Sydney--A shark _ a schoolboy's leg while he was surfing with his father at a beach in Sydney on February 23. It was the third shark attack along the coast of Australia's largest city in a month. The 15yearold boy and his father were in the water off Avalon, on Sydney's northern beaches, around dawn when he was attacked. The city's beaches are packed with locals and tourists during the summer months. "The father heard a scream and turned to see his son thrashing   about in the water," police said. "Fortunately, the shark swam away and the boy was helped to the shore by his father." Lifesaving Club spokesman Nick Miller said, "It got him around the top of his left leg and the father came and dragged him out of water." He said the boy was bleeding heavily when he was brought to the shore. "There was a lot of pain, as you can imagine." The teenager was airlifted to hospital for treatment for leg injuries. Police said the bites "cut through to the bone", but the boy did not appear to have sustained any fractures  . He was in a stable condition now. Several beaches were closed after the attack. Water police and lifeguards were searching for the shark, while police hoped to identify its species by the shape of the bite marks. But they said it was too early to say what type of shark attacked the boy. "I don't even know if he saw it," Miller said. Many shark species live in the waters off Sydney's beaches, but attacks on humans are still relatively rare. However, there were two attacks on successive days earlier this month, one on a navy diver in Sydney harbor,not far from the famous Opera House, and the other on a surfer at the city's worldfamous Bondi beach. Fishermen say shark numbers are on the rise. There is a ban on commercial fishing in the harbor, which has increased fish stocks. Marine experts also claim environmental protection has created a cleaner environment, attracting sharks closer to the shore as they chase fish. Many shark species, including the Great White--the maneaters made famous in Steven Spielberg's Jaws--are protected in Australian waters. The report mainly tells us  _  .
shark attacks on humans are on the rise sharks attacked humans three times in one month a boy was attacked by a shark at a Sydney beach shark numbers are increasing in the waters off Sydney's beaches