Weekend Argus (Saturday Edition)
Poaching, nets see local great whites facing threat of extinction
The loss of the sharks would see an increase in the Cape fur seal population, which in turn would affect fish populations, writes SHEREE BEGA
AT FIRST, Dr Sara Andreotti got sick. Very seasick. Out on a large catamaran, the shark scientist would, on her worst days, implore her crew to take her back to shore.
“I didn’t have my sea legs,” said the 32-year-old Italian. “The moment we hit the ocean, the seasickness would arrive – I had to drink seasickness tablets every day.”
But Andreotti, of the evolutionary genomics group at Stellenbosch University’s botany and zoology department, was living her dream: studying great white sharks.
On the catamaran, equipped as a research vessel and loaned by world-famous shark cage diver Michael Rutzen, Andreotti would spend months-long voyages at sea, cruising Gansbaai and South Africa’s vast coastline, searching for great white sharks and counting them all on a shoestring budget.
The sea has always called to Andreotti; she worked as guide for a natural marine reserve in Italy when aged 16. Her fascination brought her to South Africa in 2007, where she encountered great white sharks and fell “in love with these magnificent animals”.
“Everyone has a misconception that the great white is a mindless killing machine, but that is not the case,” she said. “They appear to think about everything they do. Of course they are formidable predators, but that doesn’t mean they’re targeting humans like people believe… It’s very stressful if you consider you want to spend your life studying them.”
But it’s South Africa’s great white sharks, not its humans, that are in dangerous waters.
This week Andreotti revealed the results of the groundbreaking six-year study she led; there are only between 353 to 522 individual such sharks left off South Africa.
The iconic species is on the brink of extinction. “The chances for their survival are even worse than what we previously thought,” she warned. “Their numbers might already be too low to ensure their survival.”
Her pioneering research, recently published in the journal Marine Ecology Progress Series, was conducted with Rutzen – who helped Andreotti locate the sharks – and the Department of Environmental Affairs. It represents the largest field research study on South Africa’s great whites undertaken to date.
Our great white population is in “double jeopardy” – not only are their numbers worryingly low, but they have the lowest genetic diversity of all great white shark populations worldwide.
Andreotti and her fellow researchers blame the impact of shark nets and baited hooks in KwaZulu-Natal, poaching for shark jaws, habitat encroachment, pollution and the depletion of food sources for the sharp decline.
Rutzen, who is known as “Sharkman” for his epic free-dives with great white sharks to dispel the myth they are man-eating monsters, agreed. “In the 1990s, it was not uncommon to have 20 great whites around our boats. We’re lucky these days if we have between one and three… Shark nets are not a protection device, but a killing device.”
The end of great whites will affect the ecological stability of South Africa’s marine environment. “A decrease in white shark numbers will lead to an increase in the Cape fur seal population, which in turn will have an impact on fish populations and thus on fisheries,” notes the paper.
Between 2009 and 2011, Andreotti and Rutzen collected nearly 5 000 photographs of the dorsal fins of white sharks frequenting Gansbaai, a shark hotspot. The notches in dorsal fins are like a unique fingerprint with a specific number of notches on their trailing edges. The researchers had to be sure the sharks, who all have “different personalities”, got close enough to their boat to take a clear picture of the dorsal fin and to collect a biopsy for genetic analysis.
According to Andreotti, there are now 52 percent fewer than estimated in previous similar studies.
Using chum to lure the sharks to their boat was very “dodgy”, said Andreotti. “They see the head of a dead tuna running away from them… that’s probably something they have not seen in their lives and they probably don’t like it.”
They had to be certain the sharks they identified and counted in Gansbaai were representative of the entire white shark population. So they set sail again, spending another four years sailing along the coastline, collecting biopsy samples and snapping photos of dorsal fins.
“The subsequent genetic analysis then proved that there is only one population and that the same sharks are roaming the coastline,” said Andreotti.
Her genetic study shows an effective population size of only 333 individuals. “The threshold is calculated at 500 for other species to prevent inbreeding depression. If that applies to white sharks, we’re already in big trouble because my estimates don’t even reach 350.”
Between 1978 and 2008, 1 063 white sharks were killed in shark protection measures, she said. “We can’t be protecting sharks on one side and killing them on the other. Every time a shark comes too close, we kill it. Human beings need to change their attitude towards the oceans. There are cobras on mountains, but we still go hike there. The sooner we start looking at sharks in the same way, the better.”
Stellenbosch University has developed the Sharksafe Barrier, an environmentally friendly artificial magnetic kelp, which may be implemented in December, said Rutzen. Sharks are repelled by magnetism.
Shark nets “are something we should stop tomorrow”.
“But pollution and management of the food sources is something that will take much longer to be fixed, as well as poachers, who are always difficult to control,” Andreotti said.
There is a move to include great whites on Appendix 1 of the Convention on International Trade in Endangered Species of Wild Fauna and Flora, in September, which will afford white sharks greater protection. Andreotti said understanding population dynamics can play a critical role in developing conservation strategies for species in peril.
“We must do what we can while we can,” said Rutzen, who foresees the imminent demise of the local cage diving industry. “Our great whites are facing a tough battle. Now we know from our research what the facts are, so we can hopefully help save them.”
Until their study, said Rutzen, most conservation efforts were based on “gut feelings and people’s perceptions”. But the bleak findings have also caused some controversy. On the university’s Facebook page this week, users like Greg Kellermann wrote that shark numbers had exploded and he “still can’t understand the motivation for claiming their near extinction”.
Andreotti said: “Simply put, seeing a shark 20 times does not mean there are 20 sharks.
“This is the largest photo identification and genetic database of great white sharks in South Africa, and will serve as the benchmark for future observations and the conservation of this top predator.” sheree.bega@inl.co.za