Farming of mud crabs: First ever application of feed pellets with reassuring results.

Abstract

the freshly moulted crab. During this period the water crabs are fed with the natural feed materials The potential for culture of mud crabs in India is enormous. However, at present there is only a limited extent of mud crab grow-out culture, besides fattening and soft shell culture in certain parts of the country. The mud crabs Scylla manquebarica and Scylla serrata are the most popular brackishwater crab species available in India. Md crabs are farmed in traditional shrimp raising fields in the States Andhra Pradesh, West Bengal, Berala, Karnataka and Tamil Nadu. The production in these natural fields is reported to be 10-35 kg/ ha/yr. Juvenile mud crabs are also collected from natural resources and farmed on a small scale in earthen ponds with fencing and in cages made of bamboo material. They are stocked at the rate of 1-2 mo/m2 and fed with natural feed materials like trash fish, clam meat, and animal wastes from butchers' shops in fresh condition. Mud crabs are also farmed along with milkfish and grey mullets in some pockets (Kathirvel et al., 2004). In addition, fattening of soft, post-moulted mud crabs that are known as water crabs are also practised in earthen ponds and cages. The fattening is only for a period of 25-30 days just to harden mentioned above. Once they become hard they are harvested and sold in live condition for export. Production of soft shell crabs for a mixed consumer market using grow-out crabs to the moulting stage in cages with formulated feeds is being carried out by Water Base Limited. Except for soft shell crabs, all the grow-out culture is based on natural feed materials. With the availability of hatchery produced crablets, the limitation for wider adoption of grow-out farming will depend on the availability of low cost feeds. The present report presents results of formulated pellet feeds used for fattening and normal farming of mud crabs in grow-out ponds for the first time, in India. A formulated pellet consisting of trash fish, mantis shrimp, shrimp meal, soybean meal, fish oil, wheat flour and other additives and binder (proximate composition given in Table 1) was developed for feeding mud crabs based on laboratory experiments. The feed was processed by grinding the ingredients in a micro-pulveriser and homogenising in a mixer and pelletised in a ring-die pellet mill at 95-100° C having three stage steam conditioning using 6 mm diameter die. The length of the pellets was in the range of 5-8 mm. The pellets were subjected to post- pellet condition for 20 minutes. The dry pellets were in tact in water for more than four hours.