Freshwater Colloquium 鈥� Stock assessment and management of lake whitefish in Wisconsin waters of Green Bay and Lake Michigan
Join the School of Freshwater Sciences for a Colloquium with guest speaker: Dr. Iyob Tsehaye
Lake whitefish stocks in Wisconsin鈥檚 Lake Michigan waters have historically been managed as a single stock originating from North鈥揗oonlight Bays. However, over the last couple of decades, this stock has declined in line with broader Lake Michigan trends linked to dreissenid mussel-induced food web shifts. Conversely, the southern Green Bay population has seen a substantial resurgence after a century-long collapse. Telemetry and tagging data reveal minimal mixing between these groups: Green Bay-spawned fish rarely migrate to the lake side of the Door Peninsula, and North鈥揗oonlight Bays fish largely remain in northern Lake Michigan. This divergence in productivity and distribution, further evidenced by the emergence of a major recreational fishery in Green Bay, necessitates a shift in management. Separate stock assessments confirm that whitefish abundance is now significantly higher within Green Bay than on the lake side of the peninsula. Even so, assessment models show the number of whitefish in Green Bay has declined by about half since their peak around 2012. While the decline of lake whitefish is likely driven largely by food-web disruptions caused by invasive mussels, fishing pressure also plays a role. These findings suggest that spatial harvest allocations must be readjusted to reflect the contemporary regional productivity of these distinct stocks.
Iyob Tsehaye is a Great Lakes Quantitative Fisheries Research Scientist with the Wisconsin Department of Natural Resources (DNR). His research focuses on the assessment and management of recreationally and commercially important fisheries, such as lake whitefish, yellow perch and walleye, as well as investigating predator-prey interactions to inform stocking decisions for salmonine predators. Before joining the DNR in 2015, Iyob was a postdoctoral researcher at the Quantitative Fisheries Center at Michigan State University. He earned his PhD and MSc degrees from Wageningen University in the Netherlands and his Bachelor鈥檚 degree from the University of Asmara in Eritrea.
This presentation is open to students, faculty, staff, alumni and the public.