[Grain Policy of a Great Country] The seafood freedom of this generation of young people depends on the "smart factory" in the sea

The Central Government's No. 1 Document for 2025 was released, proposing to support the development of deep-sea aquaculture and the construction of marine ranches. Deep-sea aquaculture is an important way to establish a big food concept and get food from the ocean, and is an important part of developing the marine economy. At this year's two sessions, the issue of deep-sea aquaculture has become a hot topic of social concern.

The classification system is cleverly laid out , and marine aquaculture has a clever way to adapt to the environment

Over the past half century, my country's marine aquaculture model has been advancing in constant exploration, from traditional to modern, from extensive to intensive, from focusing on output to focusing on quality, and from pursuing economic benefits to pursuing ecological and green development.

Aquaculture has formed a diverse classification system based on different breeding sites and methods. According to the breeding site, it can be divided into tidal flat breeding, shallow sea breeding, harbor breeding, deep water breeding, marine ranching and factory breeding; according to the breeding method and facilities, it can be divided into: supratidal pond breeding, intertidal seedling breeding, seabed seedling proliferation, rope breeding, net cage breeding, trellis breeding, deep-water anti-wave cage breeding and large mobile ship breeding, etc. These breeding methods create suitable environmental conditions according to the ecological habits of the breeding objects, promote the large-scale reproduction and rapid growth of the breeding organisms, and meet people's needs.

The farmed objects can generally be divided into fish, shrimps, crabs, shellfish, algae and sea cucumbers, covering hundreds of specific species, and can be farmed according to local conditions.

The diversity of aquaculture models reflects the need to adapt to different environmental conditions and breeding goals. For example, pond farming, as a traditional breeding method, is suitable for the breeding of various freshwater fish and some marine fish; factory farming achieves high-density breeding by artificially controlling breeding conditions, and is suitable for fish with high water quality requirements; bottom seeding and raft farming are more suitable for the breeding of fish, shellfish and algae in the marine environment; cage farming is a high-density breeding method carried out in open waters, suitable for fast-growing fish; and three-dimensional integrated multi-trophic level breeding is to raise a variety of aquatic organisms in the same water at the same time, making full use of the differences in resource utilization between different species to achieve improved breeding benefits.

Healthy concept becomes dominant, green breeding model brings ecological innovation

The development of aquaculture has not been smooth sailing. In the early 1990s, freshwater and marine aquaculture diseases broke out on a large scale, which attracted the attention of government departments and aquatic science and technology workers. The concept of healthy aquaculture came into being and gradually became the strategic orientation of aquaculture development. In order to adapt to the needs of environmental changes, the aquaculture industry urgently needs to transform to a green, healthy and efficient aquaculture model. In this context, a variety of green aquaculture models have been explored and gradually promoted and applied.

What are the green marine aquaculture models?

1. Factory-scale recirculating aquaculture model

In the pursuit of green, healthy and efficient aquaculture, recirculating aquaculture technology has gradually emerged. This technology achieves efficient use of aquaculture water and low emission of pollutants by building a closed circulation system, effectively improving aquaculture efficiency and quality.

Traditionally, agriculture is considered to be a typical "weather-dependent" industry, but this perception has been revolutionized by the development of modern agriculture. Modern aquaculture can fully draw on the industrial production model to achieve standardized production of aquatic products in a factory environment, and land-based factory fish farming is a typical example.

Land-based factory farming in my country can be divided into two modes: open water aquaculture and closed recirculating water aquaculture. Open water aquaculture is located in the supratidal zone of the seaside, with low-arched fish farming workshops and cement pools built, using natural seawater or seaside well water as the water source, and using water pumps or high tide water intake to achieve continuous renewal of the aquaculture water body.

3D diagram of recirculating aquaculture system (Photo courtesy of Yellow Sea Fisheries Research Institute)

Factory-scale recirculating aquaculture is built based on modern technology and equipment, equipped with facilities and equipment systems for fully artificially controlled aquaculture production conditions. It integrates multiple disciplines such as modern engineering, electromechanical, biology, environmental protection and feed. It is not only a high-tech, environmentally friendly production system, but also represents the highest level of modern intelligent fish farming.

Interior view of factory-scale recirculating aquaculture (Photo courtesy of the Yellow Sea Fisheries Research Institute)

2. Multi-nutrient level integrated breeding technology model

Marine multi-trophic level aquaculture (IMTA) optimizes the development and utilization of organisms at different trophic levels from the ecosystem level, integrates multiple ecosystem service functions (such as food supply, climate regulation and cultural services, etc.), and maximizes aquaculture benefits. This model scientifically matches the different living spaces of aquaculture organisms, allowing fish, shrimp, shellfish, crabs, and algae to find comfortable living spaces, making full use of aquaculture water space to increase aquaculture production.

There are many forms of integrated marine aquaculture systems, such as algae farming combined with cage farming, fish cage farming combined with shellfish farming, etc. Shrimp and mussels, clams and crabs are also a typical model.

Multi-level three-dimensional aquaculture (provided by the Yellow Sea Fisheries Research Institute)

The multi-trophic level integrated aquaculture implemented in Sanggou Bay, Rongcheng, Shandong is a successful exploration. Its model realizes the efficient use of energy in the aquaculture system, and has become an effective way to improve water quality, increase protein production, and expand the aquaculture capacity of offshore waters. It also helps to alleviate the negative impacts of climate change.
In 2016, the Food and Agriculture Organization of the United Nations (FAO) and the Network for Aquaculture in Asia and the Pacific (NACA) selected the Sanggou Bay integrated aquaculture model as one of the 12 typical successful cases of sustainable intensive aquaculture in the Asia-Pacific region for global promotion.

Principle of multi-level three-dimensional aquaculture (provided by the Yellow Sea Fisheries Research Institute)

3. New model of deep-water wind and wave resistant cage aquaculture

With the rise of the marine economy, the deep-water cage aquaculture model has become increasingly important. Relying on the advantages of deep-sea resources, this model has brought revolutionary changes to the aquaculture industry.

As the name implies, deep-water cage farming is to raise fish in relatively deep waters (usually more than 20m deep) with strong resistance to wind, waves and currents. The structure of deep-water cages mainly includes cage frames, aquaculture nets, mooring systems and supporting facilities, such as underwater monitoring, automatic feeding, automatic fish collection, water quality monitoring, high-pressure net washing machinery, etc. Through efficient and intensive farming methods, this model not only improves the output and quality of aquatic products, but also brings more substantial economic benefits to farmers.

Fish harvested from deep-water cage culture (provided by the South China Sea Fisheries Research Institute)

After years of exploration and experimentation, we have successfully broken the blockade of foreign deep-water cage technology and developed a deep-water cage aquaculture model with Chinese characteristics. At present, the country is committed to promoting the further development of the domestic deep-water cage industry, promoting the establishment of relevant technical systems, and combining it with the industrial structure adjustment of the fishery industry to promote the prosperity of the deep-sea aquaculture industry. Deep-water cage aquaculture is becoming a new favorite in the era of marine economy.

" Migratory bird " north-south relay breeding solves climate problems in aquaculture

Aquaculture systems are highly dependent on the natural environment. Although farmers have continuously adapted to environmental changes during the production process, the increasingly severe climate crisis over the past 50 years has brought unprecedented challenges to aquaculture, especially marine aquaculture, and the livelihoods of fishermen have also been seriously threatened.

As a major aquaculture country, a unique model has been quietly emerging in the past 20 years, which is called the North-South Relay Model. The successful North-South Relay Model includes sea cucumbers, abalone, and grouper, while the land-sea relay model includes the cultivation of high-end species such as turbot, large yellow croaker, and shrimp, as well as some shellfish.

In recent years, sea cucumbers have gradually become popular among the public and have become a dietary and health product for the public, thanks to the unconventional "northern sea cucumber farming in the south" model. "Northern sea cucumber farming in the south" refers to taking advantage of the relatively warm climate in the south in winter, introducing sea cucumber seedlings from Liaoning, Shandong, Hebei and other places, and farming them in the south. In early winter every year, sea cucumber seedlings from Dalian, Qingdao and other places will "migrate south" thousands of miles away, rushing to the south to spend the winter before freezing, and taking advantage of the temperature difference to allow the sea cucumbers to continue to grow.

The same is true for abalone. In my country, there are not only abalones that have established their own homes in the north and south, but also migratory abalones. Why does abalone farming also have to be relayed from north to south? From the habits of abalone, too low or too high temperatures will lead to slow growth and cause a large number of deaths. In winter, abalones in the water temperature conditions of Shandong waters almost stop growing, and once they encounter a cold wave, they will suffer a catastrophe. After being transported to the waters of Fujian, during the five or six months of wintering period, the abalone seedlings can grow to 3 to 4.5 cm, and the survival rate can reach up to 97%. This back-and-forth migration from north to south not only greatly improves the survival rate of abalone, but also shortens the growth cycle of abalone by more than one year, making abalone, which was originally a marine delicacy, available on the tables of ordinary people.

China's marine aquaculture industry is gradually transforming towards intensive, factory-based and integrated aquaculture, and the land-sea relay and the north-south relay have brought a new Chinese solution to it. This model is not only expected to solve many challenges faced by traditional agriculture, such as weather dependence, environmental problems and food safety issues, but also indicates a broad market prospect.

Author: Liu Yadan, Researcher, former Assistant Secretary-General of the Chinese Society of Fisheries and Chief Scientific Communication Expert of China

Scientific review: Wang Qingyin, former director of the Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, former chairman of the Chinese Society of Fisheries

Planning: Wu Yuetong

Editor: Li Xinzhe