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Project J.1.a - Temporal trends and variability in the spatial distribution of tropical tuna purse-seine fishing

01 May 2022 - 31 May 2023

Funded
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