The European green crab is a highly adaptable predator originating from Western Europe and Africa. The crab first appeared along the Western U.S. in 1989, likely hitchhiking across the ocean in the ballast water of cargo ships and boats. These invaders feast on shrimp, oysters, clams and small Dungeness crabs, taking away important food for local shorebirds and migratory seabirds, and threatening critical commercial fisheries.
Green crabs are found in shallow intertidal and subtidal habitat, mostly in protected bays, making Seadrift and Bolinas Lagoons and ideal location. Seadrift Lagoon, a manmade lagoon tidally linked to Bolinas Lagoon, has held the highest density of green crabs along the entire west coast with numbers reaching over 300,000! By removing green crabs at Seadrift Lagoon we improve native species diversity and reduce the threat of dispersal to Bolinas Lagoon.
Since 2009, GFA and researchers from the Smithsonian Environmental Research Center, UC Davis, and Portland State University have been working with volunteers to remove these crabs. Each summer project managers implement four week-long removal events, dispersing 90 crab traps each day and recording data (size, sex, physical characteristics) for every crab. Thanks to volunteers, we are able to remove thousands of crabs from Seadrift Lagoon every summer. After removal, all crabs are donated to local farms for use as fertilizer. The crabs provide a great source of calcium and nitrogen nutrients to the soil, making this a truly surf-to-turf project!
Thanks to this project, Seadrift Lagoon’s biodiversity has rebounded, while green crab numbers in Bolinas Lagoon remain low. If you’re interested in joining the project, visit GFA’s volunteer webpage to sign up, and check out the Green Crab Project website for more information about the removal effort.