More than 150 whales were stranded in a remote area off the coast of the Australian state of Tasmania. (Photo credit: Marine Conservation Program via CNN Newsource)

(CNN) — Australian wildlife officers have made the difficult decision to euthanize 90 false killer whales stranded on a remote beach in Tasmania, after rough ocean conditions made it impossible to refloat them.

More than 150 whales were found stranded near the Arthur River on the island’s west coast late Tuesday, according to Tasmania’s Department of Natural Resources and Environment.

By Wednesday morning, only 90 were still alive, and while rescuers attempted to send two back out to sea, wind and rough seas meant they immediately returned to shore.

The animals appear to be false killer whales, authorities say. (Photo credit: Tasmania’s Marine Conservation Program via CNN Newsource)

“It’s quite rough, and the animals just can’t get past the break to get out. They just keep turning around and coming back towards the beach,” said Shelley Graham, incident controller with Tasmania Parks & Wildlife Service.

Aerial images showed the whales spread out along the beach, some half-buried in sand, while others were trapped in shallow waters near rocky outcrops.

The last time so many false killer whales were stranded in Tasmania was 50 years ago in June 1974 when a pod of 160 to 170 were found at Black River beach on the island’s northern coast. It’s not clear how many survived.

Whales stranded near Arthur River, on the west coast of Tasmania. (Photo credit: Tasmania’s Marine Conservation Program via CNN Newsource)

In the latest stranding, authorities said the decision had been made to euthanize the animals to minimize their suffering. After many hours on the beach, they had become disorientated and distressed.

In recent mass stranding operations, machinery has been used to move stranded whales to more secluded areas, so they can be stabilized in the water before release.

But it was not possible to send equipment to the remote and inaccessible location, said Brendon Clark, a liaison officer at the Tasmania Parks and Wildlife Service.

Members of the public had previously been warned to stay away from the latest stranding, for their own safety, as the whales are large, weighing between 500 kilograms to about three tons, Clark said.

Whales are a protected species in Tasmania, even when deceased, and interfering with a carcass is an offense.

Animal behaviorists and marine scientists say that survival rates for beached whales is low, and the animals “can only survive for around six hours on land before they start to deteriorate.”

“It’s not often clear why whales strand, but they have been stranding for many centuries across the world’s coastlines, including en mass,” said Dr Angus Henderson at the Institute of Marine and Antarctic Studies, University of Tasmania.

“There are many natural causes such as lead animals getting sick, lost or disoriented, as well as other factors such as weather and magnetic anomalies… This is the third mass stranding in 5 years on the west coast of Tasmania, but whether this is a pattern with a discernible cause is yet to be determined.”

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