The Russian sturgeon (Acipenser gueldenstaedtii), also known as the diamond sturgeon or Danube sturgeon, is a species of fish in the Acipenseridae family. It is found in Azerbaijan, Bulgaria, Georgia, Iran, Kazakhstan, Romania, Russia, Turkey, Turkmenistan, and Ukraine. It is also found in the Caspian Sea. This fish can grow up to about 235 cm (93 in) and weigh 115 kg (254 lb). Russian sturgeon mature and reproduce slowly, making them highly vulnerable to fishing.