According to a recent report, spanning from 1969 to 2022, agriculture has been identified as the most predominant factor for fish deaths in Ireland, attributing to 23% of all causes. Inland Fisheries Ireland (IFI) unveiled an exhaustive study on 2,107 instances of fish deaths in Irish water bodies over the period of 53 years, providing a cumulative insight into related trends, locations, causes, and measures taken for species revival.
The root cause of fish deaths, subsequent to agriculture, was found to be eutrophication – a process that sees an overgrowth of algae and excessive vegetation decreasing the dissolved oxygen content in the water. Other contributing factors include industrial operations, municipal activities, mining, construction, and other miscellaneous operations.
The study further revealed that close to 19,000 fish, including species like Atlantic salmon, trout, eel, and lamprey, perished in as many as 30 registered fish-kill incidents between January 2023 and July 2024. “Fish deaths originating from pollution are catastrophic for local communities. Many of these fatal incidents are needless, preventable, and unlawful”, stated Dr. Ronan Matson, the main author of the report.
He further asserted the ripple effect of such ecological degradation, especially with an ongoing environmental shift, has grievous long-term effects on biodiversity. As a remedial measure, it is necessary to strictly adhere to best practices during any work in or around water bodies.
The Department of the Environment is currently reviewing the legislation concerning inland fisheries. With an objective to strengthen the current sanctions, the department is contemplating revising penalties associated with fishery, environmental, and other offences.
The report highlighted that no county has been spared from fish deaths since 1969. Co Laois registered the most significant percentage of fish deaths attributed to municipal sources, a countdown that doubles since 2007, following Co Laois, the list includes Cork, Cavan, Dublin, and Tipperary.
An investigation has been launched following the recent discovery of approximately 300 deceased trout and eels in a Co Donegal river. It has been observed that Co Cork and Co Cavan were areas with the most significant percentage of fish fatalities, while Co Roscommon and Co Westmeath recorded the least from 1969 to 2022.
The areas with the highest fish deaths were typically the east, south, and north midlands, areas which also happened to have widespread agricultural activities and large city populations. Mainly, the brown trout and Atlantic salmon were the species that bore the brunt of these fatalities with roach and European eel closely following.
Rivers bore the maximum impact with 81 percent of cases reported, followed by lakes at 12 percent, and then manmade bodies of water like ponds and canals with 5 percent. Strikingly, a surge in fish deaths has been linked with heatwave and drought periods. Publicly recognised heatwaves (five successive days exceeding 25 degrees) were noted in the summers of 1976, 1983, 1989, 1995, 2003, 2006, 2013, 2018 and most recently, 2022.
Moreover, meteorological droughts were a common phenomenon during these summers. Conversely, the number of reported fish deaths was relatively low in 2012, a year that experienced one of Ireland’s rainiest summers on record. Notably, the death of numerous wild Atlantic salmon in a Sligo river has also instigated additional investigations.