The protein requirement of brown trout (Salmo trutta) fry

International audienc

Groundwater Contribution to Sewer Network Baseflow in an Urban Catchment-Case Study of Pin Sec Catchment, Nantes, France

Sewer systems affect urban soil characteristics and subsoil water flow. The direct connection observed between baseflow in sewer systems under drainage infiltrations and piezometric levels influences the hydrological behavior of urban catchments, and must consequently be considered in the hydrologic modeling of urban areas. This research studies the groundwater contribution to sewer networks by first characterizing the phenomenon using experimental data recorded on a small urban catchment in Nantes (France). Then, the model MODFLOW was used to simulate the infiltration of groundwater into a sewer network and model dry weather flows at an urban catchment scale. This application of MODFLOW requires representing, in a simplified way, the interactions between the soil and the sewer trench, which acts as a drain. Observed average groundwater levels were satisfactorily simulated by the model while the baseflow dynamics is well reproduced. Nonetheless, soil parameters resulted to be very sensitive, and achieving good results for joint groundwater levels and baseflow was not possible

Méthodes de production de filtreurs-proies et amélioration de leur qualité alimentaire

National audienc

Biofloc contribution to antioxidant defence status, lipid nutrition and reproductive performance of broodstock of the shrimp Litopenaeus stylirostris: Consequences for the quality of eggs and larvae

International audienceThe aim of this study was to determine biofloc contributions to the antioxidant status and lipid nutrition of broodstock of Litopenaeus stylirostris in relationship with their reproductive performance and the health of larvae produced. Shrimp broodstock reared with Biofloc technology (BFT) compared to Clear water (CW) exhibited a higher health status with (i) a better final survival rate during the reproduction period (52.6% in CW against 79.8% in BFT); (ii) higher glutathione level (GSH) and total antioxidant status (TAS), reduced oxidized/reduced glutathione ratio and a higher spawning rate and frequency as well as higher gonado-somatic index and number of spawned eggs. Finally, larvae from broodstock from BFT exhibited higher survival rates at the Zoe 2 (+ 37%) and Post Larvae 1 (+ 51%) stages when compared with those from females from CW treatment. The improved reproductive performance of the broodstock and higher larvae survival rate resulting from BFT treatment may be linked to the dietary supplement obtained by the shrimp from natural productivity during BFT rearing. Indeed, our study confirms that biofloc particulates represent a potential source of dietary glutathione and a significant source of lipids, particularly essential phospholipids and n-3 highly unsaturated fatty acids (HUFA) for shrimps. Thus, broodstock from BFT treatment accumulated phospholipids, n-3 HUFA and arachidonic acid, which are necessary for vitellogenesis, embryogenesis and pre-feeding larval development. The predominant essential fatty acids, arachidonic acid (ARA), eicopentaeonic acid (EPA) and docosahexaenoic acid (DHA), had levels in the eggs that were, respectively, 2.5, 2.8 and 3 fold higher for BFT compared to the CW treatment.ăStatement of RelevanceăToday, the influence of biofloc technology on shrimp broodstock is not enough described and no information was available on the larvae quality.ăăMoreover, two key pieces of new information emerge from the present study. Firstly, biofloc is a source of further dietary lipids that can act as energetic substrates, but also as a source of phospholipids and essential fatty acids necessary to sustain reproduction, embryonic and larval development. Second, improving the reproduction of the broodstock also leads to an improvement in the quality of the larvae.ăăWe think that our research is new and important to increase knowledge on biofloc topic. We believe the paper will contribute to the development of more efficient and therefore more sustainable systems

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

Dietary arginine degradation is a major pathway in ureagenesis in juvenile turbot (Psetta maxima)

International audienc

Excess dietary arginine effects urea excretion but does not improve N utilisation in rainbow trout Oncorhynchus mykiss and turbot Psetta maxima

International audienc

Dietary arginine degradation is a major pathway in ureagenesis in juvenile turbot (Psetta maxima)

International audienc

Nitrogen utilisation and ureogenesis as affected by dietary nucleic acid in rainbow trout (Oncorhynchus mykiss) and turbot (Psetta maxima)

International audienc

The effects of dietary marine protein hydrolysates on the development of sea bass larvae, Dicentrarchus labrax, and associated microbiota

Résumé posterInternational audienc