Updated blue shark catches and standardized CPUE for the Portuguese pelagic longline fleet in the Indian ocean, between 1998 and 2019

The Portuguese pelagic longline fishery in the Indian Ocean started in the late 1990’s, targeting mainly swordfish in the southwest region. This working document analyses catch, effort and standardized CPUE trends for blue shark captured by this fishery. Nominal annual CPUEs were calculated in biomass (kg/1000 hooks), and were standardized with Generalized Linear Mixed Models (GLMMs) using year, quarter, season and targeting as fixed effects, and vessel as random effects. The standardized CPUE trends show a general decrease in the initial years between 2000 and 2005, followed by a more stable period with some oscillations until 2019. A comparison is made with a standardization without the targeting effects. These results present an updated annual index of abundance for the blue shark captured by the Portuguese pelagic longline fleet in the Indian Ocean that can now be considered for utilization in the 2021 IOTC blue shark stock assessment.