Impacts of Yangtze Cascade Dams on Migratory Fishes and Restoration

As the river basin with the highest freshwater biodiversity in China, the Yangtze River has seen its hydrological rhythms and habitat connectivity in both its main and tributary streams profoundly reshaped by the extensive construction of cascade dams. This paper aims to systematically analyze the chain of threats posed by cascade barriers to key migratory fish species, such as the Chinese sturgeon and the 'Four Major Carp Species', and to objectively evaluate the effectiveness and limitations of existing ecological restoration technologies. The research findings indicate that physical barriers and the absence of hydrological signals have led to a reduction of approximately 99% in the natural spawning grounds of the Chinese sturgeon, whilst the natural spawning output of the 'Four Major Carp Species' has fallen by more than 98%. Artificial flood pulse creation under ecological water regulation can effectively trigger spawning of semi-anadromous fish, yet conventional fish passage facilities achieve less than 5% passage efficiency for large benthic migratory fish. This study provides crucial theoretical grounds and decision-making support for refining coordinated protection strategies across the main and tributary rivers of the entire basin, and for optimizing the joint regulation system of multiple dams, against the backdrop of the 'Ten-Year Fishing Ban on the Yangtze River'.