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Document: ISSF 2013-08: Relationship between Gross Tonnage and Overall Length for Vessels on the ICCAT Record

The use of Unique Vessel Identifiers (UVIs) that allow for the accurate identification of fishing vessels globally is recognized as an essential tool for combatting IUU fishing and improved monitoring. For this reason, UVIs are of interest to markets, RFMOs and NGOs. The FAO is working towards the establishment of a Global Record that would use UVIs, but this project is not expected to become operational until several years from now. Today, the most widely recognized UVI scheme is the IMO ship identification number scheme, which was introduced by the IMO in 1987 and administered by IHS Fairplay on behalf of IMO. IMO numbers are relatively simple to obtain for vessels greater than 100 Gross Tonnes. At its discretion, IHS Fairplay can also assign IMO numbers to vessels under 100 GT.

In the context of moving rapidly towards a Tuna UVI system while the FAO Global Record develops, several members of tuna RFMOs have recently expressed interest in considering whether or not IMO numbers should be required for vessels on their authorized lists, at least for large-scale ones. For instance, this was discussed at a July 2013 meeting of ICCAT on Integrated Monitoring Measures.

There are questions, both technical and legal, about which fishing vessels are eligible to obtain IMO numbers. This document deals with only one technical question: How vessel size relates to GT, and in particular how the 100 GT “threshold” and vessel length relate to each other. The analyses are made using data from the ICCAT Record of Vessels Authorized to Operate on the Convention Area.

While vessel owners will usually know the GT of their vessels (or they can have the vessels measured), fishery managers that rely on the RFMO vessel records will often not know them. This document is intended to help managers understand some of the difficulties that could potentially be encountered if they were to require IMO numbers for vessels above a given length (e.g., 20 or 24 m LOA).

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