Invasive European crabs found at Annette Island

An invasive species with the potential to wreak havoc on important commercial and subsistence fisheries has been found in Alaska for the first time. Biologists with the Metlakatla Indian Community said they've found growing evidence of European green crabs at Annette Island.

Scientists said the crustaceans uproot eelgrass beds in search of food, which serve as habitat for herring and salmon. They also compete with native crab species and prey on other shellfish, including scallops and juvenile oysters.

Scientists had been looking for the crabs for years. And to their relief, they had come up empty. Then came the first troubling find on the beaches of Annette Island: three shells from European green crabs, discovered July 19..

"Well, everybody was pretty much shocked, I guess, is the best word," Dustin Winter, director of Metlakatla Indian Community's Fish and Wildlife department, said July 22.

Winter said the find, credited to Natalie Bennett, an intern with Sealaska Heritage Institute assisting with the program, was the first evidence of the invasive species' presence in Alaska.

After the first three shells were discovered on a beach, "five more carapaces and two fully intact juvenile carcasses were identified," Metlakatla Indian Community said in a statement.

Then came worse news. Monitors found 13 live green crabs in the waters around Annette Island. The Metlakatla Indian Community announced July 27 they had found 10 live crabs - four late last week and six on July 26. Then the mayor said three more crabs were caught on July 28, for a total of 13.

The crabs are largely falling into salmon traps around Tamgas Harbor.

The tribe has been working with the National Oceanic and Atmospheric Administration to monitor the seas and shores for signs of the crab. The crustaceans are two to four inches wide, not counting their legs, with spines on their heads.

Metlakatla biologists started setting traps in 2020 after a shell fragment was found in Haida Gwaii, an island chain off the coast of northern British Columbia.

"It started out kind of small, but it's turned into quite the project now," Winter said. "We have three, sometimes four, people working every other week, setting pots and pulling pots and recording what kind of crabs they're catching."

As of July 22, they still haven't located a live specimen, Winter said. But NOAA Fisheries biologist Linda Shaw said the discovery means it's time to take action.

"I think that it definitely is a reason for concern, but not any kind of panic. I think that it's a wake-up call that they are moving our way," she said. "They are detected here now, so we need to take it seriously, but we are not in the situation - yet - that Washington state is," Shaw said July 22.

In Washington, Gov. Jay Inslee declared an emergency in January over the state's green crab infestation. The state has spent millions fighting the spread of the species. Last year, the Lummi Nation, near Bellingham, reported capturing 70,000 during a five-month span.

"In the past year, their populations have exploded in Washington state and Oregon," Shaw said.

They're a particular threat to fellow shellfish, she said. "They compete with juvenile Dungeness crab. They are shellfish predators, so things like clams, they would directly eat," she said. "And then there's also anecdotal information from British Columbia that they predate on juvenile salmon."

Invasive European green crabs have been found in U.S. waters since the 19th century - scientists say their microscopic larvae likely hitched a ride in the ballast tanks of ships crossing the Atlantic. And they've hurt native species - the crabs are blamed for the decline of the soft-shell clam fishery in Maine.

They were first found on the West Coast in 1989 in San Francisco Bay and have been spreading north and south ever since.

Shaw said the crabs tend to spread with El Niño, the weather pattern characterized by higher-than-normal sea surface temperatures in the central and eastern Pacific. She said warming ocean temperatures associated with climate change also play a role.

"Warmer temperatures would allow for greater survival and reproductive timeframe," Shaw said. "If it's warmer, they have more chances to reproduce, they have better growth and they have a longer season to survive in."

Trapping the crabs is, for now, thought to be the most effective approach, the fisheries biologist said.

"Enclosed bays and areas are places where we might be able to do intensive trapping to, if not eradicate, at least control them, especially in areas where you have resources at risk that are important," Shaw said.

It's also important to know where the crabs are, so scientists are asking the public to keep an eye out for them. Though they're called green crabs, they're found in a variety of colors. Shaw said they're most identifiable by the spines on either side of their eyes.

"We like to say, 'find the five spines,'" Shaw said. "Green crab have five spines on either side, right and left, of their eyes, and then three bumps in the middle. And those are the only crabs in Alaska right now with those characteristics."

Officials are asking anyone who finds green crabs to report them to the Alaska Invasive Species Hotline at 1-877-INVASIV.

Additional reporting by KRBD's Raegan Miller.


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