Crab cannot be classified as fish, being an aquatic animal with arms like spanner used to catch prey and small legs. Crabs are in high demand not only in the local market but also have an high export value too. The special feature of crab is that it can be sold live, as they have the ability to live without water for hours together. As a result the freshness and taste can be preserved for a longer period and this make crab dishes tasty too and they are more popular than fishes. Two types of crabs are usually grown, one being the ‘Scylla serrate’ and the other ‘Scylla tranquebarica’. In these, there are crabs that have bigger in size and smaller ones. We can cultivate the small crabs and farm them in artificial ponds. Also crabs are cultivated in backwaters or places close to the back waters. The crabs that are having thinner shell and are small in size does not have demand in the market. But these crabs can be transformed through fattening process. For fattening, first we have to build cages using bamboo or wood and place it in the lake or pond. These cages have to be kept in water for almost 25 days. The small varieties of crab with thin shell and size are grown in these cages.
Earlier crab used to be just an aquatic animal caught from the sea or backwaters. But today crabs are cultivated commercially on a large scale.