A SURVEY OF SELECTED EASTERN CAPE ESTUARIES WITH PARTICULAR REFERENCE TO THE ICHTHYOFAUNA

The physical environment and ichthyofauna of 10 estuaries, the East Kleinemonde, Klein Palmiet, Great Fish, Mtati, Mpekweni, Mgwalana, Bira, Gqutywa, Ngculura and Keiskamma, was sampled over a four year period. The ichthyofauna of each estuary was sampled once during winter and once during summer in that period, with the physical environment being sampled on two occasions per season. This investigation provides baseline ichthyofaunal and physical information for these estuaries, the majority of which have never been studied before. The fish data presented for these systems includes species composition, relative abundance, richness and diversity, longitudinal distributions and length frequency data. Descriptions of the physical environment within each estuary are also presented. The permanently open estuaries had a greater proportion of marine and freshwater species relative to the temporarily open/closed systems which were dominated by marine species dependent on estuaries and estuarine resident species. The permanently open estuaries had a higher Margalef's species richness index relative to the temporarily open/closed systems but the Shannon-Wiener species diversity index did not follow any discernible trend. There were minor longitudinal distribution trends when analysing the community as a whole, with patterns for individual species being more pronounced. The length frequency histograms for estuarine resident species differed between estuary types, while those for the marine migrant species were similar in the different estuary types