Invasive Species — European Green Crab (Carcinus maenas)

Multiple pathways can introduce the European green crab to new regions. Human-mediated pathways include the aquarium and live food trades, aquaculture, on fouled ship hulls, and within the ballast water tanks of vessels moving from areas with green crab presence. Ocean currents and marine debris generated from the Tōhoku tsunami are natural pathways that can result in new populations gaining establishment.

Genetic analysis of crabs from San Francisco, where European green crabs were first detected on the west coast of North America in 1989, indicates that founding populations originated from the East Coast. Possible vectors for introduction to the area include dumping seaweeds used in packing Atlantic seafood products such as lobsters or bait worms into marine environments and crabs being transported in ballast water.

Of greatest concern to Alaska is the potential for larvae to travel in ocean currents from Vancouver, British Columbia, into state waters where they could settle out into potentially suitable habitat. If they are able to successfully establish breeding populations green crabs could disperse into the many inlets and bays of southeast Alaska shorelines, and potentially extend as far north as the Gulf of Alaska. Because of Alaska’s vast size and limited population, it is possible that the green crab would become established in remote areas and remain undetected for many years.