Lake Michigan is warming. A new report says that could mean trouble for game fish.

A warmer and wetter climate in the Midwest could lead to the displacement of some cold water fish species in southern Lake Michigan and trigger mass die-offs in smaller inland lakes, according to a report published this week by Purdue University.

As the atmosphere warms due to the proliferation of greenhouse gases, so too are the Great Lakes, warns a Purdue University-led report on the impacts of climate change in Indiana. Summer surface water temperature in Lake Michigan has warmed about 3 degrees since 1980, and is projected to accelerate, rising at least 1 degree a decade, experts say. A hotter climate could become a problem for some game fish, like trout and salmon, that depend on cold, oxygen-rich waters.

“I think it might be a surprise to a lot of people that Lake Michigan is warming,” said Tomas Hook, a professor of fisheries and aquatic sciences at Purdue and director of the Illinois-Indiana Sea Grant.

The warming is expected to reduce the amount of time cold water fish spend in the southern basin of Lake Michigan, where the chance of catching these species is already limited because it’s shallower and more tepid than the rest of the lake. Now, much of the lake is so deep and cold in open water that most fish can’t survive there, but warming will likely open up more habitat for the majority of fish, Hook said. However, whether they will be able to find sufficient food in those new waters is unclear.

Temperatures in Illinois and Indiana have risen more than 1 degree over the past century, but scientists expect the warming to accelerate. Summer temperatures in Illinois could resemble Texas or Oklahoma by the end of the century, according to the U.S. Environmental Protection Agency’s archives.

The statewide average temperature for Illinois this summer was 75 degrees, 1.4 degrees above normal. This summer, Lake Michigan was measured at about 5 degrees above its long-term season average.

At a recent meeting in Portage to discuss the report, Labovitz, the national lakeshore superintendent, remarked about the changes he’s noticed. The Indiana Department of Natural Resources has received reports of armadillo sightings. Beach season has unofficially extended into October. And, he is trying his luck growing sweet potatoes, a crop harvested in Southern states and California.

Hook, the Sea Grant director, said state resource managers have been accounting for short-term considerations, like invasive species or pollution, but the new study — part of a series of reports detailing the far-reaching impacts of climate change in Indiana — recommends they account for climate change by incorporating strategies such as pumping oxygen into the bottom of some small lakes.

Because these are such complex systems, it’s difficult for even experts to predict what the end result will be, said Jeffrey Dukes, director of Purdue’s Climate Change Research Center.

“The bottom line is that these sort of changes are already happening,” Dukes said. “We already have things that are stressing aquatic ecosystems, and this is only going to increase the stress for many species. We don’t know how many are going to deal with the changing climate on top of everything else. It’s going to cause problems for cold water species, but it’s going to mix things up for all species.”


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