CNN —
Hundreds of pilot whales have died after being stranded near shark-infested waters on a remote South Pacific island chain, according to rescue teams and conservationists.
New Zealand’s Conservation Department told CNN that nearly 500 whales have washed up on the Chatham Islands, 840 kilometers (520 miles) east of the main South Island, in two separate mass strandings reported by local residents over the weekend.
Dave Lundquist, a technical advisor for the department’s marine engineering, said it is not attempting to refloat stranded whales in the area due to the risk of shark attacks to both humans 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’s the kindest option,” Lundquist said.
Daren Grover, executive director of rescue organization Project Jonah, said most of the pilot whales were dead when they came ashore and the survivors were in poor health.
“Having so many whales in one place is unusual, but certainly not unusual,” he said.
Adding to the risk posed by sharks, it’s “nearly impossible” for rescue teams to travel to the Chatham Islands on short notice, he said, making the whale rescue even more difficult.
The mass stranding incident comes less than a month after about 200 pilot whales died off the coast of Tasmania, Australia.
It’s common for pilot whales to strand, but the behavior isn’t well understood, according to the Department of Conservation. Most scientists believe that individual whales strand because they are sick and are reaching the end of their natural lifespan.
The Chatham Islands, home to around 600 people, are among the three most important “stranding hotspots” in New Zealand. In 1918, the archipelago experienced the largest recorded stranding in the country, with about 1,000 pilot whales, according to the ministry.