CASTLECONNELL’S Pat Joyce nearly fell off his fishing stand when he spotted what looked like a single small jellyfish in Lough Derg.
The angler thought that perhaps he was mistaken as, everyone know, there is no such thing as a freshwater jellyfish. Two weeks later, again fishing for bream in the tranquil surrounds of Scarriff Harbour just off Lough Derg, Pat noticed not one but hundreds of tiny jellyfish moving on and below the surface.
He immediately contacted the EPA and they put him on to Inland Fisheries Ireland (IFI). Staff sped to the scene and collected up to 20 live specimens. They really did exist!
Dr Joe Caffrey, invasive species specialist with IFI, immediately organised a site visit to Lough Derg with a team of experts including Dr Tom Doyle, a jellyfish expert from the Coastal & Marine Research Centre in UCC, and Dr Dan Minchin from the Lough Derg Science Group. The survey revealed small numbers of the jellyfish at Scarriff harbour, but specimens were also recorded from two other locations within the lake – at Rossmore harbour and at Dromineer.
So what is this jellyfish, where did it come from and why was it never spotted in Ireland before? Dr Doyle identified them as the free-swimming life stage of a species called Craspedacusta sowerbii.
Suzanne Campion, IFI head of business development, said it is the first official record for this species in Ireland.
“This freshwater jellyfish hails from the Yangtze River Valley in China but currently has a worldwide distribution. It was initially discovered in exotic aquatic plant tanks in Regent’s Park, London in 1880 but has since spread widely throughout the globe.
“The jellyfish is about the size of a euro coin and broadly resemble their marine cousins. It is more or less transparent with a distinctive white/greenish cross and a white/cream circular outline. It possesses in the region of 250 – 300 small tentacles.
“It is probable that the discovery of this jellyfish relates to the wonderfully warm summer that we experienced in Ireland this year, when water temperatures in many watercourses exceeded 25 degrees C for prolonged periods,” said Ms Campion.
Experience in other countries suggests that blooms of such freshwater jellyfish occur only sporadically and that they last, in any one year, for only a few weeks.
“So it is possible that we may not see such a sight again for many years,” said Ms Campion, who stresses that the freshwater jellyfish is not harmful to humans and that, while they do capture their tiny prey by stinging, the stinging cells are not sufficiently powerful to harm humans. The jellyfish do not appear to have any significant effect on the biology or ecology of the waters they are recorded in, probably due to their sporadic occurrence and the short period that the jellyfish blooms are in any water body.
Minister for State Fergus O’Dowd said our inland fisheries resource must be protected.
“Anglers are the eyes and ears on our rivers and lakes. I ask all anglers to continue to assist in the protection and conservation of this resource, reporting any invasive species they come across to the IFI hotline immediately,” said Minister O’Dowd.
If you spot jellyfish in your local watercourse, please contact IFI on www.fisheriesireland.ie or on the 24 hour hotline 1850347424, www.jellyfish.ie or www.nbdc.ie