Durban – The South African great white sharkis heading for possible extinction, according to research by Stellenbosch University.
“The chances for their survival are even worse than what we previously thought,” the university’s Dr Sara Andreotti of the department of botany and zoology, warned.
She is lead author of the study published in the journal, Marine Ecology Progress Series. It is the first of its kind conducted on great whites and shows there are between 353 to 522 such sharks left in South African waters.
“The numbers in South Africa are extremely low. If the situation stays the same, South Africa’s great white sharks are heading for possible extinction.”
The university said the findings were based on six years of fieldwork conducted at Gansbaai and along the country’s coastline.
Andreotti and Michael “Sharkman” Rutzen, of Shark Diving Unlimited, who had been operating a white shark cage diving operation at Gansbaai for the past 15 years, tracked down the sharks.
After two years at Gansbaai, the pair spent another four years sailing along the coastline collecting biopsy samples and photographing dorsal fins.
“When looking at the number of adults counted with the photo identification work, we have come to the conclusion that South Africa’s white sharks faced a rapid decline in the last generation and that their numbers might already be too low to ensure their survival,” Andreotti said.
Shark nets, poaching
Shark nets and baited hooks on the eastern seaboard were among the reasons behind the rapid decline. Other contributing factors were poaching, habitat encroachment, pollution, and depletion of their food sources.
Between 1956 and 1976, the number of large sharks caught in KwaZulu-Natal’s shark-netting programme declined by over 99%. Between 1978 and 2008, approximately 1 063 white sharks were killed in shark protection measures, she said.
Illegal poaching for trophies like jaw sets and fins was another threat.
The loss of such a predator would have a cascade of detrimental effects on the ecological stability of the marine environment. Urgent measures to stop the decline needed to be put in place.
Rutzen said no one really knew the exact number of great white sharks left in the oceans.
“Many speculate that population numbers are increasing, but their claims cannot be backed up by solid research or an extensive database like the one created by Dr Andreotti and her team of collaborators.”
The study had to be replicated on an international scale and techniques for collecting data on population numbers of vulnerable species such as the great white had to be standardised.
“While everyone is working on their own, the king of the ocean could be on the brink of extinction,” he said.