Bringing Back the Trout: Metapopulation Viability of Bonneville Cutthroat Trout in a Fire-Impacted Watershed

Wildland fires are becoming more frequent, larger, and more severe as forested western landscapes regress back toward natural mean fire frequencies after decades of fire suppression. Although native fish communities co-evolved with and are resilient to natural fire perturbations, uncharacteristic fires can be at odds with fish conservation, especially in physically or biologically fragmented modern watersheds. We estimated the extinction rate of a Bonneville cutthroat trout (Oncorhynchus clarkii utah) metapopulation under specified fire regimes on Fishlake National Forest in south-central Utah. We parameterized this model to include demographic stochasticity, movement between subpopulations, and occurrence and synchrony of fire by drawing values from a normal distribution centered on realistic mean values (published or estimated). We simulated these values for each year of a 100-year period using matrix population projection. We conclude that resilience of Bonneville cutthroat trout metapopulations increases with increased subpopulation connectivity and reduced synchrony of fire perturbations. Managing native fish populations to increase resilience to wildfire should include removal of barriers, if possible, as well as promoting asynchronous fire occurrence to allow discrete subpopulations of fish to recover and contribute to overall metapopulation stability.