The common chub, also known as the European chub or simply chub, is a species of European freshwater ray-finned fish in the carp family Cyprinidae, that frequents both slow and moderate rivers, as well as canals, lakes and still waterbodies of various kinds.

The Caspian Sea is the world's largest inland body of water, often described as the world's largest lake and sometimes referred to as a full-fledged sea. An endorheic basin, it lies between Europe and Asia: east of the Caucasus, west of the broad steppe of Central Asia, south of the fertile plains of Southern Russia in Eastern Europe, and north of the mountainous Iranian Plateau. It covers a surface area of 371,000 km2 (143,000 sq mi), an area approximately equal to that of Japan, with a volume of 78,200 km3 (19,000 cu mi). It has a salinity of approximately 1.2%, about a third of the salinity of average seawater. It is bounded by Kazakhstan to the northeast, Russia to the northwest, Azerbaijan to the southwest, Iran to the south, and Turkmenistan to the southeast.