Illegal Fishing, Your Number's Up!

IMO ship identification numbers would ensure the transparency of fishing operations, help end illegal fishing, and improve safety and security at sea

Navigate to:

Illegal Fishing, Your Number's Up!
Illegal fishing

South Korea’s coast guard accused two Chinese vessels in November of fishing illegally in South Korean waters. No IMO numbers are visible on the hull of either ship.

© Yonhap/EPA/Redux

Note: This fact sheet was updated March 17, 2017, to reflect new eligibility standards for IMO numbers and current mandates by regional fisheries management organizations.


Unlike merchant vessels, automobiles, and even cellphones, there is no global mandate that requires fishing vessels to have unique identifying numbers that stay with them from construction to scrapping. Although the 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 (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 (IMO). The IMO number is used throughout the maritime industry as the first point of reference in identifying a ship and remains unchanged even if the ship is reflagged to another country or sold. Requiring IMO numbers would increase the transparency of fishing vessel operations and help authorities identify fishing vessels engaged in illicit activity— and owners who try to conceal it.

What are IMO numbers?

The IMO introduced its Ship Identification Number Scheme in 1987 to help prevent maritime fraud and enhance safety and security. The system, which became mandatory for cargo and passenger ships in 1996, is widely recognized by users and stakeholders as the best available global identifier. IHS Maritime and Trade (IHSM), a division of the global information and analytics company IHS Global Ltd., administers the scheme on behalf of the IMO. The unique seven-digit vessel number, preceded by the letters “IMO,” provides the foundation of IHSM’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, and IHSM continually updates and cross-checks this information against multiple data sources.

How IMO numbers help combat IUU fishing

Requiring IMO numbers for fishing vessels would improve the monitoring, control, surveillance, and enforcement of fishing operations in many 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 regional fisheries management organization (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.
  • Give retailers and seafood buyers accurate information about the vessels catching and landing their fish.

Mandatory IMO numbers for fishing vessels would improve transparency in the fishing industry and likely lead to better practices in related areas. For example, seafood processors and retailers could refuse to buy or sell fish caught by vessels that are eligible for but do not have IMO numbers, and banks and insurance companies could decline to finance or insure vessels that lack the numbers.

The value of these identifiers extends beyond protection of the world’s fisheries and could improve safety and security at sea. Reports from United Nations bodies, including the Office on Drugs and Crime and the

International Labour Organization, have found that a lack of transparency in the fishing sector enables criminals to perpetrate drug smuggling, rights abuses, and human trafficking using fishing vessels.

Mandatory IMO numbers would help improve crew safety at sea by enabling authorities to better track compliance with relevant agreements, including 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—to implement and enforce policies on IMO numbers. Nearly all RFMOs have mandated IMO numbers for vessels authorized to fish in their waters. The United Nations Food and Agriculture Organization (FAO) and several RFMOs also support use of IMO numbers as the principal identifier for fishing vessels.

Illegal fishing ship

The crew of an illegal fishing vessel paints a new name on the hull at sea in an effort to avoid enforcement for crimes committed under a prior name. Mandatory IMO numbers would make vessels easier to positively identify.

© Australian Fisheries Management Authority

In August 2016, the IMO expanded this system of identification numbers to include fishing vessels that weigh less than 100 gross tons and are as small as 12 meters in length.1 As more fishing vessels get these unique, permanent numbers, authorities will more easily be able to identify those engaged in IUU fishing. FAO’s Committee on Fisheries has also agreed that the IMO number will be used as the official unique vessel identifier of the Global Record of Fishing Vessels, Refrigerated Transport Vessels, and Supply Vessels. By providing a single access point for certified information on vessels used for fishing and fishing-related activities, the FAO hopes to close the global information gap on those involved in IUU fishing.2

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

  • All RFMOs should require that every eligible vessel authorized to fish in their waters have an IMO number.
  • Coastal States should mandate that all eligible foreign-flagged ships have IMO numbers as a condition of license before being authorized to fish in their waters.
  • Flag States should mandate that all vessels have IMO numbers.
  • Port and market States should require that all eligible foreign fishing vessels that come into their ports have IMO numbers.
  • Banks financing the purchase or repair of larger fishing vessels should require IMO numbers.
  • Companies that insure larger fishing vessels should make IMO numbers a condition for issuance of policies, and the insurance coverage should be void for any vessel that is successfully prosecuted for illegal fishing.
  • States should promptly ratify the 2012 Cape Town Agreement, which establishes international rules on fishing vessel safety.
  • Seafood buyers and retailers should require that all eligible supply vessels have IMO numbers.


1 International Maritime Organization, “Circular Letter No. 1886/Rev. 6,” 8 August 2016,

2 United Nations Food and Agriculture Organization “Report of the 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” (2010), 3,;

Composite image of modern city network communication concept

Learn the Basics of Broadband from Our Limited Series

Sign up for our four-week email course on Broadband Basics

Quick View

How does broadband internet reach our homes, phones, and tablets? What kind of infrastructure connects us all together? What are the major barriers to broadband access for American communities?

Pills illustration
Pills illustration

What Is Antibiotic Resistance—and How Can We Fight It?

Sign up for our four-week email series The Race Against Resistance.

Quick View

Antibiotic-resistant bacteria, also known as “superbugs,” are a major threat to modern medicine. But how does resistance work, and what can we do to slow the spread? Read personal stories, expert accounts, and more for the answers to those questions in our four-week email series: Slowing Superbugs.