Effects of barotrauma and mitigation methods on released Australian bass Macquaria novemaculeata

The effects of barotrauma on the short-term mortality and physical condition of Australian bass Macquaria novemaculeata were investigated after being: (1) conventionally angled and released during two tournaments in deep impoundments and (2) released untreated or subjected to venting or recompression during a manipulative experiment. All fish were released into two 20 m deep bathy-cages and monitored for 3 days. Of 238 M. novemaculeata angled during the tournaments, 43 (18·1%) had clinical signs of barotrauma or were vented and five of these later died (11·6% mortality). Catch histories varied significantly between both barotrauma and non-barotrauma fish and tournaments, but only hook ingestion significantly influenced mortality (P < 0·05). During the manipulative experiment, venting significantly influenced mortality (13·3%) compared to no treatment or recompression (no deaths). Magnetic resonance images and dissections of barotrauma fish indicated large variation among clinical signs. On the basis of these results, wherever possible M. novemaculeata suffering barotrauma should be immediately released with no treatment. Fish that are unable to resubmerge should be recompressed, while those held in live wells and released in shallow water should be vented.     

Release method and anatomical hook location: effects on short-term mortality of angler-caught Acanthopagrus australis and Argyrosomus japonicus

One field and 3 aquaria experiments were done to quantify the short-term mortality of yellowfin bream Acanthopagrus australis and mulloway Argyrosomus japonicus after being angled and subjected to 3 general handling treatments. Anglers were supplied with identical J-type hooks and asked to handle hooked fish by either (1) physically removing the hook or (2) cutting the line (5 cm from the mouth of the fish) and leaving the hook in. Some hooked A. japonicus were subjected to a third handling treatment where the line was cut underwater without exposing the fish to air. Technical and biological data were collected before all fish were released into sea cages and monitored for 5 d. Control fish were seined and similarly caged and monitored. Concentrations of plasma glucose and cortisol were collected from a sample of fish on the first and last day of the experiments. Significant predictors of mortality for both species involved the presence of blood at the mouth and an interaction between anatomical hook location and hook removal. A. australis and A. japonicus that had their ingested hooks removed experienced the greatest mortalities (87.5 and 72.7%, respectively). Typically, these fish suffered damage to their oesophagus, stomach wall and vital organs. Mortality rates of A. australis and A. japonicus were significantly decreased to 1.7 and 16%, respectively, when they were released with their lines cut, with some of these fish free of hooks after 5 d. In contrast, few mortalities occurred in either species when the hooks were removed or the lines cut on mouth-hooked fish or in A. japonicus when it was released with no air exposure. For A. australis, the field- and aquaria-based experiments provided comparable results in terms of identifying treatment-specific effects, but there were potential biases in rates of hook ingestion. Irrespective of the treatment of fish, all experiments caused physiological changes measured as elevations in either plasma cortisol or glucose. We concluded that anglers should cut the line from hook-ingested A. australis and A. japonicus, but remove the hook from mouth-hooked individuals to prevent subsequent ingestion. Further research is required to examine the longer-term consequences of these handling practices on fish health.     

Condition factor and diet of Chrysichthys nigrodigitatus and Chrysichthys auratus (Siluriformes: Bagridae) from Aiba Reservoir, Iwo, Nigeria

Chrysichthys nigrodigitatus and C. auratus are important, highly valued and threatened freshwater species. To contribute with their ecological knowledge, the condition factor and diet of these two congeneric species were studied between April 2005 and April 2006. Food items of fish were evaluated by occurrence and numerical abundance methods, and the possible changes among sexes, seasons and sizes were considered. Results showed that generally C. nigrodigitatus were better conditioned than C. auratus. The males of C. nigrodigitatus and females of C. auratus were in better condition than their respective opposite sex throughout the year, and during the wet season compared to the dry. The food items of C. nigrodigitatus and C. auratus were similar and comprised twelve species belonging to five groups: Insecta (three species), Crustacea (five species), Arachnida (one species), Rotifera (one species) and Mollusca (two species). Other food items included fish scales, unidentified green eggs, plant parts, detritus and sand. Insecta and Crustacea dominated the food items in both species. For C. nigrodigitatus, insect consumption increased with fish size, while Crustacea items decreased (from 89.59% for 8.1cm - 12.0cm size class to 1.58% for 20.1cm - 26.0cm size class). However, while C. auratus smaller sized fish preferred Crustacea (98.72% for 8.1cm -12.0 cm size class), larger sized fish had both groups in relatively similar amounts. Schoener Overlap Index for both species and between seasons is 1.00. Diet breadth ranged from 0.00-1.47 for C. nigrodigitatus and 0.00-1.32 for C. auratus. Food Richness ranged from 0.00-1.44 for both species. Gut Repletion Index for C. nigrodigitatus and C. auratus are 76.39% and 76.27% respectively. Although, there is considerable similarity and overlap in the utilization of food resource for both coexisting species, condition factor and feeding behavior suggest strategies to reduce intra- and interspecific competition.     

Characteristics of Ontario muskellunge (Esox masquinongy) fisheries based on volunteer angler diary information

This paper consolidates and summarizes information on Ontario muskellunge, Esox masquinongy, sport fisheries derived from angler diary programs sponsored by the Ontario Ministry of Natural Resources (OMNR) and Muskies Canada Incorporated (MCI) from 1979 to 2004. Interest in muskellunge as a sport fish has increased substantially over the past 10–15 years. Muskellunge catches were found to be highly correlated with angling effort. Catch rates, expressed in terms of catch-per-unit-of-effort (CUE), have improved over the past decade to the point where, in 2001, the provincial CUE was 0.119. The long term catch rate is 0.069. This improvement in angling quality is attributed to new minimum size limit regulations and increased catch-and-release angling practices. Over the period from 1979–2004, release rates by muskellunge anglers have averaged 94%. Based on a sample size of 9,499 fish, the mean size of angled muskellunge over the past 26 years was 37.0 inches (94 cm). Numerous fish exceeding 50 inches (127 cm) are angled from Ontario waters each year. The incidence of lymphosarcoma, a highly contagious, malignant blood cancer, has averaged only 2% since 1979. Based on an analysis of this information, Ontario’s muskellunge fisheries appear to be stable and sustainable. Volunteer angler diary programs provide an accurate and cost-effective means to monitor the status of muskellunge fisheries in Ontario.     

Tagging of Atlantic cod (Gadus morhua) with intragastric transmitters: effects of forced insertion and voluntary ingestion on retention, food consumption and survival

The effects of intragastric tagging on transmitter retention, food consumption and survival were investigated in Atlantic cod ( Gadus morhua L.) under laboratory conditions. Cod (60–84 cm) were intragastrically tagged with two different sizes of dummy acoustic transmitters (16 × 45 and 16 × 82 mm) using the methods of forced insertion and voluntary ingestion. Cod that were tagged by forced insertion began to regurgitate transmitters the first day after tagging and continued to do so throughout the period of study. The percentage of fish retaining transmitters in this group dropped to 50% after 32 days. By comparison, cod that were tagged by voluntary ingestion exhibited a 44-day delay in the onset of initial regurgitation. This was followed by a rapid rate of regurgitation, with the percentage of fish retaining transmitters in this group dropping to 50% after 60 days. These retention times are prolonged in comparison to previous studies and have been attributed to the lower temperature regime used in this study. Transmitter size did not significantly affect the duration of retention. During the first 20 days following tagging, the average food consumption per fish was higher in the voluntary ingestion group compared with the forced insertion and sham groups. Mortality levels were 13, 44 and 56% for the voluntary ingestion, forced insertion and sham groups, respectively, over the period of study. We associate low food consumption and high mortality rates in the first 20 days of the experiment with high levels of stress due to handling. The findings indicate that voluntary ingestion is a more viable technique for the intragastric tagging of cod in field studies.     

Lateral line reception in still- and running water

The lateral line of fish is composed of neuromasts used to detect water motions. Neuromasts occur as superficial neuromasts on the skin and as canal neuromasts in subepidermal canals. Fibres of the lateral line nerves innervate both. There have been extensive studies on the responses of lateral line nerve fibres to dipole stimuli applied in still water. However, despite the fact that many fish live in rivers and/or swim constantly, responses of lateral line nerve fibres to dipole stimuli presented in running water have never been recorded. We investigated how the peripheral lateral line of still water fish ( Carassius auratus) and riverine fish ( Oncorhynchus mykiss) responds to minute sinusoidal water motions while exposed to unidirectional water flow. Both goldfish and trout have two types of posterior lateral line nerve fibres: Type I fibres, which most likely innervate superficial neuromasts, were stimulated by running water (10 cm s(-1)). The responses of type I fibres to water motions generated by a vibrating sphere were masked if the fish was exposed to running water. Type II fibres, which most likely innervate canal neuromasts, were not stimulated by running water. Consequently, responses of type II fibres to a vibrating sphere were not masked under flow conditions.     

Mortality and physical damage of angled-and-released dusky flathead Platycephalus fuscus

We completed 2 experiments to quantify the mortality and physical damage (fin, blood and scale loss) of angled dusky flathead Platycephalus fuscus during a live weigh-in tournament (Expt 1) and after being immediately released by anglers (Expt 2). In each experiment, 84 and 79 angled P. fuscus were placed into up to 6 replicate tanks and, along with appropriate numbers of controls, monitored for mortalities over 5 d. Five and 7 of the angled fish died within 12 h, providing mortalities of 3.6 and 8.9% in Expts 1 and 2, respectively. One control fish died, which was attributed to an incorrectly inserted tag. None of the continuous or categorical variables collected during angling and subsequent release, or the experimental design, could explain the few observed mortalities to treatment fish. However, knotted large-mesh landing nets caused significantly greater fin damage than knotless fine-mesh designs in both experiments (p < 0.05). Furthermore, although water quality had no measured impact on the confined fish, the samples taken from anglers' live wells (mostly for Expt 1) were significantly poorer than the environment from which the fish were caught (p < 0.05). These latter differences may have had a cumulative negative impact on fish that manifested as the observed deaths. Simple changes to the post-capture handling of P. fuscus, involving appropriate landing nets and live wells, should reduce some angling impacts on this species.     

Reproductive biology of Zearaja chilensis (Chondrichthyes: Rajidae) in the south-east Pacific Ocean

Between 2000 and 2002, three artisanal landing sites were sampled in southern Chile, with data on population structure and reproductive development collected from 5477 yellownose skates Zearaja chilensis. Total length (L(T) ) ranged from 33 to 158 cm for females and 34 to 155 cm for males. No sexual dimorphism was evident in disc size (length or width) or in L(T)-mass relationships. The smallest mature female was 95 cm L(T) and the size at which 50% were mature (L(T50) ) was 109 cm. Males matured between 80 and 90 cm L(T) with a L(T50) of 88 cm. Although the largest Z. chilensis captured by the artisanal fishery was 155 cm L(T) , 89% of landings comprised relatively small, immature fish. This situation may compromise the stock integrity if intrinsic vulnerability and probable long-life span of Z. chilensis are considered. Consequences for the survival of the species and possible signs of a fishery collapse must be reviewed by management authorities by consideration of both artisanal and industrial landings in Chile.     

西藏拉鲁湿地和茶巴朗湿地外来鱼类群落结构及变动趋势

研究于2019—2021年在西藏拉鲁湿地和茶巴朗湿地使用刺网和地笼等组合渔具开展了鱼类实地调查, 分析了外来鱼类物种组成、优势种和群落功能多样性, 并结合已发表的文献资料, 探讨了西藏湿地外来鱼类群落结构的变动趋势及影响。结果表明, 共采集到外来鱼类10种, 隶属于4目5科, 包括鲫(Carassius auratus)、麦穗鱼(Pseudorasbora parva)、鲤(Cyprinus carpio)、丁鱥(Tinca tinca)、棒花鱼(Abbottina rivularis)、泥鳅(Misgurnus anguillicaudatus)、大鳞副泥鳅(Paramisgurnus dabryanus)、鲇(Silurus asotus)、小黄?(Micropercops swinhonis)和中华青鳉(Oryzias sinensis)。外来鱼类的个体数和重量分别占本地种和外来种总渔获物的94.86%和70.71%, 其中主要组成为鲫和麦穗鱼等小型鱼类。相对重要性指数(IRI)表明鲫、麦穗鱼、大鳞副泥鳅和鲤4种为拉鲁湿地外来鱼类优势物种, 鲫、麦穗鱼和小黄?3种为茶巴朗湿地的优势物种。在拉鲁湿地和茶巴朗湿地鱼类种类组成、个体数量和生物量中外来鱼类均已占据优势地位, 且外来鱼类的群落功能多样性(FD)亦高于土著鱼类。结合历史数据, 西藏拉鲁湿地和茶巴朗湿地已记录外来鱼类12种, 其中具高度入侵风险物种达6种, 外来鱼类物种数从2000年左右的2种增加到现在的10种, 且丁鱥和中华青鳉分别在西藏自然水体中和茶巴朗湿地中首次被发现。此外, 两个湿地12种外来鱼类均为拉萨市场中的常见经济鱼类及携带鱼类, 是由于放生而进入湿地自然水体中, 且鲫、大鳞副泥鳅和麦穗鱼等均已建立自然种群。因此, 加强对放生的科学管理及开展外来鱼类的长期监测, 是防范外来鱼类入侵及高原湿地生物多样性保护的迫切任务。     

Ontogenetic changes in temperature preference of Atlantic cod

Final thermal preferendum ( T ) experiments were conducted in a horizontal thermal gradient tank from the beginning of August 2001 to mid‐November 2001 using Atlantic cod Gadus morhua from 6·5 to 79·0 cm fork length ( L _F). The value of T varied significantly ( P  < 0·005) with L _F( T  = 7·23–0·054 L _F), with smaller (younger) fish choosing higher temperatures than larger (older) fish. The preferendum varied from 6·9° C for fish of 6·5 cm to 3·0° C for those of 79·0 cm. Experiments comparing fish positions in the gradient tank between thermal gradients of 0·5–11·0 and 4·5–14·5° C demonstrated that fish positions were determined by temperature selection instead of undesirable tank effects. This study is the first to demonstrate the effect of ontogeny on temperature preferences of a marine fish species.     

池养条件下银鲫与鲫鱼的生物学特性比较及其在生产上的意义

银鲫在我国分布于黑龙江流域和新疆额尔齐斯河等水域中。在四川省池养条件下,比较了银鲫与本地鲫的形态、食性、生长、繁殖、含肉量、鱼肉营养成分和起水率等生物学特性。形态差别主要在于银鲫体型较高,头略短,侧线鳞和脊椎骨数稍多。食性相似。银鲫生长较本地鲫约快150%。银鲫在2足龄左右第一次性成熟,产卵盛期较本地鲫略晚1个月,性比为(?)34.1%(体长6.1—14.5厘米)—(?)5.95%(体长15.4—18.5厘米)。银鲫的肥满度,含肉量,鱼肉含脂量以及起水率均较本地鲫高。初步讨论了银鲫的某些生物学特性在其养殖和选育上的经济意义。       

异育银鲫易钓性的表型基础和生态结果及饥饿响应

为考察鲤科鱼类易钓性种内差异的表型基础、生态结果及饥饿响应, 研究以异育银鲫(Carassius auratus gibelio)幼鱼为实验对象, 在饥饿前(对照组)测定其表型特征(能量代谢、游泳能力和个性行为)并垂钓, 随后在饥饿1周后再次垂钓(饥饿组), 最后进行2周的恢复摄食生长实验(恢复组)。垂钓实验具有4个重复, 每个重复的样本量为40尾, 垂钓1.5h即停止, 垂钓20尾为钓出组, 剩余20尾为未钓出组。研究发现: 除钓出组的相对代谢空间(FAS)小于未钓出组外, 钓出组的外部形态(体重、体长和肥满度)、能量代谢参数(标准代谢率SMR、最大代谢率MMR和代谢空间AS)、游泳能力(最大匀加速游泳能力U_cat和最大有氧运动能力U_gt)及个性行为(探索性、活跃性和勇敢性)与未钓出组均无明显差异(所有P>0.05); 在经历捕食者模拟袭击后, 实验鱼勇敢性的潜伏时间比大于探索性, 导致勇敢性的运动时间比和穿门频率小于探索性。SMR与U_cat及U_gt不相关(P>0.05), 但MMR和AS与U_cat及U_gt均呈正相关(P<0.05); 能量代谢参数与个性行为存在部分相关。饥饿增加异育银鲫的垂钓总时间、单尾平均垂钓时间和单尾垂钓时间的变异系数。钓出组在饥饿期的特定生长率(SGR)小于未钓出组, 而恢复期钓出组的SGR与未钓出组无显著差异; 除MMR和AS外, SMR与饥饿期及恢复期的SGR均呈负相关(P<0.05), 即SMR越高个体在饥饿期间的体重下降更快, 在恢复摄食后生长却较慢。研究表明: 异育银鲫幼鱼的易钓性可能不具备表型基础, 并且因环境食物匮乏而降低; 虽然饥饿期间两种易钓性表型个体的生态结果存在差异, 但该生长差异在营养恢复后消失, 表明异育银鲫的易钓性具有一定的环境依赖性。     

东江七种鱼类的生活史类型研究

本文通过渐近体长(L∞)、渐近体重(W∞)、生长系数(K)、初次生殖年龄(Tm)、最大年龄(Tmax)、瞬时自然死亡率(M)和性腺指数(Gl)等7个生态学参数来分析鱼类种群生活史类型。根据r-选择和K-选择的典型特征以及各参数间相互关系的显著性,性腺指数、瞬时死亡率和生长系数是判断东江7种鱼类种群偏向rF)和改变渔业补充年龄(tc)时的产量变化,分析产量变化曲线可知,作为偏向r型的种群,提高捕捞强度不能增加渔业产量,适当的捕捞强度可以取得较高的产量;在低龄阶段提高起捕年龄能增加一定产量,但到达一定年龄后再提高起捕年龄,反而引起产量大幅度下降。只有合理控制捕捞强度和起捕年龄,才能获取最大持续产量。       

Ingestion and ejection of hooks: effects on long-term health and mortality of angler-caught yellowfin bream Acanthopagrus australis

Ninety juvenile yellowfin bream Acanthopagrus australis were angled from holding tanks, allowed to ingest nickel-plated, carbon-steel J-hooks and released (with their lines cut) into individual experimental tanks during 2 experiments in order to assess their (1) long-term (up to 105 d) health, mortality and rate of hook ejection and (2) short- and medium-term (< 42 d) temporal changes in health during hook ingestion. Equal numbers of control fish were scooped from holding tanks and similarly monitored in experimental tanks. Of 20 hook-ingested fish released during Expt 1, 3 died within 8 d, providing a non-significant mortality of 15%. Between Day 6 and Day 56 post-release, 13 of the surviving individuals ejected their hooks, which were typically oxidized to about 94% of their original weight and often broken into 2 pieces. At Day 105, there were no significant differences between the 20 control and 17 hook-ingested/-ejected fish in terms of their ability to digest and assimilate food (measured as changes in apparent digestibility coefficients), stress (measured as concentrations of plasma cortisol and glucose) or of morphological parameters that included weight (Wt) and maximum height (MH), maximum width (MW) and maximum girth (MG). During Expt 2, 3 individuals that still contained ingested hooks and 3 controls were sampled on each of 9 occasions between Day 3 and Day 42 post-release. All fish were sampled for blood cortisol and glucose and were then euthanized before being weighed and measured for total length (TL), MH, MW and MG. Hook-ingested individuals were also X-rayed to determine the position and orientation of hooks. There were no significant differences in plasma glucose between hook-ingested and control fish. Irrespective of the treatment of fish, concentrations of cortisol were elevated on some sampling occasions, indicating variable, acute stress. The MH and MG of fish were not significantly different between groups. Significant differences were detected for MG and Wt, with hook-ingested fish having weights similar to those of the control fish but a relatively greater MW (owing to stomach distension from ingested hooks) until 2 wk post-release, after which both morphological parameters generally declined. There was no significant temporal progression of hooks in the stomach of treatment fish; however, some hooks reorientated to positions that may have precluded passage along the digestive tract. We conclude that, for the J-hooks examined, cutting the line is an appropriate strategy that results in the greater majority of released hook-ingested yellowfin bream surviving with minimal negative long-term effects.     

Construction of a taste-blind medaka fish and quantitative assay of its preference-aversion behavior

In vertebrates, the taste system provides information used in the regulation of food ingestion. In mammals, each cell group within the taste buds expresses either the T1R or the T2R taste receptor for preference-aversion discrimination. However, no such information is available regarding fish. We developed a novel system for quantitatively assaying taste preference-aversion in medaka fish. In this study, we prepared fluorescently labeled foods with fine cavities designed to retain tastants until they were bitten by the fish. The subjects were fed food containing a mixture of amino acids and inosine monophosphate (AN food), denatonium benzoate (DN food) or no tastant (NT food), and the amounts of ingested food were measured by fluorescence microscopy. Statistical analysis of the fluorescence intensities yielded quantitative measurements of AN food preference and DN food aversion. We then generated a transgenic fish expressing dominant-negative Galpha(i2) both in T1R-expressing and in T2R-expressing cells. The feeding assay revealed that the transgenic fish was unable to show a preference for AN food and an aversion to DN food. The assay system was useful for evaluating taste-blind behaviors, and the results indicate that the two taste signaling pathways conveying preferable and aversive taste information are conserved in fish as well as in mammals.     

Sublethal effects of angling and release on golden perch Macquaria ambigua: implications for reproduction and fish health

The present study tested the hypothesis of no delayed sublethal effects of mild angling and release on the feeding, growth, somatic condition and gonadal development of golden perch Macquaria ambigua during gametogenesis. Subsamples of adult M. ambigua (n = 17–21 of 207), originally captured from the wild and stocked into ten 0·1 ha earthen ponds, were angled and released during early and late gametogenesis. Wild samples that were concurrently collected throughout the experiment underwent rapid and synchronous gonadal development and many spawned. While no spawning occurred in the ponds, most M. ambigua underwent normal gonadal development to maturity, including the angled fish. Angled fish also fed, maintained condition and actually grew faster than non‐angled captive controls. Although females that were angled during late gametogenesis more readily ingested and retained baited hooks, neither their subsequent condition nor gonadal development was significantly affected. The predominance of null results was attributed to the combined effects of the flexible reproductive strategy of M. ambigua, the benignness of mouth hooking and immediate release, and possible methodological issues arising from differential hooking success of more aggressive and resilient individuals. The findings support earlier catch‐and‐release research, but contrast with reports of acute reproductive effects following capture and handling for aquaculture broodstock. This discrepancy highlights the need for research to specifically address welfare questions relevant to recreational fisheries across various species and angling scenarios.     

鱼类培养细胞核发育潜能的研究

本文用细胞核连续移植方法,从鲫鱼囊胚细胞的继代培养细胞,获得一尾存活达三年之久的移核鱼,但性腺未分化,不育。并从性成熟的鲫鱼短期培养肾细胞,获得一尾完成发育的性成熟的成鱼。实验结果提示鱼类囊胚细胞的继代培养细胞核和已分化的成鱼体细胞核仍具发育的全能性,为用细胞核移植方法进行鱼类体细胞育种的可能性提供了依据。     

On the biology of the catfish Chrysichthys auratus (Geoffory) in the man-made Tiga Lake in Northern Nigeria

SUMMARY. (1) A study was made of the biology of Chrysichthys auratus , a bottom-feeding omnivore, in Tiga Lake, a man-made lake in Northern Nigeria.
(2) Ripe females were present from April to September, coinciding with the hot season and rise in water level. First spawning took place at age II in females. No ripe males were found, and this was attributed to their spatial separation. Absolute fecundity was related to length and ranged from 327 to 1466 in forty-six females.
(3) Hyaline rings on the centra of lumbar vertebrae were counted to age 235 fish. The first ring is laid down at the end of the second year, after which the rings were formed annually, probably during the breeding season. The fish live for up to 6 years. There is a good fit of the growth curve to the von Bertalanffy equation. Growth is slow and a smaller maximum size is attained than in rivers.     

Surface folds in superficial epidermal cells of three species of teleost fish

Scanning electron microscope studies of fish epidermis demonstrate whorled arrangements of microfolds on the surface of superficial epidermal cells in the following species of teleost fish: the guppyfish Poecilia reticulata (Peters), the goldfish Carassius auratus auratus (L.), and the clown anemone fish Amphiprion percula (Lacépède). The pattern is most pronounced in epidermal cells covering the scales, but is also seen in the epidermal cells of the tail and body fins. The whorled pattern was not present on the gill epithelium or the surface of the eyes. These observations differ from transmission electron microscope studies which have described the skin surface as being composed of microvilli.     

Detection of the herpesviral hematopoietic necrosis disease agent (Cyprinid herpesvirus 2) in moribund and healthy goldfish: validation of a quantitative PCR diagnostic method

Cyprinid herpesvirus 2 (CyHV-2) is a pathogen of goldfish Carassius auratus auratus L. that causes herpesviral hematopoietic necrosis (HVHN) disease. The disease is associated with necrosis of hematopoietic tissues and anemia with high mortality. We have developed a real time 5'-nuclease PCR method (Taqman) that quantitatively detects CyHV-2 with a linear response over 8 logs of target concentration. The coefficient of variability on replicate samples tested on different days was 13% and the calculated sensitivity approached 1 target molecule per reaction. The assay does not cross-react with other similar fish herpesviruses, including CyHV-1 (carp pox) and CyHV-3 (koi herpesvirus), but reliably detects known CyHV-2 positive fish. The assay detects CyHV-2 not just in clinical cases of HVHN but also in apparently healthy 1 yr old goldfish fingerlings and even in 3 to 5 yr old broodfish.