Date of Award


Document Type


Degree Name

Master of Science (M.S.)


Biological Sciences

First Advisor

Victor L. Loosanoff

First Committee Member

Edmund H. Smith

Second Committee Member

John S. Tucker

Third Committee Member

Walter Narchi


Two species of oviparous oysters, Crassostrea virginica (Gmelin, 1790), the Eastern oyster, and Crassostrea gigas (Thunbert, 1793), the Japanese oyster, were introduced into Tomales Bay, California, for commercial purposes. Because these oysters do not propagate in Tomales Bay, new shipments of adult oysters or oyster spat must be periodically sent from the east coast of the United States or from Japan. It is the purpose of this study to compare the seasonal gonadal changes which occur in the two species of adult oysters in Tomales Bay with one another, and to compare them with the seasonal gonadal changes which occur in the same species of oysters in other regions. The differences in gonadal changes will be related to variances in environmental conditions and to specific or racial characteristics.

The introduction of oysters into a new environment is valuable for both commercial and scientific reasons. Although it has long been known that C. virginica and C. gigas do not propagate in Tomales Bay, no one has ever done a detailed study of their reproductive cycle or the seasonal histological changes in their gonads. This study, therefore, extends the knowledge concerning an oyster's reaction and adaptation to its new environment.





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