European green crab

European green crab are an adaptable, invasive coastal species, spreading along the West Coast and in Alaska. These small but aggressive crabs can damage eelgrass beds, eat small clams, outcompete native species like Dungeness crab, and threaten shellfish farms. Their shell is distinctive from  crabs native to Alaska; five spines on either side of the eyes and three bumps between the eyes.

European green crab are an invasive species in the United States, first appearing on the East Coast in 1817. It wasn’t until 1989 that they were detected on the West Coast, and since then their range has continued to expand northward. They migrated to Washington in 1998, British Columbia in 1999, and Haida Gwaii on the northern Pacific coast of Canada in 2020.

Since first being detected in Alaska by biologists working with the Metlakatla Indian Community (MIC) on Annette Island in 2022, green crab have been found in multiple locations. Molts were found by a group of Metlakatla high school students, MIC biologists, and Alaska Sea Grant staff on Gravina Island in 2024 and, most recently, at multiple locations in and around Ketchikan by University of Alaska Southeast-Ketchikan faculty and students, by the Ketchikan Indian Community and other community members. They are expanding quickly in Southeast Alaska.

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The Facts

​​Predation: Green crabs are effective predators, especially of young clams, a vital subsistence food. They can dig up to six inches into the seafloor and consume as many as 40 clams a day.

Competition: These invaders pose a threat to native species, including Dungeness crab, by competing for food and space. In places like California, their presence has been linked to a decline in native shore crab.

Habitat destruction: Green crabs destroy eelgrass beds, which provides critical habitat for juvenile salmon, Pacific cod, and other fish and shellfish.

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Learn more about European green crabs from our partners:

• ADFG Green Crab Information
• Washington Sea Grant Crab Team
• Kachemak Bay National Estuarine Research Reserve
• Metlakatla Indian Community

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Where are they now?

Scientists, Tribes, agencies, and community members are working together to trap and track their spread. New detections are updated on a map, supported by the Alaska Department of Fish & Game, as crabs and molts are found. Follow along!

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In the news

• July 3, 2025: Alaska Beacon - Green crab discoveries in Ketchikan show the invasive threat is spreading in Alaska
• June 25, 2025: Alaska Sea Grant - Invasive European green crabs expanding in Alaska
• June 17, 2025: KRBD - Invasive green crabs found on popular Ketchikan beach
• September 25, 2024: Alaska Sea Grant Fellowship spotlight: Alyssa Sanchez - European Green Crab
• July 18, 2024: KTOO interview with Alaska Sea Grant Directory Ginny Eckert and others on European Green Crab Awareness Day (skip to 34:15 for the interview)
• August 1, 2023: UAF - Alaskans can help identify invasive crab species
• June 15, 2023: Alaska Sea Grant - Supporting European green crab early detection

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Want to learn more or get involved?

The Alaska Department of Fish and Game provides an array of information on European green crab and ways to help, including protocols for early detection monitoring. Click the link or scan the QR code to the right to learn more.

Order a sticker from Alaska Sea Grant to help you identify European green crab on your local beach, or contact Alaska Sea Grant to help with early detection efforts.