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Total Allowable Catches (TAC’s) have been implemented for numerous stocks by tRFMO. However, for IOTC’s tropical tuna stocks (yellowfin tuna [Thunnus albacares], skipjack tuna [Katsuwonus pelamis] and bigeye tuna [Thunnus obesus]), catch controls, while intended to ensure that overall fishing mortalities are not exceeded, have failed to maintain catches at the desired level because some IOTC CPCs have consistently exceed targets, and other CPCs were excluded from such controls. This document presents a Case for IOTC to consider moving from a system that involves primarily output-based controls to another that relies on input-based controls for its purse seine fishery. It evaluates how successful the different tRFMO have been in managing their tropical tuna stocks showing that input-based controls, as those used in the Pacific Ocean, are more effective than TACs to manage multi-species fisheries for such stocks. Finally, it shows an example of how the decision support tool presented by Sharma & Herrera (2019c) could be used to set seasonal closures for IOTC purse seine fisheries; and demonstrates that the new scheme proposed can assist the IOTC in achieving more effectively its management objectives for tropical tuna stocks.
