Snow crab is a cold-water species with an upper thermal limit of 6‒7°C. It is the second most valuable fishery in Atlantic Canada. Its distribution has been shown to expand during cold periods and shrink in warmer periods. An extreme warming event documented in the deep waters at the mouth of the Laurentian Channel off Nova Scotia, starting in 2012, propagated onto the Scotian Shelf, with temperatures reaching 7‒9°C on the western Scotian Shelf. This warming was accompanied by pronounced declines in catches in this fishing area, suggesting local mortality due to thermal stress in the absence of local colder refugia. The warming event also propagated into the deep channels of the Gulf of St. Lawrence and is still ongoing. In this ecosystem, changes in the distribution and abundance of snow crab and other important commercial cold-water species, such as Greenland halibut and Northern shrimp, have been partly caused by deep water warming of more than 1°C.
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