Warming Lake Superior already affecting fishWarm water might already be changing the makeup and distribution of fish in Lake Superior, a new study suggests.
By: John Myers and LaReesa Sandretsky, Lake County News Chronicle
Warm water might already be changing the makeup and distribution of fish in Lake Superior, a new study suggests.
Increasing water temperatures over the last three decades have made conditions more favorable for chinook salmon, walleye and lean lake trout but less favorable for cold water-loving siscowet lake trout.
The research was conducted by the University of Wisconsin-Madison, funded by Wisconsin Sea Grant and led by Tim Cline, now at the School of Aquatic and Fishery Sciences at the University of Washington.
The research builds on work by Jay Austin and other researchers at the University of Minnesota Duluth’s Large Lakes Observatory who found that average Lake Superior surface water temperatures increased 2.5 degrees Celsius between 1979 and 2006, among the most dramatic examples of climate change in North America.
Don Schreiner has worked at the Minnesota Department of Natural Resources office and hatchery located along Scenic Highway 61 where the French River runs into Lake Superior for 25 years. In his research, he said he’s noticed the slow change in the lake habitat.
“What we’ve seen with climate change is that Lake Superior is moving towards the habitat of Lake Huron,” Schreiner, supervisor for the Lake Superior Fisheries of Minnesota, said.
“I think our biggest message is that these are changes that already have happened. These are not projections of temperatures years from now,” said Cline, the study’s lead researcher s. “We think Lake Superior deserves attention because these are some of the biggest temperature changes we’ve seen anywhere. We wanted to see how that may be already affecting the fish.”
Schreiner estimates that the change in the fish population will be more obvious in 20-30 years and his biggest worry is that warmer waters will make life easier for nonnative and invasive species.
“One of my biggest concerns would be making Lake Superior hospitable to nonnative species,” he said, adding that fish like the alewife, which don’t naturally occur in Lake Superior, will prosper in warmer temperatures and compete with native fish.
The researchers picked lake trout, siscowet, salmon and walleye because they are among the most important species for sport angling and the region’s tourism economy.
“We found that the number of days with preferred temperatures and the amount of water available within the preferred temperature range has increased significantly for lean lake trout, salmon and walleye,” Cline said. Meanwhile, higher water temperatures have forced siscowets to move farther from shore.
Cline cautioned, however, that the decline in water with preferred temperatures doesn’t necessarily mean the number of fish has changed correspondingly.
“We don’t know if there are that many fewer siscowet and more walleye,” Cline said. “But we think the lake already is seeing changes in the makeup and distribution of fish.”
Schreiner agreed, but added that many other factors affect fish populations. The office at which Schreiner works is responsible for managing fish populations in Lake Superior, which includes setting quotas for commercial and sport fishermen.
“Temperature is just one thing that affects fish,” Schreiner said.
He commended the research Cline and his team did, making sense of large amounts of data and creating a temperature model that can reveal more about the effects of global climate change.
“They did a really nice job of pulling all of the information together. I think it’ll just grow from there,” Schreiner said.