Fish head to the poles as waters warm

New study out of UBC off ers clear insight into changing habitats

THE STUDY

Researchers have produced the strongest evidence yet that climate change is forcing hundreds of valuable fi sh species toward the poles.

The paper, published in the ICES Journal of Marine Science on Friday, concludes that Canadian and Arctic waters may end up with more species and greater abundance. But fisheries in the tropics, where people depend more heavily on seafood, may become hollowed out.

“The variety of species available for fisheries in the tropics will decrease,” said co- author William Cheung of the University of British Columbia. “It may be good news for the Arctic — our projections are that the Arctic will be a hot spot for species invasion. There will be more variety of fi sh species available for the Arctic region.”

WHAT’S NEW

Previous studies have suggested that warming ocean waters will aff ect the distribution of fi sh stocks. Cheung’s paper gives the clearest and broadest picture yet of those eff ects.

Using a combination of three different mathematical models and the latest climate data, he forecast the probable distribution of 802 commercially exploited fi sh species. Those species include commonly harvested fi sh such as cod, tuna, herring and halibut.

On average, Cheung found the fi sh are slowly moving toward the South and North poles at a rate of between 15 and 26 kilometres a decade. The eff ect is more pronounced in the Arctic, where warming is happening the quickest.

SOME UNKNOWNS

The fi ndings mean challenges as well as opportunity, Cheung warns. How the invasive species will interact with existing species and ecosystems is unknown. Their movements are also likely to create problems for international fisheries management, as stocks shift across diff erent jurisdictions.

“They could destabilize existing management agreements between countries.”

That’s already happening in some parts of the ocean, Cheung said. Scandinavian countries are negotiating how they’ll deal with changes in the location of Atlantic mackerel stocks.

FOR THE NORTH

Cheung cautioned northern countries not to rush to exploit new fi sh stocks until scientists have a chance to learn what’s happening with them and how they’ll interact with existing populations. He praises a U. S. decision to enact a moratorium on new commercial fi shing in the Arctic. Canada has enacted no such fi shing ban.

“We know from our previous experience that if we don’t manage the fisheries well, it will collapse quite easily. It would be much better to be conservative and careful at fi rst.”

WHAT’S NEXT

The study points to the need for governments to start thinking now about how climate change will aff ect natural resources such as fisheries in the future, Cheung said.

“Things are much more easy to manage when there’s not a vested interest already there,” he said. “We really need to look into these longterm projections and scenarios and start to think about how the fisheries should be managed now.”