Block by block, artificial reefs restoring fish stocks off coast of Fujian province

FUZHOU — Fishermen in the city of Putian in East China's Fujian province are doing something very cool out at sea — they are using giant but hollow cement Rubik's cubes to build reefs to shelter fish.

Multiple holes on the surface of the cubes allow fish to easily navigate these artificial reefs, making them suitable as places to live, breed and hide from potential predators. These efforts are about more than just protecting the fish, as they also contribute to curbing illegal fishing, safeguarding local fishery resources and alleviating seabed "desertification", said Wang Qinghua, from the marine fishery station in Nanri township.

Huge engineering ships are used to transport hundreds of reef cubes, which are then gradually lowered into the coastal waters of Nanri Island, Putian. Cranes handle the cubes in a process resembling the grabbing of toys with a gigantic claw machine. Once the cubes have been released, crews dive into the water to check their stability, allowing for the adjustment of positions to prevent or correct any tilting that may occur.

"As the seawater slowly reduces the alkalinity of the cement, small algae will attach to and grow on the cubes to form the artificial reef, thereby attracting more fish to it. Additionally, a variety of benthic organisms and corals will also attach to the cubes, forming a distinct ecosystem with the artificial reef as its foundation," explained Yan Zhihong, head of the water technology station in Putian's Xiuyu district.

To monitor and manage fish stocks and these artificial reef areas, Nanri Island has launched an underwater online observation program. "We have monitoring equipment on the reefs that are connected to the internet to provide real-time monitoring of the living conditions of the fish and measure water temperature, oxygen levels, changes in currents and so on," Yan said.

These monitoring efforts have revealed the artificial reefs have become thriving habitats for a diverse range of colorful fish species. Some large fish have even approached the surveillance cameras out of curiosity. "We discovered a variety of fish, including crab-like blunt-toothed sturgeon and Japanese sturgeon," Yan added.

During the 1990s, the waters surrounding Nanri Island had an abundance of marine fishery resources, including significant numbers of shrimp and fish. However, overfishing depleted the biodiversity in the area.

"As a result, the fish population significantly decreased, and the smiles vanished from the faces of our fishermen," said Chen Yacong, a local fisherman.

Thanks to more than 2,700 reef cubes placed in nearby waters since 2012, the local marine environment is on the mend. "Over the past few years, there has been an increase in the number of fish, which means we can now earn more money without having to spend as much time on the water," Chen said.

In late 2018, the waters surrounding Nanri Island were designated as Fujian's first national-level marine pasture demonstration area.

Experts and researchers who assessed the area found that the biomass and resource density of the reef area had both increased significantly after the casting of the artificial reef, while the reef area is also able to effectively shelter juvenile fish of economic species. This means the reef-building program has proved to be a beneficial solution — both economically and ecologically.

"We are continuing our efforts to breed more fish fry and release them in the reef area. From 2020 to the end of 2023, over 80 million fry of all kinds of fish were released in these waters," said Yan.

Xinhua