Adaptable cod climate pointer

A research project at Scott Base in Antarctica on bald rock cod living in icy waters has suggested an unexpected capability to adapt to global warming.

The Antarctic fish was able to adjust its cardiovascular system and metabolism to adapt to rising water temperatures.

"This research is extremely exciting as it shows that Antarctic fish are much more flexible than was previously thought," said Associate Professor Bill Davison, of Canterbury University, who led the project.

"Global warming is affecting the whole planet, but the biggest changes are happening in Antarctica.

"The fact that these fish can cope with what is quite a massive change in temperature gives us some hope for the future of the Antarctic fauna."

Further tests on the rock cod at Canterbury University showed that the fish accustomed to freezing Antarctic waters could thrive in warmer conditions.

The fish, which are found under the sea ice, normally live in constant water temperatures of -1.8C.

But in aquariums at Scott Base and Canterbury University the fish became accustomed to water of 4C.

Professor Davison said the fish were made to swim through a tunnel in waters of varying temperature.

He said fish fresh from the ocean swam well in water measuring up to 2C but became less efficient as the temperature rose.

But once they had adjusted to the warmer "climate" the fish swam well in water measuring as high as 8C.

He said that the bald rock cod belonged to a group of animals known as stenotherms which, until these findings, had been thought to have been incapable of surviving outside their normal environmental temperature.

But Professor Davison said the results could not just be looked at in isolation. "What we really need to be looking at is the whole ecosystem, rather than one component."

Frank Seebacher, a Sydney University specialist in integrative physiology at the school of biological sciences who participated in the project, said he was flabbergasted by the results.

"Although we proposed the hypothesis on the basis of scientific reasoning we were astounded by the extent to which these animals were able to cope with warm water," he told the ABC.

The fish they caught for the project were kept at either their natural temperature, -1C, or at 4C for five weeks before their swimming performance was tested.

Previously the belief was that the upper lethal temperature, where 50 per cent of the fish die, was anything over 6C.

Sea change

* Bald rock cod in the Antarctic normally live at -1.8C.

* They swim well at up to 8C, suggesting they could adapt to global warming.

- NZPA