Sibling juvenile vundu Heterobranchus longifilis reared at 27 ± 1 °C under 12L:12D were fed during the day, at night or over the entire 24-h cycle, for periods of 14-15 d. Nighttime feeding gave the highest growth rates, best feed conversion, lowest mortality, fewest losses due to cannibalism and least growth heterogeneity. The trends were seen in fish of all ages and weights (31−101 d and 0.3−30.0 g), but differences were significant only for the smallest fish that were reared at the lowest stocking biomass (< 3.5 g·L−1). The effects of daytime and nighttime feeding were examined in 151-d old (85 g) juveniles stocked at different biomasses (3.4 and 13.6 g·L−1). The growth of vundu was density-dependent, being impaired at low stocking density, but this was substantially mitigated under nighttime feeding. Rearing at high stocking density, feeding at night or in darkness, may act through similar mechanisms that involve changes in the level of aggressive behaviour. It is suggested that nighttime feeding in intensive catfish culture could be replaced by 24-h feeding under conditions of permanent darkness.

The structure of gonads and gametes is highly diversified in siluroid fishes; in some groups the testes are composite with an anterior part formed of spermatogenetic tissues and the posterior part of seminal vesicles which may or may not store spermatozoa. For catfish species of aquacultural interest, ovaries present the same general morphology as in other teleosts with oviducts. Spermatozoa are biflagellated in the Channel catfish (Ictalurus punctatus) and monoflagellated in the European catfish (Silurus glanis) and African catfishes (Clarias gariepinus, Heterobranchus longifilis). The egg size shows considerable intergroup differences, from 0.8–1.2 mm in some Pimelodidae and Clariidae up to 15–20 mm in Ariidae. In numerous cases, the eggs are adhesive and develop either a surrounding sticky layer (Ictalurus, Chrysichthys, Silurus) or an adhesive attachment disc (Clarias, Heterobranchus). Fertilization is in general external but internal fertilization is reported in some species. The annual sperm production was measured in European catfish and Channel catfish as 1.7 × 1011 and 1.8 × 1010 spermatozoa.kg-1 body weight, respectively. In females, the fecundity ranges from about 50 eggs per spawn in ariids up to more than 100 000 eggs.kg-1 body weight, e.g. in pimelodids and clariids. A large variety of controlled reproduction systems are found in the siluroids. In some cases (Ictalurus, Chrysichthys, Hoplosternum), spawning occurs naturally in ponds or tanks provided that adequate spawning substrates are available; fertilized eggs are collected immediately after spawning and placed into incubators until hatching. But for most species, although natural or semi-natural spawning could be achieved in captivity, the tendency at the present time is to develop techniques using hormonal-induced ovulation and artificial insemination in order to control the various steps of reproduction and to allow gamete preservation and manipulation. Oocyte maturation and ovulation or spermiation can be induced in many species by a large variety of hormones (GnRHs, fish gonadotropins, hCG, various steroids etc). Some information is available on gamete biology and preservation. Sperm motility is short-lived, not exceeding 70–80 s of forward movement as in most other freshwater teleosts. A peculiarity of the European catfish sperm is the activation by urine during sampling which could be prevented by direct collection in an immobilizing solution (NaCl 200 mM, Tris HCl 30 mM, pH 7.0). Spermatozoa cryopreservation was successfully attempted in several species. Ova generally survive only a few hours after ovulation and fertilization must be carried out soon after. Methods for gamete collection, insemination and incubation of eggs are described for the most widely cultured siluroid species.

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.

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 thereasons 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.

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.

An overview is given of our present knowledge on taxonomy, phylogeny and biogeography of catfishes or Siluroidei, one of the worlds economically important groups of fresh and brackish water fishes. In an introductory chapter, the taxonomic position of catfishes in the ichthyological classification is discussed; their external morphology is briefly described and synapomorphies showing their monophyly are listed. In the following chapter, cattish systematics are presented. Thirty three families with 416 genera and 2 584 species are presently recognized, but these numbers are continuously changing; it is therefore obvious that the systematics of many taxa are still rather poorly known. For each family, data (if any) supporting their monophyly are given together with a short description of their external morphology. The valid genera are listed, with for each genus, the number of presently recognized species with a reference (if any) to a recent revisionary study. Contributions to the phylogenetic study of catfishes are scarce, and dealing only with a few families and with a limited number of taxa within the families. As a resultsonly few data on catfish phylogeny are presently known. Therefore, also our knowledge on historicalbiogeography of catfishes is seriously limited, until more date become available on interfamilial and intergeneric relationships.

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 Ictalurus punctatus sont détaillées. La question du parasitisme des autres Siluroidei élevés ou potentiellement intéressants est posée.

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.

Selection, hybridization, and genome manipulation in the Siluroidei is reviewed. Selection topics include strain evaluation, qualitative traits, quantitative traits, mass selection, family selection, inbreeding, and crossbreeding. Hybridization is discussed with reference to culture traits. Genome manipulation technologies-sex reversal, gynogenesis, androgenesis, polyploidization, and gene transfer-are considered with application to genetic improvement of Siluroidei. Strains of ictalurid catfish Vary significantly for traits such as growth, disease resistance, harvestability, reproduction, body conformation and carcass yield. Growth of domestic strains can be 250% greater than that of wild strains. Strain differences have also beenidentified for clariid, bagrid, and silurid catfishes. Mass selection has increascd growth rate by up to 30%. Heritability estimates predict a response to selection for the traits of disease resistance and tolerance to low oxygen levels. Crossbreeding strains of Ictalurus punctatus have improved growth, disease resistance and reproductive performance. Two generations of inbreeding depressed body weight of I. punctatus as much as 30%, and can reduce viability and reproductive performance. Hybridization of I. punctatus X I. furcatus has resulted in a 20% increase in growth. Traits for tolerance to oxygen deficit, feed conversion, disease resistance, harvestability, and carcass yield were also improved. Interspecific, intergeneric, and interfamilial hybrids have been made with clariid fishes; heterotic growth was indicated. Hybridization has also been used to combine desirable traits of parental species. Sex reversal of I. punctatus using estrogen treatment followed by progeny testing can result in monosex, all-male populations. Gynogenesis and androgenesis are approaches to production of inbred lines of catfish, but thus far have limited application in aquaculture. Polyploidization has been applied in several ictalurid, silurid, and clariid fishes, but predicted improvements in performance have not been realized. Gene transfer has been accomplished in I. punctatus and Clarias gariepinus using microinjection and electroporation; the foreign genes have been expressed and inherited. Transgenic I. punctatus containing salmonid growth hormone genes grew 20–40% faster than controls.

The genetic characterization of catfishes by means of phenotypic markers, karyotyping, protein and DNA polymorphisms contributes to or forms an integral part of the disciplines of systematics, population genetics, quantitative genetics, biochemistry, molecular biology and aquaculture. Judged from the literature, the general approach to research is pragmatic; the Siluroidei do not include model species for fundamental genetic research. The Clariidae and the Ictaluridae represent the best studied families. The systematic status of a number of species and families has been either elucidated or confirmed by genetic approaches. Duplication of ancestral genes occurred in catfishes just as in other vertebrates. The genetic structure of and gene flow among natural populations have heen documented in relatively few cases, while the evaluation of strains for aquaculture (especially Ictaluridae and Clariidae) is in progress. The mapping of genetic markers has started in Ictalurus.It appears that a more detailed knowledge of catfish populations is required from two perspectives. First, natural populations which are threatened by habitat loss and interfluvial or intercontinental transfers are poorly characterized at the genetic level. Secondly, the selection of suitable strains for aquaculture should be encouraged. Implementation should pose no problems given the present powerful means, such as DNA characterization combined with protein polymorphisms and phenotyping, to solve the above-mentioned issues.

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, Ompok bimaculatus, 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.

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 increasedlipid 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 thespecific 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.

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.