(de Haan, 1853) (Asian shore crab)

Habitat: Shallow hard-bottom, marine intertidal waters; tolerates wide ranges of temperature and salinity.
Life History: Maximum size is approximately 1.6 inches in carapace width; breeding season is from May to September; females can produce 50,000 eggs per clutch with 3-4 clutches per season.
Native Range: Western Pacific Ocean from Russia and Korea south to Hong Kong.
Nonindigenous Range: Atlantic coast along every state from Virginia to Maine.
Impacts: Direct competition with native crabs.
Comments: Possible ballast water introduction; may have been introduced back in the 1960s, but specimens not identified until 1988.

  (Linnaeus, 1758) (European green crab)

Habitat: Marine to brackish waters; semi-protected rocky coasts, soft or hard bottoms.
Life History: Up to 6 cm in carapace length and 10 cm in width; larvae need at least 19 ppt salinity to metamorphosize; larval settlement greatest in late summer with temperatures above 18^oC; molting peaks in winter; prey items are clams, mussels, oysters, and gastropods.
Native Range: Northeast Atlantic Ocean from northern Europe to northern Africa.
Nonindigenous Range: Coastal areas from Maine to Maryland.
Impacts: Introductions had a negative impact on soft-shell clams, young oysters, and native crabs in the Northeast beginning in the 1950s.
Comments: Earliest documentation in North America from 1817 on the East Coast.  First collected on the West Coast in San Francisco Bay in 1989.