Sterlet (Acipenser ruthenus) lives entirely in freshwater and unlike other sturgeons does not migrate from the Black Sea. Nowadays it is the most widely distributed sturgeon species in the Danube River basin. It is listed as Vulnerable. Facts and Figures- After a decline of stocks in the Danube in previous centuries, the species numbers have been increasing since the 1980s.- The average reproductive age of this species is comparably low, about 8 years. In the Danube it is even lower – about 7 years.- This species is largely sedentary, undertaking only short spawning migrations. Tagging has revealed a maximum migration distance in the Danube of just over 300 km.- The only available catch data for the Danube is for 1958-1981, where catches ranged from 117 tonnes in 1963 to 36 tonnes in 1979, with an average catch of 63.5 tonnes per year. - Hungary, Bulgaria and Romania have all reported re-stocking programmes for their stretches of the Danube.