Developing Conservation Priorities for Native Fish in the Lower Colorado River Basin

Our goal was to identify riverine fish species inadequately represented within the existing network of conserved lands in the Lower Colorado River Basin.  We first compiled datasets for biological, environmental, and anthropogenic metrics that are important predictors of native and nonnative fish distributions in the southwest U.S.  We developed a threat index based on landscape-level threats (e.g., road density, urban lands, etc.).  Next we modeled distributions for native and nonnative fish species using aspects of land use, climate, topography, water potential, and major river basin (e.g., Virgin River, Upper Gila, etc.).  Conservation priorities were developed by combining the threat matrix, distribution models, and additional data such as habitat fragmentation and nonnative species richness.  To describe the network of conserved lands, we used a dataset that categorized lands on a 1 - 4 scale that reflected whether lands had permanent protection from conversion of natural land cover and a mandated management plan to maintain a natural state.  Status 1 and 2 indicate the highest levels of protection.  Based on predicted distribution and known occurrences of native species, most had less than 10% of their distribution within status 1 and 2 lands.  Among major river basins, nearly 40% of lands within the Little Colorado and Virgin River basins have high conservation values (≥0.9) but are not protected.  These results could provide a useful framework to overlay potential for protection, predicted urban growth, etc. when making decisions regarding placement of reserve networks or selecting larger areas for restoration efforts.