Large numbers of jellyfish (pelagia noctiluca) have been stranded over a three-month period along the west coast. This is an exceptional event, according to Marine Institute scientists, and this is the first time they have been recorded in such numbers in Irish waters.
They were first detected in Donegal in August and spread to other parts along the western cost in the following months. The numbers were so large that they killed cultivated salmon when they collected against fish cages as a result of the wind and tidal patterns. Small specimens or broken pieces of tissue entered the cages and the fish, it is believed, were stung.
This species, noted for its physical beauty, has amber brown to red-brown patches and sometimes flecks of pink with trailing mouth parts and tentacles. It can grow to about 12 cm in bell diameter. It is easily distinguished from species normally found in Irish waters because it has small pimples which appear on the swimming bell and eight tentacles which extend from the bell's edge. Their stings are produced by special cells that turn themselves inside-out when touched, and in doing so release a toxin.
Dr Dan Minchin of the institute's fisheries research centre in Abbotstown, Co Dublin, would like sightings of the species to be reported to him (email: dminchin@frc.ie).