Preliminary projection of distribution shift for Pacific saury in the Northwestern Pacific Ocean under climate change

Pacific saury (Cololabis saira) is an economically and ecologically important pelagic species in the Northwestern Pacific Ocean. The spatial distribution of Pacific saury has been showing signs of shifting northeastward over the last decade, which potentially impacts its stock assessment and management due to the change of fish availability. By employing a spatio-temporal model, sdmTMB, we assessed the potential shift in the distribution pattern for Pacific saury under two future climate scenarios (SSP245 and SSP585). The sdmTMB model was developed based on the catch per unit effort (CPUE) data of stick-held dip net fisheries collected by China during 2013 to 2022 and environmental variables including sea surface temperature (SST) and mixed layer depth (MLD), as well as spatial and spatio-temporal random field components. The center of gravity (COG) movements manifested conspicuous annual fluctuations during 2013-2022. The inclusion of spatio-temporal random fields contributed to a northward shift of 0.14° and the latitudinal displacement of 0.03° under SSP245 and SSP585. The projected maps of the fitted models indicated potential shift in the distribution of Pacific saury. Future stock assessment and fishery management for Pacific saury should consider the spatial dynamics under changing environments.