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Reproductive Biology of Mud Crabs (Scylla Olivacea) Collected from Paikgachha, Khulna, Bangladesh

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Reproductive Biology of Mud Crabs (Scylla Olivacea) Collected from Paikgachha, Khulna, Bangladesh JOURNAL OF ADVANCED VETERINARY AND ANIMAL RESEARCH ISSN 2311-7710 (Electronic) http://doi.org/10.5455/javar.2021.h483 March 2021 A periodical of the Network for the Veterinarians of Bangladesh (BDvetNET) VOL 8, NO. 1, PAGES 44–50 ORIGINAL ARTICLE Reproductive biology of mud crabs (Scylla olivacea) collected from Paikgachha, Khulna, Bangladesh Prianka Paul1 , Md. Sherazul Islam1, Sumona Khatun1, Joyanta Bir2 , Antara Ghosh3 1Department of Fisheries and Marine Bioscience, Jashore University of Science and Technology, Jashore, Bangladesh 2Fisheries and Marine Resource Technology Discipline, Khulna University, Khulna, Bangladesh 3Department of Aquaculture, Sher-e-Bangla Agricultural University, Dhaka, Bangladesh ABSTRACT ARTICLE HISTORY Objective: This study was carried out to estimate the sex ratio, maturity size, gonadosomatic Received October 31, 2020 index (GSI), and peak breeding season of mud crabs. Revised December 11, 2020 Materials and Methods: Samples were collected randomly from the estuary and river of the study Accepted December 24, 2020 area. Sampling was carried out monthly from April to September at every full moon during one Published March 05, 2021 high tide. A total number of 240 specimens were sampled, where 53 individuals were hermaphro- KEYWORDS dite. The crabs were shifted alive to the biology and histology lab for detailed biological study. Sex was determined. Male and female sex ratio and breeding season were also investigated. Mud crabs; Scylla olivacea; maturity Results: The male:female ratio was 1:0.96 and the ovarian development was categorized into five stage; gonadosomatic index stages based on internal observations, viz. immature (stage I), underdeveloped (stage II), early developed (stage III), late developed (stage IV), and mature (stage V). The maturity percentages were 37%, 19%, 13%, 11%, and 20%, respectively. 50% maturation was estimated at 82.36 mm inter- © The authors. This is an Open Access nal carapace width (ICW). The highest mean GSI value was 7.97 ± 3.03. The mature stage was found article distributed under the terms of in all the working periods. This shows that females have activated ovaries in all the working months, the Creative Commons Attribution 4.0 and the species are continuous breeders. A higher frequency of vitellogenic ovary and higher GSI License (http://creativecommons.org/ value were found in September. The maximum GSI value was found in the size group 70–79 mm. licenses/by/4.0) Conclusion: The study shows that the capture from the wild sources of mud crabs without any regulation can threaten the population structure. The capture of female mud crabs should be more than 82.36 mm ICW, which will help conserve and protect young crabs. Introduction Recent information from the Department of Fisheries of Bangladesh is the world’s largest deltaic country and is enriched with a large number of aquatic species. Because directly or indirectly associated with mud crab aquaculture of Bangladesh’s geographic condition, these resources pro- forBangladesh their livelihood states that .about Mud crabs300,000–400,000 (Scylla spp.) peopleare one are of [1]. The the most delicious seafood items and attain high economic value worldwide, especially[6] in tropical and subtropical vide a feasible circumstance to develop fisheries countries [7]. The growing demand for mud crabs in Asia, agriculturalfisheries sector’s GDP national[2] economic contribution is 3.69% Europe, and America has led to increased mud crab produc- exportedto the Gross mud Domestic crabs coming Product from (GDP) the mangrove and 22.60% forests to the of tion [7, . It is a euryhaline species found in coastal waters the Sundarbans . There were 60% of the country’s the mangrove8] area. Biochemically, mud crabs are enriched [4] [3]. In Bangladesh, 60% of people’s daily with a 2–30 ppt salinity and is particularly dominant ,in need for animal protein comes from supplementary fish- rounded. Bangladesh’s areas suitable coastline for coastal has 710 aquaculture km associated [5]. with with 15%–25% protein, 1% fat, and 2%–3% Scyllaminerals olivacea [8 9] 618,780 ha of mangrove tidal flats and 80,000 ha of sur that make them a popular food item globally and with high Correspondence Prianka Paul [email protected] Departmentmarket of Fisheries prices. andFor Marine these reasons,Bioscience, mud Jashore crab University of Sci- ence & Technology, Jashore, Bangladesh. How to cite: Paul P, Islam MS, Khatun S, Bir J, Ghosh A. Reproductive biology of mud crabs (Scylla olivacea) collected from Paikgachha, Khulna, Bangladesh. J Adv Vet Anim Res 2021; 8(1):44–50. http://bdvets.org/javar/ Paul et al. / J. Adv. Vet. Anim. Res., 8(1): 44–50, March 2021 44 is a highly exploited species associated with mangrove eco- - systems because of over-harvesting. In the southeast and ical parts. This study aims to identify the maturity size, southwest regions of Bangladesh, Chittagong, Cox’s Bazar, ovariancrab such development as maturity size,stages, peak gonadosomatic season, and other index, biolog and breeding season of S. olivacea. manyNoakhali, years Bhola, . Potuakhali,According toBarguna, Export PromotionKhulna, Bagerhat, Bureau Material and Methods and Satkhira,[11] mud crab aquaculture has been practiced for [10] [12] Ethical approval crabs2001 are exported, crab export from Bangladeshearned $33 that million is harvested in 2018–19, from The Research Ethics Committee of the Faculty of Biological thewhich Sundarbans was $23.28 million. in 2015–16 . Around 99% of Science and Technology, Jashore University of Science and Due to the increasing demand for mud crabs in the local Technology, Jashore, Bangladesh, had given ethical approval [13] incomeand international source [14, markets,15]. Crab most collection families and in fattening the greater are during(approval the number:present study FBST/JUST/AECA-4012/2018 followed the institutional guideDate:- alternativeKhulna area sources have chosen of income to grow and crabssustainable as their livelihood primary line,April following 02, 2018). the All international procedures andcarried national out involving guidelines. fish for the disadvantaged people in southwest Bangladesh. Despite tremendous opportunities, the mud crab trade is Study site subject to wild capture, mostly from coastal mangroves, S. olivacea crabs were collected primarily from estuaries and there is no absolute procedure for hatchery produc- tion [7]. As a result, the natural populations of mud crab (Fig. 1). For further study, mainly breeding aspects were are declining throughout southeast Asia due to over-ex- studiedand rivers in thenear Fisheries Paikgachha and upazilaMarine Biosciencein the Khulna laboratory district ploitation, loss of mangrove habitat, water pollution, and at Jashore University of Science and Technology. coastal environment degradation. Approximately, less than - Study period . For this cause, extensive management80% of the crab activities populations are speedilyare being needed caught beforefor the reach mud The study was carried out over a calendar year from April crabing the to firstsustain size its of population maturity [16] through over-exploitation. It month from the study site. to September 2018, and samples were collected each is essential to know the biological aspects about the mud Figure 1. Study area (Paikgachha upazila in Khulna district). http://bdvets.org/javar/ Paul et al. / J. Adv. Vet. Anim. Res., 8(1): 44–50, March 2021 45 Sample collection units during data processing. The processed data were then Live crabs were collected randomly from the estuary and datatransferred sheets towere a master correlated sheet with from computer which classified spreadsheets tables carried out monthly from April to September on each full towere ensure prepared data accuracy. to reveal the study’s findings. Preliminary river of Khulna and Shatkhira regions. The sampling was- Results and Discussion weremoon thenduring transported high tide. Aalive total to of the 240 Biology specimens Laboratory were sam of thepled Department where 53 individuals of Fisheries were and hermaphrodites. Marine Biosciences The crabs at Sex ratio Jashore University of Science and Technology for detailed biological study [17]. S. olivacea collected from the months of April to September Sex identification The sex ratio was analyzed basedS. onolivacea 187 specimens of - 2018. Out of 187 specimens of , 95 specimensTable 1). mine the sex. In male S. olivacea were male and 92 specimens were female. The total The abdominal flap of each crab was observed to deter The highest number of females was found in August, male:female ratio was determined to be 1:0.96 ( , the abdominal flap was narrower like a “V” shape, female crabs had a wider irregular abdomens (Fig. 2) . The female crab’s abdom- while the lowest was in September. Viswanathan et al. “U”-shaped abdomen, and hermaphrodite mud crabs had [23] recorded the sex ratio of males and females as 1:0.87, [18] and Rajendran [24] gradually the shape changes with its life stages. which is quite similar to the present study. Kannathasan inal flap is a little bit narrower at the first stage of life, and the southeast coast of the Bay of Bengal of India. Ali et al. Determination of sex ratio [25] recorded the sex ratio as 1:1.01 in which is in agreement with the present study. The ratio of males to females of the collected samples was observed the sex ratio of males and females as 1:0.94, estimated by the following formula : Maturity size Female crab (Nos) [19] The common minimum legal size used in many open Sex Ratio = Male crab (Nos) ) 27]. The current study found that thewater size mud at crabinitial fisheries maturation only for(M female) of female crabs was S. olivacea at least Where GSI = gonadosomatic index, GW = gonad weight, 50 50% maturity (M [26, ). Ali et al. [17] and TW = total body weight [17]. 50 ) to be approx- Investigating the breeding season was estimated at 82.36 mm (ICW) (Fig. 3 50 mmdetected (CW). that Similarly, the size M at first maturity (M Breeding season was determined by counting the mature wildimately Scylla 95.5 paramamosain mm CW, which was lay witnessed at a size inclass Thailand of 91–100 .
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