A new report by the International Seafood Sustainability Foundation (ISSF) combines vessel registry information from all five tuna RFMOs into a single global resource for understanding longline fleet composition, fishing capacity, and vessel characteristics.
This report, Characteristics of Longline Fleets Registered in Tuna Regional Fisheries Management Organizations as of June 2026, by Dr. Josu Santiago harmonises vessel registry information from the world’s five tuna RFMOs.
Longline fisheries play a significant role in supplying global tuna markets, yet information about the size and composition of the worldwide fleet has historically been unavailable from a single source, instead being dispersed across multiple RFMO vessel registries. By bringing these records together into a standardised dataset, the report provides fisheries managers, scientists, and other stakeholders with a comprehensive resource for evaluating longline fleet composition, vessel characteristics, and fishing capacity while identifying opportunities to improve the completeness and consistency of vessel information.
‘Understanding the capacity and composition of the global tuna longline fleet is essential to effective fisheries management,’ said Dr. Victor Restrepo, VP Science and Chair of the Scientific Advisory Committee at ISSF.
‘This report provides a clearer picture of the global fleet while identifying practical opportunities to improve vessel information that supports fisheries science and management.’
The outcome is a harmonised dataset comprising 7288 unique longline vessels, of which 2283 are equal or greater than 24 metres in length. It provides global and RFMO-specific analyses of vessel numbers, vessel size, gross tonnage, fish hold volume, and estimated fish carrying capacity, comparisons of the largest longline fleets by flag state and across individual tuna RFMOs and analysis of vessels authorised across multiple RFMO convention areas. The report also makes recommendations to strengthen vessel registry completeness, consistency, traceability, and transparency.
The assessment demonstrates that vessel counts alone provide an incomplete picture of fleet capacity because many smaller vessels are absent from RFMO registries, while a relatively small number of large vessels account for most fishing capacity. Although vessels measuring 24 metres or longer represent approximately 31% of registered longline vessels, they account for approximately 86% of estimated fish hold capacity. As a result, Fish Hold Volume (FHV) – which represents the effective storage capacity available for catches – emerges as a more meaningful indicator of operational fleet capacity than vessel numbers alone.
Based on these analyses, the report also identifies opportunities to improve RFMO vessel registries through more complete reporting of vessel characteristics, broader inclusion of smaller vessels where appropriate, wider use of International Maritime Organization (IMO) numbers, and continued improvements in registry consistency.
