Climate Change is Affecting The Kind of Fish You Can Catch in Michigan’s Inland Lakes

“Climate change is having an effect on lakes in Michigan right now, so we’re seeing decreased ice coverage,” said Joe Nohner with the Michigan Department of Natural Resources.

He says over the decades, the decrease in the amount of ice on inland lakes has been substantial.

“For example, Gull Lake over in Barry and Kalamazoo counties, we’ve lost about 22 days of ice in a typical year since the 1920s,” he said about the lake where the Michigan State University Kellogg Bird Sanctuary is located.

“But less ice cover is just one symptom of larger changes. We’re seeing shorter ice periods. We’re seeing warming summer surface water temperatures, so lakes are getting warmer. And then we’re seeing changes in fish communities potentially as a result of those warming temperatures,” Nohner said.

Cold-water fish such as cisco are disappearing from some lakes. 

Gretchen Hansen at the University of Minnesota said other cool-water fish such as walleye are struggling.

“Species like walleye and perch that spawn in the spring, they need a long, cold winter for those eggs to develop. And so there is a decent amount of evidence that if they don’t have enough sustained cold temperatures in the winter, their eggs aren’t going to be as high quality and they’re not going to survive as well,” she said. 

Some fish also suffer during the hotter summers and not because of warming lakes alone. More intense rainstorms are washing fertilizer and other nutrients from farmland into some lakes. 

The National Oceanic and Atmospheric Administration describes it this way: “Excess nutrients that run off land or are piped as wastewater into rivers and coasts can stimulate an overgrowth of algae, which then sinks and decomposes in the water. The decomposition process consumes oxygen.” 

In other words, lawn and farm fertilizers make algae grow. Then it dies and sinks to the bottom of the lake. Those rotting plants rob the deep cool water areas of oxygen. 

It’s called hypoxia or a “dead zone,” and it can kill fish and other aquatic life in a lake.

“In the summertime, if it’s too warm up above and all the oxygen goes away down below, they get squeezed out and they die. But if we can keep forested watersheds, we can keep oxygen in that bottom water. And so fish can find that cool water refuge that they need to make it through a hot summer,” Gretchen Hansen in Minnesota said. 

Forested land slows the rainstorm runoff and vegetation buffers can take up some of the nutrients before they get into a lake.

Some lakes are bigger and deeper and set in natural areas. They will not be affected by climate as much in the immediate future. 

Small lakes surrounded by development are not going to fare as well. 

Jordan Read, who works in a U.S. Geological Survey office in Wisconsin, said lakes and watersheds that can be better protected should be. Others are going to warm further and, for some of them, not much can be done.

There are going to be winners and losers among the fish in those warmer lakes. 

“There are fish that prefer warmer waters and they’re going to benefit from warmer lakes, and then there are others like walleye, which is critical in the Midwest, that are cool-water fish. So as we see warmer waters, we’ve also seen a decrease in walleye and we’ve seen a coincident increase in smallmouth bass because they’re going to do better with those warmer waters,” Read said.

It would take too much money and too much disruption of the people who live around lakes to protect some of them enough to slow the changes underway because of climate change.

“It might be viable to just accept the reality of a warmer lake and potentially start talking to young kids when they’re fishing about how much fun it is to reel in a bass as opposed to continuing to go after walleye,” Read said.

But people who’ve been catching walleye at their local lake usually don’t want to hear something like that. They want the fisheries managers to stock more walleye. That’s not sustainable if the fish can’t reproduce in the warmer water.

Joe Nohner at the Michigan DNR says it’s all very complicated. Lakes are reacting so differently to the multiple issues caused by climate disruption.

“We’ve got so many stressors on inland lakes. We’ve got invasive species, we’ve got nutrients, we’ve got loss of habitat from a number of different things, and all of these stresses are interacting and it makes every lake so complicated. And so it’s really hard to predict what’s going to happen in a given lake, which is, of course, everybody’s question. Everybody wants to know what’s going to happen in my lake and we just don’t know,” he said. 

Year to year, there will be weather variability. For example, there will be varying ice cover. The overall trend is certain though: Inland lakes are warming. That’s going to mean change.