Gametogenic cycle and biochemical composition of the clam Mactra chinensis (Mollusca: Bivalvia): Implications for aquaculture and wild stock management

Seasonal variations in the condition index and biochemical composition of the clam Mactra chinensis were studied from April 2008 to March 2009 on the eastern coast of China in relation to the reproductive cycle and environmental factors. Histological analysis indicated that the gametogenesis of M. chinensis comprised two phases: a resting phase (November-February) and gametogenesis, including ripeness and spawning, during the rest of the year. Gametogenesis began in March and was completed during June-July. Spawning occurred in August when water temperature was higher and food availability was high. A significant decrease in the glycogen content of all tissues in both males and females during sexual maturation suggests that carbohydrates play the most important role in reproduction of this species. Lipid biosynthesis during gametogenesis was associated with glycogen breakdown. The protein content in the female gonads showed a synchronous increase with the oocyte diameter and lipid content, suggesting that the female gonads could accumulate protein and lipid as vitellin. The RNA/DNA ratio is a valuable indicator of maturation both in males and females. The information obtained in this study provides a basis for fisheries resource administrators to design biologically sound management measures for this species, and is crucial for initiating its aquaculture.