Spatio-temporal model for CPUE standardization: Application to blue shark caught by longline of Japanese research and training vessels in the western and central North Pacific

This working paper provides a standardized CPUE of blue shark caught by Japanese research and training vessels (JRTVs) longline fishery for 1994-2020 in the western and central North Pacific. A statistical filtering method was used to remove unreliable set-by-set data after 2000s collected by JRTVs. The nominal CPUE of the JRTVs was then standardized using the spatio-temporal generalized linear mixed model (GLMM) to provide the annual changes in the abundance indices in the North Pacific Ocean. The predicted abundance indices of blue shark revealed a downward trend until 2008 and an upward trend thereafter with a stable trend in recent years. The CPUE trends predicted from the fishery-independent data widely collected in the North Pacific Ocean is a very useful information about the abundance in this region.