Illinois Natural History Survey - University of Illinois

Lake Trout Research in Lake Michigan

Scott M. Miehls and John M. Dettmers

Historically, lake trout was the dominant top predator in Lake Michigan. This important native fish was extirpated from the lake, however, by a combination of comercial overfishing and sea lamprey predation. Since the late 1960s lake trout have been stocked to re-establish adult spawning stocks and to provide a sport fishery. Although stocking has established lakewide adult populations, no consistent natural recruitment of lake trout has occurred in Lake Michigan during the past 30 years.

Recent sampling by the Indiana Department of Natural Resources has revealed the potential for successful natural reproduction in the southern basin of the lake. To better understand factors influencing lake trout reproduction, we conduct research in the vicinity of the breakwall at Burns Harbor, IN. During the fall spawning season, adult lake trout are collected and fin-clipped for genetic analysis. The extent of predation on lake trout eggs is also studied in the fall. This research is accomplished through use of egg collection baskets placed along the breakwall and on adjacent submerged reefs. In the spring, fry are collected using fry traps placed in the same locations. From this sampling, viability of the eggs can be determined and genetic analysis can be conducted for both the eggs and fry.

This research is part of a collaborative study between the Illinois Natural History Survey and the Indiana Department of Natural Resources. The objective is to gain a better understanding of factors affecting lake trout spawning and reproductive success in southern Lake Michigan. This research will tell us more about what conditions and spawning habitat are needed for successful lake trout reproduction and possibly which genetic strains are better suited for reproductive success. Insights from this research will provide managers with additional tools to improve lake trout numbers in southern Lake Michigan and to provide better angling opportunities for this fish in the future.

Illinois Natural History Survey

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