By Kieran Cooke
In California's San Joaquin Valley
Caviar has long been one of the world's most exclusive and expensive commodities.
It takes eight years before farmed sturgeon starts producing eggs
Now aquaculture specialists and fish farmers who have spent years perfecting techniques of rearing sturgeon - the eggs of which are used to make the caviar - are hoping to cash in on the seemingly insatiable appetite the world's moneyed elite has for a product often referred to as "Black Gold."
"Maybe our time has come," says Peter Struffennegger, manager of Stolt Sea Farm in the US, one of the biggest sturgeon farms in the West.
"For years we've been investing in what is a very tricky, complex business.
"Caviar consumers are a very picky bunch. Traditionally, they've always demanded caviar from wild sturgeon, but now, at last, there are signs they're getting used to the idea of the farmed variety. Finally we might start making some money."
The Stolt farm, owned by a Dutch/Swedish/Norwegian conglomerate, is set amidst the rice paddies of northern California's San Joaquin Valley, about half an hour's drive north of Sacramento, the state capital.
Transforming sturgeon eggs into 'black' gold is a delicate procedure
In circular tanks, tens of thousands of sturgeon of varying ages and size dive and splash about.
In a packing room workers in protective clothing delicately wash, grade, weigh and salt the precious eggs.
Stolt's most prestigious caviar costs more than $120 (£67) for 50 gram, or $70 per ounce.
If that seems expensive for what is no more than a few teaspoons full, it's a bargain compared with the money deep-pocketed caviar aficionados have to pay for an equivalent amount of Beluga, the most highly prized caviar, which comes from the Caspian Sea.
One top London store is charging £195 ($340) for a 50gr tin of Beluga.
"Prices keep rising, but it seems the demand for caviar is stronger than ever," says Mr Struffennegger.
"For us the big challenge is changing consumer attitudes, getting across the idea that caviar from farmed sturgeon can be every bit as good and tasty as from fish caught in the wild."
Traditionally caviar has come from wild sturgeon caught in waters round the Black Sea coast or, as is the case with the famous Beluga, from the Caspian Sea.
However, overfishing and rampant poaching in the years since the break-up of the old Soviet Union have resulted in a dramatic decline in wild sturgeon stocks.
As a result, earlier this year administrators of the Convention on International Trade in Endangered Species (Cites) placed a global ban on exports of caviar from the wild, endangered sturgeon fish caught in the countries in the area.
In addition the US, the world's biggest caviar market, has its own ban on imports of Beluga caviar.
For Stolt and others, trying to make money out of farmed sturgeon has been a tough business.
Sturgeon are among the most complex of the world's fish.
Professor Doroshovj says Russia developed sturgeon breeding
In the wild, they can live for more than 100 years, measure more than 6m and weigh up to 1,800kg.
The female wild sturgeon only starts producing its sought after eggs after 15 or 20 years.
"Through fine tuning feed and other aquaculture techniques we've managed to bring the egg production cycle down to between eight and ten years," says Mr Struffennegger.
"But that's still a hell of a long wait for a return on what has been a very big investment."
The shiny white bellies of the female sturgeon are slit open in order to extract the eggs.
"With most fish you judge their worth from the outside - by their size and texture," says Mr Struffennegger.
"With sturgeon you don't know how valuable they are till you kill them and open them up.
"You might find there are very few eggs inside and all those years of effort have been in vain."
There have been other problems.
Though the waters of the nearby Sacramento River have stocks of native white sturgeon, the fish are protected and cannot be fished for commercial use.
Last year, Stolt Sea Farm produced eight metric tonnes of caviar
For the initial farmed stock a small amount of eggs and milt or sperm was extracted from these wild fish, which were then returned to the river.
Professor Sergei Doroshov, a Moscow marine scientist who left the old Soviet Union in the late 70's and took up a post at the University of Davis near Sacramento, led a team which, after years of research, managed to perfect techniques of culturing and breeding sturgeon under controlled conditions.
"Sturgeon breeding programmes were developed in Russia many years ago, but the science was a very closely guarded secret," says Professor Doroshov.
"And sturgeon are unlike most other fish: you cannot even tell what sex they are until they are four or five years old."
Snobbery and mystery
Initially, the Stolt farm raised sturgeon primarily for their meat, its firm texture popular in a variety of cooking.
Then, as concern grew about the rapidly decreasing population of wild sturgeon and prices of caviar rose, the main thrust of the business switched to sturgeon eggs.
Stolt produced its first caviar - 13kg of it - in 1994.
Last year production rose to more than eight metric tonnes.
While some of Stolt's caviar is sold under its own Sterling brand name, most is marketed indirectly through Petrossian, a firm started by two Armenian brothers in the 1920's in Paris that has become one of the world's most famous caviar brand names.
"Marketing is crucial to the whole business," says Mr Struffennegger.
"There is an element of snobbery about it: the rarer the caviar, like Beluga, the more expensive it is.
"There's also plenty of mystery. Somehow, despite the bans and the collapse in the population of the Caspian sturgeon, there are still stocks of wild caviar on the market. Poaching and smuggling continues.
"Some still prefer the caviar that comes from wild sturgeon - even though they might not be able to tell the difference from the farmed variety. I let others do the caviar tasting. I'm a meat and potatoes kind of guy anyway."