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No Access No Fish!

Photo 1: Temporary pipe culvert, no good for fish passage!

Photo 2: New redesigned bridge installed to replace temporary culvert ensuring fish passage.

 It’s a simple statement but it’s critical, if adult fish access is blocked then there will be no spawning, no juveniles and no fish for the future!  Ensuring fish access is therefore a key part of the Trust and Boards work. Recent years have seen a substantial increase in river works within our three river catchments, including wind farm developments, rail and road upgrades, power line upgrades and these have all required new access roads with numerous river crossings.

Bridges and culverts must allow fish passage and there are good clear guidelines to assist with their design available from SEPA and while most designers adhere to these principles occasionally things don’t go to plan!

During the construction of the Tomatin-Knocknagael Power Line a temporary culvert was installed on the Allt Dubhach, a small tributary of the Farnack (R. Nairn), for vehicle access to the works compound, as shown in Photo 1. A site environmental inspection undertaken by Scottish Hydro Electric Transmission (SHET) and their Contractors MSVE identified the pipes were too small with the downstream end being above the water level leading to a blockage of fish access. The culvert could also have increased the potential of flooding surrounding land upstream.

SEPA, Nairn District Salmon Fisheries Board and the FNLFT were immediately notified of the potential obstruction and after discussion on site with SHET, MSVE and their ecological consultants from Mabbetts, the pipes were lowered to improve fish’s migration chances in the short term but clearly the design and approach was not suitable as a temporary measure as deemed by SEPA. Indeed during a second site visit adult salmon were observed being unable to swim through the pipes due to the high water velocities!

So a redesign was initiated and resulted in a new clear span bridge being installed in April 2018 ensuring the adult salmon and trout can now move freely within the burn (Photo 2).

Thanks to SHET and MSVE for replacing the culvert quickly, to Cameron Scott (SEPA) and to Ali Skinner (Nairn Bailiff) and for keeping a watchful eye on river developments.

SEPA River Crossing Guidelines can be download from the following link:

https://www.sepa.org.uk/media/151036/wat-sg-25.pdf