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Caractérisation de l'adaptation comportementale des téléostéens en élevage : plasticité et effets de la domestication

Abstract : The present work aims at a better understanding of the adaptation to farming conditions through a behavioural approach based on the comparison between wild vs. domesticated populations of three species: a marine species, sea bass (Dicentrarchus labrax), two freshwater species, arctic charr (Salvelinus alpinus) and brown trout (Salmo trutta). The thesis is divided into two parts which objectives were : 1) to test the impact of biotic and abiotic factors selected based on their importance in aquaculture on sea bass and artic charr behavioural plasticity (behavioural modifications in response to environmental changes). 2) to characterize the domestication effect on behaviour through the comparison between wild vs. domesticated sea bass and brown trout at different ages and under different experimental conditions (challenges, maze).In the first part, experiments performed on arctic charr showed that an artificial shelter induced a lower mobility, better growth performances and a higher level of survival during the endogenous feeding period, that egg size and social environment play an important role on feeding behaviour and mobility during the weeks following the first exogenous feeding period. These results illustrated behavioural flexibility in response to abiotic and biotic factors. The findings could be used to improve culture performances and welfare of arctic charr. The experiments performed on sea bass showed that a plant-based diet do neither modify the learning abilities under self-feeding conditions nor the cognition under a test situation in a maze, but has an impact on swimming activity (the mean velocity decreased and the total distance travelled decreased) and on the short-term release of cortisol (plasmatic concentration lower than the control group). Another experiment showed that, under self-feeding conditions, size grading and the resulting social environment have no major influence on feed-demand, feeding rhythm, food wastage, social structure, growth performances and physiological status. At last, a three-week fasting period does not modify the social structure and high-triggering fish are exactly the same individuals before and after the fasting period. Individual’s triggering activity levels could therefore be considered as personality traits but further research is needed to verify this hypothesis.In the second part of the thesis, the experiment performed on brown trout showed an impact of domestication on swimming activity before and after a light-elicited stress, using a biological material controlled by genotyping. Angular velocity was higher in wild fish while mean velocity and total distance travelled were higher in domesticated fish. All the experiments carried out on sea bass compared wild-caught fish (from the larval stage) to domesticated fish (industrial standard). The first one showed the interplay of age and ontogeny on swimming activity and escape response rate. These variables decreased in fish from both origins. The impact of domestication was shown through differences between wild-caught and domesticated larvae (angular velocity and vigilance level higher in wild fish). They showed that domestication has no influence on gregarism, and cognition in sea bass but there was a high individual variability. The ability to discriminate familiarity was shown only in domesticated fish. The behavioural approach developed in this thesis was demonstrated to be relevant to reveal plasticity in response to a few abiotic and biotic factors among the numerous ones that remain to be investigated. Plasticity plays an important role in the adaptation of fish to culture conditions. Domestication impact on behaviour was also demonstrated as well as the interplay of age and ontogeny. This thesis followed the path and brings new insights for research programs targeting fish selection based upon personality traits in order to improve adaptation for aquaculture or restocking purposes.
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David Benhaïm. Caractérisation de l'adaptation comportementale des téléostéens en élevage : plasticité et effets de la domestication. Sciences agricoles. Université de La Rochelle, 2011. Français. ⟨NNT : 2011LAROS341⟩. ⟨tel-00718400⟩

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