European Green Shore Crab, Carcinus maenas

The European green shore crab is native to Europe's North Atlantic coast. The first of this species invaded North America not too long after the formation of the United States. In the early 1800's, this crab established itself along the eastern seaboard from New Jersey north to Nova Scotia, Canada. Now, almost 2 centuries later, the European green shore crab has found a new home in California.

The first of this species on the U.S. west coast was discovered in the San Francisco Bay in 1989. Throughout the nineties, it has advanced north along the coast, inhabiting bay and estuarine mudflats and occasionally regions of rocky platforms. The European green shore crab has the potential to live on the west coast all the way from Baja California up to southern Alaska. Despite its name, the crab's shell (technically called a carapace) can vary from dark, mottled green to orange or red with yellow patches. Bodies of adults are usually no smaller than 2.5 inches (66 mm) across, and each has four pairs of walking legs. The European green shore crab has three teeth between its eyes and five to either side.

This crab poses a serious threat to sea life all along the coast because it can eat everything it sees, figuratively speaking. One adult crab can consume 40 half-inch clams a day and will attack and devour other crabs even as large as itself. This pest also eats oysters, mussels, marine worms, small crustaceans, and shellfish. All this eating means less food for other fish and birds. It also means less food for people who harvest sea life from the oceans. This crab is a mean, green, eating machine!