A study by the Spanish tuna fleet in the Indian Ocean, three years after the introduction of its Code of Good Practice, integrated into its Fisheries Improvement Project (FIP), shows that the contribution of the purse seine gear to the mortality of main by-catch species is practically zero, compared to figures recorded for other gears such as longlines and drift nets. This study estimates levels of fishing mortality at 0.15%, for sharks and rays (Chondrichthyes), less than 0.3%, for turtles and zero for marine mammals.