Effects of Stocking Density on Growth Performance, Physiological Responses, and Transcriptomic Profile of Penaeus monodon

Stocking density plays an important role in P. monodon aquaculture. However, its underlying molecular mechanisms remain unknown. In this work, after a 40-day culture period, we studied the effects of different stocking densities (G1: 50, G2: 100, G3: 150 ind/m3) on P. monodon, assessing their growth performances, physiological indexes, and transcriptome profiles. It was found that increased stocking density greatly decreased the growth performance and survival rate as well as the level of immune enzymes (alkaline phosphatase, acid phosphatase) and antioxidant component (total antioxidant capacity, superoxide dismutase, reduced glutathione) activities. Transcriptomic analysis showed that there are 2284 differentially expressed genes in all groups. Enrichment analysis of WGCNA results indicated that the green module associated with G2 was enriched for amino acid metabolism, lipid metabolism and immunity-related pathway. Furthermore, the G3 associated turquoise module was dominated by stress response, detoxification and energy metabolism pathways. Together, high stocking density causes the occurrence of oxidative stress, disturbance to immune system and alteration of metabolism profiles in P. monodon, whereas medium density (G2) is favorable to maintain physiological homeostasis. The results provide theoretical support to optimize aquaculture practice and contribute valuable information for subsequent studies.