Caviar..The food

Caviar is fish roe or eggs, sieved to remove fatty tissues and membrane, and lightly salted with non-iodized salt. This is an old preserving and curing method that is still effective today.

Of course, all female fish lay eggs to reproduce, so they all have roe. However, not all fish roe is suitable for nor considered to be caviar. By most definitions and to a purist, true caviar comes from the sturgeon and the sturgeon alone.

The sturgeon is a saltwater anadromous fish (meaning it moves to freshwater to spawn) which makes its home in the Black and Caspian Seas between Europe and Asia, and also the Pacific Northwest and Southern Atlantic coasts of the United States.

The sturgeon can grow to over 3,000 pounds, but usually averages about 60 pounds. The flesh of the fish, as well as its prized eggs, is quite delicious.

The most prized caviar comes from the beluga, osetra, and sevruga varieties of sturgeon. Nowadays you will also find caviar from other fish varieties, including salmon, lumpfish and tuna, as well as in different forms.

Extracted from : About.com