高容量鱼池初级生产力和产氧、耗氧值特点的初步研究

本文总结了亩净产为1500～2600公斤的高容量(高载鱼晕)鱼池水域初级生产力和产氧、耗氧值的特点，在透明度为28～40厘米的条件下，“水呼吸”耗氧量占31．3％；池鱼呼吸（考虑到活动和摄食生长因素)占61．8％，与一般精养鱼池“水呼吸”耗氧要占约70％，池鱼占20％和其它因子的耗氧占10％的情况有着明显的区别；高容量鱼池在透明度为35～40厘米时，2米深水柱毛产氧量约等于水呼吸耗氧晕，而一般精养鱼池2米深水柱的毛产氧量要小于水呼吸耗氧量。由此证明，高容量鱼池所采取的排除底层污泥的池塘改造措施以及经常排除底层负氧水、及时添补新鲜水的水质控制技术，对于减少“水呼吸”耗氧量，改善池水溶氧条件是有效的。高容量鱼池由于载鱼量高，仅依靠水体的产氧，溶氧的收、支还不平衡，因此，使用增氧设备自然是重要的增产措施。     

对虾养殖的水化学管理

当今对虾养殖，由于细菌性，病毒性等病害外源性感染的机率较大，养殖户大都采用封闭式、半封闭式养殖管理模式，因此虾池的水质调控尤为重要。为了使对虾养殖能持续健康发展，生产上通常的几项化学指标是可以根据养虾的不同阶段而加以管理的。一、前期管理经过清淤、暴晒、消毒后的池塘，经过7－10天左右毒性消失后，进入稳定状态，可以认为此时的水质是最佳的。在该阶段的水质管理，主要是补充适量的有机或无机N．P．K肥，培养浮游植物和浮游动物。我们知道浮游植物光合作用产氧量占海水池塘溶氧收入可达91．3～100％，是池塘中氧的主要…     

冰封期越冬池塘的生物增氧

北方地区冰封期时间比较长 ,特别是东北、西北等地区 ,冰封期最长的可达１５０天以上 ,冰下水温低（约为１～３℃） ,对鱼类的安全越冬影响很大。影响鱼类安全越冬的最主要外因就是越冬池塘的溶氧量。越冬池塘封冰后 ,水中溶氧在自然状况下 ,同时存在耗氧和产氧两个方面的因素。耗氧主要是由于水中的生物呼吸和有机物的氧化等原因造成的。而产氧主要是由于水生维管束植物（某些沉水植物）及浮游植物的光合作用的结果。生物增氧 ,简单地说 ,就是根据具体情况 ,创造一切有利条件 ,促进冰下浮游植物的生长、繁殖并在光合作用中产生氧气 ,作为越…     

夏秋季节防鱼浮头

夏秋季节，水温高，鱼池投饵施肥量大，水中有机物和耗氧因子多，易发生鱼缺氧浮头现象，甚至造成死鱼事故的发生。防止鱼浮头是夏秋季养殖工作的重要内容，现介绍有关技术，供养殖者参考。 1鱼浮头的原因 1.1天气 天气不好，阴雨连绵，光照不足，浮游植物光合作用弱，溶氧供不应求，易造成浮头事故的发生；此外，下午或傍晚雷雨后，池塘水急剧对流，也易发生浮头。 1.2水质 因水质过肥或败坏，水中有机质耗氧多，也易造成浮头及死鱼事故的发生。 1.3鱼池条件 鱼池底质淤泥较多，残饵、粪便等物质腐烂消耗大量的氧气，也会使池水缺氧，鱼…     

中国对虾与罗非鱼施肥混养的基础研究↑（*）

用４个海水池塘陆基围隔（５ｍ×５ｍ），进行了封闭式施肥混养中国对虾（Ｐｅｎａｅｕｓｃｈｉｎｅｎｓｉｓ）与台湾红罗非鱼（Ｏｒｅｏｃｈｒｏｍｉｓｍｏｓａｍｂｉｃｕｓ×Ｏ．ｎｉｌｏｔｉｃｕｓ）的基础研究。结果表明，在不同密度条件下，对虾成活率４５．０％～８６．７％（平均６６４．２％），产量为７５．７～１１１．８ｋｇ／ｈｍ２（５７ｄ），生产力为０．１９／ｍ２·ｄ。池塘对中国对虾的负荷力为１７０．０ｋｇ／ｈｍ２。其中某些围隔对虾死亡较多的原因是负荷量超过了负荷力，发生饵料缺乏和自残。在限定罗非鱼放养量（８×１０３尾／ｈｍ２）的条件下，鱼虾最适放养尾数配比为１∶３，中国对虾（体长５．５５ｃｍ）的最适放养量为２４×１０３尾／ｈｍ２左右。     

鱼类浮头的原因及解救办法

造成鱼类浮头的直接原因是缺氧或氨中毒。一、缺海造成的浮头这种现象多发生在高温季节，半夜和清晨较为常见。引起池塘缺氧的因素比较多，主要有以下四个方面：1．池塘中鱼的放养密度过高，水中氧气供不应求。2．雷雨过后，由于地中表面水层和池底水层温差大，引起泡水上下对流，池底的腐败物随之翻起，加快其分解，消耗大量氧气，造成缺氧。3．饲料或肥料投入过多，造成水质过肥，浮游植物大量繁殖，白天由于光合作用产生大量的氧气，使溶氧过他和；夜晚由于鱼类和浮游植物均因呼吸作用而耗氧，使溶氧大大减少，甚至降到临界点，导致鱼的…     

增氧设备在水产养殖中的应用

养殖水体中的溶氧水平关系到养殖水生动物的生存、生活和生长，进而关系到养殖成败和养殖效益的高低。根据对我国传统池塘养殖水体中溶氧水平的监测和数据分析，在水体总溶氧量中，70％左右的溶解氧来自于水体中的植物尤其是浮游植物的光合作用，30％左右来自于大气的溶入。通常情况下，水体上层的溶氧量较高，池塘底层水体的溶氧量较低，往往低于lmg／L。溶氧水平的高低直接影响着养殖鱼、虾的摄食量、饲料转化率以及生长速度。据有关资料显示，养殖鱼类在溶氧Nc3mg／L时的饲料系数要l：t4mg／L时增大1倍；在溶氧量7mg／L时，     

家鱼池塘底泥耗氧率与理化因子的相关性分析

采用原位底泥耗氧测定法,研究了10口家鱼鱼池底泥耗氧率与底部水体理化因子(溶氧、温度、pH值、氧化还原电位)和底泥有机质含量及深度的相关关系。结果显示:池塘平均底泥耗氧率(SOD)为0.91 g/(m2.d),变动范围为0.76～1.09 g/(m2.d)。双变量相关性分析表明,底泥耗氧率与池塘底部水体理化指标的相关性均达到极显著水平(P<0.01),与溶氧相关性最高(Pearson相关系数为0.779),其次是温度、pH值和氧化还原电位,相关系数分别为0.587、0.557和-0.421;底泥耗氧率与底泥深度相关性达到显著水平(P<0.05)。偏相关分析结果表明,底泥耗氧率与溶氧和温度呈极显著相关(P<0.01),与其它因素均未达到显著水平。影响底泥耗氧率最重要的环境因子是溶氧,其次是温度。利用BP神经网络分析影响SOD的理化因子,以溶氧、温度和底泥深度为BP神经网络模型的输入变量建立BP神经网络模型对SOD进行预测分析,BP神经网络模型训练和测试相关系数分别为0.911和0.879,平均相对误差分别为11.6%和10.4%,预测值与真实值偏差较小,拟合度较高,可有效预测池塘底泥耗氧率。     

春季鱼类浮头的原因及解救办法

在春季，午后阳光充足、气温较高时容易发生浮头。症状是鱼类感到呼吸困难，浮在水的上层，不时将口伸出水面吞取空气。浮头严重时，鱼还会窒息死亡。 这种春季鱼类浮头多是由于氨中毒造成的。 引发氨中毒的主要原因是： １．池塘老化、池底有机物过多。有机物分解产生大量的氨，造成鱼的浮头； ２．投饵过多，残余饲料分解产生氨，使水体中的氨浓度过高，导致鱼体浮头； ３．池水过瘦，水中浮游植物量较少。由于溶氧主要来源于浮游植物的光合作用，浮游植物少，则溶氧低，氨氮就不能通过氧化作用变成无毒的亚硝酸氮，从而氨在水中积累造成…     

大口鲇鱼种耗氧率和窒息点的观测

对平均全长７．６ｃｍ和１１．６ｃｍ的大口鲇鱼种耗氧率和窒息点进行了测定。结果表明：小规模鲇种耗氧量比大规格低，但耗氧率比大规格高。２种规格鱼种的最高耗氧率分别出现在白天１０：００和１２：００左右。鱼种溶氧窒息点分别为０．３３ｍｌｇ／Ｌ和０．３６ｍｇ／Ｌ，与四大家鱼相似或销强，适合养殖和长途运输。     

Association between the interannual variation in the oceanic environment and catch rates of bigeye tuna (Thunnus obesus) in the Atlantic Ocean

The environmental processes associated with variability in the catch rates of bigeye tuna in the Atlantic Ocean are largely unexplored. This study used generalized additive models (GAMs) fitted to Taiwanese longline fishery data from 1990 to 2009 and investigated the association between environmental variables and catch rates to identify the processes influencing bigeye tuna distribution in the Atlantic Ocean. The present findings reveal that the year (temporal factor), latitude and longitude (spatial factors), and major regular longline target species of albacore catches are significant for the standardization of bigeye tuna catch rates in the Atlantic Ocean. The standardized catch rates and distribution of bigeye tuna were found to be related to environmental and climatic variation. The model selection processes showed that the selected GAMs explained 70% of the cumulative deviance in the entire Atlantic Ocean. Regarding environmental factors, the depth of the 20 degree isotherm (D20) substantially contributed to the explained deviance; other important factors were sea surface temperature (SST) and sea surface height deviation (SSHD). The potential fishing grounds were observed with SSTs of 22–28°C, a D20 shallower than 150 m and negative SSHDs in the Atlantic Ocean. The higher predicted catch rates were increased in the positive northern tropical Atlantic and negative North Atlantic Oscillation events with a higher SST and shallow D20, suggesting that climatic oscillations affect the population abundance and distribution of bigeye tuna.     

Growth performance,digestive enzyme activity and immune response of Japanese sea bass,Lateolabrax japonicus fed with fructooligosaccharide

In this experiment, a feeding trial was performed to determine the effects of fructooligosaccharide (FOS) on growth performance, digestive enzyme activity and immune response of Japanese sea bass, Lateolabrax japonicus juveniles (initial weight 38.3 ± 0.5 g), and the fish were examined following feeding with six levels of FOS (0, 0.5, 1, 2, 4 and 6 g/kg) for 28 days. Significant enhancement of weight gain (WG) and specific growth rate (SGR) was found in fish fed 1 g/kg FOS incorporated diets (p < .05), while the feed conversion ratio (FCR) in the 1, 2 g/kg FOS groups reduced significantly compared with the control (p < .05). Besides, the crude lipid in the 4, 6 g/kg FOS groups increased significantly compared with the control (p < .05). On the other hand, the erepsin and lipase activities significantly elevated in intestine of fish fed 2 g/kg FOS (p < .05) and the lysozyme activity in serum of fish fed 2 g/kg FOS were significantly higher than that in the control (p < .05). Moreover, the alkaline phosphatase activities in serum of fish fed 0.5, 1, 2 g/kg FOS were significantly higher than in control (p < .05). Regression analysis showed that the relationships between dietary FOS levels and either SGR, FCR, erepsin or lysozyme activities were best expressed by regression equations, and the optimal inclusion levels are 1.37, 1.80, 3.06, 3.11, 1.93 and 1.80 g/kg for SGR, FCR, erepsin, lipase, lysozyme and total superoxide dismutase activities, respectively. Overall, this study revealed that FOS incorporated diets could beneficial for L. japonicus culture in terms of increasing the growth, digestion and immune activities. Under the present experimental condition, the optimal supplementary level of FOS in the diet of L. japonicus is 1–3 g/kg.     

Involvement of gonadal steroids in final oocyte maturation of white perch (Morone americana) and white bass (M. chrysops): in vivo and in vitro studies

Plasma estradiol-17 (E₂), testosterone (T), 17,20-dihydroxy-4-pregnen-3-one (DHP) and 17,20,21-tri-hydroxy-4-pregnen-3-one (20-S) levels were measured by radioimmunoassay (RIA) in white perch (Morone americana) and white bass (M. chrysops) that were induced to undergo final oocyte maturation (FOM) with human chorionic gonadotropin (hCG). Plasma DHP levels increased in females of both species in association with oocyte germinal vesicle migration (GVM) and germinal vesicle breakdown (GVBD) and decreased thereafter. Plasma 20-S levels also increased with oocyte GVM in white bass, but were several-fold lower than DHP levels. Circulating E₂ and T levels were greatest during GVM and GVBD in both species and decreased to low levels during oocyte hydration and ovulation. Follicles from white perch and white bass which received a priming injection of hCG in vivo, produced both DHP and 20-S in vitro after exposure to hCG and their oocytes underwent GVBD. Ovarian incubates from unprimed fish of either species produced only E₂ and T and their oocytes did not complete GVBD. Oocytes from unprimed bass, but not perch, matured when follicles were exposed to hCG in vitro. Both trilostane and cycloheximide blocked in vitro production of DHP and 20-S and oocyte GVBD by white perch follices. DHP and 20-S were equipotent inducers of FOM in the GVBD bioassay. None of several other structurally-related steroids tested were effective within a physiological range of concentrations. These results indicate a role for DHP and 20-S in the control of FOM in white perch and white bass.     

Cardiac,ventilatory and metabolic responses of two ecologically dissimilar species of fish to waterborne cyanide

Changes in heart rate, ventilatory activity and oxygen consumption were determined in trout (Salmo gairdneri) and brown bullhead catfish (Ictalurus nebulosus) during exposure to a steadily increasing concentration of waterborne cyanide selected to produce death in 8–9 hours for each species. The lethal cyanide concentration for the bullheads was an order of magnitude higher than for trout. Trout developed an immediate and gradually increasing bradycardia throughout the exposure period. Cyanide produced tachycardia in the bullhead followed by a gradual onset of bradycardia as the concentration of cyanide was raised. Pericardial injection of atropine (a muscarinic cholinergic antagonist) indicated that bradycardia in the trout was due initially to increased vagal tone but later due to the direct effect of cyanide on the heart. Hyperventilation in the trout persisted throughout the exposure period, although the rate and amplitude fluctuated and was variable between individual fish. During the last hour of exposure (highest cyanide concentration), ventilation was characterized by rapid, shallow breaths followed by a sudden respiratory arrest. The bullheads exhibited hyperventilation during the first 3 hours of exposure followed by a gradual, linear drop in ventilation rate and amplitude until death occurred. Cardiac and ventilatory responses in both species were attributed to stimulation of central and peripheral chemoreceptors by cyanide. Evidence is presented which suggests the initial response in the bullheads was due, at least in part, to gustatory stimulation by the cyanide. Oxygen consumption of the trout remained above pre-exposure levels for the majority of the test period. Oxygen consumption in the bullhead paralleled the changes in heart and ventilatory rates. Whole-body lactate levels of fingerlings of both species during cyanide exposure were measured to estimate the extent of anaerobiosis. Whole-body lactate levels were much greater in the bullheads than the trout, indicating a higher capacity for anaerobiosis, possibly due to a greater fuel supply. Overall, the trout responded to cyanide in a manner similar to that produced by environmental hypoxia whereas the bullheads experienced a gustatory stimulus which masked the hypoxia-like response.     

An overview of stress physiology of fish transport: changes in water quality as a function of transport duration

This study brings an integrated analysis about the relationship between water deterioration and its physiological consequences in live fish transport. The analysis was focused on the transport water and its deterioration, and physiological challenges imposed on the fish. Usual commercial handling procedures employed to mitigate fish stress during transport were discussed. Future topics of research for the establishment of safer fish transport protocols were proposed. Transport was classified into short (≤8 h) or long transport (>8 h). The main issue in short transports should be the prevention of water pH reduction, while in long transports it is the increase in ammonia. Plasma cortisol is the most employed marker for stress and is acutely elevated upon short episodes of transport, but remains elevated even in long‐transport events. Plasma glucose is perhaps a better marker for handling stress. Plasma lactate, pH, osmolality CO₂ and ions should be more often evaluated. Plasma Na⁺ and Cl^‐ are very useful markers of acidosis, due to their respective exchange for H⁺ and , for acid–base regulation. The establishment of species‐specific transport protocols should be preceded by such combined analyses of water and physiological parameters.     

Are hatchery‐reared abalone naïve of predators? Comparing the behaviours of wild and hatchery‐reared northern abalone,Haliotis kamtschatkana (Jonas, 1845)

Abalone populations have declined worldwide, generating interest in enhancement using hatchery‐reared individuals. In many cases, such restoration efforts have met with limited success due to high predator‐induced mortality rates. Furthermore, the mortality rates of outplanted hatchery abalone are often considerably higher than for wild individuals. This study uses northern abalone (Haliotis kamtschatkana) as a case study to determine whether hatchery‐reared abalone behave differently than their wild counterparts. In the field, outplanted hatchery‐reared abalone were significantly less responsive than wild abalone, in terms of number of abalone responding and intensity of response, to nearby movement and to physical contact with an inert probe. Also, when encountering a cue to which all abalone responded (a seastar predator), hatchery‐reared individuals remained subdued. Anti‐predator behavioural deficits in hatchery‐reared abalone were more pronounced in 4‐year‐old individuals than in 1‐year‐old individuals, suggesting an influence of either age or amount of time spent in the hatchery environment. These behavioural differences are expected to increase the vulnerability of hatchery‐reared abalone to predators, and are likely a major cause of their elevated predator‐induced mortality when outplanted.     

Effects of cadmium on the kinetics of calcium uptake in developing tilapia larvae, Oreochromis mossambicus

The toxic effects of Cd²⁺ on Ca²⁺ influx kinetics in developing tilapia (Oreochromis mossambicus) larvae were evaluated. Addition of 20 µg l^-1 of Cd²⁺ to the environment of 0 and 3 day-old larvae competitively inhibited the Ca²⁺ uptake within 4h resulting in a great increase in K_m values for Ca²⁺ influx (19.3 and 17.4 fold, respectively) as compared with their respective controls. Consequently, the actual Ca²⁺ influx of larvae in solutions of 0.2 mM Ca²⁺ are suppressed by 32–45%. Also, 3 day-old larvae were more sensitive to internally accumulated Cd²⁺ than 0 day-old larvae. Although the Ca²⁺ influx in 0 and 3 day-old larvae may be restored to the levels of their respective controls with 24h of being transferred to a 20 µg l^-1 Cd²⁺ solution, total body Ca²⁺ content was significantly reduced in 3 day-old larvae. Increased Ca²⁺ uptake efficiency ensures sufficient Ca²⁺ for normal growth. However, rapid increase in Ca²⁺ influx after hatching also leads to higher Cd²⁺ uptake. Exposure to Cd²⁺ will lead to a drop in body Ca²⁺ content resulting in retardation of larval growth. Therefore, we conclude that if Ca²⁺ uptake is interfered with at this critical stage of development, larvae will not be able to maintain normal levels of body Ca²⁺ and will show signs of Cd²⁺ poisoning.     

Migratory dynamics of stream-spawning longnose gar (Lepisosteus osseus)

Abstract– Literature evidence suggests that lake-dwelling longnose gar (Lepisosteus osseus) enter tributary streams to spawn, Until the present study, the dynamics of this breeding migration had never been investigated quantitatively. During the summers of 1991 and 1992, longnose gar were captured as they entered Weaubleau Creek, Missouri, a tributary of Harry S. Truman Reservoir. The in-stream spawning migration began in early April and ended in late May, and was positively correlated with stream flow and water level, and negatively correlated with water temperature. In-stream residence times ranged from 15 to 94 days, with males exhibiting longer residence times than females. Once in-stream, longnose gar travelled as far as 10 km upstream and occupied certain pools at greater relative frequencies. Although the reason for this preferential utilization is not completely understood, it may relate to pool depth and riffle proximity. Longnose gar disperse from the spawning stream great distances, with gar captured in Weaubleau Creek being recaptured up to 48 km away. This information should provide fisheries biologists the means to consider the reproductive ecology of this species in their conservation and management decisions.     

Nutritional regulation of hepatocyte fatty acid desaturation and polyunsaturated fatty acid composition in zebrafish (Danio rerio) and tilapia (Oreochromis niloticus)

The desaturation and elongation of [1-¹⁴C]18:3n-3 was investigated in hepatocytes of the tropical warm freshwater species, zebrafish (Danio rerio) and Nile tilapia (Oreochromis niloticus). The hepatocyte fatty acid desaturation/elongation pathway was assayed before and after the fish were fed two experimental diets, a control diet containing fish oil (FO) and a diet containing vegetable oil (VO; a blend of olive, linseed and high oleic acid sunflower oils) for 10 weeks. The VO diet was formulated to provide 1% each of 18:2n-6 and 18:3n-3, and so satisfy the possible EFA requirements of zebrafish and tilapia. At the end of the dietary trial, the lipid and fatty acid composition was determined in whole zebrafish, and liver, white muscle and brain of tilapia. Both zebrafish and tilapia expressed a hepatocyte fatty acid desaturation/elongation pattern consistent with them being freshwater and planktonivorous fish. The data also showed that hepatic fatty acid desaturation/elongation was nutritionally regulated with the activities being higher in fish fed the VO diet compared to fish fed the FO diet. In zebrafish, the main effect of the VO diet was increased fatty acid Δ6 desaturase activity resulting in the production of significantly more 18:4n-3 compared to fish fed the FO diet. In tilapia, all activities in the pathway were greater in fish fed the VO diet resulting in increased amounts of all fatty acids in the pathway, but primarily eicosapentaenoic acid (EPA; 20:5n-3) and docosahexaenoic acid (DHA; 22:6n-3). However, the fatty acid compositional data indicated that despite increased activity, desaturation of 18:3n-3 was insufficient to maintain tissue proportions of EPA and DHA in fish fed the VO diet at the same level as in fish fed the FO diet. Practically, these results indicate that manipulation of tilapia diets in commercial culture in response to the declining global fish oil market would have important consequences for fish fatty acid composition and the health of consumers. Scientifically, zebrafish and tilapia, both the subject of active genome mapping projects, could be useful models for studies of lipid and fatty acid metabolism at a molecular biological and genetic level. This revised version was published online in August 2006 with corrections to the Cover Date.     

Production of diatom–bacteria biofilm isolated from Seriola lalandi cultures for aquaculture application

Controlled incorporation of selected microalgae and bacteria in aquaculture systems can be beneficial because they can act as microbiological control. That is why the characteristics of biofilm generated naturally in Seriola lalandi culture cages were analysed, their potential benefit to the growth of larvae was studied, and their controlled use for improving the larval viability and as a vector to improve incorporation of previously studied probiotic bacteria was tested. According to biodiversity results, these biofilms are composed of a diatom–bacteria mix showing a decrease in biodiversity in laboratory culture conditions being dominated by Navicula phyllepta and bacteria of the family Rhodobacteraceae. This can be produced on mesh substrates incorporated in bioreactors with rapid growth rate and adhesiveness. Preliminary results from the addition of substrates with this specific biofilm in larvae culture systems showed that it is consumed by the larvae without negative effects, while positive effects on the viability of larvae in combination with probiotics were observed. Considering preliminary results, the addition of these specific substrates with diatom–bacteria biofilms could be a good improvement for aquaculture systems and together with the use of probiotics can contribute to maintaining a stable and controlled system improving the viability of the larval fish culture in its early stages.