Evaluating Lake Sturgeon Spawning Site Use and Relative Contribution of Tributary Spawning Groups to Harvest in the Lake Winnebago System

Abstract

The Lake Winnebago System (LWS) population in east-central Wisconsin represents one of the largest self-sustaining populations of lake sturgeon Acipenser fulvescens in North America that supports an annual spearing fishery each February. Lake sturgeon spawn at more than 70 locations within tributaries to the LWS, but the extent and timing of spawning at many sites remains unknown. Understanding the use of spawning locations is important in allocating sampling effort needed to mark fish and obtain population estimates used in setting safe harvest levels for the fishery. Furthermore, some spawning sites represent habitat improvement efforts implemented by the Wisconsin Department of Natural Resources and little to no evaluation has been performed at these sites to determine relative use and potential for successful hatching. Our objectives were to describe lake sturgeon use, measure egg deposition rates and survival, and verify whether hatching is occurring at selected spawning locations in the Wolf River drainage, including sites where habitat improvements have occurred. Spawning sites were visited repeatedly during 2024 and 2025, lake sturgeon were visually counted along defined transects, and sampling for eggs and larvae was conducted. Relative use and hatching success varied among locations, and we documented larval production at several new locations. Additionally, the broad range of spawning sites used by lake sturgeon creates the potential for multiple discrete spawning groups with unequal vulnerabilities to harvest. We utilized the passive integrated transponder (PIT) recapture histories of harvested sturgeon to determine the relative contribution of spawning groups to spearing harvest to prevent the over-exploitation of particularly vulnerable groups. Our results may help the Wisconsin Department of Natural Resources strategically allocate spring sampling effort so that more sites can be sampled and could provide guidance regarding future habitat improvement projects.