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 (Perca schrenkii) for aquaculture in such environments. Through acute stress experiments, we determined its 96 h median lethal salinity (LC₅₀) to be 12.396 ppt, with a safe concentration of 3.72 ppt. Physiological analysis revealed a critical salinity threshold of 13 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 60-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 P. schrenkii 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.