Behavioral Thermoregulation of Fishes in Relation to Heated Effluent From a Power Plant On the Cumberland River, Tennessee

Laboratory-derived thermal preferences and critical maxima of fishes frequently dictate power plant discharge protocols. To better understand thermal tolerances and develop more accurate criteria, fish were tagged with temperature-sensing ultrasonic transmitters to record thermoregulatory behavior in and around the discharge at the Tennessee Valley Authority‘s Cumberland Steam Plant on the Cumberland River. Tagged fish were manually tracked to describe their distribution near the discharge plume. Additionally, an array of submersible receivers in the vicinity of the discharge have logged thousands of observations since July 2012 of temperatures used by five species representing different habitat and feeding guilds: Blue Catfish Ictalurus furcatus, Channel Catfish Ictalurus punctatus, Smallmouth Buffalo Ictiobus bubalus, Largemouth Bass Micropterus salmoides, and Striped Bass Morone saxatilis.  Most fishes spent at least some time in the thermal plume and two Smallmouth Buffalo resided there even when water temperatures exceeded 34^oC.  In October 2012, Largemouth Bass were recorded making forays into the thermal plume (25°C) followed by several hours of occupying cooler water nearby (20°C).  On two occasions in late summer 2012, five tagged fish absent from the area were simultaneously recorded near the plume after a sudden drop in its temperature of 6°C.  Monitoring will continue throughout 2013.