Seasonal and diel behaviour of radio-tagged Clarias gariepinus in Lake Ngezi, Zimbabwe (Pisces: Clariidae)

Seasonal and diel behaviour of six sharptooth catfish, Clarius gariepinus (Burchell), was monitored in Lake Ngezi, Zimbabwe, from May 1986 to February 1987. All specimens were equipped with surgically-implanted radiotransmi tters, 48–49 mHz, after they were anaesthetized in 6 mg l^-1 quinaldine. This represented the first known use of this methodology in subSaharan Africa.
It was determined that C. gariepinus exhibited three movement patterns on a day-to-day basis: long-distance movements ( 2200 m), moderate movements (c. 40–200 m) and local movements (<40 m). Major movements were not restricted to night-time conditions, nor were inshore/offshore movements related to time of day. Seasonal activity peaks occurred in July/August 1986 and again in January 1987, with rate of swimming exceeding 470 m/h on some occasions. Home range of some individuals encompassed the entire lake (> 5 km²).