Standardized catch rates in biomass for the blue shark (Prionace glauca) caught by the Spanish longline fleet in the South Atlantic during the period 1997-2013

Standardized catch rates per unit of effort (CPUE) were obtained for the stock of the South Atlantic blue shark (Prionace glauca) using General Lineal Models (GLM) for a total of 4,027 trips of the Spanish surface longline fleet targeting swordfish, during the 1997-2013 period. The main factors considered were year, area, quarter, gear and ratio between swordfish and blue shark catches. The significant model explained the 87% of CPUE variability in blue shark. A major part of this variability was explained by the targeting criteria and the gear style. Other factors were also significant, but less important. The standardized CPUE obtained suggests a stable trend of the South Atlantic blue shark stock and differs substantially from the nominal CPUE trends observed during the period considered.