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This study provided a CPUE standardization of blue marlin (Makaira mazara) caught by the Taiwanese longline fishery in the Indian Ocean for time periods of 1980-2011 and 1995-2011. The delta-lognormal GLM model is adopted to perform the CPUE standardization analysis since blue marlin is caught by Taiwanese longline fleet as bycatch species and large amount of zero catches are recorded in the operational data sets. The results indicate that the influence of incorporating environmental effects on CPUE standardization is not significant for blue marlin in the Indian Ocean. The trends of CPUEs in Area 1 (MONS) and Area 3 (Coastal area) revealed substantial decline trends before early 1990s and increased until later 1990s, while the CPUE in Area 2 (ISSG) continuously increased before 1995s. The CPUEs slightly increased before 1998 and 2002 for Area 1 and Area 2 respectively, revealed decreasing patterns until 2008, and they sharply increase in recent years. However, the trend of CPUE in Area 3 obviously increased before 1999 but the continuously decreased thereafter. The area-aggregated CPUE generally reveals a trend for five phases: fluctuated before 1986, sharply decreased during 1986-1990 when the catch began increasing; increased gradually during during1991-1999; decrease gradually during 2000-2007; CPUE obviously increased in recent years.
