高坝导致的河流气体过饱和及其对鱼类的影响

高坝泄洪是导致水中气体过饱和的主要因素,不仅能致鱼类气泡病,而且会给水生生物带来严重的危害。本文主要就气体过饱和及气泡病做了具体描述,首先叙述了气体过饱和的研究概况、导致气体过饱和的原因和水温、压强等影响气体过饱和的因素,具体分析了鱼类不同生活阶段、液静压、温度、间歇性的暴露、探知和躲避能力导致其对气体过饱和忍耐大小的状况,并对气泡病的内部损伤如血液中形成的气栓、外部症状如身体各个部位形成的气泡做了具体的描述。     

健康养殖专栏

鱼类气泡病的防治鱼类“气泡病”多发生在多年养殖、塘底淤泥厚的池塘或池水很肥的池塘。在夏秋季,若池水很肥,浮游植物通过光合作用产生大量氧气,下午通常出现溶氧过饱和现象,较小的鱼体吞食了氧气气泡后就容易得气泡病。冬季结冰后,阻断了水体和大气的气体交换,由池底淤泥、残饵、粪便分解产生的甲烷、氨氮和二氧化碳气体,在水中大量富积,此时可看到水底冒出大量的气泡（气体过饱和）,从而使鱼得气泡病。气泡病的预防：最好每年在秋放前清一次淤,将塘泥挖去１５～２０ｃｍ。在夏秋季每１５天用“底净”２５公斤／亩全池均匀泼洒…     

慢性气泡病发生机理及其衍生后遗症的危害

水温形成的养殖水体上下分层非常普遍且明显。晴天上表水层藻类光合作用产生的氧气,与池底有机物处于缺氧还原环境下脱氮产生的氮气,在上下水层不能进行交流的情况下,经常处于过饱和的现象。生存在这样水体的鱼类,不论是在鱼苗阶段还是成鱼阶段,过饱和游离气体将不可避免地进入其体内,使其患上气泡病。相对于鱼苗气泡病的急性发病症状,患上气泡病的成鱼不会有明显症状,称作慢性气泡病。目前由于人们对慢性气泡病产生机理了解不多或存在认识误区,致使气泡病常常成为继发病原性疾病的诱因,也是滥用药的入口。因此,我们应充分认识慢性气泡病发生机理,采取科学有效措施,消除气体过饱和的现象。     

一例新型气泡病病例分析

鱼类气泡病是由养殖水体中溶解的过饱和气体析出气泡引起鱼苗失去游泳能力或失去消化功能,可致鱼苗大量死亡.通过目检、鱼体解剖、显微镜检、水质检测等方式对一起死鱼案例调查,分析了因高压和机械作用产生空气气泡致鱼死亡原因,提出解决方案,为水产养殖场建场和养殖管理提供参考.     

中国对虾气泡病成因机制

中国对虾气泡病成因机制中国科学院海洋研究所虾病专家张乃禹近几年对中国对虾气泡病成因及防治方法进行了研究，张乃禹通过实验，对中国对虾气泡病成因机制研究获得了较理想的结果，他认为，水温突然升高使水中溶解气体过饱和是导致对虾气泡病的必不可少的重要条件，但不...     

总溶解气体过饱和对达氏鲟急性致死效应

为探讨总溶解气体(total dissolved gas,TDG)过饱和对达氏鲟(Acipenser dabryanus)耐受性的影响,选取达氏鲟幼鱼为研究对象,开展不同浓度的TDG过饱和水体急性暴露室内实验。结果表明:达氏鲟受TDG过饱和水体胁迫后,生理异常现象和气泡病症状较明显,表现出对TDG过饱和水体的低耐受性。在饱和度为125%、130%、135%和140%的TDG过饱和水体浓度下半致死时间分别为4.4、2.54、2.36和2.23 h,达氏鲟死亡率随暴露时间和TDG饱和度的增加而增加。     

三峡工程运行后长江中游溶解气体过饱和演变研究

为了分析三峡工程运行后泄洪对长江中游溶解气体过饱和的影响，本文建立了长江中游溶解氧数学模型，对不同流量下长江中游的溶解氧过饱和演变进行了模拟预测。模拟结果表明，三峡和葛洲坝过坝水流的溶解氧饱和度在40000m3/s～50000m3/s和100000m3/s附近存在两个峰值，长江中游河道天然情况下溶解氧过饱和恢复速度较为缓慢，平均每100km降低5%，洞庭湖水的汇入能显著降低长江干流的溶解氧过饱和度。当三峡出库流量超过40000 m3/s时，其影响范围可达400km以上。本文讨论了溶解气体过饱和的不同指标间的关系，对气体过饱和可能造成的影响以及对长江中游鱼类目前的影响进行了阐述，认为通过三峡水库的调度减小出库高流量次数和历时是减缓下游溶解气体过饱和的有效手段。     

融冰期越冬鱼类气泡病及其防治

北方越冬期鱼类在冰下经历一个漫长的冬季，在东北可达四个月之久。覆冰后水体形成一个封闭的系统，冰下水环境也相对稳定。春季一旦覆冰融化，水体环境发生很大变化，特别是融冰阶段，原来溶解在水体中的各种气体快速释放到空气中，总溶解气体压力快速下降，池中鱼类气泡病的发病率很高，春季低温期正适合水霉的继发感染，因此水霉病引起气泡病的死亡率非常高。本文总结了融冰期气泡病的发病原因、症状及防治方法，希望给北方地区越冬管理带来一些帮助。     

鱼类及其它水生动物气泡病

一、水生动物气泡病的研究简况潜水员从深水中被骤然提升到水面,就会因压力突然减少使血液中的溶解气体以气泡状态游离出来,阻塞了血管造成死亡。鱼类也有类似的疾病,称为“气泡病”、“减压病”或“气体栓塞病”。     

虹鳟气泡病的危害与对策

虹鳟气泡病的危害与对策气泡病是一种非病原体引起的鱼病。凡水中某种气体过饱和，均可引起鱼患气泡病，主要危害苗种。虹鳟是一种对溶氧量要求较高的鱼类，最适溶氧量９～１２毫克／升。当水中溶氧量降至５毫克／升时，其呼吸即感困难；夏季，虹鳟的溶氧量致死点为３毫克...     

长薄鳅对过饱和总溶解气体的回避特征研究

高坝泄洪过程中,高速水流造成下游水体的总溶解气体(Total Dissolved Gas,TDG)过饱和极易使得水体中的鱼类患上气泡病,进而对下游水体的鱼类生存造成威胁。为了探究长薄鳅(Leptobotia elongate)幼鱼对TDG过饱和水体的探知回避能力,本实验以2月龄的长薄鳅为研究对象,记录其在不同TDG饱和度水体中的反应和趋向。结果表明,在120%TDG过饱和水体中,长薄鳅回避率为-20%,其对该饱和度下的水体表现出了一定的趋向性;TDG饱和度为130%时,长薄鳅回避率为-2%,无明显回避能力;TDG饱和度为140%时,长薄鳅展现出微弱的回避特征,其在清水与过饱和水体之间往复游动,最终回避率为12%;150%TDG过饱和水体中,长薄鳅体现出敏锐的探知能力,1~2 min后开始频繁游动,同时具有一定的回避能力,回避率为34%。长薄鳅的回避率与过饱和水体浓度呈现较强的线性相关关系,水体TDG饱和度越高,实验鱼回避现象越明显。     

The tolerance threshold of Chinese sucker to total dissolved gas supersaturation

Total dissolved gas (TDG) supersaturation generated in the river may result in gas bubble disease to Chinese sucker (Myxocyprinus asiaticus Bleeker) and cause their mortality. To assess the effects of TDG supersaturation on Chinese suckers in laboratory, juvenile fish were exposed to different levels of TDG supersaturated water. All of the fish died when the TDG saturation reached and exceeded 125%, but none died at TDG of 120% saturation in 96 h. To evaluate the effects of intermittent exposure of TDG supersaturation, Chinese suckers were exposed to TDG of 130% for a specific duration and then provided a recovery period at 100% saturation. The results showed that some remission is possible for intermittent exposure. Because of the characteristics of natural rivers, experiments exploring the TDG supersaturation detection and avoidance abilities of Chinese suckers were conducted and demonstrated the fish can avoid TDG supersaturation in both the horizontal and vertical directions when higher TDG levels were available. The results indicate the tolerance threshold of juvenile Chinese suckers is a TDG level of 120% saturation.     

Hatching rate of Chinese sucker (Myxocyprinus asiaticus Bleeker) eggs exposed to total dissolved gas (TDG) supersaturation and the tolerance of juveniles to the interaction of TDG supersaturation and suspended sediment

Flood discharge containing excessive suspended sediments (SS) can result in total dissolved gas (TDG) supersaturation downstream of dams. It has been confirmed that high TDG levels and excessive SS cause serious threats to fish survival. To explore the effects of TDG supersaturation on the hatchability of Chinese sucker (Myxocyprinus asiaticus Bleeker) eggs, eggs were exposed to 100%, 125%, 130% and 135% TDG supersaturated water. The results showed that the hatching rates were 78.25%, 75.35%, 71.30% and 67.50% at the 100%, 125%, 130% and 135% TDG respectively. The hatching rate decreased with increasing TDG levels. Furthermore, acute lethality experiments were carried out to investigate the interaction of TDG supersaturation and SS on Chinese sucker. Half‐year‐old juveniles were exposed to TDG supersaturated water with SS concentrations of 0, 200, 600 and 1,000 mg/L, and the TDG levels were 125%, 130%, 135% and 140% respectively. The fish exhibited abnormal behaviours and signs of gas bubble disease. Mortality increased with increasing TDG levels and SS concentrations. The Chinese suckers only survived for 2.5 hr at 140% TDG and 1,000 mg/L SS. Moreover, an increase in SS in TDG supersaturated water could cause a decrease in the median lethal time (LT₅₀). When the TDG level reached 140%, the LT₅₀ declines significantly at 600 and 1,000 mg/L SS. The interaction of TDG supersaturation and SS was significant at LT₅₀ (F = 22.81, df = 9, p < 0.001). The results indicate that the combined effect of TDG and SS could be great on Chinese sucker.     

Effects of gas-supersaturated water on Rana catesbeiana tadpoles

Rana catesbeiana tadpoles were exposed to gas supersaturated water which resulted in inflation of the gastrointestinal tract with gas. Affected tadpoles floated on the surface, either with their left sides elevated or on their backs. These clinical signs, similar to those of gas bubble disease, could be reversed by reducing the dissolved gas levels. Based on post-exposure observation for 30 days, a 4-day exposure to a ΔP of 160 to 170 mm Hg had no effect on survival. A 10-day exposure increased mortality and the levels of systemic Aeromonas hydrophila bacteria, the etiology of a serious amphibian disease, “Redleg”. Bacterial levels returned to control levels after a 6-day recovery period.     

Oxygen-induced gas bubble disease in rainbow trout, Oncorhynchus mykiss (Walbaum)

Abstract. An Aquatector oxygen injection unit was used to supersaturate a hatchery water supply to 200% oxygen saturation (18–20mg/l) and increase the total gas pressure to 120% of saturation. Nitrogen saturation was reduced to near 100%. Rainbow trout, Oncorhynchus mykiss (Walbaum), held in the treated water developed signs of gas bubble disease in 4 days, and 50% died within 20 days. We demonstrated that supersaturated total gas pressure due to excessive oxygen saturation causes gas bubble disease in the absence of supersaturated nitrogen gas. It is recommended that users of oxygen injection systems closely adjust the amount of oxygen added to the water to keep the total gas pressure near saturation.     

Effect of Silver Carp Hypophthalmichthys molitrix and Freshwater Mussel Elliptio complanata Filtration on the Phytoplankton Community of Partitioned Aquaculture System Units

Growers produce over 2.8 million kg of catfish (over $350 million wholesale revenue) annually in the United States. The microbiology of the phytoplankton community in culture water affects the growth and flavor of the catfish and is a consideration for growers. Filter feeders, like silver carp and freshwater mussels, in controlled growth systems are used to adjust the phytoplankton species. Our goal was to successfully control the algal populations with filter feeders in catfish production. We used silver carp Hypophthalmichthys molitrix as a filter feeder in Partitioned Aquaculture System (PAS) water. Silver carp completely eliminated the cyanobacteria Microcystis by size and biovolume reduction. This created the desired effect of small green algae dominating the algal community. A significant but opposite change was observed when freshwater mussels Elliptio complanata filtered PAS water resulting in Microcystis biovolume and size dominance in the PAS; a less desirable algal community. This study also showed an immediate shift in the phytoplankton community when silver carp and mussels were interchanged between PAS waters. The size-selective filtration by the two filter-feeding taxa was important in determining the composition of the PAS phytoplankton community, and it was apparent that filtration with silver carp successfully depleted undesirable algae.     

三角帆蚌钩介幼虫在5种寄主鱼体寄生效果的比较

选用黄颡鱼、草鱼、鲢、鳙和鲫作为三角帆蚌(Hyriopsis cumingii)的寄主鱼,分析了寄苗悬液钩介幼虫密度和寄苗时间对5种鱼初始寄苗量的影响,并对寄生在这5种鱼上的钩介幼虫发育情况进行了观察。结果表明:无论高密度寄苗还是低密度寄苗,长时间寄苗还是短时间寄苗,黄颡鱼和草鱼的寄苗量都明显高于鲢、鳙和鲫。提高寄苗悬液钩介幼虫密度,寄主鱼的寄苗量显著增加,但增加寄苗时间,寄主鱼的寄苗量未见显著提高。黄颡鱼和草鱼的稚蚌脱苗率显著高于鲢、鳙和鲫,寄生在鲢、鳙和鲫鳃上的钩介幼虫约80%未发育至稚蚌便提前脱落。不论在寄苗量方面,还是在稚蚌脱苗率方面,黄颡鱼和草鱼均是三角帆蚌钩介幼虫的最佳寄主。     

几种淡水鱼血清免疫复合物含量与其抗病能力关系的研究

采用2．0％和3．5％PEG沉淀法，研究了鲫鱼、草鱼、鳙鱼、鲶鱼和罗非鱼血清免疫复合物。统计结果表明，免疫复合物含量在同一鱼类的不同PEG浓度处理间均有显著差异；在不同鱼类的同一PEG浓度处理间，除鳙鱼和鲶鱼间无显著差异外，其余均有显著差异。实验发现，血清免疫复合物的含量变化与各种淡水鱼在分类上的地位及抗病能力明显相关。     

鲤、鲢、鳙、草鱼消化道消化酶种类和活性的比较研究

采用聚丙烯酰胺凝胶电泳方法研究了鲤、鲢、鳙、草鱼亲鱼消化道消化酶的种类；用比色法及滴定法分别测其消化酶相对活性。结果表明：鲤、鲢、鳙、草鱼4种鱼消化道的蛋白酶、淀粉酶活性与食性有明显的相关性。其中，蛋白酶活性依次为鲤〉鲢〉鳙〉草鱼；淀粉酶活性依次为草鱼〉鲤〉鳙〉鲢。脂肪酶活性与食性的关系不明显。四种鱼消化酶的表达与消化...