Climate change (CC), affecting the survivorship and behavior of bivalves, is progressively posing serious threats to aquaculture. The European clam Ruditapes decussatus (L., 1758) is among the most commercially important bivalve species in the aquaculture market. Rising temperatures caused by CC can induce physiological responses and, above certain thresholds, mass mortality events. In this study, we investigated the thermal tolerance of R. decussatus in the laboratory conditions, assessing the species’ metabolic response (respiration rate, RR) to a wide range of temperatures (8-38 °C). Then, using these responses we obtained the best Thermal Performance Curve (TPC), by comparing 24 models. The best fitting Deutsch model was finally used to create seasonal Thermal Habitat Suitability (THS) maps under both current (2017-2022) and future (RCP 4.5 and RCP 8.5, 2050) temperature scenarios in a Sardinian coastal lagoon. RRs increased from 0.07±0.04 mgO₂ h⁻¹ gWW⁻¹ (at 8°C) to 1.55±0.40 mgO₂ h⁻¹ gWW⁻¹ (at 26°C), then started to drop at 30°C (to 0.54±0.33 mgO₂ h⁻¹ gWW⁻¹) and was nihil at 38°C (death of all specimens). We report here that R. decussatus shows an optimum thermal point (T_opt) at ca. 26.71 °C and a critical thermal maximum (CT_max) at 38 °C. An increase (up to 60%) in the extension of R. decussatus occurrence probability was observed in both RCP 4.5 and RCP 8.5 IPCC future temperature scenarios, possibly anticipating a better thermal environment for the performance of this species in otherwise less favorable seasons. On the other hand, a slightly worst environment would appear in summer (ca -1.5% of favorable thermal habitat). These findings highlight the urgent need for adaptive aquaculture strategies to optimize clam farming under future climate conditions.

This work has been developed within the framework of the project e.INS www.einsardinia.eu (Next Generation EU- PNRR - M4 C2 I1.5 CUP F53C22000430001.