Tasty invasion: Blue crab migrating to Canada's doorstep

Saturday, March 7, 2015, 12:02 PM - Seafood lovers partial to the blue crab can usually be confident their meal won't come from Canadian waters.

The species is abundant from the Gulf of Mexico up to the U.S. Atlantic Coast, but its usual stomping grounds have until recently been thought to extend no further than Cape Cod in Massachusetts.

But that may be changing, thanks to warming waters. New research says the crabs have been found as far north as the Gulf of Maine and even Nova Scotia in recent years, pointing to warmer ocean waters as the driver.

In a study published last month in the Journal of Crustacean Biology, lead author David Samuel Johnson says ocean temperatures in 2012 and 2013 were around 1.3^oC warmer than average, possibly promoting the species' northward expansion.

"Recent observations and continued warming in the northwest Atlantic may signal a permanent poleward expansion of Callinectes sapidus into the Gulf of Maine," Johnson writers, referring to the blue crab's scientific name. "If so, then a key goal for ecologists and managers will be to understand the effect of Callinectes sapidus on Gulf of Maine food-webs and fisheries."

The blue crab one of the more popular crustaceans, with a global catch of around 94,000 tonnes in 2012.

It'll take awhile for its impact to be felt on the fishery in areas where it is not traditionally fished, but even its small presence in Nova Scotia waters has been welcome.

CBC News says there may be thousands of them in the area, and Parks Canada officials say they actually compete successfully against the invasive green crab. The latter destroys eel grass, robbing several species' of their home, but the blue crab does not -- and has in fact been seen occasionally feeding on green crabs themselves.

SOURCES: Phys.org | Journal of Crustacean Biology | CBC | FAO