Are we creating killer sharks?

An increase in attacks by great white sharks is alarming Cape Town residents. But maybe people are to blame, writes Scott Calvert

After yelling to his brother that a great white shark was swimming his way, Achmat Hassiem watched as it changed course - to head towards him. The 13-foot shark bit his right foot, shook violently and took him under. Seconds later, Hassiem was pulled into a nearby boat, alive - but without his foot.

This episode in False Bay last August was the latest in a string of great white incidents around Cape Town that have stirred emotions about a creature often demonised, intensifying a debate about how to balance safety and conservation.

Some surfers say "rogue" sharks that repeatedly turn up near people should be killed. Researchers insist rogue sharks do not exist and that a hunting ban imposed by South Africa in 1991 is key to the endangered species' long-term survival.

Looking for clues to explain the trend, some people have pointed a finger at the growing cage-diving industry that puts tourists in an underwater cage and lures great whites with bait. So far no research has found any link between cage diving and attacks. Others suggest that overfishing has lured hungry sharks closer to shore. Some say there are simply more people in the water.

What everyone agrees is that there has been an increase in unprovoked shark bites on people, or small craft, along Cape Town's nearly 200 miles of shoreline. In the past four years, 13 have been recorded, three of them fatal; in the previous 42 years, there were 17, only one fatal. Nearly all of the attacks are thought to have involved great whites. In two of the recent fatalities - a swimmer and a spear fisherman - the bodies were never recovered.

"We're looking for a balanced approach to this issue without flying off the handle," said Gregg Oelofse, Cape Town's environmental policy and research co-ordinator. To that end the city is expanding to 11 beaches a shark-spotting programme that a group of surfers started at two beaches in 2004. Lookouts on hillsides or in towers sound a siren to warn of a shark and can close a beach until it swims away.

The city plans to put independent observers on cage-diving vessels in False Bay to ensure that operators do not feed sharks - which could condition them to associate boats with food - and do not abuse the animals by enticing them to smack the cage solely to thrill tourists.

Cape Town is also exploring the viability of using exclusion nets to repel sharks from certain beaches. Unlike shark nets used off Durban's Indian Ocean coast, exclusion nets have fine mesh that does not entangle sharks or other creatures. The nets could be removed whenever whales were present.

Apart from the shark spotting, none of the measures would enhance safety for surfers, kayakers and surf-ski riders who venture a couple hundred yards from shore. (Nets work only in calmer water between the shore and breakers.) The relative newness of kayaking and surf-skiing as sports in Cape Town, along with advanced wetsuits enabling surfers to remain in the chilly water for hours, have raised the odds of shark-human encounters, Oelofse said. Most involve great whites, considered the top fish predator of the seas, and might occur when a shark mistakes a person for a seal or is simply curious or aggressive.

Long-time surfer Paul Botha has riled shark researchers by calling for "selective culling" of rogue sharks. He questions how they know rogues are a myth when so much about great whites - their mating, breeding, migration patterns, population - is so poorly understood.

He also calls for sonar buoys to track sharks, a system he likens to the use of closed-circuit cameras in cities to deter crime. The technology exists, but some experts say it might not be feasible or practical. One existing option for surfers is to wear electronic "shark shields" that emit weak pulses shown to repel sharks.

Botha, an event promoter, blames the rise in great white incidents on three factors: over-fishing that has deprived sharks of food; the 1991 protections that he thinks have raised the shark population; and cage diving. Most of his unscientific views are not shared by researchers, such as University of Cape Town doctoral student Alison Kock. She says an increase in people using the water, not more sharks, explains the trend, which is part of a global pattern.

Because it takes the sharks a decade to mature sexually, it is "physiologically impossible" that the 1991 protections have caused a significant population boom.

She dismisses the theory of a rogue shark by pointing out that hundreds of great whites have been identified and thousands of people enjoy Cape Town's waters, yet attacks are still rare even with the recent spate.

"If these sharks were man-eaters, there would be an attack every day," she said. And because great whites are migratory rather than resident, killing five or 10 would make little immediate difference as five or 10 more would replace them.

- LA Times/Washington Post Service