In attendance: Jeromy Grant, Julian Narvaez, Taylor Stumpf (Metlakatla Indian Community, Department of Fish and Wildlife), Linda Shaw (NOAA), Ricky Conteras, Nicki Shelton Erica Drahozal, Ian Johnson, Niccole Williams and Brynn Presler-Marshall
What are these crabs and what do they do?
European green crabs, as the name suggests, are shore crabs native to Europe and are considered invasive in the United States–so invasive in fact that they’re on the list of 100 worst invaders world wide. They were introduced on the east coast some time in the 1700s, but didn’t make it to the west coast until the late 1900s. They’re now steadily making their way north, and were detected in Metlakatla just 250 miles south of Hoonah earlier this summer.
European Green Crabs can be devastating to the environment. They can out-compete Dungeness crabs for food, since a green crab can eat up to 40 clams and mussels a day. In Maine, softshell clam production fell by 80 percent after green crabs were introduced. By far their most devastating effect though is destroying eelgrass beds, which serve as a vital nursery for juvenile Dungees and salmon fry. Because of these effects, detecting their presence early on before they’ve had a chance to establish themselves is critical. As of September 15, 2022, Metlakatla has trapped 121 green crabs, and while that may seem like a large number, it’s miniscule compared to the over 70,000 removed from a single estuary in Washington last year. By beginning to monitor for green crabs early, we have the best chance of catching the problem early and nipping it in the bud before it really gets going.
To find out more about what a full-scale infestation can look like and how that impacts the environment, check out this video!
Questions and Answers
What crabs are they mistaken with? Purple and Green shore crabs. Those crabs have 3 spines on the side, not 5. Red rock crabs can also be similar, but have 9 spines on each side. Color isn’t everything for the European Green Crabs, they can be red or green. Look for the five spines!common-crab-id
Where are the green crabs imported from? European Green Crabs were probably first introduced to the west coast in ballast water of ships. They were first found in the 1980s in San Francisco and have been making their way north since then. They were found on Haida Gwaii in 2020 and in Metlakatla in July of 2022.
Will otters help control green crabs? Otters have been documented to eat them, but probably not at large enough numbers to control an infestation.
Is there a known sea surface temperature that green crabs prefer? They’ve been found in water temperatures from -1 C (33.8 F) to 22 C (71.6 F). There are models for the current and predicted sea temperatures, with potential habitat ranging up into the southern Bering sea.
Where is the best place to look for crabs on the tideline? The carapaces (shells) can be really high up on the tideline–Metlakatla discovered their first one in the grass above the beach, where it had most likely been transported after a large storm. They can also be found lower down in tide pools. The prefer areas with eel grass beds and some freshwater input, but broadly speaking can be found anywhere where you’d harvest any other crabs or shellfish.
Can we remove them? State regulations currently prohibit removing or possessing European Green Crabs or their shells. If you find something you suspect of being an invasive crab, please take photos with some sort of size reference (a coin or hand next to the crab works well) and send to the environmental office. We are hoping to get a permit that would allow community members to collect suspected European green crabs to bring in, but are still working on that.
Is there a best way to document them? Please send any photos or questions to Jeromy Grant (firstname.lastname@example.org) or call the HIA office at 907-945-3545.
Where do we go from here?
We have the opportunity for very early detection right now and want to hit from as many different angles as possible. While we’re still in the early stages of mobilization, there are plans in place for targeted trapping, shore surveys and larval monitoring. You may see our traps deployed near Long Island or Neka Bay–if you do, please feel free to look but don’t remove them. We also have a new light trap deployed in the Harbor to monitor for crab larvae, which would allow for even earlier detection than if we find molts on the beach, and are looking into adapting our current work on environmental DNA to search for the trace genetic material they leave behind in the water.
The best way you can help is to keep an eye out while beach combing or harvesting. All of Metlakatla’s crabs have been found in areas with other crabs and shellfish, so if you’re out digging clams or cockles, it’s the perfect opportunity to keep an eye out for green crabs. While they’re unlikely to be caught in traditional crab pots (because they’re much smaller than legal-size Dungeness), if you find any unknown or potentially invasive crabs in your pots, please take pictures and send them our way!