Gary G. Williams, Tennessee Valley Authority, Water Management, 17 Ridgeway Road, Norris, TN 37828

Radio telemetry was used to determine if brown trout (Salmo trutta) and rainbow trout (Oncorhynchus mykiss) were vacating their summer habitats in search of refuge as a result of marginal water temperatures in the Hiwassee River (Appalachia tailwater) in Polk County, Tennessee. Eleven resident holdover brown trout and 13 resident holdover rainbow trout greater than 14 inches were surgically implanted with radio transmitters equipped with temperature sensors. Study results showed that none of the tagged fish throughout the study migrated into a thermal refuge such as cooler tributaries, closer proximity to the source of coldwater in the tailwater, spring seeps above or below ground, deep pools, etc. Ambient thermal monitoring showed that maximum average daily water temperatures were approximately 19.4^oC (67^oF) through the period between September and October when tailwater temperatures are typically the warmest. It has been previously hypothesized that water temperatures were thought to be the limiting factor influencing numbers of resident-holdover fish. We recommend that other mechanisms should be considered to be the limiting factors on growth and survival of trout rather than thermal habitat conditions.