European Green Crab Removal Project

green crab volunteers

The European green crab is origianlly from Western Europe and Africa and first appeared along the Western U.S. in 1989, likley hitchhiking its way across the ocean in the ballast water of cargo ships and boats. These highly adaptable predators feast on shrimp, oysters, clams and small Dungeness crabs, taking away important food sources for local shorebirds and migratory seabirds. Their appetite also poses economic impacts, as they reduce the population of species critical for the regions commercial fisheries.  As far back as the early 1900s, scientists link green crabs to significant decline of the scallop and clam industries of the east coast, and today they are said to contribute up to $22 million dollars in damage to U.S. commercial fisheries each year. As furocious eaters these crabs all but destroy or drive out other native crab species as well as other large invertebrates and fish, which can cause an imbalance to the natural ecosystem, severly impact species diversity, and weaken habitat health.

Green crabs are found in shallow intertidal and subtidal habitat, mostly in protected bays, making Seadrift and Bolinas Lagoons and ideal location. In fact, 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! What's worse is that Seadrift Lagoon is poised to be a source for green crab larvae dispersal to Bolinas Lagoon and possibly the open ocean. By removing green crabs at Seadrift Lagoon we hope to improve native species diversity while reducing the threat of dispersal to other bays and estuaries.

Since 2009, researchers from the Smithsonian Environmental Research Center, UC Davis, and Portland State University have been working with volunteers to remove these crabs. Each summer, from June - September, project managers implement four week-long removal events.  During each removal week 90 baited traps are released into Seadrift Lagoon, and after 24 hours, their contents are recorded. The process is repeated four times for each removal week and with the help of volunteers, allows the removal of thousands of crabs each week! After removal the green crabs are bagged, frozen, and sent 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 community based surf to turf project!

Join us for the 2017 removal season! All training and equipment is provided and friends and family are welcome, but please be at least 15 years of age to participate. Volunteers helping the project are trained to handle the crabs, identify important characteristics like the health, sex, and size of each crab and record that information onto data sheets.  If you are interested in receiving crabs or becoming a volunteer for this year's project, contact Kate Bimrose at kbimrose@farallones.org.   For more information about the project check out the Green Crab Project website.