China has postponed the annual dredging for a dam on the Yangtze River for about two weeks to ensure propagation of Chinese sturgeons, navigation engineering authorities said Monday.

The dredging project, originally scheduled in late November, started on Dec. 5 and will finish on Dec. 20 to clear away some 70,000 cubic meters of silt from the bottom of the Gezhouba Dam, said the navigation engineering bureau of Yichang section of the river.

The project started after wild Chinese sturgeons spawned in the downstream of the dam on Nov. 23 and Nov. 24.

Chinese sturgeons are listed as one of the most endangered species as lingering Yangtze River pollution and disruptions from ship's navigation usually hold off conservation efforts.

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.

After the Gezhouba Dam was built across the main stream of the river in 1981, Chinese sturgeons' migration route was cut off. But researchers said sturgeons had found new spawning grounds downstream the dam over the past 20 years.

Thought to have lived at the same time as dinosaurs, Chinese sturgeons can grow to 2 to 5 meters in body length and weigh up to 500 kilograms.