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  The Age 12 Jun 07
Global warming could kill off reef fish

Any rise in sea temperatures due to global warming could decimate fish populations on Australia's Great Barrier Reef, researchers say.

A three-and-a-half year study of fish near Lizard Island at the northern end of the reef, off Queensland, showed that whether they survived from eggs depended not only on their genes but also on their environment.

Monica Gagliano, of the ARC Centre of Excellence for Coral Reef Studies (CoECRS) and James Cook University (JCU), said water temperatures in the summer breeding season of the Ambon Damselfish varied between 25 and 31 degrees, but the upper end of the range was already of concern.

"What we did is to test what would happen if the water started getting warm according to the predictions for climate change," Dr Gagliano said. "From our experiments, if the temperature was to rise even just a few degrees, it could have quite dramatic consequences on just how many of those eggs do survive.

"From my experience, at 31 degrees, 50 per cent of the eggs are already gone."

The outlook was even more grim if the predicted rise of at least one degree happened in the next 10 years, she said.

This was too short a timeframe for fish to evolve through natural selection to adapt to the higher water temperature, but the behaviour of their parents may have an influence in helping their offspring survive.

This would be the subject of Dr Gagliano's future research.

"My next question will be can the parents predict somehow what is going to happen and adjust their behaviour so their babies will be able to survive in a changing environment," Dr Gagliano said. "Do they have a plan B?"

Their actions could range from giving birth in a different area with slightly cooler water or not breeding at all, she said.

The behaviour of the tiny yellow Damselfish could also have wide repercussions for other species, including commercial species.

"The characteristics of their life, like how parents behave and how they produce their eggs and what the eggs do are very similar throughout species, including commercial species such as coral trout," she said.

Dr Gagliano's research and those of her colleagues Dr Mark McCormick and Dr Mark Meekan from the Australian Institute of Marine Science (AIMS) have recently been published in prestigious science journals.
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