Growth and mortality of hatchery-reared bay scallops, Argopecten irradians, were determined over an 18 month period (July 1994-December 1995) at two locations in the Damariscotta River, Maine, north of its natural distribution. Growth occurred primarily between May and October when mean water temperature exceeded 10 °C. Final mean shell height (56.3 mm) was significantly greater (p ≤ 0.0005) at the upriver site than at the downriver site in association with a higher mean water temperature. Cumulative mortality (43-49%) over this period occurred primarily over the winter months, in conjunction with mean water temperatures below 5 °C. Although it is possible to rear bay scallops to commercial size in Maine, the short growing season, high winter mortality, and costs associated with over-wintering and fouling will likely deter commercial culture.