Updated standardized catch rates in biomass for the south Atlantic stock of blue shark (Prionace glauca) from the Spanish surface longline fleet for the period 1997-2021

This paper provides an update of standardized catch rates in weight of blue shark using a Generalized Linear Model (GLM) from a total of 7,139 trips carried out by the Spanish surface longline fleet targeting swordfish in the South Atlantic stock for the period 1997-2021. The criteria used to define explanatory variables were similar to those used in previous papers. The main factors considered in the analysis were year, quarter, area, targeting criteria of skippers, gear and the interaction quarter-area. The results indicate that the target criteria of the skippers was the most important factor which explained the CPUE variability followed by gear and in less extent the other factors analyzed. The GLM results explained 84% of CPUE variability in gutted weight. The results showed an increasing trend reaching a peak in 2017 then a slight decrease until 2020 followed by an increased trend in most recent years.