People in Kerry are asked to report any sightings of dead fish or fish in distress over the current hot spell.
Inland fisheries Ireland (IFI) is concerned about reduced oxygen levels in lakes, rivers and streams at this time, as it can lead to increased mortality.
Separately, IFI is asking boat owners to carefully check, clean and dry their boats and equipment when travelling from one waterway to another over the bank holiday weekend.
This helps stop invasive species spread in rivers.
Anyone who encounters distressed fish, fish kills, illegal fishing or pollution can contact the confidential 24/7 number on 0818 34 74 24.