NatureScot find critically-endangered freshwater pearl mussels in Scottish lochs in Sunderland and Trossachs

Critically-endangered freshwater pearl mussels have been found in Scotland’s lochs for the first time, new research has found.

The pearl mussels are known to live in Scottish rivers, but researchers who used remotely-operated underwater drones and snorkelling equipment have discovered pearl mussels in two lochs, in Sutherland and the Trossachs.

The survey, which was carried out by NatureScot, found that the mussels were likely to have entered the lochs by clinging to the gills of a host fish, either trout or salmon.

They spend the first year of their lives attached to the fish, before falling off to live independently.

Freshwater pearl mussels are rare in Scotland, mainly due to illegal fishing, poor water quality and habitat damage.

As filter feeders, freshwater pearl mussels are also vulnerable to water pollution and engineering work in rivers.

The effects of these threats mean that, in Scotland, the species is on the brink of extinction in some rivers.

NatureScot is leading efforts to conserve the species.

NatureScot’s Iain Sime, who led the latest project, said: “Other mussel species, including the much more widespread swan and duck mussels, are known to live and breed in Scottish lochs, but up until now we’ve had no evidence to suggest that pearl mussels routinely do this, too.

“This project was an exciting first step in exploring our lochs and we’re keen to do further surveys to better understand more about this critically-endangered species.

“We don’t yet know whether they can breed in lochs and we want to learn more about a loch pearl mussel’s relationship with their host fish.

“As a result of the research, we’ll be extending our conservation management advice for freshwater pearl mussels to include lochs as well as rivers.”