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

We used stable isotope analysis to investigate differences in Guadalupe bass Micropterus treculii resource use that might be associated with population-level variation in main-stem river versus tributary stream habitats. Micropterus treculii from main-stem sites had more enriched δ¹³C and δ¹⁵N signatures compared to those collected in tributaries, likely reflecting greater importance of algae as a basal resource and influences of urban wastewater in main-stem habitats. Documenting ecological variation across ecosystem types is important to inform fish conservation efforts, especially for species that occupy a range of stream sizes.