Résumé: Given the strong effects of behavioural hierarchies on growth in many cultured species and the key role of feed efficiency in aquaculture economics, understanding the nature of the interaction of these variables is important for the sustainability of aquaculture. The relationship between agonistic behaviour, growth and feed efficiency in Nile tilapia, Oreochromis niloticus, was studied by rearing 120 fish in eight aquaria. Fish were video-recorded to estimate the occurrence of agonistic behaviour during a fasting and a refeeding period. Growth, feed intake and feed conversion efficiency (FCE – calculated as the inverse of feed conversion ratio (FCR)) were subsequently measured individually for each fish. Fish showed 58% less agonistic traits during the fasting period compared to the feeding period, but generally, an aggressive fish during the fasting period was also aggressive during the refeeding period. The nature of agonistic behaviours between individuals was used to assess the presence of hierarchical relationships between fish. There were dominance hierarchies established in each experimental aquarium that despite minor shifts were maintained throughout the experiment. Agonistic behaviours were strongly correlated with each other, the aggression Index (AI) and with hierarchy rank. PCA analysis of the agonistic behaviours summarising the behavioural information showed little or no correlation between agonistic behaviour, fish growth or FCE. FCE was correlated with body weight gain (BWG). These results suggest that agonistic interactions in juvenile Nile tilapia do not have a large impact on growth and feed conversion efficiency.

Résumé: We investigated links between swimming behavior and muscle bioenergetics in two emblematic Mediterranean fish species that have very different ecologies and activity levels. European sardines Sardina pilchardus are pelagic, they swim aerobically, school constantly and have high muscle fat content. Gilthead seabream Sparus aurata are bentho-pelagic, they show discontinuous spontaneous swimming patterns and store less fat in their muscle. Estimating the proportion of red and white muscle phenotypes, sardine exhibited a larger proportion of red muscle (similar to 10% of the body mass) compared to gilthead seabream (similar to 5% of the body mass). We firstly studied red and white muscle fiber bioenergetics, using high-resolution respirometers, showing a 4-fold higher oxidation capacity for red compared to white muscle. Secondly, we aimed to compare the red muscle ability to oxidize either lipids or carbohydrates. Sardine red muscle had a 3-fold higher oxidative capacity than gilthead seabream and a greater capacity to oxidize lipids. This study provides novel insights into physiological mechanisms underlying the different lifestyles of these highly-prized species.

Résumé: Constructed wetlands (CWs) are environmentally-friendly methods for mariculture wastewater purification. The hydraulic regime is a key factor in the effectiveness of sub-surface flow CW treatment. The objectives of this study were to investigate the effects of five hydraulic operating regimes (i.e. Intermittent, Continuous, Batch I, Batch II and Batch III) on the purification performance of CW treated with mariculture wastewater and to assess the correlations between enzyme activities (i.e. urease, dehydrogenase) and purification performance of CW. Fifteen pilot sub-surface CWs with Salicornia bigelovii were investigated for the performance of CW as well as urease activity (UA) and dehydrogenase activity (DA). Over the experiment, removal efficiencies of TAN, NO3−-N, TN and COD under five hydraulic operating regimes were 26.6 to 37.2%, −6.0 to 16.5%, 9.4 to 16.8% and 33.9 to 44.6% respectively, corresponding to removal rates of 147.6 to 456.9 mg m−2 d−1, −18.1 to 229.2 mg m−2 d−1, 174.0 to 603.6 mg m−2 d−1 and 501.9 to 1421.6 mg m−2 d−1 respectively. CW with a Batch III operating regime had the best treatment performance, with mean removal efficiencies of TAN, NO3−-N, TN and COD of 37.2%, 16.5%, 14.9% and 34.0% respectively, with the corresponding removal rates of 456.9, 229.2, 603.6 and 873.6 mg m−2 d−1. As for enzyme activities, the UA was significantly higher in CW under Batch II than in Intermittent and Continuous operating regimes and the DA in CW with Batch I was significantly higher than under an Intermittent operating regime. UA and DA had significant positive correlations with COD concentrations but negative correlations with TAN and TN concentrations. The correlation analysis results showed that UA and DA can be an important indicator in evaluating removal performance of CW with Salicornia bigelovii in marine aquaculture wastewater treatment.

Résumé: Marine intrusion was simulated in a choked and in a restricted coastal lagoon by using a 3D-hydrodynamic model. To study the spatiotemporal progression of seawater intrusion and its mixing efficiency with lagoon waters we define Marine Mixed Volume (V-MM) as a new hydrodynamic indicator. Spatial patterns in both lagoons were described by studying the time series and maps of VMM taking into account the meteorological conditions encountered during a water year. The patterns comprised well-mixed zones (WMZ) and physical barrier zones (PBZ) that act as hydrodynamic boundaries. The choked Bages-Sigean lagoon comprises four sub-basins: a PBZ at the inlet, and two WMZ's separated by another PBZ corresponding to a constriction zone. The volumes of the PBZ were 2.1 and 5.4 millions m(3) with characteristic mixing timescale of 68 and 84 days, respectively. The WMZ were 123 and 433 millions m(3) with characteristics mixing timescale of 70 and 39 days, respectively. (C) 2017 Elsevier Ltd. All rights reserved.

Résumé: The Object-oriented Simulator of Marine ecoSystem Exploitation (OSMOSE) is one of the end-to-end models developed for ecosystem dynamic simulation and management strategy evaluation (MSE) in support of ecosystem-based fishery management (EBFM). However, the implementation of such integrated models has been limited due to lack of data, and their performance in advising fisheries management has been rarely evaluated. We developed an end-to-end model (OSMOSE-JZB) representing organisms of high and low trophic levels in the Jiaozhou Bay, a temperate bay in China with limited available data. We evaluated the performance of the model for simulating the ecosystem dynamics by comparing the model-predicted species biomass, size structure, trophic level, and mortality with relevant data derived from scientific surveys and literature. In general, the model-predicted species biomass and size ranges were consistent with observations. However, the size structure of the two dominant fish species showed some discrepancies between the model simulations and observations. The predicted mean trophic levels from OSMOSE-JZB were closer to the values derived from an Ecopath model of the same region, compared to the values derived from empirical isotope analysis. The model's output suggested that predation mortality appeared to be the main source of mortality for younger individuals compared to starvation and fishing mortality. This study suggests that the OSMOSE-JZB performs well under a data-poor situation and can be considered as a baseline ecosystem model for developing EBFM.

Résumé: Growing evidence suggests that telomeres, non-coding DNA sequences that shorten with age and stress, are related in an undefined way to individual breeding performances and survival rates in several species. Short telomeres and elevated shortening rates are typically associated with life stress and low health. As such, telomeres could serve as an integrative proxy of individual quality, describing the overall biological state of an individual at a given age. Telomere length could be associated with the decline of an array of physiological traits in age-controlled individuals. Here, we investigated the links between individuals’ relative telomere length, breeding performance and various physiological (body condition, natural antibody levels) and life history (age, past breeding success) parameters in a long-lived seabird species, the king penguin Aptenodytes patagonicus. While we observed no link between relative telomere length and age, we found that birds with longer telomeres arrived earlier for breeding at the colony, and had higher breeding performances (i.e. the amount of time adults managed to maintain their chicks alive, and ultimately breeding success) than individuals with shorter telomeres. Further, we observed a positive correlation between telomere length and natural antibody levels. Taken together, our results add to the growing evidence that telomere length is likely to reflect individual quality difference in wild animal.

Résumé: The direct impact of oxidation-reduction potential (ORP) on fish welfare and water quality in marine recirculating aquaculture systems (RAS) is poorly documented. In this study, the effects of the fish size (S-1, S-2, S-3) and ORP level (normal, four successive levels) on the performance of European sea bass (Dicentrarchus labrax) were investigated. Three size fish were distributed into two RAS (RAS and RAS O-3). Ozone was injected into RAS O-3 to increase the ORP level. The ORP was stabilized to four successive levels: 260-300, 300-320, 320-350, and 300-320 mV in fish tanks during four periods (P1-4). At the last day of each period, the hematological parameters, plasma protein and mortality of sea bass were analyzed. Two-way ANOVA revealed that several hematological parameters, including pH, hematocrit, concentrations of oxygen, carbon dioxide, glucose (Glu), ionized calcium, kalium, and hemoglobin, were significantly influenced by the increased ORP levels over the experimental period. The alteration in blood Glu and plasma protein concentration showed that ORP around 300-320 mV started to stress sea bass. Once the ORP exceeded 320 mV in the tanks during the P-3 period, mortality occurred even when total residual oxidants/ozone-produced oxidants was only 0.03-0.05 mg L-1 in the fish tanks. At the same time, plasma protein decreased notably due to appetite depression. After the decrease in ORP during the P-4 period, mortality continued. In conclusion, the results strongly suggest that for European sea bass in RAS, the ORP should not exceed 320 mV in the tanks. Once ozonation damaged fish, the effect seemed to be irreversible. However, how ORP affected related hematological parameters still need the further investigations.

Résumé: A 9 week growth trial was performed at two rearing densities; low (similar to 25 kg m(-3)) and high (similar to 100 kg m-3), in combination with either static water or a water current corresponding to 0.9 body lengths s(-1), to investigate the effects of density and exercise on the bioenergetics of rainbow trout reared at 19 degrees C, particularly routine metabolic rate (RMR), specific growth rate (SGR), and feed conversion ratio (FCR). The growth trial showed that high rearing density resulted in significantly lower SGR and increased FCR, with no significant alleviating effects of a water current, although slight improvement in both parameters were observed at low density. A significant linear relationship between SGR and FCR suggested that increased energy expenditure was the primary cause of reduced growth. Hourly measurements of instantaneous oxygen uptake, during a period of similar growth (200-350 g), revealed clear effects of the experimental conditions. Energetic budgets were calculated from feed intake and routine metabolic rate (RMR) and revealed that whilst feed intake was similar for all groups, a higher RMR in the high density groups resulted in a higher daily rate of energy utilization for routine activity, leading to slower growth. However, a lower RMR in fish subjected to a current resulted in a greater proportion of energy being retained, leading to significantly higher SGR for the selected period, at both low and high density. Furthermore, the presence of a water current was observed to induce schooling behaviour, which is known to reduce aggression and stress. It is thereby likely that the presence of a current had a positive effect on welfare in addition to its effect on energy metabolism. We conclude that the presence of a water current to some extent could alleviate the negative effects of high density at 19 degrees C, a relatively high temperature experienced in farming of rainbow trout during hot seasons. (C) 2011 Elsevier B.V. All rights reserved.

Résumé: The contribution of air breathing to aerobic metabolic scope and exercise performance was investigated in a teleost with bimodal respiration, the banded knifefish, submitted to a critical swimming speed (U-crit) protocol at 30 degrees C. Seven individuals (mean +/- s.e.m. mass 89 +/- 7. g, total length 230 +/- 4. mm) achieved a U-crit of 2.1 +/- 1. body. lengths. (BL). s(-1) and an active metabolic rate (AMR) of 350 +/- 21. mg. kg(-1). h(-1), with 38 +/- 6% derived from air breathing. All of the knifefish exhibited a significant increase in air-breathing frequency (f(AB)) with swimming speed. If denied access to air in normoxia, these individuals achieved a U-crit of 2.0 +/- 0.2. BL. s(-1) and an AMR of 368 +/- 24. mg. kg(-1). h(-1) by gill ventilation alone. In normoxia, therefore, the contribution of air breathing to scope and exercise was entirely facultative. In aquatic hypoxia (P-O2=4. kPa) with access to normoxic air, the knifefish achieved a U-crit of 2.0 +/- 0.1. BL. s(-1) and an AMR of 338 +/- 29. mg. kg(-1). h(-1), similar to aquatic normoxia, but with 55 +/- 5% of AMR derived from air breathing. Indeed, f(AB) was higher than in normoxia at all swimming speeds, with a profound exponential increase during exercise. If the knifefish were denied access to air in hypoxia, U-crit declined to 1.2 +/- 0.1. BL. s(-1) and AMR declined to 199 +/- 29. mg. kg(-1). h(-1). Therefore, air breathing allowed the knifefish to avoid limitations to aerobic scope and exercise performance in aquatic hypoxia.

Résumé: The autonomic regulation of the heart was studied in European sea bass (Dicentrarchus labrax) during digestion and aerobic exercise by measuring cardiac output (Q), heart rate (f(H)), stroke volume (V(s)) and oxygen consumption (MO(2)) before and after pharmacological blockade by intraperitoneal injections of atropine and propranolol. The significant rise in MO(2) (134 +/- 14 to 174 +/- 14 mg kg(-1) h(-1)) 6 h after feeding (3% body mass) caused a significant tachycardia (47.7 +/- 10.9 to 72.6 +/- 7.2 beats min(-1)), but only a small elevation of Q. MO(2) of fasting fish increased progressively with swimming speed (0.7-2.1 BL s(-1)) causing a significant tachycardia (43 +/- 6 to 61 +/- 4 mL min(-1) kg(-1)) and increased Q but V(s) did not change. Inactive fish were characterized by a high vagal tone (98.3 +/- 21.7%), and the tachycardia during digestion and exercise was exclusively due to a reduction of vagal tone, while the adrenergic tone remained low during all conditions. Intrinsic f(H), revealed after double autonomic blockade, was not affected by digestion (71 +/- 4 and 70 +/- 6 min(-1), respectively), indicating that non-adrenergic, non-cholinergic (NANC) factors do not contribute to the tachycardia during digestion in sea bass. (C) 2010 Elsevier Inc. All rights reserved.

Résumé: The functional significance of chemoreflexive hypoxic bradycardia was explored in Atlantic cod Gadus morhua L. (mean mass similar to 800 g, acclimated to a seawater temperature of 11 degrees C) by investigating responses to progressive hypoxia following section of the cardiac branches of cranial nerve X Cardiac denervation had no effect on oxygen uptake rate (M(O2)), gill ventilation rate (f(G)) or opercular pressure amplitude (P(OP)) under normoxic conditions, but caused a significant increase in heart rate (f(H)), to 50 +/- 1 beats min(-1) by comparison to 40 +/- 2 beats min(-1) in sham-operated cod (mean +/- s.e.m., n=9). Sham-operated cod exhibited transient profound bradycardia following oxygen chemoreceptor stimulation by bolus injection of sodium cyanide into the buccal cavity (2 mg in 2 ml seawater), but this cardiac chemoreflex was abolished in denervated cod. Both groups, however, exhibited similar marked transient chemoreflexive hyperventilation following NaCN. When exposed from normoxia (PO(2)similar to 18 kPa) to progressive hypoxia at nominal water PO(2)'S of 8, 6, 5, 4 and 3 kPa, both groups exhibited the same pattern of homeostatic regulation of M(O2), with no significant difference in their mean critical PO(2) (P(crit)) values, which were 7.40 +/- 0.81 kPa and 8.73 +/- 0.71 kPa, respectively (n=9). Both groups exhibited significant bradycardia during progressive hypoxia, although denervated fish always had higher mean f(H). The incipient threshold for bradycardia coincided with P(crit) in sham-operated cod whereas, in denervates, the threshold was below their P(crit) and bradycardia presumably reflected direct effects of hypoxia on the myocardium. The sham-operated group displayed a significantly more pronounced ventilatory response than denervates in hypoxia, in particular for P(OP). In sham-operated cod, peak ventilatory responses occurred in deep hypoxia below P(crit) whereas, in denervates, more modest peak responses coincided with Pit and, in deep hypoxia, they exhibited a significant decline in f(G) below their normoxic rate. Only a minority of shams lost equilibrium in hypoxia whereas a majority of denervates did, some of which failed to recover. The results indicate that chemoreflexive bradycardia plays no role in the homeostatic regulation of oxygen uptake by cod in hypoxia, but does contribute to maintenance of overall functional integrity below P(crit). (C) 2009 Elsevier Inc. All rights reserved.

Résumé: The objective of this study was to compare fish performance and welfare at different stocking densities in a recirculating system (RS) and a flow through system (FTS) under field conditions. During the 77 days experiment, the fish survival rate was high (99.3%) and stocking density increased from 57 to 98108 kg m(-3). No significant differences in growth were observed between RS and FTS until day 56. Later, growth decreased in the FTS, while it remained similar to the farm reference at 50 kg m(-3) in the RS. Final weight was 17% higher in RS than in FTS. The maximum carrying capacity of the RS was near 100 kg m(-3), limited by NO2 increase up to safe level at the end of the experiment, the maximum carrying capacity of the FTS was near 85 kg m(-3), probably limited by CO2 concentration (17.8 +/- 5.7 mg l(-1)). In the RS, the relative length index of pectoral and dorsal fins was lower than in the FTS, which may be attributed to the tank hydrodynamics. In both systems, an improvement of the pectoral and dorsal profile was observed at the end of the experiment, attributed to a swimming activity reduction that may have decreased contact between individuals. In the RS, high caudal fin deterioration (50% versus 20% in FTS) was observed irrespective of stocking density, that could be linked to the highest water velocity modifying the fish swimming activity. The results confirm that when water quality is maintained in safe level ranges, high densities can be used in trout RS without fish performance and pectoral or dorsal fin deterioration, but with a major caudal impairment. (C) 2008 Elsevier B.V. All rights reserved.