CARL R. RUETZ III, D. B. Warnell School of Forest Resources, University of Georgia, Athens, Georgia 30602, USA

CECIL A. JENNINGS, U.S. Geological Survey, Biological Resources Division, Georgia Cooperative Fish and Wildlife Research Unit, D. B. Warnell School of Forest Resources, University of Georgia, Athens, Georgia 30602, USA

We estimated instantaneous growth and mortality of alevin channel catfish Ictalurus punctatus from the Oconee River, Georgia. The Oconee is a regulated river characterized by highly-variable, unpredictable flows. Our objective was to estimate alevin growth and mortality in this regulated system. We modeled growth and morality with exponential equations and estimated these parameters with regression techniques. Instantaneous growth was 0.0062 (SE = 0.0008) and instantaneous mortality was 0.0731 (SE = 0.0104). Published estimates of instantaneous growth and mortality are lacking for young-of-the-year (YOY) ictalurids. Our growth model predicted that YOY catfish would be 25 mm by mid-September. This size is much smaller than that (i.e., 60 mm) reported for similarly-aged alevins in other systems. Our results suggest that flow regulation may affect YOY fish population dynamics, but the mechanisms for such actions are unknown. Nonetheless, we attribute the low growth and mortality of YOY catfish in the Oconee River to the regulated flows in the system. Further, we hypothesize that the highly-variable, unpredictable flows that accompany hydropower generation may 1) increase energy demands for alevins and leave less energy available for growth, and 2) increase turbidity and thereby reduce alevin vulnerability to predators, which then results in low alevin mortality.