05/15/2013 04:34 EDT | Updated 07/15/2013 05:12 EDT

UBC study finds fish species shifting to the north because of climate change

Climate change has been forcing fish to head north in search of cooler seas for nearly four decades, according to newly published research.

In paper published Wednesday in the journal Nature, a University of British Columbia scientist said global fisheries are being increasingly dominated by warm-water species, which will cause major changes in the industry.

"We expect to see a change in the fishery's catch," said William Cheung. "The fishing industry will have to adapt to change in the new species."

Scientists have long looked for a way to measure the impact of the gradually warming ocean created by climate change, but haven't found one. Cheung's approach was to use fish as a kind of thermometer to measure what's going on.

He correlated global fisheries records with what's already known about what temperature each species prefers. Using that information, he calculated something he calls the mean temperature of the catch.

"We looked at the change in mean temperature of the catch over the large ecosystems in the world," he said. "We find that after accounting for the effects of fishing as well as the effects of natural ocean variation, the mean temperature of the catch is increasing."

That mean temperature is increasing by nearly two degrees per decade, Cheung said, and has been rising for about 40 years.

The effects are already becoming apparent.

Fishers off New England are starting to see more and more fish usually found near the tropics. The distribution of Atlantic mackerel has shifted from Norway to Iceland, creating problems in fishing regulation.

More troubling is the likely effect on the tropics. When tropical commercial species head a little north as the ocean becomes too warm, there's nothing coming in to replace them.

"In the tropics, if trends continue, it means the habitat for tropical species will be reduced," said Cheung.

That's likely to create challenges for those who depend on them.

"The high-latitude regions are mostly developed countries and they have the capacity to help with adaptation," Cheung said.

"But with the tropics, lots of them are developing countries where they do not have these well-developed institutions or social capacity to deal with these changes. At the same time, they are much more dependent on the resources, making these regions even more vulnerable."

Cheung said his work doesn't necessarily shed light on the abundance of the fishery, just its makeup. The changes, however, could work to the advantage of more northern fishers.

"In terms of the Arctic we expect to see increased opportunities," he said. "We are already seeing these changes."

He said more study needs to be conducted on those emerging fisheries before they are commercially exploited.

"We still don't have a good management strategy for potential fishing opportunities in the Arctic."

The U.S. has banned commercial fishing in its Arctic waters until more research is conducted. Canada has yet to make such a move.

Arctic fisheries are emerging as one of the main issues at the Arctic Council, the eight-nation body that has become the chief diplomatic forum for northern issues. Canada has just taken over as chairman of the council for a two-year term.