Comparison of Growth of the Pacific Oysters, Crassostrea gigas, Cultured with Korean and Japanese Spats
Woo-Geon Jeong, Sang-Man Cho, Soo-Kyung Moon and Bo-Young Jeong
Department of Aquaculture Gyeongsang National University, Tongyoung 650-160, Korea
To study the growth of transplanted Pacific oysters, Crassostrea gigas, we sampled Korean and Japanese oysters attached in Chinhae Bay near Gaduk Island and in Seto inland sea in Japan, respectively, suspended in Pukman Bay. Water Temperature ranged from 11.2 to 27.8¡É (mean 19.84 ¡¾ 5.47¡É) on the surface, and 11.1 to 23. 6¡É(mean 18.31 ¡¾ 4.18¡É) on the bottom. Salinity ranged from 31.45 to 34.57 (mean 33.10 ¡¾ 1.16) on the surface, and from 31.69 to 34.35 (mean 33.24 ¡¾ 1.06) on the bottom. salinity was the lowest in September and October, and the highest in December. Growth of oysters in shell height showed a significant difference after being suspended at the farm, reaching 70.3 ¡¾ 12.5 mm in the Korean oysters and 96.2 ¡¾ 14.6 mm int the Japanese oysters in December. While the Korean oysters showed relatively low growth rate and cessation of growth after sudden growth between June and July, the Japanese oysters showed continuous growth during the whole farming period, although stepwise growth was observed. It was not until September that meat weight showed a significant difference between the two. After September, there was a sudden increase in the Japanese oysters, reaching 7.5 ¡¾ 2.9 g in December, but growth of the Korean oysters showed slow growth rate during whole farming period, reaching 4.6¡¾1.9 g in December. here was an obvious decrease in the meat weight of Japanese oysters in December, which might be attributed to restriction of food. Condition factors rebounded in October in the Korean oysters and in September in the Japanese oysters, respectively, attaining 12.8 in the Korean oysters and 15.3 in the Japanese oysters at the end of investigation on December. Shell length-height regression equations were as follows: Korean oysters: Sh=2.922St - 4.8024 (r2=0.8541) Japanese oysters: Sh=3.623St - 5.1239 (r2=0.7782) This showed the possibility of morphological transformation in the shell of the Korean oysters since shell height was longer than those reported by Bae et al. (1976) and Lee et al. (1992).
  
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