How long does it take for a mud crab to grow to legal size?
Ponds can be constructed in tide-fed estuaries, backwaters and creeks. The crab ponds are established in traditional fish/shrimp farms, by converting one portion adjoining the brackishwater canal, as shown in Plate 2 A & Fig.2 A., which would help increase the overall income of traditional fish/shrimp farmers.
Earthen ponds of 0.1 to 0.4 lia in size and rectangular in shape having a sandy or muddy or clay loamy bottom soil are constructed with a minimal digging, which provides ample soil for bund construction. The wider axis of the pond may face the backwater canal in order to liave a greater tidal effect through a traditional wooden sluice.
Before stocking, the ponds are prepared by removing unwanted organisms by netting. To prevent the escape of stocked crabs from the pond, fencing with suitable materials such as casuarina poles, bamboo split matting, G.I.chicken wire mesh, nylon netting and asbestos sheet to a height of 1 m is erected either in the inner edge of the pond (Plate 2 B & Plate 3 A & B) or on the top of the earthen bund. The fencing may be positioned at 45 degree angle towards the inner side of the pond, which will prevent the climbing and escape of small crabs. Since mud crabs are highly cannibalistic, earthen and PVC pipes and wom-out tyres may be placed as hide-outs/shelters to reduce the fighting among the normal hard crabs and mortality of the soft "water crabs". A row of earthen mounds may be constructed in such a way that they remain submerged during the high tide and exposed during the low tide, in order to serve as natural habitat.
Since there is no dependable hatche it technology available for mud crab seed production, tlie stocking material at all sizes has to be collected from wild using nylon drag net, cast net, lift net and bamboo trap. The young crabs abound in estuaries, mangroves, backwaters, brackishwater lakes and creeks. The other source for small crabs and "water crabs" in live condition is from the commercial catches.
Crabs with a size range of 8G to 100 g may be stocked at a rate of 1 to 5 per square metre, depending upon their availability.
The reared crabs are fed once in a day, preferably in the late evening either with trash fish or molluscan meat (bivalve/gastropod) at a rate of 5 to 10 % of stocked biomass, depending upon the observed feeding intensity and the size recorded at regular and periodical sampling of the reared crabs.