Sat, Feb 14, 2009 - Page 6 News List

Climate change to cause dark night of the shoal: study


Climate change will cause key species of fish to migrate toward the poles, badly depleting many commercial fisheries, scientists said in a study published on Thursday.

“The impact of climate change on marine biodiversity and fisheries is going to be huge,” said its lead author, William Cheung of the School of Environmental Sciences at the University of East Anglia in the UK.

Cheung’s team used a high-powered computer model, based on knowledge of 1,066 species of fish, their habitat and climate change, to predict what might happen by 2050 based on three scenarios for global warming.

Warmer water will lead to “large-scale redistribution” of these species, with most of them moving toward the poles, shifting on average by more than 40km per decade, they said in the report in the journal Fish and Fisheries that was to be presented at a meeting in Chicago yesterday.

Cheung said the report, written with scientists in the US and projecting average shifts of more than 200km over five decades, was the first to model climate impacts for more than 1,000 species such as herring, tuna, sharks or prawns.

Stocks of many species are already under pressure from over-fishing or pollution.

In the North Sea, a northward shift of cod could cut numbers by 20 percent. At the same time, North Sea stocks of the more southerly European plaice might rise by more than 10 percent.

And some cod populations off the east coast of the US might decline by half by 2050, the report said.

“Countries in the tropics will suffer most from reductions in catches,” Cheung said.

The UN Climate Panel says emissions of greenhouse gases, mainly from burning fossil fuels, are stoking climate change such as droughts or rising seas.

Overall, Cheung said total fish catches from the world’s oceans would be little changed by mid-century despite the shifts.

“It’s more about reshuffling the catch,” he said.

The study made computer models for the movements of 1,066 species — 836 types of fish and 230 invertebrates, such as crabs and lobsters.

Some species could die off, such as fish that thrive in cold waters and would have nowhere to go if the oceans warmed.

“Some species will face a high risk of extinction, including Striped Rock Cod in the Antarctic and St Paul Rock Lobster in the Southern Ocean,” the University of East Anglia said.

Cheung said shifts were under way. Trawlers off the western US, for instance, were having to travel further north to catch the same fish. That led to problems, for instance, of coping with currents or rocks in unfamiliar waters.

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