Hydrological Regulation Disrupts Estuarine Spawning Grounds via Salinity Front Displacement but Preserves Nursery Habitats: Evidence From the Yellow River

Global rivers are increasingly threatened by fragmentation and sediment accumulation in reservoirs and dams. The Water‐Sediment Regulation Scheme (WSRS) has been widely implemented to mitigate these challenges, yet its ecological impacts on estuarine fisheries remain poorly quantified. Critically, WSRS operations often coincide with the spawning season of many marine fish species, raising concerns about disruptions to reproductive success and juvenile recruitment. Here, we propose a quantitative framework linking the distribution patterns of estuarine spawning and nursery grounds to two key hydrodynamic fronts—the salinity front and the suspended sediment front. Based on a 12‐year (2011–2022) observational data set, we reveal consistent spatial relationships: spawning grounds are primarily associated with the salinity front, whereas nursery grounds are mainly located near the suspended sediment front. We further demonstrate that WSRS significantly alters the salinity front, disrupting the established distribution pattern of spawning grounds. This disruption corresponds to a 34.5% reduction in total egg production in estuarine waters—a substantial potential impact on population replenishment. In contrast, WSRS has a minor effect on nursery grounds, with juvenile fish continuing to aggregate near the suspended sediment front. Our findings provide quantitative evidence linking hydrological regulation to estuarine spawning habitat functionality via frontal dynamics. This study offers a transferable framework to inform the balance between water‐sediment management and fisheries conservation in major river‐estuary systems with similar frontal structures.