Sensitivity analysis of single-sex and age-structured stock assessment model of Antarctic Toothfish (Dissostichus mausoni) at Subarea 48.6

The single-sex and age-structured stock assessment model of Antarctic Toothfish (Dissostichus mausoni) at Subarea 48.6 was successfully moved from CASAL to Casal2 software. However, the age data used in our model likely caused issues in the output. This paper presents the result of sensitivity runs with the change in age parameters and input datasets. Age data was corrected by Ross Sea female data and Spanish combined-sex data collected in area 48.6. In addition to this, scenarios of the removal of tag data and standardized CPUE values in the early years, as well as the increase in mortality, were tested. The MPD results showed that the correction of age data caused an increase in the biomass of all models (ranging from 39,334 to 55,726 tons) compared to the Model2021. However, some issues still remain, such as fits of tag-recaptures after the year 2017, especially in the first two recapture years, updates of IUU fishery information and standardized CPUE fits. Therefore, this document did not discuss the MCMC diagnostic plots. The next step is to fix identified issues in MPD analysis and proceed MCMC diagnostic analysis.