Search Results (96)

Vaccination is the most effective method to counteract infectious diseases in farmed fish. It secures aquaculture production and safeguards the wild stock and aquatic ecosystem from catastrophic contagious diseases. In vaccine development, recombinant subunit vaccines are favorable candidates since they can be economically produced in large quantities without growing many pathogens, as in inactivated or attenuated vaccine production. However, recombinant subunit vaccines are often weak or deficient in immunogenicity, resulting in inadequate defenses against infections. Technologies that can increase the immunogenicity of recombinant subunit vaccines are in desperate need. Enhanced green fluorescence protein (EGFP) has a low antigenicity and is susceptible to folding changes and losing fluorescence after fusing with other proteins. Using these valuable features of EGFP, we comprehend two amphipathic alpha-helical peptides, AH1 and AH3, derived from Hepatitis C virus and Influenza A virus, respectively, that can induce high immune responses of their fused EGFP in fish without affecting their folding. AH3-EGFP has the most elevated cell binding, significantly 62% and 36% higher than EGFP and AH1-EGFP, respectively. Immunizations with AH1-EGFP or AH3-EGFP significantly induced higher anti-EGFP antibody levels 300–500-fold higher than EGFP immunization after the boost injection in rainbow trout. Our results suggest that AH1 and AH3 effectively increase the immunogenicity of EGFP without influencing its structure. Further validation of their value in other recombinant proteins is necessary to demonstrate their broader utility in enhancing the immunogenicity of subunit vaccines. We also suggest that EGFP and its variants are promising candidates for initially screening proper immunogenicity-enhancing peptides or proteins to advance recombinant subunit vaccine development. Full article

This study investigated the seasonal and spatial dynamics of off-flavour compounds—geosmin and 2-methylisoborneol (2-MIB)—in an intensive rainbow trout (Oncorhynchus mykiss) aquaculture system for human consumption in western Spain. Weekly water and fish flesh samples were collected over a 12-month period from three farms supplied by the River Tormes. Physicochemical parameters, determination of geosmin and 2-MIB by SPME-GC-MS, microbial counts, and microbial community composition were assessed alongside volatile compound concentrations. Geosmin and 2-MIB showed marked seasonal variation, with peak levels in water and fish flesh during spring and summer, correlating positively with temperature. Geosmin accumulation in fish was highest in the downstream farm, suggesting cumulative exposure effects. In contrast, 2-MIB was detected only in water and at lower concentrations. Microbial analyses revealed high bacterial and fungal diversity, including cyanobacterial taxa such as Phormidium setchellianum and Pseudoanabaena minima, known producers of geosmin and 2-MIB. These findings highlight the importance of water microbiota and environmental conditions in off-flavour development. Managing cyanobacterial populations and monitoring spatial-temporal variability are essential to mitigate the development of earthy or musty flavours and economic losses in aquaculture systems. Full article

Global warming represents one of the most pressing environmental challenges to cold-water fish farming. Heat stress markedly alters the mucosal symbiotic microbiota and intestinal microbial metabolites in fish, posing substantial barriers to the healthy artificial breeding of rainbow trout (Oncorhynchus mykiss). However, the relationship between mucosal commensal microbiota, intestinal metabolites, and host environmental adaptability under heat stress remains poorly understood. In this study, rainbow trout reared at optimal temperature (16 °C) served as controls, while those exposed to maximum tolerated temperature (24 °C, 21 d) comprised the heat stress group. Using 16S rRNA amplicon sequencing and ultra-high-performance liquid chromatography–mass spectrometry (UHPLC-MS), we analysed the mucosal commensal microbiota—including gastrointestinal digesta, gastrointestinal mucosa, skin mucus, and gill mucosa—and intestinal metabolites of rainbow trout under heat stress conditions to explore adaptive and regulatory mechanisms. Analysis of microbial composition and diversity revealed that heat stress exerted the greatest impact on the diversity of gill and skin mucus microbiota, followed by gastrointestinal digesta, with relatively minor effects on the gastrointestinal mucosa. At the phylum level, Proteobacteria, Firmicutes, and Bacteroidetes were predominant in the stomach, intestine, and surface mucosa. At the genus level, Acinetobacter showed the greatest increase in abundance in skin and gill mucosa under heat stress, while Enterobacteriaceae exhibited the most pronounced increase in intestinal digesta, gastric digesta, and gastric mucosa. Differential metabolites in the intestinal digesta under heat stress were predominantly enriched in pathways associated with amino acid metabolism, particularly tryptophan metabolism. This study provides a comprehensive characterisation of microbiota and metabolic profile alterations in rainbow trout under heat stress condition, offering a theoretical foundation for understanding the response mechanisms of fish commensal microbiota to thermal stress. Full article

Global food production, both aquatic and terrestrial, is rife with sustainability issues. Aquaculture is a rapidly growing industry that is on track to surpass wild-caught fishery production by 2030. The integration of aquaculture and agriculture systems could help to reduce some of their respective and shared environmental issues. Integrated Aquaculture–Agriculture (IAA) has been shown to provide a variety of benefits to both aquaculture and agriculture including increased system water use efficiency (WUE), a reduction in fertilizer use, and increases in total farm yield and resilience. This study was performed to examine the potential for rainbow trout aquaculture effluent to improve the yield, nutrient composition, and WUE of lettuce, as well as act as a partial fertilizer replacement. We used four irrigation treatments throughout the experiment: city water, aquaculture effluent, city water with added organic fertilizer, and aquaculture effluent with added organic fertilizer. Throughout the trial, there were some issues of herbivory in the growing plot, but overall, the lettuce receiving city water with organic fertilizer (30. ± 3.4 g/plant) showed significantly higher fresh biomass than effluent treatments (18 ± 1.4 g/plant and 17 ± 2.9 g/plant) at the end of the trial. We did not detect any significant differences among treatments in the macro- and micronutrients of the lettuce shoots and roots. However, the WUE of effluent treatments (4.4 ± 0.030 kg/m³ and 1.0 ± 0.070 kg/m³) was greater than that of organic fertilizer (0.28 ± 0.050 kg/m³) and control treatments (0.23 ± 0.040 kg/m³). The results indicate that adopting IAA in California could improve statewide WUE and conserve water for sustainable agricultural production. Full article

Seasonal changes in geosmin and selected terpenes in rainbow trout (Oncorhynchus mykiss) in an outdoor recirculated aquaculture system (RAS) in Denmark were followed over three months. In the water, geosmin varied from 4.1 to 25.7 ng/L, but no seasonal trends were obvious. Variable trends occurred for geosmin relative to concentrations of inorganic N (ammonium, nitrite, and nitrate) and phosphate, and did not indicate a general relationship. The geosmin content of the fish ranged from 669 to 2264 ng/kg and covaried with geosmin in the water. The average number of the geoA gene (encoding geosmin synthase) was 2.41 × 10⁵ copies/L in the water and 3.29 × 10⁷ copies on each bio-element in the biofilter. In only one of the three examined RAS units, geosmin in the water and on the bio-elements covaried with the number of geoA copies. Among the identified four terpenes in the fish flesh, α-pinene was dominant and made up 55.9–62.8% of the terpenes. The presence of aroma-active terpenes in the fish suggests that not only geosmin concentrations should be considered when characterizing taste profiles of farmed rainbow trout. Full article

An attempt to apply extracts of the brown algae Cystoseira myrica and Cystoseira trinodis for the quality enhancement of fish was carried out. Aqueous, ethanolic, and aqueous–ethanolic (1:1, v/v) extracts of both algae were included, respectively, in the icing system employed for the chilled storage of farmed rainbow trout (Oncorhynchus mykiss). Chemical and microbiological quality indices were determined for a 0–16-day storage period. At the end of the experiment, all alga-treated fish revealed lower (p < 0.05) pH values and lower (p < 0.05) lipid hydrolysis (free fatty acid assessment) and oxidation (thiobarbituric acid index) development when compared to Control samples. Regarding microbial activity development (aerobe, psychrophilic, Enterobacteriaceae, proteolytic, and lipolytic counts), lower average values were detected in most cases in fish corresponding to alga-treated batches; preservative effects were found more important at advanced storage times. In general, water and water–ethanol extracts led to higher (p < 0.05) inhibitory effects than their counterpart ethanol extracts. Higher (p < 0.05) total polyphenol values were detected in water and water–ethanol extracts of both algae than in their counterpart extracts obtained only with ethanol. A novel, simple, and practical strategy for the quality enhancement and commercialization of chilled farmed rainbow trout is proposed by employing different extracts obtained from both Cystoseira species. Full article

The major histocompatibility complex (MHC) consists of genes involved in immune response and molecular discrimination between self and non-self. MHC genes are the most polymorphic in vertebrates. The origin and maintenance of polymorphism in MHC genes in populations is still unresolved. Mechanisms such as sexual selection and heterozygote advantage have been suggested as explanations for this high variability. In this study, a farmed population of rainbow trout (Oncorhynchus mykiss) characterized by the presence of specific MHC class IIB gene haplotypes at a frequency higher (30%) than that expected from random matings was investigated. Therefore, it was hypothesized that disassortative matings occur with an adaptive advantage for females, resulting in improved reproductive performance when mated with individuals with similar MHC haplotypes. Genetic analyses of the breeders were performed to define the MHC haplotypes and to perform specific matings. The effect of mating was evaluated by analyzing the survival rate of the offspring at various stages of incubation until swim-up. The reproductive performance of the offspring derived from specimens with similar haplotypes showed a better survival trend during the first life stages and reduced malformations. The results obtained are in contrast with the heterozygous advantage theory, therefore it was hypothesized, as for other salmonid species, the presence of a positive selection towards locally adapted MHC genes that promotes reproduction between genetically similar individuals. Full article

In an aquaponic system, fish and plants are cultivated together in a symbiotic environment where they mutually benefit, using significantly less water than traditional farming methods. The main aim of this study was to investigate the occurrence of antimicrobial resistance in two aquaponic systems implemented in two Chilean high schools using rainbow trout and lettuce cultures. When water samples (fish tank, biofilter, and plant raft) were analyzed over a three-month period, no resistance to oxytetracycline was detected, whereas the occurrence of resistance to florfenicol was rather small, ranging from 0.01% to 3.1% of bacterial culturable counts. Eighteen isolates were recovered from various sources as representatives of the florfenicol-resistant population, and all of them belonged to the Pseudomonas genus, showing a multi-drug-resistance phenotype and exhibiting simultaneous resistance to 7–13 antimicrobials. All isolates exhibited resistance to amoxicillin, chloramphenicol, florfenicol, and furazolidone and susceptibility to meropenem, oxytetracycline, oxolinic acid, flumequine, ciprofloxacin, and enrofloxacin. Five and two isolates carried the amphenicol-resistance-encoding genes floR and cmlA, respectively, whereas no carriage of integrons or the fexA, fexB, pexA, optrA, and cfr genes encoding for florfenicol resistance was detected. Eleven isolates carried plasmids, but only two of them were able to transfer their plasmid content by conjugation. The knowledge of the microbiome associated with aquaponic systems is still scarce, and their role as potential reservoirs of antimicrobial-resistant bacteria and related genes of these systems must be elucidated. Full article

Rainbow trout, or mykiss (Oncorhynchus mykiss), is one of the most popular species used in aquaculture and has been naturalized worldwide, including in the Central Asian Balkhash basin, which has unique aboriginal fish fauna. Both rainbow trout from European farms and wild mykiss from Kamchatka were introduced to some mountain lakes and rivers of the Balkhash basin about 50 years ago. This study investigates the current distribution and life history traits of the alien species and its possible impact on the local fish fauna. This study showed that the rainbow trout occupies various habitats in the Ili River basin: mountain lakes, fast-flowing mountain rivers, and lowland rivers with slow currents and warm water (up to +27 °C). Rainbow trout from European fish farms dominate the mountain Middle Kolsay Lake, while the wild trout from Kamchatka occupies the small Ulken Kokpak River. Both co-occur in the Chilik River. Contrary to that in other regions, the distribution of rainbow trout in the Balkhash basin remained almost the same after their introduction. Broad intrapopulation variability in terms of size, growth rate, and maturation age was revealed, apparently as a result of adaptation to the new environment and intrapopulation competition. In particular, the growth rate has decreased, but life span, surprisingly, has increased as compared to the originally introduced fish. Intrapopulation variation in growth and maturity patterns was also noted. Differences in skin coloration between highland (cold-water) and lowland (warm-water) populations were discovered. The feeding mode of naturalized trout is insectivorous (insect imago), indicating that it occupies its own niche in the local fish communities. The largest population of rainbow trout was recorded in the Lower Kolsay Lake, lowering the population of native fish species, while in other localities, no negative impact on local fish communities was recorded. Full article

Farmed fish are regularly subjected to various stressors due to farming practices, and their effect in the context of a disease outbreak is uncertain. This research evaluated the effects of unpredictable repeated stress in rainbow trout challenged with the ciliate Ichthyophthirius multifiliis, known to cause white spot disease in freshwater fish. Before and after the pathogen exposure, fish were handled with a random rotation of three procedures. At 7 days post-infection (dpi), the parasite burden was evaluated in fish and in the tank’s water, and the local and systemic immune responses were investigated in the gill and spleen, respectively. The fish mortality was recorded until 12 dpi, when all the fish from the infected groups died. There was no statistical difference in parasite burden (fish and tank’s water) and infection severity between the two infected fish groups. The immune gene expression analysis suggested a differential immune response between the gill and the spleen. In gills, a T helper cell type 2 immune response was initiated, whereas in spleen, a T helper cell type 1 immune response was observed. The stress has induced mainly upregulations of immune genes in the gill (cat-1, hep, il-10) and downregulations in the spleen (il-2, il-4/13a, il-8). Our results suggested that the unpredictable repeated stress protocol employed did not impair the fish immune system. Full article

Given the overexploitation of fisheries and the growing consumption of sea products, aquaculture is emerging as an alternative to meet the demand for protein at regional, national, and global levels. In northern Chile, the foothills of the Andes offer an opportunity for sustainable economic diversification. In this study, results of a rainbow trout (Oncorhynchus mykiss) culture in a recirculation system are presented, analyzing its growth and performance under altitude conditions. The research was carried out in Copaquilla, a small area in the foothills of northern Chile, 3000 m above sea level. Five thousand 15 g juvenile trout were acquired and transported by land from the Rio Blanco fish farm, successfully traveling more than 2100 km. During the 20-month-long culture, several growth parameters were evaluated, including specific growth rate, percentage of weight growth, feed conversion factor, survival, and Fulton’s condition factor. All these parameters were within the normal growth range for trout, evidencing good-quality growth of the organisms. The results offer evidence that rainbow trout farming at 3000 m above sea level is viable and presents a viable performance, opening new opportunities for aquaculture in northern Chile. Full article

A fundamental aspect of fish farms is their energy consumption, which is essential for various activities like water supply, pool aeration, thermal conditioning, lighting, filtration, and recirculation systems. Due to volatile prices and rising energy use, costs have surged, requiring energy-optimization solutions for economic viability and pollution reduction. In this context, this study aims to evaluate renewable energy integration in these installations based on real data, assessing current operations, proposing renewable energy optimization, and exploring hydrogen systems for energy needs, using HOMER PRO^® to analyze different scenarios. For this purpose, it targets a rainbow trout farm in Estonia, and by simulating the various hybrid configurations proposed, it aims to optimize its energy production and storage, ensuring feasibility and technical integration. The results of the simulations primarily demonstrate the potential for using the byproduct of electrolysis to cover the oxygen demand in these types of processes, reducing the demand for raw materials. Additionally, it is observed that storage enhances performance in isolated systems; however, the economically viable integration of hydrogen technology requires three assumptions: a regulatory framework allowing surplus energy sales to the grid, an existing infrastructure for hydrogen trading, and high energy purchase prices. Full article

The production and release of cortisol during stress responses are key regulators of growth in teleosts. Understanding the molecular responses to cortisol is crucial for the sustainable farming of rainbow trout (Oncorhynchus mykiss) and other salmonid species. While several studies have explored the genomic and non-genomic impacts of cortisol on fish growth and skeletal muscle development, the long-term effects driven by epigenetic mechanisms, such as cortisol-induced DNA methylation, remain unexplored. In this study, we analyzed the transcriptome and genome-wide DNA methylation in the skeletal muscle of rainbow trout seven days after cortisol administration. We identified 550 differentially expressed genes (DEGs) by RNA-seq and 9059 differentially methylated genes (DMGs) via whole-genome bisulfite sequencing (WGBS) analysis. KEGG enrichment analysis showed that cortisol modulates the differential expression of genes associated with nucleotide metabolism, ECM-receptor interaction, and the regulation of actin cytoskeleton pathways. Similarly, cortisol induced the differential methylation of genes associated with focal adhesion, adrenergic signaling in cardiomyocytes, and Wnt signaling. Through integrative analyses, we determined that 126 genes showed a negative correlation between up-regulated expression and down-regulated methylation. KEGG enrichment analysis of these genes indicated participation in ECM-receptor interaction, regulation of actin cytoskeleton, and focal adhesion. Using RT-qPCR, we confirmed the differential expression of lamb3, itga6, limk2, itgb4, capn2, and thbs1. This study revealed for the first time the molecular responses of skeletal muscle to cortisol at the transcriptomic and whole-genome DNA methylation levels in rainbow trout. Full article

Aquaculture products are important parts of human nutrition due to their healthy components; however, they may contain elements that are potentially toxic to consumers. The aim of the study was to detect the concentration of As, Cd, Hg, and Pb by inductively coupled plasma optical emission spectroscopy in rainbow trout (Oncorhynchus mykiss) originated from an aquaculture farm in Italy. The amount of As was 1.65 ± 0.49 mg/kg; however, the total As cannot be evaluated due to the absence of official regulation. The calculated EDI and THQ for the inorganic As content were below the reference values. The level of Cd was higher than the regulated limit in 30% of the samples; however, its EDI and THQ were below the recommended limit. The concentration of Hg was below the regulated maximum limit in all the samples. The detected amount of Pb was above the maximum limit in 10% of the samples; however, EDI and THQ were below the reference dose and recommended value. Despite higher concentrations of Cd and Pb than the official regulated limit, HI was below 1 for adults; thus, the consumption of the investigated rainbow trout is safe, but it was above the official regulated limit for children, resulting in a slight risk, particularly during long-term intake. Full article

Infectious pancreatic necrosis virus (IPNV) causes economic losses with a highly variable mortality rate worldwide, especially in rainbow trout. The virus has a double-stranded bi-partite RNA genome designated segment A and B. New complete genome sequences of nine rainbow trout isolates from Turkey were determined and subjected to phylogenetic analysis, identifying all as genotype 5 (serotype Sp). A time-dependent change in the extended pathogenicity motif of VP2 from P217T221A247 (PTA) to PTE P217T221E247 over a period of 10 years was identified. A wider analysis of 99 IPNV sequences from Turkey and Iran revealed the emergence of the motif PTE from 2007 to 2017, inducing significant morbidity in fry by 2013. In fact, displacement of the PTA motif, by the PTE motif in IPNV isolates appeared to be connected to a production peak of rainbow trout in 2013. An additional CAI analysis provided more evidence, indicating that rainbow trout culture in Turkey has an influence on the evolution of IPNV. Full article