Triploid Rainbow Trout Oncorhynchus Mykiss Research Articles

Digestive characteristics and blood chemistry profile of triploid rainbow trout Oncorhynchus mykiss: influence of body size and seasonal variation

Two experiments were conducted to evaluate the effects of body size and seasonal variation on organ indexes, digestive enzymes and plasma biochemistry parameters of triploid rainbow trout. Results in experiment 1 showed that compared with small fish, large fish had significantly (P < 0.05) higher values of organ indexes, higher plasma nutrient contents as well as higher specific activities of lipase in pyloric caeca and amylase in the intestine. Results in experiment 2 showed that fish in spring or winter had greater intestine length as well as lower specific activities of protease and lipase in pyloric caeca (P < 0.05). Fish in autumn had the highest specific activities of acid protease in the stomach and alkaline protease in pyloric caeca, lipase in pyloric caeca as well as nutrient contents in plasma, while fish in summer had the lowest liver and viscera weight as well as plasma nutrient contents. Based on data of organ indexes, digestive enzymes and plasma biochemistry parameters, the physiological status of triploid rainbow trout were affected by fish size and seasonal variation. Normal reference ranges of organ indexes and plasma biochemical parameters of triploid rainbow trout were preliminarily established, which are partly different from diploid trout.

Effects of dietary Antarctic krill Euphausia superba meal on growth performance and muscle quality of triploid rainbow trout Oncorhynchus mykiss farmed in sea water

The present study was conducted to investigate the effects of replacement of dietary fish meal by Antarctic krill Euphausia superba meal on growth performance, body composition and organoleptic quality of triploid rainbow trout Oncorhynchus mykiss (initial body weight: 102.06 ± 0.04 g) farmed in sea water. The basal diet contained 51% of fish meal. Based on it, five isonitrogenous and isolipidic experimental diets were formulated with the protein replacement ratio of fish meal by krill meal as 0, 15%, 30%, 60% and 100%, respectively (DM0, DM15, DM30, DM60 and DM100, respectively). After an 8-week feeding trial, results showed that increasing levels of dietary krill meal linearly and quadratically increased significantly FBW, SGR and FI (P < 0.05). Significant positive linear trends were found between the increasing levels of dietary krill meal and carotenoid concentrations, redness (a*), yellowness (b*) and chroma (C*) in muscle; and significant negative trends were found in the lightness (L*) and hue (H*) responses (P < 0.05). The pH and liquid holding capacity (LHC) were not affected by dietary krill meal levels (P > 0.05). A positive quadratic trend was found between the dietary krill meal level and the springiness, and a negative linear trend in cohesiveness occurred (P < 0.05). The content of fluorine in vertebra increased linearly and quadratically significantly (P < 0.05) but the content of fluorine in muscle was not significantly affected by increasing levels of dietary krill meal (P > 0.05). The highest fluorine content in muscle was within the safe edible limit for humans. These results suggested that Antarctic krill meal could improve the growth performance and muscle pigmentation of triploid rainbow trout farmed in seawater.

State of gonads of yearlings of triploid rainbow trout Oncorhynchus mykiss exposed to androgenic hormone under high-mountain conditions of South Vietnam

Changes in the morphology of gonads under the effect of methyltestosterone in juveniles of triploid rainbow trout Oncorhynchus mykiss incubated and cultivated in a trout farm under climatic conditions of South Vietnam have been studied. It was shown that the effect of the androgenic hormone intensifies the formation and development of testes in triploid rainbow trout at an age of 1+, decreasing the proportion of sterile individuals and the proportion of fish with anatomical and cytological anomalies in the structure of gonads. The relationship between the found anomalies in the structure of the genital system of trout and its triploidization, hormonal effect, and abiotic environmental conditions is discussed.

The in vitro blood-O2 affinity of triploid rainbow trout Oncorhynchus mykiss at different temperatures and CO2 tensions

Blood-O(2) affinity, Hill number and predicted arterial-O(2) saturation did not differ between diploid (2N) and triploid (3N) rainbow trout Oncorhynchus mykiss blood when compared under various temperature and CO(2) partial pressure combinations. These results suggest that reduced hypoxia and warm-water tolerance and aerobic capacity of 3N fishes are not due to altered blood-O(2) affinity. Further investigation into O(2) transport-diffusion capacity and intracellular pH within 3N fishes may further unravel the mechanisms behind reduced 3N tolerance of suboptimal environments.

Amitosis‐like nuclear division in erythrocytes of triploid rainbow trout Oncorhynchus mykiss

This work shows that the atypical erythrocytes in triploid rainbow trout Oncorhynchus mykiss were morphologically similar to those of toads. The nuclei of the cells can be bell-shaped, constricted or irregular. It is presumed that such nuclear division is probably amitosis.

Triploid and Diploid Rainbow Trout Do Not Differ in Their Stress Response to Transportation

AbstractWe examined the neuroendocrine and cellular stress responses of diploid and triploid rainbow trout Oncorhynchus mykiss to transportation. Juvenile diploid and triploid rainbow trout (28 and 26 g/fish average weight, respectively) were stocked at 100 g/L in replicate 70‐L tanks and subjected to transportation for an 8‐h period. Subsequent levels of plasma cortisol and glucose and of cellular hepatic glutathione (GSH) and heat shock protein 70 (Hsp70) were similar between ploidy groups, indicating that triploid fish respond to transportation in much the same way as diploid fish. A stationary treatment was also included that involved confinement of experimental fish in similar tanks without transport to determine to what extent high‐density containment contributed to the stress response in the absence of the noise and vibration of transport. Unexpectedly, fish in the stationary treatment had significantly higher plasma cortisol and glucose levels than the transported fish; however, this might be attributable to a confounding effect of hyperoxia, as oxygen levels fluctuated between 150% and 460% saturation in the stationary tank, while those in the transported tank remained within 100–200% saturation. We suggest that when long stops are necessary while transporting fish, water agitators be used to preclude the additional stress of excessive gas saturation. This may be particularly important for triploid fish, which had lower hepatic GSH levels than diploid fish as well as a low level of mortality in the stationary treatment, unlike the diploid fish.

Relative Survival and Growth of Triploid and Diploid Rainbow Trout in Two Idaho Reservoirs

Abstract The objective of this study was to determine whether triploid rainbow trout Oncorhynchus mykiss grew faster or lived longer than diploid rainbow trout stocked in two southeastern Idaho reservoirs. In October 1996, triploid and diploid rainbow trout were differentially marked and stocked in equal proportions. Relative survival and growth rates were estimated by means of gill-net and electrofishing samples collected through October 2000. In both reservoirs, the relative survival rate (total catch) was significantly higher for triploid fish. The final catch ratios (triploid: diploid) were 1.4:1 and 1.9:1 in the Treasureton and Daniels reservoirs, respectively. We also observed ontogenetic differences in growth. At age 1, mean lengths and weights were similar for the triploid and diploid fish in each reservoir. During the second year, diploids weighed significantly more than triploids. The trend reversed as the diploid fish matured: age-3 and older triploids matched or exceeded diploid fish in length...

Relative Return to Creel of Triploid and Diploid Rainbow Trout Stocked in Eighteen Idaho Streams

Introductions of fertile nonnative hatchery trout have led to interspecific and intraspecific hybridization of native salmonid stocks throughout North America. Use of sterile triploid hatchery trout in stream-stocking programs could reduce genetic risks to native stocks while addressing public demand for consumptive fishing opportunity. Techniques to produce triploid salmonids are well developed, and triploid rainbow trout Oncorhynchus mykiss are readily available from commercial sources. However, there is no published information on the return to creel of triploid trout in stream recreational fisheries. We purchased mixed-sex triploid and diploid rainbow trout eggs from a commercial supplier and reared the resulting fish to catchable size. Flow cytometry was used to verify triploid induction rates in the triploid group. Estimated cost to produce a triploid catchable rainbow trout was about 15% higher than for a diploid fish. We jaw-tagged and stocked 300 triploid and 300 diploid fish into each of 18 streams throughout Idaho and used tag returns to assess relative return to creel and timing of returns for the two groups. In all, 1,849 tags were returned by anglers, 931 from triploid fish and 918 from diploid fish. Overall returns were not significantly different between groups (paired t-test; P = 0.80). Mean time to harvest also did not differ between groups (paired t-test; P = 0.35). These results suggest that triploid rainbow trout can provide stream angling opportunity equal to that provided by fertile diploid fish. Although there are other concerns regarding the stocking of hatchery trout in streams containing native trout, we suggest that using triploid rainbow trout in stream-stocking programs can help balance the demands for both consumptive fishing opportunity and conservation of native stocks.

Muscle fibre growth dynamics in diploid and triploid rainbow trout

The effect of triploidy on muscle fibre growth was determined by comparing hyperplasia and hypertrophy of white muscle fibres in all‐female, diploid and triploid rainbow trout Oncorhynchus mykiss (100–400 mm total length). Conventional morphometry and protein and DNA concentrations were used to assess muscle fibre hyperplasia and hypertrophy in white muscle samples derived from an anterio‐dorsal location. Muscle fibre distributions were significantly different between triploids and diploids in trout &lt;300 mm. The proportion of fibres &lt;20 μm was higher in diploids than in triploids and the proportion of fibres in the 20–40 μm category was higher in triploids than in diploids. This indicates that the hyperplastic fibres of triploids are larger than those of diploids. Larger hyperplastic fibres in triploids are probably due to the combined effect of increased nuclear size in triploids and the relatively high nucleus: cell ratio observed in small muscle fibres. These larger fibres may be less favourable to cellular metabolic exchange because of their smaller surface area to volume ratios, and perhaps account for reduced viability and growth observed in triploids during early life stages. On the other hand, the lack of difference in the distribution of fibres &lt;20 μm between diploids and triploids at larger body size ranges (301–400 mm) imply that triploid trout may have higher rates of new fibre recruitment and growth capacity at these sizes. There was no difference between diploid and triploid trout in the mean size of muscle fibres; however, the number of fibres per unit area was reduced by 10% in triploids. No differences were observed in protein or DNA concentrations in muscle tissues between the two genetic groups. Since triploid nuclei have 1·5 times more DNA than diploid nuclei, this deviation from the expected muscle DNA concentration (1·3–1·4 times more DNA in triploids when the 10% reduction in fibre density is considered) suggests that the number of nuclei per muscle fibre is reduced. In both diploids and triploids, mean fibre size increased with body length while fibre density decreased. Similarly, protein concentration in the muscle tissue increased and DNA concentration declined with increasing body length. Protein/DNA ratio was strongly and positively correlated with fibre size. These results demonstrate that changes in DNA and protein concentrations can be used to assess hyperplasia and hypertrophy in muscle tissues. However, the morphometric procedure provides better insight into muscle fibre growth as it enables the direct visualization and analysis of muscle fibre distribution patterns.

Steroid Activation of the Brain–Pituitary Complex Gonadotropic Function in the Triploid Rainbow TroutOncorhynchus mykiss

Testosterone and estradiol were implanted into triploid rainbow trout, and their effects on brain and pituitary salmon gonadotropin-releasing hormone (sGnRH) content and on gonadotropin (GtH2) levels in the pituitary and blood were studied. In the hypothalamic areas, neither steroid altered sGnRH content. In the brain tissues (ventral telencephalon and preoptic areas), testosterone (0.5 mg/kg BW) significantly increased sGnRH contents and larger doses induced a more rapid increase. Estradiol induced a similar increase which occurred later than the response to the same dose of testosterone. Both steroids also stimulated pituitary sGnRH, with estradiol being less potent. Only testosterone induced long-term increases in plasma GtH2 content. Both steroids may act on the synthesis and release of GnRH, with testosterone having a greater influence on the control of gonadotropin secretion, especially at the end of the cycle.

Non-specific Defense Activities of Triploid Rainbow Trout.

Triploid rainbow trout Oncorhynchus mykiss were compared with diploid trout in complement activity monitored by hemolytic and bactericidal activities, and in neutrophil activity by visual phagocytosis and luminol-dependent chemiluminescence.No significant differences were detected in complement activity and neutrophil activity between diploid and triploid trout. These results indicate that non-specific defense activities of triploid trout are similar to those of diploid trout, and that the triploidy does not fundamentally affect the susceptibility of the fish to diseases.

Field Performance of Triploid and Diploid Rainbow Trout in South Dakota Ponds

Triploid fish theoretically divert energy from sexual development and reproductive behavior into somatic growth. We found lengths, weights, and relative weights of triploid rainbow trout Oncorhynchus mykiss to be significantly (P ≤ 0.05) less than those of diploid fish at the age of 45 months in three South Dakota ponds. Gonadal development in triploid females was negligible in 1989 and 1990 and reduced in triploid males during 1990. Catches of triploid fish were always lower than catches of diploid fish, suggesting lower survival. Physiological factors, perhaps environmentally induced, may have diminished the growth potential of triploid rainbow trout. Results of this study indicate that the use of triploid rainbow trout is not justified as a means of obtaining increased growth and survival under the conditions present in our study ponds.