For Southern Garfish (Hyporhamphus melanochir), one of the most significant inshore fishery species of South Australia, the current levels of stock status are poor.  Nevertheless, the stock assessments are based on spatially-limited, fishery dependent data, which may not be indicative of the status of the broad geographic stock.  A recent FRDC-funded project (2015/018) has considered population characteristics of Southern Garfish throughout heavily and lightly fished areas of Gulf St. Vincent, using fishery independent sampling.  The night-time sampling operations involved: visual counts of juveniles and adults that provided estimates of relative abundance; and dab netting that collected specimens to inform on size, age and sex.  Between 2016 and 2018, thirteen localities were sampled twice (spring/summer and autumn/winter) at three depth zones (0-5 m, 5-10 m, 10-15 m).  The results demonstrated unexpectedly high spatial complexity in the dispersion of fish with respect to size, age and sex that resulted in spatial differences in abundance, biomass, size structures and sex ratios at several spatial scales.  At the regional scale, these data suggest three populations located in the eastern, northern and western parts of the gulf that experienced different demographic processes.  The implications for stock assessments are considered.