Results of the double tagging study conducted in sharks

A total of 1,323 shark specimens were double tagged in the period 2012 – 2013, being blue shark (Prionace glauca, BSH) the most represented (95.5%). During 2012 – 2014 recaptures of 15 blue shark and one shortfin mako (Isurus oxyrinchus, SMA) were recorded. Eleven of these sharks had both tags and the remaining five had only one. Nine sharks were at liberty for more than three month, five of which had only one tag (four Stainless steel head dart tags (SSD) and one plastic head intra-muscular tag-small (PIMS)). Comparing recaptures of blue sharks (double or single tagged) as a proxy of tags efficiency, we found a 4.09% of recaptures for SSD (n = 220) and a 0.55% for ICCAT tags (n = 1,818). Although based in few recaptures, this study suggests that SSD would work better than ICCAT tags for shark species.