Floods can generate major recruitment events in riverine fishes, but where these cohorts subsequently disperse, and the processes determining their redistribution across river networks, remain poorly understood. This is particularly important in regulated rivers, where hydrology, infrastructure and river-network structure may modify natural dispersal processes. We examined the redistribution of golden perch (Macquaria ambigua) across the southern Murray–Darling Basin following widespread flooding in 2022–2023, asking three questions: who was moving, where did they go and what shaped their redistribution? We combined basin-scale acoustic telemetry of 457 juvenile, sub-adult and adult fish with otolith 87Sr/86Sr analysis of 248 individuals to reconstruct natal origins and early-life dispersal histories. Fish sampled following the floods represented mixed-origin cohorts from geographically distinct regions of the Basin, with some individuals having already dispersed 100’s-1000’s of kilometres from their natal region by approximately 2.5 years of age. Following tagging, approximately 65% of fish moved >40 km upstream, often rapidly and directionally, with some individuals travelling >800 km within months. Despite differences in hydrology between years, fish showed broadly similar patterns of redistribution across the river network. Discharge influenced movement initiation, but proportional tributary discharge generally did not predict routing at confluences. Instead, redistribution was strongly structured by confluence identity, with some tributaries receiving and retaining disproportionately large numbers of migrants. These findings demonstrate that redistribution following major recruitment events is a network-scale process in which discharge initiates movement, while river-network structure, confluence-scale routing and tributary retention shape where dispersing fish ultimately contribute to populations. Understanding where cohorts originate, how they redistribute and which habitats function as sources, pathways or destinations provides an evidence base for managing population recovery across regulated river networks.