Results from the updated stock assessment model of the revised South African sardine stock structure hypothesis, with alternative weightings of catch by stock off the west coast

Results from the model for the updated South African sardine assessment are shown. The results show that the new way of modelling coast‐dependent – and no longer stock‐dependent – growth has only a small impact on the results and the standard deviation about the mean length‐at‐age off the south coast is not much larger than that off the west coast, despite immigration of sardine of a different mean length from the west coast. Allowing for time‐varying growth rates – and not age at which length is zero – does improve the fit to the data. The model alternative which additionally fits to parasite prevalence‐at‐length data is also included. Some initial alternatives for allowing for different weightings by stock in catches off the south‐west and north‐west coast are provided for further discussion.