DNR/Purdue studies could improve glacial lake fishing

Indiana DNR Release:


Fisheries—and fishing—in several northern Indiana glacial lakes might improve in coming years thanks to the findings of biologists from the Department of Natural Resources and researchers from Purdue University.

Starting in May, the groups worked together, primarily studying Adams (LaGrange), Crooked (Noble) and Dewart (Kosciusko) lakes and Lake Maxinkuckee (Marshall). The group also collected data from Robinson (Whitley), Knapp (Noble), and Cree (Noble) lakes.

Preliminary results show that the area that separates the warm, well-oxygenated upper-water layer from the cool, oxygen-depleted layer below, a divider known as the thermocline, ranged between 16 and 22 feet deep in all the lakes studied.

"Knowing where the thermocline is and how it changes over time helps us determine where to set our sampling gear to obtain accurate estimates of fish populations and better manage the resource for anglers" said Steve Donabauer, an assistant fisheries research biologist with the DNR Division of Fish and Wildlife.

Observations also showed that the upper and lower water layers began to mix in autumn, a process known as fall turnover, which started near the end of September in shallow lakes such as Cree, where the maximum depth is 26 feet. Fall turnover replenishes oxygen and nutrients throughout an entire water column of the lake, making deeper parts of a lake more habitable to fish.

"Only the deepest lakes have yet to turnover," Donabauer said. "Crooked Lake is 109 feet deep and it still has a well-defined thermocline present at 55 feet." Historical records indicate that fall turnover typically occurs near the end of November in Crooked, but Donabauer said he thinks the lake won’t turnover until the middle of December this year.

“Fall turnover is usually a difficult time for anglers because fish spread out into deeper habitats not previously occupied during the warm-water season,” said Nate Thomas, an assistant fisheries biologist with the DNR’s Division of Fish and Wildlife. "A few weeks after turnover, fishing will get better as fish again concentrate in more predictable habitats such as channels, shallow bays, along drop-offs and near underwater islands."

Any changes in the way the DNR manages the fisheries will occur after the final report is made available in late 2010.