Optimal stocking density enhances culture performance for all‑male culture of Chinese mitten crab Eriocheir sinensis

The culture of all-male Chinese mitten crab, Eriocheir sinensis, represents a promising strategy to enhance productivity. However, the lack of optimal stocking density for all-male culture of E. sinensis hinders the development of standard culture protocols. This study aimed to determine the optimal stocking density for all-male culture of adult E. sinensis, based on a comprehensive assessment of culture performance, total edible yield, and economic analysis. All-male juveniles with an initial average weight of 8.67 ± 0.36 g were stocked at four different stocking densities (1, 2, 3, and 6 inds./m²) with five replicates for each treatment, and the culture experiment lasted 34 weeks during the grow-out culture period in net-enclosure culture facilities. The results showed that specific growth rate, final body weight (FBW), and survival rate significantly decreased with increasing stocking density (P < 0.05). The meat yield of 6 inds./m² treatment was significantly higher than that of the 2 inds./m² treatment (P < 0.05), but there was no difference in the hepatosomatic index, gonadosomatic index, and total edible yield among the density treatments (P > 0.05). The total yield per unit varied between 168.24 and 289.31 g/m², with the lowest and the highest values at stocking densities 1 ind./m² and 6 inds./m² treatments respectively. Economic efficiency analysis showed total cost significantly increasing with increased stocking densities (P < 0.05). Total return and net profit were affected by stocking density and peaked at a stocking density of 3 inds./m². The highest break-even yield (BEY) and the lowest return on investment (ROI) were obtained at a density of 6 inds./m² (P < 0.05), whereas no significant differences were observed among the 1 ind./m², 2 inds./m², and 3 inds./m² treatments. Moreover, the net profit and ROI followed a quadratic regression on the stocking density, with a maximum at 3.3 inds./m² and 2.5 inds./m², respectively. Based on the observations above, a stocking density of around 2‒3 inds./m² was considered reasonable during the grow-out culture period of E. sinensis in a net-enclosure culture system.