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.

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.

Fish are vital for material cycling and energy flow in aquatic ecosystems. The genus Triplophysa, with over 100 known species, is significant in the Central Asian highlands’ freshwater ecosystems. T. strauchii and T. tenuis, as representatives, occupy distinct ecological niches and face challenges from climate change and human activities. There is a lack of research on Triplophysa fishes’ digestive systems, especially comparative studies, so this research aims to fill this gap. In September 2024, 40 samples of T. strauchii were collected from Sayram Lake and 40 samples of T. tenuis were collected from the Muzat River in Xinjiang. After acclimation, morphological observations (measuring fish and digestive tract parameters) and histological analyses (paraffin sectioning, HE staining, and microscopy) were carried out. The data were sorted in Excel and analyzed with an independent samples t-test in SPSS 27.0. Morphologically, T. strauchii has an obtuse snout, terminal mouth, specific upper lip papillae, and an S-shaped intestine about (1.45 ± 0.11) times its body length, while T. tenuis has an arc-shaped subterminal mouth, fringed papillae, and a spiral-shaped intestine around (0.82 ± 0.09) times its body length. Both possess a digestive tract, glands, and a hepatopancreas attached to the mesentery. Histologically, a large number of club cells were found in the oropharyngeal cavities of both species; their secretions have an adhesive effect on food, aiding food selection. Their digestive systems vary in structure and cell composition: the oropharyngeal cavity has three layers; the esophagus has four layers with more goblet cells in T. strauchii; the stomach has three regions without goblet cells and a thicker muscular layer in T. strauchii; the intestinal wall has four layers with different villi and goblet cell distributions; the hepatopancreas has lobules; and T. strauchii has a typical portal area. In conclusion, this study systematically compared the gastrointestinal systems of T. strauchii and T. tenuis for the first time, revealing significant structural differences related to their niches and feeding patterns as adaptations to specific environments. It fills the research gap, provides a basis for exploring fish ecological adaptation and environmental impacts on digestion, offers new ideas for Triplophysa protection strategies, and guides fish evolutionary biology research and Triplophysa resource protection and utilization.

Spotted stone loach (Triplophysa strauchii), a common fish species in Xinjiang, China, is ecologically pivotal within the local ecosystem; regrettably, human-induced factors like habitat destruction, pollution, and overfishing have gravely imperiled its survival, and compounding this is the dearth of research on the morphological disparities among its geographically diverse populations. Thus, between April and October 2024, 198 specimens were procured from Sayram Lake, Khamusigou Reservoir, and Chaiwopu Lake using cage traps and gillnets; post-collection, an array of morphological metrics were meticulously measured, and then statistical methods such as one-way analysis of variance (ANOVA), principal component analysis (PCA), stepwise discriminant analysis, and cluster analysis were employed for comprehensive data interrogation. Findings show that, across all sampled populations, the mean values of the total length (X1), body length (X2), body height (X3), and body width (X4) of the Chaiwopu Lake population are significantly lower than those of the Sayram Lake population and the Khamusigou Reservoir population; except for head length, the Khamusigou Reservoir population has lower variability in other morphological traits compared to the others. Moreover, significant divergences were detected in multiple trait ratios among the populations; PCA yielded five principal components, cumulatively accounting for 77.45% of the total variance, spotlighting the key ratios; discriminant analysis further validated highly significant morphological distinctions (p < 0.01), with the Khamusigou Reservoir population having the highest discriminant accuracy; cluster analysis graphically showed the Sayram Lake and Chaiwopu Lake populations clustering together while the Khamusigou Reservoir population formed a separate cluster; and the Chaiwopu Lake population had the most pronounced divergence in morphological traits. This research not only provides novel perspectives on the adaptive evolutionary mechanisms of T. strauchii but also serves as a cornerstone for formulating evidence-based conservation and management strategies for this species.