Brachymystax Lenok Research Articles

Acute warming in winter eliminates chemical alarm responses in threatened Qinling lenok Brachymystax lenok tsinlingensis

Knowledge of how temperature influences animal behavior is critical to understanding and predicting impacts of changing climate on individual species and biotic interactions. However, the effects of climate change, especially winter warming in freshwater systems, on fish behaviors and the use of chemical information have been largely unexplored. Qinling lenok Brachymystax lenok tsinlingensis, an endangered salmonid species endemic to the Qinling Mountain Range, China, is currently experiencing population decline and is a potential biological indicator of warming winter climate effects on freshwater fishes due to its temperature sensitivity and required habitat of small, cold-water streams. Our objective was to determine if transient winter warming (increases of ~4 °C) consistent with seasonal maxima in line with near-future climate projections will affect antipredator responses to damage-released chemical alarm cues in B. lenok tsinlingensis. Wild fish were collected during winter and held in captivity under food deprivation for four days, during which half were acclimated to a warmer temperature (6 °C) while the other half were maintained at ambient levels (2 °C). Individual acclimated fish were then exposed to injections of either conspecific alarm cues to simulate elevated predation risk or stream water as a control treatment. Focal fish demonstrated responses consistent with antipredator behaviors to alarm cues at ambient temperature, but no significant behavioral responses to alarm cues were found relative to controls at the warmer temperature. These results support our hypothesis that winter warming will negatively influence antipredator responses and indicate that projected warmer temperature patterns in winter may have significant impacts on chemically mediated predator-prey interactions in cold-water streams.

Effects of dietary LNA/LA ratios on growth performance, tissue fatty acid composition and immune indices in Manchurian trout,Brachymystax lenok

This study aimed to assess the effects of different linolenic acid (LNA, 18:3n-3) and linoleic acid (LA, 18:2n-6) ratios in diet on growth performance, fatty acid composition in muscle and liver and non-specific immunity in serum, liver and intestines of juvenile Manchurian trout (Brachymystax lenok). With casein, soybean meal and corn protein meal as main protein sources, a vegetable oil-based (VO-based) diet with iso-nitrogen (40%) and iso-lipid (18.5%) was prepared by adding different proportions of linseed oil, corn oil and palm oil. The LNA/LA ratio in the VO-based diets was 0.02, 0.55, 1.06, 1.61 and 2.17 (constant composition of LNA and LA). The control group (CON) used fish oil (FO) as the sole lipid source. Healthy juvenile Manchurian trout (body weight: 7.00 ± 0.07 g) were fed in a recirculating aquaculture system for 9 weeks. The results showed that VO-based diets did not affect the growth of Manchurian trout, but decreased DHA and EPA levels in the dorsal muscle of Manchurian trout. Levels of LA, arachidonic acid (ARA) and n-6 polyunsaturated fatty acids (PUFA) of liver in VO-based diets were significantly higher than those in CON diet and decreased with an increasing LNA/LA ratio in the diet. The composition of LNA, DHA, EPA and n-3 PUFA of dorsal muscle and liver in VO-based diets increased with increasing LNA/LA ratio. In the liver and proximal intestine (PI), lysozyme (LZM) activity increased with the increasing LNA/LA ratio in the VO-based diet. However, it decreased in the mid-intestine (MI) and distal intestine (DI). Acid phosphatase (ACP) activity in liver was significantly high when the LNA/LA ratio in the diet was 1.06 (p < .05). Alkaline phosphatase (AKP) activity in the MI increased with the increasing dietary LNA/LA ratio. The LNA/LA ratio in the diet did not affect the growth of Manchurian trout juveniles, and a diet with an LNA/LA ratio between 0.55 and 1.06 was beneficial for non-specific immunity in Manchurian trout.

Analysis of the rates of development and growth of Brachymystax lenok Savinovi during artificial reproduction by the industrial method

The article presents the results of the first research on artificial reproduction in industrial conditions of the endemic, narrow-areal subspecies of Brachymystax lenok Savinovi, which lives in lake Markakol, East Kazakhstan region. The indicators of the heat sum characteristic for each stage of development, the rate of development and growth of the Markakolsky lenok from the moment of pre-breeding to late juveniles are described. To develop technological approaches for artificial fish reproduction, one of the most important points is to determine the optimal conditions for each stage and assess the risks (loss of fish products). At the stage of insemination and transportation of eggs to the place of incubation, the loss was 50 %. The largest losses of fish products were registered during the incubation stage. The most painlessly passed the period of holding and lifting on the float, where the loss was only 3 %. When growing pre-larvae and larvae in the pool, the daily waste did not exceed 1 %. Small-sized animals that were unable to adapt to artificial feeds fell into the waste. Losses during this period amounted to 15 % of the previous stage. In General, the yield of juveniles from the moment of fertilization to the end of the experiment was 16 %. The crucial factor in the development and growth of Lenok Markakolosky is the temperature regime. For the period of embryonic development, the most favorable water temperature is 7–8 °C. From the moment of hatching, the water temperature must be increased to 10–12 °C, and the optimal temperature for the cage growing of fingerlings varies from 12 to 14 °C.

De novo assembly and microsatellite marker development of the transcriptome of the endangered Brachymystax lenok tsinlingensis

Brachymystax lenok tsinlingensis is an endemic freshwater fish in Northeast Asia, but experienced a dramatic population decline due to over-exploitation, deteriorated habitats and global climate change. It has been listed as a threatened or endangered species in South Korea and China, respectively. However, the conservation and restoration work in wild B. lenok tsinlingensis populations require large amount of genetic and molecular data to support effective management of genetic resources, while the corresponding information is very limited. This study was conducted to generate transcriptome assembly and annotation, as well as to develop novel microsatellite markers for B. lenok tsinlingensis. We collected gill and liver tissues and performed transcriptome sequencing. Then the first transcriptome for B. lenok tsinlingensis was de novo assembled and annotated. Microsatellite markers were searched in the assembled transcripts and characterized within ninety individuals collected from three natural sites. A total of 110,712 protein-coding transcripts were assembled, of which 82,861 transcripts were successfully annotated. This assembly displayed a high level of completeness with retrieving 94% of the single-copy orthologs conserved across vertebrate species. Furthermore, 75,891 microsatellite loci were identified from this transcriptome assembly and 20 polymorphic markers were randomly selected for characterization. The microsatellite markers and the first transcriptome assembly would provide valuable resources for investigating genetic diversity and phylogeographic structure of wild populations and molecular mechanisms responding to stressful environments (e.g. increased water temperature) to guide future conservation studies and breeding programs.

Динамика и современное состояние ихтиофауны реки Амазар после строительства гидроузла ЦПК «Полярная»

The ecosystem of the Amazar River, the first large tributary of the Upper Amur, has experienced considerable anthropogenous influence over the last 20 years. The construction of the water reservoir in the middle reaches of the river was the most extensive interference into the ecosystem. In 2018-2019 integrated hydrobiological, hydrochemical, and ichthyological research was conducted in the Amazar River during the navigation season. The article analyzes the current state of ichthyocenosis as the most vulnerable component of the ecosystem of the middle reaches of the river Amazar and the newly formed reservoir. The results of the ichthyological survey have established the presence of 15 species from 7 families. The new data are compared with the results of previous research. The authors make a conclusion concerning the changes which have occurred in the species composition in the Amazar River over a 27-year period. The initial data was collected on the ichthyofauna of the recently constructed water reservoir. It predominantly includes coarse fish (Lagowski’s minnow (Phoxinus lagowskii), Amur gudgeon (Gobio cynocephalus), Amur bitterling (Rhodeus sericeus), and Amur sleeper (Perccottus glenii). Manchurian trout (Brachymystax lenok) and Upper Amur grayling (Thymallus grubii) were observed in the reservoir only during spawning and downstream migration. The findings show that the ichthyofauna of the reservoir is formed by non-target fish. The largest diversity of species was observed in the downstream water of the Amazar River. It was determined that spawning migration through the fish pass extended from the first decade of May through the first decade of June. It was observed that at the beginning migration was dominated by older Manchurian trout and grayling, while at the end of the migration period there were mainly cyprinids and immature Manchurian trout and grayling. The authors suggest that the size of migrating fish should be taken into consideration to ensure the effective operation of the fish pass. Absence of water flow control in the fish pass and a lack of consideration for the size of fish may result in both, insufficient water level for large mature salmon fish, and prohibitively high speed of the current for the small cyprinids.

Биология рыб озера Фролиха (Северный Байкал, Восточная Сибирь)

The fish fauna of Lake Frolikha comprises 12 species confirmed by our recent studies: roach Rutilus rutilus (L.), minnow Phoxinus phonixus (L.), stone loach Barbatula toni (Dyb.), spine loach Cobitis melanoleuca Nichols, pike Esox lucius L. lenok Brachymystax lenok (Pallas), Arctic charr Salvelinus alpinus (L.), Baikal black grayling Thymallus baicalensis (Dyb.), burbot Lota lota (L.), sand sculpin Leocottus kesslerii (Dyb.), stone sculpin Paracottus knerii (Dyb.) and perch Perca fluviatilis L. Biological peculiarities of these fishes are determined by unique geographical position and limnic characteristics of Lake Frolikha. Being a typical glacial lake it is located at rather low altitude a.s.l. and is adjacent to the unparalleled ecosystem of Lake Baikal. An underdeveloped shallow coastal zone with sparse aquatic vegetation, which is characteristic of glacial lakes, determines some biological traits of Lake Frolikha cyprinids. As compared with other mountain lakes of Baikal Rift Zone (BRZ), roach and minnow have lower rates of linear and weight growth as well as unusual population sex ratios. Male to female ratio in roach is 2:1 and in minnow it is 1:1 whereas in other lakes it reaches 1:4 and 1:10 respectively. The presence of native Baikal species in Lake Frolikha provided abundant food for piscivores: sand sculpins are the dominant food item of lenok, Arctic charr and perch. Lenok and perch demonstrate prominent linear and weight growth rate in the lake. In other lakes of BRZ with less abundant prey fish species Arctic charr typically diverge into several trophic forms, but in Lake Frolikha they established a monomorphic mostly piscivorous population. Charr from Lake Frolikha are relatively small and short-lived representatives of the large form of Transbaikalian charr. Their unique feature is river spawning, which is not observed in any other charr population within BRZ. Due to special protection regime of the territory, which minimizes catch losses, several fish species maintain natural unaffected structure of their populations evidenced by the abundance of old fish. The population of lenok is represented by 19 age groups, the population of roach – by 15 groups and that of burbot – by 12 groups. Alternatively, populations of small-sized prey species such as minnow and sand sculpin, which are heavily influenced by numerous predators include fewer age groups than in other mountain lakes of BRZ.

Aннотированный список рыбообразных и рыб водоемов и водотоков бассейна верхнего Иртыша Восточного Казахстана с комментариями по их таксономии и зоогеографии

Приводится список рыбообразных и рыб, обитающих в водоемах и водотоках бассейна Верхнего Иртыша. Список содержит 43 вида, относящихся к 7 отрядам, 10 семействам и 30 родам. Включены все зарегистрированные на настоящий момент виды, валидность которых была пересмотрена в соответствующих систематических ревизиях. Три вида таймень Hucho taimen Pallas, 1773, нельма Stenodus leucichtys nelma Pallas, 1773, сибирский осетр Acipenser baerii Brandt, 1869 внесены в Красную Книгу Республики Казахстан. В бассейне Верхнего Иртыша к редким ценным видам, нуждающимся в сохранении генофонда из-за возможности его утраты, кроме уже внесенных в Красную Книгу Республики Казахстан можно отнести еще ряд видов: минога тихоокеанская Lethenteron camtschaticum Tilesius, 1811, стерлядь Acipenser ruthenus Linnaeus, 1758 маркакольский ленок Brachymystax savinovi Mitrofanov 1959.

Numerical simulation of effects of inlet water depth of ecological fishway on the suitability of passing fish

Ecological fishways can not only restore the free passages of migratory organisms, but also play the role of ecological corridor. Currently, the behavior and ecology of the target fish were not fully taken into account in the design of fishways. So this paper takes the swimming ability of Hueho taimen, Brachymystax lenok and Thymallus arcticus in Buhe River as indicators, presents a systematic numerical investigation on effects of different inlet water depth in ecological fishway using a three-dimensional hydrodynamic model (EFDC). The numerical results indicate that the inlet water depth is a key factor in the ability to pass fish. It is shown that the two schemes with different slopes and roughness have significant differences in the flow field distribution under the same inlet water depth; the differences are the location where the maximum velocity occurs and the range beyond the upper limit of the velocity. In addition, when the inlet water depth increases to 0.8m, the flow field distribution of both designs are more suitable for fish passage. The outcomes of this study will be helpful to improve the design of the entrance of Buhe River fishway and make the target species more suitable for passing through.

Influence of dietary linseed oil as substitution of fish oil on whole fish fatty acid composition, lipid metabolism and oxidative status of juvenile Manchurian trout, Brachymystax lenok

In this study, juvenile Manchurian trout, Brachymystax lenok (initial weight: 6.43 ± 0.02 g, mean ± SE) were received for nine weeks with five types of diets prepared by gradually replacing the proportion of fish oil (FO) with linseed oil (LO) from 0% (LO0) to 25% (LO25), 50% (LO50), 75% (LO75), and 100% (LO100). The eicosapentaenoic (EPA) and docosahexaenoic (DHA) composition decreased with increasing inclusion level of LO (P < 0.05). With increasing LO inclusion level, triglyceride (TAG) content of serum increased significantly, however, there was a decrease in high-density lipoprotein cholesterol (HDL) (P < 0.05). LO substitution of FO up-regulated the gene expression level of lipid metabolism-related genes Fatty Acid Desaturases 6 (FAD6), Acetyl-Coa Carboxylase (ACCα), Sterol Regulatory Element Binding Protein 1 (SREBP-1), and Sterol O- Acyl Transferase 2 (SOAT2), and down-regulated the gene expression level of Peroxisome Proliferator-Activated Receptor a (PPARα) (P < 0.05). The SOD activities of both serum and liver in LO100 were significantly lower than in LO25 (P < 0.05). The CAT activity of the liver in LO100 was significantly lower than in LO0 and LO25 (P < 0.05). This study indicates that the Manchurian trout may have the ability to synthesize LC-PUFAs from ALA, and an appropriate LO in substitution of FO (<75%) could improve both the lipid metabolism and the oxidation resistance.

A Comparison of Two Methods for Determining the Genome Size of Taimen

To compare the two methods for determining the genome size of Taimenes (Hucho taimen). The present study determined genome size (or C- values) of 30 individuals of Taimenes by the method of PI (propidium iodide) and DAPI (4’,6-diamidino-2-phenylindole), through the flow cytometry, using chicken erythrocyte DNA content as a standard. The result showed that (1) With the method of PI and DAPI through the flow cytometry, DNA content in blood erythrocyte was 5.65±0.25 pg•2C-1 and 5.04±0.12 pg•2C-1(Fig. 1 and Fig. 2), and genome size (Gb) were 2.70 ± 0.12 Gb and 2.41 ± 0.06 Gb. By Independent-Samples T Test, the genome size (Gb) of blood erythrocyte determined by PI was significantly greater than that determined by DAPI(Table 1). (2)Several of the main support salmonids were clustered by furthest neighbor of any two C-values with the measure of euclidean distance. From the Fig. 3, we found that taimen and fine scale (Brachymystax lenok)first clustered into the same subgroup 1, brook trout (Salvelinus fontinalis) and Atlantic salmon (Salmo salar) clustered into the same sub-group 2, rainbow trout (Oncorhynchus mykiss) and pelyad (Coregonus peled) clustered into the same sub-group 3, Subgroup 1 and subgroup 2 firstly clustered into the same team, then come together with subgroup 3. The result indicates that (1) PI method can more accurately reflect the distribution of DNA content in blood erythrocyte of taimen, and more accurate prediction genome size of taimen.(2)Cluster analysis of C-values of several salmons may be related to their respective origin distribution and the filter feeding characteristics of Pelyad.

Effects of stocking density on growth performance and metabolism of juvenile Lenok (Brachymystax lenok)

A 127 day growth trial was conducted to investigate the impact of stocking density on growth performance and metabolism of the lenok (Brachymystax lenok). Juvenile lenok were stocked in triplicate at 4 initial densities (0.74, 1.53, 3.15, and 6.11 kg m−3). Samples were taken at days 30, 60, 97 and 127 of the experiment. At day 30, a lower specific growth rate (SGR) with higher feeding rate (FR) and lower feed efficiency (FER) in the low stocking density group (D1; initial density, 0.74 kg m−3) was observed compared with the high stocking density group (D4, initial density, 6.11 kg m−3). In contrast, a reduced SGR in D4 at days 97 and 127 was observed compared with D1. However, significant metabolic differences of plasma and liver were only observed between D1 and D4 using nuclear magnetic resonance (NMR)-based metabolomics analyses at the end of the experiment, including activation of energy metabolism, alterations in amino acid metabolism, changes in choline metabolism and repression of lipid metabolism. Gas chromatography-mass spectrometer (GC–MS) was then used to identify specific fatty acid in plasma, and the results showed that there were significant reductions of n-3PUFA, n-6 PUFA, MUFA and SFA in D4 compared with D1 at day 127. In conclusion, high stocking density resulted in detrimental effects on growth performance and alterations in metabolism of the lenok, suggesting that the welfare of the lenok at this size could be adversely affected by high fish density.

Global metabolic responses of the lenok (Brachymystax lenok) to thermal stress

High temperature is a powerful stressor for fish living in natural and artificial environments, especially for cold water species. Understanding the impact of thermal stress on physiological processes of fish is crucial for better cultivation and fisheries management. However, the metabolic mechanism of cold water fish to thermal stress is still not completely clear. In this study, a NMR-based metabonomic strategy in combination with high-throughput RNA-Seq was employed to investigate global metabolic changes of plasma and liver in a typical cold water fish species lenok (Brachymystax lenok) subjected to a sub-lethal high temperature. Our results showed that thermal stress caused multiple dynamic metabolic alterations of the lenok with prolonged stress, including repression of energy metabolism, shifts in lipid metabolism, alterations in amino acid metabolism, changes in choline and nucleotide metabolisms. Specifically, thermal stress induced an activation of glutamate metabolism, indicating that glutamate could be an important biomarker associated with thermal stress. Evidence from Hsp 70 gene expression, blood biochemistry and histology confirmed that high temperature exposure had negative effects on health of the lenok. These findings imply that thermal stress has a severe adverse effect on fish health and demonstrate that the integrated analyses combining NMR-based metabonomics and transcriptome strategy is a powerful approach to enhance our understanding of metabolic mechanisms of fish to thermal stress.

Molecular Cloning, mRNA Expression, and Nutritional Regulation of a Fatty Acyl Δ6-Desaturase-like Gene of the Manchurian Trout, Brachymystax lenok (Pallas)

The fatty acyl delta-6 desaturase (Δ6-desaturase) is a key rate-limiting enzyme in the biosynthesis of long-chain polyunsaturated fatty acids (LCPUFAs). To study the effects of different oil sources in the feed on the nutritional regulation of Δ6-desaturase-like gene mRNA expression, the fulllength cDNA of the Δ6-desaturase-like gene was cloned from the liver of Manchurian trout (Brachymystax lenok). A 9-week feeding trial was performed, and the fish received diets with three different oil sources: fish oil (FO), sunflower oil (SO), and linseed oil (LO). The results showed that the 2448 bp long full-length cDNA contained an open reading frame (with a length of 1365 bp), encoding 454 amino acids. Gene expression analysis indicated that Δ6-desaturase-like gene mRNA is widely distributed throughout different tissues, with highest expression levels in both the liver and the brain. The linolenic acid (ALA) and linoleic acid (LA) compositions were highest in LO and SO diets, respectively. The eicosapentaenoic acid and docosahexaenoioc acid composition in LO and SO diets were significantly lower than in the FO diet. Fish fed with SO and LO showed significantly higher liver expression levels of Δ6-desaturase-like gene mRNA than those fed with FO. This indicates that SO and LO in the diet affected the nutritional regulation of the Δ6-desaturase-like gene mRNA in the liver of the Manchurian trout. In addition, these data suggest that the Manchurian trout has the ability to synthesize long-chain unsaturated fatty acids (LC-PUFAs) from ALA and LA.

Effect of variation in the dietary ratio of linseed oil to fish oil on growth, body composition, tissues fatty acid composition, flesh nutritional value and immune indices in Manchurian trout,Brachymystax lenok

In order to study the effects of linseed oil substitution on the growth, body composition, tissue fatty acid composition, flesh nutritional value and immune indices of juvenile Manchurian trout, five feed types containing different levels of linseed oil (LO) mixed with fish oil (FO) were prepared: 0 (0 LO); 250 g/kg (25 LO); 500 g/kg (50 LO); 750 g/kg (75 LO); and 1000 g/kg (100 LO); and fed to juvenile Manchurian trout (initial weight 6.43 ± 0.02 g) for 9 weeks. The results showed that substitution of FO with 750 g/kg LO did not affect the growth of juvenile trout, with protein content in the dorsal muscle, and lipid content in the liver not showing any significant difference (p > 0.05). The highest lipid content found in muscle samples occurred for the 25 LO diet. The fatty acid composition found in the dorsal muscle and the liver of the Manchurian trout reflects the fatty acid composition in the diet, where the relative amount of linolenic acid (ALA), linoleic acid (LA) and docosahexaenoic acid (DHA) found in these organs has a positive linear correlation with their relative composition in the diet (p < 0.05). As the amount of LO in the diet was increased, the composition of ALA found in the sampled organs increased, while the composition of DHA and eicosapentaenoic acid (EPA) decreased. At the same time, the index of atherogenicity (IA) and thrombogenicity (IT) of the muscle samples from the 75 LO and 100 LO diets was significantly lower than for the 0 LO and 25 LO diets (p < 0.05), while the flesh lipid quality (FLQ) in the 100 LO diet was significantly lower than for the other diets (p < 0.05). The aspartate transaminase (AST) activity decreased initially, and then increased, as the level of LO replacement for FO was increased, with the 25 LO diet being significantly lower than for other groups (p < 0.05). The alanine aminotransferase (ALT) activity in serum samples from the 100 LO diet was higher than that from other diets. The lysozyme (LZM) activity in both serum and liver tissue first increased to a peak for the 25 LO and 50 LO diets, respectively, and then decreased as the level of LO was further increased. There was no significant change in the alkaline phosphatase (AKP) activity in the liver samples; however, the acid phosphatase (ACP) activity decreased significantly from the highest value for 0 LO feed group. In conclusion, the composition of fatty acids in the dorsal muscle and the liver was found to be modified by the diets, and with the diet containing less than 750 g/kg LO, being both beneficial for growth, and improved immunity, while maintaining the nutritional value of the lipid content in the dorsal muscle during the 9‐week period.

The response of larvae Brachymystax lenok during continuous and single pulses exposure to copper, zinc, lead and cadmium

The continuous and single pulses exposure of Cu, Zn, Pb and Cd on larvae Brachymystax lenok were tested in this study. The first-order kinetics was employed to obtain better comprehension on the time-toxicity relationship of tested heavy metals in continuous exposure test. For difference in time-varying exposure or recovery, 50% lethal time-averaged concentration (TAC) was used to assess the pulsed toxicity, which took both time and concentration into consideration in exposure and post-exposure period. TAC assessment to the single pulses and the regression analysis of first-order kinetic to continuous exposures demonstrated that Cu and Zn showed greater toxicity than Pb and Cd, indicating a slower uptake and/or depuration effect for zinc or copper. Furthermore, the results showed that recovery effect of larvae to all four metals was found in 24 h exposure followed by 72 h in fresh water, while for 72 h exposure and 24 h non-exposure the delayed lethal phenomenon occurred.

Characterization, expression, and functional analysis of the hepcidin gene from Brachymystax lenok

Hepcidin, a cysteine-rich antimicrobial peptide, is an important effector molecule in the innate immune system. Recently, Brachymystax lenok has become to be a valuable cold-water fish in China, particularly as the wild resources are rapidly declining. In this study, the hepcidin gene of Brachymystax lenok (Blhepc) has been cloned. The 870-bp mRNA contains a coding sequence (CDS) of 267 bp that encodes 88 amino acid residues. Amino acid sequence identities of Blhepc with hepcidin in Oncorhynchus mykiss, Salmo salar, and Hucho taimen were found to be 93.18%, 89.77% and 93.18%, respectively. Phylogenetic analysis indicated that Blhepc was clustered in the family Salmonidae. The putative signal peptide and the mature peptide contained 24 and 25 amino acid residues, respectively. The RXXR motif for recruitment of propeptide convertase was identified upstream of the mature peptide of Blhepc by sequence analysis. The N-terminal amino acid residues of the mature Blhepc peptide were Q-SH-L, a structure involved in regulating iron metabolism. Eight conserved cysteine residues in the mature peptide were held together by four disulfide bonds. Expression profiling of Blhepc indicated its highest level in the liver; its expression was stronger in males than in similar-aged females. Moreover, its expression in the liver increased significantly with age. Expression of Blhepc in six immune tissues showed increase in various degrees when challenged with Aeromonas salmonicida and Aeromonas hydrophila. A synthetic Blhepc mature peptide was validated to have significant antimicrobial activity against gram-negative and gram-positive bacteria and fungi in vitro. These results show that Blhepc may be an important component in the innate immunity of Brachymystax lenok, which could provide antimicrobial activities against invading pathogens.

Population genetic analysis of aquaculture salmonid populations in China using a 57K rainbow trout SNP array.

Various salmonid species are cultivated in cold water aquaculture. However, due to limited genomic data resources, specific high-throughput genotyping tools are not available to many of the salmonid species. In this study, a 57K single nucleotide polymorphism (SNP) array for rainbow trout (Oncorhynchus mykiss) was utilized to detect polymorphisms in seven salmonid species, including Hucho taimen, Oncorhynchus masou, Salvelinus fontinalis, Brachymystax lenok, Salvelinus leucomaenis, O. kisutch, and O. mykiss. The number of polymorphic markers per population ranged from 3,844 (O. kisutch) to 53,734 (O. mykiss), indicating that the rainbow trout SNP array was applicable as a universal genotyping tool for other salmonid species. Among the six other salmonid populations from four genera, 28,882 SNPs were shared, whereas 525 SNPs were polymorphic in all four genera. The genetic diversity and population relationships of the seven salmonid species were studied by principal component analysis (PCA). The phylogenetic relationships among populations were analyzed using the maximum likelihood method, which indicated that the shared SNP markers provide reliable genomic information for population genetic analyses in common aquaculture salmonid fishes. Furthermore, this obtained genomic information may be applicable for population genetic evaluation, marker-assisted breeding, and propagative parent selection in fry production.

Isolation of Polymorphic RAPD-SSR Markers from Xinjiang Arctic Grayling (Thymallus arcticus grubei) and a Test of Cross-Species Amplification

A total of 18 polymorphic microsatellite loci were isolated and characterized from RAPD products in the Xinjiang Arctic Grayling (Thymallus arcticus grubei). The number of alleles (Na) per locus varied from 2 to 10. Observed (Ho) and expected (He) heterozygosities ranged from 0.64 to 0.92, and from 0.63 to 0.88, respectively. Considerable differences were found among HBH, FH and FY populations in the number of alleles, effective number of alleles, number of genotypes at all of these loci. These new RAPD-SSR markers have provided a helpful tool for genetic analyses and resources conservation of T. arcticus grubei. Five additional fish species, Amur grayling (Thymallus grubii), Taimen (Hucho taimen), Sea perch (Lateolabrax japonicus), Lenok (Brachymystax lenok) and Red seam bream (Pagrosomus major) were assessed for cross-species amplification. Three of the five species showed at least one polymorphic locus. In addition, seven loci were found to be polymorphic in at least one species.

Comparative Analysis of Content of Omega-3 Polyunsaturated Fatty Acids in Food and Muscle Tissue of Fish from Aquaculture and Natural Habitats

Two fish species reared in aquaculture (pink salmon Oncorhynchus gorbuscha and whitefish Coregonus lavaretus) and ten fish species from natural habitats (whitefish C. lavaretus, tugun Coregonus tugun, broad whitefish Coregonus nasus, least cisco Coregonus sardinella, vendace Coregonus albula, boganid charr Salvelinus boganidae, charr Salvelinus alpinus complex, northern pike Esox lucius, sharp-snouted lenok Brachymystax lenok, and taimen Hucho taimen) have been studied. The content of two long-chain polyunsaturated omega-3 fatty acids (PUFAs), eicosapentaenoic acid (20:5n-3, EPA) and docosahexaenoic acid (22:6n-3, DHA), in the muscle tissue of the fish and in their food (intestine contents) are compared. In the aquacultures of whitefish and pink salmon, the total content of EPA and DHA is significantly higher in feed than in the muscle tissue of the fish, which indicates losses of PUFA in the two-link food chain of the aquaculture during their transfer to the upper trophic level. EPA and DHA losses in aquaculture, which are confirmed by numerous literature data, mean an inefficient usage of the available sources of PUFAs and the aggravation of the global deficit of these biochemicals in the human diet. A study of natural fish populations reveals the accumulation of EPA and DHA in their biomass compared to food in many cases, although opposite phenomena are also observed. An assumption on the presence of an optimal, physiologically adequate species-specific level of PUFA in the fish muscle tissue has been made based on our data and literature data. If the level of PUFAs in the muscles is lower than optimal, their accumulation (bioaccumulation) from food and/or de novo synthesis are observed. When the optimal level is exceeded, the content of EPA and DHA in biomass approaches maximum species-specific values; however, part of these PUFAs entering from food is not digested or is catabolized. According to the obtained data, the species of the order Salmoniformes have an optimal level of 2 to 6 mg/g of wet weight. It has been found that in aquaculture approaching to maximum values of EPA + DHA content was accompanied by their losses (scattering) in the food chains, while in natural ecosystems the maximum values of PUFA content in the fish biomass are achieved by their accumulation from the lower trophic level. Boganid charr S. boganidae had the highest content of EPA + DHA in the muscle tissue among all known fish species (32.78 mg/g of wet weight).

Effects of water temperature on feeding and growth of the lenok Brachymystax lenok (Pallas) with different sizes

Effects of water temperature on feeding and growth of the lenok <i>Brachymystax lenok</i> (Pallas) with different sizes