Dynamics and utilization of surf zone habitats by fish in the South-Western Cape, South Africa

Bibliography: leaves 188-216.The main objectives of this study were to examine, by means of beach seine netting, the composition, abundance and size structure of fish assemblages frequenting surf-zone habitats in the south-western Cape, South Africa, to investigate temporal and spatial variations in these assemblages in relation to physical environmental parameters, and to assess the importance of this habitat as a nursery and feeding ground for littoral fish. In all, 54 fish species from 29 families were recorded, with three species (Atherina breviceps, Liza richardsonii and Rhabdosargus globiceps) dominating numerically. Two separate surveys were designed to provide a comprehensive assessment of the factors influencing spatial variability in the composition abundance and community structure of the surf fish assemblages in this region. In the first, surf ichthyofaunal assemblages at 11 localities, selected to encompass as wide a range of physical parameters as possible, were sampled at monthly intervals for a period of two years. Results of this study indicated that the degree of wave exposure, the presence of emergent rock on the shore and turbidity were responsible for most of the spatial variability in abundance and community structure observed. In the second survey, samples were collected at eight localities spanning an exposure gradient from highly exposed, open ocean beaches to extremely sheltered marine sandy beaches, in order to isolate and carefully examine the influences of wave exposure on surf fish assemblages. Two important trends were evident in the abundance and community structure of teleost catches in this study. Overall abundance increased markedly as wave exposure decreased, while highest species richness and diversity, and lowest dominance were recorded at intermediate levels of exposure