Genetic structure supports existing genetic management units for Walleye in Minnesota and establishment of a new southern unit

Objective Walleye Sander vitreus stocking policy in Minnesota advocated using source populations from within major watershed-based genetic management units in the northern part of the state, but any of the northern strains could be stocked in a southern Minnesota universal zone. The identification of genetically distinct populations in southern Minnesota called for an assessment of remnant southern ancestry across the universal stocking zone. Methods Genetic structure among 23 statewide Minnesota Walleye populations was assessed based on 13 microsatellite DNA markers using Bayesian cluster analysis, a tree diagram of genetic relationships, principal coordinates analysis, and FST, a quantitative measure of genetic divergence. Ancestry that was associated with genetic clusters from southern Minnesota was then estimated for 27 populations across the universal stocking zone. Measures of genetic diversity, heterozygosity, allelic richness, and effective population size were estimated within the statewide populations. Results STRUCTURE assigned high levels of ancestry (0.54–0.93) to distinct genetic clusters that were associated with the major watersheds, and a dendrogram based on genetic distance and principal coordinates analysis grouped populations mostly according to watershed. Remnant ancestry in the southern populations persisted at varying levels (0.08–0.91), but 19 of 29 populations had estimates exceeding 0.4. Statewide populations did not appear to be threatened by low genetic diversity or effective population size. Conclusion Genetic structure that is consistent with the major watersheds and persistence of native local ancestry across southern Minnesota support existing northern genetic management units and the establishment of a new unit in the south, with historical southern source populations that are suitable for renewed stocking efforts.