Effect of stock enhancement using Ecopath model on the ecosystem of Nanlang waters

The Pearl River estuary fishery is one of the four famous fishery waters in China and one of the waters most disturbed by human activities. In order to analyze the impact of stock enhancement on the ecosystem and ecological capacity of estuarine waters, this study is based on the survey data of fishery resources and ecological environment from historical and current surveys, using Ecopath with Ecosim (ewe) 6.5 software, a 6-year material balance model of Nanlang waters was constructed, systematically study the changes of ecosystem energy flow, general characteristics and food web structure of the waters. The research results show that: in 2005 and 2016-2020, the energy flow in Nanlang waters is mainly concentrated in trophic level Ⅰ-Ⅳ, the nutrition structure is basically the same, the grazing food chain and the detritus food chain are the main energy flows in the system, the energy utilization rate of primary producers is high, and the conversion efficiency of total energy flow is low, The waters ecosystem is in the development stag. Compared with 2005, the fishery resources biomass, nutrient level and system energy conversion efficiency of have increased from 2016 to 2020, and the total primary production/respiration ratio (TPP/TR) of the system gradually approaches 1, the system connectivity index (CI) and the system omnivory index (SOI) slightly increase, the ecosystem tends to mature, and the overall scale of the ecosystem expand. Meanwhile, the ecological capacity of the Lateolabrax japonicus and the Acanthopagrus latus was 5 times and 94 times higher in 2020 than in 2005. Therefore, it is concluded that the stock enhancement can not only improve the stability, complexity and maturity of the waters ecosystem, but also help to improve the ecological capacity of the waters.