The blue shark Prionace glauca is the main bycatch species of the French swordfish-targeting longline fishery operating in the south-west Indian Ocean. Using observer and self-reported data collected aboard commercial longliners between 2007 and 2020, we propose a standardized CPUE series for blue shark for this fishery estimated with a lognormal generalized linear mixed model (GLMM) to be used for stock assessment. We propose to use the standardized CPUE for the period comprised between 2011 and 2020 where the monitoring effort has been consequent in comparison with previous years. Throughout 2011-2020, the standardized CPUE for the blue shark shows a significant decreasing trend.