Rescuers find 200 more pilot whales stranded on an Australian coast, raising the total to 470 in the largest mass stranding ever recorded in the country.

Rescuers working to save a pod of whales stranded on a sandbar in Macquarie Harbour on the rugged west coast of Tasmania, September 22, 2020.
Rescuers working to save a pod of whales stranded on a sandbar in Macquarie Harbour on the rugged west coast of Tasmania, September 22, 2020. (AFP)

Rescuers trying to refloat a pod of stranded whales in a remote Australian harbour say they have found another 200, taking to 470 the total number that have become stuck.

The long-finned pilot whales are trapped in two separate locations in Macquarie Harbour, on the rugged and sparsely populated west coast of Tasmania, a spokeswoman for the state's environment department said.

"It has been confirmed that approximately 200 whales that were undetected up until this point were found" at a spot seven to 10 kilometres (four to six miles) further in the harbour, she said.

Parks and Wildlife Service manager Nic Deka said the second pod was discovered early Wednesday morning by an aerial surveillance crew who believed most had already died.

"We already have staff on the way to make an assessment, but certainly from the air didn't appear to be in a condition that would warrant rescue," he told reporters in the nearby town of Strahan.

"Most of them appear to be dead but we will wait for advice from the ground crew before we make a final call on what we do."

READ MORE: Hundreds of stranded whales being rescued in Australia

Largest stranding in history

About 270 whales were found Monday, sparking a major effort to free the giant mammals that were mostly stranded on a sandbar only accessible by boat.

At least 90 of those whales have already died, though scientists were hopeful the survivors would hold out for the several days it was expected to complete the rescue mission.

Rescuers spent Tuesday wading in the cold shallows to free about 25 creatures, using boats fitted with special slings to guide them back to the open ocean.

Wednesday's discovery of another 200 whales makes the mass stranding the largest recorded in Tasmania's history.

Officials have now expanded their search area to see if more whales are stuck nearby.

READ MORE: Over 300 whales die in New Zealand's largest strandings in years

Saving the giant mammals

The rescue crew of 60 conservationists, skilled volunteers and local fish farm workers are concentrating their efforts on the roughly 200 whales on a sandbar, where the creatures are partially submerged in water.

"What we do know is the mortality has increased – that's inevitable – but there are still a significant number that are alive so we'll continue to work with those," Deka said.

Several of the whales rescued Tuesday re-stranded overnight in line with predictions by whale behaviour experts, but Deka remained upbeat about the rescue mission.

"The good news is the majority of whales that were rescued are still out in deep water and swimming," he said.

"They haven't stranded. So we've been more successful than not."

The causes of mass strandings remain unknown, but scientists have suggested the highly sociable pilot whales may have gone off track after feeding close to the shoreline or by following one or two whales that strayed.

READ MORE: Shark attack could be behind New Zealand whale strandings

Rescuers working to save a pod of whales stranded on a sandbar in Macquarie Harbour on the rugged west coast of Tasmania, September 22, 2020.
Rescuers working to save a pod of whales stranded on a sandbar in Macquarie Harbour on the rugged west coast of Tasmania, September 22, 2020. (AFP)
Source: AFP