The green crab is a common sight in Rhode Island's salt marshes and tide pools.
The green crab is a common sight in Rhode Island's salt marshes and tide pools.
E. Zabel, courtesy of URI

Green Crab (Carcinus maenus)

Color: From dark to light green with yellowish mottling. Females have an orange green back and a red abdomen.
Size: Up to 2 1/2 inches from front to back of carapace; carapace is 3 inches wide.
Habitat: Rocky shores and jetties on mud banks, salt marshes, and in tidal pools.
Seasonal appearance: All year; move to deeper waters in winter.

Description

Green crabs have four pairs of walking legs, which they use to scurry sideways. Their fifth pair of legs is their front pinchers, which are almost equal, but one claw is slightly larger and blunt. Green crabs are distinguishable from other intertidal crabs by their color and the shape of their carapaces, although they are often mistaken for the white-fingered mud crab when young. The green crab carapace is usually square with several points (teeth) along the edge. There are three sharp teeth between the eye sockets; and along the side of the carapace, there are five teeth curved toward the side of each eye socket.

Life History and Behavior

The green crab is one of the most common intertidal crabs found in New England. Juvenile green crabs are found in and around the rocks and seaweeds of the intertidal zone. They are frequently exposed with receding tides. Adult crabs forage on the subtidal shore, following the tide and staying submerged much of the time. During the winter months, adults and large juveniles migrate into deeper waters in Narragansett Bay, while juveniles remain in the harsh intertidal zone, burrowing under rocks and marsh grasses throughout the year. This species can tolerate a wide range of environmental extremes in intertidal zones including cold temperatures, drying out, and low salinities.

Green crabs are scavengers, feeding mostly on and around mussel beds. They also prey on small worms, mollusks, and crustaceans. In turn they are a favorite food for many other intertidal inhabitants, including gulls, herons, and fish such as the tautog. The green crab is a voracious crab and is often called the "angry crab." It is an aggressive fighter and moves quickly.

Critter Fact The green crab was introduced to Rhode Island waters from Europe and has become one of the most common crabs along New England shores.

Special Notes


Adapted from The Uncommon Guide to Common Life on Narragansett Bay. Save The Bay, 1998.