Fishery experts are baffled by the deaths of hundreds of eels in a small lake on the island of Inishbofin, Co Galway.
Dead eels have been discovered along a 250 metre zone of the shoreline of Lough Bofin andlarge numbers of eels travelled overland in a bid to escape from the lake.
According to Mr Kevin Rogers, senior environmental officer with the Western Health Board, numerous live eels are seeking refuge underneath rocks that form a shingle causeway which links the lake to the sea.
Mr Rogers explained: "Unusually, everywhere you look there are dead and living eels.
"They are doing their best to get out of the lake for whatever reason."
Fishery officers say they are puzzled by the incident, particularly as oxygen levels in the lake are not seriously depleted.
The eels ranged in size from one metre downwards. Dead eels have been sent for pathological examination.
Islander Mr John Day raised the alarm last week by contacting fishery board officials.
The incident was also reported by Dr John Mercer, a marine biologist who lives on the island and is familiar with the area.