Management of water resources in regulated rivers is a balancing act between environmental requirements and anthropogenic uses. Understanding the environmental flow requirements for fish spawning migrations and upstream dispersal is essential for the effective management of dam releases and fishway operations. Here we used a combination of underwater passive acoustic telemetry and flow records to reveal the minimum natural flows required to stimulate migratory movements in three catadromous fish species: Macquaria novemaculeata, Mugil cephalus and Trachystoma petardi. Over a 12-month period the movements of 190 fish were tracked throughout an array of 46 acoustic receivers. The acoustic array was installed throughout the Logan River basin in south east Queensland, from the river mouth to approximately 140 km upstream. M. novemaculeata moved downstream on relatively small flow events in June and July, travelling up to 110 km from the release location to the lower estuary where presumed spawning grounds are located. Not all M. novemaculeata moved to the estuary on one flow, some moved part way and continued to the estuary on the second flow event. Only one M. novemaculeata was observed moving past the tidal limit during the upstream dispersal in spring. Some M. cephalus tagged in November migrated downstream on low flows commencing in February. T. petardi have generally moved upstream, however no clear migration patterns have yet emerged. Over the next two years experimental flow releases which simulate natural migratory triggers will be used to test hypotheses. The outcomes will inform water resource planning in south east Queensland.