Strains Of Rainbow Trout Research Articles

Feed intake and growth of fast and slow growing strains of rainbow trout ( Oncorhynchus mykiss) fed by automatic feeders or by self-feeders

Rainbow trout (8.5–9.5 g) of two strains (C and M) differing in growth potential were compared with respect to feeding motivation and feeding rhythms, over a 65-day experimental period, employing self-feeding or automatic feeding. Growth rate, feed gain ratio, feed intake and pattern of feeding activity of fish fed with self-feeders, were recorded, as was body composition of both strains. The final weight of fish of the fast-growing strain, strain C, fed using self-feeders, was significantly higher (82.6 g) than that observed for fish of the slow-growing strain, strain M (69.3 g). When the automatic feeders were used, no significant differences were found between the strains in terms of body weight gain (65 g). Results observed for feed gain ratio were also similar between the two strains. Although the voluntary feed intake (VFI) did not vary significantly with the genetic origin of the fish, strain C displayed a consistently higher VFI compared to strain M. The retention efficiency of nutrients and energy were similar between strains but significantly different between feeding systems. With regard to body composition, when fish were fed by means of self-feeders, no significant differences were found between the two rainbow trout strains. However, when fed automatically, dry matter and lipid content were highest in the strain M fish. The energy and protein content of the whole fish were not significantly influenced either by the feeding system or by the strain of the fish used.

Two immunogenetical parameters in five Danish rainbow trout (Oncorhynchus mykiss) strains and their relation to body weight

The distribution of different phenotypes of the complement component C3 and a possible correlation with body weight were investigated in five Danish strains (A, C, D, E, J) of farmed trout (Oncorhynchus mykiss Walbaum). All strains showed the presence of the f1 and f2 alleles; two of these strains also expressed the s allele. Most common was the f1 allele (> 68%); rarest was the s allele (<9% or absent). In the J strain, a significantly higher frequency of the f1 allele was observed. Only in the D strain was a linkage indicated between the mean values of body weight of trout and different C3 phenotypes (P = 0.002); the mean body weight of individuals with the f1 phenotype was also lower than that of the f1/f2 and s/f1 phenotypes. This result, however, is not conclusive, as it was observed in only one of the five strains and because the number of individuals in some of the phenotype groups was very small. The reactivity of monoclonal antibody Hyb106-1 that reacts with a carbohydrate epitope on the serum immunoglobulin molecule was also investigated in the five rainbow trout strains. The percentage of positively reacting trout sera varied from 9% to 43%. In the D and the E strains, positive individuals showed a significantly (P = 0.036, resp. P = 0.005) lower body weight than did the negative individuals. No linkage between the reactivity with monoclonal antibody Hyb106-1 and the f1 and f2 alleles of complement component C3 was observed. However, individuals that reacted negatively with the carbohydrate marker expressed only the s allele, possibly caused by a low number of samples expressing the s allele.

Rainbow trout offspring with different resistance to viral haemorrhagic septicaemia

To study immunological and immunogenetical parameters related to resistance against viral haemorrhagic septicaemia (VHS), attempts to make gynogenetic strains of rainbow trout selected for high and low resistance to VHS were initiated in 1988. The first gynogenetic generation of inbreeding resulted in the more resistant offspring E8 and the low resistance offspring K3; the K3 offspring having the same high mortality as the susceptible reference strain of outbred trout in infection trials. A second gynogenetic generation derived from the E8 strain resulted in some low resistance offspring, and two gynogenetic families in which all, or nearly all, fish survived challenge with VHS virus.In this study, an attempt to associate the distribution of different MHC class II genotypes with low and high resistance gynogenetic offspring was performed. Two different MHC haplotypes could be distinguished, and in both low and high resistance families all three genotypes were found, which could be explained by the fact that the mother fish carried the heterozygous genotype. Although no significant differences in MHC II genotypes were found between the high and low resistance offspring, a significantly different distribution of haplotypes in the low resistance offspring was observed, that could not be explained by a one- or two-locus model.

Use of Formalin during Incubation of Rainbow Trout Eyed Eggs

Abstract The influence of daily formalin treatments on eyed egg and fry mortality was evaluated during the incubation of eyed eggs of Cleghorn strain rainbow trout Oncorhynchus mykiss in vertical-flow incubators. The study was initiated in 1995 and replicated yearly through 1998. In 1997 and 1998, significant (P < 0.05) increases in survival were observed in trays of eggs treated with formalin at 1,667 mg/L for 15 min daily from egg eye-up until just before hatch compared with incubation trays where dead eggs were manually removed for control of Saprolegnia sp. In 1996, 1997, and 1998, significant mortality reductions were observed prehatch when using formalin. A significant improvement in survival from hatch to fry swim-up occurred only in 1998. No significant differences in survival occurred during any life stage in 1995. Yearly differences in formalin influences are attributed to changes in the age of broodfish, spawning frequency, and sample sizes. Both formalin treatments and hand picking of dead egg...

Greater predation by Double-crested Cormorants on cutthroat versus rainbow trout fingerlings stocked in a Wyoming river

We studied the relative vulnerability of Yellowstone cutthroat trout (Oncorhynchus clarki bouvieri) versus rainbow trout (Oncorhynchus mykiss) stocked as fingerlings in the North Platte River, Wyoming, to Double-crested Cormorant (Phalacrocorax auritus) predation. Cutthroat fingerlings decreased as a fraction of the population from stocking in late June to electrofishing surveys in the following October and March. In contrast, the fraction of cutthroat fingerlings among tagged fingerlings eaten by cormorants collected on the river was significantly greater than that in the population when originally stocked. More limited data from pellets regurgitated by adult cormorants at a nearby colony and in American White Pelicans (Pelecanus erythrorhynchos) collected on the river showed the same trend toward greater percentages of cutthroat trout being consumed than were present among trout stocked. There were no differences in cormorant predation rates on the Eagle Lake strain of rainbow trout reared under shaded versus partially shaded conditions, or between Auburn and Bar BC strains of Snake River (Yellowstone) cutthroat trout. On the North Platte River, cutthroat trout fingerlings were more susceptible to cormorant predation than rainbow trout of similar size that were stocked simultaneously.

Survival Traits of Naturalized, Hatchery, and Hybrid Strains of Anadromous Rainbow Trout during Egg and Fry Stages

Abstract Two strains of anadromous rainbow trout Oncorhynchus mykiss, naturalized steelhead and “kamloops” (not the pure Kamloops strain from British Columbia, hence not capitalized) currently inhabit the Minnesota waters of Lake Superior and may have the potential to hybridize. This could compromise the genetic integrity of the naturalized steelhead population. Both strains are supplemented by annual stocking, despite the fact that the steelhead population reproduces naturally. Egg viability and fry behavior experiments were undertaken to evaluate the potential for hybridization and to provide information for future management of the two strains. The kamloops eggs were slightly smaller, but sizes overlapped substantially with steelhead egg sizes. Mortalilty of kamloops eggs from spawning to hatching was greater than steelhead eggs. Steelhead fry exhibited a greater fright response (wariness) than kamloops fry when startled by movement over their tanks. Hybrid egg survival and wariness traits were interme...

Embryotoxicity of Great Lakes lake trout extracts to developing rainbow trout

Planar halogenated hydrocarbons (PHHs), such as polychlorinated dibenzo- p-dioxins, dibenzofurans, and biphenyls are present in aquatic systems, and are known to produce adverse effects in fish. This study investigated the embryotoxicity of PHH mixtures through the nanoinjection of environmental extracts into newly fertilized eggs from two strains of rainbow trout. Organic extracts were obtained from whole adult lake trout collected from Lake Michigan in 1988 and Lake Superior in 1994. The graded doses of the final extracts used for injection were quantified as 2,3,7,8-tetrachlorodibenzo- p-dioxin toxic-equivalents (TEQs) based on the concentrations of dioxins, furans and non- o-PCBs in each, and as equivalent amounts found in the eggs of the original lake trout (eggEQ). Total TEQs in the lake trout were 14.7 pg TEQ/g in the Lake Michigan sample and 7.3 pg TEQ/g in the Lake Superior sample. The extract of the Lake Michigan lake trout was embryotoxic to rainbow trout; LD 50 values were 35 eggEQ (15–90, 95% F.L.) in the Arlee strain and 14 eggEQ (5–99, 95% F.L.) in the Erwin strain of rainbow trout. The LD 50 values of the Lake Michigan extract in either of these strains of rainbow trout fall within the actual range of TCDD LD 50 values based on TEQs. This indicates that an additive model of toxicity is appropriate to quantify PHHs in relation to early life stage mortality in fish. Gross lesions characteristic of exposure to PHHs (i.e. yolk-sac edema, craniofacial deformities, and hemorrhaging) increased in a dose-related manner. The lowest observable adverse effect concentrations (LOAEC) for these gross lesions and cumulative mortalities suggests that current concentrations of PHHs in lake trout from Lake Michigan are above a threshold for adverse effects and these compounds may have implications on the lack of recruitment in certain Great Lakes lake trout populations.

Growth dynamics of white and red muscle fibres in fast‐ and slow‐growing strains of rainbow trout

Compared with fish of a slow‐growing strain, fast‐growing rainbow trout exhibited significantly smaller white fibre diameters, throughout development from hatching to 24 cm body length, although possessing similar total number of fibres. In contrast, in red muscle, no differences were observed in fibre diameter between the two strains, but the fast growing fish showed a significantly higher number of red fibres. The differences in growth rate between the two strains were related to the mean white fibre diameter and were found to be matched by proportional adjustments in recruitment of new fibres to the growing muscle. Thus, the largest and fastestgrowing strain showed evidence of sustained higher recruitment of muscle fibres that endowed this strain with the potential to maintain rapid somatic growth for longer and accomplish greater muscle growth.

Growth dynamics of white and red muscle fibres in fast- and slow-growing strains of rainbow trout

Growth dynamics of white and red muscle fibres in fast- and slow-growing strains of rainbow trout

The variability of the gustatory sensibility in salmonids, with special reference to strain differences in rainbow trout, Oncorhynchus mykiss

To determine the functional variability of the gustatory system in salmonids, we examined electrical responses of the palatine nerve to amino acids in nine strains of rainbow trout (Oncorhynchus mykiss), four additional Oncorhynchus species, and two Salvelinus species. All species exhibited extreme sensitivity to L-proline. Besides the Pro receptors (interacting with L-proline, hydroxy-L-proline, and L-alanine), Phe (L-phenylalanine, L-leucine), AGP (L-α-amino-β-quanidinopropionic acid, betaine), and Arg receptors (L-arginine) were involved in amino acid detection. On the basis of the functional receptor types, the rainbow trout strains fell into two groups: (1) Kamloops, Manx, Mount Lassen, Sunndalsøra, Tagwerker, and Victoria and (2) Nisqually, Nikko, and steelhead. The former group originates primarily from inland waters, whereas the latter originates from coastal waters. Response patterns of other salmonid species were similar to those of group 2 rainbow trout. Response patterns did not change as a result of environmental conditions. We thus conclude that the functional variability of the gustatory system is not attributable to local environmental factors but rather may be genetic in origin. Similar variability may exist in responses to other chemicals, including toxicants, and we conclude that in studies employing salmonids it is important to identify the stock of fish in addition to the species.

Boron Stimulates Embryonic Trout Growth

Boron is present in our soil, water and air. Cyanobacteria require it for nitrogen fixation, and vascular plants require it for the formation of cell walls and membranes. I report here how boron affects the growth of embryonic rainbow trout (Oncorhynchus mykiss). Fertilized ovum from the Mt. Whitney rainbow trout strain were incubated at (12.5°C) in Type 1 ASTM ultrapure grade water supplemented with boric acid (99.5% purity) during the 1995 and 1997 spawning seasons. Boron concentrations of the incubation solutions were determined by direct measurement using the curcumin procedure or inductively coupled plasma-mass spectrometry. In the 1995 study boron ranged from 1 to 936 μmol/L. Ca, Na and Mg salts were included in the incubation solutions to approximate concentrations in natural water. In the 1997 study fertilized eggs were incubated in ultrapure water supplemented with boric acid alone over a range from 2.2 to 90.6 μmol/L. The 1995 study used 144 embryos per B concentration and the 1997 study used 96 embryos per B concentration. Growth and teratogenicity were evaluated at the eye, hatch and 2-wk posthatch developmental stages. Boron stimulated growth in a dose-dependent manner in both studies (P < 0.001), and exposure was associated with an increase in B body concentration (P < 0.05). No teratogenic or microbicidal effects were apparent. These results are consistent with those expected of an element essential for vertebrate development.

Voluntary feed intake, feed and nutrient utilisation in slow and fast growing rainbow trout strains

Two rainbow trout strains differing in their growth performance were used to study possible interactions between genotype, dietary composition and feed level on their feed utilisation efficiency and voluntary feed intake. Two diets (35 and 45 % of crude protein) and two feeding levels (to satiation or at a restricted level of 2 % of body weight), were used. The two diets were distributed, in duplicate, for each strain, during a four month growth trial. At the end of the experiment the digestibility of the two diets was determined in each strain, using chromic oxide, as a marker, and an automatic system for the faecal collection. The body composition of both strains was also analysed. The final weight of fish of the fast growing strain, fed to satiation, was significantly higher than that observed for fish of the slow growing strain. No significant differences were found between the strains's body weights, when a dietary restriction was made. Results observed for the feed-gain ratio were also similar between the two strains. The apparent digestibility coefficient (ADC) of dry matter and energy were significantly different between the two diets but similar for both strains. Concerning protein digestibility no significant differences were observed for diets, although one of the strains appeared to show a higher ADC for protein. Body composition as well as nitrogen and energy retention were similar for both diets and strains.

Biochemical growth characterization of fast and slow-growing rainbow trout strains: effect of cell proliferation and size

Concentrations of RNA and DNA, determined in two rainbow trout strains, Cornec and Mirwart, over a period of 9 months, were used to assess and characterize growth potential. More rapid growth and higher muscle nucleic acid concentrations in the Cornac strain trout, suggest a more metabolically active strain with higher rates of protein synthesis. On the other hand, the higher concentration of muscle DNA, in the Cornec strain, suggests a smaller cell size and a larger number of cells per unit weight issue. The faster decrease of DNA concentration, with increasing body weight, in the Mirwart strain, reflected a lower percentage of hyperplasia and consequently a lower capacity for growth.

Intrastrain and interstrain variability in biotransformation enzyme activities of rainbow trout (Oncorhynchus mykiss)

We assessed the intrastrain and interstrain variability of cytochrome P450 enzyme activities and conjugation reactions of different rainbow trout (Oncorhynchus mykiss) strains. The study protocol was divided into two parts: in two separate experiments, monooxygenase (7-ethoxyresorufin O-deethylase, EROD) and conjugation (glutathione S-transferase, GST; UDP-glucuronosyl transferase, UDPGT) enzyme activities were measured from liver and kidney samples of commonly used rainbow trout breeds. In the preliminary study, the differences in the basal biotransformation enzyme activities were detected in two separately cultivated rainbow trout strains. Results indicated significant intrastrain (UDPGT, GST) and interstrain (EROD) differences in biotransformation enzyme activities. In the experimental study, corresponding enzyme activities were measured from three different rainbow trout strains exposed to beta -naphthoflavone (BNF), a polycyclic aromatic hydrocarbon (PAH) type model compound.The results revealed significant interstrain differences, especially in hepatic EROD and GST\b activities. However, UDPGT activities in the liver, as well as the measured monooxygenase and conjugation activities in the kidney, showed no notable variance between strains.The present work addresses intrastrain differences between hatcheries and highlights the need for intercalibration of rainbow trout strains used in experimental studies in aquatic toxicology.

Localized Genetic Effects of a Long-Term Hatchery Stocking Program on Resident Rainbow Trout in the Metolius River, Oregon

Abstract Hatchery rainbow trout Oncorhynchus mykiss have been stocked in the Metolius River in central Oregon since 1938, and legal-sized (≥160 g) yearling trout were stocked annually from 1947 until 1995. In 1996, management objectives shifted to emphasize wild trout, and hatchery stocking ceased. We examined allozyme and mitochondrial DNA (mtDNA) variation among three naturally occurring populations of rainbow trout in the Metolius River to investigate possible hybridization with hatchery-produced rainbow trout. We also examined two commonly used hatchery strains of rainbow trout, one of which has supplied nearly all of the catchable hatchery trout in the Metolius. Both allozyme and mtDNA data showed the two hatchery samples to have genetic characteristics typical of hatchery populations derived from coastal rainbow trout O. mykiss irideus. Rainbow trout sampled from the lower Metolius River, approximately 30 km downstream of the headwaters, had allozyme and mtDNA characteristics typical of interior rai...

Assessment of genetic variability among strains of rainbow and cutthroat trout using multilocus DNA fingerprints

DNA fingerprint banding patterns of mixed DNA samples from 17 to 28 individuals from five strains of rainbow trout ( Oncorhynchus mykiss) and two strains of cutthroat trout ( Oncorhynchus clarki) were analyzed to quantify genetic differences among the seven populations. Levels of within-population genetic variability were estimated by comparing DNA fingerprint banding patterns of individuals. Three multilocus oligonucleotide probes were used to detect the DNA fingerprints of individuals and mixtures. Scanning image analysis and customized software programs were used to assign band identity and to determine the degree of band-sharing between and within populations. The distinct genetic differences we identified between the Yellowstone cutthroat ( O. c. bouvieri) strain and the westslope cutthroat ( O. c. lewisi) strain, and between the two cutthroat subspecies and the five rainbow trout strains, are consistent with previous studies. Lower genetic variabilities were observed within the cutthroat trout strains, which is consistent with their previously reported lower heterozygosities at protein loci. Varying levels of genetic variability were identified within the rainbow trout strains, and the low level of variability detected among individuals from one of the strains is probably associated with previously observed symptoms of inbreeding depression in that strain. Our results suggest that multilocus DNA markers can be best utilized in studies of genetic variability among closely related populations and in breeding programs.

Detection of Single Strand Conformation Polymorphisms (SSCPs) on Mitochondrial DNA Fragments between Two Domesticated Strains of Rainbow Trout &lt;i&gt;Oncorhynchus mykiss&lt;/i&gt;

Detection of Single Strand Conformation Polymorphisms (SSCPs) on Mitochondrial DNA Fragments between Two Domesticated Strains of Rainbow Trout &lt;i&gt;Oncorhynchus mykiss&lt;/i&gt;

Identification of sex chromosome molecular markers using RAPDs and fluorescent in situ hybridization in rainbow trout.

The goal of this work is to identify molecular markers associated with the sex chromosomes in rainbow trout to study the mode of sex determination mechanisms in this species. Using the RAPD assay and bulked segregant analysis, two markers were identified that generated polymorphic bands amplifying preferentially in males of the Mount Lassen and Scottish strains of rainbow trout. Chromosomal localization using fluorescent in situ hybridization of a 900 bp probe developed from one of these markers revealed a brightly defined signal on a chromosome that could morphologically be classified as the Y chromosome.

History and Fluctuating Asymmetry of Utah Salmonid Broodstocks

Abstract The level of potential inbreeding in Utah salmonid broodstocks was assessed by fluctuating asymmetry (FA) of five bilateral meristic characters. Counts were made of the following characters on the left and right sides of 40 fish: gill rakers on the lower first branchial arch, gill rakers on the upper first branchial arch, mandibular pores, pectoral fin rays, and pelvic fin rays. Data from state hatchery records for the last 20 years were examined for trends in development to the eyed stage, percent hatch, and percent cripples (deformity). A brief history of Utah broodstocks is also presented. The mean FA for each of the strains of five species varied from 1.25 (Sand Creek strain rainbow trout Oncorhynchus mykiss) to 3.15 (Bonneville cutthroat trout O. clarki utah), with no consistent differences among species. The meristic counts were variable, and the overlap made differentiation among strains and species based upon these counts impossible. From 1972 to 1993, percent survival to the eyed egg sta...

Genetic effects and growth performance in pure and hybrid strains of rainbow trout, Oncorhynchus mykiss (Walbaum) (Order: Salmoniformes, Family: Salmonidae)

Progeny from a cross of two strains of rainbow trout, Oncorhynchus mykiss (Walbaum), displayed about 7% heterosis in their growth rate. Variance component analysis showed that dams accounted for 20.3% to 65.8% variability in growth while sires accounted for none. Maternal effects were significant, but showed a diminishing trend over the study period. Additive genetic effects were nonsignificant. The Mount Lassen strain was better in maternal ability which indicated that source of dam was important. Interactions between sires and dams were significant with source of dam being important. Heritability for weight based on half-sib sire component of variance was estimated at 0.020 ± 0.001 and 0.269 ± 0.016 based on the dam component. Heritability for growth rate was 0.27 ± 0.04 based on the sire component and 0.88 ± 0.35 based on the dam component. Fulton's condition factor was lower in the hybrids. Egg size was correlated with fish size in the early growth phase. It was concluded that crossbreeding of rainbow trout strains could be advantageous owing to the display of hybrid vigour in the progeny.