Understanding the movement ecology of freshwater fishes, and how these patterns are affected by flow, is important for identifying key threats to populations and predicting their response to management strategies. We used acoustic telemetry to investigate the day-to-day behaviour and movement patterns of eel-tailed catfish (Tandanus tandanus) and examine how their behaviour was affected by natural changes to the flow regime in a subtropical river. Movement patterns varied within the tagged population: 29% were sedentary, 64% undertook interpool movements and 7% undertook reach-scale movements. The mean maximum distance travelled was 0.75 km (±0.33, s.e.) and the maximum distance travelled was 16.9 km downstream. Fish moved upstream and downstream between pools mostly at dawn and dusk, presumably to feed in riffles. Most interpool movements were undertaken during low-flow conditions (<0.2 m s^–1 and <6.0 m³ s^–1). Generally, the population responded inconsistently to flow events; however, the greatest movement response was detected during the first post-winter flow. Although fish preferred to move on an event fall, several fish continued to move throughout the study reach under baseflow conditions. Management strategies protecting low-flow conditions that maintain connectivity between daytime refuges and riffles may be important for the species’ conservation. The effective delivery of post-winter flow events, particularly in perennial systems, is likely to provide critical dispersal opportunities and aid long-term population viability.