Updated standardized CPUEs of blue shark in the Portuguese pelagic longline fleet operating in the North Atlantic (1997-2021)
This document updates the catch, effort and standardized CPUE for the north Atlantic blue shark captured by the Portuguese pelagic longline fleet. Nominal annual CPUE were calculated in biomass (kg/1000 hooks) and were standardized with Generalized Linear Models (GLM) and Generalized Linear Mixed Models (GLMM) using year, quarter, area, gear type, targeting effects and area: quarter interactions as fixed factors, and year:area as random effects. Sensitivity analyzes were carried out for the model type (lognormal, tweedie, gamma or delta lognormal), targeting effects (ratios or cluster analysis), and definition of areas. Model goodness-of-fit was carried out with AIC and the pseudo R2, and model validation with residual analysis. This paper updates the previous index from the Portuguese fleet to be considered for use in the 2023 ICCAT blue shark stock assessment. The final standardized CPUE results show an overall increasing trend from the start of the time series in 1997 until 2015, and then a relatively stable period between 2015 and 2021 with yearly oscillations.