Egg distribution and spawning habitat of northern pike and muskellunge in a St. Lawrence River marsh

Coexistence of northern pike Esox lucius and muskellunge Esox masquinongy in the Niagara and St. Lawrence rivers has been hypothesized to depend on segregation during spawning. However, large overlap in the use of spawning areas by these two species occurs in the Thousand Islands section of the upper St. Lawrence River. In this study, egg collections in Point Marguerite Marsh in the upper river revealed a partial temporal and spatial overlap in egg deposition by northern pike and muskellunge. Northern pike began spawning earlier but overlapped with muskellunge spawning for 2 weeks, May 13–27. Northern pike eggs were collected over a larger area than muskellunge eggs and at all locations where muskellunge eggs were collected. Both species deposited eggs over three dominant genera of vegetation: pondweeds Potamogeton, duckweeds Lemna, and stonewort Chara. Northern pike spawned over a wider range of water depths (0.5–2.6 m) than muskellunge (0.8–1.5 m) and selected habitats with denser, taller vegetative cover. The temporal and spatial overlap of northern pike and muskellunge egg deposition suggests that mechanisms other than spawning segregation permit these two species to coexist in the St. Lawrence River.