Chinese scientists announced here on Thursday that the artificial propagation of the rare Chinese sturgeon would no longer count on wild fish as they have made successful artificial insemination and spawning of cultured sturgeons.

Director Shang Zhenyang of the Chinese Sturgeon Research Institute (CSRI) of the China Three Gorges Corporation said that the reproductive breakthrough achieved on Wednesday night marked "a milestone" in the protection of the vertebrate species dating back 140 million years.

The two sturgeons under experiment, one female and one male, were both sexually mature and of the first filial generation of the artificially-bred at the institute's breeding farm in the Three Gorges Dam area.

In 100 to 120 hours, the inseminated eggs would grow into fries, researchers say.

Since the experiment kicked off four years ago, researchers from the CSRI and the Institute of Hydro ecology have broken through a number of technical difficulties in domestication, artificial induction of gonadal maturation and ovulation.

The objective of the program is to raise cultured sturgeons to sexual maturity and then artificially breed the second filial generation.

A past popular practice in sturgeon cultivation was made through the first filial generation of wild fish. But scientific monitoring over the past years showed that the population of wild sturgeon in China had remained small.

Lingering Yangtze River pollution and the disruptions from ship's navigation also hindered the natural propagation, which holds off the efforts to preserve the stocks.

Normally, artificially bred fries at the Three Gorges breeding farm will be sent back to the river after they grow up to 15 cm long. But researchers said they were yet to decide whether or not to release the upcoming new fries.

Born in the Yangtze River and growing in the sea, Chinese sturgeons turn sexually mature at the age of 15 and migrate back to the upstream Jinsha River for spawning.

As the Gezhouba Dam was built across the main stream of the Yangtze River in 1981, Chinese sturgeons' migration route was cutoff. But researchers said that sturgeons had found new spawning grounds downstream the dam as a result of adaption for more than 20 years.

An incomplete survey made by the Yangtze River Fisheries Research Institute in 2006 showed that the number of sturgeons migrating back to the Yangtze River for spawning dwindled from about 2,176 a year in the early construction of the Gezhouba Dam to 500. No new statistics were released.

The CSRI, established in 1984, is a domestic authority in Chinese sturgeon protection, and has over the years released more than five million sturgeons of various sizes. Its parent, China Three Gorges Corporation, has invested more than 40 million yuan in the research of sturgeon artificial propagation.

Amid warning for the extinction of the ancient species native to China's East and Yellow Seas apart from the Yangtze River, the Chinese government invested in 2007 about 10 million yuan in a monitoring and rescuing center in the Chinese sturgeon nature reserve which is 38 kilometers downstream the Three Gorges Reservoir and covers a water area of 80 square kilometers.

(Xinhua News Agency October 1, 2009)