GENETIC INFLUENCES ON WALLEYE AND SMALLMOUTH BASS SPAWNING GROUPS IN LAKE ERIE: 95 YEARS OF THE BALLVILLE DAM AS A BARRIER TO GENE FLOW IN THE SANDUSKY RIVER

In 1911, construction of the Ballville Dam on the Sandusky River blocked native fishes, including Lake Erie walleye, from spawning in their ancestral upstream habitats and reduced spawning habitat to a short reach below the dam. Our genetic data and tagging studies show that Lake Erie walleye migrate to their natal tributary and lake reef sites for spawning, and then mix in the Lake. The Sandusky River spawning group of walleye persists - although it was dramatically reduced in size and suitable habitat – which may have reduced genetic variability through bottleneck effects. In addition, the dam divided resident fishes, such as smallmouth bass, into two groups – upstream and downstream, which may have both reduced genetic variability and led to genetic divergence. We examined variation at 10 and 8 nuclear DNA microsatellite loci, respectively, comparing genetic diversity of contemporary spawning groups of walleye and smallmouth bass in the Sandusky River/Bay with other reef and tributary spawning sites in Lake Erie. Results showed that walleye and smallmouth bass spawning below the Ballville dam have comparable levels of genetic variability to other western Lake Erie sites, as measured by heterozygosity and numbers of private alleles. Gene flow levels among some western basin locations – but not others – and the Sandusky River/Bay region are relatively high, and may account for this similarity. The Sandusky River/Bay walleye and smallmouth bass spawning groups below the dam thus exhibit no evidence of long-term genetic bottlenecks. We plan to collect further data for both species, including sampling of smallmouth bass resident above the dam for a “before” study in the event that the Ballville dam is removed – paving the way for an “after” study of its genetic effects.