img323 img324 img325 img326 img327 img328 img329 img214 img215 img216 img217 img348 img349 img350 img351 img352 img353 img162 img163 img164 img165 img166 img167 img168 img169 img330 img331 img332 img333 img334 img335 img336 img081 img082 img083 img084 img085 img306 img307 img308 img309 img310 img311 img196 img197 img198 img199 img200 img032 img033 img034 img035 img023 img024 img025 img026 img027 img058 img059 img060 img061 img062 img063 img064 img065 img066 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, 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. 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. 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. 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. img354 img355 img356 img357 img358 img359 img360 img337 img338 img339 img340 img341 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 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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. img312 img313 img314 img315 img316 img317 img036 img037 img038 img039 img040 img041 img201 img202 img203 img204 img205 img086 img087 img088 img089 img090 img028 img029 img030 img031 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. 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(1984). biology and culture of seabass (lates calcarifer). naca training manual series 3, 67 pp. figure 11. dissolved oxygen (mg/l) at low, medium and high fish densities. 21research paper al-rashdi, gallardo, yoon, al-masroori largo db, diola ag, marababol ms. (2016). development of an integrated multi-trophic aquaculture (imta) system for tropical marine species in southern cebu, central philippines. aquaculture reports 3: 67–76. macdonald ba, robinson sm, barrington ka. (2011). feeding activity of mussels (mytilus edulis) held in the field at an integrated multi-trophic aquaculture (imta) site (salmo salar) and exposed to fish food in the laboratory. aquaculture 314(1): 244-251. neori a, chopin t, troell m, buschmann ah, kraemer gp, halling c. (2004). integrated aquaculture: rationale, evolution and state of the art emphasizing seaweed biofiltration in modern mariculture. aquaculture 231: 361-391. neori a, shpigel m, ben-ezra d. (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 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 provide insight into potential negative impacts. adding this knowledge to 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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. 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. 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. 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 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. 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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. 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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(1997). composition of essential oil of zataria multiflora. planta medica 63: 371-372. shi n, ruan h, jie y, chen f, du y. (2020). sensitivity and efficacy of fungicides against wet bubble disease of agaricus bisporus caused by mycogone perniciosa. european journal of plant pathology. 157: 873-885. tanovic b, potocnik i, delibasic g, ristic m, kostic m, markovic m. (2009). in vitro effect of essential oils from aromatic and medicinal plants on mushroom pathogens: verticillium fungicola var. fungicola, mycogone perniciosa, and cladobotryum sp. archives of biological sciences belgrade 61: 231-237. tian j, ban x, zeng h, he j, chen y, wang y. (2012). the mechanism of antifungal action of essential oil from dill (anethum graveolens l.) on aspergillus flavus. plos one 7: 1-10. wang w, li x, chen b, wang s, li c, wen z. (2016). analysis of genetic diversity and development of scar markers in a mycogone perniciosa population. current microbiology 73: 9-14. white tj, bruns td, lee sb, taylor jw. (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, new york, p. 315-322. zhang cl, xu jz, kakishima m, li y. (2017). first report of wet bubble disease caused by hypomyces perniciosus on pleurotus citrinopileatus in china. plant disease 101(7): 1321. zhou c, li d, chen l, li y. (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. 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. 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. 2001. the origin of transparent exopolymer particles (tep) and their role in the sedimentation of particulate matter. continental shelf research 21: 327-346. pettis, r.j., b.w. erickson, r.b. forward jr, and d. rittschof. 1993. superpotent synthetic tripeptide mimics of the mud crab pumping pheromone. int. j. prot. and peptide research 42: 312-319. preiser, h.s., a. ticker, g.s. bohlander, and d. w. tayor. 1984. coating selection for optimum ship performance. in: marine biodeterioration an interdisciplinary study. eds. j.d. costlow and r.c. tipper. naval institute press pp 223-229. qian, p.-y., s.c.k. lau, h.-u. dahms, s. dobretsov, and t. harder. 2007. marine biofilms as mediators of colonization by marine macroorganisms: implications for antifouling and aquaculture. marine biotechnology 9: 399-410. rittschof, d. 2000. natural product antifoulants: one perspective on the challenges related to coatings development. biofouling 15: 119-127. rittschof, d. 2009. novel antifouling coatings: a multiconceptual approach, pp 179-188, in, flemming h-c, ps murthy, r venkatesan, ke cooksey (eds) in, marine and industrial biofouling. springer publishing, ny. rittschof, d., a.s. clare, d.j. gerhart, sr avelin mary, and j. bonaventura. 1992. barnacle in vitro assays for biologically active substances: toxicity and settlement inhibition assays using mass cultured balanus amphitrite amphitrite darwin. biofouling 6: 115-122. rittschof, d., c.h. lai, l.m. kok, and sl-m teo. 2003. pharmaceuticals as antifoulants: concept and principles. biofouling 19(suppl): 207-212. turner, r. d. an overview of research on marine borers: past progress and future directions. in: marine biodeterioration an interdisciplinary study. eds. j.d. costlow and r.c. tipper. naval institute press pp 3-16. sutherland, j.p., and r.h. karlson. 1977. development and stability of the fouling community at beaufort, north carolina. ecological monographs 47: 425-446. woods hole oceangrpic institution. 1952. marine fouling and its prevention. annapolis, u.s. naval institute. img361 img362 img363 img364 img342 img343 img344 img345 img346 img347 img318 img319 img320 img321 img322 img042 img043 img044 img045 img046 img047 img048 img049 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. img091 img092 img093 img094 img095 img096 img097 img157 img158 img159 img160 img161 img162 img163 img164 img206 img207 img208 img209 img210 img211 img212 img213 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. img050 img051 img052 img053 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. (2008). transmission electron microscopic studies on the granular leukocytes of guinea fowl (numida meleagris). the indian journal of animal sciences 78(11): 1265-1267. hult a. (2015). towards a detailed understanding of the red blood cell storage lesion and its consequences for in vivo survival following transfusion. umeå universitet. medical dissertations, new series no 1727, page: 1-58. jones mp. (2015). avian hematology. clinics in laboratory medicine 35: 649–659. johnson eh, al-amri ash, al-abri m, al-marzooqi w. (2020). ultrastructure morphology of lymphocytes of the arabian oryx (oryx leucoryx). journal of veterinary medicine series c: anatomia histologia embryologia 49: 425-429. maxwell mh. (1973). comparison of heterophil and basophil ultrastructure in six species of domestic birds. journal of anatomy 115: 187–202. maxwell mh, robertson g w. (1998). the avian heterophil leucocyte: a review. world’s poultry science journal 54: 168–178. maxwell mh, siller wg, buildings k, west mr. (1972). the ultrastructural characteristics of the eosinophil granules in six species of domestic bird. journal of anatomy 112: 289–303. maxwell mh, trejo f. (1970). the ultrastructure of white blood cells and thrombocytes of the domestic fowl. the british veterinary journal 126: 583–584. mohd ki, meena m, balwinder s, ishwar s. (2016). ultrastructural study on the granulocytes of uttara fowl (gallus domesticus). veterinary world 9: 320-325. salakij c, jarernsak s, kreangsak p, naul an, pornchai s, kwanjai k. (2014). quantitative and qualitative morphologic, cytochemical, and ultrastructural characteristics of blood cells in captive asian water monitors. veterinary clinical pathology 43: 538–546. sards. (2016). sustainable agriculture and rural development strategy towards 2040 government of the sultanate of oman. page: 1-113. shaat i, al-habsi r. (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. 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 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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. 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. 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(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. img365 img366 img367 img368 img369 img370 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. 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. 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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(camelus dromedarius). animal reproduction science, 101: 172-178. 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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__________________________________________________ *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 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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. 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. img024 img025 img026 img027 img028 img016 img017 img018 img019 img020 img021 img022 img054 img055 img056 img057 img188 img189 img190 img191 img192 img193 img194 img195 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): 40 – 46 reveived 5 aug. 2014 accepted 19 feb 2015 culture conditions affect the nutritional value of the copepod acartia tonsa arne m. malzahn1,2,*, nicole aberle-malzahn2, katherina schoo1,3, maarten boersma2 1department of marine science & fisheries, college of agricultural and marine sciences, sultan 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 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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. img054 img055 img056 img057 img058 img059 img013 img014 img015 img016 img017 img018 img019 img020 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. 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., singh, v., indiramma, a.r. and prakash m. 2013. shelf stable multigrain halwa mixes: preparation of halwa, their textural and sensory studies. journal of food science and technology, 50, afst(i), india, issn: 0972-2610, pp.879-889. besbes, s., drira, l., blecker, s., deroanne, c. and attia h.. 2009. adding value to hard date (phoenix dactylifera l.) compositional, functional and sensory characteristics of date jam, food chemistry, vol.112, elsevier, london, issn: 0308-8146, pp.406–411. benmeddour, z., mehinagic, e., meurlay, d.e. and louaileche, h. 2013. phenolic composition and antioxidant capacities of ten algerian date (phoenix dactylifera l.) cultivars: a comparative study, journal of functional foods, 5: 346 –354. bower, j.a. and saadat, m.a. 1998. consumer preference for retail fat spreads: an olive oil based product compared with market dominant brands. food quality and preference, 9: 367-376. chandini ,s.k., rati, r.e.and jamuna p. 2005. effect of varietal differences and 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. img029 img030 img031 img032 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. img110 img111 img112 img113 img114 img005 img006 img007 img008 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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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 ind