Zusammenfassung: Vor etwa 100 Jahren wurde Gasterosteus aculeatus an mehreren Stellen der Donau ausgesetzt.
Die so eingebürgerten Populationen haben sich nicht nur gehalten, sondern auch ausgebreitet. Entlang der Donau in Österreich ist der Dreistachlige Stichling regelmäßig anzutreffen.

Zusammenfassung: The Enns River runs through the Gesäuse National Park and is generally characterized by relatively pristine morphological features. During the late 1990s the fish densities of this stretch collapsed, including the dominant species of this river zone, the European grayling. River restoration efforts have been undertaken to improve habitat quality and connectivity of the Enns River but also its largest tributary in the Gesäuse, the Johnsbach River, which had been heavily alternd for flood protection. However, due to intense sediment transport in the Johnsbach River, the newly built ground sills might still pose barriers for fish migrating from the Enns into the Johnsbach River. To check whether grayling enter the Johnsbach for spawning and whether these sills are passable for grayling during their migrations, we took environmental DNA samples from both the Enns River and the Johnsbach River and applied a qPCR protocol originally developed for Arctic grayling. We received positive signals of European grayling in the Enns River, as well as the Johnsbach River but only during the spring spawning season. This suggests that at least a few grayling individuals manage to pass the sills and migrate into the Johnsbach River to attempt to spawn.