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Fisheries > Culture Fisheries > Clams

Farming Systems

Selection of Farm Site

Clams are bottom cultured and this method is substrate specific. The occurrence of natural clam populations throws much light in selecting the site with particular reference to tide level, substratum and water salinity. The clam farms are located in estuaries, bays and other sheltered areas close to the shore. About 1-2 hours exposure at each low tide is desirable as it is easy to remove the predators. Clams are rarely grown in ponds.

The type of substratum preferred varies with the species. For example M. casta thrives well on sandy bottom, while A. granosa prefers mud flats. Also the salinity range tolerated differs between species. While V. cyprinoides prefers low-saline waters, few species tolerate prolonged high saline conditions. In areas subjected to heavy rains or freshwater drain from the land, clam farms are located in areas where there is little wave action. Areas prone to frequent changes of contour and vulnerable to pollution are avoided.

Bottom culture

The ground is leveled and cleared of predators such as boring gastropods, starfishes, crabs and skates. Bamboo poles are planted on the boundary of the farm as markers. The movements of the clams are limited and in many areas fencing is not necessary. At high tide, seed measuring 10-25 mm in length are taken in a boat and planted in the farm, taking care to get even disposal as far as possible. The stocking density varies with the species cultured and the size of the seed. In the case of A. granosa in 1000 to 2000/m2 are stocked and thinned more than once to achieve a final density of 300 to 600/m2. A stocking density of 400/m2 is suggested for 10 mm seed and 300/m2 for 20 mm seed.  

A recent development in clam culture is the use of 10 mm mesh synthetic netting as a measure of protection for young clams. After seeding the farm, the netting is laid and is held in stretched position by stakes driven into the substratum at the periphery of the farm. Except for watch and ward work and eradication of predators if they occur, no other maintenance job is necessary during the grow-out   phase. The clams are harvested after 5 or 6 months either by handpicking or by a hand operated dredge.

dredge

Dredge used for clam harvesting

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