Scientists of the subsidiary organization of the “National agrarian science and educational center” JSC - LLP «Fisheries Research and Production Center» spoke about the application of innovative technologies in the aquaculture.
Thus, Marlenov Eldar Berikuly, the head of the laboratory of ichthyology at LLP «Fisheries Research and Production Center», spoke during an online consultation on the topic “Innovative technologies in aquaculture (aquaponics, biofloc, high-intensity cage farms)”.
An innovative technology is one that uses the latest scientific advances, or a technology that has not been previously used in a particular country. The main 3 technologies that can be used in our country are aquaponics, biofloc and high intensity cages.
Aquaponics
Aquaponics is a high-tech agricultural method that combines aquaculture (growing aquatic animals) and hydroponics (growing plants without soil on nutrient solutions).
In simple terms, aquaponics is a RAS (recirculating aquaculture system) with the addition of a hydroponic plant growing unit. The nutrient solution here is the water that comes out of the fish pools. Fish pools accumulate organic metabolic products in the form of ammonia and excrement. Also uneaten food is organic. To remove these substances, a water purification system is installed in the RAS, which is represented by mechanical and biological filters. From the point of view of chemistry, nitrogenous and phosphorus-containing compounds accumulate in the recirculating water. Solid organic matter in the form of excrement and uneaten food is removed from the water by a mechanical filter, and the ammonia in the biofilter is converted to nitrite and then to nitrate. Nitrate is not toxic to fish at a concentration of up to 40 mg / l, but it still accumulates in recirculating systems in large quantities. Adding a hydroponic growing unit to a plant reduces the concentration of all organic substances, including nitrate, in the water, which allows creating optimal conditions for fish.
As for the plants, they also grow in optimal conditions, since the water from the fish pools contains all organic substances, macro and microelements. Thus, a symbiosis between fish and plants is created, where optimal conditions for fish are obtained and we also get additional production from plants. This method also saves water. For example, in recirculating water systems, it is necessary to change water about 10% of the total volume, and in aquaponic systems, water replenishment is only 2% - this is only compensation for evaporation and the needs of the plant.
Aquaponic farms can be in the form of covered greenhouses, as well as in the open air. Artificial lighting can be used, which makes it possible to install aquaponics even in closed buildings.
Biofloc
By cultivating animals that are low in the food chain, such as tilapia, feed costs can be kept to a minimum. Many types of tilapia typically consume decaying plant and animal matter or "detritus", algae, and even bacterial clumps. By incorporating waste nitrogen into a usable, consumed form by cultivated species, two problems are simultaneously solved: reducing the amount of protein and eliminating water exchange to maintain water quality. The way to solve this problem is to use bioflocks technology. How does this system work?
Aquatic bacteria exist in much larger numbers attached to the substrate than floating freely in the water column. By suspending solid waste in water through aeration and mixing, various communities of bacteria, algae and protozoa can thrive, attached to free floating detritus or residual organic matter.
This provides additional nutrition for the cultured organism, which can feed on this "ecological food". Over the course of weeks or months, depending on the feed introduced, the solids turn into suspended, feathery aggregates, which are referred to here as "flakes". These flakes are called biofloc slurry.
Advantages of biofloc technology:
• simplicity of raising fish or shrimp
• lack of complex filtration systems, such as in RAS
• saving water and space in comparison with pond farms
• high levels of biosafety
• low feed conversion rate
• intensification of animal rearing
• the possibility of producing marine species in inland waters.
• reduction of energy, capital and operating costs,
• oxygenation with “green” water, here you can add chlorella suspension
• consistently high water quality
• increasing the productivity of animals, for example, tilapia eats detritus and thereby improves feeding efficiency
To grow fish with a biofloc system, you need to have pools or ponds and an aeration system, which is mainly represented by propeller aerators. This type of aerator is cheap and energy efficient. The aeration should be continuous and the water in the pools or ponds should be constantly moving.
Mechanical cleaning is absent here, and nitrification is provided by bacteria that inhabit detritus. The size of the flakes ranges from about 50 microns in systems with aerators, such as propeller pumps that crush the flakes, to a few millimeters in systems with softer aeration, such as diffused air.
Tilapia consume about 1.5 grams of flake protein per kg of fish, which is about 25 percent of their protein requirement. Studies of biofloc flake systems have shown that lower protein feeds with 24% protein produce similar tilapia growth on 35% protein feeds, indicating the contribution of biofloc to the protein consumed by fish (feed typically accounts for 40-60% of the intensive aquaculture systems). That is, using the biofloc system when growing tilapia, we can feed the fish with cheaper feed compared to recirculation. This, in turn, will increase the economic efficiency of tilapia cultivation.
Recent research also shows that bioflocks can be harvested from culture systems, dried and added as an ingredient to aquaculture pellets, replacing 2/3 of fishmeal and 100 percent plant meal. However, the economic viability of using flakes as a dry feed ingredient remains uncertain. Higher fishmeal prices could make dried biofloc a viable economic alternative.
High-intensity cage culture
Today, traditional cage farming is used in Kazakhstan. Floating and semi-submerged cages are used. Mainly objects such as trout and sturgeon are grown, less often carp. An alternative to conventional cages is high intensity forced water exchange cage systems.
For example, if in traditional cages, water exchange depends on hydrology and the reservoir, then in high-intensity cages it occurs due to the injection of water by turbo aerators. Due to this, up to 150 kg of fish can be obtained from 1 cubic meter of cage volume. For example, in China, metal cages with a volume of 165 cubic meters are used, where you can get up to 24 tons of fish per growing season. In Hungary, cages of 50 cubic meters made of polypropylene are used, where you can get 7 tons of fish.
The design of intensive cages is very different from traditional ones. The cages are in the form of a rectangular box with blank side walls and a lattice in the end sides. Water is pumped from the side wall and comes out on the other side, carrying fish excrement with it. The power of the turbo aerator is selected in such a way that the required volume of water flow is created to remove organic matter, while there is no excessive flow, since the fish overcoming the current spends a lot of energy on this, which will increase the feed coefficient and reduce its growth. The constant exchange of water in such cages allows a very large volume of fish to be raised on a small area and does not depend on the oxygen regime of the reservoir, as is the case in traditional cages. The only drawback of this technology is the relatively high cost of cages and dependence on the source of electricity. However, it should be noted that the material from which the cages are made is stainless metal and polypropylene, which are very durable. Another plus of this technology is the compactness of the farm due to the very high density of fish stocking.
Online lectures of our speakers can be viewed on our YouTube https://www.youtube.com/channel/UCuS5M4RaYq2Kt-qUtNYDcpQ/ and in Instagram https://www.instagram.com/fishrpc/
