This work is an attempt to trace changes in the fish fauna, their food supply and fish catches in the Small Aral Sea from the beginning of 1990s to the present. The purpose of our work is a comparative study of changes in the fishery value of the water reservoir at different stages of its development, including during the last anthropogenic regression. Both literature data and those obtained by the authors in the period 1991–2015 were used. Not only data related to the fauna and fish catches proper, but also data on their food supply, represented mainly by invertebrates, were taken into account. The stabilization of the level of the Small Aral Sea, which followed the construction of the Kokaral dam, greatly changed the situation. The gradual decrease in the salinity of the water reservoir allowed the fish living in the Syr Darya to return to the sea. There are currently 16 species of fish in the sea that can be found in commercial catches.

The results of studies of some morphological, size-age and demographic characteristics of Dryagin char are presented. A distinctive feature of this char from the Boganid char common in Lake Sobachye is a wide body. Its height in mature fish reaches 27.9% of the body length. Dryagin’s char has 112–133 (121.6) perforated scales in the lateral line, 21–29 (26.11) rakers on the first gill arch. The Dryagin char differs from the Boganid char in the color of immature and adult fish. In the control catches, fish aged from 3 to 14 years were noted, fish aged 8–10 years dominated. The length of Dryagin’s char (SL) ranged from 318 to 810 mm, weight — 472–10 700 g. The sex ratio was approximately 60:40 in favor of males. At the age of 6 years, the fish reaches sexual maturity, the maturation period is extended to 8–9 years. The minimum values of individual absolute fecundity in char were noted at the age of 6 years — 3833, the maximum — 18 270, the average value of the trait — 8140 eggs. The value of fecundity functionally depends on the mass of the fish (correlation coefficient 0.83) and its size (correlation coefficient 0.77). It is concluded that the large size, with almost the same maturation time of Dryagin char and Boganid char, makes the former a more preferable object for introducing native species into aquaculture for the Krasnoyarsk Territory.

This article describes the results of an exploration of the current state of some reservoirs of the Ulan district of the East Kazakhstan region: a pond on the Karasu River 7 km upstream of the village of Privolnoye, a pond on the Karasu River 2 km upstream of the village of Mitrofanovka, a pond on the Peschanka River and a pond on the Tugulka River according to hydrochemical and hydrobiological indicators, in order to determine the status and suitability of water objects in fish breeding. Research works was carried out in 2021. Inspections of reservoirs were carried out sporadically, in connection with this, these water objects can be considered poorly studied. For the analysis of temporal changes, hydrochemical and hydrobiological samples were taken in spring, summer and autumn. The content of biogenic compounds and main ions was studied, the results obtained were compared with the values given in the Unified Classification System for Water Quality in Water Bodies, and their seasonal dynamics was also considered. The article defines the class of the reservoir by chemical composition, the category by mineralization and the class of hardness. According to the results of research, water objects are characterized by an optimal oxygen regime, slightly alkaline reaction (pH 7.2–8.7) and low salinity (310–438 mg/dm³). According to the classification of the main ions, the waters of the surveyed ponds belong to the hydrocarbonate class, the calcium group, the first type. It was determined that the concentration of biogenic compounds in 2021 does not exceed the established fishery standards. The values of the abundance and biomass of zooplankton and benthos in different seasons of research are estimated, an assessment of the trophic status of the reservoirs was given according to hydrobiological indicators and a brief physical and geographical characteristic of water objects is described. In general, the trophic class of ponds in the Ulansky district varied from very low class to high class in terms of hydrobiological indicators, which indicates a good supply of food resources. It can be noted that the maximum indicators of the development of the forage base were observed in the summer period. Based on the results of the analyzes obtained, the status and category of the studied water bodies were determined.

The cultivation of aquaculture facilities under controlled conditions consists of several stages — the formation of a breeding stock, the production of offspring and cultivation of marketable products. The duration of each stage depends on the biological characteristics of a particular aquaculture facility and environmental factors. In aquaculture of tropical species, as a rule, installations with a closed water supply cycle are used, which makes it possible to create conditions for their maintenance year-round, depending on the tasks set. At the same time, the organization of the necessary optimal temperature, hydrochemical regime, feeding regime at each technological stage allows you to control, influence and regulate the vital functions of hydrobionts, especially the duration of the reproductive cycle. Special attention is paid to the reproduction of objects. The study of biological and technological features and the creation of technology for reproduction and offspring of the Australian red-lobed cancer in industrial conditions is quite an urgent issue. The purpose of this work was to study the repair and uterine groups of cancers, their reproductive activity, as well as some features of obtaining and rearing young Australian red-lobed cancer in the conditions of ultrasound. The research work was carried out based on the scientific and experimental complex of aquaculture “BIOS” of the Volga-Caspian branch of the VNIRO Federal State Budgetary Institution ("KaspNIRKH"). The temperature conditions of keeping crayfish producers, obtaining, rearing and rearing young crayfish in the ultrasound were studied and their biological indicators were monitored. In the course of the study, the age of producers who showed reproductive activity for the first time and the output of larvae from the female, as well as the size and mass indicators of repair-uterine groups and undergrown juveniles (body weight, body length, absolute gain, etc.).

The results of a study of the biological effect of feed probiotic additives “Subtilis-Zh” (0,04 ml/kg of feed) and “ATYSH” (0,08 g/kg of feed), which are based on cultures of bacteria B. subtilis, B. licheniformis, E. faecium and L. acidophilus, on growth, morphological and biochemical parameters of blood, as well as amino acid and chemical composition of carp muscle tissue. The analysis of the growth intensity showed a significant increase in body weight from the 4th week of the experiment in groups receiving separately the probiotic “Subtilis-Zh” and jointly the probiotics “Subtilis-Zh” and “ATYSH”. Hematological indicators demonstrate a significant increase in the concentration of leukocytes in the experimental group that consumed the complex of probiotic drugs “Subtilis-Zh” and “ATYSH” in comparison with the control by 19,8% (P < 0,05), respectively. A similar blood pattern was observed when studying a carp leukogram, where a significant increase in lymphocytes was found. The number of red blood cells in the blood corresponded to normal physiological values. At the same time, the indicator of hemoglobin content has increased significantly, which indicates active metabolic processes. The use of the feed probiotic additive “Subtilis-Zh” favorably affected the growth, development and hematological parameters of carp. The combined use of this drug with the feed probiotic additive “ATYSH” allowed to normalize the own bacterial flora of the intestine and strengthen the resistance of the fish organism to the effects of pathogens.