During fish larval development, numerous traits must evolve to answer various needs, among which behavioral and physiological traits. These changes are particularly important during the transition from endogenous to exogenous feeding. Concerning behavior, larvae have to disperse in the environment to search for a territory for hunting and this has for consequences modifications of group structure and inter-individual relationships. This dispersion is possible only if swimming skills are acquired and if larvae are able to digest prey, notably with appropriate intestine enzymes. Currently, in the context of global warming, we know that several life history traits will be modified: temperature has a direct and strong impact on ectotherms, and particularly fish, such as brown trout (Salmo trutta). This stenothermal fish species is particularly impacted by temperature, which has been described for both juveniles and adults. Nevertheless, we have almost no information on the effects of temperature on early life stages. In this study, we looked for a potential link between behavioral modifications and intestinal enzyme development in function of water temperature. We explored the influence of temperatures (4, 6, 10, 12°C) on behavior and physiological development at the onset of exogenous feeding. Three parameters were used to determine group structure: the nearest neighbor distance for dispersion, the interindividual distance mean for group cohesion and its variance for group homogeneity. The interindividual relationships between larvae were studied by counting the number and type of contacts between individuals. The physiological development of the digestive abilities was studied through the development of the intestinal enzymes, namely Alcaline Phosphatase (PAL) and Leucine Alanine (Leu-Ala). Indeed, during larval development, the intestinal maturation (i.e. switch from an endogenous to an exogenous feeding) PAL increased while the Leu-Ala decreased. Behavioral results showed that dispersion of larvae increased with temperature. The group structure was significantly more dispersive and more homogenous at 12°C than at 10 and at 4C°; larvae were more separated from each other. The PAL increased from endogenous to exogenous feeding without showing differences with temperature. These first results suggest that temperature did not modify in the same way the behavioral and physiological traits during the early life stages of brown trout.