It's a crisp autumn day, and I'm standing on the banks of a gently flowing river, watching as a lucrative catch is about to be landed. Bumping snouts as they swim around the circular condemned cell of a commercial fish farm are about 100 female sturgeon - over a metre long and the shape of small sharks, with sleek bellies pregnant with millions of eggs. One of them pokes her head out of the water and looks at me with a curious golden eye.
It is a valedictory glance. In a few moments, she, along with her companions, will be landed and efficiently dispatched by a knock on the head. For her eggs are black gold. Once salted, tinned and packed, they will become caviar, the sought-after delicacy of the rich the world over. The caviar from this tank alone will sell for more than Dh1.3 million. For centuries caviar has been one of the most famous and lucrative exports from central Asia. But today I am standing not on the banks of the Caspian Sea, the sturgeon's traditional breeding ground, but 2,500km to the west, beside a tributary of the Dordogne river in the wine-growing region of Bordeaux, south-west France. And what I am watching is not so much a massacre as a rescue operation.
It wasn't so long ago that caviar seemed destined to disappear forever. The sturgeon, a splendid cartilaginous beast that has swum the rivers of the earth since the era of the dinosaurs, was in danger of extinction. According to UN estimates, numbers had fallen by more than 90 per cent since the late 1970s. After the break-up of the Soviet Union, over-fishing and poaching had taken a heavy toll on the sturgeon population. Everyone wanted a piece of this lucrative action. And who could blame them? A large beluga female may contain up to 50kg of caviar, worth some Dh3m on the open market.
But the results have been devastating. The beluga, the biggest variety of sturgeon, is a magnificent carnivore that can live for more than 100 years, and grow to nearly 6 metres long. Even a decade ago, beluga used to be caught in hundreds of tonnes from the Caspian. Now, barely 100 fish a year are landed, and none has been allowed to reach its full magnificence. By some estimates there are fewer than 1,000 beluga sturgeon left in the entire sea, and few sturgeon of any variety that have matured to caviar-bearing age.
In an attempt to save the sturgeon, Cites, the Convention on International Trade in Endangered Species of Wild Fauna and Flora, lays down strict quotas to protect their numbers. Last year, almost no caviar was allowed to be exported. This year, it granted the countries around the Caspian - Azerbaijan, Kazakhstan, Iran, Russia and Turkmenistan - permission to export 3.7 tonnes of beluga caviar, and 96 tonnes of other varieties of caviar. That's 15 per cent below the level set in 2005, but still far too much for concerned environmentalists.
But the real environmental disaster comes as a result of illegal fishing. The waste from poaching is immense. Wild sturgeon may not become sexually mature until they reach the age of 15, and can go years between spawnings. But because it's impossible to tell merely by looking at a sturgeon whether it's carrying any eggs - or even whether it's male or female - the poachers realise their mistake only once the fish is dead.
Faced with the prospect of the annihilation of an extremely profitable source of revenue, caviar smuggling is no longer something that governments can afford to turn a blind eye to. The UAE used to be a major staging point in caviar smuggling, with traders exploiting loopholes in local law to deal in the Caspian Sea sturgeon. In 2001, Cites announced that much of the Dh92m worth of caviar that left the country that year appeared to be illegal. Now, the problem is taken extremely seriously. The UAE's Cites management authority raided an Abu Dhabi retailer in 2006 and confiscated 45kg of unlicensed caviar, then worth an estimated Dh180,000. And last July, an unlicensed plant in Ajman was raided by the Ministry of Environment and Water and Ajman Municipality and found to be processing and trading in illegal caviar, which had no import permits issued by the UAE's Cites management authority. The penalty for selling such illegal caviar can be imprisonment for three months and a fine of up to Dh30,000.
Meanwhile, Russia's caviar police use speedboats and helicopters to track down poachers. Last year, a Tupolev aeroplane landed at a high-security military airbase outside Moscow, where security is so tight that even police are not allowed in without permission. But the interior ministry had been tipped off; the plane was stormed and found to be carrying suitcases full of caviar, and the gang turned out to include military personnel alongside smugglers. In March this year, in a desperate attempt to preserve stocks, Russia proposed a five-year ban on sturgeon fishing for all countries bordering the Caspian Sea. And this autumn, the UK announced the formation of its first "caviar squad", headed by a senior policeman, which will tour the country's smart restaurants and upmarket food stores to find out where black-market caviar is on sale.
"You'll find black market caviar everywhere," says an employee of a major caviar importer, "even in high-end luxury shops. The problem is that there's not enough legal stuff to go around." So despite the serious penalties, it's a rare five-star chef who hasn't been offered caviar off the back of a lorry - or rather, a boat. Beluga now starts at around Dh59 a gram. Almas caviar, the rarest "golden" variety, made of the eggs of an albino sturgeon or an Oscietre sturgeon more than 80 years old (with a taste described as "walnuts and cream"), costs twice that and there's a four-year waiting list for it at Caviar House & Prunier, the leading importers. (Which puts the reported two-year waiting list for a Hermès Birkin bag into some sort of perspective.)
But delicious as it is, no responsible gourmet can feel comfortable eating wild caviar, knowing that it may be contributing to the extinction for this magnificent fish. The good news is, that doesn't mean giving up on the delicacy entirely. The best hope for the future, for the fish and foodies alike, lies in caviar farming. Gourmets used to turn up their noses at the farmed stuff, claiming it tasted muddy and lacked the texture of wild caviar. But the increasing sophistication of the farms, and the techniques they employ, is producing a product that is all but indistinguishable in taste and texture. In any case, there is no longer any real choice.
In the middle of Abu Dhabi's desert, an ambitious project is under way in an industrial park on the outskirts of the capital to create an immense sturgeon farm. The Dh300m project, owned by Bin Salem Group and its German partner United Food Technologies, hopes to provide up to 40 tonnes of caviar a year from fish kept in 64 swimming-pool sized basins. There is a huge local market for caviar among the city's wealthy denizens, in its luxury hotels and on the cruise ships that put into port. But the middle of a desert is not an obvious place to put a farm for Siberian fish. Sturgeon need cool water if they are to produce caviar, so sophisticated water technologies are required to chill it to the optimum 20-22C, and ensure that it can be filtered and re-used.
But it can be done: there are several successful caviar farms in California, for instance. Even at the Prunier caviar farm in Bordeaux, where I have come to watch the caviar-farming process, the water in the summer months can be uncomfortably hot for the 150,000 acipenser baerii that splash about in its giant pools. "The trouble is that the Siberian summer only lasts two months, while ours goes on for six," worries Laurent Sabeau, the general manager. Today, though, there's a distinct nip in the air, and the Siberian sturgeon seem perky, poking their snouts out of the water and rolling over to show off their white bellies.
Close up, they're magnificently decorative, like Chinese water dragons. Some are pale grey, others the soft blue bloom of a plum. Their fins are a jagged row of knobs, and white whiskery barbels dangle from their chins. Their heads are beautifully patterned with a cobweb of white lines and whorls. When one of them pokes her pointy nose out of the water and gives me a friendly nudge, I almost lose my appetite for the black stuff.
But Sabeau maintains a firmly unsentimental approach to his fish. As well he might, seeing as each female is potentially worth some 5,000 (Dh23,000) in eggs alone. No wonder the place is protected by guard dogs at night. The fish arrive as fingerlings, immature sturgeon that have been bred from existing stock. Once the fish reach three years, they are individually scanned using ultrasound, to check their gender. Males and females are separated, and the males are killed for their increasingly popular meat. (Male sturgeon aren't necessary for the production of caviar, which is produced spontaneously by the females. During spawning in the wild, they would release their mature eggs into the water which would then be fertilised by the males' sperm.)
The females are left to mature further, in shallow tanks about 15 metres long, swimming in water filtered directly from the nearby Isle river, a tributary of the Dordogne. Once the sturgeon reach maturity, usually at the age of seven, they will be scanned to see whether they are spawning. A biopsy is taken, to make sure that the eggs are ready. This is an exact science: harvest too early and the caviar will be rough and dry because the fat is still in the fish's belly, not the eggs; harvest too late and the caviar will be soft and lack distinctive beads, while if the eggs are white when the biopsy is taken, the fish needs another year to mature.
Only when the eggs are perfect are females put into the "refining tanks", which are filled with clear water, and left unfed for a fortnight. "We've discovered that the river algae leaves a bad taste in the caviar otherwise," explains Sabeau. Meanwhile, at Agroittica Lombarda in Calvisano, Italy, each female white sturgeon has a microchip containing its genetic information, first recorded weight, diet and pond of origin, implanted in the back of its head. Its life history can be immediately read by running a scanner over its head. The idea is to ensure genetic diversity in the stock; the information also helps to chart when each fish is likely to mature. But the rewards are such that investment in technology is well worth it.
It is a long way from the hit and miss approach of Caspian Sea fishermen. One wonders what the poverty-stricken villagers who sustained themselves on the roe scooped from the bellies of their catch, would make of it all. The popularity of caviar is not a new phenomenon. It dates back to ancient times (even the Egyptians had a technique for preserving fish eggs in salt) and has been prized across the globe. Aristotle wrote of the "trumpet fanfare announcing the arrival of heaping platters of caviar" at ancient Greek banquets; Rabelais mentioned it in the 16th century, and by the mid-18th century, it was being sent as a diplomatic gift by Peter the Great to Louis XV. Alas, the fish jam failed to please the French king, who spat it out onto the carpet at Versailles. The fishermen of the Gironde estuary had a similarly cavalier attitude to the black gold. Emile Prunier, a Parisian restaurateur, was so appalled to discover that they were chucking the costly roe overboard as waste that he set up local caviar packing centres.
His restaurant swiftly became the only one in the world to sell caviar that had been caught just 24 hours earlier. Although sturgeon are no longer being fished out of the Gironde, Prunier still boasts that it can offer this fresh caviar - thanks to its caviar farm, a relatively new venture, created in response to the environmental crisis in the Caspian Sea. When the Prunier caviar farm started up in 1994, it produced a mere 30kg of caviar. This year, the harvest is anticipated to be 6,000kg.
But that still isn't enough for Sabeau's customers. While we wait in his office, he has a long and detailed altercation with a German importer who is desperate for some more stock. "We just don't have it," Sabeau expostulates. "You'll get it in a week." Then, wearing white plastic overalls, immaculate white wellington boots, a hairnet and face mask, he stomps into his tiny factory to see about getting it.
The process of farming sturgeon may be both slow and expensive, but its culmination is almost absurdly quick. The fish is stunned, its throat cut, and hung upside down while the blood drains away. Then, with an expert flick of a long knife, a young fishmonger slits open the smooth belly and fistfuls of black pearls gush out on to the table. They are immediately weighed - this one is a good haul of 2.5kg - and then put in a bowl.
It is Sabeau's task to grade the caviar, which he does by examining the colour and size. Large pale grains, the most prized, are packed as "Heritage", the others are divided between the various Prunier brands (Tradition, Malossol, Paris, St James) while damaged eggs go to make pressed caviar. Then, the eggs are rinsed, rubbed with surprising vigour through a metal sieve, salted and shaken to get rid of excess water, before being carefully spooned into the tin.
The only mystery is in the different varieties of salt used to flavour the eggs. The journey from fish to tin, though done exclusively by hand, takes about five minutes. I'm given a small but costly tin to take away with me. Although I passionately love the stuff, it gives me a pang to think of my curious friend of an hour before, now neatly filleted while her eggs start their journey to the tables of the wealthy. But at least it means a glimmer of hope on the horizon for her few remaining relations still swimming in the Caspian Sea.