Bonamiosis in natural stocks of Ostrea puelchana and O. stentina in San Matías Gulf (Patagonia, Argentina).

KROECK, MARINA A.; MORSAN, ENRIQUE M.; OEHRENS-KISSNER, ERICA M; DOLDAN, MARÍA DEL S.; ZAIDMAN, PAULA C.; CALVO, MANUELA

Lelystad

Workshop; 5th Microcell Working Group meeting; 2012

Central Veterinary Institute, Lelystad, the Netherlands

Oysters are one of the best known groups of molluscs and one the highest importance in commercial aquaculture. However, flat oysters have almost disappeared from the shellfish market due to high mortalities produced by parasites of the genus Bonamia that severely affected oyster farms around the world. In Argentina, experimental marine aquaculture began with flat oysters of the native specie Ostrea puelchana. The first commercial cultures began in 1995 and in 1996 an abnormal mortality was reported in San Antonio Bay (San Matías Gulf, North Patagonia, Argentina) and Bonamia sp. was identified as a possible aetiological agent. The presence of this pathogen was the first record for this genus in the SW Atlantic Ocean and it is the only know OIE Notifiable Disease of aquatic organisms known in Argentina.. The prevalence of infection by Bonamia sp. in 1996–2001 period clearly defined the culture area inside San Antonio Bay as the focus of infection from which the parasite spread.Infection radiated from this focus through the oysters beds located at the SW and NE of the bay. Another specie of oyster without commercial value, Ostrea stentina cohabits with Ostrea puelchana in shallow waters of the San Matías Gulf. The density of the populations of this species in some beds of the gulf has dramatically decreased in the last decade. Recent histopathological studies revealed the presence of a Bonamia-like pathogen similar to that affects O. puelchana.In this presentation we: i) review the presence/abundance records of O. puelchana in San Matías Gulf and chronicle the changes across decades; ii) decribe the taxonomic, pathogenic and epidemiological information concerning the local specie of Bonamia obtained until 2006, and iii)update of result obtained during an ongoing project. This project is intended to evaluate the relation between the parasite infection and sexuality,individual size, demographic composition and spatial distribution in the populations of O. puelchana and O. stentina. This study will enable the elaboration of a diagnosis on the potential of flat oyster farming in different areas of the San Matías Gulf.