The dry‐season diet of freshwater fishes in monsoonal tropical rivers of Cape York Peninsula, Australia

Abstract

Abstract – Fish assemblages in three rivers of eastern Cape York Peninsula, northern Australia, were sampled during the early part of the monsoonal dry season, and the diet of 23 species was quantified. Spatial variation (between‐river) in diet was, in general, not pronounced. Sufficient specimens were collected to enable examination of ontogenetic changes in the diet of four species. Interspecific and ontogenetic variation in diet were most strongly related to differences in body size and mouth gape, with larger species or age classes feeding on fish and large aquatic invertebrates. Other gradients upon which dietary differences were arranged included gradients in detritivory and reliance on terrestrial invertebrates. Significant trophic separation was evident in the fauna despite aquatic invertebrates being the most important food item in most species. Seven, and possibly eight, trophic groups were recognized. Notable features of the trophic organization were the prevalence of omnivory and piscivory and relatively small representation by detritivores. Planktivores were essentially absent. Much of the observed trophic structure within the fishes of Cape York Peninsula could be ascribed to the effects of phylogenetic determinants of body size, morphology and foraging mode. The trophic structure within rivers of eastern Cape York Peninsula is compared to other aquatic systems in tropical northern Australia.Note