Empowering industry to maximise fish size and quality in the South Australian Sardine Fishery

This project was designed 1) to empower the South Australian Sardine Fishery to autonomously manage the size and quality of fish harvested; 2) to distinguish and predict the habitat preferences of adult and juvenile sardines; and 3) to predict sardine spawning habitat. The system includes a custom-built electronic measuring board linked to a database that includes the location, catch quantum (nearest t) and size of fish taken (nearest mm). The database is linked to GIS software that produces maps showing the distribution of target and non-target sized fish. This information is used in near real-time by industry to optimize the size of fish harvested. Generalised additive models were developed that have an acceptable ability to predict the presence/absence of juvenile (85%), and adult (72%) sardines. Adults occur mostly in waters 40-85 m deep with SSTs from 17.5-21ºC and low to intermediate chl a concentrations, whereas juveniles occur in depths of <35 m, SST of <17ºC or >22ºC and very low or very high chl a concentrations. A full model including depth, SST, surface salinity, surface chl-a and depth of the chlorophyll maximum (DCM) predicted spawning habitat with a cross validation accuracy averaged across all years of 71%. An operation model restricted to factors readily available from bathymetric and satellite information (i.e. depth, SST and chl a) had a slightly lower predictive capacity (68%). The ability to predict the spawning habitat will help to ensure that future surveys include all areas likely support high densities of sardine eggs.