Researchers at Voyageurs National Park Study Genetically Distinct Muskellunge

Lucy Jones worked as an Aquatic Ecology and Fisheries Intern at Voyageurs National Park in 2019. One of her duties was to assist in a mark-recapture survey of a genetically-distinct population of muskellunge in Shoepack Lake.

Photo by Jaime LeDuc

There are many benefits of preserving genetic diversity. Genetic diversity allows species and populations to be more resilient to environmental stressors. When geographical isolation of populations occur, the populations have the potential to diverge and become genetically unique. Voyageurs National Park is home to a genetically-distinct strain of muskellunge, Esox masquinongy, which resides in Shoepack and Little Shoepack Lakes. The Shoepack Lakes have been isolated for approximately 7,000-9,000 years (Gorman et al. 2014). Compared to most other populations of muskellunge, Shoepack Lake muskellunge exhibit much slower growth rates and smaller overall body size but occur in much higher densities. Therefore, the angler catch per unit effort is higher than other muskellunge populations. During a study of the Shoepack muskellunge population that began in 2001, a beaver dam failed due to heavy rain causing the lake to lose 50% of its surface area. It was noted that, toward the end of the study, the population had started to decline (Frohnauer et al. 2007).

Today, the lake has returned to its pre-dam failure levels. During the years following the dam failure the muskellunge population in the lake may have been under significant biological and environmental stress due to the reduction in available habitat. It is the job of interns and technicians at Voyageurs National Park, like Lucy, to assist the National Park Service and the Minnesota Department of Natural Resources with an assessment of the health of the Shoepack muskellunge population. This research is being done through a mark-recapture survey. A portion of the fish were captured, marked, and released in the first phase of the study. During the second phase, a subset of the marked fish were recaptured along with newly captured fish. This information will be used to make a population estimate which will help Voyageurs National Park and the Minnesota Department of Natural Resources decide how to best protect and manage this unique population.