A new study out of the University of Manitoba shows some lake predators are changing their behaviour due to climate change, which may have a wide-ranging effect on aquatic ecosystems.

Researchers watched the feeding habits of lake trout at the IISD Experimental Lakes Area in northwestern Ontario over an 11-year span and found the fish can quickly adapt their behaviour — moving to deeper and cooler parts of the lake to feed — as water temperatures rise.

Matthew Guzzo, a PhD candidate in the U of M's department of biological sciences and lead author of the study published in the proceedings of National Academy of Sciences, said as temperatures rise, lake trout move from shallow, more productive waters to the deep part of the lake where water is cooler but food is of a lower quality.

"When you shorten the period when fish can access an area of the lake where the rich food is, it's going to impact … how much they can grow," said Guzzo.

"And if you're seeing changes in their growth that could impact the ability of a lake trout population to sustain itself — if a lake trout population can't get enough energy to produce eggs or spawn, obviously that population might be in trouble."

Findings not all bad for trout

Lake trout are also top predators, and Guzzo said when a top predator is forced to change what it eats, it impacts not only its own well-being, but the whole food web around it as well.

The study's findings are important for understanding how lake trout and other temperature-sensitive fish will respond to climate change, said Guzzo.

"Lake trout have been called a sentinel species or a canary in a coal mine, for looking at climate change because Lake Trout adapted during the last glaciation under the ice, so they're really temperature sensitive," he said.

"If we need to pick a species to study the impact of warming on lakes or lake food webs, they're a really good species to do it on."

And the study's results aren't necessarily all bad news for lake trout, Guzzo noted. The adaptability observed by researchers might mean the species will adjust to climate change over the long term, he said.

"In reality because these fish can adjust their behaviour and avoid the thermal conditions that they don't like, it may mean that some of these predictions of species range contractions are pretty conservative — maybe these fish can adjust and live in these lakes," he said.

"A lot of the studies are doom and gloom and say that they're going to go extinct, but maybe they can adapt."