(a) To assemble and further develop an integrative methodology for in situ evaluation of the effects of turbidity and hypoxia on fish physiological and/or behavioural performance. (b) To determine experimentally the threshold values beyond which oxygen and turbidity levels are liable to alter fish physiological and/or behavioural performance. (c) To integrate the results obtained in a conceptual and predictive model. Main expected achievements: [1] establishment of a link between laboratory studies, studies in mesocosms and field studies, using the most advanced techniques for monitoring behaviour in various environmental conditions. [2] an understanding of the impact of water turbidity and oxygenation on three major components of the behavioural repertoire of fish: habitat selection, predator-prey interactions and schooling-aggregation. [3] Predictive ability for the effect of the environmental variables studied on ecologically relevant behaviour.