Muskellunge Management: Fifty Years of Cooperation Among Anglers, Scientists, and Fisheries Biologists

Realized Effects of Implementing a Genetic Broodstock Management Plan for Muskellunge in Wisconsin

Zeb Woiak, Justin A. VanDeHey, and Brian L. Sloss

doi: https://doi.org/10.47886/9781934874462.ch63

Abstract.—In 2006, the Wisconsin Department of Natural Resources’ Muskellunge Esox masquinongy propagation program underwent a series of strategic modifications aimed at protecting the genetic integrity of native populations and ensuring long-term sustainability of Muskellunge fisheries in Wisconsin. In addition to refined broodstock management strategies, mating and rearing strategies were refined to minimize changes in genetic diversity throughout the propagation process. To evaluate this goal, two specific criteria were developed. First, allele frequencies should not differ between the progeny life stages and the broodstock. Second, ≥95% of rare alleles found in the broodstock (alleles present at frequencies ≤5%) should be conserved within the progeny. Samples were collected during 2012 and 2013 at Governor Tommy Thompson Hatchery (GTH) and Art Oehmcke Hatchery (AOH) and were analyzed at 14 microsatellite loci. Overall, conservation of genetic diversity levels between life stages predicted by the prescribed changes to the propagation program was apparent and likely represented major improvements over historical techniques. Nevertheless, current results identified areas for further refinement. At each hatchery, at least one of the two specific criteria was met during both years. For example, AOH conserved more than 95% of rare alleles in both production years, but significant shifts in allele frequencies were observed during both years for the pooled fingerling sample and in the majority of individual rearing pond comparisons. The Governor Tommy Thompson state fish hatchery consistently demonstrated stability in allele frequencies among life stages during both years of the study. However, during 2013, less than 95% of the rare alleles present in the GTH broodstock were conserved in the progeny. Differences identified in the gamete collection protocols, specifically standardization of egg volume from each parental pairing (reducing variance in family size), will improve conservation of genetic diversity among life stages at both hatcheries.