A fish barrier is a structure, either natural or man-made, that prevents the upstream movement of fishes and aquatic organisms. The Bureau of Reclamation constructs fish barriers to prevent upstream movements
of nonnative aquatic organisms into streams with native fish populations. Reclamation's barriers are either physical drop structures (low waterfalls) or electrical fields. Electrical barriers are used in situations where
water gradients are insufficient to install a drop barrier. In general, drop barriers are preferred because they function passively (in other words, they do not depend upon the sometimes unreliable transmission of electricity).
Reclamation selects fish barrier locations based on the recovery philosophy that existing populations of rare native fishes must be protected against further threats of nonnative species invasions, and that those populations must also be replicated into additional protected streams. Therefore, some proposed barrier locations protect existing rare populations, while others will serve as replication sites for existing populations found elsewhere. For more information on the fish barriers constructed by the Program, please visit the Physical Fish Barriers and Electrical Fish Barriers pages.
Additional Information on the Justification for Fish Barrier Construction: