Salmon Muscle Tissue Research Articles

First report of the presence of Pseudoterranova sp. in the body cavity of salmon (Salmo salar) from the Baltic Sea

Abstract Despite salmon (Salmo salar L.) being an important fish in the Baltic Sea ecosystem and its fisheries, knowledge about the parasite fauna of this top predator is scarce. The Anisakidae nematodes (Anisakis spp., Pseudoterranova spp., Contracaecum sp.) found in Baltic Sea fish species are zoonotic parasites that are hazardous to human health. Due to the marked increase in the numbers of grey seal (Halichoerus grypus), the definitive host of Contracaecum sp. and Pseudoterranova spp., increased dispersion of these parasites has been observed in recent years. The aim of our study was to investigate salmon caught in Polish marine waters for the presence of Anisakidae nematodes. Parasitological inspection of the body cavities of 89 individual salmon was conducted in 2012 and revealed the presence of a Pseudoterranova sp. L3 larva. The presence of the parasite is reported here for the first time in the muscle tissue of salmon from the Baltic Sea. The presence of Anisakidae nematodes in commercially important fish species may have implications for human health since these parasites pose a risk of anisakidosis.

Evaluation of Lipid Oxidation Characteristics in Salmon after Simulation of Cold Chain Interruption Using Rapid Evaporation Ionization Mass Spectrometry.

Temperature fluctuations occurring during the cold chain logistics of salmon contribute to lipid oxidation. This study aimed to simulate cold chain interruption through freeze-thaw operations and evaluate the lipidomics data from salmon samples subjected to different numbers of freeze-thaw cycles by using rapid evaporative ionization mass spectrometry (REIMS) combined with an intelligent surgical knife (iKnife). The results indicated significant differences in the relative abundance of characteristic ions among the samples (p < 0.05). A total of 34 ions with variable importance for the projection values ≥1 were identified as potential biomarkers, including m/z 719.4233 ([PCC36:5-NH(CH3)3]-), m/z 337.3134 ([FAC22:1]-), m/z 720.4666 ([PEC35:6-H]-), m/z 309.2780 ([FAC20:1]-), m/z 777.4985 ([PCC40:4-NH(CH3)3]-), m/z 745.4421 ([PCC38:6-NH(CH3)3]-/[PEC38:6-NH3]-), m/z 747.4665 ([PCC38:5-NH(CH3)3]-/[PEC38:5-NH3]-), etc. The degree of lipid oxidation was found to be associated with the number of freeze-thaw cycles, exhibiting the most significant alterations in the relative abundance of lipid ions in the 8T samples. Additionally, sensory evaluation by the CIE-L*a*b* method and volatile analysis by headspace solid-phase microextraction gas chromatography-mass spectrometry demonstrated significant differences (p < 0.05) in color and odor among the salmon samples, with a correlation to the number of freeze-thaw cycles. The primary compounds responsible for alterations in salmon odor were aldehydes with lower odor thresholds. In summary, the iKnife-REIMS method accurately differentiated salmon muscle tissues based on varying levels of lipid oxidation, thus expanding the application of REIMS.

Shotgun-Based Mass Spectrometry Analysis of Phospholipid and Triacylglycerol Molecular Species and Eicosanoids in Salmon Muscle Tissue on Feeding Microbial Oil.

The continuous growth of aquaculture places a growing demand on alternative sources of fish oil (FO). Certain microorganisms provide a sustainable replacement for FO due to their content of EPA and DHA, which are essential for fish health. Appreciable evidence shows that changes in feeding sources may alter the nutritional components of salmon; however, the influence of diets on lipid species remains unclear. In this study, the identification and semi-quantification of lipid molecular species in salmon muscle during feeding with a microbial oil (MO) were carried out by focusing on triacylglycerol (TAG) and diacyl-phospholipid using shotgun-based mass spectrometry analysis. DHA in the MO diet was efficiently incorporated into phospholipid structures on feeding, followed by accumulation in salmon muscle. The MO diet elevated the level of certain EPA-containing TAGs, such as TAG C52:5 (16:0_16:0_20:5) and TAG C54:6 (16:0_18:1_20:5), indicating that the MO diet may be an excellent source for enhancement of the abundance of ω3 lipids. Further, prostaglandins (PGs) PGE2 and PGF3α were identified and quantified for the first time in salmonid tissue.

Effects of Replacing Fishmeal with Algal Biomass (Pavlova sp. 459) on Membrane Lipid Composition of Atlantic Salmon (Salmo salar) Parr Muscle and Liver Tissues

A 12-week feeding trial examined the dietary impact of replacing fishmeal (FM) with algal biomass (AB) derived from Pavlova sp. strain CCMP459 (Pav459) in Atlantic salmon diets. Three distinct diets were formulated: a control diet featuring 20% FM and 7% fish oil (FO), an experimental diet incorporating a 50:50 blend of FM and AB Pav459 and reduced FO (10% FM; 4.5% FO; 10% AB), and a second experimental diet with full replacement of FM with AB Pav459 and further reduction in FO (1.75% FO; 20% AB). Replacing FM with AB Pav459 showed no significant effects on the growth performance of Atlantic salmon. Fish across all diets exhibited growth exceeding 200% from their initial weight. Analysis of total lipid content after the 12-week trial revealed no significant differences among the diets. However, individual proportions of omega-3 (ω3) and omega-6 (ω6) fatty acids varied. Fatty acid profiling in muscle and liver tissues showed distinct compositions reflective of dietary treatments. Linoleic acid (LA) and α-linolenic acid (ALA) exhibited higher proportions in total fatty acids than in membrane lipids. Docosahexaenoic acid (DHA) emerged as the predominant fatty acid in the membranes of both liver and muscle tissues. Furthermore, an analysis of sterol composition in Pavlova and salmon muscle tissue showed the presence of important sterols, including conventionally animal-associated cholesterol. This emphasizes the suitability of microorganisms, such as Pav459, for synthesizing diverse nutrients. Stable isotope analysis demonstrated direct incorporation of eicosapentaenoic acid (EPA) and DHA from diets into salmon tissues. Notably, minimal biosynthesis from the precursor ALA was observed, reaffirming the utility of Pav459-derived fatty acids. The EPA+DHA proportions in the fillet consistently met daily human consumption requirements across all dietary conditions, supporting the use of Pav459 algal biomass as an alternative to FM.

Eumelanin Detection in Melanized Focal Changes but Not in Red Focal Changes on Atlantic Salmon (Salmo salar) Fillets

Superficial discolored spots on Atlantic salmon (Salmo salar) fillets are a serious quality problem for commercial seafood farming. Previous reports have proposed that the black spots (called melanized focal changes (MFCs)) may be melanin, but no convincing evidence has been reported. In this study, we performed chemical characterization of MFCs and of red pigment (called red focal changes (RFCs)) from salmon fillets using alkaline hydrogen peroxide oxidation and hydroiodic acid hydrolysis. This revealed that the MFCs contain 3,4-dihydroxyphenylalanine (DOPA)-derived eumelanin, whereas the RFCs contain only trace amounts of eumelanin. Therefore, it is probable that the black color of the MFCs can be explained by the presence of eumelanin from accumulated melanomacrophages. For the red pigment, we could not find a significant signature of either eumelanin or pheomelanin; the red color is probably predominantly hemorrhagic in nature. However, we found that the level of pigmentation in RFCs increased together with some melanogenic metabolites. Comparison with a “mimicking experiment”, in which a mixture of a salmon homogenate + DOPA was oxidized with tyrosinase, suggested that the RFCs include conjugations of DOPAquinone and/or DOPAchrome with salmon muscle tissue proteins. In short, the results suggest that melanogenic metabolites in MFCs and RFCs derive from different chemical pathways, which would agree with the two different colorations deriving from distinct cellular origins, namely melanomacrophages and red blood cells, respectively.

Assessment of the palatability of Atlantic salmon by NMR spectroscopy

H-NMR spectroscopy was used to study the metabolic profile of Atlantic salmon muscle tissue during heat treatment and storage to assess the taste of products. It has been established that when steaming fish, the amount of compounds such as trimethylamine (TMA), taurine (Tau), glutamic acid (Glu), lysine (Lys), proline (Pro), serine (Ser), γ-aminobutyric acid (GABA), creatinine (Cret) increased in broth compared to raw fish, and Tau and Cret accumulated in cooked fish. The content of TMA, which gives a fishy smell to the product, increased dramatically in cooked fish, regardless of the cooking duration, and at the same time an increase in dimethylamine (DMA) was observed in cooked fish. The processing of the data array of the content of metabolites by the method of principal components was carried out and a clear separation of fish and broth samples was revealed, as well as the difference between fish stored for a long time and the original sample. The taste qualities of fish raw materials before and after heat treatment were evaluated using the taste active value (TAV) of the main compounds characterizing sweet, bitter, sour tastes, as well as umami taste. The values of the taste threshold of compounds, which are widely used for a comprehensive assessment of various food products, were taken for calculations. The TAV for the broth when steaming Atlantic salmon for 30 min was 6.27 ± 0.06, and with an increase in time to 60 min, it decreased to 5.61 ± 0.09. During long-term storage of fish, there was a sharp decrease in the umami taste index and an increase in bitter taste, which is due to hydrolytic processes occurring during product spoilage. It is concluded that the NMR spectroscopy method makes it possible to quantify the change in the main metabolites in Atlantic salmon samples during heat treatment and storage, and TAV calculated from the content of free amino acids, nucleotides and organic acids provides an objective description of the taste of the product.

Electrical conductivity of salmon muscles – analysis of the influence of muscle position and electrical current direction during ohmic heating

Abstract In this study, the heating penetration in salmon muscle tissue was evaluated during ohmic heating (OH) at 20 kHz. The electrical conductivities (ECs) in five muscle-tissue sections (fat content from 7.85 to 21.15 %) of salmon were measured under different conditions of applied frequency (50 Hz–20 kHz), temperature (5–70 °C), and direction of the electric current (parallel or series) in relation to the muscle arrangement. Significant differences in the ECs of the five sections were found, especially at high frequencies. A lower fat content and the parallel current direction resulted in higher ECs than a higher fat content and the series current direction. Empirical equations were derived to determine the EC values of all five sections of the salmon fillet based on their temperature dependence. The cooking losses after OH processes were low in the order of parallel &lt; series &lt; minced. These results are of potential value for the design of the OH process for salmon-based products.

Visualization, modeling and analysis of salmon muscle structure: Based on micro-CT

Seafood analogs using culture cells or plant-based materials are rising for future food supply, but their bionic design is still an issue on finely simulating the multiscale structure and function of fishes. For salmon, we compared the back, belly and tail tissues via micro computed tomography (micro-CT) scanning with optimized tissue contrast and spatial resolution. The optimum staining conditions of salmon muscle tissue for micro-CT was 3.75 % IKI (iodine-potassium iodide) solution for 7 days, and the muscle could be separated well from fat and connective tissue. The results of visualization analysis were correlated with the texture profile analysis. A relatively high magnification (3 µm/pixel) was used with fiber tracing procedure to analyze the connection of muscle fiber bundles surrounded by soft tissue. Single muscle fiber (e.g., diameter 117 µm) was successfully and artificially separated from whole visualized tissue through manual division. Overall, this study showed a novel ultra-high-resolution method based on micro-CT to conduct digital analysis of muscle fascicle architecture, and constructed printable model of bionic animal/plant tissue for food design.

Effects of Replacement of Fish Oil with Microbial Oil (Schizochytrium sp. T18) on Membrane Lipid Composition of Atlantic Salmon Parr Muscle and Liver Tissues

A 16-week feeding trial was conducted to investigate effects of replacing dietary fish oil (FO) with docosahexaenoic acid (DHA)-rich microbial oil (MO) from Schizochytrium sp. (T18) on membrane lipid composition of Atlantic salmon parr liver and muscle tissues. Four nutritionally balanced diets were formulated with varying levels of FO, MO, and canola oil (CO), including a control diet with 20% FO, a secondary control diet with 10% FO and 10% CO, and two experimental diets that completely replaced FO with a low (5%) and high (10%) proportion of MO. No significant differences were observed in growth parameters (81–98 g; weight gain), total lipid class composition, and total sterol content among the dietary treatments. However, there were significant differences in the proportions of individual ꞷ3 and ꞷ6 fatty acids in both liver and muscle tissues, reflecting the different dietary treatments. Notably, the presence of low eicosapentaenoic acid (EPA) in the MO diets did not affect the growth performance of the fish, suggesting a lower requirement for EPA in the diet and a greater necessity for DHA. The results also showed that DHA was present in very high proportions in the cellular membrane, particularly in muscle tissue, with low levels of linoleic acid and alpha-linolenic acid. Overall, the findings suggest that MO derived from Schizochytrium sp. (T18) could be a potential substitute for FO in the diet of farmed Atlantic salmon.

Refreshing DNA-Based Nanoprobes by Alcohol for Heavy Metal Detection: Toward Sustainable Sensing Nanomaterials

Increasing the applications of disposable nanomaterials yet with potential environmental risk and the resulting nanowastes have become a problem of public concern worldwide. However, efficient recovery of useful materials from nanowastes is currently limited by their tiny size, high physicochemical activity, and unpredictable aggregation. We have developed a conceptually new strategy for recycling nanoprobes by alcoholic solvent “refreshing”. In specific, DNA-functionalized gold nanoparticles and nanorods are employed as colorimetric nanoprobes for Hg(II) and Ag(I) ions, respectively, both of which rely upon target-induced DNA terminal base pairing and the subsequent base pair stacking assembly of the nanoprobes. Upon the introduction of isopropanol to the “waste” aggregates, however, the DNAs are denaturalized to release heavy metal ions, leading to restoration of individual nanoprobes. The fine modulation of DNA hybridization not only affords sensitive detection but also addresses the recycling of the nanoprobes with high efficiency (>80%) while preserving the detection performance irrespective of the nanoprobe shape and surface-grafted DNA sequence. We further demonstrate the use of the recycled nanoprobes in the detection of Hg(II) species from salmon muscle tissue. With the generality of the recovering method and the combined features of the renewable nanoprobes, including high recycling efficiency and retained functionality, sustainable sensing nanomaterials are within reach.

Biomarkers of Oxidative Stress in the Muscle Tissue of Atlantic Salmon (Salmo salar L.) Treated in vitro by Extracts of Chelidonium majus L.

Consistent with our previous studies, we continue to evaluate the antioxidant potential of representatives belonging to the Papaveraceae family collected from the northern part of Poland using a muscle tissue model of Atlantic salmon (Salmo salar L.). Therefore, in the present study, oxidative stress biomarkers (2-thiobarbituric acid reactive substances (TBARS), aldehydic and ketonic derivatives of oxidatively modified proteins (OMP), total antioxidant capacity (TAC)) and also activity of antioxidant enzymes (catalase, superoxide dismutase, glutathione peroxidase) were used for evaluating the in vitro antioxidant activity of root and stalk extracts derived from great celandine Chelidonium majus L. (CM) collected in urban and rural agglomerations of Kartuzy district (Pomeranian province, northern part of Poland). Freshly collected roots and stalks were washed, weighed, crushed, and homogenized in 0.1 M phosphate buffer (pH 7.4) (in the proportion of 1:19, w/w) at room temperature. Incubation of salmon muscle tissue with extracts derived from both the stalks and roots of CM harvested from rural areas resulted in a decrease in lipid peroxidation. The incubation of salmon muscle tissue with extracts derived from both the stems and roots of CM harvested from rural areas resulted in a decrease in lipid peroxidation. Similarly, the use of extracts derived from the roots of CM collected from urban areas resulted in a decrease in TBARS levels. These results suggest that it can be argued that the presence of secondary plant metabolites in CM extracts protects structures of cell membranes against the damaging effects of free radicals. On the other hand, analysis of levels of protein oxidation after incubation of muscle tissue with CM extracts showed that extracts derived from both roots and stalks of CM harvested from urban areas reduced levels of ketonic derivatives of oxidatively modified proteins. Analyzing the total antioxidant capacity after the incubation with CM extracts under in vitro conditions, we concluded that extracts mainly derived from the stalks of CM harvested from both urban and rural areas effectively increase TAC levels. These results are reflected after analysis of antioxidant enzyme activity, where we observed statistically significant increases in superoxide dismutase and catalase activity. On the other hand, the incubation of CM extracts with muscle tissue resulted in a statistically significant decrease in glutathione peroxidase activity compared to the control samples.

Biogeochemical processes create distinct isotopic fingerprints to track floodplain rearing of juvenile salmon.

Floodplains represent critical nursery habitats for a variety of fish species due to their highly productive food webs, yet few tools exist to quantify the extent to which these habitats contribute to ecosystem-level production. Here we conducted a large-scale field experiment to characterize differences in food web composition and stable isotopes (δ¹³C, δ¹⁵N, δ³⁴S) for salmon rearing on a large floodplain and adjacent river in the Central Valley, California, USA. The study covered variable hydrologic conditions including flooding (1999, 2017), average (2016), and drought (2012-2015). In addition, we determined incorporation rates and tissue fractionation between prey and muscle from fish held in enclosed locations (experimental fields, cages) at weekly intervals. Finally, we measured δ³⁴S in otoliths to test if these archival biominerals could be used to reconstruct floodplain use. Floodplain-reared salmon had a different diet composition and lower δ13C and δ³⁴S (δ¹³C = -33.02±2.66‰, δ³⁴S = -3.47±2.28‰; mean±1SD) compared to fish in the adjacent river (δ¹³C = -28.37±1.84‰, δ³⁴S = +2.23±2.25‰). These isotopic differences between habitats persisted across years of extreme droughts and floods. Despite the different diet composition, δ¹⁵N values from prey items on the floodplain (δ¹⁵N = 7.19±1.22‰) and river (δ¹⁵N = 7.25±1.46‰) were similar, suggesting similar trophic levels. The food web differences in δ13C and δ³⁴S between habitats were also reflected in salmon muscle tissue, reaching equilibrium between 24-30 days (2014, δ¹³C = -30.74±0.73‰, δ³⁴S = -4.6±0.68‰; 2016, δ¹³C = -34.74 ±0.49‰, δ³⁴S = -5.18±0.46‰). δ³⁴S measured in sequential growth bands in otoliths recorded a weekly time-series of shifting diet inputs, with the outermost layers recording time spent on the floodplain (δ³⁴S = -5.60±0.16‰) and river (δ³⁴S = 3.73±0.98‰). Our results suggest that δ¹³C and δ³⁴S can be used to differentiate floodplain and river rearing habitats used by native fishes, such as Chinook Salmon, across different hydrologic conditions and tissues. Together these stable isotope analyses provide a toolset to quantify the role of floodplains as fish habitats.

Analysis of Se and Hg biomolecules distribution and Se speciation in poorly studied protein fractions of muscle tissues of highly consumed fishes by SEC-UV-ICP-MS and HPLC-ESI-MS/MS

Distribution of Se and Hg in sarcoplasmic, myofibrillar and alkali-soluble protein fractions extracted from muscle tissue of tuna, swordfish and salmon (wild vs. farmed) is investigated for the first time. SEC-UV-ICP-MS analyses revealed that Se and Hg are mostly bound to proteins of 2–12 kDa and up to 574 kDa, respectively. Moreover, Se and Hg appeared associated to proteins of same molecular weight, evidencing that Se–Hg interaction may occur at the level of the fish tissue evaluated. Important differences were found between farmed and wild salmon, suggesting the effect of the type of feed and growing conditions on Se and Hg content and their distribution through protein fractions. Finally, Se speciation studies performed by HPLC-ICP-MS and confirmed by HPLC-ESI-MS/MS showed SeMeSeCys as the only Se specie found in soluble, sarcoplasmic, myofibrillar and alkali-soluble proteins of all fishes analysed, except in soluble proteins extracted from tuna, where SeMet was also identified.

Experimentally derived trophic enrichment and discrimination factors for Chinook salmon, Oncorhynchus tshawytscha.

Stable isotope analysis (SIA) can provide important insights into food web structure and is a widely used tool in ecological conservation and management. It has recently been augmented by compound-specific stable isotope analysis of amino acids (CSIA-AA), an innovation that can provide greater precision when analyzing trophic level and food web connectivity. The utility of SIA rests on confidence in its constituent parameters such as the trophic enrichment factor (TEF). There is increasing emphasis on the need to experimentally derive species and tissue specific TEFs for studies utilizing SIA. Chinook salmon, Oncorhynchus tshawytscha, is a species with high potential for study using SIA due to the difficulty in observing its ecology during its marine phase and the significance of the conservation consequences of recent population declines. Bulk and amino acid-specific TEFs were determined for juvenile and adult Chinook salmon fed specific diets. Three controlled feeding studies were performed: adult salmon were fed a biofeed, juvenile salmon were fed a biofeed, and juvenile salmon were fed krill. Bulk and compound-specific stable isotope data were collected from diet samples and from salmon muscle tissue after a minimum of 8weeks of controlled feeding. Bulk isotope signatures were measured using EA-IRMS and CSIA-AA signatures using GC/C-IRMS, allowing the TEFs to be calculated. The bulk isotope TEFs were higher than those predicted for similar marine organisms and averaged 3.5‰ for ∆15 N and 1.3‰ for ∆13 C. The TEFs derived for nitrogen isotopes of amino acids were in line with expectations for this approach: the mean value for ∆15 NGlu - ∆15 NPhe was 7.06‰ and, using a multi-AA approach, the value for ∆15 NTrophic - ∆15 NSource was 6.67‰. For carbon isotopes of amino acids, the derived TEFs of Iso, Leu and Phe were near 0‰, as was that of Met, supporting their use of as source amino acids in future CSIA studies. This study presents Chinook salmon-specific TEFs for bulk and amino acid SIA. It supports the application of future research applying SIA to the study of Chinook salmon and validates previous research on species-specific TEFs.

Shotgun Lipidomics for the Determination of Phospholipid and Eicosanoid Profiles in Atlantic Salmon (Salmo salar L.) Muscle Tissue Using Electrospray Ionization (ESI)-MS/MS Spectrometric Analysis.

Shotgun lipidomics was applied to identify and quantify phospholipids (PLs) in salmon muscle tissue by focusing on the distribution of ω-3 fatty acids (e.g., docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA)) in the form of phospholipids, as well as to identify and quantify eicosanoids, which has not yet been attempted in Atlantic salmon muscle. Shotgun lipidomics enabled the identification of 43 PL species belonging to four different classes: phosphatidylcholines (PCs), phosphatidylethanolamines (PEs), phosphatidylserines (PSs), and phosphatidylinositols (PIs). Among others, 16:0-22:6 PtdCho m/z [M + Na]+ at 828.4 was the predominant PL species in salmon muscle tissue. The present study provided the quantification of individual phospholipid species, which has not been performed for salmon muscle tissue so far. In addition, two eicosanoids—prostaglandin E2 (PGE2) and prostaglandin F3α (PGF3α)—were identified for the first time in salmon muscle. Thus, the rapid and high-throughput shotgun lipidomics approach should shed new light on phospholipids and eicosanoids in salmon muscle tissue.

Anisotropic diffusion assessment in salmon (salmo salar) composite muscle tissue: Theoretical and image-processing experimental approaches

A simple method to study the diffusion of a probe molecule into muscle tissue, which considers real composite architecture and anisotropy, was proposed. An anisotropic diffusion study of methylene blue (MB) as a probe molecule into the composite muscle tissue of salmon (Salmo salar) was performed using an image-processing technique. The concentration profile was determined in the middle sagittal plane by considering the muscle fiber orientation angle (θ). The mean value of the angle was θ=31±1.2°, and the fractional anisotropy values showed an anisotropic behavior for all samples tested. The presence of the discontinuity between muscle and connective tissue was characterized by the distribution coefficient. The simulation using the generalized minimum residual method iterative solver in COMSOL Multiphysics™ software described the anisotropic condition of the tissue with root mean square values of less than 27%. Significant differences were found in effective diffusion coefficient values between the muscle and connective tissue at 2°C (p-value<0.05). Further studies may consider other diffusing molecules and muscle tissues.

Evaluation of triacylglycerol (TAG) profiles and their contents in salmon muscle tissue using ESI-MS/MS spectrometry with multiple neutral loss scans

Identification and quantification of triacylglycerols (TAGs) in salmon muscle tissue were conducted using electrospray ionization (ESI)-MS/MS in a triple quadrupole mass spectrometer. The confirmation of three fatty acid moieties of individual TAGs was determined using the multiple neutral loss (NL) scanning mode. A total of 98 TAGs were identified, and the predominant TAG species were 16:0–18:0–20:5 (10.4%), 18:1–18:2–22:6 (9.0%), and 18:0–18:1–22:6 (16.4%) in salmon muscle tissue. NL scanning was an effective means to confirm the three fatty acid moieties of the TAGs, leading to the rapid and accurate identification of individual TAGs. To the best of our knowledge, this is the first application of multiple neutral loss scanning to identify TAGs in salmonoid tissue, and many TAG species have been newly identified (i.e., 18:1–18:2–22:6, 16:0–18:2–20:5, 18:1–18:2–20:5, etc.). This study showed that the shotgun lipidomic approach along with NL scans is a useful means for studying TAG metabolism in fish.

CHEMICAL COMPOSITION AND ENERGY CONTENT OF PACIFIC SALMONS IN THE OKHOTSK SEA

The main bioenergetic parameters of pacific salmons are presented on the data obtained in marine expeditions in 2003–2015. Among the examined species, the minimum energy content is registered in the muscle tissue of chum salmon and pink salmon, and the maximum energy content — in the muscles of king salmon. Total amount of the energy accumulated by juvenile pink salmon during its life within the Okhotsk Sea is estimated as 532 kcal or 27 % of the total energy accumulated in the whole marine period of its life, for juvenile chum salmon this amount is 492 kcal (11 %). The rest is accumulated by adults during their feeding in the ocean: pink salmon, without ranking by age and sex, gains in the North Pacific on average 1 442 kcal or 73 % of the total energy accumulated in the marine period of life, chum salmon — 4 071 kcal (89 %).

Facilitating local analysis in northern regions: microwave plasma-atomic emission spectrometry for mercury determination in wild Atlantic salmon

ABSTRACTAn analytical procedure was developed to quantify mercury concentration in wild Atlantic salmon (Salmo salar) muscle tissue by cold-vapour microwave plasma-atomic emission spectrometry (CV-MP-AES) with microwave-assisted acid digestion. Muscle samples were collected from the Atlantic salmon Food, Social, and Ceremonial fisheries in Lake Melville, Labrador (Canada). Muscle samples were digested with nitric acid and hydrogen peroxide, mercury was stabilised with thiourea, reduced with NaBH4, and quantified by CV-MP-AES. Analysis of fish protein certified reference material (CRM, DORM-3) by CV-MP-AES was used to assess the accuracy and precision of the procedure. CRM recovery averaged 88% with a relative standard deviation of less than 8%. The limits of detection were as low as 0.22 µg∙L−1 in solution which translate to 0.02 µg·g−1. Mercury concentrations in salmon muscle tissue quantified by CV-MP-AES were not significantly different from results obtained by cold vapour-atomic fluorescence spectrometry (CV-AFS) from an accredited laboratory. Our results indicated that the CV-MP-AES procedure is appropriate for the quantification of mercury at background levels (range 0.15–0.29 µg∙g−1 dry weight) in wild fish of Labrador.

Selenium and selenium species in feeds and muscle tissue of Atlantic salmon

Selenium (Se) is an essential element for animals, including fish. Due to changes in feed composition for Atlantic salmon (Salmo salar), it may be necessary to supplement feeds with Se. In the present work, the transfer of Se and Se species from feed to muscle of Atlantic salmon fed Se supplemented diets was studied. Salmon were fed basal fish feed (0.35 mg Se/kg and 0.89 mg Se/kg feed), or feed supplemented either with selenised yeast or sodium selenite, at low (1–2 mg Se/kg feed) and high (15 mg Se/kg feed) levels, for 12 weeks. For the extraction of Se species from fish muscle, enzymatic cleavage with protease type XIV was applied. The extraction methods for Se species from fish feed were optimised, and two separate extraction procedures were applied, 1) enzymatic cleavage for organic Se supplemented feeds and 2) weak alkaline solvent for inorganic Se supplemented feeds, respectively. For selenium speciation analysis in feed and muscle tissue anion-exchange HPLC-ICP-MS for analysis of inorganic Se species and cation-exchange HPLC-ICP-MS for analysis of organic Se species, were applied. In addition, reversed phase HPLC-ICP-MS was applied for analysis of selenocysteine (SeCys) in selected muscle samples. The results demonstrated that supplemented Se (organic and inorganic) accumulated in muscle of Atlantic salmon, and a higher retention of Se was seen in the muscle of salmon fed organic Se diets. Selenomethionine (SeMet) was the major Se species in salmon fed basal diets and diets supplemented with organic Se, accounting for 91–118% of the total Se. In contrast, for muscle of salmon fed high inorganic Se diet, SeMet accounted for 30% of the total Se peaks detected. Several unidentified Se peaks were detected, in the fish fed high inorganic diet, and analysis showed indicated SeCys is a minor Se species present in this fish muscle tissue.