Research says climate change is driving hundreds of fish species north from their usual seas and some of the biggest effects will be along Canada's Pacific coast.
That is likely to create new challenges for governments seeking to regulate and share catches between competing jurisdictions, said James Morley of Rutgers University in New Jersey.
Morley found that even if climate change is kept under two degrees, species off Canada's west coast will move by an average of more than 200 kilometres.
"Even in the best-case scenario, on the west coast we still expect to see some pretty substantial shifts of species northward."
Morley looked at the impact of warming seas on 636 species of marine life on the Atlantic and Pacific coasts. About one-quarter of those species have some commercial value, he said.
He used extensive data about where those species hang out and collected oceanographic information on currents, water temperature and the shape of sea floors. He ran all that through 16 different climate models, once to estimate the impact of two degrees of warming and once to estimate for four degrees.
Previous studies have already suggested that climate change will drive fish stocks northward. The size of Morley's dataset makes his conclusions, published in a paper this week in the online journal publication PLOS-One, more detailed and specific.
He concludes that with no more than two degrees warming — the goal agreed to in the Paris agreement — fish stocks on the Pacific coast will migrate north by an average of 236 kilometres. The Atlantic side will see average movement of about 100 kilometres.
If the climate warms by four degrees — the so-called business-as-usual case — many Pacific stocks are likely to school as far as 1,500 kilometres north of the current centre of their habitat. The east coast shift would be about 600 kilometres.
"They were pretty large changes throughout the west coast."
The effect of climate change is more pronounced on the west coast because the difference in temperature between northern and southern water is less than in the east. That means western fish must travel further to find cooler water.
In terms of abundance, it's hard to pick winners and losers, said Morley. That depends on factors such as food availability as much as on temperature.
"For some regions, the outlook for existing fisheries is generally negative but for other regions, fisheries could become more lucrative. It really depends on the species."
Pollock, one of the most commonly caught species in the world, are expected to diminish.
"For walleye pollock, which is a huge fishery globally, we're definitely anticipative of a reduction in habitat suitability overall."
Fisheries on both coasts are managed through a delicate network overseen by two countries and a number of states and provinces. The change in where those fisheries occur is going to make that more challenging, said Morley.
"Fisheries management is based on the assumption on stock not really exhibiting any long-term change, just a lot of variability. Regional management entities really need to change their view on how these stocks are managed.
"We need to start anticipating what these changes are going to be."
Those changes are already under way, said Morley.
"They're definitely happening and pronounced in some regions."
The federal Ministry of Fisheries and Oceans did not provide a response to a request for comment.
— Follow Bob Weber on Twitter at @row1960
Bob Weber, The Canadian Press
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