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Major Clean-up and Repair to Sea Lamprey Pass

In glorious sunshine late last week and early this week, MulkearLIFE, with the support of IFI colleagues Noel Sheehan and Flan Ryan, undertook a major repair and clean-up to the sea lamprey fish passes on Annacotty weir. These fish passes, specifically designed to improve sea lamprey passage, were installed a year ago and have been shown to be remarkably successful during the 2011 spawning season. They were shown to be extremely beneficial in assisting sea lamprey passage above the first man man-made barrier on the Mulkear. The maintenance and repair work was in preparation for the 2012 season.


Cleaning Annacotty weir and Sea Lamprey fish pass (Image: Ruairí Ó Conchúir)

In an Irish context, Sea Lamprey usually spawn in May or June but this may vary according to a range of factors including water temperature. For the 2012 season MulkearLIFE aims to ensure that the project is not caught out by an early arrival of Sea Lamprey into the Mulkear system. Thus the major maintenance and repair work was undertaken a month earlier than normal. This was in large part facilitated by very low rainfall totals throughout much of the month which meant that water levels in the river have been continually falling since mid March. The very settled, dry, warm conditions may also be a trigger to an earlier than usual return of sea lamprey into the Mulkear system thus the planned work was brough forward by a month. The glorious Spring and warm tempatures have resulted in nature bursting into life. Large numbers of River Lamprey were noted on the early morning of the 26th March.


River Lamprey on the face of Annacotty weir (RHB) (Image: Ruairí Ó Conchúir)

The first two pairs of sand martins to be seen by MulkearLIFE this year were also noted while the work was underway on the morning of the 26th March.


The first sand martins of 2012 – Annacotty, 26 March (Image: Ruairí Ó Conchúir)

Sea lamprey are a sizeable fish in their adult phase – some are in excess of one meter in length and up to two kilogram in weight. The weir at Annacotty acts as the first major barrier to sea lamprey on the upward passage in Mulkear system. It excludes lamprey from their traditional spawning grounds in the upper reaches of the catchment. At the same time is leaves them extremely vulnerable to attack. Thus the maintenance and repair work undertaken over the past number of days involved a full clean-up of the entire face of the weir including the sea lamprey passes. More importantly, it has included the replacement of damaged or broken sheets and the entire realignment of the fish pass following the pounding it received over the winter.


Damming upstream section of Sea Lamprey pass (Image: Ruairí Ó Conchúir)

To undertake this work successfully the river first had to be dammed. This was done by way of placing sandbags on the upstream sections above the sea lamprey passes. Once the vast majority of the water was displaced from the face of the weir an immense clean-up operation commenced to remove moss, dirt and grime. This in turn reveled a number of sheets on the sea lamprey passes which had been damaged or displaced. These sheets, where required, were replaced and the stainless steel substrate and sheets were once again bolted onto the face of the weir. This necessary but backbreaking work was made considerably less strenuous due to the support role of Noel Sheehan and Flan Ryan.


The finished job, two fully functional passes awaiting lamprey (Image: R. Ó Conchúir)

MulkearLIFE is confident that the design of the two sea lamprey fish passes on Annacotty weir, which have now been repaired and re-installed, will once again prove successful. This design is a first for Ireland in that it is the first ever instance where a fish pass has been specifically designed to help sea lamprey passage using the design developed by MulkearLIFE. Monitoring of passage will commence once the first sea lamprey are noted back into the system which maybe at any stage between now and late April / early May.


Last year, lamprey ascend fish pass at Annacotty weir, July 2011 (Image: R. Ó Conchúir)

Further information regarding the project’s work with Sea Lamprey may be viewed on this website including extensive video footage in the projects Video Gallery and on the project’s new YouTube Channel.

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Mulkear LIFE, Inland Fisheries Ireland, Ashbourne Business Park, Dock Road, Limerick, Ireland
Phone: +353 (0)61 300 238   Email: limerick@fisheriesireland.ie