We propose to use long-term fish-population data from a relict reach of the Pecos River, New Mexico to assess population dynamics of imperiled prairie-river minnows, including Arkansas River shiner. Development of viable management strategies requires basic understanding of population ecology. Rigorous, quantitative ecological methods can be used to analyze continuous, long-term demographic data, but such data are rarely available for imperiled, non-game fishes. Data available for the Pecos River provide a unique opportunity to apply quantitative methods to prairie-river minnow conservation and management. Analyses proposed here would determine (1) whether population regulation is density dependent or flow-regime dependent and (2) which prairie-minnow species and life stages are most sensitive to climatic variability and water-resource management activities.