Three Gorges dam affecting Chinese sturgeon

China`s Three Gorges dam has affected reproductivity of the wild Chinese sturgeon.

Updated: Jun 02, 2010, 15:41 PM IST

Beijing: China`s Three Gorges dam, the world`s largest hydro-electric power project, has affected reproductivity of the wild Chinese sturgeon, a protected fish species whose origin dates back to the era of dinosaurs.

The rising water at the Three Gorges reservoir which is fast filling up has put off the reproductive period of the sturgeon for about a month and may further reduce their numbers, according to a leading Chinese expert.

Wild Chinese sturgeon regarded as special as they were believed to be the contemporaries of the now extinct dinosaurs were ranked first class of animals and species that needed protection in China.

"Their reproductive time has gradually been delayed since the Three Gorges reservoir began to store water in 2003," Chief Engineer with the Chinese sturgeon research institute Xiao Hui told state-run China Daily.

The sturgeon migrates to lay eggs every year to Yangtze River on which the dam was built.

According to the institute`s study, the reproductive period was delayed for a week after the water level reached 135 meters, 15 days when the level touched 156 mts and a month when it reached 175 mts.

The current spawning site of wild Chinese sturgeon remains in the lower reaches of the river.

The site is seven-kilometre away from another large hydroelectric plant, where the Gezhou Dam stopped the sturgeon from swimming to the upper reaches of the river since it was completed in 1981.

"After the Three Gorges reservoir began to store water, the water level of the lower reaches of the river has remained low. It also needs more time to reach a proper water temperature (usually between 17 and 21 C) for the sturgeon to lay eggs," Xiao said.

Every September to November, sturgeon swims against the sea to lay eggs in the Yangtze River.

"Since the young fish have insufficient time to grow into adult fish, their survival rate could be cut when they swim back into the sea," she said.

At present, about 300 wild Chinese sturgeon migrate to the river every year to lay eggs, experts said.

Although there is no evidence so far to show whether the delay in their reproductive period will lead to a decrease in the number of wild sturgeon, Chinese authorities started taking measures to protect them.

"The Ministry of Agriculture once allowed us to catch 10 wild Chinese sturgeon every year for study, but it has been banned since last year," Xiao said. Three Gorges dam was designed to produce 22,500 mw of
hydro power.