Protecting sharks and humans from up high
When a shark is sighted, the shark spotters will encourage all water users to clear the water
From the ridges flanking False Bay, a group of people constantly scan the blue waters below. The spotters are on the lookout for sharks, armed with antiglare sunglasses, a pair of binoculars and a walkie-talkie.
According to new research, published in journal PlosOne, manual shark spotting works. The research also found a strong overlap between shark activity and when people go swimming. The research, using spotter data from False Bay’s beaches between 2006 and 2014, found that shark sightings — and water users — were highest in the spring and summer months, and lowest in June and July.
Shark activity peaks during the day between 9am and 4pm — when people want to swim in the water. This is according to research undertaken by University of Cape Town doctoral candidate Tamlyn Engelbrecht.
"Despite this," the authors write, "there was a low rate of shark-human incidents, which we attribute to the Shark Spotters programme."
On average, there are fewer than one shark attack every two years. While the research does show that there are many sharks around, it also highlights "how little conflict there is".
The initiative is unique, says Sarah Waries, programme manager at Shark Spotters and a co-author of the paper. "In other areas, they’ve implemented aspects of the programme, but nowhere runs [their programme] the way we do."
The Shark Spotters sit on the mountains overlooking the beaches. If they see the shadow of a shark entering an area, they communicate to people on the beach, who — literally — flag the presence of a shark.
There are four different flags they can raise: a green flag (which means good spotting conditions. All clear), a black flag (poor spotting conditions), a red flag (high shark alert. Caution advised) and a white flag (Shark sighted … leave the water).
"When a shark is sighted in close proximity to water users, the siren will sound and shark spotters will actively encourage all water users to clear the water," the authors write.
Waries describes the system as an environmental solution. Shark Spotters provides shark safety services to the City of Cape Town, but is also funded by international not-for-profit Save our Seas.
Gregg Oelofse, manager of the City’s coastal management department, says it asks water users in the Cape to work with shark spotters to stay safe, rather than killing sharks or excluding them from their marine habitats.
The programme operates on eight beaches and in the winter months, there are 16 spotters, increasing to about 30 in summer when sharks are more active. Cape Town has one of the highest aggregations of great white sharks outside a major city in the world.
"It started here," Waries says. "Other places in the world are still using lethal control of sharks, like Durban, Australia and Reunion Island. The idea is that if there are fewer sharks in the area, so there are fewer sharks to bite people."
But this strategy is taking a toll on ocean ecosystems and biodiversity. Research at the University of Stellenbosch has found that the South African great white — an apex predator, sitting at the top of the ocean food chain — is under threat. These predators maintain the balance and health of the oceanic ecosystem, eating weak or sick animals and in the process, controlling population sizes.
But more than 90% of SA’s great white sharks share the same genetic sequence, according to research by Sara Andreotti published in 2015. This is problematic as it makes the species less able to adapt to disease or changing environmental conditions, such as climate change.
Andreotti, now a postdoctoral researcher in the management and conservation of great white sharks at the university, conducted a follow-up study, published last year.
Writing in The Conservation, Andreotti says: "The results of our study paint a very gloomy picture, with an estimated 333 breeding white sharks, based on samples collected around the entire coastline, for the South African population."
A species requires at least 500 breeding individuals to avoid inbreeding and to make the population sustainable, she says. Lethal control of sharks has negative effects on the environment, notes Waries.
"Shark spotters is the environmentally responsible solution because we’re not impacting shark populations at all.
"We’re trying to educate people, get people to move out of the way of sharks and understand about shark risks and then they can make an informed decision to minimise the risk of encountering a shark."
She says that the system could be taken to other beaches, but it has one major limitation: there needs to be an elevation close to the sea. "It’s limited at this stage by elevation, but we’re looking at ways to overcome that, such as camera systems."
But the programme also benefits science and research, Waries says. "The shark spotters are not just looking for sharks. They’re collecting data, filling in data sheets every day, and those sheets contain everything from the weather conditions to marine activity, sharks, dolphins, whales."
The spotters are citizen scientists and even though "they’re not trained as scientists, they collect data that can be scientifically analysed, and published in peer-reviewed journals".