| Fish Screen |
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Information AboutFish Screen |
| CATEGORIES ABOUT FISH SCREEN | |
| aquatic ecology | |
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DESIGN Fish screens may be positive barriers (devices such as a perforated metal plate that physically prevent fished from passing) or behavioral barriers (devices that encourage fishes to swim away). Most behavioral barriers are experimental and of unproven effectiveness. Positive barriers are effective and widely used. Besides simply preventing fishes from passing, they are designed to minimized stress and injury that occur when fishes impact the screen or are subjected to excessive changes in water velocity and direction. The cost of a fish screen varies from thousands of US dollars to millions in the case of very large custom-designed systems that filter a large flow of water. Maintenance costs (repairs, removing trash, and adjusting the equipment for changes in stream conditions) can be significant. LEGAL REQUIREMENTS The United States Fish And Wildlife Service mandates positive-barrier fishscreens in most new diversions from waterways where endangered or threatened fish species occur. Some existing unscreened diversions whose construction pre-dates fish-screen mandates are allowed to continue operating by Grandfather Rule . GEOGRAPHIC SPREAD Fish screens are common at large water diversions in California , where they protect endangered and threatened runs of Salmon and other fishes. SEE ALSO |
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