河蟹“颤抖病”及其预防技术

河蟹“颤抖病”始见于199。1年的池塘养殖，很少量的成蟹出现此病症。1995年以后病情迅速蔓延，导致河蟹养殖成活率逐年下降，许多塘口绝产绝收。“颤抖病”的病症：病蟹体瘦、壳软，活力差，腹部及附肢指节、掌节有红色水锈、不能正常蜕壳或蜕亮后不久便死；临死前活动呆滞，附肢僵硬并不停地痉挛（这是“颤抖病”这一俗称的由来），易并发黑鳃病和聚缩虫病。解剖病蟹可见肠道水肿、肌肉萎缩、肝脏糜烂等症状。有关单位初步研究表明：“颤抖病”的病原为病毒。发病时间及特征：7、8、9三个月是“颤抖病”的发病高峰期，高温季节该病表现为…     

河蟹颤抖病的防治新方法介绍

河蟹颤抖病是近年来在我国河蟹主产区的高发疾病之一，严重影响河蟹养殖效益的提高，可以说养殖业者“谈抖色变”。其主要症状为：发病初期，病星摄食减少，蜕壳困难，活动能力减弱，而后病星爬到池岸边或伏于水草上，步足连续颤抖，口吐泡沫，不能爬行，病餐肉质糊化，内脏病变，肠道、胃及鳃严重发炎肿胀，通常在短时间内迅速感染，继而引起批量死亡。根据流行病学调查及病原学研究表明：河蟹颤抖病的发生及发展不是孤立原因造成的，而是多种因素的综合复杂体现，因此在预防及治疗河蟹颤抖病的过程中，若一味采用“头痛医头；脚痛医脚”的…     

河蟹“颤抖病”病原初步研究

本文对健康河蟹和患典型“颤抖病”的河蟹进行了病原体检查和病理学研究，发现一种大小介于细菌和病毒之间的微生物。根据该微生物的大小、形状、内部结构、寄生部位及其在细胞内的繁殖方式，可以判定其为类立克次体生物（Rickettsia-like organisms,简称RLOs)。人工感染实验验证该生物为“颤抖病”的真正病原体。     

河蟹养殖中的心腹大患——颤抖病的有效防治方法

河蟹养殖所发生的颤抖病从１９９７年开始时的来势凶猛，发展到近两年已传遍全国各地的养蟹区，特别是长江中下游地区，颤抖病已成为养蟹者的心腹大患，几近谈“抖”色变，成为养蟹业发展的一大障碍，每年给蟹民们带来的直接经济损失无法统计。笔者在农村从事渔业生产指导工作４０年，现对防治此病提出几点见解，供广大水产科技工作者及蟹农们参考。一、症状病蟹反应迟钝，行动缓慢，螯足握力减弱，吃食减少，或者不吃食，最典型症状为螯足颤抖，环爪、爪尖着地，腹部离开地面，甚至倒立。故称颤抖病，也叫环爪病、抖抖病。二、流行、危害情…     

呼肠孤病毒引起河蟹颤抖病的人工感染与药物防治研究

自 1995年发现河蟹“颤抖病” (或称“抖抖病” )以来，到 1999年止，全国各河蟹养殖主要省区均发生了颤抖病的报道。刚开始发现颤抖病时，以池塘河蟹精养池发病为多，流行季节在 5～ 10月，高发季节在 6～ 9月，主要危害 2龄蟹；至今，除池塘精养池仍发病外，其它不同养殖方式下的养殖河蟹也有发病，只是池塘精养池的发病率最高， 1龄蟹发病现象也很严重，流行季节呈明显延长，从 4月到 11月均有发病，高发季节在 5～ 10月，具明显的暴发特征，疫区损失严重。国外对蟹类病毒已有一定研究，但不涉及中华绒螯蟹〖 1、 2、 3、 4、 5〗，国内…     

河蟹颤抖病的防治初探

河蟹颤抖病是当前河蟹养殖中危害最大的疾病,严重地阻碍了河蟹养殖业的发展。据不完全统计,九九年该病的发生率达50％以上,死亡率达30％以上,甚至个别池塘达到死亡率在80％以上,给养殖户造成严重的经济损失,因此,养殖业者谈“抖”色变。河蟹颤抖病,又叫“宽爪病”或“抖抖病”等,其主要症状为：病蟹的援食减少,活力能力减弱或爬到池岸边或伏于水草之上,反应迟钝,步足连续颤抖,口吐泡沫,背部向下很难翻身。病蟹解剖后,蟹体的肉质糊化,甚至步足肌肉萎缩,中空。有些病蟹肝脏病变,肠道发炎,无食或少量食物,有些病蟹伴有腹水…     

夏季河蟹常见病害防治

一、颤抖病 河蟹颤抖病又称环爪病、抖抖病,主要是由病毒感染引起河蟹的步足颤抖、环爪的疾病。     

河蟹健康养殖试验示范技术

“河蟹健康养殖试验示范”是由江苏省水产局（现省海洋与渔业局）１９９９年下达，江苏省水产技术推广牵头承担的省水产科技项目。该项目是针对近几年河蟹颤抖病的暴发而提出。项目区采用多种健康养殖技术与生态防病技术，结合疫病测报，有效控制了河蟹疾病特别是颤抖病的发生，经济效益显著，达到了试验预期效果，现将项目区实施情况总结如下。１ 基本情况１．１ 试验塘口 该项目共建４个示范区，分别设在金坛指前镇水产养殖场、扬州市宝应大洼子绿优水产养殖场、通州南兴乡水产养殖场、泗洪半城镇水产养殖场。示范区实施面积计 ２ ２３亩…     

浅析河蟹颤抖病

对引起河蟹颤抖病的细菌说、病毒说以及环境因子说这三种观点，通过实验及解剖分析发表了不同的见解。认为对河蟹颤抖病应彩病原加症状的命名方法。     

纯化病毒复制中华绒螯蟹“颤抖病”的组织病理观察

采用石蜡切片及超薄切片技术，对人工感染纯化病毒后具典型颤抖症状的中华绒螯蟹进行病理学观察。结果显示：人工感染“颤抖病”病毒发病与自然发病的病理变化相似，病蟹的肝胰脏、鳃、心脏及腹神经节等组织器官发生了病变，其病理特征主要表现为细胞浊肿、变性、坏死，某些细胞的细胞核固缩、碎裂或崩解；超薄切片电镜下可见细胞内存在病毒样颗粒，线粒体内嵴受损严重。病变严重的区域，组织细胞坏死，结构崩解。提示肝胰脏、鳃、心脏及神经组织是病毒感染主要靶器官。     

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.     

Protein and amino acid composition from the mantle of juvenile O ctopus vulgaris exposed to prolonged starvation

Protein and amino acid composition of the mantle of juvenile O ctopus vulgaris (Cuvier, 1797) during fasting for 27 days were determined. Average protein content of octopus mantle was of 711.19 ± 46.80 g kg^?1 DW, and it decreased with increasing fasting days. The non‐essential amino acids content was higher (486.18 ± 11.08 g kg^?1 protein) than essential amino acids (425.82 ± 9.15 g kg^?1 protein) at the start of the experiment (unstarved animals). The results suggest that the amino acid profile of the mantle where the most abundant amino acids are Arg, His, Lys, Gly, Leu and Pro could indicate a prolonged fasting condition (>20 days) or poor nutrition of O . vulgaris. This study supports the idea of using mantle for metabolic needs of starved O . vulgaris suggesting that the degradation pathway of amino acids to pyruvate and tricarboxylic acid cycle intermediates was favoured contrary to the degradation pathway of ketogenic amino acids. Special considerations should be taken concerning Thr, Ile, Ser, Ala, Asx (Asp, Asn), Glx (Glu, Gln) (because of their fast intake) and Lys and His (due to their stable contents) during a prolonged period of fasting.     

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.