Gametogenic Development of a Grooved Carpet Shell Clam (Ruditapes decussatus, Linnaeus, 1758) Population in the Baldaio Lagoon (N.W. Spain) Amidst Climate Change

The impact of climate change on marine bivalves, particularly on their reproductive processes, is a current issue of concern. The aim of this study was to investigate how seawater temperatures influenced the gonadal development and overall condition of the grooved carpet shell clam (Ruditapes decussatus, Linnaeus, 1758) population in the Baldaio lagoon (N.W. Spain) over the last 20 years. Adult clams were collected, and biometric, histological, and biochemical analyses were performed. Gonadal development phases were assessed, several condition indices were calculated, water temperatures were recorded, and statistical analyses were carried out. Results indicated variations in reproductive timing, including changes in gonadal maturation, an earlier spawning period, and prolonged maturation phases, which contrasted with previous reproductive patterns described for this species. These findings coincided with thermal changes in the lagoon, where mean minimum temperatures increased and maximum temperatures decreased, and the annual thermal range was reduced in comparison with historical data (1998–1999). Biochemical composition and condition indices also reflected variations linked to temperature fluctuations, suggesting that warmer water temperatures may alter energy storage and reproduction. This highlights the importance of continuous environmental monitoring to better understand the effects of climate change on clam populations and to improve management strategies that could help to restore natural R. decussatus populations.