Title: Estimating ecological carrying capacity and management of enhancement species in Tangshan marine ecosystem (Bohai Sea, China) based on ecosystem model.

The Tangshan marine ecosystem is one of the areas in Bohai Sea that are gazetted for marine farming through stock enhancement. The sea cucumber, shellfish, black rockfish and yellow rockfish are the main target species for enhancement, but there is limited information of the ecological carrying capacity of these species. In this study, a food web model of Tangshan marine ecosystem is developed using Ecopath with Ecosim (EwE) modelling framework and used to estimate the potential biomass of selected species that can be released without destabilising the ecosystem. The model, which is not spatially resolved, consists of 19 functional groups chosen on the basis of functional role in the ecosystem and availability of data. The pedigree index, reflecting the overall quality of the input parameters, is within the intermediate range of the global Ecopath models. The model shows that Tangshan marine ecosystem is a relatively immature system, phytoplankton-based, and less resilient to ecosystem disturbances. Nevertheless, the ecosystem has the capacity to support more than 200% increase in biomass of blackfish, yellow croaker, sea cucumber and shellfish relative to the present level. The main conclusion from this study is that the Tangshan marine ecosystem can support stock enhancement for multiple species within the limits of the ecological capacity assessed by the model. It is important to note, however, that the ecological capacity in this study is based on the principle of mass balances, with limited consideration of spatial effects and changes in species life history. The parameter-combination used to achieve mass balances, from which the ecological carrying capacity is determined, is one of the possible parameter-combinations that can achieve similar results. This implies the present model should be considered as a best working hypothesis rather than a definitive representation of the Tangshan marine ecosystem.