| Abstract: | Abstract Small and juvenile fish from three intermittently open estuaries in south-eastern Australia were sampled with a seine net to investigate species richness and the effect of estuary openings on assemblages. A total of 7285 fish were captured, representing 29 species. The most numerous fish were hardyhead, Atherinosoma microstoma Günther, flathead gudgeon, Philypnodon grandiceps Krefft, and non-native mosquito fish, Gambusia holbrooki Girard. Economic species included sand whiting, Sillago ciliata Cuvier, and sand mullet, Myxus elongatus Günther. Significant differences in the numbers of species and the numbers of individuals were found between estuaries, but were not observed for individual estuaries before and after opening. However, fish assemblages changed after opening, with several species recruiting from the ocean. Small, intermittently open estuaries present a complex management problem. These waterbodies are easily degraded in terms of water quality and sedimentation, and are often opened mechanically as a result of flooding or health concerns. The importance of these areas as fish habitats and the recorded changes in fish assemblages after opening suggest that careful management is required, including improved assessment of the impact of entrance manipulation. |
