Contributions of different spawning strategies and locations to lake whitefish fisheries in southern Green Bay

GBGLW

January 2022 - December 2025

Lake whitefish recruitment has declined in several management zones around the Great Lakes, yet recruitment has markedly increased in southern Green Bay following a resurgence of spawning in some tributaries. This progression seems to suggest that restoring tributary spawning might help offset declines in whitefish recruitment in other areas. However, assuming that tributary spawning is primarily responsible for the expansion of lake whitefish in southern Green Bay is purely speculative. In reality, the importance of tributary spawning to the lake whitefish stock in southern Green Bay remains unknown and available evidence (e.g., telemetry, larval sampling) suggests that whitefish also spawn outside of tributaries at locations that have yet to be identified, representing a major obstacle in understanding stock dynamics. Additionally, the resurgence of tributary spawning appears to be relegated to only a few Green Bay tributaries that once supported whitefish spawning and the relative importance of individual tributaries to the overall stock has not been evaluated. Southern Green Bay provides a unique opportunity to identify spawning strategies contributing to successful recruitment in a contemporary context, which will help guide future restoration efforts. Use of telemetry will allow us to test the following working hypotheses related to the contributions of different spawning strategies and locations to lake whitefish fisheries in southern Green Bay: 1) there is abundant open-water spawning habitat located throughout Green Bay; 2) few fish (< 10%) will show evidence of switching between tributary and open-water spawning; 3) annual spawning site fidelity to specific rivers or open-water zones will be high (> 90%); 4) most whitefish (> 75%) in commercial and recreational catch will show evidence of consistently spawning outside of tributaries; 5) fishery contributions will vary among individual tributaries with relatively minor contributions (< 5%) from the Peshtigo and Oconto rivers; and 6) relative contributions of different spawning strategies or specific spawning locations will not vary between fisheries.

• Determine the location of potential open-water spawning locations in Green Bay.
• Determine the proportion of lake whitefish displaying evidence of switching between tributary and open-water spawning strategies.
• Determine annual spawning site fidelity for specific tributaries and open-water zones.
• Determine the relative contribution of different spawning strategies (tributary vs. open water) and spawning locations to commercial and recreational fisheries occurring in southern Green Bay.
• Determine whether these contributions vary among fisheries.

• Southern Green Bay provides a unique opportunity to identify spawning strategies contributing to successful lake whitefish recruitment in a contemporary context, which will help guide future restoration efforts.
• If most whitefish in southern Green Bay spawn in tributaries, restoring this spawning strategy might provide a viable management tool in other places.
• Conversely, if a relatively low proportion of lake whitefish in southern Green Bay spawn in tributaries, restoring river spawning may be less likely to offset population declines in other portions of the Great Lakes.

• Daniel Dembkowski (University of Wisconsin Stevens Point) - dan.dembkowski@uwsp.edu
• Daniel Isermann (Wisconsin Cooperative Fishery Research Unit)
• Daniel Dembkowski (University Of Wisconsin Stevens Point)
• Scott Hansen (Wisconsin Department Of Natural Resources)
• David Caroffino (Michigan Department Of Natural Resources)
• Thomas Binder (Michigan State University)
• Todd Hayden (Great Lakes Fishery Commission)
• Chris Vandergoot (Michigan State University)
• Ted Treska (United States Fish And Wildlife Service)

• USGS, Wisconsin Cooperative Fishery Research Unit, University of Wisconsin-Stevens Point
• Wisconsin Department of Natural Resources
• Michigan Department of Natural Resources
• Department of Fisheries and Wildlife, Michigan State University
• Hammond Bay Biological Station, USGS
• USFWS, Green Bay Fish and Wildlife Conservation Office
• Lake Erie Biological Station, USGS

• Great Lakes Fish and Wildlife Restoration Act
• Great Lakes Restoration Initiative
• Great Lakes Acoustic Telemetry Observation System