IN some cultures, pearls are symbolic of tears.

Brides are cautioned against wearing them, and they are rarely used in engagement rings, since some believe them to bring sadness.

Such is superstition. But the pearl is also among the most beautiful products of nature, and as such is a highly prized commodity. And that is its tragedy, certainly in the case of the freshwater mussel pearl.

It is at the centre of a lucrative but illegal trade, one which has contributed to a sharp decline in mussel numbers ¬ over the last century freshwater pearl mussels have been lost from more than one-third of rivers where they once occurred. This should concern us all, for they are filter feeders, and help keep our rivers clean, benefiting species such as salmon and trout.

Poachers care naught for that, and will open mussel shells by the hundred, thus killing the mollusc inside, despite the fact that pearls are rarely found. Now, as part of a nationwide conservation project, volunteers in Wester Ross are to be trained to spot and report pearl mussel crime.

We wish them well. It is to be hoped that in future, there will be no more talk of tears when the freshwater mussel is discussed. It is a natural asset that is precious in more ways than one.