Rainbow Trout Eggs Research Articles

Investigation of the Use of Hops (Humulus lupulus) and Calendula (Calendula officinalis) As Disinfectants on the Hatching Efficiency of Rainbow Trout (Oncorhynchus mykiss)

This study investigates the potential application of plant-based resources with antimicrobial properties, namely hops (Humulus lupulus) and calendula (Calendula officinalis), as viable alternatives to commercial disinfectants for the prevention of fungal growth during the incubation period of rainbow trout (Oncorhynchus mykiss) eggs. Fertilized eggs were examined with daily 20-minute baths in 0.25 mg, 0.5 mg, and 1 mg concentrations throughout the incubation period (33-35 days). Control group, commercial formaldehyde, hops, and calendula groups were examined in triplicate for each concentration. As a result, the lowest hatching ratio was observed in the control group with 84.77%, while the hatching ratios in the other groups were as follows: commercial disinfectant group with 86.22%, hops group with 87.44% (0.25 mg), calendula group 88% with (0.25 mg), calendula group with 89% (0.5 mg), calendula group with 89.33% (1 mg), hops group with 89.55% (0.5 mg), and the highest hatching ratio was found in the hops group with 90.66% (1 mg). The lowest survival rate was observed in the control group with 85.22%, with the survival rates of the other groups were 86.44% in the commercial disinfectant group, 87.55% (0.25 mg) in the hops group, 88.55% (0.25 mg) in the calendula group, 88.88% (0.5 mg) in the calendula group, 89.33% (1 mg) in the calendula group, 89.55% (0.5 mg) in the hops group, and the highest survival rate was 90.11% (1 mg) in the hops group. In conclusion, it was specified that plant-based by-products (hops and calendula) could be used as alternative disinfectants to commercial chemicals in the disinfection of rainbow trout eggs and fry, and the most appropriate concentration was 1 mg.

Transglutaminase mediates the hardening of fish egg envelope produced by duplication of factor XIIIA gene during the evolution of Teleostei.

During the fertilization of fish eggs, the hardening of the egg envelope is mediated by transglutaminase (hTGase). After fertilization, TGase undergoes processing. We isolated hTGase from extracts of unfertilized and water-activated rainbow trout eggs. Rainbow trout hTGase (Rt-hTGase) appeared as an 80 kDa protein, and its processed form was 55 kDa. Their N-terminal amino acid sequences were nearly identical, suggesting processing in the C-terminal region. The specific activities were not significantly different, indicating that C-terminal processing does not activate the enzyme itself. We cloned the cDNA by reverse transcription polymerase chain reaction (RT-PCR) using degenerate primers followed by RACE-PCR. The deduced amino acid sequence of the cDNA was similar to that of factor XIII subunit A (FXIIIA). Molecular phylogenetic and gene syntenic analyses clearly showed that hTGase was produced by duplication of FXIIIA during the evolution to Teleostei. The 55 kDa processed form of Rt-hTGase is predominantly composed of an enzyme domain predicted from the amino acid sequence of the cDNA. It is hypothesized that the C-terminal domain of Rt-hTGase binds to egg envelope proteins, and that processing allows the enzyme to move freely within the egg envelope, increasing substrate-enzyme interaction and thereby accelerating hardening.

Transcript level of telomerase reverse-transcriptase (TERT) gene in the rainbow trout (Oncorhynchus mykiss) eggs with different developmental competence for gynogenesis.

Expression of the telomerase reverse-transcriptase (TERT) gene and activity of telomerase have been reported in the somatic tissues and gonads in fish irrespective of their age and size. Nevertheless, little is known about TERT expression in the fish eggs. In the current study, the presence of the TERT transcripts was confirmed in the rainbow trout ovulated eggs before and after activation with nonirradiated and UV-irradiated (gynogenesis) sperm. Eggs originating from eight females had high and comparable quality expressed by similar hatching rates. However, survival of the gynogenetic larvae that hatched from eggs activated with UV-irradiated sperm and further exposed to the high hydrostatic pressure (HHP) shock for duplication of the maternal chromosomes varied between females from 2.1 ± 0.4 to 40.5 ± 2.2%. Increased level of TERT transcripts was observed in eggs originating from two females, and gametes from only one of them showed improved competence for gynogenesis (27.3 ± 1.9%). In turn, eggs from the female that exhibited the highest survival after gynogenetic activation were characterized by the lowest expression of the TERT gene. Telomerase in rainbow trout eggs may compensate erosion of the telomeres during early embryonic development; however, its upregulation does not assure better development after gynogenetic activation.

Metabolic Rates of Rainbow Trout Eggs in Reconstructed Salmonid Egg Pockets

In situ evaluations of the metabolic rates (i.e., respiration and excretion) of salmonid eggs are mostly indirect, focusing on the sampling of hyporheic water from wild or artificial nests. Comparatively, experimental studies carried out under controlled, laboratory conditions are less abundant due to methodological difficulties. This study presents a novel experimental setup aimed to address this issue and enable the measurement of oxygen and dissolved inorganic nitrogen fluxes in simulated rainbow trout (O. mykiss) egg pockets. The experimental setup consists of reconstructed egg pockets in cylindrical cores under flow-through conditions. Live and dead eyed-stage eggs were incubated in a natural, sterilised gravel substrate. Hyporheic water circulation was ensured using peristaltic pumps, with the possibility to collect and analyse inflowing and outflowing water for chemical analyses. Microcosm incubations, with closed respirometry of eggs in water alone, were also carried out in order to infer the importance of microbial respiration in the simulated egg pockets. The results show an increasing trend in oxygen demand, due to the development of biofilm in the reconstructed egg pockets and increased egg respiration rates. Moreover, egg pockets showed positive ammonium net fluxes connected with the advancing developmental egg stage, while nitrate removal peaked during the last phase of the experiment, mainly due to the formation of oxic-hypoxic interfaces, leading to couple nitrification–denitrification processes. The suggested approach enables to test a number of in situ situations, including the effects of extreme hydrological conditions, sediment clogging and sudden changes in water chemistry or temperature on the survival and metabolic performances of nests, at different egg development stages.

Complete genome sequence and potential pathogenic assessment of Flavobacterium plurextorum RSG-18 isolated from the gut of Schlegel's black rockfish, Sebastes schlegelii.

Flavobacterium plurextorum is a potential fish pathogen of interest, previously isolated from diseased rainbow trout (Oncorhynchus mykiss) and oomycete-infected chum salmon (Oncorhynchus keta) eggs. We report here the first complete genome sequence of F. plurextorum RSG-18 isolated from the gut of Schlegel's black rockfish (Sebastes schlegelii). The genome of RSG-18 consists of a circular chromosome of 5,610,911 bp with a 33.57% GC content, containing 4858 protein-coding genes, 18 rRNAs, 63 tRNAs and 1 tmRNA. A comparative analysis was conducted on 11 Flavobacterium species previously reported as pathogens or isolated from diseased fish to confirm the potential pathogenicity of RSG-18. In the SEED classification, RSG-18 was found to have 36 genes categorized in 'Virulence, Disease and Defense'. Across all Flavobacterium species, a total of 16 antibiotic resistance genes and 61 putative virulence factors were identified. All species had at least one phage region and type I, III and IX secretion systems. In pan-genomic analysis, core genes consist of genes linked to phages, integrases and matrix-tolerated elements associated with pathology. The complete genome sequence of F. plurextorum RSG-18 will serve as a foundation for future research, enhancing our understanding of Flavobacterium pathogenicity in fish and contributing to the development of effective prevention strategies.

Good practices in aquaculture production and pathogen detection in rainbow trout farms

Objective: Evaluate compliance with Good Aquaculture Production Practices (BPPA) in Aquaculture Production Units (UPAs) for the incubation of rainbow trout eggs and detection of Aeromonas salmonicida and Aeromonas hydrophila using the Polymerase Chain Reaction (PCR).
 Design/methodology/approach: Seven egg incubation UPAs were located in Puebla and three in Veracruz. A structured questionnaire was applied to assess compliance with BPPA. Samples were taken from batches of trout hatchlings and analyzed for the presence of A. salmonicida and A. hydrophila using PCR. The results were compared with the health characteristics of the fish from each batch.
 Results: The UPAs certified for BPPA complied with authority recommendations and did not present fish morbidity. The UPAs that complied with fewer BPPA regulations had sanitary/health problems. Aeromonas hydrophila was detected in fish from UPAs that were less compliant with BPPA regulations. Aeromonas salmonicida was not detected.
 Study limitations/implications: Failure to comply with BPPA can cause infection from other trout pathogens that were not considered in this study.
 Findings/conclusions: Compliance with BPPA reduces health risks in the UPAs that incubate trout eggs.

Experimental exposure of rainbow trout eggs to water mould, Saprolegnia parasitica (Oomycota): intraspecific differences in pathogenicity

AbstractIn in vivo infection trials, rainbow trout eyed eggs were exposed to three Saprolegnia parasitica (Oomycota) isolates, which differed in biological and genetic characteristics. Infection prevalence, hatching rate, hatching dynamics of fish eggs were quantified, and the study was complemented with histopathology and phylogenetic analyses. We experimentally detected intraspecific differences in the pathogenicity of S. parasitica on rainbow trout eggs. The isolate from rainbow trout eggs was the most virulent to eggs of the same host, whereas isolates from carp skin and fry did not cause as much damage to the eggs. Comparing the outcome of two experimental settings, we confirmed that invasion of fish eggs is more effective by hyphae growth than by the actively moving zoospores. In addition, our findings highlighted that S. parasitica isolates with 100% identical ITS DNA sequences, could differ significantly in virulence. These isolates can be clearly distinguished based on a 650-bp DNA fragment of the DNA-directed RNA polymerase II subunit (RPB2) gene.

Corrigendum: Microbial control during the incubation of rainbow trout (Oncorhynchus mykiss) eggs exposed to humic acid

Corrigendum: Microbial control during the incubation of rainbow trout (Oncorhynchus mykiss) eggs exposed to humic acid

Identification and genetic characterization of Saprolegnia parasitica, isolated from farmed and wild fish in Finland.

Oomycete infections in farmed fish are one of the most significant disease issues in salmonid aquaculture worldwide. In the present study, Saprolegnia spp. in different farmed fish species in Finland were identified, and the molecular epidemiology of especially Saprolegnia parasitica was examined. We analysed tissue samples from suspected oomycete-infected salmonids of different life stages from a number of fish farms, as well as three wild salmonids. From collected oomycete isolates, the ITS1, 5.8S and ITS2 genomic regions were amplified, analysed phylogenetically and compared with corresponding sequences deposited in GenBank. Of the sequenced isolates, 91% were identified as S. parasitica. Isolates of yolk sac fry were identified as different Saprolegnia spp. Among the isolates from rainbow trout eggs Saprolegnia diclina dominated. In order to determine potential dominating clones among the S. parasitica, isolates were analysed using Multi Locus Sequence Typing (MLST). The results showed that one main clone contained the majority of the isolates. The MLST analysis showed four main sequence types (ST1-ST4) and 13 unique STs. This suggests that the Saprolegnia infections in farmed fish in Finland are not caused by different strains originating in the farm environment. Instead, one main clone of S. parasitica is present in Finnish fish farms.

Эффективность использования солевого раствора при искусственном осеменении икры радужной форели Oncorhynchus mykiss (Waibaum, 1972) и ладожской палии Salvelinus alpinus lepechini (Gmelin, 1788)

In order to increase the level of fertilization of eggs, the effect of buffer solution on sperm activity and the effectiveness of its use as a medium for insemination eggs of rainbow trout which was grown in conditions of flowing water and in recirculation aquaculture system (RAS), as well as Ladoga palia, were tested. In male trout and palia, the number of motile spermatozoa and their activity were higher in solution than in water. In trout which was grown in running water, the percentage of eggs fertilization increased significantly when use solution only in cases when the eggs were contaminated with the contents of burst eggs. In fish grown in the RAS, the replacement of water with a buffer solution increased the level of fertilization in all test variants, regardless of the presence or absence of contamination of the eggs. In Ladoga palia, the result of insemination was the same in water and in solution.

Microbial control during the incubation of rainbow trout (Oncorhynchus mykiss) eggs exposed to humic acid

IntroductionCultured fish species are increasingly exposed to fungi and bacteria in the rearing environment, often causing disease and mortality causing aquaculture producers to rely on the use of chemical therapeutants which may have negative consequences for both human and environmental health. This study investigated the effect of humic acid as a treatment to reduce fungal and bacterial infections to increase survival during the incubation of rainbow trout (Oncorhynchus mykiss) eggs.MethodsHumic acid, an aqueous extract of oxidized lignite was added to water entering both stacked tray and jar type incubators at a dosage rate of 5 mg/L from fertilization until hatching.ResultsThe water treatment eliminated observable fungus and significantly improved survival until hatching in the treated incubator trays (77.2%) compared to the untreated controls (55.5%) (p ≤ 0.001). Egg survival was not improved in the incubator jars. The humic acid reduced bacterial diversity, but only in the stacked tray incubators and altered bacterial composition of the water after 20 days of treatment.DiscussionThe treatment increased the bacterial abundance of Burkholderiales, positively associated with healthy fish eggs and decreased the abundance of Flavobacterium and Aeromonas, known fish pathogens. These findings support the topical treatment of humic acid as a potential alternative treatment to prevent fungal infections and reduce mortality during incubation of rainbow trout eggs.

Determination of Usage Doses of Some Chemical Substances in the Prevention of Fungal Infections in Rainbow Trout Eggs

Bu çalışmada, döllenmiş gökkuşağı alabalığı (Oncorhynchus mykiss) yumurtalarında görülen mantar etkenlerine karşı koruyucu tedbirlerin alınması amaçlanmıştır. Döllenmiş yumurtalarda mantar oluşumunu önlemek için farklı dozlardaki formaldehit (0,5, 1 ve 2 ml/l), iyot (0,5, 1 ve 2 ml/l), hidrojen peroksit (5, 10 ve 15 ml/l), elma sirke (1, 5 ve 10 ml/l) ve kaya tuzu (5, 10 ve 15 gr/l) 10'ar dakika süreyle günde bir kez kullanılmıştır. Bu kimyasal maddelerin farklı konsantrasyonlarındaki deneme sonuçları karşılaştırıldığında en iyi yaşama oranının 2 ml/l dozunda iyot uygulanan grupta olduğu tespit edilmiştir. Çalışma sonunda I. denemenin kontrol gurubundaki yumurtaların tamamının mantarlaşmaya bağlı olarak öldüğü tespit edilmiştir. Gökkuşağı alabalığı kuluçkahanelerinde sürdürülebilir bir üretim için döllenmiş yumurtaların ilk günden itibaren günde en az bir kez 2 ml/l dozunda polivinil pirolidon-iyot ile 10 dakika süreyle dezenfekte edilmesi gerektiği belirlenmiştir.

Copper uptake in adult rainbow trout irradiated during early life stages and in non-irradiated bystander trout which swam with the irradiated fish

Purpose This investigation forms part of a wider study into the legacy effects of exposure of rainbow trout eggs 38 h after fertilization, eyed eggs, yolk sac larvae (YSL) or first feeders to a single 0.5 Gy X-ray dose, including the induction of a bystander effect, by the irradiated fish, to non-irradiated fish. Fish may be exposed to multiple environmental stressors, including waterborne metals, during their lifespan and, while there are data on how the legacy of early life stage irradiation and bystander effect induction is affected by waterborne aluminum and cadmium, there are no studies into the effects radiation or the radiation induced bystander effect on metal uptake. Therefore the aim of this investigation was to determine if the legacy of early life stage irradiation included an effect on copper uptake by adult fish and by non-irradiated bystander adult trout which swam with the irradiated fish. Methods The four early life stages mentioned above were exposed to a single 0.5 Gy X-ray dose and then maintained, for two years with no further irradiation. At two years old the irradiated fish were allowed to swim, for 2 h with non-irradiated bystander trout (also two years old). After this time copper uptake was determined using 64Cu. Results Copper uptake was increased in adult trout irradiated as eggs at 48 h after fertilization and as first feeders but eyed egg or YSL irradiation had no effect. Copper uptake was also increased in the bystander trout which swam with trout irradiated as eggs at 48 h after fertilization and as eyed eggs but there was no effect on non-irradiated adult trout which swam with trout irradiated as YSL or first feeders. Conclusions When put in context with the proteomic changes observed in these fish we propose the increased copper uptake in adult trout irradiated as eggs at 48 h after fertilization could be part of an anti-tumorigenic response and the increase in copper uptake in adult trout irradiated as first feeders could be part of a potentially protective pro-apoptotic response. Similarly we propose the increase in copper uptake in non-irradiated adult trout, induced by trout irradiated as eggs at 48 h after fertilization or as eyed eggs, was part of the universally anti-tumorigenic nature of the X-ray induced bystander effect in fish. However this was exclusive to embryonic irradiation.

Antifungal activity of some essential oil nanoemulsions against Saprolegniasis in rainbow trout (Oncorhynchus mykiss) eggs

Antifungal activity of some essential oil nanoemulsions against Saprolegniasis in rainbow trout (Oncorhynchus mykiss) eggs

Determination of the Element Values of Rainbow Trout (Oncorhynchus mykiss Walbaum, 1792) Eggs

The objective of this study was to determine the amount of the elements of rainbow trout (Oncorhynchus mykiss Walbaum, 1792) eggs obtained from different stations. The study was conducted in 5 different production areas that are producing the most rainbow trout eggs in Turkey. Element analysis (Na, Mg, Al, P, K, Ca, Cr, Mn, Fe, Co, Ni, Zn, As, Se, Cd, Ba, Pb, Hg, and Cu) of rainbow trout eggs were performed using ICP-MS (Inductively Coupled Plasma- Mass Spectrometer). At the end of the study, it was determined that the daily consumption limit for selected elements (Ca, P, Mg, Zn, Mn, Ni and Se) was not exceeded in individuals consuming 100g of rainbow trout eggs per day. The daily intake recommended by the European Communities Commission was determined to be sufficient for the K, Ca, P, Mg, Fe, Zn, Cu and Mn elements in rainbow trout eggs. The Cd and Pb values of rainbow trout eggs obtained from different stations were determined significantly less than the values included in the Turkish Food Codex. The results of this study were thought to be important for both consumers and juvenile rainbow trout producers.

Prefertilization Exposure of Rainbow Trout Eggs to Per- and Polyfluoroalkyl Substances to Simulate Accumulation During Oogenesis.

Aqueous film-forming foams (AFFFs) are used in firefighting and are sources of per- and polyfluoroalkyl substances (PFAS) to the environment through surface runoff and groundwater contamination at defense and transportation sites. Little is known regarding the toxicity and bioaccumulation of newer AFFF formulations containing novel PFAS. To mimic maternal transfer of PFAS, prefertilization rainbow trout eggs were exposed to three PFAS using novel methodologies. Batches of unfertilized oocytes were exposed for 3 h to 0, 0.01, 0.1, 1, or 10 µg/ml separately to perfluorooctanoic acid, perfluorohexanoic acid, or perfluorooctanesulfonic acid in either coelomic fluid or Cortland's solution. After exposure, the gametes were fertilized and rinsed with dechlorinated water. Egg yolk was aspirated from a subset of fertilized eggs for PFAS quantification. Each PFAS was detected in yolks of eggs exposed to the respective PFAS, and yolk concentrations were directly proportional to concentrations in aqueous media to which they were exposed. Exposure in coelomic fluid or Cortland's solution resulted in similar concentrations of PFAS in egg yolks. Ratios of PFAS concentrations in oocytes to concentrations in exposure media (oocyte fluid ratios) were <0.99 when exposed from 0.01 to 10 µg/ml and <0.45 when exposed from 0.1 to 10 µg/ml for both media and all three PFAS, demonstrating that the water solubility of the chemicals was relatively great. Prefertilization exposure of eggs effectively introduced PFAS into unfertilized egg yolk. This method provided a means of mimicking maternal transfer to evaluate toxicity to developing embryos from an early stage. This method is more rapid and efficient than injection of individual fertilized eggs and avoids trauma from inserting needles into eggs. Environ Toxicol Chem 2021;40:3159-3165. © 2021 SETAC.

Prevention of Saprolegniasis in rainbow trout (Oncorhynchus mykiss) eggs using oregano (Origanum onites) and laurel (Laurus nobilis) essential oils

The present study investigated the antifungal effects of essential oils of oregano (Origanum onites) and laurel (Laurus nobilis) on Saprolegniasis, a disease that occurs in rainbow trout eggs during the incubation period. Oregano and laurel were ground after drying, and essential oils were obtained by water distillation method using a Clevenger apparatus. The essential oils were added to potato dextrose agar (PDA) at the rates of 1-1000ppm, and the minimum inhibitory concentration (MIC) was determined as 250ppm whereas the minimum lethal concentration (MLC) was determined to be 500ppm for both plants. In the in vivo trials, fertilized eggs were treated with predetermined doses either by bathing during water hardening and incubation period or only during incubation period, and death rates were monitored during embryological development. The best larvae hatching rate was determined in 500ppm oregano and 500ppm laurel groups treated during water hardening plus daily as 82.11% and 79.87%, respectively. According to the results, it was determined that oregano and laurel essential oils exhibited better results in all doses compared with the negative control group, and 500ppm dose had a better effect than the positive control group treated with formalin.

Comparisons among rainbow trout, Oncorhynchus mykiss, populations of maternal transcript profile associated with egg viability

BackgroundTranscription is arrested in the late stage oocyte and therefore the maternal transcriptome stored in the oocyte provides nearly all the mRNA required for oocyte maturation, fertilization, and early cleavage of the embryo. The transcriptome of the unfertilized egg, therefore, has potential to provide markers for predictors of egg quality and diagnosing problems with embryo production encountered by fish hatcheries. Although levels of specific transcripts have been shown to associate with measures of egg quality, these differentially expressed genes (DEGs) have not been consistent among studies. The present study compares differences in select transcripts among unfertilized rainbow trout eggs of different quality based on eyeing rate, among 2 year classes of the same line (A1, A2) and a population from a different hatchery (B). The study compared 65 transcripts previously reported to be differentially expressed with egg quality in rainbow trout.ResultsThere were 32 transcripts identified as DEGs among the three groups by regression analysis. Group A1 had the most DEGs, 26; A2 had 15, 14 of which were shared with A1; and B had 12, 7 of which overlapped with A1 or A2. Six transcripts were found in all three groups, dcaf11, impa2, mrpl39_like, senp7, tfip11 and uchl1.ConclusionsOur results confirmed maternal transcripts found to be differentially expressed between low- and high-quality eggs in one population of rainbow trout can often be found to overlap with DEGs in other populations. The transcripts differentially expressed with egg quality remain consistent among year classes of the same line. Greater similarity in dysregulated transcripts within year classes of the same line than among lines suggests patterns of transcriptome dysregulation may provide insight into causes of decreased viability within a hatchery population. Although many DEGs were identified, for each of the genes there is considerable variability in transcript abundance among eggs of similar quality and low correlations between transcript abundance and eyeing rate, making it highly improbable to predict the quality of a single batch of eggs based on transcript abundance of just a few genes.

Inter-clutch egg differences and androgenesis in rainbow trout (Oncorhynchus mykiss, Walbaum 1792)

Abstract Ionizing radiation (IR) is applied to inactivate the nuclear genome in rainbow trout eggs during induced androgenetic development. However, IR-generated reactive oxygen species (ROS) may affect developmental potential of eggs and reduce the effectiveness of androgenesis. To verify this assumption, androgenetic development of rainbow trout was induced in eggs irradiated with 350 Gy of X-rays. Survival rates, pH of the ovarian fluid and activity of antioxidant enzymes, including SOD, CAT and GPx, were examined in non-irradiated and irradiated eggs originating from four females. Survival rates of androgenetic embryos developing in eggs produced by different females varied from 1% to 57% and these inter-clutch differences were significant. Eggs from female F4, which showed the highest developmental competence for androgenesis, also showed increased activities of SOD, CAT and GPx enzymes. The pH value of the ovarian fluid of each female was over 8 before and after irradiation, therefore it seems that radiation did not affect the ovarian fluid pH. Considering the above-mentioned inter-clutch differences, a strong maternal effect on the effectiveness of androgenesis can be assumed. Eggs with increased activity of antioxidant enzymes before irradiation should be expected to show increased developmental competence for androgenesis.

The first detection and in vivo pathogenicity characterization of Saprolegnia delica from Kashmir Himalayas

Saprolegniosis caused by ubiquitous oomycetes pathogen Saprolegnia spp. poses a serious threat to the welfare and fortitude of the fish industry, therefore having potential to inflict severe socio-economic losses to the stakeholders involved in aquaculture trade. In this study, Saprolegnia delica was isolated for the first time from naturally infected farmed fish in Kashmir Himalayas, India. The isolate was identified by a combination of (macro and micro morphological) and molecular approaches, the latter involving sequencing of the entire internal transcribed spacer region. The identified S. delica was further evaluated for its pathogenic potential in an artificial setting by using in vivo models, Scale Carp (Cyprinis carpio communis) fingerlings and Rainbow Trout (Oncorhynchus mykiss) eggs. We used intraperitoneal injection and bath immersion means for challenging the host, our results indicated that S. delica is highly pathogenic to both, the fish fingerlings of scale carp and the eggs of rainbow trout. Also, intraperitoneal inoculation was observed to cause higher mortality (55%) in scale carp fingerlings compared to the bath immersion method. The postmortem and histopathology analyses revealed that S. delica is severely infecting skin, gills, eyes and other visceral organs, which led to the infection of multiple organs causing high mortality. However, severity of the disease depends on the route of infection in fingerlings, the time of exposure and the concentration of spores inoculated to eggs. The study presents the first isolation and detection of S. delica infecting rainbow trout in fish farm of Kashmir valley, hence, provides a way forward for the establishment of management strategies aimed at controlling saprolegniosis.