Cooperative Fish and Wildlife Research Units Program: Tennessee
Education, Research and Technical Assistance for Managing Our Natural Resources

Little is known about the actual thermal experience of fish that live in both spatially and temporally variable thermal environments in areas around heated effluents. Do they completely avoid water that exceeds a laboratory-derived avoidance temperature or do they sometimes temporarily occupy temperatures that might be detrimental if exposed to indefinitely? Do fish in proximity to heated discharges use cool refuges in summer when temperatures throughout a larger area are often higher than preferred or optimal? Do they move about on a regular basis such that their exposure to excessively warm temperatures is tempered by periods at cooler temperatures? Do thermal discharges result in direct mortality or do fish exhibit behaviors that limit exposure to sub-lethal durations? These are old questions that may have been explored before, but new telemetry technology could provide better answers. Transmitters are smaller than in the past allowing their use in more varied sizes of fish. Enhanced memory allows data to be collected more frequently and archived if necessary for later downloading. Receiver systems are more sophisticated allowing for automatic and more frequent data collection. A telemetry study that tracks the thermal experience of individual fish near a thermal discharge over several weeks will provide valuable information on actual thermal exposure. In this study several species of fish are being tagged with ultrasonic transmitters and their location and the temperature of the water they are inhabiting near a power plant is being monitored continuously with an array of submersible receivers. These data will be used by power producers and regulators to redefine the upper limits of temperature that fish can be exposed to during routine power plant operations.