Reef relief for marine ecosystems

China joins world in building artificial reefs to revive fish stocks

Sun Xianli used to make a good living from the sea, but since 2011 his income has fallen dramatically. In 2012, Sun's crop of mussels at his "sea ranch" failed, and he lost his main source of revenue.

"The water was filthy. After the reef died out, other creatures died out," says the 50-year-old from Rizhao, a coastal city in Shandong province.

Sun is not the only victim of the worsening maritime environment. Coral reefs all over the world are experiencing a significant decline.

According to a report released at the International Coral Reef Symposium in Australia in 2012, it was agreed by scientists that the marine environment in general, and coral reefs in particular, are being adversely affected by climate change. Most scientists believe the rate of change is potentially beyond the capacity of coral reefs to adapt and recover.

To cope with climate change, the construction of artificial reefs along China's vast coastline is helping to restore the maritime ecosystem, replenish fish stocks and improve the lives of sea farmers.

In 2013, a desperate Sun used a local government subsidy to sink concrete blocks in the shallow coastal waters to create a sustainable habitat for marine creatures that would attract large numbers of fish.

"The government started a project to build an artificial reef in 2013. They told me the blocks would become a new home for the fish and restore the damaged environment," he says. "Now the reef is my only hope."

Coral reefs, which comprise only about 0.5 percent of the ocean floor, are complex structures built up over thousands of years as a result of the deposits of calcium carbonate skeletons from reef-building coral species. These reefs are often referred to as the "rain forest of the sea".

Artificial reefs, which are used extensively in Europe, the United States and Japan, were first introduced in China in the 1980s, but have been built in large numbers only in recent years. The continuing deterioration of the underwater environment in coastal areas has resulted in the structures increasingly being used to promote marine life and fishing, and the scale in China is rapidly approaching that of Japan and the US, according to the State Oceanic Administration.

"Fish gather around reefs. That's common knowledge among fishermen," Sun says. "In 2008, we caught fish worth 300,000 yuan ($47,000; 41,700 euros) in the waters near a 10-meter shipwreck, so I believe our artificial reef will attract a lot of fish."

The Rizhao government has built six large artificial reefs using concrete blocks, tubes and rocks. The largest covers 98 hectares and includes more than 100,000 concrete blocks, each 1 cubic meter. By providing hard surfaces to which algae and invertebrates such as barnacles and coral can attach, artificial reefs attract large numbers of marine creatures and provide homes and food for fish.

"Artificial reefs attract fish, which breed in the waters around them and boost the population. That allows us to reduce the scale of sea farming and the pollution it causes. It also means we can reduce the scale of long-range fishing to protect marine life in the deep oceans," says Zhu Jingyou, deputy director of the Rizhao Oceanic and Fishing Administration. "The development of artificial reefs will be an important part of our job in the coming years."

Although artificial reefs were first used in Japan to boost fish stocks and marine agriculture after World War II, a similar practice had been employed on a very small scale in certain parts of China for centuries.

During the Ming Dynasty (1368-1644), fishermen in the coastal areas of southern China embedded bamboo poles in the sea bed and filled the spaces between them with rocks and tree branches to create environments that would attract fish.

In the 1980s, Shandong and Guangdong provinces undertook a number of reef pilot projects, but a lack of investment meant the scale was too small to be profitable or benefit the local fishing. industry, according to Liang Zhenlin.

"Now, artificial reefs have spread along the coastline, from the Guangxi Zhuang autonomous region in the south to Liaoning province in the north," Zhu adds. "They play an important role in the rejuvenation of the underwater environment and replenishing the fish population."

The function of the reefs varies according to location. Those in southern China are mainly used to promote environmental conservation efforts, while those in the north are used in the production of high-end marine produce, including sea cucumbers and abalone, both of which are firmly in the luxury food bracket.

The country's vast 18,000-km coastline and the large expanse of water are advantageous for the development of artificial reefs and could see China's system quickly outstrip those in Japan and the US, meaning both the environment and the fishing industry could benefit in a shorter time.

In 2013, Dongtou, an island county in Zhejiang province, spent 230 million yuan on the construction of the country's largest artificial reef. Dubbed the "ocean ranch", it is composed of 90,000 cubic meters of concrete blocks across 150 hectares of ocean, which has produced a marine-life propagation area of more than 1,000 hectares.

"If we don't start building more reefs now, it will be too late," says Lin Shaozhen, senior engineer at the Zhejiang Marine Culture Research Institute.

According to a 2014 report by the State Oceanic Administration, China's fishery resources have declined rapidly in recent decades, especially bell fish and large yellow croakers. Other species have simply vanished, and the proportion of high-end fish in the total annual catch fell to 30 percent from 50 percent in the 1960s.

"We're not only building reefs, but also cultivating and releasing various fish fry," Lin says, as she stood in a greenhouse-type structure that houses pools stocked with 40-day-old large yellow croakers that will be transferred soon to "sea ranches" and reach adulthood in six months.

She says the reef will provide a natural habitat for the fry, which means their diet will be entirely natural and unaffected by human food waste.

Despite the acceleration in their development, the artificial reefs need to be regulated to ensure that they are effective and environmentally friendly, and their location and standards should be carefully assessed to prevent damage to the fragile maritime ecosystem, Lin says, adding that experience could be gained from the US and Europe, where there are also long coasts.

Artificial reefs in Europe have been developed over the past 40 years. Most have been placed in the Mediterranean Sea, but there is an increasing interest on the part of northern European countries. Fish stock enhancement and fishery management are the main purposes of reef construction in the Mediterranean and on the Atlantic coast of the Iberian Peninsula, while nature conservation, restoration, research and recreation have been the main aims in the other European regions to date, according to the Brazilian Journal of Oceanography's report on artificial reef construction in Europe, released in 2011.

"Most artificial reefs in Europe are made of specially designed concrete units. Several kinds of production and protection modules have been tested," Lin says. "And what's more, we could learn from them that the restoration of the maritime environment requires a systematic approach that focuses on controlling pollution, preventing over-fishing, and safeguarding the future for coastal people."

pengyining@chinadaily.com.cn

(China Daily European Weekly 09/25/2015 page16)