Optimal stocking density of all-male giant freshwater prawn enhanced farming performance and economic profit in rice-prawn co-culture system

Rice-fish co-culture is a widely adopted sustainable farming practice in China, contributing significantly to global food production. Among the species considered for integration, all-male giant freshwater prawns ( Macrobrachium rosenbergii) show great potential. However, the optimal stocking density for these prawns in rice-prawn co- culture system remains underexplored. This study investigated the effects of six stocking densities: T1 (control), T2 (0.5 prawn/m2), T3 (1.0 prawn/m2), T4 (2.0 prawns/m2), T5 (4.0 prawns/m2), and T6 (8.0 prawns/m2). Key performance indicators, including prawn growth, yield, rice production, food sources, and economic returns, were evaluated. Results showed that T2 (0.5 prawn/m2) achieved the highest prawn body weight but the lowest prawn yield, while T6 (8.0 prawns/m2) resulted in the highest rice yield but the lowest prawn body weight. Stable isotope analysis (delta 13C and delta 15 N) revealed no significant differences in prawn tissue across treatments, with benthic organisms identified as the primary food source, surpassing supplemental feed. Economic analysis indicated that T4 (2.0 prawns/m2) generated the highest net profit and return on investment (ROI). Regression analysis further suggested that a stocking density of 1.85 prawns/m2 maximized the net profit, while 0.90 prawn/m2 yielded the highest ROI. The current study emphasizes that an optimal stocking density of 0.90 prawn/m2 to 1.85 prawns/m2 is recommended for all-male prawns in the rice-prawn co-culture system. These findings could provide a scientific foundation for developing the rice-prawn co-culture model in China and globally, highlighting its significant implications for optimizing cultivation techniques and formulating policies.