Gymnocephalus Balon
Balon's ruffe (Gymnocephalus baloni), also known as the Danube ruffe, is a species of freshwater ray-finned fish, a ruffe, from the family Percidae.
It inhabits areas with sand or mud substrates. It is active at night and feeds on small invertebrates.
Endangered species in Croatia, the main reason for the decrease in numbers is due to changes in river flow, regulation of watercourses and pollution.