Myrcia sylvatica essential oil in the diet of gilthead sea bream (Sparus aurata L.) attenuates the stress response induced by high stocking density

The effects of diet supplemented with Myrcia sylvatica essential oil (EOMS) on growth and stress tolerance to different stocking densities were assessed in Sparus aurata. Initially, three experimental groups were established: (i) control, (ii) 1.0 and (iii) 2.0 ml EOMS/kg dry feed. After 90 days, nine fish per group were anaesthetized, weighed and sampled for metabolic analysis. The remaining fish were divided into two different conditions: low (LD—5 kg/m³) and high (HD—40 kg/m³) stocking densities, constituting a final experimental setup with six treatments. After 22 days, 10 individuals per treatment were anaesthetized and sampled for biochemical analysis. EOMS feeding for 90 days did not interfere with growth, although it was effective in reducing cortisol levels and the activation of lipid and carbohydrate metabolism. The HD interfered in growth performance, increased the lactate levels in the control group, reducing also hepatic glycogen levels without dependence on diet supplementation. The 2.0 ml EOMS + LD group increased the growth parameters and decreased the cortisol and triglycerides levels. Additionally, metabolism adjustment was observed to provide energy during LD and HD conditions, indicating that diets supplemented with EOMS produce metabolic reorganization to maintain body homeostasis, suggesting its use as a beneficial supplement in fish.     

Anaesthesia of Atlantic halibut (Hippoglossus hippoglossus) Effect of pre‐anaesthetic sedation,and importance of body weight and water temperature

The efficacy of the anaesthetic agents benzocaine, metacaine (MS‐222), metomidate, 2‐phenoxyethanol, quinaldine and isoeugenol was studied in Atlantic halibut (Hippoglossus hippoglossus). Fish with an average body weight of 33 g were anaesthetized at 8 °C and fish with an average body weight of 1243 g were anaesthetized at 8 and 15 °C. Agents were tested individually and as combination anaesthesia comprising pre‐anaesthetic sedation, followed by anaesthesia. Induction and recovery times varied in relation to the body weight and water temperature. Large fish had longer induction times and shorter recovery times, and displayed reduced responsiveness to handling compared with small fish. A higher temperature resulted in shorter induction times, longer recovery times and increased responsiveness to handling. Lower dosages were used for all agents in combination anaesthesia. In small fish, this had no effect on the induction times but resulted in shorter recovery times and reduced responsiveness to handling. In large fish, combination anaesthesia resulted in shorter induction times whereas no uniform trend in recovery times and no differences in responsiveness to handling were observed. Neither individual agents nor combinations blocked all reflex reactions to external stimulation in all fish of any treatment group. MS‐222 and benzocaine, used separately or in combination anaesthesia, were the most effective agents in reducing reflex reactions.     

Essential oil of Aloysia triphylla in Nile tilapia: anaesthesia,stress parameters and sensory evaluation of fillets

The optimum concentration of anaesthetic used to facilitate fish handling can be determined based on induction and recovery time, among other factors. This study aimed to evaluate the effectiveness of the essential oil of Aloysia triphylla (EOAT) as an anaesthetic in the handling of Nile tilapia juveniles. Nile tilapias exemplars were immersed at 0 (control group), 10, 20, 30, 40, 80, 150, 300 and 450 μL L^?1 EOAT to evaluate sedation, anaesthesia and recovery time. The stress response was evaluated by the determination of plasma glucose, cortisol, lactate and paraoxonase levels in anaesthetized (300 μL L^?1 EOAT) and non‐anaesthetized fish. Fillets from both groups were evaluated for organoleptic characteristics (taste and odour). Concentrations of 80–450 μL L^?1 EOAT were effective in inducing anaesthesia. There was a significant reduction in plasma cortisol levels one hour after handling in individuals anaesthetized with 300 μL L^?1 EOAT compared to the control group. Tasters did not detect differences in fillet taste and odour between fish exposed and not exposed to EOAT. A concentration of 300 μL L^?1 EOAT is recommended for handling Nile tilapia because it presents good anaesthetic induction and recovery times, causes a reduction in plasma cortisol levels one hour after handling and does not affect the taste or odour of the fillets.     

Change in blood stress and antioxidant markers and hydromineral balance of common carp (Cyprinus carpio) anaesthetized with citronellal and linalool: Comparison with eugenol

The present study aimed to investigate the effects of anaesthesia with citronellal and linalool on stress, antioxidant and hydromineral responses of common carp. Eugenol was used as control anaesthetic, as it is a common anaesthetic in aquaculture. The fish (110 ± 5.65 g) were exposed to 406 mg/L citronellal, 982 mg/L linalool or 43 mg/L eugenol within 5 min (short‐term anaesthesia) or 10 and 20 mg/L of each anaesthetic for 3 hr (long‐term exposure), before blood sampling. The results showed that the short‐term anaesthesia had no significant effects on plasma lactate, sodium, chloride and phosphorus levels and blood catalase (CAT) and superoxide dismutase activities. The short‐term anaesthesia with linalool led to higher stress responses (increased cortisol and glucose levels) and oxidative stress (increased malondialdehyde [MDA] level and decreased total antioxidant capacity [TAC] and glutathione peroxidase [GPx] activity) compared to the eugenol and citronellal. Citronellal group had significantly higher cortisol and lower TAC level and GPx activity compared to eugenol group. Under the long‐term exposure, increase in anaesthetic concentration led to significant increase in plasma cortisol, glucose and phosphorus levels. The linalool‐treated fish had significantly higher cortisol and MDA levels compared to the other groups. The eugenol group had significantly higher lactate and phosphorus and lower TAC levels compared to the other groups. Although citronellal causes slight increase in plasma cortisol level, it induces lower tissue damages compared to eugenol. Thus, citronellal might be an alternative anaesthetic for carp anaesthesia based on the present tested parameters.     

Effects of repeated handling, with or without anaesthesia, on feed intake and growth in juvenile rainbow trout, Oncorhynchus mykiss (Walbaum)

The effects of weekly anaesthetization with clove oil and tricaine methanesulphonate (MS‐222) on feed intake and growth were examined in juvenile rainbow trout, Oncorhynchus mykiss (Walbaum), held individually. Repeated handling without anaesthetics significantly reduced feed intake and weight gain compared with an unhandled control group during an 8‐week experiment. When anaesthetics were used during handling the feed consumption and weight gain were significantly (MS‐222) or not significantly (clove oil) higher than in fish handled without anaesthesia. When compared with the unhandled control group, neither of these two anaesthetics had significant effects on feed intake but, in contrast to MS‐222, repeated anaesthesia with clove oil had a significant negative effect on growth. However, the effects of MS‐222 and clove oil on the growth were not significantly different from each other. Feed conversion ratio (feed/gain) of MS‐222‐anaesthetized fish was significantly higher compared with unhandled control and handled control fish but was not significantly different from fish anaesthetized with clove oil. These results suggest that both MS‐222 and clove oil alleviate handling stress in juvenile rainbow trout, and that these two anaesthetics are rather similar with respect to their effects during repeated exposures.     

Dietary β‐carotene improves growth performance and antioxidant status of juvenile Piaractus mesopotamicus

This study was conducted to investigate the effects of dietary synthetic β‐carotene on growth performance, haematological and immunological parameters, energy reserves and antioxidant status of juvenile fish Piaractus mesopotamicus. Two hundred and ten fish (12.24 ± 2.98 g) were fed with a control extruded feed (CEF) and the same diet supplemented with β‐carotene (BEF) for 90 days. A higher weight gain and specific growth rate were found in fish fed BEF in comparison with those fed CEF. In addition, BEF‐fed fish showed lower liver somatic index and a higher percentage of eosinophils. No statistical differences were found in energy reserves, except for plasma triglycerides which decreased in fish fed with BEF. Regarding oxidative stress markers, decreased activities of antioxidant enzymes were found in intestine and gills of BEF‐fed fish (SOD and GST, respectively). In the liver, both LPO levels and CAT activity decreased in fish fed with BEF. Additionally, lower brain LPO levels without changes in the antioxidant enzymes were observed in BEF‐fed fish. The inclusion of dietary synthetic β‐carotene improved growth and antioxidant status, and had a plasma triglyceride‐lowering effect in juvenile P. mesopotamicus.     

Assessment of tissue-specific effect of cadmium on antioxidant defense system and lipid peroxidation in freshwater murrel, Channa punctatus

The effects of different concentrations of cadmium chloride on the extent of lipid peroxidation (LPO) and alterations in the antioxidant enzyme activities were studied in liver, kidney and gill tissues of freshwater murrel, Channa punctatus. The fish specimens were exposed to 6.7, 13.4 and 20.1 mg l⁻¹ sublethal concentrations of cadmium chloride and the oxidative stress was assessed after 24, 48, 72 and 96 h post-exposure. The biomarkers selected for the study were thiobarbituric acid reactive substances for assessing the extent of lipid peroxidation and antioxidant defense system such as reduced glutathione (GSH), glutathione reductase (GR), glutathione peroxidase (GP_X), glutathione-S-transferase (GST), catalase (CAT) and superoxide dismutase (SOD) activities. In general, the cadmium exposure elevated the LPO in subject tissues of treated group and modulated the activities of GPx, GST, SOD, CAT, GR and level of GSH after given exposure as compared to the control. All enzymes activities, except CAT (in kidney and gills), and amount of LPO elevated significantly (P < 0.05) in treated group with respect to control in all tissues, while significant difference was not observed between the exposed concentrations and within exposure duration. The results indicated that increase in LPO level and the fluctuation in antioxidant defense system in fish could be due to cadmium-induced increase in the production of reactive oxygen species (ROS). The potential role of these parameters as biomarkers of heavy metal pollution in aquatic system is discussed.     

Effect of dietary l‐carnitine on growth performance and antioxidant response in Amur minnow (Phoxinus lagowskii Dybowskii)

l ‐carnitine (LC) is required for transporting long‐chain fatty acids into the mitochondria, where β‐oxidation takes place, and it works as an antioxidant molecule against reactive oxygen species. This study evaluated the effects of LC on the growth and antioxidant function of Amur minnow (Phoxinus lagowskii Dybowskii). Five isonitrogenous (380.4 g/kg) and isoenergetic (17.63 MJ/kg) diets were supplemented with five LC levels: control level (0 mg/kg) and treatment levels (50, 400, 750, or 1,100 mg/kg) were fed to fish (18.19 ± 0.56 g) for 120 days. The results showed that the growth performance of fish fed a diet containing 400 mg/kg of LC was significantly higher than that of the control and those fed other LC level treatments. Similarly, the 400 mg/kg treatment had the best feed efficiency. Further, the levels of total antioxidant capacity and total glutathione in the serum and hepatopancreas of fish fed a diet containing 750 mg/kg of LC were significantly increased; however, malondialdehyde levels were significantly reduced compared to those of the control group. The activities of antioxidant enzymes of 750 mg/kg treatments in the serum and hepatopancreas were significantly higher than those of the control group, including total superoxide dismutase, catalase, glutathione peroxidase and gamma‐glutamyl‐cysteine synthetase. Finally, 750 mg/kg treatment significantly upregulated the mRNA relative expression of antioxidant enzymes and nuclear factor erythroid‐2‐related factor 2 and inhibited the mRNA level of kelch‐like ECH‐associated protein 1 in the hepatopancreas. In conclusion, the dietary LC level of 400–750 mg/kg could improve the growth performance, feed utilization and antioxidant defense system of Amur minnow under the culture conditions.     

Influence of dietary zinc on lipid peroxidation,protein oxidation and antioxidant defence of juvenile Jian carp (Cyprinus carpio var. Jian)

This study was conducted to study the effects of dietary zinc on lipid peroxidation, protein oxidation and antioxidant defence of juvenile Jian carp (Cyprinus carpio var. Jian) by feeding fish with increasing levels of zinc (15.3, 26.9, 40.8, 58.2, 68.9 and 92.5 mg Zn kg^?1) for 6 weeks. Results indicated that malondialdehyde (MDA) content and protein carbonyls (PC) in serum were the highest in fish fed diet containing 15.3 mg zinc kg^?1 diet (P < 0.05). Serum antisuperoxide anion (ASA), superoxide dismutase (SOD), glutathione peroxidase (GSH‐Px), glutathione reductase (GR) activities and glutathione (GSH) content were improved with increasing dietary zinc levels up to 40.8 mg zinc kg^?1 diet (P < 0.05) and levelled off (P > 0.05). Serum antihydroxy radical (AHR), catalase (CAT) and glutathione‐S‐transferase (GST) activities followed the similar pattern to that observed in ASA. The MDA and PC levels, ASA, AHR, SOD, CAT, GPx, GR, GST activities and GSH content in intestine, hepatosomatic and muscle tissue followed the similar pattern to that observed in serum. The present results indicated that zinc decreased lipid peroxidation and protein oxidation and improved antioxidant defence in fish.     

Anaesthetic efficacy and biochemical effects of 1,8‐cineole in rainbow trout (Oncorhynchus mykiss,Walbaum, 1792)

The aim of the present study was to investigate the anaesthetic efficacy and biochemical effects of 1,8‐cineole (cineole) in rainbow trout (Oncorhynchus mykiss). The fish were exposed to 200, 300, 400, 500, 600 and 800 μl/L cineole and time of induction of anaesthesia and recovery from anaesthesia were recorded. Thereafter, the fish haematological and biochemical responses to anaesthesia with different concentrations of cineole were studies. Moreover, the haematological and biochemical response of fish anaesthetized for 300 s with either cineole (283 μl/L) or eugenol (25 μl/L) were compared. Cineole at the concentrations of 200–800 μl/L induced stages 2, 3 and 4 anaesthesia within 109‐29.3, 226‐59 and 418‐117 s respectively. Increase in anaesthesia induction time led to higher stress responses and enzymes’ activity characterized by elevation in red blood cell (RBC), white blood cell (WBC), blood haematocrit and haemoglobin, and plasma cortisol, glucose and lactate levels, and aspartate aminotransferase (AST), alkaline phosphatase (ALP), lactate dehydrogenase and creatine phosphokinase (CPK) activities. However, cineole concentrations had no significant effects on plasma alanine aminotransferase (ALT) activity and ions levels. Comparison of cineole with eugenol showed that cineole showed less change in blood RBC and plasma AST, ALP, CPK, cortisol and glucose levels compared to eugenol. In conclusion, cineole is efficient to anaesthetize trout at concentrations of 200–800 μl/L. Increase in cineole concentration shortens anaesthesia induction time, stress response and probably tissue damage. The concentrations of 600–800 μl/L cineol is recommended for rapid sampling as it causes the least stress and enzymatic responses. The present results suggest that cineole causes slightly lower side effects in trout compared to eugenol.     

Histological and antioxidant responses in Rhamdia quelen sedated with propofol

Morphometry of gills and antioxidant/oxidant status in gills, brain, liver and blood of Rhamdia quelen sedated with propofol were studied. The purpose was to investigate structural and functional responses upon administration of the drug in order to validate its use for the species. The fish were exposed to 0, 0.4 or 0.8 mg L^?1 propofol for 1, 6 or 12 h, which are times normally used in live fish transport. Propofol induced an increase in chloride cell in the non‐respiratory epithelium of the gill. Standard biochemical assays (thiobarbituric acid reactive substances and lipid hydroperoxides) indicated that the lowest concentration of propofol did not induce lipoperoxidation in gills, brain, liver or blood. The oxidative status of enzymatic (catalase, superoxide dismutase and glutathione‐S‐transferase) and non‐enzymatic (non‐protein thiols) antioxidants differed among the tested sites. Apart from the blood, superoxide dismutase was the enzyme to show the highest activity in the presence of propofol, which is known to possess antioxidant properties that resemble those of vitamin E. The absence of chloride cells in the respiratory epithelium (lamella) in association with the stability of the lamellar structure (i.e. lamellar area, total height of lamella and width of lamella) indicate that ion and oxygen uptake were preserved under propofol sedation. Thus, 0.4 mg L^?1 propofol should be considered to sedate R. quelen during lengthy procedures, such as transport, for it was able to maintain ionic and respiratory homeostasis as well as prevent peroxidative damage in vital organs.     

Use of MS‐222 (tricaine methanesulfonate) and propofol (2,6‐diisopropylphenol) as anaesthetics for the tetra Astyanax altiparanae (Teleostei,Characidae)

The aim of this study was to evaluate the anaesthetic effect of MS‐222 and propofol and determine their optimal concentrations for safe handling of the tetra Astyanax altiparanae in the laboratory. The fish were separated by length into three classes: I (1.5–5.0 cm), II (5.1–8.0 cm) and III (greater than 8.1 cm). Pilot tests were performed to evaluate the appropriate anaesthetic concentrations for inducing the five possible anaesthetic stages: I – sedation; II – light anaesthesia; III – deep anaesthesia; IV – surgical anaesthesia; and V – spinal collapse. After defining the maximum and minimum concentrations required to induce stage IV anaesthesia, the animals were exposed to five intermediate concentrations (n = 10 fish/concentration) of each anaesthetic for 15 min. The animals were then transferred to clean water to evaluate the time required for recovery. In addition, blood glucose levels were measured for class II and class III fish subjected to the previously defined ideal concentrations for each of the tested anaesthetics (n = 10 fish/treatment). Both evaluated substances are suitable to anaesthetize A. altiparanae. The optimal MS‐222 concentration was 90 mg L^?1, and this result was similar for all three size classes. The optimal propofol concentrations for inducing surgical anaesthesia in the size classes I, II and III were 0.22, 0.23 and 0.27 respectively.     

The ability of clove oil and MS-222 to minimize handling stress in rainbow trout (Oncorhynchus mykiss Walbaum)

The effects of 60‐mg L^?1 clove oil and 60‐mg L^?1 tricaine methanesulphonate (MS‐222) on the blood chemistry of rainbow trout were compared after exposure to handling stress via caudal puncture blood sampling. Fish sampled by caudal puncture and subsequently exposed to anaesthetics showed a typical handling stress response over a 48‐h period. There were no significant differences between the responses of fish exposed to equal concentrations of clove oil and MS‐222, with the following exceptions: the blood glucose at full anaesthesia, and lactate at full recovery increased significantly in the clove oil‐exposed fish. In a subsequent experiment, the stress response observed in fish sampled by caudal puncture and exposed to clove oil and MS‐222 was compared with a non‐anaesthetized control group. The increases in plasma cortisol levels were significantly lower at recovery in fish treated with either anaesthetic compared with the control fish. Fish exposed to MS‐222 had significantly higher cortisol levels at 1 h. These findings show that few differences exist between the anaesthetic effects of clove oil and MS‐222 on the physiological response of fish to stress. However, clove oil is more effective at reducing the short‐term stress response induced by handling and blood sampling, and is recommended as an alternative fish anaesthetic.     

Responses of antioxidant enzymes,lipid peroxidation,and Na<Superscript>+</Superscript>/K<Superscript>+</Superscript>-ATPase in liver of the fish <Emphasis Type="Italic">Goodea atripinnis</Emphasis> exposed to Lake Yuriria water

Lake Yuriria, located in the heavily populated and polluted Mexican Central Plateau, receives domestic sewage, industrial effluents, and municipal wastewaters that are still directly discharged without treatment into the tributaries and the lake. Pollutants in water and sediments include heavy metals, aromatic hydrocarbons, and organochlorine pesticides. Activities of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), as well as Na⁺/K⁺-adenosine triphosphatase (Na⁺/K⁺-ATPase) activity, and lipid peroxidation (LPO) were evaluated in the livers of the fish Goodea atripinnis after 96 h of exposure to water collected in March and June 2005 from three sites: Y (limnetic zone), L (Lerma tributary), and C (la Cinta tributary). Physical and chemical parameters of the lake water were also analyzed. Increases in CAT activity and LPO levels at all three sites were detected compared with control fish (P < 0.05), while GPx and SOD activities decreased significantly (P < 0.05). Na⁺/K⁺-ATPase activities were similar to the control in fish exposed to limnetic water from both March and June but were higher than control at the two tributary sites in March (P < 0.05); fish exposed to water from the Lerma tributary in June exhibited lower Na⁺/K⁺-ATPase than the control (P < 0.05). During March, CAT and Na⁺/K⁺-ATPase activities were increasing more than in June in Y and L, respectively, while in June, SOD and GPx were depleted more than March in L and Y and L, respectively. Despite the antioxidant defenses of the fish liver, exposure to all water samples from Lake Yuriria exerted alterations in hepatic LPO levels, antioxidant enzymes, and Na⁺/K⁺-ATPase activities that could substantially impair the mechanisms of fish defenses against oxidative stress.     

Effects of dietary myrcene administration on antioxidant gene responses in common carp (Cyprinus carpio), exposed to copper sulphate

In the present study, common carp (Cyprinus carpio) were fed with diet supplemented with 0% (M0) or 0.5% (M0.5) myrcene for 6 week and exposed to ambient copper (0.2 mg/L) for further 2 weeks. Gene expressions of superoxide dismutase (sod), catalase (cat), glutathione peroxidase (gpx), glutathione reductase (gr) and glutathione S‐transferase (gst) were assayed in the fish brain and kidney, and thiobarbituric reactive substance (TBARS) levels were determined in blood plasma. The results showed that there was no significant difference in TBARS levels between the M0 and M0.5 treatments, before the copper exposure; however, the M0 had significantly higher TBARS levels compared to the M0.5, after the copper exposure. The antioxidant genes showed different patterns in the fish brain and kidney. The genes were up‐regulated in the fish brain by dietary myrcene and copper exposure. However, in the fish kidney, the M0.5 treatment showed no change in sod, cat, gpx before and after the copper exposure. The results suggest that myrcene is capable to induce antioxidant enzymes that prepare the fish for a further oxidative condition (i.e. copper exposure). Dietary myrcene at 0.5% level is suggested for common carp before treatment with copper sulphate.     

Effects of pyridoxine on antioxidative parameters in juvenile Jian carp (Cyprinus carpio var. Jian)

To investigate the effects of dietary pyridoxine (PN) on antioxidant status of fish in serum, intestine and trunk kidney, 1050 juvenile Jian carp (11.7 ± 0.1 g) were used for the experiment. The carp were divided into seven groups and fed diets containing graded levels of PN (0.20, 1.71, 3.23, 4.96, 6.32, 8.58 and 12.39 mg kg^?1 of diet) for 80 days. Results of the study showed that content of malondialdehyde in serum, intestine and kidney tissues was the highest when fed the diet containing 1.71 mg PN kg^?1 diet (P < 0.05). Meanwhile, the protein carbonyl content of intestine and kidney tissue showed a downward trend to a point (P < 0.05). Conversely, activities of superoxide dismutase, catalase, glutathione peroxidase (GSH‐Px), glutathione S‐transferase, glutathione reductase and glutathione (GSH) content in serum, intestine and kidney tissue were generally higher in PN‐supplemented diets than unsupplemented diet (P < 0.05). The present results indicated that the PN decreased lipid peroxidation and protein oxidation in fish, and partly because of its improved antioxidant enzymes activities and levels of GSH.     

Effects of Dietary Inclusion of Chlorella vulgaris on Growth,Blood Biochemical Parameters,and Antioxidant Enzyme Activity in Olive Flounder,Paralichthys olivaceus

This study was carried out to investigate the effects of dietary inclusion of defatted Chlorella on growth performance, body composition, blood biochemistry, and antioxidant enzyme activity in olive flounder. Four isonitrogenous (51% crude protein) diets were formulated to contain 0 (control), 5, 10, or 15% Chlorella meal (CM) (designated as Con, CM5, CM10, and CM15, respectively) and fed to triplicate groups of fish (104.4 g) to apparent satiation twice daily for 8 wk. At the end of the feeding trial, significant enhancement (P < 0.05) in growth performance was obtained at over 10% CM compared to fish fed the control diet. No significant changes in dorsal muscle and liver proximate composition were found following CM administration. The groups fed CM‐containing diets revealed significantly lower plasma cholesterol concentration than those fed the control diet. Dietary CM affected antioxidant enzyme activity; significantly higher plasma catalase activity was found in fish fed ≥10% CM and total antioxidant capacity increased in CM5 and CM10 groups compared to the control. However, plasma glutathione peroxidase and superoxide dismutase activities were not significantly influenced by dietary CM. Also, significant enhancement in 1,1‐diphenyl‐2‐picryl‐hydrazyl radical scavenging activity was found in dorsal muscle of fish fed CM15 diet compared to the control. The findings in this study showed that dietary inclusion of 10–15% CM can enhance growth performance and affect antioxidant enzyme activity and lipid metabolism in olive flounder.     

Effect of dietary supplementation of palm fruit extracts on the transcriptomes of growth,antioxidant enzyme and immune‐related genes in common carp (Cyprinus carpio) fingerlings

This study investigates the effects of date palm extracts [DPE] (Phoenix dactylifera L. Arecaceae) on growth, immune function and antioxidant system in common carp fingerlings (Cyprinus carpio). One hundred and twenty fish (4.06 ± 0.13 g) were divided into six groups fed on control diet or diets containing 200 mL kg^?1 DPE for 8 weeks. At the end of feeding trial, the expression of different genes was measured. Selected genes were grouped into three categories: growth factor genes in brain and liver [growth hormone (GH), insulin‐like growth factors I and II (IGF‐I and IGF‐II), antioxidant‐related genes in liver [glutathione S‐transferase‐alpha (GST‐α), glutathione reductase (GR) and glutathione peroxidase genes (GPX)] and immune‐related genes in head kidney [interleukin‐8 (IL‐8), interleukin‐10 (IL‐10) and transforming growth factor‐beta (TGF‐β) genes]. The relative expression of the growth‐related genes in fish fed DPE showed no significant increase compared to control group (P > 0.05). On the other hand, DPE altered the expression of genes encoding antioxidants enzymes in liver of fingerlings which was statistically significant with respect to the control samples in case GPX (P < 0.05). Also, DPE caused remarkable increases in the expression of the immune‐related genes (IL‐8, IL‐10 and TGF‐β) analysed on head kidney of common carp fingerlings compared to the control group (P < 0.05). In conclusion, it can be suggested that administration of DPE in early stages of common carp culture can promote immune efficacy and increase the antioxidant activity.     

The use of clove oil, metomidate, tricaine methanesulphonate and 2-phenoxyethanol for inducing anaesthesia and their effect on the cortisol stress response in black sea bass (Centropristis striata L.)

Juvenile and adult black sea bass (Centropristis striata L.) were exposed to various concentrations of four anaesthetics to determine practical dosages for handling as well as for procedures such as bleeding, ovarian biopsy or tag implantation. In experiment 1, juveniles exposed to either 2.0 mg L^?1 metomidate, 15 mg L^?1 clove oil, 70 mg L^?1 tricaine methanesulphonate (TMS) or 200 mg L^?1 2‐phenoxyethanol (2‐PE) reached stage II of anaesthesia in 3–5 min and could be handled for weighing and measuring. All fish had completed recovery to stage III within 6 min. In experiment 2, the established concentrations of each anaesthetic were tested on juveniles to determine their ability to prevent a reflex to a subcutaneous needle puncture. All of the fish exposed to clove oil (20 mg L^?1) and 40% of the TMS‐treated (70 mg L^?1) fish reacted while none of the fish anaesthetized in metomidate (2.0 mg L^?1) or 2‐PE (200 mg L^?1) responded to the needle puncture. In experiment 3, metomidate (5.0 mg L^?1), clove oil (30 mg L^?1) TMS (125 mg L^?1) or 2‐PE (300 mg L^?1) were all effective for performing an ovarian biopsy or tag implantation on adults. In experiment 4, TMS (125 mg L^?1) exacerbated the cortisol response to a short handling stressor during a 30 min exposure. Fish anaesthetized in 2‐PE (300 mg L^?1), metomidate (5.0 mg L^?1) or clove oil (40 mg L^?1) had increased cortisol levels associated with the handling stressor but there were no further increases during the remainder of the experimental period. The results demonstrate that these anaesthetics are effective for sedation and anaesthesia of black sea bass and that the best choice is dependant upon the procedures to be performed.     

Comparison of the effects of six stunning/killing procedures on flesh quality of sea bass (Dicentrarchus labrax,Linnaeus 1758) and evaluation of clove oil anaesthesia followed by chilling on ice/water slurry for potential implementation in aquaculture

The effects of different stunning/killing procedures on flesh quality of European sea bass were investigated: (1) anaesthesia with clove oil, (2) anaesthesia with 2‐phenoxyethanol, (3) percussive stunning, (4) immersion in ice/water slurry, (5) chilling on ice and (6) anaesthesia with clove oil followed by immersion in ice/water slurry. Muscle pH values were significantly lower in sea bass anaesthetized or stunned by a blow to the head compared with fish immersed in ice/water slurry, chilled on ice or immersed in ice/water slurry after clove oil anaesthesia. Lightness was highest in sea bass anaesthetized by 2‐phenoxyethanol or percussively stunned and lowest in ice‐chilled fish. Redness and yellowness were highest in fish chilled on ice and lowest in fish anaesthetized with clove oil. Liquid loss, fat loss and shear values were not significantly different among the procedures. In general, lipid oxidation values during refrigerated or frozen storage did not significantly differ among treatment groups. Combination of clove oil anaesthesia followed by chilling on ice/water slurry appears to improve both flesh quality and welfare of sea bass, although the implementation of further studies is warranted to consolidate this finding.