NADH-dependent cytochrome b5 reductase and NADPH methemoglobin reductase activity in the erythrocytes of Oncorhynchus mykiss

Methemoglobin is oxidized hemoglobin that cannot bind to or dissociate from oxygen. In fish, it is most commonly caused by exposure to excess nitrites and can lead to abnormal swimming, buoyancy, or death. The methemoglobin concentration in mammals is determined by the balance of oxidizing agents versus reducing enzymes in erythrocytes. The objective of our studies was to characterize the enzymes that reduce methemoglobin in fish erythrocytes. Whole blood was collected from healthy rainbow trout. Methemoglobin was induced in vitro by NaNO₂ exposure. Methemoglobin reduction in controls was compared to reduction in samples with added NADH, NADPH, or NADPH and methylene blue. Rainbow trout whole blood was also fractionated into cytosol, microsomal, and mitochondria/plasma membranes/nuclei fractions. The fractions were compared for NADH-dependent cytochrome b5 reductase (CB5R) activity and for nitrite induction of methemoglobin. The CB5R activity in rainbow trout erythrocytes was compared to the CB5R activity in equine, feline, and canine erythrocytes. Rainbow trout erythrocytes had significant NADPH methemoglobin reductase activity in the presence of methylene blue (P < 0.001). The CB5R activity was greatest (P < 0.001) in the plasma membrane/mitochondria/nuclei fraction. The CB5R activity in rainbow trout erythrocytes was not significantly different than canine or equine activity but was significantly lower than feline CB5R activity (P < 0.0001). Methemoglobin in rainbow trout erythrocytes can be reduced by CB5R or NADPH-dependent methemoglobin reductase. Unlike mammalian anuclear erythrocytes, which are dependent on soluble CB5R, the nucleated RBCs of rainbow trout use membrane-bound CB5R to reduce methemoglobin.     

Production Characteristics of Rainbow Trout,Oncorhynchus mykiss and Brook Trout,Salvelinus fontinalis Under Seasonal Pond Conditions

Abstract

The production characteristics of juvenile rainbow trout, Oncorhynchus mykiss and brook trout, Salvelinus fontinalis were compared under winter pond conditions. Juvenile rainbow trout (55.1 ±1.5 g) and brook trout (28.9 ±0.4 g) were stocked at a density of 8,750 fish/ha into six 0.04-ha ponds. After 163 days, survival, growth, and feed conversion were similar (P >0.05). The results of this study suggest that brook trout may attain growth rates similar to rainbow trout under winter pond conditions in temperate regions of North America.     

饲养条件下花羔红点鲑和虹鳟生长、摄食的比较

红点鲑属 (Ｓａｌｖｅｌｉｎｕｓ)是一群珍稀冷水鱼类 ,在鱼类分布区系上属北极淡水类群。迄今为止 ,红点鲑属在国内外共描述有 34个种类以上 (包括地方变异型 ) ,其中在我国仅分布有 2种 ,即花羔红点鲑Ｓ .ｍａｌｍａ (Ｗａｌｂａｕｍ)和白斑红点鲑Ｓ .ｌｅｕ ｃｏｍａｅｎｉｓ (Ｐａｌｌａｓ)。红点鲑属鱼类具有体色艳丽、生长率高、耐高密度和营养价值高等特点 ,在美国、加拿大、挪威、俄罗斯和日本等十多个国家被认为是有广阔发展前景的增殖、游钓和养殖的对象 ,是持续渔业发展的一个重要组成部分。发展鲑鳟渔业 ,开发冷水资源 ,增产优…     

Comparison of Post‐mortem Mass Changes in Myosin Heavy Chain and Textural Characteristics among Oncorhynchus mykiss (Walbaum, 1972), Salmo trutta fario (Linnaeus, 1758) and Salvelinus fontinalis (Mitchill, 1814)

In this study, post‐mortem myofibril proteins change in myosin heavy chain (MHC) mass using sodium dodecyl sulphate‐polyacrylamide gel electrophoresis (SDS‐PAGE), texture properties such as hardness, stickiness, cohesiveness, elasticity, chewiness, gumminess and stress relaxation test parameters (Fmax, Fmin and Fmax‐Fmin) were determined and compared on the days 0, 3, 6 and 9 in three different trout species (Oncorhynchus mykiss, Salmo trutta fario and Salvelinus fontinalis). In terms of texture properties, post‐mortem hardness, cohesiveness, elasticity, chewiness and gumminess were decreased day by day, whereas stickiness, Fmax, Fmin and Fmax‐Fmin were significantly increased (p < .05). According to SDS‐PAGE results, a decreased value on MHC was determined (p < .05). Texture properties and SDS‐PAGE results were found different among groups (p < .05). Correlation between chewiness, gumminess, MHC and hardness; between chewiness and gumminess; between Fmin, Fmax‐Fmin and Fmax; between Fmin and Fmax‐Fmin were significant. As a result of the study, S. fontinalis exhibited least deterioration in comparison with other species and it was determined that SDS‐PAGE results and texture properties support each other.     

Pancreas disease in farmed Atlantic salmon, Salmo salar L., and rainbow trout, Oncorhynchus mykiss (Walbaum), in Norway

The present paper describes, for the first time, clinical signs and pathological findings of pancreas disease (PD) in farmed Atlantic salmon, Salmo salar L., and rainbow trout, Oncorhynchus mykiss (Walbaum), in sea water in Norway. Similarities and differences with reports of PD from Ireland and Scotland are discussed. Samples of 68 rainbow trout from disease outbreaks on 14 farms and from 155 Atlantic salmon from outbreaks on 20 farms collected from 1996 to 2004 were included in the present study. The histopathological findings of PD in Atlantic salmon and rainbow trout in sea water were similar. Acute PD, characterized by acute necrosis of exocrine pancreatic tissues, was detected in nine Atlantic salmon and three rainbow trout. Salmonid alphavirus (SAV) was identified in acute pancreatic necroses by immunohistochemistry. Most fish showed severe loss of exocrine pancreatic tissue combined with chronic myositis. Myocarditis was often but not consistently found. Kidneys from 40% and 64% of the rainbow trout and Atlantic salmon, respectively, had cells along the sinusoids that were packed with cytoplasmic eosinophilic granules. These cells resembled hypertrophied endothelial cells or elongated mast cell analogues. Histochemical staining properties and electron microscopy of these cells are presented. SAV was identified by RT-PCR and neutralizing antibodies against SAV were detected in blood samples.     

Mortality related to pancreas disease in Norwegian farmed salmonid fish,Salmo salar L. and Oncorhynchus mykiss (Walbaum)

High mortality during the salmonid seawater phase is a continuous problem for the salmonid aquaculture industry, although the mortality levels show a large variation both in farms with a disease history and those without. We wanted to examine the mortality patterns in farms with pancreas disease (PD) and compare it to farms without this diagnosis. Further, we wished to investigate the factors influencing the maximum mortality in both groups. We examined data from all salmonid farms in Norway stocked after January 2003 and slaughtered before December 2007. In total, 1884 cohorts were included, and 150 of these were diagnosed with PD. We found that season accounted for more of the variation in mortality than water temperature in PD‐positive cohorts and that infection pressure influenced the mortality in non‐PD cohorts, suggesting outbreaks of disease that are not diagnosed. We also found that the mortality in PD cohorts decreased significantly from 2003 to 2007, suggesting that increased knowledge about PD and targeted actions have been effective. Our study further suggests that crude mortality figures may be of limited use when wanting to examine a particular disease and risk factors for increased mortality. We suggest farmers and legislation should turn to a more modern approach with cause‐specific mortality records.     

Movements of Atlantic salmon, Salmo salar L., parr and brook trout, Salvelinus fontinalis (Mitchill), in lakes, and their impact on single-census population estimation

Three small Newfoundland lakes were fished to estimate the population sizes of Atlantic salmon, Salmo salar L., parr and brook trout, Salvelinus fontinalis (Mitchill), and to study within-lake movements of the species. The whole shoreline of the lakes was seined, the catches in different sections were recorded separately and the fish were given different marks. Estimates for the lakes derived from different subareas were constantly lower than the estimate derived by using the data from the whole shoreline. If estimates of the different sub-areas were extrapolated according to their proportion of the shoreline, they were positively biased, and showed higher variance. Significant correlations between the movement rates and the accuracy of sub-area population estimates and recapture rates were found. Validation of the assumption of random mixing of marked and unmarked fish, when a spatially stratified sampling is carried out, is emphasized.     

Branchial lesions associated with intermittent formalin bath treatment of Atlantic salmon, Salmo salar L., and rainbow trout, Oncorhynchus mykiss (Walbaum)

Two trials were conducted to assess the effects of repeated prophylactic formalin treatments on the gill structure of salmonids. In trial 1, which involved Atlantic salmon, Salmo salar L., approaching smoltification in a commercial facility, fish were treated with either 167 or 250 mg l^-1 formalin for 90 min every 2 weeks for 12 weeks. Formalin-treated salmon had slight, but not significant, increases in the frequency of lamellar fusion, numbers of lamellar mucous cells, and numbers of an endemic gill ciliate, Trichophyra piscium, after 6 and 12 weeks of treatment. In trial 2, which involved juvenile rainbow trout, Oncorhynchus mykiss (Walbaum), fish were treated with 200 mg l^-1 formalin for 60 min twice weekly for 12 weeks. Significant effects were limited to an increase in the numbers of mucous cells present on gill lamellae. In both trials, there was no evidence of lamellar oedema or necrosis of lamellar epithelial cells.     

Effect of growth hormone on muscle protein synthesis in rainbow trout (Oncorhynchus mykiss) and Atlantic salmon (Salmo salar)

This paper reports on the effect of administration of mammalian growth hormone (GH) on muscle protein synthesis as measured in white muscle using the phenylalanine flooding technique. The effect of exogenous GH was compared with that of insulin and prolactin, and with endogenous GH.The rate of protein synthesis in white muscle of rainbow trout 6 h after the injection of bovine GH or bovine insulin was twice (2.6 and 2.9% d^–1) that of the control saline-injected fish (1.2% d^–1). A metabolic effect of GH, as observed with insulin, is suspected.The rates of change in body weight and body length and the fractional rate of protein synthesis in muscle of rainbow trout were enhanced by mammalian GH administration. The effect of GH on muscle RNA/protein ratios was not significant. An opposite effect of antibodies against salmon GH (Lebailet al. 1989) on growth rate and muscle protein synthesis rate was found in rainbow trout. It is suggested that the effects of exogenous and endogenous GH on capacity and efficiency of muscle protein synthesis were similar.The long-term effects of mammalian GH on presmolt Atlantic salmon was also tested. The same trends were found with ovine prolactin supplementation in Atlantic salmon but not as high as those observed with ovine GH.     

Alterations in iron, zinc and major plasma proteins of rainbow trout, Oncorhynchus mykiss (Walbaum), and brook trout, Salvelinus fontinalis (Mitchill), with sterile peritonitis induced by oil-adjuvanted multivalent bacterin vaccination

The early humoral responses of rainbow trout, Oncorhynchus mykiss (Walbaum), and brook trout, Salvelinus fontinalis (Mitchill), with sterile inflammation induced by intraperitoneal Lipogen Triple vaccination were compared to determine if genetic differences in susceptibility to furunculosis in salmonids correlated with different acute phase responses to vaccination. Similar severe acute sterile peritonitis occurred in response to Lipogen Triple in both species. Both species also had a rapid transient reduction in plasma iron concentration at 3 days. Moderate hypoferraemia persisted to day 14 in brook trout, but returned to normal by day 7 in rainbow trout. Plasma zinc decreased sharply 3 days after vaccination in rainbow trout and returned nearly to control levels by day 10; however, plasma zinc did not change in brook trout. Two-dimensional sodium dodecyl sulphate polyacrylamide electrophoresis of plasma proteins revealed that increased amounts of a 48-kDa protein group coincided with the hypoferraemic response in rainbow trout. In addition, a modest elevation in a 16-kDa protein group also occurred in rainbow trout. These studies demonstrated the rapid changes in plasma iron in both species and mild elevation of two putative acute phase plasma proteins associated with vaccine-induced inflammation in rainbow trout.     

Effect of Dietary Inclusion of N-Acetyl Cysteine on Mucus Viscosity and Susceptibility of Rainbow Trout, Oncorhynchus mykiss, and Atlantic Salmon, Salmo salar, to Amoebic Gill Disease

The treatment of amoebic gill disease (AGD) in cultured Atlantic salmon, Salmo salar L., using mucolytic agents has been previously reported. The agent L‐cysteine ethyl ester reduces salmonid mucus viscosity and potentially increases the flushing of the gill. In the present study, the effects of the mucolytic agent N‐acetyl cysteine (NAC) were assessed. Cutaneous mucus from rainbow trout, Oncorhynchus mykiss Walbaum, and Atlantic salmon was shown to have reduced viscosity when mixed in vitro with 100 or 200 μg/mL NAC. Saltwater‐acclimated rainbow trout and Atlantic salmon were fed an oil‐incorporated, NAC‐medicated diet (8 g NAC/kg diet) for up to 24 d and challenged with inoculation of 300 cells/L Neoparamoeba spp., the etiological agent of AGD. Control fish were fed normal oil‐coated pellets and received no NAC. NAC medication failed to reduce the severity of gill lesions associated with AGD even though the mucus viscosity from medicated fish was less than that of controls. Oral NAC medication does not appear to be an effective method for controlling AGD in salmonids despite reducing cutaneous mucus viscosity.     

Association between initial weight and weight gain in brook trout, Salvelinus fontinalis Mitchill, and brown trout, Salmo trutta L.

Abstract. Individual weighings of samples of brook trout, Salvelinus fontinalis Mitchill, and brown trout, Salmo trutta L., al the initiation and termination of their growth period, enabled estimating the association of weight gain on initial weight. In both cases the regressions were positive and the correlations significant. Variation in initial weight among tested individuals and groups is expected to bias growth estimates of these groups in programmes of genetic testing, as a result of this association. Obviating this bias requires an adequate correcting technique, involving the estimation of an environmentally generated correction factor. Phenotypic regression coefficients, as estimated in this investigation, cannot serve as correction factors, but may be regarded as maximum estimates.     

Blood electrolyte and prolactin regulation in rainbow trout, Oncorhynchus mykiss (Walbaum), exposed to nitrite

Abstract. Rainbow trout, Oncorhynchus mykiss (Walbaum), exposed to environmental nitrite for 3h showed significantly reduced chloride concentrations from 120·9 ± 0·5 to 113·8 ± 2-4 mmol/1, the result of nitrite uptake by the gills with a compensatory loss of blood chloride. This change could be prevented by injection of 10 mg/kg sulpiride, which stimulates prolactin secretion through antagonism of dopamine D₂ receptors, thus increasing circulating prolactin levels. Prolactin is known to decrease membrane permeability and the increased levels of the hormone probably account for the relatively unchanged (compared to controls) plasma chloride and potassium levels in nitrite-exposed, sulpiride-treated fish.     

Angiotensins stimulate in vitro ovulation and contraction of brook trout (Salvelinus fontinalis) follicles

The effects of salmon angiotensin I (sAI) and human angiotensin II (hAII) on in vitro ovulation of preovulatory (preOV) brook trout (Salvelinus fontinalis) follicles were investigated. Both angiotensins increased levels of ovulation above that in controls after 12 hours of incubation. The increase was statistically significant in incubates with greater than 1 M hAII. The effects of the angiotensins on follicle contraction were also studied indirectly by measuring the decrease in weight of punctured follicles taken prior to germinal vesicle breakdown. At 1 M, both angiotensins significantly decreased the weight of punctured follicles after 16 hours of incubation. The angiotensin-stimulated decrease in weight was not blocked by indomethacin (10 g/ml), indicating that follicle contraction was not prostaglandin-dependent. The data indicate that angiotensins might be directly involved in brook trout ovulation and the stimulatory effects of angiotensins on ovulation may be attributed to their effects on follicle contraction.This work was supported by NIH grant #HD25924-02.     

Comparison of the performance of brown trout, Salmo trutta L., and rainbow trout, Oncorhynchus mykiss (Walbaum), in a put-and-take fishery

Abstract. Stock and catch statistics for a small (5–5ha) lowland put-and-take trout fishery have been used to investigate the relative catchability of brown, Salmo trutta L., and rainbow, Oncorhynchus mykiss (Walbaum), trout. Brown trout were consistently less vulnerable to fly fishing than rainbows, and were particularly difficult to catch between mid-June and September. As a consequence, the turn-over of rainbow trout stock was more rapid than that of brown trout, but eventual recapture levels of both species were similar at around 90% of the fish stocked. In these circumstances, brown trout could be regarded as a long-term investment for fishery managers, with rainbows providing more'instant'sport.     

The influence of Gyrodactylus salaris Malmberg 1957 (Monogenea) on the epidermis of Atlantic salmon,Salmo salar L., and brook trout,Salvelinus fontinalis (Mitchill): experimental studies

The effect of Gyrodactylus salaris on the epidermal structure of hatchery-reared brook trout parr and Norwegian Atlantic salmon parr was evaluated. Both species were initially susceptible to this parasite, but whereas populations on salmon increased until the host died, brook trout responded to, and eventually eliminated, their infections. Salmon skin samples taken 14 days p.i. showed a reduced mucous cell concentration (less than 1500 cells mm^–2 on the head compared with 2000 cells mm^–2 in controls; the same trend was also seen in other sites) and the epidermis was thinner (48 μm compared with 60 μm on pectoral fins; similar trend seen in other sites) than in uninfected controls kept under identical conditions. Brook trout skin samples were taken 50 days p.i., when the hosts had responded to, and almost eliminated, their infections. No change was then observed in mucous cell density, while the number of epidermal cell layers and the epidermal thickness of brook trout had increased slightly following infection. These results are related to the nature of the host response, and the thinning of the epidermis and loss of mucous cells may in some way be related to the inability of Norwegian salmon parr to respond to the parasite.     

Reduction of brown trout, Salmo trutta L., salmon, S. salar L., and rainbow trout, Oncorhynchus mykiss (Walbaum), smolt bycatches in eel pound nets

Two types of bycatch reduction devices (BRDs) were tested in the Randers Fjord, Denmark, aimed at deflecting the surface-oriented smolts of brown trout, Salmo trutta L., salmon, Salmo salar L., and rainbow trout, Oncorhynchus mykiss (Walbaum), before they became trapped, while retaining the catches of eel, Anguilla anguilla (L.). The methods tested were: a) placing a floating guard net between the wings; and b) submerging the pot net (i.e. last enclosure before fyke net) 55–100 cm below mean sea level. After each haul the pound net-setups were changed from the control to one of the types of BRD, and vice versa. Both methods significantly reduced the bycatch of brown trout smolts, while catches of legal-sized eels were not affected. Submerging the pot net reduced smolt catches of all species; mean reductions were 91.1% for brown trout, 74.5% for rainbow trout, and 86.1% for salmon.     

Detection and antigenic characterization of salmonid alphavirus isolates from sera obtained from farmed Atlantic salmon, Salmo salar L., and farmed rainbow trout, Oncorhynchus mykiss (Walbaum)

A simple method of detecting the presence of the salmonid alphaviruses (SAVs), salmon pancreas disease virus (SPDV) and sleeping disease virus (SDV), from serum samples is described. Using a 96-well tissue-culture plate format, test sera are diluted in medium and added to chinook salmon embryo (CHSE-214) cells. After incubation for 3 days at 15 degrees C, plates are fixed and stained using a monoclonal antibody (mAb)-based immunoperoxidase (IPX) detection system, and virus-infected cells are observed microscopically by white light. Application of this screening test, which is now used routinely in our laboratory in conjunction with an IPX-based virus neutralization (IPX-VN) test for detecting antibodies to SAVs, has resulted in the recovery of 12 additional isolates from salmon sera and four additional isolates from trout sera. A low level of antigenic variation was detected when these SAV isolates were investigated by indirect immunofluorescence using a panel of mAbs raised to reference SPDV and SDV isolates.     

Competitive exclusion of brown trout Salmo trutta L., by rainbow trout Oncorhynchus mykiss Walbaum, in lake tributaries, New Zealand

Spawning runs of brown trout Salmo trutta L., and rainbow trout, Oncorhynchus mykiss Walbaum, were compared in three tributaries of two lakes for timing, numbers and redd characteristics. Redd characteristics for the two species in four other streams were examined. No significant differences in redd characteristics between the two species were observed, but in all lake tributaries the possibilities of superimposition of spring spawning rainbow trout on redds of brown trout were examined. A common feature was the high ratio of numbers of spawners to the area of preferred spawning gravel, and it was concluded that in the lake tributaries, superimposition resulted in increased mortality of brown trout eggs, and in one case elimination of the brown trout population. Management possibilities for control of the species proportions in comparable situations are discussed.