Ultrasonic telemetry was used to determine seasonal temperature selection by adult flathead catfish (Pylodictis olivaris) in a 93-ha reservoir in west Texas, Buffalo Springs Lake. We implanted temperature-sensing ultrasonic transmitters in 29 flathead catfish and monitored them from June 1993 through June 1995. During the summer months, flathead catfish were found in the warmest lake waters (24.5-31.5 C) even though cooler well-oxygenated water was available. As lake temperatures decreased in fall and winter, flathead catfish were located in the warmest available water. Coldwater habitats were utilized only when the reservoir was not stratified. There was no significant difference in temperature selection by flathead catfish based on size, sex, year, or month. Other habitat variables may be more important to the overall habitat selection by flathead catfish in Buffalo Springs Lake.
