Scientists have taken to the air to study a rare New Zealand dolphin off the west coast of the North Island and ensure it does not get tangled in fishing nets.
Maui dolphins - formerly known as the North Island Hector's dolphin - number fewer than 100.
Scientists from Otago University andthe Department of Conservation last month made the first of two aerial surveys between Maunganui Bluff, near Dargaville, and Pariokariwa Pt, north of New Plymouth.
The study aims to see how far offshore the dolphins are found and whether this changes seasonally, to check that they are not in danger from fishing nets and trawlers.
World Wildlife Fund (WWF) conservation director Chris Howe said a set-net ban in the region was only to 4 nautical miles offshore, and trawling was banned only to 1 nautical mile.
"We cannot underestimate the risk Mauis face from fishing activity outside these areas."
The survey is jointly funded by DoC and WWF. A winter survey is planned for July.
Otago University zoology lecturer Dr Liz Slooten said that around Banks Peninsula, the dolphins came much closer to shore in summer than winter.
"The Banks Peninsula marine mammal sanctuary protects most of the population in summer, but in winter only 35 per cent is inside the protected area.
"If that is the case in the North Island, it might be necessary to extend the offshore boundary."
