Lake Sturgeon Spawning Fidelity to Green Bay Rivers

Spawning river fidelity of lake sturgeon is difficult to assign considering the relatively long inter-spawning intervals and the complexity of conducting assessments on large waterbodies with multiple spawning rivers, like Green Bay of Lake Michigan. In addition, movement patterns of adult sturgeon are likely impacted due to a small population size compared to historic estimates (< 1%) and hydroelectric dams which have altered spawning behavior. Green Bay lake sturgeon have been genotyped (N=907) and indirectly assigned to assumed spawning river groups (Menominee, Lower Michigan, Peshtigo-Oconto, and Fox-Wolf); but direct tagging studies have indicated mixing of adult sturgeon between genetically assigned spawning rivers. Using acoustic telemetry, we observed the movements of lake sturgeon (N=98) into four Green Bay rivers (Menominee, Peshtigo, Oconto, and Fox). Acoustic receivers allowed us to identify seasonal movement patterns of these sturgeon for multiple years. Movements were routinely detected during both spawning and non-spawning seasons; but most fish were only briefly detected in the subject rivers and occupied the greater Green Bay waters for the remainder of the year. Genotypic assignments can corroborate that implanted fish originated from the rivers where they were tagged; but it appears from our acoustic telemetry data that mixing of these spawning stocks occurred during spring spawning periods.