H. vittatus is the main and most efficient predator in lake Kariba and is also present in very large numbers. The impact of predation falls mainly on small and young fish of the families Characidae and Cichlidae of which the latter are very important economically. Due to the particular (unstable) environmental conditions prevailing in Kariba, the young of many commercially important species, in particular Tilapia (the young of Labeo spp. stay up the rivers) are excessively exposed to predation during a critical period of their lives.