‘Like the flip of a switch, it’s gone’: has the ecosystem of the UK’s largest lake collapsed?

Lough Neagh's flies were seen as a nuisance. Now their sudden disappearance is a startling omen for a lake that supplies 40% of Northern Ireland's water

• Photographs by Alexander Turner

Declan Coney, a former eel fisher, knew there was something wrong when the famed swarms of Lough Neagh flies failed to materialise. In past years, they would appear around the Northern Irish lake in thick plumes and wisps" - sometimes prompting mistaken alarm of a fire incident, Lough Shore residents say.

Clothes left out on a washing line would be covered in them", Coney says. So would any windshield on a vehicle travelling around the lough's 90-mile shoreline. Conservationists marvelled at their courtship dances, hovering above treetops.

Former eel fisher, now lake monitor, Declan Coney: This is the first year ever that you'd find there's no flies here'