Many fish, including large conger eels, have drowned in a sheltered bay in Kerry, and are being found washed up on beaches.
The species found on the shores of Brandon Bay included wrasse, several hundred large conger eels and ling.
Mr Kevin Flannery, of the Department of the Marine in Kerry, said people had assumed a toxin or pollution was the cause.
However, it emerged that the fish had drowned. Recent north-westerly gales had whipped up the water surrounding the basin of Brandon Bay. The fish could not escape and even the hardiest drowned.
"Sand and silt fouled up their gills and choked them - the fish drowned in other words," Mr Flannery said. He added that he had only come across the phenomenon once before.
"It goes to show the extreme bad weather we have had," Mr Flannery said. He also appealed to the public to look out for turtles which he expected to appear with prevailing southerly winds.