Easter Island is best known for its mysterious Moai statues, which dominate part of the hilly coastline and stare at the horizon like ancient watchmen of the once bountiful ocean. Just beyond the reach of their gaze lies a large stretch of open water, known as the high seas, that provides a vital spawning ground for many overfished and highly migratory species, including tuna and sharks.

The seas were once plentiful, notes Alberto Hotus, president of the Easter Island Elder’s Council, who fondly remembers when a fishing boat could easily bring back enough to feed the whole island. “[This] does not happen anymore,” he says with a hint of sadness. “There are no tuna, no fish.”

Residents of the island, also known as Rapa Nui, have long claimed that vessels are fishing illegally in their waters. Many local fishermen attest to seeing the distant glimmer of foreign vessel lights at night.

“People on the island have been complaining about illegal fishing for years,” says Marta Hotus, the governor of Easter Island. Evidence of these activities, such as buoys and long nets—fishing gear that is not used by the locals—even regularly washed ashore.

The Rapa Nui people once used their celestial-based navigation skills to “conquer the islands by navigating across the seas,” says Mayor Pedro Pablo Edmunds Paoa. He describes them as the “Phoenicians of the Pacific,” referring to the ancient Mediterranean civilization renown for having mastered deep-sea navigation, covering great distances in their ships of trade and war.

Moai statues keep watch on Easter Island (Credit: Flickr/David Berkowitz)

Moai statues keep watch on Easter Island (Credit: Flickr/David Berkowitz)

But the illustrious navigational past of the Rapa Nui alone is no match for the industrial scale of illegal fishing operations. Nor can it reverse the impact on the livelihoods of a community whose very survival has long been tied to the ocean’s bounty.

“What I see in the sea makes me sad because I see fishermen go out and come back with nothing,” says Sara Roe, president of the Hanga Piko fishing association on Easter Island. “Coming back with nothing means that they won’t have bread for their kids, there will be no food for the household, so that is a problem for the people.”

The case of Easter Island partly demonstrates the difficulties faced by governments in monitoring remote areas of the high seas, which in turn become fertile ground for illegal fishing operations. Governments around the world have recognized the scale of the problem and are seeking solutions, but their resources vary enormously.

What role can advances in technology play in putting an end to illegal activities on the high seas that pillage an estimated $23.5 billion worth of fish each year? Because, let’s face it – trying to look for illegal fishing activities taking place across an area covering half the planet is akin to looking for a needle in a haystack.

The answer, some companies say, is by monitoring the seas from the sky.

Stuart Martin, CEO of the U.K.-based firm Satellite Applications Catapult, says that satellite data is now playing a “key role” in helping to end illegal fishing activities. It’s also helping to make the protection of livelihoods in many villages a “reality rather than an idealistic goal.”

John Amos, president of the U.S. non-profit group SkyTruth, agrees. Satellite data and real-time vessel tracking, he says, is “evolving quickly” and “shining a light on the commercial fleet that has been operating largely out of sight since humans first sailed over the horizon.”

Catapult keeps an eye on the seas

Catapult keeps an eye on the seas (Credit: Catapult)

Out of sight, out of mind

Located some 4,000 kilometers (2,300 miles) west of Chile, Easter Island’s isolated location coupled with the vast size of its surrounding ocean makes it vulnerable to illegal fishing—a criminal activity taking place on a global scale, fueled in part by the assumption that no one is watching. With the advent of more affordable space-based satellite technologies and their pioneering integration into custom monitoring platforms, there are more eyes than ever on the sea.

“The big change in the last few years that will accelerate into the future is the reduced costs of launching and developing highly effective satellites. As the number and usefulness of satellites increases, more data is available for effective monitoring,” explains Brad Soule, Senior Fisheries Analyst at Catapult’s Ocean Sustainability Business Unit.

As the Rapa Nui community became increasingly concerned with threats to their ocean environment, so did conservation groups, who sought an innovative way to answer their call for greater protection. SkyTruth, an organization that specializes in satellite-based remote sensing technologies, was soon enlisted by The Pew Charitable Trusts and the Bertarelli Foundation to monitor and identify the best ways to protect the island’s waters.

The information compiled as part of the project prompted the Chilean Navy to increase its patrol efforts of the province. Likewise, in late 2015, the findings contributed to the announcement of a 631,368 square kilometers (243,630 square miles) marine park around the area, now considered to be the third-largest fully protected area of ocean in the world.

“In early 2012, Pew contacted us to ask if it was possible to monitor the activity of ships – including fishing vessels – in the waters of Easter Island Province,” said John Amos, an expert in using satellite images, aerial photographs and other kinds of remote sensing and digital mapping.

He had founded SkyTruth in 2001.

In January 2013, they began a monitoring program that used satellite radar images to detect the presence of ships, and satellite-collected Automatic Identification System (AIS) broadcasts to identify those vessels. At the time, this was the first instance of these two different technologies being combined in this way to monitor a country’s waters for illegal fishing activity.

Moai statue sits near a small harbor on Easter Island (Credit: Flickr/Ronald Woan)

Moai statue sits near a small harbor on Easter Island (Credit: Flickr/Ronald Woan)

Data collected between January and October 2013, including 163 satellite images, detected 73 vessels in and around Easter Island’s waters. Of these, 31 were identified using AIS (to include 22 cargo ships, 5 fishing vessels, 1 cruise ship, and 3 undefined). More than half (the remaining 42 vessels) could not be identified using their AIS broadcasts, but based on their size and location were determined by SkyTruth to be commercial fishing vessels. More than half of those vessels (a total of 25) were detected within Easter Island’s Exclusive Economic Zone.

Knowing where to look

“To stop illegal fishing and other crimes taking place on the ocean, authorities first need to be able to recognize and track vessels,” argues Pew’s Tony Long in his article “Satellite Tracking Can Unmask Illegal Fishing Vessels.” The former British naval commander now directs the organization’s Ending Illegal Fishing Project.

Unlike mobile phones or cars, fishing vessels are not required to have an identification number. This means that identifying vessels at sea is not a straightforward exercise and requires the integration of differing but complimentary tools into a monitoring platform.

So how does it work?

The monitoring project conducted off Easter Island, for example, pioneered the combined use of two key tools—radar imagery and the Automatic Identification System (AIS)—to track and identify vessels.

Radar satellites can identify ships by beaming microwave (radar) energy down at the Earth’s surface and collecting the energy that is reflected back toward the satellite. According to SkyTruth’s Amos, steel-hulled ships are “strong reflectors of microwave energy and appear as very bright targets or radar images of the ocean.”

This allows for the observation of vessel activities without their participation or knowledge, an especially vital tool for ships that deliberately switch off their transceivers in order to avoid detection or don’t have them installed.

These radar images can yield basic information, including the exact location of a vessel at the moment the image was acquired, its approximate size and in some cases, the direction it’s moving. “But there is little information in a radar image that allows us to identify the vessel, or determine if it’s a fishing vessel rather than a cargo ship or other type of ship,” says Amos.

Radar satellite vessel detection (Credit: European Space Agency/Annotation by SkyTruth)

Radar satellite vessel detection (Credit: European Space Agency/Annotation by SkyTruth)

To fill the gap, SkyTruth combined radar satellite imagery with a second monitoring component known as a satellite-collected Automatic Identification System (AIS)—a form of automatic transceiver similar to a global positioning system (GPS) that is broadcast by vessels. Unlike other transceivers, such as the government-controlled Vessel Monitoring System (VMS), AIS was not designed for monitoring purposes. Instead it’s primarily used to prevent vessels from colliding at sea.

The use of AIS transceivers, however, is a relatively new approach in the fight against illegal fishing. “I think that AIS has only recently started to be used because it was not designed for fisheries monitoring purposes,” says Brad Soule from Catapult, adding that the number of satellites available for monitoring AIS do make it a useful tool for other maritime domain awareness purposes as long as you “account for some of the security issues that have already been addressed in traditional vessel monitoring systems.”

Collecting the AIS data was only the first step towards building a more accurate picture of the types of activities and behavioral patterns of vessels in Easter Island waters, as it’s the actual correlation and overlaying of data sources which facilitates the identification of vessel types.

Tracking vessels that don’t want to be tracked

Despite huge advances in satellite monitoring technology, “it can still be rigged to fool its users, and AIS and VMS are no different,” states Tony Long from Pew. Effective use of vessel tracking systems to detect illegal fishing activities therefore requires an understanding of how vessels circumvent the system in order to go unnoticed. Moreover, it’s vital that users have a thorough understanding of the differing behavior patterns and movements between cargo vessels and fishing vessels when monitoring their tracks on a screen.

Off the coast of Easter Island, SkyTruth collected AIS data that revealed distinct patterns of vessel movement and enabled the detection of suspected illegal activity. For example, vessels that move very slowly and frequently change directions are typically engaged in fishing activities, whereas those moving in straight lines at a steady speed are more likely to be cargo ships moving between South America and Asia.

Vessels that aren’t broadcasting AIS signals could be deliberating switching them off to avoid detection, but Amos says that this lack of signal could also result from gaps in orbiting satellite coverage.

To ensure continued monitoring coverage, SkyTruth regularly collected radar satellite imagery to see if any vessels appeared to be operating in Easter Island waters that were not broadcasting an AIS signal. “In many cases,” says Amos, “we could not find any AIS signals for vessels that appeared on the satellite imagery.”

So who were these vessels?

Amos calls them the dark fleet: vessels that “operate in stealth by not publicly broadcasting their identity.” In other words, vessels likely to be carrying out illegal fishing activities.

“In the remote waters of Easter Island,” Amos says, “we can assume a vessel larger than 20 meters that is not broadcasting AIS is probably a commercial fishing vessel.”


Easter Island’s isolated location in the Pacific is some 2,300 miles from the coast of Chile (Credit: Map by TUBS., CC BY-SA 3.0)

Keeping one step ahead

As demonstrated by the Skytruth study—where over half of the vessels monitored did not transmit an AIS signal—illegal fishing vessels are increasingly aware that they are being monitored through their safety and anti-vessel collision transceiver.

Even transceivers which are designed for monitoring purposes, such as the government enforced Vessel Monitoring System (VMS), face the challenge of having the devices tampered with once installed. VMS is not applied universally and the mandatory ping rate varies per country, with most setting it at every 1- 2 hours. Experts recommend a ping rate of multiple times per hour in order to capture 100% of fishing locations.

With illegal fishing operations increasingly becoming aware of how the current traditional monitoring systems can be fooled, how reliable is the data being generated for analysts?

“It’s a good question and an important one,” says Soule from Catapult.

“AIS was never designed for fisheries and marine reserve monitoring. It is only recently that it has become a useful tool by virtue of the growth in the number of fishermen who want to demonstrate transparency and compliance in their operations. But you are right, by itself AIS is not a panacea without an understanding of the vessels’ identities and thereby likely activities in the context of the area of operation and specific jurisdictions.”

Adding information from another transceiver is one way to help build a more accurate picture.

“We also use vessel monitoring system (VMS) data, when it is made available, to monitor the activities of fishing vessels,” says Soule. One of the marked differences between AIS and VMS, is that the latter can be required by governments or vessel owners and do not broadcast positions publicly.

An experienced fisherman from a North African country explained that one way around collecting more accurate VMS data would be for governments to require vessels to have their systems on two weeks before the fishing season begins. This would “allow for better control, ahead of season” and provide a better understanding of that vessel’s behavior patterns.

Beyond the use of positional data relayed by transceivers to monitor specific areas, the addition of a variety of sensors, “including satellite radar and optical imagery” is also a key data component to detect the presence of vessels, explains Soule.

This year, the U.S. government plans to further develop an application to assist in detecting ocean vessels in countries including Indonesia and the Philippines, using the Visible Infrared Imaging Radiometer Suite (VIIRS), another form of space-based sensor. VIIRS is capable of detecting lights—including from boats that use lights to attract fishery catch at night—in order to target potentially illegal activities.

Advances are also being made in the speed at which the merging of data is being processed, which is a huge step forward in providing real time coverage of remote areas, especially when working in tandem with authorities who can deploy patrols to carry out further investigations.

“Previously it took a team of analysts 18 hours or more to analyze the data and be able to find a vessel of interest. This system brings together all of those datasets in less than 18 milliseconds,” explains Nick Wise, head of Catapult’s Ocean Sustainability business unit.

The new system in question is the recently launched Project Eyes on the Sea, a maritime monitoring and surveillance data platform that was developed in partnership with Catapult and the Pew Charitable Trusts.

Catapult operation room (Credit: Jennifer Gillam)

Catapult operation room (Credit: Jennifer Gillam)

This platform uses and merges multiple sets of data, including Vessel Monitoring Data (government collected data), synthetic aperture radar (SAR) data, optical imaging as well as AIS, and has been designed to enable enforcement efforts to focus on specific problem areas and vessels, cutting in time and money.

“We consider anything that provides a position, an identity, and some behavioral information—or any combination of these, and bring together many data sources that don’t usually exist in the same system,” explains Soule, adding that the system enables an analyst to “know where to look next.”

In the future, it will be able to merge and incorporate other sources of information third-party surveillance and crowd-sourced images that could originate from any person, ship, aircraft, or unmanned vehicle. Despite recent technological advances in monitoring, the high seas—an area representing two-thirds of the world’s ocean—remain notoriously difficult to monitor and patrol for illegal fishing activities. Less than one percent of the open ocean is accorded protection.

“At the moment, the high seas are the weakest link because of their poor management and lack of governance,” explains Professor Alex Rogers of Somerville College, Oxford.

Future ocean surveillance: What’s on the horizon?

Advanced technologies, remote surveillance tools, and satellite monitoring of the high seas have long been accessible to the military, as well as (though to a much lesser degree) governments, fisheries management agencies, and private companies such as international couriers. Since 2013, however, an important shift has taken place towards increasing access to satellite data, and also understanding the gaps in data which allow for illegal vessels to circumvent whatever moderate level of monitoring was taking place to avoid detection.

However, for all the progress made, satellite-based technological advances alone cannot be relied upon to curb illegal fishing or monitor newly protected areas on the high seas.

Nor is space-based monitoring not without its own evolutionary problems, as it “requires significant computational horsepower to bring the data together and compare the different sources to identify abnormalities,” according to Soule.

Satellite-based technological advances greatly reduce the human power needed to process vast quantities of data and are likely to become fully integrated into monitoring platforms ten years from now. As satellite coverage of transceivers expands and more and more governments require vessels to install them, however, they are unlikely to be relied upon alone.

Vessel ID registration is still not mandatory in all regions, which means that unlike traffic offenses on a speed camera, it will take some time before we have a global or even regional database linking a vessel’s ID to a tracking system, although huge progress is being made in national waters.

In the future, illegal fishing practices may also be curbed by the universal and mandatory application of electronically tracking fish at points of catch and sale, a regulation that an increasing amount of regional fisheries organizations are moving towards. In the long run, this is likely to shrink the market for illegal catches.

Today, on-site enforcement action and regular patrols in the air, at sea, and in ports, coupled with prosecution for crimes committed remain vital components in the global fight against illegal fishing.

Twenty years from now, however, if autonomous anti-collision drone technology continues to evolve at the predicted rate, future high-seas satellite monitoring platforms are likely to integrate this aerial surveillance tool not only as a key monitoring feature, but also one that expedites enforcement.

The current reality, however, is that policing remote areas of the open ocean is left in most instances to governments who have neither the means nor the human resources to properly enforce existing regulations in such remote locations. Overcoming such challenges may well require the increased use of satellite and autonomous aerial surveillance technologies — bridgingthe gap between sea and sky in a very modern way.

Mona Samari is an expert on fisheries management and the founder of the Tunisian Environmental Reporters Network. She has also worked as a consultant for a number of conservation groups, including  the Pew Charitable Trusts. This article reflects solely her own personal views and not those of this organization.


  1. Great article. My first thought was why don’t governments make it the law to have a specific GPS tracking device on every boat so it can be tracked always, and have it so that of its removed it can send out a beacon much like a human tag for criminals who can’t leave a radius without the law knowing. Then I saw the bit about the transceivers mentioned for not colliding. It’s quite a simple thing to stop illegal activity.

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