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1.
Respiratory parameters of grass carp were studied during dissolved oxygen (DO) changes from normal DO to hypoxia, then return to normal DO at 15, 25, and 30 °C acclimation, respectively. The results showed that with increases of acclimation temperature at normoxia the respiratory frequency (fR), oxygen consumption rate (VO2), respiratory stroke volume (VS.R), gill ventilation (VG), and VG/VO2 of grass carp increased significantly, but the oxygen extraction efficiency (EO2) of fish decreased significantly (P < 0.05). With declines of DO levels, the fR, VS.R, VG, and VG/VO2 of fish increased significantly at different acclimation temperatures (P < 0.05). A slight increase was found in VO2, and the EO2 of fish remained almost constant above DO levels of 3.09, 2.91, and 2.54 mg l?1 at 15, 25, and 30 °C, while the VO2 and EO2 began to decrease significantly with further reductions in DO levels (P < 0.05). After 0.5 h of recovery to normoxia from hypoxia at three acclimation, the fR, VS.R, VG, and VG/VO2 of the fish decreased sharply; meanwhile, the VO2 and EO2 increased sharply (P < 0.05). The respiratory parameters of fish gradually approached initial values with prolonged recovery time to normoxia, and reached their initial values in 2.5 h at 25 and 30 °C acclimation. The critical oxygen concentrations (Cc) of fish for VO2 were 2.42 mg l?1 at 15 °C, 2.02 mg l?1 at 25 °C, and 1.84 mg l?1 at 30 °C, respectively. The results suggest that grass carp are highly adapted to varied DO and short-term hypoxia environments.  相似文献   

2.
Atlantic sturgeon (Acipenser oxyrhynchus), which are bottom dwelling and migratory fish, experience environmental hypoxia in their natural environment. Atlantic sturgeon, acclimated to either 5 or 15°C, were subjected to a 1 h severe (<10 mm Hg) hypoxia challenge in order to document their physiological responses. We measured hematological parameters, including O2 transport (hemoglobin, hematocrit), ionic (chloride, osmolality), and metabolic (glucose, lactate) variables under normoxic conditions (~160 mm Hg), immediately following a 1 h exposure to hypoxic water, and following a further 2 h of recovery from this challenge in normoxic water. In a second experiment, we assessed the opercular beat frequency before, during, and after hypoxic exposure. Hemoglobin concentrations and hematocrit were significantly different between fish held at 5°C vs. 15°C and also significantly different between normoxia prior to hypoxia and following recovery. Plasma lactate concentrations increased following hypoxia at both temperatures, indicative of an increase in anaerobic metabolism. In contrast, a significant increase in plasma glucose concentrations in response to hypoxia only occurred at 5°C, suggesting different fuel demands under different temperatures. Changes in opercular beat frequency (OBF) were dependent on temperature. At 5°C, OBF increased upon exposure to hypoxia, but returned to pre-exposure levels within 35 min for the remainder of the experiment. During hypoxia at 15°C, OBF increased very briefly, but then rapidly (within 20 min) decreased to levels below control values. Following a return to normoxia, OBF quickly increased to control levels. Overall, these findings suggest that Atlantic sturgeons are relatively tolerant to short-term and severe hypoxic stress, and the strategies for hypoxia tolerance may be temperature dependent.  相似文献   

3.
Gill respiratory surface area and oxygen consumption during aquatic respiration were measured in the facultative air-breathing loricariid fish,Hypostomus plecostomus. The fish did not surface to breathe atmospheric air in normoxic water; air-breathing was evoked by environmental hypoxia (water oxygen tension=35±2, mmHg) and did not show size-related threshold differences for air breathing.During gradual hypoxia, without access to atmospheric, air,H. plecostomus was found to be an oxyregulator and showed a reduced range of water oxygen tension in which the oxygen consumption remained constant in smaller fish. The critical oxygen tensions were 55 and 33 mmHg at 25°C for fish of 14–30 g and 31–80g body weight, respectively.The gill respiratory surface area (total lamellae area) is reduced, however, the lamellar frequency per mm of gill filament is high which facilitates the gas exchange. Moreover, the increase of gill respiratory surface area (b=0.666) is higher than the increase in routine VO2 (b=0.338) showing a positive relationship between the gill respiratory surface area /VO2 ratio and body mass (b=0.328); this indicates that the fish have greater gill respiratory surface area per unit of routine VO2 as they grow.  相似文献   

4.
Adriatic sturgeon (Acipenser naccarii) were maintained on a commercial diet enriched either in long chain polyunsaturated fatty acids of the 3 series (3 LCPUFA) or in saturated fatty acids (SFA). The effects of dietary fatty acid composition on spontaneous locomotor activity in normoxia and hypoxia (O2 tension = 10.5 ± 0.8 kPa), and on oxygen consumption (MO 2) in normoxia, in hypoxia (O2 tension = 6.6 ± 0.8 kPa) and during recovery were then investigated. The effects of adding supplementary vitamin E to the fat-enriched diets were also studied.Dietary fatty acid composition had effects on spontaneous locomotor activity and MO 2 in normoxia. Activity levels were higher in all sturgeon fed extra dietary fats (without vitamin E), when compared with control animals, but fish fed 3 LCPUFA had a significantly lower MO 2 than those fed SFA, with intermediate MO 2 in controls. In hypoxia, sturgeon 3 LCPUFA did not alter activity or MO 2 whereas those fed SFA reduced both and controls reduced MO 2. During recovery, both animals fed SFA and controls had a higher MO 2 than sturgeon fed 3 LCPUFA. The data indicate that fish fed 3 LCPUFA are more tolerant of hypoxia than controls or those fed SFA, as they did not reduce either activity or MO 2, and consumed less O2 during recovery.Vitamin E supplements modified the effects elicited by dietary fats. All sturgeon fed vitamin E had low activity levels in normoxia and hypoxia. Sturgeon fed vitamin E with 3 LCPUFA had a higher MO 2 in normoxia than those fed 3 LCPUFA alone; reduced MO 2 in hypoxia, and during recovery increased MO 2 to a rate higher than that of animals fed 3 LCPUFA alone. In normoxia, sturgeon fed vitamin E with SFA had a similar MO 2 to those fed SFA alone but did not change MO 2 in hypoxia or during recovery. Thus, the effects of vitamin E were dependent on fat composition of the diet. Vitamin E with 3 LCPUFA removed the beneficial effects on MO 2 and responses to hypoxia obtained with 3 LCPUFA alone, but vitamin E with SFA allowed sturgeon to maintain aerobic metabolism in hypoxia, a more effective response than that observed in fish fed SFA alone.  相似文献   

5.
This study investigated the production performance of the Atlantic salmon postsmolt (Salmo salar L.) subjected to cyclic oxygen reductions (hypoxia) of varying severity. Triplicate groups (N = 955) were kept at constant 80% O2 (control) or subjected to 1 h and 45 min of hypoxia (50, 60 or 70% O2, termed 80:70, 80:60 and 80:50 groups) every 6 h at 16°C for 69 days. Feed was provided in normoxia. One third of the fish were kept further for 30 days in normoxia to study possible compensatory growth. Cyclic hypoxia did not alter the oxygen uptake rates of fish, measured in night‐time. Fish subjected to 50% and 60% O2 reduced feeding by 13% and 6% compared with the controls, respectively, with corresponding reductions in specific growth rates. Feed utilization was not reduced. Compensatory growth was observed in fish from the 80:50 group, but full compensation was not achieved. The main conclusions were that feeding in normoxia does not fully alleviate negative effects of cyclic hypoxia on feeding and growth, when oxygen is reduced to 60% or below in hypoxic periods, that feed utilization is maintained, and that compensatory growth may lessen negative effects.  相似文献   

6.
This study examined ammonia, urea, creatinine, protein, nitrite, nitrate, and phosphorus (P) excretion at different water hardness, humic acid, or pH levels in silver catfish (Rhamdia quelen) juveniles. The fish were exposed to different levels of water hardness (4, 24, 50, or 100 mg L?1 CaCO3), humic acid (0, 2.5, or 5.0 mg L?1), or pH (5.0, 6.0, 7.0, 8.0, or 9.0) for 10 days. The overall measured nitrogen excretions were 88.1 % (244–423 μmol kg?1 h?1) for ammonia, 10.9 % (30–52 μmol kg?1 h?1) for creatinine, 0.02 % (0.05–0.08 μmol kg?1 h?1) for protein, 0.001 % (0.002–0.004 μmol kg?1 h?1) for urea, 0.5 % (0.64–3.6 μmol kg?1 h?1) for nitrite, and 0.5 % (0.0–6.9 μmol kg?1 h?1) for nitrate, and these proportions were not affected by water hardness or humic acid levels. The overall P excretion in R. quelen was 0.14–2.97 μmol kg?1 h?1. Ammonia excretion in R. quelen usually was significantly higher in the first 12 h after feeding, and no clear effect of water hardness, humic acid levels, and pH on this daily pattern of ammonia excretion could be observed. Water hardness only affected the ammonia and P excretion of R. quelen juveniles in the initial and fifth days after transfer, respectively. The exposure of this species to humic acid increased ammonia excretion after 10 days of exposure but did not affect P excretion. An increase in pH decreased ammonia and increased creatinine excretion but did not change P excretion in R. quelen. Therefore, when there is any change on humic acid levels or pH in the culture of this species, nitrogenous compounds must be monitored because their excretion rates are variable. On the other hand, P excretion rates determined in the present study are applicable to a wide range of fish culture conditions.  相似文献   

7.
Carp respond to water hypoxia with an evaluation in the rate of gill ventilation. In order to characterize closer the adequate stimulus for the increase in respiratory drive specimens of carp, Cyprinus carpio L., were exposed simultaneously to moderate environmental hypoxia (PwO2? 75mmHg, 10kPa) and elevated water nitrite concentration (089 ± 0-lmmol/l) for 24h. The differential effects of these treatments were utilized to distinguish between the responses to an immediate reduction in water and arterial Poa (P,O2), and to the slowly developing reduction of arterial oxygen content (CaO2) and functional oxygen saturation (SaO2). After onset of hypoxia gill ventilation quickly increased, leading to a reduction in PaCO2. Slowly rising blood methaemoglobin levels resulted in a gradual decline in CaO2 and SaO2 over 24h, whereas P002 remained steady for the entire exposure period. This pattern of lowered Paco2 and PaO2, essentially constant for 24 h, together with the lack of any correlation with changes in CaO2, suggests PO2 (Pa,O2 and/or Pwo2) as the primary stimulus in the regulation of ventilation of carp.  相似文献   

8.
Galaxias maculatus is an osmeriform native fish of the Southern Hemisphere, in which the crystalline larvae is considered as a luxury delicacy, for this reason, it has been commercially exploited in Chile, Argentina and New Zealand. However, the fisheries have been rapidly decreasing due to the overexploitation and the predation of introduced species. Because of these events, there is a need to determine a carrying capacity for an intensive fish culture. In order to optimize stocking densities for fish culture, this paper proposes objectives to determine oxygen consumption (OC) rates, dissolved oxygen concentrations that produce signs of hypoxia and the average time elapsed between food intake and peak OC in G. maculatus. In the oxygen experiments under routine metabolism conditions, we found that G. maculatus adults and whitebait showed signs of asphyxia at dissolved oxygen concentrations between 1.3 and 2.2 mg L?1 and that adults tolerated dissolved oxygen levels as low as 1.3 mg L?1. The results showed that G. maculatus individuals with an average weight of 0.04 g consumed 0.048 mg O2 h?1, whereas individuals with an average weight of 1.4 g consumed 0.345 mg O2 h?1. Galaxias maculatus increased the OC rate by 31%, from 0.39 to 0.51 mg O2 h?1 g?1, occurring 14 min after food intake. The carrying capacities for industrial cultures of G. maculatus, were estimated using an allometric equation (OC=0.2363 ×W 0.612 ), a water flow rate of 1 m3 h?1 and an input oxygen concentration of 10 mg L?1 at 12 °C. The density culture of whitebait (4 g) can be allowed to reach 8–11 kg m?3; therefore, these stocking densities reduce the risk of hypoxia and mortality, ensuring the appropriate growth and feed conversion rates.  相似文献   

9.
We describe a computer-operated recirculating respirometer system (ca. 140 L water) with six respirometer chambers and a reference chamber (L × W × H: 26 cm × 12 cm × 20 cm; volume 6.24 L) that simulates diurnal dissolved oxygen (DO) fluctuations normally occur in aquaculture ponds. A gas-mixing device, “Digamat” proportionately dissolves gaseous nitrogen and oxygen (and if desired, carbon dioxide) in water to achieve DO levels from 1.0 to 40.0 kPa (0.3–14.0 mg L?1) at different temperatures. A series of computer-operated valves sequentially allow water from respirometer chambers to a single oxygen probe to measure DO concentration. Oxygen consumptions of fish as the differences in DO concentrations between respirometer and reference chamber are used to calculate different metabolic rates (standard, routine, and active), and critical (P c) and recovery (P r) oxygen tensions of individually reared unfed and fed fish. An experiment was conducted to evaluate the ability of the system to measure metabolic parameters for individually reared Nile tilapia (Oreochromis niloticus L.) at three temperatures (low: 22.5, optimum: 27.5 and high: 33.5 °C). The fed fish had significantly higher P c and P r values at optimum and high temperatures than unfed fish. At low and high temperatures, both fed and unfed fish had higher P c and P r than at optimum temperature. The standard metabolic rate was significantly higher at higher temperatures (44.9, 51.7, and 77.7 mg O2 kg?0.8 h?1 at 22.5, 27.5, and 33.5 °C, respectively).  相似文献   

10.
Hypoxia results in elevated circulating epinephrine for many fish species, and this is likely important for maintaining cardiac function. The aims of this study were to assess how hypoxia impacts contractile responses of ventricular compact and spongy myocardium from rainbow trout (Oncorhynchus mykiss) and to assess how and if epinephrine may protect myocardial performance from a depressive effect of hypoxia. Work output and maximum contraction rate of isolated preparations of spongy and compact ventricular myocardium from rainbow trout were measured. Tissues were exposed to the blood PO2 that they experience in vivo during environmental normoxia and hypoxia and also to low (5 nM) and high (500 nM) levels of epinephrine in 100% air saturation (PO2 20.2 kPa) and during hypoxia (PO2 2 kPa, 10% air saturation). It was hypothesized that hypoxia would result in a decrease in work output and maximum contraction rate in both tissue types, but that epinephrine exposure would mitigate the effect. Hypoxia resulted in a decline in net work output of both tissue types, but a decline in maximum contraction rate of only compact myocardium. Epinephrine restored the maximum contraction rate of compact myocardium in hypoxia, appeared to slightly enhance work output of only compact myocardium in air saturation but surprisingly not during hypoxia, and restored net work of hypoxic spongy myocardium toward normoxic levels. These results indicate hypoxia has a similar depressive effect on both layers of ventricular myocardium, but that high epinephrine may be important for maintaining inotropy in spongy myocardium and chronotropy in compact myocardium during hypoxia.  相似文献   

11.
The objective of this study was to determinate the lethal concentration of dissolved oxygen (DO) over 96 hours of exposure (LC50–96h) for diploid and triploid jundia Rhamdia quelen juveniles. Diploid and triploid fish weighing approximately 4 g were subjected to DO concentrations varying between 0.4 and 1.3 mg O2 L?1; water temperature was maintained at 27?°C and pH at 6.3. The LC50–96h for diploids of Rhamdia quelen was 0.535 mg O2 L?1, while the value obtained for triploids was 6% greater. These results demonstrated that triploids of Rhamdia quelen juveniles have greater sensitivity to hypoxia compared to diploids.  相似文献   

12.
Regulation of arterial partial pressure of O2 (PaO2) in Atlantic salmon (Salmo salar) was investigated during resting conditions in normoxic and hyperoxic water. Dorsal aorta cannulated adult Atlantic salmon (1.2–1.6 kg, n = 8) were exposed to 2 week sequential periods of normoxia [16.7 ± 1.1 kPa (mean ± SD)] and hyperoxia (34.1 ± 4.9 kPa) in individual tanks containing seawater (33.7 ± 0.2 ppt) at stable temperature conditions (8.7 ± 0.7°C) and a light regime of L:D = 12:12. Tank design and sampling procedures were optimized to provide suitable shelter and current for the fish, and to allow repeated, undisturbed sampling of blood from free-swimming fish. Fish were sampled regularly through the experimental period. PwO2, PaO2, blood ion composition (Na+, K+, Cl−), acid–base status (pH, PCO2, HCO3 −), haematocrit and glucose were measured. The most frequently observed PaO2 values were in the range of 60–80% of PwO2, both during normoxia and hyperoxia, and PaO2 values were significantly lower during normoxia than during hyperoxia. Blood pH, PCO2 and HCO3 − were significantly elevated during hyperoxia, while, Na+, Cl− and Hct were significantly lower. K+ and glucose showed no significant differences. This study demonstrates a lack PaO2 regulation in Atlantic salmon to low partial pressures, in contrast to previous reports for many aquatic gill breathing animals. Both during normoxia and hyperoxia, PaO2 reflects PwO2, and alterations in external PO2 consequently result in proportional arterial PO2 changes. Physiological adaptation to hyperoxia, as illustrated by changes in several blood parameters, does not include down-regulation of PaO2 in Atlantic salmon. The lack of PaO2 regulation may make Atlantic salmon vulnerable to the oxidative stress caused by increased free radical formation in hyperoxic conditions.  相似文献   

13.
Variations in respiratory and acid-base status were studied in turbot (Scophthalmus maximus) during progressive severe hypoxia followed by recovery under normoxic conditions. The first behavioural strategy of turbot under hypoxia was an increase in amplitude and frequency of ventilation. Consequently, standard O2 consumption remained unchanged over a broad range of O2 tensions, until a low critical level of 30 mmHg. The hyperventilation induced a moderate blood alkalosis, compensated by a lactic acidosis. The fact that blood pH did not decrease below control values could be explained by the retention in white muscle of most of the lactate produced and by a high capacity for H+ excretion. During the recovery period, the marked increase in O2 uptake corresponding to an oxygen debt repayment, was partly related to the lactate elimination. When total energy contributions of aerobic and anaerobic processes were assessed in terms of ATP, the anaerobic contribution, estimated at the deepest hypoxia level, was higher than 20% of the total energy budget and appeared to totally compensate for the decline in aerobic metabolism. Moreover, the high value of O2 tension in arterial blood in normoxia and during recovery from hypoxia showed high diffusing capacity of gills in turbot. Our results explain the high tolerance of turbot for O2 deficient waters.  相似文献   

14.
The effects of acclimation temperature (15, 20, 25 °C) on routine oxygen consumption and post-exercise maximal oxygen consumption rates (MO2) were measured in juvenile shortnose sturgeon (Acipenser brevirostrum LeSueur, 1818). The routine MO2 of shortnose sturgeon increased significantly from 126.75 mg O2 h?1 kg?1 at 15 °C to 253.13 mg O2 h?1 kg?1 at 25 °C. The temperature coefficient (Q 10) values of the routine metabolic rates ranged between 1.61 and 2.46, with the largest Q 10 values occurring between 15 and 20 °C. The average post-exercise MO2 of all temperature groups increased to a peak value immediately following the exercise, with levels increasing about 2-fold among all temperature groups. The Q 10 values for post-exercise MO2 ranged from 1.21 to 2.12, with the highest difference occurring between 15 and 20 °C. Post-exercise MO2 values of shortnose sturgeon in different temperature groups all decreased exponentially and statistically returned to pre-exercise (resting) levels by 30 min at 15 and 20 °C and by 60 min at 25 °C. The aerobic metabolic scope (post-exercise maximal MO2-routine MO2) increased to a maximum value ～156 mg O2 h?1 kg?1 at intermediate experimental temperatures (i.e., 20 °C) and then decreased as the temperature increased to 25 °C. However, this trend was not significant. The results suggest that juvenile shortnose sturgeon show flexibility in their ability to adapt to various temperature environments and in their responses to exhaustive exercise.  相似文献   

15.
Effects of eugenol (AQUI‐S®20E, 10% active eugenol) sedation on cool water, yellow perch Perca flavescens (Mitchill), and warm water, Nile tilapia Oreochromis niloticus L. fish metabolic rates were assessed. Both species were exposed to 0, 10, 20 and 30 mg L?1 eugenol using static respirometry. In 17°C water and loading densities of 60, 120 and 240 g L?1, yellow perch controls (0 mg L?1 eugenol) had metabolic rates of 329.6–400.0 mg O2 kg?1 h?1, while yellow perch exposed to 20 and 30 mg L?1 eugenol had significantly reduced metabolic rates of 258.4–325.6 and 189.1–271.0 mg O2 kg?1 h?1 respectively. Nile tilapia exposed to 30 mg L?1 eugenol had a significantly reduced metabolic rate (424.5 ± 42.3 mg O2 kg?1 h?1) relative to the 0 mg L?1 eugenol control (546.6 ± 53.5 mg O2 kg?1 h?1) at a loading density of 120 g L?1 in 22°C water. No significant differences in metabolic rates for Nile tilapia were found at 240 or 360 g L?1 loading densities when exposed to eugenol. Results suggest that eugenol sedation may benefit yellow perch welfare at high densities (e.g. live transport) due to a reduction in metabolic rates, while further research is needed to assess the benefits of eugenol sedation on Nile tilapia at high loading densities.  相似文献   

16.
We studied the physiological status of juvenile turbot (Scophthalmus maximus L.) under severe hypoxia (1 and 2 mg/L dissolved oxygen, DO), hypoxia (3 and 5 mg/L DO), hyperoxia (11 and 14 mg/L DO) and normoxia (7 mg/L DO, control) conditions. The respiratory rates, haematology parameters, acid–base balance status and gill structure were analysed to find the effects of different DO concentration on turbot. Fish mortality was only observed under severe hypoxia conditions. Severe hypoxia caused an increase in respiratory rates and red blood cell counts, as well as an increase in haemoglobin and haematocrit levels in the fish. In fish exposed to hypoxia conditions, the respiratory rate increased overall as the DO concentration decreased. Lower pCO2 and HCO3? levels led to a high blood pH, while the pO2 remained stable. In hyperoxia groups, respiratory rate decreased as the DO concentration increased. The levels of pCO2 and HCO3? significantly increased (P < 0.05), while the pO2 level and blood pH did not change obviously. The gill structure was damaged after prolonged exposure to hyperoxia, but no obvious damage was found in hypoxia groups. The fish that survived the hypoxia or hyperoxia treatment were able to restore the structural integrity of the gills after 14 days' recovery. The results suggest that juvenile turbots can tolerate a wide range of DO concentrations. However, even mild hyperoxia condition (11 mg/L DO), which is widely used in fish culture, has adverse effects on juvenile turbot physiology.  相似文献   

17.
The oxygen consumption (02) and ammonia excretion (N) of juvenile and adult common wolffish was measured in culture tanks in the laboratory. The oxygen consumption and ammonia excretion were affected by temperature (C), fish size and feeding rate. For juveniles (0.5 kg; 7C) the diel oxygen consumption rate varied between 37 and 62 mg O2 kg-1 h-1 and ammonia excretion between 2.3 and 5.7 mg N kg-1 h-1. The corresponding rates for adult fish (6.9 kg; 7C) were 29-44 mg O2 kg-1 h-1 and 1.2–3.1 mg N kg-1 h-1. The weight-specific oxygen consumption (mg O2 kg-1 h-1) was described by the following formulae: O2 (7C) = 0.17* W0.83 and O2 (12C) = 0.39 * W0.73 and the corresponding ammonia excretion (mg N kg-1 h-1) by: N(7C) = 0.024 W0.75 and N(12C) = 0.073 W0.60, where W is fish weight in g.  相似文献   

18.
The impact of feeding, fish size (body weight from 18.5 to 56.5 g) and water temperature (20 and 23 °C) on oxygen consumption (OC, mg O2 kg–1 h–1) and ammonia excretion (AE, mg TAN kg–1 h–1) was studied in Eurasian perch held in recirculation systems. OC for both fed and feed-deprived (3 days) fish was higher at 23 °C (278.5 and 150.1 mg O2 kg–1 h–1) than at 20 °C (249.3 and 135.0 mg O2 kg–1 h–1; P < 0.01). AEs for both fed and feed-deprived fish were also significantly higher at 23 °C than at 20 °C (P < 0.001). Water temperature and fish size had a significant impact on the oxygen:feed ratio (OFR, kg O2 kg–1 feed fed day–1) and ammonia:feed ratio (AFR, kg TAN kg–1 feed fed day–1; P < 0.001). Their average values at temperatures of 20 and 23 °C were 0.17 and 0.19 kg O2 kg–1 feed fed day–1 and 0.009 and 0.011 kg TAN kg–1 feed fed day–1, respectively.  相似文献   

19.
The effect of feeding frequency (one, three, and continuous feeding), feed ration (0.2, 0.5, 0.8% of total fish biomass), and feeding per se on the oxygen consumption (OC, mg O2 kg−1 h−1) and ammonia excretion (AE, mg TAN kg−1 h−1) of juvenile tench (body weight 15–19 g) and variations in these parameters in daily cycles were examined. Fish metabolism was studied in a recirculating system (rearing tanks of 0.2 m3, water temperature 23 °C). It was found that oxygen consumption and ammonia excretion depended significantly on feed ration. An increase of feed ration from 0.2 to 0.8% of fish biomass caused an increase of OC and AE from 126.80 mg O2 kg−1 h−1 and 1.95 mg TAN kg−1 h−1 to 187.35 mg O2 kg−1 h−1 and 8.80 mg TAN kg−1 h−1 (p<0.05). There was no dependence between feeding frequency and the mean rate of oxygen consumption. However, the relationship between feeding frequency and ammonia excretion by juvenile tench was statistically significant (p<0.05). Feeding frequency significantly affected daily fluctuations of AE and OC. It was found that diurnal variations in metabolic rates were strictly related to tench feeding, and the daily variations of AE were significantly higher than OC.  相似文献   

20.
Abstract Temperature and oxygen gradients exist in nearly every water body, but anthropogenic activities can subject fish to rapid changes in these important environmental variables. These rapid changes in temperature and oxygen (generally referred to as temperature or oxygen shock) may have sub‐lethal consequences depending upon the magnitude and the fish species. This study quantified physiological changes in largemouth bass, Micropterus salmoides (Lacepède), exposed to two levels of heat and cold shocks and to two levels of hypoxic and hyperoxic shocks. Following a cold shock from 20 °C to 8 °C, plasma cortisol and glucose increased after 1 h and lactate dehydrogenase activity increased after 6 h. Plasma glucose and K+ concentrations increased 1 h after a heat shock from 20 °C to 32 °C but not after 6 h. Bass subjected to a hypoxic shock from 8 to 2 mg O2 L?1 showed decreased plasma K+ and increased plasma glucose and white muscle lactate. No changes in physiological parameters were observed in bass subjected up to 18 mg O2 L?1 hyperoxia. Results from this study suggest that largemouth bass can tolerate a wide range of temperature and oxygen shocks, but temperature decreases of 20 to 8 °C and hypoxia as low as 4 mg O2 L?1 should be avoided to minimise physiological perturbations.  相似文献   

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