Cost-effective, non-destructive solutions to developing a pre-recruit index for Snapper

Throughout the 2000s, the two main stocks of South Australia’s (SA) Snapper (Chrysophrys auratus) fishery demonstrated very different changes in fishery production associated with progressive deterioration in stock classifications. For the Spencer Gulf/West Coast Stock (SGWCS), annual catches have declined to very low levels and in 2018 and 2019 the stock classification was changed to ‘depleted’. In contrast, the Gulf St. Vincent Stock (GSVS) increased to unprecedented levels due to numerous strong recruitment year classes, but since 2015 has also experienced considerable declines and was classified as ‘depleting’ in 2019. For Snapper in SA, the population dynamics and fishery productivity are fundamentally driven by temporally variable recruitment. Annual estimates of recruitment as an indicator of future trends in fishable biomass are of significant importance and having a pre-recruit index as an indicator of future abundance and fishable biomass, provides a powerful, fishery-independent addition to the stock assessment capability. This investment seeks to improve the understanding of the processes and environmental influences that drive the variation in recruitment of Snapper in SA and develop a sampling regime to provide regional estimates of the pre-recruit index. The sampling strategy will be validated in following years to provide relative estimates of the recruitment rates for Snapper.