Aerial photo taken on July 23, 2019 shows a fishpond, which used to be an abandoned mine, at Shangzhuang Village in Qian'an City, north China's Hebei Province. (Xinhua/Mu Yu)

Aerial photo taken on July 23, 2019 shows a fishpond, which used to be an abandoned mine, at Shangzhuang Village in Qian'an City, north China's Hebei Province. (Xinhua/Mu Yu)

A staff member shows fish caught from the fishpond, which used to be an abandoned mine, at Shangzhuang Village in Qian'an City, north China's Hebei Province, on July 23, 2019. (Xinhua/Mu Yu)

A staff member works on a fishpond, which used to be an abandoned mine, at Shangzhuang Village in Qian'an City, north China's Hebei Province, on July 23, 2019. (Xinhua/Mu Yu)