Coastal Aquaculture and Mariculture (2+1)

Unit 6 - Culture of Crustaceans

6.2.1. Culture methods

• Select a suitable site, free from pollution, year round brackish water supply. Best salinity is 18-30ppt, temperature 25-30^oC.
• Rectangular ponds 0.5 to 1 ha with water depths 0.6-1.0m are constructed. Shelters are provide for crabs to hide during moulting. They are placed in strategic places all over the pond. Canals and trenches also serve as hide outs.
• The ponds are drained and dried for two weeks. Piscicides are used to remove unwanted fish. To prevent crabs from escaping the ponds by crawling over bunds, install nylon net fencing of 1-2 mesh close to the perimeter of the ponds. Support the nets vertically using bamboo poles or wooden posts and horizontally with bamboo splits. Install plastic sheets along top edge of net fence.
• Grow natural food following methods used for fish/shrimp culture. Introduce water to a depth of 0.6-1.0m. One to two weeks after water culture stock the ponds with juveniles of size 30-40g at the rate of 5000-10000 per ha.
• If the juveniles are small nursery rearing in net cages placed in the ponds is necessary. Stock the ponds at the rate of 120 juveniles per square meter. Feed with trash fish/Acetes. Cover net cages with coconut fronds. Sort the stock every week and stock 5cm juveniles in grow-out ponds.
• Exchange 10-30% water every spring tide. Check for leaks in dikes, gates and net fence. Feed chopped trash fish, animal waste, snails etc. @ 10% biomass initially and gradually reduce to 6% as culture progresses. Feed twice a day in morning and evening. The feed may be placed in trays or broadcast. Monitor and maintain optimum water quality.
• Selectively harvest crabs more than 250g using scoop nets or traps. After 3-5 months when all the remaining crabs have attained marketable size harvest totally by draining the pond and hand picking of crabs.