An improved fish passage apparatus is combined with hydroelectric power generation to facilitate migration of fish between water bodies of different heights with minimal injury or trauma to fish. It may also be optimized for power generation when fish are not moving through it. The fish passage apparatus comprises parallel connecting tubes providing fluid communication between upper and lower water bodies, upper valves in each connecting tube adapted to control flow of water to or from an upper water body, lower valves in each connecting tube adapted to control flow of water to or from a lower water body, and working tubes opening into each connecting tube between the upper and lower valves a working portion of which extends functionally vertical to above a water level of the upper body of water and to below a water level of the lower body and is vented at its top such that water can flow freely in and out of the working portion.