Abstract: To identify the key environmental drivers of glass eel (Anguilla japonica) recruitment in the north coast of the Yangtze River Estuary, we developed a generalized additive model (GAM) using fishing log data from 21 selected commercial vessels during the licensed fishing seasons (2022-2024) and ten synchronized environmental variables. The results revealed a significant temporal decline in glass eel resources over the three years, with a progressive delay in the timing of peak catches. In the optimal GAM, sea surface salinity, dissolved inorganic phosphorus (DIP), and dissolved inorganic nitrogen (DIN) were the key environmental factors influencing glass eel recruitment, with explanatory contributions of 17.0%, 15.1%, and 13.0%, respectively. DIP showed an oscillating rise with rapid (0.13-0.17 mmol·m^-3), slow (0.17-0.25 mmol·m^-3), and stable (>0.25 mmol·m^-3) phases. DIN exhibited bimodal oscillations, decreasing (5-6 mmol·m^-3), increasing (6-18 mmol·m^-3), and then sharply declining (18-20 mmol·m^-3). Our results indicated that nutrients (DIP and DIN) and sea surface salinity are key environmental drivers influencing glass eel recruitment in the north coast of the Yangtze River Estuary. These findings elevate the role of nutrients from ambiguous background factors to critical determinants of recruitment dynamics, offering a novel perspective for understanding fluctuations in glass eel resources. This new perspective provides a crucial theoretical foundation for the scientific management of glass eel resources.

Key words: the north coast of the Yangtze River Estuary, Anguilla japonica, GAM, nutrient, eel fry fishing season