Fish Passage

Fish passage is focused on allowing fish to move upstream past barriers in the river, most commonly dams or diversion structures. There are many methods and techniques to providing upstream fish passage; the choice of the best technique requires a detailed understanding of the needs of the individual project and the strengths and weakness of each available method. OneFish understands the swimming capabilities of a wide range of fish species, how to model the specific site hydraulics, and regularly works with state and federal wildlife managers to determine passage priorities and appropriate design criteria.

Some of the more common methods for upstream passage include:
  • Technical fishways – permanent engineered structures that create well defined hydraulics, allowing fish to swim upstream through a series of pools 
  • Nature-like fishways – bypass channels or rock ramps that reduce the velocity of water, allowing fish to swim around the existing dam or diversion 
  • In-stream rock structures – weirs or rock riffles that achieve the same upstream water level but moderate the gradient moving downstream to decrease water velocities and elevation steps 
  • Dam removal – to provide restoration of natural channel conditions when practical and appropriate 

In some cases, resource professionals may want to introduce intentional barriers to passage in order to protect native fish from invasive species. Effective design of these barriers requires an understanding of the fish species present, their swimming abilities, the goals at each site, and the hydraulics of the river.

Please visit the following pages to see some example fish passage projects.