Impact of environmental factors on the CPUE of threadfin bream in the South China Sea based on Structural Equation Modeling

The South China Sea, as a critical area for global marine biodiversity, has a unique marine ecosystem that plays an irreplaceable role in maintaining regional ecological balance and fishery resources. To achieve a deeper understanding of the potential impacts of environmental changes on the resources of threadfin bream (Nemipterus spp.) in the South China Sea, this study explores the effects of environment factors on the catch per unit effort (CPUE) of Nemipterus spp. and its influencing mechanism based on Structural Equation Modeling (SEM). The research analyzes fishery logbook and environmental data collected from the South China Sea during 2018 - 2021, examining the influence of sea surface temperature (SST), sea surface salinity (SSS), sea surface height (SSH), chlorophyll-a (Chl.a) concentration, and precipitation on the CPUE of Nemipterus spp.. The results show: ① The annual average CPUE of Nemipterus spp. exhibits significant interannual variability, accompanied by cyclical fluctuations across different months, with fishing seasons from May to July closely related to fishing intensity during both open and closed fishing months. ② The relationship between CPUE of Nemipterus spp. and environmental factors shows pronounced seasonal variations. SSS and SST emerge as the primary factors influencing CPUE. SST and SSH playing dominant roles in the spring, while SSS and precipitation being the primary factors are the primary factors in summer, and SST in autumn and winter. The study indicates that management strategies for Nemipterus spp. fisheries need to be adjusted according to seasonal changes to accommodate the impact of environmental factors on the catch volumes of Nemipterus spp.. Conversely, the impact of environmental factors on CPUE is relatively subdued in autumn and winter. This study clarifies the interactions among marine environmental factors and their specific effects on Nemipterus spp., with the aim of providing a critical foundation for the scientific formulation of fishery management strategies and the conservation of marine ecosystem in the South China Sea.