When fishing boats go dark at sea, they’re often committing crimes — we mapped them

In January 2019, the Korean-flagged fishing vessel Oyang 77 sailed south towards international waters off Argentina. The vessel had a known history of nefarious activities, including underreporting its catch and illegally dumping low-value fish to make room in the hold for more lucrative catches.

At 2 a.m. on January 10, the Oyang 77 turned off its position transponder at the edge of Argentina’s exclusive economic zone — a political boundary that separates Argentina’s national waters from international waters, or the high seas. At 21:00 on 11 January, Oyang 77 turned its transponder back on and reappeared on the open sea. During the 19 hours that the ship was dark, no information was available as to where it had gone or what it was doing.

In a recent study, I worked with colleagues at Global Fishing Watch, a nonprofit organization working to advance ocean stewardship by increasing the transparency of human activity at sea, to show that these periods of missing transponder data actually contain useful information about , where ships go and what they do. And authorities like the International Maritime Organization can use this missing data to help fight illegal activities at sea, such as overfishing and exploitation of workers on fishing boats.

Illegal fishing causes economic losses estimated at $10 billion to $25 billion annually. It has also been linked to human rights abuses, such as forced labor and human trafficking. Better information about how often boats go dark at sea can help governments figure out where and when these activities may be taking place.

Countries can combat illegal, unreported and unlicensed fishing by checking paperwork, verifying catches and sharing information across borders.

Going dark on the sea

The high seas are the Wild West of the modern world – a vast body of water far from oversight and authority, where outlaws engage in illegal activities such as unauthorized fishing and people smuggling. Surveillance there is aided by location transponders, called the Automatic Identification System, or AIS, which work much like the Find My iPhone app.

Just as thieves can turn off phone location tracking, ships can disable their AIS transponders, effectively hiding their activities from surveillance. It is often unclear whether it is legal to walk in the dark in this way. AIS requirements are based on many factors, including the size of the vessel, which country the vessel is flagged to, its location in the sea and what species its crew is trying to catch.

AIS requirements are based on many factors, including the size of the vessel, which country the vessel is flagged to, its location in the sea and what species its crew is trying to catch.

A ship that disables its AIS transponder disappears from the view of anyone who might be watching, including authorities, scientists and other vessels. For our study, we reviewed data from two private companies that combine AIS data with other signals to track assets at sea. Spire is a constellation of nanosatellites that pick up AIS signals to increase the visibility of vessels in remote areas of the world. Orbcomm tracks ships, trucks and other heavy equipment using internet-enabled devices. We then used machine learning models to understand what caused vessels to disable their AIS devices.

By investigating where and how often such episodes occurred between 2017 and 2019, we found that ships deactivated their transponders for around 1.6 million hours each year. This represented about 6 percent of global fishing vessel activity, which is consequently not reflected in global inventories of what types of fish are caught where.

World map showing zones where large parts of boats deactivate their transponders

This map shows the proportion of fishing vessel activity hidden by AIS deactivation events from 2017 to 2019. Heavy AIS deactivation occurred adjacent to Argentina, West African nations, and in the Northwest Pacific—three regions where illegal fishing is common. In contrast, the debilitating hot spot near Alaska occurs in intensively managed fishing grounds and likely represents vessels going dark to avoid competition with other boats. Global Fishing Watch, CC BY-ND

Vessels often passed in the dark on the high seas edge of exclusive economic zone boundaries, which can hide illegal fishing in unauthorized locations. That’s what Oyang 77 did in January 2019.

Money laundering of illegal catch

The AIS data we reviewed showed that Oyang 77 deactivated its AIS transponder a total of nine times during January and February 2019. Each time it went dark at the edge of Argentine national waters and reappeared several days later back on the open sea.

During the ninth disabling event, the vessel was seen fishing without a permit in Argentine waters, where the Argentine Coast Guard intercepted it and escorted it to the port of Comodoro Rivadavia. The ship’s owners were later fined for illegal fishing in Argentina’s national waters and their fishing gear was confiscated.

It is not unusual to see fishing vessels disable their AIS transponders near floating coolers, indicating that they wish to hide these transmissions from surveillance.

AIS deactivation is also highly correlated with transhipment events – the exchange of catch, crew and supplies between fishing vessels and reefer vessels or “coolers” at sea. Reefers also have AIS transponders, and researchers can use their data to identify loitering events when reefers are in one place long enough to receive cargo from a fishing vessel.

It is not unusual to see fishing vessels disable their AIS transponders near floating coolers, indicating that they wish to hide these transmissions from surveillance. While the transfer of people or cargo may be legal, when poorly monitored it can become a means of laundering illegal catches. It has been linked to forced labor and human trafficking.

Valid reasons for turning off transponders

Making it illegal for vessels to disable AIS transponders may seem like an obvious solution to this problem. But just as people can have legitimate reasons for not wanting the government to monitor their phones, fishing vessels can have legitimate reasons for not wanting their movements monitored.

Many vessels disable their transponders in high-quality fishing grounds to hide their activities from competitors. Although the ocean is vast, certain species and fishing methods are highly concentrated. For example, bottom trawlers fish by dragging nets along the ocean floor and can only operate over continental shelves where the bottom is shallow enough for their gear to reach.

Modern pirates also use AIS data to intercept and attack vessels. In response, ships often disable their transponders in historically dangerous waters of the Indian Ocean and Gulf of Guinea. Making AIS deactivation illegal would make fishing vessels more vulnerable to piracy.

An electronic display shows triangles representing nearby ships within concentric circles.

An AIS-equipped system on board a ship displays the bearing and distance of nearby vessels in a radar-like display format. Clipper/Wikipedia, CC BY

Instead, in my opinion, researchers and maritime authorities can use these AIS disabling events to make inferences about which vessels are behaving illegally.

Our study reveals that AIS deactivation near exclusive economic zones and loitering reefers is a risk factor for unauthorized fishing and transshipments. At sea, real-time data on where vessels disable their AIS transponders or change their apparent position using false GPS coordinates could be used to focus patrols on illegal activities near political borders or on transshipment hotspots. Port authorities could also use this information on land to target the most suspicious vessels for inspection.

President Joe Biden signed a national security memorandum in 2022 pledging US support to combat illegal, unreported and unregulated fishing and related labor abuses. Our study points to a strategy to use phases when ships go dark to combat illegal activities at sea.The conversation

This article is republished from The Conversation under a Creative Commons license. Read the original article.


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