Mud crab nursery rearing practices
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The need for seeds for expansion of the mud crab industry led to the development of the hatchery technology. The nursery technology was developed as this served as a link between the hatchery, which produces megalopae or early crab instars, and the grow-out phase which requires bigger crab juveniles for a higher yield. The nursery has two phases, the first ending with production of crablets with 1- 1.5 cm carapace width (CW) and the second phase with crablets of 2.5-3.0 cm ICW. The more commonly recommended system employs stocking of megalopae or crab instars in net cages installed in ponds. Locally available unprocessed food and commercially available shrimp formulated diet are used for feeding. However, recent studies have successfully used formulated nursery diet for mud crab. One of the main problems in the nursery is cannibalism, and several strategies have been investigated and tried to address the problem.
Parado-Estepa, F. D., Quinitio, E. T., & Rodriguez, E. M. (2015). Mud crab nursery rearing practices. In E. T. Quinitio, F. D. Parado-Estepa, Y. C. Thampi Sam Raj, & A. Mandal (Eds.), Proceedings of the International Seminar-Workshop on Mud Crab Aquaculture and Fisheries Management, 10-12 April 2013, Tamil Nadu, India (pp. 89-92). Tamil Nadu, India: Rajiv Gandhi Centre for Aquaculture (MPEDA).
PublisherRajiv Gandhi Centre for Aquaculture (MPEDA)
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BookEJ Tobias-Quinitio, GXS Libunao, FD Parado-Estepa & AT Calpe - 2015 - Aquaculture Department, Southeast Asian Fisheries Development Center; Philippine Council for Agriculture, Aquatic and Natural Resources Research and Development (PCAARRD)
Series: Aquaculture extension manual; No. 61"The production of soft-shell crabs is well established in other Asian countries but its sustainability is already being threatened due to the decreasing mud crab population in the wild where the seedstocks are sourced. In the Philippines, production of soft-shell crabs has only been practiced recently due to lack of seedstock and technology. Sourcing of crablets from the natural environment is not encouraged due to dwindling populations of all sizes of mud crabs. Instead, it is recommended that crablets for soft-shell crab production come from hatcheries. The project on soft-shell mud crab production at SEAFDEC/AQD started in 2012 and was later funded by the Philippine Council for Agriculture, Aquatic and Natural Resources Research and Development of the Department of Science and Technology. The project is adopting the individual crab culture sytem of Thailand and Myanmar in pilot-scale and uses hatchery-reared crablets grown to 60-100 g in earthen ponds and stocked in trays. The pilotscale soft-shell production set-up is showcased at the Dumangas Brackishwater Station of SEAFDEC/AQD using crab boxes available in the country. Various sectors are interested to learn how soft-shell crabs are produced. Hence, the previous manual on Soft-shell Mud Crab Farming by Emilia T. Quinitio and May Myat Noe Lwin published in 2009 was revised to include the recent refinements using hatchery-reared crabs and locally available materials. This manual includes sections on the biology of mud crab, how to set-up the facility, management of soft-shell crab production and the cost and return analysis. We hope that various sectors will benefit from this revised manual" -- Foreword
Conference paperK Ganesh, GK Dinakaran, T Sundaresan, K Satheesh Kumar, KV Gangadharan, S Viswanathan, S Pandiarajan & YC Thampi Sam Raj - In ET Quinitio, FDP Estepa, YC Thampi Sam Raj & A Mandal (Eds.), Proceedings of the International Seminar-Workshop on Mud Crab Aquaculture and Fisheries Management, 10-12 April 2013, Tamil Nadu, India, 2015 - Rajiv Gandhi Centre for Aquaculture (MPEDA)Soft-shell crab production is being practiced in many Asian countries but the major source of seedstock is from the wild, which could no longer sustain the increasing demand. Commercial scale soft-shell crab production can become sustainable only if there is a continuous supply of seedstock not dependent on wild stock. Rajiv Gandhi Centre for Aquaculture (RGCA) under the Marine Products Export Development Authority (MPEDA) has established a pilot-scale mud crab hatchery at Thoduvai, Nagapattinam District, Tamilnadu in 2004 with the technical assistance from SEAFDEC/AQD. At present, RGCA has the biggest mud crab hatchery in India and a demonstration farm at Karaikal, U.T. of Puducherry, where nursery rearing, grow-out and soft-shell crab production are conducted using hatchery- produced mangrove crabs or mud crabs, Scylla serrata. This paper presents the results of the soft-shell crab production using hatcheryproduced S. serrata juveniles maintained in perforated low density polyethylene (LDPE) boxes. The duration of the molt interval, time of molt (day or night) and the increase in body weight and carapace width of each size group (40-60, 61-80, 81-100, 101-120, 121-140, 141-160, 161-180 g) after molting were determined.Results showed that the percentage increase in body weight and carapace width increased as the crabs grew bigger. Likewise, the molt interval was longer in bigger-sized groups of crabs. Sixty to seventy percent of the population molted during night time and the next molt occurred within 25 days in 80-160 g size groups. Soft-shell crabs in boxes within the water surface and juvenile crabs (2.5 cm CW initial size) for culture until market size in the pond can be a viable technology technology for mud crab growers.
Monosex culture of the mud crab Scylla serrata at three stocking densities with Gracilaria as crab shelter AT Triño, OM Millamena & CP Keenan - In CP Keenan & A Blackshaw (Eds.), Mud Crab Aquaculture and Biology. Proceedings of an International Scientific Forum, 21-24 April 1997, Darwin, Australia, 1999 - Australian Centre for International Agricultural ResearchThe effects of three levels of stocking density (0.5, 1.5 or 3.0/m2) and monosex culture (male or female) on the growth, survival and production of Scylla serrata were investigated. Juvenile crabs were stocked in 150 m2 enclosures in earthen ponds with Gracilaria as shelter and fed a mixed diet of 75% fresh brown mussel flesh and 25% fish bycatch. There was no interaction between stocking density levels and monosex culture (P<0.05) so the data were pooled for each sex or stocking density treatment. Results showed that highest survival was obtained from a stocking density of 0.5/m2 (P<0.05). Crab growth at different stocking densities was not significantly different (P>0.05). Highest return on investment (ROI) and lowest production costs were attained from 0.5/m2. Partial budgeting analysis showed that no net benefit accrued from stocking beyond 1.5/m2. Male crabs attained significantly better (P<0.05) final weight and specific growth rate than female crabs. Length, width, survival and production between male and female crabs were not significantly different (P>0.05). Male and female monoculture gave high net revenue and ROI of more than 100 but male monoculture is more profitable. Overall the results suggest that the culture of male or female mud crabs at 0.5–1.5/m2 with Gracilaria is economically viable.