9 research outputs found
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, pĂȘche, marchĂ© 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 donnĂ©es disponibles dans la littĂ©rature sur les deux espĂšces de rougets-barbets. La prĂ©sence (rouget de roche) ou lâabsence (rouget de vase) de pigmentation sur la premiĂšre nageoire dorsale est le seul critĂšre permettant de distinguer aisĂ©ment les deux espĂšces. La rĂ©partition gĂ©ographique du rouget de roche est plus septentrionale que celle du rouget de vase. Dans le milieu naturel, la ponte des deux espĂšces est observĂ©e au printemps et en dĂ©but dâĂ©tĂ©. Les juvĂ©niles gagnent le fond Ă une taille de 3 Ă 4 cm. La croissance des deux espĂšces est lente.Les dĂ©barquements de la pĂȘche mondiale de rouget de vase dĂ©croissent depuis 1989 (4.500 tonnes en 1997). Chez le rouget de roche, les tonnages dĂ©barquĂ©s ne cessent de croĂźtre (15.000 tonnes en 1997). En France, seul le rouget de roche est pĂȘchĂ© (2.900 tonnes en 1997). Le prix moyen de vente en criĂ©e du rouget-barbet est passĂ© de 44,2 F/kg en 1992 Ă 29,5 F/kg en 1998. Au dĂ©tail, 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 lâobjet de tentatives dâaquaculture, qui restent cependant limitĂ©es. Des Ćufs de qualitĂ© satisfaisante ont Ă©tĂ© obtenus durant plusieurs annĂ©es Ă partir de reproducteurs captifs. LâĂ©levage larvaire reste difficile, en grande partie, en raison de la petite taille de la larve (longueur totale de 3 mm Ă lâĂ©closion). Câest une espĂšce extrĂȘmement sensible aux manipulations dont la croissance obtenue Ă partir de juvĂ©niles de pĂȘche est relativement lente. Cependant, la taille commerciale (correspondant Ă un poids de 100 g) devrait ĂȘtre atteinte au cours de la deuxiĂšme annĂ©e post-Ă©closion.Les atouts du rouget de roche pour lâaquaculture sont nombreux: chair rĂ©putĂ©e, juvĂ©niles disponibles dans le milieu naturel, reproduction en captivitĂ© ne prĂ©sentant pas de difficultĂ©s majeures et prix de dĂ©tail Ă©levĂ©. Cependant, quelques incertitudes persistent tant sur la phase Ă©closerie que sur le grossissement. Le rouget de vase semble ĂȘtre un moins bon candidat Ă lâĂ©levage en raison dâune croissance infĂ©rieure relevĂ©e 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 100â500 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 Ă long terme de concentrations constantes en azote ammoniacal ont Ă©tĂ© Ă©tudiĂ©s chez deux lots diffĂ©rents de turbot (53 et 73 g) en conditions contrĂŽlĂ©es (environnement et alimentation). Au cours des 84 jours d'expĂ©rience, les concentrations en NH3 ont Ă©tĂ© stables (coefficient de variation, 12-16 %) ainsi que le pH ambient (7,88-7,99). La survie a Ă©tĂ© maximale jusqu'Ă 0,33 mg.lâ1 NH3 et Ă 0,73, des taux de mortalitĂ© de 50 % ont Ă©tĂ© observĂ©s au jour 52-77 selon le lot. La croissance a Ă©tĂ© arrĂȘtĂ©e Ă 0,73 mg.lâ1 NH3 et significativement affectĂ©e Ă partir de 0,14-0,33 mg.lâ1 NH3. Chez le lot le plus tolĂ©rant (53 g), la concentration n'induisant pas d'effet sur la croissance pour une durĂ©e d'exposition de 84 jours a Ă©tĂ© de 0,14 mg.lâ1 UIA-N. Au jour 28, le taux de croissance spĂ©cifique a Ă©tĂ© rĂ©duit de 50 % Ă 0,60-0,75 mg.lâ1 NH3, Les variations du taux de croissance spĂ©cifique et du taux d'alimentation en fonction de la concentration en NH3 ont eu le mĂȘme profil avec quelques diffĂ©rences observĂ©es entre les 2 lots. L'exposition prolongĂ©e Ă des concentrations en NH3 excĂ©dant 0,33-0,70 mg.lâ1 a entraĂźnĂ© une baisse des performances alimentaires. Les modifications majeures de la composition corporelle des poissons ont Ă©tĂ© une augmentation de la teneur en eau pour toutes les concentrations. Une augmentation du taux journalier d'excrĂ©tion urĂ©ique a Ă©tĂ© aussi observĂ©e au-delĂ de 0,33 mg.lâ1. Les seuils de tolĂ©rance sont dĂ©pendants de la durĂ©e d'exposition. Les seuils de perturbation de la croissance du turbot juvĂ©nile correspondent aux concentrations rencontrĂ©es en conditions d'Ă©levage 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
Effects of temperature, stocking density and farming conditions on fin damage in European sea bass ( Dicentrarchus
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 O2lâ1 and 0.28 ± 0.01 mg lâ1 total ammonia nitrogen (T-AN), L: 5.15 ± 0.07 mg O2lâ1 and 0.54 ± 0.01 mg T-AN lâ1) and 3 stabilized stocking densities: 24.8 ± 0.2, 74.2 ± 0.5 and 120.0 ± 0.9 kg mâ3) 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 mâ3. There was no significant difference in final weight between 25 and 74 kg mâ3, but at 120 kg mâ3 it was 27% and 19% lower in H and L water respectively than at 25 kg mâ3. Feed intake (FI) from day 0â85 was significantly affected by water quality,
1.5% in H compared to 1.1â1.0 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 (HCO3â) 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