Deep-sea fishing companies must intensify supervision over their vessels and monitor them 24 hours a day to ensure they are operating legally, according to a notice released amid the restoration of the domestic ocean fishing industry.

The Ministry of Agriculture and Rural Affairs also urged such vessels to follow international rules and regulations when operating in deep waters and warned of severe punishment for them if international disputes arise due to their illegal operations, according to a recent notice released by the ministry.

"With improving situations in COVID-19 epidemic prevention and control domestically, deep-sea fishing companies are restoring operations, and signs of production against regulations have started to appear recently," said the notice, released to fishery authorities and enterprises across China.

The notice is aimed at further enhancing safety management of deep-sea fishing and preventing major international incidents — such as fishing across boundaries — from occurring during the coronavirus pandemic, the ministry said.

Deep-sea vessels should avoid operating in disputed waters and take intensified security measures when passing high-risk areas such as those prone to pirates.

They should cooperate when approached by law enforcement vessels of other countries for boarding and inspection while also taking proper epidemic control and prevention measures, the notice said, adding that evading or resisting such inspections with violence or dangerous means is prohibited.

However, they should report to domestic fishing authorities if they encounter improper confrontational behavior from law enforcement officers from other countries, according to the notice.

The notice also said domestic vessels fishing in public waters must stay at least 1 nautical mile (1.85 kilometers) away from the boundary of 200 nautical mile special economic zones of other countries to prevent illegal fishing and to maintain the lawful interests of domestic vessels.

Lin Guangji, president of Fujian Provincial Association on Ocean and Fishery Economy, said stricter supervision over the deep-sea fishing industry is necessary to ensure safety and legal operation.

"Due to various reasons, such as imprecise location and movements of sea currents, incidents such as domestic fishing vessels entering special economic zones have occurred before, which has resulted in disputes or even violence," he said.

Despite requirements by law and regulations, some Chinese vessels fishing in public seas, especially those owned by small private companies, may choose to turn off the contact devices on their ships from time to time so authorities cannot trace them, he said.

"Ensuring 24-hour monitoring over all such vessels will greatly reduce the chances of vessels fishing across boundaries driven by economic benefits and prevent related diplomatic incidents from occurring," Lin said.