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How fish and shrimps could be recruited as underwater spies

BBC Technology 06 Jun 2019 11:10
A goliath grouperImage copyright Getty Images

We have a long history of trying to use animals as spies, weapons and warning systems, but the latest plans to use marine organisms as motion sensors may be the strangest yet.

When a beluga whale was spotted wearing a harness recently, some speculated that it had been trained to spy for the Russian army.

That's not as far-fetched as it sounds. Ever since the 1960s, the US Navy has been training dolphins to detect mines and help rescue lost naval swimmers. Russia's been known to do the same.

And sharks, rats and pigeons have been enlisted over the years as eavesdropping devices, with mixed results.

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The latest project from the US Defense Advanced Research Projects Agency (Darpa) aims to improve military intelligence by using a range of aquatic creatures - from large fish to humble single-celled organisms - as underwater warning systems.

"We're trying to understand what these organisms can tell us about the presence and movements of all kinds of underwater vehicles in the ocean," says Dr Lori Adornato, programme manager of the Persistent Aquatic Living Sensors (Pals) project.

Living creatures react in various ways to the presence of vehicles. One of the most familiar is the phenomenon of bioluminescence - some marine organisms glow with light when disturbed. This is the focus of one of Darpa's strands of research.

"If you have an organism like noctiluca present on the surface of the ocean and an underwater vehicle that's close to the surface, you will be able to see that from the air because of the bioluminescent trail," explains Dr Adornato.

"We want to understand if it is possible to distinguish the response of the organisms to natural versus manmade disturbances, or perhaps even certain types of manmade objects," says Vern Boyle, vice president of advanced programs, emerging capabilities at project participant Northrop Grumman.

Image copyright Darpa/PALS

"Our non-invasive undersea surveillance and monitoring technologies will be subtly integrated into goliath grouper habitats," says principal investigator Laurent Chérubin of Florida Atlantic University.

These elements of the project involve monitoring what's known as the soundscape, explains Alison Laferriere of project partner Raytheon BBN Technologies. Many species of fish constantly make sound to communicate or in response to external threats.

"If a vehicle comes in to their environment, the thought is that they might change their behaviour in some way that we might be able to detect," she says.

Behaviour is an important indicator that potential sub-sea interlopers may be around.

Image copyright Getty Images

"We can implant miniature depth sensor tags on the fish so we can detect the movement, and there is already the technology in place for that to be a real-time system."

"You've got to compare with the system right now, and the amount of money they're spending on planes, ships, hydrophone equipment, monitoring equipment. All of that gets them very small snapshots, whereas the system we're talking about would last months," she says.

Image copyright Getty Images

As with conventional sonar systems, measuring the time it takes for the sound signal to return, and its strength, can reveal the size, shape and distance of underwater objects.

This is important because you don't want your surveillance system to be detectable or to make its own noise that interferes with the sensors.

Why bother using a lot of energy to detect underwater vehicles when you could get a colony of shrimp to do it for you?

"There is a global push to work with animals for remote sensing," says Dr Thomas Cameron, lecturer at Essex University's biological sciences school, "both in the case of free living animals or in farming and aquaculture.

"What is unique in this program is the focus on wild free living organisms and the push to see what we can learn about signalling in the marine environment by focusing on vocal, visual and movement behaviours."

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DarpaMs LaferriereUS NavyAlison LaferriereEmma Woollacott
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