- Objectives
- 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
- Background
- 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
- Duration
- 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
- Deliverables
- Workshop report
- Indices of relative abundance
- Length compositions
- Project report to SAC-14, 2023
