Depleted stocks mean catch is harder to come by, Cui Jia and Liu Ce report from Shandong and Liaoning provinces.

China has the world's largest fishing fleet, with more than 1 million vessels, according to the Ministry of Agriculture. This port, Shidao, is the largest fishing port in north China.Photos by Cui Meng / China Daily

Wang Xinqing kept count as bins of Yellow Sea fish were heaved from two of his boats onto trucks waiting at Shidao port, Shandong province. He figured the catch would produce little profit, but he expected that.

"I ordered the boats to come back when the storage was only half full," Wang said. "That way at least we wouldn't lose the catch.

"If the boats stayed in South Korean fishing grounds longer and caught the eye of South Korea coastguards, they almost certainly would find some reasons to fine us, even though we have a fishing permit and did everything according to regulations."

Not everyone does things by the book. "If we don't cheat, we can't earn a living," one fisherman said.

But it's a risky business. Fish stocks are depleted in Chinese waters and South Korea is getting tougher in protecting its own waters.

"The book" was set out in June 2001 under the Sino-South Korea Fishery Agreement. It defined sea areas for fishing and requires boats from one country to obtain a permit to fish in waters under the other's administration.

China has similar agreements with Japan, signed in 1997, and Vietnam, in 2000.

The 2001 agreement was considered provisional at the beginning, but the territories did not change when China and South Korea established exclusive economic zones in 2005. Under international maritime law, a state has special rights over the exploration and use of marine resources in such a sea zone.

The Chinese have worked resource-rich fishing grounds off South Korea for more than a thousand years, said Li Yongkai, deputy director of oceanic administration of Rongcheng city, which administers Shidao, the largest fishing port in northern China.

Because of the agreement, Li said, a great number of Chinese fishing vessels had to retreat from that area. Fishermen complain they cannot survive by fishing just in China's territory, where marine resources have declined dramatically.

Bohai Sea, where Shidao port sits, used to have 70 types of marine products with commercial value, according to a study released in July by Tianjin Bohai Sea Marine Products Institute. Pollution and overfishing have cut that number to 10.

"China's overfished and depleted waters are forcing Chinese fisherman farther and farther out into sea, where they are running into more and more trouble with Korean coast guards." Li said.

'Don't have a choice'

In the first year of the fisheries agreement, 2,796 Chinese and 1,402 South Korean fishing boats were granted permits, according to China's Ministry of Agriculture. For this year, South Korea has issued about 1,900 permits to Chinese boats. Only 217 go to Rongcheng this year, 89 fewer than last year. More than 2,300 fishing boats are registered there.

South Korea's government has repeated pledges to crack down on illegal Chinese fishing boats in the exclusive economic zone. Some fishermen try their luck without permits.

"To avoid bumping into South Korean coast guards, those fishermen have to go out in harsh weather, with strong wind and huge waves," Li said. "Coast guards won't risk their lives to patrol, but to survive, our fishermen will."

South Korea caught 10 boats from Rongcheng that were fishing without permits last year, compared with 30 the year before. Tang Fuyang, owner of Lurongyu 1492, was one who pushed his luck too far. He was fined 410,000 yuan ($64,900) on Nov 3.

"My whole year's earning went down the drain because of the fine, and I couldn't even afford to pay my crew," Tang said. "But trust me, I really don't have a choice."