Habitat Suitability Criteria for Nonnative Species and Relationships between Fish Populations and Flow Regime in Four Arizona Streams

Abstract

Nonnative species invasions and streamflow alteration are two of the primary causes of native fish depletion in the southwestern U.S. Previous research in Arizona has focused on the habitat needs of native species, without understanding the habitat selection of nonnative species. Additionally, fish populations and streamflow can vary significantly throughout a single Arizona stream, so it is important to understand how spatially variable flows affect fish assemblages. This research has two objectives: 1) to define suitable habitat for nonnative species, and 2) to explore the relationships between the distributions of various fish species throughout time and space in four Arizona streams. 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. I defined suitable habitat for seven nonnative species across these four streams, and results indicated that nonnative species were generally using warmer temperatures and shallower depths compared to available habitat, but many habitat results varied by species. Relationships between streamflow characteristics and species assemblages also varied by species. I found that 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. These results can inform decision-makers and fisheries managers in streamflow allocation, habitat restoration, and nonnative species removals.