Proteins related to antioxidant defence systems and energy maintenance play a vital role in resisting starvation in fish. However, studies on the underlying molecular mechanism of starvation stress in the jade perch Scortum barcoo are very limited. Thus, the proteomic changes in S. barcoo during fasting were investigated by stable isotope labelling and high‐performance liquid chromatography‐tandem mass spectrometry (iTRAQ‐LC‐ MS/MS) in the present study. Therefore, a total of 3324 proteins were identified, including 134 that were significantly altered (p < 0.05, fold change >1.20 or <0.83) in the experimental groups compared with the control group. Among all the differentially expressed proteins, only protein‐disulphide reductase (TXNDC12) was upregulated. One‐third of the differentially expressed proteins were enriched in the amino acid metabolism pathway, tricarboxylic acid (TCA) cycle pathway, fatty acid metabolism pathway and oxidative phosphorylation pathway. Proteins differentially expressed in the experimental group, including AASS, OGDH, ACAD8, FAH, BHMT, AOC3, AOC2 and HIBADH, are components of pathways that control the metabolism of amino acids. The results suggested the involvement of antioxidant defence in the response to an oxidative imbalance, and GSH, SOD and AKP were regulated under conditions of starvation stress. In conclusion, the data indicated that starvation‐induced changes in protein levels that might affect metabolism and the antioxidant system.

Effective culture and management of adult tri-spine horseshoe crab, Tachypleus tridentatus can ensure that stock enhancement programs and aquaculture systems are maintained. To explore suitable feed for animals during the breeding season, Pacific oyster (Ostrea gigas) (oyster group; OG) and frozen sharpbelly fish (Hemiculter leucisculus) (frozen fish group; FG) were selected to feed 20 T. tridentatus male and female pairs, respectively. At the end of the experiment, intestinal samples were obtained to measure digestive enzymes activities. The intestinal flora were determined by 16S rDNA sequencing. No eggs were observed in the FG and one T. tridentatus adult died. No animals died in the OG, and 9.7 × 10 4 eggs were obtained. These results show that oysters are more suitable for the development and reproduction of adult T. tridentatus than frozen fish. Additionally, the digestive enzyme activity analysis revealed that animals in the OG exhibited higher protein digestibility than those in the FG, but no significant differences in lipid and carbohydrate uptake were observed between the groups. Furthermore, the intestinal flora analysis showed that operational taxonomic units (OTUs) and the Chao1 index were significantly higher in the OG than in the FG, but no significant difference was observed in the Shannon or Simpson indices between the groups. Our data indicate that the oyster diet improved the intestinal microbial diversity of T. tridentatus. We hypothesize that nutrients, such as oyster-based taurine, proteins, and highly unsaturated fatty acids, improve protease activity in the T. tridentatus digestive tract, alter the intestinal floral structure, and improve the reproductive performance of T. tridentatus.

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