in land-based tanks homarus (i.e., from 80-100 g) cultured in cages and fed with trash fish show high survival (about 75%). after 5-8 months, they can be harvested at the marketable size of 150–300 g (vijayakumaran and radhakrishnan, 1984; vijayakumaran et al. 2009; priyambodo and sarifin, 2009; rao et al., 2010). the size of sampled lobsters in al-wusta and dhofar region of the sultanate oman in 2003–2007 (24,060 individuals) ranged between 22.6 and 127.7 mm cl (al-marzouqi et al., 2009) and weight between 15 to 1350 g. based on von bertalanffy growth parameters (cl inf = 128.9 mm, k = 0.33 and t 0 = -0.35) estimated by al-marzouqi et al. (2007) we calculated the age of the smallest juvenile lobsters (22 mm cl) in the catches as 2.5 months. the percent of juvenile lobsters (<40 mm) in catches is insignificant, the size of sub-adult lobsters in traps is usually more than 45 mm cl weighing more 100 g. this corresponds with the initial size of lobsters used in our experiment in 2010 (45.3 mm cl, 118.9 g). estimated age of these individuals according to the von bertalanffy parameters mentioned above was about 1 year. according to al-marzouqi et al. (2007) p. homarus reaches a maximum size at the age of 8-10 years. during 11 months of rearing in our tanks the lobster size increased to 66.0 mm and 304.0 g. calculations using the von bertalanffy equation (al-marzouqi et al., 2007) showed that the age of lobsters at 70 mm cl is 2.02 years. therefore, it needs approximately one year for p. homarus growing in captivity in oman from initial sub-adults of 40-45 mm cl and weight of about 100 g to reach a legal size of 70 mm cl and weight of about 350 g. according to estimates from al-marzouqi et al. (2007) the lobsters reach the length at first maturity of 65.7 mm cl at the age of approximately two years, so the targeted growout period in captivity (about one year) is appropriate to obtain mature females in oman. in our 2010 experiment weight increments of the p. homarus were 0.55 g.day-1 with sgr of 0.28%. that is low in comparison with data reported from india and indonesia where growth rates were 0.75-0.85 g.day-1 and sgr 0.50-0.58% (kaleemur et al., 1997; radhakrishnan and vijayakumaran, 1990; rao et al., 2010; srikrishnadhas et al., 1983). possibly, the slower growth rate of lobsters in captivity in indoor tanks at mirbat can be attributed to low water temperature (<20oc) during the summer time and isufficient food. nevertheless the present study demonstrated the possibility of the development of lobster culture in oman. conclusion lobsters are a very important natural and economic resources in oman. currently, stock recovery is a serious problem that requires not only good conservation measures, but also the development of their artificial cultivation. it is known that young lobsters have a very high mortality rate in nature (z = 2.07). (al-marzouqi et al. (2007), calculated values show that just 13% of lobsters may survive during the second year after settling on the sea bed. on the contrary, our data combined with current literature data show that in captivity in tanks and sea cages survival rates can be significantly higher (about 70-75%). this suggests that farming of lobsters not only can improve the commercial production but could also help in enhancing the natural stock. the current fishery management in oman banned the exploitation of juvenile lobsters. but in the case of successful results of the experimental lobster growing in sea cages it will be possible to recommend that one omani company organizes the collection of sub-adult lobsters and their fattening in sea cages (from october to june) for commercial production. in addition they will release all reared egg-bearing females to the sea to facilitate the restoration natural stocks. results of many investigations indicate that sea cage culture is a biologically feasible way of growing juvenile lobsters to market size. in order to develop the possibility of lobster culture in oman we propose the continuation of research in floating sea cages. acknowledgments we are grateful to h.e. dr. hamed al-oufi, the undersecretary of ministry of agriculture and fisheries wealth and dr. saoud al-habsi, the director general of the fisheries research, for the opportunity provided to carry-out the aquarium component of the lobster project and financial support. we are also thankful to mr. salem al-ghassani, formerly director of fisheries research center-salalah, for his kind support in fulfilling this project. we express our thanks to the technical staff at (mau) mr. basheer and mr. salem khoom who participated in laboratory work related to the project. references al-abdessalaam, t.z.s. 1995. marine species of the sultanate oman: an identification guide. ministry of aquaculture and fisheries, marine science and fisheries centre, sultanate of oman. muscat printing press. 412pp. al-abdulsalaam, t.z. 1989. effects of exploitation on life history characteristics of spiny lobster populations (panulirus homarus) off oman. m.sc. thesis, oregon state university, corvallis, oregon, usa. al-marzouqi, a., a. al-nahdi, n. jayabalan, and j.c. groeneveld. 2007. an assessment of the spiny lobster panulirus homarus fishery in oman – another decline in the western indian ocean? western indian ocean journal of marine sciences 6:159–174. al-marzouqi, a., n. jayabalan, a. al-nahdi, and a. al-hosni. 2007. lobster fisheries in the sultanate of oman project phase i (2002-2005). ministry of fisheries wealth, marine science and fisheries centre. 50pp. al marzouqi, a., j.c. groeneveld, a. al-nahdi, n. jayabalan, and a. al-hosni. 2009. lobster fisheries 42 balkhair et al. 43 experimental rearing of spiny lobster in land-based tanks in the sultanate of oman project phase ii (20052008). ministry of fisheries wealth, marine science and fisheries centre. 90pp. anonymous. 2006. fisheries statistics book (2005) for the sultanate of oman. directorate of general planning and investment promotion. statistics and information department. ministry of agriculture and fisheries, muscat, 240pp. anonymous. 2010. fisheries statistics book (2009) for the sultanate of oman. directorate of general planning and investment promotion. statistics and information department. ministry of agriculture and fisheries, muscat, 209pp. chittleborough, r.g. 1974. review of prospects of rearing rock lobsters. australian fisheries 33:4-8. hart, p. and r. van barneveld. 2000. rock lobster enhancement and aquaculture in australia. in: 2000 australian aquaculture yearbook, p. shelley (editor), 39-41. national aquaculture council, executive media pty ltd, melbourne. hattori, t. and y. oishi. 1899. hatching experiment on ise lobster. report of the imperial fisheries institute 1: 76-132. hung, l.v. and l.a. tuan. 2009. lobster seacage culture in vietnam. in: spiny lobster aquaculture in the asia–pacific region, k.c. williams (editor), 10-17. proceedings of an international symposium, nha trang, vietnam, 9–10 december 2008. aciar proceedings 132, canberra. james, p. 2007. lobsters do well in sea cages: spiny lobster on-growing in new zealand. bulletin of fisheries research 20:69-71. jeffs, a.g. and p. james. 2001. sea-cage culture of the spiny lobster jasus edwardsii in new zealand. marine and freshwater research 52:1419-1424. kaleemur, r.m.d., m.t.l. joseph, and b. srikrishnadhas. 1997. growth performance of spiny lobster panulirus homarus (linnaeus) under mass rearing. journal of aquaculture in the tropics 12:243-253. kittaka, j. 1994. culture of phyllosomas of spiny lobster and its application to studies of larval recruitment and aquaculture. crustaceana 66:258-270. kittaka, j. and k. kimura. 1989. culture of the japanese spiny lobster panulirus japonicus from egg to juvenile stage. nippon suisan gakkaishi 55:963-970. kulmiye a.j. and k.m. mavuti. 2005. growth and moulting of captive panulirus homarus in kenya, western indian ocean. new zealand journal of marine and freshwater research 39:539–549. mohan, r. 1997. size structure and reproductive variation of the spiny lobster panulirus homarus over a relatively small geographic range along the dhofar coast in the sultanate of oman. marine and freshwater research 48:1085–1091. phillips, e.s., j.s. cobb, and r.w. george. 1980. general biology. in: the biology and management of lobster, vol. 1., j.s. cobb and e.s. phillips (editors), 1-82. press,new york. priyambodo, b. and sarifin. 2009. lobster aquaculture industry in eastern indonesia: present status and prospects. in: proceedings of an international symposium spiny lobster aquaculture in the asia– pacific region, kevin c. williams (editor), 36-45, nha trang, vietnam, 9–10 december 2008. aciar proceedings 132, canberra. radhakrishnan, e.v. 1994. commercial prospects for farming spiny lobsters. aquaculture towards the 21st century. in: proceedings of the infofish aquatech 94 conference, 96-102. colombo, sri lanka, 27-31 august 1994. radhakrishnan, e.v. 2004. prospects for grow-out of the spiny lobster, panulirus homarus in indoor farming system. in: program and abstracts, 7th international conference and workshop on lobster biology and management, hobart, tasmania, 8-13 february 2004. radhakrishnan, e.v. and m. vijayakumaran. 1990. an assessment of potential of spiny lobster culture in india. cmfri bulletin 44:416-427. rao g.s., r.m. george, m.k. anil, k.n. saleela, s. jasmine, h.j. kingsly, and g.h. rao. 2010. cage culture of the spiny lobster panulirus homarus (linnaeus) at vizhinjam, trivandrum along the south-west coast of india. indian journal of fisheries 57:23-29. ritar, a.j. 2001. the experimental culture of phyllosoma larvae of southern rock lobster (jasus edwardsii) in a flow-through. aquacultural engineering 24:149-156. ritar, a.j., c.w. thomas, and a.r. beech. 2002. feeding artemia and shellfish to phyllosoma larvae of southern rock lobster (jasus edwardsii). aquaculture 212: 183–94. ritar, a.j., g.g. smith, g.a. dunstan, m.r. brown, and p.r. hart. 2003. artemia prey size and mode of presentation: effects on the survival and growth of phyllosoma larvae of southern rock lobster (jasus edwardsii). aquaculture international 11: 163-180. serfling, a.a. and r.f. ford. 1975. ecological studies of the peurulus larvae stages of the california spring lobster panulirus interruptus. fishery bulletin 73:360377. srikrishnadhas, b.v., v. sunderraj, and m.d. kuthalingam. 1983. cage culture of spiny lobster panulirus homarus. in: proceedings of the national seminar on cage and pen culture, pp. 103-106, fisheries college and research institute, tuticorin, india. vijayakumaran, m. and e.v. radhakrishnan. 1984. effect of eyestalk ablation in the spiny lobster panulirus homarus (linnaeus): 2. on food intake and conversion. indian journal of fisheries 31:148-155. vijayakumaran, m., r. venkatesan, t.s. murugan, t.s. kumar, d.k. jha, m.s. remany, j.m.l. thilakam, s.s. jahan, g. dharani, s. kathiroli, and k. selvan. 2009. farming of the spiny lobsters in sea cages in india. 42 balkhair et al. 43 experimental rearing of spiny lobster in land-based tanks new zealand journal of marine and freshwater research 43:623-634. yamakawa, t., m. nishimura, h. matsuda, a. tsujigado, and n. kamiya. 1989. complete larval rearing of the japanese spiny lobster panulirus japonicus. nippon suisan gakkaishi 55:745. zar, j.h. 1984. biostatistical analysis. englewood cliffs, n.j: prentice-hall inc. 620pp. received: february 12, 2012 accepted: may 30, 2012 sultan qaboos university journal for scientific research agricultural and marine sciences, 11 s.i., 71-76 (2006) ©2006 sultan qaboos university 71 water metering pilot project: a case study of water demand management in the sultanate of oman zaher khalid al suleimani* and bushra khalfan al wohaibi water resources affairs, ministry of regional municipalities, environment and water resources, p.o. box 461, pc. 112, ruwi, sultanate of oman abstract: the sultanate of oman is experiencing increased pressure on its groundwater resources. this is mainly due to agricultural enterprises, which consume about 92 % of national water resources, as well as an upsurge in industrial, commercial and domestic water use. the ever-growing population, diversification of economic activities and the ensuing rise in national prosperity have meant an increasing demand for water. this has resulted in a marked depletion of groundwater supplies, intrusion of seawater, and deterioration of ground water quality in the case of the al batinah region. a scientific and effective water demand management strategy for the sultanate is therefore needed. accordingly, the ministry of regional municipalities, environment and water resources (mrmewr) have conducted several studies related to water demand management in the agricultural, industrial and domestic sectors. one of these studies was the water metering pilot project (wmpp), initiated in 1994 with the objective of evaluating patterns of water use on a number of randomly selected farms in the southern al-batinah. the results obtained over a period of seven years confirm that water metering alone does not help reduce the quantity pumped. these findings have encouraged other advanced studies on water demand management in industrial, commercial, domestic and agriculture sectors in different areas of the sultanate. keywords: water meters, water abstraction, water quality. introduction the sultanate of oman is one of the countries that have scarce renewable water resources due to its location within the arid zone characterized by low rainfall and high summer temperatures. annual rainfall varies from 50 mm/yr, in central oman to 300 * corresponding author. e-mail: ddgwrw@mrmewr.gov.om تقییم تجربة تركیب عّدادات على اآلبار الزراعیة في سلطنة عمان زاھر خالد السلیماني وبشرى خلفان الوھیبي الخالصة: تعاني الموارد المائیة في السلطنة من تزاید الضغط علیھا بفعل النمو المطرد في أعداد السكان والتوسع الھائل في قطاع الزراعة الذي یستھلك حوالي 92% من مجمل الموارد المائیة في السلطنة، كما أن حرص الحكومة على سیاسة التنوع االقتصادي الرامیة إلى ازدھار السلطنة و الحفاظ على التنمیة المستدامة في البالد قد أسھمت إلى حد بعید في استنزاف الموارد المائیة الوطنیة. فتدھور جودة المیاه وخاصة في سھل الباطنة ال یشي فقط بدرجة التدھور في مخزون المیاه الجوفیة بل أیضا تشیر إلى الحاجة الماسة لوضع خطط فعالة إلدارة الطلب على المیاه مبنیة على أسس علمیة راسخة، من ھنا حرصت وزارة البلدیات اإلقلیمیة و البیئة وموارد المیاه على تنفیذ العدید من الدراسات المتعلقة بإدارة الطلب على المیاه في مختلف القطاعات: الزراعیة، الصناعیة،التجاریة والمنزلیة. ومن ھذه الدراسات، مشروع تركیب العدادات في منطقة جنوب الباطنة التي بدأت في عام 1994 بھدف تقییم أنماط استخدام المیاه في عدد من المزارع التي تم اختیارھا بشكل عشوائي في منطقة جنوب الباطنة، ولقد تم تقسیم المشروع إلى مرحلتین على مدى سبع سنوات، وفر فیھا المشروع كمیة ھائلة من البیانات المتعلقة بجودة المیاه ومعدالت الضخ باإلضافة إلى أنماط الفالحة وأنظمة الري. یتم من خالل ھذه الورقة استعراض نتائج مشروع تركیب العدادات مبینا دور ھذه النتائج في وضع ٍأسس لدراسات أخرى على إدارة الطلب على المیاه في القطاعات الصناعیة و التجاریة والمنزلیة،باإلضافة إلى دراسة توسیع تركیب العدادات لتشمل مناطق أخرى في السلطنة. al suleimani and al wohaibi 72 mm/yr in the mountain ranges, with an average of 100 mm, of which 80% is lost by evaporation. a further 5% drains off into the seas, leaving only about 15% for aquifer recharge. omani traditional agriculture has maintained an unstable balance between water resources and the various uses. furthermore, the rapid increase in population, expansions in economic activities since the renaissance, beginning from the 1970s, and the introduction of modern technology in well drilling, have added even more pressure on the situation. at present, renewable water resources in oman are overexploited and in some areas, particularly the al batinah coast, water abstraction far exceeds recharge rates. consequently, groundwater levels have declined and the resulting intrusion of seawater has led to the abandonment of several farms. this paper presents the highlights of a water metering pilot study that was conducted during the period 1994 2000 by the ministry of regional municipalities, environment and water resources for selected farms in the southern al batinah (mrmewr, 2000). the objectives were to evaluate water use patterns and relate them to previous studies on water demand management in agriculture, as well as to compare different types of water meters and their adaptability to omani conditions. research methodology selection of farms the farms were selected using well inventory maps and considering farm size, cropped area, types of crops, water quality and the number of wells in each farm. the farms selected were located in the lower catchments of wadi taww, al manumah and ma’awil, in wilayat barka in the southern al batinah. these areas were associated with deterioration in water and soil quality caused by over abstraction of water due to increasing agricultural activities. farmers were approached through letters to explain the objectives of the pilot project, after which they were administered with questionnaires to collect relevant information. the project was undertaken in two phases. the first phase started in march 1994, when one hundred and eleven water meters were installed on wells in 27 farms, covering a total area of 475.5 ha. the second phase started in 1996 and involved the installation of 315 meters on wells in 115 farms covering a total area of 1425.5 ha (table 1). a crop survey was conducted on each farm after the installation of the water meters. the total area was recorded as well as the area allocated to each crop in each farm. metering and monitoring activities helical vane type meters with nominal diameters (nd) of 50, 80 and 100 mm were supplied by four different manufacturers and installed on the selected farms. in 1997 a water meter-testing workshop was held in barka for the purposes of acquainting participants with procedures for the calibration and evaluation of the efficiency of the water meters installed in the farms. in order to examine its suitability for the climate of the area, each meter was calibrated, maintained and examined periodically. meters with 10% or more variation were subjected to thorough servicing, whereas defective ones were replaced. the cost of meter installation depends on the type of the meter, the diameter and the other equipment required for installation. for this project, most of the meters were of 3 inches diameter, and the cost of installation ranged between 250 and 280 omani rials (us$ 650750) per meter. different monitoring activities were conducted to collect data for evaluating the feasibility of this project. monthly water meter readings were taken and water quality was checked regularly by measuring the electrical conductivity, wherever possible. monitoring table 1. farms and meters in each phase. phase year no. farms no. wells no. meters remarks first 1994 27 110 111 one well with two meters second 1996 115 314 315 one well with two meters total 142 424 426 water metering pilot project: a case study of water demand management in the sultanate of oman 73 activities also included periodic surveys of cropping patterns and irrigation methods in each farm plot. in particular, data on uniformity of sprinkler and bubbler systems were collected from 41 farms in 1999. results and discussion crop survey results of the crop survey showed that the total area in the first phase (1994) was 475.44 ha for 27 farms, and the cropped area amounted to 400 ha, of which 25% was covered by grass, while palm trees represented 21% (table 2). winter vegetables covered 20% of the entire area, mixed trees accounted for 20%, while citrus and mango accounted for 11%. in the second phase (1996), 115 farms covering an area of 1,425 ha were studied. of the entire area, 905 ha were cultivated with the following proportion of crops and trees: grass (39%), palm trees (16%), vegetables (8%), mixed trees (14%) and citrus and mango (15%). in 1998, 142 farms with a total area of 1979.5 ha were studied in phases one and two. of the entire area, 1,207 ha or 61% of the total area was covered with vegetation. a breakdown of the cropping pattern shows that grass covered 35% of the area while palm trees covered 20%, vegetables accounted for 11%, mixed trees covered 17% and citrus and mango occupied 13%. in 2000 the final crop survey was conducted over 33 farms, of which 6 were from the first phase and 27 from the second phase. the total cropped area was 173.04 ha, with grass covering 30%, palm trees, 21%, vegetables 8%, mixed trees 16% of the area and citrus and mango covered 10%. water abstraction annual water abstraction in the 142 farms covered in the project varied from one year to another due to the changes in the size of the cropped area (table 3). it was observed that the lowest average abstraction rate per hectare occurred in 1994, during the first phase, with an average of 17,850 m3/ha/year. conversely, the maximum average abstraction rate took place in 2000 with an average of 24,220 m3/ha/year, and this increase was attributed to the expansion of the area cultivated with grass and alfalfa, covering 44 % of the total cropped area, as shown in the last column of table 2. irrigation systems modern irrigation was applied in 60% of the total cropped area (table 4). the irrigation methods table 2. crop survey. year 1994 1996 1998 2000 no. of farms 27 115 142 33 area/percentage ha % ha % ha % ha % alfalfa 10.50 3 76.06 8 54.18 4 24.36 14 dates 85.68 21 143.64 16 236.80 20 36.12 21 grass 99.54 25 356.58 39 418.32 35 52.50 30 citrus & mango 42.84 11 133.56 15 161.28 13 17.64 10 winter vegetables 81.06 20 68.46 8 136.90 11 13.86 8 mixed tree 79.38 20 126.42 14 199.90 17 28.14 16 total (ha) 400 905 1207.5 173.04 table 3. cropped area and average water abstraction per hectare. 1994 1996 1998 2000 water abstracted (m3) 712,811 18,804,561 24,733,562 4,191,066 cropped area (ha) 400 905.1 1207.5 173.04 average abstraction rate (m3/ha/year) 17,580 20,778 20,483 24,220 al suleimani and al wohaibi 74 included flooding, which was used in 39% of the cropped areas, and spray guns, used in 30% of the area. other methods were sprinklers, used in 17% of the area, bubblers applied in 7% of the area, and drip irrigation, which served 8% of the area. water requirements the average abstraction rate per cropped area is considered a good indicator of the efficiency of water use in agriculture, and water consumption per unit area is the index for measuring water loss. data obtained from the 1998 survey was used to calculate water losses, as it covered the largest number of farms. the water requirement for the farms was based on the studies conducted by the ministry of agriculture and fisheries (maf, 1995), and converted to the requirement per unit area by the assumption that every ha contains 250 palm trees or 386 trees (citrus and mango). the water abstraction was 24.7 mm3, with an abstraction rate of 20,481 m3/ha. comparisons indicated that 75 farms over-abstracted water, whereas 67 farms abstracted less than the crop water requirement and accounted for 37% of the total water abstraction. the total water over-abstraction was estimated to 17%. in 2000 the water requirements were estimated to 32.1 mm3, while the total water pumped, according to meter readings was 41.9 mm3 resulting in 30% water over-abstraction. the results obtained over a period of seven years (table 5) confirm that water metering alone does not help reduce the quantity pumped as over-abstraction ranged from 17 to 30 %. water quality over-abstraction caused a decrease in the water table and an increase of water salinity due to direct intrusion of sea water. the quality of water in 375 wells was monitored. by comparing the 2000 data with 1996 data, it was observed that 228, or 61% of the wells, suffered an increase in salinity by more than 20% compared with 1996. furthermore, it was observed that 86 wells (23%) suffered an increase in salinity ranging from 1 to 20 %. on the other hand, there were 61 wells (16%) which had a decrease in salinity, with 20 of them reducing salinity by as much as 20%. most of these wells are located in the recharge areas of the wadi alfulaij and wadi taw recharge dams. water meter performance the results of water meters performance tests indicated that irmaj meters recorded the highest accuracy level at 93%, while kent scored 89% (table 6). meinecke brand had an efficiency of 88%, and wolltex was 84% accurate. though they were not the most accurate, kent meters showed a better capability to adapt to climatic conditions and water quality with only 4% replacement compared to woltex, which recorded 15%, and meinecke with 26%. by far the most vulnerable was irmaj, with 60% replacement. the performance of water meters was affected by a variety of technical and environmental problems, such as, the inability of the meters to read more than 999999, the rusting of the screws due to their vulnerability to saline water, the damage of the impeller as a result of the accumulation of sand, and dirt due to the absence of filters. further studies in water demand management based on the findings of this pilot project, especially the observation of over-abstraction of water and the salinization phenomenon, the mrmewr launched four different demand management oriented studies. the aims of these studies was to assess the possible alternatives to control water demand rather than supply in the agricultural, industrial, commercial and domestic sectors. the following are brief descriptions of some of such studies. study on water demand management in the industrial and commercial sectors this study aimed primarily at industrial and commercial establishments like hotels, restaurants, private schools and private hospitals and other organizations that rely on groundwater. this study is meant to serve as a benchmark and reference for policy and decision-making as well as an evaluation tool for future water allocation and tariff options in the commercial and industrial sector. the study, which is table 4. area covered by different irrigation systems. irrigation system area (ha) % drip 238 8 bubbler 194 7 sprinkler 477 17 spray gun 852 30 flood 1114 38 total 2875 100 water metering pilot project: a case study of water demand management in the sultanate of oman 75 expected to last for a period of 16 months, commenced in august 2005 and should be completed by november 2006. technical and financial study on installing water meters on tube wells the aim of this study is to assess the technical and financial feasibility of installing water meters on tube wells throughout oman to control water abstraction, and assess the policy implications of such a mechanism. the project is expected to help policy makers have a better view in water resources management with detailed data for the allocation of groundwater resources, especially operational agricultural tube wells. the study commenced in august 2005 and is due in april 2006. on farm water demand management practices using water saving technologies and modern irrigation systems the focus of this study is to evaluate the efficiency of modern irrigation systems along with new control and management instruments, such as scheduling, applied for the prevention of water loss. the study commenced in august 2005 and should be completed by february 2007. pilot study for improving domestic water demand efficiency using water saving technologies this study aims at assessing the adaptability of water saving technologies in the omani setting. the study commenced in june 2005 and should be completed by may 2006. conclusions over the period 1994 2000 total water abstraction from a representative sample of metered wells exceeded the water requirements by 17 to 30 %. table 6. performance of different water meters. meter type reading accuracy (%) damaged (%) replaced (%) irmaj 93 57 60 kent 89 2 4 meinecke 88 5 26 wolltex 84 36 15 ta bl e 5. e st im at io n of w at er o ve rab st ra ct io n ab ov e th e re qu ir em en t. y ea r 19 94 19 96 19 98 20 00 n o. o f f ar m s 27 11 5 14 2 33 a bs tr ac ti on r eq ui re m en t a bs tr ac ti on r eq ui re m en t a bs tr ac ti on r eq ui re m en t a bs tr ac ti on r eq ui re m en t m m 3 7. 12 82 11 5. 59 79 42 18 .8 04 56 1 15 .5 01 49 2 24 .7 33 56 2 21 .1 72 67 9 4. 19 10 66 3. 21 47 62 c ro pp ed a re a (h a) 40 0 90 5 1, 20 7. 5 17 3 a ve ra ge . (m 3 /h a) 17 82 13 99 5 20 77 8. 52 17 12 9 20 48 3. 28 17 53 3 24 22 0. 2 18 57 9 % o ve r ab st ra ct io n 27 21 17 30 al suleimani and al wohaibi 76 fifty-three percent of the total number of farms were responsible for 63% of total abstraction, and were causing the problem of over-abstraction. this implies that not all farmers are overpumping. however, the 63% of those who are overpumping are causing damage to water resources of the whole community. salinity increased in 84% of the wells, with 61% recording more than 20% increase and another 23% experiencing an increase in salinity by 1 to 20%. these results clearly indicate that installing water meters does not solve the problem of over-abstraction, unless it is accompanied by other control measures. on the other hand, 16% of the monitored wells located on the recharge areas of wadi al fulaij dam recorded a decrease in salinity by as much as 20%. this shows the importance of dams in recharging aquifers. in regard to meter suitability, kent water meters proved to be the best among the four brands tested, in terms of accuracy of measurement of water, resistance to salinity and accumulation of sand and dirt due to the absence of filters and to harsh weather conditions. the water metering pilot project allowed estimation of overpumping in the agricultural sector and showed the need to undertake more advanced studies on water demand control and management. references mrmewr (ministry of regional municipalities, environmental and water resources). 2001. water metering pilot project data compilation report. directorate general of water resources management, mrmewr, sultanate of oman. pp. 10-83. maf (ministry of agriculture and fisheries). 1995. a guiding manual for water requirement for crops in the sultanate. ministry of agriculture and fisheries pp. 3-20. rout, r.s. 1995. social and economic aspects of water metering in the sultanate of oman. international conference on water resources management in arid countries, muscat, sultanate of oman, 12-16 march 1995. pp 25-30. research paper journal of agricultural and marine sciences vol. 20 (2015): 16-23 reveived 5 aug. 2014 accepted 19 feb 2015 *1 daniel rittschof ( ) duke university marine laboratory, beaufort nc 28516 usa. email: ritt@duke.edu. 2 department of pharmacy, national university of singapore, 18 science drive 4, singapore 117543. 3 tropical marine science institute, national university of singapore, 18 kent ridge road, singapore 119227. 4 department of biological sciences, marquette university, p.o. box 1881, milwaukee, wisconsin 53201-1881 usa. introduction biofouling is the accumulation of biological materi-als onto surfaces submerged in water. biofouling occurs at molecular, microbial and macro-organism levels and the different levels may either interact or occur independently of other levels. fouling of surfaces in marine environments is most complex and exemplifies a dynamic range of potential interactions (figure 1, clare et al., 1992). molecular fouling is often referred to as the conditioning film. every surface submerged in the ocean interacts with biological molecules and rapidly within seconds a conditioning film forms. conditioning films occur at the air/water interface, at the interface of currents and internal waves and whereever there is a physical boundary. films form virtually instantaneously. an example is the phenomenon called sublation in which air bubbles strip surface active organic molecules from water. conditioning films take on stable physical chemical characteristics after about 3 days. fouling and its next generation management: a perspective daniel rittschof 1*, christina chai 2, serena lay ming teo 3 and james s. maki 4 الرتاكم احليوي على األسطح املغمورة وإدارته املستقبلية: وجهة نظر دانيل ريتشوف1* وكريستينا تشاي2 وسريينا الي مينج تيو3 وجيمس ماكي4 abstract. the last 50 years of fouling research and management taught us that indiscriminate use of toxic approaches damages ecosystem services of estuaries and oceans critical to man’s existence. next generation environmentally benign management requires knowledge of the fouling process and an understanding of the consequences of different management options. an intermediate step may be additives that fit with existing business models and distribution systems, but that carry a much reduced environmental footprint. subsequently, the evolution of a next generation hull fouling management system with limited toxicity easy clean surfaces should replace or augment the existing commercial easy-release coatings. these new technologies require new business models and infrastructure. the path for a new commercial hull coating, from a concept to the actual product takes 25 to 35 years to complete. major challenges include fitting in with existing business models and systems and meeting regulations. leveraging on our experience in the development of additives as a case example, we offer a perspective on what the new fouling management systems might involve and discuss issues to be addressed as limited toxicity easy-clean coatings gain market share. as existing business cannot easily adapt to a different business model, evolution of new management solutions will require resources, a necessary long term perspective, and close working relationships between business and science to enable products in the global market. keywords: fouling management, foul release, low toxicity antifouling, ship coatings, aquaculture net coatings املســتخلص: علمتنا الـ50 ســنة األخرية يف جمال أحباث وإدارة الرتاكم احليوي على األســطح املغمورة أن االســتخدام العشــوائي لألســاليب الســامة تضر باخلدمــات البيئيــة ملصبــات األهنــار واحمليطــات، تلــك اخلدمــات األساســية لوجــود اإلنســان. إن اجليــل القــادم مــن اإلدارة الغــري ضــارة بالبيئــة يتطلــب معرفــة بعمليــة الرتاكــم احليــوي علــى األســطح املغمــورة، وفهمــا لتبعــات اخليــارات اإلداريــة املختلفــة. ميكــن أن تكــون املضافــات الصناعيــة، الــي تنســجم مــع منــاذج إدارة األعمــال ومــع أنظمــة التوزيــع وهلــا أثــر بيئــي منخفــض، خطــوة وســطية حنــو تلــك اإلدارة املســتقبلية. وتبعــا لذلــك ، فــإن تطويــر جيــل قــادم مــن نظــام إدارة عمليــة الرتاكــم علــى األســطح لبــدن الســفن، تكــون مستــه حمــدودة و لــه خاصيــة التنظيــف الســهل لألســطح، ســيحتم اســتبدال أو دعــم الطــاءات التجاريــة احلاليــة الســهلة اإلزالــه. هــذه التقنيــات اجلديــدة تتطلــب منــاذج وبنيــة حتتيــة جديــدة إلدارة األعمــال، كمــا أن الــدرب لتصنيــع طــاء جتــاري لبــدن الســفن، مــن مرحلــة التصــور إىل املنتــج احلقيقــي، ستســتغرق 25 إىل 35 عامــا. تشــمل التحديــات الرئيســية إنســجام النمــاذج واألنظمــة احلاليــة إلدارة األعمــال والتماشــي مــع القوانــن. اعتمــادا علــى خربتنــا يف تطويــر املضافــات كمثــال عملــي، نقــدم رؤيتنــا حــول مــا ستشــمله أنظمــة إدارة الرتاكــم احليــوي علــى األســطح املغمــورة، ونناقــش مســائل جيــب اإللتفــات إليهــا مــع زيــادة احلصــة الســوقية للطــاءات ذات الســمية احملــدودة و الســهلة التنظيــف. ومبــا أن إدارة األعمــال احلاليــة ال تســتطيع أن تتأقلــم بســهولة مــع منــوذج خمتلــف إلدارة األعمــال، فــإن تطويــر حلــول إداريــة جديــدة ســيتطلب مــوارد، ورؤيــة ســتكون بالضــرورة طويلــة األمــد، وعاقــات عمــل وثيقــة بــن املؤسســات التجاريــة والقطــاع العلمــي، حــى منكــن هــذه املنتجــات مــن التواجــد يف الســوق العامليــة. الكلمــات املفتاحيــة: إدارة الرتاكــم احليــوي علــى األســطح املغمــورة، ختليــص وإزالــة الرتاكــم احليــوي علــى األســطح املغمــورة ، املضــادات املنخفضــة الســمية للرتاكــم احليــوي علــى األســطح املغمــورة، طــاءات الســفن، طــاءات شــباك اإلســتزراع املائــي 17research article rittschof1, chai, teo, maki fouling by microbial organism is called microfouling. microfouling is broadly defined to include the diverse community of organisms, including bacteria, diatoms, fungus, cyanobacteria and other microbes which science is just beginning to discover (maki and mitchell, 2002; qian et al., 2007; dobretsov, 2010). microfouling attachment events are often relatively rapid, on the order of hours for firm attachment. attachment is based on the same kinds of chemistry as molecular fouling. however, the development and evolution of the microbial biofilm is a much slower process and may take hours to days. macrofouling is the term normally applied to multicellular mobile as well as sessile organisms visible to the naked eye (woods hole ocenaographic institution, 1952; turner, 1984; crisp, 1984; haderlie, 1984; clare et al., 1992). in practice, research focus has been mainly on the sessile organisms. the initial events in sessile macrofouler attachment occur in minutes, use specialized glues, and attachment is roughly as fast or faster than for microbial fouling. the extremes of the possible fouling scenarios are depicted in figure 1a and b. at one end of the spectrum is the classical sequential scheme that occurs in systems that have co-evolved. in this scenario molecular fouling occurs first followed by microfouling which is followed by algal and invertebrate larval fouling. in fouling communities the best example of this scenario is settlement of calcareous tube building worms like hydroides elegans (hadfield 2011, and references therein). in biofouling systems managed on man-made structures and especially in polluted and eutrophic harbors, this scenario is rare because the marofoulers are “weed species” that that are found in these harbors globally. many “weed species” were brought to harbours by ships so long ago that the origins of some globally common foulers are unknown. the other end of the macrofouling spectrum is depicted in the scenario of figure 1b. in this scenario there are two kinds of sinks, 1) surfaces and 2) aggregation of surface active molecules, polymers and propagules. marine snow (alldredge and silver 1988, alldredge and gotschalk 1990, passow et al., 2001) is an aggregate of bacteria, polymers and propagules that aggregate in the water column and precipitate as long strands. these strands stick to submerged surfaces as do individual microand macrofoulers. in this scenario what settles on the surface is what is most abundant and arrives on the surface first. as small molecules are vastly more common than microor macrofoulers, they would colonize a new surface first. subsequent events follow no particular order, and the space is filled largely on a first come first serve basis. this is the dominant scenario for most fouling communities in harbors around the world. once colonization of a newly submerged surface begins, the interactions can become bewilderingly complex. certain fouling organisms may inhibit the colonization by others (rittschof et al., 1992b). predation and sloughing create space for growth (sutherland and karlson 1977). longer lived superior competitive species eventually dominate unprotected surfaces. in most instances, the dominance occurs at least seasonally and often on the order of several years to decades (sutherland, 1977). surfaces coated with toxic substances, such as ablative fouling management systems generally support smaller amounts of fouling. well-functioning systems have a continuous film of microfouling and macrofouling cover from 5 to 20%. setting aside the morass of biological detail, the basic “take-home” messages are (rittschof, 2000): 1. all man-made surfaces submerged in water will foul. 2. fouling has enormous economic impacts contriba b figure 1. (a) successional fouling vs (b) stochastic fouling. 18 squ journal of agricultural and marine sciences, 2015, volume 19, issue 1 fouling and its next generation management: a perspective uting to an overall increase in operational costs. 3. fouling is biologically diverse and has passive and active living components. thus, multifunctional solutions including some form of toxin may be necessary for management of fouling. 4. fouling management needs to be minimally toxic because toxins are indiscriminate in their impact on ecosystem services essential to global health. commercial fouling management coatings management of surface fouling preceded environmental awareness by several thousand years (woods hole, 1956). as human populations increased and environments degraded, one consequence was terribly toxic fouling management solutions were discontinued in favor of coatings containing less environmentally damaging toxins. in recent history, the environmental impacts of some of the toxic additives (lead and organotins, for example) were replaced with toxins like copper and zinc. this “mix and kill” business model focuses on stable toxins like copper oxide that can be mixed easily into the paint are effective and have chemistry that is compatible with curing of the polymer film. business models for fouling management systems may be broadly grouped by looking at fouling management products. the first group of products focuses on release of biological active chemicals and consists of antifouling coatings of two major types: 1) resin/rosin coatings and 2) ablative copolymer coatings. the resin/ rosin coatings are thick spongy coatings that release toxic compounds, historically copper ions at a controlled rate. the ablative copolymer coatings are harder coatings that self polish by hydrolysis of the matrix and release toxic compounds as they polish. historically these coatings all released copper ions (wods hole oceanographic insitituiton, 1952, preiser et al., 1984). as environmental regulations restrict the amount of copper that can be released into the environment, the solution that is consistent with the presumed business models is to reduce copper release but retain efficacy of the coating by releasing a different broad spectrum toxin, usually one or more long lived organic biocides. the biocides of commercial choice are broad spectrum stable biocides that have chemistry compatible with curing of the polymer film. most of these biocides are stable, long lived organic biocides (half lives on the order of a year or more) that do not interfere with the cure of the antifouling film. (rittschof pers. observation) sometimes the literature refers to these long lived organic biocides as “booster biocides”. since these biocides are just as toxic or more toxic than copper ions, they are better considered as co-biocides. the toxic biocide fouling management business models originated over 50 years ago. over time due to massive increases in commercial shipping, the mix and kill model has become increasingly unsustainable because it is environmentally unsound (rittschof 2009 and references therein). as a result of environmental degeredation, governments are generating more strict regulations on toxin levels which force the businesses to find and incorporate new kinds of toxins to mix into paints. then, as the new additives gain market share the new toxins build up in the environment, environmental impacts become apparent, new regulations are imposed and the cycle repeats itself. it is clear to those in the industry that mix and kill will be replaced with a different strategy. another consequence of the mix and kill model is it impacts development of new products. in development, the performance of new fouling management is compared to a standard of an existing coating with desired fouling management performance, but with unacceptable environmental impacts. new approaches are eliminated if they do not perform as well as the environmentally unacceptable alternatives. thus, new business models and evaluations are needed before major changes in the industry can take place (rittschof, 2000). for most economies, governmental regulations (fig.  2) have a major impact on every aspect of the business of generating, shipping, applying and removal of antifouling coatings. on the other hand, basic and figure 2. government regulations. figure 3. intellectual property. 19research article rittschof1, chai, teo, maki applied research on fouling coatings development is the least regulated of these components. one of the most difficult and expensive transitions is the regulatory path that moves intellectual property, e.g., the development of new fouling management additives, to commercial availability. there are significant temporal and financial barriers to additive development (rittschof, 2000; 2009). in the late 1990s satisfying the regulatory process for the short lived additive, the isothiazalone sea nine 211 was reported to take over 10 years and cost approximately us $11,000,000. another fascinating aspect of coatings development is the development of intellectual property (ip). although an academic might think that government funded research is the source of intellectual property, the reality is that most of what becomes commercially valuable intellectual property is developed in-house by companies at various nodes of the product production and application chain (fig. 3). ip can be patented or become a trade secret. often companies keep their ip as trade secrets because patenting provides competitors with know-how and the information that facilitates the discovery of similar unprotected alternatives. the academic business model of protecting ip by patenting does not provide the advantage that trade secrets provide during research and development. for development of novel fouling management alternatives there are “top-down” and “bottom-up” projects. japan uses “top-down” projects to train researchers who then move into the private sector (i.e., the fusetani biofouling project). the european union ambio project (figure 4.) is an example of a “top-down” project that features government funded collaboration between academia and industry. this preplanned and phased project is transitioning to phase ii. since we are not involved directly in this project, we do not know the details of the relationships between the members of this group. the “bottom up” approach to development of novel additives and coatings is usually initiated by individual or small groups of academic researchers (fig. 5). when initiated, the “bottom-up” approach is focused on a more narrow research thread and concepts. the research program usually starts as a whitepaper or workshop. the work is not extensively preplanned but evolves as the research concept develops. with a “bottom up” process one starts with a small team that grows and changes as the program matures. the bottom-up approach is less structured and requires less initial outlay of funds. the research and team are organic in the sense that participants are recruited to the program as the research need is identified. this approach is attractive to academics because they are in control of the directions the research takes and can address issues like toxin half life from the beginning. it starts with hypothesis testing of a conceptual frame work with application as a long term goal. as an example, we document herewith an academic journey detailing our research efforts to generate an environmentally benign anti-fouling additive suitable for marine coatings. at this time of writing, we are 13 years into a journey that –based on the sea nine 211 experience may take 25 to 35 years for successful completion. in 1999, a white paper was raised presenting the case that pharmaceuticals provide a good source of potential antifoulant additives. the rationale was that one could interrupt the transduction cascade that initiates metamorphosis of macrofouling larvae to prevent settlement and adhesion (rittschof et al., 2003). the general logic stream was: evolution is real; invertebrates and vertebrates share biochemical and signaling pathways; pharmaceuticals that impact signaling pathways in vertebrates have potential for interrupting pathways that initiate metamorphosis of macrofouling organisms; pharmaceuticals have known chemical synthesis and properties as well as biochemical mechanisms of action and degradation pathways. the plan was to begin the research by choosing molecules that could be adapted to the mix and kill business model but that would interrupt macrofouling metamorphosis transduction cascades, but with the caveat that all components would have biological half lives of less than a month. our white paper acknowledged that some form of short lived toxin would be necessary to enable effective figure 4. multidisciplinary targeted government programs. figure 5. academic style inspired research. 20 squ journal of agricultural and marine sciences, 2015, volume 19, issue 1 fouling and its next generation management: a perspective delivery of other active ingredients across the biofilm. we postulated that there were pharmaceuticals that are low toxicity and high potency, thereby enabling them to fit into a business model modified from mix and kill, to mix and inhibit. in reality many of the animals on a hull would actually be killed. however, the advantage was we could minimize the impact on non-target species by employing biodegradable short lived compounds. up front the plan included the concept of therapeutic ratio (tr) the concentration required for toxicity vs. the concentration required for efficacy as well as biodegradation studies (rittschof et al., 1992). the tr is the ratio is the number generated by dividing the concentration required to kill fifty percent of the larvae by the concentration required to inhibit 50% of the larvae from settling. a tr of 1 is a toxic mechanism. a tr of 25,000 is a molecule that prevents settlement but does not kill larvae and was the kind of result we were looking for. our original upper cut-off for consideration was an ec50 < 25 ug/ml. the cut-off was chosen based upon calculations of levels of compounds that could be loaded into a coating that would result in a coating with a commercially viable lifetime. when sent to us funding agencies the white paper was not taken up. however, asia was booming economically and the maritime industry was moving their business to meet the demand from a huge expansion of ports in china. for the research we had in mind, we looked to singapore for necessary attributes: high investment in education and r&d, legal frameworks for technology protection, and physical presence of a vibrant pharmaceutical/chemicals and shipping industry. we, dan rittschof, duke university, james s. maki from marquette university and serena teo at the tropical marine science institute of the national university of singapore developed a white paper. dr. teo organized a workshop in singapore around that whitepaper and this resulted in several agencies expressing interest. subsequently, the agency for science, technology and research (a*star) in singapore funded the initial work. the tmsi team began as a team of planners/researchers (teo, maki and rittschof ) two post-doctoral fellows and two technicians. the program began with biofouling bioassays and pharmaceuticals. the laboratory and field bioassays were fast, highly quantitative and designed for microgram amounts of material. we started with a sense of humor. everyone brought in samples of the pharmaceuticals they had in their refrigerators. we could do the research and generate the data we needed with less than 500 micrograms (<< than one pill) of any pharmaceutical. we subjected each pharmaceutical to microbial and barnacle bioassays. in short order we categorized the drugs by their vertebrate mode of action, effectiveness, toxicity, water solubility and therapeutic ratio. in retrospect, this was a good idea because as time passes and techniques of metabalomics and proteomics become more sensitive, an abundance of systems that were first described in vertebrates are represented in invertebrates. many common pharmaceuticals are extremely potent at interrupting larval barnacle settlement. we tested 20 compounds with 8 known primary mechanisms of action in vertebrates. we found compounds effective at nanogram per ml concentrations and with therapeutic ratios from less than one (highly toxic) to over 1250 minimally toxic, but effective (rittschof et al., 2003). an ec50 < 40 ng/ml with an lc50 > 25 ug/ml was an exciting experimental result. our team generated similar data for over 20 strains of marine bacteria (chong et al., 2010). we found compounds that were bactericidal, bacteriostatic and that inhibited bacterial adhesion. multiple functions of biologically active molecules are the rule rather than the exception. from these initial studies, we chose to focus on a pharmaceutical which is and opiod e2 receptor agonist in vertebrates. most travelers know the pharmaceutical as imodium®. a glance at the structure and knowledge of how the drug works in humans is sufficient to begin the conversation about our next set of challenges (fig. 7). anyone who has taken imodium® is aware of two things 1) the drug works quickly; 2) the drug works for a relatively long time. these features are great. they support the observation that the drug is highly potent and stable. although stability is great for a mix and kill business plan, this drug is too stable for large scale use in the environment, especially if the commercial product gained market share. the result could be disastrous for the environment and would definitely cause huge discomfort to many environmental scientists, as has been demonstrated by compounds such as irgarol which is a photosystem ii inhibitor, and other organic toxins with half lives longer than 3 months. our research led to new targets: how to simplify and de-engineer molecule so it would still be effective, but it would break down. a new partnership was thus formed: with synthetic chemists in the a*star institute, institute of chemical engineering sciences (ices) interested drug design. figure 6. overview of testing methods . 21research article rittschof1, chai, teo, maki this group included synthetic and polymer chemistry expertise. the challenge was in bridging the gap between chemistry and biology. we took advantage of knowledge gained in a qsar study conducted by pettis et al., (1989) with biologically active peptides. in that study it was discovered that simple alkyl chains could be used to replace rings. this is important because rings have many other biological activities and break down slowly. from the earlier drug screening we identified imodium® (fig. 7-1) as the most promising starting point. however, the molecule is remarkably large, endowed with complex resonance and likely to generate a bewildering array of biologically active components (pharmacophores) as it breaks down. we decided to look for a smaller less stable pharmacophore with the biological activity we wanted. we divided the molecule approximately in half and found that both halves were biologically active. when we looked at the halves, we made the decision to see if the left hand side of the molecule on figure 7 (1) could be modified because it resembled part of a peptide. based on previous qsar experience with the peptide receptor (pettis et al., 1989) and with our talented synthetic chemists a series of molecules that substituted 4 carbon chains for the two refractory rings. we incorporated the one amide nitrogen we kept into a ring and found that was an excellent pharmacophore. we called the molecule on figure 7 (2) the “two legged man”. it had substantial biological activity, was easy to synthesize and it became the center of another patent disclosure. these new discoveries enabled us to gain more funding and continue to grow our team. we increased the involvement of polymer chemists, as the new challenge was in finding ways to deliver our biologically active molecules from conventional antifouling coatings such as the zinc acrylate self polishing coating (fig. 8). looking ahead to future easy release coatings we also began to work with a polydimethyl siloxane film. we began the process of finding ways to deliver pharmacophores in a curable matrix. the simplest way forward was to generate a low solubility powder that could be mixed into the coating. another attractive option was to attach pharmacophores to particles which could be mixed into coatings (fig. 9). part of this approach was adding a handle onto the molecules to enable attachment or to enable generation of a block for a polymer or copolymer. bioassays guided the chemistry as we needed modifications that did not destroy the desired biological activity. scientific progress is double edged sword. whereas academic pursuits favor the dissemination of information, business models inevitably involve intellectual property (ip) issues. in order for successful commercialization, ip must be protected in order for a company to be interested. given the organic nature of the bottom up research, ip ownership issues were not clearly defined at the onset as partnerships changed and the research evolved. a consequence is a variable number of (fundfigure 7. deengineering to an active pharmacophore. figure 8. the next program phase 22 squ journal of agricultural and marine sciences, 2015, volume 19, issue 1 fouling and its next generation management: a perspective ing) agencies had rights to the technology, resulting in patent ownership which was complex. most agencies do not have an understanding of a development process that often spanns 10 to 15 years to commercialization. deliverables were considered only within the confines of the specific project on hand. as such, research progress was stalled and research teams compromised, while intellectual property issues were negotiated. it would appear then that the first challenge, which seems a deviation from the path to productivity, is to sort out the ip. as researchers are interested in going forward with development and had immediate goals of a fun job, they routinely decline or sell their right to the property. this suggests that the progress of technology development may lie out of the hands of researchers and in the hands of ip professionals, lawyers and administrators. but, unhappily for project progress, none of these groups are familiar with product development. as a consequence, there remain conflicting perspectives. in addition to the formidable challenge of ip, commercialization of environment technologies must meet necessary regulatory requirements that demand once again, scientific data (rittschof, 2000). given the potential variety of inter-related technology that may arise out of any given patent, these data requirements will vary from sector to sector, and between regions. thus, it appears that sustainable environment research today demands a new integrated research-business model that embraces multiple cross-disciplinary conversations and elements throughout the product life cycle (fig. 10). such a model is necessary to expedite technology development as risks for investors increase exponentially over time. on both fronts we have hope. the world is changing very quickly with respect to globalization and fouling management goals. this is especially true due to continued growth of human populations. there is increasing understanding of the importance of marine products in feeding the world. with the global crash of natural harvest fisheries aquaculture is increasingly important. combined with climate change and sea level rise societal understanding that biologically viable coastal oceans are central to the future of the planet has improved. one tenet of that understanding is toxic inputs must be reduced. these societal pressures will accelerate change and provide opportunities to develop alternative approaches. figure 8 depicts the next phase of our program. we believe our children will benefit from our efforts. references alldredge, a.l., and m.w. silver. 1988. characteristics, dynamics and significance of marine snow. progress in oceanography 20: 41-82 alldredge, a.l., and c.c. gotschalk. 1990. the relative figure 9. creating environmentally benign biologically active small molecules. figure 10. the existing pathway for r&d places the initial research at a distance from environment policy. such a model is not optimal for the development of environment benign technologies as a first selective step ranks technologies by efficacy alone, thereby eliminating benefits from optimization of candidates that can meet regulatory requirements. an improved holistic development model would include multiple interactions between different stakeholders to facilitate faster evolution of the technology. 23research article rittschof1, chai, teo, maki contribution of marine snow of different origins to biological processes in coastal waters. continental shelf research 10: 41-58. choong, a.m.f., j.s. maki, j.t.b. ikhwan, c-l chen, d. rittschof, and sl-m teo. 2010. pharmaceuticals as antifoulants: inhibition of growth and effects on adhesion of marine bacteria. pp 221-246. in, j chan & s wong,eds, biofouling: types, impact and anti-fouling, nova science publishers, inc. clare, a.s., d. rittschof, d.j. gerhart, and j.s. maki. 1992. molecular approaches to nontoxic antifouling. invertebrate reproduction and development 22: 6776. crisp, d.j., 1984. overview of research on marine invertebrate larvae. 1940-1980. in: marine biodeterioration an interdisciplinary study. eds. j.d. costlow and r.c. tipper. naval institute press pp 103-125. dobretsov, s. 2010. marine biofilms. . in: s. dürr and j.c. thomason, eds., biofouling. wiley-blackwell, oxford. pp 123-136. hadfield, m.g. 2011. biofilms and marine invertebrate larvae: what bacteria produce that larvae use to choose settlement sites. annual review of marine science 3: 453-470. haderlie, e.c. 1984. a brief overview of the effects of macrofouling. in: marine biodeterioration an interdisciplinary study. eds. j.d. costlow and r.c. tipper. naval institute press pp 163-166. maki, j.s., and r. mitchell. 2002. biofouling in the marine environment. pp 610-619. in: g. bitton, ed., encyclopedia of environmental microbiology. john wiley & sons, new york. passow, u., r.f. shipe, a. murray, d.k. pak, m.a. brzezinski, and a.l. alldredge. 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and its prevention. annapolis, u.s. naval institute. agricultural and marine sciences, 14:35-40 (2009) ©2009 sultan qaboos university 35 ___________________________________________ *corresponding author. e-mail: hemkot@squ.edu.om transport modeling analysis to test the efficiency of fish markets in oman khamis s. al-abri, hemesiri kotagama*, andrew palfreman and houcine boughanmi department of natural resource economics college of agricultural and marine sciences, sultan qaboos university p.o. box 34, al khod 123, sultanate of oman abstract: oman’s fish exports have shown an increasing trend while supplies to the domestic market have declined, despite increased domestic demand caused by population growth and income. this study hypothesized that declining fish supplies to domestic markets were due to inefficiency of the transport function of the fish marketing system in oman. the hypothesis was tested by comparing the observed prices of several fish species at several markets with optimal prices. the optimal prices were estimated by the dual of a fish transport costminimizing linear programming model. primary data on market prices and transportation costs and quantities transported were gathered through a survey of a sample of fish transporters. the quantity demanded at market sites was estimated using secondary data. the analysis indicated that the differences between the observed prices and the estimated optimal prices were not significantly different showing that the transport function of fish markets in oman is efficient. this implies that the increasing trend of fish exports vis-à-vis the decreasing trend of supplies to domestic markets is rational and will continue. this may not be considered to be equitable but it is efficient and may have long-term implications for national food security and have an adverse impact on the nutritional and health status of the rural poor population. policy makers may have to recognize the trade off between the efficiency and equity implications of the fish markets in oman and make policy decisions accordingly in order to ensure national food security. keywords: oman, fish markets, transport model, prices, efficiency and equity. introduction the marketing component of the fisheries sector in oman is changing rapidly from a traditional system restricted to meeting domestic market requirements to a more modern pattern supplying regional and global export markets. such changes, as evident in other countries, have had beneficial as well as adverse socio-economic effects (bush, 2004). in oman, along with the growth of exports of fishery products, the availability of fish in the domestic market has declined despite the increase in population and per capita income. bush (2004), quoting international center for living aquatic resource management (1999), suggests that the interplay of domestic needs and international trade will increasingly make fish a politically sensitive commodity. given the bulkiness and perishability of fish, and particularly in oman because the fish landing sites and domestic markets are geographically widely distributed, the efficiency of fish transportation is an important factor affecting the share of fish available for domestic consumption. this paper presents a quantitative assessment of the efficiency of fish transport in oman to test if the distribution of fish between domestic and export markets is efficient. the study hypothesized that the domestic demand العمانیة األسماك أسواق كفاءة إلختبار النقل نماذج تحلیل البوغانمي وحسین بالفيرمان وأندرو كوتقاما* وھمسیري العبري خمیس ھده فرضیة والدخل. السكان لنمو نتیجة المحلي الطلب ارتفاع بالرغم من المحلیة في األسواق انخفض العرض بینما تصاعدیا اتجاھا األسماك العمانیة صادرات الخالصة: أظھرت السوق أسعار وذلك بمقارنة ھده الفرضیة بتحلیل الدراسة قامت عمان. في األسماك تسویق منظومة في نتیجة لعدم كفاءة النقل جاء لألسماك المحلي العرض انخفاض ھي أن الدراسة وكلفة النقل لألسعار المعلومات األولیة جمعت األسماك. نقل كلفة لتقلیل الخطیة البرمجة نموذج طریقة باستعمال المثلى األسعار حددت أسعارھا المثلى. مع أنواع األسماك من للعدید مھمة غیر المثلى واألسعار أسعار السوق بین الفرق أن النتائج أظھرت ثانویة. معلومات باستعمال األسماك على الطلب حدد األسماك بینما لناقلي طریق استبیان عن األسماك وكمیات ظاھرة عقالنیة ھي المحلي) للعرض تنازلي اتجاه من یقابلھ (وما للصادرات االتجاه التصاعدي أن دلك من ویستنتج كفئة. تعتبر العمانیة األسواق في النقل مھمة أن مما یدل إحصائیا أصحاب على یجب الضعیف. الدخل ذوي الریف لسكان الغذائي والوضع الغذائي باألمن تتعلق المدى طویلة تأثیرات عنھا ینتج فقد الظاھرة ھده كفاءة من وبالرغم تتواصل. وسوف الغذائي. األمن وذلك لتحقیق أسواق األسماك االقتصادیة في والكفاءة العدل معیار بین یوفقوا أن القرار والعدالة. الكفاءة االسعار ، ، النقل نماذج ، السمك أسواق ، عمان مفتاحیة: كلمات 36 al-abri and others 37 transport modeling analysis to test the efficiency of fish markets in oman for fish in oman is under-supplied vis-à-vis over-supplied to export markets due to inefficiency of the transportation function of oman’s fish market, and concludes by rejecting the hypothesis. the paper is in four sections. the first section presents a brief summary of the fisheries sector and fish markets in oman. the second section notes research literature and the third outlines the analytical method. the fourth section presents and interprets the results of the analysis. fisheries sector and markets in oman the fisheries sector has contributed to about 0.6% of the gross domestic product and comprised about 1.2% of the non-oil sector of oman in 2005 (ministry of national economy, 2006). in spite of the small proportionate contribution of the sector to the national economy, fisheries activities have the potential to be a sustainable source of income compared with other nonrenewable natural resources, such as oil and natural gas. furthermore, fisheries activities provide full time or part time jobs for 20,870 fishermen and 3,250 persons working in fish transportation activities in oman. many of these live in rural areas and are relatively poor. moreover, fisheries activities have been intimately associated with the traditional indigenous heritage and culture of oman. over the years (1996 to 2004), fish exports from oman have greatly increased. this is despite the increase in domestic demand for fish, resulting from population growth and rising per capita income in the sultanate (omezzine et al., 2003). as is evident in figure 1, during the period 2000 to 2004, the total fish landed in oman has increased by 29% and exports have increased by 83%. however, during the same period fish available to the domestic market has decreased by 12%. the trend of decreasing availability of fresh fish in the domestic market may cause concerns among the domestic consumers and in the long run may have adverse implications for the nutritional status and health of the rural poor. this study investigated if the above trend is due to inefficiency of the transport function of the fish market. theory and literature spatial market efficiency can be assessed by examining trade volumes, prices or both. each measurement has important shortcomings in isolation from the other. assessment based on trade volume measurement cannot establish whether spatial equilibrium conditions are reached. assessment based on price data alone does not reveal information about the optimal trading volumes. al abri (2008) analyzed the efficiency of fish transport in oman using both measurements of prices and trade volumes. this paper restricts its analysis of fish market efficiency to price data, for sake of brevity. transportation theory and modeling examines the optimal transportation of commodities in markets. the transportation problem can be identified as a network flow problem. it is generalized as a network of a set of m supply nodes, a set of n demand nodes, and a set of arcs connecting them. each supply node si has a fixed amount si of a commodity, which it can supply. each demand node dj has a fixed demand dj for that commodity, and for each arc (i,j) connecting supply node si to demand node dj there is an associated cost per unit flow cij. the model is solved by minimizing cij in order to determine the optimal allocation of product from supply nodes to demand nodes. although often referred to as the transportation model, it can be adapted to simulate the operation of a competitive market. the dual of a transport cost minimization model enables the estimation of competitive equilibrium market prices, given the cost of transportation, and supply and demand constraints (dorfman, et. al., 1958). thie (1988) provides comprehensive guidance on the application of linear programming in modeling transportations problems. transport modeling using linear programming has been extensively used in both, empirical academic research and in practical business management as exemplified by smith et al. (2007). however empirical application of transport modeling for the fisheries markets is scanty. an example is a study by borisova et al. (2003). the study examined the potential to increase aquaculture producer and processor profits through improvements in transport management. the study determined the optimal markets and shipment patterns using an integer linear programming model. few studies investigating the structure and performance of fish markets in oman have been done in recent years. omezzine (1996) reported that fish transporters preferred selling in export markets despite lower prices than those received in domestic markets. among many factors that explain such behavior is the ability to sell large amounts of fish particularly in dubai. al jabri (1999) analyzed the degree of market integration within omani fish markets. the study concluded that the omani fish market was not a perfectly competitive market. a similar study (maf, 2002), using the same methodology, has confirmed al jabri’s (1999) conclusion. omezzine et al. (2003) highlighted the figure1. fish landed, exported and domestically marketed. source: maf (2005). 36 al-abri and others 37 transport modeling analysis to test the efficiency of fish markets in oman importance of providing market information of potential demand and prices etc, to improve the transportation function of fish markets in oman. methodology in order to test the hypothesis that the transport function of the fisheries market in oman is inefficient, the study compared the observed prices of several fish species at different markets with optimal prices. the optimal market prices were estimated from the dual of fish transport costminimizing linear programming model. this study was based on the transporting of fresh fish between the landing sites and domestic and export markets by truckers. a purposive sample to best represent fish landing sites and markets in oman was obtained, in consultation with researchers and experts on fisheries sector. the selected fish landing sites were; masirah, mahoot, jalan and sohar and the fish market sites were the domestic markets of nizwa, ibri, and seeb. the export market was dubai. figure 2 shows the transport routes followed by truckers from landing sites to markets. the four fish landing sites of the sample represented 21% of total fish landed by traditional fishermen, 35% of fish exports and 54% of fish available for the local market (maf, 2003 and authors’ estimates). the three domestic markets of the sample represented 17% of oman’s population and 9.5% of fish consumption in oman (mne, 2003). a sample consisting of 60 truckers was interviewed using a structured questionnaire. this sample represented about 2% of the trucker population (3250 truckers) in oman. the fish transported by the sample of truckers during the study period was 7255 tons, consisting of kingfish, 29% (scomberomorur commerson), sardine, 55% (sardinella longiceps), long tail tuna, 9% (thunnus tonggol) and scavenger, 7% (lethrinus nebulosus). the analysis explained in detail in this paper is for kingfish. the results of a similar analysis for sardines and a composite of fish are presented. the transportation model the primal of the transport cost-minimizing model that was used in the study is given below. minimize: tc = σi σj cij * xij (1) constrained to: σj xij ≤ si (2) σi xij ≥ dj (3) xij ≥ 0 (4) where: tc = total cost from transportation of fish from all landing sites to all markets. cij = cost per ton (or/ ton) of fish transported form i th landing site to jth market. xij = tons of fish transported from i th landing site to jth market. si = quantity (tons) of fish supplied from i th landing site. dj = quantity (tons) of fish demanded at j th market. the dual of above primal transport cost minimization model is as follows: maximize: s = dj * vj si * ui (5) constrained to: vj ui ≤ cij (6) vj , ui ≥ 0 (7) where: ui = comparative locational value of the fish at landing site. vj = price of fish at market site in competitive market equilibrium. the dual model estimates the optimal price at each output market, which equates supply and demand over the whole market. the outcome of this calculation represents shadow prices because they are the opportunity cost of an optimal allocation of fish between the various markets. the parameters cij, si , were estimated based on the field survey and dj were estimated using secondary data from figure 2. fish transport routes. 38 al-abri and others 39 transport modeling analysis to test the efficiency of fish markets in oman the household income and expenditure survey conducted by the ministry of national economy, oman (2003). demand for fish consumption at dubai was estimated based on data of fish imports to dubai central market (dcm). the linear programming model was solved using microsoft excel solver. analysis and results to illustrate the model the paper reproduces only the kingfish data and lp model. similar data is available (al-abri, 2008) for the other species considered in the analysis (sardine and composite). using fish prices at landing sites reported by truckers and the operating cost of transport estimated on survey data the variable cost (sum of operating cost of transport and purchase price of fish at landing site) of transporting a ton of kingfish from landing sites to markets were estimated and is given in table 1. supply of kingfish from landing sites: as illustrated in table 2, the sample of truckers transported 2,034 tons of kingfish per year. it was observed that nearly 72% of kingfish fish was transported to dcm and thus only 28% of the fish was delivered to domestic markets. consumer demand for kingfish at market sites: table 3 shows the estimated annual demand for kingfish at market sites. the transportation model assumes that the fish market is equilibrated in terms of demand and supply from all landing sites and market sites. the sample estimate of supply of kingfish was 2034 tons per year. this quantity of supply apportioned to the market sites based on the proportional demand of each site and the estimates are given in table 3. optimized solution of the dual of transport cost minimizing model: the matrix of the cost minimizing dual linear transportation model with the optimized solution is given in table 4. the vj’s are the optimal prices of fish at market site in competitive market equilibrium. (recall that the observed unit variable cost includes the price paid for fish at landing sites, so the ui’s work in the model as an increment to the landed price to ensure that the variable costs are not exceeded in the optimization calculation). the estimated optimal prices are compared with the observed prices of kingfish, in figure 3. it is observed that except in nizwa, where the observed price is higher than the optimal price, in all other markets the optimal and observed prices of kingfish are almost the same. this implies that, the transport function of the fish marketing system in oman is efficient, contrary to the hypothesis of the study. the optimal prices of sardine and composite fish were estimated using the same methodology adopted in estimating the optimal prices for kingfish. the optimal and observed prices of kingfish, sardines and composite fish are given in table 5. a paired t-test indicated that a statistically significant difference between the optimal and observed prices did not exist (t = 1.8989; n = 12). acknowledging the implication of inadequacies of the small number of observations on robustness of statistical testing, it could be concluded that, since the observed and optimal prices of different fish prices at different markets are not significantly different, the transport function of fish market in oman is efficient. conclusion the analysis indicates that the transport function of fish markets in oman is broadly efficient, and favors the supply of relatively more fish to export markets than domestic markets. truckers also confirmed that the reasons for transporting fish to export markets instead of the domestic markets was because of profitability, and table 1. variable cost (ro1/ ton) of transport: kingfish. markets landing sites masirah jbba mahoot ibri 874 1250 1370 nizwa 771 1233 1312 seeb 799 1252 1370 dubai 874 1304 1387 1rial omani (ro) = $us 2.60 (may 2008). note: sohar landing site did not have kingfish, hence was not considered in the analysis. table 2. observed quantity (tons/year) of kingfish transported. landing sites markets total ibri nizwa seeb dubai masirah 62 0 0 183 245 jalan 0 0 219 548 767 mahoot 73 219 0 730 1,022 total 135 219 219 1461 2,034 table 3. estimated demand for kingfish at markets (tons/ year). item markets totalibri nizwa seeb dubai estimated demand 1368 590 768 2196 4,922 proportioned demand 0.28 0.11 0.16 0.45 1.00 supply apportioned to demand 565 244 317 907 2034 38 al-abri and others 39 transport modeling analysis to test the efficiency of fish markets in oman table 4. dual transport cost minimizing model: kingfish. maximize dj * vj – si * ui 2,559,928 solution vj and uj 1338 1312 1340 1387 541 88 0 observed unit variable cost (or/ton) vj=1 vj=2 vj=3 vj=4 ui =1 ui =2 ui =3 objective function coefficients 565 244 317 907 -245 -767 -1022 constraints x11 1 -1 796 <= 874 x12 1 -1 771 <= 771 x13 1 -1 799 <= 799 x14 1 -1 845 <= 874 x21 1 -1 1250 <= 1250 x22 1 -1 1225 <= 1233 x23 1 -1 1252 <= 1252 x24 1 -1 1299 <= 1304 x31 1 -1 1338 <= 1370 x32 1 -1 1312 <= 1312 x33 1 -1 1340 <= 1370 x34 1 -1 1387 <= 1387 notes: vj = price of fish at market site j on competitive market equilibrium. ui = comparative locational value of the fish at landing site. i landing sites 1= masirah, 2 = jalan, 3= mahoot j markets; 1 =ibri, 2 = nizwa, 3 = seeb, 4 = dubai x11 = masirah-ibri x21 = jalan-ibri x31 = mahoot-ibri x12 = masirah-nizwaa x22 = jalan-nizwaa x32 = mahoot-nizwaa x13 = masirah-seeb x23 = jalan-seeb x33 = mahoot-seeb x14 = masirahdubai x24 = jalandubai x34 = mahootdubai figure 3. observed and optimal sale prices of kingfish by market sites (or/ton). table 5. observed and optimal fish prices (or/ton). fish species market observed optimal kingfish ibri 1475 1338 nizwa 1800 1312 seeb 1375 1340 dubai 1533 1387 sardine ibri 190 189 nizwa 200 169 seeb 220 191 dubai 251 243 composite ibri 572 531 nizwa 485 383 seeb 595 669 dubai 650 653 40 al-abri and others the ability to sell large quantities in export markets. given that the transport function of the fish market in oman is efficient, this trend of transporting to export markets is rational and will continue. the implication is that in the long-run domestic markets may have lesser availability of fish from its own fisheries. this may not be considered to be equitable although it is efficient. policy makers may have to recognize the trade off between efficiency and equity implications of the fisheries markets in oman and make policy decisions accordingly. references al-abri, khamis. s. 2008. efficiency of fish markets in oman: transport modeling analysis. unpublished msc thesis, sultan qaboos university (squ), sultanate of oman. al-jabri, o. 1999. fresh fish markets in oman: a market integration analysis. unpublished msc thesis, squ, sultanate of oman. al-jabri, o., a. omezzine and h. boughanmi. 2003. fresh fish markets in oman: a price integration analysis. journal of international food and agribusiness marketing 14:77-93. bush, s.r. 2004. scales and sales: changing social and spatial fish trading networks in the siiphandone fishery, lao pdr. singapore journal of tropical geography 25:32-50. borisova, t., g. d’souza, d. miller and c. zabriskie. 2004. optimum shipment patterns for west virginia aquaculture products part i: growers, wvu division of resource management paper resmwp04-01. june 2004. 31 pp. dorfman, r., p.a. samuelson and r.m. solow. 1958. linear programming and economic analysis, rand cooperation. dubai municipality. 2004. statistical year book. dubai municipality, uae. eddie, g.c. 1983. road transport of fish and fishery products. fao, fisheries technical paper, 232, fipp/ t232, rome. international centre for living aquatic resource management (iclarm) 1999. iclarm strategic plan 2000-2020, makati city: iclarm. ministry of agriculture and fisheries (maf) 2003. fisheries statistical books. ministry of agriculture and fisheries, sultanate of oman. ministry of agriculture and fisheries (maf) 2004. fisheries statistical books. ministry of agriculture and fisheries, sultanate of oman. ministry of national economy (mne). 2006. statistical year book, 2005. ministry of national economy, sultanate of oman. ministry of national economy (mne). 2003. household survey data, ministry of national economy, sultanate of oman. omezzine, a., h. boughanmi and h. al oufi. 2003. demand elasticities of fresh fish commodities in oman. journal for scientific research-agricultural sciences 8:55-61. omezzine, a., l. zaibet and h. al-oufi, 1996. the marketing system of fresh fish products on the masirah island in the sultanate of oman. marine resources economics 11:203-210. smith, janna d., c.r. cassady, r.o. bowden and l.m. ainsworth. 2007. optimizing delta and pine land company’s bag seed distribution, http: //www.ise.mastate.edu/ncit/ thie, p. 1998. an introduction to linear programming and game theory. department of mathematics, boston college, usa. zaibet, l., h. boughanmi, t. al hinai and a. al marshudi. 2004. internationalization of oman fisheries firms after the european union ban. journal of agricultural and marine sciencesagricultural sciences 9:1-6. received: may 2008 accepted: march 2009 agricultural and marine sciences, 17:21-31 (2012) ©2012 sultan qaboos university 21 ____________________________________________ *corresponding author. e-mail: basunia@squ.edu.om development and performance evaluation of a solar tunnel date dryer in oman mohammad ali basunia1*, hamid hamad al-handali1, mohammed issa al-balushi1, mohammad shafiur rahman2, and osman mahgoub3 عمان في للتمور افف النفقي الشمسي واداء تطوير تقييم وعثمان الرحمن شفيع ومحمد البلوشي عيسى ومحمد احلنظلي حمد وحامد بسيونيا علي محمد محجوب طوله تصميم نفق مت في عمان ، الريفية املناطق في للمزارعني احملدودة التمور واإلمكانات حصاد طريقة االعتبار بعني األخذ اخلالصة: بعد املرة في حديثاً احملصودة التمور من كيلوجرام ١٨٠-٢٠٠ حوالي ليجفف النفق هذا صمم وقد ، التمور جتفيف بغرض متران وعرضه ١٢مترا يتم للتمور. كمجفف استخدامه مت االخر والنصف الهواء كصفيحة معدنية تستخدم كقاعدة لتسخني النفق نصف الواحدة. استخدم التمر حيث يوجد الشمالي النصف في التجفيف منطقة اجلنوبي إلى النصف في منطقة التجميع من مروحة بواسطة اجلاف دفع الهواء ٣٠ درجة الى ٥ بني ما الشمسي حرارة النفق درجة رفع مبكان السهل من وكان الدائري. نصف التصميم ذو في النفق التجفيف لغرض من كجم ١٩٠,٢ باستخدام اختبار النفق مت ثانية. / متر ٠,٥ من يقرب مبا للهواء املتدفق تسارع مع اخلارجي احمليط حرارة درجة فوق مئوية التمر لدرجة جتفيف مت في التجفيف. النفق كفاءة وذلك لتقييم الرطب) الوزن ٣٢,٨٪ (من قدره أولية مبحتوى رطوبة حديثاً احملصود التمر الشمس). أشارت العينة ألشعة تعرض من ساعة حوالي عشرين (أي غضون يومني في الرطب) الوزن ١٨,٦٪ (من قدرها نهائية رطوبة الشمس أشعة حتت الطلق الهواء في التجفيف الطبيعي أسرع من تأثير كان له النفق الشمسي باستخدام التجفيف أن إلى النتائج باستخدام ساعة) ٢٠) يومني من أقل قدرها فترة خالل في للتخزين اآلمن الرطوبة محتوى مستوى إلى الوصول أمكن حيث املباشر، و نوعية أن التحسن في التجربة وأكدت الطلق. الهواء في الشمسي الطبيعي للتجفيف يوماً ٥-٧ ب النفق الشمسي مقارنة مجفف ملموساً واللمعان كان حيث اللون من اففة التمور .جودة الرطوبة مستوى ، شمسي جتفيف نفق التمور ، ، مفتاحية: التجفيف كلمات abstract: taking into consideration the date harvesting and landholding capacities of the marginalized rural farmers in oman, a 12 meter long and 2 meter wide tunnel was designed and constructed to dry about 180-200 kg of freshly harvested dates per batch. half of the tunnel base was used as a flat plate air heating solar collector and the other half as a dryer. the drying air was forced from the collector region (south side) to the drying region (north side) of the half circled tunnel where the product is to be dried. the drying temperature could be easily raised by some 5-30 oc above the ambient temperature inside the tunnel at an air velocity of approximately 0.5 m/sec. the test was conducted with 190.2 kg freshly harvested dates with initial moisture content of 32.8% (wet-basis) to analyze the performance of the dryer. the dates were dried to a final average moisture content of 18.6% (wet-basis) within two days (20 hours). the results indicated that the drying was faster in a solar tunnel dryer than the natural open air sun drying. it was possible to reach the moisture content level for safe storage within less than two days (20 hrs) with a solar tunnel dryer and 5-7 days in open air natural sun drying. the improvement in the quality of dates in terms of color and brightness was distinctly recognized. keywords: drying, dates, solar tunnel dryer, moisture content. 1department of soils, water and agricultural engineering, 2department of food science and nutrition, 3department of animal and veterinary sciences, college of agricultural and marine sciences, sultan qaboos university, p.o. box 34, al-khod123, sultanate of oman introduction drying is very important because it is the cheapest, easiest and most common method of preserving and storing of perishable agricultural products. there are various methods and techniques to dry grain and other agricultural products. each method has its own advantages and limitations. dried products are becoming a common alternative to freshly harvested products due to many advantages (lutz et al., 1987). annual production of dates in oman is estimated about 200,000 tones (ampratwum, 2003). most of the dates are still dried by the traditional method of open air natural sun drying. this method of drying normally takes 14 to 21 days in oman (ampratwum, 2003). the traditional open air natural sun drying methods often yield poor quality dried products. in most cases the drying yard is not properly fenced. the product is not protected against dust, rain and wind, or even against insects, birds, rodents and domestic animals during the drying process. thus, the final product is contaminated with microorganisms and infection with disease-causing germs. the dates dried in this way have a short shelf-life and may not be free from contamination. the solar drying 22 basunia et al. 23 development and performance evaluation of a solar tunnel date dryer in oman facilities combine the advantages of traditional and industrial methods, namely low investment costs and high product quality. ampratwum (2003) reported the construction procedures and test results of a natural convection solar date dryer at sultan qaboos university, but due to low drying rates and capacity, it had not gained popularity in oman. a successful new solar tunnel drier was designed and developed at the university of hohenheim, germany, to meet the drying requirements of small farmer cooperatives (lutz et al., 1987; esper et al., 1994, 1996). this dryer is classified as a solar dryer that has been successfully tested under field conditions in about 30 countries under different climatic conditions in drying various agricultural products (schirmer et al., 1996; mastekbayeva et al., 1998; bala and mondal, 2001; basunia and abe 2001a, 2001b; ei-sebaii et al., 2002; bala et al., 2003). this new dryer design eliminated the dependence on grid electricity since the power consumption of the fan could be supplied by batteries or solar pv panels. unfortunately, the solar tunnel dryer has not yet been tested here in oman where solar energy is abundant and can be used for drying of dates and other agricultural products. the original design of the dryer (20 × 2 m), however, had a capacity that is suitable for use in a large farm. in order to adapt its design for small and medium scale rural farmers of oman, a scaled down (12 × 2 m) prototype of the tunnel dryer was designed and fabricated for the experiment at the department of soils, water and agricultural engineering at sultan qaboos university, oman. materials and methods the prototype solar tunnel dryer consists of a flat plate air heating solar collector and drying tunnel, fabricated as a single unit (fig. 1). the tunnel is 2.0 m wide, with a collector and dryer length of 6.0 m, respectively. the light-weight aluminum frames were used as the upper structure for the entire tunnel to support the transparent plastic cover. the tunnel was placed on concrete block substructures 700 mm above the ground surface. the plywood planks (0.9 × 2.0 m) of 4 mm thickness were used as the bed both for the dryer and collector parts of the tunnel to make the base of the tunnel almost air-tight. over the wooden base, black painted metallic sheets (0.9× 2.0 m) of 0.25 mm thickness were used as the absorber plate in the collector section of the tunnel. the steel wire mesh net was spread over the wooden dryer base to dry the desired product. a 0.2 mm thick uv stabilized colorless polyethylene sheet was used as the transparent cover over the entire tunnel (collector and dryer area). the entire tunnel became almost air-tight except the inlet opening (south side) for fixing a fan and the exit side (north side) for the moist air. the light weight (30 × 1 mm) aluminum flat bars were cut into pieces, each having a length 3140 mm and were bent to half-circles before being fixed onto the wooden base of the tunnel. figure 1. a rough sketch of a solar tunnel dryer used in this study without plastic cover and part of wooden base of the tunnel (1air inlet to the collector, fan, 2south side wooden cover, 3collector part (12 m2), 4light weight aluminum frame, 5dryer part (12 m2) 6air outlet from the dryer, 7concrete block sub-structures, 8wooden frame to support bends and base of the tunnel; 9metallic wire mesh net over wooden base in the dryer part, 10absorber plate (black painted metallic sheet over wooden base, not visible in figure, 12 m2) 1 2 3 10 4 7 8 5 9 6 m 6 m 2 m 6 22 basunia et al. 23 development and performance evaluation of a solar tunnel date dryer in oman a solar-powered fan of 40 watt capacity was installed at the holes made on the wooden cover plate, 150 mm above the metallic absorber sheet at the air input side of the tunnel. thus, the drying air was forced from the collector region to the dryer region where the product is to be dried. the fan has an air handling capacity of 7.3 m3/min against a maximum static pressure of 157 pa (16 mmh 2 o). the design of the dryer was based on the consideration that the temperature of air heated in the collector and forced to pass through the dryer section would not exceed 60 oc. this is based on the principle of low temperature drying of agricultural crops. the maximum permissible temperature for fruits and vegetable drying is about 60oc to maintain the optimum quality of the dried product; the temperature at the outlet of the collector and at the entrance of the dryer should not exceed this limit. prior to the operation of the dryer, thermocouples were installed to record the temperatures at different locations within the tunnel. nine thermocouples were connected within the tunnel, three at each of the mid-points of the collector, the dryer and of the whole tunnel. the copper constantan thermocouples were used to measure the temperature by fixing them inside the tunnel. the drybulb temperatures in the collector part of the tunnel were measured at 50 mm above the surface of the black metallic sheet, 50 mm below the inner surface of the transparent plastic cover and at the mid point (500 mm above the absorber plate) of these two surfaces along the lengthwise center of the tunnel. similarly, the thermocouples were connected at the mid-points of the dryer part and the tunnel, respectively, to measure the temperature profiles both in the vertical and horizontal directions of the entire tunnel. also, two thermocouples were used to measure the dryand wet-bulb temperatures of the ambient air. thus, in total, eleven thermocouples were used to measure the temperatures at different locations. so the dry-bulb temperatures in the collector and dryer represented the average of three readings, respectively. the temperature inside the tunnel represented the average of nine readings. the thermocouples used for measuring the temperatures had an accuracy of ±0.5 oc. an anemometer was used to measure the velocity at the exit of the dryer. a pyranometer of moll – goregynstic type was used to measure the solar radiation incident on a horizontal surface. the sensitivity of pyranometer was 10.5 mv/(cal.cm2.min). the thermocouple probes, anemometer and pyranometer were connected through an interface of an ad (analog to digital) converter then to a personal computer for data collection. the temperatures, air velocity and solar radiation data were recorded simultaneously at intervals of 30 minutes. experiments were conducted to evaluate the performance of the dryer at no-load and full-load conditions. the moisture content of whole dates was determined by using oven drying method. the sample of whole dates was kept at 100 oc for 20 hours (aoac, 1984). date samples were collected at intervals of one hour from the tunnel on the first day and then at two hour intervals on the second day of drying. also, a test sample of about 1 kg was conducted in the open air (control) under natural convection and simultaneously in the solar tunnel dryer to compare their drying rates. the drying efficiency of the dryer was calculated from the measured solar energy input to the collector and the electrical energy supplied by the single fan during operations. the solar radiation incident directly on the drying portion of the tunnel was not considered for calculation of the drying efficiency as this energy had little effect on drying. most of the energy directly input from the solar radiation on the dryer portion passed through the exit because of relatively higher air velocity and absence of open space in the dryer base. the following parameters were considered for estimating the drying efficiency of the experimental solar tunnel dryer: (a) measured average total (diffuse and beam) solar irradiation on a horizontal surface to calculate solar irradiance on the collector surface, (b) geometric factor and efficiency of the collector at the test site, (c) total electrical energy input to the fan during operation from photovoltaic solar cells, and (d) initial and final mass of the dates and thus the amount of water removed from the dates in a given period of time. the following equation was developed to calculate the drying efficiency of the dryer: ( ) ( )trasp lw cbcte vr d .... .100 h h + = where is the drying efficiency in percent; wr is the mass of moisture removed from the product in kg; lv is the latent heat of vaporization of water in mj/kg; pe is the total electrical energy required to run the ac fan during operation in mj; st is the measured total solar irradiation on a horizontal surface in mj/(hr.m2); ac is the area of the collector in m2; rb is the geometric factor at the test site; and is the efficiency at the test site and t is the total drying time per hour. results and discussion no-load tests (test without product) the dryer was placed in the open farmyard of the agricultural experimental station (aes) of sultan qaboos university. the no-load tests with and without fan were conducted to know the temperature and air flow characteristics at different weather conditions and also, the temperature gradient both in the collector and dryer regions of the tunnel. figure 2 shows the variations of ambient, collector and dryer temperatures with time of day. the drying air temperature could be easily raised by some 5-30 oc above the ambient temperature at an air flow rate of 0.5-0.6 m/sec. the difference between the drying air temperature and ambient temperature gradually increased from morning till mid-day (0-30 oc) ( ) ( )trasp lw cbcte vr d .... .100 h h + = ( ) ( )trasp lw cbcte vr d .... .100 h h + = (1) 24 basunia et al. 25 development and performance evaluation of a solar tunnel date dryer in oman then gradually fell (30-0 oc ) in the afternoon (fig. 2). the highest temperature 69 oc was observed at around 1:00 pm. however, the temperature could be maintained within 4060 oc by controlling the exit area of the tunnel, particularly from 11:30-15:30 hours when temperatures exceeded 60 oc. this indicated that solar tunnel dryer can be easily used to dry dates. in no-load tests the maximum difference between the average temperatures of the dryer and collector parts was about 2 oc. this indicated the uniformity of temperatures inside the entire tunnel. there was almost no temperature gradient in the vertical direction of the whole tunnel, either in the dryer (fig. 3) or the collector parts of the tunnel (fig. 4). figures 5-7 show the temperature profiles in the horizontal direction through the bottom, middle and top along the breadthwise center of the tunnel. there was almost no temperature gradient observed in the horizontal direction either in the dryer or collector parts of the tunnel due to proper mixing of the drying air by the fan (figs. 5 to 7). tests were conducted from 6:00 am to 6:00 pm. 20 30 40 50 60 70 6:00 12:00 18:00 0:00 6:00 12:00 18:00 t em pe ra tu re ( oc ) time (hr) ambient (ave. 35.0 oc) collector (ave. 48.2 oc) dryer (ave. 50.3 oc) figure 2. variations of ambient, dryer and collector air temperatures with time of the day (august 8-9, 2008) under no load condition (with fan). 20 30 40 50 60 70 6:00 12:00 18:00 0:00 6:00 12:00 18:00 t em pe ra tu re ( oc ) time (hr) collector top (ave. 48.8 oc) collector middle (ave. 47.9 oc) collector bottom (ave. 47.9 oc) figure 3. variations of temperatures at the bottom, middle and top (vertical temperature profile) of the collector center along the length with time of the day (august 8-9, 2008) under no load condition (without product). t em pe ra tu re ( o c ) t em pe ra tu re ( o c ) ___ambient (ave. 35.0 oc) ---collector (ave. 48.2 oc) dryer (ave. 50.3 oc) ---collector top (ave. 48.8 oc) ---collector middle (ave. 47.9 oc) ___ collector bottom (ave. 47.9 oc) 24 basunia et al. 25 development and performance evaluation of a solar tunnel date dryer in oman 20 30 40 50 60 70 6:00 12:00 18:00 0:00 6:00 12:00 18:00 t em pe ra tu re ( oc ) time (hr) dryer top (ave. 49.8 oc) dryer middle (ave. 50.5 0c) dryer bottom (ave. 50.7 oc) 20 30 40 50 60 70 6:00 12:00 18:00 0:00 6:00 12:00 18:00 t em pe ra tu re ( 0c ) time (hr) collector bottom (ave. 48.5 oc) dryer bottom (ave. 51.4 oc) figure 4. variation of temperatures at the bottom, middle and top (vertical temperature profile) of the dryer part with time of the day (august 8-9, 2008) under no load condition (without product). figure 5. variations of temperature in the horizontal direction of the tunnel through the bottom (5 cm from the base) along the center with time of the day (august 8-9, 2008) under no load condition (without product). t em pe ra tu re ( o c ) t em pe ra tu re ( o c ) ---dryer top (ave. 49.8 oc) ---dryer middle (ave. 50.5 oc) ___ dryer bottom (ave. 50.7 oc) -----collector bottom (ave. 48.5 oc) ____ dryer bottom (ave. 51.4 oc) 26 basunia et al. 27 development and performance evaluation of a solar tunnel date dryer in oman 20 30 40 50 60 70 6:00 12:00 18:00 0:00 6:00 12:00 18:00 t em pe ra tu re ( oc ) time (hr) collector middle (ave. 47.5 oc) dryer middle (ave. 50.5 oc) figure 6. variations of temperature in the horizontal direction of the tunnel through the middle (50 cm from the base) along the center with time of the day (august 8-9, 2008) under no load condition (without product). 20 30 40 50 60 70 6:00 12:00 18:00 0:00 6:00 12:00 18:00 t em p er at u re ( o c ) time (hr) collector top (ave. 49.5 oc) dryer top (ave. 50.6 oc) figure 7. variations of temperature in the horizontal direction of the tunnel through the top ( 90 cm from the base) along the center with time of the day (august 8-9, 2008) under no load condition (without product). t em pe ra tu re ( o c ) t em pe ra tu re ( o c ) ----collector middle (ave. 47.5 oc) ___ dryer middle (ave. 50.5 oc) ----collector top (ave. 49.5 oc) ___ dryer top (ave. 50.6 oc) 26 basunia et al. 27 development and performance evaluation of a solar tunnel date dryer in oman a no-load test was also conducted without the fan being used. it was also observed that the highest temperature inside the tunnel rose to 75 oc when the fan was not in operation (figs. 8 and 9). the difference between the average temperatures inside the tunnel with and without fan was about 10 oc. this indicated the operation of the dryer without fan use would cause overdrying of the product particularly during 11:30 am3:30 pm. mercer (2008) mentioned that to avoid damage, temperatures below 60oc are quite appropriate for many food-drying applications. figure 10 shows the variations of measured total (beam and diffuse) solar radiation on the horizontal surface with time of the day. it clearly indicated that an average 500 w/m2 solar energy was incident on the horizontal surface which can be easily utilized in drying dates. 20 30 40 50 60 70 80 6:00 12:00 18:00 0:00 6:00 12:00 18:00 t em pe ar at ur e (o c ) time (hr) top (fan) middle (fan) bottom (fan) top (without fan) middle (without fan) bottom (without fan) figure 8. variations of temperatures in dryer part of the tunnel with and without fan under no-load conditions with time of the day (august 8-11, 2008). 20 30 40 50 60 70 80 6:00 12:00 18:00 0:00 6:00 12:00 18:00 t em p ea ra tu re ( o c ) time (hr) top (fan) middle (fan) bottom (fan) top (without fan) middle (without fan) bottom (without fan) figure 9. variations of temperatures in collector part of the tunnel with and without fan under no-load conditions with time of the day (august 8-11, 2008). t em pe ra tu re ( o c ) t em pe ra tu re ( o c ) 28 basunia et al. 29 development and performance evaluation of a solar tunnel date dryer in oman of the tunnel were closed with a polyethylene sheet so that air could not pass through the tunnel. the moisture content was reduced to 21.5% from an initial 32.8% wet-basis in 12 hours drying on the first day. the next day drying was started at 6:30 am and continued till 5:00 pm when the products reached their final moisture content of 18.5 % (w.b.). samples were collected for moisture content determination at the end of drying and it was found to be around 18.5% (wet-basis). the variations of the dryer and collector air and the ambient air temperatures with drying time (6:00-19:00 hr/ day) in two days are shown in figure 11. the variations of test with freshly harvested dates the full test load with 190.2 kg of freshly harvested dates (khalas variety) was conducted to study the dryer performance on july 27-28, 2009. the average initial moisture content of the freshly harvested dates was 32.8% (wet-basis). the dates were spread on a wire mesh net in a single layer thickness placed over the plywood bottom of the drying section of the tunnel. the drying was started at 6:30 am and continued till 6:30 pm. the approximate sun rising and setting time was 6:00 am and 7:00 pm, respectively. after termination of the first day drying, the product was kept undisturbed in the dryer and both ends 0 200 400 600 800 1000 6:00 12:00 18:00 0:00 6:00 12:00 18:00 s ol ar ir ra di an ce ( w /m 2 ) time (hr) average = 485 w/m2 (10/08/09) average = 500 w/m2 (11/08/09) figure 10. variations of solar radiation with time of the day (august 8-9, 2008) under no load condition (without product). 25 35 45 55 65 75 85 6:00 12:00 18:00 0:00 6:00 12:00 18:00 0:00 t em p er at u re ( o c ) time (hr) exit (ave. 55.2 oc) mid-point (ave. 56.2 oc) inlet ( ave. 44.6 oc) ambient (ave. 36.2 oc) figure 11. variations of ambient, dryer and collector temperatures with time of the day (july 27-28, 2009,) in drying freshly harvested dates. t em pe ra tu re ( o c ) ____ exit (ave. 55.2 oc) mid-point (ave. 56.2 oc) -----inlet (ave. 44.6 oc) _._. ambient (ave. 36.2 oc) s ol ar ir ra di an ce ( w at t/ m 2 ) 28 basunia et al. 29 development and performance evaluation of a solar tunnel date dryer in oman 0 200 400 600 800 1000 1200 6:00 12:00 18:00 0:00 6:00 12:00 18:00 drying time (hr) s ol ar ir ra di an ce ( w at t/m 2) average = 490.9 w/m2 figure 12. variations of solar radiation with time of the day (july 27-28, 2009) in drying freshly harvested dates. 10 15 20 25 30 35 40 0 4 8 12 16 20 m o is tu re c o n te n t (w .b .) time (hr) solar dried naturaly dried figure 13. variations of moisture content with drying time with solar tunnel dryer and natural open air sun drying. solar radiation with drying time are shown figure 12. the average drying air temperature and ambient temperatures were 52.0 and 36.2 oc , respectively, and the average total radiation on a horizontal surface was 490.9 w//m2. the average temperature in the collector part was lower than the average temperature in the dryer part because of the fan at the air entrance side of the collector. to compare the drying rates of the solar tunnel dryer and natural convection open air drying, two separate tests were conducted with about 100 gm samples under the same weather conditions. the samples from the tunnel dryer and open air drying were taken at one hour interval for the first four hours of drying, starting from 6:30 am and then at two hours intervals till 6:30 pm in order to measure the moisture content against the drying time. the variations of moisture content in the solar tunnel drying and natural open air sun drying with time is shown in figure 13. the moisture removal rate was much higher in the solar tunnel dryer than with the open-air natural sun drying (fig. 13). drying efficiency the amount of water removed in two days drying from the product in reducing its moisture content from 32.8% s ol ar ir ra di an ce ( w at t/ m 2 ) 30 basunia et al. 31 development and performance evaluation of a solar tunnel date dryer in oman to 18.6% wet-basis was 32.8 kg. the latent heat of vaporization of water is 2.5 mj/kg, and it was considered that the energy requirement in low temperature drying would be very near to the latent heat of water vaporization. the total energy input to the fan in 20 hours was 2.88 mj. the average measured total (beams and diffuses) solar radiation incident on a horizontal surface in two days was 1.77 mj/(m2.hr). the geometric factor and efficiency of the collector for muscat, oman was considered as 1.50 and 35%, respectively (duffie and beckman, 1991; sodha and chandra, 1994). the area of the collector was 12.0 m2 and time of the drying was 20 hours. the average drying efficiency of the solar tunnel was found to be 36.4% in drying dates. the total capacity of the dryer is estimated to be about 200-220 kg of freshly harvested dates, but 190.2 kg was loaded. therefore, the drying area of the dryer was not fully utilized which explains the low efficiency of the drying system. the average collector, dryer and ambient air temperatures in two days drying were 52.6, 51.9 and 36.20c, respectively and the averages of relative humidity were 34.0, 46.5 and 55.0%, respectively. it was also observed that the average relative humidity of the air leaving the dryer was fairly low (37.6%), while the ambient air relative humidity was 55.0%. this indicated that the potential of the air exiting the dryer was not fully utilized. the relative humidity of the air leaving the dryer could be raised to the relative humidity of the ambient air if the length of the dryer was greater. it is also true that in an overflow drying system, as in a tunnel dryer, it is not possible to fully utilize the harvested energy as the drying air is passed over the product to be dried. the much softer skin of the dates allows easy diffusion of moisture through it to the drying air at the initial stage of drying. the thickness of the date’s muscles also contributed to faster drying, as the average thickness was only about 2 mm. in general, the drying efficiency is reduced considerably during the final stage of drying. this is due to much less mass transfer from the inner part of the dates to the surface after it is dried to a certain extent. this indicates that the diffusion of moisture from inside the product to the surface of the product becomes much more difficult. conclusions this paper describes the design, construction and experimental investigation of a solar tunnel dryer. the noload tests clearly indicated that the drying temperature can be easily raised to 5-30 oc above the ambient temperature while the average air flow velocity inside the tunnel was 0.5 m/s. the average drying air temperature could be easily attained 50-55 oc . the experiments were carried out with 190.2 kg freshly harvested dates and the performance of the dryer was compared to open-air natural sun drying. a considerable reduction in drying time in comparison with natural open air sun drying was obtained. the thermal efficiency of the dryer was found to be approximately 36.4%. these investigations show that a solar tunnel dryer can be used for low temperature drying of dates and other agricultural products in the rural areas of oman where electricity is not available. 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m.a. leon, and s. kumar. 2002. energy program,report. asian institute of technology (ait), p.o. box 4, klong luang, pathumthani 12120. 30 basunia et al. 31 development and performance evaluation of a solar tunnel date dryer in oman mastekbayeva, g.a., m. a. leon, and s. kumar. 1998. performance evaluation of a solar tunnel dryer for chili drying. paper presented at the asean seminar and workshop on drying technology, phitsanulok, june 3-5. mercer, d.g. 2008. solar drying in developing countries possibilities and pitfalls. international union of food science and technology 4:1-11. schirmer, p., s. janjai, a. esper, r. smitabhindu, and w. muhlbauer. 1996. experimental investigation of the performance of the solar tunnel dryer for drying bananas. renewable energy 7:119-129. sodha, m.s. and r.i. chandra. 1994. solar drying systems and their testing procedures: a review. energy conservation and management 35:219-267. received: january 26. 2010 accepted: december 16, 2012 32 basunia et al. agricultural and marine sciences, 12:13-20 (2007) ©2007 sultan qaboos university 13 *corresponding author. e-mail: hamid_chaloub@hotmail.com differential response of barley (hordeum vulgare l.) to salinity hamid ali ghaloub*, saleem k. nadaf and saif ali al-khamisi agriculture production research center, rumais, ministry of agriculture, p.o. box 50, pc 121, sultanate of oman abstract: four elite barley cultivars (jimah 51, jimah 54, jimah 98 and jimah 136) along with two local cultivars, beecher (late maturity) and duraqi (early maturity), were investigated for their response to five levels of irrigation water salinity viz. control (1 ds m-1), 3, 9, 12 and 15 ds m-1 during the winter seasons of 2002-03 and 2003-04 in pots containing sandy loam soil. the results indicated that the main effects of years, salinity and cultivars were highly significant (p<0.01) with respect to all the characters studied. among the interactions, the effects of year x salinity and year x cultivar were highly significant (p<0.01) for all the characters, whereas that of salinity x cultivar was highly significant (p<0.01) for only two characters viz. plant height and dry matter yield. however, 3-factor interaction was not significant (p>0.05) for any character. adverse effects of salinity were evident in the cultivars for all characters. salinity tolerance of cultivars was assessed using the concepts of both stress susceptibility index at each higher salinity level in relation to control (lowest salinity level) and mean value over the salinity treatments with respect to each character. among all the cultivars tested, jimah 136 was found to have a consistently high degree of salinity tolerance. all other cultivars, however, responded differentially to different levels of salinity for different characters. keywords: barley, hordeum vulgare, salinity, growth attributes, forage yield. introduction irrigation is the key to agricultural productivity in arid and semi-arid regions. of late, these regions have been affected either by soil salinity due to poor irrigation practices or by water salinity due to sea water intrusion near the coast. under such conditions, researchers have to seek saline tolerant cultivars of crops grown in the region, which can then be subjected to crop improvement for high yield and quality. plant breeders, along with physiologists, are now modifying محصول الشعیر إلجھاد الملوحة استجابة الخمیسي وسیف نداف وسلیم علي جلوب حمید أصناف من صنفین 136) مع وجماح ،98 وجماح ، 54 وجماح ، 51 (جماح الشعیر من مختارة أصناف دراسة (4) تمت الخالصة: ماء ملوحة من مستویات لخمس استجابتھا مدى على وذلك للتعرف (مبكر النضج) ودوراقي النضج) (متأخر بیشر ھما المحلیة الشعیر في 2003-2004م وذلك 2002-2003م و األعوام في الشتویة المواسم خالل ( دیسیسمن/م 12 و15 ، 9 ، 3 ، (الشاھد) 1 ) الري الصفات المعنویة لجمیع عال كان والملوحة واألصناف السنوات تأثیر أن إلى أشارت النتائج طمییة. رملیة تربة على تحتوي أصص الصفات األصناف عال-المعنویة لجمیع والسنوات مع والملوحة السنوات تداخل تأثیر كان للتداخالت فقد بالنسبة أما الدراسة ، تحت بینما . ھكتار) (طن/ الجاف والوزن سم) النبات ( الرتفاع بالنسبة المعنویة عال الملوحة األصناف مع تداخل بینما كان ، الدراسة تحت كل على ظاھرًا السلبي الملوحة كان تأثیر . األصناف والسنوات) (الملوحة ، الثالثة العوامل بین للتداخل معنوي تأثیر ھناك یكن لم بالشاھد، وكذلك وعالقتھ الملوحة من اإلجھاد لكل مستوى مقاومة معامل أساس على الملوحة تحمل تقییم تم الصفات جمیع في صنف استقرارا في األعلى واألكثر كان 136 جماح الصنف بان ظھر صفة. بالنسبة لكل الملوحة واإلنتاج لمعامالت النمو قیم متوسط على المختلفة. الملوحة تحملھا لمستویات درجة األخرى في األصناف تفاوتت بینما للملوحة تحملھ ghaloub, nadaf and al-khamisi 14 15 differential response of barley to salinity crops to suit adverse saline soil or irrigation water conditions while maintaining reasonable and reliable grain or forage yields (shannon, 1985; wyn jones and gorham, 1986; gorham, 1991; qualset and corke, 1991; nadaf et al., 2001). forage yields of barley (hordeum vulgare l.) are directly dependent upon agronomic growth attributes like plant height, number of tillers, leaf length and leaf number per plant (jaradat et al,, 2004), which have been proved stable and consistent indicators of forage yield. salinity (mcleod, 1982), drought (fukai et al., 1990) and other environmental stresses like temperature (hockett, 1990) can greatly affect development of these stable characters. several workers described the effect of salinity on different growth and yield related characters right from seedling (salim, 1991) to adult ((rawson et al,, 1988; mcleod, 1982; hocket and nilan, 1985) stages of barley. in oman barley is grown for forage during winter. several exotic cultivars have been selected, based on their high forage productivity in comparison with local barley cultivars. in light of the above information, the present investigation was conducted consecutively in 200203 and 2003-04 utilizing promising barley cultivars at the agriculture research center, rumais, oman. this investigation was undertaken to determine the effect of different salinity levels of irrigation water on four agronomic traits associated with forage barley in order to enable selection of the cultivars highly tolerant to salinity for general cultivation at saline sites or use in barley breeding. materials and methods four cultivars of barley (jimah 51, jimah 54, jimah 98 and jimah 136) recommended by the ministry of agriculture and fisheries, oman, for cultivation in oman, along with two local checks viz. duraqui (early cultivar, flowers within two months) and beecher (late cultivar, flowers within three months) were used in the study. the physical and chemical characteristics of the experimental soil are presented in table 1. the trial was conducted consecutively for two years, during the winter seasons of 2002-03 and 200304 in two-factor completely randomized design with three replications using six cultivars under six levels of irrigation water salinity, viz. control (1 ds m-1), 3, 6, 9, 12 and 15 ds m-1 in pots of 20-cm diameter. in both years, the crop was planted in mid-november and harvested for forage as and when the cultivars attained 50 % flowering stage. except for duraqui, which attained 50 % flowering between 56 and 60 days, other cultivars took about 80-87 days after planting. in both years, fresh soil initially collected from the same land was used. four plants grown in each pot were fertilized with the recommended dose of 100 kg n, 90 kg p2o5 and 60 kg k2o/ha in the form of urea, triple superphosphate and potassium sulphate, respectively. the entire quantities of potassium and phosphate fertilizers along with 1⁄4 nitrogen fertilizer were applied before planting, whereas the remaining nitrogen was applied in three splits of 1⁄4 n each, one week after planting, at heading and milky grain stages, respectively. the pots of each cultivar were frequently irrigated with water corresponding to the described levels of salinity till their germination and later thrice a week till a week prior to harvest. sea water of electrical conductivity 48.5 + 2 ds m-1 was used as a source of salinity as it incorporates several salts commonly encountered in saline soils, namely high concentrations of sodium, chloride, sulphate and boron and a low calcium to magnesium ratio. the salinity treatments were prepared in 100-liter plastic drums by diluting the seawater by control water. protective measures against pests and diseases were taken whenever necessary. the observations on plant height (cm), number of tillers/ plant and green matter weight (g)/ plant were recorded at 50 % flowering and dry matter weight (g) was recorded in the laboratory after drying green matter in the oven at 70°c for 18-24 hrs (aoac, 1984). the table 1. values of some chemical and physical characteristics of the experimental soil. characteristic value chemical: ec (1:5) ds/m 2.58-2.16 ph (1.5) 7.40-7.50 caco3 (%) 27.80 n (%) 0.076 av.p (ppm) 833.90 physical: gravel (%) 0.0 coarse sand (%) 0.60 fine sand (%) 63.30 silt (%) 27.60 clay (%) 8.50 texture sandy loam ghaloub, nadaf and al-khamisi 14 15 differential response of barley to salinity data on the above characters were subjected to statistical analysis according to the methods of gomez and gomez (1984) using the mstatc computer program (mstat, 1989). a stress susceptibility index (s) for the cultivars was determined on the basis of each character in the high salinity irrigation treatment relative to the control (fischer and maurer, 1978; kelmen and qualset, 1991). the s is defined as: s = [1(yij / yic)] / [1(y.j / y.c)], where yij = character expression of ith genotypes in the jth saline treatment, yic = character expression of the same cultivar in the control treatment, y.j = mean character expression of all cultivars in the jth saline treatment, and y.c = mean character expression of all the cultivars in the control treatment. low s values indicate low susceptibility or high tolerance to environmentally induced stress. results and discussion table 2 shows the anova with respect to plant height, number of tillers, green matter weight / plant and dry matter weight/plant. the results indicate that the main effects of years, salinity and cultivars were highly significant (p<0.01) with respect to all the characters studied. among the interactions, the effects of year x salinity and year x cultivar were highly significant (p<0.01) for all the characters, whereas effects of salinity x cultivar were highly significant (p<0.01) for only two characters, viz. plant height and dry matter yield. however, 3-factor interaction was not significant (p>0.05) for any character. adverse effects of salinity were evident in the cultivars for all characters. salinity tolerance of cultivars was assessed using the concepts of both stress susceptibility index at each higher salinity level in relation to control (lowest salinity level) and mean value over the salinity treatments with respect to each character. however, stress susceptibility index values were found to vary for each character among the cultivars with different levels of salinity. plant height in both years, in general there was significant reduction in mean plant height with increased level of salinity (p<0.05) from the controls to higher levels of salinity (table 3). however, means of plant height at 3 ds m-1 and 6 ds m-1 were not significantly (p>0.05) different during 2002-03. decrease in plant height from control to 3 ds m-1 was significant in both the years (table 3): 7.1 % in 2002-03 and 5.7 % in 2003-04. the decrease from control to 6 ds m-1 was 6.9 % in 2002-03 and 16.2 % in 2003-04, whereas the reduction in plant height was 35.0 % in 2002-03 and 29.8 % in 2003-04 at 15 ds m-1 as compared to control. with respect to mean plant height across salinity levels, in 2002-03, j-136 (67. 8 cm) recorded the significantly (p<0.05) highest mean plant height, followed by early local check, duraqui (63.0 cm) and j-54 (56.3 cm), while in 2003-04, duraqui (48.6 cm) and j-54 (42.8 cm) cm) were significantly taller than other cultivars. stress table 2. statistical parameters in respect of plant height, number of tillers, green matter weight/plant and dry matter weight/plant, both in g. *significant at 0.05 level of probability; ** significant at 0.01 level of probability; ns not significant. characters statistical parameters plant height (cm) number of tillers green matter dry matter lsd lsd lsd lsd f-test (5%) f-test (5%) f-test (5%) f-test (5%) year ** 1.53 ** 0.91 ** 7.65 ** 1.69 salinity ** 2.65 ** 1.57 ** 13.26 ** 2.93 year x salinity ** 3.74 ** 2.22 ** 18.75 ** 4.15 varieties ** 2.65 ** 1.57 ** 13.26 ** 2.93 year x varieties ** 3.74 ** 2.22 ** 18.75 ** 4.15 salinity x varieties ** 6.48 ns ns ** 7.19 year x salinity x varieties ns ns ns ns 0 cv (%) 11.61 26.0 20.05 11.61 ghaloub, nadaf and al-khamisi 16 17 differential response of barley to salinity ta bl e 4. m ea n nu m be r of t ill er s/ pl an t of b ar le y cu lti va rs d ur in g th e w in te rs 2 00 203 a nd 2 00 304 a lo ng w ith t he ir s tr es s su sc ep tib ili ty i nd ex es ( sc j) b as ed o n nu m be r o f t ill er s/ pl an t. t he m ea ns w ith d if fe re nt le tte rs a re s ig ni fi ca nt ly d if fe re nt a t p ≤0 .0 5 ac co rd in g to l sd a nd s tr es s su sc ep tib ili ty in de x of ‘j ’ ( ds ), hi gh s al in ity tr ea tm en t r el at iv e to ‘c ’ ( ds ), lo w s al in ity tr ea tm en t. c ul tiv ar 20 02 -2 00 3 20 03 -3 00 4 sa lin ity l ev el (d s/ m ) st re ss s us ce pt ib ili ty in di ce s sa lin ity l ev el (d s/ m ) st re ss s us ce pt ib ili ty in di ce s c on tr ol 3 6 9 12 15 m ea n s c 3 s c 6 s c 9 s c 12 s c 15 c on tr ol 3 6 9 12 15 m ea n s c 3 s c 6 s c 9 s c 12 s c 15 j 51 14 9 10 15 15 8 12 b 2. 37 0. 97 -0 .2 8 -0 .3 4 1. 16 24 21 19 20 16 11 19 a 1. 05 0. 89 0. 48 0. 72 0. 97 j 54 15 14 16 16 16 11 15 a 0. 46 -0 .2 2 -0 .1 3 -0 .2 3 0. 67 24 25 21 19 18 18 21 a -0 .2 3 0. 59 0. 68 0. 58 0. 47 j 98 13 8 7 5 5 5 7 c 3. 02 1. 61 3. 57 2. 31 1. 60 27 23 21 17 12 13 19 a 1. 06 0. 98 1. 10 1. 18 0. 96 j 13 6 8 11 8 8 6 7 8 c -2 .9 6 0. 14 0. 25 0. 74 0. 21 27 25 20 18 15 11 19 a 0. 64 1. 03 0. 99 0. 95 1. 05 b ee ch er 13 9 5 8 5 7 8 c 2. 37 2. 00 2. 13 2. 09 1. 12 23 22 19 13 9 6 15 b 0. 13 0. 64 1. 25 1. 24 1. 31 d ur aq i 10 12 5 9 5 6 8 c -1 .4 7 1. 52 0. 21 1. 84 0. 97 14 6 6 5 4 3 6 c 4. 95 2. 42 1. 84 1. 57 1. 44 m ea n 12 a 11 ab 9b 10 b 9b c 7c 23 a 20 b 18 b 15 c 12 d 10 d ta bl e 3. m ea n pl an t h ei gh t ( cm ) o f b ar le y cu lti va rs d ur in g th e w in te rs 2 00 203 a nd 2 00 304 a lo ng w ith th ei r s tr es s su sc ep tib ili ty in de xe s (s cj ) b as ed o n pl an t h ei gh t. t he m ea ns w ith d if fe re nt le tte rs a re s ig nf ic an tly d if fe re nt a t p ≤0 .0 5 ac co rd in g to l sd a nd s tr es s su sc ep tib ili ty in de x of ‘j ’ ( ds ), hi gh s al in ity tr ea tm en t r el at iv e to ‘c ’ (d s) , l ow s al in ity tr ea tm en t. c ul tiv ar 20 02 -2 00 3 20 03 -3 00 4 sa lin ity l ev el (d s/ m ) st re ss s us ce pt ib ili ty in di ce s sa lin ity l ev el (d s/ m ) st re ss s us ce pt ib ili ty in di ce s c on tr ol 3 6 9 12 15 m ea n s c 3 s c 6 s c 9 s c 12 s c 15 c on tr ol 3 6 9 12 15 m ea n s c 3 s c 6 s c 9 s c 12 s c 15 j 51 60 .0 60 .7 54 .3 53 .0 47 .7 38 .7 52 .4 d -0 .1 6 1. 37 0. 72 0. 73 1. 01 59 .2 45 .3 42 .7 36 .6 33 .3 25 .1 40 .4 b 4. 12 1. 72 1. 33 1. 82 1. 93 j 54 71 .7 62 .3 64 .7 56 .3 43 .7 39 .3 56 .3 c 1. 83 1. 41 1. 32 1. 38 1. 29 50 .7 50 .4 41 .7 38 .1 41 .2 34 .5 42 .8 b 0. 11 1. 09 0. 87 0. 78 1. 07 j 98 68 .7 57 .5 60 .3 54 .0 48 .0 37 .3 54 .3 cd 2. 28 1. 76 1. 32 1. 06 1. 30 42 .2 40 .5 38 .6 30 .1 30 .6 29 .2 35 .2 c 0. 72 0. 53 1. 00 1. 15 1. 04 j 13 6 72 .3 73 .3 71 .7 65 .0 65 .3 59 .0 67 .8 a -0 .1 9 0. 13 0. 63 0. 34 0. 53 39 .6 41 .5 35 .3 32 .4 34 .0 33 .3 36 .0 c -0 .8 5 0. 66 0. 63 0. 59 0. 53 b ee ch er 61 .7 60 .5 59 .3 52 .0 45 .7 47 .0 54 .4 c d 0. 27 0. 55 0. 97 0. 92 0. 68 48 .7 42 .5 36 .7 35 .6 40 .7 41 .2 40 .9 b 2. 24 1. 52 0. 94 0. 68 0. 52 d ur aq i 78 .2 68 .7 73 .7 65 .3 45 .3 46 .7 63 .0 b 1. 69 0. 83 1. 01 1. 48 1. 15 54 .8 58 .2 52 .3 37 .7 44 .6 43 .9 48 .6 a -1 .1 0 0. 28 1. 09 0. 78 0. 66 m ea n 68 .8 a 63 .8 b 64 .0 b 57 .6 c 49 .3 d 44 .7 e 49 .2 a 46 .4 a 41 .2 b 35 .1 c 37 .4 c 34 .5 c ghaloub, nadaf and al-khamisi 16 17 differential response of barley to salinity (111.1 g/plant). stress susceptibility index values of j136 were low in relation to the control and consistent in both years at all higher levels of salinity, indicating its superiority in tolerance to salinity. dry matter yield (g/plant) dry matter yield also showed progressive and significant (p<0.05) decreases from the control to higher salinity levels in both years (table 6). dry matter yield was significantly reduced (p<0.05) by 16.22 % in 2002-03 and by 19.87 % in 2003-04 from the control at 3 ds m-1. it was further reduced significantly (p<0.05) by 41.8 % in 2002-03 and 35.0 % in 2003-04 from the control at 6 ds m-1. further decrease was to the extent of 54 % or more in 2002-03 and 46.89 % in 2003-04 or more from control. with respect to dry matter yield over salinity levels, in 2002-03, j-51 (47.1 g/plant) recorded the significantly (p<0.05) highest mean dry matter yield followed by j54 (40.6 g/plant) and beecher (40.2 g/plant), while in 2003-04, j-54 (28.5 g/plant) recorded the significantly (p<0.05) highest mean green matter yield, followed by j-136 (27.7 g/plant) and j-51 (27.4 g/plant). stress susceptibility index values of j-136 were low and consistent in both years at all higher levels of salinity in relation to the control, indicating their superiority in tolerance to salinity. other workers have also observed adverse effect of salinity on growth of barley as reductions in plant height, number of tillers, green matter and dry matter yields (demiral et al., 2005). many authors have reported variability in salt tolerance within species (shannon, 1985; kelmen and qualset, 1991; gonzales, 1996) but the criteria of selection for salt tolerance have not been consistent among investigators. salinity tolerance of a crop can be assessed either in terms of its physiology as a small relative growth reduction due to salinity or on an absolute plant basis as revealed by high growth rate in the presence or absence of salinity (rawson et al., 1988). on the other hand, shannon (1985) discussed salinity tolerance in terms of either relative tolerance, or by mean productivity differences between saline and non-saline environments, or across a range of saline environments with their merits and demerits in respect of both low yielding and high yielding lines. later, kelmen and qualset (1991) applied the concept of relative tolerance for selection of a cultivar using its stress susceptibility index with reference to particular susceptibility index values of j-136 were low and consistent in both years at all higher levels of salinity, indicating their superiority in tolerance to salinity. number of tillers/plant the numbers of tillers per plant were significantly (p<0.05) higher during 2003-04 than during 2002-03. there was a significant reduction in mean number of tillers with increased level of salinity (p<0.05) from the control to higher level of salinity up to 12 ds m-1 in both years. however, means of number of tillers in the control and 3 ds m-1 were not significantly (p>0.05) different in 2002-03, whereas those at 12 ds m-1 and 15 ds m-1 were not significantly (p>0.05) different in any of the years (table 4). the decrease in the number of tillers from the control to 3 ds m-1 was 11. 8 % in 2003-04. the decrease from the control to 6 ds m-1 was 29.5 % in 2002-03 and 23.0 % in 200304, whereas the reduction in the number of tillers was 39.1 % in 2002-03 and 54.9 % in 2003-04 at 15 ds m-1 as compared to the control. with respect to mean number of tillers/plant over salinity levels, in 2002-03, j-54 (14.9) recorded the significantly (p<0.05) highest mean number of tillers, followed by j-51 (11.8) and j-136 (8.1), whereas in 2003-04, j-54 (20.8) recorded the significantly (p<0.05) highest mean number of tillers, followed by j-136 (19.2) and j-51 (18.8). stress susceptibility index values of j-54 and j-136 were low and consistent in both years at all higher levels of salinity, indicating their superiority in tolerance to salinity. green matter yield (g/plant) green matter yield showed a progressive and significant (p<0.05) decreasing trend from the control to higher salinity levels in both years (table 5). green matter yield was significantly reduced (p<0.05); from the control by 13.4 % in 2002-03 and by 31.7 % in 2003-04 at 3 ds m-1. it was further significantly reduced (p<0.05) by 38.4 % in 2002-03 and 48.2 % in 2003-04 at 6 ds m-1 from the control. further decrease was to the extent of 55 % or more from the control. with respect to mean green matter yield over salinity levels, in 2002-03, j-136 (199.2 g/plant) recorded the significantly (p<0.05) highest mean green matter yield, followed by beecher (194.45 g/plant) and j-98 (191.3 g/plant), whereas in 2003-04, j-136 (124.7 g/plant) recorded the significantly (p<0.05) highest mean green matter yield, followed by j-98 (118.9 g/plant) and j-54 ghaloub, nadaf and al-khamisi 18 19 differential response of barley to salinity ta bl e 5. m ea n gr ee n m at te r w ei gh t/p la nt ( g) o f ba rl ey c ul tiv ar s du ri ng th e w in te rs 2 00 203 a nd 2 00 304 , a lo ng w ith th ei r st re ss s us ce pt ib ili ty in de xe s (s cj ) ba se d on g re en m at te r w ei gh t/p la nt . t he m ea ns w ith d if fe re nt le tte rs a re s ig ni fi ca nt ly d if fe re nt a t p ≤0 .0 5 ac co rd in g to l sd a nd s tr es s su sc ep tib ili ty in de x of ‘j ’ ( ds ), hi gh sa lin ity tr ea tm en t r el at iv e to ‘c ’ ( ds ), lo w s al in ity tr ea tm en t. c ul tiv ar 20 02 -2 00 3 20 03 -3 00 4 sa lin ity l ev el (d s/ m ) st re ss s us ce pt ib ili ty in di ce s sa lin ity l ev el (d s/ m ) st re ss s us ce pt ib ili ty in di ce s c on tr ol 3 6 9 12 15 m ea n s c 3 s c 6 s c 9 s c 12 s c 15 c on tr ol 3 6 9 12 15 m ea n s c 3 s c 6 s c 9 s c 12 s c 15 j 51 28 6. 58 28 2. 20 16 8. 67 14 9. 60 12 2. 67 82 .9 3 18 2. 11 a 0. 11 1. 07 0. 87 0. 90 0. 92 27 3. 33 11 0. 00 83 .3 3 76 .6 7 56 .6 7 30 .0 0 10 5. 00 b 1. 88 1. 44 1. 25 1. 13 1. 11 j 54 30 8. 13 24 4. 20 18 7. 47 13 5. 17 11 2. 43 66 .6 3 17 5. 67 a 1. 55 1. 02 1. 02 1. 00 1. 02 20 8. 87 15 0. 00 12 3. 33 84 .4 3 60 .0 0 40 .0 0 11 1. 11 ab 0. 89 0. 85 1. 03 1. 02 1. 01 j 98 31 1. 43 28 6. 87 21 3. 30 15 4. 43 10 9. 40 72 .5 0 19 1. 32 a 0. 59 0. 82 0. 92 1. 02 1. 00 22 5. 38 16 3. 51 11 5. 63 98 .9 3 59 .3 2 51 .1 0 11 8. 98 a b 0. 87 1. 01 0. 97 1. 05 0. 97 j 13 6 34 3. 50 28 4. 67 19 5. 20 15 8. 80 13 3. 13 79 .6 7 19 9. 16 a 1. 28 1. 12 0. 98 0. 96 1. 00 21 5. 47 16 7. 13 11 3. 30 11 8. 10 83 .1 3 50 .9 7 12 4. 68 a 0. 71 0. 98 0. 78 0. 88 0. 95 b ee ch er 34 2. 67 29 5. 67 20 0. 07 13 8. 40 11 5. 60 74 .5 0 19 4. 48 a 1. 02 1. 08 1. 08 1. 04 1. 02 18 2. 23 14 4. 44 10 6. 67 85 .5 7 53 .3 3 40 .0 0 10 2. 04 b 0. 65 0. 86 0. 92 1. 01 0. 97 d ur aq i 23 1. 40 18 5. 57 15 8. 47 83 .2 7 67 .4 0 42 .3 3 12 8. 07 a 1. 48 0. 82 1. 16 1. 11 1. 06 13 9. 03 11 4. 40 10 2. 70 63 .7 0 59 .1 3 35 .7 9 85 .7 9c 0. 56 0. 54 0. 94 0. 82 0. 93 m ea n 30 3. 95 a 26 3. 19 b 18 7. 19 c 13 6. 61 d 11 0. 11 e 69 .7 6f 20 7. 39 a 14 1. 58 b 10 7. 49 c 87 .9 0d 61 .9 3e 41 .3 1f ta bl e 6. m ea n dr y m at te r w ei gh t/p la nt ( g) o f ba rl ey c ul tiv ar s du ri ng th e w in te rs 2 00 203 a nd 2 00 304 a lo ng w ith th ei r st re ss s us ce pt ib ili ty in di ce s (s c. j) b as ed o n dr y m at te r w ei gh t/p la nt . t he m ea ns w ith d if fe re nt le tte rs a re s ig ni fi ca nt ly d if fe re nt a t p ≤0 .0 5 ac co rd in g to l sd a nd s tr es s su sc ep tib ili ty in de x of ‘j ’ ( ds ), hi gh s al in ity tr ea tm en t r el at iv e to ‘c ’ ( ds ), lo w s al in ity tr ea tm en t. c ul tio va r 20 02 -2 00 3 20 03 -3 00 4 sa lin ity l ev el (d s/ m ) st re ss s us ce pt ib ili ty in di ce s sa lin ity l ev el (d s/ m ) st re ss s us ce pt ib ili ty in di ce s c on tr ol 3 6 9 12 15 m ea n s c 3 s c 6 s c 9 s c 12 s c 15 c on tr ol 3 6 9 12 15 m ea n s c 3 s c 6 s c 9 s c 12 s c 15 j 51 78 .4 0 71 .7 3 43 .7 7 36 .9 3 30 .3 7 21 .4 0 47 .1 0 a 0. 52 1. 06 0. 98 1. 01 1. 00 63 .6 2 30 .7 0 23 .9 7 21 .1 7 15 .8 0 9. 13 27 .4 0 bc 2. 60 1. 78 1. 42 1. 22 1. 18 j 54 75 .2 7 55 .2 7 40 .7 0 28 .9 3 26 .5 0 16 .8 0 40 .5 8 b 1. 64 1. 10 1. 14 1. 06 1. 06 45 .4 2 37 .1 7 35 .9 9 23 .8 2 16 .4 7 11 .7 4 28 .4 4 ab 0. 91 0. 59 1. 02 1. 03 1. 02 j 98 38 .9 7 41 .0 3 29 .4 0 23 .2 7 18 .5 3 12 .3 3 27 .2 6 d -0 .3 3 0. 59 0. 75 0. 86 0. 94 37 .6 6 36 .5 4 27 .5 0 26 .1 0 15 .0 3 13 .9 0 26 .1 2 a 0. 15 0. 77 0. 66 0. 97 0. 87 j 13 6 51 .9 7 41 .0 7 26 .1 3 30 .1 3 24 .7 0 20 .2 7 32 .3 8 c 1. 29 1. 19 0. 78 0. 86 0. 84 40 .4 9 35 .6 3 26 .0 0 28 .6 6 21 .2 9 14 .0 0 27 .6 8 a 0. 60 1. 02 0. 62 0. 77 0. 90 b ee ch er 72 .3 0 57 .5 7 38 .8 0 29 .5 3 26 .0 7 16 .6 3 40 .1 5 b 1. 26 1. 11 1. 10 1. 05 1. 05 39 .4 5 37 .0 4 27 .5 0 22 .0 0 13 .9 7 11 .2 8 25 .2 1 ab 0. 31 0. 87 0. 94 1. 05 0. 98 d ur aq i 34 .4 3 27 .6 8 25 .6 7 12 .8 3 11 .0 0 7. 40 19 .8 4 e 1. 21 0. 61 1. 16 1. 12 1. 08 21 .8 3 22 .0 0 20 .5 7 10 .3 3 12 .6 7 7. 33 15 .7 9 bc -0 .0 4 0. 17 1. 12 0. 68 0. 91 m ea n 58 .5 6 a 49 .0 6 b 34 .0 8 c 26 .9 4 d 22 .8 6 d 15 .8 1e 41 .4 1a 33 .1 8b 26 .9 2c 22 .0 1d 15 .8 7e 11 .2 3f ghaloub, nadaf and al-khamisi 18 19 differential response of barley to salinity characters in high saline environments relative to low saline environments. in the present study, we have assessed the salinity tolerance of cultivars using the concepts of both stress susceptibility index at each higher salinity level in relation to the control and the mean value over the salinity treatments with respect to each character. we selected the most tolerant cultivars considering the information of all the characters under study. among test cultivars, tolerance to different salinity levels has been found consistent for traits like plant height and number of tillers, especially at higher levels of salinity (tables 3 and 4). similar observations have been made in wheat (nadaf et al., 2001) and in perennial rangeland and forage grass species (nadaf et al., 2004). among all the cultivars tested, the salinity tolerance of j-136 was higher and more consistent as it scored low values of stress susceptible index under high salinity levels in respect of all the four characters studied, viz. plant height, number of tillers, green matter and dry matter yield. it also had high mean values for three characters, viz. plant height, number of tillers and green matter yield. all other cultivars, however, responded differentially to different levels of salinity for different characters. acknowledgements the authors wish to thank mrs. majda s.s. al-zadjali and mr. muneer s.s. al-yahyai of the soil and water laboratory for their assistance in plant, soil and water analyses. references aoac. 1984. official methods of analysis. 14th ed. association of official analytical chemists, washington d.c., usa. demiral m.a,, m. aydin and a. yorulmaz. 2005. effect of salinity on growth chemical composition and antioxidative enzyme activity of two malting barley (hordeum vulgare l.) cultivars. turkish journal of biology 29:117-123. fischer, r.a. and r. maurer. 1978. drought in spring wheat cultivars: i. grain yield responses. australian journal of agricultural research 29:897-912. fukai, s., searle, c., baiquni, h. and s. choenthong 1990. growth and grain-yield of contrasting barley cultivars under different plant densities. field crops research 23:239-254. gomez, k.a. and a.a. gomez. 1984. statistical procedures for agricultural research. 2nd ed. the international rice research institute, philippines. gonzales, l.m. 1996. principle component analysis and variety classification in relation to rice seedling tolerance. international rice research notes (irrn) 21:56-57. gorham, j. 1991. role of the physiologist in breeding for salt tolerance. plant salinity research, new challenges. proceedings of the international conference on agriculture management of saltaffected area in agadir morocco. r. choukar-alla (editor), publ. i.a.v. hassan, morocco. hockett, e.a. 1990. handbook of cereal science and technology, k.j. lorenz and k. kulp (editors), chapter 3, pp. 133-198. markel dekker, inc. hockett, e.a. and r.a. nilan. 1985. barley. d.c. rasmusson (editor), no. 26 in the series agronomy, chp. 8, pp. 190-231. american society of agronomy, crop science society of america, soil science society of america, 677 s. segoe road, madison, wi 53771. jaradat a.a., m. shahid and a. al-maskri. 2004. genetic diversity in the batini barley landraces from oman. ii. response to salinity stress. crop science 44:997-1007. kelmen, w.m. and c.o. qualset. 1991. breeding for salinity stressed environments: recombinant inbred wheat lines under saline irrigation. crop science 31:1436-1442. mcleod, e. 1982. feed the soil. organic agriculture research institute, p.o. box 475, graton, ca., 95444. mstatc. 1989. crop and soil sciences department, michigan state university, version 1.42, 19871989. nadaf, s.k, s.m. al-farsi and s.a. alhinai. 2004. response of indigenous rangeland forage species to salinity imposed from germination stage. arabian peninsula region program (aprp). international center for agricultural research in the dry areas (icarda). annual report of 20032004. pp 133-139. nadaf s.k., s.a. khamisi., a.h. al-lawati and o.a. sidahmed. 2001. response of wheat (triticum aestivum l.). to salinity. i. agronomic traits and yield attributes. sultan qaboos university journal of scientific research agricultural sciences 6: 15-32. ghaloub, nadaf and al-khamisi 20 qualset, c.o. and h. corke. 1991. plant breeding to develop varieties for crop production with alternating saline and non saline irrigation: a case study of wheat in california. plant salinity research, new challenges. proceedings of the international conference on agriculture management of salt-affected areas held in agadir morocco. r. choukar-alla (editor). publ. i.a.v. hassan, morocco. rawson, h.m., r.a. richards and r. munns. 1988. an examination of selection criteria for salt tolerance in wheat, barley and tritical cultivars . australian journal of agricultural research 39:759-772. salim, m. 1991. comparative growth responses and ionic relations of four cereals during salt stress. journal of agronomy and crop science 166:204209. shannon, m.c. 1985. principles and strategies in breeding for high salt tolerance. plant and soil 89: 227-241. wyn jones, r.g. and j. gorham. 1986. the potential for enhancing the salt tolerance of wheat and other important crop plants. outlook on agriculture 15: 33-39. received: march 2006 accepted: march 2007 agricultural and marine sciences, 15:33-39 (2010) ©2010 sultan qaboos university 33 __________________________________________________ *corresponding author. e-mail: goatfarm@isb.paknet.com.pk meat production potential of small ruminants under the arid and semi-arid conditions of pakistan mohamed fatah ullah khan* and faisal ashfaq small ruminants research program, animal sciences institute, national agricultural research centre, park road, islamabad-45500, pakistan في باكستان الجافة وشبھ الجافة الظروف الصغیرة تحت المجترات من اللحوم إمكانات إنتاج أشفاق وفیصل خان فتاح اهللا محمد من رأس ملیون ٥٣,٨ حوالي بالبالد یوجد باكستان. في الجافة وشبھ الجافة الظروف تحت اإلقتصادیة النشاطات أھم من والماعز الضأن إنتاج یعتبر الخالصة: من ٪٤٠ لحوالي مصدرًا الصغیرة المجترات تشكل حیث اللحوم إنتاج الصغیرة المجترات تربیة من الرئیس الھدف ویعتبر الضأن من رأس ملیون و٢٦,٥ الماعز باكستان في الماعز عــدد في الــزیــادة معدل كــان زاد. قد الحیوانیة المنتجات من للفرد اإلستھالك معدل أن لوحظ وقــد البالد. في المنتجة الحمراء اللحوم مجموع واألغنام الماعز ــالالت س أھــم مناقشة سیتم الورقة ھــذه في الماعز. تعداد ناحیة من آسیا في الثالث المركز في باكستان وكانت آسیا في األعلى وھــو ٪٤ حوالي إستغالل إمكانیة على شــواھــد ھناك ولكن التجاري المستوى على الــبــالد فــي والــضــأن الماعز لتسمین نظام یوجد ال اللحوم. إلنــتــاج األھمیة ذات باكستان فــي وسط التجاري التسمین عملیات على اإلعتماد یجب والتصدیر المحلي والماعز الضأن لحوم من الطلب على الزیادة ولمقابلة اللحوم. إلنتاج المحلیة والماعز الضأن في باكستان. الخاص المزارعین والقطاع keywords: feedlot, mutton, goat breeds, pakistan. abstract: sheep and goat production is one of the major economic activities under the arid and semi-arid condition of pakistan. the country has 53.8 million goats and 26.5 million sheep. the main purpose of raising these small ruminants in the country is meat production. the small ruminants share about 40% of total red meat produced in the country. it has been observed that in the last several years the overall per capita consumption of the animal food products is increasing. overall annual growth rate of goats in pakistan is 4%, which is the highest in asia. pakistan ranks third in asia in small ruminant population. some famous sheep and goat breeds of pakistan which have potential for mutton production will be discussed in the paper. there is no feedlot fattening system functioning in the country on a commercial level. the indicators suggest that there are good prospect for sheep and goat to be used as meat animals. in order to meet the increasing demand of mutton locally as well as for export, feedlot operations are required to be introduced among the farmer communities and in the private sector in pakistan. introduction small ruminants contribute largely to the livelihoods of the livestock-keeping households of low and medium income farmers in the developing world. the keeping of small ruminants is mainly concentrated in the developing areas of the world. small ruminants make up a large proportion of the domestic ruminants in asia in terms of numbers and in contribution to meat production. asia accounts for 52% of the world’s small ruminant population as reported in table 1 (faostat, 2006). in pakistan small ruminants (sheep and goats) are raised by landless or poor farmers with minimum landholdings. pakistan has about 34 goat and 28 sheep breeds (isani and baloch, 1996). the majority of sheep and goat breeds in pakistan are meat type animals. some breeds like beetal, dera din panah (ddp), kamori, nachi and damani are known as dairy goat breeds but are not comparable to the improved dairy goat breeds from europe and north america. the meat supplied by small ruminants is preferred over meat from large ruminants in pakistan particularly, goat meat. moreover, the value of goat meat is higher than the meat supplied by sheep and any other livestock species such as cattle and buffalo. growth dynamics and distribution of small ruminants sheep and goats make up a large population of domestic animals in pakistan. the population of sheep and goats and their overall growth is presented in table 2. according to pakistan national livestock census (2006) goat has the highest growth rate of 3.98% per annum among all the domestic livestock in pakistan. sheep has a growth rate of 0.84% per annum, lowest among the livestock. according to the faostat (2006), goats in pakistan are increasing at a rate of 3.78% annually, which is the highest in 34 khan and ashfaq 35 meat production potential of small ruminants under the arid and semi-arid conditions of pakistan asia. the reason for the higher annual growth rate of goat is the national preference for goat meat as compared to the meat of other ruminants. moreover, the higher growth rate of the goat population can also be attributed to their suitability to the environment and their twinning ability. punjab has the highest goat population (37%) followed by sindh (23%) baluchistan (22%) and nwfp (18%) as shown in table 2, whereas baluchistan has the highest sheep population (48%) followed by punjab (24%), sindh (15%) and nwfp (13%). after 1998, in the opinion of the authors, the sheep population has further decreased in baluchistan province due to persistent drought between 1998-2000. it has been estimated that 30% of the total livestock population has been lost due to drought (azam, 2005). there is substantial increase in the total population of small ruminants over the last twenty years. however, this increase is in the number of animals rather than a per head increase of the produce. sheep and goat breeds pakistan has 28 breeds of sheep and 34 breeds of goat which are listed below in tables 3 and 4. a lot of variation exists in characteristics among various sheep and goat breeds. sheep breeds differ from thin tailed to fat tailed sheep and more variation exists in growth and wool production. similarly, goat breeds differ in growth, reproduction and milk production. goats are also kept primarily for meat production. some goat breeds such as beetal, dera din panah, nachi and kamori are known as milk breeds. these are breeds whose meat is also most liked in their respective areas, especially beetal and kamori. therefore, these breeds are known as dual purpose. teddy is a small size breed, which has gained wide distribution and popularity over the last 30 years because of its prolificacy and faster growth rate. meat and goat production total meat production from small ruminant in asia has been presented in table 5. the asian continent contributes 61% of the total mutton and goat meat produced in the world. china produces 54% of total mutton and goat meat in asia. pakistan ranks third in asia for mutton and goat meat production after india. for the last two years, india’s mutton and goat meat production is maintained at a consistent level. pakistan contributed about 7% of mutton and goat meat produced in asia (faostat, 2006). there is no system of producing mutton and goat meat on scientific and commercial lines that is common in the developed countries and this system is known as feedlot fattening. almost all the mutton production is supplied from the conventional production system with minimum nutrition inputs and thus the carcass weight is usually low table 1. population of small ruminants in the world and major countries in asia (million heads). region 1996 2000 2005 sheep goat sheep goat sheep goat world 1060.01 689.43 1053.64 722.15 1079.73 807.24 asia 411.94 441.84 414.40 454.24 456.65 519.29 china 127.63 149.91 131.09 148.40 170.88 195.76 india 55.29 119.48 59.60 121.40 62.50 120.00 pakistan 23.54 41.17 24.08 47.43 24.90 56.70 source: faostat, 2006. table 2. population and growth trend of small ruminants in pakistan (million heads). province 1986 1996 2006 % annual growth rate punjab sheep goat 6.69 10.76 6.11 15.24 6.36 (24%) 19.83 (37%) -0.25 +4.21 sindh sheep goat 2.62 6.76 3.76 9.89 3.96 (15%) 12.57 (23%) +2.56 +4.30 nwfp sheep goat 2.23 4.20 2.82 6.59 3.36 (13%) 9.60 (18%) +2.55 +6.45 baluchistan sheep goat 11.11 7.30 10.81 9.48 12.80 (48%) 11.78 (22%) +0.75 +3.05 total pakistan sheep goat 22.69 29.95 23.54 41.20 26.48 53.78 +0.84 +3.98 source: pakistan national livestock census, 1986, 1996 and 2006. 34 khan and ashfaq 35 meat production potential of small ruminants under the arid and semi-arid conditions of pakistan table 3. sheep breeds in pakistan (n=28). punjab 7 buchi, lohi, thalli, kajli, cholistani, salt range, sipli sindh 3 dumbi, kachhi, kooka nwfp 7 balkhi, damani, kaghani, hashtnagri, michni, tirahi, waziri baluchistan 4 balochi, bibrik, harnai, rakhshani northern area and ajk 7 baltistani, gojal, kail, kali, koh-i-ghizer, pahari, poonchi source: isani and baloch, 1996. table 4. goat breeds in pakistan = 34. punjab 4 beetal, dera din panah, nachi, teddy sindh 14 barbari, kamori, chappar, bari, bugi toori, sindh desi, bujri, jattan, kacchan, kurri, lohri, pateri, tapri, tharki nwfp 3 kaghani, damani, gaddi baluchistan 3 lehri, khurasni, kajli northern area andajk 10 baltistani, beiari, buchi, jararkheil, jattal, kohai-ghizer, kooti, labri, pamiri, shurri source: isani and baloch, 1996. table 5. comparative meat production (million tons). 1996 2000 2005 sheep goat sheep goat sheep goat world 7.02 3.09 7.59 3.73 8.44 4.53 asia 2.98 2.11 3.48 2.67 4.50 3.41 china 1.00 0.81 1.44 1.30 2.40 1.90 india 0.21 0.45 0.22 0.46 0.24 0.47 pakistan 0.15 0.28 0.16 0.31 0.17 0.37 source: fao, 2006. compared to the potential present in some of our sheep and goat breeds. absence of feedlot fattening is one of the major constraints against a higher quality and quantity of meat production. in pakistan total mutton and goat production is 782 thousand tons as shown in table 6. it accounts for 40 percent of total red meat production in the country (anonymous, 2006). the slaughtered number of sheep and goats was about 15.73 million heads. of the total meat production in pakistan, 69.5 % is contributed by goats (anonymous, 2007). when total mutton production data from 1976 to 1996 was reviewed, the mutton and goat meat production increased at a rate of 4.59 percent per annum (khan et al., 2003). later increase in mutton and goat meat per year is about 2-3% (table 6). it means that mutton and goat meat production has increased at a slower rate than the previous years. comparison of per capita meat consumption (kg) indicates a growing demand for meat in pakistan in the years to come (table 7). this relates to the increasing population growth and the prevailing livestock production systems. growth and fattening of small ruminants planned studies on the growth rate of sheep and goats at different ages have not been undertaken. however, some information has been taken on different sheep and goat breeds maintained at the state livestock farms and these were reported by hasnain (1985), isani and baloch (1996). birth weight, weaning weight, mature body weight and dressing percentage of selected sheep and goats breeds found in different parts of country are presented in tables 8 and 9. in the previous papers, only those sheep and goat breeds have been reported which have an adult body weight not less than 30 kg. among sheep breeds in pakistan kajli and lohi sheep breeds have the highest adult body weight and these breeds have the highest daily growth rate. a similar observation was also made by ahmed and rehman (1996) who reported the highest growth rate in kajli sheep in their experiments under farm conditions. most of the sheep breeds have a carcass percentage between 45 to 55%, which means that these breeds are not fed efficiently. similarly, the mature body weight of ten selected goat breeds of pakistan which have a good meat production potential are reported in the paper. isani and baloch (1996) reported the highest weaning weight of 30 to 36 kg in the male of jattan and kacchan and kamori breeds, which have the highest growth rate of 270 g/day. on the other hand, goat breeds of punjab like beetal, dera din panah and nachi have a weaning weight of 25, 25 and 15 kg in male kids respectively, as reported by hasnain (1985). growth rate/day of these breeds are 177, 185 and 36 khan and ashfaq 37 meat production potential of small ruminants under the arid and semi-arid conditions of pakistan 107 g under traditional farming system. the average daily weight gain of damani and nachi usually ranged from 5070 g/day (khan et al., 2003) under rangeland conditions which is lower than their genetic potential. most goat breeds, like sheep breeds found in pakistan, have 50% dressing percentage which is high as compared to indian goat breeds like beetal, jamnapari and serohi (acharya, 1988). the mutton and goat production gap between the conventional farming system and commercial farming system is significantly wide. under traditional farming system of pakistan, small ruminant’s weight gain ranges from 50-70 grams, whereas daily weight gain under balanced feeding and management program reported by table 6. meat production from small ruminants in pakistan (000 tons). source of meat 1995-96 2005-06 % annual increase (1996-2006) sheep 214 238 1.12 goat 374 544 4.54 total of pakistan 588 782 3.30 source: anonymous, 2006. table 7. per capita meat consumption (kg/annum). countries 1983 1993 2020 developed world 74 76 83 developing world 14 21 30 pakistan 11 16 47 source: anonymous, 2003. table 8. production traits of selected sheep breeds in pakistan. breeds province birth wt (kg) weaning wt (kg) growth rate (g/d) adult wt (kg) dressing percentage kail ajk 2.5 15.0 104 41 45 baluchi baluchistan 3.0 21.5 154 38 45 balkhi nwfp 3.5 22.5 158 55 50 kajli punjab 4.0 21.5 146 78 55 lohi punjab 3.3 21.0 149 61 50 salt range punjab 3.0 21.0 150 35 45 thalli punjab 3.7 20.0 137 35 50 dumbi sindh 3.0 20.0 142 40 40 kachhi sindh 3.1 22.5 162 42 50 kooka sindh 4.0 26.0 183 52 45 source: isani and baloch, 1996; qureshi et al., 2002; rafiq et al., 2003; shah and khan, 2004. hasnain (1985) in beetal is 247, nachi 359 and ddp 134 g/day. an improved system of production like energy and protein supplementation in feed resulted in an increase in the reproduction performance, survivability and growth rate in small ruminants (rafiq et al., 2003). similarly, the average daily gain (adg) can be improved by 61-141% and the carcass weight by 34-79% owing to improved feeding management. in fact according to the review of wilson (1992), feeding is one of the most important factors to influence meat production and carcass quality of small ruminants. however, in tropical less-developed countries, because of the high cost of concentrate, solutions must be aimed at developing new feeding strategies. the range in productivity and adg illustrates existing possibilities for higher animal performances through a combination of nutrition management and breeding of adapted genotypes. results of some selected studies under improved feeding and management are given in table 10. potential of sheep and goat as meat animals the primary objective of sheep and goat farming in pakistan is meat production maintained under different production systems. under the traditional production system, growth rate per day of these species is very low with respect to their genetic potential. few planned studies on the fattening potential of sheep and goat have been conducted at the livestock production research institute (lpri) okara and national agricultural research centre, islamabad. the main findings of these studies are reported in tables 11 and 12. khan et al. (2003) conducted some fattening trials on male beetal kids, crossbred goat under field conditions and the data on these trials are presented in table 12. these animals were fed on a ration having 20 % roughage and 80 % concentrate and having 15-16% crude protein 36 khan and ashfaq 37 meat production potential of small ruminants under the arid and semi-arid conditions of pakistan table 9. production traits of selected goat breeds in pakistan. breeds province birth wt (kg) weaning wt (kg) growth rate (g/d) adult wt (kg) dressing percentage gaddi nwfp 2.8 23.6 173 50 50 beetal punjab 3.7 25.0 178 46 50 dera din panah punjab 2.7 25.0 186 45 50 nachi punjab 2.0 15.0 108 45 45 teddy punjab 1.6 12.0 80 32 50 jattan sindh 3.5 36.0 271 78 50 kacchan sindh 3.5 35.0 263 68 48 kamori sindh 3.5 35.0 263 72 50 kurri sindh 3.0 24.0 175 50 50 pateri sindh 3.6 30.0 178 70 45 source: isani and baloch, 1996; hasnain, 1985. table 10. effect of system of production on growth and carcass characteristics. authors and conditions variable traditional system improved management improvement (%) wilson (1992): (hay/concentrate ratio: 40/60 vs. 20/80) dressing percentage 38 49 29 fat thickness (mm) 1.6 3.8 137 moniruzzaman et al. (2002): black bengal in bangladesh slaughter weight (kg) 9.0 12.3 37 hot carcass weight (kg) 3.4 5.2 53 dressing percentage 34 42 23 rafiq et al. (2003): salt range daily weight gain (g/d) 112 131 16 weaning weight (kg) 7.6 9.0 20 alexandre et al. (2004): creole, africa daily weight gain (g/d) 36 87 141 hot carcass weight (kg) 6.5 8.7 34 khan et al. (2006): balkhi sheep daily weight gain (g/d) 158 276 75 weaning weight (kg) 22.5 33.0 47 table 11. fattening potential breeds nos. of animal age (month) final bwt, (kg) d.wtg, (g/d) total wt gain (kg) fcr thalli 30 4 38.1 119 14.6 13.8 lohi 30 4 36.3 125 12.5 11.7 kajli 30 4 37.1 109 11.5 11.2 beetal 30 4 30.1 67 10.5 15.7 dera din panah 30 4 30.6 62 9.1 13.8 teddy 30 4 17.2 40 5.7 16.2 cp: 14 %, tdn: 71% source: khan and pasha, 1990. 38 khan and ashfaq 39 meat production potential of small ruminants under the arid and semi-arid conditions of pakistan and 71-80% total digestible nutrients. keeping in view the data presented in the above table and the weight gains under traditional farming system, it can be concluded that there is a great potential to bridge the gap between demand and supply. on the basis of reported birth weight, weaning weight, growth rate/day, mature body weight and dressing percentage, the following small ruminant breeds have potential for meat production (table 13). the above-mentioned small ruminant breeds can be used for fattening under the feedlot system. export of mutton and goat meat keeping in view the data presented in the tables 8 and 9 and weight gains under the traditional farming system, it can be concluded that there is a great potential to bridge the yield gap of about 200 % which can be achieved through balanced feeding and management under feedlot farming system. the data on the export of meat is given in table 14. it clearly shows that the demand for pakistani meat is increasing year by year, especially in the gulf states. keeping in view the generation of more demand for export, efforts should be made to increase meat production by introducing the feedlot fattening system into pakistan. conclusions • annual growth rate of 4 % and 0.8% was observed in goats and sheep, respectively during 1986-2006. • productivity per unit of small ruminant is low under the prevailing production system. • higher growth potential in on-farm trials were observed as compared to field observations. references acharya, r.m. 1988. goat breeding and meat production. in: proceedings of a workshop on the goat meat production in asia. c. devendra (editor), 14-29. tando jam, pakistan. anonymous. 2003. tcp/pak/0168 livestock action plan. food and agriculture organization of the united nations, islamabad, pakistan. anonymous. 2006. agricultural statistics of pakistan 2005-06. government of pakistan, ministry of food, agriculture and livestock, food, agriculture and livestock division (economic wing), islamabad. anonymous. 2007. economic survey of pakistan 2006-07, government of pakistan, finance division, economic adviser’s wing, islamabad. ahmed, m.k. and a. rehman. 1996. production performance of different sheep breeds under standard table 12. fattening of sheep and goats under intensive feeding system. breeds days nos. of animal age (months) initial bwt, (kg) final bwt, (kg) dwg (g/d) total wt gain (kg) fcr beetal goat 69 14 6 30.20 41.50 163 11.29 beetal x teddy goat 69 14 6 24.10 35.35 163 11.25 beetal goat 65 201 10-12 28.00 42.28 220 14.30 crossbred goat 60 60 10-12 20.90 32.47 193 11.57 salt range lambs 90 16 5-6 21.30 38.22 188 18.00 8.02 balkhi lambs 90 18 3-4 34.00 56.00 244 22.00 9.00 cp: 15-16%, tdn: 71-80% source: sharif and jabbar, 1999; khan et al., 1997, 2000, 2006. table 13. proposed potential sheep and goat breeds for meat production in pakistan. province species breed punjab goat sheep beetal, dera din panah, teddy kajli, lohi, salt range and thalli sindh goat sheep barbari, kacchan, kamori, jattan, pateri dumbi, kachhi and kooka nwfp sheep balkhi baluchistan sheep baluchi aj and k sheep kail table 14. export of meat. year production (000 tons) export (000 tons) % 2002-03 702 1.09 0.15 2003-04 720 0.53 0.07 2004-05 740 1.90 0.25 2005-06 782 4.01 0.51 2006-07 827 5.84 1.03 source: minfal, 2007. 38 khan and ashfaq 39 meat production potential of small ruminants under the arid and semi-arid conditions of pakistan feeding and management condition. in: proceedings of regional seminar on small ruminants. w. ahmad, m. nawaz and t. aziz (editors), islamabad, pakistan. alexandre, g., r. arquet, g. gravillon, j.l. weisbecker and n. mandonnet. 2004. carcass characteristics of creole goat of guadeloupe (fwi) as a function of feeding management. in: proceedings of eighth icg, abstract, submitted for publication. azam, m. 2005. assessment of socio-economic impacts of drought in pakistan in: final reportpcrwr – ministry of science and technology, islamabad. faostat. 2006. fao animal statistics. http://www. faostat.fao.org hasnain, h.u. 1985. sheep and goats in pakistan. animal production and health paper no. 56, fao, rome, italy. isani, g.b. and m.n. baloch.1996. sheep and goat breeds of pakistan. press corporation of pakistan. p.o. box 3133, karachi. khan, a.g., a. azim, m.a. nadeem and m.a. khan. 1997. effect of growth fattening diets on the growth performance of intensified afghani lambs. small ruminant research 25:39-42. khan, a.g., a. anjum, m a. nadeem and m. ayaz. 2000. the effect of formaldehyde treatment of solvent and mechanical extracted cottonseed meal on performance, digestibility and nitrogen balance in lamb. asianaustralasian journal of animal science 13:785-790. khan, a.g., a. azim and m.i. anjum. 2003. prospects of goat as meat animals of pakistan. in: proceeding of the international seminar on goat production in saarc countries. m. afzal and r.h. usmani (editors), pakistan agricultural research council, islamabad. khan, h.a. and t.n. pasha. 1990. fattening potential of different indigenous breeds of sheep/goats for mutton production. khan, m.f., m. rafiq, f. ashfaq and m.m. shahid. 2006. economic production traits of balkhi sheep breed for mutton production in pakistan. in: proceedings of the 12th aaap animal science congress, busan, korea. livestock census. 1986. agricultural census organization, statistics division, government of pakistan, gulberg, lahore. livestock census. 1996. agricultural census organization, statistics division, government of pakistan, gulberg, lahore. livestock census. 2006. agricultural census organization, statistics division, government of pakistan, gulberg, lahore. minfal. 2007. ministry of food, agriculture and livestock, government of pakistan. moniruzzaman, m., m.a. hashem, s. akhtar and m.m. hossain. 2002. effect of different feeding systems on carcass of black bengal goat. asian-australasian journal of animal science 15:61-65. qureshi , m.a., m. abdullah, a. ghaffar and m.f. khan. 2002. performance of kajli sheep at khizarabad: production as influenced by some environmental factors. journal of animal production science 12: 118-121. rafiq, m., m.f. khan and k.m. aujla. 2003. economic benefits of flushing and supplemental feeding of salt range ewes on pothwar ranges of pakistan. pakistan journal of biological sciences 6:115-121. shah, m.h. and m.f. khan. 2004. establishment of a nucleus flock of highest genetic merit for breeding, production and propagation. 25th annual report 2003-04. livestock production research institute, bahadurnagar, okara, pakistan. pp. 48. sharif, a. and a. jabbar. 1999. personal communication. livestock production research institute, bahadurnagar, okara. wilson, r.t. 1992. goat meat production and research in africa and latin america. in: pre-conference proceedings of the 5th international conference on goats, new delhi, march 1992. invited papers, 2: 458-772. agricultural and marine sciences, 15:9-14 (2010) ©2010 sultan qaboos university 9 ______________________________________________ *corresponding author. e-mail: osmahgob@squ.edu.om an assessment of omani native sheep fiber production and quality characteristics osman mahgoub1*, isam t. kadim1, ahmed al-dhahab1, reynaldo b. bello2, issa s. al-amri3, and aisha a. ambu ali4 and samera khalaf1 1department of animal and veterinary sciences, college of agricultural and marine sciences, 2agricultural experiment station, college of agricultural and marine sciences, 3college of medicine and health sciences, po box 35, al-khod 123, sultanate of oman, 4department of marine sciences and fisheries, college of agricultural and marine sciences, po box 34, al-khod 123, sultan qaboos university, sultanate of oman abstract: wool production and quality measurements were carried out on 100 omani native female sheep (body weight 38.6 ± 5.5 kg; age 993 ± 488 d). sheep were kept in partially shaded pens and fed ad libitum rhodes grass hay (crude protein 8.83%) plus a daily amount of 200 g general ruminant concentrate (crude protein 16.5% dm). animals were shorn once a year and samples were taken from the left mid-side site to determine fleece and fiber characteristics. the scanning electron microscope (sem) was used to study the fine appearance of the wool fibers. a skin sample was used to study the histological arrangement and number of secondary and primary follicles. the greasy fleece weight (gfw) in omani sheep ranged between 0.502.65 kg (mean 1.12 ± 0.43 kg) and the gfw expressed as a percentage of bw ranged between 1.0-7.6 with a mean of 2.9 ± 1.16. clean wool yield in omani sheep fleece ranged between 57.1 and 88.4% with a mean of 76.4 ± 7.6. omani sheep fleece contained various staple shapes and had a mean staple length of 22.9 ± 1.16 cm, 4.3 ± 0.8 crimps per staple; and a mean fiber diameter of 46 ± 12 µm. electron microscopy revealed three types of fibers; wrap-around, angled type and polygonal and elongated scales. this study indicated a wide variation in the wool characteristics of omani native sheep fleece, which suggested that selection may be employed to improve wool production and quality in these sheep. keywords: oman, sheep, wool, fleece, assessment. العماني الضأن صوف وخصائص إلنتاجیة تقییم خلف وسمیرة أمبوعلي وعائشة العامري وعیسى بیلو ورینالدو الذھب وأحمد كاظم محجوب وعصام عثمان وتراوحت كیولوجرام (٥,٥±) ٣٨,٦ وزنھا متوسط ، العماني الضأن إناث من مئة على الصوف وخصائص إنتاجیة لتقییم منھجیة قیاسات ــراء إج تم الخالصة: إضافة خــام) بروتین ٪٨,٨٣) ــرودس ال حشیشة دریــس على الشھیة حسب تغذیتھا وتمت مظللة نصف حظائر في الضأن إیــواء تم یــوم. ٩٩٣ إلى ٤٨٨ بین أعمارھا لدراسة األیسر الجانب منتصف منطقة من عینات ــذت وأخ العام في ــدة واح مــرة الضأن جز تم یومیًا. ــام) خ بروتین ٪١٦,٥) المركز العلف من ــرام ج ٢٠٠ إلــى الحویصالت توزیع لدراسة الجلد من عینات جمع تم الصوف. أللیاف الدقیقة الخصائص لدراسة الماسح األلكتروني المجھر إستخدم واأللــیــاف. الصوف خصائص الخام الصوف وزن وكان كیلوجرام) ٠,٤٣ ± ١,١٢ قدره (بمتوسط كیلوجرام ٢,٦٥ و ٠,٥ بین العماني الضأن في الخام الصوف جزة وزن تــراوح والثانویة. األولیة الضأن صوف احتوى .٪٧,٦ ± ٧٦,٤ بمتوسط قدره ٪٨٨,٤ و ٥٧ النظیف بین الصوف وزن تراوح .١,١٦ ± ٢,٩ قدره بمتوسط ٧,٦ – ١,٠ الحي الحیوان وزن إلى منسوبًا سمك متوسط ــان ك بینما للخصلة، تــمــوجــات ٠,٨ ± ٤,٣ متوسط لھا ــم، س ١,١٦ ± ٢٢,٩ طولھا متوسط ــان ك مختلفة أشــكــال ذات خصل على العماني أوضحت الطویلة. والمنبسطة والمسسنة الملتفة الحراشیف ذات األلــیــاف: من ــواع أن ثالثة وجــود األلكتروني المجھر ــة دراس أوضحت میكرون. ١٢ ± ٤٦ اللیفة ونوعیة إنتاجیة لتحسین ــي ــوراث ال اإلنتخاب استخدام إمكانیة ــى إل اإلنتباه یلفت مما العماني، الــضــأن ــوف ص خصائص فــي كبیر تباین ھناك أن ــة ــدراس ال ــذه ھ فیھ. الصوف introduction sheep are important animals worldwide for the provision of animal protein and wool. their other products such as fiber, milk, skins or dung are also important as a source of income for small holders in the less developed parts of the world. oman has 361,000 sheep, 1,018,000 goats, 320,000 cattle and 118,000 camels (anonymous, 2005) with an estimated 3% annual increase in animal numbers. there is one major breed of sheep in oman kept in small flocks by nomadic and semi-nomadic pastoralists as well as by smallholder in settled villages. under almost all these conditions, sheep graze poorquality range grass and browse acacia shrubs and other trees, or they are feed rhodes grass hay, dates, dried fish sardines, banana stems and household leftovers. omani sheep, which are found over most of the northern parts of the country, are predominantly black but white sheep are not uncommon. they are thin-tailed (with slightly thicker base), small in size and unthrifty in appearance; males are mostly horned and females polled (anonymous, 1978). the average adult live 10 mahgoub and others 11 an assessment of omani native sheep fiber production and quality characteristics weight of omani sheep raised under traditional systems range between 22 and 25 kg (anonymous, 1978). under intensive management, omani sheep showed improved performance in the form of high growth rates and good carcass composition compared to those raised under traditional systems (al-nakib et al., 1996; mahgoub and lodge, 1994a, b). in oman, meat is the major product of sheep. little milk is consumed but their fiber is used by bedouins to make rugs, artifacts for household and racing camels. the local sheep are described as having coarse wool (anon, 1978) although no studies have been carried out to determine their skin cover fiber quality. the objective of this study was to evaluate the production and quality characteristics of omani sheep fiber. materials and methods animals experimental measurements were carried out on 100 omani native female sheep kept in the agricultural experiment station of the college of agricultural and marine sciences, sultan qaboos university. the sheep ranged in body weight between 29-51 kg (mean 38.6 ± 5.5 kg) and age between 285-2072 d (mean 993 ± 488 d). sheep were kept in partially shaded pens and fed ad libitum rhodes grass hay (dm 93.4%; with cp 8.83% dm, crude fiber 41 %dm, crude fat 1.8 %dm and ash 9.4 %dm) plus a daily amount of 200 g general ruminant concentrate (dm 92.7%; with cp 16.5% dm, crude fiber 2.26% dm, crude fat 3.34 %dm and ash 5.9% dm). water and mineral salt blocks were available ad libitum. animals were subjected to routine animal health procedures including regular vaccination and deworming. animals were weighed monthly. fleece measurements sheep were shorn once a year using an electrical commercial shearing device with a hand piece. greasy fleece weight was determined by weighing the fleece of sheep immediately after shearing on a digital scale. prior to shearing, a sample was taken from the left mid-side site, over the last rib, using the same shearing device. the wool yield was determined by weighing a sample from the mid-side site in an aluminum tray. the sample was then hand-washed thoroughly using a commercial detergent then dried in an oven at 70ºc for 24 hours. the tray plus sample were reweighed and the yield was computed as the difference in weight between greasy fleece weight and dry clean weight. staple and fiber characteristics mid-side site samples were used to study the fiber attributes in omani sheep. staple length was measured by carefully spreading the staple on a board and measuring it to the nearest mm from the cut base to the point at the tip where the bulk of fibers end using a ruler. the number of crimps was counted on each staple without maximum stretching. fiber diameter was determined using a microscope equipped with a caliper in the eyepiece, which was calibrated to a slide measure. a sub-sample of fibers was taken randomly and fitted to a microscope slide and fixed with a tape. the width of twenty fibers from each sample was measured at the middle of the fiber. histology skin samples were taken from the right mid-side site (over the last rib) from 16 omani sheep to study follicle structure while the sheep were controlled in the lateral recumbence position. the wool was clipped and the area disinfected with a multipurpose disinfectant. a shot of a local anesthetic was given and a circle of 5 mm diameter was made using a circular stainless steel cutter. scalpel blade and forceps were used to remove the skin sample, which was fixed in 10% buffered formalin for histology. blocks were prepared, sectioned and stained with haematoxlin/ eosin stain to enable studying the arrangement of primary and secondary follicles. electron microscopy the scanning electron microscope was used to study the cuticle scale pattern of wool fibers. about 10-15 fibers of about 1 cm length from each sample were cleaned in graded ethanol dilutions (25, 50, 75, 90 and 3×100%, 10 min each). they were blotted dry in filter paper then mounted in stubs. the fibers were placed in sputter coater, coated with gold particles for 1 min, and viewed with jeol jsm-5600lv scanning electron microscope. results and discussion wool production characteristics the gfw in omani sheep ranged between 0.50-2.65 kg with a mean of 1.12 ± 0.43 kg (table 1). this weight is within the range for tropical and sub-tropical sheep reported by gatenby (1986) but is well below that of specialized wool-producing breeds with gfw of about 4-5 kg. tabbaa et al. (2001) reported a gfw of 2.1 kg in 53 kg awassi sheep and a range of 1.2-1.9 kg gfw for other middle east carpet wool sheep. awassi is a major multipurpose sheep in the middle east and, in jordan fleeces were estimated to represent about 2.5% of the value of products from its commercial production beside meat and milk. the frequency distribution of the gfw is presented in figure 1. it represents a normal distribution bell curve slightly skewing to the left. the curve indicates that it is possible to improve wool yield in omani sheep by exploiting the elite group at the right end (with more than 2 kg gfw) to improve the average through selection because of the high heritability score for the gfw. ghoneim et al. (1974) reported that the heritability score for fleece weight in awassi iraqi sheep was 0.47 by paternal half10 mahgoub and others 11 an assessment of omani native sheep fiber production and quality characteristics sib correlation and 0.16 by regression of offspring on dam. repeatability was 0.32 by intraclass correlation and 0.36 by correlation between pairs of records. the authors recommended that for improvement of fleece weight, breeding stock should be selected for fleece weight at first shearing when they are 18 m old. to overcome the effects of the wide range of body weight in animals used in the present study, gfw was expressed as a percentage of bw and it ranged between 1.04 and 7.56 with a mean of 2.94 ± 1.16 kg (figure 2). this is higher than 2.2 kg gfw adjusted for bw in yearling awassi sheep (tabbaa et al., 2001). there was a trend oft fleece weight in kg or as a percentage of body weight, to increase with age with a maximum of 1.5 kg in 1267 d old sheep then slightly decreased to about 1.0 kg by the 1908 d group of age (figure 2). similarly, tabbaa et al. (2001) found that gfw was higher in yearling awassi sheep than in lambs but there was no difference between yearling and mature sheep in gfw. ghoneim et al (1974) reported that sex, age, year of shearing and type of birth table 1. omani sheep wool production parameters. statistical function body weight (kg) age (days) greasy fleece weight (kg) yield (%) greasy fleece weight/body weight mean 38.63 993.29 1.12 76.41 2.94 sd 5.49 488.30 0.43 7.56 1.16 maximum 51.00 2072.00 2.65 88.42 7.79 minimum 29.00 285.00 0.50 57.14 1.04 median 38.00 956.50 1.03 77.18 2.70 mode 39.00 300.00 0.70 na 2.70 significantly affected fleece weight. the fleece weight was the highest at the first and second shearings. yield in omani sheep fleece ranged between 57.14 and 88.42% with a mean of 76.4 ± 7.56 (table 1). this yield is comparable to that of 74-62% reported for tropical and subtropical sheep by gatenby (1986). the majority of omani sheep are black since black is a dominant color in omani sheep. however, some white omani sheep are also available and there are breeding programs for their improvement in breeding stations in the country (dr tag elsir issa, personal communications). such programs would be beneficial for improvement of omani sheep wool production. fleece characteristics the mid-side site position over the last rib was reported to be closely representative of both follicle and wool characteristics and therefore, much used in sampling (gatenby, 1986). this site has been used for assessing omani sheep fleece characteristics in the present study. figure 1. frequency distribution of the greasy fleece weight in omani sheep. 12 mahgoub and others 13 an assessment of omani native sheep fiber production and quality characteristics there were different staple shapes in omani sheep fleece (figure 3) ranging from rectangular aggregate of small staples to oval, but most had pointed tips. sheep producing coarse wool usually have more tippy staples. staple length in omani sheep fleece ranged between 12-37 cm with a mean of 22.86 ± 4.31 cm (table 2). this indicates that fleece from local sheep is longer than that reported for most tropical and subtropical sheep (gatenby, 1986). tabbaa et al. (2001) reported a staple length of 14 cm in awassi sheep. the number of crimps ranged between 2-6 (mean 4.30±0.80) indicating that the fleece of native omani sheep is more straight than curly. because of its crimp, or curl, wool has considerable resilience and with its high tensile strength and elasticity, gives fine woolen fabrics the ability to retain shape better than cloth made from other natural fibers. the length of omani sheep wool is much longer than that reported for carpet wool breeds (4-12 cm) and more similar to that of english long lustrous wool (dr. m. salehi, personal communication, 2008). the fiber diameter in omani sheep is presented in table 2. it ranged between 24-67.5 µm (mean 45.9 ± 12.26 µm). this ranks it among the carpet wool-producing sheep (gatenby, 1986). tabbaa et al. (2001) reported a fiber diameter of 36 µm. shepherd (1959, cited by gatenby, 1986) indicated that the range of fiber diameter for carpet wool should be 11-90 µm with 85% of the fibers in the range of 21-60 µm. according to dr salehi (personal communication, 2008), the diameter range of fibers in carpet wools range between 11-90 µm. the wide range in fiber diameter in omani sheep indicates a wide variation, which may be exploited using selection to improve the fineness of wool in these sheep. average fiber diameter is a trait with high heritability score of 0.45-0.60 (beatson, 1988) renders it rapidly responding for efficient selection programs. carpet wools consist of a mixture of true wool, hair, heterotypical and kemp fibers. the morphology, microscopy and dimension of each fiber types in carpet wool are different. the average diameter of carpet wools is between 25-35 µm in unimproved and native breeds in middle east or asian countries and between 35-45 um in improved carpet wool in new zealand and (dr m. salehi, personal communication ,2008). more detailed studies are needed to determine fleece characteristics of omani sheep figure 2. fleece weight (kg) and fleece weight as percentage of body weight expressed on various age groups of omani sheep. figure 3. three different types of omani sheep fleece. 12 mahgoub and others 13 an assessment of omani native sheep fiber production and quality characteristics using larger numbers of animals with separation of fibers to determine the percentage of each fiber type. fiber structure the outer surface of wool fiber enables it to be differentiated from hair mainly by the nature of the scales that cover the fiber. wool scales are numerous, minute, and pointed and are attached only at their bases causing interlock under pressure. the number of scales varies with the fineness and curliness of the fiber. accordingly, micrographs taken for the omani sheep fibers indicate that they look like fairly typical wool rather than hair fibers (figure 4). the micrographs also showed that there were three different wool fiber types available in omani sheep similar to those described by woods and orwin (1982) and shown in figure 4. the first type is a wrap-around scale pattern on keratinized wool fiber which is usually seen in fine wool fibers such as merino (dr joy wood, personal communication). scales in omani sheep of this type appears to be more numerous and pointed than in woods and orwin (1982) study. the second fiber type is the angled type of scale pattern which occur in medium diameter fibers. the angles of the omani sheep scales are not as steep as for those reported by woods and orwin (1982). the third type of fiber is the polygonal and elongated scale pattern type which usually occurs in coarse fibers. this is mainly observed in large-diameter fibers as for woods and orwin (1982). wool follicle arrangement (primary and secondary) determines wool characteristics. primary follicles give rise to coarser wool whereas secondary follicles give rise to true finer wool. ratio of primary (occurs in trios) to secondary follicles determines wool density and fineness with merinos having 15-25 of sec/prim ratio, omani sheep (table 2) would therefore have very coarse wool with a minimum number of primary and secondary follicles as well as low secondary/primary ratio. in specialized fine wool breeds such as the merino, primary follicles are arranged in the form of three "trios". other arrangements such as line and rectangular, are also observed in coarser wool breeds. omani sheep follicles are arranged in line with very few secondary follicles (figure 5). potential of wool production from omani sheep although it may currently appears to be a product of less significance, wool production from omani native sheep may be improved as an extra source of income to farmers. gatenby (1986) pointed out two major economical advantages of wool production in the tropics. first, there is no antagonism between meat and wool production, as the increase in body sizes tends to increase fleece weight. second, wool production can be economical in arid areas table 2. characteristics of omani sheep wool. statistical function staple length (cm) number of crimps number of crimp/cm fiber diameter (µm) no of primary follicles no of secondary follicles sec/prim mean 22.86 4.30 0.19 45.9 22.9 12.8 0.6 sd 4.31 0.80 0.03 12.26 8.2 10.5 0.4 maximum 37.00 6.00 0.29 67.50 43 40 1.6 minimum 12.00 2.00 0.12 24.00 1 0 0 median 23.00 4.00 0.18 45.25 22 10.5 0.51 mode 23.00 4.00 0.17 45.50 22 11.5 0.53 wrap-around scale angled type polygonal & elongated figure 4. micrographs showing various types of wool fiber structure in omani native sheep. 14 mahgoub and others with meager nutritional resources, as wool can grow even if sheep are losing weight. it is understood that in order to improve the wool industry, attention should be paid not only to genetical improvement of sheep, but also to improved management, nutrition, shearing operations, handling and storage of wool. to improve fleece quality characteristics experts may assess wool on living animals by visual appraisal and without sophisticated methods. therefore, omani natives may be trained to do on-farm assessment of promising wool-producing animals. there are some individual sheep selected for their pure white color and finer fibers at wadi qurayat breeding center (dr. tagelsir ali, personal communication). such sheep would be more suited for improved wool production in oman. improvement of fineness of wool is important but it should be taken into consideration that there is a negative relationship between wool quantity and quality as wool weight per unit of metabolic live weight significantly decreases with decreasing mean fiber diameter (saul et al., 1993). acknowledgement the authors would like to thank dr. joy l woods, wool fibre science and protein chemistry group, wool research organization of new zealand (inc.), for advice on identification of fibre types. thanks are due to wadi qurayat research station, ministry of agriculture, oman, for help with sampling. references al-nakib, f.m.s., e.s.s. al-shukaily, s.s.s. alhanai and s.a.m. al-nabhani. 1996. comparative performance of omani goats and sheep. journal of agricultural science, cambridge, 127:117-121. anonymous. 1978. livestock sector review and project identification final report, vol. 1. the sector review. a report prepared for oman ministry of agriculture and fisheries by hunting technical services ltd. and the sudanese investment and consultations co. ltd. muscat, oman 103pp. anonymous. 2002. statistical year book 2002. ministry of agriculture and fisheries, muscat, sultanate of oman (unpublished), 87pp. beatson, p. 1988. the theory of genetic improvement. in: wool production and preparation for profit. r.h. sanderson, d.j. cottle and l.f. story (editors), 35-37. lincoln college wool bulletin no.3. lincoln college, new zealand. gatenby, r.m. 1986. sheep production in the tropics and the sub-tropics. longman, new york, usa. 351pp. ghoneim, k.e., a.h. taha, n.t. kazzal and r.k.abdallah. 1974. effects of non-genetic factors and estimation of genetic parameters on fleece weight of awassi sheep in iraq. tropical agriculture (trinidad) 51:51-56. mahgoub, o. and g.a. lodge. 1994a. growth and body composition of omani local sheep. 1. live-weight growth and carcass and non-carcass characteristics. animal production 58:365-372. mahgoub, o. and g.a. lodge. 1994b. growth and body composition of omani local sheep. 2. growth and distribution of musculature and skeleton. animal production 58:373-379. orwin, d.f.g. and j.l. woods. 1982. the effects of within-fibre diameter variability and other fibre characteristics on the luster of wool. journal of the textile institute 74:118-130. saul, g.r., a.j.f. russell and a.r. sibbald. 1993. potential of different sheep breeds to improve wool production on uk hill and upland sheep farms. small ruminant research 11:1-9. tabbaa, m.j., w.a. al-azzawi and d. campbell. 2001. variation in fleece characteristics of awassi sheep at different ages. small ruminant research 41:95-100. woods, j.l. and d.f.g. orwin. 1982. the cytology of scale pattern formation in the wool follicle. journal of ultrastructural research 80:230-242. figure 5. histological section of omani sheep skin showing the arrangement of primary and secondary fibers. research paper journal of agricultural and marine sciences vol. 21 (1): 25 – 32 doi: http://dx.doi.org/10.24200/jams.vol21iss0pp25-32 received 15 sep 2014 accepted 11 nov 2016 fish landings and oman shelf area sergey a. piontkovski1*, h.e. hamed s. al-oufi2, and nadir m. al-abri2 *1 sergey piontkovski ( ) sultan qaboos university, college of agricultural and marine sciences, dpt. of marine science and fisheries. box 34, al-khod 123. sultanate of oman. email: spion@squ.edu.om. 2 ministry of agriculture and fisheries wealth. po 467, muscat 113. sultanate of oman. introduction long-term estimates of fisheries production over various ecosystems of the world ocean have in-dicated a large proportion of this production to be associated with shelf waters (caddy, 1993; caddy et al., 1998). on a regional scale, the arabian sea is the basin notorious for a variety of continental shelf geomorphology. the eastern part has a huge shallow shelf area underlying the coast of india. the marine fish production of this country has increased six times in the last 50 years and reached ~3.2 million tons in 2008, providing employment to about one million fishermen (rao, 2010). the western part of the arabian sea faces a much less extended shelf along the omani coast. oman fishery incorporates commercial and artisanal constituents with the latter accounting for 96% of landings. in 2008, the fishery landed ~102,000 metric tons and employed ~ 38,000 fishermen operating 14,796 fishing boats, 90 % of which are fiberglass boats 8-10 meters in length (fisheries statistics book, 2008). artisanal landings exhibit seasonal variation associated with monsoonal winds as well as the variety of fishing efforts. shelf areas change notoriously from ~2,000 km2 in the northernmost part of the arabian sea to ~17,000 km2 in its southern part. the role of the shelf area as the factor affecting fish landings is poorly understood in regional fishery. in the arabian sea demersal fishes accounted for 33% of the total landings along the omani shelf during the latest decade (2002-2012). however, while important, the demersal fishes are still poorly investigated in terms of spatial-temporal distribution of standing stock exhibiting gradual variance (mcilwain et al., 2011). we aimed to seek the relationship between the shelf area and the biomass of demersal fishes, which might be useful in management of shelf resources because this management is gradually affected by available set of regionally sensitive indicators linking shelf geomorphology, fishery, and the fish community structure (trenkel and rochet, 2003). also, the evaluation of relationship is regionally important because the shelf area affects the carrying capacity, which is a measure of the biomass of populations that can be supported by the ecosystem (mantua and hare, 2002). االنتاج السمكي و اجلرف القاري العماين سرجي بيتكوفيسكي1* ومحد العويف2 ونادر العربي2 abstract. data from five field surveys carried out along the shelf in the 20-250m depth range and historical data on artisanal fishery were analyzed. a positive linear relationship between the demersal fish biomass and the shelf area was pronounced for a certain (intermediate) stratum only: 50-100m. no statistical link was found for the strata above it (25-50m) and beneath it (100-150m and 150-250m). the pronounced one was associated with the low boundary of the oxygen minimum zone impinging on the shelf. annual landings of demersal fishes in the region with the largest shelf area exceeded landings in the region with the smallest area by as much as 1.6 times. the ratio of small pelagic to demersal fish landings decreased as a factor of 10, from small to large shelf areas. keywords: fish landings; arabian sea; continental shelf; oxygen minimum zone; oman املســتخلص:مت حتليــل بيانــات مخــس مســوحات مسكيــة أجريــت يف منطقــة اجلــرف القــاري يف أعمــاق تــراوح بــن 20-250 مــر باإلضافــة اىل البيانــات التارخييــة للصيــد احلــريف، حيــث تبــن وجــود عالقــة خطيــة بــن انتــاج االمســاك القاعيــة ومســاحة اجلــرف القاعــي لبعــض الطبقــات فقــط )50-100 مــر(. كمــا أنــه مل يتبــن وجــود عالقــة احصائيــة للطبقــة االعلــى )25-50 مــر( او الطبقــة األدىن )100150 مــر و150-250 مــر(. أن الطبقــة الــي ثبــت وجــود عالقــة خطيــة بــن االنتــاج واملســاحة تبــن ارتباطهــا بطبقــة ذات تركيــز متــدين مــن االكســجن املــذاب املالمــس لقــاع اجلــرف. وقــد تبــن أن االنتــاج الســنوي مــن االمســاك القاعيــة يف املنطقــة ذات املســاحة االكــرب مــن اجلــرف يزيــد عــن انتــاج املناطــق ذات املســاحة االقــل بواقــع 1.6 مــرات. كمــا أن نســبة انتــاج امســاك الســطح الصغــرة مقارنــة بامســاك القــاع تقــل مبقــدار 10 اضعــاف كلمــا انتقلنــا مــن منطقــة اجلــرف ذات املســاحة الصغــرة للمناطــق ذات املســاحات االعلــى. الكلمات املفتاحية: االنتاج السمكي، حبر العرب، اجلرف القاري، طبقة ذات أكسجن متدين 26 squ journal of agricultural and marine sciences, 2016, volume 21, issue 1 fish landings and shelf area in oman materials and methods seasonal surveys (these consisted of five voyages of r/v “mustagila1”) were carried out along the shelf in the 20250 m depth range from the ras al hadd region to the southernmost part of the omani shelf (to the yemen boarder). these surveys encompassed 4 shelf zones (a, b, c, and d) with 4 depth strata in each zone (fig. 1). the independent 1 “mother” trawl was used for all demersal fish surveys. all “mustaquila1” trawl surveys were standardized in a way that duration, speed, strata and gear were the same during all voyages standardizing in effect sampling effort. this allowed the total biomass to be compared over regions, depth strata and periods. a towing speed of 3.5 knots, a standard towing distance of 2.0 nautical miles, and trawl rigging to achieve sweeping gear angles of less than 20º were used. tows were carried out during daylight. the catch was weighted on motion compensated scales and identified to species. data on the total biomass for each survey (in metric tons) were retrieved from cruise reports (mckoy et al., 2009) averaged by strata and zones, for all demersal fish and shark species, combined and based on their size range. biomasses from the trawl survey was calculated using wingspread as the area swept. fish surveys were accompanied by conductivity temperature depth profiles (ctd). conductivity, temperature, density, depth, and dissolved oxygen concentration were measured using an rbr ctd probe deployed from the vessel (table 1). a simrad ek60 acoustic backscatter with 38khz, 120 khz and 200 khz transducers was used for routine acoustic surveys. the nearshore transects across the shelf began at a 200  m depth and extended up to 8km offshore. when deep-scattering layers were identified figure 1. scheme of shelf stratified sampling during the “mustaqila1” surveys (mckoy et al, 2009). a-d: shelf zones corresponding to (a) al-sharkiyah region, (b) al-wusta region), and (c+d) dhofar region. table 1. general characteristics of the “mustaqila1” voyages. voyage code time range no. of demersal stations no. of ctd stations no. of video camera stations no. of pelagic mark identification tows oma0701 sep-oct 2007 101 386 18 16 oma0702 nov-dec 2007 104 459 30 41 oma0801 jan-mar 2008 120 644 34 58 oma0802 apr-jun 2008 123 603 40 40 oma0803 aug-sep 2008 129 520 24 47 27research article piontkovski, al-oufi and al-abri on the sounder, pelagic trawls were used to catch the organisms. later on, catches were sorted by species. the p55 midwater trawl with a 10  mm liner in the cod end was used to sample mesopelagic organisms. along with data on the “mustaqila 1” surveys, we used historical data on fish landings which are routinely monitored by the department of fisheries statistics based on a sampling system established by the oman-american usaid project (mathews et al., 2001). monthly traditional (artisanal) landings were retrieved from the annual reports published by the ministry of agriculture and fisheries wealth (fishery statistics book, 2008). results the “mustaqila 1” field surveys began in september 2007 and captured a weakening south-west monsoon. during this monsoon, the omani shelf was occupied by the east arabian current (oman coastal current) directed north-westward and fed by limbs of the somali current (böhm et al., 1998). the ctd casts carried out along the shelf all implied fairly stable intra-seasonal structure in vertical distribution of temperature, salinity, density, and the dissolved oxygen concentration (figure 2). these major parameters resembled the thermocline, the picnocline and the oxycline all pronounced in the range from 30 to 100 m. for example, the temperature decreased from 21 ºc to 18 ºc in this layer; the oxygen concentration dropped from 2.7 to 0.2 ml l-1. the seasonal mode of monsoonal winds changes these patterns; however, the seasonality was analyzed elsewhere (piontkovski and al-oufi, 2014). given plots exemplified the location and strength of vertical gradients, which are important in the context of subsequent discussion. as far as the vertical distribution of demersal fish biomass is concerned, data from all surveys covering all strata and seasons allowed us to elucidate an exponential decrease of mean biomass over depth, from 20 to 250m (figure 3). the deviations from this trend are the ones in which the biomass in the intermediated stratum (50-100  m) exceed that in the stratum above (20-50  m) and strata below (100-150 m and 150-250 m). all these deviations were noticed for zones a, c, and d, and all dealt with the fall season, in which the dissolved oxygen concentration was minimal in comparison to other seasons. the 50-100m stratum was located in the low part of the oxycline. the biomass of demersal fishes in this stratum (for the “deviates”) exceeded the upper stratum biomass by a factor of two and the low stratum biomass by a factor of 30. data on the above displayed vertical distribution of temperature, salinity, dissolved oxygen concentration, and biomass over strata were subjected to the principal component analysis (pca) to understand the role of measured environmental factors in terms of their contribution to the total variance of the biomass. the pca is a data compression procedure which enables to reduce the number of variables to a few principal components (factors) reflecting the compression result. a statistical technique of pca is based on a rotation of the coordinate system of the variables in a way that in the new coordinate system of these variables is maximally uncorrelated. we used the varimax –normalized matrix of vari18 20 22 24 0 50 100 150 200 temperature d ep th (m ) 0 1 2 3 4 oxygen 1026 1027 density 36 37 38 39 salinity figure 2. vertical profiles of temperature, salinity, density, and dissolved oxygen concentration (september 2007, zone a). 28 squ journal of agricultural and marine sciences, 2016, volume 21, issue 1 fish landings and shelf area in oman ables. the varimax procedure amounts to a variance maximizing rotation of the original variable space. the transformed product was further treated as the measure of similarity between variables. the extraction of eigenvectors of the matrix enables one to reduce the diversity in the system of numerous variables to a few principal components (factors) in which the component scores are standardized units based on a correlation matrix. in other words, the eigenvectors are the results of the projection of the original variable axes into the space of new principal components. eigenvectors forming the principal components are based on the similarity coefficients in linear combinations of variables. once the internal structure of principal components is elucidated and these components are interpreted in some way, the relationship between the first two components (most important by loading) might be analyzed in the form of a scatterplot. in the space of two components, distances between sites approximate the euclidean distance of the transformed data. in our case, the similarity of distribution of variables over the space of the first two factors (principal components) showed an obvious split of data into three clusters (fig. 4). the first principal component explained 69% of the system total variance, whereas the other 31% were attributed to the second component. in terms of internal structure, the first and the second principal components are different by variables driving the factor load. for instance, first principal component (factor 1) is a complex of physical-biological variables in which variations of the biomass coupled with temperature and oxygen in the thermocline and oxycline have the highest scores by contributing to this factor. in terms of coupling in the space of two principal components, the biomass in the layer 50-100  m and the size of shelf areas are standing most close to each other (fig. 4). as for factor 2 contributing the remaining of the system total variance , it is loaded exclusively by physical variables (which are temperature, salinity, and oxygen coupling in layers beneath the thermocline). further on, to analyze statistical coupling between the parameters contributed to the first principal component, the ridge multiple regression was employed. the essence of ridge regression is the estimation of regression coefficients in the form of β! = xtx +ki( )−1 xt y (1) where k is the ridge parameter, i is the identity matrix, and x is the design matrix. when x has a linear dependence, the matrix xtx is close to singular. small positive values of k reduce the variance of the estimates. in turn, the reduced variance of ridge estimates gives a smaller mean square error when compared to least-squares estimates. ridge regression is tightly associated with the outcomes of the principal component analysis. it allows the large variance principal components to have a larger influence on the final model compared to the low variance principal components. in our case, the result of the ridge multiple regression might be characterized by the summary for the dependent variable (which is the biomass) implying that the size of shelf is the variable explaining a dominant part of the biomass variations over 0 50 100 150 200 0 20000 40000 60000 biomass (t) d ep th (m ) zone a c d figure 3. vertical distribution of demersal fish biomass. depth values on the vertical axis stand for the upper boundary of the trawl strata (20-50, 50-100, 100-150, and 150-250  m). mean b is averaged biomass (over all zones and voyages). a, c, and d are shelf zones (from figure 1). horizontal axis stands for a wingspread biomass for all fish and shark species over the total survey area. mean b(x) = 76025.5 exp (-0.03 depth); r= -0.89, p= 0.1 (linear fit). t155t105ox155 s155 ox105 s105 s55 s25ox25 t25 b150−250 b50−100 shelf ox55t55 b20−50 0.0 0.5 1.0 −1.0 −0.5 0.0 0.5 1.0 1.5 factor1 fa ct or 2 figure 4. mean wet weight (kg/m2) of macro-fouling communities developed on ceramic tiles exposed to fouling in marina bandar al rawdah. 29research article piontkovski, al-oufi and al-abri the omani shelf. the parameters of the ridge multiple regression were as follows: r2=0.98, standard error= 0.12, p < 0.07. the variation of the size area and other geomorphological characteristics of the omani shelf is quite diverse (figure 1). one could observe a wide area between 17on to 19on, a midsize fragment between 21°n to 22°n, a narrow strip zone in the southernmost part (17on17.5°n), a “bath-type” fragment in the westernmost part of the shelf in the sea of oman (not shown in the figure), among other types of fragments. this diversity sounds potentially important for carrying capacity characterizing the biomass of organisms the shelf could accommodate. the analysis of the variance of the total biomass of demersal fishes implied that the variance over different shelf regions (zones a to d) during one season exceeded the variance within a zone over seasons (sampled by 5 consecutive voyages). correspondently, we computed regressions linking the biomass with the shelf size for all voyages carried out during different seasons (table 2). high values of the determination coefficient (r2) pointed out the usefulness to assemble all five voyages in one plot. the generalized regression synthesizing the whole shelf and representing the total biomass of demersal fish as a positive linear function of the shelf area is displayed in figure 5. the coefficient of determination (r2) has pointed out that the statistical link in figure 5 explained 66% of observed biomass variation. as far as shelf characteristics are concerned, the shelf areas overlooking the western arabian sea exhibited almost 9 fold range extending from ~2000 km2 to ~17000km2. interestingly, the relationship between the demersal fish biomass and the shelf area was pronounced for a certain (intermediate) stratum only: 50-100 m. no statistical link was found for the strata above it (25-50  m) and beneath it (100-150  m and 150-250  m). the pronounced one was associated with the low part of the oxygen minimum zone impinging on the shelf. species diversity of demersal fishes was quite high. the taxonomic analysis of trawls carried out onboard enabled the abundant families and groups to be summarized, in terms of their contribution to the total trawlable biomass (table 3; mckoy et al., 2009). the percentage of 28 categories given in the table was low in general (constituting 7% for groups and 6% for families), with no spatial pattern pronounced over shelf zones. data on trawl catches from the “mustaqila1” voyages were compared to data on artisanal landings of demersal fishes along the omani shelf, for the year 2008. historical data available from the statistical reports of the ministry of agriculture and fisheries wealth resemble three major regions of fishery in the western arabian sea, namely al-sharkiyah, al-wusta, and dhofar. annual landings of demersal fish in dhofar (with the largest shelf ) area exceeded landings in al-sharkiyah by as much as 1.6 times (with the smallest shelf area). in terms of sustainability it might be noticed that the averaged long-term ratio for these two regions is 1.7 (2008-2012). we emphasized the fact that the biomass-to-shelf area relationship is coupled with the location of the seasonal oxycline (fig. 2) associated with the 30-100m depth range. the oxycline location exhibits seasonal as well as interannual fluctuations, discussed elsewhere (piontkovski and al-oufi, 2014). in order to understand whether the shelf area could affect the carrying capacity of pelagic fishes we analyzed two groups of data. the first one was represented by acoustic assessments of sardine biomass over regions during the “mustaquila1” voyages. the second one was data on artisanal landings of total pelagic fish and sardines (analyzed separately) retrieved from archives (fisheries statistics book, 2012). sardines were selected for both cases because they contribute about 30-50% table 2. parameters of regression equations representing the total biomass of demersal fish (y) as a positive linear function of the shelf size (x). voyage time range equation r2 p-level oma0701 sep-oct 2007 y= -18367.54 + 4.32x 0.98 0.05 oma0702 nov-dec 2007 y= -5580.91 + 3.33x 0.82 0.05 oma0801 jan-mar 2008 y= 2169.85 + 2.41x 0.91 0.05 oma0802 apr-jun 2008 y= 6136.36 + 2.85x 0.76 0.05 oma0803 aug-sep 2008 y= 1273.59 + 1.11x 0.49 0.05 0 20000 40000 60000 5000 10000 15000 shelf area (km2) b io m as s (t ) figure 5. relationship between demersal fish biomass and shelf area (50-100 m; all voyages). y = -1032.3 + 2.7x; r2=0.66. grayed area: 95% confidence level. 30 squ journal of agricultural and marine sciences, 2016, volume 21, issue 1 fish landings and shelf area in oman to omani artisanal landings over regions. in analyzing landings, we had to partially alter the shelf regions, in order to take into account (to eliminate as the factor) the number of boats involved. therefore, the regions selected for this analysis were the muscat shelf (with 1710 boats active in 2008), the al-wusta region (with 1801 boat), and dhofar (with 2075 boats). no statistical relationships were found between the shelf area and landings, as well as the shelf area and acoustically measured sardine biomass. this indicates that the standing stock of dominant pelagic species and their landings were not constrained by the shelf area. one of the integrative characteristics featuring the structure of fish communities is the ratio of small pelagic to demersal biomass reported from fish landings (caddy et al., 1998). we calculated this ratio using historical data on pelagic and demersal fish landings available for the three shelf regions of the western arabian sea, namely al-sharkiya (with the shelf area of 6,090 km2), al-wusta (7,666 km2), and dhofar (17,433 km2). in general, these regions correspond to zones a, b, and c+d, in figure 1. the ratio of small pelagic to demersal group landings (the p/d ratio) was plotted as the function of shelf area (fig. 6). we selected data for the years when the number of boats was not much different over regions (i.e. about 20%). this enabled us to exclude the factor of fishing efforts. the p/d ratio has decreased by a factor of 10, from small to large shelf areas. the key variable regulating the decline of this ratio was pelagic landings which exhibited the 6 fold decrease complemented by the 3 fold increase in demersal landings, from small to large areas. discussion the global scale comparisons pointed out that narrow oceanic shelves tend to have less demersal species than wide shelves and shelf seas (bergstad, 2009). in our case, data on the percentage of 28 taxonomic categories (table 3) enable us to assume that variations of shelf area (in a given range) do not affect the diversity on the level of groups and families which occur in relatively uniform proportions through all shelf areas regardless of their size. as the factor affecting demersal community, the shelf size seems to be coupled with the concentration of dissolved oxygen. in terms of vertical distribution of dissolved oxygen, the range of depth from 30 to 100 m was the most subjected to oxygen deficiency because of the location of oxycline. therefore, the statistically significant relationship between demersal fish biomass and the shelf area was observed for this particular layer. a positive linear regression linking the total biomass with shelf area was quite stable, because it was observed throughout the seasonal cycle (i.e. all five voyages of r/v “mustaqila 1”). table 3. contribution of groups and families (%) into the total biomass of mesopelagic fishes over regions per zone. family or group a b c d rays and skates 17.8 batoidea 19.9 22.9 13.1 11.8 catfhish 10 2.1 siluriformes 6.5 12.9 0.2 0.5 lizardfishes 16 synodovtidae 14 1.9 4 0.3 sea basses 1.5 1.7 5.8 serranidae 0.6 0.2 0.9 0.7 jacks 1.5 2.6 pompanos 2.3 4.7 7.7 3.4 carangidae 5.4 3.9 snappers 2.3 4.8 lutjanidae 0.4 0.1 0.3 0.4 grunts 5.6 3.7 5.8 haemulidae 10.9 15.3 4.1 7.7 threadfin breams 24.3 17 4.7 nemipteridae 20.4 13.2 16.8 1.7 emperors 3 12.3 8.2 11 lethrinidae 1.2 1.9 4 21.2 porgies 7.7 4.3 19.4 23 sparidae 10.8 9.3 17.6 16.9 drums 1.2 1.7 6 5.5 sciaenidae 0.4 1.4 0.4 17.4 barracuds 6.2 10 sphyraenidae 1.2 1.6 0.3 1 cutlassfishes 5.3 2.3 trichiuridae 1.1 2.6 0.4 0.1 pufferfishes 14.2 2.3 tetraodontidae 0.2 0.1 0.3 0.4 0 1 2 3 4 5 al−sharqyia(6090) al−wusta(7666) dhofar(17433) regions p /d ra tio figure 6. relationship between the p/d ratio and shelf area (2010-2012). numbers in parentheses: shelf area of regions (km2). shaded rectangles stand for 25-75% quartiles of distribution. 31research article piontkovski, al-oufi and al-abri seasonal cycle of oxygen deficiency forces demersal fish to migrate closer to the coast, which can lead to a compression of the habitat and subsequent increase of landings in shallow waters. indeed, data on some abundant groups are consistent with this hypothesis. for instance, the emperor (lethrinus nebulosus (forsskål, 1775); one of abundant species) was in highest landings in november-december, which is the time of maximal oxygen depletion along the shelf (piontkovski and al-oufi, 2014). carrying capacity of the omani shelf builds up differently, for pelagic and demersal fish communities. the standing stock of the pelagic community is not constrained by the shelf area, whereas the demersal fish stock does. along with that, both communities are affected by vertical distribution of the dissolved oxygen concentration (mcilwain et al., 2011; piontkovski and al-oufi, 2014). de leiva moreno et al. (2000) compared the pelagic to demersal landings ratio (the p/d ratio) over 14 shelf areas from enclosed european seas. they noticed that the ratio is affected not only by the shelf area but by the productivity (in the form of chlorophyll-a concentration), and characteristics of geographical enclosure associated in turn with catchments of basins. the statistical linkages elucidated between the p/d ratio and the chlorophyll-a concentration, as well as between the ratio of catchment basin and chlorophyll allowed authors to suggest that the p/d ratio may be a useful indirect index of availability of nutrients over european shelves. also, they noticed that high p/d ratios are usually accompanied by high concentrations of surface chlorophyll-a. according to their summary, the oligotrophic shelf regions (of levant, aegean, ionian, and sardinia) can be characterized by mean p/d ratio ~0.7; mesotrophic shelves (balearic, gulf of lions, adriatic, north sea, and irish sea) have p/d ~ 2.23; eutrophic shelves (of the sea of azov, sea of marmara, black sea, and baltic sea) are featured by p/d ratios standing higher. interestingly, the omani shelf p/d ratio covered all three categories-from oligotrophic through to eutrophic shelves (fig. 6); this implied high variability of key structural indices of the ecosystem mediated by shelf geomorphology in association with environmental parameters. with this regard, the relationship we elucidated between the demersal fish biomass and the shelf area might play a useful role in understanding mechanisms mediating standing stocks of demersal fishes (as well as their landings) over shelves with different geomorphology. in terms of impacts, shelf geomorphology is coupled with the other parameters, such as the concentration of dissolved oxygen. in the western arabian sea, large supply of oxygenated waters originated from the south and advected horizontally by western boundary current (resplandy et al., 2012). however, the ventilation rate of the oxycline associated with advection over large-sized versus small shelf areas could be different. therefore the correlation between the p/d ratio and oxygen concentration at 100m over four shelf areas distinct by its size, was high (r= 0.9, p= 0.01). acknowledgements this work is a contribution to the cooperation program between sultan qaboos university and the ministry of agriculture and fisheries wealth. studies were supported by the research council grant # org/ebr/11/002 references bergstad, o.a. 2009. fish: demersal fish (life histories, behavvior, adaptations). in: marine ecological processes: a derivative of the encyclopedia of ocean sciences. j.h.steele, s.a.thorpe, and k.k.turekian (eds.). london: elsevier. böhm, e., morrison, j.m., manghnani, v., kim, h-s., and flagg, c.n. 1999. the ras al hadd jet: remotely sensed and acoustic doppler current profiler observations in 1994-1995. deep-sea research ii, 46: 15311549. caddy, j. f. 1993. toward a comparative evaluation of human impacts on fishery ecosystems of enclosed and semienclosed seas. reviews in fisheries science 1: 57–95. caddy, j. f., carocci, f., and coppola s. 1998. have peak fishery production levels been passed in continental shelf areas? some perspectives arising from historical trends in production per shelf area. journal of northwest atlantic fishery science 23: 191–219. de leiva moreno, j.i., agostini, v.n., caddy, j.f., and carocci, f. 2000. is the pelagic-demersal ratio from fishery landings a useful proxy for nutrient availability? a preliminary data exploration for the semi-enclosed seas around europe. ices journal of marine science 57: 1091-1102. fishery statistics book. 2008. ministry of fisheries wealth: sultanate of oman. muscat. fishery statistics book. 2011. ministry of fisheries wealth: sultanate of oman. muscat. mantua, n.j. and hare, s.r. 2002. large-scale climate variability and the carrying capacity of alaska’s oceans and watersheds. in: the status of alaska’s oceans and watersheds, pp.62-84. accessed 16.01.2014. http://www.iser.uaa.alaska.edu/people/ colt/personal/final_report_part2.pdf#page=4 mathews, c.p., al-mamry, j., and al-habsy, s. 2001. precautionary management of oman’s demersal fishery. in: first international conference on fisheries, aquaculture and environment in the nw indian ocean. sultan qaboos university: muscat. mcilwain, j.l., harvey, e.s., grove, s., shiell, g., al 32 squ journal of agricultural and marine sciences, 2016, volume 21, issue 1 fish landings and shelf area in oman oufi, h., and al jardani, n. 2011. seasonal changes in a deep-water fish assemblage in response to monsoon-generated upwelling events. fisheries oceanography 20: 497-516. mckoy, j., bagley, n., gauthier, s., and devine, j. 2009. fish resources of the arabian sea coast of oman: project summary. in technical report 1. bruce shallard and associates: muscat. piontkovski, s.a., and al-oufi, h.s. 2014. the oxygen minimum zone and fish landings along the omani shelf. journal of fisheries and aquatic science 9: 294310. rao, g s. 2010. current status and prospects of fishery resources of the indian continental shelf. in: coastal fishery resources of india conservation and sustainable utilization. meenakumari, b., boopendranath, m.r., edwin, l., sankar, t., gopal, n. & ninan, g. (eds.) society of fisheries technologists: delhi, pp.1-13. resplandy, l., levy, m., bopp, l., echevin, v., pous, s., sarma, v.v.s.s., and kumar, d. 2012. controlling factors of the oxygen balance in the arabian sea’s omz. biogeosciences 9: 5095-5109. trenkel, v.m., and rochet, m-j. 2003. performance of indicators derived from abundance estimates for detecting the impact of fishing on a fish community. canadian journal of fisheries and aquatic sciences 60: 67-85. research paper journal of agricultural and marine sciences vol. 21 (1): 8 – 18 doi: http://dx.doi.org/10.24200/jams.vol21iss0pp7-18 received 15 aug 2014 accepted 09 sep 2015 impact of reclaimed water irrigation on soil salinity, hydraulic conductivity, cation exchange capacity and macro-nutrients saif a. al-khamisi1*, malik al-wardy2, mushtaque ahmed2, and sanmugam a. prathapar3 * saif al-khamisi ( ) directorate general of agricultural and livestock research, ministry of agriculture and fisheries, p.o. box 50, seeb 121, sultanate of oman. email: saif.alkhamisi@gmail.com 2 department of soils, water and agricultural engineering, sultan qaboos university, box 34, al khod 123, sultanate of oman. 3iwmi india office, international water management institute, india. introduction the sultanate of oman is an arid country, with annual rainfall around 100 mm per year, requir-ing alternative water resources for irrigation. reclaimed water forms a promising non-conventional water resource in oman. when considering reclaimed water (rw) reuse for crop irrigation, an evaluation of the advantages, disadvantages and possible risks has to be made. the planners should consider piping reclaimed water (rw) to areas where groundwater of good quality is available to conjunctively use and meet crop water requirements (alkhamisi et al., 2013). the level of impact depends on the degree of purification, the method and the location of reuse and develop in the form of pollution of the soil on the groundwater or on the surface water (papadopoulos 1995; kretschmer et al., 2002). the impact of rw on soil appears in the decrease of hydraulic conductivity because of high organic matter, blockage by suspended solids and growth of microorganisms. the movement of water in the soil depends on hydraulic gradients, soil permeability and infiltration rate. after 11 years of reclaimed wastewater irrigation, the availability of nutrients and nonessential elements, soil salinity and sodicity increased 2 to 3 times in comparison to soils irrigated with well water (pereira et al., 2011). adriel et al. (2005) found that the secondary-treated sewage effluent أتثري الري مبياه الصرف الصحي املعاجلة على ملوحة الرتبة والتوصيل اهليدروليكي وسعة تبادل الكتايوانت والعناصر املغذية الكربى سيف اخلميسي ومالك الوردي ومشتاق أمحد وسامنوجن براثابار abstract. field studies were conducted at agriculture research center, oman during the year 2010/2011 to monitor the impact of reclaimed water irrigation on soil physical and chemical properties after wheat, cowpea and maize cultivation (in rotation). three different water sources (groundwater (gw), desalinized water (dw), and reclaimed water (rw)) were used as the treatments in randomized completely block design (rcbd) with 3 blocks (replicates). samples were taken from four depths (30, 45, 60 and 90 cm) after harvesting time of the three crops. soil salinity (ece) in all soil depths decreased with time. organic carbon did not show significant difference between harvest timings of wheat and cowpea. organic carbon increased with time in soil irrigated with reclaimed water. the saturated hydraulic conductivity of the soil, ksat didn’t show significant difference among the water types and their interaction with soil depths. total nitrogen was the highest after cowpea harvest in reclaimed water irrigation. the soil phosphorus and potassium were not affected by any of the three water irrigation types. the highest concentrations of phosphorus and potassium were found to be in the upper soil layers. overall, no adverse impacts of reclaimed water irrigation were observed after growing three crops of rotation. keywords: reclaimed water; soil salinity; hydraulic conductivity; cec, macronutrients املســتخلص: أجريــت جمموعــة مــن الدراســات امليدانيــة يف املديريــة العامــة للبحــوث الزراعيــة واحليوانيــة بســلطنة عمــان خــال العــام 2011/2010م هبــدف رصــد أثــر ميــاه الــري املعاجلــة مــن الصــرف الصحــي علــى عــدد مــن خصائــص الرتبــة الفيزيائيــة والكيميائيــة بعــد زراعــة حماصيــل القمــح واللوبيــا ))rw( وامليــاه املعاجلــة ،)dw( وامليــاه احملــاة )gw( والــذرة الشــامية )بالتنــاوب(. اســتخدمت ثــاث مصــادر خمتلفــة مــن ميــاه الــري )امليــاه اجلوفيــة كمعامــات يف تصميــم القطاعــات العشــوائية الكاملــة)rcbd( بثــاث مكــررات. ومت أخــذ عينــات الرتبــة مــن أربعــة أعمــاق )30، 45، 60 و 90 ســم( بعــد حصــاد كل حمصــول مــن احملاصيــل الثاثــة. أشــارت النتائــج إىل أن ملوحــة الرتبــة )ece( يف مجيــع أعمــاق الرتبــة قــد اخنفضــت مــع مــرور الوقــت. ومل يظهــر الكربــون العضــوي أي فــرق معنــوي كبــر بــن توقيــي حصــاد القمــح وحصــاد اللوبيــا ووجــد بأنــه يف ازديــاد مــع مــرور الوقــت يف الرتبــة املرويــة بامليــاه املعاجلــة. فيمــا مل يظهــر التوصيــل اهليدروليكــي املشــبع )saturated hydraulic conductivity( فرقــا كبــرا بــن أنــواع امليــاه وتداخلهــا مــع أعمــاق الرتبــة. كان أعلــى تركيــز للنيرتوجــن بعــد حصــاد اللوبيــا يف الرتبــة املرويــة بامليــاه املعاجلــة يف حــن مل يتأثــر تركيــز الفوســفور والبوتاســيوم يف الرتبــة بــأي مــن أنــواع ميــاه الــري الثاثــة. ووجــد بــأن أعلــى تركيــز للفوســفور والبوتاســيوم كان يف الطبقــات العليــا مــن الرتبــة ويف العمــوم مل ياحــظ أي آثــار ضــارة مــن ميــاه الصــرف الصحــي املعاجلــة وذلــك بعــد ري الثاثــة حماصيــل والــي مت زراعتهــا بالتنــاوب. الكلمات املفتاحية: املياه املعاجلة ، ملوحة الرتبة ، التوصيل اهليدروليكي ، سعة تبادل الكاتيونات ، العناصر الكربى 9research article al-khamisi, al-wardy, ahmed, prathapar application caused an increase in the soil total nitrogen, but did not change the total carbon and available p concentrations. mohammad and mazahareh (2003) found that the rw irrigation decreased soil ph and increased soil salinity, soil phosphorus (p), potassium (k) levels and the soil fertility improved. soil salinity was reduced in the upper root zone (15 cm) through the continuous irrigation as the salts moved to the lower layer (30 cm) (abdelrahman et al. 2011). rw can be a form of fertilizer since it has an important contribution of n, p and organic matter and can save farmers money on fertilizer. usually, rw is more saline than tap water, and therefore, when reused in irrigation can create salinity problems (beltrao et al., 2003). rw applications reduced soil porosity, translation of pore size distribution towards narrower pores and as a result lead to a decrease in permeability (rosa et al., 2007). after two years, soils irrigated with rw showed slightly significant changes in the physical and chemical properties such as ph, electric conductivity, soc, nitrogen, esp, sodium adsorption ratio and hydraulic conductivity ksat (zema et al., 2012). percolation of rw through the soil profile can reduce its saturated hydraulic conductivity (ksat) depending on the rw quality, soil chemical properties and the pore size distribution in the soil (lado and ben-hur, 2009). levy et al. (2005) demonstrated that hydraulic conductivity of mediumand finetextured soils was lower than 2 cm/h for nonsodic soils, however in the loamy sand table 1. average values of ec (ds/m), ph, nitrogen (mg/l), cations and anions for the three irrigation water types. parameter unit groundwater desalinized water reclaimed water ecw ds/m 0.97 1.06 0.88 ph 7.8 7.5 7.7 nitrogen n-no3 -(nitrate) mg/l 14.31 0.463 28.70 phosphorus p3 mg/l 0.074 nd 9.413 potassium k+ mg/l 3.626 17.83 22.93 cations &anions (mg/l) sulfate so4 2mg/l 78.77 39.87 81.17 bicarbonate hco3 mg/l 209.27 152.53 107.99 carbonate co3 mg/l trace trace trace calcium ca2+ mg/l 15.43 38.91 58.21 magnesium mg2+ mg/l 41.21 30.01 20.29 sodium na+ mg/l 109.90 140.07 94.07 chloride clmg/l 125.84 276.49 140.02 zinc zn2+ mg/l 0.446 0.461 0.546 copper cu+ mg/l 0.026 0.026 0.027 manganese mn2+ mg/l 0.004 0.011 0.048 nickel ni mg/l 0.042 0.04 0.019 boron b mg/l 0.279 1.269 0.799 molybdenum mo mg/l 0.063 0.083 0.112 silicon si mg/l 0.187 0.974 0.959 vanadium v mg/l 0.01 0.064 0.043 cobalt co2+ mg/l 0.303 0.320 0.250 lead pb4+ mg/l nd nd nd chromium cr2+ mg/l 0.022 nd nd cadmium cd2+ mg/l nd nd nd copper cu+ mg/l nd nd nd barium ba2+ mg/l 0.048 0.069 0.072 sulfide s-2 mg/l nd 5.581 22.97 aluminum al+3 mg/l 0.088 0.096 0.093 nd= not detected 10 squ journal of agricultural and marine sciences, 2016, volume 21, issue 1 impact of reclaimed water irrigation on soil characteristics rate of wetting had no effect on the ksat. tarchitzky et al. (1999) reported that the hydraulic conductivity ksat decrease to 20% of its initial value after using reclaimed water. irrigation with rw has adverse effects on soil health and environment and this is also due to increased ph and salinity. application of rw increased soil salinity, organic matter, and decreased soil ph (khan et al., 2012). singh et al. (2009) concluded that rw irrigation modified the physicochemical properties of the soil. rw irrigation affected soils through increased organic matter, electrical conductivity and concentration of n, k, and p compared to the control treatment (saffari and mahboub, 2012). kayikcioglu (2012) observed a decrease in n and microbial activities due to the lack of c availability in rw. however, no effect was observed on soil organic carbon content due to low content. based on these recommendation of transferring the reclaimed water to agricultural area in oman, this study was carried out with the objective to assess the impact of rw irrigation on soil properties such as salinity, hydraulic conductivity, cation exchange capacity and macro-nutrients considering time of harvest and soil depth. material and methods experimental design and soil sampling field experiments were laid out in a completely randomized block design (rcbd) with three replicates (blocks) on 9 plots of 2.5 m width and 3 m length. the three different water sources, groundwater (gw), desalinized water (dw), and reclaimed water (rw), were used as treatment. wheat (triticum aestivum l.) was used in the first period of the experiment (mid-november to mid-march), cowpea (vigna unguiculata l.) in the second period (april to mid-july) and maize (zea mays l.) crop was in the third period (august to november). six soil samples were taken from the experimental site prior the experiment layout at a depth of 30 cm and subjected to chemical and physical analysis. after laying out the experiment, soil samples were taken from each treatment location (reclaimed water, desalinized water and groundwater treatments) at four depths (0-30, 30-45, 45-60 and 60-90 cm) and subjected to chemical analysis. the analyses included soil salinity (ece), soil ph, carbon contents (organic and inorganic carbon) and macro-elements (n, p and k). irrigation water application and treatments the irrigation system was operated to run under a pressure of 1 bar before planting. the application of the 3 water types was adjusted according to the reference evapotranspiration-et0. daily reference evapotranspiration (et0) was calculated using penman-monteith equation (allen et. al., 1998). the water applications were altered during the different stages of the crop growth (initial, development and late stages) according to each crop coefficient. irrigation water was applied at 3 days intervals to compensate for evapotranspiration (etc) losses. etc was calculated using equation (1): et c = k c *et 0 (1) where kc is the crop coefficient for that stage and et0, the reference evapotranspiration. table 2. textural composition of the studied soil. sample no. clay(%) silt(%) coarse sand (%) fine sand (%) soil type bulk density (g/cm3) particle density (g/cm3) porosity 1 7.46 1.88 38.98 51.68 sandy 1.59 2.61 0.39 2 7.52 1.82 19.84 70.82 sandy 1.38 2.40 0.43 3 5.52 1.82 29.84 62.82 sandy 1.49 2.37 0.37 4 11.46 5.76 15.64 67.14 loamy sand 1.43 2.35 0.39 5 7.46 3.76 22.46 66.32 loamy sand 1.52 2.56 0.41 6 5.46 1.88 27.52 65.14 sandy 1.57 2.46 0.36 average 7.48 2.82 25.71 63.99 loamy sand 1.49 2.46 0.39 0.0 0.5 1.0 1.5 30 45 60 90 soil depth (cm) e c e (d s /m ) figure 1. wet weight (g/m2) of macro-fouling communities developed on acrylic, fiberglass, wooden and aluminum plates exposed for 4 months horizontally at the depth of 1m in marina shangri la. data are means + 1 standard deviation. means that are significantly different according to a hsd test (anova: p< 0.05) are indicated by different letters above the bars. 11research article al-khamisi, al-wardy, ahmed, prathapar the reference evapotranspiration (et0) was expressed and then transformed to volume (cubic meter) through multiplying by the area of the plot. the amount of irrigation water applied at the first period (wheat) was 451 mm gw, 465 mm dw and 464 mm rw. however, in the second period (cowpea) it was 1523 gw, 1551 mm dw and 1536 mm rw. in the third period (maize), it was 1054 mm gw, 1048 mm dw and 1043 mm rw for the total irrigation period. measurement of soil ece & ph the saturated paste method was used to measure the soil salinity (ece) and ph. the soil solution ec was measured using ec/ph meter. the ec and ph meter were calibrated before use. measurement of hydraulic conductivity, ksat the hydraulic conductivity ksat of a soil is a measure of the soil’s ability to transmit water when subjected to a hydraulic gradient. hydraulic conductivity is determined by darcy’s law, which is for one-dimensional vertical flow. this experiment was practiced to determine the hydraulic conductivity of a sandy loam soil by the constant head method. the methodology used for the experimental determination of ksat in laboratory was based on procedures adapted from bear (1972). measurement of cec the cation exchange capacity cec was determined using the sodium acetate method (rhoads, 1990). sodium concentration in the supernatant liquid was determined using a inductively coupled plasma optical emission spectrometer (icp-oes). table 3. soil electric conductivity (ece), ph, hydraulic conductivity (ksat), cation exchange capacity (cec), total carbon (tc%), inorganic carbon (ic%), organic carbon (oc%), n, p and k contents for the three water types treatments before planting at depth 30 cm. parameter water irrigation treatments groundwater desalinized water reclaimed water mean ece (ds/m) 1.77 1.88 2.21 1.95 ph 7.07 7.17 7.20 7.14 ksat(cm/s) 0.0327 0.0307 0.0187 0.0274 cec(cmol/kg) 3.92 3.63 3.99 3.85 total carbon (%) 6.09 6.02 5.52 5.88 inorganic carbon (%) 3.81 4.01 3.76 3.86 organic carbon % 2.29 2.01 1.75 2.02 nitrogen (%) 0.33 0.32 0.33 0.33 p (mg/kg) 23.23 25.70 29.17 26.03 k (mg/kg) 60.00 90.00 70.00 73.33 table 4. soil salinity, ece (ds/m) and ph irrigated with 3 different water types immediately after harvest of 3 different crops. treatments (water type) harvest timing after wheat after cowpea after maize mean soil salinity groundwater 2.058 0.863 0.439 1.120 b desalinized water 2.143 1.102 1.150 1.465 a reclaimed water 1.171 1.059 0.687 0.972 b mean 1.791 a 1.008 b 0.759 b soil ph groundwater 7.89 8.23 8.20 8.11 b desalinized water 7.89 8.20 8.18 8.09 b reclaimed water 8.06 8.26 8.26 8.19 a mean 7.95b 8.23a 8.21a *means followed by similar letters are not significantly different. 12 squ journal of agricultural and marine sciences, 2016, volume 21, issue 1 impact of reclaimed water irrigation on soil characteristics measurement of total nitrogen, phosphorus and potassium a foss tecator™ 2400 kjeltec analyzer unit was used to determine nitrogen content in the soil samples following kjeldahl’s method. samples of each treatment were analyzed for phosphorus (p) using biochram™, libra s22, spectrophotometer and potassium (k) was determined using sherwood™, m410 flame photometer (sherwood, 2012). measurement of carbon content (organic and inorganic carbon) total carbon and inorganic carbon were determined using toc analyzer toc-v cpn from shimadzu, japan. total organic carbon content was determined by difference between the total carbon content and the inorganic carbon contents (total carbon = inorganic carbon + organic carbon). statistical analysis all data obtained from the effects of different irrigation water types treatments on soil physical and chemical contents were subjected to a statistical analysis using analysis of variance (anova). the least significant difference (lsd) at α = 0.05 was performed to compare means using spss, chicago, ill.; and mstatc software, east lansing, mich. according to the methods of gomez and gomez (1984). standard errors (se), represented by error bars, were used to compare series in the charts. results and discussion water and soil structure analysis prior to planting quality of irrigation water the analysis of irrigation water used in the various treatments (water types) is reported in table 1. the salinity of irrigation water (ecw) ranged from 0.97 ds/m (groundwater) to 1.06 ds/m (desalinized water). the ph values ranged from 7.5 for the dw to 7.8 for the gw. the total nitrogen values were 28.7, 14.31 and 0.463 mg/l in rw, 3.0 3.5 4.0 4.5 5.0 5.5 30 45 60 90 soil depth (cm) in o rg a n ic c a rb o n ( % ) species cowpea maize wheat figure 2. soil inorganic carbon contents (%) at four soil depths after harvest of 3 different crops. table 5. soil ph at four soil depths (30, 45, 60 and 90 cm) irrigated with 3 different water types. treatments soil depth (water type) 30 cm 45 cm 60 cm 90 cm groundwater 8.03 8.11 8.11 8.17 desalinized water 7.99 8.10 8.11 8.17 reclaimed water 8.15 8.14 8.29 8.19 mean 8.06bc 8.11ab 8.17a 8.17a *means followed by similar letters are not significantly different table 6. soil total carbon content (%) and organic carbon content (%) after harvest of 3 different crops at four soil depths. soil sample collection time (harvesting) soil depth (cm) 30-cm 45 cm 60 cm 90 cm mean a) total carbon content (%) after wheat 5.897 5.906 6.129 6.226 6.040a after cowpea 5.619 5.505 6.715 6.722 6.140a after maize 5.177 5.608 6.173 5.973 5.733b mean 5.564b 5.673b 6.339a 6.307a b) organic carbon content (%) after wheat 1.766 1.488 1.522 1.358 1.534b after cowpea 1.610 1.261 2.338 1.951 1.790a after maize 1.476 1.768 1.672 1.564 1.620b mean 1.618b 1.505b 1.844a 1.625b *means followed by similar letters are not significantly different. 13research article al-khamisi, al-wardy, ahmed, prathapar gw and dw, respectively. the rw was higher in so4, k, ca, zn, cu and mn (table 1). values of other elements concentrations (mg/l) for the three irrigation water types are presented in table 1. lead (pb), cadmium (cd) and copper (cu) were not detected in all types of irrigation water. chromium was below detection levels in dw and rw whereas the gw contained 0.022 mg/l. the rw had higher concentration of mo (0.112 mg/l), ba (0.072 mg/l) and s (193.4 mg/l). however, ni (0.042 mg/l) was the highest in groundwater. desalinized water contains higher values of b (1.269 mg/l) v (0.064 mg/l), co (0.320 mg/l) and al (0.096 mg/l) in comparison to gw and rw. physical properties of the experimental soil the soil physical constituents represented in clay, silt and sand %, and the bulk density, particle density and porosity of the experimental soil is presented in table 2. the analysis of six random soil samples before planting indicated that the texture of the experimental soil ranged between sandy to loamy sand with a porosity of 0.36 to 0.43. fine sand was the dominant constituent of the experimental soil structure (63.99%). the bulk density ranged between 1.38 to 1.59 g/cm3 with an average of 1.49 g/cm3 and the average particle density was 2.46 g/cm3 (table 3). chemical properties of the experimental soil before planting the soil ece analysis of the three water types before planting are presented in table 3. soil ece before planting ranged between 1.77 to 2.21 ds/m. it was higher than that at harvesting of each crop. generally, the analysis before planting showed a lower soil ph. the hydraulic conductivity (cm/s) and cation exchange capacity (cm mol/kg) of the experimental soil before planting are also presented in table 3. the total carbon tc%, inorganic carbon ic%, organic carbon oc%, n, p and k contents in the plots of the water types treatments before planting are presented in table 3. table 7. soil organic and inorganic carbon content (%) irrigated with three water irrigation types after wheat, cowpea and maize harvest. water type harvest type inorganic carbon (%) organic carbon (%) groundwater irrigation wheat 4.533a 1.605b cowpea 4.174b 1.889a maize 4.008bc 1.596b desalinized water irrigation wheat 4.419a 1.680b cowpea 4.406a 1.871a maize 4.389a 1.262c reclaimed water irrigation wheat 4.566a 1.315c cowpea 4.471a 1.610b maize 3.941c 2.003a *means followed by similar letters in columns are not significantly different at α=0.05. 0.0 0.5 1.0 1.5 2.0 2.5 after maize after cowpea after wheat crop o rg a n ic c a rb o n ( % ) water dw gw rw figure 3. soil organic carbon contents (%) with 3 different water types immediately after harvest of 3 different crops. dw = desalinized water, gw = groundwater, rw = reclaimed water. 0.0 0.1 0.2 0.3 desalinized water groundwater reclaimed water irrigation water n itr o g e n ( % ) crop cowpea maize wheat figure 4. soil total nitrogen (n%) with 3 different water types immediately after harvest of 3 different crops. 14 squ journal of agricultural and marine sciences, 2016, volume 21, issue 1 impact of reclaimed water irrigation on soil characteristics soil analyses after harvest effect of reclaimed water on soil salinity and ph the analysis of variance for soil salinity (ece) showed significant differences (p<0.05) between the treatments, the timing and their interaction whereas there were no significant differences with respect to soil depth and its interactions with the treatments and harvest timing. regarding the soil ph, there were significant differences (p<0.05) among the treatments, soil depth and the harvest timing. the interactions between the treatments, soil depth and the timing didn’t show any significant differences. the means of the soil salinity (ds/m) for the water types (groundwater, desalinized water and reclaimed water) after each crop harvesting (after wheat, cowpea and maize crop harvest) are presented in table 4. the soil irrigated with desalinized water showed the highest salinity (1.465 ds/m). this is likely due to higher salinity of the dw (1.06 ds/m) compared to gw (0.97 ds/m) and rw (0.88 ds/m) (table 1). gw had a slightly higher salinity than reclaimed water (1.12 and 0.972 ds/m, respectively). soil salinity decreased with the time: it started with 1.791 ds/m after wheat crop followed by the cowpea (1.008 ds/m) then after the maize crop (0.759 ds/m). the main factor governing the soil salinization is the irrigation procedures. rate of irrigation during the summer season was enough to prevent the rise of salt from the deeper layers. although there were no significant differences in soil salinity with soil depth, the upper layer (15 cm) had the lowest soil salinity for all three water types compared to the lower layers (fig. 1). this is in agreement with belaid’s et al. (2010) findings that salinity decreases with harvest timing. belaid et al. (2010) found that ece increased with soil depth (0.92, 1.87 and 2.07 ds/m in 0-30, 30-60 and 60-90 cm, respectively) in a fluvisol soil but decreased in a calcisol soil and ph increased with soil depths in both soil types under rw irrigation. irrigation with rw was observed to slightly reduce the soil ph and did not markedly increase the soil salinity when compared to background values (jun-feng et al., 2007). the means of soil ph for the water types after each crop is presented in table 4 and fall within a narrow range. the soil ph was higher in the reclaimed water treatments (8.19). however, the desalinized water (8.09) and groundwater (8.11) were not significantly different. there was an increase in soil ph after each crop harvest: soil ph after wheat was 7.95 and increased to 8.23 and 8.21 after cowpea and maize crops, respectively. soil ph also increased with soil depth until 60 and 90 cm (table 5). belaid et al. (2010) found an increase in soil ph after reclaimed water irrigation. the last two depths (60 and 90 cm) didn’t show significant difference. no negative effects with respect to changes in soil ph or salinity occurred when using rw from the albacete stp (manas et al., 2012). 4.66 4.191 5.298 cowpea maize wheat 0 2 4 phosphorus (mg/kg) c ro p figure 5. phosphorus content (mg/kg) after the harvest of 3 different crops. table 8. soil saturated hydraulic conductivity, ksat (cm/s) irrigated with 3 different water types at four soil depths. treatments (water type) soil depth soil mean ksat before planting 30 cm 45 cm 60 cm 90 cm mean groundwater 0.0156 0.0197 0.0439 0.0830 0.0406 0.0327 desalinized water 0.0375 0.0183 0.0310 0.0869 0.0434 0.0307 reclaimed water 0.0318 0.0241 0.0313 0.0930 0.0451 0.0187 mean 0.0283 c 0.0207 c 0.0354 b 0.0877 a 0.0274 *means followed by similar letters are not significantly different 100 53 50 cowpea maize wheat 0 30 60 90 120 potassium (mg/kg) c ro p figure 6. potassium content (mg/kg) after the harvest of 3 different crops. 15research article al-khamisi, al-wardy, ahmed, prathapar effect of reclaimed water on soil organic and inorganic carbon the analysis of variance did not show significant differences in carbon content (total carbon, tc%; organic carbon, oc% and inorganic carbon, ic%) or between water types (groundwater, desalinized and reclaimed water). however, there were significant differences in tc and oc percentage (p<0.05) with soil depth and harvest timing treatments. with respect to ic%, there were no significant differences (p>0.05) among all treatment except for the interactions of the harvest timing with both water types and soil depth. the interaction of treatment × soil depth × harvest timing didn’t show significant differences at α=0.05 with respect to all the three forms of carbon (tc, oc and ic %). the percentage soil total carbon contents during three different times of harvesting at four soil depths is presented in table 6. the upper two depths (30 and 45 cm) were significantly different (p<0.05) from the lower depths (60 and 90 cm). the soil tc% was the highest at 60 cm (6.339 %) and 90 cm (6.307 %) depths followed by 45 cm (5.673 %) and 30 cm (5.564 %) depths. the soil tc% was higher after wheat and cowpea harvest in comparison to that after maize. it was 6.140 % after cowpea followed by 4.040 % after wheat and 5.733% after harvesting of maize. the soil inorganic carbon (ic %) decreased with time of harvest in groundwater (-10%) and reclaimed water treatments (-14%) but it did not show difference with desalinized water irrigation (fig. 3). the soil irrigated by rw after maize harvesting had the lowest ic content but the soil after wheat and cowpea had no significant difference in ic. the results suggest an increase of ic % in soil with the increase of soil depth after each harvesting time (fig. 2). the increase was 7, 12, and 18% with respect to 45, 60 and 90 cm, respectively after wheat harvesting. it was 6, 9, and 19% after cowpea harvesting at the same depth. after maize harvesting, the increase was 4, 22, and 19%, respectively (fig 2). the organic carbon did not show significant difference (p<0.05) after wheat and cowpea harvest and increased over time in the soil irrigated with reclaimed water (fig 3). organic carbon also increased in the soil that was irrigated with groundwater and desalinized water. soil organic and inorganic carbon contents with three water irrigation types after wheat, cowpea and maize harvest are presented in table 7. soil organic carbon contents % during three different times of harvesting at four soil depths is illustrated in table 7. organic carbon percentage at soil depth 60 cm was the highest followed by that of 90, 30 and 45 cm. the oc% (1.97%) was higher after cowpea harvest than that after the wheat and maize harvest (1.534 and 1.620%, respectively) (table 6). the soil organic carbon was higher before planting. percentage of organic carbon seems to increase with time in reclaimed water irrigation after maize and cowpea harvesting. jueschki et al. (2008) found that oc accumulate in the topsoil but decrease after long-term irrigation with secondary rw. organic carbon was found to be higher after cowpea harvest compared to that after wheat and maize harvest. kone et al. (2008) studied the impact of farming system on soil status using legumes crops and reported that soil organic carbon increased over time under all legume based systems. effect of reclaimed water on saturated hydraulic conductivity, ksat the statistical analysis didn’t show significant difference at p<0.05 between water types and the interaction between water types and soil depths in respect to soil saturated hydraulic conductivity, ksat. however, ksat(cm/s) increased with soil depths (table 8). the highest saturated hydraulic conductivity was at 90 cm (315.7 cm) followed by that of 60 cm (127.4 cm). the soil depths of 30 and 45 cm had the lowest saturated hydraulic conductivtable 9. soil cation exchange capacity (cec) (cm·mol/kg) irrigated with 3 different water types at four soil depths. soil depth (cm) water type groundwater desalinized water reclaimed water mean 30 cm 12.63 13.52 11.25 12.47c 45 cm 22.49 21.44 22.65 22.20b 60 cm 20.95 20.43 20.65 20.68b 90 cm 42.17 31.81 33.46 35.81a mean 24.56 21.80 22.00 cec before planting 3.92 3.63 3.99 *means followed by similar letters are not significantly different at α=0.05. table 10. total soil nitrogen (%) after harvest of 3 different crops at four soil depths. soil depth (cm) nitrogen (%) wheat cowpea maize 30 0.0254 b 0.0238 b 0.0155 d 45 0.0157 cd 0.0354 a 0.0146 d 60 0.0058 e 0.0322 a 0.0170 cd 90 0.0055 e 0.0180 cd 0.0216 bc *means followed by similar letters are not significantly different at α=0.05. 16 squ journal of agricultural and marine sciences, 2016, volume 21, issue 1 impact of reclaimed water irrigation on soil characteristics ity (101.8 and 74.5 cm, respectively). lado and ben-hur (2009) stated that ksat of a sandy soil was not affected because of its large pore size. the hydraulic conductivity was not affected by irrigation of all types of water (rw, gw and dw). in a 15-year study, irrigation with effluent decreased the steady-state ksat from 82 to 29 cm/h in the topsoil samples, and from 93 to 35.5 cm/h in the subsoil samples (gharaibeh et al., 2007). this decrease could have resulted from changes in chemical properties of the soil caused by long-term irrigation with secondary rw. our study, on the other hand, was for one year only and used tertiary treated wastewater in sandy to sandy loam soil resulting in limited change in soil conductivity. effect of reclaimed water on soil cation exchange capacity (cec) the soil cation exchange capacity (cmol·kg-1) is presented in table 10. there was a significant difference at p<0.05 between soil depths but no significant differences (p<0.05) were found between the water type nor with its interaction with soil depth. the cec increased with soil depths. the highest value of cec was at 90 cm (35.81  cmol·kg-1) followed by depths 45 and 60 cm (22.20 and 20.68  cmol·kg-1, respectively). the minimum cec was 12.47 cmol·kg-1 in the top soil depth 30 cm (table 9). kiziloglu (2008) found an increase in soil cec which ranged from 32.1 to 39.2 cmol·kg-1 in a soil irrigated with tww. rusan et al. (2007) found cec to be 32.1 cmol·kg-1 after 2 years of tww irrigation. in hong kong, jim (1998) found that cec decreased with soil depth, despite observing low values (10.72, 7.43, 7.05 and 2.21 cmol·kg-1 at depths 0 to 10, 10 to 33, 33 to 53 and 53 to 66 cm, respectively). he reasoned that this decrease was due to the lack of inorganic colloids which did not provide enough exchangeable sites for nutrient adsorption. effect of reclaimed water on total nitrogen, phosphorus and potassium the analysis of variance quantifying the effect of water type, soil depth and harvesting on soil total nitrogen concentration revealed significant differences (p<0.05) between harvest and its interaction with the soil depth. however, no significant differences (p<0.05) were observed with respect to the water types nor with their interaction with depth and harvest. all the interactions (water type × soil depth, water type × harvest timing, soil depth × harvest timing and water type × soil depth × harvest timing) were non-significant with respect to phosphorus and potassium contents. the soil total nitrogen was highest after cowpea harvest in all types of irrigation types (fig. 4). this is likely due the nature of cowpea as a leguminous crop that has high nitrogen fixation potential compared to wheat and maize crops. the nitrogen content before planting was highest (0.320.77%). the highest n concentration appeared after cowpea harvesting at the soil depths 45 and 60 cm (0.0354 and 0.0322, respectively). the lowest was after wheat harvest at the deepest layers of 60 and 90 cm (0.0058 and 0.0055%, respectively) and then it increased after cowpea harvest. the nitrogen content was 0.0172% after the maize harvest which did not significantly differed from that after wheat (0.013 %). the cowpea increased n % to 0.027 % (fig. 4). total soil nitrogen (n%) after the different harvest at four soil depths is presented in table 10. the maximum total nitrogen was found in the soil samples after cowpea at soil depth 45 and 60 cm (0.0354 and 0.0322 %, respectively) followed by that after wheat at depth 30 cm (0.0254 %) which did not significantly differ from the soil after cowpea at 30 cm (0.0238 %) and after maize at 90 cm (0.0216 %). the lowest n found in the soil after maize at depths 30 and 45 cm (0.0155 and 0.0146 %, respectivetable 11. phosphorus and potassium content (mg/kg) with 3 different water types at four soil depths. soil depth (cm) treatments (water type) groundwater desalinized water reclaimed water mean phosphorus (mg/kg) 30 cm 5.25 6.03 4.75 5.34 a 45 cm 4.37 4.71 5.18 4.76 b 60 cm 4.05 5.33 4.49 4.62 bc 90 cm 3.82 4.40 4.23 4.15 c mean 4.38 5.12 4.66 potassium (mg/kg) 30 cm 87.78 73.33 74.44 78.52 a 45 cm 85.56 78.89 78.89 81.11 a 60 cm 66.67 62.22 61.11 63.33 b 90 cm 57.78 48.89 50.00 52.23 c mean 74.44 65.83 66.11 *means followed by similar letters are not significantly different at α=0.05. 17research article al-khamisi, al-wardy, ahmed, prathapar ly). generally, the total n was found to be higher in the top soil (30-45 cm) compared to lower (60-90 cm) after wheat and cowpea. this is in agreement with rusan et al. (2007) after barley grown for two years in jordan. however, the soil after maize was not consistently affected. phosphorus concentration in the soil did not vary significantly with irrigation water types. however, the difference was significant between soil depths. the upper layers (30 and 45 cm) contain higher phosphorus compared to the lower layers (60 and 90 cm). the soil at 30 cm was the highest (5.34 mg/kg) in p, whereas, the depth 45 cm (4.76 mg/kg) was not significantly different from 60 cm soil depth (table 11). the lowest value of phosphorus was at soil depth 90 cm (4.15 mg/kg). also, p fertilizer applied to the soil is not highly mobile by water irrigation using drip irrigation system. generally, phosphorus content will decrease with depth with all water types (rusan et al., 2007). the average phosphorus in the experimental soil (26.03 mg/kg) was higher before planting (table 3). this could be because phosphorus has slower movement due to its adsorption by soil. concerning the harvest timing, it is found that the soil after maize (5.30 mg/kg) had the highest p concentration compared to that after wheat and cowpea harvest (4.66 and 4.20 mg/kg, respectively) (fig. 5). rw supplied the essential macro nutrients (p and n) and enhanced the c and n turnover in the soil after 15-years irrigation (belaid et al., 2012). soil potassium content (mg/kg) for the three water type irrigation treatments at four soil depths is presented in table 11. the potassium at 30 cm (78.52 mg/kg) did not significantly differ from that at depth 45 cm, though it was higher at the lower depth (81.11 mg/kg). although there was no significant difference between water types, the soil irrigated with groundwater showed elevated potassium concentration in all soil depths. potassium decreased with depths of 60 and 90 cm (63.33 and 52.23 mg/kg, respectively). mohammad and mazahreh (2003) reported potassium at soil depth 30 cm to be 581 mg/kg and 638 mg/kg at 60 cm after secondary rw irrigation. that could be due to the fact that potassium exists in the soil as a mineral and the transfer of mineral potassium to other states is a very slow process which causes it to be lower in deeper soil layers and not available for plant uptake during a single growing season. however, the results in figure 6 showing that the potassium decreased to about 50% in the three seasons, from 100 mg/kg after wheat harvesting to about 54 and 53 mg/kg after cowpea and maize, respectively. the movement of k from topsoil and through the soil profile varies with soil texture (schjoning et al., 2004). conclusion salinity of soils irrigated by reclaimed water was lower compared to those irrigated with desalinized water or groundwater. the soil organic carbon was found to be the highest after maize harvest under rw irrigation. rw irrigation did not alter soil hydraulic conductivity or cation exchange capacity but increased the nitrogen in the soil compared to dw and gw and enhanced further after cultivation. the rw did not affect neither soil phosphorus nor potassium. generally, reclaimed water can be used as a source of water irrigation in oman without any adverse effect to soil with respect to hydraulic conductivity, cation exchange capacity, organic carbon and the macro-nutrients (nitrogen, phosphorus, and potassium). acknowledgements the authors acknowledge the financial support provided by sultan qaboos university through the project feasibility of managed aquifer recharge using treated wastewater in oman (sr/agr/swae/09/01). references abdelrahman, h.a., s.a. al-khamisi, m. ahmed, and h. ali. 2011. effects of treated wastewater irrigation on element concentrations in soil and maize plants. communications in soil science and plant analysis 42: 2046-2063. adriel, f. m.a. josé, and m.c. regina. 2005. maize growth and changes in soil fertility after irrigation with treated sewage effluent. ii. soil acidity, exchangeable cations, and sulfur, boron, and heavy metals 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sultan qaboos university 21 ________________________________________________ *corresponding author. e-mail: ahtash582000@yahoo.com carcass characteristics of the libyan purebred mahali goat and their crosses with damascus and morcia granada goats abdelkareem e. ahtash1*, abdulla s. biala1, aiad f. magid1 and hamed m. marhoun2 1department of animal production, faculty of agriculture, al-fateh university, tripoli, libya 2department of animal production, faculty of agriculture, omar mokhtar university, al-bayda, libya غرانادا مورثیا الدمشقي وماعز الماعز مع وھجنھ اللیبي النقي للماعز المحلي الذبیحة خصائص مرھون ، حمد مجید عیاد ، بیالة عبداهللا ، عبدالكریم أحتاش الدمشقي مع المحلي من الھجن وكذلك ، غــرانــادا ومورثیا والدمشقي المحلي الماعز من الــســالالت في الذبیحة خصائص لتقییم الــدراســة ھــذه أجریت الخالصة: الجسم. واألعضاء ، العینیة العضلة مساحة ، التصافي نسبة ، الذبیحة وزن ، الحي الــوزن : التالیة الخصائص درست وقد س). (م غرانادا مورثیا مع والمحلي ق) (م العضلة مساحة ، (٪٥٢,١) التصافي نسبة ، كجم) ٣٤,٣) الذبیحة وزن ، كجم) ٦٥,٨) الحي الــوزن في الدمشقي للماعز المعنوي التفوق النتائج توضح ٢٤,٢) الذبیحة ووزن ، كجم) ٥٠) الحي ــوزن ال في تفوقت 1⁄2ق 1⁄2م التھجین مجموعة النقیین. غرینادا مورثیا وماعز المحلي الماعز على ( سم² ٢٢,٧) العینیة في تفوقت 1⁄4م ق 3⁄4 التھجین مجموعة . دم 1⁄2 التھجین مجموعات باقي على ( ــم² س ٢١,٢) العینیة العضلة ومساحة ، (٪٤٨,٤) التصافي ونسبة ، كجم) الدراسة ھذه أوضحت . دم 3⁄4 ــرى األخ التھجین مجموعات على ( ² سم ٢١,٢٧) العینیة العضلة ومساحة ، كجم) ٣١) الذبیحة وزن ، كجم) ٦١,٧) الحي ــوزن ال اللحم. وإنتاج ووزن الذبیحة الحي الوزن زیادة في مفیدا الدمشقي بساللة المحلي الماعز تھجین بأن abstract: this study was conducted to evaluate the carcass characteristics of mahali (m), damascus (d) and morcia granada (g) goats and their crosses. live weight, carcass weight, dressing-out %, rib eye muscle area, non-carcass components and kidney fat were measured. the results showed significant superiority of damascus goats in live weight (65.8 kg), carcass weight (34.3 kg), dressing-out %( 52.1%), rib eye muscle areas (22.7 cm²) over the mahali and morcia granada goats. the crossbred group (1/2 m ҳ 1/2 d) was superior in live weight (50 kg), carcass weight (24.2kg), dressing-out %( 48.4%), and rib eye muscle area (21.2cm²) over other crossbreds. the crossbred group (3⁄4d ҳ 1⁄4m) was superior in live weight (61.7kg), carcass weight (31 kg) and rib eye muscle area (21.3cm²) over the other 3⁄4 crossbreds. this study indicated that crossing between mahali ҳ damascus breed was beneficial for increasing live weight, carcass weight and meat production. keywords: bbeeds, crossbreeding, carcass. introduction goat production is one of the most important animal production activities in libya. it represents the second rank in livestock population after sheep (ahtash, 2006). the relative importance of goat as compared to livestock comprises 2022% of the total animal unit during the period 1990-2004. the goat population in libya ranged between 1.5-2.0 million heads and 90 % of this number represents the local goat breed (mahali) which is distributed around the coastal area of libya. extensive production is the main system used for goat production in libya, where they are raised either independently or in the form of mixed flocks with sheep. they are also raised on a large scale with a small number of animals in rural regions. mahali goats are considered to be as dual purpose animal (meat and milk). the mahali goat contributed about 12.3% of the total meat production in 1966, however, with meat of sheep the contribution reached 30% by year 2000 (ahtash, 2006). shreha (1989) reported that as per capita the contribution of goat meat estimated to be around 33.6% of total red meat consumed in libya. magid et al. (1984) and magid (1995) showed that the mahali goat was lower in productivity compared to other breeds. the average live body weights of mahali goat at weaning and 7 month of age were 9.9 and 16 kg, respectively, while dressing-out % at 22 ahtash and others 23 carcass characteristics of the libyan purebred mahali goat and their crosses with damascus and morcia granada goats 7, 10, 12 months of age were 46%, 52%, 49%, respectively (magid, 1987). damascus and morcia granada goat breeds were therefore, imported for crossing with mahali goats to improve its low productivity. the main objective of this study was to evaluate carcass characteristics of mahali goat and their crosses with damascus and morcia granada goats. materials and methods location the study was conducted in bir-elghanem research station (south west of tripoli) under the authority of animal wealth research center. the region is classified as semi-arid, and characterized by rainy winter and dry summer. the ambient air temperature ranges from 9-42oc and the relative humidity between 63-81% with annual precipitation between 190-350 mm. flock management intensive close system was practiced at bir-elghanem station, the animals were raised under half-opened yard, and the water was available ad-libitum. the average quantity of concentrate was 0.5-1.0 kg /head/ day, and the roughages ranged 1.0-1.5 kg/head/day. carcass evaluation thirty-eight bucks at 14 month age were randomly selected for carcass evaluation. these bucks belong to 10 breeding groups that represents three pure goat breeds [mahali (m), damascus (d) and morcia granada (g)], first crosses generation (m ҳ d, d ҳ m,m ҳ g and g ҳ m) and second crosses generation [ 3⁄4m ҳ 1⁄4d, 3⁄4d ҳ 1⁄4m and 3⁄4m ҳ 1⁄4g]. the animals were fastened for 24 hrs and weighed prior to slaughter. the weights of carcass, head, legs, skin, empty rumen, intestine, kidney, heart, spleen, kidney fat, abdominal fat, and longissimus eye muscle area were recorded. statistical analysis statistical analyses were carried out using analysis of variance producers (sas, 1998) to evaluate the effect of breed and their crossing on carcass characteristics. carcass characteristics were analyzed for the fixed effect, where the model used included the effect of breeding group on all carcass characters. duncan’s multiple range tests was used to test the significance of difference among least square means. results and discussion the results showed significant effect of breeding group on all traits studied except omental and mesenteric fat weights. live and slaughter weights and dressing % the results showed that breeding group had highly significant (p<0.01) effect on live and slaughter weight and dressing % (table 1). the damascus goat breed is superior in live weight, slaughter weight and dressing % when compared to the other pure and crossbred groups. table 1. least squares means ± s.e. of live weight (kg), slaughter weight (kg) and dressing % of kids in breeding groups. trait s.v no. live weight (kg) slaughter weight (kg) dressing (%) breeding group ** ** ** dd 4 65.8 ± 2.2 a 34.3 ±1.13 a 52.1± 0.9 a mm 3 38.8 ± 2.5 cd 19.0 ± 1.31 cd 48.9± 1.1 bc gg 4 33.6 ± 2.2 d 16.3 ± 1.13 d 48.0± 0.9 bc 1⁄2m1⁄2d 4 50.0 ± 2.2 b 24.2 ± 1.13 b 48.4± 0.9 bc 1⁄2d1⁄2m 4 48.0 ± 2.2 b 22.4 ± 1.13 bc 46.7± 0.9 c 1⁄2m1⁄2g 4 34.2 ± 2.2 d 16.3 ± 1.13 d 47.5± 0.9 bc 1⁄2g1⁄2m 4 40.2 ± 2.2 cd 19.1 ± 1.13 cd 47.4± 0.9 bc 3⁄4m1⁄4d 4 44.4 ± 2.2 bc 22.1 ± 1.13 bc 50.3± 0.9 ab 3⁄4d1⁄4m 4 61.7 ± 2.2 a 31.0 ± 1.13 a 50.1± 0.9 abc 3⁄4m1⁄4g 3 40.3 ± 2.5 cd 19.3 ± 1.31 cd 47.9± 1.1 bc average mean 46.1 ± 1.8 22.6 ± 1.01 48.8± 0.4 ** : p<0.01. means with same letters in the same column, do not differ significantly. goat breeds: m: mahali; d: damascus; g: morcia granada (g) 22 ahtash and others 23 carcass characteristics of the libyan purebred mahali goat and their crosses with damascus and morcia granada goats the average live weight, slaughter weight and dressing % of pure damascus were 65.8kg, 34.3kg and 52.1%, respectively. whereas, the average of the same traits in mahali were 38.8kg, 19kg and 48.9% and for morcia granada were 33.6kg, 16.3kg and 48%. the dressing percentage of mahali goat in this study was in agreement with that recorded by biala et al. (1999) in their study with the same breed where they found the dressing % was 49%. while the dressing % of damascus goat was 49.9% as reported by shaker et al. (1985), which was lower than that obtained in this study, aboul-naga, (1984) reported a significant effect of breed on live weight of barki goat and 1⁄2shami1⁄2barki at an age of 8 months. the average live weight of mahali goat in this study was greater than that reported by biala et al. (1999) which was 33 kg at 13 months of age. it is obvious from table 1 that the crosses of mahali with damascus had the highest live weight, slaughter weight and dressing % compared to the crossbred of mahali with morcia granada, which reflects the great growth potentiality of damascus breed in comparison with morcia granada breed. the average live weight, slaughter weight and dressing % of the crossbred 3⁄4 d1⁄4m were 61.7 kg, 31 kg and 50.1 %, respectively. these values were not significantly different from values obtained by the purebred damascus goat. the crossbred 1⁄2m1⁄2d and 1⁄2d1⁄2m differ significantly (p<0.01) in live weight, slaughter weight and dressing % (50kg, 24.2kg, 48.4% and 48 kg, 22.4kg, 46.7% in respective order) from the purebred damascus and mahali goats. the crossbred of mahali with morcia granada (1⁄2m1⁄2g) showed the lowest live weight and slaughter weight compared with other crossbred groups, however, it was not significantly different from both pure breeds (m and g). this indicates the inferiority of the morcia granada breed to improve meat production. these results were in agreement with the study of abdelsalam et al. (1994) who found that the body weight of crossbred damascus x barki kids was intermediate between those of their purebred parents. abdelsalam et al. (2000) reported that the damascus breed sired barki goats produced a heavier litter and the crossbred exceeded the barki in milk yield and litter weight. al-ojaili (1995) concluded that crossbreeding of dhofari goats with a temperate breed (anglo-nubian) was beneficial for increasing meat production in oman. misra (1983) evaluated kids of the black bengal, jamunapari and beetal breeds and their crosses; they concluded that the large breeds have potential merit for improving meat production in small and medium sized goat breeds in india. in his study with spanish goats and their cross with the boer goat breed. oman et al. (1999) found that the crossbred was greater in live weight than spanish goat breed. the results obtained by mia et al. (1993) in their study with different breeds (black bengal, barbari and anglo-nubian, and barbari black bengal cross) showed that the body weight of crossbred kids remained intermediate to kids of their purebred parents. mioc et al. (2001) reported a significant difference in dressing % due to the difference in breeds. it was shown that with an increase in body weight the dressing % increased (dhanda et al., 2003). the half bred groups from mahali with both damascus and morcia granada did not differ significantly; however, 1⁄2d1⁄2m had the lowest dressing % (46.7%). the hybrid groups 3⁄4m’1⁄4d and 3⁄4d1⁄4m had a higher dressing percentage (50.3 and 50.1%, respectively) than the half bred groups, although the difference was not significant. the differences among crossing groups in dressing % could be referred to the difference of the stomach and intestine content at time of slaughtering (van niekerk and casey, 1998). rib eye muscle areas a highly significant effect of breeding groups (p<0.01) on rib eye muscle areas was found. as shown in table 2, the damascus goat had the greatest rib eye muscle areas (22.7 cm²), while the mahali goat had the lowest one (14.4 cm²) and the morcia granada breed was intermediate in this trait (18.7 cm²). the half-bred of mahali with damascus goats was superior in this trait among half-bred of mahali with morcia granada, the same trend is found with 3⁄4d1⁄4m crossbred. it is obvious that this trait was improved in mahali goats by crossbreeding with the damascus goat breed. the variation in rib eye muscle areas resulted from the differences in live weight of crossing groups (kadim et al., 2003). the authors found in their study of three omani breeds, that the green mountain goat had the greatest rib eye muscle areas (130 mm²) compared with dhofari breed (119 mm²) and batina breed ( 106 mm²). oman et al. (2000) reported that angora kids had significantly smaller longissimus muscle area compared to spanish, boer x spanish and spanish x angora kids. edible parts, kdney and spleen weight table 2 shows the significant effect of crossing group (p<0.01) on edible parts, kidney and spleen weights. damascus goat breed exceeded (2.43 kg) the pure breed of mahali and morcia granada goat on edible parts weight (1.41 kg and 1.31 kg respectively). half bred of mahali with damascus goats and 3⁄4d1⁄4m crossbred were superior on edible parts weight compared with 1⁄2m1⁄2d and 3⁄4m1⁄4g. results reflect the influence of large live body weight of the damascus breed among the other breeds. edible parts expressed as a percentage of carcass empty weight for damascus, mahali and morcia granada were 3.91%, 3.9% and 4.23% respectively. wahid et al. (1985) reported differences on edible parts weight due to crossing that affects live weight. the results of this study were in agreement with the study of mioc et al. (2001) who found a significant effect of breed (p<0.05) on edible parts weight, where the alpine goat exceeded the sannen breed on this trait. the same trend was found with kidney and spleen weight, where the damascus purebred and 3⁄4d1⁄4m crossbred goat had the heaviest weight of kidney compared 24 ahtash and others 25 carcass characteristics of the libyan purebred mahali goat and their crosses with damascus and morcia granada goats with mahali and the morcia granada. the heaviest spleen weight recorded on damascus purebred, 3⁄4d1⁄4m and 3⁄4m1⁄4d crossbred compared with other purebred and crossbred groups. mahali and morcia granada goats did not differ significantly in the weight of both kidney and spleen. this finding was in agreement with the study of shaker and masry (1983), who reported the significant effect of crossing groups on kidney weight. the variation in the kidney and spleen weight could be due to differences in slaughter weight (dhanda et al., 2003). stomach and intestine weights results show the significant effects (p<0.01) of breeding group on stomach and intestine weights (table 3). there is table 2. least squares means ± s.e. for rib muscle area (cm²), edible parts (kg), kidney weight (kg) and spleen weight (g) of kids in breeding groups. trait s.v no. rib muscle area (cm²) edible parts (kg)δ kidney weight (g) spleen weight (g) breeding group ** ** ** ** dd 4 22.7 ± 1.3 a 2.43 ± 0.07 a 175.0 ± 6.9 a 112.5 ± 7.8 a mm 3 14.4 ± 1.5 d 1.41 ± 0.08 de 101.6 ± 7.9 cd 41.6 ± 9.0 d gg 4 18.7 ± 1.3 abc 1.31 ± 0.07 e 118.8 ± 6.9 bc 56.3 ± 7.8 bcd 1⁄2m1⁄2d 4 21.2 ± 1.3 ab 1.86 ± 0.07 c 137.5 ± 6.9 b 62.5 ± 7.8 bcd 1⁄2d1⁄2m 4 20.7 ± 1.3 abc 1.76 ± 0.07 c 131.2 ± 6.9 b 68.8 ± 7.8 bc 1⁄2m1⁄2g 4 16.3 ± 1.3 cd 1.30 ± 0.07 e 87.5 ± 6.9 d 49.2 ± 7.8 cd 1⁄2g1⁄2m 4 17.6 ± 1.3 bcd 1.51 ± 0.07 de 137.5 ± 6.9 b 68.7 ± 7.8 bc 3⁄4m1⁄4d 4 17.8 ± 1.3 bcd 1.60 ± 0.07 cd 137.5 ± 6.9 b 81.2 ± 7.8 b 3⁄4d1⁄4m 4 21.3 ± 1.3 ab 2.18 ± 0.07 b 156.2 ± 6.9 a 81.2 ± 7.8 b 3⁄4m1⁄4g 3 20.4 ± 1.5 abc 1.63 ± 0.08 cd 125.0 ± 7.9 b 66.6 ± 9.0 bcd average mean 19.2 ± 0.5 1.71 ± 0.06 131.7 ± 4.4 69.7 ± 3.8 ** : p<0.01 means with same letters in the same column, do not differ significantly. goat breeds: m: mahali; d: damascus; g: morcia granada (g) δ edible parts=heart, liver and lung weights. table 3. least squares means ± s.e. for stomach and intestine weight (kg), weight of fat around the stomach and intestine (g) and weight of fat around the kidney of kids in breeding groups. trait s.v no. stomach and intestine (kg) fat around stomach and intestine (g) fat around kidney (g) breeding group ** ns * dd 4 4.7 ± 0.2 a 793.8 ±170.7 a 375.0 ± 83.3 b mm 3 2.9 ± 0.23 cd 783.3 ± 197.1 a 133.3 ± 96.2c gg 4 2.9 ± 0.2 cd 550.0 ± 170.7 a 112.5 ± 83.3c 1⁄2m1⁄2d 4 3.9 ± 0.2 b 737.5 ± 170.7 a 337.5 ± 83.3 b 1⁄2d1⁄2m 4 3.3 ± 0.2 c 712.5 ± 170.7 a 325.0 ± 83.3 b 1⁄2m1⁄2g 4 2.4 ± 0.2 d 650.0 ± 170.7 a 231.2 ± 83.3c 1⁄2g1⁄2m 4 3.0 ± 0.2 cd 975.0 ± 170.7 a 475.0 ± 83.3 a 3⁄4m1⁄4d 4 3.1 ± 0.2 c 762.5 ± 170.7 a 387.5 ± 83.3 b 3⁄4d1⁄4m 4 4.0 ± 0.2 b 987.5 ± 170.7 a 362.5 ± 83.3 b 3⁄4m1⁄4g 3 3.1 ± 0.23 c 833.0 ± 197.1 a 391.6 ± 96.2 b average mean 3.4 ± 0.12 776.9 ± 52.7 315.8 ± 29.6 ns = non signifiant: p>0.05; * : p<0.05; ** : p<0.01 means with same letters in the same column, do not differ significantly. goat breeds: m: mahali; d: damascus; g: morcia granada (g) 24 ahtash and others 25 carcass characteristics of the libyan purebred mahali goat and their crosses with damascus and morcia granada goats a clear superiority of damascus breed goats with regards to these traits (4.7 kg) over the other pure and cross bred groups. crossbred 1⁄2m1⁄2d and 3⁄4d1⁄4m did not differ in these traits and were 3.9 kg and 4.0kg respectively. the other crossbred groups had the lowest stomach and intestine weights among crossing groups. fat around stomach and intestine did not differ significantly due to the effects of breeding groups (table 3). the greatest weight of stomach and intestine obviously correlated with breed size, hence the damascus goat had the greatest live weight among the other pure and crossbred groups. it was concluded that the increase in weight of stomach, intestine and fat around these parts is related to the increase in slaughter weight (economides and olymbios, 1991). weight of fat around stomach, intestine and kidney though differences among crossing groups on weight of fat around stomach and intestine were not significant (p>0.05), the fat weight around stomach and intestine ranged between 550 – 793.8 gm on pure breeds (m,d,g), 650 – 975 gm on half-bred groups and 762.5 – 987.5 gm on three-quarter crossing groups. fat around stomach and intestine as a percentage of empty weight ranged between 1.26-2.53%. these results were in agreement with the study of pralomkarm et al. (1995), who reported using local thailand goats and their crosses with the anglonubian breed and the non-significant differences between crossing groups on fat weight around stomach and intestine. fat weight around kidney differs significantly among breeding groups (p<0.05). damascus goats had the highest fat around kidney (375 gm) compared with pure bred mahali and morcia-granada breeds (133 gm and 112.5 gm respectively), while the half-bred groups ranged between 231 – 475 gm. three-quarter crossing groups did not differ significantly on fat around kidney and they ranged between 362-391 gm. mahgoub and lu (1998) studied two different goat breeds, they found significant superiority of dhofari goats on fat weight around kidney among omani batina. differences on fat weight around kidney were caused by the variation on live weight due breeding groups effect (treacher et al., 1987). carcass by products head, legs and hide represents the largest part of carcass by products which affect slaughter weight and dressing %. increasing the weight of those residuals was accompanied by a reduction on dressing % and carcass weight. the damascus goats and 3⁄4d1⁄4m had the largest weight of head, legs and hide (table 4), and they differ significantly from other crossing groups. in general, mahali and morcia granada breeds have the lowest weight of head, legs and hide, the same trend found on the different crosses of mahali with morcia granada in comparison with the different crosses of mahali with damascus breeds. although the head weight of damascus was larger than other pure breed, but represent the lowest as a percentage of empty weight of carcass (6.86%). it is obvious from these results that increasing crossing of mahali with the damascus breed increased the weight of head, legs and hide while it decreased with crosses of mahali with morcia table 4. least squares mean ± s.e. for head legs and hide weight (kg) of kids in breeding groups. trait s.v no. head weight (kg) legs weight (kg) hide weight (kg) breeding group ** ** ** dd 4 4.3 ± 0.14 a 1.71 ± 0.10 a 5.10 ± 0.20 a mm 3 2.6 ± 0.17cd 0.91 ± 0.12 d 2.65 ± 0.23 ef gg 4 2.5 ± 0.14 d 1.03 ± 0.10 cd 2.05 ± 0.20 f 1⁄2m1⁄2d 4 3.4 ± 0.14 b 1.28 ± 0.10 bc 3.70 ± 0.20 c 1⁄2d1⁄2m 4 3.4 ± 0.14 b 1.24 ± 0.10 bc 3.45 ± 0.02 cd 1⁄2m1⁄2g 4 2.4 ± 0.14 d 0.83 ± 0.10 d 2.47 ± 0.20 ef 1⁄2g1⁄2m 4 2.7 ± 0.14 cd 0.91 ± 0.10 d 2.58 ± 0.20 ef 3⁄4m1⁄4d 4 3.1 ± 0.14 bc 1.13 ± 0.10 cd 3.00 ± 0.20 de 3⁄4d1⁄4m 4 4.0 ± 0.14 a 1.50 ± 0.10 ab 4.40 ± 0.20 b 3⁄4m1⁄4g 3 2.8 ± 0.17 cd 1.05 ± 0.12 cd 2.58 ± 0.23 ef average mean 3.2 ± 0.11 1.17 ± 0.05 3.25 ± 0.16 ** : p<0.01 means with same letters in the same column, do not differ significantly. goat breeds: m: mahali; d: damascus; g: morcia granada (g) 26 ahtash and others 27 carcass characteristics of the libyan purebred mahali goat and their crosses with damascus and morcia granada goats granada. breed effects were significant on head and hide as a percentage of body weight (amin et al., 2000). however, johnson et al. (1995) reported a non significant effect of breeding groups on legs as a percentage of body weight. conclusion it is concluded that crossbreeding of mahali goat with damascus breed improved growth rate of the indigenous goats, and the breed crosses demonstrated an advantage in carcass characteristics mainly due to large live body weight and good growth rate. however, there is a need for further studies to evaluate other economically important traits in different crossbreds raised under different goat production systems. the large damascus breed has a potential merit for improving meat production by medium-sized mahali breed in libya. references abdelsalam, m.m., a.e. haider, a.m. aboul-naga, i.s. el-kimary and m. eissa. 1994. improving performance of desert barki kids by crossing with zaraibi and damascus goats. egyptian journal of animal production 31:85-97. abdelsalam, m.m., m. eissa, g. maharam, a.i. haider. 2000. improving the productivity of barki goat by crossbreeding with damascus or zaraibi breeds. alexandria journal of agricultural research 45:33-42. aboul-naga, a.m. 1984. small ruminants in the near east. vol.1. a.w. qureshi and h.a. fitzhugh (editors), fao 1987. ahtash, a. 2006. goat production. in: proceeding of regional workshop on recent advances in goat production under arid condition. h.m. el-shaer, talib m. ali elam and a. mehrez (editors), 310-316. desert research center and fao, cairo, egypt. al-ojaili, a.a. 1995. production traits in dhofari and dhofari×anglo-nubian goats in oman. international journal of animal science 10:13-16. amin, m.r., s.s. husain and a.b.m.m. islam. 2000. evaluation of black bengal goats and their cross with jamnapari breed for carcass characteristics. small ruminant research 38:211-215. biala, a.s., a.f. magid, m.y. masry, and s.k. salem. 1999. meat characteristics of some goat breeds in jamahiriya. agriculture research journal 5:32-45. 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(in arabic). mia, m.m., a. ali and m.a.r. howlider. 1993. growth performance of black bengal, barbari, anglo-nubian and barbari×black bengal goats. indian journal of animal science 63:1214-1215. mioc, b., v. pavic and a. ivankovic. 2001. some carcass traits and chemical composition of different muscle groups in alpine and sannen kids. journal of animal science 46:8387. misra, r.k. 1983. genetic analysis of growth, survivability, efficiency of feed conversion and carcass yield and composition in sirohi (goat) and its crosses with beetal. ph.d. thesis. university kurukshetra, haryana, india, 152pp. oman, j.s., d.f. waldron, d.b. griffin and j.w. savell. 1999. effect of breedtype and feeding regimen on goat carcass traits. journal of animal science 77: 3215-3218. pralomkarn, w., s. saithanoo, s. kochapakdee and b.w. norton. 1995. effect of genotype and plane of nutrition on carcass characteristics of thai native and anglo nubian x thai native male goats. small ruminant research 16:21-25. sas. 1998. sas user’ guides: statistics. ver. 6.12. sas inst., cary, nc. shaker, b., m. dsouki, t. hamoud and a. al-sayed. 1985. primary experiment for fattening shami male goats. ministry of agriculture on syria arabic republic. goat resources on arab country. acsad. (in arabic). shaker, b. and a. masry. 1983. a study of qualitative traits and some productive traits on gabli goat and 26 ahtash and others 27 carcass characteristics of the libyan purebred mahali goat and their crosses with damascus and morcia granada goats their crosses with shami goat. goat resources on arabic country, syria arabic republic. acsad. (in arabic). shreha, a. 1989. horizones of animal wealth on jamahiriya. camels research center. (in arabic). treacher, t.t., a. mowlem, r.m. wilde and b. butlerhogg. 1987. growth efficiency and carcass composition of castrated male sannen and sannen –angora kids on a concentrate diet. annales de zootechine 36:341-342. van niekerk, w.a., and n.h. casey. 1998. the boer goat. 2. growth nutrient requirements, carcass and meat quality. small ruminant research 1:355-368. wahid, a., h. rozimah and s.k. koh. 1985. introduction of sannen to anglo-nubian×local and jamunapari×local cross-bred goats, carcass characteristics. proceedings of the 9th annual conference, malaysian society of animal production, held at university pertanian, selangor, 11-12 march 1985, pp 27-31. agricultural and marine sciences, 13:43-52 (2008) ©2008 sultan qaboos university 43 *corresponding author. e-mail: brett_human@yahoo.com length and weight relationships for 31 species of fishes caught by trawl off the arabian sea coast of oman brett a. human* and haithem al-busaidi marine science and fisheries centre po box 227, pc 100 muscat sultanate of oman abstract: len g t h a n d w eig h t mea su r emen t f o r 31 f ish spec ies en c o u n t er ed in t h e ar a bia n sea , o f f t h e oma n coast, were collected by demersal trawling during march 2007 and march 2008. a total of 3,261 specimens were measured for total length, or fork length, where appropriate, and green weight. several commonly caught commercial species undergo onboard processing (dressing) prior to packaging, and dressed weight to green weight regressions and conversion factors were calculated for 12 of these species. the relationships obtained in this study were compared with those of other studies for the same fish species. these data are fundamental to understanding the biological parameters of fishes, and can be applied to fisheries stock assessment and management models. introduction an industrial demersal trawl fishery exists off the coast of the sultanate of oman, operating between north of masirah island to the al-hallaniyat islands in the arabian sea, in depths between 50 to 150m (fig. 1). this fishery was initiated by the government of the sultanate of oman in the late 1970’s to develop an alternative economy to petroleum products (johannesson, 1991). in 1986, seven foreign trawlers and two omani vessels were operating in the oman demersal trawl keywords: demersal trawling, arabian sea, length-weight relationships. fishery (mcclure, 1987). by 2003, the number of industrial vessels trawling in the oman demersal trawl zone had expanded to 20, all of which were foreign (anon., 2004). reported landings peaked in 1997 at 34,549 mt (accounting for 29% of the total oman landings for that year), and landings for 2003 were reported to be 19,608 mt (14% of the total oman landings). human (2007) reported the species composition and quantum of fishes caught during a brief survey of the demersal fishing area. the marine science and من الجرف بطریقة األسماك المصطادة من نوعا وثالثون إلحدى والوزن عالقات الطول لسلطنة عمان العرب ساحل بحر ھومان انتوني برت البوسعیدي ھیثم عمان لساحل العرب بحر في صیدھا صادف التي األسماك من نوعا وثالثون إلحدى والوزن الطول قیاسات جمعت الخالصة: الشوكي والطول الكلي تم قیاس الطول ولقد .٢٠٠٨ ومارس ٢٠٠٧ بین مارس الفترة خالل وذلك القاعیة الجرف بواسطة سفینة األحشاء نزع بعملیة تمر المصطادة الشائعة من األنواع التجاریة ممكنا. العدید ذلك كان ما متى عینة ٣٢٦١ مجموعھ لما والوزن الكلي الثني التغیر وتم حساب معامل التغلیف وقبل األحشاء نزع وبعد قبل ھذه األنواع أوزان قیاسات جمع تم ولقد السفینة. مصنع داخل األنواع. من نفس األخرى الدراسات مع الدارسة في ھذه علیھا الحصول تم العالقات التي تمت مقارنة األسماك. نوعا من ھذه عشر human and al-busaidi 44 45 length and weight relationships for 31 species of fishes caught by trawl figure 1. chart of the sultanae of oman showing the demersal trawl fishery zone (lubna al-kharusi). human and al-busaidi 44 45 length and weight relationships for 31 species of fishes caught by trawl fisheries centre is currently undertaking a project to investigate the biology, and assess the stocks of 13 species of commercially important demersal fishes (see al-nahdi et al., 200x; al-waeli et al., 200xa; and al-waeli et al., 200xb in this issue). in addition to this, the ministry of fisheries wealth is currently conducting a 15-month project, the fish resources assessment survey of the arabian sea coast of oman, to estimate the current biomass of the fisheries resources in the arabian sea, off the oman coast. this survey is due to be completed in september 2008. the last survey and assessment of this fishery was by the r.v. rastrelliger from late 1989 to late 1990 (johannesson, 1991), some 17 years ago. in that study, the demersal stock of the entire omani coastline, from the musandam peninsula to salalah was assessed. the only other major fisheries resources assessment conducted along the omani coastline was by the r.v. dr. fridtjof nansen, which conducted demersal biomass estimates using acoustic methods in 1983 and 1984 (strømme, 1986). a small scale fisheries resources assessment was conducted in the arabian gulf and the northern gulf of oman during 2003-2004 (valinassab et al., 2006). these studies did not provide length or weight relationships. length and weight relationships are basic, yet represent fundamental data that are essential to understanding the biological parameters of fishes, which can then be applied to fisheries stock assessment and management (gonzales et al., 2000; muto et al., 2000; morato et al., 2001; can et al., 2002; wigley et al., 2003; abdurahiman et al., 2004; and frota et al., 2004). this study provides length and weight relationships for 31 fish species encountered during a recent survey of the oman demersal fishing zone. additionally, most of the more commonly caught, commercially important species undergo processing (dressing) prior to packaging. landings of these species are reported in dressed weight, therefore it is essential to know the dressed weight to green weight (total wet weight) conversion factors to convert landed weight into total weight for fisheries modelling and management purposes. materials and methods the area demarcated for demersal trawling within the sultanate of oman is south of 21ºn, north of 17ºn, in water not less than 50m deep, or not closer than 10nm to the coast, in the arabian sea within the omani eez (fig. 1). sampling was conducted in this area from 5th march 24th march, 2007, during commercial fishing operations (bottom trawling). between 27th february 18th march, 2008, fishes were sampled from the demersal trawl zone, and areas of the arabian sea, in a depth range between 20-200m, extending south of the demersal trawl zone to the yemen border, during part of the third cruise of the fish resources assessment survey of the arabian sea coast of oman. the f.v. al-mustaqila i, a factory stern trawler with a gross tonnage of 1226 tonnes and overall length (l.o.a) of 45.2m (chris carey, personal communication), was used as a sampling platform. a trawl net of multiple mesh sizes (110mm in the cod-end), a ground rope of 100m, and a door spread whilst trawling approximately 100m wide at 100m depth was used during commercial fishing operations. the wingtip spread was approximately 35m, and the opening of the mouth of the trawl was between 5.56m (monitored by sensors on the headline). the trawl warps used were 32mm dyform warps. the trawling speed was approximately 4 knots. the same vessel is being used for the fish resources assessment survey of the arabian sea coast of oman. the trawl warps are the same, however the bottom trawl gear is different to that used for commercial fishing. for that survey, a trawl net of multiple sizes with a cod-end mesh size of 40mm, a ground rope of 100m, and a door spread whilst trawling approximately 100m wide at 100m depth was used during commercial fishing operations. the wingtip spread was approximately 35m, and the opening of the mouth of the trawl was between 5.5-6m (monitored by sensors on the headline). the trawling speed was approximately 3.5 knots (neil bagley, personal communication). fishes were collected and sorted inside the onboard fish processing factory. species were identified using smith & heemstra (1986), alabdessalaam (1995), randall (1995), or carpenter et al. (1997). all length and weight measurements were taken on freshly captured fishes. during commercial fishing, fish were measured on a measuring board, and the same balance was used for the entire cruise. for fish measured during the fish resources assessment survey of the arabian sea coast of oman, data were captured directly onto a niwa (national institute of water and atmospheric research ltd., new zealand) computer controlled digitising work station. these human and al-busaidi 46 47 length and weight relationships for 31 species of fishes caught by trawl gross conversion factors for converting dw to gw, and vice versa, given in table 4. it was possible to compare only a few species presented here to studies that had been conducted previously. of the literature examined for this study, all presented length-weight relationships as a power curve, or an alogarithmic transformation thereof, in the form: wt = a.lb (1) where wt is weight, l is length, a is a scaling constant, and b is an allometric growth coefficient. the allometric growth coefficient from equation (1) has been used as an indicator of a wide range of biological parameters, including rate of weight gain relative to growth in length, rate of gonad development, rate of feeding, growth rate, ontogenetic change, sexual dimorphism, maturity, age structure, and condition; as well as a predictor of weight at age; for biomass estimation and stock assessment purposes (morato et al., 2001; can et al., 2002; abdurahiman et al., 2004; and frota et al., 2004). however, it has been noted that the allometric growth coefficient is highly variable due to factors such as interand intrapopulation differences, gender, seasonality, annual variability, food availability (quantity and quality), reproductive state, migratory activities, temperature, salinity, as well as sampling biases such as length range of the sample population due to gear selectivity (muto et al., 2000; morato et al., 2001; can et al., 2002; frota et al., 2004; akyol et al., 2007; and see wigley et al. (2003) for a comparison of the effects of season, gender and length range, within an area). most of the literature examined for this study gave ranges and statistical significance values for allometric growth coefficients, however, given the variability and number of factors that influence the allometric growth coefficient, it is very difficult to assign true biological meaning to this coefficient (see frota et al., 2004). the allometric growth coefficient can best be considered as a general indicator of the condition (ie. weight of the fish relative to length) of a fish species within restricted temporal and spatial limits. additionally, this study found that exponential curves provided a better description of length-weight data for some species, and the type of length measurement used, compared to power curve regressions, indicated by higher r2 values (data not shown). data have been incorporated into the total database for that survey. linear measurements were taken in a straight line and did not follow the natural curves of the animal (see compagno, 2001; and human, 2006). total length (tl) was the greatest straight line measurement from the anterior tip of the snout to the posterior tip of the caudal fin, with the caudal fin lying straight and not in its natural position, and was applied to fishes lacking a forked tail and sharks. fork length (fl) was the straight line measurement from the anterior tip of the snout to the anterior margin of the fork in the caudal fin, in fish with a forked caudal fin. all length measurements were taken to the nearest 5mm, and all weight measurements to the nearest 5g during commercial fishing, whereas, all length measurements were taken to the nearest 1mm, and all weight measurements to the nearest 1g during the fish resources assessment survey of the arabian sea coast of oman. to determine dressed weight to green weight conversion factors, fish were sorted by species into bins (typically 4-10kg per bin, consisting of 1 to 6 specimens depending on size) and weighed for green weight (gw). the bin was then given to factory workers who processed the fish. the processing of bony fishes involved removal of the head, tail, and entrails; while processing of sharks involved removal of the head, fins, tail, entrails, and a section of the abdomen from the insertion of the pelvic fin to the insertion of the pectoral fins. the fish were then placed back into the bin and reweighed for dressed weight (dw). regressions were performed on length-weight relationships. in all length-weight regressions, the data were fitted with either power or exponential curves, depending on which type of curve provided the best fit based on least squares. all gw-dw relationships were linearly regressed, and conversion factors were determined for the latter. results and discussion a systematic list of the species reported in this study is given in table 1, which also lists the family to which the species belong, and the english common name. due to space constraints, graphs of all of the regressions will not be presented here. the length and weight regressions are tabulated as follows: tl-gw (11 species; n = 1194; table 2); fl-gw (20 species; n = 1904; table 3); and gw-dw (9 species; n = 163) with human and al-busaidi 46 47 length and weight relationships for 31 species of fishes caught by trawl synodontidae the brushtooth lizardfish appears to be a common bycatch species both in the arabian sea, and in the eastern mediterranean sea. abdallah (2002) reported the length-weight relationship for the brushtooth lizardfish as wt = 0.003tl3.30 (r2 = 0.953; n = 465) from the trawl fishing ground off alexandria, egypt, while can et al. (2002) reported wt = 0.0117tl2.7971 (r2 = 0.90; n = 100), and akyol et al. (2007) reported wt = 0.0046tl3.109 (r2 = 0.951; n = 80), from turkish waters in the aegean sea. abdurahiman et al. (2004) reported wt = 1.34x10-6tl3.306 (r2 = 0.99; n = 2774) from karnataka, india, arabian sea. fork length was measured for this species in the current study (table 3), therefore, while it is not possible to make a direct comparison between this study and other studies, the allometric growth coefficients between studies are equivalent for this species from different geographic locations and different time periods, suggesting that the brushtooth lizardfish has consistent growth parameters over time and space. frota et al. (2004) reported the length-weight relationship for snakefish off brazil as wt = 7x104fl3.881 (r2 = .976; n = 21). the lower values for both the scaling constant and the allometric growth table 1. systematic listing of fish species, including family and english common name, for which length-weight relationships are reported in this study. family species common name carcharhinidae rhizoprionodon acutus milk shark muraenesocidae muraenesox cinereus daggertooth pike conger clupeidae dussumieria elopsoides slender rainbow sardine ariidae arius bilineatus roundsnout sea catfish ariidae arius dussumieri blacktip sea catfish synodontidae saurida undosquamis brushtooth lizardfish synodontidae synodus dermatogenys clearfin lizardfish synodontidae trachinocephalus myops snakefish triglidae lepidotrigla bispinosa bullhorn gurnard platycephalidae kumococius rodericensis spiny flathead carangidae alectis indicus indian threadfish carangidae carangoides chrysophrys longnose jack carangidae decapterus russelli indian scad carangidae seriola rivoliana almaco jack haemulidae pomadasys commersonnii spotted grunt nemipteridae nemipterus randalli randalls threadfin bream lethrinidae lethrinus nebulosus spangled emporer sparidae argyrops spinifer king soldierbream sparidae cheimerius nufar santer seabream sparidae pagellus affinis arabian pandora sciaenidae argyrosomus hololepidotus southern meagre pinguipedidae parapercis alboguttata bluenose sandperch paralichthyidae psuedorhombus arsius largetooth flounder trichiuridae trichiurus lepturus largehead cutlassfish scombridae sarda orientalis striped bonito scombridae scomber japonicus chub mackerel drepanidae drepane longimana barred sicklefish balistidae sufflamen fraenatus bridled triggerfish ostraciidae tetrosomus gibbosus thornback trunkfish tetraodontidae lagocephalus guentheri diamondback pufferfish diodontidae cyclichthys spilostylus yellowspotted burrfish human and al-busaidi 48 49 length and weight relationships for 31 species of fishes caught by trawl table 2. summary of the regression of total length (tl) against green weight (wt), including species common name, sample size, regression equation, r2 value, and size range, for 11 species of fishes caught using demersal trawl gear off oman. length is in millimetres and weight is in grams. common name n regression r2 tl size range arabian pandora 68 wt = 2x10-5tl2.9424 0.9811 100 425 barred sicklefish 157 wt = 2x10-5tl3.0841 0.9176 257 419 bridled triggerfish 117 wt = 2x10-5tl3.0406 0.9926 130 355 chub mackerel 112 wt = 3x10-6tl3.195 0.9526 210 390 daggertooth pike conger 35 wt = 33x861e0.0037tl 0.7541 700 1040 king soldier bream 85 wt = 3x10-5tl2.8572 0.9707 250 640 largehead cutlassfish 390 wt = 2x10-7tl3.2066 0.8551 675 1210 largetooth flounder 74 wt = 4x10-6tl3.1671 0.9945 82 391 striped bonito 51 wt = 8x10-6tl3.0324 0.9723 400 655 thornback trunkfish 71 wt = 16.885e0.0132tl 0.8629 158 250 yellowspotted burrfish 34 wt = 7x10-4tl2.4868 0.9225 191 391 table 3. summary of the regression of fork length (fl) against green weight (wt), including species common name, sample size, regression equation, r2 value, and size range, for 20 species of fishes caught using demersal trawl gear off oman. length is in millimetres and weight is in grams. common name n regression r2 fl size range arabian pandora 68 wt = 4x10-5fl2.8851 0.984 90 385 blacktip sea catfish 79 wt = 134.4e0.0053fl 0.876 330 630 bluenose sandperch 65 wt = 4x10-6fl3.1647 0.9586 72 180 brushtooth lizardfish 200 wt = 3x10-6fl3.2185 0.9889 60 319 bullhorn gurnard 167 wt = 6x100-5fl2.6944 0.9888 45 217 chub mackerel 112 wt = 5x10-6fl3.1769 0.9583 190 350 clearfin lizardfish 91 wt = 0.3791e-0.0318fl 0.8772 80 141 diamondback pufferfish 35 wt = 2x10-5fl3.0134 0.9837 74 440 indian scad 83 wt = 5x10-6fl3.1762 0.9694 75 217 king soldier bream 85 wt = 6x10-5fl2.8206 0.9738 215 575 longnose jack 89 wt = 8x10-5fl2.7666 0.9827 233 660 randalls threadfin bream 98 wt = 0.6977e0.03fl 0.9479 70 129 roundsnout sea catfish 180 wt = 1x10-5fl3.0973 0.9784 222 447 santer seabream 145 wt = 3x10-5fl2.9356 0.994 104 575 slender rainbow sardine 35 wt = 3.6748e0.0157fl 0.7682 155 196 snakefish 82 wt = 9x10-7fl.3.5225 0.9149 76 154 spangled emporer 136 wt = 2x10-5fl2.9998 0.9949 239 603 spiny flathead 40 wt = 1x10-5fl2.9576 0.978 72 271 spotted grunt 63 wt = 2x10-3fl2.2189 0.6665 589 715 striped bonito 51 wt = 4x10-6fl3.2119 0.9779 365 580 human and al-busaidi 48 49 length and weight relationships for 31 species of fishes caught by trawl coefficient obtained in this study (table 3) indicate that snakefish have a poorer general condition in the arabian sea off oman compared to that off brazil at the time of that study. carangidae abdurahim et al. (2004) provided a length-weight relationship of wt = 0.073tl2.306 for male indian scad (r2 = 0.86; n = 199), and wt = 0.024tl2.647 for female indian scad (r2 = 0.93; n = 150), from off india. the scaling constant was found to be much lower, and the allometric growth coefficient much higher in the current study (table 3) compared to that of abdurahim et al. (2004), and although fork length was used in the current study compared to total length used by abdurahim et al., it is unlikely that this difference alone accounts for the differences in parameters, and may indicate that indian scad in the arabian sea measured during this study are of better general condition than those of india at the time of abdurahim et al.’s study. lethrinidae spangled emporer was studied from all coastal waters off oman by al-mamry (2006) who reported for males a length-weight relationship of wt = 2x10-5tl2.859 (r2 = 0.976; n = 502); females wt = 2x10-5tl2.856 (r2 = 0.971; n = 779); and sexes combined wt = 2x105tl2.847 (r2 = 0.973; n = 1281). the length-weight relationships for this species restricted to the arabian sea off oman (mcilwain et al., 2006) are males wt = 5.21x10-2fl2.732 (r2 = 0.94; n = 407); females wt = 3.09x10-2fl2.867 (r2 = 0.98; n = 377); and sexes combined wt = 3.43x10-2tl2.839 (r2 = 0.97; n = 784). the results obtained in the current study (table 3) are similar to those studies above, indicating that the general condition of spangled emporer off oman has remained constant. sparidae weight-length relationships for arabian pandora of wt = 2.38x10-2fl2.975 (males; r2 = 0.95; n = 718), wt = 2.39x10-2fl2.973 (females; r2 = 0.92; n = 630), and wt = 2.38x10-2fl2.974 (sexes combined; r2 = 0.94; n = 1348) were provided by mcilwain et al. (2006) from the arabian sea of oman. both the scaling constant and the allometric growth coefficient were found to be lower in the current study (table 3), indicating that the general condition of arabian pandora in the arabian ta bl e 4. s um m ar y of th e re gr es si on o f g re en w ei gh t ( g w ) a ga in st d re ss ed w ei gh t ( d w ), in cl ud in g sp ec ie s co m m on n am e, s am pl e si ze , r eg re ss io n eq ua tio n, a nd r 2 va lu e, f or 1 2 co m m er ci al ly im po rt an t f is h sp ec ie s fr om t he o m an d em er sa l t ra w l z on e th at w er e pr oc es se d ab oa rd th e f. v . a lm us ta qi la i be fo re b ei ng la nd ed . a ls o in cl ud ed a re th e co nv er si on fa ct or s fo r c on ve rt in g dr es se d w ei gh t ( d w ) t o gr ee n w ei gh t ( g w ), an d vi ce v er sa . w ei gh ts a re in k ilo gr am s. c om m on n am e n r eg re ss io n r 2 d w w ei gh t r an ge d w à g w g w à d w a lm ac o ja ck 22 g w = 1 .6 61 8x d w + 0 .1 39 0. 97 62 2. 31 0 5 .7 70 1. 70 7 0. 58 5 in di an th re ad fi n 14 g w = 1 .7 38 6x d w – 0 .0 86 6 0. 96 44 1. 55 5 5 .7 15 1. 71 5 0. 58 3 k in g so ld ie r b re am 28 g w = 1 .6 88 6x d w + 0 .1 88 7 0. 97 70 0. 49 5 6 .0 90 1. 75 4 0. 57 0 l ar ge he ad c ut la ss fi sh 22 g w = 1 .4 77 xd w 0. 12 26 0. 96 54 2. 57 5 6 .5 10 1. 44 9 0. 69 0 m ilk s ha rk 23 g w = 2 .1 47 1x d w + 0 .1 17 7 0. 98 27 0. 62 0 5 .2 35 2. 23 2 0. 44 8 so ut he rn m ea gr e 13 g w = 1 .6 18 9x d w + 0 .5 27 0. 98 33 1. 16 0 7 .8 40 1. 83 4 0. 54 5 sp an gl ed e m po re r 15 g w = 1 .8 15 8x d w + 0 .1 85 4 0. 99 13 0. 65 5 6 .2 80 1. 73 9 0. 57 5 sp ot te d gr un t 7 g w = 1 .7 87 2x d w + 0 .2 12 6 0. 99 39 1. 16 0 4 .8 40 1. 90 9 0. 52 4 st ri pe d bo ni to 19 g w = 1 .5 00 5x d w + 0 .1 28 2 0. 99 19 1. 14 0 – 6. 84 0 1. 53 9 0. 65 0 human and al-busaidi 50 51 length and weight relationships for 31 species of fishes caught by trawl the southwest atlantic ocean. bernardes & rossiwongtschowski (2000) reported wt = 1x10-7tl3.220 (r2 = 0.986; n = 2471), while in the same year muto et al. (2000) reported wt = 1.342x10-7tl3.192 (r2 = 0.945; n = 485), from different regions of the brazilian coast. later, frota et al. (2004) gave the length-weight relationship of this species using preanal length, wt = 0.0338lpa2.653 (r2 = 0.966; n = 111) from brazil. two studies report length-weight data for this species from the arabian sea. abdurahiman et al. (2004) reported for males wt = 0.001tl2.819 (r2 = 0.91; n = 200), and females wt = 0.001tl3.029 (r2 = 0.95; n = 200), from southwest india, while al-nahdi et al. (200x) reported for males wt = 2.67x10-6tl2.803 (r2 = 0.91; n = 52), females wt = 6.77x10-7tl3.113 (r2 = 0.91; n = 245), and for sexes combined wt = 1.23x10-6tl2.989 (r2 = 0.92; n = 388). both the scaling constant and the allometric growth coefficient are similar between all studies, including the current study (table 2), indicating that the condition of fish and the growth parameters of this species are similar between the arabian sea and the western atlantic. scombridae the allometric growth factor reported here for chub mackerel (table 3) is less than that reported by santos et al. (2002) who gave a length-weight relationship of wt = 2.1x10-3tl3.408 for this species from off of portugal, however, this may be an artefact of the use of total length in that study, compared to the use of fork length in the current study. although lengthweight relationships were not provided by mallicoate & parrish (1981), they conducted a detailed growth analysis of this species from off california, usa, in the western pacific. balistidae sahayak (2005) provided the length-weight relationship for bridled triggerfish from indian seas as wt = 9.05x10-10tl2.7296 (r2 = 0.9301; n = 514). the larger scaling constant and allometric growth coefficient indicate that this species had a better general condition at the time of this study in the arabian sea (table 2), compared to off india in 2005. conclusion this study provides length and weight relationships for fishes from the arabian sea coast of oman using demersal trawl gear. many weight-length relationships sea off oman had decreased slightly during the time interval between the two studies. al-mamry (2006) reported length-weight relationships for king soldier bream of wt = 5x105tl2.692 (r2 = 0.968; n = 398) for males, wt = 6x105tl2.642 (r2 = 0.976; n = 347) for females, and wt = 6x10-5tl2.666 (r2 = 0.977; n = 745) for sexes combined, from all coastal waters of oman. mcilwain et al. (2006) studied king soldier bream captured off oman in the arabian sea only, and found the following weight-length relationships for that species: wt = 8.86x10-2fl2.626 (r2 = 0.97; n = 492) for males, wt = 8.42x10-2fl2.64 (r2 = 0.98; n = 438) for females, and wt = 8.6x10-2fl2.635 (r2 = 0.98; n = 930) for sexes combined. these values were slightly smaller than that reported here (table 3), which may indicate that the condition of the fish have improved slightly during the period between the two studies. santer seabream were studied from the arabian sea off oman by mcilwain et al. (2006), and gave length-weight relationships for males wt = 3.15x102fl2.872 (r2 = 0.99; n = 458), females wt = 3.38x102fl2.849 (r2 = 0.98; n = 499), and for sexes combined wt = 3.12x10-2fl2.875 (r2 = 0.98; n = 957). in the current study (table 3), the scaling constant was lower, however, the allometric growth coefficient was higher, indicating that growth rate may have increased at the cost of general condition and may reflect the impact of heavy fisheries pressure on this species in this area. paralichthyidae weight-length relationships for largetooth flounder from off of india were given for males wt = 4x103tl3.256 (r2 = 0.98; n = 147), and females wt = 3x10-3tl3.378 (r2 = 0.99; n = 160) by abdurahiman et al. (2004). these values indicate that the general condition of largetooth flounder was better off india at that time period than off oman in the arabian sea at the time of this study (table 3). trichiuridae the largehead cutlassfish is a common catch in the indian ocean and the atlantic ocean, but most length-weight relationships come from the atlantic ocean. sheridan et al. (1984) reported a lengthweight relationship of wt = 5.248x10-8tl3.37 (r2 = 0.97; n = 853) from the northern gulf of mexico, northwest atlantic ocean. all other reports from the atlantic ocean come from off the brazilian coast in human and al-busaidi 50 51 length and weight relationships for 31 species of fishes caught by trawl for the fishes found in the arabian sea off the coast of oman are reported for the first time. given the intensity at which this zone is being fished (human, 2007), as well as the fishing intensity that is occurring in other fishing sectors of oman (anon, 2004; and henderson et al., 2007), it is hoped that the data presented in this study will aid in improving the management of the fisheries off the arabian sea coast of oman. acknowledgements the authors are indebted to all of the crew aboard the f.v. al-mustaqila i, particularly nikolayevich vyacheslav gettun and viktor terentyev during the 2007 cruise. mohamed al-jabri (protein products international) and ernie chadwick (previously of ppi) arranged seatime for the authors during commercial fishing operations. the authors were generously allocated hold space for storage of frozen specimens, and numerous factory workers assisted with the processing of fishes for the green weight-dressed weight comparisons. the authors thank the captains of cruise oma0801 fish resources assessment survey of the arabian sea coast of oman, chris carey and john baxter, and the crew. special thanks are extended to the voyage leader, neil bagley, and the rest of the scientific staff from niwa. figure 1 was generously supplied to the authors by lubna al-kharusi. earlier drafts of the manuscript were reviewed by johan groeneveld, n. jayabalan, and lubna alkharusi (marine science and fisheries centre). references abdallah, m. 2002. length-weight relationship of fishes caught by trawl off alexandria, egypt. naga, 25(1):19-20. abdurahiman, k.p., t. harishnayak, p.u. zacharia, and k.s. mohamed. 2004. length-weight relationship of commercially important marine fishes and shellfishes of the southern coast of karnataka, india. naga, 27(1&2):9-14. akyol, o., h.t. kinacigíl, and r. şevík. 2007. longline fishery and length-weight relationships for selected fish species in gökova bay (aegean sea, turkey). international journal of natural and engineering sciences, 1:1-4. al-abdessalaam, t.z.s. 1995. marine species of the sultanate of oman. an identification guide. ministry of agriculture and fisheries, sultanate of oman. muscat. 412pp. al-mamry, j.m.a. 2006. biology and fisheries management of argyrops spinifer and lethrinus nebulosus in the arabian sea. school of ocean sciences, university of wales. bangor, wales. x + 421pp. al-nahdi, a., e. al-rasadi, h. al-waili, and j. almamry. 200x. biology and stock assessment of largehead hairtail trichiurus lepturus from the arabian sea. agriculture and marine science. x(x):xx-xx. al-waili, h., a. al-marzouqi, m. al-boloshi, and i. anbory. 200xa. biology and stock assessment of mullet crenimugil crenilabis from the arabian sea. agriculture and marine science. x(x):xx-xx. al-waili, h., a. al-marzouqi, a. al-nahdi, w. alamry, and b. sadeq. 200xb. biology and stock assessment of geelbeck croaker atractoscion aequidens from the arabian sea. agriculture and marine science. x(x):xx-xx. anonymous. 2004. fisheries statistics book 2003. directorate general of planning & investment promotion, statistics & information department, ministry of agriculture and fisheries. muscat, sultanate of oman. 240pp. bernardes, r.a. and c.l.d.b. rossi-wongtschowski. 2000. length-weight relationship of small pelagic fish species of the southeast and south brazilian exclusive economic zone. naga, 23(4):30-32. can, m.f., n. başusta, and m. çekíç. 2002. weightlength relationships for selected fish species of the small-scale fisheries off the south coast of ískenderun bay. turkish journal of veterinary and animal sciences, 26:1181-1183. carpenter, k.e., f. krupp, d.a. 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report. department of marine science and fisheries, college of agriculture and marine science, sultan qaboos university muscat, sultanate of oman. vi + 134pp. human, b.a. 2006. size-corrected shape variation analysis and quantitative species discrimination in a morphologically conservative catshark genus, poroderma smith, 1837 (chondrichthyes: carcharhiniformes: scyliorhinidae). african natural history, 2:1-15. human, b.a. 2007. report on the f.v. al-mustaqila i oman cruise #3. 4th – 24th march, 2007. unpublished report for the ministry of agriculture and fisheries. muscat, sultanate of oman. may 2007. vii + 71pp. johanneson, k.a. 1991. assessment of major marine stocks of demersal, small pelagic and mesopelagic species. r/v rastrelliger acoustic and trawling survey results. november 1989 november 1990. fao rome. xiii, 77pp + appendices. mallicoate, d.l. and r.h. parrish. 1981. seasonal growth patterns of california stocks of northern anchovy, engraulis mordax, pacific mackerel, scomber japonicus, and jack mackerel, trachurus symmetricus. california cooperative oceanic fisheries investigations report, 22:69-81. mcclure, r.e. 1987. the fisheries of the sultanate of oman. annual report 1986. rda contribution #11-87. ministry of agriculture and fisheries muscat, sultanate of oman. iii + 30pp. mcilwain, j, g.v. hermosa, m. claereboudt, h.s. al-oufi, and m. al-awi. 2006. spawning and reproductive patterns of six exploited finfish species from the arabian sea, sultanate of oman. journal of applied ichthyology, 22(2):167-176. morato, t., p. afonso, p. lourinho, j.p. barreiros, r.s. santos, and r.d.m. nash. 2001. length-weight relationships for 21 coastal fish species of the azores, north-eastern atlantic. fisheries research 50:297-302. muto, e.y., l.s.h. soares, and c.l.d.b. rossiwongtschowshi. 2000. length-weight relationship of marine fish species of são sebastião system, são paulo, southeastern brazil. naga, 23(4):27-29. randall, j.e. 1995. coastal fishes of oman. crawford house publishing pty ltd. bathurst, new south wales, australia. 439pp. sahayak, s. 2005. length weight relationship of sufflamen fraenatus (latreille, 1804) and zenodon niger (ruppell, 1835). indian journal of fisheries, 52(3):357-360. santos, m.n., m.b. gaspar, p. vasconcelos, and c.c. monteiro. 2002. weight-length relationships for 50 selected fish species of the algarve coast (southern portugal). fisheries research, 59:289-295. sheridan, p.f., d.l. trimm, and b.m. baker. 1984. reproduction and food habits of seven species of northern gulf of mexico fishes. contributions in marine scienc, 27:175-204. smith, m.m. and p.c. heemstra. 1986. smiths’ sea fishes. macmillan south africa (publishers) (pty) ltd. johannesburg. xx +1047pp. strømme, t. 1986. pelagic and demersal fish resources of oman results of r/v dr. fridtjof nansen surveys in oman, 1983-1984. undp/ fao programme glo/82/001. institute of marine research bergen, norway. 123pp. valinassab, t., r. daryanabard, r. dehghani, and g.j. pierce. 2006. abundance of demersal fish resources in the persian gulf and oman sea. journal of the marine biological association, united kingdom, 86:1455-1462. wigley, s.e., h.m. mcbride, and n.j. mchugh. 2003. length-weight relationships for 74 fish species collected during nefsc research vessel bottom trawl surveys, 1992-99. woods hole laboratory massachusetts, united states of america. vi + 28pp. agricultural and marine sciences, 14:49-53 (2009) ©2009 sultan qaboos university 49 __________________________________________ *corresponding author. e-mail: sergey@squ.edu.om bioactive compounds from omani sea cucumbers sergey dobretsov1*, iman mohammed al-mammari1 and bassam soussi2, 3 1department of marine science and fisheries, college of agricultural and marine sciences, sultan qaboos university, po box 34, al-khod 123, sultanate of oman 2 unesco chair in marine biotechnology, sultan qaboos university, sultanate of oman 3 department of clinical sciences, sahlgrenska academy, university of gothenburg, sweden abstract: antimicrobial, anti-diatom and anti-larval activities of both water soluble (water extracts) and non-water soluble metabolites (methanol: chlorophorm, 1:1 extracts) of the sea cucumbers holothuria atra and holothuria edulis from bander al-khiran region, oman were tested in this study. there was no significant effect of the extracts from sea cucumbers on bacterial (3 reference bacteria from seawater and pathogens escherichia coli, staphylococcus aureus, klebsiella pneumoniae, pseudomonas aeruginosa, streptococcus pneumoniae, streptococcus pyogenes, staphylococcus epidermidis) and the diatom chaetoceros sp. growth. both water extracts and methanol: chlorophorm extracts caused significant mortality of artemia salina nauplia. this study suggests that omani sea cucumbers might be a good source of toxic anti-larval compounds. keywords: sea cucumber, biofouling, antifouling, secondary metabolites, sea of oman. introduction any natural and man-made substrates in the marine environment are quickly colonized by micro(bacteria, diatoms and protozoa) and macroorganisms (algae and invertebrates) in a process known as “biofouling” (railkin, 2004). the adverse effects of biofouling on ships and boats are high frictional resistance, speed reduction, increase of corrosion and high fuel consumption (yebra et al., 2004). biofouling can also clog water intake lines in power plants and membranes in desalination plants (flemming and ridgway, 2009). so far, the most effective methods of biofouling control are based on the application of highly toxic substances like tributyl tin (tbt), copper or organic compounds (e.g. sea-nine, isothiazolone) (thomas, 2001; yebra et al., 2004). all these antifouling compounds kill marine organisms and pollute the marine environment (see reviews of evans, 1999; yebra et al., 2004). therefore, novel antifouling compounds are urgently needed (dobretsov et al., 2006). class holothuroidea includes approximately 1200 known species of sea cucumbers, which are found throughout the world’s oceans and in great ranges of latitudes and depths, but their greatest abundance occurs in the indo-pacific region (conand, 2004). while sea cucumbers have a massive exoskeleton, they are less susceptible to predation and biofouling compare to other marine organisms. this suggests that sea cucumbers might have a chemical defense mechanism (fusetani, 2004). therefore, chemical compounds from sea cucumbers could be used for antifouling defense and biomedical applications. sea cucumbers contain numerous polar and non-polar secondary metabolites that can be used for drug discovery (paul et al., 2008). these compounds are commonly utilized for treating weakness, impotence, constipation and frequent urination (hamel and mercier, 2004). recently, antitumour, antiviral, anticoagulant and antimicrobial compounds have been isolated from sea cucumbers (kelly, 2005). these البحر العماني لدي خیار المركبات البیولوجیة النشطة وبسام سوسي المعمري محمد وإیمان سیرجي دوبریتسوف من والمستخلصة (١:١ (مستخلص المیثانول:كلوروفورم بنسبة الذائبة وغیر البحر) میاه (مستخلصات الذائبة، المواد األیضیة بعض قدرة إختبار إلى الدراسة ھدفت ھذه الخالصة: عدم وجود الدراسة بینت وقد والیرقات. والدایاتوم المیكروبات نشاط على منع عمان، في بندر الخیران منطقة من (,holothuria atra holothuria edulis) البحر حیوان خیار escherichia coli, staphylococcus aureus, klebsiella pneumoniae, pseudomonas میاه البحر و بكتریا (٣ من البكتیریا نمو على المستخلصات من تأثیر أي كل أدت بینما ،.chaetoceros sp نوع أوالدایاتوم من (aeruginosa, streptococcus pneumoniae, streptococcus puogenes, staphylococcus epidermidis للیرقات. على سموم مضادة العماني البحر خیار حیوان من مركبات إحتواء بعضا إمكانیة إلى ھذه الدراسة تشیر فإن وعلیھ .artemia salina یرقات وفاة إلى المستخلصات بحر عمان ثانویة، أیضیة مواد الترسبات، مضادات الحیویة، الترسبات البحر، خیار كلمات مفتاحیة: 50 dobretsov, al-mammari and soussi 51 bioactive compounds from omani sea cucumbers organisms are also remarkably rich in vitamins, trace elements, and polysaccharides (condroitin sulfate), which reduce arthritis pain and inhibit viral activities (hamel and mercier, 2004). saponins, such as holothurins, are one of the major natural products isolated from sea cucumbers (bhakuni and rawat, 2005). these water soluble glycosides showed haemolytic and cytotoxic activity in vivo and in vitro (kelly, 2005) and can be used for treatment of cancer and fungal infections. antifouling compounds have not been isolated from sea cucumbers so far (fusetani, 2004). the main aim of this study was to investigate the antimicrobial, anti-diatom and anti-larval potential of water soluble and non-soluble extracts from the sea cucumbers holothuria atra and h. edulis in laboratory experiments in vitro. material and methods preparation of the extracts several specimens of the sea cucumbers holothuria atra and h. edulis were collected 24.09.07 from bandar alkhiran area (23o31’13.9”n 58o43’58.68”e) at the depth 4 m. these sea cucumbers were kept on ice and frozen at -20oc in the laboratory. after 2 weeks, the sea cucumbers holothuria atra and h. edulis were defrosted and cut into small pieces and separated into 2 approximately equal portions. the first portion of the sea cucumbers was extracted with distilled sterile water. for this, 500ml of water was added to 649g (wet weight) of the black sea cucumber h. atra or 663g (wet weight) of the red sea cucumber h. edulis and incubated at 40c in the fridge for 2 days. the second portion the sea cucumbers was extracted with 1:1 methanol:chloroform solution. for this, 500 ml of 1:1 methanol:chloroform solution was added to 660g (wet weight) of the sea cucumbers h. atra and h. edulis. these samples were extracted for 2 weeks at room temperature (23oc). after that, the samples containing water soluble metabolites were filtered and preserved in the freezer for the bioassays (see below), while the methanol:chloroform extracts were filtered and concentrated under vacuum using a rotary evaporator. the water bath temperature was +40-50°c. after evaporation the remaining sample was mixed with new 1:1 methanol:chloroform solution and transferred into small labelled containers. finally, all extracts were dried at room temperature. bioassays preparation of the bacterial media bacteria were growing either in liquid marine broth (difco) or on the surface of nutrient agar (oxoid). broth were prepared on distilled water according to the manufacturer’s protocols. flasks with media were autoclaved at 121oc in order to sterilize them. anti-bacterial assay three strains of unidentified marine bacteria (reference1, reference2, and reference5) isolated from bandar alkhiran water column (23o31’13.9”n 58o43’58.68”e) and bacterial pathogens escherichia coli, staphylococcus aureus, klebsiella pneumoniae, pseudomonas aeruginosa, streptococcus pneumoniae, streptococcus pyogenes, staphylococcus epidermidis obtained from squ hospital were used in this bioassay. before the assay, all strains were sub-cultured in the marine broth for 24h at + 30oc. two hundred μl of the bacterial culture was spread on each petri dish. water extracts of sea cucumbers were pipetted and loaded on paper disks (1 mm2 in diameter). there were 3 disks containing 50 μl (wb50) and 20 ml (wb20) of the water soluble extracts of holothuria atra, as well as with 20 μl (wr20) and 50 μl of h. edulis (wr50). for the controls, 3 disks containing 20 and 50 μl of sterile water were used. twenty μl of chloroform: methanol extracts of h. atra (b20) and h. edulis (r20) were added to 3 disks. all disks were dried at room temperature (23oc) and placed into petri dishes containing bacterial strains under investigation. the experiment was run with 3 replicates. petri dishes were kept at room temperature (23oc) for 2 days. the observed zones of growth inhibition between the disc and the bacterial film were measured to the nearest 0.2 mm. anti-diatom assay prior to the experiment, the diatom chaetoceros sp. (provided by prof. u. riebesell, ifm-geomar) was cultivated in the f2 media for 2 weeks at room temperature (23oc). when a visible film developed in the culture flask, diatom suspensions were prepared by brushing the culture flask with a sterile paint brush. this algal suspension was then used in the following experiments. anti-diatom activity of the sponge extracts was tested according to a protocol developed by dobretsov and qian (2002). five hundred μl of the water extracts of h. edulis or h. atra were added to petri dishes in 3 replicates containing 5 ml of diatom suspension (about 12 x 104 cells ml-1). methanol: chloroform extracts of h. atra and h. edulis were evaporated and re-dissolved in dimethylsulfoxide (dmso). then, 100 μl extracts were added to petri dishes in 3 replicates containing 5 ml of diatom suspension. five hundred μl of sea water or 100 μl of dmso were used as the controls. the petri dishes were incubated for 4 days with continuous light at 23oc. after that, the unattached diatoms and water were poured out. then, 15ml of 90% acetone was added to each petri dish to extract chlorophyll a. the amount of chlorophyll a in each sample was measured using a spectrophotometer following lorenzen (1967). anti-larval assay prior to the experiment, the brain shrimp artemia salina nauplia were cultivated. for this, we added 2g of the a. salina eggs into 1l of sterile seawater. eggs with seawater were kept in a covered container (volume 1l) with aeration at room temperature (23oc). after two days, the larvae hatched. photopositive nauplia were collected and used in the bioassay. fifty mμl of a. salina culture 50 dobretsov, al-mammari and soussi 51 bioactive compounds from omani sea cucumbers containing 10-20 larvae was added to each cell of multiwell dishes containing 500 mμl of sterile sea water. then, 500 μl or 50 μl of the water extracts from h. edulis and h. atra were added to the cells. additionally, 50 μl of methanol: chloroform extracts of these sea cucumbers evaporated and re-dissolved in dmso was applied to other cells. five hundred μl of seawater or 100 μl of dmso were used as the controls. each treatment was repeated 4 times. after 24h, the amounts of swimming and dead larvae were counted using a microscope. statistical analysis chlorophyll a concentrations were log transformed to ensure normality and homogeneity of variance (zar, 1996). the percent values of larval survival were arcsinetransformed. to improve the arcsine-transformation, those replicates with zero survival were given the value of 1/(4n) (n = number of larvae in a single replicate) (zar, 1996). in all cases, the normality assumption was verified by the shapiro-wilk test (shapiro and wilk, 1965). the differences between the experimental and control treatments were determined by one-way anova followed by an lsd post-hoc test (zar, 1996). in all cases, the threshold for significance was 5%. results anti-bacterial assay none of the tested extracts (water extracts and chloroform: methanol extracts) of h. atra and h. edulis inhibited growth of reference bacteria and pathogens. at the same time, we observed halos (reduction of bacterial growth) in the case of reference bacteria 1 in the presence of water extracts from h. edulis (wr20) and from h. atra (wb20 and wb50). anti-diatom assay the results of the diatom test showed that there were no significant changes (p>0.05, anova) in diatom growth after 4d of experiment (fig.1). none of the extracts caused reduction of chlorophyll a concentration. anti-larval assay all tested extracts changed mortality of artemia salina larvae (fig. 2). in all cases, water and methanol: chloroform extracts of h. edulis and h. atra caused significantly high (anova, p<0.05) mortality of larvae compared to the controls. all larvae died in the presence of methanol: chloroform extracts of h. atra and h. edulis. water extracts of both species at 50 μl and 500 μl caused moderate mortality of a. salina larvae. discussion and conclusions in this study, we have investigated anti-microbial, antidiatom and anti-larval activities of both water-soluble and non-water soluble metabolites from two species of sea cucumber specimens from the sea of oman. our findings suggest that polar and non-polar metabolites of the sea cucumbers h. atra and h. edulis can kill larvae of invertebrates and cannot be used as non-toxic antifouling compounds. our results show that neither chloroform: methanol (non-polar) nor water (polar) extracts of the sea cucumber figure 1. the effect of water and chloroform: methanol extracts (1:1) of the sea cucumbers h. atra and h. edulis on growth of the diatom chaetoceros sp. the data are the mean chlorophyll a concentration (mg m-3) ± se (standard error) measured after 4d experiments with 500 μl of the water extracts of h. edulis (500wr) and h.atra (500wb), as well as 100 μl methanol:chloroform extracts of h. edulis (100mcr) and h.atra (100mcb) re-dissolved in dimethylsulfoxide (dmso). five hundred μl of seawater (sw) and 100 μl of dmso (dmso) were used as the controls. treatments 52 dobretsov, al-mammari and soussi 53 bioactive compounds from omani sea cucumbers h. edulis and h. atra affected the growth of tested pathogens. this can be explained by the fact that the investigated sea cucumbers most likely have never been exposed to the human pathogens tested in this study and, therefore, may lack such a defense. furthermore, the tested extracts did not demonstrate antimicrobial activity against naturally occurring bacterial strains. this suggests that h. edulis and h. atra lack antimicrobial defense in the present experiment set up. this result contradicts findings of stonik et al. (1979) suggesting that sea cucumbers produce different antimicrobial water-soluble glycosides. additionally, tested reference bacteria might not be harmful to these sea cucumbers and, therefore, the sea cucumbers have not evolved any antimicrobial defense against them. none of the tested compounds affected the growth of the diatom chaetoceros sp. this result suggests that the sea cucumbers h. atra and h. edulis have no or very low antidiatom activity. to our knowledge, anti-diatom activity of sea cucumbers has not been reported previously. we found that the methanol: chloroform and water extracts from h. atra and h. edulis caused high mortality and low survival of artemia salina larvae compared to the controls. these results suggest that some toxic secondary metabolites are present in the extracts of sea cucumbers. these metabolites potentially can be used as cytotoxic compounds for cancer treatments. previously, holothurins and asterosaponins that are toxic to the larvae of marine invertebrates have been isolated from sea cucumbers (fusetani, 2004). similarly, several triterpene glycosides isolated from psolus patagonicus (dendrochirotida: psolidae) showed a high level of mortality against the brine shrimp artemia salina and revealed antifungal activity against the fungi cladosporium fulvum, fusarium oxysporum and monilia sp. (muniain et al., 2008). thus, in line with these findings, our data suggest that secondary metabolites from sea cucumbers have promising potential for biomedicine applications. overall, very little information is available about the biology, ecology and biotechnological potential of holothuroids along the arabian sea coast of oman (rashdi et al., 2007). the present study is the first investigation of anti-microbial, anti-diatom and anti-larval activity of both water-soluble and non-water soluble metabolites from two species of sea cucumbers from the sea of oman coast. further studies of sea cucumber metabolites are needed in order to elucidate the structure of possible novel secondary metabolites useful in biomedical applications. figure 2. the effect of water and chloroform: methanol extracts (1:1) of the sea cucumbers h. atra and h. edulis on mortality of artemia salina nauplia. the data are the mean percentage of mortality ± se (standard error) in experiments with 500 μl (500) and 50 μl (50) of the water extracts of h. edulis (wr) and h. atra (wb), as well as 50 μl (50) of methanol: chloroform extracts (mcb and mcr) of sea cucumbers re-dissolved in dimethylsulfoxide (dmso). five hundred μl of seawater (sw) or 100 μl of dmso (dmso) were used as the controls. different letters above the bars indicate data that are significantly different in the lsd test (p < 0.05, oneway anova). treatments 52 dobretsov, al-mammari and soussi 53 bioactive compounds from omani sea cucumbers acknowledgements this investigation was supported by the squ grant (ig/ agr/fish/09/03) to sd and the hm fund for strategic research (sr/agr/food/05/01) and university of gothenburg sahlgrenska academy to bs. we thank dr. michel claereboudt for his help in collecting sea cucumbers and dr. hussain al-massroori for arabic translation of the manuscript. we acknowledge help of prof. ulf riebesell who kindly provided diatoms for this experiment. references bhakuni, d.s. and d.s. rawat. 2005. bioactive marine natural products. springer anamaya, india. conand, c. 2004. present status of world sea cucumber resources and utilization: an international overview. in: advances in sea cucumber aquaculture and management. a. lovatelli, c. conand, s. purcell, s. uthicke, j.f. hamel and a. mercier (editors). 13-23. geneva: fao fisheries technical paper. dobretsov, s. and p.y. qian. 2002. effect of bacteria associated with the green alga ulva reticulata on marine microand macrofouling. biofouling 8:217228. dobretsov, s., h.u. dahms and p.y. qian. 2006. inhibition of biofouling by marine microorganisms and their metabolites. biofouling 22:43-54. evans, s.m. 1999. tbt or not tbt?: that is the question. biofouling 14:117-129. flemming h.c. and h. ridgway. 2009. biofilm control: conventional and alternative approaches. in: marine and industrial biofouling. r. venkatesan, p.s. murthy, k. cooksey and h.c. flemming (editors), 4:103-119. fusetani, n. 2004. biofouling and antifouling. natural product reports 21:94-104. hamel, j.f. and a. mercier. 2004. synchronous gamete maturation and reliable spawning induction method in holothurians. pp 359–372. in: advances in sea cucumber aquaculture and management. a. lovatelli, c. conand, s. purcell, s. uthicke, j.f.hamel and a. mercier (editors), 425 pp. fao fisheries technical reports no. 463, fao, rome. kelly, m.s. 2005. echinoderms: their culture and bioactive compounds. progress in molecular and subcellular biology 39:139-165. lorenzen, c. 1967. determination of chlorophyll and phaeopigments: spectrophotometric equations. limnology and oceanography 12:343-346. muniain, c., r. centurioìn, v.p. careaga and m.s. maier. 2008. chemical ecology and bioactivity of triterpene glycosides from the sea cucumber psolus patagonicus (dendrochirotida: psolidae). journal of marine biology association, uk, 88:817-823. paul, v.j. and r. ritson-williams. 2008. marine chemical ecology. natural product reports 25:662-695. railkin, a.i. 2004. marine biofouling: colonization processes and defenses. boca raton, fl, usa crc press. rashdi, k.m., m.r. claereboudt and s.s.al-busaidi. 2007. density and size distribution of the sea cucumber, holothuria scabra (jaeger, 1935), at six exploited sites in mahout bay, sultanate of oman. journal of agricultural and marine sciences 12:43-51. shapiro, s.s. and m.b. wilk. 1965. an analysis of variance test for normality (complete samples). biometrika 52: 591-611. stonik, v.a., a.d. chumak, v.v. isakov, n.i. belogortseva, v.ya, chirva and b. elyakov. 1979. glycosides of the sea invertebrates. 7. structure of holothurin-b from holothuria atra khim. prir soedin 15:522-52. thomas, k.v. 2001. the environmental fate and behaviour of antifouling paint booster biocides: a review. biofouling 17:73-86. yebra, d.m., s. kiil and k. dam-johansen. 2004. antifouling technology past, present and future steps towards efficient and environmentally friendly antifouling coatings. progress in organic coatings 50: 75-104. zar, j.h. 1996. biostatistical analysis. 3rd edition. prentice hall international, inc., upper saddle river. received: march 2009 accepted: may 2009 agricultural and marine sciences, 13:64-72 (2008) ©2008 sultan qaboos university 64 65 hydrographical observations during a red tide with fish mortalities at masirah island, oman *corresponding author. e-mail: saud.salim@yahoo.com: hydrographical observations during a red tide with fish mortalities at masirah island, oman 1ministry of fisheries wealth, marine science & fisheries center, muscat, oman 2ministry of fisheries wealth, aquaculture center, muscat, oman 3nizwa university, nizwa, oman abstract: harmful algal blooms (habs) can have a significant impact on the distribution and survival of coastal fishes and invertebrates, and consequently they can affect local economies where fishing is an important activity. in october 2005, extensive algal blooms with brownish/orange discoloured water and fish mortalities were observed east of masirah island. satellite images revealed cooler upwelled surface water along a broad front just prior to the event, followed by a gradual warming period coinciding with the mortalities. depth profiles of dissolved oxygen (do), temperature, salinity and ph taken on 19th october (during the fish mortality event) showed a pronounced thermocline at ~15 m depth and minimum do of 0.82 ml/l at 25 m depth, and a slight improvement in do to 1.3 ml/l was measured on 22nd october (after the event). demersal fishes of several families were prominent among mortalities. no bacterial infestation was found in fish samples and no human poisoning was reported. planktological data showed that marine dinoflagellates noctiluca scintillans and prorocentrum micans and toxic blooms of cyanobacterium trichodesmium erythraeum were present. keywords: introduction official documentation of red tide events along the coast of oman began in 1978, and fish, mollusk and crustacean mortalities associated with these events have often been reported in the region (claereboudt et al. 2001). the causes of mortalities are not always clear – these may be the result of harmful algal blooms (habs) dominated by toxic dinoflagellates (e.g. peridinium, dinophysis, prorocentrum spp.) which may poison fish or other organisms when they release their toxins, or alternatively the result of oxygen depletion in confined areas during the bacterial oxidation of collapsed blooms. claereboudt et al. (2001) suggested that mortalities during a red tide (mainly the non-toxic diatom coscinodiscus spp.) in the gulf of oman in 2000 were driven by oxygen saud s. al busaidi*1, khalfan m. al rashdi2, hamed m. al gheilani1and shehla amer3 األسماك ونفوق األحمر المد أثناء الھیدروغرافیة البیانات عمان سلطنة مصیرة، جزیرة في عامر شھالء الغیالني، حمد الراشدي، خلفان البوسعیدي، سعود وبالتالي الساحلیة، المیاه والالفقاریات في األسماك توزیع وحیاة مھم في تأثیر الضارة الطحالب الزدھار أن یكون یمكن الخالصة: مصیرة جزیرة شرق في المیاه اصطبغت ٢٠٠٥م، عام من أكتوبر في المھمة. األنشطة من الصید كان االقتصاد المحلي أینما في وجود الصناعیة األقمار صور وبیَّنت األسماك. الكثیرمن نفوق إلى أدى مما للطحالب الكبیر االزدھار البرتقالي بسبب البني/ باللون درجة حرارة في تدریجي ارتفاع ثم أعقبھا األسماك، ونفوق حدوث ظاھرة االزدھار قبیل باردة (انبثاقات) بحریة صاعدة تیارات التي الحموضة ومعدل والملوحة، الحرارة، ودرجات الذائب، األعماق لألكسجین قراءات الظاھرة. حدوث مع بدایة متزامنا المیاه كمیة األكسجین بینما قلت ١٥مترا، حوالي عمق على حراري انحدار وجود بجالء بینت الظاھرة) حدوث (أثناء ١٩اكتوبر یوم أخذت حدوث (بعد ٢٢أكتوبر یوم ١,٣مل/لتر إلى قلیال الكمیة ھذه وارتفعت ٢٥مترا، ٠,٨٢مل/لتر على عمق بلغت حیث كثیرا الذائب لم كما عینات األسماك في بكتیري تلوث وجود یكتشف النافقة. لم األسماك اقتصادیا ضمن ھامة قاعیة ھناك اسماك الظاھرة).وكانت ازدھار إلى البحریة إضافة األسواط لثنائیات ازدھار وجود البحریة العوالق عینات تحلیل وأظھر المستھلكین. بین تسمم أي تسجیل یتم الخضراء-الزرقاء. الطحالب agricultural and marine sciences, 13:64-72 (2008) ©2008 sultan qaboos university 64 65 hydrographical observations during a red tide with fish mortalities at masirah island, oman depletion below the thermocline and not by toxicity. other red tide events in oman have been attributed to noctiluca blooms (thangaraja et al., 2000), which are known to affect the water quality by depleting the oxygen in seawater or by contributing to higher levels of ammonia (okaichi and nishio, 1976). massive fish and invertebrate kills were reported along the coast of masirah island around 13th october 2005 and mortalities continued up to at least the 19th of the month. during this period fishers noted that some fish species were lethargic, and could be caught easier than usual. seawater in the immediate area was discoloured, brown and orange, suggesting a large phytoplankton bloom. sst, water temperature, dissolved oxygen, ph and salinity were measured from the surface to 30 m depth during and after the event, and water samples analysed to identify the predominant algal groups. affected fish were identified to family level. based on these observations, we suggest a possible cause for the mortality event. methods phytoplankton samples were taken from five sites along the eastern coast of masirah island (a 45 km stretch) on october 18th and 19th (during the fish kill) and on october 22nd (thereafter). from north to south, the sites were al ghudhuba (20º42΄n; 58º 55΄22e) alaijah (20º42´n; 58º55΄22 e and 20º34´57 n; 58º57΄43 e), rasiyah (20º31΄ 01 n; 58º59΄29e and 20º31΄24n; 59º00΄29e), naghat (20º27΄41n; 58º58΄03e) and amq (20º22΄22n; 58º54΄58e) (fig. 1). phytoplankton samples were collected using a bongo net (80 µm figure 1. study sites in masirah island, arabian sea. al-busaidi and others 66 67 hydrographical observations during a red tide with fish mortalities at masirah island, oman mesh size) and niskin bottles, and were preserved with formaldehyde (4%, velikova and larsen, 1999), and studied under a microscope, without staining. samples were taken from all five sites on 18th and 19th october, and again at two badly affected sites at al-aijah (2nd position) and rasiyah on 22nd october. water quality parameters ph, temperature, salinity and dissolved oxygen (do), were measured from the surface and at 5m depth intervals up to 30 m depth using hydrolab (data sonde 4a). sst of the gulf of oman and arabian sea between ras al hadd and salalah (including masirah island) was available for the 26th of september, and the 3rd, 12th and 13th of october from noaa-14 avhrr (advance very high resolution radiometer) imagery. dead fish were identified to family level whenever possible, and bacteriological examination of the frozen samples was done in a specialised laboratory (bacteriology section, department of laboratories, ministry of health). samples were analyzed for the presence of colioformis, esherichia coli, salmonella, shigella, vibrios, staphylococcus aureus, cyanobacteria, bacillus cereus, clostridium and listeria monocytogenes. results and discussion phytoplankton samples showed the presence of noctiluca scintillans, (fig. 2), prorocentrum micans (fig. 3) and trichodesmium erythraeum (fig. 4), whilst the dinoflagellate p. micans was the dominant species. blooms of p. micans generally occur in zones receiving high solar energy and anthropogenic inputs, which are rich in nutrients and dissolved organic matter (anderson et al., 2002; subba rao et al., 1995). in several parts of the world, fish kills have been attributed to low dissolved oxygen levels generated by high biomass blooms and not necessarily due to toxicity. for example, from 1980–1989, at least 50% of fish killed in the gulf of mexico and 69% in the south atlantic, usa, were attributed to low dissolved oxygen (lowe et al., 1991). similarly, low do levels have also been the most popular cause for the fish mortality in oman. in most cases the dominant red tide causing species in the gulf of oman is noctiluca scintillans (thangaraja et al., 2000). noctiluca scintillans is also non-toxic but can reduce water quality by depleting oxygen and raising ammonia levels (okaichi and nishio, 1976). the identification of the marine cyanobacterium trichodesmium erythraeum was less straightforward than that of diatoms and dinoflagellates because of the lack of distinct and unique morphological characteristics. nevertheless, our identification was based on the morphological description of post et al. (2002), who described colonies with trichomes arranged in parallel bundles or rafts (tufts) floating on the surface in the gulf of aqaba. an extensive surface bloom of t. erythraeum was also previously observed in the central basin of the arabian sea during the spring intermonsoon of 1995 (capone et al., 2000), a period of calm winds similar to the conditions at masirah island in october 2005. trichodesmium erythraeum is capable of utilizing ammonia and urea (ohki et al., 1991), and it does contain toxic, water-soluble material which is the progenitor of major toxins carried by some ciguateric fish. release of these water-soluble toxins into ambient seawater may constitute a health hazard for humans (endean et al., 1993). the satellite image from 26th september shows a broad front of cooler surface water (approx. 20°c) stretching alongshore from ras al hadd to salalah, and enveloping masirah island (fig. 5a). by 3rd october, upwelling have intensified to the south of masirah island (15–17°c), with warming surface waters towards the north of the island (fig. 5b). a narrow band of cooler coastal waters (around 20–21°c) is apparent along the east coast of masirah island and northwards to ras al hadd on the 12th of october (fig. 5c), but by 13th october temperatures seem to have increased along the entire coastline (fig. 5d). these images suggest that upwelling events occurred over a period of at least 2 weeks before fish kills were reported at masirah island, but the mortalities themselves, or at least the reports thereof, coincided with warmer surface temperatures. unfortunately, no earlier images were available to show the sst conditions leading up to the 26th of september, nor were images available for the period of most reported mortalities after 13th october. a pronounced thermocline at 15 m depth was apparent at rasiyah on 19th october, and below this depth temperature declined from 26.2°c to 21.6°c at 25 m depth (table 1, fig. 6). do likewise declined from 6.57 ml/l at 15 m depth to 0.82 ml/l at 25 m. similar temperature and do profiles (minimum do of 1.3 ml/l at 20 m) occurred at al-aigah, although the al-busaidi and others 66 67 hydrographical observations during a red tide with fish mortalities at masirah island, oman figure 3. phytoplankton (prorocentrum micans) found in masirah island red tide. figure 4. phytoplankton (trichodesmium erythraeum) found in masirah island red tide. figure 2. phytoplankton (noctiluca scintillans) when alive (green) and while decaying (red) found in the masirah island red tide. al-busaidi and others 68 69 hydrographical observations during a red tide with fish mortalities at masirah island, oman sea surface temperature (3rd october 2005)sea surface temperature (26th september 2005) sea surface temperature (13th october 2005)sea surface temperature (12 october 2005) sea surface temperature (0c) sea surface temperature (0c) sea surface temperature (0c) sea surface temperature (0c) figure 5. satellite images show the variation in temperature before, during and after the red tide blooms in arabian sea (oman upwelling zone). source of images: remote sensing station at ministry of fisheries wealth, (satellite noaa 14). al-busaidi and others 68 69 hydrographical observations during a red tide with fish mortalities at masirah island, oman d ep th (m ) d ep th (m ) d ep th (m ) d ep th (m ) rasia (19.10.2005) (do (ml/l) rasia (22.10.2005) (do (ml/l) al-aigah 2 (19.10.2005) (do (ml/l) al-aigah (22.10.2005) (do (ml/l) temperature oc temperature oc temperature oc temperature oc figure 6. show the relation between depth, dissolved oxygen (do) and temperature (t), during and after red tide in two stations. table 1. temperature (temp), dissolved oxygen (do), salinity (sal.) and ph during red tide bloom. location date/ time distance from shore latitude/ longitude depth (m) ecological parameters temp (oc) do (ml/l) sal. (%o) ph al-aigah 19/10/2005 2 km 20o 34’ 13 n 0 26.15 7.11 36.58 7.95 7:10 am 58o 59’ 11 e 5 26.08 6.83 36.64 8.00 15 24.02 3.44 36.70 7.78 20 22.07 1.30 36.65 7.68 rasia 19/10/2005 2 km 20o 31’ 24 n 0 26.44 6.40 36.64 8.04 8:00 am 59o 00’ 29 e 5 26.29 6.42 36.66 8.09 10 26.18 6.35 36.65 8.13 15 26.15 6.57 36.65 8.16 20 23.64 3.40 36.68 7.89 25 21.61 0.82 36.60 7.66 al-busaidi and others 70 71 hydrographical observations during a red tide with fish mortalities at masirah island, oman table 2. temperature (temp), dissolved oxygen (do), salinity (sal.) and ph after red tide bloom in two stations after red tide blooms. location date/ time distance from shore latitude/ longitude depth (m) ecological parameters temp (oc) do (ml/l) sal. (%o) ph al-aigah 22/10/05 7:10 am 2 km 20o 35’ 19 n 58o 57’ 11 e 0 5 25.79 25.81 6.51 5.93 36.61 36.66 7.95 8.04 10 25.79 5.91 36.67 8.07 15 23.40 2.34 36.62 7.82 20 25 22.51 22.39 2.12 1.87 36.58 36.57 7.80 7.79 rasia 22/10/05 8:00 am 2 km 20o 31’ 01 n 58o 59’ 29 e 0 5 26.12 25.63 6.16 6.36 36.62 36.65 8.08 8.11 10 15 24.62 23.84 6.25 4.68 36.60 36.59 8.12 8.02 20 21.82 1.65 36.58 7.79 25 21.64 1.32 36.57 7.77 30 21.64 1.31 36.59 7.78 thermocline appears to have been shallower at 5–10 m depth (table 1, fig. 6). a marginal increase in do was seen at both sites on the 22nd of october – at rasiyah the do at 25 m depth had increased from 0.82 to 1.32 ml/l, and at al-aigah the increase at 20 m depth was from 1.3 to 2.12 ml/l (table 2, fig. 6). salinity and ph profiles were similar on 19th and 22nd october, with salinity remaining between 36.57‰ and 36.70‰ irrespective of depth, and ph fluctuating between 7.66 and 8.16 (fig. 7). dead and weakened fish and invertebrates were observed on or near the surface of the water and along the tide line on the shore. fishers caught larger than usual quantities of jobfishes (lutjanidae) and remarked that the fish seemed lethargic, easier to catch than usual, and were schooling. large numbers of swimming crabs (portunidae) were observed in surface layers. we identified lutjanids, sciaenids, carangids, lethrinids and sparids among the dead fishes. most of these families form part of the demersal assemblage in coastal waters (al-abdessallaam, 1995). samples of dead fish analyzed for presence of bacteria showed that none of the samples were infected with colioforms, e. coli, salmonella, shigella, vibrios, staphilococcus aureus, cyanobacter, bacillus cereus, clostridium, or listeria monocytogenes. these fish were therefore safe for human consumption, and fisherman who continued to consume the fish during the red tide event did not report any adverse reaction. most demersal fish species require a do of at least 2 ml/l (al gheilani, 2007) to survive, and the do levels of <1.4 ml/l below 15 m depth at both sites are unlikely to sustain some species over an extended period. therefore stress induced by low oxygen conditions below the thermocline may have been the cause of mortalities where fish could not move away. fish that could move away may have been displaced from their habitat, but the effects of this on their condition can only be surmised. the low oxygen conditions were apparently the result of blooms and collapse of the dinoflagellates p. micans and n. scintillans and the cyanobacterium t. erythraeum following on a series of upwelling events with nutrient enrichment of surface waters. the breakdown of the thermocline during such upwelling, and the mixing that brings cooler nutrient-rich waters to the surface layers can be caused by wind forcing or lower air temperatures during fall or winter (lindell and post, 1995; genin et al., 1995). no cell counts of the three predominant phytoplankters were done, and it is therefore difficult to rule out poisoning of fish by toxins released by t. erythraeum. nevertheless, most al-busaidi and others 70 71 hydrographical observations during a red tide with fish mortalities at masirah island, oman rasia (19.10.2005) ph al-aigah 2 (19.10.2005) ph rasia (22.10.2005) ph al-aigah (22.10.2005) ph salinity (ppt) salinity (ppt) salinity (ppt) salinity (ppt) d ep th (m ) d ep th (m ) d ep th (m ) d ep th (m ) figure 7. show the relation between depth, ph and salinity, during and after red tide in two stations. al-busaidi and others 72 evidence points to low oxygen conditions below the thermocline during the red tide event as an indirect cause of fish mortalities. acknowledgments we thank ahmed al-aisry and hilal al-shaqsi from the marine ecology laboratory at the marine science and fisheries centre, ministry of fisheries wealth for providing satellite images and hydrolab data. thanks are also due to the staff of fisheries directory at alwusta region for providing 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atmospheric administration, 69pp. okaichi, t. and s. nishio. 1976. identification of ammonia as the toxic principle of red tide of noctiluca miliaris. bulletin of plankton society, japan, 23:75-80. ohki, k., j.p. zehr, p.g. fallowski, and y.fiujita. 1991. regulation of nitrogen fixation by different nitrogen sources in the marine non-heterocystous cyanobacterium trichodesmium sp. nbb1067. journal of archeology and microbiology, 156: 335-337. post, a.e., z. dedej, r. gottlieb, d.n. thomas, m. elabsawi, a. el-naggar, m. el-gharabawi, and u. sommer. 2002. spatial and temporal distribution of trichodesmium spp. in the stratified gulf of aqaba, red sea. marine ecological progress series, 239:241-250. subba rao, d.v., y. pan, and s.j. smith. 1995. allebopathy between rhizosolenia alata (brightwell) and the toxigenic pseudnitzchia pungens f. multiseries. in: harmful marine algal blooms, p. lassus, g. arzul, e. erard-le deen, p. gentien and c. marcaillon-le-baut, (editors), 329-334. paris, lavoiser. thangraja, m., a. al-aisri, and h. al-shaqsi. 2000. phytoplankton blooms, red tide phenomena and recorded impacts in oman. marine science and fisheries center annual report, ministry of agriculture and fisheries, sultanate of oman, 22pp. velikova, v. and j. larsen. 1999. the prorocentrum cordatum/prorocentrum minimum taxonomic problem. grana 38:108-112. research paper journal of agricultural and marine sciences vol. 21 (1): 47 – 56 doi: http://dx.doi.org/10.24200/jams.vol21iss0pp47-56 received 05 mar 2015 accepted 01 nov 2016 effect of rootstock on muskmelon cultivar reaction to vine decline disease and yield under arid conditions q.s. al mawaali1,2, a.m. al-sadi2, f.a. al-said2 and m.l. deadman2* 1* mike deadman ( ) sultan qaboos university, college of agricultural and marine sciences, dpt. of cropscience. box 34, al-khod 123. sultanate of oman. email: deadman@squ.edu.om 2 directorate general of agricultural & livestock research, ministry of agriculture and fisheries, p o box 50, a’seeb 121, oman introduction china, turkey, iran, egypt and usa were the main producers of melons in the world in 2012 (fao, 2014). in oman, about 410ha were cultivated, with a total production of 12,500t in 2012 (fao, 2014). despite the high demand, these crops suffer from several diseases caused by different fungi, bacteria and viruses. muskmelon vine decline is considered the factor most limiting muskmelon production and losses have been reported to exceed 90% (al-rawahi et al., 1998; alsa’di et al., 2008a). the disease also affects production elsewhere (zitter et al., 1996; martyn, 2008). monosporascus cannonballus is frequently the primary pathogen of late-season vine decline (zitter et al., 1996; robinson and decker-walters, 1997; martyn, 2008) although other pathogens including macrophomina phaseolina, fuأتثری األصول على استجابة ٔاصناف الشمام ملرض التدهور واالنتاج حتت الظروف اجلافة قیس املعولی1,2 وعبداهلل السعدي2 وفهد ٓال سعید2 ومایكل دیدمان2* abstract. monosporascus cannonballus, rhizoctonia solani and pythium aphanidermatum are the main causal agents of muskmelon vine decline disease in oman. this study was conducted to examine the response of six cucurbit rootstocks grafted on four muskmelon scions to the causal agents and fruit quality and quantity. the response of 10 day old palmira seedlings to artificial inoculation with r. solani pathogen alone revealed more damage to muskmelon seedling whereas p. aphanidermatum and m. cannonballus caused less damage when inoculated singly but more disease severity index when combined with r. solani. artificial inoculation of different rootstocks produced significantly no damping-off and very low vine decline disease severity index on mubyeongjangsoo, titan, tetsukabuto, rsscih7458, ezra and strong tosa rootstocks. all rootstocks produced high grafting success and low graft failure with the four selected muskmelon cultivars. rootstocks enhanced early harvesting of grafted tamara but had no effect on other scions. fruit shape was almost not significantly affected by grafting except samit grafted on strong tosa and caramel grafted on mubyeongjangsoo produced significantly different fruit shapes compared to ungrafted controls in the spring 2013 trial. fruits from both grafted shahd and tamara showed no significant differences in rind brightness, redness and yellowness from the control. various effects of rootstock were found on harvesting, fruit number and weight, chlorophyll content, and stem diameter of the scion. rootstocks enhanced early harvesting and increased fruit number and fruit weight in grafted tamara scions. there was no significant effect of grafting on fruit tss. the study shows positive effects of grafting on tolerance to vine decline and on fruit quality and yield. keywords: grafting; melon vine decline; fruit quality; integrated disease management. املســتخلص: لقــد أجریــت هــذه دراســة لتقییــم جنــاح التطعیــم، ومقاومــة األصــول ملــرض تدهــور و مــوت حمصــول الشــمام وتأثــر التطعیــم علــى كمیــة االنتــاج وجــودة الثمــار.مت تنفیــذ التجــارب يف حقلــن منفصلــن يف ســلطنة عمــان، وأظهــرت النتائــج أن صنــف الشــمام ســوادي املطعــوم علــى ســتة أصــول مــن القرعیــات أعطــى جناحــا كبــرا يف التطعیــم: حیــث تراوحــة نســبة التطعیــم بــن 97.6-99.1٪ )98.6٪( و 92.4-96.9٪ )95.3٪( يف ظــل ظــروف احلقــل يف خریــف عــام 2012 وربیــع 2013 علــى التــوايل. مل تظهــر النتائــج وجــود فــروق معنویــة بــن الســتة معامــات والشــاهد )الشــمام الغــر مطعــوم( مــن حیــث اختبــار تفضیــل املســتهلكن للرائحــة وصابــة وشــكل الثمــار و فیتامــن c وحمتــوى املــواد الصلبــة الذائبــة )الســكروز٪( أو الرقــم اهلیدروجیين يف ربیع p( 2013< 0.05(. وأشارت النتائج اىل اخنفاض تركیز الفوسفور والصودیوم بشكل ملحوظ يف الثمار لكا املومسن يف مجیع املعامات باملقارنة مع الشاهد )p< 0.05(. كما زاد حمتوى البوتاسیوم زیادة كبرة يف الثمارعندما مت استخدام أصلي rsscih7458 ومويب ینج ســو )p >0.05(. وأظهــرت النتائــج أن أصــل الســرنج تــوزاء أعطــى نســبة0٪ لفشــل التطعیــم ، وأظهــر مقاومــة جیــدة ملــرض تدهــور حمصــول الشــمام وكمیــة إنتــاج جیــدة وحمتــوى مرتفــع مــن املــواد الصلبــة الذائبــة )الســكروز٪( باملقارنــة مــع غــره مــن األصــول. كمــا أشــارت النتائــج أن أصلــي الســرنج تــوزاء وتیتســوكابوتو حصــا علــى أعلــى قبــول الختبــار تفضیــل املســتهلكن مــن حیــث لــون القشــرة واللــون اللحــم والقبــول العــام الختبــار تفضیــل املســتهلكن يف ربیــع عــام 2013، وكانــا أیضــا أقــل تأثــرا بالتغــرات املومسیــة. عمومــا ميكــن أن نقــول أن التطعیــم علــى االصــول املقاومــة المــراض الربــة أدى إىل حتســن بعــض مســات جــودة الثمــار باإلضافــة إىل زیــادة مســتوى املقاومــة لألمــراض لصنــف الشــمام ســوادي. ومــع ذلــك، هنــاك حاجــة إىل عمــل جتــارب إضافیــة لتأكیــد النتائــج ولتقــدمي التوصیــات النهائیــة للمزارعــن. الكلمات املفتاحية: التطعیم، الشمام، مرض التدهور، جودة الثمار، االدارة املتكاملة للمرض 48 squ journal of agricultural and marine sciences, 2016, volume 21, issue 1 effect of rootstock on muskmelon cultivar reaction to vine decline disease and yield under arid conditions sarium spp., phoma spp., pythium spp., phytophthora drechsleri, rhizoctonia solani, acremonium cucurbitacearum and verticillum dahliae have been implicated (zitter et al., 1996; pivonia et al., 1997; aegerter et al., 2000; al-sa’di et al., 2011b; el-kolaly and abdel-sattar, 2013). in oman monosporascus cannonballus, rhizoctonia solani and pythium aphanidermatum have been reported as causal agents of muskmelon vine decline (al mawaali et al., 2013). the use of grafted plants for controlling soilborne diseases has been established for many decades (lee, 1994) with the additional benefit of increasing yields and tolerance to low-temperature, salt and soil wetness, improving water and nutrient uptake and plant vigor, and extending harvest duration (lee, 1994; lee and oda, 2003). in oman the use of grafting is increasing. al-mawaali et al. (2012) reported that grafted cucumber plants (on hybrid rootstock varieties titan and hercules) showed no symptoms of damping-off and vine decline and also produced a significant increase in yield. benefits in terms of disease reduction notwithstanding, issues remain to be resolved before grafting can be widely adopted within a commercial arena. incompatibility between rootstock and scion (andrews and marquez, 1993; davis et al., 2008) can affect undergrowth or overgrowth of the scion, leading to decreased water and nutrient flow through the graft union, causing vine decline or wilting of the grafted plant. graft incompatibly can be measured through failure to unite into a strong union, failure of the grafted plant to grow in a healthy manner, or premature death after grafting. no previous research has been reported evaluating the potential of grafting under the harsh and arid conditions of oman. it is not clear whether grafting could reduce vine decline disease. furthermore, little is known about the effects of grafting on muskmelon fruit quantity and quality. the main objective of this study was to characterize the response of rootstocks and to evaluate the technique as part of a management system for vine decline disease of muskmelon. specific objectives were to examine the response of six cucurbit rootstocks to the pathogens causing vine decline of muskmelon in in vivo and field and the effect of the rootstocks on quality and yield of muskmelon. materials and methods optimization of inoculation protocol ten seeds of muskmelon palmira were sown in sterile soil (91% sand) in 15cm pots. seedlings were thinned to five per pot after emergence. five day old cultures of pythium aphanidermatum and rhizoctonia solani and 8 day old monosporascus cannonballus colonies, all on pda (25gl-1) were blended in 50ml sterile distilled water (sdw) and 50ml of the inoculum was added to the soil surface in each pot when seedlings had reached 10 days old. the three causal agents were used in different treatment combinations. in control pots a 90mm disc of macerated pda blended in 50ml sdw was used as a negative control (table 1). pots were held at 33±2oc day and 23±2oc night in a completely randomized design under glasshouse conditions, with a 12hr day length. five pots were used for each treatment and the experiment was repeated once. plants were irrigated daily with 100ml of water (0.3ds/m and ph 8.1) and 1% aqueous (20:20:20) npk fertilizer (kristalon, hungary) was applied once per week. percent plants exhibiting damping-off and/or wilt symptoms were recorded every 2d after inoculation. after 28d, the soil was gently washed from the roots and disease on hypocotyls (h), primary roots (r1r) and secondary roots (r2r) was assessed. isolation from roots and crowns of five randomly selected plants was done on pda to confirm infection by the inoculated pathogen (tsay and bor-kai tung, 1995; bruton et al., 2000). disease ratings for h, r1r and r2r were as follows: 1 = healthy with no lesions or discoloration, 2 = slight discoloration, 3 = moderate discoloration and/or with lesions, 4 = moderate disintegration or up to 25% root mass reduction compared with controls, and 5 = severe maceration, with more than 50% root mass reduction and/or plant wilt. a disease severity index (dsi) showing the extent of damage on muskmelon was calculated as follows: dsij = (hj + r1rj + r2rj)/3 (bruton et al., 2000). response of rootstocks to pathogen inoculation from the results of the optimization test the combined inoculum of m. cannonballus + rhizoctonia solani + p. aphanidermatum was used to test rootstock response. positive-inoculated and negative non-inoculated muskmelon palmira seedlings were included as controls. twenty five seeds of each positive-inoculated and negative non-inoculated muskmelon palmira and of each of the 11 tested rootstock were sown and distributed in five 15cm pots with sterile soil (91% sand). inoculation procedures and post-inoculation conditions were as described above. five pots were used for each treatment and the experiment was repeated once. irrigation, fertilization, disease incidence and disease assessments were as described previously. field trials and effects on fruit yield and quality based on the results of the seedling trials and research reported elsewhere (al-mawaali et al., 2013), rootstock varieties tetsukabuto, mubyeongjangsoo and strong tosa were used for grafting with the commercial muskmelon cultivars samit, shahd, caramel and tamara. field experiments were carried out at two locations with a history of severe muskmelon decline attributed to m. cannonballus, rhizoctonia solani and pythium spp. including p. aphanidermatum (al-sa’di et al., 2008a; 49research article al mawaali, al-sadi, al-said and deadman al-mawaali et al., 2013). site 1 has sandy soil with ph 8.1 and ec 6.29 ds/m (barka, 23º 39. 189′ n and 57º 46.268′ e) while site 2 has sandy loam soil with ph 8.2 and ec 2.05 ds/m (al-seeb, 23º 35.925′n and 58º 9.799′e ). inoculum potential of the soils of the two experimental sites was estimated through dilution plate technique before graft transplant. the estimated inoculum densities were 8.2 ascospores g-1 soil, 9.6 cfua g-1 soil and 19.7 cfua g-1 soil for m. cannonballus, r. solani and pythium spp., respectively at site 1 and 2.6 ascospores g-1 soil, 6.5 cfua g-1 soil and 7.3 cfua g-1 soil) for m. cannonballus, r. solani and pythium spp., respectively at site 2. under greenhouse conditions tongue approach grafting was done 12-16 days after scion and rootstock seeds were sown (oda, 1999) and graft success was recorded. 150 plants of each muskmelon scion were selected after successful grafting on each rootstock. non-grafted seedlings of each muskmelon cultivar were included in each design as a control. field trial design was completely randomized at site 2 and a complete block design at site 1; in both cases using four replicates with 15  seedlings in each replication. distance between plants was 1  m with 2  m between treatments and 2  m between rows. irrigation was for 15  min, twice per day for two weeks, then for 20  min for weeks 3-4 and 25  min until the end of the season. the irrigation water had ph 7.7 & ec 0.91 ds/m at site 1 and ph 7.6 & ec 0.3 ds/m at site 2) . npk (20:20:20) fertilizer was applied at a rate of 0.6 g per plant twice a week for the first month. npk (12:12:36) + te was applied at a rate of 1.2  g per plant twice a week starting at week five until final harvest (maf, 2007; maf, 2009). minimum and maximum temperatures during february may 2013 at site 1 were 13.4 and 43.3 ºc, respectively, and it was 15.9 and 42.9 ºc, respectively during september december 2013 at site  2. the survival rate of grafted plants was measured after 15 days and expressed as percent of total grafted plants. flowering time was expressed as the number of days from sowing to first male and female flower appearance (yetisir and sari, 2003). the numbers of dead plants and those with damping-off or wilt symptoms were recorded every 7d for 90d. vegetative growth was sampled 50 d after transplanting. from each replicate 5 plants were measured for each sampling event (yetisir and sari, 2003). stem diameter of scion (cm) was recorded after first node (leonardi and romano, 2004). leaf chlorophyll was measured (konica minolta sensing, japan, esr 81423044) using the 4th fultable 1. pathogen inoculum combinations used to incite vine decline disease on muskmelon palmira. inoculum combination dose monosporascus cannonballus 50 ml (monosporascus) + 100 ml pda m. cannonballus + pythium aphanidermatum 50 ml (monosporascus) + 50 ml (pythium) + 50 ml pda m. cannonballus + rhizoctonia solani 50 ml (monosporascus) + 50 ml (rhizoctonia) + 50 ml pda m. cannonballus + r. solani + p. aphanidermatum 50 ml (monosporascus) + 50 ml (rhizoctonia) + 50 ml (pythium) r. solani + p. aphanidermatum 50 ml (rhizoctonia) + 50 ml (pythium) + 50 ml pda p. aphanidermatum 50 ml (pythium) + 100 ml pda r. solani 50 ml (rhizoctonia) + 100 ml pda control 150 ml pda pda: difco potato-dextrose agar figure 1. stunting of plant growth and gradual death or wilt of the leaves. figure 2. slight to moderate discoloration and disintegration of the hypocotyl tissue with loss of root mass. 50 squ journal of agricultural and marine sciences, 2016, volume 21, issue 1 effect of rootstock on muskmelon cultivar reaction to vine decline disease and yield under arid conditions ly expanded leaf from the apex of the main stem (yetisir and sari, 2003). fruit number and weight (kg) were recorded for each plant (leonardi and romano, 2004). at leaf senescence, which occurred 30-45  d after pollination, the effect of rootstock on marketable fruit quality, and fruit shape was analyzed by assessing fruit length, width and circle ratio. fruit total soluble solids (tss) was determined for three ripening fruits per replicate by refractometer (eclipse brix refractometer, uk) (lee and oda, 2003; yetisir and sari, 2003). immediately after harvest, rind color (hunter color values: brightness (l), redness (a), and yellowness (b)) of marketable fruits were measured (minolta colorimeter cr-310, minolta, serial no. 79581006, japan) (crinò et al., 2007). statistical analysis differences between treatment means for parametric data were analyzed using anova and tukey’s studentized range test under glm analysis (sas v8, sas institute, cary, nc, u.s.a). treatment mean ranks for non-parametric data were compared using kruskal-wallis analysis with means separated using the method of gwet (2010). correlation analysis was used to test consistency between trials. results inoculation protocol optimization and assessment of rootstock response to vine decline pathogens the combination of p. aphanidermatum and r. solani showed the highest disease incidence (96%) and dsi (4.9) in the first trial with a significant difference from the control and m. cannonballus inoculation alone (p < 0.05). r. solani caused the highest damage to hypocotyls, primary roots and secondary roots in second trial and was second in the first trial, with a significant difference from the control (p < 0.05) (table 2). disease incidence and dsi arising from different combinations of the three pathogens showed moderate discoloration with lesions to moderate maceration of hypocotyl tissue and moderate discoloration to severe maceration of primary roots and secondary roots with no significant difference between the different combinations and all showed a significant difference from the control (p < 0.05) (table 2). none of the tested rootstocks showed damping-off or mortality with the exception of sharad and connecticut field which showed significant levels of mortality in both trials following inoculation with a mixture of selected virulent pathogens (table 3). mubyeongjangsoo, titan, tetsukabuto, rsscih7458, ezra and strong tosa showed slight tissue discoloration and lower dsi values in the first and second trials with a significant difference compared with the positive, inoculated muskmelon control and sharad and connecticut field rootstock (p > 0.05) (table 3). the above-ground symptoms were stunting of plant growth and gradual death or wilt of the leaves (fig. 1). this was associated with water-soaked areas in the hypocotyl of seedlings, after which the seedlings collapsed. slight to moderate discoloration and disintegration of the hypocotyl tissue, primary roots and secondary roots with loss of root mass were found in sharad, connecticut field and the positive inoculated muskmelon control (fig. 2), with no significant differences between these three treatments in the first trial (p > 0.05) (table 3). evaluation of selected cucurbit rootstocks against vine decline disease under field condition and their effect on fruit quality and yield of muskmelon high graft success was found between mubyeongjangsoo rootstock and samit muskmelon scion (98.4%), table 2. response of 10 days old muskmelon palmira seedlings to artificial inoculation with different pathogen combinations. i n o c u lum ++ spring 2013 i n c i dence mean damage rating rank * (%) rh r1r r2r dsi ‡ pa + rs 96 a 122.9 ab 114.9 ab 115.8 ab 4.9 a rs 92 a 156.1 a 154.1 a 153 a 4.8 a mc + pa + rs 88 a 96.7 b 96.2 b 95.2 b 4.7 a mc + rs 80 ab 119.1 ab 111.6 ab 113 ab 4.5 a mc + pa 80 ab 114.6 ab 124.3 ab 128.1 ab 4.3 a pa 68 ab 98.2 b 100.4 b 95.6 b 4.0 a mc 32 bc 74.6 b 85 b 82.6 b 3.2 a control 0 21.7 c 17.5 c 20.5 c 1.1 b fall 2013 rs 48 a 126.2 a 125 a 125.4 ab 4.4 a pa 44 ab 102.1 ab 101.6 a 102 ab 3.0 ab mc+pa 36 ab 113.9 ab 111.1 a 110.9 ab 3.5 ab pa+ rs 28 ab 129.5 a 129.1 a 129 a 3.4 ab mc + pa + rs 12 ab 124.7 a 122.1 a 121.8 ab 2.9 ab mc + rs 8 ab 115.4 ab 117.7 a 117.6 ab 3.3 ab mc 0 66.9 bc 78.5 a 77.2 b 2.4 bc control 0 25.2 c 18.8 b 20.2 c 1.0 c ++ mc m. cannonballus, pa p. aphanidermatum, rs rhizoctonia solani. * values with the same letter in the same column are not significantly different from each other at p < 0.05 (tukey’s studentized range for disease incidence and dsi; gwet’s (2010) method of mean separation for rh, r1r and r2r). ‡ dsi disease severity index (bruton et al., 2000). 51research article al mawaali, al-sadi, al-said and deadman strong tosa rootstock with shahd and caramel (97.4% and 98.4% respectively) and lower graft failure with tamara, shahd and samit (0%, 2.5% and 3.3%, respectively), and tetsukabuto with tamara (97.5%) and lower graft failure with caramel (1.1%) (table 4). disease incidence showed variation between rootstock and scion at both sites. disease incidence for all rootstocks with different scions ranged from 0-20% (mean = 6.7 %) at site 1 and 2.2-24.5 % (mean = 11.5%) at site  2 (table  5). mubyeongjangsoo rootstock grafted with samit, significantly lowered the disease level compared to tetsukabuto and strong tosa in site 1 (p < 0.05). tetsukabuto and strong tosa rootstocks grafted with shahd significantly reduced disease level at site 2 compared to the control treatment (non-grafted shahd) (p < 0.05) and mubyeongjangsoo grafted with caramel significantly lowered disease level at site 1 compared to the control treatment (non-grafted caramel) (p < 0.05). all rootstocks grafted with tamara maintained average disease levels at both sites and below the average disease table 3. assessment of 11 different rootstocks for resistance/tolerance to the pathogens causing vine decline disease in muskmelon crop in oman, with plant damage rating (rh= hypocotyl; r1r= primary root; r2r= secondary roots). treatment+ spring 2013 disease incidence (%) mean damage rating rank* dsi‡ rh r1r r2r negative control (-) 0 101.5 a 38.7 a 82.6 a 1.02 a tetsukabuto 0 119.6 a 71.8 ab 108.2 abc 1.22 ab titan 0 113.5 a 95.4 ab 108.2 abc 1.26 ab mubyeongjangsoo 0 113.5 a 119 abc 92.9 ab 1.3 abc rsscih7458 0 131.6 a 165.6 c 103.1 abc 1.5 abcd strong tosa 0 125.6 a 156.3 bc 123.6 abc 1.52 abcd ezra 0 131.6 a 160.8 bc 159.4 abc 1.64 bcd baromashi 0 167.7 ab 160.4 bc 175.3 bc 1.78 cd squash t1 0 246 b 156.3 bc 154.3 ab 1.9 d dinero f1 0 164.1 ab 198.8 cd 185.4 cd 1.94 d sharad 4 ab 175.8 abc 260.4 d 270.3 de 2.78 e connecticut field 4 ab 267.9 d 274.3 d 287.8 e 3.2 e positive control 8 b 260.6 cd 261.3 d 267.8 de 2.94 e fall 2013 negative control (-) 0 87.0 a 54.5 a 75.0 a 1.01 a tetsukabuto 0 136.4 abc 148.7 bc 143.2 abcd 1.5 abc titan 0 117.9 ab 157.3 bc 137.5 abcd 1.46 abc mubyeongjangsoo 0 117.9 ab 115.5 ab 114.8 ab 1.34 ab rsscih7458 0 136.4 abc 153 bc 120.4 abcd 1.46 abc strong tosa 0 164 abcd 178.2 bc 191.1 bcde 1.78 bcd ezra 0 192.1 bcd 141.9 ab 143.2 abcd 1.62 bcd baromashi 0 161.2 abcd 125.3 ab 112.3 ab 1.44 abc squash t1 0 204 bcd 179.4 bc 188.6 bcd 1.9 cde dinero f1 0 216.8 cd 158.6 bc 157.8 abcde 1.74 bcd sharad 0 139.3 abc 236.4 cd 244.4 ef 2.1 de connecticut field 4 a 231.6 d 279.2 d 283.7 f 2.86 f positive control 20 b 214.4 cd 190.8 bcd 207.1 def 2.39 ef *a values with the same letter in the same column are not significantly different at p < 0.05 (tukey’s studentized range for disease incidence and dsi; gwet’s (2010) method of mean separation for rh, r1r and r2r). low values for rh, r1r and r2r are indicative of low level disease. ‡ dsi disease severity index (bruton et al., 2000). + titan (hybrid) ramiro arnedo, spain, tetsukabuto (hybrid squash) national seeds production company l.t.djapan, hyb squash (t1) seminis, china, mubyeongjangsoo (hybrid squash) seminis® china, rsscih7458 (hybrid squash) seminis® korea, strong tosa (f1 hybrid) syngenta seeds – china melon dinero (f1 hybrid) syngenta seeds, peru, ezra f1 (squash) nickerson-zwaan, holland, baromashi (pumkin) lal teer seeds, bangladesh, connecticut field (pumpkin) bonanza seeds, usa bottle gourd (f1 sharad) united genetics, india and control (palmira hybrid muskmelon cultivar) nickerson-zwaan, the netherlands. 52 squ journal of agricultural and marine sciences, 2016, volume 21, issue 1 effect of rootstock on muskmelon cultivar reaction to vine decline disease and yield under arid conditions levels of the control (non-grafted tamara), showing significant differences when compared to mubyeongjangsoo and strong tosa at site 1 and tetsukabuto at site 2 (p < 0.05) (table 5). the three rootstocks caused variation in flowering with different scions at both sites (table 5). flowering of table 4. initial graft success and failure in the field for selected rootstocks with different muskmelon scions. scions + rootstock a greenhouse graft success (%) field graft failure (%) spring 2013 fall 2103 spring 2013 fall 2103 samit + tetsukabuto 94 98.8 6.7 2.2 samit + mubyeongjangsoo 98 98.8 10.0 0.0 samit + strong tosa 95 95.2 6.7 0.0 shahd + tetsukabuto 95 98.8 10.0 0.0 shahd + mubyeongjangsoo 95 98.8 6.7 0.0 shahd + strong tosa 96 98.8 3.3 2.2 caramel + tetsukabuto 95 98.8 0.0 2.2 caramel + mubyeongjangsoo 95 100.0 3.3 0.0 caramel + strong tosa 98 98.8 6.7 4.5 tamara + tetsukabuto 95 100.0 10.0 0.0 tamara + mubyeongjangsoo 96 95.2 3.3 2.2 tamara + strong tosa 95 96.4 0.0 0.0 a rootstock: tetsukabuto (hybrid squash) national seeds production company l.t.djapan, mubyeongjangsoo (hybrid squash) seminis® china and strong tosa (f1 hybrid) syngenta seeds – china; scions: samit muskmelon (hybrid ) asgrow, usa, shahd (hybrid ) trust seeds, jordan, caramel (hybrid) clause, china and tamara ( hybrid) hollar seeds, usa. table 5. initial graft success and failure in the field for selected rootstocks with different muskmelon scions. values with the same letter in the same column are not significantly different from each other (p > 0.05, tukey’s studentized range test). treatments + incidence (%) flowering (%) fruits (103 ha-1) fruit weight (t ha-1) chlorophyll stem diam. (cm) site 1 site 2 site 1 site 2 site 1 site 2 site 1 site 2 site 1 site 2 site 1 site 2 samit control 3.3c 26.7a 6.7b 31.1a 24.7a 20.2a 36.6a 31.2ab 49.8b 49.7a 0.88a 1.2a samit + tets 13.3b 22.2ab 56.7a 35.6a 21.0ab 21.0a 34.3ab 38.6a 49.4b 50.0a 0.65b 1.2a samit + mub 3.3c 24.5ab 63.3a 31.1a 18.4b 18.7a 33.4ab 34.3ab 55.5a 53.0a 0.70b 1.0b samit + st 20.0a 15.5b 53.3a 33.3a 17.2b 16.3a 28.6b 28.4b 48.9b 50.7a 0.73b 1.1ab shahd control 0.0 11.1a 36.7a 48.9a 27.7a 21.7a 38.0a 26.9a 52.7ab 54.2a 0.83a 0.73a shahd + tets 6.7b 2.2b 36.7a 26.7a 23.9ab 22.7a 32.2ab 31.6a 51.6ab 52.9a 0.68b 0.88a shahd + mub 16.7a 6.7ab 43.3a 40.0a 20.9b 20 .0a 24.7b 30.5a 55.5 a 57.0a 0.68b 0.95a shahd + st 3.3b 2.2b 56.7a 35.6a 25.0ab 19.7a 35.4a 29.5a 50.8b 55.9a 0.83a 0.8a caramel control 10.0a 4.5b 3.3b 71.0a 30.1a 22.4a 38.6a 28.7a 47.2a 52.2b 0.90a 1.1a caramel + tets 6.7ab 8.9ab 56.7a 57.8b 28.7a 18.5b 34.1a 21.8a 47.2a 57.7a 0.88a 1.0a caramel + mub 3.3b 8.9ab 56.7a 75.6b 28.1a 21.0ab 33.4a 25.6a 50.8a 56.1ab 0.88a 1.0a caramel + st 3.3b 15.5a 50.0a 73.3a 28.9a 19.7ab 30.2a 22.0a 48.1a 56.1ab 0.93a 1.1a tamara control 6.7a 15.5a 23.3a 31.1a 19.7b 13.6b 28.6ab 17.0a 55.2ab 53.1 c 0.83b 0.9a tamara +tets 3.3 ab 8.9 b 40.0a 40.0 a 18.3b 16.5a 26.6ab 23.0a 54.5ab 58.9ab 1 .0a 0.83b tamara + mub 0.0 11.1ab 36.7a 48.9a 22.1ab 16.5a 25.6b 19.4a 58.2a 60.2a 0.85b 0.93ab tamara + st 0.0 11.1ab 20.0a 46.7a 26.3a 16.7a 33.2a 17.8a 53.5b 55.8bc 0.9ab 0.95a + rootstock: tetsukabuto (hybrid squash) national seeds production company l.t.djapan, mubyeongjangsoo (hybrid squash) seminis® china and strong tosa (f1 hybrid) syngenta seeds – china; scions and control non-grafted muskmelon cultivars: samit muskmelon (hybrid ) asgrow, usa, shahd (hybrid ) trust seeds, jordan, caramel (hybrid) clause, china and tamara ( hybrid) hollar seeds, usa., 53research article al mawaali, al-sadi, al-said and deadman the control showed no significant differences with grafted shahd and tamara on all rootstocks (p > 0.05). there was a clear effect of grafting on fruit maturity of tamara at both sites. harvesting of grafted tamara was advanced at both sites compared to non-grafted treatments (day 62 in spring to day 59 in fall for grafted plants, day 65 to day 64 for controls). there was no clear effect of grafting on fruit maturity of samit, shahd and caramel at either site. most rootstocks caused variations in fruit number and fruit weight at both sites among the seasons with significant differences between the control and other treatments. grafted tamara on strong tosa showed significantly higher fruit number than non-grafted tamara at both sites and with tetsukabuto and mubyeongjangsoo at site 2 (13.6 on control, 16.5, 16.5 and 16.7 (1000 ha-1), respectively) (p < 0.05) (table 5). a significant reduction in fruit weight was observed when samit muskmelon was grafted on strong tosa compared to control (non-grafted samit) at site 1 (28.6 and 36.6 ton ha-1 on control, respectively) (p < 0.05) and between the control (non-grafted shahd) and shahd grafted on mubyeongjangsoo at site 1 (38 and 24.7 ton ha-1, respectively) (table 5). only mubyeongjangsoo increased chlorophyll content of leaves of all grafted cultivars with significant differences in some seasons with some cultivars. stem diameter of the control (non-grafted samit) was significantly bigger than grafted samit at site 1 and with the mubyeongjangsoo rootstock at site 2 (p < 0.05) (table 5). there was no effect of grafting on grafted shahd and tamara fruit tss, fruit shape and hunter color values. tss levels were not significantly affected by grafting for samit, shahd, caramel and tamara scions with tetsukabuto, mubyeongjangsoo and strong tosa rootstocks (table 6). fruit shape was significantly affected only when samit was grafted onto strong tosa and when caramel was grafted onto mubyeongjangsoo compared to the control plant fruits at site 1, in spring 2013 (p < 0.05) (table 6). a significant negative correlation was found between leaf chlorophyll content and stem diameter at site 1, in spring 2013 (r = 0.542, p < 0.05) and between leaf chlorophyll content and disease incidence in the spring 2013 (r = 0.594, p < 0.05). a significant positive correlation was found between yield and stem diameter in spring 2013 (r = 0.513, p < 0.05) and in fall 2013 (r = 0.741, p < 0.01). no correlations were found between disease incidence and any of the other parameters studied. hunter color values of fruit rind showed no significant difference for rind brightness between control table 6. effect of grafting on scion fruit total soluble solids (tss), shape and rind color (hunter color values) of different muskmelon cultivar scions. values with the same letter in the same column are not significantly different from each other (p > 0.05, tukey’s studentized range test). treatments b tss (%)a fruit shape a rind hunter color values a brightness redness yellowness site 1 site 2 site 1 site 2 site 1 site 2 site 1 site 2 site 1 site 2 samit f1 (cont) 8.6ab 9.5a 3.4a 3.2a 81.9a 79.3 b 11.2a 9.6a 37.5 a 36.6a samit f1 + tets 8.9a 10.1a 3.0ab 3.2a 83.7a 87.5a 8.0 b 8.6a 34.5a 38.2a samit f1 + mub 7.7 b 9.2a 3.1ab 3.6a 77.7a 82.9ab 6.2 c 6.9a 35.9a 38.8a samit f1 + st f1 9.0 a 8.9a 2.9 b 4.2a 77.7a 80.0 b 6.7 bc 6.8a 37.8a 42.2a shahd f1 (cont) 10.2a 11.0a 1.4a 1.1a 72.8a 77.1a 8.3 ab 9.8a 39.1a 43.9a shahd f1 + tets 9.7a 10.4a 1.3a 1.6a 78.2a 72.8a 9.9 ab 11.2a 39.0a 37.7a shahd f1 + mub 10.2a 11.5a 1.0 a 1.2a 74.7a 72.3a 10.3a 10.7a 35.5a 37.0a shahd f1 + st f1 10.0 a 11.1a 1.1a 1.3a 76.2a 81.0a 7.7 b 9.0a 35.0a 40.5a caramel f1 (cont) 11ab 10.9a 2.5a 1.7a 79.4a 79.7ab 9.8a 13.6a 38.4a 41.4 b caramel f1 + tets 12 .0 a 10.4a 1.8ab 1.6a 79.1a 81.9ab 8.8ab 10.3ab 40.1a 42.6 b caramel f1+ mub 9.7 b 9.5a 1.3 b 1.3a 77.0a 87.8a 7.3 b 8.3 b 40.1 a 53.1a caramel f1 + st f1 10.3 b 9.5a 1.8ab 1.6a 79.6a 74.9 b 7.2 b 5.8 c 38.9a 42.7b tamara f1 (cont) 9.1a 10.2ab 2.0a 0.8a 71.4a 74.0a 4.4 c 5.8 b 34.6a 30.7a tamara f1 +tets 9.4a 10.5 ab 2.1a 1.3a 74.9a 74.4a 5.6 bc 6.9 b 34.9a 35.2a tamara f1 + mub 9.6a 11.0a 1.6a 0.9a 78.2a 79.6a 7.9a 7.5 b 36.0a 37.8a tamara f1 + st f1 8.7a 9.7 b 1.5a 1.1a 76.6a 80.6a 7.3ab 12.1a 37.8a 41.2a + rootstock: tetsukabuto (hybrid squash) national seeds production company l.t.djapan, mubyeongjangsoo (hybrid squash) seminis® china and strong tosa (f1 hybrid) syngenta seeds – china; scions and control non-grafted muskmelon cultivars: samit muskmelon (hybrid ) asgrow, usa, shahd (hybrid ) trust seeds, jordan, caramel (hybrid) clause, china and tamara ( hybrid) hollar seeds, usa., 54 squ journal of agricultural and marine sciences, 2016, volume 21, issue 1 effect of rootstock on muskmelon cultivar reaction to vine decline disease and yield under arid conditions treatments and grafted shahd, caramel and tamara. whereas fruits from samit grafted onto tetsukabuto revealed significantly higher rind brightness from the control treatment at site 2 in fall 2013 (p < 0.05) (table 6). there was no significant difference for rind redness between controls of shahd at both sites among the seasons (p > 0.05). rind redness of grafted samit fruits showed a significant reduction compared to the control in spring 2013, and showed a significant increase in fruits from tamara grafted onto strong tosa at both sites among the seasons (p < 0.05). rind yellowness showed no significant differences between control treatments and grafted samit, shahd and tamara on all rootstocks in both seasons (p > 0.05). only fruits from caramel grafted on mubyeongjangsoo significantly increased rind yellowness compared with control non-grafted caramel and this was at site 2, in fall 2013 only (p < 0.05) (table 6). discussion in oman m. cannonballus, r. solani and p. aphanidermatum are causal agents of vine decline of muskmelon (al-mawaali et al., 2013). in the current study the response of 10-day old palmira seedlings to artificial inoculation with r. solani pathogen alone revealed more damage to muskmelon seedling. nearly the same result was found by al-mawaali et al. (2013) when the responses of 10-day and 20-day old muskmelon seedlings (cv. palmira f1) to artificial inoculation with fungi isolated from declining muskmelon plants showed that r. solani produce the highest average of disease severity index with 2.55 dsi. artificial inoculation with p. aphanidermatum and m. cannonballus caused less damage when inoculated singly but more disease severity index when combined with r. solani. similar results were found by pivonia et al. (1997) and el-kolaly and abdel-sattar, (2013) where a combination of p. aphanidermatum and m. cannonballus showed higher mortality than was caused by either pathogen alone; the combination of p. aphanidermatum with m. cannonballus and r. solani resulted in higher mortality than caused by each pathogen alone. however, future studies should be undertaken to compare the response of different pathogens interacting with different inoculation times. grafting was initially developed to overcome soil borne diseases and to increase the yield of grafted crops, to encompass tolerance of low-temperature, salt and soil wetness, improve water and nutrient uptake, increase plant vigor, extending harvesting time duration and in melon crop should ideally be resistant to fusarium oxysporum, m. cannonballus, melon necrotic spot virus (mnsv) and meloidogyne spp. (lee, 1994; lee and oda, 2003). in the present study, the assessment of rootstock response to vine decline pathogens showed that mubyeongjangsoo, titan, tetsukabuto, rsscih7458, ezra and strong tosa rootstocks showed no damping-off or mortality and showed resistance or tolerance when inoculated with a mixture of m. cannonballus, r. solani and p. aphanidermatum and showed the lowest dsi values. previously, al-mawaali et al. (2012) reported that titan and hercules rootstocks reduced damping-off and wilt disease and also resulted in a significant increase in the yield of the grafted cucumbers. in this study more evaluations were done for three rootstocks (mubyeongjangsoo, tetsukabuto and strong tosa) and four muskmelon scions. the results showed that all rootstocks produced high graft success and lower graft failure with the scions with higher graft success and lower graft failure of some rootstock to some scions. this could indicate a good affinity related to fortuitous selection. traka-mavrona et al. (2000) and lee and oda (2003) reported that taxonomic affinity plays an important role in the success of grafting with some significant exceptions and could reflect the ability of these rootstocks to affect a strong union with the scion providing more efficient uptake of water and minerals. field evaluation for the response to disease produced different reactions of rootstocks with scion cultivars among seasons. however some rootstocks significantly lowered the disease level in field condition compared to other rootstocks which produced better graft success and lower graft failure with different scions. this may suggest a good potential adaptation of those rootstocks to environmental factors such as drought tolerance and could be related to the root structure which is believed to be a main factor in the grafting of susceptible melons onto tolerant and/or resistant cucurbita spp. rootstocks for control of m. cannonballus (martyn, 2008; lee and oda, 2003). similarly, the use of c. maxima, c. maxima x c. moschata, and c. moschata x c. moschata rootstocks against monosporascus in israel, shows their efficacy as a method in the management of this disease (edelstein et al., 1999; cohen et al., 2007). this has been correlated to a well-developed, vigorous root system that quickly replaces dead or infected roots (martyn, 2008; lee and oda, 2003). however, low graft success and high graft failure after transplanting in some rootstocks could be related to environmental factors or lack of skill of the grafter as reported in pervious study by davis et al. (2008). in the current study, the three rootstocks decreased stem diameter of grafted samit and produced various effect on other scions and caused variations in flowering and fruit maturity in both seasons. although, strong tosa, tetsukabuto and mubyeongjangsoo increased fruit number and fruit weight in grafted tamara that could reflect the significant positive correlation between stem diameter and yield at both sites. this could be collated to the effect of grafting on the amount of hormones produced and their influence on scion organogenesis. davis et al. (2008) reported that watermelon grafted onto bottle gourd showed early formation of female flowers but when grafted onto pumpkin, bottle gourd and wax gourd flowering was delayed. 55research article al mawaali, al-sadi, al-said and deadman only tetsukabuto produced higher average fruit weight at both sites on grafted samit; the same rootstock showed a decrease in fruit number and fruit weight for shahd and caramel. this may be related to taxonomic affinity, to the strength of the enhancement of undesirable physiological disorders by the rootstock (lee and oda, 2003; leonardi et al., 2003). however, in pervious assay, many farmers used a rootstock with a less vigorous root system rather than interspecific hybrid rootstocks to obtain earlier harvest and better quality rather than high yield (lee and oda, 2003). there was no clear effect of grafting on fruit maturity of samit, shahd and caramel at either site. only mubyeongjangsoo enhanced chlorophyll content of leaves of all scions with a significant difference in some seasons with some cultivars. three types of rootstock effects on melon color values of fruit rind, fruit shape and tss (sweetness) have been demonstrated (increase, no change and decrease). this can be due to the effect of different production environments, type of rootstock/scion combination used, and harvest date (davis et al., 2008). in the present study, various effects of grafting were observed in color values of fruit rind that could reflect the effect of grafting on the amount of hormones produced and their influence on scion organogenesis. fruit shape almost was not affected by grafting for shahd and tamara with tetsukabuto, mubyeongjangsoo, and strong tosa. however, fruits obtained from grafted samit plants on strong tosa and from caramel grafted on mubyeongjangsoo were significantly different in shape from control plant fruits in spring 2013. also tss was not affected by grafting in samit, shahd, caramel and tamara scions with tetsukabuto, mubyeongjangsoo, and strong tosa rootstocks. this result could be related to a good uptake and translocation of water and nutrient from soil. on the other hand, a reduction in uptake of water and nutrient from soil can cause a decrease in chlorophyll content in leaves and this causes a decrease in photosynthesis and is reflected in a decrease in yield and fruit quality (rivero, 2003; hu et al., 2006; xu et al., 2006). it can be concluded that following artificial inoculation, no damping-off and very low disease severity index was observed in mubyeongjangsoo, titan, tetsukabuto, rsscih7458, squash ezra and strong tosa rootstocks. an effect of rootstock was found on harvesting, fruit number and weight, chlorophyll content, and stem diameter of the scion. rootstocks enhanced early harvesting and increased fruit number and fruit weight in grafted tamara scions. there was no significant effect of grafting on fruit flesh tss. strong tosa f1 hybrid, tetsukabuto (hybrid squash), mubyeongjangsoo (hybrid squash) can be used as rootstocks for tamara f1 muskmelon. future research is also required to examine more cucurbit rootstocks for muskmelon against vine decline disease resistance and for the improvement of fruit yield and quality. strong tosa f1 hybrid, tetsukabuto (hybrid squash), mubyeongjangsoo (hybrid squash) rootstocks showed high resistance to m. cannonballus and p. aphanidermatum but were infected by rhizoctonia solani. integrated disease management tactics including cultural management, sanitation, tillage, crop rotation and chemical management using tachigaren (hymexazol)), metam sodium (vapam™), fluazinam (frowncide™ isk, japan) and fludioxinil (cannonball™, syngenta) should be tested in oman for their compatibility with grafting as part of an integrated disease management package. strong tosa f1 hybrid, tetsukabuto (hybrid squash), mubyeongjangsoo (hybrid squash) rootstocks may be tested with other scions such as watermelon for resistance against 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press, st. paul, minnesota, usa. 87 pp. agricultural and marine sciences, 19:51-61 (2014) sultan qaboos university 51 ___________________________________________ *corresponding author/e-mail: hemkot@squ.edu.om economic analysis determining the optimal replanting age of date palm 1department of natural resource economics, 2department of soils, water and agricultural engineering, college of agricultural and marine sciences, sultan qaboos university, p.o. box 34, al-khod 123, sultanate of oman النخيل غرس إلعادة األمثل العمر لتحديد التحليل االقتصادي زكري1 وسليم بوغامني1 وحسني العلوية1 وأماني كوتاجاما1 هميسرس مباقا1 ومسافيري جياسوريا2 وهيمانثا اإليرادات صافي بني مقارنة عن عبارة األول النموذج النخيل. غرس إلعادة األمثل العمر لتقدير حتليليني منوذجني استخدام مت اخلالصة: على اعتمدت النموذجني كال في اتبعت التي التحليلية اخلطوات متعددة. لفترات اخلطية البرمجة النموذج الثاني عبارة عن السنوية و من واالقتصادية واملتغيرات االجتماعية واحملصول النخلة عمر بني عن العالقة احلصول علي البيانات مت املال. راس ألصل األمثل البديل نظرية العمر الدراسة قدرت احلمراء. و بهالء و ازكي واليات الداخلية من محافظة نخيل في مزارع من مالكي مزارعاً 34 وزع على استبيان خالل متأثراً النخيل غرس العمر األمثل إلعادة وكان ومتفقة. متقاربة نتائج النموذجني، من سنة. وقدم كٌل 55-50 إلعادة غرس النخيل ب األمثل للتغيرات أن يثبت لم النخيل. إلعادة غراسة األمثل العمر من تقلل الفائدة أسعار انخفاض أن حيث الفائدة، أسعار في بالتغيرات فقط مستوى سنويا على مليون ب7 اإلضافية العائدات النخيل. قدرت غرس األمثل إلعادة العمر في تأثير أي والتكلفة والعائد في األسعار النخيل. غرس إعادة حالة في السلطنة عمان سلطنة متعددة، لفترات اخلطية البرمجة ، الغراسة إعادة النخيل, مفتاحية: كلمات abstract: two alternative analytical models were used to estimate the economically optimal age of replanting date palm, namely; comparison of equivalent annual net revenue (cean) and multi-period linear programming model (mplp). solution procedures of both models are based on the theory of optimal replacement of capital assets. data on date palm age-yield relationship and other socioeconomic variables were gleaned through a farm survey of 34 large commercial farms, in izki, bahla, and al-hamra wilayats in the aldakhilya governorate of the sultanate of oman. the study estimated the optimal age of replanting date palms as 50-55 years. both models, cean and mplp gave consistent estimates. the optimal age to replant date palms was sensitive only to changes in the interest rates. low interest rates shortened the optimal age of date palm replanting. changes in date price, yield and variable production costs did not change the optimal age of replanting date palms. the incremental revenue that could be accrued to the sultanate of oman through replanting date palms was estimated as 7 million or/ year. keywords: date palm, replanting, multi-period linear programming, sultanate of oman. introduction the sultanate of oman is ranked ninth in world date (phoenix dactylifera l.) production with a production of 255,871 tons, which represents 3.63% of the world production (faostat, 2010). date palms occupy about 42% of the total agricultural land in the sultanate of oman. since the year 2000 date production has declined. some factors that have contributed to the decline of date production are the non-availability of skilled labor to carry out field operations, occurrence of pests and diseases, harvest and post-harvest loses and degradation of soil and water quality (al-yahyai, 2007). the government of the sultanate of oman since 2009 has embarked on a programme of planting one million date palm trees, to rejuvenate the date sector. the planting of date palms could either be on new lands, or by the replanting of old unproductive date palms in existing agricultural lands. replacing of unproductive old plants with new plants (commonly referred to as replanting) hemesiri b. kotagama1*, amani juma t. al-alawi1, houcine boughanmi1, slim zekri1, hemanatha jayasuriya2, and msafiri mbaga1 52 kotagama et al. 53 economic analysis determining the optimal replanting age of date palm is an agronomic practice in perennial crop management to maximize and sustain income overtime. further replanting does not require substantial incremental resources than presently committed. this is particularly important in the sultanate of oman where water is extremely scarce. replanting date palms provides an opportunity to use the presently committed resources and improve farms towards economic production systems, which will improve the livelihood of farm dependents and increase the contribution to the nation’s national income. however, the agronomic practice of replanting date palms has not been formally adopted and promoted in the sultanate of oman. this study has estimated the economically optimal age to replant date palms in the sultanate of oman. the second section of the paper presents a review of literature on analytical methods used to estimate optimal age of replanting of perennial crops. the third section presents the analytical methodology adopted in this study to estimate the optimal age to replant date palms. the fourth section presents the results. the final section summarizes findings and draws conclusions and recommendations towards improving date palm farm income through optimal replanting in the sultanate of oman. review of literature faris (1960) is a widely quoted source that has proposed analytical techniques to determine the optimum replacement age of assets. the author has presented decision rules that could be followed in deciding the replacements of assets that have (1) a short production period with revenue being realized by the sale of the asset (example: buying and selling feeder cattle); (2) a long production period with revenue being realized by the sale of the asset (example: forestry); (3) a long production period with revenues being realized throughout the life of the asset (example: perennial crops). a long production period with revenues being realized throughout the life of the asset best represents date palm plantations. the rule of replanting for such crop assets as faris (1960) derived was that; the optimum replanting age is the age that makes the annual net revenue from “present” palms equal to the anticipated amortized present value of the net revenue from the “future” palms (replanted palms). the amortized present values of the net revenue of the future palms are obtained on the accumulated present values of net revenues over sequence of years. perrin (1972) has through mathematical derivations confirmed on a continuous time scenario the principles of decision making on asset replacement that was proposed by faris (1960) on a discrete scenario. the decision criteria on asset replacement proposed by faris (1960) and perrin (1972) has been applied to estimate the replanting age of plum trees considering stochasticity of yield (ward and farris, 1968). they have compared a stochastic model based on dynamic programming with a deterministic model and have concluded that both models provided essentially the same estimate of replanting age. the study has estimated that low producing plum trees should be replanted in 24 years with the same variety of plants. a similar study determining optimal replacement age of beef cows using stochastic models has been reported by bentley et.al. (1976). kearnev (1994) has used an inter-temporal linear programming model for a pip fruit orchard replacement decisions in new zealand under changes of market conditions and technical advances. the replacement decisions resulted in an increase of the orchard’s gross margin substantially. lower interest rates were found to shorten the replanting age. a similar study has been conducted by oppenheim (2003) using multi-period linear programming to evaluate orchard (apple and pear) adjustment strategies in new zealand. etherington (1977) has used a stochastic model to determine the optimal replacement of rubber trees in peninsular malaysia. the model is based on the principles of deterministic asset replacement proposed by perrin (1972). groenewald and dutoit (1985) used a deterministic model of asset replacement and estimated the optimal age of replanting of avocado in orchards as 18 years. it is reported that new technology that increases net returns shortens the replanting age whilst it is also sensitive to inflation. white (1986) using a dynamic programming framework and larry et.al. (1990) using procedure and principles proposed by faris (1960) have developed computer software models to determine the optimal age of orchard crops. mwinjaka et.al. (1999) used a backward method dynamic programming model to determine the replacement age of coconut palms in tanzanian farming systems. the results showed that coconut palms should be replanted when the palms are at the age between 60-80 years to obtain maximum net-returns over time. al-shuaibi (2001) developed a model that could explain the factors that affect the decision of date growers to plant new palms using new lands or replanting the old date orchards. the study reports that initially, young palms with less than 15 years of age have low production, then production begin to increase substantially and reaches a peak production of 75 kg per palm with an age of 25 years after which the yield declines with increasing age of date palms. ismail and mamat (2002) have estimated the optimal age of oil palm replanting in malaysia using a deterministic model. they have estimated that the optimal age to replant oil palms is between 25-26 years. the age of replanting decreases with price increases of palm oil. cembalo (2002) has developed a multi-period mathematical model to account for perennial crop decisions such as replanting, storage, marketing and financial investments. the variability of returns has been incorporated by introducing a quadratic objective function that accounts for uncertainty of perishable crop production and marketing and the possible risk-averse behavior of the owner-managers. finally, the multi-period structure of the model and risk concerns are embedded in a multi-objective framework 52 kotagama et al. 53 economic analysis determining the optimal replanting age of date palm reflecting the conflicting objectives tree-crop managers often pursue. the model has been used to empirically analyze a farm in salerno province in italy. thang et.al. (2009) investigated the optimal replanting rule for coffee in vietnam using a fixed-form optimization approach. the paper also has provided a detailed review of programming techniques that have been and could be potentially used to analyze multi-period optimization problems. one of the most challenging aspects in estimating the optimal replanting age of perennial crops is establishing the age-yield relationship. ideally agronomic experiments under a controlled situation would provide credible information. however, such data is rarely available and is a major limitation to empirical estimation of the optimal age forreplanting of perennial crops such as date palm. ward and faris (1968) in their investigation on replanting policies for plum trees have collected data from plum tree farmers in california. they collected data of only a single variety of plums (santa rosa) to avoid the problem of yield differences between varieties. data had been collected through personal interviews with farmers. a deficiency in data collection has been realized because farmers have already replanted the old trees and were unable to provide data about old trees. another problem has been that even individual blocks in the plantation had trees of different age groups. further the amounts harvested have depended upon the prevailing prices. cembalo (2002) recorded data of a farm that had kept data on age-yield relationship consistently over time. the study by mwinjaka et.al. (1999) on determining the optimal age for replanting coconuts in tanzania collected data on ageto-yield relationship by taking a physical count of nuts in samples of plants (592 plants) of different age groups (1 to 90 years). analytical methods two alternative analytical methods, that are based on principles of decision making on asset replacement were used in this study to estimate the optimal replanting age of date palms. these methods are referred to as the comparison of equivalent annual net revenues (cean) and the multi-period linear programming (mplp) model. the analysis of the cean model is restricted to data related to a single palm whilst the mplp model is able to analyze a whole date palm farm with palm-trees of different ages. comparison of equivalent annual net revenues (cean) model the principles on decision making of asset replacement that were proposed by faris (1960) have been mathematically elucidated by perrin (1972). etherington (1977) has applied perrin’s (1972) mathematical exposition on principles to decision making of asset replacement, to analyses of decision making of the replanting of rubber trees. this study has adopted etherington’s (1977) exposition to explain the economic principles of deciding the age of replanting of date palms. for a life period of a date palm, which yields over years, the present value of the flow of net revenues is given by equation (1). where c(0,s,1)is the present value of the flow of net revenues from a life period ‘1’ of a palm planted in year ‘0’ and replaced in year/age ‘s’ by a series of ‘m’ trees. the flow of net revenues consists of net revenues over ‘t’ years and a salvage value m(s). ρ the interest rate. for a series of life periods the replanting problem is to find ‘s’ that maximizes the present value of the net revenues as given in equation (2) over a series of life periods up to infinity ‘ ‘. �(0,�,∞) = �(0,�,1) + ��� � �(0,�,1) + ��� �� �(0,�,1) + the series in equation (2) reduces to equation (3) as the number of life periods tends to infinity. in order to find ‘s’ the replanting age at which the net revenues over time is maximized the first derivative of equation (3) is maximized to get equation (4). equation (4) is that discounted marginal net revenue which is equal to the annuity formed from the discounted total flow of net revenues from date yields plus the salvage value of the tree. the annuity is equivalent to the average annual earnings over years to infinity. thus equation (4) states that marginal and average net revenues are equal or average annual net revenues are maximized. equation (4) can be presented as equation (5) considering discrete age and thus discrete interest rate ‘r’. if the salvage value is ignored then equation (5) can be presented as equation (6) which states that the optimal age of replanting is where the discounted marginal net revenues (mnr) are equal to the annuity formed from the discounted total flow of net revenues (anr) from date palm yields of palms replanted over years. information of �(0,�,1) = � � (�)���� � � �� + �(�)��� � (1) ∞ (2) �(�,�,∞) = 1 1 − ���� �(0,�,1) (3) [�(�) ��(�)]���� [� �(�)��� � �� �(�)] � ��� − 1 � � (4) (5)[�(�) + ∆�(�)] = ���(�)(1 + �)�� + �(�) � � � � (1 + �)� − 1 (6)[�(�)](1 + �)�� = ���(�)(1 + �)�� � � � � (1 + �)� − 1 54 kotagama et al. 55 economic analysis determining the optimal replanting age of date palm equation (5) is portrayed in figure 1. according to figure, 1 if mnr of the existing palm at an age of the palm is higher than the anr from replanting the palm then the existing palm should not be replanted and if mnr of the existing palm at an age of the palm is lower than the anr from replanting the palm then the existing palm should be replanted. an excel spreadsheet model was developed to generate information for equation 6 to compare mnr and anr and determine the optimal age of replanting. as per the model developed above (equation 6) on deriving the decision rule on date palm replanting, the data required to solve the model are age-yield relationship of date palms, net returns from dates (thus input use quantities and prices, date prices) and the interest rate. the age-yield relationship need to be considered for the existing palm and the potential palm that would be replanted. the age-yield relationship represents the technology in terms of the variety of the date palm. if the same variety is considered for replanting, the age-yield relationship will be the same for estimating mnr and anr. if a technologically improved variety is considered for replanting then the mnr would be for the existing palm and the anr would be of the improved variety. in this study the age yield relationship for date palm is considered as having a 60 year life which is considered in 12 age categories of 5 years each. multi-period linear programming (mplp) model agricultural decision making about perennial crops in particular is characterized with multiple year dynamics, where a present decision influences future decisions (mccarl and spreen, 1997). in this study the decision to replant or (not-replant) date palm in a given year (i.e. the time path of replanting) has an influence on the future flow of net revenue from date palms. multi period linear programming models (mplp) are widely known and have been used in agricultural systems modeling (hazel and norton, 1986). mplp models recognize inter temporal linkages in farm activities and maximize the net present value of profit (or an appropriate objective) given constraints of resources overtime. each time period is linked through availability of resources and activities as appropriate. in designing mplp models decisions ought to be taken on, the length of the time horizon, the length of intervals within the time horizon, the rate of inter-temporal time preference (interest rate) and risk conditions if such is to be considered in decision making (cembalo, 2002). there exist tradeoffs between these choices in terms of complexity, largeness and convenience of solving models. the choice and justification of an interest rate in multi-period models is crucial and it depends on several factors such as measures of real and nominal interest rates, opportunity cost of capital, returns from alternative investments, considerations of risk and personal time preferences. salvage values are typically estimated and included by capitalizing the net returns beyond the final year of the model. non-inclusion of salvage values would bias solutions to investing in early periods (cembalo, 2002). the structure of the model used in this study to determine the optimal age of replanting date palms and also to determine the optimal replanting schedule for farms in oman is based on the generalized mplp model structure proposed by mccarl and spreen (1997) and is explained below. maximize: -1000 0 1000 2000 3000 4000 5000 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 55 57 59 n r & a cp v n r (o r/ h a) age of palm (years) nr (or/ha) acpvnr (or/ha) mnr=anr figure 1. principle on determining the optimal replanting age of a perennial crop. � � (1 + �)�� �� ��,� ���� (7) 54 kotagama et al. 55 economic analysis determining the optimal replanting age of date palm subject to: where equation (7) is the objective function which maximizes the present value of the net revenue of date palm of different ages over years. equation (8) constraints the resource use for date palm cultivation to resource availability. equation (9) specifies the initial inventory, i.e. areas of date palm of different ages that exists in the farm. equation (10) transfers date palm age cohorts of a time period to the next time period sequentially as date palms age. the equation (11) specifies non-negativity of the decision variables, i.e. area of date palms. the specification of variables is as follows: x1,e is the decision variable viz; area of land under palms t (age intervals) under cultivation of elapsed age e. t : t1 ... t12; the segregation of age of date palms (60 years) into 12 intervals of 5 years each is done to keep the model within limits of manageability, whilst being practically useful in decision making on replanting of date palm. e : e1 ... e12 ; discrete time representation is used in 12 time periods of 5 year intervals resulting in 60 years. since the objective is to determine the time path of replanting (i.e., to determing at what age the palms should it be replanted) a sufficient age is necessary to allow for adjustment which needs to be incorporated in the model structure. yearly specification would make the model excessively large. r : the interest used is 4%. ce : net revenue per unit of land at different ages of the date palm, are the same values derived and used in the cean model (estimated based on age-yield relationship, input use and prices and product price). aie: the resource use aie is considered in terms per unit land. i: only land is considered as a constraint. this because the main objective of the model is to determine the optimal replanting schedule for an existing farm and it is considered that replanting does not require substantial additional resource commitments other than resources used for the existing date palm. bit: the availability of land is the average farm size as found through the farm survey. k: the life of a palm is considered as 60 years. the initial inventory of age distribution of date palms in farms as found through the farm survey is used in the model to determine the replanting schedule for existing farms vis-à-vis new farms where it is the total availability of land. the excel solver was used to solve the linear programing model. data collection methods the core datum required for this study is the age-yield relationship of date palm varieties cultivated in the sultanate of oman. a survey was done to obtain the above datum through a purposive sample of farms. the sample included farmers from whom the above information could be reliably obtained, i.e., commercial date palm farms and elderly farmers who had a memory of age-yield relationship of date palms. the sample size was limited to 34 farmers given the nature of data collected that required extensive time to interview the respondents and the limitation of other resources as finance and personal. results and discussion farming system and agronomic practices the survey was conducted in three wilayats from aldakhilya governorate namely, izki, bahla, and alhamra. the distribution of the farms among the wilayats was that izki was represented with 44%, farms, bahla and al-hamra with 41 and 15% farms, respectively. the average age of farmers was 59 years. the high average age was due to purposive selection of elderly farmers. the average number of years associated with farming of the respondents was 42 years. most (56%) of the respondents have not had formal education. the average farm size was estimated as 1.2 hectares. the three main date varieties that were cultivated are khalas, fardh and khasab which represent 48, 20 and 11% of the palms, respectively. the average farm had 125 date palms per hectare. date palm growers are not practicing any standard on distancing of palms; row to row and plant to plant distance varies considerably throughout the date palm farms. the average distance between date palms is about 4.2 meters. almost all farms (98%) had intercropped with annual and perennial crops between date palms. the most common intercrops were orange, lemon, alfalfa, garlic, onion and wheat. the most common livestock enterprises found in the surveyed farms were sheep, goats, cows and poultry (average of 6 goats per farm and one cow per farm). the most used fertilizer was animal manure. eighty-two percent of the farmers fertilized date palm with animal manure and the average application was 49 kg per palm. water use could not be quantified as the use was expressed in terms of hours of water distributed to the farm through open channels. according to the survey, 65% of the farmers said that they have replanted their date palms in the past. lack of awareness of the age of plant, lack of water and lack of space are the justifications for not replanting by those who had not replanted. the number of date palms that had been replanted in the past ranges from minimum of ���� ��,� ≤ ��� ��� ��� � ��� � ��� ��,� = ��,�∗ ��� � < � −����,��� + ��,� ≤ 0 ��� ��� � ��� � > 0 ��� � ≤ � ��,� ≥ 0 ��� ��� �,�. (8) (10) (9) (11) ��,�∗ : 56 kotagama et al. 57 economic analysis determining the optimal replanting age of date palm 1 date palm to maximum of 30 palms replanted per farm. morphological characteristics, more specifically height of the date palm, was the main factor that was considered in deciding to replant a palm. the height of the palm relates to the labor intensive practices of pollination and harvesting. hence farmers consider the incremental costs associated with height of palm when deciding when to replant. fifty-three percent of the respondents replant when the harvesting is not feasible because of excessive height of palms. the other reasons that influenced the decision to replant are declining yield with age in terms of reduced number of bunches, reduced number of fruits per bunch, reduced quality of the fruit and the effect of reduced prices of different varieties. there also prevails a perception among farmers that, as the age of the date palms increase, the better will be the fruit quality. thirty-five percent of the farmers mentioned that the quality of the date fruit change with the increased age of the palm. among these 35% farmers, 50% said that the quality will be better as the age increases, while the remaining 50% said that as age increases the quality of the fruit will decrease in terms of size and color. fifty percent of the farmers who replanted date palm had used new date palm varieties to replace the old palm. khalas dominates the varieties that farmers use to replant the old varieties. better quality and price are the factors that influence farmers’ decisions in the choice of this variety. some farmers retain ‘suckers/ off shoots’ from the mother palm, whilst inducing the mother palm to decay. majority of the farmers do not make any use of the old palm trunks. the farm survey data indicated that 48% of the palms in the sample farms were khalas variety. almost all (99%) the palms are less than 50 years and about 95% are less than 40 years of age. more than 50% of the palms are less than 20 years in age. this could be due to the fact that the large commercial farms have been cultivated post 1970s. base data used in cean and mplp models the age-yield data for khalas as found through the sample survey is given in table 1. the average yield is higher than nationally reported yields of 45 kg/palm, since the sample was purposive and represented large commercial farms. using the data in table 1 a best-fit curve on the age-yield relationship of the khalas date variety was estimated (fig. 2). the equation of the best fit on the age-yield relationship was used to re-estimate the ageyield relationship of the khalas date variety (table 1). table 1. age-yield relationship for khalas date variety. age of palm (yrs) yield (kg/palm) survey predicted 1 to 5 59.4 62.3 6 to 10 89.5 102.0 11 to 15 187.2 133.7 16 to 20 131.7 157.2 21 to 25 150.0 172.7 26 to 30 148.0 180.0 31 to 35 207.5 179.3 36 to 40 218.0 170.5 41 to 45 120.0 153.6 46 to 50 144.0 128.6 51 to 55 nr* 95.6 56 to 60 nr* 54.4 *nr indicates not reported by farmers in the sample. y = -3.6943x2 + 48.846x + 19.105 r² = 0.5735 -50.0 0.0 50.0 100.0 150.0 200.0 250.0 1 to 5 6 to 10 11 to 15 16 to 20 21 to 25 26 to 30 31 to 35 36 to 40 41 to 45 46 to 50 51 to 55 56 to 60 y ie ld ( k g/ p al m ) age of palms (years) figure 2. age-yield relationship of khalas date variety and the estimated function. 56 kotagama et al. 57 economic analysis determining the optimal replanting age of date palm number of palms per hectare was considered as 125 as found through the survey. it was considered that the same variety (khalas) is replanted, hence the same age-yield relationship was considered for the potential replanting palms. sensitivity analysis for an increase and decrease of 25% of the base yield was done. using the average price of dates over the period 1961 to 2011 in the sultanate of oman, as reported in fao statistics, a trend line on price prediction was estimated. based on the trend line the predicted price of 0.250 or/kg was considered as the base price. a decrease and increase of 25% of the base price was considered for sensitivity analysis. the cost of production estimate of 914 or/ha for date palm cultivation provided by the ministry of agriculture and fisheries wealth, sultanate of oman was used as base cost. an increase and a decrease of cost by 25% were considered for sensitivity analysis. a 4% interest rate was used in the study based on the average for the period 2002 to 2010 of the interest rate spread of the sultanate of oman as reported by the world bank. sensitivity analysis was done for 1 and 10% interest rates. results from cean model analysis the estimated optimal age for replanting of existing khalas date variety with the same variety under base data of yield, price, interest rate and cost is given in figure 3. the results of the sensitivity analysis are given in table 2. it is estimated that on base conditions the optimal age to replant is 52 years. the optimal age of replanting is -1000 0 1000 2000 3000 4000 5000 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 55 57 59 n r & a cp v n r ( o r /h a) age of palm (years) nr (or/ha) acpvnr (or/ha) figure 3. results of the base model with age-yield relationship of khalas variety. table 2. results on optimal age of replanting and sensitivity analysis for khalas variety: cean model. factors base model sensitivity analysis price change cost change interest change change in yield increase by 25% decrease by 25% increase by 25% decrease by 25% increase to 10% decrease to 1% increase by 25% decrease by 25% age (yr) 60 60 60 60 60 60 60 60 60 average yield (kg/yr/tree) 132 132 132 132 132 132 132 165 99 average yield (kg/ha) 16450 16450 16450 16450 16450 16450 16450 20561 12336 price (or/kg) 0.25 0.31 0.19 0.25 0.25 0.25 0.25 0.25 0.25 average gross return (or/ha) 4111 5261 3225 4111 4111 4111 4111 5141 3084 average cost (or/ha) 914 914 914 1142 686 914 914 914 914 average net return (or/ha) 3197 4186 2210 2969 3427 3197 3197 4226 2170 interest 0.04 0.04 0.04 0.04 0.04 0.10 0.01 0.04 0.04 age of replanting (yr) 52 52 52 52 52 56 49 52 52 58 kotagama et al. 59 economic analysis determining the optimal replanting age of date palm sensitive only to the interest rate. a decrease in the interest rate (1%) shortens optimal replanting age to 49 years and an increase in the interest rate (10%) lengthens the optimal replanting age to 56 years. results from mplp model analysis the mplp model was solved for base data and then sensitivity analysis was done on price, yield and interest rate changes, similar to the analysis with the cean model. the results are reported in table 3. in reporting the results of the mplp model analysis, the upper value of the range of the period is reported. the cean and mplp models have produced consistent results on the estimation of the age of replanting (compare tables 2 and 3). considering results of both models and results of sensitivity analysis on price, cost, interest and yield changes it could be concluded that date palms should be replanted at about 50 yrs. replanting schedule for date palm plantations in oman data on age distribution of date palm plantation in the sultanate of oman is not available. an estimation was made using the fao stat data that has reported area harvested by year. the yearly data on area harvested was averaged for 5 year periods and reported in table 4. the incremental area planted during a period (period n) is estimated by deducting area harvested in period n from area harvested in period n+1 (every period is considered as 5 years). the area planted with date palms at a given period increases the area harvested after 5 years as fruiting occurs after 5 years of planting. it is estimated that from the area of date palms in year 2000 (35508 ha) at least 14000 ha (or about 40%) is older than 40 years. from 2000 to 2010 the area has decreased down to 31353 ha. table 3. results on optimal age of replanting and sensitivity analysis for khalas date palm: mplp model. factors base model sensitivity analysis price cost interest yield increase by 25% decrease by 25% increase by 25% decrease by 25% increase to 10% decrease to 1% increase by 25% decrease by 25% age (yr) 60 60 60 60 60 60 60 60 60 average yield (kg/yr/tree) 132 132 132 132 132 132 132 165 99 average yield (kg/ha) 16450 16450 16450 16450 16450 16450 16450 20561 12336 price (or/kg) 0.25 0.31 0.19 0.25 0.25 0.25 0.25 0.25 0.25 average gross return (or/ha) 4111 5261 3226 4111 4111 4111 4111 5141 3084 average cost (or/ha) 914 914 914 1142 686 914 914 914 914 average net return (or/ha) 3197 4187 2210 2969 3427 3197 3197 4226 2170 interest 0.04 0.04 0.04 0.04 0.04 0.10 0.01 0.04 0.04 age of replanting (yr) 55 55 55 55 55 55 50 55 55 table 4. approximate estimates of age of date palm plantations in the sultanate of oman. year planted present age of plantation (yrs) area harvested (ha) area planted (ha) before 1960 > 51 13000 13000 1961-1965 46-50 13000 0 1966-1970 41-45 13000 1000 1971-1975 36-40 14000 6100 1976-1980 31-35 20100 1900 1981-1985 26-30 22000 3000 1986-1990 21-25 25000 4000 1991-1995 16-20 29000 6508 19962000 11-15 35508 0 2001-2005 5-10 31353 0 2006-2010 <5 31353 0 58 kotagama et al. 59 economic analysis determining the optimal replanting age of date palm the mplp model was used to estimate the replanting schedule (area to replant by periods) for the sultanate of oman by considering the present age distribution of palms in the sultanate of oman (table 4) as initiating data and considering a 35508 hectares of date plantations in the sultanate of oman, with data on age-yield relationship, prices, cost of production etc., considered as the same as of the base model. the results of the model provided the replanting schedule given in table 5. the area in hectares in the second column of the table 5 are the areas that should be replanted in the identified periods of the first column. this information on the date palm replanting schedule is reproduced as table 6. table 5 shows how the age classes of date palms shifts over time and gets replanted. it is noted that when considering existing palms of different ages such as in a single farm, some palms would be replanted even earlier than 50 years. consider the column on age group 41-45 years in table 5, it is noted that 3000 ha gets replanted at age 45 along with 1900 ha at age 46-50 years. further 4000 ha and 6508 ha too gets replanted after 41-45 years. although the optimal age of replanting was estimated as 50 years for date palm cultivated as an age-homogenous new plantation, the optimal age for replanting of an age-heterogeneous existing plantation could be less. thus, the mplp model provides a more comprehensive analysis and realistic results on the optimal replanting age for whole farms. the mplp model developed in this study could be used for developing optimal date palm replanting schedules for individual farms by extension officers, whilst considering realistic conditions resource availability and institutional capacity of implementing agencies. the estimated (using the mplp with base data) present value that would be generated with and without replanting existing date palm plantations in oman (35508 ha with age distribution given in table 4) is given in table 7. it was estimated that if date palms were replanted optimally table 5. optimal age distribution schedule of date palm plantations in oman. year/ period date palm area (ha) by age (yrs) 0-5 5-10 11-15 16-20 21-25 25-30 31-35 36-40 41-45 46-50 51-55 56-60 2010-2015 13000 0 0 6508 4000 3000 1900 6100 1000 0 0 0 2016-2020 0 13000 0 0 6508 4000 3000 1900 6100 1000 0 0 2021-2025 1000 0 13000 0 0 6508 4000 3000 1900 6100 0 0 2026-2030 6100 1000 0 13000 0 0 6508 4000 3000 1900 0 0 2031-2035 4900 6100 1000 0 13000 0 0 6508 4000 0 0 0 2036-2040 4000 4900 6100 1000 0 13000 0 0 6508 0 0 0 2041-2045 6508 4000 4900 6100 1000 0 13000 0 0 0 0 0 2046-2050 0 6508 4000 4900 6100 1000 0 13000 0 0 0 0 2051-2055 0 0 6508 4000 4900 6100 1000 0 13000 0 0 0 2056-2060 0 0 0 6508 4000 4900 6100 1000 0 13000 0 0 2061-2065 0 0 0 0 6508 4000 4900 6100 1000 0 13000 0 2066-2070 13000 0 0 0 0 6508 4000 4900 6100 1001 0 0 table 6. date palm replanting schedule for the sultanate of oman. year/period area (ha) to be replanted 2010-2015 13000 2016-2020 0 2021-2025 1000 2026-2030 6100 2031-2035 4900 2036-2040 4000 2041-2045 6508 2046-2050 0 2051-2055 0 2056-2060 0 2061-2065 0 2066-2070 13000 60 kotagama et al. 61 economic analysis determining the optimal replanting age of date palm they would generate a net revenue 2218 million or and if not replanted the net revenue would be 1856 million or in present value over 60 years and 4% interest. the benefit of replanting over not replanting is 361 million or in present value, which is equivalent to 16 million or when amortized over 60 years and 4% interest. this implies that if a replanting is undertaken as scheduled in table 6 the sultanate of oman could gain 16 million or per year in the future. however, this is an upper-bound estimate because the sample considered for this study is a purposive sample of large commercial farms reporting an average yield of 132 kg/palm. this yield is 3.5 times higher than the national average date palm yield of 45 kg/palm. also the upper-bound estimate assumes that at present farmers do not replant date palms. however, the survey found that 65% of the farmers responded to having replanted (at least one palm) date palm in the past years. thus this is an upper-bound estimate of the rate of replanting adopted. given the above reasons the upper bound value was subjected to a sensitivity analysis by considering the national average yield of 38 kg/palm and a 65% rate of replanting as being currently adopted (table 8). thus, the average benefit from replanting date palms based on the sensitivity analysis is 7 million or/yr. the revenue from date palms in year 2011 in oman was or 52.6 million (fao stat, 2010). thus replanting of date palms could increase the revenue by more than 13% over the current (2011) revenue from date palms in the sultanate of oman. conclusions and policy suggestions the study estimated the optimal age of replanting date palm as 50-55 years. the optimal age to replant date palms was sensitive only to changes in the interest rate. low interest rates shortened the optimal age of date palm replanting. changes in price, yield and cost did not change the optimal age of replanting date palms. this implies that the results obtained for khalas variety could be extended to the other varieties, since the major differences among varieties is related to consumer preferences, and thus the price of the dates. it was estimated that about 37% of the date palms in the sultanate of oman are more than 50 years old. the study derived the optimal replanting schedule for date palm for the sultanate of oman given the current age distribution of date palms. on the average, the benefit of replanting date palms for the sultanate of oman is about or 7 million per year. thus, the sultanate of oman could increase the revenue from the date palm sector by about 13% based to the revenue of the date sector in 2010 (or 52.6 million), by adopting the derived replanting schedule. the study reveals the significant benefit the sultanate of oman could gain by initiating a national program to encourage farmers to replant old unproductive date palms. government would also have to plan extension activities and allocate resources for such a program. since replanting, unless well planned at the farm level would incur reductions in the farm cash flow for short periods, cash flow support through financial institutions and/or government subsidies could be considered to encourage farmers. this study considered the replanting of the khalas date palm variety with the same variety. the models developed in this study can be used to comparatively examine the possibility to replant with other date palm varieties, that are high yielding and better quality. the government could also support farmers through a planned program of propagation of date palm and providing such high yielding varieties with modern technology such as tissue culture etc. the replanting program suggested in this study is the technical ideal. it would however be necessary to develop a replanting program that is practically feasible within constraints of technology and resources. two alternative analytical models based on the theory of optimal replacement of capital assets were used to estimate the optimal age of replanting of date palms: the cean and mplp models. the mpdl model is analytically superior to the cean model as the mplp model is able to use strengths of linear programming for whole-farm planning. the cean model could only analyze the optimal age for a single palm, whilst the mplp could analyze a whole farm with date palms with different ages and also consider resource constraints as land, water, labor, capital, etc. the data used for the study was restrictive in terms of the sample size and due to the adoption of purposive sampling method. this, however, was inevitable given the nature of data to be collected, particularly the age-yield relationship table 7. estimated benefits of replanting date palm plantation in the sultanate of oman. scenario present value (million or) amortized value (million or) without replanting 1856 82 with replanting 2218 98 benefit of replanting 361 16 table 8. sensitivity analysis on benefits of replanting date palm in the sultanate of oman. variables benefit (million or/yr)yield (kg/palm) current replanting rate (%) 132.0 0.0 16.0 38.0 0.0 4.6 132.0 60.0 5.6 38.0 60.0 1.6 average 7.0 60 kotagama et al. 61 economic analysis determining the optimal replanting age of date palm of date palm. it is recommended that agronomic research be undertaken to establish the age-yield relationship of this vital crop. a larger random sample and a more elaborate data collection process involving more financial, personnel and time resources could have improved the validity of the study. the analytical methodology adopted in the study was theoretically and operationally robust. both models namely cean and mplp models can be used by extension officers in developing date palm replanting schedules and advising farmers. acknowledgments this study was funded by an internal research grant provided by the sultan qaboos university, sultanate of oman, on project code ig/agr/econ/11/01, with dr. hemesiri kotagama, dr. slim zekri, and dr. hemanatha jayasuriya, all from the college of agricultural and marine sciences, sultan qaboos university. references al-shuaibi, a. 2001. the econometrics of investments in date production in saudi arabia. the international journal of applied economics and finance 5:177-184. al-yahyai, r. 2007. improvement of date palm production in the sultanate 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mathematical programming for economic analysis in agriculture, macmillan publishing company, new york, usa. ismail, a. and m.n. mamat. 2002. the optimal age of oil palm replanting, malaysian palm oil board. p.o. box 10620, 50720 kuala lumpur, malaysia, pp 11-18. malaysian palm oil board (mpob), 2002. kearnev, m. 1994. an inter-temporal linear programming model for pip fruit orchard replacement decisions. maf policy technical paper 94/6, maf information bureau, new zealand. larry, l.b., g.d. bishop, and p.j. rathwell. 1990. a computer model for peach orchard replacement. acta horticulturae 276:295-299. mc carl, b.a. and t.h. spreen. 1997. applied mathematical programming using algebraic system, e book: http://agecon2.tamu.edu/people/faculty/mccarlbruce/mccspr/thebook.pdf. mwinjaka, s., c. chiduza, a.e. temu, c. sukume, and l. diehl. 1999. coconut palm replacement model for tanzanian farming systems, journal of agricultural economics and development 3:61-70. oppenheim, p.p. 2003. the evaluation of orchard adjustment strategies: a linear programing approach to the development of rural policy in the sme sector. proceedings of small enterprise association of australia and new zealand 16th annual conference 2003. perrin, r.k. 1972. asset replacement principles. american journal of agricultural economics 54:6067. thang. t.c., m. burton, and d. mrennan. 2009. optimal replanting and cutting rule for coffee farmers in vietnam. proceedings aares 53th annual conference, http://ideas.repec.org/p/ags/aare09/47638.html. ward, l.e. and j.e. faris. 1968. a stochastic approach to replacement policies for plum trees, giannini foundation monograph number 22. university of california division of agricultural sciences, giannini foundation of agricultural economics. white, g.b. 1986. a dynamic programming computer model for orchard replacement. acta horticulturae 184:191-198. world bank. 2011. (http://www.tradingeconomics.com/ oman/interest-rate-spread-lending-rate-minus-depositrate-percent-wb-data.html). received: january 15, 2013 accepted: april 28, 2013 agricultural and marine sciences, 14:1-8 (2009) ©2009 sultan qaboos university 1 ________________________________________________ *corresponding author. e-mail: saleem_nadaf@yahoo.com effect of spacing on seed yield of indigenous rangeland and forage grass species grown under drip irrigation saleem k. nadaf*, safaa m. al-farsi, saleh a. al-hinai, abdul aziz s. al-harthi and ahmed n. al-bakri seed and plant genetic resources laboratory, plant production research center, directorate general of agriculture and livestock research, ministry of agriculture, po box 50, pc 121, sultanate of oman abstract: two indigenous rangeland forage species, cenchrus ciliaris and coelachyrum piercei, were investigated for their response to varying inter-row (50 and 100-cm) and inter plant spacing (25, 50 and 100-cm) under drip irrigation along with the perennial popular forage, rhodes grass (chloris gayana). expression of traits, such as plant stand, plant height, number of tillers, number of panicles and seed yield, differed under varying inter-row and inter-plant spacing in different harvests. the grass species produced higher seed yield due to less interplant competition under wider (100-cm) than under narrow row (50-cm) spacing. chloris gayana produced highest mean seed yield in wider inter-plant spacing (100-cm) under both inter-row spacings, viz. 100-cm (488 kg/ha) and 50-cm (449 kg/ha), followed by cenchrus ciliaris (449 kg/ha under 100-cm and 377 kg/ha under 50-cm row spacing) and coelachyrum piercei (274 kg/ha under 100-cm and 210 kg/ha under 50-cm row spacing). in respect of seed quality for samples harvested selectively or in bulk, the three grasses showed very low germination when tested immediately (1-2 weeks) after harvest, not only for bulk seed (0 to 1.5%) but also for selected seed (0.8% to 2.8%). mean germination of grass species recorded after 12 months of harvests was significantly greater (53 %) than that recorded after 5 months (34 %) of harvests. of the three grass species, cenchrus ciliaris recorded significantly (p<0.01) highest germination % (50 %) followed by chloris gayana (41 %) and coelachyrum piercei (39 %). selected seeds had significantly (p<0.01) higher germination (53 %) than bulk seeds (33 %). keywords: grass species, cenchrus ciliaris, chloris gayana, coelachyrum piercei, spacings, growth attributes, seed yield, germination, sultanate of oman. introduction the sultanate of oman has a large area of rangelands especially in the dhofar mountain areas of south oman and the mountains of the north oman. more than 90 germplasm samples of different indigenous forage species have been collected under the international center for agriculture research in the dry areas (icarda) arabian peninsula research program (aprp) between 1998 and 2002. these are part of the local genetic diversity and are under use by الحشائش بذور في إنتاج للنباتات البینیة والمسافة الزراعة خطوط المسافة بین تأثیر دراسة بالتنقیط الري تحت نظام المحلیة الرعویة البكري وأحمد الحارثي وعبدالعزيز الھنائي صالح و الفارسي وصفاء نداف سلیم القائم الجمع خالل برنامج تجمیعھما تم والتي والدخنة اللبید وھي األعشاب الرعویة من نوعین دراسة تم العربیة الجزیرة لشبھ لبرنامج (ایكاردا) األولى المرحلة ضمن الخالصة: و٥٠ ١٠٠) النباتات بین البینیة والمسافة سم) (٥٠و١٠٠ الزراعیة بین الخطوط المسافات تأثیر مدى دراسة البرنامج. حیث تمت من الثانیة المرحلة خالل وذلك ایكاردا بالتعاون مع وإنتاج البذور الزھار وعدد االشطاء وعدد النبات طول مثل تحت الدراسة الصفات أبدت بالتنقیط. نظام الري تحت وذلك الرودس حشیشة إلي إضافة النوعین ھذین على سم) و٢٥ الزراعیة المسافة بزیادة البذور إنتاج ارتفاع النتائج أظھرت األولى. السنة بعد معنویًا ارتفاعا البذور إنتاج شھد الحصدات. قد بمختلف الزراعیة واضحًا باختالف المسافات اختالفًا ٣٨٤ و كجم/ھكتار ٤٤٣ اللبید تاله كجم/ھكتار و٤٠٦ كجم/ھكتار ٤٧٥) حصدات لتسع البذور إلنتاج معدل أعلى الرودس أعطى سم). ٥٠ عند( بمثیلتھا سم) ١٠٠) الخطوط بین المتكاملة للبذور سواء متدنیة بالبذور اإلنبات نسبة كانت التوالي. لقد الري على خطوط سم بین و٥٠ سم مسافة ١٠٠ عند كجم/ھكتار و١٩٩ كجم/ھكتار ٢٤١ الدخنة كجم/ھكتار ثم أشھر ٥ و(٣٤٪) بعد شھرًا بعد ١٢ (٪٥٣) معنویًا أعلى إنبات نسبة تسجیل تم أسبوع). ١-٢) الحصاد بعد مباشرة اختبارھا عند الثالثة لألنواع (٪٢,٨ – ٠,٨) المنتقاه أو (٪٠-١,٥) أعلى كانت معنویًا المنتقاه بالبذور اإلنبات نسبة أن أن كما (٪٣٩) الدخنة ثم (٪٤١) الرودس (٥٠٪) تاله إنبات نسبة أعلى اللبید بذور الثالثة أعطت االنواع بین من الحصاد. من .(٪٣٣,٠٨) المتكاملة بالبذور مقارنة (٪٥٣,٢١) سلطنة عمان. ، االنبات البذور ، انتاجیة ، النمو مظاھر ، الزراعة خطوط بین المسافة ، الحشائش الرعویة مفتاحیة: كلمات 2 nadaf and others 3 effect of spacing on seed yield of indigenous rangeland and forage grass species grown under drip irrigation grazing animals. rangeland grass or pasture species appear to have been neglected as material for investigation, especially concerning the agronomic aspects of seed production. as grass species have evolved as perennials for vegetative forage yield, they have very low seed productivity (chatterjee and das, 1989 and boonman, 1972). as such, the productivity and availability of seeds in the inflorescence per se at harvest have been observed to be important factors in the seed production of any grass species (chatterjee and das, 1989: loch and clark, 2000). plant density is less meaningful in perennial pasture species as subsequent branching or tillering can compensate more rapidly for low plant density establishment. however, row spacing, continued cultivation and thinning of stands provide means of influencing shoot density (humphreys, 1978). row culture has been recommended for many tropical pasture species. owen (1951) found paspalum dilatatum to give a seed yield of 182 kg/ha in row culture as compared to 139 kg/ha in broadcast swards. some studies have demonstrated merits of low seeding rates or wide spacing for perennial grass seed crops (evans, 1959 and 1962; lambert, 1963). low plant density tends to produce high fertility of tillers and more efficient seed production, since barren shoots contribute little to developing grain. on the other hand, in annual pasture crops like stylosanthes humilis, shelton and humphreys (1971) found that the seed rate and the row spacing had special significance in balancing seed yield. seed yield was highest to the extent of 690 kg/ha at an optimum density (850 plants/ m-2), whereas both very low (10 to 250 plants/ m-2) and very high densities (3800 plants/ m-2) reduced seed yield. indigenous rangeland grass species, being more palatable for grazing animals and favoured by herders, are decreasing in the rangelands. in order to popularize these pasture species for cultivation under existing fodder production systems or re-vegetation of barren rangelands, seed production methods have to be standardized for specific irrigation system towards maximization of seed yield. investigations were therefore undertaken over 2001-2003 under icarda-aprp in these two indigenous rangeland species and existing forage species under drip irrigation. the objective was to study the effect of interrow and inter-plant spacing on the seed yield and related characters and to select appropriate inter-row and inter plant spacings to produce maximum seed yield. materials and methods the grass species under study included two indigenous rangeland forage species, buffel grass-cenchrus ciliaris l. (uae) and coelachyrum piercei l. (uae), collected under icarda-aprp phase–i (peacock et al., 2000) and rhodes grass (chloris gayana kunth.)katambora. the trial was set out in a modified three factor randomized complete block design, with three replications involving three grass species as the first factor, two inter-row spacing (50 and 100-cm) as the second factor and three inter-plant spacing (25, 50 and 100-cm) as the third factor. this was done under drip irrigation on a site consisting of sandy soil at livestock research station, rumais (table 1). there were three and two four-meter rows per plot respectively at 50 and 100-cm spacing. four to five seeds were sown just within 2.50 cm depth of sandy soil (table 1) at drip points. ten to fifteen granules of systemic insecticide, carbofuron (furadon) were broadcast around each hill to protect seeds from ants. the crop was fertilized with 150 kg n, 150 kg p2o5 and 150 kg k2o per hectare per year in the form of urea, triple super phosphate and potassium sulfate. the entire quantities of potassium and phosphate fertilizers were applied after the establishment of seedlings while 1/3 n was applied in two split doses 1/2 n with p and k or after each harvest and remaining 1/2 n at flag leaf emergence. nine seed harvests were taken up during the period of experimentation. the first harvest of the grass species was taken 125-135 days after seeding, whereas subsequent harvests were done at intervals of 60-70 days after visual confirmation of seed formation from the plot samples. the data on five traits were recorded at harvest: plant stand (zero to 10 scale (0-100%)), plant height (cm), number of tillers/ plant, number of panicles per plant and seed yield (with husk) (g) per plot (1m x 4m). these are considered as stable and reliable indicators of growth. the plant stand of each plot was scored on a recommended scale of zero to 10, where score multiplied by 10 indicates plant stand in percentage. plant height (cm) from ground to tip of the panicle and number of panicles were recorded on five randomly selected plants, whereas seed yield was recorded from the plants of three random sites of 1 m2 in each plot. the data were subjected to anova considering harvests, inter-row spacing, inter-plant spacing and grass species as factors using the mstat-c computer program (gomez and gomez, 1984). the bulk seed and selected seed samples of each harvest were tested for germination table 1. values of some physical and chemical characteristics of the experimental soil at the livestock research center, rumais. chracteristics physical: coarse sand (%) 21.70 fine sand (%) 63.00 silt (%) 3.90 clay (%) 11.40 texture sand chemical: ec (1:5) ds 5.70 ph (1:5) 7.80 soluble cations (meq./100g) na 65.90 k 0.77 soluble anions (meq./100g) cl 59.50 n (%) 0.04 av.p (meq./100g) 15.76 2 nadaf and others 3 effect of spacing on seed yield of indigenous rangeland and forage grass species grown under drip irrigation using the top of paper (tp) method with five replications (agrawal, 1980) not only at harvest but also after five and twelve months of each harvest. the data on germination were subjected to anova, considering harvests, seed type, time of test and grass species as factors. the comparisons of means were made using corresponding lsd’s for the factors and interactions whose effects were found significant. results and discussion table 2 shows the anova with respect to plant stand (%), plant height (cm), number of tillers / plant, number of panicles / plant and seed yield (kg/ha). in respect of plant stand the main effects of all factors and effects of 2factor interactions (harvest x inter-row spacing, harvest x interplant spacing, harvest x grass species, inter-row spacing x grass species and inter-plant spacing x grass species) and that of one 3-factor interaction (such as harvest x inter-row spacing x grass species) were highly significant (p<0.01). in the case of plant height, the main effects of all factors, effects of 2factor interactions (harvest x interrow spacing, harvest x inter-plant spacing, harvest x grass species and inter-row spacing x grass species), effects of two 3factor interactions (harvest x inter-row spacing x grass species and inter-row spacing x inter-plant spacing x grass species) and also the effect of four factor interaction, were highly significant (p<0.05). for number of tillers, the main effects of all factors and their interactions except the effects of one 2-factor interaction (harvests x inter-plant spacing) and one 3factor interaction (harvest x inter-plant spacing x grass species) and that of 4-factor interaction, were significant to a highly significant (p<0.01). in number of panicles, effects of the main factors and effects of four 2factor interactions (inter-row spacing x inter-plant spacing, harvests x grass species, inter-row spacing x grass species and inter-plant spacing x grass species) and also effects of two 3-factor interactions (harvest x inter-row spacing x grass species and inter-row spacing x inter-plant spacing x grass species) were highly significant (p<0.05). in respect of seed yield (with husk), all the main effects and all the effects of interactions, except that of two 2-factor interactions (inter-row spacing x inter-plant spacing and inter-row spacing x grass species), were highly significant (p<0.05) (table 2). there was differential expression of the traits in the three grass species under varying inter-row and inter-plant spacing. table 3 depicts the means over nine harvests of five characters studied under two inter-row and three interplant spacings. only the significant interactions involving grass species with other factors have been discussed. plant stand (%) chloris gayana and cenchrus ciliaris appeared more persistent as evidenced by higher mean plant stands over harvests during period of experimentation. chloris gayana had significantly (p<0.05) higher mean plant stand (91.7 %) than cenchrus ciliaris (88.1 %) under inter-row spacing of 100-cm. however, there was no significant difference (p>0.05) between the plant stands of chloris gayana (90.7 cm) and cenchrus ciliaris (90.8 cm) under inter-row spacing of 50-cm (table 3). coelachyrum piercei was less persistent with low plant stands. in general, plant stands persistency of all grass species was of higher order under inter-row spacing of 100-cm. this is also evidenced by significantly (p<0.05) higher mean value of plant stands (87.7%) found under inter-row spacing of 100-cm than that under 50-cm (82.6 %) (table 3). plant height among the grass species, both cenchrus ciliaris and chloris gayana had recorded mean plant height of over 100 cm, significantly different (p<0.05) to coelachyrum piercei (62.6 to 72.7 cm) in both the row-spacings (table 3). cenchrus ciliaris had significantly higher mean plant height (p<0.05) of 114.5 cm at 100-cm row spacing than at 50-cm row spacing (110.5 cm). on the other hand, chloris gayana had no differential response to two row-spacings (p>0.05) in respect of plant height (table 3). interplant spacings had no significant effect in either of the row spacings with respect to mean plant height over harvests (tables 2 and 3). cenchrus ciliaris had significantly higher values of plant height under all interplant spacings in both the row spacings than chloris gayana and coelachyrum piercei. in respect of the effect of the row spacing, 100-cm row spacing had significantly higher (p<0.05) mean plant height (96.9 cm) than 50-cm (92.4 cm) (table 3). there existed highly significant effects of 3-factor interaction involving grass species, row and plant spacings (tables 2 and 3). as a result, cenchrus ciliaris was found to show significantly (p<0.05) the highest plant height in interplant spacing of 100 cm under both inter-row spacings viz. 100-cm (115.5 cm) and 50-cm (113.8 cm), followed by chloris gayana that had 106.7 cm at 100-cm and 104.6 cm at 50 cm row spacing (table 3). number of tillers/plant among the grass species, there were differential patterns of tillering depending on row spacing. cenchrus ciliaris excelled significantly (p<0.05) in tillering as compared to other two species and exhibited similar patterns of tillering, irrespective of row-spacing, as evidenced by the highest mean number of tillers found in 50-cm (101) and 100-cm (111) (table 3). conversely, chloris gayana and coelachyrum piercei exhibited differential tillering, depending on the row-spacing. chloris gayana was able to produce more tillers, to the extent of 109 in wider (100-cm) row-spacing than that (77 tillers) in narrow rowspacing (50-cm), whereas coelachyrum piercei showed heavy tillering (101 tillers) in narrow row-spacing while it was lower in tillering (86 tillers) in wider row-spacing. among the row-spacings, the mean number of tillers in 100-cm (102) was significantly (p<0.05) higher than in 50-cm (93). among the inter-plant spacings, grasses 4 nadaf and others 5 effect of spacing on seed yield of indigenous rangeland and forage grass species grown under drip irrigation t ab le 2 . s ta tis tic al p ar am et er s in re sp ec t o f p la nt s ta nd (% ), pl an t h ei gh t ( cm ), nu m be r o f t ill er s / p la nt , n um be r o f p an ic le s/ p la nt a nd s ee d yi el d (k g/ ha ). c ha ra ct er pl an t s ta nd (% ) pl an t h ei gh t ( cm ) n um be r o f t ill er s/ pl an t n um be r o f pa ni cl es / p la nt se ed y ie ld (k g/ ha ) st at is tic al p ar am et er s fte st l sd (5 % ) fte st l sd (5 % ) fte st l sd (5 % ) fte st l sd (5 % ) fte st l sd (5 % ) h ar ve st ** 0. 12 ** 2. 76 ** 5. 15 ** 3. 3 ** 24 .1 7 in te rro w s pa ci ng ** 0. 06 ** 1. 3 ** 2. 43 ** 1. 56 ** 11 .4 h ar ve st x in te rro w s pa ci ng ** 0. 17 ** 3. 91 ** 7. 28 n s ** 34 .1 9 in te rpl an t s pa ci ng ** 0. 07 * 1. 59 ** 2. 97 ** 1. 91 ** 13 .9 6 h ar ve st x in te rpl an t s pa ci ng ** 0. 21 ** 4. 79 n s n s ** 41 .8 7 in te rro w s pa ci ng x in te rpl an t s pa ci ng n s n s ** 4. 2 ** 2. 7 n s h ar ve st x in te rro w s pa ci ng x in te rpl an t s pa ci ng n s n s * 12 .6 1 n s ** 59 .2 1 g ra ss s pe ci es ** 0. 07 ** 1. 59 ** 2. 97 ** 1. 91 ** 13 .9 6 h ar ve st x g ra ss s pe ci es ** 0. 21 ** 4. 79 ** 8. 92 ** 5. 72 ** 41 .8 7 in te rro w s pa ci ng x g ra ss s pe ci es ** 0. 1 ** 2. 26 ** 4. 2 * 2. 7 n s h ar ve st x in te rro w s pa ci ng x g ra ss s pe ci es ** 0. 3 n s * 12 .6 1 ** 8. 09 ** 59 .2 1 in te rpl an t s pa ci ng x g ra ss s pe ci es ** 0. 12 n s * 5. 15 ** 3. 3 ** 24 .1 7 h ar ve st x in te rpl an t s pa ci ng x g ra ss s pe ci es n s ** 8. 29 n s n s ** 72 .5 2 in te rro w s pa ci ng x in te rpl an t s pa ci ng x g ra ss s pe ci es n s ** 3. 91 ** 7. 28 * 4. 67 ** 34 .1 9 h ar ve st x in te rro w s pa ci ng x in te rpl an t s pa ci ng x g ra ss s pe ci es n s ** 11 .7 3 n s n s ** 10 2. 6 c v (% ) 3. 81 7. 76 14 .2 9 13 .3 5 13 .6 8 *s ig ni fi ca nt a t 0 .0 5 le ve l o f p ro ba bi lit y ** si gn if ic an t a t 0 .0 1 le ve l o f p ro ba bi lit y n s n ot s ig ni fi ca nt 4 nadaf and others 5 effect of spacing on seed yield of indigenous rangeland and forage grass species grown under drip irrigation ta bl e 3. m ea ns ( ov er n in e ha rv es ts ) of p la nt s ta nd ( % ), pl an t h ei gh t ( cm ), nu m be r of ti lle rs / p la nt , n um be r of p an ic le s/ pl an t a nd s ee d yi el d (w ith h us k) ( kg /h a) o f tw o in di ge no us r an ge la nd fo ra ge g ra ss s pe ci es a nd r ho de s gr as s un de r t w o in te rro w a nd th re e in te rpl an t s pa ci ng s. r ow s pa ci ng 50 c m 10 0 cm c ha ra ct er in te rpl an t s pa ci ng c en ch ru s ci lia ri s l (l oc al ) c oe la ch yr um pi er ce i l (l oc al ) c hl or is g ay an a l. c v. k at am bo ra m ea n (i nt er -p la nt ) c en ch ru s ci lia ri s l (l oc al ) c oe la ch yr um pi er ce i l (l oc al ) c hl or is g ay an a l. c v. k at am bo ra m ea n (i nt er -p la nt ) pl an t s ta nd (% ) 25 c m 90 .9 66 .1 91 .0 82 .7 92 .0 74 .1 95 .9 87 .3 50 c m 89 .4 60 .9 89 .0 79 .8 91 .4 72 .3 94 .4 86 .0 10 0 cm 92 .1 72 .2 92 .0 85 .4 92 .2 80 .4 96 .9 89 .8 m ea n (g ra ss s pe ci es ) 90 .8 a 66 .4 b 90 .7 a 91 .9 b 75 .6 c 95 .7 a r ow m ea n 82 .6 b 87 .7 a pl an t h ei gh t ( cm ) 25 c m 10 4. 9 b 63 .8 c 10 2. 7 b 90 .5 11 5. 5 a 72 .0 d 99 .0 c 95 .5 50 c m 11 2. 8 a 62 .6 c 10 2. 0 b 92 .5 11 2. 6 a 71 .7 d 10 6. 7 b 97 .0 10 0 cm 11 3. 8 a 64 .5 c 10 4. 6 b 94 .3 11 5. 5 a 72 .7 d 10 6. 7 b 98 .3 m ea n (g ra ss s pe ci es ) 11 0. 5 a 63 .6 c 10 3. 1 b 11 4. 5 a 72 .1 c 10 4. 1 b r ow m ea n 92 .4 b 96 .9 a n um be r o f t ill er s/ p la nt 25 c m 10 9. 2 a 10 9. 0 a 75 .0 c 97 .7 a 99 .0 c 84 .0 d 10 4. 0 c 95 .7 c 50 c m 96 .1 b 96 .0 b 79 .0 c 90 .4 b 10 9. 0 bc 86 .0 d 10 9. 0 bc 10 1. 3 b 10 0 cm 98 .8 b 99 .0 b 76 .0 c 91 .3 b 12 6. 0 a 88 .0 d 11 5. 0 b 10 9. 7 a m ea n (g ra ss s pe ci es ) 10 1. 4 a 10 1. 3 a 76 .7 b 11 1. 3 a 86 .0 b 10 9. 3 a r ow m ea n 93 .1 b 10 2. 2 a n um be r o f p an ic le s/ pl an t 25 c m 63 .0 a 63 .4 a 43 .0 d 56 .5 a b 68 .0 d 57 .0 e 73 .0 c d 66 .0 c 50 c m 57 .0 b 57 .2 b 52 .0 c 55 .4 b 71 .0 d 67 .0 d 77 .0 c 71 .7 b 10 0 cm 63 .0 a 63 .3 a 50 .0 c 58 .8 a 90 .0 a 70 .0 d 83 .0 b 81 .0 a m ea n (g ra ss s pe ci es ) 61 .0 a 61 .3 a 48 .3 b 76 .3 a 64 .7 b 77 .7 a r ow m ea n 56 .9 b 72 .9 a se ed y ie ld (w ith h us k) (k g/ ha ) 25 c m 39 5. 5 b 18 2. 6 c 37 5. 6 b 31 7. 9 48 0. 1 ab 21 2. 2 e 46 5. 3 ab 38 5. 9 50 c m 37 9. 4 b 20 3. 0 c 39 1. 8 b 32 4. 8 39 8. 7 c 23 6. 1 e 47 0. 6 ab 36 8. 5 10 0 cm 37 7. 1 b 21 0. 2 c 44 9. 4 a 34 5. 6 44 9. 5 b 27 3. 6 d 48 7. 8 a 40 3. 7 m ea n (g ra ss s pe ci es ) 38 4. 0 19 8. 6 40 5. 6 44 2. 8 24 0. 6 47 4. 6 r ow m ea n 32 9. 4 b 38 6. 0 a fi gu re s w ith s im ila r o r a bs en ce o f l et te rs in c ol um ns a nd ro w s of e ac h ch ar ac te r a re n ot s ig ni fi ca nt ly d iff er en t a t p > 0. 05 .. 6 nadaf and others 7 effect of spacing on seed yield of indigenous rangeland and forage grass species grown under drip irrigation followed by cenchrus ciliaris that produced 377 kg/ha and 449 kg/ha, respectively, under both 50-cm and 100cm row-spacings (table 3). germination % table 4 shows germination percentage of bulk and selected seed samples of three grass species recorded after about five and twelve months of nine harvests along with relevant statistical parameters. the results indicated that the main effects all the factors, viz. harvests, seed type, time of test and grass species, effects of 2-factor interactions such as harvests x time of test, harvest x grass species and time of test x grass species and a 3-factor interaction viz. harvests x time of test x grass species, were highly significant (p<0.01). the results of germination reflect the quality of seed that could be produced in two kinds of harvest usually employed by seed growers: selective or bulk harvest. all three grass species showed very low germination % when tested immediately (1-2 weeks) after harvest not only for bulk seed (0 to 1.5%) but also for selected seed (0.8% to 2.8%). however, germination percentage was gradually improved further on storage at room temperature. this is evident by the fact that mean germination percentage of grass species recorded after 12 months of harvests was significantly (p<0.01) greater (52.62%) than that recorded after 5 months (33.67%) of harvests. this indicates that dormancy exists in freshly harvested grass seed, which gets broken down gradually depending upon the longevity of storage of seed. of the three grass species, cenchrus ciliaris recorded significantly (p<0.01) the highest germination % (49.68 %), followed by chloris gayana (41.05%) and coelachyrum piercei (38.71%). selected seed had significantly (p<0.01) higher germination % (53.21%) than bulk seed (33.08%) (table 4). lower germination percentage in bulk seed could be attributed to inclusion of immature seed of late formed panicles, possible loss of viable good quality seed due to shattering and possible loss of viability of a fraction of seed due to delay in harvesting the seed (nadaf et al., 2004). this is not unexpected, as harvesting good quality seed is a major problem faced by grass seed growers. grass seed growers often face substantial loss of good quality (viable) seeds while harvesting due to lack of knowledge about the appropriate harvesting time. it has been observed that some tropical grass species may produce good yields of seeds to the extent of 1000 kg/ha and above, but only a small proportion (perhaps 5-7% in setaria anceps) is commercially recoverable (chatterjee and das, 1989). in expanding the cultivation of perennial forage species, a limited supply of good seeds is an important constraint, which is also relevant to under-exploited indigenous rangeland pasture species. in developing better technology for seed production of pasture species, agronomic practices need to be devised which assist the seed producers to realize the yield potential of the rangeland pasture species. the results of the present investigation over nine harvests showed the significantly highest production of tillers in 25-cm spacing (98 tillers) as compared to others under 50cm row spacing, whereas the highest number of tillers was found in 100-cm inter-plant spacing (110 tillers). this was significantly different to the tillers produced in inter-plant spacings viz. 50-cm (101 tillers) and 25-cm (96 tillers). in respect of tillers, a high significant effect of 3-factor interaction was found involving grass species, row and plant spacings (tables 2 and 3). as a result, cenchrus ciliaris (109 tillers) and coelachyrum piercei (109 tillers) were found to produce significantly (p<0.05) more tillers in inter-plant spacing of 25 cm than in others under 50cm row-spacing where as cenchrus ciliaris produced the significantly (p<0.05) highest number of tillers (126) followed by chloris gayana (115) in inter-plant spacing of 100 cm as compared to others (table 3). number of panicles/plant the mean number of panicles over nine harvests in wider row-spacing (100-cm) was significantly (p<0.05) higher (73) than that (57) in narrow row-spacing (50-cm) (table 3). chloris gayana and cenchrus ciliaris produced significantly (p<0.05) more panicles to the extent of 78 and 76, respectively than coelachyrum piercei (65) under wider row-spacing (100-cm). on the other hand, cenchrus ciliaris (61) and coelachyrum piercei (61) produced significantly more panicles than chloris gayana under narrow row-spacing (50-cm). among the interplant spacings, grasses showed the significantly highest production of panicles in 100-cm spacing to the extent of 59 and 81 panicles, as compared to others, under 50cm and 100-cm row spacings, respectively. there was also a significant effect of 3-factor interaction involving grass species, row and plant spacings (tables 2 and 3). as a result, cenchrus ciliaris was found to produce significantly (p<0.05) more panicles (63) in both interplant spacings of 25-cm and 100-cm under 50-cm rowspacing, whereas cenchrus ciliaris produced significantly (p<0.05) more panicles (90), followed by chloris gayana (83), in inter-plant spacing of 100 cm, as compared to others (table 3). seed yield (with husk)/ ha mean seed yield of the grass species was significantly highest (386.0 kg/ha) in wider row spacing (100-cm) as compared to 329.4 kg/ha in narrow row-spacing. the seed yield of three grass species and the seed yield in three inter-plant spacings were found to be not significant (p>0.05) under both row-spacings (table 3) as 2-factor interaction effects involving row-spacing and grass species, and row-spacing and inter-plant spacing were not significant (p>0.05) (table 2). however, there were significant (p<0.05) effects of 3-factor interaction involving grass species, row and plant spacings (tables 2 and 3). as a result, chloris gayana was found to produce the significantly (p<0.05) highest seed yield in inter-plant spacing 100-cm to the extent of 449 kg/ha and 488 kg/ha, 6 nadaf and others 7 effect of spacing on seed yield of indigenous rangeland and forage grass species grown under drip irrigation table 4. mean germination % of bulk and selected seed samples of three grass species recorded after five and twelve months of nine harvests. harvests time of test (after) cenchrus ciliaris coelachyrum piercei chloris gayana mean over grass species bulk seed selected seed mean bulk seed selected seed mean bulk seed selected seed mean bulk seed selected seed mean i sept 01 5 mo 28.20 48.10 38.15 25.20 45.30 35.25 18.35 38.15 28.25 23.92 43.85 12 mo 58.27 78.27 68.27 43.27 63.27 53.27 37.37 57.37 47.37 46.30 66.30 mean 43.24 63.19 53.21 34.24 54.29 44.26 27.86 47.76 37.81 35.11 55.08 45.10 ii jan feb 02 5 mo 26.25 46.25 36.25 23.56 43.56 33.56 22.75 42.75 32.75 24.19 44.19 12 mo 49.35 69.35 59.35 34.33 54.33 44.33 48.66 68.66 58.66 44.11 64.11 mean 37.80 57.80 47.80 28.95 48.95 38.95 35.71 55.71 45.71 34.15 54.15 44.15 iii apr may 02 5 mo 31.21 51.11 41.16 26.32 46.15 36.24 21.35 41.33 31.34 26.29 46.20 12 mo 50.38 70.38 60.38 31.67 51.67 41.67 49.33 69.33 59.33 43.79 63.79 mean 40.80 60.75 50.77 29.00 48.91 38.95 35.34 55.33 45.34 35.04 55.00 44.02 iv jul aug 02 5 mo 27.25 47.13 37.19 19.35 39.22 29.29 17.36 37.31 27.34 21.32 41.22 12 mo 61.32 81.32 71.32 28.13 48.13 38.13 40.67 60.67 50.67 43.37 63.37 mean 44.29 64.23 54.26 23.74 43.68 33.71 29.02 48.99 39.00 32.35 52.30 42.33 v oct nov 02 5 mo 26.75 46.33 36.54 24.36 44.15 34.26 19.25 39.27 29.26 23.45 43.25 12 mo 52.67 72.67 62.67 39.19 59.19 49.19 38.33 58.33 48.33 43.40 63.40 mean 39.71 59.50 49.61 31.78 51.67 41.72 28.79 48.80 38.80 33.43 53.32 43.38 vi jan feb 03 5 mo 29.05 49.20 39.13 22.58 42.41 32.50 22.55 42.15 32.35 24.73 44.59 12 mo 48.32 68.32 58.32 35.13 55.13 45.13 43.79 63.79 53.79 42.41 62.41 mean 38.69 58.76 48.72 28.86 48.77 38.81 33.17 52.97 43.07 33.57 53.50 43.54 vii apr may 03 5 mo 28.75 48.53 38.64 24.62 44.15 34.39 20.36 40.33 30.35 24.58 44.34 12 mo 37.93 67.93 52.93 28.33 48.33 38.33 39.33 59.33 49.33 35.20 58.53 mean 33.34 58.23 45.79 26.48 46.24 36.36 29.85 49.83 39.84 29.89 51.43 40.66 viii july aug 03 5 mo 24.26 44.15 34.21 18.79 38.24 28.52 19.33 39.46 29.40 20.79 40.62 12 mo 52.68 72.68 62.68 27.17 47.17 37.17 37.69 57.69 47.69 39.18 59.18 mean 38.47 58.42 48.44 22.98 42.71 32.84 28.51 48.58 38.54 29.99 49.90 39.95 ix oct nov 03 5 mo 27.02 47.08 37.05 23.99 43.63 33.81 22.03 42.14 32.09 24.35 44.28 12 mo 49.98 69.98 59.98 41.79 61.79 51.79 40.67 60.67 50.67 44.15 64.15 mean 38.50 58.53 48.52 32.89 52.71 42.80 31.35 51.41 41.38 34.25 54.22 44.24 mean over harvests 5 mo 27.64 47.54 37.59 23.20 42.98 33.09 20.37 40.32 30.35 23.73 43.61 33.67 12 mo 51.21 72.32 61.77 34.33 54.33 44.33 41.76 61.76 51.76 42.44 62.81 52.63 mean 49.68 38.21 41.05 33.08 53.21 statistical parameters: f-test lsd (at 5% level) f-test lsd (at 5% level) harvests ** 1.67 harvests x grass species ** 2.90 seed type ** 0.79 seed type x grass species ns harvests x seed type ns harvests x seed type x grass species ns time of test ** 0.79 time of test x grass species ** 1.36 harvests x time of test ** 2.36 harvests x time of test x grass species ** 4.09 seed type x time of test ns seed type x time of test x grass species ns harvests x seed type x time of test ns harvests x seed type x time of test x grass species ns grass species ** 0.96 cv (%) 8.38 8 nadaf and others chatterjee, b.n. and p.k. das. 1989. forage crop production principles and practices. oxford and ibh pub. co. pvt. ltd. new delhi. 450p. evans, g. 1959. seed rates of grasses for seed production. pasture varieties of rye grass, cocksfoot and timothy. empirical journal of experimental agriculture 27:291. evans, g. 1962. seed rates of grasses for seed production. ii. breed varieties of tall fescue, meadow fescue, cocksfoot (hey type), and phalaris hybrid. empirical journal of experimental agriculture 30:181. gomez, k.a. and a.a. gomez. 1984. statistical procedures for agricultural research. second edition. the international rice research institute, philippines. humphreys, i.r. 1978. tropical pasture seed production. fao plant production and protection paper. food and agriculture organization of the united nations. rome. pp 39-42. lambert, d.a. 1963. the influence of density and nitrogen in seed production stands of s37 cocksfoot (dactylis glomerata l.). journal of agricultural science 61:361. loch, d.s. and m. clark. 2000. production, harvesting and processing of native grass and herbaceous legume seeds: the reality and the challenge. first regional technical coordination meeting (rtcm). aprp phase ii. dubai, uae. 16-18 october 2000. nadaf, s.k., s.m. al-farsi and s.a. al-hinai. 2004. seed multiplication of rangeland forage species in the sultanate of oman. seed information 27:12-14. owen, c.r. 1951. improvement of native dallies grass in louisiana. louisiana agri. exp.sta. bull. 449:24. peacock, j.m., m.e. ferguson, g.a. alhadrami, i.r. mccann, a. al hajoj, a. saleh and r. karnik. 2000. conservation through utilization a case study of the indigenous forage grasses of the arabian peninsula. paper presented at the international conference on the conservation of biodiversity in the arid regions. kuwait. march 27-29, 2000. shelton, h.m. and l.r. humhreys. 1971. effect of variation in density and phosphate supply on seed production of stylosanthes humilis. journal of agricultural science, cambridge, 76:325-336. skerman, p.j. and f. riveros. 1989. tropical grasses. fao plant production and protection series, no. 23. pp 266-274 and 283-288. young iii, w.c., h.w. youngberg and t.b. silberstein. 1998. management studies on seed production of turftype tall fescue: ii. seed yield components. agronomy journal 90:478-483. received: march 2005 accepted: may 2007 indicate that the grass species behave differentially for their optimum performance in varying inter-row and inter-plant spacing. this is particularly true for seed yield (table 3). wider inter-row spacing significantly (p<0.05) influenced formation of more panicles and higher seed yield, irrespective of grass species (table 3). chatterjee and das (1989) also speculated that in grass species like cenchrus ciliaris, seed crop sown in wider spacing produces greater seed yield. in the case of perennial pasture species, low plant density at establishment results in higher plant densities later on. the low plant density in the beginning would lead to high percentage fertility of tillers as each hill of grass has less or an absence of interplant competition (chatterjee and das, 1989 and young iii et al., 1998). in the present study, cenchrus ciliaris and rhodes grass (chloris gayana), exhibited varying seed yields in the two inter-row spacings in most of the harvests, perhaps due to differential response of species to inter-plant competition. conversely, boonman (1972) observed that seed yield was independent of row spacing in chloris gayana cv. mbarara. in the perennial pastures, however, optimum plant density and row spacing are influenced by plant cultivar, soil fertility, moisture supply and age of plant stand. the seed yield (with husk) levels of chloris gayana and cenchrus ciliaris found in the present study are comparable with the seed yield levels reported elsewhere. skerman and rivoros (1989) reported clean (naked) seed yield of 100-650 and 10-60 kg/ha in respect of chloris gayana and cenchrus ciliaris, respectively, and chatterjee and das (1989) reported seed yield (naked) of 500 to 600 and 100-200 kg/ha in respect of chloris gayana and cenchrus ciliaris, respectively. acknowledgements we are grateful to the director general of agriculture and livestock research and director of plant production research center, for their assistance and encouragement in conducting experiments. aprp-icarda is gratefully acknowledged for financial and technical assistance. references agrawal, r.l. 1980. seed technology. oxford and ibh pub. co., 449-474. boonman, j.g. 1972. in : chatterjee, b.n. and p.k. das. 1989. forage crop production principles and practices. oxford and ibh pub. co. pvt. ltd. new delhi. 450p. research paper journal of agricultural and marine sciences vol. 20 (2015): 62-65. reveived 5 aug. 2014 accepted 19 feb 2014 improving the quality of tiger shrimp penaeus monodon through dietary incorporation of algae as a source of natural pigment kunal mondal*, subhra bikash bhattacharyya and abhijit mitra * department of marine science, university of calcutta, 35 b.c. road, kolkata 700019, india . kunal mondal ( ) email: bottu.marine@ gmail.com. introduction inclusion of algae as dietary supplement in animals have been investigated previously as a source of pigment (strand et al., 1998). the effects of dietary inclusion of algae have resulted in improved performance including better animal product quality (moss, 1994; penaflorida and golez, 1996; cruz-suarez et al., 2000). to be more specific the commercial production of shrimps and prawns as an edible food product represents one of the fastest growing areas of aquaculture (rosenberry, 2005) with high consumer appeal and attractive market for shrimps due to their body colouration or pigmentation which is a direct measure of its astaxanthin content. carotenoid utilization by aquaculture species is well documented as it plays a regulatory role in providing antioxidant and pro-vitamin a activity, enhancing immune response, improving reproductive performance, growth, maturation and photo-protection (howell and matthews, 1991). they also help the species to resist environmental stress (meyers, 1994). algae and higher groups of plants are the major producers of carotenoids which comprises a family of over 600 natural fat soluble pigments (britton et al., 1981). studies reveal that alternative utilization of plant pigments in formulated diets have improved the body pigmentation حتسني نوعية روبيان النمر )penaeus monodon( إبستخدام الطحلب كمصدر طبيعي للصبغة يف الغذاء كونال موندال* وسوفرا بيكاش باتاشاريا وأهبيجيت ميرتا abstract. tiger shrimp is one of the major candidate species for export oriented aquaculture which dominates the seafood market in regions of european union, japan and usa. carotenoid content in seafood has now become one of the important criteria in determining the quality of edible product. recent trends in supplementing fish diets with natural pigment source are an alternative to the utilization of expensive synthetic pigments. in this context, green algae enteromorpha intestinalis was selected as a source of natural pigment for inclusion in the diet of tiger shrimp penaeus monodon. astaxanthin being an important category of carotenoid pigment was monitored in shrimp muscle tissue during the feeding trial. significant variation (p<0.05) was observed between the experimental groups as confirmed through anova thus exhibiting higher astaxanthin content of shrimps (18.70 ± 4.48 ppm) fed with e. intestinalis incorporated diet as compared to control (15.80 ± 2.33 ppm). the present programme therefore emphasizes on the quality improvement of aquaculture product by dietary inclusion of algae as a natural pigment source. keywords: shrimp; aquaculture, feed, algae, pigment. املســتخلص: يعتــر روبيــان النمــر أحــد أهــم األنــواع املســتزرعة للتصديــر الــي هتيمــن علــى ســوق املأكــوالت البحريــة يف مناطــق االحتــاد األورويب واليابــان والواليــات املتحــدة األمريكيــة، وحاليــاً يعتــر حمتــوى الكاروتــن )carotenoid( املوجــود يف املأكــوالت البحريــة أحــد أهــم املعايــر املســتخدمة يف حتديــد جــودة املنتجــات الصاحلــة لالســتهالك. ويتــم التوجــه حاليــاً الســتخدام الصبغــات الطبيعيــة كبديــل للصبغــات االصطناعيــة عاليــة التكلفــة املســتخدمة يف الغــذاء الســمكي، ويف هــذا الســياق مت اختيــار الطحلــب األخضــر )enteromorpha intestinalis( كمصــدر طبيعــي للصبغــة إلدراجهــا يف الغــذاء املســتخدم لروبيــان النمــر )penaeus monodon(. متــت متابعــة نســبة األستاكســانثن )astaxanthin( والــذي يعتــر أحــد اهــم فئــات الكاريتينويــد )carotenoid( يف األنســجة العضليــة للروبيــان خــالل جتــارب التغذيــة، وقــد لوحــظ وجــود اختــالف هــام )p >0.05( بــن اجملموعــات التجريبيــة كمــا أثبتــه اختبــار حتليــل التبايــن )anova( والــذي يظهــر وجــود حمتويــات أعلــى لـــ astaxanthin )18.70 ± 4.48 جــزء يف املليــون( يف الروبيــان الــذي تغــذى علــى وجبــات حتتــوي علــى e. intestinalis مقارنــة مــع الروبيــان املتحكــم يف غذائــه )15.80 ± 2.33 جــزء يف املليــون(، وبالتــايل فــإن الرنامــج الــذي مت اســتخدامه يثبــت حتســن جــودة منتجــات الكائنــات البحريــة املســتزرعة مــن خــالل إدراج الطحالــب كمصــدر طبيعــي للصبغــة يف غذائهــا. الكلمات املفتاحية: الربيان، االستزراع السمكي، أعالف األحياء املائية، الطحالب، الصبغة 63research article mondal, bhattacharyya, mitra of farmed crustaceans, particularly penaeids in order to achieve better market price (lorenz, 1998; liao and chien, 1994). therefore the present work is an attempt to utilize enteromorpha intestinalis as a natural dietary pigment source for farmed tiger shrimp (penaeus monodon) in relation to its quality improvement. materials and methods collection of algae and preparation of experimental diets live and healthy algae enteromorpha intestinalis was collected from bali island (22º 04´ 35.17˝ n latitude and 88º 44´ 55.70˝ e longitude) of indian sundarbans during low tide. the collected material was rinsed in ambient water and then with distilled water, oven-dried at 50ºc and finally processed to make powder. experimental diet was formulated through incorporation of algae (dietent) at a level of 5%. simultaneously a control diet (dietc) was also formulated to study the comparative performance (table 1). feeding trial a feeding trial was run at bali island (22º04´ 35.17˝n latitude and 88º 44´ 55.70˝ e longitude) of sundarbans in grow-out ponds for 90 days of experimental duration (fig. 1). shrimp juveniles were procured from hatchery and stocked in experimental ponds at a density of 2 individuals/m2. experimental diets were randomly assigned, the culture species were fed twice daily and the uneaten feed was checked at regular intervals. astaxanthin analysis the astaxanthin content in shrimp muscle tissue was analyzed according to the spectrophotometric method outlined by schuep and schierle (1995). its value in % was converted to ppm level for easy interpretation of data. the body colouration of shrimps after boiling was compared by roche salmofantm colour score. statistical analysis the collected data were finally subjected to one-way analysis of variance (anova). all statistical calculations were performed with spss 9.0 for windows. results and discussion the average astaxanthin content in muscle tissue was higher in shrimps fed with dietent as compared to dietc (table 2). a darker orange-red colouration was observed in shrimps fed with dietent after boiling them in water for 5 minutes when compared with roche salmofantm colour score. the colour score was 30 for dietent fed shrimps whereas a score of 27 was recorded from shrimps fed with dietc. anova results showed significant variation (p<0.05) in average astaxanthin content which may be attributed to the capability of p. monodon to easily convert the fraction of algal astaxanthin into tissue astaxanthin. the enteromorpha figure 1. map showing the p. monodon farming site at bali island of indian sundarbans. table 1. formulation of experimental diets. ingredients diet control diet enteromorpha fish meal 35 30 soybean oil cake 11 11 mustard oil cake 11 11 rice polish 23 23 wheat flour 16 16 oyster shell dust 2 2 shark oil 2 2 enteromorpha intestinalis (source of astaxanthin) 0 5 table 2. variations in astaxanthin content of p. monodon (ppm muscle tissue) fed with experimental diets. days of culture (doc) diet control diet enteromorpha 0 12.83 ± 0.22 13.02 ± 0.27 30 15.21 ± 0.22 17.62 ± 0.55 60 16.96 ± 0.53 20.71 ± 0.76 90 18.22 ± 1.23 23.47 ± 1.31 average 15.80 ± 2.33b 18.70 ± 4.48a *means with different letters(a,b) in a row differ significantly (p<0.05); values are means of three replicates 64 squ journal of agricultural and marine sciences, 2015, volume 19, issue 1 improving shrimp quality through dietary incorporation of natural algal astaxanthin sample selected for the investigation is found to contain 120.78 ppm astaxanthin as reported from the present study region (mitra et al., 2013; banerjee et al., 2009; chakraborty and santra, 2008). carotenoid, particularly astaxanthin content of feed is one of the major factors influencing the colour development in animals (moretti et al., 2006) but at the same time scientific knowledge about several factors like dietary pigment source, their dosage level, feeding duration, dietary composition and magnitude of carotenoid esterification is also required to identify these interaction processes (meyers and latscha, 1997; bjerkeng, 2000; buttle et al., 2001; gomes et al., 2002; white et al., 2002). the present study showed significantly different astaxanthin content of the farmed shrimp which are in agreement to the observations that crustaceans exhibit strong tendency towards selection of specific carotenoids at a specific rate for their metabolic absorption (meyers and latscha, 1997). similar work conducted from the present study region reveal that p. monodon when fed with diet containing red algae catenella repens at a level of 5% improved the body astaxanthin content (banerjee et al., 2010). the search for natural astaxanthin was not only limited to the algal resources, rather salt-marsh grass porteresia coarctata was also tested as a natural dietary astaxanthin source in p. monodon feed with better results from the present geographical locale (mitra et al., 2011, 2013). in continuation such natural carotenoid supply to the diet of shrimps has been studied for p. japonicus and litopenaeus vannamei too from different parts of the globe. the ingredients of natural origin that have been used in the diet are red yeast (phaffia rhodozyma) and microalgae dunaliella salina (chien and jeng, 1992); chnoospora minima (menasveta et al., 1993); spirulina sp. (liao et al., 1993; chien and shiau, 1998); haematococcus pluvialis (chien and shiau, 1998) and isochrysis galbana (pan et al., 2001). an usual trend of marked increase in the body carotenoid content has been observed when organisms were fed with plant pigment source diets. for example, feed supplemented with 50 ppm algal material (dunaliella salina) improved the body colouration of p. monodon (boonyaratpalin et al., 2001). three types of diet when provided to p. semisulcatus containing natural carotenoid sources like red pepper and marigold flower resulted in higher carotenoid accumulation in body tissues (gocer et al., 2006). however research findings from mexico also reported that feed incorporated with cultivated green alga ulva clathrata significantly improved the body pigmentation of farmed shrimp l. vannamei (cruz-suarez et al., 2009). conclusions improved product quality of farmed p. monodon clearly reflects the transforming potential of algal astaxanthin into the body tissues 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effect of esterification on the absorption of astaxanthin in rainbow trout, oncorhynchus mykiss (walbaum). aquaculture research 33: 343-350. research paper journal of agricultural and marine sciences vol. 20 (2015): 34-39 reveived 6 mar. 2014 accepted 19 feb. 2015 natural glues and fouling management by interfering with glue curing daniel rittschof 1 *, tara essock-burns1, gary dickinson2, s. zmina1 and n. alberman1 * university marine laboratory, beaufort nc 28516, usa. daniel rittschoff ( ) email: ritt@duke.edu 2 department of biology, the college of new jersey، 2000 pennington road, ewing, nj 08628-0718 ,usa. introduction this paper considers barnacle biology and adhe-sion; silicone disruption and the potential im-pacts of silicones as a fouling management tool. we begin with a review of barnacle biology and our املواد الغروية الطبيعية وإدارة الرتاكم احليوي على األسطح املغمورة من خالل التدخل يف تصلب الغراء دانيال ريتشوف1* وتارا إسوك-بارنز1 وقاري ديكنسون2 و س. زمينا1 و ن. ألربمان1 abstract. multidisciplinary approaches and modern technology provide insights to glue curing that are stimulating and controversial. our team applies classic and modern theory and techniques to the study of barnacle glue. techniques include physical measures, bacteriology, behavior, physiology, biochemistry, microscopy, spectroscopy, tomog raphy, tandem mass spectrometry, molecular biology and proteomics. theory is grounded in evolution and previous literature. here, we use data from these techniques to support the hypothesis that barnacle glue curing is similar to blood clotting and propose a model for how glue cures. similar to blood clotting, barnacle glue curing involves en zymatic activation of precursors and rearrangement of structural molecules to form a crosslinked material. barnacle larval settlement, bacteriology and biochemical data show glue contains large amounts of small peptides. their role in glue curing has been overlooked. the peptides comprise 15 to 30% of partially cured glue. because they have little secondary structure, the peptides can associate with binding domains on the substrate and interface with the larger, well-described structural proteins known in barnacle glue. enzymes participate in curing of barnacle glue. siloxanes impact glue-curing enzymes. they potentiate trypsin activity and inhibit transglutaminase activity. changing enzyme activity impacts how glue cures. disrupting the curing process of biological glues is central to effective cleaning strate gies for fouling management. thus silicones that interfere with enzyme activity have potential as additives in easy clean surfaces. the environmental impacts of organosilicones that are generated by biological processes need to be addressed keywords: barnacle; glue; silicone; fouling املســتخلص: توفــر التوجهــات متعــددة التخصصــات والتقنيــة احلديثــة فهمــا عميقــا وحمفــزا وجدليــا ملوضــوع تصلــب الغــراء. ولقــد قــام فريقنــا بتطبيــق النظريــات والتقنيــات الكالســيكية واحلديثــة لدراســة غــراء قشــريات النــو )تســمى الصــي يف عمــان( ومشلــت هــذه التقنيــات القياســات الفيزيائيــة وعلــم البكريــا وعلــم الســلوك و الفســيولوجيا والكيميــاء احليويــة وعلــم اجملهــر والتحليــل الطيفــي والرســم املقطعــي وقيــاس الطيــف الكتلــي الــراديف والبيولوجيــا اجلزيئيــة وعلــم الربوتينــات، وأمــا النظريــات فقــد اســتندت إىل نظريــة التطــور والبحــوث الســابقة. وقــد اســتخدمنا هنــا بيانــات مــن التقنيــات املذكــورة آنفــا لدعــم نظريــة أن تصلــب غــراء قشــريات النــو يشــبه ختثــر الــدم، ولوضــع منــوذج لكيفيــة حــدوث هــذا التصلــب. وبالتشــابه مــع ختثــر الــدم، يتطلــب تصلــب غــراء قشــريات النــو تنشــيطا إنزمييــا للمــواد األوليــة وإعــادة ترتيــب للجزيئــات اهليكليــة لتكويــن مــادة متقاطعــة الرابــط. وتظهــر عمليــة اســتقرار يرقــات قشــريات النــو والبيانــات البكريــة والكيميائيــة احليويــة أن غــراء هــذه الكائنــات حيتــوي علــى كميــات كبــرة مــن الببتيــدات الصغــرة الــي مت إغفــال دورهــا يف تصلــب الغــراء، وهــذه الببتيــدات تؤلــف 15 إىل 30 % مــن الغــراء املتصلــب بشــكل جزئــي. وبســبب أن هياكلهــا الثانويــة قليلــة، فــإن هــذه الببتيــدات ميكــن أن تقــرن مبناطــق االرتبــاط علــى الســطح وتتحــد مــع الربوتينــات اهليكليــة األكــرب واملعروفــة يف غــراء قشــريات النــو. أمــا االنزميــات فتشــارك يف عمليــة تصلــب غــراء هــذه الكائنــات. وتقــوم السيلوكســينات بالتأثــر علــى األنزميــات املؤديــة إىل تصلــب الغــراء، حيــث أهنــا حتفــز نشــاط الريبســن وتثبــط نشــاط الرانســغلوتامينيز. ويؤثــر التغــر يف نشــاط األنزميــات علــى كيفيــة تصلــب الغــراء. ويعتــرب تعطيــل عمليــة التصلــب للغــراءات احليويــة عامــال مركزيــا يف اســراتيجيات التنظيــف ألجــل إدارة الراكــم احليــوي علــى األســطح املغمــورة. لذلــك هنــاك إمكانيــة الســتخدام املــواد الســيليكونية الــي تتدخــل يف النشــاط األنزميــي كمــواد يف األســطح ســهلة التنظيــف. وســيكون مــن الضــروري اإللتفــات إىل التأثــرات البيئيــة للمــواد الســيليكونية العضويــة الــذي تتولــد عــن طريــق العمليــات احليويــة. الكلمات املفتاحية: قشريات النو )الصي( ، الغراء، السيليكون ، الراكم احليوي على األسطح املغمورة. work on barnacle glue. there is a much more extensive body of work by many other researchers over the last 50 years that provides the context for our contribution. here we acknowledge their major contributions by listing the names of at least one member of each group. they include d. crisp, graham walker, p.j. cheung, g.c. walker, a. yule, larman, gabbott, k. kamino, j. r. saroyan, e. lindner, c.a. dooley, e. holm, d. wendt, p. gateholm, g. swain, e. singer, a. s. clare, c. wang, r. stewart and our research colleagues, k. wahl, d, barlow and d. burden. it is in the context of this larger body of 35research article rittschof, essock-burns, dickinson, zmina, alberman literature that our studies are conducted. next, we review what is known of silicones (polydimethyl siloxanes, pdms) as foul release surfaces and show that barnacle glue cures incompletely on silicones. using pure enzymes, we support the hypothesis that incomplete glue curing is due to alteration of trypsin and transglutaminase enzyme activities by molecules leaching from silicones. polydimethyl siloxane (pdms) is a central component in most foul-release coatings. pdms films have a large amount of space within the polymer, which can be loaded with small molecular weight silicone oils (d4 and d5). these low water solubility oils migrate to the surface of the films and can diffuse into natural glues disrupting enzyme activity (rittschof et al., 2011). finally, we discuss studies of the effects of molecules leaching from commercial silicones (iphone covers and medical grade silicone) on invertebrate and vertebrate embryo development. the impact on embryo development suggests that we should look carefully at potential environmental impacts of silicone leachates. barnacle biology and glue curing the discussion and simple model that follow need to be reconciled with the larger body of knowledge about barnacle glue and other biological adhesives as well as with the reality of how a barnacle grows. we began the reconciliation by watching barnacles grow with timelapse videos that show growth and morphology in the baseplate. the two short videos are time-lapse videos of the process (supplemental information in burden et al., 2012). this first video shows growth of the margin of a rapidly growing juvenile barnacle. the bright areas within the barnacle are regions of active calcification. the very edge is calcification of a lateral plate. the bright spikes about 200 microns from the edge are parts of the calcifying base plate. the edge and base grow continuously when viewed in 30-minute time lapse. the second video is imaging of growth using timelapse epifluorescence microscopy. although it cannot be seen in the video, we know that a non-fluorescent “glue” is present under the entire baseplate and at the edge of calcification. as the barnacle grows, detritus figure 1. the bricks and mortar model of barnacle glue curing. we call the model bricks and mortar because the present hypothesis is the structural proteins with their secondary and tertiary structure are analogous to bricks, the peptides which have no secondary structure are mortar, the proteolytic are enzymes are activating and the transglutaminase and oxidases cure cement the bricks and mortar and substrate together. interestingly, peptides that escape crosslinking function as pheromones for barnacle settlement, and predatory snail and bacterial chemoattractants. 36 squ journal of agricultural and marine sciences, 2015, volume 19, issue 1 natural glues and fouling management by interfering with glue curing on the surface moves toward the periphery. this video shows that there is a second highly fluorescent episodic deposition through channels that appear intermittently. the next panel shows the less fluorescent glue in the top panel and then the second fluorescent glue in the bottom panel. we hypothesize the second episodic glue deposition is related to the molt cycle, which is consistent with older literature (crisp and bourget, 1985). finally, the next short video is a tomographic image of the side and base plates of a living barnacle grown on a transparent surface. one can see that there are uncalcified and calcified regions in the base plate and can see the well known concentric growth ring structure. we will test the hypothesis that the second fluorescent solution is important to calcification. as growth slows down and the barnacle continues to molt, the calcification becomes continuous. we developed hypotheses about barnacle glue curing based on barnacle morphology. from the literature and light microscopy of living barnacles with vital stains we saw that living tissues are found in the channels, calcified base plate and parietal plates (gohad et al. 2009) x-ray tomography showed the channels and living spaces in the plates are very extensive (wahl et al., 2011). to feed these tissue cells and remove waste the barnacle must be able to circulate the equivalent of a blood. bourget and others reported that barnacle cuticle often tore as it expanded (bourget and crisp, 1975; crisp and bourget, 1985). damage to the cells or plates should cause bleeding. since barnacles rip their cuticle when they molt and other crustaceans such as lobster, crayfish and crabs, routinely bleed when they molt this seems a reasonable hypothesis. hardening cuticle following molt is necessary in all crustaceans and leaking of hemolymph is inherent in this process (terwilliger, 1999). we hypothesized that as blood and hemolymph clot (cure) in aqueous solution that barnacle glue curing could be a form of blood clotting or wound healing as seen in other crustaceans (söderhäll and cerenius, 1998; wang et al., 2001; theopold et al., 2004; tassanakajon et al., 2013). we set out to falsify our hypothesis that barnacle glue curing was a form of wound healing. after 5 years of research, we concluded that the hypothesis was strongly supported by every experiment (dickinson et al., 2009). wahl’s laboratory at the us naval research lab has subsequently further substantiated and expanded the hypothesis (barlow et al., 2010; wahl et al., 2011; burden et al., 2012, 2014). the new factual expansion is that there are two separate secretions that are barnacle glue. one has no apparent duct structure and is presumably blood delivered through tears in the cuticle when it stretches, as the barnacle grows. the other glue secretion is essentially a spot weld a distance many microns from the glued edge of the expanding plate. the second glue is delivered through capillaries and ducts associated with the molt, which were first reported well over a century ago (wahl et al., 2011). barnacles are cyclical animals, growing, molting and reproducing throughout their lives. the timing of these events is critical to understand aspects of adhesion. barnacle glue like most other marine glues, but unlike most man made adhesives, forms adhesive bonds and cures in water. early workers implicated quinone cross-linking as part of glue curing (lindner and dooley, 1974). unlike other well-studied glues, mussel glue (waite, 1987) and sand castle worm glue (wang & stewart, 2011, 2013), barnacle glue is not rich in l-dopa but may perform quinone cross-linking through modification of tyrosines (lindner and dooley, 1984). barnacle glue is mainly protein and studies starting with cured glue show the glue is never completely solubilized (kamino et al., 2006). kamino and coworkers (2006, 2008) have identified and sequenced a set of structural proteins that are major components of glue. we, and others, are working to understand the assembly of these glue components as they relate to barnacle development and growth. barnacle glues are related to wound healing in that coagulation is enzymatically driven. trypsin-like enzyme activity activates pro-forms of structural proteins, as well as additional serine proteases and crosslinking enzymes (dickinson et al., 2009). as with trypsin-like enzymes we found with western blots there is specific binding by antibodies to the crosslinking enzyme, transglutaminase. there is substrate specific transglutaminase activity in curing barnacle glue/blood and specific chemical derivatives followed by acid hydrolysis show about 4% cross-linking in cured barnacle glue. hyaline cells (similar to platelets in blood) are hemocytes that appear to rupture and appear to be the source of the transglutaminase. molecules like heparin that prevent blood clotting and interfere with transglutaminase activity reduce adhesion strength of reattached barnacles. at present we are tracking down antimicrobial, cross-linking, and reactive oxygen species (ros). in order to understand the transition from glue curing to calcification, collaborators are probing the roles of kinases and phosphoproteins in the glues. we have preliminary data indicating that there are oxidases and peroxidases as well as ros associated with the growing edge of the barnacle baseplate (dickinson et al., 2009). the model below synthesizes all that we know about the role of enzymes, peptides and proteins in glue curing (fig. 1). this model is based upon our work with glues that contain variable amounts of both barnacle cement secretions, bcs1+ bcs2 (burden et al., 2012). silicones and foul release the “baier adhesive minimum” (baier, 1970), is a surface energy range where biological glues stick most poorly. at the baier minimum it is difficult to exclude water, essential for adhesive bond formation (waite, 2002). at the minimum there is little opportunity for 37research article rittschof, essock-burns, dickinson, zmina, alberman strong ionic bonds or covalent bonds. the surface energy is characterized by mixed, weak van der waals and weak hydrogen bonding as in the siloxane molecules, d4 and d5 (molecules 1 and 2). siloxane films like pdms (molecule 3) have the surface energy of baier’s adhesive minimum. pdms was the lining of barnie clark’s artificial heart and has been studied for decades because of its foul release properties. interestingly, monolayers of siloxane molecule generated by silane technology have the same critical surface energy, but are not as effective at reducing adhesion of natural glues. it has been hypothesized that the low modulus of pdms film enables adhesive failure. the hypothesis is supported experimentally (brady and singer, 2000). as glue curing is related to blood clotting we looked for impacts of pdms like molecules on blood clotting and found a patent from the 1950s, which claimed that dimethyl silane multilayers interfered with blood clotting in glass tubes. in the 1990s swain’s group at florida institute of technology did extensive studies on barnacle adhesion to pdms films (kavanagh et al., 2005). studying fracture mechanics of barnacle release from pdms films they noticed what they described as a “viscous sublayer” (fig. 2, http://www.youtube.com/fwlhge3ft-i). in essence, the barnacle was floating on a thin layer of liquid glue. our group looked at that video, along with the patent on dimethyl silane interruption of blood clotting and hypothesized that molecules leaching out of the surfaces into the biological glues were interfering with curing much as two part epoxy cures incorrectly when mixed in the wrong proportions in our studies of liquid glue. because we found enzymes, we looked to see if molecules on the surface of silicones would alter enzyme activity. we found that molecules leach out of silicones (fig. 3) and that those molecules alter the activity of at least trypsin and transglutaminase enzymes (rittschof et al., 2011). interestingly, although the impacts on barnacle glues include differences in morphology and adhesion strength between individual barnacles and between different specific silicone films, the general effect (as shown in figure 2), is that molecules leaching out of silicones enhance trypsin like proteolytic activity and inhibit crosslinking by transglutaminase (rittschof et al., 2011). the result is more small peptides, fewer intact glue proteins and less crosslinking. all effects are consistent with generation of the viscous sublayer observed in the florida institute of technology high-speed video of barnacle detachment (fig. 2). this finding is exciting because it provides a mechanism for disrupting the curing of biological adhesives using additives to pdms and other polymers. although pdms and other soft coatings might not be appropriate for a hull or propeller/impeller coating, these coatings could be used where soft coatings would be tolerated such as sensor coatings and coatings that could be cleaned by a water jet rather than a brush. brushing a soft coating is not a good idea because many attached foulers have calcareous shells, which act as an abrasive and cut into the coating during brushing. silicone leachates and organismal impacts we discovered during the silicone work that a non-chemical catalyst was conjugating silicone molecules to a steroid (fig. 3). we hypothesize the catalyst was microbial metabolism of silicone compounds (rittschof et al., 2011). knowing that molecules leaching out of silicone alter enzyme activities prompted the question if complex biological systems are impacted by silicone leachates. as embryo development is a very sensitive assay, we chose to test development of an invertebrate, sea urchin embryos, and a vertebrate, japanese medaka fish embryos (feng and rittschof, 2011). in the first series of experiments we tested foul release coatings and model systems. when that series indicated urchin and fish development were impacted, we moved to more figure 2. the viscous layer of glue underneath a barnacle attached to silicone (modified from kavanagh et al., 2005). 38 squ journal of agricultural and marine sciences, 2015, volume 19, issue 1 natural glues and fouling management by interfering with glue curing general silicone surfaces and pure molecules. in that series of experiments we used medaka embryos and tested medical grade silicone, silicone iphone covers, silicone coffee lids and pure small silicones d4 and d5 (molecules 1 and 2). for invertebrate and vertebrate toxicology experiments we used a cork borer and cut circles of silicone that fit snugly in the bottom of 24 well polystyrene plates. we added 2 milliliters of nih embryo rearing medium to each well and then each well received one pre-gastrula developing medaka egg. each treatment had 30 replicates. for the small silicone monomers we did a dilution series of d4 silicone (3.0 mg/ml and 0.3 mg/ml) in glass scintillation vials. in plate assay and vial assays the embryos were maintained and 25°c photographed daily and the water was changed every two days. we were surprised that all treatments had an effect on medaka embryo development. exposing the embryos to silicones reduced mortality presumably due to microbiocidal activity of the leachates in the static conditions. another consistent impact was the inability of hatched embryos in experimental treatments to inflate their swim bladders. finally, seen occasionally in the experimental treatments and never in the controls were developmental abnormalities including lack of development of a head, circulatory system disorders, small eyes and only one eye (fig. 4). the total impact of these treatments is the subject of a manuscript being prepared for submission in a toxicology journal. all technology has positive and negative impacts. our ultimate goal is to maximize the positive impacts while minimizing the negative impacts. often, the negative impacts only become apparent when a particular technology gains market share or societal acceptance. as a consequence, rather than proactive solutions, society is forced into reactive solutions. we suggest that the rational way forward is to begin any development process by including studies that 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comparative biology, 42: 1172-1180. wang, c. s., and r. j. stewart. 2011. localization of the bioadhesive precursors of the sandcastle worm, phragmatopoma californica (fewkes). journal of experimental biology, 215(2): 351-361. wang, c. s., and r. j. stewart. 2013. multipart copolyelectrolyte adhesive of the sandcastle worm, phragmatopoma californica (fewkes): catechol oxidase catalyzed curing through peptidyl-dopa. biomacromolecules, 14(5): 1607–1617. wang, r., s. y. lee, l. cerenius, and k. söderhäll. 2001. properties of the prophenoloxidase activating enzyme of the freshwater crayfish, pacifastacus leniusculus. european journal of biochemistry, 268(4): 895902. agricultural and marine sciences, 14:17-25 (2009) ©2009 sultan qaboos university 17 _______________________________________________ *corresponding author. e-mail: sherin.sherif@uaeu.ac.ae revenue determinants for abu-dhabi fishermen and assessment of input allocative efficiency sherin a. sherif* and mohamed s. gheblawi department of agribusiness and consumer science uae university, al-ain, p.o. box 17555, uae abstract: this study examined the fishing industry in abu dhabi, the main fish-producing emirate in the uae, from the fishermen’s point of view. marginal analysis was used to identify the most prominent fishing-revenue determinants along with assessing the allocative (price) efficiency of inputs used. a log-log total value product (tvp) function was estimated for a representative cross-section random sample of 131 abu-dhabi fishermen. this revealed that (1) labor, fishing effort, boat capacity, boat boarding expenses, and expenditures on oil and lubricants are the five main determinants of total revenue for the individual fishermen in abu dhabi; (2) boat-purchase price constituted a huge investment cost to fishermen distributed over the lifetime of the boat; although only one-third of fishermen acquire loans for this purpose; (3) the only type of records fishermen keep were those pertinent to monthly revenues; and (4) price efficiency is found not to be achieved for any of the five prominent inputs that have great impact on total fishermen’s revenues, as three inputs were found to be under-utilized in varying degrees, whereas two were found to be significantly over-utilized. keywords: abu-dhabi fishing industry, allocative efficiency, revenue determinants. introduction fishing is the oldest industry in the uae, along with pearl extraction, yet little information about it is publicly available and the recording of time-series data started only in 1998. the uae government has generously supported fishermen over the years with a tendency towards gradual reduction of support as a general government policy. during the period 1997-2003, on average, fish production in the uae contributed 12% to the value of agricultural production. in 2003, the value of fish production was about aed 1.1 billion (one us dollar equals aed 3.675), with an annual growth rate of 15% since 1999. uae production of pelagic and demersal fish amounted to 103,255 tons in 2003, whereas the catch from crustaceans reached 2,201 tons. total fish production has been steady between 1997 and 2003 at an average of 112.5 thousand tons (ministry of environment and water, 2004). fish production is concentrated in four main regions of uae: abu dhabi (32% of uae’s fish production), the central region (27%), the eastern region (22%), and the northern region (17%). between 1999 and 2003, the number of people engaged in fishing as full or part timers increased by about 53%, from 10,172 to 15, 543 individuals. for the same period, the total number of fishing boats increased by about 40%, from 3,321 to 4,688 boats (fao, 2003). given the importance of fish as a source of livelihood to many emiratis, the lack of information on this industry, the anticipated government withdrawal from supporting the industry, and the non-existence of economic studies on the uae’s fishing resources in general, and fishermen as individual producers in particular, it is important to examine the industry from a microeconomic perspective. this paper’s main objective is to examine the economic السعریة لمدخالت اإلنتاج الكفاءة وتقییم ظبي أبو في لصائدي األسماك العائد محددات القبالوي محمد و شریف شيرين من السمكیة البحث الصناعة ھذا ویدرس الجدیدة. السیاسات خالل من للتالشي طریقھ في یبدو الدعم ھذا أن غیر ولسنوات عدیدة، بسخاء الصیادین اإلمارات حكومة الخالصة: تدعم بإمارة أبو صید األسماك قطاع في المستخدمة اإلنتاج السعریة لمدخالت الكفاءة وتقییم العائد محددات أھم على ھذه الدراسة للتعرف في الحدي استخدم التحلیل نظر الصیادین. وجھة ومن ظبي. أبو من أسماك ١٣١ صائد عشوائیة مكونة من قطاعیة لعینة المزدوجة اللوغاریتمیة الكلي اإلنتاج قیمة دالة استنبطت .٪٣٢ بنسبة السمكي اإلنتاج یتركز فیھا التي ظبي الزیوت والمنفق على القارب المركب، ومصروفات اإلقامة علي وطاقة الصید، العمال، وجھد (١) یعتبر اآلتي: األسماك لصائدي القطاعیة العینة دراسة التي أوضحتھا النتائج أھم ثلث ولكن الصید. قارب عمر ھائلة للصیاد موزعة على استثماریة تكلفة القارب شراء ثمن یعد (٢) التوالي. على ظبي، أبو في العائد الكلي للصیاد الواحد محددات أھم من والشحوم، ألي تتحقق ال الكفاءة السعریة أن وجد (٤) الشھریة. العائدات ھي حول الصیادون بھا یحتفظ التي السجالت الوحیدة أن یبدو (٣) لھذا الغرض. قروض على یحصلون فقط الصیادین المدخالن بینما متفاوتة وبدرجات توظف بقلة األوائل الثالثة المدخالت أن حیث وجد األسماك لصائد الكلیة العائدات على كبیر بشكل تؤثر والتي الرئیسیة المذكورة من مدخالت اإلنتاج المركب. شراء سعر تحدید في المھمان العامالن ھما بالقدم المركب وطول بالحصان المركب طاقة أن وجد (٥) كما یوظفان بكثرة. الرابع والخامس العائد ، محددات السعریة الكفاءة ، ظبي بأبو السمكیة مفتاحیة: الصناعة كلمات 18 sherif and gheblawi 19 revenue determinants for abu-dhabi fishermen and assessment of input allocative efficiency status and production practices of individual fishermen in the uae’s main emirate of abu dhabi, where fish production is most concentrated, and to assess fishermen’s economic efficiency. a comprehensive field survey that covered a representative cross-section random sample of the fishermen registered in the fishing cooperative of abu dhabi was conducted in the fall of 2006. this main objective was achieved through the identification of the different variable inputs utilized in the production process, the ranking of these inputs in terms of their relative importance to the value of output, the assessment of the responsiveness of the value of output to changes in input levels, and the assessment of price (allocative) efficiency of the most prominent inputs in the production process. literature review several studies on the economics of fishing have been performed worldwide. due to the dynamic nature of fishing problems and the lack of property rights in this industry in most if not all nations the common themes of fishing literature include the dynamics of overfishing, the inefficient allocation of resources and fishery pollution (fao, 2004; and ruseski, 1998). these studies show that, for production to be efficient, inputs have to be used in proportion to their relative scarcity. in commercial fisheries, private producers turn to market mechanisms for allocating capital and manpower. this is not the case, however, for the resource as long as access is open and free. under such conditions the resource value is not taken into account in allocating production factors. resources are used as though they were inexhaustible. as long as resources are considered not constraining, the need for rationing their use is less critical (jolly and clonts, 1993). other studies adopted production function estimation and/or revenue factors configuration when addressing input-output relationships in the fishing industry and assessment of economic efficiency on the micro level by examining fishermen’s behavior. for instance, gupta (1983) attempted to study the input-output relationship in fish farming in india through the estimation of the production function and the derivation of the optimum input combination. he utilized cross-section data and found that fish farming was subject to constant returns to scale (doubling of inputs doubles output), production technology was far from optimum, and application of the optimum production technique reduced production costs and raised the profit rate. esmaeili (2006) examined the technical efficiency of the iranian fishing industry and identified factors that could be causing inefficiency. a stochastic production function among fishery vessels was estimated. the results indicated that technical efficiency in the fishery was relatively low, wooden vessels of medium size were more efficient than small fiberglass vessels, vessel instrumentation had a significant impact on efficiency, and having a satellite connection on the boat and high level of education for the skipper were important considerations that influenced fishing efficiency. eggert (2000) examined the level and determinants of technical efficiency for a sample of swedish demersal trawlers. the data on per-trip gross revenues, fishing effort, gear choice, month of fishing, and vessel attributes were analyzed using a translog stochastic production frontier, including a model for vessel-specific technical inefficiencies. output elasticities and returns to scale were also examined. the technical inefficiency effects were found to be highly significant in explaining the levels and variation in vessel revenues. the inefficiency model indicated that fishermen were more efficient the more hours they fished, that older vessels were less efficient, while the size of vessel did not influence efficiency. the above literature indicates that both the production function and the revenue approaches could be used interchangeably. the first approach was utilized when physical quantities of fish catch were known, whereas when revenues that result from this catch were obtained, total revenue functions were deployed. as stated earlier, the total value product function approach was implemented in this study. materials and methods by definition, and according to marginal analysis economic theory, the production function embodies technical or production efficiency information. it indicates the maximum amount of output obtainable from the utilization of a specific quantity of inputs, given the existing technology level governing the input-output relationship. the said input-output relationship is assumed to be known with certainty. moreover, inputs included in the production function are assumed to be homogeneous, and prices of both inputs and outputs are assumed to be known with certainty. economic efficiency, on the other hand, refers to the combinations of inputs that maximize individual or social objectives. it is defined in terms of two conditions: necessary and sufficient. the first is met in the production process when estimating the production function. the second varies with the objectives of the individual fisherman. in most of the economic literature under perfect knowledge the individual fisherman’s objective is assumed to be profit maximization, i.e. allocative efficiency. it is defined as profit maximization through equating the value of marginal product of the variable input to its unit price. in case a total value product function is estimated, when the physical quantity of output produced is not known and its corresponding value is known instead, the optimality condition (i.e. allocative efficiency condition) occurs where the marginal value product of the input (mvp) is equal to the marginal input cost (mic) (egna and boyd, 1997, grafton and lane, 1998). inputs theoretically known to impact the level of output are boat capacity (in horsepower), fishing effort (in days), mesh size (in squared centimeters), labor (in man/days), 18 sherif and gheblawi 19 revenue determinants for abu-dhabi fishermen and assessment of input allocative efficiency fossil fuel (in monetary cost or physical amounts), food and boarding of boat crew (in monetary terms), stationary or movable fishing traps (in numbers or cubic meters), and equipment on board (connected or unconnected to satellite communication). in this study, data could not be collected for some of these inputs, however. there are, of course, other factors that affect profitability, such as maintenance, seasonality of fish types, fraud (when there are fewer fishing permits than fishing boats), fishing licenses, and pollution. these factors are not addressed in this study. in addition to the use of some secondary data available on the fishing industry in abu dhabi, a comprehensive cross-section field-survey was designed to collect primary data from a random sample of fishermen who were registered in the abu-dhabi fishermen’s cooperative. a total of 131 fishermen were interviewed in person, representing about 9% of the total population of fishermen who were registered in the abu dhabi fishermen’s cooperative. the questionnaire was divided into four main sections: general information (22 questions), fixed costs (11 questions), inputs and variable costs (22 questions), and output and returns (9 questions). the empirical model since the interviewed fishermen kept records on revenues and not on the amounts and types of commercial fish catch, the best empirical alternative was to estimate a total value product function (tvp), which is equivalent to a monthly total revenue function, which incorporates the total value of the fish catch per fisherman per month and the factors associated with that monthly revenue. then an identification of the total revenue determinants rather than the production determinants was made. the estimated total value product (revenue) function is a log-log function as follows: ln_retn = a0 + a1 ln_effort + a2 ln_bhp + a3 ln_labor + a4 ln_board + a5 ln_oil + e ....…...........(1) where (ln_retn) is total monthly revenues in aed or tvp as the dependent variable, and five independent variables affect total revenues, all in the logarithmic form: ln_effort, ln_bhp, ln_labor, ln_board, and ln_oil, which respectively stand for fishing effort in fishing days (which is the outcome of multiplying the fishing times per month (ftim) and the length of the fishing trip in days (tday)), boat capacity in horsepower, number of laborers on board, the boarding expenses of the fishing-boat crew in aed, and costs of oils and lubricants. on the other hand, ai (i = 0 to 5) stands for the estimated regression coefficients while “e” is the equation error term. since the function was of the log-log type, the estimated regression coefficients of equation (1) represented elasticities of the value of fish catch; i.e. the responsiveness of fisherman’s revenue to percentage changes in the value of the independent variables. the statistical estimation of the alternative tvp function utilized the technique of multiple regression analysis through the implementation of the ordinary least squares (ols) procedure. statistical tests, such as the f-ratio, pvalues, and the student’s t-test, were all utilized to test for the significance of the estimated function, the estimated regression coefficients, and the null hypotheses regarding allocative efficiency of input use. the spss package was used in fitting data to the model. results and discussion historically, emirati fishermen were given considerable incentives by the government by way of providing interest-free loans for boat purchases and engines to promote the fishing industry in the country (fao, 2004). table 1 shows the changes in the numbers of fishermen in the emirate of abu dhabi from 1998 to 2002. the table shows that the number of fishermen declined dramatically in the years 2000 and 2001 before climbing back to 4,827 fishermen in 2002. the reasons behind these fluctuations in fishermen numbers, and consequently the numbers of engines, boats, and fish quantities harvested, are probably due to the declarations by the ministry of environment and water (mew) (formerly known as the ministry of agriculture and fisheries) that governmental support to the fishing industry would gradually decline. boat engines and maintenance used to be offered for free by the government of the uae to the fishermen before the year 2000. thereafter, the government subsidized boat engines by 50%, while the cost of maintenance was totally incurred by fishermen. in addition, personal interviews with experts of the marine resources research center, located in umm alquwain, the main marine research institute in the uae, revealed that emirati youth were not very interested in working in the fishing industry, and prospective investors were in standby status, waiting to see where government support for the industry would end up. moreover, aquaculture experts revealed there were informal governmental declarations that the whole industry would be turned over to emiratis by limiting the number of foreign workers and fishermen to a minimum (wahba and anwahi, 2006). table 1. number of fishermen, engines, boats, and fish quantities harvested in abu dhabi. year number of fishermen number of marine engines offered number of boats fish quantities harvested in tons 1998 4847 73 1783 29534 1999 4847 111 1783 30273 2000 3051 90 856 34184 2001 3488 75 903 42909 2002 4827 60 979 30457 20 sherif and gheblawi 21 revenue determinants for abu-dhabi fishermen and assessment of input allocative efficiency in abu dhabi, there are twelve different commercial fish species. the species lethrinus sp. is the most caught type in terms of both quantity (21,056 tons) and value (aed 210 million) (mew, 2003). descriptive statistics of the sample table 2 summarizes the descriptive statistics of all of the variables mentioned. the preliminary examination of the study’s cross section random sample of 131 abu dhabi fishermen showed the following: •about 97% of fishermen were found to be owners of boats; 95% of the fishermen who owned boats that are priced at aed 300,000 or more were full-time fishermen, and prices of boats ranged from aed 10,000 to more than aed 300,000, with the most expensive boat priced at aed 450,000. •about 62% of the fishermen interviewed were found to own only one boat; 53% of those fishermen were emiratis, and 41% were indians. •about 5% of the fishermen interviewed were university graduates, and none claimed to be a full-time fisherman; 35% of the fishermen were either illiterate or had only primary education. •the risk encountered in the profession of fishing was concentrated in three main areas/types: fishermen falling from boats, bad weather conditions, and determination of traps sites. price risk was claimed by fishermen to be due to excess supply of fish, unreliability of foreign labor, low product prices, and spoiled fish. auctioning (dallal) was the most common selling method. winter was claimed to be the favorite season for fishing by almost every individual fisherman due to fish being closer to the shores for warmth. •only 10% of fishermen stated that they did not experience difficulties obtaining fishing licenses, whereas 34% of fishermen stated that they did not care about the cleanliness of the marine environment. •fishermen were found to record no information and data in general, other than those pertaining to monthly revenues. •maintenance costs per month ranged between a minimum of aed 25 and a maximum of aed 1000. about 8% of fishermen insured their boats. •about 21% of fishermen used nets, 7% used lines, and 72% used traps (gargour) as their main fishing method. •about 53% used large traps, 14% used average sized traps, and only 5% used small traps. the price of the traps ranged between aed 90 and aed 250. the minimum and the maximum trap numbers used by the typical fisherman in the sample were found to be 20 and 350 traps, respectively. •the numbers of boats run on diesel and petrol (gasoline) were estimated at 89 boats and 42 boats, respectively; 94% of fishermen revealed they had advanced equipment on board, with 75% of boats found to be satellite connected. table 2. descriptive statistics of the variables. variable name units of measurement code sample mean standard deviation boat purchase price aed bopr000 141.58 92.717 license cost aed lcos 220.76 86.343 boat lifetime years bolt 22.31 9.026 maintenance cost aed/month mainmo 184.51 160.430 boarding cost aed/trip/labor board 122.96 120.219 cost of importing a laborer aed labc 4368.70 1118.521 labor number/boat labor 4.82 1.707 labor salaries aed/labor/month salar 712.44 205.599 cost of oil, lubricants, and grease aed/month oil 333.47 143.166 cost of ice aed/trip ice 143.93 102.477 fishing trips number/month ftim 6.30 3.872 fishing days number/trip tday 3.79 1.863 fishing effort days effort 18.54 4.745 fuel cost aed/trip fuelc 641.76 280.086 total returns aed/month retn 25225.19 15369.947 boat capacity horsepower bhp 208.28 67.472 boat length feet boatl 32.26 14.405 20 sherif and gheblawi 21 revenue determinants for abu-dhabi fishermen and assessment of input allocative efficiency •food and boarding expenses for fishermen varied between aed 20 and aed 600 per trip. about 89% of fishermen interviewed stated that they worked all year round. the number of workers per boat ranged from two laborers to eight laborers maximum. the corresponding salaries ranged from a minimum of aed 400 to a maximum of aed 1100. •costs of oils, lubricants and grease ranged from aed 70 to aed 750 per month. ice consumption ranged from a minimum of aed 20 per trip to a maximum of aed 500 per trip. water and electricity consumption was found to be free of charge. fuel costs per trip varied from a minimum of aed 80 to a maximum of aed 990 per month. •fishing trips per month (ftim) ranged from 2 to 22 trips. however, the number of days such trips took (tday) ranged from a minimum of one day to a maximum of 8 days. this means the interaction of the two variables ftim and tday, or equivalently the fishing effort (effort), ranged from a minimum of 5 days to a maximum of 24 days per month. •monthly fishing revenues varied a great deal amongst fishermen. the minimum was aed 2500 and the maximum was aed 50,000. •boat length in feet (boatl) and boat capacity in horsepower (bhp) were found to be the two main factors determining the price of the boat (bopr000), whereas both boatl and bhp were not correlated. •boat horsepower (bhp) ranged from a minimum of 75 to a maximum of 350. boat lengths varied from a minimum of 10 feet to a maximum of 90 feet. total value production function estimation the estimated total value product (revenue) function was as follows: ln_retn = 3.00 + 0.520 ln_effort + 0.388 ln_bhp + 1.264 ln_labor + 0.133 ln_board + 0.210 ln_oil ..... .(2) other previously-mentioned independent variables that might affect revenues, such as mesh size, trap cost, trap numbers, equipment on board, and cost of fuel used, were of two types. the first pertained to those factors where insufficient data was available. the second type dealt with having enough data on the variable by almost all of the interviewed fishermen. however, answers were so similar to the extent that lack of variations resulted in the factor having no impact on revenue levels. an example of the first type was the factor dealing with mesh size (only 26 fishermen responding). examples of the second type were trap costs, trap numbers, and equipment on board, where significant variations in answers were not obtained. table 3 displays the detailed statistical results of the above function, showing strong statistical significance, as represented by the high r-squared and significant f-ratio and t-statistic. table 4 lists the correlation matrix of equation (2) above. this emphasizes partial correlation coefficient of the five independent variables that were statistically significant at the 1% level; however, the highest partial correlation coefficient of 0.507 was found between the two independent variables fishing effort (ln_effort) and labor (ln_labor). this meant that estimated partial correlation coefficients were in the neighborhood of the safe 0.5 range or less. a test of multicollinearity was made to ensure the nonexistence of a serious multicollinearity problem amongst the five explanatory variables. in statistics theory, the two synonymous tests used here were the tolerance values and the variance inflation factor tests (vif). in addition, the test of the condition indices (eigen values) was also utilized. tolerance is defined as (1 – r2), where r2 is the multiple r of a given independent variable regressed on all other independent variables. if the tolerance value is less than some cut-off value, usually 0.20, the independent variable should be dropped from the analysis due to multicollinearity. this is better than using the simple partial correlation coefficient rule of dropping the independent variable if r > 0.80, since tolerance looks at the independent variable in relation to all other independents and thus takes interaction effects into account as well as simple correlations. vif may be used in lieu of tolerance as vif is simply the reciprocal of tolerance. the rule of thumb is that vif > 4.0 when multicollinearity is a problem. some authors use the more lenient cut-off of vif ≥ 5 when multicollinearity is a problem. condition indices over 15 indicate possible multicollinearity problems and values over 30 indicate serious multicollinearity problems (wooldridge, 2003). table 3. estimated total value product function. variable value of estimated coefficient standardized coefficients model statistics (constant) 2.622** (.776) ln_effort .520** .190 r2=.810 (.129) ln_bhp .388** .151 (.117) ln_labor 1.264** .598 (.122) ln_board .133** .124 f-ratio =106.389 (.049) ln_oil .210** .123 (.072) standard errors are between parenthesis. **means variable is significant at α= 0.01. 22 sherif and gheblawi 23 revenue determinants for abu-dhabi fishermen and assessment of input allocative efficiency the estimated regression coefficients represent elasticities of the value of fish catch. for instance, a 10% increase in the fishing effort results in increasing total revenue by 5.20%; a 10% increase in the boat’s capacity results in increasing revenue by 3.88%; a 10% increase in the number of laborers on the fishing boat results in increasing revenue by 12.64%; a 10% increase in the boarding expenses of the fishing crew results in increasing revenues by 1.33%; and a 10% increase in the amount of money spent on oil, lubricants, and grease results in increasing revenues by 2.10%. the elasticity estimates obtained for the first three explanatory variables in equation (2), namely effort, bhp, and labor are economically rational. as the fishing effort, boat capacity, and number of laborers increase, more revenues may be realized. the rational explanation for the increases encountered in revenues when boarding expenses increase is that when boarding is comfortable and adequate for the crew, a better working atmosphere is availed, which may lead to more devotion to work and consequently better fishing practices. the positive and significant elasticity associated with the oil and lubricants may be an indication of good boat maintenance and consequently less boat problems. the estimated standardized regression coefficients (beta) showed that labor was the most prominent factor affecting the fishermen’s revenue, followed by the fishing effort, the boat capacity, boarding expenses, and oil and lubricants expenses respectively. the five factors accounted for 81.0% of the variations in the fishermen’s revenues. the statistical examination of the significance of multicollinearity showed that the tolerance values of the three estimated coefficients were above 0.2 (the critical value), meaning no serious multicollinearity. the vif was below 4 (the critical value) implying, once again, no serious multicollinearity. however, the condition index of the three remaining independent variables (i.e. labor, boarding, and oil and grease) were above the critical value of 30, indicating some possible multicollinearity problems that may be associated with these inputs (table 5) (hutcheson, 1999). however, the f-ratio and t-statistic (table 3) show the statistical significance of the estimated tvp function and the estimated coefficients of the independent variables, respectively. this significance of the f-ratio, combined with the significance of the student’s t-statistic, may show no serious multicollinearity (wooldridge, 2003). tvp function given loan acquisition personal interviews with the fish and marine experts at the marine resources research center revealed lack of knowledge on the exact amounts fishermen can get should they need to acquire interest-free loans for buying boats or other major fishing equipment. governmental loans to fishermen were assessed on a case-by-case basis and they table 4. the correlation matrix of the best fitted total value product function. ln_retn ln_effort ln_bhp ln_labor ln_board ln_oil ln_retn pearson correlation 1 .586** .532** .864** .498** .325** sig. (2-tailed) .000 .000 .000 .000 .000 n 131 131 131 131 131 131 ln_effort pearson correlation .586** 1 .364** .507** .315** -.010 sig. (2-tailed) .000 .000 .000 .000 .914 n 131 131 131 131 131 131 ln_bhp pearson correlation .532** .364** 1 .473** .138 .097 sig. (2-tailed) .000 .000 .000 .117 .272 n 131 131 131 131 131 131 ln_labor pearson correlation .864** .507** .473** 1 .486** .312** sig. (2-tailed) .000 .000 .000 .000 .000 n 131 131 131 131 131 131 ln_board pearson correlation .498** .315** .138 .486** 1 .025 sig. (2-tailed) .000 .000 .117 .000 .776 n 131 131 131 131 131 131 ln_oil pearson correlation .325** -.010 .097 .312** .025 1 sig. (2-tailed) .000 .914 .272 .000 .776 n 131 131 131 131 131 131 ** correlation is significant at the 0.01 level (2-tailed). 22 sherif and gheblawi 23 revenue determinants for abu-dhabi fishermen and assessment of input allocative efficiency vary from one fisherman to another. the current trend adopted by the mew is to eliminate loans provision as a general governmental policy (wahba and anwahi, 2006) . a division of the 131 fishermen into two groups was made to distinguish between fishermen who did obtain loans to buy the boats (30 fishermen) and those who did not obtain loans to buy their boats (101 fishermen). this was done to see if acquisition of a loan designed for covering the largest investment cost item (the boat purchase) had a significant effect on the corresponding tvp function. equation (3) shows the tvp function for the 101 fishermen who did not acquire loans: ln_retn = 2.09 + 0.522 ln_effort + 0.523 ln_bhp + 1.230 ln_labor + 0.119 ln_board + 0.262 ln_oil …...... (3) the function is statistically significant with an f-ratio of 83.173 and r2 = 0.814 and all of the five explanatory variables statistically significant. differences in the estimated regression coefficients from the original estimated revenue function (equation 2) were negligible. in other words, the function obtained was similar to that accounting for all fishermen interviewed. this was, however, not the case for the small group of fishermen who acquired loans, however, where the estimated tvp function was statistically insignificant. assessment of price efficiency of input use the assessment of price (allocative) efficiency for the five inputs that possessed the most significant impact on tvp for the whole sample of fishermen required the estimation of the marginal value product (mvp) for each of the five said inputs and contrasting that to the corresponding marginal input cost (mic) for each of them as a ratio. if the ratio of the mvp of the input is equal to its corresponding mic, then the input is optimally utilized, i.e. the amount of the input used is the profit-maximizing level. however, if the ratio is greater than one or less than one, then the said input is under-utilized or over-utilized respectively. the mvp of the input is the outcome of multiplying the inputs estimated regression coefficients obtained from the tvp function by the ratio of the average :tvp and average input level as in the following equation mvpx = β* (average tvp/average x) …... (4) where mvpx is the mvp of the input x, β is the estimated regression coefficient of the said input x, tvp is total value product, and x is the level of the input used. table 6 shows the estimated mvpx and the corresponding micx for the five mentioned inputs. the mic for labor is the average monthly salary the laborer table 5. multicollinearity results of the fish total value product function. variable vifa condition indexb (constant) 1.000 ln_effort 1.449 11.423 ln_bhp 1.353 16.999 ln_labor 2.186 25.570 ln_board 1.374 38.802 ln_oil 1.181 69.981 (a) critical value of the variance inflation factor (vif) is 4. (b) critical value of the condition index is 30. table 6. calculations of the marginal value product of the inputs and its corresponding marginal input cost. mvpx mvpx calculation mvpx (dirhams) micx calculation micx (dirhams) effort (0.522) * (25,225/18.45) 713.610 (712.44 + 4439)/(18.542) 277.856 bhp (0.523) * (25,225/208.28) 63.341 (1) (676.9/267.664) (2) (711.0/267.664) (1) 2.529 (2) 2.656 labor (1.230) * (25,225/4.82) 6437.133 naa 712.44 board (0.119) * (25,225/122.96) 24.412 na 122.96 oil (0.262) * (25,225/333.47) 19.818 na 333.47 ana not applicable. 24 sherif and gheblawi 25 revenue determinants for abu-dhabi fishermen and assessment of input allocative efficiency obtained (table 2). the mic for the fishing effort is the outcome of dividing the average labor salaries and the skipper’s salary by the average fishing effort. the mic for the boat capacity can be made in two ways: (1) either the outcome of dividing the average boat purchase price (bopr) by the average boat capacity used in horsepower (bhp) yields the price per the single horsepower (pphp); then this pphp is divided by the boat lifetime in months (boltm) to obtain the price per horsepower per month (pphpm), or (2) directly utilizing the bhp regression coefficient (0.711) obtained from an estimated boat price function not reported here which regressed boat purchase price on boat length and boat horsepower, divided by the boltm, which is the boat lifetime in months to get the price (cost) of the single horsepower per month. the mic for the boat boarding variable is the average boarding expenses experienced in the fishing boats, whereas the mic for the oil and lubricants variable is the average oil, lubricants, and grease expenses spent on fishing boats of the sample (table 2). table 7 shows the assessment of (allocative) price efficiency for the five mentioned variables. the table shows that none of the five inputs was optimally used. the three inputs (effort, boat capacity, and labor) were all under-utilized in varying degrees since their mvps outweighed their corresponding mics, with fishing effort being the closest input to optimal utilization. the two other inputs, namely boarding of the fishing crew and the expenses on oil, lubricants, and grease, were both significantly over-utilized. this is because their mvps were far less than their corresponding mics. since the five ratios were significantly far from one, there was no need to conduct a “t-statistic” to test the null hypothesis that the ratio of vmp of the input to the input’s mic is equal to one. conclusions since 32% of uae’s fish production is concentrated in the emirate of abu dhabi, the examination of the status of fishermen in this emirate is of importance to policy makers in the ministry of environment and water (mew) and is anticipated to be indicative of the status of the whole fishing industry in the uae. this cross-sectional study is an exploratory examination of the industry and further studies are needed. the study came up with the following conclusions and results: (1) about half of the interviewed fishermen (53%) were emiratis, contrary to the common belief that nationals are the minority in the abu dhabi fishing industry. this is a large percentage of nationals for a given industry in the uae, where nationals compose only 20% of the resident population. this necessitates more attention from the mew to the livelihood and economic wellbeing of fishermen in the form of providing information to fishermen and concerned scientists and researchers; (2) labor, fishing effort, boat capacities, fishing crew boarding, and oils and lubricants respectively were the five variables that had a major impact on the value of the fish catch (revenues) in abu dhabi for the whole sample of fishermen interviewed. these five variables accounted for 81 percent of the variations in fishing revenues. however, none of the five inputs was found to be optimally utilized. fishing effort, boat capacity, and labor were all underutilized to varying degrees, with the first variable closest to being optimally utilized. boat boarding expenses and oil and lubricants expenses were both found to be greatly over-utilized, and (3) the fishing boat was found to be the largest investment item for the interviewed fishermen. unfortunately, because of the inadequate sample size of fishermen who acquired loans, no significant conclusions could be made of the impact of loan acquisition on fishing revenue. however, the total revenue function for the fishermen who did not acquire loans for boat purchase was very similar to that of the total sample. acknowledgment financial support for this research was provided by the research affairs sector of the uae university through grant # 01-03-6-11/06. references eggert, h. 2000. technical inefficiency and its determinant factors in a demersal trawl fishery: the swedish norway lobster fishery. paper presented at the 10th annual conference of the european association of environmental and resource economists, university of crete, rethymnon, greece. egna, h.s. and c.e. boyd (editors). 1997. dynamics of pond aquaculture. crc press. esmaeili, a. 2006. technical efficiency analysis for the iranian fishery in the persian gulf. ices journal of marine science: journal du conseil 63:1759-1764. food and agriculture organization of the united nations. 2003. fao yearbook of fishery statistics vol. 82. fao fisheries series no. 50. fao, rome. food and agriculture organization of the united nations. 2004. the international plan of action for the management of fishing capacity. fao, rome. table 7. assessment of price efficiency of the most prominent inputs affecting total value product for the fishermen. input name ratio of (mvpx/micx) input status effort (659.811/277.856) = 2.375 under-utilized bhp (1) (40.451/2.529) = 15.995 (2) (40.451/2.656) = 15.230 under-utilized labor (7892.030/712.44) = 11.077 under-utilized board (24.412/122.96) = 0.199 over-utilized oil (19.818/333.47) = 0.059 over-utilized 24 sherif and gheblawi 25 revenue determinants for abu-dhabi fishermen and assessment of input allocative efficiency grafton, r.q. and d.e. lane. 1998. canadian fisheries policy: challenges and choices. canadian public policy 24:33-47. gupta, g.s. 1983. production function and optimum input mix in fish farming in india. no 464, iima working papers from indian institute of management ahmadabad. research and publication department, iima. hutcheson, g. and n. sofroniou. 1999. the multivariate social scientist: introductory statistics using generalized linear models. thousand oaks, ca: sage publications. jolly, c.m. and h.a. clonts. 1993. economics of aquaculture. the haworth press. ministry of environment and water. 2003. annual statistical bulletin. dubai. united arab emirates. ministry of environment and water. 2004. uae agriculture information centre.http: / / w w w. u a e . g o v. a e / u a e a g r i c e n t / s tat i s t i c s / fisheries.htm and http://www.uae. gov.ae/uaeagricent/ fisheries/fishasfood_e.stm. ruseski, g. 1998. international fish wars: the strategic roles for fleet licensing and effort subsidies. journal of environmental economics and management 36:70-88. wahba, o.m. and a.a. anwahi. 2006. coral reefs and marine protected area experts. marine resources research center. umm al-quwain, uae. personal communications. wooldridge, j.m. 2003. introductory econometrics. thompson/southwestern. received: june 2007 accepted: march 2008 research paper journal of agricultural and marine sciences vol. 21 (1): 2-7 doi: http://dx.doi.org/10.24200/jams.vol21iss0pp1-6 received 15 sep 2014 accepted 08 nov 2015 genetic and environmental factors affecting 305-day mature equivalent milk yield of holstein friesian cows in the united arab emirates mohamed elnour elboshra1, tagelsir eisa ali2* and ali ahmed hassabo3 العوامل الوراثية والبيئية اليت تؤثر على إنتاجية احلليب من أبقار اهلولستاين فريزاين يف دولة اإلمارات العربية املتحدة حممد النور البشرى1, تاج السر عيسى علي2 وأمحد علي حسابو3 abstract. the main objective of this research was determining the effect of sire of cow, year and season of freshening, lactation number, and their different interactions on 305-day mature equivalent (me) milk yield of holstein friesian cows in the united arab emirates (uae). it also aimed to estimate sire and error variance and heritability of 305-day me milk yield. the data was collected from al salamat dairy farm in al ain. the average size of the herd was 1000 animals during the experimental period. the dairy comp 305 computer program was used for compiling the data. the data under the study covered the years 2004 to 2007. the climatic temperature during the summer (april to september) varied from moderate to very hot. the winter (october to march) had lower temperature and higher relative humidity than the summer. all the effects were fixed except for random sire and residual error term. the overall least-square mean of the 305-day me milk yield was 11060±355 kg/305 days. the data showed a significant effect of sire of cow (p≤0.001), year of freshening (p≤0.001), lactation number (p≤0.01), year x season of freshening (p≤0.01), and year of freshening x lactation number (p≤0.001) on milk yield. however, the effect of season of freshening showed non significant effect. no significant seasonal differences were found in 2004. however, in the year 2005 and 2006, the summer fresheners had significantly higher yield than those of the winter season. the 305-day me pertaining to summer vs. winter were 11691±400 kg vs. 11483±410 kg and 11522±369 kg vs. 11041±374 kg for the year 2005 and 2006, respectively. however, the reverse was true in 2007 with the fresheners during summer that have lower 305-day me (10286±372kg) than those freshening during winter (10672±388 kg). the differences among the three lactations were relatively high in 2004 (9837 to 12116 kg), compared to 2005 2006 (11267 to 11747 kg) and 2007 (9853 to 11355 kg). the heritability of 305-day me was 0.31 indicating that a significant response to selection would be achieved through a well-designed progeny testing and cow evaluation program. املســتخلص:كان اهلــدف األول مــن هــذا البحــث هــو دراســة تأثــر األب وســنة اإلنتــاج وموســم اإلنتــاج ورقــم الــوالدة والعالقــة فيمــا بــن هــذه العوامــل علــى اإلنتاجيــة الســنوية للحليــب )إنتــاج احلليــب املعــدل لــر305 يــوم( يف أبقــار اهلولســتاين فريزيــان بدولــة اإلمــارات العربيــة املتحــدة. أمــا اهلــدف الثــاين فــكان حســاب معامــل التوريــث بعــد حتديــد مقــدار التبايــن لــأب وللخطــأ العشــوائي. مت مجــع بيانــات هــذا البحــث مــن مزرعــة ســيح الســالمات يف مدينــة العــن بدولــة اإلمــارات العربيــة املتحــدة. كان متوســط حجــم القطيــع خــالل ســنوات الدراســة )2004-2007م( هــو 1000 رأس مــن األبقــار. مت إســتخدام برنامــج الديــري كومــب )2000( لتجميــع هــذه البيانــات وحتريرهــا. تباينــت درجــات احلــرارة خــالل فــرة الصيــف )أبريــل إىل ســبتمرب( مــن متوســطة إىل عاليــة مــع درجــات رطوبــة عاليــة أيضــاً. ويف فــرة الشــتاء )أكتوبــر إىل مــارس( تنخفــض درجــات احلــرارة وتزيــد الرطوبــة النســبية بدرجــة كبــرة مقارنــة بفصــل الصيــف. مت إســتخدام برنامــج هــاريف للمربعــات الصغــرى واإلحتمــاالت الكــربي للتحليــل اإلحصائــي. حــوت املعادلــة اإلحصائيــة لتحليــل إنتاجية احلليب على أب البقرة ورقم الوالدة وســنة اإلنتاج وموســم اإلنتاج والتفاعل بن ســنة اإلنتاج وموســم اإلنتاج كان بن ســنة اإلنتاج ورقم الوالدة باإلضافــة إىل اخلطــأ العشــوائي. كان تأثــر مجيــع العوامــل ثابتــاً مــا عــدا تأثــر األب واخلطــأ العشــوائي فــان تأثرمهــا عشــوائياً. كان املتوســط العــام إلنتاجيــة احلليب 11060±355كجم. كان تأثر األب )p>001( وســنة اإلنتاج )p>001( ورقم الوالدة )p>001( والتفاعل بن ســنة اإلنتاج وموســم اإلنتــاج )p>0,01(, وكذلــك ســنة اإلنتــاج ورقــم الــوالدة )p>0,01( دااًل معنويــاً علــى إنتاجيــة احلليــب الســنوية للبقــرة بينمــا كان تأثــر موســم اإلنتــاج غــر دال معنويًــا علــى تلــك الصفــة اإلنتاجيــة اهلامــة. مل يكــن هنــاك تأثــر ملوســم اإلنتــاج يف ســنة 2004. ولكــن عنــد دراســة الســنوات 2005 و 2006 وجــد أن إنتاجيــة البقــرة يف فصــل الصيــف كانــت أعلــى منهــا يف فصــل الشــتاء. وبنــاءاً علــى ذلــك وجــد أن متوســط إنتاجيــة البقــرة يف هذيــن املومســن )الصيــف مقابــل الشــتاء( هــو 11691±400 كجــم مقابــل 11483±410 كجــم و11522±369 كجــم مقابــل 11041±374 كجــم للســنوات 2005 و 2006 علــى التــوايل. ولكــن العكــس كان صحيحــاً يف عــام 2007 حيــث وجــد أن األبقــار الــي بــدأت موســم إنتاجهــا يف فصــل الصيــف لديهــا أقــل إنتاجيــة )10286±372 كجــم( مــن مثيالهتــا الــي بــدأت مومسهــا يف فصــل الشــتاء )10672±388 كجــم (. كانــت الفروقــات بــن الــوالدات كبــرة نوعــاً مــا يف عــام 2004 )تراوحــت مــن 9837 إىل 12116كجــم(, وصغــرة يف عامــي 2005 و 2006 )تراوحــت مــن 11267 إىل 12747كجــم( ومتوســطة يف عــام 2007 )تراوحــت مــن 9853 إىل 11355كجــم(. كان معامــل التوريــث هــو 0,31 ممــا يــدل علــى أن هنالــك فرصــة كبــرة للتحســن الوراثــي مــن خــالل برنامــج إختبــار النســل الذائــع الصيــت. الكلمات املفتاحية: دولة اإلمارات العربية املتحدة ، أبقار حليب ، هولستاين فريزيان، انتاج احلليب ، البيئة 1 alain dairy farm, alsalamat dairy farm, alain, uae. 2* tagelsir eisa ali ( )dept of presidents’ affairs alain, mnc, alain,uae. email: tagali@hotmail.com 3alnileen university, faculty of agriculture science, khartoum, sudan. 3research article elboshra, ali and hassabo introduction there is an increasing demand of animal products in all countries around the world. however these demands exert more pressure on the countries in the arid zone to increase the animal production (philip, 2010). it is well-known that the indigenous cattle are low-producing animals. thus, almost all the countries in the tropics and sub-tropics have imported high milk producing cattle from temperate zone. the dairy cattle such as friesian and holstein-friesian are the most commonly imported cattle. al ain dairy farm is a leading dairy company in uae. several problems have been encountered in raising these animals in the tropics. heat stress was one of the most important problem (yousef, 1985). furthermore, yousef (1985) defined heat stress as the magnitude of forces external to the body system which tend to displace its system from their resting or ground state. climate is a combination of elements that include temperature, humidity, rainfall, air movement, radiation, barometric pressure, and ionization (johnson, 1987). the relationship between the animal and environment determines the degree to which the animal remains in thermal equilibrium with its environment (finch, 1976). effects of heat stress are more severe in hot humid climates, but dairy cattle raised in areas with relatively moderate climates are also exposed to periods of heat burden. so the thermal environment is a major factor that affects milk production and reproductive performance of dairy cows especially in animals with high genetic merit (koppock et al,1982). dairy cattle research tended to concentrate on genetic improvements in order to increase milk production. little attention had been paid to the thermoregulatory ability of the modern cow, as her capacity to produce milk (murphy et al. 1983). tao and dah (2013) reported that cows which were heat stressed during late gestation have impaired mammary growth before parturition and decreased milk production in the subsequent lactation. ray (1992) found that milk production was depressed for cows calving in summer and fall. heat stress threatens the normal metabolic balance and usually produces positive feedback, which affects the performance of the animal when the heat exceeds the upper critical temperature (uct). high producing cows are affected more than low producing and dry cows as the thermonuteral zone (tnz) shifted down as milk production, feed intake, and heat production increased (koppock et al, 1982). johnson et al. (1963) showed that cows consumed less feed as ambient temperature and combined ambient temperature and percent relative humidity (rh) were increased. berman et al. (1985) suggested that the upper limit of ambient temperatures at which holstein cattle may maintain a stable body temperature was 25 to 26°c, and that above 26°c, practices should be instituted to minimize the rise in body temperature. however, in the humid area, one of the major challenges is the combined effects of high rh with high ambient temperature. when the temperature reaches 29°c with 40% rh the milk yield of holstein, jersey and brown swiss cows was 97%, 93%, and 98% of the normal yield, respectively. but when the rh was increased to 90%, the yields of these breeds decreased to 69%, 75%, and 83% of the normal values, respectively (binaca, 1965). knowledge of other non-genetic factors that influence production is important for better assessment of genetic ability of dairy farm. knowledge of the interaction between genetics and environment is also very important for successful selection and progeny testing programs. moreover increased milk production can be achieved by implementation of environmental modification such as installation of cooling facilities through shades, water spray, and fans (armstrong 1994). furthermore, armstrong (1994) stated that the economic benefit should be determined before installing these equipments to reduce heat stress. a point to mention is that environmental modifications can not only be used to protect the animals, but they can also be used to protect dairy products from deterioration of their quality. intawiwat et al. (2013) developed green polyethylene film for protection of dairy products to reduce degradation of photosensitizers. beede and collier (1986) and chase (2005) identified three management strategies to minimize the effects of heat stress: physical modification of the environment (shading and cooling), genetic development of heat-tolerant breeds and improved nutritional management practices. for accurate selection of bull and better evaluation of dairy farms, 305-day me milk yield was used. the 305-day me milk yield is the standardized milk yield according to some factors. the most important factors in this standardization are lactation length, calving age and milking frequency (suleyman, 2006). standardizing records according to these factors will raise accuracy in selection as they reflect the genetic structure of animals. this method is also important for proper evaluation of strength of the cow in milk production as well as estimation of the excepted of subsequent lactations yield (suleyman, 2006). while superior bulls or cows are being selected for breeding, their ability to transfer this genetic merit to their progeny should be considered by breeders. in simple terms heritability (h2) measures the degree to which the phenotypic value of an individual reflects the actual genetic merits of that individual. this study focuses on the performance of the holstein friesian cows in the united arab emirates with the following specific objectives: 1-to determine the effect of sire of cow, lactation number, year of freshening, season of freshening, and year x season of freshening, and year of freshening x lactation interaction on 305-day me milk yield of the holstein friesian cows in uae. 2-to estimate heritability of 305-day me milk yield 4 squ journal of agricultural and marine sciences, 2016, volume 21, issue 1 genetic and environmental factors affecting milk yield of holstein friesian cows in the united arab emirates using sire and residual variance components for holstein friesian in uae. materials and methods area of study and climate this study was conducted in sei’h al salamat dairy farm which is one of al ain farms for livestock and animal production. it is located in al ain city, found in the eastern part of uae. this farm was initially established in 1987 with 300 milking cows. now the farm has 1000 milking cows and 750 rearing heifers for replacement. the latitude at sei’h al salamat dairy farm area is 24°12’n and the longitude is 55°46’ e. the ambient temperature, relative humidity and rainfall were taken from al ain weather station, located in the same farm area. climatic condition in the uae is generally hot and humid during april to september and warm to cool from october to march. the rh throughout the year is high in the coastal area and decreases gradually toward the interior region. al ain city is about 200 km away from the costal area, so it is less humid than the costal area. the maximum temperature during the period of study gradually increased from 26.6º c in january and reached the peak of approximately 44.0º c during the period from june to august and then declined gradually to reach 27.2º c in december. on the other hand the maximum rh started with a peak of 93% in january and declined to the lowest value; of approximately 62%; during may to august, then gradually increased to reach 91% in december. these results indicated that the months with high maximum temperature has low rh and this was very important and helpful in the use of evaporative cooling system. similar tendency were observed with the minimum monthly temperature and rh months. management system according to the routine management based on personal communication with the farm managers, the breed of cattle studied was holstein friesian. the sheds were free-stall and each was 72x63 meters in dimension and accommodated 125 cows. the shaded area was 15.5% of the total area of the shed. the space between adjacent sheds was 4.5 meters wide and it was roofed and used as feeding area. all the cows’ standing and feeding area were covered with concrete. the sheds were equipped with fans, sprinkles and korral kool system (american cooling system using sprinkles and fans controlled by a computer). during the years of the study (2004-2007), all the different groups of cows were covered with the cooling system. cow shower was fixed at the exit of milking parlor. the cows were fed total mixed ration (tmr) which was formulated in the farm according to the need of the different cow groups. the cows were milked four times a day. the daily milk yield per cow was measured two times a month. drinking water was available on a 24hour basis, providing eight inch as water space per cow. intensive management practices were implemented in order to counteract the heat stress. dairy comp 305 program (valley agricultural software, 2000) was used for cow management. the program monitored milk production, conception rate, pregnancy rate, culling rate and me milk yield calculation. animal health and vaccination based on the personal communication with the veterinarian in charge, the program of treatment and vaccination against infectious disease (e.g. foot and mouth disease, rinder pest, clostridium, brucela, rota virus, corona virus and e coli) was designed and applied by qualified staff. sick animals were isolated and treated. the application of preventive measurement was started at the gate of the farm by good bio-security and foot and wheel bath. the cow sheds were cleaned three to four times daily. the flies and insects were controlled by al ain municipality. samples specimens were sent to the laboratory for investigation when necessary. the farm received feedback report from the milk factory showing the composition analysis and microbiology counting of total bacteria and coli-form for the farm raw milk on daily basis. corrective action was taken if necessary. data collection the data for the current study were collected from se’h al salmat dairy farm, during the years 2004 to 2007 inclusive. cow milk record consisted of cow identification table 1. distribution of me yield records by year x season of freshening subclass1. year of freshening season of freshening total summer winter 2004 47 57 104 2005 110 107 217 2006 227 166 393 2007 323 114 437 total records 707 444 1151 1me: 305-days mature equivalent 5research article elboshra, ali and hassabo number (id), sire id, dam id, cow date of birth, cow date of calving, cow lactation number, days open, me milk yield and days in milk. the data were thoroughly edited and records with missing information were discarded. the total numbers of cow records which were used to determine the genetic and environmental factors affecting 305-day me milk yield as well as to estimate heritability for this economically important trait were 1151 record distributed by year and season of freshening (table 1). statistical analysis the statistical model which was used to analyze the 305day me milk yield data is presented as follows: yijklm=µ + si + aj + bk + cl + abjk + acjl + eijklm where yijklm = ijklm th me milk yield/cow. µ = fixed mean constant to all observation. si = effect of i th sire of cow for i =1 to 50 (random) aj = effect of j th year of freshening group for j = 2004 to 2007 (fixed) bk = effect of k th season of freshening group for k = 1 for summer and 2 for winter (fixed) cl = effect of l th lactation number for l = 1 to 3 (fixed) abjk = effect of jk th year x season of freshening interaction (fixed) acjl = effect of jl th year of freshening x lactation number interaction (fixed) eijklm = effect of ijklm th residual error term (random). first, conventional analysis of variance was carried out with all the factors assumed to be fixed except for the random residual error term. then, harvey least square and maximum likelihood computer program (1988) was used to fit this model (model 2) and also to estimate the sire (σs²) and error (σe²) variance components. for the variance component estimation, the sire of cow and residual error variance term were assumed to be random and have the following distribution n~ (0, σs²) and n~ (0, σe²), respectively. the sires were un-related and errors un-correlated. the heritability (h²) of 305-day me milk yield was estimated as follows: h² = 4 σs²/ (σs²+ σe²) results factors affecting 305-day me milking yield results in table 2 show that the effects of sire of cow (p ≤ 0.001), year of production (p ≤ 0.001) and lactation number (p ≤ 0.01) were significantly affecting me milk yield. furthermore, the effects year x season of freshening (p ≤ 0.01) and year of freshening x lactation number (p ≤ 0.001) interactions were also highly significant. however, the effect of season of freshening had non significant (p > 0.05) effect. since the interactions had significant effect on me mild yield, then the main effect of the individual factors has little value and will not receive any further discussion. the least-square means for the effect of year x season of freshening and year of freshening x lactation number interactions were also depicted on figures 1 and 2 respectively. heritability of 305-day me milk yield the heritability of milk yield measures the portion of the genetic merit that is transferred from the parent to their progeny. in the present study, a sire model was used and maximum likelihood method was utilized to estimate sire and error variance components. the result in table 3 shows that the heritability for me mature equivalent milk yield was 0.31. table 2. analysis of variance for 305-day me milk yield¹. source d.f. sum of square mean squares p-value sire of cow 49 331659687 6768565 *** year of freshening 3 112576245 37525415 *** season of freshening 1 800652 800652 ns lactation number 2 25277098 12638549 ** year x season 3 32795915 10931972 ** year x lactation 6 116558474 19426412 *** residual error 1086 2968086550 2733045 1*p ≤ 0.05, **p≤ 0.01 ***p≤ 0001, ns=not significant table 3. estimation of variance components and heritability of 305d me milk yield1. source value sire variance ( σs² ) 230137 residual variance ( σe² ) 2733045 heritability (h² ) 0.31 1h² = (4 σs²/ σs²+ σe²) 6 squ journal of agricultural and marine sciences, 2016, volume 21, issue 1 genetic and environmental factors affecting milk yield of holstein friesian cows in the united arab emirates discussion results indicated that the effects of year of freshening (p ≤ 0.001) and lactation number(p ≤ 0.01) on 305day me milk yield were highly significant. this finding is close to that of suleyman (2009) who used the same least-square method to analyze milk yield of holstein cows in turkey. the interaction of year x season of freshening on 305 day-me milk yield was highly significant (p ≤ 0.01). similar results were also reported by ray et.al. (1992). the results in figure 1 show that during the years 2004 the difference between 305-day me milk yield of summer and winter calving was insignificant. however, during the years 2005 (11691±400 kg vs. 11483±410 kg) and 2006 (11522±369 kg vs.11041±374 kg) cow freshening during the summer season gave significantly higher average me milk yield than those freshening during the winter season. however, in the year 2007 those freshening during the summer season gave significantly lower 305-day me milk yield (10286±372  kg) than their winter counterparts (10672 ±388  kg). the superiority of the summer freshening over the winter freshening during the years 2005 and 2006, occurred as a result of provision of the efficient cow cooling system. on the other hand the inferiority of the summer freshening in the year 2007 was due to the increase of the numbers of cows without a parallel increase in the cow cooling system a fact that rendered the cooling system inefficient. these results are in agreement with ray et al. (1992) who reported that in the absence of efficient cooling system, the summer season had significantly lowered 305-days me milk yield (7387± 193  kg) than the winter season (7765± 193  kg) in arizona. as it was mentioned above, the effect of year of freshening x lactation number interaction on 305-days me milk yield was highly significant (p ≤ 0.001). this interaction is evident in fig. 2 where the difference among lactation fluctuated with years of freshening. the largest difference observed among lactations in the year 2004, 2005, 2006 and 2007 was 2279, 449, 122 and 1502 kg, respectively. the change of differences among lactations, with increasing years might indicate unavoidable management differences from one year to another. another reason of year of freshening x lactation number interaction was the change in ranking of the lactations with years of freshening. a point to mention is that the second-parity cows had the highest 305-days me milk yield in the year 2004 (12116±453 kg) while the first lactation cows had the highest 305 day me milk yield in the years 2007 (11355±407 kg). another point to mention is that the third-parity cows had the lowest 305-day me yield throughout the years 2004 to 2007. the heritability of 305-day me milk yield was 0.31. this result is close to the value of 0.29 which was reported by ojango and pollott (2001) in kenya. estimates of heritability for milk yield from european breeds kept in the tropics were lower than those from similar breeds kept in temperate countries (lobo et al., 2000). the farm under study imports semen of high quality progeny tested breeding bulls. but a heritability of this magnitude suggests that a successful sire evaluation program could be established. conclusion and recommendations the least-square mean of 305-day me milk yield for holstein friesian cows was 11060 ±355 kg /305 days/ cow. the effect of genetic (sire of cow) and non genetic interacting factors (year and season of production and lactation number) had significantly affected me milk yield. the heritability of me milk yield was 0.31 indicating that improvement programs would be effective. reproductive performance of holstein friesian cattle should be investigated in future studies. acknowledgements i acknowledge the support of engineer abdulla saif al darmaki, chief executive officer of al ain farms for livestock production. i would also like to thank dr. saleh abdu al shorepy of the university of the united 2004 2005 2006 2007 10000 10500 11000 11500 12000 12500 milk production (l) y ea r season summer winter figure 1. effect of year and season of freshening on 305day me milk yield. 5000 7500 10000 12500 15000 2004 2005 2006 2007 year m ilk p ro du ct io n (l ) lactation lact 1 lact 2 lact 3 figure 2. effect of year and season of lactation number on 305-day me milk yield. 7research article elboshra, ali and hassabo arab emirates, for his support and excellent information about heat stress. this manuscript was typed and edited by mr. walid mirghany mohammed of the department of the president’s affair in uae. references armstrong, d.v. 1994. heat stress interaction with shade and cooling. journal of dairy science, 77: 2044-2050. beede, d.k. and collier, r.j. 1986. potential nutritional strategies for intensively managed cattle during thermal stress. journal of animal science, 62:543-554. bennet, c. 2001. genetic and management. virginia polytechnic institute. publication no. 404-084. berman, a., folman, y. , kaim, m., mamen, m., herz, z. , wolfenson, d., arieli, a. and graber, y. 1985. upper critical temperatures and forced ventilation effects for high-yielding dairy cows in a subtropical climate. journal of dairy science, 68: 1488-1495. chase, l.e. 2005. climate impacts on dairy cattle. department of animal science, cornell university, ithaca, ny. publication no. 14853. collier, r.j. 2006. major advances associated with environmental effects on dairy cattle. department of animal sciences, university of arizona, tucson 85721. finch, v.a. 1976. an assessment of the energy budget of boran cattle. journal of thermal biology , 1: 143-148. harvey, w.r. 1988. mixed model least-squares and maximum likelihood computer program pc-1 version. ohio state university. intawiwat, n., wold, j.p., skaret, j., rukke, e.o. and pettersen, m.k. 2013. minimizing photooxidation in pasteurized milk by optimizing light transmission properties of green polyethylene films. journal of dairy science, 96: 6818-6829. johnson, h.d. 1987. bioclimates and livestock. bioclimatology and the adaptation of livestock. in: world animal science. h.d. johnson (editor), elsevier science publ. co., new york. lobo, r.n.b., madalena, f.e. and vieira, a.r. 2000. average estimates of genetic parameters for beef and dairy cattle in tropical regions. abstract. animal breeding, 68: 433-462. murphy, m.r., davis, c.l. and mccoy, g.c. 1983. factors affecting water consumption by holstein cows in early lactation. journal of dairy science, 66: 35-38. ojango, j.m. and pollott, g.e. 2001. kenyan farms genetics of milk yield and fertility traits in holstein-friesian cattle on large-scale. journal of animal science, 79: 1742-1750. ray, d.e., halfback, t.j. and armstrong, d.v. 1992. season and lactation number effects on milk production and reproduction of dairy cattle in arizona. journal of dairy science, 75: 2976-2983. suleyman, c. 2009. milk yields traits of holstein cows at p.s. farm in turkey. journal of animal and veterinary advances 8:6-10. issn: 1680-5593 medwell journal, 2009. suleyman, c.m.e.t. 2006. calculation of adjustment factors for standardizing actions to mature age and 305-day and estimation of heritability and repeatability of standardized milk yield. cumhuriyet university, turkey. journal of animal science, 29: 897-993. tao, s. and dah, g.e. 2013. invited review: heat stress effects during late gestation on dry cows and their calves. journal of dairy science , 96: 4079-4093. thornton, p.k. 2010. livestock production: recent trends, future prospects. philosophical transactions of royal society b, 365: 2853-2867. valley agricultural software. 2000. dairy comp 305, version 2000. tulare, ca 93274 usa. yousef, m. k. 1985. basic principles. stress physiology in livestock. vol. 1. crc press, boca, raton, fl. agricultural and marine sciences, 18:25-29 (2013) sultan qaboos university 25 ___________________________________________ *corresponding author/e-mail: rramadan@kfu.edu.sa surgery of the dulaa in the camel (camelus dromedarius) ramadan o. ramadan department of clinical studies, college of veterinary medicine and animal resources, king faisal university, po box 1757, kingdom of saudi arabia abstract: the present study was carried out on 45 native adult dromedary camels suffering from disorders of the dulaa. clinical signs were those of dysphagia and or dyspnoea. twenty-four camels (53.33%) were unable to inflate or extrude their dulaas. these signs were associated with pharyngeal swelling. therefore the animals were examined radiographically. fifteen (33.33%) camels suffered from collapsed and persistent protrusion of the dulaas. four (8.9%) camels had previous episodes of dysfunction of the dulaa and the owner requested elective surgical excision. the remaining 2 (4.44%) animals had previous excision by healers and developed granulation tissue. surgical management was achieved after light sedation using xylazine (2% rompun, bayer) supplemented with local infiltration analgesia or followed by induction of anaesthesia using ketamine hydrochloride (ketamidore). the operations were carried out either through the oral cavity or following a pharyngostomy incision at the inter-mandibular region. in the latter instances, temporary tracheotomy was needed. the prevalent surgical affections were impaction with food material associated with ulcer or echymosis or abscesses. less severe maladies were those of persistent protrusion accompanied with edema, haematoma, lacerations, small foci of abscesses and gangrene. the prognosis was favourable. the study included surgical anatomy, magnetic resonance imaging (mri), as well as radiography of the dulaa in health and disease. keywords: dulaa, soft palate, dromedary camel surgery, mri. اجلمال في اللهاة جراحة رمضان عمر رمضان في مرضية آفة فيصل بسبب امللك جلامعة البيطري التعليمي للمستشفى أدخلت اجلمال التي 45 من الدراسة على هذه أجريت اخلالصة: ثم اإلكلينيكي للفحص اجلمال هذه خضعت وقد البلع أو لصعوبة الطعام على تناول القدرة عدم إما للمستشفى التردد وكان سبب اللهاة. الفم. جتويف خارج الهدارة طرد او تستطيع الهدير ال (%53.33) جمال أن 24 الدراسة أوضحت احلاالت. بعض في السينية األشعة استخدام ملكانها الطبيعي تستطيع اجلمال إعادتها وال خارج الفم (%33.33) اجلمال من 15 هدارة احلنجرة. وكانت منطقة انتفاخ من تشكو كما كانت بواسطة بيطار الهدارة استئصال مت (%4.44) الفحول 2) من تبقى ( وما احليوان صاحب رغبة على بناء اجلمال (%18.9) من أربعة لهاة وأزيلت الرمبون مبهدئ احليوان تهدئة مت اللهاة تلبك حالة ففي املرض، نوع حسب اجلمال عالج ومت العالج. إعادة اجلراحة إلكمال الفحل وطلب صاحب البعير. صاحب رغبة حسب إزالتها ثم الهدارة وتفريغ اجلمل إدخال اليد داخل فم ومن ثم مناسبة (فاحتة فم) عكامة باستخدام الفم فتح ثم مت ذلك تعذر وإذا إزالتها. ثم اللهاة قاعدة عند املوضعي البنج تسريب ثم اجلمل تهدئة من متكننا فقد الفم خارج الهدارة موجودة كانت أما عندما السفلي الفك فرعي اجللد بني مت شق نفس اليوم في جراحية أخري عملية وفي القصبة الهوائية، الرغامي داخل األنبوب إدخال ثم اجلمل تخدير يسهل ومواد بسوائل اجلمل وتغذية الطيف عريض حيوي مبضاد احليوان حقن العملية اجلراحية وأعقب من قاعدتها. اللهاة استئصال ثم داخلها. وجود خراج أو اللهاة أو تهتك وتلبك واجلروح، الدموية، والقيلة والقرحة، الورمي، لتشمل خطورة األقل اللهاة إصابات وتنوعت هضمها. احلديثة. هذه التقنية حتت الرقبة ومنظر التشريحية بالنواحي لالستدالل على املرض املغناطيسي نافق بالرنني جمل ورقبة رأس دراسة مت وقد املقطعية األشعة النام الواحد جمال ذات جراحة احللق , سقف كلمات مفتاحية: اللهاة، introduction the dulaa is a unique diverticulum on the ventro-rostral part of the soft palate of the dromedary camel (hegazi, 1949; mukasa-mugerwa, 1981). it is extruded from the bucal cavity during the rut or under excitation (arnautovic and abdel magid, 1974; wilson, 1988). a small minority of camels do not protrude the dulaa throughout their lifetime. the presence of dulaa outside the buccal cavity makes it vulnerable to trauma (cross, 1917). several reports describe the affections of the dulaa in arabian camels (bhargava, 1973; vashishta et al., 1980; gahlot, 1993; ramadan, 1994; barvalia et al., 1998; rollefson et al., 2001; gahlot et al., 2007). these reports have shown that minor ulcerations with subsequent flaccidity of the dulaa may lead to its impaction with feed (ramadan and abdin-bey, 1987; bolbol and 26 ramadan 27 surgery of the dulaa in the camel shazly, 1992). furthermore, neglected injuries may lead to gangrene of the organ with subsequent dysphagia and dyspnoea (gahlot et al., 1988). despite the importance of the dulaa, its radiographic findings, and surgical management is rarely documented (ramadan, 1990; ramadan, 1994). this review is intended to provide details of the clinical appearance of the dulaa and focus on its surgical management. materials and methods clinical animals a prospective study was performed of camels admitted to the veterinary teaching hospital. each camel was examined clinically and radiographs were taken on the lateral view whenever needed. forty-five animals were subjected to surgical interference as follows: group i: (=4; 8.90%) elective excision of dulaa; group ii: (=2; 4.33%) re-excision of remnant of dulaa because the healer was unable to achieve complete excision; group iii: (=:15; 33.33%) animal was unable to return the dulaa back into the mouth. the dulaa was edematous, engorged, showing signs of haematoma and one case contained remnant of food particle. it was thus hanging at mouth commissure (fig. 1); and group iv (=24; 53.33%) the animals were showing discomfort when swallowing; dysphagia, dyspnea were present and the animals were unable to extrude the dulaa (fig 2). the reasons were lacerated wounds (5), gangrene (4), ulcers (7), abscesses (2) or impaction with feed material (6). cadaver the head and neck of a 13-year-old male camel, which died for reasons not related with dulaa, was disarticulated at c3-c4.and subjected to mri. three dimensional pulse sequence were performed (t1-w; t2-w ; stir) using a human 1.5 tesla mr scanner. the stored plates were studied for understanding the imaging anatomy. surgical technique elective excision the camel was secured on the sternal position. it was then sedated using 2% xylazine hydrochloride given intravenously at the dose of 0.2 mg/kg body weight. a further injection of ketamine hydrochloride was given at the dose of 0.5 mg/kg body weight. the mouth was widely opened using a varnell mouth gag while the tongue was pulled through the interdental space. an assistant introduced his hand into the mouth in a cone manner to grasp the dulaa. once in position, it was fixed with a long thread of non-absorbable suture material (perlone no: 7 metric) to prevent it from accidental slipping. the dulaa was pulled as far as possible. the blood vessels were double clamped and cut between the clamps. further pairs of haemostats were applied across the dulaa and the organ was cut between themusing a pair of surgical scissors. the stump of the dulaa was sutured using a no; 5 metric polyglactin 910 on atraumatic needle. the animal received a local and a systemic course of broad-spectrum antibiotics as well as a course of vitamin k3. the owner was advised to feed the animal 5 liters of milk mixed with honey for one week. figure 1. a camel protruding an impacted dulaa. figure 2. a camel suffering from impaction of dulaa, note distended pharynx and extension of neck. 26 ramadan 27 surgery of the dulaa in the camel excision of a dulaa hanging between mouth commissure the animal was secured in the sternal position and sedated with 2% xylazine hydrochloride (0.2 mg/kg body weight) together with 10% ketamine hydrochloride at the dose of 1 mg/kg body weight given intravenously. the dulaa was pulled as far as possible (fig. 3). local analgesic (2% lignocaine hydrochloride) was also injected at the base of the organ. the operation was completed as for the elective technique described above. management of the dulaa which remains inside the pharynx evacuation followed by excision of the dulaa the animal was sedated and provision of a temporary tracheotomy was undertaken by preparing the ventral part of the neck for an aseptic operation. a hand was gently introduced into the mouth as for elective procedure. the dulaa was pulled out and cleaned off any debris, thereafter resection was undertaken according to owner’s desire. when it was not possible to pull the dulaa outside the mouth, the animal was rolled to its side for pharyngostomy. excision of the dulaa through the ventral part of the pharynx the animal was lightly sedated and the ventral part of the neck was approached aseptically. a 10 cm long skin incision was made at the level of the third cervical vertebrae. the incision was deepened by blunt dissection to expose the ventral cervical muscles. the fused bellies of the sternothyrohyiodeus muscle were separated. the trachea was pulled to the operative field and the annular ligament was incised. a temporary tracheotomy tube or a suitable endotracheal tube was inserted down the trachea. now the ventral pharynx was prepared for an aseptic operation. a 15 cm long skin incision was made at the mid inter-mandibular space starting from the cricoids cartilage rostraly. the incision was continued below the belly of the left sternothyrohyiodeus. the muscle was retracted dorsally. the pharynx was thus entered. care was exercised to avoid damaging the blood vessels. the hand was pushed rostrally to grasp the dulaa. the latter was primarily evacuated before resection (4 animals) or pulled out through the wound with its content and resected (figs. 4 and 5). results and discussion of primary interest in this study is the use of radiography for detection of pharyngeal lesions when the dulaa cannot be extruded by the animal. radiographs illustrate the larynx, proximal trachea, esophagus, the naso and oropharynx but are unable to delineate a normal dulaa or a dulaa showing non-opaque lesion (figs. 6 and 7). under such a situation, the dulaa is collapsed and covered by the figure 3. excision of extruded dulaa. figure 4. ventral part of a camel pharynx during surgery. figure 5. ventral part of a camel pharynx after resection of dulaa. 28 ramadan 29 surgery of the dulaa in the camel vertical ramus of the mandible. also subtle radiolucent lesions predisposing to dysphagia could not be diagnosed with certainty. however, when the dulaa was impacted with feed particles its size and density increases. it pushed caudally to press against the epiglottis thus interfering with breathing. elective resection of the normal dulaa is not infrequently carried out by healers. their technique is fraught with complications such as hemorrhage, infection or fibrous hyperplasia due to incomplete resection. the latter situation gave us an opportunity to re-excise the dulaa which was responsible for dysphagia and respiratory distress. the present investigation provides evidence that it is possible to treat affections of the dulaa through two surgical routes (the intra-oral and pharyngostomy incision). the intra-oral method is simple, less time consuming and does not subject the animal to the risk of general anaesthesia however, it may be applied to a severely impacted or indurate dulaa. simple amputation has been attempted by some authors (m’zah et al., 1993; ramadan, 1994). the main complication of the conventional surgical resection is post-operative bleeding and possible infection (gahlot, 1988). surgical resection showed drastic progress over the years and recently thermocautery provides quick and efficient amputation of the organ (reece and chawla, 2001). persistent protrusion of the dulaa in most instances occurson its own (cross, 1917; ali, 1993; gahlot, 1993), but in the present study, it was associated with impaction in one animal and with bilateral fracture of the mandible in two other camels. there have been questions raised concerning the inability of some camels to extrude their dulaa. in two animals studied by the present author, the dulaas were shorter and less elastic than normal. this may be a congenital anomaly. in the present study, disorders of the dulaa occur between the ages of 4-13 years (average 8 years). other authors reported that injuries should never occur in camels less than 9 years (dioli et al., 1992). impaction, ulcers and abscess were observed more commonly in older animals. mri is a useful modality, providing excellent image contrast and resolution that allows excellent visualization of anatomic details (fig. 8). to date mri studies are restricted to cadavers or newborn camels (arincebia et al., 2005). acknowledgments thanks to my colleagues and house surgeons at the veterinary teaching hospital, king faisal university for their help during the study. references ali, m.a., a.s. saleh, and h.a. yousef. 1993. unexpected soft palate hanging in a dromedary.assiut. veterinary medical journal 28:272-276. figure 6. lateral radiograph of the pharynx of a camel normal 1= 2nd cervical vertebra; 2= end of dulaa; 3= pharynx. figure 7. lateral radiograph of a camel with impaction of dulaa. note radio-opacity cranial to larynx (d) and trachea (tr). figure 8. mri image of normal pharynx t2w/tse/sag tr: 5000 te: 100 tse factor: 17 note dulaa (d), tongue (t), pharynx (3), trachea (tr). 28 ramadan 29 surgery of the dulaa in the camel arencibia, a., m.a. riverol, f. gil, j.a. rami’rez, j.a. corebera, g. rami’rez, and j.m. va’zquez. 2005. anatomy of the craniocephalic structures of the camel (camelus dromedarius) by imaging technique 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radiology of the dromedary camel. king faisal university. ramadan, r.o. and m.r. ahdin-bey. 1987. impaction of the distensible part of the soft palate (dulaa) in the camel. veterinary medical revue i:72-74. reece, j.e. and s.k. chawla. 2001. prolapse of the soft palate in a male arabian camel (camelus dromedarius). veterinary record 21:656-657. rollefson, i-k., p. mundy, and e. mathias. 2001. a field manual of camel diseases. itdg publishing, london, uk. vashishta, m.s., r.p. singh, and c. kala. 1980. a rare abscess on pharyngeal surface of a camel. livestock advisor 5:68. wilson, r.t. 1988. the camel. london longman house, essex, u.k. received: march 16, 2013 accepted: december 3, 2013 research paper journal of agricultural and marine sciences vol. 21 (1): 64– 75 doi: http://dx.doi.org/10.24200/jams.vol21iss0pp65-76 received 02 may 2015 accepted 19 jun 2016 serum biochemistry parameters in the omani racing arabian camels (camelus dromedarius) yasmin elhag eltahir1*, hassan mohammed ali2 , b.e. hago2 and o. mahgoub1 *1 yasmin eltahir ( ) sultan qaboos university, college of agricultural and marine sciences, dpt. of animal and veterinary sciences. box 34, al-khod 123. sultanate of oman. email: yasmin@squ.edu.om. 2 al-adhid veterinary & agricultural services, po box 110, al-qabil 419, sultanate of oman. 3 camel breeding center, directorate of veterinary services, royal diwan affairs, po box 34, al-khod 123, sultanate of oman introduction the dromedary camel (camelus dromedarius) is of great importance to nomadic and rural com-munities mainly in the arid regions of africa, the middle east and the indian sub-continent. it provides high quality animal protein in the form of milk and meat and as a mean of transportation and work. over the past few decades the camel has gained popularity and importance as a racing animal in the arabian gulf region. the camel is well suited to harsh environments characterخصائص كيمياء الدم يف إبل السباق وحيدة السنام يف سلطنة عمان يامسني احلاج الطاهر وحسن حممد علي وبدر الدين هجو وعثمان حمجوب abstract. blood samples were collected from thirty, 2-year old female arabian camels from the eastern region of oman. camels were managed in the traditional way in the arabian gulf region, primarily fed fresh alfalfa and barley grain. blood was drawn into serum vaccutainers from jugular venipuncture. serum samples were analyzed by spectrophotometric analysis using a cx7/cx7 serum chemistry analyzer (synchron, beckman). means, standard deviations and minimum and maximum values were calculated using excel spreadsheets on microsoft office 2007. the sas (2000) package was used to produce coefficient of determination (r2) between the eight serum mineral values. the following mean values ± standard deviation were recorded: glucose: 92.8±19.2 mg/dl; total protein (tp): 6.17 ± 0.34 g/dl; albumin: 32.21 ± 9.933 mg/dl; blood urea nitrogen (bun): 15.48 ± 4.49 mg/dl; creatinine: 1.64 ± 0.238 mg/dl; uric acid: 0.28 ± 0.041 mg/dl; total globulins (tg): 0.28 ± 0.041 mg/dl; cholesterol: 40.52 ± 13.225 mg/dl; total bilirubin: 0.34±0.124 mg/dl; alkaline phosphatase (alp): 113.9±29.75 (iu/l); aspartate aminotransferase (ast): 88.8±70.03 (iu/l); alanine aminotransferase (alt): 13.3±5.97 (iu/l); gamma-glutamyl transpeptidase (ggt): 21.3±10.18 (iu/l); lactate dehydrogenase (ld); 419.9±160.38 (iu/l); creatine kinase (ck): 46.3±16.2 (iu/l); sodium (na): 144.5±5.80 mmol/l; potassium (k): 4.23±0.42 mmol/l; calcium (ca): 9.63±0.43; phosphorus (p): 9.56?±0.76 mg/dl; iron (fe): 107.8±25.54 µg/dl; copper (cu): 72.5±8.08 µg/dl; chlorine (cl): 113.0±4.52 mmol/l. findings of the current study provide baseline values that may be used by clinicians for racing camels in oman. there were some significant correlations especially between macro minerals (na, ca, k, and p) that may be used to estimate their values with less cost by reducing the number of elements to be analyzed. keywords: omani camels; blood profile; serum minerals; trace elements. املســتخلص: مت مجــع عينــات دم مــن 32 ناقــة عربيــة عمرهــا حــوايل ســنتني مــن املنطقــة الشــرقية مــن ســلطنة عمــان. متــت تربيــة هــذه اإلبــل علــى الطريقــة التقليديــة إلبــل الســباق يف منطقــة اخلليــج العــريب حيــث متــت تغذيتهــا علــى الربســيم األخضــر وحبــوب الشــعري. مت مجــع عينــات الــدم يف أنابيــب مجــع املصــل ذاتيــة الســحب مــن الوريــد الودجــي. ومت حتليــل العينــات بطريقــة التحليــل الطيفــي باســتخدام جهــاز حتليــل مصــل الــدم )ســينكرون بيكمــان(. مت حســاب متوســط القيــم واالحنــراف املعيــاري والقيــم الدنيــا والعظمــى باســتخدام برنامــج أكســل علــى احلاســوب يف نظــام ميكروســوفت أوفيــس )2007(. مت اســتخدام برنامــج ســاس )2000( إلجيــاد معــدل التبايــن بــني مثانيــة مــن قيــم تركيــز املعــادن يف الــدم. مت احلصــول علــى املتوســطات التاليــة ± االحنــراف املعيــاري: اجللوكــوز )mg/dl 19.2±92.8( و الربوتــني الكامــل )g/dl 0.34 ± 6.17( والــزالل )mg/dl 9.933 ± 32.21( والنيرتوجــني )mg/dl 0.041 ± 0.28( اليوريــك ومحــض )mg/dl 0.238 ± 1.64( والكرياتينــني )mg/dl 4.49 ± 15.48( الــدم يف واليوريــا 0.124±0.34( الكامــل والبيلريوبــني )mg/dl 13.225 ± 40.52( والكوليســرتول )mg/dl 0.041 ± 0.28( الكامــل والغلوبيولــني mg/dl( واأللكااليــن فوســفاتيز )iu/l 29.75±113.9( واألســبارتيت أمينوترانســفرييز )iu/l 70.03±88.8( واألالنــني أمينوترانســفرييز )iu/l( 160.38±419.9( ديهادروجينيــز والالكتيــت )iu/l 10.18±21.3( ترانســبيبتيديز غلوتاميــل والغامــا )iu/l 5.97±13.3( والكرياتينــني كاينيــز )iu/l 16.2±46.3( والصوديــوم )mmol/l 5.80±144.5( والبوتاســيوم )mmol/l 0.42±4.23( والكالســيوم )9.63±0.43( والفوســفور )mg/dl 0.76±9.56( واحلديــد )µg/dl 25.54±107.8( والنحــاس )µg/dl 8.08±72.5( والكلوريــن )mmol/l 4.52±113.0(. ميكــن لنتائــج هــذه الدراســة أن توفــر قيمــاً أساســية خلصائــص مصــل الــدم يف اإلبــل ميكــن أن تكــون ذات فائــدة لألطبــاء البيطريــني املعاجلــني يف جمــال إبــل الســباق يف ســلطنة عمــان. وكان هنــاك بعــض االرتباطــات املهمــة بــني القيــم املختلفــة خاصــة بــني املعــادن الكبــرية )الصوديــوم والكالســيوم والبوتاســيوم والفوســفور( ممــا ميكــن مــن اســتخدامها لتقديــر قيــم هــذه املعــادن لتخفيــض تكلفــة حتليــل العينــات بتخفيــض عــدد املعــادن الــي جيــب حتليلهــا. الكلمات املفتاحية: اإلبل العمانية ، خصائص الدم ، معادن مصل الدم ، العناصر الدقيفة 65research article eltahir, al-adhid,hago, mahgoub ized by scarcity of water and vegetation as well as high ambient temperatures and rough terrain. this is because of its unique anatomical and physiological adaptations to such environments. there are about 250,000 camels in the sultanate of oman (faostat, 2014) with the highest population in the southern part of the country (dhofar) followed by the al-sharqiyah (eastern) and dhahirah regions (omaf, 2012). camels in the eastern region of oman are mainly kept for racing. good racing camels can be worth hundreds of thousands of dollars in the arabian gulf camel markets and great care is taken in raising and training these camels the traditional way. this includes a diet of green alfalfa, barley grain and sometimes honey, gee, milk and even eggs. biochemical values are useful for evaluating health status in animals including camels although in the latter species, some traits such as minerals homeostasis is very efficient and lead to a relatively constant levels irrespective of intake. however, published information on these parameters in camel shows a wide range of values which could be attributed to differences in breed, age, sex and sampling or analytical methods (mohamed and hussein, 1999). the metabolic profile of camels is affected by season, mineral supplementation and health status (faye et al., 1995). due to variations in haematological and biochemical parameters resulting from variations in these factors each laboratory is advised to establish what should be considered normal values for racing camels in their own region (mohamed and hussein, 1999). serum mineral levels are also affected by degree of hydration which is variable in camels raised under traditional range grazing systems (ayoub and saleh, 1998). however, this may not apply to racing camels as they are typically well looked after and not deprived of water or feed. macro and micro minerals are essential elements for animal functioning and health. trace elements such as co, se, cu, zn and fe are integral components of some enzymes and other important constituents of biologically active compounds. there are some published reports on biochemical values in camels. these include animal blood serum mineral values from sudan (abu damir et al., 2008; ahmed et al., 2003; mohamed, 2004), saudi arabia (al-busadah, 2007; al-shami, 2009; osman and al-busadah, 2003; ), kuwait (mohamed and hussein, 1999), united arab emirates (faye et al., 2008; wernery et al., 1999), iran (badiei et al., 2006; mohri et al, 2008), pakistan (zia-ur-rahman et al, 2007), nigeria (mohammed et al., 2007), kenya (kuria et al., 2006) and even europe (faye et al., 1995). there are also some reports on the serum mineral values in the bactrian camel (wernery et al., 1999; zongping, 2003). camel racing is a demanding process with animals being kept on strict diet and strenuous exercise prior to races and running for up to 10 km distances in some races. certain post-race haematological and biochemical changes occur but return to pre-racing levels after a period of rest (mohamed and hussein, 1999). there is a however, scarcity of information on omani camel serum biochemical profile . el tahir et al. (2010) reported some serum mineral values of omani female racing camels. therefore, this investigation has been carried out to provide basic reference levels of selected serum biochemistry parameters for clinicians and researchers working with the dromedary camels in the sultanate of oman. materials and methods animals and sampling blood samples were collected from thirty female, 2-year omani arabian camels (camelus dromedarius). the age of the animals was determined by asking owners and examining the dentition. the camels were raised in al-sharqiyah (eastern) region of oman around al-mudhaibi in the style adopted by most racing camel owners in the gulf region. they were fed approximately three kilograms of alfalfa plus one kilogram of soaked barley in the morning and three kilograms of alfalfa plus 2 kilograms of soaked barley in the evening (as fed). they were offered approximately 20 liters of water daily. all animals were tested for trypanosomiasis using buffy coat test and internal parasites using faecal egg counts. serum analytical methodology eight milliliter blood samples were drawn into plain vaccutainers tubes from jugular venipuncture. samples were centrifuged at 300 rpm for 5 min to separate the serum which was subsequently transported in a cool box to the laboratory at sultan qaboos university where they were stored at -20 ºc until analysis. serum samples were analyzed in the camel breeding unit of the diwan royal affairs, sultanate of oman for glucose; total protein (tp), albumin, blood urea nitrogen (bun), creatinine, uric acid, total globulins (tg), cholesterol, total bilirubin, alkaline phosphatase (alp), aspartate aminotransferase (ast), alanine aminotransferase (alt), gamma-glutamyl transpeptidase (ggt), lactate dehydrogenase (ld), creatine kinase (ck), sodium (na), potassium (k), calcium (ca), phosphorus (p), iron (fe), copper (cu) and chlorine (cl). all analyses were carried out by spectrophotometric analysis using a cx7/cx7 serum chemistry analyzer (synchron, beckman). statistical analyses means, standard deviations and minimum and maximum values were calculated using excel spreadsheets on microsoft office 2007. the sas (2000) package was used to produce pearson coefficient of correlations (r) between the eight serum mineral values. excel spreadsheets on microsoft office 2007 were used to calculate regression lines between na and other macrominerals ( 66 squ journal of agricultural and marine sciences, 2016, volume 21, issue 1 serum biochemistry parameters in the omani racing arabian camels (camelus dromedarius) polynomial). results and discussion general health general health of experimental animals appeared to be excellent by the standards of racing camels in the gulf region. they were well groomed and well looked after. racing camel owners in the arabian gulf region are known to care for the health and body condition of their animals. all animals tested negative for trypanosomiasis (buffy coat test). trypanosomiasis (surra disease) is widely spread among camels in the region and usually has a negative impact on their performance and blood profile. for instance ahmadi-hamedani et al. (2014) reported that serum analyses of camels heavily infected with trypanosoma evansi indicated anemia, leukocytosis, hyperproteinemia, hypoalbuminemia, hyperglobulinemia, reduction a/g ratio, increased α1 and β globulins and decreased α2 globulins and increased concentration of gamma-glutamyl transferase enzyme compared to non-infected camels. faecal sample analyses (egg counts) showed no significant internal parasites infestation. the animals had been dewormed by albendazole 2500 mg/animal by owners. serum chemistry profiles several serum profiles had been measured in experimental animals and are grouped as: glucose, protein (albumin, total globulin and total protein), bun, kidney function parameters (creatinine and uric acid), cholesterol, total bilirubin, liver enzymes (alp, ast, ggt, ld, and ck), co2, and minerals (na, ca, k, po4, fe, cu, cl,). range, mean and standard deviation values are presented in table 1. correlation within these groups was studied (tables 2-4). the standard deviation indicates the degree of variation in these parameters. wide variations in metabolic parameters exist in published literature and were mainly attributed to variability in nutritional regimes, mineral supplementation, season and presence of disease (faye et al., 1995). these authors distributed camels to four groups as follows: (1) class with low protein, high minerals and high ggt; (2) class with low cu table 1. means, standard deviations, maximum and minimum values of serum biochemistry parameters in female omani racing camels; n is the number of observations used for each parameter . parameter n mean (sd) min. max. glucose (mg/dl) 29 92.8 19.23 56.0 158.0 albumin (g/dl) 28 2.8 0.17 2.50 3.10 tg (mg/dl) 29 32.2 9.93 11.0 66.0 total protein (g/dl) 29 6.2 0.34 5.5 6.8 uric acid (mg/dl) 29 0.3 0.04 0.2 0.3 creatinine (mg/dl) 27 1.6 0.24 1.3 2.2 bun (mg/dl) 27 15.5 4.49 8.0 26.0 cholesterol (mg/dl) 29 40.5 13.23 4.0 77.0 total bilirubin (mg/dl) 29 0.3 0.12 0.1 0.6 enzymes alp (iu/l) 29 113.9 29.75 50.0 187.0 ast (iu/l) 29 88.8 70.03 57.0 374.0 alt (iu/l) 29 13.3 5.97 9.0 37.0 ggt (iu/l) 29 21.3 10.181 13.0 64.0 ld (iu/l) 28 419.9 160.38 303.0 971.0 ck (iu/l) 29 46.3 16.18 29.0 107.0 minerals fe (µg/dl) 29 107.8 25.54 56.0 158.0 cu (µg/dl) 29 72.5 8.08 54.0 89.0 ca (mg/dl) 29 9.6 0.48 8.70 10.3 po4 (mg/dl) 29 9.6 0.76 5.0 8.5 k (mmol/l) 29 4.2 0.42 6.5 5.0 cl (mmol/l) 29 113.1 4.52 105.4 127.2 na (mmol/l) 29 144.5 5.80 132.3 160.5 na/k 29 28.1 2.86 21.2 33.9 co2 (mmol/l) 29 18.3 1.65 13.9 22.3 67research article eltahir, al-adhid,hago, mahgoub and cerulplasmin; (3) class with high mineral values and protein indicators; and (4) class with intermediate values. glucose the blood glucose level or concentration is the amount of glucose in the animal’s blood which is the primary source of energy for the body’s cells besides blood lipids. the animal’s body naturally tightly regulates blood glucose levels as a part of metabolic homeostasis. glucose is transported from the intestines or liver to body cells via the bloodstream, and is made available for cell absorption via the hormone insulin. monitoring blood glucose levels is very essential to determine animal health particularly in racing camels which have a strict diet regime and usually go through rigorous training and competition. the glucose levels in omani camel serum ranged between 56 and 158 mg·dl-1 with a mean of 92.8±19.23 mg·dl-1 (table 1). this is an equivalent of 5.14 mmol. these levels are within the range reported for normal values in 2-12 year old arabian camels (76-129 mg·dl-1) by wernery et al. (1999) and indoor (130.2 mg·dl-1) and free grazing (105 mg·dl-1) saudi camels (al-shami, 2009). that was also well within the range reported for camels of various ages and breeds (yadav and bissa, 1998). the latter authors observed that blood glucose levels varied widely over a range of 27.6-214.4 mg·dl-1. glucose levels in camel blood are reported to be generally higher than in those of ruminants (bhatia, 1986). blood glucose levels in camels are affected by a variety of factors. glucose levels in camels are strongly affected by age with levels decreasing with advanced age (roussel et al., 1982; elias and yagil, 1984) and by season (mehrotra and gupta, 1989) with wet season samples having higher glucose levels than dry season ones (mohammed et al., 2007). indoor raised camels had higher serum glucose levels than free grazing camels (al-shami, 2009). this is mainly attributed to the better level of nutrition in the former group, which was fed a concentrate diet plus hay. glucose levels were much higher in saudi camels (134.4 mg·dl-1) than cattle (49.0 mg·dl-1) or sheep (65.0 mg·dl-1) raised under similar conditions (osman and al-busadah, 2003). the levels of glucose in omani racing camels falls within those of camels reported from different regions of the world indicating that they were healthy and not affected by type of nutrition or rigorous exercise. total serum protein serum total protein is made up mainly of albumin and globulin. the total protein test is a faster and cheaper biochemical test for measuring the total amount of protein in serum. low concentrations below the reference range usually reflect low albumin concentration such as in the cases of liver disease or acute infection whereas high levels are observed in conditions causing an increase in immunoglobulins or during dehydration. the mean tp in omani camels (table 1) was 6.17  mg·dl-1 (range of 5.5-6.8 ± 0.34 mg·dl-1 which are within range reported for normal values in 2-12 year old arabian camels (6.0-7.8 mg·dl-1) by wernery et al. (1999) and the range reported by yadav and bissa, (1998) for camels of various sexes, breeds and ages. faye et al. (1995) reported a range equivalent of 5.138.66 mg·dl-1for female camels raised in france. mean value of tp in egyptian camels was 7.60 ± 0.25 mg·dl-1 (seleim et al., 2003) and was 5.3-7.5 mg·dl-1 in nigerian camels (mohammed et al., 2007). the values are also comparable to those of saudi camels (range of 4.910.2 mg·dl-1) reported by al-busadah (2007) and sudanese camels 7.0 mg·dl-1 reported by omer et al. (2008). however, the value in the current study was lower than that reported for indian camels of similar age (yadav and bissa, 1998). yadav and bissa, (1998) reported that total serum protein content may be influenced by age, sex, pregnancy, rut or disease. tp was higher in serum of male camels during the rutting season than in the non-breeding season (koudier et al., 1988) and mohammed et al. (2007) reported that female camels had higher levels than males. osman and al-busadah (2003) reported table 2. coefficients of determination (r2) and their significance between some serum biochemistry parameters in omani racing camels. bun crea tp alb glu tg chol tbil bun 1 0.51** -0.06 -0.20 -0.12 0.15 0.33 -0.46* crea 0.51** 1 0.21 0.03 -0.03 0.48* 0.27 -0.08 tp -0.06 0.21 1 0.84*** 0.40* 0.029 0.34 0.40* alb -0.20 0.03 0.84*** 1 0.53** -0.23 0.38* 0.27 glu -0.12 -0.03 0.40* 0.53** 1 -0.57** -0.00 -0.03 tg 0.15 0.48* 0.03 -0.23 -0.57** 1 0.02 0.14 chol 0.3301 0.26953 0.33732 0.37598 -0.00055 0.01791 1 723 tbil -0.46* -0.08 0.40 0.27 -0.03 0.14 0.01 1 *: p<0.05; **; p<0.01; ***; p<0.001 68 squ journal of agricultural and marine sciences, 2016, volume 21, issue 1 serum biochemistry parameters in the omani racing arabian camels (camelus dromedarius) comparable values in saudi camels (7.1 mg·dl-1) which were lower than in cattle (8.2 mg·dl-1) but comparable to sheep (6.9 mg·dl-1). total protein levels recorded in the present study indicate normal levels of healthy and normally hydrated animals. albumin blood serum albumin, is the most abundant protein dissolved in animal blood plasma. it is a globular protein produced by the liver and is essential for maintaining the osmotic pressure needed for proper distribution of body fluids between blood vessels and body tissues. albumin in the urine usually denotes the presence of kidney disease. the mean value of albumin in omani racing camels was 2.80 ± 0.167 mg·dl-1 with a range of 2.5-3.1 mg·dl-1 (table 1). these are well within range reported for normal values in 2-12 year old arabian camels (2.8-5.6 mg·dl-1) by wernery et al. (1999); nigerian (23-40 g/l, equivalent for 2.3-4.0 mg·dl-1; mohammed et al., 2007) and saudi camels which ranged between 3.1-6.2 mg·dl-1 (al-busadah, 2007). comparable level (3.3 mg·dl-1) was reported for egyptian camels (seleim et al., 2003) and 22.3-46.3 g/l (equivalent for 2.23-4.63 mg·dl-1) for french female camels (faye et al., 1995). similar levels (3.3 mg·dl-1) were reported in sudanese camels (omer et al., 2008). sarwar et al. (1992) reported that albumin levels in camels are higher than those in ruminant animals. however, osman and al-busadah (2003) reported comparable values in saudi camels (3.7 mg·dl-1), cattle (4.5 mg·dl-1) and sheep (3.5 mg·dl-1) raised under similar conditions. sex effects on albumin had been reported with females having higher levels of albumin than males (mohammed et al., 2007). therefore, albumin levels in omani racing camels in the present study indicate normal healthy animals. these values may be used as guiding reference for professionals in the field. total globulin (tg) globulins are insoluble proteins in water or highly concentrated salt solutions but soluble in moderately concentrated salt solutions. the plasma globulins can be separated into five fractions by serum protein electrophoresis. these fractions are the alpha1, alpha2, beta1 and beta2 globulins, and the gamma globulins. the globulins are involved in the inflammatory process, clotting factors, complement components and immunoglobulins. the mean value of tg in omani racing camels was 3.22 ± 0.99 mg·dl-1 with a wide range of 1.106.60 mg·dl-1 (table 1). tg in indian camels ranged between 3.16 3.56 (patodkar et al. (2010). tg in saudi camels of various breeds and sexes (al-busadah, 2007) ranged between 1.5-5.4 mg·dl-1). levels of 4.32 g/l were reported for egyptian camels (seleim et al., 2003) and 21.5-49.9 g/l (2.15-4.99 mg·dl-1) were reported for french female camels (faye et al., 1995). levels of globulins in omani racing camels were consistent with those of total proteins and albumins indicating healthy animals. values may be used as reference for racing camels in oman. blood urea nitrogen (bun) bun is a test for urea nitrogen in the animal’s blood which is formed when protein breaks down. bun levels higher than normal may indicate excessive protein in the gi tract, dehydration, kidney failure or diseases, shock or urinary tract obstruction. lower-than-normal levels may indicate: liver failure, low protein diet, malnutrition or over-hydration. racing camels reared in a very strict way may be exposed to some of these conditions. the mean bun in omani racing camels was 15.48 ± 4.49 mg·dl-1 (5.51 mmol) with a wide range of 8-26 mg·dl-1(table 1). these figures are comparable to those of 15.4±4.52 mg·dl-1 reported by mohamed and hussein (1999) in kuwaiti racing camels. reports on bun values in the literature vary a lot. the range of normal values in 2-12 year old arabian camels in uae was 10-17 mg·dl-1) reported by wernery et al. (1999). a wide range (4.1-69 mg·dl-1) was also reported by faye et al. (1995) in female camels raised in temperate regions. yadav and bissa (1998) reported a range of 1178 mg·dl-1. values of 24.9 mg·dl-1were reported in sudanese camels. levels of 37.0 mg·dl-1were reported for egyptian camels (seleim et al., 2003). bun values in omani female camels in the present study (5.5 mg·dl-1) appear to be within the range reported for bun levels in the blood of saudi camels ranged between 3.2-6.2 mg·dl-1 (al-busadah, 2007). the range of bun in nigerian camels was 2.4-8.5 mg·dl-1 with females having higher levels than males (mohammed et al., 2007). indoor raised camels had higher levels (5.6 mmol/l) than free grazing ones (3.1 mmol/l) as a result of better level of nutrition (al-shami, 2009). saudi camels (osman and al-busadah, 2003) had comparable levels of urea to sheep (49.8 vs. 52.6 mg·dl-1), which were much higher than those in cattle (17.2 mg·dl-1). values of bun in omani racing camels in the current study are in line with normal values of total protein and its component indicating healthy animals. they may be used as clinical reference for the breed. creatinine serum creatinine is an important indicator of renal health. it is a byproduct of muscle metabolism that is excreted by the kidneys. creatine is synthesized primarily in the liver and the kidney then transported through blood to the other organs, muscle, and brain. the mean value of creatinine in omani racing camels was 1.6 ± 0.24 mg·dl-1 with a range of 1.32.2 mg·dl-1(table 1), which are similar to normal values in 2-12 year old arabian camels in uae (1.3-2.2 mg·dl-1) 69research article eltahir, al-adhid,hago, mahgoub reported by wernery et al. (1999). they are also comparable to those of 1.97 mg·dl-1 reported by mohamed and hussein (1999) in kuwaiti racing camels. lower levels of 0.93 mg/dl were reported for egyptian camels (seleim et al., 2003). creatinine values recorded in the present study are equivalent to 0.15 mmol/l which appears to be comparable to creatinine levels in serum of saudi camels with a range of 0.16-0.53 mmol/l (al-busadah, 2007) mohammed et al. (2007) reported a range of 47-118 µmol/l with levels higher during the wet season. osman and al-busadah (2003) reported comparable values in saudi camels (1.5 mg·dl-1) to cattle (1.3 mg·dl-1 but higher than sheep (1.0 mg·dl-1). creatinine values recorded in the current study are in line with values of protein and bun indicating that omani racing camels has healthy renal function. they may be used as clinical references for the breed. uric acid uric acid (c5h4n4o3) is a heterocyclic compound of carbon, nitrogen, oxygen, and hydrogen that forms ions and salts known as urates and acid urates. it is a product of the metabolic breakdown of purine nucleotides. uric acid is associated with several medical conditions including gout, diabetes and the formation of kidney stones. uric acid is reabsorbed by renal tubules in mammals. the mean value of uric acid in omani racing camels was 0.28 ± 0.041 mg·dl-1 with a range of 0.2-0.3 mg·dl-1 (table 1). seleim et al. (2003) reported a higher value of 1.68 mg·dl-1 in egyptian camels. the uric acid values in the present study (166.5 µmol/l) were comparable to the 160-273 µmol/l reported by haroun (1994) for saudi camels and the 217 µmol/l for fasted and fed llamas reported by bakker et al. (1996). uric acid values in camel and llama are considerably higher than those typically observed in cattle and sheep (bakker et al., 1996). therefore, low levels of uric acid (0.2-0.3 mg·dl-1) indicate healthy kidney functions in omani racing camels and may be used as clinical references for the breed. cholesterol cholesterol is a modified steroid lipid molecule and is an essential structural component of animal cell membranes. it is required to maintain membrane structural integrity and fluidity. it also serves as a precursor for the biosynthesis of steroid hormones, bile acids, and vitamin d. the liver cells typically produce greater amounts than other cells. the mean value of cholesterol in omani racing camels was 40.52 ± 13.225 mg·dl-1 with a wide range of 4.077.0 mg·dl-1 equivalent of 1.1 mmol/l (table 1). these figures are comparable to those of <33 mg·dl-1 reported by mohamed and hussein (1999) in kuwaiti racing camels. cholesterol levels in blood of saudi camels ranged between 1.91-4.2 mmol/l (al-busadah, 2007). system of management significantly affected cholesterol levels in camel blood. al-shami (2009) reported values of 82.1 and 60.5 mg/l in indoor and free grazing camels. osman and al-busadah (2003) reported values of 58.4 g/ dl in saudi camels which were comparable to those in sheep (69.6 mg·dl-1) but significantly less than those in cattle (149.4 mg·dl-1). the data indicated that cholesterol levels in omani camels serum were within normal range and may be used as clinical reference in the breed. total bilirubin bilirubins are produced by the breakdown of heme and reduction of biliverdin. it normally circulates in plasma and is taken up by liver cells and conjugated to form bilirubin diglucuronide, the pigment excreted in the bile although some leakage of bilirubin monoand diglucuronides does occur, but these normally account for less than 5% of circulating bilirubin. in the bile, more than 80% is conjugated as the diglucuronide form. failure of the liver cells to excrete bile, or obstruction of the bile ducts can cause an increased amount of bilirubin in the body fluids and lead to obstructive jaundice. the mean value of total bilirubin in omani racing camels was 0.34±0.124 mg·dl-1 (5.8 µmol/l) with a table 3. coefficients of determination (r2) and their significance between some serum biochemistry parameters in omani racing camels alp ast alt ggt ld ck co2 uric alp 1 0.03 0.05 -0.00 0.13 0.21 -0.13 -0.13 ast 0.03 1 0.98*** 0.94*** 0.94*** 0.11 0.07 0.16 alt 0.05 0.98*** 1 0.91*** 0.93*** 0.12 0.15 0.08 ggt -0.00 0.94*** 0.91*** 1 0.89*** 0.17 0.16 0.20 ld 0.13 0.94*** 0.93*** 0.89*** 1 0.16 0.01 0.19 ck 0.21 0.11 0.12 0.17 0.16 1 0.09 0.28 co2 -0.13 0.07 0.15 0.16 0.01 0.09 1 -0.01 uric -0.13 0.16 0.08 0.20 0.19 0.28 -0.01 1 *: p<0.05; **; p<0.01; ***; p<0.001 70 squ journal of agricultural and marine sciences, 2016, volume 21, issue 1 serum biochemistry parameters in the omani racing arabian camels (camelus dromedarius) range of 0.10-0.60 mg·dl-1. these figures are comparable to those of 0.51±0.30 mg·dl-1 reported by mohamed and hussein (1999) in kuwaiti racing camels. mohri et al (2008) reported a value of 5.3 µmol/l total bilirubin in serum of iranian camels which is similar to that recorded in omani camels in the present study. therefore, the range of 0.10-0.60 mg·dl-1 should be regarded as a normal reference level of the breed. serum enzymes liver serum enzyme tests, also known as liver function tests, are tests carried on blood serum that detect inflammation and damage to the liver as well as liver functioning. liver enzymes include: aspartate aminotransferase (ast), alanine aminotransferase (alt), gamma-glutamyl transpeptidase (ggt). liver function tests include alt, ast, ggt, alkaline phosphatase, pt, inr, albumin, and bilirubin. alkaline phosphatase (alp) the mean value of alp in omani racing camels was 113.9±29.75 iu/l with a range of 50-187. seleim et al. (2003) reported a lower value of 19.9 iu/l in egyptian camels. the mean alp levels in saudi camel serum (osman and al-busadah, 2003) was 60 u/l which was not different from those in cattle (50 u/l) but much lower than that in ewes (112.4 u/l). aspartate aminotransferase (ast) liver enzyme measurements reflect hepatocyte membrane integrity, hepatocyte or biliary epithelial necrosis, cholestasis, or induction phenomenon rather than liver function tests. duration and magnitude of transaminase activities measured sequentially can predict disease activity and severity and roughly estimate the number of involved cells. aminotransferases, ast and alt are present in high concentrations in liver and several other tissues. ast activity is higher in kidney, heart, and skeletal muscle than liver. the mean value of ast in omani racing camels was 88.8±70.03 iu/l with a range of 57-374 iu/l. that appears to be higher than ast levels in blood of saudi camels ranged between 24.1-35.1 iu/l (al-busadah, 2007) and the 31.4 iu/l in egyptian camels (seleim et al., 2003). osman and al-busadah (2003) reported a mean value of ast in saudi camels of 164.6 u/l which was comparable to that in sheep (141.6 u/l) but much higher than that in cattle (72.4 u/l). further studies are needed to determine whether the differences in ast between omani camels and camels in other parts of the world are genetic or clinical. alanine aminotransferase (alt) the alt activity is highest in liver and it is a bout 10,000fold greater than plasma enzyme activity in healthy animals, it has high diagnostic utility to detect liver lesions. the mean value of alt in omani racing camels was 13.3±5.97 iu/l with a range of 9-37. that appears to be comparable to the range of alt levels in blood of saudi camels ranged between 8.0-14.5 iu/l (al-busadah, 2007). seleim et al. (2003) reported a value of 19.9 iu/l in egyptian camels. osman and al-busadah (2003) reported a mean value of alt in saudi camels of 17.2 u/l which was comparable to that in sheep (21.0 u/l) but it was less than that in cattle (34.0 u/l). this indicate normal and healthy liver functions in omani racing camels. gamma-glutamyl transpeptidase (ggt) ggt is one of the liver enzymes. it is concentrated in the liver, but also present in the gallbladder, spleen, pancreas, and kidneys. ggt blood levels are usually high when the liver is damaged. this test is often done with other tests that measure liver enzymes if there’s a possibility of liver damage. the mean value of ggt in omani racing camels was 21.3±10.18 iu/l with a range of 13-64. a wide range of ggt (1-49 iu/l) was reported in female camels raised in france (faye et al., 1995). osman and al-busadah (2003) reported a mean value of ggt in saudi camels of 25.6 iu/l which was comparable to that in cattle (29.0 iu/l) but much lower than that in sheep (77.0 iu/l). these data indicated that omani camels has normal liver functions and figures obtained in the current study may be used as clinical reference. lactase dehydrogenase (ld) the ld is not organ-specific, therefore its levels should be considered in relation to other enzymes. the mean value of ld in omani racing camels was 419.9±160.38 (iu/l) with a range of 303-971. that appears to be higher than ld levels in blood of saudi camels ranged between 225-280 iu/l (al-busadah, 2007). however, osman and al-busadah (2003) reported a mean value of ld in saudi camels of 455 iu/l which was comparable to that in sheep (382.4 iu/l) but much lower than that in cattle (726.8 iu/l). combined with other values of liver enzymes, bilirubin indicate that omani racing camels were healthy. these values may bused for clinical reference. creatine kinase (ck) skeletal muscles are the major source of ck in the body and the enzyme is used for diagnosis of muscular abnormalities. the mean value of ck in omani racing camels was 46.3±16.2 (iu/l) with a range of 29-107. this appears to be higher than ck levels in blood of saudi camels ranged between 29.1-30.3 iu/l by al-busadah (2007) who reported that values in saudi camels are lower than those reported for other camels in iraq (al-ani et al., 1988). osman and al-busadah (2003) reported an exceptionally high value of ck in saudi camels (408.6 iu/l) which was much higher than that in sheep (121.6 iu/l) and cattle (119.0 iu/l). normal values of ck in omani racing camels indicates healthy animals. this is import71research article eltahir, al-adhid,hago, mahgoub ant because racing camels usually has a very rigorous training and competition exercise regime. serum mineral contents table 1 gives the means, standard deviation, maximum and minimum values of some minerals in omani camel serum. generally the macro mineral with the highest concentration in the omani camel serum was the na and within trace elements fe and zn. sodium (na) sodium is an essential mineral for cell and body functions. its importance is evident in racing camels which exercise and compete rigorously and therefore, are usually subjected to severe stress. na content in camel serum ranged between 132.3 and 160.5 with a mean 144.5±5.80 mmol/l. this value was comparable to that of 150-164 mmol/l in emirate camels (ayoub and saleh, 1998; wernery et al., 1999) and 100 – 190 mmol/l reported for “majaheem”, “maghateer” and “awarik” saudi camels (busadah, 2007). similar ranges of values were reported for saudi (al-shami, 2009) and nigerian (mohammed et al., 2007). some studies reported a higher range of 300-390 mmol/l (hassan et al., 1968 in sudanese camels). na values obtained in the current study were equivalent to those reported for saudi camels by osman and al-busadah (2003). the latter authors reported that na levels in camels are higher compared to those in cattle and sheep which were in agreement with previous reports (abdalla et al., 1988). na values in the current study were slightly lower than those reported for rutting and non-rutting male camels (zia-rahman et al., 2007). na serum levels in the omani dromedary were comparable to those in the bactrian camels of 148±32 mmol/l reported by liu (2003) and 129-161 mmol/l reported by wernery et al. (1999). chloride (cl) cl is an essential electrolyte found in all body fluids and is responsible for maintaining acid/base balance, transmitting nerve impulses and regulating fluid in and out of cells. cl levels in omani camels ranged between 105.4 and 127.2 mmol/l with a mean of 113.0±4.52 mmol/l. these were comparable to the 114-120 mmol/l in uae camels (wernery et. al., 1999). higher chloride levels were recorded in egyptian camels was 301.9 mmol/l (seleim et al., 2003). potassium (k) potassium is the main intracellular ion for all types of animal cells. it is essential for maintaining fluid and electrolyte balance in the animal body. animals use sodium and potassium differentially to generate electrical potentials in animal cells, especially in nervous tissue. therefore, potassium deficiency in animals results in various neurological dysfunctions. mean k values in omani camels of 4.23±0.42 mmol/l (range of 6.5-8.7 mmol/l) were comparable to those reported for saudi camels (2.9-6.2 mmol/l by al-busadah, 2007; 4.2-6.8 mmol/l by al-shami, 2009; 4.0 by osman and al-busadah, 2003); uae (4.2 mmol/l by ayoub and saleh, 1998; 3.5-5.5 by wernery et al., 1999); sudanese (omer et al., 2008; mcgrane and kenyon, 1984); nigerian (mohamed et al., 2007); egyptian (4.29 mmol/l by seleim et al., 2003), and other camels (higgins and kock, 1986). kuwaiti camels had levels of 3.0-4.7 meq/l ( mohamed and hussein, 1999); there were some reports on differences between camel and other species in levels of serum k contents. for instance kamalu et al. (2003) reported that k was higher in cattle serum than in camels. k values in the current study were lower than those reported for rutting and non-rutting male camels (zia-rahman et al., 2007). mohammed et al. (2007) reported that male camels had higher k levels than females in nigerian camels. k serum levels in the female omani dromedary were comparable to those in the female bactrian camels of 4.23±0.66 mmol/l (liu, 2003) and 2-12 bactrian camels (wernery et al., 1999). the na/k mean ratio was 28.1 which were lower than that reported for camels in the uae (39.5) by ayoub and saleh (1998) mainly due to higher levels of na in omani camels compared to the emirate ones. however, generally na and k levels in omani racing camels were within normal levels and may be used as clinical reference for the breed. calcium (ca) in animals, ca contributes to bone formation, neutralizes rumen excess acidity, enters into the composition of body fluids such as blood, enters into the composition of secretions such as hormones and milk. the range of ca values in omani camels’ serum was 8.7-10.3 mg·dl-1 (mean 9.63±0.43) which is equivalent to 2.41 mmol/l. these values were comparable to those reported for uae camels (9.5-11.5 mg·dl-1) and 2.8 mmol/l reported for iranian camels (mohri et al., 2008). ca values in omani camels were at the lower range compared to saudi camels (7.6-13.1 mg·dl-1), al-busadah, 2007); uae camels (11.3 mmol/l; ayoub and saleh, 1998) and temperate camels (11.5 mg·dl-1, faye et al., 1995). nonetheless, extremely lower ranges (1.62.8 mmol/l) were reported in some studies (higgins and kock, 1986; mcgrane and kenyon, 1984; mohamed et al., 2007). osman and al-busadah (2003) reported values of 9.0 meq/l for saudi camels and wernery et al. (1999) there were no differences between ca values obtained for female camels in the current study and values reported for non-rutting male camels (zia-rahman et al., 2007). ca serum levels in the female omani dromedary were higher than those in the female bactrian camels of 2.26±0.22 mmol/l (liu, 2003) and 2.4-2.7 mg/dl 72 squ journal of agricultural and marine sciences, 2016, volume 21, issue 1 serum biochemistry parameters in the omani racing arabian camels (camelus dromedarius) reported by wernery et al. (1999). phosphorus (p) the phosphorus serves in the number of metabolic functions in the animal body with about 80% of its body concentration used for maintenance and support of the skeleton co-precipitated with calcium. phosphorus is also a major constituent of the cells, membranes and body fluids and plays an important role in the energy supply. it also acts as a buffer and is involved in phospholipids and fatty acids transfer, the formation of amino acids and structure of dna and rna. the p serum levels in omani camels ranged between 5.0 to 8.5 mg·dl-1 (3.1 mmol/l) with a mean of 6.56±0.76 was comparable to that in egyptian camels (6.8 mg/dl; seleim et al., 2003). at its upper level it was higher than the upper range (3.4-7.7 mg·dl-1) reported for uae camels (3.5-6.0 mg·dl-1; wernery et al., 1999), kuwaiti (mohamed and hussein, 1999) and saudi camels (3.8 mg·dl-1) reported by osman and al-busadah (2003). the latter author’s findings indicated that serum p levels in camels are lower than those of cattle and sheep. there were some reports on differences between camel and other species in levels of serum p contents. for instance kamalu et al. (2003) reported that p was lower in cattle serum than in camels. values recorded for p in the present study were higher than those reported for the bactrian camel (1.65-2.01 mg·dl-1) by wernery et al. (1999) in uae. iron (fe) iron plays an important role in forming complexes with molecular oxygen in hemoglobin and myoglobin which are common oxygen transporting proteins in animals. iron is found at the active site of many important enzymes dealing with cellular respiration and oxidation and reduction in plants and animals. therefore, iron is important for racing animals because of its role in haemoglobin synthesis in the blood. fe in omani racing camels had a wider range (56-158 μg·dl-1) but its mean value (107.8±25.54 μg·dl-1) was comparable to the range reported for kuwaiti racing camels (63-170 μg·dl-1) by mohamed and hussein (1999). wernery et al. (1999) reported a range of 87-135 μg·dl-1 in 2-12 year old racing camels in the uae. osman and al-busadah (2003) reported a fe level of 80 μg·dl-1 in saudi camels. lower values of fe (46.2 μg·dl-1) were reported in iranian 5-year old female camels (badiei et al., 2006). there were no differences between values obtained for female camels in the current study and values reported for non-rutting male camels (zia-rahman et al., 2007). however, there are some reports that age has an effect on fe levels in camels. for instance faye et al. (2008) reported that older camels (>8 years) had highest fe levels (283 μg·dl-1) compared to those of 3-7 years of age. the omani dromedary camels had apparently higher levels of fe compared to the bactrian camel (4957 μg·dl-1) as reported by wernery et al. (1999). copper (cu) copper is a trace element essential for proper functioning of organs and metabolic processes in animals. high or low levels of cu intake can produce adverse health effects. cu deficiency cause ataxia or shallal specially in young animals which is common in oman. cu levels in omani camels ranged between 54.0 and 89.0 μg·dl-1 (mean 72.5±8.08 μg·dl-1). mohamed (2004) reported a comparable value of 57.6-72.4 μg·dl-1 in sudanese adult camels. serum cu levels could be quite variable as reported in camels raised in temperate regions (7-114 μg·dl-1) by faye et al. (1995). normal cu levels in ruminants range is 70-140 μg·dl-1 or 11-22 µmol/l according to abu damir et al. (2008) and 70-120 μg·dl-1(12-19 µmol/l) according to faye et al. (2008). plasma cu levels were significantly lower in camels (61 μg·dl-1) than cattle (111 μg·dl-1) as reported by bengoumi et al. (1998). faye et al. (2008) reported that normal serum cu levels in ruminants are between 70 and 120 μg·dl-1 and camel serum cu values are within this range (faye and bengoumi, 1994). consequently, the camels at the bottom of the range in the current study may be regarded as at a risk of being cu deficient. cu deficiency was observed in oman in other animals such as goats with reports of ataxia. copper deficiency in camels table 4. coefficients of determination (r2) and their significance between some serum biochemistry parameters in omani racing camels fe cu ca po4 k cl na fe 1 0.23 0.19 0.26 0.08 0.24 0.24 cu 0.23 1 0.21 -0.10 -0.25 0.27 0.20 ca 0.19 0.21 1 0.17 0.59** 0.69*** 0.80*** po4 0.26 -0.10 0.17 1 0.34 0.31 0.42* k 0.08 -0.25 0.59*** 0.34 1 0.54** 0.56** cl 0.24 0.27 0.69*** 0.31 0.54** 1 0.92*** na 0.24 0.20 0.80*** 0.43* 0.56** 0.92*** 1 *: p<0.05; **; p<0.01; ***; p<0.001 73research article eltahir, al-adhid,hago, mahgoub was also reported in east africa (faye and bengoumi, 1997) and even lower values of cu (20.5 μg·dl-1) were reported in iranian 5-year old female camels (badiei et al., 2006). racing camels in oman are usually kept in confined enclosures and their diet is strictly monitored. the basic fodder is fresh alfalfa which contains higher levels of cu compared to rhodesgrass hay (4.6 vs. 2.8 ppm) the other common roughage (abu damir et al., 2008). however, alfalfa has higher levels of molybdenum (2.2 vs. 0.6 ppm) and so4 (4.7 ppm). it is well established that excess molybdenum, inorganic sulfate, iron or zinc interferes with copper absorption in ruminants (abu damir et al., 2008). as mineral supplementation is not widely used with camels in oman, care should be taken to supplement these animals for cu. cupric oxide needle capsules which are safe and effective compared to mineral blocks (abu damir et al., 2008) may be a supplement of choice for cu. there were no differences between values obtained for female camels in the current study and values reported for non-rutting male camels (zia-rahman et al., 2007). also no sex effects on cu levels were observed by abdalla et al. (1988) and bengoumi et al. (1995). however, faye et al. (2008) reported that females had higher levels of cu than males (62 vs. 56.7 μg·dl-1). sex differences in mineral contents in camels may be more related to physiological status effect rather than sex per se. correlations between serum mineral values a correlation analyses was carried out between various blood parameters and coefficient of determination (r2) was listed in tables 2, 3 and 5. there was a significant correlation between bun and creatinine as well as between tp and albumin (table 2). therefore, either of these parameters may be used to estimate the other. relation between tp and protein is obvious as tp equals albumin plus total globulins. there were also high correlations between ast, alt, ggt and ld (table 3). these are liver function enzymes and could be used to estimate one another to reduce cost of analyses. the macro elements na, ca, and k had significant correlations. this was similar to reports in omani racing camels (eltahir et al., 2010). although there are not many reports on this aspect, kuria et al. (2006) reported a significant positive correlation between na and ca but a negative correlation between na and p. on the contrary there were no significant correlations within trace elements but there was a significant correlation between cl and ca, k and na (table 4). from a practical point of view, correlations between certain elements would reduce the cost of analyses for these elements as values of some of them may be estimated from other elements using regression equations. conclusions findings of the current study provide baseline values that may be used by clinicians for racing camels in oman and camels raised under similar conditions. values recorded for all serum metabolic profiles, enzymes and minerals were within the ranges reported for racing camels in the gulf region and indicated normal health of these animals. there were some significant correlations between some serum parameters that may be used to estimate their values which will reduce cost by reducing the number of elements to be analysed. references abdalla, o.m., i.a. wasfi and f.a. gadir. 1988. the arabian race camel normal parameters. 1. haemogram, enzymes and minerals. comparative biochemistry & physiology, 90:237-239. abu damir, h, t.a. abbas, and m. alhaj ali. 2008. copper status in breeding and racing camels (camelus dromedarius) and response to cupric oxide needle capsules. tropical animal health & production, 40: 643-648. ahmadi-hamedani, mahmood, khosro ghazvinian, mohammad mehdi darvishi. 2014. hematological and serum biochemical aspects associated with a camel (camelus dromedarius) naturally infected by trypanosoma evansi with severe parasitemia in semnan, iran. asian pacific journal of tropical biomedicine, 4: 743-745. ahmed, muna mm, m.e. awad and m.e.s. barri. 2003. some micro mineral profile in the serum of female camels as affected by the physiological state. pakistan journal of biological sciences 6: 1853-1855. al-ani, f.k., h.a. husayni and dm power. 1988. a comprehensive biochemical analysis of the blood of camel (camelus dromedarius). comparative biochemistry & physiology b, 89: 35-37. al-busadah, k.a. 2007. some biochemical and haematological indices in different breeds of camels in saudi arabia. scientific journal of king faisal university (basic and applied sciences, 8: 131-142. al-shami, s.a. 2009. comparative determination of serobiochemical constituents in in-door and free grazing camels. journal of animal & veterinary advances, 8: 896-898. ayoub, m.a. and a.a. saleh. 1998. a comparative physiological study between camels and goats during water deprivation. proceeding of the 3rd annual meeting of animal production under arid conditions, university of united arab emirates, 1:71-87. badiei k., k. mostaghni, m., pourjafar and a. parchami. 2006. serum and tissue trace elements in iranian 74 squ journal of agricultural and marine sciences, 2016, volume 21, issue 1 serum biochemistry parameters in the omani racing arabian camels (camelus dromedarius) camels (camelus dromedarius). comparative clinical pathology, 15:58-61. bakker, m., x.b., chen, , d.j. kyle, e.r. orskov and d.a. bourke. 1996. urinary and plasma purine derivatives in fed and fasted llamas (lama glama and l. guanacoe). comparative biochemistry & physiology, 113b 367-374. bengoumi m., b. faye, k. le kasm and j.c. tressol. 1995. facterus de variation des indicateurs plasmatiques du statut nutritionnel en oligo-elements chez le dromadaire au maroc. 1. valeurs usuelles et variations physiologiques. revue d’élevage et de médecine vétérinaire des pays tropicaux, 48:271-276. bengoumi m., a.k. essamadi,, j.c. tressol and b. faye. 1998. comparative study of copper and zinc metabolism in cattle and camels. biological trace element research, 63: 81-94. bhatia, j.s. 1986. special aspects of physiology of digestion in camel. farm animals, 1: 15-20. elias, e. and r. yagil. 1984. hematological and serum biochemical values in lactating camels and their newborns. refuah veterinarith, 41: 7-13. faostat (2015) food and agriculture organization of the united nation statistics. 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(veterinary bulletin 58: 7385). kuria, s.g., r.g. wahome, m.m. wanyoike and c.k. gachuri. 2006. effect of mineral supplement on plasma mineral concentration of camels (camelus dromedarius) in kenya. international journal of agricultural biology, 8: 168-171. liu, z.p. 2003. studies on the haematology and trace element status of adult bactrian camels (camelus bactrianus) in china. veterinary research communications, 27: 397-405. mcgrane, j.j. and s.j. kenyon. 1984. laboratory diagnosis manual for field veterinarians in the sudan. overseas development administration, london. mehrotra v. and m.l. gupta. 1989. seasonal variation in certain blood constituents in camel. indian journal of animal science, 59: 1559-1561. mohammed a.k., a.k.b. sackey, l.b. tekdek and j.o. gefu. 2007. serum biochemical values of healthy adult one humped camel (camelus dromedarius) introduced into sub-humid climate in shika-zaria, nigeria. journal of animal & veterinary advances. 6: 597-600. mohamed h.e. 2004. the zink and copper content of the plasma of sudanese camels (camelus dromedarius). veterinary research communications, 28, 359363. mohamed h.a. and a.n. hussein. 1999. studies on normal haematological and serum biochemical values of the ‘hijin’ racing camels (camelus dromedarius) in kuwait. veterinary research communications, 23: 241-248. mohri m., h.r. moosavian and m.j. hadian. 2008. plasma biochemistry of one-humped camel (camelus dromedarius): effects of anticoagulants and comparison with serum. research in veterinary science, 85: 554-558. omaf (oman ministry of agriculture & fisheries). 2012. results of the agricultural census 2012. department of statistics and information, directorate general of planning and investments promotion, ministry of agriculture and fisheries, sultanate of oman. (http://maf.gov.om/pages/pagecreator.aspx75research article eltahir, al-adhid,hago, mahgoub ?lang=en&i=0&cid=0&cmsid=800631&did=0) accessed october 26th 2015. omer, s.a., h. agab, h.a. samad gussey and i.y. turki. 2008. effect of feed type on some blood constituents of sudanese growing camel (camelus dromedarius) calves. sudan journal of veterinary medicine & animal husbandry, 47: 107-116. osman t.e.a. and k.a. al-busadah. 2003. normal concentrations of twenty serum biochemical parameters of she-camels, cows and ewes in saudi arabia. pakistan journal of biological sciences, 6:1253-1256. roussel, j.d., t.j. aranas and s.h. seyby. 1982. metabolic profile testing in holstein cattle in louisiana. american journal of veterinary research, 43: 1658-1660. saeed, a. and m.m. hussein. 2008. change in normal haematological values of camels (camelus dromedarius): influence of age and sex. comparative clinical pathology, 17: 263-266. sas institute inc. 2000. sas for windows, version 6.0, ed. sas 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(camelus dromedarius). animal reproduction science, 101: 172-178. research paper journal of agricultural and marine sciences vol. 20 (2015): 47-53 reveived 5 may 2014 accepted 19 feb 2015 protein resources and aquafeed development in the sultanate of oman stephen goddard 1* and fahad saleh ibrahim 2 1* sultan qaboos university, center of excellence in marine biotechnology, box 50, al-khod 123, sultanate of oman. stephen goddard ( ) email: sgoddard@squ.edu.om 2aquaculture centre, ministry of agriculture and fisheries wealth p.o. box 427, muscat 100, sultanate of oman. introduction aquaculture, the farming of fish, shellfish and seaweeds continues to be the fastest growing sector of global agri-food business. aquaculture production has increased and diversified whilst output from the capture fishery has remained stable or declined over the same period. in 2011 global aquaculture production was 63.6 million tonnes, whilst the capture fishery landed an estimated 90.4 million tonnes of fish and shellfish for direct human consumption and 23.2 million tonnes of fish for reduction to fish meal (fao, 2012). the growth in aquaculture production has been paralleled by the growth of the aquafeed industry. global aquafeed production was an estimated 40 million tonnes, a doubling of the 2003 requirements. the dependence of the aquafeed industry on finite quantities of fish meal and marine oils has brought into question the continued growth of the aquaculture industry and has stimulated a major research effort to find alternative, renewable supplies of protein and oils, which can be utilized in aquafeeds. the annual global production of fishmeal is around 5 million tonnes, which is derived from 22 million tonnes of raw materials. 75% comes from small fish, mostly small pelagic species, such as menhaden, anchovy, sardines and sand eels, whilst the remainder is derived from the by-products of fish processed for human consumption (shephard and jackson, 2012). global production of fishmeal is relatively stable, unless disrupted by the warm waters of an el nino. however prospects موارد الربوتني وتطوير أعالف األحياء املائية يف سلطنة عمان ستيفن جودارد1* وفهد صاحل ابراهيم2 abstract. the continued growth of intensive aquaculture is dependent on the development of sustainable protein sources to replace conventional fish meals in aquafeeds. practical alternatives are plant-derived protein, protein from micro-organisms and protein from under-utilized marine resources. the challenges are to find alternative ingredients with high protein, suitable amino acid content, high palatability and absence of anti-nutritional factors. there is considerable biotechnology-based research in this area, including genetic modification of plant-based proteins, use of probiotics to enhance digestibility and the renewed application of fermentation technologies to produce single cell proteins. research in oman is focused on the utilization of marine protein resources. fisheries by-catch and processing waste have been evaluated as liquid hydrolysates and as meals for inclusion in aquafeeds and new research is planned on the utilization of meso-pelagic fish (myctophids), which occur in abundance in the arabian sea and the sea of oman. initial studies have been conducted on the biochemical composition of the lantern fish, benthosema pterotum, which revealed favorable protein, amino acid and long-chain pufa content. potential limiting factors were high levels of saturated lipids and the heavy metals arsenic and cadmium. these results will be discussed within a general review of marine resources and aquafeed development in oman. keywords: aquaculture, oman, protein, aquafeed املســتخلص: يعتمــد اســتمرار منــو االســتزراع الســمكي املكثــف عــل تطويــر مصــادر الربوتــن املســتدامة ليحــل حمــل مســحوق الســمك التقليــدي يف األعــاف. وتكمــن البدائــل يف مشــتقات الربوتــن النبــايت، والربوتــن املشــتق مــن الكائنــات الدقيقــة والربوتــن الناتــج عــن املــوارد البحريــة غــر املســتغلة. وتكمــن التحديــات يف العثــور علــى املكونــات البديلــة الــي حتتــوي علــى نســب عاليــة مــن الربوتــن، ومســتويات األمحــاض األمينيــة املناســبة، وذات االستســاغة العاليــة، وليــس لديهــا العوامــل املضــادة للتغذيــة. هنالــك أحبــاث قائمــة بشــكل كبــر علــى التكنولوجيــا احليويــة يف هــذا اجملــال، مبــا يف ذلــك التعديــل الوراثــي للربوتينــات ذات األصــل النبــايت، واســتخدام معينــات حيويــة لتعزيــز اهلضــم وكذلــك التطبيقــات املتجــددة يف تكنولوجيــات التخمــر إلنتــاج بروتينــات ذات خليــة واحــدة. وتركــز األحبــاث يف ســلطنة عمــان علــى االســتفادة مــن مــوارد الربوتــن البحريــة. وقــد مت تقييــم الصيــد اجلانــي ومعاجلــة املخلفــات مــن التصنيــع الســمكي علــى شــكل بروتينيــات ســائلة كوجبــات إلدراجهــا يف أعــاف األحيــاء املائيــة. كمــا أن البحــوث اجلديــدة املخطــط إجرائهــا ســتكون علــى اســتخدام األمســاك البحريــة املتوســطة الســطحية كســمك الفنــار، والــي تتواجــد بكثــرة يف حبــر العــرب وحبــر عمــان. وقــد أجريــت دراســات أوليــة علــى التكويــن الكيميائــي احليــوي ألمســاك الفنــار، والــي كشــفت عــن مســتويات مواتيــة مــن الربوتــن، واألمحــاض األمينيــة وسلســلة طويلــة مــن حمتــوى األمحــاض الدهنيــة أومغــا-3 غــر املشــبعة. إال العوامــل احملتملــة الــي قــد حتــد مــن جودهتــا هــي املســتويات العاليــة مــن الدهــون املشــبعة واملعــادن الثقيلــة والزرنيــخ والكادميــوم. وســتناقش هــذه النتائــج مــن خــال اســتعراض عــام للمــوارد البحريــة وتطويــر أعــاف األحيــاء املائيــة يف ســلطنة عمــان. الكلمات املفتاحية: االستزراع السمكي، عمان، الربوتن، أعاف األحياء املائية. 48 squ journal of agricultural and marine sciences, 2015, volume 19, issue 1 protein resources and aquafeed development in the sultanate of oman for increasing fishmeal supplies from established fisheries are limited and alternative supplies of protein from unexploited and underutilized marine resources, plants and terrestrial animals are being linked to sustainable growth of the aquafeed industry. the aquaculture industry in oman is in its earliest stages and all aquafeeds are currently imported from international suppliers. there has however been a program of research into marine protein resources conducted by sultan qaboos university and the ministry of aquaculture and fisheries wealth. to the present this work has focused on the potential production of hydrolysates and fish meals manufactured from fishery by-catch and processing waste; potentially useful raw materials which are otherwise discarded. some recent attention has also focused on the future potential to harvest and process lantern fish (myctophidae) from the arabian sea and the sea of oman fish silage a practical method of processing fish processing waste and by-catch is through the production of acid silages (hydolysates). these are prepared by acidifying minced raw materials, which results in rapid hydrolysis caused by the fish digestive enzymes present in the raw material. the resulting viscous liquids can then be used directly as a wet ingredient in aquafeeds or can be dried into a stable powder. in studies in oman, acid silages were prepared by first mincing and then acidifying either whole sardines or fishery waste using propionic acid. the resulting mixture (ph < 4) liquefies, as proteins are reduced amino acids, polypeptides and peptides. the resulting liquid is most commonly co-dried, with finely ground cereal and used as a dry ingredient in formulated aquafeeds. in early studies in oman fish silage was concentrated and co-dried with wheat bran (3:1) in solar cabinet driers for testing as an aquafeed ingredient in feeds formulated for the blue tilapia, oreochromis aureus. analysis of the manufactured sardine silage showed that its amino acid content and profile exceeded the recommended nutritional requirements for tilapia and was highly digestible (goddard and al-yahyai, 2001). the chemical and nutritional properties of dried sardine silage were examined as a potential protein supplement for aquafeeds (goddard et al. 2003). the indian oil sardine, sardinella longiceps, accounts for 95% of the total landings of small pelagic fish and quantities considerably in excess of local requirements for direct human consumption are landed. traditionally, surplus catches are dried on the beach and sold as cattle and camel food; practices which result in problems of rancidity and contamination. procedures for the manufacture and drying of silage were examined as an alternative method for processing surplus catch into a protein-rich aquafeed ingredient. methods were developed to take advantage of ambient temperature conditions in a hot, arid region. feeding experiments using diets containing 0%, 10%, 20% and 30% co-dried silage resulted in growth and feed conversion efficiencies comparable with commercial grade fish meal, when incorporated into practical diets. significantly lower weight gain and higher feed conversion ratios were recorded in the treatment group fed 40% co-dried silage (goddard et al. 2003). no significant differences between the treatment groups were found following proximate analysis of whole carcasses. the results showed that co-dried silage could be incorporated in formulated feeds for juvenile oreochromis aureus up to inclusion levels of 30%, without impairing, growth or feed conversion. silage drying in order to further examine the practicality of manufacturing dried fish silage in oman, drying experiments were conducted in a commercial poly-tunnel (goddard and perret 2005). triplicate samples of each mixture were placed in stainless steel dishes (85 mm diameter, 25 mm depth) on a 1 m high table in the center of a 20 x 9 m poly-tunnel located at the agricultural experiment station of sultan qaboos university (23º 35’ n, 58º11’ e). the poly-tunnel was oriented north-south and was covered with a single 0.2 mm uv-inhibited polyethylene film. the experiments were conducted in june, which is generally the hottest month of year in the a’seeb area, oman. the containers of mixtures were spread randomly on a 1-m high, perforated metal bench which allowed air to flow around the dishes. the samples were weighed in situ at regular interval over the 4-day drying period. readings at 5 min intervals, averaged every hour, were recorded from twelve temperature and relative humidity sensors connected to a delta-t logger. the data logger was connected to a pc that was used to download recorded data from the logger. ten sensors were positioned along the poly-tunnel’s longitudinal and perpendicular axis to verify the presence of temperature and humidity gradients while the remaining two sensors where installed outside of the greenhouse. solar radiation was also measured every hour during the 4-day period using a pyranometer. the results from these experiments clearly showed that fish silage, mixed with cereal (wheat bran) could be dried to a stable (<10%) moisture content within 3 days (fig.1). the potential use of poly-tunnels for large scale co-drying of fish silage with cereals in tropical regions is indicated from the present study. the inclusion of co-dried fish silage as a major ingredient in aquafeeds could reduce dependence on expensive, imported fish meals and present an opportunity to cycle fishery waste, including by-catch, over-catch and processing waste, through aquaculture. the advantages of fish silage lie in its simple, inexpensive manufacturing technology which can be applied in remote locations or 49research article goddard, ibrahim on-board small fishing vessels. fish meals from by-catch and processing waste research has been conducted in oman into the potential use of fisheries by-catch in aquafeeds through the manufacture of conventional fish meals from selected by-catch from oman’s capture fishery. three experimental batches of fish meal (fish meals b, c and d) were prepared in a modern, commercial fish meal factory (rusail fish meal and oil factory, oman) from the raw materials listed in table 1. approximately one ton of fish, obtained from the offshore fleet of the oman fisheries company, was used to prepare each batch of meal. fish meal e, manufactured from combined sardine and tuna processing waste, was obtained from a commercial tuna and sardine cannery and fish meal plant (dhofar fisheries industries company, oman). fish meal a was a commercial anchovy meal. the composition of each meal is shown in table 2. five experimental feeds were formulated to contain each fish meal. varying amounts of each meal were substituted against wheat bran whilst all other ingredients were the same in each diet. the ingredients were ground, blended in a food mixer, extruded through a 4mm die, dried at room temperature and stored at -20ºc. a total of 450 fish (mean weight + sd, 5.1 + 0.3 g) were randomly assigned to 15, 80-l outdoor circular tanks. tanks were individually aerated and supplied from a header tank at a rate of 5 l h-1. mean ambient water temperature during the feeding experiments was 28 + 2.4 oc. fish were fed to apparent satiation twice a day at 0700 and 1800 by slowly introducing feed until the feeding response ceased. each of the five diets was fed to three groups, each of 30 fish and records of feed consumption were maintained for each treatment group. the parameters of growth and feed utilization calculated were specific growth rate (sgr), food conversion ratio (fcr), and protein efficiency ratio (per) and phosphorus retention were calculated as the key parameters of table 1. species composition of the fish batches used to make the meals for use in the experimental diets. (after goddard et al., 2008). fish meal common name species commercial fish meal a anchovy unknown by-catch b catfish indian mackerel spangled emperor threadfin bream moontail bigeye tigertoothed croaker oblique-banded croaker largehead hairtail bluefish olive grunt arius spp rastrelliger kanagurta lethrinus nebulosus nemipterus japonicus priacanthus humrur otollithes rubber umbrina ronchus trichiurus lepturus pomatomus saltatrix pomadasys olivaceous c chub mackerel indian scad scomber japonicus decapterus russelli d catfish arius spp processing waste e yellowfin tuna indian oil sardine thunnus albacores sardinella longiceps table 2. growth and feed utilisation by oreochromis niloticus fed test diets containing fisheries by-catch and processing waste meals for 9 weeks 1,2 (after goddard et al., 2008). diet variable 1 2 3 4 5 sem 1 initial fish weight (g) 4.9 5.2 5.3 4.9 5.0 0.08 final fish weight (g) 26.6 a 30.1 ab 31.0 ab 33.5 b 29.8 ab 0.75 weight gain (%) 520.5 a 554.6 a 576.3 ab 658.5 b 594.1 ab 14.5 specific growth rate (% d-1) 3. 2.7 a 2.8 a 2.8 a 3.1 b 2.8 a 0.05 feed consumption (g d-1) 0.53 a 0.53 a 0.54 ab 0.57 b 0.55 ab 0.06 feed conversion ratio 4 1.55 a 1.34 b 1.34 b 1.36 b 1.40 b 0.03 protein conversion ratio 5 1.64 a 1.87 b 1.92 b 1.81 ab 1.77 ab 0.03 phosphorus retention 6 18.33 ab 20.05 b 15.93 ab 13.94 b 15.30 b 0.08 survival (%) 98.8 98.8 96.6 97.3 96.6 1 pooled standard error of mean 2 mean values in each row followed by the same letter were not significantly different (p>0.05) 3 specific growth rate, sgr = (ln initial wt – ln final wt)/t 4 food conversion ratio, fcr = g dry food fed/g wet wt gain 5 protein efficiency ratio, per = g wet wt gain/g protein fed. 6 phosphorus retention = 100 x [g phosphorus/fish end – g phosphorus/fish start] / g phosphorus in consumed feed 50 squ journal of agricultural and marine sciences, 2015, volume 19, issue 1 protein resources and aquafeed development in the sultanate of oman growth and feed utilization (table 2). each of the 5 diets tested was readily consumed during the feeding experiments and supported favorable growth in juvenile tilapia (table 2). whilst some mortalities occurred (1.2-3.4%) no trends were apparent and these were not attributed to any nutritional deficiencies in the diets. fish fed diet 4 had significantly higher levels of food intake and growth and reduced feed conversion ratios. no significant differences were observed in the moisture, protein, ash or phosphorus content of the fish at the end of the 9-week feeding period. some significant differences in lipid content were observed however. lipid levels in fish, which had been fed diet 1, were significantly higher than values from fish receiving diets 2-5, and lipid levels in fish fed diet 2 were significantly lower than valued from fish receiving diets 1, 3-5. the phosphorus content of the diets ranged from 1.04 – 1.69% and phosphorus retention values ranged from 15.30 20.05%. phosphorus retention values were significantly higher in those fish fed diets 1 and 2, which had the lowest phosphorus content. the five fish meals used in the study were manufactured from different raw materials and showed a range of proximate compositions. the meals were selected on the basis of their ash and protein content, which are indicators of quality. those manufactured from the bycatch species and from fish processing waste contained more ash and less protein than the commercial anchovy meal. fish meals containing more than 15% ash may be categorized as high ash meals (hardy and barrows 2002) and typically have lower protein content. this trend was apparent in the four locally manufactured meals. high ash content is of particular concern with regard to excretion of phosphorus into the aquatic environment and phosphorus content is an important parameter of quality in fish meals used in aquafeeds. phosphorus content of the experimental feeds were higher than recommended dietary levels, which have been estimated at 0.7-1.0 % depending on fish size and dietary ingredients (viola et al. 1986). in the present study phosphorus retention was highest in fish fed diets with the lowest phosphorus content. no significant differences were seen, however, in the values of phosphorus from whole body analysis between any of the treatment groups at the end of the feeding experiment. values for weight gain (sgr) were consistent with, or exceeded, published data for tilapia fingerlings (el-saidy and gaber 2002). diet 4, containing catfish meal, supported the most favorable growth, exceeding the performance of fish fed a commercial anchovy meal (diet 1). catfish meal contained the highest levels of each essential amino acid, with the exception of methionine. the results clearly indicate the potential to use fishery by-catch meals in practical diets for tilapia. with details of the proximate composition of by-catch species, fish meals can made from different species or batches of species with known protein, lipid or ash content. these can then be blended to meet the specific requirements of aquafeed formulation. limitations on the use of fisheries by-catch and processing waste for the manufacture of silages and fishmeals for use in aquafeeds lie in the handling, maintenance of quality and logistics of using small quantities often in remote locations. figure 1. drying curves for the three fish silage (fs) and wheat bran (wb) mixtures of the ratios 85fs : 15wb (mixture 1) 75fs : 25wb (mixture 2) and 65fs : 35wb (mixture 3). (after goddard and perret, 2005). 51research article goddard, ibrahim lantern fish (myctophidae) mesopelagic fish are found throughout the world’s oceans and current estimates of 1000 million tonnes reveal that they dominate the world’s total fish biomass, forming a deep-scattering layer at depths between 200 and 1000 m (irigoien et al. 2014). surveys have revealed high densities in the sea of oman and the arabian sea (gjøsæter, 1984), where the dominant species is benthosema pterotum. this is a small species of lantern fish attaining a maximum size of 30 50mm, over an estimated lifespan of one year or less (hussain and al-khan, 1987). the regional distribution of lantern fish (table 3) has encouraged some commercial fishing in the sea of oman by iranian vessels. the trials followed a series of fishery surveys conducted between 1993 and 1998 (valinassab, 2007). trial catch rates (< 30 t daily per boat ) were too low however to support a viable fishery and further trials were indicated to identify more efficient gear and vessel size (valinassab et al., 2007). there is also some small-scale utilization of myctophids, collected from the arabian sea, for fish meal manufacture in india (sebastine et al., 2011). specimens of b. pterotum were collected during the rv mustaqila survey of the oman fishery in 2007-8, freeze-dried in the department of marine science and fisheries at sultan qaboos university and sent to ewos innovation for analysis in norway. total protein and amino acid content shows that fish meal from lantern fish is comparable with a commercial south american anchovy meal, except for slightly lower protein and lower histidine content (table 4.). whilst not reviewed in the present paper, parallel studies on lipid classes and fatty acid analysis of the freeze-dried fish revealed higher levels of saturated fats (40%) than are typical of commercial fish oils (20-30%). the samples also contained higher levels of phospho-lipids. n-3, long-chain pufa values were comparable to those of south american fish oils (elmowafi et al., 2010). the estimated levels of heavy metals in fish meal manufactured from lantern fish showed that both cadmium and arsenic are close to current upper limits set by the european union (table 5). if confirmed in more extensive studies this would potentially restrict the inclusion of lantern fish meal to < 30% in a formulated aquafeed, assuming that fish meal was the only source of these metals. persistent organic pollutants (pop) were low in the analysed sample and were well below the upper limit for dioxins and dioxin-like compounds in feed ingredients (table 5). further testing for ‘old’ organochlorine pesticides (eg. ddt) is necessary. these preliminary results of the biochemical content of lantern fishes are of limited value since they came from a single sample. a full program of sample collections at different seasons and from different geographical areas is necessary in order to more fully evaluate their biochemical and nutrient composition and presence of contaminants. results from oceanographic and fishing surveys show a high myctophid biomass available and there are clear indications that the species would be highly resilient to fishing, given the short nature of their life-cycle. at present however it is not clear whether this species is a single or multiple spawner (dalpadado,1988) although there is some evidence that two periods of maximum spawning occur, one in march-june and one in september to november (gjosaeter, 1984). prior to commercial exploitation further studies are needed to provide more details of the life-cycle, population structure and biomass of benthosema pterotum. whilst initial use of myctophids in the region has been in the manufacture of fishmeal (valinassab, 2007) recent research in taiwan has demonstrated the potential to manufacture protein-rich hydrolysates from the myctophid, benthosema pterotum (chai et al., 2012). conclusions marine resources exist in oman which could contribute to the manufacture of aquafeeds. the potential to manufacture fish silages and fish meals from fisheries by-catch and processing waste has been established. challenges table 3. regional distribution of myctophids. area biomass (mt) density (g m-2) density (t nm-2) sea of oman (oman) 5 73 250 sea of oman (pakistan) 3 35 120 arabian sea 33 22 75 gulf of aden 5 24 83 total 46 table 4. essential amino acid and total protein content of a single sample of freeze-dried lantern fish collected from the arabian sea compared with commercial anchovy meal (after el-mowafi et al., 2010). values in g kg-1. amino acid freeze dried fish fish meal anchovy meal arginine 36.4 37.5 37.9 histidine 14.0 14.4 21.4 isoleucine 24.0 24.7 30.2 leucine 46.3 47.7 50.0 lysine 50.4 51.9 53.3 methionine 18.1 18.6 18.5 phenylalanine 24.8 25.5 26.6 threonine 27.5 28.3 28.3 tryptophan 6.7 6.9 n/a valine 29.3 30.2 35.5 protein (n x 6.25) 63.2 65.1 66.7 1 calculated values derived by adjustment of the freeze-dried lantern fish amino acid values to an 8% lipid and 10% moisture fish meal. 52 squ journal of agricultural and marine sciences, 2015, volume 19, issue 1 protein resources and aquafeed development in the sultanate of oman lie however in the maintenance of quality in otherwise discarded materials. a necessary step in their utilization is to establish the value of these materials to both fishermen and end-users through commercial use. this may be anticipated in the future as aquaculture develops in oman and creates increasing demand for aquafeeds. the known stocks of lantern fish present an opportunity for oman to develop fishmeal manufacturing on an international scale. this must be preceded however by detailed studies of the resource and development of appropriate fishing methods in order to establish an economically-viable and sustainable fishery. acknowledgements the authors thank dr. adel el-mowafi, ewos innovation, norway, for the biochemical and data analysis of a sample of lantern fish collected from the arabian sea. references chai, h-j., y-l. chan, t-l. li, y-c. chen, c-h. wu, c-y. shiau, and c-j.wu. 2012. composition characterization of myctophids (benthosema pterotum): antioxidation and safety evaluations for myctophids protein hydrolysates. food research international 46: 118-126. el-mowafi, a., d. nanton, and m. berntssen. 2010. evaluation of lantern fish (benthosema pterotum) as marine source in fish feeds: nutrient composition and contaminents assessment. proc.of the 3rd global fisheries and aquaculture research conference, foreign agricultural relations, egypt 29 nov-1 dec pp 12-23. el-saidy, d.m.s.d., and m.m.a. gaber. 2002. complete replacement of fishmeal by soybean meal with dietary l-lysine supplementation for nile tilapia, oreochromis niloticus (l.) fingerlings. journal of the world aquaculture society 33: 297-306. food and agricultural organisation. 2012. the state of world fisheries and aquaculture. fao, rome. gjøsæter, j. 1984. mesopelagic fish, a large potential resource in the arabian sea. deep-sea research. 31: 1019-1035. goddard, j.s., and d.s.s al-yahyai. 2001. chemical and nutritional characteristics of dried sardine silage. journal of aquatic food product technology 10: 3950. goddard, j.s., e. mclean, and k. wille. 2003. co-dried sardine silage as an ingredient in tilapia oreochromis aureus diets. journal of aquaculture in the tropics 18: 257-264. goddard, j.s., and j.s.m. perret. 2005. co-drying fish silage for use in aquafeeds. animal feed science and technology 118: 337-342. goddard, j.s., g. shagaa, and a. ali. 2008. fisheries bycatch and processing waste meals as ingredients in tilapia, oreochromis niloticus, diets. aquaculture research 39: 518-525. hardy, r.w., and f.t. barrows. 2002. diet formulation and manufacture. in: fish nutrition (ed. by j.e.halver and r.w. hardy) 3rd edn. academic press, san diego, usa. hussain, s.m., and j. ali-khan. 1987. fecundity of benthosema fibulatum and benthosema pterotum from the northern arabian sea. deep sea research 34: 1293-1299. irigoien, x., t.a. klevjer, a. rostad, u. martinez, g. boyra, j.l. acuna, a. bode, f. echevarria, j.i. gonzolez-gordillo, s. hernandez-leon, s. agusti, d.l. aksnes, c.m. duarte, and s. kaartvedt. 2014. large mesopelagic fishes biomass and trophic efficiency in the open ocean. nature communications doi: 10.1038/ncomms4271. saetersdal, g, g. bianchi, t. stromme, and s.s.venema. surveys of mesopelagic fish in the northwest arabian sea 1975-1984. workshop on mesopelagic fishes, muscat, oman, 7-9 may, 2001. sebastine, m., k. chakraborty, k.k. bineesh, n.g.k. pillai, e.m. abdusamad, and k.k. vijayan. 2011. proximate composition and fatty acid profile of the table 5. heavy metal and residue content measured in a single sample of the lantern fish, benthosema pterotum, collected from the arabian sea (after el-mowafi et al., 2010). heavy metals measured values in fish (mg kg-1) estimated values in fish meal maximum legal content, eu1 compliance arsenic 13.8 16.0 15.0 risk cadmium 1.73 2.0 2.0 risk lead 0.09 0.10 10.0 compliant mercury 0.10 0.10 0.50 compliant residues dioxins (pcdd, pcdf and pcb’s) 0.249 teq pg/g 4.25 compliant 53research article goddard, ibrahim myctophid diaphus watase (jordan and starks, 1904) from the arabian sea. indian journal of fisheries 58: 103-107. shephard, c.j. and a.j. jackson. global fishmeal and fish oil supply – inputs, outputs and markets. 6th world fisheries congress, edinburgh, uk. 2012. tacon, a.g.j., m.r. hasa, and m. metian. 2011. demand and supply of feed ingredients for farmed fish and crustaceans – trends and prospects. fao fisheries technical paper 564. rome, fao. valinassab, t., g.j. pierce, and k. johannesson. 2007. lantern fish (benthosema pterotum) resources as a target for commercial exploitation in the oman sea. journal of applied ichthyology 23: 573-577. viola, s., g. zohar, and y. arieli. 1986. phosphorus requirements and its availability from different sources for intensive pond culture species in israel. part 1. tilapia. bamidgeh 38: 3-12. research paper journal of agricultural and marine sciences vol. 20 (2015): 24 – 29 reveived 15 aug. 2014 accepted 19 feb 2015 biofouling on artificial substrata in muscat waters sergey dobretsov sergey dobretsov ( ) sultan qaboos university, college of agricultural and marine sciences, dpt. of marine science and fisheries. box 34, al-khod 123. sultanate of oman. email: sergey@squ.edu.om introduction in marine environment any undefended natural and man-made substrate is quickly colonized by microand macro-organisms in a process known as “biofouling” (clare et al. 1992; wahl et al. 2012). biofouling is a multi-stage process. the first stage involves the formation of a biofilm mainly composed of bacterial and diatoms incorporated in a polysaccharide matrix (qian et al. 2007). at the second stage, spores of microalgae and larvae of invertebrates settle on the substrate covered with biofilms (clare et al. 1992). microbial biofilms (micro-fouling) either enhance or inhibit settlement of macro-fouling organisms (dobretsov et al. 2006). biofouling caused significant problems for industries and navies alike (callow and callow 2002; schultz et al. 2011). biofouling reduce speed of boats and ships, clogs aquaculture nets, water intakes and heat exchangers (okamura et al. 2010; schultz et al. 2011; sievers et al. 2014). additionally, biofouling organisms increase corrosion, shear stress and drag, eventually leading to higher fuel consumption and increased production of co2 by ships. in order to control and deal with biofouling around the world, countries spend annually more than us$5 billion (dobretsov et al. 2006). current antifouling methods are based on the usage of toxic metals, such as copper and zinc, and organic compounds, such as sea nine (yebra et al. 2004). these compounds pollute marine environment and are toxic to marine organisms and humans (ali et al. 2013; thomas et al. 2002). due to high environmental risks the use of one of the highly successful antifouling agent – organoالرتاكم احليوي على األسطح اإلصطناعية يف مياه مسقط سرجي دوبريتسوف abstract. macro-fouling communities developed on acrylic, aluminum, wood and fiberglass panels were investigated after 4 months exposure in marina bandar al rawdah and marina shangri la. wet weight of biofouling was about 2-fold higher in marina bandar rawdah and different communities were formed on the front and back sides of the panels. differences between communities on different materials were less pronounced. in the second study, wet weight and community composition of macro-fouling communities on ceramic tiles at the depth of 1 m and 5 m in marina bandar al rawdah were investigated. during 2008 – 2010, there were no differences between biomass of communities, while in 2011 biomass of macro-fouling was higher on tiles at 5 m. in december 2008 the minimal weight (0 kg/m2) and in september 2011 the maximal weight (26.3 kg/m2) of macro-fouling communities were recorded. in total, 27 invertebrate fouling species were found, which mostly (33%) belonged to phylum ectoprocta. three invasive bryozoan (bugula neritina, zoobotryon verticillatum and schizoporella errata) and one invasive tunicate (ciona intestinalis) species were observed. overall, this study indicates high biofouling pressure in muscat marinas and suggests necessity of future studies of fouling communities in oman waters. keywords: biofouling; invasive species; biomass; sea of oman. املســتخلص: مت البحــث يف جمتمعــات املرتاكمــات احليويــة الكبــرة الــي تكونــت علــى ألــواح مــن األكريليــك ، واأللومنيــوم، واخلشــب، واألليــاف الزجاجيــة بعــد أربعــة أشــهر مــن التعــرض يف ميــاه مارينــا بنــدر الروضــة ومارينــا شــاجنري ال. كان الــوزن الرطــب للرتاكــم الســطحي احليــوي يف مارينــا بنــدر الروضــة أكثــر حبــوايل الضعفــن مــن املوقــع اآلخــر، وكان هنــاك اختــاف يف مكونــات جمتمعــات املرتاكمــات احليويــة بــن الوجهــن األمامــي واخللفــي لأللــواح ، و كانــت الفــروق بــن املــواد املختلفــة أقــل وضوحــا مــن الفــروق بــن وجهــي األلــواح. ويف جتربــة أخــرى، متــت دراســة الــوزن الرطــب واملكونــات اجملتمعيــة جملتمعــات املرتاكمــات احليويــة الكبــرة علــى قطــع البــاط اخلــزيف )الســراميك( علــى عمقــي مــرت و مخســة أمتــار يف ميــاه مارينــا بنــدر الروضــة. بــن عامــي 2008 و2010 ، مل تظهــر فــروق يف الكتلــة احليويــة بــن جمتمعــات املرتاكمــات احليويــة يف العمقــن، ولكــن يف 2011 كانــت الكتلــة احليويــة جملتمعــات املرتاكمــات احليويــة الكبــرة أعلــى علــى قطــع البــاط املوجــودة عنــد عمــق مخســة أمتــار. ســجل أدىن وزن )0 كيلوجــرام للمــرت مربــع( يف ديســمرب 2008،وأقصــى وزن )26.3 كيلوجــرام للمــرت املربــع( يف ســبتمرب 2011 . إمجاليــا، ُوجــد 27 نوعــا مــن الافقاريــات املرتاكمــة علــى األســطح ، bugula :احليوانــات األشــنية(. ومت إكتشــاف ثاثــة أنــواع غازيَــة )دخيلــة( مــن هــذه الشــعبة هــي( ectoprocta تنتمــي لشــعبُة )%وكان معظمهــا )37 cliona intestinalis :هــو tunicataونــوع غــاٍز )دخيــل( مــن قربيــات البحــر neritina, zoobotryon verticillatum, schizoporella errata . بشــكل عــام، تشــر هــذه الدراســة إىل مســتوى عــال للرتاكــم احليــوي علــى األســطح يف ميــاه مراســي القــوارب يف مســقط، وتقــرتح ضــرورة القيــام بدراســات مســتقبلية حــول جمتمعــات املرتاكمــات احليويــة يف امليــاه العمانيــة. الكلمات املفتاحية: : الرتاكم احليوي على األسطح املغمورة، األنواع الدخيلة )الغازية(، الكتلة احليوية، حبر عمان 25research article dobretsov tin (tbt) – has been banned globally in 2008 (guardiola et al. 2012). therefore, there is a strong need to develop non-toxic or low toxic “environmentally friendly” antifouling solutions. for the development of a successful antifouling defence one need to investigate occurrence of biofouling species on different materials, depths, and during different seasons. while there is a strong indication that biofouling cause numerous problems for boat and ship owners, aquaculture and desalination plants in oman, there is limited information about biofouling in oman waters. it has been shown that the alga ulva sp. and the barnacle balanus amphitrite were the major macro-fouling species in oman waters (dobretsov et al. 2013). few publications describe biofouling communities in arabian gulf. high diversities of fouling organisms, such as algae, sponges, cnidarians, annelids, arthropods, molluscs and echinoderms, were found on fish cages in kuwait waters (mohammad 1976). another study conducted on the legs of oil platforms in abu dhabi demonstrated that the highest biomass of fouling organisms was observed at the depth of 5 m, while the highest number of individuals were found at the surface (stachowitsch et al. 2002). not only the exposure depth but also chemical and physical properties of the substratum affect formation of biofouling communities (connell and glasby 1999). it was demonstrated that higher densities of macro-fouling organisms were found on black but not on white substrata in oman waters (dobretsov et al. 2013). different macro-fouling communities were formed on wooden and metal substrata (scheer 1945). we hypothesized that formation of macro-fouling communities in oman waters is different and depends on the type of substrata, exposure depth and location. the main aims of this study were: 1) to investigate the formation of macro-fouling communities on acrylic, aluminum, wood and fiberglass panels in two marinas in muscat waters; 2) to study long-term (>3 years) dynamics of macro-fouling communities on ceramic tiles at the depth 1 m and 5 m in marina bandar al rawdah and 3) to identify main macro-fouling species present in muscat waters. materials and methods experimental sites this study was conducted at marina bandar al rawdah (23° 34’ 55” n 58° 36’ 27” e) and marina shanri la (23° 32’ 56” n 58° 39’ 23” e), muscat, sultanate of oman. these are semi-closed marinas with limited current (110 cm/s) few kilometers apart from each other. marina bandar al rawdah is relatively old (opened in 1996) and polluted, while shangri la is a new, unpolluted marina constructed in 2007. during the experiment, the average water temperature was 26.8ºc and salinity was 35.5 ppt. both marinas have similar temperatures and salinities, table 1. list of invertebrate fouling taxa recorded during this study in muscat waters with their taxonomic position. i phylum porifera class demospongiae, family mycalidae mycale sp. family chalinidae chalina sp. ii phylum cnidaria class hydrozoa, family campanulariidae obelia sp. iii phylum mollusca class bivalvia family ostreidae saccostrea sp. family pteriidae pinctada fucata class gastropoda family vermetidae vermetus sp. iv phylum annelida class polychaeta family serpulidae hydroides elegans serpula vermicularis v phylum arthropoda class maxillopoda family balanidae balanus amphitrite balanus trigonus vi sub phylum tunicata class ascidiacea family ascidiidae phallusia nigra acidia sp. family cionidae ciona intestinalis* family didemnidae didemnum sp. family botryllidae botrylloides sp. family polycitoridae eudistoma sp. vii phylum ectoprocta class gymnolaemata family bugulidae bugula sp. bugula cf neritina family lepraliellidae celleporaria cf aperta celleporaria vermiformis family schizoporellidae schizoporella errata family membraniporidae biflustra sp. as well as amounts of dissolved nutrients. the average depth at the experimental sites for both marinas is about 6m at low tides. 26 squ journal of agricultural and marine sciences, 2015, volume 19, issue 1 biofouling on artificial substrata in muscat waters experimental design two experiments were conducted. in the first study, acrylic, aluminum, wooden and fiberglass panels (size=250 x 150 x 3 mm) were exposed vertically to biofouling at the depth of 1m for 4 months (october 2011 january 2012) in marina bandar al rawdah and marina shanri la. each experimental set up contained one acrylic, aluminum, wooden and fiberglass panel attached by ties to a pvc pipe. pipes were attached to marina pontoons by ropes. the distance between the set ups was ~1m. there were 3 replicated set-ups in this experiment. at the end of experiment, the panels were retrieved and brought to the laboratory on ice. presence of dominant species was recoded. biofouling was scraped individually from front and back side of each panel using a knife. wet weight ± 0.1g of biofouling developed on both sides (front and back) of the panels was recorded. collected macro-fouling was storied in 70% alcohol and used for taxonomic identification. in the second study, ceramic tiles (size = 152 x 152 x 5 mm) were placed vertically at the depth 1m and 5m in marina bandar al rawdah. there were 5 replicated tiles for each depth. each tile was attached to individual ropes that were tied to pontoons. the distance between ropes was ~0.5m. every month tiles were retrieved and their individual wet weight ± 0.1g and presence of dominant species on the front size of the tiles were recorded. individual pictures of tiles were made and used for identification of species. then, tiles were deployed back to the sea. the experiment was conducted from february 2008 till december 2011. analysis of data presence of invasive species was detected by analysis of collections and photographs with the help of global invasive species database (www.issg.org). bryozoan species were identified by dr. andrey ostrovsky and species of decapods were identified by dr. sergey khvorov. for each experiment the mean wet weight was calculated. the data were square root transformed in order to ensure normality of variances. the normality data assumption was verified with the shapiro–wilk’s test. the effect of the type of substratum, its side and the exposure depth on wet weight of fouling communities was investigated by analysis of variance (anova) followed by a post-hoc hsd test. all calculations were performed using statistica 11.0 (statsoft, usa) software. in all cases, the threshold for significance was 5%. results experiment 1 wet weight of macro-fouling communities developed on front and back sides of acrylic plates in marina shangri la was similar to each other (fig.1). in opposite, weight of biofouling developed on the back side of fiberglass, wooden and aluminum plates was significantly (anova, hsd, p<0.05) higher than ones on the front side. it table 2. dominant fouling taxa found on acrylic, fiberglass, wooden and aluminum plates exposed for 4 months horizontally at the depth of 1m in marina shangri la and marina bandar al rawdah. location shangri la bandar al-rawdah front side back side front side back side acrylic red algae barnacles bryzoa red and green algae barnacles bryzoa bryozoa barnacles sponges bryozoa barnacles sponges fiberglass red and green algae barnacles red and green algae barnacles bryozoa barnacles sponges bryozoa barnacles sponges wood red algae barnacles red algae barnacles bryozoa barnacles bryozoa barnacles aluminum red algae barnacles oysters barnacles green algae bryozoa barnacles bryozoa barnacles figure 1. wet weight (g/m2) of macro-fouling communities developed on acrylic, fiberglass, wooden and aluminum plates exposed for 4 months horizontally at the depth of 1m in marina shangri la. data are means + 1 standard deviation. means that are significantly different according to a hsd test (anova: p< 0.05) are indicated by different letters above the bars. 27research article dobretsov was easy to scrape biofouling from acrylic, fiberglass and aluminum but not from wooden plates. wet weight of macro-fouling communities developed on different substrata exposed horizontally in marina bandar al rawdah was significantly similar (anova, hsd, p>0.05), except front size acrylic and fiberglass substrata (fig.2). again, it was difficult to remove biofouling from wooden plates. biofouling communities formed on different substrata were slightly different in each marina (table 1). for example, in marina shangri la bryozoans were found only on acrylic plates. at the same time, there were drastic differences between biofouling communities formed in both marinas. red and green algae were found only in marina shangri la but tunicates phallusia nigra (table 2) were observed only in marina bandar al rawdah. only in marina shangri la different communities were developed on front and back sides of the plates (table 1). experiment 2 wet weight of macro-fouling communities developed on ceramic tiles increased during the first year of study (fig.3). in december 2008 the minimal weight (0 kg/m2) of macro-fouling communities was recoded. on september 2011, the highest weight of communities (26.3 kg/m2) was detected on tiles that exposed to fouling at the depth of 5m. during first 3 years of the study, there were no significant differences between wet weight of fouling communities developed on tiles at 1m and 5m (fig.3). in opposite, in the last year of study, tiles exposed to fouling at 5m depth had the highest weight of communities. the average wet biomass on substrata at 1m depth was 10.3 ± 4.1 kg/m2, while at 5m depth was 14.0 ± 6.6 kg/m2. macro-fouling species during this study 7 different phyla of invertebrates were detected (table 2, fig. 4). in total, 27 fouling species were found. most of them (33%) belonged to bryozoa (phylum ectoprocta) (fig.4). among this group the most dominant were bugula neritina and schizoporella errata. b. neritina was mostly present during winter months (december – february), while s. errata dominated during summer and autumn (june october). in total, 4 invasive species was recorded. three invasive species (b. neritina, zoobotryon verticillatum and s. errata) belong to bryozoans and one (c. intestinalis) belongs to tunicates (table 2). discussion any unprotected substratum in marine environments gets quickly fouled by macro-fouling species (scheer 1945). our hypothesis was that fouling pressure on acrylic, aluminum, wood and fiberglass panels would be different. while our data demonstrated different biomass of fouling on some of these substrata (fig. 1 and 2), we observed that location (marina bandar al rawdah or shangri la) and position (front or back) of panels played a major role in the formation of biofouling communities. higher biomass was recorded on the front size of the panels in marina bandar al rawdah, while in marina shangri la biomass was higher on the back side of vertical panels. this could be due to differences in light intensity on front and back sides of the panels. it has been shown that orientation of the panels and light intensity affected formation of fouling communities (connell and glasby 1999; fairfull and harriott 1999). biomass of macro-fouling communities in marina bandar al rawdah was more than 2-fold higher than one in marina shangri la. this could be explained by differential fouling pressure due to the presence of different species in marinas. while temperature, salinity, currents, and nutrients were similar in both marinas, high organic and inorganic pollution in marina bandar al rawdah could enhance growth of certain species. it has been shown that aquatic pollution increases success of invasive and fouling species and reduce survival of local species (crooks et al. 2011; mayer-pinto and junqueira 2003). figure 2. wet weight (g/m2) of macro-fouling communities developed on acrylic, fiberglass, wooden and aluminum plates exposed for 4 months horizontally at the depth of 1m in marina bandar al rawdah. data are means + 1 standard deviation. data that are significantly different according to a hsd test (anova: p< 0.05) are indicated by different letters above the bars. figure 3. mean wet weight (kg/m2) of macro-fouling communities developed on ceramic tiles exposed to fouling in marina bandar al rawdah. 28 squ journal of agricultural and marine sciences, 2015, volume 19, issue 1 biofouling on artificial substrata in muscat waters the average wet biomass of fouling communities detected on ceramic tiles was higher than 10 kg/m2. after 4 months, the highest biomass 5.9 kg/m2 was detected on acrylic plates in marina bandar al rawdah. these biomasses are extremely high in comparison with the highest biomass (about 1.5 kg/m2) recorded on the oil platforms legs in the gulf region (stachowitsch et al. 2002). unfortunately, data about biomass of fouling communities in iranian waters are not available. our experiment suggests that biofouling in muscat and possibly in oman waters are more intensive than in other gulf regions. this could lead to more devastating effects on marine installations, desalination plants, ships and equipment working this area. experiment 2 conducted in marina bandar al rawdah showed that only in 2011 biomass of macro-fouling communities was higher on tiles exposed to fouling at 5m. previously, the highest biomass of fouling was observed on the oil platform legs in uae at the depth of 5m, while highest number of individuals was found at the depth of 0m (stachowitsch et al. 2002). in december 2008 the minimal weight of 0 kg/m2 of macro-fouling communities was recorded (fig. 3). possibly it was due to harmful algal blooms (habs) caused by the marine ichthyotoxic dinoflagellate cochlodinium polykrikoides (richlen et al. 2010). during habs of november 2008 – january 2009 the cochlodinium species were responsible for killing thousands of tons of fish, damaging coral reefs, impacting coastal tourism and desalination plants in the gulf region (richlen et al. 2010). while hab in the arabian gulf and the sea of oman has lasted for more than eight months till july 2009, biomass of fouling communities is quickly recovered after february 2009. current study is the first documented impact of habs on biofouling communities. during this study 27 species of biofouling invertebrate organisms belonging to 7 phyla were detected (table 2). previously, 76 species belonging to algae, sponges, cnidarians, annelids, arthropods, mollusks, echinoderms and chordates were observed on shells of pinctada fucata in kuwait waters (mohammad 1976). polychaetes, such as serpula vermicularis, hydroides chomoceros, and spirobranchus semperi, constituted more than 55% of all biofouling species. presence of sessile filter feeders, such as porifera, bivalves, cirripedia and ascidia, and small mobile forms, such as polychaetes and amphipods, was recorded of the legs of oil platforms in uae (stachowitsch et al. 2002). in our study, biofouling communities were dominated by bryozoan species (phylum ectoprocta). differences in fouling species could indicate presence of different fouling species existing in the gulf and the sea of oman. our study is the first one that demonstrated presence of invasive species in oman fouling communities. alien species include 3 invasive bryozoan (b. neritina, z. verticullatum and s. errata) and one tunicate (c. intestinalis) species (table 2). previously, only 11 alien and 6 species with un-identified biostatus were recorded in oman (www.issg.org). most of these species were found in terrestrial but not in marine environments. interestingly, invasive tunicate c. intestinalis was not recorded in this part of the world (therriault and herborg 2008). invasive species decrease biodiversity of indigenes communities and have serious impacts on fisheries and aquaculture (mollo et al. 2008). most of invasive species spread by ballast waters or by biofouling on ship hulls (gollasch 2002). while there is no data about the impact of these invasive species on marine communities and fisheries in oman, their detection is an alarming signal, which shows that early warning and control measures have to be developed in the nearest future. acknowledgements this work was supported by hm sultan qaboos research trust fund sr/agr/fish/10/01 and the internal grant, ig/agr/fish/12/01. we acknowledge the help of dr. andrey ostrovsky and dr. sergey khvorov in fouling species identification. references ali, h. 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identification and phylogeny of the fish-killing dinoflagellate cochlodinium polykrikoides.” harmful algae 9(2): 163-72. scheer, b. t. 1945. “the development of marine fouling communities.” biological bulletin 89(1): 103. schultz, m. p., j. a. bendick, e. r. holm, and w. m. hertel. 2011. “economic impact of biofouling on a naval surface ship.” biofouling 27(1): 87-98. sievers, m., t. dempster, i. fitridge, and m. j. keough. 2014. “monitoring biofouling communities could reduce impacts to mussel aquaculture by allowing synchronisation of husbandry techniques with peaks in settlement.” biofouling 30(2): 203-12. stachowitsch, m., r. kikinger, j. herler, p. zolda, and e. geutebrück. 2002. “offshore oil platforms and fouling communities in the southern arabian gulf (abu dhabi).” marine pollution bulletin 44(9): 853-60. therriault, t. w., and l.-m. herborg. 2008. “predicting the potential distribution of the vase tunicate ciona intestinalis in canadian waters: informing a risk assessment.” ices journal of marine science: journal du conseil 65(5): 788-94. thomas, k. v., m. mchugh, and m. waldock. 2002. “antifouling paint booster biocides in uk coastal waters: inputs, occurrence and environmental fate.” science of the total environment 293(1–3): 117-27. wahl, m., f. goecke, a. labes, s. dobretsov, and f. weinberger. 2012. “the second skin: ecological role of epibiotic biofilms on marine organisms.” frontiers in microbiology 3: 292. yebra, d. m., s. kiil, and k. dam-johansen. 2004. “antifouling technology—past, present and future steps towards efficient and environmentally friendly antifouling coatings.” progress in organic coatings 50(2): 75-104. research paper journal of agricultural and marine sciences vol. 21 (1): 19 – 24 doi: http://dx.doi.org/10.24200/jams.vol21iss0pp19-24 received 15 aug. 2014 accepted 19 feb 2015 an assessment of longnose trevally (carangoides chrysophrys) (cuvier, 1833) fishery in the arabian sea, oman issam h. al-rasady1 and anesh govender2 1 issam h. al-rasady ( ) marine sciences and fisheries center, ministry of agriculture and fisheries wealth po box 427, muscat 100, sultanate of oman. email: asamrasadi@hotmail.com 2 department of marine science and fisheries, college of agricultural and marine sciences, sultan qaboos university, po box 34, al-khod 123, sultanate of oman. introduction the rapid increase in fishing efforts and improved fishing efficiency in the last two decades have resulted in depletion of many fisheries stocks in the world (fao, 2007). this trend also applies to omani fisheries. for example, kingfish (scomberomorus commerson) catch in omani waters has declined from above 20000 mt in the late 1980’s to around 6000 mt in recent years, although the maximum yield was reported in 1988 at 27000 mt (goso, 2003). the catch of spiny rock lobster (panulirus homarus) declined from above 1900 mt in 1988 to only 180 mt in 1999 (goso, 2000). the ministry of agriculture and fisheries wealth plans to protect the economically important fish stocks from overfishing and longnose trevally carangoides chrysophrys belong to this category. carangoides chrysophrys is found in the indian ocean from the red sea and arabian gulf to the western of the pacific ocean from new south wales to the ryukyu islands (lieske and myers, 1994). insular localities for the species in the indian ocean include madagascar, comoros and the seychelles (smith-vaniz, 1984). longnose trevally carangoides chrysophrys, abundant in omani waters (al-abdessalaam, 1995), has a high economic value and supports both the commercial industrial and commercial traditional fisheries. oman is one of the countries in the world that contributes significantly to the reported global capture production of carangids (fao, 2005). though no separate catch statistics are available for c. chrysophrys in oman, large jacks catch data include nine commercially important species of the family carangidae, including longnose trevally and reported landings of 2359 mt were estimated for a value of 1.822 million omani rials (1 or = 2.6 usd) (goso, 2008). the current fishing regulations in oman apply only to the mesh size of the demersal trawler, which operate in coastal shallow and deep water of more than 50 m depth withتقييم املصائد السمكية للصال يف حبر العرب املطل على سلطنة عمان عصام محيد الرصادي1 . أنيش جوفندر2 abstract: the present study assessed the fishery state of longnose trevally (carangoides chrysophrys) in the north west arabian sea. key population parameters were estimated, and yield and spawning stock biomass per recruit analyses were conducted. the equation presented by alagaraja (1984) for estimating natural mortality resulted in m = 0.29 year-1 and lead to the best estimate of longevity. hence this value was used in the yield and spawning stock biomass per recruit analyses. the total mortality (z) was estimated as 0.39 year-1, based on a catch curve analysis. length-at-50% and age-at-50% captures were 38.21cm and 4 years respectively. the yield and spawning biomass per recruit analyses indicate that the current fishing mortality rate (fcurr) was lower than the fishing mortality corresponding to the maximum yield per recruit (fmax) and was also higher than the target reference point (f0.1) , suggesting that overfishing, currently, does not occur. however, any increase in the fishing effort in the future may lead to overfishing. keywords: mortality, length-at-50% capture, yield per recruit, longnose trevally املســتخلص: قامــت هــذه الدراســة بتقييــم مصائــد مسكــة الصــال (carangoides chrysophrys) يف الشــمال الغــريب لبحــر العــرب. وأجريــت التحاليــل ملوشــرات مصائــد األمســاك الرئيســية. وقــد أســفرت املعادلــة الــي قدمهــا alagaraja )1984( لتقديــر الوفيــات الطبيعيــة مبعــدل 0.29 يف الســنة وأعطــت أفضــل مؤشــر ألقصــى عمــر. وبالتــايل مت اســتخدام هــذه القيمــة يف تقديــر الكتلــة احليويــة للمخــزون البيــاض. وقــدر جممــوع الوفيــات )z( مبعــدل 0.39 يف الســنة. اســتنادا إىل حتليــل منحــى الصيــد فقــد كانــت أطــول 50٪ مــن األمســاك املعرضــة للصيــد حــوايل 38.21ســم اي يف عمــر 4 ســنوات. وتشــر حتليــات الكتلــة احليويــة للمخــزون البيــاض إىل أن معــدل وفيــات الصيــد احلــايل (fcurr) أقــل مــن وفيــات الصيــد املقابلــة ألقصــى قــدر مــن احملصــول الــذي ميكــن حتصيلــه (fmax). وكان أيضــاً أعلــى مــن النقطــة املرجعيــة املســتهدفة )f0.1(، ممــا يشــر إىل أن هــذا النــوع مــن األمســاك ال يتعــرض حاليــا للصيــد اجلائــر. ومــع ذلــك فــإن أي زيــادة يف جهــد الصيــد يف املســتقبل قــد تــؤدي إىل اإلفــراط يف صيــد هــذا النــوع مــن األمســاك. الكلمات املفتاحية: معدل الوفيات. الطول عند 50٪ من النضج اجلنسي. االنتاج لكل عنصر جديد. الصال 20 squ journal of agricultural and marine sciences, 2016, volume 21, issue 1 an assessment of longnose trevally (carangoides chrysophrys) fishery in the arabian sea, oman in the continental shelf and enforce a minimum mesh size for the main net of 210 mm and 110 mm in the cod end (rrwfmcs, 1999). minimum landing size limits in oman fishing regulations are applied only on crustaceans (lobster) and molluscs (abalone) (rrwfmcs 1999) because they represent an unreasonable amount of additional labour for the fleet if applied to commercial fisheries where catches are large (king, 1995). yield per recruit models are widely used in fisheries management. in this study we developed an age-structured yield per recruit (ypr) and spawner biomass per recruit (spr) models for the carangoides chrysophrys stock in the northwestern arabian sea to provide scientific advice to the fisheries managers. methods sampling freshly landed fish were randomly selected and purchased from commercial fishermen at two landing sites on the arabian sea coast of the sultanate of oman: al lakbi (18011’1” n; 56032’56” e) and raysut (16057’37” n; 53059’52” e). sampling took place from april 2005 to september 2006. specimens were caught with handlines, gillnets and traps. annual strong southwest monsoon winds (between may and september) result in poor weather conditions forcing fishing activity in al lakbi to cease; hence, all biological sampling took place at raysut (al-rasady et al., 2012; al-rasady et al., 2013) for a more detailed description of the sampling programme). population parameters various models were used in this study for estimating the instantaneous natural mortality rate (m) for each sex and combined sexes (table 1). where k = coefficient of von bertalanffy growth model, tm = maximum age or fish life span, and tm50% = the age at 50% maturity. in order to choose the best estimate of natural mortality, the criterion proposed by alagaraja (1984) was used as suggested by gonçalves et al. (2003): (tm)=4.605/m the method which gave the best estimate of longevity was applied and evaluated by a sensitivity analysis which varied m by ±10% in the per recruit analysis. instantaneous total annual mortality rates (z) was estimated using numbers at age data for each sex and combined with a pooled regression equation where the z value was estimated according to ricker (1975) from the right desending limb of a linearized age catch curve excluding age groups older than 14 yrs and those not fully recruited to the fishery (2 yrs old fish and younger for females and 3 yrs old fish and younger for males and sex combined) as suggested by sparre and venema (1989). the instantaneous fishing mortality (f) was estimated by subtracting the instantaenous natural mortality rate (m) from the instantaneous total mortality rate (z). length at 50% capture (lc) was estimated from the length frequency data by the method as suggested by griffiths et al. (2006). selectivity curves were generated by fitting a logistic function to the plot of probability of capture (chen et al., 1992) i.e. numbers in a particular size class divided by the total number of fish sampled (expressed as percentage) against size class (l), from which the value of the parameter (lc), the smallest size class at which 50% of the fish were fully recruited to the fishery was obtained. the logistic equation was: p l = 100 1+exp −r l−l c( )( ) (1) where pl = percentage of capture in length class l and r = the width of the ogive. the von bertalanffy (1934) equation was used to convert lc to an ageat50% capture (tc): t c =t 0 − 1 k ln 1− l c l ∞ ⎛ ⎝ ⎜ ⎞ ⎠ ⎟ (2) where lc = length-at-50% capture l∞ = the asymptotic length.9 table 1. emprical equations used to calculate natural mortality (m) for carangoides chrysophrys in the arabian sea. (k) growth coefficient of the von bertalnaffy growth model, (tmax) maximum age or fish life span, and (tm 50%) the age at 50% maturity. references equation assumpation rikhter and efanov (1976): m = 1.52 t m50%( ) 0.72 ⎛ ⎝ ⎜ ⎜ ⎞ ⎠ ⎟ ⎟ −0.155 close association between m and tm 50% hoenig (1983): ln m( )=1.44−0.982ln tm( ) relation between m and tmax alagaraja (1984): m = −ln 0.01( )/tm relation between m and tmax ralston (1987): m =0.0189+2.06k relation between m and growth rate 21research article al-rasady , govender per recruit analysis two variables, the spawner biomass per recruit (sbr) and yield per recruit (ypr) (beverton and holt, 1957), were calculated for various estimates of fishing mortalities ranging from 0 to 1 yr−1. the sbr was calculated using the following equation: sbr = sb r = exp − fs t −m( )t( ) t=0 tmax ∑ a lt( ) b g t (3) where sb = the total spawner biomass (in g), r = the number of recruits (set to 1, by definition), f = instantaneous fishing mortality rate, m = instantaneous natural mortality rate, a and b = constants of the length–weightrelationship of combined sexes, lt = the predicted von bertalanffy mean length-at-age t and tmax = the maximum observed age in the fishery (year) gt = the fraction of mature fish at age t andwas assumed to be knife-edged i.e. g t = 0,if t <t m 1,if t ≥t m ⎧ ⎨ ⎪ ⎩⎪ (4) where tm = the age at 50% maturity. st is the gear selectivity at age t and is also assumed to be knife-edged i.e. s t = 0,if t <t c 1,if t ≥t c ⎧ ⎨ ⎪ ⎩⎪ (5) where tc= the age at 50% capture. yield per recruit in number (yprs) was calculated as: ypr s = yp s r s = f s ,t f s ,t +m st=0 tmax ∑ e− fsss ,t −ms( )t 1−e− fsss ,t −ms( )( ) (6) where yps is the total yield in numbers for a cohort throughout its lifespan. yield per recruit (ypr) in mass was calculated from the following equation: ypr mass( ) = yprta lt( ) b t=0 tmax ∑ (7) where a and b are parameters of the length–weight relatable 2. natural mortality rates (m) estimated from different equations (table 1) for carangoides chrysophrys in the arabian sea. te= predicted longevity in years. method m (year -1) te (yr)male female combined rikhter and efanov (1976): 0.40 0.40 0.40 11.65 hoenig (1983): 0.28 0.28 0.28 16.61 alagaraja (1984): 0.29 0.29 0.29 16.00 ralston (1987): 0.49 0.54 0.53 08.63 y = 4.71 + − 0.35 ⋅ x, r 2 = 0.83 −2 0 2 4 4 8 12 16 age (years) lo g of f re qu en cy figure 1. age-based catch curves for males (top) , females (middle) and combined sex (bottom) for carangoides chrysophrys in the arabian sea. y = 4.98 + − 0.35 ⋅ x, r 2 = 0.82 −2 0 2 4 4 8 12 16 age (years) lo g of f re qu en cy y = 5.83 + − 0.39 ⋅ x, r 2 = 0.86 0 2 4 6 4 8 12 16 age (years) lo g of f re qu en cy 22 squ journal of agricultural and marine sciences, 2016, volume 21, issue 1 an assessment of longnose trevally (carangoides chrysophrys) fishery in the arabian sea, oman tionship of combined sexes. biological references point (fmax) and (f0.1) were estimated in order to compare them to the current fishing mortality and determine the status of the longnose trevally stock. results the von bertalanffy growth model parameters (l∞ , k, to and tmax) were obtained from al-rasady (2013) and the length-weight relationships constants (a sex combined ,b sex combined ) were obtained from al-rasady (2012). natural mortality and longevity, calculated for each sex and for the combined sexes, are shown in table 2. hoenig’s and alagaraja’s equations gave the best estimates of longevity, while the rest of the methods underestimated the longevity of longnose trevally. total mortality rates (z) for each sex and combined sexes are shown in figure 1. the total mortality rate for the combined sexes was higher than for each sex separately but the difference between z for each sex was small. fishing mortality (f) is presented in table 3. the z for the combined sexes was only used for estimating the fishing morality. fishing mortality had positive values when based on hoenig’s and alagaraja’s equations, but negative values based on the other models. fishing mortality estimated by hoenig was higher than the alagaraja method. the total length at which 50% of longnose trevally were caught in the fishery was 38.2 cm (fig. 2). this translates to an age of about 4 years using the von bertalanffy growth model. parameters used to assess the status of longnose trevally stock in the arabian sea using a per recruit analysis are given in table 4. at the current fishing mortality rates (fcurr) the spawning biomass per recruit (sbr) was at 46.85% of that at the absence of fishing mortality for the base case of and 36.95% and 59.02% for the -10% m and +10% m respectively (fig. 3). ypr curves, in mass suggests that a maximum yield can be attained at an fmax value equal to 0.147 year-1, 0.143 year-1 and 0.151 year-1 for the base case of m and -10% m and +10% m respectively (table 5). the estimates of f0.1 were nearly identical to the estimates of fmax (table 5). discussion equations of hoenig (1983) and alagaraja (1984) provide reasonable estimates of m for longnose trevally in the arabian sea. griffiths et al. (2006) used various equations to estimate the natural mortality, including hoenig’s (1983) equation, for the talang queenfish, scomberoides commersonnianus (carangidae). however, they excluded hoenig’s (1983) m estimate from the yield per table 3. populations dynamic parameters of carangoides chrysophrys in the arabian sea used in the per recruit analysis. parameter value a 0.0291 b 2.7702 l∞ 73.01 cm k 0.25 yr-1 t0 -1.21 yr tmax 16 yrs tc 3.85 yrs tm 4.83 yrs m 0.29 yr-1 -10% m 0.26 yr-1 +10% m 0.32 yr-1 fcurr m 0.0976 yr -1 fcurr -10% m 0.1264 yr -1 fcurr +10% m 0.0688 yr -1 table 4. estimates of biological reference points for longnose trevally carangoides chrysophrys captured in the arabian sea for varying values of natural mortality (m). estimates of fishing mortality (f) are in the unit yr-1. base case -10% of m +10% of m f0.1 0.146 0.142 0.15 fmax 0.147 0.143 0.151 0 25 50 75 100 20 40 60 80 total length (cm) fr ac tio n re ta in ed figure 2. selectivity curve for carangoides chrysophrys in the arabian sea showing the mean size at 50% capture. table 5. fishing mortality estimates for carangoides chrysophrys in the arabian sea. z = instantaneous total mortality rate and m is the instantaneous natural mortality rate and are given for the combined sexes. f = instantaneous fishing mortality rate. negative value of fishing mortality are unrealistic. method z (yr-1) m (yr-1) f (yr-1) rikhter and efanov (1976): 0.39 0.40 -0.01 hoenig (1983): 0.39 0.28 0.11 alagaraja (1984): 0.39 0.29 0.10 ralston (1987): 0.39 0.53 -0.14 23research article al-rasady , govender recruit analysis due to the large uncertainty and the fact that it tends to underestimate the maximum age (griffiths et al., 2006). in our study hoenig’s (1983) equation overestimated the maximum age and hence we choose the estimate of m from the alagaraja (1984) equation. the estimate of natural mortality in this study was 0.29 year−1 which is near the higher limit of natural mortality estimated for talang queenfish, s. commersonnianus, in northern australia (0.16–0.26 yr−1) (griffiths et al., 2006) and substantially lower than that observed for the fast growing species carangoides bajad and gnathanodon speciosus in the arabian gulf (grandcourt et al., 2004). total mortality rate in this study was 0.39 yr-1. values of the total mortality rate (z) were 1.16 and 1.83 yr−1 for c.bajad and g.speciosus from the arabian gulf, respectively which is high, possibly due to high growth rates and/or higher fishing effort (grandcourt et al. 2004). natural mortality estimates other than those based on hoenig’s (1983) and alagaraja’s (1984) equations lead to negative values of f which are unrealistic. the estimates of fmax and f0.1 were nearly identical in value. this is not surprising as the ascending limbs of the yield per-recruit curves (fig. 4) show little curvature (other than at the top of the curve) i.e. the ascending limbs are generally linear with a constant slope which abruptly changes at the top over a very short range of fishing mortality increase and then rapidly declines. the current fishing mortality rate (fcurr), by traps and handline, is well below the maximum fishing mortality fmax and f0.1 estimates. however, any future increase in fishing effort will lead to overfishing of the stock because carangoides chrysophrys has a slow growth rate coupled with a high longevity. stocks with low growth rates generally require low fishing effort to maximize the yield (king, 1995) and species with low population growth rate have a greater tendency to be overfished (nowlis and roberts, 1999). maximum fishing mortality (fmax) is usually greater than the fishing mortality at the maximum sustainable yield (fmsy), and exploiting the stock at fmax over an extended period may deplete the spawning stock and reduce future recruitment (clarke, 1991). harvesting at fmax, may in fact, lead to commercial extinction (doubleday, 1976; beddington and may, 1977; beverton, 1994; caddy and mahon, 1995) at the current fishing mortality rates (fcurr), for all the three cases of the natural mortality, the spawning biomass per recruit (sbr) is between (36.95 – 59.02) when compared to an unexploited stock. values of sbr lower than 20% is a source for concern as there would be high possibility of future recruitment failure (caddy, 1998). values of length and age at 50% capture are lower than the length and age at 50% maturity which results in immature fish being caught. the current fishing mortality rate (fcurr), for carangoides chrysophrys from the arabian sea is at an optimum level and should be maintained. however, any increase in the fishing effort may lead to overfishing of this fishery. references al-abdessalaam, t. z. 1995. marine species of the sultanate of oman, identification guide. ministry of agriculture and fisheries, marine science and fisheries center, publication no. 46/95. alagaraja, k. 1984. simple methods for estimation of parameters for assessing exploited fish stocks. indian journal of fisheries, 31: 177-208. 0 1000 2000 3000 0.0 0.1 0.2 0.3 0.4 0.5 fishing mortality s pa w ni ng b io m as s pe r r ec ru it (g ) model f0.1 fcurr fmax figure 3. spawning biomass per recruit curves for carangoides chrysophrys in the arabian sea using different natural mortality rates. the current estimated mortality rate (m = 0.2878) is the continuous line. the dotted line corresponds to current mortality -10%, whereas the dashed line corresponds to m +10%. the black triangles are fcurr, the open circles are fmax and the black squares are the target reference point f 0.1. 0 50 100 150 0.0 0.1 0.2 0.3 0.4 0.5 fishing mortality y ie ld p er re cr ui t ( g) model f0.1 fcurr fmax figure 4. yield per recruit (g) curves for carangoides chrysophrys in the arabian sea using different natural mortality rates. the current estimated mortality rate (m = 0.2878) is the continuous line. the dotted line corresponds to current mortality -10%, whereas the dashed line corresponds to m +10%.the triangles are fcurr, the circles are fmax and the squares are the target reference point f0.1. 24 squ journal of agricultural and marine sciences, 2016, volume 21, issue 1 an assessment of longnose trevally (carangoides chrysophrys) fishery in the arabian sea, oman al-rasady, i., a. govender, and s.m. al-jufaili. 2012. reproductive biology of longnose trevally (carangoides chrysophrys) in the arabian sea. oman. environmental biology of fishes, 93: 177-184. al-rasady, i., a. govender, and s.m. al-jufaili. 2013. age and growth of longnose trevally (carangoides chrysophrys) in the arabian sea. journal of applied ichthyoogy, 29: 1056–1060. beddington, j.r. and r.m. may. 1977. harvesting natural populations in a randomly fluctuating environment. science, 197: 463-465. beverton, r.j.h. and s.j. holt. 1957. on the dynamics of exploited fish populations, fishery investigations series ii, volume xix, ministry of agriculture, fisheries and food. beverton, r.j.h. 1994. the state of fisheries science. in: the state of the world’s fisheries resources, c.w. voitlander (editor), 25-54. oxford & ibh pvt. ltd., new delhi. caddy, j.f. and r. mahon. 1995. reference points for fisheries management. fao fisheries technical paper 347. caddy, j.f. 1998. a short review of precautionary reference points and some proposals for their use in data-poor situations. fao fisheries technical paper 379. chen, y., d.a. jackson, and h.h. harvey. 1992. a comparison of von bertalanffy and polynomial functions in modeling fish growth data. canadian journal of fisheries and aquatic sciences, 49: 1228-1235. doubleday, wg. 1976. environmental fluctuations and fisheries management. icnaf sel. pap. 1: 141-150. fao, 2005. the state of world fisheries and aquaculture. produced by the editorial production and design group.publishing management service fao. viale delle terme di caracalla, 00100 rome, italy pp. 150. fao, 2007. the state of world fisheries and aquaculture. produced by the editorial production and design group.publishing management service fao. viale delle terme di caracalla, 00100 rome, italy pp. 150. gonçalves, j.m.s., l. bentes, r. coelho, c. correia, p.g. lino, c.c. monteiro, j. ribeiro, and k. erzini. 2003. age and growth, maturity, mortality and yield-perrecruit for two banded bream (diplodus vulgaris geoffr.) from the south coast of portugal. fisheries research, 62: 349-359. goso. 2000. ministry of agriculture and fisheries, annual statistic report for 1999. maf, muscat, sultanate of oman. 198pp. goso. 2003. ministry of agriculture and fisheries, annual statistic report for 2002. maf, muscat, sultanate of oman. 198pp. grandcourt, e.m., t.z. al abdessalaam, f. francis, and a. al shamsi. 2004. population biology and assessment of representatives of the family carangidae carangoides bajad and gnathanodon speciosus (forssk°al, 1775), in the southern arabian gulf. fisheries research, 69: 331-341. griffiths, s.p., g.c. fry, and t.d. velde van der. 2006. population dynamics and fishery benefits of a large legal size of a pelagic sportfish, the talang queenfish, scomberoides commersonnianus, in northern australia. fisheries research ,82: 74-86. hoenig, j.m. 1983. empirical use of longevity data to estimate mortality rates. fisheries bulletin, 82: 898– 902. king, m.g. 1995. fisheries biology, assessment and management, fishing news books, oxford. lieske, e. and r. myers. 1994. collins pocket guide. coral reef fishes. indo-pacific and caribbean including the red sea. haper collins publishers. pp. 400. nowlis, j.s. and c.m. roberts. 1999. fisheries benefits and optimal design of marine reserves. fisheries bulletin, 97: 604-616. ricker, w.e. 1975. computation and interpretation of biological statistics of fish populations. fisheries research board canada bulletin no. 191. rrwfmcs. 1999. report of a regional workshop on fisheries monitoring, control and surveillance. gcp/int/648/nor – field report c-3 (en) muscat, sultanate of oman. smith-vaniz, w.f., 1984. carangidae. in w. fischer and g. bianchi (eds.) fao species identification sheets for fishery purposes. western indian ocean fishing area 51. vol. 1. fao, rome. sparre, p. and s.c. venema. 1989. introduction to tropical fish stock assessment. part 1manual, fao fisheries technical paper, 306/1 rev. 2. von bertalanffy, l. 1934. untersuchungen über die gesetzlichkeiten des wachstums. 1. allgemeine grundlagen der theorie. roux’ arch, entwicklungsmech. org., 131:613:653. research paper journal of agricultural and marine sciences vol. 21(1): 57 – 63 doi: http://dx.doi.org/10.24200/jams.vol21iss0pp57-64 received 15 jun 2015 accepted 19 feb 2016 an estimate of the willingness to pay for treated wastewater for irrigation in oman slim zekri*1, samiha al harthi1, hemesiri kotagama1 and shekar bose1 *1 slim zekri ( ) sultan qaboos university, college of agricultural and marine sciences, dpt. of natural resource economics. box 34, alkhod 123. sultanate of oman. email: zekri@squ.edu.om introduction agriculture in the sultanate of oman depends totally on groundwater based irrigation. the ministry of regional municipalities and water resources has indicated that the annual groundwater over-pumping exceeded 316 mm3 (mrmwr, 2013). further to quantitative scarcity of water, the degrading quality of groundwater has posed an added constraint (zekri, 2008; zekri, 2009). land affected by groundwater salinity due to over-extraction of ground water and sea water intrusion has been estimated as 70% of the agriculturally arable land area of the country (al-rawahy et al., 2010). thus, finding alternatives to overcome the shortage of irrigation water is a national priority and use of treated wastewater (tw) is being considered as an alternative. there are 58 wastewater treatment plants in the sultanate of oman that treat domestic and commercial wastewater. forty four of those are operated by ministry of regional municipalities and water resources. thirteen plants are located in muscat the capital city and are operated by haya a semi-private company and are currently producing around 100,000 m3/day of tw. it is expected that the volume of tw will increase with increased connection of houses to the sewage network. قابلية الدفع ملياه الصرف الصحي املعاجلة للّري يف عمان سليم زكري*1 ومسيحة احلارثية1 ومهيسري كوتاجاما1 وشيكار بوص1 abstract. the volume of treated wastewater (tw) produced in oman is increasing, due to increased connection of houses to the sewage network and increased construction of wastewater treatment plants. despite 68% of the tw been used for irrigating urban landscapes, 10.3 mm3 tw has been discharged to the sea in 2014. wastewater treatment plants are owned and operated by private companies, which aspire to sell excess tw, particularly to farmers, in order to recover cost of wastewater treatment. this paper has used the contingent valuation method (cvm) to estimate the farmers’ willingness to pay (wtp) for tw for farm irrigation. seventy two farmers responded to a face-to face interview on eliciting wtp to purchase tw as irrigation water, out of a total population of 400 farmers in seeb region who have farms in proximity to a wastewater treatment plant. the results indicated that farmers’ wtp for tw was on average 0.111 or/m3. wtp for tw was significantly affected by the income of farmers and whether the farm is a market oriented or non-market hobby oriented farm. the percentage of farmers willing to pay the average price or higher was 38%. most farmers are not willing to pay the price currently charged by the wastewater treatment company for landscaping irrigation (0.220 or/m3) given the large volumes required for farm irrigation. even rich farmers maintaining hobby farms are willing to pay only 0.128 or/m3 versus 0.087 or/m3 by the market oriented farmers. the wtp for tw is higher than the prices reported (or 0.005 to 0.023 or/ m3) for groundwater used in agriculture in oman. . keywords: treated wastewater, contingent valuation method, willingness to pay, irrigation, oman. املســتخلص: يتزايــد حجــم ميــاه الصــرف الصحــي املعاجلــة يف ســلطنة عمــان نتيجــة لزيــادة ربــط املنــازل بشــبكة الصــرف الصحــي وزيــادة بنــاء حمطــات ملعاجلــة هــذه امليــاه. وعلــى الرغــم مــن أن 68٪ مــن ميــاه الصــرف الصحــي تســتخدم لــري املناطــق اخلضــراء داخــل املــدن، فقــد مت تصريــف 10.3 مليــون مــر مكعــب مــن ميــاه الصــرف الصحــي إىل البحــر ســنة 2014. وتديــر هــذه احملطــات شــركات خاصــة ، حيــث تطمــح إىل بيــع الفائــض مــن امليــاه املعاجلــة خاصــة للمزارعــن مــن أجــل تغطيــة تكلفــة معاجلــة هــذه امليــاه. وقــد اســتخدمت هــذه الورقــة طريقــة التقييــم احملتملــة لتقديــر مــدى قابليــة املزارعــن للدفــع مقابــل اســتعمال ميــاه الصــرف الصحــي املعاجلــة ثالثيــاً للــري. وقــد مشلــت العينــة 72 مزارعــا مــن جممــوع 400 مــزارع يف منطقــة الســيب الذيــن لديهــم مــزارع بالقــرب مــن حمطــة معاجلــة ميــاه الصــرف الصحــي حيــث مت إجــراء مقابــالت وجهــا لوجــه حــول اســتغالل احملطــة ومــدى القابليــة الســتعمال امليــاه املعاجلــة ثالثيــاً للــري. أوضحــت النتائــج أن معــدل القابليــة للدفــع للميــاه املعاجلــة بلــغ 0.111 م / م3 يف املتوســط. وقــد تأثــرت النتائــج بشــكل كبــر بدخــل املزارعــن ومــا إذا كانــت املزرعــة موجهــة حنــو الســوق أو غــر موجهــة حنــو الســوق. وتقــدر نســبة املزارعــن املســتعدين لدفــع متوســط الســعر أو أعلــى بـــ ٪38 وأن معظــم املزارعــن ليســوا علــى اســتعداد لدفــع الثمــن الــذي تتحملــه حاليــا شــركة معاجلــة ميــاه الصــرف الصحــي لــري املناطــق اخلضــراء )0.220 لاير / م3( و ذلــك بالنظــر إىل الكميــات الكبــرة املطلوبــة للــري الزراعــي. أمــا املزارعــن األغنيــاء الذيــن ميتلكــون مزارعــا و ميارســون الزراعــة علــى وجــه اهلوايــة فهــم علــى اســتعداد لدفــع 0.128 فقــط للمــر املكعــب مقابــل 0.087 لاير / م3 مــن قبــل املزارعــن املوجهــن حنــو الســوق. جديــر باملالحظــة أن القابليــة للدفع للمياه املعاجلة أعلى بكثر من األســعار املتعامل هبا )0.005 إىل 0.023 لاير / م3( بالنســبة ملياه األفالج املســتخدمة يف الزراعة يف الســلطنة. الكلمات املفتاحية: مياه الصرف ، أسعار املياه، طريقة التقييم احملتلم 58 squ journal of agricultural and marine sciences, 2016, volume 21, issue 1 an estimate of the willingness to pay for treated wastewater for irrigation in oman the major client of haya is muscat municipality that is buying 68% of the supply of tw at a price of 0.220 or/ m3 to irrigate public landscapes. although tw utilization has increased due to the expansion of public landscaping projects and some industrial uses, the volumes unutilized and disposed to the sea are also increasing. tw can be considered as an alternative or a complement to groundwater for farm irrigation. apart from the direct benefits of irrigation on improving productivity of crops and livestock, use of tw for farming will have a positive impact on the environment, reduce the dependency on groundwater, contribute to water scarcity alleviation, and ensure sustainability of farming. although haya, the supplier of tw, is keen to charge a price for the supply of tw to ensure financial viability and sustainability of its business, farmers’ willingness to pay (wtp) for tw is unknown, as tw has not been marketed for farm irrigation thus far. this paper assesses the farmers’ wtp for tw for farming, using the contingent valuation method (cvm). the paper is organized as follows: section 2 gives an overview of the tw supply and use in muscat, section 3 provides a review of literature particularly on the use of cvm in estimating the wtp for tw. section 4 presents the sampling and survey methods and the econometric model used to validate the estimated value of tw. section 5 and 6 presents the results and conclusions, respectively. treated wastewater supply in muscat table 1 shows the volumes of tw produced, marketed (utilized for landscape irrigation) and the unutilized volumes discharged to the sea or wadis (water ways) by wastewater treatment plants in muscat, during 2014. the total annual volume of tw discharged to the sea has been 10.3 mm3 or 32% of the total tw produced in 2014. a new wastewater treatment plant which is expected to be commissioned by beginning of 2016 in seeb will produce initially, 55,000 m3/day and 80,000 m3/day by 2025, of tw. the expected increase in tw supply up to year 2025 is given in figure 1. the current cost of producing tw by haya is around 0.800 or/m3. the prices charged on sales of tw vary from 0.231 or/m3 for commercial users to 0.154 or/m3 for residential users (figure 2). thus, on average haya receives 0.170 or/m3 on sales of tw. figure 3 shows the subsidy paid by the government to haya for the services provided on treating wastewater. the subsidy covers the difference between the cost of treatment and the revenue from tw sale plus the average price paid by the different users. taking into account that 68% of the tw is marketed the net price received by haya for each cubic meter is 0.150 or/m3. as a result, the total governmental subsidy to haya represents 0.481 or/m3 or 60% of the total cost. to transform the wastewater treatment industry into an unsubsidized self-financed table 1. production and use of tw during 2014 in muscat. plant production (m3) utilized (m3) discharged to sea (m3) utilization (%) al ansab 22,476,724 15,479,297 6,997,427 69% darsait 6,569,436 4,280,083 2,289,353 65% shattie al qurum 1,470,757 415,800 1,054,957 28% al mabella 637,848 637,848 0 100% al khoudh 308,476 292,319 16,157 95% madinat alsultan qaboos 432,961 432,961 0 100% al amerat 336,962 320,321 16,641 95% quraiyat 138,130 107,676 30,454 78% bawsher 79,937 47,370 32,567 59% al manuma 53,121 53,121 0 100% jibroo 34,922 34,922 0 100% hail al ghaf 49,182 0 49,182 0% total 32,588,456 22,101,718 10,486,738 68% 100000 150000 200000 2012 2014 2016 2018 2020 2022 2024 year t re at ed w at er p ro du ct io n m 3 da y− 1 figure 1. estimate of tw production in muscat (m3/day) from year 2012 to 2025. source: haya water company (2012) 59research article zekri, al harthi, kotagama and bose sustainable industry, users should at least pay part of the cost of wastewater treatment. one of the options is to sell part of the tw to farmers for crop irrigation. the re-use of tw in the agricultural sector is stimulated by the severe water scarcity and deteriorated water quality. groundwater salinity in the batinah coastal area is the consequence of over-pumping (oman salinity strategy, 2011). the use of tw can partially reduce the pressure on groundwater over pumping. literature review haya water company is interested to know how much farmers would be willing to pay for tw and how much of tw they would be willing to buy, if a project of transferring water from the treatment plants to farms was implemented. such estimates would enable the company to examine the financially sustainability of tw transferring investment. a large proportion of farm owners in the study area are hobby/leisure, i.e. famer owners undertaking farming as a hobby and not for financial profits. on the other hand, tw is not yet available to farmers in oman and thus its value is wholly unknown. these circumstances warrant the use of cvm to estimate the value of tw. a comprehensive theoretical review (gunatilake, 2003) of the cvm and its applications to estimate wtp for water supply is provided by gunatilake, et.al. (2007). cvm uses survey techniques to elicit wtp of non-marketed commodities and where revealed or indirect methods of valuation cannot be applied. in cvm respondents express their wtp on a ‘described’ hypothetical situation, as in this study the supply of tw. very few studies have been undertaken to estimate wtp for tw as compared to studies on supply of fresh water for irrigation and domestic use, using cvm. abu-madi (2004) has used cvm with a bidding game to determine farmers’ willingness to pay for reclaimed wastewater in jordan and tunisia. farmers were asked to respond yes or no in favor of paying prices for tw varying between us$ 0 to 0.25/m3 with bids increasing by us$ 0.05/m3. a logit model was used where the dichotomous responses to seven bids are entered as dependent variable. results indicated that higher prices of conventional water as well as higher farmer’s profit increase farmers’ wtp for tw. about 84% of the interviewees showed interest to take reclaimed tw if the price was us$0.05/m3. the percentage declined to 47% when the price was us$ 0.10/m3. tziakis et al., (2009) have estimated the benefits from wastewater treatment and reuse using cvm in northwest crete. a tobit regression model with two dependent variables has been used, viz; wtp for the provision of wastewater treatment and wtp for recycled water as a percentage of the price of fresh water. their results showed that farmers wtp for recycled water on average was 61.2% of the freshwater price or $/m3 0.01 and that farmers with higher income (1200-1800 €/month) are willing to pay for recycled wastewater with higher average bids than those with lower income (less than 1200 €/month). alebel et al., (2009) have used cvm in addis ababa, ethiopia to determine the value of improved wastewater irrigation. the authors have found that the number of years with irrigation experience, education, total annual revenue, and the kind of policy option significantly affected farmers’ wtp for wastewater. the authors have highlighted that household’s wtp for wastewater for crop production increases with higher income from farming. alcon et al., (2010) estimated murcia’s citizens’ non-market benefits (ecological and social) of improved treatment of wastewater used in agriculture on the segura river. they used cvm to determine citizens’ wtp to preserve the river’s ecological status. the maximum wtp was elicited through an open-ended question while the payment vehicle is a monthly increase in the water bill. a tobit model was used and the independent variables were the age, education level, gender, income size of the household and visits to the segura river. results showed that the average wtp was $0.34/m3. respondents with larger families were willing to pay less while those who use the river for recreation are willing to pay more than people who do not. alfarra et.al., (2013) analyzed farmers’ wtp for tw in the jordan valley in order to evaluate the future de0.154 0.193 0.231 0.17 0.8 0.0 0.2 0.4 0.6 0.8 residential governmental commercial average treatment cost o m an i r ia ls m −3 figure 2. cost of water treatment and prices paid by users for tw. 0 60 19 21 100000 0 25 50 75 100 pe rc en ta ge s item charges for wastewater treatment price for tw reuse subsidy wastewater treatment cost figure 3. subsidy (in %) to wastewater treatment in muscat. 60 squ journal of agricultural and marine sciences, 2016, volume 21, issue 1 an estimate of the willingness to pay for treated wastewater for irrigation in oman mand of tw given the expansion in supply and whether farmers will be paying a higher price in the future so as to cover a greater portion of the cost. farmers were paying 0.01 $/m3 for both fresh and tw. six bids were presented to farmers with prices of tw ranging from the current price to a price ten times higher. an ordered logit model which is an extension of the logistic regression model for dichotomous dependent variables was used. the wtp was used as a dependent variable and 12 independent variables ranging from cultivated area to religious prohibition were used in the model. the main findings were that; higher farm profits related to higher bids; low water prices negatively influences the farmers‘ decision on wtp and farmers with high concerns on health made low bids on wtp. azahara et al., (2012) in spain and tang et al. (2013) in china used cvm to estimate the wtp for ‘guaranteed’ water supply for irrigation under scarcity conditions and the willingness to pay for irrigation water, respectively. azahara et al., (2012) have indicated that the respondents with higher gross income per hectare were willing to pay more for the improvement of the service of guaranteed water supply than farmers with lower income. tang et al., (2013) have indicated that, as expected of economic theory, households with higher income have a higher mean wtp for irrigation water. methodology the objectives of this paper were to estimate the farmers’ wtp for tw and to identify the socio-demographic factors affecting wtp. shakhakhit, the study area is located in the batinah coastal region, in northern oman as shown in the map (figure 4). the area is very close to the new seeb water treatment plant where a main tw network connection already exists as shown in figure 4. but the sub-connections to the farms are expected to be provided subject to farmers’ wtp and the financial viability of such an investment. there are about 400 farms ranging from 1 to 36 acres/farm in the study area. palm dates are the dominant crop due to its tolerance to groundwater salinity. most of the farms are individually owned whilst the rest are family farms with multiple owners. survey design and data collection a random sample of 100 farmers out of a total population of 400 farmers was targeted. the list of farm owners and their phone numbers was provided by the ministry of agriculture and fisheries. appointments were arranged with the farm owners for a face to face interview at the farm. only 72 farmers responded to the interviews. the questionnaire was divided into four sections. section (1) provided the background and purpose of the survey; section (2) covered the demographic, socioeconomic profile of the households, and socioeconomic profile of figure 4. study area and al seeb treatment plant (stp). 61research article zekri, al harthi, kotagama and bose the respondent; section (3) addressed the current water supply conditions and consumption behaviors; section (4) presented the contingent valuation (cv) market scenarios followed by questions eliciting wtp values. econometric model to validate the estimate of wtp, the following regression model was developed with variables that were expected to be related to farmers’ wtp for treated wastewater. wtp = α 0 +α 1 (income)+α 2 (year)+α 3 (area) α 4 (cost)+α 5 (d 1 )+α 6 (d 2 )+ε t , ε t ∼n 0,σ 2( ) (1) where: wtp = willingness to pay (or/m3) income = monthly income of household (or) year = years owning the farm area = farm area (acres) cost = monthly cost of alternative water (or) the dummy variables d1 and d2 are defined as follows: d1= 0, if the respondent live in the farm and ‘1’ otherwise d2= 0, if hobby farm and ‘1’ if business oriented farm and εt is the error term. a general-to-specific modelling procedure was applied by including all independent variables in the initial step and then search for the best combination of independent variables that yielded the best model based on the highest r2 value, lower sum square error (sse) of residuals, expected sign and significance of coefficient estimate, joint significance of the variables, and residual normality (jarque and bera, 1987). results the average age of the farm owners was 47 years. the average number of years of owning the farm was 18.5. most farms are family owned with several owners. sixty three percent of the families are living in the farms and the remaining visit their farms only during weekends or holidays. all the farms are managed and operated by expatriate workers. none of the farmers interviewed depended on farming exclusively as a source of income. farmers are engaged in their own business or employed in the government or private sector. thirty three percent of the interviewees were self-employed, with 31% of them earning a monthly income of above 3,000 or (1  omani rial = 2.6 us$). the average farm area was 10.2 acres while the average cropped area was 4.64 acres. eighty eight percent of the farmers use groundwater despite the high salinity. fifty eight percent of the farmers declared that the quality of groundwater was extremely poor. some farmers used desalinated groundwater or bought tw supplied by bourses. on average the monthly cost of water used for irrigation is 70 or per farm regardless of the source of water. the survey showed that the dominant crops are date palm in 94% of the farms followed by alfalfa and rodhes grass cultivated for animal feed. these crops are grown as they could tolerate water salinity. a number of other crops were cultivated in a very limited area that were not productive due to high water salinity. on being asked if they would accept to use tw for irrigation, 86% of the respondents agreed to use tw, whilst 8% were undecided and 6% disagreed. farmers considered the use of tw as an opportunity to bring back or improve farm production in farms that have been heavily affected by salinity. the respondents who were undecided and disagreed about using tw were asked to justify the reasons for their response. only 44% of them mentioned concerns of adverse health impact and distrust about the water quality. a bidding game was used to elicit the farmers wtp for tw and the estimated average wtp for tw was 0.105 or/m3. in order to identify the factors affecting the wtp a regression analysis was done. results are shown in table 2. two variables (income and the farm type as hobby farm or commercial farm) are significant at 5% level. the positive relation between wtp and income validates the wtp estimate. although not all variables are individually significant they are jointly significant since the f-stat is higher than f-critical (2.505 > 2.37). a normality test was conducted and the calculated jb was 5.1179 < 5.999 table affirming that the residuals were normally distributed. the observed mean of wtp was found to be 0.105 or/m3 and the predicted mean wtp was 0.111 or/m3. the mean wtp (0.128 or/m3) for hobby farmers (40% of the sample) is much higher than wtp (0.087 or/m3) expressed by the market oriented farmers (60% of the sample). correlation analysis showed that the wtp of hobby farmers was significantly related with income. the higher the income the higher the wtp to pay was. however for the market oriented farms there was no correlation between income and wtp. figure 5 shows the demand curve for tw of the farmers in shakhakhit area. the volume of tw (m3) purchased by each farmer was estimated based on farmer’s current expenditures on water for irrigation dividtable 2. results of the regression analysis. variables estimated coefficients t-statistics income 0.0254 2.56* live -0.0169 -0.92 area -0.0001 -0.07 cost 0.0000 0.54 d2 -0.0354 -2.21* summary statistics: r2 = 0.16, sse = 0.06, f-test (joint test) = 2.51*, mse = 0.004 62 squ journal of agricultural and marine sciences, 2016, volume 21, issue 1 an estimate of the willingness to pay for treated wastewater for irrigation in oman ed by his wtp for tw. the curve shows that the total demand would reach 545,563 m3/year when prices vary from 0.310 to 0.055 or/ m3. this volume is very small compared to the capacity of seeb plant which will start at 20 mm3/year. in case haya water company uses the average wtp of 0.111 or/m3 the demand will reach around 300,000 m3/year. finally if the price of water will be 0.055 or/m3 it is expected that demand will reach 609,000 m3/year. the estimates show that the expected demand volumes are too small compared to the seeb plant capacity even at low price. consequently, in such a situation, haya water company will have to propose a regressive tw price for farmers. the lower the price the higher the volume demanded by farmers will be. the objective is to distribute the fixed costs over the largest possible volume of water. experiences from the long active agricultural water markets in oman show that the water prices are rather on the low side varying from 0.005 to 0.023 or/m3 (zekri et al. 2006). further investigations are required, such as through use of linear programming farm models, to estimate the value of wtp and confirm the results obtained in this study. conclusions groundwater quality is worsening in the batinah region of oman due to over-pumping of water for farming. some of the highly productive farms have become unproductive over time. given the increased salinity tw is being viewed as an alternative to groundwater for farm irrigation. volumes of tw in muscat are increasing due to more houses being connected to the sewage network and increased construction of treatment plants. currently 32% of the tw is discharged to the sea and it would increase in the future. the potential to use tw to irrigate farms is considered, whilst charging a price that would enable the private companies supplying tw to be financially viable and sustainable. cvm was used to evaluate the farmers’ wtp for tw in shakhakhit, seeb. the study area was chosen because of its close proximity to the new water treatment plant constructed in seeb. seventy two questionnaires were completed for the study from a total number of 400 farms which represents 18% of total population. the average calculated wtp is or 0.111 per m3. the percentage of farmers willing to pay above this price is 38%. sixty two percent of the farmers are willing to pay this price and below. haya water company is currently selling the tw at 0.220 or/m3 which most of farmers do not accept to pay as it would make farming unprofitable. hobby farmers are willing to pay more for tw than commercial farms. the mean wtp was 0.128 or/m3 for the hobby farms and 0.087 or/m3 for the market oriented farms. the demand that could be generated by conveying the tw up to shakhakhit farms is very small compared to the seeb treatment plant estimated to 20 mm3/year and represents less than 5% of total plant capacity. the estimated wtp was validated by an econometric model in which wtp for tw was the dependent variable and farmer’s income, whether farmer lived in the farm, years owning the farm, farm area, cost of alternative irrigation water and the whether the farm is a hobby or market oriented farm were independent variables. the results as expected indicate that farmers’ wtp for tw is significantly affected by income and whether the farm is a market oriented or hobby farm and thereby validates the wtp estimate. references abu-madi m.o.r. (2004) incentive systems for wastewater treatment and reuse in irrigated agriculture in the mena region: evidence from jordan and tunisia. phd thesis, delft university of technology, delft, the netherlands. alcon f., pedrero, f., martin-ortega, j., arcas, n., alarcon, j.j., de miguel. m. d. (2010)the non-market value of reclaimed wastewater for use in agriculture: a contingent valuation approach. spanish journal of agricultural research 2010 8(2). alebel b, weldesilassie, oliver. f, eline. b, stephan. d (2009) the economic value of improved wastewater irrigation: a contingent valuation study in addis ababa, ethiopia. journal of agricultural and resource economics 34(3): 428–449. alfarra a., sonneveld, b. g. j. s., hoetz, h. (2013) farmers’ willingness to pay for treated wastewater in the jordan valley, sky journal of agricultural research 2(6): 69 – 84. alrawahy s., ahmed m., hussain n. (2010) management of salt-affected soils and water for sustainable agriculture, technical report, college of agricultural and marine sciences, sultan qaboos university, department of agricultural and water resource. azahara, m., julia. m., rutoc. e., berbel j. (2012) the economic value of guaranteed water supply for irrigation under scarcity conditions, agricultural water management 113 :10– 18. 0.1 0.2 0.3 0 100,000 200,000 300,000 400,000 500,000 600,000 volume (m3) p ric e (r o m −3 ) figure 5. demand function for tw in shakhakhit area. 63research article zekri, al harthi, kotagama and bose gunatilake herath (2003) environmental valuation: theory and practice, sandee, isbn 955-98121-0-6. gunatilake herath, jui-chen yang, subhrendu pattanayak, and kyeong ae choe (2007) good practices for estimating reliable willingness-to-pay values in the water supply and sanitation sector, economics and research department, asian development bank, manila, philippines. erd technical note series no. 23, asian haya (2012) bank, manila, philippines. jarque c. m., and bera a. (1987) a test of normality of observations and regression residuals. international statistical review, 55 (2): 163-172. ministry of regional municipalities and water resources (2013) http://www.mrmwr.gov.om/en/page.aspx?id=82&li=8&type=w_sec&slide=true tang z., nan z., and liu j. (2013) the willingness to pay for irrigation water: a case study in northwest china. global nest journal 15, (1): 76-84. tziakis i., pachiadakis i., moraitakis m., xideas k., theologis g., tsakarakis k. p. (2009) valuing benefits from wastewater treatment and reuse using contingent valuation methodology, desalination 237: 117125 zekri s., kotagama h., and boughanmi h. (2006) temporary water markets in oman. agricultural and marine sciences, 11 (si): 77-84. zekri s. (2008) using economic incentives and regulations to reduce seawater intrusion in the batinah coastal area of oman. agricultural water management, 95: 243-252 zekri s. 2009. controlling groundwater pumping online. journal of environmental management, 90: 3581–3588. 55 abstracts of the first international conference on plant protection (icpp) complied by muhammad shahid* and edited by mohammad farooq department of plant sciences, college of agricultural and marine sciences, sultan qaboos university, p. o. box 34-123, al-khod 123, oman *e-mail: mshahid@squ.edu.om overview plant sciences department, college of agricultural and marine sciences, sultan qaboos university organized “first international conference on: plant protection (icpp)” on 5-7 december 2022, and this event was take place at conference hall, squ. the conference speakers represented algeria, china, egypt, finland, india, iran, iraq, libya, morocco, sudan, syria, tunisia, pakistan, poland, itlay, uk and researchers the gcc (saudi arabia, uae, qatar and oman) nationals. the main objective of the icpp was to disseminate the latest scientific advances in all aspects of plant protection and encourage collaboration between researchers. this conference was an important event to exchange knowledge and the latest research findings on pests of economic importance, fungal, viral, phytoplasma and bacterial diseases, post-harvest diseases, pests and mycotoxins, integrated pest and disease management, insect-host-pathogen interactions, biological control, quarantine and phytosanitary measures, and weeds and their management. all particiapant of the conference were agreed and willing to share their research findings that will generate more innovation, and lead to greater productivity and contribution towards resolving challenges facing agriculture. all national and international participants benefitted from this conference and convinced to establish fruitful collaborations. each of the institutions and researchers that participated were involved in high level and strong research in themes relevant to the conference and thus the conference provided a valuable and novel opportunity for interaction in relation to research. overall, the icpp conference was very successful in terms of organization, management, implementation, selection of topics and participants and all the guests have thoroughly enjoyed talks and learn new things from from different speakers working in diverse areas. mshahid@squ.edu.om 56 keynote presentations nano-enabled approaches for sustainable crop protection t. ahmed institute of biotechnology, zhejiang university, hangzhou 310058, china email: temoorahmed@zju.edu.cn abstract agriculture is the most important sector providing food and different raw materials to the growing global population. in the last few decades, biotic and abiotic environmental stresses affect the production and quality of agricultural food worldwide. the extensive use of traditional preventive measures comprising toxic chemicals has become more problematic due to severe ecotoxicological challenges. the global population is predicted to increase from 7 to 9 billion by 2050, highlighting the need to increase agricultural food production to achieve global food security. nano-enabled approaches have recently attracted attention as a sustainable platform to improve crop nutrition and protection. engineered nanomaterials (enms) have gained enormous consideration due to their unique physical and chemical properties, viz., small size, high surface area to volume ratio, superior efficiency, and supply of micronutrients to plants. the targeted use of enms has tremendous potential for improving the efficiency of agricultural systems with low biodiversity effects, which contributes to the improvement and maintenance of food security. several recent studies have revealed that enms enhanced plant biotic and abiotic stress resistance by improving plant growth, physiological parameters, photosynthetic capacity, nutrient content and phytohormone profile. overall, previous studies demonstrated that enms application has great potential as a novel strategy for crop biotic and abiotic environmental stress management. keywords: agriculture; crop protection; enms; nanotechnology, stress resilience mailto:temoorahmed@zju.edu.cn 57 plant viruses, their impact and control strategies i. amin national institute for biotechnology and genetic engineering (nibge), jhang road faisalabad, pakistan email: imranamin1@yahoo.com abstract phytopathogenic viruses are a major biotic constraint to agricultural productivity and, throughout the warmer parts of the world, many of the most devastating diseases of crops are caused by arthropod-borne viruses of the family geminiviridae. the symptoms caused by these viruses include enations, leaf curling and stunting, which resemble developmental abnormalities. family geminiviridae has recently been expanded from nine genera (curtovirus, mastrevirus, turncurtovirus, becurtovirus, grablovirus, eragrovirus, capulavirus, topocuvirus and begomovirus) to 14 genera by the addition of the genera citlodavirus, maldovirus, mulcrilevirus, opunvirus and topilevirus. whitefly-transmitted begomoviruses, the biggest genera of this family are a major limiting factor for the production of numerous dicotyledonous crops throughout the world. with the increasing concerns over the use of insecticides as well as the adoption of agricultural practices that favor the build-up of both vector and virus populations including, for example, widespread monoculture and overlapping cropping seasons, as well as the lack of suitable sources of natural resistance (so-called host-plant resistance) in many crop species the problems due to these viruses are increasing. transgenic approaches paved the way to a virtually unlimited source of virus resistance for application in agriculturally significant plant species. several transgenic approaches have been used for the development of resistance against geminiviruses including pathogen-derived approaches e.g. rna interference. the recent advancements in targeted genome engineering via clustered regularly interspaced short palindromic repeats (crispr) and crispr-associated cas (crispr/cas) have unprecedented potential to develop virus resistance and crop improvement. keywords: geminiviridae, begomoviruses, resistance, rnai, crispr mailto:imranamin1@yahoo.com 58 building resilience to vector-borne plant pathogens via studying insect vectors s. hogenhout department of crop genetics, john innes centre, norwich research park, norwich, nr4 7uh, uk e-mail: saskia.hogenhout@jic.ac.uk abstract sap-feeding insects of the order hemiptera, such as aphids, psyllids, leafhoppers and spittlebugs/froghoppers, are vectors of a wide range of plant pathogens, including viruses, phytoplasmas, liberibacter species and xylella fastidiosa. these pathogens are spreading globally and are threats to global agriculture and landscapes. research on mechanisms involved in plant-pathogen interactions has shown that the pathogens have evolved sophisticated mechanisms to modulate plant development and immunity, including the suppression of plant defences to their sap-feeding insect vectors. however, it is equally important to gather knowledge on the insect vectors. for example, genome sequence data of leafhoppers were essential for revealing a phytoplasma achilles’ heel and obtaining increased plant resistance to the phytoplasma and its insect vector. to improve our knowledge on insect vectors, the past few years my lab and i made use of recent advances in low-input next generation sequencing technologies and generated genomic and transcriptomic resources for ±40 mostly small hemipteran insect species. one of these species is the x. fastidiosa insect vector philaenus spumarius, known as the meadow spittlebug, which is one of the most common insects in the uk. our data gave insights into how p. spumarius dispersed globally. moreover, we found that the p. spumarius populations that occur in the x. fastidiosa outbreak regions of southern italy belong to a different haplogroup and have higher migration rates, distinct phenology and different plant host preferences compared to uk populations. this research has provided key information that will help to reduce the likelihood of arrival and potential impacts of x. fastidiosa outbreaks in the uk and elsewhere. keywords: aphids, psyllids, leafhoppers, liberibacter species, xylella fastidiosa mailto:saskia.hogenhout@jic.ac.uk 59 scent of a killer: microbial volatilome and the biological control of postharvest fungi s. oufensou1, b. tilocca2, z. ul-hassan3, s. jaoua3 and q. migheli1* 1department of agricultural sciences and nrd – desertification research centre, university of sassari, viale italia 39, i-07100 sassari, italy 2department of health sciences, university “magna græcia” of catanzaro, viale europa, i-88100 catanzaro, italy 3department of biological and environmental sciences, college of arts and science, qatar university, p.o. box 2713, doha, qatar e-mail: qmigheli@uniss.it abstract the use of synthetic fungicides represents the most common strategy to control postharvest pathogens. however, the long-term application of chemicals is responsible for increased levels of environmental pollution and favours the selection of fungicide-resistant mutants. consequently, an increasing number of research efforts have been devoted to exploring the use of biological control approaches to reduce the incidence of diseases during the postharvest stages. among the various mechanisms exerted by microbial biocontrol agents, the production of volatile organic compounds (vocs) represents a most promising tool, especially when direct contact between the pathogen and its antagonist is not feasible. their potent bioactivity, the absence of residues on fruit and grain commodities, and the ease of application in different agricultural systems make the use of vocs a sustainable and effective alternative to synthetic fungicides in the management of plant pathogens in closed environments. in this review, we shall focus on the most recent literature available on microbial volatilome and its role in the biological control of postharvest pathogens of fruit, vegetable and grain, including mycotoxin-producing fungi. keywords: volatile organic compounds, chemical, postharvest, mycotoxin mailto:qmigheli@uniss.it 60 invited presentations improving seed treatment methods: a key factor to reduce the risk to honey bees and other pollinators to maintain biodiversity h. abdelgader director integrated pest management of agricultural pests agricultural research corporation, wad medani, p. o. box 126, sudan email for correspondence: abdelgaderh@yahoo.com abstract bees are one of the reasons, for the possibility of human development on earth, which otherwise would have been very different and the conditions for human development may not have existed. pollinators support the reproduction of nearly 85% of the world’s flowering plants. however, these important species are endangered through the use of pesticides. highly specialist techniques should be used when treating seeds with plant protection products. this study was conducted to to reduce the drift generated from seeds by drilling, hence saving pollinators, as well as reducing the risks to people. the study investigated the amount of drift generated from seeds of two varieties of cotton using two formulations of the neonicotinoid insecticide imadocloprid through measuring the fine dust particles from various treatments using the heubach methods. the increase in drift generated through heubach meter through tested formulation of imadocloprid relative to the control treatment were in the range of 336-378% and 221-287 for the water dispersible powder formulation (ws) for hamid and barakat cotton varieties, respectively. for the flowable concentrate (fs) formulation, the percentage increase in the drift over the control was ranging 8295% and 15-445 for hamid and barakat varieties respectively. the values for the fs formulation ranged between 7-8.8 and 2.64-14.7 for hamid and barakat, respectively. the flowable concentrate formulation for seed treatment is better than the water dispersible powder formulation in reducing the drift generated from pesticide treated seeds and can play important role in improving seed dressing technology to save various pollinators. keywords: seed treatment, pollinators, biodiversity, pesticies and insecticies mailto:abdelgaderh@yahoo.com 61 cryopreservation and in vitro conservation of virus free plant genetic resources and species tolerant to biotic and abiotic stresses t. abouzedan1*, m. alsameen2, f. al-bisky1, and k. almaarri2 1national commission for biotechnology, p.o.box. 31902, syria 2horticultural dept, faculty of agriculture, p.o.box. 30621, damascus university, syria * email for correspondence: zthuraia@gmail.com abstract biotechnology plays a major role not only in the production of plants tolerant to biotic and abiotic stresses, but also in the conservation of plant genetic resources to establish gene bank. in this investigation, cryopreservation by encapsulation –dehydration technique of grape virus-free plants and iris aurantica has been established for the first time in syria. factors affecting different stages of cryopreservation (pre-freezing, capsulation, dehydration, and freezing stage) have been studied to improve the survival rate of virus-free plants after re-freezing. the use of cryopreservation technology is the only way to ensure the long-term preservation of virus-free grapes and iris by storing shoot apex in liquid nitrogen (-196oc) and storing them at very low temperatures, such as the freezing point of co2 (-80oc). in vitro preservation was conducted to develop a technology for short-term conservation and relieve of growth and increase the period between transfers of iris aurantica. in this study, the best osmotic agents for in vitro conservation was sucrose compared to mannitol and sorbitol, and the best medium concentration was 1/10 ms. the cultured stored at (3°c) gave the highest survival (93.33%) and lengthened the time period between transfers up to 6 months. keywords: stresses, tissue culture, fruit plants, vegetable plants mailto:zthuraia@gmail.com 62 flyash and biochar induce defense response activation against bacterial leaf spot in chili pepper a. akhter1*, m. asif1, h. khan2, w. anwar1, m. khurshid3 1faculty of agricultural sciences, department of plant pathology, university of the punjab, lahore 54590 – pakistan 2faculty of agricultural sciences, department of entomology, university of the punjab, lahore 54590 – pakistan 3school of biochemistry and biotechnology, university of the punjab, lahore 54590 – pakistan *e-mail: adnanakhter.iags@pu.edu.pk abstract biochar plays an important role in improving the plant growth and activating defense mechanisms against biotic and abiotic stresses. in our study, the focus was on the effect of biochar made from rice straw and flyash on plant growth and development of xanthomonas campestris pv. vesicatoria causing bacterial leaf spot in chilies. chilli pepper plants were grown in different substrate compositions containing either only soil or amended with rice straw biochar (rsb) /and flyash at the rate of 3%, each. all of the soil substrate compositions received compost at the concentration of 20% as an organic nutrient source. rice straw biochar had a positive effect on plant growth, in the form of increased root and shoot weight as compared to plants grown in flyash and only soil treatment. moreover, rsb had shown a significant in vitro inhibitory effect on different pathogenic fungi and bacteria accounting for more than 50%. disease severity and incidence were significantly minimized among the plants grown in rsb containing substrate as compared to other substrate compositions. overall, our findings indicated a positive effect of rsb amendment on plant health, as well as by inducing a defense response in chilli plants against bacterial leaf spot. biochar addition in soil not only improves its fertility but also helps in achieving long-lasting c sequestration goals. the ability of biochar to influence plant growth and defense pathways contributes towards its ability of disease suppression. keywords: environment protection, disease management, organic soil amendment, biochar file:///c:/users/thahertech/downloads/adnanakhter.iags@pu.edu.pk 63 impact of conservation tillage and residue management on soil biological indicators in ricewheat cropping system of pakistan s. ali1*, a. zahid1*, m. ahmad2, a. fatima3, w. anwar4, t. raza1, m. arif1 and a. ayub1 1department of agronomy, university of the punjab, lahore 2department of agronomy, pir mehr ali shah-arid agriculture university rawalpindi. 3department of environmental sciences, lahore college for women university, lahore 4department of plant pathology, university of the punjab, lahore * e-mail: sajid.agronomy@pu.edu.pk abstract intensive tillage practices and burning of the residue decline the soil quality dynamics especially the soil biotic health along with other parameters. conservation tillage and residue management are the promising sustainable strategies for improving the soil quality. a study to evaluate the impact of different tillage and residue management strategies on soil biotic health such as microbial biomass carbon (mbc) soil organic carbon (soc) and metabolic quotient (qco2), etc., were started in 2014 with the scenarios i) rice/wheat residue was burned and removed, ploughing of field 3–4 times and planked (sc-1); (ii) rice/wheat residues were chopped with straw chopper incorporated by disc plow, ploughing of field 2–3 times and planked (sc-2); (iii) rice residues were retained and wheat was planted with zero till (zt) at 3–5 cm depth, whereas wheat residues were removed for non-puddled direct seeded rice sowing (sc-3); (iv) rice residue was retained and wheat was planted with zt at 3–5 cm depth, while wheat residues were removed for transplanting puddled rice sowing (sc-4); (v) rice/wheat residues were retained and wheat/rice were planted with zt drill at 3 to 5 cm depth (sc-5) in rice wheat cropping systems.the results indicated that mbc, bsr, soc and qco2 increased by 24.6%, 13.98%,4.1% and -4% (negative value showed good efficiency) under conservation tillage whereas conventional tillage showed reduction i.e. 18.94% 10.3% 2.1%, 7.1% on the uppermost soil surface and decreased along with soil depth in all tillage and residue management practices. in conclusion, conservation practices have significant impact on soil biotic health. the adaption of climate smart technologies i.e., conservation tillage is need of time for sustainability of soil and environmental health of rice wheat cropping system. keywords: intensive tillage, soil quality, conservation tillage, soil microbial carbon, metabolic quotient and sustainable soil health mailto:sajid.agronomy@pu.edu.pk 64 production virus free plants of grapes and potato by meristem culture from infected plants k. almaarri1, r. massa1, t. abouzadan2, m. alsameen1, and f. al-bisky2 1horticultural dept, faculty of agriculture, p.o.box. 30621, damascus university, syria 2national commission for biotechnology, p.o.box. 31902, syria * e-mail: kmaarri@yahoo.com abstract in this study, more than 30 viruses infect potato and potato virus virus y (pvy) is one of the most common and destructive viruses. meristem length 300 micrometer were exised from infected potato plants of binella cultivar, and cultured on solidified ms medium. virus infection in in vitro plantlets was determined by (das-eliza). the result showed a good rate of virus free plants. the rate of pvy elimination was improved after chemotherapy (37c for 40 days) and chemotherapy (20mg/l of ribaverin) combined with meristem tips. the virus (glrav-3) grapewine leafrollassociated virus is the most common and destructive viruses found in grapes in the south of syria. meristems length 300 micrometer were exised from infected grape plants of halwany cultivar, and cultured on medium containing 1/2ms plus 30g/l sucrose, 0.5mg/l bap. the virus status of in vitro plantlets were detected by (daseliza). several treatment were tested in order to improve the virus elimination percentage. the best rate (87%) of the virus elimination was obtained by using ribaverin (20 mg l-1)combined with meristem tips. keywords: ribavirin, tissue culture, grape wine, chemotrheropy kmaarri@yahoo.com 65 cultivation of pleurotus ostreatus on different agricultural residues w. anwar department of plant pathology, university of the punjab, lahore, pakistan e-mail: waheedanwar.dpp@pu.edu.pk abstract edible mushrooms have been used for their nutritional and commercial value since ages. among 3000 edible mushrooms, pleurotus oystreatus is one of the most cultivated in asian countries due to the suitability of the environment and easy cultivation techniques using different agricultural waste materials. in this study, we used three agricultural wastes as substrates viz., rice, wheat and cotton straw in 9:8:7 ratio along with four supplements viz., bread waste, tea waste, banana peel and biochar in 1:2:3 ratio, with the control of rice, wheat and cotton straw without supplements. fresh and dry weight of mushrooms was calculated to check the moisture content of mushroom bodies being produced on any of the used substrates. among the used supplements in three substrates, all of the supplements provided a good source of nutritional add up to mushroom bodies by giving the growth in each cultivation bag with no significant difference. the moisture content of mushrooms collected from these combination series also gave positive results with fluctuating readings in first, second and third flushes. however, in the substrates without addition of supplements, rice remained on the top for having high fresh and dry weight of cultivated mushroom. for moisture content, cotton without supplements provided the lowest reading for retention of moisture content which is the ultimate goal of storage of mushrooms. keywords: organic waste, mushroom production, eco-friendly, oyster mailto:waheedanwar.dpp@pu.edu.pk 66 the role of allelopathy in organic weed management in field crops z. cheema department of agronomy, university of agriculture, faisalabad-38040, pakistan e-mail: cheemaza@gmail.com abstract continuous and excessive pesticide usage is posing severe environmental threats and health hazards for humans. this is also causing changes of weed flora and development of herbicide resistant weed biotypes in field crops. managing the emergence of new of new weed biotypes requires innovative tools. allelopathy, a naturally occurring phenomenon in agricultural ecosystems, has been evaluated as a possible alternative to chemical weed management and growth promotion. we have extensively explored the potential allelopathic plants including sunflower, sorghum, mulberry, rice, maize, brassica, eucalyptus and moringa for organic weed management and growth enhancement in field crops in a series of studies. allelopathy has been employed through intercropping, crop rotations, mulching and plant water extracts for weed management and plant water extracts for growth promotion. we have proved that, if wisely planned, allelopathy offers a pragmatic option for weed management and growth promotion in field crops. in agricultural systems, crop rotations are practiced to reduce the ill effects of monocultures, but the subsequent crop may be affected by the allelochemicals released by the preceding one. therefore, allelopathic nature of the crops must be considered while making the crop rotations. keywords: allelopathy, crop rotation, weed management, agriculture crops mailto:cheemaza@gmail.com 67 a distinct strain of chickpea chlorotic dwarf virus isolated from begomovirus infected cotton induced downward leaf curling leading to cup shape structures in nicotiana benthamiana m. haider faculty of agricultural sciences, university of the punjab lahore pakistan e-mail: haider65us@yahoo.com abstract cotton leaf curl disease in the indian subcontinent is associated with several distinct begomoviruses that interact with a disease-specific dna satellite named cotton leaf curl multan betasatellite (clcumb). however, we isolated the distinct strain (l) of leafhopper transmitted chickpea chlorotic dwarf virus, cpcdv-l (genus mastrevirus, family geminiviridae) from cotton plants affected by leaf curl disease in a small number of plants. the question as to whether cpcdv-l contributes to the development of disease symptoms such as leaf curling and enations remains to be answered. standard methods were used to produce partial direct and tandem repeat constructs of cpcdvl for agrobacterium-mediated inoculation in the binary vector pbin19. the role of cpcdv-l in the induction of typical disease symptoms was studied by agrobacteriummediated inoculation of the partial repeat construct into nicotiana benthamiana. cpcdv-l induced downward leaf curling leading to cupping in n. benthamiana. keywords: geminiviradae, mastrevirus, betasatellite, cpcdv haider65us@yahoo.com 68 comparative toxicity of biorational insecticides against the red flour beetle tribolium castaneum and the rusty grain beetle cryptolestes ferrugineus h. khan institute of agricultural sciences, university of the punjab, quaid-i-azam campus, lahore, university of the punjab e-mail: azhar.iags@pu.edu.pk abstract increased environmental pollution and hazards to public health associated with the use of conventional insecticides necessitate the need to explore biorational insecticides for the management of insect pests. thhis study was conducted to evaluate the relatively safe biorational insecticides against two notorious pests of stored grains, the red flour beetle tribolium castaneum and the rusty grain beetle cryptolestes ferrugineus, to determine their susceptibility to selected chemicals. the toxicity of eight biorational insecticides abamectin, emamectin benzoate, imidacloprid, acetamiprid, thiamethoxam, indoxacarb, fipronil and spinosad was reviewed by diet incorporation method. all insecticides were evaluated for their toxicity at various concentrations. mortality of the insects was dose-dependent, and spinosad was proved to be the most effective insecticide against c. ferrugineus, with 100 percent mortality at the lowest concentration of 1 ppm. thiamethoxam displayed maximum mortality against t. castaneum at 4 ppm. overall results affirmed the less susceptibility of t. castaneum as compared to c. ferrugineus against most of the insecticides used in the current study. keywords: toxicity, pesticides, beetles, chemicals mailto:azhar.iags@pu.edu.pk 69 molecular approaches associated with resistance in crop plants: markers and transcriptome ‐ proteomics strategies and applications m. nasr-esfahani1*, and n. abbasi2 1plant protection research department, esfahan agriculture and natural resource research and education center, esfahan, areeo, iran. 2plant pathology department, college of agriculture, marvdasht branch, islamic azad university, marvdasht, iran. *email for correspondence: mne2011@gmail.com; m.nasr@areeo.ac.ir abstract the steady growth of the worldwide population necessitates a substantial increase in crop productivity. improvement of disease resistance in crops has great potential to increase productivity by preventing the huge losses caused by the plant pathogens. on the other hand, the most modern varieties, which have been selected for enhancement of yield values, are relatively more susceptible to pathogens under high fertilizer inputs. in addition, new pathogen variants often cause an increased threat to crops. thus, the level of understanding reached in the genetics and molecular mechanisms of plant pathogen interaction and stress response, as well as the variety of new approaches tested and biotechnologies discovered, have made the past two decades of research and development a very exciting period in the field of plant biotic stress control. success stories like the production and commercialization of resistant plants, and today’s availability of powerful molecular techniques, such as genomics and proteomics, have elicited studies that pursue their final objective of increasing plant stress resistance by investigating the plant stress response. while less work has been done on the dual role of particular genes covering resistance to more than a disease at a time. however, the stress control methods which have been investigated or postulated to date are, in most cases, of general significance and could be readily applied to commercial plants in the near future. this talk briefly reviews some of the most interesting molecular approaches to controlling biotic stresses, with particular attention to fungal pathogens and cereal cyst nematodes. additionally, investigation of the alterations in transcript activity of the defense-related genes and enzymes opens a new trend in research on defense signaling pathways and crop defense responses. further, the molecular basis of crop resistance and shed new light on the interaction and overlap between different forms of biotic stress. keywords: molecular markers, fungi, nematodes, wheat, pepper mne2011@gmail.com;%20m.nasr@areeo.ac.ir%20 70 management of fruit flies through chemosterilant bait and microbial natural pesticides s. saeed1*, m. hasnain1, u. naeem-ullah1 and s. ullah2 1institute of plan protection, mns university of agriculture, multan, 60000, punjab, pakistan 2department of horticulture, mns university of agriculture, multan, 60000, punjab, pakistan *e-mail: shafqat.saeed@mnsuam.edu.pk abstract fruit flies are harmful economic pests that infect a broad range of fruits and vegetables across the world due to their high reproductive capacity, polyphagous nature, host range, mobility, and environmental adaptability. traditional management methods are no longer viable due to the massive fly populations, pesticide resistance, pest outbreak, environmental risks and health hazard residues. this study was conducted to evaluate the chemosterilizing and mortality factors by using a combination of exclusion experiments. infection through chemosterilant and entomopathogenic fungi has also been demonstrated to reduce fruit fly fecundity, fertility, adult emergence and mortality that can contribute to fruit fly suppression in the long-term. pyriproxyfen, novaluron, lufenuron, buprofezin, and flubendiamide (50-300 ppm/ 5 ml diet) were tested in oral bioassays against the newly emerged beauveria zonata under lab conditions. the results showed that fecundity and adult emergence is higher at low doses and vice versa. among the investigated chemicals, lufenuron induced the lowest fecundity 31.05% and the lowest adult emergence rate of 19.85% at 300 ppm/5 ml of treated diet. whereas in crosses between treated males with treated females, lufenuron treatment resulted in the lowest fecundity (45.52%) and adult emergence rate (51.73%) as compared to other crosses. generation-wise reduction percentage observed in g1, g2 and g3 was 54.69, 24.47 and 11.51% respectively. pathogenicity of b. bassiana showed 4-6% larval mortality and the pupal survival was reduced by 87-92% on the sand substrate and caused malformation. keywords: chemosterilant technique, pathogenicity, induced sterility, fecundity, adult emergence shafqat.saeed@mnsuam.edu.pk%20 71 genome-wide identification and characterization of wrky transcription factor gene family in citrus reticulata and its response against various biotic and abiotic stresses m. shafiq department of horticulture, faculty of agricultural sciences, university of the punjab, lahore, pakistan *e-mail: shafiq.iags@pu.edu.pk abstract wrky is an important group of transcription factors (trfs) gene family and was identified primarily in plants. wrky trfs play vital roles in modulating gene expression during several biotic and abiotic stresses, senescence and different hormone responses. the dna-binding domain of these proteins is a conserved heptapeptide sequence wrkygqk. although the mandarin citrus (citrus reticulata) genome has been published but functional studies are still necessary to understand mandarin citrus. the mining of c. reticulata genome identify 46 crwrky genes that are classified into three main groups (g1-g3) with five subclasses (iia–iie) in g2, and all were present on 29 different scaffolds representing numerous segmental duplication (100%) events. through multiple sequence analysis, it is predicted that wrkygqk domain and metal chelating zinc-finger motif c2h2 is present in 45 genes while wrkygqk domain is replaced with wrkygkk only in crwrky20. comparative relationship of crwrky with other plant species using dual synteny analysis revealed that the divergence between c. reticulata and c. grandis occurred after the divergence of c. clementine, c. sinensis, c. medica and c. ichangensis. cis elements of crwrky genes provide information about their significant role in cold stress in c. reticulata. the transcriptome analysis from previously generated rna seq data, indicated that crwrky gene play critical role in different organs and tissues of plants under various biotic as well as abiotic stresses. keywords: characterization, transcription factors, biotic factors, abiotic factors mailto:shafiq.iags@pu.edu.pk 72 food webs and date palm agro-ecological community characteristics k.s. shameer 1*, t. almandhari2,3 and i. hardy1 1department of agriculture, faculty of agriculture and forestry, viikki campus, p.o. box 27 (latokartanonkaari 5), fi-00014, university of helsinki, finland 2school of biosciences, sutton bonington campus, university of nottingham, uk 3department plant protection, ministry of agriculture, fisheries wealth & water resources, oman * e-mail: drshameer.ks@gmail.com abstract understanding the inter-organism interactions in ecological communities allows assessment, and even prediction, of how communities respond to natural and anthropomorphic impacts. the trophic interrelationships of invertebrates within a community often form an extensive feeding web composed of several trophic levels. food webs, or trophic webs, can be constructed directly from empirical field studies or, alternatively, by using literature records to map all the trophic interrelationships in natural and agro-ecosystems. for terrestrial communities, this includes the plants, herbivores and the complex of natural enemies associated with these herbivores. the food webs that were recently constructed for coconut palm and date palm agroecosystems infer large-scale community ecology consequences of shared and nonshared natural enemies, such as the relative importance of direct and apparent competition. the plant-insect community characteristics of date palm agro-ecosystem can be explained with emphasis on the prospects of better pest management strategies against lesser date moth, batrachedra amydraula meyrick. keywords: date palm, agro-ecosystems, pest management, batrachedra amydraula mailto:drshameer.ks@gmail.com 73 effect of aqueous extract of hanzal (citrullus coloynthis l.), senemeka (senna alexandrina mill) and ummjelajel (aristolochia bracteolate l.) on the leaf miners (liriomyza spp.) on the snake melon crop m. younis, f. salah* and a. eisa university of gezira, sudan *e-mail: faizaruba2@gmail.com abstract due to ecological imbalance and hazards caused by insecticides use, plant products or plant extracts were suitable alternative to pesticides. this study was conducted to evaluate the effect of water extracts of hanzal (citrullus coloynthis l.), ummjelajel (aristolochia bracteolate l.) and sennameka (senna alexandrina mill) on vegetable leaf miners (liriomyza spp.) infesting snake melon. snake melon plots were sprayed weekly with water extracts of hanzal, sennameka and ummjelajel at 10% concentration (w/v) and control was sprayed by water with molasses and gum arabic. the infestation percentage on leaves and mean number of active mines were counted twice weekly. the aqueous extracts of hanzal, sannemeka and ummjelajel reduced the infestation and number of active mines significantly compared to control. no significant differences between hanzal, sannameka and ummjelajel. hanzal had lower mean percentage leaf infestation followed by sannameka and ummjelajel (season one). hanzal recorded lower number of active mines in season two followed by sannemeka. also hanzal recorded the least number of active mines than sannameka, season two. from this study it is recommended to use hanzal at 10% w/v for control of leaf miner species on snake melon crop. keywords: aqueous extract, ccitrullus coloynthis, senemeka, ummjelajel, snake melon. mailto:faizaruba2@gmail.com 74 arthropod diversity as protection against outbreaks of insect pests s. venn department of invertebrate zoology & hydrobiology, faculty of biology & environmental protection, university of łódź, banacha 12/16, 90 237, łódź, poland. e-mail: stephen.venn@helsinki.fi abstract arthropods comprise a speciose and diverse group of organisms. in recent years, there has been increasing awareness that many arthropod taxa have declined dramatically during the anthropocene. in many parts of the temperate region in particular, there is considerable concern that declines in insect and arthropod diversity are already having a negative impact on the provision of essential ecosystem services, such as pollination in particular. one possible impact of declining insect diversity is an increase in outbreaks of pest species, many of which also benefit from global warming. in some sectors, there have been large-scale initiatives to enhance biodiversity at local levels, to improve the provision of ecosystem services and nature-based solutions. agro-ecology, for instance, has brought the introduction of beetle banks and wildflower strips in agricultural environments. the purpose of these is to provide supplementary habitat for pollinating insects, ensuring provision of pollination to crops, and also to maintain populations of predatory arthropods, to control phytophagous pests and prevent outbreaks. ecosystem homogeneity tends to increase vulnerability to pest outbreaks, whereas heterogeneity and ecological complexity, such as presence of communities of parasitoids and hyperparasitoids should enhance resilience to pests. unlike mos t of the temperate region, oman represents a biodiversity hotspot, with diverse assemblages of arthropods and plants. the high level of biodiversity should ensure the potential to maintain a high level of resilience. at locations affected by ecological homogenization, there should be good potential for supporting beneficial taxa for the provision of biocontrol.keywords: anthropocene, biocontrol, ecosystem services, nature-based solutions. stephen.venn@helsinki.fi%20 75 oral presentations: plant pathology efficacy of green synthesized silver-based nanomaterials against early blight of tomato caused by alternaria solani m. usman1, m. atiq1*, n. rajput1, s. sahi1, m. shad2, s. iqbal1, a. arif1, a. nawaz1 1department of plant pathology, university of agriculture faisalabad, pakistan 38000. 2school of biological sciences, university of punjab, lahore, pakistan. *e-mail: dratiqpp@gmail.com abstract tomato production is significantly harmed by the interruption of fungal diseases. alternaria solani is responsible for substantial yield losses in tomato crops grown in greenhouse and field conditions. silver based green synthesized nanomaterials (agnms) are reported as best performers in various agricultural applications and proposed to be best alternatives in plant disease management. two green based agnms at three different concentrations were evaluated against the incidence of a. solani and on the components of antioxidant defense system of tomato plants. results of current study indicated that the application of green based agnms reduced the disease incidence of a. solani with significant increase in tomato production, ascorbate (ascorbic acid), photosynthetic pigments, flavonoids and antioxidant activity in the leaves of inoculated plants as compared to healthy ones. it is concluded that the application of green based agnms may be a viable approach for the management of early blight of tomatoes. keywords: solanum lycopersicum, early blight, nanotechnology, management mailto:dratiqpp@gmail.com 76 estimation of green synthesized silver and copper nano-particles for the management of leaf spot caused by curvularia lunata on brinjal m. atiq1*, i. naeem2, n. rajput1, s. sahi1, m. usman1, s. iqbal1, a. nawaz1, h. ahmad1 1department of plant pathology, faculty of agriculture, university of agriculture, faisalabad, pakistan. 2department of botany, faculty of basic sciences, university of agriculture, faisalabad, pakistan. *e-mail: dratiqpp@gmail.com abstract plant-derived nanostructures have revolutionized the arena of nanotechnology and “green” synthesis of nanostructures with strong characteristics is great challenge for researchers. in the present study, cunps and agnps along with their complex utilizing moringa oleifera plant extract as reducing and stabilizing agent were synthesized. different concentrations (0.25, 0.50 and 0.75%) of these nanoparticles were applied using poisoned food technique to evaluate antifungal activity against curvularia lunata in vitro, as well as in vivo to check the efficacy of exogenously applied nanoparticles to control against curvularia leaf spot of brinjal for better outcomes and eco-friendly management. under in vitro conditions, [cu-ag] nps complex expressed maximum inhibition (13.862) comparatively to cunps with growth inhibition (21.809) and agnps with minimum growth inhibition (23.315); however, control showed maximum fungal growth (38.647). under field conditions, spray with [cu-ag] nps complex expressed determined reduction in disease intensity at different days’ interval (7, 14, 21) with infection index value (16.183, 13.217 and 10.657) followed by cunps with infection index value (27.717, 24.740, 20.907) and agnps with infection index value (33.147, 29.153, 25.743) as compared with control showed maximum fungal growth with infection index value (35.243, 38.393, 40.750). the present research aimed to highlight the biosynthesized cunps and agnps as biological control against curvularia leaf spot of brinjal. keywords: green nanotechnology, curvularia lunata, nanoparticles, moringa oleifera dratiqpp@gmail.com%20 77 evaluation of chemicals and plant defense activators against red rot of sugarcane caused by colletotrichum falcatum a. nawaz, m. atiq*, s. sahi, n. rajput, m. usman, s. iqbal, g. kachelo and h. ahmed department of plant pathology, university of agriculture, faisalabad, pakistan *e-mail: ahmadnawazmohsin@gmail.com abstract red rot of sugarcane (saccharum officinarum l.) caused by colletotrichum falcatum is considered as the most destructive disease in many sugarcane growing countries. c. falcatum may decrease weight of cane by up to 29% and sugar loss by 31%. in this study, nine commercial fungicide formulations were tested in lab conditions: shincar exhibited minimum fungal growth (4.13) followed by nativo (15.62), amister top (26.19), topsin m (37.64), ridomil gold (45.19), allite (52.49), score (59.44), antracol (67.71) and rovral (76.81) as compared to control. in green house salicylic acid + kh2po4 exhibited minimum disease incidence (10.40) followed by salicylic acid spray (13.92) and kh2po4 spray (20.25) as compared to control. in field carbendazim spray exhibited minimum disease incidence (10.10) followed by salicylic acid spray (21.60), carbendazim + salicylic acid+ kh2po4 drench (32.17), kh2po4 spray (43.62), carbendazim drench (51.19), salicylic acid drench (58.49), kh2po4 drench (65.52), coragen (chlorantraniliprole) drench (74.297) and micro-nutrients spray (82.854) as compared to control. under lab conditions, shincar showed best result while in green house salicylic acid+ kh2po4 and in field condition carbendazim showed the best results. keywords: incidence, destructive disease, salicylic acid, fungicides, biofuel ahmadnawazmohsin@gmail.com%20 78 antifungal potential of essential oils for the management of early blight of potato (alternaria solani l.) m. subhani* and a. hassan department of plant pathology, faculty of agricultural sciences, university of the punjab, lahore, pakistan, 54590 *email for correspondence: nasirsubhani.iags@pu.edu.pk abstract potato is the most important vegetable crop grown worldwide. one of the most destructive foliar potato diseases in the world is early blight incited by alternaria solani. although it has been shown that a variety of chemicals can effectively manage the disease, ongoing use of these agrochemicals for disease control may result in toxicity to those organisms which are not the primary targets. this this study, the essential oils like black seed, carom, cinnamon, clove, lemon, and linseed oils at different concentrations (200, 400, 600, 800, and 1000 µg/l) were used check the growth inhibition of a. solani. black seed oil reduced fungal growth by 73, 52, 38, 25 and 12 percent, respectively. linseed has reduced the fungal growth by 80, 61, 45, 26 and 9 percent, respectively. lemon oil has reduced the fungal growth by 66, 48, 35, 21 and respectively. clove oil has reduced the fungal growth by 73, 59, 46, 28 and 10 percent, respectively. carom oil significantly reduced the fungus growth by 75, 59, 49, 30 and 10, respectively. cinnamon oil reduced fungal growth by 72, 48, 38, 23 and 9 percent, respectively. this study proved that control of this plant pathogen is possible through the use of essential rather than chemicals. this strategy can also help to decrease number of fungicides used, so lowering risks and dangers to environment and human health, particularly when used on vegetables grown for fresh consumption. keywords: early blight of potato, essential oils, fungicides nasirsubhani.iags@pu.edu.pk 79 mushroom biodiversity in oman s. hussain 1,2,*, m. al-kharousi 2, m. al-muharabi 2,3, d. al-maqbali 2, z. al-shabibi 2, a. al-balushi 2, m. al-yahya'ei 2, n. al saady 2, r. velazhahan 1 and a. al-sadi 1 1department of plant sciences, college of agricultural and marine sciences, sultan qaboos university, po box 34, alkhoud 123, sultanate of oman 2oman animal and plant genetic resources center (mawarid), ministry of higher education, research and innovation, p.o. box 515, p.c. 123, muscat, sultanate of oman 3sultan qaboos comprehensive cancer care & research center, p.o. box 566, p.c. 123, muscat, sultanate of oman 4department of chemistry, college of science, sultan qaboos university, muscat, p.o. box 36, p.c. 123, sultanate of oman *e-mail: shahpk85@gmail.com abstract mushrooms are a diverse group of macrofungi that possess unique sporocarps. approximately, more than 30,000 species of mushrooms have been reported worldwide. most of these species belong to agaricomycotina, a subphylum in basidiomycota. during the macrofungal exploration in the year 2018, about 100 samples of mushrooms were collected in different regions of dhofar, located in the south of oman. these samples were characterized morphologically and phylogenetically, representing 30 species, belonging to 22 genera and 15 families of agaricomycotina. among these mushrooms, some are economically important edible mushrooms such as termitomyces schimperi and pleurotus opuntiae. other mushrooms, like ganoderma mbrekobenum, coriolopsis caperata, and lentinus tigrinus have proven industrial applications. similarly, five species are reported and described as new to science. it seems that southern and northern oman where considerable rainfalls occur during summer and spring could influence the emergence of various mushrooms. these mushrooms could be utilized in different industries such as food, medicine, nutraceuticals, biofertilizers, etc. keywords: agaricaceae, agaricus phylogeny, desert mushrooms, taxonomy mailto:shahpk85@gmail.com 80 establishment of two sudanese isolates of beauveria bassiana in date palm seedlings as a prerequisite for prophylactic protection against pests and diseases h. yousif1, e. edriess2,3, m. ali2* 1faculty of natural resources and environmental studies, alsalam university, alfulah, sudan 2department of plant protection and environmental studies. faculty of agriculture, al zaiem al azhari university, khartoum north, sudan. 2department of bio pesticides and bio fertilizersenvironment and natural resources and desertification research institute, p.o. box 6096, khartoum, sudan * e-mail: fataloope@yahoo.com abstract endophytic fungi, which live within host plant tissues asymptomatically, are important mediators of plant-herbivore interactions. we tested the ability of two isolates of beauveria bassiana, an entomopathogenic fungus, to colonize the seedlings of date palm (cv. mejdhool) using fungal spore suspensions applied as foliar spray, injection and soil drench. the two isolates of b. bassiana successfully established inside the aforementioned seedlings via all colonization techniques which were used. mean of recovery was calculated by cutting the leaves of the treated plant and culturing it on selective media. the mean of establishment of the three colonization techniques for recovery after 6 months were as follows 95.00±9 and 100.00±0.00 in case of spray method for isolate e and m, respectively. for injection, the records were 75.00±17.73 and 87.50±14.88 for e and m, respectively. for drench, 40.00±15.12 and 60.00±18.52 for e and m, respectively.in all treatments, the uninoculated control registered 0.00±0.00. the study was continued for one year recording declining in establishment in second half of the year in all treatment and all protocols. scanning electron microscope (sem) images of the treated leaf surface revealed that numerous conidia were present inside the plant tissues. sem images of inner surface of treated leaf epidermis showed the spores and hyphae of the fungus. this work was carried out to establish the fungus in the plant hoping that this fungus would protect the plant against pests and diseases. keywords: date palm, beauveria bassiana, endophyte, pests fataloope@yahoo.com 81 natural increase of pectobacterium soft-rot disease by pseudomonas azotoformans, a carrot endophytic bacterium f. ansari1, r. khakvar1 and r. mokarram2 1plant protection department, faculty of agriculture, university of tabriz, tabriz, iran 2department of food science and technology, faculty of agriculture, university of tabriz, iran *e-mail: khakvar@tabrizu.ac.ir carrot is one of the main agricultural crops in northwest iran. in recent years, the bacterial soft-rot disease has gradually become a big issue for carrot production in this region. the current study was conducted to find the main causal agent of this disease. suspected soft-rot tuber samples were collected from the infected farms and warehouses. after bacteria isolation and purification, the isolates were examined by biochemical and molecular assays. in total, over 50 bacterial isolates with soft-rot capability were isolated and stored. the results confirmed that pectobacterium carotovorum subsp. carotovorum is the main and prevalent causative agent for this disease in the area. but all severe p. carotovorum infections were associated with infection with a pseudomonas azotoformans strain with low pectolytic capability. in the in vitro assay, severe soft-rot symptoms could be seen in the synchronous inoculation with both p. carotovorum and pseudomonas strains while single inoculation with p. carotovorum strains had moderate disease severity. it seems that this recent rising softrot epidemy in the region is the result of an association or mix-infection between p. carotovorum and p. azotoformans. keywords: potato, mix infection, epidemy, warehouse, northwest iran mailto:khakvar@tabrizu.ac.ir 82 pathogenicity and genetic diversity of pythium species associated with damping-off of cucumbers in oman i. al-mahmooli1,2*, a. al-sadi1, r. velazhahan1, m. finckh2, a. šišić2 and s. hussain1 1department of plant sciences, college of agricultural and marine sciences, sultan qaboos university, al-khod, muscat 123, oman 2faculty organic agricultural sciences, kassel university, fachbereich 11 fachgebiet ökologischer pflanzenschutz nordbahnhofstraße1a d-37213 witzenhausen, germany e-mail: issah@squ.edu.om abstract a total of 166 isolates of pythium spp. were recovered from 282 soil and root samples collected from cucumber roots and rhizosphere soil of 10 governorates of oman, from july 2019 to july 2020. based on ribosomal dna (rdna) internal transcribed spacer (its) regions, 4 species of pythium were identified. pythium aphanidermatum was the most abundant species (86.75 %), followed by p. spinosum (10.24 %), p. myriotylum (1.2 %) and p. splendens (0.6 %). pathogenicity to cucumber of 34 isolates including p. aphanidermatum (26) p. spinosum (8), p. splendens (1) and p. myriotylum (1) was tested. p. aphanidermatum, p. spinosum and p. myriotylum developed symptoms of dampingoff with a range of 86.7 to 100%, while p. splendens was avirulent. tolerance tests of 15 isolates of p. aphanidermatum to hymexazol (0, 10, 100 and 1000 µl l-1) revealed that this species could grow in the presence of up to 100 µl l-1hymexazol while growth was inhibited at 1000 µl l-1with p. aphanidermatum br010 from al buraimi, exhibiting the highest level of tolerance followed by br013. phylogenetic analyses were conducted based on the sequences of internal transcribed spacer (its) and coi (cytochrome c oxidase subunit i) genes. pythium species were separated into different clades based on similarities to its and coi. amplified fragment length polymorphism fingerprinting among 93 strains of p. aphanidermatum produced 93 genotypic features and 781 polymorphic loci. overall, genetic diversity of p. aphanidermatum populations in the country was low (h=0.1101). analysis of molecular variance (fst= 0.11435) revealed gene flow and a moderate level of genetic variability among p. aphanidermatum populations. it is concluded that p. aphanidermatum is the most prevalent species, mainly involved in damping-off disease of cucumbers in the greenhouses in oman. most of these isolates exhibited differences in susceptibility to fungicide and showed no resistance to hymexazol. keywords: cucumis sativus, damping-off, phythium spp., genetic variability, hymexazol issah@squ.edu.om%20 83 isolation, identification, and application of actinobacterial strains for controlling sudden decline syndrome of date palm in uae k. al-wahshi1,2†, g. purayil1†, e. saeed3, h. abufarajallah1, s. aldhaheri1, s. abuqamar1* and k. el-tarabily1,3,4* 1research station section, abu dhabi agriculture and food safety authority, abu dhabi, united arab emirates 2department of biology, united arab emirates university, al-ain, united arab emirates 3khalifa center for genetic engineering and biotechnology, united arab emirates university, al-ain, united arab emirates 4harry butler institute, murdoch university, murdoch, wa, australia e-mail: khawla.alwahshi@adafsa.gov. abstract date palm is a traditional tree in the united arab emirates (uae) and the arabian gulf region. these trees suffer from serious diseases, including sudden decline syndrome (sds). the fungal pathogen fusarium solani was associated with sds on date palms in the uae. this study was carried out to isolate and identify native actinobacterial strains isolated from the rhizosphere of date palm and evaluate their potentiality to produce antifungal metabolites, cell-wall degrading enzymes (cwdes) and 1-aminocyclopropane-1-carboxylic acid (acc) deaminase (accd). two most inhibitory isolates in virto, namely streptomyces tendae uae1 (st) and streptomyces violaceoruber uae1 (sv), were determined as promising biocontrol agents (bcas). both isolates showed antagonism under greenhouse conditions, the acc deaminaseproducing sv were significantly more effective in reducing the incidence and severity of sds compared to acc deaminase-non-producing st. the severity of symptoms in infested date palm seedlings were extremely reduced by sv compared to st. on a scale of 5.0, the estimated disease severity indices in fusarium solani-diseased seedlings were significantly (p < 0.05) reduced from 4.8 to 1.5 and 0.5 by st and sv, respectively. the acc levels of both the root and shoot tissues were significantly reduced in sv + fusarium solani seedlings to comparable levels of healthy seedlings. the acc levels greatly increased in planta grown in soils infested with the pathogen alone or edited with st prior to f. solani infestation (st + fs). this is the first findings demonstrate the effectiveness of rhizosphere actinobacterial bcas in protection against sds on date palm in the uae and the other arid land. keywords: date palm, fusarium solani, rhizosphere, sudden decline syndrome khawla.alwahshi@adafsa.gov 84 association of multiple begomoviruses with leaf curl disease of papaya trees in kingdom of saudi arabia z. khalid1, k. hussain1,2, m. amer1,3, m. amir1, i. al-shahwan1, m. al-saleh1* 1plant protection department, college of food and agriculture sciences, king saud university, saudi arabia. 2department of bioinformatics and biotechnology, government college university faisalabad pakistan. 3viruses and phytoplasma research department, plant pathology research institute, agricultural research center, egypt * e-mail: malsaleh@ksu.edu.sa abstract begomovirus is the largest genus in family geminiviridae and includes more than 445 virus species. begomoviruses are characterized by single-stranded circular monopartite or bipartite genome and transmitted by whitefly (bemisia tabaci). begomoviruses cause severe disease in many economically important crops throughout the world. typical disease symptoms of begomovirus including severe leaf curling, vein thickening, vein darkening and reduced leaf size were observed in papaya plants in the dammam district of the eastern province of saudi arabia during the summer of 2021. a total of 10 samples were collected. total genomic dnas were isolated from naturally infected papaya tree samples and subjected to pcr amplification using universal diagnostic primers for begomoviruses and associated satellites. three pcr amplified genomic components of begomoviruses and betasatellite namely p61begomo (645 bp), p62begomo (341 bp) and p62beta (563 bp) were sent for sanger dna sequencing to macrogen inc. these partial viral genome sequences were submitted to genbank database and accession numbers on206051, on206052 and on206050 were assigned to p61begomo, p62begomo and p62beta respectively. phylogenetic analysis and pairwise nucleotide sequence identity studies showed that p61begomo was identified as tomato yellow leaf curl virus, p62begomo was identified as dna a component of a bipartite begomovirus watermelon chlorotic stunt virus and p62beta was confirmed as begomovirus associated betasatellite; cotton leaf curl gezira betasatellite. t keywords: papaya, tylcv, betasatellite, wmcsv, clcugb mailto:malsaleh@ksu.edu.sa 85 aphid/whitefly-transmitted viruses-a global threat to cucurbit production k. bananej plant virology research department, iranian research institute of plant protection, agricultural research, education and extension organization (areeo), tehran, iran. e-mail: k_bananej@yahoo.com abstract cucurbit crops are economically important for human nutrition, worldwidevarious plant viruses from different genera are currently threatening cucurbit crop production in the world. aphid-transmitted viruses (atvs) and whitefly-transmitted viruses (wtvs) have been expanded throughout the world and cause economically important diseases. zucchini yellow mosaic virus (zymv) is a typical example of atvs in cucurbits. within a decade, zymv spread to all the major cucurbit cultivation areas worldwide. wtvs are also responsible for considerable yield losses and are typical examples of “emerging” viruses. bemisia tabaci complex and trialeurodes vaporariorum are vectors of wtvs. most damaging whitefly-transmitted viruses (wtvs) include: begomoviruses (geminiviridae), criniviruses (closteroviridae), and torradoviruses (secoviridae). the high rate of recombination may be contributing to the recent emergence of new virus diseases. changes in the vector populations coupled with polyphagy and long distance movement of b. tabaci, may be involved in the emergence and establishment of wtvs in new regions. climate change and global warming are of great concern to agriculture worldwide and are among the most discussed issues in today’s society. insecticides are frequently used in atvs and wtvs management programs, however, indiscriminate use has resulted in resistance development, and control failures have been reported from many parts of the world. relaxation of quarantine regulations, intensification and diversification of agriculture with changes in cropping practices and cultivation of crops in new areas specifically with different climates are factors allowing the successful spread of atvs and wtvs in the world. keywords: cucurbit crop, plant viruses, atvs, wtvs mailto:k_bananej@yahoo.com 86 current status and coat protein-based comparative in silico analysis of zucchini yellow mosaic virus (zymv) infecting cucurbits in pothwar, pakistan m. ahsan1, m. ashfaq2*, m. mehmood2, m. shakeel3, m. hamza2 1institute of environmental and agricultural sciences, university of okara, okara, pakistan 2plant pathology, institute of plant protection, muhammad nawaz shareef university of agriculture, multan, pakistan 3department of plant pathology, faculty of agriculture and environment, the islamia university of bahawalpur, pakistan e-mail: mashfaq@mnsuam.edu.pk abstract cucurbits are major vegetable crop in pakistan. zucchini yellow mosaic virus (zymv) is one the main limiting factors that causes huge losses and is a menace to cucurbits not only in pakistan but also worldwide. the present study was conducted to know the spread and variation of zymv isolates infecting cucurbits in pothwar region of pakistan using molecular techniques. collected cucurbit samples were subjected to serological detection of tested potyviruses exhibited that zymv ranked first with 35.2% disease incidence followed by papaya ringspot virus (prsv) with 2.2% and watermelon mosaic virus (wmv) with 0.5% incidence during 2016. whereas, zymv and wmv depicted higher disease incidence i.e., 39.7% and 2.4%, respectively and prsv showed lower disease incidence i.e. 0.3% during 2017. detected zymv isolates revealed 95.8-97.0% and 94.6-97.9% nucleotides identities among themselves and isolates retrieved from ncbi, respectively. phylogenetic analysis revealed that four pakistani zymv isolates clustered with italian, polish, and chinese zymv isolates in one group while another isolate clustered with egyptian isolates. newly detected zymv isolate (mk848239) seems to be a recombinant of pakistani and italian isolates i.e., mk848237 and mk956829, respectively with recombination breakpoint between 266 and 814 nucleotide position number as detected by recombination analysis. this study helped us to detect the recombinant viral strain with higher disease incidence across the pothwar region that may result in colossal losses in the future. therefore, screening of available germplasm against recombinant viral strain(s) to identify the resistant sources, will be helpful in future breeding programs. keywords: zymv, wmv, prsv, coat protein, in silico, potyviruses mailto:mashfaq@mnsuam.edu.pk 87 identification of tomato brown rugose fruit virus in tomato and current research in palestine o. al-abdallah1*, r. alkownie2 and i. abbassi3 1national agricultural research center (narc) ministry ofagriculture, palestine 2biology and biotechnology department, faculty of science, an-najah national university, nablus, palestine 3microbiology department, al-quds university, palestine * e-mail: oalabdallah@gmail.com abstract tomato, a top cash crop, is infected by a number of viruses that cause drastic yield losses. recently an unusual viral syndrome that resembled with that induced by tobacco mosaic virus has been observed in northern palestine. a study aimed at revealing the cause of the disease, identified the presence of a putatively undescribed tobamovirus. the virus genome was entirely sequenced and shown to be composed of 6391 nucleotides. sequence analysis indicated that this virus is an isolate of tomato brown rugose fruit virus (tbrfv). this is the first time tbrfv was detected in palestine on tomato and the name tomato brown rugose fruit virus-palestinian isolate (tbrfv-ps) is suggested. molecular tools were developed for specific detection of the virus. moreover, 15 different commercial tomato varieties were selected among those commonly cultivated by tomato farmers in palestine to assess their tolerance to tbrfv infection. upon inoculation with tbrfv, the typical viral symptoms appeared on all the different varieties. plant samples were collected at different times during the growing period to assess and quantify tbrfv infection and confirm its sequence by ngs technology. these results will be used to assess the tolerance of the selected 15 tomato varieties to the tbrfv and, consequently, advise the farmers. keywords: tomato, tobamovirus, tbrfv, ngs mailto:oalabdallah@gmail.com 88 analysis of volatile organic compounds produced by antagonistic bacteria isolated from biofumigated soil d. al-daghari1*, a. al-sadi1, m. al-harrasi1, j. al-sabahi2 and r. velazhahan1 1department of plant sciences, college of agricultural and marine sciences, sultan qaboos university, al-khoud, muscat 123, sultanate of oman 2 central instrumentation laboratory, college of agricultural and marine sciences, sultan qaboos university, al-khoud, muscat 123, sultanate of oman *e-mail: s90142@student.squ.edu.om abstract the bacterial antagonists viz., pseudomonas aeruginosa b1-squ, pseudomonas indica b2squ, serratia marcescens b3-squ and pseudomonas brenneri b4-squ isolated from biofumigated soil which were found effective against pythium aphanidermatum in in vitro dual culture assay were tested for their potential to produce volatile organic compounds (vocs). the results of two-sealed-base-plates assay revealed that all the tested bacterial strains produced antimicrobial vocs against p. aphanidermatum with the maximum inhibition with p. brenneri (b4-squ) followed by s. marcescens b3-squ, p. aeruginosa b1-squ and pseudomonas indica b2-squ. the solid-phase microextraction followed by gas chromatography-mass spectrometry analysis revealed that 1-butanol, 3-methyland disulfide, dimethyl were the major compounds in p. aeruginosa b1-squ. the major compounds detected in p. indica b2squ were 1-butanol, 3-methyl-, disulfide, dimethyl and 1,2-propanediamine. the major volatile compounds identified in s. marcescens b3-squ were disulfide, dimethyl and 1,2-propanediamine. 1-butanol, 3-methyl-, 1,2-propanediamine and disulfide, dimethyl were found as the major compounds in p. brenneri b4-squ. the production of vocs may be one of the modes of action of antagonistic bacterial strains to suppress p. aphanidermatum. keywords: bacterial antagonists, volatile organic compounds (vocs), p. aphanidermatum. s90142@student.squ.edu.om 89 plant nematodes associated with crop plants in jazan region, southwest of saudi arabia m. m. m. mohamed 1, f. alyahya2*, m. yassin2,3, m. el-qurashi2, y. gboyega2, and h. yousif2 1plant pathology department, national research center, dokki, giza, egypt 2department of plant protection, collage of food & agricultural sciences, king saud university, riyadh. kingdom of saudi arabia. 3department of crop protection, collage of agriculture, khartoum university, khartoum, sudan. * e-mail: fayahya@ksu.edu.sa abstract a survey of plant-parasitic nematodes genera associated with different crops in open fields in the jazan region, southwest of saudi arabia, including jazan city and jazan governorates locations (abu-arish, sabya, damad, baysh, fifa, samtah, uhud-al masarha) was carried out during the 20212022 growing season. a total of 609 plant roots and rhizosphere soil samples were collected. samples were extracted in the laboratory using centrifugal-flotation method for soil samples, direct examination of plant roots, and extracted nematodes were identified. the most fruit, vegetable and field crops were infected by root-knot nematodes (meloidogyne incognita) and other dominant genra were lesion nematodes (pratylenchuszeae,), citrus nematodes (tylenchulus semipenetrans), stunt nematodes (tylenchorhynchus spp.), spiral nematode (helichotylenchus spp.), lance nematodes (hoplolaimus spp.), needle nematode (longidorus spp.), dagger nematodes (xiphinema spp.), stubby-root nematodes (trichodorus spp.), reneformis nematodes (rotylenchulus reniformis), ring nematodes (criconemalla spp. and cricoemiodes spp.). the previous plant-parasitic nematode genera associated with fruit crops including: mango, papaya, banana, fig, guava and citrus, and vegetable crops including tomato, okra, eggplant, and field crops including maize, sorghum, rhodes grass and coffee tree. most of these genera were recorded for the first time on plant hosts in the governorates of jazan. keywords: plant-parasitic nematodes, diversity, root, soil mailto:fayahya@ksu.edu.sa 90 oral presentations: biocontrol of postharvest pathogen antifungal activity against aspergillus flavus and aflatoxin b1 detoxification potential of omani medicinal plants r. velazhahan1*, a. al-sadi1, j. al-sabahi2, m.waly3, s. babu4 and k. al-farsi5 1sultan qaboos university, college of agricultural and marine sciences, department of plant sciences, al-khoud, muscat, sultanate of oman 2central instrumentation laboratory, college of agricultural and marine sciences, sultan qaboos university, al-khoud, muscat 123, sultanate of oman 3sultan qaboos university, college of agricultural and marine sciences, department of food science and nutrition, al-khoud, muscat, sultanate of oman 4sultan qaboos university, college of science, central analytical and applied research unit, al-khoud, muscat, sultanate of oman 5oman botanic garden, muscat, oman *e-mail: velazhahan@squ.edu.om; abstract aflatoxins are secondary metabolites produced by aspergillus flavus and a. parasiticus and are common contaminants of several food commodities including groundnut, maize, rice, chilli and pistachios. more than 20 different types of aflatoxins have been described. among them, aflatoxin b1 (afb1) is highly toxic and most frequently found in food products. afb1 is highly stable and heat-resistant and exhibits carcinogenic, mutagenic, teratogenic and immunosuppressive effects in humans and animals. the aflatoxigenic fungi invade the agricultural commodities at pre-harvest and/or postharvest stages and secrete aflatoxins under favourable conditions. several strategies have been employed in order to minimize the levels of afb1 in foods and feeds. among them, detoxification has been considered as a promising strategy to reduce the risk of aflatoxin contamination of foods. plant products are considered as a source of biologically safe, cost-effective and complementary approach for detoxification of aflatoxins. in an effort to identify medicinal plants for detoxification of afb1 we observed that the aqueous extracts and/or essential oils of a few traditional medicinal plants of oman including heliotropium bacciferum, ocimum dhofarense and zataria multiflora were capable of degrading afb1 in vitro. furthermore, the essential oil of z. multiflora showed direct antifungal activity against a. flavus. the alterations in the chemical structure of afb1 upon treatment with the medicinal plant extracts/essential oils were elucidated by liquid chromatography-mass spectrometry analysis. the biological toxicity of the degraded products of afb1 was determined by using brine shrimp bioassay. the findings of this suggest the potential use of these omani medicinal plants in detoxification of afb1 in foods and feeds. keywords: aspergillus flavus and a. parasiticus, aflatoxin b1, medicinal plant extracts 91 antifungal activity of aqueous extract of citrus paradisi seeds on fusarium tricinctum of durum wheat (triticum durum) l. bendifallah university of boumerdes, boumerdes, algeria email for correspondence: leila.bendifallah@gmail.com abstract wheat cultivation is faced with many constraints, including fungal diseases. these are the cause of considerable grain yield loss. the causative agents of these diseases are mostly carried by the seed. the use (in seed treatment) of chemical pesticides is harmful to man and the environment. the use of nonpolluting biofungicides is necessary. this present work concerns the in vitro and in vivo study of the fungicidal effect of the aqueous extract of citrus paradisi seed powder on fusarium tricinctum of durum wheat triticum durum. the in vitro results show that this extract has a strong inhibitory activity at a dose of 20%, 30% and 40% with an inhibition rate of 51.76%, 57.64% and 67.5% respectively. this rate reaches 100% for the concentration of 50%, therefore the antifungal activity of the extract is highly effective. in in vivo mode, the antifungal effect is weak compared to the in vitro test. keywords: fungi, antifungal, leaf extract, wheat mailto:leila.bendifallah@gmail.com 92 biological control of fusarium wilt of tomato by the application of penicillium spp. and chenopodium murale a. javaid*, s. naqvi, i. khan department of plant pathology, faculty of agricultural sciences, university of the punjab, quaid-i-azam campus, lahore 54590, pakistan *e-mail: arshad.iags@pu.edu.pk, arshadjpk@yahoo.com abstract fusarium wilt of tomato, caused by fusarium oxysporum f. sp. lycopersici, is an economically important soil-borne disease of tomato especially in warmer regions of the world. fungicides used to control this disease not only pollute the environment but also cause health hazards. in the present study, this disease was controlled by application of two antagonistic species of penicillium, namely p. digitatum and p. expansum, and dry biomass of a weed chenopodium murale as soil amendments. the antagonistic fungi and different doses of dry biomass of the weed (1%, 2% and 3%) were applied in pathogen inoculated pot soil either separately or in combinations. the highest disease incidence (100%) was recorded in positive control where only fungal pathogen was applied. while in combination of different treatments of soil amendments reduced disease incidence to 3–23%. the lowest disease incidence (3%) was recorded in 2% c. murale biomass + p. expansum treatment. all the soil amendment treatments significantly enhanced shoot and root growth as well as fruit yield as compared to positive control. the highest fruit biomass was recorded in 2% c. murale biomass + p. digitatum treatment. among physioloagoical parameters, the highest activities of peroxidase (pox), catalase (cat) and polyphenol oxidase (ppo) were recorded in the positive control. these enzymatic activities were significantly lowered when soil was amended with antagonistic fungi or c. murale biomass. effect was more pronounced where c. murale biomass was applied either alone or combined with penicillium spp. in conclusion, application of 2% c. murale biomass + p. digitatum has the potential to significantly reduce fusarium wilt of tomato and enhance tomato growth and yield. keywords: biological control, fusarium wilt, tomato, penicillium spp. arshad.iags@pu.edu.pk arshadjpk@yahoo.com%20 93 biological control in oman: applications and potentials m. al-ansari director of nurseries and plant protection, royal courts affairs, oman e-mail: msansari@rca.gov.om abstract biological control, the most important pillar of organic farming, depends on natural organisms that act as agents to control pathogens and diseases. biological control agents include parasites and predators, microbial pesticides from fungi, bacteria, viruses, nematodes, and protozoa, insect pheromones, pesticides extracted from plants, and plants genetically modified to resist pests. in oman, the three primary biological control methods were implemented successfully in the field. first, introducing new natural enemies and establishing a permanent population, i.e. classical biological control, in 1984, the parasitoid wasp, encarsia opulenta silvestri, imported from usa (florida) (hymenoptera: aphelinidae) was introduced to target the citrus blackfly (cbf) aleurocanthus woglumi ashby (homoptera: aleyrodidae), and during 1985, the coccinellid beetle, chilocorus nigritus [fabricius], was introduced from india in the south to target the coconut scale insect, aspidiotus destructor sign., (homoptera: diaspididae). second, conservation of existing natural enemies, e.g. local leptomastix dactylopii (hymenoptera:encyridae) is parasitic wasp that target citrus mealybug. third, mass rearing and periodic release, on a seasonal basis, e.g. mass rearing program of trichogramma that used to control (lipidoptera) pomegranate butterfly, lesser date moth corn borer and eggplant shot & fruit borer. notably, local agents are potentially better than introduced ones because of their adaptation to physical factors such as temperature and salinity. for example, trichoderma asperellum. therefore, more efforts should be invested in identification of new local agents to control challenging pathogens and diseases. keywords: biological control, parasitoid wasp, trichoderma asperellum mailto:msansari@rca.gov.om 94 biocontrol susceptibility of biosurfactants against common plant and food pathogens m. awadh department of biology, college of science, university of bahrain, zallaq, bahrain, email for correspondence: mawadh@uob.edu.bh abstract biological surface-tension reducing agents have been recently considered in a context of biocontrol agents of plant-pathogens. in comparison with chemical pesticides, microorganisms are studied as a promising source for antimicrobial compounds which exhibit the advantages of biodegradability and environmentally friendly. ththis study was conducted to isolate a biosurfactant-producing bacterial strain from local agriculture soil and assess the antimicrobial activity of the produced biosurfactant against some plant and food stuff pathogens. the oil displacement test and wilhelmy method were utilized to assess the production of biosurfactants in the cell-free culture supernatants. the agar disk-diffusion assay was utilized to assess the antimicrobial activity of the produced biosurfactants by the isolated strain. the hydrophobic moiety of rhamnolipids biosurfactant 3-(3-hydroxyalkanoyloxy) alkanoic acids (haas) were detected in the biosurfactant extract by gc-ms. a biosurfactant-producing strain pseudomonas sp. mysr was successfully isolated from agriculture soil in bahrain and characterized by sequencing of the 16s rdna. the mysr was grown in nutrient broth and the surface tension of the cell-free culture supernatants have been reduced from 73.7 mn/m ± 0.03 to a minimum of 40.1 mn/m ± 0.16 after 6 days of incubation. the application of antimicrobial assay of the produced biosurfactant against common plant and food stuff pathogens by the grampositive strains such as bacillus subtills and staphylococcus aureus revealed inhibition zone diameters of 1.3 ± 0.22 cm and 1.02 ± 0.1 cm, respectively. this is the first isolation of biosurfactant producing bacteria with antimicrobial susceptibility from agriculture soil in bahrain. keywords: biosurfactants, plant pathogens, biocontrol agents, pseudomonas sp. mailto:mawadh@uob.edu.bh 95 sodium alginate coating incorporated with pomegranate peel extract extending the shelf life and keeping quality of strawberry m. hosseinifarahi *1,2, m. radi 2,3 and e. faridony1 1department of horticultural science, yasuj branch, islamic azad university, yasuj, iran. 2sustainable agriculture and food security research group, yasuj branch, islamic azad university, yasuj, iran. 3department of food science, yasuj branch, islamic azad university, yasuj, iran *e-mail: mehdi.hosseinifarahi@iau.ac.ir abstract since the synthetic fungicide application to control postharvest decay caused by fungi may bring potential risks to consumers, the use of alternative strategies such as natural compounds and plant extracts for decay control and extending shelf life of strawberry is required. in the present study, the effect of pomegranate peel extract and sodium alginate on the quality of strawberry fruit was investigated, solely or in combination, for up to 16 days. the results showed that the utilization of pomegranate peel extract and sodium alginate coating significantly maintained the strawberry fruit´s quality during the storage period. moreover, fruit treated with pomegranate peel extract and sodium alginate exhibited optimal postharvest quality during storage. results of the sensory indices also demonstrated that pomegranate peel extract and sodium alginate at concentrations of 1.5 g/l and 10 g/l, respectively, preserved significantly fruit quality during storage. generally, the optimum values for quality traits were recorded at 1.5 g/l of pomegranate peel extract. therefore, sodium alginate + pomegranate peel extract 1.5 g/l treatment could be a promising strategy to improve the quality of strawberry fruits during the storage period, which could provide a perspective for a natural alternative to synthetic plant protection products. keywords: fungal decay, sensory evaluation, shelf life, rot mailto:mehdi.hosseinifarahi@iau.ac.ir 96 oral presentations: entomology fruit flies and their management in oman: research experience since 2003 a. al-wahaibi, a. al-raeesi, s. al-ansari, w. alsaadi, s. al-rawahi, m. al-issai, a. al-kiyumi, a. al-alawi, s. al-owaisi, h. al-maqbali, m. al-abdali entomology lab, department of plant sciences, college of agricultural & marine sciences, sultan qaboos university *e-mail: wahaibi@squ.edu.om abstract fruit fly species in oman were investigated via sampling of fruits from cultivated and wild plants and hanging traps. a total of 13 species of tephritids were identified using morphological and molecular techniques. three unidentified species could be new to science. moreover, 2-3 species of braconid parasitoids and one figitid species, mostly associated with fruit fly infested ziziphus fruits, were collected. a new lure for female fruit flies, consisting of a combination of urea and watermelon seeds, exhibited effectiveness on par with commercial lures such as torula yeast and ceratrap. in terms of physical barriers, row covers significantly reduced zucchini fruit damage even when applied as a wall around the planting line. an experiment, involving combining growing melon in the greenhouse with a honeybee hive for flower pollination, proved successful in producing a large number of undamaged fruits. in terms of biological control, we managed to set up a system for rearing of major pestiferous fruit fly species and their parasitoids. we currently have two active cultures of bactrocera zonata and b. dorsalis, and one active culture of diachasmimorpha longicaudata (dl), a braconid parasitoid imported from kenya. we hope in the future to produce large numbers of dl wasps for augmentative release in oman. fruit fly cultures have served as stock for testing plant extracts as repellents against female b. zonata and b. dorsalis and for testing beauveria bassiana formulations for control of adults and larvae of b. zonata. studies of fruit fly population dynamics and height of flight have shown that yellow sticky traps, set at different heights from 0.5 to 3.5 m, captured significantly more males than females. additionally, most fruit flies were captured at 2m and lower. the population of male b. dorsalis in me traps was highest from april to june, and lowest from november to january. conversely, the population of male b. zonata in me traps peaked from september to december, and dropped to its lowest levels from april to july. keywords: fruit flies, yellow sticky traps, b. dorsalis, b. zonata mailto:wahaibi@squ.edu.om 97 metarhizium anisopliae compatibility and synergistic interactions with insecticides against different aphid species a. nawaz1⃰, f. razzaq1, m. dildar gogi1, g. fernández-grandon2, a. ali1, m. khan1, m. arshad1, zain ul abidin1, a. ijaz1 1department of entomology, university of agriculture, faisalabad, pakistan. 2natural resources institute, university of greenwich, central avenue, chatham maritime, kent, me4 4tb, uk. *email for correspondence: nawazrajpoot@yahoo.com abstract in this study, single and combined effects of eight insecticides and the entomopathogenic fungi, metarhizium anisopliae (metschin.) against cabbage aphid and cotton aphid species under in vitro conditions were evluated. six of the insecticides tested were found to be highly compatible (flonicamid, imidacloprid, nitenpyram, dinotefuran, pyriproxyfen and spirotetramat), showing positive integration with the fungus and were selected for bioassays. the combination mixtures (1:1 ratio of m. anisopliae: insecticide) were significantly more toxic to aphid species than individual treatments. maximum mortality of cotton aphid (91.68%) and cabbage aphid (88.36%) was recorded with the combination of flonicamid and m. anisopliae (2.4 × 106 cfu/ml) 72 h after application. while minimum mortality 17.08% and 16.66% was observed with the individual treatment of m. anisopliae (2.4 × 106 cfu/ml) against cotton aphid and cabbage aphid respectively. the results indicates that m. anisopliae has the potential to control cotton aphid and cabbage aphid within a short period of time when combined with insecticides. the combined insecticide m. anisopliae were consistently more toxic than individual treatments. the present study utilized co-toxicity coefficients and synergy factors to calculate the efficacies of different insecticides + m. anisopliae formulations. the toxicity of insecticides, based on their lc50 and lc90 values increased when mixed with m. anisopliae. in addition, the synergy factor (sf) and co-toxicity coefficient (ctc) values indicated synergistic interactions at different time intervals. the high values of co-toxicity coefficients, which were accompanied by insect mortalities > 90% for some treatments, illustrate the effectiveness of this dual-attack method of insect pest control. the synergistic efficacy revealed the potential of fungus-insecticide integration against sucking insect pests. keywords: entomopathogenic fungi, insecticides, synergistic interaction, m. anisopliae nawazrajpoot@yahoo.com 98 discovery of novel small molecule inhibitors against helicoverpa armigera sterol-carrier protein-2(hascp2) through computational and biological methods m. imran forman christian college, lahore, pakistan email for correspondence: muhammadimran@fccollege.edu.pk abstract insects lack important gene encoding enzymes in the de novo cholesterol synthesis pathway and are dependent on exogenous cholesterol provision by host plants for two important functions; to form structural components of cells and tissues, and precursors for steroid hormones. this external cholesterol uptake is mediated by an interplay of scp-2, a sterol carrier protein-2. scp-2 takes up cholesterol molecules from the plasma membrane and shuffles them to the metabolic pathways. therefore, potential inhibitors that could be capable enough to block the function of scp-2 can downregulate the cholesterol uptake in insects and this can be achieved by identifying novel small inhibitor molecules by adopting in silico computational techniques followed by in vitro validation of screened inhibitors. in this study, a pharmacophorebased virtual screening approach was employed to screen 68 million compounds containing different databases. hits of pharmacophorebased vs were further passed through eon-based virtual screening which gave 106 hits. moreover, fred and glide based virtual screening finally gave 8 potential hits and their binding modes were verified by molecular dynamic simulations. cloned and purified hascp-2 protein was used to validate the binding trend of selected hits with receptor hascp-2 by probe based, fluorescent binding and displacement assay, and their ic50 values were calculated. cytotoxicity assay was carried out by cell-based assay. insecticidal agent toxicity assay of molecules in insect sf9 cell line showed that the percentage of cytotoxicity in cells is positively correlated with tested concentrations of small inhibitor molecules. in conclusion, hierarchical virtual screening followed by in-vitro binding assay and cell-based assay yielded a novel scaffold to block the function of hascp-2further optimization can lead to a better and more active insecticide-like small molecule. keywords: insecticide, toxicity, protein, conventional and biological methods mailto:muhammadimran@fccollege.edu.pk 99 prospects for microbials based ipm of red palm weevil: from laboratory to date palm orchards w. wakil department of entomology, university of agriculture, faisalabad 38040, pakistan senckenberg german entomological institute, d-15374 müncheberg, germany e-mail: waqaswakeel@hotmail.com abstract red palm weevil (rpw) damages more than 29 different palm species in economic trade zones of date palm, particularly in south east asia, the middle east and africa. as an invasive pest for the last 30 years, its infestation has been recorded in half of the date producing countries. synthetic insecticides and fumigants have remained the mainstay of date palm growers for decades to combat this pest. however, chemical control is challenging due to the cryptic nature of rpw. moreover, chemical insecticides have had negative effects on the environment and human health, and pests has developed resistance against many of these chemicals. the urge to explore more effective, sustainable and environmentally friendly alternatives to control rpw has revealed the potential of microbial control agents in the integrated pest management (ipm) of this invasive insect pest. microbial pest control relies on use of pathogens such as entomopathogenic fungi, nematodes and bacteria and they have a high degree of host specificity. entomopathogenic fungi and nematodes are the best promising agents to be included in an ipm program against this pest. their incorporation with other control approaches has a number of benefits including being safe, cheap, lacking non-target effects and self-perpetuation. this talk will underpin an analysis of pathogen mode of contact and infection, auto-dissemination potential and the spread mediated by infected adults, endophytic behavior of some strains, and use in combination with other agents (new-chemistry synthetic insecticides) for the control of rpw. the pros and cons of microbes will be highlighted, with an emphasis on the work of a leading research team that has spearheaded projects in pakistan. keywords: entomopathogens, synthetic insecticides, ipm, red palm weevil, date palm waqaswakeel@hotmail.com 100 effect of communication towers on the performance and behavior apis mellifera l. (hymenoptera: apidae) (the internal activities) in baghdad, iraq a. alnaimee1, f. salah2*, s. abdallad2 and k. shaher1 1faculty of agriculture. university of baghdad, iraq 2faculty of agricultural sciences, university of gezira, sudan *e-mail: faizaruba2@gmail.com abstract beekeeping is one of the most important branches of agricultural investments, and bees represent 80% of pollinating insects of cultivated crops. many factors affect their activities, including electromagnetic radiation. this study was conducted to investigate the effect of the radiation emitted by communication towers on honey bee communities. the first location was 500 m, the second was 150 m from the telecommunication tower and the third transaction was placed directly under the tower. the height of the tower was 30 m and the amount of radiation emitted from it was 925 mhz. the results of the internal activity, measuring the activity of the queen in laying eggs, showed that the highest rate of activity in the first treatment, followed by second treatment while the lowest rate was recorded on the third treatment. the area of the closed brood was highest in the first treatment followed by the second treatment and the lowest rate in the third treatment. the results showed that the highest drone brood of the third treatment was 6.76 inches, and the first and second treatments recorded 4.48 and 14.1 inches, respectively. as for the results of pollen area, there were significant differences for the first and second treatments, while the third treatment recorded the lowest rate. the measurement of the speed of achievement of wax foundation showed significant differences between the two treatments, where the second treatment surpassed the rest of the transactions within four days, followed by the first treatment and the third transaction recorded the lowest. the highest rate of density of bees was recorded in the first treatment and the lowest rate for the third treatment. in conclusion, the communication towers have negative effect on the internal activities of apis mellifera. keywords: apis mellifera, insect, pollination, communicaiton mailto:faizaruba2@gmail.com 101 impact of the type of vegetation and soil physicochemical characteristics on the abundance of mole cricket crop pests a. noutchom university of yaound, yaound, cameroon e-mail: simeunou@gmail.com abstract mole crickets are burrowing insects known to be serious crop pests because of their feeding on the root system. successful mole cricket management requires knowledge of their bio-ecology. this study was conducted to assess the impact of habitat characteristics on the abundance of mole crickets in three agro-ecological zones of cameroon. in each area, four types of vegetation, namely forest, agroforestry, fallow land, and a crop field, were surveyed. in each type of vegetation, mole crickets were collected through pitfalls and soil characteristics such as ph, humidity, and sand content were evaluated. the results show that mole crickets were affected by the type of vegetation and soil characteristics. mole crickets were more abundant in crop fields and grassy fallows than in agroforestry and forests. the abundance of mole crickets was higher in soils with a ph range of 5-6 and was very low in soils with a ph range of 3-4 (07 individuals). the abundance of mole crickets was higher in soils with a moisture content of between 5% and 20% (150 individuals), while it was very low between 20% and 35% (02 individuals). the abundance of mole crickets was higher in soils whose sand content was between 40% and 55% (94 individuals) and very low between 25% and 40% (15 individuals). these results will aid in implementing sustainable management of mole crickets in cameroon. keywords: pests, mole cricket, vegetable crops mailto:simeunou@gmail.com 102 spatio-temporal distribution patterns of pest species (lepi-doptera: noctuidae) affected by meteorological factors in an agroecosystem z. hussain1, z. sarwar1*, a. akbar2 1department of entomology, fast bahauddin zakariya university multan. 60800, pakistan 2department of statistics, bahauddin zakariya university multan. 60800, pakistan *e-mail: zmsarwar@bzu.edu.pk abstract knowing pests' spatio-temporal distribution patterns is essential for forecasting population outbreaks and designing control tactics or long-term management plans. the family noctuidae is one of the biggest families of the lepidoptera order. the noctuid's moths are well represented in all zoogeographic regions in various habitats and have innumerable ecological and economic importance. despite extensive studies on the species' ecology, knowledge is rare about noctuid moths' spatial and temporal distribution patterns in an agroecosystem. therefore, in this study, the spatial and temporal fluctuations in abundance of spodoptera litura, hadena tripoli, helicoverpa armigera, hadena jahangiri, spodoptera exigua, hadena stigmosa, spodoptera furgiperda, agrotis ipsilon, aletia l album, callopistria placodoides, callopistria repleta, earias insulana, agrotis cinerea, mythimna loreyi, earias vitella, lacanobia oleracea, euplexia conducta, helicoverpa platigera, mamestra brassicae, leucania venalba, diarsia hoenei, ctenopulsia albostriata, chrysodeixis furthatai and aletia decisissima were determined. yellow light traps were mounted in 11 different selected localities of district multan. the maximum species abundance was observed in september but declined in december, january, and february. the spatial contour maps were used to determine the species' dissemination over space. meteorological factors such as temperature and humidity showed a significantly positive correlation while rainfall showed a significantly negative correlation with species richness. maximum species abundance was recorded in crop areas as compared to forest areas. this study provides a scientific basis for developing and timely applying control strategies for localized pest control. keywords: spatio-temporal, lepidoptera, noctuidae, genitalia, abundance mailto:zmsarwar@bzu.edu.pk 103 repellent and oviposition deterrent effects of some wild plants against peach fruit fly, bactrocera zonata (saunders) m. binyameen*, a. nawaz, and m. abbas department of entomology, faculty of agricultural sciences and technology, bahauddin zakariya university, multan, pakistan * e-mail: mbinyameen@bzu.edu.pk abstract bactrocera zonata saunders is a polyphagous and devastating pest of fruits and vegetables. due to the resistance development in insects against synthetic insecticides, there has been a shift in interest to develop plant-derived, eco-friendly chemicals compatible with integrated pest management (ipm). this study evaluated the efficacy of essential oils of curcuma longa, mentha spicata, chenopodium ambrosioides, origanum vulgare, ocimum basilicum, origanum majorana, mentha longifolia, eucalyptus globulus, lepidium apetalum, azadirachta indica, parthenium hysterophorus, syzygium aromaticum and conyza canadensis on adult repellence, oviposition deterrence, and pupal recovery of b. zonata. fruits were treated with 0.01%, 0.1% and 1% concentrations of essential oils with five replications for each treatment. in multi-choice bioassay, total of eight bananas including control were used. seven bananas treated with seven different essential oil while the control was treated with ethanol were placed in front of the 24 h starved b. zonata females (20) in single replication. moreover, oviposition deterrence and repellency were observed for 5 h from the onset of experiments. essential oil of m. spicata and o. vulgare proved very effective as a repellent, and oviposition deterrent followed by c. longa, c. ambrosioides, o. basilicum, o. majorana, m. longifolia against b. zonata. the results suggested that we can control the pest using plant based essential oils without harming the environment. keywords: repellency, oviposition deterrence, fruit fly, chemicals, essential oils mailto:mbinyameen@bzu.edu.pk 104 characterization of fruit flies (diptera: tephritidae) present in oman s. al-ansari department of plant sciences, college of agricultural and marine sciences, sultan qaboos university e-mail: s89106@student.squ.edu.om abstract fruit flies are important pests of fruits and vegetables. they cause significant economic losses to farmers. this study was conducted to determine the fruit fly species present in oman, their distribution and host plants. fruit samples were collected from different locations around oman during 2019 and 2020. fruits were kept in jars with sand until larvae emerged and pupated. fruit flies were identified morphologically using characteristic features on the thorax, abdomen, and wings and molecularly via dna extraction, pcr, and sequencing procedures. there were nine fruit fly species in oman. the polyphagous bactrocera dorsalis and bactrocera zonata were collected from fruits of different trees (mostly cultivated fruit trees), while dacus ciliatus was collected from cucurbit fruits (cultivated and wild cucurbits such as citrullus colocynthis or handhal). bactrocera cucurbitae was collected from fruits of cultivated cucurbits. carpomiya vesuviana and carpomiya incompleta were collected from fruits of ziziphus species (wild and cultivated). dacus persicus was collected from the wild plant, calotropis procera (sodom’s apple or shakhar). bactrocera oleae was collected from fruits of wild olive (olea europea) in aljabal alakhdhar area. capparimiya savastani was collected from flower buds of wild capparis species, mostly from c. cartilaginea. except for b. cucurbitae (not found so far in dhofar) and b. olea (found only in addakhilyyeh governorate), most fruit fly species were found in all of the surveyed governorates. both b. dorsalis and b. cucurbitate have been recorded only on cultivated host plants. the most widely distributed fruit flies were b. zonata and d. ciliatus. two species, c. savastani and b. olea, are confirmed to be present in oman for the first time. molecular fingerprinting allowed the correct identification of dacus persicus, as specimens from oman were previously known in error as d. longistylus, a closely related species found in africa. keywords: tephritidae, diversity, distribution, dacus persicus, bactrocera oleae. mailto:s89106@student.squ.edu.om 105 chitinase of trichoderma longibrachiatum for the control of aphis gossypii h. shafiq*, w. anwar, k. zohaib and r. kalsoom department of plant pathology, faculty of agricultural sciences, university of the punjab, lahore, pakistan *e-mail: firstfcbp@yahoo.com abstract chitinase-producing fungi have now attracted attention as potential agents for the control of insect pests. in the present study, entomopathogenic fungi were used for the control of aphis gossypii. chit1 gene family 18 glycosyl hydrolases were isolated, amplified and characterized from the genomic dna of trichoderma longibrachiatum. the amplified chit1 was closely related to family 18 of glycosyl hydrolyses. fungal chitinase (chit1) was expressed in the cotton plant for transient expression through geminivirus-mediated gene silencing vector of cotton leaf crumple virus (clcrv). transformed cotton plants showed greater chitinase activity than control, and they were virulent against nymphs and adults of a. gossypii. about 38.75 % and 21.67% mortality of both nymphs and adults were recorded by using chit1 of t. longibrachiatum. thus, t. longibrachiatum has the potential to control aphids through fungal chitinase and can be used as an effective approach in the future. keywords: entomopathogenic fungi, chitinases, transient expression, trichoderma longibrachiatum, aphis gossypii mailto:firstfcbp@yahoo.com 106 oral presentations: integrated pest and disease management understanding pyrenophora tritici-repentis wheat pathosystem in algeria for best management strategy involving host resistance under an integrated disease management strategy h. benslimane1*, n. ouaar1, a. benbelkacem2, p. singh3, s. omata2, a. yahiaoui3 1department of botanic, national high college of agriculture (ecole nationale supérieure agronomique), 1 avenue pasteur, hassen badi, algiers, algeria 2institut national de la recherche agronomique d’algérie, unité de recherche de constantine, station itgc, el-khroub, algeria 3international maize and wheat improvement center (cimmyt), carretera méxico-veracruz km. 45, el batán, texcoco, c.p. 56237, méxico / *e-mail: h.benslimane@ensa.dz abstract tan spot, caused by pyrenophora tritici-repentis, is a serious disease of wheat in algeria. in the integrated disease management program, focus on the development of host resistance, besides other management practices aimed to control tan spot disease, is an important component of the overall strategy. understanding the biology and population structure of the pathogen is essential to reach this aim. for this purpose, several isolate collections sampled across wheat growing areas in algeria for several seasons were studied. pathogen populations showed a wide range of morphological and physiological variations. races population structure analysis, using a modified differential host set, highlighted the presence of races 1, 4, 5, 6, 7, and 8, and a new virulence pattern was discovered. amplification of toxa and toxb , the main virulence genes, showed the genome of isolates sampled from algerian fields harbored both genes, their distribution through growing wheat areas have been established. additionally, fluorescent amplified fragment length polymorphism, revealed high genetic diversity. accordingly, deployment of resistant cultivars has been conducted and available germplasms of wheat, (116 genotypes) mainly from the national program of wheat improvement, were evaluated against races 1 and 5. the reaction was initially evaluated under controlled conditions at the seedling stage, and then the observed resistant genotypes were evaluated in the field with and without fungicide treatments. altogether, 13 genotypes showed resistant or moderately resistant reactions to race 1, while 23 genotypes, showed resistant responses to race 5. however, only 1 landrace and 6 cultivars were resistant to both races 1 and 5. based on these results, we recommend cultivation of some of these resistant cultivars, and use of these resistant sources in the breeding programs. keywords: pyrenophora tritici-repentis, wheat, pathogen variability, resistance h.benslimane@ensa.dz%20 107 use of epiphytic bacteria for the control of major citrus foliar fungal diseases e. abdellatif1*, w. rouissi2, m. kałużna3, a. hamdane1 1laboratory of bioaggressors and integrated protection in agriculture lr14agr02, the national agronomic institute of tunisia, university of carthage, 43 avenue charles-nicolle, 1082 tunis, tunisia 2laboratory of plant protection, the national institute of agronomic research of tunisia, rue hedi karray, 2049, tunisia 3the national institute of horticultural research, konstytucji 3 maja 1/3, 96-100 skierniewice, poland *e-mail: abd-emna@yahoo.fr abstract citrus spp. is an important fruit crop for the tunisian economy. however, they are affected by several in field and postharvest fungal diseases. alternaria spp. and colletotrichum spp. are the causal agents of alternaria and anthracnose diseases. phyllosticta citricarpa that was recently detected in tunisia is the plant pathogenic fungus that causes citrus black spot. the development of these fungi in the presence of multiple applications of copper per year to manage citrus diseases warrants an investigation into the effects of copper on growth of the isolates. the effect of copper on the reduction of the growth of the isolates in media amended with different concentrations of cuso4 (0, 4 3, 6 µm) was evaluated and radial colony growth was assessed. colletotrichum sp. and phyllosticta sp. showed to be resistant to the highest tested concentration of cuso4 (3, 6 µm). however, alternaria sp. was moderately sensitive with a reduced radial growth from 61, 3 mm for the negative control to 24, 3 mm for a copper concentration of 3, 6 mm. biological control of these plant diseases with antagonistic bacteria from the citrus phyllosphere was tested and determined as a promising biological control strategy. keywords: alternaria sp., colletotrichum sp., phyllosticta sp., copper resistance, biological control, antagonistic bacteria mailto:abd-emna@yahoo.fr 108 neem oil encapsulated chitosan nanoparticles on the toxicity, feeding and reproductive physiology of cotton bollworm helicoverpaarmigera k. murugan1*, r. rajaganesh1, m. vasanthakumaran1 and n. alkenani2. 1department of zoology, school of life sciences, bharathiar university, coimbatore641 016, tamil nadu, india 2department of biological sciences, king abdul-aziz university, jeddah saudi arabia. 80200 e-mail: kmvvk@buc.edu.in abstract nanobiotechnology is among the emerging fields and its applications in agriculture are attracting the scientific community. in this study, the influence of neem oil encapsulated chitosan nanoparticles (no-chnps) on the feeding, growth and reproductive performances of polyphagous insect pest helicoverpa armigera in the cotton ecosystem was evaluated. the nanoparticles treated insects showed growth deformities with extended larval and pupal durations and reduced fecundity and it may be due to the hormonal impact on the growth and reproduction. the treatment with nanoparticles considerably affected the feeding performances on the amount of food consumed and efficiency of conversion of ingested and digested food values. there was strong evidence from the experimental results that the decreasing trend of digestive enzymes and lesser faecal pellet egestion, which implies that the nanoparticles bind the gut receptors and hindered the feeding regulations of insect species. the parasitisation (larval parasitoid, (campoletischlorideae) of as well as the survival of the earthworm (eudriluseugeniae) population does not affected by neem oil encapsulated nanomaterials. hence, these formulations can be used for the integrated management of helicoverpa armigera in the agro-ecosystem. overall, this research highlights the potential of no-chnps for the development of newer control tools against control of cotton bollworm; also highlighting some risks concerned the employ of nanoparticles in aquatic/terrestrial environments. keywords: crop insect pest, neem, biological control, neem molecule, parasitoid, earthworm, plant protection. mailto:kmvvk@buc.edu.in 109 the efficacy of abamectin insecticide product by gyah corporation as a nematicide for root-knot nematodes management s. mardani1, m. nasr-esfahani2*, m. olia1, h. molahosseini3 and h. khankahdani4 1department of plant pathology, agricultural faculty, university of shahr-e-kord, shahr-e-kord, iran 2plant protection research department, esfahan agriculture and natural resource research and education center, esfahan, areeo, iran 3soil and water research department, esfahan agriculture and natural resource research and education center, esfahan, areeo, iran 4horticulture crops research department, hormozgan agricultural and natural resources research and education center, areeo, bandar abbas, iran *e-mail: mne2011@gmail.com; m.nasr@areeo.ac.ir abstract root-knot nematodes (rkn), meloidogyne spp. with the dominant species, meloidogyne javanicaare is considered as the important plant pathogens of agricultural products globally. in this study, chemical management was carried out rkn, m. javanica to investigate the efficacy of iranian abamectin insecticide product [acaricideabamectin (vermectin® 1.8% ec, gyah corp., iran)] verses normal abamectin available in the market each at the rate of 8 l.ha, on cucumber “viola” and the controls (infested to rkn and without any chemical pesticides treatments) at the two highly infested-rkn farmer greenhouses in isfahan, iran. the results indicated a highly significant reduction in rkn population and increase in biomass parameters at 1% level of significance, respectively. parameters of rkn in the soil and plant root revealed that the number of nematode larvae, second instar larvae (j2) in the soil was reduced by 95% by the normal abamectin and 93% by the iranian abamectin product in comparison to the initial population, respectively. the number of j2 and eggs in the root was also reduced by 89% in the normal abamectin followed by 91% in the iranian abamectin; gall-index reduction was 56% and 58%; and egg-mass index with 79% and 74% reduction in the roots; and the lowest percentage of reproduction rate was 5.4% and 8.3% in the respective treatments accordingly. the same trend was almost followed for the growth factors parameters (biomass), bgps. the highest stem fresh and dry weight was recorded in the normal abamectin followed by iranian abamectin. the longest stem and root length and root fresh and dry weight was recorded in the iranian abamectin followed by normal abamectin. in total, the results showed that iranian abamectin insecticide is competitive as a nematicide for the management of cucumber rkn compared to normal abamectin, and is a suitable alternative in rkn management, and could be extended to other agricultural crops accordingly. keywords: biomass, cucumber, egg-mass, gall-index, larvae, root, shoot, soil. 110 screening of mango germplasm for resistance against ceratocystis manginecans a. al-adawi*, r. al-maqbali, s. al-kaabi, m. al-sadrani and m. al-jabri ghadafan agriculture research station, department of agriculture research in north al-batinah governate, ministry of agriculture, fisheries and water resources, sultanate of oman * e-mail: aliadawi74@gmail.com abstract the resistant polyembronic mango varieties were evaluated against ceratocystis manginecans, the causal agent of mango decline disease. three omani, zangibari ahmer, mascati and nanat hamad; two indian, benishan and pairi; twenty-five australian and fifteen brazilian mango varieties were included in the inoculation experiment. mango seeds of the above-mentioned varieties were obtained from the mango gene bank in sohar agricultural research station, planted in plastic bags containing sandy soils with peat moss and maintained under shade house until inoculation. artificial inoculation on 8-month-old seedlings was carried out under greenhouse conditions using two isolates of c. manginecans (gcc55 & 120). stems of grafted cultivars were exposed at the mid and were inoculated with a disc of 4 mm diam of c. manginecans isolates grown in malt extract agar. the results of the inoculation revealed the sensitivity of varieties nam doc mai 4, indochinese late, carabao townsville, cecilia carvalha 1 to c. manginecans infection with average lesion lengths of 34.5, 29.5, 22.7, and 22.45 cm, respectively. on the other hand, several polyembryonic mango varieties including carabao, xaoi boui, jasmin and k.p were found tolerant to the pathogen. in another experiment six australian, six brazilian, two omani, two indonesian, two thai, one sri lankan and one indian varieties were also tested. the results revealed high sensitivity of varieties paire, trusso, vellai colomban, cecilia carvalha 2 to c. manginecans infection whereas several polyembryonic mango varieties including dura, elephants tusk and mullimby gold were found tolerant to c. manginecans. some of monoembryonic mango varieties including zangibari ahmer and banat hamed showed tolerance to infection. keywords: mango, polyembronic, monoembryonic, ceratocystis manginecans, resistance mailto:aliadawi74@gmail.com 111 management of fusarium oxysporum f. sp. cubense associated with banana wilt disease in oman s. al-kaabi*, m. al-jabri, m. al sadrani, r. al-maqbali and a. al-adawi ghadafan agriculture research station, department of agriculture research in north al-batinah governate, ministry of agriculture, fisheries and water resources, sultanate of oman *e-mail: alkaabisaif@hotmail.com abstract panama disease in banana crop caused by fusarium oxysporum f.sp. cubense has recently been reported in oman. disease survey in banana farms revealed occurrence of tropical race 4 of the disease in farms in wilayat of north al batinah governorate. the goal of this study was to find resistance/tolerant banana cultivars to banana wilt disease to replace the current susceptible banana cultivarsgrand nain regarded as one of susceptible cultivars and used as control in this trail. grand nain plants were planted within all the rows and were as barrier rows between experiment rows. totally, 1500 tissue culture plants of all cultivars tested were planted in the plot with an area of 1.5 faddan. disease incidence in the plot was assessed periodically after 6 months of planting and plant samples were collected to confirm presence of the causal agent of banana wilt disease. the results showed that fhia 3 and fhia 21 are more tolerant to the disease than the others with 95 and 84%, respectively, of the plants surviving and reaching fruiting stage. conversely, wilting of grand nain and williams started within 6 months, with percentages of 94 and 84%, respectively. cultivars of fhia 18 and b3 were moderate in sensitivity with mortality rate of 42 and 52%, respectively. diagnosis of the banana wilt disease from plant samples collected from all the banana cultivars planted in the plot were all positive for the presence of banana wilt causal agent. keywords: panama disease; banana wilt, fusarium oxysporum f.sp. cubense mailto:alkaabisaif@hotmail.com 112 abu dhabi efforts in date palm trees pests’ control m. al-hammadi, m. al-hashmi*, m. al-maamari technical services division, abu dhabi agriculture & food safety authority. p.o. box: 52150, abu dhabi, uae. e-mail: matar.almaamari@adafsa.gov.ae abstract the abu dhabi agriculture and food safety authority (adafsa) is implementing an integrated strategy that seeks to maintain agricultural biosecurity in the farms of the emirate of abu dhabi by implementing several programs concerned with the palm tree with the aim of reducing the economic damage caused by pests and preserving the ecosystem from the indiscriminate use of agricultural pesticides. this study was conducted to reduce the spread of the main pests that affect palm trees and control them within the critical economic limit, reducing the chances of environmental pollution where only infected palms are treated, improving the productivity and quality of dates. the results indicated a decrease in the rates of infection in all pests that affect the trunk of the palm since the start of the program in 2016. where the incidence of red palm weevil decreased by 66%, the incidence of long-horned palm stem borer also decreased by 27%, and the injury to the palm borer decreased by 11%. moreover, as for the lesser date moth affliction and the dust mites, the indicator fluctuates due to its dependence on weather conditions. moreover, 363,525 palm trees were uprooted and chopped and more than 2.5 million red weevils were cached through pheromone traps. by oct. 2022 and since the beginning of the program, 174,582 farms with a total number of 48,034,544 million palm trees have been dealt with. keywords: date palm, insects, control, red palm weevil 113 assessment of the toxic effects of neonicotinoid pesticides on honeybees foraging, homing ability and colony growth under field and semi-field conditions m. saleem* and m. akbar department of agriculture and agribusiness management, university of karachi, karachi, pakistan *e-mail: shoaibsaleemkhan@gmail.com abstract the honey bee (apis mellifera) is one of the most important pollinator groups in the agriculture ecosystem, providing approximately 50% of global crop pollination services. the downturn in honeybee’s populations is now a worldwide concern. one of the main factors contributing to the decline in honeybee populations is the impact of agrochemicals, in particular neonicotinoid insecticides. we conducted five independent experiments to study the effects of formulated neonicotinoids viz. imidacloprid, clothianidin and thiamethoxam at field realistic doses on the mortality of bees, foraging, colony population, brood termination rate (btr), and homing time in the field and semi-field conditions. the application of neonicotinoids resulted in an increased number of dead bees during the post-application period in first and second week as compared to third and fourth week. there was a rapid and significant reduction in foraging activity of honey bees in the tunnel that gradually increased as the time passed. population per colony decreased as the time passed, and showed a significant decrease until day +15, but the mean population started to increase and recovered at day +18. after 30 days’ observation of marked eggs, brood termination rate (btr%) at brood fixing day (bfd) 20 was 27.66% in control group and the neonicotinoids treated group caused a significant reduction in the brood development of marked eggs, resulting in a btr of 44.33, 52.00 and 60.00%, respectively. the average homing time to hive after release was 4 minutes for neonicotinoids treated groups (imidacloprid 69.8% and in case of clothianidin 89.8%), which was higher than the untreated group (control 53.3%) as honeybees reached back to hive in 2 min. these results confirm the sensitivity of the test methods and indicate that these three tested neonicotinoids could be used in future, as appropriate toxic reference formulated agrochemicals in field and semi-field experiments. keywords: honeybees, neonictoinoids, flight activity, homing ability, colony growth, brood termination rate. mailto:shoaibsaleemkhan@gmail.com 114 successful testing and development of a biofungicide for the management of mango sudden death disease m. khan1*, m. shafiq1, m. ashfaq1, s. saeed2, m. malik3 1plant pathology, institute of plant protection, mns university of agriculture, multan, pakistan 2entomology, institute of plant protection, mns university of agriculture, multan, pakistan 3plant pathology, mango research institute, multan, pakistan *e-mail: arslan.khan@mnsuam.edu.pk abstract mango (mangifera indica l.) is famous throughout the world for its flavor and unique taste. due to various biotic factors, the yield and production of mango is greatly affected. among the biotic factors, the sudden death disease of mango is very destructive and economically important. the present research was conducted to test and formulate an eco-friendly, user-friendly, persistent, sustainable, toxicity-free, and effective bio-fungicide for the management of mango sudden death disease. the testing of bio-fungicide was performed in the laboratory, nursery, and field conditions. under lab conditions, the dual culture method was adopted to assess the antagonistic effect of bio-control agent against ceratocystis fimbriata and showed 100% inhibition of the pathogen. under greenhouse, three treatments, i.e. t1 (biofungicide), t2 (thiophenate methyl), and t3 (bio-fungicide+chemical fungicide along with control (t0) were used. six-month old mango plants were selected and decontaminated. ten-day old culture of c. fimbriata was inoculated to the healthy mango plants fifteen days before the application of treatments. the results showed that the mortality in t0 was 81% whereas in plants, treated with t1, the mortality was (19%) followed by t2 (29%). in the combination, t3, mortality was noted (24%). under field conditions, bio-fungicide was applied to the infected plants. the plants were tagged and treated. the infected plants were recovered and significant results were calculated. bio-fungicide comprises the biological control agent in liquid formulation along with adjuvants to enhance efficacy. the product is very effective for the treatment of infected mango plants in the nursery as well as in the field. keywords: bio-fungicide, biological management, mango sudden death, mango file:///c:/users/thahertech/downloads/arslan.khan@mnsuam.edu.pk 115 suppressive activities of newly synthesized fungicides against plant pathogenic fungi o. al-sudairy1*, v. rethinasamy1, r. abdel-jalil2, e. moghadam2, a. al-ansari3, a. al-sadi1 1department of plant sciences, college of agricultural and marine sciences, sultan qaboos university 2chemistry department, college of science, sultan qaboos university, 132 muscat, oman 3department of biology, sultan qaboos university, p.o. box 36, 123 al-khoud, muscat, oman. *e-mail: omaralsudairy@gmail.com abstract numerous pharmaceutical and biological molecules are composed of heterocyclic subunits such as benzimidazoles. these subunits were reported to have therapeutic applications like antifungal, anticancer and antibacterial agents. moreover, benzimidazole and its derivatives were also used as fungicides. here, several newly synthesized compounds containing benzimidazole were tested against plant pathogenic fungi including alternaria, cochliobolus, rhizoctonia and fusarium using the well diffusion method. 100 l of benzimidazole compounds were added into the well at two different concentrations (1000 ppm and 5000 ppm) and the inhibition zone was measured. at least five of the compounds inhibited fungal growth at both concentrations. scanning electron microscopy (sem) images showed different effects of those compounds on the structure of the hyphae like hyphae swelling and bursting. the study shows promising results of some of the compounds on the plant pathogenic fungi. greenhouse experiments are needed to confirm the applicability of the compounds in the field. keywords: pathogenic fungi, fungicides, benzimidazole compounds file:///c:/users/thahertech/downloads/omaralsudairy@gmail.com 116 assessment of pre-harvest interval (phi) of synthetic and bio-pesticides sprayed on solanaceous (potato and eggplant) crops m. akbar *, a. sultan, w. siraj, m. saleem department of agriculture & agribusiness management, university of karachi, pakistan * e-mail: faheemakbar@uok.edu.pk abstract pesticides are a concern for sustainability of environment and global stability. in order to avoid their adverse effects on human health, it is imperative to assure maximum residue limits (mrls) in food commodities. in view of the above concerns, the present study was designed to assess the pre-harvest interval (phi) of synthetic pesticides and biopesticides sprayed on solanaceous crops viz., potato and eggplant. conventional pesticides such as imidacloprid and profenofos, and biopesticides such as spinosad and biosal (neem compound) were sprayed at the rates of 49.4, 988, 35.5 and 158 g a.i. ha-1 respectively. the pesticide residues were analyzed after 0, 1, 3 and 7 days of application using high performance liquid chromatography. degradation rate constants and half-life were calculated using first order degradation kinetics by fitting on the data obtained. conventional pesticides were more persistent in the crops (average half-life: in eggplant 2.9, and 2.27 days for imidacloprid and profenofos respectively, while in potato it was 2.64 and 2.82 respectively), whereas, for bio pesticides (spinosad average half-life: 2.73 and 2.83 in eggplant and potato respectively). however, average half-life of azadirachtin was observed 0.98 and 1.67 in eggplant and potato respectively. the crops treated with bio pesticides were found safer for human consumption even after few hours of spray when compared with codex and eu mrls. whereas profenofos treated crops were not found to be fit for consumption even after 7 days of application, as they were not degraded down to the eu and codex mrl within usual pre-harvest interval (phi). imidacloprid being biorational (low risk) pesticide degraded quickly and the crop was also safe for consumption on the next day of application. keywords: pre-harvest interval, synthetic and bio pesticides, mrls, half life mailto:faheemakbar@uok.edu.pk 117 oral presentations: weeds science impact of invasive plant species on the livelihoods of farming households: evidence from parthenium weed invasion in dhofar, oman f. al-shahri and m. farooq* department of plant sciences, college of agricultural and marine sciences, sultan qaboos university, al-khoud 123, oman. *e-mail: farooqcp@squ.edu.om abstract parthenium weed (parthenium hysterophorus l.) is one of the most problematic invasive plant species worldwide. since 1998, this weed has invaded the mountains and grazing lands in the dhofar governorate. it has disturbed the native flora and biodiversity to a large extent in the invaded areas. invasive plant species often have negative impacts on agriculture and society in addition to their detrimental effects on biodiversity and the environment. a field survey study was carried out to assess the socio-economic effects of a highly invasive plant species, parthenium weed (parthenium hysterophorus l.) across the dhofar governorate of the sultanate of oman. the farming communities of reported significant effects of parthenium weed on their crop and livestock production, health, and social well-being. farmers were well aware of parthenium weed presence, its biology, habitat, and mode of dispersal across the landscape. all the major crops cultivated were infested by varying degrees of weed densities. parthenium weed also infested the fodder collection and grazing sites affecting livestock production negatively. a significant proportion of farmers also reported negative effects of the weed on animal and human health. most farmers reported parthenium weed as a very challenging weed to manage. about one-third of farmers were willing while the rest were likely to participate in a potential management program in the future. this situation demands a comprehensive strategy for the integrated management of parthenium weed across the governate. keywords: weeds, parthenium, weed management, adverse effect mailto:farooqcp@squ.edu.om 118 allelopathic activity of euphorbia hirta against avena fatua and rumex dentatus and identification of potential allelochemicals m. akbar, taqdees, t. khalil* department of botany, university of gujrat, gujrat, 50700, pakistan. *e-mail: tayyaba.khalil@uog.edu.pk abstract in the present research, allelopathic activity of euphorbia hirta was investigated against rumex dentatus and avena fatua. e. hirta extract was prepared in dh2o (10 g:100 ml w/v) as 100% extract concentration. lower concentration (50%) was prepared by adding dh2o to 100% extract. the allelopathic activity of e. hirta was evaluated by growing r. dentatus and a. fatua either alone or grown side by side with wheat plants in pots. there were 5 treatments viz., dh2o, half dose herbicide, full dose herbicide, 50% plant extract, and 100% plant extract. in in vivo bioassays, the effect of 50% and 100% plant extract of e. hirta on shoot dry biomass of a. fatua and wheat was nonsignificant in general, while there was 50% and 67% significant decline in shoot dry biomass of r. dentatus, respectively, when grown alone. moreover, when r. dentatus was grown side by side with wheat, there was 71% and 86% decrease in shoot dry weight of r. dentatus at 50% and 100% extract concentrations of e. hirta, respectively. the reference herbicides, sulfosulfuron, at full dose, significantly inhibited shoot dry weight of a. fatua by 14%, while, fluroxypyr meptyl + florasulam + mcpa isooctyl, completely eradicated r. dentatus, when planted side by side with wheat. the gas chromatography mass spectrometry (gcms) analysis of e. hirta extract depicted the presence of a number of potent allelochemicals, notably quercetin, hexadecanoic acid, methyl ester, β-sitosterol, afzelin, gallic acid, neophytadiene, stigmasterol, trans,trans2,6dimethyl-2,6octadiene-1,8-diol, and 2,3,5-trimethyl-1h-pyrrole. keywords: herbicidal, rumex, avena, allelopathic, weeds mailto:tayyaba.khalil@uog.edu.pk 119 weed management in wheat using allelopathic crop residue mulches under rice-wheat cropping system s. hussain1, m. farooq2, m. sanaullah3, i. ashraf1, m. khan3, h. rehman1, s. cheema1* 1department of agronomy, university of agriculture, faisalabad-38040, pakistan 2department of plant sciences, college of agricultural and marine sciences, sultan qaboos university, al-khoud 123, oman 3institute of soil and environmental sciences, university of agriculture, faisalabad38040, pakistan * e-mail: sardaralam35@gmail.com abstract weeds pose a severe threat to wheat productivity in rice-wheat cropping system (rwcs). mulching residues of allelopathic crops into soil could be one of the viable organic strategies to manage weeds and sustain productivity. a two-year field experiment was conducted to study the effect of residue mulch of allelopathic crops on the weed population in wheat. the study consisted of three allelopathic crop residue mulch (crm) treatments (wheat, rice and sorghum) each applied at 4 t ha-1 and three nitrogen (n) sources (ammonium sulphate, calcium ammonium nitrate and urea) each applied at 125 kg n ha-1. plastic mulch and no mulch were used as controls. results indicated that all mulches significantly inhibited dry biomass and density of all types of weeds during both growing seasons; however, the highest inhibition of weeds was found with plastic mulch. among allelopathic mulches, maximum suppression in dry biomass and density of narrow leaved weeds (nlws), broad leaved weeds (blws) and total weeds (tws) was found in wheat mulch followed by sorghum and rice mulch. compared with the control (no nitrogen), nitrogen applications generally increased the growth of weeds in terms of thei dry biomass only. the highest grain harvest was recorded in plastic mulch treatments followed by sorghum and wheat mulch. calcium ammonium nitrate exhibited higher grain yield than other nitrogen sources. a negative correlation was found for grain yield and soil water soluble phenolics with dry biomass and density of weeds. in crux, use of allelopathic crms may be a pragmatic approach to manage weeds, improving competitiveness of crop plants with weeds and wheat productivity. keywords: weed dynamics, crop residue mulches, allelopathy, rice-wheat cropping system mailto:sardaralam35@gmail.com 120 improved crop rotations with dry out periods controlled purple nutsedge under cotton-wheat system j. iqbal1, s. bashir2, m. javaid2, m. saddiq1, s. bashir2 1department of agronomy, ghazi university dera ghazi khan punjab pakistan 2department of soil and environmental science, ghazi university dera ghazi khan punjab pakistan * e-mail: jiqbal@gudgk.edu.pk abstract cyperus rotundus is c4 and fast-growing plant replicated through the extensive underground system and tuber. it is highly competitive and causes a significant reduction in cotton production. in recent times, herbicide and nonchemical methods have been practiced to control this noxious weed species. field studies were conducted from 2018 through 2020 to determine the influence of crop rotation having dry out periods and the effect of herbicide for the control of purple nutsedge in cotton, maize, sunflower, and mungbean. during this study, crop rotation sequences were included (1) cotton-wheat-cotton-wheat-cotton (2) do (dry out period) after wheatmaize-wheatdo -maize-wheat-cotton (3) do after wheat-sunflower-wheatdo sunflower-wheat-cotton (4) mungbeando -wheat-mungbeando -wheat-cotton. the experimental field layout was rcbd in a split-plot arrangement with four replicates. the crops were grown in main plots, and in the subplot, the weedy check and weed control with herbicide was maintained. overall, herbicide treatment significantly suppressed the c. rotundus growth than weedy check and improved the crop growth and yield. in crop rotations, the maximum weed infestation was recorded in the cotton-wheat system. while the purple nutsedge infestation was suppressed in the rotation having sunflower, followed by maize and mungbean rotations. fallow tillage (dry out period) might have played a significant role in controlling purple nutsedge in sunflower and maize fields as high temperatures prevailed during may and june months. in 3rd-year cotton, improvement was evaluated in crop rotation field. crop rotation significantly improved the cotton yield by suppressing the purple nutsedge growth. in conclusion, nonchemical methods such as crop rotation with allelopathic crops having some dry-out period can be included as a reliable approach for controlling c. rotundus under the cotton-wheat system. keywords: cyperus rotundas, crop rotation, dry out period, cotton, sunflower, maize mailto:jiqbal@gudgk.edu.pk 121 effect of aqueous extract of three plants grown under stress environment on purple nutsedge s. aimen1*, j. iqbal2, a. aziz1 1department of botany, the women university multan punjab pakistan 2department of agronomy, ghazi university dera ghazi khan punjab pakistan *e-mail: saraaiman170@gmail.com abstract purple nutsedge (cyperus rotundus l.) is one of the top ranked worst weed species with strong competitive abilities which is difficult to control by general herbicides. research was conducted to investigate the herbicidal potential of three different plant species (cymbopogon citratus, tamarix dioca and desmotachya bipinnata) to control purple nutsedge. the aqueous extract of three plants were applied on tubers of purple nutsedge immediately after tuber’s sowing. during pot study, different concentrations of plants extract 25%, 50%, 75%, 100%, crude extract and control were applied on purple nutsedge tubers. the results showed that extracts of highest concentration (100% concentration) of two plants cymbopogon citratus and desmotachya bipinnata completely suppressed the tuber sprouting. cymbopogon citratus proven to the best plant comparatively to tamarix dioca and desmotachya bipinnata against purple nutsedge. treatments like crude water extract and 25% concentration were unable to control purple nutsedge as their effect was same as compared to control. aqueous extract of cymbopogon citratus provided complete suppression of purple nutsedgeat 100% and 75% concentrations. significant reduction in biomass were observed at 50% concentration. desmotachya bipinnata at 75% concentration caused significant reduction in root length, shoot length, root fresh weight, shoot fresh weight, root dry weight, shoot dry weight, and tuber density. while in case of tamarix dioca, only 100% treatment was proven effective to reduce the growth attributes. cymbopogon citratus can be used as bioherbicide as it showed maximum suppressive potential against purple nutsedge. keywords: allelopathy, herbicide, purple nutsedge, leaf extract mailto:saraaiman170@gmail.com 122 weed spectrum and management studies in barleybased cropping systems under conventional and conservative tillage practices m. naeem and m. hussain* department of agronomy, bahauddin zakariya university, multan, pakistan *e-mail: mubashiragr@gmail.com abstract weeds significantly alter the productivity of barley-based cropping systems due to competition for nutrients, moisture and space. tillage practices and crop rotation seem a viable weed management option with minimal environmental and health hazards. this 2-year field study was conducted to monitor the weed spectrum in barley-based cropping systems under conventional and conservative tillage practices. barley was sown after maize, cotton, mungbean, sorghum and in fallow field with five tillage practices, i.e., zero tillage, minimum tillage, strip-tillage, conventional tillage and bed sowing. higher bulk density and soil porosity were noted in zero tillage and maize-barley cropping systems, whereas bed sowing and cotton-barley system had lower bulk density and soil porosity. zero-tilled barley had more diversity, density and biomass of grassy, broadleaved and total weeds, while bed-sown barley recorded the lowest values of these parameters. different cropping systems significantly affected weed dynamics. cotton-barley and mungbean-barley cropping systems recorded the maximum weed infestation, while the minimum was noted in sorghumbarley cropping system. the densities and biomasses of weeds like common goosefoot, bitter dock, fat hen, field bindweed, yellow trefoil, yellow sweet clover, salt marsh, corn spury and bermuda grass were higher in cotton-barley and mungbeanbarley cropping systems compared to the rest of the cropping systems. the densities and biomasses of all weeds except perennial sow thistle, bitter dock, fat hen, and yellow trefoil were suppressed in sorghum-barley cropping system. the bed-sown barley had lower weed flora which resulted in higher allometric traits of barley and ensured more grain yield; while more compacted soil layer and higher weed density under zero tillage yielded opposite results. the conventional tillage with cotton-barley system proved more economical compared to the rest of the combinations. therefore, sorghum can be rotated in barley-based cropping systems once in every three to four years for better weed control. keywords: cropping system, tillage, weed control, conservation mailto:mubashiragr@gmail.com 123 poster presentations: miscellaneous management of phytophthora spp. associated with citrus gummosis by using chemicals and nanoparticles h. ahmad, n. rajput*, m. atiq, s. sahi, g. kachelo, m. usman, a. nawaz, m. wahab department of plant pathology, university of agriculture, faisalabad, pakistan *e-mail: nasir.ahmed@uaf.edu.pk abstract citrus is the most valuable fruit industry in the world as well as in pakistan, due to its different nutritional aspects. but this fruit industry is facing huge losses due to various biotic and abiotic diseases. citrus gummosis caused by water loving fungus phytophthora species is also one of the major diseases of citrus around the globe. this study was conducted to evaluate five different chemicals (kasumin, evito, cabrio top, topsin m, kocide @ 100, 200 and 300 ppm concentrations) and three treatments of plant based nanoparticles (silver, copper and their combination @ 0.25, 0.5 and 1% concentrations) against phytophthora spp. under lab conditions through poisoned food technique. among fungicides, the least mycelial growth was observed by application of evito at 300 ppm concentration followed kasumin and kocide at same concentration, whereas among nanoparticles combination of silver and copper nanoparticles was found most effective against the mycelial growth followed by solo application of silver and copper at 1 % concentration respectively. keywords: silver, copper, evito, kasumin, kocide mailto:nasir.ahmed@uaf.edu.pk 124 regret to inform you: editor's tips to avoid journal rejection q. migheli1*, s. arthurs2 and m. wright3 1department of agricultural sciences and nrd – desertification research centre, university of sassari, viale italia 39, i-07100 sassari, italy 2biobee usa, 100 clemwood st., suite b salisbury, md 2184, usa 3department of plant and environmental protection sciences, university of hawaii at manoa, 3050 maile way, honolulu, hi 96822, usa * e-mail: qmigheli@uniss.it abstract it is estimated that over 50 percent of manuscripts submitted to peer reviewed scientific journals are rejected. the submission of subpar manuscripts reflects the growing importance of research assessment based on bibliometrics and the “publish or perish” paradigm. as a consequence, a great deal of scientific effort, public funding, and precious time are wasted both by the authors and during the review process. several common factors contribute to manuscript rejection. in most instances, the problems stem from poor writing and grammar or lack of clarity. this makes it difficult to understand the rationale for the paper, methods used, and conclusions reached. other major reasons for rejection include poor experimental design, and inadequate replication of treatments. a lack of focus and conciseness is a common theme, especially with less experienced authors. in many instances, submitting authors tend to pad the introduction and discussion with well-established but not directly relevant background information on biological control with which the readership should be familiar. lack of novelty is another major hindrance to publication: some authors submit “variations on a theme” by reporting substantially similar experiments to prior published research. an increasing proportion of manuscripts are rejected due to unethical behavior of the authors, such as plagiarism or double submission. finally, let us point out that a rigorous peer review process is the only way to distinguish a respectable journal amidst the increasing panoply of debatable, if not fraudulent, editorial initiatives we are experiencing. for the sake of young researchers’ scientific growth, we have an obligation to guide our students and early-career scholars away from predatory pay-to-publish journals. publishing in respected journals with high reviewing and editorial standards will help the scientific community retain their scientific trustworthiness. keywords: peer review, editorial, scientific journals, ethical publishing, rejection 125 poster presentations: plant pathology efficacy of pre-harvest application of epiphytic yeast meyerozyma guilliermondii squcc-33y and tamarindus indica leaf extract on alternaria alternatainduced postharvest fruit rot of tomato s. al-maawalia department of plant sciences, college of agricutural and marine sciences, sultan qaboos university e-mail: samia.sa@live.com abstract alternaria fruit rot caused by alternaria alternata is one of the major constraints in tomato (solanum lycopersicum mill) production in oman. due to increasing public concern about the harmful effects of chemical fungicides, the use of natural products or naturally existing beneficial microorganisms has been preferred for the management of fruit diseases. the inhibitory effect of methanolic extracts of 10 medicinal plant of oman on growth of a. alternata and the effect of postharvest application of the most efficacious plant extract on suppression of a. alternata fruit rot of tomato were evaluated. tamarindus indica leaf extract was very effective against a. alternata and produced clear zone of inhibition in the disc diffusion assay. scanning electron microscopic examination revealed morphological abnormalities in a. alternata mycelium. postharvest treatment of tomato fruits with aqueous leaf extract (1%) of t. indica reduced the lesion size of fruit rot by 64.1% when challengeinoculated with a. alternata. ultra-performance liquid chromatography (uplc) profiling showed phenolic acids viz., ellagic acid (37.3%), vanillic acid (30.3%), ferulic acid (24.1%) and flavonoid, rutin hydrate (98.1%) as major components of t. indica extract. the effect of pre-harvest application of meyerozyma guilliermondii squcc-33y and t. indica leaf extract in controlling postharvest fruit rot was evaluated. greenhouse and field tests revealed that pre-harvest application of m. guilliermondii at weekly intervals starting from fruit set to harvest stage significantly reduced the development of postharvest fruit rot when challenged with a. alternata, whereas t. indica extract had no significant (p > 0.05) effect. m. guilliermondii significantly (p < 0.05) increased the total soluble solids of tomato fruits compared with control. this study suggests that m. guilliermondii may be exploited as a biocontrol agent in the field for the management of alternaria fruit rot of tomato keywords: leaf extract, fungus, tomato, biocontrol mailto:samia.sa@live.com 126 role of some safe compounds in controlling root rot and seedlings production of artichoke s. m. kamel1; f. a. mostafa1*, s.f. el-gobashy1and m. k. abd elhalem2 1plant pathology research institute, agricultural research center 12619, giza, egypt 2potato and vegetatively propagated vegetables dep. hort. res. inst., agric. res. center, giza, egypt. *e-mail: fatmamostafa27@yahoo.com abstract globe artichoke (cynara scolymus l.) is an important export vegetable crop. seedlings are one of the methods for planting artichoke but root rot hampers the production of healthy seedlings. artichoke can be affected by many diseases that reduce the number of seedling and quality, particularly root rot diseases caused by rhizoctonia solani and fusarium solani. the present work was conducted to study the efficacy of some ecofriendly compounds (e.g., essential oil, hydrogen peroxide, organic compounds and potassium sorbet) in controlling artichoke root rot diseases. the results indicated that using clove oil, hydrogen peroxide and fulvo copper to treat artichoke seedling led to increase inhibition percentages in vitro and efficacy percentages in greenhouse at root rot diseases. treating with clove oil and fulvo copper exhibited a significant increase in the activity of polyphenoloxidase, peroxidase and chitinase in artichoke seedling compared with a control. the highest plant length, plant weight, number of leaves per plant and spad meter were achieved by using clove oil, while using mint oil provided the highest length of roots and plants as well as the highest number of buds. keywords: artichoke, controlling, essential oil, root rot 127 efficiency of citrullus colocynthis as inhibitor of fungi associated with date fruits and its relation with climate change m. hussein plant pathology department, faculty of agriculture and natural resources, aswan university, aswan, egypt e-mail: mmon3m@gmail.com abstract this study sought to identify fungi related to date fruit mold. rhizopus stolonifer, aspergillus fumigatus, a. terreus, a. niger, a. flavus, alternaria alternata, cladosporium cladosporioides, and penicillium chrysogenum were found to be the most common species. twenty-two isolates of r. stolonifer, 17 of a. niger, 15 of a. flavus, 12 of a. fumigatus, 10 of a. terreus, 9 of a. alternata, 6 of c. cladosporioides, and 5 of p. chrysogenum were discovered in association with palm date fruits. it has also been investigated how the occurrence and spread of these fungcould relate to climate change and the changes of temperature and humidity. citrullus colocynthis utilization under different temperature and humidity results in a reduction in the prevalence of the pathogens. because dates are rich in nutrients and can support human nutrition and wellness, these associated fungal pathogens are a representation of the potentially dangerous associated microorganisms that seriously harm humans. as a result, there is an urgent need for biological methods to control these diseases of the edible fruits. keywords: biological control, fungus, efficacy, date palm mailto:mmon3m@gmail.com 128 pathogenicity of three entomopathogenic fungi to aphis fabae scopoli (hemiptera: aphididae) o. abdelaziz1,2*, m. senoussi2, m. benkahoul3, m. meziani1, a. birgücü4, i. karaca4, s. chibani1 1applied biochemistry laboratory, faculty of life science and nature, constantine 1 university, constantine algeria 2laboratory of biomolecules and plant breeding, life science and nature department, faculty of exact science and life science and nature, university of larbi ben mhidi oum el bouaghi, algeria. 3laboratory of biology and environment, faculty of life science and nature, constantine 1 university, constantine, algeria 4faculty of agriculture, department of plant protection, isparta university of applied sciences, 32260 isparta, turkey *e-mail: abdelaziz.wided@umc.edu.dz abstract aphids (hemiptera: aphididae) are one of the most significant threats to agriculture and forests. aphis fabae scopoli (hemiptera: aphididae), known as the black bean aphid, is one of the most important species causing yield losses in several cultivated crops. e.g., beans, tomatoes, potatoes, and tobacco, as well as numerous wild and ornamental plant species; its wide host range includes >200 host plant species throughout the world. the goal of the present study was to investigate the effect of three entomopathogenic fungi (epf) (beauveria bassiana, cladosporium cladosporioides, and verticillium alfalfae) on a. fabae. the selected epf were isolated from the agricultural soil of the national institute of plant protection (inpv) in constantine, algeria, and were tested against the aphid insects that were collected from the same area. a. fabae were exposed to each fungal spore suspensions (107conidia/ml) for 10 s. percent mortality was recorded at 1, 3, 5, and 7 days post treatment. percentage mortalities, 7 days post treatment, were, 98,15%, 97,62% , and 92.92% by v. alfalfae, b. bassiana and c. cladosporioides, respectively. the tested fungal isolatescan be effectively utilized as biocontrol agents against this aphid species. among them, v. alfalfae, was the most promising one, indicating the potentiality of this species as a new resource of biocontrol against a. fabae. keywords: aphis fabae, mortality rate, verticillium alfalfae, beauveria bassiana, cladosporium cladosporioides. 129 bioassay of sudanese and indian isolates of beauveria bassiana (balsamo) vuillemin to adult stage of musca domestica (diptera: muscidae) m. adam1, h. mohammed1, m. kambal2, m. elbashirali1,* 1department of zoology, faculty of science, university of khartoum 2department of bio pesticides and bio fertilizers, environment and natural resources and desertification research institute, p.o. box 6096, khartoum, sudan *e-mail: alifataloope@yahoo.com abstract the house fly, musca domestica (l), is a worldwide pest of agricultural and public health importance that has plagued humans throughout recorded history. the insect acts as a vector for many pathogenic diseases to both humans and animals. development of resistance to chemical insecticides is ongoing concern. beauveria bassiana (balsamo) vuillemin is one of the alternatives to chemical insecticides and a potent bioinsecticide. the present study was conducted to evaluate the pathogenicity and bioassay of four b. bassiana isolates, namely one indian isolate, itcc no 6628, and three local sudanese isolates. the adult of m. domestica were treated using topical application; one group was sprayed and the second group was treated by spores obtained from 15-days old petri plates cultured in pda. the four isolates of b. bassiana were found pathogenic to the adults of house flies. the lethal time to 50% mortality (lt50) values were recorded in hours. powder application registered results as follows: 131 hours for the isolate m, 110 hours for isolate e, 99 hours for isolate s and 108 hours for isolate itcc no 6628. when the spray method was tested, the lt50 were as follows s= 212, a= 172, e =156 and m=145 hours. the potential of all tested isolates against adult of house flies was proven, with best performance of the indigenous isolate coded m. however, further studies are required to determine lc50 and development of appropriate formulation. keywords: house fly, beauveria bassiana, mycoinsecticides, biopesticides. mailto:alifataloope@yahoo.com 130 identification of fusarium spp. associated with dry root diseases in omani lime m. al-jabri*, s. al-kaabi, m. al-sadrani and a. al-adawi ghadafan agriculture research station, department of agriculture research in north al-batinah governate, ministry of agriculture, fisheries and water resources, sultanate of oman *e-mail: nakaa@live.com abstract the disease incidence of omani lime decline was reported in a number of governorates in oman. disease symptoms of the affected lime trees include vascular discoloration of roots and crown and wilting of infected trees. the aim of this research is to identify the causal agent of this symptom. samples were collected from affected lime trees from madha in musandam governorate; shinas, liwa, suhar and rustaq in al batinah governorates; and salalah in dhofar governorate. plant samples with disease symptoms were cultured in a nutrient medium (potato dextrose agar, pda) to isolate pathogens associated with the disease symptoms. fusarium spp. were isolated from all samples collected after identifying through light microscopy. dna was isolated from culture of fusarium isolates and pcr amplification of translation elongation factor (tef) genes were performed and amplified gene regions were sequenced. blast search of sequenced fusarium sp. isolates in gene bank (ncbi) resulted in 99-100% similarity for isolates from lime with fusarium solani isolates in gene bank. pathogenicity test was carried out on healthy omani lime seedlings with isolates of f. solani to fulfill koch’s postulates. results of inoculation trial confirmed pathogenicity of f. solani in lime seedlings and symptoms of vascular discoloration and wilt of seedlings were observed in inoculated seedlings within six months. keywords: dry root rot; fusarium; lime; vascular discoloration mailto:nakaa@live.com 131 artificial microrna-mediated resistance against oman strain of tomato yellow leaf curl virus m. al-roshdi, u. ammara, j. khan, a. m. al-sadi and m. s. shahid† department of plant science, college of agricultural and marine sciences, sultan qaboos university, muscat, oman *e-mail: mshahid@squ.edu.om abstract tomato yellow leaf curl virus (tylcv) is a global spreading begomovirus exerting a major restraint on world tomato production. in this transgenic approach, an rna interference (rnai) based construct consisting of sequences of an artificial microrna (amirna), a group of small rna molecules necessary for plant cell development, signal transduction and stimulus to biotic and a biotic disease was engineered targeting ac1/rep gene of oman strain of tylcv-om. the rep-amirna constructs presentan effective approach in regulating the expression of rep gene against tylcv as a silencing target to create transgenic tomato plant tolerance against tylcv infection. molecular diagnosis by pcr followed by a southern hybridization analysis was achieved to confirm the effectiveness of agrobacterium-mediated transformation in t0/t1 transformed plants. a substantial decrease in virus replication was observed when t1 transgenic tomato plants were challenged with tylcv-om infectious construct. although natural resistance options against tylcv infection are not accessible, the outcomes of this study advised that transformed plants expressing amirna could be an essential approach for engineering tolerant plants against tylcv infection and conceivably for the inhibition of viral disease against different strains of whitefly transmitted begomoviruses in oman. keywords: rna interference, agrobacterium-infiltration; artificial microrna; gene silencing; southern blotting. mailto:mshahid@squ.edu.om 132 citrus tristeza virus: occurrence in tunisia orchards and the use of tolerant rootstocks as a mean of control a. najar1*, i. hamdi1, h. snoussi2, h. askri3 and a. jemmali1 1plant protection laboratory, national institute of agronomic research of tunisia, carthage university, tunis 1004, tunisia; 2horticultural laboratory, national institute of agronomic research of tunisia, carthage university, tunis 1004, tunisia; 3laboratory of non-conventional water valorization, national institute for agricultural engineering, water and forestry, carthage university, tunis 1004, tunisia *e-mail: asmanajara@yahoo.fr abstract citrus is one of the most important horticultural crops in tunisia. citrus varieties are traditionally grown on sour orange (citrus aurantium), a rootstock with high degree of susceptibility to citrus tristeza virus (ctv). the presence of this quarantine virus has been reported for the first time by najar et al (2021). recent surveys, serological and molecular analysis of collected samples from the cap bon region (main citrus area) revealed that virus spreading reached drastic levels. in addition, 7870 samples tested by direct tissue-blot immunoassay (dtbia), showed that 17% of the tested trees are infected with ctv. this result was confirmed by rt-pcr using total rna and the universal primer pair pin1/pin2. open reading frame sequences (~409 bp) were obtained from rt-pcr products of seven isolates selected (genbank accession number mw447905-mw447911) using specific primers t30k17+(5’gttgtcgcctaagttcggca-3’) and t30k17-(5’tatgacatcaaaaatagctgaa-3’; hilf et al., 2005). sequence analysis showed high identity across all ctv isolates from tunisia (98%-99%) and with mild ctv strain n4 from china (mk779711; 98%-100%) and variants kc517490 (96%-100%) and kc517489 (97-99%) from the usa. taking into account the imminent risk of introducing and dissemination of this quarantine virus, we introduced some tolerant rootstocks since 2005 to select those adapted to tunisian conditions. as a result of this experimental trial, four rootstocks: citrus volkameriana, swingle citrumelo, carrizo citrange and c-35 gave the best agronomic performances with tunisian sweet orange “maltaise demi-sanguine”. these rootstocks grafted with different citrus varieties have been planted since 2017 in different farms belonging to various climate regions. preliminary data revealed the general superiority of citrus volkameriana in growth and yield in different sites with all varieties. on other hand, c-35 performed better or equivalent to the control (sour orange). keywords: citrus, ctv, dtbia, rt-pcr, rootstock, agronomic performance mailto:asmanajara@yahoo.fr 133 biological, serological and molecular characterization of algerian pvy isolates l. allala-messaoudi1*, l. glais2,3, m. kerkoud4, s. boukhris-bouhachem5 and z. bouznad1 1département de botanique, laboratoire de virologie végétale, école nationale supérieure agronomique, hassan badi16200, el-harrach, alger, algérie 2fn3pt/rd3pt, 43-45 rue de naples, 75008 paris, france 3igepp, agrocampus ouest, inra, université de rennes 1, 35650 le rheu, france 4diag-gen, 8 rue le notre, 79066 angers, france 5inrat, laboratoire de protection des végétaux, rue hedi karray, ariana, 2049 tunis, tunisia *e-mail: linmess4@gmail.com abstract the high incidence of pvy in all the regions studied and its remarkable symptomatological variability, led to the study of the diversity of pvy populations circulating in potatoes and given the emergence of new strains in the world, especially in tunisia and neighboring countries. from a panel of 185 samples, serologically confirmed as being only infected with pvy, of which 96.7% belong to the serotype-n, and only 3.2% to serotype-o. a series of 31 pvy isolates were analyzed by biotyping on tobacco and by molecular typing (rt-pcr, sequencing), targeting nucleotide sequence polymorphism in the 5'ntr / p1 region and recombination within the junction of three hc-pro / p3 (rj2), vpg / nia (rj3) and cp (rj4). 28/31 serotype-n pvy isolates inducing rib necrosis on tobacco were identified as recombinant pvyntn isolated for the first time in algeria. the other three strains were serotype pvy-o, two of which were identified as pvyn-wi inducing rib necrosis on tobacco. this result is of high interest because, to our knowledge, this is the first report of isolated pvyn-wi in north africa. keywords: pvyntn, pvyn-wi, solanaceae, diversity, recombination mailto:linmess4@gmail.com 134 first report of four viruses in the genus potyviruses and carlavirus infecting omani garlic crop a. al-shaqsi, a. al-ghaithi, m. al-nasri, i. al-raeesi, q. al-mawali, a. al-naabi, m. al-rabani, a. al-maharbi, y. al-hadrami directorate general of agricultural and livestock, ministry of agriculture rumais, oman *e-mail: alghaithia1985@gmail.com abstract omani garlic is considered an important crop due to its economic and nutritional value. viral infections of garlic were reported worldwide associated with garlic crop loss. despite its importance, little attention was given to investigate viral infection on omani garlic. this study was conducted to detect the viruses associated with garlic plants. viral-like symptoms such as yellowing of garlic tips on leaves followed by complete yellowing, mottling or striping were observed on different garlic plants. in symptomatic garlic plants, four viruses were detected, namely onion yellow dwarf virus (oydv) and leek yellow stripe virus (lysv), which belong to the genus potyviruses, and two other garlic common latent virus (gclv) and garlic latent virus (glv), belonging to the genus carlavirus. in addition, the study aimed to map the distribution of the viruses between different governorates. the survey was conducted between 2011 until 2020 and covered six governorates. more than 150 samples were collected from each governorate and screened by serological methods (double antibody sandwich enzyme linked immunosorbent assay (das-elisa) using specific antisera to each virus. the survey highlighted the presence of three viruses: oydv, gclv and glv in al bahatina north, al buraimi and al dahera. four viruses were detected in al dhakhilia governorate. none of the samples from dofar governorate was positive. this study reported for the first time the presence of four viruses on omani garlic. further studies will be done to investigate the potential role of management strategies in order preventing losses in garlic production. keywords: oydv, gclv and glv garlic virus, eliza, antibody mailto:alghaithia1985@gmail.com 135 the ribosomal intergenic spacer (igs) in the potato and tobacco cyst nematodes, globodera pallida, g. rostochiensis and g. tabacum m. madania; l warda; a. vierstraeteb; s. de boera and m. moensc acanadian food inspection agency, 93 mount edward road, charlottetown laboratory, charlottetown, pe, canada. bbiology department, gent university, k.l. ledeganckstraat, 35 9000. gent belgium. cresearch institute for agriculture, fisheries and food (ilvo), 9280 merelbeke, belgium and department of plants and crops, ghent university, coupure links 653, ghent belgium. *e-mail: madani.mehrdad@gmail.com abstract the potato cyst nematodes globodera pallida and g. rostochiensis (pcn), and tobacco cyst nematode (tcn), g. tabacum, are the most widespread parasitic nematodes of potato and tobacco worldwide. ribosomal dna provides useful molecular data for diagnostics, the study of polymorphisms and for evolutionary research in eukaryotic organisms including nematodes. here we present data on the structure and organization of a rarely studied part of the intergenic spacer (igs) region of the pcn and tcn genomes of cyst nematodes. this region has shown potential for diagnostic purposes and population studies in other organisms including nematodes. in nematodes, the ribosomal rna gene cluster comprises three genes: 5.8s, 18s and 28s rrna, which are separated by spacer regions: the intergenic spacer (igs), nontranscribed spacer (nts), externally transcribed spacer (est) and the internally transcribed spacer (its). the intergenic spacer (igs) region consists of an external transcribed spacer (ets) and a non-transcribed spacer (nts) which is located between the 28s of one repeat and the 18s gene of the next repeat within the rrna genes cluster. in this study, the first flanking portion of the igs was amplified, cloned and sequenced from pcn and tcn. primers were then designed to amplify the whole igs sequence. pcr amplification of igs from g. tabacum, g. pallida, and g. rostochiensis yielded respectively: a single amplicon of 3 kb, three amplicons sized 2.5, 2.6 and 2.9 kb, and two amplicons sized 2.8 and 2.9 kb. globodera spp. has more than one variant copy of the igs, with both long and short repetitive dna elements. an approximately 400 bp long region without any internal repetitive elements, was identified in a position between the two repetitive regions. this suggests that there is a 5s gene in the igs of these species. keywords: cyst nematodes, potato, igs, pcr, 5s gene, 28s gene. mailto:madani.mehrdad@gmail.com 136 top ten plant parasitic nematodes of economic importance in arid and semi arid area, threatening green house and field crops m. madani formerly a researcher at the canadian food inspection agency, charlottetown, pe; and university of manitoba, winnipeg, mbcanada. *e-mail: madani.mehrdad@gmail.com abstract more than 4000 species of plant parasitic nematodes (ppn’s) have been described worldwide. nematodes are responsible for crop losses of 8.8 to 14.6 % equal to $ 100 to 157 billion usd annually, demonstrating their potential threat to food security. this is a quick review of the most important parasitic nematodes: soybean cyst nematode heterodera glycines, a major pathogen of soybean (glycine max), causing $1 billion in damages annually in american agriculture. stem nematodes, including ditylenchus spp., especially in fababean (vicia faba) and pea (pisum sativum), of which 4 m tons of production are produced in canada, is an aggressive species with the economic threshold level in europe being 0.8 eggs/g of soil, and complete crop failure at 64 eggs/g of soil. root-knot nematodes (meloidogyne spp), a cosmopolitan species with a wide host range in almost all crops and capability for producing complex disease and synergism with other pathogens. root lesion nematode (pratylenchus spp), is a serious pathogen in field crops as well as ornamental and fruit trees. this results in yield loss of 58% at 2 specimens/cm3 of soil. cereal cyst nematode (ccn), heterodera trifolii and h. avenae, a pathogen of cereals and grain that can be spread from seeds. crop losses of $4 million in europe and $70 million in australia have been reported by this species. potato cyst nematodes globodera pallida and g. rostocheinsis, with the damage threshold of 1 to 2 eggs/g of soil. with the fact that prairie ranks as one of the main potato producers with about 60,000 acres, special attention has to be given to this nematode. stubby root nematode thrichodorus spp, and spiral nematodes helicotylenchus spp are the most common nematodes in corn (zea mays) fields. keywords: soybean, pulse crops, nematodes, control management, arid, semi-arid. mailto:madani.mehrdad@gmail.com 137 screening for resistance and genetic population structure analysis associated with wheat to heterodera filipjevi – isfahan pathotype n. abbasi*1, m. nasr-esfahani2 m. mossavi1 1plant protection department, islamic azad university, marvdasht branch, marvdasht, iran 2plant protection research department, esfahan agriculture and natural resource research and education center, esfahan, areeo, iran. *e-mail: nili.abs.13.63@gmail.com abstract bread wheat (triticum aestivum l.) is a major staple food for the world’s population. the cereal cyst nematode (heterodera filipjevi) is a soil-dwelling phytoparasitic nematode worldwide, which has a wider distribution than the other species globally. in this research, the reaction of a collection of wheat genotypes including promising lines to the h. filipjevi were assayed at the field conditions. we also analyzed the genetic variability of the wheat cultivars using seven simple sequence repeat (ssr) primer pairs. the reproduction factor including the number of females and cysts per plant, the number of eggs and second-stage juveniles (j2), were recorded to estimate the reduction and or increase in populations. there was a highly significant effect among the tested genotypes in terms of cyst, eggs and second juvenile numbers, and reproduction factors. the highest number of cysts were in genotypes pishtaz with 291.33, followed by pishgham with 272.67, whereas the lowest numbers were in m90-7 with 108.67 cysts. in terms of eggs and second juveniles, the highest numbers of 7 were in the genotypes ark; and the lowest one 1.97 in parssy variety. the reproduction factors revealed that the highest amount (104.52%) was found on the ark variety, whereas the lowest one (29.45%) was found on parssy. five out of seven used ssr primers produced 20 polymorphic bands, of which the number of alleles in each gene locus varied within 3-7 bands. the polymorphism information content (pic) value also ranged from 0.44 to 0.81, with the mean of 0.65, shannon information index (i) between 0.29 and 0.63 with an average of 0.47 per locus, and nei's gene diversity (h) value varied from 0.16 to 0.44 with an average of 0.32. the average number of effective alleles was 1.52, ranging between 1.21 and 1.8. the gene locus xgwm 140 showed the highest diversity in the population genetic structure. keywords: genotypes, wheat, ssr, pic, primers, markers. mailto:nili.abs.13.63@gmail.com 138 surveillance of huanglongbing disease (hlb) associated with citrus in north al-batinah governorates m. al sadrani*, m. al jabri, s. al kaabi, r. al maqbali and a. al adawi ghadafan agriculture research station, department of agriculture research in north al-batinah governate, ministry of agriculture, fisheries and water resources, sultanate of oman *e-mail: m.alsadrani2015@gmail.com abstract historically omani acid lime (ol) has been considered as one of the most important economic crop as their fruits were exported to different countries. witches’ broom disease reported since 1970s on ol caused losses on more than 250,000 trees. therefore, local production covers only 38% of local market. huanglongbing (hlb) is one of the most serious diseases reported worldwide: this is a bacterial disease, the causal agent being related to candidatus liberibacter genus. this study was conducted to evaluate healthy status of mother citrus trees in citrus gene bank in a research station located in the northern al-batinah governorates, as well in acid lime farms. during this study, 188 citrus samples were collected from citrus gene bank and 57 samples collected from ol farms in willayats; liwa, suhar, shinas and ibri; and from aljabal alakhdar province. dna were extracted by ctab method. the a2&j5 primer pair was used to amplify β-operon region, while the oi1/oi2c primer pair allowed to amplify 16s-rdna gene regions by pcr. amplified dna was sequenced and restriction enzyme were used. results of hlb tests showed that 10 positive samples were collected from citrus gene bank and 17 infections from other locations. furthermore, analysis results reveal concordance of results obtained using either dna sequencing or cutting amplified gene region through xbal enzyme as both methods identified infected with candidatus liberibacter asiaticus. this is the first report of hlb disease in the tahiti lime, sour and pineapple orange in oman. the report also describes for the first time the occurrence of the disease in a’dhahirah region. keywords: hlb; yellow dragon disease; polymerase chain reaction mailto:m.alsadrani2015@gmail.com 139 the effect of potassium chloride on the germination of rice (oryza sativa l.) seeds a. ali1 and a. ali2* 1catholic central high school, 450 dundas street, london, on, n6b 3k3, canada 2earth sciences research centre, sultan qaboos university, muscat, oman. al-khod 123, oman *e-mail: arshadali@squ.edu.om abstract rice (oryza sativa l.) germinates in a moist environment with an optimal temperature range of 15℃ to 30℃. rapid germination is often achieved when the seed coat, which can inhibit the permeability of gases and water, is removed. therefore, due to a limited amount of time to carry out this experiment, brown rice, which has its seed coat (hull) removed, was used. the method of germination was adapted from the wet papertowel procedure. changes to the procedure were applied to obtain data specific to this experiment. a clear pattern can be observed when analyzing the trend between concentration of kcl and the percentage rate of germination. the trendline has a negative slope—therefore, it corresponds to a negative correlation between the two variables tested. it can be concluded that as the concentration of potassium chloride (mol dm-3) increases, the rate of germination of rice (%) decreases. the experimental data suggested that as the concentration of kcl exceeds 0.001 mol dm-3, the rate of the successful germination of rice decreased significantly. furthermore, the seeds were able to germinate efficiently in a solution concentration of 0.001 mol dm-3, which was closest to the control (only water). therefore, it can be concluded that the “delayed” rate of germination due to increasing kcl concentration was likely caused by chemical toxicity. this could have been due to an excessive amount of cl-, which causes salinity stress to seeds. similarly, excess k+ hampers the overall growth of a plant. keywords: seed soaking, germination, soaking, chemical toxicity mailto:arshadali@squ.edu.om 140 using bioengineering approaches to express halophyte genes to improve salt tolerance in tobacco m. al-bloushi ministry of municipality and environment, doha, qatar e-mail: heartymoonf@yahoo.com abstract salinity is a major concern for the agricultural production sector, which limits agriculture sector. tobacco (nicotiana tabacum) is widely grown as commercial crop, it is sensitive to moderate resistance to salt stress. producing salt-resistant tobacco plants, agrobacterium tumefaciens-mediatedtransformation was used to overexpress genes from the halophytes, (spbadh), (mchkt1), (ssnhx1) and (ahbadh). transgenic lines were evaluated for expression and salt tolerance. this study shows transgenic tobacco over expressing ahbadh6 and spbadh5 were more salt-tolerant at germination and seedling than wild-type tobacco.transgenic survived at 200 mm nacl, wild-type died after a week of treatment. overexpression ahbadh6 and spbadh5 transgenic lines accumulated more chlorophyll and proline as single gene transformants used enhanced osmoregulatory capability, which decreased the toxic impact of na+. salt tolerance was assessed in halophytes at 0, 100, 200, and 300 mm nacl. halophyte plants treated with nacl for 4 weeks to evaluate survival. the plant growth and survival at nacl concentrations of 0 to 300 mm salt had similar effects on all four species, with no detrimental effects on development. salt had a substantial effect on all parameters. when compared tountransformed tobacco, transgenic plants carrying salt-tolerant transgenes behaved considerably differently to salt stress. notably, salt stress had a substantial impact on biomass, plant shoot, and plant root, proline and chlorophyll levels in untreated plants, when compared to wild-type. compared to the other lines, ahbadh6 and spbadh5 demonstrated a high degree of salt tolerance throughout the germination and seedling stages. as a result, these two lines might be employed to increase the development of plants grown in saline conditions. in conclusion, halophyte salt tolerance genes have promising potential for improving salt tolerance incrops. keywords: bioengineering, biotechnology, tobacco abiotic stresses mailto:heartymoonf@yahoo.com 141 new technology and integrative approaches for identification of plant pathogens m. madani formerly a researcher at the canadian food inspection agency, charlottetown, pe; and university of manitoba, winnipeg, mb-canada *e-mail: madani.mehrdad@gmail.com abstract dna-based technology has proven useful for identifying and diagnosing plant pathogens, including species and subspecies of nematodes that cause plant diseases. traditionally and in many cases, agarose gel electrophoresis is a method of choice for separation of dna bands. however, it is a challenging step especially when dealing with the limited amount of starting materials used for loading the gel. this is especially true when comparing amplified bands smaller than 50 bp. the newly introduced capillary gel electrophoresis (cge) with the capability of running only 12 μl of pcr (polymerase chain reaction) product can separate amplicons with a few bp difference in length. the second approach is performing melting curve analysis as an additional step at the end of the real-time pcr cycles. similar to cge, the generated results are visualized on the computer monitor, which eliminates the time-consuming process of agarose gel preparation and staining. the third technique is loop-mediated isothermal amplification (lamp) which is a pcr-free based amplification of the target dna of the pathogen. cocktail reaction prepared in an eppendorf tube, which, after incubation at a certain temperature, will allow us to interpret the results based on color changes. the third approach is integrative analysis, by compiling data derived from microscopy and host preference together with phylogenetic and dna analysis of more than one molecular marker. this approach will enable us to determine the species identity and accurate diagnosis of the target pathogen, especially those closely related to it, thereby planning an effective control management strategy. keywords: molecular diagnostic, nematodes, pcr, electrophoresis mailto:madani.mehrdad@gmail.com 142 innovative process of using a metallophyte, brassica sp., for the determination of atmospheric pollution in an urban area a. sedki1,2,*, h. sebban1, n. lekouch1, a. pineau2 1department of biology, fssm-ucamarrakech, morocco (trace elements for unesco-institute-morocco) 2trace elements for unesco-institutefrance *e-mail: sedki@uca.ac.ma abstracts studies relating to the field of air and the metrology of atmospheric pollutants have been evolved in synergy. although the physico-chemical measurement of contaminants was efficient and precise, it was often difficult to translate the observed values into the form of potential risks for living organisms and human health. due to this reason, the monitoring of atmospheric pollution has been supplemented for several decades by the use of bioindicator organisms similar to metallophytes. in the urban atmosphere, metallic trace elements are released in the form of small particles of different sizes in solid and/or liquid state and can negatively affect ecosystems and human health. in order to monitor the air quality and metal trace element levels in the city of marrakech, two bioindicators otala lactea (snail) and brassica sp. (plant) were used. two essential elements (zn and cu) and two toxic elements (pb and cd) were dosed in the tissues of snails and plants exposed for 4 weeks in 5 stations to different sources of pollution (road, industrial, residential, etc.). the determination of these elements was carried out by icp-ms after mineralization by acid digestion. the assay results showed that snails and plants accumulated more trace elements in areas with high traffic and industrial activity. snails accumulated more cd (0.39 μg/g and 4.48 μg/g), zn (144.32 μg/g and 216.72 μg/g) and cu (84.09 μg/g and 156.07 μg/g) from the atmosphere, and plants accumulated more pb (0.84 μg/g 9.48 μg/g). otala lactea are micro-concentrators of pb and macro-concentrators of cd from the air and can thus be used as bioindicators of atmospheric pollution. in addition, plants of the brassicaceae family, to which brassica sp. belongs, are confirmed bioindicators of air pollution. keywords: metallic trace elements, biomonitoring, bioindicators, atmosphere mailto:sedki@uca.ac.ma 143 poster presentations: entomology new record of aphanogmus clavicornis thomson (hymenoptera: ceraphronidae) as a larval parasitoid of tomato leafminer (tuta absoluta meyrick) in syria r.youssef1*, n. abo kaf2, a. al tawaha3 1plant protection department, faculty of agriculture, tishreen university, latakia, syria 2 plant protection department, faculty of agriculture, tishreen university, latakia, syria 3department of biological sciences, al hussein bin talal university, ma'an, jordan *e-mail: rawa.m.youssef@tishreen.edu.sy abstract tomato (solanum lycopersicum l.) is an important edible and nutritious fruit regarded by nutritionists as a vegetable. it is an important source of vitamins and significantly contributes to economic development. however, the production of tomatoes is heavily affected by climate change, insect pests, disease and the new devastating pest of tomatoes, the tomato leaf miner, tuta absoluta (meyrick) (lepidoptera: gelechiidae). this study included a description of aphanogmus clavicornis thomson, 1858 (hymenoptera: ceraphronoidea), a primary parasitoid of t. absoluta whose larvae feed on all parts of the tomato plant. it is the first record of t. absoluta as a host of genus aphanogmus worldwide and a first record of a. clavicornis in both syria and the middle east. description, biology and the taxonomic characters of the new species were provided. the new record of natural parasitism of t. absoluta by a. clavicornis would add knowledge on biological control of the pest and could become an additional option for the integrated pest management of those crops where t. absoluta is a key pest. it would be interesting to investigate if a. clavicornis can be produced in large scale under laboratory conditions and test its potential use as a biological control agent within integrated pest management programs. keywords: tomato; aphanogmus clavicornis; tuta absoluta; first record; syria mailto:rawa.m.youssef@tishreen.edu.sy https://www.gbif.org/species/159973547 144 iranian tea (camellia sinensis) seed powder: as potential pesticide/fertilizer products to improve plant growth e. kahneh*, s. ramzi tea research center, horticultural science research institute, areeo, lahijan, iran *e-mail: e.kahneh@areeo.ac.ir abstract every year, large amounts of seeds are produced in iran's tea gardens, which currently have no use. seed powder is the residue of tea seeds after oiling, which is in the form of a cake or powder. it is 60-70% organic matter and more than 15% protein and contains 12-18% saponin. by turning it into organic fertilizer and other plant products, it is possible to help the gardener's economy and better management of the tea garden. preliminary research has shown the positive and stimulating effects of tea seed products on some plants. research has shown that consumption of these products, in addition to increasing plant yield, has fungicidal effects and increases plant resistance to other plant pathogens. this powder has no residual harmful effects and is economical and easy to obtain. it is also used on farms as an organic insecticide and does not harm the growth of plants and their roots. compared to other poisons, it is safer, more efficient, and more convenient. it also can regulate the concentration of heavy metals, improve plant root growth, control and eliminate pests and diseases, and increase resistance to diseases. considering that a lot of seeds are produced in tea gardens every year, which have already been used to produce tea seedlings. however, with the development of seedling production by cuttings and the introduction of improved cultivars, these seeds are currently of no use. if it is possible to find an application for them, it will help the gardener's economy, and develop and manage the tea garden better. keywords: pesticides, camellia sinensis, plant growth mailto:e.kahneh@areeo.ac.ir 145 anti-insects potentialities of the algerian saharian plant euphorbia guyoniana (euphorbiaceae) againt tribolium castaneum (coleoptera: tenebrionideae) f. acheuk and m. belaid laboratoire valcore, département de biologie, faculté des sciences, université de boumerdes, boumerdes, 35000, algeria. *e-mail: f.acheuk@univ-boumerdes.dz abstract superior plants are a diverse source of potent bioactive agents, some of which have significantly contributed to the successful use of natural products in insect’s pest management. in order to evaluate the bio-insecticidal potential of an algerian desert plant: euphorbia guyoniana, a study was conducted on tribolium castaneum: red flour tribolium. a crude ethanolic extract was prepared and then tested in the laboratory during the adult stage. five different doses were tested. the results of the phytochemical study showed that the plant is rich mainly in flavonoids, gallic tannins, alkaloids, saponosides and glucosides. the plant does not present anthocyanins, leuco-anthocyanins, catechins, coumarins and iridoids. for the insecticidal activity, the repulsive of the extract at a dose of 700 μg/is low, it is 33.33 ± 23.09%. according to the percentages ranking of mcdonald et al. (1970), the extract of this plant is classified in the 2nd class. the extract of this plant proved toxic against the adults of this insect, and the total mortality (100%) was reached 48 h after treatment with the highest dose (700 μg/insect). the ld50 obtained at the shortest time (6 hours after treatment) is 169.82 μg/insect. the extract of this plant did not inhibit the ache activity on the tested adults. the results suggest that this plant does not have a neurotoxic effect on the triboilum. the encouraging results obtained with the extract of this plant suggest the possibility of the use of metabolites of this plant for the formulation of botanical bio-pesticides. keywords: euphorbia guyoniana, tribolium castaneum, toxicity, crude extract. mailto:f.acheuk@univ-boumerdes.dz 146 new report of bacillus thuringiensis var. tenebrionis infected apricot stem borer larvae sphenoptera ahia-ahmedi cobos in northern of iraq j. mohammed1, a. abbas1 , a. al-kaisse1, a. allallah2 1plant protection directorate, ministry of agriculture, baghdad, iraq 2ministry of education, baghdad, iraq abstract in this study, morphological, physiological, biochemical and molecular characteristics were used to diagnose a bacterium isolated from the larvae of the apricot stem borer. the results obtained that all morphological, physiological, biochemical characteristics were typical for the b. thuringiensis cry (crystal protein formation) which is toxic to the insect order coleoptera. the confirm the diagnosis, polymerase chain reaction (pcr) technique carried out using specific primers for the crystal formation strain. the results showed a fragment with the expected size of 461 bp corresponding to the cry3 gene. keywords: bacillus thuringiensis, apricot, bacterium, pcr 147 the presence of tobacco whitefly (bemisia tabaci gennadius), and onion thrips (thrips tabaci lindquist) on different cucumber plant cultivars in the field conditions q. ahmed and s. fliah department of plant protection, college of agricultural engineering sciences, university of baghdad, al-jadriya campus, baghdad, iraq *e-mail: qasim.h@coagri.uobaghdad.edu.iq abstract the study was conducted to determine the susceptibility of different cucumber cultivars (jumbo green, ghazeer, nefer and sahem) to sucking insect pests; onion thrips thrips tabaci lind, and tobacco whitefly bemisia tabaci genn., during the 2018 summer season in the experimental fields of college of agriculture, university of baghdad, iraq. the results showed that the infestation of cucumber cultivars with sucking pest’s onion thrips t. tabaci and tobacco whitefly b. tabaci occurred on all cultivars during the entire month of july. the nefer and sahem cultivars were more susceptible to high infestation by the adult of whitefly where the average were 5.21 and 5.05 adults per leaf, respectively, compared with the cultivars of ghazeer and jumbo green where the average were 4.06 and 4.02 adults per leaf, respectively. at the same time, the nymph average of whitefly was 55.80 and 55.20 nymphs per leaf on ghazeer and jumbo green, respectively, followed by sahem and nefer cultivars, which were 47.80 and 38.10, respectively. the average of thrips nymphs were recorded on all cultivars, which were 4.52, 3.57, 3.06 and 2.96 nymphs per leaf on sahem, nefer, ghazeer and jumbo green, respectively. during july and early august, the green lacewing, parasitoids, and coccinellids were found to be linked with whitefly and thrips pests on all cultivars. in the field trail, no significant differences between oxamthrine and biotrin pesticides compared to eucalyptus extract treatment to control whiteflies and thrips. keywords: whitefly, thrips, mortality, onion, cucumber mailto:qasim.h@coagri.uobaghdad.edu.iq 148 yield losses and economic impact of pseudococcus viburni (hemiptera: pseudococcidae) on iranian tea (camellia sinensis): a case study s. ramzi*, e. kahneh tea research center, horticultural science research institute, areeo, lahijan, iran *e-mail: s.ramzi@areeo.ac.ir abstract the tea mealy bug, pseudococcus viburni signoret (hemiptera: pseudococcidae) causes significant reduction of crop yield and it is considered as one of the most important tea pests in northern iran. in recent years, the population of p. viburni increased because of favorable weather conditions, established on tea buds, lateral leaves and other vegetative parts and imposed damages in the form of yellowing of leaves and weakness. the growth of bushes stopped and estensive leave fall occurred. because of economic importance of tea in gilan and mazan daran provinces, it is necessary to reduce the damages in a safe way. therefore, a plot of garden with an area of five hectares was selected in korfistan village of rudsar city to investigate the effect of tea mealybug damage on the yield of green tea leav es. in 2021, the intensity of infection was about 45%. the yield of green leaves decreased from 43,818 kg to 24,382 kg by 44.36% losses when no control measure was taken. once the control operation using summer oil was done after the first round harvest, the yield of green leaves in the second harvest increased from 29212 kg to 36573 kg, equivalent to 25.2%. the total yield of green leaves decreased from 73030 kg to 60955 kg in two subsequent years, respectively. failure to comply with garden management or delay in control operations caused a 16.5 percent decrease in green leaf yield in 2021 compared to 2020. among the control methods, the use of safe methods is of great importance in the production of healthy tea, because the direct use of tea leaves by humans as a daily drink. keywords: pseudococcus viburni, tea green leave, summer oil, damage mailto:s.ramzi@areeo.ac.ir 149 status of present and expected future spread of agricultural pests and their management in relation to climate changes a. ali1 and m. arif2 1department of plant protection, collage of agriculture, al-anbar university, alanbar, iraq 2plant protection directorate, ministry of agriculture, abu-ghraib, baghdad, iraq *e-mail: abdulsattararif@yahoo.com abstract climate change is correlated with impacts on biodiversity and the productivity of agricultural crops and spread of pests. well-documented examples include the red palm weevil rhychophorus ferrugineus which is widely spreading in most date palm growing countries. the spread of some pests such as, the mexican black scale, saissetia miranda was recorded for the first time on fig trees in iraq. the green pit scale insect, palmapsis phoenicis causes serious damage to palm trees and production in sudan and lebia. the unusually warm winter may assist the establishment of invasive pests, such as the fall armyworm spodoptera frugiperda which feeds on wide range of crops, and tephritid fruit flies. the desert locust are expected to change their migratory routes and geographical distribution. the bacterial disease on olive caused by xylella fastidiosa have become endemic. the bayoud disease caused by the fungus (fusarium oxysporum f. sp. albedinis is a limiting factor for palm cultivation in north africa. the increase of rainfall will lead to an increase in the spread of fungal diseases such as the palm flower rot caused by the fungus mauginiella scaettae. drought and shortages in freshwater along with increase in salinity and desertification resulted in big decline in suitable areas for cultivation. these factors present serious challenges that require urgent worldwide cooperative action. successful results of integrated management were well documented in different arab countries. however more efforts are still needed to deal with the ongoing and rising challenges. keywords: agriculture pests, climatic changes, ipm, rpw. file:///c:/users/thahertech/downloads/abdulsattararif@yahoo.com 150 grasshoppers and locusts species as agricultural pests in constantine region, eastern algeria n. benkenana*, c. derrouiche¹; a. abed ¹, i. guerfi laboratoiry of biosystématic and ecology of arthropods, university frères mentouri, constantine 1, route aïn-el-bey, 25000, constantine, algeria. *e-mail: benkenanan@yahoo.co.nz abstract the constantine region is located in the semi-arid bioclimatic stage. different crops are grown in this region mainly; cereals (wheat, barley and oats), vegetables (tomato, potato and bean), and fruit trees (apple, pepper and peach). the locust and grasshoppers fauna in this region totals the presence of 43 species. they are divided into five families and eleven sub-families. the species ocneridia volximii, praephippigera pachygaster, dociostaurus marocanus, aiolopus thalassinus thalassinus, calliptamus barbarus barbarus and gryllus sp are species harmful to cereals. anacridium egyptium is reported as important pests of fruit trees. thalpomena algeriana and praephippigera pachygaster species are observed on several vegetables. they can reach the status of potential pests in the region of constantine if the climatic conditions favor their development. keywords: locusts, grasshoppers, constantine, cereals, vegetables, pests https://www.bing.com/ck/a?!&&p=762f47000b978bcajmltdhm9mty1otexntmzmizpz3vpzd0ynwfmowe2zs0wztexltrmm2qtywrmmy00zge0mziyytnknjymaw5zawq9nte3nq&ptn=3&hsh=3&fclid=fb7ca12f-0f62-11ed-a2cd-efd2fa2038d4&u=a1ahr0chm6ly9saw5rlnnwcmluz2vylmnvbs9yzwzlcmvuy2v3b3jrzw50cnkvmtaumtawny85nzgtms00mdiwltyzntktnl8xmty3&ntb=1 https://www.bing.com/ck/a?!&&p=762f47000b978bcajmltdhm9mty1otexntmzmizpz3vpzd0ynwfmowe2zs0wztexltrmm2qtywrmmy00zge0mziyytnknjymaw5zawq9nte3nq&ptn=3&hsh=3&fclid=fb7ca12f-0f62-11ed-a2cd-efd2fa2038d4&u=a1ahr0chm6ly9saw5rlnnwcmluz2vylmnvbs9yzwzlcmvuy2v3b3jrzw50cnkvmtaumtawny85nzgtms00mdiwltyzntktnl8xmty3&ntb=1 file:///c:/users/thahertech/downloads/benkenanan@yahoo.co.nz 151 assessment of effective pesticides against tephritid fruit flies (diptera: tephritidae) and their increasing invasion potential of in temperate regions of pakistan n. nazir university of poonch rawalakot azad jammu and kashmir, pakistan *e-mail: nailanazir9@gmail.com abstract fruit flies (diptera: tephritidae) are insect pest with great potential of invasion to new host plants in diverse climatic conditions. this pest is invasive in temperate region of azad jammu & kashmir (aj&k) pakistan transported via fruits and vegetables of punjab and khyber pakhtunkhawa (kpk) markets. during the current study diversity and distribution of fruit flies along with altitudinal gradient, phylogenetic analysis, their host range and efficacy of various pesticides for its control has been assessed. a total of eleven species of fruit flies bactrocera diversa, b. scutellaris, b. tau, b. cucurbitae, b. dorsalis, b. nigrofemoralis, b.zonata, b. correcta, dacus ciliatus, d. longicornis and d. sphaeroidalis under two genera bactrocera and dacus of family tephritidae were recorded, among which bactrocera diversa and dcaus ciliatus were new records to this area. species host range, richness evenness and abundance trend was recorded along with altitudinal gradient of selected localities. the susceptibilities of b. diversa to different insecticides were evaluated using micro-drop method and mortality was checked after 3, 6, 8 and 24h of exposure. overall results showed that cypermethrin is most effective to kill 50% of both larval and adult stage. this study is a baseline for the implementation of future control strategies. keywords: tephritid fruit flies (diptera: tephritidae), pesticies mailto:nailanazir9@gmail.com 152 comparing the effects of different types of pesticides on plant growth l. el-baesy department of plant sciences, collage of agricultural and marine sciences, sultan qaboos university, al-khoudh-123, oman *e-mail: s135456@student.squ.edu.om abstract pesticides are chemicals that help protect plants from any external damage caused by insects or parasitic weeds. the research aims to compare different effects of pesticides on plant protection. a quantitative research methodology is used in this research. an experiment was conducted using different types of pesticide that have been tested separately for a given time period. afterwards, data from each experiment was recorded. it has been shown that each type of pesticide serves a distinct purpose. the results obtained prove that the usage of pesticides has a positive effect on plant growth, which prevents parasites and pests from invading the plant. pesticides can promote healthy plant growth and many other positive outcomes. despite this, it has an impact on the surrounding environment and has the potential to contaminate the soil. recommendations are made for future research to improve plant protection from external damage via the use of organic pesticides. keywords: pesticides, quantitative, weeds, crop system mailto:s135456@student.squ.edu.om 153 management of damping-off disease of chili caused by pythium aphanidermatum using synthetic chemicals n. rajput1*, m. atiq1, s. sahi1, a. hameed2, m. usman1, a. nawaz1, g. kachelo1 and h. ahmed1 1department of plant pathology, university of agriculture, faisalabad pakistan 2institute of plant protection, muhammad nawaz sharif university, multan pakistan *e-mail: nasir.ahmed@uaf.edu.pk abstract chili (capsicum annum l.) is very valuable crop all over the world as well as pakistan. it is commonly cultivated in subtropics and temperate regions. damping off disease in chili caused by pythium aphanidermatum is responsible for a potentially serious threat towards seedling mortality in both nurseries and field crop. the present study was designed to determine the pathogen of damping-off of chili and its management through chemicals in vitro. for this purpose, the pathogen was isolated from samples shown typical symptoms of damping-off on pda media, purified and identified on the basis of morphological characteristics. to fulfill the koch’s postulate pathogenicity test was conducted. for the management of damping-off disease of chili an experiment was designed where six fungicides were used i.e contaf plus, flint max, score, ellectus super, fossil, topsin m with three different concentrations (100, 150 and 200 ppm). to check their efficiency against isolated pathogen by using poisoned food technique. result showed that all the chemicals has excellent inhibition effect on growth of p. aphanidermatum at different levels, where ellectus super expressed the best results to inhibit fungal growth (4.11mm) at 200 ppm concentration followed by flint max (5.11mm) and score (6.66 mm). keywords: contaf plus, flint max, score, ellectus super, fossil, topsin m mailto:nasir.ahmed@uaf.edu.pk 154 integrated pest and disease management tomato blight management with organic soil biochar amendment k. zohaib1*, w. anwar1, a. akhter1, h. khan2, m. ul haq1 and m. haider1 1department of plant pathology, university of the punjab, lahore, pakistan 2department of entomology, university of the punjab, lahore, pakistan *e-mail: karamat174@gmail.com abstract sustainable agriculture deals with the efficient use of resources for the benefit of human and its environment. by this way we can fulfill the requirement of food, feed and fiber efficiently. application of heavy doses of chemicals like fertilizers or pesticides are not suitable for sustainable agriculture. biochar usage represents an alternative way to control diseases and to enhance plant growth. this study focuses on the effective use of different concentrations of biochar and composts to promote the growth of plant biomass and nutrients availability like n, p and k in the presence and absence of alternaria solani. two types of biochars (wood biochar and green waste bochar in 3% and 6%, concentrations) and compost were used as a soil amendment. all different biochar concentrations significantly influenced plant biomass and disease reduction. among the 6% wood biochar amended soil treatment was found more effective in above and below ground plant biomass development. under stress condition nitrogen and phosphorus contents were increased in tomato. it was observed that nitrogen content increased by 12.44% and phosphorus content increased by 55.17%. disease incidence was 90% in tomato plants when they were grown in soil and it was reduced to 40% when they were grown in 6% green waste biochar amended soil. moreover, it was observed that disease severity was reduced to 47% in 6% wood biochar amended soil. in conclusion, biochar has positive impact in reduction of early blight in tomato by reducing the incidence of disease and enhancing the plant growth parameters. keywords: alternaria solani, biocontrol, carbon sequestration, organic waste mailto:karamat174@gmail.com 155 the effects of some beauveria bassiana isolates and their secondary metabolites on the tea mealy bug, pseudococcus viburni sigornet (hemiptera: pseudococcidae) s. ramzi*, a. seraji and e. kahneh tea research center, horticultural science research institute, areeo, lahijan, iran *e-mail: s.ramzi@areeo.ac.ir abstract the effects of beauveria bassiana isolates collected from rice fields of amol (am-118) and orchards of tehran (bb3) were investigated on the tea mealybug, pseudococcus viburni. in the study, both conidial exposure and biochemical experiments were adopted to fully understand pathogenicity. the lc50 concentrations of bb3 and am118 isolates were determined 2×103 and 18×105 spore/ml against third nymphal instars while the lt50 values were recorded 3.66 and 6.63 days, respectively. the higher activity of endochitinase in am-118 was recorded in comparison of the higher activity of exochitinase in bb3. moreover, the higher activities of fungal proteases namely pr1 and pr2 were recorded in am-118 and bb3, respectively. the secondary metabolite extracted from am-118 showed the lc10, lc30 and lc50 values of 0.716, 1.578 and 2.727% while those for bb3 were recorded as 0.333, 0.873 and 1.704%, respectively. the lc30 concentration of each isolate led to significant increase duration of egg incubation, nymphal stages and survival of adults. secondary metabolite of bb3 decreased the activity of alt after 24 and 48 hrs, ast after 24 h while it increases ggt activity. similar results were observed in case of acidand alkaline phosphatases as well as ldh. secondary metabolites increased the activity of esterase using anaphthyl and b-naphthyl acetate and gst using cdnb and dcnb after both time intervals. finally, a formulation of wettable powder of bb3 was prepared with the persistence of 7 days. the formulation caused nymphal mortality 3 days after exposure. keywords: native isolate, beauveria bassiana, pseudococcus viburni, virulence mailto:s.ramzi@areeo.ac.ir 156 use of a potential probiotic strain as a fermentation starter for the tunisian olive variety ‘meski’ n. chammem, a. oueslati, h. atrous, l. ayed, a. mejri, m. hamdi university of carthage, laboratory of ecology and microbial technology, national institute of applied sciences and technology (insat), tunisia *e-mail: nadia.chammem@insat.ucar.tn abstract more than fifty lactic acid bacteria strains were isolated from the brine and the flesh of tunisian olive varieties submitted to different processes. the isolates were tested for their morphological, physiological and probiotic properties. a potential probiotic strain was then selected to be inoculated as a starter culture during a fermentation process. the olive variety meski was treated according to the spanish style. two trials were attempted: a spontaneous fermentation and a controlled one, and the brines were about 10% (w/v) nacl. during the days of the fermentation processes conducted, brines and olive samples were analyzed for physicochemical and microbiological parameters. polyphenols content and antioxidant activities were determined for olives for each trial and in different stages of the process. the population dynamics showed that lactic (acid?) bacteria dominated in the inoculated fermentation reaching 108 ufc/ml on the day 12, coliforms disappeared by the 19th day. total phenolic content in the olives and the antioxidant activity was higher in the controlled fermentation than in the spontaneous one. use of selected starters in olive fermentation processes could be a solution for local food producers to provide not only safe artisanal foods but also products of high quality. keywords: table olives, process, lactic acid bacteria, starter, antioxidant activities. mailto:nadia.chammem@insat.ucar.tn 157 poster presentations: biological control semiochemical-based strategies as a promising tool for conservation biological control agents m. arif plant protection directorate, ministry of agriculture, iraq *e-mail: mokhtar.a.arif@gmail.com abstract biological control is an important component of integrated pest management (ipm) that is based on the use of natural enemies, such as predators, parasitoids, and pathogens, to reduce or mitigate the pest populations. in this context, the knowledge of the chemical ecology of natural enemies, herbivores, and host plants is important in the development of an effective ipm program. moreover, due to the expansion of agricultural fields, landscapes, and habitats, implementing conservation biological control may be necessary to enhance the ecological services provided by natural enemies. the manipulation of the behavior of predators and parasitoids through the use of stimuli that increase their presence in the fields can lead to an improvement in their performance to achieve conservation biological control. recently, the development of semio-chemical based tools has increased greatly, as they are considered effective for manipulating insect behavior with the objective of enhancing the biological control against herbivores. therefore, the use of semiochemicals that attract the parasitoid and predators in the proximity of the source can enhance the biological control level to protect the crop. keywords: kairomone, pheromones, ipm, parasitoids, predators mailto:mokhtar.a.arif@gmail.com 158 investigation on the effect of cmc film including thyme essence in packaging for increasing shelf life and postharvest quality of cherry fruit m. hosseinifarahi1,2*, m. radi2,3, h. zafarzadeh3 and f. bagheri3 1department of horticultural science, yasuj branch, islamic azad university, yasuj, iran 2sustainable agriculture and food security research group, yasuj branch, islamic azad university, yasuj, iran 3department of food science, yasuj branch, islamic azad university, yasuj, iran *e-mail: mehdi.hosseinifarahi@iau.ac.ir abstract the aim of this study was to investigate the effect of essence treatments of thymus l. and carboxymethyl cellulose coating to increase the shelf life and improvement in the quality and organoleptic properties of postharvest cherries (prunus avium l.). the study was laid out in a completely randomized design, with three replications. the effect of carboxymethyl cellulose coating (205 and 305 thickness) and essence treatments of thymus l. (2 and 4%) alone and in combination was investigated in weekly basis for 3 weeks. various factors such as the percentage of decay, total soluble solids (tss%), the reaction juice ph, vit c, anthocyanins, phenols, antioxidants, percentage weight loss and organoleptic properties of the fruit were measured. the results showed that the effect of essence treatments of thymus l. and carboxymethyl cellulose coating on tss%, percentage weight loss, fruit percentage of decay, vit c, anthocyanins, phenols and organoleptic properties fruit were significant at the 1% level. also, the results showed that the effect of storage duration on fruit percentage of decay, tss%, anthocyanins, phenols, antioxidants and organoleptic properties of the fruit were significant at the 1% level. means comparison showed that the carboxymethyl cellulose coating at (305) and essence treatments of thymus l. (4%) compared to the control increased the tss%, ph, organoleptic properties of the fruit and decreased the decay percentage. based on these results, application of carboxymethyl cellulose coating at (305) and essence treatments of thymus l. (4%) for shelf life improvement of cherries is recommended. keywords: carboxymethyl cellulose, cherries, decay, thymus l., shelf life. mehdi.hosseinifarahi@iau.ac.ir%20 159 nano-emulsified clove oil on fumigant toxicity and as pulse protectant against stored product pest, callosobruchus maculatus n. al-kenani1*, k. murugan2, r. rajaganesh2, m. vasanthakumaran2 1department of biological sciences, faculty of science, king abdul-aziz university, jeddah p.o. box 80203, jeddah 21589, saudi arabia. 2department of zoology, school of life sciences, bharathiar university, coimbatore641 016, tamil nadu, india *e-mail: nalkenani@kau.edu.sa abstract the cowpea weevil, callosobruchus maculatus fabr. (coleoptera: bruchidae), is a major pest of leguminous grains and other pulse grains in tropical and subtropical countries. prevention of food losses during postharvest storage without creating environmental problems is therefore of paramount economic importance. hence, alternative bioinsecticide management of stored product is needed for environmentally sound post-harvest storage. micro-and nanoemulsions have been intensively investigated due to the easiness of preparation, namely through high-pressure homogenization, microfluidization or ultrasound-assisted processes that can be scaled-up, allowing to potentiate their applicability in several fields. our findings demonstrated the applicability and efficacy of nanoemulsified essential oil clove, syzygium aromaticum l., in the management of c. maculatus. application at the rate of 20, 40, 60, 80 and 100 ppm of oil and its emulsified concentrations determined significantly lower infestation rates on cowpea (vigna unguiculata). a good fumigant toxicity and reduced population buildup of the beetle and could be achieved. the nano-emulsified concentrates considerably reduced oviposition, increased the adult mortality, presented a good fumigant toxicity and reduced population buildup of the beetle. keywords: callosobruchus maculatus, nanoemulsion, esstential oil, pulse protectant, fumigant toxicity nalkenani@kau.edu.sa 160 develop a low cost simple attractants food lure for fruit fly (bactrocera zonata saundres) s. musaed1*, m. jaddou2, s. al shamsi1 1research station section, abu dhabi agricultural and food safety authority, abu dhabi, united arab emirates 2integrated pest management consultants, jorden *e-mail: safa.musaed@adafsa.gov.ae abstract the fruit fly, bactrocera zonata (saundres) is a globally dangerous insect pest for most fruit trees. among the various alternative strategies for managing b. zonata, using methyl eugenol traps is the most outstanding alternative. the present study aimed to reach and evaluate a simple and low-cost attractant food lure using different combinations of food odor attractants mixed with para-pheromone methyl eugenol to attract b. zonata. different ratios from food-based synthetic attractants, named as protein hydrolysate, torula yeast, bread yeast, apple vinegar, ammonium acetate, ammonium sulfate, sodium tetraborate, were mixed with different ratios of the parapheromone methyl eugenol 99%. eleven treatments were chosen to be evaluated under field conditions represents three orchards for three weeks, each orchard was considered as a replicate. the combination of methyl eugenol (1 ml) + apple vinegar (15 ml) + torula yeast (3.6 g) + water (235 ml) + sodium tetraborate (5 g) were significantly the highest attractive combinations compared with the other treatment (1897.3 flies/ trap). furthermore, there were addition four promising combinations of food odour attractants, which had no significant differences in flies captured (1596.3, 1130.5, 1440, and 1388.7 fruit flies/ trap), respectively. these findings have opened a new avenue in increasing the efficiency of traps by choosing the most attractive foodbased lure formula, which can be adopted by farmers for mass trapping as a main component in the integrated pest management program. keywords: bactrocera zonata, methyl eugenol, para-pheromone, attractants, fruit fly safa.musaed@adafsa.gov.ae%20 161 effect of aqueous extract of hanzal (citrullus coloynthis (l.)) senemeka (senna alexandrina mill) and ummjelajel (aristolochia bracteolate l.) on the leaf miners (liriomyza spp.) on the snake melon crop m. younis, f. salah* and a. eisa university of gezira, sudan *e-mail: faizaruba2@gmail.com abstract due to ecological imbalance and hazards caused by insecticides use, plant products or plant extracts were suitable alternative to pesticides. this study was conducted to evaluate the effect of water extracts of hanzal (citrullus coloynthis (l.)), ummjelajel (aristolochia bracteolate l.) and sennameka (senna alexandrina mill) on vegetable leaf miners (liriomyza spp.) infesting snake melon. randomize complete block design (rcbd) with 4 treatments and 4 replications were used. snake melon plots were sprayed weekly with water extracts of hanzal, sennameka and ummjelajel at 10% concentration (w/v) and control was sprayed by water with molasses and gum arabic. the infestation percentage on leaves and mean number of active mines were counted twice weekly. the aqueous extracts of hanzal, sannemeka and ummjelajel reduced the infestation and number of active mines significantly compared to control. no significant differences between hanzal, sannameka and ummjelajel. hanzal had lower mean percentage leaf infestation followed by sannameka and ummjelajel (season one). hanzal recorded lower number of active mines in season two followed by sannemeka. also hanzal recorded the least number of active mines than sannameka, season two. this study uggesttd recommended to use hanzal at 10% w/v for control of leaf miner species on snake melon crop. keywords: aqueous extract, citrullus coloynthis, senemeka, ummjelajel, snake melon. mailto:faizaruba2@gmail.com 162 poster presentations: micsellanous section compost produced from the leachate of the landfill and alkaline lime sludge for soil amendment and plant protection k. fares1*, m. mobaligh1, z. madani2 1pnae laboratory, faculty of sciences, marrakech, morocco 2cluster valbiom, morocco e-mail: fares@uca.ac.ma abstract in addition to its role as an organic amendment, compost can play a role in plant protection. due to the high water content and the landfill option in several arab countries without upstream sorting, household waste generates large quantities of leachate that pose problems. the transformation of this leachate into compost using alkaline lime sludge and the green constitutes a new solution. two barrels were filled with 100 l of leachate: the lime sludge was added to barrel 2 while barrel 1 was the control. after 24 hours, the green waste was added to the 2 barrels. after homogenization, the contents of the two barrels were dumped to form 2 windrows which were followed for 90 days. the contact time of 24 h allowed reducing the load of faecal streptococci, by 85.7% and the bad odors disappear within the first 3 days. the temperature had shown an increase from the first week: 58.5 °c for the windrow with sludge and 56.6 °c for the control; humidity was kept around 50-60% by regular watering. the degradation of organic matter is better in the presence of lime sludge (31%). despite the alkaline nature of the lime sludge, the ph of the final compost remains acceptable for many plants. within particular 38% ds of organic matter, the final quality of the compost complies with nfu44-051; no toxicity was observed; the final compost could therefore be used as an organic amendment for palm grove as well as for the rehabilitation of degraded sites in arabic countries. keywords: leachate, green waste, lime sludge, compost, palm groves. fares@uca.ac.ma research paper journal of agricultural and marine sciences vol. 21 (1): 33 – 46 doi: http://dx.doi.org/10.24200/jams.vol21iss0pp33-46 received 17 sept 2015 accepted 15 feb 2016 spatio-temporal dynamics of land use changes in response to external pressures in oman: greenhouse cropping as an example michael l. deadman1*, abdullah m. al-sadi1, malik m. al-wardi2, khalifa s.m. al-kiyumi3, w.m. deadman4, and fahad a. al said1 *1 michael deadman ( ) sultan qaboos university, college of agricultural and marine sciences, department of crop sciences . box 34, al-khod 123. sultanate of oman. email: mikedead@squ.edu.om. 2squ, cams, department of soils, water and agricultural engineering. 3 ministry of agriculture and fisheries wealth, p o box 467, muscat 113, sultanate of oman. 4department of archaeology, durham university, south road, durham, dh1 3le, uk introduction under the theoretical umbrella of land use/land cover change research, much attention has naturally focused on agro-forestry dynamics, including deforestation (asner et al., 2005; nepstad et al., 1999), agricultural expansion (maeda et al., 2010) or intensification (lambin et al., 2000; armsworth et al., 2006), desertification (pando-moreno et al., 2004), urbanization of productive agricultural land (seto et al., 2000; seto et al., 2002; seto et al., 2010) and the causes and consequences of farm abandonment (mottet et al., 2006; diaz et al., 2011). as a science and subject for debate on global sustainability issues, land use/land cover studies seek to motivate greater observation and monitoring of land changes. it also promotes understanding of changes as a coupled human–environment system, development of spatially explicit models of land change and integrated assessments of system outcomes, such as vulnerability, resilience, or sustainability (turner et al., 2007). across the arabian peninsula little attention has been paid to the driving forces and consequences of land use/land cover change. this is remarkable given the dramatic economic and societal changes that have taken place in these “high-income less developed” (odedokun, 1996) countries in relatively short periods of time; countries where rates of population growth are globally amongst the highest. the mean rate of population increase for the gulf cooperation council (gcc) countries, plus yemen, is variously estimated at 2.2 or 2.3% الديناميكية الزمانية واملكانية للتغريات يف استخدامات األراضي نتيجة الضغوط اخلارجية: زراعة البيوت احملمية كمثال مايكل ديدمان1* وعبداهلل السعدي1 ومالك الوردي2 وخليفة الكيومي3 ووليام ديدمان4 وفهد آل سعيد1 abstract. further from the northern coast of oman new farm developments were more frequent than closer to the coast; they were also larger. the density of farms was highest close to muscat although the distance enclosing 50% of farms had shifted away from muscat during the study period. the dominance of muscat is likely to be related to access to markets and infrastructure development. the increase in groundwater salinity was also highest close to muscat and may be responsible for the shift in greenhouse density. salinization of groundwater is severe close to the coast and was responsible for the reduced density of greenhouses near the coast. land abandonment was highest close to muscat and to the coast, reflecting changes in groundwater salinity and urbanization pressure. less evidence was available for a direct shift from farmland to urban land use. recent urban developments were largely located in areas already abandoned by agriculture. the paper also discusses likely future trends in land use change given that oman’s population is increasing at over 2% annually and demand for urban land is increasing. the identification of a “salinity corridor” within which much of the future land use change may occur is discussed. keywords: land cover; greenhouse protected cropping; agricultural intensification; groundwater salinity; urbanization; transport infrastructure. املســتخلص: تناقــش هــذه الورقــة التغــر احلاصــل يف توزيــع املــزارع يف حمافظــي مشــال وجنــوب الباطنــة، وبينــت الدراســة بــأن إنشــاء املــزارع اجلديــدة بعيــدا عــن الســاحل هــو األكثــر شــيوعا حاليــا ومتتــاز هــذه املــزارع أيضــا مبســاحات زراعيــة أكــر، وبالرغــم مــن أن املــزارع بــدأت بالتحــول بعيــدا عــن مســقط أوضحــت الدراســة بــأن أكثــر املــزارع مــا زالــت ترتكــز قريبــا منهــا وذلــك بســبب ســهولة الوصــول لألســواق والبــى التحتيــة. وقــد تكــون الزيــادة الشــديدة يف ملوحــة امليــاه اجلوفيــة هــي الســبب يف التغــر يف كثافــة البيــوت احملميــة بعيــدا مــن مســقط والســاحل. وأدت هــذه الزيــادة الشــديدة يف ملوحــة امليــاه اجلوفيــة والضغــط العمــراين إىل هجــر األراضــي الزراعيــة والتخلــي عنهــا واســتخدامها كمناطــق تطــور عمــراين وحضــري جديــدة. وتناقــش هــذه الورقــة أيضــا االجتاهــات املســتقبلية يف التغــر يف اســتخدام األراضــي خاصــة يف ظــل تزايــد الطلــب علــى املناطــق العمرانيــة بســبب الزيــادة الســكانية والــي تقــدر باثنــن يف املئــة ســنويا وحتديــد ممــر امللوحــة الــذي قــد حتــدث فيــه كل هــذه التغــرات يف اســتخدام األراضــي. الكلمات املفتاحية: الغطاء األرضي، الزراعة احملمية، التكثيف الزراعي، ملوحة املياه اجلوفية، التحضر، البنية التحتية للنقل 34 squ journal of agricultural and marine sciences, 2016, volume 21, issue 1 dynamics of land use changes in response to external pressures in oman: greenhouse cropping annually (cia, 2010; un, 2007). omar et al. (1998) have described a scenario in kuwait where irrigated desert lands, with minimal rainfall and loss of natural vegetation to crop production activities, are prone to soil erosion, sand encroachment and increasing both soil and groundwater salinity. this pattern of change is reflected, at least in some of its manifestations, across the region. salinization of irrigated land is an issue especially where coastal aquifers are depleted by agriculture and other activities at a rate that is substantially faster than rain-mediated recharge. seawater intrusion into the aquifer due to excessive pumping is a direct and well documented consequence not just in the middle east (kacimov et al., 2009) but also elsewhere where river water levels have fallen (kotera et al., 2008). salinization might therefore be considered as a potentially major driver behind land use change. as an increasingly important sector of land-based agriculture, greenhouse cropping has expanded rapidly since 2000. the technology was introduced into oman in the late 1980s to help relieve some of the constraints facing the agricultural sector, in particular the hot climate and shortage of water (maf, 1994). given the rapidly changing dynamics of greenhouse utilization, the sector might be considered as a proxy for intensive agriculture and thus serve as a tool for studying the vectors of land-use change, at least within the al batinah region where most greenhouses are located. significant changes in the total number of greenhouses have been brought about because many farmers have realized the importance of this technology for their financial benefit. furthermore, the ministry of agriculture and fisheries (maf) has encouraged land use change by offering monetary incentives in the form of subsidies for greenhouse construction, resulting in a boom in development conceptually similar to that observed elsewhere (macleod and moller, 2006; see also lambin et al., 2001) and perhaps best expressed as agricultural intervention towards productivism as defined by wilson and rigg (2003). although in new zealand subsidies seemingly caused intensification (macleod and moller, 2006), in oman there is a potential disjoin between so-called intensification represented by greenhouse construction and the destination of extensive agriculturalists displaced by greenhouse crop producers. the al batinah governorates represent the most agriculturally active region of oman; it is subdivided into administrative districts (wilaya, sing. = wilayat, fig. 1a) each having their own local markets, but with the western-most of these closer to dubai in the united arab emirates than to muscat. the marketing of farm produce from these western wilaya is likely to be influenced by dubai as much as by muscat (zekri, 2010). across most of the region the majority of greenhouse crop production is marketed locally or at al mawaleh central market in muscat municipality, close to the high-density population of the capital area (zekri, 2010). al mawaleh is a significant marketing outlet for all fruit and vegetables produced across oman, handling in excess of 10,000 t of fruit and vegetables monthly and integrating with other, smaller markets in muscat and elsewhere (omezzine et al., 2002). al mawaleh central market, specifically, and the urban spread of muscat in general, might therefore be expected to emerge as one of the major driving forces behind major land use change at the rural/peri-urban interface close to the capital area. al batinah is very much a transition zone where change is unlikely to be simple and unidirectional, but complex and in all probability influenced by a multiplicity of regional as well as local factors (amanor and pabi, 2007). the urbanization of agricultural land, especially around the periphery of the capital area is exerting pressures on current land use distribution. oman’s population is increasing at approximately 2% annually (cia, 2010; un, 2007) greatly increasing the demand for housing. oman is committed to diversifying the economy away from hydrocarbon related exports (fasano and iqbal, 2003) and as non-hydrocarbon revenues have grown (imf, 2008), the recent years have seen increases in both the large and small to medium sized industrial enterprises, further increasing demand for building land beyond the common boundary shared by muscat and wilayat barka. such rapid urbanization might therefore be identified as a major driving force behind land use change in al-batinah. salinity is a threat to the permanence of irrigated agriculture in arid and semi-arid regions of the world whether rainfall induced (asseng et al., 2010) or brought about by seawater intrusion into local aquifers (ghassemi et al., 1997). the latter inductor is dominant in oman and in similar regions of the world. the over abstraction of groundwater for irrigation purposes has resulted in high water salinity in many parts of oman, especially in the coastal zone of al-batinah, due to sea water intrusion. the water resources master plan (mwr, 2000) reported that the total deficit in fresh water for some parts of al-batinah amounted to 92.8 mm3 and sea water intrusion accounted for 45.8 mm3 of water recharged into the aquifers. al-barwani and helmi (2006) studied water salinity changes and rainfall in south al-batinah region from 1989 to 2005 and reported that salinity intrusion and groundwater salinity has increased despite the high rainfall events between 1995 and 1997. they have also reported that the area covered by high water salinity (>16 ds·m-1) has increased from 17% in 2000 to 32% in 2005 in barka, while it has increased from 29% to 38% in as-suwayq. the fresh water zone (< 2 ds·m-1) in both areas has decreased to 0 km2 in 2005. given that most greenhouse growers in oman use soil-based cultivation techniques (icarda, 2002) and that irrigation water with an electrical conductivity (ecw) value greater than 1.5 ds·m-1 (equivalent to 1.5 mmhos·cm-1) is considered poor quality for most greenhouse crops. salinization clearly has the potential to be a third major driving force 35research article deadman, al-sadi, al-wardi, al-kiyumi, deadman, al said for land use change. under investigation is the proposal that externalities have influenced greenhouse expansion projects. specifically, a series of testable hypotheses are established to determine the extent, if any, of attraction or repulsion effects from (1) proximity to local markets and population centers, (2) irrigation water salinity and proximity to the coast (and thus higher groundwater salinities) (3) urban expansion and (4) transport infrastructure (barka district only). future agricultural zone planning for land use change depends on current knowledge of the spatial distribution of new greenhouse developments and an intuitive understanding of the sustainability of high densities of greenhouses in certain areas. to achieve this it is necessary at an early stage, to observe and monitor land change to gain an understanding of these changes as a coupled human–environment system, prior to the development of spatially explicit models of land change (turner et al., 2007). as amanor and pabi (2007) have pointed out, land use change is unlikely to be represented by a simple or linear evolution but is more probably represented by complex interactions between human and environmental influences, including spatial and temporal oscillations between extensive and intensive agriculture. in the current study only those districts through which the current coastal highway passes were included. this coastal highway links muscat with shinas, leads onward to dubai and abu dhabi in the uae and locally spawns numerous off-shoots, especially in those wilaya closest to muscat. the coastal highway represents an infrastructure interface and therefore its impact on local land use change could be significant (lambin et al., 2000). these wilaya also have rapidly changing groundtable 1. number and area of active farms and numbers of greenhouses (2001 2009), newly active farms (2004 2009) and farms abandoned (2004 2009) in each wilayat (figures in brackets represent percent of total). 2001 2002 2003 2004 2009 new abandoned farm number barka 30 (-49.2) 52 (-57.1) 54 (-54) 69 (-56.1) 105 (-49.5) 51 (-41.8) 18 (57. 8) al musanaah 5 (-8.2) 8 (-8.8) 9 (-9) 9 (-13) 23 (-10.8) 17 (-13.9) 1 (8. 9) as suwayq 5 (-8.2) 5 (-5.5) 7 (-7) 9 (-13) 33 (-15.6) 25 (-20.5) 0 (0) al khaburah 7 (-11.5) 7 (-7.7) 8 (-8) 12 (-9.8) 15 (-7.1) 7 (-5.7) 5 (-11.1) saham 6 (-9.8) 9 (-9.9) 9 (-9) 10 (-8.1) 18 (-8.5) 9 (-7.4) 1 (-4.4) sohar 4 (-6.6) 5 (-5.5) 5 (-5) 5 (-4.1) 10 (-4.7) 6 (-4.9) 1 (-2.2) liwa 1 (-1.6) 1 (-1.1) 1 (-1) 3 (-2.4) 3 (-1.4) 2 (-1.6) 2 (-4.4) shinas 3 (-4.9) 4 (-4.4) 6 (-6) 5 (-4.1) 5 (-2.4) 5 (-4.1) 5 (-11.1) total 61 91 100 123 212 122 45 greenhouse number barka 133 (-43.8) 340 (-58.2) 362 (-57.7) 458 (-60.6) 825 (-51.5) 402 (-50.6) 182 (-56.9) al musanaah 22 (-7.2) 63 (-10.8) 64 (-10.2) 64 (-8.5) 130 (-8.1) 82 (-10.3) 82 (-25.6) as suwayq 16 (-5.3) 16 (-2.7) 19 (-3) 31 (-4.1) 292 (-18.2) 153 (-19.3) 0 (0) al khaburah 51 (-16.8) 49 (-8.4) 50 (-8) 56 (-7.4) 130 (-8.1) 29 (-3.6) 9 (-2.8) saham 38 (-12.5) 58 (-9.9) 59 (-9.4) 61 (-8.1) 111 (-6.9) 46 (-5.8) 6 (-1.9) sohar 30 (-9.9) 32 (-5.5) 27 (-4.3) 32 (-4.2) 75 (-4.7) 46 (-5.8) 4 (-1.3) liwa 2 (-0.7) 2 (-0.3) 2 (-0.3) 14 (-1.9) 7 (-0.4) 6 (-0.8) 1 (-0.3) shinas 12 (-3.9) 24 (-4.1) 42 (-6.7) 36 (-4.8) 31 (-1.9) 31 ((3. 9)) 36 (-11.3) total 304 584 627 756 1601 795 320 farm area barka 763.8 (-62.3) 860.3 (-61.2) 871.1 (-58) 1179.1 (-56.1) 1246.5 (-33.3) 533.5 (-24.2) 466 (-82.2) al musanaah 43.9 (-3.6) 77.7 (-5.5) 90.3 (-6) 90.3 (-4.3) 265.2 (-7.1) 205.7 (-9.3) 30.9 (-5.4) as suwayq 278.3 (-22.7) 278.3 (-19.8) 331.4 (-22.1) 393 (-18.7) 880.8 (-23.5) 487.8 (-22.1) 0 (0) al khaburah 46 (-3.8) 68.7 (-4.9) 68.7 (-4.6) 92 (-4.4) 138.8 (-3.7) 66.9 (-3) 20.1 (-3.5) saham 52.7 (-4.3) 72.5 (-5.2) 94.2 (-6.3) 107.3 (-5.1) 162.4 (-4.3) 70 (-3.2) 14.8 (-2.6) sohar 21.4 (-1.7) 21.4 (-1.5) 21.4 (-1.4) 203.3 (-9.7) 977.3 (-26.1) 777.5 (-35.2) 3.4 (-0.6) liwa 6.2 (-0.5) 6.2 (-0.4) 0 (0) 10.9 (-0.5) 21.5 (-0.6) 17.3 (-0.8) 6.7 (-1.2) shinas 13.4 (-1.1) 21.5 (-1.5) 25.2 (-1.7) 25.2 (-1.2) 49.9 (-1.3) 49.9 (-2.3) 25.2 (-4.4) total 1225.7 1406.5 1502.2 2101 3742.4 2209 567.1 36 squ journal of agricultural and marine sciences, 2016, volume 21, issue 1 dynamics of land use changes in response to external pressures in oman: greenhouse cropping water salinity (fig. 1b) as well as pressures of land use change through urbanization. they are also the districts within which over 95% of greenhouses in al batinah are located. materials and methods in 2001, 2002, 2003, 2004 and 2009, a gps unit was used to collect geospatial information about each farm with active greenhouses in each wilayat. for each farm the number of productive greenhouses was recorded. during each survey note was taken of new farms and of farms that had been abandoned since the previous survey. for a random selection of 100 farms in the 2009 survey, location and greenhouse number was verified against google earth® satellite imagery. all farm boundaries were fixed and farm sizes determined within google earth®. within the gis environment, wilaya boundary information was used to separate farms into the various administrative districts (fig. 1a) and al mawaleh central market was used as a fixed reference point for distance calculations. distances from the entrance of each farm to the nearest paved road were similarly estimated. a b figure 1. a. bluemarble next generation image of northern oman showing administrative districts (waliya) (altered after nasa world wind); inset shows study area within the arabian peninsula; b. kriged model of groundwater salinity (ds·m-1) for the 30 km wide al batinah coastal strip with the position of the existing main highway. table 2. logistic model estimates for distance (nearest km) to 50% of cumulative farm, greenhouse number and farm area from al-mawaleh central market. 2001 2002 2003 2004 2009 new farms abandoned farms % farms (r², p) 42 (.912, 0.001) 47 (.943, 0.001) 49 (.948, 0.001) 51 (.963, 0.001) 60 (.989, 0.001) 65 (.987, 0.001) 46 (.890, 0.01) % greenhouses (r², p) 48 (.884, 0.001) 53 (.968, 0.001) 55 (.971, 0.001) 54 (.968, 0.001) 57 (.985, 0.001) 56 (.980, 0.001) 38 (.760, 0.05) % farm area (r2, p) 42 (.927, 0.001) 44 (.945, 0.001) 47 (.946, 0.001) 54 .964, 0.001) 81 (.929, 0.001) 93 (.889, 0.01) 27 (.720, 0.05) 37research article deadman, al-sadi, al-wardi, al-kiyumi, deadman, al said proximity to local markets, population centres and the coast the sigmoidal cumulative percent farm number, farm area and cumulative percent greenhouse number at increasing distances from al mawaleh within muscat were calculated and modeled using a logistic function (equ. 1) to estimate numbers of farms and greenhouses within fixed distance intervals. y = k 1−be −rx( )( ) (1) where y is the estimated number of farms or greenhouses; k is the upper asymptote here fixed to 100%; b and r are constants of regression and x is distance from almawaleh market. proximity to and effects of groundwater salinity farm number, farm area and greenhouse number within 1 km-wide intervals from the coast were calculated in gis. because greenhouse numbers were skewed towards the coast, cumulative sigmoidal totals were fit to the gompertz function as an asymmetric sigmoidal model with a point of inflection at 100/e (equ. 2). y = k e −be −rx( )( )⎛ ⎝⎜ ⎞ ⎠⎟ (2) where y, k, b, r and x are as in equation 1. during the 2004 survey, irrigation water was collected from all farms with active greenhouses and water salinity (ecw) was measured. in 2005, ministry of regional municipalities and water resources’ data for 937 monitoring wells and boreholes was kriged within arcgis 9.3 3-d analyst, using the ordinary kriging method with a spherical model, to provide spatial information on estimated groundwater salinity (ds·m-1, fig. 1b). this enabled correlations to be made between kriged groundwater salinity for farm locations and salinity of collected irrigation water samples to determine likelihood values for the use of water resources by farmers alternate to groundwater supplies. the special case of wilayat barka given the proximity of wilayat barka to muscat and the disproportionately large number of greenhouses in that district, a detailed study was conducted to examine the interactions between farm and greenhouse location and changing salinity levels, urbanization and infrastructure development. cumulative farm and greenhouse number and farm area was related to distance from muscat (al mawaleh) and the northern coast and to kriged groundwater salinity. in addition, areas of individually identified parcels of urban land were estimated for 2005 using landsat etm+ imagery and 2009 using google earth® images to provide gis-based data. cumulative urban area was modeled using the logistic function (equ.  1). farm and greenhouse distribution relative to the network of paved roads was quantified by buffering roads to provide distances between farm entrance and the nearest paved road. finally, a network of 500m2 grids was used to cover the surface area of wilayat barka and urban and farmland land use cover was estimated from satellite imagery data for 2005 and 2009 (urban area) and 2004 and 2009 (farm area). results farm and greenhouse numbers and farm area during the study period the number of farms with greenhouses in al-batinah increased from 61 in 2001 to 212 in 2009 and the total number of greenhouses over the same period increased from 304 in 2001 to 1601 in 2009 (table 1). the mean number of greenhouses per farm was 4.98 in 2001, increasing to 7.53 in 2009. in 2001 almost 30% of farms (19/61) had only a single greenhouse; in 2009 the modal greenhouse number had increased to 4.0. in 2001 only 8 farms had more than 10 greenhouses (maximum = 25), in 2009 53 farms had more than 10 greenhouses (maximum = 54). furthermore, of the 9 farms with 30 or more greenhouses in 2009, more than half of these had commenced greenhouse crop production post 2001. between 2004 and 2009 32 farms ceased greenhouse crop production, removing 320 greenhouses from the productivity arena (table 1). the highest table 3. gompertz model estimates for distance (nearest 0.1 km) to 50% of cumulative farm, greenhouse number and farm area from the northern coast of oman. 2001 2002 2003 2004 2009 new farms abandoned farms % farms (r², p) 5.0 (.992, 0.001) 5.1 (.990, 0.001) 5.1 (.988, 0.001) 5.2 (.990, 0.001) 5.3 (.996, 0.001) 5.2 (.999, 0.001) 4.5 (.990, 0.001) % greenhouses (r², p) 5.0 (.990, 0.001) 5.1 (.991, 0.001) 5.1 (.992, 0.001) 5.2 (.990, 0.001) 5.6 (.990, 0.001) 5.8 (.982, 0.001) 4.3 (.982, 0.001) % farm area (r2, p) 4.7 (.984, 0.001) 4.8 (.984, 0.001) 4.8 (.985, 0.001) 4.9 (.985, 0.001) 4.5 (.992,0.001) 5.5 a (.998, 0.001) 4.1 (.982, 0.01) 5.3 a (.996, 0.001) 4.2 (.977, 0.01) a recalculation following exclusion of two farms (see text for details) 38 squ journal of agricultural and marine sciences, 2016, volume 21, issue 1 dynamics of land use changes in response to external pressures in oman: greenhouse cropping level of abandonment was in barka (57.8% of all abandonments), followed by al khaburah and shinas (11.1%) and then al musanaah (8.9%). the 2009 results showed that the majority (62%) of farms with greenhouses had land areas less than 10 ha (fig. 2); less than 3% of farms were larger than 50 ha. of particular relevance here is the overall decline in the preeminence of barka in terms of farm number, declining from a high of 57% of all farms in 2002 to less than 50% of farms in 2009 (table 1). this decline was reflected in the relatively low number (41.8%) of new-start farms in this district contained with a large proportion of total farm abandonments (57.8%). although over 50% of new greenhouses were located in barka, this represented less than 25% of new farm area, suggesting the development of relatively small farms with heavy emphasis on protected agriculture. eighteen farms (representing 57.8% of the total) were abandoned in barka, this represented 82.2% of the total agricultural land area lost between 2004 and 2009, representing relatively large farming areas. the situation for new farm developments in sohar shows an opposite trend to that for barka. in terms of land area, farms in sohar represented 26.1% of total area in 2009 and 35.2% of total land area brought into protected agriculture between 2004 and 2009. comparatively, the number of farms and greenhouses in sohar in 2004 and 2009 was low; a small number of large, but diversified, farms are now operating in this district. two further observations warrant comment. a high proportion of farm abandonments were in shinas (11.1% of total farm number and 11.3% of total greenhouse number), yet the contribution of these farms to total abandoned farm area was low (4.4%), suggesting the loss of small farms with high greenhouse to land area ratios. secondly, there was a significant increase in the prominence of as suwayq district. in 2002 as-suwayq accounted for 5.5% of farms and 2.7% of greenhouses; by 2009 the same district accounted for 15.6% of total farm number and 18.2% of total greenhouse number. new start farms in as suwayq represented 20.5% of total new farms and 19.3% of newly constructed greenhouses on these new farms and between 2004 and 2009 no farms were abandoned in as suwayq (table 1). 3.2. proximity to muscat based on the fitted logistic model, the estimated distance from muscat (al mawaleh market) to 50% (half distance) of cumulative number of farms, number of greenhouses and total land area for the years of the survey, together with half distances for new (between 2004 and 2009) and abandoned (post 2004) farms are shown in table 2. the half distance for all indicators extended to greater distances from muscat during the period between 2001 and 2009 from 42 to 60 km, from 48 to 57 km and from 42 to 81 km respectively for farm number, greenhouse number and total farm area, respectively. this appears to indicate a movement westwards (away from muscat) of active greenhouse crop production and is reflected in the half distances for farm number, greenhouse number and farm area for new farms which were 65, 56 and 93 km respectively, whilst those for abandoned farms were table 4. percent farm number, greenhouse number and farm area with kriged groundwater salinities above 4.2 ds m-1, based on cumulative totals at increasing estimated salinities. 2001 2002 2003 2004 2009 new farms abandoned farms % farms (r², p) 60.8 (.995, 0.001) 55.8 .995, 0.001) 55.2 (.995, 0.001) 52.0 (.997, 0.001) 37.2 (.996, 0.001) 32.5 (.996, 0.001) 67.3 .990, 0.001) % greenhouses (r², p) 45.3 (.984, 0.01) 37.6 (.984, 0.01) 37.4 (.988, 0.01) 36.9 (.987, 0.01) 22.1 (.998, 0.001) 22.9 (.998, 0.001) 60.6 (.963, 0.05) % farm area (r2, p) 53.3 (.933, 0.05) 49.9 (.940, 0.05) 48.2 (.940, 0.05) 39.8 (.944, 0.05) 14.3 (.989, 0.01) 12.7 (.975, 0.01) 74.1 (.882, 0.01) table 5. logistic model estimates for distance (nearest km, within wilayat barka) to 50% of cumulative farm, greenhouse number and farm area from al mawaleh central market. 2004 2009 new farms abandoned farms % farms (r², p) 28 (.961, 0.01) 29 (.945, 0.05) 29 (.933, 0.05) 25 (.977, 0.01) % greenhouses (r², p) 28 (.963, 0.01) 29 (.944, 0.05) 26 (.948, 0.05) 27 (.935, 0.05) % farm area (r2, p) 28 (.941, 0.05) 31 (.939, 0.05) 31 (.933, 0.05) 24 (.922, 0.05) 0 10 20 30 5 10 15 20 25 30 35 40 45 50 >50 farm size (ha) pe rc en ta ge o f t ot al fa rm s figure 2. frequency distribution of land area for farms with greenhouses in al batinah region. 39research article deadman, al-sadi, al-wardi, al-kiyumi, deadman, al said 46, 38 and 27 km. for all years and categories and for all indicators, the exponential model was an accurate and significant fit for the data (table 2). the data in table 2 appear to corroborate that of table 1 and would fit with an increase in the relative contribution of farms in the as suwayq district and a decrease for wilayat barka, especially over the latter part of the survey period. 3.3. distance from the coast and groundwater salinity based on the 2009 data there was an increase in mean farm size with increased distance from the coast; farms adjacent to the coast had a mean area of 5.5 ha whilst those 5 km distant from the coast had a mean area of 17.4 ha. beyond 5 km there was relatively little discernable change in mean farm size (fig. 3). for all years and for new and abandoned farms and for farm number, greenhouse number and farm area the fit of the gompertz model was a significant reflection of the collected data (table 3). both estimated farm number and greenhouse number half distances increased between 2001 and 2009 from 5.0 to 5.3 and from 5.0 to 5.6 km respectively, reflecting the southward movement of active protected agriculture production. in the case of farm area, the half distance decreased from 4.7 km in 2001 to 4.5 km in 2009, with a half distance of 4.1 km for new farms. this was primarily a consequence of two farm (id 173 and id 174), located 2 and 3 km from the coast, and with areas of 182 ha and 756 ha respectively commencing production in the wilayat of sohar, some 168 km and 170 km distant from al mawaleh in regions only moderately affected by salinity (table 1). when these farms are excluded from the analysis the half distance for 2009 farms increased to 5.5 km and for new farms it increased to 5.3 km (table 3). farms close to the coast contributed disproportionately to the number of abandoned farms (50% within 4.5 km), loss of greenhouses (4.3 km) and loss of farm area (4.2 km). 0 5 10 15 20 25 2 3 4 5 6 7 8 9 10 11 12 13 distance from the coast (km) m ea n fa rm s iz e (h a) figure 3. mean farm size in al-batinah region in relation to distance from the northern coast of oman. y = −0.3739x + 7.1364 r 2 = 0.829, p < 0.001 5 10 15 20 4 8 12 distance from the coast (km) e st im at ed g ro un dw at er s al in ity d s /m figure 4. kriged groundwater salinities for farm locations (small circles) in al-batinah region relative to distance from the coast. large circles represent mean farm size for each 1 km interval. 5 10 15 20 50 100 150 200 distance from al−mawaleh (km) e st im at ed g ro un dw at er s al in ity d s /m figure 5. kriged groundwater salinity values for farm locations in al-batinah region (small circles) in relation to distance from al-mawaleh central market. large circles represent mean values for 5 km intervals. 40 squ journal of agricultural and marine sciences, 2016, volume 21, issue 1 dynamics of land use changes in response to external pressures in oman: greenhouse cropping although the relationship between kriged groundwater salinity, based on kriged 2005 borehole data, and irrigation water salinity (2004) taken directly from greenhouses was significant (p = 0.0004), irrigation water salinity was consistently lower than the estimated groundwater salinity (p(intercept) < 0.001), apparently confirming the widespread practice of importing potable water to supplement well water to minimize crop toxicity damage. there is no evidence to confirm that farm wells and boreholes are accessing the same depth of water. the highest kriged groundwater salinity at farm locations was in excess of 20  ds·m-1 (fig. 4); many farms having salinity levels above 10 ds·m-1. there was a significant (r2 = .829, p < 0.001) decrease in estimated farm mean groundwater salinity with increasing distance from the coast (fig. 4). kriged groundwater salinity levels were also highest close to muscat (fig. 5). all farms having estimated salinities above 10  ds·m-1 were within 25 km of al mawaleh. further peaks of salinity (above 5  ds·m-1) were observed at regular intervals along the al batinah coastal belt, especially at approximately 50, 125, 150 and 200 km from al mawaleh (fig. 5). groundwater salinity was lowest over a greater distance within as suwayq wilayat, approximately 90 – 120 km from al mawaleh. based on kriged groundwater salinity levels calculated using 2005 borehole data (fig. 1b), and the exponential model (equ. 1), the proportion of farms with salinities above 4.2 ds·m-1 where a 50% reduction in cucumber yield might be expected to occur (ayers and westcott, 1985) was 60.8, 55.8, 55.2, 52.0 and 37.2% in 2001, 2002, 2003, 2004 and 2009, respectively. over 67% of farms abandoned between 2004 and 2009 had groundwater salinities above 4.2  ds·m-1; less than 33% of new farms were located in such areas of high groundwater salinity (table 4). in terms of total greenhouse number and total farm area, 60.6% of all abandoned greenhouses and 74.1% of abandoned land area was located in areas with salinities above the 50% yield reduction threshold (4.2 ds·m-1); less than 23% of new greenhouses and less than 13% of the area of new farms were located in such regions. the average kriged groundwater salinity of new farms developed between 2004 and 2009 was 4.08 ds·m1; that of farms abandoned during the same period was 7.17 ds·m-1. although increased groundwater salinity was understandably correlated with farm abandonment away from greenhouse production, it was also significantly related to the extent of direct investment in new protected cropping structures (fig. 6). farms located in regions with low estimated groundwater salinities showed significantly increased numbers of greenhouses per farm compared with those at sites where the groundwater salinity was higher. at 2 ds·m-1 there was a net increase of almost 7 greenhouses per farm. 3.4. the situation in wilayat barka the dynamics of land use change in wilayat barka are the most fluid: it is the district closest to muscat and therefore most vulnerable to increasing demand for land use change to housing and industrial developments; it also has the most greenhouses (table 1) despite having the highest groundwater salinity levels (fig. 5), and has the most highly developed transport infrastructure (fig. 7a). within barka, during the entire study period, there were 134 farms, including those abandoned during the study, occupying a total of 1729 ha and with over 1000 greenhouses. as of 2009 there were 825 greenhouses on 105 farms occupying almost 1250 ha. the majority of the active farms were located to the south of the coastal highway, and up to 14 km distant from the coast (fig. 7b, fig. 8). the farms that had been abandoned table 6. gompertz model estimates for distance (nearest 0.1 km) to 50% of cumulative farm, greenhouse number and farm area from the northern coast of oman in wilayat barka. 2004 2009 new farms abandoned farms % farms (r², p) 6.2 (.992, 0.001) 6.4 (.996, 0.001) 6.3 (.995, 0.001) 5.6 (.985, 0.001) % greenhouses (r², p) 6.2 (.987, 0.001) 6.9 (.994, 0.001) 7.1 (.987, 0.001) 5.1 (.979, 0.01) % farm area (r2, p) 5.7 (.988, 0.001) 6.6 (.997, 0.001) 6.3 (.996, 0.001) 4.3 (.968, 0.05) y = −0.−0.5678x + 5.9389 r 2 = 0.393, p < 0.016 −25 0 25 50 4 8 12 16 estimated groundwater salinity (ds/m) c ha ng e in g re en ho us e nu m be r p er fa rm figure 6. change in number of greenhouses per farm between 2004 and 2009 (small circles) relative to increasing estimated groundwater salinity. large circles represent the mean change in greenhouse number per farm for 1 ds·m-1 intervals. 41research article deadman, al-sadi, al-wardi, al-kiyumi, deadman, al said between 2004 and 2009 were closer to the main highway and therefore closer to the northern coast of oman, figs. 7c, 7d, fig. 8). using the wilayat barka data, the exponential change (equation 1) in farm and greenhouse number and farm area with increasing distance from al mawaleh was used to determine the distance within which 50% of the total of these parameters of agricultural activity occurred (table 5). in all cases, the exponential model was a significant model of the observed change over distance and suggested that the abandonment of farms was proportionately higher closer to muscat with 50% of abandoned farms being located within 25 km of al mawaleh, but 50% of all 2009 farms and 50% of new farms both being located within 29 km of al mawaleh. the model for greenhouse number showed a similar trend, with 50% of greenhouses on abandoned farms being located closer to al mawaleh (27 km) than 50% of greenhouses on 2009 farms (29 km) although 50% of greenhouses on new farms were actually closer to muscat (26 km) primarily because of the development of two new small farms (id 191 and id 4 with 40 and 32 greenhouses on 7.8 and 8.2 ha) located close to al mawaleh (19 and 21 km respectively) but some distance from the coast (8 and 9 km, respectively). the model for farm area suggested the preferential abandonment of farms close to al mawaleh (50% within 24 km) whilst 50% of new farm area was within 31 km of al mawaleh. the new farms that emerged relatively close to al mawaleh were, however, further from the northern coast. the data for barka suggests the preferential abandonment of farms closer to the coast (table 6). the threshtable 7. percent farm number, greenhouse number and farm area in barka wilayat with estimated groundwater salinities above 4.2 ds m-1, based on cumulative totals at increasing salinities. 2004 2009 new farms abandoned farms % farms (r², p) 58.0 (.992, 0.001) 48.0 (.989, 0.001) 46.8 (.983, 0.001) 73.4 (.988, 0.001) % greenhouses (r², p) 57.8 (.971, 0.01) 42.6 (.988, 0.001) 44.3 (.905, 0.01) 71.0 (.981, 0.001) % farm area (r2, p) 63.3 (.911, 0.01) 41.5 (.979, 0.001) 40.6 (.788, 0.05) 88.7 (.987, 0.001) figure 7. map of barka wilayat showing groundwater salinity levels related to location of land abandoned to farming and recent urban developments. 42 squ journal of agricultural and marine sciences, 2016, volume 21, issue 1 dynamics of land use changes in response to external pressures in oman: greenhouse cropping old of 50% of abandoned farm number, greenhouse number and farm area was located at 5.6, 5.1 and 4.3 km respectively, closer to the coast than for 2009 farms (6.4, 6.9 and 6.6 km) and farms developed between 2004 and 2009 (6.3, 7.1 and 6.3 km, respectively). table 7 shows the apparent importance of groundwater salinity in determining farm abandonment and location of new farm developments. over 73% of abandoned farms, 71% of the cumulative greenhouse numbers and 88.7% of the cumulative total abandoned farm areas were located in regions with estimated groundwater salinities in excess of 4.2  ds·m-1. new farms were predominantly located in areas with lower (<4.2 ds·m-1) groundwater salinities (only 46.8% of farms, 44.3% of greenhouses and 40.6% of total farm area was located in regions above 4.2 ds·m-1 of ecw, table 7). the distribution of farms with active greenhouse crop production in 2009 follows closely the distribution of paved roads in wilayat barka (figs 7a, 7b). this is true not only for the main highway, but also the minor roads heading south, away from the coast. the distribution of abandoned farms also appeared closely related to the pattern of transport infrastructure (fig. 7d), especially those interior roads towards the eastern part of the district. in both cases, there was a significant relationship between exponential cumulative farm number and distance to paved roads (r2 > 0.93, p < 0.001) with more than 50% of farm entrances being within 500m of a paved road. as of 2009, over 600 parcels of urban land were individually identified in barka as housing developments, small industrial units, retail outlets and public service buildings. most of this urban land was north of the coastal highway, between the road and the northern coast of oman (fig. 7c, fig. 9). this contrasts significantly with the distribution of agricultural land (fig. 8). an exponential model of cumulative total urban area relative to the coast suggested that 75% of the total was within 6.1 km of the coast (r2 = 0.967, p= 0.001) and showed only a relatively small change from 2000 when 75% of the total was within 5.9 km of the coast (r2 = 0.967, p= 0.001), suggesting urban infill rather than the development of new urban sites. this infill hypothesis is also reflected by the distribution of urban land relative to al mawaleh. in 2000, 75% of the cumulative urban land area was within 43 km (r2 = 0.973, p= 0.001) whilst in 2009 the threshold distance was 40 km (r2 = 0.974, p= 0.001), suggesting only a slight expansion of the urban area away from muscat and this occurring with a linear trajectory, mostly between the border of muscat and barka town. analysis of the grid overlying barka wilayat (figs. 7a-d) clearly shows the relationship between the kriged groundwater salinity data and active (2009) and abandoned farms (2004-2009). although some active farms remain in high ecw areas, especially around a’rumais village, most were in regions with much lower salinities, and almost all are south of the highway. in contrast, the majority of abandoned farms are located in areas of high groundwater salinity either in the area close to the border with muscat to the east, or within the zone of the high salinity tongue extending south from a’rumais. the location of urban land cover follows closely the distribution of transport infrastructure, especially on the northern side of the highway and within the barka town urban district (fig. 7c). figure 7c also appears to show that urban land cover largely occupies a different set of grid squares to those occupied by abandoned farms, and as such urban land cover does not represent a change in land use from agriculture, at least in terms of intensively farmed agricultural land lost since 2004. urban expansion is, rather, seen as a complex mixture of infilling within regions of exceptionally high groundwater salinities close to the coast and ribbon development along the main highway. this notwithstanding, there remain, as of 2009, extensive areas of land close to the coast where the groundwater salinity is extremely high but where urban development has not, so far, taken place. discussion in the current paper greenhouse (protected) cropping is used as a proxy for high intensity agriculture. that greenhouse cropping systems are intensive means of food production may appear self-evident. they normally require large amounts of labour and capital per unit area of land per year and usually involve extending the growing season of crops (jensen and malter, 1995). the world bank has promoted the development of green0 20 40 60 −7.5 −5.0 −2.5 0.0 distance from the main highway (km) g re en ho us e nu m be r figure 8. number of greenhouses on farms in barka wilayat, al-batinah region, in relation to the position of the coastal highway. positive and negative distances are north and south of the highway respectively. large circles represent mean position relative to the coastal highway of active farms (2009, dark green) and abandoned farms (pre 2009, light grey). 43research article deadman, al-sadi, al-wardi, al-kiyumi, deadman, al said house production systems through development aid, stating “the removal of trade barriers, coupled with growing consumer demand for quality produce all year round, has further stimulated this move towards high value, intensive forms of horticultural production” (jensen and malter, 1995). the sustainability of high intensity greenhouse production systems might be a less easily resolvable debate (franze and ciroth, 2011; benito et al., 2009; downward and taylor, 2007), especially in arid and semi-arid regions where water availability for irrigation is often the limiting factor for agricultural development. in a life-cycle analysis of the environmental impact of greenhouse crop production systems, muñoz et al. (2008) evaluated water consumption per kg of tomato as approximately 50% less for greenhouse production compared to open field production. yet as pandey et al. (2002) point out from a study in niger, it is the appropriate use of agriculture intensification technology that is vital in sustainable, increased crop production. however, improvements in irrigation efficiency may merely induce growers to irrigate for longer (peterson and ding, 2005). meanwhile, in the arid arena of oman, the production intensification through greenhouse construction argument rests on the need to extend the growing season in a pincer movement, starting earlier after the end of summer and pushing the cessation of production later into the spring, relative to open field production. unless water use efficiency is improved, more irrigation will be applied per year. the results show that most farms with greenhouses are less than 10 ha (fig. 2) and that mean farm size increases with distance from the coast (fig. 3). al batinah is a region based on small farm cultivation and this has, in part been influenced by islamic inheritance law whereby land is fragmented as it passes between generations (zekri, 2010). older farms are, in general, nearer to the coast and have thus been more fragmented over a longer period of time than more recently established farms inland. alternatively, as zekri (2010) suggests, other socio-economic causes of fragmentation exist, including the selling of parts of farms for urban development. the danger here is that continued fragmentation reduces agricultural sustainability (fan and chan-kang, 2005). when modeling the expansion of agriculture in kenya’s eastern arc mountains, maeda et al. (2010) identified the main factors driving the spatial distribution of land brought into agriculture as distance to markets, proximity to already established agricultural areas and distance to roads. the dominance of the muscat capital area in determining the distribution of intensive agricultural production units is similarly apparent here. although there was an outward extension, between 2004 and 2009, of the distance within which 50% of cumulative farms (42 km to 60 km), greenhouses (48 km to 57 km) and farm area (42 km to 81 km), and the 50% threshold for new farms developed between 2004 and 2009 was further from muscat, the overwhelming majority of intensive agriculture remained close to the main market in al mawaleh (table 2). transport infrastructure was also a clear driver for land use: 50% of farms with greenhouses were within 500 m of the nearest paved road (fig. 7b). notwithstanding the market and infrastructure drivers of land use for intensive (greenhouse) agricultural production, clustering of land use components was clear (see fig. 7b for wilayat barka). land use clustering is a well-documented social–spatial externality (lewis et al., 2008) resulting from processes related to changes in information flows (diffusion of information, foster and rosenzweig, 1995) or imitation (schmit and rounsevell, 2006), transaction costs, fixed costs, infrastructure, and other factors. but clustering was also observed in abandonments away from intensive agriculture (fig. 7d) and abandonments were disproportionately closer to muscat; in this case the principal drivers are more likely to be biophysical, mediated through socio-economic, rather than purely socio-economic. in oman, there is little direct evidence of a linear momentum from agricultural land use to urban land use. even in barka, where urban pressures are greatest, figure 7c shows that co-habitation by abandoned farms and urban land parcels within the individual 250,000 m2 (25 ha) cells superimposed on the wilayat, is low. in barka, the growth of urban developments has almost entirely been restricted to the strip of land between the existing highway and the coast (figs. 1b, 7, 8, 9). this land area is mostly dominated by highly saline soils previously abandoned by productivist agriculture (fig. 7d). as intensive agriculture has been driven out of what might be called a “saline corridor”, it has been replaced by a mixture of land cover types, including urban developments and abandoned agricultural lands reclaimed by natural vegetation and quasi pre-productivist rural land use with extensively grazed goat herds dominating. in southern chile diaz et al. (2011) recorded an almost 50% level of agricultural land abandonment between 1985 and 2007 0.0 0.3 0.6 0.9 1.2 −10 −5 0 5 distance from the main highway (km) a re a (h a) figure 9. distribution of urban land in barka wilayat, al-batinah region in relation to the position of the coastal highway. positive distances and negative distances are north and south of the highway respectively. 44 squ journal of agricultural and marine sciences, 2016, volume 21, issue 1 dynamics of land use changes in response to external pressures in oman: greenhouse cropping in their study area, with important drivers of the return to arboreous shrubland being identified as, amongst others, soil quality. they also identified policy-driven subsidies as an important socio-economic factor behind land abandonment. it is clear that in the al batinah “saline corridor”, soil salinity is the major driver of land use change, encouraging a trajectory towards abandonment; it is also possible that the continuing government subsidies offered to farmers in oman for the construction of greenhouses are similarly driving the abandonment of land in marginal areas: growers are unlikely to expand the number of productive units when yields are at risk from high groundwater salinities unless expensive potable water is imported. in any case, in this area small farm size may also preclude expansion. recent literature has concentrated on land-use / land -cover as drivers of change in groundwater quality. perhaps predictably, singh et al. (2011) found that land use change towards urbanization and industrialization in punjab, india resulted in a reduction in groundwater quality over 1989-2006. a similar outcome has been reported in western turkey (sanli et al., 2009) although twarakavi and kaluarachchi (2006) reported an increase in groundwater quality when urbanization displaced agriculture as the dominant land use and levels of nitrate and other agrochemical residues declined. xu et al. (2007) examined the impact of land use on changes in groundwater nitrate quantity using spatially integrated data during the 1960s to 1990s. not surprisingly nitrate levels rose as agriculture intensified and later fell as groundwater levels themselves dropped or land became urbanized. more interestingly vector differences in groundwater quality changes were observed for different land uses and land use changes (desert to agriculture, desert to urban and agriculture to urban). in oman, the impact of intensive agriculture on groundwater quality close to the coast is already well documented, greater interest now lies in the consequent land use change trajectories. the government has adopted the expedient socio-economic position of responding to the decline in agriculture caused by the change in groundwater quality by introducing an industrialization or urbanization policy along the “salinity corridor”, including the compulsory purchase of farm land. whether this would have occurred in the absence of the groundwater quality change reducing the tenacity of intensive agriculture is debatable. what is clear is that the next decade is likely to bring urbanization and financial investment in infrastructure to oman at a previously unseen scale. major transport projects are planned for the “saline corridor”; these are certain to result in significant industrial and urban land use changes as an additional highway runs the length of the coast between the wilaya of barka and shinas. inland, a new highway and rail system is to be developed that is likely to attract urban development along the roads connecting these highways (anonymous, 2010) the results of the current study suggest an overall movement of the intensive agriculture (proxied by greenhouse developments) zone inland and away from muscat (see fig. 7b for barka wilayat vectors), away from the coast with its high soil salinity and following the improving internal transport infrastructure. the largest net change in recent intensive agricultural activity has been the increase, especially in terms of farm area, in wilayat as suwayq (table 1). this district is the lowest in the apparent extent of groundwater salinity (fig. 1b) and has the lowest percent area affected by salinities above 9 dsm-1 (zekri, 2010). this momentum will need to be addressed at the socio-economic policy level to prevent a future decline of groundwater salinity in this district. conclusion oman is a rapidly changing country. a high rate of population growth and policy-driven industrial diversification away from petrochemicals is encouraging urbanization at the expense of traditional agriculture. intensive agriculture appears to be responding by moving away from areas of most rapid urban change and away from areas of highest groundwater salinity: new, large farms are being developed inland as small, traditional farms close to the coast and close to muscat are abandoned. this movement appears to be facilitated by expanding 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