Sydney: Climate change could bring about unpredictable alterations in one's personality. Coral reef fish, for instance, can become more aggressive in warmer water, says a new study.

Experiments with two species of young damselfish on Australia's Great Barrier Reef have shown that some reef fish are either consistently timid, or consistently bold.

These individual differences are even more marked as water temperatures rise.

A slight rise of just one or two degrees may have only a small effect on some fish but the behaviour of others can be transformed - leading them to become up to 30 times more active and aggressive.

"We now know that personality is common in animal populations, and that this phenomenon may have far-reaching implications for understanding how animals respond to ecological and environmental challenges," says Peter Biro.

Biro of the University of New South Wales (UNSW) School of Biological, Earth and Environmental Sciences, led the study with colleagues Christa Beckmann and Judy A. Stamps.

"Our results also suggest that temperature variations are much more significant than we thought in the way they affect the behaviours of individual animals."

"For instance, individual variations in activity and boldness can affect food acquisition, encounter rates with predators and even the likelihood of an individual being captured by sampling or harvesting gear," Biro adds.

The scientists used fish that were captured just as they were ending their larval stage in open water and had not yet settled onto the reef, and so were naive to social hustle and bustle of reef fish life. They then directly manipulated water temperatures in lab tanks at Lizard Island Research station.

Placed by themselves in tanks, the fish were free to explore or to take refuge in a short piece of plastic pipe. The scientists observed how far and how often the fish ventured from the pipe. In cooler water, individual fish differed greatly in their activity levels, says an UNSW release.

They all became more active to varying degrees when the water was warmed, with some becoming up to 30 times more active, bold and aggressive.

These findings were published in the Proceedings of the Royal Society B. IANS