A bypass system for postspawned American shad Alosa sapidissima began operation in 1980 on the Connecticut River canal system at Holyoke Dam. The purpose of the bypass was to enable downstream migrants that enter the canal to exit and avoid death due to delay or passage through hydroelectric turbines at water use facilities. The bypass system had the following elements: (1) an underwater AC electrical or acoustic barrier to prevent American shad from leaving the bypass area, (2) an underwater DC electrical field to immobilize fish for collection, and (3) a collection box with transfer pipe to carry fish to the river below the dam. During studies of the bypass system from 1979 to 1983, we found that the fish barriers were ineffective, the collection system was partially effective for American shad but not for anadromous species that passed through trashracks, and American shad could be immobilized and transported at high velocity through a pipe and have only low mortality (4–9%). Radio‐tagged American shad, unwilling to pass through trashracks at water exits on the canal, behaved like trapped fish and were delayed an average of two or more days before dying or exiting the canal. An estimated 10 of 47 (21%) of the radio‐tagged fish were passed. In 1980, when the greatest number of American shad were passed, an estimated 142,000 (37% ofthe fish lifted at the dam) survived spawning and used the bypass. After several years of operation, it was evident that, even with major improvements, the bypass could not pass the available American shad, and it was not useful for protecting other anadromous migrants that did not avoid trashracks.
