Walleye are one of the most sought-after species in freshwater sportfishing, a delicacy on Midwestern menus and a critically important part of the culture of many Indigenous communities. They are also struggling to survive in the warming waters of the Midwestern United States and Canada.
According to a new study published in the journal Limnology and Oceanography Letters, part of the problem is that walleye are creatures of habit, and the seasons — especially winter — are changing so fast that this iconic species of freshwater fish can’t keep up.
The timing of walleye spawning — when the fish mate and lay their eggs — has historically been tied to the thawing of frozen lakes each spring, says the study’s lead author, Martha Barta, a research technician at the University of Wisconsin–Madison. Now, due to our changing climate, walleye have been “unable to keep up with increasingly early and more variable ice-off dates,” Barta says.
Within a few days of ice-off, when a lakes’ frozen lid has melted away, walleye begin laying eggs and fertilizing them. In a normal year, that timing sets baby fish up for success once they hatch. But, Barta says, “climate change is interrupting the historical pairing of ice-off and walleye spawning, and that threatens the persistence of walleye populations across the Upper Midwest.”