Mud crabs can be grown in pens installed in existing mangroves for up to 3 months. The pen can be rectangular, square or irregular shape and the size ranges from 500-1,000 m2. The use of net enclosures in mangroves offers an alternative to pond culture. It also promotes a better image for brackishwater aquaculture that had been linked to the historical clear-cutting of mangroves to make way to ponds.
Lean crabs may also be fattened using pens set in mangroves within 30-45 days. Mud crab pen culture is recommended in sites with mature mangrove trees in lower part of the intertidal zone.
- Enclose the selected area with bamboo slats or nets (durable enough that cannot be destroyed by crabs) with bamboo pole or wood support that are buried at least 50 cm in the soil. Consider an effective height of 2.0-2.5 m or higher than the highest tide in the site. Put an overhang of about 30 cm on top end of the fence.
- Allot about 20% of the total pen area for canals (0.5 m deep) to hold water during low tide. Dig canals in the middle, away from the bamboo partitions to prevent the crabs from escaping to the outside through deep burrows.
- Stock 200-300 g S. serrata or 100-150 g for S. olivacea and S. tranquebarica and grow them in 2-3 months. For fattening, stock lean crabs bigger than the above and fatten within 30-45 days. Stocking can be done in 3-4 consecutive days if quantity is not enough for stocking in one day.
- Feed crabs with fish and molluscs (snails, small bivalves, etc), animal entrails and/or corn (boiled) once or twice daily. Chop animal entrails or fish to the size appropriate to the mouth size of crab.
- Maintain good water exchange by ensuring that water flows in and out of the pen during each tide.
- Inspect canals. A depth of at least 0.5 m should be maintained to permit water to accumulate during low tide.
- Select and harvest market size crabs
- Harvest all crabs when they have reached market size. Tie and rinse crabs. Keep crabs in cool place.