Scientists describe the Canadian crabs that migrated from Nova Scotia to Maine as aggressive and angry — very much unlike the stereotypical Canadian.
The variety of green crabs are threatening to cause problems in the local ecosystem, demolishing eelgrass, and eating soft-shell clams.
Researchers from the University of New England have studied about 200 Canadian green crabs for a paper that will be published in the coming months.
Angry Canadian Crabs
According to researchers, the green crabs from Nova Scotia are the same species as the green crabs that have been living in the waters of Maine. However, unlike the aggressive migrants, the local green crab populations are described to be "meek and chill."
The green crabs of Maine shrink and hide whenever there is a threat. In comparison, the green crabs of Nova Scotia are always ready to fight any potential predator, even humans.
"Any time I went down to grab one they went to grab me instead," said Luis Logan, the graduate student who was tasked to label the crabs captured from Nova Scotia.
The researchers recount that whenever a person gets near, the green crabs from Nova Scotia assume a fighting position, ready to use their pincers to attack. At one point, a green crab jumped out of the water, ready for a brawl.
The green crabs displayed the same level of aggressiveness during the study. When placed on a bed of eelgrass, the green crabs shredded the plants, determined to find and devour any prey.
Getting Comfortable
These Canadian green crabs first entered the United States in the 1800s and caused a dramatic decline of the soft-shell clam population. Eventually, however, they moved to Nova Scotia.
Markus Frederich, marine sciences professor at the University of New England, said that the Canadian green crabs comprise two to three percent of the green crab population on the ocean floor off the coast of Maine. However, they expect to see the number to grow and compete with the local and docile green crabs that have called Maine their home for more than a century.
Eventually, the researchers said that the Canadian green crabs will move further south and no one can do anything about it.
The researchers will next explore whether a specific gene is responsible for the green crabs' aggressiveness. They will also be looking at "hybrid vigor," a theory suggesting that the green crabs have grown more aggressive to establish themselves.
