Abstract
In the frame of this thesis, we first studied the establishment of personality in teleost, the consistency across context and different life stages as well as the associated physiological mechanisms. Personality appeared consistent across contexts over a short time period but it was no longer the case over a long period of time, especially between different life stages. Physiological mechanisms of stress regulation, as well as activity and neural plasticity, differed according to individual boldness. Then, we studied the physiological and behavioural responses of teleost fish chronically exposed to an environmentally relevant mixture of POP (PCBs and PBDEs), as well as those of their unexposed offspring. Different behavioural alterations in larval photomotor response, boldness and a behavioural syndrome linked to anxiety have been observed between generations up to the F2 or F4 generations. Alterations in the expression of enzymes responsible of DNA methylation were also observed suggesting that epigenetic mechanisms are involved in the transmission of these behavioural alterations in unexposed offspring. Behaviour was also studied under stressful water quality conditions in order to set behavioural welfare indicators. Results showed that individuals cope with these alterations in oxygen levels or NH3 concentration by decreasing their swimming activity and group cohesion. In addition, we observed that the normal thigmotaxis behaviour was inhibited during exposure to degraded water quality. It suggests a hierarchy of behavioural adaptations depending on stress severity. Finally, we studied the behavioural responses to a decrease in oxygen level according to personality: bold individuals decreased their activity and swimming cohesion with greater amplitude than shy individuals which decreased with higher amplitude thigmotaxis behaviour. These abilities to cope with stress, depending on the personality of teleost fish, bring new perspectives to face both ecological and aquaculture issues.