Great white shark close to extinction

New research claiming nets to blame for numbers drop is rebuffed by board

LONG lining, trophy hunting and other fishing are more likely to affect shark populations than the nets off KwaZuluNatal’s bathing beaches.

That is according to uMhlanga-based KZN Sharks Board scientist Dr Matt Dicken yesterday, following explosive research findings released this week by Stellenbosch University’s Dr Sara Andreotti. She has warned the great white shark is on the edge of extinction, with her research citing more than 1 000 being killed in “shark protection measures” from 1978 to 2008.

Andreotti said the results of a six-year study indicated there were only “353 to 522 individual great white sharks left in South Africa. The chances for their survival are worse than we thought. Their numbers might already be too low to ensure their survival,” she said.

Her research, which has been published in the journal Marine Ecology Progress Series, blames the impact of shark nets and baited hooks in KwaZulu-Natal, poaching for jaws, habitat encroachment, pollution and the depletion of food sources for the estimated sharp decline.

For her research Andreotti, with shark cage diver Michael Rutzen, identified and counted the population in Gansbaai off the Cape coast, collecting samples and taking photographs of their dorsal fins.

“The subsequent genetic analysis proved there was only one population (consisting of 333 sharks) and that the same sharks are roaming the seas.

But these findings have been countered by the board, whose figures indicate the average number of great white sharks caught in shark safety gear over the past 10 years is 26, with five of those being released alive.

Dicken said, “This equates to an average mortality of 21 sharks per annum along a 320km stretch of coastline.

“Although there are no other official catch records, it is likely that white sharks are either incidentally or deliberately caught, targeted and killed in higher numbers in other fisheries, especially shark long lining. As an example, commercial fisheries off the coast of Baja, California catch over 100 juvenile whites annually.”

The board safety gear is made up of 22km of nets and 107 drum lines.

Dicken said the population estimate provided by Andreotti’s research was “surprisingly low”, adding this was “a sentiment shared by all other white shark researchers” he had spoken to. He was unaware of any scientific evidence which pointed to a dramatic reduction in the population of white sharks in South Africa.

“There is evidence in some locations that the population is in fact increasing,” he said.

Over the past 25 years, the board has halved the number of nets along the coast which, according to Dicken, has resulted in a decreased number of great whites being caught. It has been “pursuing the development of an electrical shark-repelling cable which, thanks to funding from the KZN government, has made significant progress in the past four years,” he said.

A short prototype cable was successfully tested off Mossel Bay this year.

Regarding the differing data from different researchers, Dicken said that there were several experienced shark researchers working on white sharks at other congregating sites in the Eastern and Western Cape.

“Ideally, we need to combine all these studies to improve our accuracy and confidence in an estimate of the white shark population in South Africa. This is something we are working on,” said Dicken.

The director of education at uShaka Sea World, Jone Porter, said great whites were uncommon in KZN waters, as they preferred colder water.

“It’s easy to blame the shark nets. Other problems include by-catch by fisheries which sees sharks being caught accidentally in their nets. There’s also a huge recreational fishing fraternity here, trophy hunting for jaws, and there’s pollution coming down rivers.”

Porter said there was a huge variety of sharks in KZN waters, with top predators being ragged tooth, tiger and Zambezi. “These play a key role in maintaining ocean health.”