Do not confuse it with another fish called the kutum, Rutilus kutum Rutilus frisii, called the vyrezub, Black Sea roach, or kutum, is a species of fish in the Cyprinidae family, native to the basins of the Black Sea, Sea of Azov, and Sea of Marmara from the rivers of Bulgaria to western Transcaucasia and in Lake Iznik (Turkey). The related Caspian Sea fish Rutilus kutum (also called kutum, Caspian kutum) has been treated as a subspecies of R. frisii (i.e. R. frisii kutum.), but the name kutum is applied to R. frisii itself in FishBase, referring to official names of FAO and AFS.