Occurrence of young and small-sized fishes in different habitats within a subtropical South African estuary and adjacent harbour

This paper investigates the association of assemblages of 0+ juveniles and small fishes with different shallow-water habitats in Mhlathuze Estuary and the adjacent Richards Bay Harbour. Prior to harbour development, these systems comprised a single large estuarine system. Sampling was conducted on a quarterly basis using a fine-mesh (1 mm) small seine net (8 m). Habitats sampled were all important as nursery areas for juvenile fishes but they supported different fish assemblages. The most distinct assemblage occurred in eelgrass, which is restricted to the estuary. Several species were strongly associated with this habitat, and its scarcity in other subtropical South African estuaries may be limiting to species richness. Mangrove fringes in both systems and sandbanks in the estuary supported similar fish compositions. Fishes associated with mudflats in the estuary and harbour were similar in community structure. Ecologically important prey species used these mangrove, estuary-sandbank and mudflat habitats as juveniles and adults. Harbour sandbanks had fish assemblages dissimilar to sandbanks in the estuary and other habitats in the area.