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The article discusses the prospects of optimizing the technology of growing African catfish in high-tech industrial aquaculture. The goal was to determine the range of biologically active substances that can increase the productivity, organoleptic qualities of fish grown in recirculating aquaculture systems and optimize their living conditions. For this purpose, a complex of biologically active substances was tested, including probiotics, prebiotics, amino acids, and natural sorbents. It was introduced into feed and added to the water of fish tanks. Studies have shown that the developed complex of biologically active substances accelerates growth and development, guarantees the growth of fish biomass, reduces the level of bacterial pollution of the fish habitat, and normalizes hydrochemical parameters in the tanks. Improving the technology of fish farming in recirculating aquaculture systems (RAS) involves changing the ideology of feeding and keeping fish. The results of our studies show that, under conditions of artificial breeding in RAS, it is necessary to use cultures of living microorganisms probiotics that improve intestinal microbiocenosis in fish feeding and introduce them into the fish habitat. Probiotics should be used with prebiotics containing vitamin-amino acid complexes that stimulate the development of symbiotic microbiota. The use of natural sorbents plays an important role. The proposed set of ingredients increases the organoleptic qualities of fish. The studies were supported by the Russian Foundation for Basic Research with grant 18-016-00127.

This article is devoted to the study of the qualitative and quantitative characteristics of the African Catfish Clarias gariepinus eggs produced at different durations of the inter-spawning interval. Eggs were produced artificially using sex hormones. In industrial aquaculture, the African Catfish Clarias gariepinus does not reproduce naturally. Therefore, the problem of obtaining high-quality eggs that will be used for in-vitro fertilization is urgent. To implement artificial spawning of fish in industrial aquaculture, it is necessary to correctly choose the effective hormonal stimulator and empirically select its dose. Sex hormones are involved in regulating the duration of the inter-spawning interval and affect the quality of eggs produced both for fertilization and for food purposes. The pituitary gland of the African Catfish Clarias gariepinus and surfagon were used as gametogenesis stimulators. The aim of the work was to study the optimal duration of the inter-spawning interval and the effect of hormonal inducers used to stimulate artificial spawning in industrial aquaculture. The use of the catfish pituitary gland in fresh or acetonated form as a hormonal stimulator provided higher-quality eggs, compared to the synthetic hormonal drug - surfagon. Stimulation with acetonated pituitary injections reduced the inter-spawning interval of the African Catfish Clarias gariepinus to three months, and the use of surfagon prolonged the inter-spawning interval to four months. Reducing the duration of the inter-spawning interval is important for the production of the African Catfish Clarias gariepinus eggs for food purposes. Studies have shown that reducing the optimal duration of the inter-spawning interval negatively affects the quality of the produced eggs and their quantity. This research was financially supported by a grant from the Russian Foundation for Fundamental Research, project No. 18-016-00127. Keywords: aquaculture, African Catfish Clarias gariepinus, eggs, inter-spawning period, sex hormones, oocytes

There is a possibility of developing a pathological process in the body of fish in the conditions of high-tech industrial aquaculture and at high planting densities, creating chronic stress. Histological studies allow early detection of the initial stages of possible pathology at the cellular level. The studies have shown that apparently healthy individuals of African catfish grown in recirculating aquaculture systems (RAS) revealed pathology of cells and tissues of the gastrointestinal tract. They had edema of the internal muscle layer of the stomach and intestines, detachment of the epithelial layer from the gastric mucosa, violation of the structural organization of gastric fields on histological sections. Thinning of intestinal villus, reduction of their length and branching, violation of their structure up to destruction were also revealed. The study of the tissues of the stomach and intestines was carried out using a research motorized universal microscope Axio Imager.M2 (Carl Zeiss, Germany). To correct the pathological process, the experimental group of fish received a “sporothermin” probiotic with feed, which belongs to the probiotics of the last generation. It is an antagonist of a wide range of pathogenic and opportunistic microbiota and is used as an alternative to antibiotics. The composition of “sporothermin” includes spore forms of bacteria Bacillus subtilis and Bacillus licheniformis, which in the gastrointestinal tract of fish turn into vegetative forms. Bacteria Bacillus subtilis and Bacillus licheniformis are not representatives of the intestinal microbiocenosis of the African catfish, but they regulate its structure by reducing the level of pathogenic and opportunistic microbiota. Pathology of cells and tissues of the gastrointestinal tract have been identified in the fish of the experimental group treated with the sporothermin probiotic.

The article discusses prospects for use of the theory of adaptogens in demand in medicine and in the fish breeding practice. The obtained results show that the adaptogens use at the early stages of catfish ontogenesis (Clarias Gariepinus, Burchell 1822) can cause the condition of nonspecific increased resistance and expand the adaptive flexibility range of this specie. Adaptogen trekrezan used in our experiments (Oxyethylammonium methylphenoxiacetate) is a synthetic analogue of the natural ginseng. Its application in the embryo culture process has shown positive results. It has reduced the level of the developmental anomaly, increased the first stage larvae hatching and their viability, significantly decreased the mortality rate and reduced the level of cannibalism common for catfish larvae. We have determined that the larvae breeding in the trekrezan medium has considerably increased their growth rate, and weight gain. The obtained results are new, and the adaptogens use at the early stages of ontogenesis in industrial catfish aquaculture is recommended. The Russian Foundation for Basic Research has supported our study with the grant No. 18-416-730005.