Preliminary stock assessment model in Stock Synthesis 3.30 for the Pacific saury in Northwestern Pacific Ocean

In this study, a preliminary stock assessment model in Stock Synthesis 3.30 was developed for the Pacific saury in the Northwestern Pacific Ocean (WNPO) by incorporating historical catch, standardized catch-per-unit-effort (CPUE), and length composition data. This document describes the methodology for the upcoming age-structured stock assessment and contains information on input data, model structure, and parameterization. We also examined the model diagnostics on the preliminary model. Virgin recruitment (R0) likelihood component profile showed a conflict between relative abundance index and size composition data, and the recruitment deviations component was relatively informative within the total likelihood. This study recognized that there is still uncertainty in life history parameters including maturation, growth, natural mortality, as well as the input length composition data. To improve the stock assessment in the future, we recommend continuing model development work, reducing data conflicts and modelling uncertainties, and re-evaluating and improving input assessment data. These preliminary results cannot and should not be used to determine stock status and conservation of the WNPO saury.