Hunters blamed for whale shark losses

Kate Tarala, thewest.com.au 29 May 08;

Scientists fear Indonesian fishermen hunting whale sharks are responsible for a 40 per cent drop in numbers along the Ningaloo Reef in the past 10 years.

“They are after the fin for the shark fin soup trade, not because they contain a lot of the material used to make the soup, but so restaurants through southern China can advertise the fact that they’ve actually got shark fin,” researcher Mark Meekan said. “The flesh of the animal is also cooked up to the consistency of tofu, in a dish called ‘tofu fish’, which is quite popular.”

Researchers from the Australian Institute of Marine Science, who presented their findings at the second annual Ningaloo Research Symposium at Murdoch University, are also worried by a drop in the size of whale sharks along the reef. The average of 6m to 7m observed in the 1990s has dropped to about 3m to 4m.

“That is important because the sharks don’t become sexually mature until about six to seven metres long. It’s a real worry. The population is becoming more and more composed of juveniles,” Dr Meekan said.

Deaths from ship strike could also contribute to the population decline. “Twenty-five per cent of the whale sharks at Ningaloo bear scars from ships,” Dr Meekan said. “These animals spend a lot of time at the surface, they float around. A modern container vessel moves at 25 knots, so the ship would not even notice if it hit one.”

Natural predation was not likely to account for the drop in the number of whale sharks at Ningaloo Reef.

At smaller sizes whale sharks might be pursued by killer whales, great white sharks or tiger sharks, but its thick skin makes it a difficult meal to catch.

The AIMS team used satellite tagging to track whale sharks for up to eight months after leaving Ningaloo Reef. Dr Meekan said it was alarming to find that some whale sharks travelled well into the waters of Indonesia and South-East Asia, where hunting was a real threat.