Bay Scallops and Eelgrass

Long Island Sound eelgrass. Photo/Cornell Cooperative Extension Marine Program/SeagrassLI.org
Long Island Sound eelgrass. Photo/Cornell Cooperative Extension Marine Program/SeagrassLI.org

The following information was provided by SeagrassLI.com, a website of the Cornell University Cooperative Extension of Suffolk County. SeagrassLI.com is dedicated to the restoration of Long Island eelgrass.

The story of the Long Island bay scallop can’t be told without mention of eelgrass, as the 2 populations share a history. Not surprisingly, when epidemics such as the eelgrass Wasting Disease of the early 1930s and the brown tide blooms of the 1980s occurred on Long Island, resulting in large-scale die-offs of eelgrass, bay scallop populations also plunged. “In 1982, the harvest of 500,000 pounds of bay scallops from the Peconic Estuary accounted for 28% of all U.S. commercial landings and had a dockside value of $1.8 million. After the appearance of the brown tide in 1985, the bay scallop population was virtually eliminated. Through restoration efforts, Cornell Cooperative Extension is working diligently to bring both of these populations back to pre-brown-tide levels.

Bay scallop, Argopecten irradians. Photo/Cornell Cooperative Extension Marine Program/SeagrassLI.org
Bay scallop, Argopecten irradians. Photo/Cornell Cooperative Extension Marine Program/SeagrassLI.org

Arguably, the most important role eelgrass plays in the life history of the bay scallop is the structure and protection it provides during its post-larval phase. Although other substrates and structures (including stones, shells and algae) can be used as attachment sites for “spat” or settled scallops, eelgrass has long been documented as their preferred habitat. Juvenile bay scallops use byssal threads to attach themselves onto elevated portions of eelgrass blades, staying out of reach from crabs, whelks, and other benthic (sea floor) predators.

The scallop spat that attach to the upper canopy of eelgrass (20-35 cm above bottom) have a significantly greater chance of surviving compared to those at the base of the eelgrass shoots or on unvegetated bottom. Also, there is a direct relationship between eelgrass density and scallop survival, which means that the denser the eelgrass, the higher the chances of scallop survival.

Adult scallops are also protected by eelgrass. For example, large, above-water predators like sea gulls have a hard time pinpointing an adult scallop within an eelgrass meadow opposed to one on a sandy bottom. The presence of a continuous eelgrass meadow can also help prevent adult scallops from being washed up on shore during a storm.

Learn more about the relationship between bay scallops and eelgrass.