Editor's note: This report focuses on Quanzhou as part of our special series, "Rising Star Cities," about Chinese cities whose annual GDP exceeds 1 trillion yuan ($155 billion). At the end of 2021, there were 24 such cities. Click here for more stories on Quanzhou, an ancient trading hub known for its cultural diversity. You can also explore our earlier coverage of Ningbo, Changsha and Chongqing.

Quanzhou is one of the major port cities in Fujian Province, south China that is abundant in marine and fishery resources. The mariculture equipment in Quanzhou City has been improved to support a sustainable economic expansion of the fishing sector.

For people living in the fishing villages of Quangang District in the northeast of Quanzhou City, fish farming is their main source of income.

Aquaculture in ocean involves the use of buoys for oyster cultivation or open-net pen and cage systems – mesh cages between 45 and 75 cubic meters that are installed in the ocean with fish inside.

Before 2019, fish farmers at Quangang District used foam plastics buoys or wooden-made tanks and cages – material that's cheap but not durable particularly when typhoons come.

"I used to see a lot of broken foam plastic flushed to this beach after typhoon," said Xiao Xiancheng, a Huiyu Village native who works in Quanzhou City.

Traditional near-shore fish farms cause a range of environmental issues as well as economic loss. Predatory fish get tangled in the nets, and the high concentration of fish within the pens can lead to a high concentration of waste, chemicals and diseases filtering into nearby ecosystems, putting fish in danger of bacterial contamination or lack of oxygen.

Besides, traditional near-shore aquaculture wooden cages are extremely vulnerable against typhoons and large winds and waves and can thus only be deployed in inner bays or harbors with better shelter conditions. For example, Typhoon Maria in 2018 which hit Ningde City in Fujian Province destroyed more than 70,000 traditional wooden fishing tanks, causing 600-million-yuan (roughly $80 million) worth of loss.

China's Ministry of Agriculture and Rural Affairs released technical specifications for using plastic fishing raft in 2021 to solve those issues.

Fish farmers at Quangang District started renovating their systems as early as April 2019, according to its official report.

However, farmers there were unwilling to switch to plastic rafts at the beginning as the process was too "tiresome," said Xiao Wenzhang, a local farmer at Xiao Cuo (a village that Xiao's family lives) of Quangang District.

"Fish are easily tangled to death when we change these rafts," he said, "but I'd rather give it a try with about 100 rafts first" as Xiao manages the fish farming raft in the region.

Later, the local municipal bureaus of finance, agriculture and water resource jumped in to assist farmers with the system renovation.

"The government has invested a lot to change them, otherwise the wrecked foam plastic and wood raft would be left in the water, which not good for the ocean," said Xiao.

As of December 27, 2021, the villages of Xiao Cuo and Huiyu had completed installation of 8,832 new plastic raft and and over 19 million yuan had been allocated for the project.

Farmers only need to pay an annual rental fee at 200 yuan per raft that can last five years or more compared to the one-year life expectancy of the foam plastic ones.

Foam buoys used for shellfish aquaculture have been upgraded to long-lasting and ecological-friendly plastic ones as well.

The director of the service center of Fengwei County in Quangang District, Chen Zhujin told CGTN that farmers there started switching to plastic buoys in 2021 and completed the system upgrade within a year.

"We have about 10,000 mu (666.67 hectares) of oysters hanging under these buoys that have been upgraded to plastic ones," said Chen, out of the 60,000 mu (4,000 hectares) of mariculture area near the Meizhou Bay surrounding Fengwei County.

According to the bureau of agriculture and water resource of Quangang District, the area will introduce marine industrial parks to complete the industry train and invest into smart aquaculture vessels.

Read more: China delivers world's first 100,000-tonne 'mobile fish farm'