Freshwater Pearl Mussel Ark Project

In 2007, a partnership project between the FBA, Natural England and the Environment Agency was set up to create an ‘ark' facility at Windermere to conserve dwindling populations of the freshwater pearl mussel Margaritifera margaritifera from English rivers, and to develop a captive breeding and reintroduction programme.

The aim of the project is to use adult mussels for captive breeding purposes and to rear juvenile mussels to a size suitable for reintroduction into native rivers. Over the last eight years, the FBA has attempted rearing from nine populations of pearl mussel from English rivers. We currently house and continue breeding from six populations, using the adult mussels for broodstock.

We have learned much during the last eight years and our oldest cohort of juveniles is now over seven years old.

We hold cohorts of juvenile mussels from different populations spanning several different years and collect additional cohorts each year. Reintroduction of juveniles to their native rivers is not advisable until they are robust enough to survive. Mussels require very clean, well oxygenated water and substrate in which to bury but the condition of most pearl mussel rivers will not support recruiting populations at this time . Using the excellent research facilities at the FBA, it has been possible to carry out investigations to improve captive rearing techniques. These investigations include:

1. Research into suitable gravel size and cleaning regimes for juvenile mussels has improved survival of juveniles during their first, most vulnerable years.
2. Trials using different host fish species (Atlantic salmon, brown trout, sea trout and Arctic charr) for different mussel populations have generated interesting results indicating population-specific host fish preferences.
3. The FBA assisted with the collection of genetic material for a study on the genetics of this species in England, Scotland and Wales.
4. A study looking at the suitability of a fluorescent dye for marking juvenile mussels to aid with monitoring.
5. Measurements of glochidia over the encystment period have been taken for several populations over a number of years and appear to show differences in development rate.

Project supported by: