Global Warming and the Blue Crab

Blue Crab

There are few species more iconic or more important to Virginia than the blue crab. This species, a foundation for coastal Virginia’s economy, is a staple on the plates of many Virginians. However, recent reports have shown that blue crabs are projected to be detrimentally impacted by climate change in a way that can also wreak havoc on the sensitive Chesapeake Bay ecosystem.

Carbon pollution from burning coal, oil and gas is causing climate change that is threatening fish and wildlife across the globe and in Virginia. If we don’t make changes soon, Virginia will continue to have warmer temperatures in all seasons, an increase in the frequency, duration, and intensity of hurricanes and other severe weather events, as well as an increase in the sea level of up to 2 feet or more.

A Threatened Bay

The Chesapeake Bay is our nation's largest estuary and sustains more than 3,600 species of plants and animals. However, if global climate change continues unabated, projected rising sea levels and water and air temperatures will significantly reshape the region's coastal landscape, threatening recreational and commercial fishing including crabbing in Virginia. According to the National Oceanic and Atmospheric Administration’s Chesapeake Bay Office, the Bay shoreline is being affected at a faster rate than the global average because land in the region is already naturally subsiding.

The temperatures in the Bay have already increased by almost 2 degrees Fahrenheit since 1960 and are projected to continue to increase by an additional 3 to 10 degrees by 2100—an immense change that will have a dramatic effect on the estuary and the species it supports. Warming temperatures in the Chesapeake Bay are predicted to also greatly impact eelgrass, a seagrass that provides essential habitat for juvenile blue crabs. This impact was seen in 2005 as high Chesapeake temperatures caused a massive die-off of the seagrass.

Predator Meet Prey

Increased carbon pollution is expected to cause blue crabs to grow abnormally large shell, turning this species into large predators that could significantly alter the fragile Chesapeake ecosystem. Their main prey like oysters are expected to suffer from weaker, slower-growing shells due to acidic water conditions caused by the ocean absorbing more carbon dioxide. The larger, hungrier blue crabs will have the ability to eat many more oysters, potentially throwing the whole food chain out of whack. This shift in the predator-prey balance would harm efforts to rebuild the stocks of both species.

Impacts to Virginia's Economy

Virginia regional fishing and tourism industries rely heavily on both blue crabs and oysters as a summer food staple, with more than one third of the annual national blue crab catch coming from the Chesapeake Bay. The average annual commercial harvest of blue crab in the Bay area between 2000 and 2009 was over 55 million pounds, and the dockside value of the blue crab harvest Bay-wide in 2009 was approximately $78 million, making the blue crab the most economically important shellfish in the Bay area.

Although climate change is expected to lead to abnormally large blue crab shells, this does not mean the crab harvest will do well or that crab lovers will benefit. This is because studies have shown that the same conditions that lead to increased growth in crab shells also resulted in the production of less meat under those shells. As carbon-absorbing crabs put more energy into building larger shells, less energy goes into other critical life processes like tissue growth and reproduction.

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