Genetic Diversity and Population Differentiation of European Mudminnow (Umbra krameri) in Austria

The European Mudminnow ( Umbra krameri )—a species adapted to slow-flowing, oxygen-poor backwaters and marshes with dense vegetation—was declared extinct in Austria in 1975. However, it has since been rediscovered at two isolated sites: Fadenbach in the Nationalpark Donau-Auen and Jesuitenbach. Captive breeding programs have since been initiated to support reintroduction and safeguard remaining genetic diversity. To inform conservation strategies, we assessed genetic diversity, structure, and effective population sizes (Ne) using polymorphic microsatellite markers. Preliminary results reveal significant genetic differentiation between the two wild populations and between captive stocks and their presumed source in Fadenbach. Overall genetic diversity is low, and Ne estimates suggest a high risk of inbreeding, genetic drift, and further loss of adaptive potential. Although sample sizes are limited, these findings point to critical conservation concerns, especially for the Fadenbach population. Importantly, this study emphasizes the utility of genetic monitoring as a central tool for evidence-based conservation planning—supporting adaptive management, preventing further genetic erosion, and promoting the long-term survival of this critically endangered species in Austria and beyond.