Riparian contributions to the diet of terapontid grunters (Pisces: Terapontidae) in wet-dry tropical rivers

The diets of terapontid assemblages in 22 catchments across Australia's wet-dry tropics were investigated in relation to the direct use of terrestrial-riparian inputs, as well as the role of ontogeny and morphology in mediating consumption of allocthonous material. The diet of several species was restricted almost entirely to instream trophic resources throughout their life history. In contrast, ontogenetic diet shifts towards increasing consumption of terrestrial prey types were a prominent feature of the dietary ecology of some terapontids, with collective allocthonous dietary items making a significant contribution (up to 42%) to diet in larger size classes of several species. For those species consuming terrestrial-riparian material in their diet, terrestrial invertebrates were the most common prey item; however, terrestrial vegetation, principally riparian fruits, and terrestrial vertebrates were also important dietary inclusions in the larger size classes of particular species. A large mouth gape was the morphological feature most strongly associated with consumption of terrestrial food resources within the Terapontidae. Results indicate that the direct consumption of terrestrially derived food sources in northern Australian aquatic systems may be more important than previously asserted, and that additional research is required to better clarify the role of terrestrial subsidies to these ecosystems.