Wisconsin Fishery Project
Spawning site contribution and movements of lake whitefish in northwestern Lake Michigan
July 2017 - June 2021
- Great Lakes Fish and Wildlife Restoration Act
- University of Wisconsin-Stevens Point
Lake whitefish support important commercial and recreational fisheries on Lake Michigan, with the northern third of the lake supporting the majority of harvest. Genetic analyses indicate lake whitefish harvest in northwest Lake Michigan (zones WI-1, WI-2, WFM-00 and WFM-01) represents a mixed-stock fishery largely supported (≈ 75%) by fish assigned to Big Bay de Noc (BBDN) and Green Bay genetic stocks. Previous tagging suggested the BBDN stock spawned on reefs within BBDN and were usually recovered by the fishery in Green Bay north of Chambers Island or along the lake side of the Door Peninsula. Most fish from the Green Bay stock were thought to spawn on reefs along the lake side of Door Peninsula near North and Moonlight bays (NMB) and the majority of tags were recovered along both sides of the Door Peninsula. These studies suggest lake whitefish exhibit relatively high spawning site fidelity. However, inferring general movements from tags recovered in fisheries could be biased because fishing effort is unevenly distributed in time and space. Recruitment in both NMB and BBDN areas appears to be in decline. Conversely, whitefish assigning to multiple stocks now spawn in tributaries to Green Bay (primarily the Fox and Menominee rivers) where spawning had not occurred for 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 that whitefish behavior has changed, BBDN and NMB stocks are not functionally discrete, and recruitment failure is not occurring in Green Bay as a whole. Use of 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 determine movements of tributary spawners, which have not been described in previous work. Use of telemetry and high-reward tags will also allow us to estimate mortality rates for these stocks, which are needed for determining safe harvest levels.