The prehistoric sturgeon was once abundant in the United States, consumed on both coasts and exported to Europe, where the roe was processed as caviar. By the end of the 19th century, stocks had collapsed, and today, wild fish are almost impossible to obtain. Of the seven North American species of sturgeon, only two — white and green (Acipenser medirostris) — are still harvested on the West Coast on a very limited scale. Most sturgeon now on the market is white sturgeon, farm-raised in California. Said to resemble the famed beluga, white sturgeon is prized for its superior flavor. Though wild fish lived for 100 years and reached weights of 2,000 pounds, market size of a full-grown farmed sturgeon is 18 to 22 pounds. The fish are cartilagenous, with no internal skeleton. Instead of scales, they have rows of sharp, bony shields or plates, called “buttons,” along their bodies.