The ongoing story of the European green crab invasion offers us scientific, social and even psychological drama, which I would like to update by mentioning four new developments:
- The somewhat mysterious finding of a partially eaten green crab on the Bellingham waterfront,
- A “story map” that spells out much of what we know about European green crabs in Puget Sound, including maps, photos and videos.
- Information about Harper Estuary in South Kitsap and other areas where groups of citizen scientists are on the lookout for green crabs, and
- Reports of a new breed of European green crab in Maine that attacks people and may prove to be more destructive than the green crabs that have lived in the area for a very long time.
Green crab found in Bellingham
Since my last report on green crabs (Water Ways, May 9), a partially eaten carcass of an invasive crab was spotted along the Bellingham waterfront in Squalicum Harbor, where the crab was being eaten by a seagull.
Photo: Angela Foster/WDFW
The big question, which might never be answered, is where did this crab come from? If it grew up locally, it would be the first sign of a green crab anywhere in Whatcom County. Since 2016, a trapping program designed specifically to catch green crabs — including two monitoring stations near Bellingham — has turned up no green crabs in the area.
The seagull could have caught the crab from the bay or nearby shorelines, or sport or commercial crab harvesters could have dumped the crab from their pots, according to Emily Grason, who manages the Crab Team volunteer trapping effort for Washington Sea Grant.
Casey Pruett, director of Marine Life Center in Bellingham, spotted the gull eating the crab at the boat ramp adjacent to the center in the busy Squalicum Harbor marina, Emily noted. Casey told her that green crabs have never been reported in crab pots in the harbor nor along the shoreline.
Marinas are often home to large Dungeness and rock crabs, which are good competitors and even predators of green crab, Emily wrote in the Crab Team Blog.
“In our region, green crab tend to do best in very muddy isolated habitats, such as saltwater lagoons, pocket estuaries and salt marshes,” she wrote. “If green crab become abundant enough elsewhere, however, some population spillover could occur into habitats like marinas where they have lower survivorship.”
The hunt for European green crabs throughout Puget Sound is meant to provide an early warning to hold the population in check wherever the invaders first show up. On the East Coast, where the crabs have become established, they have been known to eat large numbers of shellfish and destroy important habitat, such as eelgrass beds.
The single partially eaten crab in Bellingham has set off cautionary alarm bells, but since the discovery at the end of May, the monitoring traps have captured no other green crabs. Washington Department of Fish and Wildlife is planning a more extensive trapping effort next month, Emily told me.
Meanwhile, 44 green crabs have been trapped so far this season along Dungeness Bay near Sequim, which has turned out to be a hotbed of invaders. That number is fairly close to what was seen during the same time period the past two years, so we can hope that the population is not expanding. Another single crab was trapped in nearby Sequim Bay, but a more extensive trapping effort turned up no additional green crabs.
Green crab “story map”
In a new “story map” produced in a collaboration between Puget Sound Institute and Washington Sea Grant, the viewer is able to scroll through text, maps and video that explains what researchers know about the European green crab invasion.
An entertaining and instructive video from 2016 recounts the first sighting of a green crab in Puget Sound, following years of trapping that thankfully never caught a green crab. The video was produced by Katie Campbell of EarthFix, a partnership of public radio and television stations in the Northwest. A second video, produced in 2017 by the College of the Environment at the University of Washington, updates the story with images from Dungeness Spit.
The expansion of the green crab population is mapped on a
worldwide,
West Coast and Puget Sound scale. The impacts of the crab and
efforts to keep the population under control are described in the
story map, along with a practical outlook for long-term
success.
The production can be launched from this page. Be sure to click on the full-screen option. The project is housed on the UW’s ArcGIS online portal, where one can find other interesting projects.
Credit for the design of the story map goes to Kris Symer of Puget Sound Institute. Emily Grason provided scientific expertise and editing of the material.
Harper Estuary crab hunt
In many areas of Puget Sound, community volunteers get together regularly to participate in a ongoing hunt for green crabs in their local waters, a hunt they hope will not be successful. I first wrote about the Crab Team in 2016 for the Encyclopedia of Puget Sound. Coincidentally, my story, which featured volunteers at Zelatched Point on Hood Canal, was published just a month before the first green crab in Puget Sound was found in the San Juan Islands.
Earlier this year, I joined another team of volunteer scientists on Fidalgo Bay, where a single shell of a green crab was found last year. The story, also published in the Encyclopedia of Puget Sound, was mostly about the state’s aquatic reserves and how citizen scientists play a key role in studying the environmentally valuable areas. On the outing, I was able to see how the volunteers measured the spawning success of surf smelt in the bay.
One thing I noticed in these and other citizen-science excursions is a high level of camaraderie among the folks working together, learning together, sharing laughs and enjoying nature. For those interested in science, there are plenty of opportunities in the Puget Sound region.
I’m hoping to compile a list of all the citizen science projects taking place throughout Puget Sound. If you are involved in a group that could use more members, please send me a link to the program’s website or the email address of an organizer. I will try to keep the list updated for those who would like to join a group. It would be great if such a list already existed, but I have not found one with good contact information. One can search on the internet for the term “citizen science, Puget Sound” or a more specific location.
Meanwhile, Jeff Adams of Washington Sea Grant has posted a nice description of South Kitsap’s Harper Estuary, which is undergoing a major shoreline restoration. Community members are monitoring for marine life, including shoreline vegetation. Green crabs have not been found so far, but more than 5,000 hairy shore crabs were caught in traps there during the first two seasons, as shown in the graphic accompanying Jeff’s blog post.
I’ve written about Harper Estuary on several occasions, but I was intrigued by several bits of history from Jeff that I had never heard before.
For general information about joining the Crab Team or looking for green crabs on your own, check out “Get involved with Crab Team” on the Crab Team website.
Aggressive invaders in Maine
I’m waiting for someone to write a horror story about a new breed of aggressive European green crab that would rather attack people than run from them.
David Sharp, a reporter for the Associated Press, wrote about these new arrivals under the headline: “Canadian crabs with bad attitude threaten coastal ecosystem.”
The story tells us about an aggressive European green crab that has migrated to Maine form Nova Scotia in Canada.
“What we’re seeing is this insane level of aggressiveness,” said Markus Frederich, a professor at the University of New England who is studying the new invaders.
“Anytime I went down to grab one, they went to grab me instead,” he was quoted as saying. “They are the most aggressive crabs ever seen. We don’t understand yet why they are so aggressive.”
Frederich worries that the crabs may be more destructive than the green crabs that were introduced to the U.S. East Coast 200 years ago. “The crabs have a high potential for destroying soft-shell clams, eelgrass beds and who knows what else,” he said.
In a head-to-head test, subject crabs of both varieties were placed in an eelgrass bed. The Canadian invaders “shredded the eelgrass like Edward Scissorhands in their efforts to scarf down marine organisms seeking refuge,” Sharp wrote in his story.
The two strains of green crab are believed to originate from different parts of Europe, arriving at different times and in different parts of North America. One theory is that the aggression is gene-related, perhaps a result of hybridization of the two varieties of the same species.
The first green crab was discovered in Long Island Sound in 1817, according to Emily Grason, who provided some background information in response to questions from Crab Team members curious about the aggressive crabs. They wanted to know if we should be worried about them in the Pacific Northwest.
Once the invasion started, the population spread mostly northward along the East Coast, with southward movements apparently limited by warm temperatures and native blue crabs, she said.
The second strain of crabs arrived in the 1980s. Genetic evidence suggests it came from a more northern region of Europe and established themselves in a more northern part of the East Coast. Though some news stories have mentioned “mutant” crabs, Emily says the two types of European green crabs are simply distinct “haplotypes” of the same species, because they remained genetically isolated from each other.
Studies linking behavior to genetics is underway in Frederich’s lab at the University of New England. He has even placed green crabs on a treadmill, but results of his work have not yet been published. As a result, we don’t know what temperature range and other habitat conditions are favorable to the northern variety. Review the UNE news release.
If interstate and international shipping companies are careful about their practices involving invasive species — such as treating ballast water in ships — we might not see a second wave of green crabs on the West Coast.
