Our organization, Protect Henderson Inlet (PHI), has as its key goal the preservation of the Salish Sea, especially Henderson Inlet. As we experience the beauty and wonder of the marine environment around us, we are constantly challenged to learn more about the creatures that live there, including the things that threaten them. Through our interactions with scientists and educators at the University of Washington, Washington State University, The Washington Department of Natural Resources, the Washington Department of Fish and Wildlife, and others, we become better informed about invasive species that actively threaten our marine environment. Read on to learn about a current threat that you can help watch for.
Thanks to Tonni Johnston, vice president of PHI, for the following writeup.
Originating from – drumroll . . . Europe(!), the European Green Crab is one of the world’s most destructive invasive species according to the International Union for the Conservation of Nature. This green crab is a predator that eats other crabs, especially favoring the Dungeness. It also eats eelgrass, the protective plant that provides a nursery for forage fish and is a refuge for sea birds. The EGC (European Green Crab) larva is so tiny that it travels undetected for the most part, sometimes in seaweed. Other challenges to controlling the EGC include its high reproduction rate of 250,000 eggs per brood and its ability to thrive in a wider range of temperatures and salinity levels than our native species.
EGC rode in ballast water from the East Coast to California where it was first detected in 1989, clawed and ate its way up the coast where it was spotted in British Columbia in 2012, and is now beginning to enter Puget Sound. Trapping teams hauled in more than 100,000 green crabs in Washington in 2021, when the population exploded here. Keep in mind that Puget Sound is the second-largest estuary in the United States, and that predators in other estuaries tend to drive out natives. A very real fear is that the EGC will soon thrive here, as it has in Grays Harbor and Willapa Bay, and that it will negatively impact many species throughout our estuary, Puget Sound.
Oh no! What can we do?? Stena Troyer from Gig Harbor’s Harbor Wild Watch Education trains citizen scientists, and on September 27th, 2024, she met with 13 of us through PHI on Otis Beach of Henderson Inlet. She guided us through the steps to identify and report a bad critter: The European Green Crab.
Stena explained that we can make a difference by helping the WSU and Washington Sea Grant scientists who are already at work on the problem. For Puget Sound, early detection of the EGC is super important. The more eyes on the beach, the better, even when we see no Green crabs. She helped us install the app MyCoast.org for submitting any data we collect.
Beginning by choosing our own fun critter names [Stellar sea lion (Stena), Geoduck (George), Tuna (Tonni), Coelacanth, Barnacle, Guppy, Pipefish, Dogfish, Dolphin, Lune, Rockweed, Limpet, Dogfish 2, and Mussel], we settled into a bench, chair, or porch swing seat to learn more about this creature we’re up against.
Realizing we needed some vocabulary, Stena explained that crabs molt as they grow, leaving behind their shells. She likened a crab molting to a person removing a glove from their hand. She passed around examples of many different kinds of molts – European Green Crabs, shore crabs, hairy helmet crabs, graceful crabs, black clawed crabs, and cancer crabs which include red rocks and Dungeness. Stena taught us that the most durable part is the body, called the carapace. There are marginal teeth along the side of the carapace. The bumps in the middle are known as the rostrum. There are also 4 pairs of walking legs and 2 pinchers.
The name, European Green Crab can be deceiving because the color can be green or it might be tomato soup colored or it might be white if bleached. The EGC has five spines, known as marginal teeth, on either side of its wide eyes. EGCs have diamond shaped carapaces. We broke into groups across three or four tables to sort through all the various carapaces and identify which ones they were. She worked alongside us and gave us picture guides that can be accessed here:
https://wsg.washington.edu/crabteam/moltsearch/. The site also lists dates of future trainings (highly recommended).
She showed us how to run our fingernail along the edge of a carapace to count the marginal teeth (spines).
Shore crabs (native) only have 3 marginal teeth. And they’re more square in shape than EGCs. If startled when live, shore crabs do the huddle dance where they more or less stay in place under the cover of a rock or some seaweed.
Hairy helmet crabs are the ones most often confused for EGCs. The Hairies have 6 marginal teeth but the sixth can be overlooked.
Black-clawed crabs can be easily confused too with a similar overall shape to the EGC, except black-clawed stay small and have 3 marginal teeth. When live black-clawed are startled, they often do the very scary stance, raising their black claws towards you.
Spider crabs are easy because they look very different from EGCs.
When it comes to the Cancer crabs – the Dungeness, the Graceful, and the Red Rock, they all have 10 marginal teeth. The Dungeness has more pointed teeth, with the 10 being at the widest point of the carapace. Dungeness pinchers have spiny teeth. The Graceful crab’s 10th tooth is one notch behind the widest point. The Red Rock’s teeth are rounded. It also has 5 bumps on a protruding rostrum. Red Rocks have black pinchers.
With some knowledge in our heads and buckets in hand, it was time to hit the beach! Stena had us form groups of 4 and directed each group to pick a section of wrack line aka strand line or seaweed junk line. Twenty minutes of human time is the length of a timed survey for submission to the MyCoast app. Since we were in four-person groups, she set the timer for five minutes to collect all the crab carapaces we could find, including the very, very small ones.
When the five minutes were up, each group sorted like crabs together, answered a short questionnaire in the app, and took a photo of the grouped carapaces that included the caliper she’d given each of us to show relative size. None of our groups found EGCs, thank goodness. Stena told us to celebrate that we are still in the time of zeros. Yay! If we had found an EGC molt, she told us that we should measure it individually and keep it. If we were to someday find an EGC alive, we were directed not to disturb it but to submit the report asap and also to immediately call it in.
Together with new and old friends, and with the guidance of Stena, at the end of the training, we felt less powerless against the threat. And we each now proudly owned a gnarly Molt Search sticker.
Questions going forward:
Where will I put my cool crab sticker?
Will our three and five-year-old grandkids be interested in doing surveys? Answer: Yes!
When the WSU/WSG crab team gets an EGC call, will they catch enough of them to keep the other crabs and the eelgrass safe?
What is different in Europe that makes the EGC harmless there?
Are EGCs good eating?
To get answers to these and other burning questions, you can sign up for this fun training with Stena and her associates at the Wild Harbor Watch website noted above, or join us at PHI for any of our educational meetings or beach walks. You may join our contact list through the website to get notices about our sessions. See you on the beach!