Research links dramatic declines in Chesapeake Bay oyster population to warmer winters — not overfishing

Warmer winters — not overfishing — have depleted Chesapeake Bay oyster populations in recent decades, according to scientists at the National Oceanic and Atmospheric Administration and the Maryland Department of Natural Resources.

Researchers link oyster declines to a weather pattern that brought warmer winters from the early 1980s into the early 2000s, and say the resulting warmer waters reduced reproduction rates, increased predation of juveniles and allowed deadly oyster diseases to thrive.


At the same time, fewer and fewer watermen were trawling bay waterways for oysters, researchers say.

It’s not just oysters — the changing environment affected clams, scallops and quahogs up and down the U.S. East Coast, according to the study authored by scientists at NOAA and DNR.


Researchers found that oyster harvests up and down the coast fell by 93 percent from 1980 to 2010. Meanwhile, the number of commercial fishermen hunting for shellfish fell by an average of 89 percent over a similar period.

In Maryland, the oyster harvest peaked at 3.4 million bushels in 1955, according to the study, published in the journal Marine Fisheries Review.

Over the two-decade period when winter temperatures warmed, the state’s oyster harvest fell from close to 3 million bushels to fewer than 150,000 bushels. Over that same stretch, the number of watermen harvesting oysters fell from more than 1,200 to fewer than 100.

The trend may be reversing, though. Cold winters have been more common in the mid-Atlantic and Northeast since the mid-2000s, allowing shellfish harvests to rebound somewhat, the researchers said.