A sighting of a whale inside Dublin Port is being investigated by the Irish Whale and Dolphin Group (IWDG).

Amateur footage of the mammal breathing at the surface near the Stena berth of the port has been posted on social media.

Locals suggested it was about 20 metres in length.

The IWDG has requested that members of the public supply them with images or video footage of the whale.

The group depends on such records to monitor migratory patterns and carry out research.

“An unusual sighting of a whale inside Dublin Port has been reported to IWDG,” said the group.

“We are currently reviewing available photos and video footage to confirm the species of this animal. However, if anyone in the area has sighted it and has any additional photos, videos or information about it we would appreciate if you could let us know.”

Conal O’Flanagan, a member of the IWDG, said the animal was probably a minke whale that was spotted off Sutton on Tuesday.

“We got a call yesterday afternoon to say a whale had been spotted off Red Rock in Sutton,” he said. “I met the guy who spotted it, but the animal had left. It sounded like a minke whale from his description. It had been seen in fairly shallow water, and minke whales shouldn’t be seen in shallow waters.

‘In some distress’

“They tend to be in deeper waters, so I thought it might be in some distress, but the man who spotted it said it seemed to be moving well and had last seen it heading out to deeper waters.

“However, when I heard about the whale in Dublin Port and saw the video footage, it also looks like a minke, so I wouldn’t be surprised if it’s the same animal, and not in a good state.”

Mr O’Flanagan said the whale’s chances of survival were slim. “Minkes, unless they are following a shoal of fish or whatever, shouldn’t really be halfway up the River Liffey,” he said.

“They are found in smallish numbers in the Irish Sea. I’ve seen them at Howth cruising by, but they normally keep some distance from the shore.

“We would expect this whale to make its way back out to sea, but unfortunately most of them wash up live stranded or dead stranded on the coast. It’s not a good sign.”

There have been increased sightings of whales in Irish waters over recent years, although it is unusual to see them so far upriver.

However, a common dolphin was spotted swimming in the river Liffey in Dublin last month. A number of people took to social media to share videos of the dolphin swimming around the North Wall Quay area and near Butt Bridge.

The waters off Cork and Kerry are hotspots for humpback whales, but the IWDG has in recent weeks received two sighting reports of humpback whales in Donegal Bay.

So far this year, the IWDG has received and validated 98 humpback whale sightings from Irish waters, of which 51 were in Co Kerry, and 42 were in Co Cork. There was one each from counties Clare, Down and Antrim.

It has been more than 11 years since the last validated sighting of a humpback whale from any waters around Donegal and Sligo.