Diet of the Australian bass, Macquaria novemaculeata (Perciformes : Percichthyidae), in the Sydney Basin

Abstract

Stomach contents of Australian bass, M. novemaculeata, sampled from the Hawkesbury River and Georges River in the Sydney Basin, New South Wales, between November 1977 and January 1982 were analysed by the occurrence and points methods. Stomach fullness was also recorded. A total of 143 aquatic and terrestrial animal taxa were present in the diet, and these were grouped into 19 food types for analysis. M. novemaculeata is a euryphagic carnivore. Season and habitat type had significant effects on composition of the diet. Insects were the most important food type, followed by fish and large crustaceans. A large proportion of the diet of bass was derived from allochthonous sources, mainly during summer, and especially in lotic habitats. Mean stomach fullness was highest in spring and lowest in winter. Young M. novernaculeata (TL 11-47 mm) from the Hawkesbury River estuary fed on far fewer prey taxa (mainly chironomids and copepods) than did adults. Dietary overlap occurs between M. novemaculeata and many other carnivorous freshwater vertebrates in the Sydney Basin. However, persistent competitive clashes are generally avoided, either by differences in microhabitat preference and feeding behaviour or by larger-scale habitat partitioning.