Analysis of ecosystem change recent years based on Ecopath models in the Aoshan Bay ecosystem

Ecopath model is a snapshot of a particular ecosystem at a time to quickly reflect the real-time status, characteristics and nutritional relationships of remaining systems in the water. Based on Aoshan Bay fishery resource data collected in 2006, 2013 and 2018, Ecopath models of the Aoshan Bay ecosystem were constructed for these 3 years using EwE 6.6 software. The models of the Aoshan Bay ecosystem included 15 functional groups. Based on the 3 models, we compared and analysed changes in ecosystem structure and phylogenetic characteristics. The trophic interactions between the 15 functional groups were aggregated within four effective trophic levels at 2006, 2013 and 2018. Most of the functional groups were laid within the trophic levels TL 2 and TL 3. The average trophic levels in 2006, 2013 and 2018 were 2.318, 2.444 and 2.410, respectively. The calculated ecotrophic efficiency (EE) value for this ecosystem was highest for Zooplankton (EE = 0.898, 2006), Nibea albiflora (EE = 0.857, 2013) and other demersal fishes (EE = 0.963, 2018). In this study, the calculated TPP/TR was 4.572 (2006), 4.484(2013), 5.347(2018), which indicates the ecosystem is in a developmental stage (not fully mature), the highest mature ecosystem is 2013 and gradually decrease in 2018. In 2013, the FCI is 4.814 and higher ecosystem's maturity than 2006 and 2018, indicating high utilization of primary productivity and detritus. Through analysis of Ecopath models for different years, the characteristics of ecosystem changes in the Aoshan Bay over the past decade were revealed, indicating that the Aoshan Bay ecosystem is still in an unstable and immature state, which provides scientific reference materials for the restoration of fishery resources in this sea area.