Inland Fisheries Ireland (IFI) has found no definitive cause for the deaths of nearly 1,100 adult salmon in Co Sligo’s Ballisodare River, according to a recent report.
Despite investigations by IFI, the Marine Institute, and the Department of Agriculture, no single factor has been identified to explain the mortality event, which occurred between June 28 and July 21, 2024.
The deaths, affecting 12.8 per cent of the 8,451 salmon returning to the river, are thought to have been caused by a combination of factors. The report suggests that stress at sea, possibly linked to phytoplankton exposure, may have compromised the salmon’s gills and ability to breathe. Low river water levels likely exacerbated these conditions, facilitating the spread of disease.
No evidence of significant pollution was found, although ammonia levels in effluent discharge from a nearby wastewater treatment plant exceeded licence limits in recent years. However, no direct link to the salmon deaths was established.
The river has since reopened for catch-and-release angling after a temporary closure in July.
