| The worms Polydora. damage the oysters, Crassostrea gigas, by foraging the shell, training the formation of galleries and chambers with mud. The IFREMER'S REMORA network which has in charge to survey the oysters Crassostrea gigas in France, has showed an increase of the infestation of oysters since 1993 (first year of the network). The study had for goal first to estimate the spatial and temporal variations of the infestation of the oysters in 1999, by using two methods: the infestation index, the number of worms by individual and a quality index, the Polydora Index (IP varies from 0 to 1) which is based on 5 classes of the oysters quality (from 0 to 4) in relation to the aspect of the valves |
