New Zealand's conservation office on Tuesday said all 240 pilot whales stranded on the remote Pitt Island have died, just days after 215 whales died on a beach on nearby Chatham Island.
Dave Lundquist, marine technical advisor at the Department of Conservation, in an email said a technical team on Monday had assessed the situation and euthanized the surviving whales.
"This decision is never taken lightly, but in cases like this it is the kindest option," Lundquist said. The conservation department does not try to refloat whales in the area due to the risk of shark attack to both humans and whales, he said.
Daren Grover, general manager at charity Project Jonah, which deals with stranded whales, said there were also not enough people in the area to help with refloating.
"This decision is never taken lightly, but in cases like this it is the kindest option."
Dave Lundquist
Description of the island
The Pitt Island and Chatham Island make up the Chatham Islands archipelago which lies about 840 kilometers (521.95 miles) off the east coast of New Zealand's South Island. Around 800 people live on the larger Chatham Island, with 40 people living on Pitt Island.
Grover said given the position of the archipelago near where subtropical and sub-Antarctic oceans meet there was an abundance of sea life in the area which attracted the likes of whales.
The Chatham Island stranding occurred on Saturday, and also involved surviving pilot whales being euthanized.
Nearby New Zealand and neighboring Australia are hot spots for mass whale strandings owing to large colonies of pilot whales living in the deep oceans surrounding both island nations. The cause of whale stranding is unknown.