Contribution and Movement of Lake Whitefish in Lake Michigan

GBLWF

October 2017 - December 2021

Important mixed-stock fisheries for lake whitefish occur in northwest Lake Michigan, where harvest is largely supported (~ 75%) by fish assigned to Big Bay de Noc (BBDN) and North-Moonlight Bays (NMB) genetic stocks. Previous conventional tagging suggested the BBDN stock spawned on reefs within BBDN and were usually recovered in Green Bay north of Chambers Island or along the lake side of the Door Peninsula. Most fish from the NMB stock were thought to spawn on reefs along the lake side of Door Peninsula near NMB and were recovered along both sides of Door Peninsula. These studies also suggested whitefish show high spawning site fidelity, but inferring movements from tag recoveries is likely biased due to uneven spatial allocation of fishing effort. Recently, recruitment in both NMB and BBDN areas has declined dramatically. However, whitefish now spawn in tributaries to Green Bay (primarily the Fox and Menominee rivers) where spawning had not occurred in nearly a century and these fish are rarely recovered outside of Green Bay (~1%). Furthermore, age-0 lake whitefish are being captured in greater abundance at many locations, indicating population expansion, not decline. Wisconsin DNR has proposed actions to reduce harvest in the NMB area, but commercial fishers argue whitefish behavior has changed and data suggest recruitment failure is not occurring in Green Bay as a whole. Use of telemetry will allow us to test the following hypotheses based on our conceptual model of whitefish movements: 1) lake whitefish spawning in the Fox and Menominee rivers will remain south of Chambers Island and not leave Green Bay; 2) most adult whitefish (~ 75%) spawning in BBDN will remain north of Chambers Island, but will not leave Green Bay; 3) more than half of the whitefish spawning near NMB will not enter Green Bay; 4) NMB fish entering Green Bay will remain north of Chambers Island and begin to leave Green Bay in October and 5) lake whitefish will show high spawning-site fidelity (> 90%).

• Determine if lake whitefish spawning in the Fox and Menominee Rivers remain south of Chambers Island and do not leave Green Bay.
• Determine if most whitefish (~ 75%) spawning in BBDN remain north of Chambers Island, but do not leave Green Bay.
• Determine if more than half of the whitefish spawning near NMB never enter Green Bay.
• Determine if NMB fish entering Green Bay remain north of Chambers Island and begin to leave Green Bay during October.
• Determine if lake whitefish exhibit high spawning-site fidelity (> 90%).
• Provide estimates of natural and fishing mortality rates for these stocks.

• Understanding lake whitefish movements and stock structure in northwestern Lake Michigan is an immediate research need of fishery managers in Wisconsin and Michigan. Telemetry coupled with genomics will allow us to test current understanding of stock structure, stock-specific movements, and spatial distribution relative to fishing effort. We will also estimate mortality rates for these stocks, which are needed for determining safe harvest levels.

• Thomas Binder (Michigan State University) - tr.binder@gmail.com
• Daniel Isermann (Wisconsin Cooperative Fishery Research Unit)
• Scott Hansen (Wisconsin Department Of Natural Resources)
• David Caroffino (Michigan Department Of Natural Resources)
• Troy Zorn (Michigan Department Of Natural Resources)
• Chris Vandergoot (Michigan State University)
• Charles Krueger (Michigan State University)
• Todd Hayden (Great Lakes Fishery Commission)

• USGS, Wisconsin Cooperative Fishery Research Unit, University of Wisconsin-Stevens Point
• Department of Fisheries and Wildlife, Michigan State University
• Hammond Bay Biological Station, U.S. Geological Survey
• Wisconsin Department of Natural Resources
• Michigan Department of Natural Resources
• Lake Erie Biological Station, U.S. Geological Survey

• Great Lake Fish and Wildlife Restoration Act
• Great Lakes Restoration Initiative