Editor's Note: This week, Wisconsin Public Radio will be re-broadcasting a series produced by Michigan Radio  last month called “In Warm Water: Fish & the Changing Great Lakes.” WPR's Chuck Quirmbach reports on water temperature changes and fish populations in the Great Lakes for part one.
Scientists say one way climate change is harming the Great Lakes is by warming the water too quickly in the spring.
That warm-up can decrease food for tiny creatures in the lakes – the creatures that game fish like trout and salmon eat.
As his small research boat zooms near the breakwater in Milwaukee, scientist John Janssen looks at the monitor in the boat's dashboard and reads the Lake Michigan surface water temperature.
Janssen has paid a lot of attention to water temperatures in the nearly 40 years he's been studying the Great Lakes.
For more than a decade, he's been at the University of Wisconsin-Milwaukee. Janssen and other scientists have noticed that all the Great Lakes have tended recently to warm earlier in the spring. He said in deeper water lakes like Michigan, Superior, Huron and Ontario, that's an especially vital change that affects the lake food web.
“With the faster warming up, there's not as much time for the phytoplankton to grow, and as a consequence there's not as much food to feed the zooplankton that feed on the phytoplankton and there's not enough food for the little baby fish, so you can't support the big fish that people love to catch,“ he said.
Janssen said the big fish like whitefish, brown trout and salmon might not grow as much.
But scientists say climate change is complex, and brings many things, including more frequent heavy rainstorms. Janssen said the big storms wash nutrients off the land, and into the Great Lakes.
That might provide a bit more food for the little critters at the bottom of the food web, but Janssen said anglers might still have to get used to catching smaller fish.
Will The Fishing Change?
Jason Woda fires up the engine on the Trophy Hunter, the charter fishing boat he operates in Milwaukee. Woda's been in the business for 14 years, helping anglers reel in trout and salmon. He's not a denier of climate change, but said the faster warming of Lake Michigan hasn't made much of a difference to his business.
“I don't see it changing a lot,” said Woda. “Everything is kind of controlled; everything has a check and a balance as far as food and forage base, biomass and the number of fish we put in. There's a whole bunch of checks and balances there.”
Woda says unless there’s a gigantic climate shift, he’s more worried about the daily weather, fuel prices, and spending too much on fishing tackle. One of Woda’s customers, Luke Plese, said he’s not much on governments doing anything to limit climate change. He’s more of an adaptation guy already. And, anyway, Plese says five hours on Lake Michigan is not just about fishing.
“You’re out for the time with friends and get to know charter guys or, you’re with a work outing or a family reunion. That’s the aspect I see of it,” he said.
And Plese said if by mid-century, his children are anglers, they’ll have to learn, too, to deal with water temperatures and climate.
“Four years from now, my kids better be able to adapt, to make the best of what they have,” he said.
If the climate scientists are right, a charter boat ride in 2053 will be a different experience.