Walleye spawning strategy in Saginaw Bay, Lake Huron: Tributaries or open water?

The walleye population of Saginaw Bay, Lake Huron, has surpassed recovery targets and now exceeds 14 million fish, yet the relative contribution of different spawning habitats remains poorly understood. The objectives of this study were to quantify the proportion of walleye spawning in known tributary habitats versus offshore reef (open-water) areas and to evaluate whether migratory and resident individuals differ in spawning location. Mature walleyes (n = 343) were surgically implanted with acoustic transmitters following spring spawning during 2022–2023 in the open waters of Saginaw Bay, representing a mixed-origin post-spawn population. Acoustic receivers were deployed in tributaries, across the bay, and in the main basin of Lake Huron. Spawning location (tributary versus open water) was assigned based on detections within a 4-week window corresponding to the spring spawning period. Totaled across three spawning seasons, 65% of individuals spawned in open water and 35% in tributaries. Additionally, 61% of tagged fish migrated to the main basin during summer and early fall, whereas 39% remained resident within the bay year-round. No statistically significant differences in spawning location were detected between migratory and resident individuals. Open-water spawning was therefore prevalent, indicating diversified reproductive sources within the population. Among tributaries, the Tittabawassee River was most frequently used. These findings suggest that recent increases in population abundance may be supported, in part, by the recovery or persistence of open-water spawning and provide important guidance for habitat restoration and long-term fisheries management for Saginaw Bay walleye.