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Project L.1.a - Develop habitat models for bycatch species caught in the EPO to support ecological risk assessments (ERAs)

01 Jun 2018 - 01 Oct 2022

Program(s) in charge: Ecosystem & Bycatch Program
  • To use presence-only catch data to develop habitat models for all bycatch species caught in EPO tuna fisheries to facilitate mapping of their geographic range.
  • To make distribution maps available in a format suitable for use as base maps for ecological risk assessment models (PSA, EASI-Fish)
  • Many bycatch species caught in EPO tuna fisheries lack sufficient biological and catch data to undertake traditional stock assessment to determine their vulnerability to fishing.
  • Data-limited Ecological Risk Assessment (ERA) methods are now increasingly used to determine the most vulnerable species to fishing, which have a strong reliance on estimating impacts using the overlap of fishing effort with a species’ distribution.
  • Given the success of using the EASI-Fish approach for assessing the vulnerability of data-poor bycatch species in the EPO (e.g. sharks, devil rays, leatherback turtles), further development of SDMs for other species is required.
Relevance for management
Developing habitat models for bycatch species will improve the fishing mortality estimates using ERAs, from which their status can be determined and guide managers.
24 months
Workplan and status
  • Jun-Dec 18: model development using data-rich species
  • Jan-Feb 19: apply habitat model to bycatch species
  • Mar-April 19: Finalize habitat maps for bycatch species
  • May 19: present final model and assessment results at SAC-10.
  • Jun 21-Sept 22: use Pacific-wide datasets to explore the use of a range of alternative SDMs in isolation or as ensembles for shark species caught in EPO pelagic fisheries
External collaborators
  • Presentations at SAC-10, SAC-13 and at WCPFC, if required.
  • Procedure, if successful, to be used annually within ERA models to assess the vulnerability of bycatch species in the EPO.
Updated date: 01 May 2023
Progress summary for the reporting period
  • Initial models were developed using Integrated Nested Laplace Approximation (INLA) and Generalized Additive Models (GAMs) for one species of mobulid, and the leatherback turtle, which formed the basis of EASI-Fish assessments for these species.
  • Subsequent explorations of SDMs were undertaken in 2021-2022 for 32 shark species caught in the EPO, in collaboration with SPC staff.
  • In 2022, IATTC staff collaborated with SPC staff and combined all available Pacific-wide datasets to develop SDMs from an ensemble of four models for 32 shark species caught in EPO pelagic fisheries. The SDMs were then used in a vulnerability assessment for sharks in the EPO using the EASI-Fish approach.
Challenges and key lessons learnt
  • Even highly sophisticated models in data-rich settings can predict habitat poorly, depending on the environmental data used for the prediction.
  • It is likely that many more presence points occur within the EEZ of coastal nations in the EPO, however, obtaining high resolution data from domestic fisheries is a major challenge.
  • Although the collaboration with SPC utilized data from across the entire Pacific, the SDMs predicted relatively low probability of occurrence for several very common species in the EPO. This was thought to be due to relative differences in relationships between presence and some environmental variables across a vast environmental gradient of the Pacific Ocean. It was found that predicting presence at the RFMO scale produced significantly more realistic distribution maps and that a ensemble approach to SDMs may be required in future for large scale SDMs, such as the basin scale.
  • Because of potential differences in methods, SPC-IATTC are currently considering putting together a working group to discuss best practices in SDMs for tunas, sharks and other prioritized species.
Five manuscripts that use the habitat models have been published in scientific journals or given as IATTC presentations:
  • Griffiths, S.P., Lezama-Ochoa, N., 2021. A 40-year chronology of spinetail devil ray (Mobula mobular) vulnerability to eastern Pacific tuna fisheries and options for future conservation and management. Aquatic Conservation: Marine and Freshwater Ecosystems 31, 2910–2925.Griffiths, S.P., Lezama-Ochoa, N., Román, M.H., 2019. Moving towards quantitative ecological risk assessment for data-limited tuna fishery bycatch: application of “EASI-Fish” to the spinetail devil ray (Mobula mobular) in the eastern Pacific Ocean. 9th Meeting of the IATTC Working Group on Bycatch, 11 May 2019, San Diego, California, USA. Document BYC-09-01.
  • Griffiths, S.P., Kesner-Reyes, K., Garilao, C., Duffy, L.M., Román, M.H., 2019. Ecological Assessment of the Sustainable Impacts of Fisheries (EASI-Fish): a flexible vulnerability assessment approach to quantify the cumulative impacts of fishing in data-limited settings. Marine Ecology Progress Series 625, 89-113.
  • Griffiths, S.P., Wallace, B., Swimmer, Y., Alfaro-Shigueto, J., Mangel, J.C., Oliveros-Ramos, R., 2020. Vulnerability status and efficacy of potential conservation measures for the east Pacific leatherback turtle (Dermochelys coriacea) stock using the EASI-Fish approach. 10th Meeting of the IATTC Working Group on Bycatch, 10 September 2020, La Jolla, California, USA. Document BYC-10-01. 
  • Griffiths, S.P., Fuller, L.M., Potts, J., Nicol, S., 2022. Vulnerability assessment of sharks caught in eastern Pacific Ocean pelagic fisheries using the EASI-Fish approach. 13th Meeting of the Scientific Advisory Committee of the IATTC, 16-20 May 2022, La Jolla, California, USA. Document SAC-13-11, 80.