Elasmoid scales of pike-perch (Sander lucioperca), white amur (Ctenopharyngodon idella), carp (Cyprinus carpio), freshwater bream (Abramis brama) and crucian carp (Carassius carassius) were processed without hydrolysis by “dry” method in order to study the characteristics of the obtained finished product, which determine its further use as additives for food and other purposes. The essence of the method consisted in washing the scales, its subsequent drying, grinding and separation, with obtaining two fractions enriched with both organic (cotton-like product) and inorganic (powder) components. FT-IR spectroscopy was used to characterize the scale samples and their enriched fractions. Characteristic bands known for collagen, in particular for Amide I, Amide II, Amide III, Amide A, were observed in the IR spectra of all the samples studied. The bands (inorganic part) at ~1022 cm–1 and at ~599 cm–1 indicate valence asymmetric vibrations of PO43– groups. Numerous bands for all experimental samples in the wavelength region 3900-3500 cm–1 can be caused by vibrations of OH groups, which is associated with the presence of water in the tested samples. Comparison of the absorption intensity in the region of characteristic frequencies of collagen and hydroxyapatite calculated by the IR method can be one of the approaches for the development of a rapid method for the determination of their quantitative content in fractions obtained from fish scales. Organic and mineral additives from fish scales can be recommended as components of formulations of various food products, as well as raw materials in tissue engineering, orthopedics and dentistry.

This work is the result of hydrobiological and ichthyological work of the Institute of Water Problems of the North of the Karelian Scientific Center of the Russian Academy of Sciences during the implementation of various topics (governmental and economic-contractual) in the water area of the Topo-Pyaozersky (Kuma) reservoir. The main object of discussion of the article is the whitefish Coregonus lavaretus (L.), namely the state of its population. Calculations of its abundance and biomass in the current study period have been carried out. Taking into account that the nature of commercial production and its unilateral orientation on the part of registered and unregistered fish harvesters remain at a high level, limiting the catch of whitefish should remain an indispensable condition for the preservation and stability of their biological resources. To carry out this catch, it is necessary to carry out a number of measures, in terms of more complete fishing on the main sections of the lake and the conservation of caught fish. As additional measures for this, it is advisable to introduce a ban on whitefish fishing in areas with the largest concentrations during the spawning period. Summary of all the above – whitefish fishing is currently being carried out against the background of a new man-made situation affecting its products, previously modified by other anthropogenic factors. All this exacerbates the problem of fisheries regulation, because other anthropogenic factors often turn out to be unstable and fluctuate (including dramatically) both by year and by season. For example, water levels during the spawning period may vary significantly due to the activities of the Kama HPP, determined by the interests of electricity consumers. As a result, optimal catch rates were calculated – up to 24 tons, or 21.7% of the value of the fishing stock (with a maximum withdrawal of 23.4%).

The purpose of the presented work is to assess the adequacy and selection of optimal parameters of mathematical models of fish growth in application to forecasting the growth of aquaculture trout in closed water supply installations (CWSI). To perform the assessment and comparison, 8 nonlinear mathematical models of fish growth were considered. Tabular (parametric) models of feed for trout cultivation in the CWSI were taken as a standard, and on their basis the selection of optimal parameters was carried out, bringing each of the mathematical models closer to the standard one. The results were compared using an estimate of the standard error, the Akaike information criterion adjusted for a small sample size, and the Bayesian information criterion. As a result, the parameters providing the best approximation of the considered mathematical models of fish growth to the reference tabular function are obtained. As a result of the error estimation, it was found that the three-parameter von Bertalanfi model demonstrates the best accuracy. At the same time, other models (with the exception of exponential) have also demonstrated accuracy sufficient for practical use. The practical significance of the work is the conclusions on the adequacy of the use of nonlinear mathematical models for modeling trout growth in the CWSI, as well as the presented model parameters that provide the best approximation to the reference tabular function.

Establishing quantitative levels of chemical elements in the blood plays a leading role in studying the mi-croelement status of the body. The purpose of the work was to study the microelement composition of the blood and spleen of the Russian sturgeon Acipenser gueldenstaedtii (Brandt, 1833). The objects of the study were females and males of Russian sturgeon of different ages. The determination of metals was carried out using atomic absorption spectrometry. In each sample, iron, copper, manganese, zinc, nickel, cobalt, chromium, lead, and cadmium were determined. Specific features of the accumulation of chemical elements in the blood and spleen of Russian sturgeon have been revealed. The content of iron and zinc in the blood and spleen of fish is in the greatest quantities. At the same time, the concentration of zinc in the blood of fish, as well as the concentration of iron, depends on the systematic position of the fish, and falls within the limits of the concentrations of chemical elements according to A. P. Vinogradov: the content of iron and zinc in the blood of Teleostei is generally higher than in the blood of Elasmobranchii. Russian sturgeon belongs to the subclass Chondrostei and has characteristics of cartilaginous and bony fish, perhaps this can explain the amount of iron and zinc found in the blood. A positive correlation was revealed between iron and copper in the blood of female and male Russian sturgeon. At the same time, no gender differences were found in the content of chemical elements in the blood of female and male Russian sturgeon, with the exception of nickel, the concentration of which is higher in the blood of males. It has been shown that as fish age, the concentration of nickel, manganese, lead and copper in the blood increases.

The object of research in this work is the Caspian vimba Vimba vimba persa (Pallas), one of the commercial fish species of the Caspian Sea. Fish samples taken in the middle part of the Caspian Sea in the autumn period from 2020 to 2023 were analyzed. The work includes studies of Fe concentration in organs and tissues (muscle tissue, gonads, liver, gills, gastrointestinal tract) and food coma of the Caspian vimba Vimba vimba persa (Pallas) aged 2 and 3 years old. It was revealed that Fe accumulation in the liver occurs to a greater extent in the body of the Caspian vimba, and to a lesser extent in muscle tissue. A comparative analysis of the metal concentration was carried out depending on the sex and age of the fish. It was found that females accumulate Fe to a lesser extent than males. The average concentration of Fe in the body of 2-year-old females was 184.11 mg/kg of dry matter, and in 3-year-old females 163.58 mg/kg of dry matter. The average concentration of Fe in the body of males aged 2 years was 203.39 mg/kg of dry matter, and in males aged 3 years 225.92 mg/kg of dry matter. There is also an increase in the concentra-tion of Fe in the body of males upon reaching the age of 3, and a slight decrease in concentration in females. There are sexual differences in the distribution of metal in fish organs (liver, gills, gonads). Of particular interest is the dynamics of metal in the gonads (increases in females, decreases in males). There occurs redistribution of metal in the organs and tissues of fish.

Nowadays in the food and nutrition industry special attention is paid to the creation of non-toxic, easily recy-clable packaging materials of a new assortment, capable of providing reliable protection of products from harmful factors. The object of the study was biodegradable film compositions based on fish gelatin and agar, with the addition of plasticizing agent - glycerol. Experimental and analytical studies were carried out using standard and original methods. Modeling of the process of thermal treatment of film compositions was carried out, the experimental dependence of moisture absorption of films on temperature (range 120-160 °C) and duration of the thermal modification process (10-30 minutes) was established. The possibility of thermal modification of biodegradable film compositions was determined. The rational mode of thermal treatment of films is the temperature interval of 140 °C for 20 minutes, which allows to keep the moisture absorption index at the maximum level (842%), exceeding the initial index by 8.4 times, during 120 hours. The established parameters of thermal structuring allow to keep organoleptic quality indicators of films at a high level and to obtain a homogeneous, porous and elastic film. Thermally modified films at temperatures of 140 and 160 °C are characterized by increased dissolution time up to 40 and 70 minutes respectively at dissolution temperature of 60 °C and up to 15 and 30 minutes respectively at dissolution temperature of 75 °C. It is shown that thermal modification of biodegradable films will contribute to compliance with safety requirements, environmental friendliness, absence of toxicity. Thermal modification allows to increase functional and technological properties of composite biodegradable films, which can be used to create a wide range of modern packaging barrier materials.

The purpose of this work was to establish the informative value of methods of structural analysis of biological fluids in determining the prospects of using atherina (Atherina boyeri caspia (Risso, 1810)) as a source of dietary protein in aquaculture. For the first time, solid-phase structures of atherina muscle homogenates were studied. It is known that the solid phase of biological fluids formed under conditions of wedge-shaped dehydration is a visualization of biochemical processes occurring in an organism or organ. The study of the morphological picture of a dried drop (facies) makes it possible to establish associative links between the features of the structuring of the studied liquid and its composition, as well as to determine the nature of the impact of environmental factors on a living system. The results of the study made it possible to establish the main type of homogenate facies and its morphological parameters, which indicate the consistency of biochemical processes and the presence of high-grade protein in the muscle tissue of the Caspian atherina, caught both in the spring and autumn seasons. The size and weight parameters of fish, the content of water-soluble protein in muscle tissue are characterized. For the first time, a comparative analysis of the level of water-soluble protein and solid-phase structures of muscle homogenates of Caspian atherina caught in different seasons in the coastal waters of Dagestan was carried out. Atherina is a food component for many fish living in the Caspian Sea. It was determined that in October, the content of muscle water-soluble protein in atherina tended to increase relative to March. During the feeding period, the accumulated part of the protein components turns into lipid components, which accumulate intensively, therefore, there are no significant seasonal differences in the content of water-soluble protein. It has been established that the biochemical processes occurring in muscle tissues are reflected in the solid-phase structures of biological fluids formed under conditions of wedge-shaped dehydration. The obtained results of the trend towards an increase in water-soluble muscle proteins in the body and an increase in the population in recent years indicate the importance of the use of Caspian atherina in the quality of live feed at fish farms.

A study of the feed additive “Faybramax Plus”, which is a metabiotic for the management of fish autoflora and comprehensive prevention of bacterial infections, was conducted on sterbel yearlings with an initial weight of 130 g. The experience takes place in swimming pools. The water supply in the pools was carried out from a well. The conditions of detention corresponded to the technology of fish farming. The duration of the experiment was 60 days. The number of fish in the group was 150. The control group 1 received a full-fledged combo feed; group 2 was given a full-fledged compound feed + 0.3% of the feed additive “Faybramax Plus”; Group 3 consumed full-fledged compound feed + 0.6% of the feed additive “Faybramax Plus”; group 4 was fed full-fledged compound feed + 1.0% of the feed additive “Faybramax Plus”. It was found that when using the studied feed additive, the live weight of fish in the experimental groups increased by 1.9–6.0% at the end of cultivation. The protein content in the body of sterbel was higher compared to the control by 1.8–7.5%. The cost of the resulting products (increase) compared with the control, it decreased by 4.87–13.78% per group. Profit when using the feed additive “Faybramax Plus” increased by 345.11–1,068.23 rubles per group. The level of profitability increased by 2.71–7.66% per group compared to the control. As a result of the conducted research, it was found that the use of the feed additive “Faybramax Plus” produced by the company SYMBIO is most effective in a percentage ratio of 0.6% by weight of feed, as a result of which the level of profitability increases by 7.66%.

Fish, as a food component, is very beneficial for human health. It is rich in protein, valuable fatty acids, vitamins and minerals. However, when consuming it, there is a risk of toxic substances entering the human body that ac-cumulate in the tissues of aquatic organisms, for example, heavy metals. The purpose of the work is to determine the biochemical parameters in the muscles of pike perch from the reaches of the Rybinsk reservoir, which differ in anthropogenic load, and to assess the risks of human consumption of this species. The amount of water, dry matter, lipids, protein, minerals and carbohydrates in muscle tissue was determined using standard methods. To assess the threat to human health associated with the potential duration of exposure to heavy metals from walleye consumption, target and cumulative hazard ratios were calculated. The assessment of carcinogenic risk to human health was determined using the target and general cancer risk index. Calculated indicators were obtained based on data on the content of heavy metals in the muscles of pike perch, established earlier. In the muscles of pike perch specimens from the Sheksninsky and Volzhsky reaches, no significant differences between biochemical parameters were found. According to the ratio of protein and lipids in muscle tissue, the studied individuals belong to category A, and according to the amount of lipids – to fish with a low-fat content. The estimated dietary intakes for weekly intakes of heavy metals from pike perch meat was below the reference values. The target and total hazard coefficient turned out to be less than one, which indicates that there is no potential non-carcinogenic risk for humans when consuming pike perch meat. The target cancer risk indices for Cd, Pb, Al and Cr are within acceptable ranges. The total risk of developing cancer for these metals is more than 1 in 100,000.

The results of optimizing the formulations of snack products based on fish raw materials are presented. Formu-lations of combined fish-growing snacks with high biological value, attractive organoleptic characteristics and long shelf life have been developed. Ground carp, buckwheat and cucumbers flour, red cabbage, beetroot and flaxseed were used as ingredients in the preparation of combined fish-vegetable snacks. The technology of cooking combined fish-vegetable snacks has been developed. Modern research methods were used to assess their nutritional value. The organoleptic evaluation of ready-made fish-growing snacks was carried out according to a 5-point system. The nutritional and energy value of the prepared snacks was evaluated. It is noted that ready-made fish-growing snacks satisfy the human body's need for more than 50% in proteins, β-carotene, pyridoxine, iron, selenium, zinc. This indicates the functionality of fish-growing snacks and their increased nutritional value. The need for carbohydrates is satisfied by only 2.5-3.2%. There is also satisfaction of the need for fats, riboflavin, calcium, phosphorus (above 15%). 100 g of fish-growing snacks satisfy 15-16% of the energy requirement. The largest amount of nutrients necessary for the body is contained in formula 3 due to the content of buckwheat flour and beetroot. Light in weight and containing all the necessary nutritional elements, snacks can be used on long hikes and in emergency situations to ensure proper nutrition.