Fish life history and habitat use in the Northwest Territories : Dolly Varden (Salvelinus malma) / by D.B. Stewart, N.J. Mochnacz, J.D. Reist, T.J. Carmichael, and C.D. Sawatzky.: Fs97-4/2915E-PDF

"Northern-form Dolly Varden occur west of the Mackenzie River Valley from the Gayna River north to the coast and then west along the North Slope. These fish require cold, clean water and follow a stream-resident, riverine, or anadromous life history. Most stream-resident fish are isolated from the sea. Riverine fish are mostly residual males that mature early and remain in fresh water despite having access to the sea. Most fish with access to the sea undergo smoltification and undertake marine feeding sojourns during the summer. Differences in habitat use by these life-history types and in the seasonal requirements of eggs, fry, juveniles, and adults are summarized. All life histories and life stages are closely associated with discharging groundwater in small streams. These groundwater springs maintain suitable incubation and rearing conditions through the winter, and prevent small areas of streams from freezing, thereby providing overwintering habitat. To support the assessment, avoidance and mitigation of environmental impacts in the Mackenzie Valley, the potential impacts of development activities and climate change on survival of the species are reviewed. Northern populations have narrow habitat requirements for spawning, rearing, and overwintering life stages which make them vulnerable to extirpation by habitat fragmentation and disruption. Their extensive marine migrations and predictable seasonal concentration during freshwater migrations and at wintering areas makes the anadromous fish particularly vulnerable to overharvesting"--Abstract, page v.

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