Decision Notice - Westslope Cutthroat Trout Expansion and Genetic Rescue in South Fork Willow Creek

Mar 20, 2025 3:35 PM

Montana Fish, Wildlife & Parks (FWP) is proposing to expand the nonhybridized westslope cutthroat trout (WCT) Oncorhynchus lewisi population in South Fork Willow Creek (Smith River drainage) into its fishless headwaters above a bedrock barrier that currently limits upstream fish movement in the drainage. The section of South Fork Willow Creek where WCT will be introduced is entirely within the Helena-Lewis and Clark National Forest, Belt Creek-White Sulphur Springs Ranger District. Presently, the nonhybridized population of WCT in South Fork Willow Creek is isolated to a 0.25-mile reach of stream between two bedrock barriers. While small, isolated populations may be safer from hybridization and competition with nonnative fishes, they are at increased risk of extinction from catastrophic events (e.g. fire, drought) and may eventually suffer negative consequences of inbreeding (Wang et al. 2002). The most recent genetic analysis of this population indicates genetic variation is very low compared to other WCT populations in the Missouri River drainage and is a clear candidate for assisted translocation focused on providing gene flow. FWP is proposing translocation of a small number (5-10 adults) of individuals from a nearby population of nonhybridized Smith River WCT to alleviate genetic load and increase fitness and persistence probability of the South Fork Willow Creek population (Kovach et al. 2022). There is an estimated 4.6 miles of suitable habitat that is presently fishless above the upper bedrock barrier. Expansion and translocation of nonhybridized WCT into the fishless headwaters of upper South Fork Willow Creek would likely secure this population resulting in 4.8 miles of protected WCT habitat and a population of over 2,500 individuals.

PURPOSE AND NEED The intent of the proposed action would be to support the following FWP goals and objectives: • Prevent the loss of a unique genetic lineage of WCT native to north central Montana • Expand the current WCT range in effort to meet WCT conservation goals for the Smith River subbasin • Reduce the likelihood of ESA-listing of WCT. • Establish a self-sustaining WCT conservation population in upper South Fork Willow Creek • Increase the amount of protected WCT habitat in the Smith River drainage by 24.2% (from 19.0 miles to 23.6 miles). • Use the expanded South Fork Willow Creek WCT population as a donor stream for future WCT conservation efforts in north central Montana

Based on the environmental review provided in the Draft EA, and in accordance with all applicable laws, rules, regulations, and policies, FWP determined the proposed action (Alternative 2), will not have significant adverse impacts on the human environment associated with the proposed action and constitutes a reasonable and appropriate strategy to achieve identified objectives. Therefore, preparation of an EIS is unnecessary. FWP hereby adopts the Draft EA as final and approves the Alternative 2, the proposed action. With this DN, FWP hereby adopts the Final EA, without modifications, and approves the proposed action.