Contrasting Patterns of Spatial Genetic Structure Within and Among Muskellunge Populations in Ontario: Relevance for Management and Rehabilitation Efforts

Mitochondrial and microsatellite data show extreme contrasts in variation within and among native populations of muskellunge across Ontario. Mitochondrial sequence data show little evidence of geographic structuring among Great Lakes and inland populations across Ontario, corresponding with distribution-based predictions of a single postglacial source. By contrast, microsatellite data show pronounced differences among regional populations, as well as significant structuring among local populations in Lake Huron and Georgian Bay that reflect high site fidelity and strong isolation by distance. Inland populations of muskellunge in two regulated waterways in southeastern Ontario show contrasting patterns of spatial structuring: the Trent-Severn Waterway and Kawartha Lakes show remarkable homogeneity among formerly isolated waterbodies, whereas muskellunge in the Ottawa and Rideau Rivers show contiguous but largely separate genetic populations with borders coinciding with historical rather than contemporary barriers to dispersal. These combined data suggest that muskellunge are capable of showing a remarkable degree of site fidelity, and that this is likely more influenced by habitat availability than species vagility. The pronounced degree of population structuring is also providing valuable baseline data for assessing muskellunge reintroduction and rehabilitation efforts in northern Lake Huron (Spanish River) and Lake Simcoe. The remarkable degree of resolution of the genetic data is also providing insights into muskellunge mating systems, demographic structure within local populations, and dispersal among local and regional populations. As well as shedding light on biological processes within natural populations, the genetic data also highlight the vulnerability of local populations and the benefits of low-impact (catch and release) fisheries and current management practices for ensuring a sustainable future for this charismatic but challenging species.