[en] Knowledge of behavioral responses of aquatic organisms to thermal discharges at power plants is essential to evaluate thermal exposure and subsequent effects on survival and ecological success. Instantaneous responses of juvenile salmon that encountered a simulated river-thermal plume interface were assessed in a model raceway with a thermal discharge. Fish movement and response to the discharge were recorded on videotape. Juvenile chinook salmon (Oncorhynchus tshawytscha) tested under three discharge conditions (no plume, ambient plume and heated plume) avoided plume temperatures greater than 9 to 11⁰C above ambient. Fish occasionally oriented to the discharge current, but were not attracted to the thermal component of the plume when plume ΔT's were below the avoidance level of 11⁰C. Fish did not pass to the lower end of the raceway when plume ΔT exceeded 9 to 11⁰C. The responses noted in our experiments suggest organismic behavior may prevent juvenile salmon in nature from experiencing lethal conditions from thermal discharges and have application in waste heat management and utilization