Comparison of brown trout (

Brown trout and rainbow trout (average weight 100 g) were reared in fresh water at 12 °C under the same conditions before transferring brown trout to sea water, in order to compare phosphorus utilisation in both species. Apparent phosphorus availability, orthophosphate excretion and phosphorus accretion in the fish were directly determined. Thus, actual phosphorus mass balance was built. Rainbow trout raised in fresh water had a higher phosphorus retention coefficient (maximum 50 %) than brown trout reared in fresh water (maximum 45 %). Transferring brown trout to sea water induced a reduction in phosphorus retention (maximum 39 %). Orthophosphate excretion, ranging 7-20 mg phosphorus per kg wet weight per day, represented 10-20 % of ingested phosphorus. Phosphorus availability was lower in brown trout raised in sea water (65 %) than brown trout raised in fresh water (76 %). Phosphorus balance measurements showed that 90 to 98 % of phosphorus flow could be accounted for

Comparison of brown trout (Salmo trutta) reared in fresh water and sea water to freshwater rainbow trout (Oncorhynchus mykiss) .1. Growth and nitrogen balance

Brown trout and rainbow trout (average weight 100 g) were reared in fresh water at 12 degrees C under the same conditions before transfer of brown trout to sea water, in order to compare nitrogen utilisation in the two species. Apparent protein digestibility (ADC), nitrogen (ammonia and urea) excretion, protein productive value (PPV) and actual observed nitro en mass balance were determined. Rainbow trout raised in fresh water had a higher growth rate (1.1 vs 0.8%. d(-1)), better food conversion ratio (0.7 vs 1.0), better ADC (91 vs 85%) and PPV (45 vs 35%) and lower ammonia excretion rates than brown trout reared in fresh water. Transferring brown trout to sea water induced lower PPV (30%) and ammonia and urea excretion. Salinity did not modify metabolic efficiency in brown trout. Fat content was higher in brown trout (7.7-8.9% ww) than in rainbow trout (5.7-7.6% ww). Nitrogen mass balance indicated that compounds other than ammonia and urea were produced in higher quantities by seawater brown trout. Behaviour, less domestication and specific ability to utilise protein could explain the differences between the two species.Des truites communes (fario) et des truites arc-en-ciel de 100 g de poids moyen ont été élevées à 12 °C dans des conditions strictement identiques, avant le transfert des truites communes en eau de mer, dans le but de comparer l'utilisation de l'azote chez les deux espèces. La digestibilité apparente des protéines (ADC), l'excrétion ammoniacale et uréique, et l'accrétion protéique (PPV) des poissons ont été estimées. Les bilans de masse ont été construits avec ces données. Les truites arc-en-ciel élevées en eau douce ont présenté un meilleur taux de croissance (1.1 vs 08 %.j−1), un meilleur coefficient de transformation de l'aliment (0.7 vs 1.0), de meilleurs ADC (91 vs 85 %) et PPV (45 vs 35 %), ainsi qu'une excrétion ammoniacale plus faible que les truites communes élevées en eau douce. Après transfert en mer, l'excrétion ammoniacale et l'excrétion uréique ont diminué chez la truite commune, ainsi que la rétention protéique (30 %). La salinité n'a pas modifié l'efficacité métabolique de la truite commune. Le contenu lipidique de la truite commune (7.7-8.9 % poids frais) était plus élevé que celui de la truite arc-en-ciel (5.7-7.6 % poids frais). Le bilan de masse de l'azote a indiqué que les autres molécules que l'ammoniaque et l'urée étaient excrétées en plus grandes quantités par la truite commune en eau de mer. Le comportement, une domestication moins avancée et une capacité distincte d'utilisation des protéines pourraient expliquer les différences entre les deux espèces

Impact de la pisciculture marine intensive sur l'environnement : contribution à la modélisation de l'utilisation de l'azote par le turbot

Ce document présente une étude visant à déterminer le flux de nutriments produits par un élevage de turbots en conditions contrôlées. Les paramètres d'excrétion et de production de fèces ont été abordés en fonction des quantités d'aliment ingéré, en même temps que l'excrétion d'azote corporel. L'étude montre que le turbot est un animal plus économe que la truite arc-en-ciel pour ce qui concerne l'utilisation des protéines. Ceci est explicable par des particularités physiologiques. L'utilisation de modè les "salmonidés" pour l'estimation de l'impact environnemental des piscicultures marines est donc déconseillée

Gene expression pattern of digestive and antioxidant enzymes during the larval development of reared Atlantic bluefin tuna (ABFT), Thunnus thynnus L.

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 antioxidant 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 (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

Identification of Hypoxia-Regulated Genes in the Liver of Common Sole (Solea solea ) Fed Different Dietary Lipid Contents

Coastal systems could be affected by hypoxic events brought about by global change. These areas are essential nursery habitats for several fish species including the common sole (Solea solea L.). Tolerance of fish to hypoxia depends on species and also on their physiological condition and nutritional status. Indeed, high dietary lipid content has been recently shown to negatively impact the resistance of sole to a severe hypoxic challenge. In order to study the molecular mechanisms involved in the early response to hypoxic stress, the present work examined the hepatic transcriptome in common sole fed diets with low and high lipid content, exposed to severe hypoxia. The activity of AMP-activated protein kinase (AMPK) was also investigated through the quantification of threonine-172 phosphorylation in the alpha subunit. The results show that hypoxia consistently regulates several actors involved in energy metabolism pathways and particularly AMPKα, as well as some involved in cell growth and maintenance or unfolded protein response. Our findings reveal that (1) the expression of genes involved in biological processes with high energy cost or implicated in aerobic ATP synthesis was down-regulated by hypoxia, contrary to genes involved in neoglucogenesis or in angiogenesis, (2) the consumption of high lipid induced regulation of metabolic pathways going against this energy saving, and (3) this control was fine-tuned by the regulation of several transcriptomic factors. These results provide insight into the biological processes involved in the hepatic response to hypoxic stress and underline the negative impact of high lipid consumption on the tolerance of common sole to hypoxi