An investigation into the relative resistance of Irish flat oysters Ostreaedulis L. to the parasite Bonamia ostreae (Pichot et al., 1980)

The parasite Bonamia ostreae has caused significant mortalities in the flat oyster Ostrea edulis. To date, methods of control and eradication have pro ved largely unsuccessful. Research is now concentrating on development of a population of oysters that has increased resistance to bonamiasis. This st udy evaluated the relative resistance of three Irish strains of flat oyster s to this disease: two naive strains that had not previously been exposed t o the parasite, and one that has been exposed to B. ostreae since the 1980s and has been selectively bred from survivors. In both field and laboratory trials, oysters from the selected strain showed lower prevalence of infect ion, intensity of infection and mortalities compared to the two naive strai ns. Development of a strain showing some resistance to B. ostreae would all ow oysters to be grown to market size before significant mortalities occurr ed, and would also allow restocking of areas that have been decimated by th e disease. (C) 2001 Elsevier Science B.V. All rights reserved.