Dictionary of Ichthyology  

bypass systems = moving screens lowered into turbine intakes to divert fish away from turbines at hydroelectric dams. Bypassed fish can then be returned directly to the river below the dam. In some cases facilities exist to load bypassed fish onto barges or trucks for transport to a release site downstream from all dams in a series.

juvenile fish bypass, U. S. Army Corps of Engineers from Wikimedia Commons: http://commons.wikimedia.org/wiki/File:Juvenile_fish_bypass.jpg

Canadian Museum of Nature