瓦氏黄颡鱼幼鱼标准代谢的初步研究

研究了平均体质量为6.231、1.32 g和21.21 g瓦氏黄颡鱼幼鱼的标准代谢,并分析了幼鱼利用蛋白质、脂肪和糖类作为能源物的供能情况。通过测定幼鱼在禁食和静息状态下的耗氧率、排氨率和二氧化碳排出率,计算出幼鱼的呼吸熵、氧氮比和能耗率。试验结果表明,瓦氏黄颡鱼幼鱼的耗氧率、排氨率和能耗率均随幼鱼体质量的增加而显著下降(P<0.01),且耗氧率、排氨率和能耗率与体质量呈负相关关系,而呼吸熵与体质量则呈正相关关系。不同体质量幼鱼的二氧化碳排出率和氧氮比差异不显著;根据氧氮比的分析结果可知,瓦氏黄颡鱼幼鱼主要利用脂肪和蛋白质供能,且随着体质量的增长,脂肪供能的比例逐渐增大。结果显示,瓦氏黄颡鱼幼鱼对糖类的利用能力较为有限,有必要对该鱼的糖需求和利用率进行进一步的研究。     

低氧胁迫对鲻幼鱼生长、能量代谢和氧化应激的影响

为研究低氧胁迫对鲻幼鱼生长、能量代谢和氧化应激的影响,实验将其放在溶解氧(DO,mean±SE)含量分别控制在(1.66±0.41)、(4.35±0.53)、(7.03±0.36)mg/L的条件下养殖10 d,然后恢复至接近饱和溶解氧含量7.0 mg/L的条件下养殖30 d,研究其特定生长率、排氨率、耗氧率、氧氮比和血浆、肌肉、肝脏及鳃组织的总抗氧化能力(T-AOC)、过氧化物歧化酶(SOD)活力、抗超氧阴离子活力(ASOR)、丙二醛(MDA)含量、乳酸(LD)含量、总谷胱甘肽(T-GSH)、还原型谷胱甘肽(GSH)和氧化型谷胱甘肽(GSSG)含量。结果表明:低氧胁迫对鲻幼鱼的生长、能量代谢影响显著,较严重缺氧组鲻的体质量、特定生长率(SGR)、耗氧率和排氨率显著低于其他处理,不具有补偿生长的能力;而轻微缺氧组获得完全补偿生长。低氧胁迫对鲻氧化应激指标影响显著,胁迫结束时鲻通过提高某些抗氧化酶的活力来增强抗氧化能力,以提高其应对恢复正常溶解氧环境可能带来的氧化应激的能力,同时在恢复溶氧后鲻氧化应激反应也较强烈。在恢复溶解氧阶段,肝脏中GSH显著增加,说明鲻体内的保护机制被激活。肝脏和鳃中MDA的含量在低氧胁迫后与溶解氧含量呈明显的负相关性,在复氧30 d后仍然高于对照组,表明低氧胁迫加强鲻肝脏和鳃组织脂质过氧化反应。     

Effect of dietary protein and lipid level on metabolic utilization of diets by european sea bass (Dicentrarchus labrax) juveniles

Two trials were performed with sea bass juveniles to study the effect of dietary protein (trial I) and lipid (trial II) levels on the metabolic utilization of diets at 25 °C. The effect of water temperature (18 and 25 °C) on metabolism was also tested in trial I. For that purpose, oxygen consumption and ammonia excretion were measured both in fed and in 9-days starved fish. In trial I, diets were formulated to be isoenergetic (GE: 19.4 kJ g^–1) and to have 36, 42, 48 and 56% protein; in trial II, diets were formulated to be isonitrogenous (48% protein) and to have 12, 18, 24 and 30% lipid. In trial I, feed intake (g kg^–1 day^–1), and daily ammonia excretion and oxygen consumption significantly increased with water temperature. However, when expressed relatively to intake there was no significant effect of temperature on ammonia excretion (% N intake) or heat production (% GE intake). Heat increment of feeding (% GE intake) was neither affected by diet composition nor by water temperature. The relative contribution of protein catabolism to total energy expenditure significantly increased with dietary protein level, but was not affected by water temperature. In trial II, both daily ammonia excretion and oxygen consumption were inversely correlated to dietary lipid levels. Nitrogen excretion, heat production, heat increment of feeding, non-fecal losses (% intake) and the relative contribution of protein to total energy expenditure were also inversely related to dietary lipid levels. Results of this study indicate that the main effect of water temperature was to modify feed intake, not the metabolic utilization of diets. Indeed, expressed relatively to nitrogen or energy intakes, both nitrogen and energy budgets were not significantly affected by water temperature. A decrease of dietary protein to energy ratio, by modifying either dietary protein or lipid levels, spared protein utilization for metabolism, and this effect was essentially due to a decrease of non-fecal nitrogen excretion and of the heat increment of feeding.     

Energy balance of juvenile <Emphasis Type="Italic">Cyprinus carpio</Emphasis> after a short-term exposure to sublethal water-borne cadmium

Stress in fish can be assessed by means of a bioenergetic approach, based on the evaluation of changes in their physiological parameters. The objective of this study was to determine the impact of sublethal water-borne cadmium (Cd) on the energetic balance of juvenile Cyprinus carpio under laboratory conditions after a short-term exposure. Fish were exposed to a concentration of Cd (0.15 mg Cd l⁻¹) for 2 weeks. This concentration is environmentally realistic since it is usually found, even at higher values, in heavily polluted periurban water bodies of Argentina. No mortality was recorded among the animals used in the experiments. Food intake, food assimilation and assimilation efficiency, fecal production, liver glycogen content, oxygen consumption, oxygen extraction efficiency, specific metabolic rate, ammonia excretion and ammonia quotient (AQ), condition factor, and liver somatic index were determined. The overall balance was expressed as the scope for growth (SFG). The morphological indices and the liver glycogen content of Cd-exposed fish showed no significant differences when compared to those of controls. There was a significant decrease in the food intake, fecal production, and food assimilation rates as well as in AQ; the SFG exhibited a highly significant decrease. The remaining parameters (assimilation efficiency, oxygen consumption, oxygen extraction efficiency, specific metabolic rate, and ammonia excretion) increased after the exposure to Cd. We concluded that the sub-chronic exposure of Cyprinus carpio to a sublethal concentration of Cd causes important alterations in the energy-related homeostasis of fish. Most of the responses are indicative of physiological adaptations to compensate an increased energy requirement due to the impairments caused by the metal.     

Energy partitioning in cultured juvenile Pacific bluefin tuna,Thunnus orientalis (Temminck & Schlegel, 1844)

The characteristics of dietary utilization, energy conversion efficiency, metabolic rate and energy partitioning were measured for cultured Pacific bluefin tuna (PBT) juveniles fed on an artificial diet. Thirty‐one juveniles (1.1 ± 0.3 g BW) were stocked into each of two 2500 L tanks to measure oxygen consumption (?O₂), swimming speed, digestibility and growth performance. ?O₂ elevated until 2.5 ± 0.3 times of pre‐feeding level within 1.5 h after feeding, except for the first feeding, and returned to pre‐feeding level within 3 h. Swimming speed fluctuation was corresponded with the ?O₂ fluctuation, and both parameters were stable from 02:00 to 06:00 and also during the whole day for starved fish. These indicate that feeding has strong influence on their metabolic rate. Energy partitioning for faecal, urinary and branchial, heat increment and voluntary activity, standard metabolism, and retained energy were calculated to be 17.2%, 5.9%, 14.9%, 41.3% and 20.7% of total ingested energy, respectively. The results indicate that, unlike other fish, juvenile PBT distribute large amount of energy for maintenance, which allows only a little proportion of ingested energy available for growth.     

温度对黄金鲈(Perca flavescens)耗氧率和排氨率的影响

在不同水温(15、20、25和30℃)下,对体重(46.1±4.5)g黄金鲈(Perca flavescens)的耗氧率和排氨率进行了测定与分析。结果显示:黄金鲈的耗氧率和排氨率均随温度的升高而显著增加(P<0.01);耗氧率和排氨率与温度的关系可用指数方程拟合,其方程分别为:RO=0.0682 e0.0633t,R2=0.9879;RN=2.4593 e0.0904t,R2=0.9703;随着温度的升高氧氮比(O:N)逐渐降低;耗氧Q10值和排氨Q10值均在20~25℃之间最小。结果表明:在各温度水平下黄金鲈基础代谢消耗底物主要均以蛋白质为主,脂肪其次,然而随着温度的升高,黄金鲈利用糖类和脂肪供能的比例逐渐下降,而蛋白质供能的比例逐渐增加。黄金鲈的最适生长温度为20~25℃。     

温度对三疣梭子蟹呼吸代谢及其相关酶活力的影响

为研究温度对三疣梭子蟹Portunus trituberculatus呼吸代谢的影响,以三疣梭子蟹幼蟹(1.17±0.03)g和成蟹(57.57±1.16)g为实验材料,设5个实验温度水平(15、18、21、24、27℃),测定其在不同温度下的耗氧率和排氨率以及成蟹肝胰脏和肌肉组织中的丙酮酸激酶(PK)、己糖激酶(HK)和琥珀酸脱氢酶(SDH)的活力。实验结果显示,三疣梭子蟹耗氧率和排氨率均随温度的升高而升高。幼蟹耗氧率在各个温度水平下差异显著(P0.05),成蟹耗氧率仅在15-18℃与21-27℃之间差异显著(P0.05);幼蟹和成蟹排氨率在15-18℃与21-27℃之间差异显著(P0.05)。幼蟹和成蟹的氧氮比随温度的升高总体呈下降趋势,其氧氮比范围为1.38-3.02,表明三疣梭子蟹以蛋白质为主要代谢能源物质。随实验温度升高,成蟹肝胰脏中的PK活力呈上升趋势,而成蟹肌肉组织中的PK和HK的活力则随温度升高总体呈下降趋势。温度对三疣梭子蟹肝胰脏组织中SDH的活力影响显著(P0.05),SDH的活力随温度的升高呈上升趋势,在27℃时达到最大值。综上所述,无氧代谢方面,随实验温度的升高,三疣梭子蟹成蟹肝胰脏组织的糖酵解速率增大,肌肉组织对葡萄糖的利用能力下降;有氧代谢方面,成蟹肝胰脏SDH活力随实验温度的升高而升高,一定程度上反应了三疣梭子蟹在高温环境下有氧代谢加强。     

流速对鲫游泳行为和能量消耗影响的研究

通过自制的鱼类游泳试验装置,研究了流速对鲫（Carassius auratus）游泳行为和能量消耗的影响。结果表明,鲫的摆尾频率、摆尾幅度随游泳速度变化有明显的规律。随着游泳速度的增加,鲫的摆尾频率与幅度都相应地增加。流速小于3倍体长/s与大于3倍体长/s,摆尾频率差异性显著（P〈0.05）,而摆尾幅度差异性不明显。鲫单位时间耗氧率随着流速的增加而显著增加,并且随着速度的增加,鲫用于游泳所消耗的能量占总能量消耗逐渐趋于稳定,运动净耗氧率最大为90%。水温（16±1）℃时,体长12～20cm鲫的相对极限流速为其（3.85±1.10）倍体长/s,绝对极限流速为（0.66±0.10）m/s;相同流速的温度环境中,随着体重的增加,耗氧量呈增加趋势。在相同的流速下,水温（10±1）℃时的游泳耗氧量小于（16±1）℃,而净耗氧率较大;温度（16±1）℃时,2.5倍体长/s的游泳速度有利于鲫生长代谢的能量积累。     

Effects of swimming speed and dissolved oxygen on geosmin depuration from market-size Atlantic salmon Salmo salar

Common off-flavor compounds, including geosmin (GSM) and 2-methylisoborneol (MIB), bioaccumulate in Atlantic salmon Salmo salar cultured in recirculating aquaculture systems (RAS) resulting in earthy and musty taints that are unacceptable to consumers. To remediate off-flavor from market-ready salmon, RAS facilities generally relocate fish to separate finishing systems where feed is withheld and makeup water with very low to nondetectable GSM and MIB levels is rapidly exchanged, a process known as depuration. Several procedural aspects that affect salmon metabolism and the associated rate of off-flavor elimination, however, have not been fully evaluated. To this end, a study was carried out to assess the effects of swimming speed and dissolved oxygen (DO) concentration on GSM levels in water and fish flesh during a 10-day depuration period. Atlantic salmon (5–8 kg) originally cultured in a semi-commercial-scale RAS (150 m³ tank) were exposed to a concentrated GSM bath before being transferred to 12 replicated partial reuse depuration systems (5.4 m³ total volume). Two swimming speeds (0.3 and 0.6 body lengths/sec) and two DO levels (90% and 100% O₂ saturation) were applied using a 2 × 2 factorial design (N = 3), and each system was operated with a 5-h hydraulic retention time, creating a water flushing to biomass ratio of 151 L/kg fish biomass/day. Geosmin was assessed at Days 0, 3, 6, and 10 in system water and salmon flesh. A borderline effect (P = 0.064; 0.068) of swimming speed was measured for water and fish, respectively, at Day 3, where slightly lower GSM was associated with low swimming speed (0.3 body lengths/sec); however, differences were not detected at Days 6 or 10 when salmon are commonly removed for slaughter. Overall, this research indicates that significant improvements in GSM depuration from RAS-produced Atlantic salmon are not expected when purging with swimming speeds and DO concentrations similar to those tested during this trial.     

体重对青海湖裸鲤排氨率和排氨量的影响

为了解体重对青海湖裸鲤(Gymnocypris przewalskii)排氨率和排氨量的影响,在21℃左右的水温下,结合对青海湖裸鲤耗氧率和呼吸频率的测定,采用酚盐分光光度法测定并研究了不同体重下青海湖裸鲤的排氨量、排氨率。结果表明:不同体重的青海湖裸鲤在基础呼吸代谢过程中其排氨量方面有极显著的差异(P<0.01)。青海湖裸鲤的排氨量随着体重的增加而增加,呈幂指数关系。不同体重的青海湖裸鲤的排氨率等也有显著差异(P<0.01),随着体重的增加排氨率相对降低。     

Starvation resistance and metabolic response to food deprivation and recovery feeding in Fenneropenaeus chinensis juveniles

Starvation resistance in the juveniles of Chinese shrimp, Fenneropenaeus chinensis Osbeck, was studied by point-of-no-return (PNR) and point-of-reserve-saturation (PRS) experiments. Changes in oxygen consumption rate, ammonia-N excretion rate, and oxygen consumed to nitrogen excreted (O:N) ratio were investigated immediately before and after the period of recovery feeding for each regime to assess metabolic response during starvation and refeeding. There was a significant change in survival rate and wet weight of test shrimp throughout the PNR and PRS experiments (P < 0.05). The estimated PNR and PRS for F. chinensis juveniles could be directly calculated from the selected equations as PNR₅₀ = 7.86 days, PNR₁₀₀ = 21.42 days, PRS₀ = 1.16 days, and PRS₅₀ = 11.75 days. A decrease in metabolic rate during starvation as a means of conserving energy was found in F. chinensis juveniles. Furthermore, although F. chinensis juveniles only utilized protein as an energy source during starvation, they showed a shift from pure protein during starvation to an equal utilization of protein and lipid or a lipid-carbohydrate mixture during later satiate feeding. The results in the present study indicate that F. chinensis juveniles have the ability to withstand and recover from relatively prolonged starvation after longer initial feeding periods. The knowledge derived from the understanding of starvation resistance and the corresponding metabolic response of F. chinensis juveniles will be useful in the design of feeding regimes in this species.     

鲢幼鱼运动能量代谢研究

可靠的能量消耗估算可以更好地衡量鱼体在上溯过程中的能量分配方式,为鱼道水力设计提供依据,实现鱼道过鱼的高通过率。为探究鲢(Hypophthalmichthys molitrix)幼鱼运动过程中游泳行为和能量消耗的关系,利用丹麦Loligo Systems公司生产的鱼类行为视频跟踪系统,对24尾鲢幼鱼进行了室内游泳行为实验。采用流速递增法测得鲢幼鱼的活动代谢率,水体溶氧量由每个流速工况下等时距读取,静水条件下通过AutoRespTM测定水体溶氧变化值,计算标准代谢率;利用水槽上方架设的摄像头(25帧/s)记录鱼体运动行为,连接uEye Cockpit程序观测鱼体运动情况,采用LoliTrack进行运动行为分析,获取鱼体运动行为学参数。结果表明,鲢幼鱼的游泳速度与摆尾频率(TBF)呈显著正相关关系,其耗氧率(MO2)与摆尾频率(TBF)的拟合方程为MO2=318.3+1.04TBF2.87(R2=0.99,P0.001),拟合指数值为2.87,且摆尾频率的幂指数越大,表征鱼体游泳效率越低。实验测得鲢幼鱼的标准代谢率(SMR)为(284.47±30.75)mg/(kg·h),耗氧率方程得到的标准代谢率拟合值为318.3mg/(kg·h),与实测值较为接近;通过建立活动代谢率(AMR)与鱼体重量(M)及游速(U)的关系,得出鲢幼鱼生物能量模型AMR=10.39 M0.12 U0.39(R2=0.95,P0.001)。生物能量模型的建立,可以为鱼道不同过鱼目标的水力设计提供参考。     

溶氧水平对黄颡鱼稚鱼摄食、生长及呼吸代谢的影响

在(28±0.5)℃循环水环境中设置4种溶氧水平,分别为2.92 mg/L(G1组)、4.71 mg/L(G2组)、6.77 mg/L(G3组)、9.68 mg/L(G4组),研究初始体重为(1.62±0.02)g的黄颡鱼(Pelteobagrus fulvidracoR.)稚鱼的生长、摄食及呼吸代谢规律。结果显示:G3组特定生长率(SGR)、饲料效率(FE)均显著高于其它各试验组(P<0.05)。试验鱼的耗氧率、排氨率与溶氧水平无正相关性,G3组的耗氧率、排氨率始终显著高于其它三组。第6周测定发现:摄食后1~4 h内耗氧率和排氨率均呈现迅速上升,到达最大值后再缓慢下降,二者均在09∶00和21∶00出现高峰,G3组的耗氧率高峰值分别为0.345、0.331 mg/g.h,G3组的排氨率高峰值分别为24.194、17.770μg/g.h。结果表明:不同溶氧条件下,黄颡鱼稚鱼的耗氧率、排氨率变化过程具有类似的特征,二者在能量代谢机制上相互关联;在6.77 mg/L的溶氧水平下,黄颡鱼稚鱼生长最快、呼吸代谢最为旺盛。     

Proteolytic enzymes in fish development and the importance of dietary enzymes

The development of proteolytic enzymes (trypsin, chymotrypsin and aminopeptidase) was studied in three species of fish: Coregonus sp. (hybrids of C. wartmanni and C. lavaretus from Lake Constance), Salmo gairdneri and Rutilus rutilus. Enzyme activity increased more or less with increasing age, particularly in R. rutilus. In this species (a stomachless cyprinid), the level of proteolytic activity was considerably higher than that of S. gairdneri and Coregonus. However, in trout, the low activity of pancreatic enzymes may be compensated by the action of the stomach whereas in coregonids the stomach is not developed until 50 days (body weight without gut content: 65 mg; temperature: 10°C) after hatching. In coregonids this may lead to insufficient digestion of proteins which nevertheless can be compensated by the use of exogenous (dietary) enzymes ingested together with the natural diet. In coregonid larvae fed with Moina sp., exogenous trypsin represents a very high portion of the total tryptic activity. In juveniles older than 60 days (> 150 mg) and in the other two species, the exogenous portion of tryptic activity is less important. Furthermore, a change in the pattern of tryptic isozymes has been found during development of coregonids. It is concluded that low enzyme production as well as the absence of a stomach in the first few weeks after hatching are two important reasons for difficulties in rearing coregonids on an artificial diet.     

Feeding and growth of exercised and unexercised juvenile Atlantic salmon in freshwater,and performance after transfer to seawater

Juvenile Atlantic salmon (Salmo salar), selected from the upper modal group, were first held for 122 days (from December to May) in freshwater, and then for 49 days in seawater (34% salinity). In freshwater, the fish were exposed to either standing water or water currents corresponding to a swimming speed of 1 Bl s^–1. Natural light conditions prevailed throughout the whole experiment.In the freshwater phase, food intake, growth rate and condition factor of the fish increased with increasing daylength. Condition factors, however, decreased slightly during the last month of the freshwater period, suggesting that the fish underwent parr-smolt transformation. The growth rate and food intake of the fish subjected to standing water were approximately 15% lower than those of fish exposed to water currents.Transient suppression of appetite and growth, and an increase in plasma concentration of Cl^–, were seen after exposure of the fish to seawater. Within 28 days, all these parameters had been restored to pre-transfer levels. Previous exercise did not appear to have influenced the hypoosmoregulatory capacity of the fish. Growth rate and food intake observed during the seawater phase were similar, irrespective of the treatment experienced by the fish during freshwater rearing.     

Modelling oxygen consumption rates of post-smolt Atlantic salmon in commercial-scale,land-based farms

Oxygen consumption rates of post-smolt Atlantic salmon (Salmo salar L.) were recorded during various growth trials at four land-based salmon farms in south-west Norway, during the period 1988–1992. Principle component analysis indicated that fish size, water temperature and current speed had the greatest influence on oxygen consumption of fish in all the farms. A multiple regression analysis showed that 70% of the variation in the oxygen consumption could be explained by these three parameters. The predicted effect of fish size, water temperature and current speed on oxygen consumption are consistent with those reported in studies conducted on salmonids held in tunnel respirometers. The model described in this study may be a useful tool for the estimation of oxygen and water requirements needed for the design and operation of land-based farms.     

The impact of varying feeding regimes on oxygen consumption and excretion of carbon dioxide and nitrogen in post-smolt Atlantic salmon Salmo salar L.

Oxygen consumption, carbon dioxide excretion and nitrogen excretion from 2 kg Atlantic salmon Salmo salar L. were studied at land-based outdoor tanks, throughout a 10 day period. Fish were fed six feed rations (0 [fasting fish], 0.15, 0.30, 0.45, 0.60 and 0.75% BW day^-1) of commercially extruded dry feed at two provision regimes: between 07.00-09.00 h and 19.00–21.00 h (periodic feeding); and between 07.00-21.00 h (continuous feeding). Fish were acclimatized to the feeding regime for 5 days prior to the start of the experiment. From days 5 to 10 of the study, oxygen consumption was measured automatically every 15 min. During day 10, carbon dioxide excretion, ammonia and urea excretion were measured hourly throughout a 24 h period. During the experiment, the water temperature and salinity were 8.5C and 33.5 ppt, respectively. Significant linear relationships between feed ration and metabolic rates were evident. Increased feed ration influenced oxygen consumption, carbon dioxide excretion, ammonia and urea excretion, ammonia quotient and the respiration quotient, proportionally. The two feed provision regimes caused the establishment of different daily rhythms in metabolic excretion. Only small differences in total daily excretion were however recorded for each feed ration. Ammonia and respiratory quotient results clearly showed that fish became more dependent on fat oxidation as an energy source, when feed was restricted.     

盐度对三疣梭子蟹成熟前后呼吸代谢的影响

为了探讨三疣梭子蟹对不同盐度水平的生理响应以及成熟前后的生理变化,实验采用水化学和酶学方法,研究了盐度(15、20、25、30和35)对成熟前后三疣梭子蟹耗氧率、排氨率、氧氮比(O∶N)以及己糖激酶(HK)、丙酮酸激酶(PK)、琥珀酸脱氢酶(SDH)和乳酸脱氢酶(LDH)4种呼吸代谢酶活力的影响。结果发现:1.盐度与规格的交互作用对三疣梭子蟹呼吸代谢无显著影响(P>0.05);2.盐度对三疣梭子蟹耗氧率的影响不显著(P>0.05),但显著影响其排氨率(P<0.05);成熟前后的三疣梭子蟹耗氧率和排氨率差异显著(P<0.05);3.盐度对三疣梭子蟹O∶N未产生显著影响(P>0.05),三疣梭子蟹成熟前O∶N显著高于成熟后(P<0.05);4.除LDH外,盐度对三疣梭子蟹呼吸代谢酶活力影响不显著(P>0.05);除鳃中SDH和LDH外,三疣梭子蟹呼吸代谢酶活力随生长发育发生显著变化(P<0.05)。研究表明,规格对三疣梭子蟹呼吸代谢的影响高于盐度,长时间盐度驯化可能减弱甚至消除三疣梭子蟹在不同盐度水平下代谢的差异。     

Ammonia nitrogen excretion in Mandarin Fish (Siniperca chuatsi) and Grass Carp (Ctenopharyngodon idellus) fed practical diets: the effects of water temperature

To understand the actual production of fish culture about the utilization of dietary protein and excreta impact on the environment between mandarin fish (Siniperca chuatsi) and grass carp (Ctenopharyngodon idellus), the study to investigate the effect of temperatures (19 ± 0.5°C, 24 ± 0.5°C and 29 ± 0.5°C) on ammonia‐N excretion in mandarin fish and grass carp under fed and fasted states was conducted. These two species were fed a practical diet containing 325.2 g kg^?1 crude protein at 3% body weight per day. The ammonia‐N excretion rate was significantly increased when temperature increased from 19 to 29°C, and a linear relationship between ammonia‐N excretion rate and temperature. The maximum ammonia‐N excretion levels of mandarin fish and grass carp were observed at 4–8 h and 2–4 h after feeding, respectively, and the minimum values for both species were observed at 24 h after feeding. Under the feeding condition, mandarin fish had a lower ammonia‐N excretion level compared to grass carp at 24°C and 29°C. The average amount of ammonia‐N excreted by mandarin fish at 24 h is significantly higher than grass carp under fasting conditions, except 19 ± 0.5°C. These results indicated that mandarin fish might make better use of protein at higher temperature than grass carp when fed practical diets in commercial production. These results of this study suggested that mandarin fish had a lower ammonia‐N excretion level compared with grass carp, making a less contribution to environmental loading in an intensive fish culture.     

温度对斑点叉尾[鱼回]幼鱼耗氧率和氨氮排泄率的影响

采用封闭流水式装置,研究斑点叉尾[鱼回]幼鱼(Ictalurus Punctatus)(约9~11 g)在不同温度条件下(18,22和26℃)的耗氧率和氨氮排泄率变化情况。结果表明,在18,22和26℃时斑点叉尾[鱼回]幼鱼的耗氧率分别为(171.66±33)mg/(kg·h),(97.22±26)mg/(kg·h)和(171.83±44)mg/(kg·h),26℃处理组的耗氧率最高,与22℃处理组具显著差异(P<0.05);氨氮排泄率也表现出随水温的升高而升高的趋势,18,22和26℃时其氨氮排泄率分别为(0.40±0.01)mg/(g·h),(0.44±0.01)mg/(g·h)和(0.58±0.01)mg/(g·h)。在22~26℃,斑点叉尾[鱼回]幼鱼的耗氧率和氨氮排泄率均随温度升高而升高。