Lake minnow, Rhynchocypris percnurus (Actinopterygii, Cypriniformes, Leuciscidae), in Lithuanian inland waters: Distribution and current population state

The endangered lake minnow, Rhynchocypris percnurus (Pallas, 1814), has been known from Lithuanian inland waters for over 20 years, but we have a very limited understanding of its current population size. The main purpose of this study was to provide a concise account of the species in Lithuania, including a rough assessment of threats to its populations and habitats. In 2018–2019, we investigated 360 small water bodies across the country, all of which were potentially suitable for lake minnows. Results revealed that lake minnows were present in only 12 water bodies, all concentrated in one regional park in the southern part of the country. However, by 2024 the species had gone extinct at nine of these sites due to habitat loss. At present (2025), only one viable Lithuanian population of this species can be considered to exist. Our results conclusively show that the species is on the very edge of extinction. Urgent action is needed to protect this species in Lithuanian waters, with special emphasis on revitalizing its most suitable habitats and translocating fish from the only currently known population in Lithuania.