"Green crabs from Nova Scotia are the same species as their cousins that already inhabit Maine waters, but are ornerier and angrier, threatening to accelerate harm to the coastal ecosystem by gobbling up soft-shell clams and destroying native eelgrass, a researcher said. 

The new crab variant that originated in northern Europe is hardier and adapted to colder water than the more docile crab, which originally came from southern Europe.

Green crabs, even the docile ones, are considered a scourge that can devour soft-shell and juvenile clams. They can destroy eelgrass that provides a hiding place for juvenile sea creatures."

Via CBC NS