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Barrel Jellyfish Reported in Larger Numbers Along Entire East Coast

28th May 2023
A Barrel jellyfish
A Barrel jellyfish washed up on a beach Credit: Tom Doyle

Barrel jellyfish have been washing up in unusually large numbers along the entire coastline as far as Cork in the past few months.

As The Irish Times reports, sightings have been recorded from Lough Foyle off Derry, right around to West Cork, by the National Biodiversity Data Centre (NBDC).

University College Cork (UCC) scientist Dr Tom Doyle says the barrel jellyfish – so named because they can weigh up to 25 kilos – “looks scary”, but don’t really sting.

Translucent in colour, they resemble “cauliflowers”, and have eight oral arms or tentacles with thousands of little mouths to feed on plankton, he explains.

A Barrel jellyfish photographed in France in 2022Looks scary”, but don’t really sting" - A Barrel jellyfish photographed in France in 2022 Photo: Tom Doyle

“The reports of their geographical spread began early in the year when we had 15 washed up in 30 days on our beaches,” he says.

“Normally, we would only hear of them off Rosslare in Co Wexford, where there can be several thousand barrel jellyfish,” he says.

A total of 96 confirmed barrel jellyfish have been formally filed to date with the NBDC, extending almost halfway around the coast.

Doyle has also received reports through his Big Jellyfish Hunt social media page.

Open water swimmers in south Dublin Bay have noticed more of them, along with jellyfish resembling Mauve's stingers, while there have been only occasional sightings off the west coast.

Seasoned Galway Bay open water swimmer Paddy McNamara said barrel jellyfish weren’t very common generally in the bay.

However, McNamara says he has noticed a change in the last couple of years, where there are more frequent sightings of Lion’s Mane, one of the largest jellyfish with flowing tentacles and a more venomous sting.

He doesn’t believe the more frequent sightings relate to more open water swimming, which exploded during the pandemic.

“Lion’s mane jellyfish were rare enough here in Galway Bay up to two years ago, but now they are regarded as quite common on the west coast,” McNamara says.

Galway Bay water temperatures are “normal” for this time of year, he says, at just over 14 degrees Celsius. Team

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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!