Working Group on New Stock Assessment Models for Pacific Saury – Progress Summary for 2024

In 2024, three scientific meetings were held by the Working Group on New Stock Assessment Models (WG NSAM) to advance the development of age-structured stock assessment models for Pacific saury (Cololabis saira). The focus of these meetings was to explore the potential of applying existing stock assessment packages, primarily Stock Synthesis (SS), and to refine input data and model configurations for enhanced stock management. The WG NSAM made significant progress in refining the SS model by integrating new data, applying time-varying parameters, adjusting age structure and selectivity assumptions, and improving its biological realism. However, several challenges remain, including inconsistencies among the model structure, data, and biology, difficulties in fitting size composition data, strong retrospective patterns, and limited predictive capability. Despite these challenges, The WG NSAM made important strides in model development, which will serve as the foundation for further improvements in future meetings. This report summarizes both the progress made and the challenges encountered, with an outlook on the next steps in the development process.