Updates on the seed production of mud crab
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2015Author
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Abstract
Widespread interest in mud crab species is increasing because these are highly prized both in domestic and export markets. Among the three mud crab species commonly found in the Philippines, Scylla serrata, S. olivacea, and S. tranquebarica, S. serrata is preferred by farmers because it is larger and less aggressive than the other species. Likewise, S. serrata is the most widely distributed species in the Indo-west Pacific region.
Hatchery-produced seedstock are presently used by some crab farmers in their grow-out operations. In the hatchery phase, feeding mud crab larvae with shrimp formulated diets and natural food was found to reduce the occurrence of molt death syndrome, one of the major problems in seed production. Larvae given 25% formulated diet (FD) + 75% natural food (NF; rotifers and Artemia) and 50% FD + 50% NF showed better performance than those larvae fed 100% FD, 100% NF and 75% FD + 25% NF indicating that usage of natural food, especially the expensive Artemia, can be reduced. Since the early crab instar (C) produced in the hatchery need to be grown further before stocking in grow-out ponds, two phases of nursery culture have been developed. C1-2 are grown to 1.5-2.0 cm carapace width (CW) size in the first phase and further grown to 3.0-4.0 cm CW in the second phase. Nursery rearing is done in net cages installed in ponds for easy retrieval. A combination of mussel or trash fish and formulated diet is used as feed.
Domestication of the mud crab S. serrata as a prerequisite to selective breeding has been done at SEAFDEC/AQD. Likewise, defining criteria for the determination of quality of newly hatched zoeae for stocking in the hatchery was initiated. Newly hatched zoeae were subjected to starvation and stress test using formalin. Starvation failed to elicit responses that were significantly different between the good and poor quality larvae hence it is not suitable for larval quality evaluation. Based on three-year data, the formalin stress test gave mean cumulative mortalities of 2.38±0.32, 8.24±0.88, 20±1.58 in good quality larvae, and 43.74±2.39 while 22.93±4.19, 63.68±7.17, 84.29±3.88 and 97.65±1.06 for poor quality larvae at 0 (control), 20, 30 and 40 ppm formalin, respectively. As formalin level increased, cumulative larval mortality also increased regardless of the quality of the larvae. Formalin stress test proved to be a reliable method to determine whether a batch of newly hatched zoeae was of good or poor quality.
Suggested Citation
Quinitio, E. T., Parado-Estepa, F. D., Huervana, J. J., & Burlas, M. R. (2015). Updates on the seed production of mud crab. In M. R. R. Romana-Eguia, F. D. Parado-Estepa, N. D. Salayo, & M. J. H. Lebata-Ramos (Eds.), Resource Enhancement and Sustainable Aquaculture Practices in Southeast Asia: Challenges in Responsible Production of Aquatic Species: Proceedings of the International Workshop on Resource Enhancement and Sustainable Aquaculture Practices in Southeast Asia 2014 (RESA) (pp. 207-212). Tigbauan, Iloilo, Philippines: Aquaculture Dept., Southeast Asian Fisheries Development Center.
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Conference paperISBN
9789719931041Related items
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Mud crab production trials at the College of Fisheries and Marine Sciences, Aklan State University, New Washington, Aklan
(Aquaculture Department, Southeast Asian Fisheries Development Center, 2017)Two hatchery and nursery trials have been conducted at the College of Fisheries and Marine Sciences, Aklan State University (ASU) for the Multi-species Hatchery and Fishfarm Project from August to September 2014 and April to May 2015, in collaboration with the Aquaculture Department (AQD), Southeast Asian Fisheries Development Center (SEAFDEC) under the National Mud Crab Science and Technology Program of the PCAARRD-DOST. Two ASU staff underwent training on Mud Crab Hatchery, Nursery and Grow-out Operations at SEAFDEC/AQD from September to October 2013. This was followed by SEAFDEC/AQD’s provision of technical assistance during the actual hatchery and nursery operations using Scylla serrata at ASU. Survival rates of 3% and of 66-76% were recorded in the hatchery and nursery phases, respectively. The natural food consisting of rotifer and Artemia, and commercial formulated diet were fed to S. serrata larvae (zoea to megalopa). Juvenile crabs were fed formulated feeds and molluscs. Water temperature ranged from 27 to 30°C and salinity from 29 to 33 ppt in the hatchery. Initial results and insights are discussed and evaluated as guide for future hatchery and nursery protocols. -
Overview of the mud crab industry in the Philippines
Quinitio, Emilia T.
(Aquaculture Department, Southeast Asian Fisheries Development Center, 2017)
Mud crab farming has long been established in the Philippines and the country is the second top producer in the world. Except for Scylla paramamosain, the three other species, S. serrata, S. tranquebarica and S. olivacea are commonly found in the country, but S. serrata is the preferred species for farming. Crab seeds for farming are mainly from the wild and in recent years, a small percentage from the hatchery. Due to the apparent decline of the wild crab stocks, provincial and municipal ordinances have been issued by a number of Local Government Units (LGUs) along with the Bureau of Fisheries and Aquatic Resources (BFAR) to conserve and manage the remaining resources. From the hatchery, megalopa or crab instars are grown in net cages installed in the nursery pond. Mud crab farming engages mostly in long-term grow-out culture of juvenile crabs to market size for 3-5 months, short-term fattening of lean crabs for 15-45 days, and recently, soft-shell crab production. Polyculture of juvenile crabs to market size with one to three other commodities in earthen brackishwater ponds is usually practiced. Mud crabs for soft-shell crab production are mainly from the wild, while SEAFDEC/AQD demonstrates the use of hatchery-produced juvenile mud crabs as seedstock. Refinement is continuously being done to improve the economic viability of producing crabs, although basic technologies have been developed for all phases of culture (hatchery, nursery, grow-out, fattening and soft shell crab production). The major issues facing the industry are the lack of seedstock, difficulty of zoea 5 to molt to megalopa stage, cannibalism particularly at the nursery phase, species identification at the juvenile stage, use of fish as aquafeed, diseases, effects of climate change and quality of crabs at postharvest. In 2012, the Philippine Council for Agriculture, Aquatic and Natural Resources Research and Development (PCAARRD) of the Department of Science and Technology (DOST) started funding projects under the National Mud Crab Science and Technology Program (NMCSTP) to address these issues. The major aim of the Program was to improve the production, profitability and sustainability of crab farming. SEAFDEC/AQD leads in capacity building with focus on the sustainability of the mud crab industry. Various collaborations and research studies on mud crab culture enabled SEAFDEC/AQD to package mud crab technologies, conduct local and international training courses and on-site technology demonstrations, and publish extension manuals and scientific publications since the mid1990s. Research and Development activities have been translated into improved production. With the recent developments and refinements of technologies, it is expected that the Philippines will increase its production by 25-50% in the next 5 years. -
Use of rotifers-fed microalgal paste in the seed production of mangrove crab Scylla serrata in the Philippines
Huervana, Joana Joy; ; Villa-Franco, Annie (Springer, 2022-09-09)
Despite the progress in the production of artificial diets for marine larvae, feeding during the early life stages of most aquaculture species still relies on live feeds such as rotifers. Advanced rotifer culture techniques are also available, however, in the Philippines, majority use batch cultures with fresh microalgae. These microalgae are prone to collapse resulting to inadequate supply of food for the rotifers that are fed to the larvae. Mangrove crab is one of the economically important aquaculture species in the country where mass seed production requires sufficient and steady supply of rotifers. Thus, here we examined the possibility of substituting fresh culture of green microalgae Tetraselmis tetrathele (FA) with flocculated T. tetrathele paste (FP) and commercially available Tetraselmis sp. (CP) as feed for rotifers (Brachionus rotundiformis) in the seed production of mangrove crab. Rearing of larvae was done until crab instar 1 (DOC 24) where growth and survival were taken to evaluate the viability of rotifers-fed microalgal paste. It was observed that the growth index (FA–6.93 ± 0.07; FP–6.91 ± 0.07; CP–6.96 ± 0.05) was similar for all treatments (P > 0.05) at termination. Comparable survival rates were noted for FA and FP at 1.08 ± 0.59% and 3.21 ± 2.09%, respectively (P > 0.05) while a significantly higher survival (P < 0.05) was recorded for CP at 7.73 ± 1.90%. These findings suggest that the algal paste tested are potential alternatives to fresh microalgae and this technique could benefit hatchery operators who lack the capital for setting up the facility and technical skills to maintain microalgae production.
