The effects of suspensoids on fish

The author reviews the nature and sources of turbidity in inland waters in the Southern Hemisphere, and summarizes results of studies carried out in 3 areas of southern Africa, namely a turbid man-made lake (Le Roux lake, South Africa), a turbid natural lake (Chilwa lake, Malawi), and estuaries in Natal, to investigate the effects of turbidity on fish. In the lakes, turbidity appeared to reduce the availability of food and the growth rate and maximal size of the fish. Resuspension of sediment by wind action caused fish mortalities as a result of de-oxygenation. In estuaries, however, moderate turbidity appeared to be beneficial to fish by providing protection from predators. Published results from experiments, mainly in the Northern Hemisphere, on the effects of suspended solids on fish are reviewed. The principal effects of suspended solids on fish, and the interaction between high turbidity loads and various parameters which affected fish production and yield, are illustrated diagrammatically. A bibliography of 131 references is appended.