Thursday, July 14, 2005

Unexpected guest in an unexpected place

A pop-off satellite tag on a great white shark has tracked her into waters previously thought to be mostly uninhabited by the fierce predators. "Tessa", a 4m adult female, was tagged by a team of international and New Zealand scientists at the Chatham Islands in early April. Since then, she has travelled more than 1000km north - when the team fully expected her to travel south or southwest. Great whites are considered cold-water sharks, so Tessa's route towards the tropics was surprising, said Department of Conservation marine ecologist Clinton Duffy. "We are fascinated.

We've no idea where she will go now," he said. They expected that Tessa and the other four sharks, including "Levi", a 3.5m male great white tagged in the same project as Tessa in April at the Chathams, would head either to the sub-Antarctic Islands south of Stewart Island to feed on one of their favourite foods, sea lions, or head towards Australia. The tag showed Tessa had swum a distance equivalent to half a kilometre an hour and her final pinpointed location was about 800km off New Zealand's East Cape in deep water. The shark obviously took a roundabout route because the sharks normal cruising speed was between 3-4km an hour, Mr Duffy said.

Tessa's tag detached on schedule just over a week ago. It then began transmitting data via satellite to New York-based marine scientist and team member Dr Ramon Bonfil. Once all the data is run through a specially designed computer program, scientists will know exactly where Tessa went. Three other sharks are yet to drop their tags and it would be interesting to see if the others followed a similar route, Mr Duffy said. The project is finding out more about one of the ocean's most deadly predators. Many scientists believe the great white is now more endangered.


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