Hot And Bothered – How Climate Change Will Make Fish More Reckless

[Luringbream]

Hot and bothered – how climate change will make fish more reckless

26 Jun 2007

The effects of climate change won't kill young fish outright, but it will increase their metabolism, making them more hungry and more likely to get eaten by predators according to an important new study by fish scientists in Australia and Canada.

In what's being claimed as a first "whole system" demonstration of the impact of water temperature fluctuations on fish populations, the scientists assert that what's true for trout in Canadian lakes will also be true for tropical fish off the coast of Australia, and for fish in general.

Dr Peter Biro and Professor David Booth from the UTS Faculty of Science and Professor John R. Post of the University of Calgary, have drawn their conclusions from data on rainbow trout collected from experimental lakes in British Columbia.

Animal behaviourist Dr Biro said the controlled conditions in the experimental lakes, with experimentally created fish populations, had allowed the researchers to collect data on fish behaviour and survival over two years with differing average temperatures. A total of 17 lake years of data was used.

He said the results were a basis to predict climate-induced mortality in fish populations at the scale of entire populations and water bodies.

"In contrast to laboratory results, data obtained from whole-population experiments in small lakes allow us to extrapolate our findings to the population level, be it in freshwater environments or the oceans, near the poles or in the tropics, the results are that general," Dr Biro said.

"Relatively small increases in water temperature can dramatically reduce survival in fish populations. Temperature change has an impact on physiology, but even more importantly, it also affects behaviour.

"Fish populations are often highly adapted to their local climates, and temperatures in excess of their evolved optimum level for growth increase metabolism and drive fish to feed more.

"This behavioural mechanism for compensating for low growth rates in warm years has a high mortality cost.

"For young fish being more visible is risky. If they're foraging more because they're hungry they're much more likely to encounter predators, and more likely be detected by them once encountered.

"In the experimental lakes fewer than half as many trout survived on average when temperatures were just 2.7ºC above the optimum.

"Those populations at high temperatures and low food abundance experienced the lowest survival, with only a few percent of the original cohort of young fish surviving their first growing season before winter.

"Given there is a clear trend towards increased summer air temperatures in recent decades, we predict that enclosed freshwater fisheries in particular will experience increased frequency of poor survival rates leading to significant economic loss," Dr Biro said.

The results of the research have been published in the USA-based scientific journal Proceedings of the National Academy of Sciences. The article is published online here; http://www.pnas.org/cgi/content/abstract/0701638104v1

DAN

Edited June 28, 2007 by Luringbream