Caviar is the processed, salted roe of various species of fish, most notably sturgeon. It is commercially marketed throughout the world as a delicacy and is eaten principally as a garnish or spread, as with hors d'oeuvres.
The most well known fishery for caviar is the Caspian Sea, with Russian, Iranian, Azerbaijani, and Kazakh fishermen account for most of the catch. Overfishing in the Caspian Sea and the long time required for sturgeon to become sexually mature (up to 25 years, depending on species) has led many groups to recomend against using Caspian caviar. American aquaculture (fish farming) produces caviar from farm raised white sturgeon and Atlantic salmon, which is considered to be more environmentally friendly. Commercial caviar production involves killing the fish and extracting the ovaries; caviar is generally not considered to be vegetarian for this reason.
The Monterey Bay Aquarium's Seafood Watch Program rates Caspian caviar as "avoid", and farm produced caviar as a "best choice". 
Grades of Caviar
It comes in a number of basic grades:
- Beluga - The most expensive of caviars.