Gloomy picture for great whites
Share this article:
Durban - A new study into South Africa’s great white sharks suggests there are now less than 600 of these fearsome predators left along the country’s southwest coastline.
Presenting the results of a five-year study at the Sharks International conference in Durban last week, Italian-born marine biologist Sara Andreotti said there was an urgent need to protect this apex group of predators from further decline – even though South Africa became the first country in the world to pass laws, in 1991, to protect them legally and outlaw their killing.
Andreotti said the study suggested there were now between 480 and 580 great whites left between Port Nolloth, near the Namibian border, and Algoa Bay, near Port Elizabeth.
Though Andreotti’s estimates exclude much of the KwaZulu-Natal and Eastern Cape coastline, the results paint a precarious picture about the conservation status of the South African population of highly mobile great white sharks, which have been persecuted by fishermen and were once hunted deliberately for shark-jaw trophies.
The last known scientific estimate of great whites along the South African coastline was done about 20 years ago, when Geremy Cliff of the KwaZulu-Natal Sharks Board estimated there were about 1 300 great whites between Richards Bay in KwaZulu-Natal and Struisbaai in the Western Cape.
At a global level, the number of great white sharks is thought to have plummeted by nearly 80 percent between 1986 and 2006 in the north-west Atlantic, with indications of similar population crashes in other parts of the world over the same time period.
Andreotti’s research, part of her doctoral thesis with the evolutionary genomics group at Stellenbosch University, is based on two different methods between 2009 and last year: genetic tissue samples taken from great whites between Port Nolloth and Algoa Bay and photographic identification of individual great white shark fins in Gansbaai, where large numbers of the sharks gather yearly to feed, mainly on seals.
She said estimating shark populations accurately was extremely challenging because of their elusive nature and ability to migrate over vast distances. Satellite tracking records have revealed that some great whites from South Africa migrate as far as New Zealand and Australia.
Andreotti, who hopes to extend her study to include estimates along the KwaZulu-Natal coastline, said there was a critical need to improve long-term conservation strategies “before it is too late”.
“We need to look at non-invasive and non-lethal bather protection strategies.”
Andreotti said she was not campaigning against legally sanctioned shark net schemes, but urged the KwaZulu-Natal Sharks Board to accelerate its efforts to introduce non-lethal bather-protection methods.
It is believed an average of 25 great whites die every year in the province’s bather-protection system, which includes nets and baited drumlines.
The KwaZulu-Natal Sharks Board has also been working for several years on developing a non-lethal electrical repellent cable as an alternative to shark nets, but no announcements have been made recently on the progress of this research.
In Cape Town, a new experimental shark exclusion barrier scheme was established at Fish Hoek beach early last year, with preliminary results suggesting not a single shark had been killed. The only reported death was a cormorant.
l Andreotti’s study was conducted in collaboration with five other researchers from Stellenbosch University, Shark Diving Unlimited in Gansbaai and the Department of Environmental Affairs in Cape Town. - The Mercury