Caviar made of sturgeon eggs is known as "soft gold". It is one of the three most expensive foods in the world including saffron essence and truffle par.

There are more than 20 kinds of sturgeons, but only three of them Beluga, Ossietra and Sevruga are recognized as raw materials of real caviar on the traditional market.

In 2011, some sturgeon stocks from the Caspian Sea, the traditional source for making caviar over the past century, became unwelcome to world buyers and consumers started looking for an alternative.

As early as 1997, the Chinese Academy of Fishery Sciences imported tens of millions of fertilized sturgeon eggs from Russian Siberia for hatching. At the same time, its scientists also carried out breeding of wild sturgeons in the Heilongjiang River in northeast China.

In the summer 2003, as only being able to live in water between 15-23 degrees Celsius, many tons of sturgeons transported to the Thousand Island Lake, east China's Zhejiang province, died in batches due to water temperature rising to as high as 35 degrees Celsius.

Now the Hangzhou Sturgeon Technology Co., Ltd. has raised over 20 million sturgeons in the lake after overcoming numerous difficulties. Every summer when water becomes a bit warmer, fishermen would move all the sturgeons from the lake to a huge pool on an island. Here, giant pumps pumped lake water from 15 meters deep to fill the pool for cooling the sturgeons.

Another difficulty at that moment was to identify the male from the female sturgeons before they reached three years old. "The male are not worth much, if male and female are raised mixed together for seven to ten years, we will no doubt make no money," said Wang Bin, a researcher with the Chinese Academy.

Not being able to tell the sturgeon's gender from their appearance, fishermen ultimately had to invite experts from Hungary to do the sex determination.

It was a huge task -- more than 20 million sturgeons each had to do B ultrasound or puncture samples for microscopic examination.

“Eggs can be extracted only during the first 11 weeks of the sturgeon's stage 4 maturity, that is, during the eighth year of its life," Wang said. "This is very difficult to master. If a little bit too early, eggs are not rich enough, vice versa, eggs get withered."

Once extracted, 16 processing operations for the eggs must be completed within 15 minutes, when everything is done by human hands depending on their feels. The difficulty is that at that time, no Chinese fishermen knew well about how to handle these high-priced, fragile products. Having no choice, they invited processing masters from Iran to help out at high cost.