This study aimed to evaluate the influence of stocking density on growth performance, nutritional quality, and immune-related gene expression of Eriocheir sinensis and water quality in pond ecosystems. E. sinensis were randomly divided into five density groups (G1: 1.2 inds/m²; G2: 1.5 inds/m²; G3: 1.8 inds/m²; G4: 2.1 inds/m²; G5: 2.4 inds/m²) based on their breeding densities, and three replicates were set up for each density group, for a total of fifteen ponds. After 169 days of breeding, the muscle, hepatopancreatic tissue, and hemolymph of E. sinensis, randomly selected from each group, were collected for analysis. Body weight (BW), carapace length, and carapace width increased with breeding time, and the BW of E. sinensis in G3 was higher than that in the other groups. In the muscle and hepatopancreas, the crude lipid content in the G3 group was higher than that in the other groups (p > 0.05). In the muscle tissue, the contents of total, essential, and delicious amino acids in the G3 group were higher than those in the other groups. The expression levels of immune-related genes in G5 were higher than those in the other groups. The value of pH decreased and NO₂-N increased significantly in the G5 group and pH, as a synergetic factor of culture density, affected the growth performance of E. sinensis. In conclusion, stocking density has a certain impact on the growth performance, nutrition quality, and immunity of E. sinensis and water quality in pond ecosystems, and a stocking density of 1.8 inds/m² can be considered optimal for rearing in pond ecosystems of the Poyang Lake region.

This study explored the effects of replacing live fish feed with artificial compound feed on the growth performance, nutritional composition, digestive performance, and gut microbiota of Chinese giant salamander (Andrias davidianus). The experiment was divided into three groups, each with three biological replicates. The salamander juveniles were fed artificial compound feed (S), live fish (H), and frozen fish (D) for 184 days. Results showed no significant differences in growth performance among the three groups (p > 0.05). The water content in the S group was significantly higher than that in the H group (p < 0.05), and the crude fat content was slightly higher, whereas other nutritional components showed no significant differences (p > 0.05). The analysis of amino acid composition found no significant differences among the three groups of Chinese giant salamanders (p > 0.05). The analysis of fatty acid composition revealed that the feed group had significantly lower levels of polyunsaturated fatty acids compared with the other two groups (p < 0.05), and significantly higher levels of saturated fatty acids (p < 0.05). There were no significant changes in digestive enzyme activity among the three salamander groups (p > 0.05). There were also no significant differences in the remaining antioxidant indicators in the intestine and liver among the three groups of salamanders (p > 0.05). The S group had significantly higher Pielou_e and Shannon indices (p < 0.05), thereby indicating a greater diversity and evenness of the gut microbiota. In conclusion, replacing live feed with artificial compound feed does not affect the growth performance, nutritional composition, antioxidant capacity, and digestive function of Chinese giant salamander juveniles. Moreover, it enhances the diversity and richness of the gut microbiota, providing effective data to support the development of artificial feeds for giant salamanders.