Fundamental study on ecosystem in East China Sea by an integrated model of low and high trophic levels

As the main nutrient inputs of ECS, nutrient concentrations of the Yangtze River increase significantly due to high-speed economy development, which play a very important impact on the East China Sea ecosystem. In this study, by integrating MEC model and Ecosim model, we analyzed the impacts of Yangtze nutrient fluxes change and fishery on the ecosystem of ECS. The results show that in only consideration of nutrition influx changes of the Yangtze River, the biomass of high trophic level will increase varying from 5% to 10%, especially in which most of trophic level 3 creatures will raise about 10%. When only considering the fishery impact, yellow croaker and hairtail as the main fishery product of ECS were under drastic pressure and close to extinct and small fish and anchovy increase about 30% to 40% rapidly due to the decline of predators. Under comprehensive consideration of fishery and nutrition influx changes, the result shows the main fish production decrease significantly, average trophic level recession and small fish take the main position of ecosystem. The increase of nutrients input has a certain benefit for the ecosystem to slow the decline tendency of fish. The integrated model provides a prospect that we can study the entire ecosystem from the prospective of both environmental and fishery factors, extending from lower to higher trophic ecosystem, to achieve a top-down and bottom-up management.