An assessment of headwater isolation as a conservation strategy for cutthroat trout in the Absaroka Mountains of Wyoming
Kruse, Carter G.
Hubert, Wayne A.
Rahel, Frank J.
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Isolation of native cutthroat trout (Oncorhynchus clarki) populations in headwater tributaries (by means of human-made barriers that prevent upstream movement of exotic Salmonidae) has been used (as an approach) to preserve extant populations from hybridization and competition. We evaluated this conservation strategy for Yellowstone cutthroat trout (O. c. bouvieri) in the Absaroka Mountains of northwestern Wyoming. We surveyed four existing populations to assess the potential for isolating Yellowstone cutthroat trout populations in 23 individual headwater tributary streams. It appeared that 21 of the populations would be large enough to minimize demographic risks of extinction, but only seven populations may be large enough (effective population size > 500) to lower the risk of extinction due to genetic limitations. Additionally, there is high potential for unpredictable environmental events to cause severe reductions in population size or local extinctions of Yellowstone cutthroat trout populations above barriers due to the unstable flow and habitat conditions. Isolation of Yellowstone cutthroat trout populations in headwater tributaries upstream from barriers appears to have a low probability of preserving sustainable populations of Yellowstone cutthroat trout in the Absaroka Mountains in the long term