Genetic Divergence of Nearby Walleye Spawning Groups in Central Lake Erie: Implications for Management

Abstract

Spawning-site philopatry may lead to genetic differentiation among reproductive populations, despite their locations being in close proximity within single bodies of water. Identifying and maintaining locally differentiated spawning groups of Walleye Sander vitreus constitute an agency management priority of the multi-agency Walleye Task Group advisory for the Great Lakes Fishery Commission. Although genetically separable spawning groups of Walleyes have been identified from several areas in the Great Lakes, those in central Lake Erie were previously unknown. The Ohio Division of Wildlife (ODW) collected Walleyes for the present analysis from two spawning groups in Lake Erie's central basin, located just 2 km apart-one in the Grand River, Ohio, and the other at the nearby central basin reef. The hypothesis of whether the two spawning groups were genetically different was tested by analyzing variation at 14 nuclear DNA microsatellite loci from Walleyes (n = 147) reproducing in 2012 at the two sites and among three separate years (1996, 2003, and 2012) in the Grand River (to evaluate temporal trends). Results revealed relatively high genetic diversity in both spawning groups, with the reproductive population in the Grand River having significantly greater allelic richness and representation of private alleles. The Grand River Walleye runs showed a slight temporal decline in allelic richness from 1996 to 2003, which coincided with ODW reports of declining numbers of Walleyes reproducing there. The two spawning groups differed in genetic composition suggesting that they are closely related, yet are separable reproductive subpopulations, with both contributing to the overall diversity of Lake Erie Walleye. Their maintenance and integrity thus may need management attention and further monitoring.

Mixed‐stock analysis using Rapture genotyping to evaluate stock‐specific exploitation of a walleye population despite weak genetic structure

“…The largest stock spawns on open‐lake reefs, whereas the others spawn in three large tributaries (Maumee, Sandusky, and Detroit rivers; DuFour et al, 2015; Fraker et al, 2015; Figure 1). Spawning occurs in the central basin on nearshore reefs and in the Grand River, Ohio (Stepien et al, 2018). Although the contributions of their resulting offspring to the lake‐wide fishery remains unknown, we suspect them to be less than the western basin stocks because their spawning populations are smaller.…”

“…Pie charts display the posterior probability of each DAPC cluster proportion averaged across all individuals collected at that spawning location (color scheme is identical to that used for spawning locations). Lake basins (western, central, and eastern) are delineated by dashed black lines Grand River, Ohio (Stepien et al, 2018). Although the contributions of their resulting offspring to the lake-wide fishery remains unknown, we suspect them to be less than the western basin stocks because their spawning populations are smaller.…”

Mixed-stock analysis in the age of genomics: Rapture genotyping enables evaluation of stock-specific exploitation in a freshwater fish population with weak genetic structure

“…1). Spawning is known to occur in the central basin on nearshore reefs and in the Grand River, Ohio (Stepien et al 2018). Although the contributions of the resulting offspring to the lake-wide fishery remains unknown for these stocks, it is suspected to be much less than that from the western basin stocks.…”

Beyond Bonferroni revisited: concerns over inflated false positive research findings in the fields of conservation genetics, biology, and medicine

“…Eight of the twenty articles that applied the BY-mis approach also cited the Benjamini and Yekutieli (2001) article. Of the 28 relevant articles [excluding Hauser et al (2018) and Stepien et al (2018) as these papers cited but did not apply the BY-mis approach], only eight articles (29%) provide enough information to calculate the alternate multiple testing corrections for the data provided for the specific study. Four of these eight articles show an reduction in the number of significant tests when BY-mis is replaced with BY-FDR, whereas the other four have tests that either are negative (one article) or are so strongly significant that all the tests also pass Bonferroni correction (three articles).…”