Kaipara's elusive great white sharks studied

Wednesday, 4 February 2015

One day of fishing has turned up a wealth of new information for shark researchers on the Kaipara Harbour.

The great white is remarkably elusive but Department of Conservation marine technical adviser Clinton Duffy said he was part of a group that managed to hook six on January 17.

Duffy is studying the species in northern New Zealand as part of his PhD as a student in marine science at the University of Auckland.

He said the six sharks, which were all released, ranged in size between 2 and 3.4 metres.

The group also filmed a 3m female and saw a 2m white shark released by another boat.

Duffy said the sharks were all in a very small area not far down Kaipara River from Shelly Beach.

A 2.5m white shark was also observed on the surface outside the harbour - about 9km off South Head by another fisherman.

Duffy's group managed to tag three of the six sharks whose movements have since been tracked around the North Island.

Bruce Goorney of the White Shark Conservation Trust was also on the boat and said the day was a turning point after minimal success over the years in the Kaipara.

He said the group was initially buoyed by numerous reports from recreational fishermen encountering white sharks in the area and commercial fishermen whose nets were destroyed by the species.

'We have always known they are there but they have remained elusive to us - till now!'

The crew caught three more white sharks between 1.8m to 3.5m in the same area the next day but lost them all before they could be tagged.

Duffy's PhD looks at the movements and spatial ecology of the species and is part of a larger collaborative research programme between the university, DOC and NIWA which began on the Chatham Islands 10 years ago.

His field work in the Kaipara and Manukau harbours involves fishing for white sharks, mainly juveniles between 1.8m to 3.5m and deploying two types of satellite tag on them.

Pop-off archival transmitting (PAT) satellite tags are used to study long distance movements and diving behaviour of the sharks, whereas SPOT satellite tags provide more accurate information on their local travels.

'My hope is that the different types of data obtained from these tags will enable me to build up a picture of how these sharks use the coastal waters along the northwest North Island, including the harbours, and how they relate to other white shark populations within New Zealand, Australia and elsewhere in the southwest Pacific,' the Three Kings, Auckland resident said.

Duffy tagged his first white shark, a 1.8m male, in 2012 in the Kaipara, helped by Scott and Sue Tindale of Dairy Flat.

'That shark was tagged with a PAT tag which Scott and I recovered from a beach near Tapora nine months later. The data on that tag indicated that although it hadn't ventured far from Kaipara Harbour it had dived to more than 200 metres depth on several occasions.'

Last year, the trio SPOT tagged a 1.5m male.

'The smallest white shark I have ever seen in Kaipara Harbour, but unfortunately the tag failed to transmit.'

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