The impact of farming of the edible oyster Crassostrea madrasensis on the sediment characteristics in Ashtamudi Lake was studied. The meat weight in the 25 m2 trestle (rack) farm with approximately 30,000 oysters was found to increase from 27 kg in March to 228 kg in September with a corresponding total shellon weight of 188 kg and 1431 kg respectively. The effect of farming on the top 1-5 cm and 5-10 cm column of the farm substrate was studied separately. Sediment in both the columns beneath the farm and the reference site (non-farm) in the estuary was predominated by fine sand (about 70%) followed by silt, clay and coarse sand. The average organic carbon content in the two sediment columns during the crop period were 0.87 (1-5 cm) and 0.73 (5-10 cm). Though there were variations in the sediment texture and organic carbon content between the farm and the reference sites the impact due to short term oyster farming on these parameters was not significant.

Oyster biomass, impact, sediment texture, silt, clay, coarse sand, organic carbon