The freshwater pearl mussel is a rare type of shellfish that belongs to the mollusc family. As their name suggests they can only live in freshwater - in rivers and streams. They need clear, oxygen rich water with little silt and the rivers of the Scottish Highlands provide this. They live longer then sea mussels and can survive for more than 100 years.

Pearl mussel numbers right across Europe have dropped dangerously low due to water pollution, dredging and hunting for their valuable pearls to make jewellery.

Half the world’sknown breeding population of pearl mussels are found in Scotland and we are lucky to have a small population in an area of deep water in the National Park. The location of this population is kept a secret to protect the animals from criminals who might kill them in the hope of finding a pearl to steal. Fresh water pearl mussels are a protected species and it is highly illegal to kill, injure or disturb them.

Freshwater pearl mussels are filter feeders; they eat tiny pieces of animal and plant matter that gets caught in their gills whilst ‘cleaning’ the water. Fully grown pearl mussels can filter up to 50 litres of water a day and in large numbers, this can improve the quality of the water for fish like salmon and trout.

The freshwater pearl mussel has a fascinating life cycle that starts when the eggs develop inside the female. The male mussels then release sperm into the water which are absorbed by the female mussels. The eggs are fertilised and in the summer the female mussels release millions of baby mussels (larvae) into the surrounding water where they get swept downstream. Only one in 10,000 larvae survive, but those that do are carried back upstream on the gills of young fish where they drop off on sand or gravel and grow.

However, there is a long road ahead, with 95% of young dying in the 10-12 years before they become sexually mature. With such a high risk of fatality in their early years, it is extremely important that pearl mussels are left undisturbed to breed and continue the survival of this ancient shellfish.

It is hoped that further survey work will be carried out in the National Park to look for additional surviving populations. It is also hoped that we may be able to carry out a reintroduction programme to rivers where the mussels have been wiped out in the past.