The research found that as the water in which the fish live warms, they are less able to perform activities crucial to survival, such as evading predators, finding food and accumulating sufficient energy reserves to breed.

Published in Global Change Biology, the study measured the rates at which six species of fish living on coral reefs near the equator use oxygen across different temperatures, both at rest and during maximal performance. Many species in this region only ever experience a narrow range of temperatures, said Jodie Rummer, the study’s lead author, and so are likely to be adapted to perform best at those temperatures. Given that oceans are projected to warm by 2–3°C by the end of this century, many equatorial marine species may be at risk. ‘Such an increase in warming leads to a loss of performance,’ Rummer explained. ‘We found that four species of fish are living at or above the temperatures at which they function best.’

According to Rummer, as temperatures rise, species may be forced to move away from the equator to find refuge in areas with more forgiving temperatures. ‘This will have a substantial impact on the human societies that depend on these fish,’ she said.

This story was published in the April 2014 edition of Geographical Magazine