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Basking Sharks off Kerry Have Different Genes to Cousins in Donegal

7th February 2020
Darren Craig taking a mucus sample from a basking shark off West Kerry Darren Craig taking a mucus sample from a basking shark off West Kerry Photo: Dr Simon Berrow, GMIT

Basking sharks which were sampled off the west Kerry coast in early Spring have proved to be genetically different to all other such sharks tested in the north-east Atlantic, according to a newly published study writes Lorna Siggins.

The study on the migration routes of basking sharks also shows that the animals prefer to swim “en famille” to known feeding locations.

Researchers from the Galway-Mayo Institute of Technology (GMIT) participated in one of the most comprehensive studies of the genetics of one of the world’s largest fish.

The project findings, led by the University of Aberdeen, Scotland, were published this week in the journal, Scientific Reports.

Hunted off the south Irish coast by Norwegians until the 1980s, and off the west coast for the Achill fishery in the 1950s and 1960s, the basking shark is known among coastal communities as the “sunfish” due to its preference for swimming just below the surface.

Two Basking Sharks Image Nigel MoyterTwo Basking Sharks Photo: Nigel Moyter

It is also known as “liop an dá” (unwieldy beast with two fins) or more generally “liabhán mór”, denoting a great leviathan.

It is protected in some waters and was recently classified on the International Union for Conservation of Nature “red list” for endangered species

The plankton-eating fish is distinctive for its open mouth. It has been estimated that a seven-metre shark, cruising wide-mouthed at a speed of two knots, will filter 1,484 cubic metres of sea-water per hour.

Basking sharks can grow to more than ten metres, can dive to depths of more than a thousand metres, and feed on plankton in areas of the northeast Atlantic including the west coast of Scotland, Ireland and the Isle of Man.

The researchers note that “up until recently very little was known” about their biology, as they only appear briefly at the sea surface each spring before “vanishing into the ocean depths”.

Through establishing a register of genetic profiles with regular swabbing, the researchers were able to identify individual basking sharks when they arrived to feed. The results revealed that the fish repeatedly returned to the same feeding sites in successive years.

Fieldwork off Donegal by GMIT’s Dr Simon Berrow and Emmet Johnston of the Irish Basking Shark Study Group led to a “breakthrough” in sampling, by collecting skin mucus samples in large groups of sharks - quickly, and with minimum disturbance.

The researchers say that one of the “most surprising” findings among the “cosmopolitan” filter feeders is that basking sharks sampled off Ireland in spring were genetically distinct from other north-east Atlantic fish, including those sampled later in the year off Co Donegal.

Published in Marine Wildlife
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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