Invasive green crab found in new Olympic Peninsula location

European green crab like this one from Willapa Bay are a source of concern elsewhere in the Pacific Northwest, displacing native species. However, they have failed to achieve much success in the bay.

SEQUIM — A new population of invasive European green crab has been found at Dungeness Spit near Sequim, rekindling concern over the potential for damage to local marine life and shorelines, according to University of Washington News and Information.

Staff and volunteers from U.S. Fish and Wildlife Service, which manages Dungeness Spit National Wildlife Refuge, captured a total of 13 European green crab over the past two weeks as part of the UW-based Washington Sea Grant Crab Team early detection program. These numbers indicate that the invasive crabs are more abundant at Dungeness Spit than at the two other known locations in Washington’s inland waters.

On the state’s outer coast, the crab were first observed in Willapa Bay in 1998 and 1999, prompting a major interdiction effort that was eventually canceled in 2003 when the species showed little sign of prospering here.

“A few green crab continue to be caught [in Willapa] by researchers from Oregon State University and local shellfish growers, but not in any numbers showing an increase from previous years’ detections,” said Allen Pleus, the Washington Department of Fish and Wildlife’s aquatic invasive species unit lead. “All crabs caught appear to be periodic settlers from juveniles flushed up the coast during El Niño years.”

Pleus cited scientific research suggesting Willapa Bay has not supported a self-sustaining population due to a lack of relatively warm winters and the fact that the bay’s circulation patterns don’t keep larvae close to shore where they can land and settle.

However, elsewhere in the state, the crab continue to spark major worries.

The first discovery of this globally damaging invasive crab in Washington’s Salish Sea was made by Crab Team volunteers last August on San Juan Island, followed quickly by a detection at the Padilla Bay National Estuarine Research Reserve, near Mt. Vernon. In both cases, rapid-response trapping and removal by a joint-agency team showed that the crabs were present, but still very rare in those locations.

“This is a very different situation,” said Crab Team program coordinator Emily Grason. “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.”

Experts immediately responded to the initial detection with a rapid-response trapping effort and are currently working on a plan with local stakeholders for ongoing response and removal efforts for the area.

“Directly addressing the threat of green crab requires both early detection and rapid response, with the goal of finding isolated populations when they are still rare and reducing or eliminating them,” Pleus said.

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 U.S. In places where the crab has become abundant, it has been blamed for damaging shellfish harvests and decimating sea grass beds. Research on the West Coast has indicated that native organisms such as shore crabs, young Dungeness crabs and shellfish could be harmed by green crab.

Concerned 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, visit the Crab Team website: wsg.washington.edu/crabteam. Anyone who thinks they have found a green crab should leave the crab in place and email photographs to the Crab Team at crabteam@uw.edu.

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