STUDY ON THE ANNUAL VARIATION OF THE OVARY OF SILVER CARP IN THE LAKE IN HEILONGJIANG PROVINCE

In view of the cold weather in Heilongjiang Province silver carp has specificity inits gonadal maturation cycle. The matured female silver carps sometimes have no op-portunities to spawn in the year, their oocytes do not show any degeneration UntilSeptember when the average temperature is about 13℃. Because of the low temperaturebeginning from autumn, only 6--11% of oocytes will be proceed to degeneration andabsorption, and most of the degenerated eggs of adult fish remain in the stage ofquiescence during the winter. Until the May of next year the water temperature raiseto 17--19℃ many degenerated eggs begin to be absorbed. Both the absorption of thedegerated eggs and the development of the new eggs occur at the same time. At thebeginning of June there isn't any trace of the degenerated eggs but the new oocyteshave developed to the mid of stage IV.