“UPEI is the ideal location to study the spread of invasive species like green crabs,” says Dr. Pedro Quijon. “I can be in one spot and see a complete infestation, then drive an hour away and find a location where the crabs have yet to migrate.”
Quijon is an Associate Professor of Biology at UPEI. He’s studying a species of crab native to Europe that first crossed the Atlantic over a century ago to the New York / New Jersey area. In the years since, the population of green crabs has slowly migrated north, an was confirmed for the first time in Prince Edward Island in 1997.
“The green crab eats everything,” says Quijon. “It has its favourites, for sure. It starts with soft-shell clams, then moves down to mussels, then harder-to-eat oysters. If none of these are available, it will even eat worms or snails.”
The green crab’s appetite and lack of predators on this side of the Atlantic make it a devastating foe to the shellfish industry. “Fifty years ago, Maine had a robust soft-shell clam fishery,” says Quijon. “Green crabs moved into the area and within a decade decimated the industry.”
Quijon explains the green crab is also bad news for eelgrass — the long grass that grows along PEI’s shores just under the low tide which provides nursery habitat for countless coastal species.
“Adult crabs will unintentionally uproot eelgrass as they dig for food,” says Quijon. “We have also learned juvenile crabs, who aren’t strong enough to get at the meat inside large clams or other shellfish, will actually eat the tender tissues of eelgrass.”
Green crabs are slowly building their populations from eastern PEI and moving west, mainly along the southern shore. Quijon says high numbers of crabs have established themselves in the Charlottetown area, but Summerside has yet to be measurably affected.
“It is only a matter of time,” says Quijon. “They will also eventually establish themselves in Malpeque Bay. The shellfish industry needs to be ready.”
Quijon says shellfish farmers in places where the crabs are already established have had to adapt.
“Maine, for example, has been able to rebuild its soft-shell clam industry by adapting its aquaculture,” he says. “They need to protect the younger clams, also known as seeds. Each farm has to have a series of nets or fences capable of keeping out crabs to mitigate their impact. It is an extra expense, one that the industry has had to adapt to. But it is part of their new reality if they wish to continue.”
“It’s a great opportunity for them and a rewarding experience for us as faculty,” he explains. “When I was a student, getting involved in research meant long summers away in the field. These students can do their research at any point on the Island, and still be able to sleep at home in their comfortable beds. It’s a real advantage.”