Puget Sound Shoreline, Rae A. McNally

European green crabs pose a threat to Puget Sound ’s thriving shellfish industry. Luckily, they’re not in the Sound yet. However, a 2006 study from Oregon State University predicts that small breeding populations of green crabs in estuaries in Oregon , Washington , British Columbia and even Southeast Alaska will continue to produce a supply of crab larvae through 2012.

These larvae will continue to put Puget Sound at risk.

European green crabs are native to Europe , as their name implies. These shore-dwelling crabs grow up to 3-inches across the carapace. The common name for this species is misleading—their color varies widely from dark green to light yellow.

What’s the problem?

In 1998, scientists discovered a small breeding population of European green crabs in Willapa Bay and Grays Harbor on the coast of Washington.

Small but mighty, European green crabs are voracious foragers and can easily open bivalve shellfish such as clams, oysters and mussels. In Humboldt Bay , Calif. , researchers reported a 40 percent drop in Manila clam harvest since the European green crab became established there in 1995.

 

Green crabs prey on Dungeness crabs of the same size or smaller. Because the two species both live in intertidal areas, green crabs may reduce populations of small juvenile Dungeness by preying on them.

The commercial Dungeness crab fishery is a multi-million dollar industry in Washington State as well as an important sport fishery.

Preventing green crabs from establishing in the first place is the most effective way to lessen the potential adverse effects that European green crabs could have on Dungeness crab populations.

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How did green crabs get to the Pacific Northwest?

Green crabs first arrived in California prior to 1990. By 2000, they had dispersed as far north as Port Eliza on the northern coast of Vancouver Island, B.C. Researchers believe these crabs arrived on the West Coast in ballast water, as hitchhikers with imported shellfish stock, or in their packing, and were dispersed by currents created during El Niño and La Niña years and other natural events.

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What’s being done in Washington State?

In the last several years, the Puget Sound Partnership’s Conservation and Recovery Plans have provided funding to support a volunteer monitoring effort for European green crabs. In 2006, more than 100 volunteers monitored about 80 sites along the Strait of Juan de Fuca and in Puget Sound . So far, no crabs have been found in Puget Sound waters.       

>> Learn more

For more information about ballast water management and the Puget Sound Partnership's Aquatic Nuisance Species Program, contact Kevin Anderson, 360.725.5452.

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HIGHLIGHTS
2006 Green Crab study from Oregon State University | PDF