Update of Virtual Population Analysis and State-Space Assessment Model for Operating Models of Chub Mackerel Stock Assessment in NPFC

The Technical Working Group for Chub Mackerel Stock Assessment (TWG CMSA) in NPFC has decided to use an operating model (OM) for comparing the performance of different four assessment model candidates. In this paper, we report the updated results of tuned virtual population analysis (VPA) and state-space assessment model (SAM), candidate stock assessment models proposed by Japan, under the determined scenarios to include biological uncertainties on natural mortality, weight, and maturity. We changed a few model configurations from the previous analysis to avoid overfitting and stabilize parameter estimation, which will be useful to the application of these models to pseudo-data generated from OM.