Reproductive Dynamics of the Razor Clam <em>Solen marginatus </em>Pulteney, 1799 (Bivalvia: Solenidae) in Ria Formosa Lagoon (Southern Portugal)

The present study describes the reproductive cycle of the razor clam (Solen marginatus) from the Ria Formosa lagoon in the Algarve region (southern Portugal), using histological preparations of gonads from samples collected monthly over 18-month period, more precisely from January 2023 to June 2024. Simultaneously, the mean gonadal index (GI) was estimated and its relationship with fluctuations in seawater temperature and chlorophyll concentration was examined. The reproductive cycle of S. marginatus showed a seasonal pattern, with a resting period between August and October, followed by the onset of gametogenesis in November, which lasted until March. Ripe individuals were observed between February – March and May, with the spawning period occurring primarily between May and July. The mean GI reflected the temporal variation of the gonadal cycle, and it was observed that reproduction in this species is strongly influenced by fluctuations in seawater temperature, but is not significantly correlated with chlorophyll concentration. The information gathered in this study is of utmost importance, as it enables the proposal of evidence-based management measures, aimed at promoting the sustainable exploitation of this resource. According to these new findings, a closed season prohibiting the razor clam harvesting in Ria Formosa lagoon between May and July is proposed.