Caspian Sea
The Caspian has characteristics common to both seas and lakes. It is often listed as the world's largest lake, although it is not a freshwater lake. It contains about 3.5 times more water, by volume, than all five of North America's Great Lakes combined. The Caspian was once part of the Tethys Ocean, but became landlocked about 5.5 million years ago due to plate tectonics. The Volga River (about 80% of the inflow) and the Ural River discharge into the Caspian Sea, but it has no natural outflow other than by evaporation. Thus the Caspian ecosystem is a closed basin, with its own sea level history that is independent of the eustatic level of the world's oceans.
Salmo ciscaucasicus
Salmo ciscaucasicus or the Caspian salmon is a salmonid fish endemic to the Caspian Sea and inflowing rivers . It was described in 1967 originally as a subspecies of "Salmo trutta". "S. ciscaucasicus" lives on the western shore of the lake from northern Azerbaijan to the Ural River, while the main breeding river is Terek. It lives at depths down to 50 metres. Males can reach a maximum standard length of 130 centimetres.