A pod of blue whales, the world’s largest mammals, have been sighted off the coast of County Cork.

The sighting, 60 miles west of Dursey Island, is only the second on record in Irish waters. It was recorded by the Irish Whale and Dolphin Groups yacht, Celtic Mist, which was on its maiden research voyage.

The group told the Irish Times that the two 25-meter whales surfaced within 200 meters of the yacht on the Porcupine Bight. They believe there could have been three whales in the water as they saw three “blows” of seawater in a short period of time, according to Patrick Lyne.

Blue whale sightings in this area have been rare in recent years although it is thought they were fairly common before large-scale commercial whaling of the massive animals who inspired Herman Melville’s novel “Moby Dick”.

Lyne told the Irish Times that its estimated there are now only three to 4,000 blue whales left in the northern hemisphere.

These whales are usually found in the deep waters close to the continental shelf and they are regularly spotted north of Ireland. Adult male blue whales can be up to 33 meters long and weigh up to 178,000 kilograms.

According to the West Cork Times, the US Navy are using underwater recording equipment and have detected their mating calls off the west and northwest coasts of Ireland. Their research indicates that 30 to 50 blue whales may pass through Ireland’s waters every year.

Recent sighting close to Ireland include that of University College Cork researchers, at Rockall Trough, in 2011. Also, in 2008 the Irish Whale and Dolphin Groups photographed two other blue whales feeding among fin whales along the shelf slopes.

In Donegal, this August, researchers were lucky enough to catch another rare sighting on video, when seven killer whales were spotted. In the last 40 years only three have been sighted near Ireland.

Here’s a National Geographic video on the blue whale: