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In April and May 2019 a collaborative study was conducted between national scientists with expertise in Japanese, Korean, Seychelles, and Taiwanese longline fleets, an independent scientist, and an IOTC scientist. The meetings addressed Terms of Reference covering several important issues related to yellowfin and albacore tuna CPUE indices in the Indian Ocean. The study was funded by the Indian Ocean Tuna Commission (IOTC) and the International Seafood Sustainability Foundation.
Terms of Reference
1. Validate and improve current methods for developing indices of abundance for bigeye tuna, using up-to-date fishery catch effort data
2. Provide indices of abundance for selected IOTC species to be presented at the IOTC Working Parties in 2019.
3. The analyses will consider data to be provided by key industrial fisheries operating in the Indian Ocean, including data from Japanese, Taiwanese, Korean, Seychelles longline fleets.
4. Analyses will be carried out in a meeting scheduled in April 2019. After the preliminary discussions between the consultant and participating data providers, the joint standardisation analysis will be carried out combining datasets from key fleets. The consultant is expected to undertake any analyses deemed relevant or necessary during the meeting.
Tasks will include the following, to the extent possible in the available time:
5. Load, prepare, and check each dataset, given that data formats and pre-processing often change between years and data extracts, and important changes to fleets and reporting sometimes occur in new data.
6. Apply cluster analyses or alternative methods for identifying targeting. Develop CPUE standardizations for bigeye tuna using reliable data from each CPC. Continue to explore residual patterns spatially and among clusters, fleets and vessels through time, and change models where necessary to address any problems identified
7. Develop maps showing the spatial coverage by the CPUE data used in the joint analysis over-time with emphasis on the most recent years, as requested by the IOTC Scientific Committee during its 21th session.
8. Document the analyses in accordance with the IOTC Guidelines for the presentation of CPUE standardisations and stock assessment models, adopted by the IOTC Scientific Committee in 2014; and provide draft reports to the IOTC Secretariat no later than 60 days prior to the relevant IOTC Working Party meeting.
All work is subject to the agreement of the respective fisheries agencies to make the data available.
In addition to bigeye tuna as described in the TOR, we also generated indices for yellowfin tuna.
This document covers only the joint indices of abundance, describing their development for bigeye and yellowfin tuna.
Other issues are covered in related papers that describe the data preparation, cluster analyses, and individual indices for each fleet.
