Seasonal variations in biochemical composition and nutritional quality of Crassostrea hongkongensis, in relation to the gametogenic cycle.

Variations in the biochemical composition and nutritional quality with annual changes in gonad development were investigated to identify the optimal harvesting time of C. hongkongensis. The glycogen levels in the mantle, muscle, and gonad-visceral mass were significantly lower in June than in December, associated with changes in the expressions of ChGS and ChGP. Protein content consistently exceeded 52% of dry weight. The only significant change in protein levels was an increase between April and June in the gonad-visceral mass, which was associated with the gonadal transition from proliferation to maturation. Moreover, C. hongkongensis consistently had a well-balanced essential amino acid profile, meeting the essential amino acid requirements of preschool children. The lipid content and fatty acid composition of C. hongkongensis varied with the reproductive cycle, but the omega-3:omega-6 ratio was consistently higher than those of C. gigas and C. virginica. In summary, the optimal harvest time of C. hongkongensis was during the inactive stage of most gonads (from August to February at Beihai).