Wicklow Bridges Project – Assessment of the risk of barriers to migration of fish species in County Wicklow

IFI Report (2012)

To carry out an ecological survey of a selection of Culverts and Bridges in the County for which there are most likely to be fish/mammal passage problems or other impediments for wildlife.



Where barriers impede or block access of migratory fish to large portions of catchments a direct reduction in the production potential of these systems results. Biodiversity and associated economic value suffer as a result.

• European Eel stocks are currently outside safe biological limits – obstacles to migration in river systems were identified as one of several factors causing this dramatic decline.

• Species such as the Atlantic salmon, River Lamprey and Sea Lamprey are listed under Annex IIa and Va of the Habitats Directive. The Habitats Directive defines certain types of natural habitat and certain species which are seriously threatened as having priority in order to favour the early implementation of measures to protect them.

• The Standing Scientific Committee on Salmon’s report The Status of Irish Salmon Stocks in 2011 with precautionary Catch Advice for 2012, includes information on Irish salmon stocks, the current status of these stocks relative to the objective of meeting biologically referenced “Conservation Limits” and the catch advice which will allow for a sustainable harvest of salmon in 2012 and into the future. According to this report a number of Wicklow Rivers are failing to achieve their Conservation limits, these include the Avoca, Slaney, Vartry, Liffey and Dargle.

• “In Ireland, the Water Framework Directive Freshwater Morphology Programme of Measures and Standards identified barriers to fish migration as one of the principal issues placing channels “at risk” in terms of failing to achieve good or high status as required under WFD” (Gargan et al, 2011).

Wicklow Bridges Project Findings

• Assessments undertaken as part of the Wicklow Bridges Project confirmed numerous impediments to fish passage on watercourses throughout County Wicklow. The scale of the problem in the Avoca catchment alone is highlighted in Figure 4. This map demonstrates that approximately 50% of the entire catchment is potentially impaired (fish migration partially or fully blocked).

• The assessments undertaken through the Wicklow Bridges project represent an important step in the process of establishing a comprehensive baseline of barriers to fish passage in the Eastern and South Eastern River Basin Districts.

• We believe that the works recently undertaken at Mullyclagh Bridge, (Figures 15-17) demonstrate a relatively simple solution to fish passage issues at most existing scour protection aprons. We understand that the cost of the works undertaken at the Mullyclagh Bridge site were in the region of €5000. We would be hopeful that many of the fish passage issues highlighted at smaller bridge and culvert sites could be rectified with similar solutions when routine bridge repairs/maintenance operations are being carried out by relevant authorities (Wicklow County Council or the National Roads Authority).

• The size and scale of the works required for the provision of solutions to fish passage issues at larger bridge/weir/dam sites means that the associated costs are likely to be far higher and unlikely to be included within the budget of bridge maintenance/repair works. The costs associated with larger projects mean that these works will often require specific funding which in many cases may be prohibitive.

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