ASSESSMENT OF FOOD AND FEEDING HABITS OF CLAM (Meretrix casta) FROM THREE DIFFERENT ESTUARINE ENVIRONMENTS OF TAMILNADU, SOUTH EAST COAST OF INDIA

The estuarine clam Meretrix casta (Gmelin, 1791) is considered as nutritional important to human food. The clams are bottom dwelling filter feeders, feeding on available organic matter of phytoplankton in water column is an important food source for suspension feeders such as bivalves. Therefore, direct observation of gut contents is needed to identify the feeding of bivalves.

The clams were collected and gut contents were identified from three different estuaries (Vellar estuary, Uppanar estuary and Pennaiyar estuary). The investigation showed that maximum numbers of food items were recorded during the post monsoon season in all the estuaries while a minimum numbers of food items were observed during the summer season. The gut contents of the clam M. casta, were identified from their food compositions as follows: Phytoplankton (85.93%)> others (Partially digested materials) (4.41%)> detritus (3.57%)> Unidentified particles (3.37%)> zooplankton (2.73%) in the Vellar Estuary and phytoplankton (84.18%)> others- (4.70%)> detritus (4.45%)> Unidentified particles (3.65%)> zooplankton (3.03%) in the Uppanar Estuary while in the Pennaiyar estuary, the composition of food items recorded as were phytoplankton (85.53%)> others (4.93%)> Unidentified particles (3.34%)> zooplankton (3.18%) > detritus (3.02%) respectively. The present study is reflecting important basic features of clam feeding behavior in estuary where phytoplankton as the main source of nutrition. Though, it is evidently observed that M. casta is an opportunistic filter feeder in its feeding habit and that intakes advantage of both benthic and planktonic food substances.