Considerable numbers of rainbow trout (Oncorhynchus mykiss) are captively produced then stocked into many wild aquatic systems in Western Australia despite a lack of understanding of their impact on the highly endemic native fish and freshwater crayfish of the region. The diet of an introduced, yet self‐sustaining population of O. mykiss was examined at Churchman Brook Reservoir in the Canning River Catchment, Western Australi...