The Mgobezeleni lake-system in Zululand is described and a checklist of decapod crustacea, molluscs and fish presented. The biota consists of freshwater, estuarine and marine forms. Several uncommon or rare species were found. The effect of various man-made changes on the system is assessed, with particular reference to the mangrove community. Constantly high water levels and excess fresh water have decimated theBruguieria gymnorhizaforest and associated fauna respectively.