Temporal and Spatial Genetic Consistency of Walleye Spawning Groups

Population genetic compositions of the three largest spawning groups of Lake Erie walleyes Sander vitreus (Maumee River, Sandusky River, and Van Buren Bay reefs) were tested for temporal and spatial consistency across 14 years using nine nuclear DNA microsatellite loci from 726 adult walleyes collected in 1995, 1998, 2003, 2007, and 2008. Previous genetic work focused on a one-time “snapshot”; an earlier study by our laboratory found genetic connectivity among the three spawning groups in 2003, whereas most other spawning runs across Lake Erie were genetically distinct. Present results show overall year-to-year genetic consistency of walleye spawning groups; no significant differences were found among collection dates within an annual run, between sexes, or among age-cohorts. Overall, walleyes spawning at the Van Buren Bay reefs were genetically divergent from those spawning in the Maumee and Sandusky rivers, reflecting geographic distance; the latter two groups were genetically closer, with slight differences that suggested more recent divergence, higher gene flow, or both. Individual year comparisons among the three sites showed some stochasticity, and the spawning groups appeared to be more similar in some years than in others. The Van Buren Bay spawning group in 1995 was the most divergent sample and had the greatest genetic self-assignment (100%); this may reflect some changes over time. Results demonstrate the importance of sampling over several years of spawning runs to understand overall patterns of walleye genetic stock structure, which show remarkable genetic consistency across an open-lake system. Received July 8, 2011; accepted November 14, 2011