GENOMY

Context

Yellowfin tuna (Thunnus albacares), a species of high commercial value, mainly inhabits tropical and subtropical waters of the Pacific, Indian and Atlantic Oceans. In the Pacific, this species is managed as two separate stocks by the Western and Central Pacific Fisheries Commission (WCPFC) and the Inter-American Tropical Tuna Commission (IATTC). However, uncertainty about the population structure of yellowfin tuna in the eastern Pacific Ocean (EPO) has made a reliable quantitative assessment difficult. Previous studies have suggested the existence of two distinct stocks in the northeastern and southwestern EPO, based on restricted movements and regional fidelity, as well as maturity-related phenotypic variability. Although genetic studies conducted so far are inconclusive, tools such as single nucleotide polymorphisms (SNPs) and otolith microchemistry have shown potential to discriminate stocks and better understand connectivity between different areas of the Pacific.

These uncertainties in yellowfin tuna population structure can negatively impact management and conservation models, increasing the risk of overfishing or loss of sustainable opportunities. Accurate knowledge of their population structure is key to improving the assessment of their status and ensuring their long-term sustainability. Future research using genetic markers and otolith microchemistry, along with Close Kin Mark Recapture (CKMR) studies, is essential to develop effective management models and ensure the resilience of this species in the eastern Pacific.

Objectives

The main objective of this pilot project is to establish the necessary basis for the design and promotion of an ambitious regional study, in collaboration with the Inter-American Tropical Tuna Commission (IATTC). Its purpose is to address one of the main uncertainties in the assessment of yellowfin tuna, related to its population structure, and to pave the way for future studies, such as the CKMR study. To this end, appropriate methodologies will be defined, the necessary logistics will be ensured and working networks will be created to support this initiative.

The project is organized into six specific objectives:

• To design and initiate the implementation of an optimal sampling strategy to assess the population structure of yellowfin tuna in the EPO and adjacent areas.
• Generate essential data to analyze the genetic structure and population connectivity of yellowfin tuna within the EPO.
• Evaluate the feasibility of using otolith microchemistry as a tool to study yellowfin tuna population structure and connectivity in this region.
• Identify the most suitable sample sources for future CKMR design.
• Form a working group to develop a roadmap for the design of the CKMR study.
• Strengthen collaborations with the IATTC to develop new ideas to help reduce uncertainty in the assessment of yellowfin tuna in the EPO.

Expected impact

This study will contribute to lay the foundations for the study of yellowfin tuna population structure in the EPO using genetic markers and otolith microchemistry, in close collaboration with the IATTC, which in the future will help to reduce the uncertainties of the assessment models, contributing to the improvement of scientific advice and a better informed fisheries management, based on the best available science, which will allow maximizing fishery production in a sustainable manner.