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

Predicting how stream fishes may respond to habitat restoration efforts is difficult due, in part, to an incomplete understanding of how basic biological parameters such as growth and ontogenetic habitat shifts interact with flow regime and riverscape ecology. We assessed age-specific Guadalupe bass habitat associations at three different spatial scales in the South Llano River, a spring-fed stream on the Edwards Plateau of central Texas, and the influence of habitat and flow regime on growth. Substrates were classified using a low-cost side-scan sonar system. Scale microstructure was used to determine age and back-calculated size at age. Over 65% of captured Guadalupe bass were age-2 or age-3, but individuals ranged from 0-7 years of age. There was considerable overlap in habitat associations among age classes 1-3+, but age-0 Guadalupe bass tended to associate with greater proportions of pool and run mesohabitats with submerged aquatic substrates. While habitat metrics across multiple scales did not have a large effect on growth, discharge was negatively correlated with growth rates. Understanding age-specific Guadalupe bass habitat associations at multiple scales will increase the effectiveness of restoration efforts directed at the species and the use of low-cost side scan sonar seemed to provide an effective means of generating these data that can be adapted for other stream fishes.