|Neylon, S. (2007) An assessment of the impact of culverts on Atlantic salmon (salmo salar) migration through freshwater. MSc, Institute of Technology, Sligo.
|The Atlantic salmon (Salmo salar L.) is a migratory fish species that spends a number
o f years in freshwater before migrating to the sea to feed and grow, and then returning
to freshwater to spawn. It requires unhindered access to upstream spawning areas in
order to complete its life-cycle. Culverts are structures that allow rivers to flow under
roads or embankments and, if poorly designed and constructed, they may restrict the
upstream passage o f Atlantic salmon.
Five spawning streams on the River Moy, a productive Atlantic salmon river in Co.
Mayo, were surveyed and a total of seventy culverts were inspected. The suitability o f
these culverts, in terms o f unhindered salmon migration, was assessed based on specific
fish passage criteria detailed in the National Roads Authority (NRA) guidelines. Further
analysis o f salmon spawning, fish survey and water quality information from the River
Moy was conducted in order to validate the findings from the field work. In order to
assess the level o f awareness within local authorities o f fish passage issues, a culvert
questionnaire was sent to senior engineers within each o f the twenty-nine Irish Local
Preliminary results indicate that poorly installed culverts have restricted the distribution
o f Atlantic salmon in several parts of the River Moy catchment. Where culverts were
found to breach a number o f the key fish passage criteria outlined in the NRA
guidelines, there was no evidence o f any salmon being present upstream o f these
culverts. Similarly, where salmon were found upstream o f culverts, the majority o f
those culverts matched the NRA criteria. However, such findings can only be confirmed
by baseline electrofishing surveys upstream and downstream o f the studied culverts.
Such surveys would positively confirm the presence or absence o f salmon.
Water quality was not found to be a factor limiting salmon distribution on the River
Moy. with the majority o f spawning streams having a biological quality class o f Q4 or
greater. Twenty out o f twenty-nine culverts questionnaires were returned and results
indicated that the level o f fish passage awareness within the Local Authorities is low. It
is apparent that the NRA guidelines need to be expanded and improved, to cover
existing problem culverts, and that further field surveys are required to determine the
extent o f the problem across the wider River Moy catchment.
|Fishes -- Seasonal distribution.
|Salmon -- Habitat -- Conservation.
|An assessment of the impact of culverts on Atlantic salmon (salmo salar) migration through freshwater
|Master Thesis (taught)
|Institute of Technology, Sligo.
|Creative Commons Attribution-NonCommercial-NoDerivs CC BY-NC-ND
|Environmental Science ITS