Cooperative Fish and Wildlife Research Units Program: Texas
Education, Research and Technical Assistance for Managing Our Natural Resources

1. Habitat heterogeneity at multiple scales is a major factor affecting fish assemblage structure. However, assessments that examine these relationships at multiple scales concurrently are lacking. The lack of assessments at these scales is a critical gap in understanding as conservation and restoration efforts typically work at these levels. 2. We used a combination of low-cost side scan sonar surveys, aerial imagery using an unmanned aerial system e, and fish collections to evaluate the relationship between physicochemical and landscape variables at various spatial scales (e.g., micro-mesohabitat, mesohabitat, pool-run-riffle complex, stream reach) and stream fish assemblage structure and habitat associations in the South Llano River, a spring-fed second order stream on the Edwards Plateau in central Texas during 2012-2013. 3. The finest spatial scale (micro-mesohabitat) and the intermediate scale (pool-run-riffle complex) had the greatest explanatory power for variation in fish assemblage structure. 4. Many of the fishes endemic to the Edwards Plateau exhibited similar associations with physicochemical and landscape variables 5. Low-cost side scan sonar proved to be a cost-effective means of acquiring information on the habitat availability of the entire river length and allowed for the assessment of how a full suite of riverscape-level variables influenced local fish assemblage structure.