Warning: This story contains a graphic image.

There are serious concerns that someone has deliberately shot a resident Auckland Leopard seal.

Photo: Supplied / Giverny Forbes

Owha, who is well-known to boaties in the Waitematā harbour, was spotted with a bleeding nostril on Saturday.

NIWA marine biologist Krista Hupman said it had now been confirmed by three separate vets that the blood was most likely the result of a bullet wound.

"It could be life threatening. At the moment it's touch-and-go to see how she goes, we are monitoring her very closely," she said.

"Unfortunately to intervene we would have to sedate the animal and we would have to bring her in for X-rays."

Sedation could be deadly for Owha, so Dr Hupman said she hoped that could be avoided.

There was some good news, however, Owha had been out and about since Saturday and was lazing on her favourite pontoon.

"That's a good sign that she's doing normal behaviour, but also there is quite a lot of blood coming from the wound," Dr Hupman said.

"She doesn't appear to be putting her head down as normal and one of her nostrils she isn't breathing out of so that could all be signs that the injury is quite bad."

The environment officer for the Ngāti Paoa Trust Board, Karla Allies, has also been checking on the 3-metre giant.

"I am definitely worried, the pictures I've seen look like she's been shot in the face.

"My concern is if it's a bullet, it's quite close to her brain really, but I also know that sea mammals are amazingly resilient and it may just be a spear hole. There's a definite hole, something has happened and it's not from another animal."

Owha is known to be quite mischievous in the harbour, biting boats and stealing inflatables.

But, Dr Hupman said Owha had never been aggressive to a human.

"The last thing we want to do is to provoke her to not like humans, so curiosity was better for us than any form of aggression she might show."

In a statement, the Department of Conservation said it would investigate the incident soon as possible.

"Whilst at this time we would welcome reports from the public regarding Owha's location and behaviour, we also remind people to stay at least 20 metres away."

Dogs should also be kept on a lead so Owha was not caused any undue stress.

Under the Marine Mammals Protection Act it is an offence to disturb, harass, harm, injure or kill a seal.

Any person charged with one of these offences could face up to two years' imprisonment or a fine of up to $250,000.

The Department of Conservation says anyone with information about the incident should call 0800 LEOPARD.