As few as 2% of elvers may pass Shannon dams

It has recently been reported by Ireland’s independent scientific committee on salmon that the numbers of Annex II listed Atlantic salmon passing the dams on the River Shannon is less than 5% of the conservation escapement target. The River Shannon is bottom of the league of all the rivers in Ireland in meeting this minimum conservation target.

“The recapture rate for eels released in the river channel further below the Parteen regulating weir was less than 2%”

But what about eels? To mitigate for the impacts of their hydropower dams, the ESB runs ‘trap and transport’ schemes for upstream migrating juvenile eels (elvers), and downstream migrating silver eels. This is a key part of Ireland’s eel management plan. However, we believe that the ESB have exaggerated the benefits for silver eels while failing to provide an effective programme to facilitate upstream recruitment of juvenile eels.

The elver run in 2014 was widely considered to be the best since the 1980’s. However, the elver catches on the River Shannon and Erne were unremarkable and the upturn in elvers was not registered at any of Ireland’s elver index trapping sites. There was also a major elver kill at the ESB elver traps in the Erne in 2014.

The ESB have numerous models in relation to silver eel escapement past their turbines, but they largely ignore the efficiency of their elver traps which facilitate upstream elver migration past their dams – the future of the critically endangered European eel. The only research that ESB have undertaken on elver trap performance has shown that the efficiency of their trap and transport programme for elvers falls well short of the 60% that would be required to meet the requirements of Council Regulation (EC) No 1100/2007. Indeed, these studies have concluded that the efficiency is at best 15.20% but may be less than 2%.

According to the the ESB funded research “In 2008 the recapture rates from mark and recapture experiments (where eels were released adjacent to the trap) did not vary greatly and the average recapture rate was 15.20%. There was no significant difference in the length frequency distribution of eels released and recaptured suggesting that the use of VIE is appropriate as it does not adversely affect the behaviour of different sizes of eels. In 2009 the recapture rates for eels released adjacent to the Parteen trap entrance ranged from 8.61 to 12.64%. The recapture rate for eels released in the river channel further below the Parteen regulating weir was less than 2% and the low average recapture rates overall suggest that a large proportion of potential migrant eels fail to locate or successfully use the trap“.

Salmon stocks on the Shannon are less than 5% of what they should be and these two species have been impacted on in similar ways by the ESB dams.

entrance to elver trap 2
The ESB’s elver trap at Ardnacrusha during 2015; no water attraction, mats clogged with algae. Very few elvers arriving at this dam can find this trap. There is no other way past this blocked migration pathway for elvers. In previous years the trap was not even operated.
entrance to elver trap
The ESB’s elver trap at Ardnacrusha during 2015 – clos-up photo illustrating no water attraction and mats clogged with algae. 
The Ardnacrusha elver trap was not operating by the first week of May 2014. As well as being inefficient, the ESB’s elver traps have not been operated appropriately in the past. The ESB have claimed that they were undertaking maintenance on this trap at the time we took this photo. However, there is no maintenance going on here on the evening of the 1/5/14. It was a week later before this trap was operating and we have detailed records, photos and witnesses which can prove this.
This is Ardnacrusha elver trap on the morning of Sunday 20th April 2014. This trap is derelict and there is no “maintenance” works ongoing here – as claimed by ESB/IFI who said the trap was just down for 2 hours maintenance.

The silver eels are in the upper Shannon and have to be got downstream past the ESB turbines with the least public relations impact. Various models and assumptions favouring ESB are rolled out exhaustively – but even based on ESB models thousands of critically endangered silver eels die passing the turbines each year. Mortality rates are almost certainly higher than the ESB say and we have done our best to expose this.

But why are there not similar models for elver migration on the Shannon?
Facilitating elver migration upstream would just be creating a problem for the future for the ESB would it not? There would then be a requirement to manage those stocks, manage fisheries and then again facilitate downstream migration through and around their dams. Why would a commercial company such as ESB invest in creating a future problem for itself? Well perhaps it doesn’t – you could argue that the ESB have an apparent policy of being seen to be doing something but not achieving anything in relation to migratory fish.

As we approach World Fish Fish Migration Day 2016 this page will continue to highlight the failure of the ESB to meet the requirements of the Eel Regulation on the River Shannon, and the failure of Ireland’s state fisheries agency to regulate the ESB and meet their own obligations to monitor juvenile eel recruitment under Ireland’s eel management plan.

The traditional eel fishermen in Ireland have had their livelihoods taken from them. However far more importantly the future of the European eel in Ireland is being severely compromised by allowing a commercial company to be responsible for its survival. Inland Fisheries Ireland and the ESB have failed to monitor juvenile eel recruitment accurately and open up eel migration pathways in Ireland. There has be a major change in the way we approach eel management in Ireland to help the critically endangered European eel and the ecosystems that depend on it and restore its fisheries.

For further reading see the following:-