Inland Fisheries Ireland (IFI) has published a major new report on 2,107 fish kills occurring in Irish rivers and lakes between 1969 and 2022.
The detailed study is the first comprehensive overview of related trends, locations, causes and population recoveries over the 53-year period.
Fish Kills in Ireland-History, Current Status and Recovery reveals that the most common known cause of fish deaths was agriculture, followed by eutrophication, industrial, municipal, mining, construction and other activities.
Separately, IFI records show that almost 19,000 fish died in 30 recorded fish kill occurrences between January 2023 and July 2024. Fish mortalities included Atlantic salmon, trout, eel and lamprey of all ages.
Dr Ronan Matson, lead author on the new report, and Eastern region director at IFI said: “Fish kills caused by pollution are heartbreaking for local communities. Many of these lethal events are needless, avoidable, and criminal.
“The ripple effect of ecological damage on biodiversity is long-lasting — at a time of rapid environmental change. Best practice must always be adhered to in all works in or near watercourses.
“IFI staff deploy an emergency response to any fish kill incident. It is crucial that any signs of concern are reported to IFI immediately to its 24/7 number, 0818 34 74 24. This enables officers to respond swiftly, find a cause and prosecute those responsible.”
The Department of the Environment, Climate and Communications is currently carrying out a review of inland fisheries legislation. Existing sanctions are being examined, and it would include a potential update of penalties in respect of fishery, environmental, and other offences.
Fish Kills in Ireland-History, Current Status and Recovery is based on historic reports compiled by fisheries environmental officers, and it found that:
- Fish kills occurred in every county since 1969
- The highest percentage of fish kills attributed to municipal sources – a source which has more than doubled since 2007 - was recorded in Co. Laois, followed by Cork, Cavan, Dublin and Tipperary
- Counties Cork and Cavan had the highest proportion of fish kills, while Co Roscommon and Co Westmeath had the lowest in the period from 1969-2022
- Fish kill hotspots were prevalent in the east, south, and north midlands, coinciding with intensive agricultural activity and large urban centres
- Agriculture was the most significant reported cause of fish kills in Ireland from 1969 to 2022, accounting for 23% of overall causes
- This was followed by eutrophication, where algal blooms and excessive plant growth from nutrients deplete available oxygen in the water (13%), industrial (12%), other (9%), municipal (discharge or effluent from water/wastewater treatment plants or other facilities) (8%), mining (3%) and construction (2%)
- Brown trout and Atlantic salmon were the main fish species impacted by fish kill incidents, followed by roach and European eel
- The time period involving the recovery of fish populations varied in sample sites, but took at least three years
- Rivers were the most impacted waterbody type(81%), followed by lakes (12%), and artificial waterbodies such as ponds and canals (5%)
Digitised details relating to the new study are now available to the public on IFI’s open data portal.
