Blue Crabs and Chesapeake Bay Pollution

Dirty Waters Cause of Blue Crab Population Decline

Jan 2, 2009

A report from the Chesapeake Bay Foundation (CBF) describes how pollution is killing crabs.

A late December 2008 report from the Chesapeake Bay’s leading policy and advocacy organization states that pollution has been a major factor in the decline of the Bay’s blue crab population. The blue crab population has plummeted from 791 million in 1990 to 260 million in 2007.

The report is the most comprehensive assessment of pollution’s impact on the Chesapeake Bay’s blue crab and was developed based on interviews with 12 leading researchers and water quality experts. The report also contains information from government data sources and scientific papers.

Key Findings of Bad Waters Report

The key finding of the Report, Bad Water and the Decline of Blue Crabs in the Chesapeake Bay, is that dead zones kill an estimated 75,000 tons of bottom-dwelling clams and worms each year, enough to feed 60 million crabs annually. Dead zones are the result of nitrogen and phosphorus pollution which feeds algae and causes it to grow in massive "blooms." When the algal blooms die and the dead growth falls to the bottom of waterways, its decomposition uses a lot of oxygen. Bottom-dwelling species are victims of oxygen starvation.

In addition, murky waters that result from algal blooms and sediment runoff from roads, building sites, and other impervious surfaces don't allow light to penetrate to underwater grasses that need sunlight to promote their growth. Such underwater grass provides key habitat for crabs, especially juveniles, to eat, reproduce, and hide from predators. More than half the eelgrass beds in the lower Bay have died since the early 1970s.

The Commerce Department has declared the Chesapeake Bay crab fishery an economic disaster. CBF President William C. Baker says that it is now well past time for the federal Environmental Protection Agency to do its job. He asks that they bring forward a plan to enforce the Clean Water Act and reduce Bay pollution to levels that will restore water quality. “It’s not just the crabs that are suffering; people are. Jobs have been lost and the economy has been damaged.”

Loss of an Icon

Blue Crabs are a signature local food specialty. Many regional restaurants have built their reputation around Old Bay-seasoned crab cakes, buttery sautéed lump meat, and succulent soft shell crab dishes. The decline threatens the industry from waterman to restaurateur. Tourism officials also tout Chesapeake Bay seafood.

According to the Virginia Institute of Marine Science (VIMS), jobs relating to crabbing in Maryland and Virginia fell 40 percent between 1998 and 2006. VIMS estimates the economic cost to Maryland and Virginia restaurants, crab processors and wholesalers was about $640 million over the same time period.

Fisheries Management

Past fisheries management decisions in Maryland and Virginia are also to blame for the falling population. Policies have allowed more crabs to be harvested than scientists say are necessary to maintain the population. Even so, better management cannot ensure robust numbers of blue crabs if the waters continue to be so polluted.

Last Word

In the final section of CBF’s Bad Waters 2008, the reporters noted that, “a court threw out recent federal clean air rules.” In late December, the U.S. Court of Appeals for the District of Columbia allowed the rules to stand until they can be rewritten by the EPA or the underlying law can be changed by Congress.