Growth rate,catalase and superoxide dismutase activities in rock carp(Procypris rabaudi Tchang) exposed to supersaturated total dissolved gas

Total dissolved gas supersaturation(TDGS) appears when the pressures of gases in a solution exceed the barometric pressures.TDGS is often caused by flood discharge at dams.It may lead to gas bubble disease(GBD) for fish and biochemical responses of selected fish and other aquatic organisms.The purpose of this study was to determine the impact of long-term TDGS levels on the growth and biochemical responses of rock carp(Procypris rabaudi Tchang) dwelling in the upper reaches of the Yangtze River.Three-year-old rock carp were exposed to TDGS levels at 100%,104%,108%,112%,and 116% for 42 d.Samples were taken every 7 d after the start of the trial in order to determine catalase(CAT) and superoxide dismutase(SOD) activities in gill and muscle tissues.Samples were taken at Days 0 and 42 of exposure to determine growth rate.Little effect was found on growth rate in all treatment groups.SOD and CAT activities varied in different tissues,according to time of exposure and TDGS levels.The biochemical response of fish exposed to TDGS was more obvious in gill tissue than in muscle tissue.Surveys of SOD and CAT activities in different tissues offer important information about the effect of TDGS on the rare fish in the Yangtze River,and may help evaluate the risk to the aquatic eco-environment and aquatic ecosystem in the downstream of the Yangtze River.

Effects of gas supersaturation on lethality and avoidance responses in juvenile rock carp(Procypris rabaudi Tchang)

Laboratory experiments were conducted to determine the effects of total dissolved gas （TDG） supersaturation on acute lethality and avoidance responses in juvenile rock carp （Procypris rabaudi Tchang）. The juvenile rock carp were exposed to water with different levels of supersaturation （105%, 115%, 120%, 125%, 130%, 135%, 140%, and 145%） and depth of 0.20 m at 25℃ for 60 h. Median lethal time （LT50） was used to assess the lethal responses corresponding to different levels of gas supersaturation. The results show that half of the juvenile rock carp died at the 120%, 125%, 130%, 135%, 140%, and 145% levels of supersaturation, and the LT50 corresponding to different levels of supersaturation was 18.7, 15.4, 8.2, 6.6, 3.5, and 1.7 h. When the level of supersaturated water is below 115%, the mortality is negligible. Avoidance responses were observed 5 min after the fish were put into equilibrated water （99%, 0.08 m deep） and water with different supersaturated levels （105%, 115%, 125%, 135%, and 145%, 0.08 m deep） at 25 ℃. The fish exhibited strong avoidance responses in supersaturated water when the gas supersaturation was above 135%. However, they exhibited an obvious preference to supersaturated water when the gas supersaturation was below 115%. Thus, the juvenile rock carp can likely survive in water with a supersaturated level of 115%.

岩原鲤幼鱼的蛋白质需求量

本试验旨在确定岩原鲤幼鱼的蛋白质需求量。试验选用均重为(7.93±0.16)g的岩原鲤幼鱼540尾,随机分成6个组(每组3个重复,每个重复30尾),饲喂以明胶和酪蛋白为蛋白质源的蛋白质水平分别为25.1%、30.3%、34.8%、40.4%、44.8%、49.7%的纯化试验饲料98 d。结果表明:岩原鲤幼鱼的生长性能指标(增重率、特定生长率、饲料系数、肌肉RNA/DNA)、抗氧化指标[总抗氧化能力(T-AOC)、超氧化物歧化酶(SOD)活性、丙二醛(MDA)含量]及肝功能指标[谷草转氨酶(GOT)、谷丙转氨酶(GPT)、谷氨酸脱氢酶(GDH)活性及GOT/GPT]均在饲料蛋白质水平为40.4%时达到最佳值,除与饲料蛋白质水平为44.8%时的T-AOC差异不显著(P>0.05)外,与其他各组均有显著差异(P<0.05)。肠道蛋白酶、胰蛋白酶、脂肪酶活性随饲料蛋白质水平的增加呈先升后降的趋势,在40.4%组达到最高值,显著高于其他各组(P<0.05);而淀粉酶活性则反之。在40.4%组,全鱼粗蛋白质含量达最大值,显著高于除44.8%组外的其他各组(P<0.05);粗脂肪含量达最小值,显著低于其他各组(P<0.05);而全鱼水分和粗灰分含量不受饲料蛋白质水平的影响(P>0.05)。以增重率、饲料系数、肌肉RNA/DNA分别为效应指标与饲料蛋白质水平进行回归分析,得出岩原鲤幼鱼的蛋白质需求量为38.57%～40.25%。

短期饥饿和再投喂对岩原鲤仔鱼生存生长以及RNA/DNA和RNA/蛋白质比率的影响(英文)

研究通过对岩原鲤仔鱼在饥饿和再投喂条件下其生存、生长率、RNA/DNA和RNA/蛋白质比率的测定,评估了仔鱼对饥饿的耐受能力和恢复能力。在(19.5±0.5)℃水温下,将岀膜后第16天的岩原鲤仔鱼随机分成6个组:1个持续投饲对照组,实验组分别禁食1、2、3、4、5d后再投喂,实验共进行10d。每天分别从各组取9尾鱼测定体重、体长、RNA、DNA、蛋白质含量。实验结果显示,饥饿处理组仔鱼存活率和以上各项生长指标均随饥饿时间的增加而下降,在恢复投喂后均表现不同程度的补偿生长,其中饥饿1、2、3d的仔鱼在恢复投喂后显示出完全补偿生长,几乎弥补了饥饿所产生的影响,平均终体重与对照组比较无显著差异。饥饿4、5d的仔鱼显示部分补偿生长,恢复投喂只少量减轻了饥饿的影响,平均终体重与对照组相比存在显著差异。饥饿1、2、3d的仔鱼和4、5d的仔鱼在恢复投喂后分别需要1—2d和4d时间才能达到与对照组无显著差异水平。仔鱼生长率变动范围从0.59%到8.00%WW/day,仔鱼RNA/DNA比率、RNA/蛋白质比率与生长率的回归方程为:GR=3.63RNA/DNA 1.74(R2=0.80)和GR=120.14RNA/Protein 2.33(R2=0.31),两种比率均与生长率呈显著线性相关,RNA/DNA比率对生长变化的拟合度更好。结果表明,仔鱼阶段食物缺乏很可能是影响岩原鲤仔鱼存活、生长的主要因素。RNA/DNA更适合作为评定岩原鲤仔鱼营养条件和生长的指标。

鱼类在TDG过饱和含沙水体中的耐受性

为探讨高坝泄洪引起的总溶解气体(TDG)过饱和含沙水体对鱼类的影响,以岩原鲤和鲢鱼为研究对象,开展TDG过饱和含沙水体对不同鱼类的急性暴露试验,根据鱼类受TDG过饱和含沙水体胁迫后的异常行为和死亡率、半致死时间等指标来分析不同鱼类受胁迫后的耐受性和差异性。试验结果表明:试验初期,试验用鱼出现较明显异常行为和气泡病症状,且岩原鲤早于鲢鱼;相同TDG饱和度下,随着含沙量的增加,试验用鱼半致死时间缩短,且岩原鲤半致死时间短于鲢鱼,表明鲢鱼比岩原鲤具有更强的适应能力和耐受能力;当TDG饱和度较高时,即使含沙量低,也会造成试验用鱼的大量死亡;过饱和TDG是导致试验用鱼死亡的主要原因,但不能忽略泥沙对试验用鱼死亡的促进作用。

TDG过饱和高含沙水体对岩原鲤的急性效应研究

大坝泄洪水体具有泥沙浓度高且总溶解气体(Total Dissolved Gas,TDG)过饱和的特点,TDG过饱和含沙水体威胁着下游河道鱼类的生存,正成为日渐突出并日益受到广泛关注的生态环境影响之一。为进一步探讨TDG过饱和含沙水体对鱼类影响的规律,选一年龄岩原鲤幼鱼为实验对象,以中值粒径为7μm的泥沙为实验用沙,对TDG饱和度为100%、125%、130%、135%、140%的水体,分别设置0、200、600、800、1000 mg/L的含沙量实验工况,开展含沙水体TDG过饱和的持续暴露实验。实验结果表明:岩原鲤幼鱼受TDG过饱和含沙水体胁迫时,TDG饱和度越高,含沙量越大,岩原鲤幼鱼半致死时间越小,泥沙加速了该鱼类在过饱和TDG含沙水体中的死亡,但过饱和TDG仍是引起岩原鲤死亡的主要因素。此外,TDG饱和度为100%的各含沙实验组(200~1000 mg/L)中,泥沙单独作用未造成岩原鲤幼鱼死亡。