At-Sea Transshipment in Tuna Fisheries 

Why Oversight Is Essential for Sustainability

In tonnes, tuna and tuna-like species were the third-largest seafood catch to be transshipped at sea, according to recent data published in a 2020 Food and Agriculture Organization of the United Nations (FAO) report.

Transshipment Icon

Tuna Regional Fisheries Management Organizations (RFMOs) regulate transshipment in their regions. With some exceptions, purse seiners are required to transship in port. Other gears, such as longline, may engage in transshipment at sea under certain regulatory conditions. Tuna RFMOs also mandate observer coverage — either on the carrier vessel or on the fishing vessel — and require the submission of transshipment data.

But gaps persist — particularly in the regulation of at-sea transshipment, including the types of data collected, the level of monitoring, and data-reporting recipients and timelines. These gaps can increase the likelihood of illegal, unreported, and unregulated (IUU) fishing activities, including mis-reporting of catches and overfishing, which undermine fisheries management.

At ISSF, we are helping to improve tuna transshipment policies, practices, monitoring, and compliance — through our conservation measures for seafood companies and vessels, best practices research, RFMO benchmarking analysis, and advocacy outreach.

The Issue

“Transshipment” is the process of transferring fish or fish products at sea or in port, either from one fishing vessel to another fishing vessel — or to a vessel used solely for the carriage of cargo — for further transport.

Because large commercial fishing vessels can be at sea for weeks or months at a time, at-sea transshipment is common in many oceans, including in tuna fisheries. In fact, based on the most recent data reported by FAO, transshipment of fisheries at sea globally has been steadily increasing since 2013, nearly quadrupling by 2017.

Transshipment on the high seas allows vessels to send their catch to shore in a timely manner, for processing and marketing, without interrupting their fishing operations.

But since it takes place far from land, at-sea transshipment that is poorly monitored and under-regulated increases vessels' opportunities for overfishing and illegal activities.

Illegal Fishing Risks

If flag States and RFMOs do not comprehensively regulate and monitor transshipment in their regions, vessels have more opportunity to engage in illegal, unreported, or unregulated (IUU) fishing activities when catches are transferred in the middle of the ocean, and thereby evade detection.

Rigorous government and RFMO management measures — that is, rules that address fishing activity, data collection, observer coverage, vessel monitoring systems, port state inspections, authorized vessel lists, and much more — are critical for preventing illegally caught fish from entering the global supply chain.

In addition, if fishing vessels are not compelled to document their transshipments properly, important data for fisheries monitoring and management are lost or compromised — including, most fundamentally, the type, size, and location of their catch. 

Requiring vessels to collect and provide accurate transshipment data ensures “product traceability” in the seafood supply chain. Robust data also allows scientists to assess stock health — and enables authorities to track vessel compliance.

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At worst, at-sea transshipment can be exploited by unscrupulous fishers to hide illicit activities. IUU fishing, which can take these and other forms, is more likely when transshipment is poorly regulated:

  • Fishing without authorization and/or license(s)
  • Exceeding fishing quotas
  • Underreporting catches
  • Fishing in closed, restricted areas
  • Failing to follow bycatch mitigation measures to protect at-risk marine species

RFMO Oversight Gaps

Given these risks, tuna transshipment must be well regulated and well monitored by Regional Fisheries Management Organizations (RFMOs) and national governments.

Map showing areas covered by the four tropical RFMOs.

Each of the four tropical-tuna RFMOs, for example, prohibits purse seiners — and other vessels under certain conditions — from transshipping at sea.

But at-sea transshipment overall has increased in recent years. In 2017 alone, approximately 94,780 tonnes of tuna and tuna-like species were transshipped at sea, as noted by the Food and Agriculture Organization (FAO) of the United Nations in a recent report.

As an exception to that trend, the number of reported transshipment events decreased in 2020-2021 due to the pandemic and overall reductions in fishing activities and port calls. At that time, however, in the Western and Central Pacific 83% of transshipments were unobserved.

In the Indian Ocean Tuna Commission (IOTC) in 2019, there were about 180 reported infractions among 1,300 transshipment events — or in 14% of cases.

Since RFMOs suspended vessels’ observer data-collection requirements during COVID, in 2021 the Western and Central Pacific Fisheries Commission (WCPFC) region had 539 known transshipments, of which 83% were unobserved.

Contrary to best practices, the International Atlantic Tropical Tuna Commission (IATTC), along with IOTC, allows carrier vessels flagged to non-members to operate in RFMO Convention Areas.

ICCAT recently revised its transshipment recommendation to include stronger port inspection requirements linked to its port state measure.

Best Practices

As the number of at-sea transshipments has increased over time, it has become even more imperative for RFMOs to better oversee and regulate vessel activity in their regions. 

To support tuna RFMOs in that effort, ISSF has identified opportunities for improvement in their current transshipment measures.

While these best practices are focused on at-sea transshipment, a number of these practices can also improve transshipment when it takes place in port.

Tuna RFMO Measures Regulating Transshipment

Benchmarking of certain current tuna RFMO requirements regulating at-sea transshipment against best-practice recommendations

Green CheckmarkPriority reform in place Yellow '...'Partial reform in place Red 'X'Does not have priority reform in place

To strengthen their at-sea transshipment policies to prevent IUU activities and overfishing, RFMOs should follow these best practices, which are detailed in ISSF reports and other resources:

Management Icon

Management Practices

Checkmark Prohibit vessels from acting as both a fishing vessel and carrier vessel on the same trip
Checkmark Require carrier vessels to be flagged to an RFMO member or Cooperating Non-Member
Checkmark Establish publicly available record of vessels authorized for at-sea transshipment
Checkmark Require that vessels have IMO number in order to be authorized to transship
Checkmark Establish and implement guidelines for how vessels receive authorization to transship at sea
Data Reporting Icon

Data Reporting Practices

Checkmark Require reporting of information on at-sea transshipment events
Checkmark Require annual summarized information on transshipments and compliance with reporting requirements to be publicly reported
Checkmark Require advanced notification to authorities (RFMO, coastal States) at least 48 hours before at-sea transshipment
Checkmark Require post-transshipment activity declarations be provided electronically to authorities of intended landing State and/or port State at least 48 hours prior
Checkmark Establish procedures to share data from transshipment among tuna and non-tuna RFMOs
Monitoring Icon

Monitoring Practices

Checkmark Require that vessels authorized to conduct at-sea transshipment have operational vessel monitoring systems (VMS) and that VMS position data are provided in near-real time
Checkmark Require use of Automatic Identification System (AIS) by vessels engaged in at-sea transshipment activities
Checkmark Require 100% observer coverage (human, electronic, or combination) onboard fishing and carrier vessel for all at-sea transshipping events
Checkmark Require binding measures and specific training to ensure human observer safety
Checkmark Ensure mandatory data collection protocols for transshipment observers, including data for scientific and compliance purposes

Stakeholder Steps

In these and other ways, seafood companies, food retailers, NGOs, and other sustainable-fishing stakeholders can join ISSF in pushing for better oversight of tuna transshipment:

Checkmark Collect key data elements on transshipped tuna in your supply chain. Talk to suppliers about practices of source vessels and request they follow best practices.
Checkmark Advocate to RFMO member governments, including where you have business interests or source tuna, and participate in national RFMO advisory bodies
Checkmark Publicly support ISSF position statements and NGO Tuna Forum advocacy

ISSF Resources

ISSF researches and analyzes RFMO and government policies and regulations on transshipment and many other issues in sustainable fishing.

Visit the ISSF site to explore our scientific and advocacy publications, blogs, infographics, and more.

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