The potential for fish passage facilities to induce “reservoir ecological traps for fish” represents an issue that urgently requires in-depth examination and discussion in China’s fish passage research. Current research on fish passage technology focuses primarily on two questions: how fish downstream of dams pass upstream and how many fish can pass through fish passage facilities. Systematic investigations into post-passage survival, reproduction, and downstream migration of fish remain scarce, making it difficult to determine whether reservoirs function as ecological traps. Focusing on ecological traps encountered by fish after dam passage, this study synthesizes relevant literature and engineering reports on post-passage ecological traps, reviews the relationship between hydraulic engineering projects and fish passage facilities, summarizes the requirements and ecological effects of fish dam passage, delineates the ecological challenges faced by fish after passage and the mechanisms by which they may become trapped, develops an ecological trap assessment framework aligned with the life-history requirements of migratory fishes, elucidates the impacts of ecological traps on key life-history behaviors, and emphasizes that future research should adopt a multidimensional perspective integrating upstream and downstream migration, fish behavior, hydroecology, and habitat suitability to comprehensively evaluate the ecological effects of fish passage facilities and promote a shift toward ecosystem-oriented design and management to enhance their effectiveness in maintaining river connectivity and conserving migratory fish populations.