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Environmental pollution, disease transmission and food safety caused by intensive pond aquaculture is causing a bottleneck in its development, and a transformation to an integrated aquaculture model is the only way to achieve sustainable development. Integrated aquaculture practices require an evaluation index system that includes a set of ecological indicators that characterize ecosystem changes for use in benefit assessment. In this study, two Ecopath models, white shrimp Litopenaeus vannamei monoculture and integrated aquaculture using L. vannamei with the hard clam Mercenaria mercenaria, were constructed. Based on their representativeness and applicability, the 10 evaluation indicators output from the model were divided into four categories (trophic structure, niche competition, energy utilization and resistance to external disturbances) in order to construct an integrated aquaculture evaluation index system. The results showed that both the monoculture system and the integrated aquaculture system were composed of three integer trophic levels, with the highest effective trophic level being benthic (2.65). The effective trophic levels of L. vannamei in the monoculture and integrated aquaculture ecosystems were 2.03 and 2.02, respectively. The prey overlap index of L. vannamei and M. mercenaria in the integrated aquaculture ecosystem was 0.516, and M. mercenaria had a weak negative effect on L. vannamei. Functional groups with the highest ecotrophic efficiency (EE) values in the monoculture and integrated aquaculture systems were Artemia and microzooplankton, respectively. The EE values of phytoplankton, detritus and benthic bacteria in the integrated aquaculture system were higher than those in the monoculture system. The energy flowing to trophic level II and detritus accounted for 7.7% and 92.3% of the total primary production in the monoculture system, respectively, and accounted for 52.2% and 47.8% in the integrated aquaculture system, respectively. The calculated total net primary production/ total biomass (TPP/TB) and calculated total net primary production/ sum of all respiratory flows (TPP/TR) values of the integrated aquaculture system were lower than those of the monoculture system, while Finn’s cycling index (FCL) and Finn’s mean path length (FML) values were higher than those of the monoculture system. In general, compared with the monoculture system, the integrated aquaculture system showed no significant change in the trophic structure of each functional group, acceptable competition for ecological niches among cultured animals, substantially higher utilization of primary productivity and detritus, and greater system stability and resistance to disturbance. The integrated aquaculture evaluation index system provides a methodological basis for the development of new integrated aquaculture models and has implications for the evaluation of integrated aquaculture ecosystems. |
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