TUNA BAI

Context

Tropical tuna fisheries —skipjack, yellowfin and bigeye tuna— are among the most important fisheries worldwide, both in terms of fleet size and the vast ocean areas in which they operate. The Basque freezer purse-seine tuna fleet has a strong presence in the Indian and Atlantic Oceans and provides key information for the management of tuna stocks by international organisations such as ICCAT and IOTC.

Traditionally, stock assessments have relied on abundance indices derived from catch per unit effort (CPUE). However, the introduction of technological innovations, particularly the use of fish aggregating devices (FADs) equipped with geolocation and echo-sounder buoys, has increased fishing efficiency and called into question some of the assumptions underpinning CPUE-based indices.

Against this background, BAIs (Buoy Acoustic Abundance Indices based on acoustic data from buoys deployed on FADs) emerged as an alternative that is independent of fishing activity. Since 2019, BAIs have gradually been incorporated into assessments for different species and oceans:

• 2019: incorporation of the BAI for skipjack tuna in the Indian Ocean.
• 2020: incorporation of the BAI for yellowfin tuna.
• 2021: first BAI indices developed for the Pacific (skipjack) and Atlantic (bigeye tuna).
• 2022–2024: consolidation and expansion to new species and areas —skipjack and yellowfin in the Atlantic and Pacific—, with growing recognition by management organisations such as IOTC, ICCAT and IATTC.

The project “Abundance indices for tropical tuna based on acoustic buoy data (BAI)” continues the research undertaken within the TUNA-BAI project family, exploring new analytical methodologies and consolidating an acoustic-data-based monitoring platform to strengthen tuna stock assessment and management across the three oceans.

Objectives

The project aims to strengthen the use of BAI indices as an independent tool for the sustainable management of tropical tuna. More specifically, it will:

1. Retrieve and standardise acoustic data collected by buoys deployed on FADs during 2023.
2. Generate results to support the presentation of updated BAI indices to the scientific committees of IOTC, ICCAT and IATTC.
3. Explore new methodological approaches identified in the IM-24-TUNA-BAI project to improve the quality and applicability of the indices.

Expected impact

The project will support the continued development of a robust tool that complements traditional CPUE-based indices, providing an independent and more accurate alternative to support the work of the scientific committees of IOTC, ICCAT and IATTC. At the same time, it will help consolidate collaboration between the tuna fleet, acoustic data providers and other key stakeholders, with a view to integrating them into the new 2025 proposal.

Thanks to the cooperation established to date with the fleet and buoy providers, acoustic data have been transformed into valuable inputs for the models presented to fisheries management bodies. The increasing use of this information is turning buoys into a strategic monitoring platform, essential for generating tropical tuna abundance indices (BAIs) and advancing towards more sustainable fisheries management based on the best available scientific evidence.

Funding