Home-range estimates are an important input to species recovery plans. Our aim was to estimate the home-range size of the endangered Macquarie Perch in the lower Cotter River catchment, Australia. In total, fourteen home-range estimates were calculated from intensive radio-tracking of adult individuals over a minimum of five diel periods in either autumn (n = 5) or spring (n = 9). Home-range (95% Kernel) and core area (50% Kernel) were calculated by Kernel estimation and corrected for overlap with land. Seasonal estimates of home-range and core area were not asymptotic in relation to cumu- lative number of radio-fixes in four of fourteen cases. The mean within-season home-range of adult Macquarie perch was 5.5 ha ranging from 0.2 to 18.4 ha, based on 10 cumulative estimates that were asymptotic in relation to radio-tracking effort. All five individuals radio-tracked in autumn occupied a single core area, whereas in spring, six individuals occupied a single core area and three individuals each occupied three core areas. Despite individuals moving on a scale almost comparable to Cotter Reservoir (48.5 ha), only a single radio-tagged individual was found to leave the reservoir and enter the river. Regional fisheries managers are generally aware of the requirement for Macquarie perch to access flowing water for spawning in south-eastern Australia; however, in the Cotter River catchment, the protection of habitat for this species within Cotter Reservoir is also paramount. Our study highlights the importance of reservoirs for conserving a threatened aquatic species.