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.
Danube Delta
Its acute isolation and harsh conditions of living, based mainly on subsistence, made the Danube Delta a place of emigration, or transit at least. Very few of those born in the region stay there through adulthood; at the same time, the origins of its inhabitants vary widely, as people from many parts of Romania can be found in the delta. The total population has remained more or less constant throughout the 20th century; there were 12,000 inhabitants in the 1890s, and 14,000 before the Second World War. Romanians account for approximately 80% of the population, and Ukrainians for 10%. Other people living in the delta include ethnic minorities such as Greeks, Turks and Bulgarians (in 1992). Distinctive to the region, but very rare as an ethnic entity, are the Lipovans, descendants of the Orthodox Old Rite followers who fled from religious persecution in Russia during the 18th century.