Keeping the sharks at bay
SA’s underwater electric fence could be the answer
DOZENS of people are attacked by sharks every year. Fear among tourists is rife and industry profits are taking a hit. A new underwater electric fence — developed and tested in South Africa — aims to stop sharks from getting close to bathers.
Nasief Jaffer, a 24- year- old surfer, emerges from the ocean, surfboard expertly tucked under one arm. He is at Muizenberg beach, one of South Africa’s top holiday destinations.
A black flag featuring the white outline of a shark is flapping in the wind behind him. “Caution”, the flag indicates. “Shark- spotting conditions are poor.” Unperturbed by the disclaimer, Jaffer shrugs. “I go surfing several times a week. I trust the shark spotters,” he says.
The Shark Spotters is a beach- safety organisation that aims to protect swimmers and surfers from attacks on Cape Town’s popular southern peninsula. The Atlantic Ocean around Cape Town is home to the largest Great White population in the world, the most dangerous and aggressive of all shark. For 10 hours each day, shark spotters take up positions on mountains overlooking nine popular beaches, searching the water for predators. If they see a shark, they alert a colleague on the beach, who sounds a siren and raises a white flag. Within minutes, everyone clears out of the water.
But the Shark Spotter programme, although lauded as a success, has a major weakness: human error.
“It’s a highly responsible job. It’s very stressful, especially on days with poor visibility,” says shark spotter Liesel Lott, while scanning the ocean with binoculars.
Pressure mounts during the summer, which is the sharks’ in- shore hunting season. “We expect to sight sharks every day at this time of year,” says Shark Spotters field manager Monwabisi Sikweyiya.
Over the past decade, more than 1 700 sharks have been spotted near the beaches of Cape Town’s southern peninsula alone, most of them Great Whites. Some as close as 50 metres to the shore.
National conservation and research organisation the Sharks Board records an average of six shark attacks per year in South Africa. That might not sound like much, but every accident raises fears, and memories of Steven Spielberg’s iconic movie Jaws.
“Shark attacks have huge impact on tourism,” says Sharks Board chief scientist Geremy Cliff.
On South Africa’s east coast, nets prevent the predators from getting too close to the shore. But the meshwork catches not only sharks, which drown when immobilised, it also kills other sea animals, including dolphins, turtles and rays.
As a result, the Sharks Board has spent the past three years developing an environmentally friendly solution to keep sharks at bay: an underwater electric fence that harms neither humans, sharks nor any other marine animal. The fence consists of a cable fixed to the sea floor from which vertical cables rise to the surface. The cables emit a low- frequency signal, creating an electric fence that repels sharks whose noses are extremely sensitive to electricity.
If humans accidentally touch the cable, they feel only a tingling sensation. Two 100- metre- long prototypes have been installed at Glencairn beach, 12 kilometres from Muizenberg. A high- definition camera on a peak opposite the bay films water activity to show if the fence effectively repels sharks.
“It’s a world first. The design stretched our technical capability,” says Claude Ramasami, project manager at the Institute for Maritime Technology which developed the fence.
Installing electricity safely in water, an ever- shifting sea bottom, the force of the waves pounding the equipment and corrosion, all add to the difficulty.
By the end of March, the Sharks Board hopes to have sufficient data to prove the electric fence is working.
“If we’re successful, it could be installed around the globe,” says Sharks Board project manager Paul von Blerk, who is overseeing the trial phase. Initial data indicates positive results, he adds. This would, for example, make bathing safer in the United States, which recorded 47 unprovoked shark attacks in 2013, or in Australia, where 10 accidents were reported that year, according to the International Shark Attack File of the Florida Museum of Natural History.
Even surfers like Jaffer say they would welcome the electric fence. “I’d feel much safer,” he admits.
— Sapa- dpa.
Bathers are informed about the shark- spotting programme at Muizenberg beach, Cape Town. Could an electric fence make bathers even safer from shark attack?