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1.
Abstract Hidrostal pumps have been successfully employed in live fish transport, yet their effectiveness in fish passage is incompletely understood. This study investigates juvenile salmonid mortality in experimental passage trials through Hidrostal pumps at an agricultural pump facility in Washington State, USA. The effects of impeller pitch, rotational speed and fish body size on passage survival were examined. Hatchery‐reared salmonids [Oncorhynchus mykiss (Walbaum) and Oncorhynchus kisutch (Walbaum)] were introduced to low‐ and high‐pitch impeller assemblies operating at two speeds. Instantaneous mortality rates ranged from 0 to 4% for high‐pitch trials and from 3 to 10% for low‐pitch trials. Larger fish experienced sublethal injury at higher rates (approximately 60% injured) than smaller fish (approximately 23% injured) and exhibited greater susceptibility to injury at higher pump speed. Injury between trials was compared by ranking according to severity and summed for each treatment; greater injury severity was found for the low‐pitch impeller and from higher rotational speeds. Although injury and mortality rates to fish passing through Hidrostal pumps may be reduced through the use of higher‐pitch impellers and lower operational speeds, the use of pump‐bypass facilities may be warranted where acceptable impact thresholds are low.  相似文献   

2.
The emergence of a new sublineage of viral hemorrhagic septicemia virus (VHSV) within the Laurentian Great Lakes has caused concern for aquaculture in the United States. Because of the occurrence of VHSV in a new geographic location, new host species have been identified and the complete host range has not been determined. This study confirmed the high resistance of rainbow trout, Oncorhynchus mykiss, to VHSV type IVb infection. In addition, the experimental susceptibility of hybrid striped bass, Morone chrysops ♂ × Morone saxatilis ♀, to VHSV type IVb infection was examined but determined to be highly dependent on age of fish and exposure temperature. No mortality was observed in adult fish infected via intraperitoneal (IP) injection at 15 C, whereas yearling fish infected via IP injection under the same conditions experienced 20.8% mortality. Among yearling fish infected via IP injection, mortality increased to 100% when exposure to VHSV occurred at 10 C. An LD50 for yearling hybrid striped bass exposed to VHSV at 10 C by IP injection was determined to be 1.4 × 104 pfu (SE = 2.1). Thus, at 10 C, yearling hybrid striped bass experience a high mortality when exposed to VHSV IVb by IP injection.  相似文献   

3.
Apparent digestibility coefficients (ADCs) of nutrients (crude protein, amino acids, crude lipid, fatty acids, and minerals) were determined for fish meals derived from menhaden, Asian carp (combination of silver and bighead carps), and common carp in feeds for hybrid striped bass and rainbow trout. Extruded test diets were formulated to contain a 70 : 30 mixture of reference diet and test ingredient with yttrium oxide (1 g kg?1) serving as the inert marker. Diets were randomly assigned to triplicate tanks and fish were fed once per day at 2% body weight. Fecal samples were collected by manual stripping. The ADCs were calculated according to standard procedures. The composition and digestibility of Asian carp and common carp meals was broadly similar to menhaden meal. Protein digestibility ranged from 86.5% (Asian carp meal) to 93.1% (common carp meal). Lipid was highly digestible with ADCs >100% for all ingredients. Although the Asian carp meal was less digestible than the other two fish meals, it was still a highly digestible ingredient. Our data suggest that fish meals derived from Asian or common carp would be valuable feedstuffs in diets for hybrid striped bass, rainbow trout, and possibly other cultured fishes.  相似文献   

4.
The potential for commercial culture of hybrid striped bass is promising in many areas of the United States. While several different striped bass hybrids are candidates for culture, differential performance has not been thoroughly evaluated. Comparative performance of two striped bass hybrids was evaluated in six, 757–1, fiberglass tanks receiving a continuous flow of ambient pond water for 397 d. Three replicate tanks were stocked with 50 fingerlings (66 fish/m3) of either striped bass female × white bass male (mean weight 23 g) or striped bass female × yellow bass male hybrids. Fish were fed a 35% protein ration throughout the study, and weight was recorded for all fish at stocking and at 21-d intervals. White bass hybrids grew significantly faster (0.94 g/d) than yellow bass hybrids (0.59 g/d). Survival to harvest averaged 65% and 44% for yellow bass and white bass hybrids, respectively. A significant difference from the expected 1:1 sex ratio occurred for yellow bass hybrids (100% female), but not for white bass hybrids (56% female). Mean condition factor, 1.63 and 1.39, and fillet percentage, 30.7% and 28.4%, was significantly higher for white bass hybrids compared to yellow bass hybrids.  相似文献   

5.
New and viable species for aquaponics and integrated multi‐trophic aquaculture (IMTA) in freshwater systems can improve yields and sustainability of aquaculture. Freshwater crayfish species such as Astacus astacus and Pontastacus leptodactylus are omnivorous feeders and considered candidates for feeding on faecal matters in existing aquaculture systems. Feeding trials were conducted to determine growth response and RNA/DNA ratio in freshwater crayfish fed fish waste. Carapace length and wet weight were measured to determine the growth response. Juvenile A. astacus was fed faeces of hybrid striped bass (Morone chrysops × Morone saxatilis) and rainbow trout (Oncorhynchus mykiss), while adult P. leptodactylus was fed with two commercial pellet diets and pikeperch (Sander lucioperca) faeces. The nutritional composition of hybrid striped bass faeces was close to optimal diet composition of A. astacus, and crayfish showed significantly higher carapace growth, weight gain and weight gain per moult as the group fed rainbow trout faeces. The growth of P. leptodactylus was significantly lower in terms of weight gain and weight gain percentage per moult for crayfish fed on pikeperch faeces. Thus, this study can recommend a co‐cultivation of hybrid striped bass and A. astacus within one system, but cannot recommend co‐cultivation of P. leptodactylus with pikeperch. Additionally, this study showed controversial results of RNA/DNA ratio and weight gain of both crayfish species. Thus, RNA/DNA ratio cannot be approved for investigations on crayfish physiological status in controlled feeding experiments if animals are fed with an inadequate diet.  相似文献   

6.
To investigate potential use of dietary β-1,3-glucan for health management of hybrid striped bass, juvenile fish were fed diets supplemented with yeast glucan (MacroGuard®) at 0.05%, 0.1% or 0.2% of diet for 4 weeks, followed by immune response assays and a bath challenge with Streptococcus iniae . Dietary glucan significantly ( P <0.05) enhanced neutrophil oxidative radical production, and fish fed 0.1% glucan had a significant ( P <0.05) reduction in mortality (10%) after bacterial challenge compared with fish fed the control diet (46.7%). However, accumulative mortality of fish fed 0.2% glucan was not significantly different from that of fish fed the control diet. To further elucidate this observation, macrophages from sub-adult hybrid striped bass were isolated and cultured in L-15 medium with 10% foetal calf serum and penicillin/streptomycin supplemented with 0.2, 0.5, 1, 2, 5, 20 and 100 μg soluble glucan (MacroGuard®) mL−1 for 24 and 48 h. Intracellular superoxide anion production was significantly ( P <0.001) increased by 0.5 μg glucan mL−1, but significantly ( P <0.001) suppressed by doses >5 μg glucan mL−1. It is concluded that dietary yeast glucan has potential for use in diet formulations of hybrid striped bass to limit the adverse effects of S. iniae , but dosage should be an important consideration in administration.  相似文献   

7.
Abstract— Grow-out performance of striped bass Morone saxatilis , palmetto bass ( M. saxatilis ♀ × M. chrysops ♂ ) and backcross hybrids [sunshine bass ♀( M. chtysops ♀ × M. saxatilis ♂) × M. saxatilis ♂] was examined in a two-part study. During part I fish (mean weight = 20.1 g) were stocked at a density of 56 fish/m3 in 1.8-m3 cylindrical fiberglass tanks connected to a central biological filter. Fish were fed a 38% protein trout ration daily and the study duration was 273 d. At harvest, no differences ( P > 0.05) in mean weight or feed conversion were detected among the fish types. However, there were differences in specific growth, with the striped bass having a significantly higher growth rate than the palmetto bass and the backcross hybrids being intermediate. The condition factor (K) for striped bass was also significantly lower (1.2) than that recorded for either of the other two groups. In addition, survival of striped bass (91%) was significantly higher than that of backcross hybrids (74%), while survival of palmetto bass (87%) was intermediate. The survival of backcross hybrids was adversely impacted by an infestation of the dinoflagellate Amyloodinium sp . During part II stocking density in each tank was reduced to 19 fish/m3. The study lasted 104 d. At harvest, no differences were detected in weight, survival, or feed conversion. However, there were significant differences in specific growth, length and K. Striped bass and backcross hybrids gained weight faster than palmetto bass. Length and K were inversely related with all groups being significantly different. Striped bass had the largest TL and the lowest K while, palmetto bass were the shortest with the highest K.  相似文献   

8.
In 1978 a cooperative pilot study was initiated by the Marine Resources Research Institute and DØMSEA Farms, Inc. to examine the feasibility of rearing striped bass (Morone saxatilis) x white bass (M. chrysops) hybrids to marketable pan-size in estuarine net-pens. The first study was begun in July 1978 when a total of 1,070 hybrid fingerlings (mean weight, 1.7 g) were stocked in 3.05 × 2.44 × 1.83 m deep net-pens moored to a commercial marina dock on the Stono River near Charleston, S.C. During the first month these fish suffered a 76% mortality, apparently as a result of feeding only a dry salmon ration. Thereafter, the remaining fish were fed the dry ration mixed approximately half-and-half with ground fish. At the end of one year, these fish had attained a mean weight of 523.0 g, with 74.6% survival. A second experiment was begun in July 1979 when 900 hybrid fingerlings (mean weight, 3.0 g) were stocked in each of three 3.05 × 2.44 × 1.83 m net-pens at the marina (stocking density, ?66 fish/m3). The fish were fed a mixture of dry salmon feed and ground fish throughout. At the end of one year, survival and weight averaged 88% and 310.2 g, respectively. Biomass in the pens at this time averaged 16 kg/m3. Little growth or active feeding occurred at temperatures < 15°C. In contrast, salinity variations had no apparent effect on growth. However, a period of decreasing salinity in early spring coincided with an outbreak of a bacterial disease (cf. Vibrio anguillarum) among striped bass fingerlings reared in adjacent pens. Fish which had been treated with a vaccine solution did not succumb to the disease, while approximately 50% mortality occurred among non-vaccinated fingerlings.  相似文献   

9.
Catch‐and‐release fishing has increased in many fisheries, but its contribution to fishing mortality is rarely estimated. This study estimated catch and release mortality rates of striped bass, Morone saxatilis (Walbaum), for the spring recreational fishery in the Hudson River. Treatment fish (caught with live bait on spinning gear) and control fish (captured by electric fishing) were placed in in situ holding pens for 5 days. Mortality rates were estimated using conditional instantaneous mortality rates and additive finite mortality rates. Influences of variables (playing and handling time, hook location, degree of bleeding and fish length) on hooking mortality rates were examined by logistic regression. Conditional instantaneous mortality rates and additive finite mortality rates were 31 and 28%, respectively. Hook location significantly affected the survival of striped bass. Angling catch, effort, and release rates must be integrated with associated hooking mortality rates before this component of overall population mortality can be incorporated into management decisions.  相似文献   

10.
Gram-positive cocci recovered from diseased rainbow trout from a farm in England were characterized by different methods, including pulsed field gel electrophoresis, as virulent Lactococcus garvieae serogroup 2 (pulsotype A1). Groups of rainbow trout were kept at a range of temperatures and injected intraperitoneally (i.p.) with one of the UK isolates, L. garvieae 00021. The 18 °C and 16 °C groups showed 67% and 28% mortality, respectively, by day 27 post-injection. Fish kept at 14 °C or lower were less susceptible (≤3% mortality). Raising the temperature of all groups to 18 °C at day 27 post-injection did not result in recurrence of the disease, even though viable bacteria were recovered from all groups 42 days later. Grayling were highly susceptible, with 65% mortalities when challenged with 200 colony forming unit fish−1 by i.p. injection and 37% mortalities when exposed to effluent water from tanks containing affected rainbow trout. Other fish species tested, Atlantic salmon, brown trout and seven cyprinid species, were less susceptible. Viable L. garvieae was isolated from the internal organs of all species tested at the end of the trials, suggesting that they may pose a threat as possible carriers to susceptible farmed and wild fish.  相似文献   

11.
Four 0.1 hectare earthen ponds were stocked with 16,500 hybrid striped bass (female Morone saxatilis × male M. chrysops ) per hectare on 22 June 1982. Mean weight at stocking was 5.2 g ± 0.10 SE. Fish were fed to satiation two or three times daily with a dry commercial salmonid diet, and the ponds were aerated mechanically during periods of low dissolved oxygen during warm weather. Survival at harvest on 6 March 1983 averaged 84.7%, and mean weight of the fish was 170.2 g ± 2.66 SE. Average weights of fish from individual ponds ranged from 149.0 to 189.7 g. The ponds were restocked on 1 April 1983 with 10,000 fish per hectare averaging 193.6 g. Ten months later, average survival in 3 ponds was 83.9% (range, 81.3–87.0%) and mean weight was 656.3 g ± 5.51 SE. Average weights of fish from individual ponds ranged from 632.5 to 690.7 g. All fish in one pond died in June as a result of an aerator failure. Standing crop at harvest in the three remaining ponds averaged 5, 504 kg/ha (range, 5,247–5,765 kg/ha). Improvements in culture techniques resulted in approximately a 138% increase in production per hectare over that reported in a prior study. Results demonstrated that hybrid striped bass offer considerable potential for commercial aquaculture in warm temperate latitudes of the United States.  相似文献   

12.
A 12‐week feeding trial was conducted to evaluate the effects of fish oil replacement by soybean oil, on lipid distribution and liver histology of two commercially important finfish species: rainbow trout (Oncorhynchus mykiss) and European sea bass (Dicentrarchus labrax). Sea bass (16.2 ± 0.5 g; mean ± SD) and rainbow trout (52.1 ± 0.5 g) juveniles were fed one of three isonitrogenous (500 g kg?1 CP) and isoenergetic (19 kJ g?1) diets, containing 0% (control, diet A), 25% (diet B) and 50% (diet C) soybean oil. At the end of the experiment, lipid deposition was evaluated in muscle, liver and viscera. Cholesterol and triglycerides levels were also determined in plasma. Tissue total, neutral and polar lipid composition (g kg?1 total lipids) showed no significant differences within species, regardless the dietary treatment. The same trend was observed for plasma parameters (P > 0.05). Viscera were the preferential tissue of lipid deposition, with 252–276 and 469–513 g kg?1 total lipid content in trout and sea bass, respectively. Dietary fish oil replacement had no effect on either hepatic lipid droplets accumulation or degree and pattern of vacuolization in the observed liver sections. These data suggest that both sea bass and trout can be fed diets containing up to 50% soybean oil without adverse effects on tissue lipid composition or liver histology.  相似文献   

13.
加州鲈肌肉生长抑制素(MSTN)cDNA的克隆和序列分析   总被引：1，自引：2，他引：1  
肌肉生长抑制素是抑制肌肉生长和发育的生长调控因子。对运用RT-PCR和RACE技术从加州鲈成鱼肌肉总RNA中扩增得到的MSTN cDNA全序列进行了序列分析。结果表明,加州鲈MSTN cDNA全长为1626bp,其开放阅读框为1 134bp,共编码377个氨基酸,前面的22个氨基酸为信号肽,中间有四个氨基酸(RARR)为蛋白水解加工位点;该基因总共有13个半胱氨酸残基,后面9个在蛋白水解加工位点之后的C端生物活性区,与其它脊椎动物比较,它们的位置完全一致,对该基因的结构和功能非常重要。与GenBank中已知的条纹狼鲈、金鲷、斑马鱼、虹鳟、斑点叉尾鮰、人、猪、鸡、鸽MSTN的ORF相比较,核苷酸序列同源性为63%~94.4%,氨基酸同源性为61.4%~96%,特别是在C端生物活性区氨基酸同源性为88.1%~100%,高度的保守性反映了该基因受到了高度的进化限制以及功能的重要性。加州鲈MSTN基因的克隆为研究该基因打靶和鱼类肌肉发育调控机理奠定了基础。  相似文献   

14.
A shortage of marine raw ingredients, such as fish oil, is predicted in the near future. The use of suitable alternative lipid sources, such as vegetable oils, is crucial for sustainable growth of the aquaculture sector. Three isonitrogenous (50% Crude Protein) and isoenergetic (19 kJ g−1) diets, in which fish oil was gradually replaced by soybean oil (0, 25 and 50% of the oil fraction) were tested for 12 weeks, using European sea bass (Dicentrarchus labrax) and rainbow trout (Oncorhynchus mykiss) juveniles. No dietary effects (p>0.05) on growth performance, feed conversion, digestibility or body composition were observed with either species. The results obtained suggest the inclusion of soybean oil up to 50% of the dietary lipid is possible, in diets for sea bass and/or rainbow trout juveniles.  相似文献   

15.

Two commercial trout diets (Oncorhynchus mykiss) and one commercial pike perch diet (Sander lucioperca) were fed to hybrid striped bass (Morone chrysops × M. saxatilis) (mean initial weight ± SD of 60.7 g ± 12.1; mean initial length SD of 17.2 cm ± 1.1) for 69 days at rations of approximately 1% average body weight. While final body weight (FBW), final length (FBL) and condition factor (Cf) were not significantly influenced by diets, specific growth rate (SGR) in hybrid striped bass fed with the pike perch diet (1.15) was significantly higher than those fed with either of the two trout diets (1.04 and 1.07). The feed conversion ratio (FCR) in hybrid striped bass fed with the pike perch diet (1.0) was significantly lower than the FCR in hybrid striped bass fed with either of the two trout diets (1.1 and 1.2). When hybrid striped bass (mean initial body weight: 65.7 ± 4.5 and 127.7 ± 2.9 g) were fed with the pike perch diet twice per day until satiation for 52 days, the SGR was 1.7 and 1.15% d?1 in fishes with an average body weight of 116 and 183 g, respectively. Present results demonstrate that growth performance in hybrid striped bass can be improved when fishes are fed with commercial pike perch diets rather than using commercial trout diets as is the current practice.

  相似文献   

16.
Abstract. The epidemiology of epizootic haematopoietic necrosis virus (EHNV) infection was studied in farmed rainbow trout, Oncorhynchus mykiss (Walbaum). Estimates of mortality during five outbreaks on a commercial farm from 1986 to 1992 ranged from 0033 to 0.2% per day and total mortality did not exceed 3–4% in any outbreak. Affected fish were 0+ and less than 125 mm forklength. Clinical signs were non-specific, and laboratory examination was required to confirm the diagnosis. At the height of the outbreak in 1992, EHNV was demonstrated by virus isolation and antigen capture ELISA in 89% of clinically affected fish and 51% of dead fish, while the prevalence of infection in apparently healthy in-contact fish was 4%. Two and 4 months later the virus was not detected in a group of apparently healthy fish that had been affected earlier. Antibodies specific for EHNV were not found in rainbow trout from the infected farm; however, strong humoral responses were detected by ELISA in two immunized fish, indicating that the virus was immunogenic. These data suggested that EHNV was poorly infective but highly virulent in rainbow trout. Clinical EHNV infection was positively correlated with high rearing density and a low rate of water exchange, and therefore, with presumed poor water quality. Water temperature, which ranged from 11 to 17°C during outbreaks, did not appear to determine the incidence of clinical infection. EHNV infection in farmed rainbow trout was preceded by infection in free-living redfin perch, Perca fluviatilis L., in the water catchment, but it was uncertain whether this represented the source of infection for rainbow trout.  相似文献   

17.
It has been reported that metabolic rates of striped bass Morone saxatilis and hybrid striped bass M. chrysops♀ x M. saxatilis♂ are different. A series of experiments were conducted to further characterize oxygen consumption and metabolism of striped bass and its hybrid, the sunshine bass. Oxygen consumption was measured to determine standard and routine metabolic rates of striped bass and hybrid striped bass in a freshwater, flow‐through tank system. Additionally, blood chemistry stress indicators of the two bass groups were compared in both fresh and brackish water. Hematocrit (% PCV) and hemoglobin were measured in order to compare oxidative efficiencies of the bass. Plasma glucose, chlorides, and cortisol levels were measured to compare the relative stress status of the two bass types reared under experimental conditions. No significant differences were found in average daily oxygen consumption between striped bass and sunshine bass for either standard metabolism (P= 0.92), or routine metabolism (P = 0.86). Standard metabolic rates of oxygen consumption were 69 ± 4.1 and 68 ± 3.5 mg 02/kg3/4 bw/h for sunshine bass and striped bass respectively. Routine metabolic rates were 132 ± 30 and 125 ± 30 mg O2/kg3/4 bw/h for sunshine bass and striped bass respectively. While there were no significant differences in oxygen consumption between species, normal feeding activity generally resulted in increased oxygen consumption by the fish. Striped bass had significantly lower hematocrit values (P= 0.0001), but significantly higher hemoglobin concentrations than sunshine bass maintained in freshwater (P= 0.0001). Striped bass had significantly higher (P= 0.0001) levels of plasma glucose compared to sunshine bass (176 ± 8.6 vs. 103 ± 5.6 mg/dL respectively). Plasma chloride levels for striped bass (123 ± 1.9 mEq/L) were significantly higher (P= 0.041) than plasma chloride levels of sunshine bass (117 ± 1.7 mEq/L). Plasma cortisol levels were significantly higher (P= 0.0081) for striped bass (147 ± 8.4 ng/mL) compared to sunshine bass (119 ± 5.6 ng/ mL) when reared in freshwater. When maintained in brackish water, sunshine bass had significantly higher hematocrit values (P= 0.0001), and hemoglobin concentrations (P= 0.0012) when compared to striped bass. However, sunshine bass had significantly higher hemoglobin concentrations (P= 0.0012) when compared to striped bass. In addition, plasma glucose levels were significantly lower (P = 0.0079) for sunshine bass (79 ± 4.1 g/dL) when compared to striped bass (115 ± 11 g/dL). There were no significant differences between the bass in levels of chlorides or cortisol. No differences were detected in oxygen consumption. However, hybrid striped bass may have more efficient oxidative metabolism due to elevated hemoglobin concentrations. While striped bass hemoglobin values tended to be higher in brackish water than in freshwater, sunshine bass hematocrit or hemoglobin values generally were significantly higher than striped bass in both fresh and brackish water. Based on these results, hybrid striped bass may be capable of directing more energy towards growth than striped bass due to more efficient oxidative metabolism and lower losses of energy related to increased stress.  相似文献   

18.
Francisella orientalis is a highly virulent, emerging bacterium that causes mass mortalities in tilapia. This pathogen also affects numerous other warm-water fish species, including three-line grunt, hybrid striped bass and various ornamental fish. This study sheds light on two new species of fish that are susceptible to F. orientalis. Asian seabass and largemouth bass showed variable levels of susceptibility in a bacterial challenge experiment. After intraperitoneally injected with a dose of 106 CFU/fish, a total of 64.28% and 21.42% mortalities were obtained in Asian seabass and largemouth bass, respectively. Meanwhile, Nile tilapia showed acute mortality of 100%. All fish showed typical lesions of francisellosis, including multifocal granulomas in the spleen and head kidney. Immunohistochemical analysis revealed strong positive signals inside the granulomas of all fish. The bacterial recovery in solid media from infected fish was highest in Nile tilapia (85.71%), followed by Asian seabass (35.71%) and largemouth bass (21.42%). PCR results tested 100% positive for Nile tilapia, and 78.57% and 21.42% for Asian seabass and largemouth bass, respectively. In conclusion, Asian seabass and largemouth bass are susceptible to this pathogen, which warrants new management strategies when employing predation polyculture systems of these species with tilapia.  相似文献   

19.
Abstract. Eight-day-old striped bass, Morone saxatilus (Walbaum) larvae, and one-month-old juveniles were held in varying salinities and exposed to a range of concentrations of potassium permanganate. Lethal concentrations of potassium permanganate for 50% of the larval fish exposed for96h (96h LC50) were 1middot;02, 2 middot;11, 1 middot;41 and 1 middot;73mg/1 for salinities of 0, 3, 6and 9 g/l, respectively; The 96h LC50S for juveniles were 0 middot;96, 3 middot;26, 1 middot;63 and 1 middot;48 mg/l for salinities of 0, 5, 10 and 15g/l, respectively. There were significant differences in 96h LC50 values at different salinities for both life stages. The 96 h LC50 values derived for both life stages revealed a decrease in toxicity as salinity increased from 0 to 3–5g/l. Results indicated potassium permanganate to be toxic in fresh water to striped bass larvae and fingerlings at recommended treatment levels (3 middot;0mg/l).  相似文献   

20.
Two separate feeding trials were conducted to determine the total sulfur amino acid requirement of hybrid striped bass. Semipurified diets containing 35% crude protein from fish muscle and crystalline amino acids were supplemented with graded levels of methionine. Each diet was fed to juvenile fish in triplicate aquaria receiving freshwater for 8 weeks. Fish fed the basal diet which contained 0.38% methionine and 0.13% cystine experienced complete mortality within 1 week. Prior to death, some fish fed inadequate methionine were observed to have bilateral cataracts. Weight gain and feed efficiency of fish were significantly (P<0.01) affected by supplemental methionine. Regression analysis of weight gain data using the broken-line model indicated a total sulfur amino acid requirement (±s.e.) of 1.0% (±0.02%) of dry diet or 2.9% of dietary protein.  相似文献   

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