Green Crab

Carcinus maenas
Native range: Atlantic Europe, North Africa
Invasive range: Northeast coast of North America, Pacific Northwest, Japan, Australia, South Africa, and South America
Habitat: Thrives on a variety of substrates, from soft mud and sand to rocks and aquatic vegetation. Reproduces well in a wide range of temperatures and salinities.
Description: Five spines on each side of carapace, with three rounded lobes between eyes. Top often mottled brown to dark green, yellow flecks. Underneath green, orange, or red. Adults about 2.5 inches wide, occasionally to four inches.

Since the green crab was first recorded off southern Massachusetts in 1817, it has been hard to ignore. A few minutes of rock-flipping in Maine can turn up dozens of them, brandishing their claws as they retreat to the crags. From Long Island to Nova Scotia on this side of the Atlantic, and from Norway to Portugal in their native range, I’ve collected hundreds of them in an effort to understand how the species arrived on our shores and then spread from New York to Prince Edward Island. DNA analysis suggests that at least two separate invasions have occurred. Green crab larvae can live up to sixty days in plankton and would have little problem surviving a transatlantic journey. One lineage, stretching from Chesapeake Bay to Halifax, probably arrived in the ballast of ships around the time of the American Revolution.

Atlantic Canada, however, has at least three additional lineages, likely the result of invasions that occurred as recently as the 1990s. The local chamber of commerce brags about the new ice-free super-port that was created when the Strait of Canso, between the Nova Scotia mainland and Cape Breton, was closed off by a causeway a few decades back. Ships from the Norwegian and British coasts regularly visit this port, unloading unrefined oil and clay, before heading back across the North Atlantic. They may have released the green crab, which feasts on native mussels and clams, critical to the economy and ecology of the Canadian Maritimes. The descendants are now found from Prince Edward Island to Long Island Sound.

These new invaders may have a few different nucleotides in their DNA, but they look and, I suspect, taste the same as the garden variety we already have here in the States. Although green crabs are small, their meat is tasty, especially when they’re in midmolt. The trouble is finding the things when they’re soft, or between shells. Blue crabs have physical cues that enable crabbers to predict when they’re about to molt, but few people can detect this moment in green crabs. I have been fortunate to discover a few softies in my exploration of the intertidal zone in Maine, but molting crabs are generally shy when they’re in this vulnerable stage–other crabs will quickly subdue them–and difficult to find.

In Italy, a closely related species, Carcinus aestuarii, is eaten with relish along the Adriatic. Fishermen harvest the crabs just before they molt: moleche, as the crabs are known, are so popular around Venice, that populations crashed in the 1980s. But the clues to predict molting in North America remain elusive: either it’s difficult to tell when green crabs are about to molt, or Venetian fishermen know just the right season to collect. Or perhaps the crabbers don’t want to reveal their secret.

After Italian cooks have the softshells in hand, the crabs are placed in an egg mixture, then fried. A fellow biologist tried this. He ended up with nothing but a few live, hand-dipped crabs, spreading yolk and breadcrumbs around the kitchen, as they scrambled to escape their deep-fried fate. Our recipe is adapted from a Venetian newspaper.