An invasive crab species that has been in the Maritimes since the late 1950s is poised to migrate further north as climate change makes regions such as Newfoundland and Labrador, and Quebec, more hospitable. If the crab populations aren’t contained, they could cause millions in damages to Atlantic Canada’s economy, say researchers.
The crustacean in question is the European green crab—a small yet aggressive creature that hails from Europe and has arrived in North America from both Norway and southern Europe. While the crab is just now making its way to northern Canada, the species has been in North America since 1817, says Piero Calosi, a professor of marine evolutionary physiology and global change biology at the Université du Québec à Rimouski (UQAR).
After first arriving in New England from Spain and Portugal via the ballasts of ships, the crabs soon migrated to Nova Scotia and New Brunswick. By the 1980s, a cold-water adapted strain from Norway landed in the frigid waters between Nova Scotia and Newfoundland. The two strains eventually converged in Nova Scotia and created a hybrid European green crab that has been slowly travelling to the northern ends of the Maritimes. Green crabs have now arrived on the southern side of the Chaleur Bay, at the northernmost border of New Brunswick.
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Since 2004, a notable population has also invaded the Magdalen Islands, located off the northwest coast of Cape Breton. This, alongside New Brunswick’s northern coastal waters and in Newfoundland, is where Calosi says the crabs have increased in numbers in recent years. The fear is that they will successfully make the jump to the southern coast of Gaspesie, and possibly from Newfoundland to the north coast of Quebec and southern Labrador.
“They move quite fast. They colonize new areas quite rapidly,” says Calosi. “In the Chaleur Bay, some occasional observations of juveniles and adult green crabs were reported in recent years.”
As of now, the invasive crabs haven’t fully established themselves in the region, but Calosi says it’s just a matter of time. “At some point, there will be enough individuals to reproduce and warm enough conditions to colonize more areas.”
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Since the crabs feast on several key aquatic species, including clams, mussels, and even baby lobsters, and can damage seagrass meadows, which help prevent coastal erosion and are a natural nursery for many shellfish species, their continued colonization of Atlantic Canada could have massive impacts on the health of marine ecosystems in the region. In New England, for example, the European green crab is responsible for a 75 per cent decrease in clam production.
“A regular or average green crab can eat around 20 clams in one hour,” says Calosi. “And these are small individuals, but there are hundreds of thousands in some places.”
On top of the environmental damages, Atlantic Canada’s fisheries and aquaculture industries could take a massive hit, with researchers predicting between $8.79 and 22.86 million in losses.
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While it’s unknown when exactly the crabs will arrive in more northern climes, the team of researchers at UQAR and the Maurice Lamontagne Institute at Fisheries and Oceans Canada (DFO) in Quebec is using climate change data and analyzing the temperature tolerance of the different genetic lineages (including the hybrids) of the crab to predict their further invasion.
To help slow the spread of the European green crab and other invasive species, the Canadian government has imposed rules; these include ballast water regulations and mandatory cleaning, drying, and draining of boats and marine equipment. On top of that, says Calosi, the DFO manages a monitoring program throughout the province and collaborates with local organizations such as the Area of Prime Concern Committee (ZIP des Îles) on the Magdalen Islands to set traps and remove as many green crabs as possible from priority sites.
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