Using Stable Isotopes to Investigate Reemergence of Riverine Lake Whitefish Migrations in Northern Lake Michigan

The Lake Whitefish (Coregonus clupeaformis) constitutes the largest commercial fishery in Lake Michigan, and is an economically and ecologically important species throughout the Great Lakes.  River spawning migrations of Lake Whitefish greatly declined in the early 20th century, but have reemerged in the past decade.  The primary drivers for reemergence of Lake Whitefish migrations in northern Lake Michigan (specifically Green Bay tributaries) are currently unknown; additionally, little is known regarding the ecology of these river-spawning populations.  We compared stable isotope signatures (δ¹⁵N, δ¹³C) of multiple river- and nearshore-spawning Lake Whitefish populations in northern Lake Michigan to identify potential differences among migratory and non-migratory populations.  Results indicated river-spawning Lake Whitefish were significantly different in stable isotope signatures from nearshore-spawning Lake Whitefish in northern Lake Michigan.  These results will help identify migratory and non-migratory Lake Whitefish populations during non-spawning season sampling, therefore informing management and further study of the drivers of these new migrations.