Rainbow Trout Oncorhynchus Mykiss Research Articles

Growth performance, health status, gut microbiome, and expression of immune and growth-related genes of rainbow trout (Oncorhynchus mykiss) fed diets with pea protein replacement of fish meal

The need for fish meal constrains fish farming and significantly impacts sustainability of the aquaculture industry. Hence, it is important to investigate the use of plant-based protein sources in fish diets. The present study was conducted to determine the effects of different levels of fish meal (FM) replacement by pea protein (PP) in a 60-day feeding experiment in rainbow trout, Oncorhynchus mykiss. Effects on growth performance, body composition, hematology, serum biochemistry and immunology, and immune (TNF-α, IL1-ß and Il-8) and growth-related (GH and IGFI) gene expression were investigated. Five experimental diets (45% protein and 20% lipid) differed in replacement level of FM by PP at rates of 0% (control (PP0)), 25% (PP25), 50%(PP50), 75%(PP75) and 100%(PP100). Fish were fed with experimental diets in triplicate twice daily. The best growth performance was obtained in PP0 and PP25 groups. While fat ratios of fish fillets significantly differed (p < 0.05), there was no significant effects on protein ratios (p < 0.05). There was no significant change in the hematological values of fish, except those fed the PP100 diets, which displayed a reduction in eyrthocyte counts, hemoglobin content and hematocrit. As PP supplementation increased fish showed elevated serum glucose, total protein, cholesterol and myeloperoxidase activity and decreased glutamic pyruvic transaminase and alkaline phosphatase activity. Fish fed diets with between 25 and 75% replacement showed a decline in lactic acid bacteria in the gut. Significant increases in expression were observed in the liver of the PP25 fish relative to the 0% control for all immune and growth-related genes except for IL1-ß. These data suggest that up to 25% of FM can be replaced by PP without any adverse effects on rainbow trout.

Pelagic fish spared from ocean catch by integrating Black Soldier Fly Larvae in U.S. aquaculture production

The sustainability challenges associated with utilizing forage fish sourced from ocean catch as fish meal and fish oil in the aquaculture industry has increased the demand for alternative feeds. Previous research indicates that Black Soldier Fly Larvae (BSFL; Hermetia illucens) can partially replace fish meal and/or fish oil in the diets of farmed aquaculture species without compromising fish growth or efficiency. The objective of our study was to identify the amount of pelagic fish from ocean catch that could be spared from fish meal and fish oil production by integrating BSFL in the diets of three aquaculture species, Atlantic Salmon (Salmo salar), Rainbow Trout (Oncorhynchus mykiss), and Whiteleg Shrimp (Litopenaeus vannamei) in the United States. Annual output for these aquaculture species was collected for 2017–2019. For each specie, we calculated the total metric tons (MT) of spared pelagic fish, by taxa, from fish meal and fish oil production based on total lifetime food intake and dietary replacement rates of fish meal and fish oil by BSFL as established in previous literature. At the highest level of dietary BSFL substitution for fish meal and/or fish oil that did not sacrifice performance of the three aquaculture species, 40,843 MT of pelagic fish could be spared from ocean catch in the U.S. per year. Therefore, integrating BSFL in the diets of aquaculture species could reduce the demand for pelagic fish sourced from ocean catch and positively contribute to the sustainability of aquaculture production.

Rainbow trout (Oncorhynchus mykiss, Walbaum 1792) adenocarcinoma investigation with various diagnostic imaging techniques.

Diagnostic imaging techniques provide a new aspect of the ante-mortem and post-mortem diagnostics in fish medicine. Ultrasonography, computed tomography (CT) and magnetic resonance imaging (MRI) can provide more information about the internal organs and pathognomic lesions. The authors used diagnostic imaging techniques to evaluate and describe the neoplastic malformation in a 3-year-old female rainbow trout (Oncorhynchus mykiss). The fish was examined with Siemens Somatom Definition AS + CT scanner and Siemens Biograph mMR scanner. The animal was lethargic and showed anorectic signs and muscular dystrophy. During the post-mortem investigation, histopathology and immunohistochemistry were also performed allowing us to identify the neoplasms. The results showed a large soft tissue mass in the first mid-intestine segment, which proved to be an adenocarcinoma. This subsequently led to digestion problems and absorption disorders. Immunohistochemically, neoplastic cells of carcinoma revealed E-cadherin and pancytokeratin positivity. This is the first study to report the use of MRI and CT for studying gastrointestinal adenocarcinoma in rainbow trout.

Dietary Supplementation of Chromium Picolinate does not affect Growth Performance and Feed Conversion Ratio of Rainbow Trout (Oncorhynchus mykiss)

Aims: A growth experiment was conducted to explore the impact of dietary chromium on the growth performance and feed conversion ratio of rainbow trout (Oncorhynchus mykiss).&#x0D; Study Design: Original Research Article&#x0D; Place and Duration of Study: Fisheries Research Station (FRS), Trishuli Nepal, between November 1 to January 29, 2023.&#x0D; Methodology: A total of 270 healthy and equal sized- O. mykiss (initial weight: 27g) were fed on a non-supplemented basal diet (Cr-Pic0), or a basal diet supplemented with 0.4g/kg Cr-Pic (Cr-Pic0.4), or a basal diet supplemented with 1.2g/kg Cr-Pic (Cr-Pic1.2) for 90 days. Each diet was randomly assigned to three replicate groups of 30 fish per flowthrough raceway tanks for 90 days and fed to apparent satiation twice daily.&#x0D; Results: Upon conclusion of the feeding trial, the results showed no significant differences in final weight, weight gain, specific growth rate, or condition factor among treatments (P&gt;0.05). There were also no significant differences in the survival rate and feed conversion ratio of the rainbow trout fed various experimental diets (P&gt;0.05).&#x0D; Conclusion: The results suggest that growth performance, food conversion, and survival of rainbow trout fingerlings are not affected by 0.4 or 1.2 mg/kg supplementation of Cr-Pic in diet.

A meta‐analysis revealing the technical, environmental, and host‐associated factors that shape the gut microbiota of Atlantic salmon and rainbow trout

AbstractSalmonids, specifically Atlantic salmon (Salmo salar) and rainbow trout (Oncorhynchus mykiss), are commonly farmed and their gut microbiota plays important roles for optimal growth, health, and physiology. However, differences in experimental design, technical factors and bioinformatics make it challenging to compare the results from different studies and draw general conclusions about their influence on the fish gut microbiota. For a more comprehensive understanding of the gut microbiota, we collected all the publicly accessible 16S rRNA gene sequencing data with clearly stated sample metadata from freshwater Atlantic salmon and rainbow trout intestinal contents and mucosa sequenced on the Illumina MiSeq platform. A total of 783 samples from 19 published studies were included in this meta‐analysis to test the impact of the technical, environmental, and host‐accociated factors. This meta‐analysis revealed that all the tested factors significantly influenced the alpha and beta diversities of the gut microbiota of salmon and trout. Technical factors, especially target region and DNA extraction kit, affected the beta diversity to a larger extent, while host‐associated and environmental factors, especially diet and initial fish weight, had a higher impact on the alpha diversity. Salmon had a higher alpha diversity and higher abundance of Enterococcus and Staphylococcus than trout, which had higher abundance of Weissella and Mycoplasma. The results of this meta‐analysis fill in a critical knowledge gap that demonstrate technical methodologies must be standardized and factors associated with host and environment need to be accounted for in the future design of salmonid gut microbiota experiments.

Effect of dietary fish oil sparing with blended vegetable oils on growth, fatty acid composition and lipid-metabolism-related genes expression in juvenile rainbow trout (Oncorhynchus mykiss)

Abstract A nutritional study was conducted to evaluate the influence of dietary fish oil (FO) sparing by using a mixture of vegetal oils (VO) on rainbow trout (Oncorhynchus mykiss) juveniles (30.0 g). A basal diet was supplemented with the experimental oils at a 10% level, including FO (FO diet), a blend of VO (sunflower, soybean and rapeseed oils with a 1:1:1 ratio), and a mixture (1:1 ratio) of FO and the blends of VO (MIX). In a raceway system, 450 fish were stocked in nine rectangular concrete tanks (50 fish/ tank−1). Three experimental diets, with three replicates each, were offered to fish up to visual satiation for eight weeks. Growth performance did not change among groups (P&gt;0.05). The highest and lowest proportions of n-3 polyunsaturated fatty acids (PUFA), n-3 long chain-PUFA, especially docosahexaenoic acid, and n-3/n-6 PUFA ratio were in the whole body of FO and the VO groups, respectively (P&lt;0.05). Serum catalase and glutathione peroxidase activities in VO group were higher than others. Serum superoxide dismutase activity in fish fed FO and VO diets was higher than MIX group (P&lt;0.05). VO group had higher serum lysozyme, alternative complement pathway, and total immunoglobulin levels than other experimental groups. MIX group had highest serum triglyceride, cholesterol, and low-density lipoproteins. Serum high-density lipoproteins, aspartate aminotransferase, and alanine aminotransferase levels in VO treatment were in the lowest level compared to others (P&lt;0.05). The highest relative transcription levels of fatty acid synthase, delta-6 fatty acyl desaturase, and apolipoprotein b-100 genes were in the liver of fish fed the MIX diet. The relative transcription level of the fatty acid-binding protein1 gene did not change (P&gt;0.05). In summary, the results of this study revealed that dietary FO sparing with VO did not adversely affect the growth and health indices of rainbow trout; nevertheless, it had adverse effects on its nutritional values by reducing whole-body n-3 LC-PUFA content.

Ancestry and genetic structure of resident and anadromous rainbow trout (Oncorhynchus mykiss) in Argentina.

Since the first introduction from North America more than a century ago, rainbow trout (Oncorhynchus mykiss) have rapidly established self-sustaining populations in major river basins of Patagonia. Many generations later, only the freshwater resident life history is expressed in the Chubut and Negro rivers of northern Argentinian Patagonia, whereas both the resident and anadromous life histories are found in the Santa Cruz River of southern Argentina. Despite previous studies that have tried to identify the sources of these introduced populations, uncertainty still exists. Here we combined data from many single-nucleotide polymorphisms and microsatellite loci in O. mykiss populations from Argentina and North America to evaluate putative source populations, gene flow between Argentinian river basins, and genetic diversity differences between Argentinian and North American populations. We found that populations from northern and southern Patagonia are highly differentiated and have limited gene flow between them. Phylogeographic analysis also confirmed that they have separate origins, with the northern populations most closely related to the domesticated rainbow trout strains that are raised worldwide and the Santa Cruz River populations most closely related to North American populations from California and Oregon that have an anadromous component. In addition, fish with different life histories in the Santa Cruz River were found to constitute a single interbreeding population. No evidence was found of reduced genetic variation in introduced rainbow trout, suggesting multiple contributing sources. In spite of these advances in understanding, significant questions remain regarding the origins and evolution of the introduced O. mykiss in Patagonia.

Comparative study of heat shock and pressure shock for triploidy induction in rainbow trout (Oncorhynchus mykiss)

The study was aimed to explore the effective physical treatment for successful triploidyinduction to take the advantage of improving growth in coldwater aquaculture candidatefish, rainbow trout Oncorhynchus mykiss. Comparison was made between two commonphysical treatments viz.,, heat shock and pressure shock to prevent the extrusion of secondpolar body in newly fertilised eggs. Heat shock was given on the fertilised eggs at threetemperature levels viz., 26, 28 and 30ºC with four exposure timings of 5, 8, 10 and 12 min.Pressure shock was applied at three different levels of pressure i.e 9000, 9500 and 10000 psifor 3 different exposure times of 3, 5 and 7 min. Poidy verification of the treated eggs wasdone by counting the chromosome number in karyotyping. Results of the field operationsreflected 86-90% triploidy induction for pressure shock at9500 psi for exposure time of 5 minwith 72-80% survival from fertilisation to swim-up fry stage and 80% triploidy induction forheat shock at 280C for 10 min with 60-66% survival from fertilisation to fry stage. Appropriatecentigrade temperature minutes (CTM) was calculated as 300-375 min, which is variable atdifferent locations and environmental conditions. Study concluded that pressure shock ismore effective over heat shock for triploidy induction in rainbow trout. CTM, Heat shock, Karyotyping, Pressure shock,Triploidy induction

Effects of dietary astaxanthin supplementation on growth performance, antioxidant status, immune response, and intestinal health of rainbow trout (Oncorhynchus mykiss)

A feeding trial was conducted to assess the impacts of dietary astaxanthin from wall-broken Haematococcus pluvialis (WBHPA) on the growth performance, antioxidant status, immune response, and intestinal health of rainbow trout (Oncorhynchus mykiss). Six experimental diets were formulated with various concentrations of WBHPA, ranging from 0 to 8.4 g/kg (containing 0 to 125 mg/kg astaxanthin). Each diet was fed to triplicate groups of rainbow trout (mean initial weight of 561 g) twice daily for 9 consecutive weeks. The survival rate and feed intake of fish exhibited no significant differences among the dietary groups (P > 0.05). Similarly, dietary inclusion of 25 to 100 mg/kg astaxanthin did not significantly affect the weight gain and daily growth coefficient (P > 0.05), but excessive inclusion of astaxanthin (125 mg/kg) slightly depressed these parameters (P < 0.05). Dietary inclusion of 25 to 50 mg/kg astaxanthin increased the activities of intestinal digestion and absorption enzymes (lipase, creatine kinase, and alkaline phosphatase), while the inclusion of 25 to 75 mg/kg astaxanthin improved the immune response of fish. Furthermore, regardless of inclusion level (25 to 125 mg/kg), dietary astaxanthin supplementation strengthened the intestinal mucosal barrier function and improved antioxidant activity, thereby promoting intestinal development. Conclusively, 25 to 75 mg/kg astaxanthin from WBHPA was recommended to be included in diets for rainbow trout.

Complexities and opportunities: A review of the trajectory of fish farming in Zimbabwe

AbstractZimbabwe is currently rated as one of the top 10 fish producers in Sub‐Saharan Africa. Fish farming in Zimbabwe is dominated by the culture of Nile tilapia (Oreochromis niloticus) followed by rainbow trout (Oncorhynchus mykiss). Over 90% of the cultured fish is O. niloticus, which comes from Lake Kariba. Since the first decade of the 21st century, there has been a significant increase in fish production from two tons to eight tons annually. The increase in fish production has been attributed to the government and donor‐funded fishery programs. In this review, current practices, opportunities, and challenges for aquaculture in Zimbabwe are highlighted. The current practices include intensive, semi‐intensive, and extensive aquaculture systems. Consistent high market demand for fish and numerous water bodies with potential for cage culture are some of the drivers for aquaculture. Despite the industry's significant growth, there are still a number of management and production issues that need to be resolved. Weaknesses in structural issues and operational frameworks in Non‐Governmental Organizations, lack of credit facilities, subsidies, limited technology, obfuscated governance, weak fish disease surveillance mechanisms and legal frameworks, and constrained human resources capacity are some of the challenges plaguing fish culture in Zimbabwe. Cogent aquaculture policies, sustainable subsidies, intensive training of human resources and fisheries experts, strengthened disease surveillance, cheaper alternative fish feeds, reliable viable fingerling production, concerted value chain efforts, and exploration of lucrative export markets is a panacea for the fledgling aquaculture industry in Zimbabwe.

Effects of dietary pectin on the growth performance, intestinal barrier, and antioxidant status of juvenile rainbow trout (Oncorhynchus mykiss)

To evaluate the effects of dietary pectin on growth performance, intestinal barrier, and antioxidant status of juvenile rainbow trout (Oncorhynchus mykiss), 10-week feeding trial was conducted. Five isoproteic and isoenergetic diets were formulated to contain 0% (P0), 4% (P4), 8% (P8), and 16% (P16) pectin as well as 0.02% pectinase (PE) at the expense of wheat starch, respectively. Dietary inclusion of 416% pectin linearly promoted the feed intake and growth performance but depressed the feed efficiency, but significant differences were only observed between the P16 and P0 groups. Similarly, dietary inclusion of 816% pectin significantly increased the foregut trypsin and amylase activities but decreased the foregut and midgut sucrase activity. The midgut muc2 gene expression level was significantly down-regulated by the inclusion of 16% pectin. Dietary inclusion of 2% pectin increased the abundance of Proteobacteria and Stenotrophomonas but reduced the abundance of Actinobacteria, Bacteroides and Helicobacter; while the lowest values of observed species, Chao1 and ACE indices of intestinal flora were found in the P8 group. Fish fed with the P8 diet exhibited the lowest plasma catalase and midgut glutathione S-transferase activities as well as malondialdehyde content, but the highest midgut malondialdehyde content. Dietary inclusion of 816% pectin significantly depressed the plasma growth hormone (GH), insulin-like growth factor-1 (IGF-1) and mechanistic target of rapamycin contents as well as alanine aminotransferase activity, the hepatic adenosine monophosphate deaminase and glutamate dehydrogenase (GDH) activities. Dietary treatment with 0.02% pectinase did not affect the growth performance, but depressed the foregut sucrase activity, the midgut amylase and sucrase activities, increased the plasma GH and IGF-1 contents as well as hepatic GDH and aspartate aminotransferase activities. In conclusion, high-dose of dietary pectin (816%) may promote the feed intake and intestinal digestive enzyme activities and thereby improve the growth performance of rainbow trout.

High protein-low carbohydrate diet can improve hypoxia tolerance of triploid rainbow trout (Oncorhynchus mykiss): Effects on physiological and metabolic responses to acute hypoxia

Triploid rainbow trout is a hypoxia-sensitive fish species, and is susceptible to death in summer with high water temperature induced acute hypoxia. The study was conducted to evaluate the effect of high protein diet and high carbohydrate diet on hypoxic tolerance of triploid rainbow trout. Two isolipidic and isoenergetic diets with low protein-high carbohydrate level (LPHC) and high protein-low carbohydrate level (HPLC) were specifically formulated. After the feeding trial with 80 days, two group fish were treated with acute hypoxic challenge. Plasma biochemical parameters, hepatic anti-stress, antioxidant and immune related genes expression, and hepatic glucose, lipid, protein and amino acid metabolism related genes expression were then analyzed. The results showed that compared with HPLC diet, LPHC diet could result in excessive plasma levels of alanine aminotransferase (ALT; 36.3 VS 14.0 U/L), aspartate aminotransferase (AST; 978 VS 366 U/L), alkaline phosphatase (ALP; 374 VS 204 U/L), creatine phosphokinase (CPK; 7538 VS 4937 U/L) and lactate dehydrogenase (LDH; 940 VS 451 U/L). In addition, HPLC diet could remodel metabolism of glucose, lipid and protein based on the mRNA expression levels of the genes regulating glycometabolism, lipometabolism, and protein and amino acids metabolism. HPLC diet also enhanced the mRNA expression levels of the genes regulating anti-stress (HSP70, HIF-1a and HIF-2a), antioxidant (Nrf2, SOD, CAT, GPx and HO-1) and immune (IFN-γ, IL-1β, TNF-α and IL-8). In total, LPHC diet could aggravate hypoxic stress of triploid rainbow trout, while HPLC diet could improve fish hypoxic tolerance.

Effects of Different Astaxanthin Sources on Fillet Coloration and Energy Deposition in Rainbow Trout (Oncorhynchus mykiss)

A 9-week feeding trial was conducted to investigate the effects of different dietary sources of astaxanthin on fillet coloration, texture, and nutrient composition in rainbow trout (Oncorhynchus mykiss). Eight diets were formulated to contain 0, 25, 50, 75, 100, and 125 mg/kg astaxanthin from wall-broken Haematococcus pluvialis (WBHPA), 100 mg/kg astaxanthin from wall-unbroken H. pluvialis (WUHPA), or chemically synthesized astaxanthin (CSA). Each diet was fed to triplicate groups of rainbow trout (mean initial weight of 561 g) twice daily (07:00 and 17:00) to apparent satiation for 9 weeks. Results showed that at the 100 mg/kg astaxanthin inclusion level, the CAS group had higher fillet gross energy, dorsal fillet redness, and dorsal fillet color card score compared to the WBHPA-100 group, with both being higher than the WUHPA group (P&lt;0.05). Fillet astaxanthin content, dorsal fillet yellowness, and lateral line redness and yellowness did not differ significantly between the CSA and WBHPA-100 groups (P&gt;0.05), but were higher than the WUHPA group. When WBHPA was used, the inclusion of 50–100 mg/kg decreased fillet lightness but increased fillet redness, while better fillet texture was served at 75–125 mg/kg. Dietary 25–125 mg/kg WBHPA inclusion increased fillet astaxanthin and gross energy concentrations, with minor effects on fatty acid compositions of fillet. Inclusion of over 100 mg/kg astaxanthin regardless of source decreased fillet threonine and serine contents, and the WBHPA-100 group had lower fillet glycine and alanine contents compared to the control group (P&lt;0.05). In conclusion, CSA had the most significant impact on fillet coloration and energy deposition in rainbow trout, while WUHPA had the least favorable effect. Additionally, the wall-breaking treatment of H. pluvialis can improve the effect of astaxanthin on fillet coloration and nutrient composition in rainbow trout, with a recommended dose range of 75–100 mg/kg.

Pharmacokinetic behaviour and pharmacokinetic-pharmacodynamic integration of doxycycline in rainbow trout (Oncorhynchus mykiss) after intravascular, intramuscular and oral administrations.

Doxycycline (DO) has been used in fish for a long time, but there are some factors that have not yet been clarified regarding its pharmacokinetic (PK) and pharmacodynamic (PD) properties. Therefore, the aim of this study was to investigate the PK and PK/PD targets of DO after 20mg/kg intravascular (IV), intramuscular (IM) and oral (OR) gavage administration in rainbow trout (Oncorhynchus mykiss). Plasma samples were collected at specific time points and subsequently analysed by HPLC-ultraviolet. The PK/PD indices were calculated based on the MIC90 (Aeromonas hydrophila and Aeromonas sobria) values obtained for the respective bacteria and the PK parameters obtained for DO following both IM and OR administration. After IV administration, the elimination half-life (t1/2 ʎz), area under the concentration vs. time curve (AUC), apparent volume of distribution at steady-state and total body clearance of DO were 34.81h, 723.82hµg/mL, 1.24L/kg and 0.03L/kg/h, respectively. The t1/2λz of the DO was found to be 37.39 and 39.78h after IM, and OR administration, respectively. The bioavailability was calculated 57.02% and 32.29%, respectively, after IM and OR administration. The MIC90 of DO against A. hydrophila and A. sobria was 4µg/mL. The PK/PD integration showed that DO (20mg/kg dose) for A. hydrophila and A. sobria with MIC90 ≤4µg/mL achieved target AUC/MIC value after IM administration. These results suggest that when rainbow trout was treated with 20mg/kg IV and IM administered DO, therapeutically effective concentrations were reached in the control of infections caused by A. hydrophila and A. sobria.

Comparative study of the gut microbial communities collected by scraping and swabbing in a fish model: a comprehensive guide to promote non-lethal procedures for gut microbial studies.

In the present study, we propose the use of swabs in non-lethal sampling procedures to collect the mucosa-adhered gut microbiota from the posterior intestine of fish, and therefore, we compare the bacterial communities collected by conventional scraping and by swabbing methods. For this purpose, samples of the posterior intestine of rainbow trout (Oncorhynchus mykiss) were collected first using the swabbing approach, and after fish euthanasia, by mucosa scraping. Finally, bacterial communities were compared by 16S rRNA gene Illumina sequencing. Results from the current study revealed that similar values of bacterial richness and diversity were found for both sampling procedures. Similarly, there were no differences between procedures when using qualitative metrics (Jaccard and unweighted UniFrac) for estimating inter-individual diversity, but the quantitative metrics (Bray-Curtis and weighted UniFrac) showed a higher dispersion when samples were obtained by swabbing compared to scraping. In terms of bacterial composition, there were differences in abundance for the phyla Firmicutes and Proteobacteria. The cause of these differential abundances may be the inability of the swab to access to certain areas, such as the basal region of the intestinal villi. Moreover, swabbing allowed a higher representation of low abundant taxa, which may also have an important role in host microbiome regardless of their low abundance. Overall, our results demonstrate that the sampling method is a factor to be considered in experimental design when studying gut bacterial communities to avoid potential biases in the interpretation or comparison of results from different studies. In addition, the advantages and disadvantages of each procedure (swabbing vs scraping) are discussed in detail, concluding that swabbing can be implemented as a reliable and non-lethal procedure for posterior gut microbiota studies, which is of particular interest for animal welfare and the 3Rs principle, and may offer a wide range of novel applications.

Generation and genetic analysis of a rainbow trout (Oncorhynchus mykiss) clonal line produced by gynogenesis

The efficiency of heat-shock treatments for producing gynogenetic double haploids was evaluated using a rainbow trout (Oncorhynchus mykiss) strain locally adapted in Brazil (2002 broodstock). Eleven and 15 females produced by conventional reproduction (FC) or meiotic gynogenesis (FG) were used as egg donors, respectively. Oocytes from each female were randomly divided into five uneven lots which were submitted to different treatments: (C2n) Normal diploid control, (H) Haploid control, (G-Me) Meiotic gynogenetic, (G-Mi) Mitotic gynogenetic, and (4 n) Control of suppression of the 1st cell cleavage. Homozygous yellow-colored (Dominant albino - DA) males were used as semen donors. Gynogenesis was induced by insemination of eggs with DA semen genetically inactivated by ultraviolet irradiation. Diploidization of gynogenic individuals was induced by an early heat shock to block 2nd polar body extrusion (G-Me), or a late heat shock to suppress first mitosis (G-Mi). Overall mean survival rates to eyed-egg and first feeding stages of treated groups, relative to respective C2n control group were: 19.21 and 14.90%, 13.02 and 8.09%, and 29.94 and 16.48%, for treatments G-Me, G-Mi and 4 n, respectively. When compared with C2n, all treatments showed lower survival rates at both stages. Survival of G-Me and G-Mi progeny from FG females were significantly higher when compared to progeny from FC females for both stages. Progenies from two different females observed to be 100% homozygous in analyzed informative microsatellite markers were used in subsequent cycles of gynogenic reproduction. One line originally derived from a single gynogenic female was reproduced for nine successive generations of meiotic gynogenetic reproduction. Forty animals from the ninth successive generation of gynogenetic reproduction were analyzed with a low-density SNP (Single Nucleotide Polymorphism) panel. All individuals were observed to be homozygous for identical alleles at all SNPs, therefore indicating that the established mitotic gynogenetic line is composed of 100% clonal individuals.

Organ-specific biotransformation in salmonids: Insight into intrinsic enzyme activity and biotransformation of three micropollutants

Aquatic ecosystems continue to be threatened by chemical pollution. To what extent organisms are able to cope with chemical exposure depends on their ability to display mechanisms of defense across different organs. Among these mechanisms, biotransformation processes represent key physiological responses that facilitate detoxification and reduce the bioaccumulation potential of chemicals. Biotransformation does not only depend on the ability of different organs to display biotransformation enzymes but also on the affinity of chemicals towards these enzymes. In the present study, we explored the ability of different organs and of two freshwater fish to support biotransformation processes through the determination of in vitro phase I and II biotransformation enzyme activity, and their role in supporting intrinsic clearance and the formation of biotransformation products. Three environmentally relevant pollutants were evaluated: the polycyclic aromatic hydrocarbon (PAH) pyrene (as recommended by the OECD 319b test guideline), the fungicide azoxystrobin, and the pharmaceutical propranolol. Comparative studies using S9 sub-cellular fractions derived from the liver, intestine, gills, and brain of brown trout (Salmo trutta) and rainbow trout (Oncorhynchus mykiss) revealed significant phase I and II enzyme activity in all organs. However, organ- and species-specific differences were found. In brown trout, significant extrahepatic biotransformation was observed for pyrene but not for azoxystrobin and propranolol. In rainbow trout, the brain appeared to biotransform azoxystrobin. In this same species, propranolol appeared to be biotransformed by the intestine and gills. Biotransformation products could be detected only from hepatic biotransformation, and their profiles and formation rates displayed species-specific patterns and occurred at different magnitudes. Altogether, our findings further contribute to the current understanding of organ-specific biotransformation capacity, beyond the expression and activity of enzymes, and its dependence on specific enzyme-chemical interactions to support mechanisms of defense against exposure.

Effect of ploidy on growth, fillet composition and colour of large rainbow trout (Oncorhynchus mykiss) in the Black Sea

The purpose of this study was to determine the growth performance and fillet quality parameters of large rainbow trout (Oncorhynchus mykiss) and of different ploidy (diploid-DTS and triploid- TTS) cultured in the Black Sea. This study was carried out in a commercial fish farm in Sinop, Black Sea of Turkey. Triploid groups had a higher weight and a better feed conversion rate than the DTS at the end of the 150-day study. Crude protein and crude fat ratios were respectively higher in the DTS and TTS groups; while ploidy affected the biochemical and fatty acid compositions of the large rainbow trout, it had no effect on the amino acid compositions. The colour of fillets was affected by the crude fat ratio of the fillet. This study indicated that large rainbow trout produced in the Black Sea, regardless of its ploidy, were of high quality, nutritious and healthy for human consumption. Furthermore, it demonstrated yet again that large rainbow trout is of sufficient quality to compete with other salmonid species in the national or international markets.

Air bubble curtain improves the welfare of captive rainbow trout fry and fingerlings

Fish welfare is becoming a priority for the fish farming industry. The search for practical, easy-to-implement methods to promote farmed fish welfare is therefore essential. Environmental enrichment aims to improve the psychological and physiological needs of a captive animal by increasing the complexity of its environment. During previous studies, we observed that fish seemed to be positively affected by short diffusions of air bubbles. In this study, we evaluated the effects of an innovative enrichment strategy consisting of introducing into the tank at the earliest stages of life, a pipe generating a curtain of air bubbles. Using rainbow trout (Oncorhynchus mykiss) as a captive fish model, we compared the short- (∼7 weeks) and long-term (∼21 weeks) effects of this bubble curtain diffused for one hour four times a day (Bubble condition) to a standard condition without bubbles (Control) on fish growth, aggressive and abnormal behaviors, as well as on fish motivation to access a bubble curtain, their emotional responses and their learning abilities. We found that bubble diffusion decreased aggressive and abnormal behaviors during diffusions in both the short-term and the long-term experiments. In the long-term experiment, this decrease was also observed during feedings and neutral periods when no bubble was diffused. Bubbles were found to be attractive for young Control fish (bubble-naive fish) subjected to a motivation test in the short-term experiment. When subjected to the emotional reactivity test, Bubble fish seemed less fearful, exhibiting a lower maximum velocity than Control fish in the long-term experiment only. However, the other behavioral parameters measured during this test, appetite and plasma cortisol levels were similar between treatments, irrespective of the experimental period. The latency to consume the reward observed in the spatial learning test in the long-term experiment was decreased in Bubble fish compared with Control fish, showing enhanced learning abilities in fish that experienced bubbles for 21 weeks. Growth parameters and fin erosion index did not differ between treatments. We conclude that repeated bubble diffusions act as an environmental enrichment for fish, combining physical, occupational, and sensory enrichment via the tactile stimulations provided by the air bubbles. This type of enrichment had a positive impact on the behavior of farmed rainbow trout in the long term, and would make it possible to integrate the notion of “positive welfare” into fish farms, while guaranteeing easy technical maintenance.

A new approach in rainbow trout (Oncorhynchus mykiss Walbaum, 1792) industry: "Turkish Salmon" production and marketing trends

With favorable environmental conditions and the adoption of new technologies, Türkiye has 1703 enterprises producing trout as of 2022. These enterprises collectively produce 167,286 tons of trout per year, including portioned fish (200-250 g), fillet candidates (400-600 g), and fillets (known as Turkish Salmon) (&gt;3000 g). The production chain for Turkish Salmon involves hatcheries, dam lake net cage systems, and offshore net cage systems. There are 680 hatcheries producing trout eggs and fry, with a total annual production of 1,360,029,485 eggs. Additionally, 622 pond/dam lake net cage systems are used for producing Turkish Salmon candidates weighing 400-600 g, with a total production capacity of 163,525,079 kg per year. Offshore net cage systems in the Black Sea region, spread across six provinces, are utilized for Turkish Salmon production. Production planning is underway for two provinces, with a total planned production area of 15,650,000 m2 and a projected capacity of 221,188,000 kg per year. Türkiye is actively involved in the global aquaculture sector, paying close attention to its advancements. Türkiye has a strong egg/juvenile production capacity compared to other countries involved in trout production globally. However, the importation of biotechnology-applied and observed eggs continues, posing biological and genetic risks to Türkiye's natural aquatic areas. Over the past 20 years, Türkiye's trout production has grown significantly, reaching 167,286 tons per year, marking it as a significant food production industry. This success can be attributed to favorable environmental conditions, increasing consumer demand, the adoption of new technologies, and consistent investments. However, the rapid growth in the trout farming sector over the past five years has led to an uncontrollable decline in survival rates. This decline can be attributed to the spread of diseases, incorrect treatment methods, improper breeding management practices, flawed business management, unregulated fish transport, and compromised sanitary and environmental conditions.