Hammerhead info sought

Orokawa, the tagged hammerhead shark, isn't going far.

Fishermen in the Bay of Islands are being asked to keep a look out for a young hammerhead shark by the name of Orokawa, with scientists tracking the beast by satellite.

The young 137cm shark, tagged near Deep Water Cove recently by fisherman Scott Tindale, is the first electronically tagged hammerhead to provide useful data in New Zealand waters.

"We were anchored within casting distance of the rocks and saw a hammerhead swimming towards us on the surface," Mr Tindale said.

"I cast a bait towards him and he took it straight away. Because he was small we were able to get him in the boat, oxygenate his gills with seawater from a deck hose, and tag and release him within five minutes."

NIWA shark expert Dr Malcolm Francis has been contracted by the Government to find out more about the biology, behaviour and stock status of hammerhead sharks in a bid to determine whether they are threatened by overfishing. Some hammerhead sharks can attack humans, but there have been no reports of deaths.

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.

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," Dr Francis said.

"This is the first time detailed information on hammerhead shark movements has been obtained in New Zealand waters."

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.