ABSTRACT
Two species, the northern quahog Mercenaria and the southern M. campechiensis, family Veneridae, are extant and native only on the east coast of North America. Northern quahogs have several common names—hard clams, round clams, and hard shell clams as well as the trade names of littlenecks, chowders, necks, nicks, sharps, and blunts. The northern quahog has a thick shell with heart-shaped lunule longer than wide; the exterior has concentric growth ridges that are more distinct near the beaks. The central exterior of the shell becomes “smoothish”. Northern quahogs are found in salinities of 20 to 30‰ in mainly estuarine areas although they occasionally occur in higher and lower salinities. Winter mortality occurred in hatchery-reared seed of southern quahogs when planted in shallow estuarine areas of Virginia and North Carolina. The southern quahog has greater annual shell growth than the northern species, shown by experiments in which hatchery-reared seed of the two species were planted in the same area.
