Flowing Aquaculture System: A New Direction For Efficient Fisheries

In the field of aquaculture, flowing aquaculture system is gradually emerging and becoming a highly anticipated aquaculture method. With its unique aquaculture concept and technology, it has brought new vitality and opportunities to the development of fisheries.​

1. The principle and charm of flowing aquaculture system​

Flowing aquaculture system, as the name suggests, is the high-density intensive breeding of fish in a fish pond with water flow exchange. Its core principle is to cleverly use the power of water flow to create an excellent living environment for fish. Usually, reservoirs, lakes, rivers, mountain streams, springs, etc. are used as water sources. With the help of water level differences, diversion or interception facilities and water pumps, water is allowed to flow continuously through the fish pond, or the discharged water is purified and re-injected into the fish pond. Water flow plays a vital role here. It not only continuously inputs dissolved oxygen to meet the breathing needs of fish, but also can promptly remove fish excrement, effectively maintain the good water quality of the pond water, and lay a solid foundation for the high-density intensive breeding of fish.​

2. Various types of flowing aquaculture system​​

• Open flowing aquaculture system​

• Normal temperature flowing aquaculture system: This is the primary form of flowing aquaculture system, which has many significant advantages. It requires a small investment, the pond construction process is relatively simple, and daily management is also quite convenient. It completely uses natural water sources, and the water temperature is not artificially adjusted. Since the discharged water is no longer reused, but new water is continuously injected, it can always maintain good water quality conditions. In the past, family-style fish farming in mountainous areas of my country, as well as temples and parks for raising ornamental fish, often adopted this method. After the 1970s, many fish species such as non-carp, carp, grass carp, roundhead bream, eel, and perch have successively become the objects of aquaculture under this form, and the scope of aquaculture has also expanded from simple edible fish farming to the breeding of fry and fish species. In normal temperature flowing aquaculture system, there is a key point, that is, under certain conditions, the flow rate and output are positively correlated. Therefore, making full use of the terrain difference when building the pond, so that the fish pond can obtain a large flow, and the water flow in and out of the fish pond does not require additional power, has become a key factor in determining whether this farming method has production value.​

• Warm water: The outstanding feature of open warm water fish farming is the ability to regulate water temperature. It cleverly uses natural water sources with a temperature higher than the air temperature, such as hot springs, deep wells, or warm drainage from industrial and mining enterprises (mainly power plants), as the main water source or water source for regulation, and injects it into the fish pond together with natural room temperature water. By accurately controlling the flow of both, the appropriate temperature of the pool water can be maintained. This farming method has obvious advantages. It can not only increase the breeding density, but also significantly accelerate the growth and development of fish. In the low temperature season, it can keep the pool water at a temperature suitable for fish growth, thereby effectively extending the growth period of fish and shortening the breeding cycle. At the same time, it can also promote or inhibit the gonadal development of broodstock. In low temperature areas, using warm water to cultivate broodstock can advance the breeding period of broodstock, thereby increasing the feeding time of seedlings, creating favorable conditions for cultivating large-sized fish species.

Closed-loop flowing aquaculture system: Closed-loop flowing aquaculture sysytem is also known as circulating filtration fish farming. Its biggest feature is that the sewage discharged from the pond is purified and then injected into the fish pond again, so the total water consumption is greatly reduced compared with the previous two forms, and the water temperature can also be kept constant by heating. The basic technology of this farming method originated from aquariums. As early as the late 19th century, countries such as the Netherlands, the United States, and the United Kingdom began to use circulating filtration to treat water for fish farming, allowing the water to be reused for decades. In the 1960s, due to the pollution of waters in many countries and the increasing demand for live fish in the market, this farming method was gradually introduced into the field of seed breeding and edible fish production, and developed into a new farming process. In the circulating filtration fish pond, the discharged sewage contains harmful substances such as fish excrement and ammonia produced by the decomposition of residual bait, which will hinder the growth of fish, so it must be filtered and purified before reuse. The general treatment process is to aerate the discharged sewage first, then settle it, and remove suspended solids such as fish feces, leftover bait and debris. Then, use a biofilter or a biorotor for biological purification. The biofilter further clarifies the water by blocking some suspended matter remaining in the water in the gaps of the filter material (pebbles, yellow sand, plastic particles, mesh, etc.) or depositing it on its surface. At the same time, with the help of the microbial community (biofilm) growing on the surface of the filter material, the ammonia and nitrite dissolved in the water are oxidized into non-toxic substances to complete the sewage purification process. The biorotor uses the microbial community growing on the surface of the disc (cylinder) to oxidize the organic matter in the water. The purified water is then aerated and enters the fish pond. If it is a warm water circulation filtration system, it is also necessary to use steam or hot water boilers for heating after filtration. During the whole process, the water quality needs to be strictly monitored and managed according to the standards. In addition, due to the high density of fish farming under this breeding method, it is necessary to feed granular bait with comprehensive nutrition to prevent fish from nutrient deficiencies and avoid bait loss. Moreover, in the circulating filtration fish pond, the occurrence and transmission speed of fish diseases are extremely fast, so a strict epidemic prevention system must be established. Once fish diseases are found, the sick fish must be isolated and treated quickly, and the entire system must be disinfected. The area of closed circulation fish ponds is usually small, generally only a few square meters to dozens of square meters, and most of them are built indoors. The entire device covers multiple parts such as the fish pond system (fish pond and inlet and outlet pipes, etc.), purification system (sedimentation tank, filter tank), water supply system, air supply system, heating system, etc., and is centrally controlled and modernized through the control and monitoring system. This highly integrated and intelligent management method makes it have a strong control ability over the fish farming environment and a large production potential, especially suitable for the breeding of excellent fish and precious fish. It has extremely high use value in large cities, industrial and mining areas or areas lacking sufficient water sources. However, its construction cost is expensive, the technical level of management is high, and the energy consumption is also high.​

3. Significant advantages of flowing aquaculture system​​

• Excellent water quality: Continuously flowing water continuously brings sufficient dissolved oxygen to the fish pond, while taking away fish excrement and leftover bait in time, effectively preventing water quality deterioration, greatly reducing the risk of fish disease, and providing a clean and healthy growth environment for fish. For example, in some fish farms that adopt flow-through aquaculture, the incidence of fish has decreased by [X]% compared with traditional pond aquaculture.​

• Fast growth: Good water quality and sufficient dissolved oxygen enable fish to grow in a more suitable environment, accelerate metabolism, and significantly increase growth rate. Taking rainbow trout as an example, under flow-through aquaculture conditions, its growth cycle is shortened by [X] months compared with ordinary aquaculture methods, and the output is also greatly increased.​

• High-density aquaculture: Flow-through aquaculture creates conditions for high-density aquaculture, greatly increasing the aquaculture volume per unit area, and effectively improving the utilization efficiency of land and water resources. According to statistics, in the same area of aquaculture area, the output of flow-through aquaculture can be increased by [X] times compared with traditional pond aquaculture.​

• Precise management: With the help of modern monitoring and control technology, key factors such as water flow, water temperature, dissolved oxygen, and feeding can be precisely controlled to achieve scientific breeding and improve breeding efficiency. For example, sensors are used to monitor water quality parameters in real time, and water flow and oxygenation equipment are automatically adjusted to ensure that fish are always in the best growth state. ​​​

• Looking forward to the future of flowing aquaculture system​

With the continuous advancement of science and technology and the growing demand for the quality and quantity of aquatic products, flow-through aquaculture will usher in a broader space for development. On the one hand, in terms of technological innovation, the aquaculture equipment and management system will be further optimized to improve the intelligence and automation level of aquaculture. For example, artificial intelligence technology will be used to achieve real-time monitoring and precise control of water quality and fish growth conditions, develop more efficient water treatment technology and feed formula, reduce aquaculture costs, and improve aquaculture benefits. On the other hand, in terms of sustainable development, flowing aquaculture system will pay more attention to ecological environmental protection, and reduce the waste of water resources and pollution to the environment by optimizing the aquaculture model. At the same time, it will strengthen the integration and development with other industries, such as combining with tourism and leisure agriculture, develop more distinctive fishery products and services, and enhance the added value of the industry. In addition, with the continuous increase in global demand for aquatic products, flowing aquaculture system is expected to play a greater role in the international market and promote the international development of fisheries.​

As an efficient, environmentally friendly and sustainable farming method, flowing water aquaculture is leading the aquaculture industry into a new stage of development with its unique advantages and charm. It not only brings higher economic benefits to farmers, but also makes positive contributions to ensuring food safety and protecting the ecological environment. I believe that in the future, flowing water aquaculture will continue to innovate and develop, bringing more surprises and well-being to people.