But its popularity has exacted a heavy ecological toll.
In January the U.N. Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) ordered a temporary halt to sturgeon caviar exports by major producers in the Caspian Sea and other areas because of rapidly falling stocks of fish.
Importers with the caviar already in stock can still sell it, but they cannot order more.
The directive, combined with the U.S. import suspension, has turned the market's attention to the paddlefish, a freshwater fish that inhabits the Ohio, Mississippi, and Missouri rivers.
It is a relative of the sturgeon but has gray eggs instead of the familiar black ones of Caspian sturgeon.
With demand shifting toward paddlefish caviar, wildlife officials say they are now watching the fish's numbers more carefully.
"The ban leaves a void that domestic stocks in the U.S. may fill," said Doug Henley, a biologist with the Kentucky Department of Fish and Wildlife Resources in Frankfort, Kentucky.
"[But] sturgeon and paddlefish are long-lived fish that don't reproduce every year. So if they are fished hard now, we won't see it for three to four years."
Commercial paddlefish catches are allowed in only a handful of U.S. states, including Kentucky and Tennessee.
Those two states account for more than 98 percent of the paddlefish eggs harvested in the U.S.
About 42,100 pounds (19,100 kilograms) of eggs were caught in both states in 2001, according to Traffic North America, a wildlife trade monitoring network that works closely with CITES and the U.S. Fish and Wildlife Service.
Kentucky monitors paddlefish stocks every year, Henley says. So far the state imposes no limits on catches, but they may be considered if the caviar import restrictions continue.
"Even if the ban is lifted, we will have to monitor the paddlefish carefully," said Simon Habel, director of Traffic in Washington, D.C. "The last thing we want to see is what happened in the Caspian Sea happen here."
Wildlife experts like Henley and Habel are more concerned about harvests of wild fish like paddlefish than of trout, which is being grown in aquaculture facilities.
In Appalachia (interactive map), Shuckman's Fish and Sunburst Trout are forerunners of what boosters say could become an important industry in the region.
"There is a huge economic possibility," said Eason of Sunburst, which hatches its own rainbow trout in a large aquaculture facility built atop a former tobacco farm.
"People are eating more fish, so this is a realistic economic avenue."
Eason says Sunburst grows 500,000 pounds (225,000 kilograms) of rainbow trout a year that are used in caviar, smoked fish, and other products.
Like paddlefish, trout in the wild are seasonal, with egg harvests starting in the fall.
But by growing the fish in a controlled setting, the reproductive cycles can be tweaked, creating a year-round supply of roe, Eason said.
And it only takes two years until trout eggs can be harvested, compared to six to eight years for paddlefish.
Getting a year-round supply is one reason Shuckman, who says he ships several hundred pounds of paddlefish roe a year, is expanding into trout caviar. He is doing so in a joint project with Southeast Kentucky Community and Technical College.
The college, with private and public funding, has constructed a rainbow-trout aquaculture center with five 3,500-gallon (13,250-liter) tanks on the site of an abandoned coal mine in Lynch, Kentucky.
The facility uses water from the mine. When coal is mined, water naturally flows to the lowest coal seam, explains Paul Pratt, who heads the aquaculture program.
The water is pure but has no oxygen. It is pumped out of the mine and allowed to fall through fresh air, a process that frees carbon dioxide and adds oxygen to the water.
Kentucky State University recently joined the pilot project, adding 10,000 fingerling, or finger-size trout, to the fish already at the community college.
"We're hoping to diversify the economy here, which has been primarily coal for steel production," Pratt said.
"We have five tanks inside the building, and the fish are designated primarily for Shuckman's. He said he wanted fish, so we're going to call his hand."
Free E-Mail News Updates
Sign up for our Inside National Geographic newsletter. Every two weeks we'll send you our top stories and pictures (see sample).
SOURCES AND RELATED WEB SITES