Fish Screen Program 

Fish screens are a proven technology used to protect a wide variety of aquatic species from entrainment into water diversions, including several species of endangered and threatened Pacific salmon. When fish are “entrained,” or drawn out of their natural habitats by hydraulic forces from a water diversion, they are most often injured or killed. Surveys of water users’ canals have shown that considerable numbers of salmon, steelhead, and other fishes can be entrained into gravity and pumped water diversions from California’s waterways in a single day. Fish screens represent a reliable technology that can reduce the cumulative impacts of entrainment. Fish screens, designed and built to National Marine Fisheries Service (NMFS)-Southwest Region’s standards, offer a fine mesh, “positive barrier” between a natural fish-bearing stream and a water diversion point- eliminating entrainment and impingement of most juvenile and adult fish.  NMFS-Southwest Region’s Habitat Conservation Division plays an important role in California’s fish screening program through its leadership and oversight; as well as by conducting field research, performance assessments, and diving inspections.

NMFS engineers are involved in all phases of federally-sponsored fish screen projects:  

• NMFS engineers developed fish screen design criteria based on the latest scientific research to ensure fish screens are designed to provide adequate protection to our living aquatic resources. 
• NMFS engineers work with State, Federal, and local governments as well as private landowners and water users to develop fish screen designs specific for each water diversion’s conditions.  Every site is different, with its own set of engineering challenges.
• NMFS engineers and other technical experts inspect screen construction practices and materials at critical stages of the construction process to ensure the end product will meet stringent standards set by the agency.
• NMFS personnel conduct or oversee post-construction evaluations of fish screens to ensure they are constructed and tuned to meet design criteria.
• NMFS engineers monitor completed fish screens over time, using SCUBA gear when required, to ensure the screens have not been damaged, are being maintained, and to research the efficacy of screen design elements.
• Knowledge gained from fish screen inspections is used to better future fish screen designs.
• NMFS engineers work with screen manufacturers to create new technologies to provide reliable screening solutions to water users of all sizes.

As of 2007, many of the largest water diversions in California’s Central Valley have been fitted with state-of-the-art fish screens, but thousands of smaller diversions throughout the state continue to operate with no screen in place. 

Back to Fisheries Bio-Engineering Projects

03/11/08