Aspects on The Ecology of Labeo Capensis and Labeo Umbratus in The Vaal River

Studies on bivalves in the Swartkops estuary have indicated that spatfall occurs during late summer. After adult populations had been dtc'nvttfrrt by floods in 1971 spat made up a large proportion of the bivalve population in 1973. Growth rates vary at different intertidal levels and in different parts of the estuary and growth has been shown to vary seasonally. In two species age determinations from growth rings corresponded well with age determinations from size frequency histograms.