Distribution, habitat, and population dynamics of the European weatherfish (Misgurnus fossilis L., 1758) in the north-easternmost part of Germany

This study analyses a distribution database of fishes and cyclostomes from the German federal state of Mecklenburg-Western Pomerania and evaluates a monitoring programme initiated in 2008, with a focus on the ecology of the European weatherfish. Over 35 years, the species was recorded across nearly the entire state, but it was rarely found in high abundances. While the species’ natural habitats have largely disappeared as a result of land cultivation, the weatherfish is now predominantly found in extensive, human-made drainage systems, where it co-exists with other fish species adapted to warm, oxygen-poor conditions. Since 1990, the frequency of detections indicates a stable population status. To date, ten monitored populations normally exhibited low population densities, often below one individual per 100 m 2 . However, several populations occasionally exhibited densities far exceeding the average. These temporary increases were primarily driven by a single age class, indicating irregular reproduction or recruitment dynamics. This pattern should be considered when assessing the species’ conservation status according to the EU Habitats Directive. Furthermore, populations exhibiting such dynamics are more susceptible to local extinction than those with continuous reproduction. Therefore, maintaining metapopulation connectivity is critical for effective conservation. Improving upstream passability within drainage systems and their connecting watercourses is recommended to enhance the stability of the overall population.