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Spatial planning, including zoning and site-selection steps, is necessary to determine locations that minimize environmental impacts of aquaculture and respect ecosystem carrying capacities. This study aimed to analyse potential benthic waste deposition in a broad range of fish farming situations to facilitate zoning. To this end, we simulated waste dispersion for 54 aquaculture scenarios combining three red drum (Sciaenops ocellatus) farm types (Small, Medium, and Large) based on real farm characteristics and 36 sites with contrasting hydrodynamics in Mayotte’s North-East Lagoon. Key forcing variables and parameters of the particle-dispersion model for farms (layout and solid waste fluxes), species (feed- and faeces-settling velocities) and sites (depth and barotropic currents) were obtained. From the outputs of the 54 simulations, relationships between hydrodynamic regimes and deposition rates, area of influence and distance of influence of the farm were analysed. Critical limits of current intensity that reduced deposition rate below selected deposition thresholds were identified. For instance, to prevent deposition rates greater than 12 kg solids m−2 year−1, the mean current intensity should exceed 10.2 and 6.8 cm s−1 for Medium and Large farms, respectively. The study confirmed that production level is not the main factor that influences deposition rates; instead, management of the entire farm (cage position, distance between cages) must be considered to predict impacts more accurately and guide site selection.

BackgroundEphippidae fish are characterized by a discoid shape with a very small visceral cavity. Among themPlatax orbicularishas a high economic potential due to its flesh quality and flesh to carcass ratio. Nonetheless, the development of its aquaculture is limited by high mortality rates, especially due toTenacibaculum maritimuminfection, occurring one to three weeks after the transfer of fishes from bio-secure land-based aquaculture system to the lagoon cages for growth. Among the lines of defense against this microbial infection, the gastrointestinal tract (GIT) is less studied. The knowledge about the morphofunctional anatomy of this organ inP. orbicularisis still scarce. Therefore, the aims of this study are to characterize the GIT in non-infectedP. orbicularisjuveniles to then investigate the impact ofT. maritimumon this multifunctional organ.MethodsIn the first place, the morpho-anatomy of the GIT in non-infected individuals was characterized using various histological techniques. Then, infected individuals, experimentally challenged byT. maritimumwere analysed and compared to the previously established GIT reference.ResultsThe overlapped shape of the GIT ofP. orbicularisis probably due to its constrained compaction in a narrow visceral cavity. Firstly, the GIT was divided into 10 sections, from the esophagus to the rectum. For each section, the structure of the walls was characterized, with a focus on mucus secretions and the presence of the Na+/K+ATPase pump. An identification key allowing the characterization of the GIT sections usingin totohistology is given. Secondly, individuals challenged withT. maritimumexhibited differences in mucus type and proportion and, modifications in the mucosal and muscle layers. These changes could induce an imbalance in the trade-off between the GIT functions which may be in favour of protection and immunity to the disadvantage of nutrition capacities.

International audience; Environmental sustainability of aquaculture is a complex issue involving effects at local (e.g. benthic deterioration), regional (e.g. eutrophication) and global (e.g. catches for feed production) scales as a consequence of farming operations (e.g. waste emissions) and industrial processes involved in the product value chain. Integrating these effects using a holistic and multi-scale framework is essential to assess the environmental sustainability of innovative production systems such as Integrated Multi-Trophic Aquaculture (IMTA), in which organisms of different trophic levels are co-cultured on the same farm to minimize aquaculture waste. The environmental performances of theoretical production scenarios of red drum (Sciaenops ocellatus) sea cage monoculture and an open-water IMTA co-culturing of red drum and sea cucumber (Holothuria scabra) were assessed with mathematical models at local and global scales. First, the particulate waste bioremediation potential of sea cucumber production was estimated using an individual-based bioenergetic model. Second, environmental impacts of the monoculture and the IMTA systems were estimated and compared using life cycle assessment (LCA), calculated per kg of edible protein and t of product, including uncertainty analysis. Given the current limits to stocking density observed for sea cucumbers, its co-culture in sea cages suspended beneath finfish nets may decrease slightly (by 0.73%) farm net particulate waste load and benthic impact. The monoculture and IMTA showed little difference in impact because of the large difference in production scales of finfish and sea cucumber species. Removing 100% of finfish feces particulate waste requires cultivating sea cucumber at scale similar to that of finfish (1.3 kg of sea cucumber per kg of finfish). Nonetheless, LCA showed trends in IMTA performance: lower eutrophication impact and net primary production use but higher cumulative energy demand and climate change impacts, generating an impact transfer between categories. Intensification of sea cucumber culture could increase local and global environmental benefits, but further research is necessary to design rearing units that can optimize production and/or bioremediation and that can be practically integrated into existing finfish monoculture units. The methodology defined here can be a powerful tool to predict the magnitude of environmental benefits that can be expected from new and complex production systems and to show potential impact transfer between spatial scales. We recommend applying it to other IMTA systems and species associations and including socio-economic criteria to fully assess the sustainability of future seafood production systems.

Robust and accurate prediction of fish farm waste is a first and crucial step in managing the cause–effect chain that leads to local environmental impacts of aquaculture. Since aquatic production is diversifying with new fish species and extending to new areas for which data can be scarce, it is important to develop parsimonious approaches with fewer data requirements and less scientific complexity. We developed the Farm productIon and Nutrient emiSsions (FINS) model, which simulates fish farm operation and estimates fish biomass, feed inputs, and waste emissions from sea cages using simple modeling approaches and a variety of data sources. We applied FINS to red drum (Sciaenops ocellatus) culture in Mayotte by collecting relevant input data (growth, digestibility) from experimental trials. Three explorative farming scenarios—small, medium, and large—were defined from field survey data to examine and compare emissions of a range of potential commercial culture conditions and production scales (23, 299, and 2079 t year−1, respectively). Comparison of the three scenarios showed that waste emissions per ton of fish harvested during routine operations, and thus environmental impacts, were higher for longer culture cycles (medium farm) because of lower feed conversion efficiency. The FINS model is a simple alternative tool to assess and compare environmental impacts of different farming systems and practices for new aquaculture species and regions. It provides important drivers to assess local environmental impacts of fish farms and can therefore facilitate the process of licensing new farming systems for decision-makers.

En Europe, la pisciculture marine s’est developpee en deux vagues successives : celle du saumon atlantique, puis celle du bar et de la daurade. L’elevage de « nouvelles especes de poissons marins » repond a de nombreux avantages complementaires. Cet article presente l’etat de la production de ces « nouvelles especes », l’historique des recherches menees, les problemes et perspectives lies au developpement de leur elevage.

Melatonin contributes to synchronizing behaviors and physiological functions to daily and seasonal rhythm in fish. However, no coherent vision emerges because the effects vary with the species, sex, moment of the year or sexual cycle. And, scarce information is available concerning the melatonin age, receptors, which is crucial to our understanding of the role melatonin plays. We report here the full length cloning of three different melatonin receptor subtypes in the sea bass Dicentrarchus labrax, belonging, respectively, to the MT1, MT2 and Mellc subtypes. MT1, the most abundantly expressed, was detected in the central nervous system, retina, and gills. MT2 was detected in the pituitary gland, blood cells and, to a lesser extend, in the optic tectum, diencephalon, liver and retina. Mel1c was mainly expressed in the skin; traces were found in the retina. The cellular sites of MT1 and MT2 expressions were investigated by in situ hybridization in the retina of pigmented and albino fish. The strongest signals were obtained with the MT1 riboprobes. Expression was seen in cells also known to express the enzymes of the melatonin biosynthesis, i.e., in the photoreceptor, inner nuclear and ganglion cell layers. MT1 receptor mRNAs were also abundant in the retinal pigment epithelium. The results are consistent with the idea that melatonin is an autocrine (neural retina) and paracrine (retinal pigment epithelium) regulator of retinal function. The molecular tools provided here will be of valuable interest to further investigate the targets and role of melatonin in nervous and peripheral tissues of fish. (c) 2008 Published by Elsevier Inc.

In order to evaluate the effect and consequence of lateral system inactivation on fish nocturnal feeding, the differential growth of groups of European sea bass maintained in different rearing conditions were compared. Whereas some fish with intact lateral system (placebo fish) were placed under a photoperiod of 12-L: 12-D, other placebo fish were kept in the dark. In the same way, fish deprived of lateral system by section of their lateral system nerves and antibiotic treatment were placed under a photoperiod of 12-L: 12-D and the others in the dark. For each of these four rearing conditions, two sets of experiment were realized. Percent mortality, feed rhythm, averaged daily feed demand, specific growth rate and feed efficiency were compared among these four groups of fish. After four months of experiment, results revealed that, under a photoperiod of 12-L: 12-D, fish showed a diurnal feed rhythm whereas no rhythm appeared in fish kept in the dark. In addition, as reported by other authors, the average daily feed demand, the quantity of ingested food and specific growth rate were greater in fish maintained under a photoperiod of 12-L: 12-D than those kept in the dark. The fish lateral system inactivation did not affect mortality, feed intake, specific growth rate or feed efficiency. These results demonstrated that lateral system is not the major sensory organ leading to European sea bass nocturnal feeding; chemoreception system undoubtedly taking over. If the olfactory system explains equal feed intake between placebo and treated fish, the greater specific growth rate in treated than in placebo fish indicates the action of another mechanism, such as a "booster effect" of antibiotics used for lateral system inactivation on fish. (c) 2005 Elsevier B.V. All rights reserved.

In the present paper, we describe the performance of a bite-and-pull feed-demand system adapted to the behavior of European sea bass. The system is activated by the fish biting and pulling on, which generates an electrical signal that triggers the feed distributor. Experiment I was designed to test the sensor under laboratory conditions, using four groups of four naive fish per sensor (non-trained fish, NTF) and eight groups of four fish per sensor (small groups) that had been trained to use the system 1 year earlier (TF). Experiment II compared the bite-and-pull trigger (BPT) with a screened hanging-rod trigger (ST) using 16 groups of 48 sea bass per sensor (medium groups) under laboratory conditions. Experiment III evaluated the performance of the BPT sensor under farming conditions using four groups of 1000 sea bass per sensor (large groups) held in sea cages. Some of the advantages of the BPT sensor over other sensors are: (1) a shorter learning period, 11-12 days in exp. I, 1-2 day in exp. II and 1 day in exp. III; (2) absence of temporal constraints, allowing sea bass to feed at night (60% of nocturnal demands in exp. II; 23% and 47% of nocturnal demands in September and February, respectively, exp. III); (3) prevents accidental activation by fish, wind or waves; (4) low feed waste when reward level is set correctly; and (5) low costs, durability, and easy replacement of its components. All these features make the BPT a useful system for sea bass self feeding in sea cages.

Five practical diets in which the supply of protein from fish meal was decreased gradually from 100% to about 2% and replaced by plant protein sources were formulated. European seabass weighing about 190 g were fed these diets for 12 weeks at a water temperature of 22 °C. Feed was dispensed using automatic self-feeders and voluntary feed intake (VFI) was closely monitored. We did not find any significant difference among diets in the apparent digestibility coefficients (ADC) of dry matter (80–82%), protein (94–96%), energy (88–92%) or phosphorus (49–58%). Replacement of fish meal by plant protein ingredients did not influence VFI. All groups had very good growth rates (DGI above 1.3%/day) and there were no significant differences in growth rate, feed efficiency or in daily nitrogen gains among groups. There was, however, a slight increase in fat deposition in fish fed diets with plant protein sources. Ammonia nitrogen and soluble phosphorus excretion rates were measured. Nitrogen and phosphorus balance studies indicated that fish meal replacement by plant ingredients led to a slight increase in nitrogen losses (from 83 to 103 g N/kg weight gain) but led to a significant reduction in total phosphorus losses (from 13 to 5 g P/kg weight gain). These results combined with the remarkable acceptability of diets containing high levels of plant protein ingredients with identical growth performances of European seabass show clearly that dietary fish meal levels can be considerably reduced without any adverse consequence in terms of somatic growth or nitrogen utilisation.

Chronic effects of ammonia were studied in juvenile seabass, Dicentrarchus labrax (mean weight= 11 g), exposed for 63 days to eight stable ammonia concentrations, ranging from 0.24 to 0.90 mg l(-1) unionised ammonia nitrogen (UIA-N), respectively, from 6.1 to 22.3 mg l(-1) total ammonia nitrogen (TA-N). Temperature (21.8 degreesC), pH (8.0), salinity (37.0 ppt), and oxygen concentration (over 80% saturation at the outlet) were maintained constant. Fish were fed using a self-feeder device, and they were starved during the last 8 days. Mortality of 28.9 and 42.6% occur-red within the first 8 days at the two highest UIA-N concentrations, respectively, 0.90 and 0.88 mg l(-1). From days 0 to 55, a 1.8-fold increase in weight gain was observed under the 0.90-mg l(-1) UIA-N condition, compared to a 3.4-fold increase in the control. Weight gains were negatively correlated to ambient ammonia concentrations. Weight loss, or a transient period of growth stagnation, was observed from the onset of ammonia exposure to day 13 in seabass exposed to concentrations above 0.43 mg l(-1) UIA-N. After day 13, weight gains were observed in all groups, indicating that the fish were able to adapt to increased ambient ammonia concentrations over time. By the end of the experiment, plasma ammonia levels were positively related to ambient ammonia concentrations, and oxygen consumption recorded in fasting fish was significantly dependent on ammonia concentrations. In seabass juveniles, the 0.26-mg l(-1) UIA-N concentration, under an average pH of 8.0, can be considered as a safe long-term limit conditions in seawater.

The effects of tagging with acoustic transmitters on the growth of juvenile seabass, Dicentrarchus labrax (L.) (initial mean mass±SD, 173 g ± 23.4) in a 47 d tank experiment, and sole, Solea solea (L.) (103.2 g ± 14.8) in a 72 d tank experiment and (104.0 g ± 18.4) in a 58 d salt marsh mesocosm experiment were examined. Twenty externally tagged seabass grew more slowly than the 20 with surgically implanted tags, which reached the same mass as nine control fish. Movements of the external transmitter's harness caused abrasions of the skin and loss of the tag in 60% of the cases. We thus recommend implanting transmitters for telemetry studies of juvenile seabass weighing between 120 and 214 g and carrying a tag that represents 2.2–2.5% of body mass. Both tank and mesocosm experiments conducted on juvenile sole concluded that the externally attached tag retention rate was good, but at the expense of the fish growth rate.

The individual growth variability of passive integrated transponder tagged sea bass was studied using data sets from two different experiments. In experiment 1 (n = 485), fish submitted to different photoperiod regimes were held in fourteen groups of individual weight of 88 ± 13 g (mean ± SD). In experiment 2 (n = 748, initial weight 243 ± 30 g) fish were held in fifteen groups and had either free or restricted access to diets with three lipid levels. After adjustment for treatment and tank effects, individual growth curves were analysed using multivariate analysis (principal component analysis and clustering) and were modelled using the summary statistics technique. Different growth profiles where characterized. All of them appeared to be curvilinear. They differed in their level (initial and final weight), slope (slope, specific growth weight, gain) and especially the ratio of males, which showed sexual growth dimorphism. The fish with similar initial weight proved to have very different growth performances, regardless of the treatment effect. Within the same sex, part of the variability between the growth profiles could be explained by differences in the social interactions and in the genetic potential of growth among individuals.

Triplicate groups of juvenile seabass (initial weight of 241 g) were fed during 13 weeks three isonitrogenous experimental diets containing different lipid levels, 12% (LL group), 21% (ML group) and 30% (HL group). At the end of the experiment, fish weight gain was similar among the 3 dietary groups. Intestinal brush border membranes were purified for each dietary group; one part of the brush border fraction was dedicated to enzyme assays, the remaining fraction being used for lipid extraction followed by fatty acid analysis. The fatty acid composition of the brush border membrane differed among the 3 groups, although the 3 experimental diets had the same fatty acid composition. The increase in dietary lipid level resulted in a lowering in (n-3) polyunsaturated fatty acid (PUFA) paralleled with an increase in monounsaturated fatty acid. A significant reduction in the brush border enzyme activities, namely alkaline phosphatase, aminopeptidase N, gamma-glutamyl transpeptidase and maltase, was also observed with the elevation of the dietary lipid level. The change in activity of intestinal digestive enzymes, which are membrane-bound proteins, could be attributed to the modification of fatty acid composition and fluidity of the brush border membranes (BBM). Such lowering in PUFA and increase in monounsaturated fatty acid in BBM, concomitant with a decline in membrane enzymatic activity, has been described as a malnutrition indicator in mammals. It raises the question of possible disorders of gut functions in fish fed increasing lipid levels.

Self-feeding systems allow fish to freely express feeding activity. A simple rod at the water surface can act as a trigger and provide fish with a way of obtaining pellets from a feeder. Such a rod presented to experienced European seabass, Dicentrurchus Zubran, may lead to feed wastage, probably as a result of unintentional fish contacts with the trigger. Trigger protection screens have been designed to prevent fish contacting the trigger by chance, and the efficacy of such screens was tested. Nocturnal and diurnal feed delivery and feed wasted were compared under conditions where the rod was unprotected or protected by semi-cylindrical or cylindrical screens. Tests were conducted using an unrestricted self-feeding regime (reward: 0.2 g pellet per kg of body weight and per fish contact) in juvenile seabass (57 g body weight) fed for 28 days at 21.3 "C. Fish were subjected to a 4-h L:20-h D (1ight:dark) photoperiod. The daily feed demand pattern and the nocturnal and diurnal feed wastage were recorded. Fish activated the trigger predominantly at night, except in the case of one group exposed to a trigger protected by a semi-cylindrical screen. In the latter, trig- gering activity was progressively distributed throughout the 1ight:dark cycle. The cylindrical screens markedly reduced feed wastage and seabass were able to locate and activate the trigger (even in total darkness) to obtain a reward. 0 IfremerMsevier, Paris

The aim of this study was to determine whether mortality observed during the larval development of reared bluefin tuna (Thunnus thynnus) could be related to improper expression profiles of key genes involved in digestive or anti-oxidant response capabilities. Tuna larvae were sampled at hatching, 2, 5, 10, 15 and 20 dph (days post hatching) for the relative quantification of transcripts encoded by genes involved in digestive (trypsinogen 1 [TRYP1], alpha-amylase [AMY], aminopeptidase N [ANPEP]) and antioxidant (catalase 32 [CAT]) functions. The levels of expression of ANPEP related to the development and maturation of intestinal function increased from 5 to 20 dph. Furthermore, AMY and TRYP1 genes which are pancreatic enzymes implicated in carbohydrate and peptide digestions exhibit a typical peak of expression at 5 and 15 dph respectively. The antioxidant enzyme, CAT, exhibited higher mRNA levels during the first stage of larval development. In conclusion, our investigation indicates that the expression of genes involved in digestive and antioxidant physiological processes followed typical patterns which could not explain high mortality rate observed during the first stage of larval development, SI

During the first 2 years of larval rearing trials with Atlantic bluefin tuna, survival was a challenging issue. As bacterial colonization of the gut has been shown to play a key role for other species, we studied the profiles of the microbiota associated with individual larvae at different stages in three distant hatcheries. The Bacterial Community Profile (BCP) was quantified based on PCR-DGGE analyses of partial amplicons from 16S rDNA. Considerable individual variability in BCP was observed before onset of feeding, and the BCP did not show regular fluctuation during ontogenesis. Microalgae were added to the rearing tanks in two of the three hatcheries, but it was not possible to distinguish the effect of location from the effect of algal addition on BCP. In one hatchery, the larvae were reared either with algal addition or in mesocosm, but due to high individual variability, no significant difference in BCP was detected between the two groups. It was hypothesized that this variability was caused by differences in health, physiological status and developmental stage of the larvae. A practical conclusion from the study is the need to analyse a considerable number of individuals to reflect statistically significant differences between the microbial communities associated with rearing groups., Sí

SUMMARY The posterior lateral line system (PLL) of teleost fish comprises a number of mechanosensory organs arranged in defined patterns on the body surface. Embryonic patterns are largely conserved among teleosts, yet adult patterns are highly diverse. Although changes in pattern modify the perceptual abilities of the system, their developmental origin remains unknown. Here we compare the processes that underlie the formation of the juvenile PLL pattern in Thunnus thynnus, the bluefin tuna, to the processes that were elucidated in Danio rerio, the zebrafish. In both cases, the embryonic PLL comprises five neuromasts regularly spaced along the horizontal myoseptum, but the juvenile PLL comprises four roughly parallel anteroposterior lines in zebrafish, whereas it is a simple dorsally arched line in tuna fish. We examined whether this difference involves evolutionary novelties, and show that the same mechanisms mediate the transition from embryonic to juvenile patterns in both species. We conclude that the marked difference in juveniles depends on a single change (dorsal vs. ventral migration of neuromasts) in the first days of larval life.

In self-feeding conditions, a few individual sea bass (Dicentrarchus labrax (L., 1758)) display strong activity in striking the food dispenser, whereas the remaining individuals of the group actuate the feeder weakly or never. Here, we investigated the effects of removal of the individuals showing dominant activity on the social and feeding behaviours in groups of juvenile sea bass. Following removal, new fish showing a dominant self-feeding activity quickly appear. They always come from the group of fish that have a low number of triggering actuations. This observation shows that it takes less time, about 5 days after the removal of dominant triggerers vs. 14 days at the beginning, for the re-establishment of the behavioural structure, suggesting the possibility of social transmission between individuals. The fish that show weak triggering activity seem to reach the high-food triggering level without obvious signs of competition. This experiment reveals the importance of the food-demand behavioural structure: the fish displaying the highest activity lead to a general food distribution and play a dominant role in feeding the entire group. Functional plasticity in this role within individuals is also demonstrated, indicating that the high-triggering function is essential for the group and not for the individual themselves., Au sein d'un groupe de bars (Dicentrarchus labrax (L., 1758)) placés en auto-nourrissage, quelques individus disposent d'une activité forte de déclenchement volontaire du distributeur d'aliments. Les autres poissons du groupe disposent d'une activité de demande faible voire nulle. Ici, nous avons étudié l'impact du retrait des poissons à forte activité sur le comportement alimentaire et social de groupes de bars juvéniles. De nouveaux individus à forte activité réapparaissent rapidement, provenant exclusivement de la classe de poissons de faible demande. Cinq jours en moyenne suffisent après le retrait, contre 14 jours au début de l'expérience, pour que la structure comportementale se rétablisse suggérant l'existence d'une transmission sociale entre les individus. Ces poissons de faible activité semblent de plus atteindre leur nouvelle fonction sans aucun signe de compétition. Cette expérience révèle d'abord l'importance de la structure de la demande alimentaire puisqu'elle réapparaît après le retrait. Elle montre également que l'activité des forts manipulateurs conduit à une distribution générale de l'aliment et contribue à nourrir le groupe en entier. L'étude montre enfin une plasticité fonctionnelle indiquant que seule la fonction de manipulateur fort est essentiel pour la stabilité du groupe, non l'identité des individus par elle-même.

The individual food-demand behavior of juvenile European sea bass (Dicentrarchus labrax, L.) reared in groups under self-feeding conditions was investigated. The triggering activity on self-feeder, i.e. index of the food-demand activity, agonistic interactions and territorial behavior were monitored for periods of 42 to 68 days in six groups of 50 fish. The specific growth rate was calculated and the brain serotonergic activity was used as a stable index of social stress. Inter-individual differences appeared in triggering activity and three groups were distinguished: 3-5 high-triggering fish, 17-30 low-triggering fish and the remaining individuals were null-triggering fish. There were no significant differences in specific growth rates calculated at the end of the experiment (day 42 or day 68) between individuals with high, low, and null food-demand (ANOVA, p > 0.05). No territorial or agonistic behaviors were observed, however, there were significant differences in brain scrotonergic activity between the three triggering groups (ANOVA, p=0.050 in telencephalon and p=0.004 in cerebellum). Specifically, high-triggering fish had lower serotonergic turnover than low or null-triggering fish. We put forth the hypothesis that fish with low or null-triggering activity could be stressed by the high activity of high-triggering individuals. (c) 2006 Elsevier Inc. All rights reserved.

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.

The chronic effects of exposing sea bass (average initial weight 100 g) to ammonia in water at 22 degreesC were first evaluated over a 61-day period (period 1, P1) during which nine different groups were submitted to nine ambient ammonia levels ranging from 0.014 to 0.493 mg 1(-1) NH3-N (0.53-16.11 mg 1(-1) total ammonia nitrogen (TA-N)) and fed using self-feeders. At the end of P1, the fish were starved for 10 days (P2). Their recovery capacity was tested over 43 days (P3) after which the exogenous ammonia supply was stopped in all treatments and the fish were allowed to feed. After 20 days of exposure a highly significant effect of ammonia was evident from the decrease in feeding activity, voluntary feed intake (VFI) and specific growth rate (SGR), and the increase in the feed conversion ratio (FCR). Ammonia exposure had no effect on circadian feeding rhythm or hourly actuation profiles. At the end of PI, the fish seemed to have adapted to all ambient ammonia concentrations tested since feeding and growth parameters were independent of ammonia levels. But they were unable to compensate for growth losses. Physiological adjustments were observed: plasma TA-N concentrations were positively related to ambient TA-N while there was no major disturbance in plasma urea. Plasma tri-iodo-thyronine concentrations were affected by ambient ammonia concentrations and there were no significant changes in hydromineral balance. During P2, oxygen consumption and urea excretion did appear to have been affected by ambient ammonia. When the exogenous supply of ammonia was stopped (M), fish exhibited hyperphagia and compensatory growth. In fish previously exposed to the highest ammonia levels, SGR and VFI were highest, and their FCR was improved. At the end of the experiment the final average weights were similar in all of the treatments (range 337-396 g). Depending on the concentrations used, ammonia exposure may enhance subsequent fish appetite and growth rate and have a similar effect on growth performances as restricting feeding level. Within the range tested, no detrimental effect of ammonia on the metabolic capacity of the fish, measured by oxygen consumption and urea excretion, or on their physiological status was recorded, and the fish had a good recovery capacity. In the conditions of the experiment, the non-observable effect concentration (NOEC) was 6 mg 1(-1)., Les effets d'une exposition prolongée à l'ammoniaque, sur des bars (poids moyen 140 g) dans de l'eau à 22 °C, ont été évalués dans un premier temps durant une période de 61 jours (période 1, P1). Les poissons, nourris par des distributeurs « self-service », étaient alors répartis en neuf groupes soumis à neuf niveaux différents de concentration d'ammoniaque, de 0,014 à 0,493 mg l¿1 de NH3-N (0,53 à 16,11 mg l¿1 d'azote ammoniacal total (TA-N)). À la fin de P1, les animaux ont été mis à jeun pendant dix jours (P2). Leur capacité de récupération a été ensuite testée durant 43 jours (P3) après que l'alimentation en ammoniaque eût été supprimée et que les animaux aient pu de nouveau s'alimenter. Après 20 jours d'exposition, l'activité alimentaire, les aliments ingérés volontairement (VFI) et le taux de croissance spécifique (SGR) ont diminué significativement sous l'effet de l'ammoniaque, pendant que le taux de transformation de l'aliment (FCR) a augmenté. L'exposition à l'ammoniaque n'a pas eu d'effet sur les activités circadiennes d'alimentation, ni sur les rythmes horaires de demande alimentaire. À la fin de P1, tous les poissons ont semblé s'être adaptés aux concentrations testées. En effet, les paramètres de croissance et d'alimentation étaient revenus à la normale. Cependant, les poissons n'avaient pas compensé leur retard de croissance. Quelques ajustements physiologiques ont pu être observés : le taux de TA-N du plasma était positivement corrélé au taux d'ammoniaque ambiant, mais pas celui de l'urée. Le taux de tri-iodo-thyronine du plasma a été modifié, mais pas l'équilibre hydrominéral. Durant P2, la consommation d'oxygène et l'excrétion d'urée n'ont pas été affectées. Quand l'apport d'ammoniaque a pris fin (P3), les poissons ont montré de l'hyperphagie et ont manifesté une croissance compensatrice. Les poissons préalablement soumis aux plus fortes concentrations présentent les meilleurs SGR et VFI. À la fin de l'expérimentation, les poids moyens des poissons étaient comparables dans tous les traitements (entre 337 et 396 g). Selon sa concentration, l'ammoniaque peut entraîner une augmentation de l'appétit et du taux de croissance, ultérieurement, similaires à ceux d'un rationnement alimentaire. Dans la gamme testée, aucun effet préjudiciable de l'ammoniaque n'a été observé, ni sur les capacités métaboliques de l'animal, mesurées par sa consommation d'oxygène et l'excrétion d'urée, ni sur ses caractéristiques physiologiques. Les animaux ont montré une très bonne capacité de récupération. Dans les conditions de l'expérience, la concentration, pour laquelle aucun effet n'a pu être observé, était de 6 mg l¿1.

All during fish postmortem evolution, structural muscle proteins are targets for various proteases. During the prerigor period (24 hours at 4 degrees C for sea bass), cytoskeletal proteins are affected by the first proteolytic events. These cleavages disrupt connections between myofibrils and the extracellular matrix, induce segmentation of myofibril cores, and modify the rheological properties of tissue. Dystrophin, a cytoskeletal actin-binding protein, is a relevant in situ marker for muscular proteolysis in the prerigor period. The immunodetection of dystrophin allowed the monitoring of early proteolysis during fish storage. Using antidystrophin antibodies directed toward the carboxy-terminal region, a highly sensitive domain exposed to calpain activity, we showed that proteolysis kinetics are strongly influenced by the muscular lipid content. In particular, comparison between low-fat diets (11.3% lipid) and high-fat diets (30% lipid), used during sea bass farming (90 days), revealed a faster proteolysis rate during the first 8 hours of storage at 0 degrees C with the high-fat diet. The origin of this faster proteolysis is discussed on the basis of a possible activation or translocation of calpains related to lipid accumulation in muscle fibers and cytoskeleton alterations.

Seabass (Dicentrarchus labrax) swimming activity was compared between natural environments and aquaculture facilities. Behaviour under natural conditions was assessed in a saltmarsh pond (250 m2, 18 × 14 × 0·8 m) using acoustic telemetry. From several surveys, we documented the diel activity rhythm and demonstrated group effects on swimming patterns and amplitudes by comparing activity of solitary fish with that of a fish living in a group of 60. Consequences of weather variability were also analysed and revealed a high sensitivity of fish to atmospheric conditions for both swimming and demand-feeding behaviour. Behaviour in fish tanks was also studied using acoustic telemetry, as part of the EUREKA EU1 960 ‘Aqua-Maki 2’ project investigating aspects of fish culture in re-circulating tanks under high density. A re-circulating hexagonal tank (5·4 × 5·4 m, 1·8 m depth, 48 m3) was equipped with positioning and demand-feeding systems, oxygen and temperature probes. Initial density was 50 kg m3 in March and rose to 90 kg m3 at the end of the experiment in May. During this period, the movements of nine fish were continuously recorded for 24 h each, reaching a total of six 24 h episode at eight days interval. Swimming activity was analysed in terms of activity rhythms and space occupation specially around feeding events. The two data set and main results will be presented and compared to assess seabass behavioural plasticity and sensitivity to husbandry conditions.

This parer concerns eggs of captive iish and gonads of vild fish, from the Brittany coast obtained in the 7-18°C thermal range. ihe diameters of egp, 1.07-1.32 mm are compared to those observed in other areas, especially along the hlediterranean coast. The duration of embryogenesis as a function of temperature and the efficiency of different incubators are discussed. The quality of eggs in relation with larval survival is discussed through the biochemical composition of the egp collected in captivity compared to that of wild fish gonads. The absolute values of lipids, proteins, fatty acids, lipid classes, phosphatides and minerals measured, also the positive relations obtained between egg dry weight, diameters, mortality during incubation are prcsented as criteria of egg quality. Keysords : Sea Bass, Dicentrarchus labrax, egg, embryos, aquaculture.

This paper describes the large-scale production of eggs and larvae of sea bass (Dicentrarchus labrax ) and shows how spawning can be planned to produce viable eggs throughout the year by manipulation of photoperiod and temperature. The rearing temperature was 9.5-22 degree C during spawning and 9-24 degree C during the gametogenesis. The photoperiodic cycles tested were normal (i.e. the photoperiodic cycle observed at Palavas-les-Flots, Mediterranean coast, France, 1984/1987) advanced by 3 to 5 months and delayed by 2 months.