Understanding population structure and connectivity is vital for managing and conservation of important fish. Discrete populations of conspecifics may respond differently to exploitation and habitat changes due to variations in growth rates, size at maturity, mortality rates, life history (etc.). Traditionally, demersal fish were suggested to be panmictic, due to pelagic early life stages and the connectivity of marine habitats. However, a growing body of evidence, in part unleashed by new scientific techniques, is suggesting otherwise. Large bodied sciaenids form traditional, recreational and commercial fisheries in many parts of the world. However, their life history makes them susceptible to human activities. Mulloway (Argyrosomus japonicus) is a large bodied sciaenid that has biology typical of members of this fish family (i.e. estuary association). In the southern hemisphere mulloway has iconic status due to the accessibility to large fish from the beach and estuary, however, the species is poorly understood, particularly in southern Australia. To improve our understanding of mulloway we investigated genetic population structure across its Australian range. Whilst within South Australia (SA) we closely scrutinised mulloway populations using multiple approaches, including a combined approach incorporating genetics, otolith chemistry and morphology. Also within SA we utilised otolith chemistry to determine their use of estuaries and satellite telemetry to determine movement ecology and the interaction with protected area boundaries. The results have provided new information which could help manage and conserve mulloway; whilst furthering our understanding of population structure approaches and demersal fish in general.