Rainbow Trout Oncorhynchus Mykiss Fry Research Articles

First feeding a plant-based diet to rainbow trout Oncorhynchus mykiss fry

First feeding a plant-based diet to rainbow trout Oncorhynchus mykiss fry

Energy metabolism responses in muscle tissue of rainbow trout Oncorhynchus mykiss fry to CO2-induced aquatic acidification based on metabolomics

We investigated the impacts of carbon dioxide (CO2)-induced acidification on energy metabolism in muscle tissue of rainbow trout Oncorhynchus mykiss fry. Fry were exposed to freshwater in equilibrium with air containing CO2 at volume concentrations of 380, 1000 and 2000 ppm for 30 days. At this critical and sensitive life stage, we showed dose-dependent reductions in weight gain and changes in energy metabolism under projected future CO2 levels. Rainbow trout fry exposed to elevated CO2 concentrations produced more energy in muscle tissue because ATP levels were significantly elevated. Fry exposed to 1000 ppm CO2 had a higher activity of pyruvate kinase (PK), higher concentrations of pyruvate, acetate, 2-oxoglutarate, phenylalanine, tyrosine, inosine, uracil and uridine, and lower concentrations of anserine and IMP in muscle tissue based on metabolomic analysis. We infer that the increased ATP production in fry exposed to 1000 ppm CO2 is produced through glycolysis. In the 2000 ppm group, the protein content of muscle was lower than in the control, and the activities of PK, cytochrome C oxidase (COX), Na+/K+-ATP and Ca2+/Mg2+-ATPase were significantly higher. Concentrations of pyruvate, 2-oxoglutarate, histidine, anserine and IMP were significantly lower, and alanine, methionine, leucine, isoleucine, valine, lysine, pantothenate, uracil and inosine were significantly higher. Accelerated tissue decomposition may have sustained the higher production of ATP in the 2000 ppm group.

Spatial and Temporal Variation of Whirling Disease Risk in Montana Spring Creeks and Rivers

Spring creeks are important spawning and rearing areas for wild trout, but the stable flows, cool temperatures, and high nutrient levels that characterize these unique habitats may also make them highly susceptible to establishment and proliferation of the whirling disease pathogen Myxobolus cerebralis. We evaluated the spatial and temporal dynamics in whirling disease risk by using sentinel rainbow trout Oncorhynchus mykiss fry in nine different spring creeks and their conjoining rivers or reservoirs in Montana over a 20-month period. Whirling disease risk was high in five of the seven pathogen-positive spring creek study sites; at these sites, prevalence levels exceeded 90% and over 50% of sentinel fry had moderate to high infection severity scores. Spring creeks generally had higher disease prevalence and severity than paired river or reservoir sites. Fine sediment levels varied widely among springs creeks with high and low whirling disease risk, and we found no significant association between fine sediment level and infection severity. The low risk measured for some spring creeks was likely attributable to the pathogen invasion being in its early stages rather than to environmental characteristics limiting the severity of infection. High whirling disease risk occurred over a wide range of temperatures at spring creek sites (4.5-13°C) and river sites (1.7-12.5°C). There was an unusual seasonal cycle of infection in spring creeks, with peak infection levels occurring from late fall to early spring and declining to near zero in late spring to early fall. The low infection risk during spring suggests that spring-spawning trout would be at a low risk of infection, even in spring creeks with otherwise high disease severity. In contrast, fry of fall-spawning trout may be much more susceptible to infection in spring creek environments.

Korean and Japanese Isolates of Viral Hemorrhagic Septicemia Virus from Olive Flounder are Pathogenic to Rainbow Trout Fry

We evaluated the pathogenicity of Korean and Japanese isolates of viral hemorrhagic septicemia virus (VHSV: genotype IVa) from olive flounder Paralichthys olivaceus using rainbow trout Oncorhynchus mykiss fry. The cumulative mortalities of fish challenged with FYeosu05 (Korean) and Obama25 (Japanese) isolates at 106.5 TCID50/fish were 64 and 48%, respectively. No mortality was observed among the fish challenged with either of the isolates at 105.5 TCID50/fish, or in mock-challenged fish. The affected fish exhibited darkening of the body, an expanded abdomen, pale gills, an enlarged spleen, and diffuse necrosis in the splenic and interstitial hematopoietic tissues. We re-isolated VHSV from all mortalities using cell culture and confirmed their presence by reverse transcription loop-mediated isothermal amplification (RT-LAMP). We thus concluded that Asian VHSV isolates from olive flounder are pathogenic to rainbow trout fry, although with low virulence.

Viral haemorrhagic septicaemia virus (VHSV) genotype II isolated from European river lamprey Lampetra fluviatilis in Finland during surveillance from 1999 to 2008

We examined the occurrence of viral haemorrhagic septicaemia virus (VHSV) in the main spawning stocks of wild European river lamprey Lampetra fluviatilis in the rivers of Finland from 1999 to 2008. Pooled samples of internal organs (kidney, liver and heart or brain) from 2621 lampreys were examined for the presence of VHSV by standard virological techniques. VHSV was isolated from 5 samples from the rivers Lestijoki and Kalajoki, which flow from Finland into the Bothnian Bay of the Baltic Sea. The presence of VHSV was confirmed by immunofluorescent antibody technique (IFAT), ELISA and RT-PCR. Phylogenetic analysis based on the full-length VHSV glycoprotein (G) gene sequence revealed that the isolates were most closely related to the VHSV strain isolated in 1996 from herring Clupea harengus and sprat Sprattus sprattus in the Eastern Gotland Basin of the Baltic Sea, and were therefore assigned to VHSV genotype II. The partial G gene sequences obtained (nt 1 to 672-1129) of all 5 lamprey VHSV isolates were identical, and so were the entire G genes (nt 1 to 1524) of 2 isolates sequenced. The virulence of one of the lamprey isolates was evaluated by an experimental infection trial in rainbow trout Oncorhynchus mykiss fry. No mortality was induced postinfection by waterborne and intraperitoneal challenge, respectively, while 2 genotype Id isolates originating from Finnish rainbow trout caused marked mortality under the same conditions. The infection in the European river lamprey is thought to be independent from the epidemic in farmed rainbow trout in Finnish brackish waters, because the isolates from rainbow trout were of a different genotype. This is the first report of VHSV found in the European river lamprey. The role of wild river lampreys in maintaining the infection in the marine environment remains unclear.

Effect of Different Levels of Fine‐Sediment Loading on the Escapement Success of Rainbow Trout Fry from Artificial Redds

AbstractIncreased sedimentation from logging operations can affect water flow over salmonid redds, potentially impairing embryonic development in incubating eggs and fry. Effects may result from reduced oxygen delivery or waste removal or from physical entrapment of fry by sediment cap formation. A system of artificial redds was used to examine the effects of varying loads of mixed fine sediments on the escapement success of rainbow trout Oncorhynchus mykiss fry. Replicates of 80 eyed rainbow trout eggs were seeded in redds loaded with low (11.8%), medium (21.2%), high (28.6%), or no (0%) additional fine sediments. Interstitial oxygen saturation was determined in each chamber throughout incubation and emergence. Total percent emergence, residual yolk sac remaining, prevalence of deformities, and condition factor were determined in emergent fry. Fry began to emerge at 507.6 degree‐days postfertilization, and overall emergence was more than 70% in all treatment levels. Emergence rate patterns approximated a normal distribution in all treatment groups except for the high‐sediment‐loaded redds. Emergence of fry from the high‐sediment‐load chambers was greater initially and exhibited a slower, more continuous pattern. The formation of a sediment cap in the redds with high‐sediment loading appears to have significantly altered the emergence pattern of developing fry. Mean oxygen saturation was more than 79% in all groups and was not correlated to sediment load. Residual yolk was not different among fry from any of the groups throughout the emergence period. Fry condition factor decreased significantly over the sampling period, but there were no statistically significant differences among treatments.

Stationary phase culture supernatant containing membrane vesicles induced immunity to rainbow trout Oncorhynchus mykiss fry syndrome

Flavobacterium psychrophilum is the causative agent of bacterial cold water disease (BCWD) and rainbow trout ( Oncorhynchus mykiss) fry syndrome (RTFS). Logarithmic phase formalin-killed cells (FKC) of F. psychrophilum induced immunity to BCWD in ayu ( Plecoglossus altivelis) by using an oral administration. In this study, we investigated the effective antigens of logarithmic phase cells in rainbow trout. Rainbow trout fry immunized with logarithmic phase FKC resulted in near complete protection, but the vaccine effect was low in fry immunized with stationary phase FKC. Scanning electron microscopy showed that logarithmic phase cells had many membrane vesicles (MVs) on the surface of F. psychrophilum cells. The MVs were released into medium at the stationary phase. MVs rich supernatant was collected from the stationary phase culture supernatant by using an ammonium precipitation method. Immunization with MVs rich supernatant combined with stationary phase FKC resulted in a relative percentage survival (RPS) of 94–100%, but immunization with MVs rich supernatant only resulted in no protection against F. psychrophilum infection. These data show that MVs have an adjuvant efficacy and suggest that combination of MVs and cells is necessary to obtain efficient protection.

Dietary Na does not reduce dietary Cu uptake by juvenile rainbow trout

Rainbow trout Oncorhynchus mykiss fry in moderately hard water were exposed to control or high levels of dietary Cu (c. 6 and 580 ug Cu g food−1) at one of three levels of Na (1·5, 3·0 or 4·5%) in the diet, i.e. six experimental groups. Fish were fed a 4% body mass ration daily for 28 days and 10 individuals from each group were sampled every 7 days. Concentrations of Cu and Na were measured in the gills, liver, gut and remaining carcass of sampled fish. Growth was not affected and no consistent differences were found in mass, total lengths (LT) or indices of body condition among any of the groups on any sampling day. Copper concentration was significantly higher in tissues of Cu‐exposed groups, although within treatment types (control Cu v. high Cu diet), it did not differ consistently among groups that received different levels of dietary Na. Tissue Na concentration did not differ among any of the groups and did not show any marked changes over time. In Cu‐exposed groups, the proportion of total body Cu burden contained in the liver approximately doubled over time, from c. 30% on day 7 to c. 60% on day 28. In unexposed fish, the liver maintained c. 25% of the total Cu burden throughout the experiment. In contrast, the proportion of the total body Cu burden contained in the gut decreased somewhat over time in Cu‐exposed fish, from c. 40% on day 7 to c. 30% on day 28, and remained fairly stable at c. 25–30% in control groups, i.e. approximately equal to liver values. In all groups, the carcass contained by far the largest portion of the total Na content (>80%). Measurements made 36 h post‐feeding indicated that all six groups had much higher Na efflux relative to influx, suggesting that the fish were eliminating excess Na taken up from the diet, and differences in Na influx rates were small. Na efflux rate was significantly higher in the high Cu and high Na group than in the high Cu and low Na group. The results indicate that at the concentrations used in this experiment, dietary Na has little effect on dietary Cu uptake by juvenile rainbow trout, and dietary Cu has little effect on Na homeostasis.

Experimental bath infection with Flavobacterium psychrophilum, inducing typical signs of rainbow trout Oncorhynchus mykiss fry syndrome

Flavobacterium psychrophilum infection in salmonid fish, known as rainbow trout fry syndrome (RTFS) or bacterial coldwater disease (BCWD), is widespread in fish farms and natural waters. Despite many studies in which attempts at infection were made, an adequate method of infection has not yet been established. In this study, we evaluated a bath infection method in which we used bacteria at different stages of growth in the infection of rainbow trout Oncorhynchus mykiss. Rainbow trout with a mean body weight of 1.3 or 5.6 g, respectively, were infected by immersion in a bacterial suspension at different stages of growth (18 to 66 h shaking culture at 15 degrees C). The fish immersed in a logarithmic phase culture showed higher mortality than those in other culture phases. Indeed, 1.3 and 5.6 g fish showed typical clinical signs including ulcerative tissue of the trunk and lack of caudal fin edge. F. psychrophilum was detected by immunohistochemistry (IHC) in these tissue samples. These results indicate that experimental bath infection using a logarithmic phase bacterial solution is the most appropriate method for studies of infectious mechanisms.

Distribution ofMyxobolus cerebraliswithin a Free-Flowing River System during the Migration Period for Juvenile Anadromous Salmonids in Idaho

Abstract To gain a better understanding of the pathogen-associated risk to resident and anadromous salmonid populations, the distribution, prevalence, and intensity of Myxobolus cerebralis infections were assessed during the smolt migration period in the Salmon, Snake, and Clearwater rivers of Idaho. Sentinel exposures of rainbow trout Oncorhynchus mykiss fry (0.6 g) occurred at 10 locations beginning at the headwaters of the Salmon River and extending downstream to the Snake and Clearwater rivers from April 18–28 and May 15–25, 2001. Following exposure, fish were examined for the prevalence and severity of infection by means of histological, pepsin−trypsin digest, and nested polymerase chain reaction analyses. Infections did not occur in the portions of the Snake or Clearwater rivers included in this study but were found in the Salmon River at five locations during April and seven locations during May. The results during April demonstrated moderate to high prevalence of infection (65% and 75% at 900 and ...

Reduced territorial defence in rainbow trout fry exposed to a paper mill effluent: using the mirror image stimulation test as a behavioural bioassay

Rainbow trout Oncorhynchus mykiss fry exposed to a paper mill effluent showed increased EROD (ethoxyresorufin‐O‐deethylase) activity and reduced territorial aggression in mirror image stimulation (MIS) tests. These results suggest that the MIS test could be a useful tool to detect sublethal behavioural effects of pollution in fish fry.

Otolith Marking of Rainbow Trout Fry by Immersion in Low Concentrations of Alizarin Complexone

Experiments conducted on rainbow trout Oncorhynchus mykiss fry at Gaden Trout Hatchery, Jindabyne, New South Wales, Australia, sought to mark fish otoliths by immersion in the chemical alizarin complexone at a concentration consistent with minimal mortalities and clear markings. The fish were immersed in three concentrations of a solution of the chemical (10, 20, and 30 mg/L) for four periods (6, 12, 18, and 24 h). The pH of the solutions was adjusted to 8.8–8.9 with sodium bicarbonate, which increased the solubility of alizarin complexone. Marks were always detectable at all experimental concentrations under reflected light and/or ultraviolet light microscopy. All fry treated at a concentration of 10 mg/L survived for all exposure times. However, treatment and posttreatment mortality (within 28 d after treatment) at 20 and 30 mg/L were substantial over all periods. The treatment for 18 h at a concentration of 10 mg/L was chosen to mark a batch of 10,000 rainbow trout. Otoliths from these treated fish still had clear marks when harvested 157 d after treatment. The successful marking of rainbow trout without mortality using a concentration far lower than previously reported makes this treatment suitable and economical for batch marking of large numbers of small fish.

Dynamics ofMyxobolus cerebralisin the Lostine River, Oregon: Implications for Resident and Anadromous Salmonids

Myxobolus cerebralis, the myxozoan parasite causing whirling disease in salmonids, was first detected in northeastern Oregon in 1986. To better understand the potential impact of M. cerebralis on resident and anadromous salmonids in this region, a series of studies was conducted in the Lostine River, where infected fish were first reported. Rainbow trout Oncorhynchus mykiss fry were exposed in sentinel cages for 14 d at five sites from near the river's mouth to the headwaters during the period from July 1998 to November 1999. A subsample of exposed fry was assayed for the presence of DNA of M. cerebralis by polymerase chain reaction. Following four exposures, fish were held in the laboratory for 5 months of observation. The severity of infection in these fish was determined by histological examination, enumeration of spores isolated from the cranial cartilage, and observation of clinical signs. Sentinel fry became infected throughout the river from March to November, although the prevalence of infection increased in groups exposed in late summer. Infection prevalence was highest among fish exposed at the lower river site, ranging from 22.2% to 100%. Among fish held for 5 months, only those exposed in the lower river developed cranial lesions, whirling behavior, and black tail. The parasite's oligochaete host Tubifex tubifex was consistently identified only from the lower river site. Of the water quality measurements taken at each location, only conductivity correlated with infection prevalence (P < 0.001). These data indicate that juvenile rainbow trout, steelhead (the anadromous form of rainbow trout), and chinook salmon O. tshawytscha, which emerge during times of peak infection, are exposed to M. cerebralis and are likely to become infected in this river.

Standardization of experimental infection with Flavobacterium psychrophilum, the agent of rainbow trout Oncorhynchus mykiss fry syndrome.

Rainbow trout fry syndrome (RTFS) is a septicaemic infection of young rainbow trout Oncorhynchus mykiss occurring at low temperatures and responsible for severe economic losses in European fish farming. The causative agent, Flavobacterium psychrophilum, is a gliding bacterium, and difficulties in culturing it have long been an impediment to investigations on pathogenesis and immunity. Successful attempts at experimentally inducing the disease have been reported, but no experimental model resulting in well-controlled and quantitatively reproducible effects has been described. Recent improvements in F. psychrophilum cultivation made it possible to produce bacterial suspensions with nearly constant viability and to complete challenge injections in rainbow trout fingerlings, using accurately adjusted infective doses. Parenteral injection resulted in significant mortality, which was higher when administered intramuscularly (IM) than intraperitoneally (IP). Lethal doses 50 % lower than 10(3) colony forming units were consistently obtained in trout weighing 3 to 5 g, and the regular shape of the cumulative mortality curves appeared to lend itself to quantitative analyses. Bath experiments produced milder effects, although mortality ranging between 45 and 60 % was obtained in 6 g trout when skin lesions or stressors were induced along with bacterial exposure. Temperature, salinity and the process of preserving isolates (at least over short periods of time) did not seem to be associated with the severity of infection. Nevertheless, infection trials performed at 2 different locations differing both in water quality and in the system of fish maintenance resulted in different mortalities. These findings notwithstanding, the proposed IM model appears easy to apply under standardized experimental conditions and should contribute to effective advances in the study of the disease.

Evaluation of the protective immunogenicity of the N, P, M, NV and G proteins of infectious hematopoietic necrosis virus in rainbow trout oncorhynchus mykiss using DNA vaccines.

The protective immunogenicity of the nucleoprotein (N), phosphoprotein (P), matrix protein (M), non-virion protein (NV) and glycoprotein (G) of the rhabdovirus infectious hematopoietic necrosis virus (IHNV) was assessed in rainbow trout using DNA vaccine technology. DNA vaccines were produced by amplifying and cloning the viral genes in the plasmid pCDNA 3.1. The protective immunity elicited by each vaccine was evaluated through survival of immunized fry after challenge with live virus. Neutralizing antibody titers were also determined in vaccinated rainbow trout Oncorhynchus mykiss fry (mean weight 2 g) and 150 g sockeye salmon Oncorhynchus nerka. The serum from the 150 g fish was also used in passive immunization studies with naive fry. Our results showed that neither the internal structural proteins (N, P and M) nor the NV protein of IHNV induced protective immunity in fry or neutralizing antibodies in fry and 150 g fish when expressed by a DNA vaccine construct. The G protein, however, did confer significant protection in fry up to 80 d post-immunization and induced protective neutralizing antibodies. We are currently investigating the role of different arms of the fish immune system that contribute to the high level of protection against IHNV seen in vaccinated fish.

Simultaneous demonstration of infectious pancreatic necrosis virus (IPNV) and Flavobacterium psychrophilum in paraffin-embedded specimens of rainbow trout Oncorhynchus mykiss fry by use of paired immunohistochemistry

DAO Diseases of Aquatic Organisms Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials DAO 29:227-232 (1997) - doi:10.3354/dao029227 Simultaneous demonstration of infectious pancreatic necrosis virus (IPNV) and Flavobacterium psychrophilum in paraffin-embedded specimens of rainbow trout Oncorhynchus mykiss fry by use of paired immunohistochemistry Evensen Ø, Lorenzen E The Gram-negative bacterium Flavobacterium psychrophilum, which is the causative agent of rainbow trout fry syndrome (RTFS), and infectious pancreatic necrosis virus (IPNV), the causative agent of infectious pancreatic necrosis (IPN), are both highly pathogenic for rainbow trout fry. Several 'persistent' cases of RTFS have been observed concomitant with IPNV. Cultivation alone might not be sufficient for evaluation of the disease situation as both pathogens can be cultivated from fish that do not show any clinical signs of disease. In such cases it may be difficult to decide which pathogen should be considered the primary cause of the mortality observed. Further, it may be difficult to cultivate the bacterium in later stages of the disease or from dead fish that have been transported without cooling. In the case of (suspected) double infections it is therefore suggested that immunohistochemistry be included as a supplementary diagnostic tool, allowing correlation of the presence of either pathogen with pathological lesions. In the present study, fry representing different stages of RTFS from 3 clinical outbreaks were shown to suffer from ongoing double infections as demonstrated by immunohistochemistry and supported by cultivation of the 2 pathogens. The general finding was that single cells of the exocrine pancreas were positive for the virus, whereas bacteria were mainly demonstrated in the interstitial tissue surrounding the pancreatic islets. In some endothelial cells of the head kidney, both pathogens were detected in the same cell. These findings as well as various protocols in relation to the methodology are discussed. Rainbow trout fry syndrome · Flavobacterium psychrophilum · Infectious pancreatic necrosis · IPNV · Paired immunohistochemistry Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in DAO Vol. 29, No. 3. Publication date: June 19, 1997 Print ISSN:0177-5103; Online ISSN:1616-1580 Copyright © 1997 Inter-Research.