In order to investigate the effects of temperature on the growth performance, biochemical indexes and genes expression in juvenile hybrid sturgeon (Acipenser baerii♀ × Acipenser schrenckii♂), five temperature treatment groups (18 °C, 21 °C, 24 °C, 27 °C, 30 °C) were set in this study. After 25 days of domestication, the specific growth rate (SGR) and relative weight gain rate of juvenile sturgeon increased at first and then decreased with the increase in temperature in the range of 18–30 °C and reached the highest value at 21 °C. A quadratic equation was used to fit the regression equation of SGR and temperature (T). The result showed that the temperature of the maximum SGR is 23.45 °C. Moreover, the expression level of the growth hormone (gh) and the content of blood glucose (GLU) increased significantly at 21 °C, while the expression level of the growth hormone receptor (ghr) in the liver decreased significantly. When the temperature exceeded 27 °C, the thyroid hormone levels were significantly affected, and the levels of total antioxidants (T-AOC) and reduced glutathione (GSH) were significantly higher than those in the control group. In addition, with the increase in temperature, the expression levels of hsp70 and hsp90 in the liver increased significantly, while the expression level of the luteinizing hormone (lh) in the brain decreased significantly. To summarize, the effect of temperature on the growth and development of juvenile sturgeon mainly occurs through the effects of glucose metabolism, thyroid hormone level, total antioxidant capacity and growth-related genes. Therefore, in a temperature range between 21 and 24 °C, juvenile sturgeon can obtain the maximum growth rate and survival rate.

The purpose of this study was to investigate the periodic seasonal changes in endocrine activity and gonadal development of female rainbow trout (Oncorhynchus mykiss) in a high-altitude cold-water environment. The fish were sampled monthly from January to November and the levels of plasma hormones (estradiol (E₂), cortisol and thyroid hormones (TH_S)) and vitellogenin (VTG) were measured by ELISA. Moreover, the transcriptions of sex-related genes in the ovary, brain, and liver were detected by qRT-PCR. The results showed a seasonal fluctuation of plasma hormones and VTG together with the development of the ovary, which reached a peak from August to October. Similarly, the transcription of hypothalamic gonadotropin-releasing hormone-2 (cgnrh-2), hypothalamic gonadotropin-releasing hormone receptors (gnrhr) and follicle-stimulating hormone (fsh) in the brain varied from January to September, but the highest level was detected in September to November. In addition, the transcription of sex-related genes located in the ovary and liver increased significantly during August to October, accompanied by a continuous increase in the gonadosomatic index (GSI) and a decrease in the hepatosomatic index (HSI). Therefore, plasma hormones and sex-related genes regulate the development and maturation of O. mykiss oocytes with the change in seasons and peaked in November. The results of this study provide a reference for improving the efficiency of the artificial reproduction of O. mykiss.

Temperature is a critical factor influencing fish health and aquaculture success. This study investigates the physiological, histological, and microbiota responses of juvenile Schizothorax grahami to chronic thermal stress across six temperature treatments. We found that exposure to temperatures exceeding 27 °C resulted in complete mortality in juvenile S. grahami, with the upper thermal tolerance range between 24 °C and 27 °C. Chronic thermal stress caused a significant decline in serum glucose (Glu), triglycerides (TG), and total cholesterol (TC) at 24 °C, indicating rapid energy depletion, while reduced serum enzyme activity of catalase (CAT) and total superoxide dismutase (T-SOD) at 24 °C group further reflected a decrease in antioxidant capacity. Histological examination revealed adaptive intestinal villus hypertrophy with increased length and muscularis thickness at temperature under 24 °C. Furthermore, the relative abundance of Cetobacterium and Fusobacteriota suggested either adaptive responses or stress-related dysbiosis that may contribute to weakened host immune function. Overall, our findings highlight the vulnerability of juvenile S. grahami to rising temperatures, with moderate thermal stress inducing adaptive responses, while higher temperatures impair metabolism, gut integrity, microbial health, and may even lead to lethality. These results underscore the need for effective conservation strategies to protect this critically endangered species in the face of climate change.

1. The balitorid genus Hemimyzon (Teleostei: Balitoridae) currently comprises 18 valid species (Fricke et al. 2026), widely distributed in headwaters of major rivers in East and Southeast Asia. Spe...