Issue Brief

Illegal Fishing, Your Number's Up!


Unlike merchant vessels, automobiles, and even cellphones, fishing vessels are not required to have unique identifying numbers that stay with them from construction to scrapping. Although fishing vessels have names, call signs for radio transmissions, and other identifiers, these are not permanent and can be changed by owners quickly and easily.

The lack of mandatory, unique, and permanent identifying numbers makes it difficult for authorities to distinguish specific vessels engaged in illegal, unreported, and unregulated, or IUU, fishing, and to track misconduct and gather evidence when they suspect unlawful activity. As a result, vessel owners, even those who have been blacklisted for IUU fishing, can circumvent control measures and continue to fish without being traced. They can operate for years with no accurate record of their activities, operating condition, or compliance status.

The solution: mandatory, unique, and permanent ship identification numbers in accordance with the standards of the International Maritime Organization, or IMO. The IMO number is used throughout the maritime industry as the first point of reference in identifying a ship; the number remains unchanged even if the ship is re-flagged to another country or sold. IMO numbers would increase the transparency of fishing vessel operations and help authorities identify fishing vessels and owners who try to conceal illicit activity.

What are IMO numbers?

The IMO introduced its Ship Identification Number Scheme in 1987 to help prevent maritime fraud and enhance safety and security; it has successfully served for decades to identify merchant vessels and is widely recognized by users and stakeholders as the best available global identification system for ships. In 1996, the system became mandatory for cargo and passenger ships. IHS Maritime, a division of the global information and analytics company IHS, administers the scheme on behalf of the IMO. The unique seven-digit vessel number, preceded by the letters “IMO,” provides the foundation of IHS Maritime’s global maritime database. The number stays with a vessel until it is scrapped and never changes, regardless of the ship’s owner, country of registration or name. The records based on the IMO number provide an independent audit trail for each vessel; IHS Maritime continually updates and cross-checks this information against multiple data sources.

How IMO numbers help combat IUU fishing

Research published in 2010 in the journal Science cited the lack of IMO numbers for fishing vessels as a prime factor in the failure of port officials to identify and act against IUU fishing operations.1

Recent analysis by Pew found numerous inaccuracies and inconsistencies in vessel records of regional fisheries management organizations, or RFMOs.2 In one RFMO’s records, researchers found instances of the same vessel listed with different flags, tonnage, and length; vessels listed twice under different names and flags; multiple vessels listed with the same radio call sign; and vessels that had sunk still listed as authorized to fish. These problems were found in other RFMOs as well. The analysis also found multiple cases of a vessel using different names and identifiers with different RFMOs, further confounding efforts to accurately monitor those ships’ activities.

Requiring IMO numbers for fishing vessels would improve the monitoring, control, surveillance, and enforcement of fishing operations in numerous ways. It would:

  • Allow flag states to consistently and accurately manage vessels under their authority.
  • Give national authorities information to help them police their waters more effectively.
  • Bring clarity, consistency, and accuracy to RFMO records to determine whether vessels were authorized to fish in their waters.
  • Help port authorities ensure that they are accepting only legally caught fish.

Mandating IMO numbers for fishing vessels would improve transparency in the fishing industry and would likely lead to better practices in related areas. For example, seafood processors and retailers could refuse to buy or sell fish caught by vessels without IMO numbers, and banks and insurance companies could set policies to only finance and insure vessels that have IMO numbers.

The value of these identifiers extends beyond protection of the world’s fisheries and could improve safety and security at sea. Reports from U.N. bodies such as the Office on Drugs and Crime and the International Labour Organization identify vulnerabilities related to lack of transparency in the fishing sector that enable criminals to perpetrate serious crimes such as drug smuggling, rights abuses, and human trafficking using fishing vessels.3

Mandatory IMO numbers would help improve crew safety at sea by enabling authorities to better track compliance with the International Convention on Standards of Training, Certification and Watchkeeping for Fishing Vessel Personnel, and the international treaty on fishing vessel safety, known as the Cape Town Agreement.

International support is increasing for IMO numbers

In November 2013, the IMO General Assembly extended application of the voluntary IMO Ship Identification Number Scheme to fishing vessels of 100 gross tonnage and larger. This move will help regulatory bodies—from countries to RFMOs—implement and enforce policies on IMO numbers.

Multiple RFMOs have mandated IMO numbers for vessels authorized to fish in their waters. The U.N. Food and Agriculture Organization and the Workshops on the Consolidated List of Authorized Vessels of Tuna RFMOs also support use of IMO numbers as the principal identifier for fishing vessels.

Pew advocates a worldwide system of mandatory IMO numbers for fishing vessels and recommends the following actions:

  • Each RFMO should require that every vessel authorized to fish in its waters has an IMO number.
  • Coastal states should mandate that foreign-flagged ships have IMO numbers before they are permitted to fish in their waters.
  • States should promptly ratify the 2012 Cape Town Agreement, which establishes international rules on fishing vessel safety.
  • Port states should require that all foreign fishing vessels that come into their ports have IMO numbers.
  • Banks financing the purchase or repair of larger fishing vessels should make financing conditional upon the vessels having IMO numbers.
  • Companies that insure larger fishing vessels should condition the issuance of policies upon the vessels having IMO numbers and the insurance coverage should be void for any vessel that is successfully prosecuted for illegal fishing.


  1. Stefan Flothmann et al., “Closing Loopholes: Getting Illegal Fishing Under Control,” Science 328, no. 5983 (2010): 1235–36.
  2. See Pew information briefs prepared for the International Commission for the Conservation of Atlantic Tunas, Nov. 2012,; Western and Central Pacific Fisheries Commission, Dec. 2012,; Indian Ocean Tuna Commission, May 2013,; and Inter-American Tropical Tuna Commission, June 2013,
  3. Report of the Joint Meeting of Tuna RFMOs (2007), p. 2 and Appendix 14,; Reports of the First and Second Workshops on Exchange of Information and Maintenance of the Consolidated List of Authorized Vessels of Tuna Regional Fisheries Management Organizations, T-RFMO Consolidated List of Authorized Vessels Technical Report No. 1 (2011), p. 8, and T-RFMO CLAV Technical Report No. 2 (2012); Report of the U.N. Food and Agriculture Organization Technical Consultation to Identify a Structure and Strategy for the Development and Implementation of the Global Record of Fishing Vessels, Refrigerated Transport Vessels and Supply Vessels, Report No. 956 FIRO/R956 (En) (2010), p. 3,; and Report of the Thirtieth Session of the Committee on Fisheries, FAO Fisheries and Aquaculture Report No. 1012 FIPI/ R1012 (En) (2012), p. 9 and para. 56,