Freshwater Pearl Mussel Project – Phase Two Update

Freshwater Pearl Mussels on the Mawddach nestled in the thick mats of weed

Our work to protect and restore populations of the Freshwater pearl mussel has continued this month, building on the solid foundations already put in place during phase one.

This is long-term, technical restoration work focused on improving river processes, habitat condition, and public understanding of one of the UK’s most endangered native species.

Earlier in the project, we completed a number of key interventions:

• Removed a small weir to restore fish passage

• Installed hundreds of tonnes of spawning gravels to support salmon and trout

• Placed boulders strategically to diversify flow and create scour

• Identified and flagged a broken sewage pipe that had been impacting water quality

These actions were designed around a simple principle: if we restore conditions for fish, we restore conditions for freshwater pearl mussels.

Phase One &Two: What we’ve delivered

Habitat and river restoration

• Continued in-channel improvements, including boulder placement to refine flow diversity and maintain clean gravels

• Addressed excessive weed growth linked to nutrient pollution, following identification of a sewage input

• Expanded spawning habitat to support salmon and trout populations

Riparian and catchment work

• Created new riparian woodland corridors, planting sessile oak, willow, and alder

• Designed planting to:

  • stabilise banks

  • provide future woody material to the channel

  • increase shading and habitat complexity

• Restored hectares of wetland and quaking bog, improving hydrology and natural water storage

• Carried out peat depth surveys to map deep peat and guide future interventions

• Installed road runoff ponds to monitor pollutants entering the system from nearby roads, particularly during summer low flows when impacts are most acute

Why this matters

Freshwater pearl mussels are entirely dependent on salmon and trout during their life cycle. Without healthy fish populations, mussels cannot reproduce.

The work delivered in this phase supports:

• Cleaner gravels for fish spawning

• Improved flow conditions to prevent silt build-up

• Reduced nutrient impacts from pollution sources

• Better-connected habitat across the catchment

This is about restoring the system, not just the species.

Education and community involvement

Alongside the practical work, we’ve continued to invest in local engagement:

• Developed a project book with local school children

• Worked with the Prysor Angling Association, who:

  • delivered educational sessions

  • hosted visits to their hatchery

  • introduced pupils to fishing and river stewardship

This work ensures that restoration is understood and supported locally.

What’s next

We are now recruiting Freshwater Pearl Mussel Ambassadors.

This network will:

• raise awareness of the species

• support monitoring and citizen science

• act as local advocates for river conservation

  Contact us on admin@northwalesriverstrust.org if you want to become an advocate for these rare and beautiful species.