Oral Presentation International Conference on River Connectivity (Fish Passage 2018)

Finding assessing and fixing fish passage problems in Ireland (#193)

James J King 1 , Alan Cullagh 1 , James Barry 1 , Brian Coghlan 1
  1. Inland Fisheries Ireland, DUBLIN, Ireland

The EU Habitats and Water Framework Directives (WFD) have highlighted migration barrier issues for diadromous fish in Europe. The Irish National Barriers Programme is developing desk-and field protocols to create a GIS layer of river barriers, for use in infrastructural development and conservation management, particularly for Atlantic salmon and sea lamprey. Desk-based analysis of aerial imagery and map sources generated 2928 potential barriers in the Barrow catchment (3,025km²). Of all potential barriers, 300 fish obstructions were surveyed, ranging across 1st to 6th order channels. The field survey collected geo-location, photo imagery and structure dimensions at identified barriers. The majority were bridge issues (n=132), weirs (n=82) or culverts (n=62). There was a significant relationship between mean stream gradient and barriers per river km. Individual sub catchment assessment within the Barrow highlighted both geographical and historical influences on barrier distribution. The 19 Barrow sub catchments displayed a range of fragmentation ranging from 0.28- 0.8 barriers per river km. Of 792 potential barriers, the field assessment identified low discharge or no fishery habitat, requiring development of rules to streamline desk-based surveys in order to eliminate such locations from further field campaigns. Where barrier mitigations are proposed, the SNIFFER and ICE protocols provide a detailed assessment of the structure and its fish passage issues. In the longer term, the national GIS layer will be used to prioritise passage easement requirements as WFD Programmes of Measures. Currently, easements are undertaken more opportunistically, where public authorities are already committed to secure or replace bridge structures, re-align roads or carry out flood relief works in channels. There is a strong preference for barrier removal, where feasible, and for more nature-like solutions, such as bypass channels and rock ramps of appropriate gradient to facilitate all fish species, as opposed to conventional engineered solutions.