Climate change forcing fish stocks north: study

A study has produced the strongest evidence yet that climatechange is forcing hundreds of valuable fish species toward thepoles.

The paper, published in the ICES Journal of Marine Science onFriday, concludes that Canadian and Arctic waters may end up withmore species and greater abundance.

But fisheries in the tropics, where people depend more heavily onseafood, may become hollowed out.

"The variety of species available for fisheries in the tropicswill decrease," said co-author William Cheung of the University ofBritish Columbia.

"It may be good news for the Arctic our projections are thatthe Arctic will be a hot spot for species invasion. There will bemore variety of fish species available for the Arctic region."

Previous studies have suggested that warming ocean waters willaffect the distribution of fish stocks. Cheung's paper gives theclearest and broadest picture yet of those effects.

More than 800 species studied

Using a combination of three different mathematical models andthe latest climate data, he forecast the probable distribution of802 commercially exploited fish species. Those species includecommonly harvested fish such as cod, tuna, herring and halibut.

On average, Cheung found the fish are slowly moving toward theSouth and North poles at a rate of between 15 and 26 kilometres adecade. The effect is more pronounced in the Arctic, where warmingis happening the quickest.

He checked his conclusions by using the same method to model thepast movements of fish. When Cheung compared the modelling resultswith actual fisheries data, the two matched up.

"We found that, overall, our projections are consistent with theobservations in the last 30 years."

Some countries already seeing new species

Cheung warns that the finding means challenges as well asopportunity.

How the invasive species will interact with existing species andecosystems is unknown. Their movements are also likely to createproblems for international fisheries management, as stocks shiftacross different jurisdictions.

"They could destabilize existing management agreements betweencountries."

That's already happening in some parts of the ocean, he said.

Scandinavian countries are negotiating how they'll deal with changesin the location of Atlantic mackerel stocks.

"Norwegian fisheries are already changing noticeably."

Cheung cautioned northern countries not to rush to exploit new fish stocks until scientists have a chance to learn what's happeningwith them and how they'll interact with existing populations. Hepraises a U.S. decision to enact a moratorium on new commercialfishing in the Arctic.

Canada has enacted no such fishing ban.

"We know from our previous experience that if we don't managethe fisheries well, it will collapse quite easily. It would be muchbetter to be conservative and careful at first."

Cheung said his study points to the need for governments to startthinking now about how climate change will affect natural resourcessuch as fisheries in the future.

"Things are much more easy to manage when there's not a vestedinterest already there," he said.

"We really need to look into these long-term projections andscenarios and start to think about how the fisheries should bemanaged now."