DNA barcoding of minor fish fauna: a case study in the Province of Bolzano/Bozen, Italy

The fish fauna of the Province of Bolzano/Bozen (northern Italy) currently includes at least 35 species, mostly defined on a morphological basis. Naturally occurring fish are presumably native to the northern Adriatic Catchment, as the alpine divide is considered an absolute migratory barrier for ichthyofauna. However, in the past, fish from north of the Alps have been repeatedly introduced in the Province of Bolzano. The aim of this study is to clarify, through genetic analysis, which species of the minor fish fauna are occurring in the Province of Bolzano. Over 600 individuals from different populations of 10 fish genera – Alburnus, Carassius, Cobitis, Gambusia, Gasterosteus, Padogobius, Rutilus/Leucos, Sabanejewia, Scardinius, and Squalius – were sampled to carry out DNA barcoding with the cytochrome oxidase I (COI) marker. Fish were weighed, measured and photographed, and before their release into the wild, a fragment of anal fin was collected for genetic analysis. Overall, COI barcodes were successfully obtained for 9 of the 10 target genera, allowing the identification of most individuals. Moreover, 51 haplotypes were found in the study area, 25 of which were never published before. Genetic diversity levels varied widely among species, ranging from 23 haplotypes (Alburnus arborella) to one haplotype for an allochthonous species (Gambusia holbrooki). This study highlights the presence of several undescribed haplotypes for A. arborella, Gasterosteus aculeatus, Leucos aula, Padogobius bonelli, Sabanejewia larvata, Scardinius hesperidicus, and Squalius squalus. The obtained dataset represents the first, although partial, DNA barcoding assessment for freshwater fish on a regional-administrative scale in Italy.