ABSTRACT
The Pacific oyster, Crassostrea gigas (Thunberg, 1793), also referred to as the Japanese oyster or giant oyster, is one of the most important species of bivalves cultured worldwide. The basic life history of the Pacific oyster is similar to that of the eastern oyster, C. virginica [1] with both functioning as protandrous hermaphrodites. The young are functionally male during their first spawning, while adults function as separate male or female animals in any given reproduction season [2]. Sexual maturity is reached during the first year, and spawning generally occurs in the summer months (June to August in the west coast of United States). Oysters are highly prolific, and males generally produce 5 x 1010 sperm per gram of gonad wet weight [3].
