Physiological Thresholds and Adaptation Mechanisms of the Ili Perch (Perca schrenkii) to Chloride-Type Saline Water

Global freshwater scarcity necessitates the exploitation of alternative water resources for aquaculture. Chloride-type saline-alkaline water, characterized by high salinity but moderate pH, is widely distributed in arid regions worldwide and represents a vast, underutilized resource. This study comprehensively evaluated the potential of the endemic Ili perch (<i>Perca schrenkii</i>) for aquaculture in such environments. Through acute stress experiments, we determined its <b>96</b> h median lethal salinity (LC₅₀) to be <b>12.396</b> ppt, with a safe concentration of <b>3.72</b> ppt. Physiological analysis revealed a critical salinity threshold of <b>13</b> ppt, beyond which osmoregulatory collapse (indicated by plasma Na⁺/K⁺ dysregulation and Na⁺-K⁺-ATPase suppression), oxidative damage (elevated malondialdehyde), and immune suppression occurred. In contrast, chronic <b>60</b>-day exposure to salinities up to 7 ppt demonstrated successful long-term acclimation. Acclimated fish re-established ion homeostasis, as plasma ion levels normalized, and exhibited sustained antioxidant enzyme (SOD, CAT) and immune parameter (AKP, ACP, IgM) activities without signs of damage. Our findings establish <i>P. schrenkii</i> as a highly promising species for chloride-type saline-alkaline aquaculture. The study provides a physiological framework for its adaptation and offers evidence-based salinity guidelines for its sustainable cultivation, thereby contributing to the expansion of aquaculture into non-traditional water resources.