Factors affecting the distribution, abundance and diversity of rock-pool fishes on the Cape Peninsula, South Africa

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Abstract
A quantitative description of the fish communities inhabiting rock pools on the Cape Peninsula, South Africa, and the relationships between the physical characteristics of the pools and the distribution, abundance and diversity of the resident fish fauna are given. A total of 1 541 fish, representing 21 species, were collected from 84 rock pools using the ichthyocide Rotenone. The mean density was 7,42 fish m−2 (49,60 gm−2) of pool area or 0,58 fish m−2 (3,67 gm−2) of the whole intertidal zone in which the pools were situated. Clinus superciliosus, C. cottoides and Chorisochismus dentex were the most abundant species, together comprising 75% of the biomass and 60% of the number of fish caught. The number of species, number of individuals and biomass of fish in the pools all correlated significantly (P < 0,01) with pool size and the amount of rock cover available. In addition, the number of species decreased up the shore. These three environmental factors in combination accounted for between 58% and 88% of the observed variance in diversity, number and biomass of fish in the pools. Rock cover was the single most important variable, explaining up to 76% of the variance. Possible reasons for the importance of rock cover and its relationship with pool size, are discussed.

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