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Westslope Cutthroat Trout Oncorhynchus clarki lewisi Westslope cutthroat trout are a native species whose native distribution includes portions of the upper Missouri River basin east of the Continental Divide and the Columbia River basin west of the Divide. The species also occurs in lakes, including large lakes such as Flathead Lake, Montana and Pend Oreille Lake, Idaho. This range includes parts of Montana, Idaho and Alberta Canada, with a population in the John Day River drainage of Oregon as well, and a number of other possible populations in Washington and British Columbia. The historical distribution of westslope cutthroat trout and the changes to it are difficult to ascertain for researchers, and as a whole is too complex to relate here. As a summary, Behnke states that westslope cutthroats historically had the largest native range of any cutthroat subspecies, but that range has been vastly reduced.
Westslope cutthroat trout are threatened by a number of nonnative trout species that have been stocked throughout its range, mainly brook, brown and rainbow trout, but also the “native” Yellowstone cutthroat trout. Besides competition and predation pressure from these other species, westslope cutthroat populations are heavily impacted from hybridization with rainbow and Yellowstone cutthroat trout. As with most wild trout populations in the West, westslope cutthroat trout are susceptible to whirling disease, from the invasive Eurasian Myxobolus cerebralis parasite, where it occurs. There are a number of issues that threaten the continued existence of westslope cutthroat trout in their native range, but there are also a number of conservation efforts that are currently underway to keep populations sustainable, and attempts to restore some populations to their previous state before man-made impacts occurred. References: Behnke, R.J. 1992. Native Trout of Western North America. American Fisheries Society Monograph 6. Behnke, R.J. 2002. Trout and Salmon of North America. The Free Press, New York. Brown, C.J.D. 1971. Fishes of Montana. Big Sky Books, Bozeman, MT. |
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