Abstract
In order to apply acoustic telemetry for tracking catfish, we first examined the effects of transmitter implantation on health of catfish in indoor water tanks using six catfish. As a result, the 5 weeks observation showed that there was no falling off of the dummy transmitter and death of fish, while the body weight of test individuals decreased slightly. Next, for better understanding of the behavioral activity of catfish，the tracking survey was conducted in a small stream named the Yagawa River in Tochigi Prefecture. Five catfish caught in the stream were tagged with the acoustic transmitteres and released， and their behavior were monitored in the detection range of the receivers. Three of the five acoustically tagged catfish were successfully monitored for more than 100 days in the study area. For a long time，these individuals have been settled in the same place where the log mattress bank was constructed. This result indicates that catfish has strong site fidelity and favor burrow habitats such as log mattress. The hourly signals of two fish were detected at nighttime more than that in the daytime from October to November. These signal detection patterns in autumn suggest that they stayed inside burrows in the daytime and moved outside their burrows at nighttime，which is considered to be typical nocturnal activity patterns of catfish. From December to January, however, hourly signals of three fish were detected all day and detection patterns were arrhythmic. These signal detection patterns in winter imply that catfish were active all day. Thus, this study quantified long term nocturnal activity patterns of catfish and for the first time found seasonal changes of these patterns. These new findings about behavioral activities of catfish provide information necessary for its conservation considering the catfish's life history in a river.
