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With the gradual decrease in freshwater resources, the available space for freshwater aquaculture is diminishing. As a result, saline-alkaline water aquaculture has emerged as a crucial method to fulfill the increasing demand. This study investigates the impact of alkaline water on the growth performance, tissues (gill, liver, and kidney), digestive enzyme activity, and intestinal microbiology in grass carp (Ctenopharyngodon idella). The aquarium conditions were set with sodium bicarbonate (18 mmol/L (LAW), 32 mmol/L (HAW)) to simulate the alkaline water environment. A freshwater group was the control (FW). The experimental fish were cultured for 60 days. The findings revealed that NaHCO3 alkaline stress significantly reduced growth performance, caused alterations in the structural morphology of gill lamellae, liver, and kidney tissues, and led to decreased activity of intestinal trypsin and lipase amylase (P < 0.05). Analysis of 16S rRNA sequences demonstrated that alkalinity influenced the abundance of dominant bacterial phyla and genera. Proteobacteria showed a significant decrease under alkaline conditions, while Firmicutes exhibited a significant increase (P < 0.05). Furthermore, alkalinity conditions significantly reduced the abundance of bacteria involved in protein, amino acid, and carbohydrate metabolism, cell transport, cell decomposition, and environmental information processing. Conversely, the abundance of bacteria associated with lipid metabolism, energy metabolism, organic systems, and disease functional flora increased significantly under alkalinity conditions (P < 0.05). In conclusion, this comprehensive study indicates that alkalinity stress adversely affected the growth performance of juvenile grass carp, likely due to tissue damage, reduced activity of intestinal digestive enzymes, and alterations in intestinal microorganisms. [ABSTRACT FROM AUTHOR]

To research the relationship between meat quality and short‐term starvation in the blunt snout bream backcross variety [Megalobrama amblycephala♀ × (M. amblycephala♀ × Culter alburnus♂) ♂], we addressed the effect of fasting and re‐alimentation on essential nutrients and histology structure, flavour nucleotides in muscles, and analyzed the changes of taste profile in backcross variety by electronic tongue. Our data showed that the essential nutrients, equivalent umami concentration (EUC) and taste profile were found to slightly change in 5‐days fasting stage meat; meanwhile, the histology of the gut and liver has no significant change. However, the flavour composition was improved to enhance meat quality in comparison with control. When prolong starvation to 10‐days or 20‐days, the flavour components promoted continuously, and the crude fat levels were decreased, although the histologically injured intestine and liver are aggravated. Therefore, in addition to cross‐breeding to improve meat quality, short‐term starvation for 5 days without histological damage is also a way to improve meat quality in blunt snout bream backcross variety. [ABSTRACT FROM AUTHOR]