Food web structure and ecosystem attributes of integrated multi-trophic aquaculture waters in Sanggou Bay

Abstract Sanggou Bay is well known as an exemplary coastal water of Integrated Multi-Trophic Aquaculture (IMTA). IMTA as practiced in China is highly ecologically efficient, through the combination of extractive and fed species. In this paper, Ecopath model was used to study the food web structure and function of Sanggou Bay ecosystem. According to the model, Sanggou Bay ecosystem ranged from 1.00–3.89 in trophic level. Sanggou Bay ecosystem was dominated by low trophic levels, of which aggregated trophic level I and II (TL I and TL II). TL I and TL II contributed 83.64 % and 16.36 % in biomass. Aquaculture species (kelp, oyster, scallop and abalone) were all in TL I and TL II, together accounted for 97.30 % in biomass of all functional groups. Kelp accounted for 81.12 % of the total biomass. Transfer efficiency of the ecosystem was 10.85 %. Aquaculture harvest had a positive influence on scallop, oyster and kelp, but had a negative influence on abalone. All functional groups in Sanggou Bay ecosystem had negative self-impacts, that could be interpreted as intraspecific competition for resources. Oyster, scallop and abalone showed negative impacts on each other. From the system properties, connectance index (CI) was 0.26 and system omnivory index (SOI) was 0.08, these suggested that Sanggou Bay was influenced by human activities. The ratio of production to respiration (P/R) was 3.57, the ecosystem production is much more than respiration. This presented that IMTA in Sanggou Bay showed a way to minimize the disturbance of aquaculture to protect the ecosystem and improve economic benefits for stakeholders. This paper may provide reference for research and management of ecosystem structure and function of aquaculture waters.