Walleye Spawning Habitats Buffer Interannual Recruitment Variability in Saginaw Bay, Lake Huron

Following the precipitous decline of alewives in Lake Huron, early life survival and subsequent recruitment of walleye in Saginaw Bay has dramatically increased.  However, the mechanisms facilitating increased early life survival of walleye have not been fully explored.  Previous studies suggest that the majority of young walleye are produced via natural reproduction in the Tittabawasee River, but it is not clear if other habitats have become important for reproduction during this period of walleye resurgence. During 2009 and 2010, we collected larval walleye in various Saginaw Bay habitats using a push net, paired bongo nets, and a neuston net. We estimated the ages of walleye larvae using otolith incremental analysis. To further evaluate the suitability and potential utilization of alternative spawning habitats, we placed egg mats in areas of historical walleye spawning reefs.  In 2011, we also characterized habitat quality using a towed side-scan sonar of surrounding potential reef structure. We observed interannual variability in spatial and temporal distributions of walleye (e.g., walleye emerged earlier during a warm year, 2010, as compared to a cold year, 2009). Based on age determinations and capture locations, we speculate that walleye are successfully reproducing in multiple habitats. Young walleye in Saginaw Bay appear to benefit from a diverse set of habitats. Such diversity could temper interannual recruitment variability, and hence, should be a goal for managers.