Maritime incidents in the East and South China Seas, such as the one that sparked a major row between China and Japan, could intensify in a fight over dwindling fish stocks, experts say.
Past incidents have been sparked by regional competition for strategic sea routes and the search for oil, but fishermen from Japan, China, Taiwan, South Korea, the Philippines and Vietnam are increasingly heading outside their own territorial waters -- and into disputed areas -- to earn a living.
Beijing and Tokyo are still at odds two months after a Chinese trawler collided with two Japanese coastguard vessels near a contested island chain in the East China Sea -- seen as a harbinger of further conflicts.
"Fish stocks are depleting very rapidly in eastern Asia and there is a scramble for fish," Jonathan Holslag, a researcher at the Brussels Institute of Contemporary Chinese Studies, told AFP.
"We have gas and oil people involved as well and this is politically the most sensitive issue, but... fishing companies bring a greater risk of incidents or tensions," Holslag added.
The industry -- which is vital in Japan, the region's key consumer -- has the "great potential of becoming a political problem," he warned.
In both the East and South China Seas, white tuna is the most plentiful, and as Holslag explains, the price per kilo -- about 13.50 dollars, five times the average price of the most popular fish in China -- makes it "worth the risk".
Fish has become "a kind of new gold in Asia", he said.
Chinese fishermen ply the waters near the mainland, but also travel as far away as the Pacific islands of Fiji and Tonga, or the waters off east African nations such as Kenya and Tanzania, which have given them special concessions.
But in the East and South China Seas, they are treading on the competing territorial claims of more than a half-dozen Asian countries, most of which involve tiny island chains that are potentially resource-rich.
Yves Tiberghien, a visiting professor at the National Chengchi University in Taiwan, says fish stocks were at the heart of the recent China-Japan clash.
"It's clear that tensions are mounting in a region where resources are fewer and fewer, and demand is on the rise," Tiberghien said.
"China is consuming more and more fish, and global fish stocks are down, especially in that region -- it makes perfect sense that Chinese boats are going to go farther and farther" and into disputed waters, he added.
In August and September, he said, more than 80 boats from coastal Fujian province headed to the islands at the heart of the China-Japan dispute -- known as the Diaoyus in China and the Senkakus in Japan, and also claimed by Taiwan.
Chinese fishermen have been working there for generations, but in recent years, Japan's coastguard has been increasingly active, confronting Taiwanese and Chinese boats in a similar fashion to the September 7 incident.
That collision led to the captain's arrest, sparking outrage from Beijing. Despite a few brief meetings between the Chinese and Japanese premiers in the interim, ties are still fraught with complications.
"The Japanese coastguard was initially mild in its dealings with the Chinese fishermen. In the last two years, they have become more strict," one veteran Chinese fisherman told the website sinovision.net.
"There are a lot of fish around the Diaoyus," said another fisherman quoted by the website. "This is not just a question of patriotism -- our sole motivation for going there is to fish."
China's fisheries department has sent patrol boats to the area around the disputed islands to "protect the rights of the fishermen" -- an act which Tokyo has protested.
Since the start of the year, the department says it has offered assistance to more than 400 fishing expeditions in the South China Sea near the Spratlys -- also claimed by the Philippines, Vietnam, Malaysia, Brunei and Taiwan.
Despite the increased tensions, fishermen say they will not allow politics to interfere with their daily lives.
After the arrest by Tokyo of Chinese captain Zhan Qixiong, who was later released, one fisherman told sinovision: "No one said, 'We won't go to the Diaoyu anymore.'
"Even Captain Zhan said he would go fishing in the Diaoyus again."
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