Sand gaper (Mya arenaria) is one of America’s most commercially important clam fisheries. This species inhabits intertidal zones and subtidal depths to almost 200m from Labrador, Canada through Florida along the east coast of the United States and in Western Europe from Norway to the Black Sea, and although its Western Atlantic range appears extensive, softshell clam populations are most abundant from Maine to the Chesapeake Bay. This species has been introduced along the Pacific coast of the United States, from Alaska through California and it is sometimes known commonly as the long-neck or steamer clam (MacKenzie 1997).

The softshell clam is a marine/estuarine bivalve species of the Family Myidae. This species attains a maximum shell length of about 15 cm (10-11 in the Chesapeake Bay), with an oval, elongated shell ranging from white to dark grey in color. Settlements are found in most temperate ecoregions of the Atlantic and Pacific oceans, most especially in the Cold Temperate Northwest Atlantic (CTNA) biogeographic province (Spalding et al. 2007)

However studies evaluating the genetic diversity of M. arenaria populations are scarce and show very little population differentiation across its natural distribution, St-Onge et al. (2012), showed the existence of six spatially distinct genetic clusters of M. arenaria subpopulations, five of which were situated exclusively within the Cold Temperate Northwest Atlantic (CTNA) province. For management purposes it is important to refer that the Lower Atlantic Canada and US Coasts clusters cover three distinct ecoregions each.