In the present investigation, size dependent oxygen consumption rate (OCR) of estuarine clam Katelysia opima in relation to lowered salinity ranges (100% to 10%) was estimated seasonally. The sensitivity of clam K. opima increased with increase in size in summer season. During summer season, under low salinity stress conditions, increment in OCR was more prominent in medium (30-35 mm in length) and larger (40-45 mm in length)
size clams as compared with smaller size (20-25 mm in length); though time taken by all three sized clams for OCR stabilization was same. During post-monsoon season, larger clam entered the stress condition earlier than that of medium and small sized clam exposed to lower salinity ranges. Smaller clam delayed their response to lower salinity of their habitat during post monsoon season. Time taken by clams to acclimatize in salinity stress conditions is prolonged in smaller clam compared to medium and larger clams in K. opima during winter season. These results indicate that time taken by the clam K. opima for recovery and acclimatization differs with size of clam, range of lower salinity and season.

Katelysia opima, oxygen consumption rate, salinity, size groups, exposure period, seasons.