Presence of Bonamia and its relation to age, growth rates and gonadal development of the flat oyster, Ostrea edulis, in the Ría de Vigo, Galicia (NW Spain)

Oyster spat coming from the same spawn were divided into three length groups and cultured on an oyster raft for 9 months in order to determine the relation of Bonamia presence to age, growth rates, gonadal development and mortality. The results suggest that the presence of Bonamia is better related to the size than to the age of the oyster. The parasite was first detected in the fast growing group than in the slow growing one. Statistical analysis showed that Bonamia infection level and gonadal development stage were independent.