Modern slavery enters the tuna supply chain undetected primarily because fishing vessels operate in remote ocean areas with limited oversight, and fish often change hands multiple times before reaching a processor or retailer. By the time tuna arrives at a supermarket, it may have passed through transshipment vessels, multiple ports, and several intermediaries — each step creating an opportunity for labor abuses to be obscured. The sections below break down exactly where the gaps are, what the warning signs look like, and what seafood buyers can do about it.
What makes fishing vessels so difficult to monitor?
Fishing vessels are difficult to monitor because they operate in international waters, far from port authorities, labor inspectors, or independent observers. Many spend months at sea without returning to port, conducting fish transfers directly onto refrigerated carrier vessels — a practice known as transshipment. This means the crew on a fishing boat may go unseen by any external authority for an extended period.
Several factors compound the problem. Some vessels operate under flags of convenience, registering in countries with minimal enforcement capacity. Others disable or manipulate their Automatic Identification System (AIS) transponders to avoid detection, making their movements invisible to satellite monitoring systems. Observer coverage — where a human inspector physically boards a vessel — remains patchy across many ocean regions, and electronic monitoring systems are not yet universally required.
The result is a significant visibility gap at the very start of the supply chain. Crew members on these vessels may have limited ability to communicate with the outside world, and labor abuses may go unreported simply because there is no reliable mechanism to report them.
What can be the warning signs of forced labor on fishing boats?
Warning signs of forced labor on fishing boats include deceptive recruitment, debt bondage, document confiscation, withheld wages, and physical confinement. These indicators often appear in combination rather than in isolation, and they may be difficult to detect without direct access to crew members or detailed vessel records.
Industry experience points to several patterns that correlate with labor risk. Vessels that conduct frequent at-sea transshipments without returning to port reduce the opportunity for crew to leave or report abuses. Unusually long fishing trips, especially those exceeding six months, may indicate that crew members are unable to disembark voluntarily. Recruitment through informal brokers, particularly in countries with weak labor protections, increases the risk that workers have been misled about their conditions.
Satellite analytics can also reveal behavioral patterns associated with forced labor risk. Vessels that linger in areas with no fishing activity, avoid known port entry points, or show irregular movement patterns may warrant closer scrutiny. Combining these signals with crew welfare certifications and observer data provides a more complete picture than any single data source alone.
How might illegally caught or forced-labor fish reach supermarket shelves?
Illegally caught or forced-labor fish reaches supermarket shelves through a process of gradual documentation laundering, where fish caught under illegal or abusive conditions is mixed with legally sourced product at processing facilities, assigned new paperwork, and sold into mainstream supply chains. By the time it reaches a retailer, the original source may be effectively untraceable.
The journey typically works like this. A fishing vessel operating outside legal boundaries — or using coerced labor — offloads its catch onto a carrier vessel at sea. That carrier may visit multiple vessels before reaching port, blending catches from different sources. At the processing facility, fish from various origins are combined, filleted, canned, or frozen, and assigned documentation that reflects only the processing location rather than the vessel of origin.
Retailers and brands purchasing from processors several steps down the chain may have no visibility into what happened before processing began. Without first-mile data linking the final product back to a specific vessel and fishing trip, there is no reliable way to verify that the fish on the shelf is free from labor abuse or illegal fishing.
Why can’t existing certifications alone stop modern slavery in seafood?
Existing certifications alone cannot stop modern slavery in seafood because most certification schemes audit at the level of the fishery, company, or facility — not at the level of individual fishing trips or vessel-level crew conditions. Certifications provide a snapshot of compliance at a point in time, but they do not continuously monitor what happens at sea between audits.
Environmental certifications such as MSC focus on stock sustainability and fishing practices rather than labor conditions. Social audits like SMETA or BSCI evaluate factory and processing environments, but they typically do not reach back to the fishing vessel. Even certifications specifically designed for crew welfare, such as the FISH Standard for Crews, depend on periodic audits that may not capture conditions on every trip, on every vessel, in every fleet.
There is also a structural limitation: certifications are issued to the entity that applies for them, not to every vessel supplying that entity. A certified processor may source from dozens of vessels, some of which may not meet the same standards. Without batch-level traceability linking the certified claim back to a specific vessel and fishing event, the certification cannot fully guarantee the conditions under which any particular fish was caught.
Which regulations are forcing seafood companies to act on labor risk?
Several regulations are now requiring seafood companies to take concrete action on labor risk, with the most significant coming from the EU and the USA. These rules are moving beyond voluntary reporting and toward mandatory due diligence, import controls, and supply chain documentation requirements that cover labor conditions as well as environmental compliance.
In the USA, the Uyghur Forced Labor Prevention Act (UFLPA) creates a rebuttable presumption that goods produced in certain regions involve forced labor, placing the burden of proof on importers. The US Seafood Import Monitoring Program (SIMP) requires documentation of catch origin for high-risk species including tuna. Separately, US Customs and Border Protection has used its Withhold Release Order authority to detain seafood shipments linked to forced labor on specific vessels.
In the EU, the Corporate Sustainability Due Diligence Directive (CSDDD) requires larger companies to identify, prevent, and address human rights and environmental harms across their supply chains. The EU IUU Regulation already mandates catch certificates for all imported seafood, and some authorities are expanding their scrutiny to include labor conditions as part of import compliance checks. Companies that cannot produce verifiable documentation of labor conditions could face import rejections, fines, or reputational consequences in these jurisdictions.
How can digital traceability detect forced labor at the first mile?
Digital traceability can detect forced labor at the first mile by combining real-time satellite vessel tracking with labor-risk analytics, crew welfare certifications, and observer data — all linked to a specific batch of fish before it enters processing. This approach makes it possible to flag risk at the source rather than discovering a problem after the product has moved downstream.
Satellite VMS and AIS data can identify behavioral patterns associated with labor risk, such as vessels that avoid port entry, conduct frequent at-sea transshipments, or operate in areas inconsistent with their declared fishing activity. When this movement data is combined with social-compliance records — such as BSCI, SMETA, or Fair Trade certifications — and linked to a unique Raw Material ID assigned at port discharge, buyers can verify both the fishing event and the labor conditions associated with it.
Electronic monitoring (EM) systems and human observers add another layer of verification by providing independent, on-vessel evidence of crew treatment and fishing practices. When all of this data is stored digitally per batch and made available to buyers, processors, and regulators, it becomes much harder for forced-labor fish to enter the supply chain undetected. The key is that this verification happens before processing begins, not after.
What should seafood buyers ask suppliers about labor conditions?
Seafood buyers should ask suppliers for vessel-level documentation that links each batch of fish to a a specific fishing trip, vessel identity, and verifiable labor compliance records. Asking for a processor’s social audit certificate is not enough — buyers need evidence that reaches back to the vessel where the fish was actually caught.
Useful questions to put to your suppliers include:
- Can you provide the vessel names and flag states for the fishing trips that supplied this batch?
- Is satellite VMS or AIS tracking data available for those vessels during the relevant fishing period?
- What social compliance certifications apply at the vessel level, and when were they last audited?
- Is there observer or electronic monitoring coverage for these vessels?
- How are catches from multiple vessels separated or documented when transshipment occurs?
- Can you provide a unique batch or lot identifier that traces this product back to its point of origin?
Suppliers who cannot answer these questions with documented evidence may not have the first-mile visibility needed to give reliable assurances about labor conditions. As regulations tighten in jurisdictions such as the EU and the USA, the ability to produce this kind of verifiable documentation is becoming a practical requirement rather than a differentiator.
SmarTuna’s digital traceability platform captures exactly this kind of first-mile data — linking vessel activity, social-compliance records, and batch documentation into a single verifiable chain that gives buyers the evidence they need to answer these questions with confidence.
Frequently Asked Questions
How do I get started with implementing first-mile traceability if my company has never tracked beyond the processing level?
Start by mapping your existing supply chain to identify which vessels, flag states, and fishing regions supply your processors — even if this information is incomplete at first. Request vessel names and trip documentation from your current suppliers as a baseline audit, and identify where the data gaps are. From there, you can work with a digital traceability provider to systematically close those gaps, beginning with your highest-volume or highest-risk supply chains before scaling across your full supplier base.
What is the difference between AIS and VMS data, and why do both matter for detecting forced labor risk?
AIS (Automatic Identification System) is a publicly broadcast signal that any vessel over a certain size is required to transmit, making it visible to satellite and terrestrial receivers — but it can be switched off or manipulated. VMS (Vessel Monitoring System) is a private, fisheries-authority-mandated tracking system that is harder to tamper with and typically required by the flag state or regional fisheries management organization. Using both together creates a cross-reference check: unexplained gaps or discrepancies between a vessel’s AIS and VMS records are a strong indicator that something may be wrong, whether that is illegal fishing, unreported transshipment, or an attempt to conceal labor abuses.
Can small or mid-sized seafood buyers realistically demand this level of supply chain transparency, or is it only feasible for large retailers?
Increasingly, yes — digital traceability platforms have made vessel-level data more accessible and cost-effective than it was even five years ago, and the documentation requirements under regulations like SIMP and the EU IUU Regulation already apply regardless of company size. In practice, smaller buyers can start by prioritizing transparency requirements for their top two or three suppliers rather than attempting a full-portfolio overhaul at once. Framing requests around regulatory compliance — rather than purely ethical positioning — also tends to make suppliers more responsive, since they face the same legal exposure.
What is the biggest mistake seafood companies make when trying to address forced labor risk in their supply chains?
The most common mistake is treating a processor-level social audit as sufficient evidence that the entire supply chain is clean. A SMETA or BSCI audit of a cannery tells you about conditions inside that facility on the day of the audit — it says nothing about the dozens of fishing vessels that supplied the raw material. Companies that rely solely on these certificates create a compliance blind spot at exactly the point in the supply chain where forced labor is most likely to occur: on the vessel, far from any auditor.
How should a seafood company respond if a supplier cannot provide vessel-level documentation?
Treat the absence of documentation as a risk signal rather than a neutral data point, especially if the species or sourcing region is already flagged as high-risk. In the short term, request a remediation timeline from the supplier and document the gap in your own due diligence records — this matters if regulators ever scrutinize your import history. In parallel, begin qualifying alternative suppliers who can provide first-mile data, both as leverage and as a genuine contingency. As EU and US regulations tighten, the inability to produce vessel-level records is shifting from a reputational concern to a potential import barrier.
Are there specific tuna fishing regions or fleet types that carry a higher forced labor risk than others?
Yes. Risk is generally higher in distant-water fleets operating in the Western and Central Pacific, the Indian Ocean, and parts of the South Atlantic — regions where observer coverage is thin and vessels may spend extended periods at sea without port calls. Flag-of-convenience registrations, particularly from countries with weak maritime labor enforcement, are a consistent risk indicator across all ocean regions. Longline and purse seine vessels that rely heavily on migrant labor recruited through informal brokers in Southeast Asia have historically shown the highest concentration of documented labor abuse cases, though this does not mean other fleet types are automatically low risk.
How will upcoming EU regulations change what seafood importers need to document about labor conditions?
The EU Corporate Sustainability Due Diligence Directive (CSDDD) will require in-scope companies to conduct ongoing human rights due diligence across their full supply chain — not just at the direct supplier level — and to take remediation action when harms are identified. Combined with existing EU IUU catch certificate requirements and increasing scrutiny of labor conditions at border control, importers should expect to need documented evidence of vessel identity, fishing event data, and labor compliance records as a standard part of import compliance, not just as a response to a specific investigation. Companies that build these documentation systems now will be significantly better positioned than those who wait for enforcement to begin.