Ships in the Hauraki Gulf are being urged to slow down after it was discovered another rare Bryde's whale was killed by ship strike.
The 14.5-metre female whale was found dead on Motuihe Island on Sunday.
New Zealand is one of the few places in the world with a resident population of critically endangered Bryde's whale. They primarily live in the Hauraki Gulf, where there are thought to be about 200.
A necropsy on Wednesday confirmed the whale died from injuries after it was struck by a vessel, says the Department of Conservation's Phil Brown.
"Ship strike poses the greatest threat to Bryde's whales in the Hauraki Gulf Marine Park. This latest death highlights the urgent need to take action to address this problem."
Forty-two Bryde's whales had died in the last 16 years. Of the 18 examined, 16 were most likely to have died as the result of ship strike, he said.
The department, academics, environmental groups and shipping firms had been working together to try to prevent more ship strikes.
The shipping representatives have agreed to implement measures including slowing their ships down in the gulf when they can, establishing shipping lanes away from areas the whales are seen and establishing a Hauraki Gulf large whale warning system.
Hauraki Gulf Forum chairman John Tregidga wants the shipping industry to establish a 10-knot speed limit in the gulf.
"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," he said.
However, if the speed was reduced to 10 knots, the Bryde's whale would have a 75 percent chance of surviving a strike.