Danube
The Danube was once a long-standing frontier of the Roman Empire, and today flows through 10 countries, more than any other river in the world. Originating in Germany, the Danube flows southeast for , passing through or bordering Austria, Slovakia, Hungary, Croatia, Serbia, Romania, Bulgaria, Moldova and Ukraine before draining into the Black Sea. Its drainage basin extends into nine more countries. The Danube river basin is home to fish species such as pike, zander, huchen, Wels catfish, burbot and tench. It is also home to a large diversity of carp and sturgeon, as well as salmon and trout. A few species of euryhaline fish, such as European seabass, mullet, and eel, inhabit the Danube delta and the lower portion of the river.
Traisen (river)
The Traisen is formed from the rivers "Türnitzer Traisen" and "Unrechttraisen". Its total length, including the "Türnitzer Traisen", is . It is a tributary of the Danube in the Lower Austrian region of Mostviertel. Its two sources begin near St. Aegyd am Neuwalde and Türnitz respectively. After meeting, they flow through the municipalities of Türnitz, Lilienfeld, Traisen, Wilhelmsburg, and St. Pölten, before meeting the Danube at Traismauer. In the course of building the Danube Factory Altenwörth, the mouth of the Traisen was relocated to Altenwörth in the municipality of Kirchberg am Wagram.