Invasive Species of Eastern USA Blog

Southern Maine clams threatened by invasive species, warming climate

By Will Graff
The Forecaster

FREEPORT, ME — Small, green crabs are wreaking havoc along the Harraseeket River, and could soon devour the soft-shell clam population into extinction.

As water temperatures continue to rise and the winters get warmer, experts and clammers say the crabs, which eat spat – clams in larval stage – combined with coastal acidification, could drive 1,800 licensed clammers out of work and drastically alter the ecosystem.

Chad Coffin, president of the Maine Clammers Association, said the crabs have essentially taken over two-thirds of the productive clam flats in the last two decades, eating the mussels and scallops along the way. The devastation of clams has accelerated in the last decade and the problem is only getting worse, he said.

Green crabs, originally from Japan, were first recorded on Long Island, N.Y., in the mid-1860s and weren't seen in Casco Bay until the early 1900s, Beal said. The green crab popualtions have been kept in check by severe cold snaps, Beal said, experienced frequently throughout the last century, allowing clams and other shellfish to recover.

But now, a warming climate has changed all that. Scientists fear the area might not have those same extended periods of cold experienced in previous decades, leading to larger and larger populations of green crabs, and as a result, the disappearance of clams. ...

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