Scientific Name:Carncinus maenas
Common Name:Green Crab (others: European Green Crab, Joe Rocker)
Native Range:The Atlantic coasts of Europe and northern Africa, from Iceland and Norway to Mauritania
Established Range:C. maenas has successfully established itself in North America, South America, Africa, and Australia. On the East Coast, it can be found from Canada to South Carolina.
Established in Rhode Island?Yes, throughout Narragansett Bay
Date and Location of Introduction:1817, Massachusetts
Method of Introduction:Hard ballast or ballast water
Habitat:C. maenas tolerates a wide range of intertidal and subtidal habitats and conditions. This crab is frequently found along protected and semi-protected sandy, rocky, and cobble beaches, and can also be found in salt marshes, seagrass beds, and mudflats. It can survive in waters with salinities between 4 and 54 parts per thousand, and temperatures between 0 and 30° Celsius.
Average Life Span:4 to 7 years
Diet:The diet of C. maenas consists mostly of macroinvertebrates such as clams, scallops, snails, mussels, and crustaceans. They are also known to eat juvenile fish, worms, and algae. The green crab has a voracious appetite.
Breeding:C. maenas breeds in the summer months, and females may reproduce multiple times within that period. An average of 185,000 eggs can be produced in a single clutch.
Concerns:C. maenas is considered one of the world's worst invasive species because of its ability to rapidly and easily spread and colonize, and because of its insatiable appetite for commercially important shellfish and crustaceans. Scientists have found that it has serious negative impacts on the habitats that it has invaded. This crab can outcompete local mud crabs for food and space, and will often displace them. Additionally, they can decimate shellfish populations and are widely blamed for the collapse of the New England soft-shelled clam fishery in the 1990's.
Control:Once established, C. maenas is extremely difficult to eradicate. Selective trapping has been used in the past as a means of effectively controlling C. maenas in small salt ponds and bays. Incentive systems, such as bounty systems and the creation of commercial markets for C. maenas, have proven largely ineffective at reducing invasive populations. At this time, no effective biological, genetic, or chemical controls have been developed.
Identification Card:Courtesy of Salem Sound Coastwatch
Works Cited:Grosholz, Edwin, and G. Ruiz. 2002 Management Plan for the European Green Crab. Aquatic Nuisance Species Task Force, http://www.anstaskforce.gov/Species%20plans/GreenCrabManagementPlan.pdf
ISSG. 2009. Ecology of Carcinus maenas. The Global Invasive Species Database, http://www.issg.org/database/species/ecology.asp?fr=1&si=114
NIMPIS. 2010. Carcinus maenas (European green crab). National Introduced Marine Pest Information System, http://www.marinepests.gov.au/nimpis
Perry, Harriet. 2010. Carcinus maenas. USGS Nonindigenous Aquatic Species Database, Gainesville, FL. http://nas.er.usgs.gov/queries/factsheet.aspx?SpeciesID=190