Warming waters in the Gulf of St. Lawrence are disrupting commercial fishing

The waters are warming and here is how it is changing fishing.

“The latest report on the state of the Gulf of St. Lawrence ecosystem could not be clearer: It shows undeniably that the system is warming rapidly.

This warming is occurring both in its surface layer, which is directly exposed to global warming, and in its deepest layer, due to the recent increase in the inflow of warm water from the Gulf Stream into its deep channels through the Cabot Strait.

At depth, warming is combined with a significant decrease in oxygen levels, which amplifies habitat changes for marine species.

By affecting both near-surface and deep-sea organisms, the current warming is influencing the entire ecosystem and provoking a real upheaval in the balance of the species living there. This is having direct repercussions on the commercial fishing sector.

As a Canada Research Chair in fisheries ecology, I am interested in the causes and consequences of changes in the dynamics of commercially exploited species. In this article, I explain the changes underway in the balance of species that inhabit the bottom waters of the Gulf of St. Lawrence.

The decline of cold water species

Following the historic collapse of Atlantic cod stocks in the early 1990s, caused by a combination of overfishing and very cold conditions, species of Arctic origin, including northern shrimp, snow crab and Greenland halibut, took advantage of the cooling and a decrease in predation and competition in the system to settle comfortably in the Gulf of St. Lawrence.

The dominance of these species lasted for more than two decades, allowing for the development of lucrative fisheries, whose revenues not only replaced, but greatly exceeded the value of revenues from the cod fishery prior to its collapse. However, as these species now face rapid warming of their habitat, their abundance is declining.

Northern shrimp in hot water

Shrimp can be considered a true barometer of the state of the demersal marine ecosystem, i.e. the layer of water located near the bottom, since its distribution fluctuates rapidly according to changes in the temperature of the environment. Preferring waters with temperatures between 1°C and 6°C, shrimp has seen a marked decrease in its habitat over the last decade.

Data from the monitoring survey conducted by Fisheries and Oceans Canada show that, due to the warming of the shrimp’s habitat, the area it occupies has decreased by half since 2008, and the abundance estimate in 2021 is among the lowest values in the history of monitoring this resource. This decrease in abundance has resulted in a 12 per cent reduction in allowable catch in 2022. With an additional 18 per cent reduction announced for 2023 and a high cost of diesel, the profitability of businesses that rely on this resource is threatened in the near term.”

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Photo Credit: Original Author

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