Spatio-temporal variability of density distribution of Pacific saury (Cololabis saira) and its relationship to basin-scale Ocean environmental variability in the North Pacific

This study is the first to perform integration and spatio-temporal decomposition of gridded data from all members of the North Pacific Fisheries Commission to analyze variability in nominal catch per unit effort (CPUE) of Pacific saury (Cololabis saira), a species of significant socio-economic importance in the Northwestern Pacific. The results reveal three leading CPUE modes linked to basin-scale environmental factors: subsurface temperature in the Oyashio Current region, Kuroshio Extension dynamics, and biological productivity in the Kuroshio-Oyashio Extension region. These modes reflect long-term trends and shifts in density distribution of Pacific saury across the Northwestern Pacific. The first mode reveals a distinct seasonal fishing pattern, while the second and third modes indicate zonal and meridional distribution shifts, respectively. The results also suggest a correlation between CPUE variability and the North Pacific Gyre Oscillation, implying a connection to basin-scale ocean environmental variability. The results are valuable for refining Pacific saury stock assessments and understanding the wider marine ecosystem's relationship to ocean environmental change.