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Alfonso, S., Sadoul, B., Cousin, X., & Begout, M. - L. (2020). Spatial distribution and activity patterns as welfare indicators in response to water quality changes in European sea bass, Dicentrarchus labrax. Appl. Anim. Behav. Sci., 226, Unsp-104974.
Résumé: In aquaculture, fish are exposed to unavoidable stressors that can be detrimental for their health and welfare. However, welfare in farmed fish can be difficult to assess, and, so far, no standardized test has been universally accepted as a welfare indicator. This work contributes to the establishment of behavioural welfare indicators in a marine teleost in response to different water quality acute stressors. Groups of ten fish were exposed to high Total Ammonia Nitrogen concentration (High TAN, 18 mg.L-1), Hyperoxia (200 % O-2 saturation), Hypoxia (20 % O-2 saturation), or control water quality (100% O-2 saturation and TAN < 2.5 mg.L-1) over 1 hour. Fish were then transferred in a novel environment for a group behaviour test under the same water quality conditions over 2 hours. Videos were recorded to assess thigmotaxis, activity and group cohesion. After this challenge, plasma cortisol concentration was measured in a subsample, while individual behavioural response was measured in the other fish using novel tank diving test. Prior to this study, the novel tank diving test was validated as a behavioural challenge indicative of anxiety state, by using nicotine as anxiolytic drug. Overall, all stress conditions induced a decrease in activity and thigmotaxis and changes in group cohesion while only fish exposed to Hypoxia and High TAN conditions displayed elevated plasma cortisol concentrations. In post-stress condition, activity was still affected but normal behaviour was recovered within the 25 minutes of the test duration. Our work suggests that the activity, thigmotaxis and group cohesion are good behavioural indicators of exposure to degraded water quality, and could be used as standardized measures to assess fish welfare.
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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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LI, X., PRZYBYLA, C., TRIPLET, S., LIU, Y., & BLANCHETON, J. - P. (2015). Long-term effects of moderate elevation of oxidation–reduction potential on European seabass (Dicentrarchus labrax) in recirculating aquaculture systems. Aquacultural Engineering, 64, 15–19.
Résumé: The long term effects of moderate elevation ORP (oxidation–reduction potential) around 300–320 mV on the growth, hematological parameters and the ability of European seabass (Dicentrarchus labrax) to react against bacterial infection was studied in recirculating aquaculture systems (RASs). Two RASs, one with a moderate ozonation (RAS-O3) and a control (RAS-C) were used in this experiment. After 60 days, seabass reared in the RAS-O3 were more able to react against a Vibrio anguillarum infection. It was in spite of the fact that seabass in the RAS-O3 showed decreased feed intake, feed conversion rate, growth rate and modified hematological parameters compared with the fish in RAS-C. It is obvious that an ORP level of 300–320 mV is too high for seabass to adapt in terms of the growth performance and the hematological parameters. However the increased ORP resulted in a better ability of the fish to react against bacterial infection. Our results strongly suggest that ORP for seabass in RAS should be elevated but not exceeding 300 mV and a slightly increased and well controlled ORP level (above 240–270 mV) has a positive effect on the disease resistance of fish. For the future, molecular methods could be utilized to identify which functional groups of microbe are contributing to the ORP effect and investigate how ORP influenced fish physiology in RASs.
Mots-Clés: Oxidation–reduction potential; Seawater; European seabass; Welfare; RASs
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McKenzie, D. J., Hoglund, E., Dupont-Prinet, A., Larsen, B. K., Skov, P. V., Pedersen, P. B., et al. (2012). Effects of stocking density and sustained aerobic exercise on growth, energetics and welfare of rainbow trout. Aquaculture, 338, 216–222.
Résumé: Two stocking densities, “low” (L, between similar to 19 and similar to 25 kg m(-3)) and “high” (H, between similar to 75 and similar to 100 kg m(-3)) were compared for effects on specific growth rate (SGR), feed conversion, energetics and welfare of rainbow trout reared at 14 degrees C either in static water (S) or swimming in a gentle current of similar to 0.9 bodylengths s(-1) (C). Trout (initial mass similar to 110 g) were reared for 9 weeks in circular tanks (volume 0.6 m(3)), in triplicate of four conditions (LS, LC, HS, HC). Fish were fed ad-libitum daily: waste pellets were swirl-collected at the outflow to calculate feed intake. SGR was measured each three weeks for the last six weeks of the trial. The tanks functioned as intermittent-stopped flow respirometers, to permit metabolic rate to be measured as instantaneous oxygen uptake once per hour. Mean (+/-SD) SGR was significantly lower at H than L (1.51 +/- 0.03 vs 1.44 +/- 0.04% day(-1), respectively, n = 6) and lowest in HC. When compared over a similar interval of mass gain, H groups had approximately 25% higher metabolic rates than L, with the highest rates in the HC condition. As a result, fish in the H groups dissipated a greater amount of feed energy as metabolism and, across all groups, there was a direct negative relationship between the quantity of energy dissipated and their SCR. There was no evidence of a neuroendocrine stress response, plasma cortisol was around 1 ng ml(-1) in all conditions. An acute crowding stress increased plasma cortisol to above 120 ng ml(-1) in all groups, but C groups recovered to control levels within 8 h whereas S groups required 20 h. Respirometry on individuals revealed that H fish had approximately 14% higher metabolic rates than L fish, indicating that increased metabolic rate in rearing tanks was in part physiological. The H groups had approximately 15% lower critical swimming speeds than the L groups which, together with their raised metabolic rate, indicated a physiological impairment Thus, high density reduced SGR by raising energy dissipation, at least partially as a physiological response by the fish, although there was no evidence of an endocrine stress response. The only beneficial effect of C was in recovery from acute stress. (C) 2012 Elsevier B.V. All rights reserved.
Mots-Clés: Aerobic scope; charr salvelinus-alpinus; Cortisol; Critical swimming speed; current issues; feeding-behavior; fish welfare; juvenile arctic charr; oncorhynchus-mykiss; respiratory physiology; respirometry; salmon salmo-salar; Stress; stress-response; swimming performance; Welfare indicator
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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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