Original URL: http://www.theregister.co.uk/2012/10/01/climate_change_shrink_fish/

Climate change threatens to SHRINK FISH AND CHIP SUPPERS

Teeny oxygen-starved cod will hit global food supplies

By Brid-Aine Parnell

Posted in Science, 1st October 2012 10:59 GMT

Climate change could threaten the quintessential British meal, the venerable fish and chips, which will only be available in small portions or not at all if boffins are correct.

The scientists have warned that the body weight of fish, including North Sea haddock and cod, will drop if oceans warm up. The theory goes that warmer waters increases the metabolic rate in fish, which will increase the demand for oxygen. If there isn't enough oxygen to go around, then the fish body weight will drop, it is believed.

According to computer models, the maximum body weight for more than 600 species could shrink by 14 to 20 per cent between the years 2000 and 2050.

“We were surprised to see such a large decrease in fish size,” study lead author William Cheung, an assistant professor at the University of British Columbia Fisheries Centre, said.

“Marine fish are generally known to respond to climate change through changing distribution and seasonality. But the unexpectedly big effect that climate change could have on body size suggests that we may be missing a big piece of the puzzle of understanding climate change effects in the ocean.”

The researchers already know that the number of fish in the world's oceans is likely to decline with climate change, but the study shows that the ones that are left will still get smaller.

The fishes' growth is linked to their oxygen supply, an idea another UBC boffin, Daniel Pauly, first suggested thirty years ago. But this is the first time his idea has been applied to the global fish population.

“It’s a constant challenge for fish to get enough oxygen from water to grow, and the situation gets worse as fish get bigger,” Pauly, who also worked on this study, said.

“A warmer and less-oxygenated ocean, as predicted under climate change, would make it more difficult for bigger fish to get enough oxygen, which means they will stop growing sooner.”

The biggest effects of fish shrinking are likely to be seen in the tropics, but colder seas will also see the migration of those tropical fish as they warm, another factor impacting the size of fish in those waters.

The study was published in Nature Climate Change. ®