Passive acoustic methods are increasingly used to study cetacean habitat use and behaviour. The Timing Porpoise Detector (T-POD; www.chelonia.co.uk) is a self-contained acoustic data logger, which records echolocation by cetaceans. This study used nine T-PODs to document habitat use by bottlenose dolphins in Doubtful Sound, New Zealand, over a 12-month period, collecting data over 76,104 h (of a possible 78,840). T-POD records show that dolphin distribution varied seasonally, with inner fiord sites being used most often in summer and autumn, and outer fiord sites during winter and spring. This seasonal pattern was positively correlated with surface water temperature. Echolocation activity in general and buzzes, which are usually indicative of foraging, were both significantly more common during dawn and/or dusk, suggesting crepuscular foraging. T-POD data suggest that parts of the 'Dolphin Protection Zone', in which boat traffic is restricted, are used frequently while other parts are not, and provide a basis for refining this management tool.