The present study was undertaken to describe the species composition, size composition and distribution of the fish fauna associated with the temporarily open/closed East Kleinemonde Estuary on the south east coast of South Africa. Data collected on the estuary mouth condition from March 1993 to August 1997 indicated that this system was predominantly closed, while open mouth conditions were unseasonal and prevailed for only a short duration following periods of high rainfall.
Fishes were sampled throughout the estuary between April 1993 and January 1997 using seine and gill nets. A total of 30 species belonging to 17 families were recorded, including the critically endangered estuarine pipefish Syngnathus watermeyeri
. Besides the estuarine pipefish, an additional five species capable of completing their life cycle within the estuary were recorded. The ichthyofaunal community was dominated by marine-spawning species (n = 18) with varying degrees of dependence on estuaries as nursery areas. The marine species that are not dependent on estuaries as nursery areas were represented by three species, while the euryhaline freshwater species, obligate catadromous species and facultative catadromous species were each represented by one species. The dominant members of the estuarine-spawning group were well represented by all post-larval life-history stages, whereas the mean individual size of each of the marine-spawning species indicated that juvenile size classes dominated this group.
Classification and ordination of both the small and large mesh seine net fish assemblages revealed a high degree of similarity throughout the estuary, with the exception of a distinct grouping associated with sandy substrata in the lower reaches of the system. Catch per unit effort (CPUE) data provided evidence of spatial segregation by several species as well as within some families (e.g. Gobiidae).