Task 7: Investigating Bycatch Risk in the Western Pacific Tuna Longline Fishery

Award Period
Award Amount
Agency Name
Nature Conservancy
Award Number
SB200210-Task 7
PI First Name
PI Last Name
Christopher Costello
Area/s of Research
Marine Conservation, Policy and Education

Collect data and relevant information (October 2020 - March 2021; jointly with TNC and GFW): The goal of this initial stage is twofold:

  1. Gather and match logbook and observer data (e.g. FSM EM data, Japanese logbook data, transshipment data, etc.) to GFW vessel tracking data and oceanographic data (e.g. SST, bathymetry) to create a database of vessels and relevant catch information, both target and bycatch.
  2. Compile a list of potential risk indicators associated with vessels that:
    a. have bycatch of threatened species;
    b. have a relatively high proportion of bycatch to target species, and;
    c. have bycatch of high value vs. low value and likely discarded species.

Indicators will be assembled based on a review of the literature and through expert input, and will include both vessel characteristics and observed vessel behaviors (e.g. distance from shore, transshipments, relationship to environmental conditions including SST, bathymetry, etc.) The vessel/catch database and the list of risk indicators will be used to train a predictive model to assess bycatch risk at the vessel level.

Develop and validate model (April - September 2021; jointly with GFW):

In close collaboration with GFW, we will use our list of likely risk factors and our training vessel/catch database to train a predictive model to identify vessels likely engaged in high risk bycatch fishing (based on vessel characteristics and observed behaviors). By tracking target catch as well as bycatch, our approach will explicitly identify vessel behaviors associated with high catch per unit effort of bycatch compared to target catch. Given appropriate underlying data, our trained model provides a framework that can theoretically be applied to tuna longline vessels operating at any spatial scale, from country-level (e.g. Federated States of Micronesia), to regional (e.g. Parties to the Nauru Agreement), to RFMO-wide, to global to obtain a vessel-specific bycatch “risk score.” Model results will be used to identify bycatch hotspots, which will be validated using cross-validation methods and by external experts.

Dissemination of results (October - December 2021):

A summary of our key findings will be reported to TNC, along with a detailed description and walkthrough of the bycatch risk assessment framework. We will work with our partners to assist in the development of strategic and effective outreach and communications materials for stakeholders and in-country partners, specifically creating a webinar to share findings with fisheries management agencies and stakeholder groups. Our results will be written up as a paper for submission to a high-impact, peer-reviewed publication.


  • Complete risk-scoring framework to inform prioritization of monitoring, control, and surveillance resources (September 2021)
  • Webinar to NORMA, WCPFC, and/or staff (Fall 2021)
  • Complete draft of a publication to be submitted for peer-review in a high impact journal (December 2021)