Potential effects of global climate change on survival and growth of brown trout (salmo trutta l.)consequences of temperature and floods on young stages

Résumé

Global Climate Change will increase precipitations in the temperate and Northern coast of Europe during winter and spring. In riverine ecosystems, precipitations affect strongly the discharge of running waters and, thus, it is predicted that streams will face more severe floods. Additionally, air and water temperature will increase all over the world. These new environmental conditions can alter the phenology of species and predator/prey interactions. Newborns of brown trout (Salmo trutta L.) start their exogenous feeding in March/April. This stage is a critical step as individuals undergo huge physiological and behavioral changes. To allow a good development and a high survival rate, preys have to be abundant, particularly during early ontogenesis when fish are most vulnerable to food scarcity and predation. In this thesis, experiments in controlled-environment were conducted to estimate the effect of water velocity on the drift of preferred prey taxa for salmonids and to understand the effect of temperature on the metabolism of alevins facing starvation. Experiments in semi-natural conditions were set up to better understand the effects of floods on invertebrate communities and on survival, behavior and growth of first-feeding alevins. Our data support that floods affect trout differently depending on when they start feeding (early or late spring) and the availability of prey in their environment.