CAIRNGORMS National Park has announced the preparation of an “ambitious plan” to help an endangered species of mussel.
The population of freshwater pearl mussels has been rapidly declining in recent years.
Freshwater pearl mussels hold an essential role in the rivers' biodiversity, as they help to preserve other species and indicate the wellbeing of rivers.
Cairngorms National Park said they can filter “50 litres of water a day”, which benefits other species including salmon, trout and otters.
They are also said to improve the water quality of the River Spey near Aviemore and the River Dee near Aberdeen.
Spey Fisheries Board, the Spey Catchment Partnership and the Park Authority are working on plans “to move threatened populations of pearl mussels from the main stem of the River Spey to safer habitats in the upper tributaries of the river,” Cairngorms National Park declared.
Dr Susan Cooksley, catchment partnership manager and freshwater ecologist at the James Hutton Institute, a scientific research group in Scotland, said: “The freshwater pearl mussel is a highly sensitive indicator of a river’s overall health.
“The recovery strategy that is proposed aims to support the species from all sides, protecting the existing mussels, restoring habitat, and then reinforcing the population.”
Subject to a licensing agreement, the recovery strategy will start in the spring of 2025.
River Dee and freshwater pearl mussels
On the River Dee, measures are already in place to protect the species such as eDNA monitoring, which can detect very small amounts of DNA to help pinpoint where action is needed.
The work, led by the James Hutton Institute, highlighted a loss of 90% of the freshwater pearl mussels since 2002 in the River Dee.
One of the main causes of the decline is thought to be the 2015 Storm Frank, as it “swept the population away but also tore up the riverbed, leaving it highly unstable for mussels to anchor on,” Cairngorms National Park said.
Dr Peter Cosgrove, the Cairngorms National Park Authority board member and Director of Alba Ecology, said: “The survey highlighted the devastating effects Storm Frank had on our pearl mussel population which is why this plan is so critical."
A study by the James Hutton Institute found that “conservation breeding” might help reinforce the River Dee mussel population.
As this species of mussels takes five to 10 years to reach maturity, this technique will be part of the long-term Cairngorms recovery strategy.
“The good news is that extensive river restoration work is already underway and we will continue to build on that work going forward.”
River Dee will undergo habitat restoration in preparation for adult mussel reintroduction.
“Catchment scale restoration is the key to resilient rivers where nature and people can thrive in the face of climate change,” said Dr Cooksley.
“The work already underway on the River Dee will prepare the way for future population reinforcements.”
