One of the objectives of providing fish passage is to improve fish populations. Connectivity at large scales is difficult to implement, especially given the costs and time-frames involved. Indeed, the need for fish passage over multiple barriers and large scales is often questioned. With limited evidence available to indicate improvement to populations, this can be a hard proposition to prosecute. Golden perch is a wide-ranging, mobile fish species of thee Murray-Darling Basin (MDB) in south-eastern Australia. It has migratory movements of both adults and juveniles, in addition to drifting eggs and larvae. It is a popular angling species, but like most native MDB fishes, it must compete for both water and habitat access with irrigation needs and infrastructure. This species is distributed across the MDB (almost 1 M km2) and this paper utilises new knowledge of the movements of this species through its inclusion in a metapopulation model to illustrate how actions in any location have the ability to alter populations in other regions of its range. Reinstatement of key flow components, together with connectivity, both of which greatly affect movements, are vital to the management of golden perch populations. Predictions from population modelling provide theoretical indications of the need for landscape-scale connectivity, and the potential benefits to golden perch populations. This approach may be applicable to prosecuting the case for fish passage for many other species.