Standardized abundance index for recruitment of chub mackerel from Northwest Pacific summer surveys up to 2023

We conducted CPUE standardization of surface trawl surveys in summer for Pacific chub mackerel using the Vector Autoregressive Spatio-Temporal (VAST) model. We estimated local densities of young-of-the-year fish in the Northwest Pacific from 2002 to 2023 with consideration for environmental factors of sea surface temperature (SST) and 50m-depth temperature as well as spatial autocorrelation. The analysis showed high levels of recruitment index have frequently occurred since 2013. Model diagnostics found no serious problems in residual patterns. We propose this standardized recruitment index to be used as the abundance index of age 0 fish in the Technical Working Group for the Chub Mackerel Stock Assessment (TWG CMSA).