Socialist Federal Republic of Yugoslavia
Regarding rivers, the Danube was navigable throughout its entire course in Yugoslavia, linking the ports of Belgrade, Novi Sad, and Vukovar with Central Europe and the Black sea. Long stretches of rivers Sava, Drava and Tisza were also navigable.
Danube bleak
The Danube bleak is an elongate slim fish which can reach but a more normal size is 15 to 30 centimetres (6 to 12 in). There are 57 to 70 scales along the lateral line. The abdomen is compressed into a keel and the posterior end of this has no scales. The dorsal fin has eight to nine branched rays while the anal fin has fifteen to nineteen. This fish is morphologically quite variable which may be due to local adaptations to various habitats but is more likely to be due to several species being involved.