Historical Changes in Large River Fish Assemblages of the Americas
Stability, Change, and Species Composition of Fish Assemblages in the Lower Mackenzie River: A Pristine Large River
Ross F. Tallman, Kimberly L. Howard, and Sam Stephenson
Abstract.—The Mackenzie River is the second longest river in North America and drains 1.8 × 106 km2. of Arctic and sub-Arctic Canada. Thirty-eight fish species have been recorded in the lower Mackenzie River. These species represent a unique mixture of fishes from the Beringian and Agassisian refugia. Many of the species important for subsistence and commercial fisheries in the lower Mackenzie River have complex life cycles and undertake long migrations to spawn, rear, and overwinter. The lower Mackenzie River is a relatively pristine environment with no dams or major industry, a low human population, and species only lightly harvested. This explains why the species composition is relatively stable. However, recently, the effects of climate change may be starting to influence the species composition in terms of greater frequency of rare species such as Pacific salmon. Moreover, a major gas pipeline proposed for the lower Mackenzie River region will probably disturb the fish assemblage structure.