Walleye Sander vitreus is the most important exploited Lake Erie fish, whose genetic stock structure is important to resource management. Past research shows that the genetic composition of walleye spawning in Lake Erie tributary and reef sites significantly differs. Using high-resolution nuclear microsatellite markers, the present study is the first to test whether the genetic composition of walleye spawning population groups is temporally stable. We employ 15 nuclear microsatellite loci to test the genetic structure of ~1500 walleye spawning in the Maumee, Sandusky, Grand (OH), and Grand (ON) Rivers, Van Buren Bay, Cattaraugus Creek, and Lake St. Clair across 14 years. Preliminary results show consistency among the Maumee River walleye runs in 1995, 1998, 2005, 2006, 2007, and 2008, with 2003 being significantly different. Similarly, the Sandusky River runs in 1995, 1998, 2005, 2007, and 2008 are congruent and differ from 2003. The 2003 Spawning groups in Van Buren Bay versus the Maumee, Sandusky, and Grand (OH) Rivers showed unusually high inter-run gene flow. The 2003 year class was the most successful in decades, and possible correlation with high gene flow is further examined. Our investigation thus illustrates the importance of testing temporal patterns of genetic variation to understand stock structure

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