| A review was given to summarize the development of studies on the disease of scallop Chlamys farreri and humoral immunology of molluscans, and the effect of environmental challenge on anti-disease activities of culture scallops and on virulence of pathogenic organisms. Then a series of studies were given to study the correlations between environmental factors, biologic factors, pathogen, and the mass mortality and anti-disease of the scallop C. farreri. The results were summarized as follows:Investigation was conducted to study the correlation between the annual growth, mass mortality of the cultured scallop, C. farreri and the annual changes of water temperature and the populations of total heterotrophic bacteria and Vibrios in Sanggou Bay. Every month from May 23rd, 2002 to April 22nd, 2003, samples were collected at the selected sites from Sanggou Bay, the main culture area of the scallop. The populations of total heterotrophic bacteria and Vibrios were investigated with the methods of MPN (Most probable Number) and VPC (Vibrio TCBS Plate Count), respectively. At the same time, the seawater temperature, scallop growth and mortality were also recorded. The results showed that the monthly average highest and lowest seawater temperatures appeared in August and February, which were 23.75 and 2.43 respectively. The daily average highest and lowest temperatures were 25.40癈 on September 2nd and 0.87癈 on January 29th. Variations in populations of the total heterotrophic bacteria and Vibrios in the seawater where scallops were cultured and in the tissue of scallop C. farreri had the same trends, which generally reflected the change of water temperature. The populations of the total heterotrophic bacteria and Vibrios in the seawater increased gradually from May and reached to their maximums at August 10th, 2002, being 1.50X 105cells/ml and 8.00 X104cfu/ml, respectively. For the tissue of scallop C.farreri, it was August 25th, 2002 that the populations of the total heterotrophic bacteria and Vibrios reached their maximums which were 3.15 X 106cells/ml and 1.94 X 106cfu/g, respectively. Then the populations decreased until March 23rd, 2003 for the total heterotrophic bacteria and April 22nd, 2003 for Vibrios. The minimums of the total heterotrophic bacteria were 3.30 X 102cells/ml and 2.25 X 104cfu/g in the seawater and in the tissue of scallop, respectively. When the seawater temperature was lower during the period from December to March, the Vibrios could be isolated from the tissue of scallop and the minimum was 4.00 X 102cfu/g, but not from the seawater. Generally, the populations of the total heterotrophic bacteria and Vibrios in the scallop C.farreri were higher than those in the seawater. The scallop grew faster in the periods from April to July and from September to December. There were significantly positive correlations between the seawater temperature and the populations of total heterotrophic bacteria and Vibrios in the seawater and in the tissue of scallop C.farreri, and the mortality of the scallop.In order to study the correlation between the mass mortality of the cultured scallop, C. farreri and the annual changes of water temperature and the acute virus necrobiotic disease virus in Sanggou Bay, an investigation was conducted. Every month from July 6th, 2003 to October 9th, 2003, samples were collected at the selected sites from Sanggou Bay, the main culture area of the scallop. After tissue homogenation, differential centrifugation and ultracentrifugation, the viral crude extraction was got and detected with negative staining electron microscopic technique and ELISA technique. The result of negative staining showed that the sphereovirus causing the mass mortality of scallop C. farreri, which had reported by Wang (2002), was found in all samples. But the infecting intensity was different in the six samples. The infecting intensity was at the same level in the samples of July 6th, August 4th, September 22nd and October 9th. The highest infecting intensity of virus was found in September 7th when the...
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