Relationship Between Native and Nonnative Fish Presence and Components of the Hydrograph in Streams of the Mogollon Rim Emphasis Area, Arizona
Streams of the southwestern United States contain some of the most unique and endangered fish species on the planet. Conserving these species requires knowledge of what physical and biological conditions enable them to live at a particular location. Our current knowledge is focused primarily on the need for adequate baseflow, and some on flood flow; however, information about the relative importance of various other parts of the hydrograph could improve our management decisions, especially because water interests want to harvest parts of the hydrograph outside of baseflow. The goal of this project is to identify relationships between select native and nonnative fish species presence with the five components of the hydrograph described above. Four streams in the Mogollon Rim region of Arizona were sampled during summer base flow conditions (May – October) of 2017 to collect information on fish distributions and habitat conditions. A 20-year dataset from fish sampling in the Verde River by the Arizona Game and Fish Department was used to examine temporal shifts in fish assemblages as they relate to streamflow. Streamflow data from USGS stream gages, the USGS StreamStats application, and the National Hydrography Dataset (NHD) provided metrics to characterize streamflow throughout the study sites. These metrics included estimates of 2-year flood flows, 10-year flood flows, 100-year flood flows, mean annual flows, mean channel velocity, stream power at mean flow, and stream power at 2-year flood flow. Relationships between streamflow characteristics and species assemblages varied by species. Certain native species, like Sonora Sucker, consistently demonstrated positive relationships with spatial flow characteristics across all four streams, demonstrating a preference for areas with higher velocities, flow, and power. Results for other species were more variable by stream, and differences often split the four study streams into similarities among Tonto Creek and the Verde River, the two larger systems dominated by nonnative species, as opposed to the Blue River and Eagle Creek, the two smaller systems dominated by nonnative species. Management strategies are optimized when tailored to specific species and streams. Field work and data analysis on this project concluded Fall 2018, and a thesis on this subject was completed in December 2018. Results are now being prepared for publication.