14 July 2005

Tagged whale sharks 'surprise' scientists

Australian scientists tracking massive whale sharks said on Wednesday that they are demon swimmers just like other shark species.

The whale shark is the ocean's biggest fish but is not dangerous to humans because its diet is plankton sucked in through its fine mesh gills.

Australian Institute of Marine Science (AIMS) researchers began tagging whale sharks off Western Australia's Ningaloo Reef two months ago.

Information from the transponders they attached to the sharks showed that there is no set pattern to their travels.

"One's been hanging around the bottom of Java in Indonesian waters for about a couple of weeks," AIMS researcher Mark Meakin said. "A couple of others have swum up towards Christmas Island and now seem to be headed out, out into the open Indian Ocean somewhere."

He added: "A couple of other sharks, on the other hand, seem to be quite happy at Ningaloo and have only just left there after we tagged them a couple of months ago in May."

Last year Australian scientists fitted great white sharks with satellite tags. Bruce, one of four great whites tagged on its dorsal fin, swam 6 000km in a seven-month tour of the east coast.

Meakin said the tags were yielding lots of information about the whale shark's behaviour.

"They not only give the shark's position, they also tell you about the water temperature it's been swimming in and the depth it's been diving to," Meakin said. "Now these sharks are pretty champion divers. Some of them are getting over a kilometre down into the inky blue and cold water. What they're doing down there we have absolutely no idea."

Source: www.iol.co.za


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