WHALE SHARKS PROTECTED FROM…DEADLY SWIMMERS?
12.29.07 - Leído 68 veces. Enviar esta notaJennifer Viegas
New limits on ecotourism are resulting in boom times for the gentle giants
WASHINGTON, U.S.; December 29, 2007.- Based on thousands of remarkable underwater images, marine scientists have concluded that the world’s largest shark is thriving in western Australia, thanks to well-managed ecotourism that appears to benefit both people and ocean wildlife there.
The 5,100 images represent the most extensive photo survey ever conducted of whale sharks, with nearly 10 times more data than any other previous study. Marine scientist Brad Norman took many of the photographs himself while swimming alongside the 20-ton ocean giants, which can be over 65 feet long.
“It really is a privilege to be able to swim alongside the largest fish in the ocean, given the fact that this species is so rare and vulnerable to extinction,” Norman told Discovery News. “They are so graceful — a true gentle giant. And it’s not only the great length that is awesome, it’s also their girth. Literally the size of a bus underwater!”
Norman and computer programmer colleague Jason Holmberg are both members of ECOCEAN, a research, education and conservation organization. They, along with NASA astronomer Zaven Arzoumanian, teamed up for the project, which used Hubble space telescope software to analyze the sharks.
The high-tech software was needed to pick out minute differences among the photographed sharks so the researchers could track individuals. Each whale shark has speckles and stripes on its skin that, like fingerprints, are believed to appear in unique patterns.
The study, published in the January issue of Ecological Applications, the journal for the Ecological Society of America, determined more and more whale sharks are returning to the northern area of Ningaloo Marine Park in western Australia from April to June each year, when the krill, jellyfish and other small prey that the whale sharks feed upon are plentiful.
Although the sharks are enormous creatures with 6,000 teeth, they’re relatively peaceful fish that feed by simply opening their mouths. Finely meshed gill-rakers keep prey in while filtering water out. The only real danger to humans is an accidental slap from the shark’s gigantic tail. Such a hit could probably knock a diver out cold.
Two thirds of the whale sharks that come to the reef, which meets the beach of Australia’s North West Cape, are repeat visitors, providing further evidence that a series of “Code of Conduct” rules are working at Ningaloo.
“This (code) includes a limit on the number of people in the water at any one time with the sharks, minimum distances that boats and snorkellers must keep from the sharks, and definitely no touching of the sharks,” Norman explained. “Industry participants are very strict on ensuring these guidelines are abided by.”
Although the measures appear to be working in western Australia, the World Conservation Union Red List of Threatened Species still lists whale sharks as “vulnerable to extinction.”
The large filter feeders continue to be hunted and sold as meat in Singapore, Hong Kong and other places. Taiwan, which used to have a major whale shark fishery, introduced a ban on whale shark hunting just this year. Taiwan joins Australia, Honduras, India, the Maldives, Mexico, the Philippines, South Africa and the United States in protecting whale sharks.
Roland Mau, Ningaloo Marine Park Coordinator in western Australia’s Department of Environment and Conservation, told Discovery News that data collected by “spotter planes” and other tracking methods implemented by his department was mostly inconclusive about whale shark numbers, although a population decline was not suspected.
“I was pleasantly surprised to read that the analysis of the data indicated a growing population,” Mau said.
The protective measures at Ningaloo are also in place in the Philippines. Norman hopes that, in the future, other places where whale shark ecotourism has developed will implement the conservation methods to ensure a safe future for the ocean giants.
(Discovery News)
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