Zach Janssen caught this 11-pound rainbow trout near East Peoria. Photo courtesy of Zach Janssen.

Big trout likely went deep to survive Illinois summers

June 21, 2013 at 08:47 AM

Central Illinois is not known for supporting populations of cold-water fish like the huge rainbow trout Zach Janssen caught last week.

Janssen was fishing in a lake on private property near East Peoria when he hooked the trout that weighed 11 pounds and was 27 inches long.

“I caught it Friday night while night fishing for catfish,” Janssen said. “It’s a decent sized strip pit in East Peoria on the way to Spring Bay, approximately 30 acres in size and 80 some feet deep at the center.

“A few people on the lake said they thought the rainbow trout had been fished out, but I guess not.”

That’s because trout had not been stocked in the lake in about a decade, he said.

Normally, trout cannot withstand the heat of Illinois summer. Fish stocked in spring and fall as part of the state’s “catchable trout” program are expected to be caught by anglers and don’t survive long.

Dan Stephenson, assistant chief of fisheries for the Illinois Department of Natural Resources, said the fish stood a better chance of survival in a lake that was 80 feet deep.

“Trout are a cold-water species that cannot tolerate temperatures above 70 degrees,” he said. “Deep lakes such as this stratify into layers with the top 20 feet or so having equal amounts of oxygen and the temperature is the same.

“In the summer, that layer has enough oxygen for trout but is too warm,” he said. “In the next 20 feet or so the temperature drops rapidly to 39 degrees and the oxygen runs out. In the bottom 20 feet or more, the temperature is 39 degrees and there is no oxygen.”

Stephenson said the fish survived in that middle layer where there was just enough oxygen and temperatures stayed cool.

The sun often heats water to 70 to 90 degrees during the summer months.

“They can feed (in the cool water layer) or take short excursions to upper levels to feed and then return,” he said. “Areas of the lake where the temperature and oxygen levels allow for survival are called ‘thermal refuges.’”

Trout also have survived the summer in Devils Kitchen Lake in southern Illinois, which is 80 feet deep, and at Siloam Springs in west-central Illinois, where the water is 60 feet deep.

“It’s a great fish and a great story,” Stephenson said.

Chris Young can be reached at (217) 788-1528 or .(JavaScript must be enabled to view this email address). Follow him at

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