eDNA metabarcoding survey of fish communities in the Danube and its tributaries

In complement to the JDS4 traditional fish survey (TFS, mainly by electrofishing), a eDNA metabarcoding-based has been implemented within framework of monitoring program organized DNAqua-Net and in collaboration with INTERREG "MEASURES" program. Water samples were collected at 29 sites from source mouth Danube River, 18 tributaries. Two water (mean volume L per sample) each site filtered situ. Twelve PCR replicates performed sample using teleo primers. total, 80 taxa detected, which 19 corresponded farmed or food due release waste waters, most often downstream large cities. Of remaining 61 taxa, 50 identified species level, six genus five higher taxonomic level. Concerning river itself, 69 57 species/markers detected along River TFS surveys, respectively. these both methods. Nine captured alone, gaps reference librairies too colosely related barcodes. Eight only eDNA. Except for Salvelinus group, all benthic species, are difficult catch electrofishing rivers ( Acipenser ruthenus, stellatus, Benthophilus sp., Romanogobio uranoscopus, Sabanejewia balcanica, Umbra krameri ). The richness tended increase upstream relative number DNA sequences showed clear succession river. Barbatula barbatula, Cottus gobio, Hucho hucho, Lampletra planeri, Phoxinus phoxinus Thymallus thymallus restricted Upper whereas A. Neogobius fluviatilis, S. balcanica Scardinius erythrophtalmus Vienna mouth. Abramis brama, Alburnus alburnus, Cyprinus carpio, Silurus glanis, S ander spp, Z ingel streber course; Alosa spp. Syngnathus abaster Iron Gate; stellatus U. on (Danube delta). calculation index, based common metrics used intercalibrate national assessment methods European scale, classified as being moderate ecological status. Comparison indicative status calculated same method TSF data similar classification 13 difference one class seven sites.