On behalf of the Nyköpingsåarna Water Conservation Association, an eDNA survey with multi-species analysis of fish and freshwater mussels is being conducted in the Nyköpingsån River and its tributaries. A total of 23 locations are being surveyed, primarily upstream of migration barriers, to analyze species presence and how these barriers impact fish and mussel populations. The study aims to provide a scientific basis for future conservation and action programs that can help preserve biodiversity and improve migration opportunities within the water system.
The survey identified 22 fish species and six mussel species, including several of high conservation value. Among them were red-listed species such as European eel (Anguilla anguilla), burbot (Lota lota), and wels catfish (Silurus glanis), as well as the threatened mussel species thick-shelled river mussel (Unio crassus), depressed river mussel (Pseudanodonta complanata), and painter’s mussel (Unio pictorum). The results indicate that migration barriers affect the distribution of several species, with brown trout (Salmo trutta), lampreys (Lampetra spp.), and pike (Esox lucius) detected only downstream of dams, suggesting that these structures limit upstream movement for certain species. The high precision of eDNA confirms its value as an effective tool for large-scale environmental monitoring, providing a detailed picture of species occurrences and ecosystem health.
By combining eDNA with traditional survey methods, a more comprehensive and accurate analysis of fish populations and aquatic species can be achieved. The study provides crucial insights for decision-makers, fisheries management organizations, and environmental authorities, contributing to improved management strategies and targeted restoration efforts to enhance connectivity and biodiversity in the Nyköpingsån River.
