Fish

The streams of the Hintergebirge (lower section of the Großer Bach and the Reichramingbach), which are already in the valley and shallow, are also colonized by grayling. The bullhead occurs as an inhabitant of the river bed, but is absent in streams with a strong sediment overlay. Particularly noteworthy is the only occurrence of autochthonous brown trout in Upper Austria, which are the original native Danube strain.

Almost all streams of fishing interest were used for a long time before the national park was established; only a few small, very remote watercourses were spared. Man determined which species and breeds should occur here. American species were introduced in the form of the brook trout and especially the rainbow trout. The latter gradually pushed back the native fish species (especially the brown trout). Although brown trout were also introduced regularly and in large numbers, they were again not the Danube species typical of the area, but those from the Atlantic region. Over many decades, an alien fish population has established itself, which does not meet the objectives of today's national park with a near-natural, native biocoenosis. For this reason, the national park administration launched an ambitious fishing program. This was successful, as the populations of foreign species have now collapsed and the native fish fauna is once again one of the most natural in Upper Austria.

The Große Feichtausee, the only large still water body in the national park, was originally free of fish. Stocking with foreign trout caused serious and lasting changes to the biocoenosis in the lake. The more demanding trout have now disappeared, but the minnow, a small fish species that was introduced as food for the trout, has survived.