Dispersal and kinship patterns of a pelagic-spawning riverine fish highlight the value of connectivity over large spatial scales

Managing fish populations in regulated rivers requires an understanding of the spatial and temporal scale of their dispersal, the locations of key spawning and nursery habitats and the hydraulic processes that interplay with their life history. Golden perch (Macquaria ambigua), an Australian freshwater pelagic-spawning fish, highlights the worldwide challenges of managing riverine species that rely on hydraulic conditions to sustain critical metapopulation processes. This study aimed to quantify the spatial scale of early life history golden perch dispersal after a drought-breaking in-channel flow event in early 2020 in a regulated lowland river. Otolith microchemistry (87Sr/86Sr) and single nucleotide polymorphisms (SNPs) determined natal origins and sibling relationships, respectively, of young-of-year (YOY) caught in a floodplain nursery with larval fish captured upstream. For fish collected in the floodplain nursery, dispersal distances ranged to ~1600 km. Otolith microchemistry attributed 52% of YOY as localised in origin, 44% as originating in the midcatchment and 4% from the most upstream sample locations. Genetic analyses identified a full-sibling pair captured 900 km apart and 31 half-sibling pairs that linked YOY to larval fish captured at a diversity of upstream sites. Our study highlights the range of spatial scales over which ELH dispersal can occur for golden perch and emphasises the importance of interconnected flowing river habitats in sustaining metapopulation processes. We illustrate the positive results that increased riverine connectivity can yield for fish with similar life history strategies.