Saturday, November 22, 2008

Recovered tags give more information on Great White sharks

One of three electronic transponders so far discarded near Tonga by great white sharks tagged at the Chatham Islands has been recovered from the Ha'ateiho Reef.

Roger Miller and Bruce Dixson from Waste Management Ltd's Nuku'alofa office, found the $5200 tag at the coordinates it transmitted.

Mr Miller lives about 1.5 kilometres from the beach but was unable to find the tag before it stopped transmitting on November 7, the Matangi Tonga newspaper reported.

Last night the tag again transmitted briefly and Department of Conservation scientist Clinton Duffy in Auckland was able to send the new coordinates.

"We were able to track it by GPS to within 20 metres of its location and then we saw it lying on the reef," said Mr Miller. "It was slowly moving down the coastline".

There was no reward for the recovery but Mr Miller said that Air New Zealand's Nuku'alofa agent had offered to carry the tag free of charge back to Auckland.

The data it contains will be analysed by New Zealand marine scientists to trace the shark's diving behaviour and temperature preferences, and a record of light levels to roughly estimate the path it travelled.

The information may provide clues to why the sharks are travelling to Tonga, when local fisheries archives show no record of the species there.

Six great white sharks were tagged in the Chathams in April, and so far three tags have recently surfaced in Tonga, but this is the only one to be recovered.

The researchers said the tags appeared to have detached prematurely, and they hope two tags thought to still be attached will stay on until January to see if those sharks return to NZ waters.


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