Thirty-nine whales have died in the first major New Zealand stranding of the summer, in Golden Bay.
A dozen of the pod were found dead this morning after they washed up on the high-tide mark at Farewell Spit last night.
The Department of Conservation (DOC) made the "difficult decision" to euthanase the remaining 27 when it became clear an attempt to refloat them was unlikely to succeed.
The location of the whales high up on the beach, low tides and strong winds would have hampered any refloat attempt, Golden Bay conservation services manager John Mason said.
"We carefully weighed up the likelihood of being able to refloat them and get them safely back out to sea," he said.
"But our staff, who have extensive experience in dealing with mass whale strandings in Golden Bay, determined that due to various factors it was unlikely they could be rescued.
"Twelve of the whales have died and rather than prolong the suffering of the remaining 27 whales we decided to humanely euthanase them."
Whale conservation charity Project Jonah reported the stranding on its Facebook page with "great sadness".
"This is a strong reminder that we are in peak stranding season and for medics to have their strand bags ready to go," it said.
Stranding season is from November to March. They are an almost annual occurrence at Farewell Spit.
In November 2012, 28 whales died after stranding in the area.
In January of that year, 99 whales stranded themselves at the spit.
Despite refloating efforts, 40 had to be euthanased.