The assessment of fishways is primarily performed to determine the effectiveness and for identifying factors that limit the passage of fish beyond man-made barriers. Traditional methodologies rely on capturing fish that successfully ascend the fishway compared with the species and size classes of those that are attempting to ascend. This approach relies on the ability to representatively sample fish and the assumption that methods such as trapping do not significantly modify their behaviours. Other methodologies utilise transponder or telemetry tagged fish that are detected within or near the fishway. The requirement to capture and tag a diversity of fish species can negatively impact on a meaningful result for movement through the fishway. Both methodologies however are often unable to resolve many aspects of fish behaviour. Dual-Frequency Identification Sonar (DIDSON) is a relatively new tool for viewing real time behaviour of fish within and around fishways and can reveal many aspects that may affect the overall success of a fishway. This study presents the findings of an assessment program at Wyaralong Dam on Teviot Brook in South-east Queensland. A combined approach of traditional trapping and a DIDSON acoustic camera was used to assess the efficiency of a fishlift on a 27m high dam. Results demonstrated not only the strategies utilised by fish to successfully move through a fishway but also behavioural responses to external stimuli, diel patterns of movement and use of the fishway structure as habitat. Use of this technology has the potential to optimise fishway operation and achieve more successful fishway designs by revealing fish behavioural responses that would not otherwise be obtained.