A description is provided of the anomalous conchiolin deposits which are formed by Pinctada maxima and which are associated with unusual mortalities. Comparisons are made with brown ring disease found in Ruditapes philippinarum and juvenile Crassostrea virginica. In P. maxima, the deposits are not organized into a ring but rather are broad-based and result in retraction of the mantle with the deposits lying outside the edge of the mantle. Vibrio sp. have been implicated in causing the diseases of P. maxima and R. philippinarum whereas the etiological agent of the disease in C. virginica is unknown. It is suggested that the coccoid bodies formed in the mantle of C. virginica, but not in affected P. maxima and R. philippinarum, are sequestered portions of cytoplasm formed as a result autophagocytosis. Stimuli which could be responsible for inducing sequestration are discussed. The ultrastructure of the presumptive autophagosomes is described and compared to similar bodies found in C. gigas infected with a herpes-like virus.

Successful commercial production of most cultured fish species has been facilitated by the intensification of larval rearing techniques. Siluroidei species are no exception and early attempts at larval rearing in ponds were soon superseded by intensive hatchery production, at least for those species that are farmed on a commercial scale. The review focuses on alternative life history strategies and how these may provide clues to the early nutrition and feeding of siluroid fishes, as well as on the development and efficacy of practical feeds and feed application. The paper highlights several commonalities in terms of the nutritional and feeding requirements of the larvae of the various species cultured on a commercial and subsistence basis. The requirement for live feed for some species appears to be of short duration and all species can be successfully weaned onto dry feed at a relatively early stage. This is considered to be one of the reasons why the intensification of larval rearing of Siluroidei fishes has, in general, been highly successful. The review also comments on the live food/dry food debate and clearly reveals that our knowledge of Siluroidei larval nutrition and feeding is sorely lacking for many species, in comparison to other groups of fish. This emphasises the need for a concerted fundamental research effort.

In the late 1980's juvenile oysters, Crassostrea virginica, spawned and cultured in New England and New York, began experiencing up to nearly 100% mortalities in some batches of juveniles. The cause of these mortalities was not ascertained immediately, but examination of dead and dying oysters did not reveal a previously recognized disease syndrome. Early studies showed that it was not an environmental or genetic problem, thus we hypothesized that a new, transmissible disease agent caused the observed mortality. This was verified under laboratory conditions where the disease was readily transmissible. Transmission was enhanced by warm water temperatures, 22–26 °C, and salinities of 18–30 ppt. Also, the infectious agent was filterable and sensitive to erythromycin, supporting the hypothesis that the causative agent may be a protistan parasite in the 2–6 μm size range. No evidence to support a viral or bacterial etiology was found.

The spionid polychaete Polydora sp. can live and reproduce inside the oysters' shell, excavating a U-shaped burrow the central portion of which is filled with detritus and particles of dissolved shell. The oyster responds by secreting an organic layer, confining the worm, and later covering it with calcitostracum. This process creates a characteristic "mud blister". Crassostrea gigas were analysed for the organic matrix amino acid content and 14 metals of the whole shell of normal oysters and severely Polydora infested ones. Amino acid, DOPA and FT-Raman analyses were also performed on isolated membranes from the characteristic mud blister and on prismatic layer insoluble matrix (PLIM) of infested oysters, with the aim of detecting any differences between the two organic matrices. Membranes and PLIM composition differ from whole normal shell organic matrix by having lower aspartate and glycine and higher levels of virtually all hydrophobic amino acids, especially alanine. There are no significant differences between membranes and PLIM in the ratio of charged to non-polar amino acids, respectively 0.54 and 0.59. L-DOPA content is also similar in the two matrices with 0.45 (± 0.18) and 0.57 (± 0.30) ng.mg−1 protein for PLIM and membranes respectively. The FT-Raman spectra of membranes is very similar to that of PLIM, suggesting that they have identical composition. Zinc, iron and manganese are significantly higher in infested than in normal shells. Infested oysters can provide an excellent opportunity for investigating normal biological calcification processes.

Emphasis on physiological adaptations to environmental changes in the catfish (Siluroidei), is a rather recent development like that of their use in aquaculture. The siluroid fishes with smooth scaleless skin and sensory barbels are adapted to live in a variety of aquatic environments ranging from freshwater and brackishwater to swamps and marshes both in temperate and tropical regions. However, very little has been explored on their expected wide range of physiological adaptations. Most of the results obtained in siluroid fishes are similar to those reported for other teleosts such as cypriniform species. However, there are some air-breathing siluroids, found in the tropical areas, with accessory air-breathing organs. Besides tolerating periods of water deprivation, some of these fishes have been shown to possess-special physiological and biochemical adaptive mechanisms to tolerate a wide range of adverse physico-chemical conditions in the ambient environment. Some of the physiological adaptive mechanisms of Siluroidei in general, and air-breathing species in particular, to important physico-chemical factors such as oxygen,temperature, ammonia and xenobiotics are reviewed and discussed.

Tous les grands groupes de parasites de poissons, aussi bien Protozoaires que Métazoaires, ont été signalés chez les Siluroidei. D'après leur localisation, chez l'hôte on peut distinguer: les ectoparasites qui vivent sur le tégument et/ou sur les branchies ; les mésoparasites que l'on rencontre surtout dans le système digestif; les endoparasites qui sont dans le corps (cavités ou tissus). Une accumulation anormale de parasites, par rapport à l'équilibre généralement observé dans la nature, engendre des effets pathogènes chez les poissons en aquaculture. Trois facteurs semblent importants dans le déterminisme de cette accumulation: 1) la vitesse de multiplication, liée au mode de reproduction, en particulier asexué; 2) la taille de l'organisme parasite, qui peut faciliter l'envahissement de l'hôte et 3) le type de cycle biologique, direct (monoxène ou holoxène), ou indirect (hétéroxène). La bibliographie consacrée aux Siluroidei montre que les agents pathogènes ou les parasites les plus étudiés dépendent de la forme d'élevage pratiquée (industrielle ou artisanale). Les parasitoses les plus couramment citées pour leur importance chez Ictaluruspunctatus sont détaillées. La question du parasitisme des autres Siluroidei élevés ou potentiellement intéressants est posée.

Based on an extensive literature search, the present overview discusses the economic relevant diseases of Siluroidei, cultured for human consumption. One herpes virus and two irido viruses play a significant role for channel catfish (Ictalurus punctatus), sheatfish (Silurus glanis ) and yellow bullhead (1. melas )culture, respectively. There is only one fish species-specific bacterial disease which has an economic impact in the catfish industry: Edwardsiella ictaluri. Secondary infections with opportunistic bacteria and fungi are of interest in all catfish species cultured both under intensive and extensive circumstances. Etiology, pathology, prevention and treatment are shortly discussed for all diseases. Also some diseases of unknown etiology, which occur in African (Clarias gariepinus ) and Asian (C. batrachus ) catfish, are described.

Specificities of the structural, chemical, physical and sensory characteristics of the flesh are reviewed and related to different aspects of flesh quality. Potential for processing of catfish is high in terms of mechanization but rather low in terms of processing yields. The variability observed in body conformation traits supports the possibility to improve processing yields by genetic selection. Little is known on the structure of catfish flesh but a higher cohesiveness due both to greater connective tissue strength and probably a greater homogeneity of muscle tissues is observed, compared to other freshwater species. Although the presence of adipose tissues has not been demonstrated, intermuscular adipose tissues contributes with red muscle to lipid deposits in commercial size. Lipid content in catfish flesh increases with age but even at commercial size it is still lower than what is reported in other cultured fish. There is however a tendency in recent years for an increase in lipid content in catfish flesh due to increased lipid content in the diet. Thus, further information on the control of lipid deposits is required in future especially in a view to improve taste and processing yields. The lipid composition of neutral lipids reflects that of the diet with high levels of monounsaturated fatty acids and a low w3/w6 ratio. Flesh colour is very subtle but it could be controlled either by the use of pigment supplementation in the diet or by rearing non pigmented catfish. Other physical characteristics of the flesh are very stable during the cooking process. Cooked flesh has a relatively low water-holding capacity and a low resistance to mechanical stress (compression, extrusion) thus contributing to the juiciness and tenderness of the flesh. The sensory characteristics of the flesh are somewhat neutral but consumers are able to detect the specific characteristics of different species such as Channel catfish, African catfish and European catfish. Significant efforts to standardize the sensory evaluation of Channel catfish have been made in the USA but flavor and aroma of catfish seem to be more related to the fish itself than to other factors such as the diet composition. New data is available on off-flavors related to geosmin and methyl-iso-borneol. Specific control of the phytoplankton species which produce these compounds appears to be possible. Storage on ice affects the flesh acceptability as it does for other fish species, but catfish flesh seems to be stable at least physically during freezing. Traditional processing is used for preservation of the flesh. New processing methods have been tested for the diversification of catfish products or to produce substitutes for other animal products. Catfishes are generally shown to be suitable for processing.

Production of channel catfish (Icta1urus punctatus), the most widely cultured foodfish in the United States, is confined for the most part to the southern states. The states of Alabama, Arkansas, Louisiana, and Mississippi account for more than 95% of total commercial production and processing. Mississippi accounts for more production and processing than the rest of the United States combined. Channel catfish are native to the United States. However, the farm-raised catfish, processed into many different consumer products, is considered to be a newly developed fish for marketing purposes. Production methods include intensive tank culture, raceway culture, and open pond systems. The open pond method accounts for almost all of the commercial production because it is more profitable. The other methods usually represent special situations as opposed to general cost effective systems. The culture of catfish in North America attained industry status in 1974 as production methods were adopted to provide fish for processing throughout the year. This development enhanced market development and tremendously contributed to the growth of the industry over the past 20 years. The industry is still in its infancy and shows much potential for continued growth in the United States. This potential is based upon the following: products from farm-raised catfish are widely accepted by consumers; the resources required are available for expansion on an economically efficient basis; and institutional support in terms of research, education, and market development is available to the industry.

Les travaux sur l'élevage des poissons Siluroidei originaires d'Amérique du Sud sont rares et se situent, pour la plupart, au niveau expérimental; cependant le potentiel de ces espèces dans le développement de l'aquaculture dans cette région est considérable. L'essentiel de l'information disponible concerne la reproduction induite. Des méthodes de reproduction contrôlée ont été établies pour plusieurs espèces, comme Pseudoplatystoma fasciatum, P. coruscans,Leiarius marmoratus, Sorubim lima. Pimelodus blochii, Calophysus macropterus, Rhamdia sapo (Pimelodidae) et Eremophylus mutisii (Trichomycteridae). Pour les Siluroidei dont le corps est couvert de plaques osseuses, Hoplosternum littorale (Callichthyidae) et Hypostomus sp (Loricariidae) peuvent aussi être mentionnés, de même que Arius herzbergii (Ariidae) pour les espèces d'origine marine. Chez les Pimelodidae, les techniques d'incubation sont similaires à celles habituellement employées avec succès pour les autres espèces de tendance rhéophile, du fait de la nature pélagique des œufs (flottants ou semi-flottants), d'une fécondité élevée et d'une absence de soins parentaux. Ainsi, les méthodes de reproduction employées sont voisines de celles qui ont été définies pour Colossoman macroponum (Serrasalmidae, Characoidei). espèce originaire du bassin amazonien et désormais élevée à l'échelle commerciale. L'élevage des larves et des juvéniles est reconnu comme la phase la plus critique de la gestion de l'élevage de ces poissons-chats. Ceci résulte principalement de la qualité des aliments et un mode de distribution, et d'un important cannibalisme. Les données sur la production et la commercialisation des alevins restent limitées vraisemblablement parce que la production n'est pas consolidée; celle-ci tend cependant à se mettre en place. en particulier pour les Pimelodidae, pour lesquels il existe une forte demande sur le marché des poissons d'ornement. Pour réduire le cannibalisme et ses conséquences chez des espèces d'importance économique, la production d'hybrides entre espèces de Pimelodidae piscivores et omnivores a été tentée avec un certain succès pour les croisements suivants : P. fasciatum, L. marmoratus, P. blochii, Practocephalus hemiliopterus, P. blochi, P. fasciatum. Les résultats montrent une bonne compatibilité génétique. La production piscicole des Siluroidei d'Amérique du Sud reste très faible. Les statistiques de pêche se rapportant à ces poissons sont incomplètes, voire inexistantes dans la région. L'élevage des espèces sud-américaines de poissons-chats pourra se dèvelopper lorsque leurs cycles biologiques en captivité seront mieux maîtrisés. l'élevage larvaire notamment, et lorsque les paramètres économiques conditionnant la rentabilité des exploitations auront été mieux évalués.

The African catfish Clarias gariepinus is undoubtedly the most suitable species for aquaculture throughout its distributional range. The reasons for this. which relate principally to the biology and ecology of the species, are briefly reviewed and commented upon. the species is currently farmed on a commercial and subsistence basis in over 12 African countries, the most important of which in terms of tonnage produced are Nigeria, South Africa, Zambia and Chana. The scientific and technological foundation for the farming of African catfish is sound. and has been developed mainly in The Netherlands, South Africa, Belgium and the Central African Republic. Most of the important culture parameters, inclusive of spawning, incubation, larval nutrition and rearing, production and feed formulation have received adequate attention for the successful farming of the species in Africa. Production levels. depending on the type of operation, range from < 1 to 40 t/ha per year, and exceed 800 kg/m3/year under ultra-high density commercial culture conditions. Food conversion ratios vary between 1:6 using agricultural waste, to 1:1.1 using formulated, least-cost feeds. Significant progress has also been made in the development of the technology for the farming of a related species, Heterobranchus longifilis and the hybrid of this species with Clarias gariepinus. Despite the technological kow-hnow, total recorded production of clariid catfish in Africa in 1993 was a mere ca. 4500 tonnes. Despite the fact that there may be a considerable margin of error in the reported production figures the farming of catfish in Africa is a marginal activity. The reasons for this are manifold and can be primarily pinned on market forces. inadequate regional infrastructures, production costs, the socio-economics of fish farming and the philosophy upon which aquaculture development in Africa is largely based. Nevertheless the future potential for the farming of clariid catfish throughout their distributional ranges is immense.

Outre Clarias gariepinus introduit en pisciculture au début des années 1970, d'autres poissons-chats (Siluroidei) africains ont vu leurs potentialités aquacoles faire l'objet d'une évaluation approfondie depuis une quinzaine d'années. Il s'agit des espèces appartenant aux genres Chrysichthys (Claroteidae) et Heterobranchus (Clariidae) étudiées principalement en Côte d'Ivoire, au Nigeria et au Bénin, et pour l'essentiel dans le cadre d'une aquaculture en milieu lagunaire ou estuarien. C'est en Côte d'Ivoire, au début des années 1980. que la reproduction de Chrysichthys nigrodigitatus, puis celle de Heterobranchus longifilis, a été obtenue pour la première fois en captivité suite aux travaux conduits par le Centre de Recherches Océanographiques d'Abidjan. Depuis, les cycles d'élevage des ces deux espèces ont été maîtrisés et un premier transfert vers le développement effectué. La pisciculture de C. nigrodigitatus est principalement monospécifique, de type intensive ou semi-intensive, en enclos lagunaires (Côte d'Ivoire) ou en étangs saumâtres (Nigeria). En Côte d'Ivoire (lagune Ebrié), le développement de son élevage se concrétise depuis 1991 par une production annuelle de l'ordre de 200 à 300 tonnes. H. longifilis présente une biologie très similaire à celle de C. gariepinus, mais avec l'avantage d'une croissance plus rapide. La production commerciale de cette espèce s'amorce actuellement en Côte d'Ivoire. L'élevage de type intensif en enclos lagunaires semble constituer l'une des voies appropriées pour le développement de l'élevage de ce poisson ; mais sa pisciculture en étangs d'eau douce connaît également des résultats encourageants. A partir de l'expérience ivoirienne, des projets de développement de l'aquaculture de H. longifilis sont en cours de réalisation au Niger et au Cameroun. La littérature récente fait également état d'élevages expérimentaux de H. bidorsalis au Nigeria. Des hybrides entre H. longifilis ou H. bidorsalis et C. gariepinus ont été produits en Afrique du Sud. en Côte d'Ivoire et au Nigeria. Toutefois, l'intérêt réel de l'utilisation de ces hybrides en aquaculture en comparaisn des espèces parentales reste à démontrer. Les résultats obtenus en Côte d'Ivoire indiquent que C. nigrodigitatus et H. longifilis constituent désormais une possibilité de diversification de la production, voire une alternative à l'utilisation de C. gariepinus, pour la pisciculture africaine. Une synthése des données existantes sur la biologie et l'élevage de ces espèces est présentée.

The commercially important fish which contribute substantially to the total inland fish production in South Asia areAurichthys aor, A. seenghala, Mystus cavasius, M. gulio, Rita rita, Wallago attu, Ompokbimaculatus, Heteropneustes fossilis, Clarias batrachus, Silonia silondia and Pangasius pangasius. These are widely distributed in all the South Asian countries; Pakistan, India, Bangladesh, Sri Lanka and Myanmar except Bhutan and the Maldives. In comparison to carp culture, catfish culture has just begun in the region. Techniques of seed production have been standardized in C. batrachus, H. fossilis and W. attu which can be spawned even repeatedly at short intervals of 30-40 days. Such methods are, however, in an experimental stage for other species. C. batrachus is the most popular and its traditional culture in rice fields is well known. It is now being incorporated in carp ponds and semi-intensive and intensive monoculture systems have also been developed. The species fetches a very high price in India and Bangladesh and has a great export potential. C. macrocephalus and C. gariepinus have been introduced in Bangladesh with considerable success but their impact on the indigenous species needs to be studied. A vast grow-out potential exists all over the region for small catfish in carp nurseries as a second crop. Extensive culture of large catfish in derelict ponds could be an intermediate step in their improvement through control of all trash fish. With increased seed availability, semi-intensive and intensive mono-culture systems, being tried experimentally, could be developed in the view of an industrial production of catfishes as new export items from the region, if conditions for proper water quality management, aeration and partial replenishment, and availability of adequate pelleted feed could be met.

La production aquacole de Siluroidei en Europe concerne le silure glane (Silurus glanis), indigène, et des espèces introduites assez récemment, comme le silure africain (Clarias gariepinus ) ou les poissons-chats américains tels que Ictalurus punctatus, I. nebulosus et I. melas. Quelques tentatives de production expérimentales d'Heterobranchus logifilis et H. bidorsalis sont aussi en cours. Les différentes espèces de Siluroidei sont produites dans des systèmes d'élevage variés, en monoculture dans les circuits en eau chaude, fermés ou non, en polyculture d'étang ou en systèmes intensifs en cages ou en bassins. Les Clariidés sont le plus souvent produits dans des circuits fermés thermorégulés du fait de leurs exigences vis-à-vis de la température, mais quelquefois en étang, lors de la saison chaude. Les Ictaluridés sont élevés en étang en conditions intensives ou semi-intensives. le silure glane est produit soit en polyculture d'étang comme carnassier d'accompagnement, soit en eau chaude (effluents thermiques ou sources géothermiques), les circuits fermés thermorégulés étant de plus en plus abandonnés. En France particulièrement. des systèmes de production intensive en bassins sans renouvellement d'eau ou avec lagunage des effluents tendent à se développer; les coûts de production y sont relativement bas et les rejets dans l'environnement quasi-inexistants. La production de Siluroidei en Europe, peu importante actuellement, ne concerne que peu de pays, notamment, l'Allemagne, la France, l'Italie, la Belgique, la Hongrie, la République Tchèque et les Pays-Bas. les chiffres font apparaître des évolutions de la production de Siluroidei très variables suivant les espèces et les pays (évaluation de la quantité totale produite en 1993 : environ 4 195 tonnes, dont 2 080 tonnes de I. melas, 1 210 tonnes de C. gariepinus, 602 tonnes de S. glanis, 302 tonnes de I. punctatus). En Europe orientale, la consommation de Siluroidei est en régression, du fait du renchérissement du coût de production et de la baisse du niveau de vie mais aussi de la difficulté d'exporter vers l'Union européenne. En Europe de l'Ouest, la transformation du poisson sous forme de filet (près de 90 % de la production de (C. gariepinus) permet d'améliorer la commercialisation des Silures en conquérant des marchés dont il reste toutefois à préciser l'importance. Les caractéristiques de la chair des Siluroidei (chair blanche sans arêtes intramusculaires, bon rendement, qualités organoleptiques) augurent favorablement d'un développement de la production en Europe dans les années à venir.