Joint op to boost fish stocks in Beibu Gulf

China and Vietnam conducted a joint marine stock enhancement operation in the Beibu Gulf on Tuesday, aiming to strengthen fisheries conservation and increase fishermen's incomes on both sides.

The latest release, held in Dongxing, Guangxi Zhuang autonomous region, involved about 272 million juvenile fish and shrimp, including yellowfin sea bream and red sea bream.

Fishery resources in the Beibu Gulf, one of the most biodiverse marine areas shared by the two countries, remain under pressure despite years of conservation efforts, said Zhang Dianchang, head of the South China Sea Fisheries Research Institute at the Chinese Academy of Fishery Sciences.

Long-term monitoring data shows fishery resource density in the eastern Beibu Gulf, including shared fishing zones, fell from 1,161 kilograms per square kilometer in 2006 to 317 kg in 2019.

Joint stock enhancement programs aim to replenish natural populations through artificial breeding and the release of species suited to the local ecosystem, Zhang said.

Since 2017, China and Vietnam have conducted nine joint stock enhancement operations in the Beibu Gulf, releasing about 770 million aquatic seedlings. Zhang said the recapture rate of released species has remained above 5 percent, while catches of key released species have increased by more than 10 percent year-on-year. Incomes of coastal fishermen have risen by more than 20 percent, he added.

Local fishermen say they have noticed visible improvements in fish stocks. "I've been fishing in this area for many years, and over the past few years I really feel there are more fish," said Ye Fengzheng, a fisherman in the region.

Ye said he once caught a tagged fish released under the program. And he later reported the catch using the phone number on the tag.

China has expanded the use of tracking technologies, including external tags and molecular markers, to study migration patterns. Tagged sea bream released in the Beibu Gulf have been recaptured along both Guangxi and Vietnamese coastal waters.

Officials and scientists say the program emphasizes scientific management rather than large-scale indiscriminate release. Researchers have assessed the ecological carrying capacity of target waters, including food availability and water quality, to avoid ecological imbalance caused by excessive stocking.

"Released species are not simply any available seedlings. They need to have reliable genetics, suitable size and strong vitality," said Su Zhongxing, general manager of Guangxi Fuqun Marine Seedling Reproduction.

He said hatcheries gradually adjust water temperature and salinity to help juveniles adapt to marine conditions, while transport protocols carefully control oxygen levels, stocking density and temperature to improve survival rates after release.