A Synergistic Strategy of Fishing Closure and Stock Enhancement to Restore Dongting Lake Based on an EwE Modeling Approach

Freshwater lakes worldwide are undergoing rapid degradation, raising concerns about the effectiveness of recent large-scale conservation interventions. China’s ‘10-year fishing ban’ represents one of the world’s most ambitious fishery moratoria, yet its ecosystem-level consequences remain poorly quantified. Using data from the two seasonal surveys conducted in Dongting Lake in 2019, we applied a mass-balanced Ecopath with Ecosim model to evaluate how fishing closure, and its combination with multi-species stock enhancement, affects trophic structure, energy flows, and system stability from 2021 to 2030. Simulations show that the closure-only scenario nearly doubles total ecosystem production, yet yields limited improvement in maturity indicators, reflecting a slow recovery of food web complexity. Across the tested closure-plus-enhancement scenarios, the highest projected system omnivory index occurred under scenario S5 (from 0.24 to 0.27), whereas the highest projected Shannon diversity index (from 0.59 to 0.64) and total transfer efficiency (from 10.80% to 11.12%) occurred under scenario S1, relative to the 2019 baseline. Based on the level-wise responses of the L9 treatments, a recommended combined scenario consisting of 1.04 t bighead carp, 4.30 t grass carp, and 1.14 t silver carp, with no additional black carp stocking, was constructed. Under this scenario, the model projected enhanced biomass recovery and a shorter restructuring period for key functional groups. Our study provides a reference for predicting ecosystem responses following the ‘10-year fishing ban’ and also provides data for ecosystem-based assessments for stock enhancement.