Most of them were stranded during the weekend but rescue efforts have been hampered by the island’s remote location.
New Zealand’s Department of Conservation on Wednesday said a total of 97 pilot whales and three dolphins died in the stranding, adding they were notified of the incident on Sunday.
“Only 26 of the whales were still alive at this point, the majority of them appearing very weak, and were euthanised due to the rough sea conditions and almost certainty of there being great white sharks in the water which are brought in by a stranding like this,” said DOC Biodiversity Ranger Jemma Welch.
Mass strandings are reasonably common on the Chatham Islands. In 1918, up to 1,000 animals died in a single mass stranding.
Mass whale strandings have occurred throughout recorded modern history, and why it happens is a question that has puzzled marine biologists for years.
In late September, several hundred whales died in shallow waters off the Australian coast in one of the world’s biggest mass whale strandings.