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Project H.4.a - Conduct regular stock assessments of tropical tunas
Program(s) in charge: Stock Assessment Program
Update the assessments of bigeye, yellowfin, and skipjack tunas
  • Assessments of bigeye, yellowfin, and skipjack are conducted every year
  • Bigeye and yellowfin assessments use the Stock Synthesis modeling platform
  • Skipjack assessment is based on stock status indicators
  • Assessments are updated annually, using the most recent data
  • Major improvements to the assessments (methods and assumptions) are implemented periodically
Relevance for management
  • The staff’s management advice for tunas is based on its stock assessments
  • The duration of the seasonal closures recommended by the staff for bigeye and yellowfin are based on the F multipliers estimated in the assessments
Every year (March-May)
Workplan and status
  • 15 March: data for previous year available; assessments initiated
  • Three weeks before SAC meeting: Assessment reports posted on IATTC website
  • Mid-May: Present assessments at SAC meeting
Stock assessment reports for the SAC and the IATTC; presentations at SAC and IATTC meetings
Updated date: 01 May 2023
Progress summary for the reporting period
  • Benchmark assessment conducted for bigeye 2020
  • Benchmark assessment conducted for yellowfin 2020
  • Interim assessment conducted for skipjack 2022
  • Indicators constructed for the three species 2023
Challenges and key lessons learnt
  • The results of the bigeye and yellowfin assessments were considered unreliable, and they were improved for the 2020 benchmark assessments (Projects H.1.a and H.1.b). 
  • There is uncertainty about the stock structure of yellowfin tuna
  • The risk analysis for bigeye tuna shows a bimodal pattern
  • SAC-11-06 Bigeye tuna: benchmark assessment
  • SAC-11-07 Yellowfin tuna: benchmark assessment
  • SAR-23 Skipjack tuna: interim assessment
  • SAC-12-06 Assessment methods for skipjack in the EPO: a proposal relying on recent data from the IATTC regional tuna tagging program (2019-2022)
  • SAC-14-04 Stock status indicators (SSIs) for tropical tunas in the eastern Pacific Ocean