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.
Internationalization of the Danube River
On December 28, 1854, during the Crimean War (France, Britain, Sardinia, and Turkey versus the Russian Empire), the allies sent to Russia a note urging the internationalization of the river as one of the bases for a peace treaty:
. . . it would be desirable that the course of the Lower Danube . . . be withdrawn from the territorial jurisdiction. . . . In every case the free navigation of the Danube could not be secured if it be not placed under the control of a syndical authority, invested with the powers necessary to destroy the obstructions existing at the mouths of the river, or which may hereafter be formed there.