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| Green crab (Carcinus maenas) Credit: P. Erickson for MIT Sea Grant College Program |
Carcinus maenas
History:
• Believed to have first arrived in eastern North America around 1817, most likely in the dry ballast of cargo ships
• Negative impacts on soft-shell clams and other bivalves have been documented since 1950s
Characteristics:
• Green to dark brown, sometimes with yellow, orange, or red, with darker mottling
• Walking legs green, speckled with black
• Carapace (shell) has 5 spines on each side
• Can grow up to 3.9 in (10 cm) wide
Habitat:
• Salt marshes, sandy beaches, and rocky shores
• Usually on mud, sand, or pebbles
• Prefers sheltered areas
• Usually near the low-tide line
• Tolerates wide range of salinities (as low as 6 ppt)
Known Distribution:
• Newfoundland to Delaware; has become the most common crab in many locations throughout this range
• Native to North Atlantic coast of Europe and the North African coast
Impacts:
• Has become a dominant predator, feeding on clams, oysters, crabs, and mollusks
• Often blamed for collapse of soft-shell clam industry and reduction of other commercially important bivalves, including scallop and northern quahog
Common Vector(s):
Shipping: Ballast water