Using physiological approaches to quantify potential effects of anthropogenic alterations to river systems on fishes

Abstract

In this dissertation, I used an ecophysiological approach to study the effects of dams on fishes via studies on swimming performance, metabolic rate, and thermal tolerance. The first study focused on 4 fish species (Channel Catfish, Redbreast Sunfish, Alabama Bass, and Tallapoosa Bass) from the Tallapoosa River in an area that is impacted by a hydropeaking dam. Given the lack of swimming data for three of the species and the only available data for Channel Catfish being from a lentic population, I quantified the critical swimming speed of fishes along with their active metabolic and resting metabolic rates, including in conditions relative to an area impacted by a hydropeaking facility. This work may be used to inform bioenergetics models and study the interactions of temperature, activity, and metabolism of these species. Next, I used juvenile Largemouth Bass to test the efficacy of using an enzymatic approach to quantify organismal thermal tolerance by comparing a traditional thermal tolerance metric, critical thermal maxima, with the temperature at peak enzymatic activity. Finally, combining the approaches used in the first and second study, I compared the swimming performance, active metabolic rate, standard metabolic rate, and enzymatically determined thermal maxima of juvenile Paddlefish. Overall, the swimming performance and metabolic rates documented here show differences across temperatures and species likely driven by each species’ ecological niche, and I show that enzymatic assays may be suitable for estimating organismal thermal optima and tolerance.