Keep an eye out for invasion of European green crab in Puget waters

Scientists are asking for help to keep the European green crab from invading Puget Sound in Washington state.
Scientists are asking for help to keep the European green crab from invading Puget Sound in Washington state. Courtesy to The Bellingham Herald

Scientists say they need help keeping a hungry green invader out of Whatcom County waterways and the Puget Sound.

It’s called the European green crab, and it isn’t wanted in Washington state because it is an aggressive eater of plants and critters its size and smaller. Considered one of the world’s worst invasive species, Carcinus maenas could prey on native shore crab, compete with native fish for food and hurt the shellfish industry here, according to marine researcher Washington Sea Grant at the University of Washington.

“They are voracious omnivores who will consume shellfish as well as clams,” said Jeff Adams, a marine ecologist with Washington Sea Grant.

The team includes volunteer citizen scientists who are being asked to help monitor the area’s shorelines, including pocket estuaries, for the unwanted crab during the summer. The monitoring effort also asks beachgoers to help out by keeping an eye out, and taking pictures of the predator if they suspect that they see one.

This is the first full season for the effort.

The European green crab hasn’t yet been found in the region – “That’s good,” Adams said – but there has been increased concern since 2012, when the first known colony of the crabs in the Salish Sea was found near Victoria, B.C.

They were discovered in Washington state waters in 1998, in Willapa Bay and Grays Harbor.

Officials don’t want them to become established and spread, so finding them early and eradicating them before their populations can get out of control are the goals.

They are native to the shores of the Baltic Sea and northeastern Atlantic Ocean, ranging from northern Africa to Norway and Iceland. They’ve been a problem on the East Coast, where they are multiplying and have been blamed for the collapse of the soft-shell clam industry in parts of Maine.

They were first found on the West Coast, in San Francisco Bay, in 1989. They then spread south to Monterey Bay and north to Humboldt Bay in California as well as Coos Bay in Oregon.

And then the strong, warm currents from the 1997-98 El Nino pushed them farther north into Washington state waters. Monitoring efforts are more crucial now than ever, officials said, because the last two years have been marked by some of the strongest El Niño conditions to date.

Crab monitoring

European green crab like a variety of coastal habitats and can thrive in wide ranges of temperature and salinity, especially muddy habitats such as salt marshes with deeply cut channels and sloughing banks, according to the Washington Sea Grant.

To help get more eyes out there, an online map has been created to show more than 400 places in the Puget Sound area as well as around the Strait of Juan de Fuca and the San Juan islands that could be suitable habitat for these shore crabs.

They include a few in Whatcom County, such as Sandy Point, Drayton Harbor and Post Point Lagoon.

If they come here, couldn’t we just take care of the problem by eating them?

Well, they’re much smaller than the native Northwest crabs we like to eat, such as Dungeness and red rock, Adams said.

They are edible, he said.

“Are they really desirable?” Adams said. “Not so much.”

Kie Relyea: 360-715-2234, @kierelyea

How to help

▪ Assist scientists by becoming a volunteer monitor. To do so, contact Jeff Adams at jaws@uw.edu or go to devseagrant.s.uw.edu/wordpress and type “Green Crab Monitoring Program” into the search window. Then select “Get Involved.”

▪ Report possible European green crab sightings by emailing crabteam@uw.edu. Attach photos, taken from different angles and distances, of the crab to the email. You will be contacted if more information is needed.

Green crab ID

Identifying the European green crab can be challenging, partly because the color of its top shell can vary widely. Plus, several native Northwest crabs are green, too.

Here’s what to look for:

▪ Adult green crabs are about 3 inches across at the widest part of their back shell, making them smaller than adult Dungeness and rock crabs.

▪ It’s the only crab likely to have five spines (or teeth) present from each eye to the widest point along the front edge of the back shell.

▪ Juveniles can change color to match their surroundings each time they molt. Adults are usually dark-greenish with yellow markings, and often have some orange at the joints. The underside of the crab is off-white, but can often be bright yellow or even red.

▪ Check out “Identifying Green Crabs” on the Crab Team website (https://wsg.washington.edu/greencrab) for more on how to recognize this species.