AUTHORS: Braden Lensing, Wisconsin Cooperative Fishery Research Unit, University of Wisconsin-Stevens Point; Daniel Dembkowski, Wisconsin Cooperative Fishery Research Unit, University of Wisconsin-Stevens Point; Joshua Raabe, University of Wisconsin-Stevens Point; Jason Breegemann, Wisconsin Department of Natural Resources; Daniel Isermann, U.S. Geological Survey, Wisconsin Cooperative Fishery Research Unit, University of Wisconsin-Stevens Point
ABSTRACT: Previous research indicates that lake sturgeon Acipenser fluvescens recruitment is limited in the Lower Fox River below De Pere Dam. Habitat enhancements in the form of an offshore reef have been proposed to potentially improve the recruitment of lake sturgeon. However, identifying spawning habitats for other species could help to ensure that restoration efforts for lake sturgeon do not result in loss of spawning habitat for other species. The Lower Fox River supports spawning runs of walleye Sander vitreus and lake whitefish Coregonus clupeaformis, both of which support important fisheries in southern Green Bay. Our objectives are to 1) describe spatial variation in walleye and lake whitefish egg densities in the LFR below De Pere Dam to inform placement of the lake sturgeon spawning reef; 2) determine if spatial variation in egg densities are related to a suite of environmental variables (e.g., flow, depth, and substrate), 3) determine if spatial distributions of eggs are similar for walleye and lake whitefish, and 4) describe the timing (e.g., start, peak, end, and duration) of walleye and lake whitefish spawning. Heat maps generated from relative egg densities illustrate the spatial distribution of walleye and lake whitefish egg densities and reveal significant overlap in egg deposition between the two species, as well as notable overlap with three of four proposed reef locations. The 2023 lake whitefish spawning period spanned 14 days, beginning on November 8 and concluding around November 21. In contrast, the 2024 walleye spawning season lasted 38 days, commencing on March 18 and ending about April 25.
