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1.
This study evaluated the effect of short-term baths with the essential oils (EOs) of Lippia sidoides, Ocimum gratissimum and Zingiber officinale on the survival, haematological, biochemical and histopathological parameters of native fish tambaqui ( Colossoma macropomum), challenged with Aeromonas hydrophila. After challenge, the fish infected with A. hydrophila received therapeutic baths of 60 min, for five consecutive days. Treatments were as follows: challenged and not treated; challenged and treated with 10 mg L ?1 of gentamicin; challenged and treated with EO of L. sidoides (2.5 and 5.0 mg L ?1); challenged and treated with EO of O. gratissimum (5.0 and 10.0 mg L ?1); challenged and treated with Z. officinale EO (5.0 and 10.0 mg L ?1). The highest survival rates were 89.5% (fish treated with 5.0 mg L ?1 of O. gratissimum EO) and 75.0% (fish treated with 5.0 mg L ?1 of L. sidoides EO). Reductions in the haematocrit percentage, haemoglobin and erythrocyte number were observed in fish treated with L. sidoides and Z. officinale EOs compared with control fish. Mild to moderate damage to the liver tissue of fish after challenge and EO treatments were observed. It is suggested that baths containing O. gratissimum and L. sidoides EOs consist in a viable treatment to increase survival rates of C. macropomum infected with A. hydrophila. 相似文献
2.
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 (CL 50?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. CL 50?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
3.
The Catarina scallop Argopecten ventricosus is a highly valued resource. Although its hatchery spat production has already been reported, the effects of initial larval stocking density have never been reported for production purposes. This study evaluates A. ventricosus growth and survival in triplicate using three stocking densities: low (LD; 2 larvae mL?1), medium (MD; 4 larvae mL?1), and high (HD; 6 larvae mL?1). Three-day old larvae were reared in 18-L plastic carboy at 25.6?±?0.5 °C and fed with a microalgal blend of Isochrysis galbana and Chaetoceros calcitrans (1:1 cell number ratio) for 7 days, equivalent to 10 post-fertilization days (PFD). Higher specific growth rate was recorded at LD (15.8?±?0.2%) after 8 PFD of culture compared to MD (1.6?±?0.5%) and HD (4.1?±?1.8%) densities. The least time required for 60% of the larvae to reach the pediveliger stage was recorded at LD condition (10 PFD). Higher survival was recorded at HD (58.8?±?3.1%) at 8 PFD compared to MD (53.5?±?3.1%) and LD (43.9?±?3.0%). After 8 PFD, stocking density was highly related to larval growth and survival. To increase production and growth, and reduce the time required to reach pediveliger stage, stocking density should start with 6 larvae mL?1 and be reduced to 2 larvae mL?1 at 7 PFD.
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4.
Heterobranchus longifilis larvae were reared over a 35 d period to evaluate the effects of stocking densities and feeding regimes on growth and survival. In experiment 1, larvae (12.3?±?2.1 mg) were stocked into glass aquaria at densities of 1, 2, 5, 10, 15, 20, and 25 larvae L ?1. Larvae were fed on Artemia nauplii ad libitum. Significant variations in terms of growth performance and feed utilization occurred at all levels of density treatments. Specific growth rate (SGR), body weight gain (BWG), and feed efficiency (FE) of the larvae decreased significantly as density increased. However, survival rate increased with the increase of stocking density. In experiment 2, larvae (13.4?±?1.1 mg) stocked at a density of 15 larvae L ?1, in the same conditions as experiment 1, were fed on three different regimes: Artemia nauplii; 35%?protein beef brain; and 35%?protein commercial catfish feed (CN +). SGR, BWG, and coefficient of variation (CV) of larvae fed on Artemia nauplii were significantly higher than those fed on beef brain and CN +. The survival rate of larvae fed on beef brain was significantly higher (88.40?±?9.75%) than those of Artemia (69.21?±?6.69%) and CN + (40.40?±?6.22%). The results of this study suggest that the optimum stocking density is 15 larvae L ?1 and the beef brain can be used as alternative feed to Artemia in rearing H. longifilis larvae. 相似文献
5.
A 60-day feeding trial was conducted to estimate the optimum phosphorus requirement of juvenile bighead carp (Aristichthys nobilis). Fish (initial body weight: 2.42?±?0.08 g) were hand-fed with six isoproteic (437 g kg?1) and isolipidic (68 g kg?1) diets containing graded phosphorus levels (0.90, 4.40, 8.30, 11.90, 15.50, and 19.30 g kg?1) thrice daily to apparent satiation. Each diet was randomly assigned to triplicate tanks, and each tank was stocked with 30 fish. The highest weight gain rate (WGR, 288.94%) and specific growth rate (2.28% day?1) and the best feed conversion rate (FCR, 1.91) were recorded in fish fed 8.30 g kg?1 phosphorus. The body composition analysis showed that the phosphorus contents in the whole body, muscle, vertebra, and plasma of fish fed the phosphorus-supplemented diets were higher than those of fish fed the control diet, whereas the phosphorus retention rate and crude lipid contents in the whole body and muscle presented the reverse results. The highest activity of lipase (41.97 U g?1 prot) in the intestine was found in fish fed the diet with 11.90 g kg?1 phosphorus. Further, the contents of total protein, albumin, and globulin in plasma were increased as dietary phosphorus levels ranged from 0.90 to 11.90 g kg?1 and then decreased with further increased phosphorus levels. The highest contents of triglyceride (1.85 mmol L?1) and total cholesterol (2.16 mmol L?1) in plasma occurred at dietary phosphorus level of 0.90 g kg?1. Broken-line model analysis based on WGR, FCR, and the phosphorus contents of the whole body and vertebra indicated that the optimal phosphorus requirements for juvenile bighead carp were 7.16, 9.02, 10.88, and 11.04 g kg?1, respectively. 相似文献
6.
Anaesthetic efficacy of eugenol was investigated on Flowerhorn ( Amphilophus labiatus × Amphilophus trimaculatus). A total of 104 fish with average weights of 12 ± 2.5, 28 ± 5 and 53 ±5.1 g were subjected to 25–200 mg L ?1 eugenol and behavioural responses as well as induction and recovery times were recorded. Induction and recovery times were significantly affected by eugenol concentration as well as fish weight ( P < 0.05). Generally, 49.9–127.3 s after exposure to 50–200 mg L ?1 eugenol, fish reached stage 3 anaesthesia (suitable for general handling). Fish entered stage 4 anaesthesia (suitable for surgery and blood sampling) over 57.3–140.4 s post exposure to such concentrations. Recovery time was 91.7–312 s in all weight classes for all eugenol concentrations. Mortality (23%) was only observed in 12‐g fish when were subjected to 200 mg L ?1 eugenol. This study showed the behavioural response of Flowerhorn to anaesthesia and eugenol efficacy as an anaesthetic in this important ornamental species. The general quadratic equation revealed that concentrations of eugenol and fish size along with their interactive effects have significantly contributed to the model, with concentration recording the highest beta value in all models (β = ?0.809, ?0.818 and ?0.909, P = 0.000). According to the results, minimum eugenol concentration to induce anaesthesia in less than 3 min was 50 mg L ?1. 相似文献
7.
This study aimed to evaluate the tolerance of common snook Centropomus undecimalis larvae and juveniles exposed to acute concentrations of un-ionized ammonia for 96 h at 35g L ?1 salinity, after 24 h starvation. For that, 10 larvae (20.85 ± 1.46 mm) of 47 days post hatch (DPH) per experimental unit (1.5 L) were exposed to 0.00 ± 0.00, 0.65 ± 0.04, 1.29 ± 0.09, 2.59 ± 0.18, 3.88 ± 0.27, 5.17 ± 0.34, and 6.47 ± 0.43 mg L ?1 NH 3, in triplicates, at 26.72 ± 0.08°C, dissolved oxygen at 5.72 ± 0.10 mg L ?1 and pH 8.45 ± 0.06. During this period, no mortalities were observed. Another trial was performed with five juveniles (20.35 ± 6.10 g, 13.90 ± 1.75 cm) per experimental unit (60 L) exposed to 0.00 ± 0.00, 2.26 ± 0.07, 2.68 ± 0.11, 3.20 ± 0.13, 3.68 ± 0.17, and 4.27 ± 0.16 mg L ?1 NH 3, in triplicates, at 21.90 ± 0.76°C, dissolved oxygen at 6.27 ± 0.21 mg L ?1 and pH at 8.38 ± 0.04. Fish mortality increased as ammonia concentrations increased at each day, and LC 50 96 h was 3.52 mg L ?1 NH 3. Larvae were less sensitive than juveniles, demonstrating that the environmental toxicity of ammonia to common snook is influenced by age. Sublethal exposition to ammonia caused histological damages in gills of common snook juveniles and variation on glucose levels, hematocrit, and red blood cells number, showing negative effects on fish homeostasis. Moreover, compared to other species, the common snook has great resistance to ammonia. 相似文献
8.
This study was carried out to assess the effects of Pediococcus acidilactici on zebrafish ( Danio rerio). Different levels of P. acidilactici including 0, 1 × 10 6, 2 × 10 6, 4 × 10 6 and 8 × 10 6 colony‐forming unit per g of the diet (cfug ?1) were examined in fish with 120 ± 10 mg weight for 60 days in a completely randomized design. The results showed that the best growth indices were recorded in group 4 × 10 6 cfug ?1 ( p < 0.05). The highest number of total viable count and lactic acid bacteria of intestine were found in group 4 × 10 6 cfug ?1 ( p < 0.05). The maximum activity of digestive enzymes including amylase, lipase, protease and alkaline phosphatase was observed in group 4 × 10 6 cfug ?1. The highest activity for superoxide dismutase was recorded in group 4 × 10 6 cfug ?1 while catalase, glutathione peroxidase and glutathione reductase showed the highest activity in group 8 × 10 6 cfug ?1. The most growth inhibition zone of Aeromonas hydrophylla, Flavobacterium columnare, Vibrio anguillarum and Edwardsiella tarda was found in group 4 × 10 6 cfug ‐1 ( p < 0.05). Therefore, P. acidilactici as a probiotic improved growth and immunity of the zebrafish and could be used by zebrafish farmers. 相似文献
9.
In this study, total phenolic and flavonoid contents of grapefruit peel extract (GPE) were equal to 117.3 ± 0.3 µg of gallic acid/mg and 39.30 ± 0.1 µg of quercetin/mg respectively. Caspian white fish ( n = 180, 4 ± 0.9 g body weight) was fed with supplemented diets, including 0, 6.25, 12.5 and 25 mg of GPE/kg for 60 days at 25 ± 1°C. The growth performance was markedly improved in fish fed with 25 mg/kg of GPE compared to others ( p < 0.05). Moreover, fish fed with 25 mg/kg of GPE showed a significant increase in red blood cell (2.65·10 6 cell/mm 3), white blood cell (17.75·10 3 cell/mm 3), packed cell volume (48%) and haemoglobin concentrations (8.75 g/dl) compared to the control ( p < 0.05). However, the highest alanine aminotransferase (140 U/L), alanine transaminase (14.5 U/L), and alkaline phosphatase (18.5 U/L) were observed in control group. Morphological analysis of intestine revealed the highest amount of villus width (8.4 µM), height (32.86 µM) and surface area (342.7 µM 2) in fish fed with 25 mg/kg of GPE ( p < 0.05). In conclusion, supplementing feed with GPE at 25 g/kg can improve growth performance and haemato‐biochemical parameters of Caspian white fish fry. 相似文献
10.
Juvenile rainbow trout Oncorhynchus mykiss (Walbaum) were exposed to therapeutic, and higher concentrations of chloramine‐T (Cl‐T) to assess the effects of this chemical on the antioxidant enzyme system and genetic structure. Red blood cells acetylcholinesterase, ?‐aminolevulinic acid dehydratase, paraoxonase and liver glutathione S‐transferase activity were increased at 10 and 20 mg L ?1 Cl‐T‐exposed fish, while they were decreased at 30 mg L ?1 Cl‐T‐exposed fish. On the other hand, liver catalase activity and liver protein levels increased at 10 mg L ?1 and decreased at 20 and 30 mg L ?1 concentrations of Cl‐T. Liver super‐oxide dismutase activity decreased at 10 mg L ?1 and 20 mg L ?1 Cl‐T and increased at 30 mg L ?1 of Cl‐T. Compared to control, comet assay indicated that Cl‐T did not cause significant DNA damage to red blood cells of the fish. Results indicate that 10 or 20 mg L ?1 Cl‐T can be safely used to prevent or treat external parasitic and bacterial infection of rainbow trout. 相似文献
11.
Few marine rotifer species (e.g. Encentrum linheii and Synchaeta cecilia) have been cultured successfully besides Brachionus plicatilis and B. rotundiformis, commonly used to rear larvae of many marine fish species. The development of culture techniques for marine rotifers smaller in size than the Brachionus species may be useful for rearing fish species for which the currently used prey are too large. We evaluated the possibility of culturing Colurella dicentra isolated from a Mississippi Gulf Coast estuary. An experiment was conducted to determine the effects of salinity (10–35 g L ?1) on its population growth rate. Rotifers were fed Nannochloropsis oculata at a density of 100 000 cells mL ?1 for 15 days. Colurella dicentra survived in water with a salinity of 10–47 g L ?1. Densities of up to 300 rotifers mL ?1 were sometimes attained in cultures. Salinity influenced C. dicentra production ( P<0.001). The mean rotifer numbers at 10 g L ?1 (22 840±2604 SD), 15 g L ?1 (25 980±7071 SD) and 20 g L ?1 (19 780±1029 SD) at the end of the experiment were similar ( P>0.05), but were higher ( P=0.05) than numbers at 25 g L ?1 (4240±1783), 30 g L ?1 (1300±264 SD) and 35 g L ?1 (100±101 SD). The population growth rate ( r) of the rotifers was the highest at 15 g L ?1 (0.37–0.42 day ?1), and the lowest at 35 g L ?1 (?0.33–0.06 day ?1). This is the first report of C. dicentra in the estuarine waters of the Gulf of Mexico, and also the first time it has been cultured successfully. 相似文献
12.
Ammonia is the most common contaminants found in aquaculture water that seriously endangers fish health. However, there are few studies on the strategy and mechanism on alleviating ammonia toxicity in fish. The current study aimed to observe the cytotoxic effects of ammonia and the protective effects of chlorogenic acid (CGA) on head kidney macrophage of yellow catfish from the perspective of inflammation, oxidative stress and apoptosis. The cells were randomized into normal control, ammonia group (0.23 mg L ?1), CGA group (125 µmol L ?1), CGA (5, 25, 125 µmol L ?1) + ammonia (0.23 mg L ?1) groups. Cells were pretreated with CGA for 1 h followed by ammonia for 24 h. Findings suggested that ammonia treatment reduced cell viability, increased ROS production, up-regulated antioxidant ( SOD, GPx) and pro-inflammatory ( TNF-α, IL-1, IL-6, COX-2, NF-κB p65) genes expression, down-regulated the mRNA levels of M2-type macrophage marker ( Arg-1) and anti-apoptosis ( Bcl-2), and CGA attenuated the toxic effects of ammonia. The findings may provide insight into the underlying mechanisms of ammonia toxicity and suggest that CGA can be used as a potential natural supplement to alleviate ammonia toxicity in fish. 相似文献
13.
This work evaluated the effects of food frequencies and self-feeding on the behavior, performance, and blood biochemistry of Colossoma macropomum. Juveniles weighing 3.63?±?0.05 g were distributed in 27 aquariums (40 L), with six fish per aquarium, to evaluate nine treatments in three replications in a 12L:12D photoperiod. The treatments were 24-h self-feeding (SF); daytime self-feeding at will (SFD); nighttime self-feeding at will (SFN); and feeding at fixed frequencies of two (2D), four (4D), and six times (6D) daytime and twice (2 N), four (4 N), and six times (6 N) nightly. The treatments were offered in automatic feeders, with fixed frequencies programmed. Extruded commercial feed, with 46% protein, was used. The experimental period was 40 days. In the SF treatment, the animals exhibited 95.7% nocturnal and 4.3% diurnal feeding activity (p?<?0.05). In the treatment SFD and SFN, the animals showed feeding activity throughout the day and night. Final weight, weight gain, and total feed intake were higher for animals at fixed daytime and nighttime frequencies (p?<?0.05). Feed conversion was better for animals in SF, SFD, 4D, SFN, and 4 N (0.89, 0.76, 0.91, 0.85, and 0.88, respectively) (p?<?0.05). Cholesterol and high-density lipoproteins were lower for fish in SF, SFN, 2 N, 4 N, and 6 N (p?<?0.05). SF treatment animals had lower triglyceride content, 154.20 mg dL?1 (p?<?0.05). Colossoma macropomum has nocturnal food preferences, however, with remarkable plasticity. Juveniles of this species fed four times during the day or night show good performance. Dietary patterns influenced the blood metabolic indicators of this species and the periods studied. 相似文献
14.
The present study was carried out to investigate the effect of sublethal zinc (Zn) concentrations on growth performance, biochemical variables, and Zn residues in various organs of Nile tilapia, Oreochromis niloticus (L.). Fish (25 ± 0.5 g) were exposed to 0.0, 3.5, or 7.0 mg Zn L ?1 for 1 or 6 weeks. Fish growth was significantly reduced with increasing Zn concentrations. However, fish exposed to 7.0 mg Zn L ?1 grew less quickly than those of the control group. Likewise, best feed intake and feed conversion ratio were obtained at the control group. Furthermore, glucose, aspartate aminotransferase (AST), alanine aminotransferase (ALT), creatinine, and cortisol increased significantly with increasing Zn concentrations and exposure time, with maximal values in the 7.0 mg Zn L ?1 treatment after 6 weeks. Meanwhile, highest values of serum protein and lipids were obtained in the control fish reared for 6 week, whereas their lowest values were observed in fish exposed to 7.0 mg Zn L ?1 for 1 week. There was no significant change in whole-body moisture content of fish due to Zn exposure, although crude protein and total lipid contents decreased significantly with increasing Zn concentrations. In addition, Zn exposure increased total ash contents and Zn residues in different investigated fish organs. The Zn concentrations in all fish organs were time-dependant and the Zn residues after 1 week were found to follow the order of gills > liver > kidney > muscle, meanwhile after 6 weeks it followed the order of liver > kidney > gill > muscle. The present findings revealed that liver and kidney tissues are the prime sites of Zn bioaccumulation, while Zn load in the muscle was for low as compared to other organs. 相似文献
15.
ABSTRACTThe effect of photoperiod (24L:00D, 12L:12D, and 00L:24D) and temperature (22 ± 1°C and 28 ± 1°C) on performance of Clarias gariepinus larvae was tested. Larvae weighing 3.2 ± 0.24 mg were cultured in aquaria at a stocking density of 20 fish L ?1 and fed twice a day on catfish starter diet (40% CP) at 10 % BW day ?1. Highest mean weight gain (31.00 mg), SGR (7.56% day ?1), and survival (83%) were achieved at photoperiod and temperature combination of 00L:24D and 28 ± 1°C. Percent survival of larvae differed significantly (p < .05) among treatments with optimal survival of (83%) in treatment combination of 28 ± 1°C and 00L:24D, while lowest survival (40%) in treatment combination of 22 ± 1°C and 24L:00D. 相似文献
16.
In this study, the effect of dietary Spirulina (Arthrospira platensis) on color intensity, growth performance, total ammonia–nitrogen excretion (TAN), and profitability of common clownfish (Amphiprion ocellaris) was investigated. Three isoproteic (46%) and isolipidic (13%) diets were formulated as one control (C) and two different levels (15 and 30%) of Spirulina (SP15 and SP30) substituted for fish meal and cornmeal. Ten clownfish (initial body weight of 0.55?±?0.04 g) per aquarium were distributed to nine glass aquariums (60 L) with three replicates. Fish were hand-fed a day to the satiation thrice. Clownfish were weighed in bulk, and the photographs were taken biweekly during the 12-week experiment. The determined regions of the images were standardized with a raster graphics editor and recorded the color parameters by considering both CMYK (cyan magenta yellow key) and RGB (red green blue) models. After the feeding trial, fish were starved for 3 days, and the total ammonia–nitrogen (TAN) was analyzed with the ammonia salicylate method on the next day for 12 h. At the end of the trial, the final mean weights (FMW) and specific growth rates (SGR) of SP15 (FMW: 1.95?±?0.18 g, SGR: 1.75?±?0.04%/day) and SP30 (FMW: 2.05?±?0.14 g, SGR: 1.81?±?0.05%/day) were significantly higher than the C (FMW: 1.68?±?0.12 g, SGR: 1.58?±?0.06%/day) group (P?<?0.05). Both color models have proved the enhancement of the skin coloration (significant improvements were recorded in the colors, including red, green, magenta, and key, P?<?0.05). Also, it was determined that the TAN was decreased with the increase of the Spirulina level (29.8, 22.9, and 17.6 mg-N/100 g fish/12 h for C, SP15, and SP30, respectively) in the diet (P?<?0.05). However, a high level of Spirulina in the diet negatively affected profitability. Consequently, common clownfish’s growth, color, and TAN improved with the dietary Spirulina. Considering that Spirulina is an expensive raw material, adding it into the diet at medium levels (15%) is recommended. 相似文献
17.
A feeding experiment was conducted to investigate the effects of high dietary intake of vitamin E (supplied as dl ‐α‐tocopheryl acetate) and n‐3 highly unsaturated fatty acid (n‐3 HUFA) on the non‐specific immune response and disease resistance in Japanese flounder Paralichthys olivaceus. Nine practical diets were formulated to contain one of three levels of vitamin E namely, 0, 80 or 200 mg kg ?1 (the total α‐tocopherol contents in the diets were 21, 97 and 213 mg kg ?1 based on analysis), and at each vitamin E level with one of three n‐3 HUFA levels i.e. 0.5%, 1.5% or 2.0%. Each diet was randomly assigned to triplicate groups of Japanese flounder (initial body weight: 40.5±1.0 g, mean±SD) in a re‐circulation rearing system. Fish were fed twice daily to apparent satiation at 07:00 and 18:00 hours for 12 weeks. During the experimental period, water temperature was maintained at 18±1°C, salinity 31–35 g L ?1, and pH 7.8–8.2. Dissolved oxygen was not less than 6 mg L ?1, and there were negligible levels of free ammonia and nitrite. The results showed that the increase in dietary n‐3 HUFA from 0.5% to 1.0% significantly decreased muscle α‐tocopherol contents in fish‐fed diets with 21 and 97 mg α‐tocopherol kg ?1 diet ( P<0.05). In 1.0% HUFA groups, alternative complement pathway activity (ACH 50) of fish fed the diet containing the 213 mg α‐tocopherol kg ?1 diet was significantly higher than noted for fish fed the diet containing 97 mg α‐tocopherol kg ?1 diet ( P<0.05). Fish fed the diet with 213 mg α‐tocopherol kg ?1 and 2.0% n‐3 HUFA had the highest lysozyme activity (131.7 U mL ?1) among all the dietary treatments. Fish fed the diets containing 97 and 213 mg α‐tocopherol kg ?1 with 1.0% n‐3 HUFA had significantly higher respiratory burst activity than those fed the diets containing 21 mg α‐tocopherol kg ?1 with 0.5 and 1.0% n‐3 HUFA ( P<0.05). In the disease resistance experiment, high intake of dietary vitamin E with 213 mg α‐tocopherol kg ?1 significantly decreased cumulative mortality and delayed the days to first mortality after a 7‐day Edwardsiella tarda challenge ( P<0.05). In addition, under the experimental conditions, dietary vitamin E and n‐3 HUFA had a synergistic effect on the non‐specific immune responses and disease resistance in Japanese flounder ( P<0.05). 相似文献
18.
The tongue sole Cynoglossus semilaevis, an inshore fish in China, has showed great potential in aquaculture recently. However, poor survival was recorded during the period of weaning from live Artemia to artificial diets. In this paper, the influence of co‐feeding larvae with live and inert diet on weaning performance was described. The C. semilaevis larvae were reared at 21 ± 1 °C and fed four different feeding regimes from 6 days post‐hatching (dph): A, Artemia (10 individuals mL ?1); B, Artemia (5 individuals mL ?1); C, mixed diet (10 Artemia individuals mL ?1 and 12 mg L ?1 inert diet); and D, mixed diet (5 Artemia individuals mL ?1 and 12 mg L ?1 inert diet). Rotifers were also supplied in all cases during the first days of feeding. Mixed diets of commercial formulated feed and live prey (rotifers and Artemia) allowed larvae to complete metamorphosis, achieving similar specific growth rate (SGR) (18.5 ± 1.4% and 18.7 ± 1.6%) and survival (40 ± 7.6% and 48.5 ± 6.8%) compared with larvae fed on live feed alone (SGR of 18.3 ± 1.2%, 19.3 ± 1.9% and survival of 41.2 ± 11.3%, 38 ± 4.9%). However, in metamorphosed fish, when live feed was withdrawn on 31 dph, there was significant difference ( P < 0.05) in survival and growth among treatments. Metamorphosed fish, previously fed mixture diets during larval stages, had similar survival (62.1 ± 7.6% and 62.8 ± 3.9% for regimes C and D, respectively) but higher than that obtained for fish that previously fed on live feed (49.3 ± 2% and 42.1 ± 3.9% for regimes A and B, respectively) after weaning (day 60). The SGR of weaned fish previously fed live feed was similar (3.1 ± 0.6% and 2.92 ± 0.6% for regimes A and B, respectively) but lower than that recorded for fish that was fed from day 6 to day 30 on the mixed diet (4.5 ± 1.1% and 4.9 ± 0.3% for regimes C and D, respectively). It is suggested that weaning of C. semilaevis from early development would appear to be feasible and larval co‐feeding improves growth and survival. 相似文献
19.
Experiments were designed to determine the effects of temperature and salinity on the virulence of Edwardsiella tarda to Japanese flounder, Paralichthys olivaceus. In the temperature experiment, a two‐factor design was conducted to evaluate the effects of both pathogen incubation temperature and fish cultivation temperature on pathogen virulence. E. tarda was incubated at 15, 20, 25 and 30±1°C, and the fish (mean weight: 10 g) were reared at 15, 20 and 25±1°C respectively. The fish reared at different temperatures were infected with the E. tarda incubated at different temperatures. The results of a 4‐day LD 50 test showed that temperature significantly affected the virulence of E. tarda ( P<0.01) and the interaction between the two factors was also significant ( P<0.01). For fish reared at 15°C the virulence of E. tarda was the highest at 25°C of pathogen incubation, followed by 20, 15 and 30°C. When the fish rearing temperature was raised to 20 and 25°C, the virulence of E. tarda incubated at all temperatures increased. Isolation testing demonstrated results similar to those of LD 50. The higher rearing temperature increased the proliferation rate of the pathogen in fish. In the salinity experiment, the incubation salinity of E. tarda was at 0, 10, 20 and 30 g L ?1, respectively, and the fish with mean weight of 50 g were cultured in natural seawater of 30 g L ?1. The results of one‐way anova in 4‐day LD 50 test showed that incubation salinity significantly affected virulence. Virulence was lower when the salinity of the incubation medium was at 0 and 30 g L ?1, higher at 10 and 20 g L ?1. The results of isolation test were in accordance with those of LD 50. At 20 g L ?1E. tarda had a faster proliferation rate than that at 10 g L ?1. 相似文献
20.
The optimal concentration of a panel of individual and combined carotenoid sources on skin pigmentation in fancy carp was investigated by nine experimental diets that were formulated and supplemented with astaxanthin at 25 mg kg ?1, lutein at 25 and 50 mg kg ?1, β‐carotene at 25, 50 and 75 mg kg ?1, and lutein combined with β‐carotene at 25 : 25 and 50 : 50 mg kg ?1, while a diet without supplemented carotenoid served as a control. The results showed that serum TC of fish fed diets containing supplemented with lutein plus β‐carotene at 25 : 25; 50 : 50 mg kg ?1 and lutein 50 mg kg ?1 diet were higher than the other treatments ( P ≤ 0.05). Serum TC of the respective treatments was 6.2 ± 2.0, 7.8 ± 3.3 and 7.3 ± 1.9 μg mL ?1 serum, respectively. Fish fed diets combined with lutein and β‐carotene at 25 : 25, 50 : 50 mg kg ?1 and lutein 50 mg kg ?1 diet had serum astaxanthin concentrations similar to fish fed the diet with astaxanthin alone at 25 mg kg ?1. Serum astaxanthin concentrations was 0.7 ± 0.01, 0.9 ± 0.01, 0.4 ± 0.02 and 1.7 ± 0.18 μg mL ?1 serum, respectively. The chromaticity of fish body skin of red and white position was assessed by colourimetry using the CIE L*a*b (CIELAB) system. Pigmentation response of skin redness of fancy carp fed with diets combined with lutein and β‐carotene at 25 : 25, 50 : 50 mg kg ?1 and lutein 50 mg kg ?1 were higher than other treatments ( P ≤ 0.05) but they were similar to fish fed with 25 mg kg ?1 astaxanthin diet. The redness (a* values) of fish fed diets with diets combined with lutein and β‐carotene at 25 : 25, 50 : 50 mg kg ?1 and lutein 50 mg kg ?1 were 28.3 ± 0.53, 29.9 ± 1.38, 28.8 ± 3.95 and 28.5 ± 2.49, respectively. After 3 weeks of feeding the experimental diets, the fish fed on a diet without carotenoid supplement for one week demonstrated that the same three groups still retained their redness and had an overall tendency to improve skin colouring. Finally, concentrations 50 mg kg ?1 of lutein, or the combination of lutein and β‐carotene at 25 : 25 mg kg ?1 showed the highest efficiency for improving skin pigmentation and redness of skin. 相似文献
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