Caviar comes from sturgeon. Eggs are harvested as caviar from all sturgeon species except the green sturgeon, which is poisonous. The most common varieties of sturgeon used for commercial caviar are the beluga, the sevruga and the osetra.
Most caviar is harvested from sturgeon living in the Caspian Sea, the Sea of Azov and the Black Sea. The sturgeon gather in the areas where saltwater and freshwater meet. They travel up river each year to spawn, always following the same route. This facilitates catching the fish for their eggs. Other large fish species are also harvested for their eggs or roe, but eggs from any species other than sturgeon are not considered caviar.