American ingenuity is making caviar increasingly accessible to all, but political and environmental issues have consumers asking more questions.

By definition, caviar is the salted roe, or unfertilized eggs, of the sturgeon fish. Officially, only the processed roe of sturgeon can be called caviar, but in the U.S. it has become acceptable to refer to non-sturgeon roe as caviar as long as the source precedes the word caviar (as in trout caviar).

As international demand for caviar increases, overfishing and poaching have put tremendous strain on the Caspian region and its indigenous sturgeon populations. As a result, beluga caviar has become more difficult to come by and even pricier. At nearly $100 an ounce, it remains one of the priciest foods on earth.

Consumers want to know more about the caviar's origins-how it was harvested and whether the sturgeon was killed for it. Some Caspian fisheries now use a procedure similar to a cesarean section to harvest the sturgeon's roe without sacrificing the fish. The struggling economy has also affected caviar consumption-the demand for the less expensive American paddlefish, salmon roe and white sturgeon caviar (the farmed variety boasts a flavor similar to Caspian osetra priced around $50) has shot up.

Here are the different types of caviar:

Beluga: The most expensive caviar comes from the beluga, the largest member of the sturgeon family, which is indigenous to the Caspian Sea. These prehistoric giants can live for a century and weigh up to 2,000 pounds. The highest grade roe comes from the oldest females, prized for nearly ball-bearing-size eggs ranging in color from light to dark gray. Because of the roe's high fat content, beluga delivers a smooth, buttery taste.

Osetra: Also from the Caspian Sea, the Russian sturgeon produces the roe known as osetra caviar. Weighing 100 to 400 pounds, Russian sturgeon produce roe with a somewhat smaller grain and firmer texture than that of beluga. Connoisseurs appreciate osetra caviar for the "pop" provided by the eggs' membranes. Osetra offers an intense, nutty flavor. Its distinct color-ranging from warm, golden brown to greenish gray-also sets this caviar apart.

Sevruga: From the Caspian's smaller, streamlined stellate sturgeon comes sevruga caviar, characterized by its robust, full-bodied briny flavor and small gray to black eggs. Because the stellate sturgeon matures faster than its Caspian relatives-producing roe after seven years-sevruga caviar is the most readily available and least expensive of the imported varieties. Its robust flavor, however, excites the most discerning caviar lovers.

White Sturgeon: Indigenous to North America's Pacific coast, white sturgeon can live for 100 years and tip the scales at 1,500 pounds. Two U.S. companies, Tsar Nicoulai and Stolt Sea Farm, currently produce caviar from farm-raised white sturgeon. Available under a variety of brand names-California Estate Osetra, Sterling Classic, Transmontanous, etc.-white sturgeon caviar exhibits a sweet, subtle briny flavor with a smooth finish. Eggs range from dark brown to dark gray to black and have a medium-firm texture.

Paddlefish: Also known as the spoonbill, this cousin of the sturgeon roams the large rivers of North America, notably those in Tennessee, Kentucky, Mississippi, North Dakota, and Montana. In size and color, the roe harvested from paddlefish most closely resembles sevruga caviar. The small, firm eggs deliver a silky texture and a rich, complex flavor.

Hackleback: Native to the Mississippi and Missouri River systems, the most abundant wild sturgeon in North America is also called the shovelnose. Hacklebacks produce roe consisting of small black eggs that deliver a sweet, buttery flavor.

Salmon Roe: Sometimes referred to as red caviar, these large, pearl-sized eggs typically come from wild Alaskan, Chinook, or Coho salmon. The brilliant red-orange hue of the roe offers tremendous eye appeal. The plump eggs boast a sweet, juicy flavor and explosive texture. Highly affordable, salmon roe lends itself to a whole host of cooking applications.

Trout Roe: Darker and brighter in color than salmon roe, trout roe comes from farmed freshwater trout. Usually smaller in grain than that of salmon, trout roe is less viscous and offers a milder flavor. The berries, translucent with a red dot in the center, have a firm texture that provides a pleasing bite and distinct pop.

Whitefish Roe: Known as American golden caviar, the roe of whitefish is small-grained and crunchy. Indigenous to the Great Lakes region, whitefish produce eggs of a yellowish gold color with a mellow, fruity flavor. Extremely affordable, whitefish roe is popular for entertaining large crowds. Chefs use whitefish roes flavored with all-natural ingredients such as wasabi, ginger, or saffron to garnish fresh oysters and dress up delicate sauces.