###### Abstract  
Climate change poses risks to bivalves; thus, searching for resilient alternative species is crucial for sustainable fisheries. This study examines the impact of reduced pH and elevated temperature and their combined effects on the queen scallop _Aequipecten opercularis_ in captivity. The results indicated that a low pH reduced its growth rates in both weight (0.03 \(\pm\) 0.05 g/day) and length (0.06 \(\pm\) 0.16 mm/day), as well as leading to decreases in meat yield (20.75 \(\pm\) 2.75%) and the condition index (44.21 \(\pm\) 7.19%). Conversely, elevated temperature resulted in an increased growth in length (0.07 \(\pm\) 0.23 g/day), meat yield (21.57 \(\pm\) 4.82%), and condition index (45.42 \(\pm\) 7.35%). Combined stressors initially promoted growth but ultimately produced unsustainable outcomes, resulting in a reduced meat yield (18.28 \(\pm\) 2.60%) and condition index (38.92 \(\pm\) 8.23%), along with a peak mortality rate of 27%. These findings indicate that while A. opercularis can withstand individual stressors, exposure to simultaneous stressors may compromise its long-term viability in aquaculture systems. bivalve physiology; climate change; growth rates; queen scallop Article Ocean Acidification and Sea Temperature Rise Affect the Queen Scallop _Aequipecten opercularis_ ([PERSON], 1758) in Captivity. _Aequipecten opercularis_ ([PERSON], 1758) in Captivity. _Aepep1_ (A.P. );  
1 Faculty of Natural Sciences, Juraj Dobrila University of Pula, Zagrebaka 30, 52100 Pula, Croatia;  
1 [EMAIL_ADDRESS] (LK); [EMAIL_ADDRESS] (N.I. ); [EMAIL_ADDRESS] (A.P. );  
[EMAIL_ADDRESS] (V.K. ); [EMAIL_ADDRESS] (A.Z. ); [EMAIL_ADDRESS] (M.S.) 1 Faculty of Natural Sciences, Juraj Dobrila University of Pula, Zagrebaka 30, 52100 Pula, Croatia;  
1 [EMAIL_ADDRESS] (LK); [EMAIL_ADDRESS] (N.I. ); [EMAIL_ADDRESS] (A.P. );  
[EMAIL_ADDRESS] (V.K. ); [EMAIL_ADDRESS] (A.Z. ); [EMAIL_ADDRESS] (M.S.) Footnote 13: email: jadranexpected to remain crucial even under projected climate change conditions [10,11]. By integrating the sclerochronological approach through detailed shell measurements with climatological data from advanced climate model projections, [PERSON] et al. [12] showed a robust strategy for forecasting future trends in _A. opercaluris_ growth. Ocean acidification and sea warming are major climate change drivers that significantly affect shellfish physiology and the quality of seafood [13, 14, 15, 16, 17, 18, 19]. Ocean acidification, caused by increased CO\({}_{2}\) absorption, lowers the pH of seawater [20], affecting the ability of shellfish to form and maintain their calcium carbonate shells [21, 22, 23]. This results in weaker shells and higher mortality rates, particularly in the larval and juvenile stages [15]. Sea surface warming causes an increase in the temperatures throughout the water column, altering the metabolic rates and stress levels in shellfish, which can further lead to reduced growth rates and compromised immune systems, thus altering the growing period [12, 16, 17, 18, 19, 21, 22, 23, 24, 25, 26]. These factors (lower pH and higher T) can cause physiological stress, making shellfish more susceptible to diseases and reducing their overall health and market quality [26]. The condition index and meat yield in bivalves are crucial economic indices affected by environmental changes [10, 11, 27, 28, 29]. Studies have shown that shellfish exposed to acidified and warmer waters often have a reduced meat content due to these combined stressors affecting their energy allocation [15]. This can lead to smaller, less nutritious shellfish, negatively impacting market value and consumer satisfaction [23, 30]. Changes in shellfish physiology due to acidification and warming also affect the nutritional content of seafood, potentially reducing levels of essential nutrients such as omega-3 fatty acids [23, 31, 32]. Moreover, these environmental stressors can change shellfish behavior and reproduction [33, 34, 35, 36, 37], further impacting population dynamics and availability [26].