Fish scientists were singing carols of a different nature when a tagged mako shark returned to New Zealand waters before Christmas, having left the Bay of Islands seven months earlier and travelling over 13,300km.
The 1.8 metre female mako, called Carol, had averaged 60km per day and exceeded 100km a day during some parts of her migration to Fiji and back. This week the young shark is heading south past Kaikoura in the South Island, after a lazy journey down North Island's east coast.
A Niwa team led by Malcolm Francis has been tracking Carol using a satellite reporting device known as a Spot tag, which was attached in the Bay of Islands in June.
"It's the first mako shark we've tagged with fancy technology like this," Dr Francis said.
Conventional plastic identification tags tell little about the timing of mako shark movements, the route that they take or distance travelled, he said.
While it is not a new discovery that mako sharks travel from New Zealand to northern Queensland, New Caledonia and other tropical Pacific locations - as caught tagged sharks have proven for years - Carol's journey got off to a baffling false start, Dr Francis said.
After having the latest tracking gear fitted to her dorsal fin in the Bay of Islands, Carol (named after a researcher's mother) "headed off toward Fiji but only got half way there when she turned around and came back".
She then "hung around" Ninety Mile Beach for six weeks before heading off again, that time making it all the way to Fiji. She returned three months later, spending time at Coromandel, Bay of Plenty and Hawke's Bay, before heading further south.
The tag has so far provided researchers with remarkable and previously unknown details of the timing and long-distance migratory movements, Dr Francis said.
Carol spends a lot of time at the ocean's surface, reporting her location to the satellite several times daily. She is still a tiddler at 1.8m - her species reaches 3m - and at only four or five years old, is still about 15 years off breeding age.
To follow Carol's travels on a GHRI interactive website go to: http://www.nova.edu/~johnmatt/makosharks.htm.