Aerial photo shows the view of Qutang Gorge, one of the Three Gorges on the Yangtze River, in Southwest China's Chongqing. [Photo/Xinhua]

Authorities vowed on Tuesday to maintain a harsh clampdown on illegal angling along the Yangtze River and uproot the underground network that produces banned fishing gear and sells the unlawful catch.

A decadelong moratorium on fishing was imposed on the country's longest river in 2021 with the aim of restoring its ecological health.

After three years, the fish population in the river has recovered markedly, but the moratorium still faces constant threats from illegal fishing, which is becoming "more concealed" and harder to detect, Tang Renjian, minister of agriculture and rural affairs, said at a news conference organized by the State Council Information Office in Beijing.

In response, he said authorities will step up nighttime surveillance as well as patrols near river sections close to provincial borders, which are more susceptible to poaching because of jurisdictional vacuums.

Scrutiny will also be increased over "unregistered, unlicensed and unregulated" trawlers and banned fishing practices such as electric shock fishing.

"Relying on automated and intelligent monitoring methods, we are enhancing round-the-clock monitoring and supervision of critical water areas," Tang said.

The State Council, China's Cabinet, issued a guideline last month on "steadfastly advancing" the ban, amid rumors that the moratorium has led to fish overpopulation in the Yangtze.

Ma Youxiang, a vice-minister of agriculture and rural affairs, told the news conference that while it has increased by a quarter since 2021, the total fish population in the Yangtze is only slightly more than a third of the preindustrial level.

He said restoring fish populations is a lengthy task, citing the examples of Qinghai Lake in China and the Rhine River in Western Europe, where decades of moratoriums have failed to substantially restore fish stocks.

Tang described the ban as a long-term, complex and arduous historical task closely linked to the Chinese nation's sustainable development.

The current state of the Yangtze can only be described as "in the early stages of recovery from a serious illness" after decades of overfishing and pollution, he said.

Ministry of Public Security data show it has solved more than 20,000 cases involving violations of the ban since 2021.Over that period, illegal fishing in the main waterways of the Yangtze has decreased by almost a third, and less than 10 percent involves more destructive organized crimes.

Tian Yonghao, who oversees the ministry's Public Security Bureau, told the news conference that his administration will step up patrols on sections susceptible to poaching and embrace information technology and use undercover investigations to combat-related crimes.

He said it will collaborate closely with related departments "and strengthen control of prohibited fishing gear and the sale of illegal fishery products".

The fishing ban on the Yangtze is part of a growing effort by China to restore the ecological health of its rivers and seas.

Last month, the agriculture ministry said it would impose the strictest summertime fishing moratorium in the annual "Shining Sword" mission aimed at warding off illegal fishing on rivers and at sea.

Collaboration will also be stepped up with maritime neighbors to fight illegitimate angling across borders during the moratorium, which usually lasts from May through September, officials said.