(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:  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.  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.  Predictive ability for the effect of the environmental variables studied on ecologically relevant behaviour.