Temperatures Selected in a Power Plant Thermal Effluent by Adult Yellow Perch (Perca flavescens) in Winter

Abstract

Winter-temperature selection by yellow perch (Perca flavescens) was monitored by radio telemetry near the thermal discharge from a power plant on the Upper Mississippi River. Ten fish were equipped with temperature-sensing radio transmitters. Temperature selection was monitored with an automatic recording system and manually with standard radio frequency receivers. The selected mean winter temperature for all locations was 5.4 °C; when fish were in the discharge area mean temperature selected was 6.3 °C. Ninety-one percent of the temperatures was recorded from fish in the discharge bay. Response to temperature varied greatly among individual fish, and they selected significantly lower temperatures in the field than in laboratory experiments. These field-selected temperatures correspond closely to those required for gametogenesis and spawning success in this species.Key words: Perca flavescens, thermal requirements, radio telemetry, temperature selection