Background/Aims: The movement ecology of freshwater fish is crucial to understanding population dynamics, species persistence, and ecosystem function. Golden perch is a long-lived, potamodromous fish species and are highly mobile with their life cycle movements occurring across various spatial and temporal scales and are critical in maintaining population connectivity, genetic diversity, and recruitment success. Juvenile Golden perch are thought to typically remain in downstream habitats for extended periods, often up to three years, before initiating upstream migrations into tributaries across Victoria and New South Wales. In Autumn 2022, a large cohort of juvenile Golden perch recruits were detected in the lower Murray River during population surveys at Victorian anabranches at Lindsay and Wallpolla islands. Microchemistry analysis indicated that the recruits were spawned in either the Darling or lower Murray rivers and had subsequently drifted downstream into the Victorian anabranches. We hypothesized, that the recruits would remain in the lower Murray area for at least 24 months of age.
Methods: In spring 2022, we acoustically tagged 21 of these recruits (0+ age fish) with V5 (179 days) acoustic tags at running water and wetland habitats at Wallpolla and Lindsay islands, respectively. In one of the tagging locations, the wetland was dry by November 2023.
Results: Using multiple lines of evidence (population surveys, otolith microchemistry and acoustic tracking), we found that most individuals remained in the tagging area, but three individuals migrated up-to 450 kilometres upstream with the migrations coinciding with a large natural flood.
Conclusion: Three fish (<16 months of age) undertook extensive upstream movements (>450 km) indicating the phenomenal dispersal potential of this species. Fish that remain within the anabranch systems may represent a cohort of future immigrants into Victorian and NSW tributaries. Given the potential for future dispersal, the need for re-connection of these habitats is critical if fish are to disperse (at ages of >16+ months). Therefore, consideration should be given to providing connecting flows to known populations with large abundances of juveniles allowing movement opportunities at large spatial scales and the preservation of population resilience.