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- Temporal trends and variability in the spatial distribution of tropical tuna purse-seine fishing
- Objectives
- Evaluate the reliability of the data obtained on identification of FADs.
- Develop spatial-temporal indices and statistics of tropical tuna purse-seine fishery distribution in the EPO.
- Understand the dynamics of the purse-seine fishing operations and fishing behavior in the eastern Pacific Ocean.
- Background
- Catch per unit effort (CPUE) standardization and model-based stock assessments are the standard for assessing the abundance and stock status of exploited species.
- However, these approaches are complex and it can be difficult to identify all covariates for estimating stock size while controlling for changes in fishing efficiency.
- If these approaches are not properly implemented, they can lead to hyperstability, wherein CPUE values remain constant despite stock decline.
- Therefore, it is useful to complement more sophisticated stock assessment models with simpler approaches based on catch and effort data to maximize the probability of detecting overexploitation and hyperstability as early as possible.
- Time series of spatial indices of fisheries can help identify temporal patterns with a focus on long-term trends that might be indicative of declining stock status for both tuna and bycatch species or hyperstability.
- Relevance for management
- This project will contribute to advance our understanding of tropical tuna purse-seine fisheries spatial-temporal dynamics and their relationship to both target and non-target species catch and propose, as needed, conservation and management measures for the IATTC fisheries, as necessary. This project is also expected to receive feedback and support of well-established working groups in other t-RFMOs, such as the tropical tuna, FAD or Bycatch and Ecosystem working groups of IOTC and ICCAT.
- Duration
- 12 months
- Workplan and status
- Develop a series of annual spatial indices for the catch of the three major species of tropical tunas and the most important bycatch species, as a function of ocean and fishing mode.
- Examine the time series of these indices to identify trends and/or unique events with a particular eye towards any long-term trends that might be indicative of declining stock status and hyperstability.
- Analyses will be conducted adapting the methodologies developed for the Atlantic and Indian Oceans and described in SCRS/2021/148.
- External collaborators
- Institut de Recherche pour le Développement (IRD), Instituto Español de Oceanografía (IEO), Secretariat of the Pacific Community (SPC)
- Deliverables
- A report for the SAC, Bycatch Working Group and the FAD Working Group in 2023, as well as peer-reviewed publications
- Updated date: 01 May 2023
- Progress summary for the reporting period
- A first version of the code has been prepared and is ready to be run on IATTC data.
Coordination with other t-RFMOs on data availability and formatting has been achieved so results are region-specific but also comparable.
- Comments
- Due to logistical and scheduling issues with the main author of the study, the project has been extended for another year. Results will be presented in 2024.