Many Vietnamese fishing boats have stayed in port to avoid Chinese patrols
Vietnam has called on China to stop preventing Vietnamese fishermen from working in what Hanoi says are its territorial waters.
China's ban on fishing in the South China Sea was "interfering" with Vietnamese fishermen, Hanoi said.
This is the second time in three weeks that Vietnam has spoken out over the fishing ban and the increase in arrests and fines by Chinese naval patrols.
The tensions have been stoked by rival claims to parts of the South China Sea.
China has been enforcing an annual fishing moratorium since 1999 in order to conserve stocks, but this year's has been seen by many as extremely tough.
The increased Chinese naval patrols "have caused indignation among the public, bringing no benefits to bilateral relations", Vietnam's Deputy Foreign Minister Ho Xuan Son told Chinese ambassador Sun Guoxiang, according to the Vietnamese foreign ministry's website.
Mr Son also asked the Chinese authorities to "stop operations that prevent Vietnamese fishermen from going about their daily business" in areas that Vietnam claimed as under its sovereignty.
There has been growing anger in Vietnam over the ban.
Vietnamese newspapers in recent weeks have been running campaigns against what they call the "Chinese starvation of Vietnam's fishing industry".
They have described how thousands of fishermen in central provinces have stayed in port for fear of being arrested, fined or even shot at by Chinese patrol boats.
Witnesses have been quoted as saying that their boats were chased and attacked by foreign vessels.
The latest incident reportedly took place two weeks ago when a Vietnamese fishing boat was hit and sunk, but the fishermen escaped.
Nguyen Viet Thang, chairman of Vietnam's Fisheries Association, said: "Our people have always been in those areas but the Chinese now use the moratorium to arrest them."
Mr Thang urged fishermen to carry on their usual activities but to report any incidents to the authorities.
"The government needs to interfere to defend our own fishermen," he said.
There are increasingly open calls in Vietnam for the government to "stand our ground" in territorial matters.
But with the latest message, it seems Hanoi prefers to attempt a diplomatic resolution for the time being.