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Proyecto L.2.c - Assessing the efficacy of potential management options on highly vulnerable shark species in the EPO

01 may. 2022 - 31 may. 2023

  • To use the EASI-Fish ERA approach to assess the efficacy of potential conservation and management measures for reducing fishing impacts on shark species identified in project L.2.b as being highly vulnerable in the EPO
  • IATTC is committed, through the Antigua Convention, to ensure the long-term sustainability of all non-target species impacted by EPO tuna fisheries.
  • IATTC Project L.2.b used the EASI-Fish (Ecological Assessment for the Sustainable Impacts of Fisheries) approach to identify the most vulnerable elasmobranch species caught as bycatch in EPO tuna fisheries.
  • EASI-Fish has been used by the IATTC as an alternative approach to traditional population models to assess the efficacy of management measures on data-limited bycatch species including the critically endangered leatherback turtle and the spinetail devil ray.
  • The staff has been tasked to conduct conventional stock assessments for priority shark species, but the quality of the available fishery data remains prohibitive for this purpose (see section 4 on shark workplan). As an interim data-limited alternative to conventional stock assessments, EASI-Fish will be used to assess shark species identified as being highly vulnerable.
Importancia para la ordenación
EASI-Fish assessments can transparently identify vulnerable elasmobranch species in the EPO. However, vulnerability may be reduced differently for each species. Therefore, by undertaking separate EASI-Fish assessments for each vulnerable species, management measures that may be most efficient and cost-effective may be identified for each species, and for all species in concert. This will ultimately simplify the development of fewer management measures (if required) and minimize the losses of target species catch as a result.
12 months
Plan de trabajo y estatus
  • Jun-Dec 22: develop species-specific EASI-Fish assessments for the most vulnerable species identified and pose potential management strategies to reduce vulnerability
  • Jan-Apr 23: Finalize EASI-Fish assessments
  • May 23: present final species-specific EASI-Fish assessment results at SAC-14.
Colaboradores externos
  • Paper and oral presentation at SAC-14
  • Scientific journal publication
Fecha de actualización: 01 may. 2023
Resumen de los avances en el periodo del informe
  • Apr 2022: Initial EASI-Fish assessment completed for 32 shark species caught in EPO tuna fisheries (Document SAC-13-13)
  • Apr-May 2022: 20 species identified from EASI-Fish as “most vulnerable” and require further consideration and/or more detailed assessment.
  • May 2022: SAC to determine which (and how many) species are the highest priority to include in this project.
  • Aug 2022: The IATTC Scientific Coordinator gained support from the Members to use EASI-Fish to undertake a vulnerability assessment for silky and hammerhead sharks, which were the most vulnerable shark species identified in project L.2.b. Coincidentally, these species were scheduled for conventional stock assessment under Resolution C-16-05, but insufficient catch and effort data thwarted efforts to undertake these assessments.
  • Oct 2022-Mar 2023: IATTC staff reviewed and analyzed existing and newly acquired catch and effort data from the ABNJ project to use in the EASI-Fish assessments.
  • Mar-Apr 2023: EASI-Fish models run for four species (silky and hammerhead sharks) and a range of hypothetical management measures simulated.
  • Apr 2023: Final report submitted to SAC 14 (SAC-14-12).
Retos y principales lecciones aprendidas
The challenges and key lessons learned primarily related to the lack of data for the majority of species and fisheries included in the assessment. Even rudimentary morphometric relationships (e.g. length-weight) and basic biological parameters (e.g. length at first maturity) we lacking for the EPO region (and often across the entire Pacific Ocean) for many species, even those commonly caught commercially, such as thresher sharks. As a result, information for several species was derived from different ocean basins, and in the cases of some small requiem and hammerhead sharks, from other species. Although high quality spatially-explicit fishing effort data were available for the purse-seine fleet of large vessels (I.e. Class 6), data were only available at low resolution for the important industrial longline fleet, or completely lacking for some artisanal gillnet and longline fleets. This severely compromised the estimates of overlap between these fisheries and the assessed species, and in most cases results in an underestimate of fishery impact. The key lesson arising from the work is that basic biological information on sharks, and fishing effort and catch information is severely lacking in the EPO. Recommendations from the work included regional studies on the basic biology of shark species in the EPO, and improved monitoring of catch and effort in commercial (purse seine Class 1-5 and industrial longline) and artisanal fleets. The impact of the artisanal fisheries should not be ignored and so concerted efforts are required to better understand the extend of catches for near-term EASI-Fish assessments and also longer term conventional stock assessments. This required work expands significant spatial and temporal scales and is therefore costly to undertake, so close collaboration and coordination with coastal CPCs was recommended.
SAC-14-12 Vulnerability status for silky and hammerheads in the EPO: EASI-fish assessment