Climate change could be reducing fish numbers by causing them to get lost, Australian scientists have found.
The stresses of warmer sea temperatures and more acidic seawater may be affecting the development of ear bones in young reef fish, according to fish ecologist Dr Monica Gagliano of James Cook University (JCU) in Townsville and the Australian Institute of Marine Science (AIMS).
Dr Gagliano said the stress in their larval stage could make fish develop asymmetrical ear bones or otoliths, causing them to lose their way at sea during a crucial stage of their development, she said.
"If they have asymmetrical ears and they can't quite navigate to a suitable habitat to grow into an adult and reproduce, which is ultimately their aim, then they have a problem," Dr Gagliano told AAP.
"So, our data is showing that if you don't develop properly you might get lost."
Dr Gagliano and three other scientists studied damselfish, which are abundant on many reefs, including Queensland's Great Barrier Reef and Western Australia's Nigaloo Reef.
Their findings were published today in the prestigious UK scientific journal Proceedings of the Royal Society.
They found that 41 per cent had symmetrical otoliths and 59 per cent asymmetrical when they hatched.
But a few weeks later, when they were due to settle in a habitat and breed, far fewer asymmetrical fish were found to have made their way back to the reef.
"A degree of asymmetry is natural but when the environment deteriorates, asymmetrical fish become more frequent," Dr Gagliano said.
"It's quite a concern because there are consequences for the population level.
"You would expect the population to shrink and eventually when you reduce the population to the point when it is is too small, it just can't sustain itself.
"But this is a very gloomy scenario and I'm hoping that the fish can do something else and maybe devise a plan B for their navigation."
Dr Gagliano said there was evidence that other fish were similarly affected.
"We know that other species respond in the same way," she said.
Dr Gagliano worked on the project with Dr Martial Depczynski (Martial Depczynski) of AIMS Perth, Dr Stephen Simpson from Scotland's University of Edinburgh and James Moore from JCU Townsville.
