Aggressive Canadian crabs invade the coast of Maine



BIDDEFORD, MAINE Canadians are known as friendly people, but these bad-tempered brutes migrating from Canadian waters are better suited to the hockey track.

Green crabs from Nova Scotia are the same species as their cousins ​​that inhabit Maine waters, but are ornerier and wretched and threaten to speed up coastal ecosystem damage by swallowing softshell shells and destroying indigenous eels, according to a researcher .

The quarrelsome crabs from Canada currently only contain about 2 to 3 percent green crabs
The quarrelsome crabs from Canada currently only contain about 2 to 3 percent green crabs (Robert F. Bukaty / The Associated Press)

The docile green crabs shrink for a threat, while the newcomers are more inclined to swing and recharge their tongs.

"What we see is this insane level of aggressiveness," said Markus Frederich, a professor at the University of New England.

They are each genetically different.

The new crab variety that originated in Northern Europe is stronger 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 plague that can devour soft shell and juvenile bivalves. They can destroy sea grass that is a hiding place for young sea creatures.

But the Canadian crabs take it to a new level.

Louis Logan, a graduate student at the University of New England, had the unpleasant task of labeling the crabs that were caught in the Nova Scotia waters for the study.

The crabs were not in the mood for games.

At a distance of 5 feet, the pint-ready brutes, which were 4 to 5 inches wide, adopted a fighting posture. Those who grabbed him were in no hurry to let go.

"Every time I went downstairs to get one, they took me," he wrote in an e-mail.

One of them would in particular jump out of the water in his madness to attack.

In the lab, researchers launched both types of crabs on a bed of eels in a salt water pool and the difference was great. Canadian invaders fragmented the eel grass like Edward Scissorhands in their efforts to shield marine organisms seeking refuge, Frederich said.

The first round of research focused on 200 crabs from Canada and will be published in the coming months.

Further studies will focus on whether a specific gene plays a role in aggressiveness or whether a factor called hybrid strength is involved, he said. The hybrid energy theory suggests that crabs can be more aggressive as they settle, but will soften later.

The quarrelsome newcomers currently contain only about 2 to 3 percent of the green crabs that crawl on Maine's ocean floor, but those numbers will certainly grow, Frederich said.

"It will be a completely different ball game," he predicted. "It's just a matter of when more of the crabs come and compete outside Maine's green crabs."

The docile green crabs have been in the New England waters for more than a century, but they have become a big problem when the Gulf of Maine is warmed up. The bait fish crabs arrived in the 1980s of Nova Scotia, and currents brought their larvae south in the waters of New England.

Eventually the newcomers will move further south. "We can not do anything about it," he said. "The only thing we can do is learn how to live with it."


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