The first part of this project was a basic survey of fish use of intertidal habitats such as mangroves, mudflats and saltmarshes, which previously had hardly been considered in temperate Australian coastal waters.

Mangroves (Avicennia marina) and mudflats were used by at least 41 species of fish. Juvenile stages of 41% of the species were sampled and economic species were common. Mangrove habitat in temperate Australian waters supports a richer juvenile fish assemblage than adjacent mudflats, but there is little difference between habitats for the subadult/adult assemblage. Ultimately, the ‘value’ of mangrove habitats to fishes depends strongly on the time and place.

Saltmarshes were difficult to sample because of unpredictable amounts of water cover. Saltmarsh flats were generally only covered with water during low-pressure weather systems. Most fish caught in this habitat were not of commercial value. Water temperature, salinity, depth or barometric pressure did not explain variability in the number of fish species present or fish abundance. Fish species in the saltmarsh flats also live in other habitats such as seagrass, and the observed patterns of habitat use seemed to partly relate to feeding behaviour.

The second part of the fish-habitat survey work aimed to see how the use of habitats by fish changed within different parts of the habitat, and also with respect to the location of other habitats.

Results from the study will be valuable in the future detection of environmental perturbations, providing a baseline data set against which disturbance effects can be assessed. Information on habitat use, and how multiple habitats interact with each other, will put managers in a stronger position to argue for the preservation of important nursery habitat. Results from this project may also be important in advising on the appropriateness of marine park designs to ensure, among other things, fisheries sustainability.

Keywords: Mangrove, mudflat, saltmarshes, fish, zonation, landscape, seagrass, stable isotope, base for nutritional support, carbon and sulphur stable isotopes, commercial