|European Green Crab
( Carcinus maenas )
DESCRIPTION: The European green crab has an array of five spines on either side of the carapace beside the eyes and three rounded lobes between its eyes. Despite its common name, members of this crab species are not always green. From above, these crabs usually appear mottled, dark brown to dark green and may have small, yellow patches. The underside may be green or orange or even red during a molting cycle. An adult European green crab is typically about 2.5 inches long, but some have been reported to grow as large as 4 inches.
PATHWAYS/HISTORY: European green crabs feeding habits and tolerance of a wide variety of environmental conditions has enabled it to occupy numerous coastal communities outside its native range, including South Africa, Australia, Japan, and both coasts of North America.
The crab is native to Europe but was introduced to the western Atlantic coast during the early 1800s where it occurred between New Jersey and Cape Cod, Massachussetts. By the mid 1900s, it had spread north into Canada (Nova Scotia). The first documented European green crab was found on the West Coast in San Francisco Bay, California, in the late 1980s. Since then the European green crab has spread north, invading Oregon, Washingtonand British Columbia, Canada.
European green crabs introduced to San Francisco Bay probably came from the east coast. Although the mode of the introduction is unknown, these crabs likely arrived in ballast water or packing material or live bait. Dispersed from San Francisco Bay is also not known, but potential pathways include transport of larvae via ocean currents, ballast water exchange, and with the transfer of live shellfish or aquaculture equipment.
RISKS/IMPACTS: This species preys on bivalves and other crustaceans, such as soft-shell clams and scallops. Manila clam harvests have dropped by 40%since the European green crab became established in Humbolt Bay, California. European green crabs may impact native Dungeness crab (Cancer magister) , an important resource in the Pacific Northwest. The European green crab could possibly out-compete a Dungeness crab of approximately equal size for both food and habitat, according to a University of Washington study.
MANAGEMENT: The ANSTF has a European Green Crab Control Committee that has developed a management plan for this species. Please see the European Green Crab Management Plan for more information.
WHAT YOU CAN DO: Do not intentionally spread these crabs. Clean all bilge and bait wells. Clean fishing nets and other gear before moving to new destinations. If you think you have seen one of these crabs, please call our ANS Hotline (1-866-STOP-ANS).
PROFILE: adopted from the Washington Department of Wildlife's Invasive Species Fact sheet: European Green Crab