Alert over influx of Lion’s Mane jellyfish along north Dublin coast

An alert has been issued for swimmers along Dublin’s northern coastline to watch out for a rising number of Lion’s Mane jellyfish at beaches over the coming weeks.

Measuring up to three metres, their tentacles are full of stinging cells used to capture fish and other prey. Often, however, humans feel the sting instead, particularly given the recent rise in the popularity of sea swimming.

The venom can cause nausea, sweating, cramps, headaches and other symptoms and those who experience severe stings are advised to seek urgent medical attention.

“It’s easy to see where the Lion’s Mane jellyfish gets its name from,” notes the Wildlife Trust website, “the long flowing tentacles that surround the bell have all the beauty and bite of a lion.”

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On Wednesday, Fingal County Council issued an alert about the species which prefer the colder waters of the east coast.

“There have been sightings of Lion’s Mane jellyfish at some of our beaches. These jellyfish may also be spotted at our other beaches over the coming weeks,” it said.

With conditions now perfect for their arrival, the population is expected to grow between now and the middle of September.

“There will be a noticeable increase in their numbers on our beaches and in our waters,” the council said.

It noted that even when the jellyfish are dead and washed up on the beach, venom can remain a threat for a number of days. Fragments that break off in the water can also cause harm.

Council officials said that in cases where large numbers of jellyfish are spotted by lifeguards, a red flag may be raised to caution against entering the water.