Coast KZN

20 Jul 2016

Extinction threat for SA’s great white sharks

Sheree Bega

Great white populations along SA’s coast are half of what previously estimated. Photo Credit: Sara Andreotti

They have roamed South Africa’s waters for millions of years but South Africa’s great white sharks are swimming dangerously close to extinction.

This is according to the “gloomy” findings from a groundbreaking six-year great white research project, the results of which were released this morning in Cape Town.

The research by a team led by Dr Sara Andreotti and her colleagues from Stellenbosch University as well as “Shark man” Michael Rutzen of Shark Diving Unlimited, reveal there are 353 to 522 great white sharks left on the country’s coastline.

This is 52% fewer than what was estimated in previous similar studies, explains Andreotti.

Their study, which was published last month in Marine Ecology Progress Series, represents the largest field research study on South Africa’s great white sharks undertaken to date.

The findings are based on six years of fieldwork in South Africa’s shark mecca, Gansbaai, and along the South African coastline.

South Africa’s great whites, says Andreotti, are in double jeopardy. “Not only do these sharks have the lowest genetic diversity of all white shark populations worldwide; there are also only between 353 to 522 individuals left.”

Between 2009 and 2011, Andreotti and her team collected nearly 5 000 photographs of the dorsal fins of white sharks frequenting Gansbaai. But they needed to be sure that the white sharks that they identified and counted in Gansbaai were representative of the entire white shark population along the coastline.

So, they set sail again and spent another four years sailing along the coastline, collecting biopsy samples and photographs of dorsal fins. The subsequent genetic analysis then proved that there is only one population and that the same sharks are roaming the coastline.

Andreotti blames some of the reasons for the sharp decline on the impact of shark nets and baited hooks implemented on the eastern seaboard of South Africa.

Other contributing factors are poaching, habitat encroachment, pollution and depletion of their food sources. The survival of white sharks in South African water is also threatened by the illegal poaching for trophies (jaw sets) and fins.

“The loss of such an apex predator will have a cascade of detrimental effects on the ecological stability of the marine environment,” she warns.


Online Article