Fish Muscle Tissue Research Articles

Intestinal uptake and low transformation increase the bioaccumulation of inorganic arsenic in freshwater zebrafish

Arsenate [As(V)] is the main form of arsenic (As) present in freshwater taken up by freshwater fish. Data on the main uptake tissue, biotransformation, and bioaccumulation in freshwater fish exposed to As(V) were limited, and the reasons for its bioaccumulation in the muscle tissue of freshwater fish remain undetermined. Accordingly, we simulated bioaccumulation and depuration in zebrafish (Danio rerio) exposed to waterborne As(V) by employing a six-compartment physiologically based pharmacokinetic model and As speciation analysis. Modeling and biotransformation suggested that intestines were the main uptake site for waterborne As(V), instead of the gills. This novel finding was evidenced by the higher As transfer constant from water to intestines (k03 = 1.52 × 10−4 L d−1) compared to gills (k02 = 5.28 × 10−5 L d−1). The low concentration and percentage of arsenobetaine (AsB) in the intestines suggested a weak ability to synthesize AsB. Our results showed a substantial proportion of inorganic As in intestines and a relatively substantial percentage in muscle tissue. Therefore, high As(V) uptake in the intestines and lack of biotransformation contributed to high bioaccumulation of inorganic As in freshwater fish. Inorganic As posed concerns due to the human health risks associated with consuming As(V)-contaminated fish and should be addressed.

Assessment of Pesticide, Dioxin-like Polychlorinated Biphenyl, and Polycyclic Aromatic Hydrocarbon Existence around Galindez Island, and Comparison with the Organic Pollution Bibliography of the Antarctic Peninsula

Sediment, notothenioid fish, and moss samples were collected from the vicinity of Galindez Island, Antarctic Peninsula during the austral autumn of 2016 and 2017. Pesticide, Polycyclic Aromatic Hydrocarbon (PAH), and dioxin-like Polychlorinated Biphenyl (dl-PCB) concentrations were measured using High-Resolution Gas and Liquid Chromatography. Pollutant concentrations were below detection limits in sediment and moss samples. However, pesticides, PAH, and dl-PCB congeners were detected in the muscle tissue of fishes. Pesticide concentrations varied between 0.46 and 12.2 ng/g-dw, and Mecarbam was the dominant compound. Kresoxim-methyl, Mecarbam, Procymidone, Pyridaben, and Quinoxyfen were reported in the muscle tissue of the fishes, for the first time from the Antarctic. PCB-118, PCB-105, and PCB-156 were dominant dl-PCBs. The ∑12-dl-PCB concentration was 160,929 pg/g-dw, and WHO-TEQ-total dl-PCB was 8.30 pg/g-dw in Trematomus bernachii, over the consumable limit in fishes according to the European Commission. The PCB-126 concentration was 36 pg/g-dw in the muscle tissue of fish, the first reported from the Antarctic. Phenanthrene was the dominant PAH congener. The ∑16-PAH concentration was 22.5 ng/g-dw. PAH sources were local and petrogenic in the fishes, likely after long-term bioaccumulation. The flow rate is rather low around Galindez Island; accordingly, contaminant removal takes time and may demonstrate long-lasting effects including bioaccumulation in the marine food web.

Assessment of the consumptive safety of mercury in fish from the surface waters of the Vologda region in northwestern Russia.

It is known that the consumption of fish is the main source of mercury intake in human beings. In this study, the concentration of mercury in the muscle tissue of fish from different reservoirs of northwestern Russia was found to be 0.01-1.68μg/g wet weight. The features of mercury accumulation in the muscle tissue of fish, depending on their type, trophic specialization, body weight, length, and the type of water body, were also revealed. Of the fish studied, 7% had mercury concentrations above the regulatory levels of the Russian Federation. The proportion of examined fish, the consumption of which will lead to an excess of the permissible weekly intake of mercury in the individual, is 44% for preschool children (2-5years old), 34% for children of primary school age (6-10years old), and 17% for adults. Special attention is drawn to the fact that the mercury content in fish that does not exceed the sanitary and hygienic standards (normative levels) of the Russian Federation may still be unsafe for the health of the population, especially children.

Developing a robust and sensitive analytical method to detect off-flavor compounds in fish

In recirculating aquaculture systems (RAS), off-flavors that accumulate in fish muscle tissue can be problematic in terms of consumer acceptance and the reputation of farmed fish products. Although off-flavors are not toxic at low concentrations, they often give fish muscle earthy, muddy, or other unwanted flavors. Traditionally, muddy off-flavors caused by geosmin (GSM) and 2-methylisoborneol (MIB) have been detected, but a variety of other compounds and flavors have also been identified. In this study, a method based on solid phase micro extraction (SPME) coupled with gas chromatography and mass spectroscopy was developed to identify and quantify 14 off-flavor–inducing compounds in RAS–farmed fish. The selected off-flavors were quantified in circulating water and in fish from a pilot-scale RAS rearing rainbow trout (Oncorhynchus mykiss). The method showed high accuracy and precision with limits of detection and quantification at a low ng L−1 level. In this study, 13 compounds were found in the fish muscle which decreased in concentrations during the 15-day depuration period. This study showed that off-flavors in fish can also be induced by other compounds besides GSM and MIB. This emphasizes the need for sufficient off-flavor control in the RAS, but also the importance of an accurate and reliable analytical quantitation method.

Microcystin-LR at sublethal concentrations induce rapid morphology of liver and muscle tissues in the fish species Astyanax altiparanae (Lambari)

The process of eutrophication and consequent proliferation of cyanobacteria in rivers and lakes leads to increasing numbers of harmful algal blooms and higher concentration of toxic metabolites in freshwater bodies. Microcystin is a toxic metabolite produced by cyanobacteria that is frequently detected and can pose health risks to important freshwater species including fish. The aim of the present study was to evaluate the effects of microcystin-LR on the morphology of Astyanax altiparanae's liver and muscle. One hundred (n = 100) Astyanax altiparanae were divided into 5 groups (n = 20) with 24 h and 96 h of microcystin exposition at two doses of 0.5 and 1.0 μg/L. Differences were observed in the microcystin treatment with respect to histopathological analyses including cytoplastic degradation, displacement, and increase in nuclei volume and area of hepatocytes. Hyperemia and dilation of blood capillaries were seen in the liver. There were also observable changes in the size of muscle fibers and muscle inflammation. Our results demonstrate that microcystins can impact the integrity of both tissues even at sublethal concentrations. Low doses of microcystins are therefore sufficient to intoxicate fish livers and muscle tissues.

Development of a vortex oscillating clean-up column for high-throughput semi-automatic sample preparation of drug residues in fish muscle tissues

A novelty high-throughput semi-automatic sample clean-up method was developed and used for rapid analysis of 9 drug residues in fish muscle tissues combined with high-performance liquid chromatography/quadrupole-linear ion trap mass spectrometry (HPLC-QTRAP-MS/MS). The target compounds were extracted by Quick, Easy, Cheap, Effective, Rugged and Safe multiresidue (QuEChERS) method with acetonitrile. A vortex oscillating clean-up column was proposed for single step purification firstly. After centrifugation, 1 mL of acetonitrile layer was transferred into a 3 mL vortex oscillating clean-up column which packed with 150 mg C18 sorbent. The column was covered with piston, placed on a column-tube rack, vigorously agitated on a multi-tube vortex mixer. After vortex oscillation, purified extract was obtained for analysis by pushing the piston of oscillating clean-up column. The performance of the developed method was validated by analyzing 9 analytes in spiked grass carp muscle tissues. The limits of quantification (LOQs) ranged from 1.0 to 5.0 μg kg−1. The recoveries were in the range of 101–119% at the four concentration levels (2.0, 5.0, 10.0, 20.0 μg kg−1). Inter-day and intra-day relative standard deviations (RSDs) were lower than 16% for all analytes.

Multi-biomarkers approach to determine the toxicological impacts of sulfamethoxazole antibiotic on freshwater fish Cyprinus carpio

Antibiotics are increasingly detected in the aquatic environment and are raising severe concerns for human and ecological health. Sulfamethoxazole being a widely recommended antibiotic in both human and veterinary medicine is consequently found in the aquatic environment. The current research was aimed to investigate the potential bioaccumulation and sub-lethal toxicity in terms of oxidative stress and histopathology of targeted antibiotic sulfamethoxazole in Cyprinus carpio at environmentally relevant concentrations over a prolonged period. Fish were exposed for 28 days to environmentally realistic concentrations (25–200 μg/L) of sulfamethoxazole. HPLC analysis revealed an inverse relationship between dosages applied and bioaccumulation in fish muscle tissues. The highest concentrations of sulfamethoxazole in the muscle tissues exposed to 25, 50, 100 and 200 μg/L were 124, 202,104.5, and 123.2 ng/g, respectively at different sampling times. Moreover, exposure to sulfamethoxazole enabled ROS (Reactive oxygen species) production in both brain and gill tissues of fish, where the increase in ROS formation was dose and time dependent. Furthermore, histopathological analysis of gills and liver revealed various alterations including pycnotic nuclei, bile stagnation, vacuolization in the liver, and partial and complete fusion of lamella and blood congestion in gills, respectively. Organ pathological index also revealed that the intensity of tissue damage increased as sulfamethoxazole dosage was increased. Quantitative evaluation of gills morphometric parameters divulged that severity of histopathological changes increased with time for all the exposed groups at the end of exposure time (28th day) indicating physio-metabolic turmoil caused by molecular and biochemical action of sulfamethoxazole. In conclusion, the assessment of bioaccumulative potential, measurement of ROS, and histopathology of Cyprinus carpio appeared to be a useful biomarker to evaluate the toxic impacts of antibiotics on the health of fish.

Replacement of fish oil by camelina and black soldier fly larvae oils in diets for juvenile Totoaba macdonaldi and their effect on growth, fatty acid profile, and gene expression of pancreatic lipases

The present study evaluated the use of camelina (CO) and black soldier fly larvae (BSFLO) oils as replacements of fish oil (FO) in diets for juvenile Totoaba macdonaldi, and their effect on growth, proximate composition, fatty acid (FA) profile of tissues, and gene expression of bile salt-dependent (BSDL) and colipase-dependent (CDPL) pancreatic lipases. Four isoproteic (51% crude protein) and isolipidic (14% crude fat) diets were formulated based on a 2 × 2 factorial design with two lipid sources, CO and BSFLO, each tested at two levels of replacement of FO, 30 and 60%. A control diet containing 100% FO was included as a reference. Fish with an overall initial weight (mean ± standard deviation, S.D.) of 3.0 ± 0.1 g were stocked at a density of 100 fish m−3. Each diet was randomly assigned to five replicate tanks, and four tanks for the control. After 7 weeks, weight gain (WG, P = 0.0302) and thermal growth coefficient (TGC, P = 0.0408) were significantly reduced in fish fed the 60% FO replacement level in comparison to the 30% level; fish fed diets containing 30% BSFLO were the only ones achieving statistically similar WG (59.40 g) and TGC (0.175) as fish fed the control diet (WG of 60.68 g and TGC of 0.177). Muscle and liver tissues of fish reflected the FA profiles of experimental diets; fish fed BSFLO showed greater content of lauric acid (12:0) in muscle (0.14–0.17 mg g−1), while alpha-linolenic acid (18:3n-3) was higher in those fed CO (0.25–0.51 mg g−1). Docosahexaenoic acid (22:6n-3) content was statistically similar in fillets from all different treatments, demonstrating selective retention of this biologically important FA, but eicosapentaenoic acid (20:5n-3) decreased as the level of FO replacement by CO or BSFLO in diets increased. The presence of BSDL and CDPL in the digestive tract of T. macdonaldi was confirmed for the first time, but regulation of their gene expression was not significantly affected at a transcriptional level by the progressive replacement of FO by CO or BSFLO under these experimental conditions. These findings suggest that 30% of FO can be successfully replaced by BSFLO in diets for juvenile T. macdonaldi, and a 100 g fillet from fish fed this diet would provide 284 mg of DHA + EPA, satisfying the daily intake recommended for adult consumers.

Trends and Health Risk of Trace Metals in Fishes in Liaodong Bay, China, From 2015 to 2020

Due to their toxicity, non-biodegradability, and biological amplification in the food chain, heavy metal accumulation in humans via the consumption of fishes has become a problem. In this study, we analyzed the concentrations of six trace metals (Cd, Cr, Cu, Ni, Pb, Zn) in 12 marine fish species collected from Liaodong Bay, China, from 2015 to 2020, to understand the pollution status of the bay and evaluate the impact of fish consumption on human health. In addition, 5 fish species with the potential to serve as bioindicators of metal contamination were identified. In general, the average concentrations were Zn > Pb ≈ Cr > Ni ≈ Cu > Cd. There were significant differences in the concentrations in the muscle tissues of fish with different feeding strategies. The total target hazard quotient values of some fish were greater than 1 in 2015, suggesting that people were susceptible to high health risks. The year 2017 had the lowest values, which suggests that metal pollution in Liaodong Bay may have been decreasing at that time. Monitoring of metal concentrations in marine fish from Liaodong Bay warrants more study.

Organochlorine Compounds in Beached Plastics and Marine Organisms

Here we compare bioaccumulation factors in marine organisms to partition ratios in marine debris for dichlorodiphenyltrichloroethane and polychlorinated biphenyls. Both organochlorines are synthetic persistent organic pollutants emitted into the environment since the beginning of the last century in approximately equal amounts. Their vast use and dispersion have resulted in approximately similar median concentrations of the two organochlorines in some pelagic organisms, namely in the liver and muscle tissue of fish. Molluscs, on the other hand, show higher median uptake of PCBs (median = 2.34 ng/g) than of DDTs (median = 1.70 ng/g), probably reflecting more localized conditions. We found that the bioaccumulation factors can be several orders of magnitude higher than the partition ratios. For instance, the median concentrations of organochlorines in the different matrices of fish, birds, and mammals are between one to four orders of magnitude higher than those found in marine debris, when lipid-normalized; or up to two orders of magnitude when measured as wet-weight. But, in molluscs, bioaccumulation/partition equals unity, which agrees with previous studies using passive samplers. Future research should focus on reducing sources of uncertainty by 1) homogenization of chemical procedures; 2) better assessment of chemical partition equilibrium between water and polymers in environmental conditions; 3) use of (multi)polymer passive samplers better aimed at mimicking uptake of specific living tissues.

The Speciation of Arsenic in the Muscle Tissue of Inland and Coastal Freshwater Fish from a Remote Boreal Region

The Speciation of Arsenic in the Muscle Tissue of Inland and Coastal Freshwater Fish from a Remote Boreal Region

Effect of Kera-Stim®50, a feed additive containing free amino acid mix on growth, antioxidant and immune responses, digestive enzymes, and fatty acid composition in Nile tilapia (Oreochromis niloticus)

An eight-week study was conducted to investigate the effects of Kera-Stim®50, a feed additive containing free amino acid mix (KFAAs) on the growth performance, biochemical parameters, innate immune responses, muscle composition, digestive enzyme activity, and muscle fatty acid composition of Nile tilapia (Oreochromis niloticus). Five diets were supplemented with KFAAs at 0% (KFAA0), used as a control group, 0.25% (KFAA0.25), 0.50% (KFAA0.50), 0.75% (KFAA0.75), and 1.0% (KFAA1.0). Compared with the control group, we observed significant improvements in final body weight, weight gain, specific growth rate, average daily gain, protein efficiency ratio, and feed conversion ratio among fish fed diets with increasing KFAA contents in the diets (P < 0.05), especially for the groups that had more than 0.5% KFAAs in the feed. Concurrently, innate immunity parameters such as lysozyme, myeloperoxidase, catalase, superoxide dismutase, glutathione peroxidase, and glutathione reductase were mostly higher in the groups fed with more than 0.75% KFAAs in the diet (P < 0.05). The activities of digestive enzymes including amylase, protease, and lipase were enhanced by the addition of KFAAs in the feed (P < 0.05). Strikingly, significantly higher contents of monounsaturated fatty acids (mainly oleic acid (C18:1n9c)) and polyunsaturated fatty acids (especially linoleic acid (C18:2n6c) and α-linolenic acid (C18:3n3) were found in the muscle tissue of fish fed diets containing 0.75% and 1% KFAAs (P < 0.05). We concluded that the addition of at least 0.5% KFAAs can benefit the growth of Nile tilapia, and supplementation with 0.75–1.0% KFAAs can improve the immunity, antioxidant ability, digestibility, and muscle fatty acid composition of Nile tilapia.

Высокотехнологичные приемы переработки рыбного сырья, выращенного в Астраханской области

The modern level of development of fish processing technology is analyzed. A number of high-tech processes related to deep processing of aquaculture objects (paddlefish, clary catfish and tilapia), grown in the Astrakhan &#x0D; region, in closed water supply installations, have been proposed for implementation. The chemical composition of fish muscle tissue has been studied. A method has been developed to reduce the microbial contamination of raw materials using a low-frequency electromagnetic field. Methods of electrophysical and gas-liquid processing of raw materials have been adapted to real production conditions. Methods for processing secondary fish resources into edible fish meal and fish oil have been tested using gas-liquid technologies. Methods for processing water and muscle tissue of fish raw materials by electromagnetic and gas-liquid methods are proposed. The chemical composition of fish pates enriched with CO2-extracts was investigated.

Исследования санитарно-гигиенического состояния леща и воды в местах его обитания

The article highlights the data on microbiological monitoring of fish raw materials and water of the Volga-Caspian fishing channel in 2020-2021. The most indicative organisms for assessing the quality of the aquatic environment are benthos-eating fish. Bream Abramis brama (Linnaeus, 1758) is one of the valuable objects of fishing in the Astrakhan region. As a commercial object of river coastal fishing, bream has a higher bacterial contamination than fish caught in the sea. In this regard, studying the conditions for bacteriocenosis of fish raw materials, as well as the factors that determine the pathogenicity of its microflora and sanitary and epizootic monitoring by the microbiological tests remain the most relevant research of aquatic organisms. Quantitative and qualitative indicators of the bream microflora were estimated, according to the analysis of 180 species. The indicators of the water microflora were analyzed using the results of studies of 90 samples. The species identification of the isolated microflora was carried out according to the Bergey identification keys. In the samples of bream muscles there was determined the total number of facultative anaerobic microorganisms and aerobic mesophylls, presence of coliform microorganisms, as well as a causative agent of Staphylococcus aureus, pathogenic bacteria Salmonella and Listeria, and parahemolytic vibrios Vibrio. The study results were processed, according to the methods of biological statistics in the Microsoft Excel 2010 software. The results are presented as mean values and standard errors (M ± m). The general microbiological analysis of the fish muscle tissue confirmed the satisfactory sanitary state of bream Abramis brama (L., 1758) caught in the fishing area of the Volga-Caspian Canal during the study period. Pathogenic microflora in the form of E. coli bacteria, bacteria Salmonella, L. monocytogenes and St. aureus were not found

РЕГУЛЯЦИЯ АНТИОКСИДАНТНОЙ СИСТЕМЫ РЫБ БИОЛОГИЧЕСКИ АКТИВНЫМИ КОРМОВЫМИ ДОБАВКАМИ

The article contains results of the research on the influence of "Sporothermin" probiotics and "Chiktonik" vitamin-amino acid complex on the processes of free-radical oxidation of lipids in the muscle tissue of fish. Three groups of sexually mature African catfish were formed. The first test group received "Sporothermin" probiotic at a dose of 2 g / kg of feed. The second group received "Chiktonik" vitamin-amino acid complex at a dose of 2 ml / kg of feed, the third group was the control and received only LimKorm "Som" brand feeds. All groups were tested for malondialdehyde content (MDA) in three months. In the control group, the content of MDA of males was 7948.71 mmol / 100 g of tissue, females - 8119.65 mmol / 100 g of tissue. Fish reared with the probiotics had the lowest levels of lipid peroxidation. Males had the MDA level of 3931.62 mmol / 100 g of tissue, and females - 4273.5 mmol / 100 g of tissue. As for the second group, which received “Chiktonik” vitamin-amino acid complex, the MDA content was lower than in the control, but higher than in the group which received the probiotics and was 4358.97 mmol / 100 g of tissue (males), and 4957.26 mmol / 100 g of tissue (females). It can be concluded that the usage of "Sporothermin" probiotics and "Chiktonik" vitamin-amino acid complex in the diet of African sharptooth catfish leads to a decrease of free radical processes, reduces the activity of lipid peroxidation, stimulates the antioxidant system, provides resistance to oxidative stress, revitalizing and increasing the vitality of the organism fish.

Palamut (Sarda sarda) balığında paraoksonaz (PON) enzim aktivitesi üzerine cıva, bakır ve çinkonun etkisi

Since heavy metal dirtiness, which we frequently encounter in environmental pollution causes harmful effects on the organism through biochemical enzyme reactions, in this study, the effects of mercury (Hg+2), copper (Cu+2), and zinc (Zn+2) heavy metal ions, which are common in environmental pollution, on PON (paraoxonase) enzyme activity in muscle tissue of bonito (Sarda sarda) were investigated. In the study, 25 bonito (S. sarda) fish muscle tissues freshly obtained from the Samsun region sea were used. The changes in PON enzyme activity were determined by adding different volumes of heavy metal solutions. PON enzyme activities of Hg+2 heavy metal ion used in different volumes were calculated as 30.9383 U/mLdak, 29.0598 U/mLdak, 26.3799 U/mLdak, 23.9443 U/mLdak, 20.6725 U/mLdak, PON enzyme activities of Cu+2 heavy metal ion used in different volumes were calculated as 19.7949 U/mLdak, 19.4807 U/mLdak 19.1864 U/mLdak, 19.1200 U/mLdak, 18.9037 U/mLdak and PON enzyme activities of Zn+2 heavy metal ion used in different volumes were calculated as 23.8305 U/mLdak, 23.0781 U/mLdak, 22.9073 U/mLdak, 22.4324 U/mLdak, 21.8159 U/mLdak. As a result of these obtained data, activity (%) values were calculated and activity (%) graphs were drawn. As a result of the study, it was determined that increasing concentrations of Cu+2 and Zn+2 heavy metal ions caused a decrease in PON enzyme activity, but there was no statistically significant difference between the different concentrations used. It was determined that increasing concentrations of Hg+2 heavy metal ion inhibited the PON enzyme activity, caused a statistically significant decrease between the activities depending on the different concentrations used (p &lt; 0.05).

A Food-Safety Risk Assessment of Mercury, Lead and Cadmium in Fish Recreationally Caught from Three Lakes in Poland.

Simple SummaryThe research aimed to determine the content of lead (Pb), cadmium (Cd), and mercury (Hg) in water, sediment, and freshwater fish species roach (Rutilus rutilus), perch (Perca fluviatilis), and pike (Esox lucius) from the Dratów, Syczyńskie, and Czarne Sosnowickie lakes located on Polesie Lubelskie, Poland, as well as a food safety assessment for the consumer. Pb and Cd were measured by graphite furnace atomic absorption spectrometry, while Hg was measured by cold vapor atomic absorption spectrometry. The research results showed that both the waters and the sediments of the studied lakes are characterised by a low concentration of Pb, Cd, and Hg, which indicates the lack of a moderate influence of anthropopressure on these reservoirs. The range of heavy metal contents in the muscles of roach, pike, and perch for Pb was 0.0399–0.1595, 0.0305–0.0920, and 0.0296–0.1057 mg kg−1, respectively; for Cd 0.0014–0.0095, 0.0010–0.0015, and 0.0020 mg kg−1, respectively; and for Hg 0.0123–0.0499, 0.0185–0.0255, and 0.0216–0.0583 mg kg−1, respectively. The content of heavy metals in fish muscles was low and conformed to requirements as defined in the European Union (EU) food legislation. The health risk assessment with regard to the heavy metal contents in the muscles of fish confirmed the safety of this food for consumers.Heavy metals are introduced into water due to anthropogenic activities and can significantly affect an entire ecosystem. Due to their close integration with the water environment, fish are a sensitive indicator of contamination. In addition, fish is an important element in human diets, therefore, monitoring the concentrations of metallic contaminants in their meat is particularly important for food safety. This study aimed to assess the pollution of water ecosystems with selected toxic heavy metals in lakes Dratów, Czarne Sosnowickie, and Syczyńskie. The concentration of Pb, Cd, and Hg in water, sediment, and freshwater fish muscle tissue was determined, and a food safety assessment was performed. The analysis of water and sediments showed that the sediments were characterised by a significantly higher concentration of heavy metals. Presumably, this ecosystem element plays an important role in the uptake of heavy metal contaminants by fish whose levels were higher in planktonophagous and benthophagous fish species as compared to predatory fish. The food safety assessment showed that amounts of heavy metals in the muscle tissue posed no threat to the health of consumers ingesting that fish species, neither individually (THQ) nor collectively (TTHQ).

Assessment of the fatty acid composition of different parts of zebrafish fed diets incorporated with linseed and sunflower oils

This study aimed to evaluate the fatty acid composition of zebrafish fed diets containing linseed oil compared to sunflower oil. First, diets supplemented with linseed and sunflower were formulated, fish were fed for 40 days, and their parts collected for analysis. Diet composition analysis, extraction and derivatization of fatty acids, gas chromatography analysis, RNA extraction and cDNA synthesis, quantitative real-time polymerase chain reaction (qRT-PCR, and statistical analyses were performed. Linseed oil exhibited an omega-3 rich lipid profile. 18:3n-3 content incorporated into the muscle tissue of fish fed linseed oil was 50% higher than that fed sunflower oil. This higher amount of 18:3n-3 favored the production of 20:5n-3 and 22:6n-3 fatty acids by synthetic pathways in the organism since these fatty acids were not initially found in the oil composition. Furthermore, in all analyzed parts of zebrafish that were fed linseed oil, concentration of 20:4n-6 were lower, while 20:5n-3 and 22:6n-3 were higher compared to the same parts fed with sunflower oil. PCR expression assay showed no significant difference, indicating that linseed oil diet was not harmful. Thus, this work evidenced that synthesis of essential fatty acids, primarily omega-3 fatty acids, was greater in zebrafish upon consumption of diets supplemented with linseed oil.

Comparative characteristics of the trace elemental composition of chum salmon Oncorhynchus keta Walbaum, 1792 from the Sea of Japan and the Sea of Okhotsk

Content of trace elements (iron, zinc, copper, nickel, lead, and cadmium) was determined in the most popular species of Pacific salmon on the consumer market – chum salmon Oncorhynchus keta, which is the second largest catch in Russian waters (after pink salmon O. gorbuscha). Metal content in fish organs and tissues (muscle tissue, liver, and gonads) was determined by the atomic absorption method using a Shimadzu AA-6800 spectrophotometer in flame and flameless atomizers from sample extracts; the latter ones were obtained by decomposition of weighed portions of concentrated HNO3 (high purity) in a MARS 6 complex using standard samples with known concentrations. The data was statistically processed in SPSS Statistics 21. Sexually mature individuals of chum salmon (five specimens of males and females on each spot) were sampled in autumn 2018 in storage cages of salmon hatcheries on the Firsovka River (southeastern Sakhalin, Gulf of Patience) and Reidovaya River (Iturup Island, Kuril Islands), as well as in October 2019 in breeder holding cages on the Poima River (southwestern Primorye, the Sea of Japan). Muscle tissue, liver, and gonads were sampled from every individual. The elements determined were clearly divided according to content values into two groups depending on the sampling spot: Cd and Pb prevailed in organs and tissues of chum salmon from the Sakhalin-Kuril Region of the Sea of Okhotsk, whereas Fe, Zn, Cu, and Ni prevailed in the Sea of Japan fish. The reason for heavy metal contrasting distribution in fish organs and tissues is obviously environmental geochemical conditions formed in salmon feeding areas and on migration routes. In the Sea of Japan, practically enclosed, poorly connected with the Pacific Ocean by several shallow straits, the aquatic environment is under significant anthropogenic, technogenic, and terrigenous load (household and industrial drains, surface washing from coastal areas, and combustion of hydrocarbon fuel by ships). In the Sakhalin-Kuril basin, it is affected by natural phenomena: surface and underwater volcanism and post-volcanism of the Kuril Islands, as well as upwellings, which carry from the depths of the Kuril–Kamchatka Trench into the surface layer practically the entire set of chemical elements of the Mendeleev’s periodic table. At the same time, Pb, with its unusually high sorbability, is retained on any suspended particles, both living and non-living, and enters fish organisms with food. The distribution of trace elements over chum salmon organs and tissues differs significantly. Specifically, in fish muscle tissues, the lowest metal content is observed, regardless of the catch spot. The liver is characterized by increased levels of all metals, except for Ni, with the highest Fe, Zn, and Cu content recorded in the Sea of Japan fish liver. The distribution of metals in fish gonads is characterized by its own specificity, with very clear manifestation in the Primorye salmon. Thus, in female gonads, Fe, Zn, and especially Cu predominated: Cu content in female gonads from the Poima River was the same as in liver. Female gonads of the Sea of Japan chum salmon had the highest Ni concentration, although male gonads were characterized by a high, albeit very variable, content of this element as well. As for Pb and Cd, the most toxic elements monitored by sanitary services (for technical reasons, we determined their amount in the Sea of Okhotsk fish only), a well-known pattern was observed in their distribution in organs and tissues: maximum content was found in fish liver. Pb content exceeded the sanitary standard only in some individuals that came to spawn in the Firsovka River in the southeastern Sakhalin. Cd concentration in Sakhalin fish liver was 2.5–4.0 times higher than threshold limit value, and in Kuril fish liver, 2.1–5.0 times higher.

INCREASING THE EFFICIENCY OF POULTRY AND FISH FREEZING USING PROTECTIVE PECTIN COATINGS

Maintaining the quality of poultry and pond fish as much as possible is important. Freezing poultry immediately after slaughter and fish after catching allows you to solve this problem. Freezing in liquid media leads to an increase in the speed of the process and, accordingly, a better preservation of the quality indicators of products. At the same time, in the process of freezing in brines containing calcium chloride, it leads to the diffusion of calcium ions into the muscle tissue of poultry or fish and the appearance of a bitter taste. To prevent salting out of raw materials, we have proposed the use of biologically inert coatings based on pectin.&#x0D; The purpose of this study is to study the possibility of using low methoxylated pectin substances to improve product quality. The influence of a number of technological factors on the protective properties of the coating is studied. These factors include the concentration of pectin substances, the pH of the medium, the presence or absence of pretreatment of the surface of a poultry or fish carcass with citric acid. The strength of the coating and its barrier properties with respect to the diffusion of calcium ions have been studied. It is recommended to use a concentration of pectin substances of 3% with preliminary treatment of the carcass surface with 1% citric acid solution, followed by fixing the formed pectin film with 1% calcium chloride solution. Such processing allows to achieve a maximum concentration of calcium chloride in the muscle tissue of poultry or fish of no more than 0.5% – the value allowed by the standard.&#x0D; It is shown that the use of freezing in brine leads to a significant decrease in the weight loss of the product during storage compared to freezing in air – three times. The use of a coating based on pectin can reduce weight loss by a factor of eight. The quality indicators of products are also much better preserved – water retention capacity, acid number of fat and peroxide value of fat. The organoleptic properties of poultry and fish processed according to the proposed technology are noticeably superior to those of raw materials frozen both in air and in brine without applying a protective coating.