The Chishui River, a major tributary of the Yangtze, has witnessed significant rises in its fish population since a ban on fishing was introduced more than four years ago.

According to a media release from the Guizhou Department of Agriculture, "Fishery resources on the Chishui have been restored very quickly, with significant rises in both population and average size."

Monitoring data show that the number of endemic species in the tributary has risen from 32 to 37, the release stated, quoting a report from the Chinese Academy of Sciences' Institute of Hydrobiology.

It said the trend of the fish population becoming younger and smaller had been effectively curbed along the waterway, the vast majority of which runs through Guizhou province.

For example, the average weight of Spinibarbus sinensis－a fish species endemic to China－has risen from 336.9 grams to 492.5 grams, according to the department.

There has also been a marked rise in the number of Chinese sucker fish, an endangered species under State protection in China, it said.

With no dams along its length, the Chishui is the last free-flowing tributary on the upper reaches of the Yangtze. Flowing for 436.5 kilometers, it rises in Yunnan province and joins the Yangtze in Sichuan province.

Home to more than 160 species of fish, the tributary is key to biodiversity conservation in the Yangtze River Basin.

According to the Guizhou Department of Agriculture, the achievements made are due to a series of measures taken by the province to step up conservation of fishery resources following the fishing ban in the Yangtze River Basin.

A 10-year fishing moratorium was introduced on the Chishui, which lies in the Basin, on Jan 1, 2017, before being extended to all natural waterways along the Yangtze at the beginning of this year.

Authorities in Guizhou decommissioned 331 licensed fishing boats and closed all floating restaurants selling wild river fish along the Chishui.

Guizhou also established a whistleblowing mechanism to report illegal fishing. The public can report such cases and sales of wild river fish via WeChat, email and hotlines.

In addition to regularly releasing the fry of rare fish, artificial fish nests covering a total area of more than 5,000 square meters have been established in Guizhou, and 300,000 Chinese sucker fish were released into the Chishui on June 6.

The department said it now monitors the Chishui's fishery resources 60 times a year. However, it added that more efforts are needed to address sporadic occurrences of illegal fishing in the Chishui River Basin.

As well as stepping up law enforcement patrols by various government bodies, Guizhou will accelerate construction of an intelligent surveillance system to automatically report suspected illegal fishing and sand mining, the department said.

It added that the province will carry out joint law enforcement operations with Yunnan and Sichuan to crack down on illegal cross-regional fishing activities.

More coordinated joint efforts are planned in the three provinces, whose legislatures in late May approved a decision to jointly bolster efforts to protect the Chishui River Basin.

The provinces will further promote a damage compensation system to protect and improve the Basin's environment and work together to restore mountains, waterways, forests, farmland, lakes and grassland.