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High Numbers of Sperm Whales Counted off Irish West Coast in New Study

10th December 2020
Sperm whale at surface Sperm whale at surface Credit: Simon Berrow

Up to 380 sperm whales are living in deep waters off the Irish coast, a newly published study has found. 

This makes sperm whales “one of the most abundant great whale species” in these waters, expert Dr Simon Berrow says. 

Sperm whales are known for their distinctive echolocation “clicks” which can be heard over many tens of kilometres, and this allows them to be counted.

A survey team from Galway-Mayo Institute of Technology (GMIT) and the Scottish Sea Mammal Research Unit (SMRU) Consulting spent 45 days at sea in harsh weather conditions to conduct the population count.

Deploying towed hydrophone from RV Celtic Voyager © Simon BerrowDeploying towed hydrophone from RV Celtic Voyager Photo: Simon Berrow

“With high sea states and towering swell, the study relied purely on being able to detect the distinctive powerful click trains of sperm whales using a streamlined towed hydrophone or underwater microphone array,” Dr Berrow said. 

The results were published recently in the Journal of Cetacean Research and Management, following detailed sea surveys dating back to 2015.

Dr Berrow, the principal investigator on the study, noted that the deep-diving tendency of sperm whales makes them difficult to observe at sea – they can spend nearly an hour in depths below 300m. 

Only 11 individuals were sighted during 388 hours of effort, he said, but 391 acoustic detections were recorded. 

Sperm whales off Ireland’s west coast © Irish Maritime SquadronSperm whales off Ireland’s west coast Photo: Irish Maritime Squadron

“Each whale was pinpointed by comparing the exact time that each click arrived at each hydrophone in the array and then triangulating bearings from sequential clicks over extended encounters,” he said.

The whales seemed to prefer seabed areas that sloped to the northwest, including the Erris and Rockall Basins. 

There was also a dense concentration of sperm whales in the South Brona Basin canyon system near 350km west of Co Kerry

The surveys were carried out from the Marine Institute’s RV Celtic Voyager and the yacht Song of the Whale, operated by Marine Conservation Research Ltd.

The study was part of the ObSERVE-Acoustic project funded by the Department of Communications, Climate Action and the Environment and the National Parks and Wildlife Service.

More here

Lorna Siggins

About The Author

Lorna Siggins

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Lorna Siggins is a print and radio reporter, and a former Irish Times western correspondent. She is the author of Everest Callling (1994) on the first Irish Everest expedition; Mayday! Mayday! (2004) on Irish helicopter search and rescue; and Once Upon a Time in the West: the Corrib gas controversy (2010).

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Marine Wildlife Around Ireland One of the greatest memories of any day spent boating around the Irish coast is an encounter with marine wildlife.  It's a thrill for young and old to witness seabirds, seals, dolphins and whales right there in their own habitat. As boaters fortunate enough to have experienced it will testify even spotting a distant dorsal fin can be the highlight of any day afloat.  Was that a porpoise? Was it a whale? No matter how brief the glimpse it's a privilege to share the seas with Irish marine wildlife.

Thanks to the location of our beautiful little island, perched in the North Atlantic Ocean there appears to be no shortage of marine life to observe.

From whales to dolphins, seals, sharks and other ocean animals this page documents the most interesting accounts of marine wildlife around our shores. We're keen to receive your observations, your photos, links and youtube clips.

Boaters have a unique perspective and all those who go afloat, from inshore kayaking to offshore yacht racing that what they encounter can be of real value to specialist organisations such as the Irish Whale and Dolphin Group (IWDG) who compile a list of sightings and strandings. The IWDG knowledge base has increased over the past 21 years thanks in part at least to the observations of sailors, anglers, kayakers and boaters.

Thanks to the IWDG work we now know we share the seas with dozens of species who also call Ireland home. Here's the current list: Atlantic white-sided dolphin, beluga whale, blue whale, bottlenose dolphin, common dolphin, Cuvier's beaked whale, false killer whale, fin whale, Gervais' beaked whale, harbour porpoise, humpback whale, killer whale, minke whale, northern bottlenose whale, northern right whale, pilot whale, pygmy sperm whale, Risso's dolphin, sei whale, Sowerby's beaked whale, sperm whale, striped dolphin, True's beaked whale and white-beaked dolphin.

But as impressive as the species list is the IWDG believe there are still gaps in our knowledge. Next time you are out on the ocean waves keep a sharp look out!

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