Industrial fish farming technologies: recirculating aquaculture systems (RAS), cage culture and tank culture

Efficiency of technologies: comparison of RAS, ponds, and the pasture method

Industrial fish farming allows for fish rearing at maximum density in tanks, cages, and closed-loop systems in both fresh and seawater. The main difference between this approach and traditional ponds is its independence from external natural factors. Under controlled conditions, the fish farmer fully monitors the habitat, ensuring stable mass gain. This makes it possible to obtain production volumes unattainable in natural water bodies.

• Productivity in RAS — 500–1000 t/ha
• Land consumption per 1 kg of fish — 0.01 m²
• Water consumption per 1 kg of fish — 0.005 m³

Intensive methods require minimal space and water volumes per unit of production. The pasture method requires vast territories and water resources, while industrial RAS installations minimize these costs. Below is a comparison of productivity and specific resource consumption for various rearing technologies.

Practical features: cages, tanks, and recirculating aquaculture systems

The industrial segment of aquaculture is divided into lake, cage, and tank farms, as well as systems with recirculating (RAS) water supply. Lake farms improve efficiency through production concentration, mechanization, and partial automation of processes. If one needs to launch production quickly with minimal capital investment, cages are the optimal choice.

Advantages of cage farms over pond ones:

• do not require long construction times or large initial costs;
• have a simple design made of standard netting materials;
• assembled and installed without the use of expensive special machinery;
• do not occupy land areas;
• do not consume scarce freshwater.

In tank rearing, for example in trout farms, high productivity is maintained by a high frequency of water exchange. Efficiency here depends directly on feed formulation, age group control, and the level of mechanization. Tanks allow for the rational use of the site area and provide direct visual control over the stock.

Advantages of tank trout rearing:

• high stocking density due to rapid water exchange;
• compact layout and land savings;
• constant monitoring of fish health;
• minimal sludge accumulation and easy cleaning of containers;
• protection from predators and wild fish;
• convenience of feeding and harvesting mechanization.

In recirculating water supply systems, special biological ponds are used to purify water. In recirculating aquaculture systems (RAS), all life support processes are fully controlled by equipment. The purity of the environment is maintained here by a system of filters, and the water treatment unit is responsible for heating, oxygen saturation, and the removal of organic pollutants.

Thus, industrial aquaculture turns out to be an autonomous farm, independent of the processes associated with fish production in natural or partially modified aquatic ecosystems. In practice, it turns out that many functions of aquatic ecosystems are successfully performed by specialized equipment, which, as a rule, works significantly more efficiently and thereby ensures extremely high rates of fish output from fish-farming facilities.

Comprehensive technical equipment and the level of fish productivity allow us to consider industrial fish farming as the highest form of modern freshwater aquaculture. In addition to the general provisions noted, industrial fish farming possesses such attractive features:

• high concentration of production in limited areas;
• high labor productivity of personnel employed in primary production;
• possibility of locating farms near the consumer.

The latter feature makes it possible to sell fish in the most acceptable form for consumption – live and fresh.

For industrial farms using warm water, a feature such as independence from climate is characteristic. Fish farms using warm water from power plants (TPP and NPP) and industrial enterprises, as well as geothermal waters, can be located in any region of the country if there are sources of water with temperatures increased (compared to natural ones). This feature of the warm-water form of industrial fish farming makes it particularly promising in the conditions of Russia, where the climate factor over most of the territory does not contribute to the development of common forms of commercial fish farming.

In addition, using warm water makes it possible to cultivate various heat-loving fish species, which are distinguished not only by increased productivity but also by high consumer qualities.

All forms of industrial farms can be divided into three groups based on the nature of their water supply:

• Farms using water with a natural temperature (cold-water).
• Farms using water with a temperature elevated above natural levels (warm-water).
• Farms using sea or brackish water (cold-water or warm-water).

Industrial farms can operate using flow-through, recirculating, and closed-loop water supply schemes. The quantity of commercial products produced by industrial methods currently accounts for a significantly small portion compared to the pond method and does not reflect the real prospects of this direction in fish farming, but this should be considered a temporary phenomenon.

The main directions for the development of industrial fish farming in Russia are:

• cultivation of cold-loving fish (rainbow trout and its analogues, whitefish, etc.) in cages installed in water bodies with natural water temperatures (lakes, reservoirs, canals, etc.);
• cultivation of heat-loving fish in cages, tanks, and raceways using a flow-through water supply scheme or recirculating and recirculating aquaculture systems (RAS) using warm water.

The following ways to increase the efficiency of industrial farms can be identified:

• Formation and maintenance of breeding broodstocks.
• Increasing the survival rate of fish of various ages.
• Development and use of highly efficient granulated feed.
• Obtaining stocking material for pond and pasture farms at an early stage.
• Year-round breeding and the use of polycycle.
• Introduction of new highly productive fish farming objects into production.
• Year-round sale of commercial products and cultivation of expensive delicacy fish.

Given the rather cold climate of Russia, cold-water industrial farms cultivating rainbow trout and whitefish (muksun, broad whitefish, peled, pyzhian, etc.) may become more widespread, especially in the water bodies of the north and north-west of the European part, which are close to potential external markets where it will be possible to successfully sell whitefish in the first place.

Thus, the country's industrial fish farming (cage, tank, combined, recirculating water supply systems, and RAS) has great prospects when solving issues related to feed quality, stabilization of energy prices, and meeting the nutritional needs of the population.