Report of the first session of the IOTC Working Party on Tropical Tunas.

Abstract

The emphasis of the meeting was placed on bigeye tuna (Thunnus obesus), but a number of the conclusions and recommendations reached apply equally to all tropical tunas. A review of fisheries and available data confirmed that both longline and purse seine fisheries for bigeye tuna have been expanding rapidly over the current decade. There are however major gaps in catch and effort data available, in particular major longline fleets operating from Indonesia and several eastern Indian Ocean ports and some which are engaged in illegal, unregulated and unreported (IUU) fishing. Furthermore, size data for most longline fisheries are generally missing or of doubtful quality. A number of recommendations on research were formulated, dealing with improvements in fisheries and biological data collection and diffusion and with stock assessment. In particular, the process for estimating IUU catches through a vessel registry, landings database and port sampling proposed by the Permanent Working Party on Data Collection and Statistics was endorsed. The lack of reliable data limited the possibilities of conducting rigorous stock assessments; however, a number of indices were examined which, taken together, led to the conclusion that bigeye tuna stocks might be fully or overexploited. The WPTT therefore recommended an immediate halt to the increase in catches from all gears. In addition, it was deemed necessary to cut short the increased catches of juvenile bigeye tuna by purse seines fishing on FADs. A number of ways of achieving this were proposed, the most promising being suggested as time and area closures on log fishing. Some indices of skipjack (Katsuwonus pelamis) catches led to the conclusion that there may also be signs of at least localised overfishing, with possibilities of interactions between the central Indian Ocean purse seine fishery and the Maldivian pole-and-line fishery. Finally, the WPTT discussed and proposed Terms of Reference of the Working Party on Tagging. Wide-scale tagging of tropical tunas is seen as an urgent priority and a number of immediate actions were identified.