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A photo of researchers studying the green crab that migrated from Nova Scotia. Aggressive Canadian green crabs are invading US waters and threatening the local ecosystem. ( University of New England )
Scientists describe Canadian crabs that migrated from Nova Scotia to Maine as aggressive and angry, unlike the stereotypical Canadian.
The variety of green crabs threatens to cause problems in the local ecosystem, destroy eelgrass and eat soft-shelled clams.
Researchers from the University of New England have studied about 200 Canadian crabs for an article that will be published in the coming months.
Angry Canadian Crabs
According to the researchers, green crabs in Nova Scotia are the same species as green crabs living in Maine waters. However, unlike aggressive migrants, local green crab populations are described as "mild and cold".
Maine green crabs shrink and hide each time there is a threat. In comparison, Nova Scotia green crabs are always ready to fight against any potential predator, even humans.
"Whenever I went to get one, they came to take me instead," said Luis Logan, a graduate student responsible for tagging captured crabs in Nova Scotia.
The researchers say that whenever a person approaches, the green crabs of Nova Scotia take a fighting stance, ready to use their tongs to attack. At one point, a green crab jumped out of the water, ready to fight.
Green crabs showed the same level of aggression during the study. Placed on a bed of eelgrass, green crabs shredded plants, determined to find and devour any prey.
Become comfortable
These Canadian green crabs entered the United States for the first time in the 1800s and caused a dramatic decline in the soft-shelled clam population. Finally, they moved to Nova Scotia.
Markus Frederich, professor of marine science at the University of New England, said that Canadian green crabs represent two to three percent of the population of green crabs at the bottom of the ocean off Maine . However, they expect to see this number increase and compete with the local and docile green crabs that have made their home in Maine for over a century.
Finally, the researchers said that Canadian green crabs would move further south and that nobody could do anything about it.
The researchers will then explore whether a specific gene is responsible for the aggressiveness of green crabs. They will also examine "hybrid vigor", a theory suggesting that green crabs have become more aggressive in establishing themselves.
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