Bycatch of The European, and Assocated Flag, Purse-Seine Tuna Fishery in the Indian Ocean for the Period 2008-2017

This paper presents an update for the period 2008-2017 of the bycatch estimations for the European and Seychelles tuna purse seine fishery operating in the Indian Ocean. Bycatch data were collected by observers onboard. Given the situation of piracy in the area, the coverage of observers decreases progressively during the first part of the series, until 2010 when the observer program was completely suspended. As of 2011, sampling was resumed, and observation coverage progressively increased; mainly thanks to the implementation of a volunteer program by the fleet. Bycatch data, as collected by the observers, were stratified by quarter, ET sampling area and fishing mode (free school and floating object sets). The total landings of the target species (skipjack, bigeye, yellowfin and albacore tunas) in each stratum was then used as raising factor. The average of the annual total bycatch estimated for the studied period was 9,188 t. However, there are differences throughout the series. More than 90% of the weight of this bycatch occurred in FOB sets. Regarding species groups, discards of target tunas represented the major part of the bycatch during the first years of the series (64% and 46% of the total bycatch in 2008 and 2009 respectively). While in the last years, the group of other bony fishes represented the majority of the bycatch (around 50%), followed by sharks (around 15%), billfishes, rays and turtles.