Maine’s Waters Threatened By Aggressive Green Crabs From Canada

Researchers have discovered that green crabs from Canada are invading Maine’s waters and threatening the state’s coastal ecosystem with their aggressive behavior as they feed on soft-shell clams and destroy native eelgrass.

According to the Associated Press, the invading green crabs are of the same species as the crabs already found in Maine, but are noticeably “ornerier and angrier,” as they tend to waive their pincers and aggressively stalk their prey, instead of avoiding threats like their Maine-based cousins do.

“Anytime I went down to grab one, they went to grab me instead,” University of New England graduate student and researcher Louis Logan told AP.

In a study led by Markus Frederich, a University of New England professor of marine sciences, researchers described how the genetically distinct population of green crabs made their way to Maine from Nova Scotia. As noted by Live Science, the crabs measure approximately five inches (13 centimeters) in length and consume on soft-shell crabs, mussels, clams, and other creatures considered important to the state’s economy.

Generally speaking, green crabs are considered threats to the aforementioned marine animals, regardless of how docile they are. According to AP, this is because the creatures are capable of destroying eelgrass, which younger crabs and other sea creatures use as a hiding place from predators. The animals are believed to have come to North America in the 19th century through the ballast water of European ships that arrived in the continent, with the new, aggressive crab variant believed to have come from northern Europe and the more docile variant thought to have originated from the continent’s southern regions.

At the moment, Frederich believes that the fierce Canadian green crabs that arrived in Maine only make up 2 to 3 percent of the species’ population in the state. However, he warned that this figure is expected to grow in the coming years.

“It will be an entirely different ball game. It’s just a question of when more of the crabs come and out-compete the Maine green crabs.”

With Frederich set to publish his team’s initial findings in the coming months, subsequent research will center on the possible reasons why the Canadian green crabs are so aggressive, the Associated Press wrote. The researchers suspect that there are two likely theories — a gene that could influence the animals’ behavior, and the “hybrid vigor” factor, which suggests that the Canadian population will “mellow out” over time after initially using aggressive tactics to establish themselves in a new territory.