Adaptability assessment of intermuscular bone-free crucian carp (Carassius auratus) to carbonate alkalinity: Insights into morphological, biochemical, and histological parameters

Exploring the adaptation of fish to carbonate alkalinity facilitates the optimization of resource utilization in saline-alkali waters. The potential of intermuscular bone-free crucian carp ( Carassius auratus ) to be cultured in saline-alkali water remains to be fully explored. In the present study, the adaptability of intermuscular bone-free crucian carp to 0, 15, 30, 45 and 60 mmol/L carbonate alkalinity was evaluated by assessing morphological indexes, antioxidant capacities, digestive enzyme activities and immune-related enzyme activities. Our results showed that there were no significant differences ( P > 0.05) in the morphological indicators and whole-fish proximate composition, except for a significant increase in the crude ash content ( P < 0.05). The activities of hepatic total antioxidant capacity and superoxide dismutase at 30 mmol/L carbonate alkalinity were significantly elevated, accompanied by a significant decrease in the malondialdehyde content ( P < 0.05). Additionally, the activities of lipase, amylase and trypsin were not significantly different from those of the control group at 30 mmol/L carbonate alkalinity ( P > 0.05). Carbonate alkalinity significantly reduced the hepatic alanine aminotransferase and alkaline phosphatase levels ( P < 0.05), whereas no significant differences were observed in the aspartate aminotransferase and acid phosphatase levels ( P > 0.05). Notable damage to the gill lamellae and filaments was observed at 45 and 60 mmol/L carbonate alkalinity, accompanied by significant reductions in lamellar thickness, height, and basal length. In summary, our results confirmed the intermuscular bone-free crucian carp were adaptable under conditions of 30 mmol/L carbonate alkalinity, which is conducive to the sustainable development of the aquaculture industry. ● Intermuscular bone-free crucian carp shows adaptability at 30 mmol/L carbonate alkalinity. ● Proximate analysis reveals increased crude ash content under carbonate alkalinity. ● Biochemical responses indicate enhanced antioxidant activity to mitigate stress. ● High carbonate alkalinity damaged the gill of intermuscular bone-free crucian carp.