Stock assessment of Pacific saury (Cololabis saira) in the Western North Pacific Ocean through 2016 (Chinese Taipei)

The stock assessment update consisted of running the Bayesian state-space surplus production model for the Pacific saury in the Western North Pacific Ocean (WNPO) with the most recent summary of available fishery-dependent and fishery-independent data. Commercial catches of Pacific saury from Japan, Chinese Taipei, Korea, China, Russia and Vanuatu in the WNPO area were collected from 1950 to 2017. Relative abundance indices available for WNPO saury consisted of standardized catch-per-unit effort (CPUE) of stick-held dip net fisheries from Japan (1994-2017), Chinese Taipei (2001-2016), Russia catch in the Northwest Pacific Ocean (2003-2017), Russian catch in the Russian EEZ (1994-2017), Korea (2001-2016), and China (2003-2017); and biomass survey from Japan (2003-2017). Three base case models with model initial year of 1980, differing in catchability of the biomass survey index, developed in the previous assessment were updated through 2016. Although the absolute biomass estimates were sensitive to the uncertainty of catchability of Japanese survey, the updated stock status is relatively pessimistic compared to the previous assessment. It should be noted that there is a trend of decline in biomass since 2005 for all models examined.