水产养殖疫病测报信息的分析与利用

以某一塘口或养殖水体为测报基本单位,以发病、发病塘、塘口发病率、发病塘口死亡率等指标初步形成疫情分析指标体系,并以此分析处理测报信息,描述疫病的发生特点、危害程度及发展动态,初步总结了测报信息对控制疫病流行的内涵和作用。     

西泉眼水库浮游生物群落及鲢鳙鱼产力的估算

哈尔滨市西泉眼水库为新建水库,1997年5～9月对其浮游生物状况进行了初步调查。调查结果表明:西泉眼水库浮游植物和浮游动物的平均生物量分别为21.38mg/l和4.95mg/l,属超富营养型水体。据初步估计,浮游生物及细菌、腐屑等可提供的鲢、鳙鱼产力的为1358.62kg/hm~2。此外,本文还讨论了该水库的渔业利用问题。     

秦皇岛城市河流浮游植物初步调查

首次对秦皇岛市中心的护城河和马坊河分别进行了水样采集,对河水中的浮游植物作了初步调查研究。结果表明:护城河两个采样点的浮游植物分别属于硅藻、绿藻、蓝藻、裸藻和隐藻等5门中的12属,优势种群为隐藻;马坊河两个采样点的浮游植物分别属于上述5门中的15属,优势种群为硅藻和绿藻。初步判定两河受到了一定程度的有机物和氮磷等营养物的污染。     

河北省沿海异养菌与大肠杆菌和粪大肠杆菌分布数量的研究

海洋中的异养菌在海洋生态环境的物质循环中起着非常重要的作用。同时某些种群对环境、生物质量、水产品的食用安全也产生很大影响。本文对河北省沿海及河口的海水和沉积物中的异养菌群、大肠菌群、粪大肠菌群进行了初步调查,对微生物群影响环境质量的程度作出初步评价。为沿海水产养殖和水产品食用安全管理提供依据。     

一例雏鹅痛风病的诊治体会

一养鹅户鹅群陆续发病,通过流行病学调查、临床症状、病理剖解变化等初步诊断为雏鹅痛风病,并采取相应措施处理取得良好效果。     

“台湾泥鳅”人工繁殖试验

2014年5月17日-5月23日,在浙江省湖州对"台湾泥鳅"人工繁殖技术进行了初步试验。两次试验累计繁育"台湾泥鳅"水花850万尾,孵化率达到80%。通过"台湾泥鳅"激素配方、注射剂量、效应时间等问题的探索,初步得出浙江省地区"台湾泥鳅"繁殖时间为5月份和适宜水温为24℃。还讨论了"台湾泥鳅"的种质、雌雄鉴别、水温及积温对其人工繁殖时间的影响等。     

一例雏鹅痛风病的诊治

一养鹅户雏鹅陆续发病,通过发病情况调查、临床症状、剖检病变、实验室检查等初步诊断为雏鹅痛风病,并采取相应措施取得良好效果。     

草（♂）鳙（♀）杂交的初步试验

我们为了扩大养殖品种,提高单位面积产量,为人类多作贡献、今年我场进行了草鳙鱼杂交试验,初步获得了成功。由于我们的水平关系,很多问题还没有得到解决,有待今后继续探讨,现仅就我们的初步试验过程和点滴体会来谈如下几个方面的看法：     

葛洲坝下中华鲟产卵场的调查研究

本文对葛洲坝下中华鲟产卵场的地点、范围、成熟比例、产卵量、敌害鱼类危害情况等进行了研究并作出了初步评价,同时为拯救中华鲟资源提出具体意见。     

综合经营、综合养鱼和生态渔业

本文阐述综合经营、综合养鱼和生态渔业三个不同的基本概念,并把三者性质、特点和发展方向作出初步探讨,为我国养鱼业的现代化发展提供一点基础知识。     

Do wild fish species contribute to the transmission of koi herpesvirus to carp in hatchery ponds?

The koi herpesvirus (KHV) has spread worldwide since its discovery in 1998 and causes disease and mortality in koi and common carp populations with a high impact on the carp production industry. Many investigations have been conducted to examine ways of distribution and to identify possible transmission vectors. The answers, however, raise many new questions. In the present study, different wild fish species taken from carp ponds with a history of KHV infection were examined for their susceptibility to the virus. In the tissue of these fish, the virus load was determined and it was tested whether a release of the virus could be induced by stress and the virus then could be transferred to naive carp. Wild fish were gathered from carp ponds during acute outbreaks of virus‐induced mortality in summer and from ponds stocked with carp carrying a latent KHV infection. From these ponds, wild fish were collected during the harvesting process in autumn or spring when the ponds were drained. We found that regardless of season, temperature variation, age and infection status of the carp stock, wild fish from carp ponds and its outlets could be tested positive for the KHV genome using real‐time PCR with a low prevalence and virus load. Furthermore, virus transfer to naive carp was observed after a period of cohabitation. Cyprinid and non‐cyprinid wild fish can therefore be considered as an epidemiological risk for pond carp farms.     

Infectious pancreatic necrosis virus in the environment: relationship to effluent from aquaculture facilities

Effluents from three fish hatcheries were monitored for the discharge and subsequent downstream distribution of infectious pancreatic necrosis virus (IPNV). Samples of springwater and surface water, and tissues from salmonid and non-salmonid fish were assayed for IPNV. Water samples were processed to recover virus by adsorption to an electropositive, microporous filter matrix. No IPNV was detected in surface water collected above fish hatcheries or in hatchery springwater supplies. The virus could be detected for at least 19.3 km below the point of effluent discharge from hatcheries and the prevalence of IPNV infection in stream-resident fish was 2.8%.     

Host tropism of infectious salmon anaemia virus in marine and freshwater fish species

The aquatic orthomyxovirus infectious salmon anaemia virus (ISAV) causes a severe disease in farmed Atlantic salmon, Salmo salar L. Although some ISA outbreaks are caused by horizontal transmission of virus between farms, the source and reservoir of the virus is largely unknown and a wild host has been hypothesized. Atlantic salmon are farmed in open net‐pens, allowing transmission of pathogens from wild fish and the surrounding environment to the farmed fish. In this study, a large number of fish species were investigated for ISAV host potential. For orthomyxoviruses, a specific receptor binding is the first requirement for infection; thus, the fish species were investigated for the presence of the ISAV receptor. The receptor was found to be widely distributed across the fish species. All salmonids expressed the receptor. However, only some of the cod‐like and perch‐like fish did, and all flat fish were negative. In the majority of the positive species, the receptor was found on endothelial cells and/or on red blood cells. The study forms a basis for further investigations and opens up the possibility for screening species to determine whether a wild host of ISAV exists.     

Occurrence of viral haemorrhagic septicaemia in rainbow trout Salmo gairdneri Richardson reared in sea-water

Abstract. Viral haemorrhagic septicaemia (VHS) is reported for the first time in sea-water cultured rainbow trout. Heavy mortalities with typical signs and lesions A VHS virus (serotype 1) was isolated from the diseased fish. The mortalities were caused only by the VHS virus and 80 days post transfer of trout to sea-water the mortalities reached 85%, of the initial population.
The disease was experimentally transmitted to rainbow trout, both in sea-water 3·10⁴ pfu/ml of virus or by intramuscular injection of various doses of VHS₁ (7·10¹ 7·10⁴ or 7·10⁴ pfu per fish). Death occurred in all infected groups and started earlier in sea-water. Typical signs of VHS were observed in moribund fish. Viral multiplication was demonstrated to have occurred in fish organs.     

Real-time PCR for the detection and quantitative analysis of IHNV in salmonids

The rapid identification and quantification of virus in diseased fish is a goal both conservationists and commercial aquaculturists have struggled to attain. Recently a technique for the detection of viral mRNA particles that uses fluorescent tagging and amplification has been developed. Utilizing primers and fluorescent labelled probes generated for the specific identification of the nucleocapsid (N) and glycoprotein (G) genes of infectious haematopoietic necrosis virus (IHNV), and an instrument that measures cyclic emittance of fluorescence, the presence or absence of virus can be easily and rapidly confirmed. This method is not only useful in confirming viral presence but is effective in measuring the relative or absolute quantity of virus present within the sample. This allows for the determination of the health status of a carrier fish by measuring the quantity of viral genomes or transcribed viral genes present. Because this method is based on sequence detection, instead of virus isolation in cell culture, it is also effective in determining the presence of pathogenic organisms from water, fish feeds, or other potential reservoirs of infection.     

Histopathology, electron microscopy and isolation of channel catfish virus in experimentally infected European catfish, Silurus glanis L.

Abstract Two groups of European catfish, Silurus glanis L., fingerlings were infected with channel catfish virus (CCV) by either intraperitoneal injection with 10⁵ TCID₅₀ of CCV, or bathing in water containing 10⁵ TCID₅₀ of CCV per 1·0 ml. The virus was isolated from spleen, intestine and brain of CCV-injected fish at day 1 and the titres ranged from 10^2·1 to 10^3·3 TCID₅₀/g. However, the tissue distribution of CCV was irregular and no virus was isolated after day 3 post-exposure. In CCV-bathed fish, the virus was isolated only from the liver of one specimen at day 3 post-exposure. No clinical signs of CCV disease developed in any of the fish. Specimens in each regime from all sampling periods showed some minor histopathological changes, but there were no differences between treatments. Lesions included oedema and focal haemorrhage in the liver and the spleen was congested. Electron micrographs of tissue samples showed the presence of a few virus particles around the nuclei of kidney, spleen and intestinal cells, and in or around a myelinated nerve within the optic lobes of infected fish during the first 4 days of infection.     

Inhibition of infectious pancreatic necrosis virus infectivity by extracts of rainbow trout, Salmo gairdneri Richardson, tissue

Abstract. Extracts of healthy rainbow trout liver, kidney, spleen and whole fry inhibited plaque production of infectious pancreatic necrosis virus (IPNV) in cell cultures. The mode of inhibition is not known, although it appears not to be manifest at the cellular level, as pre-treatment of the cell cultures with tissue extracts did not inhibit plaque production. Any effect on the virus itself was not permanent as the inhibition could be mitigated by treatment of virus/extract mixtures with 1,1,2-trichloro-1,1,2-trifluoroethane. The inhibition may be caused by prevention or reduction of virus attachment to the cell surface or, alternatively, the tissue extract may cause aggregation of the virus and thereby reduce the number of available infectious units. The inhibitory effect is also lost by dilution of the extract, reinforcing the claim that adequate dilutions of fish extracts prior to attempted virus isolation are necessary, especially for the detection of carrier fish.     

Pathogenesis of acute and chronic diseases caused by cyprinid herpesvirus‐3

The pathogenesis of cyprinid herpesvirus‐3 (CyHV‐3) was studied using different lineages of carp/koi. After exposure to the virus, infected cells were first found in the skin by histopathology and by in situ hybridization. The epidermis of the skin was most severely damaged and often sloughed off in the fish sampled on days 5 through 8, and the fish that were highly sensitive to the virus died within 8 or 10 days after infection. Serum osmolality of the infected fish, particularly just before death, was significantly lower, suggesting that the osmotic shock consequent on the damage to the skin was the direct cause of the acute deaths. On the other hand, clinical and histopathological observations indicate that the carp of a less sensitive lineage most probably died of viral encephalitis around 3 weeks after infection. For these fish, the largest number of infected cells was found in the central nervous system (CNS) sampled on day 12. A substantial amount of viral genome was found in the CNS of carp surviving more than 1 year after the infection. Thus, the CNS is probably a major target for CyHV‐3, and the virus can persistently infect the CNS, presumably establishing latency.