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Guadalupe Bass flow-ecology relationships; with emphasis on the impact of flow on recruitment


June 2015 - May 2018


Flow regime is among the most important environmental factors influencing population dynamics for stream fishes; however, developing direct relationships between flow regime and growth, recruitment, or mortality rates has proven challenging. However without a thorough understanding of these relationships, it is difficult to develop recommendations for instream flows to benefit species of conservation concern, such as Guadalupe Bass. Guadalupe Bass is considered to be vulnerable due to its dependence upon intact stream habitats, yet the flow requirements for the species, or even how flow influences its growth, recruitment, or mortality, is not well understood. Therefore, the objectives of this study are to 1) evaluate the influence of flow regime on the growth and recruitment of Guadalupe Bass across its entire range, and to monitor the impact of changing flow regime on the growth and mortality of young-of-year through their first summer. Samples will be collected from locations within the Brazos, Guadalupe, San Antonio, and Nueces River Basins and euthanized. We will remove their sagittal otoliths and determine the age and growth history of each individual. These data will be used to reconstruct the year classes and to estimate recruitment and mean growth rates related to flow conditions.

Research Products and Activities


  • Hill SA, HM Williams, TB Grabowski, & R Verble. Population estimation of Guadalupe Bass in the North Llano River. 2018 Annual Meeting of the Texas Chapter of the American Fisheries Society. College Station, Texas. 25-26 January 2018.

Current Staff

Federal Staff: 95

Masters Students: 240

Phd Students: 143

Post Docs: 52

University Staff: 245

5 Year Summary

Students graduated: 702

Scientific Publications: 1948

Presentations: 4246



  • Timothy GrabowskiPrincipal Investigator
  • Heather WilliamsStudent
  • Rachel BittnerStudent
  • Scott HillStudent

Funding Agencies

  • Gulf Coast Prairie Landscape Conservation Cooperative


Cooperative Research Units Program Headquarters Cooperators

  1. U.S. Geological Survey