Fitting VPA and SAM to pseudo data generated from POPSIM: A first analysis for chub mackerel in Northwestern Pacific

The Technical Working Group on Chub Mackerel Stock Assessment (TWG CMSA) in NPFC determined that (1) the candidates of stock assessment models (VPA, ASAP, KAFKA, and SAM) would be compared by an operating model, and (2) the operating model would be based on POPSIM-A (NPFC 2019). POPSIM-A uses a stock assessment model as an operating model and, therefore, input data are needed for the development of operating models by fitting stock assessment model candidates (Deroba et al. 2014). At the TWG CMSA04, the TWG members have determined six scenarios or input data to fit each stock assessment model to (NPFC 2021). As intersessional works, the members have then submitted estimated results for the use of input data for the operating model POPSIM-A to the invited expert Dr. Joel Rice. The members have also determined performance measures for comparing stock assessment models, which include state variables, depletion statistics, biological reference points (BRPs), and relative fishing impacts (NPFC-2022-TWG CMSA05-WP01). We fitted VPA and SAM to pseudo datasets (PS_data_ver2.zip, available from here) and calculated performance measures. In this document, we report the results of performance measures obtained by fitting VPA and SAM to the pseudo datasets.