Evaluation of vessel effects in Japanese biomass survey for Pacific saury

Research vessel effects and fishing gear effects were evaluated in the application of the Vector Autoregressive Spatio-temporal (VAST) model to Japanese fishery-independent survey data from 2003 to 2022. Many of the vessels were assigned to specific periods and sea areas. As a result, the estimated catchability for each vessel and gear seemed to contain not only the effects of vessel and/or gear abilities but also the effects of period and sea area assigned for each vessel, although these effects should not be contained in the catchability. Therefore, we could not support the results including the estimated vessel effects and biomass index.