The authors studies the reproductive cycle and biochemical composition of the Pacific oyster Crassostrea gigas in relation to environmental factors (water temperature, salinity, chlorophyll a concentration) in the culture areas of the Rushan Bay from March 2004 to February 2005 in order to investigate its reproductive strategy. The results show that the water temperature exhibited a profound seasonal change with the highest value in summer (August, 29.5℃) and the lowest value in winter (January, 1.8℃), and the salinity had a small drop during rainfall periods in summer. The concentration of chlorophyll a exhibited a clear seasonal pattern characterized by two unequally sized peaks: a small one in April 2004 (17.7μg·L-1), and a large one in September 2004 (25.8μg·L-1). During winter, chlorophyll a concentration was low. Gonadal development of C. Gigas began in March and spawning took place during July to September. In winter, the gonad of C. Gigas entered the undif-ferentiated phase. The condition index decreased gradually during spawning, showing that C. Gigas grew up slowly during gametogenesis. The protein and lipid content increased gradually while the glycogen content decreased sharply during game-togenesis, suggesting that glycogen played an important role in the reproductive cycle of C. Gigas. An increase in the RNA/DNA ratio was found during gametogenesis, illustrating that RNA/DNA ratio was a valid indicator of sexual maturationin C. Gigas. Significant decrease in ash content was observed during spawning, indicating that substrates stored in various tissues were catabolized to supply energy during gametogenesis. The results demonstrate that C. Gigas may be considered as a conservative species in gametogenic pattern.%为了阐明长牡蛎的繁殖策略,自2004年3月-2005年2月对乳山湾养殖海区的环境因子(水温、盐度、叶绿素a含量)、长牡蛎繁殖周期及其生化成分(糖原、脂肪、蛋白质、RNA/DNA比值)的季节变化进行研究.结果显示,水温在一年中呈现显著变化,夏季水温最高,最高值为29.5℃(8月),冬季水温最低,最低值为1.8℃(1月)；盐度在夏季雨水较多的时候略有降低；叶绿素a含量在夏末秋初(8月和9月)和春季(4月)有2个峰值,冬季最低.长牡蛎的繁殖周期分为冬季的休止期和从春季到夏季的繁殖期,在长牡蛎的繁殖期,条件指数逐渐下降到最低值,表明繁殖期长牡蛎生长变慢.在长牡蛎的配子发生过程中软体部蛋白质和脂肪含量略有上升,而糖原含量显著下降,表明长牡蛎配子的发生需要储存的糖原提供能量；RNA/DNA比值在配子发生过程中逐渐升高,显示RNA/DNA比值可以作为一个指标来指示长牡蛎的性成熟.配子发生过程中,长牡蛎的灰分含量逐渐升高,表明长牡蛎通过分解自身的贮能物质提供能量,使体内有机物含量减少,从而导致灰分含量上升.实验结果表明长牡蛎的配子发生类型为保守种.
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