The International Seafood Sustainability Foundation (ISSF) has published Characteristics of Longline Fleets Registered in Tuna Regional Fisheries Management Organizations as of June 2026, a new technical report by Dr. Josu Santiago that harmonizes vessel registry information from the world’s five tuna Regional Fisheries Management Organizations (RFMOs): the International Commission for the Conservation of Atlantic Tunas (ICCAT), Indian Ocean Tuna Commission (IOTC), Inter-American Tropical Tuna Commission (IATTC), Western and Central Pacific Fisheries Commission (WCPFC), and Commission for the Conservation of Southern Bluefin Tuna (CCSBT).
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 standardized 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, Vice President of 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.”
Key report findings include:
- A harmonized dataset comprising 7,288 unique longline vessels, of which 2,283 are equal or greater than 24 m in length (large scale)
- 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
- Analysis of vessels authorized across multiple RFMO convention areas
- Recommendations to strengthen vessel registry completeness, consistency, traceability, and transparency
Report Provides First Global View of Longline Fleet Composition and Capacity
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 meters 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. Together, these enhancements would strengthen fisheries monitoring, fleet assessments, and vessel traceability.
Reliable information on fleet composition and fishing capacity supports fisheries science, monitoring, and management. This report expands ISSF’s library of technical resources by providing the first harmonized analysis of tuna longline fleets across all five tuna RFMOs, supporting more informed, science-based fisheries management.
Read the full report on ISSF’s website.
