Easing Fish Passage on the Conwy

Many of our rivers are fragmented by barriers like weirs, originally built for mills, land drainage, or water supply. While these structures may seem harmless, they can block the upstream journeys of migratory fish like salmon, sea trout, and eels—species that rely on moving between the river and the sea to complete their life cycles.

At Nant Gareg Ddu, a tributary of the Afon Conwy, the North Wales Rivers Trust has been working with specialist contractors to make the river more passable for fish. Instead of removing the small weir entirely, which can sometimes destabilise the surrounding channel the team chose a nature-based approach: adding large boulders downstream of the structure.

These carefully placed boulders help raise the water level, slow the flow, and create a series of deeper pools below the weir. This makes it easier for fish to build up energy and swim upstream, while also improving habitat for other aquatic life.

This work was delivered in partnership with Natural Resources Wales, using Sustainable Fisheries Mitigation funding.