Volunteers from the Washington Sea Grant Crab Team monitoring program discovered an invasive European Green Crab at Kala Point Lagoon on Sept. 8. 

This was the first European Green Crab found at Kala Point after four years of monitoring the site.

“We’ve done 21 sampling visits to this lagoon,” said Chris Jones, the leader of the Kala Point Lagoon crab team. “In 20.9 of those samplings, we didn’t see any green crab. And suddenly we pull this trap, and go, ‘What the heck is that?’” 

The team was shocked, surprised and worried, as the European Green Crab has been known to have devastating effects on habitats. 

“It was so much bigger than any one that I’ve ever seen … they actually grow larger here than they do in their native habitat in Europe,” said crab team member Wendy Feltham, who had seen European Green Crabs in their natural habitat on a trip to England. “We couldn’t believe it we were shocked. It was like looking for a needle in the haystack, and finding the needle.” 

The green crab, native to the coasts of Europe, has been found on the outer coast of Washington since the 1990s, but did not appear in the Salish Sea until 2012, when green crabs were discovered on the Canadian side of the Strait of Juan de Fuca. The Washington Sea Grant has been monitoring the shores of the Salish since then, searching for signs of invasion. 

“Since 2016, they’ve been found in small numbers in certain spots. The Dungeness Spit is the only site where we’ve found more than just a handful,” said Emily Grason, marine ecologist and crab team program manager. “That puts us at the early stages of a potential invasion.”

The West Coast Invasion

The green crab first appeared on the West Coast in the San Francisco Bay in 1989, according to the Washington Sea Grant website. It moved both south and north along the coast since then, and was sighted in Willapa Bay and Grays Harbor, as well as on the coast of Vancouver Island in 1998 and 1999. 

The European Green Crab has not just invaded the West Coast, but has also invaded coasts in Australia, South Africa and South America, as well as causing large amounts of damage to the East Coast of the United States and Canada, from Newfoundland down to South Carolina. 

The species was most likely introduced to non-native habitats by human dispersal. The crabs can travel in ballast water, which is water carried in ballast tanks that improves ship stability. They can also sometimes be trapped among packaging that is used to ship live seafood. Once the crab has been introduced to a habitat, they can spread easily during their larval stage of life. Green crab larvae can survive as plankton for up to 80 days, and are dispersed along the coast by ocean currents. 

“The population goes through boom and bust cycles,” Grason said. “For 20 years or so, green crabs were never found in the Salish Sea at all because of the currents in the Salish.”

Once the crabs enter a habitat, they can have devastating effects on the native species. 

“Their primary ecological role is as a predator,” Grason said. “They have damaged soft shell clam populations they compete with and consume native crab populations. The other main impact is they appear to really damage eelgrass beds and can make restoration really difficult.”

Green crabs feed on clams, oysters, mussels, marine worms and small crustaceans, as well as on juvenile crabs and shellfish, which could put native Dungeness crab, clam and oyster fisheries at risk. 

“Big news at Kala Point” 

That Saturday morning, Grason received a text from Jones, that may have sparked worry. 

“Big news at Kala Point,” wrote Jones. “I’ll call in a minute.” 

The crab team at Kala Point was in the middle of their last sampling of the season, which lasts from April to September, when they discovered the green crab among their traps. 

The crab team’s monthly research routine is a two day process. On the first day, the team sets out six crab traps in the lagoon with frozen mackerel as bait. Then, they do a shoreline survey, recording how many crab molts they find, and what the shoreline habitat looks like. That way, if green crabs are found in the area, they have a baseline for studying the effects of the crab on the habitat.

All citizen scientists, the crab team, which consists of 6 local volunteers, Wendy Feltham, Chris Jones, Lee Merrill, Eileen Cooney and Katherine Jensen, has been trained by Grason on what to look for when it comes to their crab search. Once the traps have soaked for 24 hours, they “count every little critter” in the traps, according to Jones. 

In the specialized research traps, the crab team catches anywhere from 500 to 1,000 crabs. Most of the crabs they find are small, about 1 inch long, and are native species. Most commonly found is the Hairy Shore Crab, which looks deceivingly similar to the European Green Crab.

“Lee always has a giant hand lens so we’re looking and passing it around. Sometimes we have to decide by consensus,” Feltham said. “But most of the time, we’re so familiar with the Hairy Shore Crab that we immediately sort through them.”

Crab teams like this exist all over the Salish Sea coastline, looking for green crabs and noting environmental changes. 

“We have 2,500 miles of shoreline in the Salish. We wanted to winnow down that 2,500 miles … so we looked for the best habitats for these critters to survive,” Grason said. “Muddy places like Kala Point Lagoon and the Dungeness Spit are more protective for the green crabs because the native crabs who might want to eat them don’t go in the muddy areas.”

When they found the green crab, the Kala Point crab team wrapped it in paper towels soaked with sea water, put it in a cooler and drove down to the ferry to meet Grason and hand over the crab. 

“It’s important that they get the crab live,” Jones said. “They can get much more accurate genetic samples from a live crab. Once you freeze it, it’s not useful scientifically.”

Next Steps

While the crab finding at Kala Point was not too surprising for Grason and the Washington Sea Grant researchers, it was still worrying.

“Any finding that is further and further in (the Salish) makes us really uncomfortable. Crabs getting in there are likely to survive,” Grason said.

Now that there has been a sighting, the Washington Department of Fish and Wildlife will step in and provide a deeper assessment of the area, with several days of intensive trapping. If no more green crabs are found in Kala Point Lagoon, then the crab team will rest easy for the winter, and begin their monitoring in April like normal. 

“If there are a lot of crabs found, then there will be a discussion about what trapping can be done to remove the species,” Grason said.

As for the crab team, they are happy to have been a help in the search for green crab invasion, and will continue to be citizen scientists in the future.

“I’m always worried about invasive species because most of the time invasive species cause problems, sometimes big problems, in nature,” Jones said. “I love being involved in any part of a scientific project where we’re actually making some tiny little difference out there in the scientific understanding of what’s going on.”

The crab team is also more aware of what devastation the green crab can bring to the environment.

“As part of our training, we saw places where the European Green Crab has completely gotten out of control,” Feltham said. “It’s destroyed ecosystems, it’s destroyed the biodiversity, ruined the clam industry, and we don’t want that to happen here.”

Finding Crabs

Unfortunately for most recreational beach goers, keeping an eye out for European Green Crabs, while helpful for researchers, is more complicated than it sounds. 

Firstly, distinguishing green crabs from native crabs is not simple. 

“The colors don’t really matter,” said Eileen Cooney, a member of the crab team. 

What distinguishes the green crab from native species such as Dungeness Crabs or Hairy Shore Crabs is the five spines found on the outside of the eye on the crab’s shell. 

“Green crabs aren’t really green,” Jones said.

However, even if someone is certain they have found a green crab, they should not pick it up, because it is illegal to possess the crab in Washington State. 

“This is a prohibited species in Washington,” Grason said. “If someone thinks they found one they have to leave it where it is. Then, they can email a photo or a couple photos to us and give detailed information about the location where they found it.” 

For more information about European Green Crabs, and what to do if you find one, visit wsg.washington.edu/crabteam.