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Project L.2.b - Vulnerability assessment of elasmobranch bycatch in EPO tuna fisheries using the EASI-Fish approach

01 Nov 2021 - 31 May 2022

Program(s) in charge: Ecosystem & Bycatch Program
  • To use the EASI-Fish ERA approach to assess the vulnerability status of elasmobranch species caught as bycatch in EPO fisheries
  • To identify vulnerable species using traditional biological reference points
  • IATTC is committed, through the Antigua Convention, to ensure the long-term sustainability of all non-target species impacted by EPO tuna fisheries.
  • Elasmobranchs have been identified in previous qualitative ERAs to be among the most vulnerable species to tuna fishery impacts in the EPO. However, these species lack sufficient biological and catch data for stock assessment, so data-limited approaches are required to assess vulnerability.
  • In 2019, the IATTC developed EASI-Fish (Ecological Assessment for the Sustainable Impacts of Fisheries) to quantitatively assess vulnerability using traditional biological reference points used in fisheries stock assessment (e.g. FMSY, SPR20%).
Relevance for management
The EASI-Fish assessment will transparently identify vulnerable elasmobranch species in the EPO (and across the Pacific where applicable). Vulnerable species can then be subjected to further assessment where managers can be advised on the efficacy of potential conservation and management measures that may be implemented to reduce vulnerability to sustainable levels.
12 months
Workplan and status
  • Nov 2021-Jan 2022: in collaboration with SPC, develop Pacific-wide species distribution models for 32 species of sharks.
  • Sep-Apr 22: complete EASI-Fish assessment and identify vulnerable species
  • May 22: present assessment results at SAC-13.
External collaborators
  • Paper and oral presentation at SAC-13 (SAC-13-11)
  • Scientific journal publication
Updated date: 01 May 2022
Progress summary for the reporting period
  • July-Sept 2021: Collated available effort and shark interaction data for 8 fisheries in the EPO from IATTC databases and publicly available publications
  • Sept 2021-Mar 2022: Collated available biological information for 32 shark bycatch species with supporting references and entered into the IATTC ecosystems database.
  • Nov 2021-Jan 2022: Developed species distribution models for 32 shark bycatch species using Maxent.
  • Jan-Feb 2022: Improved SDMs for 32 species by beginning a collaboration with SPC, who assisted in developing SDMs using an ensemble approach from 4 SDM algorithms using all data from the Pacific Ocean.
  • Feb-April 2022: Completed testing, diagnostics checks, and produced final results of EASI-Fish models for 32 shark species .
  • March-Apr 2022: Write final report for SAC 13 (Document SAC-13-11).
Challenges and key lessons learnt
  • Very little catch, biological and ecological information exists for most shark bycatch species resulting in the use of several approaches to estimate required model parameters
  • The IATTC database contains a large number of records where taxa are identified only to high taxonomic levels, potentially missing important presence locations that are critical for the development of SDMs, especially for rarer species.
  • Presence predictions can vary greatly depending on 1) the SDM approach used, and 2) the method used to determine probability of presence threshold values. Further research on aspects of SDMs required in this new research area.
  • The EASI-Fish assessment identified 20 shark species as “most-vulnerable”.
Griffiths, S.P., Fuller, L., Potts, J., Nicol, S., 2022. Vulnerability assessment of sharks caught in eastern Pacific Ocean tuna fisheries using the EASI-Fish approach. 13th Meeting of the Scientific Advisory Committee of the IATTC, 15-20 May 2022, La Jolla, California, USA. Document SAC-13-11.