Migration Patterns of Freshwater and Anadromous Inconnu in the Mackenzie River System

Abstract

Radiotelemetry, long-term seasonal gillnetting, and a synthesis of existing historical data revealed that both freshwater and anadromous inconnu Stenodus leucichthys in the Mackenzie River system are migratory, but their feeding/overwintering habitats and the timing and distance of their spawning migrations differ substantially. An anadromous population (Arctic Red River) began upstream migration 2–2.5 months earlier and spawned approximately 3 weeks earlier than did a freshwater population (Slave River), likely because of latitudinal differences in temperature regimes and the additional distance required by anadromous inconnu to reach spawning grounds. Little mixing occurred between anadromous inconnu in the lower Mackenzie River and freshwater inconnu in the Great Slave Lake area, and based on tagging data, a third fluvial form may exist in the upper Mackenzie River. Inconnu in the lower Mackenzie migrate more extensively and use both coastal areas and the outer Mackenzie Delta for feeding and overwintering, whereas inconnu in the Great Slave Lake area feed and overwinter in the lake and migrate shorter distances to spawn. Given these differences and the importance of inconnu for both domestic and commercial use, future research should focus on both the genetic and life history differences of the two migratory forms.