Competition between Dermestes maculatus Degeer (Coleoptera: Dermestidae) and Necrobia rufipes Degeer (Coleoptera: Cleridae) in Clarias gariepinus (Burchell), was studied at four population levels (16,30,48 and 60), three moisture-content levels (12,15 and 20%) and three temperatures (20, 27 and 32°C). Experiments were carried out using adult insects of both species in mixtures of equal and unequal numbers. Interspecific competition between N. rufipes and D. maculatus was found to have an effect on the population growth of both beetles but to different extents. The intensity of competition is dependent on temperature, moisture content and the initial density ratio. Using the replacement series approach, it was predicted that at high adult population and moisture content, N. rufipes becomes extinct and D. maculatus dominates a mixed culture. At a temperature of 20°C, D. maculatus outcompetes N. rufipes while at 32°C, both species co-exist. This observation possibly accounts for the low occurrence or absence of N. rufipes relative to D. maculatus in commercial dried fish in areas with temperatures of 20 to 30°C.