Giant Australian cuttlefish, the largest cuttlefish species in the world, is widely distributed across southern Australian waters. Through most of its range it breeds on inshore rocky reefs, but it is renowned for forming the single largest known breeding aggregation of any cuttlefish species in the world. Each winter thousands of cuttlefish aggregate at Point Lowly in Upper Spencer Gulf (USG) to spawn. Estimates of abundance and biomass of spawning cuttlefish have indicated that population density at the aggregation site has declined through time with the most dramatic decreases occurring in 2011 and 2012. The magnitude of this decline has raised concerns about the sustainability of cuttlefish and highlighted the paucity of information relating to the fine-scale population structure and dispersal of this species within USG, as most studies have concentrated on the adult component of the population. The dispersal of hatchlings away from the spawning site and residence as sub-adults is currently unknown. Recent research investigating the broader-scale population structure suggested that the USG population was genetically isolated from the rest of the State, and may constitute a separate species (Gillanders and Donnellan, ARC Linkage project). This degree of isolation imparts a greater conservation focus on the species and highlights the importance of identifying the ecological/environmental factors that are driving the observed population decline and whether certain life-history stages are more vulnerable than others.