An unintended conservation success: genetic integrity of translocated Ohrid trout (Salmo letnica) in an artificial reservoir

Abstract

The Ohrid trout (Salmo letnica), an endangered salmonid endemic to Lake Ohrid, has repeatedly failed to establish viable populations when introduced outside its native range. A rare exception occurs in Lisina Reservoir, Serbia, where introductions in the late 1970s and 1980s produced a persistent population. Using mitochondrial control region sequences and 12 nuclear microsatellite loci, we tested whether trout resembling S. letnica in Lisina indeed originate from Lake Ohrid, evaluated their genetic similarity to it, and assessed potential hybridization with co-occurring Macedonian trout (Salmo macedonicus) and Atlantic brown trout (Salmo trutta). All analyses confirmed that the Lisina fish belong to S. letnica. A previously unrecorded Ohrid lineage haplotype was detected, likely reflecting stochastic capture during translocation. Microsatellite data revealed modest but significant differentiation between Lisina and Ohrid populations, consistent with a founder effect and subsequent drift. Despite syntopy with co-occurring trout, no introgression into Lisina S. letnica was observed, indicating strong reproductive isolation. The persistence of a genetically distinct and unadmixed S. letnica population outside Lake Ohrid represents an unintended conservation success. While this does not serve as a general endorsement of species translocations, Lisina population could provide a backup resource for future restoration of the declining native Ohrid trout.