Invasive green crab could threaten marine life at Dungeness Spit

European green crab have been found in Dungeness Spit and pose a threat to native marine life.
European green crab have been found in Dungeness Spit and pose a threat to native marine life. Washington Department of Fish and Wildlife

A growing number of invasive European green crab have been found at Dungeness Spit, based on trapping done by the U.S. Fish and Wildlife Service.

Agency staff and volunteers at the Dungeness Spit National Wildlife Refuge captured 13 European green crab over the past two weeks as part of Washington Sea Grant’s Crab Team early detection program.

Such numbers indicate the crabs are more abundant at the spit near Sequim than at two other locations in Washington’s inland waters, where they also have been found.

The finds rekindle concern over the potential for damage to local marine life and shorelines.

The first discovery of the species in Washington waters occurred in August 2016 by Sea Grant Crab Team volunteers on San Juan Island. Shortly afterward, green crabs were found at the Padilla Bay National Estuarine Research Reserve near Mount Vernon.

Additional trapping and removal by the Sea Grant team, the Padilla Bay preserve, and the state Department of Fish and Wildlife showed that while the crabs were present, they were still rare.

“This is a very different situation,” Crab Team Program Coordinator Emily Grason said in a statement. “In Padilla Bay, the crabs we found were too far apart to find and mate with each other, but at Dungeness Spit, multiple crabs are being found at the same site, over successive days of trapping. This indicates a situation where the population could grow very quickly if we don’t intervene.”

The key to dealing with the invasive crabs is early detection and rapid response. The goal is to find isolated populations when they are still rare, and reduce or eliminate them, said Allen Pleus, Aquatic Invasive Species Unit lead with the state agency.

Staff at the wildlife refuge, working with the state agency and Crab Team, have already done follow-up trapping while working with local stakeholders to develop a plan for ongoing response and removal efforts.

European green crab is one of the most globally-successful invasive species, and established populations are problems in Australia, South Africa and the East Coast of the United States. Where abundant, the crabs have been blamed for damaging shellfish harvests and decimating sea grass beds.

In Washington, native organisms such as shore crabs, young Dungeness crabs and shellfish could be harmed by the invasive crabs.

Jeffrey P. Mayor: 253-597-8640

Get involved

Information: Citizens can help by keeping a lookout for European green crab when visiting salt marshes and pocket estuaries. For information on how to recognize the crab, and likely places to look, go to wsg.washington.edu/crabteam.

Reporting: Anyone who thinks they have found a green crab should leave the crab in place and email photographs to WSG Crab Team at crabteam@uw.edu.