Conservation Assessment for Native Fish in the Upper Colorado River Basin

We applied a complementarity-based approach to develop priority ranks (0 – 1; low to high) for catchments in the Upper Colorado River Basin. We used methods and a framework that we had previously developed for the Lower Colorado River Basin so both basins could be integrated into a cohesive unit. Our approach incorporated an anthropogenic threat index, fish species distribution models, and other metrics (i.e., habitat fragmentation, non‐native species richness) potentially impacting conservation value of the riverscape. We developed the anthropogenic threat index based on the presence/absence of stressors known to influence the persistence of fish species. For the species distribution models, we incorporated metrics describing the topography, hydrology, land use, climate, and biogeography of the basin to model predicted probability of occurrence for native and non-native species.

Contiguous regions with high conservation value (> 0.8) are located in the headwaters of the upper Green, Yampa, and San Juan rivers, Green‐Colorado and San Juan‐Colorado rivers confluences, and designated wilderness areas of the Rocky Mountains. This information could be used by land managers to evaluate where they might have the largest return on conservation actions. These datasets could be used to identify areas of high conservation value or to compare the relative conservation values for catchments/stream segments where restoration projects are proposed to benefit native fish species or communities.

The intent was to provide an ecologically-based conservation assessment using the distribution of native fish species and the threats to persistence that could be used by land managers in the decision-making process to strategically place conservation efforts. Potential uses are: a) identify focal conservation areas, b) identify conservation strategies (e.g., non-native removal, habitat restoration, native species reintroduction, land protection), and c) compare/contrast factors influencing the conservation value. Because the Desert Fish Habitat Partnership and the Western Native Trout Initiative share overlapping geographic regions of interest, this could be used to identify regions of mutual conservation interest.