Eels passing through turbines at Hydroelectric Stations

Through its confidential hotline number (which is now 0818 34 74 24), Inland Fisheries Ireland received a report from a member of the public late on December 8th 2021. The report related to a fish kill in the lower River Shannon, as a result of eels passing through the turbines at the ESB Ardnacrusha hydroelectric station during Storm Barra.

The caller was not from the Limerick area but had seen the report second-hand on social media. There were no reports made to the Inland Fisheries Ireland confidential hotline or to staff of Inland Fisheries Ireland in Limerick concerning the eel mortalities from any person or persons with direct knowledge of the incident.

The report into the confidential hotline was received after dark on December 8th, so no searches could start until the following day. Inland Fisheries Ireland officers undertook a detailed investigation during daylight, starting searches the next morning on December 9th which continued until December 10th.

One dead eel was recovered during searches. However, finding only one dead eel may have been due to a variety of reasons. For example, there was a time lag between the incident and the reporting of the incident to Inland Fisheries Ireland’s confidential hotline number. Therefore, dead eels may have been taken by predators or are very likely to have been swept further downstream.

Sadly, it has become a well-established fact that the operation of hydroelectric turbines results in significant mortalities of eels moving downstream to sea. In fact, the operation of the turbines at the Ardnacrusha hydroelectric station is estimated to kill over 21% of the total run of down-migrating eels.

Overall, the average eel mortality rate is estimated to be 28.5% per hydroelectric turbine, according to 2003 figures from the International Council for the Exploration of the Sea (ICES). This estimated mortality rate is referenced in Ireland’s eel management plan.

Inland Fisheries Ireland does not have a statutory role in regulating the operations of the ESB’s Ardnacrusha hydroelectric station (or any other hydroelectric stations in Ireland), and fisheries on the River Shannon are in the ownership of the ESB. However, Inland Fisheries Ireland would welcome a review of the flow and turbine operations around the time of peak silver eels’ migration. This would improve eel survival rates in the future and improve fish passage generally via the old River Shannon channel.

You can read a copy of Inland Fisheries Ireland’s report by clicking ‘Download’ below. Please note that personal identifiable information contained in this report has been redacted, in compliance with data protection legislation.

Important to note:

Fisheries on the River Shannon are in the ownership of ESB who operate ‘Trap and Transport’ as part of the mitigation measures within Ireland’s Eel management plan under EU Regulation 1100/2007.

To help Inland Fisheries Ireland respond as quickly as possible to reports, members of the public are encouraged to phone its confidential hotline number, which is open 24 hours a day, seven days a week. That number is 0818 34 74 24. As social media platforms are not monitored on a 24-hour-a-day basis, they are not suitable for making reports to Inland Fisheries Ireland.