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1.
Thermal denaturation profiles of catfish myosin when heated as myofibrils (Mf) were compared with those of tilapia. The Ca2+-ATPase inactivation rate of catfish myofibrils was the same as that of tilapia myofibrils. The conclusion was the same with isolated myosin. Catfish Mf was clearly distinguished from tilapia Mf in terms of subfragment-1 (S-1) and rod denaturation. Quick denaturation of rod relative to S-1 was characteristic of catfish Mf, while slower denaturation of rod relative to S-1 was the pattern for tilapia Mf. These patterns were greatly affected by the pH for heating. Rod denaturation was accelerated with increasing pH for heating and oppositely suppressed by lowering the pH, for both Mf. Tilapia Mf showed a S-1 and rod denaturation pattern similar to that for catfish Mf, but at 1 pH unit higher; for example, the pattern of catfish Mf at pH 7.5 was similar to that for tilapia Mf at pH 8.5. Less rigid filament structure of catfish Mf than tilapia Mf was demonstrated by studying chymotryptic digestion at various pH values. Accordingly, the difference in the S-1/rod denaturation patterns between the two fish species can be explained by the different rigidity of their myosin filaments.  相似文献   

2.
A comparison was made of some productive traits of Stirling Nile tilapia (wild type) (Oreochromis niloticus, Linnaeus) and red hybrid tilapia (Florida red tilapia× Stirling red O. niloticus) males during a 98‐day grow‐out period. Twenty‐two males from each genetic group with initial weights of 139.0 g for O. niloticus and 207.3 g for the red hybrid were placed in triplicate tanks. The fish were fed with a feed containing 36.8% crude protein. Survival was 97.0% for the red hybrid and 83.3% for O. niloticus. Daily individual weight gains were 2.95 and 2.50 g and final body weights were 473.0 and 348.8 g for the red hybrid and O. niloticus respectively. Fillet yield was similar for both the species, with 33.4% for the red hybrid and 32.0% for O. niloticus. Fresh fillet lipid content was perceptibly less in the red hybrid (0.33%) than in O. niloticus (2.07%). Some benefits of a red low‐fat tilapia genotype are discussed.  相似文献   

3.
Channel catfish (Ictalurus punctatus) (x? = 0.8 g) and all-male hybrid tilapia fingerlings (Sarotherodon mossambica ♂ × S. hornorum ♀) (x? = 35.0 g) were stocked in 0.04 ha replicated ponds in Baton Rouge, Louisiana, in March and July 1981, respectively. The ponds were stocked at densities of 11,110 catfish per ha, 11,110 catfish with 5,550 tilapia per ha, 7,400 catfish per ha, and 7,400 catfish with 3,700 tilapia per ha. The fish were fed daily at 4% of estimated catfish biomass and were harvested in November 1981. There were no differences in dissolved oxygen or water temperature among the four culture systems (P > 0.05). The presence of tilapia, however, significantly increased water turbidity, pH and chlorophyll a concentrations (P < 0.05). Tilapia did not improve water quality and may have deteriorated it. Tilapia did not affect channel catfish growth or production (P > 0.05), but the presence of tilapia did significantly increase total fish yield (P < 0.05) by 13.5 and 32.2% at low and high catfish densities, respectively. Channel catfish and tilapia averaged 390 and 245 g at harvest, respectively. Overall catfish survival averaged 61%. Tilapia survival was 72% and 61% at low and high densities, respectively.  相似文献   

4.
Catfish (mean W0 189 g) were added to ponds (525 mJ each) stocked with 230 hand-sexed, male tilapia (Wu163 g), at 0.04, 0.10 and 0.15 catfish m?2. In each pond, two female tilapias were introduced, thereby creating a sexing error of less than 1%. Feeding was fixed throughout the experiment at 2.5 kg of cottonseed cake per day per pond 6 days per week (mean feeding rate R = 41 kg ha?1 day-1). Rearing time was 125 days. Average net pond production per treatment (ranging between 7.5 and 7.9 t ha?1 year?1) and marketable production were not different between treatments but net tilapia production was significantly lower at the highest catfish density. Both catfish and tilapia growth were negatively correlated with catfish density due to feed competition near the end of the experiment. It was concluded that catfish efficiency in controlling tilapia recruitment was strongly reduced by the availability of supplementary high-protein feed. Large catfish competed with the parent tilapia for the cottonseed cake but apparently did not exploit the tilapia recruits. Yield of tilapia recruits was lowest at the highest catfish fingerling density, although this was not significant. The number of catfish fingerlings was significantly higher at the lowest catfish density, which indicated that large catfish preyed on catfish fingerlings.  相似文献   

5.
五种鱼的鳞被复盖过程及其同生长的关系   总被引：1，自引：0，他引：1  
李思发 《水产学报》1983,7(4):343-351
用茜素红染色法观察研究了904尾鲤鱼、429尾草鱼、637尾鲢鱼、70尾鳙鱼及243尾尼罗罗非鱼的仔幼鱼。五种鱼鳞片出现时全长分别为：16—19，17—19，27—32，26—31，10-14mm。完成鳞被复盖时的全长分别为24—30，24—28，47—55，48—58，19—22mm。五种鱼鳞片出现均始于侧线，但出现部位和复盖过程可分为两类：鲤、草鱼、鲢及鳙的鳞片首先出现于躯干前部，为由前向后发展型，至于具体扩展过程，鲤与草鱼相似，鲢与鳙相同；罗非鱼的鳞片首先出现于尾柄，为由后向前发展型。鳞片出现、复盖过程同全长及年龄的关系的比较观察和回归分析表明，这一过程的始末及速度主要同体长增长有关，同年龄关系不大。鳞被发育过程不仅反映了不同鱼类的不同生长规律，亦可能有助于认识鱼类间的亲缘关系。  相似文献   

6.
One of the challenges that Recirculating Aquaculture Systems (RAS) are still facing is the risk that in RAS fish grow less than in flow-through systems due to the accumulation of substances originating from feed, fish or bacteria associated with the water re-use. The present study investigated whether RAS with high and low accumulation levels of these substances affect feed intake and growth of Nile tilapia Oreochromis niloticus, African catfish Clarias gariepinus, and European eel Anguilla Anguilla. One-hundred and twenty individuals of each species were used (start body weights: Nile tilapia 264.8 ± 8.3 g; African catfish 253.2 ± 2.1 g and European eel 66.6 ± 1.3 g). For a period of 39 days, growth and feed intake were compared between high and low accumulation RAS. HIGH accumulation RAS was designed for maximal accumulation of substances in the water by operating the system at nearly-closed conditions (30 L/kg feed/d), using mature biofilters and high feed loads; and (2) LOW accumulation RAS was designed to be a proxy for flow-through systems by operating at high water exchange rates (1500 L/kg feed/d), new biofilters and low feed load. HIGH accumulation RAS induced a reduction in feed intake (42%) and growth (83%) of Nile tilapia, as compared to systems that are a proxy for flow-through conditions. This effect was not observed in European eel and African catfish. The cause of this reduced feed intake and growth rate of Nile tilapia is still unclear and should be addressed in further studies.  相似文献   

7.
Mixed-sex blue tilapia Oreochromis aureus fry were produced from indoor spawns in March and April. Fry were stocked in May at an average weight of 0.5 g at 0, 250, 750, or 2,500/ha into ponds which had been stocked previously with three catfish strains at a combined density of 10,000 fingerlings/ha. After a 167-d culture period, from 15 May until 4 November, tilapia stocked at 250 or 750/ha grew to average harvest size approaching 0.45 kg. No significant difference in average size was observed between males and females except at the 2,500 tilapia/ha stocking density. Sixty percent of the tilapia polyculture ponds yielded no reproduction at harvest and maximum reproduction observed was 13.5 kg/ha. Lack of reproduction and the undeveloped state of sampled female ovaries indicated that most females had yet to attain sexual maturity. Catfish production and catfish feed conversion was not significantly different between tilapia polyculture and catfish monoculture ponds ( P > 0.05). First seine hauls yielded over 88% of the total catfish harvest, but only an average of 3.9% of the marketable tilapia. Tilapia had no measurable impact on the incidence of catfish off-flavor at any of three sample intervals. Overall average levels of TAN and nitrites did not differ significantly between treatments; however, mean chlorophyll a concentration was significantly higher ( P > 0.05) in the 2,500 tilapia/ha treatment than at lower tilapia densities.  相似文献   

8.
Cage‐pond integration system is a new model for enhancing productivity of pond aquaculture system. A field trial was conducted using African catfish (Clarias gariepinus) and Nile tilapia (Oreochromis niloticus) in cages and carps in earthen ponds. There were four treatments replicated five times: (1) carps in ponds without cage, (2) tilapia at 30 fish m?3 in cage and carps in open pond, (3) catfish at 100 fish m?3 in cage and carps in open pond, (4) tilapia and catfish at 30 and 100 fish m?3, respectively, in separate cages and carps in open pond. The carps were stocked at 1 fish m?2. The cage occupied about 3% of the pond area. The caged tilapia and catfish were fed and the control ponds were fertilized. Results showed that the combined extrapolated net yield was significantly higher (P < 0.05) in the catfish, tilapia and carps integration system (9.4 ± 1.6 t ha?1 year?1) than in the carp polyculture (3.3 ± 0.7 t ha?1 year?1). The net return from the tilapia and carps (6860 US$ ha?1 year?1) and catfish, tilapia and carps integration systems (6668 US$ ha?1 year?1) was significantly higher than in the carp polyculture (1709 US$ ha?1 year?1) (P < 0.05). This experiment demonstrated that the cage‐pond integration of African catfish and Nile tilapia with carps is the best technology to increase production; whereas integration of tilapia and carp for profitability.  相似文献   

9.
A comparison of composition and sensory evaluation were performed on fillets of Oreochromis niloticus (wild type) and red hybrid tilapia (RHT) (Florida red tilapia ♂× red O. niloticus♀). Fifty male tilapia, 25 O. niloticus (initial weight 159.3 g) and 25 red hybrid (initial weight 132.4 g), were placed in each of three 2.0 m3 volume tanks. The fish were fed a commercial feed containing 35.9% crude protein during the 120‐day experimental period and then killed in cold water (3°C). All the fish were filleted. Twelve fillets from each treatment were used for proximate analyses, five fillets from each treatment were used for fatty acids analyses and the remaining fillets were used for sensory evaluation. The compositional analyses showed similar moisture, true protein and ash content in both genetic groups, but a lower crude fat content was measured in the red hybrid fillets (0.70%) compared with that of O. niloticus fillets (0.97%). No differences between O. niloticus and the red hybrid were observed in their fillet profile of fatty acids. In the sensory evaluation test, a difference in fillet flavour between both genetic groups was perceived. Of the 112 consumers in the preference test, 81.2% perceived a difference in fillet flavour between the two tilapias, with a general preference for the red hybrid over the wild‐type O. niloticus. The benefits of cultivating a RHT with a low lipid content are discussed.  相似文献   

10.
Four earthen ponds (250 m2 each) were stocked each with 250 small catfish (W0=39g). In treatment A, African catfish. Clarias gariepinus (Burchell), were raised in monoculture, while in treatment B catfish were raised in polyculture with an additional 125 male Nile tilapia, Oreochromis niloticus (L.) (W0=44g). Feeding of cottonseed cake was at about 4% of catfish body weight day?1. Daily feed quantities, however, were averaged over all four ponds so that each pond received the same amount of cottonseed cake. Rearing time was 118 days. In treatment A, catfish grew to an average weight of 200g. In treatment B, catfish reached 158g and tilapia 185g, Extrapolated marketable fish production was strikingly similar in all four ponds (around 4.8 t ha?1 year?1). No synergistic effect was obtained by stocking microphagous tilapia, although the feeding of cottonseed cake enhanced dense algal blooms in all ponds. Catfish did not appear to exploit the tilapia recruits, as an indirect pathway of algae cropping.  相似文献   

11.
Economic profitability of Nile tilapia production in Kenya was analysed using a model that simulated individual fish growth and took fish population dynamics in the pond into account. The results suggest that the currently practiced mixed‐sex tilapia culture is economically unsustainable. It is suggested that research and extension efforts be geared towards developing monosex Nile tilapia production systems. Nile tilapia culture with African catfish predation should be viewed as an intermediate step towards all‐male Nile tilapia culture. This will allow accumulation of both physical and human capital to support all‐male tilapia culture. Under all‐male culture, economic returns are high enough to justify investment in Nile tilapia culture using borrowed capital. However, the success of monosex culture will depend on the availability and affordability of quality fingerlings and low‐cost fish feeds. The results have a wide application in Sub‐Saharan Africa where mixed‐sex Nile tilapia culture is common.  相似文献   

12.
A 10‐week feeding trial was conducted to investigate the interaction between tilapia genotype and dietary protein level on the growth, feed utilization efficiency and body composition of Nile tilapia [Oreochromis niloticus L., F9 generation of genetically improved farmed tilapia (GIFT) strain] and red hybrid tilapia (Oreochromis sp.). Two isoenergetic diets (15.5 kJ g−1 diet) containing 25% or 35% crude protein were formulated and fed to triplicate groups of tilapia (12.8±0.2 g) at a fixed daily ration of 4% of their body weight. The growth performance of the GIFT tilapia fed 25% or 35% dietary protein was significantly higher (P<0.05) compared with red tilapia at either protein level. Increasing the dietary protein level by 10% led to a further 10% increase in the final weight of GIFT tilapia but no further increase was observed in the weight gain of red tilapia. Growth was influenced by the interaction between diet and tilapia genotype. Feed conversion ratios were 14% and 33% better in GIFT tilapia compared with red tilapia fed the 25% or 35% protein diet respectively. Protein efficiency ratio and net protein utilization were influenced by both diet and tilapia genotype, but not the interaction between the two. The apparent digestibility coefficients of dry matter and protein did not differ significantly between the two diets and tilapia genotypes but lipid digestibility was 1.2–4.7% higher for the GIFT tilapia. Tilapia whole‐body protein content was significantly influenced by both diet and tilapia genotype. The higher growth potential, better feed utilization efficiency and higher body protein content of GIFT tilapia compared with red tilapia should have a positive impact on tilapia farming in terms of production costs.  相似文献   

13.
In the eggs of the brown trout, Salmo trutta fario, lipid droplets are clearly visible beneath the oolemma on the surface of the protein yolk. When examining the distribution of lipid vesicles in egg batches of different quality, four categories of lipid vesicle distribution could be distinguished: In the first category, the lipid droplets were evenly distributed throughout the egg. These egg batches had a high quality (percentage of eggs developing to eyed stage embryos: 96.2 ± 5.2). Some lipid droplets had the tendency to coalesce in one pole of the egg in the second category. This coalescing of lipid droplets was accompanied with a reduction in egg quality to about 50% of the first category (% of eyed stage embryos: 40.6 ± 15.2). In the last two categories, the lipid droplets were mostly coalesced in one or two poles of the egg and the egg quality was very low (% of eyed stage embryos: 3.3 ± 2.9 and zero, respectively). In conclusion, examination of lipid droplets distribution, in brown trout, can distinguish between high and low quality eggs in an easy and reliable way.  相似文献   

14.
Egg quality in Arctic char, Salvelinus alpinus, kept indoors at 7 °C during spawning season was morphologically classified. Four egg categories based on lipid droplet distributions and egg diameter were characterized. Eggs with homogenous lipid vesicle distributions and a uniform size were classified as Good. Eggs with some yolk lipid droplets coalesced toward one pole but were homogeneous in size were classified as Fair. Eggs with lipid vesicles that were usually coalesced at one or two poles with were classified as Poor. The fourth egg category was Heterogeneous, in which lipid vesicle distribution and egg size were inhomogeneous. This distribution pattern of the lipid vesicle had a strong relationship with the percentage of fertilized and eyed eggs. Percentages of fertilized and eyed eggs in Good and Fair eggs were 85.5 and 83.4; 30.2 and 28.2, respectively. With Poor and Heterogeneous eggs, the percentages of fertilized and eyed eggs were zero. Egg diameter and absolute weight was increased in Poor eggs than in other egg categories. Relative weight increase during hardening after 30, 45 and 60 min were higher in Good and Fair eggs than in Poor and Heterogeneous eggs. Ovarian fluid collected from egg batches with low rates of fertilized and eyed eggs (Heterogeneous and Poor) had a lower pH and higher protein and aspartate amino-transferase enzyme than ovarian fluid from eggs batches classified as Good or Fair, while the ovarian fluid osmolality did not significantly differ. ATP contents of Poor and Heterogeneous eggs were lower than for Good and Fair eggs. In Heterogeneous eggs, both ATP and acid phosphatase contents were very variable.  相似文献   

15.
The wide use of lipid as a non‐protein energy substitute has led to lipid metabolic problems in cultured tilapia. Therefore, studies that reduce the effects of high‐fat diets in genetically improved farmed tilapia (GIFT) are required. This study evaluated the optimum level and effects of dietary α‐lipoic acid (α‐LA) on growth performance, body composition, antioxidant capacity and lipid metabolism of GIFT tilapia. The basal diet (120 g/kg lipid) was supplemented with six concentrations of α‐LA at 0 (control), L300, L600, L900, L1200 and L2400 mg/kg diet to make the experimental diets, which were fed to GIFT tilapia juveniles (initial body weight: 0.48 ± 0.01 g) for 8 weeks. The weight gain of fish improved significantly in the L300 than other dietary treatments. The intraperitoneal fat index and lipid content of fish fed on the L2400 diet decreased significantly than those fed on the control diet. The activities of superoxide dismutase and glutathione peroxidase (GSH‐Px) in serum and liver were significantly higher in fish fed on the L300 diet than the control. The reduced GSH content of fish fed on the L300 in serum and liver was significantly higher than those fed on control diet. The malondialdehyde content in serum and liver was significantly lower in L300 than in the control. The adipose triglyceride lipase gene was significantly up‐regulated in fish fed on the L2400, but the diacylglycerol acyltransferase 2 gene was down‐regulated in adipose. The liver‐type fatty acid‐binding protein gene in the liver was significantly up‐regulated in fish fed on the L300 and L600 diets. Moreover, the acyl‐coenzyme A oxidase gene in liver was significantly up‐regulated in fish fed on the L300, L600, L900 and L1200 diets. Polynomial regression analysis indicated that 439–528 mg/kg α‐LA is an appropriate dosage in high‐fat diet to improve growth performance and relieve lipid oxidative damage by accelerating lipid catabolism and reducing lipid synthesis in GIFT tilapia.  相似文献   

16.
Nile tilapia, Oreochromis niloticus (L.), and channel catfish, Ictalurus punctatus (Rafinesque), were experimentally infected by immersion with three isolates (Lake, DL8O5 and MS91452) of Streptococcus sp. from diseased fish. To enhance infection, the lateral body surface of each fish was scraped prior to bacterial exposure. The Lake and DL8O5 isolates caused exophthalmia, ocular opacity and ocular haemorrhage in some tilapia. Histopathology of these fish revealed; meningitis; polyserositis of heart, liver, spleen, ovary and kidney; splenitis; ovaritis; and myocarditis. Isolate MS91452 induced only mild granulomas in spleen, kidney and ovary of tilapia. The Lake and DL8O5 isolates induced endophthalitis, Channel catfish infected with the Lake and DL805 isolates developed similar eye lesions to tilapia. Histologic lesions caused by all three isolates in channel catfish consisted of meningoencephalitis, mild myocarditis, splenitis and ovaritis, but these lesions were not as severe as in Nile tilapia.  相似文献   

17.
Abstract. This paper examines the digestibility of different feed mixtures by three species of fish: carp, Cyprinus carpio L., tilapia, Oreochromis aureus × O. niloticus , and African catfish, Clarias gariepinus (Burchell 1822). Protein from poultry sources was digested better by tilapia than by carp or catfish, but no significant difference was found in the case of protein mainly from fish meal. Carp showed the best ability to digest fats, followed by catfish, with tilapia having the least ability. Tilapia digested carbohydrate better than the other two species, however, whether from wheat or corn sources. The same pattern applies to the digestibility of energy.  相似文献   

18.
Twelve production trials were analysed retrospectively, covering three different rearing methods in which Nile tilapia, Oreochromis niloticus (L.), were fed with combinations or cottonseed cake and brewery waste. Highest extrapolated net pond productions, including tilapia recruits, were obtained in tilapia fingerling rearing (W0 <10 g; 11.8 t ha?1 year?1). Stocking African catfish, as police-fish (0.2 catfish m?2) in mixed tilapia (W0 > 90 g) culture was effective in controlling tilapia recruitment, but net pond production was low (4.1 t ha?1 year?1). Hand-sexing of male tilapias (W0 > 90 g) only limited recruitment but resulted in a significantly higher net pond production (8.6 t ha?1 year?1) than in mixed culture. Extrapolated marketable production in the treatment stocked with hand-sexed tilapia males (tilapia only) was also higher than the extrapolated marketable production in the mixed culture treatment (tilapia and catfish combined), although this difference was not significant. Extrapolated net pond production and extrapolated net tilapia production were both significantly correlated to the daily feeding rate of cottonseed cake but not to the daily feeding rate of brewery waste. The high relative FCRs of the feed mixture were probably due to the brewery waste.  相似文献   

19.
ABSTRACT

The aim was to investigate the physicochemical properties of pepsin-solubilized collagen (PSC) extracted from fish scales of Nile tilapia. The results indicated that Nile tilapia scales are rich in collagen. Therefore, the scales are a promising cost-effective collagen source. The conversion of hydroxyproline to collagen was 12.9. Based on the patterns of sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), PSC comprised at least two different α chains, α1 and α2, and was classified to be type I with no disulfide. Fourier transform infrared spectroscopy spectrum showed that the bands of amide A, I, and II of PSC were found at 3,301, 1,631, and 1,239 cm?1 wavelength. The content of imino acids was 187 residues per 1,000 total amino acid residues. Maximum solubility was observed at pH 4, and minimum was at pH 7. Almost no change in solubility was observed in the presence of NaCl up to 2% (w/v), and the decrease was more pronounced with increasing NaCl concentration. The temperature of denaturation was 35.4°C. Results show that PSC has physicochemical properties that can be applied in the cosmetics, biomedical, pharmaceutical, and food industries.  相似文献   

20.
Abstract. Semi-purified casein/gelatin diets containing two levels of lipid (5 or 10%) and three levels of reduced glutathione (0,0·1 or 1·0%) in a factorial arrangement were fed to fingerling channel catfish, Ictalurus punctatus (Rafinesque), in aquaria for 10 weeks. Factorial analysis of variance indicated that dietary lipid had significant ( P < 0·05) effects on growth, feed efficiency and body composition of channel catfish. Diets containing 10% lipid generally produced higher weight gain and feed efficiency values as well as higher intraperitoneal fat. The higher level of dietary lipid also produced lower moisture and higher lipid (on a wet-weight basis) levels in whole-body and fillet tissues. Stability of fillet samples was estimated by 2-thiobarbituric acid (TBA) analysis which revealed that 10% dietary lipid significantly elevated fillet TBA values while glutathione did not have any effect. Therefore, dietary lipid level altered growth and body composition of channel catfish as well as oxidative stability of fillet samples while dietary glutathione was generally ineffective.  相似文献   

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