Standardized CPUE of blue marlin (Makaira mazara) caught by Japanese longline fishery in the Indian Ocean: Analysis between 1979 and 2021

We addressed to standardize CPUE of blue marlin (Makaira mazara) caught by Japanese longline fishery in the Indian Ocean. Start year is 1979 as with the indices in the last stock assessment. Three core areas (Northwest, Southwest and Central east) were used as with the previous studies. We applied the zero-inflated Poisson GLMM for the CPUE standardization (catch number). Terminal year for the Northwest CPUE was 2010 due to paucity of operations in recent years. The standardized CPUE usually showed decreasing trend. There was some difference of standardized CPUEs among quarters and between two gear depths. In the model diagnostics, we checked Pearson residuals corresponding to the explanatory variables. There are little clear trends against the explanatory variables, but Pearson residual showed some time-spatial patterns for all core areas.