Fig. 1

Sampling sites. Silurus aristotelis populations: TRI, Lake Trichonida; AMV, Lake Amvrakia; VOL, Lake Volvi. S. glanis populations: EVR, Evros river; STN, Strymon river; STH, Strymon river hatchery; AXI, Axios river; ALI, Aliakmon river; PIN, Pineios river. Sample 10 came from the Danube Delta (DDN) and is not indicated on the map.