NEMESIS Bioregion Distribution:

Native  Introduced  Cryptogenic  Failed

First Non-native North American Marine/Estuarine Record: 1817
First Non-native West Coast Marine/Estuarine Record: 1990
First Non-native East/Gulf Coast Marine/Estuarine Record: 1817

General Invasion History:

Carcinus maenas, also known as the Green Crab, is native to European Coasts from Iceland and Norway to Mauritania, West Africa. It has invaded six major regions, the Northwest Atlantic (from Maryland-Newfoundland), the Southwest Atlantic (Patagonia), the Southeast Atlantic (South Africa), the Northeast Pacific (from California-British Columbia), the Northwest Pacific (Japan) and the Southwest Pacific (Australia) (Cohen et al. 1995; Carlton and Cohen 2003).

North American Invasion History:

Invasion History on the West Coast:

In 1989, a single Carcinus maenas was collected at Estero Americano, near Bodega Harbor, California. This may have been an isolated introduction (Grosholz and Ruiz 1995). In 1990, a specimen was caught at Redwood City, on South San Francisco Bay (Cohen et al. 1995). By 1993, C. maenas was abundant throughout the Bay (Cohen et al. 1995) and by 1994 it was found from San Francisco Bay north to Bodega Harbour (120 km) (Grosholz and Ruiz 1995). In 1997, C. maenas was collected in Coos Bay, Oregon, in 1998 it was collected in Willapa Bay, Washington, and in 1998, in Barkley Sound, British Columbia (Grozholz and Ruiz 1996; Washington Department of Fish and Wildlife 1997; Fisheries and Oceans Canada 1998). It is now established as far north as Winter Harbour, Quatsino Inlet, on the west coast of Vancouver Island (50.5330 N, Klassen and Locke 2007), but is absent from Puget Sound and the Strait of Georgia. Populations in Barkley Sound show indications of rapid individual growth, characteristic of an expanding population (McGaw et al. 2011). Recruitment in the Oregon-Washington part of the range has been sporadic, depending on favorable currents and warmer water temperatures in 2003, 2005, 2006 and 2010, influenced by the Pacific Decadal Oscillation, and the El Niño Southern Oscillation (Yamada et al. 2015). Southward dispersal has been much slower, with C. maenas spreading only to Monterey Bay and Elkhorn Slough in 1993 (Grosholz and Ruiz 1995; Ruiz et al. unpublished data) and Morro Bay in 1998, the current southern limit (USGS Nonindigenous Species Program 2009). Genetic studies indicate that the West Coast populations of C. maenas originated from the East Coast (Bagley and Geller 2000; Tepolt et al. 2009; Darling 2011). The Green Crab was likely introduced to the West Coast through the live-bait trade, or less likely, in the ballast water of ships (Cohen et al. 1995; Grosholz and Ruiz 1995). Surveys in northern California (Bodega Harbor, Bolinas Lagoon, Tomales Bay) suggest that predation by native crabs (Cancer and Metacarcinus spp.) may limit the establishment of this crab to low-salinity habitats (Jensen et al. 2007).

Invasion History on the East Coast:

One of the first records of Carcinus maenas from the Atlantic Coast was Say (1817), as Cancer granulosus: 'Inhabits bays and inlets near the sea'. Thomas Say is known to have collected on the Atlantic coasts of Maryland and New Jersey, so C. maenas apparently first colonized the Mid-Atlantic region, and spread north of Cape Cod in the late 19th century.

Carcinus maenas was collected by Say (1817) on the Atlantic Coast, probably in New Jersey, but possibly from the Atlantic coast of Maryland. It was also reported, as Portunus maenoides from Long Island, in 1817 (Rafinesque 1817). Other early records are from Martha’s Vineyard, Massachusetts (Gould 1841), Long Island Sound, New York, and Newport, Rhode Island (DeKay 1844). Before 1911, it was abundant at Atlantic City, New Jersey (Fowler 1911). Carcinus maenas was collected at Cape May, New Jersey by 1900 (Almaca 1963). 'Carcinus maenas, the green crab, is not common in Delaware Bay, and has only been collected by us from the Cape Henlopen tidal flat... and from the southernmost tributary entering Delaware Bay' (Leathem and Maurer 1980). Larvae were reported in plankton by Deevey 1960 (cited by Williams 1984). On the Atlantic coast of the Delmarva Peninsula, Carcinus maenas was collected in 1874 in Hog Island Bay, in Northampton Co., Virginia: 'a single male... This is the farthest south on the Atlantic coast of the United States from which this species has been reported' (Kingsley 1879). In recent surveys, this crab was found from Delaware to Virginia, in Indian River, Assawoman, Sinepuxent and Chincoteague Bays (in 2003, de Rivera et al. 2005a; Miller and Brown 2005). In 2007, a Green Crab was caught in Chesapeake Bay, in the upper Manokin River, Somerset County (Kevin Josenhans, Maryland DNR, personal communication). 

From the Gulf of Maine northwards- Carcinus maenas was collected in Provincetown, Massachusetss in 1905, and successively spread to Casco Bay, Maine in 1922-1930; Penobscot Bay (Rockland, Bar Harbor), Maine in 1951-1953; and Passamaquoddy Bay (Maine to New Brunswick Canada) and the Bay of Fundy, Nova Scotia, in 1953 (Almaca 1963; Vermeij 1982b). Contrary to some published reports, C. maenas was not collected in the Gulf of St. Lawrence until 1994, but it is now found on both the Nova Scotia and Prince Edward Island sides of Northumberland Straits, and on the north side of Prince Edward Island (Audet et al. 2003). By 1991, it crossed the Straits of Canso onto Cape Breton Island, Nova Scotia (Audet et al. 2003), and has colonized the Bras d'Or Lakes on the island (Cameron and Metaxas 2005). In 2007, C. maenas was discovered in Placentia Bay, Newfoundland (Canadian Broadcasting Company News 2007; Klassen and Locke 2007; Blakeslee et al. 2010). The expansion from Nova Scotia into the Gulf of St. Lawrence involved an introduction of genetically distinct crabs, probably of Scandinavian origin (Roman 2006; Blakeslee et al. 2010; Darling 2011). Genotypes from this second introduction are transported by currents and are appearing in populations in the Gulf of Maine (Pringle et al. 2011; Darling et al. 2014; Williams et al. 2015). The two genotypes are hybridizing in Nova Scotia and Newfoundland, but the impacts of this introgression on the crab's temperature tolerances are unknown (Jeffery et al. 2017).

In recent decades (1990s to the present), Carcinus maenas has been partially displaced from rocky shore areas, from New Jersey to Massachusetts Bay by Hemigrapsus sanguineus (Asian Shore Crab) through competition and predation on juveniles (Lohrer and Whitlatch 2002; Griffen and Delaney 2007; Griffen 2011). Carcinus maenas has been observed to move into rocky-intertidal areas at high tide, presumably from subtidal regions, or from hiding places under boulders (James Carlton, personal communication). Carcinus maenas remains common in soft-bottom habitats where H. sanguineus is absent.

Invasion History in Hawaii:

In 1873, Carcinus maenas was collected in the Hawaiian Islands (Street 1877, cited by Carlton and Cohen 2003). There are no further records from Hawaii.

Invasion History elsewhere in the World:

In the Northwest Pacific, Carcinus spp. were recorded at Tokyo Bay in 1984. The date erroneously was given as 1958 by Sakai 1986 (cited by Carlton and Cohen 2003). Both Carcinus aestuarii (from the Mediterranean) and Carcinus maenas are present in Japan. DNA data from Bagley and Geller (2000) suggest that there was a single source population which included both species, possibly from the Iberian Peninsula, where the two species overlap (Carlton and Cohen 2003; Darling 2011). In 1999, Carcinus spp. was present in Sagami and Osaka Bays in Honshu and Dokai Bay in Kyushu, Japan (Carlton and Cohen 2003). In the Southwest Pacific, the Green Crab is established in Australia. Although regular records from New South Wales start in the 1970s, Ahyong (2005) suggests that C. maenas was established, but overlooked or misidentified, in the Sydney area since the late 19th century. In 1900, C. maenas was collected in Port Phillip Bay, Victoria (Fulton and Grant 1900), and by 1998 had spread along much of the coast of Victoria (Thresher et al. 2003). In 1993, this crab was collected on the north shore of Tasmania, and by 1998, was found in many harbors on the north and east coasts of the island. In 1976, C. maenas was collected in Adelaide Harbour, South Australia, and is established there (Furlani 1996; Thresher et al. 2003). It has not, however, become established in Western Australia's major port, Perth, where it was collected in 1965 (Furlani 1996).

In the Southern Atlantic, Carcinus spp. was collected at Table Bay Docks, Cape Town, South Africa in 1983. By 1990, Carcinus spp. ranged from Camps Bay to Cape Saldanha, a distance of 200 km (Griffiths et al. 1992). However, C. maenas failed to become established in Saldanha Bay, so that the current range is limited to Cape Town Bay and its enclosing peninsula (Robinson et al. 2005). Samples included a mix of C. maenas and C. aestuarii genotypes (Geller et al. 1997). In the Southwest Atlantic, C. maenas was collected in 2003 from Camerones Bay, Chubut Province, Patagonia, Argentina, where it is established (Hidalgo et al. 2005). Genetic studies indicate that Argentine populations were introduced from Australia (Darling 2011).

In additon to its six major established populations, Carcinus spp. (probably mostly C. maenas, but could include C. aestuarii) have been collected from many sites around the world, mostly in the tropics, where it has failed to become established, or its establishment is unknown. These sites include the Azores (Drouet 1861; Sampaio 1904, cited by Morton and Britton 2000), Rio de Janeiro and Pernambuco, Brazil (in 1857 and 1899, Carlton and Cohen 2003), the Pacific coast of Panama (in 1866, Carlton and Cohen 2003), Myanmar (Burma) (in 1933, Carlton and Cohen 2003), Ceylon (Sri Lanka) (in 1886, Carlton and Cohen 2003), Pakistan (in 1971, Carlton and Cohen 2003), the Red Sea (in 1817, Carlton and Cohen 2003), and Madagascar (in 1922, Carlton and Cohen 2003). The failure to become established in these warm waters is probably related to temperature tolerances of adult and larval stages.