Stocking density effects on growth performance, water quality, immune indexes, and economic benefits of oriental river prawns（Macrobrachium nipponense）reared in earthen ponds

Macrobrachium nipponense is favored by Chinese farmers due to its advantages such as stronger adaptability, fewer diseases and investments, better economic benefits and is eco-friendliness. However, investigations regarding M. nipponense culture remain limited to laboratory aquarium tanks. There are no established guidelines on optimal stocking density for M. nipponense related to commercial scale farming practices in earthen ponds. In this study, the effects of stocking density on growth performance, water quality, immune indices and the economic benefits of M. nipponense reared in earthen ponds were evaluated. Juvenile prawns (0.22 ± 0.03 g) were stocked at four densities: D90: 90 individuals (inds)/m², D135: 135 inds/m², D180: 180 inds/m², and D225: 225 inds/m². The results demonstrate that growth performance of M. nipponense in low densities was higher than that in high densities in the early stages, while in the later growth stages, no significant differences were found across all groups. Neither the aquatic environment nor prawn antioxidant capacity was significantly impacted across all groups, as they underwent significant changes along with changing of the seasons. Taking into account the above results and the total yield, the yield and proportion of large-sized prawns, net profit and return on investment, the final recommended stocking density is 1.8 million inds/ha (D180 density). The results of this study will provide guidance for the commercial farming of M. nipponense and give valuable insights for promoting sustainable development. • Low density promotes early growth of Macrobrachium nipponense but final weight converges across densities. • Stocking density did not significantly affect water quality or prawn antioxidant capacity, though they varied seasonally. • High-density ponds show lower microbial diversity yet harbor more nitrogen-cycling bacteria. • Optimal stocking density is 1.8 million individuals/ha, based on growth, yield, and economics.