Twelve rivers of Novgorog region were explored. One pearl mussel population was rediscovered. In the main part of the rivers pearl mussel has become extinct but the other rare mollusc appeared there – Unio crassus. The local Directorate of protected areas of Novgorod region and the administration of Valday National park were informed about preliminary results. The work on the project is still in progress. The exploration of other “pearl rivers” is planned.