Pilot whale deaths among group restranded at Farewell Spit

Rescuers are cautiously optimistic that a pod of pilot whales - which has re-stranded multiple times in Golden Bay - will stay at sea.

Department of Conservation operations manager Ross Trotter says the pod has been floating since 11.30am on Wednesday and is now in 3.5m of water.

"The pod has split into a group of 10 and a group of nine.

"At one stage they looked to be coming back in but have since headed out, so looking promising at this stage."

He said a boat had been monitoring the pod's movements, and a group would remain at Farewell Spit through low tide at about 6.30pm.

Trotter said further checks would be done at first light on Thursday.

He said mana whenua had performed a karakia over the dead whales and said they would be taken further up the spit and tethered to the tide line - "where nature would take its course".

Nearly 40 pilot whales stranded at Farewell Spit on Monday; 24 were refloated on Tuesday, but restranded overnight.

Earlier, Project Jonah said the whales had water deep enough for them to swim in for a number of hours, but returned to shore.

They would not be able to be refloated until high tide on Wednesday.

"The ones who have stranded, we'll just be looking after their welfare now and trying to keep them as comfortable as we can until we get another opportunity when the tide comes back," Trotter said.

Marine biologist Ingrid Visser told Checkpoint Golden Bay was a hot spot for whale strandings but it wasn't known why they stranded in these spots.

A decade or so ago there were some very high success rates in terms of refloating whales after they had stranded, but more recently the numbers of whales able to be saved were lower, she said.

"It depends on each event and the animals themselves, what actually triggered the stranding.

"Sometimes you'll get a female that is having a breach birth and she will come into shallow water, so that if the calf is born and is alive then the calf won't sink very deep, it's also a way for her to avoid deep water predators, then all of the rest of the group come in with her. Then if you get a place like Golden Bay where the tide drops very very fast then the animals can get stuck."

It was important that the animals were set upright as quickly as possible because they became very disoriented when they remained on their sides, she said.

"They basically swim in a semi-circle when you release them and then they'll come back on the shore."