Most Global At-Sea Transshipment Involves a Small Group of Key Carriers

130 carrier vessels conducted more than 70% of RFMO-related transshipment activities

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Most Global At-Sea Transshipment Involves a Small Group of Key Carriers
Fish in a net are transferred to a carrier vessel, somewhere in the Pacific Ocean, for transport to market.
The Pew Charitable Trusts


Transshipment, the transfer of fish or other marine wildlife between a fishing vessel and a carrier vessel at sea or in port, is an important part of the global commercial fishing industry. By moving fish to large, refrigerated carrier ships, fishing vessels can spend less time traveling to port to offload their catches, which reduces operating costs and extends fishing time. Regional fisheries management organizations (RFMO) and coastal states regulate most at-sea transshipment, but in areas where this regulatory control and monitoring are inadequate, the risk of illicit activities—such as misreporting or nonreporting of catches and trafficking of people, weapons or drugs— increases.

Policymakers and enforcement agencies seeking to improve regulation of at-sea transshipment need to understand the activities and patterns of carrier and fishing vessels and which ships interact most frequently. Previous studies have looked at the geographic scope of transshipment to find “hot spots” where large numbers of transshipment events occur, but they have not examined the global connections between the vessels involved.1 Such connections have implications for countries, businesses and market stakeholders, who all have an interest in ensuring that high seas management is transparent and that vessels and governments comply with existing rules.

With funding from The Pew Charitable Trusts, researchers from City University of New York’s John Jay College of Criminal Justice began to fill this data gap by conducting a first-of-its-kind study of the spatial patterns and network structures of carrier and fishing vessels. The researchers used Automatic Identification Systems (AIS) data, which includes a vessel’s identity, position and other information, to identify and focus on the key carriers responsible for conducting most RFMO-related transshipment events between 2015 and 2020 and describes their owners and insurers, which fishing vessels they interacted with most at-sea, and the networks of ships that the vessels belonged to.

To discern patterns within the complex global transshipment network, researchers analyzed the activities of carriers registered to seven RFMOs: the Commission for the Conservation of Southern Bluefin Tuna, the InterAmerican Tropical Tuna Commission (IATTC), the International Commission for the Conservation of Atlantic Tunas (ICCAT), the Indian Ocean Tuna Commission, the North Pacific Fisheries Commission (NPFC), the South Pacific Regional Fisheries Management Organization (SPRFMO) and the Western and Central Pacific Fisheries Commission (WCPFC). (See Appendix A for more information on the methods used in this research.)

Key findings

Identifying the carrier vessels responsible for most transshipment events provides important insights and opportunities for improving regional coordination and oversight. The key findings of this analysis are:

  • 130 key carriers (22% of the total studied) conducted 72% (8,840 of 12,322) of the detected RFMOrelated transshipments. (See Appendix B for the full list.)
  • Interactions between carriers and fishing vessels flagged to Panama and China, respectively, accounted for the single largest share, 24%, of transshipment events between any two flags.
  • Based on the identity, number and frequency of fishing vessels the carriers interacted with, as well as how often different carriers interacted with the same fishing vessels, the key carriers fall into 12 distinct “communities,” five of which accounted for 65% of all detected transshipment activities, including four that were largely associated with tuna and tuna-like fisheries and one probably associated with the squid fishery.  
  • The key carriers’ transshipment activities primarily occurred in the Eastern Central Pacific and the northern section of the Southeast Pacific, with notable hot spots found just outside of the exclusive economic zones (EEZs) of multiple countries, particularly in the Western Pacific and along the South American and West African coasts.

Based on these findings, Pew recommends that RFMOs and States should:

  • Implement globally recognized best practices to improve transshipment management.
  • Adopt data-sharing agreements between RFMOs.
  • Increase oversight of the key carrier vessels identified. 

This brief offers additional information on the key carriers, their communities and the recommendations to help fisheries managers improve control of transshipment around the globe.

Key carriers

Geographic activity

Spatial analyses of the activities of the key carriers showed concentrations of transshipment occurring across the Eastern Central Pacific and northern part of the Southeast Pacific, as well as within EEZs of the Pacific Islands, along the coasts of Peru, Argentina and South Africa, and just outside of the EEZs along the West African coastline. (See Figure 1.)

Transshipment activities were geographically broad and occurred in overlapping RFMO convention areas. For instance, the data showed encounters within the waters shared by the WCPFC, IATTC and NPFC.

A fishing boat and a carrier vessel, the Tuna Queen, conduct at-sea transshipment in the Indian Ocean.
Jiri Rezac Greenpeace

Flag trends

The study found that most carrier vessels were flagged to just a few countries: Panama (54% of key carriers); Taiwan, Province of China (10%); China (9%); and Liberia (5%). When looking at relationships between flags, Panamanian-flagged carrier vessels had the largest number, 2,082, of encounters with fishing vessels flagged to China, accounting for 24% of all detected transshipments. (See Figure 2.) Carrier and fishing vessels both flagged to Taiwan had the second-strongest connection at 1,109 encounters, or 13% of all transshipments.

Several countries, including Panama, allow foreign-owned or -controlled vessels to register under their flag through an “open registry.” In recent years, several countries have highlighted issues regarding Panama’s monitoring and control of its registered vessels. For example, in December 2019 the European Union issued a second formal warning to Panama because of the country’s persistent failures to meet its obligations to fight illegal, unreported and unregulated (IUU) fishing. And the United States National Oceanic and Atmospheric Administration recorded several violations by Panamanian-flagged vessels in its 2019 and 2021 biennial reports to Congress.2

Insurance companies

The study also explored the key carriers’ insurers and found that a relatively limited number of companies insure these vessels. The top three firms were Japan Ship Owners P&I Association, Assuranceforeningen Skuld Norway and UK P&I Club.

Global transshipping networks

The study identified 12 distinct networks or “communities” of key carriers and estimated their relative importance and contribution to the overall global network. Five of those communities, which the research team referred to as A, B, C, D and E, collectively accounted for 65% of all activities, with the top three communities (A, B and C) conducting almost half (49%) of global transshipment. (See Figure 3.) Not surprisingly, given the analysis’s focus on RFMOs that oversee tuna and squid fisheries, four of the top five communities were largely associated with tuna and tuna-like fisheries and the fifth was probably associated with squid fisheries.

Community A

The top community included 23 key carriers—mostly flagged to Panama and Liberia—that conducted nearly a quarter (22.7%) of the transshipment events examined. Community A’s transshipment activity spanned multiple ocean basins and RFMO management boundaries, with noticeable hot spots in the Western and Eastern Central Pacific regions, Indian Ocean, Southeast Atlantic and the Eastern Central Atlantic, as well as near the EEZs of the West African coast.

Community B

This group of 12 key carriers, flagged to Taiwan and Panama, engaged in the second-highest proportion of transshipment events (14.7%), primarily in the Western Indian Ocean and Western Pacific.

Community C

This group, which accounted for 11.4% of the activities and contained five key carriers, showed low overall geographic spread, with transshipment events concentrated in the southeast Pacific region and just outside the EEZs of French Polynesia and Pitcairn Islands.

Community D

Like Community A, Community D’s encounters, which made up 8.2% of activities and involved eight key carriers, were spread across the Western and Eastern Central Pacific regions—mainly the equatorial Pacific. However, unlike the other communities, this group conducted significant activity immediately outside of several EEZs, including those of the Solomon Islands, Nauru, Tuvalu, Kiribati, Tokelau and French Polynesia.

Community E

The 19 key carriers in Community E mainly engaged with Panama-flagged fishing vessels. This community operated in a wide geographic area with hot spots in the Northwest Pacific Ocean and high seas areas close to the EEZs of Russia, Peru and Argentina, which are associated with productive squid fisheries. 

The Chinese-flagged Lu Rong Yuan 609 prepares to fish for squid on the high seas near the Galapagos Islands in July 2019.
Joshua Goodman Associated Press


RFMOs and States should take the following steps to ensure that at-sea transshipment activity is appropriately regulated and supports sustainable global fisheries.

1. Implement globally recognized best practices to improve transshipment management

No single set of standards governs the management and monitoring of transshipment. As a result, practices and requirements vary widely among countries and RFMOs, which because of the global scale of the transshipment network, can lead to significant inconsistencies and gaps in regulations and reporting.

In 2022, however, the United Nations Food and Agriculture Organization adopted a globally recognized set of transshipment guidelines, creating a new benchmark for transparency in the movement of fish internationally.3 All RFMOs should use these guidelines to develop and implement reforms to strengthen the management and monitoring of transshipment in the fisheries they oversee.

2. Adopt data-sharing agreements between RFMOs

A lack of information-sharing agreements between RFMOs with overlapping jurisdictions, particularly WCPFC and IATTC, WCPFC and NPFC, and IATTC and SPRFMO—limits fishery managers’ understanding of transshipment activity in dually managed waters and of which rules and procedures individual fishing and carrier vessels are following. This creates opportunities for misreporting of the amount and type of species transshipped and other IUU activities and leaves a critical gap in monitoring of the catch and transfer of marine products in co-managed ocean basins.

RFMOs and nations with overlapping jurisdiction should adopt data-sharing memorandums of understanding to help increase monitoring of transshipment activity in co-managed areas and neighboring waters. Regional implementation of effective port State measures can also provide a basis for information-sharing and collaboration, help improve interagency cooperation, and strengthen institutional frameworks.

3. Increase oversight of key carrier vessels

Not only can increased information about key carriers and geographic trends inform the allocation of monitoring resources when capacity is limited, but it also can help fisheries managers implement effective policies based on species of interest or high value. For instance, armed with the knowledge that Community E key carriers operated in high seas areas associated with productive squid fisheries, managers could focus enhanced efforts on those vessels to increase oversight of these often poorly regulated fisheries.

RFMOs, countries, supply chain companies and insurers should focus their monitoring and enforcement efforts on the key carriers identified in this analysis. In addition, RFMOs should determine which of these carriers operate in their convention areas and routinely audit those vessels’ reported information, and countries should regularly inspect the fishing vessels that transship with these carriers. 

A purse seine vessel transfers tuna catch near Pohnpei, Federated States of Micronesia.
The Pew Charitable Trusts
Two fishing boats are seen at sea during sunset.
Plug Pattarin


By identifying the key carriers and the vessel communities of which they are a part, this study sheds light on the global reach of these carriers and the true scale of the transshipment network. These findings, in turn, highlight the need for better coordination among countries, businesses and market stakeholders, especially for oversight of activities on the high seas. To effectively manage increasing transshipment activities, stronger regulatory frameworks are needed oceanwide to ensure that vessels are operating within legal requirements and illegal catch does not reach the marketplace.


  1. G.A. Petrossian, B. Barthuly, and M.C. Sosnowski, “Identifying Central Carriers and Detecting Key Communities Within the Global Fish Transshipment Network,” Frontiers in Marine Science 9 (2022),
  2. NOAA Fisheries, “Report on IUU Fishing, Bycatch and Shark Catch,” accessed Feb. 17, 2023,
  3. Food and Agriculture Organization of the United Nations, “FAO Voluntary Guidelines for Transshipment Adopted,” accessed Feb. 17, 2023,
  4. The Pew Charitable Trusts and Global Fishing Watch, “Global Fishing Watch and Pew Unveil Technology to Accelerate Transshipment Reform,” news release, July 28, 2020,; Petrossian, Barthuly, and Sosnowski, “Identifying Central Carriers and Detecting Key Communities”; Global Fishing Watch, “What Is AIS?,” accessed Feb. 17, 2023,
  5. Global Fishing Watch, “About Global Fishing Watch Carrier Vessels,” accessed Feb. 17, 2023,
  6. Global Fishing Watch, “Carrier Vessel Portal Disclaimers,” accessed Feb. 17, 2023,
  7. Global Fishing Watch, “What Is an Encounter in the Carrier Vessel Portal?,” accessed Feb. 17, 2023,
  8. A self-contained system of Russia-to-Russia transshipments operates outside of RFMO regulation and has little or no interaction with global transshipment networks.
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