Freshwater pearl mussels - A species on the brink

Surveying for freshwater pearl musselsSurveying for freshwater pearl mussels

Devon Wildlife Trust is delivering a pioneering project to conserve a rare and endangered species on the River Torridge.

Freshwater pearl mussels in tank

Freshwater pearl mussels (Margaritifera margaritifera) were formerly widespread in England and Wales, but currently, the only remaining populations in Southern England are on the Taw and the Torridge, and in very low numbers.

On top of this, these populations are in serious decline and are not thought to have bred successfully since the 1960s.

By working with local communities, improving water quality and establishing a breeding programme, this project hopes to ensure the recovery of Devon’s last remaining mussel populations and England’s only lowland populations. The ‘Restoring Freshwater Mussel Rivers in England’ project is led nationally by the Freshwater Biological Association and funded by Biffa Award.

What are freshwater pearl mussels?

Freshwater pearl musselFreshwater pearl mussels are filter feeding molluscs that are found in river beds; they can live for over 120 years!

The species colonised most of its current range after the last ice age (around 12,000 years ago), but are now listed on the IUCN red list as critically endangered.

Healthy populations require clean, nutrient poor, well oxygenated waters in order to survive and reproduce. 

These mussels are an indicator species so if we can get river conditions right for them, it will benefit a suite of other species including invertebrates, fish, birds and mammals.

A fascinating life cycle

LifecycleFreshwater pearl mussels have a fascinating lifecycle, of which part is spent attached to the gills of young salmon and brown trout. Over 5000 juvenile mussels have been found on the gills of a single fish.

Lack of host fish in rivers is one of the problems leading to the decline in populations. However, other factors impacting populations include:

  • Habitat degradation
  • Water quality issues (resulting from inputs of nitrates, phosphates and sediments)
  • River engineering
  • Historic pearl fishing

The project

SurveyingThis project focuses on the River Torridge in North Devon and seeks to achieve one key aim - to safeguard the future of some of the most important freshwater pearl mussel populations remaining in England through river restoration, engagement of local communities and captive breeding.

This project is part of the Northern Devon Nature Improvement Area landscape scale programme. Other partners in the project include: the North Devon Biosphere, the Environment Agency, Tarka Country Trust and Westcountry Rivers Trust.

Get in touch

Izzy Moser, Project Officer
Devon Wildlife Trust
07968 850803

This project is funded by:






This project is supported by:

  • Environment Agency
  • Tarka Country Trust
  • North Devon Biosphere
  • Westcountry Rivers Trust
  • Freshwater Biological Association 
  • Taurus Foundation