How the dark fleet evades global enforcement

By Alexander Fernandez

A growing fleet of untracked vessels is reshaping global trade, fishing, and energy markets while operating largely outside international law. Known as the dark fleet, these ships disable their tracking systems to hide where they go, what they carry, and who owns them. Analysts estimate that thousands now move undetected across international waters, fishing in restricted zones, transferring sanctioned oil, and employing crews under conditions that often amount to forced labor.

es the dark fleet as a network of vessels linked to Iran, North Korea, and Russia that use deceptive shipping practices to hide ownership, routes, and cargo. According to the U.S. Department of the Treasury’s Office of Foreign Assets Control (OFAC), which issued updated maritime guidance on April 16, 2025, these tactics expose shipowners, charterers, and insurers to potential sanctions if they help conceal prohibited trade.

The first signs of the dark fleet appeared in 2017, when independent satellite researchers identified hundreds of vessels operating without tracking systems in the waters between China and North Korea. These ships were fishing in areas that had been closed under United Nations sanctions following North Korea’s nuclear weapons tests. In July 2020, Global Fishing Watch, working with scientists from the Korea Maritime Institute and Stanford University, published peer-reviewed research in Science Advances. The research team wrote, “The scale of the fleet involved in this illegal fishing is about one-third the size of China’s entire distant water fishing fleet. It is the largest known case of illegal fishing perpetrated by vessels originating from one country operating in another nation’s waters.” The study identified more than 900 Chinese vessels fishing illegally in North Korean waters during 2017 and 2018. Most had disabled their Automatic Identification System (AIS) to avoid detection.

The United Nations Panel of Experts later confirmed that many of these vessels were engaged in unauthorized fuel and seafood transfers in violation of Security Council resolutions on the Democratic People’s Republic of Korea. The panel’s 2019 report linked the activity to Chinese companies that had reflagged or disguised vessels to hide ownership. By 2019, similar concealment tactics had begun appearing outside the Korean Peninsula as vessels in other regions adopted the identity-masking methods first observed in East Asian waters.

By 2020, enforcement notices had broadened as U.S. agencies began documenting how deceptive fishing practices were extending into the energy sector. The U.S. Treasury Department and Department of State issued advisories warning that AIS manipulation and flag-hopping were being used by ships transporting sanctioned oil for Iran and Syria. These warnings marked the first time that techniques once associated with illegal fishing were applied to large-scale energy trade. Analysts now identify the 2017 to 2019 period as the point when the dark fleet shifted from a regional problem into a global system of concealed maritime activity.

By 2025, the network had expanded across major oceans and regions, appearing in shipping lanes far beyond the areas where it first emerged. In the Middle East, U.S. Navy officials have documented tankers linked to sanctioned oil exports conducting ship-to-ship transfers near the Strait of Hormuz and the Gulf of Oman. Many disable their tracking systems before loading or discharging crude and often operate at night or just outside national waters.

In the Mediterranean, reports from the Office of Naval Intelligence describe similar patterns involving ships connected to Russian and Syrian intermediaries. “Russia is continuing its malign actions by operating a ‘ghost fleet’ to evade U.S. sanctions, enrich its war machine, and even aid Iranian oil smuggling,” Sen. Joni Ernst said on April 9.

The East China and Yellow Sea continue to see heavy dark-fleet activity. Satellite images show fleets registered in China, or owned through layered shell companies, operating in restricted waters without tracking signals.

Along the coast of West Africa, maritime security agencies have documented tankers transferring oil to smaller vessels heading to informal refineries. Weak enforcement and open ship registries make the region an easy target for operators who want to avoid scrutiny.

The Western Hemisphere has likewise been drawn into the pattern, with agencies documenting unregistered fuel transfers and falsified vessel records in the Gulf of Mexico and the Caribbean Sea.

Enforcement challenges add to the problem. Many coastal states do not have enough ships, aircraft, or personnel to track foreign vessels that can disable their identification systems in an instant. Once a ship leaves port or crosses into open water, it can vanish for long periods. By the time alerts are issued, the vessel often has a new name, a new flag, or new ownership records. These factors work together to create a system where evasion is profitable, accountability is limited, and oversight cannot keep pace. As long as demand remains high and global enforcement remains uneven, the dark fleet will continue operating in new waters and markets.

Traders often work through shell companies to avoid accountability, and frequent name or flag changes give vessels new identities that slow enforcement. Financial oversight gaps also allow the fleet to expand. The U.S. Department of the Treasury and the Financial Crimes Enforcement Network have warned that some insurers and brokers do not fully verify vessel ownership. When companies rely on incomplete records, dark-fleet vessels can obtain coverage that makes them appear legitimate. This weakens sanctions and gives operators confidence that their ships can continue moving with limited interference.

Governments have expanded sanctions guidance and maritime monitoring as Iran, North Korea, Russia, and their intermediaries continue using dark-fleet tactics to move restricted cargo. OFAC has issued updated advisories through 2023, 2024, and 2025, and the U.S. Coast Guard has released notices urging companies to track AIS irregularities and unreported ship-to-ship transfers. The Department of State, the Federal Maritime Commission, and European regulators have taken similar steps, with agencies in Greece, Cyprus, Malta, and the United Kingdom issuing guidance on identity changes and flag irregularities. Asian governments, including Japan, South Korea, and Singapore, have reported fuel transfers, unauthorized fishing, and AIS deactivation linked to North Korean vessels, while Australia and Canada issued additional sanctions-related notices involving Russia and North Korea. These actions reflect a broader effort among national authorities and the United Nations to limit the impact of untracked vessels by closing gaps that allow the dark fleet to conceal ownership, routes, and cargo.

The dark fleet continues to grow because the rewards outweigh the risks. The profits from moving sanctioned oil, seafood, and other restricted goods far exceed the cost of losing a single ship or paying a fine. Many vessels are old, inexpensive to buy, and easily replaced. This makes them appealing to operators who want to move cargo quickly before regulators can identify them. Countries facing restrictions on oil exports use the dark fleet to maintain revenue through intermediaries who handle cargo transfers and false paperwork.

Global demand reinforces the system in ways that reach far beyond shipping lanes and directly affect households, workers, and coastal communities. OFAC and State Department advisories explain that when sanctions limit the availability of crude oil, buyers often turn to untracked tankers that sell at discounted prices. These shipments influence the cost of gasoline, diesel, and home heating fuel, which shapes family budgets, transportation expenses, and the operating costs of trucking and agricultural industries. United Nations findings and U.S. Department of Labor reports describe a similar pattern in the global seafood market. When licensed fleets cannot meet demand because of quotas or seasonal closures, unmonitored vessels supply additional catch that lowers wholesale prices and fills supermarket shelves. This trade makes certain products available, but it also harms lawful producers, weakens sustainable fishing programs, and places unverified or illegally sourced seafood into the food system.

The U.S. Coast Guard has warned in multiple maritime advisories that vessels operating without identification increase the likelihood of collisions, groundings, and unreported oil spills. When spills go undetected or uninvestigated, the consequences fall on coastal residents. Fisheries may be forced to suspend harvesting because contamination risks can spread across miles of shoreline. Local businesses that depend on tourism can lose critical income when beaches are closed, when water quality warnings are issued, or when cleanup operations take weeks or months.

Small towns that rely on charter fishing, recreational boating, or seasonal tourism often face the greatest losses. These warnings are supported by the International Maritime Organization, which reports that manipulation of AIS and vessel identities compromises environmental safeguards that ports and coastal industries use to assess risk, plan shipping traffic, and manage emergency response.

Environmental effects compound the economic impact. UN and regional monitoring groups have documented that unregulated fishing connected to the dark fleet accelerates the decline of already stressed fish stocks, a trend that threatens long term food security in regions that rely on fisheries for protein and local income. In areas where untracked oil transfers take place, satellite analysts have recorded sheens and residue that never undergo formal cleanup because the responsible vessels cannot be identified. These events can disrupt ecosystems, kill marine life, damage coral and coastal vegetation, and weaken the natural barriers that protect communities from storms and erosion.

As these hidden trades grow, they create a parallel supply chain that functions outside safety rules, labor regulations, environmental protections, and insurance requirements. This system affects fuel prices, food availability, coastal jobs, and the long term stability of local and national economies. What began as a regional enforcement concern has developed into a global pattern with consequences that reach into household budgets, fishing communities, and ecosystems from the Korean Peninsula to the Gulf of Mexico.