Caviar sturgeon from the Sea of Azov began reaching the tables of aristocratic and noble Byzantine Greeks in the 10th century, after the commencement of large-scale trading between the Byzantine Empire and Kievan Rus'. The main types of caviar are Beluga, Sterlet, Kaluga hybrid, American osetra, Ossetra, Siberian sturgeon and Sevruga. The rarest and costliest is from beluga sturgeon that swim in the Caspian Sea, which is bordered by Iran, Kazakhstan, Russia, Turkmenistan, and Azerbaijan. Wild caviar production was suspended in Russia between 2008 and 2011 to allow wild stocks to replenish. Azerbaijan and Iran also allow the fishing of sturgeon
HMS Sterlet (2S) reload torpedoes for a total of a dozen torpedoes. They were also armed with a 3-inch (76 mm) deck gun. Ordered on 2 March 1936, "Sterlett" was laid down on 14 July 1936 in HM Dockyard, Chatham and was launched on 22 September 1936. The boat was completed on 6 April 1938. At the onset of the Second World War, "Sterlet" was a member of the 2nd Submarine Flotilla. From 23–26 August 1939 the 2nd Submarine Flotilla transferred to its war bases at Dundee and Blyth. On 8 April 1940 "Sterlet" left for a patrol in the Skagerrak, off Norway