Tasmanian authorities plan to euthanise 90 surviving false killer whales in a group of 157 animals that have stranded on a beach near Arthur River, on the state`s remote north-west coast.

Marine conservation experts including wildlife veterinarians arrived at the site on Wednesday morning, confirming 90 animals were still alive.

Shelley Graham, the incident controller at the Tasmania Parks and Wildlife Service, said on Wednesday afternoon that attempts to refloat two of the false killer whales earlier in the day had been unsuccessful.

"Safety of the animals and of our staff is priority in this response from us," she said. "Following expert veterinary assessment, we have decided that euthanasia is necessary for animal welfare reasons."

Kris Carlyon, the deputy incident controller, said that "euthanasia of animals this size is done by firearm.

"It`s a difficult situation, but when we know it`s the best outcome for the animal for animal welfare reasons then we`ll certainly do that job and do it as quickly and humanely as we possibly can."