Native Aquatic Species of the Gila River Basin
in Arizona and New Mexico
What is a fish barrier?
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 uses 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). These fishery management tools allow for native species to
thrive in their natural habitat without the effects associated with invasive nonnatives.
Streams for installation of fish barriers were selected 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.
Some proposed barrier locations protect existing rare populations, while others will
serve as replication sites for existing populations found elsewhere. Further justification for fish barriers can
be found in the following reports: "Fish Movement Through Intermittent Stream Channels" and " Effectiveness of
Fish Barriers and Renovations for Maintaining and Enhancing Populations of Native Southwestern Fishes."
The Bureau of Reclamation implemented these management practices as conservation measures associated with the transportation and delivery of Central Arizona Project water to the Gila River basin of Arizona and New Mexico. Thus far, Reclamation has completed construction of concrete drop structures on four streams (Tule Creek, Aravaipa Creek, Sonoita Creek below Cottonwood Spring, and Fossil Creek), and has installed electrical barriers on three canals (Florence-Casa Grande Canal, Salt River Project Arizona Canal, Salt River Project South Canal). Phoenix Area Office conservation measures call for construction of drop barriers on an additional nine streams, as shown on the drop barrier page.
June 25, 2009
Joseph J. Billerbeck - firstname.lastname@example.org