The acid test of strange fish behaviour
Ocean acidification may not mess with coral reef fish after all.
The past decade has seen an accumulation of high-profile and influential studies showing that ocean acidification – the result of CO2 emissions dissolving in seawater – disrupts basic fish behaviour. But according to new research, most of it is wrong.
Acidification has been reported to interfere with smell, hearing, vision and activity levels in fish, especially in coral reef species. One well-publicised study found that it caused fish to swim towards predators rather than away from them.
Timothy Clark of Australia’s Deakin University says his interest was raised by the unusually strong effects of CO2 identified in the studies. “Yet there had been no attempt by independent research groups to replicate these profound findings.”
Working with an international team of colleagues, Clark embarked on a three-year project to do exactly that. And now, after experiments on more than 900 fish belonging to six species, using automated data collection techniques to minimise human error and bias, they have concluded that CO2 has virtually no effect on any of the behaviours previously reported.
Clark is concerned that an increasing pressure on scientists to “publish or perish” has encouraged some questionable practices.
“It is absolutely critical that scientists do everything possible to make sure they get things right, as otherwise it feeds the growing public scepticism of scientists, especially in the climate change realm,” he says. “It is possible that some scientists think that the end justifies the means, so the scientific rigour comes second to the story.”
But Philip Munday of Australia’s James Cook University, who was involved in many of the studies now being called into question, warns against putting too much faith in the new analysis. “They used different species, different life stages and changed methods in ways that could fundamentally alter the results,” he says. He is unwilling to expand on this, though, until he has published a formal defence in a journal.
Meanwhile, Clark maintains that ocean acidification does not meaningfully alter fish behaviour. “There are much greater threats facing coral reef fishes, such as ocean warming, habitat destruction and pollution,” he says. “These factors deserve more of our research attention with a goal to conserve coral reefs and all the wildlife they support.” Stuart Blackman
FIND OUT MORE
Nature: go.nature.com/34jBosI