"This paper provides a scientific approach for the eco-design of river fishways to allow upstream movement of fish past new and existing dams in China. This eco-design approach integrates principles of fish biology and engineering, a scientific field also known as bio-engineering or eco-hydraulics. We define a fishway as a structure or mechanism for conveying fish upstream past a dam. Man-made or natural stream beds can be part of the fishway. The problem is dams block access to upstream habitat used for spawning, rearing, and refuge; i. e. , dams decrease habitat connectivity. A solution to alleviate this problem is to design fishways, preferably while the dam is being designed, but if necessary, as retrofits afterward to provide a route that fish can and will use to pass safely upstream without undue delay. Our eco-design approach for fishways involves eight steps: 1) identify the primary species of importance; 2) understand the basic ecology and behavior of these fish;3) characterize the environmental conditions where passage is or will be blocked; 4)establish eco-design criteria for the fishway, either from management agencies or, if necessary, developed specifically for the given site; 5)identify fishway alternatives and select a preferred alternative; 6) where needed, identify and perform research required to resolve critical uncertainties and finalize the eco-design criteria; 7) apply the eco-design criteria and site-specific considerations to design the fishway, involving peer-review by local stakeholders in the process; 8) build the fishway, monitor its effectiveness, and apply lessons learned. Types of fishways are described, showing a range of eco-designs depending on the dam site and fish species of concern. We use the eco-design principles as a basis to recommend an approach and next steps for a fishway to pass fish upstream at Hanfeng Dam, an existing regulating dam forming Hanfeng Lake on the Pengxi River near Kaixian, China."