New drone sensor could identify sea life with minimal impact


Flanders’ Blue Cluster is working on a sensor that could be attached to an underwater drone and identify sea life – even under the sediment

Seeing through the murk

The seabed is teeming with life, but counting and identifying the creatures that live there is not straightforward. Teams of scientists have to put to sea, drag the bed for samples, and then analyse the results on board, or back in the lab.

But what if drones could be sent down to do the job instead?

This is the idea being developed by Blue Cluster, a collaboration among Flemish companies and research institutions interested in innovative marine technology. The researchers hope to develop a sensor that, mounted on an underwater drone, could count and identify the animals living on or in the seabed.

“With a swarm of 20 drones you could cover at least the same area as a survey boat, and collect much better data,” says Hans Polet, science director at Ilvo, Flanders’ research institute for agriculture, fisheries and food. Also involved in the initiative are researchers from Ghent and Antwerp universities, and the Flanders Marine Institute, Vliz.

This already has applications, such as finding tumours inside the human body or steel in concrete walls, but it hasn’t been tested under water

- Hans Polet of Ilvo

The cloudy waters of the North Sea mean that video cameras are little use when surveying the seabed, so an alternative is to develop an acoustic camera, using sonar. This would be able to “see” through the murk and pick out shapes.

But sonar will tell you nothing about what is living in the sediment. “So we thought of electromagnetic detection,” Polet says. “This already has applications on land, such as finding tumours inside the human body, or steel embedded in concrete walls, but it hasn’t really been tested under water.”

Water tends to absorb electromagnetic radiation, but it should still be possible to develop a sensor that can see five to 10 centimetres into the sediment. “That’s more than enough to pick up animals living in the top few centimetres.”

The North Sea bed is teeming with life ©Semet/iStock/Getty Images Plus

So the idea is to combine acoustic and electromagnetic imaging in a sensor carried by a drone hugging the ocean floor. “It would be like a dog sniffing the ground,” Polet says, “although the sensor would not be shaped like a dog’s nose. It would be wide, perhaps half a metre, so that it could scan a strip of the seabed.”

This would produce an image of the sea floor from which the characteristic shapes of living things – fish, crabs, starfish, shellfish – could be identified and counted. This would give a broad picture of how many and what kind of animals were in a particular location.

And with the help of artificial intelligence it might also be possible to identify the creatures more precisely. “Discriminating between species may be wishful thinking, but it will be possible in some cases,” explains Polet. “For example, a lot of crab species have very distinct shapes, so if we can determine the shape we can determine the species.”

If we can replace a survey vessel with a drone, it would be a huge step forward in terms of safety and costs

As for the underwater drones, these are already quite advanced, but controlling a swarm of them will require work. “We will need an intelligent system to steer the swarm so that it scans an area quickly and efficiently, for example making use of water currents to save energy and extend battery life.”

While awaiting funding for the project, the researchers are putting together a group of potential users to discuss how the system might be applied. One idea already on the table is to help offshore wind farm companies to monitor the impact they have on the marine environment.

Survey ships can do this to a limited extent, but it is not safe for them to get close to the turbines. “If we can replace that survey vessel with a drone that scans the sea floor, providing the same information, then it would be a huge step forward in terms of safety and cost savings.”

Precision fishing

A more futuristic application would be fishing. At present, flatfish are caught by dragging a net along the seabed, then hauling everything caught to the surface for sorting.

Fish of the permitted size and species are kept, while everything else – the by-catch – is thrown back. This is a time-consuming, energy-intensive process, which damages the seabed and is traumatic for the fish, regardless of where they end up.

Polet thinks that fish-catching drones could do better. The sensor he and his colleagues want to develop should be able to identify the species of fish and register its size.

A swarm of fishing drones could then be programmed with the quota assigned to a particular boat, and the size requirements. “We could catch only the fish that we need, and that we are allowed to catch.”

Research vessels could conceivably be replaced by the new sensor-laden drones ©Courtesy Vraag voor de Wetenschap

The fish would be killed the moment they are caught, improving welfare, with minimal disturbance to the seabed. There would be no unwanted by-catch, and the energy spent towing the heavy fishing gear would be saved.

Initial calculations suggest that a drone would only need to catch two fish an hour to make a swarm of 20 financially viable, compared to a traditional fishing boat. “If we had to catch 20 fish an hour it would be impossible, but two fish an hour might be feasible.”

Polet concedes that a lot of work needs to be done before any of this is possible. “It is a high-risk research project, but there is so much potential gain that it is certainly worth trying.”

Photo top: Blue Cluster’s drone would have broad sensors attached that could scan larger areas of the ocean floor
©Anastasiia Krivenok/iStock/Getty Images Plus