Freshwater pearl mussel
22 February 2010
The freshwater pearl mussel is one of the longest living invertebrates known, surviving for over 100 years. They can grow to between 12 - 15 cm in length. The mussels live in fast-flowing rivers and streams, where they are found half buried in sand or gravel and often between boulders. They are very sensitive to any kind of pollution and their breeding cycle depends on a host relationship with salmonid fish. This species is listed as a UK BAP species and protected by law.
(c) Louise Miles/Freshwater Biological Association
Latin name: Margaritifera margaritifera
Population numbers:
In the UK, the freshwater pearl mussel is classified as endangered having declined rapidly over the last 50 years. Most populations in England are now found in very low numbers with some populations facing extinction. Only one population (on the River Ehen in Cumbria) is considered to be secure with numbers of around 300-500,000 mussels.
Where to see and when:
The precise locations of wild populations are not made public as the mussels are very vulnerable to disturbance. Populations of the freshwater pearl mussel are found in a handful of clean fast flowing rivers across northern England with outlying populations in Shropshire and Devon.
What’s being done:
Natural England in partnership with the Environment Agency and the Freshwater Biological Association have setup a national captive breeding facility to rear juvenile mussels for potential re-stocking programmes in the future. Work is ongoing to restore their habitat, or identify suitable re-introduction sites elsewhere in their catchments, for their eventual return.
The project has two main aims:
to create an ark facility for all English pearl mussel populations to safeguard against further local extinction
to subsequently breed from captive individuals in order to release juveniles back to the wild.
More information:
Kielder Salmon Centre
: owned by the Environment Agency, the hatchery has introduced new fresh-water pearl mussel breeding beds to help save one of the UK’s most endangered species.
