Blue shark catches and standardized CPUE for the Portuguese pelagic longline fleet in the Indian Ocean
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. Model goodness-of-fit and comparison was carried out with the Akaike Information Criteria (AIC), and model validation with residual analysis. The standardized CPUE trends shows a general decrease in the initial years between 2000 and 2005, followed by an increase until 2008, and then another general decrease in the most recent years until 2016. 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 used in stock assessment models.