Inconnu (sheefish) (Stenodus leucichthys nelma)
In the Caspian Sea and in the Ural and Volga Rivers, a separate subspecies of nelma lives, now almost extinct. In some lakes and reservoirs, and possibly in some rivers, it forms a resident form.
Compared to other whitefish, the inconnu has massive head with flat forehead and very small teeth. They can get huge: the length up to 160 cm, and the weight up to 49 kg. These long-living fish do not mature until they are 10–14 years old, by the length of 70-80 cm. Unfortunately the numbers of inconnu are decreasing in most Siberian rivers due to excessive legal and illegal fishing.