Survival and extinction of the southern populations of freshwater pearl mussel Margaritifera margaritifera in Russia (Leningradskaya and Novgorodskaya oblast)

Information on the southern populations of the freshwater pearl mussel in Russia (Novgorodskaya and Leningradskaya oblast) is very scarce and has never been mentioned in the international scientific literature. Pearl fishing used to be common in this area in the fifteenth to eighteenth centuries but collapsed afterwards. Long-term field survey undertaken in 2006-2012 revealed that eight populations survived and at least 22 became extinct. The total number of mussels found was about 50,000, with the largest population in one small river consisting of approximately 40,000 individuals. Juveniles were found in six populations. The data obtained are of interest for assessing the resilience and stability of pearl mussel populations in response to potentially negative environmental and particularly anthropogenic impacts. The results are expected to inform future management strategies for conservation of suitable habitats for successful pearl mussel reproduction. The decline in host fish populations in the rivers appears to be the most significant threat to the survival of the existing pearl mussel populations.