Risk of shark attack deters rescue of 500 stranded pilot whales off New Zealand

Hundreds died after becoming stranded near the shark-infested waters of the Chatham Islands, 840 kilometres east of the main South Island in the South Pacific, rescue teams and conservationists have reported.

Dave Lundquist, a marine technical adviser for the New Zealand’s Department of Conservation, said it does not attempt to refloat stranded whales in the area due to the risk of shark attacks to both people and the whales.

The surviving whales were euthanized to prevent further suffering, he said.

“This decision is never taken lightly, but in cases like this it is the kindest option,” Lundquist said.

Daren Grover, general manager of rescue organisation Project Jonah, said most of the pilot whales were already dead when they came ashore, and the survivors were in poor health.

“Having such a high number of whales in one location is unusual, but it’s certainly not unheard of,” he said.

In addition to the risk posed by sharks, it was “almost impossible” for rescue teams to travel to the Chatham Islands on short notice, he said, compounding the difficulty of saving the whales.

On Friday, 250 beached pilot whales were found at Chatham Island, and then three days later another 240 were reported on Pitt Island, the government said.

It’s common for pilot whales to become stranded but the behaviour is not well understood, according to the Department of Conservation. Most scientists believe that individual whales strand because they are diseased and coming to the end of their natural lifespan.

The Chatham Islands, which are home to about 600 people, are among the top three “stranding hotspots” in New Zealand. In 1918, the archipelago saw the biggest recorded stranding in the country of about 1,000 pilot whales, according to the department.

A Department of Conservation team was dispatched to Chatham Island to support the lone DOC ranger stationed on Pitt Island, Project Jonah said.

"This is an incredibly isolated and remote part of the world, with a small population and known for great white sharks which pose risk to both people and whales," the group said.

"Our thoughts are with the DOC staff and local community."