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.
Looks 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.
