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Project J.2.a - Quantify the relationship between vessel operational characteristics and fishing mortality

01 Jun 2018 - 01 Jul 2020

Program(s) in charge: Stock Assessment Program
  • Evaluate the reliability of the data obtained on identification of FADs.
  • Investigate methods to determine purse-seine set type from various sources of data (i.e. Observers, vessel logbooks, canneries, etc.).
  • Evaluate the relationship between catch and number of FAD deployments.
  • Investigate more precise measures of fishing capacity that take into consideration days fished, set type, and vessel characteristics.
  • Investigate the relationship between fishing mortality and fleet capacity.
  • Evaluate alternative management measures such as closed areas, individual vessel limits, and gear restrictions.
  • The constantly increasing capacity of the purse-seine fleet in the EPO requires more stringent management measures.
  • Several management measures have been investigated as an alternative to increasing the seasonal closure.
  • However, the measure of fishing capacity used to determine the days of closure is somewhat simplistic, and a more precise measure of capacity, and the relationship between capacity and fishing mortality, need to be investigated.
  • Also, the relationship between the number of FADs deployed and catches needs to be better understood.
  • Although the staff has conducted some initial analyses, further studies need to be carried out to provide alternative management measures.
Relevance for management
The results of the project will enable the staff to refine current measures and develop alternative recommendations for managing tropical tunas in the EPO, and provide the Commission with additional tools when developing management measures.
24 months
Workplan and status
  • 2018 – Initial analyses of the data that will lead to new insights
  • 2019 – Further analyses to improve the staff’s management advice
  • 2020 – Apply the lessons learnt from the project and provide recommendations on both alternative management measures and additional data collection.
  • Multiple reports for the meetings of the SAC and the Commission, including recommendations on tuna conservation and possibly on improvements to data collection.
  • Software will be created that can be used to update the analyses with new data and/or alternative assumptions and new methods.
Updated date: 01 May 2023
Progress summary for the reporting period
  • Task 1 (Evaluate the reliability of the data obtained on identification of FADs): an extensive review of FAD data reporting under Resolutions C-16-01 and C-17-02 led to:
    • modifications of Resolution C-16-01 to require only vessels without an observers onboard to fill FAD form 9/2018;
    • multiple agreements to provide high-resolution buoy data, including biomass, in a voluntary basis for a pilot project (J.3.a, FAD-05-INF-E); 
    • continuous update of a database on buoys reported under Resolution C-17-02 and the creation of a preliminary database on buoys with biomass information; and 
    • a new pilot project on remotely and electronically identifying FADs (Project D.1.a). 
    • creation of a new high-resolution buoy database submitted to the secretariat under C-21-04.
  • Task 2 (Investigate methods to determine purse-seine set type): following promising tests of a preliminary set type classification algorithm, a new version is being developed, incorporating additional information to reduce the error rates. The tool has been proved to be useful and was published in a peer-reviewed journal in 2023 (Lennert-Cody et al. 2023).
  • Task 3 (Evaluate the relationship between catch and number of FAD deployments): see Lennert-Cody et al. 2018, SAC-10-INF-K, FAD-04-01, FAD-05-INF-A, FAD-05-INF-C, FAD-06-01, IATTC-98-INF-J. Further analysis may be required once FAD tracking data are available for the entire fleet.
  • Task 4, 5 (Investigate more precise measures of fishing capacity/the relationship between fishing mortality and fleet capacity): the staff expects to incorporate the results of its preliminary research in in-depth analyses during year 3-4 of the project. In addition, a collaboration pilot project on developing alternative abundance indices using echo-sounder buoy data is underway (J.3.a) (see FAD-05 presentation and FAD-05-INF-E, FAD-06-03). Preliminary indices were, and will be, presented in 2021, 2022 and 2023 FAD WG and SAC meetings. The buoy index developed in 2022 was used in the interim skipjack assessment (SAC-13-07). Similarly, the relationship between bigeye fishing mortality estimated by the benchmark stock assessment models and the number of OBJ sets have been investigated (FAD-05-INF-D). The document is currently being prepared to be submitted to a peer-reviewed journal.
  • Task 6 (Evaluate alternative management measures): the staff is pursuing various alternatives, including a multi-species dynamic management approach and reducing the number of active buoys allowed per vessel (see FAD-04-01, SAC-11-INF-M, SAC-12-08 and IATTC-98-INF-J).
Challenges and key lessons learnt
  • Current limits on the number of active buoys per vessel may be too high to be effective.
    The dynamic management approach looks promising for developing alternative conservation and management measures for juvenile bigeye and yellowfin in a multi-species fisheries context, as well as for sensitive bycatch species and groups.
  • Despite the new forms and training workshops, FAD data reporting is still imperfect. Training of managers, fishers and observers should continue.
  • High-resolution buoy data, which will be available for the staff in 2022 (see Res. C-21-04), are needed to link IATTC databases (i.e. observers, FAD logbooks, buoy data). A single reporting format for all CPCs is desirable and thus, the staff prepared format templates and letters to effectively receive this data directly from buoy manufacturers. Similarly, the IATTC staff prepared a buoy deactivation/reactivation reporting format to comply with C-21-04, which can be found at the IATTC website.
  • High-resolution buoy data, including biomass, is key to develop fisheries-independent abundance indices and test alternative hypothesis for fishing mortality. The buoy index was proven to be useful and was included in the skipjack interim assessment of 2022 (SAC-13-07).
  • Because active FADs, not FAD deployments, are subject to limits, analyses using this data were performed in FAD-04-01, FAD-05-INF-A, FAD-05-INF-C, FAD-06-01 and considered in SAC-11-INF-M, SAC-12-08 and IATTC-98-INF-J but may need to be repeated with high-resolution FAD tracking data in the future.
  • The relationship between bigeye fishing mortality and the number of OBJ sets is positive for all but one area in the EPO, including the predominant offshore equatorial OBJ fishing area where the majority of bigeye catch occurs (FAD-05-INF-D). This work is currently being prepared for submission to a peer-reviewed journal.
  • September 2019: American Fisheries Society 2019 annual conference
  • FAD-04-01 Active FAD limits
  • FAD-05 INF-A Floating object fishery indicators: a 2019 report
  • FAD-05-INF-C Floating object fishery indicators: a 2020 report
  • FAD-05-INF-D Relationship between floating-object effort and fishing mortality
  • • FAD-05-INF-E Tropical tuna biomass indicators from echosounder buoys in the EPO
  • FAD-06-01- Floating object fishery indicators: a 2021 report
  • SAC-11-INF-M FAD management measures
  • SAC-12-08 FAD management options
  • IATTC-98-INF-J - Active FAD limits for the purse seine fishery: staff’s considerations
Lennert-Cody, C. E., J. Lopez and M. N. Maunder (2023). "An automatic purse-seine set type classification algorithm to inform tropical tuna management." Fisheries Research 262.
Because the lead researcher of the project is now permanent staff, additional research will be conducted for some of the tasks in 2020-2024