On-native Brook Trout Salvelinus fontinalis in Bulgaria: an Established Population in the Palakariya River (Balkan Peninsula, Iskar River Basin)

In the present study, we provide data on the first established, self-sustaining population of non-native brook trout (Salvelinus fontinalis Mitchill, 1814), family Salmonidae, in Bulgaria. The brook trout was detected in upland section of the Palakariya River (Iskar basin) at an altitude between 1350 and 1500 m a.s.l. Distribution, abundance and size structure of S. fontinalis were studied in the period 2019-2021. The coexistence of individuals of different sizes (from4.1 cmto 24.6 cm); no restocking activities in the last 10 years and the suitable environmental habitat features support the contention of a self-reproducing population of S. fontinalis in the Palakariya River