Transverse obstructions like weirs and barrage weirs with locks are omnipresent in our runnig waters and severely damage the habitat of many species, especially fish. Upstream fish migration facilities enable the biological passability. The film introduces the natural habitats of different running water sections with their characteristic fauna. The biological and engineering fundamentals for building effective fish ascent facilities are demonstrated in exemplary implementations and in model. (With graphics and time-lapse)