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Haga clic para ver proyectos por tema, meta u objetivo:
- Objetivos
- Improve the yellowfin tuna stock assessment by exploring the use of an age-structured length-based catch-at-age statistical model with a monthly time step
- Antecedentes
- The assessment of yellowfin is conducted every year, using Stock Synthesis
- There are inconsistencies between the indices based on CPUE for longline and purse-seine sets on dolphins
- Management quantities are sensitive to the longline CPUE data
- The current assessment is no longer considered reliable for management advice and stock status indicators are used instead
- Recent advances in stock assessment modelling allow several important improvements of the assessment model, with regard to a spatial stock assessment model, growth curves, time-varying selectivity, recruitment assumptions, data weighting, and diagnostics
- A benchmark assessment is scheduled for 2020
- Importancia para la ordenación
- The stock assessment is used to provide management advice
- The duration of recommended seasonal closures is based on the multipliers of fishing mortality (F) estimated in the bigeye and yellowfin assessments
- Improvements in the yellowfin assessment will make the staff’s management advice more accurate and precise
- Duración
- 2018-2020
- Plan de trabajo y estatus
- 2019: Explore different hypotheses to explain the difference between the indices of abundance, improve estimates of growth, re-evaluate the natural mortality assumptions, apply data weighting, conduct diagnostic tests
- 2019: Workshop to finalize improvements to the longline CPUE and length-composition data (Project H.1.e)
- 2020: Re-evaluate the model assumptions
- Productos
- Report(s) to SAC in 2019
- Report to SAC in 2020
- Fecha de actualización: 01 abr. 2021
- Resumen de los avances en el periodo del informe
- Most of the research and analyses to improve the bigeye stock assessment (Project H.1.a) is also applicable to yellowfin.
- Several workshops were conducted that highlighted other areas where the stock assessment of yellowfin could be improved
- February 2018: CAPAM workshop on the development of spatio-temporal models of fishery catch-per-unit-effort data to derive indices of relative abundance.
- October 2018: CAPAM workshop on the development of spatial stock assessment models.
- January 2019: workshop to evaluate bigeye and yellowfin tuna ageing methodologies and growth models in the Pacific Ocean.
- February 2019: workshop to improve the longline indices of abundance of bigeye and yellowfin tunas in the EPO.
- December 2019: An external review of the assessment of yellowfin tuna was held
- May 2020: Benchmark assessment of yellowfin tuna
- November 2021: IATTC-95-05 B. Yellowfin tuna (pag.50)
- Retos y principales lecciones aprendidas
- Management quantities are sensitive to the longline index, and the research had to be refocused to address several issues identified with the assessment
- Lessons learnt from work on the bigeye assessment are applicable to yellowfin
- An additional workshop to finalize the work on improving the longline CPUE and length-composition data was needed (Project H.1.e), but was not funded. Thanks to the collaboration of Japan and Korea, the work was advanced and indices from longline data were obtained
- The standardized indices by size class from purse-seine and longline data where still incompatible pointing towards spatial differences in abundance trends of the northwest area (purse-seine index) and the southeast area (longline index), consistent with the a more complex stock structure, than the high-mixing hypothesis.
- The benchmark assessment was done by modelling several hypotheses, resulting in a reference set of 48 models.
- Time and data constraints limited the stock structure scenarios that could be included in the risk analysis
- SAC-10 INF-F Evaluating inconsistencies in the yellowfin abundance indices
- Xu et al., Fisheries Research 213
- External review report
- External review presentations
- SAC-11-07 Benchmark assessment of yellowfin tuna
- IATTC-95-05 B. Yellowfin tuna (pag.50)
- Comentarios
- The workplan for improving the bigeye assessment was changed in 2019 to encompass both bigeye and yellowfin tuna