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Executive Summary This report summarizes findings by the U.S. Fish and Wildlife Service on the feasibility of performing three management actions to promote the conservation of the humpback chub (Gila cypha) in Grand Canyon. First, we address the feasibility of establishing a captive broodstock program for humpback chub. Broodstock development is considered within the context of captive propagation policy as defined by the U.S. Fish and Wildlife Service and the National Oceanic and Atmospheric Association, and within the context of the scientific literature. Part of this policy requires that captive broodstock activities are based on the specific recommendations of recovery strategies identified in recovery plans whenever practical; a feature for which the current Recovery Goals for the species make no provision. Establishment of a captive broodstock may serve as a genetic refugium, and the activity by itself poses no risk to the wild population. However release of captive propagated individuals into the wild poses serious biological risks, and as such should not be considered as a management strategy unless all other conservation measures fail. Potential biological risks involved with release of captive propagated fish into the wild include introgression, inbreeding depression, domestication, and potential to decrease the genetic effective population size of the wild population. A captive brood stock program will require being preceded by completion of genetics studies being performed on humpback chub, development of a formal captive brood stock management plan, identification of a an adequate site equipped with a quarantine facility and capable of holding several thousand fish, development of a formal reintroduction plan, and commitment of significant long term funding. This document discusses basic questions in relation to brood stock development, and lists hatchery attributes required to raise brood stock fish. The humpback chub currently held at Willow Beach National Fish Hatchery may serve as a starting point for such an activity . Second, we address the feasibility of establishing a program for captive grow-out of wild caught age-O humpback chub for release into the wild. Modeling suggests that if -960 to 1,400 age-O humpback chub were captured per year from the Little Colorado River (LCR), and grown out to -170 mm before release, this should arrest further population decline and maintain the abundance of age-4+ humpback chub at levels estimated in .2000. Alternatively, the model predicts that if -4,300 to 6,350 age-O fish were captured per year from the LCR, and grown out to -170 mm before release, this may achieve a positive increase in the abundance of age-4+ fish to the level estimated in 1990. These predicted numbers may need to be inflated, depending upon the rate of post-release mortality (Le., they may need to be doubled). These predicted effects should be fully realized by the year 2020. The primary biological risks associated with this activity appear to be related to ethological issues, such as lack of anti-predator responses or lack of ability to feed efficiently. In addition, depending on where the fish are released, 5