The mystery of where the critically endangered Chinese sturgeons go to spawn may soon be solved, as a group of ichthyologists plan to attach electronic tags to them.

On Friday, six members of the Chinese Academy of Fishery Sciences went to a section of the Yangtze River downstream of Hubei Province's Gezhouba Dam -- the only known spawning ground of the species -- to try to catch some of the rare fish.

Ultrasonic transmitter will be attached to any sturgeon that is caught and it will be tracked at 30 monitoring sites along the river.

Born in the Yangtze, the sturgeons migrate to the sea like a salmon, where they mature before returning to their birthplaces to spawn. Previously, they returned to the Jinsha River, a major tributary of the Yangtze, but with the construction of the Gezhouba Dam across the main stream of the Yangtze in 1981, the migration route was cut off. Clearly they have found a new spawning site, downstream of the dam.

For more than 20 years, researchers found spawning sturgeons in autumn and winter downstream of the dam, but none have been seen since 2013. Researchers found signs of hope last April when they discovered a large school of juvenile sturgeons in the Yangtze estuary.

"This means they may have changed their spawning site to somewhere we know nothing about. We must find them and protect them as a matter of urgency," said Wei Qiwei, one of the lead researchers.

Sturgeons have been bred in captivity since 2009 and released into the river every year, but the number returning to spawn dwindled from 10,000 a year in the 1970s to just over 2,000 in the 1980s. Recent estimates put their numbers below 200.

The decline is believed to be the result of many factors: boat traffic, over-fishing, pollution and the effects of the Gezhouba Dam.

Research has been complicated by restrictions on catching wild sturgeons that were introduced in 2008 in an attempt to stave off the looming extinction of the species. It was only this year that the Ministry of Agriculture granted the academy clearance to collect and tag the fish.

The duration of the project will depend on how quickly the team can catch a significant number of sturgeons. "The tags should help us figure out their migration routes and new spawning grounds. It is a race against time to save this living fossil from oblivion," said academy researcher Wang Chengyou.

The Chinese sturgeon has existed for more than 140 million years and is covered by the top level of protection which Chinese state provides.

"The state of this species is an important barometer of the whole river ecosystem," Wei said, explaining that the population of sturgeon can only be brought back to a healthy level when the environment of the Yangtze is also healthy.

Chinese leaders realize the importance preserving the biodiversity of what is known locally as "the long river." As the Yangtze River Economic Belt becomes a reality, development of the network of economic hubs along the river is being conducted to the highest environmental standards, with suspension of all large-scale projects near river a possibility.

"If the Chinese sturgeon disappears, it is not only a tragedy for the species, but tragedy for the whole river and humankind," said Wei.