Diel Movement Patterns and Habitat Use of Flathead Catfish in the Lower St. Joseph River, Michigan

ABSTRACT

We examined the diel movement patterns and habitat use of seven flathead catfish fitted with ultrasonic transmitters in the lower St. Joseph River during July and August 2003. Movement rates were significantly greater during dusk, night, and dawn periods (median = 40 to 51 m/h) than during the day (median = 0 m/h). The median total distance moved by flathead catfish throughout the diel cycle was 72 m (range, 0 to 2,143 m), while the median diel range and net displacement were 44 m (range, 0 to 874 m) and 0 m (range, 0 to 874 m), respectively. Fish utilized significantly greater proportions of open-water sand, silt, and gravel habitats during dusk, night, and dawn periods (range, 22 to 40%) than during the day (6%). Water depths and flow rates associated with habitats utilized by flathead catfish were not significantly different among diel periods. Differences existed in the movement patterns and habitat use of flathead catfish within the diel cycle, and both structural and open-water habitats were important to this species.