Freshwater pearl mussel recovery reaches new milestone to help restore wild populations
18 August, 2026
This year has shaped up to be the most successful year for releases back to the wild of the freshwater pearl mussel, Margaritifera margaritifera, since the project started back in 2007.
In 2025, we reached the impressive target of 5000 pearl mussels released since the project's inception, helping to secure struggling pearl mussel populations and starting to turn the tide on the catastrophic declines during the 20th century, which saw a devastating decrease of over 90% of the Margaritifera margaritifera populations across Europe.
A monumental milestone for Margaritifera margaritifera
In 2026 however, and due to significant funding support from the EU LIFE Programme and Natural England's Species Recovery Programme, we aim to release around 4000 pearl mussels – a truly monumental effort by all involved at the FBA and across our fantastic partnerships!
Juvenile freshwater pearl mussels being released into the wild, in Cumbria (credit George Carr Media).
Recent freshwater pearl mussel releases in Cumbria
The pearl mussels released are all juveniles; freshwater pearl mussels don't become sexually mature until they are at least 6.5 cm in length (that's around 12 years old in the average population!). This means our new releases will not contribute to the next generation for at least 6 years.
Chris West, Project Manager, at West Cumbria Rivers Trust, Louise Lavictoire, Head of Science, and Jodie Warren, Pearl Mussel Officer at the FBA, during the recent freshwater pearl mussel releases (credit George Carr Media).
A patient process of population reinforcement
In the meantime reinforcement of pearl mussel populations will continue, to help support the restoration of a more natural population demographic of juveniles in their native rivers. It's a slow process requiring patience but, as the saying goes, the best things come to those who wait. So we, the FBA freshwater pearl mussel team, our partners and amazing volunteers, are dedicated to ongoing monitoring to ensure our actions are as successful as they can be, refining our methods to safeguard the future of this wonderful keystone species in our rivers.
“The FBA pearl mussel team have become a well-oiled machine when it comes to juvenile mussel releases. This year, we have doubled our efforts, successfully releasing over 3,200 juveniles, with a further 900 or so in the pipeline over the next couple of weeks. These releases are the result of many hours of hard work from the team, supported by some fantastic volunteers who have dedicated their time to tagging and measuring hundreds upon hundreds of pearl mussels.
It is incredibly rewarding to be in a position where we can return so many freshwater pearl mussels to the river systems where they belong, allowing them to establish and positively influence their environment for years to come. By continuing to refine and improve our techniques and practices, we hope to build on this success in future years, returning as many mussels as possible to their natural habitat. In doing so, we can support existing local populations while also creating space at the Species Recovery Centre for more juveniles to come through in future breeding cycles. ”
Jodie Warren (left) and Ellen Burton (right) during the recent release of freshwater pearl mussels in Cumbria (credit George Carr Media).
What are the threats for freshwater pearl mussels?
The freshwater pearl mussel (Margaritifera margaritifera) is one of the most threatened freshwater species in Europe, listed as Critically Endangered on the IUCN Red List, with populations having declined by more than 90% in many parts of Europe over the past century. This dramatic decline has been driven by a combination of pressures on the rivers and catchments on which the species depends.
Freshwater pearl mussels require clean, fast-flowing, low-nutrient rivers with well-oxygenated gravel beds, but increased fine sediment and silt can smother juvenile mussels and prevent successful recruitment. Pollution from agricultural runoff, forestry and other land uses can further degrade water quality.
Impacts of climate change, including prolonged periods of high temperatures, low rainfall and low river levels present an additional threat.
Their complex life cycle also makes them particularly vulnerable: juvenile mussels spend the early stages of their development attached to the gills of salmon or trout, meaning declines in healthy host fish populations can directly affect mussel recruitment. Historic overexploitation for their pearls has also contributed to the loss of mature mussels from many populations.
Together, these pressures have left many remaining populations small, fragmented and dominated by older individuals, with little evidence of successful natural recruitment. Protecting and restoring the rivers and wider catchments on which freshwater pearl mussels depend is therefore essential to securing their long-term recovery.
Jodie Warren and Ellen Burton during the recent release of freshwater pearl mussels in Cumbria (credit George Carr Media).
The Species Recovery Programme is a long-term government initiative, led by Natural England, to protect some of England’s most threatened species. In Cumbria, the programme is supporting major river restoration and freshwater pearl mussel recovery work across the region.
While the work is focused on one of the UK’s most endangered species, its benefits extend far beyond freshwater pearl mussels. Restoring and improving river habitats will also support fish, invertebrates, birds and other wildlife across the River Ehen, River Irt and surrounding catchments.
Many thanks to George Carr Media for the amazing photography of the freshwater pearl mussel releases in action this summer!
Interested in discovering more?
Read: Avoiding extinction: Conservation breeding and population reinforcement of the freshwater pearl mussel, 20 May, 2024 By Louise Lavictoire & Chris West
Find out more about FBA's Freshwater Pearl Mussel Ark
Established in 2007, the Freshwater Pearl Mussel Recovery project is an ongoing partnership project between the Environment Agency, Natural England and the Freshwater Biological Association.
