Abstract:Pacific oyster Crassostrea gigas summer mortality frequently occurs in Sanggou Bay recent years，but the oyster appears low mortality rate in its neighboring region Ailian bay. In this study, two typical Pacific oyster culture areas of these bays have been selected as experimental sites. The environmental factors including water temperature, salinity,pH and DO, superoxide dismutase (SOD) activity and growth situation of oysters have been monitored, and the oyster summer mortalities of two sites have been researched. The reason of Pacific oyster summer mortality in Sanggou bay has been analyzed. The results show that: in experiment period (from May to October), the total mortality rate was 37% in Yatou marine culture region of Sanggou bay (E122.498，N37.151), the highest mortality rate that appeared on August 17 was 51%. The total mortality rate was 2.5% in Ailian bay (E122.582, N37.179), the highest mortality rate that appeared on September 28 was 4.5%. One way ANOVA results show that: the mortality rate has significant positive correlation with water temperature (R=0.804, P<0.01), negative correlation with the dissolved oxygen (R=-0.377, P<0.01), negative correlation with body weight, soft weight and gonad weight and so on (R=-0.690,-0.498,-0.358, respectively), positive correlation with superoxide dismutase activity (R=0.21,P<0.05).
