'No evidence of direct pollution discharges' IFI finds of Sheelin fish kill
IFI issue report into July incident that killed over 800 fish
The major fish kill at Lough Sheelin in July was caused by low oxygen levels in the water that were intensified by high water temperatures and environmental pressures.
That was the findings of an Inland Fisheries Ireland (IFI) report that was instigated after the shocking incident and published this week. A total of 834 fish, mainly female adult brown trout, died at Captain’s Bay and lower Mountnugent River in the Lough Sheelin catchment in July 2025.
David McInerney, Shannon region director at IFI commented: "Extensive and detailed IFI investigations have found no evidence of direct pollution discharges at the impacted area.
"This fish kill involved the tragic loss of a large number of healthy wild brown trout.
"We are very aware how upsetting this unexpected event has been for anglers, the local community, and for IFI staff – many of whom have a long association with Lough Sheelin.
"IFI has been, and continues to, actively engage with landowners, anglers, and other parties to identify priority areas within the catchment to target works that can enhance its resilience."
The summary report highlighted the contributory catchment factors responsible for the large number of mortalities, including:
The presence of excessive plants and silt in the lower Mountnugent River adding to pressures on available oxygen in the water, particularly at night;
Nutrient enrichment combined with increased water temperature and low water levels;
Lake water and rainfall levels were below normal for July resulting in low river flows;
The lake temperature did not vary with depth and fish were unable to seek refuge in cooler parts of the watercourse;
The high density of large fish congregating in a short stretch of water.
IFI thank the Lough Sheelin Trout Protection Association, and other stakeholders including the local community, for their assistance throughout IFI’s investigations in recent months.
Dr James Barry Senior Research Officer at IFI added: "This incident is another sign that our inland waters and aquatic life are particularly vulnerable to multiple pressures, and climate change.
"IFI’s fisheries research and development division continues to collect evidence-based data to support informed decision-making on environmental stresses, climate mitigation and adaptation strategies."
The Summary Report into the July 2025 Lough Sheelin Fish Kill revealed the incident was caused by low levels of dissolved oxygen in both the lake and river that were exacerbated by high water temperatures and underlying catchment pressures.