Survey on the Ovarian Parasite, Marteilioides chungmuensis in the Cultured Pacific Oyster, Crassostrea gigas in Korea

In Korea, oyster culture began in the early 1900’s. Commercial oyster culture using the hanging system started in the 1960’s, on the southern coast. After the 1960’s, production of cultured oysters has increased every year to the late 1980’s with the highest production recorded at 288,078 metric tons in 1987. This upward trend stagnated in the 1990’s and production dropped to 174,117 metric tons in 2001. Since 1990, the oyster culture industry in Korea has faced difficulties because of insufficient seed collection and mass mortality of cultured oysters. National Fisheries Research and Development Institute (NFRDI) presumed that increased contaminants from the land, and self contamination in the growing area together with a genetic weakening of the broodstock caused the decline. The ovarian parasite of the oyster has been inplicated as a cause of poor seed collection and mass mortality. In Korea, the ovarian parasite was reported in 1970 for the first time, and was assigned to the genus Acanthamoeba (see Chun, 1979). Based on the morphological characters, however, Comps et al. (1986) assigned it to a new genus and species and named it “Marteilioides chungmuensis”. The infection rate of M. chungmuensis in Korea has increased every year and the parasite now occurs not only in the spawning season (August) but throughout the year. The related authorities such as Ministry of Maritime Affairs & Fisheries (MOMAF) and provincial governments have performed “Farming Area Cleaning Project” in an attempt to improve coastal conditions. Also NFRDI recommended that the oyster industry culture triploid oysters free from parasitic infection. INTRODUCTION Korean production of Pacific oysters, Crassostrea gigas, has increased since 1960s when a hanging culture method was introduced, making the country competitive with the world’s leading countries in oyster production by early 1990s. Thereafter, the production entered into a stagnant status, positioning the country 3rd in global production following China and Japan. Oyster production contributed 26.5% of total Korean marine aquaculture production in 2001 and 5.2% of marine exports. The Korean government started to invest in oyster farming following the Fisherman Income Expansion Plan and a Nation Economy Development Plan in the early 1960s. Subsequently, the Oyster Hanging Culture Fisheries Cooperative of Korea was organized in 1965. Under the Shellfish Sanitation Agreement for Export between Korea and the USA, November 1972, some farming areas could be designated as blue belts by the FDA, USA. This Park, M.S. 2005. Survey on the ovarian parasite, Marteilioides chungmuensis in the cultured Pacific oyster, Crassostrea gigas in Korea. In P. Walker, R. Lester and M.G. Bondad-Reantaso (eds). Diseases in Asian Aquaculture V, pp. 311-320. Fish Health Section, Asian Fisheries Society, Manila. Diseases in Asian Aquaculture V