Great Lakes
Kevin Wehrly is a fisheries research biologist with the MDNR's Institute for Fisheries Research lowers a Secchi disc before doing water quality testing at Cedar Island Lake in White Lake Township Tuesday, Sept. 10, 2019. MANDI WRIGHT, DETROIT FREE PRESS

Climate change transforming where fish in the Great Lakes region live

Warming temperatures in the Great Lakes are already causing population shifts among cold water and warm water fish, including those in inland lakes.

Climate change is warming the waters of the Great Lakes and other lakes and rivers in the region — a big concern to scientists and fisheries managers, as few animals are more sensitive to temperature than fish.

Different fish species need different temperature ranges to thrive. And the region's warming waters are already causing fish population shifts, with the consequences not yet fully understood.

Gretchen Hansen, an assistant professor at the University of Minnesota's Department of Fisheries, Wildlife and Conservation Biology

If you like bass, things are looking good. But if you like walleye or cisco, things aren't looking as good.

What fish can be caught where will continue to change over the next few decades — perhaps dramatically. And that will impact — and could harm — a vital economic driver in Michigan. Some 1.1 million anglers contribute $2.3 billion to Michigan's economy each year, through purchases of gear and clothing, booking hotel rooms, buying meals and more, the nonprofit Michigan United Conservation Clubs found in a study released in January.

"If you like bass, things are looking good. But if you like walleye or cisco, things aren't looking as good," said Gretchen Hansen, an assistant professor at the University of Minnesota's Department of Fisheries, Wildlife and Conservation Biology.

At the Michigan Department of Natural Resources, and its counterpart agencies in Minnesota, Wisconsin and elsewhere throughout the Great Lakes region, planning for how to manage fisheries amid these significant shifts is already a matter of urgent study.

Region's air, water getting warmer

A popular sport fish in Michigan, walleye are considered a cool-water fish — for optimal breeding and growth, they want lake conditions warmer than trout, but cooler than bass and panfish. They're having trouble finding that anymore in southern Michigan's warming inland lakes, said Kevin Wehrly, a fisheries research biologist for the Michigan DNR's Institute for Fisheries Research in Ann Arbor.

"Historically, we've stocked walleye into inland lakes in southern Michigan, and there are many of those lakes that just don't support walleye any longer," he said.

"It's most likely water temperature. Water temperature is the main driver of most (fish) species' distribution patterns."

To the north, in Ontario, studies of fish populations in thousands of inland lakes show warm-water-loving species such as smallmouth and largemouth bass are making their way into northern lakes where they've never been seen before. Those newcomers could stress the fish that already make those lakes home, as they compete in many cases for the same habitat and food.

Air temperatures in the Great Lakes region have warmed faster than the rest of the United States — by 1.6 degrees Fahrenheit between 1901-1960 and 1985-2016, as the rest of the contiguous U.S. warmed only by 1.2 degrees. By the end of the 21st century, global average temperatures are expected to rise an additional 2.7 degrees F to 7.2 degrees F, depending on future greenhouse gas emissions, with corresponding changes in the Great Lakes region, a report by 16 researchers around the Great Lakes Region, sponsored by the nonprofit, Chicago-based Environmental Law and Policy Center, found earlier this year.

The Great Lakes have warmed faster than the surrounding air in recent years, according to the Great Lakes Integrated Sciences and Assessments Program (GLISA), a collaboration of the University of Michigan and Michigan State University funded by the National Oceanic and Atmospheric Administration, part of a national network that focuses on adaptation to climate change and variability.

That warming impacts local waters as well. Summer surface water temperatures on the coldest Great Lake, Lake Superior, increased approximately 4.5 degrees F from 1979 to 2006, a significantly faster rate than regional atmospheric warming. Declining winter ice cover is the largest driving factor, according to researchers.

Fish are among the most sensitive animals to temperature, with different species needing a certain water temperature range for optimal breeding, growth and survival. Warming water from climate change is adding stresses to this balance.

NOTE Temperatures are approximate ranges

SOURCE  University of Toronto fisheries biologist Brian Shuter; Ontario Ministry of Natural Resources and Forestry

CREATED BY Brian McNamara, Detroit Free Press

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