IUU Fishing
Hannah Linder explains how a new public portal for tracking carrier vessel activity will help fishery managers ensure the transfer of catch is both legal and verifiable
The transfer of fresh catch from fishing vessels to refrigerated cargo ships is an important but often opaque part of the industrial fishing sector. A new public global monitoring portal is a turning point in efforts to manage this activity.
Fulfilling the world’s demand for wild-caught seafood would not be possible without a large fleet of refrigerated cargo vessels traversing the globe. These vessels often collect catch from fishing vessels far from shore, making it hard to monitor and control their activities. But things have just got easier.
Global Fishing Watch (GFW) and the Pew Charitable Trusts (Pew) have created the world’s first public searchable monitoring portal of carrier vessel activity, complete with vessel identity and registry information. Accessible to anyone via GFW’s online platform, the portal provides important data to fishery managers and policymakers, which can help guide the reform of transshipment policies.
Transshipment – moving fishing catch from one vessel to another – is a vital but largely hidden part of the global commercial fishing industry. It can happen at sea or in port. Transshipment at sea enables fishing vessels to skip a trip to port so they can stay on the fishing grounds longer. When transshipment occurs beyond the horizon, outside the jurisdiction of a port or coastal state, it cannot be controlled. But even in port, limited inspection capacity or inadequate procedures mean that proper oversight cannot be guaranteed.
Transshipment touches a wide range of seafood products, including salmon, mackerel, crab, and especially tuna. A recent study estimated that in the western and central Pacific Ocean alone more than US$142 million worth of tuna and tuna-like product is lost in illegal transshipments each year.
Moving catch from fishing vessels to carriers is done to reduce cost and preserve the freshness of the catch sent to market. But without effective monitoring and control, bad actors can obscure or manipulate data relating to their practices, the catches, and the catch locations. This undermines the effort to make supply chains more sustainable, and facilitates the laundering of billions of dollars of seafood from illegal, unregulated, and unreported (IUU) fishing. The lack of oversight undercuts conservation and management efforts – and it encourages the trafficking of weapons, drugs and people, and the perpetuation of poor working conditions for fishing vessel crew.
About the portal
Until GFW and Pew started working on transshipment activities a few years ago, no public global database of transshipment activities even existed. Our analyses show that official reports are often seriously delayed and incomplete; hundreds of transshipments on the high seas go unreported.
The portal builds a picture of carrier vessel activities. It is based primarily on the automatic identification system (AIS) signals transmitted by the vessels. AIS is a GPS-like device that large ships are legally obliged to use. The vast majority of cargo vessels have AIS, but fishing vessels don’t have to carry it. Nevertheless, by combining data from public vessel registries and machine learning techniques, the portal will provide greater transparency and insights into transshipment activity.
It is free to access, so users – regulators, policymakers and researchers – can pinpoint encounters between fishing vessels and carriers, analyse their tracks and identify the ports that they use. The portal also includes a carrier vessel database with information on vessel authorisations and licenses.
The portal is a particularly powerful tool for port officers. When they are notified that a carrier vessel is headed their way they will be able to verify the vessel’s recent activity – both ‘official’ (declared) and ‘observed’ (tracked via the GFW system) – and its history of compliance elsewhere. This will enable the officer to prioritise which vessels require further inspection – especially useful when they have limited inspection resources or capacity.
Below are some examples of how the portal can shed light on potential transshipment operations within the major tuna management regions.
Verifying carrier vessel activity

The carrier vessel portal can be used to identify vessels conducting transshipments in a transparent manner, authorised within a tuna Regional Fisheries Management Organisation (RFMO), complying with the transshipment regulations, and consistently transmitting AIS.
The image right shows the track of an authorised Liberian carrier vessel voyage and the associated potential transshipment events. To explain this visualisation, an encounter (yellow dot) is recorded when a carrier vessel and a fishing vessel are detected on AIS data as being within 500 metres of each other for at least two hours and traveling at a median speed of less than 2 knots while at least 10 kilometres from a coastal anchorage. This suggests a transshipment occurred. A loitering event (purple dot) also indicates a potential transshipment, but in this case AIS data for only the carrier was provided. A loitering event is recorded when a carrier travels at speeds of less than an average of 2 knots while an average of at least 20 nautical miles from shore.
Overlaid with the AIS data are the reported transshipment locations (yellow dots) provided by the International Commission for the Conservation of Atlantic Tunas (ICCAT) Regional Observer Programme. The high match rates on this map between reported transshipments and both the encounters and the loitering events indicate the effectiveness of AIS data in detecting and identifying potential transshipments at sea. This can help management authorities monitor the activities of carrier vessels and ensure they comply with transshipment regulations. The data can also be used to verify activity reported by observers on carrier vessels.
Revealing suspicious behaviour

In the previous example, the close correlation between reported transshipments and transshipment events indicated by AIS data suggests that the carrier was operating in compliance with transshipment regulations. But the portal can also reveal potentially noncompliant activity.
In the image right, we see the track of a carrier considered ‘inactive’ on the ICCAT registry list – according to public ICCAT registry records the vessel did not appear to be registered at the time for transshipping ICCAT-managed species. It had four encounters (red dots) and 58 loitering events (purple dots). We know from the ICCAT observer program that other reported transshipments between carriers and fishing vessels took place in these waters around the same time. While it is unclear what went on during these events, they were not reported in the ICCAT observer programme. So it is possible that they involved transshipment of catch that went unreported to ICCAT.
Using AIS data in this way can highlight possible reporting anomalies, and detect potentially noncompliant behaviour warranting further investigation.
Tracking vessel activity between regional fisheries management organisations

The image right shows an encounter between a fishing vessel and a carrier vessel in the Indian Ocean. This encounter (yellow dot) occurred after the fishing vessel had been fishing in an overlapping regulatory area, whereas the fishing and transshipment occurred in an overlap area between the Commission for the Conservation of Southern Bluefin Tuna Primary Area of Interest for Southern Bluefin Tuna and the Indian Ocean Tuna Commission Convention Area. The movement of fishing vessels across and between different convention areas can make accurate monitoring and management of tuna species all the more difficult. By providing a clear history of a vessel’s fishing activity prior to a transshipment, the portal can help RFMOs exchange information effectively, and ensure that catches and transhipments are legal and correctly reported, in line with each RFMO’s regulations to the relevant authorities.
A powerful tool to help guide reform
Reforming transshipment is integral to ensuring complete traceability and transparency in the seafood supply chain. Ensuring that all transshipment activities – regardless of where they occur – are legal and verifiable would significantly reduce the opportunities for illegal practices, resulting in positive incentives for those in the fishing industry who are doing the right thing. Transparency of information helps generate self-correcting behaviour, and this portal can be combined with other emerging solutions such as electronic monitoring (or electronic observer) programmes.
Regulations across the many RFMOS differ greatly, and unsurprisingly these inconsistencies are exploited by unscrupulous operators. Establishing clear and consistent rules and monitoring requirements for transshipment, both globally and across RFMOs, is essential in ensuring a strong, legal, and verifiable seafood supply chain, and in reducing the likelihood of other associated illicit activities. The analysis of carrier vessel activity provides policymakers with the evidence they need to reform transshipment. The often hidden nature of transshipment has historically hindered policy reform globally, which is why it is a key focus for GFW and Pew.
While more data and transparency are needed, the carrier vessel portal is a giant leap forward in our ability to monitor and address the transnational challenge of transshipment.
Hannah Linder is a is a fisheries analyst for Global Fishing Watch. To access the carrier vessel portal, visit: https://globalfishingwatch. org/carrier-portal