Spatial, temporal and size-class variation in the diet of estuary perch (Macquaria colonorum) in the Hopkins River, Victoria, Australia

The dietary importance of prey of estuary perch (<i>Macquaria colonorum; Percicthyidae: Günthe</i>r<i>) </i>was examined spatially, temporally and among size classes. Fish were collected from the Hopkins River, south-western Victoria, from September 1998 to February 1999. The species is a euryhaline, euryphagic carnivore with spatial, temporal and size class variations in diets. Fish caught from estuarine locations consumed primarily <i>Paratya australiensis</i> (40% IRI) while freshwater fish consumed mostly Tricopteran larvae (63.5% IRI). In both freshwater and estuarine locations, the relative importance of <i>P. australiensis</i> decreased with increasing length of fish. Diet changed seasonally, indicating opportunistic changes in prey. The species selected particular prey items relative to environmental availability (<i>P. australiensis</i>, <i>Amarinus lacustrine</i>).<br />