鱼粉的质量控制及其在淡水鱼饲料中的应用

<正>1鱼粉质量1.1鱼粉质量标准鱼粉的质量标准是鱼粉质量控制的判别标准,我国已经对鱼粉的质量标准作了修改,表1列出了新版鱼粉质量标准的主要技术参数。1.2鱼粉质量的主要内容     

Occurrence of infectious fish diseases in fish farms in northern Finland.

A total of 47 fish located in 10 lake and river systems in northern Finland were examined for furunculosis, enteric redmouth diseases (ERM), viral fish diseases and the parasite Gyrodactylus salaris. Furunculosis was found in 2 fish farms in different watercourses, ERM in 8 fish farms in 3 watercourses and viral diseases were not found at all. G. salaris was looked for only in salmon and rainbow trout and was found in both species in 3 farms belonging to 2 watercourses.     

New trends in parasitic infections of cultured freshwater fish

The 1980s are characterized by the appearance of new fish parasitoses, the clarification of the aetiology of diseases and new insights into the process of infection and the development of important parasites, especially myxosporidians. Two phaerosporoses have entered into the foreground: swimbladder inflammation (SBI) caused by Sphaerospora renicola in common carp and proliferative kidney disease (PKD) in salmonids. Both diseases must be reported in the German Democratic Republic (GDR). The connection between the "C-protozoa" in the blood and S. renicola in SBI was recently clarified by experiments by Molnar (1988). The results of our own investigations indicate that the "K-protozoa" phase of S. renicola parasitizes mainly the brain and sometimes the spleen, pancreas and liver before appearing in the swimbladder. Hedrick et al. (1988) in the USA and Odening et al. (1988b) in Europe first reported a Sphaerospora sp. in Salmo gairdneri in connection with PKD. The spectacular findings by Wolf and Markiw (1984) and El-Matbouli (1988) elucidating on the life cycle of Myxobolus cerebralis have not yet brought the revolutionary change expected for a general new estimation of myxosporidian transmission as a basis for ecotechnological control measures. Examples for the formation of new regionally specific parasite colonizations offer the far Eastern cyprinids introduced into Europe. In the GDR the silver carp is infected by Chloromyxum barbi (Myxosporidia) (Sedlazsek), the pathogenic Gyrodactylus sprostonae and two new Gyrodactylus species (Pectobathrii) (Lux). Eel parasites new to Europe are the obviously imported and highly pathogenic nematodes Anguillicola crassus and A. novaezelandiae (Paggi et al., 1982; Moravec and Taraschewski, 1988). In Central Europe the infestation of rainbow trout by the tapeworm Proteocephalus neglectus is increasing (Priemer, 1980; Hanzelova et al., 1988).     

Aphanomyces invadans and ulcerative mycosis in estuarine and freshwater fish in Florida

In the spring of 1998, the Florida Fish and Wildlife Research Institute received numerous reports of lesioned or ulcerated fish primarily from the St. Lucie Estuary on the southeast coast of Florida, an area known since the late 1970s for lesions of the ulcerative mycosis (UM) type. From these and archived reports, as well as others received from different areas of Florida, we documented that diseased specimens had randomly distributed skin ulcers (usually reddened or hemorrhagic) with raised irregular margins and, in some cases, deeply penetrating hyphae in the surrounding muscle tissue. Since 1998, 256 fish (comprising 18 species) with ulcerative lesions (from 15 different locations) were confirmed with hyphae in fresh squash preparation or by histological evaluation. Squash preparations revealed nonseptate, sparsely branching, thick-walled hyphae; histological sections revealed mycotic granulomas in the dermis that occasionally penetrated into the skeletal muscle. These pathological characteristics were consistent with UM caused by the oomycete Aphanomyces invadans in Southeast Asia, Japan, Australia, and the United States. For specific identification, six isolates from ulcerated fish were cultured and prepared for molecular characterization using established diagnostic methods. Ribosomal RNA gene sequence analysis identified three isolates as Aphanomyces invadans, one as the oomycete Achlya bisexualis, and two as the ascomycete Phialemonium dimorphosporum. A more extensive survey of 67 ulcerated skin samples from fish collected between 1998 and 2003 was performed using a polymerase chain reaction assay specific for Aphanomyces invadans. Of these, 26 (38.8%) samples from seven fish species and nine collection locations were positive. Confirmation of UM associated with Aphanomyces invadans represents new host records in Florida for the sheepshead Archosargus probatocephalus, striped mullet Mugil cephalus, white mullet Mugil curema, silver perch Bairdiella chrysoura, black drum Pogonias cromis, largemouth bass Micropterus salmoides, and American shad Alosa sapidissima.     

The anaesthetic potency of benzocaine-hydrochloride in three freshwater fish species

Anaesthesia was induced in the common carp, Cyprinus carpio, tiiapia, Oreochromis mossambicus and rainbow trout, Salmo gairdneri, at concentrations of 25; 50; 75 and 100 mg/1 of benzocaine-hydrochloride as well as neutralized benzocaine-hydrochloride at water temperatures of 15; 20 and 25 °C. The results obtained indicated intra-and interspecific differences in the susceptibility of fish to anaesthesia due to metabolic, chemoreceptive and temperature tolerance differences in and amongst the three species.     

The occurrence of bacteria pathogenic for humans in freshwater fish

Freshwater fish are of minor importance as vectors of food-borne disease in humans. These diseases can only rarely be traced back to bacterial pathogens. However, there is a number of bacteria with facultative pathogenicity for man, which are part of the natural aquatic environment. Among these bacteria, the motile aeromonads (A. sp.) have become more and more important. A review is presented on A. sp. infections which have been traced back to contact with fish or water. Critical discussion of these cases reveals that the etiological relevance of A. sp. remains unclarified. However, bacteria of this group can be associated with sometimes fatal infections in humans after contact with fish or water. As A. sp. are ubiquitous in water and can survive even in chlorinated tap water, infections are not necessarily restricted to contact with fish. Persons at risk (patients with chronic or malignant diseases, immunocompromised hosts, children, people with frequent contact with water) should be informed about the perceived risks of aeromonads and how to avoid infection. Preventive measures are the wearing of gloves for work which may easily lead to skin abrasions (f. i. gutting of fish) and total abstinence of raw seafood. As their occurrence is independent of the common indicator bacteria, A. sp. are to be included in hygienic monitoring programmes for any water.     

The food legislation evaluation of environmental chemicals in freshwater fish

During the last 1 1/2 decades different regulatory limits have been given to value pollutants in fish under food-legal aspects. Their requested target, which consists of an effective consumer's protection however has been missed by various reasons: The production and distribution of environmental pollutants cannot be suppressed by limits for food. The selective elimination of limit-exceeding individuals from a lot is impossible. Treating both, natural pollutants like geogenic mercury and anthropogenic ones similar seems to be indefensible with regard to food law. Therefore proposals are made to rule only anthropogenic pollutants by law, when regulatory limits are planned to be supplemented. In case of natural distribution less stringent advisory limits seem to be more suitable.     

鱼用饲料与鱼类健康

长期以来．多数水产养殖工作者习惯以“无病即是健康”来理解养殖鱼类的健康状态。但未发病的鱼并不表明其必定是健康的。因为疾病的发生与否是与宿主、病因(病原)和环境条件三要素密切相关。其中任何一个因素的存在与否或作用力的强弱变化，即可决定疾病是否能发生或导致疾病的终止。如养殖水体中不存在某些病原体。或者环境条件并不适合病原的孳生和繁衍，     

我国传统淡水养殖鱼类的困惑与市场出路

随着我国市场经济的发展与科技进步,在水产养殖业中,先是以热水性、温水性鱼类为代表如鳗鱼、罗非鱼、淡水白鲳等品种,后以冷水性鱼类为时尚如鳟鱼类、鲟鱼类、大鲵等,近期又以南美白虾、河蟹为主力军的名特优新淡水养殖品种层出不穷。与此同时,随着我国海洋鱼类资源保护措施的有力落实,海水鱼品种如黄鱼、鲈鱼、大菱鲆等养殖浪潮也一浪高过一浪,大有赶超淡水养殖品种的发展势头。在此背景下,传统淡水养殖品种如鳙、鲤、鲢、鲫等四大家鱼逐渐被市场冷落,养殖规模大幅缩水,商品价格直线下     

我国淡水名优鱼类的养殖现状及发展对策

随着我国经济改革的不断深入,人民生活水平不断提高,人们对名优水产品的需求与日俱增,从而促进了其养殖业的迅猛发展。以2000年为例,我国淡水养殖产量为1516万t,比1999年增长了6.68％,其中名、特、优水产养殖面积达到了324.18万hm~2,比1999年增长30.8％。名优鱼类养殖业,无论从养殖面积还是从养殖产量来看,都占据了淡水养殖业的很大份额,已成为我国水产养殖业中的一个主要经济增长点。我国的淡水名优鱼类养殖业,随着市场供求关系的变化,产业结构的不断调整,需求稳步增长,价格呈     

鱼类的营养与健康

鱼类营养与免疫功能的研究正逐步深入到特定营养素在鱼类疾病防治中的作用上。本文简要阐述了部分维生素（VA、VE和VC）、微量元素（Fe和Se）、蛋白质、碳水化合物和脂类对免疫反应的潜在影响及营养缺乏症的发病机理。综述了n-3和n-6多不饱和脂肪酸（PUFA）在非特异性和特异性体液免疫及细胞免疫中的功能性作用。此外，还介绍了细胞膜功能（如流动性和通透性）、PUFA的免疫效应与类二十烷酸如白三烯（LT）和前列腺素（PG）的形成密切相关。n-3和n-6PUFA的摄入量对巨噬细胞和白细胞产生的LT、PG数量有巨大的影响，直接影响到鱼类的免疫功能。虽然改变日粮可以潜在地防止鱼类疾病的发生，但仍需在营养素对常见疾病发生机理的特定作用上以及这些作用如何受到其它生理或环境因素的影响上做进一步的研究。     

Genotyping of Edwardsiella tarda isolated from freshwater fish culture system

The applicability of PCR-RFLP of 16S rDNA and conventional phenotypic methods for differentiation of Edwardsiella tarda associated in freshwater fish culture system was studied. In this study, by conventional biochemical tests and antibiotic resistant patterns 2 and 14 groups were obtained. But these methods failed to discriminate the isolates habitat wise. However, PCR-RFLP of 16S rDNA was found to be specific to detect habitat-specific isolates. All the fish isolates belonging to particular genotypes were found only in fish, not in water or sediment. Some of the genotypes were exclusively present in water and sediment. This study indicates the prevalence of site-specific genotypes in freshwater ecosystems. Molecular method is found to be superior to discriminate the E. tarda habitat wise to conventional typing methods.     

Occurrence of different serotypes of Erysipelothrix rhusiopathiae in retail pork and fish.

Retail pork (38 samples), cod (10 samples) and herring (10 samples) were obtained from 12 stores in the area of Lund in southern Sweden during September and October 1990. Erysipelothrix rhusiopathiae was isolated from 50% of the pork samples, 60% of the cod samples and from 30% of the samples from herring. Serotype 2 dominated on retail pork as well as on fish samples constituting 53% of the pork isolates (10 strains) and 33% of the cod isolates (2 strains). All E. rhusiopathiae isolates originating from herring were serotype 2 (3 strains). Serotypes 1b, 6, and 8 were isolated from retail pork only (6, 2 and 1 strains, respectively). Serotype 5 was isolated from cod only (3 strains) and so was serotype 9 (1 strain). The public health hazards with the occurrence of virulent strains of Erysipelothrix rhusiopathiae in retail pork and fish are discussed.     

First record of freshwater fish on the Cape Verdean archipelago

The Cape Verdean islands form a distinct aquatic freshwater ecoregion characterized mainly by temporal water bodies with an adapted invertebrate community. Freshwater fish were not previously recorded from the archipelago. During a non-exhaustive survey of freshwater bodies on five islands of the archipelago, the first presence of a freshwater fish was recorded. Using barcoding sequences, the species was identified as the guppy (Poecilia reticulata), a highly invasive species alien to the Cape Verdean Islands.     

Ranking freshwater fish farms for the risk of pathogen introduction and spread

A semi-quantitative model is presented to rank freshwater rainbow trout farms within a country or region with regards to the risk of becoming infected and spreading a specified pathogen. The model was developed to support a risk-based surveillance scheme for notifiable salmonid pathogens. Routes of pathogen introduction and spread were identified through a process of expert consultation in a series of workshops. The routes were combined into themes (e.g. exposure via water, mechanical transmission). Themes were weighted based on expert opinion. Risk factors for each route were scored and combined into a theme score which was adjusted by the weight. The number of sources and consignments were used to assess introduction via live fish movements onto the farm. Biosecurity measures were scored to assess introduction on fomites. Upstream farms, wild fish and processing plants were included in assessing the likelihood of introduction by water. The scores for each theme were combined to give separate risk scores for introduction and spread. A matrix was used to combine these to give an overall risk score. A case study for viral haemorrhagic septicaemia is presented. Nine farms that represent a range of farming practices of rainbow trout farms in England and Wales are used as worked examples of the model. The model is suited to risk rank freshwater salmonid farms which are declared free of the pathogen(s) under consideration. The score allocated to a farm does not equate to a quantitative probability estimate of the farm to become infected or spread infection. Nevertheless, the method provides a transparent approach to ranking farms with regards to pathogen transmission risks. The output of the model at a regional or national level allows the allocation of surveillance effort to be risk based. It also provides fish farms with information on how they can reduce their risk score by improving biosecurity. The framework of the model can be applied to different production systems which may have other routes of disease spread. Further work is recommended to validate the allocated scores. Expert opinion was obtained through workshops, where the outputs from groups were single point estimates for relative weights of risks. More formal expert opinion elicitation methods could be used to capture variation in the experts' estimates and uncertainty and would provide data on which to simulate the model stochastically. The model can be downloaded (in Microsoft(?)-Excel format) from the Internet at: http://www.cefas.defra.gov.uk/6701.aspx.     

Animal welfare aspects of the killing of fish

According to the Animal Protection Law (1986) fish are to be killed by methods which do not cause pain. However, the regulations do not cover the killing of non-food fish. A questionnaire, conducted among 85 fish scientists, revealed that single fish should be killed by a blow on the head, and larger numbers by electrical methods or by use of chemicals. Decapitation was proposed for eels. A regulation from 1936 stipulates the methods for the slaughtering of food fish. Mechanical or electrical stunning is compulsory except for eel and flatfish. The questionnaire showed that in general the present legal regulations are sufficient for the slaughtering of fish with the exception of eels. The commercially available apparatus for stunning and killing do not always fulfill the requirements of animal protection, slaughtering technology and safety for the user. Official testing of these apparatus as well as the evaluation of new methods--like CO2-stunning--are necessary in order to prevent the use of methods which are feasible, but do not fulfill animal welfare, especially for eel.