THE INFLUENCE OF SUSPENDED SILT ON OXYGEN-CONSUMPTION BY THE REDBREAST TILAPIA, TILAPIA-RENDALLI (BOULENGER, 1896)

The routine oxygen consumption of redbreast tilapia, Tilapia rendalli exposed to silt from the Phalaborwa Barrage was investigated under con trolled laboratory conditions. Exposure of adult fish to sublethal con centrations of silt did alter routine oxygen consumption by causing in creased rates (53-77% from initial) of oxygen consumption. This indica tes that sublethal levels of suspended silt concentrations results in an increase in oxygen consumption by the fish due to an increase in me tabolic rate associated with increased activity and stress. From the l aboratory experiments, it can therefore be predicted that sublethal re leases from the Phalaborwa Barrage will stress the resident fish popul ations. However, the extent of the impact on the fish population will depend on factors such as frequency, duration and severity of exposure as well as the species in question. Long term monitoring of the fish population below the Phalaborwa Barrage is therefore essential.