SAN JUAN (Puerto Rico) - SHARK sleuths have discovered that Atlantic basking sharks winter in the tropical Caribbean Sea, far from the cold waters off Cape Cod and Canada where the rarely seen gentle giants had been thought to linger year-round.

Researchers with Massachusetts' Division of Marine Fisheries used high-tech satellite tags to successfully track the winter movements of the deep-diving creatures - the world's second biggest fish, after the whale shark - all across the Caribbean Sea and across the equator.

The reason for the mottled brown sharks' winter jaunts to the tropics remains a mystery, but researcher Gregory Skomal said the elusive creatures may be giving birth in the Caribbean.

Samuel Gruber, a shark researcher at the University of Miami who was not involved in Mr Skomal's work, described the study as 'exciting', since the creatures' travels were previously murky.

Another marine researcher, Dean Grubbs at Florida State University, who also was not involved in the study, agreed that the insights into the huge creatures was 'certainly new and exciting.'

Mr Skomal said he was delighted that tagging technology was able to track basking sharks, so experts can better examine their movements, dive patterns and temperature preferences - especially since the species known scientifically as cetorhinus maximus appears to be dwindling.

'I just think that it is amazing that we are just learning this for the first time and it has taken the technology of the 21st century to do so. It just goes to show that new discoveries are possible - even in our own backyard,' Mr Skomal said. -- AP