Bonamiasis in native flat oysters ( Ostrea edulis L.) from two intertidal beds of the Ortigueira estuary (Galicia, N.W. Spain) with different histories of oyster culture

Abstract

Suitability for intertidal oyster culture and effects of bonamiasis are considered in a comparison of two areas of the Ortigueira estuary. One of them, Fornelos, is traditionally used for intertidal culture of oysters and it is affected by Bonamia ostreae, whilst in the other, Macelos, oyster culture has never been carried out. Oysters from natural setting of each area were cultured in their respective locations. Bonamiasis was first detected in Fornelos during the 4th month from the beginning of the experiment, when oysters were 15 months old, and caused severe mortalities before oysters could reach the minimum marketable size. At Macelos, the first cases of infection appeared only after 11 months, and this fact allowed oysters to reach marketable size before the occurrence of mass mortalities. Either proximity to Fornelos or the occasional presence of infected oysters at Macelos could be the reason for transmission of bonamiasis to oysters from Macelos. Oysters are susceptible to infection before they are 15 months old. This susceptibility does not depend on the size of oysters of the same age. Infection negatively affects growth and condition of the oysters.