Comparative spatial ecology of sympatric adult muskellunge and northern pike during a one-year period in an urban reach of the Rideau River, Canada

The reach of the Rideau River that flows through Ottawa, Ontario supports a recreational fishery for northern pike (Esox lucius) and muskellunge (Esox masquinongy). The reach is unique not only because such a vibrant esocid-based recreational fishery exists in an urban center, but that these two species co-occur. Typically, when these species occur sympatrically, northern pike tend to exclude muskellunge. To ensure the persistence of these esocid populations and the fisheries they support it is important to identify key spawning, nursery, foraging and over-wintering locations along this reach, and to evaluate the extent to which adults of the two species exhibit spatio-temporal overlap in habitat use. Radio-telemetry was used to track adult northern pike (N = 18; length 510 to 890 mm) and adult muskellunge (N = 15; length 695 to 1200 mm) on 73 occasions over one year, with particular focus on the breeding seasons (early April until the end of May [56 % tracking effort]). For the two esocids, we observed 19–60 % overlap in key aggregation areas during each season and during the spawning period. The minimum activity (average linear river distance travelled between consecutive tracking events) and core range (linear river distance within 95 % C.I. of mean river position) were greatest in the winter and fall for northern pike and in the spring for muskellunge. On average, northern pike were considerably smaller than muskellunge and had lower minimum activities and smaller core ranges, which could be a result of thermal biology, limited suitable habitat, prey availability or predation. Results from this study will inform future management of these unique esocid populations and should be considered before any habitat alterations occurs within or adjacent to the Rideau River.