The setting of spat of the edible oyster Crassostrea madrasensis on different kinds of spat collectors like oyster shells, wooden pieces, concrete pieces, concrete slabs, tiles, bamboo frames and coconut shells kept in Vaigai estuary at Athankarai was studied. It was observed that there was spat fall on concrete pieces with irregular surfaces given lime coating, on oyster shells given a coating of cement or lime and lime coated curved tiles. Oyster spat set in stray numbers on bamboo frames, Mangalore tiles and coconut shells, spat fall took place between January and April and generally only small numbers of spat were seen to set on spat collectors in the other periods of the year. Oysters attained an average size of 86.7 mm and a maximum of 110 mm at the end of one year. Average and maximum sizes of 89.6 mm and 130 mm were attained at the end of 14 months and growth of oysters was very much retarded late
