Etude des différents facteurs de mortalité des huîtres en baie de Quiberon

This training report (Intechmer-Ifremer) describes the first results of the program "Risco", on the causes of oysters mortalities in the bay of Quiberon (56, France). 3 parts of the 2010 research are presented : (1) the sonar campain with the ship "Haliotis", for identifying the nature of the bottom and benthic fauna, (2) the video campain, which allowed to precise the spatial distribution of oysters and crepidulas densities, (3) the experiment conducted in 15 stations of the bay, so as to evaluate the influence of sediment and predators on oysters mortalities (1 year and 2 years old oysters). The first results are presented on the predation exerted on oysters by starfish and oyster drills.