Sea lamprey moved back into the Mulkear system around mid May and MulkearLIFE began its comprehensive tagging operation on the 21 May 2010 at Annacotty Bridge. This was the first such prorgramme ever undertaken in Ireland. Earlier in the week, MulkearLIFE’s Project Officer, Mr. Glen Wightman had noted the presence of sea lamprey immediately below Annacotty weir with the discovery of a half eaten adult sea lamprey. Water temperatures had risen steadily all week and by the 21 May 2010 were 16.3 degree Celsius. In total 50 sea lamprey were tagged. The work was conducted with the support of the staff of Inland Fisheries Ireland (Swords) – Dr. Sean Rooney and Dr. Jimmy King and the Project Team is deeply appreciative of their support. All of the sea lamprey tagged for MulkearLIFE were released below the weir at Annacotty and an additional 30 tagged species were released above the weir. The aim was to monitor the ability of the tagged sea lamprey to move upstream above Annacotty of which only one was successful and of those released above Annacotty weir to move upstream above Ballyclogh weir of which none were successful. The tagging and tracking is of very considerable scientific importance as this is the first comprehensive programme of sea lamprey tagging ever undertaken in Ireland.
A tagged sea lamprey being released
The main objective of this work is the find out more information on their migration and upstream passage. The project hopes to identify problems, in the form of migration barriers, which are preventing the fish moving upstream. In particular, the project wishes to examine whether the weirs upstream from Annacotty are problematic. MulkearLIFE, based on the results on the tracking of the tagged sea lamprey, will likely remove the three major obstructions to sea lamprey spawning migration by retrofitting passage solutions. This will open up the catchment to spawning and recruitment of sea lamprey. By undertaking ongoing tracking of the upstream migrations, the project is begining to gain a criticaly important insight into determining migration barrieres and information on the preferred resting habitats of the sea lamprey which has helped map the spawning beds (redds).
Of the twenty lamprey tagged by MulkearLIFE only one successfully ascended Annacotty weir and travelled upstream approximately 1.5km where it encountered Ballyclogh weir which it failed to pass. The locations of lamprey were marked with handheld GPS and plotted on maps. None of the tagged lamprey placed above Annacotty weir were able to pass Ballyclogh weir indicating it is a very significant barrier. Interestingly, 5 of the 20 tagged lamprey released below Annacotty left the Mulkear system entirely and spawned in the River Shannon at Plassey (behind University of Limerick) and at Castleconnell. Similarily, of the 30 tagged and released above Annacotty weir, 5 left the Mulkear system entirely and spawned in the River Shannon at Plassey (behind University of Limerick) and at Castleconnell. These are well known sea lamprey spawning areas. During the tracking a spawning survey was conducted to map the lamprey redds. Redds are spawning nests that lamprey create to deposit their eggs. A total of 317 redds were counted on June 14. During tracking a small number of redds were also noted between Annacotty and Ballyclogh indicating a few lamprey successfully passed Annacotty. Lastly, during an otter survey one sea lamprey carcass and two redds were observed at confluence of the Killeengarriff River with the Mulkear River which is 5km upstream of Ballyclogh weir. This is the only evidence of sea lamprey successfully passing both barriers.
Dr. Sean Rooney tracking sea lamprey