Silver eel turbine passage mortalities at Ardnacrusha

We are currently assessing silver eel turbine passage mortality at Ardnacrusha hydroelectric station on the Lower River Shannon. Silver eels are adult maturing eels on their spawning migration to the Sargasso Sea after spending up to 20 years (or more) in freshwater. The European Eel Anguilla anguilla is currently listed by the IUCN as a critically endangered species. Andrew Kerr of the Sustainable Eel Group has recently pointed out that “eels are one level nearer extinction than tigers, pandas and snow leopards“.

What is immediately required here is the introduction of sustainable water management practices on the River Shannon, to include greater use of spillways and cessation of hydroelectric generation when eels are running

A selection of photos from our November survey of silver eel turbine passage mortalities on the Lower River Shannon below Ardnacrusha hydroelectric station are provided below. Tens of thousand’s of silver eels are being killed at this and other Irish hydroelectric stations each year. Click on any of the photos below to access the gallery.

The dead silver eels shown in the above photo gallery were killed trying to pass Ardnacrusha hydroelectric station on the Lower River Shannon. We found them during our surveys in November 2015. These surveys were undertaken by walking the river bank and also using a boat. However, the vast majority of these dead and dying eels are never seen as this is a large river and they are washed away or eaten by predators, or simply die and rot at the bottom of the river. Many keep going but die later and out of sight in the Shannon estuary or Atlantic ocean. These are just a few of the many thousands that are killed here each year.

That thousands of silver eels are killed by the ESB’s hydroelectric turbines on the Shannon is so well known that it is being reflected in Limerick city’s art exhibitions

The work that we are undertaking on the Lower River Shannon on silver eel turbine passage mortality is part of a European-wide effort to assess the main anthropogenic impacts on the European eel.  It is becoming increasingly clear that hydroelectric schemes are now the largest cause of mortality for this critically endangered species. Read the full post on the main ECOFACT website which can be accessed here.

That thousands of silver eels are killed by the ESB’s hydroelectric turbines on the Shannon is so well known that it is being reflected in Limerick city’s art exhibitions. The severed eel in ‘Against The Current’ by Mark Dion : “Cut into several sections, the eponymous sculpture of a severed eel indexes the cuttings of the River Shannon by modern engineering”. A video of ‘the Severed Eel’ is provided below, but we encourage you to visit Ormston House in Parnell Street, Limerick, to view it for yourself.

ESB’s trap and transport programme for eels is not working. We need new fish passes and sustainable water management on the Lower River Shannon. Read more here in this post on our main website.

Former Inland Fisheries Ireland Limerick office at Thomond weir. Tens of thousands of turbine killed silver eels floated past here each year with staff / management looking out these windows - nothing was ever said or done. The European eel is now a critically endangered species and thousands of eels are still floating past here. It is time to act and stop this carnage.

Former Inland Fisheries Ireland Limerick office at Thomond weir. Tens of thousands of turbine killed silver eels floated past here each year with staff / management looking out these windows – nothing was ever said or done. The European eel is now a critically endangered species and thousands of eels are still floating past here. It is time to act and stop this carnage.

At the time of writing the current post (early December 2015) the ESB had just commenced spilling 'excess' water though Parteen Regulating weir. They do this when there is more than 400 cumecs available - which they abstract from the Lower River Shannon for hydroelectricity generation at Ardnacrusha. The stop-start approach to spilling water damages the ecology of this Natura 2000 river and is an archaic water management approach that was last reviewed in the 1920's. But this spillage will also coincidentally coincide with peak silver eel migration so hopefully a greater proportion of critically endangered eels can avoid passing though the turbines. We are recommending the use of spillways is increased to help protect silver eels. 

At the time of writing the current post (early December 2015) the ESB had just commenced spilling ‘excess’ water though Parteen Regulating weir. They do this when there is more than 400 cumecs available – which they abstract from the Lower River Shannon for hydroelectricity generation at Ardnacrusha. The stop-start approach to spilling water damages the ecology of this Natura 2000 river and is an archaic water management approach that was last reviewed in the 1920’s. But this spillage will also coincidentally coincide with peak silver eel migration so hopefully a greater proportion of critically endangered eels can avoid passing though the turbines. We are recommending that the use of spillways is increased to help protect silver eels.

According to ICES “the status of eel remains critical and that all anthropogenic mortality affecting production and escapement of silver eels should be reduced to – or kept as close to – zero as possible.” Therefore the killing of tens of thousands of eels at Irish hydroelectric stations cannot continue. What is immediately required on the Lower River Shannon is the introduction of sustainable water management practices on the River Shannon, to include greater use of spillways and cessation of hydroelectric generation when eels are running. The peak silver migration takes place over only around 20 nights and there should be no hydroelectric generation during this period. Spilling water in the old river channel would also bring significant hydro-ecological benefits.

If you have any queries in relation to eels or eel management please do not hesitate to contact us. Also please visit the news section of our main website for further information.

  • PS: Large numbers of silver eels are also killed while passing the numerous smaller hydroelectric schemes on the River Shannon – none of which have any fish screens. For example silver eels leaving Loughs Owel and Ennel in Co Westmeath have to pass through three hydroelectric schemes on the River Brosna (Kilbeggan, Clara, Ferbane) before then passing through Ardnacrusha. These smaller schemes have turbines which spin at a higher rpm so can have even higher turbine passage mortality factor that a large station such as Ardnacrusha. Across Europe there are over 24,000 hydroelectric schemes killing silver eels on their spawning migrations. 

One response to “Silver eel turbine passage mortalities at Ardnacrusha

  1. Hydro dams and migratory fish mix, its sad to see the damage caused by Ardnacrusha and similar esb dams. Could near obsolete dams like this be decommissioned as is happening in other countries?, because it is now a museum of how not to treat the enviroment. An appropriate modern solar power plant or a modern wind powered plant would easily do the same job

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