At-sea transshipment creates forced labor risk in tuna fisheries because it allows fishing vessels to stay at sea for months or years without returning to port, removing the oversight that port-based inspections normally provide. Crew members on these vessels may have no realistic way to leave, report abuse, or seek help. The practice is widespread across the Pacific, Indian, and Atlantic Oceans, and the labor abuses linked to it are among the most serious documented in the forced labor fishing industry. This article breaks down exactly how transshipment enables that risk and what can be done about it.
What makes at-sea transshipment different from port-based transfers?
At-sea transshipment is the practice of transferring catch directly from a fishing vessel to a refrigerated cargo ship (called a reefer) while both vessels are at sea, rather than returning to port to offload. This means fishing vessels can remain operational in remote ocean areas for extended periods without ever touching land. Port-based transfers, by contrast, bring vessels into regulated spaces where authorities can inspect documents, check crew welfare, and verify catch records.
The practical difference is significant. When a vessel returns to port, there are natural checkpoints: immigration officials may interact with crew, labor inspectors may board, and local services are accessible. At-sea transshipment eliminates all of that. The fishing vessel hands off its catch to the reefer, takes on supplies and sometimes new crew, and continues fishing. No port authority sees the vessel, no independent inspector boards it, and no crew member has a realistic opportunity to disembark.
This operational structure is not inherently illegal, and it does serve a legitimate purpose in terms of fishing efficiency. But the absence of port-based oversight is precisely what makes it a high-risk environment for labor abuse.
Why does transshipment at sea make forced labor harder to detect?
Transshipment at sea makes forced labor harder to detect because it removes fishing vessels from the regulatory visibility that ports provide. Vessels operating in remote ocean zones may go months without any third-party contact, and when transshipment occurs, it often happens in international waters where no single authority has clear jurisdiction. This creates a monitoring gap that bad actors can exploit.
There are several compounding factors. First, crew members on vessels that never return to port have no practical exit point. Even if conditions deteriorate, leaving is not an option when the nearest land is hundreds of miles away. Second, documentation can be falsified or withheld before any inspection occurs. Third, observers and electronic monitoring systems are not universally required on vessels that conduct transshipment, so the only record of what happens at sea may come from the vessel operator itself.
Communication is also a factor. Crew members on distant-water fishing vessels may have limited or no access to phones or internet. Reporting abuse to labor authorities or NGOs requires communication tools that are often controlled by the vessel operator. This isolation compounds the difficulty of detection significantly.
What labor abuses are most commonly linked to transshipment vessels?
The labor abuses most commonly linked to transshipment vessels include debt bondage, wage theft, physical violence, document confiscation, and conditions that meet the international definition of forced labor. Crew members may be recruited through brokers who charge fees that create debts impossible to repay on the wages actually paid at sea. Some crew members report never receiving the wages they were promised.
Physical abuse, including beatings and deprivation of food or rest, has been documented on distant-water vessels by investigative journalists, NGOs, and government bodies. Document confiscation, where passports and identity papers are held by the captain or vessel operator, is a particularly common control mechanism because it removes a crew member’s ability to leave even when the vessel does reach port.
The extended time at sea enabled by transshipment amplifies all of these risks. A crew member who might tolerate poor conditions for a short trip has far fewer options when the voyage stretches to a year or more with no port call. Debt, isolation, and physical dependency on the vessel operator combine to create conditions that labor experts classify as forced labor even when overt violence is not present.
Book a demoHow does transshipment connect forced labor to the mainstream tuna supply chain?
Transshipment connects forced labor to the mainstream tuna supply chain by moving catch from high-risk vessels into the commercial supply chain through reefer ships that aggregate product from multiple sources. Once tuna is transferred to a reefer and mixed with catch from other vessels, the specific origin of any individual fish becomes very difficult to trace. That product then travels to processing facilities, often in Thailand, Vietnam, or Ecuador, where it enters cans and pouches sold globally.
The mixing problem is central to the risk. A reefer vessel may collect catch from dozens of fishing vessels over the course of a single voyage. If even one of those vessels has crew working under forced labor conditions, the resulting product may be indistinguishable from tuna caught by vessels with clean labor records. Without first-mile traceability that captures vessel identity, catch event data, and crew welfare documentation at the point of transfer, there is no reliable way to separate the two.
This is why brands and retailers can face liability even when they have no direct knowledge of abuse. Regulators in the US and EU increasingly hold importers responsible for what enters their supply chains, regardless of how many steps removed the abuse occurred.
Which tuna fishing regions carry the highest transshipment labor risk?
The tuna fishing regions that carry the highest transshipment labor risk are generally the Western and Central Pacific Ocean, the Indian Ocean, and parts of the South Atlantic, particularly where distant-water fleets from China, Taiwan, and South Korea operate far from their home ports. These fleets often use transshipment extensively because the fishing grounds are so remote that returning to port for every offload would be economically unworkable.
The Western and Central Pacific is the world’s largest tuna fishing region by volume, and it includes areas with limited coastal state enforcement capacity. Some Pacific Island nations have strengthened monitoring in their exclusive economic zones, but high-seas areas beyond national jurisdiction remain difficult to police. The Indian Ocean presents similar challenges, with large distant-water fleets operating in zones where observer coverage is inconsistent.
Flag state matters too. Vessels flagged to countries with weak labor enforcement or limited capacity to monitor their distant-water fleets carry a higher risk profile than those flagged to jurisdictions with active oversight programs. This does not mean all vessels from any particular flag state are problematic, but flag state governance is a relevant factor in assessing transshipment labor risk.
What regulations currently govern at-sea transshipment?
At-sea transshipment is governed by a patchwork of regional fisheries management organization (RFMO) rules, national regulations, and international frameworks, but coverage is uneven and enforcement is inconsistent. Some RFMOs, such as the Western and Central Pacific Fisheries Commission (WCPFC), have adopted transshipment monitoring measures including observer requirements on reefer vessels and reporting obligations. Others have weaker or less consistently enforced rules.
On the labor side, the ILO Work in Fishing Convention (C188) sets international standards for crew welfare on fishing vessels, including rest periods, medical care, and repatriation rights. However, as of 2026, ratification of C188 remains incomplete, and some major flag states for distant-water fishing fleets have not yet ratified it. This means the legal protections it provides do not apply uniformly across the industry.
From a trade regulation perspective, the US Tariff Act of 1930 (Section 307) prohibits the importation of goods produced with forced labor, and the Uyghur Forced Labor Prevention Act has raised the profile of supply chain due diligence requirements more broadly. The EU’s Corporate Sustainability Due Diligence Directive (CS3D) and the EU Forced Labour Regulation, both advancing through implementation in 2026, are adding further compliance pressure on companies sourcing seafood from high-risk regions. Some authorities are beginning to act on these frameworks, and companies could face import bans, fines, or reputational consequences if forced labor is found in their supply chains.
How can satellite tracking and first-mile data reduce transshipment labor risk?
Satellite tracking and first-mile data reduce transshipment labor risk by creating an independent, verifiable record of vessel activity that does not rely on the vessel operator’s own documentation. When a fishing vessel’s movements are captured via satellite VMS and AIS from the start of a trip, it becomes possible to identify patterns associated with forced labor risk, such as unusually long voyages, unregistered transshipment events, or vessel behavior inconsistent with declared fishing activity.
First-mile data capture means that at the moment catch is transferred during transshipment, a digital record is created that links the catch to a specific vessel, a specific trip, and a specific set of verification criteria. This includes not just catch data but also crew welfare documentation, social compliance certifications such as FISH Standard for Crew or SMETA, and any observer or electronic monitoring reports attached to that batch. The result is a Raw Material ID that carries verifiable labor-risk information forward through the supply chain.
This approach makes it much harder for forced-labor-linked product to enter the mainstream supply chain undetected, because the traceability record exists before the product reaches processing. By the time tuna reaches a cannery or a retail buyer, the labor-risk profile of the source vessel is already documented and verifiable rather than reconstructed after the fact.
SmarTuna’s digital traceability platform is built specifically to capture this first-mile data, integrating satellite vessel tracking with social compliance records and automated checks against labor-risk databases. For procurement teams and brands sourcing from regions where transshipment is common, that kind of upstream visibility is a practical tool for reducing exposure to forced labor in the tuna supply chain.
Frequently Asked Questions
How can a brand or retailer verify that its tuna supplier is not using vessels that conduct unmonitored at-sea transshipment?
Start by requesting full vessel-level disclosure from your suppliers, including vessel names, flag states, and trip records for every fishing vessel in their supply chain. Cross-reference those vessels against public risk databases such as the IUU Vessel List maintained by RFMOs, and check whether social compliance certifications like FISH Standard for Crew or SMETA audits are attached to specific vessels rather than just the processing facility. The key distinction to look for is whether traceability data is captured at the point of transshipment itself, not reconstructed later at the cannery level — supplier-level certifications alone are not sufficient if first-mile data is missing.
What is the difference between AIS and VMS for monitoring fishing vessels involved in transshipment, and which is more reliable?
AIS (Automatic Identification System) is a publicly broadcast signal that any vessel is required to transmit and that can be received and recorded by satellite, while VMS (Vessel Monitoring System) is a closed, fisheries-authority-controlled system that reports vessel positions directly to a flag state or RFMO. AIS is more accessible for third-party monitoring but can be switched off, a practice known as ‘going dark,’ which is itself a red flag for risk. VMS is harder to manipulate but is only visible to authorized authorities, not to supply chain buyers directly. The most robust monitoring approach uses both in combination, cross-referencing the two data streams to identify gaps or inconsistencies that may indicate unregistered transshipment events.
If a tuna product already carries an MSC or similar sustainability certification, does that mean forced labor risk has been addressed?
Not necessarily. Sustainability certifications like the Marine Stewardship Council (MSC) label are primarily designed to assess the environmental and stock management practices of a fishery, not the labor conditions of individual crew members on fishing vessels. Some certification schemes are beginning to incorporate social criteria, but as of 2026, labor welfare verification is not a core component of most environmental sustainability standards. A product can be MSC-certified and still carry forced labor risk if the vessels supplying it conduct unmonitored at-sea transshipment. Brands should treat environmental and social compliance as separate, parallel requirements rather than assuming one covers the other.
What practical steps should a procurement team take right now if they suspect forced labor risk in their tuna supply chain?
The immediate priority is to map your supply chain to the vessel level — if you cannot name the fishing vessels that caught the tuna in your products, you have a visibility gap that needs to be closed before any meaningful risk assessment is possible. Once you have vessel identities, run them against publicly available risk indicators including flag state, trip duration, and RFMO compliance history. Engage your suppliers in writing to request social compliance documentation tied to specific vessels and trips, and document that engagement as part of your due diligence record. If you are sourcing from regions with high transshipment activity and cannot obtain first-mile traceability data, that is a material risk that should be escalated to your legal and compliance teams given the current trajectory of US and EU forced labor import regulations.
Are there specific red flags in a vessel's operational profile that suggest elevated forced labor risk even before an inspection occurs?
Yes — several behavioral and operational indicators are associated with elevated forced labor risk on transshipment vessels. These include voyages lasting longer than six months without a documented port call, AIS transponder gaps or ‘dark’ periods in high-risk ocean zones, vessel flagging in jurisdictions with poor labor enforcement records, use of crew recruitment brokers known to charge high placement fees, and a pattern of transshipment events that are not reported to the relevant RFMO. Crew nationality mismatch — where crew are recruited from countries with limited consular access in the fishing region — is also a recognized risk factor. None of these indicators is definitive on its own, but a combination of several should trigger enhanced due diligence.
How does the EU Forced Labour Regulation affect companies that import canned tuna into Europe from regions where at-sea transshipment is common?
The EU Forced Labour Regulation, which is advancing through implementation in 2026, creates a framework under which EU market authorities can investigate and ban the sale of products if there is substantiated concern that forced labor was used at any stage of production — including at the fishing vessel level, not just at the processing facility. Unlike a due diligence obligation that requires companies to have a process, this regulation is outcome-based: if forced labor is found in the supply chain, the product can be withdrawn from the EU market regardless of whether the importer knew about it. For companies importing canned tuna from the Western and Central Pacific or Indian Ocean, where transshipment is common and vessel-level traceability is often weak, this creates a direct commercial and legal exposure that cannot be managed through processor-level audits alone.
Can small and mid-sized tuna brands realistically implement vessel-level traceability, or is that only feasible for large buyers with significant leverage?
Vessel-level traceability is increasingly accessible to buyers of all sizes, particularly as digital traceability platforms have developed tools designed to integrate with existing procurement workflows rather than requiring brands to build their own data infrastructure. The practical approach for smaller buyers is to work through their direct suppliers — canneries or trading companies — to require that vessel-level data and social compliance records are passed through as part of the commercial relationship, rather than attempting to monitor distant-water vessels independently. Collective purchasing commitments through industry initiatives or retailer coalitions can also increase leverage for mid-sized brands that lack the individual volume to set unilateral sourcing conditions. The barrier to entry for vessel-level traceability is lower today than it was five years ago, and the regulatory and reputational cost of not having it is rising.
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