By:- Kayla Lenz
URBANA, Ill Spring peepers are singing, and walleye harvesters are ready to go out on Mille Lacs Lake, as they have for hundreds of years. The walleye spawn is on.
Some areas of the lake are known as walleye spawning areas to locals, but which areas are the most important? New research from the Great Lakes Indian Fish and Wildlife Commission, Mille Lacs Band of Ojibwe, and the University of Illinois Urbana-Champaign identified six “hotspots” for walleye spawning and found that about 96% of walleye displayed some degree of loyalty to spawning sites throughout the lake.
Walleye, known as Ogaawag in Ojibwe, are a beloved and culturally important species for recreational anglers and indigenous harvesters alike, and protecting this species is in everyone’s best interests. But walleye populations in Mille Lacs have declined over the last several decades, hitting an all-time low in 2016 and showing slight recovery since then. Declines have largely been attributed to poor recruitment (i.e., survival from hatching to age 2) related to environmental change, habitat degradation, overfishing, and changing ecosystem dynamics.
“As the very first protectors of water and fish, we care deeply about the habitats which give life to the Ogaawag that sustain us,” said Kelly Applegate, Commissioner of Natural Resources for the Mille Lacs Band of Ojibwe. “By learning more about important Ogaawag spawning sites, we can obtain valuable knowledge, allowing us to further build on our centuries-old reputation for successfully and sustainably managing our fisheries resources.”
The science
Scientists with the Mille Lacs Band and Great Lakes Indian Fish and Wildlife Commission tracked the movements of 70 walleye during their annual spring spawning periods in 2019, 2020, and 2021. Walleye were surgically implanted with transmitters that ping (send unique numbers for that fish, time, date, temperature, and pressure information) to receivers as the walleye swim by. This information allowed researchers to identify where the most walleye were detected and where they spent the most time during their spawning period, and quantify how many fish returned to the same spawning areas between years.
The study showed walleye have very high rates of spawning site fidelity.
“Approximately 96% of the fish in this study spawned at the same site in 2019 and in 2020. These fish use the same areas to spawn year after year, which means that their reproductive success is tied to a specific place,” said lead study author Kayla Lenz, a doctoral student in the Department of Natural Resources and Environmental Sciences, part of the College of Agricultural, Consumer and Environmental Sciences at Illinois.
The authors also identified six “hotspot” locations that had higher rates of walleye detections during the spawning period than other areas in the lake. Lenz added, “These ‘hotspots’ were located in areas with rocky substrates, exposed to wind and wave action, and near undeveloped shorelines. These habitat conditions likely increase reproductive success of walleye.”
What it means
These findings have implications for protecting walleye in Mille Lacs and elsewhere, Lenz says. Environmental variables, such as wind direction, temperature, and wave action, may play a role in selecting which sites walleye return to and could be used to predict where walleye spawn in a waterbody. If these characteristics were to be altered such as a breakwall interrupting wave action on a reef, development of marinas, addition of docks, and chemical control of vegetation spawning could be disrupted, and reproduction and/or survival of offspring may decrease.
In this study, the areas that have been identified as primary walleye spawning habitats largely consist of sparse areas of shoreline with little to no human development.
“Development of these areas may have temporary or permanent negative effects on walleye reproduction and recruitment,” Lenz said. “On the other hand, watershed-level management that mitigates the effects of erosion, pollution, and climate change could benefit walleye and many species in Mille Lacs Lake.”
How the public can help
The researchers say landowners and everyday users of the lake could help protect these fish by limiting use of habitat-disturbing wake boats in spawning areas; refraining from putting out docks until after the spawning season; planting riparian buffer zones along the shoreline that help prevent erosion; and limiting use of chemicals such as herbicides, pesticides, and algicides within the watershed, which have been shown to reduce survival of young fish. These actions help to preserve habitats that are essential to the continued persistence of this beloved species.
More information about this study can be found in “Identifying Spawning Sites and Fidelity of Ogaa Implications for Fishery Stewardship,” available online in Frontiers in Fish Science [DOI:10.3389/frish.2026.1758559]. Authors include Kayla Lenz, Aaron Shultz, Carl Klimah, and Adam Ray. Funding for the study was provided by the Great Lakes Indian Fish and Wildlife Commission’s board of commissioners and U.S. Fish and Wildlife Service’s Tribal Wildlife Grant. The study was also supported by Grant or Cooperative Agreement No. G21AC10796 from the United States Geological Survey through the Midwest Climate Adaptation Science Center.
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