Summary of activities of the Indian Ocean yellowfin workplan towards a new stock assessment

In 2018, a new stock assessment was carried out for Indian Ocean yellowfin using Stock Synthesis III, a fully integrated model that is used for the three tropical tuna stocks in the IOTC (bigeye, yellowfin and skipjack). However, the lack of understanding of stock dynamics due to various uncertainties led the IOTC’s Scientific Committee (SC) to develop a workplan to address these uncertainties in 2019 before providing management advice. The adopted workplan has two main components: uncertainty on data and uncertainty on models, each one of them with a series of specific items. In this document we describe how the tasks of the workplan have been organized and undertaken. The assessments of the three tropical tuna stocks face common problems and complexities in the IOTC and therefore, parts of this workplan could contribute to the harmonization of stock assessment strategies across stocks. In this document we identify areas for improvement that are common to all stocks in the IOTC.