Salmon Fingerlings Research Articles

Infectious pancreatic necrosis virus enters CHSE-214 cells via macropinocytosis

Infectious pancreatic necrosis virus (IPNV) is a non-enveloped virus belonging to the Birnaviridae family. IPNV produces an acute disease in salmon fingerlings, with high mortality rates and persistent infection in survivors. Although there are reports of IPNV binding to various cells, the viral receptor and entry pathways remain unknown. The aim of this study was to determine the endocytic pathway that allows for IPNV entry. We observed that IPNV stimulated fluid uptake and virus particles co-localysed with the uptake marker dextran in intracellular compartments, suggesting a role for macropinocytosis in viral entry. Consistent with this idea, viral infection was significantly reduced when the Na+/H+ exchanger NHE1 was inhibited with 5-(N-Ethyl-N-isopropyl) amiloride (EIPA). Neither chlorpromazine nor filipin complex I affected IPNV infection. To examine the role of macropinocytosis regulators, additional inhibitors were tested. Inhibitors of the EGFR pathway and the effectors Pak1, Rac1 and PKC reduced viral infection. Together, our results indicate that IPNV is mainly internalized into CHSE-214 cells by macropinocytosis.

Intracellular proteolysis in Atlantic salmon Salmo salar fingerlings (0+) from different biotopes in an Arctic river (Varzuga River, White Sea Basin)

ABSTRACTThe activity of intracellular proteolytic enzymes was studied in Atlantic salmon (Salmo salar L.) fingerlings (0+) after hatching from spawning nests and dispersal in the Varzuga River main stem and its Pyatka tributary (Kola Peninsula, White Sea Basin). The study focused on calcium-dependent cytosolic proteinases (µ- and m-calpains), lysosomal proteinases (cathepsins В and D) and collagenase, and determined the free/protein-bound hydroxyproline ratio, which portrays collagenolytic activity. Compared to fingerlings from the Varzuga main stem, the intracellular proteolytic enzyme activity of cysteine proteinase and collagenase was higher in fingerlings from the Pyatka tributary, where current velocities and food availability were higher. These results indicate that there is a higher rate of intracellular protein metabolism in the juveniles from this phenotypic group.

Metabolic background for establishment of the subpopulation structure in early ontogenesis in the Atlantic salmon (the case of energy of carbohydrate metabolism)

The activity of some enzymes involved in energy and carbohydrate metabolism was studied in Atlantic salmon embryos at the eyed egg stage and in salmon fingerlings (0+) from two trophic–ecological groups: the Varzuga River bed and two tributaries, the Pyatka and Sobachii rivers (Kola Peninsula). It has been demonstrated that heterogeneity of embryos was most evident in the case of cytochrome c oxidase (CO), malate dehydrogenase (MDH), glycerol-1-phosphate dehydrogenase (G1PDH), and glucose-6-phosphate dehydrogenase (G6PDH), while the lowest level of heterogeneity was observed for lactate dehydrogenase (LDH) and aldolase. A positive correlation was revealed between the activities of CO, LDH, MDH, and G1PDH. It was noted that G6PDH showed a negative correlation with almost all enzymes under study. It was found that salmon juveniles inhabiting the tributaries were characterized by high LDH, aldolase, and G1PDH activity and lower activity of G6PDH compared to the juveniles inhabiting the main river bed. Notably, the differences in the activity of the enzymes involved in aerobic metabolism between the two groups of fingerlings under analysis were observed only in the autumn.

THE EFFECT OF THE LIPID AND FATTY ACID STATUS OF ATLANTIC SALMON, SALMO SALAR L., FINGERLINGS ON THEIR PRIMARY DISPERSAL AND FORMATION OF PHENOTYPIC GROUPS

A comparative study of the lipid metabolism in Atlantic salmon fingerlings staying after hatching near their spawning redds along the banks of the Varzuga River main channel (at rapids and riffles) and those who had migrated to tributaries – the Arenga, the Pjatka and the Falaley. The choice of habitats by fingerlings after hatching and dispersal affects the quantitative characteristics of lipids and fatty acids, and is supported by the organism’s adaptive systems, including variations in the ratios of individual lipid and fatty acid classes within physiological limits. Fingerlings from the Pjatka had higher length-weight values, the energy/structural lipids ratio(TAG+ECHOL/PL+CHOL), and the ratio of essential fatty acids 18:3ω-3/18:2ω-6 as compared to fish from other studied biotopes. The combination of ecological and trophic conditions (temperature, water flow rate, depth, riverbed particle size composition and fouling, species composition and amount of food items, and their availability) in the Pjatka are more favorable for the growth and development of fingerlings. The identified biochemical differences between the fingerlings that had migrated to the tributaries and those remaining along the main channel banks may be the basis for the formation of steady fish differentiation into groups with different lipid status and length-weight indices during further development (in fish aged 1+ and 2+). This differentiation in 0+ Atlantic salmon can be considered as a start of intrapopulation heterogeneity, affecting further choices on the fish life strategy.

Features in the Lipid Status of Two Generations of Fingerlings (0+) of Atlantic Salmon (Salmo salar L.) Inhabiting the Arenga River (Kola Peninsula).

The present research focused on determining the lipid status of salmon fingerlings (0+) in early development after dispersal form groups of spawning nests in biotopes of different hydrological conditions. The revealed qualitative and quantitative differences in the levels of phospholipids and fatty acids among two generations of Atlantic salmon fingerlings (0+) living in different biotopes of the Arenga River (a tributary of the Varzuga River) may be associated with the peculiarities of their genetically determined processes of the biosynthesis and modification of individual lipid classes and trophoecological factors (food spectrum, quality and availability of food objects, and hydrological regime). The research was organized to observe the dynamics of these developmental changes from ages 0+ to 2+.

In the Warming Arctic Seas

In the Warming Arctic Seas

Heterogeneity of lipids and fatty acids of fingerlings of Atlantic salmon Salmo salar L. different in weight and size

Lipid and fatty acid spectra have been investigated in fingerlings of Atlantic salmon distinguished by weight and length characteristics and degree of fatness. Heterogeneity in terms of fatty acids in the studied groups of fingerlings is shown which indicates the differences in the rates of biochemical reactions of synthesis and modification of lipids and fatty acids caused by phenotypic diversity. Specificities of the metabolic processes in the studied groups of salmon fingerlings are related to the qualitative variety of nutrition spectra and the availability of food in the biotope.

Puerarin Promotes Overall Health Through Blood Flow and Immune Response within Chinook Salmon (Oncorhynchus tshawytscha) Fingerlings

An 8-week study was performed to determine the effects of supplementing puerarin, the most biologically active ingredient present in the roots of kudzu (Puerarin lobata), in diets of farmed chinook salmon (Oncorhynchus tshawytscha) fingerlings. Puerarin was given to study fish through supplementation to commercial fish feed. Administration of puerarin reduced cortisol, proteins, and hematocrit levels while improving spleen somatic indices and respiratory burst response compared to fish fed a control diet without affecting growth, and thereby counteracts the negative consequences of stress induced through handling and experienced by fish reared in aquaculture.

Flavobacterium spartansii sp. nov., a pathogen of fishes, and emended descriptions of Flavobacterium aquidurense and Flavobacterium araucananum

Two strains (T16(T) and S12) of a Gram-reaction-negative, rod-shaped, yellow-pigmented bacterium were recovered from kidneys of feral spawning adult Chinook salmon (Oncorhynchus tshawytscha) and the gills of captive-reared Chinook salmon fingerlings suffering a mortality episode, respectively. Polyphasic characterization revealed that these strains possessed gliding motility, contained a flexirubin-type pigment, proteolysed multiple substrates (i.e. gelatin, casein and elastin), and had a mean DNA G+C content of 35.6 mol%. Sequencing of the 16S rRNA gene demonstrated that strains T16(T) and S12 were nearly identical to one another (>99% similarity) and were placed within the genus Flavobacterium, with Flavobacterium aquidurense CCUG 59847(T) (98.3%), Flavobaterium araucananum CCUG 61031(T) (98.2%) and Flavobacterium frigidimaris (AB183888, 98.1%) being their closest relatives. Subsequent phylogenetic analyses using neighbour-joining, maximum-parsimony and Bayesian methodologies demonstrated that strains T16(T) and S12 formed a well-supported clade within the genus Flavobacterium that was distinct from other Flavobacterium species. The major fatty acid constituents of strains T16(T) and S12 were iso-C15 : 0, C16 : 1ω6c and/or C16 : 1ω7c, iso-C17 : 0 3-OH, and iso-C15 : 0 3-OH according to fatty acid methyl ester analysis. The mean level of DNA-DNA relatedness between strain T16(T) and F. aquidurense CCUG 59847(T) and F. araucananum CCUG 61031(T) was 23 and 29%, respectively. Thus, the data accumulated in this study support the suggestion that strains T16(T) and S12 represent a novel species of the genus Flavobacterium, for which the name Flavobacterium spartansii sp. nov. is proposed. The type strain is T16(T) ( = LMG 27337(T) = ATCC BAA-2541(T)). Emended descriptions of F. aquidurense and F. araucananum are also proposed.

Intensive fish farming and the evolution of pathogen virulence: the case of columnaris disease in Finland

Ecological changes affect pathogen epidemiology and evolution and may trigger the emergence of novel diseases. Aquaculture radically alters the ecology of fish and their pathogens. Here we show an increase in the occurrence of the bacterial fish disease Flavobacterium columnare in salmon fingerlings at a fish farm in northern Finland over 23 years. We hypothesize that this emergence was owing to evolutionary changes in bacterial virulence. We base this argument on several observations. First, the emergence was associated with increased severity of symptoms. Second, F. columnare strains vary in virulence, with more lethal strains inducing more severe symptoms prior to death. Third, more virulent strains have greater infectivity, higher tissue-degrading capacity and higher growth rates. Fourth, pathogen strains co-occur, so that strains compete. Fifth, F. columnare can transmit efficiently from dead fish, and maintain infectivity in sterilized water for months, strongly reducing the fitness cost of host death likely experienced by the pathogen in nature. Moreover, this saprophytic infectiousness means that chemotherapy strongly select for strains that rapidly kill their hosts: dead fish remain infectious; treated fish do not. Finally, high stocking densities of homogeneous subsets of fish greatly enhance transmission opportunities. We suggest that fish farms provide an environment that promotes the circulation of more virulent strains of F. columnare. This effect is intensified by the recent increases in summer water temperature. More generally, we predict that intensive fish farming will lead to the evolution of more virulent pathogens.

Outbreaks of phaeohyphomycosis in the chinook salmon (Oncorhynchus tshawytscha) caused by Phoma herbarum

Phoma herbarum has been associated with two outbreaks of systemic mycosis in hatchery-reared chinook salmon (Oncorhynchus tshawytscha) fingerlings. Affected fish exhibited abnormal swimming behavior, exophthalmia, multiple rounded areas of muscle softening, protruded hemorrhagic vents, and abdominal swelling. In all affected fish, swimbladders were filled with whitish creamy viscous fungal mass, surrounded by dark red areas in swimbladder walls, kidneys, and musculature. Clinical and histopathological examinations suggest that the infection may have started primarily in the swimbladder and then spread to the kidneys, gastrointestinal tract, and surrounding musculature. Consistent microscopical findings included broad septate branched fungal hyaline hyphae, 5-12 microm in diameter within the swimbladder, stomach, and often within and adjacent to blood vessels. Profuse growths of woolly brown fungal colonies were obtained from swimbladders and kidneys on Sabouraud medium. On corn meal agar the formation of pycnidia, characteristic of Phoma spp., was detected within 10 days of incubation. Morphological and molecular analyses identified this fungus as Phoma herbarum. This report underscores systemic fungal infections as a threat to raceway-raised salmon.

Antimicrobial multiresistance in bacteria isolated from freshwater Chilean salmon farms

The intensive use of antimicrobial agents, mainly oxytetracycline, to prevent and control bacterial pathologies in Chilean salmon culture is a frequent practice. A total of 103 Gram-negative oxytetracycline-resistant bacteria recovered from various sources of 4 Chilean freshwater salmon farms were identified and investigated for their susceptibility patterns to various antibacterial agents, by using an agar disk diffusion method. Antibacterial resistance patterns of isolates were not correlated with bacterial species or strain source. A high number of bacteria resistant to amoxicillin, ampicillin, erythromycin, and furazolidone, as well as an important frequency of bacterial resistance to florfenicol, chloramphenicol, cefotaxime and trimethoprim-sulfamethoxazole was found. On the contrary, the proportion of bacteria resistant to gentamicin, kanamycin, flumequine and enrofloxacin was rather low. Resistant microflora showed a high taxonomic variability and mainly consisted of non-fermenting bacteria (77.7%). These strains mainly belonged to the species Pseudomonas fluorescens (29), Aeromonas hydrophila (10), Stenotrophomonas maltophilia (6), isolated from salmon fingerlings, and Acinetobacter lwoffii (5) isolated from pelletized feed. The occurrence of simultaneous resistance to various antibacterials was frequent. We observe a high frequency of bacteria resistant to 6–10 antibacterials (74 strains), and antibiotic resistance index (ARI) values ranging from 0.38 to 0.48 for the four salmon farms studied. These results suggest that Chilean salmon farms might play a role as reservoirs of antibacterial multiresistant bacteria, thus prompting the necessity for a more restrictive attitude towards the intensive use of antibacterials in salmon farming.

Bacterial resistance to oxytetracycline in Chilean salmon farming

The use of oxytetracycline for preventing and controlling bacterial pathogens in salmon farming is frequent in Chile, yet no studies have been performed to evaluate the ecological impact of its intensive and prolonged use. In this work, the frequency of oxytetracycline-resistant bacteria from water, pelletized feed and fingerlings from four Chilean freshwater Atlantic salmon farms, as well as the level of resistance of selected strains was investigated. Viable bacterial counts were performed by a spread plate method and antibiotic-resistant bacteria were counted in culture media supplemented with the selected antibiotic. Resistance levels of selected strains isolated in media containing antibiotic were determined using an agar plate dilution method. High proportions of low- and high-level oxytetracycline-resistant bacteria (selected in agar plates containing 30 and 100 μg/ml, respectively), mainly from pelletized feed and effluent samples of the fish farms were found. The highest proportions of resistant bacteria were found in the effluent samples, and were significantly higher ( P<0.05, Tukey's test) than those from the other samples studied. On the contrary, influent samples exhibited the lowest proportions of resistant bacteria. One hundred and three resistant Gram-negative isolates, which represented the oxytetracycline-resistant bacterial population, were randomly selected on TSA containing 30 or 100 μg/ml of oxytetracycline, from salmon farms and pellet samples, and streaked for purification on TSA plates without oxytetracycline. A large number of non-fermenting bacteria (77.7%) were identified. Among these, Pseudomonas fluorescens (28.2%), Stenotrophomonas maltophilia (5.8%), Sphingomonas paucimobilis (5.8%), Acinetobacter lwoffii (4.8%), and Pseudomonas putida (4.8%) were the most frequent. Also, an important number of strains of Aeromonas hydrophila (9.7%), Burkholderia cepacia (3.9%), Brevundimonas vesicularis (3.9%), Acinetobacter johnsonii (2.9%), Pantoea sp. (2.9%) and Moraxella sp. (2.9%) were found. P. fluorescens and A. hydrophila predominated in salmon fingerlings, whereas A. lwoffii and S. maltophilia were predominant in pellet samples. Selected strains exhibited high levels of oxytetracycline resistance, with minimum inhibitory concentrations (MICs) ranging from 64 to 2048 μg/ml, whereas MIC 90 of oxytetracycline varied between 1024 and 2048 μg/ml. This study shows the presence of an important population of oxytetracycline-resistant bacteria in the microflora of Chilean salmon farms. Therefore, the environment of these farms might play important roles as reservoirs of bacteria carrying genetic determinants for high-level tetracycline resistance, prompting an important risk to public health for workers involved in fish culturing and processing.

In vivo photostabilization of tetracycline hydrochloride by reduced glutathione for use as an ecological marker in Salmo salar

Tetracycline (TC) compounds are commonly used to mark fish because of their capacity to fluoresce. When fish are immersed in a solution of the TC compound, chelation of the TC compound by calcium results in TC deposition in mineralized tissue such as bone, scales and fin rays. Owing to photolysis of TC compounds, however, external calcified tissues such as scales and fin rays do not retain TC fluorescence. In solution, reduced glutathione (GSH) has been found to photostabilize TC compounds. Thus, the hypothesis that GSH would improve TC-induced fluorescent mark retention was tested in the present study. The study was carried out in the context of identifying a cost-effective method of marking juvenile fish for use in an enhancement hatchery application. Atlantic salmon ( Salmo salar) fingerlings were immersed in solutions of tetracycline hydrochloride (TCH) or TCH in combination with GSH, and fluorescent mark intensity in external calcified tissues (opercular flaps, fin rays and scales) was monitored for 5–10 weeks. The results indicated that GSH had a significant protective effect on TCH-induced fluorescent mark retention, presumably by photostabilizing TCH.

Lesser known aquarium fish tumor models.

The repeated use of particular species for experimental oncology in fish increases their future value by accumulating background information for these models and justifies the establishment of genetic stock centers. However, the wide diversity that exists within the class Osteichthyes and Chondrichthyes suggests that the ideal surrogate models for studying some types of neoplasms might be found among lesser known species. To help assess cultured fish as surrogates for some other types of human neoplasia, we examined cases in the archives of the Registry of Tumors in Lower Animals and reviewed reports in the literature. Spontaneous and induced neoplasms originating from a spectrum of cell types were seen in more than 215 fish species commonly raised in aquaria or cultured for study among 69 families. Prominent families include the Poeciliidae (livebearers), Cyprinidae (carps and minnows), Cichlidae (cichlids), Cyprinodontidae (killifish), Characidae (tetras), Adrianichthyidae (medakas), Aplocheilidae (rivulins), and Salmonidae (salmon and trout). The following are examples of potential fish tumor models that have received less consideration than some others: papilloma and carcinoma of the urinary bladder in oscar (Astronotus ocellatus); osteogenic neoplasms, peripheral nerve sheath tumors, and ependymoblastoma in coho salmon fingerlings (Oncorhynchus kisutch); and nephroblastoma resembling Wilms' tumor in Japanese eels (Anguilla japonica).

Environmental factors associated with a toxic bloom ofMicrocystis aeruginosa

Environmental factors associated with the occurrence of toxic cyanobacterial blooms and toxin production were investigated during the summers of 1994 and 1995 in Steilacoom Lake, Washington. A pronounced and prolonged toxic bloom of Microcystis aeruginosa occurred during summer 1994 but not during 1995. Lake characteristics that were associated with the toxic bloom in 1994 were higher total phosphorus, decreased water transparency, high water column stability, high surface water temperature and pH, and decreased lake flushing. Decreased water transparency during 1994 may have been due to significantly lower zooplankton abundance. We hypothesize that this decreased transparency was caused by increased planktivory by higher numbers of coho salmon (Oncorhynchus kisutch) fingerlings during 1994 and (or) inhibition of zooplankton grazing by Microcystis. The success of Microcystis over other cyanobacteria was associated with low nitrogen to phosphorus ratios and low nitrate-nitrogen with sufficient ammonium-nitrogen concentrations. Toxin production (i.e., micrograms of microcystin per gram of plankton biomass) was not constant over the duration of detectable toxicity; hence, no relationship was found between Microcystis abundance and microcystin concentration. However, microcystin concentration was positively correlated with increasing soluble reactive phosphorus concentrations between 1 and 10 µg·L-1, indicating that toxin production may have been limited by phosphorus.

Biochemical and Physiological Responses in Atlantic Salmon ( Salmo salar) Following Dietary Exposure to Copper and Cadmium

Three experiments were conducted with Atlantic salmon ( Salmo salar) to assess the effects of dietary exposure to copper and cadmium. The results presented here provide an overview, details of each experiment will be published in full elsewhere. In the first experiment, salmon parr exposed for four weeks to 35 and 700 mg Cu kg −1 diet had significantly elevated intestinal copper concentrations, cell proliferation (PCNA) and apoptosis rates compared to control fish. No differences were observed in gill or plasma copper concentrations among the groups. In contrast to the controls, the Cu exposed groups did not grow significantly during the exposure period. The second experiment (three months exposure) was conducted to assess the effects of dietary copper (control, 35, 500, 700, 900 or 1750 mg Cu kg −1 diet) on growth and feed utilization in salmon fingerlings. Growth was significantly reduced after three months exposure to dietary Cu concentrations above 500 mg kg −1. Similarly, copper body burdens were significantly higher in fish exposed to elevated dietary copper concentrations (above 35 mg Cu kg −1 diet). In the third experiment, salmon parr were exposed to one of six dietary cadmium concentrations (0, 0.5, 5, 25, 125 or 250 mg Cd kg −1 diet) for four months. Cadmium accumulated in the liver>intestine>gills of exposed fish. Rates of apoptosis and cell proliferation in the intestine increased following exposure to dietary cadmium. Exposure to elevated concentrations of dietary cadmium had no effect on growth in salmon parr. Results from these studies indicate that cellular biomarkers have potential as early warning signs of negative effects on the overall fitness of an organism.

Post-stocking foraging of dry feed- vs. live prey-reared salmon (Salmo salar L.) fingerlings

Post-stocking foraging of dry feed- vs. live prey-reared salmon (<i>Salmo salar</i> L.) fingerlings

Condition and performance of juvenile Atlantic salmon (Salmo salar): effects of rearing practices on hatchery fish and comparison with wild fish

This study examined the effects of various modifications of rearing practices on hatchery-reared Atlantic salmon (Salmo salar) fingerlings and compared condition and performance of hatchery fingerlings (age 0+) and yearlings (age 1+) with those of wild-reared Atlantic salmon. Reduced fish density (and increased ration) in rearing tanks promoted increased growth and condition factor and significant changes in muscle composition, including increased muscle lipid content and glycolytic enzyme activity, specfically phosphofructokinase and lactate dehydrogenase. However, these changes had no effect on anaerobic capacity. Moreover, swimming performance was poorer in fingerlings reared at low compared with normal density. Raising the water velocity from 0 to 4 cm ·s-1(~0.7 body length ·s-1) had overall beneficial effects, most notably increased endurance in fixed velocity sprint tests and a reduction of ion loss in an epinephrine challenge test. Increasing velocity to 9 cm ·s-1had no further effects. Wild fingerlings were larger with better fin quality and superior anaerobic capacity and swim performance. Even larger differences were seen between hatchery-reared and wild yearlings. It is concluded that significant changes in morphology, physiology, and muscle biochemistry of juvenile Atlantic salmon can be brought about by changing hatchery rearing conditions, but these changes are of limited effectiveness in reducing the difference between hatchery-reared and wild fish.

Phosphorus utilization by Atlantic salmon ( Salmo salar) reared in freshwater is not influenced by higher dietary calcium intake

To decrease the phosphorus (P) load of fish farms, factors affecting dietary P utilization need to be known in more detail. A study was conducted to examine the effect of dietary calcium (Ca) level on dietary P utilization of Atlantic salmon reared in freshwater. Salmon fingerlings (initial weight 42.1 g) were fed a semi-purified diet (1.3 g kg −1 Ca, 3.1 g kg −1 P) with or without Ca and P supplement for 15 weeks. Fish fed no P supplement showed bone deformities and low Ca and P content of vertebrae. An increase in supplementary Ca level from 0 to 1.5% (increase in Ca:P ratio from 0.2 to 2.1) had no significant effect on bone mineralization when dietary P content was at the requirement level of Atlantic salmon. Plasma phosphate concentration in fish fed diets supplemented with 5 g P kg −1 was decreased by dietary Ca supplementation of 15 g kg −1. An increase in supplementary Ca from 0 to 0.75% had a positive effect on bone mineralization when dietary P content was below the requirement level. Correlation between scale and bone mineralization was significant. Magnesium level in plasma and deposition in calcified tissue decreased with increasing dietary Ca and P levels. Hepatic cholecalciferol (vitamin D 3) content was 58.5 ng g −1 in fish fed without Ca or P supplements, and 9–10 ng g −1 in fish fed with either Ca or P supplements indicating its involvement in the regulation of Ca and P homeostasis. The results suggest that in commercial salmonid diets, a high Ca:P ratio is unlikely to interfere with dietary P utilization. However, the possibility of improving the performance of plant protein based diets of low Ca:P ratio by Ca supplementation exists.