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.
Podunavlje
Podunavlje (Serbian: Подунавље / "Podunavlje", ) is the name of the Danube river basin parts located in Serbia (Vojvodina, Belgrade and Eastern Serbia) and Croatia (Slavonia, Syrmia, and Baranja). Podunavlje is located on the southern edge of Pannonian Basin. In its wider meaning, the term is used in Serbian and Croatian as a description for the area around the entire flow of the river Danube.