Ontogenic effects of early feeding of sea bass (Dicentrarchus labrax) larvae with a range of dietary n-3 HUFA levels on the functioning of PUFA desaturation pathways

Four replicated groups of sea bass (Dicentrarchus labrax) larvae were fed diets containing an extra-high level of highly unsaturated fatty acids (HUFA) (XH; 3·7% EPA + DHA), a high level of HUFA (HH; 1·7 %), a low level of HUFA (LH; 0·7%) or an extra-low level of HUFA (XLH; 0·5%) from day 6 to day 45 (experiment 1; XH1, HH1, LH1, XLH1). After a subsequent 1-month period feeding a commercial diet (2·7% EPA + DHA), the capacity of the four initial groups to adapt to an n-3 HUFA-restricted diet (0·3% EPA + DHA; R-groups: XH2R, HH2R, LH2R, XLH2R) was tested for 35 d. Larval dietary treatments had no effect on larval and juvenile survival rates. The wet weight of day 45 larvae was higher in XH1 and HH1 (P < 0·001), but the R-juvenile mass gains were similar in all treatments. D-6-desaturase (D6D) mRNA level was higher in LH1 and XLH1 at day 45 (

Les rougets-barbets (Red mullets) : biologie, pêche, marché et potentiel aquacole

This work reviews data available in the literature on both species of red-mullets. The presence (red-mullet) or absence (stripped-mullet) of pigmentation on the first dorsal fin is the best criterion used to easily determine these species. The distribution of stripped-mullet is more northern than that of red-mullet. In the wild, both species spawn in spring or early summer. From a size of 3 to 4 cm, juveniles move into deeper water. The growth is not rapid. Fisheries of red-mullet decreased from 1989 (4,500 tons in 1997). On the contrary, the landings of strippedmullet increased (15,000 tons in 1997). The French production of stripped-mullet is 2,900 tons in 1997. Between 1992 and 1998, the wholesale selling price of red-mullets decreased from 44.2 F/kg to 29.5 F/kg. The retail price is comprised between 66.5 F/kg and 73.6 F/kg, depending on the distribution channel. Rearing attempts have only been carried out in stripped-mullet. However, they remain limited. Good quality eggs were collected on several years from breeders kept in captivity. Because of the small size of larvae (total length at hatching: 3 mm), larval rearing remains difficult. This species is highly sensible to handlings. Its growth is not rapid. However, the commercial weight of 100 g would be reached during the second year after hatching. The assets of stripped-mullet for aquaculture are numerous: a highly esteemed flesh, the availability of juveniles in the wild, the reproduction in captivity does not present great difficulties and a high retail price. However, some questions remain on hatchery and growing-out phases. Because of its lower growth observed in the wild, the red-mullet does not seem to be a good candidate for aquaculture.Ce travail fait le point des données disponibles dans la littérature sur les deux espèces de rougets-barbets. La présence (rouget de roche) ou l’absence (rouget de vase) de pigmentation sur la première nageoire dorsale est le seul critère permettant de distinguer aisément les deux espèces. La répartition géographique du rouget de roche est plus septentrionale que celle du rouget de vase. Dans le milieu naturel, la ponte des deux espèces est observée au printemps et en début d’été. Les juvéniles gagnent le fond à une taille de 3 à 4 cm. La croissance des deux espèces est lente.Les débarquements de la pêche mondiale de rouget de vase décroissent depuis 1989 (4.500 tonnes en 1997). Chez le rouget de roche, les tonnages débarqués ne cessent de croître (15.000 tonnes en 1997). En France, seul le rouget de roche est pêché (2.900 tonnes en 1997). Le prix moyen de vente en criée du rouget-barbet est passé de 44,2 F/kg en 1992 à 29,5 F/kg en 1998. Au détail, les prix sont compris entre 66,5 F/kg et 73,6 F/kg selon le circuit de commercialisation.Seul le rouget de roche a fait l’objet de tentatives d’aquaculture, qui restent cependant limitées. Des œufs de qualité satisfaisante ont été obtenus durant plusieurs années à partir de reproducteurs captifs. L’élevage larvaire reste difficile, en grande partie, en raison de la petite taille de la larve (longueur totale de 3 mm à l’éclosion). C’est une espèce extrêmement sensible aux manipulations dont la croissance obtenue à partir de juvéniles de pêche est relativement lente. Cependant, la taille commerciale (correspondant à un poids de 100 g) devrait être atteinte au cours de la deuxième année post-éclosion.Les atouts du rouget de roche pour l’aquaculture sont nombreux: chair réputée, juvéniles disponibles dans le milieu naturel, reproduction en captivité ne présentant pas de difficultés majeures et prix de détail élevé. Cependant, quelques incertitudes persistent tant sur la phase écloserie que sur le grossissement. Le rouget de vase semble être un moins bon candidat à l’élevage en raison d’une croissance inférieure relevée dans le milieu naturel

Teneur en ADN de la larve de

Sea bass Dicentrarchus labrax larvae were hatched and reared for 34 days in the laboratory to test a recent biochemical index (DNA/C) of larval fish nutritional condition. Variations in DNA/C ratio values were monitored during the whole larval ontogenesis of fed individuals and the effect of starvation was assessed at three developmental stages. Three main periods in the relative DNA content variations were determined in close connection with growth patterns during larval ontogenesis

How to assess fin damage in rainbow trout,

Fin condition was examined in 100–500 g hatchery-reared rainbow trout sampled in a large range of environmental conditions of an experimental farm. A method that is simple to use, requires little training, and does not need costly sophisticated equipment or reference to a model is proposed to assess fin erosion (defined as a decrease in size and profile alteration of fins). A procedure to reliably measure the length of the longest ray present in two selected fins (dorsal and pectoral) is described. Fin general profile is assessed using five levels of erosion based on the precise rank of intact or eroded rays to limit subjective bias. The suitability of the two descriptors of fin erosion under laboratory, farm or field conditions is discussed

Toxicity of ammonia to turbot juveniles: I. effects oil survival, growth and food utilisation

Long-term effects of constant exogenous ammonia concentrations were investigated in two different batches of turbot juveniles (53 and 73 g) under controlled environmental and feeding conditions. Over the 84-day experiments, ambient un-ionized ammonia (UIA-N, NH3) concentrations were steady (coefficient of variation, 12-16 %) and water pH range was 7.88-7.99. Survival was maximum up to 0.33 mg.l(-1) UIA-N and at 0.73, 50 % mortalities were observed on day 52 (73 g) or day 77 (53 g). No-growth concentration was 0.73 mg.l(-1) UIA-N in the two groups and the 84-day lowest-observable-effect concentration range 0.14-0.33 mg.l(-1). In the most tolerant group (53 g), the 84-day no-observable-effect concentration was 0.14 mg.l(-1) UIA-N. The estimated 28-day efficient concentration that gave 50 % of the specific growth rate of controls ranged from 0.60 to 0.75 mg.l(-1) UIA-N. Specific growth rate to ambient ammonia concentration patterns were different in the two groups for the lowest concentrations (0.14-0.34) and similar to food intake to ammonia pattern. Food efficiency was negatively correlated to ambient ammonia concentration, with major changes in food conversion ratio, and protein utilisation observed above 0.33-0.70 mg.l(-1) UIA-N. The main change in body composition was an increase in water content in all ammonia-exposed fish. A significant increase in urea-N excretion rate was also observed over 0.33 mg.l(-1) UIA-N. Thresholds for growth were affected by exposure duration. Turbot juveniles growth capacity may be depressed by usual ambient ammonia concentrations under intensive farming conditions.Les effets à long terme de concentrations constantes en azote ammoniacal ont été étudiés chez deux lots différents de turbot (53 et 73 g) en conditions contrôlées (environnement et alimentation). Au cours des 84 jours d'expérience, les concentrations en NH3 ont été stables (coefficient de variation, 12-16 %) ainsi que le pH ambient (7,88-7,99). La survie a été maximale jusqu'à 0,33 mg.l−1 NH3 et à 0,73, des taux de mortalité de 50 % ont été observés au jour 52-77 selon le lot. La croissance a été arrêtée à 0,73 mg.l−1 NH3 et significativement affectée à partir de 0,14-0,33 mg.l−1 NH3. Chez le lot le plus tolérant (53 g), la concentration n'induisant pas d'effet sur la croissance pour une durée d'exposition de 84 jours a été de 0,14 mg.l−1 UIA-N. Au jour 28, le taux de croissance spécifique a été réduit de 50 % à 0,60-0,75 mg.l−1 NH3, Les variations du taux de croissance spécifique et du taux d'alimentation en fonction de la concentration en NH3 ont eu le même profil avec quelques différences observées entre les 2 lots. L'exposition prolongée à des concentrations en NH3 excédant 0,33-0,70 mg.l−1 a entraîné une baisse des performances alimentaires. Les modifications majeures de la composition corporelle des poissons ont été une augmentation de la teneur en eau pour toutes les concentrations. Une augmentation du taux journalier d'excrétion uréique a été aussi observée au-delà de 0,33 mg.l−1. Les seuils de tolérance sont dépendants de la durée d'exposition. Les seuils de perturbation de la croissance du turbot juvénile correspondent aux concentrations rencontrées en conditions d'élevage intensif

Combined effects of water quality and stocking density on welfare and growth of rainbow trout ( Oncorhynchus mykiss

An 84-day experiment assessed the combined effects of two fresh water quality levels (H: 1.71 +/- 0.15 mg O(2)l(-1) and 0.28 +/- 0.01 mg l(-1) total ammonia nitrogen (T-AN), L: 5.15 +/- 0.07 mg O2l(-1) and 0.54 +/- 0.01 mg T- AN l(-1)) and 3 stabilized stocking densities: 24.8 +/- 0.2, 74.2 +/- 0.5 and 120.0 +/- 0.9 kg m(-3)) on rainbow trout. Fish were fed using demand feeders with rewards proportional to stocking density. Mass increase was significantly affected by water quality and stocking density, being highest in H water and the lowest at 120 kg m(-3). There was no significant difference in final weight between 25 and 74 kg m(-3), but at 120 kg m(-3) it was 27% and 19% lower in H and L water respectively than at 25 kg m(-3). Feed intake (FI) from day 0-85 was significantly affected by water quality, 1.5% in H compared to 1.1-1.0 in L, but there were no significant differences in apparent feed conversion (AFC). FI was not significantly affected by stocking density but AFC was impaired, it increased with stocking density. Marked changes in fish morphology and composition were related to water quality: Condition K factor and fillet fat content were significantly higher in H than in L groups. Dorsal and pectoral fin condition was affected by stocking density and water quality: fins were significantly longer and less eroded in L groups and at low stocking density. Physiological measures were within the usual ranges, but differed between treatments. Changes in plasma osmolarity, hydromineral balance (Na+) and acid base balance (HCO3-) showed that fish were more affected by water quality than by stocking density. There was no sign of acute stress in acclimated fish as cortisol and glycemia were similar under all experimental conditions. This study highlights the importance of water quality and feeding conditions when considering the effects of stocking density on fish welfare

Combined effects of water quality and stocking density on welfare and growth of rainbow trout (

An 84-day experiment assessed the combined effects of two fresh water quality levels (H: 1.71 ± 0.15 mg O2l−1 and 0.28 ± 0.01 mg l−1 total ammonia nitrogen (T-AN), L: 5.15 ± 0.07 mg O2l−1 and 0.54 ± 0.01 mg T-AN l−1) and 3 stabilized stocking densities: 24.8 ± 0.2, 74.2 ± 0.5 and 120.0 ± 0.9 kg m−3) on rainbow trout. Fish were fed using demand feeders with rewards proportional to stocking density. Mass increase was significantly affected by water quality and stocking density, being highest in H water and the lowest at 120 kg m−3. There was no significant difference in final weight between 25 and 74 kg m−3, but at 120 kg m−3 it was 27% and 19% lower in H and L water respectively than at 25 kg m−3. Feed intake (FI) from day 0–85 was significantly affected by water quality, 1.5% in H compared to 1.1–1.0 in L, but there were no significant differences in apparent feed conversion (AFC). FI was not significantly affected by stocking density but AFC was impaired, it increased with stocking density. Marked changes in fish morphology and composition were related to water quality: Condition K factor and fillet fat content were significantly higher in H than in L groups. Dorsal and pectoral fin condition was affected by stocking density and water quality: fins were significantly longer and less eroded in L groups and at low stocking density. Physiological measures were within the usual ranges, but differed between treatments. Changes in plasma osmolarity, hydromineral balance (Na+) and acid base balance (HCO3–) showed that fish were more affected by water quality than by stocking density. There was no sign of acute stress in acclimated fish as cortisol and glycemia were similar under all experimental conditions. This study highlights the importance of water quality and feeding conditions when considering the effects of stocking density on fish welfare

Somatotropin, thyroid hormones and growth in turbot (Psetta maxima): effects of temperature, ammonia and hypoxia

Somatotropin, thyroid hormones and growth in turbot (Psetta maxima): effects of temperature, ammonia and hypoxi