Invasion History

First Non-native North American Tidal Record: 2006
First Non-native West Coast Tidal Record:
First Non-native East/Gulf Coast Tidal Record: 2006

General Invasion History:

Metacarcinus magister is native to the Northeastern Pacific, from Unalaska Island, Alaska to Mexico, but is scarce south of Point Conception, California (Pauley et al. 1989). Throughout this range, it is a major commercial and recreational fishery item.

North American Invasion History:

Invasion History on the East Coast:

Only two specimens of M. magister have been found in the Atlantic Ocean, both in rather deep water in the Gulf of Maine, off Massachusetts. The first specimen was trapped on July 19, 2006 off Thatcher Island, Gloucester, in 82 m of water. The second specimen was captured a mile south of Magnolia, Essex County, in Massachusetts Bay, at a depth of 37 m (Prybot 8/21/09). Both specimens were adult males, and their occurrence on the Massachusetts coast is linked to the fishery in the Pacific Northwest that ships large numbers of live adult male Dungeness crabs to Boston markets.

Invasion History Elsewhere in the World:

One specimen of M. magister was collected in a trawl in Kushiro, Hokkaido, Japan, at 15 m (in 1979, Abe 1991). 


Metacarcinus magister has a broadly oval carapace, with the edges uneven, but not highly sculptured. Its eyestalks are short. The carapace is armed with ten lateral teeth, smoothly angled, including the orbital tooth (beside the eye). The body is widest at the tenth tooth, which is large and projecting. The fingers of the claws are about the same color as the rest of the body, and are not dark. The carpus (wrist) has a strong inner spine. The color of the carapace is beige to light brown with blue edges, and is darkest towards the front. The underside of the crab ranges from light orange to light gray-purple, while the inner sides of the legs and claws are crimson. A typical adult (the type specimen) is 120.7 mm long x 177.8 mm wide (Pauley et al. 1989).

Two similar East Coast crabs, Cancer irroratus (Rock Crab), and C. borealis (Jonah Crab) have nine lateral teeth. Cancer irroratus has a carapace with smoothly angled edges, while the carapace of C. borealis has roughly sculptured edges. The fingertips are black in C. borealis. Typical specimens of the two East Coast crabs are smaller than M. magister: C. borealis is 90 X 143 mm; C. irroratus is 78 X 119 mm (Gosner 1978; Williams 1984).

This species was assigned to the genus Metacarcinus, together with two other West Coast species, M. gracilis (Graceful Rock Crab) and M. anthonyi (Yellow Rock Crab) by Schweitzer and Feldmann (2000) in a revision of the family Cancridae. The Red Rock Crab of the West Coast (C. productus) and the two East Coast rock crabs (C. irroratus, Rock Crab; C. borealis, Jonah Crab) remain in the genus Cancer.


Taxonomic Tree

Kingdom:   Animalia
Phylum:   Arthropoda
Subphylum:   Crustacea
Class:   Malacostraca
Subclass:   Eumalacostraca
Superorder:   Eucarida
Order:   Decapoda
Suborder:   Pleocyemata
Infraorder:   Brachyura
Superfamily:   Cancroidea
Family:   Cancridae
Genus:   Metacarcinus
Species:   magister


Cancer magister (Dana, 1852)

Potentially Misidentified Species

Cancer borealis
NW Atlantic native (Gosner 1978)

Cancer irroratus
NW Atlantic native (Gosner 1978)



Life History- In crabs of the family Cancridae, the male attends the female before molting, and carries the female around, underneath his carapace. He releases the female, allows her to molt, and then copulates with her, inserting the first pair of pleopods, carrying sperm, into the female's seminal receptacles. The eggs are fertilized internally, and then extruded as a 'sponge' or a mass of eggs brooded between the abdomen and the body (Barnes 1983). The eggs hatch into zoeae, larvae about 1 mm in size and armed with long spines, which drift in the plankton. Each zoea goes through five molts, and eventually molts into a postlarval megalopa, with prominent eyes and partially developed appendages. The megalopa molts into a miniature 'first crab' which has all the features of an adult crab, and is capable of crawling on the bottom (Barnes 1983).

Ecology- Mating of Metacarcinus magister occurs in inshore waters, but the zoeae tend to drift into coastal ocean waters. The megalopae move inshore and the juveniles are common in eelgrass beds, oyster and clam beds, and estuaries. Adults tend to move into deeper, offshore waters (Pauley 1989).


crabs, fishes, birds, humans

Trophic Status:




General HabitatUnstructured BottomNone
General HabitatGrass BedNone
General HabitatRockyNone
Salinity RangeMesohaline5-18 PSU
Salinity RangePolyhaline18-30 PSU
Salinity RangeEuhaline30-40 PSU
Tidal RangeLow IntertidalNone
Tidal RangeSubtidalNone
Vertical HabitatEpibenthicNone

Tolerances and Life History Parameters

Minimum Temperature (ºC)3Normal field range (Pauley et al. 1989)
Maximum Temperature (ºC)17Normal field range (Pauley et al. 1989)
Minimum Salinity (‰)15.5Lab, cessation of activity, adults (Pauley et al. 1989)
Maximum Salinity (‰)36.2Lab, cessation of activity, adults (Pauley et al. 1989)
Minimum Reproductive Temperature9Lab, larval development (Pauley et al. 1989)
Maximum Reproductive Temperature17Lab, larval development (Pauley et al. 1989)
Minimum Reproductive Salinity15Lab, larval development (Pauley et al. 1989)
Maximum Reproductive Salinity32Lab, larval development (Pauley et al. 1989)
Minimum Duration105Larval duration, zoea + megalopa, field data, California (Pauley et al. 1989)
Maximum Duration125Larval duration, zoea + megalopa, field data, California (Pauley et al. 1989)
Maximum Length (mm)120.7Measurement of type specimen (Pauley et al. 1989)
Maximum Width (mm)177.8Measurement of type specimen (Pauley et al. 1989)
Broad Temperature RangeNoneCold temperate
Broad Salinity RangeNonePolyhaline-Euhaline

General Impacts

Dungeness crabs are an important food item in the Northeast Pacific, and are heavily fished and widely shipped. However, only three introduced specimens are known, and no ecological or economic impacts have been reported.

Regional Distribution Map

Bioregion Region Name Year Invasion Status Population Status
NEP-II Alaska south of the Aleutians to the Alaskan panhandle 0 Native Estab
NEP-III Alaskan panhandle to N. of Puget Sound 0 Native Estab
NEP-IV Puget Sound to Northern California 0 Native Estab
NEP-V Northern California to Mid Channel Islands 0 Native Estab
NA-ET2 Bay of Fundy to Cape Cod 2006 Def Unk
N165 _CDA_N165 (Charles) 2006 Def Unk
NWP-4b None 1979 Def Failed
N170 Massachusetts Bay 2009 Def Failed
N180 Cape Cod Bay 2018 Def Failed
CAR-VII Cape Hatteras to Mid-East Florida 2017 Def Failed
M040 Long Island Sound 2017 Def Failed

Occurrence Map

OCC_ID Author Year Date Locality Status Latitude Longitude


Abe, Koji (1981) First record of the Dungeness crab, Cancer magister Dana from northern Japan, Researches on Crustacea 11: 13-16

Barnes, Robert D. (1983) Invertebrate Zoology, Saunders, Philadelphia. Pp. 883

Gosner, Kenneth L. (1978) A field guide to the Atlantic seashore., In: (Eds.) . , Boston. Pp. <missing location>

Kozloff, E.N. (1996) Marine Invertebrates of the Pacific Northwest, University of Washington Press, Seattle WA. Pp. <missing location>

MIT Sea Grant 8/3/2006 First sighting of Dungeness Crab in Atlantic confirmed. <missing URL>

Pauley, Gilbert B.; Armstrong, David A.; Van Citter,Robert; Thomas, G. L. (1989) Species profiles: life histories and environmental requirements of coastal fishes and invertebrates (Pacific Southwest): Dungeness crab, Biological Report 82(11.121): 1-22

Prybot, Peter K. (8/29/2009) West Coast crab shows up off Cape Ann, Gloucester Times <missing volume>: <missing location>

Rathbun, Mary Jane (1897) Synopsis of the American Sesarmae, with description of a new species., Proceedings of the Biological Society of Washington 11: 89-92

Ruiz, Gregory; Geller, Jonathan (2021) Spatial and temporal analysis of marine invasions: supplemental studies to evaluate detection through quantitative and molecular methodologies, Marine Invasive Species Program, California Department of Fish and Wildlife, Sacramento CA. Pp. 153 ppl.

Schweitzer; Carrie E.; Feldmann, Rodney M. (2000) Re-evaluation of the Cancridae Latreille, 1802 (Decapoda: Brachyura) including three new genera and three new species, Contributions to Zoology 69(4): 223-250

Science Daily 9/1/2006 Crab nabbed, circumstances fishy; West Coast crustacean found in Atlantic Waters. <missing URL>

Steves, BP (2022) This is a test, Molluscan Research 1(1): 22-23

U.S. National Museum of Natural History 2002-2021 Invertebrate Zoology Collections Database.

USGS Nonindigenous Aquatic Species Program 2003-2024 Nonindigenous Aquatic Species Database.

Williams, Austin B. (1984) Shrimps, Lobsters, and Crabs of the Atlantic Coast of the Eastern United States, Maine to Florida, Smithsonian Institution Press, Washington, DC. Pp. <missing location>