Int. J. Aquat. Biol. (2021) 9(2): 115-123 ISSN: 2322-5270; P-ISSN: 2383-0956 Journal homepage: www.ij-aquaticbiology.com © 2021 Iranian Society of Ichthyology Original Article The Omani sandfish sea cucumber, Holothuria scabra Jaeger, 1833 (Holothuroidea: Holothuriidae): Fishery, length-Weight relationship and condition factor Saud M. Al Jufaili*1, Khalfan M. Al Rashidi2, Iman S. Al Kharusi3 1Department of Marine Science and Fisheries, Sultan Qaboos University, PO Box 34, Al-Khod 123, Sultanate of Oman. 2Directorate General of Fisheries Research, Ministry of Agriculture and Fisheries Wealth, PO Box 427, Muscat 100, Sultanate of Oman. 3Ministry of Agriculture and Fisheries Wealth, PO Box 427, Muscat 100, Sultanate of Oman. s Article history: Received 7 December 2020 Accepted 22 February 2021 Available online 2 5 April 2021 Keywords: Echinodermata Holothuroidea Fisheries management Oman Sea Abstract: The fishery of Omani sea cucumber, Holothuria scabra, is limited so far to the Mahout Bay in Al Wusta governorate. This fishery supports an uncertain number of fishermen ranging from 100 to 150. This fishery is not well-studied and has no current management program. In order to prepare a management strategy, the government has suspended this fishery for 2 years from March 2018 to March 2021. Apart from presenting a thorough review on the sea cucumber fishery in Oman, the current work presents a detailed analysis of the length–weight relationship, sex ratio, and condition factor of the H. scabra collected from four different areas during the period February-May 2019. Based on the results, the females were longer than males, that is 226±33.4 and 221±37.8 mm, respectively. The overall sex ratio of the entire/pooled sample was 0.49 which was not different from the anticipated theoretical sex ratio of 0.5. The mean Kn and the empirical weight–length equations for the total sample were between 0.12±0.01 and 1.0±0.16, and W=0.03L1.6, respectively. Introduction Sea cucumbers are non-migratory space-specific species that are found in shallow protected seagrass and muddy sea beds around and within protected bays, coral reefs, and mangrove areas (Hamel et al., 2001; Agudo, 2006). They are reported to spawn throughout the year with enhanced peaks at certain period of the year (Lokani, 1990; Battaglene and Bell, 2004). In addition, sea cucumbers reproduce asexually as well (Conand, 1996; Conand et al., 2002; Dolmatov, 2014) and their life span ranges between 5 and 12 years depending on the species (Conand, 1990). Sea cucumber larvae spend 70 days in a planktonic stage before they settle into the ground where they develop into a juvenile. The growth rate of sea cucumbers is assumed to be slow and may take up to 5 years to mature (Conand, 2008). It grows up to 0.5 cm per month (≈14 g) under favorable conditions and attains maturity between 23 and 26 cm (Agudo, 2006; Navarro et al., 2012; Omar et al., 2013; Yanti et al., 2020). Sea cucumbers are scavengers or deposit *Correspondence: Saud M. Al Jufaili DOI: https://doi.org/10.22034/ijab.v9i2.1168 E-mail: sjufaily88@gmail.com feeders (Mercier et al., 1999). There are reports suggesting existence of sea cucumbers from long ago in many places, for example Solomon Islands, India, the Philippines, and Indonesia among others (Conand, 1990; Battaglene and Bell, 1999) and are known to be harvested for decades from the Indo-Pacific region (James, 2001; Bumrasarinpai, 2006). Yet, there is not much information on sea cucumber fisheries around the world. With the increasing demand for sea cucumbers in the international market, the different types and sizes of sea cucumbers excavated in the absence of management resulted in more pressure for sea cucumber hunting and eventually to overfishing (Conand, 2008; Hair et al., 2018). Overfishing has been documented in Australia (Skewes et al., 2006), Fiji (Preston, 1988), and New Caledonia (Conand, 1990). In several countries, it was heavily exploited, which led these countries to apply moratorium on the fishery and ban fishing like in the case of the Egyptian sea cucumber (Hasan, 2003), the Papua New Guinea 116 Al Jufaili et al./ Fishery, length-Weight relationship and condition factor of Holothuria scabra (Hair et al., 2018), and Turkey (Aydin, 2017). Other countries have introduced zonation or sea cucumber marine-protected areas where fishing areas are closed for a period of up to 4 years before they are opened again. In addition, whenever open, closed season is always applied during reproductive season (Purcell et al., 2016). The price and demand for sea cucumber increased 16.6% in the international markets from 2011 to 2016 (Purcell et al., 2018). The increase in demand has an effect on the international fishing activities for sea cucumbers. The sea cucumber fishery and industry in Oman is in the initial stage, and the fishery being so far limited to small areas of Mahout Bay and targeted by small number of traditional fishermen. Omani sea cucumber, Holothuria scabra is a valuable species and an excellent source of income for the local communities and the fishery so far is an open access and hardly studied. So far, in Oman there are no fixed records of sea cucumber landings or about the actual number of fishermen involved. Furthermore, there are no data available on the basic stock assessment or population distribution of the sea cucumbers. Basically, there are plenty of missing information that needs to be understood and managed to develop the fishery. Hence, the current study reviews the Omani sea cucumber fishery and provides information on the length–weight relation and sex ratio from four main fishing areas in Oman. Materials and Methods All the available publications and reports (published and unpublished) on sea cucumbers were reviewed to understand their fishery. Fishing areas were visited and officials, fishermen, traditional processors, and traders were interviewed. The review present data on the sea cucumber landings, income, export, and any other information. As per the information obtained, the sandfish sea cucumber samples were collected from four major fishing areas viz. Ashaghia, Hofnat, Al Naqil, and Ashaghia (Fig. 1) in Mahout Bay during the period February-May 2019. The samples were measured to the nearest of 1 mm for total length (from mouth to anus) using a flexible plastic tape. An electronic balance was used to record the wet weight to the nearest 1 g for each sea cucumber. Sea cucumbers were dissected for visual sex identification purposes. Length-weight relationship was calculated using Pauly’s (1984) equation of 𝑊𝑊 = 𝑎𝑎 × 𝐿𝐿𝑏𝑏, where W is the wet weight in g, L the total length in mm, a and b the regression constants, “a” the intercept, and “b” the slope. Fulton’s condition factor (Kn) was obtained by 𝐾𝐾n = 𝑊𝑊/(𝑎𝑎 × 𝐿𝐿𝑏𝑏) (Le-Cren, 1951). The length– weight relation, the condition factor, and sex ratio were obtained for the whole sample, for each area, males, females, and unsexed sea cucumbers. The sex ratios were also presented by different length intervals and per sampling area. Results The fishery: The sandfish sea cucumber is the primary species among the other 21 different species that are identified in Oman (Claereboudt and Al- Figure 1. The Mahout Bay and the sea cucumber fishing areas. 117 Int. J. Aquat. Biol. (2021) 9(2): 115-123 Rashdi, 2011). According to the information available, it is distributed around the Mahout Bay in the Gulf of Masira along the Al Wusta governorate in sandy protected and seagrass bays. Six main fishing areas are famous in this region, Alnaqil, Al-Eigah, Wadsumah, Al-Shaghia, Al-Hofnat, and Ras-Knasah (Fig. 1). The fishery started in the 1960s at a low scale and the catch was exchanged for food. Owing to the demand from the neighboring countries, the fishery expanded in 2003 and 2004 (Al-Rashdi et al., 2007). As it is not very difficult to catch sea cucumbers, this fishery encourages women and their kids also to help in catching practice, in many cases, they give a competition to the fishermen (Fig. 2). To catch sea cucumbers easily, one requires to walk on shallow water, spot the sea cucumber, and catch it. It is reported that women make 50% of the total fishing community and men contribute up to 30%, while kids contribute 20% (MAF, 2009). Few of these people dive in traditional ways to about 3-m depth, especially during high-tide periods. Of late, the number of divers were observed to increase due to higher market demands. The intensity of fishing increases during low and extreme low-tide periods. The actual number of total fishermen involved in the fishery is not known, however, it is expected to be around 100–150 (unpublished data). There is no information about the number of traders involved; however, a vast percentage of sea cucumbers that are eviscerated, boiled, dried, re-boiled, and re-dried are collected in woven bags and exported to neighboring countries in car trunks. Collecting and selling sea cucumbers became popular among fishing people in Mahout Bay area and the landings increased from 3.6 t in 2013 to 39.4 t in 2015. Targeting sea cucumber is open throughout the year and the intensity depends on the demand and request from the traders. Every year, however, the fishermen target the sea cucumbers from November to March for 3-4 h per day with an average catch of 100 different sizes of sea cucumbers (MAF, 2009). An increase in collecting and processing sea cucumber into beche-de-mer among the fishermen and even drying undersized sea cucumbers are also observed (Fig. 3). The unlicensed number of fishermen doubled in 2004-2005, that is to 100-200, respectively, keeping in mind the increase in prices per kg to five times from 2000 to 2005 (Al-Rashdi et al., 2007). It was also noticed that the fishermen started to dry undersized sea cucumber widely within Figure 2. Women and kids wading for sea cucumbers. Figure 3. Samples of sea cucumber catches. Sea cucumbers range from large to undersized. 118 Al Jufaili et al./ Fishery, length-Weight relationship and condition factor of Holothuria scabra Mahout Bay area ultimately resulting in an increased number of fishermen. As a result, the government, as a precautionary approach, decided to suspend the fishery for 1 year starting from March 2018 to March 2019. The ministry later extended the suspension for another year until 27th March 2021. Although the suspension still exists, few people were found with approximately 1.2 t of illegal sea cucumbers in 2018 (unpublished data). The price of each sea cucumber ranges from 0.5 to 2.00 Riyal Omani (OR) (1 OR = 2.6 $), while the price per kg for the dry sea cucumbers range between 35 and 55 OR. It is worth mentioning that 100 sea cucumbers make up to almost 2 kg after drying (MAF, 2009). Length-weight relationship and sex ratio: During the present study, a total of 713 sea cucumbers were collected from four fishing areas, of which 121 were males, 116 females, and 494 unsexed. In all, 424 (59%) samples were collected from the Hofnat area, with 374 unsexed samples, 26 males, and 24 females. A total of 142 (19%) samples were collected from Al Naqil area, with 70 unsexed samples, 39 males, and 33 females. A total of 84 (12%) samples were collected from Ashaghia, with 41 unsexed samples, 23 females, and 20 males. Finally, 81 (11%) samples were collected from Aleigah with 36 males, 36 females, and 9 unsexed (Table 1, Fig. 4). The maximum length recorded was 320 mm for a male sample from Al Naqil, while the smallest sample was an unsexed sea cucumber of 70 mm length from Hofnat area (Table 1). Overall, the females were found to be longer than males, that is 226±33.4 and 221±37.8 mm, respectively. On the other hand, the heaviest sea cucumber, wet weight of 600 g, was captured from Al Naqil area, while the lowest weight recorded was 280 g from Ashaghia. Overall, males were heavier than females, that is 271±81.49 and 264.48±64.61 g, respectively (Table 2). The overall sex ratio of the entire/pooled sample was 0.49 which was not different from the anticipated theoretical sex ratio of 0.5 ( χ2=0.11; df=1; P>0.05). The sex ratio within the sampling areas Al Naqil, Aleigah, Ashaghia, and Hofnat were 0.49, 0.53, 0.5, and 0.48, respectively, and all were not different from Table 1. Descriptive statistics for the sandfish sea cucumber, Holothuria scabra from Oman. Sampling area Mean Median Mode Minimum Maximum Count Al Naqil Male 237 240 210 170 320 39 Female 252 260 260 190 300 33 Unsexed 232 235 230 130 300 70 Combined 238 240 250 130 320 142 Aleigah Male 221 220 220 160 310 36 Female 224 220 230 170 290 36 Unsexed 190 190 190 130 250 9 Combined 219 220 230 130 310 81 Ashaghia Male 208 210 210 160 310 20 Female 211 210 210 160 250 23 Unsexed 173 180 180 100 250 41 Combined 192 195 210 100 310 84 Hofnat Male 207 210 210 150 270 26 Female 207 210 220 160 290 24 Unsexed 142 140 140 70 270 374 Combined 149 140 140 70 290 424 All data Male 221 210 210 150 320 121 Female 226 220 220 160 300 116 Unsexed 158 150 140 70 300 494 Combined 179 170 140 70 320 731 119 Int. J. Aquat. Biol. (2021) 9(2): 115-123 the theoretical sex ratio of 0.5 (P>0.05). The monthly sex ratios ranged between 0.38 (Al Naqil/May sample) and 0.75 (Ashaghia/February sample) (Table 3). The sex ratio versus total sea cucumber length within the sampling areas showed no pattern and females could be more than male in any given length group or could be less than the males (Fig. 5). However, the overall sample sex ratio did not show a pattern for sea cucumbers below 180 mm or above 240 mm. The overall sex ratio showed a pattern between lengths 180 and 230 mm and is explained by the power function (sex ratio=2.1*10-7 L 2.7, r=0.97) (Fig. 6). In addition to the mean Kn, the empirical weight-length equations for the total sample, female, male, unsexed, and combined male and female H. scabra per sampling area are presented in Table 4. The length-weight relationship for the total samples collected was W=0.03L1.6 for a total of 680 male, female, and Table 2. Length (mm) and wet weight (g) data collected from the four different sampling areas during the period February–May 2019. Sampling area Mean Median Mode Minimum Maximum Count L(mm) W(g) L(mm) W(g) L(mm) W(g) L(mm) W(g) L(mm) W(g) L(mm) W(g) Al Naqil Male 237 295 240 270 210 240 170 170 320 600 39 39 Female 252 309 260 300 260 300 190 180 300 500 33 33 Unsexed 232 254 235 240 230 240 130 120 300 600 70 70 Combined 238 278 240 255 250 300 130 120 320 600 142 142 Aleigah Male 221 256 220 250 220 250 160 140 310 550 36 36 Female 224 256 220 250 230 230 170 170 290 430 36 36 Unsexed 190 198 190 230 190 230 130 100 250 280 9 9 Combined 219 219 220 220 230 230 130 130 310 310 81 81 Ashaghia Male 208 241 210 235 210 190 160 190 310 400 20 20 Female 211 246 210 240 210 260 160 150 250 340 23 23 Unsexed 173 185 180 200 180 210 100 50 250 280 41 41 Combined 192 215 195 220 210 240 100 50 310 400 84 84 Hofnat Male 207 - 210 - 210 - 150 - 270 - 26 - Female 207 - 210 - 220 - 160 - 290 - 24 - Unsexed 142 125 140 120 140 130 70 30 270 450 374 374 Combined 149 - 140 - 140 - 70 - 290 - 424 - All data Male 221 271 210 250 210 250 150 140 320 600 121 121 Female 226 264 220 250 220 230 160 150 300 500 116 116 Unsexed 158 150 150 130 140 130 70 30 300 600 494 493 Combined 179 188 170 180 140 130 70 30 320 600 731 731 Figure 4. The length–frequency distribution of male, female, and unsexed sandfish sea cucumber samples (top graph) and for the combined males and females (bottom graph). 120 Al Jufaili et al./ Fishery, length-Weight relationship and condition factor of Holothuria scabra unsexed sea cucumbers. The linear regression resulted in a high goodness of fit (R2) which ranged from 0.61 to 0.9 (Table 4). The mean condition factor (Kn) for H. scabra, ranged between 0.12±0.01 and 1.0±0.16 (Table 4). Overall, the unsexed sea cucumbers seemed to be on the lower side of the wellbeing with Kn of 0.89±0.16. Per sampling area, the males in Ashaghia had the lowest condition factor with a Kn of 0.12±0.01. Discussions The sandfish sea cucumber fishery in Oman is advancing fast to its developing stage. The number of fishermen involved increased fast. There is a tendency among fishermen to explore more fishing grounds as the demand increases. Enforcing regulations therefore Table 3. Monthly and overall sex ratios for sea cucumber samples collected from Anaqil, Ashaghia, Aleigah, and Hofnat sampling areas during the period February-May 2019. Alnaqil Ashaghia Month Sex ratio Chi-square P-value Sex ratio Chi-square P-value Feb-19 0.43 0.43 0.51 0.75 1 0.32 Mar-19 0.5 0 1 0.55 0.14 0.71 Apr-19 0.5 0 1 0.44 0.22 0.64 May-19 0.38 0.69 0.41 0.57 0.29 0.6 Overall 0.49 0.5 0.48 0.53 0.21 0.65 Aleigah Hofnat Feb-19 0.5 0 1 0.66 0.33 0.56 Mar-19 0.47 0.07 0.8 0.56 0.53 0.47 Apr-19 0.47 0.05 0.82 0.4 0.6 0.44 May-19 0.55 0.2 0.65 0.4 0.6 0.44 Overall 0.5 0 1 0.48 0.08 0.78 Feb-19 0.5 0 1 Mar-19 0.52 0.15 0.7 Apr-19 0.46 0.53 0.47 May-19 0.48 0.06 0.8 Overall 0.49 0.1 0.74 Figure 5. Sex ratio distribution based on sandfish sea cucumber length (mm). 121 Int. J. Aquat. Biol. (2021) 9(2): 115-123 could be an issue if stricter measures are applied. The overall sex ratio for samples collected for this study was not different from 1:1 (0.49), and this was different from the sex ratio within the sampling areas ranging 0.48-0.53. This result was supported by the H. scabra study from Abu Rhamada Island in the Red Sea (Hassan, 2005). The female-to-male ratio for the same species was 1.48:1 for samples collected from Kudat, Malaysia; however, the sex ratio was not significantly different (Arsad et al., 2017). The sex ratio for samples collected from Mahout Bay in Oman was reported to be 1:1 (Al-Rashdi et al., 2007). As far as the sex ratio among different length groups is considered, the sex ratio did not have a prevailing of one sex over the other. The sex ratio power function identified within this study can be used for reconstructing the sex structure from catch data and therefore can be used for sex-based management applications and assessment models. Analysis of length-weight relationship indicated that the growth is negative allometric as all the b- values obtained were lower than 3. The b-values ranged from 1.22 to 1.88 for the different sexes and for the unsexed in different sampling areas. In addition, the overall b-values were 1.4, 1.3, 1.65, and Table 4. Length-weight equations from different sampling areas with the mean condition factor provided. Sampling area Length-weight n R2 Mean Kn±SD Gender relationship Al Naqil Male W=0.07L1.53 39 0.82 1.01±0.13 Female W=0.04L1.62 33 0.61 1.01±0.13 Unsexed W=0.34L1.22 70 0.67 1±0.14 Male+female W=0.07L1.52 72 0.73 1±0.12 Combined W=0.11L1.43 142 0.7 1±0.14 Aleigah Male W=0.17L1.36 36 0.76 1±0.13 Female W=0.3L1.47 36 0.78 0.4±0.04 Unsexed - 9 - - Male+female W= 0.21L1.31 72 0.77 1.00±0.11 Combined W=0.13L1.41 81 0.82 1±0.11 Ashaghia Male W=1.02L1.02 20 0.88 1.00±0.07 Female W=0.43L1.18 23 0.63 1±0.12 Unsexed W=0.08L1.5 41 0.84 1±0.16 Male+female W=0.74L1.08 43 0.75 1±0.09 Combined W=0.13L1.41 84 0.84 1±0.13 Hofnat Male - - - - Female - - - - Unsexed W=0.01L1.88 374 0.8 1±0.17 Male+female - - - - Combined W=0.01L1.82 424 0.8 1±0.21 Total sample Male W=0.17L1.4 95 0.8 1±0.21 Female W=0.19L1.3 92 0.71 1±0.12 Unsexed W=0.33L1.65 493 0.86 0.89±0.16 Male+female W=0.18L1.34 187 0.746 1±0.12 Combined W=0.03L1.64 680 0.9 1±0.16 The equations are given by sampling areas and by genders. Figure 6. Relationship between the lower total length interval (cm) and the total sample sex ratio for the Omani sandfish sea cucumber, Holothuria scabra. 122 Al Jufaili et al./ Fishery, length-Weight relationship and condition factor of Holothuria scabra 1.64 for the male, female, unsexed, and for the combined sexes, respectively. These b-values were significantly lower than the regression coefficient of 3 (Pauly, 1983) i.e. the length growth is greater than the weight growth, results that were supported by length– weight relationship of H. spinifera, Bohadschia marmorata, Stichopus naso, and H. atra samples collected from Point Pedro and Mullaitivu in North- east region of Sri Lanka (Veronika et al., 2018) and from Gulf of Mannar, India (Venkataraman, 2007). The length-weight equations obtained by Al-Rashdi et al. (2007) was W=0.033L2.178 for H. scabra from the data collected from Mahout Bay, Oman. This was also supported by H. scabra from Fiji (W=0.1878L 2.5807) (Lee et al., 2018). 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