Thursday, November 24, 2005

Researchers lost track of tagged great white shark

Researchers tracking the Great White shark that was tagged in False Bay on Saturday could not locate it yesterday because of a fault with the acoustic tag.They were unable to pick up a signal, said Mike MeØer of the Shark Working Group, composed of representatives from marine and coastal division of the Department of Environmental Affairs, Cape Town's Iziko museums, the universities of Pretoria and Cape Town and the Natal Sharks Board.

The skiboat that had been following the shark traversed the area where it had been swimming on Sunday, from Fish Hoek to Sunrise beach and beyond, in a zig-zag pattern three times, but they were unable to locate it.MeØer said there were two possibilities: either the signal was so weak that they were not picking it up in the right spot or the shark had moved out of the area, but he doubted this.

The transmitter had a range of only 300 metres, so once the shark moved out of range, the researchers would lose the signal.The tag was intended to provide information on the four-metre shark's movements around False Bay. MeØer said it was very frustrating, as the tags had worked before without a problem and the one they really needed to work was giving problems.

The tag had shown irregular functioning from the start: it was supposed to ping at regular one second intervals but had started pinging at 1.5 second intervals before reverting back to one second, which it was not supposed to do. The wind had also created a lot of "noise on the water", MeØer said, and this added to the difficulty in detecting the signal. The researchers will again try to locate the shark today.


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