Inadequate silver eel mitigation on the Shannon

The River Shannon has a large hydroelectric scheme in its lower reaches, and there are no bypasses for silver eels migrating downstream (or indeed for other fish such as salmon kelts and smolts). The ESB – who own the fishery and operate the hydropower scheme – run a trap and overland transport programme for silver eels. The idea is to catch silver eels in coghill nets attached to the bridge at Killaloe, and then transport the captured silver eels downstream in trucks and release them below the turbines. When setting out the Shannon River Basin Eel Management Plan to meet Council Regulation (11000/2007) no changes whatsoever were made in relation to hydro generation protocols. Meanwhile, eel fishing was banned and this trap and overland transport mitigation was introduced. However, there are a number of problems with this trap and transport programme, which include the relatively low efficiency of this operation and also the impact of excessive handling on the captured eels. Most of the silver eels migrating down the River Shannon still have to pass though the turbines at Ardnacrusha hydroelectric station, with devastating consequences.

In a sustainably managed Shannon eel fishery we would maximise recruitment and replace hydroelectric turbine passage mortality with a sustainable fishery to the benefit of the eel, traditional fishermen and local communities alike

As part of a review of this programme we investigated the operation at Killlaoe, and have found that the nets are only being operated on weekdays – 4 nights per week. The nets also only cover about half of the width of the river at Killaloe, with no nets on the right side of the river and none in the large central navigation arch, where the main flow is. The photos below were taken during surveillance completed by us on Friday night and Saturday morning (7-8 November 2014) and show that ESB are clearly not operating within the protocols of even the arguably inadequate Shannon catchment eel management plan. We are now into November, with the river in flood, and silver eels outmigrating from all over the catchment – but it’s the weekend so the ESB are not providing any mitigation. All silver eels passing downstream at weekends have to go through the turbines at Ardnacrusha. Female silver eels – which are larger – are particularly vulnerable to turbine passage mortality and dominate the current run. However, even when this catch and overland transport programme is being operated it is totally inadequate in our opinion. 

Trap and transport silver eels
ESB’s silver eel “trap and overland” transport programme on the River Shannon is no more than a PR stunt – nets high and dry for 3 nights ever week; these nets cover only about 50% of the width of the river catch less than than 30% of the out-migrating silver eels when operated on week days, and damage and stress any eels caught.
Killaloe-eel-weir
Silver eel mitigation? Sorry it’s the weekend – the inadequacy of the ESB’s management programme for an endangered species exposed again!
eels-turbines
The nets when down also cover less than 50% of the river and will catch less than 30% of the eels migrating. The eels are then in the nets all night against the full flow of the river and dumped into dustbins and suffer from all the handling before being “released” below the turbines. This is not a suitable mitigation measure for an endangered species.
Ardnacrusha
Any silver eels passing downstream on weekends have to go through the turbines at Ardnacrusha with devastating consequences. Even when the catch and transport programme is operating at least 70% of the silver eels migrating downstream still have to run the gauntlet of these turbines.

Even when the ESB are running this “trap and overland transport” programme they are only catching around 30% – at very most – of the silver eels that are running. The rest of these eels – an endangered species – have to go through the ESB’s turbines at Ardnacrusha. The “lucky” silver eels that are caught in these coghill nets (during week days) are subjected to the full flow of the River Shannon while they sit in the nets overnight. This is then followed by multiple handling using nets and dustbins, and many die following the damage and stress of all this.

The ESB’s “trap and overland transport” programme for silver eels can be best described as a PR stunt in our opinion and is being used to avoid having to make any changes to hydro generation protocols. It fits in with ESB’s apparent policy of being seen to be doing something, but not actually achieving anything except protecting their interests. We believe that this programme falls well short of what should be done for this internationally endangered species on the River Shannon. It is also noted that there is significant bycatch in these nets, with thousands of perch, roach and even pollan being killed here every year.   

Most of the silver eels migrating down the River Shannon still have to pass though the turbines at Ardnacrusha with devastating consequences.
Most of the silver eels migrating down the River Shannon still have to pass though the turbines at Ardnacrusha with devastating consequences.

There are a number of other things that could be done for silver eels on the Shannon that would be preferable to the current approach. For example hydro generation could be limited to daylight hours with water released each night, during the peak periods of the silver eel run, from the regulating weir at Parteen. This would allow a significant proportion of silver eels to escape unharmed downstream, therefore avoiding both turbine mortality and mortality associated with the coghill nets and overland transport approach. The approach of spilling water would also have significant benefits for the ecology and fluvial geomorphology of the Old River Shannon, which currently receives a compensation flow equivalent to a 1:50 year drought flow the vast majority of the time. Alternatively, a new fish bypass system should be installed and this could be used to assist salmon smolts (and kelts) downstream also.

Both options would of course be more expensive for the ESB than the current trap and overland transport work, and would require changes in current hydro generation protocols. However, when it comes to protecting an endangered species everything that can be done should be done.

Clonlara eel weir
This is the site of the former Clonlara eel weir on the ‘new’ Shannon (i.e. the headrace to Ardnacrusha hydroelectric station) earlier today. When the ESB were catching silver eels commercially they set massive nets here each night during November to catch eels to sell for huge profits all over Europe. However, once they had to catch silver eels for their ‘trap and transport’ programme they decommissioned this fishery.

The current management approach on the River Shannon has resulted in eel fishing being banned, but not a single restriction was imposed on the ESB’s hydroelectric power generation activities. In a sustainably managed Shannon eel fishery we would maximise recruitment and replace hydroelectric turbine passage mortality with a sustainable fishery to the benefit of the eel, traditional fishermen and local communities alike. The current inadequacy of the silver eel trap and transport programme follows on from us exposing earlier this year that the ESB were also not operating their juvenile eel trap and overland transport programme properly. Indeed they missed the main elver run this year by failing to get their elver traps operating until the second week of May. We believe that it is time to urgently review the ESB’s activities on the River Shannon, in terms of silver eel passage, water management, and collection of elvers for restocking.