We undertook a number of Sea Lamprey Petromyzon marinus spawning surveys during 2016 and some videos from these surveys are presented on this post. Sea Lamprey is the largest of the three Irish lamprey species, and also spawns the latest. The Sea Lamprey spawning season extends from May until July, with ova taking up to a month to hatch and settle and burrow into silt deposits in backwater areas. The larvae remain in areas like this – burrowed into sit – for around 5 years – before migrating to the sea.
Adult Sea Lampreys on their spawning migrations do not home to their natal rivers, like Atlantic salmon. Instead the lampreys follow pheromones released by larvae to seek out rivers with suitable lamprey habitats.
The first video below shows Sea lampreys spawning and nest building on the Old River Shannon during May/June 2016. This is part of the Lower River Shannon SAC and is the stretch of the Lower River Shannon affected by hydroelectric abstraction.
The next video below shows Sea Lampreys and a River Lamprey active in the same redd on the River Mulkear during the 2016 spawning season. We have observed this behavior a number of times and it is unlikely that these two species successfully mate together. This spawning site was located downstream of a migration barrier on the Lower River Mulkear (Annacotty weir).
Sea lamprey is listed under Annex II of the European Union Habitats Directive (92/43/EEC) and is included in Schedule Four of the European Communities (Birds and Natural Habitats) Regulations (S.I. No. 477/2011). Sea lamprey are currently evaluated as being at ‘Unfavourable Status’ in Ireland.
The videos and photos above were all taken within the Lower River Shannon SAC.