SHANGHAI, June 6 (Xinhua) -- Officials and conservationists on Thursday released 178 Chinese sturgeon and 70,000 mullet into the Yangtze River estuary near Shanghai to help restore the wild population of the endangered species.

The Chinese sturgeon (Acipenser sinensis) is a national first-class protected animal and the mullet is a national second-class protected animal. All the sturgeon and 15,000 mullet have been marked for scientific monitoring.

The largest individual Chinese sturgeon released this time had a length of two meters, according to the Shanghai Municipal Committee of Agriculture and Rural Affairs.

Since 2004, Shanghai has been breeding and releasing rare aquatic species and set up a system for helping the fish better adapt to the wild.

In recent years, China has stepped up efforts to rescue endangered species in the river, such as Chinese sturgeon, by targeting illegal fishing, closing polluting factories and releasing captive-bred fry into the wild.