Tuesday, 28 January 2020 11:45

Researchers track fishing fleets by putting radar sensors on birds

Wildlife management has been revolutionized by the ability to track species in their natural habitats—to figure out what areas they actually occupy, where they feed, and so on. For years, that ability was limited to large mammals, which could easily handle the bulky batteries and electronics required to frequently broadcast location information.

The miniaturization of electronics, however, has opened up the list of species we can track, adding birds and fish to it, and revealing the huge ranges covered by some species.

But now, some researchers have decided to turn the tables by placing hardware on birds to keep track of us. More specifically, our fishing fleets, which often operate in remote areas that are difficult to track. The work showed that albatross species could easily carry miniature detectors that would pick up radar and identification signals from any fishing boats they get within range of. This strategy is made even more effective by the fact that albatrosses are drawn to fishing boats.

Snooping on fishing boats

The Pacific is immense, but it's dotted with islands. Some of these create exclusive economic zones where one country has access to the fish stocks; there are also some large oceanic preserves. Outside these areas, any nation is able to fish, although some at-risk species may be covered by international treaties.

Those are the rules; monitoring whether they're being obeyed is an enormous challenge, given the vast area that needs to be covered by enforcement. Complicating matters further, some of the nations in charge of the remote territories are quite distant; France, for example, has a number of islands in the remote South Pacific.

Fishing boats can use something called a Vessel Monitoring System to declare their presence, allowing them to be identified remotely. This system is often switched on only when the vessel is in exclusive waters. Most boats also carry a broadcast system called an Automatic Identification System that can be used to help avoid collisions. But these can also be switched off. Finally, most ships use radar to avoid collisions with any vessels that aren't using one of these systems.

While patrol boats in the area could use these to identify fishing vessels, vessels fishing illegally are likely to turn the broadcast systems off. And anyone who's outside of the area is out of luck. Almost none of the data is available in real time, and obtaining even delayed data is difficult. And again, vessels can simply shut these systems down, leaving them impossible to detect without on-the-site radar monitoring.

The research team here decided to do some on-the-site monitoring without splurging on a boat. To do so, the researchers decided to leverage something that was going to be heading to fishing grounds anyway: seabirds. Building on the advances in wildlife trackers, they built a device that included a GPS receiver, an antenna that can pick up radar signals, and an antenna for a satellite communications system devoted to environmental monitoring. Throw in a lithium battery and a small solar panel, and the 65 gram package can scan for radar every five minutes and send in real-time alerts whenever any vessel is present.

Who’s out there?

To get this on site, the authors went to albatross nesting grounds in the South Pacific islands Crozet, Kerguelen, and Amsterdam. The researchers chose nesting albatrosses because the males and females take turns providing time on nest and making extensive feeding trips. That way, they could attach the trackers to a nesting bird and be sure that it would take an extensive trip across the Pacific in the not-too-distant future, then return the hardware to the original location when the test was over. Overall, 169 birds gave the system a lift through the Pacific, covering everywhere from the east coast of Africa to New Zealand.

Overall, the system checked in with over 600,000 GPS locations and picked up over 5,000 radar detections. Putting those together with data obtained later, the researchers were able to determine that these corresponded to 353 different boats.

Overall, nearly 30 percent of the radar signals didn't have corresponding Automatic Identification System data, indicating that it had been shut off at the time the boat was detected. That number was reduced within a French exclusive economic zone, in the area, and mostly represented French fishing vessels. At the edge of this zone, however, the researchers detected Chinese and Spanish vessels that would switch their broadcast systems on and off.

In international waters, the number without active Automatic Identification Systems rose even higher. While some of those are undoubtedly not fishing vessels, the authors found this occurred most frequently in areas that are fished for tuna.

The data also confirmed that albatrosses will approach fishing vessels they sight, although the numbers are relatively small: only about 6 percent of the birds did this. The behavior was much more common in mature birds and seemed to vary among species.

Overall, the work represents an ingenious way of having animals assist us in protecting them. Albatross populations have been reduced due to their tendency to go after the bait used in long line fishing. It's possible that the birds themselves can help us understand the prevalence of this fishing and perhaps even identify boats that are doing it illegally.

PNAS, 2020. DOI: 10.1073/pnas.1915499117  (About DOIs).