Do not confuse with Surgeon.
The Sturgeon is a kind of fish endemic to the Black Sea and Caspian Sea in Asia. It can grow to six or eight feet long, in the wild, but that doesn't happen very often because most sturgeons these days are harvested for their eggs, or caviar, when they are still fairly young. The Sturgeon population of the Caspian Sea has plummeted since the 1950s, due to the high demand for caviar. Sturgeons are considered living fossils. Scientists estimate similar fish have existed for 200 million years.
It is currently illegal to hunt or fish for Sturgeon in the wild, so most sturgeon caviar comes from farm-raised fish. Some other species of fish produce caviar, which has taken some of the demand off of the sturgeon population. For example, beluga caviar is quite popular in Russia if you can afford it.