Trend of catch and effort on the blue shark (Prionace glauca) as bycatch of Indonesian tuna longline fishery

The blue shark or BSH (Prionace glauca) is one of bycatch species caught by Indonesian tuna longline fishery in the Indian Ocean. Updated on the catch per unit effort (CPUE) are needed to reduce an uncertainty for assessing the stocks as an input for the species management and conservation. This study provide an update on the nominal CPUE changes and spatial distribution of BSH in the eastern Indian Ocean. Data were gathered by a scientific observer program placed in commercial tuna longline of Indonesia operated in the eastern Indian Ocean from August 2005 to December 2019. Overall, the abundance of BSH increased substantially during the period of observation. The abundance of BSH also showed a variation according to latitudinal gradient where CPUE increased in high lattitude. However, the downward trend of CPUE observed in 2019 compared to 2018 suggests a precautionary approach is needed in BSH fisheries.