The Race Is On to Stop an Armored Invader on the West Coast
Tribes and scientists are mounting an urgent trapping effort to keep European green crabs from devastating a corner of Puget Sound.They’re the thugs of the shoreline. European green crabs — aggressive, versatile and voracious — are one of the most destructive invasive species in the oceans. They hitched a ride to the East Coast on ships in the 1800s, and they’ve been devastating fisheries there ever since.
Now, they’re a growing problem on the West Coast. And one Native American tribe in Washington that relies heavily on fishing and aquaculture is trying to get a budding invasion under control before it’s too late.
“The first time I caught one, my stomach dropped,” said Sarah Grossman, a researcher working with the group, the Swinomish Indian Tribal Community, on Puget Sound.
Ms. Grossman, an environmental scientist with the tribe, and others went into action trapping after a volunteer spotted the first European green crab in Swinomish waters late last year.
Since that first crab was found, teams have set about a thousand traps and have only caught 11 more of the invaders. Still, members of the tribe and others worry about what might be lurking right under their noses. The Lummi Tribe, just to the north, went from having occasional one-off sightings to tens of thousands in a matter of years.
“We’re at a really delicate time with our shellfish,” said Joe Williams, a Swinomish fisherman who is working to restore traditional clam gardening in one of the tribe’s most lucrative and culturally important fishing locations. But populations of native clams have declined in recent decades as the environment has degraded. The green crabs pose yet another threat.
“We’re really anxious about it,” Mr. Williams said. “We just don’t know how strong they will grab on here.”
When they arrived on the East Coast in the early 1800s, the crabs rapidly took over, tearing up eelgrass beds and eating any shellfish, like mussels, clams and even juvenile lobsters, in their way. Today, they cost the eastern shellfish industry an estimated tens of millions of dollars each year.
The first ones on the West Coast were spotted in 1989, most likely delivered when larvae hitched a ride on a freighter. They took hold in San Francisco Bay and quickly made their way as far north as Vancouver Island. Now, they’re even booming in Alaska. Climate change and warmer waters, which the crabs thrive in, make the issue more urgent.
Washington State declared a state of emergency over the invasion in 2022. Ecologists, shellfish growers and volunteers are rushing to find and control the crabs before they wreak havoc. They’ve removed more than 1.9 million this year alone across the state.
It’s a daunting task: A full-on European green crab invasion has never been stopped. The best hope is to manage it.
“The hardest part is that we’ll never be like, ‘OK, we’re done,’” said Lindsey Parker, a biologist who leads Washington’s green crab response. “There are populations to the north and south of us, so it’ll always be a concern.”
Ms. Grossman and others with the Swinomish tribe knew the green crabs were coming. They had seen what happened to the Lummi Tribe. “It was so close to home for so long,” Mr. Williams said. “It was just a matter of time.”
The best weapon in the ecologists’ arsenal is trapping green crabs and removing them from the ecosystem. The more traps they set and the earlier they set them, the better.
“The sooner you get on a growing population, the easier it is to keep it low,” said Todd Gray, an environmental protection ecologist for the Tulalip Tribes, which also had a first detection of green crab in 2025. “That’s the goal of early detection.”
Despite the daunting task ahead, Steve Edwards, the Swinomish chairman, is cautiously optimistic.
“We’re going to learn more every year,” Mr. Edwards said. “Will we ever get ahead of it? I hope so. But I think it’s got to be a much bigger effort.”
In Willapa Bay in southwestern Washington, the situation is beyond early detection. It’s the worst-hit spot in the state. Of the 4.7 million crabs the state has removed since 2022, a majority were pulled from the shallow, 120-square-mile bay.
Emily Grason, a marine ecologist who since 2014 has managed the green crab response for Washington Sea Grant, an organization that fosters marine ecosystems, led the bay’s annual green crab checkup in August. She spent four days with her team in sucking sulfurous muck, setting and retrieving hundreds of mackerel-baited traps. (Fish chunks combined with the rotten-egg odor of the mud do not yield a pleasant smellscape.)
It’s essentially the same trapping technique Ms. Grossman uses in Swinomish waters, but when Dr. Grason’s colleagues checked their traps, the result was different. They were teeming with European green crabs.
The crabs look like the mud smells: a kind of yellowy-green, with 10 characteristic spines lining the front of their shells and imposing little claws. They look like they’d be good invaders.
Dr. Grason was neither surprised nor happy to see them. Finding crabs might help her understand how they’re spreading, but she’d rather never set sight on one in Washington waters again.
“If I could set traps every day of my life and not come up with green crabs in them, I would consider myself successful,” she said.
The researchers found nearly three times as many crabs as they had last year, as did trapping teams working at other spots around the bay. That consistent increase, despite an intense trapping effort to suppress the population, suggests the crabs’ population could be growing, although more work is needed to tease out nuances between population growth and trapping, Dr. Grason said.
Washington isn’t alone in its efforts. Alaska, California and British Columbia perform varying degrees of trapping. One tribal community in Alaska, Metlakatla, removes tens of thousands of European green crabs each year. Sea otters, if they’re around, can help, too. And on Vancouver Island, one of the crabs’ West Coast strongholds, hundreds of thousands are removed each year.
There is such a thing as too much trapping, though.
That’s because European green crabs are cannibalistic, routinely hunting and eating their own young. This, as researchers in California accidentally discovered with disastrous effects, turns out to be a critical form of population control. In an effort to eradicate the crabs from a beach north of San Francisco, researchers trapped and removed mostly adults, leaving hordes of young without adults to cannibalize them.
Instead of falling, the population shot up in what ecologists call overcompensation.
That served as a warning: Even best efforts to remove every last crab seem to be doomed. The most realistic outcome is control, not eradication.
“Our goals are really to just keep the populations of green crab at biologically insignificant levels,” Ms. Grossman said.
The trapping teams have to find the right balance of trapping enough to control the population without creating an overcompensation situation.
“I’m really excited that our team was able to get a jump on trapping early, ” Mr. Williams said, “so we’re not coming from really far behind.”
Still, he added, “we’ll just have to learn to live with them.”
