Little Shoepack Lake muskellunge (Esox masquinongy) population estimate and genetic evaluation of muskellunge from Shoepack and Little Shoepack lakes

Maki, Ryan; Patterson, Kristen; Amundson, Joseph; Carlson, Edward; Miller, Loren; Shroyer, Steven; LeDuc, Jaime; Banta, Reece; Glase, Jay; Horvath, Jared; Howard, Megan

doi:10.36967/2305092

Little Shoepack and Shoepack lakes in Voyageurs National Park, Minnesota, are home to native populations of Muskellunge (Esox masquinongy). Due to the small size of these lakes, 20.8 ha and 123 ha, respectively, and the associated, predicted small size of these Muskellunge populations, resource managers are concerned about their persistence. A recent population assessment completed for Shoepack Lake Muskellunge indicated that the population may be below a threshold at which a genetic bottleneck could threaten its persistence. Since Little Shoepack Lake is approximately 20% of the size of Shoepack Lake, resource managers were concerned that its Muskellunge population is likely smaller and at even greater risk of extirpation due to lack of genetic variability. To assess whether additional protections were warranted and whether increasing genetic diversity through stocking might allow for genetic rescue, a population estimate was completed for the Muskellunge in Little Shoepack Lake, and a genetic assessment of Muskellunge from Little Shoepack and Shoepack lakes was completed. The estimated abundance of Muskellunge ≥ 420 mm in Little Shoepack Lake in 2021 was 137 with a 95% confidence interval of 87 to 277. The density of this population, 6.6 per ha, is the highest of any Muskellunge population assessed in Minnesota. The Muskellunge from Little Shoepack and Shoepack lakes had substantially lower genetic diversity than other regional populations. The two populations were genetically similar, yet distinct, from one another and were far more distinct from other Muskellunge populations in the region. As anticipated, the population estimate for Muskellunge in Little Shoepack Lake indicates that the population is near or below a threshold at which the risk of low genetic diversity may impact population persistence. The genetic analysis showed that cross stocking native Muskellunge between Shoepack and Little Shoepack lakes would not likely provide enough genetic diversity to greatly increase the chances of the two populations persisting. Considering the long duration that this population has persisted (up to 8,900 years in Little Shoepack Lake) and the importance of maintaining these unique strains of Muskellunge to protect regional biodiversity, cross stocking of Muskellunge between Little Shoepack and Shoepack lakes or stocking Muskellunge from other lakes is not recommended at this time. We recommend that resource managers continue to use fishing regulations, controls on angling pressure, and prevention of introductions of both fish species and aquatic invasive species as tools to help sustain these populations. Considering the fishery is effectively catch-and-release due to minimum length harvest regulations in Minnesota and that difficulty of access limits fishing pressure and catch-and-release mortality, we recommend that Little Shoepack Lake remains open for a Muskellunge angling opportunity.

Little Shoepack Lake muskellunge (Esox masquinongy) population estimate and genetic evaluation of muskellunge from Shoepack and Little Shoepack lakes

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