A PRELIMINARY ASSESSMENT OF THE IMPACT OF SOME ASPECTS OF THE HARTBEESPOORT DAM ENVIRONMENT ON PRODUCTION OF THE MAJOR FISH SPECIES

Abstract

The dominant species of fish in Hartbeespoort Dam, in terms of mass composition of catches, are shown to be Oreochromis mossambicus (Peters), Cyprinus carpio Linnaeus and Clarias gariepinus Burchell. Minimum winter temperatures are demonstrated to have a major impact on O. mossambicus standing stock and hence on production. Comparisons are made between a number of limnological parameters in the lake and published tolerances of fish to these parameters and it is concluded that deoxygenation and supersaturation of oxygen and pH are approaching levels critical to fish survival. The growth of O. mossambicus in South Africa is shown to be related to soluble reactive phosphorus concentration and to be sub-optimal in Hartbeespoort Dam, probably as a result of high phosphorus concentration.