Cleaner water blamed for spate of shark attacks

Cleaner water in Sydney Harbour and off nearby ocean beaches is being blamed for a series of shark attacks, with a 15-year-old surfer badly mauled yesterday in the third such incident in three weeks.

Andrew Lindop underwent four hours of surgery after a 6ft shark bit his thigh, down to the bone, while he was surfing with his father, Charles, at dawn off Avalon Beach. Police said Charles, who had just caught a wave, "heard a scream and turned to see his son thrashing about in the water". He dragged Andrew to shore, where he administered first aid, helped by lifesavers who used beach towels and a surfboard rope to stem the bleeding.

It was Sydney's third shark attack in 19 days, at a time when the beaches are packed with locals and tourists enjoying the summer weather. Yesterday Avalon and four neighbouring beaches in the northern suburbs were closed as a helicopter flew over the area, searching for the culprit.

A Royal Navy diver, Paul de Gelder, had to have an arm and leg amputated after being attacked by a bull shark in the harbour on 11 February. Thirty-six hours later, an 8ft great white savaged a surfer, Glenn Orgias, off Sydney's most popular tourist beach, Bondi. Surgeons managed to reattach his hand, which had been left hanging by a one-inch flap of skin.

Ironically, perhaps, measures to protect Sydney's beaches and marine environment are said to be largely responsible for the recent spike in attacks. Water quality is at its highest for decades – but cleaner water means more fish, which means more sharks closer to shore, where they encounter swimmers and surfers.

Fish stocks are also healthy because commercial fishing has been banned in the harbour since 2006, when high levels of dioxin were found in the catch.

While yesterday's incident alarmed already jittery Sydneysiders, authorities said it demonstrated the dangers of entering the water at dawn and dusk, when sharks generally feed. The state's Primary Industries Minister, Ian Macdonald, said: "We have warned people repeatedly not to swim at dawn or at dusk. These recommendations are based on scientific knowledge and people need to pay heed."

It was not immediately clear what species of shark attacked Andrew Lindop, who was in a stable condi- tion last night. Police said they hoped to identify it through the bite marks.

Among those who rushed to Mr Lindop's assistance, following the attack at about 6.45am, was a fellow surfer, David Rundall. He told local radio: "When we asked him about the pain in terms of one out of 10, he said it was a 10." Nick Miller, a surf lifesaver at Avalon, said: "It [the shark] got him around the top of his leg and his calf muscle, and the father came in and dragged him in."

The state government has launched a survey of shark numbers. But experts say more sightings do not mean more sharks and dismiss claims that sharks target bathers because of overfishing. "Humans are not part of the sharks' diet, otherwise there would be nobody safe in the water," said John West, a shark expert at Sydney's Taronga Zoo.