Fish get smaller

A hearty fillet of fish, already a rare treat because of over-trawled oceans, will become even more infrequent in the future when global warming starts to reduce fish size, scientists said.

It’s a constant challenge for fish to get enough oxygen from water to grow and the situation gets worse as fish get bigger

Researchers looked at computer models to see how warmer, and thus less oxygenated, seas affected more than 600 species of fish.

Compared to 2000, the maximum attainable body weight of these fish declined by between 14 and 24 per cent by 2050.

Fish inhabiting the Indian Ocean were the most affected, reducing by 24 per cent, followed by counterparts in the Atlantic (20 per cent) and then the Pacific (14 per cent), with tropical waters worst hit.

“It’s a constant challenge for fish to get enough oxygen from water to grow and the situation gets worse as fish get bigger,” said Daniel Pauly of the University of British Columbia in western Canada, who first raised the warming-and-growth link 30 years ago. “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 more.”

The model used the so-called A2 scenario, which sees an average rise in global atmospheric temperatures of 3.4°C by 2100 compared to 2000.

Until recently, this would have been considered a pessimistic scenario but many climatologists say it is realistic in the light of a rise in fossil-fuel emissions.