A major fish kill is under investigation after hundreds of protected wild salmon and many trout were found dead in Mayo.

Enforcement agency, Inland Fisheries Ireland (IFI), has categorised the incident at the Glore River in Kiltimagh as “serious”.

The agency believes more than 500 young salmon and trout have been wiped out in the river which provides important spawning grounds within the Moy river catchment which is renowned for its fishing.

Any kill of this scale at this crucial time for the fish threatens the reproduction cycle and could decimate stocks in the river for the next few years.

Environmental and fisheries officers were alerted to the incident last Friday and have worked over the weekend to assess the extent of the damage.

Water and fish samples have been taken from the scene for laboratory tests to determine if pollution caused the deaths.

Tracking the source of a pollution incident can be notoriously difficult and successful prosecutions are few.

It comes as Irish Water and Mayo County Council are carrying out an investigation to identify the cause of an overflow incident from Kiltimagh Water Treatment Plant.

The flow from the plant went into the River Glore, resulting in a fish kill.

Irish Water and Mayo County Council have confirmed that the treatment process at the plant has not be compromised and the water supplied by the plant remains safe to drink.

Ireland’s wild salmon are protected and can be fished only under licence as their numbers dwindle due to overfishing, poor river water quality and sea lice spread from some intensive salmon farming activities.

To report fish kills, members of the public are encouraged to call Inland Fisheries Ireland’s confidential hotline number on 1890 34 74 24, which is open 24 hours a day.