The release of almost 100 beached whales back into the wild off Tasmania is being hailed a success as authorities turn their attention to disposing hundreds of dead animals.

Rescuers had freed a further six pilot whales by 1pm on Friday – taking the total number saved to 94 – after the nation’s worst mass stranding at Macquarie Heads near Strahan on Tasmania’s west coast.

Tasmania’s Department of Primary Industries, Parks, Water and Environment revised the number of dead mammals down to 350 overnight, with planing for their disposal now being carried out.

Authorities are still trying to free between 12 and 20 whales, including some that re-beached overnight, with rescuers looking at options to refloat them and give them another chance at survival.

Five whales have now been euthanased on animal welfare grounds after being assessed by a vet.

Incident controller and Tasmania Parks and Wildlife Service regional manager Nic Deka said the collection of carcasses within Macquarie Harbour was continuing and a technique was being trialled to enable there disposal at sea.

He said they were looking at towing the dead whales out to sea 10 to 20 at a time and possibly putting a slash in them to cause them to burst, sink and decompose quicker.

Mr Deka said they hoped to be able to remove the carcasses within four or five days.

“We’re confident we can get the bulk of the carcasses out so the health of the harbour is not compromised,” he said.

Authorities are also wary of sharks being attracted to the dead whales, with one carcass showing evidence of being chomped and another reported sighting of sharks further north along the coast.

Mr Deka said they hadn’t noticed any sharks inside the harbour yet.

“It needs to be understood that this is an environment sharks are present in all the time and sharks are certainly not uncommon in this part of the world and in fact the locals fish for sharks off the beach,” he said.

“There are sharks around, the numbers may increase with carcasses in the sea but we are doing a few things to get them to decompose quickly so that if that is an issue, it’s an issue for less of a time.

“We don’t think they will enter the harbour but we’re keeping a very keen eye for that and if we get any indication that’s likely to increase in risk then we’ll reassess how’re we’re using our people and get them out of the water.”

Despite the mass deaths, Marine Conservation Program wildlife biologist Dr Kris Carlyon said saving 94 animals was a “hell of an effort”.

“We are dealing with something unique, we haven’t dealt with a stranding of this type before and we’re using new and novel techniques as part of the rescue effort,” he said.

“The best case scenario with the whales we’ve released is they rejoin as a group, reform those bonds and they’ll get on with things.”