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Project H.1.d-2 - Improve indices of abundance based on longline data (Extension)

01 Jan 2020 - 31 Dec 2022

Program(s) in charge: Stock Assessment Program
  • Improve the yellowfin and bigeye indices of relative abundance from longline data
  • Determine methods to identify targeting in longline fisheries
  • Develop spatio-temporal models for creating indices of relative abundance from longline data
  • Develop appropriate longline length-composition data for the index of abundance and for the catch
  • Continue the ongoing collaborative work
  • Indices of relative abundance derived from longline CPUE data are the most important piece of information in the bigeye and yellowfin stock assessments
  • Only the Japanese data are currently used to create these indices
  • The characteristics, tactics, and spatial distribution of the fishery have changed over time
  • The same length-composition data are used for the index and for the catch, but these could differ 
  • Collaborative research and a workshop in 2019 have substantially progressed the work towards achieving the objectives.
  • New methods, such as spatio-temporal modelling, have been developed and are used in the creation of the indices 
  • Additional research is needed to address changes in target species and factors that may change catchability so better indices of abundance by size class can be estimated  
  • Access to operational-level data for longer time periods is essential for advancing the research. Several CPCs have granted such access to the staff under bilateral MoUs renewable.
  • The staff is recommending changes in the data submission to facilitate the research on longline data 
  • Research conducted to resolve issues in using the longline CPUE and composition data needs to be presented and discussed with scientists of the relevant CPCs
Relevance for management
The indices have direct impact on the stock assessment and any improvements in the indices will directly improve the management advice for bigeye and yellowfin
Winter 2022
Workplan and status
  • 2020-2022: work with CPC scientists to progress longline research
  • Winter 2022: workshop preparation.
  • Spring/Summer 2022: one-week workshop to discuss the results of the research conducted to resolve issues in using the longline CPUE data, write workplan to finish the work.
  • Summer/Fall 2022: write workshop report, manuscript on longline indices of abundance
External collaborators
  • CPCs involved in the longline fishery, mainly China, Japan, Korea, Chinese Taipei
  • Invited speakers
  • Workshop report
  • Indices of relative abundance
  • Length compositions
  • Project report to SAC-14, 2023