Salthill beaches have been awash with dead jellyfish for the past few weeks – but experts warn that despite being dead, they can still sting.
It may have been an unusual scene for the general public but experts in the marine biology department in NUI Galway weren’t a bit surprised as this is the mating season of that particular species of jellyfish.
Dr Tom Doyle, a marine biologist and an expert in gelatinous zoo plankton (jellyfish) ecology, said however that it was a growing cause of concern to see so many of them washed ashore.
In recent years, swarms of the species known as pelagia or commonly the mauve stinger, have been observed off Irish coasts at this time of year. And though some of them would inevitably end up on the beach, Dr Doyle did concede the number of them on Salthill beaches last week was high.
He said that once the jellyfish were washed ashore and stranded on the beach, their demise was inevitable as they get their oxygen from the water.
Dr Doyle, who is based in the Martin Ryan Institute in NUIG, said there was a Facebook page devoted to the creatures called the Big Jellyfish Hunt which monitored their movements year round.
“It’s not unusual to see swarms or brooms of them in the sea at this time of year as it is their mating season. The females release their eggs and the males are queuing up behind them which explains why so many of them are spotted in the one place.
“This particular one is an oceanic jellyfish and it survives most of the year on the ocean bed but surfaces during the mating season. Our Celtic Voyager vessel observed a line of them floating on the waters in Galway Bay which was one kilometre long, five to ten metres wide and probably five metres deep.
“That is their behaviour at this time of year but the South Westerly winds and the sea currents probably drove them in towards the beach where they were stranded,” he explained.
He said that it was always a concern to see so many of them dying in that manner but that marine records showed reports of similar swarms of them in Irish waters 100 years ago.
Dr Doyle stressed that though the jellyfish were dead, they could still sting and he warned people not to pick them up. He further warned daily swimmers to be aware of them in the water so close to the shore, as they were stingers.
They vary in size. Some are as big as a closed fist while others are quite tiny, only millimetres in width.