Fig. 6 Number of eDNA copies per litre of taxa detected from the source to the mouth of the Danube River (in km). Only species with a relative abundance greater than one per thousand are represented. The size of the square is a function of the concentration of the corresponding taxa-specific eDNA per litre at a given site (see Supplementary Tab 1 for taxa abbreviation list). The separation of the Upper-, Middle- and Lower-Danube sections (vertical red lines) are based on the locations of the Gabcikovo dam (KM 1029) and the Iron Gate dams I and II (KM 1908 and KM1987 respectively)47.