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

## TL;DR

This study explores how Ili perch can survive and adapt to saline water, providing guidelines for sustainable aquaculture in saline-alkaline environments.

## Contribution

The study identifies specific salinity thresholds and physiological adaptation mechanisms of Ili perch in chloride-type saline water.

## Key findings

- The 96 h median lethal salinity (LC50) of Ili perch is 12.396 ppt.
- Ili perch can fully adapt to long-term culture in salinities up to 7 ppt.
- Salinities above 13 ppt cause osmoregulatory collapse and immune suppression in Ili perch.

## Abstract

Global freshwater scarcity has pushed the exploration of saline-alkaline aquaculture, especially in Northwest China where chloride-type saline-alkaline water is abundant but underused. Perca schrenkii (Ili perch), an endemic fish in the Ili River basin, shows promise for such aquaculture, yet its salinity tolerance and adaptation ability remain unclear. This study involved two experiments: an acute high-salinity test (11–15 ppt, 96 h) and a chronic low-salinity acclimation test (3–7 ppt, 60 days). We found the 96 h median lethal salinity (LC50) of P. schrenkii was 12.396 ppt, and it could fully adapt to long-term culture in ≤7 ppt salinity—with 3 ppt causing almost no stress. These results provide clear salinity guidelines for the safe and sustainable cultivation of P. schrenkii in saline waters.

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.