Press Release

IFI warns of hot weather ‘thermal stress’ threat that kills fish

Separate IFI appeal to boat users not to move craft from the Shannon over the June bank holiday due to invasive species spread

Friday, June 2nd, 2023: Inland Fisheries Ireland is asking the public to report any sightings of fish in distress, or that have died, over the bank holiday weekend - and during the current hot spell.

Inland Fisheries Ireland(IFI) is concerned about potential mortalities due to reduced oxygen levels in lakes, rivers and streams at this time.

fish distress hot weather

Lough Conn, Co Mayo: Daniel Cierpial Inland Fisheries Ireland

Commenting on the issue Barry Fox Head of Operations at IFI said: “During this sunny and dry weather, air and water temperatures are approaching dangerous and potentially lethal levels for salmonids in parts of the country. The risk to fish mortality may be unavoidable due to low oxygen levels and ‘thermal stress.’

“Once the water temperature exceeds the 20 degrees Celsius threshold during daylight, freshwater fish species such as salmon and trout, will suffer thermal stress. Our fisheries staff are continuously monitoring rivers, lakes and streams for any signs of fish experiencing thermal stress.

thermal stress hot weather fish in distress

Aerial view of the River Shannon in Leitrim village: Daniel Cierpial Inland Fisheries Ireland

“Fish need cold, clean water and high water levels to survive and thrive. IFI is mandated, as a State conservation agency, to protect the welfare of fish. Anyone who encounters distressed fish, and fish kills, illegal fishing or pollution, can contact our confidential 24/7 number on 0818 34 74 24.”

Separately, IFI is asking boat owners to help stop invasive species spread in rivers, lakes and canals by carefully checking, cleaning and drying their boats and equipment when travelling from one waterway to another over the bank holiday weekend.

In particular, IFI is asking users of the River Shannon and its tributaries to adopt preventative measures to halt the proliferation of non-native species that can foul, and cling to, craft when in waterways where invasive species are present.

Anglers, boat owners, cruisers, sailing, and recreational waterways users on kayaks, canoes or jet skis are being asked to implement preventative biosecurity measures in line with Check, Clean, Dry protocols.

Barry Fox of IFI added: “We are appealing to users to be proactive in reducing the advance of invasive species in our inland Irish waters. This will greatly contribute to slowing the spread of very harmful organisms such as the bloody red Shrimp, Zebra mussel - and the Quagga mussel, which was first detected on the Shannon’s lakes in 2021.

“We are asking boat owners and anglers not to move any watercraft between waterbodies due to the risks involved in carrying invasive species with them. However, if they must do so, then we urge them to make time to disinfect their boats and fishing equipment afterwards as per Check, Clean, Dry guidelines”.

These recommended methods of sanitisation include:

  • Checking craft, equipment, and clothing after leaving the water for mud, aquatic animals or plant material, removing anything found and leaving it at the site;
  • Cleaning equipment, clothing and footwear, using hot water, as soon as possible, paying attention to ropes, bilges, trailers, the inside of boats, and areas that are damp and hard to access;
  • Drying all parts of the boat/craft and trailer before leaving the site, and allowing to air dry for at least 48 hours.”


For media queries contact: John Lawrence, Communications Manager, Inland Fisheries Ireland, / 087 138 4945

Notes to Editor

About Inland Fisheries Ireland

Inland Fisheries Ireland is the State's environmental agency responsible for conserving, protecting, and managing Ireland's inland fisheries and sea angling resources. IFI was established under the Inland Fisheries Act on 1st July 2010, and operates under the aegis of the department of the Environment, Climate and Communications. There are more than 300 people working full-time in IFI at locations nationwide, and it manages a budget of approximately €31m annually.