A population of the endangered olive perchlet (Ambassis agassizii) was recorded in an off-channel wetland in the lower Lachlan River System in April 2023. Prior to this, the species had only been known from one population much high in the system in the Lake Brewster weir pool. Flow conditions over the past 3 years are likely to have provided habitat for olive perchlet and other fish that occur in off-channel habitats as well as providing dispersal opportunities. The lack of detection of olive perchlet until now may also be related to the lack of targeted monitoring of wetland fish on the lower Lachlan floodplain. This discovery prompted further and more comprehensive field based surveys, eDNA surveys, and a population genetic study which were funded and led by various State and Commonwealth agencies. This multi-disciplinary approach provided a range of information on the species current distribution and abundance, and the population genetic structure of the population. Among other key findings, the population genetic study highlighted that the population had not dispersed from Lake Brewster and were genetically distinct. The information was used to guide a plan of action involving translocation of fish to more permanent habitats, an environmental watering action and an on-going monitoring program. The success of this project relied on the support and assistance from a range of stakeholders including private landholders and the rapid response and regular communication between the various institutes and agencies.