UNIVERSITY PARK, Pa. — Because walleyes are a cool-water fish species with a limited temperature tolerance, biologists expected them to act like the proverbial “canary in a coal mine” that would begin to suffer and signal when lakes influenced by climate change start to warm. But in a new study, a team of researchers discovered that it is not that simple.
“After analyzing walleye early-life growth rates in many lakes in the upper Midwest over the last three decades, we determined that water clarity affects how growth rates of walleyes change as lakes start to warm,” said Tyler Wagner, Penn State adjunct professor of fisheries ecology. “In some lakes, warming actually led to increased walleye growth rates, in others there essentially was no change, and in others, growth rates declined. The different responses of growth rates to increasing water temperatures across lakes appear to be influenced by water turbidity.”
The research is significant, Wagner explained, because walleye fisheries in the upper Midwest are important not just ecologically, but also from an economic and cultural perspective. Because walleye fishing is a valued social activity in Minnesota and Wisconsin and hundreds of thousands of walleye fingerlings are stocked there to bolster wild populations, the region is the ideal place to study the effect of warming conditions on the fish.
According to the U.S. Environmental Protection Agency, the Midwest has gotten warmer, with average annual temperatures increasing over the last several decades. Between 1900 and 2010, the average air temperature increased by more than 1.5 degrees Fahrenheit in the region.