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.