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.

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.

This study evaluated the effects of feeding juvenile southern catfish (Silurus meridionalis) with one of six isonitrogenous and isoenergetic diets where fish meal (FM) was replaced by black soldier fly larval meal (BSFLM) at 0%, 10%, 20%, 30%, 40%, and 50% levels on growth, muscle quality, antioxidant capacity, immune response, and gut microbiota of juvenile southern catfish (Silurus meridionalis). A total of 1620 fish (9.20 ± 0.15 g) were fed one of six experimental diets for 8 weeks. Results demonstrated that a 50% replacement (H50 group) significantly improved weight gain rate, specific growth rate, and protein efficiency ratio (p < 0.001). Antioxidant capacity (T-AOC) was enhanced in groups H30 and H50, while immune markers lysozyme (LZM) and alkaline phosphatase (AKP) showed mixed responses. Muscle texture properties such as chewiness and adhesiveness were significantly altered across treatments. Gut villi remained structurally intact in all groups, and liver histology appeared normal. No significant differences were found in muscle amino acid or fatty acid profiles. Gut microbiota analysis revealed shifts in microbial composition, with increased abundance of Clostridia and Escherichia and functional enrichment in metabolic pathways at higher substitution levels. Interspecies network analysis indicated potential cooperation among beneficial microbes through metabolite exchange. It is concluded that 50% BSFLM substitution optimizes growth performance, muscle quality, and antioxidant capacity, while modulating gut microbiota, indicating its promise as a sustainable FM alternative and functional ingredient in aquafeeds.