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Tests on barrier to protect sharks

  Monday, 21 July 2014
 Tony Carnie (The Mercury)
Tests on barrier to protect sharks

Cliff said the KZN Sharks Board was committed to investigating alternative bather-protection systems that would reduce the death rate of large sharks, dolphins, turtles and other marine species. Photo Credit: Morne Hardenberg

"The KZN Sharks Board is hoping to conduct a series of renewed experiments with electric cables this year as a potential alternative to the net system that has protected bathers from shark attacks for almost half a century."

The tests will probably be held in Cape Town’s False Bay later this year and early next.

Geremy Cliff, head of research at the KZN Sharks Board, confirmed it had received funding from the provincial government that would allow it to pursue research into electrical shark repellent technologies developed initially in the early 1990s.

He was responding to queries from The Mercury about a separate series of recent shark-repellent experiments by the Sharksafe group, using plastic pipes and magnets.

Cliff said the KZN Sharks Board was committed to investigating alternative bather-protection systems that would reduce the death rate of large sharks, dolphins, turtles and other marine species.

In apparent reference to previous legal and intellectual property tussles, Cliff said: “We have learnt from our mistakes of jumping the gun when it came to developing the Shark POD (protective oceanic device), so we are progressing cautiously and will wait before publicising any successes.”

The protective oceanic device – a portable battery-powered device designed to repel sharks with electrical pulses – was initially marketed by the board in the mid-1990s until sales rights were granted to an Australian company in 2001.

Electrical pulse technologies are designed to exploit the fact that most sharks have highly sensitive electrical receptors in their snouts, known as the Ampullae of Lorenzini.

These tiny, gel-filled sacs sense electrical current from their prey at very close distances.

‘Encouraging’

Cliff said if the new experiments in False Bay were successful, the technology could be used in calmer waters in South Africa (at Fish Hoek beach in Cape Town and possibly Second Beach at Port St Johns) as well as in parts of Australia, Reunion, Seychelles or Brazil.

Maintaining and anchoring an electrical cable barrier at high energy surf-beaches in KwaZulu-Natal was likely to create challenges, he said.

Commenting on the recent plastic pipes and magnets Sharksafe trials at Gansbaai, Cliff said the results were “very encouraging” particularly as the tests involved great white sharks.

However, as the developers had acknowledged, there were gaps in the Sharksafe barrier that allowed great whites to bypass the magnetic and plastic pipe zones and so more research was needed before the technology could be used to protect swimming beaches.

Cliff said he welcomed any efforts to develop more ecologically friendly methods of protecting bathers and noted that there had been a 64 percent drop in sharks killed in the KZN shark nets over the past 30 years.

For example, an average of 1 400 sharks were caught in the nets every year during the 1980s, compared with current levels of about 570 a year (of which more than 10 percent were released alive).

Since shark nets were first deployed on the Durban beachfront in 1952 there had not been a single shark attack off the city’s beaches. Along the rest of the KZN coast, where there are 36 other protected beaches, there had been only two (non-lethal) attacks over the past three decades.

“The impact of shark attacks on coastal economies is a long-standing, worldwide phenomenon and not simply one that resulted from the hysteria following the Jaws movie. A spate of shark attacks in the Margate area in KZN in December 1957 (infamously remembered as Black December) resulted in economic disaster for the tourism industry.”

 

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