When marine biologist Sara Andreotti and her team were in the Bahamas constructing their eco-friendly shark barrier technology from South Africa recently, a manatee came to visit.
“We were very happy to see him crossing the barrier because that proved our technology is shark-specific,” said Andreotti, an extraordinary lecturer in marine biology at Stellenbosch University. “It only keeps sharks separated from humans; leaving the other marine creatures the possibility of swimming freely through it.”
She is one of four co-founders of the SharkSafe Barrier, a novel nature-inspired technology that combines the biomimicry of a kelp forest and magnetic fields to keep humans and sharks apart from each other without harming sharks or other large marine species.
In August, the technology, which was developed by marine biologists at Stellenbosch University and their collaborators — and is manufactured in the Western Cape — was installed at a private island in the Bahamas. It marked the team’s first commercial installation and is “incredibly exciting” for Andreotti.
“It’s happening obviously out of South Africa but it’s the first step to eventually bring the technology back home and replace the detrimental shark nets with the eco-friendly alternative,” she said.
The installation of a 30 metre long SharkSafe Barrier at the Berry Islands will help strengthen marine conservation efforts in the Bahamas, she said. In 2011, the Bahamas proclaimed the first shark sanctuary in the Atlantic Ocean, and, in 2018, a Marine Action Partnership for Sustainable Fisheries. Shark tourism contributes about $100 million per year to the local economy.
The SharkSafe Barrier technology successfully biomics the visual effects of a thick kelp forest, combining this with a series of permanent magnetic stimuli, to form a barrier, dissuading sharks from passing through. It is the only eco-friendly alternative to shark nets, which are behind the deaths of thousands of sharks and other marine life every year.
Further installations will likely be overseas, Andreotti said. The team is in touch with countries including New Caledonia, Réunion, Australia, Mexico, Brazil, Egypt and Dubai.
“We have a lot of requests from all over the world but because it’s a technology that has to be tailor made for every area, it takes a bit of time to get from the first contact to a final installation as we just did in the Bahamas.
Since 2020, there have been talks with Plettenberg Bay, she said. “Already, we’ve been in touch with locals, two municipalities and CapeNature to see if there is a chance to have our technology trialled out to Plettenberg Bay and we’ll see… The process in South Africa is a bit long because we also need to raise the funds for it differently from overseas clients that are ready to pay and install the barrier.”
15 years in the making
The first time Andreotti heard about the concept was in 2007 from Michael Rutzen, a white shark behaviour specialist. They wrote a draft of their project in 2008.
“The concept came from Michael who has been spear fishing in South Africa, swimming and diving out of the protection of a cage with white sharks in particular and all other large species of sharks.”
It was while diving with sharks that Rutzen realised they didn’t like to enter the kelp forest, even when pursuing Cape fur seals, something most spear fishermen in South Africa are aware of.
“But what makes Mike special is that he took the extra step of envisioning a fake forest of kelp to replace the shark nets. At the end of 2011, an American scientist [marine biologist Craig O’Connell] came to work with us to test magnets as a shark deterrent.”
Rutzen and Andreotti presented their draft to O’Connell and offered to work together. The concept was registered in 2012 as a patent through Stellenbosch University’s technology transfer company, Innovus, and commercialised two years later.
Since 2012, the technology has undergone rigorous testing in the turbulent ocean waters along the South African coast, as well as in the tropical waters of Réunion island and the Bahamas. The results from several of these case studies have been published in peer reviewed scientific journals.
The thinking behind the development of the SharkSafe Barrier concept is a combination of practical experience with sharks and marine biologists’ understanding of their behaviour, Andreotti said.
Firstly, fish and other marine animals such as seals have been observed to use kelp forests as a hiding place from predatory sharks. By bio-mimicking a natural kelp forest, created by overlapping rows of plastic pipes anchored to the seabed, the SharkSafe Barrier has proven to be an effective deterrent for predatory sharks.
Secondly, marine biologists know that most shark species are sensitive to strong permanent magnetic fields because of the presence of electro-magnetic receptors at the tip of their heads. These small gel-filled pores, which are called Ampullae of Lorenzini, are connected directly to sharks’ brains and allows them to register faint bioelectrical impulses dispersed in the water from their prey.
Using this knowledge, the developers created a strong magnetic field by inserting magnets into the kelp-like pipes. However, instead of attracting the attention of a shark, the overly strong magnetic field over stimulates the Ampullae of Lorenzini and acts as another repellent. By inserting strong magnets into the kelp-like pipes of the barrier, it further strengthens the ability of the design to repel sharks, Andreotti said.
The SharkSafe Barrier consists of high-density polyethylene pipes, which are manufactured locally by KND Fabrications in Maitland, Cape Town.
During installation in the ocean, the buoyant pipes are anchored on a grid-like structure one metre apart from one another, with large ceramic magnets staggered in the ocean-facing row. The grid is then weighted by limpet-shaped 200kg cement blocks and secured by rock anchors and sand.
It has been designed to remain in the water for at least 20 years with minimal maintenance required. This offers an opportunity for marine life to settle on the cement blocks, which anchor the barriers to the seabed, forming an artificial reef.
Two months after the Bahamas installation, “there’s very little biofouling happening so the cleaning regime is going to likely be once every three months, or not even”, Andreotti added.
The first commercial installation is the breakthrough the team has been working towards for the past 15 years. “We now have the technology to allow the rightful inhabitants of the oceans to survive and thrive, and for sea-loving humans to enjoy their time in the water safely,” she said.
This is a “win-win situation”, especially for areas that rely on ocean recreation as a main source of revenue, such as beach towns in South Africa, Brazil, New Caledonia, the Bahamas and Réunion.
“Of course, the whole reason why we’re doing this is to replace and put a stop to shark nets,” Andreotti said, noting how South Africa and Australia are among the few countries that deploy” these “lethal fishing devices around the coast” to reduce shark-human encounters.
Shark nets have been in use since the 1950s.
“We all know that shark nets are not clearly killing as many animals as fisheries but they’re using gill nets that are otherwise illegal because of the high amount of bycatch.
“They’ve been replacing shark nets with baited hooks called drumlines to reduce bycatch of dolphins and turtles in some areas but increasing the catches of large predatory sharks, including vulnerable and protected species such as the white shark. They are receiving an exemption to kill white sharks, which fisheries don’t have, of course. And on top of all that, they’re not killing sharks … for consumption but out of fear.”
On average, there are six to eight shark-related fatalities globally annually.
“In this day and era, we should look to alternatives that work better, that are actually keeping sharks separate from people, without killing marine life and that have been proven to be effective.”
Andreotti’s next step is to engage with the KwaZulu-Natal Sharks Board, to “see if they can lead the way by keeping their organisation but changing the technology.
“We have evidence that the white shark population is doing very badly in South Africa. They haven’t been seen in False Bay, Gansbaai and the number in Mossel Bay has been declining.
“Our genetic study showed that their genetic pool is not strong enough anymore and our photo ID study showed the number has been declining rapidly in the last 10 years,” she said. “If we can take any action to reduce the threats to these animals before they become extinct, it will be advisable.”