Carcinus maenas, the European green crab.

Fisheries experts are concerned about invasive European green crabs spreading in Alaska, especially during this year’s El Nino climate pattern. Research shows the crabs can expand their range during El Nino years, which often bring warmer Pacific Northwest ocean temperatures.

The small crabs thrive in nearshore eel-grass and other habitats valuable for young salmon, Dungeness crab, and other native species. They hunt worms, clams, mussels, crabs, and even young salmon, and can outcompete native species. They reproduce prolifically and can absorb ocean nutrients through their gills, an apparently unique adaptation among arthropods that aids their success.

European green crabs arrived in San Francisco Bay in 1989, likely by container ship, and have since spread. They reached Vancouver Island in 1999 and later spread north along British Columbia. In 2022, they were discovered on Annette Island south of Ketchikan, which remains their only known Alaskan population.

Monitoring for the crab is ramping up along south-coastal Alaska, including at the Kachemak Bay National Estuarine Research Reserve (KBNERR) in Homer. Scientists there have worked with University of Alaska Anchorage journalism students to produce media for state-wide education about invasive marine species.

Some scientists say the crab’s continued spread is likely as oceans keep warming. Trapping is the only known way to limit their expansion. Beach walkers are encouraged to become familiar with green crab carapaces, which are shed throughout the year, and report findings to the Alaska Invasive Species Hotline at 1-877-INVASIV.


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