Pain and suffering in fish

The question on the capability of fish to feel pain and of suffering are still subject of discussion nowadays. In the article presented, the information available in the literature to date is summarised. Based on this knowledge, the conclusion is drawn that fish are capable of feeling pain and that they are able to suffer in the sense of the word as used in the German animal welfare law.     

Management of complications of cancer chemotherapy

Although the use of anticancer agents can be associated with severe side effects, on a practical basis complications of therapy are minimal to nonexistent. The clinician usually learns to feel more comfortable with these drugs as he or she treats more patients, to the point where treating a cancer patient with chemotherapy will become routine practice.     

Warmwater fish vaccinology in catfish production

The ability of the fish industry to provide a continuous supply of fish protein depends on both proper biosecurity and strategies to significantly reduce the risk of infectious diseases. Vaccination is a safe and effective means to prevent disease and to increase the productivity and profitability of farmed fish. Vaccines are likely to be the prime prophylactic measure of the future because of rapidly developing advances in fish vaccine technology and producer acceptance. The efficacy of a vaccine is influenced by a variety of factors that must be considered in the development of vaccination strategies for fish. This review highlights some of these factors. The response to a modified live vaccine against Edwardsiella ictaluri is used for illustration.     

Intraocular oxygen tensions in normal and diseased eyes of farmed halibut

We have previously documented ocular abnormalities in farmed halibut and reported that the production of gas-filled posterior segment cysts appears to be central in the pathogenesis of many, if not all of the signs in these eyes. In a number of fish, gas bubbles may be seen in the anterior chamber of the eye, especially after trauma or strenuous exertion associated with handling. A knowledge of the composition of this gas is important in understanding fully the mechanism of gas and cyst production. Here we report investigations into the composition of gas in the globes of normal fish, fish in which intraocular cysts have been documented previously by ultrasonography and fish where post-mortem examination demonstrated both gas- and fluid-filled choroidal cysts. High levels of oxygen were demonstrated in samples of aqueous from all fish but fish with affected eyes had a statistically significantly higher partial pressure of oxygen than did fish with normal eyes.     

Mortality of fish fry as a result of specific and aspecific cercarial invasion under experimental conditions

Although the effect exerted on fish by fluke cercariae developing in fish as intermediate hosts is fairly well known, cercariae of flukes requiring intermediate hosts other than fish occur in fish ponds in much higher numbers. To study the effect of these latter cercariae on fish fry, a few days old common carp fry (Cyprinus carpio) were exposed to cohorts of xiphidiocercariae or echinocercariae shed by one or two snails acting as intermediate hosts. The observed pathogenicity of these cercariae was compared to the well-known pathogenic effect of Diplostomum cercariae. Although Diplostomum cercariae proved to be the most pathogenic, occasionally also the other two types of cercariae could kill the common carp fry by invading their body. Xiphidiocercariae ingested by the fish penetrated the intestinal wall and developed into metacercariae within the body of the fry. They could also get into the musculature through the skin. The much larger echinocercariae invaded the gill cavity where they became encapsulated, thus hampering gill function and leading to fish mortality due to oxygen deficiency. Diplostomum cercariae were more pathogenic than the cercariae of the other two flukes in that they were shed by the intermediate host in very large numbers. Although much less xiphidiocercariae and echinocercariae emerged from the intermediate host snails than Diplostomum cercariae, the former could kill the fish fry already in lower numbers. These findings prove that fluke cercariae nonspecific to fish may exert pathogenic effects on fish, and presumably contribute to the early mortality of young fry placed out into fish ponds.     

Intensive culture of fresh water fish

Recently, eel recirculation systems have provoked increasing attention in intensive fish culture, especially concerning animal welfare. "Aquaculture", "Intensive Culture", and "Recirculation Systems" are often confused with each other. This study, first of all, differentiates among these terms. The economic relevance of aquaculture in the Federal Republic of Germany is demonstrated by figures. A tendency towards intensive methods can only be seen in trout and eel culture. The problems of recirculation systems are explained comprehensively. Particular emphasis is laid on the conflict between theoretical suitability of intensive fish production and the absence of commercially working systems. At present, intensive fish culture does not pose a serious animal welfare problem in Germany. However, it is necessary to define the biological requirements of fish concerning their optimal accommodation in aquaculture facilities. According to the Law for the Protection of Animals, these requirements have to be laid down in an ordinance. Only then control is possible as to whether aquaculture systems fulfill fish welfare demands.     

Health status of salmonids in river systems in Natal. I. Collection of fish and parasitological examination

A detailed microbiological and parasitological survey of salmonids and indigenous fish in the upper reaches of selected river systems in Natal was undertaken. Fish were collected from the rivers by electro-fishing, from dams by gill netting and from hatcheries along the rivers. A total of 678 fish from 26 different sites along 8 river systems were collected. No parasites could be detected on fish from four of the rivers tested. Parasites were, however, detected on fish from large production sites in Natal and in the rivers feeding these sites. Parasites which were detected were Ichthyopthirius multifiliis, various Trichodina spp., Apiosoma sp. and Gyrodactylus sp. The heads of all fish estimated to be less than one year of age were collected and examined for the spores of Myxosoma cerebralis. All of the samples were found to be free of this parasite.     

Diseases of aquarium fish--4: treatment

Prevention and treatment of aquarium fish diseases is described. A variety of husbandry factors may predispose to disease development and these should always be considered. Any treatment should first be tried on a small sample of fish as toxicity does vary between species.     

THE PLACE OF VETERINARY ANAESTHESIA IN "THE FUTURE ROLE AND EDUCATIONAL NEEDS OF THE VETERINARY PROFESSION" AND RECOMMENDATIONS REGARDING FRAMEWORK OF EMPLOYMENT OR POSTGRADUATE TRAINING IN VETERINARY ANAESTHESIA

I would say that the ultimate position holders of the D.V.A. find themselves in, is very largely dependent on the course of events over the next few years and in no small measure to their own endeavours. I feel that the holders of the D.V.A. should view this training period as one in which they have enlarged their own over all appreciation of the subject they have studied and have therefore, gained for themselves a material advantage over other members of the profession who have not in fact followed this line of study and that although there is a certain amount of despondency in the ranks of the veterinary anaesthetists at the moment, this should not be allowed to become an obstacle in the progressive development of this group.     

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.     

Ophichthid eels in the coelom of several Natal offshore reef fish

Mummified ophichthid eels are reported from the coeloms of several Natal continental shelf reef fish species. Originally mistaken to be parasitic, these eels are in fact free-living and are eaten by fish. Once ingested, they bore their way out of the stomach, using their pointed tails and become encapsulated in connective tissue within the coelomic cavity.     

Clinical evaluation of rodents.

The clinical examination of small rodents is like that of more conventional pets in that the same systematic approach is used to arrive at a problem list. The difference with these species is that their diminutive size, high metabolic rate, and lack of patience may be problematic for the clinician. With continued practice and patience, veterinarians can begin to feel comfortable in adding small rodents to the growing components of their practices.     

Microhabitat use, not temperature, regulates intensity of Gyrodactylus cichlidarum long-term infection on farmed tilapia--are parasites evading competition or immunity?

Gyrodactylids (Monogenea) are ectoparasites of fish, some of which negatively affect commercially valuable fishes. Temperature strongly regulates population dynamics of these viviparous flatworms in farmed and wild fish populations, with most gyrodactylid species showing positive temperature-abundance associations. In agreement with epidemiological theory, numerous laboratory studies demonstrate that these parasites cannot persist in confined fish populations without periodic introduction of susceptible hosts. Extinction of gyrodactylid populations is due to host immunity, which develops in several fish species. In this one-year study, we followed populations of the recognized pathogen Gyrodactylus cichlidarum infecting four genetic groups of confined tilapia (wild type Nile tilapia Oreochromis niloticus niloticus, red O. n. niloticus, Mozambique tilapia O. mossambicus and a red synthetic population called Pargo-UNAM) kept under farming conditions and subject to natural environmental fluctuations. Based on the antecedents given, we postulated the following three hypotheses: (1) parasite abundance will be regulated by water temperature; (2) parasites will induce host mortality, particularly during periods of rapid infrapopulation growth; and (3) gyrodactylid populations will eventually become extinct on confined fish hosts. We disproved the three hypotheses: (1) parasite numbers fluctuated independently of temperature but were associated to changes in microhabitat use; (2) although gyrodactylid populations exhibited considerable growth, no evidence was found of negative effects on the hosts; and (3) infections persisted for one year on confined fish. Microhabitat use changed over time, with most worms apparently migrating anteriorly from the caudal fin and ending on the pectoral fins. Gyrodactylid populations followed similar trajectories in all fish, aggregating and dispersing repeatedly. Several instances were found where increased parasite dispersion coincided with increased intensity of infection; as well as the opposite, where increased aggregation coincided with parasite population declines. Three alternative explanations could account for these observations: that parasites (1) experience differential mortality on different anatomical regions of the fish; (2) migrate to avoid intraspecific competition; and (3) migrate to escape localized immune responses induced by infection. Our data do not allow us to demonstrate which of these alternatives is correct, so we discuss the merits of each. We provide circumstantial evidence in support of the third explanation, because as shown in other fish host-gyrodactylid interactions where immune responses have been characterized, in this study worms progressively moved away from fins with high mucus cell density to those with low density - what would be anticipated if immune defenses occur and reach the fish surface through mucus.     

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.     

草鱼与青鱼、鳙鱼与团头鲂之间的细胞核移植

在草鱼与青鱼、鳊鱼与团头鲂之间进行核移植试验,获得了不同属鱼类间的草鱼细胞核和青鱼细胞质配合的核质杂种鱼——草青移核鱼幼鱼,以及不同亚科间的鳙鱼细胞核与团头鲂细胞质配合的核质杂种鱼——鳙团移核鱼,得率分别为0.9％和1.8％。核质杂种鱼的胚胎发育特征大多与受核体鱼相似,而形态特征大多与供核体鱼相似。表明胚胎发育明显受受核体细胞质的影响,而形态性状特征主要受供核体细胞核的影响。     

鱼源病原菌对氟喹诺酮类药物的耐药性分析

本试验旨在了解北京地区鱼源病原菌对氟喹诺酮类药物的耐药现状,提供氟喹诺酮类药物在防制鱼类疾病上合理规范使用的依据。从北京地区具有典型症状的病鱼脏器或病灶分离出16株病原菌,采用纸片扩散法检测病原菌对7种氟喹诺酮类药物的耐药表型,运用PCR法分析病原菌的喹诺酮类耐药基因gyrA、qnrA和qnrS的携带情况。结果表明,鱼源病原菌对氟喹诺酮的耐药基因阳性率显著高于耐药表型检出率,可能耐药基因检测比耐药表型检测更能推测病原菌的耐药现状。50%的病原菌至少耐受1种氟喹诺酮类药物,87.5%的病原菌至少携带1种喹诺酮耐药基因,显示北京地区鱼源病原菌对氟喹诺酮类药物已在基因水平呈现出严重的耐药,有必要严格控制此类药物在鱼类养殖上的应用。     

Effect of dietary alternative lipid sources on haematological parameters and serum constituents of <Emphasis Type="Italic">Heterobranchus longifilis</Emphasis> fingerlings

The worldwide increase in aquaculture production and the decrease of wild fish stocks has made the replacement of fish oil (FO) in aquafeed industry a priority. Therefore, the use of terrestrial animal fats and vegetable oils, which has lower cost and larger supplies, may be good as substitute for FO. This study investigate the effects of total replacement of FO by two terrestrial animal fats (pork lard and poultry fat) and three vegetable oils (palm kernel oil, sheabutter oil and sunflower oil) on haematological and serum biochemical profile of Heterobranchus longifilis over 70 days. FO-diet was used as the control. The haematological parameters were significantly affected by dietary lipid sources. Serum total protein was not influenced by the dietary lipids. However, serum cholesterol was significantly higher in fish fed diet containing sunflower oil. Glucose and activities of liver enzymes in blood serum were significantly reduced in fish fed alternative lipids when compared with the control. These results indicate that FO can be replaced completely with alternative lipids without any serious negative health impacts.     

Explaining Anti-Angling Sentiments in the General Population of Germany: An Application of the Cognitive Hierarchy Model

A cognitive hierarchy framework was used for understanding the impact of two wildlife value orientations (WVO), domination and mutualism, on anti-angling sentiments in Germany. We also explored anthropomorphism (i.e., attribution of sentience and pain perception to animals), attitudes toward animal rights, and attitudes toward recreational and catch-and-release angling as constructs that might mediate the influence of WVO on the support for a ban on recreational angling. Data from 1,043 randomly selected persons were analyzed using structural equation modeling. Results supported the suitability of WVO to explain the moral acceptability of recreational fishing mediated by animal rights ideology. We found little effect of anthropomorphism on attitudes toward recreational fishing. We conclude that convincingly answering the question of whether or not fish feel pain is unlikely to alter the social climate related to recreational fishing. By contrast, an increase of mutualism WVO in Germany is likely to elevate negative resentment to recreational fishing.     

Fish pathogen screening and its influence on the likelihood of accidental pathogen introduction during fish translocations

Fish translocations are an important tool in fisheries management, yet translocating fish carries the risk of introducing unwanted pathogens. Although pathogen screening can be a useful tool for managing the risk associated with fish translocations, screening cannot eliminate this risk. This paper addresses these problems by demonstrating that two elements must be considered when designing efficient and effective aquatic pathogen screening programs: (1) how many fish to screen and (2) how long to continue screening programs when repeated testing detects zero infected individuals. The chance that infected fish are translocated despite screening is the joint probability of (1) the failure of the screening to detect infected fish in the sample and (2) the actual presence of infected fish in the translocation batch. Our analysis demonstrates that transfer of an infected fish is most likely to occur at moderately low levels of pathogen prevalence because the probability of detecting at least one infected fish through screening increases as pathogen prevalence increases. Small screening samples (i.e., with a low number of individuals) are most likely to detect infected fish when pathogen prevalence is relatively high (i.e., > 5%). Screening programs should terminate after some number of successive screening events in which no infected individuals have been detected. The number of screening events is a function of the cost of the screening program, the cost of a pathogen translocation, and the probability that an infected fish will be transferred. Furthermore, our analysis indicates that the cost of a disease outbreak has relatively little effect on the length of time the screening program should continue. A more pronounced result is that screening programs that are inexpensive or allow a higher probability of pathogen translocation should be continued longer.