Abstract: In order to explore the environmental conditions required by typical drifting-egg fish species in the lower reaches of the Jinsha River,the Coreius heterodon,a key drifting-egg fish species,was selected in this study. The purposes of this study were to quantify and integrate suitable thresholds for fish reproduction,and improve ecological operation plans to support the natural reproduction of fish. The spatial and temporal patterns of daily egg-laying activities under different hydrological and environmental conditions were analyzed. The study employed a single-indicator discrimination model and a combinatory optimization model to elucidate the daily spawning patterns of Coreius heterodon. The results indicated that ongoing ecological operation experiments positively influenced Coreius heterodon spawning,contributing to its reproductive success. A comprehensive analysis of ten key environmental factors,including water level,discharge,water temperature,initial water level,cumulative water level change,cumulative rate of water level change,initial discharge,cumulative discharge change,cumulative rate of discharge change,and initial water temperature,revealed significant correlations with the daily spawning of Coreius heterodon. Among these factors,the combination of water level,initial discharge,and cumulative discharge emerged as the most reliable rule set for determining daily spawning activity. Specifically,the study found that an initial discharge of at least 2 455 m3/s and a cumulative discharge change of at least 2 053 m3/s provided effective criteria for assessing the reproductive activity of Coreius heterodon. These findings offered valuable insights into the hydrodynamic conditions necessary to facilitate fish spawning and contribute to optimizing ecological regulation strategies. By refining ecological operation plans based on these results,river management efforts can more effectively support the natural reproduction of drifting-egg fish species in the Jinsha River,to ensure the sustainability of their populations in the long term.