The term caviar can also describe the roe of other species of sturgeon or other fish such as paddlefish, salmon, steelhead, trout, lumpfish, whitefish,[3] or carp.

[6] This position is also adopted by the Convention on International Trade in Endangered Species of Wild Fauna and Flora,[7] the World Wide Fund for Nature,[8] the United States Customs Service,[9] and France.

[11] Up to the 17th century, archaic spellings included chauiale, cavery, and cauiarie, and as early as 1625, it was becoming a three-syllable word, with the final "e" being dropped in speech.

[11] Caviar and sturgeon from the Sea of Azov began reaching the tables of aristocratic and noble Greeks in the 10th century, after the commencement of large-scale trading between the Byzantine Empire and Kievan Rus'.

[12] The Russians likely learned to process fish eggs with salt from Greek traders who had passed along the Black Sea coast, but it was not until after the Mongol invasions that the caviar industry developed in Astrakhan.

[14] In the 16th century, François Rabelais described caviar as the finest item of what is now called hors d'oeuvre.

[13] The Travels of Olearius in Seventeenth-Century Russia says "they expel the roe from the membrane in which it is contained, salt it, and after it has stood for six to eight days, mix it with pepper and finely chopped onions.

The rarest and costliest is from beluga sturgeon that swim in the Caspian Sea, which is bordered by Iran, Kazakhstan, Russia, Turkmenistan, and Azerbaijan.

The Siberian variety with black beads is similar to sevruga and is popular because of its reduced (five years) harvest period, but it has a higher brine content than other kinds.

The Chinese Kaluga hybrid varies in colour from dark grey to light golden green and is a close cousin of beluga caviar.

[citation needed] An expensive caviar example at 1 kilogram (2.2 lb) sold for £20,000 (then US$34,500) is the Iranian 'Almas' product (from Persian: الماس, "diamond") produced from the eggs of a rare albino sturgeon between 60 and 100 years old from the southern Caspian Sea.

[20] The largest caviar company in the world is the Chinese brand Kaluga Queen, which cultivates sturgeon at Qiandao Lake in Zhejiang.

[22] The ban on sturgeon fishing in the Caspian Sea has led to the development of aquaculture as an economically viable means of commercial caviar production.

[24] Cristoforo da Messisbugo in his book Libro novo nel qual si insegna a far d'ogni sorte di vivanda, Venice, 1564, at page 110, gave the first recorded recipe in Italy about extraction of the eggs from the roe and caviar preparation "to be consumed fresh or to preserve".

[27] From about 1920 and until 1942, there was a shop in Ferrara, named "Nuta" from the nickname of the owner Benvenuta Ascoli, that processed all the sturgeons caught in the Po River for caviar extraction, using an elaboration of the original Messisbugo recipe, and shipped it to Italy and Europe.

The American caviar industry started when Henry Schacht, a German immigrant, opened a business catching sturgeon on the Delaware River.

Around the same time, sturgeon was fished from the Columbia River on the West Coast of the United States, also supplying caviar.

[36] In coastal British Columbia, Fraser River white sturgeon are sustainably farmed to produce caviar.

[40] Overfishing, pollution and the Alcalá del Río dam eliminated the wild population of Acipenser naccarii.

[52] In September 2010, Kazakhstan launched a state monopoly brand, Zhaik Balyk, from the Kazakh word for the Ural River.

Another method of extracting caviar is by removing eggs through a small incision, which allows the female to continue producing roe.

They resemble beluga caviar in appearance and are either used as a food prop for television and film or enjoyed by vegetarians and other people worldwide.