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Galasso, H. L., Lefebvre, S., Aliaume, C., Sadoul, B., & Callier, M. D. (2020). Using the Dynamic Energy Budget theory to evaluate the bioremediation potential of the polychaete Hediste diversicolor in an integrated multi-trophic aquaculture system. Ecol. Model., 437, 109296.
Résumé: Integrated Multi-Trophic Aquaculture (IMTA) systems have been designed to optimize nutrient and energy use, to decrease waste, and to diversify fish-farm production. Recently, the development of detritivorous aquaculture has been encouraged, as detrivores can consume organic particulate matter, reducing benthic eutrophication and the environmental footprint of aquaculture. To this end, the polychaete Hediste diversicolor is a promising species due to its broad feeding behaviour and its resistance in a wide range of environments. In this study, an existing Dynamic Energy Budget (DEB) model of H. diversicolor was used to predict the ragworm's metabolic processes in various environmental conditions and to estimate its bioremediation capacity in an aquaculture context. First, the scaled functional response (f) was calibrated in a 98-day growth experiment with two types of food (Fish faeces and Fish feed). Then, we further validated the model using data on the ammonia excretion and oxygen consumption of individuals fed with fish faeces at four different temperatures using the previously calibrated f. Overall, we found that the DEB model was able to correctly predict the experimental data (0.51 < MRE <0.80). Lastly, different environmental scenarios of seawater temperatures and assimilation rates were compared. The bioremediation potential of H. diversicolor was estimated based on cumulated assimilation rates, which could represent 75-289 kg of fish waste year(-1) for a 100 m(2) ragworm farm (3700 ind. m(-2)). These findings suggest that the DEB model is a promising tool for further IMTA development and management.
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Jourdan-Pineau, H., Dupont-Prinet, A., Claireaux, G., & McKenzie, D. J. (2010). An Investigation of Metabolic Prioritization in the European Sea Bass, Dicentrarchus labrax. Physiol. Biochem. Zool., 83(1), 68–77.
Résumé: We investigated the ability of European sea bass (Dicentrarchus labrax) to respond simultaneously to the metabolic demands of specific dynamic action (SDA) and aerobic exercise and how this was influenced by moderate hypoxia (50% air saturation). At 3 h after feeding in normoxia at 20 degrees C, SDA raised the instantaneous oxygen uptake (Mo(2)) of sea bass by 47% +/- 18% (mean +/- SEM, N = 7) above their standard metabolic rate (SMR) when fasted. This metabolic load was sustained throughout an incremental exercise protocol until fatigue, with a 14% +/- 3% increase in their maximum aerobic metabolic rate (MMR) relative to their fasted rate. Their incremental critical swimming speed (U(crit)) did not differ between fasted and fed states. Thus, in normoxia, the bass were able to meet the combined oxygen demands of SDA and aerobic exercise. In hypoxia, the sea bass suffered a significant decline in MMR and U(crit) relative to their normoxic performance. The SDA response was similar to normoxia (84% +/- 24% above fasted SMR at 3 h after feeding), but although this load was sustained at low swimming speeds, it gradually disappeared as swimming speed increased. As a result, the hypoxic sea bass exhibited no difference in their fasted versus fed MMR. Hypoxic U(crit) did not, however, differ between fasted and fed states, indicating that the sea bass deferred their SDA to maintain exercise performance. The results demonstrate that, in normoxia, the sea bass possesses excess cardiorespiratory capacity beyond that required for maximal aerobic exercise. The excess capacity is lost when oxygen availability is limited in hypoxia, and, under these conditions, the sea bass prioritize exercise performance. Thus, environmental conditions (oxygen availability) had a significant effect on patterns of oxygen allocation in sea bass and revealed intrinsic prioritization among conflicting metabolic demands.
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Larsen, B. K., Skov, P. V., McKenzie, D. J., & Jokumsen, A. (2012). The effects of stocking density and low level sustained exercise on the energetic efficiency of rainbow trout (Oncorhynchus mykiss) reared at 19 degrees C. Aquaculture, 324, 226–233.
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.
Mots-Clés: Energetic budget; Rainbow trout; Rearing density; Routine metabolic rate; Schooling behaviour; Sustained exercise; Welfare; cardiorespiratory performance; charr salvelinus-alpinus; feeding-behavior; fish welfare; food-intake; juvenile arctic charr; oxygen-consumption; physiology; respiratory; salmon salmo-salar; seasonal temperature
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Lefevre, S., Mckenzie, D. J., & Nilsson, G. E. (2017). Models projecting the fate of fish populations under climate change need to be based on valid physiological mechanisms. Glob. Change Biol., 23(9), 3449–3459.
Résumé: Some recent modelling papers projecting smaller fish sizes and catches in a warmer future are based on erroneous assumptions regarding (i) the scaling of gills with body mass and (ii) the energetic cost of 'maintenance'. Assumption (i) posits that insurmountable geometric constraints prevent respiratory surface areas from growing as fast as body volume. It is argued that these constraints explain allometric scaling of energy metabolism, whereby larger fishes have relatively lower mass-specific metabolic rates. Assumption (ii) concludes that when fishes reach a certain size, basal oxygen demands will not be met, because of assumption (i). We here demonstrate unequivocally, by applying accepted physiological principles with reference to the existing literature, that these assumptions are not valid. Gills are folded surfaces, where the scaling of surface area to volume is not constrained by spherical geometry. The gill surface area can, in fact, increase linearly in proportion to gill volume and body mass. We cite the large body of evidence demonstrating that respiratory surface areas in fishes reflect metabolic needs, not vice versa, which explains the large interspecific variation in scaling of gill surface areas. Finally, we point out that future studies basing their predictions on models should incorporate factors for scaling of metabolic rate and for temperature effects on metabolism, which agree with measured values, and should account for interspecific variation in scaling and temperature effects. It is possible that some fishes will become smaller in the future, but to make reliable predictions the underlying mechanisms need to be identified and sought elsewhere than in geometric constraints on gill surface area. Furthermore, to ensure that useful information is conveyed to the public and policymakers about the possible effects of climate change, it is necessary to improve communication and congruity between fish physiologists and fisheries scientists.
Mots-Clés: aerobic scope; coryphaena-hippurus; energy-demand teleosts; gadus-morhua l; gill surface area; growth; makaira-nigricans; marlin tetrapturus-albidus; metabolism; metabolism-size relationship; oxygen consumption; oxygen-consumption; ram ventilation; Respiration; scaling; swimming performance; tuna katsuwonus-pelamis
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McKenzie, D. J., Palstra, A. P., Planas, J., MacKenzie, S., Begout, M. - L., Thorarensen, H., et al. (2020). Aerobic swimming in intensive finfish aquaculture: applications for production, mitigation and selection. Rev. Aquac., .
Résumé: We review knowledge on applications of sustained aerobic swimming as a tool to promote productivity and welfare of farmed fish species. There has been extensive interest in whether providing active species with a current to swim against can promote growth. The results are not conclusive but the studies have varied in species, life stage, swimming speed applied, feeding regime, stocking density and other factors. Therefore, much remains to be understood about mechanisms underlying findings of 'swimming-enhanced growth', in particular to demonstrate that swimming can improve feed conversion ratio and dietary protein retention under true aquaculture conditions. There has also been research into whether swimming can alleviate chronic stress, once again on a range of species and life stages. The evidence is mixed but swimming does improve recovery from acute stresses such as handling or confinement. Research into issues such as whether swimming can improve immune function and promote cognitive function is still at an early stage and should be encouraged. There is promising evidence that swimming can inhibit precocious sexual maturation in some species, so studies should be broadened to other species where precocious maturation is a problem. Swimming performance is a heritable trait and may prove a useful selection tool, especially if it is related to overall robustness. More research is required to better understand the advantages that swimming may provide to the fish farmer, in terms of production, mitigation and selection.
Mots-Clés: aerobic exercise; fatty-acid profile; gilthead sea bream; growth; growth-performance; juvenile atlantic salmon; maturation; oxygen-consumption; postprandial metabolic-response; rainbow-trout; salmon oncorhynchus-tshawytscha; selection; sexual-maturation; stress; sustained exercise; welfare
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