Pinter K, Haring E, Wolf M, Gruber G & Wanka A. 2025.
Natura Slovenia; DOI: 10.14720/ns.21576
Published online 31 December 2025

Abstract

The softmouth trout (Salmo obtusirostris) is endemic to the Adriatic drainage basin. This study investigated its distribution in the Upper Neretva River and the Ljuta tributary using environmental DNA (eDNA) analysis. We analysed 11 eDNA samples collected over three years (2022–2024), with PCR targeting mitochondrial marker sequences: the cytochrome c oxidase subunit 1 gene (CO1) and the control region (CR). Sanger sequencing of the PCR products confirmed S. obtusirostris haplotypes in eight out of 11 sites, with presence in Glavatičevo, the Ljuta estuary, and the Ljuta River. Generally, the results demonstrate the utility of eDNA analyses in detecting elusive species. Yet, we observed incomplete specificity for S. obtusirostris of the PCR primers used. Mixed CO1 haplotypes were detected in several samples, showing double peaks in electropherograms at diagnostic sites, i.e., nucleotides specific for S. obtusirostris as well as for S. trutta. Our findings imply that S. obtusirostris can colonize steep, turbulent habitats. Since haplotype sequencing cannot differentiate between the haplotype derived from pure S. obtusirostris or from a hybrid, further investigations are needed that refine detection methods and assess hybridization with members of the Salmo trutta complex using a combination of methodological approaches.