A total of 233,000 rare fish were released this week into a national nature reserve in the upper reaches of the Yangtze River in southwest China's Yunnan Province.

Staff at the aquatic reserve conducted the release in order to restore the population of endangered fish unique to the Yangtze, while maintaining the diversity of the river's fish population.

The batch of released animals includes 3,000 Yangtze sturgeon, which have national first-class protection status, and 70,000 mullet, which have national second-class protection.

All the fish have been marked to assist with a scientific monitoring project, which will last six years.

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