The escalating scarcity of freshwater resources necessitates the utilization of alternative saline waters for sustainable aquaculture. Perca schrenkii, an endemic fish from the Ili River basin, demonstrates considerable potential for cultivation in chloride-type saline–alkaline waters: its 96 h acute salinity tolerance is higher than that of freshwater populations of its congeneric Perca fluviatilis. This study systematically investigated the histomorphological responses of its key osmoregulatory and metabolic organs—gill, kidney, intestine, and liver—under acute (12–14 ppt for 96 h) and chronic (3–7 ppt for 60 days) salinity stress. Acute exposure induced dose- and time-dependent structural damage, including lamellar fusion in gills, glomerular reduction in kidneys, mucosal atrophy in intestines, and hepatocellular swelling. In contrast, chronic acclimation revealed active remodeling, such as lamellar shortening, renal tubular dilation, intestinal muscularis thickening, and biphasic hepatocyte adjustments. A hierarchical framework of structural adaptation was proposed, delineating Safe (≤3 ppt), Acclimation (5 ppt), Tolerance (7 ppt), and Lethal (≥13 ppt) zones. These findings elucidate the structural basis of salinity tolerance in Perca schrenkii and provide practical morphological indicators for assessing fish health in saline aquaculture.

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.

Triplophysa yarkandensis, a unique saline-alkali tolerant fish in the Tarim River Basin, exhibits unclear adaptive mechanisms of its digestive system to saline-alkali stressors. This study compared the histological characteristics of the digestive system in fish reared in saline-alkali water (salinity 5.89, alkalinity 125.60) and freshwater. Histological characteristics were analyzed using hematoxylin-eosin staining, and parameters were quantified via Image-Pro Plus software, with statistical comparisons performed using independent sample t-tests. Key findings included a 2.7-fold increase in oropharyngeal club cell density (48.50 ± 2.68 vs. 17.80 ± 2.04, p < 0.01) with denser stratified squamous epithelium in the saline-alkali group; a 74% increase in esophageal goblet cells (104.42 ± 6.67 vs. 59.94 ± 4.68, p < 0.01) alongside a 39% reduction in mucosal fold height; 87%, 24%, and 51% increases in villi number across the foregut, midgut, and hindgut, respectively, with an 84% elevation in midgut goblet cells (p < 0.01); and mild vacuolization in the hepatopancreas. Results indicate that T. yarkandensis adapts via synergistic strategies of enhanced digestive mucus secretion, epithelial structural optimization, and hepatopancreatic metabolic reprogramming. The coordinated villi proliferation and mucus secretion enhance nutrient absorption and osmotic barrier function, providing a theoretical basis for saline-alkali aquaculture.

Salinity, a critical environmental factor for fish survival, remains poorly understood in terms of how Triplophysa strauchii, a characteristic fish in Northwest China, physiologically responds to salinity stress. This study aimed to determine its salinity tolerance threshold and explore the associated physiological damage mechanisms. Six salinity gradients (11, 11.7, 12.5, 13.3, 14.3, 15.1 ppt) and a freshwater control group were established. Acute toxicity tests recorded mortality and behavior, while physiological–biochemical assays measured ion concentrations and enzyme activities in gills, kidneys, liver, intestines, and plasma over 96 h. The results showed a 96-hour median lethal concentration of 13.31 ppt and a safe concentration of 4.05 ppt. Gills and kidneys, as primary osmoregulatory organs, responded rapidly, whereas the liver and intestine lagged. Salinity ≤ 13.3 ppt allowed the fish to maintain homeostasis via physiological adjustments, but ≥14.3 ppt caused ion imbalance, immune function was significantly suppressed, and irreversible damage. These findings clarify the species’ salinity adaptation strategies, providing a basis for further research on chronic salinity stress.

Perca schrenkii populations are experiencing significant declines, yet comprehensive morphological studies are still lacking. Understanding the relationship between morphological traits and body weight is crucial for conservation and breeding programs. We analyzed 13 morphological traits in 100 P. schrenkii specimens from Hamsigou Reservoir using correlation analysis, path analysis, and principal component analysis (PCA). Body weight exhibited the highest variability (CV = 39.76%). Strong correlations were observed between body weight and body length (R = 0.942), total length, and body width. A four-variable regression model explained 94.1% of body weight variation, with body length showing the strongest direct effect (path coefficient = 0.623). The first three principal components accounted for 76.687% of the total variance. Our findings demonstrate that BL, BW, BD, and ES can effectively predict body weight, providing valuable insights for the conservation and selective breeding of P. schrenkii.

In this study, gut microorganisms of herbivorous grass carp, omnivorous carp, crucian carp, and aquatic microorganisms were collected from natural salt–alkali lakes and ponds in Xinjiang in winter to analyze their community structures. We sequenced 16S rRNA amplicons to investigate the composition and function of the microorganisms in the gut. PCoA analysis revealed that the gut microbiota of herbivorous and omnivorous fish formed two distinct clusters. Proteobacteria, Actinobacteria, Desulfobacterota, Firmicutes, and Chloroflexia are the dominant bacteria in the gut of fish. Proteobacteria, Bacteroidetes, Actinobacteria, Cyanobacteria, and Gram-negative bacteria are the dominant bacteria in the water. Carbohydrate- and protein-degrading bacteria, such as Desulfofustis, Lactiplantibacillus, and Vibrio, were predominant in omnivorous fish (CC and GRC), while cold-resistant bacteria, such as Shewanella and Psychromonas, were colonized in grass carp. This suggests that the same environment does not lead to similar gut bacteria, and that specific endogenous factors play a far more important role in shaping the microbiota composition than environmental factors.