Dryland rivers drain one-third of the worlds land mass, yet they are not studied with the same intensity as rivers located in wetter climates, such as tropical rivers. For much of the time, dryland rivers exist as a series of disconnected, waterholes that represent the only refugia available to obligate aquatic biota such as fish. Highly variable rainfall can intermittently connect these waterholes both longitudinally along river channels and laterally across floodplains. This episodic flow is an important factor in the maintenance of aquatic food webs and ultimately populations of fish.

In 2006, we investigated how the availability of food resources is linked to the natural variation in primary productivity in the Moonie River SW Queensland, a dryland river in the upper reaches of the Murray-Darling Basin. The diets of the native bony bream (Nematalosa erebi) and yellow belly (Macquaria ambigua) were examined in the months following a moderate summer flood peak as the quality of food resources diminished.

Both fish species displayed variable diets within sampling periods reflecting generalised feeding strategies typical of fish in dryland river systems. Diets also varied between sampling periods indicating the ability of both species to persist during both high and low levels of resource quality.

This interaction between the native biota and food resource conditions highlights the need to consider how future water resource development plans will affect the natural hydrology of dryland rivers, and ultimately their fish assemblages.