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National Science Week: Lighting the oceans – deterring sharks from attack

National Science Week: Lighting the oceans – deterring sharks from attack

15 August 2023

Shark attacks are rare, but surfers are at a higher risk of being bitten than other ocean users. White sharks are often responsible and are well known to bite objects at the surface of the water, most likely because this is how they capture seals.

With the assistance of funding from the Australian Research Council (ARC) Linkage Projects program, Macquarie University Professor Nathan Hart and his team have been developing innovative shark deterrent technology.

Knowing that white sharks rely heavily on vision for capturing prey, the team drew inspiration from nature and the concept of counterillumination, where some animals produce light on their underside to camouflage their dark silhouette when seen from below. In essence, they covered the underside of a seal-shaped foam decoy with LED lights and observed how this affected shark behaviour.

This simple concept led to a dramatic change in the sharks’ behaviour – they stopped attacking illuminated seal decoys.

“Through our repeated testing, we progressed from having the seal completely covered with lights through to finding the minimum amount and pattern of lighting that would deter the sharks,” Professor Hart said.

“We’ve conducted field work over several years now and we’re pretty confident in the design that we’ve got,” Professor Hart said.

“Working from first principles, our finding that the absence of a dark silhouette changes the appearance or salience of the object to the sharks, has led to a very promising technology that you could put on surfboards, stand up paddle boards, kayaks and more.”

The other side of the team’s research is trying to better understand what sharks see, as sharks have a whole range of senses.

“We’ve tried to understand more about the eye of sharks in general, but especially the white shark, we've now got quite a nice body of evidence through this ARC grant to show that sharks are colour blind and have poor acuity,” Professor Hart said.

The team created a computer model of the white shark visual system, which allowed them to compare the signals that would come out of a white shark’s eye when witnessing footage of a person swimming, or a seal swimming, or someone paddling a surfboard..

They found that once elements like colour and some of the fine detail in an image are removed, then it is quite possible that a white shark would confuse different objects. Some shark bites on humans may well be a case of mistaken identity!

Professor Hart is quick to add that while this finding does not account for all shark bites, it does suggest that some of attacks, especially by white sharks, are likely because their visual system can’t reliably tell the difference between a surfer, a swimmer and a seal.

Professor Hart and his team were also awarded funding in 2020 for another ARC Linkage Project, to improve the effectiveness of electronic deterrents to prevent shark bites.

As well as vision, sharks have electroreception. Electroreception is the ability to detect the tiny electrical signals emitted by other living organisms and is mostly used to locate prey.

Some shark deterrents use strong electrical pulses to deter sharks, potentially by overloading their highly sensitive electroreception sense, but the effective range of these devices is quite short, around 2 metres, and the strength of pulse required to deter a shark varies considerably between different shark species.

“We need to investigate the strength of the electric field that you need to repel a white shark compared to what you need to repel a bull shark. We want to understand why that is, and hopefully through that process we can develop better electronic shark deterrents,” Professor Hart.

Professor Hart is a neurobiologist and has conducted research on a range of animals.

Around 2011-2012 there was a spate of shark attacks in Western Australia.

“At the time, my colleagues and I felt that we had something to offer in this area. We’re very passionate about understanding shark sensory biology and all animal sensory biology, but this is just a particularly nice application where we were able to take what we know from the lab and through studying behaviour and try and come up with some solutions that will hopefully save some people’s lives. And hopefully also reduce the persecution of sharks because we’ll have better ways to protect ourselves from the few occasions when they do decide to bite humans.

“Hopefully in the long run we can save sharks as well, and get rid of drum lines and nets, which would be a great outcome. Not just for all the sharks that get killed, but all of the whales, the turtles, the dolphins, the rays, everything else that sometimes gets killed in those nets,” Professor Hart said.

As technology and commercial partnerships continue to evolve, the team’s research may lead to a future where beachgoers can enjoy the waters with greater peace of mind, while also protecting these beautiful creatures that inhabit our oceans.

The ARC Linkage Projects scheme facilitates collaborations between university-based researchers with industry and other research partners to work on solutions to challenges facing government, business, industry and other end-users. The research partners provide matching cash and in-kind support to leverage the funding provided by the Government.

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