Did you know that the River Kent is home to a freshwater pearl mussel population?
Words & photos by Yasmin AliEskandari, Pearl Mussel Project Officer
Unfortunately, it is very small and close to becoming extinct due to habitat degradation, pollution and land use practices, and therefore the freshwater pearl mussel (Margaritifera margaritifera) is classified as a critically endangered species.
The Freshwater Biological Association has a Species Recovery Centre where it is operating a captive breeding programme to breed juvenile mussels for release back into their native rivers. However, as the native population is so small in the River Kent, the captive breeding of adults from within the catchment is not a viable option, so we are looking to use another genetically similar population (a donor population) to restore and revitalise the existing one.
It’s all in the DNA
To do this, we need to build a picture of how related other English populations are to the River Kent (Cumbria) population. We do this by taking a hemolymph (mussel blood!) sample from each population. DNA is extracted from each sample, and a specific portion of the DNA is targeted and amplified through polymerase chain reaction (PCR). The samples will then be analysed for genetic diversity and relatedness – the more genetically diverse a population is, the more effectively they can adapt to environmental changes and pressures.
These results will help to inform the donor mussel selection process and ensure the future genetic resilience of the River Kent population, and this research will help us direct our breeding programmes in 2024.
Finding the right habitat
It’s been quite a wet summer here in Cumbria, so we took full advantage of an autumnal break in the weather to get out and survey some sections of the River Kent, looking for suitable freshwater pearl mussel habitat and any remaining populations.
Freshwater pearl mussels require a stable riverbed with a good mixture of cobbles, boulders and the presence of clean gravels for the juveniles to bury in to. Stable riverbeds are darker in colour because the substrate has been undisturbed and in place for a long time – clean and bright riverbeds indicate that the river is more mobile and therefore less suitable mussel habitat, as the mussels could become displaced.
It was great to locate some good habitat within the River Kent catchment, as well as spotting some of the many white-clawed crayfish (native to our Cumbrian rivers), trout parr and even some freshwater sponge! We were also able to locate the last remaining freshwater pearl mussels left in the River Kent – a promising sign that there is potential for reintroducing a viable population in to good habitat.
Identifying actions for catchment restoration
As well as identifying suitable habitat, it’s important that we identify potential actions for catchment restoration and work alongside local landowners to improve the river where we can.
We can help landowners to identify available funding for actions that benefit the catchment and can fund fencing, which can protect the riverbank vegetation from being grazed. Encouraging vegetation and trees to grow on riverbanks can increase shading, which results in cooler water (which the fish like!) and provides some stability to the riverbank, too.
To find out more about the project, and what types of funding and workshops are available for landowners within the River Kent catchment through this project, please feel free to contact our Catchment Management Advisers, Richard Park, [email protected] and Joe Rigby [email protected].
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