Crabs are commonly cultured with fish in earthen brackishwater pond. Cannibalism in crabs is reduced by lowering the stocking density and maximizing the space by stocking fish. Common combination of crab is milkfish. Crabs (15 g to 30 g) are stocked in the pond with fish and grown for 3 to 5 months. The culture period depends on the initial size of crabs and fish and the stocking density. Two or more crops may be done in a year, depending on the desired crab size at harvest.
- Prepare pond using standard procedure. Grow natural food such as ‘lablab’, plankton and other natural food prior to stocking.
- Stock milkfish fingerlings at 2,000-3,000/ha and crab juveniles at 500-800/ha.
- Acclimate animals to pond water before stocking.
- Feed crabs with low value fish, mollusks (snails, small bivalves, etc), animal entrails and/or corn (boiled) once or twice daily. Give an initial feeding rate of 10% of total crab biomass, reduce to 7-8% and then 3-5% daily as the crabs grow older. Use the formula:
- Amount of feeds to be given = average body weight x total number of animals x % feeding rate
- Put chicken manure inside perforated bags set at equal distances within the pond to maintain growth of ‘lablab’ and other natural food for milkfish.
- Change about 30% of water every spring tide (new moon and full moon) or during high tide whenever necessary. Maintain water depth of at least 80 cm.
- Monitor the condition of the crabs and water in the pond regularly and undertake the necessary remedial measures.
- Select and harvest market size crabs. Selective harvest reduces competition for food and space, and cannibalism.
- Harvest the crabs by using lift nets with baits early in the morning. Crabs can also be collected by scooping while they congregate near the pond gate as water is allowed to enter during water change.
- Harvest totally when crabs and milkfish have reached market size.
- Tie and wash the crabs to remove the mud. Put milkfish in ice.