Effets des fortes températures et de l'hypoxie sévère chez les jeunes stades de l'esturgeon européen (Acipenser sturio, L. 1758)

International audienceMean surface temperature, severity and frequency of hypoxic events are increasing worldwide. For fish species there is a temperature and oxygen optimal range allowing the animal to survive and growth. When environment conditions move away from this optimum, individual capacity decrease. Historically present in most large European catchments, European sturgeon population decreased until being represented by a single wild population in the Gironde-Garonne-Dordogne catchment. European sturgeon early life stages tolerance to temperature and oxygen concentration is unknown. The goal of this study is to evaluate sturgeon embryo's tolerance range to temperature and dissolved oxygen by recording effects on survival and development. Three oxygen conditions crossed to three temperatures have been tested (20°C; 26°C; 30°C; 90%; 50%; 30% oxygen saturation). Embryos have been exposed to the different temperature conditions from fertilization to exogenous feeding in parallel to a 48h oxygen challenge. Embryonic survival rate decreased with increasing temperature. At 20°C and 26°C embryonic survival rate is not impacted by oxygen concentration. But at 30°C, hypoxia seems to negatively impact embryonic survival rate. No hatching occurred when embryos have been exposed to hypoxia. In normoxia, no hatching occurred at 30°C and hatching rate was significantly higher at 20°C than at 26°C