The stranding of about 470 pilot whales on Tasmania's west coast is the largest recorded in the state's history, authorities say.
A pod of whales stranded on a sandbar in Macquarie Harbour on the rugged west coast of Tasmania on September 21, 2020. Photo: AFP / Pool
About 270 whales were discovered in Macquarie Harbour on Monday, with a further 200 found this morning.
Rescuers say it appears most of the whales discovered this morning, about 7km to 10km south of the original rescue site near Strahan, have already died.
Parks and Wildlife regional manager Nic Deka said they were found during an aerial reconnaissance to check how many whales were still alive.
"Certainly from the air they didn't look to be in a condition that would warrant rescue, most of them appeared to be dead, but we'll wait on advice from the ground crew before we make a final call on what we do," he said.
"If they can be saved we probably will send crews over there to do that."
Deka said there were several reasons why the new pod was not spotted earlier, including the distance from the other site.
"Another is that in that part of the harbour, the water is a very dark tannin colour, so we think potentially they stranded, washed back into the water and then have been washed back into the bay," he said.
"But I think in terms of how finding that earlier may have changed what we did, I don't think it would have, I think our focus would still have been on that pod close to the boat ramp, closer to the heads, that we had the most chance of getting off the bar and saving."
So far rescue teams have managed to free about 25 of the original group of whales, but a small number have since re-beached themselves.
Deka said more of the whales had died overnight.
"That's inevitable. But there are still a significant number that are alive, so we'll continue to work with those."
Rescuers work to save a pod of whales stranded on a sandbar in Macquarie Harbour on the rugged west coast of Tasmania. Photo: AFP
Wildlife biologist Kris Carlyon said euthanasia was an option as more time passed.
"We're not at a stage where we're considering euthanasia at this stage," he said.
"The animals that are still alive, we think we do have a chance with those given that they're wet, they're cool at this stage and we're pushing ahead with rescue."
Deka said there was a finite period to save the surviving animals which would end within days.
"I would expect that we would shift through a transition from rescue into the retrieval and disposal effort… we're just considering options at the present time," he said.
'It's going to be a huge operation'
James Tucker from the Marine Science Centre at Southern Cross University in New South Wales has spent a lot of time on the scenes of whale carcass disposals.
"It's going to be a huge operation with that many animals," he said.
Tucker said there were four main options for dealing with whale carcasses: dragging them out to sea, burying them, leaving them to decompose, or disposing of them at a waste management facility.
He said burying so many carcasses would be a big job, as just one whale requires a large burial pit.
"Although pilot whales are small, there are just so many," he added.
Each pilot whale weighs about three tonnes.
"If it is a location where leaving a lot of the carcasses in situ is viable, that may be considered … the most natural option is to the leave the carcasses where they are to decompose," Tucker said.
However, leaving the whales where they are would attract white sharks.
White sharks 'hang around'
Tucker said white shark behaviour changes around whale carcasses.
"We know that large sharks including white sharks do frequently scavenge on whale carcasses, it's a big source of food for those species," he said
"Some of our latest research has shown that when there's a stranded whale carcass on the beach … they tend to hang around the area a bit more so that could potentially increase the risk of there being an interaction between a human being in the water and a shark," he said.
Research a silver lining in the tragedy
The tragic loss of so many whales will provide a rare experience for scientists.
"These events are actually a really important part of marine mammal research because it's so rare that we have interactions with these creatures … we never really get a chance to study them so they are a massive resource to researchers around the world," Tucker said.
It is expected samples from the carcasses will be taken for researchers working on a range of different study projects.
According to the Federal Department of Agriculture, Water and Environment, there are no population estimates available for long-finned pilot whales, but they are considered to occur in relatively high abundance.
-ABC