Lampreys still blocked at Annacotty Weir

Annacotty weir is located on the River Mulkear, Co Limerick, Ireland. It is a tributary of the Lower River Shannon and a significant proportion of the River Mulkear is designated as part of the Lower River Shannon Special Area of Conservation (SAC). This Natura 2000 site is designated for the three Irish lamprey species, Atlantic salmon, Otters and a number of other qualifying interests.

There is a sign beside Annacotty Weir which was installed as part of the €1.75 million Mulkear LIFE project. This sign claims that lamprey tiles placed on the weir in 2011 have been a success in restoring lamprey passage at this weir. But there is no scientific basis for the claims made on this sign and the fish passage problems here remain. Indeed, there is no scientific evidence whatsoever for the claim that the lamprey tiles facilitated 93% passage as claimed on this sign.

The lamprey tiles at Annacotty weir did not help Sea Lampreys and did not help River Lampreys. This site remains a major migration barrier for migratory lampreys in the Lower River Shannon SAC. Atlantic salmon and European eels also have problems here.

This needs to acknowledged now by Inland Fisheries Ireland – and AMBER need to stop promoting these tiles as a solution for lamprey passage until more research is done. Even the best placed studded tile passes are “inadequate” for lamprey passage according to Tummers et al (2018).

Annacotty weir remains a major migration barrier for anadromous lampreys
This sign is still present at the Annacotty weir site
There is no scientific evidence whatsoever for the claim that the lamprey tiles facilitated 93% passage as claimed on this sign.

The lamprey tiles placed on Annacotty weir have not worked for either migratory lamprey species. The weir is too steep and flows are too high – no River Lampreys can use them and Sea Lampreys just cling to the base of the tiles. Any Sea Lampreys which pass here get through via the denil pass at the centre of the weir. Very occasionally River Lampreys get past when the weir floods out – but this is a rare event. A very small number of River Lampreys may also get through via leaks under the weir. But none use the lamprey tiles!

In the Tummers et al (2018) the passage efficiency achieved was 25.6% despite optimal placement – and they stated that this is “inadequate in the context of the recommended 90–100% passage efficiency target per barrier to maintain viable diadromous populations“. This means that lamprey tiles are not a suitable solution for maintaining ‘Good Conservation Status’ of an SAC population. No River Lampreys can use the tiles at Annacotty weir.

Mulkear LIFE also published the results of a radio-tracking study (Rooney et al, 2015) But this paper did not present any evidence that showed that lampreys could actually use the tiles. Indeed, they specifically state that “the expectation that increased lamprey passage should have resulted from the alterations [ ] was not observed“. This paper recommended barrier removal – an acknowledgement that the authors were indeed aware that the 93% claims could not be supported by science. The claims of 93% were not repeated in the published study – nor the method of walking out on the weir at night.

One of the lamprey tile passes is also gone from Annacotty weir – and this was the one that Inland Fisheries Ireland claimed was the most successful in their sign. But nobody ever walked out on the weir at night to survey this. The Rooney et al (2015) radio tracking study of lampreys at this weir did not present any evidence that showed that lampreys could use the tiles.

Thousands of River Lampreys have been observed trapped below this weir
Sea Lampreys cling to the weir (and lamprey tiles) but cannot ascend. Any Sea Lampreys that pass this weir do so using the denil pass at the centre of the weir.

Mistakes need to be admitted here – and we need to move forward. This weir is a legacy of an Office of Public Works – OPW flood scheme and they should now pay for it’s removal or modification. What chance have we of addressing the impact of Ardnacrusha hydroelectric scheme on the Lower River Shannon if we can’t address this relatively minor obstacle?

The Sea Lampreys issue at this weir is highlighted here:-
https://lampreysurveys.com/2018/06/05/sea-lamprey-migration-blocked-by-weir/

The River lamprey issue at this weir is highlighted here:-
https://lampreysurveys.com/2017/03/28/river-lampreys-trying-to-pass-mulkear-weir-march-2017/

Mulkear LIFE’s sign at Annacotty – its only legacy?
https://oldrivershannon.com/2015/07/12/mulkear-life-sign-at-annacotty-its-only-legacy/

The tiles at Annacotty weir did not help any lamprey species. I have worked for years to get this acknowledged. There is no scientific evidence to support the claim that 93% of lampreys can use the lamprey tile passes. One of the tile passes is gone. This sign needs to be removed as it an insult to people who care about this river and its conservation. It is also misleading and misinforming the many people who pass here each day. We need a proper solution for this site to help all migratory fish. This is not about embarrassing anyone – this is about restoring fish migration pathways.

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