Comprehensive assessment of three crayfish culture modes: From production performance to environmental sustainability

Integrated agriculture-aquaculture has emerged as a promising ecological development model. Crayfish, a popular aquaculture species, are traditionally reared either in monoculture ponds (mono-C) or in rice-crayfish polyculture system (poly-RC). In this study, we introduced a novel polyculture system by combining fruit tree with crayfish (poly-FC), aiming to compare these three crayfish culture modes in terms of production performance and ecological sustainability. The results indicated that crayfish reared in the two polyculture modes exhibited significantly higher specific growth rate and condition factor compared to those in mono-C. Crayfish cultured in poly-FC also showed better muscle quality and higher levels of crude fat and flavor or essential amino acids. Isotope mixing model showed that feed and benthic animals were the primary food sources of crayfish in mono-C, whereas aquatic plants, fruit litter or rice contributed more to those in polyculture modes. For greenhouse gas emissions, poly-FC mode emitted almost no CO₂ and N₂O even favored negative CH₄ emission, while poly-RC and mono-C modes showed positive emissions of CH₄ and CO₂, respectively. Supported by metagenomics, the sink of CH₄ in poly-FC was probably due to the lower mcr abundance but the higher pmo abundance in water. The low production and emission of N₂O in poly-FC might result from the low-abundant Nitrospirae_bacterium and its coding gene norC in sediment, consistent with the lower denitrification rate but the higher NO₃^- concentration than mono-C. Overall, our findings reveal the superiority of polyculture of fruit tree with crayfish in terms of production performance and greenhouse gas emissions in the system.