A press release from Inland Fisheries Ireland below indicates that they are satisfied with current silver eel mitigation measures used on the River Shannon. The current approach attempts to capture outmigrating silver eels in coghill nets used by contract fishermen, and transport the captured eels overland in trucks around the hydroelectric scheme. However is the ESB doing enough for silver eels on the Shannon or is this exercise little more than another public relations stunt? It is likely that the ESB catches and trucks less than 30% of the annual run of outmigrating silver eels on the Shannon.
The silver eels caught in coghill nets are are likely to suffer from significant physical damage, stress and mortality as a result of being held in nets against the full flow of the river, and other handling associated with the trucking . The rest of the spawning stock leaving the Shannon is then subjected to turbine mortality, which is likely to be significant at the turbines at Ardnacrusha. There is no fish pass for downstream migrating fish on the River Shannon.
As we enter into the peak of another silver eel migration season, we have to ask is the ESB doing enough here for silver eels? We would also ask is enough being done overall to mitigate the effect of the Shannon scheme on the endangered European Eel? 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 the Shannon lakes.
What is not clear is why our state fisheries agency Inland Fisheries Ireland is not more ambitious in what it asks for from the ESB
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 eels now, not the ESB!). One option would be to limit hydroelectricity generation to daylight hours and release water continuously each night, during the peak periods of the silver eel run, from the upstream regulating weir at Parteen. This would allow a significant proportion of silver eels to escape unharmed to the sea, therefore avoiding both turbine mortality and mortality associated with the coghill nets and overland transport approach. The approach of spilling water at Parteen Weir would also have significant benefits for the ecology and hydrogeomorphology of the Old River Shannon. The Old River Shannon currently receives a compensation flow of only 10 cubic meters per second – equivalent to a 1 in 50 year natural drought flow – and this is not sufficient to maintain the Good Ecological Status of this Internationally Important water body.
Alternatively, a new fish bypass system – catering for all downstream migrants on the River Shannon – should be installed. However, this approach would be technically challenging, expensive, and would be likely to take a few years to design and install. It is clear that the use of water spilled into the Old River Shannon would be preferable due to the range of other benefits which this would bring, and would also be a measure that could be implemented immediately and would be likely to have significant success.
Both options would of course be more expensive for the ESB than the current trap and overland transport work. However, when it comes to protecting an endangered species everything that can be done should be done.
The press release referred to above can be accessed at the following link. What is not clear is why our state fisheries agency – Inland Fisheries Ireland – is not more ambitious in what it asks for from the ESB.
The same issues on the River Shannon apply on the cross border River Erne, and also the Lee and Liffey hydroelectric schemes.