| Summary: | Polyculture is an effective way to achieve efficient utilization of nutrient resources in high-density intensive aquaculture systems. In order to study the optimal culture mode of <i>Oreochromis niloticu</i>, <i>Aristichthys nobilis</i>, and <i>Cherax quadricarinatus</i>, the budget of nitrogen and phosphorus in various polyculture systems (CH, CHC1, CHC2, CHC3) was studied with land-based enclosures. The results showed that all the three polyculture systems had higher total yields of cultured animals than the control group (two polyculture systems) (<i>p</i> < 0.05). The co-cultured organisms absorbed artificial feed or organic matter (such as plankton and sediment) from the polyculture system to different degrees. Feed was the main input of nitrogen (98.22–98.33%) and phosphorus (99.43–99.56%) in all systems. Considering the N and P outputs, 46.64–64.58% and 81.60–84.79%, respectively, accumulated in the sediment, and 34.43–52.55% and 14.89–17.30% of the N and P outputs, respectively, were harvested by aquaculture organisms. The pollution production coefficients of TN and TP in the <i>O. niloticus</i> polyculture ponds were 5.35–6.26 g/m<sup>2</sup> and 1.17–1.61 g/m<sup>2</sup>, respectively. The TN production coefficients of <i>O. niloticus</i> and the ternary polyculture groups (CHC1, CHC2, and CHC3) were lower than that of the control group (CH). The TP production coefficients showed the opposite pattern. The N and P utilization efficiencies in the group with the optimal ratio of <i>O. niloticus</i>, <i>A. nobilis</i>, and <i>C. quadricarinatus</i> (4, 0.15, and 3 ind/m<sup>2</sup>, respectively) were 2.56–12.82% and 6.62–11.03% higher, respectively, compared with those of the other groups. The N utilization efficiency was effectively improved in this group with the optimum stocking density for the polyculture systems, resulting in improved ecological efficiency and economic benefits.
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