Nets against the jaws

Sharks lurking in the surf at a top tourist beach will soon be locked out of their hunting grounds during the day.

Cape Town is getting ready to test the world's first retractable shark exclusion net in Fish Hoek, where several people have been killed by the ferocious predators.

The exclusion netting is of a finer mesh than those of gill nets.

Jeremy Cliff of the KwaZulu-Natal Sharks Board said nearly 600 sharks were entangled in gill netting each year off the KwaZulu-Natal coast.

"About 10%-15% of those are actually released, but around 450 sharks die in those nets each year," said Cliff.

Fish Hoek - about 25km from Cape Town - is popular among South African holidaymakers, but controversy has simmered for years over fatal attacks by great white sharks in the bay.

Now it is hoped the retractable netting will protect humans, without killing the sharks.

The 340m-long net will be anchored on the beach and sea bed, and pulled across the sea by fishing boats in the morning and retrieved in the evening.

Shark spotters, who already sound the alarm if sharks enter the bay, will monitor shark activity around the nets when bathers are in the water.

Gregg Oelofse, the head of Cape Town's environmental resource management department, said the net would be in place by January 2013, and if the pilot project was successful, it could be rolled out at high-risk beaches around the Peninsula.

The netting was manufactured locally, he said.

"We want to run it on a daily basis in Fish Hoek and then see if it is effective as a safety area, so that we can possibly create a complete safe zone.

"We need to see how well the net holds up against environmental conditions such as strong winds and wave action," Oelofse said.

The city also needed to monitor the net's environmental impact.

Cape Town had originally intended to deploy a permanent exclusion net similar to those used in Hong Kong and parts of Australia.

Oelofse said: "Although we were going to proceed with that design we were concerned with the high levels of marine biodiversity we have. Particularly overnight, when we could not monitor the net, there would be a risk of entanglement, and that is one thing we want to avoid during this trial period.

"And if it becomes a permanent fixture we'd like to avoid any entanglement of dolphins, whales or sharks," Oelofse said.

Alison Kock, a shark expert and consultant on the pilot project, said the effect of the net on marine ecosystems would have to be monitored.

"Because it's such a novel structure ... in terms of retrieving it daily instead of having it go in overnight, we have to monitor all kinds of interactions. Whether it's with seals, whales, dolphins or sharks," she said.

"We have to take that into consideration, and it was one of the first concerns with using this type of net. Given the design of the net there is still a possibility, if it is a very small animal. But the way of mitigating that happening is to constantly monitor the net."

Kock said some sharks might see the new net as a curiosity.

"We do know that they are quite inquisitive animals and it is possible they would investigate the structure that will be put into the Fish Hoek area.

"How they respond to that will differ between individuals," Kock said.

Angela Botha, owner of Fish Hoek Tourism, said: "I'm glad there is something to protect swimmers now. I hope it's a success as well, because other places to swim like tidal pools are unsafe now because of the dangerous people who hang around there."