Reproductive Biology and Biochemical Composition of the Reared European Clam Ruditapes decussatus (Mollusca: Bivalvia) in Oualidia Lagoon, Morocco

The reproductive cycle of the European clam Ruditapes decussatus reared in suspended double-net trays in the Oualidia Lagoon was investigated from October 2017 to February 2019. This study aimed to characterize gonadal development through histological analysis, gonadal index assessment, and the biochemical composition of key macromolecules (proteins, lipids, and carbohydrates) over an annual cycle. The results revealed that R. decussatus undergoes a prolonged spawning period from April to December, with a peak in October when 100% of the population reached the maturation stage (stage IIIA). A sexual rest phase was observed between November 2017 and December 2017. An overall sex ratio of 1:0.8 was observed, indicating a slight female bias, with no significant deviations. Statistical analyses highlighted a correlation between the gonadal index and seawater temperature, suggesting that temperature plays a crucial role in regulating reproductive activity. Biochemical analyses showed that proteins were the predominant macromolecule in clam tissues, followed by lipids and carbohydrates. Seasonal variations in biochemical composition were observed; however, no direct correlation was found between biochemical compound levels and the gonadal index (p > 0.05). These findings provide valuable insights into the reproductive biology of R. decussatus under suspended aquaculture conditions, contributing to improved management and optimization of farming practices.