Mixed stock assessment and movements of Green Bay walleyes

GBWAE

July 2017 - June 2021

Green Bay supports one of the most prominent recreational fisheries for walleyes in North America, as well as an important tribal subsistence fishery for walleyes that occurs in Michigan waters designated by the Great Lakes Consent Decree for the 1836 Treaty of Washington. Furthermore, commercial fishers in Wisconsin waters have expressed interest in establishing a walleye fishery. Joint management (Wisconsin and Michigan DNR) of the walleye population is complicated because fish spawn in many locations within the bay and its tributaries, but the movements and fishery contributions of walleyes spawning in these locations have not been determined. Managers assume that walleyes spawning in three Wisconsin tributaries (Fox, Oconto, and Peshtigo rivers) and the Menominee River, which represents the border of Wisconsin and Michigan, support the fishery in southern Green Bay. However, reef spawning is suspected and fish originating in northern Green Bay may contribute to the southern Green Bay fishery at some unknown level (e.g., = 66 % of walleyes tagged in Cedar River are generally recovered south of Chambers Island). In northern Green Bay, managers assume walleyes spawning in the Whitefish River and other tributaries to Little Bay de Noc largely support both tribal and recreational fisheries, but an unknown degree of spawning likely occurs on reefs. Moreover, Michigan DNR is actively working to restore walleye stocks in the Bays de Noc. In general, better information on walleye movements and fishery contributions will help managers determine spawning locations or regions that are important to maintaining walleye fisheries in Green Bay and which groups may be at risk of overexploitation. This information is necessary to: 1) identify when and where changes to harvest regulations may be warranted to protect fish in and around spawning locations; 2) guide upcoming treaty negotiations, as these factors could influence apportionment of harvest among user groups and will help managers understand whether harvest within Treaty waters affects walleye stocks outside of the immediate area; 3) help direct spatial allocation of sampling and restoration efforts, and 4) guide spatial allocation of harvest if a commercial fishery is considered for Wisconsin waters.

• Determine if the walleye population in southern Green Bay is largely comprised (= 80%) of fish spawning in the Fox, Oconto, Peshtigo, and Menominee rivers or if fish spawning in other locations within southern or northern Green Bay represent at least minor components (= 10%) during some seasonal periods
• Determine if the walleye population in northern Green Bay is largely comprised (= 80%) of fish spawning in the Whitefish River and other tributaries to Little Bay de Noc or if fish spawning in other locations within northern or southern Green Bay are at least minor components (= 10%) during some seasonal periods
• Determine if the walleye population in the tribal harvest zone is largely comprised (= 90%) of fish spawning in the Whitefish River and other locations in Little Bay de Noc
• Determine if stock contributions in each zone (north vs. south) vary among seasons
• Determine if a measurable proportion of walleyes (= 10%) leave Green Bay after spawning and enter Lake Michigan
• Determine if walleyes spawning within a region or a specific tributary are discrete stocks with =10% of fish straying among locations on an annual basis

• Todd Hayden (Great Lakes Fishery Commission) - thayden@usgs.gov
• Daniel Isermann (Wisconsin Cooperative Fishery Research Unit)
• Steven Hogler (Wisconsin Department Of Natural Resources)
• Troy Zorn (Michigan Department Of Natural Resources)
• Chris Vandergoot (Michigan State University)
• Daniel Dembkowski (University Of Wisconsin Stevens Point)
• Charles Krueger (Michigan State University)
• Thomas Binder (Michigan State University)

• Fox River- Lower Green Bay Natural Resource Damage Assessment
• Wisconsin Department of Natural Resources
• Michigan Department of Natural Resources
• Michigan State University
• USGS- Lake Erie Biological Station
• USGS- Hammond Bay Biological Station
• USGS- Wisconsin Cooperative Fishery Research Unit
• University of Wisconsin

• Fox River-Lower Green Bay Natural Resource Damage Assessment
• Great Lakes Fishery Commission