The relative significance of fish movement and local reproduction and recruitment as input demographic processes for fish populations can be challenging to differentiate. Nevertheless, it is significant to do so, from the perspective of understanding stock structure and appropriate spatial scales for management. Snapper is the most significant coastal, marine finfish fishery species of South Australia. During the 2000s, its component regional fisheries underwent unprecedented changes in spatial structure: an episodic fishery developed in the south east (SE) region; annual catches in Northern Gulf St. Vincent (NGSV) increased exponentially to record levels; whilst catches from Northern (NSG) and Southern Spencer Gulf (SSG) declined to their lowest levels. The demographic and fishery-related processes that underpinned these changes were unclear, which hampered developing appropriate management responses. This study used the analysis of otolith chemistry to assess the relative significance of inter-regional movement and local recruitment as input processes to the different regional populations. Transverse sections of otoliths from four year classes collected from six different regional fisheries were analysed using laser ablation – inductively coupled plasma mass spectrometry. These provided age-related estimates of elemental concentrations for Ba, Sr, Mn and Mg that were compared amongst regions. The data were interpreted to indicate the regions of origin and subsequent migration patterns of fish. The episodic fishery in the SE was related to variable recruitment into Port Phillip Bay, Victoria and subsequent mass emigration out of the bay and then westward over a distance of approximately 600 km, indicating that the Western Victorian Stock extended well into South Australian waters. Alternatively, the snapper populations in NGSV and NSG were considered separate stocks that were not connected by adult fish movement, whose contrasting trends in fishable biomass related to different recruitment patterns since the late 1990s.