Fish Fry


Extreme weather may not be good for doing field work but it can lead to extraordinary discoveries, as biologist Peter Biro can attest.

While studying the influence of water temperature on survival rates of wild rainbow trout for his PhD, Biro had to put up with the sweltering heat of 1998, one of the Earth’s hottest years on record, followed by the abnormally cool and rainy summer of 1999. While it made for uncomfortable conditions slogging through small lakes in British Columbia’s Okanagan, Biro’s perseverance paid off with findings that are considered an alarming example of how global warming could have swift and disastrous consequences for fish populations around the world.

“I wasn’t supposed to be doing climate change research but it turned out that way because my field work happened to fall during those two unusual years,” says Biro, who completed his PhD at the University of Calgary and is now a post-doctoral researcher at the University of Technology, Sydney (UTS) in Australia.

“In 1998 it was just smokin’ hot and that was followed by 1999 when it was freezing cold, and I shivered in my wetsuit every day,” Biro recalls. “In hindsight, it’s now obvious why my results were so different between the two years.”

Biro’s results led to a paper published earlier this year in the prestigious Proceedings of the National Academy of Sciences (PNAS) that is causing a stir. As the first study to examine the impacts of environmental temperature on multiple independent populations of animals, Biro and his colleagues warn that global warming could lead to the quick extinction of North America’s rainbow trout, and show how even small increases in water temperature have dramatic effects on the livelihood of all fish. The study was written by Biro, U of C ecology professor John Post and UTS professor David Booth.

“The really disturbing thing is that these results don’t just apply to rainbow trout. We expect they can be generally applied to all fish, whether they live in rivers, lakes or the ocean,” Biro said.

Working in nine small, isolated “kettle lakes” that were stocked with trout for research purposes, Biro found that more than only half as many fish survived in 1998 when the water temperature was three-degrees warmer, than the cooler year that followed. The study also uncovered the reason for the accelerated die-off: warmer temperatures speed up fish metabolisms, requiring them to feed more, which in turn exposes them to greater danger from predators.

“In warmer years they need to compensate by eating more to maintain growth, which means swimming around more to hunt food,” Biro explains. “In 1998 we found that this led to a lot of fish being killed, and as climate change continues, we can expect to see a lot more years like that.”

Biro, Post and Booth’s complete PNAS article is available online at:

For more information, contact:
Grady Semmens
Senior Communications Manager – Research
University of Calgary
Phone: (403) 220-7722


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Filed under biodiversity, climate change, conservation, global warming, nature, wildlife

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