SURVIVAL AND GROWTH OF CLAM AND OYSTER LARVAE AT DIFFERENT SALINITIES

Abstract

1. The optimum salinity for the development of straight-hinge larvae from eggs of clams from Long Island Sound is about 27.5 p.p.t. 2. The salinity range for development of eggs of these clams is from 20.0 p.p.t., at which salinity only 16 per cent to 21 per cent of the eggs develop, to 35.0 p.p.t., at which salinity only 1 per cent or less of the eggs develops normally. 3. The optimum salinity for growth of clam larvae after they reach the straight-hinge stage is 27.5 p.p.t. or higher, while 15.0 p.p.t. is the lowest salinity at which appreciable growth occurs, and 17.5 p.p.t. is the lowest at which we were successful in rearing clam larvae to metamorphosis. 4. Both the optimum salinity and the salinity range for the development of straight-hinge larvae from eggs of the American oyster appear to be governed by the salinity at which the parent oysters develop gonads. 5. The optimum salinity for the development of eggs of oysters from Long Island Sound, Peconic Bay, and Hodges Bar, Maryland was about 22.5 p.p.t. when these oysters developed gonads at a salinity of 26.0-27.0 p.p.t. 6. When Hodges Bar oysters developed gonads at a salinity of approximately 8.74 p.p.t. the optimum salinity for the development of their eggs was between 10.0 and 15.0 p.p.t. and appeared to be dependent upon the salinity at which the parent oysters were kept immediately prior to spawning. 7. The salinity range for development of normal straight-hinge larvae from eggs of these low salinity oysters was from 7.5 to 22.5 p.p.t., whereas the range for eggs from oysters conditioned at 26.0-27.0 p.p.t. was from 12.5 to above 35.0 p.p.t. 8. The optimum salinity for growth of larvae of Long Island Sound oysters, conditioned and spawned at 26.0-27.0 p.p.t., was 17.5 p.p.t. 9. The optimum salinity for growth of larvae of Hodges Bar oysters, conditioned and spawned at 26.0-27.0 p.p.t., appeared to be about 22.5 p.p.t. 10. It is still undetermined whether the optimum salinity for growth of larvae is influenced by the salinity at which the parent oysters develop gonads.