Effects of changes in plasma pH,CO2 and ammonia on ventilation in trout

We investigated ventillatory responses to a plasma alkaloids and hypocapnia,a nd the basis for the ventilatory response to sodium bicarbonate (NaHCO₃) infusion in rainbow trout. Plasma alkalosis and hypocapnia created by infusion of sodium hydroxide (NaOH) did not cause hypoventilation, whereas infusion of hydrochloric acid (HCl) caused vigorous hyperventilation, associated with an acidosis, a reduction in blood O₂ content (Ca_{O 2}) and a release of circulating catecholamines. Infusion of NaHCO₃ stimulated ventilation and caused an increase in plasma pH, total carbon dioxide content (Ca_{CO 2}) and catecholamine levels, and a reduction in oxygen tension (Pa_{O 2}). Infusion of ammonium bicarbonate (NH ₄HCO₃) caused hyperventilation and was associated with an increase in Ca_{CO 2} and plasma total ammonia (C_amm) and ammonia gas (NH₃) concentration. Infusion of sodium chloride (NaClI) and Cortland's saline had no effect on ventilation. The results indicate that trout do not exhibit the ventilatory sensitivity to pH seen in terrestrial vertebrates. Ventilatory responses to NaHCO₃ appear to have been a result of reductions in Pa_{O 2}, a release of catecholamines and an increase in Ca_{CO 2} whereas responses to NH₄HCO₃ appear to have been a result of increases in Ca_{CO 2} and C_amm.     

An analysis of carbon dioxide transport in arterial and venous blood of the rainbow trout,Oncorhynchus mykiss,following exhaustive exercise

Arterial and venous cannulations were used to examine the characteristics of CO₂ transport in pre and post branchial blood both at rest and during recovery from exercise. As in previous studies, exercise caused a marked decrease in the extracellular pH (pH_e) in both arterial and venous blood. Except for a transient increase in venous blood immediately following exercise, plasma total CO₂ ([C_{CO 2}]_pl) and whole blood total CO₂ ([C_{CO 2}]_wb) decreased in both arterial and venous blood during recovery. Exercise also resulted in an increase in red blood cell total CO₂ concentration ([C_{CO 2}]_i) and in the partial pressure of CO₂ (P_{CO 2}) in both arterial and venous blood. Activation of the adrenergic mechanism at the level of the red blood cell likely contributed to the increases observed in ([C_{CO 2}]_i) following exercise. At rest, the majority of the total [C_{CO 2}] carried in arterial and venous blood could be attributed to the plasma, with 2 and 9% carried in the red blood cells, respectively. However, exercise resulted in an increase in the percentage of C0₂ carried within the red blood cell to 13.5 and 20% in arterial and venous blood, respectively. The total CO₂ difference between pre and post branchial blood also increased following exercise suggesting an increase in CO₂ excretion.     

Effects of prolonged epinephrine infusion on blood respiratory and acid-base states in the rainbow trout: Alpha and beta effects

Rainbow trout were infused continuously for 12h with epinephrine in the presence or absence of alpha-and/or beta-adrenergic blockade to characterize the specific adrenergic mechanisms involved in the control of blood acid-base status and oxygen transport capacity. Infusion of epinephrine, alone, produced a transient respiratory acidosis, as indicated by an increase in carbon dioxide tension and a decrease in whole blood pH, yet arterial oxygen tension was elevated. Red blood cell pH increased by approximately 0.2 pH units during epinephrine infusion and this increase as well as the increase in oxygen tension were prevented by pretreatment with propranolol (a beta-adrenergic antagonist). Epinephrine infusion during alpha-adrenergic blockade caused a prolonged elevation of blood carbon dioxide tension and abolished the increases in hematocrit and hemoglobin concentrations observed during epinephrine infusion alone. Infusion of the alpha-adrenergic agonists phenylephrine (an alpha₁ agonist) or clonidine (an alpha₂ agonist) caused respiratory acidosis (decreased pH, increased CO₂ tension) and a reduction in oxygen tension. Infusion of isoprenaline (a non-specific beta agonist) caused delayed increases in carbon dioxide and oxygen tensions. We speculate that the increased carbon dioxide tension observed during epinephrine infusion is a result of beta-adrenoceptor mediated inhibition of red blood cell bicarbonate dehydration and not branchial convective or diffusive adjustments. The effects of epinephrine on blood O₂ tension, content and carrying capacity are discussed with reference to the participation of alpha- and beta-adrenergic mechanisms at the gill, spleen and red blood cell.     

Effects of sublethal, acidic aluminum exposure on blood ions and metabolites, cardiac output, heart rate, and stroke volume of rainbow trout, Oncorhynchus mykiss

Doppler flow probes were fitted around the ventral aorta of rainbow trout, which were exposed to combinations of pH and aluminum (pH 5.1–6.2, Al 0–80 g l^–1) for 60 h. Fish accumulated Al at the gill and exhibited decreased blood Na⁺, Cl^–, and Ca²⁺ concentrations, and increased K⁺, hematocrit, hemoglobin, glucose, and lactate, indicating increasing ionoregulatory disturbance with increasing Al concentration. Fish exposed to ambient water (6.2) or low-pH (5.3) water without Al exhibited slight reductions in heart rates, as well as increased stroke volume, resulting in little variation in cardiac output. In the presence of Al (20 to 40 g l^–1) at low pH (5.1–5.3), fish increased their heart rate slightly and generally maintained their stroke volume, resulting in increased cardiac output in the first two days of exposure. At the highest Al concentration (80 g l^–1, pH 5.1), tachycardia was observed, concomitant with a decrease in stroke volume. The ionoregulatory imbalance and resulting increased blood viscosity explain these increases in heart rate rather than stroke volume in fish exposed to high concentrations of Al.     

Effect of feed supplementation with kynurenic acid on the morphology of the liver,kidney and gills in rainbow trout (Oncorhynchus mykiss Walbaum, 1792), healthy and experimentally infected with Yersinia ruckeri

Kynurenic acid (KYNA) is an endogenous substance produced on the kynurenine pathway which is primarily known for its neuroactive properties. Recently, it has been proven that KYNA is a selective ligand for G protein‐coupled receptor (GPR 35), presented on immunocompetent cells such as T lymphocytes. This opens up new possibilities of its application as an immunostimulating substance in aquaculture. Thus far, no histopathological investigations in fish have been completed to evaluate influence of KYNA supplementation in feed. This study has been undertaken to determine the effect of feed supplementation with KYNA (2.5, 25, 250 mg kg^?1 of feed) for 28 days on the liver, gills and kidney in healthy fish and experimentally infected with Yersinia ruckeri. In a control group were observed a fatty liver, which is natural for this fish species in the autumn and winter season. As the dose of the supplement was increased, the fat liver changed, it decreased or completely disappeared. Additionally, inflammatory changes occurred in all the analysed organs, and their intensification was dose dependent. In the fish experimentally infected, KYNA caused aggravation of the signs in the liver, kidneys and gills, and the effect was dose dependent. The results implicate that KYNA may be a stressor for fish.     

A specific inhibitor of mammalian kallikrein,Phe-Phe-Arg-chloromethyl ketone,inhibits the production of vasoactive substances from trout plasma by kallikrein and blocks endogenous kallikrein-like activity in trout gills

The cardiovascular effects of the kallikrein-kinin system (KKS) have not been completely characterized in lower vertebrates. In the present study, a specific, irreversible kallikrein inhibitor, Phe-Phe-Arg-chloromethyl ketone (PPACMK) was used to examine: 1. the role of the KKS in blood pressure regulation in vivo; 2. the nature of the pressor substance formed by the action of kallikrein on trout plasma in vivo and in vitro; and 3. the presence of kallikrein in trout gills and kidney. Dorsal aortic cannulated rainbow trout were used for in vivo blood pressure assays and two colorimetric serine-protease assays were used to examine tissue kallikrein activity. PPACMK alone had no effect on blood pressure in vivo. Pretreatment of porcine kallikrein with PPACMK inhibited the enzyme's pressor effect in trout by 80% and significantly attenuated the synthesis of vasopressor substance(s) from heat-treated trout plasma in vitro. Approximately 30% of gill serine protease activity was inhibited by pretreatment with PPACMK; no PPACMK-sensitive kallikrein activity was observed in the kidney. Salt water adaptation did not affect kallikrein-specific activity in the gill. These results show that the salmonid KKS does not appear to be involved in the regulation of systemic blood pressure. Further, the formation of pressor substances from trout plasma in vivo and in vitro is due to kallikrein activity and the peptides generated are similar. A kallikrein, similar to the mammalian enzyme, is found in trout gills, suggesting that the salmonid KKS may be a local mediator of gill function.     

Cholesterolaemia and triacylglycerolaemia in farmed rainbow trout,Oncorhynchus mykiss

Physiological (reference) value intervals determined by the lower 2.5% and upper 97.5% quantiles were calculated for blood plasma cholesterol (CHOL) and triacylglycerol (TGL) in farmed rainbow trout, Oncorhynchus mykiss, in raceway culture. The fish were given dry pelleted diets that contained 37–47% crude protein and 7–14% crude fat and were kept at a stocking density of 50 kg m^?3 in tanks provided with running freshwater at an ambient temperature of 3–16°C and dissolved oxygen, 8.4–11.5 mg L^?1. Blood was sampled between September and November at a photoperiod of 9:00–13:00 hours: 11:00–15:00 hours (light:dark). Cholesterol levels were significantly (P = 0.0001) greater in males (4.7–12.1 mmol L^?1, n = 34, mean weight 406 ± 138 g) than immature females (3.2–9.7 mmol L^?1, n = 386, mean weight 416 ± 147 g). Physiological range for TGL in immature females and males was 2.4–14.4 mmol L^?1 (n = 249, mean weight 418 ± 149 g). The distribution and density of the quantiles in the tested reference group were made possible by the use of histograms, which showed normal distributions for CHOL in males and in females, but not for TGL, in which a sinistral asymmetry was found. Correlation and regression analyses indicated significant (P = 0.0000) dependence between the CHOL and total protein (r² = 76.2%), CHOL and Fulton's condition factor (r² = 43.3%) and CHOL and absolute weight of liver (r² = 45.5%). Fluctuation in cholesterolaemia and triacylglycerolaemia, depending on nutrition and the aquaculture method is discussed below.     

Intracellular transport of ovalbumin afterin vivo endocytosis in rainbow trout liver

The intracellular handing of a mannose-terminated glycoprotein taken up in rainbow trout liver cells by receptor-mediated endocytosis has been studied. The intracellular transport and degradation of ovalbumin (OA) were studied by means of subcellular fractionation in Nycodenz gradients and by differential centrifugation following intravenous injection of the ligand. By using OA labelled with¹²⁵I-tyramine cellobiose (¹²⁵I-TC), the subcellular distribution of labelled degradation products could be studied, since they are trapped intracellularly in the organelle where the degradation takes place. ¹²⁵I-TC-OA was shortly after injection (45 min) localized in a homogenous population of endosomes. Labelled degradation products firs appeared in an organelle with the same density distribution as the endosomes. In livers homogenized 2h after injection the degradation products appeared in organelles with increasing size and density. After 24h, the degradation products were recovered in at least two populations of lysosomes with a distribution profile which coincided with that of the lysosomal enzyme -acetylglucosaminidase.The heterogeneous distribution of the late degradation products seemed not to be due to uptake of ligand in different liver cell types as only the parenchymal liver cells took up labelled OA after intravenous injection of the ligand.     

Evidence of concealment behavior by adult rainbow trout and brook trout in winter

Abstract – There has been little investigation of the winter ecology of adult trout during winter, especially in regard to concealment behavior. We compared day vs night underwater counts of adult rainbow trout and brook trout from four streams. At water temperatures between 1°C and 9°C, daytime counts accounted for 44% and 16% of nighttime snorkeling counts for rainbow trout and brook trout adults, respectively. As winter progressed, nighttime counts declined more so for brook trout than rainbow trout, but the decline was not significant for either species. Nocturnalism of both species was higher in streams with colder water temperatures. We observed few fish within concealment structure; however, by electrofishing concealment habitat during the day, we captured 10 times more adult trout than we counted immediately beforehand by snorkeling. Adult trout were concealed in cobble-boulder substrate and woody debris during the day. ^Note     

A study of gross,histological and blood biochemical changes in rainbow trout,Oncorhynchus mykiss (Walbaum), with rainbow trout gastroenteritis (RTGE)

The mechanisms behind the pathogenesis of rainbow trout gastroenteritis (RTGE) are still unknown. This study examined the macroscopic and microscopic changes in trout with RTGE (RTGE+), as well as the blood chemistry. A total of 464 rainbow trout were sampled from 11 sites in the UK, comprising 152 RTGE+ fish and 330 random, apparently healthy fish. A case definition for RTGE was assessed by the analysis of its agreement with three laboratory tests: histopathology, packed cell volume and kidney bacteriology. Cluster analysis indicated the presence of three distinct presentations within the population of RTGE+ fish. Cluster A included gross signs associated with moribund RTGE+ fish, and clusters B and C identified gross signs consistent with concurrent diseases, notably furunculosis, enteric redmouth and proliferative kidney disease. The information gained was used to select RTGE+ fish without concurrent disease for the analysis of RTGE pathogenesis with blood biochemistry. This analysis revealed a severe osmotic imbalance and a reduced albumin/globulin ratio as indicatives of selective loss of albumin. These findings are compatible with a protein losing enteropathy.     

Estimating oxygen consumption of rainbow trout (Oncorhynchus mykiss) in a raceway: A Precision Fish Farming approach

The Precision Fish Farming (PFF) approach was applied to the estimation of fish oxygen consumption of rainbow trout in a raceway farm. A dynamic model, simulating the evolution of Dissolved Oxygen concentration, was identified: the daily oscillation of fish oxygen consumption rate was simulated by means of a sinusoidal function. The model was applied to the data set collected during a four-week field study, which was carried out in July 2019. Water temperature and Dissolved Oxygen concentration were measured with an hourly frequency in farm influent and effluent. Fish biomass was monitored on a daily basis by combining the data provided by a state-of-the art system for non-invasive estimation of fish weight distribution with mortality counting. The monitoring period was partitioned into two time-windows, as fish was not fed during the first two weeks. These windows were further partitioned into a calibration and validation set. Three model parameters, i.e. the average daily respiration rate, the amplitude of its daily oscillation, and its phase were estimated by fitting the model output to the time series of DO concentration in the effluent. The results of the calibration show that: 1) the daily average oxygen consumption rate is consistent with the literature; 2) the amplitude of the daily oscillation when fish is regularly fed is more than twice that estimated for fasting fish. The results of the validation suggest that the model could be used to implement a cost-effective automatic control of oxygen supply, based on the short-term prediction of oxygen demand.     

Swimming performance,whole body ions,and gill Al accumulation during acclimation to sublethal aluminium in juvenile rainbow trout (Oncorhynchus mykiss)

Juvenile rainbow trout (2–5 g) were chronically exposed (for 22 days) to acidified softwater (Ca²⁺ = 25 Eq/l, pH 5.2) in the presence or absence sublethal Al (30 g/l). Al-exposed fish (5.2/Al group) suffered 20% whole body Na⁺ and Cl^– losses and a 30% reduction in the maximum sustainable swimming speed (U_crit) over the initial 7 days. These disturbances were approximately 2 fold greater than those observed in the fish exposed to low pH alone (5.2/0 group). However, whole body ion levels were completely restored in the 5.2/Al fish by day 22, whereas they merely stabilized at a new reduced level in the 5.2/0 group. Increased resistance to acutely lethal Al (200 g/l at pH 5.2) was observed from day 17 onwards in the 5.2/Al fish. Despite this acclimation and recovery of whole body ions, U_crit remained significantly lower than in the 5.2/0 group throughout. Growth on a restricted diet of 1% body wt. /day was normal in the 5.2/0 group compared with controls maintained in pH 6.5 softwater, whereas 5.2/Al fish suffered a 50% reduction in growth rate on the same diet. The 5.2/Al fish accumulated large amounts of Al on the gills, reaching an initial peak after 4 days, followed by a decline at 7 days, and a secondary rise thereafter. Therefore acclimation and recovery of whole body ionic status was not associated with a reduction in the gill Al burden. Some of the metabolic costs of acclimation to Al, namely a continued impairment of swimming speed and growth, are discussed in light of the physiological and structural changes reported to occur at the gills.     

Effects of adrenaline on ionic equilibria in red blood cells of rainbow trout (Salmo gairdneri)

Effects of adrenaline on the equilibrium distributions of Na⁺ , K⁺ , H⁺ , Cl^– , and H₂O across the cell membrane of rainbow trout (Salmo gairdneri) erythrocytes were determinedin vitro, as a function of P CO₂ (1.76–7.77 torr). CO₂-carrying capacity of the blood was also examined. Plasma catecholamine concentrations inunanaesthetized, unrestrained trout were 3.1 nM adrenaline and 1.2 nM noradrenaline. Elevation of the plasma adrenaline concentrationin vitro to 4.6 × 10³ nM resulted in net gains of Na⁺ , Cl^– and H₂O by red cells, a net loss of H⁺ from red cells, and a pronounced red cell swelling. Adrenaline also reduced the CO₂-carrying capacity of trout bloodin vitro. The magnitudes of these effects increased with P_CO2 and, thus, were sensitive to blood HCO₃ ^– concentrations. The distribution of K⁺ between red cells and plasma was unaffected by adrenaline. Adrenergic-mediated ion movements and red cell swelling were sensitive to both propranolol and SITS. These results are consistent with the symport NaCl uptake model for adrenergic-mediated swelling of Baroinet al. (1984). The adrenergic response of fish erythrocytes may function to ameliorate the effects of blood acidoses on O₂-carrying capacity by maintaining red cell pH in the face of a decrease in plasma pH.     

虹鳟IgM重链恒定区的表达及兔抗血清的制备

为了能够成功表达虹鳟IgM,本研究利用生物信息学软件对虹鳟IgM的亲水性及抗原性进行了分析,根据GenBank收录的虹鳟IgM重链恒定区,参照生物信息学分析结果,设计用于扩增截短的IgM基因的引物,以虹鳟头肾RNA提取物为模板,利用RT-PCR方法扩增虹鳟截短的IgM重链恒定区部分基因片段,连接原核表达载体pET-27b,利用大肠杆菌Rosetta进行表达。SDS-PAGE及HPLC结果显示,纯化后截短的IgM大小约为47.7 ku,且纯度达到90%。利用其制备兔抗血清后ELISA分析结果显示,所制备的兔抗血清与本研究所表达的截短IgM蛋白的反应效价为1∶40 000,与虹鳟血清提取的全长IgM反应效价为1∶20 000并且呈现出抗原计量依赖性。研究表明,重组IgM蛋白与虹鳟血清中的天然IgM重链恒定区具有近似的结构,利用其所制备的兔抗血清能够与虹鳟鱼体中的天然IgM发生特异性反应。     

Effect of hydrogen peroxide and/or Flavobacterium psychrophilum on the gills of rainbow trout,Oncorhynchus mykiss (Walbaum)

The immune response and morphological changes in the gills of rainbow trout fry after immersion in hydrogen peroxide (H₂O₂), Flavobacterium psychrophilum or combined exposure were examined. The gills were sampled 4, 48, 125 and 192 h after exposure, and the regulation of expression of the following genes was investigated using qPCR: IgT, IgM, CD8, CD4, MHC I, MHC II, IL-4/13A, TcR-β, IL-10, IL-1β, IL-17, SAA and FoxP3. Bacteria were not observed in haematoxylin-and-eosin-stained gill tissue, but the presence of F. psychrophilum 16S rRNA was detected using qPCR. The 16S rRNA levels were correlated with gene expression. Although pretreatment with H₂O₂ before immersion in F. psychrophilum did not significantly alter the amount of bacteria found in the gill, the immune response was influenced: exposure to F. psychrophilum resulted in a negative correlation with expression of IL-17c1, MHC I and MHC II, while pretreatment with H₂O₂ resulted in a positive correlation with IL-4/13A and IgM. Exposure to either H₂O₂ or F. psychrophilum influenced the regulation of gene expression and damaged tissue. Exposure to both combined altered the immune response to infection and postponed healing of gill tissue.     

Extracellular fluid volume measurements in tissues of the rainbow trout (Oncorhynchus mykiss)in vivo and their effects on intracellular pH and ion calculations

Extracellular fluid volume (ECFV) estimates were determined in various tissues and whole body of resting, chronically cannulated rainbow trout (Oncorhynchus mykiss). Fish were infused with¹⁴C-inulin,³H-polyethylene glycol (PEG, M.W. 4000),³H-mannitol, or¹⁴C-mannitol, and values of ECFV determined from tissue: plasma water distribution ratios after 6 h or 13 h equilibration. Overall,³H-PEG provided the most conservative and reliable estimates after 13 h equilibration, with ECFV values in the order: brain < white muscle < red muscle < liver < heart < gill tissue.¹⁴C-inulin yielded generally similar values to³H-PEG at 13 h, but probably overestimated ECFV in liver.³H-mannitol and¹⁴C-mannitol spaces were similar to each other and far greater than³H-PEG or¹⁴C-inulin values in most tissues.³H-mannitol values increased significantly between 6 h and 13 h, in contrast to¹⁴C-inulin. Mannitol clearly overestimated ECFV in liver and gill, and probably also heart and whole body, but may have provided more realistic estimates in brain due to better penetration of the blood-brain barrier. The Cl^–/K⁺ space technique overestimated ECFV in gills, but was satisfactory in white muscle. Measurements and model calculations evaluated sources of error in intracellular pH (by¹⁴C-DMO) and ion determinations. Trapped red cells in the gills have negligible influence. Errors in ECFV are much more influential in a tissue with a high ECFV (gills) than a low ECFV (white muscle).³H-PEG is the marker of choice for intracellular pH determinations. However, even when³H-PEG is used, the potential for absolute errors in intracellular ion concentrations remains high.     

虹鳟鱼核型及DNA含量分析

采用植物血球凝素（ＰＨＡ）体内注射、肾组织细胞短期培养、常规空气干燥法制备了虹鳟的染色体，并进行了核型分析。虹鳟二倍体的染色体为６０条，其核型为２２ｍ＋１ｓｔ＋７ｔ，ＮＦ＝１０４。以外周血红血球为样本，鸡红血细胞为对照，用美国产的ＦＡＣＳｔａｒｐｌｕｓ流式细胞仪测定了虹鳟的二倍体细胞核的ＤＮＡ含量，其ＤＮＡ含量为鸡血对照的１．５１倍，绝对含量为３．４７±０．２１ｐｇ／Ｎ。     

虹鳟受精卵第一次卵裂组织学观察及四倍体制备最佳时机的研究

采用组织切片技术对虹鳟受精卵第一次卵裂进行观察,且利用热休克和静水压处理受精卵,诱导四倍体。其结果显示,静水压诱导效果较好,在受精后8h进行诱导四倍体的出现率最高,达到25～28%。热休克诱导未出现四倍体。受精卵在受精后400min(积温43.5℃.h)处于第一次卵裂前期,受精后490min(积温52.5℃.h)处于第一次卵裂中期,受精后640min(积温66.8℃.h),处于第一次卵裂后期,670min(积温69.3℃.h)处于第一次卵裂末期,700min(积温71.8℃.h)以后形成卵裂沟,并穿过整个受精卵,产生两个均等大小的两个卵裂球(blastomeres)。     

The effect of acid water on oxygen consumption,circulating catecholamines and blood ionic and acid-base status in rainbow trout (Salmo gairdneri,Richardson)

Chronically cannulated rainbow trout were exposed in acid water (pH 4.0) for 72h. The gill potential was strongly dependent on water pH, being blood side negative in neutral water, but positive in acid water. Catecholamine levels increased irregularly during acid exposure, and the Bohr and Root effects were not completely erased by the effect of catecholamines during acid exposure. Long term exposure to low water pH, although causing an acidosis in the fish, did not suppress resting oxygen consumption. Prolonged exposure to acid conditions, however, resulted in an increase in ammonia excretion. Changes in plasma sodium and chloride were similar to that reported previously for trout exposed to low calcium, acid water. We conclude that exposure of trout to pH 4 soft water, although impairing oxygen transport, does not limit resting oxygen consumption but does reduce the scope for activity. More extreme acid conditions do impair resting oxygen uptake.     

The effects of swimming exercise and dissolved oxygen on growth performance,fin condition and survival of rainbow trout Oncorhynchus mykiss

Swimming exercise and dissolved oxygen (DO) are important parameters to consider when operating intensive salmonid aquaculture facilities. While previous research has focused on each of these two variables in rainbow trout Oncorhynchus mykiss, studies examining both variables in combination, and their potential interaction, are absent from the scientific literature. Both swimming exercise (usually measured in body lengths per second, or BL/s) and DO can be readily controlled in modern aquaculture systems; therefore, we sought to evaluate the effects of these variables, separately and combined, on several outcomes in rainbow trout including growth performance, fin health and survival. Rainbow trout fry (18 g) were stocked into 12 circular 0.5 m³ tanks, provided with either high (1.5–2 BL/s) or low (approximately 0.5 BL/s) swimming exercise and high (100% saturation) or low (70% saturation) DO, and grown to approximately 1 kg. By the conclusion of the study, higher DO was independently associated with significantly (p < .05) increased growth performance. Significant differences were not noted in other outcomes, namely feed conversion, condition factor and mortality, although caudal and right pectoral fin damage was associated with low oxygen and low swimming exercise treatments respectively. Cardiosomatic index was significantly higher among exercised fish. These results suggest that swimming exercise and DO at saturation during the culture of rainbow trout can be beneficial to producers through improved growth performance and cardiac health.