600 one-year-old black porgy (20.2±3.04 cm, 34.53±2.52 g) from Lüsigang Center of Jiangsu Marine Fisheries Research Institute were divided into 2 tanks (300 fish/tank), temporarily reared in 15°C circulating water for 2 weeks, fed twice daily (3% biomass) with water changed 1/2 daily, fasted 24h pre-experiment, and oxygenated (8-10 mg/L DO) throughout. One tank kept 15°C (Control Group, CG), the other cooled 3°C/day; at 3.8°C, fish with imbalance and no gill/fin movement were Cold-Sensitive Group (CS, n=30); at 2.8°C, 10% survivors were Cold-Tolerant Group (CT, n=30). At 15°C, 3.8°C, 2.8°C,fish were anesthetized with MS222 to collect liver tissues; 54 samples (6 biological replicates/group, 3 fish/tube)