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*Station d'Hydrobiologie Saint-Pee sur Nivelle Diffusion du document : Station d'Hydrobiologie Saint-Pee sur Nivelle; National audience

*INRA, Station d'Hydrobiologie Lacustre Thonon-les-Bains (FRA) Diffusion du document : INRA, Station d'Hydrobiologie Lacustre Thonon-les-Bains (FRA); National audience

*INRA, Station d'Hydrobiologie Lacustre Thonon-les-Bains (FRA) Diffusion du document : INRA, Station d'Hydrobiologie Lacustre Thonon-les-Bains (FRA)

1 graph. Graphique etabli d'apres chiffres Bayer (1910)

The transit of three enterobacteria ( Escherichia coli, Salmonella typhimurium, Serratia sp.) normally housed in the digestive tract of homeotherms was experimentally studied in rainbow trout. Bacterial bodies occurred very soon after ingestion of the marked pellet by fish and showed that a part of the microbial population at least did not accompany the solid phase. The excretion of bacteria with the strain utilized and according to the temperature. The strains did not seem to multiply when passing through the digestive compartments.

Interspecific relationships between Atlantic salmon and coho salmon were studied at early life stages in laboratory and semi-natural stream channels. During emergence, the survival and dispersal patterns were similar for the two species in single or mixed populations. Survival of Atlantic salmon fry was reduced in the presence of older coho fry. However, no predation was observed. Microdistribution differed between the two species, with Atlantic salmon fry more numerous in riffles when coho were present. Coho juveniles had a pelagic and gregarious distribution, in contrast to the benthic behaviour of the Atlantic salmon. In laboratory streams, Atlantic salmon fry moved out or adopted a subordinate cryptic behaviour which allowed them to escape predation while negatively affecting their growth.

Effects of family differences on survival, length, weight, growth, and pyloric caeca number for juvenile rainbow trout Oncorhynchus mykiss were analyzed in binary associations of families (sib-groups), using a genetic variant with “golden” phenotype as a marker. In such an association, the performance of a family i mixed with family j depends on its own ability (P1), on the influence of the associated family (AJ), and on possible effects specific to the ij association. Experimental results showed that specific effects were negligible, and that the AJ influence was significant on body length and weight (after 3 mo of age), and opposite to the PJ value of the same family. Growth showed the same feature, but short of significance. The genetic marker caused some detrimental pleiotropic effects on length, weight, and growth, and some limited interactions with the familial factors studied. Results suggest that, when practicing selection, aquaculturists should prevent early size differences from becoming enhanced by competition, and should consider periodic size grading and multi-step selection. Results also suggest that family interactions should be accounted for when analyzing mixed-family genetic evaluation data.

The complementary DNA coding for European sea bass somatolactin was expressed in the pET-3a bacteria expression vector. The recombinant somatolactin (rbSL) was purified by size exclusion chromatography, and 95% of the protein remained in the oxidized form with negligible aggregation over prolonged cold storage. The identity of the recombinant protein was demonstrated by Western blotting with a rabbit polyclonal antibody against gilthead sea bream somatolactin. The same antibody was utilized in a radioimmunoassay procedure, using rbSL as standard and radioiodinated tracer. Curve displacements of pituitary and plasma samples paralleled the rbSL standard, and the midrange of the assay (8 ng/ml) was low enough to measure in a consistent manner the circulating SL concentration. To assess biological activity a single dose of rbSL (0.1 microg/g of body mass) was administered to juvenile gilthead sea bream by intraperitioneal injection. In comparison with saline-treated fish, rbSL did not modify the circulating amount of insulin-like growth factor I, whereas a 50% increase was found with the same dose of recombinant trout growth hormone (rtGH). Hormone treatment did not modify nitrogen-ammonia excretion, but both rbSL and rtGH increased carbon dioxide output and oxygen uptake, which in turn decreased the respiratory quotient (CO2 output per O2 uptake). This pattern of gas exchange suggests the enhancement of lipid catabolism, which is consistent with the observation that both hormones were able to inhibit the hepatic activity of acetyl-coenzyme A carboxylase. These new insights provide direct evidence for the involvement of fish somatolactin in energy homeostasis, which may serve to maintain the lipolytic tonus in different physiologic states.

The combined effects of feeding time (morning and evening) and dietary fat concentration on feed intake, growth, body composition and lipid tissue distribution were examined in rainbow trout fed on demand. To that purpose, diets with low (LE, 6% lipid) or high energy concentrations (HE, 24% lipid) were used in four treatments that combined provision of the same (HE-HE or LE-LE) or different (HE-LE, LE-HE) diets at morning and evening meals. Digestible energy intakes of the LE-HE (229 U kg(-1) d(-1)) and HE-HE (269 U kg(-1) d(-1)) groups were significantly different. There was no significant difference in the amount of energy intake between the two meals of the day in any of the treatments. The main effect of dietary treatment was on lipid intake; fish in the HE-HE, HE-LE and LE-HE treatments ingested approximately 3, 2.2 and 1.8 times more lipid than those on the LE-LE treatment. Growth, weight gain and protein gain were not affected by dietary treatment, but lipid gain reflected lipid intake; fish in the HE-HE, HE-LE and LE-HE treatments gained approximately 2.6, 2.1 and 1.7 more lipid than did fish on the LE-LE treatment. Body composition was significantly affected by dietary treatment;, whole body lipid content reflected lipid gain, and visceral lipid concentration was affected in a similar way to whole-body lipid. On the other hand, muscle lipid concentrations were similar in fish submitted to the HE-LE, LE-HE, and LE-LE treatments (< 4%), and were lower than in fish on the HE-HE treatment (ca. 5.5%). Consequently muscle lipid concentration was not directly related to lipid intake, because lipid intakes of fish on HE-LE and LE-HE treatments was higher than in those on the LE-LE treatment, while muscle lipid concentration was lower. Thus feeding fish with different diets in the morning and evening might have potential as a tool for manipulating lipid distributions and concentrations without major adverse effects on growth. (C) 2002 Ifremer/CNRS/Inra/IRD/Cemagref/Editions scientifiques et medicales Elsevier SAS. All rights reserved., Effets combinés de l'heure d'alimentation et du taux de lipides alimentaires sur l'ingestion volontaire, la croissance et la composition corporelle chez la truite arc-en-ciel. Les effets combinés de l'heure d'alimentation et du taux de lipides alimentaires sur l'ingestion volontaire, la croissance, la composition corporelle et la distribution tissulaire des lipides ont été étudiés chez des truites arc-en-ciel nourries à la demande. Pour cela, des aliments dont l'apport en énergie était faible (LE, 6 % lipides) ou élevé (HE, 24 % lipides) ont été utilisés de façon à fournir soit le même aliment (traitements HE¿HE ou LE¿LE), soit un aliment différent (traitements HE¿LE ou LE¿HE) aux poissons durant les repas du matin et du soir. La quantité d'énergie digestible ingérée par les poissons, soumis aux traitements LE¿HE (229 kJ kg¿1 j¿1) et HE¿HE (269 kJ kg¿1 j¿1), était significativement différente. Il n'y avait, quels que soient les traitements, aucune différence significative de l'ingestion d'énergie digestible entre les deux repas de la journée. En fait, le principal effet du traitement sur l'ingestion concernait les lipides, et les poissons nourris, selon les protocoles HE¿HE, HE¿LE et LE¿HE, ingéraient environ 3, 2,2 et 1,8 fois plus de lipides que ceux soumis au protocole LE¿LE. La croissance, le gain de poids et le gain protéique n'étaient pas différents entre les traitements, mais le gain lipidique reflétait le taux d'ingestion de lipides, puisque les poissons soumis aux protocoles HE¿HE, HE¿LE et LE¿HE ont eu un gain lipidique qui était environ 2,6, 2,1 et 1,7 fois plus important que ceux soumis au protocole LE¿LE. La composition corporelle des poissons était significativement différente entre les traitements ; les taux de lipides corporels reflétant les gains lipidiques, et les taux de lipides péri-viscéraux étant affectés de la même façon que les lipides corporels totaux. Cependant, les concentrations lipidiques musculaires étaient similaires entre les poissons soumis aux protocoles HE¿HE, LE¿HE et LE¿LE (< 4 %) et significativement plus faibles que chez les poissons soumis au protocole HE¿HE (5,5 %). Nous en concluons que le taux de lipides dans les muscles n'est pas directement corrélé au taux de lipides ingérés, car les poissons soumis aux traitements HE¿LE et LE¿HE ingéraient plus de lipides que ceux soumis au traitement LE¿LE, et pourtant leur taux de lipides musculaires était plus faible. Il semble donc possible de manipuler la quantité et la répartition tissulaire des lipides de la truite arc-en-ciel d'élevage, en distribuant des aliments à teneur lipidique différente, le matin et le soir.

En alimentation des poissons, le potentiel d’utilisation des glucides comme source d’énergie digestible est quelque peu controversé. Par exemple, la truite arc-en-ciel (Oncorhynchus mykiss), l’espèce la plus élevée en France, est considérée mauvaise utilisatrice des glucides, avec une hyperglycémie postprandiale prolongée et une baisse de croissance suite à un apport élevé en glucides (supérieur à 25-30 %). Afin d’améliorer l’utilisation des glucides alimentaires, une meilleure compréhension des mécanismes de contrôle nutritionnel du métabolisme du glucose s’est donc avéré nécessaire. Ainsi, en présence de glucides alimentaires, des études ont montré que la truite arc-en-ciel semble avoir des difficultés pour diminuer sa production endogène de glucose dans le foie et pour utiliser le glucose comme source énergétique au niveau musculaire. De plus, la truite présente des particularités dans le contrôle hormonal de l’homéostasie glucidique (somatostatines, glucagon-like peptide) qui jouent probablement aussi un rôle important., Dietary carbohydrates are potential sources of digestible energy. However, fish such as rainbow trout (Oncorhynchus mykiss) use dietary carbohydrates rather poorly: there is prolonged postprandial hyperglycemia. after feeding carbohydrates as wen as decrease in growth when dietary carbohydrate levels are above 25-30%. Of late, there is a regain of interest to understand the nutritional control of glucose homeostasis and utilisation in fish. Recent results show that in rainbow trout, while hepatic glucose phosphorylation is rather closely controlled by dietary carbohydrate supply, that of hepatic glucose production is not. Besides, efficiency of glucose utilisation as an energy source by muscle appears limited in fish. Further, the hormonal control of glucose homeostasis shows some specificities (somatostatines, glucagon-like peptide) which made fish distinct from mammals.

Cet article synthétise les résultats de travaux récents sur l’habitat de la truite commune pendant sa période juvénile en ruisseau. Par des approches in situ (affluents du Scorff, Bretagne) et en milieu expérimental, les variations temporelles d’utilisation de l’habitat ont été étudiées, ainsi que l’influence de certains facteurs abiotiques (vitesse de courant, profondeur, granulométrie, abris) et biotiques (prédation, compétition intraspécifique) sur les choix d’habitat de l’individu. A l’aide de la bibliographie sur le sujet, nous proposons un bilan des changements journaliers et saisonniers d’habitat du juvénile en ruisseau, depuis l’émergence jusqu’à la première reproduction. En matière de protection des milieux, l’accent est mis sur l’importance de la diversité des habitats disponibles dans les affluents où se reproduit l’espèce.

Les carotenoides sont des pigments naturels liposolubles tres diversifies et largement repandus dans la nature. Au-dela de leur role pigmentaire, ces composes sont susceptibles d'avoir des activites biologiques, certaines d'entre elles etant fondamentales : precurseur de la vitamine A, activite antioxydante ou immuno-stimulante. De plus, des enquetes epidemiologiques ont associe la consommation d'aliments riches en carotenoides et la prevention de certaines pathologies comme les cancers, les maladies cardio-vasculaires ou certaines pathologies oculaires.

The evolution of genetic variability is studied in six successive generations of a population originating from wild Helix aspersa. During the first three generations (G1 to G3), no artificial selection was applied. During the next three generations (G4 to G6), two lines were reared: a control line (C) and a line (S) selected for increased adult weight. Genetic variability is described by genealogical parameters (inbreeding, number of founders, effective number of founders and ancestors, effective number of remaining genomes) and by the additive genetic variance in adult weight. A large decrease in all parameters was observed between G1 and G2, suggesting strong natural selection: additive genetic variance in adult weight (transformed data) decreased from 0.0119 +/- 3.8 x 10(-3) to 0.0070 +/- 1.7 x 10(-3) (P0.05) and effective number of ancestors from 97.4 to 67.0. Selection also caused a large decrease during the first generation: additive genetic variance was 0.0079 +/- 2.1 x 10(-3) in G3 and 0.0040 +/- 1.1 x 10(-3) after the first selection cycle (P0.02). At the same time, the effective number of ancestors decreased from 59.2 to 29.5 and 24.2. This decrease is consistent with the theory of selection and the Bulmer effect.

In the Pacific Northwest, releasing captively reared adult salmon (Oncorhynchus spp.) for natural spawning is an evolving strategy for the recovery of imperiled populations. However, the ability of captively reared fish to spawn naturally may be compromised by their artificial rearing environments. In this study, wild coho salmon (O. kisutch) males outcompeted captively reared males and controlled access to spawning females in 11 of 14 paired trials in laboratory stream channels. In two cases where satellite males were observed participating in spawning, DNA genotyping results determined that they did not sire any of the progeny. When spawning occurred at night and was not observed, DNA results confirmed behavior-based determinations of dominance made before dark. Dominance was established soon after the males were introduced into a common arena containing a sexually active female. We hypothesize that decisions by subordinate males to avoid direct competition may have minimized conflict. The competitive inferiority of captively reared coho salmon in this and a previous study probably reflects deficiencies in rearing environments, which fail to produce appropriate body coloration and body shape and perhaps alter natural behavioral development.

A study was conducted on common carp (Cyprinus carpio L.) to determine the effects of environmental temperature experienced by embryos and larvae on the development of myotomal white muscle. Eggs from one female were divided into two groups following fertilisation and incubated at constant pre-hatch temperatures of 18 or 28 °C. At hatching, larvae from the 18 °C-incubated eggs were divided into two groups and either reared at the same temperature of 18 °C (‘cold’ group) or transferred over a period of 5 days (at 2 °C per day) to 28 °C (‘transferred’ group). Larvae hatched from eggs incubated at 28 °C were reared at the same temperature of 28 °C (‘warm’ group). Larvae were sampled at two developmental stages (stage 1, inflation of the back chamber of the swimbladder; stage 2, inflation of the front chamber of the swimbladder) and at 26 days post-hatching. The maturation of myotome shape during larval life was studied in parallel with the changes occurring in the organisation of white fibres. At stage 1, the epaxial part of the myotomes surrounding the vent had the shape of lamellae inclined backwards, and only one central layer of white fibres was present. At stage 2, the epaxial part of the myotomes began to acquire a V-shape, which was well developed at 26 days post-hatch. At stage 2 and at 26 days post-hatch, two layers of white fibres were identified: the initial central layer and a second apical layer. These differ in their orientation, the initial central layer being orientated backwards and the apical layer forwards, and in the mean fibre diameter, which is greater in the initial central layer. Studies on the effects of temperature (constant 18 °C, constant 28 °C, transfer from 18 to 28 °C at hatching) were carried out according to both the developmental stage and the length of the larvae. At stage 1, no significant differences were found between the three groups for larval standard length and muscle variables. The number of fibres in one quadrant of epaxial white muscle sectioned at the level of the vent was 100–111. At stage 2, there were significant differences between groups. Larval standard length and mass were higher in the cold group than in the warm group. The transferred larvae were of intermediate standard length but had a significantly higher cross-sectional area of white muscle than either of the other two groups. This increase in surface area was related to a 50 % greater fibre number (233) in the transferred larvae compared with the cold (165) or the warm (152) larvae. The increase in fibre number was more marked for large-diameter (>20 μm) white fibres located in the initial central fibre layer (+58–72 % in transferred larvae) than in small-diameter (⩽10 μm) white fibres mainly located in the apical layer (+18–35 %). In 26 days post-hatch samples, transferred larvae still showed a higher total number of white fibres than warm larvae, but the difference was no longer significant when the total number of white fibres was regressed against larval standard length, suggesting that this stimulation may be temporary.

A 21-day feeding trial was carried out to investigate the ability of first feeding European sea bass larvae to utilize medium-chain triacylglycerols as an alternative source of energy. Three compound diets based on soluble fish protein concentrate and yeast were supplemented with either 3% tricaproin (TC6), tricaprylin (TC8) or tricaprin (TC10). A diet containing triolein (TOL) was used as a reference diet. Diets were tested on four replicate groups of first feeding European sea bass larvae at 20°C, i.e. 6 days after hatching. At the end of the 21-day trial, TC8 yielded significantly higher survival (57±8% vs. 28±11% for the three other groups). Considered together, larvae fed TC8 and TC6 displayed better growth rates than larvae fed TOL and TC10 (final mean wet weights: 1.5±0.3 mg vs. 1.2±0.2 mg, respectively). The fatty acid composition of larval total lipid revealed a low deposit of medium-chain fatty acids (between 1 and 3% of total fatty acids) suggesting that medium-chain fatty acids were oxidized for energetic purposes. Tricaprylin and to a lesser extent tricaproin, appear to be potential energy sources for first feeding European sea bass larvae reared on compound diets.

This study was performed to assess growth rate, feed efficiency, and N and P loss of sea bass (initial body weight 3.5 g), held in 500-l tanks under ambient temperature and natural light, and fed according to the following methods: by automatic feeders that released feed continually in daylight according to feed manufacturers' recommendations (AF100%); half of the above continually in daylight (AF50%); half of the above again but in two meals only (AF50%M); and by self-feeders that supplied feed at low (SFL), medium (SFM) and high (SFH) reward. None of the feeding conditions affected the survival rate of fish. SFL fish had the highest specific growth rate, while AF50% and AF50%M the lowest. Population weight distribution in the restricted automatic-fed fish (AF50% and AF50%M) was more homogenous compared to the other feeding conditions. These two practices produced high feed efficiency ratios (0.93 and 0.95, respectively), compared to the AF100% (0.57) and self-fed ones (SFL: 0.60; SFM: 0.37; SFH: 0.21). Self-feeding at low reward of 0.6 g trigger −1 could be considered as the optimum feeding practice, combining higher weight gain, lower N and P loss, and intermediate feed supply compared to the other treatments. In the SFH method, fish did not adjust their manipulation of the self-feeders according to their feed needs. Daily feeding activity in all self-fed fish groups was independent of feeding reward.

The enzyme glucokinase (GK) (EC 2.7.1.1) plays an important role in the control of glucose homeostasis. Qualitative and/or quantitative variations in GK enzyme have been postulated by previous studies to explain why dietary carbohydrate utilisation is lower in gilthead seabream (Sparus aurata) and rainbow trout (Oncorhynchus mykiss) than in common carp (Cyprinus carpio). In this study, we report the isolation and characterisation of a full-length cDNA coding for GK in these teleosts. Amino acid sequences derived from these cDNA clones are highly similar to other vertebrate GKs. These findings, including a detailed phylogenetic analysis, reveal that GK gene highly homologous to mammalian GK exists in these fish species with similar tissue specific expression (mainly liver).

Genetic analyses were performed on the progeny of Atlantic salmon (Salmo salar L.) sampled in natural redds of three rivers flowing into the Bay of Biscay, the Nivelle, the Mandeo and the Sella. These rivers are at the southern limit of the European distribution of the species and their populations are small and endangered by human activities. Nine variable number of tandem repeat (VNTR) loci (five minisatellites and four microsatellites) were used for parentage analysis. Multiple male participation was recognized in the fertilization of eggs. A large proportion was fertilized by precociously mature parr. We demonstrate that multiple paternity derived from mature parr is crucial for the conservation of genetic variability in small populations of Atlantic salmon.

Atlantic salmon, Salmo salar, deposit their eggs in excavated depressions called nests. These nests are built from downstream to upstream within one or more redds, and each redd corresponds to a continuous area of the streambed disturbed by the female digging activities. Redd topographic measurements and egg excavation were performed to determine number of nests per redd and per female, nest depth, distances between successive nests, number of eggs deposited per nest, and egg survival in nests created by six grilse Atlantic salmon, five spawning in an experimental stream (Lapitxuri channel) and one in a natural stream (Lurgorrieta Creek, a tributary of the Nivelle River in southwest France). All females constructed a single redd, except one which built two redds in the channel. Redd surface area ranged between 2.3 and 5.7 m2. Each redd had a raised mound of gravel or dome under which most of the eggs were located, and an upstream depression or ‘pot’. Based on expected egg-to-juvenile survival rates previously obtained in the Lapitxuri channel and on juvenile recoveries, between 96 and 97% of the eggs deposited in the channel sections were retrieved. Each female constructed 7 to 11 nests over a period of 3 to 5 days. The first three nests had an average burial depth of 12.9 cm (±1.6 SD) which was greater than the last three nests (mean 9.5 cm±2.6 SD). Eggs removed from the first three nests had higher fertility rates (95.5% vs. 87.2%), greater survival (83.5% vs. 63.1%) and lower occurrences of abnormalities (1.9% vs. 5.5%) than those deposited in the last three nests. Typically, the percentage of eggs deposited per female decreased from the first to the last nest, such that the last two to three nests possessed only a small number of scattered eggs. Similar results were observed in the redd located in Lurgorrieta Creek. The adaptive consequences of the topographic features of redds and the egg allocation patterns we found are discussed.

The effects of diet processing technology on digestibility, postprandial ammonia excretion rates and plasma concentration of ammonia, glucose and cholesterol (CHOL) were determined in European sea bass. Four dietary treatments were compared: diet E0 (extruded basal fish meal diet); diet P0 (pelleted basal fish meal diet); diet E30 (extruded, 70% basal diet plus 30% wheat gluten) and diet P30 (pelleted, 70% basal diet plus 30% wheat gluten). Each dietary treatment was assigned to triplicate groups of fish (body weight: 200 g). Levels of ammonia-N excretion from fish fed the different diets were measured in water samples taken from culture tanks every 2 h. At the end of the experiment, plasma samples from 3 fish per diet, taken in alternative tanks every 2 h during 24 h, were assayed for ammonia, glucose and cholesterol determination. Nutrient digestibility was not affected by the diet processing methods used. Wheat gluten showed high apparent digestibility coefficient (ADC) values for protein, energy and organic matter. Postprandial ammonia excretion values showed maximum values between 4 and 10 h after the meal depending on treatment. Daily cumulative total ammonia excretion rates were lower in fish fed fish meal based diets than in those fed diets containing 30% wheat gluten. Irrespective of dietary formulation, fish fed extruded diets showed lower ammonia excretion than those fed the dry pelleted diets. Postprandial values for plasma ammonia ranged between 3 and 8 mg ml−1 and the pre-feeding values were reached 24 h after feeding in all treatment groups. Maximal levels of plasma glucose (120–180 mg ml−1) appeared within 6 to 10 h after feeding. Plasma cholesterol levels were lower in sea bass fed diets containing 30% wheat gluten than in those fed diets containing fish meal alone as the dietary protein source.

A 21-day feeding trial was carried out to investigate the ability of first-feeding carp larvae to utilize medium-chain fatty acids (MCFA). Six semi-purified diets, with a common casein and soluble fish protein concentrate basis, were tested on triplicate groups of 400 larvae. The diets were isolipidic (23–24% of dry matter). They differed only by triacylglycerol supplementation (10% of diet) which consisted of either triolein (TO), coconut oil (CO) or tricaprylin (TC) alone or in combination of two of these (TO+CO, CO+TC, TO+TC). Survival and growth rates of larvae fed with CO or TO were high (survival 95–97%, mean wet weight 60–67 mg after 21 days). Addition of TC (5 or 10% of diet) induced a significant mortality as early as 11 days of feeding and resulted in a final survival of less than 6%. TC also led to reduced growth rates (final mean larval weight 6–13 mg). The fatty acid (FA) composition of larvae fed with TO or CO reflected that of the diets with high levels of oleic acid (42% of total FA) in larvae fed with TO and lauric and myristic acids (17 and 10% of total FA, respectively) in larvae fed with CO. In contrast, larvae fed with TC contained only traces (0.3% of total FA) of caprylic acid but had higher levels of capric acid than other larvae (6% vs. 1–2%). Present results indicate an important difference in the utilization between MCFA supplied as CO (12:0) and TC (8:0).

Les mouvements migratoires des civelles en fonction des conditions environnementales sont étudiés à partir d'une campagne d'échantillonnage dans l'estuaire de l'Adour au cours de la saison 1997/1998. Cette campagne se déroule la nuit, pendant le flot, à 10 km en amont de la limite transversale de la mer, sur un secteur de 12 km, situé dans la zone de propagation de la marée. Les densités de civelles sont estimées à partir du poids capturé dans des filets à mailles fines par unité de volume d'eau filtré dans différents secteurs (5 stations, 3 traits de tamis par station et 2 prélèvements par trait de tamis en surface et en profondeur). Entre novembre et mars, les arrivées de civelles forment une courbe en cloche avec un pic de migration en janvier. Le flux de civelles transite dans cette zone, en surface et en profondeur, mais préférentiellement en profondeur si l'intensité de la lumière nocturne (phase lunaire) est forte et la turbidité de l'eau faible. La situation lunaire et la turbidité modifient le comportement des individus ainsi que leur accessibilité à la pêcherie. Compte tenu des observations effectuées, le schéma migratoire vertical de l'espèce peut être modélisé de la manière suivante : l'interaction entre la luminosité nocturne et la turbidité influence les déplacements de civelles dans la colonne d'eau en relation avec leur comportement lucifuge. Plus la lumière nocturne qui pénètre dans la colonne d'eau est importante et plus les civelles migrent en profondeur.

Shelf life and color stability of muscle of rainbow trout fed ketocarotenoids (astaxanthin and canthaxanthin) stored at 4 °C under vacuum-packaging conditions were studied by bacterial enumeration of mesophilic (TVC), psychrotrophic (TPC), and total coliforms (TC), TBARS (2-thiobarbituric acid reactive substances), color measurements (CIELCH), and carotenoid quantification by HPLC. An increase of TBARS values and microbial development was observed at 5 days when a loss in astaxanthin and canthaxanthin concentration occurred. A second decrease in canthaxanthin levels took place at 11 days when a maximun in TBARS values (5.9 ± 1.7 nmol of TMP/mg of lipid) was also observed. Decrease in carotenoid concentrations was not reflected by color parameters. Evidence indicated that astaxanthin is more stable than canthaxanthin under vacuum packaging at 4 °C. On the basis of a TVC limit of acceptability of 106 microorganisms/g, the shelf life of rainbow trout fillets, stored under vacuum packaging at 4 °C, was 5 days...

The influence of overripening on salmonid egg quality has often been described in artificial breeding. However, no information exists on the impact of this factor on fish reproducing naturally, although it is likely to be critical, especially in disturbed environments. Pairs of Atlantic salmon in which the size of the male and the female was evenly matched were released in a spawning channel from 1 to 12 days after ovulation. Handling did not affect egg quality. Overripening had a negative effect on egg viability. Egg mortality, infertility and malformations increased with the number of days after ovulation. In females which had just matured, 16·7% of their recovered eggs were dead, 3·1% were unfertilized and 1·7% were malformed, as compared to 25·4, 9·7 and 5·4%, respectively, in females that had been mature for at least a week. Overripening played a role in both female spawning behaviour and capacity to spawn, as females which had been mature for over a week released their eggs more quickly while they retained more ova in their abdominal cavity than early spawning females. Thus, in studies of reproductive behaviour and in particular of sexual selection, it is critical to take into account the maturation status of females since the duration of spawning activity is used by various authors to determine female sexual motivation. Alternatively, overripening may decrease the female selectivity for mates.

Apparent digestibility coefficients (ADCs) of macro- and micronutrients and energy of two diets were measured with common carp Cyprinus carpio reared at two water temperatures (18 and 25 °C). Two diets containing either soy protein concentrate (SPC) or Norwegian herring meal (FM) as a major protein source were formulated. Dicalcium phosphate was incorporated at a level of 4 % of the former diet. Duplicate groups of 20 fish (body weight: 55 g) were fed by hand twice a day to apparent satiety. After a 7-day conditioning period, faecal collection was made over 10 days using an automatic faeces collector. ADC of dry matter was not different (P > 0.05) between fish fed the two diets at 18 °C, but at 25 °C, we observed a higher ADC value in fish fed the FM diet than in those fed the SPC diet. ADC of protein was higher in fish fed the SPC diet than in the FM groups at either temperature. ADC of lipids was not different between the two groups at 25 °C but was found to be higher in fish fed the SPC diet than in the FM group at 18 °C. ADCs of energy and ash of the two fish groups remained constant at both water temperatures. Availability of phosphorus was significantly higher (P < 0.05) from fish meal based diets than from SPC based diets at both temperatures. A more striking effect of dietary protein source was found in the availability of calcium, which was lower in carp fed SCP based diets.

Gilthead seabream were fed a fish meal based diet, supplemented with graded amounts of ascorbyl polyphosphate equivalent to 0, 25, 50, 100 and 200 mg of l -ascorbate (AA)/kg, for 12 weeks. Although there were no significant differences between growth rates of each group, the feed gain ratio and voluntary feed intake were significantly lower, and the protein efficiency ratio was significantly higher for the fish fed 200 mg AA/kg, when compared with the group fed 0 mg AA/kg. An increase of the ascorbate concentration within the liver and spleen occurred with the increasing vitamin supplementation. After 12 weeks, the fish were subjected to hypoxia for 24 h to determine the influence of AA supplementation on the physiological response to this stressor. A significant hyperglycaemia occurred in fish fed all the diets 3 h after the onset of stress, although a significantly higher resting plasma glucose was observed in fish fed the AA free diet. No significant difference was found in plasma cortisol concentration with stress, with the exception of fish fed the 100 mg of AA/kg diet, where a significantly lower cortisol level was found after 9 h of hypoxia. Fish fed the non-supplemented diet showed wider variation and a tendency to increase this variable, having significantly higher levels at 9 h and 24 h of stress then all the other groups and than fish fed the 200 mg AA/kg diet, respectively. Stress had no detectable effect on liver AA concentration in all groups. However, spleen AA showed significantly increased levels between 3–6 h of hypoxic stress in fish fed 25 and 200 mg AA/kg diet and a further increase after 9 h in fish fed the 200 mg of AA/kg diet. These results suggest that the ascorbic acid requirements for seabream is less than 25 mg/kg diet based on a 12-week growth study and that it requires about a four-field increase in weight before signs of deficiency can be observed. Also, the fact that no variation in liver vitamin C concentration was be detected as a response to stress, suggests that this kind of stress does not significantly increase the utilization of this vitamin. However, a possible relation between dietary ascorbate and the physiological response to hypoxia was found, since the fish receiving the non-supplemented diet showed increased plasma glucose and a tendency to have wider plasma cortisol variations than the fish fed the supplemented diets.

Histological observations were made in common carp larvae in order to understand the origin of the phospholipid (PL) requirement of fish during their young stages. Larvae were fed for 6 or 8 days after start-feeding on semi-purified diets containing peanut oil and supplemented with or without different PL fractions enriched in phosphatidylcholine (PC) or phosphatidylinositol (PI). A group of larvae was also fed Artemia nauplii. Dietary PL deficiency was associated with an accumulation of fat droplets in the enterocytes of the anterior intestine, an increase in height of mucosal epithelium, a reduced total liver volume and mean hepatocyte volume. In contrast, diet supplementation with PC from hen egg yolk or from soybean prevented the intestinal steatosis and resulted in larger liver volume and larger hepatocyte volume. Larvae fed Artemia showed the same features as larvae fed PC-enriched diets. Hydrogenated PC also prevented the intestinal steatosis but resulted in small liver and hepatocyte size. Larvae fed PI-enriched diets exhibited intestinal steatosis, although less systematically than larvae fed PL-deficient diets, and reduced liver and hepatocyte size. Results support previous opinions that PL are needed for the absorption of neutral lipids although their beneficial effect appears to be independent of their emulsifying properties. The limiting stage seems to be the synthesis and exportation of chylomicrons or very low density lipoprotein (VLDL) by the enterocytes and not the intraluminal formation of micelles. PC appears to have a specific role for chylomicrons and VLDL synthesis and secretion, as in mammals. The reduced liver and hepatocyte size in the absence of PC could result from a decreased energy supply due to poor lipid absorption.

Kinetics of a 100 μg oral dose of astaxanthin (AX) or canthaxanthin (CX) was determined from serum AX or CX concentration−time curves in 234 immature rainbow trout, Oncorhynchus mykiss, with a mean body weight of 300 g. Carotenoid concentrations in serial serum were measured using HPLC. The net change in mean peak serum concentrations in rainbow trout fed AX or CX reached 4.4 ± 1.0 nmol/mL of serum at 18 h post-dosing for AX and 2.9 ± 0.5 nmol/mL of serum at 12 h post-dosing for CX. The maximum level of CX serum was 1.6 lower than that of AX. In terms of absorption speed, AX and CX are likely equivalent. The relative bioavailability of CX, with respect to AX taken as the reference, corresponds to 33.5%. AX was more slowly removed from the serum than CX. The mean retention time of AX (56.4 h) was 2.4-fold that of CX (23.1 h). Keywords: Astaxanthin; canthaxanthin; serum kinetics; pharmacokinetics; rainbow trout

Thirty two families (representing 397 fish of 900 g average weight) of rainbow trout. Oncorhynchus mykiss (Walbaum) (16 diploid sib-groups and their homologous triploids obtained by heat shock) were fed astaxanthin (96 mg kg-1 feed) for 39 days, resulting in a red colouring of the muscle. The colour was measured in the CIELCH colour space using a chromameter at three points of fish muscle (head, middle and tail). The effects of ploidy, sex, family and location of measurement on the colour attributes offish muscle (lightness, chroma and hue angle) were analysed. Diploid fish had a higher chroma than triploid ones (P

In wild fish, gonad maturation and spawning induce modifications in feeding behaviour and dynamics of body stores which are possibly responsible for metabolic disorders. Conversely, food manipulations can modify reproduction of captive female broodstock. A restricted diet during early stages of the life cycle delays the first maturation age, a quantitatively restricted food supply during the stages of oocyte differentiation reduces the egg number, while a reduction of food levels during the last phases of oogenesis has only a small effect on egg size, composition and hatchability. During the spawning period, salmonid female broodstock seem to be more able to utilize carbohydrates than immature fish, they valorize the energy brought in by fats and have low quantitative requirements for proteins (28%). On the other hand, Red Sea bream broodstock have higher needs for proteins (45%). The incorporation into diet of liposoluble vitamins and essential fatty acids is necessary for normal reproduction, but (n-6) fatty acids seem to play a more important role than in juveniles. Although the effects and physiological role of carotenoids are not yet well known in salmonids, they are necessary for normal development in Red Sea bream. Although little work has been done on the effects of mineral nutrition, special attention must be paid to trace elements, manganese in particular. The major part of this review concerns female broodstock, since very little interest has been devoted to males.

The effects of constant temperatures on growth, food efficiency, and physiological status were studied in four different batches of juvenile turbot. The growth responses were studied in three experiments lasting 70–85 days under 8–20° C thermal conditions. There was a positive correlation between growth and temperature from 8 to 17° C and a plateau was observed from 17 to 20° C. In fish fed to satiety, specific growth rate was positively correlated to the food intake, which was double at 20° C, compared with 8° C. Minor changes were observed in food efficiency. Body fat deposition decreased as temperature increased (25% lower at 20° C, compared with 8° C). Apparent food conversion, PER (protein efficiency ratio) and PUC (protein utilization coefficient) ranges were 0.8–0.9, 2.1–2.3 and 33–38% respectively. In 70–300 g fish, routine MO2 increased (2.5–6.5 μmol O2 h−1 g bw−1) with temperature up to 20° C, while larger turbot (500–600 g) appeared relatively thermo-independent, with a lower oxygen consumption (1.5 imol h−1 g−1). The average daily total ammonia nitrogen (TAN) and urea-N excretion per fish biomass was positively related to temperature. TAN was 30% lower at 8° C, compared with 20° C. Ingested nitrogen was mainly excreted under the final form of TAN, urea-N representing 26% of the total amount. A post-prandial peak in TAN and a delayed peak in urea-N nitrogen were observed. The hydromineral status [osmolarity, sodium, chloride and potassium blood plasma, gill (Na+-K+)-ATPase activity] of turbot was not affected by progressive changes in temperature during the acclimation period. Juvenile turbots show remarkable homeostatic capacities and so they have a relatively thermo-independent physiology within the range of temperature studied.

A trial was undertaken with juvenile Nile tilapia fed graded levels of dietary protein (0–35% DP) over 7 weeks (28°C). Measurements of nitrogen and energy utilization were made using data on ADC, comparative carcass analyses, nitrogen excretion and oxygen uptake. Data indicate that the daily protein intake for maximum N gain was c. 12 g/kg/d and the maintenance protein requirements were about of 2g/kg/d. The optimal DP/DE ratio was found to be 18mg/kJ. Differences were observed in the data on endogenous nitrogen and energy utilization depending on the dietary treatments as well as on the criteria used.

Rainbow trout (Oncorhynchus mykiss) with a mean (sd) weight of 120 (2) g were fed diets supplemented with astaxanthin extracted from the yeast Phaffia rhodozyma (OY1 = 50 mg carotenoids kg−1 feed, OY2 = 100 mg carotenoids kg−1 feed), astaxanthin (AX = 100 mg astaxanthin kg−1 feed) and canthaxanthin (CX = 100 mg canthaxanthin kg−1 feed) for 4 weeks. Muscle analyses at the end of the experiment indicated a significantly higher carotenoid concentration in the AX group, while CX and OY1 groups were similar in spite of the differences in dietary concentration. The measure of total muscle colour difference (ΔE* ab) between initial samples and 4 week ones was higher for the AX fish group but showed no significant difference between OY1, OY2, and CX. The hue and the reflectance ratio (R650:R510) of fish muscle increased in proportion to carotenoid intake. Digestibility (ADC) of yeast astaxanthin in OY1 and OY2 groups was significantly higher than that in the AX group. Canthaxanthin ADC was about one sixth of that of astaxanthin (AX group). Carotenoid retention in the muscle, expressed as a percentage of carotenoid intake, was higher for the AX group than that recorded for OY1 and OY2. According to ADC, carotenoid retention showed a marked lower value for the CX group. Muscle retentions were similar for astaxanthins from both sources.

Les premiers comportements alimentaires après l'éclosion de jeunes larves de saumon Atlantique et de truite commune ont été analysés par examen de leurs contenus stomacaux. Les échantillons de larves provenaient de paniers grillagés contenant au départ 50 oeufs, de l'une ou l'autre espèce, mélangés à des graviers et introduits dans le substrat de ruisseaux artificiels extérieurs, alimentés par un cours d'eau naturel. Dans deux cages plus grandes, munies d'un piège de dévalaison, une centaine d'oeufs de chaque espèce constituait le témoin de développement. L'analyse simultanée du déroulement de l'émergence, du degré de résorption de la vésicule, de la croissance des larves et de leurs contenus stomacaux a permis de mettre en évidence que la prise alimentaire est postérieure à l'émergence et démarre, avec la perte de poids de l'alevin, avant la fin de la résorption de la vésicule pour les 2 espèces. Le comportement alimentaire est un peu plus précoce chez les truites. Chez les saumons, la capture des proies est précédée par une phase d'ingestion de débris végétaux liée au positionnement benthique des alevins.

Much research has focused on the developmental behaviour of fish and it has been shown that their sensory and physical capabilities evolve very quickly during their early life. Thus, ontogenesis could influence fishes preferences for particular environmental factors. Little is known about the habitat preferences of trout during the post-emergence phase and it is not known if they correspond to the preference curves established by the PHABSIM method for the‘ alevin phase‘. Here, the downstream movement and habitat preferences of young emerging trout were studied in a flume. In the absence of predators, alevins preferred a water depth of 20 to 30 cm and pebble rather than gravel substratum. When emergence occurred in an area with 1+ trout and sculpin, Cottus gobio, almost all the emergent trout remained cryptic. When visible, most of them were in the shallowest area (10cm depth) where their preference for pebble substratum was less marked. The presence of 1+ trout and sculpin increased the movement downstream of young trout by 20% without changing the general and diel patterns of catches. Their presence also reduced the initial growth of 0+ trout.

International audience; A study utilizing casein-com gluten meal based diets supplemented with crystalline amino acids was conducted to determine the quantitative arginine requirement of Atlantic salmon smolts. Fish were gradually acclimated to sea water (32 ppt) and maintained for 8 weeks prior to commencement of the study. Triplicate groups of Atlantic salmon were fed to satiation diets (CP: 40% DM) containing 1. 1-3.2 g Arg/ 100 g diet (2.7-8% of protein) for a period of 8 weeks. Growth, feed utilization and nitrogen retention data showed the requirement for arginine of Atlantic salmon to be 1.6% of dry matter (4.1% of dietary protein). An arginine requirement of 1.6% of dry matter (4.1% of dietary protein) was also obtained from broken-line regression of expired (CO2)-C-14 (following an intraperitoneal injection of L-[U-C-14]arginine versus dietary concentration. Except for the loss of appetite resulting in a low feed intake and depressed growth, no nutritional deficiency signs were observed in fish fed an arginine deficient diet for 98 days. The significance of several biochemical indices measured including liver arginase activity and plasma arginine, insulin and growth hormone levels of fish fed graded levels of arginine supplement is also discussed.

Rapid eye movement (REM) sleep behavior disorder (RBD) is a parasomnia characterized by the loss of muscle atonia during paradoxical (REM) sleep (PS). Conversely, cataplexy, one of the key symptoms of narcolepsy, is a striking sudden episode of muscle weakness triggered by emotions during wakefulness, and comparable to REM sleep atonia. The neuronal dysfunctions responsible for RBD and cataplexy are not known. In the present review, we present the most recent results on the neuronal network responsible for PS. Based on these results, we propose an updated integrated model of the mechanisms responsible for PS and explore different hypotheses explaining RBD and cataplexy. We propose that RBD is due to a specific degeneration of a sub-population of PS-on glutamatergic neurons specifically responsible of muscle atonia, localized in the caudal pontine sublaterodorsal tegmental nucleus (SLD). Another possibility is the occurrence in RBD patients of a specific lesion of the glycinergic/GABAergic pre-motoneurons localized in the medullary ventral gigantocellular reticular nucleus. Conversely, cataplexy in narcoleptics would be due to the activation during waking of the caudal PS-on SLD neurons responsible for muscle atonia. A phasic glutamatergic excitatory pathway from the central amygdala to the SLD PS-on neurons activated during emotion would induce such activation. In normal conditions, the glutamate excitation would be blocked by the simultaneous excitation by the hypocretins of the PS-off GABAergic neurons localized in the ventrolateral periaqueductal gray and the adjacent deep mesencephalic reticular nucleus, gating the activation of the PS-on SLD neurons.

Four experimental diets (diets CP0, CP5, CP10 and CP15) containing 42% crude protein were formulated to contain graded levels of colzapro, a co-extruded product of rapeseed and peas, by replacement of protein from fishmeal. Another diet (CPE) with a lower protein (34%) and higher fat content was formulated to contain a high level (45%) of colzapro. A 12-week growth trial was conducted with rainbow trout (initial body weight 40 g; 18°C) to evaluate the potential use of this plant protein in trout diets. Growth performance, digestibility of nutrients, and ammonia nitrogen excretion were measured. The effects of dietary colzapro on the fatty acid composition of trout muscle were studied. Compared to the control group, fish fed diets in which 5, 10 and 15% of protein was replaced by protein of colzapro showed equivalent or slightly betten growth performance. Increasing the dietary colzapro level to 45% (diet CPE) led to a significantly lower final weight, specific growth rate and an increase in feed to gain ratio when compared with the other groups. No significant differences were observed in the digestibility of protein and fat, regardless of dietary treatment, while those of dry matter and energy were affected by colzapro incorporation. Non-faecal nitrogen loss showed a decreasing trend with increasing levels of dietary colzapro. In the muscle, n−6 fatty acids increased with increasing levels of dietary colzapro, mainly due to a rise in linoleic acid levels, while the levels of 20: 4 n−6 did not vary much between treatments. Although the levels of 22: 6 n−3 fatty acids remained stable, a decreasing trend for the total percentage of n−3 fatty acids was observed, thus affecting the n−3 n−6 ratios. Histological observations did not reveal any significant difference in thyroid cells between dietary treatments. The results obtained showed that colzapro can be utilized in rainbow trout diets at levels of up to 20% without negative effects on growth, nitrogen or energy utilization and muscle fatty acid composition.

Flesh color was analyzed in 21 dam half-sib rainbow trout families (6 fish per family) that were fed a diet containing 100 mg astazanthin per kg feed. Physical color measurements (lightness, hue, and chroma) indicated that color levels induced by astaxanthin were under genetic control, the largest familial differences being obtained from lightness measurements. Lightness was found to be positively correlated with hue and with chroma. Before genetic programs can be developed to improve flesh color, measurement techniques should be optimized in terms of concordance with visual perception, and a selection index should be designed on the basis of consumer preference.

The expressions of hexokinase IV (glucokinase, GK) and hexokinase (HK)-I genes were analysed during early ontogenesis of common carp (Cyprinus carpio). Unlike HK-I gene, which was expressed during all the stages of the development, GK was only induced by the first feeding with high levels of dextrin as a source of carbohydrate. This study confirms the high capacity of common carp to use glucose even at the very early stages of development.

The eater meter described in this paper is especially designed for fish studies. It consists of three parts: the detector, the feeder, and the interface between the detector and the feeder. The detector is a rod that closed a circuit (by contact or through a magnetic detector) when stuck by a fish, the feeder is electric and can be of any commercial model, and the interface is a simple electronic device, or a computer. Some preliminary results obtained with rainbow trout, Oncorhynchus mykiss, are also presented in order to illustrate the uses of this modular eater meter for fish.

Four diets having different digestible protein (DP) to digestible energy (DE) ratios were formulated to study the protein-sparing effect of DE from carbohydrates and to estimate the DE requirements for growth of rainbow trout. A growth trial was conducted for 8 weeks. Digestibility measurements were made over 2 weeks. Trout (initial weights 37 and 100 g for growth and digestibility trials, respectively) were fed to satiation twice a day at a constant water temperature of 17.5 °C. Apparent digestibility coefficients (ADC) for dry matter, starch and energy decreased with an increase in dietary raw starch level. The metabolic fecal nitrogen loss was estimted to be 150 mg N/ 100 g of dry diet. Fish fed a high protein diet with 48% DP, 9% digestible fat (DL) and 20% digestible carbohydrates (DC) showed the best performance for weight gain, feed conversion ratio and daily growth index. However, the highest protein efficiency ratio (2.3) and protein retention efficiency (41.4%) were observed in fish fed a diet containing 38, 9 and 30% of DP, DL and DC, respectively. The whole body composition of the fish was not affected by dietary treatments. Liver glycogen and hepatosomatic index were positively related to dietary digestible carbohydrate levels. The digestible protein requirement per unit weight gain (g DP required per kg production) varied depending upon the DP/DE ratios. On the other hand, DE requirement per unit weight increment was relatively constant (about 17.5 MJ for the production of 1 kg of rainbow trout), irrespective of the dietary treatment.

A riverine fish assemblage in French Guiana was examined over several consecutive years. Fish distribution was highly structured on at least 3 different scales: between rivers, between the different zones of the rivers and between the different biotopes studied in sampling areas. A temporal organisation of fish communities was also found, superimposed on the spatial structure. The latter was due to the seasonal variations of the water level, and allowed temporary access to flooded areas. The different space-time factors of organisation of fish communities presented here are discussed in regard to their contribution to the maintenance of the observed high species diversity.

Le comportement de remontee de sept saumons atlantiques a ete observe en aval d'un ecran electrique repulsif implante dans le canal de fuite d'une usine hydroelectrique situee sur la Nive a 20 km de la mer. Le suivi des saumons par la technique du radiopistage montre qu'ils ne restent pas bloques en position d'attente devant l'ecran et ne devalent pas d'une facon importante apres avoir subi l'effet du champ electrique. Bien qu'il existe une individualite tres marquee dans les mouvements migratoires, il n'a pas ete constate de difference sensible entre le comportement des saumons repousses par l'ecran et ceux qui ont vagabonde dans la basse Nive sans avoir penetre dans la zone d'action de l'ecran. L'efficacite repulsive de l'ecran a ete confirmee. Par ailleurs, on a observe un ralentissement important de l'activite des saumons dans la basse Nive pendant la periode estivale et des remontees rapides vers les zones de frayeres lors des coups d'eau d'automne.

The unusual presence of vitellogenin in the plasma of male and nonvitellogenic female Siberian sturgeon has been demonstrated previously (Pelissero and Le Menn, 1988; Pelissero et al., 1989a) and was attributed to dietary effects. The present study examines estrogenic effects of dietary soya bean meal and of commercial trout diet on vitellogenesis in sturgeon. The 4-month study compared three diets, one commercial (T) and two experimental synthetic diets, one containing casein alone (SC for synthetic diet made on casein), and the other casein and soya bean (SS for synthetic diet made with soya bean) as protein sources. The dietary soya bean meal contained plant isoflavonic compounds which are well known to mimic the effects of estrogens in mammals. The SC diet, free of estrogenic compounds, served as the reference diet. When fed with the SC diet, sturgeons showed significantly lower plasma vitellogenin levels (0.0045 +/- 0.0012 mg/ml) compared with those fed the commercial diet (1.24 +/- 0.37 mg/ml). The SS diet had a very pronounced effect on the plasma vitellogenin level, which at the end of the experiment had reached 6 mg vitellogenin/ml. In no case was estradiol detectable in the plasma. Plasma androgen levels were high in all the three groups throughout the study period, and not significantly different from one another. Sturgeon fed the T diet had larger livers, with enlarged hepatocytes, compared with those fed the SS and SC diets.

Duplicate groups of full-sib carp (Cyprinus carpio L.) larvae were reared at 24±0.5°C and fed six artificial diets (A to F) with the same protein sources (yeast powder 59%; dry beef liver 41%) and a diet (G) in which half of the protein source was replaced by egg powder. Diets were supplemented with different levels (0%, 5% or 10%) of cod liver oil (CLO), mineral premix (M) and vitamin premix (V). After 21 days on experimental diets (D0–D21), larvae were fed a commercial feed for 10 additional days (D21–D31). On day 21, survival of larvae fed the yeast-liver diet supplemented with CLO (5%), M (5%) and V (5%) (diet A) was 64% and mean body weight was 169 mg. Compared to diet A, diet B (CLO 10%, M 10%, V 10%) did not improve survival (68%) or mean body weight (170 mg). Larvae fed a non-supplemented diet (C) containing only yeast and liver had a lower survival rate (42%) and mean body weight (63 mg). Vitamins appeared to be a limiting factor as the larvae fed diet D with CLO 5%, M 5% and no V exhibited a very low survival rate (13%) and mean body weight (28 mg). The mineral premix also seemed necessary as results obtained with diet E (CLO 5%, V 5%, no M) were similar (survival 52%, mean weight 53 mg) to those obtained with the non-supplemented diet (C). Diet F (M 5%, V 5%, no CLO) led to an excellent survival rate (95%) and mean body weight of 189 mg on day 21. Larvae fed diet G (42.5% yeast-liver mixture, 42.5% egg powder, 5% CLO, 5% M, 5% V) reached an individual mean weight of 140 mg. It was concluded that the mineral and vitamin supplementation of the yeast-liver diets was necessary, whilst an addition of 5% CLO in these diets had a negative effect. Survival of larvae initially fed the best diet (F) was 95% and mean body weight was 755 mg after 10 additional days of feeding (D21–D31) a commercial diet. This confirmed the possibility of rearing carp larvae on artificial food with high survival and growth rates.

National audience; Many sustainable development referentials in the field of aquaculture have been developed over the last decade. The aim was twofold: to solve the various environmental and social crises in aquaculture, which have occurred after a period of rapid growth; and to meet the need for sectorial implementation of general recommendations regarding sustainable development. This transition towards a more sustainable type of aquaculture is all the more significant as it is considered as the key to territorial activity integration and provides the opportunity for questioning the future of this activity and professional organization, by modifying its image, and thus overcoming current constraints regarding access to highlycoveted coastal zones. Firstly, on the basis of system approaches developed in agriculture and commercial fishery, the authors propose a systemic approach grid for analyzing aquacultural systems. This chart must be consistent with the sustainable development referential and enabling to analyze the relationships between the aquaculture industry and territories. It also contributes to accounting for the scales according to which the sustainable development implementation process must be analyzed; on the one hand, the sustainability of aquaculture farms must be taken into account, and on the other hand, the contribution of aquaculture to territorial sustainability must be considered. Secondly, the authors analyze the conditions for implementing territorial integration by focusing on the assessment of stakeholders’ representations of these interactions in order to determine the main issues and conditions. Finally, the elaborated analytical framework is faced with the new referentials of “ecosystem approaches” which may be considered as a continuation of the study on the territorial integration of aquaculture.

Le groupe dcs Siluriformes est parfaitement adapte a la vie en biotopes difficiles et generalement turbides, des organes specialises tels que l'organe de Weber et les barbillons leur permettant dc detecter vibrations et sources de nourriture. Ces mecanismes adaptatifs de detection et d'evaluation de la qualite des proies potentielles leur permettraient une activite trophique nocturne. Cette activite trophique nocturne a d'ailleurs ete generalement observee chez divers siluriformes tels que Ictulurus punctatus (Hastings et al., 1972), Ictulurus melus (Eriksson et Van Veen, 1980), Silurus ghnis (Anthouard et al., 1987). et Hoplosternum littorule (Boujard et al., 1990). Une baisse d'intensite lumineuse est egalement susceptible de provoquer la prise de nourriture (Boujard et al., 1992). L'existence d'une activite trophique diurne spontanee est moins documentee, mais possible comme l'ont observe Randolph et Clemens (1976) chez 1. punctatus.

International audience