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Shorter, warmer winters could lead to longer blue crab season

Solomons, MD — Scientists from the University of Maryland Center for Environmental Science are predicting that warmer winters in the Chesapeake Bay will likely lead to longer and more productive seasons for Maryland’s favorite summer crustacean, the blue crab.

Researchers examined data on increasing temperatures in the Chesapeake Bay and predictions for continued warming. They found that winters will be up to 50% shorter by 2100, and overwinter survival of the blue crab will increase by at least 20% compared to current conditions.

“Blue crabs are a climate change winner in the bay. As the bay gets warmer they will do better because they are a more tropical species,” said study co-author and Professor Tom Miller of the University of Maryland Center for Environmental Science. “We always hear about those species that are going to struggle or move. Blue crab are going to do better.”

The blue crab is found along the Atlantic Coast from New England to Argentina. Maryland’s blue crabs spend their winters dormant in the muddy sediment at the bottom of the Chesapeake Bay, emerging only when water temperatures near 50° F. In recent years, this dormancy period has been becoming shorter, and trends indicate it will become shorter still—and could potentially become nonexistent.

“Water temperatures are warming and the crabs are cold blooded so their metabolic rate is directly related to warmer temperature. Warmer water means they grow faster,” said Hillary Lane Glandon, who conducted this research as a graduate student at the University of Maryland Center for Environmental Science and is now a post-doctoral research associate at the University of North Carolina in Wilmington.

Scientists predict that the shortening of winter combined with increases in average wintertime temperatures will cause a significant increase in juvenile blue crab winter survival so that the population behavior comes to resemble that currently observed in the Sounds of North Carolina and further south.

“In 100 years, we would expect winter for crabs in Solomons to look more like winter currently looks in southern North Carolina,” said Glandon. “No winter for the crabs.”

While this may sound great, don’t stock up on your mallets and Old Bay yet.

Crabbing is prohibited December through March in the lower Chesapeake Bay, which has helped in maintaining the population at sustainable levels. However, an increase in wintertime crab activity may encourage a lengthening of crabbing season similar to states such as North Carolina and Louisiana, where crabs are active year-round.

“People will be able to fish for them almost year-round. However, this challenges the traditional pattern in which waterman fish for striped bass in the spring and crabs in the summer and oysters in the winter—that traditional seasonal rotation of the harvest. It’s a cultural challenge,” said Miller.

Climate change not only signals warming temperatures but also increased variability in temperatures, further complicating wintertime management of the species. A particularly cold winter could devastate a year-round fishery.

“If crabs start moving and feeding year-round, they represent an added predation pressures on the bay’s ecosystem, and we don’t know how the ecosystem will respond,” said Miller.

The University of Maryland Center for Environmental Science (UMCES) is a leading research and educational institution working to understand and manage the world’s resources. From a network of laboratories spanning from the Allegheny Mountains to the Atlantic Ocean, UMCES scientists provide sound advice to help state and national leaders manage the environment and prepare future scientists to meet the global challenges of the 21st century. 

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