A necropsy on a Bryde's whale found dead on Motuihe Island in Hauraki Gulf has confirmed that the whale was hit by a vessel, the Department of Conservation says.

The death highlighted the urgent need to deal with ship strikes to save the critically endangered population of Bryde's whales in the gulf, the department said.

"The necropsy has confirmed the Bryde's whale was alive when it was struck by a vessel and died as a result of the injuries it received," said DoC Auckland area biodiversity manager Phil Brown.

The 14.5-metre female whale was found on rocks near Wharf Bay on Motuihe on Sunday.

The necropsy was completed yesterday and the whale was buried at Calypso Bay after being blessed by Ngai Tai representatives.

New Zealand is one of the few places in the world with a resident population of Bryde's whale.

The New Zealand population lives primarily in the Hauraki Gulf and is listed as critically endangered by DoC. There are less than 200 Bryde's whales living in the gulf.

DoC said there have been 42 confirmed deaths of Bryde's whales in the Hauraki Gulf in the past 16 years, 16 of them probably killed by vessels.

A 12m whale was killed by a container ship in the Hauraki Gulf in January, the fourth in 18 months.

DoC was working with organisations and agencies to deal with the issue of ship strike issue.

Shipping representatives had agreed to implement a number of measures, including:

* Slowing their ships down in the Hauraki Gulf when schedules permit.

* Establishing shipping lanes to reduce the area of the gulf in which ships travel.

* Establishing a Hauraki Gulf large whale warning system.

* Contribute funding for research focusing primarily on ways of reducing ship strike.

Hauraki Gulf Forum chairman John Tregidga said ship strike workshops highlighted the critical importance of ship speed to the survival of whales.

"A few large ships travel through the Hauraki Gulf at more than 20 knots. The average speed for large ships in the gulf is 14.2 knots. Scientists have estimated that if this speed was reduced to 10 knots, the Bryde's whale would have a 75 per cent chance of surviving a strike," he said.

Environmental Defence Society policy director Raewyn Peart said research last summer showed the whales were particularly vulnerable at night when they floated close to the surface.

"Ship speed is the critical factor in their decline and must be the priority for industry and legislative responses," she said.

- APNZ