Abstract
Mekong giant catfish Pangasianodon gigas is endemic to Mekong River basin and endangered
species. It is urgently necessary to learn more about the movement pattern of the catfish to con
serve. We started the Mekong giant Catfish Tracking Project (MCTP) in 2001, which is ecologi
cal research cooperatived with Thai government. The horizontal and vertical movements of the
catfish were measured by ultrasonic depth-sensitive transmitters in the reservoir. Temperature of
both the surface layer and bottom, and depth-temperature profile were surveyed using depthtemperature
data loggers. The catfish appeared to favor relatively deeper areas horizontally and
spent the majority of their time above the thermocline vertically. The catfish exhibited the as
cent to the surface at dusk and the descent to the thermocline at dawn in the reservoir. Diel
movement patterns of the catfish may be related to the foraging behavior.
