Pond management

Size of pond and Pond construction

Crab fattening is carried out in ponds, cages or pens. Small ponds ranging from 0.1 to 0.5 ha in size with a water depth of 1.5 m are generally selected for the purpose. The pond should preferably have a sandy bottom. Bunds should have a minimum of 1.0 m width at the top to prevent crabs from escaping by borrowing through the bunds. Crabs are capable of climbing over the bunds, which is prevented by fixing overhanging fences on dykes. Fencing of height between 0.5 to 1.0 m over the dyke is done with materials like bamboo sticks, bamboo poles and knotless nets, asbestos sheets, fibreglass panels, etc. As the crabs are highly cannibalistic especially on freshly moulted animals, 'refugee cages' made out of hollow bamboo pieces, cement pipes or stones are placed inside the pond to minimise mortality.

Water supply and drainage

Water exchange is through tidal water. Sluice gates may be used to regulate the inflow and outflow of the tidal water. The sluice gates are fitted with bamboo screens to prevent the escape of crabs. In regions where tidal influence is less, sea water is pumped in.

Water management involves the following:

• Exchange of water having salinity of 10-35 ppt through the sluice gate.
• Maintenance of water quality (temperature 28-32oC, dissolved oxygen 5-7 ppm, pH 7.5 to 8.5, depth 0.5 - 1.0 m).
• Cleaning of the sluice screens once in a week to ensure a free-flow of water.

Pond management

The pond is prepared by draining out the water. The pond is then allowed to dry or bake in sunlight before the liming is done. The water is let in during the high tide or sea water is pumped in to a height of 1.5 m.