Lake Mille Lacs resort owners are angry, anglers are frustrated, and they all have an opinion on what's to blame for the shocking decline in walleye in Minnesota's favorite fishing destination.
But there's one culprit that gets scant attention: global warming.
Tullibee, a cold-water loving fish that is a critical prey for walleye, is largely gone from Mille Lacs. In fact, tullibee is in trouble across the state — a clear sign that Minnesota's lakes are changing as fast as the climate and creating an uncertain future for the state's prized fishing industry.
By the end of this century, tullibee will be gone or drastically reduced in two-thirds of the lakes where it lives now, according to a sophisticated climate prediction model by state and University of Minnesota scientists. Other coldwater fish like yellow perch, burbot and lake trout are also declining, while warmwater fish like bluegill and crappies are on the rise.
"It's a pretty striking story," said Peter Jacobson, a fish biologist with the state Department of Natural Resources. He's been studying tullibee since heat-related fish kills first got his attention in the hot summer of 2006. "The recent declines have been mostly from climate."
The shift is dramatic enough to inspire an unusual effort to create refuges for the vulnerable fish species by permanently protecting some of Minnesota's cleanest, coldest lakes that are scattered like jewels across the northern forest. Before it's too late.
"It's such a daunting issue," Jacobson said.
In Mille Lacs, there's a lot more going on in the predatory life of fish than just climate change. Young walleye are getting eaten before they grow up by a rising population of northern pike and cannibalistic larger walleye. Thanks to invasive zebra mussels and laws that shut down leaky septic systems and animal feedlots, the water is cleaner and clearer, making the little walleye easier to see. The population of smallmouth bass, a fish happy in warmer waters, has exploded in recent years — but walleye don't eat them. Meanwhile, tullibee and the yellow perch that walleye do relish are disappearing, and other well established invasives like spiny water flea and milfoil are changing the ecosystem in unpredictable ways.