Eugenol is a widely used fishery anesthetic. This study investigated the effects of various concentrations of eugenol on blood physiological and biochemical indexes, and muscle flavor, in crucian carp (Carassius auratus). To determine the appropriate concentration of eugenol anesthetic for use in crucian carp transportation and production operations, we evaluated seven anesthesia groups of 20, 30, 40, 50, 60, 70, and 80 mg/L and one control group (without eugenol) to determine the effects on blood physiological and biochemical indexes, and muscle flavor. The red blood cells and platelets of crucian carp decreased significantly (p < 0.05) with eugenol treatment. With increasing eugenol concentration, the white blood cells and hemoglobin did not change significantly, whereas lactate dehydrogenase, alkaline phosphatase, alanine aminotransferase, and aspartate aminotransferase increased significantly (p < 0.05). The content of phosphorus, magnesium, and sodium increased after anesthesia, whereas the content of potassium decreased with increasing eugenol concentration. After anesthesia, the content of albumin and total protein in the serum decreased with increasing eugenol concentration (p < 0.05); triglyceride first increased and subsequently decreased (p < 0.05); blood glucose content first increased and then decreased (p < 0.05); and no significant difference was observed in total cholesterol content (p > 0.05). No significant difference was observed in muscle glycogen and liver glycogen content after eugenol anesthesia (p > 0.05). The eugenol-based anesthesia test did not indicate major liver histomorphological effects, but the very small number of gill sheet edema cases observed requires further study. Analysis of electronic nose data indicated that eugenol treatment affected the flavor of the fish. The anesthesia concentration of 20–80 mg/L had some effect on the physiology and biochemistry of crucian carp, thus providing a reference for the application of eugenol in crucian carp transportation and experimental research.

The purpose of this study was to investigate the effects of vitamin E addition to the water column on immune response, antioxidant capacity, and liver tissue structure of crucian carp (Carassius auratus) under acute cold stress. Crucian carp was placed in the aqueous solution of control group (E1), negative control group (E2), and 100 mg/L vitamin E (E3) and cooled from 20 to 5°C by cold acclimation intelligent cooling device. Samples were taken at three temperature points of 20, 10, and 5°C, respectively, and the samples were detected and analyzed. The results showed that the content of each index increased under acute cold stress. The contents of white blood cell, red blood cell, hemoglobin, platelet, lysozyme, and glutathione peroxidase in E3 treatment group were significantly lower than those in E1 and E2 treatment groups ( ). The contents of cholinesterase, alkaline phosphatase, acid phosphatase, hydrogen peroxide, superoxide anion, superoxide dismutase, peroxidase, and malondialdehyde in E3 treatment group were significantly lower than those in E1 and E2 treatment groups ( ). Under acute cold stress, the liver tissue structure of crucian carp also changed, such as hepatocyte vacuolization, and the damage degree of E3 treatment group was lower than that of E1 and E2 treatment groups. In summary, the addition of vitamin E in water to treat crucian carp can reduce the harm caused by acute cold stress to its body and provide a theoretical reference for the application of vitamin E in water to alleviate fish stress.

The aim of this work is to examine the effects of vitamin E addition to water on the structure of the gill tissue and energy metabolism of crucian carp (Carassius auratus) under cooling stress. The crucian carp were chilled using a cold acclimation intelligent chilling equipment from 20 °C to 5 °C. They were divided into three groups: the control group (E1), the negative control group (E2), and the 100 mg/L vitamin E (E3) solution. Three different temperature points (20 °C, 10 °C, and 5 °C) were used to collect, test, and analyze the samples. The findings demonstrated that in the E3 treatment group, phosphoenolpyruvate carboxykinase, acetyl coenzyme A carboxylase, total cholesterol, urea nitrogen, triglyceride, and fatty acid synthase contents were significantly lower under cooling stress than those in the E1 and E2 treatment groups (P < 0.05). The E3 therapy group had significantly greater blood glucose, glycogen, and glycogen synthase levels than the E1 and E2 treatment groups (P < 0.05). The levels of pyruvate kinase in the E1, E2, and E3 treatment groups did not differ significantly. Crucian carp's gill tissue changed under cooling stress, including capillary dilatation, and the E3 treatment group experienced less damage overall than the E1 and E2 treatment groups. In conclusion, supplementing water with vitamin E to treat crucian carp can decrease damage, improve the body's ability to withstand cold, and slow down the stress response brought on by cooling stress. This provides a theoretical basis for supplementing water with vitamin E to fish stress relief.

The anaesthetic effect of vanillin on crucian carp was investigated using different concentrations of vanillin, with a nonvanillin control. The effective concentration range of vanillin anaesthesia was determined from the behavioural characteristics of crucian carp during the anaesthesia onset and recovery phases. Physiological and biochemical indices, and the electronic nose response to the fish muscle, were measured over the range of effectiveanaestheticc concentrations. An increased concentration of vanillin shortened the time taken to achieve deep anaesthesia but increased the recovery time. The levels of white blood cells, red blood cells, haemoglobinn, platelets, alanine aminotransferase, alkaline phosphatase, lactate dehydrogenase, phosphorus, potassium, magnesium, total protein, and serum albumin were lower than the control in the vanillin treatment group. Triglycerides and total cholesterol were not significantly affected. Histology showed no effect of vanillin on the liver, except at 1.00 g/L vanillin. Vanillin resulted in a nondose-responsive effect on the gill tissue, increasing the width and spacing of the gill lamellae. E-Nose analysis of the carp-muscle flavour volatiles was able to distinguish between different vanillin treatment concentrations. GC-IMS identified 40 flavour compounds, including 8 aldehydes, 11 alcohols, 10 ketones, 2 esters, and 1 furan. Vanillin had aanaestheticic effect on crucian carp and these findings provide a theoretical basis for improving the transport and experimental manipulation of crucian carp.

Eugenol is a widely used fishery anaesthetic. This study investigated the effects of various concentrations of eugenol on blood physiological and biochemical indexes, and muscle flavor, in crucian carp (Carassius auratus). To determine the appropriate concentration of eugenol anesthetic for use in crucian carp transportation and production operations, we evaluated seven anaesthesia groups of 20, 30, 40, 50, 60, 70 and 80 mg/L and one control group (without eugenol) to determine the effects on blood physiological and biochemical indexes, and muscle flavor. The red blood cells and platelets of crucian carp decreased significantly (P<0.05) with eugenol treatment. With increasing eugenol concentration, the white blood cells and hemoglobin did not change significantly, whereas lactate dehydrogenase, alkaline phosphatase, alanine aminotransferase and aspartate aminotransferase increased significantly (P<0.05). The content of phosphorus, magnesium and sodium increased after anaesthesia, whereas the content of potassium decreased with increasing eugenol concentration. After anaesthesia, the content of albumin and total protein in the serum decreased with increasing eugenol concentration (P<0.05); triglyceride first increased and subsequently decreased (P<0.05); blood glucose content first increased and then decreased (P0.05). No significant difference was observed in muscle glycogen and liver glycogen content after eugenol anaesthesia (P>0.05). The eugenol-based anaesthesia test did not indicate major liver histomorphological effects, but the very small number of gill sheet edema cases observed requires further study. Analysis of electronic nose data indicated that eugenol treatment affected the flavor of the fish. The anaesthesia concentration of 20–80 mg/L had little effect on the physiology and biochemistry of crucian carp, thus providing a reference for the application of eugenol in crucian carp transportation and experimental research.