Feeding Ecology of a Scorpaenid Fish, the Fortescue Centropogon australis, from a Posidonia Seagrass Habitat in New South Wales

Abstract

Examination of the stomach contents of 153 predominantly sub-adult (modal standard length c. 40 mm) fortescues, C. australis, collected from an estuarine Posidonia aulstralis seagrass meadow near Sydney showed that these fish were macrophagic carnivores. Crustaceans (mainly grapsid crabs and penaeid and carid shrimps) made up 90% of the diet by estimated volume; other major food types included polychaete worms and gastropod molluscs. Minor food items included seagrass, algae and foraminiferans. This predominantly crustacean diet was found to be generally similar to that of a number of other scorpaenid species. No obvious seasonal differences in diet were detected apart from slight changes in the composition of the crustacean component. The morphology of the alimentary tract of C. australis is of a typical carnivorous type. Fortescues were found to be relatively abundant in the Posidonia habitat, representing, on average, 11 .5 % of the fish community by numbers and occurring at an average density of 1 fish per 14 m². Sub-adult fortescues appear to be highly dependent on the Posidonia habitat and its invertebrate community as a food source.