SA, Aussie sharks 'linked'
2005-10-06 20:23
Washington - A Great White named Nicole logged more than 19 300 kilometres swimming from South Africa to Australia and back, the first proof of a link between the two continents' shark populations, researchers say.
"Sharks have home ranges that are at the scale of ocean basins," said researcher Barbara A Block of Stanford University.
She added that conservation management of sharks such as the white shark and salmon shark will require international co-operation.
Tracking a shark from Africa to Australia "is one of the most significant discoveries about white shark ecology and suggests we might have to rewrite the life history of this powerful fish", said Ramon Bonfil, author of that study.
Both reports appear in Friday's issue of the journal Science.
George H Burgess, a shark expert at the Florida Museum of Natural History, said while sharks are known to travel long distances, this was the first evidence of movement between Australia and Africa.
New perspective
Enric Cortes of the National Oceanic and Atmospheric Administration's Shark Population Assessment Group in Panama City agreed this is the first direct evidence of a connection between African and Australian white sharks.
Using satellites to track sharks is new technology that may provide new perspective on their movements, he said.
Peter Klimley, a shark expert at the University of California, Davis, called a trip of that length "amazing".
He said there have been genetic indications that these two shark groups might be connected, "but that's not the same as showing actual movement".
Bonfil, of the Bronx, New York-based Wildlife Conservation Society, said he "suspected that these sharks could be doing these kinds of travels ... but there was previously no proof of this.
Everybody thought they were mostly coastal in behaviour."
A satellite tracking device temporarily attached to Nicole documented her 99-day swim from South Africa to Australia.
About six months later, she was identified from photos back off the coast of South Africa.
More than 20 other Great Whites tagged off South Africa engaged in wide-ranging coastal migration, but only Nicole headed out to sea.
Nonetheless, Bonfil said, "I don't think we got one in a million."
Nicole was tagged in November 2003 with a device that reports her position. The researchers said the shark was renamed Nicole in honour of Nicole Kidman.
Funding for the Nicole study came from conservation groups and the South African government.
On the net:
www.sciencemag.org
- AP