The Lower Colorado River Multi-Species Conservation Program (MSCP) was implemented in April 2005 in response to a need to balance use of water resources of the lower river with conservation needs of 26 native species and their habitats. It is a long-term plan that encompasses the river and its corridor from the head of Lake Mead downstream to the southerly U.S. and Mexico boundary. Two fishes, bonytail (Gila elegans) and razorback sucker (Xyrauchen texanus), are among the species covered by the MSCP. These critically imperiled, federally listed endangered species have received considerable attention over the past several decades, and they are prominent conservation targets of the MSCP. A series of ponds were constructed adjacent to the river on U.S. Fish and Wildlife Service Imperial National Wildlife Refuge near Yuma, Arizona. These ponds were built in part to provide off-channel habitat free of nonnative fishes for the survival and reproduction of bonytail and razorback sucker. Marsh & Associates was contracted to conduct a preliminary, three-year study to determine the suitability of these ponds for native fishes by developing an experimental design, implementing an initial fish stocking regimen, monitoring selected features of the habitat and fishes, interpreting field data, and making recommendations as appropriate to enhance the overall lower river backwater program for native fishes. The current phase of this project is expected to be completed in autumn 2011.