Abstract: Conventional operation of the Three Gorges-Gezhouba cascade reservoirs is eco-hydrologically mismatched, at multiple temporal scales, with the spawning requirements of Chinese sturgeon (Acipenser sinensis) at the Yanzhiba experimental site in Yichang. To address this mismatch, a refined ecological operation mechanism centered on hourly intra-daily flow redistribution is proposed. A joint optimization operation model is developed to coordinate Gezhouba’s counter-regulation capability of daytime pre-storage followed by pre-dawn release with supplementary release from the Three Gorges Reservoir (TGR). Results show that the TGR-alone supplementation strategy stably achieves the ecological targets, but causes excessive drawdown at TGR. The Gezhouba-alone counter-regulation strategy yields unstable ecological performance due to inflow conditions and limited storage capacity. The cascade coordination strategy stably achieves the pre-dawn target discharge. Compared with the TGR-alone supplementation strategy, it reduces TGR’s additional drawdown volume by 5.43×10⁸ m³ on average, reaching 5.93×10⁸ m³ in dry years, and this advantage remains robust in the sensitivity analysis of the ecological flow threshold. During the 2025 field experiment, the observed operational characteristics align well with the optimization results, and the occurrence of eggs and larvae corresponded in time with the pre-dawn high-discharge period. The findings provide a reference for reconciling ecological protection with water resource utilization during the dry season.