Fish passage improvement completed on the River Teifi

Natural Resources Wales’s (NRW) Four Rivers for LIFE project has recently undertaken fish passage improvements on the Afon Siedi, an important spawning tributary of the River Teifi SAC.

A weir 1.5km upstream from where the Siedi joins the Teifi severely restricted fish migration to the whole catchment upstream.

The weir was built in the early 1900s to power Derw Mill, but the mill leat is now disused and the weir is obsolete.

The existing structure was approximately 2.5metres high, consisting of six concrete shelves or steps varying between 40cm-80cm high each.

The vertical jumps made the structure a significant barrier to salmon and trout, and a complete obstacle to weaker swimming fish such as lamprey and eel.

A specialist fish pass contractor was employed to design and build a ‘rock ramp’ and the project team worked closely with Heneb (The Trust for Welsh Archaeology) to ensure there was no impact on the historic environment.

The work consisted of several ‘pre-barrages’ (steps) to raise water levels downstream, and rock infill to eliminate the steps and create a gradually sloping ramp.

Four Rivers for LIFE Team Leader Susie Kinghan said: “With any river barrier, the preferred option is full removal to restore natural processes, but this isn't always an option due to surrounding land constraints.”

“Fish surveys before the works showed salmon were common downstream of the weir but extremely rare upstream. Species such as lamprey and eel were completely absent from upstream reaches”.

“It is hoped that the improvements will allow fish to access good quality spawning gravels throughout the Siedi River catchment and lead to an increase in fish populations in years to come”.

The Four Rivers for LIFE Project is funded by the EU LIFE Programme with support from Welsh Government and Welsh Water.