Last year, public security bureaus investigated over 2,300 cases of illegal fishing, and cracked more than 2,000 from January to May this year, according to the Ministry of Public Security.

Meanwhile, many dams along the Yangtze are also to blame for the environmental damage and the decline in fish numbers because they make it difficult for fish to migrate and reproduce.

Niu Xinqiang, head of the Changjiang Institute of Survey, Planning, Design and Research, said that about 24,000 small hydropower stations had been built within the Yangtze River Economic Belt by the end of 2017.

The belt covers all the provincial regions the main body of the river flows through, with the exception of Qinghai province and the Tibet autonomous region. It also includes the provinces of Zhejiang and Guizhou, which boast tributaries of the Yangtze.

"These dams have cut off the passage of migratory fish, resulting in a sharp decline in the numbers of some species," said Niu, a member of the Chinese Academy of Engineering.

In a video conference held in January last year, four central government bodies－the ministries of water resources and of ecology and the environment, along with the National Development and Reform Commission and the National Energy Administration－demanded rectification of outstanding environmental and ecological problems caused by small hydropower stations.

Some of the stations were built illegally and some pose environmental and ecological hazards. According to a media release unveiled after the conference last year, the four government bodies rolled out a joint investigation that will guide the demolition and rectification work this year.

As part of the latest efforts to ensure the implementation of the fishing moratorium, the ministries of public security and of agriculture and rural affairs initiated a three-year campaign to crack down on illegal fishing.

Yu Kangzhen, vice-minister of agriculture and rural affairs, said agricultural authorities at all levels should implement targeted measures against illegal fishing and further improve law enforcement efforts with other departments.