Species Profiles: Life Histories and Environmental Requirements of Coastal Fishes and Invertebrates (North Atlantic): Softshell Clam.

Abstract : The softshell clam, Mya arenaria, is a commercially and recreationally important invertebrate that inhabits the bottom sediments of subtidal and intertidal waters of moderate to high salinity. Its range is limited by water temperatures too low for reproduction in the north and by lethal warm temperatures in the south. Clams feed by siphoning seawater and removing food particles, especially phytoplankton, with their gills. Clams are therefore sensitive to factors affecting water quality, including suspended sediments, salinity, water temperature, oxygen, and waterborne pollutants. The clam life cycle consists of mass spawning and external fertilization, the development of pelagic larvae, settlement and metamorphosis into spat, and rapid juvenile growth to maturity. Clam recruitment and the migration of spat are dependent upon inshore currents. High morality of eggs, larvae, and spat is largely offset by high reproductive potential. As the clam grows, it finds refuge most predators deep in the sediments, but it also loses its ability to burrow and is subject to suffocation by siltation. Sediment types, currents, and tidal heights all affect clam growth rates. Keywords: Estuaries, Fisheries, Shellfish, Salinity, Temperature, Feeding habits, Contaminants, Oxygen.