Climate change, not overfishing, is devastating shellfish environments

Valuable species of shellfish have become harder to find on the East Coast because of degraded habitats caused by a warming environment, according to a pair of scientists that sought to find out whether environmental factors or overfishing was the source of the decline. The scientists reached the conclusion in studying the decline in the harvest of four commercially important species of shellfish in coastal areas from Maine to North Carolina — eastern oysters, northern quahogs, softshell clams, and northern bay scallops. They reported that their findings came down squarely on the side of a warming ocean environment and a changing climate, and not excessive harvest by fishermen. One of the ways warming has negatively impacted shellfish is by making them more susceptible to predators, said the lead author of the study, Clyde MacKenzie, a shellfish researcher for the National Oceanic and Atmospheric Administration. The scientists observed that the harvest of eastern oysters from Connecticut to Virginia fell from around 600,000 bushels in 1960 to less than 100,000 in 2005. The harvest of the four species declined from 1980 to 2010 after enjoying years of stability from 1950 to 1980, they found. The scientists reported that a positive shift in the North Atlantic Oscillation led to the degradation of shellfish habitat. The oscillation is an irregular fluctuation of atmospheric pressure that impacts weather and climate, which in turn affects things like reproduction and food availability for shellfish. The study mirrors what Maine clam harvesters are seeing on the state's tidal flats, said Chad Coffin, a clammer and the president of the Maine Clammers Association. Maine's harvest of softshell clams — the clams used to make fried clams and clam chowder — dwindled to its lowest point since 1930 last year. Some near-shore shellfish harvests in the U.S. remain consistently productive, such as the Maine sea scallop fishery, which takes place in bays and coastal areas in the winter. The state's scallop fishery bottomed out at about 33,000 pounds in 2005 but has climbed in recent years, and its 2017 total of almost 800,000 pounds was the most since 1997.