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This report presents new stock assessments for the rock lobster (Jasus paulensis) fishery of the Saint Paul and Amsterdam islands with data up to the last fishing campaign of 2020/21. These new assessments are based on statistical catch at age models using all available data except tagging program data.Stock status trajectories for both stocks start from a period of unsustainable fishing in the 1980s and recovered in the 1990s. The assessment results indicate that exploitable biomass in 2020 is likely to be well above BMSY, biomass status (B/BMSY) are 1.09 (0.86 - 1.50) and 2.12 (1.66 – 2.92) for Saint Paul and Amsterdam stocks respectively, and that fishing mortality is well below FMSY. These estimates are consistent with the results of preliminary assessment from biomass dynamic models.The short-term projection scenarios that were tested show that current catch levels are compatible with the sustainability of the rock lobster stocks.

International audience

This document presents an updated summary of the French purse seine fleet targeting tropical tunas in the Indian Ocean. The statistics cover the period 1981-2020 and specifically focus on the activity of the last year of the fishery. In 2020, a total of 13 French vessels operated in the western Indian Ocean including 10 purse seiners and 3 support vessels. The total capacity weighted by the months of activity for each vessel is 10626t. The total nominal effort in 2020 was of 1805 fishing days and 2414 sets with 1898 sets on floating objects and 516 on free schools. The total catch of the French component of the EU purse seine fleet of the Indian Ocean was 58149t, being composed of 42.2%, 52.6%, 4.5% and 0.8% of yellowfin tuna, skipjack tuna, bigeye tuna and other species respectively. The most noticeable change in 2020 was the decrease of 17.7% for the total of catches in comparison to 2019, respectively 58149t and 70622t. Remarkably, yellowfin tuna and skipjack tuna proportion of catches in 2020 for free swimming school returned to the proportion prevailing before 2018, after 2 years of a different fishing strategy targeting skipjack tuna on free swimming school.

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International audience; The introduction of ecosystem-based management measures for Baltic fisheries to achieve Good Environmental Status (GES) within the MSFD (Marine Strategy Framework Directive) and the HELCOM (Baltic Marine Environment Protection Commission) requires tools that can evaluate measures to reduce the spatial footprint on the seabed. We applied the DISPLACE modelling platform at the wide-scale Baltic Sea to evaluate the effect of different spatial fishery management measures such as area closures, both in terms of impact on benthic habitats and impacts on catch, revenue and profit for international fisheries. DISPLACE simulates individual fishing vessels (>12 m length using bottom-contact gears) and how they redistribute their fishing effort given spatial or temporal closures. A new module, informed from available science for projecting benthos dynamics in response to fishing pressure, provides quantification of depletion from fishing and recovery of specific benthic habitats and seabed types. This study evaluates different scenarios and trade-offs with the objective to identify effective measures to achieve GES by 2021 as stipulated by the Baltic Sea Action Plan. A suite of time and space mitigation scenarios are defined to compare the effects of a gradient of fishing restrictions and closures in different areas, habitat types, jurisdictions, breaking down to the impact from different type of gears and on several fisheries economics. The results obtained are intended to help the EU maritime policy in finding ways to improve the management of the Baltic Sea seafloor along reducing the human footprint induced by the fishing activities, while considering biological and economic impacts.

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International audience

Many marine predator species feed on fish caught by fishers directly from the fishing gear. Known as depredation this interaction issue has substantial socio-economic consequences for fishermen and conservation implications for the wildlife. Costs for fishers include damages to the fishing gear and increased fishing effort to complete quotas. For marine predators, depredation increases risks of mortality (lethal retaliation from fishers or bycatch on the gear). Longline fisheries are the most impacted worldwide, primarily by odontocetes (toothed whales) depredation, urging the need for mitigation solutions to be developed. Most of studies assessing depredation have primarily relied on surface observation data, thus the way odontocetes interact with longlines underwater remains unclear. Besides, the way fishermen respond to depredation during fishing operations, or can influence their detectability to odontocetes, have been poorly investigated. This thesis therefore aimed at investigating these aspects through a passive acoustic monitoring, bio-logging and human ecology approaches, focusing on the French Patagonian toothfish (Dissostichus eleginoides) longline fisheries impacted by killer whales (Orcinus orca) and sperm whales (Physeter macrocephalus). Firstly, this thesis reveals that captains behave as optimal foragers but with different personal perception of competition and fishing fulfilment. Some captains would thus be more likely to stay within a patch or to haul closest longline even in presence of competition, suggesting these captains would show higher interaction rates. Additionally, the propagation of vessels’ acoustics varied depending on the type of manoeuvre (e.g. going backward vs. forward). The way captains use their vessels to navigate may therefore influence their detectability and so their depredation level. Secondly, loggers deployed on both the longlines (accelerometers) and odontocetes (GPS-TDR) revealed that killer whales and sperm whales are able to depredate on longlines while soaking on the seafloor. These observations suggest, therefore, that odontocetes can localise fishing activity before the hauling, which could be partially explained by specific acoustic signatures recorded during the setting process. Altogether, the results of the thesis suggest that depredation rates on demersal longlines are most likely underestimated. The thesis also brings some important insights for mitigation measures, suggesting that countermeasures should start from setting to hauling., De nombreux prédateurs marins se nourrissent directement des prises des pêcheurs. Ces interactions, définies comme de la déprédation, engendrent des conséquences socio-économiques considérables pour les pêcheurs ainsi que des implications de conservation pour la faune sauvage. D’un côté, la déprédation endommage le matériel et augmente l’effort de pêche pour atteindre les quotas. D’un autre côté, la déprédation augmente le risque de mortalité des prédateurs marins (prise accidentelle ou rétorsion létale par les pécheurs). La pêcherie à la palangre est la plus impactée par la déprédation, principalement par les odontocètes, ce qui incite à trouver des solutions. La majorité des études se concentrant sur la déprédation s’est principalement basée sur des observations en surface, de ce fait la manière dont les prédateurs retirent les poissons sur les lignes reste confuse. Par ailleurs, l’impact de la déprédation sur le comportement des pêcheurs ainsi que les facteurs expliquant leur détectabilité n’ont reçu que peu d’intérêt. L’objectif de cette thèse est donc d’étudier ces problématiques par un suivi acoustique, une utilisation de balises et une approche en écologie comportementale humaine, en se concentrant sur la pêcherie palangrière française ciblant la légine australe (Dissostichus eleginoides) impactée par la déprédation des orques (Orcinus orca) et des cachalots (Physeter macrocephalus). Les capitaines ont été décrits comme recherchant leur ressource selon la théorie de « l’optimal foraging », mais avec des perceptions de la compétition et du succès de pêche qui divergent. Certains capitaines seraient ainsi plus enclins à remonter les palangres au plus proche et à rester sur une zone, même en présence de compétition, augmentant alors le risque d’interaction. L’acoustique des navires a révélé que certaines manoeuvres (marche arrière par exemple) propagent différemment sous l’eau. La manière dont les capitaines manoeuvrent leur palangrier influencerait ainsi leur détectabilité et donc leur risque d’interaction avec les prédateurs. D’autre part, l’utilisation de capteurs sur les palangres et les animaux a révélé que les orques et les cachalots sont capables de déprédater sur les palangres posées sur le fond marin. Ces observations laissent à penser que les odontocètes sont en mesure de localiser l’activité de pêche bien avant la remontée de la ligne, ce qui pourrait être expliqué par une signature acoustique spécifique du déploiement de la ligne. L’ensemble des résultats de cette thèse suggère que la déprédation sur les palangres démersales est très probablement sous-estimée. Cette thèse apporte également des éléments importants pour la lutte contre la déprédation, en montrant la nécessité de protéger les palangres dans l’intégralité du processus de pêche.

To understand the genetic basis of coping style in European seabass, fish from a full factorial mating (10 females x 50 males) were reared in common garden and individually tagged. Individuals coping style was characterized through behavior tests at four different ages, categorizing fish into proactive or reactive: a hypoxia avoidance test (at 255 days post hatching, dph) and 3 risk-taking tests (at 276, 286 and 304 dph). We observed significant heritability of the coping style, higher for the average of risk-taking scores (h2 = 0.45 ± 0.14) than for the hypoxia avoidance test (h2 = 0.19 ± 0.10). The genetic correlations between the three risk-taking scores were very high (rA = 0.96-0.99) showing that although their repeatability was moderately high (rP = 0.64-0.72), successive risk-taking tests evaluated the same genetic variation. A mild genetic correlation between the results of the hypoxia avoidance test and the average of risk-taking scores (0.45 ± 0.27) suggested that hypoxia avoidance and risk-taking tests do not address exactly the same behavioral and physiological responses. Genetic correlations between weight and risk taking traits showed negative values whatever the test used in our population i.e. reactive individual weights were larger. The results of this quantitative genetic analysis suggest a potential for the development of selection programs based on coping styles that could increase seabass welfare without altering growth performances. Overall, it also contributes to a better understanding of the origin and the significance of individual behavioral differences.

International audience; The assessment of socio-economic effects of marine protected areas on fishing activity points out some methodological difficulties. As a methodology we propose a selection of two components : the fishing unit profitability and the fishery household income distribution and a comparison between a marine protected area versus an “unprotected zone”. The methodology has been applied on a case study: the Chumphon National Park versus the Chumphon Province (Gulf of Thailand). Three phases have been implemented: a bibliographical analysis, the carrying out of village monographs, the carrying out of a sample-based survey. The sample-based survey results are presented as follows : the characterization of categories of the variable “marine protected area” by quantitative variables, a multivariate analysis, the performance of Chi-square tests on the relationship between a “profit per fishing day” variable divided into two categories (“in or around MPA” and “remote from the MPA”, the measurement of the concentration of income or operating profit per fishery household and the Lorenz curves.

The macro-benthic communities of Mont-Saint-Michel Bay, located in the Norman-Breton Gulf (English Channel) along the French coast, are mainly dominated by filter-feeders which include cultivated species (oysters and mussels). The decline in shellfish farms production and the significant spreading of the invasive slipper-limpet Crepidula fornicata have conducted scientists and stakeholders to undertake a reflexion on the trophic balance between cultivated and wild (native or invasive non-native) filterfeeders. An ecological model of the bay was developed, coupling a 2D hydro-sedimentary model along with biological models for primary production and filter-feeder growth. The objectives of the project were first to provide indicators to stakeholders on the future evolution of the trophic resource taking in account environmental modifications and human pressure, and establish with them the scenarios to be developed by the model. To accomplish these objectives different focus groups were organised between scientists and stakeholders. Based on these exchanges scenarios on shellfish practices, watershed runoffs and Crepidula fornicata spreading, were investigated through numerical modeling tools. Then results of the models were presented to 6 stakeholders' focus groups and a social scientist has analysed first the interaction between scientists and stakeholders, second the perception of the models by the stakeholders and the ideas of stakeholders concerning the environmental problems face within the Bay.

International audience; We consider a stage structured model of a harvested fish population. The model is a discrete-time system involving a nonlinear recruitment function. Using Control Theory tools we show how to act on the fishing effort in order to prevent the extinction of the population. More precisely, we show how to compute the fishing effort as a feedback control (i.e., a function of the state) in order to maintain the fish population state around a desired steady state.

This article deals with a performant parallel solution for a host-macroparasite model, both deterministic and stochastic, in a marine environment. Detailed biological phenomena are reproduced, such as spatial and temporal heterogeneities in these populations. A new version of the simulator and a new parallel algorithmic solution are presented. The interdisciplinary work presented here is at the interface of ecology, mathematics and computer science.

International audience; The composition and seasonal dynamics of biofilm-associated eukaryotic communities were analysed at the metre and kilometre scale along a salinity gradient in the Westerschelde estuary (The Netherlands), using microscopy and a genetic fingerprinting technique (PCR-DGGE). Microphytobenthic biomass, measured as chlorophyll a (chl a), varied seasonally over 2 orders of magnitude, being highest in spring. Communities were dominated by epipelic diatoms, in particular by members of the genus Navicula. In spring, a few smaller epipelic diatom species dominated during biomass peaks, while during the rest of the year, communities were more diverse and were characterised by larger species. The microphytobenthic community collapsed when grazers appeared, which happened concomitantly with a rise in temperature. Spring biomass development was associated with marked changes in porewater nutrient concentrations, especially towards the estuary mouth. In the DGGE data, diatoms, ciliates, amoebae, copepods, nematodes, annelids and platyhelminthes were detected. Ordination analysis of the species counts and DGGE data were largely congruent and indicated that on the scale of the whole estuary (i.e. km scale), taxonomic turnover in microphytobenthos composition was mainly associated with the salinity gradient. At smaller spatial scales, the position of sampling localities along the tidal exposure gradient appeared to be the main determinant of species turnover, in particular in the brackish reaches of the estuary.

International audience; The effect of variations in the amount or quality of food provided on the amino acid profile of larvae, was tested in two marine fish species, the Senegal sole (Solea senegalensis) and the sea bass (Dicentrarchus labrax). The objective was to assess whether such nutritionally suboptimum dietary patterns, which simulate situations that may occur in hatcheries, result in variations in the concentration of one or more amino acids that could be used as indicators of nutritional condition of larvae. Restriction in the normal food ration by 60% had no clear effect on the amino acid profile of sea bass, while the concentration of some amino acids (Arg, Ala and Phe) showed significant variations in sole. Feeding on artificial diets, which have shown their inadequacy a priori, resulted also in no significant effect on the profile of sea bass, but in a dramatic modification of the amino acid profile in sole. In addition, changes in the amino acid profiles considered as a whole were evaluated using the cluster analysis instead of paired comparisons between amino acid concentrations in each treatment. The analysis clearly separated profiles of larvae fed restrictedly or inadequately from their controls, irrespective of the species. This demonstrated the potential value of evaluating whole changes in amino acid profile as nutritional indicator. Besides, it was demonstrated that sensitivity of larvae to nutritional changes that may be reflected in the amino acid profile is greatly conditioned by the species and developmental stage

International audience; In most estuarine ecosystems, the fish biomass is difficult to estimate, since most of the standard sampling methods are difficult to implement and may be limited to certain biotopes. Moreover, Protected Areas are no longer limited to marine ecosystems and several protected areas have been created in estuaries, lagoons or mangrove environments. In these areas, turbid waters do not allow direct diving observations and fish sampling, often performed using destructive – because efficient and non selective - gears such as trawling or seine nets, is always an ethic problem. As a consequence there is an increased need for liable, non-destructive methods to study fish assemblages in these environments. In order to describe the fish biomass distribution and evolution in the Gambia estuary, five research surveys have been conducted at different hydrological seasons. The fish assemblages were sampled by vertical echo-sounding at moored stations and at the same time and same location with a purse seine. The purpose of this work, still in process, is to compare the two methods, to try to inter-calibrate them and to seek for their complementarity. Though significant, the global direct correlation between estimations of biomass performed with the two sampling methods were too low to be considered satisfactory. Moreover the level of correlation between the two methods varies extensively following the survey, the season or the zone of the estuary taken into account. The role of the main environmental variables: depth, salinity, transparency and current strength on the quality of the correlation of the estimation made by the two methods was emphasized.

Over the 1923-1969 period a total 20 female scientific researchers (eleven from the Spanish Institute of Oceanography (IEO) and nine from the Higher Council for Scientific Research (CSIC)) had 65 articles published in the articles of these two government organisations. The articles, relating to marine and freshwater sciences, which were written solely by them or in collaboration, deal with oceanography, plankton, algology, food-fish biology, food science, etc.The time-scan of this scientific activity is being split into two sub-periods, viz.: 1923-1945 (articles solely in IEO's journals) and 1946-1969 (starting off with the first relevant CSIC's publications). We are quantifying, sorting by subjects, reviewing and evaluating the articles published in the journals of both organisations. The accomplished study shows a meaningful, generalised comparative decrease in the number of IEO's female researchers and articles in the 1960s, coincidental with the "coming into the picture" of their counterparts from the Institute for Fishery Research (IIP) under the CSIC. The study is complemented with an analysis and interpretation of the inter- and intra-organisational variations, chiefly on the basis of the comprehensive biographic references extracted from the Science Citation Index of SCI (international database)., Durante el período 1923-1969, 20 investigadoras (11 del Instituto Español de Oceanografía (IEO) y 9 del Consejo Superior de Investigaciones Científicas (CSIC)) publicaron en las revistas científicas de ambas instituciones, solas o en colaboración, 65 artículos relativos a las ciencias marinas y del agua dulce (oceanografía, plancton, biología pesquera, bromatología, algología, etc.).El entorno causal de la actividad científica estudiada se ha dividido cronológicamente en dos períodos: 1923-1945 (unicamente con revistas del IEO) y 1946-1969, desde las primeras producciones escritas del CSIC. Se ha procedido a la revisión y a la cuantificación de los artículos publicados por todas las investigadoras en las revistas de ambas instituciones, clasificándolos temáticamente y valorándolos. El estudio comparado realizado, ha mostrado un significativo descenso generalizado en el nº de artículos e investigadoras del IEO durante los años sesenta, coincidiendo con la "entrada en escena" de las investigadoras del Instituto de Investigaciones Pesqueras (IIP). Se complementa el estudio con el análisis e interpretación de las variaciones inter- e intra- institucionales, principalmente a partir del conjunto de las citas bibliográfcas extraídas de la base de datos internacional SCI (Science Citation Index)., Sur la période 1923-1969 un total de 20 femmes dans la recherche scientifique (onze de l'Institut espagnol d'océanographie (IEO) et 9 du Conseil supérieur de recherches scientifiques (CSIC)) ont publiés 65 articles dans les journaux de ces deux organisations gouvernementales. Les articles ayant trait aux sciences de l'eau douce et de la mer, rédigés uniquement par elles ou en collaboration, traitent d'océanographie, plancton, algologie, biologie des poissons comestibles, science de l'alimentation,etc. Le temps de cette activité scientifique est divisé en deux sous-périodes, viz.: 1923-1945 (les articles ne sont disponibles qu'en des journaux de l'IEO) et 1946-1969 (à commencer par les premières publications rélevantes au CSIC). Nous avons fait le point et entrepris de quantifier, classés thématiquement et soumis à une évaluation, les articles publiés par toutes les chercheuses dans les revues des deux institutions. L'étude comparée indique de façon significative une diminution générale du nombre d'articles et de chercheuses en provenance du IEO pendant les années soixante, coïncidant avec l'entrée en lice des chercheuses de l'Institut de recherche sur la pêche (IIP). Le présent examen est complété par une analyse et une interprétation des variations inter et intra- institutionnelles, notamment à partir de l'ensemble des citations bibliographiques tirées de la base des données.

International audience; Les tactiques et stratégies de pêche déployées par les chalutiers côtiers au Sénégal sont étudiées à partir des compositions spécifiques des captures obtenues lors de marées réalisées entre 1990 et 2001. Les types des marées (tactiques de pêche) sont définis à partir de la composition des captures selon quatorze stocks et les types d'unités de pêche (stratégies) sont définis à partir des listes de tactiques qu'elles peuvent mettre en oeuvre. Les deux typologies sont construites à partir de la méthode des K MEANS, méthode de classification non hiérarchique. Douze tactiques et six stratégies de pêche sont d'abord identifiées. À partir de connaissances d'experts, des regroupements ont été faits et huit tactiques et cinq stratégies de pêche sont retenues et présentées avec les articulations entre stocks, tactiques et stratégies

International audience; The aim of the study was to determine the influence of dietary phospholipid (PL) levels on survival and development of first feeding gilthead sea bream (Sparus aurata) larvae. Larvae were fed from day 4 to 23 posthatching with an isoproteic and isolipidic formulated diet with graded levels of PL from 90–150 g kg)1 dry matter (DM). A dietary PL content of more than 90 g kg)1 DM seems to be necessary for sustaining growth of first feeding sea bream larvae. The survival rates of larvae fed the formulated diets (31–40% at day 23) were similar to those generally observed in marine aquaculture hatcheries with live prey feeding sequence. However, this high survival rate was not associated with high growth and the larvae showed, at the end of the study, a high proportion of individuals with abnormal liver and calculi in the urinary bladder. It is concluded that although the diets used here cannot be used in total replacement of live preys, they constitute a solid starting point for further nutritional studies with first feeding gilthead sea bream larvae

Along the period 1923-1969, 11 women scientists from the Spanish Institute of Oceanography (IEO) and 9 from the Spanish Council for Scientific Research (CSIC) publish inside the scientific journals produced from both institutions publishers, as sole authors or in collaboration with others 65 papers on marine and freshwater sciences (oceanography, plankton, fishery biology, bromatology, algology, etc.). The studied scientific activity causal realm has been chronologically splitted into two periods: 1923-1945 (uniquely with IEO " s journals) and 1946-1969 (with only the first written CSIC productions). A revision and quantification of both institutions women scientists published papers has been performed, and they have been classified by subject and valuated. The benchmark study carried on has shown a meaningful overall disminution both in the amount of articles and women researchers from IEO along the Sixties; this reduction was coincidental with the " emergence of the CSIC women researchers ". The study has been complemented with the analysis and interpretation of the inter-and intra-institutional variation, mainly after a set of bibliographical citations extracted from the international database SCI (Science Citation Index)., En el período 1923-1969, 11 mujeres científicas del Instituto Español de Oceanografía y 9 del Consejo Superior de Investigaciones Científicas (CSIC) publicaron 65 artículos sobre las ciencias marinas y dulceacuícolas (oceanografía, plancton, biología de la pesca, bromatología, algología, etc.). El ámbito causal de la actividad científica estudiada se dividió cronológicamente en dos períodos: 1923-1945 (únicamente con revistas del IEO) y 1946-1969 (sólo con las primeras producciones escritas del CSIC). Se ha procedido a la revisión y a la cuantificación de los artículos publicados por todas las investigadoras en las revistas de ambas instituciones, clasificándolos temáticamente y valorándolos. El estudio comparado realizado, muestra un significativo descenso generalizado en el nº de artículos e investigadoras del IEO durante los años sesenta, coincidiendo con la "emergencia de las investigadoras del CSIC". Se complementa el estudio con el análisis e interpretación de las variaciones inter- e intra- institucionales, principalmente a partir de un conjunto de las citas bibliográficas extraídas de la base de datos internacional SCI (Science Citation Index)., Sur la période 1923-1969, 11 femmes scientifiques de l'Institut Espagnol d'Océanographie et 9 du Conseil supérieur de la recherche scientifique (CSIC) ont publiés 65 articles sur les sciences marines et de l'eau douce (océanographie, plancton, biologie de la pêche, bromatologie, algologie, etc.).Le domaine causal de l'activité scientifique étudiée a été chronologiquement découpé en deux périodes: 1923-1945 (uniquement avec les journaux de l'IEO) et 1946-1969 (aux seules productions écrites du CSIC). Ayant fait l'objet de révision et de quantification, les articles publiés par des femmes scientifiques des deux institutions ont été classifiés par sujet et évalués. L'étude de référence poursuivie a révélé une diminution en quantité d'articles et de chercheuses du IEO au cours des années 60; cette réduction était parallèle à "l'émergence des chercheuses du CSIC". L'étude a été complétée par une analyse et une interprétation des variations intra et interinstitutionnelles, d'après un ensemble de citations bibliographiques tirées d'une base de données internationale, SCI (Science Citation Index).

International audience

Large yellow croaker is an important marine fish species for aquaculture in China. Larval rearing of this species is still based on live prey feeding. The aim of this study was to describe the onset and development of the main digestive enzymes during larval development of this species, in order to obtain essential data for the formulation of a compound diet adapted to larvae. Enzymatic assays were conducted from day I post hatching to day 40 in larvae fed the following live prey sequence: rotifers, Artemia nauplii, copepods, and then frozen copepods. Assays were done on whole larvae until day 19, then on dissected larvae and on purified brush border membranes of intestine. Pancreatic enzymes, amylase, and trypsin, showed high activities from early stages, even before mouth opening. Mechanisms of pancreatic secretion were achieved from day 19. Enzymes of brush border membranes, alkaline phosphatase, and aminopeptidase N, increased abruptly between day 23 and 25, showing maturation of the intestinal digestive process. These data, together with data describing mouth enlargement during development, suggest that large yellow croaker larvae could be fed successfully with a compound diet from early stages, at least from day 23.

International audience

International audience

International audience

Temporal changes in the bacterial community composition (BCC) and the impact of resources and predation on this community composition have been studied in the euphotic zone of the Sep reservoir (France), using terminal-restriction fragment length polymorphism (T-RFLP) and fluorescent in situ hybridization (FISH) for Eubacteria (EUB338) and eubacterial subgroups. Net growth and grazing rates of the various subgroups were computed from experiments conducted in dialysis bags in the presence or absence of predators. There was a significant difference between the grazing rates of different bacterial groups and subclasses, the alpha-proteobacteria (ALF1b) were subjected to the highest grazing rate (max. 1.76 d -1 ). In contrast, the beta-proteobacteria (BET42a) seemed to be little consumed by bacterivorous organisms, and predation led to large variations in the grazing rates of Cytophaga-Flavobacterium (CF319a). The different composition of bacterial con- sumers (Dinobryon sp. and Cladocera) during the study could explain the observed differences in grazing impact. The mean net growth rates of total bacteria, EUB338, BET42a ALF1b, and CF319a in dialysis bags without predators were 0.21, 0.69, 0.45, 0.50 and 0.84 d -1 , respectively. Various statisti- cal analyses indicated that the BCC could depend on the organic matter excreted by the phyto- plankton. There were also positive correlations not only between net growth and/or net production of ALF1b and CF319a with the primary production and biomass of the main phytoplankton groups, but also between phytoplankton biomass, primary production (PP) and some operational taxonomic units (OTUs). Among the physical variables, input and output of water in the reservoir seem to play a role in determining the BCC in this ecosystem. The results suggest that the BCC depends on the combined impact of dominant substrate sources and selective predation by bacterial consumers.

Triplicate groups of European sea bass juveniles (60 g) were fed for 84 days two experimental diets containing either vegetable or marine oil (0.4 and 2.2% n-3 highly unsaturated fatty acid [n-3 HUFA] dry matter in LD and HD, respectively) and held at 22 or 29 degreesC (LD-22, LD-29, HD-22 and HD-29 groups). Significant differences in mass gain between the two diets and temperatures were, observed from day 28 onwards, and on day 84, weight was 18% higher in the HD-29 group than in the LD-22 group (the highest and lowest values. respectively). Over the 84-day period-SGR was significantly affected both by temperatures and diets (P=6x10(-4) and 2x10(-4) respectively), averaging 1.01 and 1.07 in the HD-22 and HD-29 groups compared to 0.92 and 1.0 in the LD-22 and LD-29 groups. Differences in growth rate between the experimental conditions were mainly explained by differences in feed intake (FI). FI was more affected by temperature than by diets (in fish fed HD, it was 1.7% day(-1) at 29 degreesC and 1.4% day(-1) at 22 degreesC, and 1.1% day(-1) and 1.3% day(-1), respectively, with LD). Feed conversion ratio (FCR) was significantly affected by temperature and diets; days 0-84 FCR was on HD and LD 1.6 and 1.7 at 29 degreesC and 1-4-1.5 at 22 degreesC. Considering growth and feeding parameters. no interaction between dietary concentration in n-3 HUTA and temperatures were observed. In acclimated fish, MO2 on routine metabolism was the highest at HD-29 (396 mg O-2 kg(-1) h(-1)) as it was dependent on FI. There was no major difference in fish whole body composition, and protein retention was more affected by temperature than by diets. Diets and temperature affected polar lipid fatty acid content, without interaction; n-3 HUFAs were lower at 29 degreesC than at 22 degreesC. Fatty acids of total and neutral lipids (NL) were mainly affected by dietary fatty acids, while some low but significant influences of temperature were observed. Interactions between the two studied factors concerned particularly n-3 HUFAs content, lower at 29 than at 22 degreesC only in fish fed vegetable oil (LD). This study demonstrated that in high-quality sea bass juveniles, a 3-month deficiency in dietary n-3 HUFA did not drastically impair fish capacity to adapt to a high temperature, 29 degreesC.

A study was undertaken to determine the effect of various dietary carbohydrate-to-lipid ratios on growth performance, whole-body composition and tissue lipid content in Senegalese sole (Solea senegalensis) juveniles. Data on the dietary regulation of key hepatic enzymes of the lipogenic and glycolytic pathways (glucose-6-phosphate dehydrogenase, G6PD; malic enzyme, ME; fatty acid synthetase, FAS; pyruvate kinase, PK and glucokinase, GK) were also generated. Four isonitrogenous (crude protein: 52% dry matter (DM)) diets were formulated to contain one of two lipid levels (11% and 21% DM). Within each dietary lipid level, the nature of the carbohydrate fraction (raw or extruded peas) was varied. Triplicate groups of 54 sole (initial body weight: 23.6+/-1.2 g) were grown in recirculated seawater over 67 days. Fish were fed using automated feeders. At the end of the study, whole-body, liver, viscera and muscle samples were withdrawn for analyses. During the experimental period, the mean fish weight about doubled in all treatments. No significant differences were found in growth performance (ranging from 1.1% to 1.4% body weight day-1) among dietary treatments. High-fat diets increased whole-body fat content. Similarly, daily fat gain ranged from 0.54 to 0.78 g kg-1 day-1 and highest values were found in fish fed high-lipid diets. Dietary treatments also affected tissue lipid content (liver, viscera and muscle), with highest values in fish fed high-fat diets. The nature of dietary carbohydrates had little influence on performance criteria, but affected tissue lipid deposition. The activities of G6PD, ME and FAS were depressed by elevated levels of dietary lipid, confirming the inhibitory effect of dietary fats on lipid biosynthesis. At both dietary lipid levels, ME and FAS activities were little affected by dietary carbohydrate. Activities of PK and GK were not affected by the starch level of the diets. In Senegalese sole juveniles, the lipogenic pathway is more susceptible to modulation by dietary means (particularly through lipid intake) than the glycolytic pathway.

Effects of porcine bile extracts added at three different dietary concentrations 0, 10 and 20 g kg-1 were studied on astaxanthin serum concentration in rainbow trout (mean weight 200 ± 7 g). Astaxanthin from micro-algae Haematococcus pluvialis and synthetic astaxanthin (CARO-PHYLL® pink) were incorporated in diets of rainbow trout at a rate of 100 mg astaxanthin kg-1 of feed. Fish were hand fed twice a day. After 5 days of feeding there was a significant effect of the pigment source on the ratio (total blood astaxanthin per unit body weight to cumulative astaxanthin intake per unit body weight). Trout receiving synthetic astaxanthin showed a significantly (P < 0.05) higher ratio than trout fed algal astaxanthin. Increasing dietary bile extract did not lead to produce any effect on this ratio. The power of the statistical analysis is discussed. Therefore, the interaction (pigment source x dietary bile concentration) showed no more effect.

Recent results have demonstrated that live yeast in diets improved gut maturation in sea bass larvae. In this study, we tested the absence and two levels of live yeast in sea bass larvae diets. Specimens were fed from time of mouth opening to 37 days after hatching a diet of 0%, 1.1%, or 5.7% wet weight of live yeast (Debaryomyces hansenii CBS 8339). Yeast incorporation improved survival 10%, and reduced malformed larvae. In groups fed 1.1% yeast, only 1% of larvae were malformed, compared to 14% in the control group. Final mean weight in groups fed 1.1% yeast was twice that of other groups. Activities and concentrations of mRNA trypsin and lipase were higher in the two groups fed yeast than in the control group, whereas activity and concentration of mRNA amylase were lower. This suggests that the pancreas matured faster in the two groups fed yeast. Activities of intestinal enzymes alkaline phosphatase, aminopeptidase N, and maltase in the group fed 1.1% yeast were higher than those in the two other groups, revealing earlier development of intestinal digestion. The best results were obtained with the diet containing 1.1% yeast cell biomass, corresponding approximately to 10(6) CFU g(-1) in the diet and 1.1 x 10(4) CFU per larva 30 days after hatching. The dose-dependent effect of yeast on rearing performance could be attributed to the amount of polyamines secreted by live yeast in the gut lumen of larvae.

Three practical isoproteic (54% protein) diets were formulated to contain graded levels of crude fat (diet L: 10%, diet M: 20% and diet H: 30%). Each diet was assigned unrestrictedly to three and restrictedly to two replicate groups of fish (IBW 243 g). In unrestricted groups, increasing the dietary lipid level led to a significant decrease in voluntary feed intake without affecting growth rate. In the feed-restricted groups, daily growth rates increased with increasing dietary fat levels. There was a significant and inverse effect of the dietary fat content on whole body moisture and fat levels, with highest lipid (ca. 20%) and lowest moisture (ca. 58%) contents in sea bass fed diet containing the highest lipid level; muscle lipid concentration was however not affected. Nitrogen retention was significantly increased by an increase in lipid concentration in the diets, with better efficiencies observed in unrestricted (ca. 31%) than in restricted groups (ca. 27%). Nitrogen loss was significantly affected by both the feeding level and the diet composition, with lowest values (ca. 60 g kg −1 ) in groups fed diet H unrestrictedly and highest values (ca. 90 g kg −1 ) in groups fed diet L at a restricted level. Soluble phosphorus excretion in H groups was less than half that in L groups, regardless of the feeding level.

Partial or total replacement of fish meal by a mixture of plant protein sources (corn gluten meal, wheat gluten, extruded peas, rapeseed meal) balanced with indispensable amino acids (IAA) was examined in juvenile gilthead sea bream (Sparus aurata) over the course of a 12-week growth trial. A diet with fish meal (FM) as the sole protein source was compared to diets with 50%, 75% and 100% of replacement (PP50, PP75, PP100). Protein retention was improved with more plant protein supply, and just a slight decrease in the final weight gain was found in fish fed PP50 and PP75 diets. However, in the PP100 group, weight gain was depressed up to 30% mainly as the result of a marked reduction of feed intake. These fish also showed a lower fat gain along with a marked hypocholesterolemic effect. Dietary treatment did not alter the hepatic activity of amino acid catabolising enzymes (alanine aminotransferase (ALAT), aspartate aminotransferase (ASAT), glutamate dehydrogenase (GDH)), although the size of the total muscle free amino acid (FAA) pool was increased by more plant protein supply. The activity of the somatotropic axis also varied among experimental groups, and the up-regulation of circulating growth hormone (GH) levels with a high plant protein supply followed the decrease in growth rates, plasma levels of insulin-like growth factor-I (IGF-I), and liver mRNA transcripts of IGF-I and GH receptors. This catabolic feature evidenced a liver desensitisation to the anabolic action of GH in the PP100 group, and to a lesser extent in the PP75 group. Taken together all these findings, up to 50-75% of fish meal replacement seems to be feasible with IAA supplementation, but further research is needed to fully identify the responsible factors for the depressed feed intake in order to achieve a full replacement in a fish species having high dietary protein requirements.

In the present study, we report the characterization in European sea bass of the partial cDNA sequences of three nuclear receptors, retinoic acid receptor (RAR)α, RARγ, retinoid X receptor (RXR)α, involved in retinoid pathways. These pathways participate to vertebrates morphogenesis processes and may be responsible for the appearance of skeletal malformations. The predicted polypeptide encoded by each cDNA sequence contains the ligand-binding domain (LBD) characteristic of nuclear hormone receptors, and the RXRα cDNA sequence also includes a partial zinc finger domain corresponding to the DNA-binding domain (DBD) of this receptor. The relative expression levels of the three receptors were determined by real-time polymerase chain reaction (RT–PCR) in European sea bass larvae. Between 10 and 42 days posthatch (dph), the expression of RARα and RARγ increased 7.3- and 35.6-fold, respectively, while RXRα expression was down-regulated with a factor of 35.4. The same trend was observed between 10 and 21 dph but was not statistically different. Using RNA/RNA hybridizations, RARα antisense probes were revealed in jaws at 5 dph, and, at 37 dph, they were detected in jaws, vertebra, liver, muscle, pectoral fins, brain, neural tissues, eyes, and branchial arches. At 37 dph, RARγ expression was found in the cartilage, eyes, and operculum, while the presence of RXRα mRNA was localised in the exocrine pancreas, liver, thyroid, kidney, heart, jaws, and teeth. These results suggested that RARα and RARγ were used for European sea bass development. RARγ would play a key role in the morphogenesis of the cephalic region, while RXRα would be essential during the early stages of development in European sea bass larvae when an intense process of differentiation occurred.

Spanish scientific community has grown on marine sciences-related research concerns for the years 1999 and 2000 in Spain. Many solutions to sea-related problems have been interesting in the context of marine biology and chemistry, big science areas like oceanology, aquaculture, fishery and ecology. A number of studies have been conducted : the Spanish aquaculture directory (ed. 1999), the report from the Ministry of Education "Marine science research in Spain (1981-1998)" (ed. 1999), the report from the Ministry of Agriculture "Evaluation of the activities of research and technological development in aquaculture on the (1982/1997)" (ed. 1999), the "White book on Aquaculture in Spain" (ed. 1999); outside of the follow-up surveys contrasting topics shown to be of concern to marine sciences in Spain., En la comunidad científica española ha crecido el interés por la investigación en ciencias marinas durante los años 1999 y 2000. Muchas soluciones a problemas relacionados con el mar han resultado de interés en el contexto de la biología y de la química marina, y en grandes áreas de la ciencia como la oceanología, la acuicultura, la pesca y la ecología. Numerosos estudios se han realizado : el directorio español de acuicultura (ed. 1999), el informe del ministerio de agricultura "Evaluación de las actividades de investigación y desarrollo tecnológico en acuicultura en el período 1982/1997" (ed. 1999), el "Borrador del libro blanco de la acuicultura en España" (ed. 1999); además de las encuestas de seguimiento que contrastan diferentes temáticas y demuestran ser útiles para las ciencias marinas en España., En Espagne l'intérêt de la communauté scientifique pour la recherche en sciences marines a crû pour les années 1999 et 2000. Bien des solutions à des problèmes en rapport avec la mer ont été intéressants dans le cadre de la biologie et a chimie marine, et dans les grands domaines scientifiques de l'océanographie, l'aquaculture, la pêche et l'écologie. Plusieurs études ont été menées : le répertoire espagnol de l'aquaculture (ed. 1999), le rapport du ministère de l'éducation "Recherche en sciences marines en Espagne (1981-1989)" (ed. 1999), le rapport du ministère de l'agriculture "Évaluation des activités de recherche et dévelopment technologique sur l'exercice 1982/1997" (ed. 1999), le "Livre blanc sur l'Aquaculture en Espagne" (ed. 1999); en outre, des études de suivi sur des sujets contrastés qui ont démontrées être utiles pour les sciences marines en Espagne.

Spanish scientific community has grown on marine sciences-related research concerns for the years 1999 and 2000 in Spain. Many solutions to sea-related problems have been interesting in the context of marine biology and chemistry, big science areas like oceanology, aquaculture, fishery and ecology. A number of studies have been conducted : the Spanish aquaculture directory (ed. 1999), the report from the Ministry of Education "Marine science research in Spain (1981-1998)" (ed. 1999), the report from the Ministry of Agriculture "Evaluation of the activities of research and technological development in aquaculture on the (1982/1997)" (ed. 1999), the "White book on Aquaculture in Spain" (ed. 1999); outside of the follow-up surveys contrasting topics shown to be of concern to marine sciences in Spain., En la comunidad científica española ha crecido el interés por la investigación en ciencias marinas durante los años 1999 y 2000. Muchas soluciones a problemas relacionados con el mar han resultado de interés en el contexto de la biología y de la química marina, y en grandes áreas de la ciencia como la oceanología, la acuicultura, la pesca y la ecología. Numerosos estudios se han realizado : el directorio español de acuicultura (ed. 1999), el informe del ministerio de agricultura "Evaluación de las actividades de investigación y desarrollo tecnológico en acuicultura en el período 1982/1997" (ed. 1999), el "Borrador del libro blanco de la acuicultura en España" (ed. 1999); además de las encuestas de seguimiento que contrastan diferentes temáticas y demuestran ser útiles para las ciencias marinas en España., En Espagne l'intérêt de la communauté scientifique pour la recherche en sciences marines a crû pour les années 1999 et 2000. Bien des solutions à des problèmes en rapport avec la mer ont été intéressants dans le cadre de la biologie et a chimie marine, et dans les grands domaines scientifiques de l'océanographie, l'aquaculture, la pêche et l'écologie. Plusieurs études ont été menées : le répertoire espagnol de l'aquaculture (ed. 1999), le rapport du ministère de l'éducation "Recherche en sciences marines en Espagne (1981-1989)" (ed. 1999), le rapport du ministère de l'agriculture "Évaluation des activités de recherche et dévelopment technologique sur l'exercice 1982/1997" (ed. 1999), le "Livre blanc sur l'Aquaculture en Espagne" (ed. 1999); en outre, des études de suivi sur des sujets contrastés qui ont démontrées être utiles pour les sciences marines en Espagne.

The aim of this study was to evaluate (1) the effects of replacement of fish oil by vegetable oils on flesh quality and (2) the effects of a washout with a return to fish oil on flesh quality of turbot. In a first period of 3 months, three isonitrogenous and isolipidic diets containing 9% of added marine fish oil (170), soybean oil (SO) or linseed oil (LO) were fed to triplicate groups of 25 marketable size turbot (initial body weight: 579 +/- 1 g) grown in sea water at the temperature of 17 degreesC. At the end of the first period, all groups of turbot were fed with the diet containing fish oil (diet FO) for a further period of 2 months. The gutted and fillet yields were not affected by the incorporation of vegetable oils. However, soybean or linseed oils significantly affected the organoleptic quality of flesh particularly odour, colour and texture. A more pronounced potatoes odour and a lower fat texture were observed in dorsal fillet of turbot fed soybean oil diet. During the washout period, the differences observed between treatments in first period on sensory attributes disappeared. This study showed that the changes in organoleptic properties occurring due to the intake of vegetable oils can be reduced with a return to a fish-oil-based diet.

The aim of the study was to investigate the replacement of fish oil by vegetable oils and the effects of a washout with a return to fish oil on growth performances and lipid metabolism. three experimental fish meal-based isonitrogenous (crude protein content: 57.5%) and isolipidic (crude lipid content: 16.5%) diets were formulated containing either 9% of added fish oil (170), soybean oil (SO), or linseed oil (LO). Each diet was distributed to triplicate groups of 25 marketable size turbot (initial body weight of 579 g) grown in seawater at water temperature of 17 T. Fish were fed once a day to visual satiety. At the end of the growth trial, which lasted 13 weeks, all groups of turbot were fed with FO diet for 8 weeks. The growth of turbot was high, but the incorporation of vegetable oils in the diets resulted in a slight decrease in growth as compared to those fed with fish oil-based diet. Feed and protein efficiency and whole body composition were not affected by dietary lipid sources. Total lipid content was low in the muscle of turbot (below 2%); ventral muscle being fatter than dorsal muscle. Liver and muscle fatty acid (FA) composition reflected dietary FA composition. Liver and muscle of fish fed with SO diet were rich in 18:2n-6, whereas those of fish fed with LO diet were rich in 18:3n-3. Liver and muscle of fish fed with SO and LO diets had lower levels of 20:5n-3 and 22:6n-3 in comparison to those of fish fed with FO diet. In turbot, hepatic lipogenic enzyme activities were low and not influenced by dietary lipid source. At the end of the second period, after transfer to FO-based diets, muscle. FA composition of fish fed previously with SO and LO diets were still different to those of fish fed with FO diet. The values of 18:2n-6 and 18:3n-3, respectively, were lower than the values found at the end of the growth period, but higher than those of fish fed with FO diet. An increase of FA levels, characteristic of fish oil, was observed in the liver and muscle of fish previously fed with vegetable oils. Data obtained show that replacement of fish oil by vegetable oils is possible with negligible impact on growth performance of turbot, that dietary lipids are an effective vector to influence the nutritional quality of finished product, and that a duration of 8 weeks is not sufficient to bring the FA profile of turbot of this size back to that of fish fed with fish oil over the whole period.

International audience

International audience

The Cervigón Collection, from the Fish Museum sited at the Institute of the Spanish Scientific Research Council (Cádiz), where is preserved the holotype for Cottunculus costacanariae, provides the paradigm (Rey Lozano, 1928; Lozano Cabo, 1950) on the transition zone between the Atlanto-Mediterranean and the Tropical faunas. The Banc d'Arguin is the central area of dispersion for the species. Added to the Internet Resource Guide for Zoology of BIOSIS and the Zoological Society of London, the collection exposes 48 fishes from the Senegal coasts. Priacanthus arenatus reveals its northern limit in the zone where it has been fished, 14º26' and 12º51'. Gobius niger L., concerns to the species described by F. De Buen, 1928. Erythrocles monodi, rarely captured far from the south of C. Verde, belongs to an Indopacific genera. Totally from Senegal, and never up to the 17º parallel, Otoperca aurita. Part of the fauna of Casablanca, and fished in April 1958 south of St. Louis, Otolithus senegalensis. Very frequent facing Senegal, but captured at the Western Sahara and Mauritania., La colección Cervigón en el museo de peces del Instituto del Consejo superior de investigaciones científicas (Cádiz), donde se conserva el holotipo del Cottunculus costacanariae, propone el paradigma (Rey Lozano, 1928; Lozano Cabo, 1950) de la zona de transición entre la fauna atlantomediterránea y la tropical. El Banco d'Arguin es la zona central de dispersión de las especies. La colección presenta 48 peces de las costas de Senegal, y se ha añadido a la Internet Resource Guide for Zoology of BIOSIS y a la Zoological Society of London. Priacanthus arenatus revela el límite norte de su dispersión en la zona en la que se pescó, 14º26' and 12º51'. Gobius niger L., sigue la descripción de F. de Buen, 1928. Erythrocles monodi, raramente capturado al sur de Cabo Verde, pertenece a un género Indopacífico. Totalmente del Senegal, y nunca más allá del paralelo 17, Otoperca aurita. Otolithus senegalensis, es un elemento único de la ictiofauna de Ccasablanca, pescado en el mes de abril de 1954 al sur de S.Luis. Muy frecuente frente a las costas de Senegal, aunque capturados en Sáhara Occidental y Mauritania, Parapristipoma mediterraneum y Paracubiceps ledanoisi. Pagellus erythrinus (L., 1758) en ésta colección presenta variaciones interesantes en el tamaño del cuerpo con respecto a los de Senegal, en gran parte por los diferentes régimenes de temperatura. En lo concerniente al desplazamiento de carácter a escala comunitaria, se puede consultar Macrorhamphosus scolopax (L., 1758), reemplazado en el Senegal por M. Gracilis, Lowe. Capturado en el Banco d'Arguin, Anodontus mauritanicus es un genus novus sp. n. y Cottunculus costae-canariae es sp. n. Los trabajos de recogida los inició el Dr. Cervigón, hoy en el museo marino de la isla Margarita (Venezuela)., La collection Cervigón au musée de poissons à l'Institut du Conseil supérieur de recherches scientifiques (Cadix), où est conservé l'holotype de Cottunculus costacanariae, propose le paradigme (Rey Lozano, 1928; Lozano Cabo, 1950) pour la zone de transition entre les faunes des régions Atlanto-Méditérranéenne et tropicale. Le Banc d'Arguin est la zone centrale de dispersion des espèces. La collection présente 48 poissons des côtes du Sénégal, et a été ajoutée à la Internet Resource Guide for Zoology of BIOSIS et à la Zoological Society of London. Priacanthus arenatus révèle la limite septentrionale de son aire de répartition, à 14º26' et 12º51'. Gobius niger L., est tel qu'a été décrit par F. de Buen, 1928. Erythrocles monodi, rarement capturé au sud du Cap Vert, appartient à un genre Indopacifique. Totalement enclavée du Sénégal, et jamais au-delà du 17e parallèle, Otoperca aurita. Otolithus senegalensis, est un élément unique de l'icthyofaune de Casablanca, pêché durant le mois de avril 1954 au sud de St. Louis. Très fréquent sur les côtes du Sénégal, mais capturé au Sahara occidental et en Mauritanie, Parapristipoma mediterraneum et Paracubiceps ledanoisi. Le Pagellus erythrinus (L., 1758) dans cette collection présente des variations intéressantes de la taille du corps par rapport à ceux du Sénégal, en grande partie à cause des différents régimes de température. En ce qui concerne la prédiction du déplacement de caractère à l'échelle communautaire, peut être consulté Macrorhamphosus scolopax (L., 1758), remplacé au Sénégal par M. Gracilis, Lowe. Saisi le long du Banc d'Arguin, Anodontus mauritanicus est un genus novus sp. n. et Cottunculus costae-canariae est sp. n. Les travaux de collecte ont été initiés par le Dr. Cervigón, maintenant installé au musée maritime situé à l'île Margarita (Venezuela).

Males of Pangasius bocourti (3.3–6.9 kg) raised in floating cages on the Mekong River were used to study the production of milt and its use for fertilization. Although spontaneous spermiation occurred in mature males, the average volume of collected milt was low (26.5 μl kg −1 ). A single human chorionic gonadotropin (hCG) injection (2000 IU kg −1 ) induced a 13-fold increase in sperm volume, 12 h after injection (344.5 μl kg −1 ). The associated sperm concentration and production were 26.9×10 9 spz ml −1 and 8.4×10 9 spz kg −1 , respectively. Injection of GnRHa (30 μg kg −1 ) with domperidone (3 mg kg −1 ) induced a lower increase of sperm volume and sperm production. The motility of spermatozoa (spz) in well water lasted only 57 s, but was doubled in low saline solution (NaCl 34 mM). Crude milt could not be stored but five-fold dilution in immobilization solution (NaCl 207 mM) allowed fertilization to be postponed for 36 h. Fertilization was triggered by well water with milt diluted 1000 times.

The solubility of protein nitrogen at pH 8 in the organisms used as live food for fish larvae (rotifers and Artemia) was determined and the molecular weight profile of soluble protein nitrogen was analysed by HPLC-gel filtration chromatography. Soluble nitrogen accounted for 61% of total nitrogen in microalgae-fed rotifers, 47% in starved rotifers and 54% in newly hatched Artemia. A remarkable similarity in the profile of molecular weight distribution of soluble nitrogen was noticed among these three types of live food. The molecular weights of soluble nitrogen was partitioned as follows, respectively, in rotifers and Artemia: 84–88% and 89% >500 Da (corresponding mainly to proteins, poly- and oligopeptides), 8–11% and 4% from 200 to 500 Da (corresponding mainly to di- and tripeptides), 3–4% and 7%

Survival, growth, nitrogen (N) and phosphorus (P) budgets and feeding behaviour were studied in groups of sea bass, Dicentrarchus labrax L., that fed using self-feeders with different feed reward and maintained at different densities (up to 35 kg m−3 or 500 fish tank−1). The experiment was conducted in 500-l indoor tanks under ambient conditions of light and temperature during two successive years. In the first year (experiment I), fish (5.5±0.1 g) were separated into five groups according to stocking density (50, 200 or 500 fish tank−1) and reward (R=0.6 g trigger−1) level: 50:R, 200:R, 200:4R, 500:R and 500:10R. Both increases in stocking density and in feed reward affected negatively all the studied parameters concerning growth and feed efficiency (FE). In the second year (experiment II), the experiment was repeated with fish of similar weight (5.3±0.0 g), which were held under the following four feeding protocols: 50:0.5R, 50:R, 500:0.5R and 500:R. The lowest feed reward fish groups presented better tendencies in growth and feed efficiency independent of stocking density. Survival was high in all feeding regimes in both experiments, but at high density (500 fish tank−1), some mortalities (