Science Advisory Report  2009/050

Recovery potential assessment of pure native Westslope Cutthroat Trout, Alberta population

Summary

• In Alberta, pure native Westslope Cutthroat Trout have declined in numbers over the past century. Of the 50 extant populations, which are estimated to contain a total of less than 5,000 mature individuals, eight (16%) are currently thought to have a low chance of recovery.
• Most, if not all, current populations are restricted to the extreme headwaters of a few major tributaries and upper mainstem of the Bow River drainage and the upper basin of the Oldman River drainage.
• All geographic areas where pure Westslope Cutthroat Trout are currently found may be critical for the long-term survival and recovery of this subspecies.
• Redds created by females for spawning and the initial development of eggs and alevins meet the SARA definition of residence.
• The recovery goal is to protect and maintain all remaining pure native, non-stocked, populations of Westslope Cutthroat Trout in Alberta, each containing at least their current number of fish, with their historical degree of connectivity within drainage systems (except where it would permit invasive non-indigenous species to establish) throughout their current range to ensure their persistence until at least 2020. The aim over the long term is to recover populations within their historic range, where possible.
• Invasive non-indigenous species, habitat damage and loss, and climate change pose significant threats to the long-term survival and recovery of pure Westslope Cutthroat Trout. Overexploitation was an important threat historically, but now is relatively minor.
• Important mitigation measures that would improve the current likelihood of survival and recovery of this subspecies include protection of pure native populations from hybridization and competition with non-indigenous species, protection, restoration and enhancement of their habitat, especially by restoring watershed ecological function, and public education (in decreasing order of importance).
• Activities that have a moderate or higher probability of jeopardizing the survival or recovery of pure native Westslope Cutthroat Trout in Alberta are not recommended. Allowable harm from controlled recreational angling (catch-and-release or harvest) may be considered. Research activities should be allowed if they are beneficial to the subspecies and will not jeopardize the survival or recovery of a population.

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