By IANS,
Sydney : Scientists have tagged a nearly four-metre long white shark, nicknamed Thomas, to track its movements across the ocean and gather more detailed information.
The tag popped up at Swaub Reefs off Rockhampton and transmitted data late in August. Department of Conservation (DOC) Scientist Clinton Duffy had tagged Thomas off Ruapuke Island in Foveaux Strait in February.
“This is only 100 kilometres from where another tag popped up last year from a shark tagged at Stewart Island after having travelled over 3,000 km,” said Duffy.
The shark tagging project, which began in 2005, is an international collaborative programme being run by the National Institute for Water and Atmospheric Research (NIWA), DOC, and Ramon Bonfil from Shark Tracker/NABU (Germany).
NIWA fisheries scientist Malcolm Francis said: “Previous tagged white sharks have dived as deep as 1,000 metres and encountered temperatures ranging from three degrees in deep water to 24 degrees in shallow tropical waters. This huge range in temperature is very unusual among fishes.
“Previously we thought great whites were cold water, coastal sharks but we now know that many make trans-oceanic migrations to tropical waters.
“The reason for their winter tropical holiday is still unknown but we think they may be searching for newborn humpback whale calves, because all tags have surfaced in or near known humpback calving sites.
“Until this year we’ve only been able to tag six white sharks in three seasons of field work. This year has greatly added to our tally with three more being tagged at Stewart Island and six more at Chatham Islands.
“Two tags have failed but we still have six more tagged sharks in the water which are due to report back between October and January, offering us an amazing insight into the secret lives of these apex predators.
“Once all the data has been transmitted from the latest shark, the project team will be able to determine the route the shark took, how deep it dived, and the water temperatures it experienced.”