Discovering sanctuaries for the Endangered thick-shelled river mussel <i>Unio crassus</i> in Kaliningradskaya Oblast, Russia
Journal: Oryx
Year: 2025

Abstract The thick-shelled river mussel Unio crassus is categorized as Endangered on the IUCN Red List, and searching for surviving populations is urgent. We surveyed for this species in Kaliningradskaya Oblast, a Russian territory lying between Poland and Lithuania, where empty shells of the species had been reported from two rivers. There are at least 125 rivers and numerous small streams in the region, and as a comprehensive survey of all of these watercourses is infeasible, we used a method