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Kilkenny Flood Relief Scheme

Photo: A typical corral used for quantitative sampling of lamprey ammocoetes. Muddy substrate and over-hanging trees are common features in sites holding significant lamprey densities.

Kilkenny City, in the southeast of Ireland, has historically suffered serious flooding. To reduce this risk a flood protection scheme was developed from 1996-1999. As part of the design process an Environmental Impact Assessment was undertaken in the River Nore. The Central Fisheries Board (CFB), working with the Southern Regional Fisheries Board, undertook a study of the fish populations and fishery habitat in 1998. This study showed significant numbers of brown trout and salmon as well as noting the presence of eel, lamprey and other species.

Photo: A bank-based excavator removing marginal soft sediment from the River Nore in Kilkenny City, Ireland

In the course of the scheme design, the River Nore was designated as a “proposed candidate Special Area of Conservation” (pc SAC) by Duchás – the Irish Heritage Service, under the EU Habitats Directive. Under Annex II of this directive each EU state is required to identify habitats as areas of conservation for threatened or endangered species. In the case of the River Nore, designations were made in relation to the Pearl Mussel (Margaritifera margaritifera), the fresh-water crayfish (Austropotamobius pallipes) and the three species of lamprey (Sea-, river- and brook lamprey). The River Nore was chosen from Ballyragget to Inistioge, as a candidate Special Area of Conservation. Therefore, Kilkenny City, with its proposed Flood Relief Scheme, is within the bounds of the proposed Special Area of Conservation or SAC.

Photo: Soft-sediment being deposited on the bank at the Bishop’s Weir site on the River Nore

Following discussions between OPW and Duchás, it was decided that a series of studies be undertaken to assess in more detail the population status of the Annex II species within the bounds of the proposed flood scheme. Long-term conservation requirements of these species were also to be identified. The Central Fisheries Board was commissioned to undertake the studies on lampreys in autumn 2001. From discussion with OPW and Duchás it was clear that the Flood Relief Scheme would proceed, despite lying inside a Special Area of Conservation. Thus, the focus of the CFB investigations was to identify aspects of lamprey ecology within the area of the flood scheme and to address conservation aspects in regard to the different life history strategies of the lampreys. Following some initial trial sampling in late autumn 2001, the sampling program began in March 2002.

Photo: The removed sediment is smoothed using the bucket of the excavator and excess water is allowed to drain off

The lamprey study was designed and undertaken by the CFB (Dr David Lyons and Dr Jimmy King) to assess lamprey usage of the river channel within the Flood Relief Scheme. Adult lamprey will only be present, in significant numbers, during the spawning season. Therefore, the initial sampling phase of the study would concentrate on developing a baseline of ammocoete distribution and density throughout the area of the scheme. It was envisaged that this would permit the development of a priority rating for different sites, in regard to their importance and, hence, conservation requirements.

Photo: A number of lamprey ammocoetes emerging from soft sediment after water draining (Photo: K Farrell, CFB)

In some cases, standard sampling methodologies were available such as redd-counting (spawning sites) and depletion electrofishing. However, other new techniques, developed for sampling juveniles, had to undergo field trials and subsequent statistical evaluation. There was little literature available in relation to salvage and translocation of juvenile populations. Similarly, there was little information on management and monitoring of lampreys from an Irish, or indeed, a European basis. Thus, the study had the opportunity to develop sampling strategies and conservation measures for lamprey ammocoetes that would be robust, repeatable, and cost-effective, whilst being amenable to replication over extended lengths of suitable juvenile habitat.

Photo: A post-metamorphosed brook lamprey on the measuring board. The features of the maturing lamprey are clearly evident: silvering of the sides, well-developed eyes, obvious gill openings and broader swimming fins (top)

Next: Sea lamprey (Petromyzon marinus)
Previous: River lamprey (Lampetra fluviatilis)

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