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1.
We investigated the growth of juvenile common snook (Centropomus undecimalis) reared at 25°C and 28°C and salinities of 0.3, 15, and 32 g L?1. Total length, weight, RNA/DNA, and protein/DNA ratios were determined after 90 days of experiment. Higher growth was observed at 28ºC compared with 25°C, at the same salinity. At 28°C and 15 g L?1 salinity, the weight (25.14 g) of juveniles was twice that of the juveniles reared at the lower temperature. At different salinities, only higher temperature affected growth, with higher weight values obtained at 15 g L?1 in comparison with 0.3 and 32 g L?1. Length was similar at 0.3 and 15 g L?1. The RNA/DNA ratio was greater in juveniles reared at a salinity of 15 g L?1 when compared with 0.3 and 32 g L?1. This study shows that the combination of higher temperature and intermediate salinity promotes better growth of common snook juveniles.  相似文献   

2.
Survival rate, growth and feed intake were determined for late juveniles (4.31 ± 0.18 g) of river prawn Macrobrachium rosenbergii in freshwater with total ammonia‐N (NH3‐N+NH4‐N) concentrations of 0.015 (control), 0.5, 1.0 and 1.5 mg L−1 for 60 days at pH 7.53 ± 0.04 and temperature 24.0 ± 2.5°C. Survival rate was significantly (P<0.05) lower (54 ± 4.2–70 ± 5.4%) for total ammonia concentrations from 0.5 to 1.5 mg L−1 [0.0139–0.0419 mg L−1 of unionized ammonia (NH3)]. Growth (0.026–0.030 g day−1 range) of the prawns did not differ for the different NH3 levels but were significantly (P<0.05) lower compared with control (0.056 g day−1). Feed intake rates also diminished significantly (P<0.05) from 77.60 ± 2.45% at control (0.015 mg L−1 NH3‐N) to 48.69 ± 2.13% at 1.5 mg L−1 NH3‐N (0.0419 mg L−1 of unionized NH3).  相似文献   

3.
Four successive life stages (zoea-III, zoea-IV, zoea-V and megalopa) of the Chinese mitten-handed crab, Eriocheir sinensis (H. Milne-Edwards), were exposed to ammonia in a series of short-term bioassays with the static-renewal method at 22°C, pH 8.0 and 25%o salinity. The greatest sensitivity was observed in the zoea-III stage. The 24-h LC50 values for zoea-III, zoea-IV, zoea-V and megalopa were 32.8, 73.1, 84.0 and 90.1 mg L?1 for NH3+ NH4+, and 1.11, 2.36, 2.77 and 3.18 mg L?1 for NH3, respectively. The 72-h LC50 values for zoea-III, zoea-IV and zoea-V were 11.9, 23.6 and 38.2 mg L?1 for NH3+ NH4+, and 0.40, 0.76 and 1.26 mg L?1 for NH3, respectively. The 96-h LC50 values for megalopa were 37.3 mg L?1 for NH3+ NH4+ and 1.31 mg L?1 for NH3. It was found that ammonia tolerance increased with larval development from zoea-III to megalopa, especially from zoea-III to zoea-IV and from zoea-IV to zoea-V. A comparison of safe levels of ammonia among the different life stages indicated that all stages were significantly different with respect to safe levels of ammonia (P < 0.05) except zoea-V and megalopa, which had the highest safe levels. In general, both the larvae and juveniles of E. sinensis are less resistant to ammonia than those of other crustacean species studied so far.  相似文献   

4.
Piaractus mesopotamicus juveniles (total length 12 ± 0.5 mm) were exposed to different concentrations of ammonia‐N (un‐ionized plus ionized ammonia as nitrogen), using the static renewal method at different temperature levels (15, 20 and 25°C) at pH 7. The 24, 48, 72, 96 h LC50 values of ammonia‐N in P. mesopotamicus juveniles were 5.32, 4.19, 3.79 and 2.85 mg L?1 at 15°C; 4.81, 3.97, 3.25 and 2.50 mg L?1 at 20°C; and 4.16, 3.79, 2.58 and 1.97 mg L?1 at 25°C respectively. The 24, 48, 72, 96 h LC50 values of NH3‐N (un‐ionized ammonia as nitrogen) were 0.018, 0.014, 0.013, 0.009 mg L?1 at 15°C temperature; 0.023, 0.019, 0.016 and 0.012 mg L?1 at 20°C; 0.029, 0.026, 0.018 and 0.014 mg L?1 at 25°C. The temperature increase from 15 to 25°C caused an increase of ammonia‐N susceptibility by 21.80%, 9.55%, 31.92% and 30.87%, after 24, 48, 72 and 96 h exposure respectively. Furthermore, we found that exposure of fish to ammonia‐N caused an elevation in total haemoglobin and blood glucose with an increase of 2 mg L?1 concentration. Ammonia levels tolerated, especially in different temperatures levels, have important implications for the management of aquaculture.  相似文献   

5.
The effects of ammonia and nitrite on survival, growth and moulting were investigated in juvenile tiger crab, Orithyia sinica (carapace length 3.91±0.15 mm, carapace width 3.84±0.23 mm, n=440), after 30 days exposure to ammonia‐N (0, 20, 50, 100 and 150 mg L?1) and nitrite‐N (0, 50, 100, 150, 200 and 250 mg L?1) using a continuous flow system. Survival rates of tiger crab exposed to ammonia and nitrite decreased linearly with the exposure time and concentration. The growth rate of tiger crab exposed to 50, 100 and 150 mg L?1 ammonia was significantly lower than that of control crabs. The growth rate of tiger crab exposed to nitrite decreased at 150, 200 and 250 mg L?1 nitrite. During the ammonia and nitrite exposure, the intermoult period of the juveniles of tiger crab O. sinica was shortened between the first and second moult, and the number of moulting of crabs exposed to a higher concentration were significantly higher than that of control crabs.  相似文献   

6.
Ammonia toxicity and morphological changes in gills of juvenile Japanese flounder Paralichthys olivaceus (5.76 ± 0.12 g) were investigated when fish were separately exposed to normal dissolved oxygen (DO) at 6.5 ± 0.5 mg L?1 and supersaturated oxygen at 16.0 ± 2.0 mg L?1 at different ammonia concentrations. Under normal oxygen, ammonia concentrations were tested from 0.04 (control) to 93.3 mg L?1 total ammonia nitrogen (TAN), whereas under oxygen supersaturation, ammonia concentrations ranged from 0.04 (control) to 226.7 mg L?1 TAN in the trial. After exposure to ammonia for 96 h, the ammonia LC50 for fish was 62.48 mg L?1 TAN (0.50 mg L?1 NH3–N) at normal oxygen and 160.71 mg L?1 TAN (0.65 mg L?1 NH3–N) at oxygen supersaturation. Light microscopic observations confirmed that gill damage in normal oxygen was more profound than in oxygen supersaturation when fish were exposed to the same level of TAN (93.3 mg L?1). Furthermore, electron microscopic scanning also showed more crimple, retraction and fibrosis on the secondary lamella surface in fish exposed to normal oxygen than those in fish exposed to supersaturated oxygen at the same TAN (93.3 mg L?1). This study suggests that supersaturated oxygen can increase ammonia tolerance in Japanese flounder through reducing gill damage by ammonia, which partially explains the merit of using pure oxygen injection in intensive fish farming.  相似文献   

7.
False clownfish, Amphiprion ocellaris, is one of the most commercialized fish species in the world, highly produced to supply the aquarium market. The high stocking densities used to maximize fish production can increase ammonia and nitrite to toxic levels. In this study, A. ocellaris juveniles (1.20 ± 0.34 g) were exposed to six concentrations of ammonia ranged from 0.23 to 1.63 mg/L NH3-N and eight concentrations of nitrite (26.3–202.2 mg/L NO2 ?-N). The LC50- 24, LC50-48, LC50-72 and LC50-96 h were estimated to be 1.06, 0.83, 0.75 and 0.75 mg/L for NH3-N and 188.3, 151.01, 124.1 and 108.8 mg/L for NO2 ?-N. Analysis of gill lesions caused by sublethal concentrations of these nitrogenous compounds showed that both nitrogenous compounds induced tissue lesions such as hyperplasia of epithelium cells, hypertrophy of chloride cells and lamellar lifting to all concentrations tested. However, histopathological alterations were more conspicuous accordingly the increase of ammonia or nitrite in fish exposed to 0.57 mg/L NH3-N or 100 mg/L NO2 ?-N. Based on our results, we recommend to avoid concentrations higher than 0.57 mg/L of NH3-N and 25 mg/L of NO2-N in water.  相似文献   

8.
Exposure to TEX‐OE®, a patented extract of the prickly pear cactus (Opuntia ficus indica) containing chaperone‐stimulating factor, was shown to protect common carp, Cyprinus carpio L., fingerlings against acute ammonia stress. Survival was enhanced twofold from 50% to 95% after exposure to 5.92 mg L?1 NH3, a level determined in the ammonia challenge bioassay as the 1‐h LD50 concentration for this species. Survival of TEX‐OE®‐pre‐exposed fish was enhanced by 20% over non‐exposed controls during lethal ammonia challenge (14.21 mg L?1 NH3). Increase in the levels of gill and muscle Hsp70 was evident in TEX‐OE®‐pre‐exposed fish but not in the unexposed controls, indicating that application of TEX‐OE® accelerated carp endogenous Hsp70 synthesis during ammonia perturbation. Protection against ammonia was correlated with Hsp70 accretion.  相似文献   

9.
Argyrosomus regius (3.0 ± 0.9 g) were exposed to different concentrations of ammonia in a series of acute toxicity tests by the static renewal method at three temperature levels (18, 22 and 26°C) at a pH of 8.2. Low temperature clearly increased the tolerance of the fish to total ammonia nitrogen (TAN) and unionized ammonia (NH3) (P < 0.05). While the 96‐h LC50 values of TAN were 19.79, 10.39 and 5.06 mg L?1, the 96‐h LC50 of NH3 were 1.00, 0.70 and 0.44 mg L?1 at 18, 22 and 26°C respectively. The safe levels of NH3 for A. regius was estimated to be 0.10, 0.07 and 0.04 mg L?1 at 18, 22 and 26°C respectively (P < 0.05). This study clearly indicates that A. regius is more sensitive to ammonia than other marine fish species cultured on the Mediterranean and Eastern Atlantic coasts.  相似文献   

10.
In this study, we tested the lower salinity tolerance of juvenile shrimps (Litopenaeus vannamei) at a relatively low temperature (20 °C). In the first of two laboratory experiments, we first abruptly transferred shrimps (6.91 ± 0.05 g wet weight, mean ± SE) from the rearing salinity (35 000 mg L?1) to salinities of 5000, 15 000, 25 000, 35 000 (control) and 40 000 mg L?1 at 20 °C. The survival of L. vannamei juvenile was not affected by salinities from 15 000 to 40 000 mg L?1 during the 96‐h exposure periods. Shrimps exposed to 5000 mg L?1 were significantly affected by salinity, with a survival of 12.5% after 96 h. The 24‐, 48‐ and 96‐h lethal salinity for 50% (LS50) were 7020, 8510 and 9540 mg L?1 respectively. In the second experiment, shrimps (5.47 ± 0.09 g wet weight, mean ± SE) were acclimatized to the different salinity levels (5000, 15 000, 25 000, 35 000 and 40 000 mg L?1) and then maintained for 30 days at 20 °C. Results showed that the survival was significantly lower at 5000 mg L?1 than at other salinity levels, but the final wet weight under 5000 mg L?1 treatment was significantly higher than those under other treatments (P<0.05). Feed intake (FI) of shrimp under 5000 mg L?1 was significantly lower than those of shrimp under 150 00–40 000 mg L?1; food conversion efficiency (FCE), however, showed a contrasting change (P<0.05). Furthermore, salinity significantly influenced the oxygen consumption rates, ammonia‐N excretion rates and the O/N ratio of test shrimps (P<0.05). The results obtained in our work provide evidence that L. vannamei juveniles have limited capacity to tolerate salinities <10 000 mg L?1 at a relatively low temperature (20 °C). Results also show that L. vannamei juvenile can recover from the abrupt salinity change between 15 000 and 40 000 mg L?1 within 24 h.  相似文献   

11.
Acute ammonia toxicity was investigated in four developmental stages of the juvenile ide, Leuciscus idus: 1, 10, 20 and 30 days after the first feeding. Mean (±SD) total length of the larvae was 8.5 ± 0.3, 15.7 ± 0.7, 23.0 ± 2.0 and 29.7 ± 2.0 mm, and standard weight was 1.6 ± 0.3, 9.2 ± 5.5, 94.9 ± 31.0 and 196.0 ± 31.7 mg, respectively. The larvae used for toxicity tests were reared in the experimental, closed recirculating system. Groups of fishes (n from 7 to 10; in respect of fish size) were exposed to the ammonium chloride solutions in 1-L glass units. Water temperature was 25 ± 0.1 °C for both the rearing and the toxicity tests. pH was not adjusted and ranged between 8.4 and 8.7. The ammonium chloride solutions were renewed every 12 h. At the same time, dead larvae were counted and removed, and the pH and temperature measurements were taken. Each acute toxicity test duration was 96 h, and lethal concentration LC1, LC50 and LC99 values were calculated for 24, 48, 72 and 96 h. The susceptibility of the ide larvae to ammonia decreased linearly with age up to 20th day and surprisingly increased during the next 10 days. The LC50 (48 h) values ranged from 0.27 mg L?1 of unionized ammonia nitrogen for 1 day after the first feeding (AFF) larvae to 1.42 mg L?1 at day 20 after first feeding. The LC50 (48 h) for 30 days AFF was as high as 0.67 mg L?1. The critical level of the unionized ammonia nitrogen for ide larvae was suggested as 0.21 mg L?1.  相似文献   

12.
Static-renewal bioassays were performed to evaluate the acute toxicity of ammonia to Eriocheir sinensis (H. Milne-Edwards) at three growing stages, namely zoea-I, zoea-II, and juvenile (0.06 g wet weight per crab). The 24 h LC50 values were 13.3, 20.2, and 109.3 mg (NH3+ NH4+) 1?1 (0.47, 0.71, and 3.10 mg NH3 I?1), the 48 h LC50 values being 6.8, 10.3, and 60.9 mg (NH3+ NH4+) 1?1 (0.24, 0.36, and 1.73 mg NH31?1), while the 72 h LC50 values were 5.7, 7.6, and 45.3 mg (NH3+ NH4+) 1?1 (0.20, 0.27, and 1.29 mg NH3 1?1) for zoea-I, zoea-II, and juveniles, respectively. The 96 h LC50 value for juveniles was 31.6 mg (NH3+ NH4+) 1?1(0.90 mg NH31?1). It was evident that the tolerance to ammonia increased during the same exposure time as the larvae developed to juveniles and decreased with prolonged exposure time. Compared with larvae, juveniles were more sensitive to the fluctuation of ambient ammonia concentrations in the certain range within which partial kills took place. The ‘safe level’ of ammonia based on the 96 h LC50 value and an application factor of 0.1 was 3.16 mg (NH3+NH4+)1?1 (0.09 mg NH3 1?1) for juveniles and those for zoea-I and zoea-II were 0.57 and 0.76 mg (NH3+ NH4+) 1?1 (0.02 and 0.03 mg NH3 1?1) based on 72 h LC50 values.  相似文献   

13.
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   

14.
Silver catfish, Rhamdia quelen (Quoy & Gaimard, 1824), is an endemic species from Latin America that is raised in cultivation ponds, and consequently may be exposed to low oxygen levels. Therefore, the objective of this study was to verify the lethal concentration (CL50?96 h) of dissolved oxygen levels for silver catfish juveniles. In addition, the effects of different dissolved oxygen levels (1.96±0.08, 3.10±0.10, 4.14±0.09, 5.20±0.07 and 6.16±0.03 mg L?1) on growth and metabolic parameters (glycogen, glucose, protein, lactate levels and catalase activity) were also investigated. CL50?96 h was 0.52 mg L?1 (CI 0.42–0.61 mg L?1) or 6.7% oxygen saturation. After exposure of silver catfish to hypoxia for 30 days, there were no changes in biochemical parameters indicating the use of an anaerobic pathway by the fish. However, the dissolved oxygen levels influenced silver catfish juvenile behaviour, survival and growth, and under the experimental conditions 5.2 mg L?1 (or 65.6% oxygen saturation) is the minimum oxygen level recommended for the growth of this species.  相似文献   

15.
The effects of total ammonia (TAN; NH4++ NH3) on the reproductive performance, survival, growth and moulting of wild Penaeus paulensis (Pérez-Farfante) broodstock were studied to determine optimal rearing conditions. Based on previously established ‘safe levels’ for P. paulensis adults (3.4 and 4.2 mg L?1 TAN), two 46-day trials were performed. In the first trial, six females and four males were stocked in 700-L tanks under three treatments (0.37, 2.53 and 6.86 mg L?1 TAN) with at least two replicates per treatment. In trial 2, ammonia levels of 0.68, 1.55 and 2.62 mg L?1 TAN were assigned to three 6000-L tanks, each stocked with 36 females and 24 males. Ammonia only influenced the survival of females and the growth of males exposed to 6.86 mg L?1 TAN (0.21 mg L?1 NH3). No further effects of ammonia on moulting and reproductive performance were detected. The present results demonstrate that up to 2.62 mg L?1 TAN, coupled with 0.07 mg L?1 NH3 and 1.50 mg L?1 NO2, will not impair reproductive performance of P. paulensis. It is suggested that water quality for the maturation of P. paulensis may be maintained through lower daily water exchange rates instead of the usual high levels (150-300%) employed on penaeid shrimp maturation systems.  相似文献   

16.
The acute tolerance of juvenile Florida pompano Trachinotus carolinus L. (mean weight±SE=8.1±0.5 g) to environmental unionized ammonia‐nitrogen (NH3‐N) and nitrite‐nitrogen (NO2‐N) at various salinities was determined via a series of static exposure trials. Median‐lethal concentrations (LC50 values) of NH3‐N and NO2‐N at 24, 48, and 96 h of exposure were calculated at salinities of 6.3, 12.5 and 25.0 g L?1 at 28 °C (pH=8.23–8.36). Tolerance of pompano to acute NH3‐N exposure was not affected by salinity, with 24, 48 and 96 h LC50 values ranging from 1.05 to 1.12, 1.00 to 1.08 and 0.95 to 1.01 mg NH3‐N L?1 respectively. Regarding NO2‐N, tolerance of pompano to this environmental toxicant was compromised at reduced salinities. Median‐lethal concentrations of NO2‐N to pompano at 24, 48 and 96 h of exposure ranged from 67.4 to 220.1, 56.9 to 140.7 and 16.7 to 34.2 mg NO2‐N L?1 respectively. The results of this study indicate that juvenile Florida pompano are relatively sensitive to acute NH3‐N and NO2‐N exposure, and in the case of the latter, especially at lower salinities.  相似文献   

17.
In the present study, the hypothesis tested was that Penaeus monodon post‐larvae (PL) experience lower growth when exposed to crushed conspecifics, which was achieved by exposing individual P. monodon PL with abundant food for 4 weeks to a gradient from 0 to 100 crushed conspecific PL L?1. Both dry weight (48.5±7.2 mg) and body size (28.0±1.3 mm) of animals exposed to 1 macerated PL L?1 were significantly (P≤0.011) higher than those of animals in treatments with 0, 5 and 10 crushed PL L?1 (average over treatments: 25.6±3.2 mg; 23.4±0.5 mm). All animals died within 1 week when exposed to 70 and 100 crushed PL L?1, and within 3–4 weeks when exposed to 50 and 30 crushed PL L?1. Exposure time affected mortality and it appeared that LC50 values decreased from 60 to 13 crushed PL L?1 from 1 to 4 weeks' exposure. Survival of P. monodon PL was negatively correlated to pH, biological oxygen demand, ammonia and nitrate. In conclusion, low dose of crushed conspecifics has a stimulatory effect on P. monodon PL, as larvae were heavier and larger, while high doses cause high mortality.  相似文献   

18.
Haematological parameters of 2‐year‐old carp (Cyprinus carpio L.) were assessed to study the protective effect of chloride on the health of fish exposed to elevated nitrite concentrations. Four groups of carp were exposed to different concentrations of nitrite and chloride for 96 h (group E1: 67 mg L?1 NO2?, 11 mg L?1 Cl?; group E2: 67 mg L?1 NO2?, 100 mg L?1 Cl?; group E3: 0 mg L?1 O2?, 100 mg L?1 Cl? and group C: 0 mg L?1 NO2?, 11 mg L?1 Cl?). The main haematological response of carp to an acute exposure to nitrite (group E1) was a significant decrease (P<0.05) in haemoglobin concentrations (53.40±6.61 g L?1), haematocrit (0.21±0.02 LL?1), erythrocyte count (1.13±0.12 TL?1), leucocyte count (7.1±4.19 GL?1) and lymphocyte count (5.28±2.51 GL?1), and a significant increase in methaemoglobin concentration (90.50±4.38%, P<0.01) and mean corpuscular haemoglobin concentration (0.27±0.2 LL?1, P<0.05). At higher chloride concentrations (group E2), a lower nitrite toxicity was observed. In group E2 carp, methaemoglobin made up 38.32±13.30%. Erythrocytes in carp exposed to nitrite showed qualitative changes. Compared with the control group C, group E1 carp showed a significantly higher number (P<0.05) of elongated erythrocytes, with the nucleus located at one cell pole (0.519±0.388 TL?1). All erythrocytes of group E1 carp had remarkably clear cytoplasms compared with the cytoplasm in the control group C. The biochemical values found were comparable with those found in controls. The main histological lesions were found in the gills of carp exposed to nitrite and consisted of hyperplasia and an elevated number of chloride cells.  相似文献   

19.
A comprehensive acute toxicity trial was conducted using a static water system to study the toxic effect of ammonia on haematology and enzyme profiles of Cirrhinus mrigala H. The LC50 of total ammonia‐nitrogen (TAN) was 11.8 mg L?1 TAN (1.029 mg L?1 NH3‐N). The sub‐lethal test revealed that with increasing concentration of TAN, the total erythrocyte counts were reduced in lower concentrations (1–4 mg L?1 TAN) followed by higher levels in fish exposed to higher concentrations (8–16 mg L?1 TAN). In contrast, the total leucocyte counts were opposite. With increasing concentration of TAN, haemoglobin and serum protein content were reduced, whereas the blood glucose level increased. As the concentration of ammonia increased, there was a reduction in acetylecholinesterase activity in the brain and liver; alkaline phosphatase activity in the serum, brain and gill; and acid phosphatase (ACP) activity in the gill. The activity of lactate dehydrogenase in the gill, liver, kidney and brain increased with increased concentration of ammonia. In addition, activities of ACP in the serum and brain, alanine aminotransferase in the serum, brain and gill, and aspartate aminotransferase in the serum, brain and gill were increased.  相似文献   

20.
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   

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