投喂频率对大西洋鲑生长和生理指标的影响

将270尾均质量约500 g的大西洋鲑随机分为5组,每组2个重复,分别以3次/d、2次/d、1次/d、1次/2 d、1次/3 d的投喂频率饱食投喂56 d,以研究投喂频率对大西洋鲑生长性能、消化率、激素水平和抗氧化指标的影响。试验结果表明,随着投喂频率的降低,大西洋鲑质量增加率和摄食量明显降低,1次/2 d试验组和1次/3 d试验组质量增加率较3次/d试验组分别显著降低50%和75%,摄食量显著降低53%和72%。饵料系数、死亡率、皮质醇和抗氧化指标呈先降后升的趋势;饵料系数和皮质醇2次/d试验组最低,1次/3 d试验组最高,较其他组分别高1.2～2.1倍和0.38～4.78倍。血浆生长激素和甲状腺激素与之呈相反趋势,2次/d试验组各项指标较好;各试验组消化率均呈升高—降低—升高的变化趋势,2次/d和1次/3 d试验组值较高。试验结果表明,500～900 g大西洋鲑的最佳投喂频率为2次/d,在此基础上提高或降低投喂频率均会对大西洋鲑造成应激,对生长和饲料利用率产生负面影响。     

投喂频率对循环水养殖系统氨氮浓度的影响

研究在相同投喂量下,不同投喂频率(3,6,8次/d)对循环水养殖系统水体氨氮水平及生物滤器氨氮去除效率的影响.结果表明:随着投喂频率增高,养殖水体氨氮变异系数由14.9%逐渐减弱到0,但总体平均浓度基本保持稳定(P>0.05);投喂后,生物滤器氨氮去除效率由67.02%升高到85.71%(P<0.05).研究发现,采用8次/d投喂频率时,养殖水体氨氮浓度更稳定,生物滤器氨氮去除效率更高.     

日投饵量与投喂频率对大西洋鲑循环水养殖水质的影响(下)

<正>二、结果与分析1.不同日投饵量养殖水体中氨氮、亚硝酸氮、COD含量变化(1)氨氮:两个系统投饵量直接影响到养殖水体中的氨氮含量,氨氮含量随日投饵量的增减而变化,投饵量增加,氨氮含量升高;投饵量减少,氨氮含量也随之降低。系统Ⅰ4月6日氨氮含量最低,为0.87毫克/升(日投饵量最低,22.04千     

日投饵次数和投饵量对静水养殖南美白对虾的影响

1 简介 通常人们认为,一日多次投饵,并按不同比例分配日投饵量可以提高对虾的生长率,减轻水质恶化。因此,养虾者多采用一日多次投饵,一天投饵3次或更多次。然而很少有人进行试验证实这种投饵方式在对虾养殖中的优越性。 该研究的目的是测定日投饵次数和每次投饵量对对虾存活和生长的影响,以及在静水养殖池中溶解总无机氮(TIN)和总活性磷(TRP)的积累。 2 材料与方法 2.1试验1:24h投饵期 将初始体重185.0±12.0mg的南美白对虾(Litopenaeus vannamei)以0.5尾对虾/L放养在容积20L的玻璃纤维水池(表面积放养密度为150尾对虾/m2),给池水充…     

两种规格大西洋鲑胃排空特征及其模型分析

为探究大西洋鲑(Salmo salar)的胃排空特征及其模型, 本研究采用胃含物分析法对两种规格[(176.15±27.52) g 和(323.33±43.91) g]大西洋鲑进行胃排空实验。经暂养 27 d 适应后, 两种规格大西洋鲑停食 48 h, 分别在饱食投喂后第 0、3、6、9、12、18 和 24 小时测定其胃含物湿重和干重, 并用 4 种数学模型拟合; 在筛选出其最佳胃排空模型后, 计算最佳干重模型下 80%干重胃排空时间作为其最适投喂频率。结果表明, 与湿重模型相比, 干重胃排空模型能更准确反映大西洋鲑胃排空时间的状况。小规格和大规格大西洋鲑的最佳干重胃排空模型分别为指数模型和平方根模型, 其 80%干重胃排空时间分别为 12.23 h 和 18.06 h。小规格大西洋鲑胃排空比大规格更快, 这可能是因为小规格大西洋鲑消化前期干燥饲料被水分软化的时间更短。本研究结果可为大西洋鲑智能投喂系统提供生物学参数, 为实际生产中智能投喂策略提供理论参考。     

投喂频率对工厂化循环水养殖星康吉鳗生长、生理指标及其水质的影响

本研究采用生理学和实验生态学方法探究了工厂化循环水养殖模式下,不同投喂频率对星康吉鳗(Conger myriaster)生长、生理指标以及水质因子的影响。选用初始体重为(150.64±5.43) g的星康吉鳗为研究对象,实验共设2组,分别为1次/天(T1组)、2次/天(T2组),每组3个重复,实验周期为70d。实验每14d检测各养殖池实验鱼平均体重和循环水系统水质指标;实验结束时,采集星康吉鳗血液、组织相关样品,用于生长、生理指标的测定与分析。结果显示,T2组终末体重(FBW)、终末体长(FBL)、增重率(WGR)、特定生长率(SGR)显著高于T1组(P<0.05),T1组饲料系数(FCR)显著高于T2组(P<0.05)。T1组血清丙二醛(MDA)显著高于T2组(P<0.05),T2组肝脏谷草转氨酶(AST)、肝脏谷丙转氨酶(ALT)、肠道胰蛋白酶(TPS)显著高于T1组(P<0.05)。T1组、T2组出口水NH₄⁺-N、NO₂^--N 24 h变化中分别有1处(24:00)和...     

投喂频率和投喂水平对长吻鮠幼鱼生长和免疫的影响

为观察不同投喂频率和投喂水平对长吻鮠(Leiocassis longirostris)幼鱼生长和免疫的影响,将平均体质量1. 15 g的长吻鮠饲养在水泥池(2 m×1 m×1 m)中,投喂频率分别为2次/d和3次/d,各投喂频率下投喂水平分别为鱼体质量的2%、4%、6%、8%和10%,每个处理组放鱼60尾,饲养为期42 d。结果显示:投喂频率为2次/d和3次/d时,试验鱼的末体质量、特定生长率与投喂水平之间存在二次相关性,两条曲线几乎重合,表明投喂频率、投喂水平对试验鱼的末体质量和特定生长率的影响是一致的;血清中丙二醛(MDA)含量在投喂频率为2次/d、投喂水平为4%和6%时较低;血清总超氧化物歧化酶(T-SOD)含量在投喂频率为2次/d、投喂水平为4%和6%时较高;血清溶菌酶(LYS)含量在投喂水平为6%、投喂频率2次/d和3次/d时显著高于其他各组(P <0. 05)。综合生长和免疫指标,在本试验条件下,投喂频率为2次/d、投喂水平为6%的投喂模式更利于长吻鮠幼鱼的生长。     

饥饿与再投喂及投喂频率对条石鲷幼鱼生长和消化酶活力的影响

研究了饥饿与再投喂及不同投喂频率对条石鲷(Oplegnathus fasciatus)幼鱼生长和消化酶活力的影响.饥饿与再投喂的实验结果表明:条石鲷幼鱼体质量、蛋白酶(胃蛋白酶、胰蛋白酶)与脂肪酶活力随着饥饿时间的延长均呈现明显的下降趋势,体质量与蛋白酶活力在饥饿6d后与对照组表现出显著性差异(P＜0.05),脂肪酶活力在饥饿9d后才与对照组表现出显著性差异(P＜0.05),而淀粉酶活力在饥饿过程中呈波动性变化;恢复投喂后,除饥饿3d的幼鱼体质量、特定生长率与对照组无明显差异外,其他各处理组均明显低于对照组;蛋白酶与脂肪酶活力在恢复投喂后均有明显回升,且蛋白酶活力与对照组相比已无显著性差异,但较长时间的饥饿处理(9～12 d)并未使脂肪酶活力恢复至对照组水平.投喂频率实验的研究结果表明:随着投喂频率的增加,条石鲷幼鱼的特定生长率呈上升趋势,在投喂频率达到投喂2次/d后,条石鲷幼鱼的特定生长率、消化酶活力及肝体指数差异均不显著.结论认为,在本实验条件下,饥饿3d后再经投喂,条石鲷幼鱼具有完全补偿生长效应,但随着饥饿时间的延长补偿生长的效应逐渐降低.对条石鲷幼鱼而言,选择日投喂两次最合适.     

投喂频率对凡纳滨对虾生长和水质的影响

研究了不同投喂频率(1,2,3,4和5次·d-1)对凡纳滨对虾生长、存活率和水质的影响。试验在室内2m3的圆形水泥池(d=1.6m)中进行,采用全封闭养殖模式,凡纳滨对虾(初始重量为0.24g)养殖密度为50尾·m-3,投喂人工配合饲料(粗蛋白含量为42.98%)。通过7周的试验,结果表明,投喂频率为1～4次·d-1时,随着投喂频率的增加,对虾增重率显著增加;投喂频率由4次·d-1增加到5次·d-1时,对虾增重率略有增加,但差异不显著。凡纳滨对虾的成活率在1次·d-1时最低,2次·d-1时最高,2～5次·d-1时随着投喂频率的增加而降低(投喂频率为1和2次·d-1之间、3和4次·d-1之间差异显著)。投喂频率为3次·d-1时饲料系数最低,蛋白质效率最高。随着投喂频率1～3次·d-1增加,饲料系数逐渐显著降低,蛋白质效率显著递增;而投喂频率从3～5次·d-1增加时,饲料系数增大,蛋白质效率逐渐下降(3和4次·d-1差异显著;4和5次·d-1之间差异不显著)。投喂频率对水环境中的pH值、H2S含量、COD、盐度等水质指标没有显著影响;在养殖后期水环境中投喂频率3～5次·d-1的NH 4和NO-2浓度较投喂频率1～2次·d-1时高。     

人工养殖陆封型大西洋鲑的生物学特性

2000年3月从美国缅因州格兰特湖(Grant Lake)引进陆封型大西洋鲑(Salmo salar)发眼卵,从孵出仔鱼开始,在人工养殖条件下,采用实验生态学方法,观察其形态特征、年龄、生长、食性、性腺发育、繁殖生态等生物学特性,研究其生长发育所需条件,分析养殖环境因子对其生长发育及繁殖生理的影响。结果表明,陆封型大西洋鲑3龄组体重(W)与叉长(L)相关方程为W=0．0131L^09949;可完全投喂用人工颗粒饲料;在淡水中饲养3年(11783度日)性腺可发育成熟。统计980尾性成熟雌鱼的产卵率可达98％以上,成熟个体平均相对怀卵量为1885粒／kg体重。成熟雄性精子数量为200亿／mL,人工繁殖时雌雄比为2：1,受精率75％～92％。     

Influence of river flow on rod catch of Atlantic salmon, Salmo salar L., from the lower River Derwent, north-west England

Abstract Twenty-seven years of daily salmon, Salmo salar L., rod catch and flow data from the River Derwent were analysed. Daily catch was standardized for each month between June and October and the mean value determined for each 2-cumec flow band. In June and July the mean standardized catch remained relatively low and stable for flows up to approximately 9 cumecs. Thereafter it increased steadily with increasing flow, reaching a peak at 21 cumecs and 41 cumecs for each month respectively. A linear model accounted for the greatest proportion of the variability in August and September with mean standardized catch increasing steadily up to a maximum value of 43 and 39 cumecs respectively. However, in October, a quadratic model was more appropriate, with mean standardized catch decreasing as flow increased up to 9 cumecs and thereafter increasing steadily with flow, reaching a maximum value at 21 cumecs. The pattern of the relationship at higher flows was not clear because of the paucity of data. These findings are discussed in relation to the management of the water resource for the maintenance of the fishery.     

Comparative feeding, growth and movements of Atlantic salmon (Salmo salar) parr from riverine and estuarine environments

Abstract– The diet composition, movcments and growth of Atlantic salmon parr rearing in the estuary of Western Arm Brook, Newfoundland were compared with those of parr from riverine habitats over 2 years. Estuarine parr consumed a variety of prey, including many freshwater taxa (mainly insects), which indicated a dependence on freshwater drift from the river. Prey of estuarine origin (amphipods and sticklebacks) were increasingly consumed between spring and autumn. Prey volume per fish and number of prey per fish increased significantly for estuarine parr between spring and autumn, suggesting an improvement in food availability. Riverine parr, however, realized a general decrease in both parameters between spring and autumn. The recapture of 16% ( n = 131) of the 829 parr marked in the estuary in 1987 and 1988 indicated a directed movement toward the head of the estuary and river mouth, as also suggested by the diet analysis. Parr from outer estuary sites were very mobile compared with parr from the estuary site closest to the river mouth, which behaved more like parr in the river proper in displaying strong site fidelity. Movement patterns of parr were primarily along the shoreline. Individual growth rates were highly variable in both environments but especially in the estuary. The mean growth of estuarine parr was 0.23 mm. d⁻¹ between May and October with some evidence of fastest growth having occurred in late spring and early summer (approx. 0.4 mm. d⁻¹); mean growth rate of riverine parr was slower, at 0.12 mm. d⁻¹. The results are discussed in the context that estuarine rearing by salmon parr represents an alternative life-history tactic for the species in river systems in eastern Canada.     

The effects of ration size on migration by hatchery‐raised Atlantic salmon (Salmo salar) and brown trout (Salmo trutta)

Abstract – The possibility to increase the proportion of migrating hatchery‐reared smolts by reducing their food ration was studied. Lake‐migrating, hatchery‐reared salmon (Salmo salar) and trout (Salmo trutta) smolts were either fed normal rations, based on recommendations from the fish‐farming industry, or reduced (15–20%) rations. They were released into the River Klarälven, western Sweden, and followed as they swam downstream to Lake Vänern, a distance of around 25 km. For both Atlantic salmon and brown trout, smolts fed a reduced ration migrated faster than fish fed a normal ration. Furthermore, a higher proportion of salmon smolts fed reduced rations migrated to the lake than fish fed normal rations in 2007 but not in 2006. This difference between years corresponded to greater treatment differences in size and smolt status in 2007 than in 2006. For trout, the proportion of migrating individuals and smolt development did not differ with ration size. Trout migrants fed a normal ration had a higher standard metabolic rate (SMR) than nonmigrants, whereas there was no difference in SMR between migrating and nonmigrating salmon. These results show that it is possible to use a reduced food ration to increase the migration speed of both Atlantic salmon and brown trout and to increase the proportion of migrating Atlantic salmon.     

Survival of migrating sea trout (Salmo trutta) and Atlantic salmon (Salmo salar) smolts negotiating weirs in small Danish rivers

Abstract – The survival of brown trout and Atlantic salmon smolts during passage over small weirs was estimated in two small Danish rivers during the spring of 1998. Parallel groups of smolts were released upstream and downstream of the weirs and recaptured in traps further downstream. The results showed a smolt loss varying from 18 to 71% for trout and 53% for salmon. Furthermore, the surviving smolts from the upstream groups were delayed for up to 9 days compared to downstream groups. The study demonstrated that an increased proportion of total river discharge allocated to fish passage increased the smolt survival. Losses may be because of fish penetrating grids erected at fish farm inlets, predation and delays, which may lead to desmoltification. The low survival may seriously threat both the long-term viability of wild populations of anadromous salmonids and the outcome of the intensive stocking programme in Denmark.     

Incidence of hybridization between Atlantic salmon, Salmo salar L., and brown trout, Salmo trutta L., in Ireland

The substantial growth of the farmed salmon industry in Europe since the 1970s has highlighted concerns regarding the genetic impact of escaped farmed salmon on wild salmonid stocks. High incidences of salmon × trout hybrids have been recorded in rivers situated near intensive salmon farming in Norway and Scotland, which may be indicative of a breakdown in reproductive isolation between salmon, Salmo salar L., and brown trout, Salmo trutta L. In the present study, salmonid fry and 0+ parr were collected from rivers in western Ireland. Allozyme and minisatellite DNA analysis were carried out on fry to determine the frequency of F1 hybrids from 10 rivers located within 38 km of salmon farms and three rivers at least 80 km from salmon farms. A total of 49 hybrids were recorded from 4135 salmonid fry (frequency = 1.2%). Mitochondrial DNA analysis showed that all hybrids arose from Atlantic salmon female × brown trout male crosses. Hybrid parr were recorded from one of the low-risk rivers (1.0%), but were present in seven out of the 10 catchments located within 38 km of salmon farms, with frequencies ranging from 0.7% to 3.1%. The results of the present survey, which represents the first extensive record of the levels of salmon-trout hybridization in Ireland, are discussed in relation to the continued growth of salmon farming in this country.     

Timing of spawning in cultured and wild Atlantic salmon (Salmo salar) and brown trout (Salmo trutta) in the River Vosso, Norway

Spawning time and size of wild and nonnative cultured female Atlantic salmon (Salmo salar L.) were studied in the River Vosso, Norway. Cultured immigrants were smaller, and peak spawning occurred 21 and 26 days earlier relative to wild salmon in 1991 and 1992, respectively. It was calculated that hatching and initial feeding of offspring of cultured females peaked 12 and 9 days earlier in spring 1992 and 19 and 8 days earlier in spring 1993 relative to offspring of wild females. Spawning time of the cultured salmon is similar to most Norwegian salmon populations and to cultured fish in other streams. In the River Vosso it also overlaps with that of brown trout (Salmo trutta L.), which may increase hybridization. The early time of breeding in nonnative fish indicates local adaptation in this trait in wild salmon. The consequences of early breeding of cultured fish are unpredictable in relation to spring temperatures but probably reduce their relative breeding success. The smaller size may also reduce the success of cultured females.     

Retention of the synthetic antioxidant butylated hydroxyanisole in Atlantic salmon (Salmo salar) fillets

Butylated hydroxyanisole (BHA) is a phenolic antioxidant that is used as a food additive, particularly in fats and oils, and it is also authorized as a feed additive in the European Union for all animal species with a maximum concentration of 150 mg kg^?1 feed (alone or in combination with ethoxyquin and/or butylated hydroxytoluene). Information on the BHA levels in food of animal origin is scarce, as is literature on the transfer of BHA from feed to animal products. Consequently, the current feeding trial was conducted under realistic rearing conditions to determine the retention of BHA in Atlantic salmon (Salmo salar) fillets. Four different concentrations of BHA in feed were tested (0, 48.5, 92.5 and 225 mg BHA kg^?1 feed), and fish were sampled after 4, 8 and 12 weeks dietary exposure, and after a 2‐week starvation period, which is representative of commercial salmon farming in Norway. The levels of BHA in salmon fillets were fairly dose dependent during the feeding period. A steady state in fillet residues was reached after 4 weeks of administration of BHA. After the 2‐week withdrawal period, BHA was not detectable (<7 μg kg^?1) in either fish fillets or livers.     

Iron status and dietary levels of iron affect the bioavailability of haem and nonhaem iron in Atlantic salmon Salmo salar

The absorption of haem iron and nonhaem iron in 155-g Atlantic salmon Salmo salar was studied by simultaneous labelling of the two forms of iron with ⁵⁹Fe or ⁵⁵Fe, respectively. Iron absorption was measured after incorporation of this element into blood and tissue 2 days after oral administration. Fish with a low iron status showed a significantly greater absorption of both haem and nonhaem iron than iron-loaded fish. The low-iron group distributed a larger proportion of the iron to kidney and spleen than the iron-loaded or control fish. Absorption of both forms of iron increased with higher doses administered, but absorption relative to dose administered decreased. There was a trend suggesting that increased levels of dietary haem iron resulted in the reduced uptake of nonhaem iron, but not vice versa . The results of the present study suggest that factors affecting bioavailability of haem and nonhaem iron in Atlantic salmon are similar to those of other vertebrates.