Dozens of fish dead in Portavoe reservoir, Donaghadee
Dozens of trout have been found dead in a reservoir in County Down.
People living near Portavoe Reservoir outside Donaghadee have claimed that water levels have dropped recently after a sluice gate was left open.
NI Water, which owns the reservoir, said the gate was opened after a recent flood but was closed again.
The Department of Culture, Arts and Leisure said it believed the fish died due to low water levels, increased temperature and a lack of oxygen.
"This physical condition is known as furunculosis and is common at this time of year under simillar physical conditions.
"On 20 June, a Northern Ireland Environment Agency (NIEA) officer investigated the dead fish at Portavoe and found no evidence of pollution, but witnessed some distressed fish in the lower levels of the reservoir.
"The NIEA officer was in agreement with DCAL as to the cause of the dead fish."
Gordon Adair, reporting from the scene for the BBC, said fish could clearly be seen struggling for air in distress.
Anglers say the sudden drop in water levels mean that there is not enough oxygen in the water for the fish.
Local fisherman Clifford Rosbotham was at the reservoir on Sunday morning and said the fish should be humanely destroyed.
He said: "You do not want to see anything suffering and the trout down there are definitely suffering.
"I am not certain what the remedy is but the trout do need to be netted and taken out and destroyed. There is no point leaving them down there to suffer like that."
The website of the Department of Culture, Arts and Leisure says that there are about 6,000 trout in the reservoir, which can be fished exclusively by fly fisherman.