One hundred and forty-five pilot whales have died after becoming stranded on Stewart Island.
A tramper found two whale pods stranded two kilometres apart at the southern end of Mason Bay on Saturday night and reported it to The Department of Conservation (DOC).
Half of the whales had already died by the time they were found and, due to the condition of the remaining whales, the decision was made to euthanise them, DOC Rakiura Operations Manager Ren Leppens says.
"Sadly, the likelihood of being able to successfully re-float the remaining whales was extremely low. The remote location, lack of nearby personnel and the whales' deteriorating condition meant the most humane thing to do was to euthanise," Mr Leppens says.
"However, it's always a heart-breaking decision to make."
DOC has notified Ngāi Tahu and is working with the iwi on what the next steps are.
The stranding is the second to occur over the weekend. In Northland a sperm whale was found beached and died overnight Saturday. And on Sunday 10 pygmy killer whales were found stranded at 90 Mile Beach.
Two have died and re-floats will be attempted on Tuesday. It is unlikely the strandings are linked.
In 2011, two tourists found a pod of 107 pilot whales beached and dying on Mason Bay.
Marine mammal strandings are a relatively common occurrence in New Zealand. DOC have responded to an average 85 incidents a year - mostly single animal strandings.