Hope for last survivors of whale stranding

Rescuers are hopeful of saving about 20 surviving pilot whales involved in Australia largest mass stranding on Tasmania's west coast.

As of Thursday evening, 88 whales from the 470-strong group stranded on sand bars in Macquarie Harbour earlier this week had been freed.

"If we'd said on Monday when we were going through our plans that we'd get 90 off the bar then we'd have been very happy with that," wildlife biologist Kris Carlyon said.

"It's a fantastic result for us."

Efforts on Friday will focus on about 20 remaining whales considered to have a good chance of surviving.

But decisions have to be made about the grim task to remove about 380 decomposing carcasses, a process that could take many days.

There are concerns they could pollute the harbour, attract sharks and pose a navigation risk.

"Our aim will be to do it as quickly as possible," parks and wildlife incident controller Nic Deka said.

They will likely be removed from the harbour on barges or towed by boats from Friday, if conditions allow.

Authorities have consulted with the CSIRO and three companies with fish farms in the harbour to determine the best method.

Dr Carlyon is hopeful the freed whales will reunite at sea, although they may face challenges if older leading females are missing.

"Tracking work in the past has shown that animals released individually do re-form after a period," he said.

"This species is generally led by matriarchs.

"If the group has lost those older females with that built-up knowledge of the area and the food resources over time, they may need to learn some behaviours."

Scientists have taken biopsy samples from the dead whales to learn more about their family links and the species' behaviour.

Pilot whales are highly social and can travel in groups of up to 1000.

Experts say the stranding is the largest ever in Australia, surpassing the 1996 beaching of 320 pilot whales at Dunsborough in Western Australia.

On Monday, 270 whales were discovered stranded at Macquarie Harbour, with another 200 found on Wednesday several kilometres further inside the harbour.