Variation in surf-zone fish community structure across a wave-exposure gradient

Fluctuations in various attributes of a surf-zone fish community were examined by beach seining at a series of sites spanning a wave-exposure gradient in the Saldanha Bay-Langebaan Lagoon system, on the South African west coast. During April 1994, 24 species, totalling 25 676 individuals and 434 kg, were captured. Three teleosts, Atherina breviceps, Liza richardsonii and Psammogobius knysnaensis, dominated numerically, while three elasmobranchs, Rhinobatos annulatus, Mustelus mustelus and Myliobatis aquila, dominated the biomass, Elasmobranchs displayed no discernible distribution patterns. Two important trends were, however, evident in the teleost catches: overall teleost abundance (mean density) increased markedly as wave exposure decreased; and highest species richness and diversity, and lowest dominance were both recorded at intermediate levels of exposure. A positive relationship between fish size and exposure was also evident for at least two of the species. These trends were attributed primarily to the availability and abundance of suitable food resources, and to physical disturbance introduced by breaking waves. (C) 1997 Academic Press Limited.