Dr Francis and Mr Tindale plan to tag a number of hammerheads in the coming year to determine whether they are resident or migratory, and what they do. Little is known about the species, its habitat or abundance in New Zealand, Dr Francis saying young hammerheads were vulnerable to capture by set nets, longlines and trawlers.
"They seem to be very sensitive to capture, and most of them die before they can be returned to the sea," he said.
Since being tagged Orokawa had crossed the outer Bay of Islands and travelled around the north side of the Purerua Peninsula.
"He is moving around a lot but not going far. He makes a lot of inshore/offshore movements, almost reaching the shore at times," Dr Francis added.
"This is the first time detailed information on hammerhead shark movements has been obtained in New Zealand waters."
The only other New Zealand hammerhead to provide useful information was a two-metre female tagged near Cuvier Island in 2011. It was recaptured east of Vava'u, Tonga, almost 2 years later and more than 2200 kilometres away, Dr Francis saying that suggested that medium to large specimens could be highly migratory, though small juveniles probably lived in New Zealand waters for the first few years of life.
Despite being common in northern New Zealand waters, hammerheads were rarely seen.
Dr Francis is now asking fishers to be on the lookout for Orokawa, and if they catch him, to release him as soon as possible. If he was found dead, the tag on his dorsal fin should be removed and returned to Dr Francis at NIWA.
Orokawa, named after Mr Tindale's boat (Calm Seas), is carrying a SPOT tag that transmits messages to orbiting satellites whenever the dorsal fin, and the tag's aerial, break the surface of the water.
The satellite estimates the position of the tag and sends that information via the Argos ground station in France, from where Dr Francis can download the data to his office in Wellington.
