Current issues in fish welfare

Human beings may affect the welfare of fish through fisheries, aquaculture and a number of other activities. There is no agreement on just how to weigh the concern for welfare of fish against the human interests involved, but ethical frameworks exist that suggest how this might be approached. Different definitions of animal welfare focus on an animal's condition, on its subjective experience of that condition and/or on whether it can lead a natural life. These provide different, legitimate, perspectives, but the approach taken in this paper is to focus on welfare as the absence of suffering. An unresolved and controversial issue in discussions about animal welfare is whether non‐human animals exposed to adverse experiences such as physical injury or confinement experience what humans would call suffering. The neocortex, which in humans is an important part of the neural mechanism that generates the subjective experience of suffering, is lacking in fish and non‐mammalian animals, and it has been argued that its absence in fish indicates that fish cannot suffer. A strong alternative view, however, is that complex animals with sophisticated behaviour, such as fish, probably have the capacity for suffering, though this may be different in degree and kind from the human experience of this state. Recent empirical studies support this view and show that painful stimuli are, at least, strongly aversive to fish. Consequently, injury or experience of other harmful conditions is a cause for concern in terms of welfare of individual fish. There is also growing evidence that fish can experience fear‐like states and that they avoid situations in which they have experienced adverse conditions. Human activities that potentially compromise fish welfare include anthropogenic changes to the environment, commercial fisheries, recreational angling, aquaculture, ornamental fish keeping and scientific research. The resulting harm to fish welfare is a cost that must be minimized and weighed against the benefits of the activity concerned. Wild fish naturally experience a variety of adverse conditions, from attack by predators or conspecifics to starvation or exposure to poor environmental conditions. This does not make it acceptable for humans to impose such conditions on fish, but it does suggest that fish will have mechanisms to cope with these conditions and reminds us that pain responses are in some cases adaptive (for example, suppressing feeding when injured). In common with all vertebrates, fish respond to environmental challenges with a series of adaptive neuro‐endocrine adjustments that are collectively termed the stress response. These in turn induce reversible metabolic and behavioural changes that make the fish better able to overcome or avoid the challenge and are undoubtedly beneficial, in the short‐term at least. In contrast, prolonged activation of the stress response is damaging and leads to immuno‐suppression, reduced growth and reproductive dysfunction. Indicators associated with the response to chronic stress (physiological endpoints, disease status and behaviour) provide a potential source of information on the welfare status of a fish. The most reliable assessment of well‐being will be obtained by examining a range of informative measures and statistical techniques are available that enable several such measures to be combined objectively. A growing body of evidence tells us that many human activities can harm fish welfare, but that the effects depend on the species and life‐history stage concerned and are also context‐dependent. For example, in aquaculture, adverse effects related to stocking density may be eliminated if good water quality is maintained. At low densities, bad water quality may be less likely to arise whereas social interactions may cause greater welfare problems. A number of key differences between fish and birds and mammals have important implications for their welfare. Fish do not need to fuel a high body temperature, so the effects of food deprivation on welfare are not so marked. For species that live naturally in large shoals, low rather than high densities may be harmful. On the other hand, fish are in intimate contact with their environment through the huge surface area of their gills, so they are vulnerable to poor water quality and water borne pollutants. Extrapolation between taxa is dangerous and general frameworks for ensuring welfare in other vertebrate animals need to be modified before they can be usefully applied to fish. The scientific study of fish welfare is at an early stage compared with work on other vertebrates and a great deal of what we need to know is yet to be discovered. It is clearly the case that fish, though different from birds and mammals, however, are sophisticated animals, far removed from unfeeling creatures with a 15 s memory of popular misconception. A heightened appreciation of these points in those who exploit fish and in those who seek to protect them would go a long way towards improving fish welfare.     

Antibacterial Agents in Mediterranean Finfish Farming: A Synopsis of Drug Pharmacokinetics in Important Euryhaline Fish Species and Possible Environmental Implications

The literature pertaining to the use of registered antibacterial agents in Mediterranean finfish farming is reviewed, with an emphasis on the Greek fish-farming industry. This review provides a scientific resource dedicated to the design of future antibacterial dosing regimes in Mediterranean fish farming, where insufficient supporting information is currently available. This paper addresses the paucity in knowledge concerning pharmacokinetics and the efficacy and environmental impact of commonly used antibacterials needed to direct future research and promote good practices in the euryhaline fish farming industry. Several registered antibacterials are currently available for combating bacterial infections, including tetracyclines, (fluoro) quinolones, potentiated sulfa, penicillin and chloramphenicol derivatives. Based on the available data, oxytetracycline (OTC) and quinolone drugs (oxolinic acid – OA and flumequine – FLU) are the most widely used in Mediterranean aquaculture. As a result these drugs have received the most extensive studies, whereas, there is considerable paucity of reliable data on pharmacokinetic and the depletion characteristics of other drugs used, particularly potentiated sulfa, penicillin derivatives and florfenicol. We find there is incomplete data on drug efficacy and minimum inhibitory concentrations (MIC) for common antibacterials used against the major bacterial pathogens of Mediterranean fish species. Furthermore, a considerable lack of data on environmental drug concentrations around Mediterranean fish farms was also identified, highlighting the need for more extensive environmental studies to monitor contamination in environmental components i.e., water and sediment, and in non-target species (flora and fauna). Prudent selection and use of antibacterials can encourage lower dosage applications, enhance treatment efficacy, and help to minimize contamination of the environment. Selection of readily bioavailable drugs which have low environmental persistence, low aquatic toxicity and high antibacterial efficacy is advised, to reduce potential losses to the environment and associated toxic effects on target species and the development of bacterial resistance. Lack of present data made it impossible to provide thorough and accurate guidance on selection and use of antibacterials and approaches for minimizing environmental impacts for the treatment of major euryhaline aquaculture species.     

Development of nori markets in the western world

Extensive effort has been made over the past decade to introduce nori (species of Porphyra) farming in North America and other western countries. A key aspect has been the evaluation of markets within these countries and in the region as a whole. This report is an overview of relevant market data, including: (1) estimates of market sizes and values; (2) trends observed in these data over time, including extrapolations into the future; (3) typical market structures from producer to consumer; (4) examples of specific marketing efforts and their status. Possible activities that could enhance future prospects for these products within the markets of the western world are discussed.     

Speciation in monogonont rotifers

Monogonont rotifers are cyclical parthenogens livingin limnic habitats with considerable seasonalvariation and often with island-like features. Theoccurrence of bisexual reproduction in these organismsmakes it feasible to define fields for generecombination, i.e. biological species. In thispaper, we analyze the structure of the diversity inmonogonont rotifers using several data sets: taxonomicand intraspecific diversity as reported inidentification keys, morphological variation reportedin ecological studies, and allozyme and matingbehavior patterns. Our analysis suggests that siblingspecies may be frequent in rotifers. Monogonontrotifers seem to meet conditions for an activespeciation, which might be particularly promoted byseasonal specialization and timing of bisexualreproduction.     

Mass propagation techniques currently being used in the spawning and rearing of marine fish species

Propagation techniques for marine fish species, applicable to public aquariums, are reviewed based on work with ornamental tropicals and foodfish species. Adult conditioning, spawning procedures, incubation of eggs, larval rearing, larval food culture, and facilities are discussed with specific references to techniques used at Instant Ocean Hatcheries, Inc, for Anemonefish (Amphiprion spp) culture in synthetic seawater.     

Cultivation of Macrocystis integrifolia (Laminariales,Phaeophyta) in southeastern Alaskan waters

The artificial culture of Macrocystis integrifolia in southeastern Alaskan waters has been initiated as a first step in a project to augment the existing herring roe-on-kelp fishery in the state. The growing of Macrocystis in Prince William Sound has the potential of considerably enhancing this fishery by eliminating the costly importation of this kelp from southeast Alaska. In an ongoing feasibility study, Macrocystis has been cultured under laboratory conditions through the embryonic sporophyte stage and outplanted in waters near Sitka, Alaska (57° N). Growth of the outplanted kelps has been monitored as a function of the time and depth of the outplanting. Preliminary results suggest that light is limiting for growth in winter and that the optimal depth for outplanting will vary with the season.     

微生物絮凝剂在养殖废水处理中的应用

微生物絮凝剂作为一种新型的絮凝剂,因其安全、高效等特性,正逐渐成为目前水产养殖废水处理研究的热点。主要从微生物絮凝剂的概念、絮凝机理、特点、研究现状、应用实例等方面,分析了微生物絮凝剂作为水质改良剂在水产养殖中的应用前景,并就今后的研究趋势作了展望。     

植物在水产养殖废水处理中的研究进展

植物在生长繁殖过程中能吸收利用、富集、吸附和固定水产养殖水体中的有机物、无机物和重金属,降低养殖水体中的TP、TN、TSS、COD和BOD。同时,植物在水体中可通过其发达的通气组织和根系传输氧气,为微生物和其他生物的代谢活动提供适宜的条件。选择合适的植物构建人工湿地,通过人工湿地中植物、微生物和基质的物理作用、化学作用和生物作用处理水产养殖废水,可建立循环的水产养殖模式。将植物应用于水产养殖废水的处理,是实现可持续发展的生态型水产养殖的基础。本文综述了近年来藻类和高等植物在水产养殖废水处理中的研究进展。     

水培经济植物对污水中磷的吸收利用及去除效果

对13种经济植物在污水水培条件下净化污水中磷的能力进行了研究。结果表明,黑麦草(Lolium multiflorum)、水芹(Oenanthe stolonifera)、莴苣(Lactuca sativavar.angustana)、酸模(Poly-gonum iapathifolium)、生菜(Lactuca sativa)、小葱(Allium ascalonicum)、五月慢青菜(Brassica chinen-sis)等品种具有较高的净化能力。在4个半月的水培中,TP的去除量分别达到10.27、10.35、6.5~6.896、.91、5.72、5.46和6.19 g.m-2;TP的去除率分别达到94.5%、95.2%、93.6%~99.3%、99.6%、99.5%、95%和89.2%。植物吸收作用是最主要的污水磷去除机制,沉淀在污水磷净化中的作用较小。污水中磷的去除与植物的生长期密切相关。黑麦草、水芹等7种植物适宜作为苏南地区冬季化粪池污水水培植物。     

The Effects of Periphyton, Fish and Fertilizer Dose on Biological Processes Affecting Water Quality in Earthen Fish Ponds

The potential of periphyton-based aquaculture in South Asia is under investigation in an extensive research program. This paper is a further analysis of data from four experiments carried out in that framework, to explore periphyton, fish and fertilizer dose effects on water quality. Factor analysis and ANOVA models applied to a data matrix of water quality parameters in ponds with and without artificial substrates (bamboo poles and kanchi sticks), with and without fish (filter feeders catla and rohu, with and without bottom feeder kalbaush), and with a standard or 50% increased fertilizer dose, allowed us to identify the underlying ecological processes governing this novel periphyton-based pond system, and construct conceptual graphic models of the periphyton–environment relationships observed. We clearly established that the phosphorus flow is mainly linked to phytoplankton activity in the water column and decomposition on the pond bottom, while nitrogen flow is mainly linked to autotrophic (photosynthesis) and heterotrophic (decomposition and nitrification) processes that take place in the periphyton in addition to the water column and pond bottom. Consequently, disruption of the pond bottom by bottom feeding fish primarily promoted phosphate cycling and phytoplankton, while periphyton development on the supplied substrates and fertilization mainly improved oxygen balance and nitrogen related processes developing in the water column. The use of bamboo poles led to better results than kanchi sticks, related to the greater autotrophic periphyton development on bamboo and to the larger surface of bamboo poles that facilitate fish grazing and periphyton dislodgment that in turn have a renewal effect on periphyton. Stocking bottom feeding fish produces a fertilizing effect through the food web that benefits the filter-feeding fish and that makes it unnecessary to increase the dose of inorganic and organic fertilizers applied to the ponds. Thus, the output of this analysis will help the fish farmers in resource constrained countries to improve their production in periphyton-based ponds just by choosing bamboo substrates, stocking a bottom feeder fish together with the filter feeders, and saving money on fertilizers.