Trout Oncorhynchus Mykiss Walbaum Research Articles

Accumulation of Astaxanthin and Canthaxanthin in Liver and Gonads of Rainbow Trout (Oncorhynchus mykiss (Walbaum, 1792)) Reared in Water Containing the Fungicide Mancozeb in Concentration Level Permitted by European Legislation

In this study, we studied the levels of both of the main pigments in Salmonidae—astaxanthin (Ax) and canthaxanthin (Cx)—accumulated in the liver, female gonads, and male gonads of rainbow trout (Oncorhynchus mykiss) reared in water containing the fungicide mancozeb (MZ) in concentration levels permitted by European legislation. Experimental fish were divided into three groups: the first was a control group, the second was fed with market feed (containing Ax and Cx), and the third was fed with market feed (containing Ax and Cx) and reared in environmental water containing permissible MZ levels. The diet preparation followed the manufacturer’s recommendations. The accumulated pigment quantities were measured using an HPLC-PDA method after selective extraction: Ax ranged from 2.490 ± 0.247 mg/kg (female gonads, second group) to 0.176 ± 0.007 mg/kg (liver, control group), and Cx—from 2.406 ± 0.166 mg/kg (female gonads, second group) to 0.103 ± 0.010 mg/kg (liver, control group). The pattern of the accumulation of both pigments in the three organs in the specimens of the three groups was sustainable: the amount of Ax was always greater than that of Cx, and the correlation between their concentrations was very high. The pigments were accumulated most intensively in the female gonads, followed by the male gonads and the liver. This trend was confirmed for all three experimental groups. However, the differences in the last third group were very small, and the levels of the xanthophylls accumulated were the lowest. A particular cause of the latter findings was the ongoing detoxification reactions and the disposal of MZ, in which Ax and Cx were involved as antioxidants.

Distribution of trout in the Upper Ob basin

Rainbow trout Oncorhynchus mykiss (Walbaum, 1792) and brown trout Salmo trutta Linnaeus, 1758 are popular aquaculture species worldwide. At the same time, it is known that when these species enter natural water bodies, they are able to form self-reproducing populations and cause significant damage to native fauna due to food competition, hybridization with native species, and predation. In the basin of the Upper Ob in the second half of the twentieth century, there was not only a large aquaculture farm specializing in trout but also work was carried out to introduce trout into natural water bodies: lakes in the basins of Lake Teletskoye and the Katun river. It is known about the formation of a self-reproducing population of brook trout in Lake Lebedinoe (in the basin of the Pervaya Koksha River, a second-order tributary of the lower reaches of the Katun River), which still exists. Currently, rainbow trout is a popular object of aquaculture in southern Siberia; it is grown mainly for the purpose of organizing recreational fishing, often in water bodies that are not isolated from the river network. This determines the regular ingress of this species into rivers. Nevertheless, currently no evidence of natural reproduction of trouts in natural water in the Upper Ob basin, except in Lake Lebedinoe. However, given the high risks associated with the potential invasiveness of trouts, it is necessary to recommend a cautious attitude towards the distribution of these species and to provide for an environmental impact assessment of projects related to their cultivation in water bodies of Western Siberia.

The presence of rainbow trout reduces drift of aquatic insects in Yungas streams (Tucumán, Argentina)

The drift or transport of individuals downstream is an important phenomenon of rivers and streams, since most aquatic organisms participate in it at some period of their life cycle. This work describes the assemblage of macroinvertebrate drift from ten sites in eight mountain streams of Tucumán, and evaluates the effect of the presence of rainbow trout (Oncorhynchus mykiss Walbaum), an exotic fish and visual predator, on this fraction of the community. Thirty-one (31) families of drifting aquatic invertebrates were identified, mainly immature insects and to a lesser extent water mites (Acari: Hydrachnidia), oligochaetes (Annelida: Oligochaeta) and nematodes (Nematoda). The richness and diversity of the sites with trout did not differ from the others, except when comparing lower and upper reaches of a same stream. Samples from rivers without trout or with low density of trout did not show significant changes in drift density of macroinvertebrates. In contrast, in rivers with high trout densities, a notable decrease in insect taxa was observed (those with large sized individuals): Baetidae (Ephemeroptera), Gripopterygidae (Plecoptera) and Leptoceridae (Trichoptera). On the contrary, the density of small Diptera, water mites, oligochets and nematodes increased in trout-streams

Detection of fish pathogen Saprolegnia parasitica in environmental DNA samples by droplet digital PCR

Oomycetes are fungal-like microorganisms parasitic towards a large number of plant and animal species. Genera from order Saprolegniales, such as Saprolegnia and Aphanomyces, cause devastating infections of freshwater animals. Saprolegnia parasitica is a widely distributed oomycete pathogen that causes saprolegniosis, a disease responsible for significant economic losses in aquaculture, as well as declines of natural populations of fish and other freshwater organisms. Despite its negative impact, no monitoring protocol for S. parasitica has been established to date. Thus, we aimed to develop a droplet digital PCR (ddPCR) assay for the detection and quantification of S. parasitica in environmental DNA samples. Saprolegnia parasitica-specific primers were designed to target internal transcribed spacer region 2 (ITS 2), based on the alignment of ITS sequences of S. parasitica and a range of Saprolegnia spp., as well as other oomycetes. The specificity of primers was tested using genomic DNA of S. parasitica (as positive control) and DNA of non–S. parasitica oomycete isolates, as well as trout/crayfish DNA (as negative control). The primers specifically amplified a segment of the ITS region of oomycete pathogen S. parasitica, while no amplification (i.e. no positive droplets) was obtained for closely related Saprolegnia spp. (e.g. Saprolegnia sp. 1 and S. ferax) and other more distantly related oomycetes. Next, the limit of detection (LOD) of the assay was established by using serial dilutions of the S. parasitica genomic DNA. The determined sensitivity of the assay was high: LOD was 15 fg of pathogen’s genomic DNA per µL of the reaction mixture. Assay performance was further assessed with environmental DNA samples isolated from water from the trout farms and natural environments, as well as (ii) biofilm from the host surface (swab samples). Water samples were collected from 21 different locations in Croatia, while swab samples were collected from S. parasitica host/carrier species: (i) skin and eggs of the rainbow trout (Oncorhynchus mykiss Walbaum, 1792) and brown trout (Salmo trutta Linnaeus, 1758), and (ii) cuticle of signal crayfish (Pacifastacus leniusculus Dana, 1852) and narrow clawed crayfish (Pontastacus leptodactylus Eschscholtz, 1823). Samples were classified into agent levels A0 to A6, depending of the number of S. parasitica ITS copies per ng of total DNA. Saprolegnia parasitica was detected in 76 % of water samples (16/21) and the range of pathogen’s ITS copies in positive samples was between 0.02 and 14 copies/ng of total DNA (agent levels A1 to A3). Regarding the swab samples, S. parasitica load was significantly higher in diseased trout than in those with healthy appearance: 9375 vs 3.28 S. parasitica copies/ng of total swab DNA (average agent level A6 vs. A2, respectively). Despite the fact that none of the sampled crayfish had signs of infection, the pathogen was detected in all tested cuticle swabs. Swabs of P. leniusculus, a known S. parasitica host, had significantly higher S. parasitica load than swabs of P. leptodactylus, S. parasitica carrier: 390 vs 83 S. parasitica copies/ng (agent level A5 vs. A4, respectively). In conclusion, our results demonstrate the applicability of the newly developed ddPCR assay in monitoring and early detection of S. parasitica in aquaculture facilities and natural freshwater environments. This would help in a better understanding of S. parasitica ecology and its effects on the host populations.

Determining diets for fishes (Actinopterygii) from a small interior British Columbia, Canada stream: a comparison of morphological and molecular approaches

AbstractAnalysis of food webs is important for defining functional components of ecosystems, but dietary data are often difficult to obtain and coarsely characterised. We compared three methods of rainbow trout (Oncorhynchus mykiss(Walbaum); Salmoniformes: Salmonidae) and prickly sculpin (Cottus asperRichardson; Scorpaeniformes: Cottidae) gut content analysis: traditional morphological taxonomy of prey items, genetic sequencing of individual prey items, and next-generation sequencing of homogenised gut contents. Prey analysis of invertebrates by morphological identification allowed order-level classifications and produced ecologically important count and mass data. Sequencing individual specimens provided greater taxonomic resolution, while next-generation sequencing of stomach contents revealed more prey diversity in the diets of both fish species as it was possible to detect prey that were degraded beyond visual recognition. Both fish species exhibited generalist feeding characteristics; however, terrestrial Insecta were a large diet component for rainbow trout. This study demonstrates an efficient approach for prey analysis using molecular techniques that complement traditional taxonomy.

Evaluation of Fertilization Indices and Stress Response of Rainbow Trout Oncorhynchus mykiss (Walbaum, 1792) in Different Temperatures

Evaluation of Fertilization Indices and Stress Response of Rainbow Trout Oncorhynchus mykiss (Walbaum, 1792) in Different Temperatures

Fishery-exteriors characteristics of the brooders of brown trout, rainbow trout and brook trout

This study aims to determine the reproductive indices of three types of salmon fish: brown trout (Salmo trutta morfa fario Linnaeus (1758), rainbow trout (Oncorhynchus mykiss Walbaum, 1792) and brook trout (Salvelinus fontinalis Mitchill, 1814) in aquaculture. For this purpose, 10 females and 10 males of each species were selected on an analogous basis and the main fishery-exteriors and reproductive characteristics were identified. The researching of relative fertility permit to establish that this indicator in brook trout females was 18.36% higher compared to rainbow trout, however, by 7.5% lower compared to the brown trout. It was found that brook trout eggs had less weight and size in comparison with other studied species. In particular, the weight and diameter of the eggs were 2.89 and 9.7% respectively lower than of rainbow trout, as well as 8.1 and 3.44% respectively lower compared to the brown trout. When studying the quantity of ejaculate, it was found that on average, brook trout males had 16.95% less of ejaculates compared to rainbow trout males, but 79.6% more than of brown trout males. When comparing the main indices of the brooders body of the studied species, it was found that the condition factor of the brook trout and rainbow trout females was quite high at 1.55–1.57, the brown trout one was 1.35, and the profile index respectively was 3.5, 3.52 and 4.0. The males' condition factor of brook trout, rainbow trout and brown trout was respectively 1.64, 1.52 and 1.35. Fishery-exteriors indicators met the requirements of brooders species and age specificity norms of the studied fish species.

COMPARATIVE INDICATORS OF FATTY ACID COMPOSITION OF RAINBOW TROUT (ONCORHYNCHUS MYKISS WALBAUM, 1792) FROM VARIOUS AQUACULTURE FACILITIES IN MACEDONIA

The objective of this study was to make a comparative analysis of the fatty acid composition of the rainbow trout (Oncorhynchus mykiss Walbaum, 1792) with consumption size of 250-300 g, from two different aquaculture facilities - coldwater fishponds (fishpond A and fishpond B) in Macedonia, at different ambient conditions in the aquatic environment, and with the use of pelleted food from different manufacturers. Considering the results of the fatty acid composition of the rainbow trout from the fishpond A and the fishpond B, it can be concluded that the content of the saturated fatty acids (SFA) is higher in the fishpond B (20.303%) compared to the fishpond A (16.155%), while the content of the monounsaturated fatty acids (MUFA) and the polyunsaturated fatty acids (PUFA) is greater in the fishpond A (MUFA - 53.364%; PUFA - 30.435%) compared to the fishpond B (MUFA - 52.359%; PUFA - 27.268%). Overall, by a comparative analysis of the qualitative properties of the rainbow trout from the both aquaculture facilities, the ambient conditions prevailing in the aquatic environment, and the used forage mixtures for feeding fish, it can be concluded that the both aquaculture facilities are producing fish with high nutritional quality in terms of the fatty acid composition.

ГИСТОМОРФОЛОГИЧЕСКАЯ ОЦЕНКА НЕКОТОРЫХ ОРГАНОВ РАДУЖНОЙ ФОРЕЛИ ONCORHYNCHUS MYKISS (WALBAUM, 1792) ПРИ ВЫРАЩИВАНИИ НА ЭКСПЕРИМЕНТАЛЬНЫХ КОРМАХ

The article presents histological characteristics of gastrointestinal tract, liver and muscles of the rainbow trout Oncorhynchus mykiss (Walbaum, 1792) juveniles (5 specimens, control group) and yearlings (2 pilot groups, 15 specimens in each group) in the basins of "Chilik pond farm, LLP" (the Almaty region, Kazakhstan) fed with imported Denmark feed "Aller Aqua" and the feed produced by the local company "Kazkorm" (without immunomodulatory probiotic drugs and with immunomodulatory probiotic drug "Biocons", concentration 0.5%). The experiment was devided into 2 series; the first series lasted 45 days (yearlings, 15 specimens), the second series lasted 75 days (yearlings, 15 specimens). The total duration of the experiment made 75 days. In both series there were used 3 variants of feed: in the control group - "Aller Aqua", in pilot groups - feed without and with "Biocons" drug, concentration 0.5%. The histopathological analysis was conducted on termination of the first and second series. The histopathological changes were registered in all studies organs: the minimum changes were observed in the gastrointestinal tract; maximum changes were seen in the liver and somatic muscular system of fish that didn’t take probiotic drug. The intensity of pathological processes grew with duration of taking feeds without probiotic drugs. In the liver of fish there were noted such pathologies as fatty degeneration, enlargement of the liver vessels, cell contact disorders, degradation and necrosis of hepatocytes, violation of the microcirculatory in the form of stasis of blood in the sinusoids. All studied individuals fed with experimental feed were observed with significant pathological changes in the structure of somatic musculature. The size/weight characteristics of fish fed without probiotic drugs were inferior to those in fish using probiotic drugs. The histopathological analysis of indicators of gastro-intestinal tract, liver and muscle, as well as the size/weight characteristics after using feed with probiotic drug showed that the feed can be recommended for practical use, as the feed is the most balanced and nutritious.

Qualitative properties of rainbow trout (Oncorhynchus mykiss Walbaum, 1792) from aquaculture facility in Bitola region (Macedonia)

The main goal of this research was to determine the qualitative properties of the rainbow trout (Oncorhynchus mykiss Walbaum, 1792) from aquaculture facility - salmonid fishpond Strezhevo which is situated in Bitola region (Republic of Macedonia). The qualitative properties of the rainbow trout are established by determination of the chemical and the fatty acid composition of the fish meat, the energy value of the meat and the microbiological analysis for the total number of microorganisms on fish skin and presence of Salmonella sp. and Listeria monocytogenes. The main purpose of the research produced additional analyzes that determine the physical - chemical properties and also a microbiological analysis of the water in which the rainbow trout resides, the chemical composition of feed used for feeding of the rainbow trout, the condition factor (CF) and the feed conversion. The results obtained during the examination of the chemical composition of the rainbow trout meat from the fishpond Strezhevo determined the mean value of 74.533% water, 20.600% protein, 3.366% fat and 1.38% ash. The energy value of the meat was 484.635 kJ/100 g. Considering the results of the fatty acid composition of the rainbow trout from the fishpond Strezhevo, it can be concluded that the content of the saturated fatty acids (SFA) is 20.303%, the monounsaturated fatty acids (MUFA) is 52.359% and the polyunsaturated fatty acids (PUFA) is 27.268%. In terms of the amount of n-6 fatty acids, it is 20.180%, while the amount of n-3 is 7.088%.

Hematological Parameters in Trout: A Comparative Study between Rainbow Trout Oncorhynchus Mykiss (Walbaum, 1792) and Brown Trout Salmo Trutta Macrostigma (Dumeril, 1858)

The aim of this study was to obtain a basic knowledge of some blood haematological parameters in two different species of trout, Rainbow trout Oncorhynchus mykiss (Walbaum, 1792) and Brown trout Salmo trutta macrostigma (Dumeril, 1858). O. mykiss was caugh t in a farming system (commercial farm Palazzolo Acreide (Siracusa, Italy) while S. t. macrostigma in natural habitat (Anapo river, Siracusa, Italy). White Blood Cell Count (WBC), Red Blood Cell Count (RBC), Haematocrit (Hct), Hemoglobin concentration (Hg b), Mean Corpuscular Volume (MCV), Mean Corpuscular Haemoglobin (MCH), Mean Corpuscular Haemoglobin Concentration (MCHC), Thrombocyte Count (TC), were measured in blood samples from a total of 40 fish (20 for each species). The fork length, total weight a nd condition factor of the individuals were measured. Unpaired Student’s t - test between two species showed statistically significant differences (P < 0.001) for RBC, Hct, MCV, MCH, MCHC and TC. No statistically significant differences were found in WBC and Hgb. These results are useful to obtain a basic knowledge of two different species of trout in order to monitor the health status of these species of great commercial value.

Potential use of bovine lactoferrin as adjuvant for the modulation of the specific immune response in rainbow trout (Oncorhynchus mykiss W.)

The present experiment was carried out in order to evaluate the potential adjuvant effect of bovine lactoferrin (bLF) in modulating the specific antibody (Ab) response to an exogenous protein, the human-γ-globulins (HγG), injected intraperitoneally in rainbow trout Oncorhynchus mykiss (Walbaum 1792). Moreover, serum natural antibody (NatAb) level, serum total immunoglobulin (IgM) level and specific Ab response to bLF were also analysed. Experimental data showed that HγG is able to stimulate a specific Ab response when not adjuvanted with Freund’s complete adjuvant (FCA), whereas bLF induces a specific Ab response only if adjuvanted with FCA. Statistical analyses revealed that neither bLF or FCA administered singly had significant effects on serum NatAb and IgM levels, whereas the specific immune response observed against HγG when adjuvanted with bLF was comparable to that achieved when FCA was used as the adjuvant. These results provide evidence of the potential for bLF to be used as an adjuvant for salmonids.

Using physiological and zootechnical profiles to evaluate welfare in farmed rainbow trout Oncorhynchus mykiss (Walbaum) under stressful conditions

The welfare of farmed animals, and more recently of farmed fish, is a growing concern in current society. Changes in living conditions represent one of the most stressful situations in fish production. It is crucial to develop tools to evaluate welfare in farmed fish throughout the various situations observed during the production cycle. The present work aims to select relevant parameters in order to evaluate the welfare of trout, by describing the physiological and zootechnical profiles of rainbow trout Oncorhynchus mykiss (Walbaum) populations during adaptation to a new environment. Ten days after transferring seven groups of farmed trout to a laboratory setting, a principal component analysis was performed on five parameters: plasma cortisol level (PCL), hepatosomatic index (HI), growth (G), food intake (FI) and food conversion ratio (FCR). PCL and FCR were positively correlated and were both negatively correlated with FI and G. FI and G were positively correlated. HI was not correlated with any other parameter. PCL was considered as being at basal levels. Descriptive statistics and the principal component analysis suggest measuring PCL, G, FI and FCR to be a relevant strategy for evaluating the welfare of trout when adapting to a new environment. The study demonstrates the relevance of this approach in evaluating specific profiles related to the welfare of farmed animals.

Occurrence and morphogenetic characteristics of Gyrodactylus (Monogenea: Gyrodactylidae) from a rainbow trout farm (Lake Ladoga, Russia).

Gyrodactylus parasite infected juveniles on rainbow trout Oncorhynchus mykiss (Walbaum, 1792) from a fish farm in Lake Ladoga were investigated. The observed cases of infection in fish featured a high prevalence, when almost all of the fish were infected. However, if an outbreak of the monogenean infection is observed in spring, the intensity of the infection may be low, and when the infection occurs in the ice-covered period (late autumn - winter), the number of parasites on the fins of a single fish may exceed 3000 specimens. Molecular identification of the parasite demonstrated that the infecting clone was identical with rainbow trout specific strain of Gyrodactylus salaris RBT widely spread in Northern Europe, but a small proportion of the parasites were the hybrid clone Gyrodactylus pomeraniae x G. lavareti. Morphological variations of hooks and other opisthaptor parts in the monogenean Gyrodactylus depending on the intensity of infection in rainbow trout were demonstrated.

Pathomorphological examination of rainbow trout (Oncorhynchus mykiss walbaum, 1792) liver as a tool for assessment of water quality and its influence on fish condition

Pathomorphological examination of rainbow trout (Oncorhynchus mykiss walbaum, 1792) liver as a tool for assessment of water quality and its influence on fish condition

Melanomacrophage accumulation in the liver, spleen and kidney of rainbow trout (Oncorhynchus mykiss walbaum, 1792) as a tool for the assessment of the environmental influence on fish

Melanomacrophage accumulation in the liver, spleen and kidney of rainbow trout (Oncorhynchus mykiss walbaum, 1792) as a tool for the assessment of the environmental influence on fish

Isolation and expression of recombinant viral protein (VP2) from Iranian isolates of Infectious Pancreatic Necrosis Virus (IPNV) in Escherichia coli

Infectious Pancreatic Necrosis Virus (IPNV) is a member of the family Birnaviridae that has been linked to high mortalities in salmonids. Bacterial based systems as live vectors for the delivery of heterologous antigens offer a number of advantages as vaccination strategies. VP2 is a structural viral protein of IPNV with immunogenicity effects. In this study IPNV was isolated from diseased fry of rainbow trout Oncorhynchus mykiss (Walbaum) using CHSE214. Then an expression vector was constructed for expression of viral protein VP2. The designed vector was constructed based upon pET-26b (+) with T7 promoter. A fragment containing the full length of the VP2 gene of Iranian Sp strain was amplified by PCR using genomic RNA of IPNV as template and cloned inpET-26b(+) plasmid. Recombinant structural viral protein VP2 was expressed as a soluble, N-terminal PelB fusion protein and secreted into the periplasmic space of Escherichia coli BL21(DE3) and Rosetta (DE3). The glucose, Isopropyl-β-D- thiogalactopyranoside (IPTG) was used as a chemical inducer for rVP2 production in 37o C. The rVP2 was extracted from the periplasm by osmotic shock treatment. The presence of gene in bacterial system of E. coli was confirmed by gel electrophoresis technique. The constructed vector could efficiently express the rVP2 into the periplasmic space of E. coli. The successful cloning and expression of the structural viral protein gene into E. coli can be used for developing a useful and safe vaccine to control IPNV infection in Iranian fish industry.

Cold tolerance performance of westslope cutthroat trout (Oncorhynchus clarkii lewisi) and rainbow trout (Oncorhynchus mykiss) and its potential role in influencing interspecific hybridization

Hybridization between rainbow trout (Oncorhynchus mykiss (Walbaum, 1792)) and westslope cutthroat trout (Oncorhynchus clarkii lewisi (Girard, 1856)) occurs commonly when rainbow trout are introduced into the range of westslope cutthroat trout. Typically, hybridization is most common in warmer, lower elevation habitats, but much less common in colder, higher elevation habitats. We assessed the tolerance to cold water temperature (i.e., critical thermal minimum, CTMin) in juvenile rainbow trout and westslope cutthroat trout to test the hypothesis that westslope cutthroat trout better tolerate low water temperature, which may explain the lower prevalence of rainbow trout and interspecific hybrids in higher elevation, cold-water habitats (i.e., the “elevation refuge hypothesis”). All fish had significantly lower CTMin values (i.e., were better able to tolerate low temperatures) when they were acclimated to 15 °C (mean CTMin = 1.37 °C) versus 18 °C (mean CTMin = 1.91 °C; p < 0.001). Westslope cutthroat trout tended to have lower CTMin than rainbow trout from two populations, second–generation (F2) hybrids between two rainbow trout populations, and backcrossed rainbow trout at 15 °C (cross type × acclimation temperature interaction; p = 0.018). Differential adaptation to cold water temperatures may play a role in influencing the spatial distribution of hybridization between sympatric species of trout.

English

In the present study, a yeast strain Saccharomyces cerevisia var. elipsoidous , acting as probiotic, was administered to rainbow trout ( Oncorhynchus mykiss Walbaum, 1792) fry during a period of 21 days and the effects of the yeast on improvement of growth and resistance against environmental stress were evaluated with respect to fish fed on yeast free feed (control group). The control treatment consisted of a standard commercial diet, and the treatments consisted of the control diet supplemented with 0, 1, 5 and 10% yeast (w/w). The results demonstrate the beneficial effects of probiotics on the characteristics of rainbow trout, as the Specific Growth Ratio (SGR), body weight gain (%BWG) and protein conversion ratio (PER) in 5% yeast-fed fish were significantly (P<0.05) enhanced by probiotic administration. On the contrary, no effect on the fry growth performance, mortality, condition factor (CF), food conversion ratio (FCR) and histological assessment was shown. A significant (P<0.05) increase in lipid content of the carcass was detected in diets with probiotic compareD to 0% and the control treatments. Ash and protein contents of the carcass increased and decreased with an increase in yeast amount, respectively. Challenge with different levels of salinity (10 and 15 ppt) after 24 h revealed 100% survival in treatments containing yeast as probiotic, and difference with control group was significant (p<0.05) indicating that S. cerevisia could enhance the resistance against salinity stress. Addition of yeast in concentration of 5% to the diet is recommended during the early period of rainbow trout fry farming to achieve the best results on growth performance and feed efficiency. Keywords: Saccharomyces cerevisia var. elipsoidous , Oncorhynchus mykiss , probiotic, survival and growth rate, carcass quality African Journal of Biotechnology , Vol. 13(10), pp. 1160-1168, 5 March, 2014

The effect of high hydrostatic pressure on the muscle proteins of rainbow trout (Oncorhynchus mykiss Walbaum) fillets wrapped with chitosan-based edible film during cold storage (4±1°C)

This study was to determine the effects of changes that occurred in the muscle proteins of fresh rainbow trout (Oncorhynchus mykiss) fillets during storage at 4±1°C as a result of packaging in vacuum (C), subject to high pressure after packaging in vacuum high hydrostatic pressue (HHP), packaged in vacuum after wrapping with chitosan film (CFW) and subject to high pressure after wrapping with chitosan-based film and packaged in vacuum (HHP+CFW ). Samples were subjected to SDS-PAGE in four-day intervals and the densitometric analyses of the gels were carried out. According to the results, minor changes were determined in the major bands of the sarcoplasmic and myofibrillar muscle fractions of trouts as a result of HHP application and CFW. The most important change occurred in the myofibrillar muscle fraction as a decrease in the densities of the bands at 200 and 31.4 kDa after HHP application. Similarly, the sarcoplasmic muscle fraction of trout fillet decreased in the densities of the bands at 39.3, 26.6 and 23.3 kDa after HHP application. In addition, it is thought that the bands that occur at 30 kDa in the myofibrillar muscle fraction and at 20.7 kDa at the sarcoplasmic muscle fraction may be related with the degradation of trouts during cold storage.