Final answer:
The most expensive caviar is from the critically endangered Beluga sturgeon, distinguished by its large, dark gray eggs. Overfishing and habitat loss have contributed to its scarcity and price. Beluga caviar is considered the pinnacle of luxury in caviar types.
Step-by-step explanation:
The most expensive caviar, which is dark gray in color, comes from the Beluga sturgeon (Huso huso), known to be the largest sturgeon species. Beluga caviar boasts large, pea-sized eggs that are cherished for their fine, silky texture and remarkable depth of flavor.
Beluga sturgeon are found primarily in the Caspian Sea, and because of overfishing and habitat degradation, they have become critically endangered, adding to the scarcity and cost of genuine Beluga caviar. Strict international regulations have been put in place to conserve the species, which, in turn, has driven up prices for this luxurious delicacy even further. While the market also offers a variety of other high-priced caviars, such as Osetra and Sevruga, Beluga caviar is particularly esteemed among connoisseurs and thus commands the highest prices.