Fish and hydroelectricity: engineering a better coexistence

Steps being taken by US utilities, under pressure from a Federal licensing agency, to restore once-vast populations of migratory fish are described. Waterways designed to help migrating fish get past dams to upstream spawning areas have been used on some rivers for decades. In some areas, however, the goal now is to get larger numbers of the offspring, and adults that survive spawning, downstream past the dams. The engineering problems that this poses are discussed, and techniques developed so far are described.<>